WO2013124417A1

WO2013124417A1 - Method for producing vinyl ester-ethylene-acrylamide copolymers

Info

Publication number: WO2013124417A1
Application number: PCT/EP2013/053560
Authority: WO
Inventors: Helmut Zecha; Holger Poths
Original assignee: Wacker Chemie Ag
Priority date: 2012-02-24
Filing date: 2013-02-22
Publication date: 2013-08-29
Also published as: DE102012202843A1

Abstract

The invention relates to a method for producing vinyl ester-ethylene-acrylamide copolymers in the form of aqueous dispersions by free-radically initiated emulsion polymers of (a) one or more ethylenically unsaturated vinyl esters of carboxylic acids having 2 to 18 carbon atoms, (b) 5 to 30% by weight of ethylene, (c) ethylenically unsaturated amides from the group comprising (c1) 0.16 to 4.0% by weight acrylamide, (c2) 0.23 to 0.65% by weight of one or more N-alkylol(meth)acrylamides, (c3)0 to 0.67% by weight of one or more N-(alkoxymethyl)acrylamides or N-(alkoxymethyl)methacrylamides, (d) 0 to 1.5% by weight of one or more ethylenically unsaturated alkoxysilanes, and optionally (e) one or more further ethylenically unsaturated monomers different from the monomers (a) to (d), wherein the total amounts used of the monomers (a) to (e) total 100% by weight, characterized in that in total 0.23 to 0.90% by weight of the monomers (c2) and (c3), based on the total weight of the monomers (a) to (e), are used, and one or more monomers (a) and monomer (b) are initially charged in whole or in part, and also optionally monomer (c1) in part, in water, and then the free-radial emulsion polymerization is initiated and remaining amounts of the monomers (a), (b), (c), optionally (d) and/or optionally (e) are added, with the proviso that at least 50% by weight of the total monomers (c) used are added from a time point at which the conversion of the monomers (a) to (e) initially charged and/or added at this time point is 8 to 50% by weight (dosage criterion) WP11116/E 73, wherein the emulsion polymerization is carried out in the absence of protective colloids.

Description

Process for the preparation of vinyl ester-ethylene-acrylic acid amide copolymers

The present invention relates to processes for the preparation of aqueous dispersions of vinyl ester-ethylene-acrylic acid amide

Copolymers by means of free-radically initiated emulsion polymerization, the aqueous dispersions thus obtainable and their use, for example as binders or adhesives, in particular for the fiber bonding of nonwovens.

Aqueous dispersions of emulsion polymers based on ethylenically unsaturated monomers have been used for some time for the consolidation of fibers for the production of nonwovens. As monomers in this case (meth) acrylic acid esters, styrene, olefins or vinyl esters are very common. Copolymerization of so-called post-crosslinking monomers imparts cross-linking properties to the emulsion polymers, so that the emulsion polymers crosslink with each other and optionally also with the fibers and thus nonwovens with higher strength can be produced.

Despite a large variety of postcrosslinking monomers, N-methylolacrylamide (NMA) has prevailed in industrial practice predominantly. For example, US 4449978 teaches copolymerizing from 1.75 to 3.5% by weight of N-methylolacrylamide and for the preparation of polymer dispersions having sufficient crosslinking properties and stabilities which make bonded nonwoven fabrics with acceptable dry and wet strengths accessible 1.25 to 8.25 wt .-% of acrylamide, based on the total amount of the monomers. Disadvantageously, polymers containing N-methylolacrylamide units can lead to a considerable introduction of formaldehyde into the

Application products lead, which is problematic for toxicological reasons. The formaldehyde can in this case come from the commercially available N-methylolacrylamide batches themselves. Thus, some 48% aqueous N-methylolacrylamide solutions contain 2% formaldehyde, as known, for example, from US 4449978. Furthermore, formaldehyde is liberated in the course of crosslinking of the N-methylol groups. Other sources of formaldehyde may be initiators or initiator systems used for the emulsion polymerization, such as this common sodium formaldehydesulfoxylate (SFS) or Formopon. Thus, US 3380851, US 3345318, DE 2512589 or DE2551556 describe the preparation of corresponding copolymers using formaldehyde sulfoxylates. However, the aqueous polymer dispersions prepared in this way contain several hundred to more than 1,000 ppm of free formaldehyde, and the nonwovens produced therewith contain over 100 ppm of free formaldehyde.

Numerous attempts have been made to reduce the content of free formaldehyde in corresponding aqueous polymer dispersions and in the nonwovens bonded thereto. Thus, the replacement of formaldehyde sulfoxylates by sulfite compounds, ascorbic acid or sulfinic acid derivatives is known from US Pat. No. 6,788,594. EP 0609849 also advises against the abandonment of formaldehyde sulfoxylates for the preparation of vinyl ester-acrylamide copolymers which contain N- (n-butoxymethyl) acrylamide or N-methylolacrylamide as the postcrosslinking monomer. US 5540987 or US 6787594 recommends the use of hydrophobic peroxide such as t-butyl hydroperoxide (tBHP) in combination with ascorbic acid or sulfinic acid derivatives, also known as Brueggolit® FF6. However, when using hydrophobic peroxides, it is difficult to control the particle sizes of vinyl ester copolymers, and very coarse and sedimentation-prone particle fractions are formed. Hitherto known processes for the preparation of vinyl ester-acrylic acid-amide copolymers even with the use of hydrophobic peroxides in combination with ascorbic acid or Brueggolit® FF6 as initiators not yet allow to provide aqueous polymer dispersions with levels of free formaldehyde of less than 25 ppm and also with to produce such nonwoven bonded fabrics having free formaldehyde contents of <10 ppm.

As nachvernetzende monomers are known from DE4432945 or

DE19631935 in addition to N-methylolacrylamide and N-alkoxymethylacrylamides known, such as N- (isobutoxymethyl) acrylamide (IBMA) or N- (n-butoxymethyl) acrylamide (NBMA). DE19631935 and DE4432945 describe emulsion polymerization processes in which the initially introduced non-postcrosslinking monomers are completely polymerized before the metered addition of the acrylamide derivatives and the remaining monomers is recorded. The same applies to a process described in EP0731207.

DE4240731 describes the preparation of copolymers using from 0.1 to 5.0% by weight of N-alkylolamides and N-alkoxyalkylamides, these postcrosslinking monomers being added only after at least 50% of the non-postcrosslinking comonomers have already been added were metered. Regarding the conversion of the initially charged or metered monomers at the time of metering of the postcrosslinking monomers, DE 4240731 shows only that the original was fully polymerized at the aforementioned time and the metered monomers were polymerized continuously during their metering. The latter results from the fact that the initiators were metered in from the beginning over the entire metering process at a constant rate, so that the monomer conversion during the metering course of the non-postcrosslinking comonomers increased and at the start of metering of the postcrosslinking monomers high values significantly above 50 wt. %, based on the monomers added to the reactor up to the time of dosing start of the postcrosslinking monomers. The processes of DE 4240731 lead to copolymers which, when used as binders, lead to nonwovens having insufficient nonwoven strengths. These statements are substantiated by the comparative example V10 below.

EP 1777241 describes by way of example copolymers of vinyl esters, N-methylolacrylamide and other monomers, which were prepared in the absence of protective colloids and in the presence of small amounts of emulsifiers by emulsion polymerization, wherein individual monomers were distributed in a certain manner on initial and dosage. However, the polymer dispersions thus obtained have a content of free formaldehyde of significantly more than 30 ppm and lead to bonded nonwovens with over 20 ppm of free formaldehyde. In EP0451554 the preparation of a binder for nonwoven fabrics is described by first the total amount of vinyl acetate is introduced and simultaneously with the beginning of the dosage the initiator to the start of the polymerization and N-methylol etheramide and other monomers were added.

DE 3727181 recommends the complete or partial replacement of N-methylolamides or N-methylol-etheramides by vinylalkoxysilanes in order to reduce the formaldehyde content. Disadvantageously, the polymers described there are not sufficiently stable in storage, so that their crosslinking action decreases rapidly. No. 2005239362 teaches the use of binders based on vinyl acetate, vinyl versatate and postcrosslinking monomers, such as N-methylolacrylamide, as well as pre-crosslinking, polyunsaturated monomers, such as triallyl cyanurate, for improving the wet and dry strength of nonwovens.

For the production of adhesives for wood, paper or packaging materials, EP2138548 recommends polymers of vinyl acetate, vinylsatates and (meth) acrylamide derivatives, which have been prepared by emulsion polymerization in the presence of fully saponified polyvinyl alcohols. Regarding the beginning of the metering of the monomers during the emulsion polymerization, EP2138548 teaches that this should take place only after polymerizing at least 50% of the monomers initially charged. To reduce the formaldehyde content, there have been numerous attempts in the past to replace acrylamide derivatives with a wide variety of alternative postcrosslinking monomers, as for example in US Pat. Nos. 6787591, EP 0237643, EP 0324382, US 4647611, US 4814226, US Pat. No. 3,456,998, US Pat. No. 5,278,222, US Pat 4808660, US 5235016, US 5252663, US 5021529 or US 2009/0036574. However, the copolymers described therein lead to bonded nonwovens, which can not satisfy their strength values by far. In addition, these alternative post-crosslinking monomers are not commercially available for industrial scale applications.

In order to avoid the formaldehyde problem discussed above, polymer dispersions have recently been described from which no formaldehyde can be released at all, as in the case of play styrene-acrylate copolymers containing unsaturated carboxylic acids or hydroxyethyl acrylates as comonomer functional units, analogous to the systems presented in US 5028655, EP 0326298 or US 5198492. Thus, the use of aqueous dispersions of styrene-butyl acrylate copolymers, which also contain units of, for example, acrylamide, (meth) acrylic acid and hydroxyethyl acrylate, as binders to nonwovens with sufficient strength values, as they are accepted in the market. An example of such an already commercially available aqueous polymer dispersion is Primal ™ NW-1845K. Disadvantageously, such styrene-acrylate dispersions give the nonwovens highly hydrophobic properties and, associated therewith, low wetting speeds as well as low water absorption capacities or long drop inink times. In many applications, however, such hydrophobic properties are undesirable and detrimental.

Although the strength values of bonded nonwoven fabrics achieved with the abovementioned functionalized styrene-acrylate polymer dispersions are also achieved and exceeded with the known N-methylolacrylamide-containing vinyl ester dispersions, the free formaldehyde content of these vinyl ester dispersions and the nonwoven fabrics bound thereto is increasingly critical. Although the released formaldehyde can be reduced by significantly reducing the proportions of formaldehyde-releasing postcrosslinking monomers, at the same time the required strength values for bonded nonwoven fabrics are no longer achieved in the previously known cases, as achieved, for example, with the abovementioned functionalized styrene-acrylate polymer dispersions become.

The strength of bonded nonwoven fabrics is known to be dependent on a variety of factors, such as the type of fiber material, the method of forming the nonwoven fabric, the properties of the polymer binder, the amount of binder application, the method of binder application on the nonwoven fabric and the drying conditions of with the aqueous polymer dispersion applied nonwoven fabric, such as drying temperature, drying time and optionally the flow conditions. Accordingly, a comparison of numerical values for strength values of bonded nonwoven fabrics is only reasonably possible if in each case identical conditions under variation of an influencing variable, for example the properties of the polymer dispersion, are used.

Essentially the following properties are relevant for the quality of bonded nonwovens: dry strength, wet strength (strength of the water-moist nonwoven), solvent strengths (strengths of the solvent-moist nonwoven), hydrophilicity, such as, for example, Drop-in time of a defined drop of water, absorption rate and absorption capacity.

Against this background, the object was to produce aqueous dispersions of vinyl ester-ethylene-acrylic acid amide copolymers by means of emulsion polymerization, which

- Have a low free formaldehyde content of if possible ^ 30 ppm, preferably of ^ 25 ppm; and also

- When used as a binder to bonded nonwovens with a low free formaldehyde content of possibly ^ 10 ppm, preferably from ^ 7.5 ppm and more preferably from ^ 5 ppm, wherein the order of the binder ^ 30 wt .-% or ^ 20 % By weight and usually at least 5% by weight and the data in% by weight, based on the dry weight of the binder, relate to the nonwoven weight and the drying conditions are for example 3 minutes at, for example, 150 ° C .;

- make bonded nonwoven fabrics with sufficient nonwoven strengths accessible, ie nonwoven strengths comparable to those obtainable, for example, with known styrene-acrylate binders, in particular with the commercial product Primal ™ NW-1845K, the disadvantages of such known binders with respect to insufficient hydrophilicity should be overcome, so in addition

- ensure sufficient hydrophilicity of bonded nonwovens, these being determined as drop inink time, "TEZ" or water uptake capacity, "capacity" as described in Section 2.4 Determination of Hydrophilicity of Bonded Nonwovens and values of "TEZ" of in particular at most 40 of at most 30, and more preferably of at most 25 seconds, or

Values for the "capacity" of preferably at least 0.5, more preferably at least 0.7 and even more preferably at least 0.9 g are to be achieved; Particle size distributions with a modal value "x-mode" of the volume distribution density function of the particle diameter (most common particle size of the volume distribution density function) with values in the range of in particular 140 to 600 nm, preferably 150 to 500 nm and more preferably 150 to 400 nm and simultaneously provide a volume fraction of particles in particular greater than 900 nm, dF3 (^ 900 nm), in particular of ^ 30% by volume, preferably of ^ 25% by volume;

a small coarse particulate fraction having particle sizes of greater than 40 μιτι, known as sieve residue or "grit ^ 40 μιτι", in particular special not more than 200 ppm, based on the weight of the dispersion;

- Have a glass transition temperature Tg of the copolymer of preferably - 15 ° C to +10 ° C and thus ensure the desired adjustable hardness or flexibility of a bonded nonwoven fabric

It was also an object to find such problem solutions which, if possible, use only commercially available starting materials which are available for industrial implementation at no extra cost. The methods should therefore also be suitable for the large-scale industrial scale.

The invention relates to processes for the preparation of vinyl ter-ethylene-acrylamide copolymers in the form of aqueous dispersions by free-radically initiated emulsion polymerization of

(a) one or more ethylenically unsaturated vinyl esters of carboxylic acids having 2 to 18 carbon atoms,

(b) 5 to 30% by weight of ethylene,

(c) comprising ethylenically unsaturated amides from the group

(cl) 0.16 to 4.0% by weight of acrylamide,

(c2) 0.23 to 0.65% by weight of one or more N-alkylol

(meth) acrylamides,

(c3) 0 to 0.67% by weight of one or more N- (alkoxymethyl) acrylamides or N- (alkoxymethyl) methacrylamides,

(d) 0 to 1.5% by weight of one or more ethylenically unsaturated alkoxysilanes, and optionally (e) one or more other ethylenically unsaturated monomers other than the monomers (a) to (d),

wherein the total amounts of the monomers (a) to (e) added up to 100 wt .-%, characterized in that a total of 0.23 to 0.90 wt .-% of the monomers (c2) and (c3) , based on the total weight of the monomers (a) to (e) are used, and

one or more monomers (a) and monomer (b) in whole or in part, and optionally monomer (c1) are initially introduced in water and

then the free-radical emulsion polymerization is initiated and

remaining amounts of the monomers (a), (b), (c), optionally (d) and / or optionally (e) are metered in with the proviso that at least 50 wt .-% of the total monomers used (c) from a Are added at the time at which the conversion of the monomers (a) to (e) initially charged and / or metered in is from 8 to 50% by weight (dosing criterion),

wherein the emulsion polymerization is carried out in the absence of protective colloids.

