An asymmetric structure powder treating agent, a preparation method and application thereof

Abstract

The application belongs to the technical field of modified silicone oil, and particularly relates to an asymmetric structure powder treating agent and a preparation method and application thereof. The asymmetric structure powder treating agent can directly react with hydroxyl groups on the surface of a heat-conducting filler, without a pre-hydrolysis step, thereby eliminating the hidden danger of alcohol release, anchoring more efficiently, effectively reducing the viscosity of the heat-conducting material, and significantly improving the long-term reliability of the heat-conducting filler in a high-temperature and high-humidity environment. The preparation of the asymmetric structure powder treating agent provided by the application comprises: ring-opening polymerization of hexamethylcyclotrisiloxane, and then end-capping with dimethyl hydrogen-containing chlorosilane; then sequentially reacting with vinyl methyl dialkoxysilane, 1,1,3,3-tetramethyldisiloxane and vinyl dimethyl acetoxy silane; and finally performing a hydrolysis reaction in a buffer solution to obtain the asymmetric structure powder treating agent. The method has mild process conditions, simple operation and is suitable for industrial production.

Description

Technical Field

[0001] This invention specifically relates to an asymmetric structure powder treatment agent, its preparation method, and its application, belonging to the field of modified silicone oil technology. Background Technology

[0002] With the rise and rapid development of emerging technologies such as 5G, artificial intelligence, and smart cars, the demand for high-performance chips will continue to increase. Facing the heat dissipation requirements of high-performance, miniaturized, and highly integrated electronic components with power exceeding 100W, the thermal conductivity of thermal interface materials needs to be increasingly higher. Therefore, the loading of thermally conductive fillers in thermal interface materials also needs to be higher, typically exceeding 90wt% or even 95wt%. To reduce the viscosity of the material and improve the aging resistance of the thermally conductive material, a large amount of powder treatment agent is usually added to improve the compatibility between the thermally conductive filler and the organosilicon matrix. Among many powder treatment agents, those containing a hydrolyzable group (-Si(OR)3) at one end and a hydrophobic long-chain alkyl or organosilicon chain structure at the other end are most commonly used. These agents can anchor the surface of the thermally conductive filler through the hydrolyzable group, while the other end is highly compatible with the organosilicon matrix, improving the dispersibility and stability of the thermally conductive filler. However, coupling agents containing hydrolyzable groups usually require hydrolysis to generate silanol groups before reacting with the thermally conductive filler, which is a relatively slow process. In addition, the molecules contain a large number of hydrolyzable groups. Due to steric hindrance and other reasons, hydrolyzable groups will remain in the treatment agent. When the thermally conductive material is packaged into electronic devices, after long-term high temperature and high humidity aging, the residual hydrolyzable groups slowly hydrolyze and release methanol or ethanol, which will corrode the precision electronic components.

[0003] In summary, existing technologies have obvious shortcomings. It is of great significance to develop a powder treatment agent that can efficiently process thermally conductive fillers, has excellent filler dispersibility, stability and aging resistance, does not release alcohols due to residual hydrolyzable groups and thus does not corrode electronic components, and does not affect the performance of electronic devices. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing an asymmetric structure powder treatment agent, its preparation method, and its applications. This asymmetric structure powder treatment agent can directly react with the hydroxyl groups on the surface of thermally conductive fillers without the need for a pre-hydrolysis step, eliminating the potential for alcohol release in existing technologies. It also offers more efficient anchoring, effectively reduces the viscosity of thermally conductive materials, and significantly improves the long-term reliability of thermally conductive fillers under high-temperature and high-humidity environments. The preparation method provided by this invention features mild process conditions, simple operation, and is suitable for industrial production.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: an asymmetric structure powder treatment agent, the structural formula of which is shown below: Where n is any integer from 5 to 30; R is a functional alkyl group.

[0006] Furthermore, R is selected from any of the following structural formulas: .

[0007] This invention also discloses a method for preparing an asymmetric structure powder treatment agent, the preparation method comprising the following steps: S1. In an anhydrous nonpolar solvent, in the presence of an initiator composition and a polar accelerator, hexamethylcyclotrisiloxane is subjected to ring-opening polymerization and then capped with dimethylhydrochlorosilane to obtain an asymmetric single-ended hydrogen-containing silicone oil. S2. The asymmetric single-ended hydrogen-containing silicone oil obtained in step S1 is mixed with vinylmethyldialkoxysilane and reacted under the action of a platinum catalyst to obtain alkoxy-modified silicone oil. S3. The alkoxy-modified silicone oil obtained in step S2 is reacted with 1,1,3,3-tetramethyldisiloxane in the presence of the catalyst tris(pentafluorophenyl)borane to obtain an asymmetric hydrogen-containing silicone oil. S4. The asymmetric hydrogen-containing silicone oil obtained in step S3 is reacted with vinyl dimethyl acetoxysilane under the action of a platinum catalyst to obtain asymmetric acetoxy-terminated polydimethylsiloxane. S5. The asymmetric acetoxy-terminated polydimethylsiloxane obtained in step S4 is hydrolyzed in a buffer solution to obtain asymmetric silanol-terminated polydimethylsiloxane.

[0008] Furthermore, in step S1, the preparation process includes ring-opening polymerization and end-capping reaction; The ring-opening polymerization involves slowly adding an initiator composition to an anhydrous nonpolar solvent pre-cooled to 0-10°C, stirring for 5-60 min, slowly adding dehydrated hexamethylcyclotrisiloxane to the above solution, stirring to dissolve, then adding a polar accelerator, and reacting at 5-50°C for 4-24 h. The end-capping reaction is carried out when the conversion rate of hexamethylcyclotrisiloxane is greater than 90%, dimethylhydrochlorosilane is added, and the reaction is continued for 0.5-4 hours.

[0009] Further, in step S1, the molar ratio of hexamethylcyclotrisiloxane to the initiator composition is (4~20):1.

[0010] Further, in step S1, the ratio between the amount of hexamethylcyclotrisiloxane and the mass of the polar promoter and the mass of dimethylhydrochlorosilane is 1 mol : (15~25) g : (5~25) g.

[0011] Further, in step S2, by mass fraction, there are 180-220 parts of asymmetric single-ended hydrogen-containing silicone oil, 6-20 parts of vinylmethyldialkoxysilane, and 0.03-0.05 parts of platinum catalyst.

[0012] Further, in step S3, the ratio between the mass of alkoxy-modified silicone oil, the amount of 1,1,3,3-tetramethyldisiloxane, and the amount of tris(pentafluorophenyl)borane is (90~120) g : (0.5~1) mol : 0.2 mol.

[0013] Further, in step S4, by mass fraction, there are 90-110 parts of asymmetric hydrogen-containing silicone oil, 11-40 parts of vinyldimethylacetoxysilane, and 0.03-0.05 parts of platinum catalyst.

