A method for preparing transparent chrome-tanned leather

Abstract

This invention relates to a method for preparing transparent chrome-tanned leather. The method uses undyed or dyed chrome-tanned leather blanks as raw materials, and prepares a clearing agent solution from monomers, initiators, accelerators, and solvents. The chrome-tanned leather blanks and the clearing agent solution are added to a rotating drum and treated at 10-45°C for 1-72 hours. The leather blanks are then heated and cured at 35-95°C for 1-72 hours, and dried to obtain transparent chrome-tanned leather. The transparent leather prepared by this method inherits the excellent comprehensive properties of chrome-tanned leather, including its chemical, physical, and mechanical properties, and offers diversity in the selection of leather types, thicknesses, and colors, meeting the requirements of different application environments in leather products and other fields. The raw materials used in this method are conventional chrome-tanned leather blanks, and the clearing agent components are also common chemical raw materials, readily available, low in cost, and easily scalable for mass production.

Description

Technical Field

[0001] This invention relates to the field of functional leather technology, and specifically to a method for preparing transparent chrome-tanned leather using chrome-tanned leather blanks as raw materials. Background Technology

[0002] Leather is an industrial product made from animal hides (including cowhide, sheepskin, and pigskin), a byproduct of animal husbandry, through a series of physical and chemical processing steps (such as soaking, hair removal, liming, softening, pickling, tanning, leveling, retanning, dyeing, fatliquoring, drying, buffing, softening, and finishing). It is a high-quality fabric and material for producing footwear, sofas, clothing, bags, car seat cushions, and other consumer goods. In recent years, consumers' demands for functional, intelligent, and personalized leather products have been continuously increasing, prompting the leather industry to constantly update and upgrade its products, striving to launch various functional and intelligent leather products, such as antibacterial leather, aromatic leather, intelligent color-changing leather, temperature-controlled leather, transparent leather, electromagnetic shielding leather, infrared stealth leather, and conductive leather, etc.

[0003] Transparent leather, as a new type of leather fabric, is widely popular in the design and manufacture of personalized and high-end leather products (such as fashion clothing, footwear, and bags). At the same time, as a new type of biomass-based natural green transparent material, it is expected to replace traditional fossil-based transparent materials, such as plastics and glass, which are difficult or non-degradable. It has broad application potential in fields such as smart home and decorative materials, flexible wearable electronic devices, soft robots, electronic skin, flexible electronic displays, luminescent materials, smart switches, information storage, solar cells, and anti-counterfeiting equipment.

[0004] Currently, there are three main types of transparent leather on the market. The first type is traditional hard transparent leather used for making shadow puppets, drumheads, etc. This is generally made by simply treating animal hides—removing hair, soaking in ash, and then stretching and drying them. Due to its hardness, brittleness, poor bending resistance, and lack of flexibility, this type of hard transparent leather has no application value in modern leather products or other emerging fields. The second type is untanned transparent leather, generally made by using polyols to make the softened, de-ashed hide transparent. While this untanned transparent leather has some softness, its physical and mechanical properties (especially mechanical strength) and wet-heat stability are poor because it hasn't undergone tanning, making it difficult to meet the performance requirements of modern transparent leather products and related products. The third type is tanned transparent leather, generally made from chromium-free tanned leather blanks (such as oil-tanned leather, zeolite-tanned leather, aldehyde-tanned leather, etc.) through different transparent processing techniques. Compared to untanned transparent leather, chrome-free tanned transparent leather exhibits significantly improved physical and mechanical properties and hydrothermal stability, which can partially meet the application requirements of transparent leather products. However, as a leather material, chrome-free tanned leather lags behind chrome-tanned leather (currently, over 90% of leather in the industry is chrome-tanned) in various aspects, including physical and mechanical properties, chemical properties, hydrothermal stability, and sensory properties. This is the main reason why chrome-free tanning cannot completely replace chrome tanning. Therefore, transparent leather prepared from chrome-free tanned leather blanks still cannot fully meet the diverse application requirements in terms of overall performance.

