Ethyl-containing alkoxyl-terminated silicone polymers, methods of making and use

Abstract

This invention provides an ethyl-containing alkoxy-terminated organosilicon polymer, its preparation method, and its applications. The preparation method includes: S1, mixing methylvinylcyclotetrasiloxane, a solvent, and a first catalyst, introducing hydrogen gas, and reacting at 50-70°C until the methylvinylcyclotetrasiloxane content is no higher than 5%, filtering to remove impurities and obtain the product; S2, under nitrogen protection, ring-opening the product obtained in step S1 with acetic anhydride in the presence of a ring-opening catalyst, neutralizing and hydrolyzing, removing impurities, and obtaining the product; S3, under nitrogen protection, reacting the product of step S2 with hexamethyldisilazane at 40-50°C for 1-3 hours, adding N,N-diethylamino-trialkoxysilane, and reacting at 50-60°C for 1-3 hours. The polymer obtained by this invention, as a thermally conductive powder treatment agent, can effectively improve the dispersion performance of powders and enhance the heat resistance of products without reducing their tensile strength.

Description

Technical Field

[0001] This invention relates to the field of thermally conductive silicone rubber synthesis technology, and more specifically, to an ethyl-containing alkoxy-terminated organosilicon polymer, its preparation method, and its application. Background Technology

[0002] Silicone rubber refers to a type of rubber whose main chain consists of alternating silicon and oxygen atoms, with two organic groups attached to each silicon atom. In existing technologies, various additives are typically added to raw silicone rubber to impart various additional properties. In the field of silicone rubber, fillers are commonly added to improve its physical properties. Fillers are usually inorganic; for example, using inorganic powders such as silica, calcium carbonate, silicon carbide, and magnesium oxide as modifiers to prepare silicone rubber composites can significantly improve the physical properties of silicone rubber. However, when using such powders for modification, the hydroxyl groups on their surface have poor compatibility with the silicone rubber system, resulting in high interfacial tension among the substances in the composite material and poor modification effect. Therefore, hydrophobic treatment of the powder using silicon functional groups is commonly used, and this method is currently widely applied.

[0003] However, in this method, functional silanes and their oligomers release small molecules during use, resulting in high VOCs and a large amount of vaporized small molecules, which can easily lead to poor mechanical properties. However, if the release of small molecules is not timely, it will also lead to poor electrical properties of the composite material. As a result, the thermal conductivity of materials modified with small molecule silane compounds is poor. Most small molecule silanes have poor modification effects on these inorganic powders and cannot meet the requirements for high thermal conductivity. Summary of the Invention

[0004] The first objective of this invention is to provide a method for preparing an ethyl-containing alkoxy-terminated organosilicon polymer. The organosilicon polymer obtained by this method can effectively improve the dispersion performance of the powder as a thermally conductive powder treatment agent, and improve the heat resistance of the product without reducing the tensile strength of the product.

[0005] The preparation method of this ethyl-containing alkoxy-terminated organosilicon polymer includes the following steps:

[0006] S1, Methylvinylcyclotetrasiloxane, solvent and first catalyst are mixed, hydrogen gas is introduced, and the reaction is carried out at 50-70°C until the content of methylvinylcyclotetrasiloxane in the system is not higher than 5%. After filtration, low-boiling-point substances are removed to obtain the product.

[0007] S2, under nitrogen protection, the product obtained in step S1 is ring-opened with acetic anhydride in the presence of a second catalyst, neutralized and hydrolyzed to remove low-boiling-point substances, and the product is obtained; the second catalyst is a ring-opening catalyst;

[0008] S3, under nitrogen protection, the product obtained in step S2 is reacted with hexamethyldisilazane at 40-50°C for 1-3 hours, and then N,N-diethylamino-trialkoxysilane is added and the reaction is continued at 50-60°C for 1-3 hours.

[0009] In a specific embodiment of the present invention, the first catalyst in step S1 is a catalyst for catalytic hydrogenation. In a preferred embodiment of the present invention, to further improve the modifying performance of the polymer as a modifier, in step S1, the first catalyst is nickel chloride, nickel powder, Raney nickel, chloroplatinic acid, or an organoplatinum compound, with nickel powder being more preferred. In a preferred embodiment of the present invention, the first catalyst is 0.03wt% to 0.05wt% of methylvinylcyclotetrasiloxane by mass.

[0010] In specific embodiments of the present invention, the introduced hydrogen gas is typically introduced slowly and continuously, and the amount of hydrogen gas is usually in excess. In specific embodiments of the present invention, the content of methylvinylcyclotetrasiloxane in the gas-phase tracking system is typically used.

