CA1152664A

CA1152664A - Coating compositions

Info

Publication number: CA1152664A
Application number: CA000324155A
Authority: CA
Inventors: Wilhelm Thoma; Gerhard Berndt; Josef Pedain; Walter Schroer; Waldemar Kling
Original assignee: Bayer AG
Current assignee: Bayer AG
Priority date: 1978-04-01
Filing date: 1979-03-26
Publication date: 1983-08-23
Also published as: DE2814173A1; US4308184A; DE2814173C2

Abstract

ABSTRACT OF THE DISCLOSURE
The present disclosure is concerned with solvent free or very low solvent coating compositions suitable for use on flexible sheet form substrates particularly textile substrates. The composition comprises a ure-thane group-containing prepolymer with OH or CONH2 terminal groups mixed with a urea or melamine formalde-hyde resin and a stable aqueous polymer dispersion or solution. The composition may also contain small amounts of an organic solvent. The coating can be applied to the substrate by direct or reverse coating techniques.

Description

~i2664 Mo-1945 LeA 18,790 COATING COMPOSITIONS
FIELD OF THE INVENTION
This invention relates to compositions cross-linkable by heating to form polyurethane plastics for coating substrates, preferably textile sheet-form materials, in particular by the reverse coating process.
For ecological and economic reasons, the coating compo-sitions are free from organic solvent or contain at most ~10 % by weight of organic solvent. They consist essen-:10 tially of linear and/or branched urethane-group-containing prepolymers having terminal OH- and/or CO-NH2- and/or ketoxime-urethane groups, aqueous dispersions of urethane polymers, vinyl polymers and/or diene polymers and/or aqueous polymer solutions and of urea and/or melamine formaldehyde resins as latent crosslinkers. The chain-extending or crosslinking reaction takes place at an elevated temperature in a coating tunnel after the coating has been applied to a substrate.
BACKGROUN~ OF THE INVENTION
It has long been known that textile materials, such as woven fabrics, knitted fabrics or non-woven fabrics, can be coated with solutions of polyurethanes by the direct or reverse coating process for the purpose of producing artificial leather and similar products.
LeA 18,790 The coating solutions may contain either urethane pre-polymers, which are reacted with polyfunctional cross-linking agents in order to establish their final plastic properties and product qualities (so-called two-component polyurethanes), or high-polymer polyurethanes which already have all their plastic properties (so-called one-component polyurethanes). The coatings thus ob-tained are used for the production of outer clothing, purses and handbags, shoe upper material, awnings, blinds, upholstered goods and many other articles.
It is known from German Offenlegungsschrift No.

2,431,846 that polyurethanes can be processed from solu-tion in a mixture of water and a single organic solvent, for example dimethyl formamide, in order to enable the solvent to be recovered and recycled for ecological and economic reasons. It is also known (German Offenlegungs-schrift Nos. 1,770,068 and 2,314,512) that coatings can be produced from ionic or non-ionic polyurethane dis-persions which are thickened with water-soluble or water-swellable polymers to establish the viscosity requiredfor spreading.
German Offenlegungsschrift No. 2,448,133 describes the coating of textiles using reactive polyurethane sys-tems which are free from volatile solvents, such as di-methyl formamide, methylethyl ketone, toluene, etc., butinstead contain, for example, PVC plasticizers of the phthalic acid ester type. The advantage of reactive systems such as these lies in the absence of conventional solvents. This advantage, however, is offset by the pres~nce of PVC plasticizers which effloresce or exude from the coatings and make the coated articles sensitive to dry cleaning. In one particular process of this type (US Patent No~ 3,~55,261), complex salts of 4,4'-diaminodiphenyl methane are dispersed as latent cross-LeA 18,~90 6i6 ~

linkers in PVC plasticizers. The disadvantage of this process lies particularly in the toxic properties of 4,4'-diaminodiphenyl methane. Another serious dis-advantage of conventional solvent-free PUR-reactive systems lies in the deep penetration of the coating composition into the textile substrate, resulting in the formation of coated articles having a hard feel and an unattractive grain.
According to the prior art (US Patent No.

3,228,820), this disadvantage is partly obviated by the addition of thixotropic agents based on finely disperse silica. Apart from the considerable amount of energy required for dispersion, however, it is also generally necessary where this procedure is adopted to add organic solvents for adjusting the necessary working viscosity.
SUMMARY OF THE INVENTION
Accordingly, the present invention relates to coating compositions comprising:
a) from about 50 to 95 % by weight, preferably from about 60 to 85 %, by weight of an optionally branched urethane-group-containing prepolymer having an average molecular weight of from about 500 to 25,000, preferably from about 2000 to 10,000 and, with particular preference, from about 3000 to 8000 and which is ionic group free and contains from about 2 to 8, preferably from about 2 to 4, and, with particular preference 2 or 3 terminal OH-and/or CONH2- and/or ketoxime-urethane groups , b) from about 2 to 20~ by weight, preferably from about 5 to 15 ~ by weight, of a urea- and~or melamine-formaldehyde resin, LeA 18,790 ~,~