[0005] Chinese patent CN110184398A discloses a method for preparing chrome-tanned transparent leather using chrome-tanned leather blanks (also known as wet blue leather, wet blue leather blanks) or dyed leather blanks as raw materials. This is currently the only reported method for producing transparent chrome-tanned leather. The method involves soaking the leather blanks in an ionic liquid compound solution (including an ionic liquid and a compound solvent composed of water, anhydrous ethanol, dimethyl sulfoxide, acetone, etc.), and then mechanically treating the mixture of the ionic liquid compound solution and the leather blanks using a rotating drum. The surface of the leather blanks is then cleaned, and the blanks are immersed in clean water. After removal and drying, the leather blanks are calendered to obtain chrome-tanned transparent leather. The main drawbacks of this method are: the ionic liquids are expensive, and the binding between the ionic liquids and leather fibers is not strong, thus posing a risk of leaching and loss of the ionic liquid upon contact with water, leading to a decrease in leather transparency. Therefore, its application in both leather and non-leather product fields is significantly limited. Summary of the Invention

[0006] The above analysis shows that using chrome-tanned leather blanks as raw materials to prepare transparent leather is expected to achieve superior comprehensive physical, mechanical, and chemical properties compared to the three types of transparent leather currently on the market (traditional hard transparent leather, untanned transparent leather, and chrome-free tanned transparent leather). To overcome the shortcomings of using ionic liquids to prepare transparent chrome-tanned leather, we conducted extensive preliminary experiments. We found that tightly encapsulating the collagen fibers in the chrome-tanned leather blanks with polymers and fully filling the fiber gaps can significantly reduce the ratio of light reflection, refraction, and scattering within the leather layer, thereby increasing the rate of light transmission through the leather layer, i.e., increasing light transmittance, thus making the chrome-tanned leather exhibit transparent characteristics. We also found that if polymers are directly used to fill the chrome-tanned leather blanks, due to their large molecular weight and the relatively tight weave of the collagen fibers, it is difficult to achieve tight encapsulation of the collagen fibers and full filling of the fiber gaps, thus failing to produce transparent chrome-tanned leather. Conversely, if the monomers corresponding to the polymer are used to soak the chrome-tanned leather blank, the small-molecule monomers can easily penetrate into the multi-level structure of the collagen fibers in the chrome-tanned leather blank (from the molecular nanoscale to the micrometer / millimeter scale). Then, in-situ polymerization reactions occur on and between the collagen fibers to form large-molecule polymers. This allows the polymer to tightly wrap the collagen fibers and fully fill the gaps between the fibers, thereby making the chrome-tanned leather transparent, thus obtaining transparent chrome-tanned leather.

[0007] Specifically, the present invention aims to provide a method for preparing transparent chrome-tanned leather, characterized by the following process flow: 1) Weighing the chrome-tanned leather blank, placing it in a rotating drum, adding a clearing agent solution of 40% to 400% of the weight of the chrome-tanned leather blank, and rotating at 10 to 45 °C for 1 to 72 hours; 2) Taking out the chrome-tanned leather blank treated with the clearing agent in step 1), while keeping the chrome-tanned leather blank flat, heating at 35 to 95 °C for 1 to 72 hours, and drying to obtain transparent chrome-tanned leather. The type of chrome-tanned leather blank used in this method is any one of cowhide chrome-tanned leather blank, pigskin chrome-tanned leather blank, and sheepskin chrome-tanned leather blank, with a thickness of 0.4 to 2.5 mm; the type of chrome-tanned leather blank is any one of undyed chrome-tanned leather blank and dyed chrome-tanned leather blank; the clearing agent solution used to prepare transparent chrome-tanned leather is composed of monomers, initiators, accelerators, and solvents, with a mass ratio of monomer:initiator:accelerator:solvent = 100∶0.01~1.0∶10~300∶10~300; The monomers contained in the clarifying agent solution are any one or a mixture of acrylic acid, methacrylic acid, acrylamide, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, acryloyloxyethyltrimethylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propane-1-sulfonate, and 1-vinyl-2-pyrrolidone; The initiator contained in the clarifying agent solution is any one of ammonium persulfate, potassium persulfate, azobisisobutyramidine hydrochloride, and azobisisobutyronitrile; The accelerator contained in the clarifying agent solution is ethylene glycol, 1,2 Propylene glycol, 1,3 Propylene glycol, glycerol, 1,4 The solvent contained in the transparent agent solution is any one of butanediol, mannitol, and sorbitol; the solvent is any one of water, ethanol, tetrahydrofuran, acetone, or a mixture thereof.

