A silicone-like touch thermoplastic elastomer composite material and a preparation method thereof

Abstract

The application provides a silicone-like hand feeling thermoplastic elastomer composite material and a preparation method thereof, and belongs to the technical field of materials. The method comprises the following steps: mixing, grinding and preparing an ammonium polyphosphate, melamine and expandable graphite mixture to obtain a flame retardant system; coating the flame retardant system with silica powder through a sol-gel reaction; modifying the silica powder coated with the flame retardant system through composite silane to obtain modified silica powder coated with the flame retardant system; mixing hydrogen-containing siloxane, fluorine-containing silane and the modified silica powder coated with the flame retardant system, adding a catalyst and reacting to obtain a composite crosslinking agent; uniformly mixing polyolefin elastomer, methyl vinyl silicone rubber, aliphatic polyether type thermoplastic polyurethane, silicone powder and the composite crosslinking agent, adding an initiator, carrying out heating and stirring reaction, extruding and granulating to obtain the silicone-like hand feeling thermoplastic elastomer composite material, which has a fine silicone-like hand feeling, high mechanical strength, dirt and weather resistance and high flame retardancy.

Description

Technical Field

[0001] This invention relates to the field of materials technology, specifically to a silicone-like thermoplastic elastomer composite material and its preparation method. Background Technology

[0002] Thermoplastic elastomers (TPEs) have attracted much attention due to their unique reversible phase structure: at room temperature, TPEs exhibit typical rubber elasticity; while at high temperatures, they can achieve plastic flow and processing. Currently, the main raw materials for TPEs are SEBS / SBS. To improve flowability and reduce costs, TPEs are generally oil-extended and have other additives added. Oil extrusion of TPEs results in a sticky surface and easy dust accumulation after long-term use, seriously affecting the user experience. Silicone products coated with silicone feel oil have a delicate, smooth feel and a good velvety texture.

[0003] Traditional TPEs generally rely on white oil filling to reduce hardness and improve flowability, but this results in a sticky surface, easy dust accumulation, and a risk of oil separation with long-term use (e.g., CN116023666B, CN119875388A). Adding low molecular weight amides or silicone slip agents can temporarily improve the feel, but they are prone to migration and precipitation, causing a greasy surface as a consequence.

[0004] In addition, when conventional hydrogen-containing siloxanes are used directly as composite crosslinking agents, the vulcanized silicone rubber has poor compatibility with matrix such as SEBS / PP, resulting in exposed silicone rubber particles, powdering, and decreased mechanical properties and wear resistance (such as CN116023666B, CN114634703A).

[0005] While dynamic vulcanized silicone rubber can provide a silky feel, the high-shear vulcanization process can easily lead to the degradation of the TPU continuous phase, which significantly reduces the tensile strength and tear strength of the material. In applications such as wearable device straps, it is prone to cracking and scrapping (e.g., CN114634703A).

[0006] Ordinary TPE and silicone rubber alloy surfaces are easily contaminated by cooking oil and sweat and are difficult to clean, lacking a long-lasting hydrophobic and oleophobic mechanism (such as CN114634703A).

[0007] High levels of halogen-free flame retardants (such as APP / magnesium hydroxide) have poor compatibility with the TPE matrix, leading to an increase in internal defects in the composite material and a significant decrease in impact toughness and tensile strength (Liu Yangbo et al., "Research Progress on High-Performance Flame Retardant Thermoplastic Elastomers"; Hu Shengli et al., "Multi-component Halogen-Free Flame Retardant Thermoplastic Elastomers").

[0008] Existing technologies mostly focus on improving a single feel or a single mechanical property, lacking a system solution that integrates functions such as silicone-like feel, high mechanical strength, stain and weather resistance, and halogen-free flame retardancy. Summary of the Invention

[0009] The purpose of this invention is to propose a silicone-like thermoplastic elastomer composite material and its preparation method, which solves the problems of existing thermoplastic elastomer composite materials that are difficult to achieve both mechanical properties and flame retardant properties, as well as poor weather resistance and stain resistance, easy powdering and exposure, and poor wear resistance. It enhances the interfacial bonding strength and thermal stability, and has a smooth feel, making it suitable for high-end scenarios such as smart wearables and medical devices that have long-term contact with the skin.

[0010] The technical solution of this invention is implemented as follows:

[0011] This invention provides a method for preparing a silicone-like thermoplastic elastomer composite material, comprising the following steps:

[0012] (1) Ammonium polyphosphate, melamine and expandable graphite are mixed and ground to prepare a flame retardant system;

[0013] (2) Add the flame retardant system to ethanol, add alkyl ester of orthosilicate and water, stir and mix evenly, add ammonia dropwise, stir and react, centrifuge, wash, dry, and obtain silica powder coated with flame retardant system;

[0014] (3) Add the silica powder coated with flame retardant system to ethanol, add composite silane, stir to react, filter, wash, dry, and obtain modified silica powder coated with flame retardant system.

