Composite layer material for cable intermediate joints and method for producing same

Abstract

The application belongs to the technical field of electric power engineering, and particularly relates to a composite layer material for cable intermediate joint and a preparation method thereof. The composite layer material for cable intermediate joint is composed of an inner semi-conductive layer, an insulating layer and an outer semi-conductive layer. The insulating layer is composed of the following raw materials: methyl vinyl silicone rubber, methyl phenyl vinyl silicone rubber, trifluoro propyl methyl vinyl silicone rubber, vulcanizing agent, auxiliary cross-linking agent, accelerator, diphenyl silicone diol, anti-aging agent, trifluoro propyl cage type silsesquioxane, and a mixture of modified nano-hydroxyapatite and nano-laponite. The composite layer material for cable intermediate joint has a consistent siloxane main chain structure and vulcanization system in three layers, which ensures the chemical compatibility between layers and realizes synchronous co-crosslinking. By adjusting the composition and ratio of silicone rubber in each layer, the prepared composite layer material for cable intermediate joint has excellent mechanical and hydrophobic water-blocking properties.

Description

Technical Field

[0001] This invention belongs to the field of power engineering technology, specifically relating to a composite layer material for cable intermediate joints and its preparation method. Background Technology

[0002] The intermediate joint of a power cable is a core accessory in power grid transmission lines for achieving conductor splicing, insulation restoration, and sealing protection. It consists of a conductor connection component, an insulation shielding system, and an outer sealing component. The conductor connection component is the core conductive part of the joint, used to achieve the electrical connection between the two cable conductors (usually a crimp terminal structure), and is the conductive foundation of the entire joint. The insulation shielding system is the functional core layer covering the outside of the conductor connection component. It is arranged concentrically from the inside to the outside, centered on the conductor connection component, and consists of three layers: an inner semiconducting layer, an insulating layer, and an outer semiconducting layer. The innermost semiconducting layer directly covers the outer periphery of the conductor connection component and is achieved by adding conductive carbon black. The semiconducting function is to homogenize the electric field on the conductor surface and prevent electric field concentration. The insulating layer, located between the inner and outer semiconducting layers, is the intermediate layer and the core layer responsible for high-voltage insulation and isolation. The outer semiconducting layer, covering the outer periphery of the insulating layer, is the outermost layer. It also achieves semiconductivity by adding conductive carbon black, and its function is to homogenize the external electric field and achieve grounding shielding. The above three layers use the same silicone rubber matrix material system and are made into a continuous and gapless integral structure through integrated injection molding and simultaneous vulcanization process, which is the core to ensure the insulation performance of the joint. The outer peripheral sealing component is an insulating sleeve that is fitted on the outside of the insulation shielding system. It relies on its own elasticity to achieve the overall outer peripheral seal of the joint, but does not participate in the insulation shielding function.

[0003] However, due to material limitations, this three-layer structure also serves as a primary channel for moisture intrusion into the connector. The reasons are as follows: the conventional silicone rubber materials of the inner semiconductive layer, insulating layer, and outer semiconductive layer have limited hydrophobicity, allowing external moisture to slowly permeate through the pores of these three layers to the periphery of the conductor connection. Furthermore, although these three layers are integrally vulcanized, the interfacial compatibility of conventional silicone rubber materials is insufficient, easily leading to microscopic interfacial defects. Simultaneously, the uneven dispersion of conductive carbon black in the semiconductive layer further exacerbates interfacial porosity, providing additional channels for rapid moisture penetration. Therefore, it is necessary to develop novel silicone rubber-based composite layer materials with excellent hydrophobic properties and interfacial compatibility. Summary of the Invention

[0004] The purpose of this invention is to provide a composite layer material for cable joints, which has excellent hydrophobicity and interfacial compatibility. In addition, this invention also provides a method for its preparation.

[0005] The composite layer material for cable joints of the present invention comprises an inner semiconductive layer, an insulating layer, and an outer semiconductive layer. The inner semiconductive layer, by weight, comprises the following raw materials: 64-66 parts methyl vinyl silicone rubber, 26-28 parts vinyl hyperbranched polysiloxane, 6-10 parts trifluoropropyl methyl vinyl silicone rubber, 22-24 parts modified acetylene black, 1.0 part vulcanizing agent, 1.8 parts co-crosslinking agent, 0.4 parts accelerator, 0.8-1.0 parts interface compatibilizer, and 0.8-1.0 parts anti-aging agent.