[0008] The method for preparing transparent leather provided by this invention has the following advantages: First, the present invention uses chrome-tanned leather blanks as raw materials. Its physical and mechanical properties, chemical properties, wet and heat stability, sensory properties and other performance indicators are superior to those of untanned leather blanks and various types of chrome-free tanned leather blanks. Therefore, the transparent leather prepared from it has better comprehensive chemical, physical and mechanical properties compared with the three types of transparent leather currently on the market (traditional hard transparent leather, untanned transparent leather and chrome-free tanned transparent leather).

[0009] Secondly, the present invention uses small molecule monomers to fully penetrate into the chrome-tanned leather blank first, and then undergoes an in-situ polymerization reaction to form a polymer. This achieves the tight wrapping of the polymer with the collagen fibers of the chrome-tanned leather blank and the full filling of the fiber gaps. This not only makes the chrome-tanned leather transparent, but also ensures that the polymer formed in situ is tightly bound to the leather collagen fibers. There is no problem of the polymer dissolving and being lost when it comes into contact with water, which would lead to a decrease in the transparency of the leather.

[0010] Third, this invention can effectively control the chemical, physical, and mechanical properties of the final chrome-tanned transparent leather by selecting chrome-tanned leather blanks of different types, thicknesses, and colors as raw materials, and by selecting different types of monomers for in-situ polymerization to form polymers with different properties, so as to meet the requirements of different application environments.

[0011] Fourth, the chrome-tanned leather blanks used in this invention are readily available and inexpensive, relying on existing leather industry practices; the components in the clarifying agent solution are also common chemical raw materials, with simple formulations and low prices; the preparation method provided by this invention is simple and can be completed using existing equipment in the leather industry. Therefore, the method of this invention for preparing transparent chrome-tanned leather is inexpensive and easily scalable for mass production. Detailed Implementation

[0012] The following embodiments are provided to illustrate the present invention in more detail. It should be noted that the following embodiments should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made to the present invention by those skilled in the art based on the above description of the present invention are still within the scope of protection of the present invention.

[0013] Example 1 A clarifying agent solution was prepared using acrylic acid as the monomer, potassium persulfate as the initiator, 1,3-propanediol as the accelerator, and water and acetone (volume ratio 7:3) as solvents. The mass ratio of these components was monomer : initiator : accelerator : solvent = 100 : 0.5 : 80 : 100. Undyed chrome-tanned cowhide blanks with a thickness of 1.0 mm were weighed and placed in a rotating drum. The clarifying agent solution, at 150% of the blank's weight, was added, and the drum was rotated at 40 °C for 7 hours. The clarified chrome-tanned leather blanks were then removed, laid flat on a heating platform, heated at 45 °C for 24 hours, and then air-dried to obtain transparent chrome-tanned leather.

[0014] Example 2 A clarifying agent solution was prepared using acrylamide as the monomer, ammonium persulfate as the initiator, 1,2-propanediol as the accelerator, and water as the solvent. The mass ratio of these components was monomer : initiator : accelerator : solvent = 100 : 0.05 : 10 : 80. A 0.4 mm thick black chrome-tanned goatskin blank was weighed, placed in a rotating drum, and 100% of its weight in the clarifying agent solution was added. The drum was rotated at 25 °C for 16 hours. The clarified chrome-tanned leather blank was then removed, laid flat on a heating platform, heated at 35 °C for 72 hours, and then air-dried to obtain transparent chrome-tanned leather.

