Manufacturing process of low-formaldehyde chrome-free tanned ecological leather

Abstract

The invention relates to a manufacturing process of low-formaldehyde chrome-free tanned ecological leather. The manufacturing process comprises the following steps: pickling and peeling leather, pre-tanning, neutralizing 1, main tanning, wringing, shaving, retanning, neutralizing 2, dyeing, oiling, removing formaldehyde, fixing, washing, discharging from a drum, and finishing in a dry state to obtain a finished product. According to the manufacturing process of the low-formaldehyde chrome-free tanned ecological leather, firstly, an organic synthesis tanning agent TWS is used for pretanning acid bare leather, then a zeolite tanning agent BS is used for retanning, the distribution uniformity and the absorptivity of a vegetable tanning agent on each layer of crust leather are improved, the binding force of the vegetable tanning agent and leather collagen is improved, and the tanning effect of the crust leather is improved. The water washing resistance, the organic solvent resistance and the shrinkage temperature of the obtained crust leather are obviously improved; and finally, the quebracho tannin extract ATO is used for capturing free formaldehyde, the content of formaldehyde in the crust leather is reduced, and the obtained crust leather is fine in grain surface, good in compactness and low in formaldehyde content, has good softness, fullness and elasticity and conforms to the characteristics of ecological instep leather products.

Description

Technical Field

[0001] The invention relates to the technical field of leather manufacturing, in particular to a low-formaldehyde chrome-free tanning ecological leather manufacturing process. Background Art

[0002] Chrome tanned leather has excellent moisture and heat stability and storage resistance, as well as good physical and mechanical properties and sensory properties. Chrome tanning has long been the main tanning method and has dominated the leather production. Chrome retanning is also a frequently used method in chrome tanned leather production. However, the utilization rate of chromium in the chrome tanning process is relatively low. During the tanning process of conventional chrome tanning methods, the utilization rate of chromium is only 65% ​​to 75%, resulting in serious waste of resources. The remaining chrome tanning agents will be discharged along with production wastewater, sludge and waste scraps, causing environmental pollution. In addition, the treatment of chromium-containing wastewater, sludge and solid waste is difficult and costly, which brings great environmental pressure to leather enterprises.

[0003] In the leather industry, formaldehyde mainly comes from the tanning or retanning process. In these two processes, aldehyde-containing tanning agents / retanning agents are usually used, such as aromatic synthetic tanning agents / retanning agents, glutaraldehyde tanning agents / retanning agents, modified glutaraldehyde tanning agents / retanning agents, etc., which will release formaldehyde during use, endangering the health of leather workers. Formaldehyde is not only present in tanning agents and retanning agents, but also in other leather materials, such as fatliquors, finishing agents, hand agents, modified protein fillers, etc. These materials are affected by external factors, such as temperature increase, water evaporation, etc., and free formaldehyde is produced and released, resulting in increased content.

[0004] Vegetable tanned leather has the advantages of being non-toxic, less polluting, and biodegradable. Condensation and hydrolysis tannins have a capture effect on formaldehyde. For example, larch, quebracho, and bayberry in condensation tannins have obvious capture effects, and chestnut in hydrolysis tannins also has a certain capture effect. Vegetable tannins do not contain heavy metal ions or formaldehyde, which meets the environmental protection requirements of clean production and the development concept of green and safe products. Since vegetable tannins themselves are natural polyphenol products modified by sulfiting, they have good water solubility, and the combination of vegetable tannins and leather collagen is mainly the interaction of hydrogen bonds and hydrophobic bonds, and the binding ability is relatively weak, especially under high temperature and mechanical force conditions, the binding force is easily destroyed. The subsequent fatliquoring process is carried out at a high temperature and rotates for a certain period of time. Vegetable tannins are easy to migrate out of the skin, so the performance of single vegetable tanning method tanned leather is unstable and the shrinkage temperature is not high. Summary of the invention

[0005] The present invention provides a low-formaldehyde chrome-free tanning ecological leather manufacturing process to solve the problem that the use of aldehyde-containing tanning agents / retanning agents in the existing tanning process will release formaldehyde and endanger human respiratory health.

