Silicon-based synthetic leather and preparation method thereof

Abstract

The invention discloses silicon-based synthetic leather and a preparation method thereof. The synthetic leather comprises base cloth, a silicone rubber layer and a surface treatment layer, wherein the surface treatment layer comprises vinyl-terminated polysiloxane, hydrogen-containing polysiloxane, a reaction inhibitor, a platinum catalyst, silicon dioxide microspheres, hyperbranched vinyl polyurethane and cyclic siloxane; the molar ratio of vinyl in the vinyl-terminated polysiloxane to silicon hydrogen in the vinyl-terminated polysiloxane is 1: (1.05-1.12), and the hyperbranched vinyl polyurethane is prepared by carrying out condensation polymerization on polyol acrylate and isocyanate in the presence of a catalyst and then carrying out end-capping reaction with a vinyl end-capping agent. The formula of the surface treatment layer is optimized, the molar ratio of vinyl to silicon hydrogen is 1: (1.05-1.12), dense vinyl of hyperbranched vinyl polyurethane (HVPUA) reacts with residual Si-H, interface bonding is enhanced by combining amino silane grafting, and silicone oil precipitation is reduced synergistically.

Description

Technical Field

[0001] The present application relates to the field of synthetic leather, and in particular to a silicon-based synthetic leather and a preparation method thereof. Background Art

[0002] Silicone-based synthetic leather is a new type of environmentally friendly material. In recent years, it has been widely used in the fields of automotive interior, furniture decoration, clothing, shoes and hats. Compared with traditional polyurethane synthetic leather, silicone-based synthetic leather has excellent weather resistance, heat resistance, chemical corrosion resistance and good biocompatibility. At the same time, no organic solvents are used in its production process, which is in line with the development trend of green environmental protection.

[0003] The performance advantages of silicone-based synthetic leather mainly come from its unique structure, which is usually composed of a silicone rubber layer, a base fabric layer and a surface treatment layer. The surface treatment layer is a key functional layer that directly affects the mechanical properties and durability of the product. At present, the surface treatment layer of silicone-based synthetic leather is mainly prepared by addition reaction, that is, vinyl polysiloxane and hydrogen-containing polysiloxane are cross-linked under the action of platinum catalyst to form a three-dimensional network structure. However, in the actual production process, due to incomplete reaction or improper formula design, a certain amount of unreacted silicone oil (including vinyl polysiloxane and / or hydrogen-containing polysiloxane) often remains in the system. These residual silicone oils gradually precipitate onto the surface of the product during subsequent use, which not only affects the appearance quality, but also causes problems such as surface stickiness and easy adsorption of dust, affecting the service life and application range of the product. Summary of the invention

[0004] The present application provides a silicon-based synthetic leather and a preparation method thereof, which controls the Si-H / Si-Vi ratio in the leather surface treatment coating system and coordinates the reaction and consumption of residual silicone oil by hyperbranched vinyl polyurethane, thereby effectively reducing the silicone oil precipitation problem on the surface of the silicon-based synthetic leather and enhancing its wear resistance.

[0005] In a first aspect, the present application provides a silicon-based synthetic leather, comprising a base fabric, a silicone rubber layer and a surface treatment layer, wherein the raw materials of the surface treatment layer comprise the following components in parts by weight:

[0006] 20-70 parts of vinyl-terminated polysiloxane, 5-30 parts of hydrogen-containing polysiloxane, 0.5-3 parts of reaction inhibitor, 0.1-1 parts of platinum catalyst, 10-80 parts of silica microbeads, 10-20 parts of hyperbranched vinyl polyurethane and 5-100 parts of cyclic siloxane; the molar ratio of vinyl in the vinyl-terminated polysiloxane to silicon hydrogen in the hydrogen-containing polysiloxane is 1:1.05-1.12; the hyperbranched vinyl polyurethane is prepared by polycondensing polyol acrylate and isocyanate in the presence of a catalyst to obtain an intermediate, and then performing an end-capping reaction with a vinyl end-capping agent; the weight ratio of the polyol acrylate, isocyanate and vinyl end-capping agent is 40-70:25-40:5-15.

[0007] In any of the above technical solutions, the hydroxyl functional group content of the polyol acrylate is greater than or equal to 3.

