A Class C Solvent-Free Organosilicon Impregnating Varnish and Its Preparation Method

Abstract

This application relates to the technical field of chemical materials, and specifically discloses a Class C solvent-free silicone impregnating varnish and a preparation method thereof. In this application, vinyl methyl phenyl silicone resin and hydrogen-containing methyl phenyl silicone resin are preferably used as the main components of the silicone impregnating varnish, and a polyorganosiloxane with a highly cross-linked network structure is formed by hydrosilylation reaction. At the same time, by adjusting the molar ratio between each structural unit, while keeping the viscosity of the resin within a suitable range, the mechanical strength, heat resistance and insulation performance of the silicone impregnating varnish have been greatly improved, thus overcoming the defects in the related technology and improving the actual application effect of the silicone impregnating varnish product.

Description

Technical Field

[0001] The present application relates to the technical field of chemical materials, and more specifically, to a Class C solvent-free silicone impregnating varnish and a preparation method thereof. Background Art

[0002] Electrical insulation impregnating resins are one of the main insulation materials used in electrical products and are indispensable insulation materials in equipment such as AC and DC motors, impregnated dry-type transformers, and power transformers. In the 1950s and 1960s, solvent-based paints were commonly used for electrical insulation impregnating resins. They generally contained about 50% organic solvents and required multiple impregnations during use, resulting in many problems such as long impregnation process time, serious environmental pollution, and poor production safety. In the 1970s, as an alternative to traditional solvent-based paints, solvent-free paints began to be vigorously promoted. Most solvent-free paints are styrene-based and generally contain 30% - 40% styrene. Their main function is to solve the drying problem inside the winding, which can effectively reduce the number of impregnations and improve production efficiency. However, the disadvantage is that there are still a large number of volatile components during baking and the storage life is short. By the 1980s, foreign countries began to steadily promote the vacuum (pressure) impregnation process on the premise of pursuing the reliability, heat resistance, and environmental resistance of electrical products, and introduced a new generation of low-volatile impregnating resins. The characteristics of this new type of impregnating resin are that it does not release a large amount of volatile components during impregnation and thermal curing, has good stability, fast curing, and the highest internal filling amount can reach 98%. In contrast, the development of domestic electrical insulation impregnating resins is not sufficient. In China, the variety of electrical insulation impregnating varnishes above heat resistance class H is limited. For decades, solvent-based silicone paints have been mainly used, and there are relatively few solvent-free impregnating resin products.

[0003] The main component of silicone impregnating varnish is polyorganosiloxane with a highly cross-linked network structure, which can be divided into condensation type and addition type according to different cross-linking and curing methods. Condensation type silicone impregnating varnish uses silicone resin prepolymers containing Si—OH, Si-OR and other groups as raw materials, and further condenses and cross-links into solid products under the action of a catalyst or heating; addition type silicone impregnating varnish uses polysiloxane containing Si-Vi bonds and siloxane containing Si-H bonds as raw materials, and undergoes a hydrosilylation reaction to cross-link under the action of a catalyst. Compared with condensation type silicone impregnating varnish, addition type silicone impregnating varnish has the advantages of not containing organic solvents, not producing by-products during the curing process, small shrinkage rate, being able to cure deeply, short production cycle and high efficiency.

[0004] A Chinese patent document with the publication number CN108329474A discloses a silicone resin for one - component addition - type silicone impregnating varnish, its preparation method and application. The silicone resin for one - component addition - type silicone impregnating varnish is prepared from a mixture of alkoxysilanes through hydrolysis - condensation reaction, capping reaction and post - treatment in sequence. Through the above process, the invention prepares a silicone resin for one - component addition - type silicone impregnating varnish with a narrow molecular weight distribution and an extremely low residual hydrogen chloride content. The one - component addition - type silicone impregnating varnish prepared from it has an extremely low volatile content at 200 °C / 1 h.

[0005] For another example, a Chinese patent document with the publication number CN107641466A discloses a solvent - free silicone impregnating varnish and its preparation method. By introducing a silicone monomer B with the structural formula SiR n X 4-n in the molecular chain of the silicone prepolymer, vinyl or silicon - hydrogen groups are reserved, and the solvent - free silicone impregnating varnish can be obtained through a hydrosilylation reaction during the later curing process. The impregnating varnish prepared by this invention has no low - molecular substances escaping during film - forming curing, does not affect electrical properties, is pollution - free, and at the same time has good electrical and mechanical properties.

[0006] Regarding the above - mentioned related technologies, the inventor believes that the silicone impregnating varnishes in the related technologies have the defect of low heat - resistance grade, and it is difficult to have both ideal insulation performance and mechanical strength at the same time, resulting in an unsatisfactory actual application effect of the product. Summary of the Invention

[0007] The silicone impregnating varnishes in the related technologies have a low heat - resistance grade, and it is difficult to have both ideal insulation performance and mechanical strength at the same time, with an unsatisfactory actual application effect. To improve this defect, the present application provides a Class - C solvent - free silicone impregnating varnish and its preparation method.

[0008] In the first aspect, the present application provides a Class - C solvent - free silicone impregnating varnish, adopting the following technical solution: A Class - C solvent - free silicone impregnating varnish is made from raw materials containing the following parts by weight: 1 part of vinylmethylphenyl silicone resin, 1 - 1.2 parts of hydrogen - containing methylphenyl silicone resin, 0.01 - 0.05 part of catalyst, and 0.01 - 0.05 part of inhibitor; the structural general formula of the vinylmethylphenyl silicone resin is (MeSi0 1.5 ) m (Me2Si0) n (PhSi0 1.5 ) x (Ph2Si0) y (Me2ViSiO 0.5 ) z, m:n:x:y:z = (0.3 - 0.45):(0.1 - 0.2):(0.2 - 0.35):(0.1 - 0.2):(0.15 - 0.25); The structural general formula of the hydrogen-containing methylphenyl silicone resin is (MeSi0 1.5 ) M (Me2Si0) N (PhSi0 1.5 ) X (Ph2Si0) Y (Me2HSiO 0.5 ) Z , M:N:X:Y:Z = (0.25 - 0.35):(0.1 - 0.2):(0.3 - 0.4):(0.1 - 0.2):(0.25 - 0.35).

