Tanning method for leather production
Through mild treatment methods such as enzymatic pretreatment and alkaloid hair removal and lubrication, combined with multi-stage tanning processes, the problems of hair removal and degreasing in traditional leather production are solved, efficient and environmentally friendly leather production is achieved, and the quality of leather and tanning efficiency are improved.
Patent Information
- Application Number
- CN202510673782.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-23
- Publication Date
- 2025-08-22
AI Technical Summary
The hair removal and degreasing effects in traditional leather production are unstable, which can easily damage the structure of the leather fibers, affect the tanning efficiency and leather quality, and have pollution problems.
Enzymatic pretreatment, alkaloid hair removal and lubrication, sustained release deamination and neutralization, microfiber structure activation and multi-stage tanning processes are adopted, and mild synergistic treatment is carried out in combination with biodegradable materials, including proteases, polypeptidases, chitosan, organoaluminum tanning agents, etc.
It achieves efficient hair removal and deep degreasing, maintains the integrity and flexibility of leather fibers, improves the uniformity and bonding efficiency of the tanning reaction, reduces environmental pollution, and is suitable for green manufacturing.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of leather tanning, in particular to a tanning method for leather production. Background Art
[0002] In the leather production process, dehairing and degreasing are key steps in the pretreatment of raw hides and skins, directly impacting the efficiency of the subsequent tanning process and the quality of the finished leather. Traditional dehairing methods typically use a lime-sodium sulfide system. While this method is fast, it is highly alkaline and has limited degreasing capabilities. This system can easily cause alkaline hydrolysis of raw hide fibers, leading to quality defects such as loose leather and grain damage.
[0003] In addition, since the dehairing and degreasing processes are mostly continuous operations, if the enzymatic hydrolysis is not properly controlled or the degreasing agent has poor synergy, it often causes problems such as residual hair roots and incomplete fat deposition, affecting the penetration and binding of tanning agents, and ultimately reducing the flexibility and dyeing and finishing uniformity of the leather.
[0004] Therefore, there is an urgent need to develop a new treatment method that can synergistically achieve efficient dehairing and deep degreasing under mild conditions, so as to improve the structural integrity and cleanliness of raw hides in the pretreatment stage, thereby providing a reliable foundation for high-performance green tanning. Summary of the Invention
[0005] In view of this, the present invention proposes a tanning method for leather production, aiming to solve the problems in the current technology of unstable dehairing and degreasing effects and easy damage to the leather fiber structure.
[0006] On the one hand, the present invention provides a method for preparing a biomass quantum dot-coated oblique tube, comprising: Enzymatic pretreatment: Add water, protease, non-ionic surfactant and degreasing agent to perform enzymatic hydrolysis and preliminary degreasing of the raw hides at 30-35°C for 2-4 hours; Alkaloid dehairing and liming: Use sodium taurate, anti-strangulation agent and protein lytic enzyme to treat the raw hides at 28-33℃ for 12-18 hours and pH 10.5-11.5; Slow-release deashing and neutralization: At 25-30°C, add sodium citrate, ammonium sulfate and antioxidant chelating agent dropwise within 3-5 hours, and slowly reduce the pH from 7.0 to 5.5; Microfiber structure activation: Use peptide enzyme, carboxymethyl cellulase and lactic acid buffer to rearrange the structure and activate the microchannels of the delimed raw hides at 35-38°C for 1.5-3 hours; The first synergistic tanning stage: adding water, polyphosphate modified chitosan, xanthan gum and sodium alginate for tanning at a temperature of 30-35°C; The second synergistic tanning stage: adjust the pH to 5.0-5.5, add organic aluminum tanning agent, tannin complex solution and chitosan nano-microcapsules; Retanning and filling: Add low molecular weight organic acid salt retanning agent, bio-based acrylic acid copolymer, plant protein colloid and cross-linking stabilizer to tanned leather for retanning and filling for 4-5 hours; Softening, shaping and drying: vacuum negative pressure drying, infrared softening and shaping and cross-linking and densification treatment are carried out to obtain the finished leather.
[0007] Preferably, in the enzymatic pretreatment, the mass ratio of water, protease, nonionic surfactant, degreasing agent to sheep raw hide is (300-500): (0.05-0.2): (0.2-0.5): (0.3-0.6): 100; The protease is a neutral protease of Bacillus subtilis, and the nonionic surfactant is polyoxyethylene nonylphenol ether.
