CS224220B1 - Method of manufacturing grain and lining leather - Google Patents

Description

The invention relates to a process for the production of grain leather and lining, in particular of pigskin and cowskin leather, in which the skin is chipped, tanned, glueed and dried, preferably by gluing to glass.

Until now, the leather has been chipped to level the thickness of the tannery raw material (L. Masner et al.:: The Tannery Handbook, 11 ·, p. 36, SNTL Prague 1963), in wet condition, after standing and leaching or after tanning. This leveling splitting achieves a preliminary thickness, the final thickness as required by the purchaser is obtained by grating. The splinter is sorted and either further processed into lining leather or used for the manufacture of glues and gelatins, while the bedding Generally, they represent waste · The production process described is suitable for the production of upper leathers, their surface treatment is performed on the face side ·

From the point of view of the economical use of the skin mass, it would be advantageous to replace the crushing by re-splitting; however, the cut of leather split in the dry state is rough and this rough surface, from which individual leather fibers are frayed in places, cannot be treated even by subsequent treatment to a sufficiently smooth surface to allow the use of these split leather as upper leather.

A completely new approach to solving this problem, not burdened by the above-mentioned disadvantages, is a method of production of full grain leather as well as lining of leather, especially of pigskin and bovine leather, in which the leather is tanned, glueed and dried best by sticking to glass The invention is characterized in that, prior to drying, they are modified in such a way that they overcoat 8 to 10-2.

224 220 percent chrome slurry and fill with from 1 to 8 percent by weight of the weight of the filler, comprising a condensation product of urea and phenol with formaldehyde of molecular weight 800 to 7500, a dispersed acrylate polymer or a copolymer of polyethylene acrylate, polybutyl acrylate, polybutyl methacrylate or which copolymer optionally contains, or is grafted with, 2 to 10 percent protein, or a synthetic polyphenolic type tanning agent having an average molecular weight of 600 to 8000, then dried and then subjected to a second splitting, this time in the dried state. a better effect is achieved in the process according to the invention if the filling is combined with hydrophobising liquor using a 3% solution of a 6-18 carbon-alkyl-alkyl compound of the carboxyl group of which has a carboxyl group they are at least partially neutralized with ammonia or low molecular weight amines up to a maximum of 5 carbon atoms in the chain, and three to fifteen percent of a mixture of synthetic lubricants with natural lubricants.

The main effect of the method according to the invention is the smoothness of the chipped side, and this smoothness allows a perfect imitation of the face side when properly treated. Thus, the obtained leatherette is usable for the production of full grain leather and its smoothness is objectively detectable by measuring the static shear friction coefficient at the moment of friction pair transition from rest to relative motion as well as by measuring the dynamic shear friction coefficient at a given frictional slip speed. Other advantages of the method according to the invention also include improved uniformity of the grain size of the full grain leather, an increase in the yield of the split leather and, in particular, the preservation of the amount of glue, while reducing the fallout of the slack. All this creates the preconditions for the development of a new assortment of upper and possibly lining leather ·

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The tanner's raw material, in particular pigskin and cowhide, is basically processed according to the usual process, i.e. splitting # in the clearing, by crushing, tilling and drying, preferably into glass plates. In order to achieve a smooth cut during the second split in the dried state, it is important to include the pre-treatment modification. drying and sieving using preparations having the ability to bind to collagen and thereby modify the physical properties of the leather. These modifying fillers are used in the process of the invention from 1 to 8 weight percent based on the weight of leather and include the condensation products of urea and phenol with formaldehyde of molecular weight 800 to 7500, dispersion acrylate polymers or copolymers from the group of polyethylene larylate , polybutyl acrylate, polybutyl methacrylate or polyacrylonitrile, which copolymer optionally contains, or is grafted with, 2 to 10 percent protein, or a synthetic polyphenolic type tan with an average molecular weight of 600 to 8,000. After drying, the leather is then split for a second time in a dry state and proceeded to surface treatments by conventional methods.

The filling effect and the smoothness of the chipped surface are further increased if the filling in the process according to the invention is combined with hydrophobic liquor using a 3% solution of an alkyl group of the C 6 -C 8 alkylcarboxylic type in which the carboxyl groups are at least partially neutralized by ammonia or low molecular weight amines having a maximum of five carbon atoms in the chain and, in addition, three to 15 percent of a mixture of synthetic lubricants with natural lubricants.

