A high thermal conductivity, low viscosity, alcohol-free silicone rubber and its preparation method

Abstract

This invention, entitled "A High Thermal Conductivity, Low Viscosity De-alcoholized Silicone Fiber and Its Preparation Method," belongs to the technical field of de-alcoholized silicone fiber technology. The technical problems to be solved are: existing de-alcoholized silicone fibers have a thermal conductivity of less than 6.0 W / (m·K), difficulty in achieving both high thermal conductivity and low viscosity, decreased mechanical strength of the cured colloid, and poor filler dispersibility. The key technical points are that the silicone fiber comprises the following raw materials: α,ω-dihydroxy polydimethylsiloxane, low-viscosity dimethyl silicone oil, crosslinking agent, multi-scale composite thermally conductive filler, surface treatment agent, catalyst, coupling agent, hydroxyl scavenger, and thixotropic anti-settling agent. The multi-scale composite thermally conductive filler is composed of large-particle-size spherical alumina, medium-particle-size near-spherical aluminum nitride, and small-particle-size lamellar boron nitride nanosheets. The silicone fiber has a thermal conductivity ≥6.0 W / (m·K) and a viscosity ≤80000 mPa·s, exhibiting excellent storage stability, curing performance, and mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of dealcohol-type silicone technology, specifically to a high thermal conductivity, low viscosity dealcohol-type silicone and its preparation method. Background Technology

[0002] For understanding the technical content of this invention: De-alcoholized room temperature vulcanizing (RTV-1) silicone rubber undergoes a condensation crosslinking reaction upon contact with moisture in the air at room temperature. The byproducts released during curing are small alcohol molecules, which are non-corrosive to metal substrates and exhibit excellent weather resistance, electrical insulation, and environmental friendliness. They are widely used in the bonding, sealing, and heat dissipation management of electronic and electrical appliances. De-alcoholized silicone rubber typically uses α,ω-dihydroxypolydimethylsiloxane (107 silicone rubber) as the base polymer, alkoxysilane as the crosslinking agent, and organotin compounds or titanates as catalysts.

[0003] With the rapid development of 5G communication, new energy vehicles, high-power LEDs, IGBT modules, and other fields, the integration of electronic devices is constantly increasing, leading to a sharp increase in heat generation per unit volume. This places increasingly higher demands on thermal interface materials. Research shows that when the thermal conductivity of silicone reaches 6.0 W / (m·K) or higher, it can significantly improve heat dissipation efficiency and meet the heat dissipation requirements of high-power electronic devices. Room temperature vulcanizing silicone rubber itself has very poor thermal conductivity, typically only 0.2 W / m·K, requiring the addition of thermally conductive fillers to improve it. However, existing de-alcoholized silicone rubber technologies face the following prominent problems in pursuing high thermal conductivity: (1) It is difficult to achieve both high thermal conductivity and low viscosity. To achieve a thermal conductivity of ≥6.0 W / (m·K), a large amount of thermally conductive filler needs to be added to the base adhesive, and the filler amount usually needs to reach 1000-1800 parts by weight of the base adhesive. The addition of a large amount of traditional high thermal conductivity fillers (such as alumina, aluminum nitride, boron nitride) will cause the viscosity of the system to rise sharply, or even lose its fluidity, which seriously limits its application in precision electronic potting and dispensing processes.

[0004] (2) Poor dispersibility of fillers and easy agglomeration and sedimentation during storage. Under high filler content, thermally conductive filler particles are prone to agglomeration due to their high surface energy and poor compatibility with silicone oil, making it difficult to disperse evenly. This results in discontinuous thermal conductivity pathways and the actual thermal conductivity is much lower than the theoretical value. At the same time, fillers with higher density are prone to sedimentation and stratification during storage, affecting the stability of product use and storage life.

[0005] (3) The contradiction between curing performance and thermal conductivity. In the formulation of traditional de-alcoholized silicone, the addition of a large amount of thermally conductive filler will hinder the penetration of moisture into the interior of the colloid, resulting in slow deep curing or even no curing. At the same time, the hydroxyl groups remaining on the surface of the filler will react with the crosslinking agent, affecting the formation of the crosslinking network, and ultimately leading to a decrease in the mechanical strength of the cured colloid.

[0006] Relevant patent documents retrieved: This document, published in China (CN114686158A) on July 1, 2022, discloses a dealcohol-type high thermal conductivity single-component room-temperature vulcanizing silicone rubber adhesive and its preparation method. The adhesive comprises, by weight, 100 parts of dihydroxy polydimethylsiloxane, 5-50 parts of dimethyl silicone oil, 1900-2500 parts of alumina, 5-10 parts of surface treatment agent, 2-15 parts of thixotropic agent, 5-20 parts of crosslinking agent, 1-5 parts of catalyst, and 0.1-3 parts of tackifier. However, its thermal conductivity is only 3.5-3.7 W / (m·K), and its elongation at break is 9%.

[0007] This document, published in China (CN121227279A) on December 30, 2025, discloses a heat-resistant, de-alcoholized, thermally conductive silicone adhesive and its preparation method. The adhesive is prepared from raw materials comprising the following components: 100 parts by weight of trimethoxysilyl-terminated polydimethylsiloxane, 1-20 parts by weight of a heat-resistant plasticizer, 100-800 parts by weight of thermally conductive powder, 3-10 parts by weight of a heat-resistant filler, 1-15 parts by weight of a silane crosslinking agent, and 0.5-5 parts by weight of a titanate catalyst. The heat-resistant filler is selected from one or more of iron oxide, cerium oxide, titanium dioxide, zirconium dioxide, carbon black, and phthalocyanine blue. However, its thermal conductivity does not reach an upper limit of 6.0 W / (m·K).

[0008] This document, published in China (CN119552629A) on March 4, 2025, discloses a high thermal conductivity, low viscosity silicone potting compound and its preparation method. The raw materials and their weight ranges are as follows: 80-90 parts of α,ω-dihydroxypolydiethylsiloxane; 4-8 parts of polyphenylsiloxane; 100-120 parts of spherical aluminum nitride; 3-7 parts of epoxy oleate; 0.8-1.2 parts of organobentonite; 0.5-0.9 parts of titanate coupling agent; 0.8-0.9 parts of dibutyltin dibutyrate; 0.15-0.20 parts of dibutyltin oxide; 0.08-0.15 parts of triphosphate; and 1.4-1.9 parts of graphite powder. This silicone potting compound has a low viscosity, but its thermal conductivity is not higher than 2 W / (m·K).

