High-temperature-resistant flame-retardant organic silicon leather and preparation method thereof

Abstract

The invention provides high-temperature-resistant flame-retardant organic silicon leather and a preparation method thereof.The organic silicon leather comprises a base cloth layer and an organic silicon coating compounded on the base cloth layer, and the organic silicon coating comprises two-component addition type liquid silica gel, hydrogen-containing silicone oil, an inhibitor, a halogen-free flame retardant and a catalyst; the halogen-free flame retardant is obtained through two-step surface modification of inorganic coating of silica sol and organic modification of vinyl silane oligomer. According to the invention, inorganic coating and organic modification methods are adopted for the halogen-free flame retardant, so that the compatibility and interface bonding of the flame retardant and an organic silicon matrix are improved, and performance degradation caused by poor compatibility is avoided, so that the coating keeps excellent mechanical properties and hand feeling while obtaining UL-94 V0-level high flame retardance.

Description

Technical Field

[0001] This invention relates to the field of silicone leather, specifically to a high-temperature resistant and flame-retardant silicone leather and its preparation method. Background Technology

[0002] Silicone leather is widely used in automotive interiors, high-end homes, public transportation, and special protective applications due to its excellent weather resistance, chemical stability, non-toxicity, environmental friendliness, and ease of cleaning. However, its main structure is usually composed of a silicone coating and a synthetic fiber base fabric (such as polyester or nylon nonwoven fabric). Since the base fabric layer is often made of flammable materials, the overall flame retardant performance of the composite material is difficult to meet stringent flame retardant standards such as UL~94 V0.

[0003] To improve flame retardancy, the industry generally adopts the method of adding halogen-free flame retardants, such as aluminum hydroxide (ATH) or magnesium hydroxide (MDH), to silicone coatings. However, these flame retardants have poor compatibility with non-polar silicone resins and have the following inherent defects: (1) easy agglomeration and migration: polar flame retardant powders are difficult to disperse evenly in non-polar silicone systems, and are prone to agglomeration and later migration, resulting in rough coating surface, poor feel, and unstable flame retardant performance; (2) deterioration of mechanical properties: the bonding force between the flame retardant and the silicone matrix is ​​weak, and it becomes a stress concentration point when under stress, resulting in a significant decrease in the tensile strength, tear strength and elongation at break of the coating; (3) insufficient thermal stability: ATH and MDH will decompose and lose water at low temperatures (starting at about 200°C), affecting their long-term stability in higher temperature processing and application environments.

[0004] To address the aforementioned issues, existing technologies often employ silane coupling agents (such as KH~550 or KH~570) to modify the surface of flame retardants, improving their dispersibility and interfacial bonding in organosilicon systems. However, traditional small-molecule silane coupling agents have limited modification effects, insufficient reinforcement of coating mechanical properties, and difficulty in completely preventing the aggregation and migration of flame retardants during long-term use.

[0005] Therefore, developing a novel flame retardant system that can fundamentally improve the interfacial compatibility between flame retardants and organosilicon matrices, while simultaneously enhancing their thermal stability and overall coating performance, has become a critical issue that urgently needs to be addressed in this field. Summary of the Invention

[0006] The main objective of this invention is to provide a high-temperature resistant, flame-retardant silicone leather and its preparation method, thereby solving the problems mentioned in the background art. This invention employs an inorganic coating and organic modification method to improve the compatibility and interfacial bonding between the halogen-free flame retardant and the silicone matrix, eliminating performance degradation caused by poor compatibility. This allows the coating to achieve UL~94 V0 level high flame retardancy while maintaining excellent mechanical properties and a pleasant feel.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A high-temperature resistant and flame-retardant silicone leather includes a base fabric layer and a silicone coating laminated on the base fabric layer. The silicone coating comprises the following components: a two-component addition-type liquid silicone, a hydrogen-containing silicone oil, an inhibitor, a halogen-free flame retardant, and a catalyst. The halogen-free flame retardant is at least one of aluminum hydroxide, magnesium hydroxide, mica powder, hindered amine intercalated modified zirconium hydrogen phosphate, attapulgite, and organomontmorillonite, with a particle size of 1-5 μm. The amount of the halogen-free flame retardant added is 30%-60% of the mass of component A in the two-component addition-type liquid silicone.