[0014] Further, in step S5, the mass ratio of asymmetric acetoxy-terminated polydimethylsiloxane to buffer solution is 1:(8~15).

[0015] Furthermore, in step S5, the pH of the hydrolysis reaction is 4.5~5.5.

[0016] Furthermore, in step S2, the reaction temperature is 40~100℃ and the reaction time is 1~12h; Furthermore, in step S3, the reaction temperature is 0~50℃ and the reaction time is 0.5~4h; Furthermore, in step S4, the reaction temperature is 40~90℃ and the reaction time is 1~12h; Furthermore, in step S5, the reaction temperature is 5~40℃ and the reaction time is 1~12h.

[0017] Further, in step S1, the initiator composition is a n-butyllithium n-hexane solution, or a mixture of a n-butyllithium n-hexane solution and dimethylphenylsilanol; Further, in step S1, the polar promoter is at least one of tetrahydrofuran, N,N-dimethylformamide, or dimethyl sulfoxide; Further, in step S1, the anhydrous nonpolar solvent is at least one of anhydrous n-hexane, anhydrous cyclohexane, or anhydrous toluene; Further, in step S2, the vinylmethyldialkoxysilane is one of vinylmethyldimethoxysilane or vinyldimethylethoxysilane.

[0018] Further, in step S5, the buffer solution is a compound buffer solution of acetic acid and sodium acetate.

[0019] The present invention also discloses the application of an asymmetric structure powder treatment agent, wherein the treatment agent is applied to the surface treatment of thermally conductive fillers; The thermally conductive filler is at least one of alumina, zinc oxide, boron nitride, aluminum nitride, diamond, and graphene.

[0020] The beneficial effects of this invention are: The asymmetric structure powder treatment agent prepared by this invention has an alkyl-modified polydimethylsiloxane structure at one end and a bis-silanol structure at the other end. The bis-silanol group can directly react with the hydroxyl groups on the surface of the thermally conductive filler without the need for a pre-hydrolysis step, eliminating the risk of alcohol release in existing technologies and providing more efficient anchoring. The other end has good compatibility with the matrix and its chain segments can move freely, effectively reducing the viscosity of the thermally conductive material. It will not release small organic molecules such as alcohols during subsequent aging, thus preventing damage to precision electronic devices and significantly improving the long-term reliability of the thermally conductive filler in high-temperature and high-humidity environments. The preparation method provided by this invention has mild process conditions, is simple to operate, and is suitable for industrial production. Detailed Implementation

[0021] The specific embodiments of the present invention will be described in detail below. The present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used is for describing particular embodiments only and is not intended to limit the invention.

[0023] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this invention are all commercially available industrial products or chemical reagents. The sources of each raw material are as follows: n-butyllithium n-hexane solution (2.5 mol / L, CAS No.: 109-72-8, Aladdin Reagent). Dimethylphenylsilanol (GC>98%, CAS No.: 5272-18-4, Maclean's Reagent) Hexamethylcyclotrisiloxane (D3, GC>99%, CAS No.: 541-05-9, Yuneng Silicon Materials) Dimethylhydrochlorosilane (CAS No.: 1066-35-9, GC>96%, Aladdin Reagent) Vinyl dimethyl methoxysilane (CAS No.: 16546-47-7, GC>95%, Guangdong Wengjiang Reagent) Vinyl dimethyl ethoxysilane (CAS No.: 5356-83-2, GC>98%, Aladdin Reagent) Tris(pentafluorophenyl)borane (B(C6F5)3, CAS No.: 1109-15-5, GC>97%, Aladdin Reagent) Vinyl dimethyl acetoxysilane ((vinyl dimethyl silyl) acetate, CAS No.: 3293-09-2, GC>95%, BOC Sciences) Acetic acid and sodium acetate buffer solution (pH 5.2 (25) o C), 3M, 0.2 μm filtered, Aladdin reagent).

[0024] This invention provides an asymmetric structure powder treatment agent, the structural formula of which is shown below: Where n is any integer from 5 to 30; R is a functional alkyl group.

[0025] Furthermore, R is selected from any of the following structural formulas: .

[0026] This invention also provides a method for preparing an asymmetric structure powder treatment agent, the preparation method comprising the following steps: S1. In an anhydrous nonpolar solvent, in the presence of an initiator composition and a polar accelerator, hexamethylcyclotrisiloxane is subjected to ring-opening polymerization and then capped with dimethylhydrochlorosilane to obtain an asymmetric single-ended hydrogen-containing silicone oil. S2. The asymmetric single-ended hydrogen-containing silicone oil obtained in step S1 is mixed with vinylmethyldialkoxysilane and reacted under the action of a platinum catalyst to obtain alkoxy-modified silicone oil.

[0027] S3. The alkoxy-modified silicone oil obtained in step S2 is reacted with 1,1,3,3-tetramethyldisiloxane in the presence of the catalyst tris(pentafluorophenyl)borane to obtain an asymmetric hydrogen-containing silicone oil.

[0028] S4. The asymmetric hydrogen-containing silicone oil obtained in step S3 is reacted with vinyl dimethyl acetoxysilane under the action of a platinum catalyst to obtain asymmetric acetoxy-terminated polydimethylsiloxane.

[0029] S5. The asymmetric acetoxy-terminated polydimethylsiloxane obtained in step S4 is hydrolyzed in a buffer solution to obtain asymmetric silanol-terminated polydimethylsiloxane.

[0030] Specifically, in step S1, the preparation of asymmetric single-ended hydrogen-containing silicone oil includes ring-opening polymerization and end-capping reaction; the specific steps include: slowly adding the initiator composition to an anhydrous nonpolar solvent pre-cooled to 0~10℃, stirring for 5~60min, slowly adding dehydrated hexamethylcyclotrisiloxane (D3) to the above solution, stirring to dissolve, then adding a polar promoter, and reacting at 5~50℃ for 4~24h; when the conversion rate of hexamethylcyclotrisiloxane is greater than 90%, adding dimethylhydrochlorosilane, and continuing the reaction for 0.5~4h.

[0031] The post-processing steps in step S1 include: after the reaction is complete, adding an adsorbent and stirring to adsorb the produced salt, then removing the adsorbent by filtration. Next, the resulting solution is washed twice with distilled water, and residual water, solvent, and unreacted monomers are removed by vacuum distillation to obtain asymmetric single-terminated hydrogen-containing silicone oil.

[0032] The post-processing operation in step S2 includes: heating after the reaction is complete and removing excess small molecules by vacuum distillation to obtain alkoxy-modified silicone oil.

