LT6133B - Method for unhairing of hides and skins - Google Patents

Abstract

The present invention appertains to light industry an can be applied for the preparation of hides and skins to tanning. The descriptive unhairing of hides and skins is carried out within two stages: A (immunization) and B (unhairing), when stage B is carried out in the solution of the stage A (amount of materials are based on raw hide or skin mass): Stage A: liquid coefficient 1-1.5, duration 1-2 hours, temperature 20-25 oC, Na2SiO3 1-3 %, regime run continously. Stage B is carried out in the solution of the stage A: liquid coefficient 1-1.5, duration 1.5-2 hours, temperature 20-25 oC, Na2S (60%) 1.3-1.5%, regime run continously. The released hair is separated by filtration in the end of the process. The use of the descripted method allow an icrease of quality of leather due to decrease of effect on collagen, and decrease of content of undissolved materials in wastewater.

Description

The invention relates to the light industry and can be used in the preparation of hides and skins.

There is a known method of balding the skin, which is carried out in two stages A and B, the latter being carried out in a solution of stage A (quantities of substances are given by weight of the raw material):

Stage A - liquid coefficient (h) - 0.6, temperature - 23-25 ° C, duration 3 hours, NaOH 2-3%, Na ₂ HP0 ₄ - 1.5-2%, Na ₂ S - 0.55-0.65%, the mode is stirred continuously.

Stage B - incl. increase to 1.0, temperature 20-25 ° C, duration 3-13 hours, Na ₂ HP0 ₄ - 1.5-2%, mode -1 hours. mix continuously, then leave at rest (see LR Patent No. 4097, IPC C14C 1/06, 1996).

Using this method, the hair is curled and run off, contaminating it with protein breakdown products. Also harmful is effluent Na ₂ HP0 ₄ .

A known method of balding is using enzymes and an alkaline medium. The conditions for baldness are as follows: k = 2-4, temperature 20-30 ° C, 12-24 hours, NaHS 0.2-0.8%, Ca (OH) 2 0.2-0.8% isolated from Streptomyces bacterial enzyme of the genus, 15-120 U / g, 3-4 hours mode, stirring continuously, remaining at rest (see European Patent No. 1304389 Al, TPK C14C 1 / 06,2001).

The main disadvantage of this method is that Ca (OH) _{2 is} used for balding, which, due to its limited solubility, forms sludge in the effluent along with NaHS. Cleaning or utilizing this sludge is a complicated and expensive process.

The closest solution to the proposed solution is the method of baldness of the skin, which is applied in two stages A (immunization) and B (balding), the latter being carried out in a solution A (quantities are given by weight of the raw material):

Stage A - incl. 1.5, duration 45 min, temperature 20-25 ° C, Ca (OH) ₂ - 1.5%, mode 15 min. stirring continuously, then leaving at rest. At the end of the process, the hair is filtered off.

Step B is carried out in the solution of Step A. Duration - 1.75-2 hours, temperature - 2025 ° C, Na ₂ S (60%) - 1.5%, mode - continuous mixing (See Willy Frendrup, Hair-saving unhairing methods in leather Processing (report) , US / RAS / 92 / 120. Regions Program for Pollution Control in the Tanning Industry in

South-East Asia, United Nations Industrial Development Organization, September 12

2000, p. 7).

This method severely destroys collagen proteins and wastewater is rich in insoluble calcium hydroxide, which makes wastewater treatment expensive and difficult.

The object of the invention is to improve the quality of the finished bat by reducing the effect of chemicals on collagen and reducing the contamination of wastewater with insoluble substances.

This objective is achieved by the application of two stages A (immunization) and B (balding), the latter being carried out in a solution A (quantities of substances are given by weight of the raw material):

Stage A - incl. - 1-1.5, duration 1-2 hours, temperature 20-25 ° C, Na2SiO3 13%, mode - continuous stirring.

Step B is carried out in the solution of Step A. See 1-1.5, duration 1.5-2 hours, temperature 20-25 ° C, Na ₂ S (60%) 1.3-1.5%, mode stirring continuously. At the end of the process, the hair is filtered off.

This method of baldness reduces collagen exposure and reduces the amount of insoluble matter in the effluent.

Specific examples of the proposed method of baldness are:

Fig. After soaking, the raw material of leather shall be treated in accordance with the following procedure:

Stage A - incl. 1.0, temperature - 20 ° C, duration 0.5 h, Na ₂ SiO ₃ - 0.5%, mode - continuous stirring.