[0008] In any of the above technical solutions, the polyol acrylate is selected from at least one of pentaerythritol triacrylate, dipentaerythritol hexaacrylate or trimethylolpropane triacrylate.

[0009] In any of the above technical solutions, the end-capping agent includes one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate.

[0010] In any of the above technical solutions, the isocyanate is selected from at least one of isophorone diisocyanate and hexamethylene diisocyanate.

[0011] In any of the above technical solutions, the catalyst is an organic tin catalyst.

[0012] Exemplarily, the organotin catalyst is dibutyltin dilaurate and / or stannous octoate.

[0013] This application uses excess Si-H (5-12%) to compensate for the side reaction loss of Si-H during the reaction process, ensuring complete reaction of the vinyl group and reducing the unreacted Si-Vi residue. Furthermore, the dense vinyl groups in the hyperbranched vinyl polyurethane (HVPUA) react with the residual Si-H to form a stable Si-C bond, thereby reducing the migration and precipitation of hydrogen-containing polysiloxanes. Moreover, the urethane bond (-NHCOO-) of HVPUA and the Si-O-Si network of the silicone rubber layer enhance the interfacial bonding force through hydrogen bonds and physical entanglement, which helps to improve the compactness of the three-dimensional cross-linked network of the silicone rubber in the surface treatment layer and effectively inhibit the migration and precipitation of residual silicone oil. In addition, the hyperbranched topological structure of HVPUA can disperse stress and improve the wear resistance of the surface coating.

[0014] This application uses high-functionality polyol acrylates to react with isocyanates to generate hyperbranched structures with high crosslink density, which can provide high-density Si-Vi groups and help improve the reaction efficiency of consuming residual Si-H. It should be noted that the role of its vinyl end-capping agent is to introduce vinyl groups at the end of the prepolymer, and its reaction activity is higher than other vinyl groups, which helps to consume residual hydrogen-containing polysiloxane. More importantly, the end-capping agent can regulate the molecular weight of the prepolymer to ensure that the prepolymer and the silicon polymer form a good interface bond.

[0015] Exemplarily, the reaction inhibitor is selected from one or more of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 1,1,3,3-tetramethyl-1,3-divinylsiloxane, 3-methyl-1-butyn-3-ol, 1-ethynylcyclohexanol, 3-phenyl-1-butyn-3-ol, 3-propyl-1-butyn-3-ol and 3-octyl-1-butyn-3-ol.

[0016] Exemplarily, the platinum catalyst is one or more of an alcohol solution of chloroplatinic acid, a platinum catalyst coordinated with tetrahydrofuran, and a platinum catalyst coordinated with divinyltetramethylsiloxane.

[0017] Exemplarily, the cyclic siloxane is selected from cyclotetrasiloxane and / or cyclopentasiloxane.

[0018] In any of the above technical solutions, the average particle size of the silica microbeads is 1 to 20 μm.

[0019] In the technical solution of the present application, other additives such as dispersants, fillers, antioxidants, and ultraviolet absorbers may be added to the surface treatment agent as needed.

[0020] For example, the surface treatment agent may be added with an organic phosphate compound, an aliphatic organic metal salt, or hydrotalcite to improve the dispersibility of the surface treatment agent and significantly enhance the surface adsorption efficiency.

[0021] In any of the above technical solutions, the surface of the hyperbranched vinyl polyurethane is grafted with an aminosilane coupling agent, and the grafting modification method is as follows:

[0022] Dissolve the aminosilane coupling agent in anhydrous ethanol, add deionized water and adjust the pH to 4-5, stir and hydrolyze to obtain a hydrolyzate;

[0023] Disperse the dried hyperbranched vinyl polyurethane powder in anhydrous ethanol, slowly drop the hydrolyzate, add the aminosilane coupling agent in an amount of 1-3% of the weight of the hyperbranched vinyl polyurethane, stir to react, cool to room temperature after the reaction is completed, adjust the pH to 7-8, separate the precipitate, wash and dry to obtain.

[0024] In any of the above technical solutions, the molar ratio of the aminosilane coupling agent to deionized water is 1:2-3.

[0025] The urethane bond of HVPUA and the Si-O-Si chain of silicone rubber have phase separation due to polarity differences, forming interface defects, resulting in a decrease in the peel strength between the surface treatment layer and the silicone rubber layer. HVPUA is surface treated with γ-aminopropyltriethoxysilane to graft -Si(OEt)3 at its end, which can form a chemical bond with silicone rubber to restore its peel strength and wear resistance.

