Preparation method and application of siloxane surface modifier containing branched alkyl

Abstract

The preparation method comprises the following steps: uniformly mixing 3, 3, 4, 4-tetramethyl-1-pentene and 2-chloro-2, 3, 3-trimethyl-butane, adding a solvent and a copper catalyst, carrying out a reaction under nitrogen and visible light conditions for 15-25 h, carrying out reduced pressure distillation to obtain 4-chloro-2, 2, 3, 3, 6, 6, 7, 7-octamethyl octane, carrying out vacuum distillation on the 4-chloro-2, 2, 3, 3, 6, 6, 7, 7-octamethyl octane, carrying out vacuum distillation on the 4-chloro-2, 3, 3, 6, 6, 7-octamethyl octane, and carrying out vacuum distillation on the 4-chloro-2, 3, 3, 6, 6, 7-octamethyl octane to obtain the siloxane surface modifier containing branched alkyl. Stirring the branched chain alkyl group and sodium dimethyl hydrosilylate in a reaction kettle at room temperature for 6-10 hours, and filtering to obtain hydrogen-containing silane containing branched chain alkyl groups; and adding a platinum catalyst and vinyl trimethoxy silane into the hydrogen-containing silane containing the branched alkyl, reacting at 130-160 DEG C, and carrying out reduced pressure distillation to obtain the siloxane surface modifier containing the branched alkyl. After the heat-conducting powder is modified by the prepared surface modifier, the compatibility of the heat-conducting powder and organic silicon resin can be effectively improved, the organic silicon heat-conducting pouring sealant prepared from the modified powder has good flowability, the flowability of the sealant does not change in the long-time storage process, and the service life of the sealant is prolonged. The storage stability and the constructability of the organic silicon heat-conducting pouring sealant are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of surface modification of thermal conductive fillers, and in particular relates to a preparation method and application of a siloxane surface modifier containing a branched alkyl group. Background Art

[0002] As electronic components become smaller and more powerful, the heat generated in the circuit is also increasing. Therefore, it is necessary to transfer the heat from the electronic components to the heat sink through thermal conductive interface materials. Common silicone thermal conductive interface materials on the market include silicone thermal conductive potting glue, silicone thermal conductive gel and silicone thermal conductive grease. As a thermal conductive interface material and adhesive, addition-type thermal conductive silicone potting glue can realize fully automated electronic device packaging with its excellent thermal conductivity, low viscosity, good flowability, waterproof effect and environmental protection characteristics. It is widely used in electronic equipment, photovoltaic inverters, new energy and other fields.

[0003] At present, there are many types of surface modifiers for thermal conductive powders in addition-type silicone thermal potting adhesives. Surface modifiers can effectively improve the compatibility between powders and vinyl silicone oils, reduce viscosity, and improve powder filling properties. Take hexadecyltrimethoxysilane surface modifier as an example. Its molecular structure is CH3(CH2) 15 Si(OCH3)3, its methoxy -OCH3 is a polar group, which can react chemically or physically adsorb with the hydroxyl group or hydrogen bond on the surface of the inorganic filler after hydrolysis, and bind to the filler surface; its CH3(CH2) 15 — is a non-polar group, which has good compatibility with vinyl silicone oil. The thermally conductive powder treated with a surface modifier can be better compatible with the resin. However, many existing surface modifiers (such as octyl trimethoxysilane, hexadecyl trimethylsilane, and γ-methacryloxypropyl trimethoxysilane) often have a relatively long straight chain structure. After these long-chain modifiers modify the surface of the powder, the molecular chains on the surface of the powder are easily entangled with each other, resulting in poor fluidity of the adhesive and enhanced thixotropy, which seriously affects the stability of the product. In addition, the non-polar group molecular chains of some short-chain surface modifiers (such as vinyl trimethoxysilane, propyl trimethoxysilane, etc.) are very short, and the surface hydroxyl groups of some inorganic thermal conductive fillers (such as alumina, boron nitride, aluminum nitride, etc.) are limited, resulting in insufficient anchoring sites for the surface modifier on the powder surface, which results in the inability of the short-chain surface modifier to exert a good modification effect. Summary of the invention