~5~G~

c) from about 3 to 50 ~ by weight, preferably from about 10 to 30 % by weight, of a stable aqueous polymer dispersion and/or aqueous polymer solu-tion having a solids content of from about 20 to 70 % by weight, preferably from about 30 ~o 50 %
by weight and, with particular preference, around 40 % by weight, and d) from about 0 to 10 % by weight, preferably from about 0 to 6 % by weight of an organic solvent.
According to the present invention, coating compositions which are completely free from organic solvents are particularly preferred. The concentra-tions of the polymer dispersion or solution are generally selected in such a way that the coating composition con-tains from about 1 to 25% by weight, preferably from about 5 to 15 % by weight, of the polymer and from about 2 to 30 % by weight, preferably from about 10 to 25 %
by weight, of water.
The present invention also relates to a process for coating substrates in which a coating composition based on a reactive system of a urethane-group-containing polymer and a urea-formaldehyde and/or melamine-formalde-hyde resin is applied to the substrate by the direct or reverse coating process and is hardened while shaping or forming, characterized in that the compositions accord-ing to the present invention are used for coating and are hardened by heating the coated substrate to a temper-ature of from about 110 to 180C, preferably to a temper-ature of from about 140 to 160C.
DETAILED DESCRIPTION OF THE INVENTION
It may be regarded as surprising that the pre-polymers, which are generally incompatible with pure water, can be mixed with aqueous polymer dispersions and/or aqueous polymer solutions up to a ratio by weight heA 18,790 ~5Z6~

of about 1:1 to form stable emulsions which retain their spreadability and their uniform levelling over prolonged periods. In addition, the film-forming capacity of the pastes thus obtained is also distinctly improved.
It is particularly surprisin~ that the coating pastes according to the present invention do not pene-trate into textile substrates. As already mentioned, this penetration of the coating compositions into the textile in conventional processes leads to a hard feel, 0 poor grain and weak adhesion of the coated articles.
The urethane prepolymers containing terminal OH- and/or CONH2- and/or ketoxime-urethane groups (component a of the coating compositions according to the present invention) are obtained from l:near or branched compounds containing from about 2 to 8, pre--ferably from about 2 to 4 and, with particular preference, 2 or 3 hydroxyl groups (for example hydroxy polyesters, but particularly hydroxy polyethers) and having molecular weights of from about 400 to 10,000, more particularly from about 1000 to 4000, and an excess of aromatic and/or cycloaliphatic and/or aliphatic polyisocyanates and the following alkanolamines (~) and/or hydroxy carbazinic acid esters (B) and/or hydroxy carboxylic acid hydrazides (C) and/or hydroxy carbamic acid esters (D) and/or hydroxy carboxylic acid amides (E) and/or aminocarboxylic acid amides (F) and/or ammonia and/or urea and/or ketoximes (G):
A) HN-R-OH
R' B) H2N-NH-COO-R-OH
C) H2N-NH-CO-R"-OH
D) HO-R-OCO-NH2 E) HO-R"-CO-NH
LeA 18,790 ~152664 F) H N-R"-CO-NH

R"' G) HO-N=C
\ R~.~
In formulae A) to G) above, R represents an optionally branched alkylene radical containing from 2 to 6, preferably 2 or 3 carbon atoms;
R' represents hydrogen, -R-OH or an alkyl radical containing frorn 1 to 6, referably 1 or 2, carbon atoms;
10 R" represents an optionally branched alkylene radical containing from 1 to 10, preferably from 3 to 5 carbon atoms; and R"' and R'-' represent Cl-C6, preferably Cl-C4-alkyl radiCalS~ C6~cl0~ preferably C6-aryl radicals or R"' and R"" together represent an alkylene radical containing from 4 to 10 carbon atoms, preferably 4 or 5 carbon atoms.
An NCO/OH-equivalent ratio of from about 1.3:1 to 2.5:1 is preferably maintained in the synthesis of the prepolymers, and NCO/OH-equiYalent ratio of from about 1.8:1 to 2.1:1 being particularly preferred, so that the terminally modified urethane prepolymers contain from about 0.3 to 6.0 % by weight, preferably from about 1.0 to 3.0 % by weight of terminal OH-groups and/or from about 0.6 to 10.0 % by weight, preferably from about 1.2 to 5.0 % by weight of terminal CONH2-groups and/or from about 2.0 to 40.0 % by weight, preferably from about 5.0 to 20.0 % by weight of terminal ketoxime-urethane groups.
LeA 18,79a According to the present invention, terminal "ketoxime-urethane" groups are groups corresponding to the following general formula:

