Salt-free high-chrome-absorption chrome tanning method for animal skin and application of salt-free high-chrome-absorption chrome tanning method

Abstract

The invention discloses a salt-free high-chrome-absorption chrome tanning method for animal skin and application of the salt-free high-chrome-absorption chrome tanning method. The salt-free high-chrome-absorption chrome tanning method is characterized by comprising the following steps of treating pretreated animal skin by using aromatic sulfonic acid or a low-molecular polycondensate thereof; regulating the pH value of the animal skin to 4.0-6.5 under the condition that no neutral salts such as sodium chloride and sodium sulfate are used; and carrying out chrome tanning under a relatively high initial pH value condition to realize salt-free high-chrome-absorption tanning. By using the salt-free high-chrome-absorption chrome tanning method, the problem that the quality and performances of leather or fur are influenced because the skin possibly has the acid expansion phenomenon under salt-free and acidic tanning conditions, the combination of chrome and the surface of the skin are excessively fast during the tanning, and the chrome cannot permeate the skin easily under the relatively high initial pH value condition is solved; and compared with the conventional chrome tanning method, the chrome tanning method disclosed by the invention is advantaged in that the chrome tanning efficiency is remarkably increased, the consumption of chrome can be reduced by more than 30%, the absorption rate of chrome is up to more than 98%, the concentration of chrome in chrome tanning effluent is reduced to be less than 50mg / L, chrome in wet blue leather is more uniformly distributed, and the chrome tanning effluent can be recycled many times. By using the salt-free high-chrome-absorption chrome tanning method, the chlorine and chrome pollution generated in the leather and fur preparation processes is remarkably reduced.

Description

technical field [0001] The invention relates to an animal skin processing technology, in particular to a salt-free chrome high-absorption chrome tanning method in leather or fur production. technical background [0002] At present, due to the excellent performance of chrome tanned leather and the integrity and diversity of its supporting products, chrome tanning is still the most important and commonly used method in the leather or fur industry. The pollution of chromium and neutral salts has become a major problem that plagues the leather or fur industry, and it is an urgent problem to be solved. [0003] In the traditional chrome tanning process, pickling is generally carried out first, that is, the pH value of the bare hide is adjusted to 2.0-3.0 with formic acid and sulfuric acid, which is conducive to the penetration of the chrome tanning agent. In order to prevent skin soreness, it is necessary to add neutral salts such as sodium chloride with 6%-10% of skin weight in...

AI Technical Summary

Problems solved by technology

Although this method can reduce or eliminate the use of neutral salts in pickling, due to the large molecular weight of such substances, it requires a large amount to adjust the pH to 2.0-3.0, which will affect the comprehensiveness of finished leather and fur products. performance

In addition, compared with the conventional pickling-chrome tanning method, although the absorption rate of chromium has increased in the initial stage of salt-free pickling tanning, the chromium concentration in the chrome tanning waste liquid is still high, above 500 mg / L

[0006] In recent years, the non-pickling chrome tanning technology (CN1348994A) has been developed. The softened animal skin is directly chrome-tanned at a higher pH value (higher than 7) without pickling, avoiding the use of neutral salts. However, it is necessary to use low-alkalinity and high-enveloped chromium powder. For tanning thicker hides, there may be problems such as difficulty in penetrating the tanning agent and the risk of soreness and swelling in the center of the hide. The absorption rate of chromium has been improved to a certain extent, which can reach 84 %, the waste chrome tanning liquor still contains a large concentration of chromium, and the amount of chromium cannot be reduced

[0007] The absorption rate of chromium in the chrome tanning process is improved by using chrome tanning auxiliaries, such as aliphatic dicarboxylic acid, glyoxylic acid, low molecular polyacrylic acid, oxazolidine, etc., the use of these auxiliaries can improve chrome However, the chromium concentration in the chrome tanning waste liquor is still above 300mg / L, but the use of neutral salt has not been significantly reduced, and the improper use of such additives will affect the uniform distribution of chromium in the leather and reduce the product’s durability. performance

[0008] Pretreatment of animal hides with synthetic tanning agents, followed by chrome tanning at an initial pH of 7.0, can increase the chromium absorption rate during the chrome tanning process, but this method may cause chromium to combine too quickly on the hide surface, thereby affecting the chromium into the hide Penetration, affecting the chrome tanning effect and the overall performance of the product

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