[0033] The preparation steps of step S3 include: dissolving the alkoxy-modified silicone oil obtained in step S2 and tris(pentafluorophenyl)borane (B(C6F5)3) in anhydrous toluene, purging with argon gas, and maintaining the temperature at 0-50°C; separately, thoroughly mixing 1,1,3,3-tetramethyldisiloxane (HMMH) with anhydrous toluene to obtain mixture B1. Under argon protection, mixture B1 is slowly added dropwise to the silicone oil solution, and the reaction is carried out for 0.5-4 hours until no more bubbles are generated, at which point the reaction is complete.

[0034] The post-processing steps in step S3 include: adding Al2O3 and stirring for 1 hour to adsorb the catalyst after the reaction is complete, and filtering to remove the solid alumina. Toluene solvent and excess HMMH are removed by vacuum distillation to obtain an asymmetric hydrogen-containing silicone oil.

[0035] The post-processing operation in step S4 includes: heating and vacuum distillation after the reaction to remove excess small molecules, in order to obtain asymmetric acetoxy-terminated polydimethylsiloxane.

[0036] Specifically, in step S1, the molar ratio of hexamethylcyclotrisiloxane to the initiator composition is (4~20):1.

[0037] Specifically, in step S1, the ratio between the amount of hexamethylcyclotrisiloxane, the mass of the polar promoter, and the mass of dimethylhydrochlorosilane is 1 mol : (15~25) g : (5~25) g.

[0038] Specifically, in step S2, by mass fraction, there are 180-220 parts of asymmetric single-ended hydrogen-containing silicone oil, 6-20 parts of vinylmethyldialkoxysilane, and 0.03-0.05 parts of platinum catalyst.

[0039] Specifically, in step S3, the ratio between the mass of alkoxy-modified silicone oil, the amount of 1,1,3,3-tetramethyldisiloxane, and the amount of tris(pentafluorophenyl)borane is (90~120) g : (0.5~1) mol : 0.2 mol.

[0040] Specifically, in step S4, by mass fraction, there are 90-110 parts of asymmetric hydrogen-containing silicone oil, 11-40 parts of vinyldimethylacetoxysilane, and 0.03-0.05 parts of platinum catalyst.

[0041] Specifically, in step S5, the mass ratio of asymmetric acetoxy-terminated polydimethylsiloxane to buffer solution is 1:(8~15).

[0042] It should be noted that in this invention, in step S1, the molar ratio of hexamethylcyclotrisiloxane (D3) to the initiator composition is limited to (4~20):1. If this range is not met, it is difficult to obtain the desired product structure. When the molar ratio of D3 to initiator is greater than 20:1, the product molecular weight is too large, and the system viscosity is too high, which is detrimental to subsequent processing and filler surface treatment. When the molar ratio of D3 to initiator is less than 4:1, excessive initiator dosage leads to a product molecular weight that is too small, resulting in low yield. The treatment agent is prone to volatilization and escape during the high-temperature service of the thermal interface material, and the end-capping selectivity decreases, easily generating double-ended active byproducts and destroying the asymmetric structure. Only by controlling the molar ratio of D3 to initiator within the range of (4~20):1 can a suitable polymerization rate (conversion rate ≥90% within 4-24h), an ideal molecular weight of 1000~3860, a narrow molecular weight distribution of 1.05~1.15, and high end-capping selectivity be simultaneously achieved, thereby obtaining a structurally regular asymmetric single-ended hydrogen-containing silicone oil.

[0043] Specifically, in step S5, the pH of the hydrolysis reaction is 4.5 to 5.5.

[0044] Specifically, in step S2, the reaction temperature is 40~100℃ and the reaction time is 1~12h; Specifically, in step S3, the reaction temperature is 0~50℃ and the reaction time is 0.5~4h; Specifically, in step S4, the reaction temperature is 40~90℃ and the reaction time is 1~12h; Specifically, in step S5, the reaction temperature is 5~40℃ and the reaction time is 1~12h.

[0045] Specifically, in step S1, the initiator composition is a n-butyllithium n-hexane solution, or a mixture of a n-butyllithium n-hexane solution and dimethylphenylsilanol; Specifically, in step S1, the polar promoter is at least one of tetrahydrofuran, N,N-dimethylformamide, or dimethyl sulfoxide; Specifically, in step S1, the anhydrous nonpolar solvent is at least one of anhydrous n-hexane, anhydrous cyclohexane, or anhydrous toluene. Specifically, in step S2, the vinylmethyldialkoxysilane is one of vinylmethyldimethoxysilane or vinyldimethylethoxysilane.

[0046] Specifically, in step S5, the buffer solution is a buffer solution composed of acetic acid and sodium acetate.

[0047] It should be noted that in this invention, the buffer solution is a mixture of acetic acid and sodium acetate, and strong acid / base systems such as hydrochloric acid or sodium hydroxide cannot be used for pH adjustment, nor can other inorganic salt buffer systems be used. The acetic acid / sodium acetate buffer solution has its maximum buffering capacity in the pH range of 4.5 to 5.5. Through the equilibrium of acetic acid molecules and acetate ions, H⁺ is released slowly and controllably, ensuring localized pH uniformity and avoiding localized over-acidity / over-alkali regions caused by strong acids / bases. Under these mild conditions, the hydrolysis of acetoxy groups proceeds smoothly, while other side reactions are significantly suppressed. Simultaneously, acetic acid is a volatile organic acid that can be completely removed by vacuum distillation, leaving no corrosive ions, ensuring the safety of the product for precision electronic components.

[0048] The present invention also provides an application of an asymmetric structure powder treatment agent, wherein the treatment agent is applied to the surface treatment of thermally conductive fillers; The thermally conductive filler is at least one of alumina, zinc oxide, boron nitride, aluminum nitride, diamond, and graphene.

[0049] To better illustrate the embodiments of the present invention, the present invention will be further described in detail below through specific examples.

[0050] Example 1

[0051] This embodiment prepares an α-n-butyl-Ω-disiloxy-terminated polydimethylsiloxane, including the following steps: S1. Slowly add 80 mL of n-butyllithium hexane solution (2.5 mol / L, 0.2 mol) to 320 mL of anhydrous toluene pre-cooled to 0 °C and stir for 60 min. Slowly add 400 g of dehydrated hexamethylcyclotrisiloxane (D3, 1.80 mol) to the above solution and stir to dissolve. Then add 32 g of dimethylformamide and react at 5 °C for 24 h. Add 20 g of dimethylhydrochlorosilane and continue the reaction for 2 h. Then add diatomaceous earth and stir to adsorb the produced salt. Then remove the adsorbent by filtration. Next, wash the obtained solution twice with 400 mL of distilled water. Remove residual water, solvent and unreacted monomers by vacuum distillation to obtain asymmetric single-terminated hydrogen-containing silicone oil, product 345 g (molecular weight 2520, molecular weight distribution 1.10, hydrogen content 0.040 wt%).

