Moisture-resistant silicon dioxide insulating material with low dielectric constant and preparation method thereof, and preparation method of coaxial cable

Abstract

The invention relates to the technical field of cables, in particular to a low-dielectric-constant moisture-resistant silicon dioxide insulating material which comprises the following raw materials in parts by weight: 40-60 parts of silicon dioxide powder, 20-50 parts of a low-dielectric material, 1-5 parts of a binder, 0.3-1 part of a plasticizer and 15-25 parts of deionized water. The preparation method of the coaxial cable comprises the following steps: (1) extruding a moisture-resistant silicon dioxide insulating material with a low dielectric constant on an inner conductor, drying, degreasing and discharging carbon, and forming an insulating layer outside the inner conductor; and (2) coating a hydrophobic coating outside the insulating layer, heating to form a film, forming a hydrophobic coating, and coating the outer conductor to obtain the coaxial cable. The problem that an existing silicon dioxide insulating material easily absorbs moisture is solved, the low dielectric property and the insulating property of the cable are guaranteed, and the unit weight of the cable is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of cables, and in particular to a low dielectric constant, moisture-resistant silicon dioxide insulating material and a preparation method thereof, and a preparation method of a coaxial cable. Background Art

[0002] Mineral insulated cable is a cable with a metal sheath (mainly made of copper, stainless steel and Incone1600 alloy, etc.), which has the advantages of fireproof, waterproof, oil-proof, explosion-proof and radiation-resistant, long life, high operating temperature, large current carrying capacity, mechanical damage resistance, halogen-free and non-toxic, overload resistance, electromagnetic shielding and excellent electromagnetic compatibility, etc. It is widely used in various fields of national economic construction, such as high-rise buildings, large shopping malls, petrochemical industry, airports, etc. Mineral insulated cable has better high and low temperature resistance and radiation resistance than organic insulated cable. Mineral insulated cable plays an increasingly important role in modern construction and industrial fields due to its excellent performance and safety.

[0003] The preparation methods of mineral insulated cables mainly include beading method, continuous filling method and extrusion method. The beading method is to preform the mineral insulation material into a ceramic column, then insert the conductor, and obtain a cable that meets the size requirements through repeated drawing and annealing. The continuous filling method is to continuously fill the mineral insulation powder into the outer conductor of the mineral insulation, and weld it at the same time, and then roll it many times to obtain a suitable cable. The continuous filling method requires an expensive production line and cannot produce small-sized products. The extrusion method is a common molding method for rubber-plastic insulated cables. It has high production efficiency and is suitable for large-scale production. However, the extrusion of mineral mud requires a suitable clay formula, and the extrusion pressure and plasticizing capacity of the extruder are also required to be high. Its advantage is that it can be produced continuously and is suitable for the production of small-sized mineral insulated cables.

[0004] Mineral insulated cables are mainly made of inorganic materials such as magnesium oxide and aluminum oxide. The temperature resistance of these materials can reach 1000℃ and the γ-ray radiation dose resistance can reach 10 8 Gy, but their dielectric constants are relatively high. The dielectric constants of magnesium oxide and aluminum oxide are about 10, which cannot be used as communication cable insulation. The density of magnesium oxide and aluminum oxide is 3.5-3.6 g / cm 3 The prepared cable is much heavier than the organic insulated cable. Compared with magnesium oxide and aluminum oxide, silicon dioxide has a lower dielectric constant and density, with a dielectric constant of about 4 and a density of 2.5g / cm 3 It is more suitable as coaxial cable insulation material.

[0005] Due to the harsh working environment conditions, mineral insulated coaxial cables require that the cables must have good resistance to high and low temperatures, radiation, low dielectric, and moisture, so as to ensure that the cables have good signal transmission performance in harsh environments such as aerospace, nuclear power, chemical industry, and steel. When magnesium oxide is used as the raw material for the insulation layer of mineral insulated cables, magnesium oxide easily absorbs moisture, thereby greatly reducing the insulation performance of the resulting mineral insulated cable; when silicon dioxide is used to replace magnesium oxide, silicon dioxide has better moisture resistance than magnesium oxide, but when used as an insulating material for communication cables, sealed terminals are still required to reduce the degree of moisture absorption.

[0006] Therefore, it is urgent to solve the moisture absorption problem of silicon dioxide as an insulating material in order to improve the application effect of silicon dioxide in coaxial cables. Summary of the invention

[0007] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a low dielectric constant, moisture-resistant silica insulating material and a preparation method thereof, and a preparation method of a coaxial cable, so as to solve the problem of easy moisture absorption when silica is used as a coaxial cable insulating material in the prior art.

[0008] To achieve the above objectives and other related objectives, the present invention is achieved through the following technical solutions.

[0009] The first aspect of the present invention is to provide a low dielectric constant, moisture-resistant silicon dioxide insulating material, which comprises the following raw materials in parts by weight: 40-60 parts of silicon dioxide powder, 20-50 parts of low dielectric material, 1-5 parts of binder, 0.3-1 parts of plasticizer, and 15-25 parts of deionized water.

[0010] The second aspect of the present invention is to provide a method for preparing a low dielectric constant, moisture-resistant silica insulating material as described above, comprising the following steps: mixing silica powder and low dielectric material, then adding a plasticizer, a binder, and deionized water to obtain a mixture, and kneading the obtained mixture under vacuum, aging, and obtaining an insulating material.

