Hydrophobic silicone rubber, preparation method thereof and composite insulator

Abstract

The invention provides hydrophobic silicone rubber, a preparation method thereof and a composite insulator. The preparation method comprises the following steps: preparing a silicone rubber compound; performing one-time high-temperature injection molding on the silicone rubber compound to obtain a silicone rubber prefabricated part; adsorbing first hydrophobic white carbon black on the surface of the silicon rubber prefabricated member; and carrying out secondary vulcanization on the silicon rubber prefabricated member adsorbed with the first hydrophobic white carbon black to obtain the hydrophobic silicon rubber. A layer of hydrophobic white carbon black is attached to the surface of the hydrophobic silicone rubber, and secondary vulcanization is performed, so that the hydrophobic silicone rubber provided by the invention has very excellent hydrophobic performance under the dual effects of a hydrophobic material and a nano concave-convex surface; and the problem of silicone rubber surface condensation caused by temperature reduction at night can be effectively solved when the composite insulator is used for external insulation.

Description

Technical Field

[0001] The invention belongs to the technical field of silicone rubber, and in particular relates to a hydrophobic silicone rubber and a preparation method thereof, and a composite insulator. Background Art

[0002] Composite insulators usually include hollow / solid insulating parts, end accessories fixed at both ends of the insulating parts, and high temperature vulcanized silicone rubber (HTV) sheds wrapped around the outer periphery of the insulating parts. For composite insulators that operate in high humidity and hot areas for a long time, the hydrophobicity of their silicone rubber sheds will decrease with the increase of operating time. At this time, when the humidity and temperature of the outside air reach a certain level, water vapor will gradually condense into dew or small water droplets on the surface of the composite insulator, and then form a continuous water belt, which is very likely to cause surface flashover; in addition, when the temperature drops at night, condensation is also prone to occur on the end accessories and silicone rubber shed surfaces of composite insulators, resulting in flashover tripping.

[0003] Faced with the problems of a significant decrease in the hydrophobicity of composite insulators after a period of service, or condensation of water vapor on the surface of the sheds after the temperature drops at night, the industry lacks effective prevention and control measures. Especially for the condensation phenomenon, it is difficult to prevent this phenomenon with general hydrophobic silicone rubber materials. The common remedial measure is to spray room temperature vulcanized silicone rubber (RTV) on the surface of the sheds with reduced hydrophobicity, but the effect lasts for a short time and cannot fundamentally solve the condensation problem. At the same time, the aging life of RTV is very short, and its compatibility with HTV is poor, and the interface is prone to "bubbling" separation. There are also ways to make HTV super hydrophobic by modifying fillers or adding hydrophobic materials, but the overall performance is very poor. From the compatibility difficulties caused by the differences between the base material and the hydrophobic material during the mixing process, to the short aging cycle and unstable hydrophobicity after actual service, it is difficult to meet the requirements of long-term safe and stable service.

[0004] The contents of the background technology section are merely the technologies known to the inventors and do not necessarily represent the prior art in the field. Summary of the invention

[0005] The purpose of the present invention is to improve the hydrophobicity of silicone rubber, thereby increasing the service life of a composite insulator.

[0006] In order to achieve the above objectives, the first aspect of the present application provides a method for preparing a hydrophobic silicone rubber, comprising:

[0007] preparing silicone rubber compound;

[0008] Injection-molding the silicone rubber compound at high temperature once to obtain a silicone rubber preform;

[0009] Adsorbing a first hydrophobic silica on the surface of the silicone rubber preform;

[0010] The silicone rubber preform adsorbed with the first hydrophobic silica is subjected to secondary vulcanization to obtain the hydrophobic silicone rubber.

[0011] In some embodiments of the present application, preparing a silicone rubber compound includes:

[0012] kneading methyl vinyl silicone rubber and fluorosilicone rubber at 110-130° C. for 10-15 minutes to obtain a first intermediate product;

[0013] The first intermediate product is heated to 150-160° C., a second hydrophobic silica and a cross-linked polytetrafluoroethylene are added, and kneaded for 15-20 minutes to obtain a second intermediate product;

[0014] The second intermediate product is heated to 170-185° C., and then modified aluminum hydroxide, silicone oil and an antioxidant are added and kneaded for 20-30 minutes to obtain a third intermediate product;

[0015] After cooling the third intermediate product to 40-60° C., a peroxide crosslinking agent is added, kneading is performed for 20-30 minutes, and then the product is discharged and allowed to stand for 2-4 days to obtain the silicone rubber compound.

