DE19935624A1 - Laminating adhesive for high-gloss foil lamination contains an aqueous dispersion of a UV-crosslinkable polymer with a polymer-bonded benzophenone derivative as photoinitiator - Google Patents

Abstract

Laminating adhesive containing an aqueous dispersion of a UV-crosslinkable polymer. Independent claims are also included for (a) a process for the large-area lamination of a UV-transparent film with another substrate, in which the claimed adhesive is applied to at least one of the substrates which are then brought together and irradiated with UV light through the transparent film; (b) laminates obtained by this process; (c) aqueous polymer dispersions of UV-crosslinkable polymer containing 0.1-15 wt% radically copolymerisable photoinitiator.

Description

The invention relates to laminating adhesives containing one aqueous dispersion of a polymer, which by UV radiation can be networked. In the case of glossy film lamination, two-component essential polyurethane solutions or chemically cross-linking aqueous solutions Dispersions used as an adhesive. The work process with The adhesive system works as follows: First, the gloss fo lie, usually oriented polypropylene OPP or poly acetate coated with the liquid adhesive. Then the Glue dried and then the coated film under pressure and heat on the substrate, usually a be printed cardboard laminated. The laminate so produced is in of the further processing often grooved or embossed. To nut or To be embossed, the adhesive layer must withstand these deformations withstand the laminate, in the groove or in the embossing points, the glossy film must not come off the substrate. Around To ensure this, the adhesive systems are usually chemically cross-linked. Since the Ver network systems take time to achieve the necessary cohesion in the The manufactured lamination must build up an adhesive layer be stored for a few hours before being grooved or can be shaped. This interim storage will increase Mend felt disadvantageous because it delayed the on order processing mean.

Chemically cross-linking polymer dispersions for the gloss films lamination are e.g. B. from EP-A-35165 or EP-A-644902 known.

UV-crosslinkable polymers and their use as adhesives are e.g. B. known from EP 377199.

The object of the present invention was therefore laminating adhesive fabrics which, after lamination, give the allow processing of the laminates; they must continue Laminating adhesives adhere well to the substrates and have the highest possible cohesion in the adhesive layer. Wei The laminating adhesives should also be transparent and free of Ko agulate, resistant to aging, lightfast and low-foaming.

Accordingly, the laminating adhesives and found their use particularly in glossy film lamination the.  

The laminating adhesive according to the invention contains as a binder an aqueous dispersion of a polymer, which by UV radiation is networkable.

For this purpose, the laminating adhesive preferably contains a photo initia goal. By irradiation with high-energy light, especially UV Light causes the photoinitiator to crosslink the polymer, preferably by a chemical grafting reaction of the photoinitia tors with a spatially adjacent polymer chain. In particular can be crosslinked by inserting a carbonyl group of Fo toinitiators in a neighboring C-H bond under formation a -C-C-O-H grouping.

The laminating adhesive preferably contains 0.0001 to 1 mol, be particularly preferably 0.0002 to 0.1, very particularly preferably 0.0003 up to 0.01 mol of the photoinitiator, or the act as a photoinitiator seed molecular group, per 100 g of polymer.

The photo initiator is e.g. B. to acetophenone, benzoin ethers, benzyl dialkyl ketols or their derivatives.

The photoinitiator is preferably bound to the polymer.

It is particularly preferably a photo initiator, wel by radical copolymerization into the polymer chain is built. For this purpose, the photoinitiator preferably contains one Acrylic or (meth) acrylic group.

Suitable copolymerizable photoinitiators are acetophenene or benzophenone derivatives, which have at least one, preferably contain an ethylenically unsaturated group. In the ethylenically unsaturated group is preferably an acrylic or methacrylic group.

The ethylenically unsaturated group can be attached directly to the phenyl ring of the acetophenone or benzophenone derivative. in the general is between phenyl ring and ethylenic unsaturated group a spacer group (spacer).

The spacer group can e.g. B. contain up to 100 carbon atoms.

Suitable acetophenone or benzophenone derivatives are e.g. B. in EP-A-346 734, EP-A-377199 (1st claim), DE-A-40 37 079 (1st claim) and DE-A-38 44 444 (1st claim) described and are by this reference also in the present application. Preferred acetophenone and benzophenone derivatives are those of the formula

wherein R ^{1 is} an organic radical having up to 30 C atoms, R ^{2 is} an H atom or a methyl group and R ^{3 is} an optionally substituted phenyl group or a C ₁ -C ₄ alkyl group.

R ¹ particularly preferably represents an alkylene group, in particular a C ₂ -C ₈ alkylene group.

