Preparation method and application of cyclic siloxane with hydrogen-containing end

Abstract

The invention discloses a preparation method and application of ring-shaped end hydrogen-containing siloxane, and is characterized in that tetramethyldisiloxane and an ethanol solution of sodium hydroxide react for 3-6 hours in a closed container at 100-120 DEG C, and after reduced pressure distillation, washing and drying, sodium dimethyl silica crystals are prepared; reacting the sodium dimethyl silica crystal with cyclooctadiene, a platinum catalyst and a solvent in a closed container at 100-120 DEG C for 2-4 hours, and carrying out reduced pressure distillation, washing and drying to obtain an annular sodium dimethyl silica crystal; and stirring the cyclic sodium dimethyl silica crystal and dimethyl chlorosilane in a closed container at room temperature for 6-10 hours, filtering out a solid reactant, and carrying out reduced pressure distillation at 100-120 DEG C to obtain the cyclic siloxane containing hydrogen at the end. Active hydrogen of the prepared ring-end hydrogen-containing siloxane is located at the tail end of a molecular chain, the influence caused by steric hindrance can be effectively reduced, and compared with traditional hydrogen-containing silicone oil, the reaction of the ring-end hydrogen-containing siloxane and vinyl is more sufficient; and secondly, the internal cyclic carbon chain structure is beneficial to improving the mechanical properties such as elasticity or strength of the organic silicon addition type adhesive.

Description

Technical Field

[0001] The present invention relates to the field of thermally conductive organic silicone adhesives, and in particular to a preparation method and application of cyclic terminal hydrogen-containing siloxane Background Art

[0002] In the thermally conductive silicone adhesive industry, adhesives based on hydrosilylation reaction are in various forms, such as thermally conductive gel, thermally conductive potting glue, thermally conductive gasket, etc. The basic raw materials involved are vinyl silicone oil, hydrogen-containing silicone oil, platinum catalyst, platinum inhibitor, thermally conductive filler and other additives. Adhesives based on hydrosilylation reaction are popular because the final product has excellent heat resistance, softness, hydrophobicity and environmental protection.

[0003] Hydrogenated silicone oil, as a crosslinking agent for silane addition, generally refers to silicone oils that contain active hydrogen atoms that can participate in crosslinking reactions at the ends or side chains of the main chain of organic silicone polysiloxane. Silicone oils that contain active hydrogen at both ends of the main chain are called terminal hydrogenated silicone oils, and silicone oils that contain active hydrogen on the side chains are called side hydrogenated silicone oils. These active hydrogen atoms generally form a crosslinked network structure with vinyl silicone oil, turning the crosslinking agent from liquid to solid.

[0004] Side hydrogen-containing silicone oil is used as the main cross-linking agent. During the silane addition reaction, some of the active hydrogen in the side chain cannot react completely in a short period of time due to the steric effect. As time goes by, the molecular chain shifts or rotates, and the silane addition reaction will continue after contacting with vinyl. As a result, after the thermal conductive silicone is formed and placed for a period of time, its hardness shows an upward trend, even exceeding its original design standard, seriously affecting the stability of product quality.

[0005] The Chinese invention patent with publication number CN 113549220 A discloses a modified hydrogenated silicone oil and its preparation method and application. The modified silicone oil is prepared by reacting hydrogenated silicone oil, 2-allylcyclohexanone and 1-allyl-3-methylimidazole chloride under certain conditions. The introduction of carbonyl, quaternary ammonium, five-membered ring and six-membered ring structures into the molecular chain of hydrogenated silicone oil improves the hydrophilicity and yellowing resistance. However, since the Si-H bond in its structure is still in the side chain, the thermal conductive organic silicone adhesive prepared by using it as a crosslinking agent still has stability problems. A Chinese invention patent with publication number CN 111423586A discloses a method for synthesizing polyhedral oligomeric silsesquioxane with a silicon-hydrogen functional group, wherein tetraethyl orthosilicate is reacted with a quaternary ammonium alkaline catalyst to obtain POSS ammonium salt, and the purified POSS ammonium salt is reacted with chlorosilane to prepare oligomeric silsesquioxane, which has good compatibility with polymers and can form a molecular-level composite. The product has a POSS structure inside, and the molecules extend outward with Si-H ends. This structure has the same effect as the present invention, but due to the high chemical activity of tetraethyl orthosilicate, it is difficult to control the reaction rate when reacting with a quaternary ammonium alkaline catalyst, and the final yield will be very low. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention aims to provide a method for preparing a cyclic terminal hydrogen-containing siloxane, and another object of the present invention is to provide an application of the cyclic terminal hydrogen-containing siloxane. The cyclic terminal hydrogen-containing siloxane has high chemical activity and low steric hindrance effect. The addition-type thermal conductive organic silicone adhesive prepared by using it as a crosslinking agent has excellent mechanical properties and good stability.

