EP0285898B1 - Preparations and processes for finishing leather and for coating textiles - Google Patents

Description

When dressing full-grain, sanded or split leather, dressing agents made from pigments, binders and other auxiliaries are applied to their surface, so that the pores of the leather are sealed on the surface. Alkaline-digested casein solutions and aqueous copolymer dispersions are generally used as binders. These copolymer dispersions are polyacrylate dispersions, dispersions of copolymers of vinyl acetate with acrylic esters or ethylene, synthetic rubber dispersions or polyurethane dispersions. Inorganic and organic pigments are used as pigments, for example iron oxide, titanium dioxide, azo pigments and phthalocyanines. The aqueous dressing liquors must be alkaline because the color mixtures generally contain aqueous alkaline casein solutions in more or less large proportions.

The leather processing industry is demanding dressings with ever higher fastness properties. In particular, the dry and wet buckling strength, rub-through resistance and swelling resistance against water and solvents are subject to ever increasing demands. To improve the physical fastness, reactive finishes have been carried out successfully for some time by using polymer dispersions with reactive groups as binders and crosslinking them on the leather with the aid of suitable polyfunctional compounds. Due to the low thermal resistance of the leather, conventional crosslinking systems, such as those used in the textile printing, nonwovens and coating sectors (e.g. with melamine resins) are not suitable. Rather, the crosslinking systems that are suitable for leather finishing have to react in an alkaline environment at room temperature or slightly above.

Self-crosslinking polymer dispersions containing two groups that react with each other - e.g. Crosslinking component A: (meth) acrylic acid, crosslinking component B: acrolein, glycidyl methacrylate or dichlorotriazinylaminoethyl methacrylate - have not proven themselves due to the poor stability in storage of the polymer dispersions.

In contrast, the process for dressing leather by treatment with a non-polymerized synthetic rubber latex, which is used in the dressing, has proven itself is reacted with oxides and / or hydroxides of divalent metals (cf. EP-B-29 170). However, this method is limited to thick-layer dressings of highly absorbent leathers with a rough surface, such as split leather and heavily sanded, non-impregnated sanding box leathers. On full-grain leather and sanding box leather impregnated with acrylate dispersions, the adhesion of the Zurich layer to the leather and the adhesion between the individual Zurich layers is inadequate because this crosslinking mechanism (salt formation) causes the film to form too quickly. In addition, the dry and wet buckling strengths are inadequate for use as upper leather, because full-grain leather and impregnated sanding box leather are coated much less with less polymer binder and these fastness properties decrease with decreasing amount of binder and layer thickness. In addition, leather that is prepared according to EP-B 29 170 is not resistant to yellowing at 160 ° C. However, this requirement must be met by upper leather - in particular white and pastel-colored leather - because this temperature occurs when molding on the sole of a shoe made of PVC or polyurethane (PUR).

The crosslinking of carboxylated aqueous dispersions of polyacrylates, polybutadienes, polyurethanes and casein solutions with polyfunctional aziridine compounds is carried out as a further aqueous reactive finish for leather finishing. The physical fastness properties are significantly improved by this process, however, because of the high reactivity of the aziridine derivatives, the processing conditions must be observed extremely carefully even at room temperature, a requirement that is difficult to implement in practice.

If e.g. If the leather is ironed between two paint jobs on continuous ironing machines at higher temperatures, which is common for nappa leather, or the leather is only given the following paint job after storage for several days (e.g. over the weekend), then the upper paint layer no longer adheres to the lower one.

Adhesion difficulties also occur between the polymer primer and the finish, namely because the commonly used finishes based on collodion or acetobutyrate or also non-reactive PUR lacquers are not applied immediately after the last primer application.

Embossed leather is particularly difficult to produce using this crosslinking system because the embossability of the leather decreases very quickly with the degree of crosslinking. In order to be able to be embossed at all, the leather must always be embossed at the same stage of cross-linking immediately after the color application. Since these requirements are difficult to meet in a leather factory, the reproducibility of the embossing effect is practically non-existent.

Another reactive process practiced in leather finishing is based on the crosslinking of carboxyl-group-containing polyacrylate dispersions with epoxides of the "Dian" type [glycidyl ether of 2,2-bis (4-hydroxyphenyl) propane].

However, networking takes longer than three weeks. Therefore, many fastness properties that are important for shoe manufacture are reached too late, e.g. the hot water swell strength for the thermosetting process, the resistance to the solvents of the adhesive and the shear strength.

