EP0163057B1 - Process for retanning mineral or combined tanned leather with polymeric tanning agents - Google Patents

Abstract

A process for the finish dressing of leathers dressed by a mineral or a combined method, by treatment with an aqueous solution of water soluble polymer dressing substances that are polymers of unsaturated monomers that contain sulfonic groups. These polymers contain, if necessary, additional basic units that do not affect the water solubility, these being derived from the comonomers that can be copolymerized with the monomers that contain the sulfonic groups and which do not contain phosphorus.

Description

The invention relates to a method for retanning mineral or combined tanned leather with polymer tanning agents.

The main tanning of leather is mainly carried out with basic salts of trivalent chromium, aluminum and / or zirconium alone or in combination with synthetic tanning agents. Subsequent retanning preferably serves to improve or modify certain characteristic properties of the leather, which are characterized by terms such as fullness, grain strength, grip, crack, levelness and others. Accordingly, there are significant differences in the target direction between main and retanning.

In addition to vegetable tanning, synthetic tanning agents - syntans - are used in retanning, the tanning effect of which can be limited. Typical representatives are low molecular weight (degree of polymerization 1-5) condensation products of formaldehyde with naphthalene and / or phenolsulfonic acids or their alkali salts.

A common disadvantage of polymers containing carboxyl groups during retanning is their clearly pronounced pH sensitivity in the usual range of use between 3 and 5 and their often inadequate stability towards the electrolyte concentrations occurring in retanning. These disadvantages very often lead to superficial spreading or smearing with all the resulting consequences for subsequent processes, e.g. the coloring. For some years now, carboxyl-containing polymers and copolymers based on acrylic acid have been used. As a rule, the polycarboxylates are used in combination with other suitable retanning agents.

From FR-A-1 533483 retanning agents based on homopolymers of vinylsulfonic acid and their copolymers with (meth) acrylic acid are already known. EP-A-0151290 (priority: 01/24/84; application date: 12/18/84; publication date: 08/14/85) describes amphoteric condensation products and their use in retanning.

The object of the invention is therefore to improve the previously known products used for retanning, in particular with regard to pH sensitivity, electrolyte stability and influencing the dyeing behavior of the leather.

The invention relates to a process for retanning mineral or combined tanned leather by treatment with an aqueous solution of water-soluble polymer tanning agent, which is characterized in that polymer tanning agent is composed of polymers of at least one unsaturated monomer containing sulfonic acid groups and, if appropriate, further water-soluble, unsaturated, copolymerizable, not phosphorus-containing monomers are used, with the exception of polymers of 5-100% by weight of vinylsulfonic acid and 0-95% by weight of (meth) acrylic acid and copolymers of 80-90% by weight of (meth) acrylic acid and 20-100% of unsaturated sulfonation products of animal or vegetable oils.

By incorporating monomers containing sulfonic acid groups into the polymers used according to the invention, substantially more favorable application properties are achieved. While syntans and the previously known polycarboxylates often lead to undesired brightening in the case of colored leathers, the polymers according to the invention surprisingly do not have these disadvantages. Despite the presence of sulfone groups, surprisingly, the subsequent dyeing of the leather with anionic dyes does not result in any undesired change in the desired shade due to lightening effects.

Suitable sulfonic group-containing unsaturated monomers for the preparation of the polymer tanning agent according to the invention are preferably those derived from a, β-unsaturated acids and their derivatives, preferably from (meth) acrylic acid and their derivatives, such as, for example, 2-acrylamido-2-methylpropanesulfonic acid. Further examples of such sulfonic acids are N- (3-sulfopropyl-N- (meth) acrylamidopropyl) -N, N-dimethylammonium betaine or a sulfopropyl- (meth) acrylic acid ester.

However, the sulfone group can also be present as a substituent in a cyclic, preferably aromatic system, while the polymerizable CC double bond is in the side chain of the cyclic system, such as aromatic α-olefins sulfonated on the ring. A typical example of this is styrene sulfonic acid. Not only the sulfonic acids themselves are suitable, but also their salts, such as the alkali and / or ammonium salts.