[0026] Exemplarily, the aminosilane coupling agent is selected from at least one of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0027] In any of the above technical solutions, the viscosity of the vinyl-terminated polysiloxane is 5000 to 20000 mPa·s.

[0028] In any of the above technical solutions, the hydrogen-containing polysiloxane comprises terminal hydrogen-containing polysiloxane and side hydrogen-containing polysiloxane in a weight ratio of 2 to 3:1, the terminal hydrogen-containing polysiloxane has 2 hydrogen atoms bonded to silicon; the side hydrogen-containing polysiloxane has at least 3 hydrogen atoms bonded to silicon.

[0029] In any of the above technical solutions, the viscosity of the hydrogen-terminated polysiloxane is 10 to 100 mPa·s, and the hydrogen content is 0.1% to 0.5%.

[0030] Preferably, the viscosity of the side hydrogenated polysiloxane is 20 to 500 mPa·s, and the hydrogen content is 0.1% to 1.0%.

[0031] The hyperbranched structure and high crosslinking density of HVPUA may lead to increased rigidity of the coating, dense crosslinking points, restricted movement of molecular segments, and reduced elongation at break. The two Si-H groups contained in the end hydrogen polysiloxane are end groups, which dominate the linear chain extension effect, provide flexibility and elongation; the at least three Si-H groups contained in the side hydrogen polysiloxane can introduce branch crosslinking points in the measurement, form a three-dimensional crosslinking network, and improve the hardness of the coating. By using the above-mentioned ratio of hydrogen polysiloxane, it is helpful to achieve a balance between the hardness and toughness of the coating and ensure its wear resistance.

[0032] The hydrogen-terminated polysiloxane has three hydrogen atoms bonded to silicon and has the structural formula shown below.

[0033]

[0034] Exemplarily, the pendant hydrogen-containing polysiloxane has three hydrogen atoms bonded to silicon, and its structural formula is shown below.

[0035]

[0036] In a second aspect, the present application provides a method for preparing silicon-based synthetic leather, characterized in that it comprises the following steps:

[0037] According to any of the above raw material ratios, vinyl-terminated polysiloxane, hydrogen-containing polysiloxane, platinum catalyst, reaction inhibitor, silica microbeads, hyperbranched vinyl polyurethane, and cyclic siloxane are mixed and evenly dispersed to obtain a surface treatment agent;

[0038] A surface treatment agent is applied on the release paper with the embossed pattern to form a surface treatment layer with a thickness of 3 to 30 microns;

[0039] The silicone rubber is made into a film and coated on a base fabric to form a base fabric with a silicone rubber layer;

[0040] The surface treatment layer is laminated to the base fabric with silicone rubber coating, and then the laminated organic silicone leather is cured.

[0041] In any of the above technical solutions, the coating is carried out by spraying, roller coating, knife coating, plasma coating, etc.

[0042] In any of the above technical solutions, the base fabric includes but is not limited to woven fabric, knitted fabric, and non-woven fabric, and the fiber type of the fabric is selected from natural fiber, synthetic fiber or regenerated fiber.

[0043] In summary, this application has the following beneficial effects:

[0044] This application optimizes the surface treatment layer formula, adopts a vinyl / silicon hydrogen molar ratio of 1:1.05-1.12, utilizes the dense vinyl of hyperbranched vinyl polyurethane (HVPUA) to react with residual Si-H, and combines aminosilane grafting to enhance interfacial bonding, thereby synergistically reducing silicone oil precipitation. The compounding of silica microbeads and hydrogen-containing polysiloxane improves wear resistance, and the ratio of end / side hydrogen-containing polysiloxane is regulated to balance hardness and toughness. HVPUA is prepared by polycondensation of polyol acrylate and isocyanate and then end-capping the vinyl group. Its hyperbranched structure disperses stress and improves the wear resistance of the coating. The final product has a silicone oil precipitation amount of ≤0.8%, and abrasion resistance times ≥6.0×10 3 Second, the elongation at break is ≥180%, which is suitable for high durability scenarios. DETAILED DESCRIPTION

[0045] Preparation Example 1, a hyperbranched vinyl polyurethane, is prepared according to the following steps:

[0046] Preparation of HVPUA: 60g of pentaerythritol triacrylate and 35g of isophorone diisocyanate were added to a reactor, heated to 70°C under nitrogen protection, 0.5g of dibutyltin dilaurate was added, and stirred for reaction for 3 hours. The temperature was lowered to 50°C, 10g of hydroxyethyl acrylate was added, and the reaction continued for 2 hours. The product was precipitated with ethanol and vacuum dried to obtain hyperbranched vinyl polyurethane (HVPUA) powder.

