Preparation method and application of keratin-based high-performance filler-reinforced acrylic resin retanning agent

Abstract

The present invention relates to a preparation method of a high-performance filler-enhanced acrylic resin retanning agent based on keratin, waste ox hair, ionized water, alkali, alkaline protease, glyoxylic acid are added after mixing evenly; benzyl hexachloride is dissolved in thionyl chloride, 10 parts of N, N-dimethylformamide, pentaerythritol, sodium hydroxide, water and ethanol are added, and rotary evaporation is performed; aluminum nitrate, chromium nitrate, ferric nitrate, manganese nitrate, carboxylated keratin, polycarboxyl ligands, pyrrolidine-3,4-dicarboxylic acid are dispersed in N, N-dimethylformamide; high-performance filler, acrylic resin, boric acid, sodium carboxymethyl cellulose, sodium tripolyphosphate are placed in a ball mill, and ball milling is performed. After the present invention hydrolyzes waste ox hair by an alkali-enzyme combination method, keratin is extracted, the aldehyde group of glyoxylic acid is used to seal the amino group, and it is converted into a carboxyl group, and the improvement of the carboxyl content helps to improve the coordination ability of keratin and metal ions, promotes the formation of high-performance fillers, and improves the yield of high-performance fillers.

Description

Technical Field

[0001] The invention relates to the technical field of leather making, in particular to a preparation method and application of a keratin-based high-performance filler-reinforced acrylic resin retanning agent. Background Art

[0002] Waste cow hair from leather making has been widely studied because it contains a large amount of keratin. Keratin is a small and medium-molecule material with amphiphilic active functional groups such as amino, carboxyl, thiol, and hydroxyl distributed on its molecular chain segments. In aqueous solution, it is more negatively charged than positively charged. The amphiphilic characteristics give keratin good hydrophilicity. Although there are many active functional groups distributed, the number of functional groups on the keratin molecule is small, and the amino and carboxyl groups tend to form hydrogen bonds within and between molecules, so its reactivity is low. In the application of leather making, it is difficult to form a stable hydrogen bond network, covalent bonds, etc. with skin collagen fibers. Therefore, how to improve the reactivity of keratin and skin collagen fibers, promote its internal circulation in the leather industry, and reduce the discharge of leather wastewater and waste has become a major research hotspot. Summary of the invention

[0003] The invention provides a preparation method and application of a keratin-based high-performance filler-reinforced acrylic resin retanning agent, so as to solve the technical problem that keratin from waste cattle hair is difficult to form a stable hydrogen bond network and covalent bond with skin collagen fibers in the application of leather making.

[0004] The present invention adopts the following technical solution:

[0005] A method for preparing a keratin-based high-performance filler-reinforced acrylic resin retanning agent comprises the following steps:

[0006] Step 1, take 100g of washed waste cow hair, add 500g of deionized water, mix well, add 8-12g of alkali, 1-5g of alkaline protease, react at 45-60°C for 3-6h, cool to room temperature, filter to remove impurities, neutralize the filtrate with sulfuric acid to 6-8, add 30-50g of glyoxylic acid, react at 30-35°C for 2-5h, and vacuum dry to obtain carboxylated keratin powder;

[0007] Step 2, dissolving 600 parts of mellitic acid in 1800 parts of thionyl chloride, adding 10 parts of N,N-dimethylformamide, reacting at 35-50° C. for 2-4 hours, removing excess thionyl chloride and N,N-dimethylformamide by rotary evaporation, then adding 80-100 parts of pentaerythritol, adding 1 part of sodium hydroxide, reacting at 20-25° C. for 3-5 hours under the protection of nitrogen, then carefully adding 300 parts of water and 300 parts of ethanol, continuing the reaction for 1-3 hours, and removing ethanol and water by rotary evaporation to obtain a polycarboxyl ligand;

[0008] Step 3, dispersing 10-30 parts of aluminum nitrate, 0-20 parts of chromium nitrate, 5-10 parts of iron nitrate, 5-10 parts of manganese nitrate, 50-100 parts of carboxylated keratin, 20-40 parts of polycarboxyl ligand, and 5-10 parts of pyrrolidine-3,4-dicarboxylic acid in 2000-4000 parts of N,N-dimethylformamide, mixing evenly, heating to 75-90° C., reacting for 48-96 hours, slowly cooling to room temperature, adding 1000-2000 parts of N,N-dimethylformamide, continuing to react for 6-12 hours, filtering to obtain a filter residue, repeatedly washing with N,N-dimethylformamide, and vacuum drying to obtain a high-performance filler;

[0009] Step 4, take 50-500g high-performance filler, 1000g acrylic resin, 10-20g boric acid, 3-5g sodium carboxymethyl cellulose, and 3-6g sodium tripolyphosphate into a ball mill, ball mill for 3 minutes, stop for 1 minute, and repeat 5 times to obtain a keratin-based high-performance filler-enhanced acrylic resin retanning agent.