The content of monomers containing sulfonic acid groups in the polymers used for retanning according to the invention is at least 3 mol%, preferably at least 5 mol%.

In addition to the basic units derived from monomers containing sulfonic acid groups, the polymers according to the invention may also contain further basic units which do not impair the water solubility of the polymer and which are derived from corresponding copolymerizable monomers which do not contain phosphorus. Preferred polymers are copolymers of at least one sulfone group-containing monomer with at least one carboxyl group-containing monomer. These copolymers can in turn contain further basic units derived from other water-soluble, unsaturated monomers. Unsaturated carboxylic acids such as maleic acid as dicarboxylic acid and unsaturated monocarboxylic acids such as (meth) acrylic acid and / or crotonic acid are primarily suitable as monomers containing carboxyl groups.

In addition, in the polymer tanning agents according to the invention, water solubilizers can be added non-impairing copolymerizable monomers (meth) acrylamide or vinyl pyrrolidone.

The molecular weight of the polymer tanning agents according to the invention can vary within wide limits. Polymers with molecular weights from 10,000 are suitable. The upper limit of the molecular weight can be, for. B. are at 150000. The molecular weight range of the polymers used is preferably between 20,000 and 100,000, in particular between 25,000 and 50,000.

• [η] = 2,5.10^-2. M^0,7

wobei [η] die Grenzviskosität in ml/g und M die Molmasse in g/Mol bedeuten, berechnet.The molar masses were determined from the intrinsic viscosity determined in 10% aqueous saline solution according to the relationship of Korotkinha (OZ Korrotkinha et al. Zh. Prikl. Khim. 38, 2533, 1965)

• [η] = 2.5.10 ^-2 . M ^0.7

where [η] is the intrinsic viscosity in ml / g and M is the molar mass in g / mol.

The retanning of the leather is preferably carried out at 0.1-5.0% by weight, based on the shaved weight of the polymeric tanning material with a liquor length of up to 300%, temperatures up to a maximum of 70 ° C. and pH values in the range of at least 2.5 -8.0.

Example 1

Polymer tanning agent from acrylic acid / acrylamide / and 2-acrylamido-2-methylpropanesulfonic acid.

100 g of deionized water, 2.5 g of acrylic acid and 1.6 g of hydrogen peroxide (35% strength) are placed in a polymerization flask equipped with a stirrer, thermometer and reflux condenser and heated to 90.degree. The monomer solution was prepared in another vessel from 135 g of acrylic acid, 86 g of acrylamide, 72 g of 2-acrylamido-2-methyl-propanesulfonic acid (AMPS) and 240 g of water.

The monomer solution was then added to the polymerization flask with stirring over a period of about 60 minutes. At the same time, 7.2 g of hydrogen peroxide (35% strength), 1.6 g of hydroxylamine hydrochloride (dissolved in 12 g of water) and 60 g of 45% strength sodium hydroxide solution were metered in proportionally to the monomer solution through further inlet ports. The reaction temperature was kept at 100 ° C. by boiling. After the end of the polymerization, the mixture was stirred for a further hour at 100 ° C. and then adjusted to pH 7.4 with sodium hydroxide solution. An approximately 40% solution of a polymer composed of acrylic acid, acrylamide and AMPS with a viscosimetrically determined molar mass of 48,000 g per mol resulted.

The solution obtained was used for retanning according to the following recipe:

The leather treated with the polymer tanning agent according to the invention showed good to very good fullness and softness with high grain strength and was dyed deeper than the leather treated with a commercially available polymer retanning agent based on acrylic acid / acrylamide copolymer.

Example 2

Polymer tanning agents from acrylamide, acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid (AMPS)

• a) nicht neutralisierte Monomerlösung
• b) teilweise wie im Beispiel 1 neutralisierte Monomerlösung

The polymerization of acrylamide, acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid was carried out in the same way as in Example 1, with the difference that the amounts of acrylamide, acrylic acid and AMPS were varied in some cases. In addition, the hydrogen peroxide and Hydroxylamine concentration achieved the desired molecular weights. The composition, the molar masses and the catalyst concentration are summarized in Table 1.

