WO1992001817A1

WO1992001817A1 - Polyurethanes for priming leather

Info

Publication number: WO1992001817A1
Application number: PCT/EP1991/001271
Authority: WO
Inventors: Rainer HÖFER; Hans-Herbert Friese; Roland Grützmacher; Gerhard Kaindl
Original assignee: Henkel Kommanditgesellschaft Auf Aktien
Priority date: 1990-07-16
Filing date: 1991-07-08
Publication date: 1992-02-06
Also published as: DE4022539A1

Abstract

The invention concerns the use of special polyurethanes in the priming bath used in leather finishing.

Description

"Polyurethanes for leather primers"

The invention relates to the use of special polyurethanes in the primer liquor of leather finishing.

Leather finishing is the protective layer that is applied to the leather that has been dried after tanning and oiling in order to protect it against moisture, dirt and damage (Ullmann's Encyklopadie der Technische Chemie, 4th edition, volume 16, pages 159-163 , Verlag Chemie Weinheim 1978). The dressing film must adhere firmly to the leather and satisfy extremely high bending and stretching requirements during further processing and during later use. Furthermore, the surface of the dressing film must be hard enough to ensure sufficient resistance to damage from dry and wet rubbing, bumping and scratching. So that the dressing film can meet these different requirements, it is applied in several thin layers of different dressing liquors, in particular the primer and finishing liquors, with respective intermediate drying and, if necessary, intermediate hangers and embossing.

The primer is intended to conceal the defects visible in the undressed leather, to level the color and thus to improve the range. The base fleets therefore contain in addition to the film-forming polymer dispersions, such as thermoplastic polyacrylates, butadiene copolymers and polyurethanes, pigments and other auxiliaries. For the use value of the finished leather, it is important that the primer withstand the mechanical stresses to which the leather is subjected during use, and in particular that it be highly flexible.

The object of the invention was to improve the physical fastness properties of finished leather.

It has been found that when certain aqueous polyurethane dispersions are used in the primer liquor, leather with surprisingly high cold flexibility and particularly good rub fastness is obtained.

The invention accordingly relates to the use of an aqueous polyurethane dispersion with a solids content of between 10 and 50% by weight and a Brookfield viscosity at 25 ° C. between 10 and 50,000 mPas, the polyurethane solids of which as components a) polyether polyols with at least 3 OH groups and an average molecular weight between 1,000 and 20,000, b) castor oil, alkoxylated castor oil, epoxidized glycerides ring-opened with C 1-6 alkyl alcohols and / or alkoxylated, epoxidized glycerides ring-opened with Ci-g alkyl alcohols, c) ionic groups bearing dihydroxy and / or diamino compounds and d) contains organic di- and / or polyisocyanates in the primer liquor of the leather finishing. The polyurethanes to be used according to the invention in the primer liquor are known compounds which, according to DE 37 04 350, are used to produce a filler in the automotive industry.

Prepared leathers have particularly good physical fastness properties, in particular cold flexibility and rub fastness properties, if they are primed with a polyurethane dispersion whose Brookfield viscosity at 25 ° C is between 10 and 10000 mPas.

The average molecular weight of the polyether polyols contained in the polyurethane solid is preferably between 3,000 and 12,000. Polyether polyols of the general formula are particularly preferred