[0011] A third aspect of the present invention provides a method for preparing a coaxial cable, comprising the following steps:

[0012] (1) Extruding the above-mentioned low dielectric constant, moisture-resistant silicon dioxide insulating material or the low dielectric constant, moisture-resistant silicon dioxide insulating material prepared by the above-mentioned preparation method onto the inner conductor by an extrusion process, drying, degreasing and removing carbon, and forming an insulating layer outside the inner conductor;

[0013] (2) Then, a hydrophobic coating is applied on the outside of the insulating layer, heated to form a film, and a hydrophobic coating is formed to cover the outer conductor to obtain a coaxial cable.

[0014] A fourth aspect of the present invention provides a coaxial cable, which is produced by the above-mentioned coaxial cable production method.

[0015] As described above, the low dielectric constant, moisture-resistant silicon dioxide insulating material and its preparation method, and the preparation method of the coaxial cable of the present invention have the following beneficial effects:

[0016] (1) The present invention uses porous silica as the insulating material and adds hollow material to further reduce the dielectric constant and density of the material, making it more suitable for high-frequency communication coaxial cables in harsh environments.

[0017] (2) The present invention reduces the hydroxyl content on the surface of the material by hydrophobic treatment of the surface of silica or low dielectric material, thereby reducing the hygroscopicity of the material; and the reduction of the hydroxyl content is beneficial to the plasticization of the mud, reduces the amount of water used, and improves the dimensional stability of the molding; the hydrophobic treatment of silica powder or low dielectric material and the addition of spherical dielectric fillers in the present invention make the mud viscosity lower, which can effectively reduce the extrusion pressure.

[0018] (3) The present invention coats a hydrophobic coating on the outside of the insulating layer of the inner conductor. The hydrophobic coating forms a dense coating on the surface of the insulating layer, which seals the gaps on the surface of the insulation and isolates it from contact with water vapor. The coating is hydrophobic, which prevents the insulation from absorbing water and maintains the dielectric properties of the insulation. At the same time, it avoids the use of complex and expensive sealing terminals, thereby reducing the preparation cost of the coaxial cable.

[0019] (4) The present invention provides a unique method for preparing a coaxial cable, which further improves the moisture resistance of the insulating layer by coating a hydrophobic coating on the insulating surface, thereby improving the transmission performance of the coaxial cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Shown is a schematic flow chart of the method for preparing the insulating material of the present invention.

[0021] Figure 2 Shown is a schematic flow chart of the method for preparing the coaxial cable of the present invention.

[0022] Figure 3 Shown is a schematic structural diagram of the coaxial cable of the present invention.

[0023] Figure 3 Description of reference numerals:

[0024] 1. Conductor; 2. Insulation layer; 3. Hydrophobic coating; 4. Outer conductor. DETAILED DESCRIPTION

[0025] In order to make the purpose of the invention, technical solutions and beneficial technical effects of the present invention clearer, the present invention is further described in detail below in conjunction with embodiments. People familiar with this technology can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0026] The first aspect of the present invention is to provide a low dielectric constant, moisture-resistant silicon dioxide insulating material, which comprises the following raw materials in parts by weight: 40-60 parts of silicon dioxide powder, 20-50 parts of low dielectric material, 1-5 parts of binder, 0.3-1 parts of plasticizer, and 15-25 parts of deionized water.

[0027] In some embodiments of the present invention, the insulating material includes the following raw materials in parts by weight: 40-50 parts of silicon dioxide powder, 20-30 parts of low dielectric material, 1-3 parts of binder, 0.3-0.8 parts of plasticizer, and 15-20 parts of deionized water.

[0028] In some embodiments of the present invention, the insulating material includes the following raw materials in parts by weight: 50-60 parts of silicon dioxide powder, 30-50 parts of low dielectric material, 3-5 parts of binder, 0.8-1 part of plasticizer, and 20-25 parts of deionized water.

[0029] In some embodiments of the present invention, the insulating material includes the following raw materials in parts by weight: 40 parts of silicon dioxide powder, 20 parts of low dielectric material, 1 part of binder, 0.3 parts of plasticizer, and 15 parts of deionized water.

[0030] In some embodiments of the present invention, the insulating material includes the following raw materials in parts by weight: 50 parts of silicon dioxide powder, 30 parts of low dielectric material, 3 parts of binder, 0.8 parts of plasticizer, and 20 parts of deionized water.

[0031] In some embodiments of the present invention, the insulating material includes the following raw materials in parts by weight: 60 parts of silicon dioxide powder, 50 parts of low dielectric material, 5 parts of binder, 1 part of plasticizer, and 25 parts of deionized water.

[0032] In some embodiments of the present invention, the silicon dioxide powder is porous silicon dioxide powder. Preferably, the purity of the silicon dioxide is 99.9%; the particle size of the silicon dioxide is 0.1-100 μm; the pore size is 1-30 nm; the specific surface area is 300-500 m 2 / g; dielectric constant 1.5~2.5.

[0033] In some embodiments of the present invention, the low dielectric material is selected from one or more of hollow glass beads, hollow ceramic beads, hollow silica microspheres, polymethylsilsesquioxane microspheres, and silica aerosol. The metal element content of the low dielectric material is less than 0.1%.

[0034] In some embodiments of the present invention, the binder is selected from one or more of a methyl cellulose aqueous solution, a hydroxypropyl cellulose aqueous solution, and a carboxymethyl cellulose aqueous solution.

[0035] In some embodiments of the present invention, the plasticizer is selected from one or more of polyvinyl alcohol, polyethylene glycol, xanthan gum, polyacrylamide, glycerol, diethylene glycol acetate, oxalic acid, dibutyl phthalate, and silicone oil.

[0036] In some embodiments of the present invention, the solid content of the insulating material slurry is 75-85%. Specifically, the solid content may be 75-80%, 80-85%, and typically but not limitedly, 75%, 80%, 85%.