[0015] (4) Mix the hydrogen-containing siloxane, fluorine-containing silane and the silica powder of the modified coating flame retardant system, add the catalyst, heat and stir to react, and obtain the composite crosslinking agent;

[0016] (5) The polyolefin elastomer, methyl vinyl silicone rubber, aliphatic polyether thermoplastic polyurethane, silicone powder and composite crosslinking agent are mixed and vulcanized in a mixer, fed into a twin-screw extruder, an initiator is added, heated and stirred to react, extruded and granulated to obtain a silicone-like thermoplastic elastomer composite material.

[0017] As a further improvement of the present invention, in step (1), the mass ratio of ammonium polyphosphate, melamine, and expandable graphite is 2-4:1-2:1; the particle size of the flame retardant system is 1-10 μm. The present invention selects ammonium polyphosphate (APP), melamine, and expandable graphite as a composite flame retardant system, controlling the particle size of the flame retardant system to 1-10 μm. APP serves as a catalyst for chemical char formation, melamine provides the gas source and nitrogen source carbon layer for foaming expansion, and expandable graphite provides the skeleton and barrier layer for physical expansion. The three components are compounded in a suitable ratio, greatly improving the synergistic flame retardant effect. Grinding the ternary flame retardant system and controlling the particle size to 1-10 μm, larger than silicone rubber particles, avoids agglomeration in the plastic phase. Furthermore, if the particle size is greater than 10 μm, a significant stress concentration effect occurs when the composite material is subjected to tension / tear, leading to deterioration of mechanical properties. The 1-10μm range is within the golden range of micrometers. The particle size matches the polymer chain entanglement size, resulting in uniform dispersion without causing severe stress concentration. This achieves flame retardant function while minimizing damage to mechanical properties.

[0018] As a further improvement of the present invention, in step (2), the mass ratio of the flame retardant system to the alkyl orthosilicate is 3-5:2-3; the alkyl orthosilicate is selected from ethyl orthosilicate or methyl orthosilicate; the ammonia water is added dropwise until the solution pH is 9-10; and the stirring reaction time is 10-15 h. Traditional TPE has poor flame retardancy, and flame retardants damage mechanical properties. A sol-gel reaction is used to construct an in-situ SiO2 inorganic coating layer on the surface of the intumescent flame retardant system, coating APP / melamine / expanded graphite into the core, constructing a core-shell microcapsule structure of inorganic SiO2 shell / expanded flame retardant core. This prevents APP from absorbing moisture and migrating, and avoids catalytic degradation caused by direct contact between highly active flame retardant components and the polymer matrix. After subsequent surface composite silane modification, the compatibility between the silica powder of the inorganic coated flame retardant system and the TPE matrix is ​​improved, which greatly improves the flame retardant performance of the composite material and significantly reduces the negative impact on mechanical properties.

[0019] As a further improvement of the present invention, in step (3), the composite silane includes a long-chain alkyl silane, an isocyanate silane coupling agent, and a silane coupling agent with double bonds, with a mass ratio of 1-3:2-5:3-8. The long-chain alkyl silane is selected from at least one of n-dodecyltriethoxysilane, n-hexyltriethoxysilane, n-octyltrimethoxysilane, n-dodecyltrimethoxysilane, n-hexadecyltrimethoxysilane, and n-hexadecyltriethoxysilane. The isocyanate silane coupling agent is KH907, and the silane coupling agent with double bonds is selected from at least one of KH570, A151, and A171. Preferably, the composite silane includes n-dodecyltriethoxysilane, isocyanate silane coupling agent KH907, and silane coupling agent KH570 with double bonds, with a mass ratio of 2:3:6. This invention employs long-chain alkyl silanes, isocyanate silane coupling agents, and silane coupling agents with double bonds to modify the surface of silica powder coated with flame retardants. By utilizing the reaction of siloxanes with the hydroxyl groups on the silica surface, active groups are introduced, enabling the powder to form a micro-crosslinked network structure with the matrix during melt blending, thereby improving filler dispersibility and interfacial bonding strength. The long-chain alkyl groups provide a hydrophobic compatibilizing effect, interacting with the polyolefin elastomer molecular chains through hydrophobic interactions and chain entanglement, significantly reducing the interfacial tension between the flame retardant powder and the polyolefin, and preventing agglomeration. At melt processing temperatures, the isocyanate groups undergo nucleophilic addition with the NH groups of the urethane bonds in aliphatic polyether TPU, chemically bonding the flame retardant powder to the continuous TPU phase, thus improving the powder's dispersibility in the matrix and enhancing the material's mechanical properties. The double bond provides a polymerizable group that can react with the methacryloyloxy double bond in subsequent steps, undergo hydrosilylation with hydrogen-containing siloxanes, or undergo melt graft copolymerization with peroxide-initiated polyolefin macromolecular free radicals. Thus, it serves as a connecting unit for the silica powder in the modified flame retardant coating system, promoting the compatibility between the matrix and the hydrogen-containing siloxanes and avoiding problems such as precipitation and powder shedding.