R ³ particularly preferably represents a methyl group or a phenyl group.

The polymer is preferably composed of free-radically polymeric sizable compounds (monomers).

The polymer preferably consists of at least 40% by weight, especially preferably at least 60% by weight, very particularly preferably at least 80% by weight of so-called main monomers.

The main monomers are selected from C ₁ -C ₂₀ alkyl (meth) acrylates, vinyl esters of carboxylic acids containing up to 20 C atoms, vinyl aromatics with up to 20 C atoms, ethylenically unsaturated nitriles, vinyl halides, vinyl ethers from 1 to 10 C Alcohols containing atoms, aliphatic hydrocarbons with 2 to 8 carbon atoms and 1 or 2 double bonds or mixtures of these monomers.

To mention are z. B. (meth) acrylic acid alkyl ester with a C ₁ -C ₁₀ alkyl radical, such as methyl methacrylate, methyl acrylate, n-butyl acrylate, ethyl acrylate and 2-ethylhexyl acrylate.

In particular, mixtures of the (meth) acrylic acid alkyl esters suitable.

Vinyl esters of carboxylic acids with 1 to 20 carbon atoms are e.g. B. Vinyl laurate, stearate, vinyl propionate, vinyl versatic acid and vinyl acetate.  

The vinyl aromatic compounds are vinyl toluene a- and p-Me thylstyrene, a-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and preferably styrene. Examples of nitriles are Acrylonitrile and methacrylonitrile.

The vinyl halides are substituted with chlorine, fluorine or bromine ethylenically unsaturated compounds, preferably vinyl chloride and Vinylidene chloride.

Examples of vinyl ethers include B. vinyl methyl ether or vinyl isobutyl ether. Vinyl ether of 1 to 4 carbon atoms is preferred keeping alcohols.

As hydrocarbons with 2 to 8 carbon atoms and two olefinic Double bonds are butadiene, isoprene and chloroprene.

Preferred main monomers are the C ₁ to C ₁₀ alkyl acrylates and methacrylates, in particular C ₁ to C ₈ alkyl acrylates and methacrylates, the acrylates being particularly preferred in each case.

Methyl acrylate, ethyl acrylate and n-Bu are very particularly preferred tyl acrylate, n-hexyl acrylate, octyl acrylate and 2-ethyl hexyl acrylate as well as mixtures of these monomers.

In addition to the main monomers, the polymer can ent ent other monomers hold, e.g. B. monomers with carboxylic acid, sulfonic acid or Phosphonic acid groups. Carboxylic acid groups are preferred. Called be z. As acrylic acid, methacrylic acid, itaconic acid, maleic acid or fumaric acid.

Other monomers are e.g. B. also hydroxyl-containing monomers, in particular C ₁ -C ₁₀ hydroxyalkyl (meth) acrylates, (meth) acrylamide.

Phenyloxyethyl glycol are also further monomers mono- (meth) acrylate, glydidyl acrylate, glycidyl methacrylate, Amino (meth) acrylates such as 2-aminoethyl (meth) acrylate called.

Monomers that are functional other than the double bond Wear groups, e.g. B. isocyanate, amino, hydroxy, amide or Glycidyl, e.g. B. improve the adhesion to substrates.

The glass transition temperature of the polymer is preferably below 60 ° C, in particular it is -50 to + 60 ° C, particularly preferred -30 to + 40 ° C and very particularly preferably -30 to + 20 ° C.  

The glass transition temperature of the polymer can be reduced usual methods such as differential thermal analysis or differential Scanning calorimetry (see, for example, ASTM 3418/82, so-called "midpoint temperature ").

The polymer is preferably produced by Emul sion polymerization, it is therefore an emulsion poly merisat.

However, the manufacture can e.g. B. also by solution poly merization and subsequent dispersion in water.

In emulsion polymerization, ionic and / or not ionic emulsifiers and / or protective colloids or stabilizers used as surfactant compounds.