[0004] In view of the problems existing in the prior art, the purpose of the present invention is to provide a preparation method and application of a siloxane surface modifier containing a branched alkyl group. The modifier can be used as a surface modifier of thermally conductive powder of organic silicone high thermal conductive potting glue, which can effectively improve the compatibility between thermally conductive powder and resin, and the problem of fluidity change will not occur during the long-term storage of the colloid. To this end, the present invention also provides the application of the siloxane surface modifier containing a branched alkyl group, which further improves the stability and performance of the organic silicone thermal conductive potting glue.

[0005] To achieve the above objectives, the present invention adopts the following technical solutions.

[0006] A method for preparing a siloxane surface modifier containing a branched alkyl group, characterized in that the preparation process is as follows: (1) 3,3,4,4-tetramethyl-1-pentene and 2-chloro-2,3,3-trimethyl-butane are mixed uniformly, a solvent and a copper catalyst are added, and the mixture is reacted for 15 to 25 hours under nitrogen protection and visible light conditions. After the reaction is completed, the mixture is filtered, and the filtrate is subjected to reduced pressure distillation at 150° C. to remove unreacted products, thereby obtaining 4-chloro-2,2,3,3,6,6,7,7-octamethyloctane; (2) Pour 4-chloro-2,2,3,3,6,6,7,7-octamethyloctane and sodium dimethylhydrogensiloxane into a closed reaction kettle, stir at room temperature for 6 to 10 hours, and filter after the reaction to obtain a filtrate, which is the hydrogen-containing silane containing a branched alkyl group; (3) Adding a platinum catalyst and vinyltrimethoxysilane to the above-mentioned hydrogen-containing silane containing a branched alkyl group, reacting at 130-160° C. for 1-2 hours, and subjecting the filtrate to reduced pressure distillation at 150° C. to remove unreacted products to obtain a siloxane surface modifier containing a branched alkyl group.

[0007] More preferably, the branched alkyl-containing siloxane surface modifier has the following molecular structure:

[0008] More preferably, the mass ratio of the 3,3,4,4-tetramethyl-1-pentene and 2-chloro-2,3,3-trimethyl-butane to the copper catalyst is 100:127-160:5-8:.

[0009] More preferably, the solvent is one of ethylenediamine and propylenediamine, and the mass ratio of the solvent to the copper catalyst is 5 to 10:1.

[0010] More preferably, the copper catalyst is one of cuprous chloride, cuprous bromide and cuprous iodide.

[0011] More preferably, the mass ratio of 4-chloro-2,2,3,3,6,6,7,7-octamethyloctane to sodium dimethylhydrogensiloxane is 100:38-57.

[0012] More preferably, the mass ratio of the hydrogen-containing silane containing branched alkyl groups, vinyltrimethoxysilane and platinum catalyst is 100:56 to 75:3.

[0013] More preferably, the platinum catalyst is a chloroplatinic acid-divinyltetramethyldisiloxane complex with a platinum content of 3000 to 5000 ppm.

[0014] More preferably, the branched alkyl-containing siloxane surface modifier is used to modify the powder; the preparation steps of the modified powder are: weigh two or more thermally conductive powders, place them in a high-speed mixer and mix them evenly, then spray a certain amount of powder surface modifier, the mass ratio of thermally conductive powder to powder surface modifier is 1000:1-10, and stir at 70°C and 1000r / min for 30min to obtain the modified powder.