Another object of the invention are the products obtainable by the aforementioned method.

The invention also relates to uses of the aforementioned process products for bonding nonwoven fabrics, as adhesives, as an additive for adhesives or as an additive for coating agents.

The point in time at which at least 50% by weight of the total monomers (c) are metered in according to the metering criterion according to the invention is also referred to below as the metering time t-DB in accordance with the invention. Preferably, the dosing time t-DB which is essential to the invention is the time at which at least 50% by weight of the total monomers (c2) and (c3) are metered in according to the inventive dosing criterion. The term "conversion" of the monomers is familiar to the person skilled in the art and is defined as the quotient of the weight of the polymers formed up to the respective time point, that is to say the polymerized monomer proportions, and the weight of the total monomers introduced into the reactor up to this point in time % and is also referred to below as current turnover (sales UiA), also known under the term "instantaneous conversion". In the following, unless otherwise stated, the term sales or current sales or sales UiA always refers to the aforementioned definition of sales.

Examples of vinyl esters (a) are vinyl acetate, vinyl butyrate, vinyl 2-ethylhexanoate, vinyl laurate, 1-methylvinyl acetate, vinyl pivalate or vinyl versatate, in particular vinyl esters of branched monocarboxylic acids having 9 to 11 carbon atoms, for example those disclosed in US Pat Trade names VeoVa® 10 VeoVa® 9 known compounds. Particularly preferred are vinyl acetate, vinyl versatate and vinyl laurate. Particularly preferred vinyl esters (a) used are 80 to 100% by weight of vinyl acetate, based on the total weight of the total vinyl ester (a) used.

The acrylamide (cl) is also known under the name 2-propenamide.

As monomers (c2), N-methylolmethacrylamide and in particular N-methylolacrylamide are preferred.

Preference is given to the use of monomer (c2), in particular N-methylol acrylamide, in the form of aqueous mixtures with the monomer (c1), where the monomers (c1) and (c2) are present in a molar ratio of 2: 1 to 1: 2, in particular 1: 1. Such aqueous mixtures have a content of monomer (c1) and monomers (c2) of preferably from 30 to 60% by weight, more preferably from 40 to 55% by weight, and most preferably about 48% by weight, based on the total weight of the aqueous mixtures. Such aqueous mixtures with a molar ratio of about 1: 1 to monomers (c1) and (c2) are also known under the name "NMA-LF" or "MAMD". As monomers (c3) are N- (isobutoxymethyl) acrylamide (IBMA), N- (isobutoxymethyl) methacrylamide (IBMMA), N- (n-butoxymethyl) acrylamide (NBMA) or N- (n-butoxymethyl) methacrylamide (NBMMA ) prefers. Particularly preferred are N- (isobutoxymethyl) acrylamide (IBMA) or N- (n-butoxymethyl) acrylamide (NBMA).

The monomers (d) are preferably vinyltrialkoxy- or alkylvinyldialkoxysilanes with branched or unbranched alkyl or alkoxy radicals having 1 to 4 C atoms. As the alkyl radical, the methyl radical is preferred. Preferred alkoxy radicals are methoxy, ethoxy, methoxyethylene, ethoxyethylene, methoxypropylene glycol ether, ethoxypropylene glycol ether radicals. Preferred examples are vinyltrimethoxysilane or vinyltriethoxysilane. The ethylenically unsaturated monomers (e) are preferably selected from the group (el) comprising acrylic acid esters and methacrylic acid esters of alcohols having 1 to 10 carbon atoms, such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n Butyl methacrylate, 2-ethylhexyl acrylate; ethylenically unsaturated dicarboxylic esters such as diisopropyl fumarate; Hydroxyalkyl (meth) acrylates such as hydroxypropyl acrylate o- hydroxyethyl acrylate and polyethylenically unsaturated monomers such as divinyl adipate, diallyl maleate, allyl methacrylate, butanediol diacrylate or triallyl cyanurate. Particularly preferred monomers (el) are butyl acrylate, hydroxyethyl acrylate or ethylhexyl acrylate.

Further preferred ethylenically unsaturated monomers (e) can be selected from the group (e2) comprising ethylenically unsaturated carboxylic acids having 1 to 10 C atoms, such as (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid or fumaric acid; and ethylenically unsaturated sulfonic acids such as 2-acrylamido-2-methylpropanesulfonic acid or vinylsulfonic acid. Particularly preferred monomers (e2) are vinyl sulfonate or its alkali metal salts, acrylic acid or 2-acrylamido-2-methylpropanesulfonic acid (AMPS).

The total amounts of the monomers (c2) and (c3), based on the total weight of the monomers (a) to (e), are from 0.23 to 0.90% by weight, preferably 0.28 to 0.85 wt .-% and particularly preferably 0.35 to 0.85 wt .-%.

Comonomer mixtures suitable for emulsion polymerization include, for example

Monomers (a), in particular vinyl acetate;

5 to 30% by weight of monomer (b), i. ethylene;

1.03 to 4.96% by weight, in particular 1.08 to 4.52% by weight of monomers (c), where the monomers c)

From 0.80 to 3.70 weight percent monomer (c1), i. Acrylamide, and

0.23 to 0.59% by weight of monomer (c2), preferably N-methylolacrylamide, 0 to 0.67% by weight, in particular 0.40 to 0.67% by weight of monomer (c3), preferably N - (isobutoxymethyl) acrylamide (IBMA) or N- (n-butoxymethyl) acrylamide (NBMA);

0 to 1.5 wt .-%, in particular 0.5 to 1.5 wt .-% of monomers (d), in particular vinyltriethoxysilane.

For the emulsion polymerization preferred comonomer mixtures

From 66 to 89% by weight of monomers (a), in particular vinyl acetate;

10 to 30% by weight of monomer (b), i. ethylene;

1.09 to 3.99% by weight of monomers (c), where the monomers c)

From 0.80 to 3.70 weight percent monomer (c1), i. Acrylamide, and

0.29 to 0.59% by weight of monomer (c2), preferably N-methylolacrylamide.

In an alternative preferred process, comonomer mixtures are used comprising

64.4 to 88.4% by weight of monomers (a), in particular vinyl acetate;

10 to 30% by weight of monomer (b), i. ethylene;

1.08 to 4.09% by weight of monomers (c), the monomers c)

0.80 to 3.50 weight percent monomer (c1), i. Acrylamide, and

From 0.28 to 0.59 weight percent of monomer (c2), preferably N-methylolacrylamide;

0, 5 to 1.5 wt .-% of monomers (d), in particular vinyltriethoxysilane. The aqueous dispersions of vinyl ester-ethylene-acrylic acid amide copolymers obtainable therewith are preferably adjusted to a pH of 6. In a further alternative preferred method comonomer mixtures are used comprising

From 63 to 93% by weight of monomers (a), in particular vinyl acetate;

5.0 to 30.0 monomer (b), i. ethylene;

1.43 to 4.52% by weight of monomers (c), where the monomers c)

0.80 to 3.50 wt% (monomer (c1), i.e., acrylamide,

0.23 to 0.35 wt .-% of monomer (c2), preferably N-methylolacrylamide and

From 0.40 to 0.67 weight percent of monomer (c3), preferably N- (isobutoxymethyl) acrylamide (IBMA) or N- (n-butoxymethyl) acrylamide (NBMA); and

0 to 1.5 wt .-%, preferably 0.5 to 1.5 wt .-% of monomers (d), in particular vinyltriethoxysilane.

The aqueous dispersions of vinyl ester-ethylene-acrylic acid amide copolymers obtainable therewith are preferably adjusted to a pH of 6.

The monomers (c2) are preferably used in the form of "NMA-LF". The proportions of "NMA-LF" are preferably from 0.5 to 1.0% by weight, based on the total weight of the monomers (a) to ( e).

In a particularly preferred embodiment, the comonomer mixture still contain 0.6 to 15 wt .-%, more preferably 0.6 to 7 wt .-% and most preferably 1.0 to 5.5 wt .-% of monomers (e ), based on the total weight of the comonomer mixture (a) to (e). Particularly preferred are 0.3 to 10% by weight, more preferably 0.3 to 3.5% by weight, most preferably 0.5 to 2.7% by weight of the monomers (el). , in particular butyl acrylate and hydroxyethyl acrylate; such as

preferably from 0.3 to 3.5% by weight and most preferably from 0.4 to 2% by weight of the monomers (e2), in particular acrylic acid and vinylsulfonate.

The percentages relating to the comonomer mixtures are in each case based on the total weight of the particular comonomer mixture from the monomers (a), (b), (c), and optionally (d) and optionally (e) and each supplement to 100% by weight.

The process according to the invention for the preparation of the copolymers by means of free-radical emulsion polymerization can be carried out in the customary polymerization reactors in the copolymerization of gaseous monomers, such as ethylene, in customary pressure reactors.

In the process according to the invention, at least part of the total vinyl ester (a) used and at least part of the total ethylene (b) used are initially charged. The template will generally contain part of the total water used.

Preferably, 5 to 50 wt .-%, more preferably 5 to 40 wt .-% and particularly preferably 5 to 30 wt .-% of the total used vinyl ester (a), in particular vinyl acetate, submitted.

Preferably, from 50 to 100 wt .-%, more preferably 75 wt .-% to 100 wt .-% and most preferably 100 wt .-% of the total used ethylene (b) are introduced.

Preferably, from 15 to 50% by weight of the total amount of acrylamide (cl) used is initially charged. It is also preferable to provide at least 0.8% by weight, particularly preferably 0.8 to 1.5% by weight, of acrylamide (c1), based on the total weight of monomers (a) to (e). Of course it is also possible not to submit acrylamide (cl).

Preferably, no monomer (c2) and / or no monomer (c3) and / or no monomer (d) is presented.

The monomers (e) can be completely or partially charged or metered. For example, ethylenically unsaturated sulfonic acids, in particular vinyl sulfonate, and / or (meth) acrylic acid esters, in particular butyl acrylate, are preferably initially charged completely. For example, hydroxyalkyl (meth) acrylates, in particular hydroxyethyl acrylate, and / or ethylenically unsaturated carboxylic acids, in particular acrylic acid, are preferably completely metered.

Preferably, the template is free of emulsifiers.

The original is heated, for example with stirring to temperatures of 30 ° C to 80 ° C, preferably 40 ° C to 70 ° C and more preferably from 45 ° C to 65 ° C. The pressure in the reactor, in which the is located, is preferably 10 bar to 100 bar. The pressure is known to depend on the reactor volume, its degree of filling, ie in particular on the amounts of water, monomers, in particular of the monomers (a) and (b), and on the temperature. The ethylene pressure set at the start of the emulsion polymerization can be kept constant over the entire reaction time, preferably over the entire metering time of the monomers (a), for example by metering in ethylene. However, it is also possible not to supplement the initially introduced into the reactor amount of ethylene or to vary the ethylene pressure during the polymerization within said limits.

The emulsion polymerization is carried out with initiation by means of conventional free-radical initiators, which are preferably used in amounts of from 0.05 to 3.0% by weight. Percent, based on the total weight of monomers (a) to (e). The free-radical formers can be activated either directly by increasing the temperature or preferably, even at low temperatures, by redox reaction. As a radical generator, the usual oxidation and reducing agents can be used. It is advantageous to add a common activator such as iron ammonium sulfate to the reactor before starting the emulsion polymerization. The addition of oxidizing and reducing agents preferably takes place by continuous metering of aqueous solutions of oxidizing agent (initiator feed 1) and reducing agent (initiator feed 2). Initiator dosing 1 and initiator dosing 2 are generally spatially separated, but metered in parallel. As a reducing agent, ascorbic acid, sodium isascorbate or sulfinic acid derivatives, also known under the trade name Brueggolit® FF6, are preferred. As the oxidizing agent, persulfate compounds are preferable, and ammonium persulfate is particularly preferable; However, it may also be advantageous to use alkali persulfate, in particular sodium persulfate, especially if ammonium ions are to be completely excluded. This can be advantageous if discoloration problems occur and should be minimized; then the combined use of sodium persulfate or potassium persulfate with Brüggolit® FF6 is recommended. The free-radical formers used are preferably not formaldehyde sulfoxylates or formopon. As a consequence of the initiation of the emulsion polymerization after starting the initiator doses 1 and 2, it is known that due to the exothermic nature of the polymerization reaction, a noticeable heating of the polymerization batch occurs. The point in time at which the heating of the polymerization batch is recognizable is referred to below as time t-RB. The heating of the polymerization batch is considered, for example, as recognizable when the polymerization mixture is heated to 0.1 ° C to 1 ° C. The increase in temperature depends, as is known, on the respective reactor volume, its degree of filling and the respective cooling conditions. The heating of the polymerization batch as a result of the exothermic nature of the incipient polymerization reaction is also evident from the fact that the temperature control switches over to cooling. It can also be seen from the fact that the pressure in the reactor, for example, increased by 0.1 to 0.5 bar. At this point in time t-RB, the conversion of the monomers initially charged or, if appropriate, previously metered in is known to be very low. The actual conversion of the monomers at any given time, based on the total weight of the monomers (a) to (e) used up to this point in time, is also referred to as the conversion UiA. In general, the conversion of the monomers UiA at the time t-RB 0 to ^ 2 wt .-%, preferably 1 to 2 wt .-%, each based on the total weight of the monomers used at the time t-RB (a) to (e ).

The remaining monomers, i. the monomers (a) to (e) not used in the initial charge are metered in after initiation of the emulsion polymerization, wherein the metering criterion according to the invention must be observed. Accordingly, starting from the dosing time t-DB essential to the invention, the following monomers are preferably metered in independently of one another in the following amounts:

in general, from 50 to 100% by weight, preferably from 50 to 85% by weight and more preferably from 55 to 75% by weight, of the total monomer (c1) used is metered in;

preferably 90 to 100 wt .-%, particularly preferably 100% wt .-% of the total monomers used (c2) are added;

preferably 90 to 100 wt .-%, particularly preferably 100 wt .-% of the total monomers used (c3) are added; preferably 95 to 100 wt .-%, particularly preferably 100 wt .-% of the total monomers used (d) is added.

These novel metered additions of the monomers (c1), (c2), optionally (c3) and / or optionally (d) may be carried out spatially separated or preferably spatially in common, one after the other or preferably simultaneously or in parallel. In this case, the dosing criterion according to the invention is to be observed.