[0020] As a further improvement of the present invention, in step (3), the mass ratio of silica powder to composite silane in the flame retardant coating system is 10:0.5-1.5, the temperature of the stirring reaction is 40-50℃, and the time is 2-4h.

[0021] As a further improvement of the present invention, in step (4), the temperature of the heating and stirring reaction is 60-70℃ and the time is 20-40min; the mass ratio of the silica powder in the fluorinated silane and the modified coated flame retardant system is 4-8:14-16; the fluorinated silane is vinyl-terminated polytrifluoropropylmethylsiloxane with a viscosity of 1000-2000 mPa·s; the molar ratio of the silane-hydrogen bond and the double bond in the system of the hydrogen-containing siloxane is n(Si-H):n(C=C)=1:0.3-0.5; and the catalyst accounts for 2-5 ppm of the total mass of the system. The composite crosslinking agent of this invention includes, on the one hand, a reaction involving the hydrosilylation of hydrogen-containing siloxanes and fluorinated silicone oil, whereby fluorinated segments are chemically grafted onto the main chain of the hydrogen-containing siloxane under the catalysis of a catalyst; on the other hand, a reaction involving the double bonds introduced on the surface of the modified powder by KH570, which can also undergo hydrosilylation with the hydrogen-containing siloxane, covalently incorporating the modified silica powder of the flame retardant system into the crosslinking agent molecule to form a composite; by controlling the molar ratio of Si-H to the total double bonds in the system, it is ensured that only a portion of Si-H participates in the reaction, while the remaining Si-H is retained until the dynamic vulcanization stage for crosslinking methyl vinyl silicone rubber. When the composite crosslinking agent of this invention is added to the system, the crosslinking reaction and phase reconstruction are carried out simultaneously. Under the action of catalyst and initiator, hydrosilylation and free radical copolymerization reactions occur. After vulcanization, the silicone rubber microparticles are mixed with the silica powder of the modified flame retardant system. The long-chain alkyl group has similar compatibility with the polyolefin matrix, while the double bond can undergo graft copolymerization with the polyolefin matrix. Its isocyanate can react with the polyurethane part, thereby effectively preventing the rubber particles from agglomerating or falling off from the matrix.

[0022] In addition, by introducing vinyl-terminated polytrifluoropropylmethylsiloxane (fluorinated silicone oil, viscosity 1000–2000 mPa·s), during processing, the terminal vinyl groups react and graft with the TPU or polyolefin matrix, chemically bonding the fluorinated segments to the material surface, significantly reducing the surface energy, and giving it long-lasting hydrophobic, oleophobic, and sweat-resistant properties, avoiding the deterioration of the feel caused by oil adsorption.

[0023] As a further improvement of the present invention, in step (5), the mass ratio of the polyolefin elastomer, methyl vinyl silicone rubber, aliphatic polyether thermoplastic polyurethane, silicone powder, composite crosslinking agent and initiator is 10-20:11-10:40-60:5-10:5-10:0.01-0.02; the polyolefin elastomer is selected from at least one of SEBS, POE and EPDM; the molecular weight of the methyl vinyl silicone rubber is 400,000 to 1,000,000, and the molar fraction of its vinyl group is 0.1-1.0 mol%; the initiator is selected from at least one of di-tert-amyl peroxide, di-tert-butyl peroxide and tert-butyl peroxide benzoate.

[0024] This invention utilizes a polyolefin elastomer and methyl vinyl silicone rubber (MVSR) as a rubber-plastic blend, which is then blended with aliphatic polyether thermoplastic polyurethane (TPU). Dynamic vulcanization and crosslinking are performed in a twin-screw extruder, controlling the crosslinking density and shear strength of the rubber phase. This allows the MVSR to crosslink in situ within the molten plastic phase and be sheared into 1-3 μm particles. The polyolefin elastomer provides a dry feel and elastic recovery, the MVSR provides the delicate, silky feel characteristic of silicone, and the TPU imparts excellent mechanical strength and resistance to yellowing. The invention also incorporates silicone powder (molecular weight 300,000–1,100,000), which is uniformly dispersed within the material to form a low-surface-energy silicon-carbon layer. This reduces the material's modulus and surface friction coefficient, providing a long-lasting dry and smooth feel, and is less prone to precipitation and stickiness.