[0008] Furthermore, the halogen-free flame retardant is obtained through a two-step surface modification process, as follows: (1) After reacting silica sol with an aqueous solution of halogen-free flame retardant, a silica sol-coated flame retardant intermediate is obtained. (2) The above intermediate was stirred and reacted with an anhydrous ethanol solution of vinyl silane oligomer to obtain a surface-modified halogen-free flame retardant.

[0009] This invention constructs a dense and stable inorganic silica coating layer on the surface of flame retardant particles using silica sol, significantly improving the thermal stability and high-temperature resistance of the flame retardant itself and delaying its decomposition at high temperatures. Subsequently, the coated powder is surface-grafted using vinyl silane oligomers. These oligomers not only modify the powder and increase compatibility, but also, through chemical bonding, anchor one end to the silica sol coating layer, firmly bonding with the inorganic coating layer, while the other end is embedded in an organosilicon crosslinking network via vinyl groups. This "rigid-flexible" interface structure provides both strong bonding force and good stress buffering, significantly improving the tensile strength, elongation at break, and other mechanical properties of the coating.

[0010] Furthermore, in step (1), the mass ratio of silica sol to halogen-free flame retardant is 3-6:1, and in step (2), the mass ratio of flame retardant intermediate to vinylsilane oligomer is 15-23:1.

[0011] Furthermore, the reaction temperature in step (1) is 40-60℃, and the reaction time is 1.5-3h.

[0012] Furthermore, the reaction temperature in step (2) is 60-80℃, and the reaction time is 1-3h.

[0013] Furthermore, the vinyl silane oligomer is prepared by hydrolysis and condensation of vinyltrimethoxysilane (VTMS) and γ-aminopropyltriethoxysilane (APTES) in a mass ratio of 3-5:1.

[0014] Furthermore, the number average molecular weight of the vinyl silane oligomer is 1000-3000, the vinyl content is 5%-8%, and the viscosity is 1000-2000 mPa·s.

[0015] Furthermore, the silicone coating also contains additives, including at least one of color paste, feel modifier, abrasion resistant agent, and vinyl silicone resin.

[0016] Furthermore, the base fabric layer is a high-density fiberglass cloth that has been treated with an acrylic emulsion containing flame retardants.

[0017] A second aspect of this invention provides a method for preparing the aforementioned high-temperature resistant and flame-retardant silicone leather, comprising the following steps: S1. Mix component A, hydrogen-containing silicone oil, inhibitor and halogen-free flame retardant in the two-component addition-curing liquid silicone under vacuum conditions to obtain flame retardant slurry. S2. Mix the flame retardant slurry with component B, catalyst and additives in the two-component addition-curing liquid silicone to obtain a mixture. S3. The mixture is coated onto release paper in two layers. After the first layer is heated and cured, the second layer is coated and then bonded to high-density fiberglass cloth and heated and cured again. Finally, it is peeled off from the release paper to obtain the high-temperature resistant and flame-retardant silicone leather.

[0018] Furthermore, the vacuum degree in step S1 is -0.08 to 0.1 MPa; the stirring speed is 500 to 1000 rpm; and the stirring time is 20 to 40 min. The stirring time in step S2 is 10 to 20 min.

[0019] Furthermore, in step S2, the thickness of the first adhesive layer is 100-150 μm, and the thickness of the second adhesive layer is 120-150 μm.

[0020] Furthermore, in step S2, the curing temperature of the first layer is 100-130℃ and the time is 3-10 min; the curing temperature of the second layer is 100-130℃ and the time is 3-8 min.

[0021] Furthermore, the catalyst is a platinum catalyst with a platinum content of 2000-5000 ppm; the inhibitor is 1-acetylenecyclohexanol.