[0015] Example 3 A clearing agent solution was prepared using acryloyloxyethyltrimethylammonium chloride as the monomer, azobisisobutyramidine hydrochloride as the initiator, glycerol as the accelerator, and ethanol and water (volume ratio 2:8) as the solvent, with a mass ratio of monomer:initiator:accelerator:solvent = 100:0.3:30:150. A 0.7 mm thick sheepskin red chrome-tanned leather blank was weighed, placed in a drum, and the clearing agent solution (180% of the leather blank's weight) was added. The drum was rotated at 10 °C for 60 hours. The clearing agent-treated chrome-tanned leather blank was then removed, laid flat on a heating platform, heated at 40 °C for 40 hours, and then air-dried to obtain transparent chrome-tanned leather.

[0016] Example 4 A clarifying agent solution was prepared using 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propane-1-sulfonate as the monomer, potassium persulfate as the initiator, 1,4-butanediol as the accelerator, and water as the solvent. The mass ratio of these components was monomer : initiator : accelerator : solvent = 100 : 0.18 : 200 : 280. A 1.2 mm thick pigskin gray chrome-tanned leather blank was weighed, placed in a drum, and 80% of its weight in the clarifying agent solution was added. The drum was rotated at 35 °C for 30 hours. The clarified chrome-tanned leather blank was then removed, laid flat on a heating platform, heated at 60 °C for 9 hours, and then air-dried to obtain transparent chrome-tanned leather.

[0017] Example 5 A clarifying agent solution was prepared using methacrylic acid as the monomer, azobisisobutyronitrile as the initiator, mannitol as the accelerator, and ethanol as the solvent. The mass ratio of these components was monomer : initiator : accelerator : solvent = 100 : 0.6 : 100 : 300. Undyed chrome-tanned cowhide blanks with a thickness of 0.5 mm were weighed and placed in a rotating drum. 50% of the blank's weight in the clarifying agent solution was added, and the drum was rotated at 15 °C for 20 hours. The clarified chrome-tanned leather blanks were then removed, laid flat on a heating platform, heated at 50 °C for 5 hours, and then air-dried to obtain transparent chrome-tanned leather.

[0018] Example 6 A clarifying agent solution was prepared using hydroxyethyl methacrylate as the monomer, azobisisobutyronitrile as the initiator, sorbitol as the accelerator, and acetone as the solvent. The mass ratio of these components was monomer : initiator : accelerator : solvent = 100 : 0.8 : 50 : 120. A 0.6 mm thick sheepskin yellow chrome-tanned leather blank was weighed, placed in a drum, and 40% of its weight in the clarifying agent solution was added. The drum was then rotated at 18 °C for 24 hours. The clarified chrome-tanned leather blank was removed, laid flat on a heating platform, heated at 55 °C for 16 hours, and then air-dried to obtain transparent chrome-tanned leather.

[0019] Example 7 A clarifying agent solution was prepared using 2-hydroxyethyl acrylate as the monomer, ammonium persulfate as the initiator, ethylene glycol as the accelerator, and water as the solvent. The mass ratio of these components was monomer : initiator : accelerator : solvent = 100 : 1.0 : 300 : 200. A 2.0 mm thick brown chrome-tanned cowhide blank was weighed, placed in a rotating drum, and 120% of its weight in the clarifying agent solution was added. The drum was rotated at 45 °C for 12 hours. The clarified chrome-tanned leather blank was then removed, laid flat on a heating platform, heated at 65 °C for 12 hours, and then air-dried to obtain transparent chrome-tanned leather.

[0020] Example 8 A clarifying agent solution was prepared using 1-vinyl-2-pyrrolidone as the monomer, azobisisobutyronitrile as the initiator, 1,3-propanediol as the accelerator, and tetrahydrofuran as the solvent. The mass ratio of these components was monomer : initiator : accelerator : solvent = 100 : 0.1 : 150 : 240. A 0.8 mm thick green chrome-tanned goatskin blank was weighed and placed in a rotating drum. A clarifying agent solution equal to 400% of the blank's weight was added, and the drum was rotated at 20 °C for 40 hours. The clarified chrome-tanned leather blank was then removed, laid flat on a heating platform, heated at 38 °C for 70 hours, and then air-dried to obtain transparent chrome-tanned leather.