The effect of the filler on the chipped side smoothness was demonstrated by measuring the static shear friction coefficient, fs, at the moment the friction pair went from rest to relative motion, i.e., into sliding, and by measuring the dynamic shear friction coefficient, fd, at the given frictional sliding speed. Optimal conditions are achieved

224 220 «v using 3» »5% filler, where fd v

The measurement of shear friction coefficient showed dependence of the used amount of filler on the smoothness of the cut, ie splitted side, as will be illustrated by the following examples, which will also explain the nature of the method in more detail. according to the invention ·

Example 1

The raw material for lining of pigskin or cowhide is processed by conventional leather operations, in particular by leveling in the clearing and tanning. · Bleaching with 2% sodium bicarbonate solution and neutralizing the bath, consisting of 0.5% calcium formate and sodium bicarbonate · Washing and combined filling with curing using one percent of the filler, which is a condensate of urea and phenol with formaldehyde, and 15% blend of synthetic and natural lubricants. Other finishing operations are usual again. The resulting leather is dried in a glued state on glass plates and chipped in a dry state. fd = 714 ·

Example 2

The production of the lining and the hides of pigskin was carried out in the same manner as in Example 1, but the filling and curing operation was carried out with four percent of the formaldehyde condensation product. urea, phenol and phenolsulfonic acid in a ratio of 0.7 to 1, 4: 0, 5: 0, 95, in the form of an approximately 40% aqueous solution in combination with three percent of an alkylcarboxylate-based hydrophobizing agent partially neutralized by a low molecular weight amine; 3 percent blend of synthetic and natural lubricants

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Finishing operations also coincided with Example 1. Measured values of static and dynamic shear coefficient: fs «405; fd »620«

Example 3

Identical to Example 2 · Eight percent of about 40% aqueous solution of formaldehyde, dihydroxidiphenylsulfone and naphthalenesulfonic acid condensation product in a ratio of · 0.7: 0.9, 9. 9, 9 was used. The measured values of static and dynamic shear coefficient were: fs a 480; fd = »705.

Example 4

The procedure was the same as in Example 1, but three percent of the approximately forty percent aqueous condensation product of phenolsulfonic acid, formaldehyde and urea in a 1: 0, 9: 0, 5 ratio were used for filling. Measured values: fs >445; fd «712.

Example 5

The processing of the pigs was carried out according to Example 2. The filling was carried out using a filler in the form of a 40% aqueous solution of the formaldehyde, phenol and urea condensation product, in a ratio of 0.9: 1 " 1: 0.4 " dynamic coefficient of shear friction: fs »415; fd = 610.

Example 6

The bovine raw material was processed according to Example 1, except that a filler composition of acrylic acid-butyl acrylate copolymers of 90:10, at a concentration of 7% and a second batch of acrylic acid-ethyl acrylate copolymers of 5:95, was used for filling. forty percent concessionation. Fs »483; fd = 651.

- 6 -,

224 220

Example. 7

Procedure similar to Example 2. Five percent of the filler composition, which consisted of an approximately 10 percent aqueous solution of acrylic acid / methacrylic acid copolymer, was used to fill leather in a ratio of 5Os 50 O · Static and dynamic shear coefficients measured: fs = 510; fd = 662 ·

Example 8

The processing of the pigs into the lining of the leather was carried out as in Example 1, but the filler was prepared by adding 40% sodium hydroxide solution followed by approximately 4% aqueous glue solution to the polyacrylic acid. dynamic shear coefficient: fs = 505; fd = 650 ·

Claims (2)

OBJECT OF THE INVENTION 1. A process for the production of grain leather and lining, in particular pigskin and cowhide leather, in which the leather is chipped, tanned, glueed and dried, preferably by gluing to glass, characterized in that before drying they are modified by shading. up to 10 percent chromic slurry and fill with from 1 to 8 percent by weight of the grouted filler composition comprising a condensation product of urea and phenol with formaldehyde of molecular weight 800 to 7500, a dispersion acrylate polymer or a copolymer of polyethylene acrylate, polybutyl acrylate, polybutyl methacrylate; polyacrylonitrile, which copolymer optionally contains, or is grafted with, 2 to 10 percent protein, or a synthetic tannins of polyphenol type having an average molecular weight of 600 to 8000, then dried and then subjected to a second split, this time in the dry state state. 2. The process of claim 1, wherein the feed is combined with hydrophobizing liquor using a 3% solution of a 6-18 carbon-alkyl-alkyl compound of the alkyl chain whose carboxyl groups are at least partially neutralized with ammonia or low molecular weight amines to a maximum of 5 carbon atoms in the chain, and three to fifteen percent of the blend of synthetic lubricants with natural lubricants.