[0037] In some embodiments of the present invention, the silicon dioxide powder or low dielectric material is treated with hydrophobicity. Specifically, the silicon dioxide is treated with hydrophobicity, and the low dielectric material is treated with hydrophobicity. Specifically, the specific steps of hydrophobic treatment are described using silicon dioxide as an example; the hydrophobic treatment of silicon dioxide includes the following steps: mixing a treatment agent and a solvent to obtain a treatment agent mixed solution, mixing the treatment agent mixed solution and silicon dioxide, heating, washing, drying, and heat treating to obtain hydrophobic silicon dioxide.

[0038] In some embodiments of the present invention, the mass percentage of the treatment agent mixture is 5-20%; specifically, the mass percentage may be 5-10%, 10-15%, 15-20%; typically but not limiting, for example, 5%, 10%, 15%, 20%.

[0039] In some embodiments of the present invention, the treating agent is selected from one or more of hexamethyldisilazane, hexamethylcyclotrisilazane, octamethylcyclotetrasilazane, polysilazane, functionalized silsesquioxane, and polyisocyanatepropylmethylsilazane; specifically,

[0040] The structural formula of the hexamethyldisilazane is:

[0041] The structural formula of the hexamethylcyclotrisilazane is

[0042] The structural formula of the octamethylcyclotetrasilazane is:

[0043] The structural formula of the polysilazane is:

[0044] The structural formula of the functionalized silsesquioxane is:

[0045]

[0046] The structural formula of the polyisocyanate propylmethylsilazane is:

[0047]

[0048] In some embodiments of the present invention, the solvent is selected from one or more of ethyl acetate, butyl acetate, tetrahydrofuran, acetone, butanone, and toluene.

[0049] In some embodiments of the present invention, the heating time is 8-12 hours; specifically, the heating time can be 8-10 hours, 10-12 hours; typically but not limiting, for example, 8 hours, 10 hours, 12 hours.

[0050] In some embodiments of the present invention, the heating temperature is 60-80°C; specifically, the heating temperature may be 60-70°C, 70-80°C; typically but not limiting, for example, 60°C, 70°C, 80°C.

[0051] In some embodiments of the present invention, the washing adopts a mixed solution of n-hexane / isopropanol; preferably, the mixed solution consists of n-hexane and isopropanol in a volume ratio of 1-5:1-5.

[0052] In some embodiments of the present invention, the drying temperature is 100-130°C; the drying time is 6-8h; specifically, the drying temperature may be 100-120°C, 120-130°C; typically but not limitatively, for example, 100°C, 120°C, 130°C; the drying time may be 6-7h, 7-8h; typically but not limitatively, for example, 6h, 7h, 8h.

[0053] In some embodiments of the present invention, the heat treatment temperature is 400-500°C, and the heat treatment time is 1-2 hours. Specifically, the heat treatment temperature can be 400-450°C, 450-500°C; typically but not limiting, for example, 400°C, 450°C, 500°C.

[0054] In some embodiments of the present invention, the mass ratio of the silicon dioxide or low dielectric material to the treatment agent is 100:5-20. Specifically, the mass ratio may be 100:5-15, 100:15-20; typically but not limiting, for example, 100:5, 100:15, 100:20.

[0055] The second aspect of the present invention is to provide a method for preparing a low dielectric constant, moisture-resistant silica insulating material as described above, comprising the following steps: mixing silica powder and low dielectric material, then adding a plasticizer, a binder, and deionized water to obtain a mixture, and kneading the obtained mixture under vacuum, aging, and obtaining an insulating material.

[0056] In some embodiments of the present invention, the number of times of kneading the mud is 3-5 times.

[0057] In some embodiments of the present invention, the aging time is 20-30 hours. Specifically, the aging time can be 20-25 hours, 25-30 hours; typically but not limiting, for example, 20 hours, 25 hours, 30 hours. The aging temperature is room temperature, that is, 20-25°C.

[0058] A third aspect of the present invention is to provide a method for preparing a coaxial cable, comprising the following steps:

[0059] (1) Extruding the above-mentioned low dielectric constant, moisture-resistant silicon dioxide insulating material or the low dielectric constant, moisture-resistant silicon dioxide insulating material prepared by the above-mentioned preparation method onto the inner conductor by an extrusion process, drying, degreasing and removing carbon, and forming an insulating layer outside the inner conductor;

[0060] (2) Then, a hydrophobic coating is applied on the outside of the insulating layer, heated to form a film, and a hydrophobic coating is formed to cover the outer conductor to obtain a coaxial cable.

[0061] The present invention reduces the surface hydroxyl content of porous silica by surface treatment and seals its surface pores, thereby reducing its adsorption capacity, especially the adsorption of water vapor, while ensuring its low dielectric properties, thereby ensuring the insulation and dielectric properties of the material. At the same time, a layer of high-temperature resistant hydrophobic coating is coated on the surface of the prepared coaxial cable insulation to further reduce the moisture absorption capacity of the finished cable.

[0062] In some embodiments of the present invention, the extrusion pressure in step (1) is 30-60 MPa; specifically, the extrusion pressure may be 30-40 MPa, 40-50 MPa, 50-60 MPa; typically but not limiting, for example, 30 MPa, 40 MPa, 50 MPa, 60 MPa.

[0063] In some embodiments of the present invention, the drying temperature in step (1) is 80-120°C, and the drying time is 6-12h; specifically, the drying temperature can be 80-100°C, 100-120°C; typically but not limitatively, for example, 80°C, 100°C, 120°C; the drying time can be 6-9h, 9-12h; typically but not limitatively, for example, 6h, 9h, 12h.