R~
-NH-C-O-N=C
O R"l' The polyesters and/or polyethers used for producing the urethane prepolymers are made up of known units, such as dialcohols and trialcohols, di-carboxylic and tricarboxylic acids, hydroxy carboxylic acids, lactones, ethylene oxide, 1,2-propylene oxide, 1,2-butylene oxide or tetrahydrofuran or mixtures thereof.
It is preferred to use polyethers and polyesters having a melting point below about 40C, polyethers and poly-esters having a melting point below about 20C being particularly preferred.
Polyhydroxyl compounds suitable for use in the production of the coating compositions according to the present invention are described in detail in German Offenlegungsschrift Nos. 2,431,846 and 2,402,840 (US Patent No. 3,984,607) and in German Auslegeschrift No. 2,457,387 (US Patent No. 4,035,213). Polyisocyanates suitable for use in the production of the urethane pre-polymers containing terminal OH- and/or CONH2- and/or ketoxime-urethane groups are also described in detail in these publications.
Suitable alkanolamines (A) are inter alia ethanolamine, N-methyl ethanolamine, 1,2-propanolamine, 1,3-propanolamine, N-methyl-1,2-propanolamine, diethanol-amine and 1,2- or 1,3-dipropanolamine; suitable hydroxy carbazinic acid esters IB) are, for example hydroxyethyl carbazinic acid esters and 2- or 3-hydroxy carbazinic LeA 18,790 6~4 propyl esters; suitable hydroxy hydrazides (C) are glycolic acid hydrazide, lactic acid hydrazide, y-hydroxybutyric acid hydrazide, ~-hydroxyvaleric acid hydrazide, ~-hydroxy caproic acid hydrazide and others. Terminal CONH2-groups are obtained in the prepolymers with inter alia hydroxy urethanes (D), such as hydroxyethyl urethane, 2- or 3-hydroxy propyl urethane and others; hydroxyamides (E), such as glycolic acid amide, lactic acid ami~e, y-hydroxybutyric acid amide, ~-hydroxy valeric acid amide, ~-hydroxy caproic acid amide and others; aminoamides (F) such as ~lycine amide, ~-alanine am~ide, y-aminobutyric acid amide, ~-aminovaleric acid amide, ~-aminocaproic acid amide and others; also ammonia and urea.
In the production of the prepolymers containing terminal ketoxime-urethane groups, masking agents used for the NCO-groups of t~e prepolymers are inter alia ketoximes of hydroxylamine and ketones such as acetone, methylethyl ketone, diethyl ketone, methyl propyl ketone, methyl-isopropyl ketone, methylisobutyl ketone, cyclo-hexanone, acetophenone or benzophenone.
According to the present invention, it is par-ticularly preferred to use prepolymers of diethylene glycol adipates and/or polyhydroxy propylene glycol ethers, tolylene diisocyanate or isophorone diisocyanate and 1,2-hydroxypropyl urethane and/or 1,2-hydroxypropyl carbazinic acid esters or methylethyl ketoxime (butanone oxime).
The coating pastes according to the present in-vention, preferably coupling coat pastes contain fromabout 3 to 50 % by weight of aqueous polymer dispersions and/or aqueous polymer solutions. Suitable polymer dis-persions are, for example, aqueous polyurethane disper-sions, aqueous latices of homopolymers and copolymers of LeA 18,790 vinyl monomers and, optionally, dienes and also aqueous dispersions of nitrocellulose solutions of the type known from the dressing of leather.
The polyurethane dispersions may contain anionic, cationic or non-ionic dispersion centers and, optionally, even external emulsifiers.
Suitable PUR-dispersions are described, for example, by D. Dieterich et al in J. Oil Col. Chem.
Assoc. 1970, 53, pages 363-379, in Die Angewandte Makromolekulare Chemie, 1972, 26, pages 85-106, in Angewandte Chemie 1970, 82, pages 53-63 and in German Offenlegungsschrift Nos. 2,550,860; 1,495,745 (US
Patent No. 3,479,310) 1,495,770 (US Patent No.
3,535,274), 1,495,847 (Canadian Patent No. 764,009);
1,770,068 (US Patent No. 3,756,992) and 2,314,512.
Preferred polyurethane dispersions are polyurethane dispersions of polyhydroxy polyesters, hexane and/or isophorone diisocyanate and ethylene diamine ethyl sulphonate corresponding to the following formula:
H N-cH2-cH2-NH-cH2-cH2 SO3 The polymer latices suitable for use in accordance with the present invention may be synthesized, for example, from the following monomers:
acrylic and methacrylic acid esters of methanol, ethanol or butanol; vinyl chloride, vinylidene chloride, vinylacetate, vinyl alcohol groups (by hydrolysis of vinylacetate residues in polymers), ethylene, propylene, acrylonitrile, styrene, butadiene, isoprene, chloroprene; also acrylamide, M-methylol acrylamide, methacrylamide, acrylic acid and methacrylic acid. Polymer latices of this type are described, for example, in US Patent No. 3,869,413) LeA 18,790 o'~6~i4 and in German Offenlegungsschrift Nos. 2,550,832;
2,627,073 and 2,627,074.
Preferred polymer dispersions are polymer dis-persions of acrylic acid butyl ester, styrene, acrylo-nitrile, acrylamide, acrylic acid and N-methylol acryl-amide and, optionally, butadiene.
In addition to the polymer dispersions mentioned by way of example, the urethane prepolymers containing terminal OH- and/or CONH2- and/or ketoxime-urethane groups may also be blended with water-soluble or water-swellable polymers, for example, with aqueous solutions of casein, caprolactam-modified casein, gelatin, cellulose ethers, polyacrylamide, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid or alginates.
The coating pastes according to the present invention are crosslinked with from about 2 to 20 % by weight, preferably with from about 5 to 15 % by weight of urea- andlor melamine-formaldehyde resins.
Crosslinking agents of this type are known in the coating industry and are also described, for example, in German Auslegeschrift Nos. 2,457,387 (US
Patent No. 4,035,213) and 1,719,324 and, in particular, in US Patent No. 3,242,230.
As already mentioned, the coating compositions according to the present invention are particularly suitable for coating sheet-form textiles, leather or skiver. The quantities in which they are applied may vary within wide limits and, in general, amount to from 30 about 30 to 300 g/m2, preferably from about 40 to 100 g~m2. The coating compositions may be applied both by the direct coating process and also, preferably, by the reverse coating process.

LeA 18,790 .~'~
.