[0016] In some embodiments of the present application, adsorbing the first hydrophobic silica on the surface of the silicone rubber preform comprises:

[0017] The silicone rubber preform in a high temperature state is placed in a pressure bed filled with the first hydrophobic silica, and the pressure is maintained at 3-5 MPa for 2-5 minutes, so that the first hydrophobic silica is adsorbed on the surface of the silicone rubber preform.

[0018] In some embodiments of the present application, the temperature of the high temperature injection molding is 150-170° C.; and / or,

[0019] The temperature of the secondary vulcanization is 180-200°C.

[0020] In some embodiments of the present application, in the step of preparing the silicone rubber compound, 30 to 60 parts of the fluorosilicone rubber, 40 to 70 parts of the methyl vinyl silicone rubber, 30 to 50 parts of the second hydrophobic silica, 10 to 30 parts of the cross-linked polytetrafluoroethylene, 100 to 130 parts of the modified aluminum hydroxide, 5 to 20 parts of the silicone oil, 2 to 4 parts of the antioxidant, and 1 to 2 parts of the peroxide cross-linking agent are used.

[0021] In some embodiments of the present application, the modified aluminum hydroxide is aluminum hydroxide modified by a long alkane silane coupling agent;

[0022] The long alkane silane coupling agent has a straight chain structure and contains 8 to 20 carbon atoms.

[0023] In some embodiments of the present application, the peroxide crosslinking agent includes one or more of dicumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane and benzoyl peroxide.

[0024] A second aspect of the present application provides a hydrophobic silicone rubber, which is prepared by any of the above-mentioned preparation methods.

[0025] In some embodiments of the present application, the coverage rate of the first hydrophobic silica on the surface of the hydrophobic silicone rubber is 80-100%.

[0026] In some embodiments of the present application, the hydrophobic angle of the hydrophobic silicone rubber is 145-165°, the hydrophobic angle of the hydrophobic silicone rubber after 2000h of UV aging is 140-160°, and the hydrophobic angle of the hydrophobic silicone rubber after 3000h of wet heat aging is 140-160°.

[0027] A third aspect of the present application provides a composite insulator, wherein the external insulation of the composite insulator adopts any of the above-mentioned hydrophobic silicone rubbers.

[0028] The present application attaches a layer of hydrophobic silica to the surface of the hydrophobic silicone rubber and performs secondary vulcanization. Under the dual effects of the hydrophobic material and the nano-concave and convex surface, the hydrophobic silicone rubber provided by the present application has very excellent hydrophobic properties. Using it for the external insulation of composite insulators can effectively solve the problem of condensation on the silicone rubber surface caused by the drop in temperature at night.

[0029] After the hydrophobic silicone rubber provided in the present application is treated under ultraviolet and humid heat conditions for a period of time, its hydrophobic angle does not decrease significantly, and its hydrophobic performance is still very good. Moreover, its mechanical properties are also very excellent, far exceeding the industry level.

[0030] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings constituting a part of the present disclosure are used to provide a further understanding of the present disclosure. The illustrative embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute improper limitations on the present disclosure.

[0032] Figure 1 This is a process flow chart for preparing hydrophobic silicone rubber provided in one embodiment of the present application.

[0033] Figure 2 It is a process flow chart for preparing silicone rubber compound provided in one embodiment of the present application. DETAILED DESCRIPTION

[0034] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0035] The disclosure below provides many different embodiments or examples for implementing the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplicity and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific examples of processes and materials, but those of ordinary skill in the art can appreciate the application of other processes and / or the use of other materials.

[0036] In addition, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those of ordinary skill in the art to which the present invention belongs. It will also be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology and the present invention, and will not be interpreted in an idealized or overly formal sense unless explicitly defined in this article.

[0037] As used herein, "about" or "approximately" includes the stated value and means within an acceptable range of deviation from the particular value as determined by one skilled in the art, taking into account the measurement in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system). For example, "about" can mean within one or more standard deviations, or within ±30%, ±20%, ±10%, or ±5% of the stated value.

[0038] The following is a more detailed description of the specific embodiments of the present invention in conjunction with the accompanying drawings and examples, so that the scheme of the present invention and its advantages in various aspects can be better understood. However, the specific embodiments and examples described below are only for the purpose of illustration, rather than for limiting the present invention.