It has now been found that top layers on leather with particularly good properties important for leather finishing, such as finishing and covering, grain and toughness, flexibility at low temperatures, dry and wet rub fastness, light fastness and heat resistance, but in particular very good dry and wet buckling strengths, very good adhesion for leather and adhesion between the individual layers of color are obtained if the treatment of the leather is carried out with aqueous preparations which contain at least one polymer containing carboxyl groups and optionally casein as a binder and a special 1,2-polyepoxide compound as well as pigments and other auxiliaries and additives as a crosslinker .

The present invention thus relates to aqueous preparation for dressing leather and for textile coating based on a carboxyl group-containing polymer as a binder and a 1,2-polyepoxide compound as a crosslinker, which may contain customary auxiliaries and additives, characterized in that the binder is a copolymer of monoolefinically unsaturated monomers with an acid number of 5-150 mg KOH / g substance and / or a polyurethane with an acid number of 5-150 mg KOH / g substance and that the 1,2-polyepoxide compound is triglycidyl isocyanurate with an epoxy value of 0.5 to 1.01.

The aqueous preparation additionally contains, if appropriate, base-digested casein. The carboxyl groups can be present as free acid or as carboxylate groups. If the preparation contains casein, which is open to the base, the polymer contains carboxylate groups.

worin

R¹

Wasserstoff oder Methyl, vorzugsweise Wasserstoff bedeuten.

The triglycidyl isocyanurate contained in the aqueous preparations according to the invention corresponds to the formula (I)

wherein

R¹

Is hydrogen or methyl, preferably hydrogen.

The triglycidyl isocyanurate of the general formula (I) contained in the preparations according to the invention is known and can be obtained by treating cyanuric acid with excess epichlorohydrin or β-methylepichlorohydrin in the presence of a suitable catalyst, e.g. Triethylamine, converted in a known manner at 20-200 ° C to trichlorohydrin isocyanurate and then treated with hydrogen chloride-releasing agents such as aqueous sodium hydroxide solution at 20-120 ° C.

The preparation of this triglycidyl isocyanurate is e.g. in U.S. Patent 3,337,509. If the three radicals R 1 are the same, two substances are obtained which are diasteromeric to one another. These compounds are then called α- or β-triglycidyl isocyanurate [cf. Appl. Chemistry (1968) pp. 851/2].

The two isomers can be obtained from the crude product by fractional crystallization from suitable solvents, for example methanol or dichloromethane. For the industrial use of the triglycidyl isocyanurate as a crosslinking agent, the crude product obtained in the preparation can generally be used.

This crude product can contain oligomeric parts of polyepoxides. Part of the epoxy groups can be hydrolyzed so that better solubility is achieved. However, the crude product should contain no less than two epoxy groups in the molecule, otherwise sufficient crosslinking will not be achieved. The raw products generally have epoxy values from 0.5 to 1.01, preferably from 0.8 to 1.01.

The epoxy value is understood to mean the number of 1,2-epoxy groups contained in 100 g of substance. The epoxy equivalent is defined as the amount of substance in grams that contains one equivalent of 1,2-epoxy groups. The determination is carried out by titration with hydrochloric acid, one mole of 1,2-epoxide groups being equivalent to one mole of hydrogen halide.

The polyglycidyl compounds contained in the aqueous preparations according to the invention can be used both without a solvent and as a solution and / or dispersion. The polyepoxides are preferably used as a solution or dispersion depending on their solubility in the medium used in each case.

Suitable solvents are water and water-miscible organic solvents. Examples include:
Amides such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone, alcohols such as methanol, ethanol, isopropanol, ethylene glycol monomethyl ether or ethyl ether, ketones such as acetone, diacetone alcohol, esters such as glycol acetate or glycerol acetate. Dimethylformamide, N-methylpyrrolidone and diacetone alcohol are preferably used.

Mixtures of triglycidyl isocyanurate with other polyglycidyl compounds, e.g. Glycidyl ethers from bisphenols, glycidyl esters from di- or polycarboxylic acids, basic glycidyl compounds such as N, N-diglycidylcyclohexylamine or N, N-diglycidylbenzylamine or heterocyclic epoxides such as glycidylhydantoins or polyglycidyltriazolidine-3,5-diones can be used.

The carboxyl group-containing polymers contained in the aqueous preparations according to the invention have an acid number of 5-150 mg KOH / g substance, the average molecular weight being 1,000 to 25,000. The OH numbers are preferably below 20, in particular below 10.

The carboxyl group-containing polymers to be used according to the invention can be copolymers whose one monomer component is an α, β-ethylenically unsaturated carboxylic acid, or polyurethanes containing carboxyl groups.

