Odor-optimized leather, preparation process and wet dyeing and finishing process of leather blank

Abstract

The invention relates to the technical field of leather, in particular to odor-optimized leather, a preparation process and a leather blank wet dyeing and finishing process. The odor-optimized automobile leather sequentially comprises a coating layer, a leather blank layer, an odor absorption layer and an elastic layer from a surface layer to a bottom layer. Wherein the leather blank of the leather blank layer is processed and manufactured by a wet dyeing and finishing process, the leather blank layer realizes smell control in the whole process of the wet dyeing and finishing process, reduces the smell formed by combining chemical materials with leather fibers, gives consideration to the physical properties of leather and meets the authentication requirements of ecological leather, and the dyeing process is allocated to the two procedures of wet dyeing and finishing; one washing procedure is matched after each time of dyeing, the odor of the dye can be reduced, in addition, the two dyeing procedures can ensure that the leather blank is uniformly dyed and is not easy to fade, and the odor absorbing layer can absorb the odor volatilized in the automobile leather, so that the odor in a compartment is optimized.

Description

Technical Field

[0001] The invention relates to the technical field of leather, and in particular to odor-optimized leather and a preparation process and a leather wet-dyeing and finishing process. Background Art

[0002] With increasing consumer concern about vehicle interior environmental issues, in-vehicle odor has also garnered significant attention from vehicle and parts manufacturers in recent years. Environmental requirements for automotive interior materials are becoming increasingly stringent. Genuine leather, a crucial component of high-end automotive interiors, significantly impacts the overall vehicle odor. The primary source of leather odor is the use of numerous chemicals during the wet dyeing and finishing process, such as chrome tanning agents, formic acid, and fatliquors. However, wet dyeing and finishing not only reduces production costs and improves product sustainability, but also effectively reduces wastewater treatment burdens, aligning with the philosophy of green production. Therefore, reducing leather odor while ensuring dyeing results is a pressing issue for the industry and is beneficial to the development of Chinese automotive technology.

[0003] To address the above-mentioned issues, the applicant has proposed a wet dyeing and finishing method for low-odor leather based on a zeolite tanning agent, application number CN202311728157.1. This method uses chrome-free tanned leather for wet dyeing and finishing. Chrome tanning agents are not used in the wet dyeing and finishing process. Zeolite tanning agents replace part of formic acid for retanning, filling, and fatliquor fixation. Low-odor materials such as polymer tanning agents, tara extracts, and synthetic fatliquors are used for retanning, filling, and fatliquor, thereby reducing the odor in the leather. This method reduces the odor in the leather by improving some of the chemical materials used in the wet dyeing and finishing process. It can neutralize the sour taste caused by chrome tanning agents or formic acid residues and reduce the odor of fish oil fatliquors. During the wet dyeing and finishing process, more than 20 chemical materials are used. The chemical materials remain in the leather. As the leather is used, small molecular acidic substances will gradually evaporate and produce an acidic odor. In addition, the leather is oxidized and decomposed into volatile small molecular substances during use, which will also emit a corrupt odor. How to neutralize, optimize and reduce the odor of genuine leather throughout the wet dyeing and finishing process is an urgent problem to be solved in the automotive leather processing industry. In view of this, the present invention is proposed. Summary of the Invention

[0004] The present invention provides odor-optimized leather and a preparation process and a leather wet dyeing and finishing process to solve the above problems.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: odor-optimized automobile leather, which includes a coating layer, a leather blank layer, an odor-absorbing layer, and an elastic layer from the surface layer to the bottom layer. The leather blank of the leather blank layer is made by a wet dyeing and finishing process. The coating layer is sprayed on the front side of the leather blank layer, the odor-absorbing layer is bonded to the back side of the leather blank layer, and the elastic layer is compounded with the odor-absorbing layer.

[0006] Furthermore, the odor-absorbing layer is woven from plant fibers and modified polyester fibers, and the odor-absorbing layer includes at least one layer, and the ratio of the plant fibers to the modified polyester fibers is 1:1-5.

[0007] Furthermore, the plant fiber includes one or more of flax fiber, ramie fiber, mulberry fiber, coconut shell fiber or kapok fiber, and the surface of the plant fiber is loaded with silver ions.