[0047] Aminosilane modification: Mix 10g of γ-aminopropyltriethoxysilane with 100mL of ethanol, add 3.6mL of deionized water, add acetic acid to adjust the pH to 5, place the mixture in a 40°C water bath, and react for 2 hours with magnetic stirring (300rpm) to obtain a hydrolyzate. Disperse 10g of HVPUA powder in 200mL of ethanol, and ultrasonically disperse for 30 minutes to obtain a HVPUA dispersion. Slowly drop the hydrolyzate into the HVPUA dispersion (the amount of γ-aminopropyltriethoxysilane added is 2% of the weight of HVPUA). Control the reaction temperature at 60°C, stir continuously at 500rpm for 5 hours, cool to room temperature, add ammonia water to adjust the pH to 7-8, and terminate the reaction.

[0048] Preparation Example 2, a hyperbranched vinyl polyurethane, is prepared according to the following steps:

[0049] Preparation of HVPUA: 45g of dipentaerythritol hexaacrylate and 35g of hexamethylene diisocyanate were added to the reactor, heated to 70°C under nitrogen protection, 0.3g of stannous octoate was added, and stirred for reaction for 2 hours. The temperature was lowered to 50°C, 12g of hydroxyethyl methacrylate was added, and the reaction continued for 1.5 hours. The product was precipitated with ethanol and vacuum dried to obtain hyperbranched vinyl polyurethane powder.

[0050] Aminosilane modification: Mix 10g of γ-aminopropyltriethoxysilane with 100mL of ethanol, add 3.6mL of deionized water, add acetic acid to adjust the pH to 4, place the mixture in a 40°C water bath, and react for 2 hours with magnetic stirring (300rpm) to obtain a hydrolyzate. Disperse 10g of HVPUA powder in 200mL of ethanol, and ultrasonically disperse for 30 minutes to obtain a HVPUA dispersion. Slowly drop the hydrolyzate into the HVPUA dispersion (the amount of γ-aminopropyltriethoxysilane added is 1% of the weight of HVPUA). Control the reaction temperature at 60°C, stir continuously at 500rpm for 5 hours, cool to room temperature, add ammonia water to adjust the pH to 7-8, and terminate the reaction.

[0051] Preparation Example 3, a hyperbranched vinyl polyurethane, prepared according to the following steps:

[0052] Preparation of HVPUA: 70g of trimethylolpropane triacrylate and 40g of hexamethylene diisocyanate were added to the reactor, heated to 70°C under nitrogen protection, 0.8g of hydroxybutyl acrylate was added, and stirred for 4 hours. The temperature was lowered to 50°C, 15g of hydroxybutyl acrylate was added, and the reaction was continued for 2 hours. The product was precipitated with ethanol and vacuum dried to obtain hyperbranched vinyl polyurethane powder.

[0053] Aminosilane modification: Mix 10g of γ-aminopropyltriethoxysilane with 100mL of ethanol, add 3.6mL of deionized water, add acetic acid to adjust the pH to 4, place the mixture in a 40℃ water bath, and react for 2 hours with magnetic stirring (300rpm) to obtain a hydrolyzate. Disperse 10g of HVPUA powder in 200mL of ethanol, and ultrasonically disperse for 30 minutes to obtain a HVPUA dispersion. Slowly drop the hydrolyzate into the HVPUA dispersion (the amount of γ-aminopropyltriethoxysilane added is 3% of the weight of HVPUA). Control the reaction temperature at 60℃, stir continuously at 500rpm for 5 hours, cool to room temperature, add ammonia water to adjust the pH to 7-8, and terminate the reaction.

[0054] Preparation Example 4, a hyperbranched vinyl polyurethane, is different from Preparation Example 1 in that aminosilane modification is not performed after the hyperbranched vinyl polyurethane powder is obtained.