[0010] In a further improvement, the alkali contains at least calcium hydroxide, and may contain sodium hydroxide and potassium hydroxide.

[0011] An application of a keratin-based high-performance filler-enhanced acrylic resin retanning agent, comprising at least a retanning process and a filling process;

[0012] Retanning process: based on the weight of wet blue leather, control the drum temperature to 30-35°C, add 50-100% water, add 3-6% keratin-based high-performance filler-enhanced acrylic resin retanning agent, 1-3% lanolin fatliquor, rotate for 30-60 minutes, then add 2-4% tannin extract, 2-4% synthetic tanning agent, 2-4% protein filler, 2-4% synthetic oil, rotate for 60-120 minutes, add 100-150% water, add 1.2-1.8% formic acid three times, rotate for 10, 10 and 20 minutes respectively, add 1-3% fatty aldehyde, rotate for 20 minutes, add 4-6% chrome tanning agent, 2-4% chrome-containing tannin, 1-3% acid-resistant fatliquor, rotate for 120-180 minutes, then add 2% sodium formate, rotate for 20 minutes, add 2% baking soda, rotate for 60 minutes, add 2% ammonium bicarbonate, rotate for 60 minutes;

[0013] Filling process: based on the weight of wet blue leather, control the drum temperature to 30-35°C, add 50-100% water, add 3-9% keratin-based high-performance filler-enhanced acrylic resin retanning agent, 3-6% small molecule acrylic resin retanning agent, 1-2% synthetic oil, rotate for 30-60 minutes, add 6-9% tannin extract, 1-3% synthetic tannin, 1-2% synthetic oil, rotate for 30-60 minutes, add 6-9% tannin extract, 3-6% synthetic tannin, 1-3% protein filler, 1-2% synthetic oil, rotate for 30-60 minutes, add 3-6% dicyandiamide resin retanning agent, 3-6% melamine resin retanning agent, 3-6% tannin extract, 1-2% synthetic oil, rotate for 60-120 minutes.

[0014] 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:

[0015] 1. This application uses an alkali-enzyme method to hydrolyze waste cattle hair to extract keratin. In order to further improve the negative charge of keratin, reduce the swelling performance of the high-performance filler made from it, and further improve the physical and mechanical properties of the high-performance filler, the aldehyde group of glyoxylic acid is used to block the amino group and convert it into a carboxyl group, thereby consuming the amino group and increasing the carboxyl content. The increase in the carboxyl content helps to improve the coordination ability of keratin with metal ions, promote the formation of high-performance fillers, and improve the yield of high-performance fillers.

[0016] 2. In order to further improve the carboxyl content of high-performance fillers, a hyperbranched organic matter with multiple carboxyl groups is prepared. This application uses pentaerythritol as the core. After primary hyperbranching, a hyperbranched structure with 15-20 carboxyl groups can be obtained. This hyperbranched structure has extremely strong coordination and chelating ability. Due to steric hindrance, the residual uncoordinated and chelated carboxyl groups can also improve the water solubility and water dispersibility of high-performance fillers. At the same time, a certain amount of carboxylated keratin and pyrrolidine-3,4-dicarboxylic acid are coordinated in the gap between the polycarboxyl ligand and the metal ion, thereby effectively improving the yield of high-performance fillers. At the same time, the high-performance filler contains a large number of aromatic ring structures, which can efficiently adsorb dyes, amino resins, synthetic tanning agents, tannins, etc. containing aromatic structures in leather making, thereby effectively improving the adsorption and binding of leather collagen fibers to retanning and dyeing materials containing aromatic structures.

[0017] 3. The carboxylated keratin of the present application has good anionicity, zeta potential ≤-35mV, and has a relatively suitable particle size and good dispersibility, with a particle size of 300-800nm ​​and a particle size distribution coefficient of 0.150-0.350. The carboxylated keratin also has excellent water solubility, with a solid content of ≥90%, a water-insoluble content of ≤2%, and a water-soluble content of ≥88%.