[0064] In some embodiments of the present invention, the temperature of degreasing and carbon removal in step (1) is 450-550°C, and the time of degreasing and carbon removal is 12-24h; specifically, the temperature of degreasing and carbon removal can be 450-500°C, 500-550°C; typically but not limitatively, for example, 450°C, 500°C, 550°C; the time of degreasing and carbon removal can be 12-18h, 18-24h; typically but not limitatively, for example, 12h, 18h, 24h.

[0065] In some embodiments of the present invention, the thickness of the insulating layer in step (1) is 0.2-1 mm; specifically, the thickness of the insulating layer may be 0.2-0.7 mm, 0.7-1 mm; typically but not limiting, for example, 0.2 mm, 0.7 mm, 1 mm.

[0066] In some embodiments of the present invention, the thickness of the hydrophobic coating in step (2) is 50-150 μm; specifically, the thickness of the hydrophobic coating may be 50-100 μm, 100-150 μm; typically but not limiting, for example, 50 μm, 100 μm, 150 μm.

[0067] In some embodiments of the present invention, the heating temperature in step (2) is 400-500°C; the heating time is 5-15 min. Specifically, the heating temperature may be 400-450°C, 450-500°C; typically but not limiting, for example, 400°C, 450°C, 500°C; the heating time may be 5-10 min, 10-15 min; typically but not limiting, for example, 5 min, 10 min, 15 min.

[0068] In some embodiments of the present invention, the solid content of the hydrophobic coating in step (2) is 20-40%.

[0069] In some embodiments of the present invention, the hydrophobic coating in step (2) comprises the following raw materials in parts by weight: 10-20 parts of resin, 10-20 parts of filler, 0.5-2 parts of penetrant, and 60-80 parts of solvent.

[0070] In some embodiments of the present invention, the hydrophobic coating comprises the following raw materials in parts by weight: 10-15 parts of resin, 10-15 parts of filler, 0.5-1 part of penetrant, and 60-70 parts of solvent.

[0071] In some embodiments of the present invention, the hydrophobic coating comprises the following raw materials in parts by weight: 15-20 parts of resin, 15-20 parts of filler, 1-2 parts of penetrant, and 70-80 parts of solvent.

[0072] In some embodiments of the present invention, the hydrophobic coating comprises the following raw materials in parts by weight: 10 parts of resin, 10 parts of filler, 0.5 parts of penetrant, and 60 parts of solvent.

[0073] In some embodiments of the present invention, the hydrophobic coating comprises the following raw materials in parts by weight: 15 parts of resin, 15 parts of filler, 1 part of penetrant, and 70 parts of solvent.

[0074] In some embodiments of the present invention, the hydrophobic coating comprises the following raw materials in parts by weight: 20 parts of resin, 20 parts of filler, 2 parts of penetrant, and 80 parts of solvent.

[0075] In some embodiments of the present invention, the solvent is selected from one or more of butanone, cyclohexanone, toluene, ethyl acetate, and chloroform.

[0076] In some embodiments of the present invention, the filler is selected from one or more of mica powder, fumed silica, polysilsesquioxane powder, and boron nitride; the particle size of the filler is 10-100nm; specifically, the particle size of the filler can be 10-50nm, 50-100nm.

[0077] In some embodiments of the present invention, the resin is selected from one or more of hexamethylcyclotrisilazane, octamethylcyclotetrasilazane, polyperhydrosilazane, polymethylsilazane, and polytriethoxysilylpropylmethylsilazane.

[0078] A fourth aspect of the present invention is to provide a coaxial cable, which is manufactured using the above-mentioned coaxial cable manufacturing method.

[0079] The present invention is further described below by way of examples, but the scope of the present invention is not limited thereto.

[0080] When the embodiment gives a numerical range, it should be understood that, unless otherwise specified in the present invention, the two endpoints of each numerical range and any numerical value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those generally understood by those skilled in the art. If specific conditions are not specified in the embodiment, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for all reagents or instruments, they are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the embodiments, according to the grasp of the prior art by those skilled in the art and the record of the present invention, any method, equipment, and material of the prior art similar or equivalent to the method, equipment, and material in the embodiments of the present invention can also be used to realize the present invention.

[0081] Example

[0082] Table 1: Ratio of raw material components of low dielectric constant, moisture-resistant silicon dioxide insulating material in Example 1-4

[0083]

[0084] Example 1

[0085] 1. This embodiment provides a low dielectric constant, moisture-resistant silica insulating material, and the composition ratio of the raw materials of the insulating material is shown in Table 1. The silica is porous silica powder, the low dielectric material is composed of hollow silica microspheres and polymethylsilsesquioxane microspheres in a mass ratio of 1:1; the binder is composed of carboxymethyl cellulose and hydroxypropyl cellulose in a mass ratio of 2:1; the plasticizer is composed of xanthan gum and glycerol in a mass ratio of 2:1;

[0086] 2. This embodiment provides a method for preparing a low dielectric constant, moisture-resistant silica insulating material as described above, comprising the following steps: mixing silica powder and a low dielectric material, then adding a plasticizer, a binder, and deionized water to obtain a mixture, kneading the obtained mixture under vacuum for 3 times, aging it for 24 hours, and obtaining a mud material.

[0087] 3. This embodiment provides a method for preparing a coaxial cable, comprising the following steps:

[0088] (1) The low dielectric constant, moisture-resistant silica insulating material described above is extruded through an extruder and wrapped around the outer periphery of the inner conductor, dried at 100° C. for 6 hours, degreased and carbonized at 500° C. for 24 hours, and an insulating layer is formed outside the inner conductor; the thickness of the insulating layer is 1 mm; the inner conductor is an oxygen-free copper conductor; and the extrusion molding pressure is 60 MPa;

[0089] (2) Then, the outer conductor is coated to obtain a coaxial cable. The outer conductor is an oxygen-free copper tube.

