Preparation method of high-property waterproof work boots upper leather

Abstract

This invention relates to a method for preparing high-performance waterproof workwear leather, comprising the following steps: rewetting → retanning → neutralization → fixation → drying and finishing. In the rewetting stage, this invention introduces a composite tanning agent and an aldehyde tanning agent. The composite tanning agent penetrates deep into the leather grain layer, selectively filling loose grain fibers and repairing surface defects; the aldehyde tanning agent can undergo a cross-linking reaction with the amino groups of collagen fibers, forming a uniform aldehyde cross-linking network in the grain layer, further sealing and reinforcing the grain structure; the synergistic effect of both makes the leather grain layer more compact and full, significantly improving the physical properties of the finished leather.

Description

Technical Field

[0001] This invention relates to the field of labor protection shoe upper leather manufacturing technology, and in particular to a method for preparing a high-performance waterproof labor protection shoe upper leather. Background Technology

[0002] Safety shoes, as the last line of defense protecting workers' feet from physical and chemical injuries, directly impact the safety and work efficiency of frontline industrial workers. With the advancement of global industrialization, the demand for safety shoes in manufacturing, construction, mining, and petrochemical industries continues to grow, and the performance requirements are becoming increasingly stringent. Cowhide leather, due to its excellent strength, abrasion resistance, and processing adaptability, has become the mainstream material for safety shoe uppers. However, traditional safety shoe leathers have revealed several problems over long-term use: insufficient tear strength makes the upper easily punctured or torn by sharp objects; low flexural strength, leading to cracks or even breakage in frequently flexed areas; and limited tensile strength, failing to meet the protective needs of high-intensity working environments.

[0003] To improve the overall physical properties of workwear leather, the industry has long relied on traditional retanning methods. However, all conventional tanning agent systems have significant shortcomings. While ordinary chromium salt retanning can stabilize the leather fiber structure and improve its basic density, its single fiber cross-linking method results in stiff, rigid leather with insufficient flexibility and resilience, making it prone to fatigue damage from prolonged bending. Amino resin retanning agents offer good filling and shaping effects, improving leather's porousness, but significantly reduce fiber extensibility, hardening and brittleness of the grain, and noticeably decreasing its resistance to flexing and tearing. Conventional aromatic synthetic tanning agents have strong astringency and high surface bonding efficiency, easily leading to over-tanning on the surface and uneven internal penetration, exacerbating performance differences between leather parts and making it highly susceptible to cracking and surface peeling under stress. Plant tannin-based tanning agents provide full filling and stable shaping, but their rigid structure compresses fiber movement space, resulting in heavy, stiff leather with weakened tensile properties, making it prone to deformation during dynamic wear. When multiple traditional retanning materials are used in combination, it is difficult to balance the firmness, softness and durability. This can easily lead to problems such as rough feel, insufficient wear resistance and structural failure after repeated bending, making it difficult to meet the actual use requirements of high strength and long cycle for work shoes.

[0004] In summary, the various tanning agents and supporting processes used in the traditional retanning of workwear leather have significant shortcomings in optimizing physical properties. Therefore, this invention develops a method for preparing workwear upper leather that focuses on high physical properties while also considering waterproofing and breathability, which has important practical application significance. Summary of the Invention

[0005] This invention provides a method for preparing high-performance waterproof workwear upper leather to solve the problems of insufficient tear strength, low flexural strength, and limited tensile strength of existing workwear upper leather.

[0006] The present invention adopts the following technical solution: A method for preparing a high-performance waterproof workwear upper leather includes the following process steps: Rehydration: Place the evenly treated wet blue leather into a rotating drum, add 100%-300% water and 1.0%-3.0% oxalic acid to the drum, maintain the temperature at 40℃, rotate for 90-150 min, adjust the pH of the bath to ≤3.0, add 2%-4% compound tanning agent (GTX, Hong Kong Fangfang Trading Co., Ltd., the same below) and 1%-3% aldehyde tanning agent (PF, Sima Chemical (China) Co., Ltd.), rotate for 60-90 min, drain the liquid, and wash with water; Retanning: Add 50%-150% water, 5%-7% chromium powder, 2%-4% acidic phenolic synthetic tannin (309, Zhejiang Shenghui Chemical Co., Ltd.), 1%-2% waterproofing agent (GWP, Sichuan Tingjiang New Material Co., Ltd., the same below), and 0.5%-1% dispersant (Densotan_A, BASF, the same below) to the drum. Rotate for 60-90 minutes, add 1%-3% oxazolidine liquid tanning agent, rotate for 60-90 minutes, drain the liquid, and wash with water. Neutralization: Add 100%-150% water to the drum to neutralize 1%-3% tannins. Maintain a temperature of 35℃ and rotate for 30-60 minutes. Add 1%-3% ammonium bicarbonate (food additive, Shandong Zhongke Green Carbon Technology Co., Ltd.) and rotate for 60-90 minutes. Add 2%-4% small molecule acrylic resin tanning agent, 1%-2% waterproofing agent, and 0.5%-1% dispersant. Rotate for 60-120 minutes and let stand overnight. Drain the liquid the next day and wash with water. Fixation: Add 200%-300% water, 1%-2% waterproofing and fatliquoring agent, temperature 50℃, rotate for 20 minutes, add 1%-2% chromium powder, rotate for 20-40 minutes, drain the liquid, wash with water at 33℃, add 1%-3% chromium powder, rotate for 90-150 minutes, drain the liquid, and wash with water at 33℃. Drying and finishing.