[0006] The present invention adopts the following technical solution:

[0007] A low-formaldehyde chrome-free tanned ecological leather manufacturing process comprises the following steps:

[0008] Pickling bare hides → pre-tanning → neutralization 1 → main tanning → squeezing → shaving → retanning → neutralization 2 → dyeing → oiling → formaldehyde removal → fixing → washing → drumming → dry finishing → finished product;

[0009] in,

[0010] Pickled bare skin: It is obtained by soaking, liming, splitting, deliming, softening, washing and pickling in a rotary drum according to the conventional process;

[0011] Pre-tanning: Based on the weight of the skin after splitting, control the pickling solution to 30%-100%, add 1%-3% of organic synthetic tanning agent TWS and rotate for 50-90 minutes;

[0012] Main tanning: after washing and changing the bath, add 30%-50% water, 2%-3% fish oil MIR 90, rotate for 30-50 minutes, then add 3%-6% of wattle bark tannin ME, 3%-6% of quebracho tannin ATO, 3%-6% of tara tannin TARA, 1%-5% of replaced tannin OSR, rotate for 50-80 minutes, then add 2%-4% of wattle bark tannin ME, 2%-4% of quebracho tannin ATO, 2%-4% of tara tannin TARA, 1%-3% of replaced tannin OSR, rotate for 60-90 minutes, add 50%-80% of water, 0.1%-0.3% of mildew preventer 1336, heat to 30-40℃, rotate for 5-6 hours, add 0.5%-1% of formic acid, rotate for 20-30 minutes, wash out of the drum, put on the horse and let it stand, and tanning is completed;

[0013] Retanning: in a drum, based on the weight of the shaved wet leather, add 100%-200% water and 1%-2% oxalic acid, rotate for 30-40 minutes, drain; add 30%-50% water and 2%-6% zeolite tanning agent BIOSIN BS, rotate for 60-180 minutes;

[0014] Formaldehyde removal: Add 3%-6% quebracho tannin extract ATO and rotate for 40-70 minutes.

[0015] Furthermore, the specific steps of the neutralization 1 are as follows: add 0.8%-2% sodium formate and rotate for 10-20 minutes, add 0.5%-1.5% baking soda and rotate for 40-90 minutes, and detect that the pH value reaches 3.8-4.4.

[0016] Furthermore, the water squeezing reduces the moisture content of the tanned wet leather from 70%-80% to 40%-45% through a water squeezing machine, so as to facilitate the subsequent shaving process.

[0017] Furthermore, the specific steps of the above neutralization 2 are as follows: add 0.6%-2% sodium formate and rotate for 10-20 minutes; add 0.3%-1.5% baking soda and rotate for 30-60 minutes, detect the pH value to reach 5.0-5.5, rotate for another 40-80 minutes, and drain.

[0018] Furthermore, the dyeing steps are as follows: adding 50%-100% water, 0.2%-0.6% dyeing auxiliary agent LU, rotating for 10-20 minutes; adding 0.5%-3% dye, rotating for 50-60 minutes.

[0019] Furthermore, the specific steps of the above refueling are as follows: add 50%-100% of water, 3%-5% of fish oil MIR 90, 8%-10% of synthetic oil PELLASTOL 94S, increase the temperature to 45°C-55°C, and rotate for 50-80 minutes.

[0020] Furthermore, the above fixing steps are as follows: adding 0.3%-0.8% formic acid and rotating for 10-20 minutes; then adding 0.3%-0.8% formic acid and rotating for 10-20 minutes.

[0021] Furthermore, the above-mentioned dry finishing includes stretching, vacuuming, hanging to dry, drying, returning water, vibrating to soften, tumbling to soften, stretching, painting, and quality inspection, that is, the finished product.

[0022] It can be seen from the above description of the present invention that, compared with the prior art, the present invention has the following advantages:

[0023] 1. The manufacturing process of the low-formaldehyde chrome-free tanned ecological leather of the present invention comprises the following steps: firstly, pre-tanning the acid bare leather with an organic synthetic tanning agent TWS, which is an amphoteric organic synthetic tanning agent containing aldehyde groups, carboxyl groups and amino groups, and has a small relative molecular weight, a fast penetration rate and a uniform dispersion, and the tanned white wet leather has a fine grain surface, a small difference in position, a white color, softness and fullness; secondly, tanning is performed with vegetable tanning agents ME, ATO and TARA, which are composed of polyphenol derivatives, and the phenolic hydroxyl groups of the vegetable tanning agents can be hydrogen bonded with the amide groups of the collagen peptide chains of the leather to generate multi-point crosslinking and produce a tanning effect; and then re-tanning is performed with a zeolite tanning agent BS, which is a zeolite tanning agent containing Alkali metal or alkaline earth metal aluminosilicates in water have silicon-oxygen tetrahedron and aluminum-oxygen tetrahedron structures, and form a cross-linked synergistic network structure with skin collagen fibers, organic tanning agents, and vegetable tanning agents, thereby improving the distribution uniformity and absorption rate of vegetable tanning agents on all levels of the leather and the binding force between the vegetable tanning agents and skin collagen. The water-resistant and organic solvent-resistant properties and shrinkage temperature of the obtained leather are significantly improved. Finally, quebracho tannin extract ATO is used to capture free formaldehyde and reduce the formaldehyde content in the leather. The obtained leather has fine grain, good firmness, low formaldehyde content, good softness, fullness and elasticity, and meets the characteristics of ecological shoe upper leather products.