A detailed description of suitable protective colloids can be found in Houben-Weyl, Methods of Organic Chemistry, Volume XIV / 1, Macromolecular Substances, Georg-Thieme-Verlag, Stuttgart, 1961, pp. 411 to 420. Both anionic and cationic come as emulsifiers nonionic emulsifiers are also considered. Preference is given to using emulsifiers as accompanying surfactants, the molecular weight of which, in contrast to the protective colloids, is usually below 2000 g / mol. Of course, if mixtures of surface-active substances are used, the individual components must be compatible with one another, which can be checked with a few preliminary tests if in doubt. Anionic and nonionic emulsifiers are preferably used as surfactants. Common accompanying emulsifiers are e.g. B. ethoxylated fatty alcohols (EO grade: 3 to 50, alkyl radical: C ₈ - to C ₃₆ ), ethoxylated mono-, di- and tri-alkylphenols (EO degree: 3 to 50, alkyl radical: C ₄ - to C ₉ ), Alkali metal salts of dialkyl esters of sulfosuccinic acid and alkali and ammonium salts of alkyl sulfates (alkyl radical: C ₈ - to C ₁₂ ), of ethoxylated alkanols (EO grade: 4 to 30, alkyl radical: C ₁₂ - to C ₁₈ ), of ethoxylated Alkylphenols (EO grade: 3 to 50, alkyl radical: C ₄ - to C ₉ ), of alkyl sulfonic acids (alkyl radical: C ₁₂ - to C ₁₈ ) and of alkylarylsulfonic acids (alkyl radical: C ₉ - to C ₁₈ ).

Other suitable emulsifiers are compounds of the general formula II

wherein R ⁵ and R ^{6 are} hydrogen or C ₄ - to C ₁₄ -alkyl and are not simultaneously hydrogen, and C and Y can be alkali metal ions and / or ammonium ions. R ⁵ , R ^{6 are} preferably linear or branched alkyl radicals having 6 to 18 carbon atoms or hydrogen and in particular having 6, 12 and 16 carbon atoms, where R ⁵ and R ^{6 are} not both hydrogen at the same time. X and Y are preferably sodium, potassium or ammonium ions, with sodium being particularly preferred. Compounds II in which X and Y are sodium, R ^{5 is} a branched alkyl radical having 12 C atoms and R ^{6 is} hydrogen or R ⁵ are particularly advantageous. Technical mixtures are frequently used which have a proportion of 50 to 90% by weight of the monoalkylated product, for example Dowfax® 2A1 (trademark of the Dow Chemical Company).

Suitable emulsifiers can also be found in Houben-Weyl, Methods der organic chemistry, volume 14/1, macromolecular substances, Georg Thieme Verlag, Stuttgart, 1961, pages 192 to 208.

Trade names of emulsifiers are e.g. B. Dowfax®2 A1, Emulan® NP 50, Dextrol® OC 50, Emulsifier 825, Emulsifier 825 S, Emulan® OG, Texapon® NSO, Nekanil® 904 S, Lumiten® I-RA, Lumiten E 3065, Dis ponil FES 77, Lutensol AT 18, Steinapol VSL, Emulphor NPS 25.

The surfactant is usually used in amounts of 0.1 to 10 wt .-%, based on the monomers to be polymerized used.

Water-soluble initiators for emulsion polymerization are e.g. B. ammonium and alkali metal salts of peroxidic sulfuric acid, e.g. As sodium peroxodisulfate, hydrogen peroxide or organic Peroxides, e.g. B. tert-butyl hydroperoxide.

So-called reduction oxides are particularly suitable tion (Red-Ox) initiator systems.  

The Red-Ox initiator systems usually consist of at least one inorganic reducing agent and an inorganic or orga African oxidizing agent.

The oxidation component is e.g. B. the already Above initiators for emulsion polymerization.

The reduction components are e.g. B. Alkali metal salts of sulfurous acid, such as. B. sodium sulfite, Sodium hydrogen sulfite, alkali salts of disulfuric acid such as Sodium disulfite, bisulfite addition compounds more aliphatic Aldehydes and ketones such as acetone bisulfite or reducing agents such as Hydroxymethanesulfinic acid and its salts, or ascorbic acid. The Red-Ox initiator systems can be more soluble when used Metal compounds, their metallic component in several people skill levels can be used.

Common Red Ox initiator systems are e.g. B. Ascorbic acid / egg sen (II) sulfate / sodium peroxydisulfate, tert-butyl hydroperoxide / Na trium disulfite, tert-butyl hydroperoxide / Na hydroxymethanesulfine acid. The individual components, e.g. B. the reduction component, can also be mixtures z. B. a mixture of sodium salt of hydroxymethanesulfinic acid and sodium disulfite.

The compounds mentioned are mostly in the form of aqueous solutions used, the lower concentration by the in the Dis persion acceptable amount of water and the upper concentration by determines the solubility of the compound in question in water is. The concentration is generally 0.1 to 30% by weight, preferably 0.5 to 20% by weight, particularly preferably 1.0 to 10 wt .-%, based on the solution.

The amount of initiators is generally 0.1 to 10 wt .-%, preferably 0.5 to 5 wt .-%, based on the polyme rising monomers. Several different In itiators are used in emulsion polymerization.