Any remaining monomers (a), (b) and optionally (e) not used in the initial charge are also metered in.

By way of clarification, it should be noted that fractions of the monomers (a) to (e) can also be added after initiation of the emulsion polymerization but before the dosing time essential to the invention, t-DB, with the premise that the dosing criterion according to the invention is adhered to.

However, it is preferred to meter in all remaining amounts of the monomers (a) to (e) not present in the initial charge, starting with or, if appropriate, after the metering time instant t-DB. It is particularly preferred to meter all remaining monomers (c) from the dosing time point t-DB essential to the invention.

For the dosing criterion according to the invention, the actual conversion of the monomers (a) to (e) initially introduced or metered in at this time into the metering time instant t-DB is 8 to 50% by weight, preferably 9 to 45% by weight. , particularly preferably 10 to 40 wt .-% and most preferably 10 to 35 wt .-% is. The data in% by weight relate here to the weight of the monomers (a) to (e) introduced or metered in up to the dosing instant in time t-DB essential to the invention.

At dosing time t-DB essential to the invention, the current conversion of the monomers initially charged and / or metered in, consisting of vinyl ester (a), amides (c), optionally alkoxysilanes (d) and optionally monomers (e), preferably 13 to 50 Wt .-%, particularly preferably 18 to 45 wt .-% and most preferably 20 to 40 wt .-%, based on the sum of the inventions Substantially dosing time t-DB submitted and / or dosed monomer amounts (a) to (e).

At the dosing time t-DB essential to the invention, the actual conversion of the vinyl acetate initially charged and / or metered in is preferably from 13 to 50% by weight, more preferably from 18 to 45% by weight and most preferably from 20 to 40% by weight. , based on the up to the invention essential dosing time t-DB submitted and / or dosed vinyl acetate.

At the dosing time t-DB essential to the invention, the actual conversion of the ethylene (b) initially charged and optionally metered in is preferably 6 and 35% by weight, more preferably 7 to 30% by weight and most preferably 8 to 30% by weight. -%, Based on the weight of up to the invention essential dosing time t-DB submitted and optionally dosed ethylene (b).

The dispersants used may be the ionic or nonionic emulsifiers customarily used in the emulsion polymerization. Preferably, up to 6% by weight, more preferably up to 3.5% by weight, more preferably up to 2.5% by weight and especially from 0.0 to 1% by weight of one or more emulsifiers used, based on the total weight of the monomers used in total. It is also particularly preferred not to use an emulsifier. Advantageously, the method according to the invention therefore also permits the at least substantial omission of emulsifiers.

The emulsifiers can be distributed on template and dosage. Preferably, the template contains no emulsifier. The emulsion polymerization is preferably initiated in the absence of emulsifiers. Any emulsifiers are therefore preferably added after the metering time t-DB essential to the invention.

Suitable emulsifiers are, for example, anionic surfactants, such as alkyl sulfates having a chain length of 8 to 18 carbon atoms, alkyl and alkylaryl ether sulfates having 8 to 18 carbon atoms in the hydrophobic radical and up to 40 ethylene or propylene oxide units, alkyl or alkyl Rylsulfonate with 8 to 18 carbon atoms, Ölsäuresulfonate, esters and half esters of sulfosuccinic acid with monohydric alcohols or alkylphenols. Suitable nonionic surfactants are, for example, alkyl polyglycol ethers or alkylaryl polyglycol ethers having 8 to 40 ethylene oxide units. The use of alkyl ether sulfates or dodecylbenzenesulfonates is preferred.

The emulsion polymerization according to the invention is carried out in the absence of protective colloids. The term protective colloids in the context of emulsion polymerizations is well known to the person skilled in the art and generally comprises water-soluble polymers, in particular polyvinyl alcohols, preferably vinyl alcohol / vinyl acetate copolymers containing from 80 to 100 mol% of vinyl alcohol units; Polyvinylpyrrolidone or hydroxyethylcelluloses. Dispensing with protective colloids serves the purpose of producing emulsion polymers having the desired particle size distributions. In addition, protective colloids can increase product viscosity and reduce the water resistance of bonded nonwoven fabrics, and can also be a source of thermal yellowing of bonded nonwoven fabrics.

In the following, preferred special embodiments of the method according to the invention will be described. At the time of the dosing time t-DB essential to the invention, it is generally begun to add to the reactor the remaining amounts, in particular of unprovided proportions of monomers (a) to (e), uncoupled amounts of emulsifiers, uncontrolled proportions of water, while the initiator doses 1 and 2 are further added to the reactor with unchanged metering rates or according to a suitable metering rate regime, so that the polymerization reaction proceeds continuously, the monomer conversion values advantageously increasing steadily.

The addition of the remaining proportions of monomers (a) to (e) and other constituents of the formulation beginning with dosing time t-DB essential to the invention is advantageously, but not necessarily, effected by continuous metering of the components alone or in mixtures. The continuous dosing of the components can in

Dosing with constant rates, continuously increasing or decreasing rates or gradually changed rates. Vinyl esters (a) are added, for example, as metering 3 to the reactor.

The monomers (c1) and optionally (c2) are added, for example, in an aqueous dosage 4, which is preferred.

The optional monomers (c3) and (d) are preferably added to the dosage 3. Monomers (c3) can also be added within the dosage 4, whereas it is preferred to dose monomers (d) within the dosage 3, or part of the dosage 3.

The optional monomers (e) are added, for example, to dosages 3 or 4. It may be advantageous to introduce water-soluble monomers (e) into the dosage 4.

Emulsifier is preferably added to the dosage 4. As a rule, dosing 3, containing vinyl ester (a) and optionally monomers (c3) and / or (d) and optionally some of the monomers (e), as well as a metering, are added almost instantaneously or slightly in time to the dosing time t-DB essential to the invention 4, containing monomers (c1) and (c2), but optionally preferably a portion of any monomers (e) and residual emulsifier, started and dosed at a constant rate over a period of 1 to 6 hours, preferably in 2 to 4 hours ,

Unincorporated monomer (b) is added to the reaction system within this time period, preferably ending before dosing 3 is terminated, for example at substantially constant pressure or at a constant flow rate as dosing 5.

In addition to the dosages 3, 4 and 5, the initiator doses 1 and 2 are added so that at the end of doses 3 and 4 at least a conversion of all previously used monomers from 60 to 95 wt .-%, preferably from 70 to 90 % By weight is reached.

Dosages 3 and 4 are preferably stopped simultaneously.

After the end of doses 3 and 4, the initiator doses 1 and 2 are generally further added until the conversion of the monomers (a) to (e) used is preferably> 95% by weight, preferably> 98% by weight. has reached. It can be beneficial for that be to increase the dosing rates of the initiator doses 1 and 2 and / or their concentrations.

To reduce any unreacted monomer levels after initiator doses 1 and 2 have ended, it may be expedient to further reduce the residual monomer content, for example by postpolymerization using customary redox components such as t-butyl hydroperoxide as the oxidant. Reduction of residual monomer levels while minimizing levels of volatile organic compounds is possible by conventional stripping with steam. As advantageous, the addition of 5 to 20 grams, preferably 8 to 12 grams of a 10% aqueous hydrogen peroxide solution per kilogram of a 50% dispersion has been found. Such addition prior to conventional steam stripping minimizes significant tendencies of possible product yellowing, particularly when ascorbic acid is used as the reducing agent.

The preferred pH range for the emulsion polymerization reaction is 2 to 6. In the absence of monomers (d) and for use of monomers (c1) of greater than 2.5% by weight, in particular more than 3% by weight of monomers (cl), based on the total weight of all monomers, however, pH values during the emulsion polymerization reaction of <4.5 and in particular of <3 are preferred. The pH during the polymerization is controlled by suitably adjusting the pH values of the reactor charge and aqueous dosages, such as, in particular, Dosage 4. The pH of the dispersion obtained is usually adjusted to values between 4 and 5. However, if monomers (d) are used, the pH of the resulting dispersion is adjusted to preferably 6, more preferably 6 to 7, otherwise the positive crosslinking effect caused by the monomers (d) will decrease within a few weeks. The pH adjustment or control of the pH can with acids such as sulfuric acid, formic acid, acetic acid; or with bases such as ammonia, caustic soda, potassium hydroxide, amines; or by using buffer substances, such as alkali metal acetate, alkali metal carbonate, alkali metal diphosphates.

The glass transition temperature Tg of the copolymers according to the invention is generally -20 ° C to + 20 ° C, preferably -15 ° C to + 10 ° C. The choice of the monomers (a) to (e) for achieving such glass transition temperatures Tg is familiar to the person skilled in the art.

The dispersions prepared by the process according to the invention generally have a solids content of from 35 to 65% by weight, preferably from 40 to 60% by weight and in particular from 45 to 55% by weight.

The Brookfield viscosity of the dispersions is preferably 50 to 2000 raPas, particularly preferably 100 to 1500 mPas (determined using a Brookfield viscometer at 23 ° C. at 20 rpm at a solids content of the dispersions of 49 to 51% by weight).

The polymers have a volume fraction of particles with dF3 900 nm) of preferably ^ 30 vol .-%, particularly preferably ^ 25 vol. % and at the same time particle size distributions with a modal value of the volume density distribution function x-mode of preferably 140 to 600 nm, more preferably 150 to 500 nm and most preferably 150 and 400 nm (determination as described below under point 1.4).

The coarse particulate fraction of the polymers having particle sizes greater than 40 μm, also known as sieve residue or "grit" is preferably 200 200 ppm, based on the weight of the dispersion (determination as described below under point 1.5).

The free formaldehyde content of the dispersions having a solids content of 45 to 55% is preferably 30 30 ppm and more preferably ≦ 25 ppm (determination as described below under 1.6). The free formaldehyde content for bonded nonwoven fabrics is preferably 10 10 ppm, more preferably ≦ 7.5 ppm, and most preferably ≦ 5 ppm (determined as described below under 2.3). Surprisingly, it has been found that in particular by the inventive amounts of the N-alkylol (meth) acrylamides (c2) and acrylamide (cl) in combination with the metering criterion according to the invention vinyl acetate-ethylene-acrylic acid amide copolymers accessible be, for example, when used as a binder to nonwoven fabric fen with the desired strength and at the same time low levels of free formaldehyde. Thus, and with the other features and in particular with the preferred embodiments of the prior invention, the objects of the invention could be achieved.

If the amounts of the monomers (c1) or (c2) according to the invention are undershot, the minimum requirements for nonwoven strengths to be achieved can no longer be met. When more than the inventive amounts of the monomers (c2) and optionally (c3) are used, the requirements with respect to the limits to be observed for the free formaldehyde content of the dispersions of in particular ^ 30 ppm, preferably ^ 25 ppm and for the free formal dehydgehalt bonded nonwovens sufficient strength of in particular ^ 10 ppm, preferably <7.5 ppm and more preferably of ^ 5 ppm no longer complied with. If the amount of acrylamide (cl) according to the invention is exceeded, this leads to aqueous dispersions whose viscosity increases sharply during storage, for example over a period of several weeks to months; then a sufficient viscosity stability during storage is no longer present. The well-balanced amounts of the individual monomers according to the invention thus contribute significantly to the solution of the invention.

It was particularly surprising here that the special design of the dosing criterion according to the invention in the preparation of the copolymers according to the invention had a decisive influence on the strengths of the nonwoven fabrics bound with the resulting aqueous dispersions.

If less than the inventive amounts of the monomers (c) or these monomers (c) at a lower actual conversion of the monomers UiA (a) to (e) are metered as required by the metering criterion according to the invention, the particle size distributions and / or Viscosities of the copolymers thus prepared are no longer guaranteed, or it results in a pronounced susceptibility of the copolymers to form coarse par- ticular components (residue on sieving), so that such a procedure is not suitable for a production process. For the same reasons, any monomers (d) used are preferably added in the amounts according to the invention and preferably in the manner according to the invention according to the dosing criterion according to the invention.

If, on the other hand, the monomers (c) are metered in at a higher actual conversion UiA of the monomers (a) to (e) than required in the metering criterion according to the invention, this has a detrimental effect on the achievable nonwoven strengths when the copolymers are used as binders for nonwoven production. Therefore, any monomers (d) used are preferably added in the manner according to the invention according to the dosing criterion according to the invention.

Overall, it has therefore proved to be essential to use the amounts according to the invention of the individual monomers and at the same time to comply with the metering criterion according to the invention, in order finally to obtain nonwovens having the desired performance properties.

In summary, the vinyl ester-ethylene-acrylic acid amide copolymers prepared according to the invention surprisingly impart the desired strengths, in particular the desired wet and solvent strengths, to the level of commercially available styrene / acrylate dispersions, without the disadvantages of the latter with respect to insufficient hydrophilicity equipped nonwoven fabrics and preferably have free formaldehyde levels for the vinyl ester-ethylene-acrylic acid amide copolymer dispersions of ^ 30 ppm and for the finished nonwoven fabrics of ^ 10 ppm, especially of ^ 5 ppm.

The vinyl ester-ethylene-acrylamide copolymers prepared by the process according to the invention are therefore particularly suitable for the production of "ultra-low-formaldehyde" nonwovens The vinyl ester-ethylene-acrylamide copolymers according to the invention can also be used in the production or surface refinement of papers for bonding cellulosic materials Ria, such as paper and paperboard, in formulations for aqueous paints, for impregnation and coating of textile fabrics, for example in the carpet backing, are used. The following examples serve to illustrate the invention in detail and should not be construed as limiting the invention in any way.

Examples

1. Test Methods for Characteristic Dispersion Characteristics 1.1 Solid Content / Drying Residue (FG)

To determine the solids content, in% by weight, based on dispersion, about 0.3 g of polymer dispersion was weighed out and dried as a thin film on an aluminum foil for 30 minutes at 150 ° C. in a circulating air drying cabinet. The drying residue was, after cooling in a desiccator over silica gel, weighed back and the solids content in% by weight, based on dispersion, from residue and weighed. To determine the solids content of process samples taken from the reactor during the polymerization, a rapid method was used: Approximately 0.3 g of the process sample was weighed and dried as a thin film on aluminum foil on a hot plate with simultaneous heating from above over a heat radiator for 1 minute - net. The results thus obtained for solids values agree very well with the corresponding results of the former method.

1.2 Turnover calculation from the solids content of process samples

The respective conversion of the monomers at the respective time ti during the emulsion polymerization reaction was calculated from the solids content FGi of a representative process sample taken from the reactor at time ti. The solids content FGi of each representative process sample was determined by the rapid method described in Section 1.1.

It was assumed that a representative process sample taken from the reactor at time ti contains the following components:

no ethylene, i. Ethylene escapes completely as a result of sampling;

representative proportions of other unreacted monomers, i. representative proportions of all unreacted monomers other than ethylene; except for ethylene, therefore, no monomers escape as a result of sampling;

Representative proportions of formed polymers, i. polymerized monomer portions;

- Representative proportions of excipients or any derived products of excipients; Auxiliary substances are all substances used in the examples or comparative examples except monomers and water;

- Representative proportions of water.