[0015] The beneficial effects of the present invention are: (1) The main chain of the non-polar group of the branched alkyl-containing siloxane surface modifier of the present invention is relatively short, and it is not easy to produce molecular entanglement; and the molecular structure of the non-polar group is relatively large, which can effectively cover the surface of the powder; it avoids the problems of poor fluidity and enhanced thixotropy caused by traditional long-chain alkyl modifiers, and improves the stability of the colloid. (2) The branched alkyl-containing siloxane surface modifier of the present invention has multiple methyl groups in its side chains, which can not only effectively reduce the mutual entanglement between molecular chains; it is also beneficial to enhance the compatibility with vinyl silicone oil. Since the three-dimensional helical structure of vinyl silicone oil and the similar structure of the modifier of the present invention are both structures with methyl groups on the outside, the two are similar and compatible, thereby effectively improving the adhesion and filling properties between the thermal conductive powder and the resin, and further enhancing the performance of the colloid. DETAILED DESCRIPTION

[0016] The specific implementation of the present invention is further described below to make the technical solution and beneficial effects of the present invention clearer and more specific. The following embodiments are exemplary and intended to explain the present invention, but cannot be construed as limiting the present invention.

[0017] Embodiment 1: (1) 100 g of 3,3,4,4-tetramethyl-1-pentene and 127.6 g of 2-chloro-2,3,3-trimethyl-butane were mixed in a closed reactor, 70.2 g of ethylenediamine and 7.8 g of cuprous iodide were added, and the mixture was reacted for 17 h under nitrogen protection and visible light irradiation. After filtering, the filtrate was distilled under reduced pressure at 150° C. for 1 h to obtain 4-chloro-2,2,3,3,6,6,7,7-octamethyloctane; (2) After preparing a sufficient amount of 4-chloro-2,2,3,3,6,6,7,7-octamethyloctane according to the above requirements, 100 g of 4-chloro-2,2,3,3,6,6,7,7-octamethyloctane and 37.7 g of sodium dimethylhydrogensiloxane were poured into a closed reactor, stirred at room temperature for 9.5 h, filtered and distilled under reduced pressure to obtain a hydrogen-containing silane containing a branched alkyl group; (3) After a sufficient amount of hydrogen-containing silane containing a branched alkyl group is prepared according to the above requirements, 100 g of hydrogen-containing silane containing a branched alkyl group is taken, 3 g of a platinum catalyst with a platinum concentration of 5000 ppm and 56.5 g of vinyltrimethoxysilane are added, and the mixture is reacted at 135° C. for 1.3 h, and then the excess unreacted product is distilled off under reduced pressure to obtain a siloxane surface modifier containing a branched alkyl group.

[0018] Embodiment 2: (1) 100 g of 3,3,4,4-tetramethyl-1-pentene and 159.5 g of 2-chloro-2,3,3-trimethyl-butane were mixed in a sealed reactor, 67.5 g of ethylenediamine and 7.5 g of cuprous bromide were added, and the mixture was reacted for 23 h under nitrogen protection and visible light irradiation. After filtering, the filtrate was distilled under reduced pressure at 150° C. for 1 h to obtain 4-chloro-2,2,3,3,6,6,7,7-octamethyloctane; (2) After preparing a sufficient amount of 4-chloro-2,2,3,3,6,6,7,7-octamethyloctane according to the above requirements, 100 g of 4-chloro-2,2,3,3,6,6,7,7-octamethyloctane and 56.5 g of sodium dimethylhydrogen siloxane were poured into a closed reactor, stirred at room temperature for 6 h, filtered and distilled under reduced pressure to obtain a hydrogen-containing silane containing a branched alkyl group; (3) After a sufficient amount of hydrogen-containing silane containing a branched alkyl group is prepared according to the above requirements, 100 g of hydrogen-containing silane containing a branched alkyl group is taken, 3 g of a platinum catalyst with a platinum concentration of 3500 ppm and 60.3 g of vinyltrimethoxysilane are added, and the mixture is reacted at 140° C. for 1.8 h, and then the excess unreacted product is distilled off under reduced pressure to obtain a siloxane surface modifier containing a branched alkyl group.