[0025] As a further improvement of the present invention, in step (5), the temperature of the twin-screw extruder is 180-220℃ and the screw speed is 350-550r / min. In the twin-screw extruder, the free radical crosslinking and grafting system reaction initiated by peroxide, the C-C crosslinking reaction of the silicone rubber phase and the melt grafting of fluorinated segments occur simultaneously. At the same time, the residual Si-H in the composite crosslinking agent undergoes thermal hydrosilylation with the side vinyl groups (or end vinyl groups) on the MVSR molecular chain, modifying the NCO groups of KH907 on the surface of the silica powder coating flame retardant system. In the molten state, it reacts with the urethane NH of TPU to form urethane bonds, enhancing the interfacial bonding strength and thermal stability. By using appropriate screw speed and reaction temperature, sufficient vulcanization and crosslinking reaction are ensured to achieve uniform dispersion and phase stability of silicone rubber particles.

[0026] This invention further protects a silicone-like thermoplastic elastomer composite material prepared by the above-described preparation method.

[0027] The present invention has the following beneficial effects:

[0028] 1. This invention utilizes the in-situ crosslinking and shearing of methyl vinyl silicone rubber into elastic microparticles under a twin-screw high-shear field, which are uniformly dispersed in a polyolefin / TPU continuous phase. The modulus is much lower than that of plastic, forming a large number of micron-sized elastic protrusions on the material surface. When a finger slides across the surface, the protrusions undergo microscopic elastic deformation and rebound, simulating the delicate touch of fully vulcanized silicone rubber. Simultaneously, silicone powder is added, which physically entangles with the matrix molecular chains in the molten state. After cooling, it forms a three-dimensional internal lubrication network that penetrates the interior of the material, continuously providing a low surface energy siloxane lubricating layer to the surface, reducing the coefficient of friction, and giving a dry and smooth feel. At the same time, the material surface can achieve low hardness and high fluidity without oil filling, and there is no risk of oil separation during long-term use.

[0029] 2. The fluorinated silicone oil of this invention is chemically grafted onto the main chain of a hydrogen siloxane crosslinking agent through a hydrosilylation reaction to form a crosslinking agent with fluorinated side chains. This crosslinks with the material matrix, avoiding the problems of easy migration and continuous loss of fluorinated components to the surface after processing, rapid decay of stain resistance over time, and easy washing off after repeated wiping or soaking in sweat, which leads to deterioration of the tactile feel, as is the case with fluorinated silicone oil introduced only through physical blending.

[0030] 3. This invention employs a sol-gel method to in-situ coat the surface of APP / melamine / expandable graphite with a SiO2 shell, forming a microcapsule structure. This prevents the hygroscopic migration of APP and avoids the catalytic degradation of the polymer matrix by the flame retardant at high temperatures. Through composite silane modification, the flame retardant particles simultaneously possess: hydrophobic compatibility with polyolefins, chemical anchoring with TPU, and reactivity with cross-linking networks. Therefore, the modified silica powder coating the flame retardant system is no longer a simple physical filler, but becomes a reinforcing node of the cross-linking network and chemically improves the mechanical properties of the material.

[0031] 4. This invention achieves multiphase interface composite through multiple chemical reactions, thereby upgrading from traditional physical mixing to chemical bonding, which greatly improves the compatibility between different materials, enhances the wear resistance of composite materials, and ensures that the surface is free of powder and exposed particles, maintaining a complete coating structure even after long-term friction.

[0032] 5. This invention overcomes the problems of traditional single materials by blending composite matrix materials. It achieves molecular-level synergy through dynamic vulcanization and reactive compatibilization. The material simultaneously possesses the dryness of polyolefins, the silkiness of silicone rubber, and the toughness of TPU, making it suitable for high-end scenarios such as smart wearables and medical devices that have long-term contact with the skin. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 The image shows the SEM image of the silica powder coated with flame retardant system obtained in step (2) of Example 1.

[0035] Figure 2 This is a cross-sectional SEM image of the silica powder in the silicone-like thermoplastic elastomer composite material prepared in Example 1. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Ammonium polyphosphate, CF-APP, Shifang Changfeng Chemical; Expandable graphite, EG-X200, Qingdao Yanhai Carbon Materials; Hydrogen-containing siloxane, hydrogen content 1.6%; Vinyl-terminated polytrifluoropropylmethylsiloxane, AFS-R-V2210, Shenzhen Guanheng New Materials; Polyolefin elastomer SEBS, MD6945, Keteng Polymer; Methyl vinyl silicone rubber, 110-3, Hesheng Silicon Industry; Aliphatic polyether thermoplastic polyurethane TPU, A885, Meirui New Materials; Silicone powder, 306, Chengdu Silike;

[0038] Example 1

[0039] This embodiment provides a method for preparing a silicone-like thermoplastic elastomer composite material, including the following steps:

[0040] (1) Mix and grind 2g of ammonium polyphosphate, 1g of melamine and 1g of expandable graphite to obtain a flame retardant system with a particle size of 1-10μm;

[0041] (2) Add 3g of the flame retardant system obtained in step (1) to 100mL of ethanol, add 2g of tetraethyl orthosilicate and 10mL of water, stir and mix for 20min, add ammonia water dropwise until the pH of the solution is 9-10, stir and react for 10h, centrifuge, wash, dry, and obtain silica powder coated with flame retardant system. Figure 1 The image shows the SEM image of the silica powder of the flame retardant coating system. As can be seen from the image, the particle size after coating is between 1 and 15 μm.