[0009] By adopting the above technical solutions, the present application preferably uses vinyl methylphenyl silicone resin and hydrogen-containing methylphenyl silicone resin as the main components of the silicone impregnating varnish. The vinyl group in the vinyl methylphenyl silicone resin and the Si-H group in the hydrogen-containing methylphenyl silicone resin can undergo a cross-linking reaction under the common control of a catalyst and an inhibitor to form a polyorganosiloxane with a highly cross-linked network structure. At the same time, the present application also limits the chain segment composition of the vinyl methylphenyl silicone resin and the hydrogen-containing methylphenyl silicone resin. By adjusting the molar ratio between the MeSi0 1.5 structural unit, Me2Si0 structural unit, PhSi0 1.5 structural unit, and Ph2Si0 structural unit, while keeping the viscosity of the resin within a suitable range, the mechanical strength, heat resistance, and insulation performance of the silicone impregnating varnish are all greatly improved, thus overcoming the defects in the related technologies and improving the actual application effect of the silicone impregnating varnish product.

[0010] Preferably, the Me2HSiO 0.5 structural unit is provided by a dimethylhydrogensiloxane monomer, and the dimethylhydrogensiloxane monomer is one of dimethylethoxysilane and tetramethyldisiloxane; the Me2ViSiO 0.5 structural unit is provided by a dimethylethenylsiloxane monomer, and the dimethylethenylsiloxane monomer is one of dimethylethenylmethoxysilane, dimethylethenylethoxysilane, and tetramethyldivinyldisiloxane.

[0011] By adopting the above technical solutions, the present application preferably selects the types of siloxane monomers that provide the Me2HSiO 0.5 structural unit and the Me2ViSiO 0.5 structural unit. Through the MeSi0 1.5 structural unit, Me2Si0 structural unit, PhSi01.5 The combined cooperation of the structural unit and the Ph2Si0 structural unit enables the silicone impregnating varnish product prepared by using the above-mentioned type of monomers to have good mechanical strength, heat resistance and insulation performance.

[0012] Preferably, the catalyst is a platinum catalyst, and the platinum catalyst is one of chloroplatinic acid-isopropanol solution or platinum-divinyltetramethyldisiloxane complex.

[0013] By adopting the above technical solution, the present application preferably selects the specific type of catalyst, and the above two platinum catalysts can both catalyze the hydrosilylation reaction.

[0014] Preferably, the inhibitor is an organic compound containing an alkynyl group, and the organic compound containing an alkynyl group is one of 1-ethynylcyclohexanol, 3,5-dimethyl-3-hexyn-1-ol, and 3-methyl-1-butyn-3-ol.

[0015] By adopting the above technical solution, the present application preferably selects the specific type of inhibitor. Selecting the above type of inhibitor can jointly control the hydrosilylation reaction with the catalyst, thereby enabling the silicone impregnating varnish product to have good mechanical strength, heat resistance and insulation performance.

[0016] In a second aspect, the present application provides a preparation method of a Class C solventless silicone impregnating varnish, adopting the following technical solution.

[0017] A preparation method of a Class C solventless silicone impregnating varnish includes the following steps:

[0018] (1) Mix a siloxane monomer, a solvent and an inorganic acid, heat and react, then cool the product to room temperature, extract to obtain an organic phase, add an inorganic base to the organic phase under heating conditions, react for a period of time and then cool, and then add a neutralizing agent and a solvent. After washing with water and removing low-boiling components, vinylmethylphenyl silicone resin is obtained;

[0019] (2) Mix a siloxane monomer, a solvent and an inorganic acid, heat and react, then cool the product to room temperature, extract to obtain an organic phase, add an inorganic acid to the organic phase under heating conditions, react for a period of time and then add a solvent. After washing with water and removing low-boiling components, hydrogen-containing methylphenyl silicone resin is obtained;

[0020] (3) Mix the vinylmethylphenyl silicone resin obtained in step (1), the hydrogen-containing methylphenyl silicone resin obtained in step (2), a catalyst and an inhibitor according to a ratio, and obtain a Class C solventless silicone impregnating varnish after stirring and reacting.

[0021] By adopting the above technical solution, the present application processes vinyl methyl phenyl silicone resin and hydrogen-containing methyl phenyl silicone resin by a secondary reaction method to obtain two silicone resins containing vinyl and Si-H groups, and then subjecting these two silicone resins to a hydrosilylation reaction to obtain a Class C solventless silicone impregnating varnish. Specifically, in the preparation step of vinyl methyl phenyl silicone resin in the method of the present application, hydrolysis and condensation reaction is first carried out with an inorganic acid, and then hydrolysis and condensation reaction is continued with an inorganic base; in the preparation method of hydrogen-containing methyl phenyl silicone resin, hydrolysis and condensation reaction is first carried out with an inorganic acid, and then hydrolysis and condensation reaction is continued with an inorganic acid; this can greatly reduce the content of unreacted hydroxyl groups in the resin structure, thereby further improving the mechanical strength, heat resistance and insulation performance of the resin.

[0022] Preferably, in steps (1) and (2) of the method, the inorganic acid mixed with the siloxane monomer and the solvent is a hydrochloric acid solution.

[0023] By adopting the above technical solution, the present application preferably selects the specific type of inorganic acid and realizes the preparation of vinyl methyl phenyl silicone resin and hydrogen-containing methyl phenyl silicone resin.

[0024] Preferably, in step (2) of the method, the inorganic acid added to the organic phase is concentrated sulfuric acid.