These copolymers containing carboxyl groups should consist of 1-25% by weight of at least one copolymerizable α, β-ethylenically unsaturated carboxylic acid having 3 to 5 carbon atoms and 75-99% by weight of at least one further copolymerizable monomer. The α, β-ethylenically unsaturated carboxylic acids can be monocarboxylic acids or dicarboxylic acids or half-esters of dicarboxylic acids with 1 to 12 carbon atoms in the alcohol component.

• I) Ester der Acryl- oder Methacrylsäure mit aliphatischen C₁-C₁₂-, cycloaliphatischen C₅-C₆-, araliphatischen C₇-C₈-Monoalkoholen, beispielsweise Methylacrylat, Ethylacrylat, n-Propylacrylat, Isopropylacrylat, n-Butylacrylat, tert.-Butylacrylat, 2-Methylhexylacrylat, 2-Ethylhexylacrylat, Dodecylacrylat und die entsprechenden Methacrylsäureester und Maleinsäurediester; Cyclopentylacrylat, Cyclohexylacrylat oder die entsprechenden Methacrylsäureester und Maleinsäurediester; Benzylacrylat, β-Phenylethylacrylat, entsprechende Methacrylsäureester und Maleinsäurediester;
• II) Aromatische Vinylverbindungen, beispielsweise Styrol, α-Methylstyrol, α-Methyl-p-isopropylstyrol, α-Methyl-m-isopropylstyrol, o-, p-Chlorstyrol, o-, p-Bromstyrol, kernsubstituierte Methylstyrole, p-tert.-Butylstyrol oder Mischungen daraus;
• III) Vinylester organischer Monocarbonsäuren, wobei die Säurekomponente 2 bis 4 C-Atome enthält, wie beispielsweise Vinylacetat und Vinylpropionat;
• IV) Monoolefinisch ungesättigte Halogenkohlenwasserstoffe, wie Vinylchlorid oder Vinylidenchlorid, vorzugsweise Vinylchlorid;
• V) Acrylnitril, Methacrylnitril, Acrylamid, Methacrylamid, Methylolacrylamid, Methylolmethacrylamid, Alkoximethylacrylamid und -methacrylamid mit 1 bis 4 C-Atomen in der Alkoxigruppe;
• VI) Butadien, Isopren;
• VII) Vinylalkylether mit 1 bis 4 C-Atomen in der Alkylgruppe, wie Vinylmethylether, Vinylethylether, Vinylpropylether.
• VIII)N-Vinyl-Verbindungen, wie N-Vinylpyrrolidon, N-Vinylphthalimid.

Examples of copolymerizable monomers are:

• I) esters of acrylic or methacrylic acid with aliphatic C₁-C₁₂, cycloaliphatic C₅-C₆, araliphatic C₇-C₈ monoalcohols, for example methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-2-butyl acrylate Methylhexyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate and the corresponding methacrylic acid esters and maleic acid diesters; Cyclopentyl acrylate, cyclohexyl acrylate or the corresponding methacrylic acid esters and maleic acid diesters; Benzyl acrylate, β-phenylethyl acrylate, corresponding methacrylic acid esters and maleic acid diesters;
• II) Aromatic vinyl compounds, for example styrene, α-methylstyrene, α-methyl-p-isopropylstyrene, α-methyl-m-isopropylstyrene, o-, p-chlorostyrene, o-, p-bromostyrene, nucleus-substituted methylstyrenes, p-tert.- Butyl styrene or mixtures thereof;
• III) vinyl esters of organic monocarboxylic acids, where the acid component contains 2 to 4 carbon atoms, such as, for example, vinyl acetate and vinyl propionate;
• IV) Monoolefinically unsaturated halogenated hydrocarbons, such as vinyl chloride or vinylidene chloride, preferably vinyl chloride;
• V) acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, methylolacrylamide, methylol methacrylamide, alkoxymethylacrylamide and methacrylamide with 1 to 4 carbon atoms in the alkoxy group;
• VI) butadiene, isoprene;
• VII) vinyl alkyl ethers having 1 to 4 carbon atoms in the alkyl group, such as vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether.
• VIII) N-vinyl compounds, such as N-vinylpyrrolidone, N-vinylphthalimide.