[0024] 2. The manufacturing process of the low-formaldehyde chrome-free tanned ecological leather of the present invention does not use chrome tanning agents or chrome-containing tanning agents throughout the entire process, and no chrome-containing wastewater, sludge, or solid waste is generated, thereby eliminating the hidden dangers of heavy metal pollution from the source and saving environmental protection management costs.

[0025] 3. The shaved leather scraps and trimming scraps of the present invention do not contain heavy metals and can be directly used to manufacture collagen to generate economic benefits.

[0026] 4. The free formaldehyde, hexavalent chromium and total chromium contents of the finished leather product of the present invention are extremely low or even undetectable.

[0027] 5. The shrinkage temperature of the finished leather product reaches above 90°C, and the physical and chemical properties are better than the standard requirements of "QB / T5796-2023 Chrome-free tanned leather for shoe uppers". DETAILED DESCRIPTION

[0028] Embodiment 1:

[0029] A low-formaldehyde chrome-free tanned ecological leather manufacturing process, the process includes: pickling bare hide → pre-tanning → neutralization → main tanning → squeezing → shaving → retanning → neutralization → dyeing → oiling → formaldehyde removal → fixing → washing → drumming → dry finishing → finished product.

[0030] (1) Pickled bare skin: soaking, liming, splitting, deliming, softening, washing and pickling in a rotary drum according to conventional processes;

[0031] (2) Pre-tanning: Based on the weight of the skin after splitting, the pickling solution was controlled to 50%, and 2% of the organic synthetic tanning agent TWS (Tingjiang New Materials Co., Ltd.) was added and rotated for 60 minutes;

[0032] (3) Neutralization: add 1% sodium formate and rotate for 15 minutes, add 1% baking soda and rotate for 50 minutes, and detect the pH value to reach 4.0-4.2;

[0033] (4) Main tanning: after washing and changing the bath, add 30% water, 2% fish oil MIR 90 (Yixiang Chemical Company), rotate for 30 minutes, then add 5% wattle bark tannin ME (Bisheng Chemical Co., Ltd.), 5% quebracho tannin ATO (Fangzheng Import and Export Co., Ltd.), 5% tara tannin TARA (Tingjiang New Materials Co., Ltd.), 4% substituted tannin OSR (Derui Leather Technology (Qingdao) Co., Ltd.), rotate for 50 minutes, then add 3% wattle bark tannin ME, 3% quebracho tannin ATO, 3% tara tannin TARA, 2% substituted tannin OSR, rotate for 60 minutes, add 50% water, 0.2% mildew inhibitor 1336 (Bachman Laboratory Chemical (Shanghai) Co., Ltd.), heat to 35°C, rotate for 6 hours, add 1% formic acid, rotate for 30 minutes, wash out of the drum, put on the horse and let it stand, and tanning is completed;

[0034] (5) Squeezing: The moisture content of the tanned wet leather is reduced from 70%-80% to 40%-45% through a squeezing machine to facilitate the subsequent shaving process;

[0035] (6) Shaving: Normal upper leather shaving thickness is 1.15-1.20mm;

[0036] (7) Retanning: in a drum, based on the weight of the shaved wet leather, add 150% of water and 2% of oxalic acid, rotate for 40 minutes, and drain; add 50% of water and 3% of zeolite tanning agent BIOSIN BS (Tiger Leather Technology (Shanghai) Co., Ltd.), and rotate for 120 minutes;

[0037] (8) Neutralization: add 1% sodium formate and rotate for 15 minutes; add 0.8% baking soda and rotate for 40 minutes. When the pH value reaches 5.2, rotate for another 60 minutes and drain;

[0038] (9) Dyeing: add 80% water and 0.4% dyeing auxiliary LU (Derui Leather Technology (Qingdao) Co., Ltd.), rotate for 15 minutes; add 1% dye and rotate for 50 minutes;

