A kind of salt-free pickling process for tanning

Abstract

The invention provides a tanning salt-free pickling process. The adding amount of materials is measured according to 100 parts of a limed skin by weight. The tanning salt-free pickling process specifically comprises the following steps: (1) conventionally deliming and softening the limed skin and washing with water; then adding 70 parts of water and adding 2 to 4 parts of a buffering agent; then rotating for 10 minutes; (2) adding 0.2 to 0.4 part of solid acid and 0.1 to 0.3 parts of the buffering agent every time and rotating for 20 minutes; repeating for 3 times; (3) adding 0.3 to 0.6 parts of the solid acid and 0.1 to 0.3 parts of the buffering agent and rotating for 60 minutes; measuring the pH (Potential of Hydrogen) value being 2.7 to 2.8, and immersing for one night; measuring the pH (Potential of Hydrogen) value being 2.7 to 2.8 at the next day; tanning according to a conventional process.

Description

technical field [0001] The invention relates to a salt-free pickling process for tanning, which belongs to the technical field of tanning industry. Background technique [0002] Pickling is a crucial process in tanning. In the traditional chrome tanning process, it is necessary to adjust the pH value of the leather before chrome tanning to make it suitable for the pH value of the tanning operation. The second is to make the collagen fibers The structure is further loosened. In order to prevent the skin from being sore and swollen during pickling, a large amount of sodium chloride needs to be used, which generally accounts for 7-10% of the skin weight. If the amount of salt is too large, it will also lead to dehydration of the leather, flat and thin leather, not plump, etc., which will affect the quality of the leather. However, without the pickling process, the internal pH value of the leather is relatively high, which cannot reach the pH value required for chrome tanning....

AI Technical Summary

Problems solved by technology

In order to prevent the skin from being sore and swollen during pickling, a large amount of sodium chloride needs to be used, which generally accounts for 7-10% of the skin weight. If the amount of salt is too large, it will also lead to dehydration of the hide, flattening of the finished leather, lack of plumpness, etc., which will affect the quality of the finished leather

However, without the pickling process, the internal pH value of the leather is relatively high, which cannot reach the pH value required for chrome tanning. Improper operation can easily cause the accumulation of chrome tanning agent to become larger, and it is difficult to penetrate into the interior of the leather and deposit on the surface of the leather, causing the surface to become excessive. Tanning, the leather becomes rough and chrome spots, etc., which seriously affect the quality of the leather

[0003] In addition, the high concentration of chloride ion in the water will also cause bitter and salty drinking water and soil salinization, which will make it difficult for plants to grow, easily corrode pipes and equipment, and endanger human health, causing dehydration, high blood pressure, thyroid disease, kidney disease, heart disease, etc. disease, gastric cancer, osteoporosis and other diseases

However, sodium chloride is difficult to treat in wastewater, and the commonly used methods mainly include the following treatment methods: 1. Silver salt or cuprous salt precipitation method, but silver salt is difficult to recover and the cost is high, and cuprous salt is easy to oxidize and difficult to control

2. Membrane separation technology, including electrodialysis and reverse osmosis, is widely used, but organic impurities in wastewater can easily cause irreversible pollution to membrane components, which limits its application range and high cost

3. Evaporation and concentration method requires high equipment corrosion resistance and high cost

[0004] Moreover, in the pickling process, formic acid and concentrated sulfuric acid are usually used to prepare the pickling solution. Careless operation can easily cause harm, because there are many cases of injuries caused by careless operators.