• a) 0-70 Gew.-% Butadien, Isopren oder deren Mischungen, vorzugsweise Butadien
• b) 0-40 Gew.-% Acrylnitril, Methacrylnitril, Acrylamid, Methacrylamid, Methylolacrylamid, Methylolmethacrylamid oder deren Mischungen, vorzugsweise Acrylnitril und/oder Acrylamid
• c) 0-60 Gew.-% Styrol, α-Methylstyrol, o-, p-Chlorstyrol, o-, p-Bromstyrol, p-tert.-Butylstyrol oder deren Mischungen, vorzugsweise Styrol
• d) 0-99 Gew.-% Acrylsäureester mit aliphatischen C₁-C₈-Alkoholresten oder Methacrylsäureester mit aliphatischen C₁-C₈-Alkoholresten oder deren Mischungen, wovon bis zu 7,5 Gew.-% durch mindestens ein Hydroxylgruppen enthaltendes, olefinisches, copolymerisierbares Monomer, wie Hydroxyalkylester der Acryl-, Methacryl-, Malein-, Fumar- oder Itaconsäure mit 2 bis 4 C-Atomen im Alkylrest ersetzt sein können;
• e) 0-20 Gew.-% Vinylacetat
• f) 1-25 Gew.-% Acrylsäure, Methacrylsäure, Itaconsäure, Maleinsäure, Fumarsäure, Itaconsäure-, Maleinsäure-und Fumarsäurehalbester mit 1 bis 8 C-Atomen in der Alkoholkomponente oder deren Mischungen, vorzugsweise Acrylsäure und/oder Methacrylsäure und/oder Itaconsäure,

wobei die Summe der Prozentgehalte von a) bis f) 100 beträgt.Preferred copolymers containing carboxyl groups consist of polymerized units of

• a) 0-70 wt .-% butadiene, isoprene or mixtures thereof, preferably butadiene
• b) 0-40% by weight of acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, methylolacrylamide, methylol methacrylamide or mixtures thereof, preferably acrylonitrile and / or acrylamide
• c) 0-60% by weight of styrene, α-methylstyrene, o-, p-chlorostyrene, o-, p-bromostyrene, p-tert-butylstyrene or mixtures thereof, preferably styrene
• d) 0-99 wt .-% acrylic acid ester with aliphatic C₁-C₈ alcohol residues or methacrylic acid ester with aliphatic C₁-C₈ alcohol residues or mixtures thereof, of which up to 7.5 wt .-% by at least one hydroxyl group-containing, olefinic, copolymerizable monomer how hydroxyalkyl esters of acrylic, methacrylic, maleic, fumaric or itaconic acid with 2 to 4 carbon atoms in the alkyl radical can be replaced;
• e) 0-20% by weight vinyl acetate
• f) 1-25% by weight of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, itaconic acid, maleic acid and fumaric acid semiesters with 1 to 8 carbon atoms in the alcohol component or mixtures thereof, preferably acrylic acid and / or methacrylic acid and / or itaconic acid ,

the sum of the percentages from a) to f) being 100.

Copolymers are understood not only as copolymers with a statistical distribution of the copolymerized monomers or block copolymers, but also as graft copolymers in which monomers have been grafted onto a preformed homopolymer or copolymer. Statistical copolymers are preferred.

The copolymers containing carboxyl groups to be used according to the invention are prepared by known processes of bulk, solution or dispersion polymerization, preferably by dispersion polymerization. The copolymers prepared in bulk or solution polymerization must be converted into a dispersion in a second step. Anionic, cationic or nonionic emulsifiers and dispersants can be used in an amount of 0.1 to 20% by weight, based on monomers, to produce such stable dispersions. Such methods have been described, for example, in "Methods of Organic Chemistry", Houben-Weyl, 4th edition, volume 14/1, pages 24-556 (1961) and in DE-OS 29 46 435.

The polymerizations can be carried out at temperatures from 0 ° C. to about 100 ° C.

Percarbonates, peresters such as tert-butyl perpivalate can be used as initiators. -Peroctoate, benzoyl peroxide, o-methoxy benzoyl peroxide, dichlorobenzoyl peroxide, azodiisobutyronitrile in amounts of 0.5 to 3% by weight, based on the amount of monomer.

Conventional molecular weight regulators such as thioglycol, thioglycerol or tert-dodecyl mercaptan can also be used.

Polyurethanes containing carboxyl groups are also known. The production of these polyurethanes or their aqueous dispersions can e.g. in such a way that prepolymers in organic solvents, e.g. Acetone, dissolves and disperses in water after addition and reaction with chain extender containing carboxyl groups. Since the systems are self-emulsifying, no emulsifiers and only low shear forces are required. After the solvent has been distilled off, the polyurethane dispersions remain.