[0011] In one specific embodiment of the present invention, in step S1, the solvent can be a polar solvent without active hydrogen, preferably one or more of xylene, DMSO, and acetonitrile. In one specific embodiment of the present invention, the amount of solvent used is 50wt% to 100wt% of the mass of methylvinylcyclotetrasiloxane.

[0012] In one specific embodiment of the present invention, step S1, the step of removing low-boiling-point substances preferably includes: distillation at -0.03 to -0.02 MPa and 50 to 70 °C until essentially no bubbles are generated.

[0013] In specific embodiments of the present invention, commonly used ring-opening catalysts in the art can be used in step S2. In a preferred embodiment of the present invention, to further improve the modifying performance of the polymer as a modifier, the ring-opening catalyst in step S2 can be sulfuric acid, hydrochloric acid, oxalic acid, trifluoromethanesulfonic acid, sodium hydroxide, or potassium hydroxide, preferably trifluoromethanesulfonic acid. In a preferred embodiment of the present invention, the second catalyst is 1 wt% to 3 wt% of the methylvinylcyclotetrasiloxane by mass.

[0014] In a preferred embodiment of the present invention, in step S2, the temperature of the ring-opening reaction can be 110-130°C, and the reaction time can be 3-5 hours.

[0015] In a preferred embodiment of the present invention, in order to further improve the modifying performance of the polymer as a modifier, in step S2, the molar ratio of the methylvinylcyclotetrasiloxane to acetic anhydride is (6-10):1.

[0016] In a specific embodiment of the present invention, the "neutralization and hydrolysis" in step S2 may specifically include: adding 2-4 wt% of an inorganic alkali aqueous solution and stirring and hydrolyzing at 50-70°C for 2-4 hours. The inorganic alkali is preferably potassium hydroxide and / or sodium hydroxide, more preferably potassium hydroxide. In a preferred embodiment of the present invention, the molar ratio of inorganic alkali to acetic anhydride is (1.8-2.0):1.

[0017] In a specific embodiment of the present invention, in step S2, the system after the hydrolysis reaction is completed is allowed to stand, the product layer is taken, and impurities are removed to obtain the product of step S2. The "impurity removal" step may include vacuum distillation (the conditions for vacuum distillation may be 100-120℃, -0.06 to -0.04 MPa) to remove impurities such as water, ethanol, and cyclic compounds, and cooling filtration to remove inorganic salts.

[0018] In a preferred embodiment of the present invention, in order to further improve the modifying performance of the polymer as a modifier, in step S3, the N,N-diethylamino-trialkoxysilane is N,N-diethylamino-triethoxysilane and / or N,N-diethylamino-trimethoxysilane, preferably N,N-diethylamino-trimethoxysilane.

[0019] In this invention, the reaction sequence of adding hexamethyldisilazane and diethylaminotrialkoxysilane in step S3 is also one of the core inventive points. The ethyl-containing alkoxy-terminated organosilicon polymer obtained under this specific reaction sequence and conditions has better modification effects.

[0020] In a preferred embodiment of the present invention, in order to further improve the modifying performance of the polymer as a modifier, in step S3, the molar ratio of acetic anhydride, hexamethyldisilazane and N,N-diethylamino-trialkoxysilane is 1:(0.45-0.5):(0.9-1).

[0021] In one specific embodiment of the present invention, in step S3, after the reaction is completed, the low-boiling-point substance is removed to obtain the final product. The specific steps for "removing the low-boiling-point substance" may include: distillation at -0.05 to -0.03 MPa and 60 to 80°C without the generation of bubbles.

[0022] The ethyl-containing alkoxy-terminated organosilicon polymer obtained by the preparation method provided by the present invention can be used as a thermally conductive powder treatment agent to treat powders (such as fillers), which can effectively improve the dispersion performance of the powders (such as fillers). The filler obtained by using the thermally conductive powder treatment agent can improve the heat resistance of the silicone rubber without reducing the tensile strength of the obtained silicone rubber.

[0023] Another object of the present invention is to provide an ethyl-containing alkoxy-terminated organosilicon polymer obtained by the above preparation method.

[0024] Another object of the present invention is to provide the application of the ethyl-containing alkoxy-terminated organosilicon polymer obtained by the above preparation method in the preparation of thermally conductive silicone rubber composite materials.