[0039] Figure 1 A method for preparing a hydrophobic silicone rubber provided in an embodiment of the present application is shown, comprising the following steps S10 to S40.

[0040] S10: preparing a silicone rubber compound.

[0041] Alternatively, if Figure 2As shown, the preparation of silicone rubber compound in the present application may include the following steps S11 to S14.

[0042] S11: kneading methyl vinyl silicone rubber and fluorosilicone rubber at 110-130° C. for 10-15 min to obtain a first intermediate product.

[0043] Among them, methyl vinyl silicone rubber and fluorosilicone rubber are base materials. Fluorosilicone rubber and methyl vinyl silicone rubber have good compatibility, and both show weak polarity. Optionally, the fluorosilicone rubber used is 30 to 60 parts, and the methyl vinyl silicone rubber is 40 to 70 parts. In some specific embodiments, the fluorosilicone rubber may be 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts or 60 parts. In some specific embodiments, the methyl vinyl silicone rubber may be 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts or 70 parts.

[0044] In some specific embodiments, the kneading temperature may be 110° C., 115° C., 120° C., 125° C., or 130° C. In some specific embodiments, the kneading time may be 10 min, 11 min, 12 min, 13 min, 14 min, or 15 min.

[0045] S12: The first intermediate product is heated to 150-160° C., a second hydrophobic silica and cross-linked polytetrafluoroethylene are added, and kneaded for 15-20 minutes to obtain a second intermediate product.

[0046] Hydrophobic silica and cross-linked polytetrafluoroethylene as hydrophobic functional fillers exhibit super hydrophobic properties and have excellent compatibility with the base rubber material.

[0047] Optionally, the hydrophobic silica is selected from any one of the commercially available Huifu hydrophobic silica, Cabot hydrophobic silica, and Hongbo hydrophobic silica, such as Huifu HB-630, Cabot TS-720, and Hongbo HP-380. The cross-linked polytetrafluoroethylene can be in powder form, which has very good hydrophobic properties.

[0048] Optionally, the hydrophobic white carbon black used is 30 to 50 parts, and the cross-linked polytetrafluoroethylene is 10 to 30 parts. In some specific embodiments, the hydrophobic white carbon black may be 30 parts, 35 parts, 40 parts, 45 parts or 50 parts. In some specific embodiments, the cross-linked polytetrafluoroethylene may be 10 parts, 15 parts, 20 parts, 25 parts or 30 parts.

[0049] In some specific embodiments, the first intermediate product may be heated to 150° C., 152° C., 154° C., 156° C., 158° C., or 160° C. In some specific embodiments, the kneading time may be 15 min, 16 min, 17 min, 18 min, 19 min, or 20 min.

[0050] S13: The second intermediate product is heated to 170-185° C., and then modified aluminum hydroxide, silicone oil and antioxidant are added and kneaded for 20-30 minutes to obtain a third intermediate product.

[0051] Modified aluminum hydroxide is used as a flame retardant, and silicone oil is used as a structuring control agent and plasticizer.

[0052] Optionally, the modified aluminum hydroxide is aluminum hydroxide modified by a long alkane silane coupling agent. Optionally, the long alkane silane coupling agent is a straight chain structure with a carbon atom content of 8 to 20. The aluminum hydroxide modified by the long alkane silane coupling agent further reduces the hydrophilicity of the aluminum hydroxide itself, and the alkane chain increases the interaction with the main chain of the silicone rubber, thereby improving the compatibility with the matrix and the filler.

[0053] Optionally, the modified aluminum hydroxide used is 100-130 parts, the silicone oil is 5-20 parts, and the antioxidant is 2-4 parts. In some specific embodiments, the modified aluminum hydroxide may be 100 parts, 105 parts, 110 parts, 115 parts, 120 parts, 125 parts or 130 parts. In some specific embodiments, the silicone oil may be 5 parts, 10 parts, 15 parts or 20 parts. In some specific embodiments, the antioxidant may be 2 parts, 3 parts or 4 parts.

[0054] In some specific embodiments, the second intermediate product may be heated to 170° C., 172° C., 174° C., 176° C., 178° C., 180° C., 182° C., 184° C., or 185° C. In some specific embodiments, the kneading time may be 20 min, 22 min, 24 min, 26 min, 28 min, or 30 min.