[0022] The beneficial effects of this invention are as follows: 1. This invention first constructs a thermally stable barrier by inorganically coating a halogen-free flame retardant with silica sol, effectively inhibiting the early thermal decomposition of aluminum hydroxide during processing and use, and ensuring the durability of the flame retardant effect. Subsequently, an organic surface is modified using a self-made vinyl silane oligomer. This oligomer can not only firmly bond with the inorganic coating layer, but its terminal vinyl groups can also participate in the addition crosslinking and curing reaction of the organosilicon coating, thereby establishing a strong and flexible "bridge" between the flame retardant and the organosilicon resin, significantly improving the mechanical properties of the coating such as tensile strength and elongation at break.

[0023] 2. This invention improves the compatibility and interfacial bonding between flame retardants and organosilicon matrices through a two-step synergistic modification method involving inorganic coating and organic modification of halogen-free flame retardants. It fundamentally solves the common industry problems of poor compatibility between flame retardants and organosilicon matrices, easy decomposition at high temperatures, and easy migration and aggregation in the system. Ultimately, it produces organosilicon leather products with excellent flame retardancy, superior mechanical properties, high thermal stability, and good hand feel.

[0024] 3. The preparation method of the present invention is simple, easy to operate and control, suitable for large-scale production, and the product is halogen-free and environmentally friendly, which is in line with the development trend of modern materials. Detailed Implementation

[0025] The embodiments of the present invention will be described in detail below with reference to the examples. The following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.

[0026] In the following examples and comparative examples, the two-component liquid silicone rubber is model D70, purchased from Hubei Xingrui Silicon Materials Co., Ltd.; the silica sol is ZJN reinforced series silica sol with an average particle size of 7-10nm, purchased from Shandong Kehan ​​Silicon Source New Materials Co., Ltd.; and the hydrogen-containing silicone oil is model DTH-080t-30 (hydrogen content of 0.75%), purchased from Jiangxi Haiduo Organosilicon Materials Co., Ltd.

[0027] This invention uses a self-made vinylsilane oligomer to modify the surface of a halogen-free flame retardant. The preparation method of the self-made vinylsilane oligomer is as follows: Vinyltrimethoxysilane (VTMS) and γ-aminopropyltriethoxysilane (APTES) in a mass ratio of 4:1 are mixed in an ethanol solvent. A hydrolysis reaction is carried out by slowly adding water dropwise in an acidic catalyst (pH=4~5) at room temperature. After the reaction is completed, the temperature is raised to 50~60℃ for reflux condensation reaction. The reaction time is controlled (about 4~8h) until the molecular weight increases to the range of 1000~3000. The reaction is then terminated. The reaction solution is neutralized and the solvent and by-products are removed by vacuum distillation to obtain the self-made vinylsilane oligomer.

[0028] Example 1: A method for preparing high-temperature resistant and flame-retardant silicone leather includes the following steps: S1. Add component A, 8g of hydrogen-containing silicone oil, 2g of 1-ethynylcyclohexanol and 50g of modified aluminum hydroxide from 100g of two-component addition-curing liquid silicone to a vacuum planetary mixer and mix for 30min at a speed of 700rpm and a vacuum degree of -0.09MPa to obtain a uniform and fine flame-retardant slurry. S2. Add 100g of component B of the two-component addition-type liquid silicone, 1g of platinum catalyst (3000ppm), 4g of color paste, and 12g of vinyl silicone resin (vinyl content of 5%) to the above flame retardant slurry. Continue stirring under vacuum for 15min to fully mix and degas the mixture. S3. Coat the above mixture onto release paper. The first layer of adhesive is 150 μm thick. After curing at 130°C for 5 min, coat the second layer with a thickness of 150 μm. Lay the high-density fiberglass cloth on the second layer, compact it, and then cure it at 130°C for 5 min. Finally, peel it off from the release paper to obtain the high-temperature resistant and flame-retardant silicone leather.