[0009] The prior art represented by the literature has at least the following unresolved technical problems or defects: (1) The thermal conductivity did not reach 6.0 W / (m·K); (2) The mechanical strength of the colloid decreases after curing.

[0010] In summary, current technologies lack a single-component, alcohol-free silicone rubber that can maintain low viscosity and good workability while meeting the requirement of a thermal conductivity ≥6.0 W / (m·K). Therefore, developing an alcohol-free silicone rubber with high thermal conductivity, low viscosity, and excellent overall performance has significant practical importance and market value. Summary of the Invention

[0011] The purpose of this invention is to provide: A high thermal conductivity, low viscosity de-alcoholized silicone rubber, and related technologies, to solve the technical problems of existing de-alcoholized silicone rubbers, such as thermal conductivity not reaching 6.0 W / (m·K), difficulty in achieving both high thermal conductivity and low viscosity, decrease in the mechanical strength of the cured colloid, and decrease in storage stability, or a combination thereof.

[0012] Terminology Explanation: Unless otherwise defined, all technical terms in this document have the same meanings as commonly understood by one of ordinary skill in the art to which the subject matter of the claims pertains. Unless otherwise stated, all patents, patent inventions, and publications cited in this document are incorporated herein by reference in their entirety. If multiple definitions exist for terms in this document, the definitions in this chapter shall prevail.

[0013] It should be understood that the above brief description and the following detailed description are exemplary and for illustrative purposes only, and do not limit the subject matter of the invention in any way. In this invention, the singular is used in conjunction with the plural unless otherwise specifically stated. It should also be noted that, unless otherwise stated, the use of “or” or “or” means “and / or”. Furthermore, the use of the term “comprising” and other forms such as “including,” “containing,” and “contains” are not limiting.

[0014] Definitions of standard chemical terms can be found in the reference "Organosilicon Chemistry and Process".

[0015] Unless otherwise stated, conventional methods within the scope of the art shall be used.

[0016] Unless specifically defined herein, the use of all commercially available products herein employs standard techniques. For example, it may be carried out using the manufacturer's instructions for use with the kit, or in accordance with methods known in the art or the description of this invention. The techniques and methods described herein can generally be implemented according to conventional methods well known in the art, based on the descriptions in the various summary and more specific documents cited and discussed in this specification.

[0017] The term "de-alcoholized room temperature vulcanizing silicone rubber" as used in this article refers to a one-component paste made by vacuum dehydration and kneading based on α,ω-dihydroxypolydimethylsiloxane as a base polymer, along with fillers, crosslinking agents, catalysts, etc. This rubber crosslinks and cures at room temperature through a condensation reaction with moisture in the air. The byproducts released during the curing process are mainly alcohols (such as methanol and ethanol).

[0018] The term "α,ω-dihydroxypolydimethylsiloxane" used in this article refers to a linear polydimethylsiloxane whose molecular chains are capped with hydroxyl groups (–OH). Commonly known as 107 silicone rubber or hydroxyl silicone oil, it is a base compound for preparing condensation-type room-temperature vulcanizing silicone rubber, and its general structural formula is HO[(CH3)2SiO]. n H.

[0019] The term "dimethyl silicone oil" as used in this article refers to a linear polysiloxane liquid with dimethylsiloxane as the repeating unit and trimethylsiloxy groups at both ends, with the chemical formula (CH3)3SiO[(CH3)2SiO]. n Si(CH3)3.

[0020] The term "crosslinking agent" as used in this article refers to silane compounds (such as methyltrimethoxysilane and tetraethyl orthosilicate) containing three or more hydrolyzable functional groups (such as alkoxy and acetoxy groups) in their molecules. Its function is to undergo a condensation reaction with the terminal hydroxyl groups of the base polymer to form a three-dimensional network structure, thus transforming the colloid from a paste-like state into an elastomer.

[0021] The term "thermal conductive filler" as used in this article refers to inorganic powder materials with high thermal conductivity (such as alumina, aluminum nitride, boron nitride, and zinc oxide) that are filled into an organosilicon matrix to form thermally conductive pathways, thereby improving the thermal conductivity of the colloid.

[0022] The term "surface treatment agent" as used in this article refers to a substance (usually a silane, titanate, or aluminate coupling agent) used to modify the surface of thermally conductive fillers in order to reduce the hydroxyl concentration on the filler surface and improve its dispersibility and compatibility in the organosilicon matrix.

[0023] The term "catalyst" as used in this article refers to a substance used to accelerate the reaction rate between the crosslinking agent and the base polymer.

[0024] The term "coupling agent" as used in this article refers to a silane compound whose molecules contain hydrolyzable groups (such as alkoxy groups) and organic functional groups (such as amino and epoxy groups) at both ends. Its function is to improve the adhesion strength between the inorganic filler and the organosilicon polymer interface, and to enhance the adhesion of the colloid to the substrate.

[0025] The term "hydroxyl scavenger" as used in this article refers to a compound that can react with free hydroxyl groups or moisture in the system to generate inert products, used to improve the storage stability of the adhesive and prevent the formation of bubbles during the curing process.

[0026] The term "thixotropic anti-settling agent" as used in this article refers to: thixotropic powders or rheology modifiers (such as fumed silica or organobentonite) that enable the colloid to form a three-dimensional network structure when at rest to prevent filler settling, and whose viscosity decreases under shear force to facilitate construction.

[0027] The term "vacuum drying" as used in this article refers to the process of heating and dehydrating materials under vacuum conditions below atmospheric pressure.

[0028] The term "kneading" as used in this article refers to the mixing process in a high-viscosity material mixing device, in which the components (base adhesive, filler, additives) are uniformly dispersed at both the macroscopic and microscopic levels by utilizing the shearing, squeezing, and folding action of the stirring paddle.