[0008] Furthermore, the modified polyester fiber includes nano-activated carbon and polyester fiber, and the mass ratio of the nano-activated carbon to the polyester fiber is 1:10-15.

[0009] The process for preparing odor-optimized automotive leather comprises the following steps:

[0010] S1, using wet dyeing and finishing process to make leather crust;

[0011] S2, the leather layer is sequentially sealed, roller-coated, embossed, roller-coated, and sprayed with antifouling treatment, and a finishing layer is sprayed on the front of the leather layer 2;

[0012] S3, preparing an odor-absorbing layer, wherein the odor-absorbing layer is woven from plant fibers and modified polyester fibers, wherein the ratio of the plant fibers to the modified polyester fibers is 1:1-5, and laminating the odor-absorbing layer to the back of the leather layer;

[0013] S4, compounding the elastic layer and the odor absorbing layer.

[0014] Furthermore, the plant fiber preparation process in S3 is as follows: the plant fiber is dispersed in a silver nitrate solution, shaken and dispersed at 80-85° C. for 5-10 hours, filtered and then dried to complete the silver ion loading;

[0015] The modified polyester fiber preparation process in S3 is as follows: placing the polyester fiber in a mixing blender, heating it until the polyester fiber is completely melted, adding nano-activated carbon, and fully mixing to form a melt, and spinning the melt through a melt spinning machine to obtain the modified polyester fiber.

[0016] The wet dyeing and finishing process for leather crust is used to prepare the above-mentioned leather crust layer, which is characterized by comprising the following steps:

[0017] The amount of each raw material is calculated based on the weight of the leather after tanning, squeezing and shaving, and is calculated as a percentage by mass.

[0018] Step 1, degreasing and tanning:

[0019] Select the leather that has been tanned, squeezed and shaved, add 200-300% of the leather weight of the leather into the drum, control the temperature in the drum to 40-50℃ and the pH value to 3-4,

[0020] Add 0.2-1% formic acid and 0.1-1% degreasing agent, rotate for 30-90 minutes, and drain;

[0021] Step 2: One-time water washing:

[0022] Add 300-400% of the weight of the leather into the steamer and control the temperature inside the steamer to 30-35℃.

[0023] Add 1-3% pre-made water washing solution, rotate for 10-40 minutes and then drain;

[0024] Step 3, retanning:

[0025] Add 100-200% of the tare weight of water into the drum and control the temperature inside the drum to 25-40℃.

[0026] Add 3-4% chrome tanning agent and turn for 60-80 minutes.

[0027] Add 1-4% sodium formate and 1-5% phenol condensate, and rotate for 10-40 minutes.

[0028] Add 0.2-1% baking soda and turn for 20-60 minutes.

[0029] Add 1-6% acrylic resin retanning agent, rotate for 30-90 minutes, and drain;

[0030] Step 4: Neutralization:

[0031] Add 100-200% of the tare weight of water into the drum and control the temperature inside the drum to 25-40℃.

[0032] Add 1-4% sodium formate and rotate for 10-40 minutes.

[0033] Add 0.2-1% baking soda, 1-6% tear-resistant fatliquor, rotate for 60-100 minutes, control the pH value to 5-6, and drain;

[0034] Step 5, secondary water washing:

[0035] Add 300-400% of the weight of the dough into the drum and control the temperature inside the drum to 30-35℃.

[0036] Add 1-3% pre-made water washing solution and 0.5-1% zeolite powder, rotate for 10-40 minutes and then drain;

[0037] Step 6: Filling:

[0038] Add 50-100% of the tare weight of water into the drum and control the temperature inside the drum to 25-40℃.

[0039] Add 3-4% acrylic resin retanning agent, 1-2% lecithin fatliquor, and rotate for 60-80 minutes.

[0040] Add 1-4% synthetic tanning agent, 2-5% tara extract, 5-10% dicyandiamide resin retanning agent, 1-5% phospholipid fatliquor, 1-5% sulfoxide condensate, and rotate for 20-50 minutes.