[0055] Preparation Example 5, a hyperbranched vinyl polyurethane, is different from Preparation Example 1 in that, in the HVPUA preparation step, an equal amount of polyether diol (Mn=400) is used to replace trimethylolpropane triacrylate.

[0056] Preparation Example 6, a hyperbranched vinyl polyurethane, differs from Preparation Example 1 in that no end-capping agent is added in the HVPUA preparation step, specifically as follows: 60 g of pentaerythritol triacrylate and 35 g of isophorone diisocyanate are added to a reaction kettle, the temperature is raised to 70° C. under nitrogen protection, 0.5 g of dibutyltin dilaurate is added, and the reaction is stirred for 4 hours. The product is precipitated with ethanol and vacuum dried to obtain a hyperbranched vinyl polyurethane (HVPUA) powder.

[0057] Example

[0058] Example 1, a silicone synthetic leather, is prepared according to the following steps:

[0059] Take 50kg of vinyl-terminated polysiloxane (12000mPa·s, vinyl content 1.8mol / kg), 10kg of terminal hydrogen-containing polysiloxane (viscosity 80mPa·s, hydrogen content 0.2wt%), 8kg of side hydrogen-containing polysiloxane (having two hydrogens at both ends and one side hydrogen, viscosity 300mPa·s, hydrogen content 0.35wt%), 0.5kg of platinum catalyst, 2kg of reaction inhibitor (tetramethyltetravinylcyclotetrasiloxane), 60kg of silica microbeads (average particle size 10μm), 15kg of hyperbranched vinyl polyurethane of Preparation Example 1, 40kg of cyclopentasiloxane, 1kg of monoalkyl phosphate, and 1kg of calcium stearate, add a planetary mixer (vacuum degree -0.09MPa), mix at 500rpm for 20 minutes, and obtain a surface treatment agent. Wherein, the molar ratio of vinyl in the vinyl-terminated polysiloxane to silicon hydrogen in the vinyl-terminated polysiloxane is 1:1.09.

[0060] The surface treatment agent was coated on the embossed release paper (pattern depth 20 μm) using a micro-gravure coater, with a wet film thickness of 20 μm. The paper was pre-baked at 90° C. for 1 minute to evaporate the solvent, thereby obtaining a surface treatment layer.

[0061] Liquid silicone rubber (Wacker LR 3003 / 50) is formed into a film (thickness 0.5mm) by a calender and bonded to a polyester base fabric (weight 200g / m 2 ). In a continuous hot press, the surface treatment layer and the silicone rubber base cloth are laminated at 140°C and 1 MPa pressure for 5 minutes.

[0062] Example 2, a silicone synthetic leather, is prepared according to the following steps:

[0063] Take 20kg of vinyl-terminated polysiloxane (15000mPa·s, vinyl content 1.2mol / kg), 15kg of terminal hydrogen-containing polysiloxane (viscosity 80mPa·s, hydrogen content 0.18wt%), 5kg of side hydrogen-containing polysiloxane (having two hydrogens at both ends and one side hydrogen, viscosity 300mPa·s, hydrogen content 0.3wt%), 0.3kg of platinum catalyst, 1kg of reaction inhibitor (tetramethyltetravinylcyclotetrasiloxane), 30kg of silica microbeads (average particle size 5μm), 10kg of hyperbranched vinyl polyurethane of Preparation Example 2, 20kg of cyclopentasiloxane, 1kg of monoalkyl phosphate, and 1kg of calcium stearate, add a planetary mixer (vacuum degree -0.09MPa), mix at 500rpm for 20 minutes, and obtain a surface treatment agent. Wherein, the molar ratio of vinyl in the vinyl-terminated polysiloxane to silicon hydrogen in the vinyl-terminated polysiloxane is 1:1.11.

[0064] The surface treatment agent was coated on the embossed release paper (pattern depth 30 μm) using a micro-gravure coater, with a wet film thickness of 30 μm. The paper was pre-baked at 80° C. for 2 minutes to evaporate the solvent, thereby obtaining a surface treatment layer.

[0065] Liquid silicone rubber (Wacker LR 3003 / 50) is formed into a film (thickness 0.5mm) by a calender and bonded to a polyester base fabric (weight 200g / m 2 ). In a continuous hot press, the surface treatment layer and the silicone rubber base cloth are laminated at 150°C and 2MPa pressure for 3 minutes.

