Boiling-resistant PU skin material and preparation method thereof

Abstract

The invention relates to the technical field of synthetic leather, and particularly discloses a boiling-resistant PU skin material and a preparation method thereof. The boiling-resistant PU skin material comprises base cloth, a bonding layer and a PU surface layer which are sequentially attached together, and the PU surface layer is prepared from, by weight, 80-90 parts of modified PU resin, 7-10 parts of composite nano filler, 1-2 parts of catalyst, 65-75 parts of organic solvent and 2-4 parts of other auxiliaries; the composite nano filler comprises boron nitride nanosheets and nano zirconium dioxide in a mass ratio of 1: (0.2-0.5). The boiling-resistant PU skin material disclosed by the invention has excellent boiling resistance, can be applied in a high-temperature and high-humidity environment, keeps good mechanical properties, and can meet the boiling-resistant performance requirements of the fields of automotive trim, electronic product outer layer protection, clothing, shoes and shoes and the like on the PU skin material.

Description

Technical Field

[0001] The present application relates to the technical field of synthetic leather, and more specifically, to a water-boiling-resistant PU surface material and a preparation method thereof. Background Art

[0002] PU surface material is a synthetic leather material with polyurethane (PU) as the main component. Due to its excellent mechanical properties, wear resistance and folding resistance, as well as diverse aesthetic expressions, it is gradually replacing natural leather and becoming the preferred material in the production of luggage, clothing and shoes, automotive interiors, outer protective products of electronic products, and furniture decoration, and its market recognition is increasing.

[0003] Polyurethane is mainly divided into polyether type and polyester type. Among them, polyether polyurethane has good hydrolysis resistance and can effectively resist the invasion of moisture, but its peel strength after bonding with the base fabric is low, especially under high temperature conditions, it is easy to separate from the base fabric. Although polyester polyurethane has good bonding properties, its hydrolysis resistance is poor. Especially in high temperature and high humidity environments, the polyurethane molecular chains in its molecular structure are prone to hydrolysis reactions, resulting in a significant decrease in the material's strength, wear resistance, flexibility and other mechanical properties, and the occurrence of cracking, differentiation and other phenomena, which seriously affect the product's appearance quality and use effect.

[0004] In the prior art, methods such as adjusting the polyurethane molecular chain structure and adding additives are often used to improve the mechanical properties of PU surface materials to meet the application requirements of specific fields. Regarding the aforementioned related technologies, the inventors discovered that while these measures have improved certain material properties to a certain extent, their boiling water resistance is still insufficient, making it difficult to meet the increasingly stringent application requirements. This is particularly true in the fields of automotive interiors, electronic product exterior protection, clothing and footwear, where PU surface materials are subject to frequent contact with water or long-term exposure to high temperature and high humidity environments, placing higher demands on their boiling water resistance.

[0005] Therefore, improving the boiling water resistance of PU materials is of great significance for improving product quality, broadening application areas and enhancing market competitiveness. Summary of the Invention

[0006] In order to improve the boiling resistance of PU surface materials, the present application provides a boiling-resistant PU surface material and a preparation method thereof.

[0007] In the first aspect, the present application provides a water-boiling-resistant PU surface material, which adopts the following technical solution: A boiling-resistant PU surface material comprises a base fabric, an adhesive layer, and a PU surface layer laminated together in sequence. The raw materials of the PU surface layer comprise, by weight, 80-90 parts of modified PU resin, 7-10 parts of composite nanofiller, 1-2 parts of catalyst, 65-75 parts of organic solvent, and 2-4 parts of other additives. The composite nanofiller comprises boron nitride nanosheets and nano zirconium dioxide in a mass ratio of 1:(0.2-0.5).

[0008] First, the inventors discovered that using boron nitride nanosheets as fillers can quickly disperse the heat of boiling, quickly extract local heat, reduce local temperature gradients, and reduce the accelerated hydrolysis of the PU matrix caused by local overheating during boiling. Furthermore, nano-zirconium dioxide has high thermal stability and can maintain structural integrity under high-temperature boiling conditions. The difference between its thermal expansion coefficient and that of the PU matrix enables nano-zirconium dioxide to form a thermal expansion compensation effect with the PU matrix, which effectively inhibits the dimensional changes caused by wet-heat cycles and prevents cracks in the PU surface material. The synergy of the two can not only effectively enhance the mechanical properties of the PU surface material, but also enhance the thermal stability of the PU surface material, ensuring that the PU surface material maintains structural integrity under wet-heat cycles.