[0055] S14: After cooling the third intermediate product to 40-60° C., a peroxide crosslinking agent is added, and the mixture is kneaded for 20-30 minutes, and then the mixture is discharged and allowed to stand for 2-4 days to obtain a silicone rubber compound.

[0056] Optionally, the peroxide crosslinking agent includes one or more of dicumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane and benzoyl peroxide.

[0057] Optionally, the peroxide crosslinking agent used is 1 to 2 parts. In some specific embodiments, the peroxide crosslinking agent may be 1 part, 1.5 parts, or 2 parts.

[0058] In some specific embodiments, the temperature of the third intermediate product may be raised to 40° C., 45° C., 50° C., 55° C. or 60° C. In some specific embodiments, the kneading time may be 20 min, 22 min, 24 min, 26 min, 28 min or 30 min.

[0059] The silicone rubber compound prepared by the above method provided in the present application has excellent hydrophobic properties.

[0060] S20: subjecting the silicone rubber compound to high-temperature injection molding at one time to obtain a silicone rubber preform.

[0061] Optionally, the temperature of high temperature injection molding is 150-170° C. In some specific embodiments, the temperature of high temperature injection molding may be 150° C., 155° C., 160° C., 165° C. or 170° C.

[0062] S30: adsorbing the first hydrophobic silica on the surface of the silicone rubber preform.

[0063] Optionally, the silicone rubber preform in a high temperature state is placed in a pressure bed filled with the first hydrophobic silica, and the pressure is maintained at 3-5 MPa for 2-5 minutes, so that the first hydrophobic silica is adsorbed on the surface of the silicone rubber preform.

[0064] In the pressure bed, through electrostatic interaction and extrusion force, a layer of hydrophobic silica is adsorbed on the surface of the silicone rubber preform, which improves the hydrophobic properties of the material.

[0065] In the present application, the first hydrophobic silica and the second hydrophobic silica are the same material, and the properties are as described above, which will not be repeated here.

[0066] In some specific embodiments, the pressure in the pressure bed may be 3 MPa, 4 MPa, or 5 MPa. In some specific embodiments, the pressure holding time may be 2 min, 3 min, 4 min, or 5 min.

[0067] S40: performing secondary vulcanization on the silicone rubber preform adsorbed with the first hydrophobic silica to obtain the hydrophobic silicone rubber.

[0068] After secondary vulcanization, the molecular chain movement and the cross-linking network are more perfect, and the hydrophobic silica constructs a nano-scale concave-convex surface on the surface of the silicone rubber preform. Under the dual effects of the hydrophobic material and the nano-concave-convex surface, the hydrophobic properties of the hydrophobic silicone rubber are further increased.

[0069] Optionally, the temperature of the secondary vulcanization is 180-200° C., and the time is 20-40 min. In some specific embodiments, the temperature of the secondary vulcanization may be 180° C., 185° C., 190° C., 195° C., or 200° C. In some specific embodiments, the time of the secondary vulcanization may be 20 min, 25 min, 30 min, 35 min, or 40 min.

[0070] The present application further provides a hydrophobic silicone rubber prepared by the above method. The hydrophobic silicone rubber provided by the present application has a layer of hydrophobic white carbon black on its surface. Under the dual effects of the hydrophobic material and the nano-concave-convex surface, the hydrophobic silicone rubber provided by the present application has very excellent hydrophobic properties.

[0071] Optionally, the coverage of the hydrophobic silica on the surface of the hydrophobic silicone rubber provided in the present application is 80-100%. In some specific embodiments, the coverage may be 80%, 85%, 90%, 95% or 100%.

[0072] Optionally, the hydrophobic angle of the hydrophobic silicone rubber is 145-165°. Optionally, the hydrophobic angle of the hydrophobic silicone rubber after 2000h of UV aging is 140-160°. Optionally, the hydrophobic angle of the hydrophobic silicone rubber after 3000h of wet heat aging is 140-160°. In some specific embodiments, the hydrophobic angle of the hydrophobic silicone rubber is 145°, 150°, 155°, 160° or 165°. In some specific embodiments, the hydrophobic angle of the hydrophobic silicone rubber after 2000h of UV aging may be 140°, 145°, 150°, 155° or 160°. In some specific embodiments, the hydrophobic angle of the hydrophobic silicone rubber after 3000h of wet heat aging may be 140°, 145°, 150°, 155° or 160°. It can be seen that the hydrophobic performance of the hydrophobic silicone rubber provided in the present application can still reach the HC1 level under ultraviolet and wet heat conditions.