in which R denotes an alkoxy radical which is derived from glycerol, diglycerol, polyglycerol with a degree of polymerization x between 3 and 6, trimethylolpropane or trimethylolethane, the index x means the degree of polymerization of the alkoxy radical, the indices y are a number between 1 and 8 and z is a number between 0 and 7, with the proviso that the sum y + z is between 1 and 8, the indices a are a number between 1 and 15, b is a number between 20 and 150, c is a number between 1 and 15, d is a number between 20 and 150 and e is a number between 1 and 15, with the proviso that the sums a + c + e between 3 and 40, b + d between 40 and 300 and c + e are between 2 and 30. Those polyether polyols of the general formula in which R is an alkoxy radical which is derived from glycerol or trimethylolpropane, the indices y 2 or 3 and z are 0 or 1, with the proviso that the sum y + z is 2 or 3, and the indices a, c and e each a number between 1 and 5 and b and d each represent a number between 30 and 100, with the proviso that the sums a + c + e between 3 and 15, b + d between 60 and 200 and c + e between 2 and 10 are. The polyether polyols of the general formula are known compounds which are obtainable in a manner known per se by alkoxylation of glycerol, diglycerol, polyglycerol with a degree of polymerization between 3 and 6, trimethylolpropane or trimethylolethane with ethylene oxide and propylene oxide.

As a further component, the polyurethane solid preferably contains castor oil, alkoxylated castor oil, preferably alkoxylated with 1 to 50 mol of ethylene oxide and / or castor oil alkoxylated with 1 to 50 mol of propylene oxide, epoxidized glycerides ring-opened with Ci-g-alkyl alcohols and / or with 1 to 10 mol Ethylene oxide and 1 to 40 mol of propylene oxide alkoxylated, ring-opened with Ci.g-alkyl alcohols, epoxidized glycerides.

The epoxidized glycerides, that is to say mixtures of epoxidized mono-, di- and / or triglycerides, required as starting materials for the production of the last two substance classes mentioned are epoxidized by unsaturated oils, for example soybean oil, linseed oil, tall oil, cottonseed oil, peanut oil, palm oil , Sunflower oil, rape oil and / or claw oil, accessible. According to the process described in DE-PS 857364, unsaturated glycerides can be obtained by Reaction with peracetic acid in the presence of acidic catalysts or with performic acid formed in situ from formic acid and hydrogen peroxide. The epoxidized glycerides are then treated with monohydric C 8 alkyl alcohols, for example methanol, ethanol, n-propanol, isopropanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol and / or 2-ethylhexanol, in the presence of catalysts, for example sodium methylate or potassium hydroxide, reacted with opening of the oxirane ring. The ring opening is preferably carried out with methanol. The ring-opened epoxidized glycerides can then be alkoxylated in a manner known per se with ethylene oxide and / or propylene oxide. The alkylene oxides are preferably used in amounts such that 1 to 10 moles of ethylene oxide and 1 to 40 moles of propylene oxide accumulate per mole of ring-opened glyceride.

In order to ensure dispersibility in water, the polyurethanes to be used according to the invention contain dihydroxy and / or diamino compounds as an additional building block which preferably contain one or more carboxylate, sulfonate and / or ammonium groups as the ionic group, for example dimethylolpropionic acid, sulfonate group-containing aliphatic diols DE-OS 24 46 440 or anionic, built-in internal emulsifiers according to DE-OS 2651 506.

Suitable organic di- and / or polyisocyanates are aliphatic and / or aromatic di- and / or triisocyanates, for example dicyclohexylmethane-4,4'-diisocyanate, 1,6-hexane diisocyanate, 3-isocyanatometh l-3.5 , 5-trimethylcyclohexyl isocyanate (isophorone diisocyanate), tetramethylene diisocyanates, trimethylhexamethylene diisocyanate, dimer fatty acid diisocyanates, 1,4-phenylene diisocyanate, Diphenylmethane diisocyanates, toluene-2,4- and / or toluene-2,6-diisocyanate, 2,4,4'-triisocyanato-diphenyl ether and / or 4 ' ₍ 4'' _f 4''' triisocyanato-triphenylmethane. Aliphatic diisocyanates, in particular isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,6-hexane diisocyanate and / or dimer fatty acid diisocyanates, are preferred.

