One-step solvent-free preparation of methylphenyl-terminated vinyl polysiloxane and silicone gel

Abstract

The invention discloses a one-step solvent-free preparation of methylphenyl-terminated vinyl polysiloxane and silicone gel. The methylphenyl-terminated vinyl polysiloxane comprises the following preparation steps: adding octamethylcyclotetrasiloxane, octaphenylcyclotetrasiloxane and dimethyl-terminated vinyl silicone oil into a reaction container and stirring evenly; introducing nitrogen after evacuating the reaction container to form an oxygen-free environment; heating the reaction container step by step to 180-200°C, and adding a catalyst between 50-80°C; the step-by-step heating includes a prepolymerization reaction below 90°C and a second polymerization reaction at greater than 90°C to obtain methylphenyl-terminated vinyl polysiloxane. The high-temperature and high-pressure resistant methylphenyl silicone gel is obtained by mixing the methylphenyl-terminated vinyl polysiloxane with an inhibitor, a crosslinking agent and a crosslinking catalyst, degassing, heating and crosslinking and curing, and can meet the performance requirements of high-power semiconductor devices for packaging materials such as high-pressure resistance and high-temperature resistance, and the product quality is stable and the production efficiency is high.

Description

Technical Field

[0001] The invention relates to the technical field of packaging insulating materials for high-power semiconductor devices, and in particular to methylphenyl vinyl-terminated polysiloxane and silicone gel prepared by a one-step solvent-free method. Background Art

[0002] As global electricity demand continues to grow, high-power power electronic devices, such as SiC-type IGBTs (insulated gate bipolar transistors), play a key role in modern energy transformation and efficient power systems. Packaging materials have a significant impact on the performance of SiC-type IGBTs. They not only need to provide mechanical support and protection, but also need to maintain electrical insulation and heat dissipation performance under high temperature and high voltage environments to ensure stable operation and long life of the device. Therefore, the performance requirements for packaging materials, especially in terms of high temperature and high voltage resistance, are becoming increasingly stringent. Although there are many silicone materials on the market that have good high temperature resistance, their high voltage resistance is still difficult to meet the needs of actual applications.

[0003] Existing technologies mostly use phenyl silicone elastomers to encapsulate high-power semiconductor devices. Therefore, how to efficiently prepare silicone materials with excellent high temperature and high pressure resistance has become a research hotspot.

[0004] Invention CN118185021A discloses a phenyl silicone elastomer for high-power semiconductor device packaging and a preparation method thereof, wherein the preparation method is: in a protective gas atmosphere, in toluene, octamethylcyclotetrasiloxane and octaphenylcyclotetrasiloxane are used as raw materials and polymerized under the catalysis of tetramethylammonium hydroxide to obtain methylphenyl polysiloxane. Similarly, invention CN111909523A discloses a production process for high-temperature vulcanized phenyl silicone rubber, wherein the raw materials of the phenyl silicone rubber include: octamethylcyclotetrasiloxane, octaphenylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane, vinyl end-capping agent, potassium hydroxide, activated carbon black, toluene, vinyl MQ silicone resin and fumed silica. In the above inventions, octamethylcyclotetrasiloxane and octaphenylcyclotetrasiloxane are used as raw materials for ring-opening polymerization to prepare phenyl silicone elastomer. The ring-opening polymerization reaction conditions are relatively mild, and the molecular weight and distribution of the polymer can be better controlled, thereby forming a stable polymer chain structure, improving the mechanical properties and thermal stability of the material, and the ring-opening polymerization does not generate small molecular by-products, which will not affect the stability of the prepared phenyl silicone elastomer product.

[0005] However, the above inventions all prepare phenyl silicone elastomers under solvent conditions. The presence of solvent will not only affect the selectivity and yield of the polymerization reaction, but may also produce a large amount of small molecule impurities. Toluene is used as the reaction solvent in the above inventions. Although the solvent is separated and removed after the reaction, a small amount of solvent is still likely to remain in the final product, affecting the insulation and pressure resistance of the material, and further leading to unstable product quality.

[0006] Therefore, on the basis of reducing by-products through ring-opening polymerization, how to develop a solvent-free or low-solvent polymerization method to simplify the process of preparing phenyl silicone elastomers, further improve production efficiency and product quality, and enhance its high-voltage resistance while maintaining its high-temperature resistance to meet the higher requirements of high-power SiC IGBT components for packaging materials is an urgent problem to be solved by technical personnel in this field. Summary of the invention

[0007] In view of the defects existing in the above-mentioned prior art, the present invention provides a one-step solvent-free preparation of methylphenyl-terminated vinyl polysiloxane and silicone gel, which simplifies the preparation process of methylphenyl-terminated vinyl polysiloxane, improves production efficiency, and at the same time meets the performance requirements of high-power semiconductor devices for packaging materials such as high voltage resistance, high temperature resistance, and stable quality.

[0008] In a first aspect, the present invention provides a one-step solvent-free preparation of methylphenyl vinyl-terminated polysiloxane, wherein the methylphenyl vinyl-terminated polysiloxane comprises the following preparation steps:

[0009] Step 1, add octamethylcyclotetrasiloxane, octaphenylcyclotetrasiloxane and dimethyl vinyl-terminated silicone oil into a reaction container and stir evenly;

[0010] Step 2: After evacuating the reaction container, nitrogen is introduced to form an oxygen-free reaction environment;

[0011] Step 3, heating the reaction vessel step by step to 180-200°C, and adding the catalyst at 50-80°C;

[0012] The stepwise heating includes a first stage prepolymerization reaction below 90° C. and a second stage polymerization reaction above 90° C. to prepare methylphenyl vinyl-terminated polysiloxane.

