MXPA01002872A - Auxiliary for liming and loosening hairs of animal skins - Google Patents

Abstract

The invention concerns an auxiliary for liming and loosening hairs of animal skins, containing, in aqueous solution:10 to 50 wt.%of a polysaccharide solution;5 to 25 wt.%of a mercapto-carboxylic acid or one of its salts;and 1 to 10 wt.%of a mercapto-alcohol or one of its alkaline salts. Said auxiliary is added during liming of animal skins, to the solution generally containing alkalis, inorganic sulphides or hydrosulphides and anionic or non-ionic surfactants, for standard production of sweatbands.

Description

ADJUVANT TO OPEN AND DEPIL ANIMAL SKINS DESCRIPTIVE MEMORY The subject of the invention is an adjuvant for opening and plucking that is used in the manufacturing process known as untanned skin removal, skinning of the epidermis and subcutaneous connective tissue, the so-called untanned skin. As is already known, the leather manufacturing process in general consists of three main cycles, namely, riparian, tanning and surfacing workshops. In the ribera workshop, the skin, salty and dry, is first restored to its hydrated green skin condition by soaking it, followed by a treatment with alkaline baths to open and depilate the skins. The depilating and opening actions are generally carried out in a single step of the procedure, the appellate procedure. Fermentative hair removal procedures and procedures in which the hair is completely destroyed by the effect of keratolyzing agents are also used. The swelling and the alkaline reaction are finally removed again by neutralization. In this condition the skin is known as untanned skin. The means used to remove the hair, the epidermis and the roots of the hair generally depend on whether it is intended to chemically destroy the hair or save it. If the hair is of little value, chemical hair removers are applied directly to the scalp of the skins whereby the roots of the hair are destroyed or at least attacked more or less. Normally a suspension of calcium that has sulfur is used for this purpose. The industrial practice is to perform this treatment (apelambramiento) on large shaking drums. The calcium suspension not only affects the hair and roots of the hair but also the substance of the skin with which the leather is produced. This change of skin, fur, is an essential component of the tanning process. To achieve an optimal appellant effect, little or no consideration is given to saving the hair even in cases where the hair could have a future use. During the dressing procedure, the skin is first opened by means of an alkaline swelling ie its structure is loosened resulting in a greater porosity of the skin and a special softness or desirable stretch, for example for adjustable leathers. In addition, some proteins that accompany the fibrillar connective tissue dissolves. The duration and intensity of the apelambramiento can only be determined empirically for each case, since the different skins react in a very different way to the apelambramiento procedure. Too much swelling can cause a "loose" or "slippery" grain, ie the upper skin layer containing the pores of hair roots, empty sweat glands and a branched system of blood vessels separating from the compact fiber layer that It is under when the skin flexes and wrinkles. The apelambramiento should include the actions of depilating and opening the skin, since they are often combined in a procedure, however, in most cases the two procedures are only partially overlapped, since generally depilation and / or destruction of Hair is done first, followed by the action of opening the skin. As in the depilation procedure, several individual factors also work together in the opening procedure. The chemicals of apelambramiento must above all attack the keratin of the hair and epidermis without destroying the collagen of the skin. Keratin can be eliminated by reduction and hydrolysis. The hydrolytic bases for this product are, for example, calcium hydroxide, hydrated lime [with 80-969% Ca (OH) 2] and caustic soda solution. Sodium sulfide, sodium hydrogen sulfide and calcium hydrogen sulfide have a reducing effect. The action of these substances also destroys the epidermis so that this layer together with the hair can be easily removed with a dull razor knife or with a machine. As in the epilators, sodium sulfide has a reducing effect on the sulphurous amino acids of keratin. After this the caustic limestone can attack more easily and cause the hydrolytic decomposition of the prekeratins in the basal cell layer of the epidermis. After the hair and the epidermis have been removed, the remnants of meat and fat adhering to the lower part of the subcutaneous connective tissue are removed with a skin-peeling knife or with a cylinder-cutting machine. The untanned skin without the epidermis and subcutaneous connective tissue contains in wet condition of 60 to 80% water and fat, the rest is approximately 98% collagen. Thanks to the European patent application EP 0 728 844 we already know a multifunctional leather processing agent for the manufacture of leather in the ribera workshop. This agent has a solution of proteolytic and lipolytic enzymes, molasses and hydrothopes and possibly other dispersed additives, swelling inhibitors, epilators or calcium solvents. This agent serves above all to improve the rehydration and elimination of dirt in the soaking, improving the depilation, inhibiting swelling in the bottle and improving the cleaning of the skin surface in the maceration bath. Although the preparation of such a combination has already provided advantages over the individual use of the aforementioned enzymes up to now, there is still the problem of finding an improved and safer appellate process in order to obtain a better leather quality. It has now been discovered that this problem can be solved with an adjuvant for opening and depilating the skins of animals in aqueous solution containing: From 10 to 50% by weight of a polysaccharide solution From 5 to 25% by weight of a mercaptocarboxylic acid or of one of its salts From 1 to 10% by weight of a mercaptoalcohol or one of its alkali salts.