Regulators can be used in the polymerization, e.g. B. in Amounts from 0 to 0.8 parts by weight, based on 100 parts by weight of the monomers to be polymerized, by means of which the molecular weight is reduced becomes. Are suitable for. B. Compounds with a thiol group such as tert-butyl mercaptan, ethyl thioglycolic acid ester, mercaptoe thynol, mercaptopropyltrimethoxysilane or tert-dodecylmercap tan. The proportion of these controllers can be used as Adhesive for composite film lamination, in particular 0.05 to 0.8 parts by weight, preferably 0.1 to 0.5 parts by weight, based on 100 parts by weight of the monomers to be polymerized. in the  If used as an adhesive for glossy film lamination the use of a controller is less preferred. The controllers do not contain polymerizable, ethylenically unsaturated Group. The regulators stop the polymerization chain and are therefore terminally bound to the polymer chains.

The emulsion polymerization usually takes place at 30 to 130, preferably 50 to 90 ° C. The polymerization medium can both only from water, as well as from mixtures of water and thus miscible liquids such as methanol exist. Preferably only water is used. The emulsion polymerization can be both Batch process as well as in the form of a feed process Lich step or gradient style. The feed process is preferred, in which one part of the bottom submitted to the polymerization temperature heated, polymerized and then the rest of the polymer risk approach, usually over several spatially separated Inlets, one or more of which are in pure monomer or contained in emulsified form, continuously, in stages or by superimposing a concentration gradient under Auf maintenance of the polymerization of the polymerization zone leads. In the polymerization z. B. for better Setting the particle size a polymer seed can be submitted.

The way in which the initiator in the course of the radika Mix aqueous emulsion polymerization the polymerization vessel is added is known to those of ordinary skill in the art. It can both completely placed in the polymerization vessel, as well according to its consumer in the course of radical aqueous emulsion polymerization continuously or in stages be used. In particular, this depends on the chemical Na structure of the initiator system and of the polymerization temperature from. A part is preferably presented and the rest after Provided the consumption of the polymerization zone.

To remove the residual monomers is usually also after End of actual emulsion polymerization, d. H. after one Conversion of the monomers of at least 95%, initiator added.

The individual components can the reactor in the feed process from above, in the side or from below through the reactor floor are given.

In the emulsion polymerization, aqueous dispersions of the Polymers usually with solids contents of 15 to 75% by weight, preferably from 40 to 75% by weight.  

For a high space / time yield of the reactor are dispersions preferred with the highest possible solids content. At feast to be able to achieve substance contents of <60% by weight, one should or adjust the polymodal particle size, otherwise the viscosity becomes too high and the dispersion is no longer manageable. The Generation of a new generation of particles can, for example by adding seeds (EP 81083), by adding excess Emulsifier amounts or by adding mini emulsions. Another advantage with the low viscosity at high Solid content is accompanied by the improved coating process keep at high solids contents. The creation of a new / new one Particle generations can occur at any time respectively. It depends on the for a low viscosity desired particle size distribution.

The polymer is in the form of its aqueous dispersion used.

The dispersion is used as a laminating adhesive for gluing large flat substrates, d. H. for the production of laminates, used.

The laminating adhesives according to the invention can only from the aqueous dispersion of the polymer and the photoinitiator exist, they can contain other additives, e.g. B. wetting agents, ver thicker, protective colloids, light stabilizers, biocides, Tackifier, plasticizer included.

The laminating adhesive according to the invention does not require the addition of crosslinkers, other reactive components or mixture compos the desired properties, especially the ge wanted to achieve cohesion.

As substrates to be glued are z. B. polymer films, especially made of polyethylene, oriented polypropylene, poly amide, polyethylene terephthalate, cellulose acetate, cellophane, with me tall (e.g. aluminum-coated (vapor-deposited) polymer film (short: metallized foils)) or paper, cardboard or Metal foils, in particular made of aluminum. The slides mentioned can also z. B. be printed with printing inks.

The laminating adhesive is strat on at least one large-area substrate, preferably with a layer thickness of 0.1 to 20, particularly preferably 2 to 15 g / m ² . B. applied by knife, brush, etc.

At least one of the two substrates to be bonded should be transparent to high-energy light, especially UV light.

Preferably after drying or venting the dispersion water (for example after 1 to 60 seconds), the coated substrate can then be laminated with a second substrate. B. 20 to 200, preferably 20 to 70 ° C and the pressure z. B. 1 to 30, preferably 3 to 20 N / m ² .