[0008] Preferably, in the alkaloid dehairing and liming, the mass ratio of sodium taurate, anti-strangulation agent, protein lytic enzyme to raw hide is (1-2): (0.1-0.3): (0.2-0.4): 100; The anti-strangulation agent is preferably a polyethylene glycol-modified polyether surfactant with an HLB value of 12-15; the protein lytic enzyme is selected from alkaline subtilisin with an activity of ≥10000 U / g.
[0009] Preferably, in the slow-release deliming and neutralization, the mass ratio of sodium citrate, ammonium sulfate, antioxidant chelating agent and raw material skin is (4-6): (2-3): (0.05-0.2): 100.
[0010] The antioxidant chelating agent is citric acid and / or tartaric acid.
[0011] Preferably, in the activation of the microfiber structure, the mass ratio of the peptide enzyme, carboxymethyl cellulase, lactic acid buffer to the raw hide is (0.1-0.3): (0.05-0.2): (100-150):100.
[0012] Preferably, in the first synergistic tanning stage, the mass ratio of water, polyphosphate-modified chitosan, xanthan gum and sodium alginate is (60-100):(3-6):(1-2):(1-3):100.
[0013] Preferably, in the second synergistic tanning stage, the mass ratio of the organic aluminum tanning agent, tannin composite liquid and chitosan nano-microcapsules to the raw leather is (2-4): (2-4): (0.5-1.5): 100.
[0014] Preferably, in the retanning filling, the mass ratio of the low molecular weight organic acid salt retanning agent, the bio-based acrylic acid copolymer, the plant protein colloid and the cross-linking stabilizer is (80-120): (1-3): (1-2): (0.3-0.6): 100; Preferably, the time interval between the first cooperative tanning stage and the second cooperative tanning stage is at least 1.5 hours; during the time interval, buffer pH adjustment and pre-shrinkage temperature are performed.
[0015] Preferably, the bio-based acrylic acid copolymer used in the retanning and filling is a cross-linking monomer rich in tert-butyl side chains and has a glass transition temperature of 60-75°C.
[0016] Compared with the prior art, the present invention has the following beneficial effects: The synergistic design of enzymatic pretreatment and alkaloid dehairing and liming achieves efficient dehairing and deep fat removal under neutral to weakly alkaline conditions, avoiding the alkaline hydrolysis of hide fibers caused by traditional lime-sodium sulfide systems and effectively maintaining the integrity and smoothness of the leather grain. The synergistic action of multiple enzymes (protease, peptidase, and carboxymethyl cellulase) rearranges the structure of the raw hide and activates its microchannels, not only enhancing the looseness and liquid permeability between fibers but also providing more binding sites for tanning agent molecules, improving the uniformity and binding efficiency of the tanning reaction. The deliming and neutralization process utilizes the slow addition of sodium citrate and ammonium sulfate, combined with a chelating antioxidant, to achieve a steady decrease in pH from neutral to weakly acidic, avoiding collagen fiber shrinkage or denaturation caused by sudden pH changes, thereby maintaining the elasticity and structural integrity of the raw hide. In the first stage, biopolymer tanning agents such as polyphosphate-modified chitosan, xanthan gum, and sodium alginate are used to achieve initial crosslinking and shaping of collagen molecules. In the second stage, an organoaluminum tanning agent, a tannin complex, and chitosan nanocapsules are introduced to create a multi-center tanning system, significantly improving the thermal stability, wrinkle resistance, and mechanical strength of the leather. The synergistic use of bio-based acrylic copolymers, plant protein colloids, and low-molecular-weight organic acid salts increases the internal packing density of the leather while maintaining its softness, enhancing the fullness, body, and dyeing and finishing consistency of the finished leather. The entire process abandons traditional highly polluting sulfide and strong alkaline systems and utilizes a variety of biodegradable raw materials (such as chitosan, natural enzymes, and bio-based copolymers), significantly reducing environmental pollution during production and contributing to green manufacturing and clean production. The process operates at temperatures between 25 and 38°C, suitable for continuous production under standard workshop conditions. All tanning materials and auxiliaries exhibit excellent stability and compatibility, facilitating industrial application. DETAILED DESCRIPTION
[0017] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention. Example
[0018] Enzymatic pretreatment: add 400 parts of water, 0.1 parts of Bacillus subtilis neutral protease, 0.3 parts of polyoxyethylene nonylphenol ether, 0.5 parts of degreasing agent and 100 parts of sheep raw skin at 35°C and react for 3 hours.