[0029] The term "planetary mixer" as used in this article refers to a vertical mixing device whose mixing mechanism includes two or more mixing blades (usually in conjunction with a wall scraping mechanism) that both revolve around the main shaft of the device and rotate around their own axis, suitable for kneading, dispersing and degassing high-viscosity paste materials.

[0030] In a first aspect, the present invention provides: a high thermal conductivity, low viscosity de-alcoholized silicone rubber, comprising the following raw materials in parts by weight: 100 parts of α,ω-dihydroxy polydimethylsiloxane, 5-20 parts of dimethyl silicone oil, 3-10 parts of crosslinking agent, 600-1200 parts of multi-scale compound thermally conductive filler, 2-8 parts of surface treatment agent, 0.5-3 parts of catalyst, 1-5 parts of coupling agent, 1-4 parts of hydroxyl scavenger, and 2-6 parts of thixotropic anti-settling agent; Preferably, the high thermal conductivity, low viscosity de-alcoholized silicone rubber comprises the following raw materials in parts by weight: 100 parts of α,ω-dihydroxy polydimethylsiloxane, 10-20 parts of dimethyl silicone oil, 5-8 parts of crosslinking agent, 800-1000 parts of multi-scale compound thermally conductive filler, 4-6 parts of surface treatment agent, 1-2.5 parts of catalyst, 2-4 parts of coupling agent, 2-3 parts of hydroxyl scavenger, and 3-5 parts of thixotropic anti-settling agent; More preferably, the high thermal conductivity, low viscosity de-alcoholized silicone rubber comprises the following raw materials in parts by weight: 100 parts of α,ω-dihydroxy polydimethylsiloxane, 10 parts of dimethyl silicone oil, 8 parts of crosslinking agent, 900 parts of multi-scale compound thermally conductive filler, 5 parts of surface treatment agent, 2.3 parts of catalyst, 3 parts of coupling agent, 2 parts of hydroxyl scavenger, and 4 parts of thixotropic anti-settling agent.

[0031] The technical features include: α,ω-dihydroxy polydimethylsiloxane, dimethyl silicone oil, crosslinking agent, multi-scale compound thermally conductive filler, surface treatment agent, catalyst, coupling agent, hydroxyl scavenger, and thixotropic anti-settling agent.

[0032] The viscosity of the α,ω-dihydroxypolydimethylsiloxane is 1000-3500 mPa·s; the viscosity of the dimethyl silicone oil is 50-100 mPa·s.

[0033] The crosslinking agent is selected from at least two of methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, and phenyltrimethoxysilane. Preferably, the crosslinking agent is selected from at least two of methyltrimethoxysilane, methyltriethoxysilane, and vinyltrimethoxysilane; More preferably, the crosslinking agent is methyltrimethoxysilane and vinyltrimethoxysilane.

[0034] The multi-scale composite thermally conductive filler is composed of large-particle-size spherical alumina, medium-particle-size near-spherical aluminum nitride, and small-particle-size sheet-like boron nitride nanosheets. Preferably, in the multi-scale composite thermally conductive filler, the average particle size of the large-diameter spherical alumina is 20-50 μm, accounting for 50%-70% of the total mass of the multi-scale composite thermally conductive filler; the average particle size of the medium-diameter near-spherical aluminum nitride is 5-15 μm, accounting for 20%-35% of the total mass of the multi-scale composite thermally conductive filler; and the average thickness of the small-diameter lamellar boron nitride nanosheets is 50-200 nm, the average sheet diameter is 2-10 μm, and they account for 5%-15% of the total mass of the multi-scale composite thermally conductive filler. More preferably, the average particle size of the large-diameter spherical alumina: the average particle size of the medium-diameter near-spherical aluminum nitride: the sheet diameter of the small-diameter plate-like boron nitride nanosheets is 5-10:2-4:1; More preferably, the average particle size of the large-diameter spherical alumina, the average particle size of the medium-diameter spherical aluminum nitride, and the sheet diameter of the small-diameter sheet boron nitride nanosheets are 6:2:1.

[0035] The surface treatment agent is a compound of titanate coupling agent and fluorinated silane coupling agent; Preferably, the mass ratio of the titanate coupling agent to the fluorinated silane coupling agent is 2-4:1; More preferably, the titanate coupling agent is selected from isopropyl tris(dioctylpyrophosphoryloxy) titanate and / or isopropyl tris(isostearoyl) titanate; the fluorinated silane coupling agent is selected from 1H,1H,2H,2H-perfluorodecyltrimethoxysilane and / or 1H,1H,2H,2H-perfluorooctyltriethoxysilane. More preferably, the surface treatment agent is isopropyltris(dioctylpyrophosphate)titanate and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, with a mass ratio of 4:1.

[0036] The catalyst is an organotitanate catalyst; Preferably, the catalyst is selected from one or more of tetraisopropyl titanate, tetraisopropyl titanate, tetrabutyl titanate, and diisopropyl titanate (ethyl acetoacetate). More preferably, the catalyst is tetraisobutyl titanate and diisopropyl di(ethyl acetoacetate) titanate.

[0037] The coupling agent is selected from one or more of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane; Preferably, the coupling agent is selected from N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane and / or γ-methacryloyloxypropyltrimethoxysilane; More preferably, the coupling agent is N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0038] Preferably, the hydroxyl scavenger is hexamethyldisilazane or vinyltrimethoxysilane; More preferably, the hydroxyl scavenger is hexamethyldisilazane; Preferably, the thixotropic anti-settling agent is fumed silica; More preferably, the specific surface area of ​​the fumed silica is 150-300 m² / g.