~15~

Small quantities (up to about 10 % by weight, preferably from about 1 to 5 % by weight, based on formaldehyde resin) of acids such as phosphoric acid, acid salts of phosphoric acid, maleic acid or p-toluene sulphonic acid, may be added as catalysts for cross-linking the formaldehyde resins, as is known. Both the formaldehyde resin and also the catalyst are preferably used in the absence of organic solvents (i.e. in pure form or in aqueous solution).
Examples of organic solvents which may be pre-sent in the coating compositions according to the present invention (for example as solvent for the catalyst) in quantities of up to about 10 % by weight, are isopropanol, butanol, dimethyl formamide, ethylacetate, butylacetate, cyclohexanone, methylethyl ketone, ethylene glycol mono-methyl ether and monoethyl ether and acetic acid esters thereof.
It is, of course, also possible to apply conven-tional coating solutions or pastes as further layers to the substrate in addition to the coating compositions according to the present invention. Conventional formu-lations such as these are described in detail as surface or coupling coats, for example in German Auslegeschrift No. 2,457,387 (US Patent No. 4,035,213).
The coating pastes according to the present in-vention are preferably used as coupling coats in the reverse coating of textiles, leather or skiver. The surface coat ~preferably a paste according to the present invention or even a conventional formulation) is initially applied to a suitable intermediate support (for example a steel band, a separating paper, a silicone matrix and the like~ in a thickness of from about 20 to 80 g/m2 and dried in a drying tunnel. The coupling coat is then applied to the dried surface coat in a thickness LeA 18,790 of from about 30 to 100 g/m2, the substrate applied, the coating heated at around 110 to 180C, preferably at from about 140 to 160C in another drying tunnel, and the coated substrate withdrawn from the separation support.
As already mentioned, however, the coating pastes according to the present invention may also be directly applied to the textile substrate by the direct coating process rather than indirectly by the so-called transfer process.
In transfer or direct coating, the pastes are applied by a known method using doctor kiss coaters, blanket coaters, reverse roll coaters, etc. In addition, it is particularly advantageous to use the modern techniques of screen printing and engraved roller printing for highly concentrated coating pastes.
The coating pastes according to the present in-vention of urethane prepolymers and aqueou3 polymer dis-persions and/or aqueous polymer solutions and urea-and/or melamine-formaldehyde resins as crosslinkers may contain various known additives such as powdered pigments, formed pigments, other coloring agents, W-stabilizers, antioxidants, crosslinking catalysts, feel-influencing agents such as silicones, cellulose esters, fillers such as chalk, kaolin or heavy spar, surface-active silica gels and others.
Unless otherwise indicated, the quantities quoted in the following Examples represent parts by weight and % by weight.
The following starting components are used for producing the prepolymers containing terminal OH- and/or CON~2- and/or ketoxime-urethane groups:

LeA 18,7g0 ;

6~4 Polyol 1: propylene-glycol-started polypropylene glycol ether (OH-number 56, average molecu-lar weight 2000);
Polyol 2: Bisphenol-A-started polypropylene glycol ether (OH-number 200);
Polyol 3: Trimethylol propane-started polyether of propylene oxide and approximately 20 ~ of ethylene oxide (OH-number 28, average molecular weight 6000); 0 Polyol 4: Polyester of adipic acid and diethylene glycol (OH-number 45, average molecular weight 2500);
TDI/80: Tolylene diisocyanate (mixture c,f 2,4- and 2,6-isomers in a ratio of 2:8);
15 IPDI: 3,3,5-trimethyl-5-isocyanatometh,yl cyclo-hexyl isocyanate;
MDI: 4,4'-diphenyl methane diisocyanate Production of the prepolymers containing terminal OH-and/or CONH - and/or ketoxime-urethane grou~:
(I) 800g of polyol 1 and 139 g of TDI/80 are mixed in a stirrer-equipped vessel and heated, with stirring to 80C. After a reaction time of from 5 to 6 hours at 80C, a constant NCO-content of approximately 3,3 % is reached. The mixture is cooled to room temperature and 800 g of the mixture are run, with stirring, into a solution of 45 g of N-methyl ethanolamine in 100 g of acetone. The components are left to react without further heating until no more NCO-groups can be detected by IR-spectroscopy. The acetone is distilled off in a water jet vacuum. Dilution with methyl glycol ether acetate to 99 ~ gives a viscosity of 100,000 mPas at 25C.
(II) 782 g of polyol 1 and 136 g of TDI/80 are mixed in a stirrer-equipped vessel and heated, with stirring, to 80C. After a reaction time of from 5 to 6 hours LeA 18,790 , _ ~2~