[0041] Add 2-5% wattle bark extract and 5-10% tara extract, and rotate for 60-90 minutes;

[0042] Step 7, fattening:

[0043] Add 50-100% of the tare weight of water into the drum and control the temperature inside the drum to 45-60℃.

[0044] Add 2-5% vegetable protein filler, 5-8% phospholipid fatliquor, 0.1-0.5% surfactant, and rotate for 50-100 minutes.

[0045] Add 1-3% acrylic resin retanning agent and rotate for 30-60 minutes.

[0046] Add 3-6% formic acid and rotate for 40-80 minutes.

[0047] Step 8: Post-washing:

[0048] Add 300-400% of the tare weight of water into the drum, control the temperature inside the drum to 55-80°C, rotate for 10-20 minutes, and drain;

[0049] Add 300-400% of the tare weight of water into the drum, control the temperature inside the drum to 40-55°C, rotate for 15-30 minutes, and drain;

[0050] Add 100-200% of the tare weight of water into the drum, control the temperature inside the drum to 30-40°C, add 1-3% of the pre-made water washing solution and 0.25-1% of the nano titanium dioxide dispersion, rotate for 30-60 minutes and then take the drum out.

[0051] Furthermore, the prefabricated washing solution comprises the following raw materials in parts by weight: 20-30 parts of persimmon tannin, 10-15 parts of eucalyptol, 10-20 parts of menthol, 10-15 parts of enzyme, and 10-15 parts of neutral soap solution.

[0052] Furthermore, the leather blank is pre-dyed in the retanning process, the leather blank is secondary-dyed in the filling process, and the leather blank is fixed in the subsequent washing process.

[0053] Furthermore, when pre-dyeing the leather during the retanning process, 1-2% dye is added to the drum and rotated for 10-30 minutes.

[0054] In the filling process, the leather body is dyed for the second time. 2-5% dye and 1-2% leveling agent are added to the drum and rotated for 30-80 minutes.

[0055] In the subsequent washing process, the leather is fixed in color. 0.5-1% of color fixing agent is added to the drum and rotated for 15-30 minutes.

[0056] From the above description, it can be seen that the odor-optimized leather and preparation process and the leather wet dyeing and finishing process provided by the present invention have the following beneficial effects: the leather layer of the present invention is processed by the wet dyeing and finishing process, odor control is achieved in the whole wet dyeing and finishing process, the residual odor of chemical materials is reduced by multiple water washing processes, and a prefabricated water washing solution and an additive are used in each washing process. The biological characteristics of the persimmon tannin in the prefabricated water washing solution are polyphenols with strong tanning, antioxidant and metal ion chelating capabilities. Menthol and eucalyptol are natural odor-masking extracts, which neutralize the odor of sulfide and fatty acid through inclusion complexation. The prefabricated water washing solution can mask odor molecules such as amines through the synergistic effect of biological extracts, reduce the odor formed by the combination of chemical materials and leather fibers, and take into account the physical properties of the leather, meeting the requirements of ecological leather certification; the dyeing process is distributed into two wet dyeing and finishing processes, and a water washing process is combined after each dyeing to reduce the odor of the dye. In addition, the two dyeing processes can ensure that the leather body is dyed evenly and is not easy to fade;

[0057] The plant fiber in the odor-absorbing layer acts as a skeleton to enhance toughness, and the modified polyester fiber makes the odor-absorbing layer soft. When the leather is required to have an elastic touch, the proportion of plant fiber can be increased. When the leather is required to have a soft and skin-friendly touch, the proportion of modified polyester fiber can be increased. The blending ratio of plant fiber and modified polyester fiber can be used to optimize the touch of car leather for odor optimization. When the car is in use, the cabin is exposed to sunlight for a long time and the temperature in the car is often high, and the odor evaporates significantly. The silver ions and nano-activated carbon in the odor-absorbing layer can absorb the volatile odor in the car leather, and the absorption of the odor in the leather is stronger after high-temperature irradiation, thereby optimizing the odor in the cabin. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 Schematic diagram of the structure of the odor-optimized leather of the present invention. DETAILED DESCRIPTION

[0059] The present invention is further described below through specific embodiments.