In the adjuvant according to the invention, the molasses are preferably used as a polysaccharide solution. The use of molasses in the processing of skin is already known as molasses, molasses can be added during all operations in the ribera workshop. The addition of molasses during the apelambramiento is particularly useful, since it clearly improves the solubility of the hydrated hair in the soaking so that the skin opens better. Although the melases generally deserve a preference for being a particularly economical saccharide solution it is also possible to use other solutions containing water-soluble carbohydrates, for example, sugar solutions with a sugar content of about 10 to 70% by weight. Another important constituent of the adjuvant according to the invention is a mercaptocarboxylic acid or a salt thereof, preferably thioglycolic acid. The use of these mercaptocarboxylic acids as keratolizing agents is already known. They are widely used for hair treatment, but also as a depilator. Thioglycolates have also been used in tanning for epilation of skins but do not have much technical importance for this application. Another constituent of the adjuvant according to the invention is a mercaptoalcohol in particular mercaptoethane in the form of sodium alcohol. It produces a pronounced epilation effect. The adjuvant according to the invention provides a clear improvement in the quality of the leather thus treated. Experts note in particular that their use results in brighter tanned skins and that this leads to a wider scale of leather qualities. An additional factor is that the use of the adjuvant in question is useful for particularly smooth untanned skins, thus minimizing the superficial loss normally experienced in the manufacture of leather from a skin. In addition, the adjuvant according to the invention causes a high calcium solubility which is a requisite for the skin to be able to open optimally. The adjuvant according to the invention provides other advantages with respect to the high environmental stress traditionally related to the manufacture of leather. The use of the adjuvant makes it possible to considerably reduce the amount of inorganic sulphides or hydrosulphides in the appellate process. The removal of these chemicals from the effluent can be a major problem. Furthermore, swelling of the skin during the apelambulation is easier to regulate with the preparation of the combination according to the invention than with the sole addition of sulfides or hydrogen sulphides. Finally, it avoids the need for primary aiiphatic amines and other organic nitrogen compounds that to date are frequently added in the depilation during the apelambulation procedure. These amines and nitrogen compounds not only spread an unpleasant odor, but must also be removed during wastewater treatment that requires greater technical effort.

