Weather-resistant high-toughness leather material and preparation method thereof

Abstract

The invention relates to the technical field of leather materials, in particular to a weather-resistant high-toughness leather material and a preparation method thereof.The weather-resistant high-toughness leather material comprises a base material layer, a reinforcing layer and a protective layer; the base material layer is made of natural leather, and the reinforcing layer is made of a fiber composite material; the fiber composite material is prepared from the following raw materials in parts by weight: 40 to 50 parts of polytetrahydrofuran ether glycol, 33 to 39 parts of diphenylmethane diisocyanate, 3 to 7 parts of perfluoroalkyl ether glycol, 2 to 4 parts of a chain extender, 0.01 to 0.04 part of an organic tin catalyst, 0.1 to 0.4 part of an antioxidant, 0.3 to 1.2 parts of an ultraviolet light absorber, 0.3 to 1 part of nano silicon dioxide and 0.3 to 1 part of a silane coupling agent. 2-5 parts of chopped aramid fiber and 1-4 parts of DMF (Dimethyl Formamide); the method has the advantage of improving the toughness and durability of the leather material.

Description

Technical Field

[0001] The present application relates to the technical field of leather materials, and in particular to a weather-resistant and high-toughness leather material and a preparation method thereof. Background Art

[0002] Genuine leather is made from animal hides through physical and chemical processes such as depilation and tanning. It is favored by consumers for its excellent hygroscopicity, comfort, and sensory qualities. However, its use in automotive seats, interiors, and furniture such as sofas requires high toughness. Existing automotive leather materials suffer from insufficient toughness, particularly after aging, which rapidly degrades, hardening, and even cracking, shortening their service life. Summary of the Invention

[0003] In order to improve the toughness and durability of leather materials, the present application provides a weather-resistant and high-toughness leather material and a preparation method thereof.

[0004] In a first aspect, the present application provides a weather-resistant and high-toughness leather material, which adopts the following technical solution: A weather-resistant and high-toughness leather material, comprising a base layer, a reinforcing layer bonded to one side of the base layer, and a protective layer coated on one side of the base layer; the base layer is natural leather, and the reinforcing layer is a fiber composite material; The fiber composite material comprises the following raw materials in parts by weight: 40-50 parts of polytetramethylene ether glycol, 33-39 parts of diphenylmethane diisocyanate, 3-7 parts of perfluoroalkyl ether glycol, 2-4 parts of chain extender, 0.01-0.04 parts of organic tin catalyst, 0.1-0.4 parts of antioxidant, 0.3-1.2 parts of ultraviolet absorber, 0.3-1 parts of nano-silica, 0.3-1 parts of silane coupling agent, 2-5 parts of chopped aramid fiber and 1-4 parts of DMF.

[0005] By adopting the above technical solution, the present application uses a polyurethane system as the bonding system, then adds aramid fibers and bonds them to the leather base layer, thereby improving the toughness of the leather. The present application also adds perfluoroalkyl ether diol to the polyurethane system, utilizing a fluoropolymer to significantly improve the weather resistance of the leather material. The long-chain perfluoroalkyl ether diol contains hydroxyl groups at both ends, which can participate in crosslinking and curing. Because of the hydroxyl groups at both ends, the addition of the perfluoroalkyl ether diol creates a crosslink density difference within the reinforcement layer. Therefore, when the leather material is subjected to external forces, the additional elasticity formed by the crosslink density difference can be buffered, thereby significantly improving its toughness. However, due to the perfluoroalkyl ether diol, the crosslink density within the polyurethane is reduced to a certain extent, and its tensile strength is slightly reduced.

[0006] Preferably, the average molecular weight of the perfluoroalkyl ether diol is in the range of 4000-20000.

[0007] By adopting the above technical solution, when the molecular weight is low, the toughness is improved less, but when the molecular weight is increased to 20,000, the toughness decreases instead; it is speculated that this is because the molecular weight is too large, the viscosity is large, and the distribution is uneven; therefore, the molecular weight range is 4,000-20,000.