[0013] On the one hand, the existing methylphenyl-terminated vinyl polysiloxane is prepared by condensation reaction, which has defects such as low atomic utilization and more inorganic small molecule impurities; on the other hand, the reaction is mostly carried out in solvent, requiring post-processing operations such as extraction, and the process is cumbersome. In addition, the small amount of residual solvent affects the purity of the product, reduces the product's heat resistance and pressure resistance, and the product quality fluctuates greatly, making it difficult to produce on a large scale.

[0014] The one-step solvent-free direct preparation of the methylphenyl-terminated vinyl polysiloxane of the present invention does not require condensation in the reaction process, directly undergoes chain-breaking polymerization from cyclic monomers, has no intermediate generation link, has high atom utilization, has no inorganic small molecule impurities, does not require post-processing operations such as extraction, has a simple process, and can realize industrial production.

[0015] Among them, in order to maintain the nitrogen atmosphere in the reactor and avoid the entry of air in step 3, the present invention preferably injects the catalyst by injection, so that octamethylcyclotetrasiloxane and octaphenylcyclotetrasiloxane are polymerized to generate methylphenyl polysiloxane, and then copolymerized with the vinyl silicone oil end-capping agent to form methylphenyl vinyl-terminated polysiloxane.

[0016] Preferably, the mass ratio of octamethylcyclotetrasiloxane to octaphenylcyclotetrasiloxane is (3-100):1, more preferably (10-50):1;

[0017] The viscosity of the dimethyl vinyl-terminated silicone oil is 5-20, and the mass ratio of the dimethyl vinyl-terminated silicone oil to the octamethylcyclotetrasiloxane is (1-5):100, preferably (1-3):100.

[0018] Preferably, the catalyst comprises at least one of tetramethylammonium hydroxide siliconate and tetramethylammonium hydroxide, and the amount of the catalyst used is 0.5 to 3% of the total mass of octamethylcyclotetrasiloxane and octaphenylcyclotetrasiloxane.

[0019] Preferably, the stepwise heating comprises the following steps in sequence:

[0020] 1.1 Heating and removing impurities: heating to 50-60℃, reducing pressure to remove impurities;

[0021] 1.2 One-stage prepolymerization reaction: heat to 80-90°C and react for 2-4 hours;

[0022] 1.3 Second stage polymerization reaction: continue to heat up to 95-120°C and react for 3-5h;

[0023] 1.4 Heating to destroy the catalyst: heating to 140-155°C and reacting under reduced pressure for 1-3 hours;

[0024] 1.5 High temperature impurity removal: heat to 160-200℃, and distill under reduced pressure for 2-4h;

[0025] The prepared methylphenyl vinyl-terminated polysiloxane has a viscosity of less than 2000 mpa·s, an impurity content of less than 2%, and a yield of more than 85%.

[0026] The present invention is based on the one-step solvent-free direct preparation of methylphenyl-terminated vinyl polysiloxane. By strictly controlling the temperature and time of step-by-step heating and combining it with the target reaction results, high-quality methylphenyl-terminated vinyl polysiloxane with low viscosity and particularly low impurity content can be prepared with stable yield and high efficiency, thereby providing a guarantee for the long-term stability of further packaged products and meeting the packaging requirements of high-end devices.

[0027] Preferably, the step-by-step heating process further comprises at least one of the following conditions:

[0028] In 1.1, the reaction vessel is evacuated, and stirred at a speed of 50 to 80 r / min for 20 to 40 min until no liquid flows out of the reaction system to obtain a decontaminated mixed solution;

[0029] In 1.2 and 1.3, nitrogen gas is introduced into the reaction vessel to maintain a nitrogen atmosphere, and the reaction is stirred at a speed of 60 to 100 r / min;

[0030] In 1.4 and 1.5, the reaction vessel is evacuated and stirred at a speed of 80 to 120 r / min.

[0031] Preferably, evacuating the reaction vessel comprises reducing the vacuum degree to -1.0 MPa to 0 MPa, preferably -0.9 MPa to -0.5 MPa.

[0032] More preferably, in the step-by-step heating, the heating rate of each step is regulated, including:

[0033] In 1.1, the heating rate is 5-10°C / min;

[0034] In 1.2, the heating rate is 3-5°C / min;

[0035] In 1.3, the heating rate is 1-3°C / min;

[0036] In 1.4 and 1.5, the heating rate is 3 to 8°C / min.

[0037] The residual catalyst will affect the purity of the finally obtained methylphenyl vinyl-terminated polysiloxane. After the reaction is completed, the system is heated to 140-155°C in step 1.4, and the reduced pressure reaction is carried out for 1-3 hours to decompose the catalyst into gases such as trimethylamine at high temperature, thereby deactivating the catalyst, making it unable to continue the catalytic reaction and volatilizing from the system to ensure the purity of the synthesized methylphenyl vinyl-terminated polysiloxane.

[0038] Similarly, in step 1.5, since the reaction is a balanced reaction, there will still be some small molecular impurities such as tetramethylcyclotetrasiloxane segments that do not participate in the reaction and segments with low polymerization degree after the reaction is completed. Therefore, the present invention further heats the reaction solution after removing the catalyst tetramethylammonium hydroxide by 160-200° C. and performs reduced pressure distillation for 2-4 hours to remove the above small molecular impurities, thereby obtaining a high-purity transparent viscous methylphenyl-terminated vinyl polysiloxane.

[0039] The obtained methylphenyl vinyl-terminated polysiloxane has a viscosity of less than 2000 mpa·s, an impurity content of less than 2%, and a yield that can be stabilized at more than 85%.

