Preparation method of chromium-free pickled leather

Abstract

The invention relates to a preparation method of chromium-free pickled leather, which can uniformly expand and be loosened properly, is beneficial to permeation and combination of tannins and dyes, and ensures that finished leather is soft and flat and fine in grain surface. Specifically, the following procedures are sequentially carried out: fur soaking, fleshing, pre-degreasing, enzyme depilating, alkali soaking, leather peeling, dealkalizing, degreasing and softening, pickling and pickled leather production, wherein the alkali soaking comprises the following steps: putting depilated leatherinto a rotary drum, controlling the liquid ratio to be 1.2-1.5, adding 0.2-0.5% of a penetrant and 0.5-0.8% of sodium hydrogen sulfide, and carrying out low-speed rotary drum treatment for 10-15 minutes; then, stopping operation of the drum and supplying water to adjust the pH value to be 7-8, sequentially adding 0.8%-1.0% of xonotlite fiber particles, 1.5%-3.0% of slaked lime and 0.8%-1.0% of alkaline leaching enzyme, performing low-speed rotary drum treatment at a low speed for 30-45 minutes, inspecting the leather, and washing the leather with water and discharging the leather from the drum after the expansion degree meets 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