An important feature of the adjuvant according to the invention is that it does not contain proteolytic or lipolytic enzymes whose use in the appellant has to date been the prevailing standard. However, enzymes not only have the disadvantage of being relatively expensive, but also require strictly controlled conditions of the process to achieve maximum results. If during the treatment of skins of animals with enzymes, an optimum temperature and pH requirements are not observed, the action of the enzymes used is often inadequate and sometimes too intense. On the one hand they are supposed to remove albumins and globulins from the remnants of blood in the skin of the animal, on the other hand they also decompose proteoglycans by coating the collagen fibers and also make the epidermis more permeable so that the leather rehydrates more quickly and is softer, cleaner and smoother after soaking. The enzymatic action cleans the proteins that do not form the leather, removes the remnants of roots of hair and fat and partially decomposes the elastin in the grain resulting in a greater softness of the skin. The complete decomposition of the elastin that can be seen again and again when the enzymatic action is too strong, is not in any favorable way, since then the grain layer partially collapses which has a negative effect on the smoothness and cleanliness of the the skin. It is essential that the structure of the collagen fibers is not damaged by the appellate process. While the action of the enzymes is intimately governed by the prevailing temperature and pH conditions, the use of the enzymes exerts a constant and careful control under the conditions of the procedure. These disadvantages are no longer present when the adjuvant according to the invention is used, since it does not depend on the enzymes. The adjuvant according to the invention can be further improved with the addition of hydrotopic substances. These are substances whose addition improves the solubility in water of other substances difficult to dissolve. This includes organic nitrogen compounds such as urea, thiourea, formamide, acetamide, n-methylacetamide, and guanidine hydrochloride. However, organic sulfonic acids, carboxylic acids and their salts, for example, eumunium sulfate and even calcium chloride have hydrotropic effects as well. The hydrotropes carry out, in the presence of proteins, a decomposition of the hydrogen bonds between the peptide chains and consequently a swelling that facilitates access to the active keratolytic ingredients and also to the anionic or nonionic surfactants used to dissolve the grease. In the process of opening and depilating the skins of animals the adjuvant according to the invention is used in an aqueous solution in addition to the usual alkalies, inorganic sulphides or hydrosulfides and anionic or nonionic surfactants which is normally applied in an amount of 0.1 to 5% by weight. The process is generally carried out at a pH value higher than 11, preferably at a pH value between 12 and 12.5 and at temperatures between 25 and 35 ° C for a period of 15 to 20 hours with intermittent stirring of the skins of animals in the agitation drums used for apelambramiento. With the skin obtained by the procedure from raw skin it is possible to manufacture particularly clean and bright leather qualities from which the roots of hair have been almost completely removed. The procedure is easily controllable and produces excellent and constant leather qualities. In addition, environmental stress is clearly reduced, since the wastewater from the process in which the adjuvant according to the invention was used, evidently contains less sulfides and no amine or other nitrogenous compounds. It is mainly suitable for processing skins of all kinds, such as sheep, goats and pigs but especially cow. The method according to the invention is explained with the following examples: EXAMPLE 1 Treatment of cowhide hair remover soaking and noque Material Salted cow skin Working drum container% details regarding salt weight Soaking to remove 200% water 30 ° C dirt 0.1% bactericidal agent 0.2% 90 minutes anionic tensioactive stirring Drainage float Main soak 150% water 28 ° C 0.3% bacterial protease 0.2% anionic surfactant 0. 1% bactericidal 0.3% soda solution 270 minutes caustic, 45% 1: 3 agitation pH 9.2-9.5 temp 27-29 ° C Drainage float Noque: 70% water 28 ° C 0.8% polysaccharide solution no there are salts of thioglycolic acid and mercaptoethanoi 1.3% sodium sulfate, 60% 1.0% hydrated lime 0.1% surfactant 30 minutes anionic stirring 15 minutes rest 2.0% hydrated lime 0.3% sodium sulfide, 60% 30 stirring minutes 30 minutes of rest 80% of water 28 ° C 0.4% of soda solution 60 minutes of caustic agitation, 45% 1: 3 30 minutes of rest after alternating: 60 minutes rest. 5 minutes of agitation total duration of 16-18 hrs pH 12.2-12.5 temp. 26-28 ° C Drainage float Wash 200% water 26 ° C 0.3% polyphosphate 10 minutes stirring Drainage float The skin is fleshed, separated and subjected to the normal procedure.