[0008] Preferably, the fiber composite material further comprises 0.5-1.5 parts by weight of a hydroxyl-terminated hyperbranched polyester.

[0009] By adopting the above technical solution, since the addition of perfluoroalkyl ether diol will reduce the tensile strength of the leather material, end-hydroxyl hyperbranched polyester is added to the system, and the polyhydroxy structure contained in it is utilized to form a cross-linking center, thereby increasing the local cross-linking density and improving the tensile strength of the leather material. In addition, the increase in the local cross-linking density further widens the cross-linking density difference in the polyurethane system, thereby further improving the toughness of the leather material.

[0010] Preferably, the average molecular weight of the hydroxyl-terminated hyperbranched polyester is in the range of 1100-5200.

[0011] Preferably, the silane coupling agent is a hydroxysilane coupling agent or an aminosilane coupling agent.

[0012] By adopting the above technical solution, the leather material prepared with hydroxysilane coupling agent has better tensile strength and elongation; it is speculated that this is because the hydroxysilane coupling agent or aminosilane coupling agent can also participate in the cross-linking of the system after coupling with the fibers and inorganic particles in the system, making the integrity of the reinforcement layer stronger, and therefore, the tensile strength and elongation of the leather material are better.

[0013] Preferably, the chain extender is one or more of ethylene glycol, 1,4-butanediol, neopentyl glycol, ethylenediamine, hexamethylenediamine, diethanolamine, and triethanolamine.

[0014] Preferably, the protective layer is a fluoropolymer coating, which comprises the following raw materials in parts by weight: 30-38 parts of DMF, 10-14 parts of acetone, 18-22 parts of polyvinylidene fluoride dispersion, 0.6-1 part of silicone leveling agent, 3-7 parts of nano-silica, 0.2-0.6 parts of silane coupling agent, 3-7 parts of alumina powder, 0.1-0.3 parts of acetic acid and 2-3 parts of HDI biuret.

[0015] By adopting the above technical solution, the fluorine-containing protective layer can further improve the weather resistance of the leather material.

[0016] In a second aspect, the present application provides a method for preparing a weather-resistant and high-toughness leather material, which adopts the following technical solution: A method for preparing a weather-resistant and high-toughness leather material comprises the following steps: S1. Preparation of substrate layer The dehaired raw cowhide is subjected to pickling treatment, tanning, softening and post-treatment to obtain a base material layer; S2, composite reinforcement layer Fiber composite material preparation: The polytetramethylene glycol and perfluoroalkyl ether glycol are mixed, vacuum dehydrated, cooled to 60-80° C., diphenylmethane diisocyanate is added, and stirred to react until the NCO content is 8-10% of the original amount, thereby preparing a polyurethane prepolymer; The polyurethane prepolymer is cooled to 50-60°C, the remaining raw materials are added to the polyurethane prepolymer, and the mixture is continuously stirred and vacuum degassed to obtain a fiber composite material, which is then sprayed on the surface of the substrate layer. After curing, the substrate layer is successfully composited with the reinforcement layer. S3, composite protective layer Preparation of fluoropolymer coating: DMF and acetone are mixed at 60-70°C, and then polyvinylidene fluoride dispersion, silicone leveling agent, nano-silica, silane coupling agent, aluminum oxide powder and acetic acid are added and stirred. Then, HDI biuret is added in 2-4 portions and stirring is continued after the addition is completed to prepare a protective layer coating; The protective layer coating is sprayed on the surface of the reinforcement layer, and then hot air dried at 75-85°C to evaporate the solvent, and then the temperature is raised to 110-130°C and kept warm for 5-10 minutes, and then the temperature is further raised to 140-155°C and kept warm for 5-10 minutes, and then the temperature is further raised to 175-185°C and kept warm for 5-10 minutes to complete cross-linking and curing to obtain a weather-resistant and high-toughness leather material.

[0017] By adopting the above technical solution, the present application prepares the base material layer, the reinforcing layer and the protective layer respectively, and then bonds and composites them. The preparation method does not require any improvement to the production equipment, is highly tolerant to process parameters, and is suitable for mass production.