[0066] Embodiment 3, a kind of organosilicon synthetic leather is prepared by the following steps:

[0067] Take 70kg of vinyl-terminated polysiloxane (20000mPa·s, vinyl content 2.5mol / kg), 20kg of terminal hydrogen-containing polysiloxane (viscosity 100mPa·s, hydrogen content 0.1wt%), 10kg of side hydrogen-containing polysiloxane (having two hydrogens at both ends and one side hydrogen, viscosity 500mPa·s, hydrogen content 0.25wt%), 0.8kg of platinum catalyst, 3kg of reaction inhibitor (tetramethyltetravinylcyclotetrasiloxane), 80kg of silica microbeads (average particle size 5μm), 20kg of hyperbranched vinyl polyurethane of Preparation Example 3, 90kg of cyclopentasiloxane, 1kg of polyoxyethylene fatty ether phosphate, and 1kg of calcium stearate, add a planetary mixer (vacuum degree -0.09MPa), mix at 500rpm for 20 minutes, and obtain a surface treatment agent. Wherein, the molar ratio of vinyl in the vinyl-terminated polysiloxane to the silicon hydrogen in the vinyl-terminated polysiloxane is 1:1.1.

[0068] The surface treatment agent was coated on the embossed release paper (pattern depth 50 μm) using a micro-gravure coater, with a wet film thickness of 50 μm. The paper was pre-baked at 80° C. for 2 minutes to evaporate the solvent, thereby obtaining a surface treatment layer.

[0069] Liquid silicone rubber (Wacker LR 3003 / 50) is formed into a film (thickness 0.5mm) by a calender and bonded to a polyester base fabric (weight 200g / m 2 ). In a continuous hot press, the surface treatment layer and the silicone rubber base cloth were laminated at 150°C and 0.5MPa pressure for 3 minutes.

[0070] Example 4, a silicone synthetic leather, is different from Example 1 in that the hyperbranched vinyl polyurethane prepared in Example 4 is used to replace the hyperbranched vinyl polyurethane in Example 1 in an equal amount.

[0071] Comparative Example

[0072] Comparative Example 1 is a silicone synthetic leather, which differs from Example 1 in that the raw material ratio and selection of the surface treatment agent are different, as follows:

[0073] 48.6 kg of vinyl-terminated polysiloxane (15000 mPa·s, vinyl content 1.8 mol / kg), 15 kg of terminal hydrogen-containing polysiloxane (viscosity 80 mPa·s, hydrogen content 0.35 wt%), 10 kg of side hydrogen-containing polysiloxane (having two hydrogens at both ends and one side hydrogen, viscosity 300 mPa·s, hydrogen content 0.35 wt%), 0.5 kg of platinum catalyst, 2 kg of reaction inhibitor (tetramethyltetravinylcyclotetrasiloxane), 60 kg of silica microbeads (average particle size 10 μm), 15 kg of hyperbranched vinyl polyurethane of Preparation Example 1, 40 kg of cyclopentasiloxane, 1 kg of monoalkyl phosphate, and 1 kg of calcium stearate. The molar ratio of vinyl groups in the vinyl-terminated polysiloxane to silicon hydrogen groups in the vinyl-terminated polysiloxane is 1:1.

[0074] Comparative Example 2 is a silicone synthetic leather, which is different from Example 1 in that the raw material ratio and selection of the surface treatment agent are different, as follows:

[0075] 50kg of vinyl-terminated polysiloxane (15000mPa·s, vinyl content 1.8mol / kg), 15kg of terminal hydrogen-containing polysiloxane (viscosity 80mPa·s, hydrogen content 0.4wt%), 10kg of side hydrogen-containing polysiloxane (having two hydrogens at both ends and one side hydrogen, viscosity 300mPa·s, hydrogen content 0.45wt%), 0.5kg of platinum catalyst, 2kg of reaction inhibitor (tetramethyltetravinylcyclotetrasiloxane), 60kg of silica microbeads (average particle size 10μm), 15kg of hyperbranched vinyl polyurethane of Preparation Example 1, 40kg of cyclopentasiloxane, 1kg of monoalkyl phosphate, and 1kg of calcium stearate. The molar ratio of vinyl in the vinyl-terminated polysiloxane to silicon hydrogen in the vinyl-terminated polysiloxane is 1:17.