[0052] S2. Mix 200g of the asymmetric single-terminated hydrogen-containing silicone oil prepared in step S1 with 12g of vinylmethyldimethoxysilane, stir for 10 minutes, add 0.05g of Castel platinum catalyst, and heat to 40℃ while stirring. React for 12h, and finally heat to 120℃ and remove excess small molecules by vacuum distillation to obtain α-n-butyl-Ω-dimethoxy-terminated polydimethylsiloxane.

[0053] S3. Dissolve 100 g of α-n-butyl-Ω-dimethoxy-terminated polydimethylsiloxane (PDM) prepared in step S2 and tris(pentafluorophenyl)borane (B(C6F5)3) (102 mg, 0.2 mmol) in 100 mL of anhydrous toluene to obtain mixture A1. Proceed under argon protection and maintain the temperature at 25 °C. Separately, thoroughly mix 1,1,3,3-tetramethyldisiloxane (HMMH) (134 g, 1 mol) with 100 mL of anhydrous toluene to obtain mixture B1. Under argon protection, slowly add mixture B1 dropwise to solution A1 and react for 0.5 h until no bubbles are generated, at which point the reaction is complete. Add 100 g of Al2O3 and stir for 1 h to adsorb the catalyst. Filter to remove the alumina solid. Remove the toluene solvent and excess HMMH by vacuum distillation to obtain 102.8 g of α-n-butyl-Ω-dihydro-terminated polydimethylsiloxane.

[0054] S4. Mix 100g of the obtained asymmetric structure hydrogen-containing silicone oil with 18.8g of vinyldimethylacetoxysilane (0.1mol) and stir for 5min. Add 0.03g of Castel platinum catalyst and react at 40℃ for 12h. Remove excess low molecular weight by vacuum distillation at 100℃ to obtain α-n-butyl-Ω-diacetoxy-terminated polydimethylsiloxane.

[0055] S5. The asymmetric acetoxy-terminated polydimethylsiloxane obtained in step S4 is mixed with 1000g of acetic acid / sodium acetate buffer solution and stirred for 1 hour. The hydrolysis temperature is 40℃ to obtain asymmetric silanol-terminated polydimethylsiloxane, which is the treatment agent structure S1 of the present invention, with a viscosity of 36mPa.s.

[0056] Example 2

[0057] This embodiment prepares an α-dimethylphenyl-Ω-disiloxyl-terminated polydimethylsiloxane, including the following steps: S1. Dissolve 30.44 g of dimethylphenylsilanol (0.2 mol) in 320 mL of anhydrous toluene and cool to 5 °C. Stir for 10 min. Under nitrogen protection, slowly add 80 mL of n-butyllithium hexane solution (2.5 mol / L, 0.2 mol) over 1 h, paying attention to the released gas. Continue the reaction for 60 min. Slowly add 400 g of dehydrated hexamethylcyclotrisiloxane (D3, 1.80 mol) to the above solution and stir to dissolve. Then add 32 g of dimethylformamide and react at 5 °C for 24 h. Add 20 g of dimethylhydrochlorosilane and continue the reaction for 2 h. Then add diatomaceous earth and stir to adsorb the produced salt. Then remove the adsorbent by filtration. The solution was then washed twice with 400 mL of distilled water. Residual water, solvent and unreacted monomers were removed by vacuum distillation to obtain asymmetric single-ended hydrogen-containing silicone oil, with a product of 330 g (molecular weight 2350, molecular weight distribution 1.15, hydrogen content 0.043 wt%).

[0058] S2. Mix 200g of the asymmetric single-terminated hydrogen-containing silicone oil prepared in step S1 with 12g of vinylmethyldimethoxysilane, stir for 10 minutes, add 0.05g of Castel platinum catalyst, and heat to 80℃ while stirring. React for 2 hours, and finally heat to 120℃ and remove excess small molecules by vacuum distillation to obtain α-dimethylphenyl-Ω-dimethoxy-terminated polydimethylsiloxane.

[0059] S3. Dissolve 100 g of α-dimethylphenyl-Ω-dimethoxy-terminated polydimethylsiloxane (PDM) prepared in step S2 and tris(pentafluorophenyl)borane (B(C6F5)3) (102 mg, 0.2 mmol) in 100 mL of anhydrous toluene to obtain mixture A2. Proceed under argon protection and maintain the temperature at 25 °C. Separately, thoroughly mix 1,1,3,3-tetramethyldisiloxane (HMMH) (134 g, 1 mol) with 100 mL of anhydrous toluene to obtain mixture B2. Under argon protection, slowly add mixture B2 dropwise to solution A2 and react for 0.5 h until no more bubbles are generated, at which point the reaction is complete. Add 100 g of Al2O3 and stir for 1 h to adsorb the catalyst. Filter to remove the alumina solid. Remove the toluene solvent and excess HMMH by vacuum distillation to obtain 104.5 g of α-dimethylphenyl-Ω-dihydro-terminated polydimethylsiloxane.

[0060] S4. Mix 100g of the obtained asymmetric structure hydrogen-containing silicone oil with 20.68g of vinyldimethylacetoxysilane (0.11mol) and stir for 5min. Add 0.03g of Castel platinum catalyst and react at 80℃ for 1h. Remove excess low molecular weight by vacuum distillation at 100℃ to obtain α-dimethylphenyl-Ω-diacetoxy-terminated polydimethylsiloxane.

[0061] S5. The asymmetric acetoxy-terminated polydimethylsiloxane obtained in step S4 is mixed with 1000g of acetic acid / sodium acetate buffer solution and stirred for 1 hour. The hydrolysis temperature is 40℃ to obtain asymmetric silanol-terminated polydimethylsiloxane, which is the treatment agent structure S2 of the present invention, with a viscosity of 42mPa.s.

[0062] Example 3

[0063] This embodiment prepares an α-n-butyl-Ω-disiloxy-terminated polydimethylsiloxane, including the following steps: S1. Slowly add 100 mL of n-butyllithium n-hexane solution (2.5 mol / L, 0.25 mol) to 320 mL of anhydrous toluene pre-cooled to 0 °C and stir for 60 min. Slowly add 400 g of dehydrated hexamethylcyclotrisiloxane (D3, 1.80 mol) to the above solution and stir to dissolve. Then add 32 g of dimethylformamide and react at 20 °C for 6 h. Add 25 g of dimethylhydrochlorosilane and continue the reaction for 2 h. Then add diatomaceous earth and stir to adsorb the produced salt. Then remove the adsorbent by filtration. Next, wash the obtained solution twice with 400 mL of distilled water. Remove residual water, solvent and unreacted monomers by vacuum distillation to obtain asymmetric single-terminated hydrogen-containing silicone oil, product 305 g (molecular weight 1850, molecular weight distribution 1.09, hydrogen content 0.055 wt%).