[0006] The insulating layer, by weight, is composed of the following raw materials: 86-88 parts of methyl vinyl silicone rubber, 6-8 parts of methyl phenyl vinyl silicone rubber, 4-8 parts of trifluoropropyl methyl vinyl silicone rubber, 1.0 part of vulcanizing agent, 1.8 parts of co-crosslinking agent, 0.4 parts of accelerator, 2-4 parts of diphenylsilanediol, 0.8-1.0 parts of anti-aging agent, 5-7 parts of trifluoropropyl cage-type silsesquioxane, and 14-16 parts of a mixture of modified nano-hydroxyapatite and nano-lithium saponite;

[0007] The outer semiconductive layer, by weight, is composed of the following raw materials: 54-56 parts of methyl vinyl silicone rubber, 9-11 parts of methyl phenyl vinyl silicone rubber, 24-26 parts of vinyl hyperbranched polysiloxane, 9-11 parts of trifluoropropyl methyl vinyl silicone rubber, 29-31 parts of modified acetylene black, 1.0 part of vulcanizing agent, 1.8 parts of co-crosslinking agent, 0.4 parts of accelerator, 0.8-1.0 parts of interface compatibilizer, 0.6-0.8 parts of release agent, and 0.8-1.0 parts of anti-aging agent.

[0008] in:

[0009] The inner and outer semiconductive layers use the same interface compatibilizer, which is vinyltris(2-methoxyethoxy)silane.

[0010] The release agent in the outer semiconductive layer is zinc stearate.

[0011] The modified acetylene black in the inner and outer semiconductive layers is the same. The preparation method of the modified acetylene black consists of the following steps: ① Mix anhydrous ethanol and deionized water evenly, then add acetic acid to adjust the pH of the system to 4.5, add KH-570 silane coupling agent and stir at room temperature for 40 min to prepare a hydrolysate; ② Add acetylene black to the hydrolysate and ultrasonically disperse for 20 min, then mechanically stir for 20 min, and reflux at 80℃ for 4 h; ③ After the reaction is complete, filter, wash three times with anhydrous ethanol, vacuum dry at 80℃ for 12 h, and then grind through a 300-mesh sieve to prepare the modified acetylene black.

[0012] In step ① of the preparation method of modified acetylene carbon black, the mass ratio of KH-570 silane coupling agent, anhydrous ethanol, and deionized water is 5:90:10.

[0013] In step ② of the preparation method of modified acetylene carbon black, the mass ratio of KH-570 silane coupling agent to acetylene carbon black is 5:100.

[0014] The vulcanizing agent in the inner semiconducting layer, the insulating layer and the outer semiconducting layer is the same, which is 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0015] The crosslinking agent used in the inner semiconductive layer, insulating layer, and outer semiconductive layer is the same, which is triallyl isocyanurate.

[0016] The accelerator is the same in the inner semiconductive layer, the insulating layer, and the outer semiconductive layer. The accelerator is N,N'-m-phenylenebismaleimide.

[0017] The anti-aging agent in the inner semiconductive layer, insulating layer and outer semiconductive layer is the same, which is 4,4'-bis(α,α-dimethylbenzyl)diphenylamine.

[0018] The same vinyl hyperbranched polysiloxane is used in both the inner and outer semiconductive layers. The vinyl hyperbranched polysiloxane was prepared according to the following literature: Zhuang Mingyan, Wang Yandong, Xi Kai. Vinyl hyperbranched polysiloxane modified release coating and its properties [J]. Acta Polymerica Sinica, 2025, 56(11): 2058-2065.