Furthermore, it was ensured that no chemical conversion of the monomers took place in the representative process samples taken.

A process sample taken from the reactor at time ti had the same composition as the reactor contents at time ti, with the only difference that the respective process sample does not contain ethylene, and thus is a representative process sample and thus contains representative proportions, for example, of unreacted monomers , except ethylene, as well as polymerized monomer proportions.

The term feedstock combines monomers, auxiliaries and water. For sales calculation, the following parameters are introduced:

- ti stands for any time during the emulsion polymerization, for example, for the invention dsierzeitpunkt t-DB; t "stands for any time at which all feedstocks have been added to the reactor.

Mon stands for all monomers; the total weight of monomers Mon is referred to as MMon; MMoniti) is the total weight of all monomers Mon, which were initially introduced into the reactor and / or metered in at time ti.

- Moni is the sum of all monomers except ethylene; the total weight of monomers Moni is called MMonl; MMonl (ti) is the total weight of all monomers Moni, which were initially introduced into the reactor and / or added up to the time ti. Monomers Moni are thus all monomers (a) and (c) to (e) subsumed.

Mon2 is ethylene; the total weight of monomers Mon2 is called MMonl; MMon2 (ti) is the total weight of all ethylene monomers which have been introduced and / or added to the reactor up to time ti.

- W stands for water; the total weight of water W is called MW; MW {ti) is the total weight of water that was introduced into the reactor and / or metered in until the time ti.

- H stands for auxiliaries; the total weight of the excipients H is called MH; MH {ti) is the total weight of all auxiliaries, which were initially introduced into the reactor and / or added up to time ti.

- UiMonl stands for the instantaneous conversion of the monomers Moni and is the weight ratio of the total weight of monomers Moni polymerized up to the time ti and the total weight of all monomers MMon1 (introduced and / or added to the reactor up to time ti) ti). UiMon2 represents the instantaneous conversion of the ethylene Mon2 and is the weight ratio of the total weight of the monomer Mon2 polymerized up to the time ti and the total weight of the ethylene MMon2 introduced and / or metered into the reactor up to the time ti ti).

- UiA stands for the instantaneous vonversion of all monomers Mon and is the weight ratio of the total weight of monomers Mon polymerized up to time ti, that is the total weight of the mixed monomers formed up to time ti, and the total weight of the monomers up to Time ti in the Reakto] and / or metered monomers MMon (ti).

- UiO stands for the total conversion of all monomers Mon and is the weight ratio of the total weight of monomers Mon polymerized up to time ti, ie the total weight of the copolymers formed up to this point in time, and the total weight of at a time t "in total monomers introduced and / or added to the reactor MMon (t _^ ).

Under the abovementioned boundary conditions, the stated conversion values in% by weight can be calculated to a very good approximation from the formulas (I) to (IV) derivable from mass balances. The results from the formulas (I) to (IV) can inevitably only approximate reality, since in this case also experimentally obtained data and thus random errors are incorporated, as is known to the person skilled in the art

(To?] ^MM ° ⁿ ^ ^{+ MH} ( ^ti ) ^{+ MW} ( ^ti )) ^~ MH {ti)

UiMonl = 100 i),

MmOn (ti)

(UiMonl) MMon \ (ti) + (UiMon2) MMonl iti)

MmOn (t _x)

The amounts of feedstocks at time ti in the reactor are easily determined from the amounts of the amounts charged in the reactor and the amounts added to the reactor until time ti.

For the process according to the invention, the monomer conversion values at the dosing time ti = t-DB crucial to the invention are decisive. 1.3 Viscosity (Bf20)

The viscosity of the dispersion was after tempering to 23 ° C with a Brookfield viscometer according to equipment specification, using spindle 2 or 3, depending on the viscosity range, at 20 rpm, measured. The viscosity is given in mPas.

1.4 Particle size values (x mode; dF3 (^ 900 nm))

To determine a particle size distribution using the Beckmann Coulter® LS 13320 measuring device according to the device specification, using the optical constants for polyvinyl acetate, the dispersion was diluted sufficiently with water. From the plot of the volume distribution density function of the particle diameter f3 (x) one determines the position of the mode value of f3 (x) as the most frequent particle diameter (x-mode) in nanometers. From the plot of the volume distribution function of the particle diameter F3 (x), the volume fraction of particles greater than or equal to 900 nm is determined as dF3 900 nm) in volume%. Under the generally given assumption that the density of the particles is independent of their size, this volume fraction corresponds to the weight fraction. 1.5 sieve residue (grit> 40 pm)

The residue of the dispersion given in parts per 10 ⁶ , based on dispersion (ppm), characterizes coarse-grained fractions in the dispersion with dimensions greater than 40 μιτι. To determine such minimally stable fractions, 100 grams of the dispersion were diluted with one liter of distilled water, then poured through a 150 mesh nylon mesh, and the passage was filtered through a mesh of mesh size 40μιτι. It was because rinsed with water until the passage was clear. The residue on the sieve fabrics was weighed back after drying and the sieve residue per sieve fabric, based on dispersion, was calculated. In Table 3, the total residue on both screens was greater than 40 μιτι indicated.

It should be expressly mentioned that the indication of residue> 40 μιτι is a very critical evaluation of Siebrückstandes. Industrially usual are> 50 μιτι or> 60 μιτι. According to experience, in the range between 40 μιτι and 60 μιτι 20% to 50% of the residue between see 40 μιτι and 150 μιτι lie.

1.6 Free formaldehyde content of the dispersion

The present polymer dispersions were diluted 1: 1 with water and transferred by ultracentrifugation (2 h at 32,000 rpm) in a clear as possible latex serum. The latex sera thus obtained were then determined photometrically according to ISO 15373 (Method A, Plastics - Polymer Dispersions - Determination of free formaldehyde).

2. Test methods for the characterization of bonded nonwovens

The binding capacity of the polymer dispersions described was characterized in a comparative manner on two different, cellulose-containing and nonwoven fabrics.

2.1 Determination of the strength values for tissue nonwovens

Typical tissue paper (100% pulp, 26 gsm, dry strength: 3.7 N / 45 mm, wet strength: 0.9 N / 45 mm, with 2 ppm formaldehyde) was mixed with a liquor of the respective 30% polymer dispersion In the gap ("gusset") of a Mathis HVF Foulard (Mathis / CH) homogeneously impregnated and dried by means of a laboratory through-air dryer (Fleissner, 3 min / 150 ° C) and crosslinked The corresponding binder orders were gravimetrically after 24 h air conditioning in standard atmosphere (ISO 139, 2005, 23 ± 2 ° C, 50 ± 3%).

To determine the respective tensile strengths, 15 strips each in the transverse direction with a width of 15 ± 1 mm and a length of 150115 mm were removed. In each case 3 of the 15 nonwoven strips were combined into a test sample by means of stapling pliers and a total of n = 5 test samples were subjected to a tear strength determination. All tear strengths were determined analogously to DIN EN 29073 (Part 3: Test Methods for Nonwovens, 1992) and the test specimens to determine the dry tensile strength by means of a maximum tensile force on a Zwick® 1445 testing machine (100 N load cell) with a TestXpert® software version 11.02 (Zwick Roell) in the dry state (dry) with a clamping length of 10011 mm, a clamping width of 15 ± 1 mm and a deformation rate of 100 mm / min. To measure the Wet Tear Stresses (wet), the strip samples were previously stored in water for 1 min and determined as described above. Solvent strengths were determined by one-minute storage in isopropanol (ISO) analogous to the above.

2.2 Determination of the strength values for airlaid nonwovens

A thermally pre-bonded airlaid web (75 gsm, 88% fluff pulp and 12% PP / PE bicomponent fibers, 0.85 mm thickness, dry strength 500 g / 5 cm, wet strength 300 g / 5 cm) became a 20% spray liquor sprayed homogeneously on both sides with a semi-automatic spray unit using the airless method (slot nozzles Unijet 8001 E, 5 bar) and then dried in a laboratory through-air dryer (Mathis LTF, Mathis / CH) at 160 ° C. for 3 min. For each tenacity test 10 fleece strips (20 cm clamping length, 5 cm clamping length) were made in the transverse direction to the machine production direction and, as described in Chap. 2.1. a maximum tensile force measurement with a deformation rate of 150 mm / min. subjected.

2.3 Determination of the free formaldehyde content of bonded nonwovens

The formaldehyde content of the nonwovens bonded to the abovementioned polymer dispersions was determined according to ISO 14184-1 (textiles determination of the content of formaldehyde, Part 1: free and hydrolyzed formaldehyde (water extraction method, 1999) or according to WSP 310.2 (11) (Standard Test Method for Free and Hydrolysed Formaldehyde in Nonwovens (Water Extraction Method - Method 1, EDANA / INDA 2011).

2.4 Determination of the hydrophilicity of bonded nonwovens

Tissue nonwoven: drop single time (TEZ):

The measurement of the droplet sinking time TEZ is used to evaluate the hydrophilicity or hydrophobicity of the filmed polymer on a film. serförmigen substrate (ability of wetting by water). The dripping time TEZ is measured as follows:

A binder-solidified tissue was placed on a four-fold handkerchief of the brand "Tempo" (function as absorbent). Subsequently, a stainless steel shadow mask (d = 14 cm, 1 cm thick) with five round holes (d = 3 cm) was placed on the corresponding nonwoven sample. Using a plastic pipette, 1 drop of a blue ink (prepared from lg Patentblau V (from Höchst) in one liter of distilled water) was added from a height of 1 cm through each of the five holes and the time [s] with recorded the stopwatch, the

Drop needed to completely penetrate the binder-bonded nonwoven fabric. Upon reaching 300 s, the test was discontinued. In each case, 10 individual measurements were taken for each nonwoven side and averaged accordingly or noted for hydrophobic binders> 300 sec.

Airlaid fleece: Relative water absorption capacity:

To assess the relative water absorption capacity, which is thus a measure of the hydrophilicity or hydrophobicity of the polymer binder on the fibers, three samples 4 × 4 cm each were cut out of the bonded airlaid nonwovens with a template. To determine the water absorption capacity, the respective sample piece was brought into contact with an edge side in a Krüss K12 tensiometer with a water supply on a precision balance. The weight of water absorption due to capillary suction was measured continuously and shown in a diagram as mass / time (sorption method Krüss LabDesk 2.5 Software).

The amount of water absorbed in grams (g) corresponds to the water absorption capacity (hereinafter referred to as capacity) of the nonwoven fabric and is read in a mass (g) against time (s) application at 180s. 3. General polymerization instructions

3-liter glass reactor

For Comparative Examples VI and V3 for the preparation of styrene-acrylate copolymers and V10 for the preparation of a vinyl acetate copolymer was a double-walled 3-liter glass reactor equipped with electronic temperature measurement and control, a reflux condenser and at least four metering options for parallel metering of two initiator components (Dosage 1 for the oxidizing agent and dosage 2 for the reducing agent, if used), monomer or Monomergemi sch (dosage 3) and an aqueous solution (dosage 4), containing, for example Emulsifier and water-soluble monomers.

For stirring, a 6-finger finger stirrer was used, the speed was variable and, unless otherwise indicated, was 200 rpm in the course of polymerization.

After addition of the aqueous portion of the reactor charge, the reactor was evacuated, the vacuum was broken with nitrogen, and nitrogen was passed through the reactor for at least 5 minutes. Subsequently, the template monomer was added while stirring and after tempering to target temperature, the reaction by parallel metering of doses 1 and 2, or started only by means of dosing 1.

After substantially complete conversion (completion of the dosage 1 and - if used - the dosage 2), the dispersion was cooled in a reactor under vacuum.

2-liter pressure reactor

For vinyl acetate-ethylene copolymerizations (VAE) of Examples 1 to 3 and 5 to 16, and Comparative Examples V4 to V8 was a double-walled 2-liter pressure reactor from Büchi, for working pressures up to 85 bar, equipped with electronic temperature measurement and control, a three - stage paddle stirrer with variable speed, safety valve and dosing options for at least five dosing options for parallel dosing of two initiator components (dosage 1 for the oxidant, dosed from above, and dosing 2 for the reducing agent, dosed from below), monomer or monomer mixture (dosing 3 ) and an aqueous solution (dosage 4) containing, for example, emulsifier and water-soluble monomers, such as For example, acrylic acid, acrylamide and N-methylolacrylamide, as well as for ethylene (dosage 5, if used).

The aqueous portion of the reactor receiver was adjusted to pH 4.0 by using 1% formic acid each and aspirated into the evacuated reactor. It was then evacuated again, the vacuum was broken with nitrogen, evacuated again and the monomer template was aspirated with stirring. Subsequently, the reactor was heated to nominal temperature of usually 50 ° C, set to target speed of usually and unless otherwise indicated 500 rpm and pressed during heating the desired amount of ethylene to mass. The setpoint temperature was kept substantially constant until it cooled.

After reaching a temperature and pressure equilibrium, i.

Stable temperature and pressure values, were in parallel the dosage 1, usually and unless otherwise stated consisting of a 10% aqueous ammonium persulfate solution and the dosage 2, usually and unless otherwise stated consisting of a 5% aqueous ascorbic acid Solution, usually with 15 grams / h, if not otherwise indicated and thus initiates the polymerization reaction of the reactor template.

After reaching the required or desired monomer conversion values, which correlate with experimentally readily available solid content values of the polymerizing reactor template and are optionally to be determined in preliminary experiments, the dosage of the metered addition 3, containing at least that, was generally and unless otherwise specified dosing vinyl acetate monomer, and the aqueous dosage 4, containing emulsifier and water-soluble monomers, in particular acrylamide and N-methylolacrylamide, started (unlike for Comparative Examples V6, V7 and V10, see just there) and simultaneously the rates of the current dosages 1 and 2 increased from usually 15 grams / h to 19 grams / h. As a rule and unless stated otherwise, doses 3 and 4 were dosed uniformly over three hours each. Depending on the further monomer conversion in the metering process and the concrete monomer composition, a further increase in the rates of meterings 1 and 2 was expedient in the metering process in order to ensure steadily increasing monomer conversion. This was achieved, for example, by increasing the Siert rates 1 and 2 to 22 and up to a maximum of 29 grams / h guaranteed.

In individual cases, unless the total amount of ethylene had been initially charged (Example 13 and Comparative Examples V8 and V9), the remaining ethylene was metered quasi continuously at constant pressure or by stepwise pressing in the metering of the dosages 3 and 4, would also be dosage with a constant mass flow rate possible. An ethylene dosage, if used, was completed at the latest with the end of the monomer feed 3.

After the end of doses 3 and 4, the batch was polymerized out by further continuous addition of doses 1 and 2 with 19 g / h in each case. Both doses were discontinued after the exotherm had ceased, but not earlier than 30 minutes after dosing of doses 3 and 4 and not later than 90 minutes after their dosing.