[0007] In order to achieve the above purpose, the present invention adopts the following technical scheme: (1) tetramethyldisiloxane and an ethanol solution of sodium hydroxide are reacted in a sealed container at 100 to 120° C. for 3 to 6 hours, and ethanol is removed by vacuum distillation to obtain a solid product, which is repeatedly washed with ethanol and filtered 2 to 3 times to remove the sodium hydroxide in the solid, and then dried to obtain sodium dimethylsiloxane crystals; (2) reacting the sodium dimethylsiloxane crystals with cyclooctatetraene, a platinum catalyst and a solvent in a sealed container at 100 to 120° C. for 2 to 4 hours, removing the solvent by distillation under reduced pressure to obtain a solid product, washing with a small amount of solvent, filtering 1 to 2 times, washing the platinum catalyst in the solid with the solvent, and drying to obtain cyclic sodium dimethylsiloxane crystals; (3) The above-mentioned cyclic sodium dimethylsiloxane crystals and dimethylchlorosilane are stirred at room temperature for 6 to 10 hours in a sealed container, the solid reactant is filtered out, and then the reduced pressure distillation is carried out at 100 to 120° C. for 1 hour to remove the remaining dimethylchlorosilane, thereby obtaining a cyclic terminal hydrogen-containing siloxane, the structural formula of which is as follows:

[0008] The reaction formula of the technical solution of the present invention is as follows:

[0009] More preferably, in the ethanol solution of sodium hydroxide, the mass ratio of sodium hydroxide to ethanol is 5 to 12:100.

[0010] More preferably, the mass ratio of the sodium hydroxide ethanol solution to tetramethyldisiloxane is 100:9-20.

[0011] More preferably, the mass ratio of the sodium dimethylsiloxane crystals, cyclooctatetraene and solvent is 100:14-18:100-150.

[0012] More preferably, the mass ratio of the cyclic sodium dimethylsiloxane crystals to dimethylchlorosilane is 100:80-90.

[0013] More preferably, the platinum catalyst is chloroplatinic acid-divinyltetramethyldisiloxane complex, and the platinum content is 1000-5000 ppm.

[0014] More preferably, the amount of the platinum catalyst is 20 to 60 ppm based on the mass of cyclooctatetraene.

[0015] More preferably, the solvent is one or a combination of octane, heptane, dichloromethane and toluene. The solvent is used to clean the platinum catalyst in the product.

[0016] The structural formula of the cyclic terminal hydrogen-containing siloxane is as follows:

[0017] More preferably, the cyclic terminal hydrogen-containing siloxane is used in a silicone addition type thermally conductive adhesive or a thermally conductive silicone sheet.

[0018] More preferably, the cyclic terminal hydrogen-containing siloxane is used in the silicone addition type thermally conductive silicone sheet as follows: 100 parts of 100-5000cP vinyl silicone oil, 400-2000 parts of thermally conductive powder, 0.3-5 parts of cyclic end hydrogen-containing siloxane, 0.1-1 parts of 1000-5000ppm platinum catalyst, and 0.01-0.1 parts of ethynyl cyclohexanol are mixed evenly, pressed into a thickness of 2mm, and cured at 120°C for 15 minutes to obtain a silicone addition type thermally conductive silicone sheet.