[0042] (3) Add 10g of silica powder of the flame retardant system prepared in step (2) to 200mL of ethanol, add 0.5g of composite silane, stir and react at 40℃ for 4h, filter, wash and dry to obtain modified silica powder of the flame retardant system; the composite silane includes n-dodecyltriethoxysilane, isocyanate silane coupling agent KH907 and double bond silane coupling agent KH570, with a mass ratio of 2:3:6;

[0043] (4) Mix hydrogen-containing siloxane, 4g of vinyl-terminated polytrifluoropropylmethylsiloxane and 14g of silica powder of the modified coating flame retardant system prepared in step (3). The molar ratio of the silane-hydrogen bond and the double bond in the system is n(Si-H):n(C=C)=1:0.3. Add platinum catalyst (calculated as platinum, accounting for 2ppm of the total mass of the system), heat to 60℃, stir and react for 40min to obtain the composite crosslinking agent.

[0044] (5) Mix 10g of polyolefin elastomer SEBS, 15g of methyl vinyl silicone rubber, 40g of aliphatic polyether thermoplastic polyurethane TPU, 5g of silicone powder, 5g of the composite crosslinking agent obtained in step (4), and platinum catalyst (calculated as platinum, content 10ppm) in a mixer at 150℃ and vulcanize. Put the mixture into a twin-screw extruder, add 0.01g of tert-butyl peroxide benzoate, stir and react at 180℃, with the screw speed at 350r / min, and extrude and granulate to obtain a silicone-like thermoplastic elastomer composite material. Figure 2 The image shows a cross-sectional SEM image of the prepared silicone-like thermoplastic elastomer composite material. As can be seen from the image, the matrix compatibility is good.

[0045] Example 2

[0046] This embodiment provides a method for preparing a silicone-like thermoplastic elastomer composite material, including the following steps:

[0047] (1) Mix and grind 4g of ammonium polyphosphate, 2g of melamine and 1g of expandable graphite to obtain a flame retardant system with a particle size of 1-10μm;

[0048] (2) Add 5g of the flame retardant system obtained in step (1) to 100mL of ethanol, add 3g of tetraethyl orthosilicate and 10mL of water, stir and mix for 20min, add ammonia water dropwise until the pH of the solution is 9-10, stir and react for 15h, centrifuge, wash, dry, and obtain silica powder coated with flame retardant system.

[0049] (3) Add 10g of silica powder of the flame retardant system prepared in step (2) to 200mL of ethanol, add 1.5g of composite silane, stir and react at 50℃ for 4h, filter, wash and dry to obtain modified silica powder of the flame retardant system; the composite silane includes n-dodecyltriethoxysilane, isocyanate silane coupling agent KH907 and double bond silane coupling agent KH570, with a mass ratio of 2:3:6;

[0050] (4) Mix hydrogen-containing siloxane, 8g of vinyl-terminated polytrifluoropropylmethylsiloxane and 16g of silica powder of the modified coating flame retardant system prepared in step (3). The molar ratio of the silane-hydrogen bond and the double bond in the system is n(Si-H):n(C=C)=1:0.5. Add platinum catalyst (calculated as platinum, accounting for 5ppm of the total mass of the system), heat to 70℃, stir and react for 40min to obtain the composite crosslinking agent.

[0051] (5) 20g of polyolefin elastomer SEBS, 20g of methyl vinyl silicone rubber, 60g of aliphatic polyether thermoplastic polyurethane TPU, 10g of silicone powder, 10g of the composite crosslinking agent obtained in step (4) and platinum catalyst (calculated as platinum, content 10ppm) are mixed and vulcanized in a mixer at 150℃, fed into a twin-screw extruder, 0.02g of di-tert-butyl peroxide is added, crosslinking is carried out at 220℃ with stirring, the screw speed is 550r / min, and extrusion granulation is performed to obtain a silicone-like thermoplastic elastomer composite material.

[0052] Example 3

[0053] This embodiment provides a method for preparing a silicone-like thermoplastic elastomer composite material, including the following steps:

[0054] (1) Mix and grind 3g of ammonium polyphosphate, 1.6g of melamine and 1g of expandable graphite to prepare a flame retardant system with a particle size of 1-10μm;

[0055] (2) Add 4g of the flame retardant system obtained in step (1) to 100mL of ethanol, add 2.5g of tetraethyl orthosilicate and 10mL of water, stir and mix for 20min, add ammonia dropwise until the pH of the solution is 9-10, stir and react for 12h, centrifuge, wash, dry, and obtain silica powder coated with flame retardant system.