[0021] Example 9 A clarifying agent solution was prepared using hydroxypropyl acrylate as the monomer, potassium persulfate as the initiator, 1,2-propanediol as the accelerator, and water and acetone (volume ratio 9:1) as the solvent. The mass ratio of these components was monomer : initiator : accelerator : solvent = 100 : 0.01 : 20 : 50. A 1.1 mm thick blue chrome-tanned goatskin blank was weighed, placed in a drum, and 250% of its weight in the clarifying agent solution was added. The drum was rotated at 42 °C for 1 hour. The clarified chrome-tanned leather blank was then removed, laid flat on a heating platform, heated at 90 °C for 3 hours, and then air-dried to obtain transparent chrome-tanned leather.

[0022] Example 10 A clearing agent solution was prepared using methacryloyloxyethyltrimethylammonium chloride as the monomer, ammonium persulfate as the initiator, glycerol as the accelerator, and water and tetrahydrofuran (volume ratio 8:2) as the solvent. The mass ratio of these components was monomer : initiator : accelerator : solvent = 100 : 0.24 : 280 : 300. Undyed chrome-tanned cowhide blanks with a thickness of 0.9 mm were weighed, placed in a rotating drum, and the clearing agent solution (350% of the leather blank's weight) was added. The drum was rotated at 30 °C for 72 hours. The clearing agent-treated chrome-tanned leather blanks were then removed, laid flat on a heating platform, heated at 70 °C for 20 hours, and then air-dried to obtain transparent chrome-tanned leather.

[0023] Example 11 A clarifying agent solution was prepared using acrylic acid and acrylamide (mass ratio 1:2) as monomers, ammonium persulfate as an initiator, 1,2-propanediol as an accelerator, and water as a solvent. The mass ratio of these components was monomer : initiator : accelerator : solvent = 100 : 0.4 : 240 : 100. A 2.5 mm thick white chrome-tanned sheepskin blank was weighed, placed in a drum, and 300% of its weight in the clarifying agent solution was added. The drum was rotated at 38 °C for 70 hours. The clarified chrome-tanned leather blank was then removed, laid flat on a heating platform, heated to 95 °C for 1 hour, and then air-dried to obtain transparent chrome-tanned leather.

[0024] Example 12 A clarifying agent solution was prepared using acrylic acid and hydroxypropyl acrylate (mass ratio 1:5) as monomers, potassium persulfate as an initiator, 1,3-propanediol as an accelerator, and water as a solvent. The mass ratio of these components was monomer : initiator : accelerator : solvent = 100 : 0.7 : 120 : 120. A 2.2 mm thick khaki chrome-tanned goatskin blank was weighed, placed in a rotating drum, and 200% of its weight in the clarifying agent solution was added. The drum was rotated at 32 °C for 24 hours. The clarified chrome-tanned leather blank was then removed, laid flat on a heating platform, heated at 85 °C for 7 hours, and then air-dried to obtain transparent chrome-tanned leather.

[0025] Example 13 A clearing agent solution was prepared using acrylamide and 2-hydroxyethyl acrylate (mass ratio 1:1) as monomers, azobisisobutyramidine hydrochloride as an initiator, ethylene glycol as an accelerator, and water as a solvent. The mass ratio of these components was monomer: initiator: accelerator: solvent = 100: 0.9: 10: 30. Undyed chrome-tanned pigskin blanks with a thickness of 1.4 mm were weighed, placed in a rotating drum, and the clearing agent solution (110% of the leather blank's weight) was added. The drum was rotated at 28 °C for 50 hours. The clearing agent-treated chrome-tanned leather blanks were then removed, laid flat on a heating platform, heated at 80 °C for 5 hours, and then air-dried to obtain transparent chrome-tanned leather.