[0009] In addition, boron nitride nanosheets and nano-zirconium dioxide can form a sheet-sphere interlaced structure inside the PU matrix, forming a maze effect, which significantly increases the tortuosity of the water molecule permeation path, thereby further reducing the water vapor permeability.

[0010] By adopting the above technical solution, the modified PU resin with strong hydrolysis resistance is used as the matrix to ensure the application performance of the PU skin material in high-humidity environments. Boron nitride nanosheets and nano-zirconium dioxide are used as composite nanofillers to further inhibit the permeation of water vapor, and significantly enhance the internal heat conduction and heat dissipation of the PU skin material, inhibiting the cracking phenomenon caused by thermal stress inside the material when boiled in water at high temperature, and effectively ensuring the water boiling resistance of the PU skin material.

[0011] Optionally, the raw materials of the modified PU resin include, by weight, 32-38 parts of cyclohexane dimethylene diisocyanate, 67-75 parts of polyether polyol, 5-15 parts of chain extender and 0.05-0.15 parts of triethylenediamine.

[0012] Optionally, the polyether polyol is a perfluoropolyether diol.

[0013] Optionally, the chain extender is an aliphatic diamine selected from any one or more combinations of ethylenediamine, hexamethylenediamine, diethylenetriamine and triethylenetetramine.

[0014] Cyclohexane dimethylene diisocyanate is an aliphatic isocyanate with higher hydrolysis stability than traditional aromatic isocyanates, and can effectively prevent nucleophilic attack by water molecules; perfluoropolyether polyol contains fluorocarbon chain segments, which can effectively block the hydrolysis path, forming a continuous hydrophobic barrier, and inhibiting the diffusion of water into the PU matrix; aliphatic diamine is a hydrophobic chain extender, which enhances the dense cross-linked network of the PU matrix, further enhances the hydrophobicity of the PU matrix, and inhibits the penetration of water molecules during the boiling process.

[0015] The modified PU resin formed by adopting the above technical solution has excellent hydrolysis resistance and weather resistance, can serve as a stable matrix for PU surface materials, enhance the ability of PU surface materials to resist high-temperature boiling environments, and effectively slow down the damage of PU surface materials caused by boiling.

[0016] Optionally, the other auxiliary agents include stabilizers, thickeners, defoaming agents and antioxidants.

[0017] Optionally, the catalyst is an organic bismuth catalyst.

[0018] Optionally, the organic solvent is DMF, HFE-7100 and ethyl acetate in a mass ratio of 1:(0.3-0.5):(0.1-0.2).

[0019] In a second aspect, the present application provides a method for preparing a boiling-resistant PU surface material, which adopts the following technical solution: A method for preparing a boiling-resistant PU surface material comprises the following steps: Prepare raw materials according to the weight of the formula, prepare a 3-5% fluorine-containing silane coupling agent solution, immerse boron nitride nanosheets and nano zirconium dioxide in the pretreatment solution, ultrasonically treat at 60-70° C. for 2.5-3.5 hours, centrifuge, wash, and dry to obtain a pretreated composite nanofiller; The pretreated composite nanofiller was added to the organic solvent and ultrasonicated for 40-60 min to form a stable suspension; Add the modified PU resin to the suspension, add the catalyst and other additives, and stir at a constant temperature of 70-80°C for 1.5-2.5 hours in a nitrogen-protected reactor to obtain a mixture; The mixture is coated on the release paper, heated and dried to form a PU surface layer on the release paper; The adhesive layer is compounded with the base fabric and pre-cured to form a semi-cured base fabric. The side of the PU surface layer away from the release paper is then compounded with the semi-cured base fabric, pressed by rollers and dried, and then peeled off from the release paper to obtain the product.

[0020] Optionally, the fluorine-containing silane coupling agent is selected from any one of perfluorodecyltriethoxysilane, perfluorodecyltrimethoxysilane and perfluorooctyltriethoxysilane.