[0029] The modified aluminum hydroxide is prepared by the following method: (1) Inorganic coating: First, 100g of aluminum hydroxide (particle size 3μm) powder is dispersed in deionized water at a solid-liquid ratio of 1:10. The temperature is raised to 50℃, and the pH is adjusted to 9 with ammonia. Then, 20g of silica sol (SiO2 content 30%) is slowly added under stirring and reacted for 2h, so that the nano SiO2 particles are adsorbed on the surface of the powder through electrostatic action. After the reaction is completed, the mixture is allowed to stand for 1.5h, the reaction solution is filtered, washed with deionized water until neutral, and finally dried at 100℃ for 3h to obtain silica sol coated aluminum hydroxide intermediate; (2) Organic modification: 80g of the above silica sol coated intermediate powder is mixed with 100mL of anhydrous ethanol solution containing 4g of self-made vinyl silane oligomer. The mixture is refluxed in a 70℃ water bath for 2h. After the reaction is completed, the ethanol is removed by rotary evaporation and then vacuum dried at 80℃ for 4h. After removal, it is lightly ground to obtain white powdered modified aluminum hydroxide.

[0030] Example 2: High-temperature resistant and flame-retardant silicone leather was prepared using the method in Example 1, with the difference being: The modified magnesium hydroxide was prepared by the following method: (1) Inorganic coating: 100g of magnesium hydroxide (particle size 2μm) was dispersed in 1000mL of deionized water, heated to 50℃, and the pH was adjusted to 9 with ammonia water; 20g of silica sol (SiO2 content 30%) was slowly added under stirring and reacted for 2h, so that the nano SiO2 particles were adsorbed on the powder surface by electrostatic action; after the reaction was completed, it was allowed to stand for 1.5h, the reaction solution was filtered, washed with deionized water until neutral, and finally dried at 100℃ for 3h to obtain silica sol coated magnesium hydroxide intermediate; (2) Organic modification: 80g of the above silica sol coated intermediate powder was mixed with 100mL of anhydrous ethanol solution containing 4g of self-made vinyl silane oligomer, and refluxed in a 70℃ water bath for 2h. After the reaction was completed, the ethanol was removed by rotary evaporation, and then vacuum dried at 80℃ for 4h. After taking it out, it was lightly ground to obtain white powdered modified magnesium hydroxide.

[0031] Example 3: A method for preparing high-temperature resistant and flame-retardant silicone leather includes the following steps: S1. Add component A, 8g of hydrogen-containing silicone oil, 2g of 1-ethynylcyclohexanol and 60g of modified aluminum hydroxide from 100g of two-component addition-curing liquid silicone to a vacuum planetary mixer and mix for 30min at a speed of 700rpm and a vacuum degree of -0.09MPa to obtain a uniform and fine flame-retardant slurry. S2. Add 100g of component B of the two-component addition-type liquid silicone, 1g of platinum catalyst (3000ppm), 4g of color paste, and 12g of vinyl silicone resin (vinyl content of 5%) to the above flame retardant slurry. Continue stirring under vacuum for 15min to fully mix and degas the mixture. S3. Coat the above mixture onto release paper. The first layer of adhesive is 150 μm thick. After curing at 130°C for 5 min, coat the second layer with a thickness of 150 μm. Lay the high-density fiberglass cloth on the second layer, compact it, and then cure it at 130°C for 5 min. Finally, peel it off from the release paper to obtain the high-temperature resistant and flame-retardant silicone leather.

[0032] The preparation method of the modified aluminum hydroxide is the same as that in Example 1.

[0033] Example 4: High-temperature resistant flame-retardant organosilicon leather was prepared using the method of Example 1, with the difference being that in the preparation of the modified aluminum hydroxide, the reaction temperature in step (1) was 60°C and the reaction time was 3h; the reaction temperature in step (2) was 80°C and the reaction time was 3h.

[0034] Comparative Example 1: The method of Example 1 was used to prepare high-temperature resistant and flame-retardant organosilicon leather, except that in the preparation of modified aluminum hydroxide, the amount of modified aluminum hydroxide added in step S1 was 70g.

[0035] Comparative Example 2: The method of Example 1 was used to prepare high-temperature resistant and flame-retardant organosilicon leather, the difference being that in the preparation of the modified aluminum hydroxide, the amount of silica sol added in step (1) was 10g.

[0036] Comparative Example 3: The method of Example 1 was used to prepare high-temperature resistant and flame-retardant organosilicon leather, the difference being that in the preparation of the modified aluminum hydroxide, in step (2), the amount of self-made vinyl silane oligomer added was 2g.