[0026] Example 14 A clarifying agent solution was prepared using acrylic acid as the monomer, ammonium persulfate as the initiator, glycerol as the accelerator, and water as the solvent. The mass ratio of these components was monomer : initiator : accelerator : solvent = 100 : 0.35 : 120 : 150. Undyed chrome-tanned cowhide blanks with a thickness of 1.8 mm were weighed and placed in a rotating drum. The clarifying agent solution, weighing 170% of the blank's weight, was added, and the drum was rotated at 25 °C for 12 hours. The clarified chrome-tanned leather blanks were then removed, laid flat on a heating platform, heated at 40 °C for 60 hours, and then air-dried to obtain transparent chrome-tanned leather.

[0027] Example 15 A clarifying agent solution was prepared using hydroxypropyl acrylate as the monomer, potassium persulfate as the initiator, 1,4-butanediol as the accelerator, and water as the solvent. The mass ratio of these components was monomer : initiator : accelerator : solvent = 100 : 0.45 : 10 : 10. A 0.4 mm thick sheepskin yellow chrome-tanned leather blank was weighed, placed in a rotating drum, and 140% of its weight in the clarifying agent solution was added. The drum was rotated at 45 °C for 3 hours. The clarified chrome-tanned leather blank was then removed, laid flat on a heating platform, heated at 75 °C for 30 hours, and then air-dried to obtain transparent chrome-tanned leather.

[0028] Example 16 A clarifying agent solution was prepared using acrylic acid and methacryloyloxyethyltrimethylammonium chloride monomers (mass ratio 3:7), ammonium persulfate as initiator, glycerol as accelerator, and water as solvent. The mass ratio of these components was monomer : initiator : accelerator : solvent = 100 : 0.20 : 20 : 20. Undyed chrome-tanned cowhide blanks with a thickness of 0.5 mm were weighed, placed in a rotating drum, and 180% of the blank's weight in the clarifying agent solution was added. The drum was rotated at 44 °C for 5 hours. The clarified chrome-tanned leather blanks were then removed, laid flat on a heating platform, heated at 50 °C for 50 hours, and then air-dried to obtain transparent chrome-tanned leather.

[0029] Example 17 A clarifying agent solution was prepared using methacrylic acid and hydroxypropyl acrylate monomers (mass ratio 5:5), ammonium persulfate as an initiator, sorbitol as an accelerator, and water as a solvent. The mass ratio of these components was monomer : initiator : accelerator : solvent = 100 : 0.50 : 120 : 130. A 1.6 mm thick sheepskin brown chrome-tanned leather blank was weighed, placed in a drum, and 160% of its weight in the clarifying agent solution was added. The drum was rotated at 30 °C for 28 hours. The clarified chrome-tanned leather blank was then removed, laid flat on a heating platform, heated at 55 °C for 32 hours, and then air-dried to obtain transparent chrome-tanned leather.

[0030] Example 18 A clearing agent solution was prepared using hydroxyethyl methacrylate monomer and azobisisobutyronitrile as initiators, ethylene glycol as an accelerator, and water and ethanol (volume ratio 6:4) as solvents. The mass ratio of these components was monomer : initiator : accelerator : solvent = 100 : 0.65 : 55 : 100. Undyed chrome-tanned goatskin blanks with a thickness of 1.0 mm were weighed, placed in a drum, and 100% of the blank's weight in the clearing agent solution was added. The drum was rotated at 27 °C for 35 hours. The clearing agent-treated chrome-tanned leather blanks were then removed, laid flat on a heating platform, heated at 58 °C for 22 hours, and then air-dried to obtain transparent chrome-tanned leather.

[0031] Example 19 A clearing agent solution was prepared using 2-hydroxyethyl acrylate monomer and azobisisobutyronitrile as initiators, glycerol as an accelerator, and water and acetone (volume ratio 7:3) as solvents. The mass ratio of these components was monomer : initiator : accelerator : solvent = 100 : 0.45 : 60 : 120. A 1.6 mm thick sheepskin red chrome-tanned leather blank was weighed, placed in a drum, and 220% of its weight in the clearing agent solution was added. The drum was rotated at 35 °C for 12 hours. The clearing agent-treated chrome-tanned leather blank was then removed, laid flat on a heating platform, heated at 69 °C for 14 hours, and then air-dried to obtain transparent chrome-tanned leather.