[0025] By adopting the above technical solution, the present application preferably selects the specific type of inorganic acid and realizes the preparation of hydrogen-containing methyl phenyl silicone resin.

[0026] Preferably, in steps (1) and (2) of the method, the extractant is selected from one of toluene, xylene and petroleum ether, and the solvent used is selected from one of methanol, ethanol, ethyl acetate and butyl acetate.

[0027] By adopting the above technical solution, the present application preferably selects the specific types of the extractant and the solvent and realizes the preparation of vinyl methyl phenyl silicone resin and hydrogen-containing methyl phenyl silicone resin.

[0028] Preferably, in step (1) of the method, the inorganic base used is one of sodium hydroxide and potassium hydroxide.

[0029] By adopting the above technical solution, the present application preferably selects the specific type of inorganic base and realizes the preparation of vinyl methyl phenyl silicone resin.

[0030] Preferably, in step (1) of the method, the neutralizing agent used is concentrated hydrochloric acid or concentrated sulfuric acid.

[0031] By adopting the above technical solution, the present application preferably selects the specific type of the neutralizing agent and realizes the preparation of vinyl methyl phenyl silicone resin.

[0032] In summary, the present application has the following beneficial effects:

[0033] 1. The present application preferably uses vinyl methyl phenyl silicone resin and hydrogen-containing methyl phenyl silicone resin as the main components of the silicone impregnating varnish. By using the hydrosilylation reaction, a polyorganosiloxane with a highly cross-linked network structure is formed. At the same time, by adjusting the molar ratio between each structural unit, while keeping the viscosity of the resin within a suitable range, the mechanical strength, heat resistance, and insulation performance of the silicone impregnating varnish are all greatly improved, thus overcoming the defects in the related art and improving the actual application effect of the silicone impregnating varnish product.

[0034] 2. The method of the present application processes vinyl methyl phenyl silicone resin and hydrogen-containing methyl phenyl silicone resin by the secondary reaction method to obtain two silicone resins containing vinyl and Si-H groups, and then makes these two silicone resins undergo the hydrosilylation reaction to obtain a Class C solventless silicone impregnating varnish. By controlling the synthesis conditions of vinyl methyl phenyl silicone resin and hydrogen-containing methyl phenyl silicone resin, the content of unreacted hydroxyl groups in the resin structure can be greatly reduced, thereby further improving the mechanical strength, heat resistance, and insulation performance of the resin. Specific Embodiments

[0035] The present application will be further described in detail below with reference to examples, preparation examples, and comparative examples. The raw materials involved in the present application can all be obtained commercially.

[0036] Examples

[0037] In the examples and comparative examples of the present application, the concentrated sulfuric acid used is 98 wt% concentrated sulfuric acid, and the concentrated hydrochloric acid is 38 wt% concentrated hydrochloric acid.

[0038] Examples 1-8

[0039] The following takes Example 1 as an example for illustration.

[0040] Example 1

[0041] This example provides a Class C solventless silicone impregnating varnish, which is prepared according to the following method:

[0042] (1) Synthesis of vinyl methyl phenyl silicone resin: Methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, and dimethylethylvinylsilane were added to a reactor in a molar ratio of 0.35:0.1:0.35:0.1:0.25. Ethanol accounting for 10% of the total monomer mass fraction was added to the reactor. The temperature was raised to 50 °C, and a 15 wt% hydrochloric acid solution accounting for 5% of the total monomer mass fraction was added dropwise. The reaction was carried out for 3 h, then the temperature was further raised to 80 °C and the reaction was carried out for 6 h. After cooling to room temperature, xylene was added. After extraction and liquid separation, the organic phase was added to the reactor. The temperature was raised to 115 °C and acid removal treatment was carried out for 60 min. Sodium hydroxide accounting for 0.2% of the total monomer mass fraction was added and the reaction was carried out for 4 h. After cooling to room temperature, concentrated hydrochloric acid and ethanol were added. After the reaction solution was washed with water until neutral, low boilers were removed under vacuum conditions to obtain vinyl methyl phenyl silicone resin; in this step, the extraction agent used was toluene;

[0043] (2) Synthesis of hydrogen-containing methyl phenyl silicone resin: Methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, and tetramethyldisiloxane were added to a reactor in a molar ratio of 0.3:0.1:0.35:0.1:0.35. Ethanol accounting for 10% of the total monomer mass fraction was added to the reactor. The temperature was raised to 40 °C, and a 15 wt% hydrochloric acid solution accounting for 4% of the total monomer mass fraction was added dropwise. The reaction was carried out for 3 h, then the temperature was further raised to 80 °C and the reaction was carried out for 6 h. After cooling to room temperature, xylene was added. After extraction and liquid separation, the organic phase was added to the reactor. Concentrated sulfuric acid accounting for 5% of the total monomer mass fraction was added and the reaction was carried out for 6 h. Ethanol was added. After the reaction solution was washed with water until neutral, low boilers were removed under vacuum conditions to obtain hydrogen-containing methyl phenyl silicone resin;

[0044] (3) Preparation of Class C solvent-free silicone impregnating varnish: The vinyl methyl phenyl silicone resin obtained in step (1), the hydrogen-containing methyl phenyl silicone resin obtained in step (2), a catalyst, and an inhibitor were added in a mass ratio of 1:1.1:0.03:0.03 for physical blending; in this step, the catalyst was chloroplatinic acid-isopropanol solution, and the inhibitor was 1-ethynylcyclohexanol.