[0060] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0061] The odor-optimized automotive leather of the present invention comprises, from the surface layer to the bottom layer, a coating layer 1, a leather base layer 2, an odor-absorbing layer 3, and an elastic layer 4. The leather base layer 2 is made by a wet dyeing and finishing process. The coating layer 1 is sprayed on the front side of the leather base layer. The odor-absorbing layer 3 is bonded to the back side of the leather base layer 2. The elastic layer 4 is compositely connected to the odor-absorbing layer 3.

[0062] The odor-absorbing layer 3 is woven from plant fibers and modified polyester fibers. The odor-absorbing layer is bonded to the base layer by a hot pressing process. The odor-absorbing layer 3 includes at least one layer and can also be formed into a multi-layer structure by sequentially hot pressing multiple layers as needed. The blending ratio of the plant fibers to the modified polyester fibers is 1:1-5. The plant fibers include one or more of flax fibers, ramie fibers, mulberry fibers, coconut shell fibers, or kapok fibers. The plant fibers 31 are made of plant fibers with larger pores. The surface of the plant fibers 31 contains silver ions. The modified polyester fibers include nano-activated carbon and polyester fibers. The mass ratio of the nano-activated carbon to the polyester fibers is 1:10-15.

[0063] The above-mentioned leather base layer 2 is made by wet dyeing and finishing process, which reduces the odor formed by the combination of chemical materials and leather fibers, while taking into account the physical properties of leather and meeting the requirements of ecological leather certification. The plant fibers in the odor-absorbing layer act as a skeleton to enhance toughness, and the modified polyester fibers make the odor-absorbing layer soft. When the leather is pursued to have an elastic touch, the proportion of plant fibers can be increased. When the leather is pursued to have a soft and skin-friendly touch, the proportion of modified polyester fibers can be increased. The blending ratio of plant fibers and modified polyester fibers can be used to optimize the touch of automobile leather. When the car is in use, the cabin is exposed to sunlight for a long time and the temperature in the car is often high, and the odor evaporates significantly. The silver ions and nano-activated carbon in the odor-absorbing layer can absorb the volatile odors in the car leather, and the absorption of the odor in the leather is stronger after high-temperature irradiation, thereby optimizing the odor in the cabin.

[0064] The preparation process of the above odor-optimized automotive leather is as follows:

[0065] S1, using wet dyeing and finishing process to produce leather crust layer 2;

[0066] S2, the leather base layer 2 is sequentially subjected to sealing, roller coating, embossing, roller coating, and antifouling spraying to form a coating layer 1 on the front side of the leather base layer 2;

[0067] S3, preparing a flavor absorbing layer and fixing the flavor absorbing layer to the back of the leather layer 2, wherein the flavor absorbing layer 3 is woven from plant fibers and modified polyester fibers;

[0068] S4, compounding an elastic layer 4 on the back side of the leather base layer 2, wherein the elastic layer 4 is made of a medium-density sponge layer, an elastic mesh and other materials.

[0069] The plant fiber preparation process in S3 is as follows: the plant fiber is dispersed in a silver nitrate solution, shaken and dispersed at 80-85°C for 5-10 hours, filtered and dried to complete the silver ion loading;

[0070] The modified polyester fiber preparation process in S3 is as follows: placing the polyester fiber in a mixing blender, heating it to be completely melted, adding nano-activated carbon, and fully mixing to form a melt, and spinning the melt through a melt spinning machine to obtain the modified polyester fiber.

[0071] The wet dyeing and finishing process of the above-mentioned crust layer includes the following steps:

[0072] The amount of each raw material is calculated based on the weight of the leather after tanning, squeezing and shaving, and is calculated as a percentage by mass.

[0073] Step 1: degreasing and retanning. The specific steps of the retanning process are:

[0074] Select the leather that has been tanned, squeezed and shaved, add 200-300% of the leather weight of the leather into the drum, control the temperature in the drum to 40-50℃ and the pH value to 3-4,

[0075] Add 0.2-1% formic acid and 0.1-1% degreasing agent, rotate for 30-90 minutes, and drain;

[0076] Step 2: One-time water washing. The steps of one-time water washing are:

[0077] Add 300-400% of the weight of the leather into the steamer and control the temperature inside the steamer to 30-35℃.