So-called blocked di- and / or polyisocyanates can also be used in combination with the above-mentioned non-blocked di- and / or polyisocyanates. The blocked di- and polyisocyanates are resistant to hydroxyl groups at room temperature and only react at temperatures above 100 ° C. Based on the total amount of the di- and / or polyisocyanates used, the content of blocked di- and / or polyisocyanates is between 0 and 60% by weight, preferably between 0 and 10% by weight. Blocked di- and polyisocyanates are prepared by reacting organic di- or polyisocyanates with one or more alcohols in amounts such that all isocyanate groups are blocked.

As a further component, the polyurethanes can contain water-soluble diamines, for example ethylenediamine and / or isophoronediamine.

In the polyurethanes to be used according to the invention, the weight ratio of components a) to components b) is between 90:10 and 10:90. Based on components a) and b), the polyurethanes contain 1 to 50% by weight. Dihydroxy and / or diamino compounds bearing ionic groups. The OH / NCO equivalent ratio is between 1: 0.5 and 1: 2.0. The polyurethanes are produced in a manner known per se, in which, for example, di- and / or polyisocyanates with a) polyether polyols, b) castor oil, alkoxylated castor oil, ring-opened epoxidized glycerides and / or alkoxylated with C 1-6 alkyl alcohols Ci-8-alkyl alcohols ring-opened epoxidized glycerides and c) dihydroxy and / or diamino compounds bearing ionic groups, optionally in the presence of solvents such as N-methylpyrrolidone and optionally catalysts such as N-methyl-orpholine at temperatures between 50 and 100 ° C to a prepolymer with terminal isocyanate groups. The prepolymer obtained is then dispersed in water at temperatures between 40 and 60 ° C. and, if appropriate, reacted with chain extenders such as diamines, for example ethylene diamine.

The aqueous polyurethane dispersions to be used according to the invention with a solids content of between 10 and 50% by weight are used in aqueous primer liquors in amounts of 5 to 80% by weight. As further constituents, the priming liquors can contain pigment preparations, film-forming substances in the form of aqueous dispersions, such as polyacrylates and / or polyurethanes, binders and fillers, for example wax dispersions or casein, matting agents, penetrators with solvent components and / or plasticizers. The primer liquors can be applied to the leather in one work step or in several successive work steps, drying being carried out at temperatures between 50 ° C. and 120 ° C. after the individual work steps. After drying, ironing or embossing can be carried out in a known manner at temperatures between 50 ° C. and 120 ° C. between the priming jobs or after the last priming job. The priming liquors can be sprayed, plushed, poured, Scraps and / or roller application can be applied to the leather. This is then given a customary finish.

The leather treated with a polyurethane to be used in the primer liquor according to the invention has excellent physical fastness properties. The finished leathers are not only characterized by a high degree of flexibility when wet and dry, but also at temperatures of -20 ° C and below. Furthermore, they have good fastness to rubbing both in the dry and in the wet state.

B e i s p i e l e

Preparation of the polyurethane dispersion I

In a nitrogen atmosphere, a mixture of 127.4 g of a dried glycerol polyether polyol of the general formula with 14 ethylene oxide units and 132 propylene oxide units, 100.7 g castor oil and 28.4 g N-methylpyrrolidone was stirred in succession at 20 ° C. with 46.8 g triethylamine salt the diethylolpropionic acid and 157.4 g of isophorone diisocyanate. The reaction mixture was then heated to 75.degree. After a constant NCO content had been reached, 539.3 g of deionized water were added at 50 ° C. to disperse and extend the chain. A polyurethane dispersion with a Brookfield viscosity at 25 ° C. of 300 Pas was obtained.

Application examples

"Parts by weight" means "parts by weight"

Example 1 cowhide leather, sanded

primer

Composition of the primer fleet:

100 parts by weight of aqueous pigment preparation 50 parts by weight of matting agent based on silica 40 parts by weight of filler based on wax dispersion 130 parts by weight of the polyurethane dispersion I according to the invention 100 parts by weight of polyacrylate dispersion 160 parts by weight of water

The primer liquor was applied to the cover by roller application. After drying at 50 ° C was minted at 80 ° C and 150 bar.