[0056] (3) Add 10g of silica powder of the flame retardant system obtained in step (2) to 200mL of ethanol, add 1g of composite silane, stir and react at 45℃ for 3h, filter, wash and dry to obtain silica powder of the modified flame retardant system; the composite silane includes n-dodecyltriethoxysilane, isocyanate silane coupling agent KH907 and double bond silane coupling agent KH570, with a mass ratio of 2:3:6;

[0057] (4) Mix hydrogen-containing siloxane, 6g of vinyl-terminated polytrifluoropropylmethylsiloxane and 15g of silica powder of the modified coating flame retardant system prepared in step (3). The molar ratio of the silane-hydrogen bond and the double bond in the system is n(Si-H):n(C=C)=1:0.4. Add platinum catalyst (calculated as platinum, accounting for 3ppm of the total mass of the system), heat to 65℃, stir and react for 30min to obtain the composite crosslinking agent.

[0058] (5) Mix 15g of polyolefin elastomer SEBS, 17g of methyl vinyl silicone rubber, 50g of aliphatic polyether thermoplastic polyurethane TPU, 7g of silicone powder, 8g of the composite crosslinking agent obtained in step (4), and platinum catalyst (calculated as platinum, content 10ppm) in a mixer at 150℃ and vulcanize. Put the mixture into a twin-screw extruder, add 0.013g of di-tert-amyl peroxide, stir and react at 200℃, with the screw speed at 450r / min, and extrude and granulate to obtain a silicone-like thermoplastic elastomer composite material.

[0059] Example 4

[0060] The only difference from Example 3 is that the composite silane is replaced by a single n-dodecyltriethoxysilane by mass.

[0061] Example 5

[0062] The only difference from Example 3 is that the composite silane is replaced by a single isocyanate silane coupling agent, such as KH907.

[0063] Example 6

[0064] The only difference from Example 3 is that the composite silane is replaced by a single double-bonded silane coupling agent, such as KH570.

[0065] Comparative Example 1

[0066] Compared with Example 3, the only difference is that steps (2) and (3) were not performed, and the silica powder of the modified coating flame retardant system in step (4) was replaced by an equal mass of flame retardant system.

[0067] Comparative Example 2

[0068] Compared with Example 3, the only difference is that step (3) was not performed, and the silica powder of the modified coating flame retardant system in step (4) was replaced by silica powder of the same mass of the coating flame retardant system.

[0069] Comparative Example 3

[0070] Compared with Example 3, the only difference is that in step (4), no modified coated flame retardant system of silica powder was added.

[0071] Comparative Example 4

[0072] The only difference from Example 3 is that vinyl-terminated polytrifluoropropylmethylsiloxane was not added in step (4).

[0073] Comparative Example 5

[0074] The only difference from Example 3 is that silicone powder was not added in step (5).

[0075] Comparative Example 6

[0076] The only difference from Example 3 is that the particle size of the flame retardant system after grinding is 30-50 μm.

[0077] Comparative Example 7

[0078] The only difference compared to Example 3 is that the screw speed is 100 r / min.

[0079] Test Example 1

[0080] The performance of the silicone-like thermoplastic elastomer composite materials prepared in Examples 1-6 and Comparative Examples 1-7 was tested.

[0081] Limiting Oxygen Index (LOI): Tested according to GB / T 2406.2-2009.

[0082] High-temperature aging test: The test was conducted according to GB / T 3512-2014. The tensile strength of the sample before and after the aging test was measured.

[0083] Tensile properties: tested in accordance with GB / T 528-2009.

[0084] DIN wear: Tested according to GB / T 9867-2008.

[0085] Water resistance, acid resistance, and alkali resistance: tested in accordance with GB / T 16807-2009.

[0086] Skin-friendly feel level: An evaluation team of 10 trained and qualified evaluators conducted blind tests on the test specimens and standard dynamic vulcanized silicone rubber reference samples using the paired comparison method (GB / T33310-2016 "Sensory Analysis Methodology: Paired Comparison Test"). Evaluators gently stroked the surface of the sample with their fingertips in the same direction and scored it according to the following standards: Level 1 (dry feel, no silky smoothness); Level 2 (slightly smooth feel, but not obvious); Level 3 (some silky smoothness, significantly different from the standard dynamic vulcanized silicone rubber reference sample); Level 4 (obvious silky smoothness, close to or reaching the level of the standard dynamic vulcanized silicone rubber reference sample).

[0087] Stain resistance: Mix cooking oil and tomato sauce in a 1:1 ratio and coat the sample evenly. Place the sample in a 60℃ oven for 8 hours. After cooling to room temperature, wipe the surface of the sample with a cotton ball soaked in an appropriate amount of alcohol and observe the surface contamination (Grade 1 is severely contaminated, with obvious discoloration at the coated area; Grade 2 is somewhat contaminated, with some discoloration at the coated surface; Grade 3 is slightly contaminated, with slight discoloration at the coated area; Grade 4 is very slightly contaminated, with almost no discoloration at the coated area).