• a) unneutralized monomer solution
• b) monomer solution partially neutralized as in Example 1

When using the polymer tanning agent with a molecular weight of 25000 b / mol according to the recipe given in Example 1, a leather is obtained which is characterized by a deeper coloration than the leather treated with a commercially available polymer retanning agent based on acrylic acid / acrylamide copolymer .

Example 3

The polymer tanning agents described in Example 2 were used in the following formulation for cowhide leather, type nappa:

The leather treated with the polymer tanning agents according to the invention was distinguished by a deeper coloration than with a commercially available polymer retanning agent produced on the basis of acrylic acid / acylamide.

Example 4

Polymer tanning agent made from acrylic acid, acrylamide and sodium styrene sulfonate

100 g of water, 2.5 g of acrylic acid and 1.0 g of hydrogen peroxide (35% strength) are placed in a polymerization flask as described in Example 1 and heated to 90.degree. The monomer solution consisting of 93.6 g of acrylamide, 48.5 g of sodium styrene sulfonate (80%), 160 g of acrylic acid and 260 g of water was mixed with the hydroxylamine solution (1.6 g in 58 g of water), 8 g of hydrogen peroxide and 60 g of sodium hydroxide solution (45% strength) are metered into the polymerization flask. The reaction temperature was kept at 100 ° C. by boiling. After the polymerization, the mixture was stirred for a further 2 hours at 90 ° C. and neutralized to pH 7.0 with sodium hydroxide solution. The polymer has a viscosimetric molecular weight of 20 OOOg / mol.

The polymer tanning agent obtained was used in accordance with the following recipe:

The leather treated according to the invention was significantly softer than the comparative leather worked with a commercially available polymer retanning agent based on acrylic acid / acrylamide copolymer with the same grain strength.

Example 5

Polymer tanning agent from methacrylic acid, acrylamide and sodium styrene sulfonate

100 g of water, 2.5 g of mathacrylic acid and 1.0 g of hydrogen peroxide (35% strength) were placed in a polymerization flask as described in Example 1 and heated to 90.degree. The monomer solution, consisting of 84.5 g of acrylamide, 35.0 g of sodium styrene sulfonate (80%), 173 g of methacrylic acid and 260 g of water, was mixed with the hydroxylamine solution (1.6 g in 58 g of water) within 2 hours. 8 g of hydrogen peroxide and 54.5 g of sodium hydroxide solution (45% strength) were metered into the polymerization flask over the course of 2 hours.

After the polymerization, the mixture was stirred at 90 ° C. for a further 2 hours and neutralized to pH 7.0 with sodium hydroxide solution. The terpolymer has a viscosimetric molecular weight of approximately 30,000 g / mol.

When used in the formulation in Example 4, the polymer tanning agent described here provided an even higher softness with the same grain strength.

Example 6

The terpolymer described in Example 5 was used in the following formulation for cowhide:

The leather produced according to this recipe was dyed deeper than the leather treated with a commercially available polymer retanning agent based on acrylic acid / acrylamide copolymer.

Example 7

The polymer tanning agent described in Example 5 was used and investigated in the following formulation for nappa:

The leather treated with the polymer tanning agent according to the invention is dyed deeper and has a higher softness than the leather treated with a commercially available polymer retanning agent based on acrylic acid / acrylamide copolymer.

Example 8

100 g of deionized water, 2.5 g of methacrylic acid and 1.0 g of hydrogen peroxide (35% strength) were placed in a polymerization vessel equipped with a stirrer, thermometer and reflux condenser and heated to 90.degree. In another vessel, the monomer solution was prepared from 80.5 g of acrylamide, 47.3 g of N- (3-sulfopropyl) -N-meth-acrylamidopropyl-N, N-dimethylammonium betaine, 164.7 g of methacrylic acid and 215 g of water . This monomer solution was then, with stirring, over a period of about 60 minutes into the polymerization vessel together with the hydroxylamine solution (1.6 g in 58 ml of water), 7.8 g of hydrogen peroxide (35%) and 56 g of sodium hydroxide solution (45% ) entered.

