Method of treating leather

FIELD: leather industry.

SUBSTANCE: method comprises pickling, tanning, and neutralizing the semifinished item. During pickling and subsequent tanning, the picking liquid is provided with acetate sodium in amount of 0.2-0.5 % and, then, chromic tanner in amount of 1.5-1.8%. The tanning is carried out until the pH of the solution reaches 4.2-4.4.

EFFECT: enhanced quality of tanning.

2 tbl

 

The invention relates to the leather industry and can be used in the manufacture of leather, chrome tanned for Shoe uppers.

The process of developing skin includes the steps of pickling - processing of raw - hide hides in the acid solution, tanning - solution containing a tanning agent, a neutralizing material after planing. It is known that chrome tanning solutions tanning with chromium compounds are very sensitive to changes in pH, dilution, which creates difficulties when carrying out the process in a production environment and affects the quality of finished leather, efficient use of raw hides. When neutralization is used bicarbonate and sodium carbonate [1].

The described method of generation of leather, mostly heat-resistant of Russian leather, including tanning prepared pickling mixture of compounds of chromium, titanium and zirconium. While tanning is carried out in the presence of a masking reagent sodium acetate in the amount of 1.0-to 1.2% by weight of the hide at pH of 3.3 to 3.8 [2].

The disadvantages of the method are: the complexity of the process due to the use of a mixture of three with significant tannins their total consumption, which, in turn, leads to contamination of wastewater salts of these metals; moreover, get skin not soft, and often hard.

Closest to the claimed ways is the production of leather, chrome tanned, according to which tanning conduct basic salts of chromium with a flow rate of 2.0-2.5% by weight of the hide in the calculation of the chromium oxide after pickling using sodium chloride 6-8%, sulfuric acid 0,6-0,8%, formic acid 0.3-0.5% for whether raw materials. Neutralization sliced semi spend bicarbonate sodium consumption 1,0-1,5% [3].

The disadvantages of the method:

the relatively high consumption of chromium compounds, sodium bicarbonate;

the high chromium content in spent tanning solution (5 g/l of chromium oxide) and in wastewater;

- low degree of binding of chromium Golem.

Raising the pH of the solution and the skin to increase the degree of extraction of chromium compounds from solution leads to the appearance of defects such as tanning screed Namin, chrome spots, decreasing the use of raw hides and finished leather. In addition, the use of fly formic acid leads to a deterioration of working conditions and environmental conditions in the workplace.

The purpose of the present invention is to enhance the tanning process, reducing the consumption of chemicals, improving the uniformity of the processing of the hide and semi-finished products increased binding of chromium compounds and reducing their content in the exhaust solutions, improving the quality of finished leather.

This goal is achieved by the fact that during the pickling and the last is next tanning with chromium compounds in pikelny fluid injected sodium acetate in a quantity of 0.2-0.5% (as anhydrous product), then chrome tanning agent 1,5-1,8% (based on chromium oxide, chromium tanning carried out until the pH of the solution is 4.2 and 4.4, and into the solution to neutralize the semi-finished product is injected sodium acetate in an amount of 0.2-0.5% and sodium bicarbonate 0.3 to 0.7 percent.

In addition, to increase the availability and reduce costs as sodium acetate using a byproduct of the production of polyesters - powder product containing, wt.%: the trihydrate of sodium acetate 95-98, the admixture of polytetramethylene 0.2 to 0.8, water - the rest.

Specific examples of the process and results of semi-finished and finished leather presented in tables 1 and 2. Used whether the bull hide light weight 20 kg

Examples of the method for performing the processing of leather.

td align="center" namest="c7" nameend="c8"> 4
Table 1
Operation, types of reagents, theExamples
123456 (prototype)
Pickling:
liquid is the ratio 0,70,70,70,70,70,7
temperature, °20-2220-2220-2220-2220-22
sodium chloride, % by weight of the hide6-76-76-76-76-76-7
sulfuric acid (100%),% 0,7-0,60,7-0,80,7-0,60,7-0,80,7-0,80,7-0,8
ant-to-one (85%), %-----0,3
sodium acetate, anhydrous, %0,20,30,350,40,5-
duration, min20 20202020-
Tanning:
chrome tanning agent basicity 40-42%in terms of oxide of chromium, %1,51,51,651,31,82,3
duration, h3,03,03,03,03,03,0
sodium carbonate, (in three doses with an interval of 30 min)0,40,40,40,40,40,4
duration, h666666
pH exhaust R-RA4,44,3 4,34,254,20a 3.9
the temperature of the welding of the skin, °103106107106106106
the salt concentration of chromium in the waste solution, g/l of chromium oxide1,21,11,21,43,24,8
Neutralization of semi-finished products after planing: sodium acetate, from the weight of shaved leather0,200,300,350,400,50
sodium bicarbonate, % by weight of shaved leather0,300,400,500,600,701,5
Table 2

The performance properties of the skin
IndicatorsExamples of skin treatment
12356 (prototype)
The quality of the finished leather, % first-class units90,391,592,291,890,590,5
Consumption of raw hides, % prototypeof 97.897,096,9to 97.198,3100
The number of hides with tannic screed %8323414
The number of the facial skin, %677272736459
The rigidity index of the skin on the device PIU-12M, g272020222832

In tables 1 and 2 in example 3 used the acetate is a byproduct of the production of polyesters, as in example 6 - the prototype.

The data show that the proposed method of processing allows tanning with chromium compounds by reducing their consumption on 28-53%, to reduce the concentration of chromium in the exhaust after tanning solution 1.5-4.3 times compared to the prototype, to increase the binding of chromium compounds due to the activation process, to reduce the consumption of other chemicals when you improve the quality of finished leather.

Chemical composition and physico-mechanical properties obtained by the proposed method skin meets the requirements of the standard on the leather for the uppers from the skins of cattle.

Beyond the value of the proposed options will reduce the effectiveness of this method (and some reduction in performance in examples 1 and 5 tables).

SOURCES of INFORMATION

1. Stakhov I.P. and other Chemistry and technology of leather and fur. M., 1985, s.

2. Auth. mon. The USSR № 1214764, CL 14 With 1/08, 1986.

3. Metelkin, A.I., Belobrova L.V. Production of Russian leather and its properties. M: Light and food industry, 1983, p.88, 89.

The method of manufacture of the skin, including pickling, tanning of the hide and the neutralization of the semi-finished product, characterized in that pikelny fluid injected sodium acetate at a flow rate of 0.2-0.5%, then chrome tanning agent 1,5-1,8% (based on chromium oxide, tanning carried out until the pH of Rabotnov solution 4,2-4,4, and the solution to neutralize the injected sodium acetate and 0.2-0.5% and sodium bicarbonate 0.3 to 0.7 percent.



 

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