EXAMPLE 2 Treatment to save cowhide hair in soaking and noque Material: cowhide skin Working drum container% details regarding salt weight Soaking for 200% water 30 ° C removing dirt: 1.-% of bactericide 2.-% of agent 90 minutes of surfactant agitation Drainage float 80 % of water 28 ° C 2.0% hydrated lime 0.1% lubricant 0.5% soda solution 30 minutes of caustic agitation 45% 1: 3 30 minutes of rest after alternating: 60 minutes of rest. 5 minutes of agitation total duration of 16-18 hrs pH 12.2-12.5 temp. 26-28 ° C Drainage float Washing 200% water 26 ° C 0.3% polyphosphate 20 minutes stirring The skin is peeled, separated and subjected to normal procedure.

Main soak: 150% water 28 ° C 3.-% bacterial protease 0.2% anionic surfactant 0.1% bactericide 0.3% solution 270 minutes of caustic soda agitation, 45% 1: pH 9.2-9.5 temp. 27-29 ° C Drainage float Noque: 70% water 28 ° C 0.8% polysaccharide solution No salts of thioglycolic acid and mercaptoethane 1.0% hydrated lime 0.1% agent 30 minutes of anionic surfactant agitation 15 minutes of rest 15 minutes of agitation 1.1% hydrosulfide 60 minutes of sodium agitation, 72% hair removal after 30 minutes (hair filter) 80% water 2.0% hydrated lime 0.1% lubricant 0.5% solution 30 minutes stirring caustic soda, 45% 1: 3 30 minutes rest after alternating: 60 minutes of rest 5 minutes of agitation total duration 16-18 hrs pH 12.2-12.5 temp. 26-28 ° C Drainage float Wash 200% water 26 ° C 15 minutes stirring Drainage float Washing 200% water 26 ° C 0.3% polyphosphate 20 minutes stirring The skin is peeled, separated and subjected to the normal procedure.

Claims (10)

NOVELTY OF THE INVENTION CLAIMS

1. - An adjuvant for opening and depilating animal skins, further characterized in that it contains in aqueous solution: from 10 to 50 weight percent of a polysaccharide solution, from 5 to 25 weight percent of a mercaptocarboxylic acid or one of its salts and of 1 to 10 weight percent of a mercaptoalcohol or one of its salts.

2. The adjuvant according to claim 1, further characterized in that molasses or a solution containing from 10 to 70 percent by weight of water-soluble carbohydrates is used as a polysaccharide solution.

3. The adjuvant according to claims 1 and 2, further characterized in that thioglycolic acid is used as mercaptocarboxylic acid.

4. The adjuvant according to claims 1 to 3, further characterized in that mercaptoethane is used as mercaptoalcohol.

5. The adjuvant according to claims 1 to 4, further characterized in that it additionally contains a hydrotropic substance.

6. The adjuvant according to claim 5, further characterized in that, as a hydrotropic substance, it contains urea, thiourea, formamide, acetamide, N-metii acetamide, guanidine hydrochloride, eumeno sulfonate or calcium chloride.

7. The adjuvant according to claims 1 to 6, further characterized in that it additionally contains an anionic or nonionic surfactant.

8. The procedure for opening and depilating animal skins by apelambration, by means of a solution containing alkalis, inorganic hydrogen sulphides or sulphides and anionic or nonionic surfactants, further characterized in that an adjuvant according to claim 1 to 7 is added to the solution.

9. The process according to claim 8, further characterized in that the adjuvant is added to the solution used to appeal in an amount of 0.1 to 0.5 percent by weight.

10. The process according to claims 8 and 9, further characterized in that it is carried out in agitation drums used for apelambramiento, preferably at a pH value between 12 and

12. 5 and at a temperature between 25 and 35 ° C for a period of 15 to 20 hours with the intermittent agitation of animal skins.