[0078] 1-3% prefabricated water washing solution is added, and the mixture is rotated for 10-40 minutes before draining. The prefabricated water washing solution comprises the following raw materials in parts by weight: 20-30 parts of persimmon tannin, 10-15 parts of eucalyptol, 10-20 parts of menthol, 10-15 parts of enzyme, and 10-15 parts of neutral soap solution. Persimmon tannin is a polyphenolic substance with strong tanning, antioxidant, and metal ion chelating properties. Menthol and eucalyptol are natural odor-masking extracts that neutralize sulfide and fatty acid odors through inclusion complexation. The prefabricated water washing solution can mask odor molecules such as amines through the synergistic effect of the biological extracts, thereby reducing odor residue in subsequent chemical materials.

[0079] Step 3: retanning. The specific steps of the retanning process are:

[0080] Add 100-200% of the tare weight of water into the drum and control the temperature inside the drum to 25-40℃.

[0081] Add 3-4% chrome tanning agent and turn for 60-80 minutes.

[0082] Add 1-4% sodium formate and 1-5% phenol condensate, and rotate for 10-40 minutes.

[0083] Add 0.2-1% baking soda and turn for 20-60 minutes.

[0084] Add 1-6% acrylic resin retanning agent, rotate for 30-90 minutes, and drain;

[0085] Step 4: Neutralization. The specific steps of the neutralization process are:

[0086] Add 100-200% of the tare weight of water into the drum and control the temperature inside the drum to 25-40℃.

[0087] Add 1-4% sodium formate and rotate for 10-40 minutes.

[0088] Add 0.2-1% baking soda, 1-6% tear-resistant fatliquor, rotate for 60-100 minutes, control the pH value to 5-6, and drain;

[0089] Step 5: Secondary water washing,

[0090] Add 300-400% of the weight of the leather into the steamer and control the temperature inside the steamer to 30-35℃.

[0091] Add 1-3% pre-made water washing solution and 0.5-1% zeolite powder, rotate for 10-40 minutes and then drain. The pre-made water washing solution and zeolite powder are combined. The pre-made water washing solution can mask odor molecules such as amines through the synergistic effect of biological extracts, reducing the residual odor of subsequent chemical materials. The zeolite powder adsorbs free fatty acids;

[0092] Step 6: Filling. The specific steps of the filling process are:

[0093] Add 50-100% of the tare weight of water into the drum and control the temperature inside the drum to 25-40℃.

[0094] Add 3-4% acrylic resin retanning agent, 1-2% lecithin fatliquor, and rotate for 60-80 minutes.

[0095] Add 1-4% synthetic tanning agent, 2-5% tara extract, 5-10% dicyandiamide resin retanning agent, 1-5% phospholipid fatliquor, 1-5% sulfoxide condensate, and rotate for 20-50 minutes.

[0096] Add 2-5% wattle bark extract and 5-10% tara extract, and rotate for 60-90 minutes;

[0097] Step seven, greasing and filling process:

[0098] Add 50-100% of the tare weight of water into the drum and control the temperature inside the drum to 45-60℃.

[0099] Add 2-5% vegetable protein filler, 5-8% phospholipid fatliquor, 0.1-0.5% surfactant, and rotate for 50-100 minutes.

[0100] Add 1-3% acrylic resin retanning agent and rotate for 30-60 minutes.

[0101] Add 3-6% formic acid and rotate for 40-80 minutes.

[0102] Step 8: Post-washing. The post-washing steps are:

[0103] Add 300-400% of the tare weight of water into the drum, control the temperature inside the drum to 55-80℃, rotate for 10-20 minutes and then drain;

[0104] Add 300-400% of the tare weight of water into the drum, control the temperature inside the drum to 40-55°C, rotate for 15-30 minutes and then drain;

[0105] Add 100-200% of the tare weight of water into the drum, control the temperature inside the drum to 30-40℃, add 1-3% of pre-made water washing solution and 0.25-1% of nano titanium dioxide dispersion, rotate for 30-60 minutes and then take the drum out. The titanium dioxide dispersion is loaded into the leather body and can decompose the odor of aldehydes in the coating layer.