Graduation

The conclusion was carried out in a known manner by spraying an aqueous dilute nitrocellulose emulsion.

The physical test of the finished leather showed the following values:

Bally Flexometer dry 100,000 flexes wet 50,000 flexes

-25 ° C 10,000 flexes

Fastness to rubbing according to Veslic dry 300 rubbing wet 100 rubbing

Application example 2 Furniture leather, full-grain

primer

Composition of the primer fleet: 100 parts by weight of aqueous pigment preparation

30 parts by weight of wax dispersion

20 parts by weight polyurethane dispersion for adhesion

30 parts by weight of matting agent based on silica

100 parts by weight polyacrylate dispersion

160 parts by weight of the polyurethane dispersion I according to the invention

350 parts by weight of water

The leather was sprayed 4 times with the primer liquor, after which

Drying at 50 ° C, ported at 80 ° C and 150 bar, sprayed again with the primer liquor and then dried at 80 ° C.

Graduation

The conclusion was carried out in a known manner by spraying an organically diluted polyurethane lacquer emulsion twice.

The physical test of the finished leather showed the following values:

Bally flexometer dry 100,000 flexes

-20 ° C 10,000 flexes

Fastness to rubbing according to Veslic dry 1,000 rubbing wet 300 rubbing alkaline perspiration solution 100 rubbing Application example 3 sheep clothing leather

primer

Composition of the primer fleet:

100 parts by weight of aqueous pigment preparation

30 parts by weight of casein solution

50 parts by weight of wax dispersion

50 parts by weight solvent-based penetrator

100 parts by weight of polyacrylate dispersion

60 parts by weight of the polyurethane dispersion I according to the invention

500 parts by weight of water

The leather was sprayed 4 times with the primer liquor and then dried at 80 ° C.

Graduation

Finally, an aqueous diluted aceto-butyrate emulsion was sprayed twice in a known manner.

The physical test of the finished leather showed the following values:

Bally Flexo eter dry 50,000 flexes wet 20,000 flexes

Fastness to rubbing after Veslic dry 150 rubbing wet 50 rubbing

Claims

Patent claims

1. Use of an aqueous polyurethane dispersion with a solids content between 10 and 50 wt .-% and a Brookfield viscosity at 25 ° C between 10 and 50,000 Pas, the polyurethane solids as building blocks a) polyether polyols with at least 3 OH groups and one average molecular weight between 1,000 and 20,000, b) castor oil, alkoxylated castor oil, epoxidized glycerides ring-opened with C 8 alkyl alcohols and / or alkoxylated, epoxidized glycerides ring-opened with C 8 alkyl alcohol, c) dihydroxy and / and ionic groups or diamino compounds and d) contains organic di- and / or polyisocyanates in the priming liquor of the leather finishing.

2. Use according to claim 1, characterized in that the aqueous polyurethane dispersion has a Brookfield viscosity at 25 ° C between 10 and 10000 mPas.

3. Use according to one or both of claims 1 to 2, characterized in that the average molecular weight of the polyether polyols is between 3000 and 12000.

4. Use according to one or more of claims 1 to 3, characterized in that polyether polyols are compounds of the general formula

are in which R is an alkoxy radical derived from glycerin, diglycerol, polyglycerol with a degree of polymerization x between 3 and 6, trimethylolpropane or trimethylolethane, the index x means the degree of polymerization of the alkoxy radical, the indices y are a number between 1 and 8 and z represent a number between 0 and 7, with the proviso that the sum y + z is between 1 and 8, the indices a a number between 1 and 15, b a number between 20 and 150, c a number between 1 and 15, d is a number between 20 and 150 and e is a number between 1 and 15, with the proviso that the sums a + c + e between 3 and 40, b + d between 40 and 300 and c + e are between 2 and 30.

Use according to one or more of claims 1 to 4, characterized in that the polyurethane solid contains aliphatic diisocyanates.