at 80C, a constant NCO-content of approximately 3.3 %
is reached. This prepolymer is cooled to room tempera-ture, after which 800 g of the NCO-prepolymer are run, with stirring, into a solution of 66 g of diethanolamine in 100 g of acetone. The components are left to react without further heating until no more NCO-groups can be detected by IR-spectroscopy. The acetone is distilled off in a water jet vacuum. Dilution with ethylene glycol monomethyl ether to 98 % gives a viscosity of 70,000 mPas at 25C.
(III) 778 g of polyol 4 and 138 g of IPDI are mixed in a stirrer-equipped vessel and heated, with stirring, to 80C. After a reaction time of 5 hours at 80C, a constant NCO-content of 2.8 % is reached. A solution of 84 g of hydrazine carboxylic acid hydroxy propyl ester in 100 g of isopropanol is added to this NCO-prepolymer at room temperature, followed by stirring at ro~m temper-ature until no more NCO-groups can be detected by IR-spectroscopy. The 91 ~ prepolymPr solution thus obtained is slightly cloudy and has a viscosity of 200,000 mPas at 25C.
(IV) 778 g of polyol 4 and 138 g of IPDI are mixed in a stirrer-equipped vessel and heated, with stirring, for 5 hours to 80C. A solution of 74 g of hydrazine car-boxylic acid hydroxy ethyl ester in 100 g of ethyleneglycol monomethyl ether is added at room temperature to the prepolymer thus obtained which contains 2.8 % of NCO-groups. The further procedure is the same as described in (III). The resulting prepolymer solution in ethylene glycol monomethyl ether is slightly cloudy and has a YiS-cosity of 300,000 mPas at 25C.
(V) 773 ~ of polyol 1 and 134 g of TDI/80 are mixed in a stirrer-e~uipped vessel and heated, with stirring, to 80C. After a reaction time of from 5 to 6 hours at 80C, LeA 18,790 ~ ~ ~2~f~4 a constant NCO-content of approximately 3.6 % is reached.
93 g of 2-hydroxypropyl urethane are added all at once to this NCO-prepolymer and the mixture is left to react at 80C until no more NCO-groups can be detected by IR-spectroscopy. Dilution with dimethyl formamide to 98 %gives a viscosity of approximately 40,000 mPas at 25C.
(VI) 785 g of polyol 4 and 139 g of IPDI are mixed in a stirrer-equipped vessel and heated, with stirring, to 80C. After a reaction time of from 5 to 6 hours, a constant NCO-content of approximately 2.8 % is reached.
75 g of 2-hydroxypropyl urethane are added all at once to this NCO-prepolymer, followed by stirring at 80C
until no more NCO-groups can be detected by IR-spectro-scopy. Dilution with methylethyl ketone to 92 % gives a viscosity of approximately 40,000 mPas at 25C.
(VII) 1500 g of polyol 1 and 333 g of IPI)I are mixed in a stirrer-equipped vessel and heated, with stirr-~ng, to 80C. After a reaction time of from 5 to 6 hours, a constant NCO-content of approximately 3.4 % is reached.
128 g of 2-hydroxypropyl urethane are added all at once to this NCO-prepolymer, followed by stirring at 80C
until no more NCO-groups can be detected by IR-spectro-scopy. Dilution with ethylene glycol monoethyl ether to 97 % gives a viscosity of 40,000 mPas at 25C.
(VIII~ 810 g of polyol 1 and 141 g of TDI/80 are mixed in a stirrer-equipped vessel. The mixture is left to react, with stirring, at 80C until a constant NCO-content of approximately 3.3 % is reached (this takes from 5 to 6 hours). After heating to 120C, 49 g of urea are added and the mixture is left to react at that temperature until no more NCO-groups can be detected ~y IR-spectroscopy. Dilution with cyclohexanone to 92 % gives a viscosity of approximately 100,000 mPas at 25C.
LeA 18,790 ) 6t~

(IX) 1600 g of polyol 3 and 20Q g of polyol 2 are de-hydrated for 30 minutes in a water jet vacuum. The polyol mixture is cooled to 40C and 200 g of MDI and 140 g of TDI/80 are added. This is followed by reac-tion for 3 to 4 hours at 60C until an NCO-content of 2.9 % is reached. When this NCO-content has been reached, 129 g of butanone oxime are added dropwise and the mix-ture is left to react at 80C until no more NCO-groups can be detected by IR-spectroscopy. A viscosity of from 60,000 to 65,000 mPas at 25C is adjusted by the addition of 22 q of methylethyl ketone and 22 g of isopropanol.
The masked NCO-group content amounts to 217 ~.
A viscosity of approximately 80,000 mPas is obtained by diluting the masked prepolymer with 115 g of dioctyl phthalate instead of methylethyl ketone and isopropanol.
(X) 1500 g of polyol 1 and 333 g of IPDI are mixed in a stirrer-equipped vessel and heated, with stirring, to 80C. After a reaction time of from 5 to 6 hours at 80C, a constant NCO-content of 3.4 ~ is reached. A
solution of 180 g of hydrazine carboxylic acid hydroxy-ethyl ester (carbazinic acid hydroxyethyl ester) in 200 g of ethylene glycol monomethyl ether is added to this NCO-prepolymer at room temperature, followed by stirring at room temperature until no more NCO-groups can be detected by IR-spectroscopy. The 91 % solution in ethylene glycol monomethyl ether is slightly cloudy and has a viscosity of 48,000 mPas at 25C.

LeA 18,790 ;~

~15;~

EXAMPLES

The surface coat solution Dl is a 25 % solution of a polycarbonate polyester urethane in dimethyl forma-mide having a viscosity of 10,000 mPas at 25C. The polycarbonate polyester urethane is obtained by the melt condensation of 1000 g (0.5 mol) of hexane diol polycar-bonate, 1125 g (0.5 mol) of a 1,4-butane diol adipate, 270 g of 1,4-butane diol (3.0 mols) and 1000 g of 4,4'-diphenyl methane diisocyanate (4.0 mols). The solution of the aromatic one-component polyurethane in dimethyl formamide is pigmented with 8 ~ ~f a stand~rd commercial-grade piqment paste consisting of an iron oxide colored pigment, polyacrylate and cyclohexanone. The pigmented surface coat solution Dl is initially applied to a separ-ation paper by doctor ~:iss coating in a coating machine comprising two spreadir,g units and two drying tunnel.s (quantity applied, wet: 120 g/m~). The di.methyl forma-mide evaporated during the passa~e through the first tunnel is delivered to a recovery unit. The coupling coat paste Hl is similarly applied in a quantity (wet) of 50 g/m2 in the second spreading unit, the textile web (a raised cotton fabric weighing 160 g/m2) is applied and the crosslinking reaction in the coupling coat is induced in the second drying tunnel at a temperature on entry of 140C and a temperature on exit of 160C.
The coupling coat paste Hl consists of 1000 g of the prepolymer (VI) containing terminal C0-NH2-groups, 300 g of a 40 % aqueous acrylate dispersion based on butylacrylate, styrene and N-methylolacrylamide ~ Acralen ATR of Bayer AG, Germany), 50 g of a ~olvent-free melamine-formaldehyde resin (~ Cymel ~01 of American Cyanamide Corp.) and 20 g of a 20 % solution of 4-toluene sulphonic acid in isopropanol.
Le A 18 790 ~15~664 The coatings produced using the coupling coat paste Hl according to the present invention show high flexural strength, firm adhesion and a soft feel, whereas coatings produced for comparison with the coupling coat paste Vl (having the same composition as Hl, but without the added dispersion) have distinctly weaker flexural strength, extremely poor adhesion and a stiff feel.