[0018] In summary, this application includes at least one of the following beneficial technical effects: 1. This application utilizes a polyurethane system as the bonding system, then adds aramid fibers and bonds them to the leather substrate layer to improve the toughness of the leather. This application also incorporates perfluoroalkyl ether diols into the polyurethane system, utilizing fluoropolymers to significantly enhance the weather resistance of the leather material. The long-chain perfluoroalkyl ether diols contain hydroxyl groups at both ends, allowing them to participate in crosslinking and curing. Because of the hydroxyl groups at both ends, the addition of the perfluoroalkyl ether diols creates a crosslink density difference within the reinforcement layer. Consequently, when the leather material is subjected to external forces, the additional elasticity created by the crosslink density difference provides a buffer, significantly improving its toughness. However, the perfluoroalkyl ether diols also reduce the crosslink density within the polyurethane to a certain extent, slightly reducing its tensile strength.

[0019] 2. The leather material prepared in this application has excellent toughness and weather resistance; its tensile strength can reach 62.54-66.21 MPa, and its elongation can reach 59.6-64.2%; after aging for 1000 hours, its tensile strength can still reach 61.9 MPa or above, and the highest can reach 66.14 MPa, and the elongation can still reach the range of 58.1-61.7%. DETAILED DESCRIPTION

[0020] The following is a further detailed description of this application in conjunction with the specific content.

[0021] raw material All raw materials in the examples of this application were purchased from commercial sources, wherein the length of aramid short-cut fiber was 5 mm and the diameter was 1-5 μm; the average particle size of nano-silicon dioxide was 50 nm; the fatliquor was purchased from Ningbo Panyi Chemical Technology Co., Ltd.; the brand of JFC was BASF; the model of chrome tanning agent was CR, brand is Lanxess; the molecular weight of polytetramethylene ether glycol is 2000, model 2000, the brand is Dow Chemical; the model of antioxidant is antioxidant 1010, the brand is BASF; the model of UV absorber is 327, brand is BASF; the model of polyvinylidene fluoride dispersion is PVDF-801, Guozi Zhonghua Blue Sky; the model of silicone leveling agent is BYK-333, purchased from BYK Chemical; the average particle size of alumina micropowder is 20μm. Example