Hydroxyarboxylic acids and / or aminocarboxylic acids are preferably used as chain extenders containing carboxyl groups. Care must be taken, particularly in the case of hydroxycarboxylic acids, to ensure that there is no significant reaction between the carboxylic acids and the isocyanate. This can be done in particular by using sterically hindered hydroxy carboxylic acids, e.g. of 2,2-di (hydroximethyl) propionic acid can be achieved. Suitable chain extenders are e.g. still glycolic acid, lactic acid, tartaric acid, citric acid, glycine, α- or β-alanine, sarcosine, methionine, 4-aminobutyric acid, 6-aminocaproic acid, glutamic acid.

To prepare the prepolymers, isocyanates are reacted with hydroxyl-containing compounds such as hydroxyl-containing polyesters, polyethers or polycarbonates.

The isocyanates used to prepare the prepolymers are preferably the technically readily available, for example the aliphatic, cycloaliphatic, aromatic diisocyanates or mixtures thereof, e.g. Tolylene-2,4-diisocyanate, toluene-2,6-diisocyanate, phenylene diisocyanate, methylene bis (4-phenyl isocyanate); Hexamethylene diisocyanate, cyclohexylene-1,4-diisocyanate, methylene bis (4-cyclohexyl) isocyanate, isophorone diisocyanate.

The hydroxyl group-containing polyesters used for the preparation of the prepolymers can be terminated or substituted on the main chain by hydroxyl groups. Examples of such polyesters are those which are prepared by reacting acids, esters, anhydrides or acid chlorides with glycols, polyglycols and, if appropriate, small amounts of triplets. Suitable glycols and polyglycols are ethylene glycol, di- and triethylene glycol, propylene glycol, 2,2-dimethyl-1,3-propanediol. Glycerol, trimethylolpropane or trimethylolethane are particularly suitable as triols. These polyols are reacted with aliphatic, cycloaliphatic or aromatic dicarboxylic acids or their derivatives such as phthalic, maleic, succinic, adipic, cork, sebacic and hexahydrophthalic acid.

The hydroxyl-containing polyethers used to prepare the prepolymers are preferably those which are obtained by reacting aliphatic di- or triols, such as, for example, ethylene glycol, propylene glycol, Glycerol or trimethylolpropane, or by reacting bisphenols such as bisphenol A or hydroquinone with ethylene oxide or propylene oxide.

The preparation of these polyurethanes or their aqueous dispersions is described, inter alia, in the following publications: DAS 1 237 306, US Pat. No. 3,479,310, GB 1,076,688.

The carboxyl group-containing polymers to be used according to the invention preferably have an acid number of 10-100 mg KOH / g substance, in particular 10 to 50 mg KOH / g substance.

Low acid numbers within the specified range result in a reduced reactivity, which can result in a quite desirable slowing down of the crosslinking reaction and vice versa.

To prepare the preparations according to the invention, the water-dispersible polymers are preferably used in the form of their aqueous dispersions, the carboxyl groups advantageously being neutralized with amines such as triethylamine, triethanolamine, dimethylethanolamine or with ammonia.

Among the casein to be used for the preparation of the preparations according to the invention, the commercially available, base-digested, ie water-soluble, is to understand made casein. The preparation of the digested casein is described, for example, in "W. Graßmann, Handbuch der Gerbereichemie und Lederfabrikation I / 1. Part", 2nd edition (1961), p. 724 ff. When using basic digested casein, it should be noted that the polymers containing carboxyl groups are neutralized with amines. The casein solutions can contain the usual casein plasticizers such as glycols, polyols, polyether glycols.

The carboxyl group-containing polymers and the triglycidyl isocyanurate are used in proportions such that 0.5 to 1.5, preferably 0.9 to 1.1, epoxy groups are accounted for by one carboxyl group.

The amount of hardener required strongly depends on the type of polymer dispersion. For example, a butadiene binder requires significantly more crosslinking agents than an acrylate binder, a strongly acidic binder (e.g. itaconic acid) with a higher content of carboxylic acid groups less than a weakly acidic binder (e.g. methacrylic acid) with a lower content of carboxylic acid groups.

To accelerate the crosslinking reaction, catalysts such as are known from the reaction of epoxides with carboxylic acids can be used in the preparations according to the invention. Suitable catalysts are tertiary amines, for example triethylamine, quaternary ammonium salts, for example tetraethylammonium chloride, sulfides or sulfonium salts. However, since the carboxyl groups are generally neutralized with amines, an additional catalyst can be dispensed with for the crosslinking reaction, so that the crosslinking on the leather surface or on the textile surface is preferably not catalyzed.

Inorganic or organic pigments can be added to the preparations according to the invention in their usually effective proportions up to 150% by weight, based on the binder. The following are examples of pigments: titanium dioxide, iron oxides, carbon black, chromium oxide, phthalocyanine and azo pigments.