[0021] By adopting the above technical solution, the surface of the composite nanofiller is modified using a fluorinated silane coupling agent under ultrasonic conditions, and fluoroalkyl groups can be grafted on the filler surface. This helps to enhance the interfacial bonding between the composite nanofiller and the fluorinated resin, while enhancing the dispersion uniformity between the boron nitride nanosheets and nano-zirconium dioxide, forming a more uniform sheet-spherical mixed structure, and at the same time improving the dispersion uniformity of the composite nanofiller in the PU matrix, preventing the occurrence of filler aggregation and the degradation of the performance of the PU surface material.

[0022] Optionally, the nano zirconium dioxide is subjected to the following pretreatment before being immersed in the pretreatment solution with the boron nitride nanosheets: Prepare 3-5% zirconate coupling agent modification liquid, immerse nano zirconium dioxide in the zirconate coupling agent modification liquid, perform ultrasonic treatment at 40-50° C. for 1.5-2.5 hours, centrifuge, wash and dry to obtain pretreated nano zirconium dioxide.

[0023] Optionally, the zirconate coupling agent is selected from any one of ZR-801, ZR-802, FD-NZ97 and DN-807.

[0024] By adopting the above technical solution, the nano zirconium dioxide modified by zirconate reduces the surface polarity of the nanoparticles and prevents the occurrence of easy agglomeration of the nanoparticles. The subsequent surface modification with a fluorine-containing silane coupling agent further enhances the compatibility between the nano zirconium dioxide and the boron nitride nanosheets and the fluorinated PU matrix. On the other hand, the zirconate modification forms a flexible interface layer on the surface of the nano zirconium dioxide, which acts as a buffer zone and can absorb the strain energy generated by the endothermic expansion of the PU surface material, further disperse the thermal stress in a step-by-step manner, and significantly reduce the occurrence of cracks in a water boiling environment.

[0025] In summary, this application has the following beneficial effects: 1. Since this application uses aliphatic isocyanate instead of traditional aromatic isocyanate to prepare modified PU resin with perfluoropolyether polyol, the fluorocarbon chain segment can effectively block the hydrolysis path, forming a continuous hydrophobic barrier, effectively enhancing the hydrolysis resistance and weather resistance of the PU resin. The use of aliphatic diamine as a hydrophobic chain extender enhances the hydrophobic and dense cross-linked network of the PU matrix, further enhances the hydrophobicity of the PU matrix, enhances the ability of the PU surface material to resist high-temperature boiling environment, and effectively slows down the damage of the PU surface material caused by boiling.

[0026] 2. In this application, boron nitride nanosheets and nano zirconium dioxide are preferably used as composite nanofillers. Both have excellent high-temperature performance and form a gradient thermal expansion compensation effect with the PU matrix, which significantly enhances the ability of the PU surface material to conduct and dissipate heat under high temperatures of boiling water, preventing cracks in the PU surface caused by high temperature. The sheet-spherical structure formed by the two forms a barrier to water molecules inside the PU matrix, further reducing the penetration of water molecules, and effectively ensuring that the PU surface material maintains structural integrity and durability in a wet and hot cycle environment.

[0027] 3. The method of the present application pre-treats the nano-zirconium dioxide with a zirconate coupling agent and then performs secondary surface modification with a fluorinated silane coupling agent together with boron nitride nanosheets. This effectively prevents the problem of nanoparticles being easily agglomerated, promotes the mixing of boron nitride nanosheets and nano-zirconium dioxide to form a sheet-spherical composite nanofiller structure, which is better dispersed in the PU matrix. At the same time, it strengthens the interfacial bonding force between the composite nanofiller and the PU matrix, thereby enhancing the comprehensive performance of the PU surface material. DETAILED DESCRIPTION

[0028] The following examples further illustrate the present application in detail.