[0007] Furthermore, the above drying and finishing process is carried out according to conventional procedures: static setting → water squeezing and stretching → vacuum drying → hanging drying → oven drying → rehydration → static setting → vibration softening.

[0008] As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following advantages: 1. Granular filling and fiber network reinforcement This invention introduces a compound tanning agent and an aldehyde tanning agent during the rewetting stage. The compound tanning agent penetrates deep into the leather grain layer, selectively filling loose grain fibers and repairing surface defects; the aldehyde tanning agent can undergo a cross-linking reaction with the amino groups of collagen fibers, forming a uniform aldehyde cross-linking network in the grain layer, further sealing and reinforcing the grain structure. The synergistic effect of both agents makes the leather grain layer more compact and full, significantly improving the properties of the finished leather.

[0009] 2. Synergistic retanning system The retanning stage employs a four-component synergistic retanning process: chromium powder, acidic phenolic synthetic tannins, a waterproofing agent, and a dispersant. Chromium powder constructs the main cross-linked framework, acidic phenolic synthetic tannins fill fiber gaps to enhance compactness, the waterproofing agent guides the directional distribution of the filler material, and the dispersant ensures uniform dispersion of each component. The four components form a synergistic mechanism, simultaneously optimizing the fiber network structure and significantly improving physical properties.

[0010] 3. Ammonium bicarbonate mild neutralization enhancement technology Ammonium bicarbonate is added during the neutralization stage. The release of CO2 gas gently stretches the fibers, promotes uniform penetration of the filling material, and improves tear strength and folding fastness.

[0011] 4. Excellent physical and mechanical properties The corrected-grain workwear leather prepared by this invention significantly outperforms the requirements of the QB / T 1873-2023 "Leather for Footwear Uppers" standard in key physical indicators such as tear strength, breaking strength, and chipping height.

[0012] 5. Excellent dynamic waterproof performance By employing a stepwise gradient addition strategy for waterproofing agents, the leather prepared by this invention exhibits excellent impermeability; it can withstand more than 15,000 dynamic waterproofing cycles and can be used for a long time in harsh environments such as dampness, high water content, and oil stains without leakage, effectively ensuring the wearer's feet remain dry and safe.

[0013] 6. Good chemical stability The chemical properties of the leather of this invention are all within the ideal range. The chromium trioxide content is 4.0%, the dichloromethane extract content is 5.4%, and the pH value is 3.5, making the leather slightly acidic and skin-friendly. Detailed Implementation

[0014] To better understand the above technical solution, the following will provide a detailed explanation of the above technical solution in conjunction with the instruction manual and specific implementation methods (the amount of chemical materials used in the processes of rewetting, retanning, neutralization, filling and fatliquoring, coloring, and water-fixing is based on the weight of the wet blue leather after even shaving. For example, if the wet blue leather weighs 100kg after even shaving, then 300% water is 300kg of water).

[0015] Example 1: A method for preparing a high-performance waterproof workwear upper leather includes the following process steps: Rehydration: Place the evenly treated wet blue leather into a drum, add 100% water and 1.0% oxalic acid to the drum, maintain the temperature at 40℃, rotate for 90 min, adjust the pH of the bath to ≤3.0, add 2% compound tanning agent (GTX, Hong Kong Fangfang Trading Co., Ltd., the same below) and 1% aldehyde tanning agent (PF, Sima Chemical (China) Co., Ltd.), rotate for 60-90 min, drain the liquid, and wash with water; Retanning: Add 50% water, 5% chromium powder, 2% acidic phenolic synthetic tannin (309, Zhejiang Shenghui Chemical Co., Ltd.), 1% waterproofing agent (GWP, Sichuan Tingjiang New Material Co., Ltd., the same below), and 0.5% dispersant (Densotan_A, BASF, the same below) to the drum, rotate for 60 minutes, add 1% oxazolidine liquid tanning agent, rotate for 60 minutes, drain the liquid, and wash with water; Neutralization: Add 100% water to the drum to neutralize 1% tannin, maintain a temperature of 35℃, and rotate for 30-60 minutes. Add 1% ammonium bicarbonate (food additive, Shandong Zhongke Green Carbon Technology Co., Ltd.), and rotate for 60-90 minutes. Add 2% small molecule acrylic resin tanning agent, 1% waterproofing agent, and 0.5% dispersant, and rotate for 60 minutes. Let it stand overnight, drain the liquid the next day, and wash with water. Fixation: Add 200% water, 1% waterproofing and fatliquoring agent, temperature 50℃, rotate for 20 minutes, add 1% chromium powder, rotate for 20 minutes, drain the liquid, wash with water at 33℃, add 1% chromium powder, rotate for 90 minutes, drain the liquid, and wash with water at 33℃. Drying and finishing.