[0019] Embodiment 3: (1) 100 g of 3,3,4,4-tetramethyl-1-pentene and 138.2 g of 2-chloro-2,3,3-trimethyl-butane were mixed in a sealed reactor, 40.6 g of propylenediamine and 5.8 g of cuprous chloride were added, and the mixture was reacted for 25 h under nitrogen protection and visible light irradiation. After filtering, the filtrate was distilled under reduced pressure at 150° C. for 1 h to obtain 4-chloro-2,2,3,3,6,6,7,7-octamethyloctane; (2) After preparing a sufficient amount of 4-chloro-2,2,3,3,6,6,7,7-octamethyloctane according to the above requirements, 100 g of 4-chloro-2,2,3,3,6,6,7,7-octamethyloctane and 52.8 g of sodium dimethylhydrogensiloxane were poured into a closed reactor, stirred at room temperature for 8.2 h, filtered and distilled under reduced pressure to obtain a hydrogen-containing silane containing a branched alkyl group; (3) After a sufficient amount of hydrogen-containing silane containing a branched alkyl group is prepared according to the above requirements, 100 g of hydrogen-containing silane containing a branched alkyl group is taken, 3 g of a platinum catalyst having a platinum concentration of 4000 ppm and 64.1 g of vinyltrimethoxysilane are added, and the mixture is reacted at 152° C. for 1.5 h, and then the excess unreacted product is distilled off under reduced pressure to obtain a siloxane surface modifier containing a branched alkyl group.

[0020] Embodiment 4: (1) 100 g of 3,3,4,4-tetramethyl-1-pentene and 148.8 g of 2-chloro-2,3,3-trimethyl-butane were mixed in a sealed reactor, 42 g of propylenediamine and 7 g of cuprous iodide were added, and the mixture was reacted for 18 h under nitrogen protection and visible light irradiation. After filtering, the filtrate was distilled under reduced pressure at 150° C. for 1 h to obtain 4-chloro-2,2,3,3,6,6,7,7-octamethyloctane; (2) After preparing a sufficient amount of 4-chloro-2,2,3,3,6,6,7,7-octamethyloctane according to the above requirements, 100 g of 4-chloro-2,2,3,3,6,6,7,7-octamethyloctane and 49 g of sodium dimethylhydrogen siloxane were poured into a closed reactor, stirred at room temperature for 7.5 h, filtered and distilled under reduced pressure to obtain a hydrogen-containing silane containing a branched alkyl group; (3) After a sufficient amount of hydrogen-containing silane containing a branched alkyl group is prepared according to the above requirements, 100 g of hydrogen-containing silane containing a branched alkyl group is taken, 3 g of a platinum catalyst with a platinum concentration of 3000 ppm and 69.7 g of vinyltrimethoxysilane are added, and after reacting at 160° C. for 2 h, the excess unreacted product is distilled off under reduced pressure to obtain a siloxane surface modifier containing a branched alkyl group.

[0021] Comparative Example 1: Comparative Example 1 is octadecyltrimethoxysilane, the number of carbon atoms of which is close to that of the present invention.

[0022] Comparative Example 2: Comparative Example 2 is octyltrimethoxysilane, and its main chain length is close to that of the main chain of the present invention.

[0023] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that it does not contain 4 outer methyl groups. The specific comparative example is: 3,3,4,4-tetramethyl-1-pentene and 2-chloro-2,3,3-trimethyl-butane in Example (1) are replaced by pentene and 2-chloro-butane, and the other steps and amounts are the same as Example 1.

[0024] Application Examples 1-7: The high thermal conductivity potting glue prepared in Examples 1-4 corresponds to Application Examples 1-4, Comparative Example 1 corresponds to Application Example 5, Comparative Example 2 corresponds to Application Example 6, and Comparative Example 3 corresponds to Application Example 7.