After completion of dosages 1 and 2, 20 grams of a 10% aqueous hydrogen peroxide solution were usually metered in 5 minutes, unless otherwise specified. Subsequently, the pH was adjusted to a value of 4.5 by adding a 12.5% aqueous ammonia solution (for Examples 8 and 9, however, to 6.2 to 6.5), the reactor contents on Cooled to 30 ° C and with portionwise addition of 0.2 grams of a silicone defoamer, emulsified in 18 grams of water relaxed. The product was then completely defoamed by gentle stirring under vacuum for up to 2 hours.

5-liter pressure reactor

The vinyl acetate-ethylene copolymerization for Comparative Example C9 was carried out in a 5-liter pressure reactor, for working pressures up to 100 bar, with analogous equipment as the 2-liter reactor.

600-liter pressure reactor

The vinyl acetate-ethylene copolymerization for Example 4 was carried out in a 600 liter pressure reactor, for working pressures up to 85 bar, with analogous equipment as the 2 liter reactor. raw materials

All raw materials used were commercially available engineering products that were not subjected to any special pre-treatment. Desalted water was used as "water" by means of ion exchange.A emulsifier A was a fatty alcohol ether-sulfate Na salt with 12 C atoms in the alkyl radical and 3 EO units (known, for example, as Genapol® ZRO or Disponil® FES27) as aqueous Solution with an active ingredient content of 27 + 1 wt .-% for use.

N-methylolacrylamide (NMA) was generally used as a "low formaldehyde" version, known for example as NMA-LF, in 48% strength by weight aqueous solution containing NMA and acrylamide (AMD) in approximately equal molar proportions, that is to say in a weight ratio of about NMA / AMD = 58.6 / 41.4 acrylamide amounts added by the use of NMA-LF were additionally added.

Vinyl sulfate monomer was used as a 25 wt .-% aqueous solution of sodium vinylsulfonate.

The vinyltriethoxysilane used was GENIOSIL® GF56 from WACKER Chemie AG.

Sampling during the polymerization reaction

To monitor the Monomerumsatzverlauf during the polymerization were starting from the beginning of dosing monomer 3 (for the examples usually vinyl acetate, optionally in admixture with other comonomers) and then every half hour to Dosierende dosage 3 and after Dosierende the dosages 1 and 2 from the reactors respectively 5 to 10 grams per sample (from the 600-liter pressure reactor 80 to 120 grams per sample) taken and analyzed for solids content. Immediately prior to each sampling, the sampling nozzle was purged from the reactor at about 5 grams (for the 600 liter reactor at about 80 grams). For the solids analysis of the process samples, the above-mentioned rapid method was used.

Comparative Example Vi

A styrene-acrylate standard dispersion with the following monomer composition in% by weight was prepared: 12.0% styrene; 71.3% butyl acrylate; 6.0% acrylamide; 6.4% methacrylic acid; 2.4% acrylic acid and 1.9% hydroxyethyl acrylate. The reactor feed consisted of 598 grams of water, 3.0 grams of Texapon K12 emulsifier and 67.3 grams of styrene.

After sublimation to 80 ° C. at a stirrer speed of 200 rpm, 15.3 grams of a 10% strength ammonium peroxydisulfate solution were added and then immediately with the metering of a monomer mixture 1 consisting of 31.5 g of styrene and 121.5 g Grams of butyl acrylate, begun; this monomer mixture was evenly dosed in 70 minutes. Immediately after completion of the monomer mixture 1, the following dosages were started:

a 7.1% ammonium persulfate solution at a rate of 67.1 g / h,

an aqueous solution of 253 grams of water, 165 grams of a 30 weight percent aqueous acrylamide solution and 12.5 grams of Texapon K12 emulsifier at a rate of 161.4 g / hr,

a monomer mixture 2 consisting of 467.5 grams of butyl acrylate, 52.8 grams of methacrylic acid, 19.95 grams of acrylic acid and 16 grams of hydroxyethyl acrylate at a rate of 208.6 g / hr.

After completion of the two last-mentioned doses, the ammonium persulfate dosage was still running for 40 minutes Auspolymerisationszeit. For the entire reaction time, the temperature was maintained at 79 to 82 ° C. After completion of the polymerization, the polymerization mixture was cooled and adjusted with water to 40 wt .-% of solids content.

Preparation of the styrene-acrylate standard dispersion (standard VI binder) was repeated as indicated.

The determined for both styrene-acrylate-standard dispersions Analytical data for the aqueous dispersion and the bonded nonwoven fabrics, which showed satisfactory compliance were telt averaged and are reported as mean values in Tables 3 and 4 below Ver ^¬ equal example VI. In particular, the following nonwoven strengths were obtained for bonded tissue nonwoven with 30% binder coverage, reported in N / 4, 5 cm: dry strength: 18.0; Nassfestig ^¬ ness: 8.1; Solvent resistance (isopropanol): 5.7; and Tied ^¬ nes airlaid web with 20% binder application means in a dry strength of 2269 g / 5 cm and a wet strength of 1124 g / 5 cm were determined.

The results of the fleece strength for the products of all the other examples and comparative examples are based on this Festig ^¬ speed values as specified in percent to one percent. Comparative Example V2

An aqueous dispersion of Primal ™ 1845K from DOW Chemical was used. The strengths of tissue webs bonded thereto were determined twice, the strengths of air laid webs bound thereto were determined three times and the results obtained were each averaged.

Comparative Example C3

A styrene-acrylate standard dispersion with the following monomer composition in% by weight was prepared: 12.4% of styrene; 74.0% butyl acrylate; 4.1% acrylamide; 6.6% methacrylic acid; 2.5% acrylic acid and 0.35% N-methylolacrylamide.

The reactor template consisted of 598 grams of water, 6.1 grams of Texapon K12 emulsifier and 67.3 grams of styrene.

a 7.1% ammonium persulfate solution at a rate of 67.1 g / h,

an aqueous solution of 316 grams of water, 108.6 grams of a 30 weight percent aqueous acrylamide solution, 5.8 grams of a 48 weight percent aqueous N-metholol acrylamide solution, and 12.5 grams of Texapon K12 emulsifier at a rate of 166.1 g / h,

a monomer mixture 2 consisting of 467.5 grams of butyl acrylate, 52.8 grams of methacrylic acid and 19.95 grams of acrylic acid at a rate of 202.6 g / hr.

After completion of the two last-mentioned doses, the ammonium persulfate dosage was still running for 40 minutes Auspolymerisationszeit. For the entire reaction time, the temperature was maintained at 79 to 82 ° C. After completion of the polymerization, the polymerization was cooled.

Comparative Example V4 A VAE dispersion having the following monomer composition in% by weight was prepared: 69.65% vinyl acetate, 23.00% ethylene, 2.93% VeoVa®10, 1.43% acrylic acid, 0.73% butyl acrylate, 0.59% vinyl sulfonate and 1.69% acrylamide.

The reactor feed consisted of 490 grams of water, 3.5 grams of a 0.1% aqueous hydroquinone monomethyl ether (HQME) solution, 27.36 grams of a 30% aqueous acrylamide solution, 22.9 grams of a 25% aqueous vinyl sulfonate solution , 4 grams of a 1% ferro- ammonium sulfate (FAS) solution, 172.3 grams of vinyl acetate, 7.1 grams of butyl acrylate, 28.5 grams of VeoVa®10, and 224 grams of ethylene.

59 minutes after the start of dosing of the initiator components with the parallel dosage of dosage 3, consisting of 506 grams of vinyl acetate, and dosage 4, consisting of 72.5 grams of water, 30.5 grams of a 28% aqueous emulsifier A, 3.5 grams 0.1% Aqueous HQME solution, 37.36 grams of a 30% aqueous acrylamide solution, 13.9 grams of acrylic acid adjusted to pH 3.9 with a 12.5% aqueous ammonia solution , After completion of doses 3 and 4 were proceeded to general polymerization rule for the 2-liter reactor. In each case 93.5 grams of dosage 1 and dosage 2 were consumed.

Comparative Example V5

A VAE dispersion having the following monomer composition in% by weight was prepared: 70.88% vinyl acetate, 22.54% ethylene, 2.10% acrylic acid, 1.01% butyl acrylate, 0.58% vinyl sulfonate and 2.90% acrylamide. The reactor feed consisted of 490 grams of water, 3.5 grams of a 0.1% aqueous hydroquinone monomethyl ether (HQME) solution, 27.40 grams of a 30% aqueous acrylamide solution, 22.9 grams of a 25% aqueous vinyl sulfonate solution , 4 grams of a 1% ferro- ammonium sulfate (FAS) solution, 200.0 grams of vinyl acetate, 10.0 grams of butyl acrylate, and 224 grams of ethylene.

60 minutes after the start of dosing of the initiator components with the parallel dosage of dosage 3, consisting of 506 grams of vinyl acetate, and dosage 4, consisting of 61.5 grams of water, 30.5 grams of a 28% aqueous emulsifier A, 3.5 grams 0, l% aqueous HQME solution, 68.5 grams of a 30% aqueous acrylamide solution, 20.9 grams of acrylic acid, adjusted to a pH of 3.9 with a 12.5% aqueous ammonia solution started , After completion of doses 3 and 4 was proceeded to general polymerization rule for the 2-liter reactor.

In each case 104 grams of dosage 1 and dosage 2 were consumed.

example 1

A VAE dispersion having the following monomer composition in% by weight was prepared: 69.30% vinyl acetate, 22.89% ethylene, 2.91% VeoVa®10, 1.42% acrylic acid, 0.73% butyl acrylate, 0.58% vinylsulfonate, 1.88% acrylamide and 0.29% N-methylolacrylamide.

59 minutes after the start of dosing of the initiator components with the parallel dosage of dosage 3, consisting of 506 grams of vinyl acetate, and dosage 4, consisting of 72.5 grams of water, 30.5 grams of a 28% aqueous emulsifier A, 3.5 grams 0.1% Aqueous HQME solution, 13.9 grams of acrylic acid, 33.98 grams of a 30% aqueous acrylamide solution, and 5.86 grams of a 48% aqueous N-methylolacrylamide solution, total 12.5% aqueous ammonia solution adjusted to a pH of 3.9, started.

After completion of doses 3 and 4 was proceeded to general polymerization rule for the 2-liter reactor.

In each case 92 grams of dosage 1 and dosage 2 were consumed.

Example 2

A VAE dispersion having the following monomer composition in% by weight was prepared: 69.12% of vinyl acetate, 22.83% of ethylene, 2.90% of VeoVa®10, 1.42% of acrylic acid, 0.72% of butyl acrylate, 0.58% vinylsulfonate, 1.99% acrylamide and 0.44% N-methylolacrylamide.

The reactor template was identical to Example 1.

58 minutes after the start of dosing of the initiator components with the parallel dosage of dosage 3, consisting of 506 grams of vinyl acetate, and dosage 4, consisting of 72.5 grams of water, 30.5 grams of a 28% aqueous emulsifier A, 3.5 grams 0.1% Aqueous HQME solution, 13.9 grams of acrylic acid, 37.63 grams of a 30% aqueous acrylamide solution, and 9.08 grams of a 48% aqueous N-methylolacrylamide solution, all at 12.5% aqueous ammonia solution adjusted to a pH of 3.9, started.

In each case 94 grams of dosage 1 and 2 doses were consumed.

Example 3

A VAE dispersion having the following monomer composition in% by weight was prepared: 68.95% vinyl acetate, 22.77% ethylene, 2.90% VeoVa®10, 1.41% acrylic acid, 0.72% butyl acrylate, 0.58% vinylsulfonate, 2.08% acrylamide and 0.59% N-methylolacrylamide.

The reactor template was identical to Example 1.

58 minutes after the start of dosing of the initiator components with the parallel dosage of dosage 3, consisting of 506 grams of vinyl acetate, and dosage 4, consisting of 72.5 grams of water, 30.5 grams of a 28% aqueous emulsifier A, 3.5 grams 0, 1% aqueous HQME solution, 13.9 grams of acrylic acid, 40.94 grams of a 30% aqueous acrylamide solution and 12.01 grams of a

48% aqueous N-methylolacrylamide solution, adjusted in total with a 12.5% aqueous ammonia solution to a pH of 3.9 started.

In each case 93.5 grams of dosage 1 and dosage 2 were consumed. Example 4

In a 600-liter pressure reactor (nominal volume 572 liters), a VAE dispersion was prepared with the same monomer composition as for Example 3.

The reactor receiver consisted of 143.5 kg of water, 1.13 grams of hydroquinone monomethyl ether (HQME), 8.70 kg of a 30% aqueous acrylamide solution, 7.25 kg of a 25% aqueous vinyl sulfonate solution, 12 , 8 grams of ferro-ammonium sulfate (FAS), 54.5 kg of vinyl acetate, 2.25 kg of butyl acrylate, 9.0 kg of VeoVa®10 and 71 kg of ethylene.

After pressure equilibrium at a temperature of 50 ° C and at a stirrer speed of 190 rpm, the reaction by parallel metering of dosage 1, consisting of a 10% aqueous ammonium persulfate solution, and dosage 2, consisting of a 5% aqueous ascorbic acid solution with started at a rate of 5.75 kg / h each.

40 minutes after the start of dosing of the initiator components with the parallel dosage of dosage 3, consisting of 160 kg of vinyl acetate, and dosage 4, consisting of 23.0 kg of water, 9.65 kg of a 28% aqueous emulsifier A, 1.13 grams HQME , 4.4 kg of acrylic acid, 12.94 kg of a 30% aqueous acrylamide solution and 3.80 kg of a 48% aqueous N-methylolacrylamide solution, in total with a 12.5% aqueous ammonia solution to a pH set from 3.9, started. Doses 3 and 4 were dosed evenly in 3 hours each. With the start of doses 3 and 4, the rates of both initiator doses 1 and 2 remained unchanged.

On completion of dosages 3 and 4, dosages 1 and 2 proceeded at a rate of 4.6 kg / hr for an additional 60 minutes. Subsequently, 6.5 kg of a 10% aqueous solution of hydrogen peroxide were added in 10 minutes and then adjusted to a pH of about 4.5 by metering a 12.5% aqueous ammonia solution. The reactor contents were then emulsified with the addition of 60 grams of silicone defoamer in 5 kg of water in a flash vessel and defoamed there for one hour under vacuum.

Example 4 was reproduced as indicated.

Both products were combined in an approximately 2.4 m ³ steam flash vessel and used to remove volatile organic compounds Steam at a steam rate of 5 m ³ / h for 2 hours under normal conditions stripped and then with 12.5% aqueous ammonia solution or water to a pH of 4.5 and a solids content of about 50 wt. -% set.

Example 5

A VAE dispersion having the following monomer composition in% by weight was prepared: 67.82% vinyl acetate, 22.40% ethylene, 2.85% VeoVa®10, 1.39% acrylic acid, 0.71% butyl acrylate, 0.57% vinylsulfonate, 3.69% acrylamide and 0.58% N-methylolacrylamide.

The reactor template was identical to Example 1.