[0073] The hydrophobic silicone rubber provided in the present application also has very good mechanical properties. Optionally, its tensile strength is 4.2-5.3 MPa, and its elongation at break is 275-360%, which is far higher than the industry level.

[0074] The present application further provides a composite insulator, the outer insulation of which adopts the above-mentioned hydrophobic silicone rubber. The outer insulation of the composite insulator provided by the present application has excellent mechanical properties and hydrophobic properties, which can effectively solve the problem of condensation on the surface of silicone rubber caused by the lower temperature at night in the prior art; and the hydrophobic property of the silicone rubber will not decrease significantly after serving for a period of time, and the hydrophobic property is still very good, far exceeding the industry level.

[0075] The present invention will be described below with reference to specific embodiments. The process condition values ​​taken in the following embodiments and comparative examples are exemplary, and their possible numerical ranges are as shown in the aforementioned summary of the invention. For process parameters not particularly noted, conventional techniques can be used. Unless otherwise specified, reagents and instruments used in the technical scheme provided by the present invention can be purchased from conventional channels or the market. It should be noted that, in the absence of conflict, the features in the embodiments in this application and the embodiments can be combined with each other.

[0076] Example 1

[0077] The methyl vinyl silicone rubber and fluorosilicone rubber were kneaded at 118°C for 13 minutes to obtain the first intermediate product. The first intermediate product was heated to 155°C, and the second hydrophobic white carbon black and cross-linked polytetrafluoroethylene were added and kneaded for 16 minutes to obtain the second intermediate product. The second intermediate product was heated to 172°C, and then aluminum hydroxide, silicone oil and antioxidant modified by long alkane silane coupling agent were added and kneaded for 24 minutes to obtain the third intermediate product. After the third intermediate product was cooled to 53°C, a peroxide cross-linking agent was added, kneaded for 28 minutes, and then the rubber was discharged and left to stand for 3 days to obtain a silicone rubber compound.

[0078] The silicone rubber compound is subjected to high-temperature injection molding once to obtain a silicone rubber preform. The temperature of high-temperature injection molding is 162°C. The silicone rubber preform in a high-temperature state is placed in a pressure bed filled with the first hydrophobic silica, and the pressure is maintained at 4MPa for 3 minutes, so that the first hydrophobic silica is adsorbed on the surface of the silicone rubber preform. The silicone rubber preform adsorbed with the first hydrophobic silica is subjected to secondary vulcanization to obtain hydrophobic silicone rubber. The temperature of the secondary vulcanization is 193°C and the time is 31 minutes. Among them, the coverage rate of the first hydrophobic silica on the surface of the hydrophobic silicone rubber is about 95%.

[0079] The specific information and dosage of each raw material are shown in Table 1 and Table 2. The properties of the prepared hydrophobic silicone rubber are shown in Table 3.

[0080] Example 2

[0081] The difference between this embodiment and embodiment 1 is that the amount of raw materials used is different, see Table 2 for details. The properties of the prepared hydrophobic silicone rubber are shown in Table 3.

[0082] Example 3

[0083] The difference between this embodiment and embodiment 1 is that the amount of raw materials used is different, see Table 2 for details. The properties of the prepared hydrophobic silicone rubber are shown in Table 3.

[0084] Example 4

[0085] The difference between this embodiment and embodiment 1 is that the amount of raw materials used is different, see Table 2 for details. The properties of the prepared hydrophobic silicone rubber are shown in Table 3.

[0086] Example 5

[0087] The difference between this embodiment and embodiment 1 is that the amount of raw materials used is different, see Table 2 for details. The properties of the prepared hydrophobic silicone rubber are shown in Table 3.

[0088] Example 6

[0089] The difference between this embodiment and embodiment 1 is that the amount of raw materials used is different, see Table 2 for details. The properties of the prepared hydrophobic silicone rubber are shown in Table 3.

[0090] Comparative Example 1

[0091] The difference between this comparative example and Example 1 is that after the silicone rubber compound is once injected at high temperature, no subsequent steps are performed, that is, there are no steps S30 and S40. The properties of the obtained hydrophobic silicone rubber are shown in Table 3.