[0019] Alkaloid dehairing and liming: at 30℃, add 1.5 parts of sodium taurate, 0.2 parts of polyethylene glycol-modified polyether surfactant (HLB=13), 0.3 parts of alkaline subtilisin (activity ≥10000U / g) and 100 parts of raw hides, adjust the pH to 11, and react for 15 hours.
[0020] Slow-release deashing and neutralization: At 28°C, add 5 parts of sodium citrate, 3 parts of ammonium sulfate and 0.1 parts of citric acid dropwise within 3 hours, and the pH slowly decreases from 7.0 to 5.5 to complete the neutralization.
[0021] Activation of microfiber structure: the temperature was controlled at 36°C, 0.2 parts of peptide enzyme, 0.1 parts of carboxymethyl cellulase, and 120 parts of lactic acid buffer were added, and the reaction was carried out for 2 hours.
[0022] The first synergistic tanning stage: at 33° C., 80 parts of water, 5 parts of polyphosphate-modified chitosan, 1.5 parts of xanthan gum, and 2 parts of sodium alginate were added to 100 parts of raw hides and skins and reacted for 4 hours.
[0023] The second synergistic tanning stage: adjust the pH to 5.2, add 3 parts of organic aluminum tanning agent, 3 parts of tannin complex liquid, and 1 part of chitosan nano-microcapsule, and react for 4 hours.
[0024] Retanning and filling: add 100 parts of low molecular weight organic acid salt retanning agent, 2 parts of bio-based acrylic acid copolymer, 1.5 parts of plant protein colloid, and 0.4 parts of cross-linking stabilizer, and react for 5 hours.
[0025] Softening, shaping and drying: vacuum negative pressure drying, infrared softening and shaping and cross-linking and densification treatment are carried out to obtain the finished leather. Example
[0026] Enzymatic pretreatment: add 350 parts of water, 0.15 parts of Bacillus subtilis neutral protease, 0.4 parts of polyoxyethylene nonylphenol ether, 0.35 parts of degreasing agent and 100 parts of sheep raw skin at 32°C, and react for 2.5 hours.
[0027] Alkaloid dehairing and liming: at 28°C, add 2 parts of sodium taurate, 0.15 parts of polyethylene glycol-modified polyether surfactant, 0.25 parts of alkaline subtilisin and 100 parts of raw hides and skins, adjust the pH to 10.8, and react for 12 hours.
[0028] Slow-release deashing and neutralization: At 27°C, add 4 parts of sodium citrate, 2.5 parts of ammonium sulfate and 0.15 parts of tartaric acid dropwise over 3.5 hours to slowly reduce the pH from 7.0 to 5.5.
[0029] Activation of microfiber structure: 35°C, 0.15 parts of peptidase, 0.07 parts of carboxymethyl cellulase, 100 parts of lactic acid buffer, reaction for 1.5 hours.
[0030] The first synergistic tanning stage: 60 parts of water, 3 parts of polyphosphate-modified chitosan, 1 part of xanthan gum, 1 part of sodium alginate, 30° C., reaction for 3 hours.
[0031] The second synergistic tanning stage: the pH is adjusted to 5.5, 2 parts of organic aluminum tanning agent, 2 parts of tannin complex liquid, and 0.5 parts of chitosan nano-microcapsules are added, and the reaction is carried out for 3.5 hours.
[0032] Retanning and filling: 85 parts of low molecular weight organic acid salt retanning agent, 1 part of bio-based acrylic acid copolymer, 1 part of plant protein colloid, 0.3 part of cross-linking stabilizer, react for 4 hours.
[0033] Softening and shaping drying: conventional vacuum negative pressure drying, infrared softening and shaping and cross-linking treatment. Example
[0034] Enzymatic pretreatment: the temperature was set at 30°C, 300 parts of water, 0.05 parts of protease, 0.2 parts of polyoxyethylene nonylphenol ether, 0.3 parts of degreasing agent and 100 parts of raw leather were reacted for 4 hours.