[0106] The leather blank is dyed during the retanning and filling processes of the wet dyeing and finishing of the leather blank. The specific steps are as follows:

[0107] During the retanning process, add 1-2% dye into the drum and rotate for 10-30 minutes.

[0108] During the filling process, add 2-5% dye and 1-2% leveling agent into the drum and rotate for 30-80 minutes.

[0109] During the water treatment process, add 0.5-1% of color fixing agent into the drum and rotate it for 15-30 minutes.

[0110] The above-mentioned odor optimizes the preparation process of automotive leather, realizes odor control in the entire wet dyeing and finishing process, reduces the residual odor of chemical materials through multiple water washing processes, and uses a combination of prefabricated washing solutions and additives in each washing process. The biological characteristics of persimmon tannins in the prefabricated washing solution are polyphenols with strong tanning, antioxidant and metal ion chelating capabilities. Menthol and eucalyptol are natural masking extracts, which neutralize the odor of sulfide and fatty acid through inclusion complexation. The prefabricated washing solution can mask odor molecules such as amines through the synergistic effect of biological extracts, reduce the odor formed by the combination of chemical materials and leather fibers, and take into account the physical properties of leather, meeting the requirements of eco-leather certification; the dyeing process is allocated to the two wet dyeing and finishing processes, and a water washing process is performed after each dyeing to reduce the odor of the dye. In addition, the two dyeing processes can ensure that the leather body is dyed evenly and is not easy to fade.

[0111] The above are only some specific implementation methods of the present invention, but the design concept of the present invention is not limited to this. 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. Odor-optimized automotive leather, characterized by: From the surface layer to the bottom layer, it includes a coating layer, a leather base layer, an odor absorbing layer, and an elastic layer. The leather base layer is made by a wet dyeing and finishing process. The coating layer is sprayed on the front side of the leather base layer. The odor absorbing layer is attached to the back side of the leather base layer. The elastic layer is compounded with the odor absorbing layer.

2. The odor-optimized automotive leather according to claim 1, characterized in that: The odor absorbing layer is woven from plant fibers and modified polyester fibers. The odor absorbing layer comprises at least one layer. The ratio of the plant fibers to the modified polyester fibers is 1:1-5.

3. The odor-optimized automotive leather according to claim 2, characterized in that: The plant fibers include one or more of flax fibers, ramie fibers, mulberry fibers, coconut shell fibers or kapok fibers, and silver ions are loaded on the surfaces of the plant fibers.

4. The odor-optimized automotive leather according to claim 2, characterized in that: The modified polyester fiber comprises nano-activated carbon and polyester fiber, and the mass ratio of the nano-activated carbon to the polyester fiber is 1:10-15.

5. A process for preparing odor-optimized automobile leather, comprising preparing the odor-optimized automobile leather according to any one of claims 1 to 4, characterized in that: The steps include: S1, using wet dyeing and finishing process to make leather crust; S2, the leather layer is sequentially sealed, roller-coated, embossed, roller-coated, and sprayed with antifouling treatment, and a finishing layer is sprayed on the front of the leather layer 2; S3, preparing an odor-absorbing layer, wherein the odor-absorbing layer is woven from plant fibers and modified polyester fibers, wherein the ratio of the plant fibers to the modified polyester fibers is 1:1-5, and laminating the odor-absorbing layer to the back of the leather layer; S4, compounding the elastic layer and the odor absorbing layer.

6. The process for preparing odor-optimized automotive leather according to claim 5, characterized in that: The plant fiber preparation process in S3 is as follows: the plant fiber is dispersed in a silver nitrate solution, shaken and dispersed at 80-85°C for 5-10 hours, filtered and dried to complete the silver ion loading; The modified polyester fiber preparation process in S3 is as follows: placing the polyester fiber in a mixing blender, heating it until the polyester fiber is completely melted, adding nano-activated carbon, and fully mixing to form a melt, and spinning the melt through a melt spinning machine to obtain the modified polyester fiber.