[0018] 4. The high-performance filler of the present application has a large specific surface area and excellent adsorption performance, and can adsorb a variety of dyes. The adsorption amount of cationic methylene blue is ≥300 mg / g, and the adsorption amount of anionic dyes acid red 359, acid yellow 159, and acid blue 350 is ≥300 mg / g.

[0019] 5. The keratin-based high-performance filler-reinforced acrylic resin retanning agent of the present application has good anionicity and dispersion properties, zeta potential ≤-20mV, particle size 1200-2000nm, and particle size distribution coefficient 0.250-0.400.

[0020] 6. The leather processed by the keratin-based high-performance filler reinforced acrylic resin retanning agent of the present application has good physical and mechanical properties, and also has certain safety and health performance. The shrinkage temperature of the crust leather is ≥90°C -1 , tearing force ≥50N, cracking height ≥7mm, bursting strength ≥300N·mm -1 , formaldehyde content ≤75ppm, hexavalent chromium ≤10ppm, trichlorophenol content ≤0.5ppm, tetrachlorophenol content ≤0.5ppm, pentachlorophenol content ≤0.5ppm, o-phenylphenol content ≤1ppm. DETAILED DESCRIPTION

[0021] Embodiment 1:

[0022] A method for preparing a keratin-based high-performance filler-reinforced acrylic resin retanning agent comprises the following steps:

[0023] Step 1, preparation of carboxylated keratin powder: take 100g of washed waste cow hair, add 500g of deionized water, mix well, add 10g of calcium hydroxide, 3g of alkaline protease (AP, Xiangyang Bio), react at 45°C for 5h, cool to room temperature, filter to remove impurities, neutralize the filtrate with sulfuric acid to 6, add 50g of glyoxylic acid, react at 35°C for 2h, and vacuum dry to obtain carboxylated keratin powder.

[0024] Step 2, preparation of polycarboxyl ligand: dissolve 600 parts of mellitic acid in 1800 parts of thionyl chloride, add 10 parts of N,N-dimethylformamide, react at 35°C for 4 hours, remove excess thionyl chloride and N,N-dimethylformamide by rotary evaporation, then add 95 parts of pentaerythritol, add 1 part of sodium hydroxide, react at 20°C under the protection of nitrogen for 5 hours, then carefully add 300 parts of water and 300 parts of ethanol, continue to react for 1 hour, remove ethanol and water by rotary evaporation to obtain polycarboxyl ligand.

[0025] Step 3, preparation of high-performance filler: 25 parts of aluminum nitrate, 10 parts of chromium nitrate, 7 parts of iron nitrate, 8 parts of manganese nitrate, 80 parts of carboxylated keratin, 25 parts of polycarboxyl ligand, 5 parts of pyrrolidine-3,4-dicarboxylic acid (CAS: 159694-26-5) are dispersed in 2000 parts of N,N-dimethylformamide, mixed evenly and heated to 75°C, reacted for 96 hours, slowly cooled to room temperature and added with 2000 parts of N,N-dimethylformamide, continued to react for 6 hours, filtered to obtain a filter residue, repeatedly rinsed with N,N-dimethylformamide, and vacuum dried to obtain a high-performance filler.

[0026] Step 4, preparation of keratin-based high-performance filler reinforced acrylic resin retanning agent: 50g high-performance filler, 1000g acrylic resin (GXL, LANXESS Chemical), 10g boric acid, 5g sodium carboxymethyl cellulose, and 6g sodium tripolyphosphate are placed in a ball mill, ball milled for 3 minutes, stopped for 1 minute, and repeated 5 times to obtain a keratin-based high-performance filler reinforced acrylic resin retanning agent.

[0027] Embodiment 2:

[0028] A method for preparing a keratin-based high-performance filler-reinforced acrylic resin retanning agent comprises the following steps:

[0029] Step 1: Preparation of carboxylated keratin powder: Take 100g of washed waste cow hair, add 500g of deionized water, mix well, add 3g of sodium hydroxide, 5g of calcium hydroxide, and 5g of alkaline protease (AP, Xiangyang Bio), react at 50°C for 4h, cool to room temperature, filter to remove impurities, neutralize the filtrate with sulfuric acid to 7, add 40g of glyoxylic acid, react at 32°C for 3h, and vacuum dry to obtain carboxylated keratin powder.