[0039] (10) Adding oil: add 70% water, 4% fish oil MIR 90, and 9% synthetic oil PELLASTOL 94S (Zima Chemical (Foshan) Co., Ltd.), raise the temperature to 50°C, and rotate for 50 minutes;

[0040] (11) Formaldehyde removal: Add 5% quebracho tannin extract ATO and rotate for 50 minutes;

[0041] (12) Fixation: add 0.4% formic acid and rotate for 15 minutes; then add 0.4% formic acid and rotate for 15 minutes;

[0042] (13) Washing, unloading, standing, and wet processing is completed;

[0043] (14) Dry finishing: including stretching, vacuuming, hanging, drying, water return, vibration softening, tumbling, stretching, painting, and quality inspection, i.e. finished product.

[0044] Embodiment 2:

[0045] A low-formaldehyde chrome-free tanned ecological leather manufacturing process, the process includes: pickling bare hide → pre-tanning → neutralization → main tanning → squeezing → shaving → retanning → neutralization → dyeing → oiling → formaldehyde removal → fixing → washing → drumming → dry finishing → finished product.

[0046] (1) Pickled bare skin: soaking, liming, splitting, deliming, softening, washing and pickling in a rotary drum according to conventional processes;

[0047] (2) Pre-tanning: Based on the weight of the skin after splitting, the pickling solution is controlled to 60%, and 3% of the organic synthetic tanning agent TWS is added and rotated for 60 minutes;

[0048] (3) Neutralization: add 1% sodium formate and rotate for 10 minutes, add 0.8% baking soda and rotate for 60 minutes, and detect the pH value to reach 4.2;

[0049] (4) Main tanning: after washing and changing the bath, add 50% water, 3% fish oil MIR 90, rotate for 30 minutes, then add 6% wattle bark tannin ME, 6% quebracho tannin ATO, 6% tara tannin TARA, 3% substituted tannin OSR, rotate for 60 minutes, then add 2% wattle bark tannin ME, 2% quebracho tannin ATO, 2% tara tannin TARA, 2% substituted tannin OSR, rotate for 90 minutes, add 80% water, 0.3% mildewproofing agent 1336, raise the temperature to 35°C, rotate for 6 hours, add 1% formic acid, rotate for 30 minutes, wash out of the drum, put on the horse and let it stand, and tanning is completed;

[0050] (5) Squeezing: The moisture content of the tanned wet leather is reduced from 70%-80% to 40%-45% through a squeezing machine to facilitate the subsequent shaving process;

[0051] (6) Shaving: Normal upper leather shaving thickness is 1.15-1.20mm;

[0052] (7) Retanning: in a drum, based on the weight of the shaved wet leather, add 150% water and 2% oxalic acid, rotate for 30 minutes, and drain; add 50% water and 5% zeolite tanning agent BIOSIN BS, and rotate for 100 minutes;

[0053] (8) Neutralization: add 1% sodium formate and rotate for 10 minutes; add 0.8% baking soda and rotate for 50 minutes. When the pH value reaches 5.0, rotate for another 60 minutes and drain;

[0054] (9) Dyeing: add 80% water, 0.4% dyeing auxiliary LU, rotate for 20 minutes; add 1% dye, rotate for 60 minutes;

[0055] (10) Adding oil: add 70% water, 5% fish oil MIR 90, and 8% synthetic oil PELLASTOL 94S, raise the temperature to 50°C, and rotate for 60 minutes;

[0056] (11) Formaldehyde removal: Add 6% quebracho tannin extract ATO and rotate for 60 minutes;

[0057] (12) Fixation: add 0.5% formic acid and rotate for 20 minutes; then add 0.5% formic acid and rotate for 20 minutes;

[0058] (13) Washing, unloading, standing, and wet processing is completed;

[0059] (14) Dry finishing: including stretching, vacuuming, hanging, drying, water return, vibration softening, tumbling, stretching, painting, and quality inspection, i.e. finished product.

[0060] Experimental data

[0061] The finished leather product of the present invention is tested according to the standard "QB / T 5796-2023 Chrome-free tanned leather for shoe uppers", and the results are shown in the following table.

[0062] Chemical properties

[0063]

[0064] Physical and mechanical properties

[0065]

[0066] From the above experimental data, it can be seen that the free formaldehyde, hexavalent chromium and total chromium content of the finished leather of the present invention are extremely low, or even undetectable. The shrinkage temperature of the finished leather reaches above 90°C, and the physical and chemical properties are better than the standard requirements of "QB / T 5796-2023 Chrome-free tanned leather for shoe uppers".