[0040] In a second aspect, the present invention provides a high temperature and high pressure resistant methylphenyl silicone gel, wherein the raw materials of the methylphenyl silicone gel include, by weight:

[0041] 80-200 parts of the aforementioned methylphenyl vinyl-terminated polysiloxane,

[0042] 0.1 to 0.15 parts of inhibitor,

[0043] 4 to 6 parts of cross-linking agent,

[0044] 0.01 to 0.1 part of cross-linking catalyst;

[0045] The cross-linking agent comprises methylphenyl side chain hydrogen-containing silicone oil and methylphenyl terminal hydrogen-containing silicone oil compounded in a mass ratio of (1-3): (7-12);

[0046] The methylphenyl-terminated vinyl polysiloxane is mixed with an inhibitor, a crosslinking agent and a crosslinking catalyst, vacuum degassed, and heated for crosslinking and curing to obtain the high temperature and high pressure resistant methylphenyl silicone gel. In particular, the combination of methylphenyl side chain hydrogen-containing silicone oil and methylphenyl-terminated hydrogen-containing silicone oil plays an important role in the subsequent heating crosslinking. Although the amount of methylphenyl side chain hydrogen-containing silicone oil is low, it is a necessary component. If only methylphenyl-terminated hydrogen-containing silicone oil is used, only an oily product can be obtained even if the heating reaction is carried out, and it will be difficult to obtain a silicone gel suitable for potting and curing.

[0047] Preferably, the cross-linking catalyst comprises a platinum silicone oil solution having a platinum content of 500 to 6000 ppm.

[0048] Preferably, the conditions for heating cross-linking and curing are curing at 90 to 120° C. for 1 to 5 hours.

[0049] Preferably, after the high temperature and high pressure resistant methylphenyl silicone gel is cured, the withstanding temperature is above 300°C, the breakdown voltage is above 40kV / mm, and the initiation voltage of the electric tree test is above 9kV.

[0050] In a third aspect, the present invention further provides a high-voltage power module encapsulation method using the high-temperature and high-pressure resistant methylphenyl silicone gel, comprising the following steps:

[0051] S1, preparing methylphenyl vinyl-terminated polysiloxane;

[0052] S2, stirring and mixing the methylphenyl vinyl-terminated polysiloxane, an inhibitor, and a cross-linking agent to obtain a mixed material;

[0053] S3, adding a crosslinking catalyst to the mixture, stirring evenly, and vacuuming to obtain a methylphenyl silicone gel precursor;

[0054] S4, applying the methylphenyl silicone gel precursor to the mold cavity accommodating the high-voltage power module, vacuum degassing and heating for cross-linking and curing to obtain a high-temperature and high-pressure resistant methylphenyl silicone high-voltage power module package.

[0055] The present invention has at least the following beneficial effects:

[0056] (1) The present invention adopts a ring-opening polymerization reaction to prepare methylphenyl vinyl-terminated polysiloxane. The conditions are relatively mild and the molecular weight and distribution of the polymer can be well controlled, thereby forming a stable polymer chain structure and improving the mechanical properties and thermal stability of the material. In addition, the ring-opening polymerization does not generate small molecular by-products and will not affect the stability of the prepared phenyl silicone elastomer product.

[0057] (2) The present invention performs ring-opening polymerization under solvent-free conditions, and there is no need to remove the solvent after the reaction is completed. There is little residual impurities, high yield and product stability, and low manufacturing cost.

[0058] (3) The high-quality methylphenyl-terminated vinyl polysiloxane prepared by a one-step solvent-free method provides continuous and stable material conditions for the preparation of high-temperature and high-pressure resistant methylphenyl silicone gel. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1(a) is a breakdown photo of the German Wacker 915HT when the voltage reaches the threshold value during the electrical breakdown experiment;

[0060] Figure 1(b) is a breakdown photo of Dow 3-4170 in an electrical breakdown test when the voltage reaches the threshold;

[0061] FIG1( c ) is a breakdown photograph of the potting example 4 when the voltage reaches the threshold value during the electrical breakdown experiment;

[0062] Figure 2(a) is a photo of a sample of German Wacker 915HT undergoing an electrical treeing experiment;

[0063] Figure 2(b) is a sample photo of Dow 3-4170 in the electrical treeing experiment;

[0064] FIG2(c) is a photograph of the sample of potting example 4 subjected to the electrical treeing experiment;

[0065] Figure 3(a) is a comparison photo of German Wacker 915HT before and after aging experiment;

[0066] Figure 3(b) is a comparison photo of Dow 3-4170 before and after the aging test;

[0067] FIG3( c ) is a comparison photo of potting example 4 before and after the aging experiment. DETAILED DESCRIPTION

[0068] In order to better understand the above technical solution, the above technical solution will be described in detail below in combination with the specification and specific implementation methods. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0069] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings, and "multiple" generally includes at least two.

[0070] It should also be noted that the term "includes", "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, so that a commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the commodity or device including the elements.

[0071] The technical solutions in the embodiments of the present invention will be described clearly and completely below.

[0072] A one-step solvent-free preparation of methylphenyl-terminated vinyl polysiloxane, a high-temperature and high-pressure resistant methylphenyl silicone gel containing the methylphenyl-terminated vinyl polysiloxane, and applications thereof.

[0073] The preparation method of the methylphenyl vinyl-terminated polysiloxane specifically comprises:

[0074] Step 1, add octamethylcyclotetrasiloxane and octaphenylcyclotetrasiloxane in a mass ratio of (3-100):1, preferably (10-50):1, and dimethyl-terminated vinyl silicone oil (viscosity of 5-20) in a mass ratio of (1-5):100 to the octamethylcyclotetrasiloxane into a reaction container, and stir evenly;

[0075] Step 2: After evacuating the reaction container, nitrogen is introduced to form an oxygen-free reaction environment;

[0076] Step 3: heating the reaction vessel step by step, the specific steps include:

[0077] 3.1 Heating and removing impurities: evacuate the reaction vessel to a vacuum degree of -0.1Mpa to 0Mpa, heat it to 50-60°C at a heating rate of 5-10°C / min, stir at a speed of 50-80r / min for 20-40min, and remove impurities under reduced pressure until no liquid flows out of the reaction system to obtain a de-impurity mixed solution;

[0078] 3.2 Adding catalyst: Adding catalyst between 50 and 80°C, wherein the catalyst comprises at least one of tetramethylammonium hydroxide silicon alkoxide and tetramethylammonium hydroxide, and the amount of catalyst added is 0.5 to 3% of the total mass of octamethylcyclotetrasiloxane and octaphenylcyclotetrasiloxane;