[0029] raw material Unless otherwise specified, the raw materials used in the examples and comparative examples of this application are all commercially available products, specifically: The base fabric is polyester warp knitted fabric with a thickness of (0.72±0.01) mm and a weight of 220 g / m 2 ; Boron nitride nanosheets, 50-100 nm in size; Nano zirconium dioxide, purity ≥99.9%, average particle size 30nm; Nano-silicon dioxide, purity ≥99.9%, average particle size 30nm; Perfluoropolyether diol, selected from Hubei Langbowan Biopharmaceutical Co., Ltd., with an average molecular weight of 2000; Polytetramethylenetetrahydrofuran diol, selected from Hyosung Chemical Co., Ltd., with an average molecular weight of 2000; Polyethylene adipate, selected from Orilon (Jining) Chemical Co., Ltd., with an average molecular weight of 2000; The release paper is TPX type release paper, brand DX820; Stabilizer, selected from Ciba Specialty Chemicals (China) Co., Ltd., light stabilizer UV-770; Thickener, a polyurethane associative thickener, selected from Anhui Feimiao Chemical Co., Ltd., product number N-140; Defoaming agent, which is a silicone defoaming agent, selected from Dongguan Defeng Defoaming Agent Co., Ltd., DF-2854; Antioxidant, selected from Kangjin Chemical, industrial grade antioxidant 168; The water-based resin is a polyester-type water-based polyurethane resin, which was selected from Anhui Feimiao Chemical Co., Ltd. and has the product number FS-1930C; Leveling agent, which is an organic silicone leveling agent, selected from Guangzhou Dachuan Fine Chemical Co., Ltd., BYK-301; The cross-linking agent is a blocked water-based isocyanate cross-linking agent with a viscosity of 1000-3000 mPa·s.

[0030] Preparation example of modified PU resin Preparation Example 1 The modified PU resin, the raw materials and amounts are shown in Table 1, wherein the polyether polyol is perfluoropolyether diol, and the chain extender is ethylenediamine.

[0031] Table 1 Components / parts by weight Preparation Example 1 Preparation Example 2 Preparation Example 3 Preparation Example 4 Cyclohexanedimethylene diisocyanate 32 34.6 36 38 polyether polyols 67 70 73.5 75 Chain Extender 5 12 13 15 Triethylenediamine 0.05 0.1 0.1 0.15 The preparation method of the modified PU resin comprises the following steps: In a reactor under nitrogen atmosphere, polyether polyol and a chain extender were added using DMF as a solvent. After stirring for 30 minutes, cyclohexane dimethylene diisocyanate and triethylenediamine were added. The temperature was raised to 70±2°C, and the reaction was carried out until the viscosity reached (8000±100) mPa·s / 25°C, and the material was discharged to obtain a modified PU resin.

[0032] Preparation Example 2 The difference between the modified PU resin and Preparation Example 1 is that the raw materials and amounts are as shown in Table 1, the chain extender is hexamethylenediamine, and the other steps are the same as Preparation Example 1.

[0033] Preparation Example 3 The difference between the modified PU resin and Preparation Example 1 is that the raw materials and amounts are as shown in Table 1, the chain extender is diethylenetriamine, and the other steps are the same as Preparation Example 1.

[0034] Preparation Example 4 The difference between the modified PU resin and Preparation Example 1 is that the raw materials and amounts are as shown in Table 1, the chain extender is triethylenetetramine, and the other steps are the same as Preparation Example 1.

[0035] Preparation Example 5 The difference between the modified PU resin and Preparation Example 1 is that the polyether polyol in the raw material is polytetramethylene glycol, and the other steps are the same as Preparation Example 1.

[0036] Preparation Example 6 The difference between the modified PU resin and Preparation Example 1 is that the polyether polyol in the raw material is replaced by an equal mass of polyester polyol, namely polyethylene adipate, and the other steps are the same as Preparation Example 1. Example

[0037] Example 1 A water-boiling-resistant PU surface material, the raw materials and their amounts are shown in Table 2, wherein the modified PU resin is prepared according to Preparation Example 1, the composite nanofiller is boron nitride nanosheets and nano-zirconium dioxide in a mass ratio of 1:0.35, the organic bismuth catalyst is bismuth neodecanoate, and the organic solvent is DMF, HFE-7100, and ethyl acetate in a mass ratio of 1:0.4:0.1.