[0019] The preparation method of the modified nano-hydroxyapatite and nano-lithium saponite mixture in the insulating layer consists of the following steps: ① Mix anhydrous ethanol and deionized water evenly, then add acetic acid to adjust the pH of the system to 4.5, add hexadecyltrimethoxysilane and stir at room temperature for 3.5 h to prepare a hydrolysate; ② Add nano-hydroxyapatite and nano-lithium saponite to the hydrolysate simultaneously and disperse ultrasonically for 20 min, then stir mechanically for 30 min, and reflux at 80℃ for 3 h; ③ After the reaction is completed, filter, wash three times with anhydrous ethanol, vacuum dry at 100℃ for 12 h, and then grind through a 300-mesh sieve to prepare a mixture of modified nano-hydroxyapatite and nano-lithium saponite.

[0020] In the preparation method of the mixture of modified nano-hydroxyapatite and nano-lithium saponite, the mass ratio of anhydrous ethanol, deionized water and hexadecyltrimethoxysilane in step ① is 72:8:20.

[0021] In the preparation method of the mixture of modified nano-hydroxyapatite and nano-lithium saponite, the mass of hexadecyltrimethoxysilane in step ① accounts for 3% of the total mass of nano-hydroxyapatite and nano-lithium saponite in step ②.

[0022] In step ② of the preparation method of the mixture of modified nano-hydroxyapatite and nano-lithium saponite, the mass ratio of nano-hydroxyapatite to nano-lithium saponite is 2:1.

[0023] The method for preparing the composite layer material for cable joints according to the present invention comprises the following steps:

[0024] (1) The inner semiconductive layer raw material, the insulating layer raw material and the outer semiconductive layer raw material are respectively added to the internal mixer for mixing and plasticizing to prepare the inner semiconductive layer rubber compound, the insulating layer rubber compound and the outer semiconductive layer rubber compound;

[0025] (2) Add the inner semiconductive layer rubber, the insulating layer rubber and the outer semiconductive layer rubber to the three plasticizing barrels of the three-layer injection molding machine for plasticizing. Then, inject the rubber into the same mold cavity from the three barrels in the order of inner semiconductive layer, insulating layer and outer semiconductive layer. After all three layers are injected, perform pressure vulcanization.

[0026] (3) After vulcanization, the composite material semi-finished product for cable intermediate joint is prepared by depressurization, cooling and demolding.

[0027] (4) The composite material semi-finished product for cable intermediate joint is placed in an oven for two-stage vulcanization to prepare the composite layer material for cable intermediate joint.

[0028] In step (1), the mixing temperature of the inner semiconductive layer raw material in the internal mixer is 95-97℃, and the mixing time is 15-17min.

[0029] In step (1), the mixing temperature of the insulating layer raw material in the internal mixer is 103-105℃, and the mixing time is 21-23min.

[0030] In step (1), the mixing temperature of the outer semiconductive layer raw material in the internal mixer is 95-97℃, and the mixing time is 15-17min.

[0031] In step (2), the mold used for injection is preheated to 173°C and evacuated to a pressure of -0.09MPa.

[0032] In step (2), the three plasticizing cylinders are plasticized at the same temperature when they are plasticized independently, which is 80°C.

[0033] In step (2), the injection pressure of the inner semiconductive layer material is 90 MPa, the injection time is 7 s, and the mold temperature is 173 ℃.

[0034] In step (2), the injection pressure of the insulating layer adhesive is 110 MPa, the injection time is 13 s, and the mold temperature is 173 ℃.

[0035] In step (2), the injection pressure of the outer semiconductive layer material is 90 MPa, the injection time is 7 s, and the mold temperature is 173 ℃.

[0036] In step (2), each layer is not vulcanized separately after injection. All three layers are vulcanized under pressure after injection. The pressure of the pressure vulcanization is 105MPa, the pressure vulcanization time is 20min, and the mold temperature is 173℃.

[0037] In step (3), the temperature is cooled to 85-88℃ at a rate of 8℃ / min before the mold is opened and the mold is removed.

[0038] In step (4), the temperature for the second stage of vulcanization is 200℃ and the vulcanization time is 5h.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] (1) The composite layer material for cable intermediate joints described in this invention adopts a consistent siloxane main chain structure and vulcanization system in three layers to ensure interlayer chemical compatibility and achieve synchronous co-crosslinking. By adjusting the composition and ratio of silicone rubber in each layer, the composite layer material for cable intermediate joints prepared is ensured to have excellent mechanical and hydrophobic water-blocking properties.