[0045] Example 2

[0046] This example provides a Class C solvent-free silicone impregnating varnish, which is prepared according to the following method:

[0047] (1) Synthesis of vinyl methyl phenyl silicone resin: Methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, and dimethylvinylmethoxysilane were put into a reactor in a molar ratio of 0.35:0.1:0.35:0.1:0.25. Ethanol accounting for 10% of the total monomer mass fraction was added to the reactor. The temperature was raised to 55°C, and a 15wt% hydrochloric acid solution accounting for 5% of the total monomer mass fraction was added dropwise. The reaction was carried out for 3 h. Then the temperature was further raised to 80°C and the reaction was carried out for 5 h. After cooling to room temperature, xylene was added. After extraction and liquid separation, the organic phase was added to the reactor. The temperature was raised to 120°C and acid removal treatment was carried out for 60 min. Sodium hydroxide accounting for 0.2% of the total monomer mass fraction was added and the reaction was carried out for 3 h. After cooling to room temperature, concentrated hydrochloric acid and ethanol were added. After the reaction solution was washed with water until neutral, low-boiling substances were removed under vacuum conditions to obtain vinyl methyl phenyl silicone resin. In this step, the extraction agent used was xylene;

[0048] (2) Synthesis of hydrogen-containing methyl phenyl silicone resin: Methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, and tetramethyldisiloxane were put into a reactor in a molar ratio of 0.3:0.1:0.35:0.1:0.35. Ethanol accounting for 10% of the total monomer mass fraction was added to the reactor. The temperature was raised to 40°C, and a 15wt% hydrochloric acid solution accounting for 4% of the total monomer mass fraction was added dropwise. The reaction was carried out for 3 h. Then the temperature was further raised to 80°C and the reaction was carried out for 6 h. After cooling to room temperature, xylene was added. After extraction and liquid separation, the organic phase was added to the reactor. Concentrated sulfuric acid accounting for 5% of the total monomer mass fraction was added and the reaction was carried out for 6 h. Ethanol was added. After the reaction solution was washed with water until neutral, low-boiling substances were removed under vacuum conditions to obtain hydrogen-containing methyl phenyl silicone resin;

[0049] (3) Preparation of Class C solventless silicone impregnating varnish: The vinyl methyl phenyl silicone resin obtained in step (1), the hydrogen-containing methyl phenyl silicone resin obtained in step (2), a catalyst, and an inhibitor were added in a mass ratio of 1:1.1:0.03:0.03 for physical blending; in this step, the catalyst was chloroplatinic acid-isopropanol solution, and the inhibitor was 1-ethynylcyclohexanol.

[0050] Example 3

[0051] This example provides a Class C solventless silicone impregnating varnish, which is prepared according to the following method:

[0052] (1) Synthesis of vinyl methyl phenyl silicone resin: Methyltrimethoxysilane, dimethyldiethoxysilane, phenyltrimethoxysilane, diphenyldiethoxysilane, and tetramethyldivinyldisiloxane were added to a reactor in a molar ratio of 0.3:0.15:0.35:0.1:0.15. Ethanol accounting for 15% of the total monomer mass fraction was added to the reactor. The temperature was raised to 50 °C, and a 20 wt% hydrochloric acid solution accounting for 5% of the total monomer mass fraction was added dropwise. The reaction was carried out for 4 h, then the temperature was further raised to 80 °C and the reaction was carried out for 4 h. After cooling to room temperature, toluene was added. After extraction and liquid separation, the organic phase was added to the reactor. The temperature was raised to 110 °C for acid removal treatment for 60 min. Sodium hydroxide accounting for 0.3% of the total monomer mass fraction was added and the reaction was carried out for 3 h. After cooling to room temperature, concentrated sulfuric acid and ethanol were added. After the reaction solution was washed with water until neutral, low-boiling substances were removed under vacuum conditions, and vinyl methyl phenyl silicone resin could be obtained. In this step, the extraction agent used was petroleum ether;

[0053] (2) Synthesis of hydrogen-containing methyl phenyl silicone resin: Methyltrimethoxysilane, dimethyldiethoxysilane, phenyltrimethoxysilane, diphenyldiethoxysilane, and tetramethyldisiloxane were added to a reactor in a molar ratio of 0.35:0.1:0.35:0.15:0.35. Ethanol accounting for 15% of the total monomer mass fraction was added to the reactor. The temperature was raised to 45 °C, and a 15 wt% hydrochloric acid solution accounting for 4% of the total monomer mass fraction was added dropwise. The reaction was carried out for 4 h, then the temperature was further raised to 80 °C and the reaction was carried out for 5 h. After cooling to room temperature, toluene was added. After extraction and liquid separation, the organic phase was added to the reactor. Concentrated sulfuric acid accounting for 6% of the total monomer mass fraction was added and the reaction was carried out for 5 h. Ethanol was added. After the reaction solution was washed with water until neutral, low-boiling substances were removed under vacuum conditions, and hydrogen-containing methyl phenyl silicone resin could be obtained;

[0054] (3) Preparation of Class C solventless silicone impregnating varnish: The vinyl methyl phenyl silicone resin obtained in step (1), the hydrogen-containing methyl phenyl silicone resin obtained in step (2), a catalyst, and an inhibitor were added for physical blending in a mass ratio of 1:1.08:0.02:0.02. In this step, the catalyst was chloroplatinic acid-isopropanol solution, and the inhibitor was 3,5-dimethyl-3-hexyn-1-ol.

[0055] Example 4

[0056] This example provides a Class C solventless silicone impregnating varnish, which is prepared according to the following method:

[0057] (1) Synthesis of vinyl methyl phenyl silicone resin: Methyltriethoxysilane, dimethyldimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, and tetramethyldivinyldisiloxane were put into a reactor in a molar ratio of 0.3:0.15:0.35:0.1:0.2. Ethanol accounting for 10% of the total monomer mass fraction was added to the reactor. The temperature was raised to 50 °C, and a 15 wt% hydrochloric acid solution accounting for 5% of the total monomer mass fraction was added dropwise. The reaction was carried out for 4 h, then the temperature was further raised to 85 °C and the reaction was carried out for 4 h. After cooling to room temperature, toluene was added. After extraction and liquid separation, the organic phase was added to the reactor. The temperature was raised to 120 °C for acid removal treatment for 30 min. Sodium hydroxide accounting for 0.3% of the total monomer mass fraction was added and the reaction was carried out for 3 h. After cooling to room temperature, concentrated sulfuric acid and methanol were added. After the reaction solution was washed with water until neutral, low-boiling substances were removed under vacuum conditions to obtain vinyl methyl phenyl silicone resin. In this step, the extraction agent used was toluene;