[0079] 3.3 One-stage prepolymerization reaction: nitrogen is introduced into the reaction vessel to maintain a nitrogen atmosphere, the temperature is raised to 80-90°C at a heating rate of 1-5°C / min, more preferably 1-3°C / min, and the reaction is stirred at a speed of 60-100 r / min for 2-4 hours;

[0080] 3.4 Second stage polymerization reaction: nitrogen is introduced into the reaction vessel to maintain nitrogen atmosphere, the temperature is continuously raised to 95-120°C at a heating rate of 1-3°C / min, and the reaction is stirred at a speed of 60-100 r / min for 3-5 hours;

[0081] 3.5 Heating to destroy the catalyst: evacuate to a vacuum degree of -0.1Mpa to 0Mpa, heat to 140-155°C at a heating rate of 3-8°C / min, stir at a speed of 80-120r / min, and react under reduced pressure for 1-3h;

[0082] 3.6 High-temperature impurity removal: evacuate to a vacuum degree of -0.1Mpa to 0Mpa, heat to 160-200°C at a heating rate of 3-8°C / min, stir at a speed of 80-120r / min, and distill under reduced pressure for 2-4h to obtain methylphenyl-terminated vinyl polysiloxane.

[0083] Through the preparation method, the viscosity of the obtained methylphenyl vinyl-terminated polysiloxane is less than 2000 mpa·s, the volatile impurity content is less than 2%, and the yield can be stabilized at more than 85%.

[0084] On the basis of preparing methylphenyl vinyl-terminated polysiloxane, a method for preparing methylphenyl silicone gel using the methylphenyl vinyl-terminated polysiloxane as a main raw material is further provided, which specifically comprises:

[0085] (1) Ingredients: Weigh the raw materials of the methylphenyl silicone gel in parts by weight:

[0086] 80-200 parts of the above-prepared methylphenyl vinyl-terminated polysiloxane

[0087] Inhibitor 0.1~0.15 parts

[0088] Crosslinking agent 4-6 parts

[0089] Cross-linking catalyst 0.01~0.1 parts

[0090] A crosslinking agent, comprising methylphenyl side chain hydrogen-containing silicone oil and methylphenyl terminal hydrogen-containing silicone oil in a mass ratio of (1-3): (7-12);

[0091] Preferably, the crosslinking catalyst is a platinum silicone oil solution, wherein the platinum content in the platinum silicone oil solution is 500 to 6000 ppm;

[0092] (2) mixing methylphenyl-terminated vinyl polysiloxane with an inhibitor, a crosslinking agent and a crosslinking catalyst, and vacuum-exhausting for 20-40 minutes;

[0093] (3) heating and cross-linking at 90 to 120° C. and curing for 1 to 5 hours to obtain the high temperature and high pressure resistant methylphenyl silicone gel.

[0094] The high temperature and high pressure resistant methylphenyl silicone gel is used as a packaging insulation material for high-power semiconductor devices, which can provide semiconductor packaging components that are resistant to high temperatures and high pressures and can be industrially produced in large quantities. The specific application includes the following steps:

[0095] S1, preparing methylphenyl vinyl-terminated polysiloxane;

[0096] S2, stirring and mixing the methylphenyl vinyl-terminated polysiloxane, an inhibitor, and a cross-linking agent to obtain a mixed material;

[0097] S3, adding a crosslinking catalyst to the mixture, stirring evenly, and vacuuming to obtain a methylphenyl silicone gel precursor;

[0098] S4. Apply the methylphenyl silicone gel precursor to the mold cavity accommodating the high-voltage and high-power module, and after vacuum degassing, heat and cross-link at 90-120°C and cure for 1-5 hours to obtain a high-temperature and high-pressure resistant methylphenyl silicone high-voltage and high-power module package.

[0099] Through the above process, the obtained methylphenyl silicone gel and its packaging have outstanding high temperature and high pressure resistance, high temperature stability and no yellowing, a breakdown voltage of more than 40kV / mm, and an electrical tree voltage of more than 9kV, which meet the higher requirements of high-power SiC IGBT components for packaging materials.

[0100] Example 1

[0101] The methylphenyl vinyl-terminated polysiloxane of this embodiment is prepared by the following steps:

[0102] S1. Add 50 g of octamethylcyclotetrasiloxane, 1 g of octaphenylcyclotetrasiloxane, and 1.5 g of dimethyl-terminated vinyl silicone oil with a viscosity of 12 into a three-necked flask and stir evenly.

[0103] S2, evacuate the three-necked flask and introduce nitrogen, observe that there are no obvious bubbles in the solution and introduce nitrogen, repeat this step 3 times to form an oxygen-free reaction environment;

[0104] S3, placing the three-necked flask in an oil bath and heating it step by step, the specific steps include:

[0105] S3.1 Heating and removing impurities: evacuate the three-necked flask to a vacuum degree of -0.5 MPa, heat it to 50°C, and heat it at a rate of 5°C / min. Stir at a speed of 60 r / min for 30 min, and remove impurities under reduced pressure until no liquid flows out of the reaction system to obtain a mixed solution for removing impurities;

[0106] Continue to raise the temperature to 65°C and add 1 g of tetramethylammonium hydroxide siliconate catalyst;

[0107] S3.2 One-stage prepolymerization reaction: nitrogen was introduced into the three-necked flask to maintain nitrogen atmosphere, the temperature was raised to 85°C at a heating rate of 2°C / min, and the reaction was stirred at a speed of 80 r / min for 3 h;

[0108] S3.3 Second stage polymerization reaction: nitrogen was introduced into the three-necked flask to maintain nitrogen atmosphere, and the temperature was continued to rise to 105°C at a heating rate of 2°C / min, and the reaction was stirred at a speed of 80 r / min for 4 h;

[0109] S3.4 Heating to destroy the catalyst: evacuate to -0.8Mpa, heat to 150℃, heating rate of 5℃ / min, stir at 100r / min, and react under reduced pressure for 2h until no bubbles emerge in the reaction system;

[0110] S3.5 High-temperature impurity removal: evacuate to -0.9Mpa, heat to 180°C, heating rate of 5°C / min, stir at 100r / min, and distill under reduced pressure for 3h to obtain methylphenyl-terminated vinyl polysiloxane.

