DD243046A1 - METHOD FOR REMAINING MINERAL PRODUCED LEATHER - Google Patents

Abstract

The invention relates to a process for the retanning of mineral-tanned leather using synthons, resin tanning agents and special aqueous copolymers consisting of the ammonium salt of acrylic acid and crosslinking CO monomers in conjunction with up to 15% ammonium sulfate. The peculiarity is that the leathers are characterized by the application of the process according to the invention by filling, softness, level dyeing and especially by good uniform millability.

Description

Field of application of the invention

The invention finds application in the leather industry. It relates to a process for retanning mineral-tanned leathers in wet-finishing, whereby high-quality leathers are obtained.

Characteristic of the known technical solutions

The selection of special retanning methods in the wet setting greatly affect the quality of leather to be produced in terms of organoleptic and aesthetics. Increasing demands on the leather quality, such as uniform filling effect in the entire leather surface, scar and grain fineness, improvement of the millability, improvement of softness and improvement of the chromaticity when reaching typical range of test parameters are conditions that must meet today fashionable leather types.

A variety of tanning agents that are currently being used extensively in retanning include chromium salts, zirconium salts, aluminum salts, exchange syntans, resin tanning agents, and vegetable tanning agents. The use of these tanning agents alone or in combination affect the leather character in various ways. By quite elaborate Naßzurichtungstechnologien can be largely produce the leather qualities that meet today's requirements.

In recent years, new Nachgerbverfahren using water-soluble polymers have been presented.

In DE 3141496 A1 is for retanning a polymeric tanning material, based on acrylamide, and amino acrylates using special conditions (amount used: 0.025% to 1%, float length of 30% to 300%, pH range 3-6, temperature 20-60 ⁰ C) which brings about a significant improvement in the dyeability of the leather, in levelness and color deepening.

Partly one finds also quite critical assessments over the use of Nachgerbstoffen on the basis of esters of the acrylic acid (leather and Häutemarkt 51, S. 607-619,1976). The use of modified polyacrylic compounds has found versatile application in recent years: the use of modified polyacrylic compounds. B. Glutinleim with homo- or copolymeric acrylic acids or their alkali metal or ammonium salts in a weight ratio of 1:12 to 12: 1 is used as a filler for leather use (DE-PS 2033973).

To avoid friction damage in the wet processes of leather production serve carboxyl-containing polymers such. B. the Na salt of an acrylamide-acrylic acid copolymer in proportions of 0.05 to 2.0 g / l (DE-OS 2942858).

DE 3248485 includes a process for retanning leather by means of polymers based on acrylic and / or methacrylic acid, which is intended to bring about a fuller, denser leather fiber structure, refinement and densification of the scars and softer feel of the leather.

DE 3005699 A1 describes a process for the neutralization of mineral-tanned leather, alkali metal salts of carboxyl group-containing polymers being used. By this method, it should lead to a charge shift in chrome-tanned leather, thereby the subsequent chemical processes, such as retanning, fats and dyeing are favorably influenced in terms of the distribution and affinity of the aids used to leather fiber. However, this neutralization process using a Na polyacrylate does not cause a special grain texture, which guarantees a good millennia of leather with appropriate softness and fullness.

In the following description according to the invention, this effect was demonstrated by the composition between the retanning agents Syntan / Harzgerbstoff and the specific polyacrylate compound.

In comparison to conventional tanning systems (chromium / synthane, chromium / glutaric dialdehyde, vegetable / synthan or chromium / vegetable) or other polymeric tanning groups such as e.g. As polyadducts, polycondensates treated leather do not have, like leather produced by the process according to the invention on a grain texture that leads to the process of Millens, to a very uniform, fine and elegantly acting millet grain over the entire leather surface.

Object of the invention

The object of the invention is to develop a retanning process which, according to the state of the art, maintains the leather quality in terms of softness, fullness, dyeability, while at the same time improving the millability. This meets the trend for fine-pored, less covering leathers with different handle variations.

Explanation of the essence of the invention

The invention has for its object to develop a process for the retanning of mineral-tanned leathers, by achieving a special grain quality for good millability while maintaining good leather properties in terms of softness, body and dyeability.

According to the invention, this object is achieved in that, in the retannage in addition to synthesizers and resin tanning aqueous copolymers, consisting of the ammonium salt of acrylic acid and crosslinking comonomers in conjunction with up to 15% ammonium sulfate, are used.

