A kind of production method of chromate-free leather

Abstract

The invention relates to a method for making chromium-free acid leather, which can expand uniformly and loosely, facilitate the penetration and combination of tanning materials and dyes, and ensure the softness and fine grain of the finished leather. Specifically, the following procedures are carried out in sequence: fur soaking→flesh→pre-degreasing→enzyme dehairing→alkali soaking→skin peeling→dealkalization→degreasing and softening→acid pickling→acid skin. The specific operation process of the alkali soaking process is: Put it in the drum, control the liquid ratio to 1.2-1.5, add 0.2%-0.5% penetrant and 0.5%-0.8% sodium hydrogen sulfide, low-speed drum for 10min-15min; then stop the drum and add water to adjust the pH value At 7‑8, add 0.8% to 1.0% of xonotlite fiber particles, 1.5% to 3.0% of slaked lime and 0.8% to 1.0% of alkaline dipping enzyme in sequence, and rotate the drum at a low speed for 30min to 45min. The skin is washed out of the drum after the swelling degree reaches the requirement.

Description

technical field [0001] The invention relates to the technical field of leather preparation, in particular to a method for making chromate-free leather. Background technique [0002] The leather processing process can be divided into a preparation section and a tanning section. The preparation section is to process the hide to meet the relevant requirements of tanning. The preparation section generally involves immersion, fleshing, dehairing, degreasing, liming, deliming and softening of the hide. The main purpose of the processes such as pickling and pickling is to separate and loosen the collagen fibers inside the hide as much as possible, but also to control the degree of expansion, otherwise it will easily lead to defects such as loose, flat and thin leather, excessive elongation, and loose surface. , especially the liming alkali process. The existing leather liming alkali process generally uses slaked lime and sodium sulfide. The concentration of hydroxide radicals prod...

AI Technical Summary

Problems solved by technology

The existing leather liming alkali process generally uses slaked lime and sodium sulfide. The concentration of hydroxide radicals produced by the hydrolysis of sodium sulfide is relatively high, and the alkalinity of the liming lye changes rapidly, so that the surface layer of the leather sheet is swollen while the inner layer is still not swollen. The uneven expansion state of the state, the internal pressure difference between the cortex increases, and the stress at the junction of different expansion layers increases, thereby damaging the fiber structure

In order to achieve uniform and slow expansion, it is necessary to add sodium sulfide in stages and supplement it with slow rotation. The time for liming and alkali is long, and it is easy to form gray spots on the raw hide, which hinders the penetration of tanning materials and dyes, resulting in brittle cracks. noodle

And sodium sulfide is also easy to make the skin swell