[0038] Table 2 Components / parts by weight Example 1 Example 2 Example 3 Example 4 Modified PU resin 81.6 86 80 90 Composite nanofillers 8.4 9 7 10 Organic bismuth catalyst 1 1.5 1 2 organic solvents 68 70 65 75 stabilizer 0.6 0.8 0.5 1 thickener 0.4 0.6 0.4 0.8 defoaming agent 0.3 0.5 0.3 0.7 antioxidants 1 1.1 0.8 1.5 The preparation method of the above-mentioned boiling-resistant PU surface material comprises the following steps: S1: preparing raw materials according to the weight of the formula, preparing a 3% perfluorooctyltriethoxysilane coupling agent solution as a pretreatment solution, immersing boron nitride nanosheets and nano-zirconium dioxide in the pretreatment solution, ultrasonically treating at 70° C. for 3.5 hours, centrifuging, washing, and drying to obtain a pretreated composite nanofiller; S2: adding the pretreated composite nanofiller to the organic solvent and sonicating for 60 min to form a stable suspension; S3: adding the modified PU resin to the suspension, adding an organic bismuth catalyst and a stabilizer, a thickener, a defoamer, and an antioxidant, and stirring the mixture at 70° C. for 2.5 h in a nitrogen-protected reactor to obtain a mixture; S4: The mixture is coated on a release paper with a thickness of (0.3±0.05) mm, and is heated and dried by a gradient heating method at temperatures of 70, 80, 100, 110, and 125° C. for a total of 4 min to form a PU surface layer on the release paper; S5: The base fabric is cleaned and dried to obtain a pretreated base fabric, and 90 parts of water-based resin, 0.8 parts of leveling agent, 0.07 parts of defoaming agent, 6 parts of thickener and 8 parts of cross-linking agent are mixed and stirred uniformly according to weight to obtain a mixed liquid, and a printing process is adopted to apply the mixed liquid on the surface of the base fabric using a mesh roller with a thickness of 0.1 mm, and then placed in an oven for baking, and the temperature is set to 150°C and the operating speed is 30 m / min. After high-temperature catalytic reaction for 1 minute, a semi-cured base fabric is formed, and the side of the PU surface layer away from the release paper is laminated to the semi-cured base fabric, pressed by a roller and then dried, and then peeled off from the release paper to obtain the base fabric.

[0039] Example 2 A boiling-resistant PU surface material, which differs from Example 1 in that the raw materials and their amounts are as shown in Table 2, wherein the composite nanofiller is boron nitride nanosheets and nano-zirconium dioxide in a mass ratio of 1:0.2, and the organic solvent is DMF, HFE-7100, and ethyl acetate in a mass ratio of 1:0.3:0.2; The preparation method of the above-mentioned boiling-resistant PU surface material comprises the following steps: S1: preparing raw materials according to the weight of the formula, preparing a 4% perfluorooctyltriethoxysilane coupling agent solution as a pretreatment solution, immersing boron nitride nanosheets and nano-zirconium dioxide in the pretreatment solution, ultrasonically treating at 70° C. for 3 hours, centrifuging, washing, and drying to obtain a pretreated composite nanofiller; S2: adding the pretreated composite nanofiller to the organic solvent and sonicating for 40 min to form a stable suspension; S3: adding the modified PU resin to the suspension, adding an organic bismuth catalyst and a stabilizer, a thickener, a defoamer, and an antioxidant, and stirring the mixture at a constant temperature of 80° C. for 1.5 h in a nitrogen-protected reactor to obtain a mixture; S4: The mixture is coated on a release paper with a thickness of (0.3±0.05) mm, and is heated and dried by a gradient heating method at temperatures of 70, 80, 100, 110, and 125° C. for a total of 4 min to form a PU surface layer on the release paper; S5: The base fabric is cleaned and dried to obtain a pretreated base fabric, and 90 parts of water-based resin, 0.8 parts of leveling agent, 0.07 parts of defoaming agent, 6 parts of thickener and 8 parts of cross-linking agent are mixed and stirred uniformly according to weight to obtain a mixed liquid, and a printing process is adopted to apply the mixed liquid on the surface of the base fabric using a mesh roller with a thickness of 0.1 mm, and then placed in an oven for baking, and the temperature is set to 150°C and the operating speed is 30 m / min. After high-temperature catalytic reaction for 1 minute, a semi-cured base fabric is formed, and the side of the PU surface layer away from the release paper is laminated to the semi-cured base fabric, pressed by a roller and then dried, and then peeled off from the release paper to obtain the base fabric.