The aqueous copolymers consist of acrylic acid and crosslinking hydroxy or epoxy group-containing acrylate monomers in proportions of from 0.2 to 10, preferably 0.5 to 4% by weight. Typical representatives of the hydroxi- or epoxide-containing comonomers are:

"Hydroxi-etiryl (meth) acr.vlat

GH ₂ o σ - R- ⁰ ^ CH ₂ - GH • - Second OH GH ₂ = G · - ι .R- CH ₂ - O GH ₉ s ^d GH ₂ β G - I ^{σ K} m - OI 1 R = Η ^: or ÖEÜ -

N -. Methylol (meth) acrylamide

Furthermore, the aqueous copolymer contains 10 to 15, preferably 12 to 14% ammonium sulfate (based on the solids content of the solution).

Through the use of crosslinkable hydroxi-containing monomers in various forms in aqueous copolymers of the ammonium salt of acrylic acid, an improvement according to the invention of the retanned leather is achieved, in particular a special grain texture for good millability. It should be noted that on the one hand achieved by the use of crosslinking comonomers good millability, but on the other hand, the softness and fullness of the leather does not adversely affected

By introducing reactive groups within the retannage at temperatures between 20 and 8O ⁰ C, a better solidification and anchoring in leather scars is achieved and achieved a lower water absorption of the leather.

These effects also have a favorable effect on the final quality of the leather. * -

Surprisingly, it has been found that the special presence of ammonium sulfate in the copolymer solution further enhances the above-mentioned good leather properties. This effect is not achieved by other salts of similar composition, not by sodium sulphate or by ammonium chloride.

A clear statement about the mode of action can not yet be made, but it is to be expected that the ammonium sulfate favorably influences the reaction of the copolymer with the leather. In this case, the beneficial effect can only be achieved if the ammonium sulfate is already present during the polymerization of the preparation of the aqueous copolymer solution.

Subsequent addition of the sulfate in the Nachgerbbad leads to no further improvement. The copolymer is used as an aqueous solution having a solids content of 40% to 60%, the pH of the solution is adjusted to 6 to 8, preferably 6.5 to 7.5.

The process of retanning can be carried out in the usual vessel technique of wet chemical treatment, such as in barrels and dyeing machineries.

The wet chemical treatment expediently begins with a washing process to remove unbound tannins from the mineral-tanned leather. Thereafter, the neutralization is carried out at 100-200% liquor using 0.5-2% formates and 1-1.5% alkaline neutralizing agent z. As carbonates or bicarbonates, preferably with the concomitant use of a conventional electrolyte-resistant anionic fatliquor. This is followed by a Zwischenwaschvorgang at 50-70 ° C in preparation for the dyeing. Thereafter, the mineral-tanned leather with an amount of water of 50-250% (based on the shaved weight) at 30-70 ⁰ C using 1: 2 metal complex dyes or other conventional leather dyes dyed in 20-40 minutes. In the same bath, the addition is carried out jointly or step by step of retanning agents using 4-8% of synthetic resins, 1-4% of resin tanning agents and 2-4% of the specific copolymer described.

Under the effect of the combination described, the leather is tumbled in the barrel or in the dyeing machine for 20-50 minutes.

The combination retanning with the described copolymer achieves a very demanding leather quality, which is particularly represented by its excellent millability. The Nachgerbbad may be followed by a conventional anionic fatliquoring immediately or after a Zwisschenabsäern for shade fixing and washing or rinsing, which is adjusted according to the desired type of product. Appropriately, is fixed by the greasing with an organic acid treatment or another small Synthanaufsatz. The downstream of the chemical wet finishing operations mechanical-physical nature, such as drying, softening and the entire color finish can be done by known methods, especially the operation of Millens gained importance with regard to the lifting of the scars obtained by the method according to the invention.

embodiment Example 1:

Starting material:

Treatment vessel:

To wash:

Entflotten:

Neutralization:

Chrome-tanned bullskin, fold thickness: 1.3 mm

Barrel or dyeing machine

200% water, 40 ^° C, 10 '

10 '

200% Wasser40 ° C30 '

2% of a neutralizing synthetic tanning agent

1.0% electrolyte resistant grease remover: 10 '

Washing: 200% water, 50 ° C, 10 '

Escape: 10 '

Coloring: 150% water, 50 ⁰ C, 20 '

+% anionic dye retanning in the same bath

4% vegetable tanning eff. 30 '

4% synthetic tanning eff. 30 '+ 3% synthetic tanning eff. 30 'Escape: 10'

Washing: 200% water, 50 ⁰ C, 10 '

Escape: 10 '

Greasing: 150% water, 50 ⁰ C, 40 '

8% fatliquoring mixture of natural and synthetic fatty substances Add-on: 0.5% of a cationic resin tanning material 10 '

Rinse: 30 ⁰ C, 10 '

All percentages refer to the shaved weight of the leather.