[0090] Example 2

[0091] 1. This embodiment provides a low dielectric constant, moisture-resistant silica insulating material, and the raw material composition ratio of the insulating material is shown in Table 1. The difference from Example 1 is that the raw material composition ratio is different. Among them, the silica is porous silica powder, the low dielectric material is composed of hollow glass microspheres and hollow silica microspheres in a mass ratio of 1:1; the binder is composed of carboxymethyl cellulose and methyl cellulose in a mass ratio of 1:1; the plasticizer is composed of diethylene glycol acetate and dibutyl phthalate in a mass ratio of 3:1.

[0092] 2. This embodiment provides a method for preparing a low dielectric constant, moisture-resistant silica insulating material as described above, comprising the following steps: mixing silica powder and a low dielectric material, then adding a plasticizer, a binder, and deionized water to obtain a mixture, kneading the obtained mixture under vacuum for 5 times, aging it for 30 hours, and obtaining a mud material.

[0093] 3. This embodiment provides a method for preparing a coaxial cable, comprising the following steps:

[0094] (1) The low dielectric constant, moisture-resistant silica insulating material described above is extruded through an extruder and wrapped around the outer periphery of the inner conductor, dried at 100° C. for 12 hours, degreased and carbonized at 500° C. for 16 hours, and an insulating layer is formed outside the inner conductor; the thickness of the insulating layer is 0.8 mm; the inner conductor is an oxygen-free copper conductor; and the extrusion molding pressure is 50 MPa;

[0095] (2) Then, the outer conductor is coated to obtain a coaxial cable. The outer conductor is a 316 stainless steel tube.

[0096] Example 3

[0097] 1. This embodiment provides a low dielectric constant, moisture-resistant silicon dioxide insulating material, and the raw material composition ratio of the insulating material is shown in Table 1. The difference from Example 1 is that the raw material composition ratio is different. Among them, the silicon dioxide is porous silicon dioxide powder, the low dielectric material is composed of silicon dioxide microspheres and silicon dioxide aerosol in a mass ratio of 10:1; the binder is carboxymethyl cellulose; the plasticizer is composed of polyvinyl alcohol and silicone oil in a mass ratio of 2:1.

[0098] 2. This embodiment provides a method for preparing a low dielectric constant, moisture-resistant silica insulating material as described above, comprising the following steps: mixing silica powder and low dielectric material, then adding a plasticizer, a binder, and deionized water to obtain a mixture, kneading the obtained mixture under vacuum for 4 times, aging it for 20 hours, and obtaining a mud material.

[0099] 3. This embodiment provides a method for preparing a coaxial cable, comprising the following steps:

[0100] (1) The low dielectric constant, moisture-resistant silica insulating material described above is extruded through an extruder and wrapped around the outer periphery of the inner conductor, dried at 100° C. for 8 hours, degreased and carbonized at 500° C. for 16 hours, and an insulating layer is formed outside the inner conductor; the thickness of the insulating layer is 0.2 mm; the inner conductor is a tungsten-copper alloy conductor; and the extrusion molding pressure is 30 MPa;

[0101] (2) Then, the outer conductor is coated to obtain a coaxial cable. The outer conductor is a titanium alloy tube.

[0102] Example 4

[0103] 1. This embodiment provides a low dielectric constant, moisture-resistant silica insulating material, and the raw material composition ratio of the insulating material is shown in Table 1. The difference from Example 1 is that the raw material composition ratio is different. Among them, the silica is porous silica powder, the low dielectric material is composed of hollow ceramic microspheres and silica aerosol in a mass ratio of 10:1; the binder is methyl cellulose; the plasticizer is composed of polyethylene glycol and polyacrylamide in a mass ratio of 1:2.

[0104] 2. This embodiment provides a method for preparing a low dielectric constant, moisture-resistant silica insulating material as described above, comprising the following steps: mixing silica powder and a low dielectric material, then adding a plasticizer, a binder, and deionized water to obtain a mixture, kneading the obtained mixture under vacuum for 5 times, aging it for 25 hours, and obtaining a mud material.

[0105] 3. This embodiment provides a method for preparing a coaxial cable, comprising the following steps:

[0106] (1) The low dielectric constant, moisture-resistant silica insulating material described above is extruded through an extruder and wrapped around the outer periphery of the inner conductor, dried at 100° C. for 10 hours, degreased and carbonized at 500° C. for 12 hours, and an insulating layer is formed outside the inner conductor; the thickness of the insulating layer is 0.5 mm; the inner conductor is a heavily nickel-plated copper conductor; and the extrusion molding pressure is 40 MPa;

[0107] (2) Then, the outer conductor is coated to obtain a coaxial cable. The outer conductor is a stainless steel tube.

[0108] Table 2 Ratio of components of hydrophobic treatment raw materials in Examples 5-8

[0109] Serial number / copy Silicon dioxide or low dielectric material Treatment agent Solvents Example 5 100 5 100 Example 6 100 10 100 Example 7 100 15 100 Example 8 100 20 100

[0110] Example 5

[0111] 1. This embodiment provides a low dielectric constant, moisture-resistant silicon dioxide insulating material, which is different from Example 1 in that: the silicon dioxide and the low dielectric material are both hydrophobically treated. The hydrophobic treatment of silicon dioxide is used to illustrate the treatment steps. Specifically, the hydrophobic treatment of silicon dioxide includes the following steps: mixing the treatment agent and the solvent to obtain a treatment agent mixture, mixing the treatment agent mixture and silicon dioxide, heating, washing, drying, and heat treating to obtain hydrophobically treated silicon dioxide. Among them, the treatment agent is hexamethyldisilazane; the solvent is composed of ethyl acetate and toluene in a mass ratio of 2:1; the mass percentage of the treatment agent mixture is 5%, and the mass ratio of silicon dioxide to the treatment agent is 100:5; the heating temperature is 70°C, the heating is 8h, and the washing is carried out using a mixed solution, which is composed of n-hexane and isopropanol in a volume ratio of 1:1. The drying temperature is 110°C, the drying time is 6h, and the heat treatment is treated at 400°C for 1h.