[0037] Comparative Example 4: The method of Example 1 was used to prepare high-temperature resistant and flame-retardant organosilicon leather, the difference being that in the preparation of the modified aluminum hydroxide, in step (2), the amount of self-made vinyl silane oligomer added was 8g.

[0038] Comparative Example 5: High-temperature resistant and flame-retardant silicone leather was prepared using the method of Example 1, except that no flame retardant was added in step S1.

[0039] Comparative Example 6: High-temperature resistant and flame-retardant silicone leather was prepared using the method of Example 1, except that in step S1, 50g of unmodified aluminum hydroxide was added, and the pretreatment was simply drying at 100°C for 3 hours.

[0040] Comparative Example 7: High-temperature resistant and flame-retardant silicone leather was prepared using the method of Example 1, with the difference being that in step S1, aluminum hydroxide modified only with KH-550 silane coupling agent was added. The pretreatment was as follows: 50g of aluminum hydroxide was dispersed in ethanol, 2g of KH-550 was added, and the mixture was refluxed at 80°C for 2 hours and then dried.

[0041] Comparative Example 8: High-temperature resistant and flame-retardant organosilicon leather was prepared using the method of Example 1, the difference being that the modified aluminum hydroxide was only organically modified.

[0042] Comparative Example 9: High-temperature resistant and flame-retardant organosilicon leather was prepared using the method of Example 1, the difference being that the modified aluminum hydroxide was only inorganically coated.

[0043] Performance Testing and Results Analysis The high-temperature resistant and flame-retardant silicone leathers obtained in the above embodiments and comparative examples were subjected to performance tests, and the test methods are as follows: (1) Flame retardant performance: tested according to UL~94 vertical burning method; (2) Mechanical properties: tensile strength and elongation at break were tested according to ASTM D412 standard; (3) Feel evaluation: Blind evaluation by 5 professionals (1~10 points, average value); The test results are shown in Table 1.

[0044] Table 1 Comparison of Performance Test Results

[0045] As shown in Table 1, Examples 1-4 exhibit excellent overall performance: a flame retardant rating of UL-94 V0, tensile strength exceeding 8.0 MPa, and elongation at break reaching a maximum of 500%, demonstrating good flexibility and tensile strength. Simultaneously, their feel score remains consistently between 7-8 points, superior to most comparative examples (6-7 points). Among them, Example 2 demonstrates the most outstanding overall performance, indicating the significant advantages of the dual surface modification method of inorganic coating and organic repair employed in this invention. This is because: the inorganic reinforcing layer constructed by forming a SiO2 coating layer on the aluminum hydroxide surface using silica sol not only improves the thermal stability and dispersibility of the filler but also provides a good foundation for subsequent organic functionalization; furthermore, the chemical bonding between the self-made vinylsilane oligomer and the organosilicon matrix crosslinking network effectively enhances the interfacial compatibility between the filler and the matrix, thereby synergistically improving the mechanical strength and toughness of the material.

[0046] The tensile strength of Comparative Examples 1-4 was significantly reduced. In particular, although Comparative Example 4 increased the amount of organic modification, excessive use caused over-crosslinking or compatibility issues, resulting in brittle material with a tensile strength of only 8.1 MPa and an elongation at break of only 380%. This indicates that the amount of organic modification needs to be controlled appropriately to ensure interfacial compatibility and mechanical balance.

[0047] Examples 1-2, while ensuring flame retardancy and mechanical properties, achieved a hand feel score comparable to Comparative Example 5 (without flame retardant) and superior to Comparative Examples 6-9. Comparative Example 5 (without flame retardant) had the highest tensile strength (12.2 MPa), but its flame retardancy was only at level V2, posing a safety hazard and limiting its practical application. This indicates that a coordinated optimization is needed between high-temperature flame retardancy and mechanical properties. Comparative Examples 6 (using unmodified aluminum hydroxide), 7 (modified only with KH-550 silane coupling agent), 8 (organic modification only), and 9 (inorganic coating only) only reached level V1, and their hand feel scores were low, indicating that a single modification method is insufficient to simultaneously achieve dispersibility, interfacial bonding, and tactile comfort. This demonstrates that the two-step synergistic modification method of inorganic coating and organic modification used in this invention is necessary to achieve uniform distribution and firm anchoring of the flame retardant in the organosilicon matrix, thereby comprehensively improving the overall performance of the material.