Step B is carried out in the solution of Step A. See -1.0, duration 2 hours, temperature20 ° C, Na ₂ S (60%) - 1.5%, mode - stir continuously. At the end of the process, the hair is filtered off.

Fig. After soaking, the raw material of leather shall be treated in accordance with the following procedure:

Stage A - incl. 1.0, temperature - 20 ° C, duration 2 hours, Na ₂ SiO ₃ - 1%, mode - continuous stirring.

Step B is carried out in the solution of Step A. See 1.0, duration 1.5 hours, temperature 25 ° C, Na ₂ S (60%) 1.3%, mode stirring continuously.

At the end of the process, the hair is filtered off.

Fig. After soaking, the raw material of leather shall be treated in accordance with the following procedure:

Stage A - incl. 1.5, temperature - 20 ° C, duration - 2 hours, Na ₂ SiO ₃ - 1.5%, mode - stirring continuously.

Step B is carried out in the solution of Step A. See - 1.5, duration 2 hours, temperature20 ° C, Na ₂ S (60%) - 1.5%, mode - stir continuously. At the end of the process, the hair is filtered off.

Fig. After soaking, the raw material of leather shall be treated in accordance with the following procedure:

Stage A - incl. 1.5, temperature - 25 ° C, duration - 2 hours, Na ₂ SiO ₃ - 3%, mode - stirring continuously.

Step B is carried out in the solution of Step A. See -1.5, duration 2 hours, temperature 25 ° C, Na ₂ S (60%) - 1.3%, mode - continuous stirring. At the end of the process, the hair is filtered off.

Fig. After soaking, the raw material of leather shall be treated in accordance with the following procedure:

Stage A - incl. 1.5, temperature - 20 ° C, duration - 2 hours, Na ₂ SiO ₃ - 3%, mode - continuous stirring.

Step B is carried out in the solution of Step A. See 1.5 hours, 1.5 hours duration, temperature-30 ° C, Na ₂ S (60%) - 4%, mode - continuous stirring. At the end of the process, the hair is filtered off.

By the known method and the variations of the proposed method shown in the examples, the baldness was obtained and its qualitative indices were determined: hair removal, swelling, welding temperature and amount of collagen protein degraded. Insoluble matter resulting from baldness per kg of skin was also determined.

Hair removal was evaluated organoleptically according to the conditional scoring system:

- hair unaffected or affected but not mechanically removable from the skin, 1 - hair remaining on the skin but easily removed mechanically, 3 outer skin layer clean.

The effect on collagen proteins was evaluated by the amount of oxyproline in the treatment solutions and the swelling. The swelling is determined gravimetrically. Insoluble matter in the treatment solution was determined gravimetrically.

Table

Indicator Measuring unit Known way Suggested method by examples 1 2 3 4 5 Hair coatings removal scores 3 1 3 3 3 3 Degradation of collagenous proteins g / kg of skin 0.058 0.028 0.041 0.016 0.052 0.064 Scratch % 35.5 24.8 26.9 24.4 27.8 36.9 Insoluble matter quantity g / kg of skin 3.46 0.98 1.34 1.98 2.76 3.51

Using less than 1% Na2S _three quantities and at a step length which is shorter than 1 h. deteriorates the hair surface is removed because the hair is just apardomi, but their relationship to the dermis is weakened slightly, and the use of more than 3% Na2S _three quantities and temperatures higher than 25 ° C, inducing effect of collagen and increases insolubles leakage.

Thus, the variants described in Examples 2, 3 and 4 are suitable for baldness. The present invention has the following advantages over the prior art:

- improves the quality of the treated leather, as collagen proteins are less affected by baldness;

- reduction of contamination of wastewater with insoluble matter due to the use of soluble Na ₂ SiO ₃ ;

Its use makes it possible to dispense with low soluble Ca (OH) ₂ , which forms sludge contaminated with sulfides and protein degradation products and is difficult to clean.

Claims (3)

DEFINITION OF INVENTION Claims 1. A method of dermatitisation of skin through two steps A and B, the latter being carried out in a solution of stage A using a hair immunizing agent, characterized in that Na2SiO3 is used as a hair immunizing agent in step A. 2. A method of balding according to claim 1, wherein in step A, 1-3% of Na 2 SiO 3 is added. 3. The method of baldness according to claim 1, wherein the duration of stage A is 1-2 hours.