[0112] 3. This embodiment provides a method for preparing a coaxial cable, which is different from Embodiment 1 in that the low dielectric constant and moisture-resistant silicon dioxide insulating material is different, and the rest is exactly the same as Embodiment 1.

[0113] Example 6

[0114] 1. This embodiment provides a low dielectric constant, moisture-resistant silica insulating material, which is different from Example 2 in that: the silica and low dielectric material are both hydrophobically treated, and the hydrophobic treatment of silica is used to describe the treatment steps. Specifically, the hydrophobic treatment of silica includes the following steps: mixing the treatment agent and the solvent to obtain a treatment agent mixture, mixing the treatment agent mixture and silica, heating, washing, drying, and heat treating to obtain hydrophobically treated silica. Among them, the treatment agent is polyisocyanate methylsilazane; the solvent is composed of butanone and toluene in a mass ratio of 2:1; the mass percentage of the treatment agent mixture is 10%, and the mass ratio of silica to the treatment agent is 100:15; the heating temperature is 70°C, the heating is 10h, and the washing is carried out using a mixed solution, which is composed of n-hexane and isopropanol in a volume ratio of 1:1. The drying temperature is 110°C, the drying time is 6h, and the heat treatment is treated at 450°C for 1h.

[0115] 3. This embodiment provides a method for preparing a coaxial cable, which is different from Embodiment 2 in that the low dielectric constant and moisture-resistant silicon dioxide insulating material is different, and the rest is exactly the same as Embodiment 2.

[0116] Example 7

[0117] 1. This embodiment provides a low dielectric constant, moisture-resistant silicon dioxide insulating material, which is different from Example 3 in that: the silicon dioxide and the low dielectric material are both hydrophobically treated. Here, the hydrophobic treatment of the low dielectric material is used to illustrate the treatment steps. Specifically, the hydrophobic treatment of the low dielectric material includes the following steps: mixing the treatment agent and the solvent to obtain a treatment agent mixture, mixing the treatment agent mixture and the low dielectric material, heating, washing, drying, and heat treating to obtain a hydrophobically treated low dielectric material. Among them, the treatment agent is polyperhydrosilazane; the solvent is composed of tetrahydrofuran and butyl acetate in a mass ratio of 1:1; the mass percentage of the treatment agent mixture is 15%, and the mass ratio of the low dielectric material to the treatment agent is 100:15; the heating temperature is 70°C, the heating is 8h, and the washing is carried out using a mixed solution, which is composed of n-hexane and isopropanol in a volume ratio of 1:1. The drying temperature is 120°C, the drying time is 7h, and the heat treatment is treated at 450°C for 2h.

[0118] 3. This embodiment provides a method for preparing a coaxial cable, which is different from Embodiment 3 in that the low dielectric constant and moisture-resistant silicon dioxide insulating material is different, and the rest is exactly the same as Embodiment 3.

[0119] Example 8

[0120] 1. This embodiment provides a low dielectric constant, moisture-resistant silicon dioxide insulating material, which is different from Example 4 in that: the silicon dioxide and the low dielectric material are both hydrophobically treated. The hydrophobic treatment of silicon dioxide is used to illustrate the treatment steps. Specifically, the hydrophobic treatment of the low dielectric material includes the following steps: mixing the treatment agent and the solvent to obtain a treatment agent mixture, mixing the treatment agent mixture and the low dielectric material, heating, washing, drying, and heat treating to obtain a hydrophobically treated low dielectric material. Among them, the treatment agent is silyl silsesquioxane; the solvent is composed of ethyl acetate and chloroform in a mass ratio of 2:1; the mass percentage of the treatment agent mixture is 20%, and the mass ratio of silicon dioxide to the treatment agent is 100:20; the heating temperature is 70°C, the heating is 12h, and the washing is carried out using a mixed solution, which is composed of n-hexane and isopropanol in a volume ratio of 1:1. The drying temperature is 130°C, the drying time is 8h, and the heat treatment is treated at 500°C for 2h.

[0121] 3. This embodiment provides a method for preparing a coaxial cable, which is different from Embodiment 4 in that the low dielectric constant and moisture-resistant silicon dioxide insulating material is different, and the rest is exactly the same as Embodiment 4.

[0122] Table 3 Ratio of raw material components of hydrophobic coatings in Examples 9-12

[0123] Serial number / copy Resin filler Penetrant Solvents Example 9 10 10 0.5 80 Example 10 20 20 2 60 Embodiment 11 15 15 1.5 70 Example 12 20 10 1.0 70

[0124] Example 9

[0125] 3. This embodiment provides a method for preparing a coaxial cable, which is different from Embodiment 5 in that:

[0126] In the step (2), a hydrophobic coating is applied outside the insulating layer, heated at 500°C for 5min to form a film, a hydrophobic coating is formed, and then an outer conductor is coated to obtain a coaxial cable. The thickness of the hydrophobic coating is 150 μm. The raw material composition ratio of the hydrophobic coating is shown in Table 3, wherein the resin is poly perhydrosilazane; the filler is composed of nano-scale mica powder and boron nitride in a mass ratio of 1: 2; the penetrant is o-phenylenediamine; the solvent is composed of cyclohexanone and ethyl acetate in a mass ratio of 1: 1.