[0022] Example 1 A weather-resistant, high-toughness leather material comprises a base layer, a reinforcing layer, and a protective layer, wherein the base layer is natural leather that has been tanned and softened, the reinforcing layer is a fiber composite material, and the protective layer is a weather-resistant polymer coating that is evenly coated on the surface of the reinforcing layer through a spraying process. The preparation method of the weather-resistant, high-toughness leather material is as follows: S1. Preparation of substrate layer and pickling treatment: soak raw hides in an acidic solution in a rotary drum for 2.5 hours, turning the drum every half hour. The raw hides are dehaired raw hides. The mass ratio of raw hides to water is 1:2. The temperature is maintained between 25-30°C. The mass fraction of sulfuric acid in the acidic solution is 1.7%, the mass fraction of sodium chloride is 4%, and the mass fraction of a wetting agent (JFC) is 0.4%. Tanning: Continue to add 4% of the hide weight of chrome tanning agent in three portions, then adjust the pH to 4.0 with sodium bicarbonate, maintain the temperature between 30-40°C, tanning time is 8 hours, drum speed is 20 rpm, then add sodium bicarbonate in five portions to adjust the pH to neutral; Softening: Add trypsin and subtilisin to a rotating drum at a rate of 1.1% and 1.3% of the hide weight, then adjust the pH to 8.0 with sodium hydroxide solution. Maintain the temperature at 35°C and the drum at a speed of 15 rpm for 15 hours. Drain the water, remove from the drum, squeeze with rollers, and shave to obtain wet hides. Post-treatment: wet leather and fatliquor were mixed in a mass ratio of 100:20 at a mixing temperature of 45°C for 2 h to prepare a substrate layer; S2, composite reinforcement layer Preparation of reinforcement layer: Calculated by weight, the amounts of raw materials for the reinforcement layer are as follows: 45 parts of polytetramethylene ether glycol, 36 parts of diphenylmethane diisocyanate, 5 parts of perfluoroalkyl ether glycol, 3 parts of 1,4-butanediol, 0.02 parts of dibutyltin dilaurate, 0.2 parts of antioxidant, 1 part of ultraviolet absorber, 0.5 parts of nano-silica, 0.5 parts of aminosilane coupling agent, 3 parts of chopped aramid fiber, 2 parts of DMF; the average molecular weight of perfluoroalkyl ether glycol is 10,000, and the corresponding model is PFPE-10000 was purchased from Juhua Group; the aminosilane coupling agent was aminopropyltriethoxysilane; The polytetramethylene glycol and perfluoroalkyl ether glycol are mixed, vacuum dehydrated at 120° C. to a moisture content of ≤0.05%, cooled to 80° C., and diphenylmethane diisocyanate is added. The mixture is stirred and reacted for about 2 hours, specifically until the NCO content is between 8-10% of the original amount. The NCO content is monitored in real time by titration to obtain a polyurethane prepolymer. The polyurethane prepolymer was cooled to 60°C, and the remaining raw materials were added to the polyurethane prepolymer. After continuing to stir for 60 minutes, vacuum degassing was performed to obtain the reinforcement layer raw material, which was then sprayed on the surface of the substrate layer. The material was first heated to 80°C for pre-baking for 1 hour, then heated to 120°C for curing for 2 hours, and cooled. After curing, the thickness of the reinforcement layer was 0.2 mm. S3, composite protective layer Preparation of a fluoropolymer coating: 35 parts by weight of DMF and 12 parts by weight of acetone were mixed at 70° C., followed by the addition of 20 parts of a polyvinylidene fluoride dispersion, 0.8 parts of an organosilicon leveling agent, 5 parts of nano-silica, 0.4 parts of aminopropyltriethoxysilane, 5 parts of alumina powder, and 0.2 parts of acetic acid. The mixture was stirred at 500 rpm for 30 minutes, and then 2.5 parts of HDI biuret was added in three portions with an interval of 3 minutes. After the addition was complete, stirring was continued for 10 minutes to prepare a protective layer coating. The protective layer coating is sprayed on the surface of the reinforcement layer, and then dried with hot air at 80°C for 15 minutes to evaporate the solvent. The temperature is then raised to 120°C and kept warm for 5 minutes. The temperature is then further raised to 150°C and kept warm for 5 minutes. The temperature is then further raised to 180°C and kept warm for 5 minutes to complete cross-linking and curing to obtain a weather-resistant and high-toughness leather material.

[0023] Example 2 A weather-resistant and high-toughness leather material, which is different from Example 1 in that the average molecular weight of its perfluoroalkyl ether diol is 4000, and the corresponding model is PFPE-4000 was purchased from Juhua Group. The remaining steps were the same as those in Example 1.

[0024] Example 3 A weather-resistant and high-toughness leather material, which is different from Example 1 in that the average molecular weight of its perfluoroalkyl ether diol is 20,000, and the corresponding model is Z-Tetraol, brand is Solvay, and the remaining steps are the same as those in Example 1.

[0025] Example 4 A weather-resistant and high-toughness leather material, which differs from Example 1 in that the raw material of its reinforcing layer also includes 1 part by weight of a terminal hydroxyl hyperbranched polyester with a molecular weight of 2400 and a corresponding model number of HyPer H103. The remaining steps are the same as those in Example 1.

[0026] Example 5 A weather-resistant and high-toughness leather material is different from Example 4 in that the amount of perfluoroalkyl ether diol added to its reinforcing layer is 3 parts by weight, and the remaining steps are the same as Example 4.

[0027] Example 6 A weather-resistant and high-toughness leather material is different from Example 4 in that the amount of perfluoroalkyl ether diol added to its reinforcing layer is 7 parts by weight, and the remaining steps are the same as Example 4.