[0025] In specific embodiments of the present invention, the filler can be treated using the alkoxy-terminated organosilicon polymer provided by the present invention, and the amount added can be 0.9-1 wt% of the filler. In thermally conductive silicone rubber, the filler may include light calcium carbonate, heavy calcium carbonate, alumina, silicon carbide, etc. In specific embodiments of the present invention, heavy calcium carbonate, alumina, and silicon carbide in a mass ratio of 2:3:3 can be used to describe the present invention. The alkoxy-terminated organosilicon polymer provided by the present invention can treat silicone rubber conventionally using fillers in the art, thereby improving thermal conductivity and tensile strength. In specific embodiments of the present invention, silicone rubber of methyl vinyl silicone raw material can be used to describe the present invention.

[0026] The beneficial effects of this invention are as follows:

[0027] 1) The method provided by this invention innovatively synthesizes a methyl ethyl cyclic compound, then uses acetic anhydride for ring opening, and finally synthesizes an ethyl-containing alkoxy-terminated organosilicon polymer with end-reactive properties by using a specific sequence and preparation method under catalytic-free conditions (i.e., step S3 of the technical solution provided by this invention). Using this ethyl-containing alkoxy-terminated organosilicon polymer as a thermally conductive powder treatment agent can effectively improve the dispersion performance of the powder and effectively improve the heat resistance of the product (preferred temperature range is -150℃ to 350℃) without reducing the tensile strength of the product.

[0028] 2) The preparation method of the ethyl-containing alkoxy-terminated organosilicon polymer provided by the present invention is mild, economical and environmentally friendly. Detailed Implementation

[0029] The specific embodiments of the present invention will be described in further detail below with reference to the examples. These examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0030] Unless otherwise specified in the examples, the conditions should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Unless otherwise specified, "%" in this invention refers to a percentage by mass.

[0031] Example 1

[0032] This embodiment provides an ethyl-containing alkoxy-terminated organosilicon polymer, the preparation method of which includes the following steps:

[0033] 1) Synthesis of methyl ethyl ring

[0034] In a 500ml three-necked flask that has been dried and purged with nitrogen, 224g of methylvinylcyclotetrasiloxane (99.52% purity by gas chromatography), 140g of xylene, and 0.075g of nickel powder were added. While stirring, 28L of high-purity hydrogen was continuously and slowly introduced, maintaining the reaction temperature at 58–62℃ for 10 hours. When the methylvinylcyclotetrasiloxane content was found to be 4.15% by gas chromatography, the hydrogen supply was stopped, the mixture was cooled, filtered, and distilled at -0.03 to -0.025 MPa and 55–60℃ to remove xylene until the system produced virtually no bubbles, yielding the product.

[0035] 2) Synthesis of hydroxyl polyethyl silicone oil

[0036] Under nitrogen protection, the product obtained in step 1), 10.21 g of acetic anhydride, and 2.7 g of trifluoromethanesulfonic acid were mixed and heated at 120–125 °C for 3.5 h. The mixture was then cooled to 70 °C, and 430 g of an aqueous solution containing 10.66 g of KOH was added. The mixture was hydrolyzed at 60 °C for 3.5 h, allowed to stand and separate for 0.5 h, and the product layer was collected. The product layer was then subjected to low boiling point at 105–108 °C and -0.06–-0.05 MPa to remove water, ethanol, cyclic compounds, etc., until no fraction was produced. The mixture was then cooled and filtered to remove inorganic salts, yielding the product.

[0037] 3) Synthesis of alkoxy-terminated organosilicon polymers

[0038] Under nitrogen protection, the product obtained from S2 was mixed with 7.75 g of hexamethyldisilazane and reacted at 40–43 °C for 1.5 h. Then, 18.37 g of N,N-diethylamino-trimethoxysilane was added and the reaction continued for 2 h. The temperature was slowly increased to 65–68 °C and distilled at -0.05–-0.04 MPa until no bubbles were generated. The temperature was then lowered to obtain 235.7 g of product.

[0039] Example 2

[0040] This embodiment provides an ethyl-containing alkoxy-terminated organosilicon polymer, the preparation method of which includes the following steps:

[0041] 1) Synthesis of methyl ethyl ring

[0042] In a 500ml three-necked flask that has been dried and purged with nitrogen, 310g of methylvinylcyclotetrasiloxane (99.52% purity by gas chromatography), 248g of xylene, and 0.155g of nickel powder were added. While stirring, 28L of high-purity hydrogen was continuously and slowly introduced, maintaining the reaction temperature at 58–62℃ for 10 hours. When the methylvinylcyclotetrasiloxane content was found to be 4.02% by gas chromatography, the hydrogen supply was stopped, the mixture was cooled, filtered, and then distilled at -0.03 to -0.025 MPa and 55–60℃ to remove xylene until the system produced virtually no bubbles, yielding the product.