After the polymerization, the mixture was stirred for a further 2 hours at 90 ° C. and then neutralized to pH 7 with 112 g of sodium hydroxide solution (45% strength).

The solution obtained was used for retanning according to the following recipe:

The leather treated with the polymer tanning agent according to the invention showed better grain strength and was dyed deeper than the leather treated with a commercially available polymer retanning agent based on acrylic acid / acrylamide copolymer.

Example 9

100 g of water and 1.0 g of hydrogen peroxide (35% strength) were placed in a polymerization flask as described in Example 1 and heated to 90.degree. The monomer solution, consisting of 136 g of acrylamide, 65.0 g of sodium styrene sulfate (80%), 94 g of maleic anhydride and 260 g of water, was mixed with the hydroxylamine solution (1.6 g in 58 g of water) within 8 hours, 8 g Hydrogen peroxide and 51.0 g of sodium hydroxide solution (45% strength) are metered into the polymerization flask within 2 hours.

After the polymerization, the mixture was stirred at 90 ° C. for a further 2 hours and neutralized to pH 7.0 with sodium hydroxide solution.

The solution obtained was used for retanning according to the following recipe:

The leather treated with the polymer tanning agent according to the invention showed significantly more color intensity than the leather treated with a commercially available polymer retanning agent based on acrylic acid / acrylamide copolymer.

Example 10

100 g of water and 4.0 g of hydrogen peroxide (35% strength) were placed in a polymerization flask as described in Example 1 and heated to 90.degree. The monomer solution, consisting of 256 g of acrylamide, 39.1 g of sodium styrene sulfonate (80%) and 260 g of water, was mixed together with the hydroxylamine solution (6.3 g in 78 g of water), 31.2 g of hydrogen peroxide in 2 hours metered the polymerization flask. The reaction temperature was kept at 100 ° C. by boiling. After the polymerization, the mixture was stirred at 90 ° C. for a further 2 hours and neutralized to pH 7.0 with sodium hydroxide solution. The solution obtained in the recipe used in Example 9 gave a leather whose softness, depth of color and brilliance turned out to be significantly better than the leather treated with a commercially available polymer retanning agent based on acrylamide copolymer.

Claims (6)

1. A process for retanning leather tanned by a mineral or combined method by treatment with an aqueous solution of water-soluble polymer tanning agents, characterized in that polymers comprising at least one unsaturated sulfonic acid group containing monomer and, if necessary, additional water-soluble, unsaturated, copolymerizable phosphorus-free monomers are used as polymer tanning agent, except for polymers comprising 5 to 100%-wt. of vinyl sulfonic acid and 0 to 95%-wt of (meth)acrylic acid and mixed polymers comprising 80-90%-wt. of (meth)acrylic acid and 20 to 10%-wt. of unsaturated sulphonation products of animal or vegetable oil.

2. A process according to claim 1, characterized in that a polymer, consisting of at least 3 mole % of units of 2-acrylamindo-2-methylpropanesulfonic acid, N-(3-sulfopropyl-N-(meth)acrylamidopropyl)-N,N-dimethyl ammonium betaine, sulfopropyl-(meth)acrylic acid ester and/or styrene sulfonic acid or their alkali and/or ammonium salts, is used as said polymer tanning agent.

3. A process according to claim 1 or 2, characterized in that unsaturated carboxyl groups containing monomers and/or (meth)acrylamid or vinylpyrrolidone are used as additional monomers.

4. A process according to claim 3, characterized in that maleic acid, (meth)acrylic acid and/or crotonic acid are used as carboxyl groups containing monomers.

5. A process according to claims 1 to 4, characterized in that the treatment of the tanned leather is carried out with 0.1 to 5.0%-wt., relative to the shaved weight of the polymer tanning agent, at a float length of up to 300%, at temperatures to a maximum of 70°C and pH values in the range of from at least 2.5 to 8.0.

6. A process according to claims 1 to 5, characterized in that retannage is carried out in combination with synthetic or vegetable tanning agents.