[0039] Based on further solutions to the technical problems of the present invention, or simultaneous solutions to multiple technical problems, the preferred solution in the technical solution provided in the first aspect of the present invention includes: The first preferred embodiment: The high thermal conductivity, low viscosity, alcohol-free silicone rubber comprises the following raw materials in parts by weight: 100 parts α,ω-dihydroxypolydimethylsiloxane, 5-20 parts dimethyl silicone oil, 3-10 parts crosslinking agent, 600-1200 parts multi-scale composite thermally conductive filler, 2-8 parts surface treatment agent, 0.5-3 parts catalyst, 1-5 parts coupling agent, 1-4 parts hydroxyl scavenger, and 2-6 parts thixotropic anti-settling agent, wherein the crosslinking agent is selected from methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, etc. The multi-scale composite thermally conductive filler comprises at least two of the following: β-aminoethyl)-γ-aminopropyltrimethoxysilane and phenyltrimethoxysilane. It consists of large-particle-size spherical alumina, medium-particle-size near-spherical aluminum nitride, and small-particle-size plate-like boron nitride nanosheets. The surface treatment agent is a mixture of a titanate coupling agent and a fluorinated silane coupling agent. The catalyst is an organotitanate catalyst. The coupling agent is selected from one or more of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane. This technical solution, while addressing the technical problem of "high thermal conductivity," further solves the technical problem of "low viscosity."

[0040] The second preferred embodiment: The high thermal conductivity, low viscosity alcohol-free silicone rubber comprises the following raw materials in parts by weight: 100 parts α,ω-dihydroxypolydimethylsiloxane, 10-20 parts dimethyl silicone oil, 5-8 parts crosslinking agent, 800-1000 parts multi-scale composite thermally conductive filler, 4-6 parts surface treatment agent, 1-2.5 parts catalyst, 2-4 parts coupling agent, 2-3 parts hydroxyl scavenger, and 3-5 parts thixotropic anti-settling agent. The crosslinking agent is selected from at least two of methyltrimethoxysilane, methyltriethoxysilane, and vinyltrimethoxysilane. The multi-scale composite thermally conductive filler is composed of large-diameter spherical alumina, medium-diameter near-spherical aluminum nitride, and small-diameter sheet-like boron nitride nanosheets. The average particle size of the large-diameter spherical alumina is 20-50 μm, accounting for 50%-70% of the total mass of the multi-scale composite thermally conductive filler; the average particle size of the medium-diameter near-spherical aluminum nitride is 5-15 μm. The small-particle-size boron nitride nanosheets have an average thickness of 50-200 nm and an average diameter of 2-10 μm, accounting for 20%-35% of the total mass of the multi-scale composite thermally conductive filler. The surface treatment agent is a mixture of titanate coupling agent and fluorinated silane coupling agent in a mass ratio of 2-4:1. The catalyst is selected from one or more of n-propyl titanate, tetraisopropyl titanate, n-butyl titanate, tetraisobutyl titanate, and di(ethyl acetoacetate) diisopropyl titanate. The coupling agent is selected from N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane and / or γ-methacryloyloxypropyltrimethoxysilane. This technical solution, while solving the technical problem of "high thermal conductivity," further solves the technical problem of "low viscosity."

[0041] The third preferred embodiment: The high thermal conductivity, low viscosity de-alcoholized silicone rubber comprises the following raw materials in parts by weight: 100 parts α,ω-dihydroxypolydimethylsiloxane, 10 parts dimethyl silicone oil, 8 parts crosslinking agent, 900 parts multi-scale composite thermally conductive filler, 5 parts surface treatment agent, 2.3 parts catalyst, 3 parts coupling agent, 2 parts hydroxyl scavenger, and 4 parts thixotropic anti-settling agent. The crosslinking agent is methyltrimethoxysilane and vinyltrimethoxysilane. The large-particle-size spherical alumina... Average particle size: The average particle size of medium-sized spherical aluminum nitride nanosheets is 6:2:1. The surface treatment agent is isopropyltris(dioctylpyrophosphoryloxy)titanate and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, with a mass ratio of 4:1. The catalyst is tetraisobutyl titanate and di(ethyl acetoacetate)diisopropyl titanate. The coupling agent is N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane. This technical solution, while solving the technical problem of "high thermal conductivity", further solves the technical problem of "low viscosity".

[0042] Secondly, the present invention provides a method for preparing the above-mentioned high thermal conductivity, low viscosity, alcohol-free silicone rubber, comprising the following steps: S1. Dry-mix the multi-scale composite thermal conductive filler evenly to obtain a multi-scale composite thermal conductive filler mixture; dilute the surface treatment agent with anhydrous ethanol and spray it onto the surface of the multi-scale composite thermal conductive filler mixture, mix and then vacuum dry to obtain a surface-modified thermal conductive filler. S2. Mix α,ω-dihydroxypolydimethylsiloxane and dimethyl silicone oil evenly under vacuum at room temperature to obtain a base adhesive mixture; S3. Add surface-modified thermally conductive filler and thixotropic anti-settling agent to the base adhesive mixture in batches, and knead in batches under vacuum conditions. After all the filler is added, continue to knead under vacuum to obtain mixture 1. S4. After cooling mixture 1, add hydroxyl scavenger, coupling agent, crosslinking agent and catalyst in sequence under nitrogen protection, and mix evenly under vacuum to obtain the finished product.

[0043] In step S1, the dry mixing speed is 800-1000 r / min, the time is 5-10 min, the surface treatment agent is diluted with anhydrous ethanol to a mass fraction of 10%-15%, the mixing speed is 800-1000 r / min, the time is 30-60 min, the vacuum drying temperature is 80-100℃, the vacuum degree is -0.08~-0.095 MPa, and the time is 2-4 h; Preferably, in step S1, the dry mixing speed is 1000 r / min and the time is 8 min, the surface treatment agent is diluted with anhydrous ethanol to a mass fraction of 12%, the high-speed mixing speed is 1000 r / min and the time is 30 min, the vacuum drying temperature is 80℃, the vacuum degree is -0.08 to -0.095 MPa, and the time is 3 h.

[0044] In step S2, the mixing is carried out in a planetary mixer at a revolution rate of 10-30 r / min for 10-15 min. Preferably, in step S2, the revolution is 25 r / min and the time is 12 min.

[0045] In step S3, the batch is 3-5 batches, the kneading time is 20-30 min, the revolution is 30-40 r / min, the dispersion disc speed is 800-1000 r / min, and the material temperature is controlled not to exceed 60℃ during the kneading process; Preferably, in step S3, the batch is 4 batches, the kneading time is 25 min, the revolution is 35 r / min, the dispersion disc speed is 1000 r / min, and the material temperature is controlled not to exceed 55℃ during the kneading process.