[0030] Step 2: Preparation of polycarboxyl ligands: Dissolve 600 parts of mellitic acid in 1800 parts of thionyl chloride, add 10 parts of N,N-dimethylformamide, react at 40°C for 3 hours, remove excess thionyl chloride and N,N-dimethylformamide by rotary evaporation, then add 80 parts of pentaerythritol, add 1 part of sodium hydroxide, react at 25°C for 3 hours under the protection of nitrogen, then carefully add 300 parts of water and 300 parts of ethanol, continue to react for 2 hours, remove ethanol and water by rotary evaporation to obtain polycarboxyl ligands.

[0031] Step 3: Preparation of high-performance filler: Disperse 20 parts of aluminum nitrate, 10 parts of chromium nitrate, 10 parts of iron nitrate, 10 parts of manganese nitrate, 50 parts of carboxylated keratin, 40 parts of polycarboxyl ligand, and 10 parts of pyrrolidine-3,4-dicarboxylic acid (CAS: 159694-26-5) in 4000 parts of N,N-dimethylformamide, mix well and heat to 80°C, react for 72 hours, slowly cool to room temperature and add 1000 parts of N,N-dimethylformamide, continue to react for 12 hours, filter to obtain the filter residue, repeatedly rinse with N,N-dimethylformamide, and vacuum dry to obtain the high-performance filler.

[0032] Step 4: Preparation of keratin-based high-performance filler-reinforced acrylic resin retanning agent: 200 g of high-performance filler, 1000 g of acrylic resin (GXL, LANXESS Chemical), 15 g of boric acid, 4 g of sodium carboxymethyl cellulose, and 5 g of sodium tripolyphosphate are placed in a ball mill, ball milled for 3 minutes, stopped for 1 minute, and repeated 5 times to obtain a keratin-based high-performance filler-reinforced acrylic resin retanning agent.

[0033] Embodiment 3:

[0034] A method for preparing a keratin-based high-performance filler-reinforced acrylic resin retanning agent comprises the following steps:

[0035] Step 1: Preparation of carboxylated keratin powder: Take 100g of washed waste cow hair, add 500g of deionized water, mix well, add 4g of alkali sodium hydroxide, 4g of potassium hydroxide, 4g of calcium hydroxide, 1g of alkaline protease (AP, Xiangyang Biological), react at 55°C for 3h, cool to room temperature, filter to remove impurities, neutralize the filtrate with sulfuric acid to 8, add 30g of glyoxylic acid, react at 35°C for 5h, and vacuum dry to obtain carboxylated keratin powder.

[0036] Step 2: Preparation of polycarboxyl ligands: Dissolve 600 parts of mellitic acid in 1800 parts of thionyl chloride, add 10 parts of N,N-dimethylformamide, react at 45°C for 2 hours, remove excess thionyl chloride and N,N-dimethylformamide by rotary evaporation, then add 90 parts of pentaerythritol and 1 part of sodium hydroxide, react at 22°C under the protection of nitrogen for 4 hours, then carefully add 300 parts of water and 300 parts of ethanol, continue to react for 3 hours, remove ethanol and water by rotary evaporation to obtain polycarboxyl ligands.

[0037] Step 3: Preparation of high-performance filler: 10 parts of aluminum nitrate, 18 parts of chromium nitrate, 7 parts of iron nitrate, 5 parts of manganese nitrate, 55 parts of carboxylated keratin, 37 parts of polycarboxyl ligand, and 8 parts of pyrrolidine-3,4-dicarboxylic acid (CAS: 159694-26-5) are dispersed in 2500 parts of N,N-dimethylformamide, mixed evenly and heated to 90°C, reacted for 48 hours, slowly cooled to room temperature and added with 1500 parts of N,N-dimethylformamide, and continued to react for 8 hours. After filtering, the filter residue was repeatedly rinsed with N,N-dimethylformamide and vacuum dried to obtain a high-performance filler.

[0038] Step 4: Preparation of keratin-based high-performance filler-reinforced acrylic resin retanning agent: 500 g of high-performance filler, 1000 g of acrylic resin (GXL, LANXESS Chemical), 20 g of boric acid, 3 g of sodium carboxymethyl cellulose, and 4 g of sodium tripolyphosphate are placed in a ball mill, ball milled for 3 minutes, stopped for 1 minute, and repeated 5 times to obtain a keratin-based high-performance filler-reinforced acrylic resin retanning agent.