[0064] S2. Mix 200g of the asymmetric single-terminated hydrogen-containing silicone oil prepared in step S1 with 18g of vinylmethyl diethoxysilane, stir for 10 minutes, add 0.04g of Castel platinum catalyst, and heat to 60℃ while stirring. React for 8 hours, and finally heat to 120℃ and remove excess small molecules by vacuum distillation to obtain α-n-butyl-Ω-diethoxy-terminated polydimethylsiloxane.

[0065] S3. Dissolve 100 g of α-n-butyl-Ω-diethoxy-terminated polydimethylsiloxane (PDM) prepared in step S2 and tris(pentafluorophenyl)borane (B(C6F5)3) (102 mg, 0.2 mmol) in 100 mL of anhydrous toluene to obtain mixture A3. Proceed under argon protection and maintain the temperature at 25 °C. Separately, thoroughly mix 1,1,3,3-tetramethyldisiloxane (HMMH) (134 g, 1 mol) with 100 mL of anhydrous toluene to obtain mixture B3. Under argon protection, slowly add mixture B3 dropwise to solution A3 and react for 0.5 h until no bubbles are generated, at which point the reaction is complete. Add 100 g of Al2O3 and stir for 1 h to adsorb the catalyst. Filter to remove the alumina solid. Remove the toluene solvent and excess HMMH by vacuum distillation to obtain 105.8 g of α-n-butyl-Ω-dihydro-terminated polydimethylsiloxane.

[0066] S4. Mix 100g of the obtained asymmetric structure hydrogen-containing silicone oil with 22.5g of vinyldimethylacetoxysilane (0.12mol) and stir for 5min. Add 0.04g of Castel platinum catalyst and react at 60℃ for 6h. Remove excess low molecular weight by vacuum distillation at 100℃ to obtain α-n-butyl-Ω-diacetoxy-terminated polydimethylsiloxane.

[0067] S5. The asymmetric acetoxy-terminated polydimethylsiloxane obtained in step S4 is mixed with 1000g of acetic acid / sodium acetate buffer solution and stirred for 1 hour. The hydrolysis temperature is 40℃ to obtain asymmetric silanol-terminated polydimethylsiloxane, which is the treatment agent structure S3 of the present invention, with a viscosity of 30mPa.s.

[0068] Example 4

[0069] This embodiment prepares an α-dimethylphenyl-Ω-disiloxyl-terminated polydimethylsiloxane, including the following steps: S1. Dissolve 36.52 g of dimethylphenylsilanol (0.25 mol) in 320 mL of anhydrous toluene and cool to 5 °C. Stir for 10 min. Under nitrogen protection, slowly add 100 mL of n-butyllithium hexane solution (2.5 mol / L, 0.25 mol) dropwise over 1 h, paying attention to the released gas. Continue the reaction for 60 min. Slowly add 400 g of dehydrated hexamethylcyclotrisiloxane (D3, 1.80 mol) to the above solution and stir to dissolve. Then add 32 g of dimethylformamide and react at 40 °C for 4 h. Add 30 g of dimethylhydrochlorosilane and continue the reaction for 2 h. Then add diatomaceous earth and stir to adsorb the produced salt. Then remove the adsorbent by filtration. The solution was then washed twice with 400 mL of distilled water. Residual water, solvent and unreacted monomers were removed by vacuum distillation to obtain asymmetric single-ended hydrogen-containing silicone oil, with a product of 290 g (molecular weight 1580, molecular weight distribution 1.12, hydrogen content 0.064 wt%).

[0070] S2. Mix 200g of the asymmetric single-terminated hydrogen-containing silicone oil prepared in step S1 with 18.5g of vinylmethyldimethoxysilane, stir for 10 minutes, add 0.04g of Castel platinum catalyst, and heat to 70℃ while stirring. React for 4 hours, and finally heat to 120℃ and remove excess small molecules by vacuum distillation to obtain α-dimethylphenyl-Ω-dimethoxy-terminated polydimethylsiloxane.

[0071] S3. Dissolve 100 g of α-dimethylphenyl-Ω-dimethoxy-terminated polydimethylsiloxane (PDM) prepared in step S2 and tris(pentafluorophenyl)borane (B(C6F5)3) (102 mg, 0.2 mmol) in 100 mL of anhydrous toluene to obtain mixture A4. Proceed under argon protection and maintain the temperature at 25 °C. Separately, thoroughly mix 1,1,3,3-tetramethyldisiloxane (HMMH) (134 g, 1 mol) with 100 mL of anhydrous toluene to obtain mixture B4. Under argon protection, slowly add mixture B4 dropwise to solution A4 and react for 0.5 h until no bubbles are generated, at which point the reaction is complete. Add 100 g of Al2O3 and stir for 1 h to adsorb the catalyst. Filter to remove the alumina solid. Remove the toluene solvent and excess HMMH by vacuum distillation to obtain 104.5 g of α-dimethylphenyl-Ω-dihydro-terminated polydimethylsiloxane.

[0072] S4. Mix 100g of the obtained asymmetric structure hydrogen-containing silicone oil with 26.3g of vinyldimethylacetoxysilane (0.14mol) and stir for 5min. Add 0.03g of Castel platinum catalyst and react at 80℃ for 1h. Remove excess low molecular weight by vacuum distillation at 100℃ to obtain α-dimethylphenyl-Ω-diacetoxy-terminated polydimethylsiloxane.

[0073] S5. The asymmetric acetoxy-terminated polydimethylsiloxane obtained in step S4 is mixed with 1000g of acetic acid / sodium acetate buffer solution and stirred for 1 hour. The hydrolysis temperature is 40℃ to obtain asymmetric silanol-terminated polydimethylsiloxane, which is the treatment agent structure S4 of the present invention, with a viscosity of 24mPa.s.

[0074] Example 5

[0075] This embodiment prepares an α-n-butyl-Ω-disiloxy-terminated polydimethylsiloxane, including the following steps: S1. Slowly add 160 mL of n-butyllithium n-hexane solution (2.5 mol / L, 0.4 mol) to 320 mL of anhydrous toluene pre-cooled to 0 °C and stir for 60 min. Slowly add 400 g of dehydrated hexamethylcyclotrisiloxane (D3, 1.80 mol) to the above solution and stir to dissolve. Then add 32 g of dimethylformamide and react at 20 °C for 8 h. Add 40 g of dimethylhydrochlorosilane and continue the reaction for 2 h. Then add diatomaceous earth and stir to adsorb the produced salt. Then remove the adsorbent by filtration. Next, wash the obtained solution twice with 400 mL of distilled water. Remove residual water, solvent and unreacted monomers by vacuum distillation to obtain asymmetric single-terminated hydrogen-containing silicone oil, product 235 g (molecular weight 1050, molecular weight distribution 1.08, hydrogen content 0.098 wt%).