[0019] The beneficial effects of the present invention are: (1) The active hydrogen of the cyclic terminal hydrogen-containing siloxane of the present invention is located at the end of the molecular chain, which can effectively reduce the influence of steric hindrance and react more fully with the vinyl group, thus avoiding the phenomenon that the conventional hydrogen-containing silicone oil and the vinyl group are not completely reacted, resulting in the hardening of the colloid thickening film; (2) The cyclic terminal hydrogen-containing siloxane of the present invention contains a cyclic carbon chain structure inside, which gives the cross-linking point a rigid structure, thereby improving the elasticity or strength of the thermally conductive silicone product, and the prepared product has excellent mechanical properties; (3) The preparation process of the present invention is simple, the yield of the target product is high, it is conducive to industrial production, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the infrared spectrum of the cyclic terminal hydrogen-containing siloxane in Example 1. DETAILED DESCRIPTION

[0021] The embodiments described below specifically illustrate the above contents of the present invention, and particularly illustrate that, based on the principles of the present invention, several adjustments and improvements may be made, and these adjustments and improvements are also considered to be within the protection scope of the embodiments of the present invention.

[0022] Embodiment 1: (1) Dissolve 5 g of sodium hydroxide in 100 g of anhydrous ethanol, then take 100 g of the sodium hydroxide ethanol solution and 9 g of tetramethyldisiloxane, react at 118° C. in a sealed container for 5.5 h, remove the ethanol by distillation under reduced pressure to obtain a solid product, wash with 10 g of ethanol, filter twice, and dry to obtain sodium dimethylsiloxane crystals; (2) Repeat the method (1) several times to obtain a sufficient amount of sodium dimethylsiloxane crystals, take 100 g of sodium dimethylsiloxane crystals, then add 14.2 g of cyclooctatetraene, 0.15 g of a platinum catalyst with a concentration of 5000 ppm and 145 g of a solvent, wherein the solvent is octane and dichloromethane in a ratio of 9:1, and then react in a sealed container at 102° C. for 3.5 h, remove the solvent by distillation under reduced pressure to obtain a solid product, then wash the crystals with 10 g of solvent, filter twice, and dry to obtain cyclic sodium dimethylsiloxane crystals. (3) Repeat the process of step (2) several times to obtain a sufficient amount of cyclic sodium dimethylsiloxane crystals. Then weigh 100 g of cyclic sodium dimethylsiloxane crystals, add 80 g of dimethylchlorosilane, stir at room temperature for 6.5 h, filter out the sodium chloride, and then distill the solution under reduced pressure at 125° C. for 1 h to remove the remaining dimethylchlorosilane to obtain cyclic terminal hydrogen-containing siloxane.

[0023] Embodiment 2: (1) 8 g of sodium hydroxide was dissolved in 100 g of anhydrous ethanol, and then 100 g of the sodium hydroxide ethanol solution and 13.5 g of tetramethyldisiloxane were reacted in a sealed container at 115° C. for 4.5 h, and the ethanol was removed by vacuum distillation to obtain a solid product, which was then washed with 10 g of ethanol, filtered three times, and dried to obtain sodium dimethylsiloxane crystals; (2) Repeat the method (1) several times to obtain a sufficient amount of sodium dimethylsiloxane crystals. Take 100 g of sodium dimethylsiloxane crystals, then add 16.0 g of cyclooctatetraene, 0.3 g of a 3000 ppm platinum catalyst and 120 g of a solvent, wherein the solvent is octane, dichloromethane and toluene in a ratio of 7:2:1, then react in a sealed container at 110° C. for 3 h, and remove the solvent by vacuum distillation to obtain a solid product. Then wash the crystals with 10 g of solvent and filter them twice. After drying, cyclic sodium dimethylsiloxane crystals are obtained. (3) Repeat the process of step (2) several times to obtain a sufficient amount of cyclic sodium dimethylsiloxane crystals, then weigh 100 g of the cyclic sodium dimethylsiloxane crystals, add 85 g of dimethylchlorosilane, stir at room temperature for 7 h, filter out the sodium chloride, and then distill the solution under reduced pressure at 130° C. for 1 h to remove the remaining dimethylchlorosilane to obtain a cyclic terminal hydrogen-containing siloxane.