[0039] Embodiment 4:

[0040] An application of a keratin-based high-performance filler-reinforced acrylic resin retanning agent, comprising a neutralization step, a retanning step, a filling step and a fatliquoring step, wherein the keratin-based high-performance filler-reinforced acrylic resin retanning agent prepared in Example 1 is added to the retanning step and the filling step;

[0041] Neutralization process: based on the weight of the wet blue leather, control the drum temperature to 36°C, add 3% neutralizing tannin (A, Unitec, Italy), 1% sodium formate, rotate for 20 minutes, add 1.2% baking soda, 0.8% sodium bicarbonate, rotate for 60 minutes, drain, add 200% water, and rinse.

[0042] Retanning process: based on the weight of wet blue leather, the drum temperature was controlled at 32°C, 50% of water was added, 3% of keratin-based high-performance filler-enhanced acrylic resin retanning agent, 3% of lanolin fatliquor (ZLN, Bisuo Chemical) were added, and the leather was rotated for 30 minutes, then 3% of tannin extract (ATO, Jinfeng Leather Chemical), 3% of synthetic tanning agent (RL, Derui Chemical), 3% of protein filler (FB, Sichuan Desail), 3% of synthetic oil (94S, Sima Chemical) were added, and the leather was rotated for 90 minutes, 100% of water was added, 1.5% of formic acid was added three times, and the leather was rotated for 10, 10 and 20 minutes respectively, 2% of fatty aldehyde (PF, Sima Chemical) was added, and the leather was rotated for 20 minutes, and 4% of chrome tanning agent (TankromAB, Turkey), 3% chromium-containing tannin (ALC, Unitec, Italy), 2% acid-resistant fatliquor (B1, Thomson Chemical), rotate for 120 minutes, then add 2% sodium formate, rotate for 20 minutes, add 2% baking soda, rotate for 60 minutes, add 2% ammonium bicarbonate, and rotate for 60 minutes.

[0043] Filling process: based on the weight of wet blue leather, control the drum temperature at 32°C, add 50% water, add 9% keratin-based high-performance filler-enhanced acrylic resin retanning agent, 3% small molecule acrylic resin retanning agent (TP340, Zhiqi Trading), 1% synthetic oil (PF, Sima Chemical), rotate for 30 minutes, add 6% tannin (ATO, Jinfeng Leather Chemical), 2% synthetic tannin (4108, Lanxess Chemical), 1% synthetic oil (PF, Sima Chemical), rotate for 3 0 minutes, add 9% tannin (ATO, Jinfeng Leather Chemical), 3% synthetic tannin (OS, Lanxess Chemical), 2% protein filler (FB, Sichuan Desaier), 1% synthetic oil (PF, Sima Chemical), rotate for 60 minutes, add 3% dicyandiamide resin retanning agent (DC-11, Lining Technology), 3% melamine resin retanning agent (MD, Lining Technology), 6% tannin (LCF, Lining Technology), 2% synthetic oil (PF, Sima Chemical), rotate for 60-120 minutes.

[0044] Fatting process: increase the drum temperature to 48°C, add 100% water, add 3% synthetic phosphoric acid fatliquor (LWK, Li Ning Technology), 3% modified neat's foot oil (NT, Li Ning Technology), rotate for 30 minutes, add 3% sulfonated synthetic oil (SA, Li Ning Technology), 3% synthetic fatliquor (BSFR, Li Ning Technology), 3% lecithin (LC, Italy Unitco), 3% lanolin (ZLN, Bisso Chemical), rotate for 120 minutes, and finally add 2.5% formic acid in 4 times, rotate for 10, 10, 10, and 30 minutes respectively, to obtain crust leather.

[0045] Embodiment 5:

[0046] The application of the keratin-based high-performance filler-reinforced acrylic resin retanning agent in this embodiment is basically the same as that in Embodiment 4, except that the keratin-based high-performance filler-reinforced acrylic resin retanning agent added in the retanning process and the filling process is prepared in Embodiment 2.

[0047] Example 6: The application of the keratin-based high-performance filler-reinforced acrylic resin retanning agent in this example is basically the same as that in Example 4, except that the keratin-based high-performance filler-reinforced acrylic resin retanning agent added in the retanning process and the filling process is prepared in Example 3.