[0067] The above is only a specific implementation of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial changes to the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A low formaldehyde chrome-free tanned ecological leather manufacturing process, characterized in that: The steps include: Pickling bare hides → pre-tanning → neutralization 1 → main tanning → squeezing → shaving → retanning → neutralization 2 → dyeing → oiling → formaldehyde removal → fixing → washing → drumming → dry finishing → finished product; in, Pickled bare skin: It is obtained by soaking, liming, splitting, deliming, softening, washing and pickling in a rotary drum according to the conventional process; Pre-tanning: Based on the weight of the skin after splitting, control the pickling solution to 30%-100%, add 1%-3% of organic synthetic tanning agent TWS and rotate for 50-90 minutes; Main tanning: after washing and changing the bath, add 30%-50% water, 2%-3% fish oil MIR 90, rotate for 30-50 minutes, then add 3%-6% of wattle bark tannin ME, 3%-6% of quebracho tannin ATO, 3%-6% of tara tannin TARA, 1%-5% of replaced tannin OSR, rotate for 50-80 minutes, then add 2%-4% of wattle bark tannin ME, 2%-4% of quebracho tannin ATO, 2%-4% of tara tannin TARA, 1%-3% of replaced tannin OSR, rotate for 60-90 minutes, add 50%-80% of water, 0.1%-0.3% of mildew preventer 1336, heat to 30-40℃, rotate for 5-6 hours, add 0.5%-1% of formic acid, rotate for 20-30 minutes, wash out of the drum, put on the horse and let it stand, and tanning is completed; Retanning: in a drum, based on the weight of the shaved wet leather, add 100%-200% water and 1%-2% oxalic acid, rotate for 30-40 minutes, drain; add 30%-50% water and 2%-6% zeolite tanning agent BIOSIN BS, rotate for 60-180 minutes; Formaldehyde removal: Add 3%-6% quebracho tannin extract ATO and rotate for 40-70 minutes.

2. A low formaldehyde chrome-free tanned ecological leather manufacturing process as claimed in claim 1, characterized in that: The specific steps of the neutralization 1 are as follows: adding 0.8%-2% sodium formate and rotating for 10-20 minutes, adding 0.5%-1.5% baking soda and rotating for 40-90 minutes, and detecting that the pH value reaches 3.8-4.

4.

3. A low formaldehyde chrome-free tanned ecological leather manufacturing process as claimed in claim 1, characterized in that: The squeezing process reduces the moisture content of the tanned wet leather from 70%-80% to 40%-45% through a squeezing machine, so as to facilitate the subsequent shaving process.

4. A low formaldehyde chrome-free tanned ecological leather manufacturing process as claimed in claim 1, characterized in that: The specific steps of the neutralization 2 are as follows: adding 0.6%-2% sodium formate and rotating for 10-20 minutes; adding 0.3%-1.5% baking soda and rotating for 30-60 minutes, detecting the pH value to reach 5.0-5.5, rotating for another 40-80 minutes, and draining.

5. A low formaldehyde chrome-free tanned ecological leather manufacturing process as claimed in claim 1, characterized in that: The specific steps of dyeing are as follows: adding 50%-100% of water and 0.2%-0.6% of dyeing auxiliary agent LU, rotating for 10-20 minutes; adding 0.5%-3% of dye, rotating for 50-60 minutes.

6. A low formaldehyde chrome-free tanned ecological leather manufacturing process as claimed in claim 1, characterized in that: The specific steps of refueling are as follows: add 50%-100% of water, 3%-5% of fish oil MIR 90, 8%-10% of synthetic oil PELLASTOL94S, raise the temperature to 45°C-55°C, and rotate for 50-80 minutes.

7. A low formaldehyde chrome-free tanned ecological leather manufacturing process as claimed in claim 1, characterized in that: The fixing steps are as follows: adding 0.3%-0.8% formic acid and rotating for 10-20 minutes; then adding 0.3%-0.8% formic acid and rotating for 10-20 minutes.

8. A low formaldehyde chrome-free tanned ecological leather manufacturing process as claimed in claim 1, characterized in that: The dry finishing includes stretching, vacuuming, hanging to dry, drying, water returning, vibration softening, tumbling, stretching, painting and quality inspection, i.e. the finished product.

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