[0043] 2) Synthesis of hydroxyl polyethyl silicone oil

[0044] Under nitrogen protection, the product obtained in step 1), 10.21 g of acetic anhydride, and 7.75 g of trifluoromethanesulfonic acid were mixed and heated at 120–125 °C for 3.5 h. The mixture was then cooled to below 70 °C, and 374 g of an aqueous solution containing 11.22 g of KOH was added. The mixture was hydrolyzed at 65 °C for 3 h, and allowed to stand for 0.5 h. The product layer was collected and subjected to low boiling point at 110–114 °C and -0.05–-0.04 MPa to remove water, ethanol, cyclic compounds, etc., until no fraction was produced. The mixture was then cooled and filtered to remove inorganic salts, yielding the product.

[0045] 3) Synthesis of alkoxy-terminated organosilicon polymers

[0046] Under nitrogen protection, the product obtained from S2 was mixed with 8.07 g of hexamethyldisilazane and reacted at 40–43 °C for 1.5 h. Then, 19.1 g of N,N-diethylamino-trimethoxysilane was added and the reaction continued for 2 h. The temperature was slowly increased to 65–68 °C and distilled at -0.05–-0.04 MPa until no bubbles were generated. The temperature was then lowered to obtain 317.4 g of product.

[0047] Example 3

[0048] This invention provides an alkoxy-terminated organosilicon polymer containing ethyl groups, the preparation method of which includes the following steps:

[0049] 1) Synthesis of methyl ethyl ring

[0050] In a 500ml three-necked flask that has been dried and purged with nitrogen, 190g of methylvinylcyclotetrasiloxane (99.52% purity by gas chromatography), 119g of xylene, and 0.0475g of nickel powder were added. While stirring, 28L of high-purity hydrogen was continuously and slowly introduced, maintaining the reaction temperature at 58–62℃ for 10 hours. When the methylvinylcyclotetrasiloxane content was found to be 4.12% by gas chromatography, the hydrogen supply was stopped, the mixture was cooled, filtered, and then distilled at -0.03 to -0.025 MPa and 55–60℃ to remove xylene until the system produced virtually no bubbles, yielding the product.

[0051] 2) Synthesis of hydroxyl polyethyl silicone oil

[0052] Under nitrogen protection, the product obtained in step 1), 10.21 g of acetic anhydride, and 1.8 g of trifluoromethanesulfonic acid were mixed and heated at 120–125 °C for 3.5 h. The mixture was then cooled to below 70 °C, and 304 g of an aqueous solution containing 7.60 g of NaOH was added. The mixture was hydrolyzed at 60 °C for 3.5 h, allowed to stand and separate for 0.5 h, and the product layer was collected. The product layer was then subjected to low boiling point at 105–108 °C and -0.06–-0.05 MPa to remove water, ethanol, cyclic compounds, etc., until no fraction was produced. The mixture was then cooled and filtered to remove inorganic salts, yielding the product.

[0053] 3) Synthesis of alkoxy-terminated organosilicon polymers

[0054] Under nitrogen protection, the product obtained from S2 was mixed with 6.78 g of hexamethyldisilazane and reacted at 40–43 °C for 1.5 h. Then, 16.3 g of N,N-diethylamino-trimethoxysilane was added and the reaction continued for 2 h. The temperature was slowly increased to 65–68 °C and distilled at -0.05–-0.04 MPa until no bubbles were generated. The temperature was then lowered to obtain 200.1 g of product.

[0055] Example 4

[0056] The preparation method provided in this embodiment is the same as that in Example 1, except that: the first catalyst in step 1) is 0.075g of nickel chloride; the second catalyst in step 2) is 2.7g of sulfuric acid; and the N,N-diethylamino-trialkoxysilane in step 3) is 22.6g of N,N-diethylamino-triethoxysilane.

[0057] The preparation method provided in this embodiment yielded 234.8g of product.

[0058] Comparative Example 1

[0059] The preparation method provided in this comparative example is the same as that in Example 1, except that:

[0060] 3) Synthesis of alkoxy-terminated organosilicon polymers

[0061] Under nitrogen protection, the product obtained from S2 was mixed with 18.37 g of diethylaminotrimethoxysilane and reacted at 40–43 °C for 1.5 h. Then, 7.75 g of hexamethyldisilazane was added and the reaction continued for 2 h. The temperature was slowly increased to 65–68 °C and distilled at -0.05–-0.04 MPa until no bubbles were generated. The temperature was then lowered to obtain 229.5 g of product.