[0048] Experimental testing

[0049] The carboxylated keratin, high-performance filler and high-performance filler-enhanced acrylic resin retanning agent obtained in Example 1, Example 2 and Example 3 were tested experimentally, and the experimental data obtained are shown in Table 1 below: Table 1

[0050]

[0051] The physical and mechanical properties, safety and health performance of the crust leather obtained in Example 4, Example 5 and Example 6 were tested experimentally, and the experimental data obtained are shown in Table 1 below:

[0052] Table 2

[0053]

[0054] 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 method for preparing a keratin-based high-performance filler-reinforced acrylic resin retanning agent, characterized in that: The steps include: Step 1, take 100g of washed waste cow hair, add 500g of deionized water, mix well, add 8-12g of alkali, 1-5g of alkaline protease, react at 45-60°C for 3-6h, cool to room temperature, filter to remove impurities, neutralize the filtrate with sulfuric acid to 6-8, add 30-50g of glyoxylic acid, react at 30-35°C for 2-5h, and vacuum dry to obtain carboxylated keratin powder; Step 2, take 600 parts of mellitic acid and dissolve it in 1800 parts of thionyl chloride, add 10 parts of N, N-dimethylformamide, react at 35-50° C. for 2-4 hours, remove excess thionyl chloride and N, N-dimethylformamide by rotary evaporation, then add 80-100 parts of pentaerythritol, add 1 part of sodium hydroxide, react at 20-25° C. for 3-5 hours under the protection of nitrogen, then carefully add 300 parts of water and 300 parts of ethanol, continue to react for 1-3 hours, and remove ethanol and water by rotary evaporation to obtain a polycarboxyl ligand; Step 3, dispersing 10-30 parts of aluminum nitrate, 0-20 parts of chromium nitrate, 5-10 parts of iron nitrate, 5-10 parts of manganese nitrate, 50-100 parts of carboxylated keratin, 20-40 parts of polycarboxyl ligand, and 5-10 parts of pyrrolidine-3,4-dicarboxylic acid in 2000-4000 parts of N, N-dimethylformamide, mixing evenly, heating to 75-90° C., reacting for 48-96 hours, slowly cooling to room temperature, adding 1000-2000 parts of N, N-dimethylformamide, continuing to react for 6-12 hours, filtering to obtain a filter residue, repeatedly washing with N, N-dimethylformamide, and vacuum drying to obtain a high-performance filler; Step 4, take 50-500g high-performance filler, 1000g acrylic resin, 10-20g boric acid, 3-5g sodium carboxymethyl cellulose, and 3-6g sodium tripolyphosphate into a ball mill, ball mill for 3 minutes, stop for 1 minute, and repeat 5 times to obtain a keratin-based high-performance filler-enhanced acrylic resin retanning agent.

2. The method for preparing a keratin-based high-performance filler-reinforced acrylic resin retanning agent according to claim 1, characterized in that: The base contains at least calcium hydroxide.

3. The use of a keratin-based high-performance filler to reinforce acrylic resin retanning agent as claimed in any one of claims 1 or 2, characterized in that: At least including retanning process and filling process Retanning process: Based on the weight of wet blue leather, control the drum temperature to 30-35°C, add 50-100% water, add 3-6% keratin-based high-performance filler-enhanced acrylic resin retanning agent, 1-3% lanolin fatliquor, rotate for 30-60 minutes, then add 2-4% tannin extract, 2-4% synthetic tanning agent, 2-4% protein filler, 2-4% synthetic oil, rotate for 60-120 minutes, add 100-150 % water, add 1.2-1.8% formic acid three times, rotate for 10, 10 and 20 minutes respectively, add 1-3% fatty aldehyde, rotate for 20 minutes, add 4-6% chrome tanning agent, 2-4% chrome-containing tannin, 1-3% acid-resistant fatliquor, rotate for 120-180 minutes, then add 2% sodium formate, rotate for 20 minutes, add 2% baking soda, rotate for 60 minutes, add 2% ammonium bicarbonate, rotate for 60 minutes; Filling process: based on the weight of wet blue leather, control the drum temperature to 30-35°C, add 50-100% water, add 3-9% keratin-based high-performance filler-enhanced acrylic resin retanning agent, 3-6% small molecule acrylic resin retanning agent, 1-2% synthetic oil, rotate for 30-60 minutes, add 6-9% tannin extract, 1-3% synthetic tannin, 1-2% synthetic oil, rotate for 30-60 minutes, add 6-9% tannin extract, 3-6% synthetic tannin, 1-3% protein filler, 1-2% synthetic oil, rotate for 30-60 minutes, add 3-6% dicyandiamide resin retanning agent, 3-6% melamine resin retanning agent, 3-6% tannin extract, 1-2% synthetic oil, rotate for 60-120 minutes.

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