[0058] (2) Synthesis of hydrogen-containing methyl phenyl silicone resin: Methyltriethoxysilane, dimethyldimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, and tetramethyldisiloxane were put into a reactor in a molar ratio of 0.3:0.1:0.35:0.2:0.35. Ethanol accounting for 15% of the total monomer mass fraction was added to the reactor. The temperature was raised to 45 °C, and a 15 wt% hydrochloric acid solution accounting for 4% of the total monomer mass fraction was added dropwise. The reaction was carried out for 4 h, then the temperature was further raised to 80 °C and the reaction was carried out for 6 h. After cooling to room temperature, toluene was added. After extraction and liquid separation, the organic phase was added to the reactor. Concentrated sulfuric acid accounting for 6% of the total monomer mass fraction was added and the reaction was carried out for 5 h. Ethanol was added. After the reaction solution was washed with water until neutral, low-boiling substances were removed under vacuum conditions to obtain hydrogen-containing methyl phenyl silicone resin;

[0059] (3) Preparation of Class C solventless silicone impregnating paint: The vinyl methyl phenyl silicone resin obtained in step (1), the hydrogen-containing methyl phenyl silicone resin obtained in step (2), a catalyst, and an inhibitor were added in a mass ratio of 1:1.08:0.02:0.02 for physical blending; in this step, the catalyst was chloroplatinic acid-isopropanol solution, and the inhibitor was 3,5-dimethyl-3-hexyn-1-ol.

[0060] Example 5

[0061] This example provides a Class C solventless silicone impregnating paint, which is prepared according to the following method:

[0062] (1) Synthesis of vinyl methyl phenyl silicone resin: Methyltrimethoxysilane, dimethyldimethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, and dimethylethylvinylsilane were charged into a reactor in a molar ratio of 0.45:0.15:0.2:0.1:0.25. Methanol accounting for 10% of the total monomer mass fraction was added to the reactor. The temperature was raised to 50 °C, and a 15 wt% hydrochloric acid solution accounting for 4% of the total monomer mass fraction was added dropwise. The reaction was carried out for 5 h. Then the temperature was further raised to 80 °C and the reaction was carried out for 4 h. After cooling to room temperature, petroleum ether was added. After extraction and liquid separation, the organic phase was added to the reactor. The temperature was raised to 110 °C for acid removal treatment for 60 min. Potassium hydroxide accounting for 0.3% of the total monomer mass fraction was added and the reaction was carried out for 4 h. After cooling to room temperature, concentrated hydrochloric acid and ethyl acetate were added. After the reaction solution was washed with water until neutral, low-boiling substances were removed under vacuum conditions to obtain vinyl methyl phenyl silicone resin; in this step, the extraction agent used was xylene;

[0063] (2) Synthesis of hydrogen-containing methyl phenyl silicone resin: Methyltrimethoxysilane, dimethyldimethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, and dimethylethoxysilane were charged into a reactor in a molar ratio of 0.35:0.1:0.3:0.15:0.25. Methanol accounting for 10% of the total monomer mass fraction was added to the reactor. The temperature was raised to 45 °C, and a 15 wt% hydrochloric acid solution accounting for 4% of the total monomer mass fraction was added dropwise. The reaction was carried out for 3 h. Then the temperature was further raised to 85 °C and the reaction was carried out for 5 h. After cooling to room temperature, petroleum ether was added. After extraction and liquid separation, the organic phase was added to the reactor. Concentrated sulfuric acid accounting for 6% of the total monomer mass fraction was added and the reaction was carried out for 4 h. Methanol was added. After the reaction solution was washed with water until neutral, low-boiling substances were removed under vacuum conditions to obtain hydrogen-containing methyl phenyl silicone resin;

[0064] (3) Preparation of Class C solventless silicone impregnating varnish: The vinyl methyl phenyl silicone resin obtained in step (1), the hydrogen-containing methyl phenyl silicone resin obtained in step (2), a catalyst, and an inhibitor were added for physical blending in a mass ratio of 1:1.2:0.05:0.05; in this step, the catalyst was platinum-divinyltetramethyldisiloxane complex, and the inhibitor was 3,5-dimethyl-3-hexyne-1-ol.

[0065] Example 6

[0066] This example provides a Class C solventless silicone impregnating varnish, which is prepared according to the following method:

[0067] (1) Synthesis of vinyl methyl phenyl silicone resin: Methyltriethoxysilane, dimethyldiethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, and dimethylvinylmethoxysilane were put into a reactor in a molar ratio of 0.45:0.15:0.3:0.1:0.25. Methanol accounting for 15% of the total monomer mass fraction was added to the reactor. The temperature was raised to 55 °C, and a 20 wt% hydrochloric acid solution accounting for 5% of the total monomer mass fraction was added dropwise. The reaction was carried out for 4 h. Then the temperature was further raised to 85 °C and the reaction was carried out for 5 h. After cooling to room temperature, petroleum ether was added. After extraction and liquid separation, the organic phase was added to the reactor. The temperature was raised to 120 °C for acid removal treatment for 30 min. Potassium hydroxide accounting for 0.1% of the total monomer mass fraction was added and the reaction was carried out for 4 h. After cooling to room temperature, concentrated hydrochloric acid and butyl acetate were added. After the reaction solution was washed with water until neutral, low-boiling substances were removed under vacuum conditions to obtain vinyl methyl phenyl silicone resin; in this step, the extraction agent used was petroleum ether;