The preparations according to the invention can contain further auxiliaries and additives such as thickeners, e.g. those based on cellulose such as carboxymethyl cellulose, polyvinyl alcohol or poly-N-vinylpyrrolidone.

The method according to the invention is suitable for leather primers and finishes as well as for textile coating. Commercially available opaque paint pastes are also used for the priming orders.

The processing can be done on full-grain, sanded and split leather or leather fiber materials of any kind. The preparations are made using the copolymers according to the invention, the crosslinker, the Caseins, pigment preparations of the type mentioned above and other additives applied to the leather in a manner known per se. The dressings can be applied by casting, printing, knife coating, brushing, spraying, brushing or plushing processes. The quantity required depends on the type and pretreatment of the leather and can easily be determined by preliminary tests.

The primer is carried out in one or more orders. By intermediate ironing or scar stamping at 70 to 110 ° C, a good fusion and thus a good finish of the primer is achieved. Subsequent opaque paint applications can then be carried out.

The viscosity of the dye liquors can be adjusted as required, depending on the type of leather and application technique. Full-grain leather, which should only be thinly coated, is primed with low-viscosity liquors using air guns, while for heavily sanded leather and split leather, the viscosity of the paint mixtures is increased due to the better filling effect with thickeners. The paint is applied to this leather using airless guns, printing or casting machines.

As a final finish on the leather prepared according to the invention, polyurethane one- and two-component lacquers, acetobutyrate lacquers, collodion lacquers or collodion lacquer emulsions of the oil-in-water and water-in-oil type are suitable.

As a final finish, aqueous polyacrylate or polyurethane dispersions according to the invention can also be applied, optionally together with casein solutions and crosslinking agents according to the invention, by spraying, printing and casting processes.

The advantages of the dressing method according to the invention can be summarized as follows:
The crosslinking reaction is slower than the crosslinking of carboxylated polymers with divalent metal oxides, for example zinc oxide, and with aziridine derivatives, but significantly faster than the reaction with epoxides of the "Dian" type. Depending on the type of polymer, the amount and type of polymerized acids and the amount of crosslinker used, the crosslinking is complete after 5 to 15 days. In contrast to the process described in EP-B-29 170, this favorable crosslinking time ensures good adhesion of the Zurich layer not only to split and sanded leathers, but also to full-grain sanding box leathers impregnated with acrylate binders.

Excellent layer adhesion also results after hot intermediate ironing and / or storage of the leather for several days. In contrast to crosslinking with aziridine compounds, there are also no adhesive difficulties between primer and finish when lacquers based on collodion or acetobutyrate or non-reactive PUR lacquers are applied.

In terms of application technology, it is also important that the risk of overcrosslinking, as in the case of crosslinking with aziridine derivatives, due to incorrect metering of the crosslinking agent, is far less present and that, once the crosslinking reaction has ended, there is no post-curing, no coarsening of the scar and no film embrittlement.

The crosslinking does not adversely affect the cold resistance of the dressing, the lightfastness and the film transparency. The dry and wet kink resistance, the dry, wet and rub-through resistance and the solvent resistance achieve very good values that cannot be achieved by other processes from aqueous systems. It is also noteworthy that the known undesirable hydrophilicity of acrylate binders is significantly reduced by the crosslinking.

Since very different carboxyl-containing polymers - polybutadienes, polyacrylates, PUR dispersions - can be used alone or in mixtures with one another or with casein as binders for the process according to the invention, the use of the process is extremely versatile. With this process, a wide variety of leathers with the highest demands in terms of aspect and fastness can be prepared.

For the preparation of colored and black split leather, it is advisable to choose synthetic rubber latices that fill well, which can be fully or partially polymerized, for white and pastel-colored split leather, which are intended for upper leather, acrylic and / or PUR dispersions that are lightfast and are still resistant to yellowing at 160 ° C. Since compared to the process described in EP-B-29 170 result in significantly better dry and wet buckling strengths, to improve the embossability and the drying of the Zurich layer - to prevent sticking of the leather when ironing and in the stack - and to improve the grip casein and inexpensive fillers such as talc, kaolin, chalk, silica, are added in higher proportions. The embossability of the coated leather is still good even after the leather has been stored for several days after the last color application. In contrast to the process described in EP-B-29 170, fine embossings do not express themselves when the leather is stacked hot.