57 minutes after the start of dosing of the initiator components with the parallel dosage of dosage 3, consisting of 506 grams of vinyl acetate, and dosage 4, consisting of 18.0 grams of water, 30.5 grams of a 28% aqueous emulsifier A, 3.5 grams 0, 1% aqueous HQME solution, 13.9 grams of acrylic acid, 95.48 grams of a 30% aqueous acrylamide solution and 12.01 grams of a

48% aqueous N-methylolacrylamide solution, adjusted to a pH of 3.6 with a total of 12.5% aqueous ammonia solution.

In each case 103 grams of dosage 1 and 2 dosage were consumed.

Comparative Example V6

A VAE dispersion was prepared with the same monomer composition as for Example 3.

The reactor template was identical to Example 1.

60 minutes after dosing start of doses 1 and 2, a dosage 3 consisting of 506 grams of vinyl acetate, parallel to a dosage 4A, consisting of 68.0 grams of water, 24.63 grams of a 26% aqueous emulsifier solution A, 2.63 grams of a 0.1% aqueous HQME solution, 10.43 grams of acrylic acid, 20.52 grams of a 30% aqueous acrylamide solution, total adjusted to a pH of 3.6 with a 12.5% aqueous ammonia solution , began. With the start of doses 3 and 4A, the rates of both initiator doses 1 and 2 were increased. Dosing 3 was dosed for 3 hours and Dose 4A was uniformly dosed for 135 minutes. To Termination of Dosing 4A immediately became Dosage 4B, consisting of 2.2 grams of water, 8.2 grams of a 26% aqueous emulsifier solution A, 0.88 grams of a 0.1% aqueous HQME solution, 3.47 Grams of acrylic acid, 20.42 grams of a 30% aqueous acrylamide solution and 12.01 grams of a 48% aqueous N-methylolacrylamide solution, total with a 12.5% aqueous ammonia solution to a pH of 3 , 6, started and dosed evenly for 45 minutes and parallel to the dosage 3 and simultaneously stopped with dosage 3.

After completion of doses 3 and 4B was proceeded to general polymerization rule for the 2-liter reactor.

In each case 100 grams of dosage 1 and 2 dosage were consumed.

Comparative Example V7

A VAE dispersion with the same monomer composition as for Example 5 was prepared.

The reactor template was identical to Example 1.

20 minutes after the start of dosing of the initiator components was started with the parallel dosage of dosage 3 and dosage 4, each having the same composition as for Example 5.

In each case 91 grams of dosage 1 and 2 dosage were consumed.

Example 6

A VAE dispersion having the following monomer composition in% by weight was prepared: 67.66% vinyl acetate, 22.51% ethylene, 2.86% VeoVa®10, 1.40% acrylic acid, 0.71% butyl acrylate, 0.58% vinylsulfonate, 3.50% acrylamide, 0.29% N-methylolacrylamide and 0.49% N- (isobutoxymethyl) acrylamide (IBMA).

The reactor template was identical to Examples 1.

60 minutes after the beginning of the dosing of the initiator components with the parallel dosage of dosage 3, consisting of 501.1 grams of vinyl acetate and 4.9 grams of IBMA, and dosage 4, consisting of 23.0 grams of water, 30.5 grams of a 28% aqueous Emulsifier solution A, 3.5 grams of a 0.1% aqueous HQME solution, 13.9 grams of acrylic acid, 88.79 grams of a 30% aqueous acrylamide solution and 6.01 grams of a 48% aqueous N-methylolacrylamide solution, total adjusted to a pH of 3.6 with a 12.5% aqueous ammonia solution.

In each case 105 grams of dosage 1 and 2 dosage were consumed.

Example 7

A VAE dispersion with the following monomer composition in% by weight was prepared: 70.57% vinyl acetate, 22.39% ethylene, 2.09% acrylic acid, 1.00% butyl acrylate, 0.57% vinyl sulfonate, 3 08% acrylamide and 0.29% N-methylolacrylamide.

The reactor template was identical to Comparative Example V5.

58 minutes after the start of dosing of the initiator components with the parallel dosage of dosage 3, consisting of 506.0 grams of vinyl acetate, and dosage 4, consisting of 51.1 grams of water, 30.5 grams of a 28% aqueous emulsifier solution A, 3.5 Grams of a 0.1% aqueous HQME solution, 20.4 grams of acrylic acid, 75.39 grams of a 30% aqueous acrylamide solution, and 6.09 grams of a 48% aqueous N-methylol acrylamide solution, totaling 12.5 % aqueous ammonia solution to a pH of 3.9, started.

In each case 101.5 grams of dosage 1 and dosage 2 were consumed.

Example 8

A VAE dispersion having the following monomer composition in% by weight was prepared: 69.59% vinyl acetate, 22.40% ethylene, 2.09% acrylic acid, 1.00% butyl acrylate, 0.57% vinyl sulfonate, 3.08% Acrylamide, 0.28% N-methylolacrylamide and 1.00% vinyltriethoxysilane.

The reactor template was identical to Example 7.

60 minutes after the start of dosing of the initiator components with the parallel dosage of dosage 3, consisting of 496.0 grams of vinyl acetate and 10 grams of vinyltriethoxysilane, and dosage 4, consisting of 51.5 grams of water, 30.5 grams of a 28% aqueous emulsifier A solution , 3.5 grams of a 0.1% aqueous HQME solution, 20.4 grams of acrylic acid, 75.12 grams of a 30% aqueous acrylamide solution. and 5.86 grams of a 48% aqueous N-methylolacrylamide solution, adjusted to a total pH of 3.9 with a 12.5% aqueous ammonia solution.

After the end of doses 3 and 4, the general polymerization procedure for the 2-liter reactor was followed, but the pH of the end product was adjusted to 6.4.

In each case 118 grams dosage 1 and dosage 2 were consumed.

Example 9

A VAE dispersion having the following monomer composition in% by weight was prepared: 69.09% of vinyl acetate, 22.40% of ethylene, 2.09% of acrylic acid, 1.00% of butyl acrylate, 0.57% of vinylsulfonate, 3 08% acrylamide, 0.28% N-methylolacrylamide, 1.00% vinyltriethoxysilane and 0.50% N- (isobutoxymethyl) acrylamide (IBMA).

The reactor template was identical to Example 7.

58 minutes after dosing of the initiator components was started with the parallel dosage of dosage 3, consisting of 491.0 grams of vinyl acetate, 5 grams of IBMA and 10 grams of vinyltriethoxysilane, and dosage 4, with identical composition as for Example 8.

After completion of dosages 3 and 4, the procedure was as for Example 8.

In each case 118 grams dosage 1 and dosage 2 were consumed. Example 10

A VAE dispersion having the following monomer composition in% by weight was prepared: 72.42% vinyl acetate, 17.80% ethylene, 2.85% VeoVa® 10, 1.39% acrylic acid, 0.71% butyl acrylate, 0, 57% vinyl sulfonate, 3.69% acrylamide and 0.58% N-methylolacrylamide.

The reactor template was identical to Example 1, with the difference that only 178 grams of ethylene were used.

55 minutes after the start of dosing of the initiator components with the parallel dosage of dosage 3, consisting of 552.0 grams of vinyl acetate, and dosage 4, consisting of 18.0 grams of water, 30.5 grams of a 28% aqueous emulsifier A, 3.5 Grams of a 0.1% aqueous HQME solution, 13.9 grams of acrylic acid, 95.58 grams of a 30% aqueous acrylamide solution and 12.01 grams of a

48% aqueous N-methylolacrylamide solution, total with one 12.5% aqueous ammonia solution adjusted to a pH of 3.6, started.

In each case 104 grams of dosage 1 and dosage 2 were consumed.

Example 11

A VAE dispersion having the following monomer composition in% by weight was prepared: 73.08% vinyl acetate, 14.97% ethylene, 0.40% acrylic acid, 8.34% butyl acrylate, 0.08% vinyl sulfonate, 2, 15% acrylamide, 0.59% N-methylolacrylamide and 0.39% Lubrizol® 2403A (acrylamidopro- panesulfonate Na salt, AMPS).

The reactor feed consisted of 523 grams of water, 3.2 grams of a 0.1% aqueous hydroquinone monomethyl ether (HQME) solution, 2.9 grams of a 25% aqueous vinyl sulfonate solution, 7.3 grams of a 5% aqueous emulsifier solution of aerosol ® A102, 11.4 grams of a 20% aqueous emulsifier solution of Genapol® PF40, 4 grams of a 1% Ferroammone Sulfate (FAS) solution, 66.0 grams of vinyl acetate, 7.7 grams of butyl acrylate, and 143 grams of ethylene.

It was, in contrast to the general polymerization rule for the 2-liter pressure reactor heated to 45 ° C at a speed of 400 rpm and polymerized.

32 minutes after the start of dosing of the initiator components was carried out with the parallel dosage of dosage 3, consisting of 632 grams of vinyl acetate and 72 grams of butyl acrylate, and dosage 4, consisting of 71.3 grams of water, 53.85 grams of a 30% aqueous emulsifier Aerosol® MA , 3.5 grams of a 0.1% aqueous HQME solution, 3.8 grams of acrylic acid, 68.48 grams of a 30% aqueous acrylamide solution and 11.66 grams of a 48% aqueous N-methylol acrylamide solution, 7.4 grams of a 50% aqueous AMPS solution, total adjusted to pH 4.0 with a 12.5% aqueous ammonia solution, has begun.

In each case 96.5 grams of dosage 1 and dosage 2 were consumed.

Example 12 A VAE dispersion having the following monomer composition in% by weight was prepared: 82.788% vinyl acetate, 12.05% ethylene, 0.56% acrylic acid, 0.76% butyl acrylate, 0.07% vinyl sulfonate, 3.20% Acrylamide and 0.59% N-methylolacrylamide.

The reactor feed consisted of 555 grams of water, 3.7 grams of a 0.1% aqueous hydroquinone monomethyl ether (HQME) solution, 2.9 grams of a 25% aqueous vinyl sulfonate solution, 1.2 grams of a 30% aqueous emulsifier solution of aerosol ® A102, 2.3 grams of a 97% aqueous emulsifier solution of Genapol® PF40, 4 grams of a 1% Ferroammone Sulfate (FAS) solution, 65.0 grams of vinyl acetate, 7.6 grams of butyl acrylate and 121 grams of ethylene.

It was, in contrast to the general polymerization rule for the 2-liter pressure reactor heated to 50 ° C at a speed of 400 rpm and polymerized.

30 minutes after the start of dosing of the initiator components was carried out with the parallel dosage of dosage 3, consisting of 766 grams of vinyl acetate, and dosage 4, consisting of 30 grams of water, 62.7 grams of a 30% aqueous emulsifier Aerosol® MA, 3.7 grams 0, 1% aqueous HQME solution, 5.6 grams of acrylic acid, 106.96 grams of a 30% aqueous acrylamide solution and 12.25 grams of a 48% aqueous N-methylolacrylamide solution, total of 12.5% aqueous ammonia solution adjusted to a pH of 4.0, started.

In each case 82 grams of dosage 1 and 2 dosage were consumed.

Example 13

A VAE dispersion having the following monomer composition in% by weight was prepared: 66.14% vinyl acetate, 28.71% ethylene, 0.74% acrylic acid, 0.67% butyl acrylate, 0.06% vinyl sulfonate, 3.10% Acrylamide and 0.59% N-methylolacrylamide.

The reactor feed consisted of 525 grams of water, 3.5 grams of a 0.1% aqueous hydroquinone monomethyl ether (HQME) solution, 2.47 grams of a 25% aqueous vinyl sulfonate solution, 6.12 grams of a 5% aqueous emulsifier solution of aerosol ® A102, 9.39 grams of a 20% aqueous emulsifier solution of Genapol® PF40, 4 grams one 1% Ferroammonium Sulfate (FAS) solution, 55.0 grams of vinyl acetate, 6.5 grams of butyl acrylate, and 185 grams of ethylene.

32 minutes after dosing of the initiator components was carried out with the parallel dosage of dosage 3 consisting of 590 grams of vinyl acetate, and dosage 4, consisting of 8.1 grams of water, 78.5 grams of a 25% aqueous emulsifier Genapol® X360, 4.0 Grams of a 0.1% aqueous HQME solution, 7.2 grams of acrylic acid, 100.75 grams of a 30% aqueous acrylamide solution, and 11.9 grams of a 48% aqueous N-methylolacrylamide solution, totaling 12.5 % aqueous ammonia solution to a pH of 4.0, started.

Starting 15 minutes after the start of dosing 3, a total of 95 grams of ethylene were dosed uniformly over a period of 120 minutes.

In each case 96.5 grams of dosage 1 and dosage 2 were consumed.

Comparative Example V8

A VAE dispersion having the following monomer composition in% by weight was prepared: 66.41% vinyl acetate, 28.83% ethylene, 0.74% acrylic acid, 0.67% butyl acrylate, 0.06% vinyl sulfonate, 3.11% Acrylamide and 0.17% N-methylolacrylamide.

The reactor template, temperature and speed were identical to Example 13.

35 minutes after the start of dosing of the initiator components with the parallel dosage of dosage 3, identical to Example 13, and dosage 4, identical to Example 13 with the exception that only 3.5 grams of a 48% aqueous N-methylolacrylamide solution were used , began.

An ethylene dosage was identical to Example 13. After completion of doses 3 and 4 was proceeded to the general polymerization protocol for the 2-liter reactor. In each case 92 grams of dosage 1 and dosage 2 were consumed. The product was adjusted to a pH of 4.5 and a solids content of about 50% with 12.5% ammonia solution.

Comparative Example V9

A VAE dispersion having the following monomer composition in% by weight was prepared: 68.37% vinyl acetate, 29.68% ethylene, 0.76% acrylic acid, 0.69% butyl acrylate, 0.07% vinyl sulfonate, 0, 12% acrylamide and 0.31% N-methylolacrylamide.

The reactor template, temperature and speed were identical to Example 13.

Thirty minutes after the start of dosing of the initiator components, with the parallel dosage of Dose 3, identical to Example 13, and Dose 4, consisting of 50.0 grams of water, 78.5 grams of a 25% aqueous emulsifier solution Genapol® X360, 4.0 grams a 0.1% aqueous HQME solution, 7.2 grams of acrylic acid, 3.80 grams of a 30% aqueous acrylamide solution, and 6.0 grams of a 48% aqueous N-methylol acrylamide solution, totaling 12.5%. The aqueous ammonia solution is adjusted to a pH of 4.0.

An ethylene dosage was identical to Example 13. After completion of doses 3 and 4 was proceeded to the general polymerization protocol for the 2-liter reactor.

In each case 88 grams dosage 1 and dosage 2 were consumed. The product was adjusted to a pH of 4.5 and a solids content of about 50% with 12.5% ammonia solution.

Example 14

A VAE dispersion having the following monomer composition in% by weight was prepared: 66.31% vinyl acetate, 21.90% ethylene, 2.79% VeoVa®10, 1.96% acrylic acid, 0.69% butyl acrylate, 0.56% vinylsulfonate, 3.28% acrylamide, 0.56% N-methylolacrylamide and 1.96% hydroxyethyl acrylate.