The adhesive-coated sub is preferably strat around a transparent polymer film.

The polymer or the dispersion is preferably used as an adhesive used for glossy film lamination.

With glossy film lamination, paper or cardboard are included glued transparent polymer films. The papers or boxes can be printed.

The laminating adhesive layer can be applied directly after the gluing through the transparent film with high-energy light, which triggers the crosslinking reactions of the photoinitiator group, be be radiant.

It is preferably UV light. For UV radiation commercially available medium pressure mercury lamps or La be used that emit in the UV range.

The radiation energy can e.g. B. 200 mJ / cm ² to 1500 mJ / cm ² be irradiated area.

Immediately after the irradiation, further processing, e.g. B. grooving or embossing the laminated substrates, for. B. the with Foil-laminated cartridge made. There is no longer any waiting time required.

With the laminating adhesive according to the invention, substrate ver bundles with high adhesive strength, also in the area of grooves or Get embossing and high transparency and high gloss.

Examples A) Preparation of polymer dispersions

The production is carried out according to the following general regulation:
The initial charge (250 g of water and 3 g of a styrene seed (33%) with an average particle diameter of 30 nm) was heated to an internal temperature of 85 ° C. and 5% feed 2 was introduced. After 10 min. Waiting period, inlet 1, which contains the monomers, and inlet 2 were started.

Feed 2 consisted of 3.0 g of sodium peroxodisulfate dissolved in 39.9 g Water. The composition of feed 1 is given in Table 1 give.

Feed 1 and 2 were metered in in 3 h and after 0.5 h polymerized.

Table 1

Composition of the polymers in parts by weight

The amount of initiator (sodium peroxodisulfate) was 0.3 part by weight, 0.4 part by weight of Dowfax 2A1 and 0.6 parts by weight of Lumiten IRA, based on those indicated in the table Given parts by weight of monomers used.

Abbreviations and explanations

Dowfax 2A1

Lumiten IRA

EHA: 2-ethylhexyl acrylate
BA: n-butyl acrylate
MA: methyl acrylate
MMA: methyl methacrylate
AS: acrylic acid
FI: copolymerizable benzophenone with acrylic group

B) glossy film lamination Gloss film lamination with cardboard (Cromoduplex cardboard) and poly propylene (pre-treated with corona) and with cardboard and Celluloseace deed

The pretreated side of the polypropylene film (PP) was with Adhesive coated. After drying with cold air, the Cardboard placed on and rolled up with a laboratory lamination roll. The tailored laminations were pressed in the roller press.

Thereafter, it was irradiated directly with UV light. The laminated samples were grooved one hour after irradiation (with 500 mJ or 1000 mJ / cm ² ) and the groove was assessed visually:

Grading

1 groove is completely fine
2 The groove is slightly open at certain points
3 The groove is clearly open at individual points
4 The groove is completely open

Table 2

Results

Claims (11)

1. Laminating adhesives containing an aqueous dispersion of a Polymers that can be cross-linked by UV radiation. 2. Laminating adhesives according to claim 1, wherein the laminating adhesive substance contains from 0.0001 to 1 mol per 100 g of polymer a photo initiator, which when irradiated with high-energy Light causes a crosslinking reaction. 3. Laminating adhesive according to claim 2, wherein the photoinitiator is bound to the polymer. 4. Laminating adhesives according to one of claims 1 to 3, wherein the photoinitiator is a benzophenone or benzo phenone derivative. 5. Laminating adhesives according to one of claims 1 to 4, wherein the polymer has a glass transition temperature of -50 to + 40 ° C Has. 6. Use of the laminating adhesive according to one of the claims 1 to 5 for glossy film lamination. 7. Process for large-area gluing of a UV-permeable Foil with a further substrate, characterized in that that a laminating adhesive according to one of claims 1 to 5 is applied to at least one of the substrates which Substrates are glued and then the UV light passes sige film is irradiated with UV light. 8. The method according to claim 7, characterized in that it the other substrate is paper or cardboard. 9. Substrate composites, obtainable by a method according to An say 7 or 8. 10. Aqueous polymer dispersions containing one by UV radiation lung cross-linkable polymer, which as a structural component 0.1 up to 15% by weight of a radically copolymerizable photoini has tiators.   11. Aqueous polymer dispersions according to claim 10, wherein the photoinitiator is one of the formula
where R ^{1 stands} for an organic radical with up to 30 C atoms, R ² for a H atom or a methyl group and R ³ for an optionally substituted phenyl group or a C ₁ -C ₄ alkyl group,
acts.