[0127] Example 10

[0128] 3. This embodiment provides a method for preparing a coaxial cable, which is different from Embodiment 6 in that:

[0129] In the step (2), a hydrophobic coating is applied outside the insulating layer, and a film is formed by heating at 450°C for 15min to form a hydrophobic coating, and then an outer conductor is coated to obtain a coaxial cable. The thickness of the hydrophobic coating is 80 μm. The hydrophobic coating, the raw material composition ratio is as shown in Table 3, wherein the resin is octamethylcyclotetrasilazane; the filler is composed of aerosol silica and boron nitride in a mass ratio of 1: 5; the penetrant is o-phenylenediamine; the solvent is composed of toluene and ethyl acetate in a mass ratio of 1: 2.

[0130] Embodiment 11

[0131] 3. The present embodiment provides a method for preparing a coaxial cable, which is different from Example 7 in that: in the step (2), a hydrophobic coating is applied to the outside of the insulating layer, heated at 500°C for 10 minutes to form a film, a hydrophobic coating is formed, and then the outer conductor is coated to obtain a coaxial cable. The thickness of the hydrophobic coating is 120 μm. The hydrophobic coating, the raw material composition ratio is shown in Table 3, wherein the resin is polymethylsilazane; the filler is composed of mica powder, polysilsesquioxane powder, and boron nitride in a mass ratio of 2: 1: 2; the penetrant is o-phenylenediamine; the solvent is composed of butanone and chloroform in a mass ratio of 2: 1.

[0132] Example 12

[0133] 3. The present embodiment provides a method for preparing a coaxial cable, which is different from Example 8 in that: in the step (2), the hydrophobic coating described above is applied to the outside of the insulating layer, heated at 400°C for 15 minutes to form a film, a hydrophobic coating is formed, and then the outer conductor is coated to obtain a coaxial cable. The thickness of the hydrophobic coating is 50 μm. The hydrophobic coating, the raw material composition ratio is shown in Table 3, wherein the resin is hexamethylcyclotrisilazane; the filler is composed of polysilsesquioxane powder and boron nitride in a mass ratio of 1:2; the penetrant is o-phenylenediamine; the solvent is composed of toluene and chloroform in a mass ratio of 2:1.

[0134] Comparative Example

[0135] Comparative Example 1

[0136] The difference between this comparative example and Example 3 is that:

[0137] This comparative example provides an insulating material, which includes the following raw materials in parts by weight: 75 parts of fused quartz, 3 parts of binder, 0.6 parts of plasticizer, and 25 parts of deionized water.

[0138] Comparative Example 2

[0139] The difference between this comparative example and Example 3 is that:

[0140] This comparative example provides an insulating material, which includes the following raw materials in parts by weight: 75 parts of magnesium oxide, 3 parts of a binder, 0.6 parts of a plasticizer, and 75 parts of deionized water.

[0141] Comparative Example 3

[0142] The difference between this comparative example and Example 3 is that no low dielectric material is added to the insulating material, that is, the low dielectric material is replaced by silicon dioxide in equal amounts. Specifically,

[0143] This comparative example provides an insulating material, which includes the following raw materials in parts by weight: 75 parts of silicon dioxide, 3 parts of a binder, 0.6 parts of a plasticizer, and 25 parts of deionized water.

[0144] Performance Testing

[0145] Volume resistivity detection method: The insulating materials obtained in Examples 1-8 and Comparative Examples 1-3 were dried, degreased and carbon removed to obtain insulating material specimens; wherein the drying conditions and the conditions for degreasing and carbon removal correspond to those in the corresponding embodiments and comparative examples; the size of the insulating material specimens is 100 mm × 100 mm × 1 mm; the prepared insulating material specimens were tested for initial volume resistivity and volume resistivity after wetting according to the test method in GB / T 31838.2 "Dielectric and resistive properties of solid insulating materials - Part 2: Resistance properties (DC method) volume resistance and volume resistivity", and the test results are shown in Table 4.

[0146] Dielectric constant detection method: Take the insulating materials obtained in Examples 1-8 and Comparative Examples 1-3, dry them, degrease and decarbonize them, and prepare insulating material specimens, wherein the drying conditions and the conditions for degreasing and decarbonizing correspond to those of the corresponding embodiments and comparative examples; the size of the insulating material specimens is 120 mm×120 mm×3 mm; the prepared insulating material specimens are tested for their initial dielectric constant and dielectric constant after being moistened according to the test method in IEC 62631-2-2Dielectric and resistive properties of solid insulating materials-Part 2-2:Relative permittivity and dissipation factor-High frequencies(1 MHz to 300 MHz)-AC methods, and the test results are shown in Table 4.

[0147] Humidity test: The insulating material specimens prepared in Examples 1-8 and Comparative Examples 1-3 were subjected to humidity tests according to GB / T2423.3-2016 "Environmental Test Part 2 Test Cab: Steady Humidity Test", and then the above-mentioned detection method was used to detect the volume resistivity and dielectric constant after humidity.

[0148] Table 4 Performance test results of insulation material specimens of Examples 1-8 and Comparative Examples 1-3

[0149]

[0150] It can be seen from Table 4 that the insulating material prepared by the present invention has good hydrophobicity, and has good dielectric properties and insulating properties. At the same time, the hydrophobicity of the silica powder and low dielectric material of the insulating material is better after hydrophobic treatment, and the volume resistivity and dielectric constant are tested under humid conditions, and the change rate is relatively small.