[0076] Comparative Example 3, a silicone synthetic leather, is different from Example 1 in that the hyperbranched vinyl polyurethane of Preparation Example 1 is replaced by an equal amount of the hyperbranched vinyl polyurethane of Preparation Example 5.

[0077] Comparative Example 4 is a silicone synthetic leather, which is different from Example 1 in that the hyperbranched vinyl polyurethane of Preparation Example 1 is replaced by an equal amount of the hyperbranched vinyl polyurethane of Preparation Example 6.

[0078] Performance testing

[0079] 1. Silicone oil precipitation: Cut a 10cm×10cm synthetic leather sample and place it in an 80℃ oven for 72 hours. Wipe the surface precipitate with a dust-free cloth, weigh the precipitate, and calculate the precipitation amount per unit area (mg / cm2 ).

[0080] 2. Abrasion resistance: Tested according to ASTM D4060-2014, using Taber abrasion tester (H18 grinding wheel, 500g load), record the number of cycles (×10 3 Second-rate).

[0081] 3. Mechanical properties: (1) Elongation at break (%) was tested according to ASTM D638-2014, using dumbbell-shaped specimens at a tensile rate of 500 mm / min. (2) Hardness (Shore A) was tested according to ISO7619-1:2004 "Rubber, vulcanized or thermoplastic, test method for indentation hardness - Part 1: Shore durometer method".

[0082] 4. Peel strength: Tested according to ASTM D1876-08, sample size 25mm×150mm, peel rate 100mm / min, record the average peel force (N / cm).

[0083] Table 1. Performance test results

[0084]

[0085]

[0086] Analysis of test results:

[0087] 1. Silicone oil precipitation

[0088] The silicone oil precipitation amount of Examples 1 to 3 is ≤ 0.8 mg / cm 2 , significantly lower than the 1.2-3.2 mg / cm of the comparative example 2 The reason may be that the Si-H / Si-Vi molar ratio is controlled at 1:1.05-1.12, which can ensure the complete reaction of the vinyl group, and the hyperbranched vinyl polyurethane (HVPUA) further consumes the residual hydrogen-containing polysiloxane and reduces the precipitation amount.

[0089] Example 4 uses unmodified HVPUA, and its precipitation amount is slightly higher (0.8 mg / cm 2 ), indicating that aminosilane grafting has an enhancing effect on the interfacial bonding.

[0090] The precipitation amount of comparative examples 1 to 2 was significantly increased (1.2 to 1.5 mg / cm 2 ), the reason is that the Si-H / Si-Vi molar ratio is not controlled to be greater than 1, resulting in a large amount of residual vinyl silicone oil in the surface treatment layer.

[0091] Comparative Examples 3 to 4 have the highest precipitation amount (2.9 to 3.2 mg / cm 2), the reason being that no end-capping agent or vinyl-free polyol was used, resulting in insufficient reactivity of HVPUA.

[0092] 2. Wear resistance

[0093] Examples 1 to 3: abrasion resistance times ≥ 6.7 × 10 3 times, which is better than 3.2-4.5×10 of Comparative Examples 1-4. 3 times. The reason is the synergistic enhancement effect of silica microbeads and HVPUA hyperbranched structure. Among them, Example 3 (high crosslinking density) has the best wear resistance (7.9×10 3 times), but the elongation at break of the surface treated layer decreased slightly (175%).

[0094] 3. Elongation at break and hardness

[0095] Examples 1-2: elongation at break ≥ 190%, hardness 75-79A, indicating that the end / side hydrogen-containing polysiloxane ratio (2-3:1) effectively balances the flexibility and hardness of the coating.

[0096] The molar ratios of Comparative Examples 1 to 2 are 1:1 and 1:1.15 respectively, and the elongation at break of the obtained surface treatment layer is relatively low (150-160%), which is due to the insufficient Si-H resulting in a decrease in the density of the cross-linking network.

[0097] 4. Peel strength

[0098] The peel strength of Examples 1 to 3 is ≥ 4.8 N / cm, which is significantly higher than the 2.5 to 4.0 N / cm of Comparative Examples 1 to 4. The reason is that the aminosilane grafting of HVPUA in Examples 1 to 3 forms a chemical bond (Si-O-Si) with the silicone rubber layer, which significantly improves the interfacial bonding strength. The peel strength of Example 4 (unmodified HVPUA) is reduced to 3.5 N / cm, proving the contribution of the interfacial hydrogen bonds and physical entanglements generated by the modification to the interfacial bonding strength.