[0088] The results are shown in Tables 1 and 2.

[0089] Table 1

[0090] Example 1 72 8.3 8.0 26.2 55 Example 2 74 7.9 7.6 27.9 53 Example 3 77 8.1 7.9 27.4 49 Example 4 64 7.4 6.9 24.6 85 Example 5 68 6.7 5.9 22.5 68 Example 6 69 6.5 6.1 22.9 74 Comparative Example 1 59 4.1 2.1 20.3 149 Comparative Example 2 60 4.6 3.0 20.9 124 Comparative Example 3 54 5.1 3.4 19.1 92 Comparative Example 4 70 7.7 7.3 25.4 58 Comparative Example 5 69 7.5 6.9 24.7 62 Comparative Example 6 62 5.5 3.6 25.1 115 Comparative Example 7 56 6.1 4.8 21.1 94

[0091] Table 2

[0092] Example 1 No change No change No change 4 4 Example 2 No change No change No change 4 4 Example 3 No change No change No change 4 4 Example 4 No change No change No change 3 3 Example 5 No change No change No change 3 4 Example 6 No change No change No change 4 4 Comparative Example 1 No change No change No change 2 2 Comparative Example 2 No change No change No change 2 3 Comparative Example 3 No change No change No change 3 3 Comparative Example 4 No change No change No change 2 4 Comparative Example 5 No change No change No change 2 4 Comparative Example 6 No change No change No change 4 3 Comparative Example 7 No change No change No change 3 3

[0093] As can be seen from the table above, the silicone-like thermoplastic elastomer composite materials prepared in Examples 1-3 of the present invention have good comprehensive properties.

[0094] In Example 4, the composite silane was replaced by a single n-dodecyltriethoxysilane by mass. Its wear resistance, stain resistance, and hand feel properties decreased. This is because the long-chain alkyl group provides a hydrophobic compatibilizing effect, which interacts with the polyolefin elastomer molecular chain and forms chain entanglement, significantly reducing the interfacial tension between the flame retardant powder and the polyolefin, preventing agglomeration, and thus having little impact on mechanical properties. However, the degree of crosslinking of the system decreased, and in the composite crosslinking agent, the vinyl-terminated polytrifluoropropylmethylsiloxane did not react with the silica powder of the modified flame retardant system. Therefore, the wear resistance, stain resistance, and hand feel properties decreased.

[0095] In Examples 5 and 6, the composite silane was replaced by a single isocyanate silane coupling agent KH907 or a silane coupling agent with double bonds KH570, etc. Although the degree of crosslinking of the system was not significantly affected, and in the composite crosslinking agent of Example 6, the vinyl-terminated polytrifluoropropylmethylsiloxane could react with the silica powder of the modified coating flame retardant system, so the impact on abrasion resistance, stain resistance, and feel was not significant. However, due to the lack of hydrophobic chains to improve compatibility and avoid agglomeration, the mechanical properties and flame retardant properties were reduced to a certain extent.

[0096] In Comparative Example 1, steps (2) and (3) were not performed, and in step (4), the silica powder of the modified flame retardant coating system was replaced by an equal mass of the flame retardant system. In Comparative Example 2, step (3) was not performed, and in step (4), the silica powder of the modified flame retardant coating system was replaced by an equal mass of the coated flame retardant system. Mechanical properties, flame retardant properties, wear resistance, stain resistance, and hand feel all decreased. This invention uses composite silane to modify the silica powder of the coated flame retardant system, which improves interfacial compatibility, prevents agglomeration, and improves material properties. The aging resistance of Comparative Example 1 is worse than that of Comparative Example 2. This is because the SiO2 inorganic coating layer can avoid catalytic degradation caused by direct contact between the highly active flame retardant components and the polymer matrix, thus improving thermal stability.

[0097] In Comparative Example 3, the silica powder without the modified coating flame retardant system was not added in step (4). The flame retardant performance decreased significantly, while the mechanical properties improved. This is because the addition of the flame retardant system will reduce the mechanical properties to a certain extent, while the present invention avoids the negative effect on the mechanical properties through coating modification technology.

[0098] In Comparative Example 4, no vinyl-terminated polytrifluoropropylmethylsiloxane was added in step (4), resulting in a decrease in oil resistance. In this invention, by introducing vinyl-terminated polytrifluoropropylmethylsiloxane, the vinyl-terminated end-position reacts and grafts with the TPU or polyolefin matrix during processing, chemically bonding the fluorinated segments to the material surface, significantly reducing surface energy, and imparting long-lasting hydrophobic, oleophobic, and sweat-resistant properties, thus avoiding the deterioration of the feel caused by oil adsorption.