Example 2: X retanning: Chrome-tanned bullskin, fold thickness: 1.3 mm 30 min Starting material: Barrel or dyeing machine " move Treatment vessel: Move 200% water, 35 ° C, 10 min To wash: Entflotten: 150% water, 35 ° C Neutralization: , 1% Ca formate, 10 min. move 1% NH ₄ -hydrogen carbonate) 1% electrolyte-resistant fatliquoring agent) Entflotten: 200% water, 50 ⁰ C, 10 min. move To wash: Entflotten: 150% water, 50 ° C Coloring: % anion. leather dye 25 min. dyeing in the same bathroom

3% of a 40% aqueous solution of a copolymer of 96 parts by weight of acrylic acid and 4 parts by weight of hydroxyethyl acrylate (adjusted with ammonia to pH = 7.5) and 14 parts by weight of ammonium sulfate (based on the solids content of the solution) 20 min. move

Trailer of 6% Synthan 3% resin tanning agent 30 min. move Absäubern: in the haggard bath 0.2% formic acid diluted 1:10, 10 min. move Entflotten: To wash: 200% water, 60 ⁰ C, 10 Tiin. move Entflotten: greasing: 200% water, 60 ^° C 0.2% emulsifier anionic / non-homogeneous 7% fatliquoring mixture of natural and synthetic fatty substances 45 min. move acidification: in the haggard bath 0.3% formic acid, diluted 1:10 10 min. move Do the washing up: 10 min., 35 ° C

Then there is a withering, stretching, drying, cleats, Millen and after-drying.

Example 3:

As Example 2 with altered composition in the retannage. Retanning: in the same bath

3% of a 45% copolymer as Example 2, consisting of 98 parts by weight of acrylic acid and

Parts by weight of N-methylacrylamide and 12 parts by weight of ammonium sulfate. 20 min. move

 Addition of 6% Synthan

3% resin tanning agent

30 min. move further treatment as example 2.

Example 4:

As Example 2 and 3 with altered composition in the retannage. Retanning: in the same bath

3% of a 45% copolymer as Example 2, consisting of 99.6 parts by weight of acrylic acid and

0.4 parts by weight of glycidyl methacrylate and 14 parts by weight of ammonium sulfate

20 min. move trailer of 6% Synthan

3% resin tanning agent

30 min. move further treatment as example 2,3.

Example 5:

As Example 2,3 and 4 with the elimination of the Absäuems, desoldering, washing and again Entf soldering after retanning.

Example 6:

As example 2,3,4 or 5 with the modified Nachgerbrezepturvon: 2% of the aqueous copolymer Nachsatz of: 8% Synthan

1.5% resin tanning agent

Example 7: '-

As example 2,3,4 and 5 with simultaneous addition of the aqueous copolymer with the Syhthan and the resin tanning agent, movement times: 45 min.

Examples:

Starting material: Chrome tanned pocketing or chrome gaps

Folding thickness: 1.5 mm Neutralization: 3% ammonium hydrogen

1% calcium formate

1% fat.

Retanning: 4% of a 40% strength aqueous solution of a copolymer of 96 parts by weight of acrylic acid and

4 parts by weight of hydroxyethyl acrylate (adjusted with ammonia to pH = 7.5) as well

14 parts by weight of ammonium sulfate (based on the solids content of the solution)

20 minutes to move

Nachsatzvon 4% synthetic tanning agent (synthetic resin tanning agent)

Greasing: 6% fatliquoring mixture

0.2% emulsifier

Retanning: 2% of a synthetic tanning agent 10 '

The leathers, retanned according to Examples 2 to 7, are retanned compared to the leathers of Example 1, over the entire leather surface by a particularly uniform, fine and elegantly effective Millkorn and softness and by a good color brilliance.

The nachgegererbten with the special Nachgerbstofformulierung split leather, as described in Example 8, have a very good grinding availability.

Claims (3)

Invention claim: 1. A process for the retanning of mineral-tanned leather in the presence of synthons and resin tanning agents, characterized in that the Nachgerbbad 2 to 4% of an aqueous copolymer consisting of the ammonium salt is added. 2. The method according to claim 1, characterized in that the aqueous copolymer contains 0.2 to 10, preferably 0.5 to 4% Hydroxi {meth) acrylate or glycidyl (meth) acrylate or N-methylol (meth) acrylate , 3. The method according to claim 1, characterized in that the aqueous copolymer solution contains 10 to 15, preferably 12 to 14% ammonium sulfate (based on the solids content).