Copolymers and their use in the treatment of leather

Details Copolymers and their use in the treatment of leather Copolymers and their use in the treatment of leather

1995-06-12

1996-09-17

Schofer, Joseph L.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

8 9421, 526320, C08F22006, C08F22028, C14C 322

Patent

active

055569307

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to copolymers built up of ethylenically unsaturated acid-groups-containing monomers, ethylenically unsaturated glycerol derivates and optional further ethylenically unsaturated monomers copolymerizable with the above monomers. The present invention further relates to the use of these copolymers in the treatment of leather.
Fat liquors and greases for leather and fur manufacturing are produced --among other methods--by introducing sulfonate and/or sulfate groups into unsaturated oils and fats. The water-soluble or water-emulsifiable compounds so obtained are used in the liquoring float, optionally together with other auxiliaries, e.g., emulsifiers or unsulfonated oils.
In addition to said fat liquors and greases which are mainly based on natural fatty substances, such as fish oil or lard oil, dissolved or dispersed polymers are used in the treatment of leather. DE-3931039 A1 describes the use of copolymers of long-chain, hydrophobic and hydrophilic monomers to render leathers and fur skins hydrophobic. The copolymers, which are used in a partially neutralized form dispersed in water, comprise as hydrophobic monomers 50 to 90%-wt. C8-C40-alkyl(meth)-acrylates, vinyl ester of C8-C40-carboxylic acids and, as preferred hydrophilic monomers, 10 to 50%-wt. acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid and itaconic anhydride. EP 0372746 A, which considers in detail the polymers proposed in literature for the treatment of leather, claims an aqueous dispersion of a copolymer for retanning, fat-liquoring and hydrophobing leather. The claimed copolymer consists of 10 to 50%-wt. of a hydrophilic monomer and 50 to 90%-wt. of a hydrophobic comonomer. The known monoethylenically unsaturated mono- and dicarboxylic acids are used as hydrophilic monomers. The hydrophobic monomers used for the production of the copolymers are C8-C22-esters of the acrylic and methacrylic acid, alkenes and vinyl esters of long-chain carboxylic acids.
The copolymers are used to treat conventionally tanned hides, e.g., hides tanned with mineral tanning agents, such as chromium-(III)-salts. To this end, the hides are deacidified after washing, washed again with an aqueous dispersion comprising 3 to 10%-wt. copolymer, relative to the weight of the tanned leather, and milled in a drum at 30.degree. to 50.degree. C. The float ratio normally amounts to 100%, i.e., the weight ratio of treatment liquid to shaved weight of the leather amounts to 1:1. After 0.5 to 2 hours of milling, the copolymer is fixed to the hide by adding a 10% formic acid solution.
The residual float is drained off and the hide is washed with water once again.
Even if an optimal amount of copolymer in the float was used, i.e., a quantity which, relative to the shaved weight, just results in a soft, supple leather, the residual bath, i.e., the liquid which is rejected after the treatment of the leather, comprises non-exhausted treating agents. Accordingly, it is an object to provide copolymers for treating, in particular for softening leather which are exhausted to a larger extent so as to relieve the waste water resulting from the leather treatment.
According to the present invention, this object is achieved by using copolymers which comprise incorporated therein by polymerization general formula (1) ##STR1## with R.sub.1 =H, methyl R.sub.2 =C.sub.12 -C.sub.24 -alkyl, C.sub.12 -C.sub.24 -alkylaryl C.sub.12 -C.sub.40 -acyl with the monomers a) and b), treatment of leathers and fur skins, whereby the sum of monomers a+b+c=100.
It is known to use the above-mentioned monomers a) and b) for the manufacture of copolymers. U.S. Pat. No. 4338239 describes a thickener for polar organic solvents and aqueous systems which comprises at least 60%-wt. monomers of group a) and 0.2 to 20%-wt. monomers of group b). These copolymers are unsuitable for fat-liquoring and greasing leathers. The copolymers according to the present invention which are suitable for softening leathers comprise 20 to 60%-wt., ethylenically unsaturated acid-groups-

REFERENCES:
patent: 4338239 (1982-07-01), Dammann

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