[0025] Application example: Preparation method of high thermal conductivity potting glue: (1) Preparation of modified powder: Weigh 60 parts of 70 micron spherical alumina, 10 parts of 20 micron spherical alumina, 20 parts of 5 micron alumina, and 10 parts of 1 micron spherical alumina, mix them evenly in a high-speed mixer, spray 0.18 parts of powder surface modifier, and stir at 70°C and 1000 r / min for 30 min to obtain modified powder; (2) Preparation of colloid: Take 100 parts of 100 cP vinyl silicone oil, add 1300 parts of the modified powder in step (1), and disperse in a high-speed disperser at 600 r / min for 30 min to obtain a colloid, which is the application example. Test various properties as required.

[0026] Performance testing method: Maximum powder filling ratio: Take 100 parts of 100cP vinyl silicone oil and gradually add the modified powder until the powder can no longer form clumps. At this time, the powder filling ratio is the maximum filling ratio. Colloid viscosity test method: stand for different time periods, and without stirring the colloid, use a rotational viscometer (model: BROOKFIELD, DVESRVTJ0) to test the viscosity, where viscosity 1 is tested using S063R parameters, and viscosity 2 is tested using S066R parameters. Thixotropic ratio = viscosity 1 / viscosity 2. Fluidity test: Weigh 65g of colloid into a four-cup funnel and let it stand for different periods of time. Without stirring the colloid, test the circular diameter of the colloid flowing on a flat surface.

[0027] The performance test data of application examples 1-7 are shown in Table 1:

[0028] Table 1

[0029] In Application Examples 1-6, the siloxane surface modifier containing branched alkyl groups in Examples 1-4 of the present invention, Comparative Examples 1, 2, and 3 are respectively used to treat a high thermal conductivity composite powder with a coarse and fine combination, and filled in vinyl silicone oil to test the viscosity, fluidity, and filling limit. In the above table, Comparative Examples 1-4 correspond to Application Examples 1-4, and Comparative Examples 1-3 correspond to Application Examples 5-7.

[0030] The siloxane surface modifier containing branched alkyl prepared by the present invention has a large non-polar group, which can effectively cover the surface of the powder, improve the filling property of the powder in the resin and reduce the colloid viscosity; and because it has a shorter main chain and numerous side chains, it is not easy to produce molecular entanglement between molecules, making the viscosity and fluidity of the silicone addition type potting glue more stable. The specific performance parameters are described as follows in conjunction with Table 1: (1) Example 1-4 Application of Siloxane Surface Modifiers Containing Branched Alkyl Groups In the formulations of Example 1-4, the results of tests at different time periods showed that the colloid viscosity and thixotropic ratio did not change significantly, while the flow diameter increased by only 4.4% during 0-24h, and the maximum filling ratio could reach 3250-3200 parts. (2) The octadecyltrimethoxysilane of Comparative Example 1 corresponds to Application Example 5. In the initial viscosity test, in the S063R parameter, the application viscosity of Examples 1-4 is 41.17%-44.13% lower than that of Comparative Example 1, and in the S063R parameter, the application viscosity of Examples 1-4 is 16.67%-20.67% lower than that of Comparative Example 1; while the thixotropic ratio increases by 36.83% in 0-24h, the flow diameter decreases by 16%, and the maximum filling number is 240-290 parts lower than that of Examples 1-4. (3) The octyltrimethoxysilane of Comparative Example 2 corresponds to Application Example 6. In the initial viscosity test, in the S063R parameter, the application viscosity of Examples 1-4 is 46.68%-49.36% lower than that of Comparative Example 2. In the S063R parameter, the application viscosity of Examples 1-4 is 33.96%-37.14% lower than that of Comparative Example 2. The thixotropic ratio increases by 26.89% in 0-24h, the flow diameter decreases by 9.8%, and the maximum filling number is 620-670 parts lower than that of Examples 1-4. (4) In the initial viscosity test of the corresponding application example 6 of comparative example 3, in the S063R parameter, the application viscosity of embodiments 1-4 is 30.75%-24.23% lower than that of comparative example 2, and in the S063R parameter, the application viscosity of embodiments 1-4 is 26.04%-29.59% lower than that of comparative example 2, while the thixotropic ratio increases by 11.08% in 0-24h, the flow diameter decreases by 4.8%, and the limit filling number is 420-470 parts lower than that of embodiments 1-4. In summary, the branched alkyl-containing siloxane surface modifier of the present invention has the characteristics of significantly improving the filling property, reducing and stabilizing the viscosity, and improving and stabilizing the flow effect in the organosilicon addition adhesive.