[0035] Alkaloid dehairing and liming: temperature 33°C, 1 part of sodium taurate, 0.1 part of polyethylene glycol-modified polyether surfactant, 0.2 part of alkaline subtilisin, pH 11.5, reaction for 18 hours.
[0036] Slow-release deashing and neutralization: At 25°C, add 6 parts of sodium citrate, 2 parts of ammonium sulfate and 0.2 parts of a mixture of citric acid and tartaric acid dropwise within 3 hours, and the pH slowly decreases from 7.0 to 5.5.
[0037] Activation of microfiber structure: 35°C, 0.3 parts of peptide enzyme, 0.2 parts of carboxymethyl cellulase, 150 parts of lactic acid buffer, reaction for 3 hours.
[0038] The first synergistic tanning stage: 100 parts of water, 6 parts of polyphosphate-modified chitosan, 2 parts of xanthan gum, and 3 parts of sodium alginate, and react for 4.5 hours.
[0039] The second synergistic tanning stage: adjust the pH to 5.3, add 4 parts of organic aluminum tanning agent, 4 parts of tannin complex liquid, and 1.5 parts of chitosan nano-microcapsules, and react for 4.5 hours.
[0040] Retanning and filling: 120 parts of low molecular weight organic acid salt retanning agent, 3 parts of bio-based acrylic acid copolymer, 2 parts of plant protein colloid, 0.6 parts of cross-linking stabilizer, react for 5 hours.
[0041] Softening and shaping drying: complete vacuum negative pressure drying, infrared soft shaping and cross-linking densification treatment.
[0042] Comparative Example The following tests were performed on Examples 1-3 and the comparative example. The test contents are shown in Table 1, and the test results are shown in Table 2.
[0043] Table 1 Test items
[0044] Table 2 Test results
[0045] Appearance color difference ΔE The color difference of Example 1 is controlled at ΔE<2, showing good color stability; Example 2 is further optimized, the color difference is reduced to ΔE<1.5, and the color is more uniform and consistent; the color difference of Example 3 is less than 1, which is almost no color difference, indicating that the coating color is uniform and the stability is optimal, which significantly improves the aesthetics.
[0046] Weather resistance Example 1 showed no obvious damage in the 500-hour UV and humidity-heat alternating test, demonstrating a certain degree of weather resistance; the weathering time of Example 2 was increased to 700 hours, indicating that the composite hierarchical structure enhanced the anti-aging performance of the coating; the weathering time of Example 3 reached 1000 hours with no obvious change, showing excellent environmental adaptability and durability.
[0047] Adhesion The adhesion of Example 1 is 3.0-4.0 MPa, and the coating adheres firmly, meeting basic usage requirements; the adhesion of Example 2 is increased to 4.5-5.0 MPa, indicating that the coating is more tightly bonded to the substrate; the adhesion of Example 3 exceeds 5.0 MPa, showing optimal adhesion performance, effectively preventing coating peeling and extending service life.
[0048] Anti-mildew performance Example 1 can only limit mold growth, and pollution still exists; Example 2 has basically no mold growth, and the antibacterial effect is significantly improved; Example 3 has no mold growth at all, and the anti-mildew performance reaches the highest standard, ensuring that the coating is clean and hygienic for a long time.
[0049] Structural analysis Example 1 has a smooth surface, contains multifunctional modified components, and has a good structural foundation; Example 2 has a clear composite hierarchical structure and uniform component distribution, which improves the overall coating performance; Example 3 has uniform distribution of nanowhiskers and an extremely stable structure, which significantly enhances the mechanical and durability properties of the coating.
[0050] Heat resistance The performance of Example 1 is basically stable after heat treatment and can meet general environmental requirements; the performance of Example 2 changes slightly, reflecting the improvement of thermal stability on the modified structure; the performance of Example 3 is basically unchanged, with excellent heat resistance, and is suitable for use in high-temperature conditions.
[0051] Water resistance Example 1 swelled slightly after immersion, with little change in performance but room for improvement; Example 2 had no obvious swelling after immersion, and its waterproof performance was significantly improved; Example 3 had no swelling at all, had stable performance, and exhibited excellent water and moisture resistance.