~ Flexural ~ strength ~ e ~
.~ ~ (Bally o ~ ~ Dry .~ ~ Flexomete r) ~ ~ ~ ~ Storage in cleaning ~ ~ room ~ ~ ~ ~ ethylacet- in ~ ~ temperature ~ z e ate (mins. perchlor--~ (in th>rRnda) -10~ at 25C) ethvlene _ feel D1/Hl 200 50 30 no change no change soft Dl/V1 100 20 10 separation heavily stiff from the damaged l substrate l _ The surface coat solution D2 is a 30% solution of a polyester urethane in dimethyl formamide/methyl-ethyl ketone (1:1) having a viscosity of 30,000 mPas at 25C. The polyester urethane was obtained from 1800 g (2.0 mols) of a 1,4-butane diol adipate, 174 g of TDI/80 (1.0 mol), 186 g of ethylene glycol (3.0 mols) and 1000 g of 4,4'-diphenyl methane diisocyanate (4.0 mols). After pigmenting, a surface coat of 30 g solids per square meter is produced under known conditions on a separation paper in the same way as described in Example 1. After the coupling coat paste H2 has been applied, the textile web is applied in the same way as described in Example 1.
LeA 18,790 The coupling coat paste H2 consists of lO00 q of the prepolymer (VI) containing terminal CO-NH2-groups, 300 g of a 50 ~ aqueous acrylate dispersion based on 90 % of butylacrylate5 % of acrylonitrile and 5% ~ ~rylamide and N-methylol acryl3~mide, 75 g of a solvent-free melamine-form-aldehyde resin ~ Cymel 301 of ACC) and 15 g of a 20 %
solution of 4-toluene sulphonic acid isopropanol.
Comparison coatings produced using a coupling coat paste V2, which has the same composition as coupling coat paste H2 but without the added dispersion, have considerably weaker flexural strength, weaker adhesion and inadequate resistance to dry cleaning.

The surface coat paste D3 is a 40 % PUR-disper-lS sion in water thickened with 2% of polyvinyl pyrrolidoneand pigmented with lS ~ of titanium dioxide, having been produced as follows: 1700 g (l.0 mol) of a mixed polyester of l,6-hexane diol, neopentyl glycol and adipic acid are reacted with 303 g (l.8 mol) of l,6-hexane diisocyanate to form an NCO-prepolymer. The NCO-pre-polymer thus obtained is converted into the polyester urethane urea by reaction in the form of an aqueous dispersion with 152 g (0.8 mol) of the sodium salt of ethylene diamine ethyl sulphonic acid as chain extender.
The coupling coat paste H3 consists of lO00 g of the pre-polymer (VII) containing terminal CO-NH2-groups, 200 g of a 40 % aqueous NBR latex from 25 % of acrylonitrile 70 % of butadiene and 5 % of N-methylolacrylamide and 1~0 g of a 50 ~ melamine-formaldehyde resin in butanol ~ Maprenal MF 800 of Cassella Company, Germany) together with 12 g of a 20 % solution of 4-toluene sulphonic acid in isopropanol.
A textile coating having high resistance to perchlorethylene, outstanding flexural strength and firm adhesion is produced from D 3 and H ~ in the same way as described in Example 1.
Le A 18 790 ti4 Comparison coatings produced using a coupling coat paste V3, which has the same composition as coupling coat paste H3, but without the added dispersion, show considerably weaker flexural strength, weaker ad-hesion and inadequate resistance to dry cleaning.

The surface coat solution D4 is a 30 ~ solution, pigmented with 8 % of a paste of organic pigment, poly-acrylate and cyclohexanone, of an aliphatic one-component polyester urethane in toluene/isopropanol/ethyl glycol ether acetate (29:29:12) having a viscosity of 22,000 mPas at 25C. The polyurethane is produced by reacting an NCO-prepolymer of 1700 g (1.0 mol) of the polyester described in Example 3 and 490 g (2.2 mols) of isophorone diisocyanate (IPDI) with 205 g (1.2 mols) of isophorone diamine in solution.
The coupling coat paste H4 consists of 1000 g of the prepolymer (VII) containing terminal CO-NH2-groups, 300 g,O~ ~ 50% aqueous polyacrylate dispersion used in Example 2 ba~ed on butylacrylate, acrylonitrile, acrylamide and N- _ methylolacrylamide, 75 g of the solvent-free melamine-formaldehyde resin used n Ex~mple 1 and 1~gof a 20% solution of

4-toluene sulphonic acid in ethylene glycol monomethyl ether. The procedure and result obtained are the same as described in Example 1. Comparison coatings produced using a coupling coat paste V4 (which has the same com-position as coupling coat paste ~4, but without the added dispersion~ have considerably poorer flexural strength, weaker adhesion, a stiff feel and inadequate resistance to dry cleaning.