[0068] (2) Synthesis of hydrogen-containing methyl phenyl silicone resin: Methyltriethoxysilane, dimethyldiethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, and tetramethyldisiloxane were put into a reactor in a molar ratio of 0.35:0.1:0.3:0.15:0.3. Methanol accounting for 15% of the total monomer mass fraction was added to the reactor. The temperature was raised to 40 °C, and a 20 wt% hydrochloric acid solution accounting for 4% of the total monomer mass fraction was added dropwise. The reaction was carried out for 4 h. Then the temperature was further raised to 80 °C and the reaction was carried out for 4 h. After cooling to room temperature, petroleum ether was added. After extraction and liquid separation, the organic phase was added to the reactor. Concentrated sulfuric acid accounting for 4% of the total monomer mass fraction was added and the reaction was carried out for 6 h. Methanol was added. After the reaction solution was washed with water until neutral, low-boiling substances were removed under vacuum conditions to obtain hydrogen-containing methyl phenyl silicone resin;

[0069] (3) Preparation of Class C solvent-free silicone impregnating varnish: The vinyl methyl phenyl silicone resin obtained in step (1), the hydrogen-containing methyl phenyl silicone resin obtained in step (2), a catalyst, and an inhibitor were added in a mass ratio of 1:1.15:0.05:0.05 for physical blending; in this step, the catalyst was platinum-divinyltetramethyldisiloxane complex, and the inhibitor was 3-methyl-1-butyn-3-ol.

[0070] Example 7

[0071] This example provides a Class C solvent-free silicone impregnating varnish, which is prepared according to the following method:

[0072] (1) Synthesis of vinyl methyl phenyl silicone resin: Methyltrimethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, and tetramethyldivinyldisiloxane were put into a reactor in a molar ratio of 0.4:0.2:0.35:0.2:0.25. Butyl acetate accounting for 10% of the total monomer mass fraction was added to the reactor. The temperature was raised to 55°C, and a 15wt% hydrochloric acid solution accounting for 6% of the total monomer mass fraction was added dropwise. The reaction was carried out for 3 h. Then the temperature was further raised to 85°C and the reaction was carried out for 5 h. After cooling to room temperature, toluene was added. After extraction and liquid separation, the organic phase was added to the reactor. The temperature was raised to 115°C for acid removal treatment for 45 min. Potassium hydroxide accounting for 0.2% of the total monomer mass fraction was added and the reaction was carried out for 2 h. After cooling to room temperature, concentrated sulfuric acid and butyl acetate were added. After the reaction solution was washed with water until neutral, low-boiling substances were removed under vacuum conditions to obtain vinyl methyl phenyl silicone resin; in this step, the extraction agent used was toluene;

[0073] (2) Synthesis of hydrogen-containing methyl phenyl silicone resin: Methyltrimethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, and dimethylethoxysilane were put into a reactor in a molar ratio of 0.25:0.15:0.35:0.1:0.35. Butyl acetate accounting for 10% of the total monomer mass fraction was added to the reactor. The temperature was raised to 40°C, and a 15wt% hydrochloric acid solution accounting for 5% of the total monomer mass fraction was added dropwise. The reaction was carried out for 4 h. Then the temperature was further raised to 80°C and the reaction was carried out for 4 h. After cooling to room temperature, toluene was added. After extraction and liquid separation, the organic phase was added to the reactor. Concentrated sulfuric acid accounting for 4% of the total monomer mass fraction was added and the reaction was carried out for 6 h. Butyl acetate was added. After the reaction solution was washed with water until neutral, low-boiling substances were removed under vacuum conditions to obtain hydrogen-containing methyl phenyl silicone resin;

[0074] (3) Preparation of Class C solvent-free silicone impregnating varnish: The vinyl methyl phenyl silicone resin obtained in step (1), the hydrogen-containing methyl phenyl silicone resin obtained in step (2), a catalyst, and an inhibitor were added in a mass ratio of 1:1.05:0.01:0.01 for physical blending; in this step, the catalyst was platinum-divinyltetramethyldisiloxane complex, and the inhibitor was 3-methyl-1-butyn-3-ol.

[0075] Example 8

[0076] This example provides a Class C solvent-free silicone impregnating varnish, which is prepared according to the following method:

[0077] (1) Synthesis of vinyl methyl phenyl silicone resin: Methyltriethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldiethoxysilane, and tetramethyldivinyldisiloxane were put into a reactor according to a molar ratio of 0.4:0.15:0.35:0.15:0.25. Butyl acetate accounting for 15% of the total monomer mass fraction was added to the reactor. The temperature was raised to 50 °C, and a 20 wt% hydrochloric acid solution accounting for 4% of the total monomer mass fraction was added dropwise. The reaction was carried out for 4 h. Then the temperature was further raised to 80 °C and the reaction was carried out for 4 h. After cooling to room temperature, xylene was added. After extraction and liquid separation, the organic phase was added to the reactor. The temperature was raised to 120 °C for acid removal treatment for 30 min. Potassium hydroxide accounting for 0.1% of the total monomer mass fraction was added and the reaction was carried out for 4 h. After cooling to room temperature, concentrated sulfuric acid and butyl acetate were added. After the reaction solution was washed with water until neutral, low-boiling substances were removed under vacuum conditions to obtain vinyl methyl phenyl silicone resin; in this step, the extraction agent used was xylene;

[0078] (2) Synthesis of hydrogen-containing methyl phenyl silicone resin: Methyltriethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldiethoxysilane, and tetramethyldisiloxane were put into a reactor according to a molar ratio of 0.25:0.2:0.4:0.1:0.35. Butyl acetate accounting for 15% of the total monomer mass fraction was added to the reactor. The temperature was raised to 45 °C, and a 20 wt% hydrochloric acid solution accounting for 4% of the total monomer mass fraction was added dropwise. The reaction was carried out for 3 h. Then the temperature was further raised to 85 °C and the reaction was carried out for 5 h. After cooling to room temperature, xylene was added. After extraction and liquid separation, the organic phase was added to the reactor. Concentrated sulfuric acid accounting for 5% of the total monomer mass fraction was added and the reaction was carried out for 5 h. Butyl acetate was added. After the reaction solution was washed with water until neutral, low-boiling substances were removed under vacuum conditions to obtain hydrogen-containing methyl phenyl silicone resin;

[0079] (3) Preparation of Class C solventless silicone impregnating paint: The vinyl methyl phenyl silicone resin obtained in step (1), the hydrogen-containing methyl phenyl silicone resin obtained in step (2), a catalyst, and an inhibitor were added for physical blending according to a mass ratio of 1:1:0.01:0.01; in this step, the catalyst was platinum-divinyltetramethyldisiloxane complex, and the inhibitor was 3-methyl-1-butyn-3-ol.