[0111] Example 2

[0112] The difference between this embodiment and embodiment 1 is that the raw material ratio of the methylphenyl vinyl-terminated polysiloxane prepared in this embodiment is different, specifically:

[0113] 50 g of octamethylcyclotetrasiloxane, 0.5 g of octaphenylcyclotetrasiloxane, 0.5 g of dimethyl vinyl-terminated silicone oil with a viscosity of 12, and 1 g of tetramethylammonium hydroxide silicon alkoxide catalyst were used.

[0114] Example 3

[0115] The difference between this embodiment and embodiment 1 is that the raw material ratio of the methylphenyl vinyl-terminated polysiloxane prepared in this embodiment is different, specifically:

[0116] 50 g of octamethylcyclotetrasiloxane, 15 g of octaphenylcyclotetrasiloxane, 2 g of dimethyl vinyl-terminated silicone oil with a viscosity of 12, and 1.5 g of tetramethylammonium hydroxide silicon alkoxide catalyst were used.

[0117] The viscosity of the methylphenyl vinyl-terminated polysiloxane of Examples 1-3 is less than 2000 mPa·s, and the volatile impurity content is less than 2%. In particular, after multiple rounds of experiments, the yield of the examples can be stabilized at more than 85%, and has the technical conditions and application prospects for large-scale production.

[0118] Comparative Example 1

[0119] This comparative example refers to the invention CN118185021A, and a ring-opening polymerization reaction is carried out in a solvent to prepare methylphenyl vinyl-terminated polysiloxane. The specific preparation steps are as follows:

[0120] 1) Preheat the oil bath to 90°C and set aside.

[0121] 2) 55 g of toluene, 50 g of octamethylcyclotetrasiloxane, 1 g of octaphenylcyclotetrasiloxane, and 1 g of tetramethylammonium hydroxide catalyst were added to a three-necked flask in sequence, and stirred with a magnetic stirrer to obtain a mixed material;

[0122] 3) At room temperature, the three-necked flask containing the mixed material obtained above was evacuated, and nitrogen was introduced after observing that there were no obvious bubbles in the solution. This step was repeated 5 times to ensure that the air in the system was removed so that the subsequent reaction could be carried out under a nitrogen environment.

[0123] 4) Seal the mouth of the flask with a gas bag filled with nitrogen to maintain a nitrogen atmosphere, then place the treated three-necked flask in the oil bath preheated to 90° C., set the magnetic speed to 500 r / min, react for 15 min, and obtain a mixed solution C.

[0124] 5) 1.5 g of dimethyl vinyl-terminated silicone oil with a viscosity of 12 was injected through a syringe, and after heating to 110° C., stirring was continued at a speed of 500 r / min for 2 h to obtain a mixed solution D.

[0125] 6) After cooling the mixed solution D obtained above to 75° C., connect it to a condensation distillation apparatus (cooling first and then distillation), connect it to a vacuum pump, adjust the air inlet valve, maintain the negative pressure at 0.08-0.09 MPa, until there are no obvious bubbles in the solution, and evacuate for 55 minutes to remove toluene to obtain a mixed solution E.

[0126] 7) After the mixed solution E was heated to 170° C., the negative pressure was 0.09 MPa, and condensation and distillation were performed for 2 h to destroy tetramethylammonium hydroxide to obtain a mixed solution F.

[0127] 8) After the mixed solution F is heated to 180° C., condensation and distillation are continued at a negative pressure of 0.09 MPa for 15 min to further remove volatile components, thereby obtaining the methylphenyl vinyl-terminated polysiloxane.

[0128] Comparative Example 2

[0129] This comparative example is prepared in the same manner as comparative example 1, but with different material ratios. The specific difference is that:

[0130] 55 g of toluene, 50 g of octamethylcyclotetrasiloxane, 0.5 g of octaphenylcyclotetrasiloxane, 1.5 g of dimethyl vinyl-terminated silicone oil with a viscosity of 12, and 0.5 g of catalyst tetramethylammonium hydroxide were used.

[0131] Comparative Example 3

[0132] This comparative example is prepared in the same manner as comparative example 1, but with different material ratios. The specific difference is that:

[0133] 55 g of toluene, 50 g of octamethylcyclotetrasiloxane, 15 g of octaphenylcyclotetrasiloxane, 2 g of dimethyl-terminated vinyl silicone oil with a viscosity of 12, and 1.5 g of catalyst tetramethylammonium hydroxide were used.

[0134] The viscosity of the methylphenyl-terminated vinyl polysiloxane obtained in Comparative Examples 1-3 is basically less than 2000 mPa·s, but the volatile impurity content is above 3%. After multiple rounds of experiments on each material ratio, the yield of Comparative Examples 1-3 is unstable and fluctuates randomly between 50-80%, which will also lead to large fluctuations in the test results and quality of subsequent silicone gel products.

[0135] Comparative Example 4

[0136] The difference between this comparative example and comparative example 1 is that the solvent removal treatment time is 30 minutes.

[0137] The viscosity of the methylphenyl vinyl-terminated polysiloxane prepared in Comparative Example 1 is less than 2000 mPa·s, but the volatile impurity content is more than 5%. After multiple rounds of experiments, the yield of Comparative Example 4 is unstable and fluctuates randomly between 40-75%. The large residual impurities, low yield and large fluctuation of Comparative Example 4 will lead to lower test results and large fluctuations in subsequent silicone gel products.