[0099] In Comparative Example 5, no silicone powder was added in step (5). The feel was significantly reduced because the silicone powder can be uniformly dispersed inside the material to form a low surface energy silicon-carbon layer, reducing the material modulus and surface friction coefficient, and providing a lasting dry and smooth feel.

[0100] In Comparative Example 6, the particle size of the flame retardant system after grinding was 30-50 μm. The mechanical properties decreased significantly. This is because when the particle size of the flame retardant system is greater than 10 μm, a significant stress concentration effect occurs when the composite material is subjected to tension / tear, leading to a deterioration in mechanical properties.

[0101] In Comparative Example 7, the screw speed was 100 r / min. Too slow a speed can lead to incomplete reaction, making it difficult for the silicone rubber particles to disperse evenly, thus causing a certain degree of degradation in all properties.

[0102] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a silicone-like thermoplastic elastomer composite material, characterized in that, Includes the following steps: (1) Ammonium polyphosphate, melamine and expandable graphite are mixed and ground to prepare a flame retardant system; (2) Add the flame retardant system to ethanol, add alkyl ester of orthosilicate and water, stir and mix evenly, add ammonia dropwise, stir and react, centrifuge, wash, dry, and obtain silica powder coated with flame retardant system; (3) Add the silica powder coated with flame retardant system to ethanol, add composite silane, stir to react, filter, wash, dry, and obtain modified silica powder coated with flame retardant system. (4) Mix the hydrogen-containing siloxane, fluorine-containing silane and the silica powder of the modified coating flame retardant system, add the catalyst, heat and stir to react, and obtain the composite crosslinking agent; (5) The polyolefin elastomer, methyl vinyl silicone rubber, aliphatic polyether thermoplastic polyurethane, silicone powder and composite crosslinking agent are mixed and vulcanized in a mixer, fed into a twin-screw extruder, an initiator is added, heated and stirred to react, extruded and granulated to obtain a silicone-like thermoplastic elastomer composite material.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of ammonium polyphosphate, melamine and expandable graphite is 2-4:1-2:1; the particle size of the flame retardant system is 1-10 μm.

3. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of the flame retardant system to the alkyl orthosilicate is 3-5:2-3; the alkyl orthosilicate is selected from ethyl orthosilicate or methyl orthosilicate; the ammonia water is added dropwise until the pH of the solution is 9-10; and the stirring reaction time is 10-15 h.

4. The preparation method according to claim 1, characterized in that, In step (3), the composite silane includes a long-chain alkyl silane, an isocyanate silane coupling agent, and a double-bond silane coupling agent, with a mass ratio of 1-3:2-5:3-8. The long-chain alkyl silane is selected from at least one of n-dodecyltriethoxysilane, n-hexyltriethoxysilane, n-octyltrimethoxysilane, n-dodecyltrimethoxysilane, n-hexadecyltrimethoxysilane, and n-hexadecyltriethoxysilane. The isocyanate silane coupling agent is KH907, and the double-bond silane coupling agent is selected from at least one of KH570, A151, and A171. Preferably, the composite silane includes n-dodecyltriethoxysilane, isocyanate silane coupling agent KH907, and double-bond silane coupling agent KH570, with a mass ratio of 2:3:

6.

5. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of silica powder to composite silane in the flame retardant coating system is 10:0.5-1.5, the stirring reaction temperature is 40-50℃, and the time is 2-4h.

6. The preparation method according to claim 1, characterized in that, In step (4), the heating and stirring reaction is carried out at a temperature of 60-70℃ for 20-40 min; the mass ratio of silica powder in the fluorinated silane and modified coated flame retardant system is 4-8:14-16; the fluorinated silane is vinyl-terminated polytrifluoropropylmethylsiloxane with a viscosity of 1000-2000 mPa·s; the molar ratio of silane-hydrogen bonds in the hydrogen-containing siloxane to double bonds in the system is n(Si-H):n(C=C)=1:0.3-0.5; and the catalyst accounts for 2-5 ppm of the total mass of the system.

7. The preparation method according to claim 1, characterized in that, In step (5), the mass ratio of the polyolefin elastomer, methyl vinyl silicone rubber, aliphatic polyether thermoplastic polyurethane, silicone powder, composite crosslinking agent and initiator is 10-20:11-10:40-60:5-10:5-10:0.01-0.02; the polyolefin elastomer is selected from at least one of SEBS, POE and EPDM; the molecular weight of the methyl vinyl silicone rubber is 400,000 to 1,000,000, and the molar fraction of its vinyl group is 0.1-1.0 mol%; the initiator is selected from at least one of di-tert-amyl peroxide, di-tert-butyl peroxide and tert-butyl peroxide benzoate.

8. The preparation method according to claim 1, characterized in that, In step (5), the temperature of the twin-screw extruder is 180-220℃ and the screw speed is 350-550r / min.

9. A silicone-like thermoplastic elastomer composite material prepared by the preparation method according to any one of claims 1-8.

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