[0080] Comparative Example

[0081] Comparative Example 1

[0082] The silicone impregnating paint prepared by referring to Example 1 of the Chinese patent with the publication number CN108329474A.

[0083] Comparative Example 2

[0084] The silicone impregnating paint prepared by referring to Example 1 of the Chinese patent with the publication number CN107641466A.

[0085] Comparative Example 3

[0086] This comparative example provides an organosilicon impregnating varnish, which is prepared according to the following method:

[0087] (1) Synthesis of vinyl methyl phenyl silicone resin: Methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, and dimethylethylvinylsilane were put into a reactor in a molar ratio of 0.25:0.1:0.4:0.1:0.25. Ethanol accounting for 10% of the total monomer mass fraction was added to the reactor, and the temperature was raised to 50°C. A 15wt% hydrochloric acid solution accounting for 5% of the total monomer mass fraction was added dropwise, and the reaction was carried out for 3h. Then the temperature was further raised to 80°C and the reaction was carried out for 6h. After cooling to room temperature, xylene was added. After extraction and liquid separation, the organic phase was washed with water until neutral, and then low-boiling substances were removed under vacuum conditions to obtain vinyl methyl phenyl silicone resin;

[0088] (2) Synthesis of hydrogen-containing methyl phenyl silicone resin: Methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, and tetramethyldisiloxane were put into a reactor in a molar ratio of 0.3:0.1:0.35:0.1:0.35. Ethanol accounting for 10% of the total monomer mass fraction was added to the reactor, and the temperature was raised to 40°C. A 15wt% hydrochloric acid solution accounting for 4% of the total monomer mass fraction was added dropwise, and the reaction was carried out for 3h. Then the temperature was further raised to 80°C and the reaction was carried out for 6h. After cooling to room temperature, xylene was added. After extraction and liquid separation, the organic phase was washed with water until neutral, and then low-boiling substances were removed under vacuum conditions to obtain hydrogen-containing methyl phenyl silicone resin;

[0089] (3) Preparation of Class C solventless organosilicon impregnating varnish: The vinyl methyl phenyl silicone resin obtained in step (1), the hydrogen-containing methyl phenyl silicone resin obtained in step (2), a catalyst, and an inhibitor were added in a mass ratio of 1:1.1:0.03:0.03 and physically blended.

[0090] Comparative Example 4

[0091] This comparative example provides an organosilicon impregnating varnish, which is prepared according to the following method:

[0092] (1) Synthesis of vinyl methyl phenyl silicone resin: Methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, and dimethylethynyl ethoxysilane were put into a reactor in a molar ratio of 0.25:0.25:0.4:0.25:0.2. Ethanol accounting for 10% of the total monomer mass fraction was added to the reactor. The temperature was raised to 50°C, and a 15wt% hydrochloric acid solution accounting for 5% of the total monomer mass fraction was added dropwise. The reaction was carried out for 3 h, then the temperature was further raised to 80°C and the reaction was carried out for 6 h. After cooling to room temperature, xylene was added. After extraction and liquid separation, the organic phase was added to the reactor, and the temperature was raised to 115°C for acid removal treatment for 60 min. Sodium hydroxide accounting for 0.2% of the total monomer mass fraction was added, and the reaction was carried out for 4 h. After cooling to room temperature, concentrated hydrochloric acid and ethanol were added. After the reaction solution was washed with water until neutral, low-boiling substances were removed under vacuum conditions, and vinyl methyl phenyl silicone resin could be obtained;

[0093] (2) Synthesis of hydrogen-containing methyl phenyl silicone resin: Methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, and tetramethyldisiloxane were put into a reactor in a molar ratio of 0.4:0.25:0.25:0.25:0.2. Ethanol accounting for 10% of the total monomer mass fraction was added to the reactor. The temperature was raised to 40°C, and a 15wt% hydrochloric acid solution accounting for 4% of the total monomer mass fraction was added dropwise. The reaction was carried out for 3 h, then the temperature was further raised to 80°C and the reaction was carried out for 6 h. After cooling to room temperature, xylene was added. After extraction and liquid separation, the organic phase was added to the reactor, concentrated sulfuric acid accounting for 5% of the total monomer mass fraction was added, and the reaction was carried out for 6 h. Ethanol was added. After the reaction solution was washed with water until neutral, low-boiling substances were removed under vacuum conditions, and hydrogen-containing methyl phenyl silicone resin could be obtained;

[0094] (3) Preparation of Class C solventless silicone impregnating varnish: The vinyl methyl phenyl silicone resin obtained in step (1), the hydrogen-containing methyl phenyl silicone resin obtained in step (2), a catalyst, and an inhibitor were added in a mass ratio of 1:1.1:0.02:0.01 for physical blending.

[0095] Performance testing test method

[0096] According to "GB / T 15022.2-2017 Resin-based reactive composites for electrical insulation - Part 2: Test methods", the silicone impregnating varnishes of each example and comparative example were subjected to performance testing. The testing items included: viscosity, Shore D hardness, curing volatiles, electrical strength, volume resistivity, dielectric loss factor, adhesion, tensile strength, flexural strength, and heat resistance performance. The results are shown in Table 1.