[0092] Table 1

[0093]

[0094] Table 2

[0095]

[0096]

[0097] Table 3

[0098]

[0099]

[0100] As can be seen from Table 3, the hydrophobic angle of the hydrophobic silicone rubber provided by the present application exceeds 150°, and the hydrophobic performance is very good. Moreover, after being treated under ultraviolet conditions for 2000 hours and under wet heat conditions for 3000 hours, the hydrophobic angle of the hydrophobic silicone rubber has not decreased significantly, and the hydrophobic performance is still very good. Moreover, its mechanical properties are also very excellent, far exceeding the industry level.

[0101] The hydrophobic performance of the hydrophobic silicone rubber provided in Comparative Example 1 is one level lower, with a hydrophobic angle of only 121°, and its ability to resist ultraviolet rays and damp heat is also relatively poor. Its mechanical properties are also relatively weak.

[0102] Obviously, the above embodiments are merely examples for clearly explaining the present invention, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for preparing a hydrophobic silicone rubber, characterized in that: include: preparing silicone rubber compound; Injection-molding the silicone rubber compound at high temperature once to obtain a silicone rubber preform; Adsorbing a first hydrophobic silica on the surface of the silicone rubber preform; The silicone rubber preform adsorbed with the first hydrophobic silica is subjected to secondary vulcanization to obtain the hydrophobic silicone rubber.

2. The preparation method according to claim 1, characterized in that: The preparation of the silicone rubber compound comprises: kneading methyl vinyl silicone rubber and fluorosilicone rubber at 110-130° C. for 10-15 minutes to obtain a first intermediate product; The first intermediate product is heated to 150-160° C., a second hydrophobic silica and a cross-linked polytetrafluoroethylene are added, and kneaded for 15-20 minutes to obtain a second intermediate product; The second intermediate product is heated to 170-185° C., and then modified aluminum hydroxide, silicone oil and an antioxidant are added and kneaded for 20-30 minutes to obtain a third intermediate product; After cooling the third intermediate product to 40-60° C., a peroxide crosslinking agent is added, kneading is performed for 20-30 minutes, and then the product is discharged and allowed to stand for 2-4 days to obtain the silicone rubber compound.

3. The preparation method according to claim 1, characterized in that: The step of adsorbing the first hydrophobic silica on the surface of the silicone rubber preform comprises: The silicone rubber preform in a high temperature state is placed in a pressure bed filled with the first hydrophobic silica, and the pressure is maintained at 3-5 MPa for 2-5 minutes, so that the first hydrophobic silica is adsorbed on the surface of the silicone rubber preform.

4. The preparation method according to claim 1, characterized in that: The temperature of the high temperature injection molding is 150-170° C.; and / or, The temperature of the secondary vulcanization is 180-200°C.

5. The preparation method according to claim 2, characterized in that: In the step of preparing the silicone rubber compound, 30 to 60 parts of the fluorosilicone rubber, 40 to 70 parts of the methyl vinyl silicone rubber, 30 to 50 parts of the second hydrophobic silica, 10 to 30 parts of the cross-linked polytetrafluoroethylene, 100 to 130 parts of the modified aluminum hydroxide, 5 to 20 parts of the silicone oil, 2 to 4 parts of the antioxidant, and 1 to 2 parts of the peroxide cross-linking agent are used.

6. The preparation method according to claim 2, characterized in that: The modified aluminum hydroxide is aluminum hydroxide modified by a long alkane silane coupling agent; The long alkane silane coupling agent has a straight chain structure and contains 8 to 20 carbon atoms.

7. The preparation method according to claim 2, characterized in that: The peroxide crosslinking agent includes one or more of dicumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane and benzoyl peroxide.

8. A hydrophobic silicone rubber, characterized in that: The method is prepared by any one of claims 1 to 7.

9. The hydrophobic silicone rubber according to claim 8, characterized in that: The coverage rate of the first hydrophobic silica on the surface of the hydrophobic silicone rubber is 80-100%.

10. The hydrophobic silicone rubber according to claim 8, characterized in that: The hydrophobic angle of the hydrophobic silicone rubber is 145-165°, the hydrophobic angle of the hydrophobic silicone rubber after 2000h of UV aging is 140-160°, and the hydrophobic angle of the hydrophobic silicone rubber after 3000h of wet heat aging is 140-160°.

11. A composite insulator, characterized in that: The external insulation of the composite insulator adopts the hydrophobic silicone rubber described in any one of claims 8 to 10.

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