[0046] In step S4, the mixture 1 is cooled to below 30°C, and the vacuum stirring time is 20-30 minutes. Preferably, in step S4, the vacuum stirring time is 25 minutes.

[0047] Thirdly, the present invention provides the application of the above-mentioned high thermal conductivity, low viscosity de-alcoholized silicone rubber in heat dissipation and sealing of high-power electronic devices, new energy vehicles or 5G communication equipment.

[0048] Examples 1-3 of this invention at least support the protection scope of α,ω-dihydroxy polydimethylsiloxane, dimethyl silicone oil, crosslinking agent, multi-scale compound thermally conductive filler, surface treatment agent, catalyst, coupling agent, hydroxyl scavenger and thixotropic anti-settling agent.

[0049] The α,ω-dihydroxy polydimethylsiloxane, in parts by weight, comprises 100 parts, and the viscosity of the low α,ω-dihydroxy polydimethylsiloxane is 1000-3500 mPa·s, which is summarized by the corresponding technical features "10 parts" and "1500 mPa·s" in the foregoing explanation and / or Examples 1-3. Therefore, those skilled in the art can reasonably infer that the technical feature "the α,ω-dihydroxy polydimethylsiloxane, in parts by weight, comprises 100 parts, and the viscosity of the low α,ω-dihydroxy polydimethylsiloxane is 1000-3500 mPa·s", its subordinate concept, its substantially equivalent technical means, and other technical means that can replace it within the scope of conventional technical means and common knowledge based on the existing level of technology should all fall within the protection scope of α,ω-dihydroxy polydimethylsiloxane.

[0050] The dimethyl silicone oil, by weight, comprises 5-20 parts, and the viscosity of the low-viscosity dimethyl silicone oil is 50-100 mPa·s, which is summarized by the corresponding technical features "10 parts, 5 parts, 20 parts" and "100 mPa·s" in the foregoing explanation and / or Examples 1-3. Therefore, those skilled in the art can reasonably infer that the technical feature "the dimethyl silicone oil, by weight, comprises 5-20 parts, and the viscosity of the low-viscosity dimethyl silicone oil is 50-100 mPa·s", its subordinate concept, its substantially equivalent technical means, and other technical means that can replace it within the scope of conventional technical means and common knowledge based on the existing technical level should all fall within the protection scope of dimethyl silicone oil.

[0051] The crosslinking agent, by weight, comprises 3-10 parts, summarized by the corresponding technical features "8 parts, 4 parts, 8.5 parts" in the foregoing explanation and / or Examples 1-3. Therefore, those skilled in the art can reasonably infer that the technical feature "the crosslinking agent, by weight, comprises 3-10 parts," its subordinate concepts, its substantially equivalent technical means, and other technical means that can replace it within the scope of conventional technical means and common knowledge based on the existing level of technology should all fall within the protection scope of the crosslinking agent.

[0052] The multi-scale composite thermally conductive filler, by weight, comprises 600-1200 parts, summarized by the foregoing explanation and / or the corresponding technical features "900 parts, 600 parts, 1200 parts" in Examples 1-3. Therefore, those skilled in the art can reasonably infer that the technical feature "the multi-scale composite thermally conductive filler, by weight, comprises 600-1200 parts," its subordinate concepts, its essentially equivalent technical means, and technical means that can replace other conventional technical means and common knowledge based on the existing technical level should all fall within the protection scope of the multi-scale composite thermally conductive filler.

[0053] The surface treatment agent comprises 2-8 parts by weight, and is a compound of titanate coupling agent and fluorinated silane coupling agent, wherein the mass ratio of titanate coupling agent to fluorinated silane coupling agent is 2-4:1; the titanate coupling agent is selected from one or more of isopropyltris(dioctylpyrophosphoryloxy) titanate and isopropyltris(isostearoyl) titanate; the fluorinated silane coupling agent is selected from 1H,1H,2H,2H-perfluorodecyltrimethoxysilane and 1H,1H,2H,2H-perfluorooctyltriethoxysilane. One or more of the silanes are summarized by the corresponding technical features in the foregoing explanation and / or Examples 1-3: "4 parts of isopropyltris(dioctylpyrophosphoryloxy)titanate and 1 part of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, 2 parts of isopropyltris(dioctylpyrophosphoryloxy)titanate and 0.5 parts of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, 6 parts of isopropyltris(dioctylpyrophosphoryloxy)titanate and 1.5 parts of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane". Therefore, based on reasonable presumption, those skilled in the art can determine that the technical feature "the surface treatment agent, by weight, comprises 2-8 parts, the surface treatment agent is a compound of titanate coupling agent and fluorinated silane coupling agent, the mass ratio of titanate coupling agent to fluorinated silane coupling agent is 2-4:1; the titanate coupling agent is selected from one or more of isopropyltris(dioctylpyrophosphoyloxy) titanate and isopropyltristearate; the fluorinated silane coupling agent is selected from one or more of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane and 1H,1H,2H,2H-perfluorooctyltriethoxysilane", its subordinate concept, its essentially equivalent technical means, and other technical means that can replace it within the scope of conventional technical means and common knowledge based on the existing technical level, should all fall within the protection scope of the surface treatment agent.

[0054] The catalyst, by weight, comprises 0.5-3 parts, summarized by the corresponding technical features "2.3 parts, 1.6 parts, and 3 parts" in the foregoing explanation and / or Examples 1-3. Therefore, those skilled in the art can reasonably presume that the technical feature "the catalyst, by weight, comprises 0.5-3 parts," its subordinate concepts, its substantially equivalent technical means, and other technical means that can replace it within the scope of conventional technical means and common knowledge based on the existing level of technology should all fall within the protection scope of the catalyst.

[0055] The coupling agent, by weight, comprises 1-5 parts, summarized by the corresponding technical features "3 parts, 1 part, 5 parts" in the foregoing explanation and / or Examples 1-3. Therefore, those skilled in the art can reasonably presume that the technical feature "the coupling agent, by weight, comprises 1-5 parts," its subordinate concepts, its substantially equivalent technical means, and other technical means that can replace it within the scope of conventional technical means and common knowledge based on the existing level of technology should all fall within the protection scope of the coupling agent.