[0040] Example 3 A boiling-resistant PU surface material, which differs from Example 1 in that the raw materials and their amounts are as shown in Table 2, wherein the composite nanofiller is boron nitride nanosheets and nano-zirconium dioxide in a mass ratio of 1:0.5, and the organic solvent is DMF, HFE-7100, and ethyl acetate in a mass ratio of 1:0.5:0.1; The preparation method of the above-mentioned boiling-resistant PU surface material comprises the following steps: S1: preparing raw materials according to the weight of the formula, preparing a 5% perfluorooctyltriethoxysilane coupling agent solution as a pretreatment solution, immersing boron nitride nanosheets and nano-zirconium dioxide in the pretreatment solution, ultrasonically treating at 60° C. for 2.5 hours, centrifuging, washing, and drying to obtain a pretreated composite nanofiller; S2: adding the pretreated composite nanofiller to the organic solvent and sonicating for 50 min to form a stable suspension; S3: adding the modified PU resin to the suspension, adding an organic bismuth catalyst and a stabilizer, a thickener, a defoamer, and an antioxidant, and stirring the mixture at a constant temperature of 7° C. for 2 h in a nitrogen-protected reactor to obtain a mixture; S4: The mixture is coated on a release paper with a thickness of (0.3±0.05) mm, and is heated and dried by a gradient heating method at temperatures of 70, 80, 100, 110, and 125° C. for a total of 4 min to form a PU surface layer on the release paper; S5: The base fabric is cleaned and dried to obtain a pretreated base fabric, and 90 parts of water-based resin, 0.8 parts of leveling agent, 0.07 parts of defoaming agent, 6 parts of thickener and 8 parts of cross-linking agent are mixed and stirred uniformly according to weight to obtain a mixed liquid, and a printing process is adopted to apply the mixed liquid on the surface of the base fabric using a mesh roller with a thickness of 0.1 mm, and then placed in an oven for baking, and the temperature is set to 150°C and the operating speed is 30 m / min. After high-temperature catalytic reaction for 1 minute, a semi-cured base fabric is formed, and the side of the PU surface layer away from the release paper is laminated to the semi-cured base fabric, pressed by a roller and then dried, and then peeled off from the release paper to obtain the base fabric.

[0041] Example 4 A boiling-resistant PU surface material is different from Example 1 in that the raw materials and their amounts are shown in Table 2, and the other steps are the same as Example 1.

[0042] Examples 5-9 A boiling-resistant PU surface material. The difference between Examples 5-9 and Example 1 is that the source of the modified PU resin in the raw materials is shown in Table 3, and the other steps are the same as Example 1.

[0043] Table 3 Example 10 A boiling-resistant PU surface material is different from Example 1 in that the nano-zirconium dioxide is pretreated as follows before being immersed in a pretreatment solution with boron nitride nanosheets: a 3% zirconate coupling agent modifying solution is prepared, the nano-zirconium dioxide is immersed in the zirconate coupling agent modifying solution and ultrasonically treated at 40° C. for 2.5 hours, and the pretreated nano-zirconium dioxide is obtained after centrifugation, washing, and drying. The other steps are the same as those in Example 1.

[0044] Example 11 A boiling-resistant PU surface material is different from Example 1 in that, before the nano-zirconium dioxide and the boron nitride nanosheets are immersed in the pretreatment solution, the following pretreatment is performed: a 4% zirconate coupling agent modifying solution is prepared, the nano-zirconium dioxide is immersed in the zirconate coupling agent modifying solution and ultrasonically treated at 45°C for 2 hours, and the pretreated nano-zirconium dioxide is obtained after centrifugation, washing, and drying; the other steps are the same as in Example 1.

[0045] Example 12 A boiling-resistant PU surface material is different from Example 1 in that the nano-zirconium dioxide is pretreated as follows before being immersed in a pretreatment solution with boron nitride nanosheets: a 5% zirconate coupling agent modifying solution is prepared, the nano-zirconium dioxide is immersed in the zirconate coupling agent modifying solution and ultrasonically treated at 50° C. for 1.5 hours, and the pretreated nano-zirconium dioxide is obtained after centrifugation, washing, and drying. The other steps are the same as those in Example 1.

[0046] Comparative Example Comparative Example 1 A boiling-resistant PU surface material is different from Example 1 in that boron nitride nanosheets are not added, and the boron nitride nanosheets are replaced by nano zirconium dioxide of equal mass. Other steps are the same as Example 1.