[0024] Embodiment 3: (1) 11 g of sodium hydroxide was dissolved in 100 g of anhydrous ethanol, and then 100 g of the sodium hydroxide ethanol solution and 18 g of tetramethyldisiloxane were reacted in a sealed container at 110° C. for 3.8 h, and the ethanol was removed by vacuum distillation to obtain a solid product, which was then washed with 12 g of ethanol, filtered three times, and dried to obtain sodium dimethylsiloxane crystals; (2) Repeat the method (1) several times to obtain a sufficient amount of sodium dimethylsiloxane crystals. Take 100 g of sodium dimethylsiloxane crystals, then add 17.5 g of cyclooctatetraene, 1 g of a platinum catalyst with a concentration of 1000 ppm and 105 g of a solvent, wherein the solvent is hexane, dichloromethane and toluene in a ratio of 5:3:2, then react in a sealed container at 116° C. for 2.5 h, and remove the solvent by vacuum distillation to obtain a solid product. Then wash the crystals with 10 g of solvent and filter them twice. After drying, cyclic sodium dimethylsiloxane crystals are obtained. (3) Repeat the process of step (2) several times to obtain a sufficient amount of cyclic sodium dimethylsiloxane crystals, then weigh 100 g of the cyclic sodium dimethylsiloxane crystals, add 90 g of dimethylchlorosilane, stir at room temperature for 8.2 h, filter out the sodium chloride, and then distill the solution under reduced pressure at 138° C. for 1 h to remove the remaining dimethylchlorosilane to obtain a cyclic terminal hydrogen-containing siloxane.

[0025] Embodiment 4: (1) 6.5 g of sodium hydroxide was dissolved in 100 g of anhydrous ethanol, and then 100 g of the sodium hydroxide ethanol solution and 11.2 g of tetramethyldisiloxane were reacted in a sealed container at 115° C. for 4.2 h, and the ethanol was removed by vacuum distillation to obtain a solid product, which was then washed with 10 g of ethanol, filtered twice, and dried to obtain sodium dimethylsiloxane crystals; (2) Repeat the method in (1) several times to obtain a sufficient amount of sodium dimethylsiloxane crystals. Take 100 g of sodium dimethylsiloxane crystals, then add 16.8 g of cyclooctatetraene, 0.57 g of a platinum catalyst with a concentration of 1000 ppm and 125 g of a solvent, wherein the solvent is octane and dichloromethane in a ratio of 7:3, and then react in a sealed container at 120°C for 2.2 hours. Remove the solvent by vacuum distillation to obtain a solid product, then wash and filter the crystals twice with 10 g of solvent, and dry to obtain cyclic sodium dimethylsiloxane crystals. (3) Repeat the process of step (2) several times to obtain a sufficient amount of cyclic sodium dimethylsiloxane crystals, then weigh 100 g of the cyclic sodium dimethylsiloxane crystals, add 87 g of dimethylchlorosilane, stir at room temperature for 7 h, filter out the sodium chloride, and then distill the solution under reduced pressure at 138°C for 1 h to remove the remaining dimethylchlorosilane to obtain a cyclic terminal hydrogen-containing siloxane.

[0026] Embodiment 5: (1) 10.5 g of sodium hydroxide was dissolved in 100 g of anhydrous ethanol, and then 100 g of the sodium hydroxide ethanol solution and 16.9 g of tetramethyldisiloxane were reacted in a sealed container at 110° C. for 3.8 h, and the ethanol was removed by vacuum distillation to obtain a solid product, which was then washed with 12 g of ethanol, filtered three times, and dried to obtain sodium dimethylsiloxane crystals; (2) Repeat the method (1) several times to obtain a sufficient amount of sodium dimethylsiloxane crystals. Take 100 g of sodium dimethylsiloxane crystals, then add 15 g of cyclooctatetraene, 0.1 g of a platinum catalyst with a concentration of 4000 ppm and 138 g of a solvent, wherein the solvent is hexane, dichloromethane and toluene in a ratio of 8:1:1, then react in a sealed container at 120° C. for 2.3 h, and remove the solvent by vacuum distillation to obtain a solid product. Then wash the crystals with 10 g of solvent and filter them twice. After drying, cyclic sodium dimethylsiloxane crystals are obtained. (3) Repeat the process of step (2) several times to obtain a sufficient amount of cyclic sodium dimethylsiloxane crystals. Then weigh 100 g of cyclic sodium dimethylsiloxane crystals, add 83 g of dimethylchlorosilane, stir at room temperature for 8.2 h, filter out the sodium chloride, and then distill the solution under reduced pressure at 138° C. for 1 h to remove the remaining dimethylchlorosilane to obtain cyclic terminal hydrogen-containing siloxane.

[0027] Comparative Example 1: Comparative Example 1 is common hydrogen-containing siloxane, produced by Zhejiang Runhe Organic Silicone New Materials Co., Ltd., model RH-H503, and containing 0.55% by mass of hydrogen.