[0048] In summary, this invention successfully produced high-temperature resistant silicone leather with high flame retardancy (UL-94 V0), excellent mechanical properties (tensile strength > 8.0 MPa, elongation at break of approximately 500%), and a good feel (score of 7-8 points) by using self-made vinyl silane oligomers to modify the surface of flame retardants and combining them with optimized preparation processes. This provides reliable technical support for the engineering application of high-end environmentally friendly flame retardant materials.

[0049] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A high-temperature resistant and flame-retardant silicone leather, characterized in that: The product comprises a base fabric layer and an organosilicon coating laminated on the base fabric layer. The organosilicon coating contains the following components: a two-component addition-type liquid silicone, a hydrogen-containing silicone oil, an inhibitor, a halogen-free flame retardant, and a catalyst. The halogen-free flame retardant is at least one of aluminum hydroxide, magnesium hydroxide, mica powder, hindered amine intercalated modified zirconium hydrogen phosphate, attapulgite, and organomontmorillonite, with a particle size of 1-5 μm. The amount of the halogen-free flame retardant added is 30%-60% of the mass of component A in the two-component addition-type liquid silicone.

2. The high-temperature resistant and flame-retardant silicone leather according to claim 1, characterized in that: The halogen-free flame retardant was obtained through a two-step surface modification process, as follows: (1) After reacting silica sol with an aqueous solution of halogen-free flame retardant, a silica sol-coated flame retardant intermediate is obtained. (2) The above intermediate was stirred and reacted with an anhydrous ethanol solution of vinyl silane oligomer to obtain a surface-modified halogen-free flame retardant.

3. The high-temperature resistant and flame-retardant silicone leather according to claim 2, characterized in that: The reaction temperature in step (1) is 40-60℃ and the reaction time is 1-3h.

4. The high-temperature resistant and flame-retardant silicone leather according to claim 2, characterized in that: The reaction temperature in step (2) is 60-80℃ and the reaction time is 1-3h.

5. The high-temperature resistant and flame-retardant silicone leather according to claim 2, characterized in that: The vinyl silane oligomer is prepared by hydrolysis and condensation of vinyltrimethoxysilane and γ-aminopropyltriethoxysilane in a mass ratio of 3-5:

1.

6. The high-temperature resistant and flame-retardant silicone leather according to claim 5, characterized in that: The vinyl silane oligomer has a number average molecular weight of 1000-3000, a vinyl content of 5%-8%, and a viscosity of 1000-2000 mPa·s.

7. The high-temperature resistant and flame-retardant silicone leather according to claim 1, characterized in that: The base fabric layer is a high-density fiberglass cloth that has been treated with an acrylic emulsion containing flame retardants.

8. A method for preparing a high-temperature resistant and flame-retardant silicone leather according to any one of claims 1 to 7, characterized in that: Includes the following steps: S1. Mix component A of the two-component addition-curing liquid silicone with a halogen-free flame retardant under vacuum conditions to obtain a flame-retardant slurry. S2. Mix the flame retardant paste with component B and additives in the two-component addition-curing liquid silicone to obtain a mixture. S3. The mixture is coated onto release paper in two layers. After the first layer is heated and cured, the second layer is coated and then bonded to high-density fiberglass cloth and heated and cured again. Finally, it is peeled off from the release paper to obtain the high-temperature resistant and flame-retardant silicone leather.

9. The method for preparing a high-temperature resistant and flame-retardant silicone leather according to claim 8, characterized in that: The vacuum degree in step S1 is -0.08 to 0.1 MPa; the stirring speed is 500 to 1000 rpm; and the stirring time is 20 to 40 min. The stirring time in step S2 is 10 to 20 min.

10. The method for preparing a high-temperature resistant and flame-retardant silicone leather according to claim 8, characterized in that: In step S2, the thickness of the first adhesive layer is 100-150μm, and the thickness of the second adhesive layer is 120-150μm.

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