The reactor template was identical to Example 1.

62 minutes after the beginning of dosing of the initiator components with the parallel dosage of dosage 3, consisting of 506 grams of vinyl acetate, and dosage 4, consisting of 29.1 grams of water, 30.5 grams of a 27% aqueous emulsifier A, 3.5 grams 0, 1% aqueous HQME solution, 20.0 grams of acrylic acid, 20.0 grams of hydroxyethyl acrylate, 84.58 grams of a 30% aqueous acrylamide solution and 12.01 grams of a 48% aqueous N-methylolacrylamide solution, all set to a pH of 3.6 with a 12.5% aqueous ammonia solution.

In each case 120 grams of dosage 1 and 2 dosage were consumed.

Example 15

A VAE dispersion having the following monomer composition in% by weight was prepared: 68.87% vinyl acetate, 21.85% ethylene, 1.95% acrylic acid, 0.98% butyl acrylate, 0.56% vinyl sulfonate, 3.28% Acrylamide, 0.56% N-methylolacrylamide and 1.95% hydroxyethyl acrylate.

The reactor template was identical to Example 7.

58 minutes after the start of dosing of the initiator components was started with the parallel dosage of dosage 3, consisting of 506 grams of vinyl acetate, and dosage 4, identical to Example 14. With the start of doses 3 and 4, the rates of both initiator doses 1 and 2 were increased immediately to 22 grams / h.

In each case 121 grams of dosage 1 and dosage 2 were consumed.

Example 16

A VAE dispersion having the following monomer composition in% by weight was prepared: 68.71% vinyl acetate, 21.96% ethylene, 1.96% acrylic acid, 0.98% butyl acrylate, 0.56% vinyl sulfonate, 3.10% Acrylamide, 0.29% N-methylolacrylamide, 1.96% hydroxyethyl acrylate and 0.49% N- (isobutoxymethyl) acrylamide (IBMA).

The reactor template was identical to Example 7.

59 minutes after the start of dosing of the initiator components was carried out with the parallel dosage of dosage 3, consisting of 501 grams of vinyl acetate and 5 grams of IBMA, and dosage 4, consisting of 30.0 grams of water, 30.5 grams of a 27% aqueous emulsifier solution A, 3rd , 5 grams of a 0.1% aqueous HQME solution, 20.0 grams of acrylic acid, 20.0 grams of hydroxyethyl acrylate, 77.89 grams of a 30% aqueous acrylamide solution, and 6.9 grams of a 48% aqueous solution of N-butyl. Methylolacrylamide solution, adjusted to a total pH of 3.9 with a 12.5% aqueous ammonia solution. With the start of doses 3 and 4, the rates of both initiator doses 1 and 2 were increased immediately to 22 grams / h.

In each case 120 grams of dosage 1 and 2 dosage were consumed.

Comparative Example V10

A VAE dispersion with the following monomer composition in% by weight was prepared analogously to Example 5 of the specification DE4240731 A1: 75.02% vinyl acetate, 21.08% ethylene, 0.84% acrylic acid, 0.73% butyl acrylate, 0.07% Vinylsulfonate, 1.50% acrylamide and 0.75% N-methylolacrylamide. The reactor feed consisted of 500 grams of water, 2.43 grams of a 25% aqueous vinyl sulfonate solution, 1.01 grams of a 30% aqueous emulsifier solution of Aerosol® A102, 9.39 grams of a

20% aqueous emulsifier solution of Genapol® PF40, 5 grams of a 1% Ferroammone Sulfate (FAS) solution, 55.7 grams of vinyl acetate, 6.34 grams of butyl acrylate, and 182 grams of ethylene. At 50 ° C resulted in an equilibrium pressure of 64 bar.

Dosage 1 consisted of 75 grams of a 10% aqueous ammonium persulfate solution; Dosage 2 consisted of 75 grams of a 5% aqueous sodium formaldehyde sulfoxylate solution (known as Bruegitolit®). Doses 1 and 2 were dosed uniformly over a total of 6 hours.

60 minutes after the start of dosing of the initiator components and not after the initial polymerization of the initial charge, as indicated in DE4240731, with the parallel dosing of Dose 3 consisting of 592 grams of vinyl acetate and Dose 4 consisting of 43.8 grams of water, 79.0 grams A 25% aqueous emulsifier solution Genapol® X360, 7.25 grams of acrylic acid, and 43.2 grams of a 30% aqueous acylrylamidlösung started and dosed both doses in parallel and even over 4 hours. One hour before the end of these dosages, a further dosage 5 containing 20 grams of water and 13.5 grams of a 48% aqueous solution of N-methylolacrylamide was dosed over a period of one hour.

Notwithstanding the general rule for polymerization in 2 - liter pressure reactor after completion of doses 1 and 2 of Cooled reactor contents and with the addition of 0.2 grams of silicone defoamer, emulsified in 10 grams of water, relaxed and defoamed under stirring in vacuo. The product was adjusted to a pH of 4.5 with 12.5% aqueous ammonia solution and to a solids content of 50% by weight with water.

Comparative Example VII

In a 5 liter pressure reactor, a VAE dispersion having the following monomer composition in% by weight was prepared: 80.78% vinyl acetate, 14.52% ethylene, 0.19% vinyl sulfonate, 4.01% acrylamide and 0.50 % N-methylolacrylamide.

This comparative example is based essentially on the "Comparative Example 1" specified in US2005 / 0239362 A1, in which no vinyl versatate was used and most of the NMA-LF (MAMD) used there is replaced by mainly acrylamide and only one portion of N-methylolacrylamide of 0.5% by weight based on total monomer was used.

The reactor receiver consisted of 1072 grams of water, 20 grams of a 25% aqueous vinylsulfonate solution, 20 grams of Rhodacal DS10 emulsifier solution, 100 grams of a 30% Aerosol® A102 aqueous emulsifier solution, 62.5 grams of a 10% aqueous solution of citric acid, 1.05 grams of Na citrate, 1.5 grams of a 10% aqueous solution of ferroammonium sulfate (FAS), 2086 grams of vinyl acetate and 375 grams of ethylene pressurized to 40 ° C at a stirrer speed of 800 rpm resulted in equilibrium pressure from 29.5 bar.

Dosage 1 consisted of a 2.5% aqueous solution of t-butyl hydroperoxide and Dosage 2 of a 5% aqueous solution of sodium isoascorbate.

10 grams of dosing 2 were dosed quickly to feed the reactor and then dosing 1 started at a rate of 40 grams / hr. 25 minutes after the start of Dose 1, exotherm was registered, followed by Dose 4, consisting of 27 grams of a 48% aqueous solution of N-methylolacrylamide, 345 grams of a 30% aqueous solution of acrylamide, and 1 gram of a 1% aqueous solution of hydroquinone monomethyl ether (HQME) started at a rate of 160 grams / hr, the rate of Dosage 1 increased to 80 grams / hr and Dosage 2 also at the rate of 80 Grams / h were restarted. The setpoint temperature has now been increased evenly from 40 ° C to 60 ° C within 60 minutes. One hour after the start of dosage 4, its rate was reduced to 106.5 grams / hr and dosed for a further 2 hours. Upon completion of Dosage 4, the rates of Doses 1 and 2 were increased to 120 grams / hr and both dosed for an additional 65 minutes.

A total of 387 grams of Dosage 1 and 380 grams of Dosage 2 were used.

After transfer of the product to a flash vessel with the addition of 1 gram of silicone defoamer in 50 grams of water, postpolymerization was carried out with 16 grams of a 10% aqueous solution of t-butyl hydroperoxide followed by 16 grams of a 10% aqueous solution of sodium isoascorbate.

The product was adjusted to a pH of 4.5 and a solids content of 50% by weight.

Comparative Example V12

In a 3 liter glass reactor, a vinyl acetate copolymer dispersion having the following monomer composition in% by weight was prepared: 76.72% vinyl acetate, 17.45% VeoVa® 10, 0.22% vinyl sulfonate, 0.56% butyl acrylate, 0 , 76% acrylic acid, 2.84% acrylamide and 1.64% vinyltriethoxysilane.

The reactor receiver consisted of 351.5 grams of water, 2.5 grams of a 0.1% aqueous solution of hydroquinone monomethyl ether (HQME), 0.5 grams of a 27% aqueous solution of Emulsifier A, 8.0 grams of a 25% aqueous solution of vinyl sulfonate, 10 grams of a 30% aqueous solution of acrylamide, total of 1% aqueous solution of formic acid adjusted to pH 5.5, 60 grams of vinyl acetate and 5 grams of butyl acrylate. The reactor mixture was heated to 50 ° C and added from 43 ° C 3 grams of a 1% aqueous solution of ferroammonium sulfate (FAS). The stirrer speed was set at 150 rpm.

Dosage 2 consisted of a 5% aqueous solution of ammonium persulfate and dosage 2 of a 1.7% aqueous solution of ascorbic acid.

At 50 ° C, the doses 1 and 2 were started at 10 grams / h and now the external jacket temperature to 50 ° C found. 10 minutes after the start of dosages 1 and 2, dosage 3 containing 624 grams of vinyl acetate, 156 grams of VeoVa® 10 and 14.7 grams of vinyltriethoxysilane was started and metered evenly over a period of 244 minutes. 5 minutes after the start of Dosing 3, Dose 4, containing 290 grams of water, 17.5 grams of a 27% aqueous solution of Emulsifier A, 17.5 grams of a 40% aqueous emulsifier solution of Genapol® X150, 6.8 grams of acrylic acid , 74.5 grams of a 30% aqueous solution of acrylamide, 2.5 grams of a 0.1% aqueous solution of hydroquinone monomethyl ether (HQME), total with a 12.5% aqueous solution of ammonia to a pH of 4.0, started and evenly dosed over a period of 231 minutes. With the start of dosage 3, the rates of doses 1 and 2 were increased to 15 grams / h and metered until 30 minutes after dosing of dosage 3.

After completion of dosages 1 and 2, two post-polymerizations were alternately dosed with 2 grams each of a 15% aqueous solution of t-butyl hydroperoxide and 2 grams of a 10% aqueous solution of sodium isoascorbate, the product cooled to room temperature and the pH adjusted to 6.3 with 12.5% aqueous ammonia solution.

Results

For the examples and comparative examples given, essential data are summarized in Tables 1 to 4:

Table 1 gives essential recipe data; Table 2 contains for the vinyl acetate-ethylene copolymers, the conditions for the dosing start of a N-methylolacrylamide-containing dosage (usually a dosage 4); Table 3 lists essential analytical data for the aqueous polymer dispersions, and Table 4 sets forth the test results for tissue and airlaid nonwovens bonded with these dispersions. Table 1: Essential recipe data

Legend to Table 1:

Column 1: Number of Examples 1 to 16 and Comparative Examples

VI to V12,

Column 2: proportion of ethylene in% by weight of the total monomer,

Column 3: proportion of ethylene used in the original in% by weight of total ethylene,

Column 4: proportion of vinyl acetate in% by weight of the total monomer, Column 5: Proportion of the vinyl acetate used in the template

% By weight of total vinyl acetate,

Column 6: proportion of acrylamide in wt .-% of Gesaratmonoraer,

Column 7: proportion of the acrylamide used in the template

% By weight of total acrylamide,

Column 8: proportion of N-methylolacrylamide in% by weight of the total monomer,

Column 9: proportion of emulsifier in wt .-% of the total monomer,

Column 10: proportion of the emulsifier used in the original in

% By weight of the total emulsifier.

Table 2: Characteristic data for the dosing start DB of a N-methylol acrylamide-containing dosage (usually a dosage 4) for vinyl acetate-ethylene copolymerizations

Legend to Table 2

Column 1: Number of Examples 1 to 16 and Comparative Examples

V4 to VII,

Column 2: time of the start of the reaction t-RB (first exothermic reaction) in minutes after the initiator doses have been started,

Column 3: Dosage time instant t-DB: time of dosing start t-DB of the dosage containing N-methylolacrylamide in minutes after the start of the initiator doses, Column 4: Solids content of the aqueous polymerization mixture in

Ge .-% at time t-DB,

Column 5: Current conversion of monomers Moni at time t-DB, as indicated in section 1.2,

Column 6: Current conversion of ethylene Mon 2 at time t-DB, as indicated in section 1.2,

Column 7: Current conversion of all monomers, UiA, at time t-DB, as indicated in section 1.2,

Column 8: total conversion of all monomers, UiO, at time t-DB, as indicated in section 2.1.

Note: With the exception of Comparative Examples V6 and V10, the current conversion values of columns 5, 6 and 7 correspond to the current actual sales values of the quantities presented in the reactor: column 5 vinyl acetate and other monomers charged except ethylene; Column 6: ethylene; Column 7: all monomers presented.

Table 3: Essential analytical data for the aqueous polymer dispersions

Legend to Table 4:

Column 1: Number of Examples 1 to 16 and Comparative Examples

VI to V12,

Column 2: solids content of the dispersion in% by weight,

Column 3: pH of the dispersion,

Column 4: viscosity of the dispersion in mPas, Column 5: modal value of the volume distribution density function of the particle diameter in nm,

Column 6: proportion of the volume fraction of the particles ^ 900 nm in

Vol. -%

Column 7: Siebrückstand greater than 40 μιτι based on the weight of

Dispersion in ppm,

Column 8: Free formaldehyde content based on the weight of the dispersion in ppm.

Table 4: Test results for bonded tissue and airlaid nonwovens indicated

Legend to Table 4:

Column 1: Number of Examples 1 to 16 and Comparative Examples

VI to V12,

Column 2: dry strength tissue nonwoven in% based on the strength value of comparative example VI, Column 3: wet strength tissue nonwoven in%, based on the strength value of Comparative Example VI,

Column 4: Solvent (isopropyl alcohol) Tissue nonwoven in%, based on the strength value of Comparative Example VI, column 5: free formaldehyde content of the bound tissue

Nonwoven fabric in ppm based on the weight of the bonded nonwoven fabric,

Column 6: Drop of Tissue Bonded Tissue Fleece in Seconds,

Column 7: Dry strength Airlaid nonwoven in% based on the strength value of Comparative Example VI,

Column 8: wet strength Airlaid fleece in% based on the strength value of Comparative Example VI,

Column 9: Free Formaldehyde Content of the Bound Airlaid

Nonwoven fabric in ppm based on the weight of the bonded nonwoven fabric,

Column 10: Water absorption capacity of the bonded airlaid nonwoven in seconds.

discussion of the results

Comparative Examples VI to V3

These comparative examples relate to functionalized styrene-acrylate dispersions.

The different nonwoven strengths for the standard binder according to Comparative Example VI are used here for reference values for all examples and comparative examples and are each defined 100% for Comparative Example VI. The commercial product of Comparative Example C2 provided nonwoven strengths at the level of the standard binder VI, with strengths in the range of ± 15%, ie 85% to 115% compared to VI found. Since the product VI is accepted commercially, strength values of at least 85% based on the strength values of the standard binder VI can be sufficiently defined.