Surface coat paste D5 is identical with ~2.
The coupling coat paste H5 is a mixture of 1000 g of the prepolymer (V) containing terminal LeA 18,790 . _ :~15~6~; ~

CO-NH2-groups, 300 g of a 40 % aqueous PUR-dispersion of polyol 1, polyol 4, TDI/80, IPDI, hydrazine hydrate and ethylene diamine ethyl sulphonate, also 75 g of solvent-free melamine-formaldehyde resin used in Example 1 and 20 g of a 20~ solution of 4-toluene sulphonic acid in iso-propanol. As described in Example 1, the surface coat is initially applied, foll~wed by application of the coupling coat paste in a quantity (dry) of 40 g/m2 by means of a cylinder screen printing machine. Com-parison coatings produced using a coupling coatingpaste V5, consisting of coupling coat paste H5 without the added dispersion, have considerably poor flexural strength,weaker adhesion, a stiffer feel and inadequate resistance to dry cleaning.

Surface coat paste D6 is identical with D2.
The coupling coat paste H6 consists of 1000 g of the prepolymer (IX) containing terminal ketoxime-ùrethane groups, 200 g of the 4~% aqueous polyacrylate dis-20 per8ion u~e~ in Example 1 based on butylacrylate,styrene~nd N-methylolacrylamide, 75 g of the solvent-free melamine-formaldehyde re~in used in Example 1 and 1~ ~ of a 20% so-lution of 4-toluene sulphonic acid in isopropanol, The procedure is the same as described in Example 1. Comparison coatings produced using a coupling coat paste V6, consisting of coupling coat paste H6 without the added dispersion, have consider-ably poorer flexural strength, weaker adhesion, a stiffer feel and inadequate resistance to dry cleaning.

The surface coat paste D7 is identical with D2.
The coupling coat paste H7 consists of 1000 g of the prepolymer (VIII) containing terminal CO-NH2-groups, 200 g of a 15 % casein solution in water, 75 g Of the ~eA 18,790 66i~

solvent-free melamine-formaldehyde resin used in Exam~le 1 and 12 g of a 20% solution of 4-toluene sulp;.onic acid in isopropanol.
The procedure is the same as described in ~xample l.
Comparison c~atings produced using a coupling coat paste V7, consisting of coupling coat paste H7 without the aqueous casein solution added, have considerably poorer flexural strength, weaker adhesion, a stiffer feel and inadequate resistance to dry cleaning.

Surface coat paste D8 is identical with D2.
The coupling coat paste H8 consists of lOOO g of the prepolymer (I) containing terminal OH-groups, 250 g of a 50 % aqueous polyal~rylate dispersion of ethylacrylate and N-methyloiacrylamide ~ lextol BV 401 of Rohm & Haas), 100 g of the solvent-free melamine-formaldehyde resin used in Example 1 and 15 g of a 20 % solution o:P 4-toluene sul~nonic acid in water.. The procedure is the same as described in Example l. A textile coating having excellent mechanical properties is obtained.
Comparison coatings produced using a coupling coat paste V8, consisting of coupling coat paste H8 without the added dispersion, have considerably poorer f~.exural strength, weaker adhesion, a stiffer feel and ;nadequate resistance to dry cleaning.
~XAMPLE 9 Surface coat paste D9 is identical with D2.
The coupling coat paste H9 consists of lOOO g of the prepolymer (III) containing terminal OH-groups, 2SO g of a 40 % aqueous PUR-dispersion (produced from 1 9 5 mol of 1,6-hexane diol/adipic acid polyester (OH-number 130),0,5 mol of1,4-butane diol 0,3 mol of the sodium salt of ethylene diamine ethyl sulphonate and 2,5 mol of 1,6-hexane diisocyanate)~
75 g of the solvent-free melamine-formaldehyde resin used in Example 1 and 15 g of 20 % solution of 4-toluene sulphonic acid in isopropanol.

The procedure is the same as described in Example 1. A textile coating having excellent mechan-ical properties is obtained.
Comparison coatings produced using a coupling

5 coat paste V9 consisting of coupling coat paste H9 without the added dispersion, have considerably poorer flexural strength, weaker adhesion, a stiffer feel and inadequate resistance to dry cleaning.
EXAMPLE ~O
Surface coat paste D10 is identical with D2.
The coupling coat paste H10 consists of 1000 g of prepolymer (II) containing terminal OH-groups, 300 g of the 40 % aqueous acrylate disper~;ion used in Example 1, ~5 g of the 40 % solvent-free ~ea-formalde-15 hyde re8in used in Exa~ple 1 and 15 g of a 20 % solutionof 4-toluene sulphonic acid in water. The procedure is the same as described in E~.ample 1. A high quality coat~ng is obtained.
Comparison coatings produced using a couplinc coat paste V10, consisting of coupling coat paste H10 without the added dispersion, have considerably poorer 20 flexural strength, weaker adhesion, a stiffer feel and inadequate resistance to dry cleaning.

The coupling coat paste Dll is identical with D2.
The surface coat paste Hll consists of 1000 g of 25 prepolymer (X) containing terminal OH-groups, 100 g of a 40 % aqueous polyacrylate dispersion (as in coupling coat Hl), 60 g ofthesolvent-free melamine-formaldehyde resin used in H 1 and 15 g of a 20% solution of 4-toluene ~ulphonic acid in water.
The procedure is the same as described in Example 1. The coated textile obtained is of outstanding quality.
Comparison coatings produced using a coupling coat paste Vll, consisting of the coupling coat paste LeA 18,790 21~64 Hll without the added dispersion, have considerably poorer flexural strength, weaker adhesion, a stiffer feel and inadequate resistance to dry cleaning.