[0138] Comparative Example 5

[0139] The difference between this comparative example and comparative example 1 is that the solvent removal treatment time is 90 minutes.

[0140] The viscosity of the methylphenyl vinyl-terminated polysiloxane prepared in Comparative Example 1 is less than 2000 mpa·s, and the volatile impurity content is about 2-3%. After multiple rounds of experiments, the yield of Comparative Example 5 is unstable and fluctuates randomly between 60-80%. Comparative Example 5 can reduce the residual impurities by extending the post-treatment time, but the yield still has large fluctuations, which not only leads to large fluctuations in the test results of subsequent silicone gel products, but also large production cycles and energy consumption.

[0141] The main material compositions and conditions of Examples 1-3 and Comparative Examples 1-5 are shown in Table 1:

[0142] Table 1:

[0143]

[0144] Potting example 1

[0145] The methylphenyl vinyl-terminated polysiloxane prepared in Example 1 is used to further prepare a high temperature and high pressure resistant methylphenyl silicone gel, which specifically comprises:

[0146] S1. Weigh the raw materials of the methylphenyl silicone gel:

[0147] (1) Methylphenyl vinyl-terminated polysiloxane 20g

[0148] (2) 1-ethynyl-1-cyclohexanol 0.01 g

[0149] (3) 1.11 g of a cross-linking agent, comprising 0.19 g of a methylphenyl side chain hydrogen-containing silicone oil and 0.92 g of a methylphenyl terminal hydrogen-containing silicone oil;

[0150] (4) 0.02 g of a cross-linking catalyst, wherein the cross-linking catalyst is a platinum silicone oil solution, wherein the platinum content in the platinum silicone oil solution is 2000 ppm;

[0151] S2, mixing methylphenyl-terminated vinyl polysiloxane with an inhibitor, a crosslinking agent and a crosslinking catalyst, and vacuum degassing for 30 minutes to obtain a methylphenyl silicone gel precursor;

[0152] S3. Apply the methylphenyl silicone gel precursor to the mold cavity, heat and crosslink at 105° C. for 3 hours, and solidify to obtain a methylphenyl silicone gel resistant to high temperature and high pressure.

[0153] Potting example 2

[0154] Potting Example 2 is similar to Potting Example 1 in that the methylphenyl vinyl-terminated polysiloxane of Example 1 is used to prepare high temperature and high pressure resistant methylphenyl silicone gel, except that the raw materials further include a cross-linking catalyst:

[0155] S1. Weigh the raw materials of the methylphenyl silicone gel:

[0156] (1) Methylphenyl vinyl-terminated polysiloxane 20g

[0157] (2) 1-ethynyl-1-cyclohexanol 0.015 g

[0158] (3) 1.11 g of a cross-linking agent, comprising 0.19 g of a methylphenyl side chain hydrogen-containing silicone oil and 0.92 g of a methylphenyl terminal hydrogen-containing silicone oil;

[0159] (4) 0.02 g of a cross-linking catalyst, wherein the cross-linking catalyst is a platinum silicone oil solution, wherein the platinum content of the platinum silicone oil solution is 2000 ppm;

[0160] S2, mixing methylphenyl-terminated vinyl polysiloxane with an inhibitor, a crosslinking agent and a crosslinking catalyst, and vacuum degassing for 30 minutes to obtain a methylphenyl silicone gel precursor;

[0161] S3. Apply the methylphenyl silicone gel precursor to the mold cavity, heat and crosslink at 105° C. for 3 hours, and solidify to obtain a methylphenyl silicone gel resistant to high temperature and high pressure.

[0162] Potting example 3

[0163] Potting Example 3 and Potting Example 2 also use the methylphenyl vinyl-terminated polysiloxane of Example 1 to prepare high temperature and high pressure resistant methylphenyl silicone gel, the difference is that the raw material ratio is different:

[0164] (1) Methylphenyl vinyl-terminated polysiloxane 20g

[0165] (2) 1-ethynyl-1-cyclohexanol 0.03 g

[0166] (3) 1.1 g of a cross-linking agent, comprising 0.19 g of a methylphenyl side chain hydrogen-containing silicone oil and 0.92 g of a methylphenyl terminal hydrogen-containing silicone oil;

[0167] (4) 0.02 g of a cross-linking catalyst, wherein the cross-linking catalyst is a platinum silicone oil solution, wherein the platinum content of the platinum silicone oil solution is 2000 ppm.

[0168] Potting example 4

[0169] Potting Example 4 and Potting Example 2 also use the methylphenyl vinyl-terminated polysiloxane of Example 1 to prepare high temperature and high pressure resistant methylphenyl silicone gel, the difference is that the raw material ratio is different:

[0170] (1) Methylphenyl vinyl-terminated polysiloxane 20g

[0171] (2) 1-ethynyl-1-cyclohexanol 0.02 g

[0172] (3) 1.11 g of a cross-linking agent, comprising 0.19 g of a methylphenyl side chain hydrogen-containing silicone oil and 0.92 g of a methylphenyl terminal hydrogen-containing silicone oil;

[0173] (4) 0.02 g of a cross-linking catalyst, wherein the cross-linking catalyst is a platinum silicone oil solution, wherein the platinum content of the platinum silicone oil solution is 2000 ppm.

[0174] Potting example 5

[0175] Potting Example 5 and Potting Example 4 also use the methylphenyl vinyl-terminated polysiloxane of Example 1 to prepare high temperature and high pressure resistant methylphenyl silicone gel, the difference is that the raw material ratio is different:

[0176] (1) Methylphenyl vinyl-terminated polysiloxane 20g

[0177] (2) 1-ethynyl-1-cyclohexanol 0.02 g

[0178] (3) 1.2 g of a cross-linking agent, comprising 0.2 g of a methylphenyl side chain hydrogen-containing silicone oil and 1.0 g of a methylphenyl terminal hydrogen-containing silicone oil;

[0179] (4) 0.02 g of a cross-linking catalyst, wherein the cross-linking catalyst is a platinum silicone oil solution, wherein the platinum content of the platinum silicone oil solution is 2000 ppm.