[0076] S2. Mix 200g of the asymmetric single-terminated hydrogen-containing silicone oil prepared in step S1 with 28g of vinylmethyldimethoxysilane, stir for 10 minutes, add 0.04g of Castel platinum catalyst, and heat to 60℃ while stirring. React for 6 hours, and finally heat to 120℃ and remove excess small molecules by vacuum distillation to obtain α-n-butyl-Ω-dimethoxy-terminated polydimethylsiloxane.

[0077] S3. Dissolve 100 g of α-n-butyl-Ω-dimethoxy-terminated polydimethylsiloxane (PDM) prepared in step S2 and tris(pentafluorophenyl)borane (B(C6F5)3) (102 mg, 0.2 mmol) in 100 mL of anhydrous toluene to obtain mixture A5. Proceed under argon protection and maintain the temperature at 25 °C. Separately, thoroughly mix 268 g (2 mol) of 1,1,3,3-tetramethyldisiloxane (HMMH) with 200 mL of anhydrous toluene to obtain mixture B5. Under argon protection, slowly add mixture B5 dropwise to solution A5 and react for 1 h until no more bubbles are generated, at which point the reaction is complete. Add 100 g of Al2O3 and stir for 1 h to adsorb the catalyst. Filter to remove the alumina solid. Remove the toluene solvent and excess HMMH by vacuum distillation to obtain 116.2 g of α-n-butyl-Ω-dihydro-terminated polydimethylsiloxane.

[0078] S4. Mix 100g of the obtained asymmetric structure hydrogen-containing silicone oil with 39.5g of vinyldimethylacetoxysilane (0.21mol) and stir for 5min. Add 0.03g of Castel platinum catalyst and react at 50℃ for 8h. Remove excess low molecular weight by vacuum distillation at 100℃ to obtain α-n-butyl-Ω-diacetoxy-terminated polydimethylsiloxane.

[0079] S5. The asymmetric acetoxy-terminated polydimethylsiloxane obtained in step S4 is mixed with 1000g of acetic acid / sodium acetate buffer solution and stirred for 1 hour. The hydrolysis temperature is 40℃ to obtain asymmetric silanol-terminated polydimethylsiloxane, which is the treatment agent structure S5 of the present invention, with a viscosity of 18mPa.s.

[0080] Example 6

[0081] This embodiment prepares an α-dimethylphenyl-Ω-disiloxyl-terminated polydimethylsiloxane, including the following steps: S1. Dissolve 15.22 g of dimethylphenylsilanol (0.1 mol) in 320 mL of anhydrous toluene and cool to 5 °C. Stir for 10 min. Under nitrogen protection, slowly add 40 mL of n-butyllithium hexane solution (2.5 mol / L, 0.1 mol) dropwise over 1 h, paying attention to the released gas. Continue the reaction for 60 min. Slowly add 400 g of dehydrated hexamethylcyclotrisiloxane (D3, 1.80 mol) to the above solution and stir to dissolve. Then add 32 g of dimethylformamide and react at 20 °C for 24 h. Add 11 g of dimethylhydrochlorosilane and continue the reaction for 2 h. Then add diatomaceous earth and stir to adsorb the produced salt. Then remove the adsorbent by filtration. The solution was then washed twice with 400 mL of distilled water. Residual water, solvent and unreacted monomers were removed by vacuum distillation to obtain asymmetric single-ended hydrogen-containing silicone oil, with a product of 330 g (molecular weight 3860, molecular weight distribution 1.15, hydrogen content 0.026 wt%).

[0082] S2. Mix 200g of the asymmetric single-terminated hydrogen-containing silicone oil prepared in step S1 with 7.5g of vinylmethyldimethoxysilane, stir for 10 minutes, add 0.05g of Castel platinum catalyst, and heat to 80℃ while stirring. React for 2 hours, and finally heat to 120℃ and remove excess small molecules by vacuum distillation to obtain α-dimethylphenyl-Ω-dimethoxy-terminated polydimethylsiloxane.

[0083] S3. Dissolve 100 g of α-dimethylphenyl-Ω-dimethoxy-terminated polydimethylsiloxane (PDM) prepared in step S2 and tris(pentafluorophenyl)borane (B(C6F5)3) (102 mg, 0.2 mmol) in 100 mL of anhydrous toluene to obtain mixture A6. Proceed under argon protection and maintain the temperature at 25 °C. Separately, thoroughly mix 67 g (0.5 mol) of 1,1,3,3-tetramethyldisiloxane (HMMH) with 100 mL of anhydrous toluene to obtain mixture B6. Under argon protection, slowly add mixture B6 dropwise to solution A6 and react for 0.5 h until no bubbles are generated, at which point the reaction is complete. Add 100 g of Al2O3 and stir for 1 h to adsorb the catalyst. Filter to remove the alumina solid. Remove the toluene solvent and excess HMMH by vacuum distillation to obtain 100.7 g of α-dimethylphenyl-Ω-dihydro-terminated polydimethylsiloxane.

[0084] S4. Mix 100g of the obtained asymmetric structure hydrogen-containing silicone oil with 11.28g of vinyldimethylacetoxysilane (0.06mol) and stir for 5min. Add 0.03g of Castel platinum catalyst and react at 80℃ for 1h. Remove excess low molecular weight by vacuum distillation at 100℃ to obtain α-dimethylphenyl-Ω-diacetoxy-terminated polydimethylsiloxane.

[0085] S5. The asymmetric acetoxy-terminated polydimethylsiloxane obtained in step S4 is mixed with 1000g of acetic acid / sodium acetate buffer solution and stirred for 1 hour. The hydrolysis temperature is 40℃ to obtain asymmetric silanol-terminated polydimethylsiloxane, which is the treatment agent structure S6 of the present invention, with a viscosity of 68mPa.s.

[0086] Comparative Example 1 α-n-Butyl-Ω-trimethoxy-terminated polydimethylsiloxane (D1) includes the following: S1. Slowly add 80 mL of n-butyllithium n-hexane solution (2.5 mol / L, 0.2 mol) to 320 mL of anhydrous toluene pre-cooled to 0 °C and stir for 60 min. Slowly add 400 g of dehydrated hexamethylcyclotrisiloxane (D3, 1.80 mol) to the above solution and stir to dissolve. Then add 32 g of dimethylformamide and react at 20 °C for 12 h. Add 21 g of dimethylhydrochlorosilane and continue the reaction for 2 h. Then add diatomaceous earth and stir to adsorb the produced salt. Then remove the adsorbent by filtration. Next, wash the obtained solution twice with 400 mL of distilled water. Remove residual water, solvent and unreacted monomers by vacuum distillation to obtain asymmetric single-terminated hydrogen-containing silicone oil, product 352 g (molecular weight 2580, molecular weight distribution 1.09, hydrogen content 0.039 wt%).