[0097] Table 1

[0098]

[0099] Combined with Examples 1-8 and Comparative Examples 1-4 and Table 1, it can be seen that the silicone impregnating varnishes prepared in each example, while ensuring appropriate viscosity, have significantly better mechanical properties, insulation properties, and heat resistance than the silicone impregnating varnishes prepared in the comparative examples. The main disadvantages of the silicone impregnating varnish in Comparative Example 1 are its low temperature resistance grade and poor mechanical strength, while the main disadvantages of the silicone impregnating varnish in Comparative Example 2 are its low temperature resistance grade and not very excellent insulation performance. In Comparative Example 3, because the secondary reaction method was not used and only one acid-catalyzed reaction was carried out, Si-OH groups still remained in the silicone resin chain. During the curing process of the silicone impregnating varnish, these unreacted Si-OH groups would continue to undergo condensation reactions, and the generated small molecules would seriously affect the curing process, resulting in a significant decline in the mechanical properties, insulation properties, and heat resistance of the silicone impregnating varnish; in Comparative Example 4, because the molar ratio between the structural units was outside the range defined in this application, the side groups in these structural units could not play a synergistic role to the greatest extent, resulting in a decline in the measured mechanical properties, insulation properties, and heat resistance of the silicone impregnating varnish in Comparative Example 4.

[0100] The above embodiments are only explanations of this application and do not limit this application. After reading this specification, those skilled in the art can make modifications to the embodiments of this application that do not make creative contributions as needed, but as long as they are within the scope of the claims of this application, they are protected by the patent law.

Claims

1. A Class C solvent-free silicone impregnating varnish, characterized in that: The organic silicon impregnation varnish is made of the following raw materials in parts by weight: 1 part of vinyl methyl phenyl silicone resin, 1-1.2 parts of hydrogen-containing methyl phenyl silicone resin, 0.01-0.05 parts of catalyst, and 0.01-0.05 parts of inhibitor; the general structural formula of the vinyl methyl phenyl silicone resin is (MeSi0 1.5 ) m (Me2Si0) n (PhSi0 1.5 ) x (Ph2Si0) y (Me2ViSiO 0.5 ) z , m:n:x:y:z=(0.3-0.45):(0.1-0.2):(0.2-0.35):(0.1-0.2):(0.15-0.25); the general structural formula of the hydrogen-containing methylphenyl silicone resin is (MeSi0 1.5 ) M (Me2Si0) N (PhSi0 1.5 ) X (Ph2Si0) Y (Me2HSiO 0.5 ) Z , M:N:X:Y:Z=(0.25-0.35):(0.1-0.2):(0.3-0.4):(0.1-0.2):(0.25-0.35); the Me2HSiO 0.5 The structural unit is provided by a dimethylhydrogensiloxane monomer, wherein the dimethylhydrogensiloxane monomer is one of dimethylethoxysilane and tetramethyldisiloxane; the Me2ViSiO 0.5 The structural unit is provided by a dimethylvinylsiloxane monomer, and the dimethylvinylsiloxane monomer is one of dimethylvinylmethoxysilane, dimethylvinylethoxysilane, and tetramethyldivinyldisiloxane.

2. The C-class solvent-free silicone impregnation varnish according to claim 1, characterized in that: The catalyst is a platinum catalyst, and the platinum catalyst is one of chloroplatinic acid-isopropanol solution or platinum-divinyltetramethyldisiloxane complex.

3. The C-class solvent-free silicone impregnating varnish according to claim 1, characterized in that: The inhibitor is an organic compound containing an alkynyl group, and the organic compound containing an alkynyl group is one of 1-ethynylcyclohexanol, 3,5-dimethyl-3-hexyn-1-ol, and 3-methyl-1-butyn-3-ol.

4. The method for preparing a Class C solvent-free silicone impregnating varnish according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Mixing a siloxane monomer, a solvent and an inorganic acid, heating the mixture to react, cooling the product to room temperature, extracting the organic phase, adding an inorganic base to the organic phase under heating conditions, reacting the mixture for a period of time, cooling the organic phase, adding a neutralizing agent and a solvent, washing the organic phase with water and removing the low boiling point, and obtaining a vinyl methyl phenyl silicone resin; (2) mixing a siloxane monomer, a solvent and an inorganic acid, heating the mixture for reaction, cooling the product to room temperature, extracting the organic phase, adding an inorganic acid to the organic phase under heating conditions, reacting the mixture for a period of time, adding a solvent, washing the mixture with water and removing low boiling points to obtain a hydrogen-containing methyl phenyl silicone resin; (3) The vinyl methyl phenyl silicone resin obtained in step (1), the hydrogenated methyl phenyl silicone resin obtained in step (2), a catalyst and an inhibitor are mixed according to a proportion, and after stirring and reacting, a Class C solvent-free organic silicone impregnation varnish is obtained.

5. The method for preparing a Class C solvent-free silicone impregnating varnish according to claim 4, characterized in that: In step (1) and step (2) of the method, the inorganic acid mixed with the siloxane monomer and the solvent is a hydrochloric acid solution.

6. The method for preparing a Class C solvent-free silicone impregnating varnish according to claim 5, characterized in that: In step (2) of the method, the inorganic acid added to the organic phase is concentrated sulfuric acid.

7. The method for preparing a Class C solvent-free silicone impregnating varnish according to claim 4, characterized in that: In step (1) and step (2) of the method, the extractant is selected from one of toluene, xylene and petroleum ether, and the solvent used is one of methanol, ethanol, ethyl acetate and butyl acetate.

8. The method for preparing a Class C solvent-free silicone impregnating varnish according to claim 4, characterized in that: In step (1) of the method, the inorganic base used is one of sodium hydroxide and potassium hydroxide.

9. The method for preparing a Class C solvent-free silicone impregnating varnish according to claim 4, characterized in that: In step (1) of the method, the neutralizing agent used is concentrated hydrochloric acid or concentrated sulfuric acid.

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