[0032] Example 20 A clearing agent solution was prepared using 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propane-1-sulfonate monomer and ammonium persulfate as initiators, 1,3-propanediol as an accelerator, and water as a solvent. The mass ratio of these components was monomer : initiator : accelerator : solvent = 100 : 0.32 : 70 : 110. Undyed chrome-tanned cowhide blanks with a thickness of 1.3 mm were weighed, placed in a drum, and the clearing agent solution (300% of the blank's weight) was added. The drum was rotated at 38 °C for 22 hours. The clearing agent-treated chrome-tanned leather blanks were then removed, laid flat on a heating platform, heated at 75 °C for 8 hours, and then air-dried to obtain transparent chrome-tanned leather.

[0033] The transparent chrome-tanned leather prepared in the above embodiments was tested for light transmittance using the method described in GB / T 2410-2008 (Determination of transmittance and haze of transparent plastics), thickness using the method described in QB / T 2709-2005 (Determination of thickness of leather in physical and mechanical tests), and tensile strength using the method described in QB / T 2710-2018 (Determination of tensile strength and elongation of leather in physical and mechanical tests). The results are shown in Table 1.

[0034] Table 1

Claims

1. A method for preparing transparent chrome-tanned leather, characterized in that... The method adopts the following process flow: 1) Weigh the chrome-tanned leather blank, place it in a rotating drum, add a clearing agent solution of 40%~400% of the weight of the chrome-tanned leather blank, and rotate at 10~45℃ for 1~72 hours; 2) Take out the chrome-tanned leather blank after the clearing agent treatment in step 1), and while keeping the chrome-tanned leather blank flat, heat it at 35~95℃ for 1~72 hours and dry it to obtain transparent chrome-tanned leather.

2. The method for preparing transparent chrome-tanned leather according to claim 1, characterized in that... The chrome-tanned leather blank used to prepare transparent chrome-tanned leather can be any one of cowhide chrome-tanned leather blank, pigskin chrome-tanned leather blank, and sheepskin chrome-tanned leather blank, with a thickness of 0.4~2.5 mm.

3. The method for preparing transparent chrome-tanned leather according to claims 1 and 2, characterized in that... The chrome-tanned leather blanks used to prepare transparent chrome-tanned leather are either undyed or dyed chrome-tanned leather blanks.

4. The method for preparing transparent chrome-tanned leather according to claim 1, characterized in that... The clarifying agent solution used to prepare transparent chrome-tanned leather consists of monomers, initiators, accelerators, and solvents, with a mass ratio of monomer:initiator:accelerator:solvent = 100:0.01~1.0:10~300:10~300.

5. A method for preparing transparent chrome-tanned leather according to claims 1 and 4, characterized in that... The monomers contained in the transparent agent solution used to prepare transparent chrome-tanned leather are any one of acrylic acid, methacrylic acid, acrylamide, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, acryloyloxyethyltrimethylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propane-1-sulfonate, 1-vinyl-2-pyrrolidone, or mixtures thereof.

6. A method for preparing transparent chrome-tanned leather according to claims 1 and 4, characterized in that... The initiator contained in the transparent agent solution used to prepare transparent chrome-tanned leather is any one of ammonium persulfate, potassium persulfate, azobisisobutyramidine hydrochloride, and azobisisobutyronitrile.

7. A method for preparing transparent chrome-tanned leather according to claims 1 and 4, characterized in that... The accelerators contained in the clarifying agent solution used to prepare transparent chrome-tanned leather are ethylene glycol and 1,2-dimethylethanol. Propylene glycol, 1,3 Propylene glycol, glycerol, 1,4 Any one of butylene glycol, mannitol, and sorbitol.

8. A method for preparing transparent chrome-tanned leather according to claims 1 and 4, characterized in that... The solvent contained in the clearing agent solution used to prepare transparent chrome-tanned leather is any one of water, ethanol, tetrahydrofuran, acetone, or a mixture thereof.

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