[0087] S2. Mix 200g of the asymmetric single-terminated hydrogen-containing silicone oil prepared in step 1 with 12g of vinyltrimethoxysilane, stir for 10 minutes, add 0.04g of Castel platinum catalyst, and heat to 80℃ while stirring. React for 2 hours, and finally heat to 120℃ and remove excess small molecules by vacuum distillation to obtain α-n-butyl-Ω-trimethoxy-terminated polydimethylsiloxane with a viscosity of 27mPa.s.

[0088] Comparative Example 2 This comparative example uses the same method as Example 1 to prepare an α-n-butyl-Ω-disiloxane-terminated polydimethylsiloxane (D2), the difference being that in step S1, 240 mL of n-butyllithium n-hexane solution (2.5 mol / L, 0.6 mol) is added. At this time, the molar ratio of hexamethylcyclotrisiloxane and the initiator composition is 3:1, which is not within the scope of the present invention.

[0089] Comparative Example 3 This comparative example uses the same method as Example 1 to prepare an α-n-butyl-Ω-disiloxane-terminated polydimethylsiloxane (D3), the difference being that in step S1, 28.8 mL of n-butyllithium n-hexane solution (2.5 mol / L, 0.0 mol) is used. At this time, the molar ratio of hexamethylcyclotrisiloxane and the initiator composition is 25:1, which is not within the scope of this invention.

[0090] Comparative Example 4 This comparative example uses the same method as Example 1 to prepare an α-n-butyl-Ω-disiloxane-terminated polydimethylsiloxane (D4), except that in step S5, hydrochloric acid is used to adjust the pH to 4.5~5.5.

[0091] Comparative Example 5 This comparative example uses the same method as Example 1 to prepare an α-n-butyl-Ω-disiloxy-terminated polydimethylsiloxane (D5), except that in step S5, sodium hydroxide is used to adjust the pH to 4.5~5.5.

[0092] To better illustrate the superior performance of the asymmetric powder treatment agent prepared in this invention, it was applied to the field of powder dispersion to treat thermally conductive fillers and prepare thermally conductive gels for performance testing. There are no special restrictions on the preparation of thermally conductive gels, as long as they can better illustrate the performance of the asymmetric fractional treatment agent prepared in this invention.

[0093] In some embodiments, the present invention prepares thermally conductive gels using the following method: 5g of single-crystal alumina AA03, 7g of zinc oxide MZN101, 8g of single-crystal aluminum nitride WANS-E01, 22g of single-crystal aluminum nitride AN-5, 18g of spherical aluminum nitride WANS-30-50C, and 40g of spherical aluminum nitride TA-F120-210C thermally conductive filler were added to a high-speed dispersion autoclave for high-speed pre-shearing. 0.5g of powder treatment agent was added to the autoclave via spraying, and the thermally conductive powder was dry-modified for 2 hours. Then, 2g of 100 viscosity vinyl silicone oil and 1g of powder treatment agent were added, and the mixture was dispersed at high speed for 2 hours, controlling the temperature below 80℃. After 2 hours, the temperature was controlled to 10-20℃, and 0.5g of hydrogen-containing silicone oil XL12 was added and dispersed for 0.5 hours. Then, 0.01g of ethynylcyclohexanol was added and dispersed evenly. Finally, 0.04g of platinum catalyst was added, mixed evenly, and vacuum degassed for 10 minutes. After filling, the mixture was cooled to -20℃ to 0℃. o Save as C.

[0094] Application Examples 1-6 Following the preparation method of the thermally conductive gel mentioned above, thermally conductive gels were prepared using the asymmetric powder treatment agents prepared in Examples 1 to 6, respectively.

[0095] Compare and contrast examples 1-5 Following the preparation method of the thermally conductive gel mentioned above, thermally conductive gels were prepared using the asymmetric powder treatment agents prepared in Comparative Examples 1 to 5, respectively.

[0096] The types and amounts of each component involved in the application examples are shown in Table 1, in g.

[0097] Table 1. Types and dosages of components involved in application examples.

[0098] The thermally conductive gel obtained from the application example was subjected to performance testing. The performance test data are shown in Table 2. The test methods involved are as follows: (1) Viscosity test: The viscosity was measured at 5r using an Anton Paar rheometer (Anton Paar MCR302e) with a PP25 rotor.

[0099] (2) Thermal conductivity: Tested according to ISO 22007-2 standard using a HOTDISK thermal conductivity meter. The thermal conductivity of the heat-conducting sheet is 6mm thick, 200mW, and measured for 2s.

[0100] (3) Tensile strength test: The prepared single-component thermally conductive silicone gel was extruded onto a fluorinated release film with a 2mm gap in the middle of the release film. It was cured at 125℃ for 60min using a flat vulcanizer, and then the tensile strength was tested according to GB / T 528 standard.

[0101] (4) Corrosion test: The thermally conductive gel was cured at 125°C for 60 min in a flat vulcanizer, cut into 25mm*25mm*2mm sheets, placed in a sealed glass bottle, and a 25mm*25mm*2mm transparent PC sheet was placed in it. The PC was then baked at 80°C for 1000 h and the PC surface was observed to see if it was corroded.

[0102] Table 2 Performance testing of thermally conductive gel

[0103] As shown in Table 2, the asymmetric structure powder treatment agent prepared by this invention has a good modification effect on thermally conductive powders. This asymmetric powder treatment agent can directly react with the hydroxyl groups on the surface of the thermally conductive filler without the need for a pre-hydrolysis step, eliminating the hidden danger of alcohol release in the prior art, making anchoring more efficient, effectively reducing the viscosity of the thermally conductive material, and will not release small organic molecules such as alcohols during the subsequent aging process, thus not damaging precision electronic devices, and significantly improving the long-term reliability of the thermally conductive filler in high temperature and high humidity environments.

[0104] According to the data in Table 2, a comparison between Application Example 1 and Comparative Application Example 1 shows that the methoxy-terminated powder treatment agent corrodes PC after a long period of aging, compared to the treatment agent prepared in this invention.

[0105] According to the data in Table 2, a comparison between Application Example 1 and Comparative Application Example 2 shows that when the molar ratio of hexamethylcyclotrisiloxane to initiator is 3:1, the amount of initiator used is relatively excessive, resulting in a product with a low molecular weight and a low yield. Because treatment agents with excessively small molecular weights are prone to desorbing from the filler surface and volatilizing during high-temperature aging, the thermally conductive gel is prone to aging and hardening, and the volatilized small molecules adsorb and contaminate the PC.