[0180] Potting example 6

[0181] In potting example 6, the methylphenyl-terminated vinyl polysiloxane of Example 2 was used to prepare high temperature and high pressure resistant methylphenyl silicone gel according to the raw material ratio of potting example 4.

[0182] Potting example 7

[0183] In potting example 7, the methylphenyl-terminated vinyl polysiloxane of Example 3 was used to prepare high temperature and high pressure resistant methylphenyl silicone gel according to the raw material ratio of potting example 4.

[0184] Potting Comparative Example 1-5

[0185] The methylphenyl vinyl-terminated polysiloxanes of Comparative Examples 1-5 were respectively used to prepare methylphenyl silicone gel according to the raw material ratio of Encapsulation Example 4.

[0186] Potting Comparative Example 6

[0187] Potting Comparative Example 6 uses the methylphenyl-terminated vinyl polysiloxane of Example 1 and prepares methylphenyl silicone gel according to the main raw material ratio of Potting Example 4, except that the crosslinking agent does not use methylphenyl side chain hydrogenated silicone oil. Potting Comparative Example 6 uses only methylphenyl-terminated hydrogenated silicone oil as a crosslinking agent, which is still in oil after heating reaction, and methylphenyl silicone gel for potting cannot be obtained.

[0188] The main raw material ratios of potting examples 1-7 and potting comparative examples 1-6 are shown in Table 2:

[0189] Table 2

[0190]

[0191] Performance testing and results

[0192] The samples prepared by potting examples 1-7 and potting comparison examples 1-5, as well as the marketed products of Wacker 915HT of Germany and Dow 3-4170 of the United States, were subjected to breakdown voltage tests, electric tree tests and aging tests. The experimental results are shown in Table 3, and comparative photos of potting example 4, Wacker 915H of Germany and Dow 3-4170 of the United States are exemplarily shown in the accompanying drawings.

[0193] The breakdown voltage of the samples prepared in the encapsulation examples 1-7 and the encapsulation comparison examples 1-5 was tested. The test method was: applying a DC voltage at a voltage increasing rate of 1 kV / s per second to test the breakdown performance of the phenyl and methyl samples under a DC electric field.

[0194] Figure 1 (a) is a breakdown photo of German Wacker 915HT when the voltage reaches the threshold value in the electrical breakdown test, Figure 1 (b) is a breakdown photo of American Dow 3-4170 when the voltage reaches the threshold value in the electrical breakdown test, and Figure 1 (c) is a breakdown photo of potting example 4 when the voltage reaches the threshold value in the electrical breakdown test. When the voltage reaches a specific threshold value, the material will undergo a breakdown phenomenon, and the voltage resistance performance of the material can be judged by the electrical breakdown test. The breakdown voltage of the samples of each embodiment of the present invention reaches more than 40kV / mm, which is much higher than the voltage resistance performance of similar foreign products.

[0195] The electrical treeing test was performed on the samples prepared in potting examples 1-7 and potting comparative examples 1-5.

[0196] The test method is: at room temperature, fix the sample with two ceramic plates and place it on the test platform. The horizontal distance between the needle tip and the ground electrode is about (2±0.1) mm. The sample is immersed in silicone oil to prevent surface discharge and flashover. Use a digital microscope image system to observe and record the experimental process. First, apply pressure from 0kV to 10kV on the sample, increase 5kV every ten minutes, and then gradually increase the frequency from 500Hz to 3000Hz AC voltage. The voltage waveform is a standard sine wave. Observe the growth of electrical trees (if the electrical tree breaks down, stop applying pressure immediately). Measure 20 times under the same conditions and at each voltage frequency to obtain statistical results.

[0197] Figure 2(a) is a sample photo of the electrical tree test of German Wacker 915HT, Figure 2(b) is a sample photo of the electrical tree test of American Dow 3-4170, and Figure 2(c) is a sample photo of the electrical tree test of Encapsulation Example 4. The accompanying drawings show the formation process of electrical trees. When a specific voltage is applied, the material will show the electrical tree phenomenon as shown in the figure. The appearance of electrical trees is an important indicator for evaluating the withstand voltage performance of materials. The voltage of the electrical tree test of the sample of the embodiment of the present invention is above 10kV, which is higher than similar foreign products.

[0198] An aging test was performed on the samples prepared in potting examples 1-7 and potting comparative examples 1-5, and the aging test was performed by placing them in a vacuum drying oven at 200° C. for 24 hours.

[0199] Figure 3(a) is a comparison photo of German Wacker 915HT before and after the aging test. Figure 3(b) is a comparison photo of American Dow 3-4170 before and after the aging test, and Figure 3(c) is a comparison photo of potting example 4 before and after the aging test. Before aging, the samples were all transparent and colorless. Thermal aging will cause the product to turn yellow and turbid. The temperature resistance of the material can be judged by the depth of yellowing and the degree of turbidity before and after aging. As can be seen from the figure, the yellow color of German Wacker 915HT and American Dow 3-4170 samples obviously deepened after aging, and the transparency decreased. The potting example 4 and other potting example samples of the present invention basically maintained their original color after aging, and were transparent, and there was no agglomeration phenomenon. Compared with similar foreign products, they have better high temperature resistance and anti-yellowing performance, and effectively overcome the defect that traditional silicone is easily oxidized, yellowed and deteriorated at high temperatures.