[0047] Comparative Example 2 A boiling-resistant PU surface material is different from Example 1 in that nano zirconium dioxide is not added, and nano zirconium dioxide is replaced by boron nitride nanosheets of equal mass. Other steps are the same as Example 1.

[0048] Comparative Example 3 A boiling-resistant PU surface material is different from Example 1 in that the nano-zirconium dioxide in the composite nano-filler is replaced with nano-silicon dioxide of equal mass, and the other steps are the same as Example 1.

[0049] Performance testing The water boiling aging performance test was performed on the water boiling aging performance test of the water boiling resistant PU surface material obtained in Example 1-12 and Comparative Example 1-3.

[0050] Boiling aging test: The boiling-resistant PU surface material obtained in Examples 1-12 and Comparative Examples 1-3 was cut into samples of 250 mm × 50 mm in size, with 3 samples in each group. The samples were placed in a container filled with distilled water, and the container was placed in a constant temperature water bath aging equipment and boiled at 100°C for 5 days. The samples were taken out after 5 days, and the tensile strength and folding fastness of the samples before and after boiling aging were tested with reference to the standards of QB / T4194-2011 and QB / T2714, respectively. The retention rate of tensile strength before and after boiling aging and the folding fastness before and after boiling aging were calculated. The state of the surface material was observed every 5,000 times to see if the surface material had any powdering, cracking, or separation from the base fabric layer. The highest number of foldings without cracking, powdering, or separation was recorded. The test was performed up to 100,000 times. The average value of the test results of 3 samples in each group was taken as the final result and the final result was recorded in Table 4.

[0051] Table 4 According to the performance test data in Table 4, it can be seen that the PU surface layer material prepared in the present application did not show any powdering, cracking, or separation from the base fabric layer after water boiling and aging, and was able to maintain good tensile strength and folding fastness. This shows that the water-boiling-resistant PU surface material of the present application has excellent water boiling resistance, can effectively enhance the ability of the PU surface material to resist high-temperature water boiling environment, and effectively slow down the damage of the PU surface material caused by water boiling.

[0052] The performance test results of Examples 1-7 and 8-9 show that the polyether-type PU resin prepared from polyether polyols has significantly better resistance to hydrolysis than the PU surface material prepared from polyester polyols. The changes in tensile strength and folding fastness of the PU surface material prepared from fluorinated polyether polyols are superior to those of fluorinated polyether polyols after water boiling aging. This is because the fluorocarbon segments of the modified PU resin prepared from perfluoropolyether polyols can effectively block the hydrolysis pathway, forming a continuous hydrophobic barrier within the PU matrix, effectively enhancing the hydrolysis resistance and weathering resistance of the PU resin. This in turn enhances the PU surface material's ability to withstand high-temperature water boiling environments, effectively mitigating damage to the PU surface material caused by water boiling.

[0053] According to the performance test results of Examples 1 and 10-12, it can be seen that after the nano-zirconium dioxide is pretreated with a zirconate coupling agent, a secondary surface modification with a fluorinated silane coupling agent is performed together with boron nitride nanosheets. Compared with the direct surface modification with a fluorinated silane coupling agent together with the boron nitride nanosheets, the secondary modified group shows a significant advantage in terms of water boiling aging resistance. This is because the zirconate coupling agent can reduce the surface form of the nanoparticles before mixing the nano-zirconium dioxide and boron nitride nanosheets, which effectively prevents the problem of easy agglomeration of the nanoparticles and promotes the mixing of the boron nitride nanosheets and the nano-zirconium dioxide to form a sheet-spherical composite nanofiller structure, which is better dispersed in the PU matrix. At the same time, the interfacial bonding force between the composite nanofiller and the PU matrix is ​​strengthened, thereby enhancing the comprehensive performance of the PU surface material.

[0054] In addition, zirconate modification forms a flexible interface layer on the surface of nano-zirconium dioxide, which can act as a buffer zone to further absorb the strain energy generated by the endothermic expansion inside the PU surface material, disperse the thermal stress in a step-by-step manner, and reduce the occurrence of cracks in a high-temperature water boiling environment.