[0106] Based on the data in Table 2, a comparison between Application Example 1 and Comparative Application Example 3 shows that when the molar ratio of hexamethylcyclotrisiloxane to initiator is 25:1, the amount of initiator is relatively insufficient, resulting in a high number-average molecular weight of the product. This excessively high molecular weight increases the viscosity of the treatment agent, preventing uniform spreading during filler surface treatment and leading to incomplete surface treatment with some filler surfaces not being effectively coated. In the subsequent preparation of the thermal interface material, significant interface defects exist between the untreated filler and the silicone matrix, with a viscosity significantly higher than in Application Example 1.

[0107] A comparison of Application Example 1 and Comparative Application Example 4 shows that in step S5, when hydrochloric acid is used to adjust the pH, the acetic acid released during the hydrolysis of acetoxy groups causes a large change in the pH of the hydrolysis system. Hydrochloric acid has no buffering effect, and the hydroxyl groups generated by hydrolysis undergo condensation at low pH values ​​to form products without functional groups, which cannot process powders and the thermally conductive gel cannot be formed.

[0108] According to the data in Table 2, a comparison between Application Example 1 and Comparative Application Example 5 shows that in step S5, when sodium hydroxide is used to adjust the pH, the acetoxy group is hydrolyzed into hydroxyl group and the acetic acid released at the same time causes a large change in the pH of the hydrolysis system. Sodium hydroxide has no buffering effect, and the hydroxyl group generated by hydrolysis undergoes condensation at low pH value to form a product without functional groups, which cannot process the powder and the thermally conductive gel cannot be formed, resulting in poor filler dispersibility and the inability to form the thermally conductive gel.

[0109] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0110] For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. An asymmetric structure powder treatment agent, characterized in that, The structural formula of the treatment agent is shown below: Where n is any integer from 5 to 30; R is a functional alkyl group.

2. The asymmetric structure powder treatment agent according to claim 1, characterized in that, R is selected from any of the following structural formulas: 。 3. A method for preparing an asymmetric structure powder treatment agent according to any one of claims 1-2, characterized in that, The preparation method includes the following steps: S1. In an anhydrous nonpolar solvent, in the presence of an initiator composition and a polar accelerator, hexamethylcyclotrisiloxane is subjected to ring-opening polymerization and then capped with dimethylhydrochlorosilane to obtain an asymmetric single-ended hydrogen-containing silicone oil. S2. The asymmetric single-ended hydrogen-containing silicone oil obtained in step S1 is mixed with vinylmethyldialkoxysilane and reacted under the action of a platinum catalyst to obtain alkoxy-modified silicone oil. S3. The alkoxy-modified silicone oil obtained in step S2 is reacted with 1,1,3,3-tetramethyldisiloxane in the presence of the catalyst tris(pentafluorophenyl)borane to obtain an asymmetric hydrogen-containing silicone oil. S4. The asymmetric hydrogen-containing silicone oil obtained in step S3 is reacted with vinyl dimethyl acetoxysilane under the action of a platinum catalyst to obtain asymmetric acetoxy-terminated polydimethylsiloxane. S5. The asymmetric acetoxy-terminated polydimethylsiloxane obtained in step S4 is hydrolyzed in a buffer solution to obtain asymmetric silanol-terminated polydimethylsiloxane.

4. The method for preparing an asymmetric structure powder treatment agent according to claim 3, characterized in that, In step S1, the preparation process includes ring-opening polymerization and end-capping reaction; The ring-opening polymerization involves slowly adding an initiator composition to an anhydrous nonpolar solvent pre-cooled to 0-10°C, stirring for 5-60 min, slowly adding dehydrated hexamethylcyclotrisiloxane to the above solution, stirring to dissolve, then adding a polar accelerator, and reacting at 5-50°C for 4-24 h. The end-capping reaction is carried out when the conversion rate of hexamethylcyclotrisiloxane is greater than 90%, dimethylhydrochlorosilane is added, and the reaction is continued for 0.5-4 hours.

5. The method for preparing an asymmetric structure powder treatment agent according to claim 3, characterized in that, In step S1, the molar ratio of hexamethylcyclotrisiloxane to the initiator composition is (4~20):1; In step S1, the ratio between the amount of hexamethylcyclotrisiloxane, the mass of the polar promoter, and the mass of dimethylhydrochlorosilane is 1 mol : (15~25) g : (5~25) g. In step S2, by mass fractions, there are 180-220 parts of asymmetric single-ended hydrogen-containing silicone oil, 6-20 parts of vinylmethyldialkoxysilane, and 0.03-0.05 parts of platinum catalyst. In step S3, the ratio between the mass of alkoxy-modified silicone oil, the amount of 1,1,3,3-tetramethyldisiloxane, and the amount of tris(pentafluorophenyl)borane is (90~120) g : (0.5~1) mol : 0.2 mol; In step S4, by mass fraction, there are 90-110 parts of asymmetric hydrogen-containing silicone oil, 11-40 parts of vinyldimethylacetoxysilane, and 0.03-0.05 parts of platinum catalyst. In step S5, the mass ratio of asymmetric acetoxy-terminated polydimethylsiloxane to buffer solution is 1:(8~15).

6. The method for preparing an asymmetric structure powder treatment agent according to claim 3, characterized in that, In step S5, the pH of the hydrolysis reaction is 4.5~5.

5.

7. The method for preparing an asymmetric structure powder treatment agent according to claim 3, characterized in that, In step S2, the reaction temperature is 40~100℃ and the reaction time is 1~12h; In step S3, the reaction temperature is 0~50℃ and the reaction time is 0.5~4h; In step S4, the reaction temperature is 40~90℃ and the reaction time is 1~12h; In step S5, the reaction temperature is 5~40℃ and the reaction time is 1~12h.

8. The method for preparing an asymmetric structure powder treatment agent according to claim 3, characterized in that, In step S1, the initiator composition is a n-butyllithium n-hexane solution, or a mixture of a n-butyllithium n-hexane solution and dimethylphenylsilanol; In step S1, the polar promoter is at least one of tetrahydrofuran, N,N-dimethylformamide, or dimethyl sulfoxide; In step S1, the anhydrous nonpolar solvent is at least one of anhydrous n-hexane, anhydrous cyclohexane, or anhydrous toluene; In step S2, the vinylmethyldialkoxysilane is one of vinylmethyldimethoxysilane or vinyldimethylethoxysilane.

9. The method for preparing an asymmetric structure powder treatment agent according to claim 3, characterized in that, In step S5, the buffer solution is a compound buffer solution of acetic acid and sodium acetate.

10. An application of an asymmetric structure powder treatment agent according to any one of claims 1-2, characterized in that, The treatment agent is used in the surface treatment of thermally conductive fillers; The thermally conductive filler is at least one of alumina, zinc oxide, boron nitride, aluminum nitride, diamond, and graphene.

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