7. A wet dyeing and finishing process for preparing the odor-optimized automotive leather according to any one of claims 1 to 4, characterized in that: The preparation of the crust layer comprises the following steps: The amount of each raw material is calculated based on the weight of the leather after tanning, squeezing and shaving, and is calculated as a percentage by mass. Step 1, degreasing and tanning: Select the leather that has been tanned, squeezed and shaved, add 200-300% of the leather weight of the leather into the drum, control the temperature in the drum to 40-50℃ and the pH value to 3-4, Add 0.2-1% formic acid and 0.1-1% degreasing agent, rotate for 30-90 minutes, and drain; Step 2: One-time water washing: Add 300-400% of the weight of the leather into the steamer and control the temperature inside the steamer to 30-35℃. Add 1-3% pre-made water washing solution, rotate for 10-40 minutes and then drain; Step 3, retanning: Add 100-200% of the tare weight of water into the drum and control the temperature inside the drum to 25-40℃. Add 3-4% chrome tanning agent and turn for 60-80 minutes. Add 1-4% sodium formate and 1-5% phenol condensate, and rotate for 10-40 minutes. Add 0.2-1% baking soda and turn for 20-60 minutes. Add 1-6% acrylic resin retanning agent, rotate for 30-90 minutes, and drain; Step 4: Neutralization: Add 100-200% of the tare weight of water into the drum and control the temperature inside the drum to 25-40℃. Add 1-4% sodium formate and rotate for 10-40 minutes. Add 0.2-1% baking soda, 1-6% tear-resistant fatliquor, rotate for 60-100 minutes, control the pH value to 5-6, and drain; Step 5, secondary water washing: Add 300-400% of the weight of the dough into the drum and control the temperature inside the drum to 30-35℃. Add 1-3% pre-made water washing solution and 0.5-1% zeolite powder, rotate for 10-40 minutes and then drain; Step 6: Filling: Add 50-100% of the tare weight of water into the drum and control the temperature inside the drum to 25-40℃. Add 3-4% acrylic resin retanning agent, 1-2% lecithin fatliquor, and rotate for 60-80 minutes. Add 1-4% synthetic tanning agent, 2-5% tara extract, 5-10% dicyandiamide resin retanning agent, 1-5% phospholipid fatliquor, 1-5% sulfoxide condensate, and rotate for 20-50 minutes. Add 2-5% wattle bark extract and 5-10% tara extract, and rotate for 60-90 minutes; Step 7, fattening: Add 50-100% of the tare weight of water into the drum and control the temperature inside the drum to 45-60℃. Add 2-5% vegetable protein filler, 5-8% phospholipid fatliquor, 0.1-0.5% surfactant, and rotate for 50-100 minutes. Add 1-3% acrylic resin retanning agent and rotate for 30-60 minutes. Add 3-6% formic acid and rotate for 40-80 minutes. Step 8: Post-washing: Add 300-400% of the tare weight of water into the drum, control the temperature inside the drum to 55-80°C, rotate for 10-20 minutes, and drain; Add 300-400% of the tare weight of water into the drum, control the temperature inside the drum to 40-55°C, rotate for 15-30 minutes, and drain; Add 100-200% of the tare weight of water into the drum, control the temperature inside the drum to 30-40°C, add 1-3% of the pre-made water washing solution and 0.25-1% of the nano titanium dioxide dispersion, rotate for 30-60 minutes and then take the drum out.

8. The wet dyeing and finishing process for leather according to claim 7, characterized in that: The prefabricated washing solution comprises the following raw materials in parts by weight: 20-30 parts of persimmon tannin, 10-15 parts of eucalyptol, 10-20 parts of menthol, 10-15 parts of enzyme, and 10-15 parts of neutral soap solution.

9. The wet dyeing and finishing process for leather according to claim 7, characterized in that: The leather blank is pre-dyed in the retanning process, the leather blank is secondary-dyed in the filling process, and the leather blank is fixed in the subsequent washing process.

10. The wet dyeing and finishing process of leather according to claim 9, characterized in that: When pre-dyeing the leather during the retanning process, add 1-2% dye to the drum and rotate for 10-30 minutes. In the filling process, the leather body is dyed for the second time. 2-5% dye and 1-2% leveling agent are added to the drum and rotated for 30-80 minutes. In the subsequent washing process, the leather is fixed in color by adding 0.5-1% of color fixing agent into the drum and rotating for 15-30 minutes.

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