[0099] 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 modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A silicon-based synthetic leather, comprising a base fabric, a silicone rubber layer and a surface treatment layer, characterized in that: The raw materials of the surface treatment layer include the following components in parts by weight: 20-70 parts of vinyl-terminated polysiloxane, 5-30 parts of hydrogen-containing polysiloxane, 0.5-3 parts of reaction inhibitor, 0.1-1 parts of platinum catalyst, 10-80 parts of silica microbeads, 10-20 parts of hyperbranched vinyl polyurethane and 5-100 parts of cyclic siloxane; the molar ratio of vinyl in the vinyl-terminated polysiloxane to silicon hydrogen in the hydrogen-containing polysiloxane is 1:1.05-1.12; the hyperbranched vinyl polyurethane is prepared by polycondensing polyol acrylate and isocyanate in the presence of a catalyst to obtain an intermediate, and then performing an end-capping reaction with a vinyl end-capping agent; the weight ratio of the polyol acrylate, isocyanate and vinyl end-capping agent is 40-70:25-40:5-15.

2. The silicon-based synthetic leather according to claim 1, characterized in that: The polyol acrylate has a hydroxyl functional group content of greater than or equal to 3.

3. The silicon-based synthetic leather according to claim 2, characterized in that: The polyol acrylate is selected from at least one of pentaerythritol triacrylate, dipentaerythritol hexaacrylate and trimethylolpropane triacrylate.

4. The silicon-based synthetic leather according to claim 1, characterized in that: The end-capping agent includes one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate.

5. The silicon-based synthetic leather according to claim 1, characterized in that: The isocyanate is selected from isophorone diisocyanate or hexamethylene diisocyanate.

6. The silicon-based synthetic leather according to claim 1, characterized in that: The viscosity of the vinyl-terminated polysiloxane is 5000 to 20000 mPa·s.

7. The silicon-based synthetic leather according to claim 1, characterized in that: The surface of the hyperbranched vinyl polyurethane is grafted with an aminosilane coupling agent, and the grafting modification method is as follows: Dissolve the aminosilane coupling agent in anhydrous ethanol, adjust the pH to 4-5, stir and hydrolyze to obtain a hydrolyzate; Disperse the dried hyperbranched vinyl polyurethane powder in anhydrous ethanol, slowly drop the hydrolyzate, add the aminosilane coupling agent in an amount of 1-3% of the weight of the hyperbranched vinyl polyurethane, stir to react, cool to room temperature after the reaction is completed, adjust the pH to 7-8, separate the precipitate, wash and dry to obtain.

8. The silicon-based synthetic leather according to claim 1, characterized in that: The hydrogen-containing polysiloxane comprises terminal hydrogen-containing polysiloxane and side hydrogen-containing polysiloxane in a weight ratio of 2 to 3:1, wherein the terminal hydrogen-containing polysiloxane has two hydrogen atoms bonded to silicon; and the side hydrogen-containing polysiloxane has at least three hydrogen atoms bonded to silicon.

9. The silicon-based synthetic leather according to claim 8, characterized in that: The viscosity of the terminal hydrogen-containing polysiloxane is 10-100 mPa·s, and the hydrogen content is 0.1%-0.5%; the viscosity of the side hydrogen-containing polysiloxane is 20-500 mPa·s, and the hydrogen content is 0.1%-1.0%.

10. A method for preparing silicon-based synthetic leather, characterized in that: The steps include: According to the raw material ratio described in any one of claims 1 to 9, vinyl-terminated polysiloxane, hydrogen-containing polysiloxane, platinum catalyst, reaction inhibitor, silica microbeads, hyperbranched vinyl polyurethane, and cyclic siloxane are mixed and evenly dispersed to obtain a surface treatment agent; A surface treatment agent is applied on the release paper with the embossed pattern to form a surface treatment layer with a thickness of 3 to 30 microns; The silicone rubber is made into a film and coated on a base fabric to form a base fabric with a silicone rubber layer; The surface treatment layer is laminated to the base fabric with silicone rubber coating, and then the laminated organic silicone leather is cured.

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