[0028] Comparative Example 2: The preparation steps of Comparative Example 2 are the same as those of Example 1, except that the cyclooctatetraene in step (2) of Example 1 is replaced with 3,7-dimethyl-1,3,6-octatriene (the cyclic structure in the molecule is changed to a linear structure), and the remaining steps and amounts remain unchanged.

[0028] The method for preparing the cyclic terminal hydrogen-containing siloxane in the embodiment of the present invention and applying it in the silicone addition type thermal conductive silicone sheet is as follows: 100 parts of 100-5000cP vinyl silicone oil, 400-2000 parts of thermally conductive powder, 0.3-5 parts of cyclic end hydrogen-containing siloxane, 0.1-1 parts of 1000-5000ppm platinum catalyst, and 0.01-0.1 parts of ethynyl cyclohexanol are mixed evenly, pressed into a thickness of 2mm, and cured at 120°C for 15 minutes to obtain a silicone addition type thermally conductive silicone sheet.

[0029] Application Examples 1-7 The cyclic terminal hydrogen-containing siloxane prepared in Examples 1-5 and Comparative Examples 1-2 were applied to the following formula as a crosslinking agent to prepare a 2.0W / (m·K) thermally conductive silicone sheet, and its various properties were tested: the application formula of Examples 1-5, Comparative Examples 1 and Comparative Examples 2 was 100 parts of 500cP vinyl silicone oil + 700 parts of thermally conductive powder + 1.0 part of crosslinking agent + 0.5 parts of 3000ppm platinum catalyst + 0.05 parts of ethynyl cyclohexanol, mixed evenly, pressed into a thickness of 2mm, cured at 120°C for 15min, and cooled to room temperature to test its various properties as shown in Table 1. The 2.0W / (m·K) thermally conductive silicone sheet prepared in Examples 1-5 corresponds to Application Examples 1-5, Comparative Example 1 corresponds to Application Example 6, and Comparative Example 2 corresponds to Application Example 7. Table 1:

[0027] Application Example 8-14 The cyclic terminal hydrogen-containing siloxane prepared in Examples 1-5 and Comparative Examples 1-3 were applied to the following formula as a crosslinking agent to prepare a 4.0W / (m·K) thermally conductive silicone sheet, and its various properties were tested: 100 parts of 500cP vinyl silicone oil + 1400 parts of thermally conductive powder + 0.9 parts of crosslinking agent + 0.5 parts of 3000ppm platinum catalyst + 0.05 parts of ethynyl cyclohexanol, mixed evenly, pressed into a thickness of 2mm, cured at 120°C for 15min, and tested for physical properties. The 4.0W / (m·K) thermally conductive silicone sheet prepared in Examples 1-5 corresponds to Application Examples 8-12, Comparative Example 1 corresponds to Application Example 13, and Comparative Example 2 corresponds to Application Example 14.

[0027] Table 2:

[0028] In application examples 1-7, the cyclic terminal hydrogen-containing siloxanes of examples 1-5 of the present invention, the common hydrogen-containing siloxanes on the market in comparative example 1, and the linear structure hydrogen-containing siloxanes of comparative example 2 were substituted into a 2.0 W / (m·K) organic silicon thermal conductive sheet to test the mechanical properties. From the data in Table 1, it can be found that: (1) In the application examples 1-5 of the ring-terminated hydrogen-containing siloxane of Examples 1-5, the tensile strength of the sheet increased by 102.37% to 106.89%, the elongation at break increased by 36.33% to 43.29%, and the samples of Application Examples 1-5 could remain folded at 180° without cracking, compared with the application example 6 of the common hydrogen-containing siloxane of Comparative Example 1. (2) The application examples 1-5 of the ring-terminated hydrogen-containing siloxanes in Examples 1-5, compared with the application example 7 of the linear hydrogen-containing siloxane in Comparative Example 2, showed that the tensile strength of the sheet increased by 70.06% to 73.85%, and the elongation at break increased by 24.84% to 31.22%. (3) Compared with comparative examples 6-7, the samples of application examples 1-5 of embodiments 1-5 can remain folded at 180° without cracking.