[0016] The above drying and finishing process is carried out according to conventional procedures: static setting → squeezing and stretching → vacuum drying → hanging drying → oven drying → rehydration → static setting → vibration and softening.

[0017] Example 2: A method for preparing a high-performance waterproof workwear upper leather includes the following process steps: Rehydration: Place the evenly treated wet blue leather into a rotating drum, add 300% water and 3.0% oxalic acid to the drum, maintain the temperature at 40℃, rotate for 150 min, adjust the pH of the bath solution to ≤3.0, add 4% compound tanning agent (GTX, Hong Kong Fangfang Trading Co., Ltd., the same below) and 3% aldehyde tanning agent (PF, Sima Chemical (China) Co., Ltd.), rotate for 90 min, drain the liquid, and wash with water; Retanning: Add 150% water, 7% chromium powder, 4% acidic phenolic synthetic tannin (309, Zhejiang Shenghui Chemical Co., Ltd.), 2% waterproofing agent (GWP, Sichuan Tingjiang New Material Co., Ltd., the same below), and 1% dispersant (Densotan_A, BASF, the same below) to the drum. Rotate for 90 minutes, add 3% oxazolidine liquid tanning agent, rotate for 90 minutes, drain the liquid, and wash with water. Neutralization: Add 150% water to the drum to neutralize 3% tannin, maintain the temperature at 35℃, rotate for 60 minutes, add 3% ammonium bicarbonate (food additive, Shandong Zhongke Green Carbon Technology Co., Ltd.), rotate for 90 minutes, add 4% small molecule acrylic resin tanning agent, 2% waterproofing agent, and 1% dispersant, rotate for 120 minutes, let stand overnight, drain the liquid the next day, and wash with water. Fixation: Add 300% water, 2% waterproofing and fatliquoring agent, temperature 50℃, rotate for 20 minutes, add 2% chromium powder, rotate for 40 minutes, drain the liquid, wash with water at 33℃, add 3% chromium powder, rotate for 150 minutes, drain the liquid, and wash with water at 33℃. Drying and finishing.

[0018] The above drying and finishing process is carried out according to conventional procedures: static setting → squeezing and stretching → vacuum drying → hanging drying → oven drying → rehydration → static setting → vibration and softening.

[0019] The safety shoe upper leather manufactured according to this invention was subjected to experimental testing, as follows: The above are merely specific embodiments of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention using this concept shall be considered as infringing upon the protection scope of the present invention.

Claims

1. A method for preparing a high-performance waterproof workwear upper leather, characterized in that, The process includes the following steps: Rehydration: Place the evenly treated wet blue leather into a drum, add 100%-300% water and 1.0%-3.0% oxalic acid to the drum, maintain the temperature at 40℃, rotate for 90-150 minutes, adjust the pH of the bath to ≤3.0, add 2%-4% compound tanning agent and 1%-3% aldehyde tanning agent, rotate for 60-90 minutes, drain the liquid, and wash with water; Retanning: Add 50%-150% water, 5%-7% chromium powder, 2%-4% acidic phenolic synthetic tannins, 1%-2% waterproofing agent, and 0.5%-1% dispersant to the drum. Rotate for 60-90 minutes. Add 1%-3% oxazolidine liquid tanning agent. Rotate for 60-90 minutes. Drain the liquid and wash with water. Neutralization: Add 100%-150% water to the drum to neutralize 1%-3% tannins. Maintain a temperature of 35℃ and rotate for 30-60 minutes. Add 1%-3% ammonium bicarbonate and rotate for 60-90 minutes. Add 2%-4% small-molecule acrylic resin tanning agent, 1%-2% waterproofing agent, and 0.5%-1% dispersant. Rotate for 60-120 minutes and let stand overnight. Drain the liquid the next day and wash with water. Fixation: Add 200%-300% water, 1%-2% waterproofing and fatliquoring agent, temperature 50℃, rotate for 20 minutes, add 1%-2% chromium powder, rotate for 20-40 minutes, drain the liquid, wash with water at 33℃, add 1%-3% chromium powder, rotate for 90-150 minutes, drain the liquid, and wash with water at 33℃. Drying and finishing.

2. The method for preparing a high-performance waterproof workwear upper leather as described in claim 1, characterized in that, The drying and finishing process is carried out according to conventional procedures: static setting → squeezing and stretching → vacuum drying → hanging drying → oven drying → rehydration → static setting → vibration and softening.

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