[0028] Example 7 A weather-resistant and high-toughness leather material is different from Example 1 in that the aminosilane coupling agent in its reinforcing layer is replaced by an equal weight portion of methyltriethoxysilane, and the remaining steps are the same as Example 1.

[0029] Comparative Example Comparative Example 1 A weather-resistant and high-toughness leather material, which differs from Example 1 in that perfluoroalkyl ether diol in its reinforcing layer is replaced by an equimolar amount of polytetramethylene ether diol, and the molar amounts of the two raw materials are calculated according to their average molecular weights. The remaining steps are the same as in Example 1.

[0030] Performance testing Detection method / test method Weather-resistant high-toughness leather materials were prepared according to the preparation methods of Examples 1-7 and Comparative Example 1, and then tested according to the following test method. The test results are shown in Table 1.

[0031] Tensile strength and elongation test: refer to the test method in ISO3376-2011 "Leather physical and mechanical tests - Determination of tensile strength and elongation" for testing; and each leather is subjected to aging test, the aging method adopts the aging method in GB / T28005-2011 "Furniture materials - Test method for light aging resistance of genuine leather", the aging time is 1000h, the temperature is 25±5℃, and the relative humidity is 60%.

[0032] Table 1 Test results of Examples 1-7 and Comparative Example 1 It can be seen from Examples 1-7 and Comparative Example 1, as well as the test data in Table 1, that the leather material prepared in the present application has excellent toughness and weather resistance; its tensile strength can reach 62.54-66.21 MPa, and its elongation can reach 59.6-64.2%; after aging for 1000 hours, its tensile strength can still reach 61.9 MPa or above, and can reach a maximum of 66.14 MPa, and its elongation can still reach the range of 58.1-61.7%.

[0033] This application utilizes a polyurethane system as the bonding system, then adds aramid fibers and bonds them to the leather substrate layer to improve the toughness of the leather. Furthermore, perfluoroalkyl ether glycol is added to the polyurethane system, utilizing fluoropolymers to significantly improve the weather resistance of the leather material. The long-chain perfluoroalkyl ether glycol contains hydroxyl groups at both ends, allowing it to participate in crosslinking and curing. Because of the hydroxyl groups at both ends, the addition of the perfluoroalkyl ether glycol creates a crosslink density difference within the reinforcement layer. This creates additional elasticity that cushions the leather material from external forces, significantly improving its toughness. However, the perfluoroalkyl ether glycol also reduces the crosslink density within the polyurethane to a certain extent, slightly reducing its tensile strength. This principle is verified by the test data from Example 1 and Comparative Example 1.

[0034] On this basis, combined with Examples 1-3, it can be seen that when the molecular weight of perfluoroalkyl ether diol is discussed, when its molecular weight is low, its toughness improvement is low, but when its molecular weight is increased to 20,000, its toughness decreases instead; it is speculated that this is because its molecular weight is too large, the viscosity is large, and the distribution is uneven; therefore, the molecular weight range of 4,000-20,000 is the optimal range.

[0035] Since the addition of perfluoroalkyl ether diol reduces the tensile strength of the leather material, a hydroxy-terminated hyperbranched polyester is added to the system, and the polyhydroxy structure contained therein is utilized to form a cross-linking center, thereby increasing the local cross-linking density and improving the tensile strength of the leather material. The increase in the local cross-linking density further increases the cross-linking density difference in the polyurethane system, thereby further improving the toughness of the leather material. This can be verified by the test data of Example 1 and Example 4. In conjunction with Examples 5-6, the perfluoroalkyl ether diol is preferably added in an amount within the range of 3-7 parts by weight.

[0036] It can be seen from the test data of Example 1 and Example 7 that the leather material prepared with the aminosilane coupling agent has better tensile strength and elongation; it is speculated that this is because the aminosilane coupling agent can also participate in the cross-linking of the system after coupling with the fibers and inorganic particles in the system, making the integrity of the reinforcement layer stronger, and therefore, the leather material has better tensile strength and elongation.