[0055] The performance test results of Example 1 and Comparative Examples 1-3 show that the use of a composite nanofiller prepared by mixing boron nitride nanosheets and nanozirconium dioxide as a filler significantly improves the boiling resistance of the PU skin material. This is because the boron nitride nanosheets as a filler can quickly disperse the heat of boiling, quickly dissipate local heat, reduce local temperature gradients, and reduce the accelerated hydrolysis of the PU matrix caused by local overheating during boiling. Furthermore, due to the high thermal stability of nanozirconium dioxide, it can maintain structural integrity under high-temperature boiling conditions. The difference in its thermal expansion coefficient with that of the PU matrix and the boron nitride nanosheets creates a gradient thermal expansion compensation effect in the PU matrix. Compared to the group using nanosilica in Comparative Example 3, nanozirconium dioxide better adapts to the thermal expansion characteristics of the PU matrix of this application, effectively suppressing the dimensional changes of the PU skin material caused by wet-heat cycling, thereby effectively preventing cracks in the PU skin material. The synergistic effect of the two not only effectively enhances the mechanical properties of the PU skin material, but also enhances its thermal stability, ensuring the structural integrity of the PU skin material under wet-heat cycling conditions.

[0056] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A boiling-resistant PU surface material, comprising a base fabric, an adhesive layer and a PU surface layer laminated together in sequence, characterized in that: The raw materials of the PU surface layer include 80-90 parts of modified PU resin, 7-10 parts of composite nanofiller, 1-2 parts of catalyst, 65-75 parts of organic solvent and 2-4 parts of other additives according to weight parts; The composite nano-filler comprises boron nitride nano-sheets and nano-zirconium dioxide in a mass ratio of 1:(0.2-0.5).

2. The boiling-resistant PU surface material according to claim 1, characterized in that: In parts by weight, the raw materials of the modified PU resin include 32-38 parts of cyclohexane dimethylene diisocyanate, 67-75 parts of polyether polyol, 5-15 parts of chain extender and 0.05-0.15 parts of triethylenediamine.

3. The boiling-resistant PU surface material according to claim 2, characterized in that: The polyether polyol is perfluoropolyether diol.

4. The boiling-resistant PU surface material according to claim 2, characterized in that: The chain extender is an aliphatic diamine, selected from any one or more combinations of ethylenediamine, hexamethylenediamine, diethylenetriamine and triethylenetetramine.

5. The boiling-resistant PU surface material according to claim 1, characterized in that: The other adjuvants include stabilizers, thickeners, defoamers and antioxidants.

6. The boiling-resistant PU surface material according to claim 1, characterized in that: The catalyst is an organic bismuth catalyst.

7. The boiling-resistant PU surface material according to claim 1, characterized in that: The organic solvent is DMF, HFE-7100 and ethyl acetate in a mass ratio of 1:(0.3-0.5):(0.1-0.2).

8. The method for preparing a boiling-resistant PU surface material according to any one of claims 1 to 7, characterized in that: The following steps are involved: Prepare raw materials according to the weight of the formula, prepare a 3-5% fluorine-containing silane coupling agent solution, immerse boron nitride nanosheets and nano zirconium dioxide in the pretreatment solution, ultrasonically treat at 60-70°C for 2.5-3.5 hours, centrifuge, wash, and dry to obtain a pretreated composite nanofiller; The pretreated composite nanofiller was added to the organic solvent and ultrasonicated for 40-60 min to form a stable suspension; Add the modified PU resin to the suspension, add the catalyst and other additives, and place the mixture in a nitrogen-protected reactor at a constant temperature of 70-80°C and stir for 1.5-2.5 hours to obtain a mixture; The mixture is coated on the release paper, heated and dried to form a PU surface layer on the release paper; The adhesive layer is compounded with the base fabric and pre-cured to form a semi-cured base fabric. The side of the PU surface layer away from the release paper is then compounded with the semi-cured base fabric, pressed by rollers and dried, and then peeled off from the release paper to obtain the product.

9. The method for preparing the boiling-resistant PU surface material according to claim 8, characterized in that: The nano zirconium dioxide is pretreated as follows before being immersed in the pretreatment solution with the boron nitride nanosheets: a 3-5% zirconate coupling agent modification solution is prepared, the nano zirconium dioxide is immersed in the zirconate coupling agent modification solution, ultrasonically treated at 40-50° C. for 1.5-2.5 hours, and the pretreated nano zirconium dioxide is obtained after centrifugation, washing, and drying.

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