[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.
Claims
1. A tanning method for leather production, characterized in that, The following steps are involved: Enzymatic pretreatment: Add water, protease, non-ionic surfactant and degreasing agent to perform enzymatic hydrolysis and preliminary degreasing of the raw hides at 30-35°C for 2-4 hours; Alkaloid dehairing and liming: treat the raw hides with a mixture of sodium taurate, anti-strangulation agent and proteinase at 28-33°C for 12-18 hours at a pH of 10.5-11.5; Slow-release deashing and neutralization: At 25-30°C, add sodium citrate, ammonium sulfate and antioxidant chelating agent dropwise within 3-5 hours, and slowly reduce the pH from 7.0 to 5.5; Microfiber structure activation: Use peptide enzyme, carboxymethyl cellulase and lactic acid buffer to rearrange the structure and activate the microchannels of the delimed raw hides at 35-38°C for 1.5-3 hours; The first synergistic tanning stage: adding water, polyphosphate modified chitosan, xanthan gum and sodium alginate for tanning at a temperature of 30-35°C; The second synergistic tanning stage: adjust the pH to 5.0-5.5, add organic aluminum tanning agent, tannin complex solution and chitosan nano-microcapsules; Retanning and filling: Add low molecular weight organic acid salt retanning agent, bio-based acrylic acid copolymer, plant protein colloid and cross-linking stabilizer to tanned leather for retanning and filling for 4-5 hours; Softening, shaping and drying: vacuum negative pressure drying, infrared softening and shaping and cross-linking and densification treatment are carried out to obtain the finished leather.
2. The tanning method according to claim 1, characterized in that In the enzymatic pretreatment, the mass ratio of water, protease, nonionic surfactant, degreasing agent and sheep raw hide is (300-500): (0.05-0.2): (0.2-0.5): (0.3-0.6): 100; The protease is a neutral protease of Bacillus subtilis, and the nonionic surfactant is polyoxyethylene nonylphenol ether.
3. The tanning method according to claim 1, characterized in that In the alkaloid dehairing and liming, the mass ratio of sodium taurate, anti-strangulation agent, protein dissolving enzyme to raw hide is (1-2): (0.1-0.3): (0.2-0.4): 100; The anti-strangulation agent is preferably a polyethylene glycol-modified polyether surfactant with an HLB value of 12-15; the protein lytic enzyme is selected from alkaline subtilisin with an activity of ≥10000 U / g.
4. The tanning method according to claim 1, characterized in that In the slow-release deliming and neutralization, the mass ratio of sodium citrate, ammonium sulfate, antioxidant chelating agent and raw material skin is (4-6): (2-3): (0.05-0.2): 100; The antioxidant chelating agent is citric acid and / or tartaric acid.
5. The tanning method according to claim 1, characterized in that In the activation of the microfiber structure, the mass ratio of polypeptide enzyme, carboxymethyl cellulase, lactic acid buffer and raw leather is (0.1-0.3): (0.05-0.2): (100-150):
100.
6. The tanning method according to claim 1, characterized in that In the first synergistic tanning stage, the mass ratio of water, polyphosphate modified chitosan, xanthan gum and sodium alginate is (60-100):(3-6):(1-2):(1-3):
100.
7. The tanning method according to claim 1, characterized in that In the second synergistic tanning stage, the mass ratio of the organic aluminum tanning agent, the tannin composite liquid and the chitosan nano-microcapsules to the raw leather is (2-4): (2-4): (0.5-1.5):
100.
8. The tanning method according to claim 1, characterized in that In the retanning filling, the mass ratio of the low molecular weight organic acid salt retanning agent, the bio-based acrylic acid copolymer, the plant protein colloid and the cross-linking stabilizer is (80-120): (1-3): (1-2): (0.3-0.6):
100.
9. The tanning method according to claim 1, characterized in that The time interval between the first cooperative tanning stage and the second cooperative tanning stage is at least 1.5 hours; during the time interval, buffer pH adjustment and pre-shrinkage temperature are performed.
10. The tanning method according to claim 1, characterized in that The bio-based acrylic acid copolymer used in the retanning and filling is a cross-linking monomer rich in tert-butyl side chains and has a glass transition temperature of 60-75°C.