[0062] Experimental Example

[0063] 20 parts of heavy calcium carbonate, 30 parts of alumina, and 30 parts of silicon carbide were vacuum dried at 100°C for 4 hours and then placed in a high-speed mixer. Under mixed conditions, 0.8 parts by weight of the treatment agent obtained in the examples and comparative examples were added, and the mixture was stirred for 30 minutes to obtain the filler for later use.

[0064] The formulation of the silicone rubber composite material compound sample is as follows: 20 parts of methyl vinyl silicone raw rubber with a vinyl content of 0.03% are added to the roller. After the rubber compound is wrapped around the roller, 3 parts of precipitated silica and 80 parts of the above-treated filler are added and mixed 5 times. Then, 0.1 parts of phthaloyl peroxide and 2 parts of carbon nanotubes are added and mixed again. The mixture is then cut into thin sheets, cold-pressed and molded, vulcanized twice, and cooled to obtain the sample.

[0065] The temperature resistance, tensile strength and thermal conductivity of the specimens were tested according to EN344, ASTM D412 and ASTM 1461-01 respectively. The specific performance results are shown in Table 1 below.

[0066] Table 1 Performance Results

[0067] Treatment agent Temperature range (°C) Tensile strength (kN / mm) Thermal conductivity (W / mK) Example 1 -150～350 2.2 4.4 Example 2 -150～350 2.1 4.0 Example 3 -140～330 1.8 4.2 Example 4 -150～340 1.9 4.3 Comparative Example 1 -120～320 1.3 3.2

[0068] Finally, the method of this invention is merely a preferred embodiment and is not intended to limit the scope of protection of this invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for preparing an ethyl-containing alkoxy-terminated organosilicon polymer, characterized in that, Includes the following steps: S1, Methylvinylcyclotetrasiloxane, solvent and first catalyst are mixed, hydrogen gas is introduced, and the reaction is carried out at 50-70°C until the content of methylvinylcyclotetrasiloxane in the system is not higher than 5%. After filtration, low-boiling-point substances are removed to obtain the product. S2, under nitrogen protection, the product obtained in step S1 is ring-opened with acetic anhydride in the presence of a second catalyst, neutralized and hydrolyzed, and impurities are removed to obtain the product; the second catalyst is a ring-opening catalyst; S3, under nitrogen protection, the product obtained in step S2 is reacted with hexamethyldisilazane at 40~50℃ for 1~3h, and then N,N-diethylamino-trialkoxysilane is added and the reaction is continued at 50~60℃ for 1~3h.

2. The preparation method according to claim 1, characterized in that, In step S1, the first catalyst is nickel chloride, nickel powder, Raney nickel, chloroplatinic acid, or an organoplatinum compound; And / or, the solvent is one or more of xylene, DMSO, and acetonitrile.

3. The preparation method according to claim 2, characterized in that, In step S1, the first catalyst is nickel powder.

4. The preparation method according to claim 1, characterized in that, In step S1, the first catalyst is 0.03wt% to 0.05wt% of methylvinylcyclotetrasiloxane by mass.

5. The preparation method according to claim 1, characterized in that, In step S2, the molar ratio of the methylvinylcyclotetrasiloxane to acetic anhydride is (6~10):

1.

6. The preparation method according to claim 1, characterized in that, In step S2, the second catalyst is sulfuric acid, hydrochloric acid, oxalic acid, trifluoromethanesulfonic acid, sodium hydroxide, or potassium hydroxide.

7. The preparation method according to claim 6, characterized in that, In step S2, the second catalyst is trifluoromethanesulfonic acid.

8. The preparation method according to claim 1, characterized in that, The second catalyst is 1 wt% to 3 wt% of the methylvinylcyclotetrasiloxane by mass.

9. The preparation method according to claim 1, characterized in that, In step S3, the N,N-diethylaminotri-alkoxysilane is N,N-diethylaminotriethoxysilane and / or N,N-diethylaminotrimethoxysilane.

10. The preparation method according to claim 9, characterized in that, In step S3, the N,N-diethylaminotri-alkoxysilane is N,N-diethylaminotrimethoxysilane.

11. The preparation method according to claim 1, characterized in that, In step S3, the molar ratio of acetic anhydride, hexamethyldisilazane and N,N-diethylamino-trialkoxysilane is 1:(0.45~0.5):(0.9~1).

12. The ethyl-containing alkoxy-terminated organosilicon polymer obtained by the preparation method according to any one of claims 1 to 11.

13. The use of the ethyl-containing alkoxy-terminated organosilicon polymer of claim 12 in the preparation of thermally conductive silicone rubber composites.