[0200] Table 3 Breakdown voltage test, electrical tree test and aging test results

[0201]

[0202] The above tests on potting examples 1-7, potting comparison examples 1-5, German Wacker 915HT and American Dow 3-4170 samples were all conducted under the same conditions and measured in parallel 20 times to obtain statistical results. In comparison, the average breakdown voltage of the potting examples is stable at above 40kV / mm, especially the parallel measurement experimental results of potting examples 3-7 are all above 45kV / mm, the voltage of the electric tree test is above 9kV, and the fluctuation range is small (about ±10%), and the minimum value basically meets the aforementioned withstand voltage range, which can be safely and stably used for high-voltage and high-power module potting, and the comprehensive performance is significantly better than similar foreign products. Due to the fluctuations in the yield and performance of the raw material methylphenyl-terminated vinyl polysiloxane, the potting comparison example has a lower pressure resistance and temperature resistance than the potting example, and its product performance fluctuates greatly (about 20-50%), and the potting quality is difficult to guarantee in a long-term stable manner.

[0203] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concepts. Therefore, the present invention is intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention.

Claims

1. A one-step solvent-free preparation of methylphenyl vinyl-terminated polysiloxane, characterized in that: The methylphenyl vinyl-terminated polysiloxane comprises the following preparation steps: Step 1, add octamethylcyclotetrasiloxane, octaphenylcyclotetrasiloxane and dimethyl vinyl-terminated silicone oil into a reaction container and stir evenly; Step 2: After evacuating the reaction container, nitrogen is introduced to form an oxygen-free reaction environment; Step 3, heating the reaction vessel step by step to 180-200°C, and adding the catalyst at 50-80°C; The stepwise heating includes a first stage prepolymerization reaction at a temperature below 90° C. and a second stage polymerization reaction at a temperature above 90° C. to prepare methylphenyl vinyl-terminated polysiloxane; Wherein, the mass ratio of octamethylcyclotetrasiloxane to octaphenylcyclotetrasiloxane is (3-100):1; The viscosity of the dimethyl vinyl-terminated silicone oil is 5-20, and the mass ratio of the dimethyl vinyl-terminated silicone oil to the octamethylcyclotetrasiloxane is (1-5):100; The step-by-step heating comprises the following steps in sequence: 1.1 Heating and removing impurities: heating to 50-60℃, reducing pressure to remove impurities; 1.2 One-stage prepolymerization reaction: heat to 80-90°C and react for 2-4 hours; 1.3 Second stage polymerization reaction: continue to heat up to 95-120°C and react for 3-5h; 1.4 Heating to destroy the catalyst: heating to 140-155°C and reacting under reduced pressure for 1-3 hours; 1.5 High temperature impurity removal: heat to 160-200℃, and distill under reduced pressure for 2-4h; The prepared methylphenyl vinyl-terminated polysiloxane has a viscosity of less than 2000 mpa·s, an impurity content of less than 2%, and a yield of more than 85%.

2. The methylphenyl vinyl-terminated polysiloxane according to claim 1, characterized in that The catalyst comprises at least one of tetramethylammonium hydroxide silicon alkoxide and tetramethylammonium hydroxide, and the amount of the catalyst is 0.5-3% of the total mass of octamethylcyclotetrasiloxane and octaphenylcyclotetrasiloxane.

3. The methylphenyl vinyl-terminated polysiloxane according to claim 1 or 2, characterized in that The step-by-step heating process also includes at least one of the following conditions: In 1.1, the reaction vessel is evacuated, and stirred at a speed of 50 to 80 r / min for 20 to 40 min until no liquid flows out of the reaction system to obtain a decontaminated mixed solution; In 1.2 and 1.3, nitrogen gas is introduced into the reaction vessel to maintain a nitrogen atmosphere, and the reaction is stirred at a speed of 60 to 100 r / min; In 1.4 and 1.5, the reaction vessel is evacuated and stirred at a speed of 80 to 120 r / min.

4. A high temperature and high pressure resistant methylphenyl silicone gel, characterized in that: In parts by weight, the raw materials of the methylphenyl silicone gel include: 80-200 parts of methylphenyl vinyl-terminated polysiloxane, 0.1 to 0.15 parts of inhibitor, 4 to 6 parts of cross-linking agent, 0.01 to 0.1 part of cross-linking catalyst; The methylphenyl vinyl-terminated polysiloxane is the methylphenyl vinyl-terminated polysiloxane according to any one of claims 1 to 3; The cross-linking agent comprises methylphenyl side chain hydrogen-containing silicone oil and methylphenyl terminal hydrogen-containing silicone oil compounded in a mass ratio of (1-3): (7-12); The methylphenyl vinyl-terminated polysiloxane is mixed with an inhibitor, a crosslinking agent and a crosslinking catalyst, vacuum degassed, and heated for crosslinking and curing to obtain the high temperature and high pressure resistant methylphenyl silicone gel.

5. The high temperature and high pressure resistant methylphenyl silicone gel according to claim 4, characterized in that: The cross-linking catalyst comprises a platinum silicone oil solution with a platinum content of 500 to 6000 ppm.

6. The high temperature and high pressure resistant methylphenyl silicone gel according to claim 5, characterized in that: The conditions for heating cross-linking and curing are 90-120° C. and curing for 1-5 hours.

7. The high temperature and high pressure resistant methylphenyl silicone gel according to any one of claims 4 to 6, characterized in that: After the high temperature and high pressure resistant methylphenyl silicone gel is cured, the breakdown voltage is above 40 kV / mm, and the initiation voltage of the electric tree test is above 9 kV.

8. A high-voltage and high-power module encapsulation method using the high-temperature and high-pressure resistant methylphenyl silicone gel according to any one of claims 4 to 7, characterized in that: The following steps are involved: S1, preparing methylphenyl vinyl-terminated polysiloxane; S2, stirring and mixing the methylphenyl vinyl-terminated polysiloxane, an inhibitor, and a cross-linking agent to obtain a mixed material; S3, adding a crosslinking catalyst to the mixture, stirring evenly, and vacuuming to obtain a methylphenyl silicone gel precursor; S4, applying the methylphenyl silicone gel precursor to the mold cavity accommodating the high-voltage power module, vacuum degassing and heating for cross-linking and curing to obtain a high-temperature and high-pressure resistant methylphenyl silicone gel high-voltage and high-power module package.

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