[0056] The hydroxyl scavenger, by weight, comprises 1-4 parts, and the hydroxyl scavenger is hexamethyldisilazane or vinyltrimethoxysilane, summarized by the foregoing explanation and / or the corresponding technical features "2 parts, 1 part, 4 parts" and "hexamethyldisilazane" in Examples 1-3. Therefore, those skilled in the art can reasonably presume that the technical feature "the hydroxyl scavenger, by weight, comprises 1-4 parts," its subordinate concepts, its substantially equivalent technical means, and other technical means that can replace it within the scope of conventional technical means and common knowledge based on the existing level of technology should all fall within the protection scope of the hydroxyl scavenger.

[0057] The thixotropic anti-settling agent, by weight, comprises 2-6 parts, summarized by the corresponding technical features "4 parts, 2 parts, 6 parts" in the foregoing explanation and / or Examples 1-3. Therefore, those skilled in the art can reasonably presume that the technical feature "the thixotropic anti-settling agent, by weight, comprises 2-6 parts," its subordinate concepts, its substantially equivalent technical means, and other technical means that can replace it within the scope of conventional technical means and common knowledge based on the existing level of technology should all fall within the protection scope of the thixotropic anti-settling agent.

[0058] The beneficial effects of this invention are as follows: The present invention has at least the following beneficial effects: 1. Compared with the prior art, the present invention has better technical effects in terms of thermal conductivity, elongation at break and tensile strength.

[0059] According to experimental tests, the present invention increases the thermal conductivity from 3.7 W / (m·K) of the prior art to 6.5 W / (m·K).

[0060] According to experimental tests, the present invention increases the elongation at break from 9% in the prior art to 85%.

[0061] According to experimental tests, the present invention increases the tensile strength from 2.1 MPa in the prior art to 2.8 MPa.

[0062] 2. Compared with existing technologies, this invention provides a technical solution with a different technical concept, and its technical effect is equivalent to or slightly improved upon existing technologies. The difference between the technical concept of this invention and existing technologies lies in the use, but is not limited to, the use of a multi-scale composite thermally conductive filler composed of large-particle-size spherical alumina (20-50 μm), medium-particle-size near-spherical aluminum nitride (5-15 μm), and small-particle-size sheet-like boron nitride nanosheets (thickness 50-200 nm, sheet diameter 2-10 μm) and a multi-element synergistic surface modification technology. This solves the technical problem of the incompatibility between high thermal conductivity and low viscosity. The resulting silicone rubber has a thermal conductivity ≥6.0 W / (m·K) and a viscosity ≤80000 mPa·s, exhibiting excellent storage stability, curing performance, and mechanical properties. It can be widely used for heat dissipation and sealing in high-power electronic devices, new energy vehicles, 5G communication equipment, and other fields.

[0063] Furthermore, based on the present invention: Based on the comparison of Examples 1-3 and Comparative Examples 1-10, this invention achieves a novel technical effect by combining large-particle-size spherical alumina, medium-particle-size near-spherical aluminum nitride, and small-particle-size plate-like boron nitride nanosheets as thermally conductive fillers, and using titanate coupling agents and fluorinated silane coupling agents as surface treatment agents, employing a multi-element synergistic surface modification technology. This results in a combination of high thermal conductivity and low viscosity, along with good mechanical properties. The combined technical effect is superior to the sum of the effects of each individual technique. Detailed Implementation

[0064] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following content is merely an exemplary description of the scope of protection claimed by the present invention, and those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, and such changes should also fall within the scope of protection claimed by the present invention.

[0065] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all instruments, devices, equipment, reagents, products, etc., used in the embodiments of the present invention are obtained through conventional commercial means.

[0066] Example 1: A high thermal conductivity, low viscosity dealcoholized silicone rubber and its preparation method It consists of the following raw materials in parts by weight: Component A: 100 parts of α,ω-dihydroxypolydimethylsiloxane (viscosity 1500 mPa·s); Component B: 10 parts of dimethyl silicone oil (viscosity 100 mPa·s); Component C: Crosslinking agent consists of 6 parts methyltrimethoxysilane and 2 parts vinyltrimethoxysilane; Component D: Multi-scale composite thermally conductive filler, totaling 900 parts, consisting of D1, D2, and D3: D1: 540 parts of spherical alumina (average particle size 30 μm); D2: 270 parts of near-spherical aluminum nitride (average particle size 10 μm); D3: 90 parts of boron nitride nanosheets (average thickness 100 nm, sheet diameter 5 μm); Component E: The surface treatment agent is 4 parts of isopropyltris(dioctylpyrophosphoryloxy)titanate and 1 part of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane. Component F: The catalyst consists of 1.5 parts of tetraisobutyl titanate and 0.8 parts of diisopropyl titanate (ethyl acetoacetate); Component G: Coupling agent is 3 parts of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane; Component H: Hydroxyl scavenger is 2 parts of hexamethyldisilazane; Component I: Thixotropic antisettling agent is 4 parts of fumed silica (specific surface area 200 m² / g).

[0067] The preparation method includes the following steps: S1. Add D1, D2, and D3 to a high-speed mixer according to the ratio and dry mix at 1000 r / min for 8 min; dilute component E with anhydrous ethanol to 12%, spray it in, and continue high-speed mixing for 20 min; vacuum dry at 80℃ for 3 h to obtain surface-modified thermally conductive filler.

[0068] S2. Add components A and B to a double planetary mixer and stir for 12 minutes at 25-30°C and 25 r / min under vacuum to obtain the base adhesive mixture.

[0069] S3. Add the surface-modified thermally conductive filler and component I to the base adhesive mixture in 4 batches, kneading each batch for 25 min (revolution 35 r / min, dispersion disc speed 1000 r / min). After all the ingredients are added, continue vacuum kneading for 50 min, controlling the temperature ≤55℃, to obtain mixture 1.

[0070] S4. Cool mixture 1 to 28°C, add components H, G, C and F in sequence under nitrogen protection, stir for 12 min for each, and finally stir under vacuum for 25 min. Fill into the container, seal with nitrogen, and the finished product is obtained.