Surface coat paste D12 is identical with D2.
The coupling coat paste H12 consists of 1000 g of a prepolymer containing terminal OH-groups and having an average molecular weight of 22,000 of a weakly branched polyester of adipic acid, diethylene glycol and trimethylol propane tmolecular weight:
2500) and a deficit of tolylene diisocyanate, 300 g of an aqueous PUR-dispersion (as described in Example 9), 150 g of a 40 ~ aqueous solution of a melamine-formaldehyde resin ~ assurit MLP of Cassella Company, Germany) and 5 g of z~.nc oleate. The general proce(~ure is identical with tha1; described in Example 1.
Comparison coat:ings produced using a coupling coat paste V12 consisting of coupling coat paste H12 without the added dispersion have considerably poorer flexural strength, weaker adhesion, a stiffer feel and inadequate resistance to dry cleaning.

LeA 1~,79Q

Claims

WHAT IS CLAIMED IS:

1. A coating composition comprising:
a) from about 50 to 95 % by weight of an optionally branched urethane-group-containing prepolymer having an average molecular weight of from about 500 to 25,000 which is ionic group free and contains from about 2 to 8 terminal groups selected from the group consisting of OH, CONH2 and ketoxime-urethane groups;
b) from about 2 to 20 % by weight of a urea- and/or melamine-formladehyde resin;
c) from about 3 to 50 % by weight of a stable aqueous polymer dispersion and/or aqueous polymer solution having a solids content of from about 20 to 70 % by weight and d) from about 0 to 10 % by weight of an organic solvent.

2. The coating composition of Claim 1, wherein component a) is a reaction product of a prepolymer produced from a polyether and/or polyester polyol containing from 2 to 4 hydroxyl groups and having a molecular weight of from about 1000 to 4000 and a polyisocyanate in an NCO/OH-equivalent ratio of from about 1.3:1 to 2.5:1, with a quantity, at least equivalent to the iscoyanate groups of the prepolymer of a chain terminator selected from the group consisting of ammonia, urea, an alkanolamine, carbazinic acid hydroxyalkyl ester, hydroxycarboxylic acid hydrazide, carbamic acid hydroxyalkyl ester, hydroxy-carboxylic acid amide, aminocarboxylic acid amide and ketoxime.
LeA 18,790

3. The coating composition of Claim 1 or 2, wherein component a) contains from about 0.3 to 6.0 %
by weight of terminal OH-groups or from about 0.6 to 10.0 % by weight of terminal CONH2-groups or from about 2.0 to 40.0 % by weight of terminal ketoxime-urethane groups.

4. The coating composition of Claim 1 or 2, wherein component c) is an aqueous polymer latex based on vinyl and, optionally, diene monomers.

5. The coating composition of Claim 1 or 2, wherein component c) is an aqueous solution of a homo-polymer or copolymer of vinyl monomers.

6. The coating composition of Claim 1 or 2, wherein component c) is an aqueous dispersion of a cationic, anionic or non-ionic polyurethane.

7. In a process for coating substrates by applying a coating composition to a substrate by the direct or reverse coating process and hardening the coating thus applied with forming or shaping, the improvement comprising coating a substrate with the compositions of Claim 1 or 2 and hardening by heating the coated substrate to a temperature of from about 110 to 180°C.

8. The composition of Claim 2, wherein component a) is the reaction product of a) a polyol selected from ethylene glycol adipate and propylene glycol ether, b) an isocyanate selected from toluene diisocyanate and 3,3,5-trimethyl-5-isocyanatomethyl cyclohexyl isocyanate and LeA 18,790 c) a chain terminator selected from 1,2-hydroxy propyl urethane, 1,2-hydroxy propyl carbazinic acid ester and methyl ethyl ketoxime.

9. In a process for reverse coating a flexible sheet form substrate wherein a top coat is applied to a release substrate and cured, a coupling coat is then applied to the cured top coat, the substrate applied to the not fully cured coupling coat, the coupling coat cured and the three layer laminate separated from the release substrate, the improvement wherein the coupling coat comprises:
a) from about 50 to 95 % by weight of an optionally branched urethane-group-containing prepolymer having an average molecular weight of from about 500 to 25,000 which is ionic group free and contains from about 2 to 8 terminal groups selected from the group consisting of OH, CONH2 and ketoxime-urethane groups, b) from about 2 to 20 % by weight of a urea- and/or melamine-formaldehyde resin, c) from about 3 to 50% by weight of a stable aqueous polymer dispersion and/or aqueous polymer solution having a solids content of from about 20 to 70% by weight and d) from about 0 to 10 % by weight of an organic solvent.

10. In the process of Claim 9, the further improvement wherein the coupling coat is cured by heating the coated substrate to a temperature between about 110 and 180°C.

LeA 18,790

11. In a process for direct coating a flexible sheet form substrate wherein the substrate is coated with an uncured coating composition and the coating is then cured, the improvement wherein said coating comprises:
a) from about 50 to 95% by weight of an optionally branched urethane-group-containing prepolymer having an average molecular weight of from about 500 to 25,000 which is ionic group free and contains from about 2 to 8 terminal groups selected from the group consisting of OH, CONH2 and ketoxime-urethane groups, b) from about 2 to 20 % by weight of a urea- and/or melamine-formaldehyde resin, c) from about 3 to 50 % by weight of a stable aqueous polymer dispersion and/or aqueous polymer solution having a solids content of from about 20 to 70% by weight and d) from about 0 to 10 % by weight of an organic solvent.

12. In the process of Claim 11, the further improvement wherein the coating is cured by heating the coated substrate to a temperature between about 110 and 180°C.

13. The product of the process of Claim 7.

14. The product of the process of Claim 9.

15. The product of the process of Claim 11.

LeA 18,790