The method according to the invention offers a particular advantage for the finishing of full-grain and weakly sanded leathers which are not intended to appear coated, for example furniture and clothing nappa. The crosslinking according to the invention has the effect that the binder film becomes "load-bearing" for larger proportions of pigment, matting and gripping agents without incisive losses in the fastness properties. This means that with pigment-rich, low-binder color approaches, errors with thinner top layers can be covered, whereby the elegant grain of the thin coated leather surface is retained and the finish does not look plastic. Leather can be trimmed with fewer work steps than usual, which despite its strong coverage appear very natural and not coated.

The following examples illustrate the process according to the invention. The parts and percentages given always refer to the weight.

example 1

100 g of a colored paste (aqueous dispersion with 55% by weight iron oxide pigment, 5% by weight binder based on butyl acrylate, methyl methacrylate, N-vinyl pyrrolidone, acrylic acid, vinyl acetate) Copolymer, adjusted to pH 9-9.5 with NH₃) with 250 g of a commercially available 13.5% aqueous ammoniacal casein solution, 100 g water and 25 g of a conventional 60% aqueous peanut oil emulsion. 500 g of the rubber latex described below are added to this mixture and then 35 g of a 40% by weight dispersion of finely powdered triglycidyl isocyanurate (®ARALDIT PT 810 from Ciba-Geigy AC) in diacetone alcohol for crosslinking. Finally, the paint liquor is adjusted with a suitable thickener to a viscosity that corresponds to a flow time of 18-30 seconds from a Ford cup with a 4 mm nozzle.

The split leather or polished vachettes to be treated receive 1 to 2 jobs using a brush, plush board, airless gun, spraying, printing or casting machine. The total application amount is 150 - 300 g / m².

After drying, the leather is ironed or scarred at 100 ° C and 300 bar with a delay of 2 to 5 seconds. Then the top color is applied with the same Fleet (order approx. 100-200 g / m²). Finally, a common collodion varnish is applied as a finish by pouring.

The finish obtained shows excellent values for the wet and dry kink resistance, good adhesion to the leather, good water swell resistance, and very good embossability. Even very fine embossments do not come out when the hot leather is stacked.

The rubber latex was produced as follows: A mixture of 18,000 g of water, 5,000 g of butadiene- (1,3), 3,000 g of acrylonitrile, 1,700 g of styrene and 333 g of 90% methacrylic acid is mixed in a 40-liter stainless steel autoclave with a cross-bar stirrer and 50 g of tert-dodecyl mercaptan are polymerized at 35 ° C. in the presence of 200 g of a sodium sulfonate of a mixture of long-chain paraffin hydrocarbons with an average chain length of 15 carbon atoms as emulsifier and 5 g of 70% tert-butyl hydroperoxide and 2.5 g of sodium formaldehyde sulfoxylate dihydrate as a redox initiator system until a solids concentration of 20% is reached. A solution of 100 g of a reaction product of isononylphenol with 20 moles of ethylene oxide and 2.5 g of sodium formaldehyde sulfoxylate dihydrate in 500 g of water is then pressed in and the polymerization is continued at 35 ° C. After a solids concentration of about 31% by weight (about 86% conversion) has been reached, the polymerization is stopped with a solution of 200 g of 25% by weight diethylhydroxylamine in 200 g of water. The received one Latex is freed of residual monomers and has a solids concentration of 31%. The acid number of the binder is 19.5 mg KOH / g solid.

Example 2

150 g of a white pigment paste (aqueous dispersion with 65% by weight of titanium dioxide pigment, 5% by weight of binder based on an ethyl acrylate, methyl methacrylate, N-vinylpyrrolidone, acrylic acid) are used for the preparation of synthetically retanned white split leather or polished Vachettes -, Vinyl acetate copolymer, adjusted to pH 9-9.5 with NH₃) with 250 g of water, 10 g of 25% ammonia water and 25 g of a conventional 60% peanut oil emulsion. 170 g of a 40% by weight carboxylated polyacrylate binder having a film hardness of ° Shore A 25 and an acid number of 24.2 (40% by weight butyl acrylate, 43.5% by weight ethyl acrylate, 10% by weight) are added to this mixture. Acrylonitrile, 2% by weight of acrylamide, 2% by weight of acrylic acid, 2% by weight of itaconic acid and 0.5% by weight of N-methylolacrylamide) and 330 g of a 40% by weight carboxyl group-containing aliphatic polyurethane ester dispersion the film hardness ° Shore A 60 and the acid number 36.8 (from a polyester of hexanediol, dimethylolpropionic acid and adipic acid, reacted with dicyclohexylmethane diisocyanate and crosslinked with diethylenetriamine, contains 8.8% dimethylolpropionic acid based on solids) and introduced as a counterion triethylammonium and then for crosslinking 42 g of a 33.3% by weight solution of triglycidyl isocyanurate in N, N-dimethylformmamide. Finally, the paint liquor is adjusted to a viscosity with a suitable thickener, which corresponds to a flow time of 18 to 30 seconds from a Ford cup with a 4 mm nozzle.