[0151] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A low dielectric constant, moisture-resistant silicon dioxide insulating material, characterized in that: The insulating material comprises the following raw materials in parts by weight: 40-60 parts of silicon dioxide powder, 20-50 parts of low dielectric material, 1-5 parts of binder, 0.3-1 parts of plasticizer, and 15-25 parts of deionized water.

2. A low dielectric constant, moisture-resistant silicon dioxide insulating material according to claim 1, characterized in that: Also includes one or more of the following characteristics: A1) the silicon dioxide is porous silicon dioxide powder, and preferably, the purity of the silicon dioxide is 99.9%; A2) the particle size of the silicon dioxide is 0.1-100 μm; A3) the low dielectric material is selected from one or more of hollow glass beads, hollow ceramic beads, hollow silica microspheres, polymethylsilsesquioxane microspheres, and silica aerosol; preferably, the metal element content of the low dielectric material is less than 0.1%; A4) the binder is selected from one or more of a methyl cellulose aqueous solution, a hydroxypropyl cellulose aqueous solution, and a carboxymethyl cellulose aqueous solution; A5) the plasticizer is selected from one or more of polyvinyl alcohol, polyethylene glycol, xanthan gum, polyacrylamide, glycerol, diethylene glycol acetate, oxalic acid, dibutyl phthalate, and silicone oil; A6) The solid content of the insulating material slurry is 75-85%.

3. The low dielectric constant, moisture-resistant silicon dioxide insulating material according to claim 1, characterized in that: The silicon dioxide or low dielectric material is treated with hydrophobicity.

4. A low dielectric constant, moisture-resistant silicon dioxide insulating material according to claim 3, characterized in that: The hydrophobic treatment of the silicon dioxide or low dielectric material comprises the following steps: mixing a treatment agent and a solvent to obtain a treatment agent mixed solution, mixing the treatment agent mixed solution and silicon dioxide or low dielectric material, heating, washing, drying, and heat treating to obtain hydrophobic treated silicon dioxide or low dielectric material.

5. The low dielectric constant, moisture-resistant silicon dioxide insulating material according to claim 1, characterized in that: Also includes one or more of the following characteristics: B1) The mass percentage of the treatment agent mixture is 5-20%; B2) the treating agent is selected from one or more of hexamethyldisilazane, hexamethylcyclotrisilazane, octamethylcyclotetrasilazane, polysilazane, functionalized silsesquioxane, and polyisocyanate propylmethylsilazane; B3) the solvent is selected from one or more of ethyl acetate, butyl acetate, tetrahydrofuran, acetone, butanone, and toluene; B4) the heating time is 8-12 hours; B5) the heating temperature is 60-80°C; B6) washing with a mixture of n-hexane / isopropanol; preferably, the mixture consists of n-hexane and isopropanol in a volume ratio of 1-5:1-5; B7) the drying temperature is 100-130°C; the drying time is 6-8h; B8) the temperature of the heat treatment is 400-500° C., and the time of the heat treatment is 1-2 hours; B9) The mass ratio of the silicon dioxide or low dielectric material to the treatment agent is 100:5-20.

6. A method for preparing a low dielectric constant, moisture-resistant silicon dioxide insulating material as claimed in any one of claims 1 to 5, characterized in that: The method comprises the following steps: mixing silicon dioxide powder and low dielectric material, then adding plasticizer, binder and deionized water to obtain a mixture, and kneading and aging the mixture under vacuum to obtain an insulating material.

7. The method for preparing a low dielectric constant, moisture-resistant silicon dioxide insulating material according to claim 6, characterized in that: The number of times of mud kneading is 3-5 times; and / or, the aging time is 20-30 hours.

8. A method for preparing a coaxial cable, characterized in that: The steps include: (1) Extruding a low dielectric constant, moisture-resistant silicon dioxide insulating material as described in any one of claims 1 to 5 or a low dielectric constant, moisture-resistant silicon dioxide insulating material obtained by the preparation method as described in claim 6 onto an inner conductor by an extrusion process, drying, degreasing and removing carbon, and forming an insulating layer outside the inner conductor; (2) Then, a hydrophobic coating is applied on the outside of the insulating layer, heated to form a film, and a hydrophobic coating is formed to cover the outer conductor to obtain a coaxial cable.

9. The method for preparing a coaxial cable according to claim 8, characterized in that: Also includes one or more of the following characteristics: 11) The extrusion pressure in step (1) is 30-60 MPa; 12) In step (1), the drying temperature is 80-120° C. and the drying time is 6-12 h; 13) The temperature of degreasing and carbon removal in step (1) is 450-550°C, and the time of degreasing and carbon removal is 12-24h; 14) The thickness of the insulating layer in step (1) is 0.2-1 mm; 21) In step (2), the hydrophobic coating comprises the following raw materials in parts by weight: 10-20 parts of resin, 10-20 parts of filler, 0.5-2 parts of penetrant, and 60-80 parts of solvent; 22) The thickness of the hydrophobic coating in step (2) is 50-150 μm; 23) In step (2), the heating temperature is 400-500° C. and the heating time is 5-15 min; 24) The solid content of the hydrophobic coating in step (2) is 20-40%.

10. The method for preparing a coaxial cable according to claim 9, characterized in that: Also includes one or more of the following characteristics: 211) The solvent is selected from one or more of butanone, cyclohexanone, toluene, ethyl acetate and chloroform; 212) The filler is selected from one or more of mica powder, fumed silica, polysilsesquioxane powder, and boron nitride; 213) The particle size of the filler is 10-100 nm; 214) The resin is selected from one or more of hexamethylcyclotrisilazane, octamethylcyclotetrasilazane, polyperhydrosilazane, polymethylsilazane, and polytriethoxysilylpropylmethylsilazane.

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