[0071] Example 2: A high thermal conductivity, low viscosity dealcoholized silicone rubber and its preparation method It consists of the following raw materials in parts by weight: Component A: 100 parts of α,ω-dihydroxypolydimethylsiloxane (viscosity 1500 mPa·s); Component B: 5 parts of dimethyl silicone oil (viscosity 100 mPa·s); Component C: Crosslinking agent consists of 3 parts methyltrimethoxysilane and 1 part vinyltrimethoxysilane; Component D: Multi-scale composite thermally conductive filler, totaling 600 parts, consisting of D1, D2, and D3: D1: 360 parts of spherical alumina (average particle size 30 μm); D2: 180 parts of near-spherical aluminum nitride (average particle size 10 μm); D3: 60 parts of boron nitride nanosheets (average thickness 100 nm, sheet diameter 5 μm); Component E: The surface treatment agent is 2 parts of isopropyltris(dioctylpyrophosphoryloxy)titanate and 0.5 parts of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane; Component F: The catalyst consists of 1 part tetraisobutyl titanate and 0.6 parts diisopropyl titanate (ethyl acetoacetate); Component G: Coupling agent is 1 part of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane; Component H: Hydroxyl scavenger is 1 part hexamethyldisilazane; Component I: Thixotropic antisettling agent is 2 parts of fumed silica (specific surface area 200 m² / g).

[0072] The preparation method is the same as in Example 1.

[0073] Example 3: A high thermal conductivity, low viscosity dealcoholized silicone rubber and its preparation method It consists of the following raw materials in parts by weight: Component A: 100 parts of α,ω-dihydroxypolydimethylsiloxane (viscosity 1500 mPa·s); Component B: 20 ​​parts of dimethyl silicone oil (viscosity 100 mPa·s); Component C: The crosslinking agent is 7 parts of methyltrimethoxysilane and 1.5 parts of vinyltrimethoxysilane; Component D: Multi-scale composite thermally conductive filler, totaling 1200 parts, consisting of D1, D2, and D3: D1: 720 parts of spherical alumina (average particle size 30 μm); D2: 360 parts of near-spherical aluminum nitride (average particle size 10 μm); D3: 120 parts of boron nitride nanosheets (average thickness 100 nm, sheet diameter 5 μm); Component E: The surface treatment agent is 6 parts of isopropyl tris(dioctyl pyrophosphoryloxy) titanate and 1.5 parts of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane; Component F: The catalyst consists of 2 parts tetraisobutyl titanate and 1 part diisopropyl di(ethyl acetoacetate) titanate; Component G: Coupling agent is 5 parts of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane; Component H: Hydroxyl scavenger is 4 parts of hexamethyldisilazane; Component I: Thixotropic antisettling agent is 6 parts of fumed silica (specific surface area 200 m² / g).

[0074] The preparation method is the same as in Example 1.

[0075] The alcohol-free, high thermal conductivity, single-component room temperature vulcanizing silicone rubber adhesive prepared in Example 1 of Comparative Example 1 CN114686158A.

[0076] Comparative Example 2 The difference from Example 1 is that 900 parts of multi-scale composite thermally conductive filler in component D are replaced with 900 parts of spherical alumina (average particle size 30 μm), while the other amounts and preparation methods are the same as in Example 1.

[0077] Comparative Example 3 The difference from Example 1 is that 900 parts of multi-scale composite thermally conductive filler in component D are replaced with 900 parts of spherical aluminum nitride (average particle size 10 μm), while the other amounts and preparation methods are the same as in Example 1.

[0078] Comparative Example 4 The difference from Example 1 is that the 900 parts of multi-scale composite thermally conductive filler in component D are replaced with 900 parts of boron nitride nanosheets (average thickness 100 nm, sheet diameter 5 μm), while the other amounts and preparation methods are the same as in Example 1.

[0079] Comparative Example 5 The difference from Example 1 is that the 900 parts of multi-scale composite thermally conductive filler in component D are replaced with 450 parts of spherical alumina (average particle size 30 μm) and 450 parts of spherical aluminum nitride (average particle size 10 μm), while the other amounts and preparation methods are the same as in Example 1.

[0080] Comparative Example 6 The difference from Example 1 is that the 900 parts of multi-scale composite thermally conductive filler in component D are replaced with 450 parts of spherical alumina (average particle size 30 μm) and 450 parts of boron nitride nanosheets (average thickness 100 nm, sheet diameter 5 μm), while the other amounts and preparation methods are the same as in Example 1.

[0081] Comparative Example 7 The difference from Example 1 is that the 900 parts of multi-scale composite thermally conductive filler in component D are replaced with 450 parts of spherical aluminum nitride (average particle size 10 μm) and 450 parts of boron nitride nanosheets (average thickness 100 nm, sheet diameter 5 μm), while the other amounts and preparation methods are the same as in Example 1.

[0082] Comparative Example 8 The difference from Example 1 is that the 900 parts of multi-scale composite thermally conductive filler in component D are replaced with 270 parts of spherical alumina (average particle size 30 μm), 450 parts of quasi-spherical aluminum nitride (average particle size 10 μm), and 180 parts of boron nitride nanosheets (average thickness 100 nm, sheet diameter 5 μm). The remaining amounts and preparation methods are the same as in Example 1.

[0083] Comparative Example 9 The difference from Example 1 is that the surface treatment agent of component E is replaced with 5 parts of isopropyltris(dioctylpyrophosphoryloxy)titanate, while the remaining amounts and preparation methods are the same as in Example 1.

[0084] Comparative Example 10 The difference from Example 1 is that no hydroxyl scavenger of component H is added, while the other dosages and preparation methods are the same as in Example 1.

[0085] Detection Example 1 The alcohol-free silicone rubbers prepared in the examples and comparative examples were subjected to performance tests on their viscosity, thermal conductivity, surface drying time, hardness, tensile strength, elongation at break and shear strength.

[0086] Detection method: Viscosity: Determined using the ring and ball method according to GB / T 2794-2022 standard; Thermal conductivity: determined according to ASTM D5470 standard method; Surface drying time: determined according to the standard method of GB / T 13477.5; Hardness: determined according to the standard method of GB / T 531.1; Tensile strength, elongation at break, and shear strength: determined according to the standard method of GB / T 528.