Claims

1. A method for preparing a siloxane surface modifier containing a branched alkyl group, characterized in that: The preparation process is as follows: (1) 3,3,4,4-tetramethyl-1-pentene and 2-chloro-2,3,3-trimethyl-butane are mixed uniformly, a solvent and a copper catalyst are added, and the mixture is reacted for 15 to 25 hours under nitrogen protection and visible light conditions. After the reaction is completed, the mixture is filtered, and the filtrate is subjected to reduced pressure distillation at 150° C. to remove unreacted products, thereby obtaining 4-chloro-2,2,3,3,6,6,7,7-octamethyloctane; (2) adding 4-chloro-2,2,3,3,6,6,7,7-octamethyloctane and sodium dimethylhydrogensiloxane into a closed reaction kettle, stirring at room temperature for 6 to 10 hours, filtering after the reaction, and obtaining a filtrate, which is a branched alkyl-containing hydrogen-containing silane; (3) Adding platinum catalyst and vinyl trimethoxy silane to hydrogen-containing silane containing branched alkyl groups, reacting at 130-160° C. for 1-2 hours, filtering after the reaction, and removing unreacted products by vacuum distillation of the filtrate at 150° C. to obtain a siloxane surface modifier containing branched alkyl groups, the molecular structure of which is as follows:

2. The method for preparing a branched alkyl-containing siloxane surface modifier according to claim 1, characterized in that: The mass ratio of 3,3,4,4-tetramethyl-1-pentene, 2-chloro-2,3,3-trimethyl-butane and copper catalyst is 100:127-160:5-8.

3. The method for preparing a branched alkyl-containing siloxane surface modifier according to claim 1, characterized in that: The solvent is one of ethylenediamine and propylenediamine, and the mass ratio of the solvent to the copper catalyst is 5 to 10:

1.

4. The method for preparing a branched alkyl-containing siloxane surface modifier according to claim 1, characterized in that: The copper catalyst is one of cuprous chloride, cuprous bromide and cuprous iodide.

5. The method for preparing a branched alkyl-containing siloxane surface modifier according to claim 1, characterized in that: The mass ratio of the 4-chloro-2,2,3,3,6,6,7,7-octamethyloctane to sodium dimethylhydrogensiloxane is 100:38-57.

6. The method for preparing a branched alkyl-containing siloxane surface modifier according to claim 1, characterized in that: The mass ratio of the branched alkyl-containing hydrogen-containing silane, vinyltrimethoxysilane and platinum catalyst is 100:56-75:

3.

7. The method for preparing a branched alkyl-containing siloxane surface modifier according to claim 1, characterized in that: The platinum catalyst is a chloroplatinic acid-divinyltetramethyldisiloxane complex, and the platinum content is 3000-5000ppm.

8. The method for preparing a branched alkyl-containing siloxane surface modifier according to any one of claims 1 to 7, characterized in that: The branched alkyl-containing siloxane surface modifier is used to modify the powder; the preparation steps of the modified powder are: weighing two or more thermal conductive powders, placing them in a high-speed mixer and mixing them evenly, then spraying a certain amount of surface modifier, the mass ratio of the thermal conductive powder to the surface modifier is 1000:1-10, and stirring at 70°C and 1000r / min for 30min to obtain the modified powder.

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