[0037] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A weather-resistant and high-toughness leather material, characterized by: The invention comprises a base material layer, a reinforcing layer bonded to one side of the base material layer, and a protective layer coated on one side of the base material layer; the base material layer is natural leather, and the reinforcing layer is a fiber composite material; The fiber composite material comprises the following raw materials in parts by weight: 40-50 parts of polytetramethylene ether glycol, 33-39 parts of diphenylmethane diisocyanate, 3-7 parts of perfluoroalkyl ether glycol, 2-4 parts of chain extender, 0.01-0.04 parts of organic tin catalyst, 0.1-0.4 parts of antioxidant, 0.3-1.2 parts of ultraviolet absorber, 0.3-1 parts of nano-silica, 0.3-1 parts of silane coupling agent, 2-5 parts of chopped aramid fiber and 1-4 parts of DMF.

2. The weather-resistant and high-toughness leather material according to claim 1, characterized in that: The average molecular weight of the perfluoroalkyl ether diol is in the range of 4000-20000.

3. The weather-resistant and high-toughness leather material according to claim 2, characterized in that: The fiber composite material further comprises 0.5-1.5 parts by weight of a hydroxyl-terminated hyperbranched polyester.

4. The weather-resistant and high-toughness leather material according to claim 3, characterized in that: The average molecular weight of the hydroxyl-terminated hyperbranched polyester is in the range of 1100-5200.

5. The weather-resistant and high-toughness leather material according to claim 1, characterized in that: The silane coupling agent is a hydroxysilane coupling agent or an aminosilane coupling agent.

6. The weather-resistant and high-toughness leather material according to claim 1, characterized in that: The chain extender is one or more of ethylene glycol, 1,4-butanediol, neopentyl glycol, ethylenediamine, hexamethylenediamine, diethanolamine, and triethanolamine.

7. The weather-resistant and high-toughness leather material according to claim 1, characterized in that: The protective layer is a fluoropolymer coating, which includes the following raw materials in parts by weight: 30-38 parts of DMF, 10-14 parts of acetone, 18-22 parts of polyvinylidene fluoride dispersion, 0.6-1 part of organic silicon leveling agent, 3-7 parts of nano-silicon dioxide, 0.2-0.6 parts of silane coupling agent, 3-7 parts of aluminum oxide powder, 0.1-0.3 parts of acetic acid and 2-3 parts of HDI biuret.

8. A method for preparing the weather-resistant and high-toughness leather material according to any one of claims 1 to 7, characterized in that: It includes the following steps: S1. Preparation of substrate layer The dehaired raw cowhide is subjected to pickling treatment, tanning, softening and post-treatment to obtain a base material layer; S2, composite reinforcement layer Fiber composite material preparation: The polytetramethylene ether glycol and perfluoroalkyl ether glycol are mixed, vacuum dehydrated, cooled to 60-80°C, diphenylmethane diisocyanate is added, and stirred to react until the NCO content is 8-10% of the original amount, thereby preparing a polyurethane prepolymer; The polyurethane prepolymer is cooled to 50-60°C, the remaining raw materials are added to the polyurethane prepolymer, and the mixture is continuously stirred and vacuum degassed to obtain a fiber composite material, which is then sprayed on the surface of the substrate layer. After curing, the substrate layer is successfully composited with the reinforcement layer. S3, composite protective layer Preparation of fluoropolymer coating: DMF and acetone are mixed at 60-70°C, and then polyvinylidene fluoride dispersion, silicone leveling agent, nano-silica, silane coupling agent, aluminum oxide powder and acetic acid are added and stirred. Then, HDI biuret is added in 2-4 portions and stirring is continued after the addition is complete to prepare a protective layer coating; The protective layer coating is sprayed on the surface of the reinforcement layer, and then hot air dried at 75-85°C to evaporate the solvent, and then the temperature is raised to 110-130°C and kept warm for 5-10 minutes, and then the temperature is further raised to 140-155°C and kept warm for 5-10 minutes, and then the temperature is further raised to 175-185°C and kept warm for 5-10 minutes to complete cross-linking and curing to obtain a weather-resistant and high-toughness leather material.

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