For Comparative Example C3, 0.35% by weight of N-methylolacrylamide (NMA) based on the total monomer was used, resulting in a content of free formaldehyde in the dispersion of greater than 40 ppm, which was significantly higher than the maximum permissible value of 30 ppm free formaldehyde, preferably ^ 25 ppm, in the dispersion. The Ver- Example V3 thus demonstrates that a proportion of 0.35% by weight of NMA in the styrene-acrylate copolymer of Comparative Example V3 can not reach the required maximum limit for free formaldehyde in the dispersion. The nonwoven strength values obtained as a result of using 0.35% by weight of NMA are for V3 on the level of Comparative Example VI, which suggests that no significant increase in nonwoven strength values is achieved by using 0.35% by weight of NMA can.

A disadvantage for Comparative Examples VI to V3 is the clearly too low hydrophilicity of bonded nonwovens, which manifests itself in very high values for the drop inink time on tissue fleece and the clearly too low capacity for airlaid nonwoven. Accordingly, Comparative Examples VI to V3 do not meet the requirements for sufficient hydrophilicity of bonded nonwoven fabrics.

Comparative Examples V4 and V5

These comparative examples relate to vinyl acetate-ethylene (VAE) copolymers without the use of N-methylolacrylamide. With these products, significantly lower wet strengths and solubility of bonded nonwovens were achieved; these strengths reach only 30% to 40% of the strengths of the standard binder VI.

Examples 1 to 5

These examples are based on Comparative Example C4, but now in Dosage 4 proportions of N-methylolacrylamide between 0.29 and 0.59 wt .-%, based on the total monomer, and in consideration of the metering criterion according to the invention were used. Surprisingly, this did not increase the free formaldehyde content in the dispersion above the critical limit of 25 ppm, as was the case for Comparative Example C3. Compared to Comparative Example C4, because of the finding for Comparative Example C3 completely unexpectedly, the wet strengths and solvent strengths were markedly increased and reached the limit values of at least 85% of the strength values based on VI and, in some cases, significantly higher nonwoven strengths specified by the standard binder according to VI as VI. The values for free formaldehyde of the bound Nonwoven fabrics are below the maximum permissible value of ^ 10 ppm, for airlaid nonwoven values were reached ^ 5 ppm.

Advantageously compared to Comparative Example VI also a significantly increased hydrophilicity was achieved at the required level.

Comparative Examples V6 and V7

For the comparative examples V6 and V7, the starting of the NMA-containing metering (metering 4) took place outside the advantageous conversion range UiA of 8 to 50% by weight monomer conversion, the inventive metering criterion is thus not maintained.

For Comparative Example V6, which is based on Example 3, in contrast to Example 3, the NMA-containing dosage was only at a conversion of the monomers UiA of 84.7 wt .-%, based on the weight of the time of NMA dosing start started in the reactor introduced monomers. As a result, significantly lower wet strengths and solvent strengths of only 70 to 80% based on the strength values of the standard binder VI were achieved; these strength values are too low. For Comparative Example C7, which is based on Example 5, unlike Example 5, the NMA-containing dosage (Dosage 4) very shortly after the start of the reaction t-RB, ie shortly after detection of exothermic reaction, ie when the jacket temperature of the reactor begins to decrease Initiation of the reaction was detected 17 minutes after dosing start of the initiator doses 1 and 2 and dosing start for dosing 4 was 20 minutes after initiator doses 1 and 2 had been started. At this time, only 4.5% of the For Comparative Example V7, this unfavorable time of dosing start of the NMA-containing dosage 4 - compared to Example 5 - led to completely changed particle size values with a modal x-mode outside the required range of 140 to 600 nm and too high a sieve residue (grit> 40 μιτι), so that the product of Comparative Example V7 as

Binder for nonwovens is not suitable.

Examples 6 to 10 Example 6 was based on Example 1, but an additional 0.49 wt .-% N- (isobutoxymethyl) acrylamide (IBMA) were used, whereby the wet strength and in particular the solvent resistance of bonded nonwoven fabrics were advantageously further increased.

Examples 7 to 10 were based on Comparative Example C5, but now each 0.29 wt .-% of N-methylolacrylamide were used and the dosing criterion of the invention was taken into account. For example 7, all of the nonwoven strengths determined could be significantly increased compared to comparative example C5, essentially as a result of the low proportion of NMA, and met the requirements set.

For Example 8, starting from Example 7, additionally and advantageously 1.0% by weight of vinyltriethoxysilane was used, whereby in particular the solvent resistance of bonded nonwovens could be significantly increased.

The additional use of 0.50% by weight of N- (isobutoxymethyl) -acrylamide (IBMA) in Example 9, starting from Example 8, again leads to an increase in the nonwoven strength values, in particular the wet strengths being markedly increased and the solvent strengths being increased to a very high extent , Overall, the product according to Example 9 gave the bonded nonwovens overall significantly higher strengths than the standard binder according to VI.

Examples 6 to 9 are also characterized by a particularly low content of free formaldehyde for the bonded nonwoven fabrics of in each case 5 ppm.

Example 10 was based on Example 1 except that a lower amount of ethylene, an increased amount of acrylamide and 0.58% by weight of N-methylolacrylamide were used. Example 10 showed clearly high nonwoven strengths above the level for the standard binder according to VI and, in addition, the required hydrophilicity of the bonded nonwovens at low levels of free formaldehyde required.

For examples 6 to 10, as for examples 1 to 5, the proportion of emulsifier used was <1.0% by weight, based on the total amount of monomer used for the polymerization, the reaction template in each case containing no emulsifier.

Examples 11 to 13 For examples 11 to 13, emulsifiers were used in a proportion of about 2.1 ± 0.2% by weight, based on the total amount of monomers used for the polymerization, with 10 to 15% of the emulsifier fraction being introduced into the reactor master. Lower particle sizes were achieved. For these examples, the proportion of ethylene monomer was varied between about 15 and about 29 wt .-% based on the total monomer.

Overall, the nonwoven strength values achieved for these examples meet the minimum requirement of at least 85% of the strength values of the standard binder according to VI, with the solvent strengths in particular being dependent on the type of emulsifiers used and being correspondingly adjustable. As a result of the selectable fraction for the emulsifier fraction based on the total monomer, these examples resulted in some of the clearly hydrophilic nonwovens.

Comparative Examples V8 and V9

Both comparative examples were based on Example 13.

Comparative Example C8 demonstrates that when using only 0.17% by weight of N-methylolacrylamide, ie less than the NMA contents of 0.23 to 0.65% by weight, based on the total monomer, of the invention, the requirements for nonwoven strengths of at least 85% of the strengths of the standard binder according to VI can no longer be met.

With Comparative Example V9, containing 0.31 wt .-% of N-methylol acrylamide but only 0.12 wt .-% based on the total monomer of acrylamide, so a smaller amount of acrylamide than the invention used according to the proportions of 0.16 up to 4.5% by weight of acrylamide based on the total monomer, the required nonwoven strengths are no longer achievable in all cases. Although the strength values for bonded airlaid nonwoven are just sufficient, for bonded tissue nonwovens the minimum requirements of 85% of the nonwoven strengths of the standard binder according to VI no longer satisfied.

Examples 14 to 16

For examples 14 to 16, in each case copious amounts of 3% by weight of acrylamide and in each case 1.96% by weight of acrylic acid and hydroxyethyl acrylate, in each case based on the total monomer, were used. For Examples 14 and 15 were each 0.56 wt .-% of N-methylolacrylamide and for Example 16, 0.29% by weight of NMA and additionally 0.49% by weight of N- (isobutoxymethyl) acrylamide (IBMA) were used. These examples resulted in products that achieved a high level of nonwoven strength overall, with the high wet strengths for bonded airlaid nonwoven and the high solvent strengths for bonded tissue nonwoven, each with low free formaldehyde values of the bonded nonwoven fabrics of ^ 5 ppm to emphasize.

As for all other examples according to the invention, the NMA-containing metering was started at a monomer conversion UiA of the monomers charged in the reactor in the range from 8 to 50% by weight, based on the weight of all monomers charged, and thus the metering criterion according to the invention was observed. Comparative Example V10

This comparative example corresponds to an example given in DE 4240731 A1 (example 5 there). This comparative example demonstrates that a late metering of N-methylolacrylamide initiated in DE 4240731 A1, in this case at a monomer conversion UiA of 81.2% by weight, based on the total weight of the catalyst, up to the time of commencement of NMA metering into the reactor added monomers, even when using 0.75 wt .-% of NMA, ie more NMA than the inventive proportions of 0.23 to 0.65 wt .-% of NMA based on total monomer, not to the required strength Accordingly, the inventive sales range (dosing criterion) UiA of 8 to 50% by weight is surprisingly decisive for the strength values to be achieved.

The proportions of free formaldehyde are impermissibly high for this comparative example.

Comparative Example VII

This comparative example demonstrates that in Gesamtvorlage all monomers - with the exception of Acrylsäureamide NMA and acrylamide - and initiation with t-butyl hydroperoxide and ascorbic acid, as described for example in US5540987, and failure to comply with the metering criterion according to the invention no finely divided dispersion products with inventively accessible particle proportions dF3 (^ 900 nm) with modal values of the volume distribution density Function of the particle diameter x-mode (most common particle size) can be achieved.

Because of the particle proportions dF3 900 nm) of 67 vol.% And a modal value x-mode of above 3000 nm produced in the present Comparative Example VII, the obtained nonwoven strength values do not reach the required level of at least 85% of the strength value of the standard binder according to VI.

For this comparative example, at the time of starting the metered addition of the acrylamides, immediately after the start of the reaction, t-RB, no determination of the conversion, UiA, was possible: the solids content obtained was practically no different from the calculated solids content of the template without monomer conversion. The dosing criterion according to the invention was therefore not fulfilled. Comparative Example V12

This comparative example relates to a vinyl acetate copolymerization for which no ethylene and no N-methylol-acrylamide was used. There were u.a. 2.84 wt .-% acrylamide and 1.64 wt .-% vinyltriethoxysilane used. At expected low values for the free formaldehyde content for the dispersion and the bonded nonwovens, nonwoven strengths are obtained at the level of the standard binder according to VI and in some cases significantly more. However, since the glass transition temperature of the resulting polymer is well above about 10 ° C, its application results in "hard" bonded nonwoven fabrics with insufficient flexibility.

Claims

Claims:

1. A process for the preparation of vinyl ester-ethylene-acrylic acid amide copolymers in the form of aqueous dispersions by free-radically initiated emulsion polymerization of

(b) 5 to 30% by weight of ethylene,

(c) comprising ethylenically unsaturated amides from the group

(cl) 0.16 to 4.0% by weight of acrylamide,

(c2) 0.23 to 0.65% by weight of one or more N-alkylol

(meth) acrylamides,

(c3) 0 to 0.67% by weight of one or more N- (alkoxymethyl) acrylamides or

N- (alkoxymethyl) methacrylamides,

(d) 0 to 1.5% by weight of one or more ethylenically unsaturated alkoxysilanes, and optionally

(E) one or more other, of the monomers (a) to (d) different, ethylenically unsaturated monomers, wherein the total amounts used in the monomers (a) to (e) add up to 100 wt .-%, characterized that

a total of 0.23 to 0.90 wt .-% of the monomers (c2) and (c3), based on the total weight of the monomers (a) to (e) are used, and

one or more monomers (a) and monomer (b) wholly or teilwei se and optionally monomer (cl) are initially introduced into water and

then the free-radical emulsion polymerization is initiated and

remaining amounts of the monomers (a), (b), (c), optionally (d) and / or optionally (e) are added with the proviso

in that at least 50% by weight of the total monomers (c) used are metered in from a point in time at which the conversion of the monomers re (a) to (e) introduced and / or metered in at that time amounts to 8 to 50% by weight. is (dosing criterion), wherein the emulsion polymerization is carried out in the absence of protective colloids.

Process for the preparation of vinyl ester-ethylene-acrylic acid amide Copolymers according to Claim 1, characterized in that the monomers (a) used are 80 to 100% by weight, based on the total weight of the monomers (a), of vinyl acetate and the vinyl acetate, if appropriate to 5 to 50 wt .-%, based on the total weight of vinyl acetate, in the reactor.

A process for preparing vinyl ester-ethylene-acrylic acid amide copolymers according to claim 1 and 2, characterized in that at least 50 wt .-% of the total monomers used (c2) and (c3) are added from a time to which the conversion of up to 8 to 50 wt.% of monomers (a) to (e) initially charged and / or metered in at this time.

Process for the preparation of vinyl ester-ethylene-acrylic acid copolymers. Interpolymers according to claim 1, 2 or 3, characterized in that no monomer (c2) and / or no monomer (c3) and / or no monomer (d) is initially charged.

A process for the preparation of vinyl ester-ethylene-acrylic acid amide copolymers according to claim 1 to 4, characterized in that 50 to 100 wt .-% of the total monomers used (cl) are added from a time to which the sales of submitted to that time and / or dosed monomials re (a) to (e) 8 to 50 wt .-% is.

A process for the preparation of vinyl ester-ethylene-acrylic acid amide copolymers according to claim 1 to 5, characterized in that 90 to 100 wt .-% of the total monomers used (c2) are added from a time to which the sales submitted to that date and / or dosed monomials re (a) to (e) 8 to 50 wt .-% is.

7. Process for the preparation of vinyl ester-ethylene-acrylamide copolymers according to Claims 1 to 6, characterized net, that 90 to 100 Ge .-% of the total monomers used (c3) are added from a time at which the conversion of the previously submitted to and / or added monomers (a) to (e) 8 to 50 Ge. -% is.

A process for the preparation of vinyl ester-ethylene-acrylamide copolymers according to claim 1 to 7, characterized in that at least 50 wt .-% of the total monomers used (c) are added from a time to which the sales submitted to that date and / or metered monomers consisting of vinyl ester (a), amides (c), optionally alkoxysilanes (d) and optionally monomers (e), 13 to 50 wt .-%, based on the sum of up to this time submitted or added Monomer amounts (a) to (e), is.

A process for the preparation of vinyl ester-ethylene-Acrylsäureamid- copolymers according to claim 1 to 8, characterized in that no emulsifier is introduced.

A process for the preparation of vinyl ester-ethylene-acrylamide copolymers according to claim 1 to 9, characterized in that 0.5 to 1.5 wt .-% based on the total weight of the monomers (a) to (e) of one or more monomers (D) are used and optionally metered in total, wherein the pH is preferably adjusted to pH ^ 6 after completion of the polymerization.

Vinyl ester-ethylene-acrylic acid amide copolymers in the form of aqueous dispersions obtainable according to claims 1 to 10.

Use of the process products of claims 1 to 10 for bonding nonwoven fabrics, as adhesives, as an additive for adhesives or as an additive for coating compositions.