[0087] The test results are shown in Table 1.

[0088] Table 1. Performance results of the dealcoholized silicone rubbers prepared in the examples and comparative examples

[0089] Note: "\" indicates that it was not detected. As shown in Table 1, the silicone rubber prepared in Examples 1-3 has a thermal conductivity ≥6.0 W / (m·K), a viscosity ≤80000mPa·s, and excellent curing and mechanical properties.

[0090] Test Example 2: Storage Stability The de-alcoholized silicone prepared in the examples and comparative examples were stored at room temperature for 6 months, and the viscosity change rate and whether stratification occurred were detected. The smaller the viscosity change rate, the more stable the storage. The absence of stratification after 6 months of storage indicates better filler dispersibility. In addition, the viscosity data also shows that the better the filler dispersibility, the lower the viscosity.

[0091] According to the results in Table 1, the silicone prepared in Examples 1-3 showed no stratification after 6 months of storage, and the viscosity increased by less than 10%, indicating good storage stability.

[0092] Verification of technical effectiveness and / or analysis of solutions to technical problems: This invention solves the technical challenge of achieving both high thermal conductivity and low viscosity through an innovative multi-scale filler compound system and multi-element synergistic surface modification technology. The resulting silicone has a thermal conductivity ≥6.0 W / (m·K) and a viscosity ≤80000mPa·s, and exhibits excellent storage stability, curing performance, and mechanical properties.

[0093] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A high thermal conductivity, low viscosity, alcohol-free type of silicone rubber, characterized in that, The raw materials include the following parts by weight: 100 parts of α,ω-dihydroxy polydimethylsiloxane, 5-20 parts of dimethyl silicone oil, 3-10 parts of crosslinking agent, 600-1200 parts of multi-scale composite thermally conductive filler, 2-8 parts of surface treatment agent, 0.5-3 parts of catalyst, 1-5 parts of coupling agent, 1-4 parts of hydroxyl scavenger, and 2-6 parts of thixotropic anti-settling agent; the multi-scale composite thermally conductive filler is composed of large-particle-size spherical alumina, medium-particle-size near-spherical aluminum nitride, and small-particle-size plate-like boron nitride nanosheets.

2. The high thermal conductivity, low viscosity, alcohol-free silicone rubber according to claim 1, characterized in that, In the multi-scale composite thermally conductive filler, the average particle size of large-diameter spherical alumina is 20-50 μm, accounting for 50%-70% of the total mass of the multi-scale composite thermally conductive filler; the average particle size of medium-diameter spherical aluminum nitride is 5-15 μm, accounting for 20%-35% of the total mass of the multi-scale composite thermally conductive filler; and the average thickness of small-diameter sheet-like boron nitride nanosheets is 50-200 nm, and the average sheet diameter is 2-10 μm, accounting for 5%-15% of the total mass of the multi-scale composite thermally conductive filler.

3. The high thermal conductivity, low viscosity, alcohol-free silicone rubber according to claim 2, characterized in that, In the multi-scale composite thermally conductive filler, the average particle size of the large-particle-size spherical alumina, the average particle size of the medium-particle-size spherical aluminum nitride, and the particle size of the small-particle-size plate-shaped boron nitride nanosheets are 5-10:2-4:

1.

4. The high thermal conductivity, low viscosity, alcohol-free silicone rubber according to claim 1, characterized in that, The surface treatment agent is a compound of titanate coupling agent and fluorinated silane coupling agent, wherein the mass ratio of titanate coupling agent to fluorinated silane coupling agent is 2-4:

1.

5. The high thermal conductivity, low viscosity, alcohol-free silicone rubber according to claim 4, characterized in that, The titanate coupling agent is selected from isopropyl tris(dioctylpyrophosphoryloxy) titanate and / or isopropyl tris(isostearoyl) titanate; the fluorinated silane coupling agent is selected from 1H,1H,2H,2H-perfluorodecyltrimethoxysilane and / or 1H,1H,2H,2H-perfluorooctyltriethoxysilane.

6. The high thermal conductivity, low viscosity, alcohol-free silicone rubber according to claim 1, characterized in that, The viscosity of the α,ω-dihydroxypolydimethylsiloxane is 1000-3500 mPa·s; the viscosity of the dimethyl silicone oil is 50-100 mPa·s.

7. The high thermal conductivity, low viscosity, alcohol-free silicone rubber according to claim 1, characterized in that, The hydroxyl scavenger is hexamethyldisilazane or vinyltrimethoxysilane, and the catalyst is selected from one or more of tetrapropyl titanate, tetraisopropyl titanate, tetraisobutyl titanate, and di(ethyl acetoacetate) titanate.

8. The method for preparing the high thermal conductivity, low viscosity dealcoholized silicone rubber according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Dry-mix the multi-scale composite thermal conductive filler evenly to obtain a multi-scale composite thermal conductive filler mixture; dilute the surface treatment agent with anhydrous ethanol and spray it onto the surface of the multi-scale composite thermal conductive filler mixture, mix and then vacuum dry to obtain a surface-modified thermal conductive filler. S2. Mix α,ω-dihydroxypolydimethylsiloxane and dimethyl silicone oil evenly under vacuum at room temperature to obtain a base adhesive mixture; S3. Add surface-modified thermally conductive filler and thixotropic anti-settling agent to the base adhesive mixture in batches, and knead in batches under vacuum conditions. After all the filler is added, continue to knead under vacuum to obtain mixture 1. S4. After cooling mixture 1, add hydroxyl scavenger, coupling agent, crosslinking agent and catalyst in sequence under nitrogen protection, and mix evenly under vacuum to obtain the finished product.

9. The preparation method according to claim 8, characterized in that, In step S1, the surface treatment agent is diluted with anhydrous ethanol to a mass fraction of 10%-15%, the vacuum drying temperature is 80-100℃, the vacuum degree is -0.08 to -0.095 MPa, and the time is 2-4 h.

10. The preparation method according to claim 8, characterized in that, In step S3, the material temperature is controlled to not exceed 60°C during the kneading process; in step S4, the mixture 1 is cooled to below 30°C.

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