The application properties of the dressing correspond to the advantageous properties described in the general part. The finish is lightfast and resistant to yellowing even at 160 ° C.

Example 3

100 g of a carbon black paste (aqueous dispersion with 16% by weight of carbon black and 20% by weight of a binder based on an isopropyl acrylate, methyl methacrylate, N-vinylpyrrolidone, acrylic acid, vinyl acetate copolymers, with aminoethanol to pH 10-10 , 5) are intensively stirred with 60 g of an ammoniacal 13.5% by weight casein solution and with 30 g of a matting paste with 30% by weight of precipitated silica and 5% by weight of the binder of the color paste according to Example 1 and then diluted with 400 g water.

Then 250 g of a 40 wt .-%. aqueous dispersion of an acrylate-based copolymer with film hardness ° Shore A 45 and acid number 24.2 (71% by weight butyl acrylate, 23% by weight acrylonitrile, 1.5% by weight acrylamide, 0.5% by weight N-methylolacrylamide, 2% by weight of acrylic acid and 2% by weight of itaconic acid) and 150 g of a 35% by weight aqueous dispersion of a copolymer on a butadiene basis with film hardness ° Shore A 63 and an acid number of 25.9 (45% by weight of butadiene, 16% by weight of styrene, 28% by weight of acrylonitrile, 6% by weight of methacrylamide, 2% by weight of methacrylic acid and 3% by weight of itaconic acid). Finally, only 22 g of a 25% strength by weight solution of triglycidyl isocyanurate in N-methylpyrrolidone are stirred in. After intensive mixing, a very opaque black binder color is obtained, which is particularly suitable for dressing polished leather. If the paint is applied with an air spray gun, the paint is used in its present form; if you want to apply the paint by plushing, the paint liquor is previously diluted with water in a ratio of 2: 1, if the paint is to be applied with a casting machine or an airless gun, the liquor is adjusted to a viscosity with a suitable thickener that has a run-off time of 16 to 28 seconds from a Ford cup with a 4 mm nozzle.

In addition to a good aspect, the finish obtained has very good dry and wet kink strengths as well as good layer adhesion and water swell resistance.

Claims (6)

1. Aqueous formulations for dressing leather and for textile coating which are based on a carboxyl-containing polymer as binder and a 1,2-polyepoxide compound as crosslinker and which, if desired, also contain customary auxiliaries and additives, characterized in that the binder is a copolymer of monoolefinically unsaturated monomers having an acid number of 5 to 150 mg of KOH/g of substance and/or a polyurethane having an acid number of 5 to 150 mg of KOH/g of substance and, if desired, base-digested casein and the 1,2-polyepoxide compound is a triglycidyl isocyanurate having an epoxy value of 0.5 to 1.01.
2. Aqueous formulations according to Claim 1, characterized in that the copolymer consists of polymerized units of

   a) 0-70% by weight of butadiene, isoprene or mixtures thereof,

   b) 0-40% by weight of acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, methylolacrylamide, methylolmethacrylamide or mixtures thereof,

   c) 0-60% by weight of styrene, α-methylstyrene, o- or p-chlorostyrene, o- or p-bromostyrene, p-tert-butyl-styrene or mixtures thereof,

   d) 0-99% by weight of acrylic esters with aliphatic C₁-C₈-alcohol radicals or methocrylic esters with aliphatic C₁-C₈-alcohol radicals mixtures thereof,

   e) 0-20% by weight of vinyl acetate

   f) 1-25% by weight of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, itaconic, maleic or fumaric monoesters having 1 to 8 C atoms in the alcohol component or mixtures thereof,

   the sum of the percentages of a) to f) being 100.
3. Aqueous formulations according to Claim 1, characterized in that the carboxyl-containing polymer consists of an aqueous polyurethane dispersion, the polyurethane dispersion being prepared in an organic solvent from pre-polymers and carboxyl-containing chain extenders and then dispersed in water.
4. Aqueous formulations according to Claim 1, characterized in that the crosslinker is a triglycidyl isocyanurate of the general formula (I)

   

   in which

   R¹   denotes hydrogen or methyl.
5. Process for coating leather or textiles, characterized in that aqueous formulations according to Claims 1 to 4 are applied to the substrates at room temperature and crosslinked at 25 to 90°C.
6. Leathers and textiles, characterized in that they have been coated by the process according to Claim 5.