[0029] In application examples 8-14, the cyclic terminal hydrogen-containing siloxanes of examples 1-5 of the present invention, the common hydrogen-containing siloxanes on the market in comparative example 1, and the linear structure hydrogen-containing siloxanes of comparative example 2 were substituted into a 4.0W / (m·K) organic silicon thermal conductive sheet to test the mechanical properties. From the data in Table 2, it can be found that: (1) The application examples 8-12 of the ring-terminated hydrogen-containing siloxane in Examples 1-5, compared with the application example 13 of the common hydrogen-containing siloxane in Comparative Example 1, the tensile strength of the sheet increased by 34.83% to 41.96%, and the elongation at break increased by 51.93% to 60.86%. (2) The application example formulations of the cyclic terminal hydrogen-containing siloxanes in Examples 1-5, compared with the application example formulation 14 of the linear structure hydrogen-containing siloxane in Comparative Example 2, the tensile strength of the sheet increased by 26.89% to 33.61%, and the elongation at break increased by 34.39% to 42.29%. (3) Compared with comparative examples 13-14, samples of examples 8-12 of embodiments 1-5 can be folded at 180° without cracking.

[0030] In summary, the cyclic terminal hydrogen-containing siloxane of the present invention has the characteristic of significantly improving the mechanical properties in the silicone addition type adhesive.

[0031] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be determined that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the present invention and the scope of patent protection determined by the submitted claims.

Claims

1. A method for preparing a cyclic terminal hydrogen-containing siloxane, characterized in that: The preparation process is as follows: (1) reacting tetramethyldisiloxane with an ethanol solution of sodium hydroxide in a sealed container at 100 to 120° C. for 3 to 6 hours, removing ethanol by vacuum distillation to obtain a solid product, repeatedly washing with ethanol, filtering 2 to 3 times, and drying to obtain sodium dimethylsiloxane crystals; (2) reacting the sodium dimethylsiloxane crystals with cyclooctatetraene, a platinum catalyst and a solvent in a sealed container at 100 to 120° C. for 2 to 4 hours, removing the solvent by distillation under reduced pressure to obtain a solid product, washing with a small amount of solvent, filtering 1 to 2 times, and drying to obtain cyclic sodium dimethylsiloxane crystals; (3) The above-mentioned cyclic sodium dimethylsiloxane crystals and dimethylchlorosilane are stirred at room temperature in a closed container for 6 to 10 hours, the solid reactant is filtered out, and then the filtrate is distilled under reduced pressure at 100 to 120° C. for 1 hour to remove the remaining dimethylchlorosilane, thereby obtaining a cyclic terminal hydrogen-containing siloxane, the structural formula of which is as follows:

2. The method for preparing a cyclic terminal hydrogen-containing siloxane according to claim 1, characterized in that: The mass ratio of sodium hydroxide to ethanol in the aluminum hydroxide ethanol solution is 5 to 12:

100.

3. The method for preparing a cyclic terminal hydrogen-containing siloxane according to claim 1, characterized in that: The mass ratio of the sodium hydroxide ethanol solution to tetramethyldisiloxane is 100:9-20.

4. The method for preparing a cyclic terminal hydrogen-containing siloxane according to claim 1, characterized in that: The mass ratio of the sodium dimethylsiloxane crystals, cyclooctatetraene and the solvent is 100:14-18:100-150.

5. The method for preparing a cyclic terminal hydrogen-containing siloxane according to claim 1, characterized in that: The mass ratio of the cyclic sodium dimethylsiloxane crystals to dimethylchlorosilane is 100:80-90.

6. The method for preparing a cyclic terminal hydrogen-containing siloxane according to claim 1, characterized in that: The platinum catalyst is a chloroplatinic acid-divinyltetramethyldisiloxane complex, and the platinum content is 1000-5000ppm.

7. The method for preparing a cyclic terminal hydrogen-containing siloxane according to claim 1, characterized in that: The mass of platinum in the platinum catalyst is 20 to 60 ppm of the mass of cyclooctatetraene.

8. The method for preparing a cyclic terminal hydrogen-containing siloxane according to claim 1, characterized in that: The solvent is one or a combination of octane, heptane, dichloromethane and toluene.

9. The method for preparing a cyclic terminal hydrogen-containing siloxane according to claim 1, characterized in that: A cyclic terminal hydrogen-containing siloxane has the following structural formula:

10. Use of the cyclic terminal hydrogen-containing siloxane as claimed in claim 9 in an addition-type thermally conductive adhesive or a thermally conductive silicone sheet.

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