[0041] (2) The composite layer material for cable intermediate joints described in this invention uses methyl vinyl silicone rubber as the matrix resin in the inner semiconductive layer, providing a basic silicon-oxygen skeleton and crosslinking reaction sites to form a continuous phase of a three-dimensional network. Vinyl hyperbranched polysiloxane is added; the low viscosity of the hyperbranched polysiloxane improves processing fluidity, and the multi-terminal vinyl groups increase the crosslinking density to compensate for the mechanical loss from the high-filler carbon black. Trifluoropropyl methyl vinyl silicone rubber is added to enhance hydrophobicity. The combination of these resins gives the inner semiconductive layer good processability, excellent hydrophobicity, and moderate elasticity. Furthermore, the interface compatibilizer vinyltris(2-methoxyethoxy)silane is added. The vinyl groups of vinyltris(2-methoxyethoxy)silane participate in the co-curing of the inner semiconductive layer, forming chemical bonds, and the methoxyethoxysilane groups improve interfacial wettability. The three-layer synchronous injection integrated curing process forms an integral structure, which, combined with the hydrophobicity of the fluorosilicone rubber, jointly inhibits water vapor permeation channels.

[0042] (3) The composite layer material for cable intermediate joints described in this invention has an outer semiconductive layer with methyl vinyl silicone rubber as the base resin, providing a basic silicon-oxygen skeleton and cross-linking reaction sites to form a continuous phase of a three-dimensional network; methyl phenyl vinyl silicone rubber is added, and the benzene ring side groups improve the rigidity of the molecular chain, and the vinyl group and methyl vinyl silicone rubber achieve co-vulcanization; the multi-terminal vinyl group of the vinyl hyperbranched polysiloxane improves the cross-linking density and compensates for the mechanical loss of the highly filled modified acetylene carbon black; trifluoropropyl methyl vinyl silicone rubber gives the outer layer good hydrophobicity; the combination of the above resins makes the outer semiconductive layer have high hardness and good hydrophobicity.

[0043] (4) The composite layer material for cable intermediate joints of the present invention uses methyl vinyl silicone rubber as the matrix resin in the insulation layer to provide a basic silicon-oxygen skeleton and cross-linking reaction sites to form a continuous phase of a three-dimensional network; methyl phenyl vinyl silicone rubber is added, and the side groups of the benzene ring improve the rigidity of the molecular chain, and the vinyl group and methyl vinyl silicone rubber are co-vulcanized; trifluoropropyl methyl vinyl silicone rubber is added, and the low surface energy characteristics of the fluorinated segments endow it with hydrophobicity, inhibiting the formation of the contamination layer. Its vinyl group participates in the free radical cross-linking reaction and is integrated into the network in the form of chemical bonds to ensure the long-term stability of the hydrophobic performance; the combination of the above resins makes the insulation layer have excellent electrical insulation and hydrophobicity.

[0044] (5) The composite layer material for cable joints described in this invention incorporates a mixture of modified nano-hydroxyapatite and nano-lithium saponite in the insulation layer in synergistic action with trifluoropropyl cage-type silsesquioxane. The nano-hydroxyapatite, after modification with hexadecyltrimethoxysilane, exhibits good compatibility with silicone rubber and effectively enhances tensile strength through crack pinning and stress transfer during tensile testing. The rigid cage-type structure of trifluoropropyl cage-type silsesquioxane disperses within the matrix, assisting in suppressing crack propagation through stress dispersion. Its fluorine content tends to accumulate on the surface, imparting hydrophobic properties. The lamellar structure of the modified lithium saponite forms a tortuous penetration path within the matrix, reducing the water molecule diffusion coefficient; its surface C 16 The long-chain fluorinated groups of the trifluoropropyl cage-like silsesquioxane and the fluorinated groups together endow the material with low surface energy properties. The trifluoropropyl cage-like silsesquioxane mainly provides surface hydrophobicity, while the modified lithium saponite provides bulk barrier properties, forming a complementary function. The hexadecyltrimethoxysilane-modified nano-hydroxyapatite and lithium saponite have alkyl surfaces compatible with silicone rubber, and the trifluoropropyl cage-like silsesquioxane is physically dispersed in the matrix. The three work synergistically to prevent filler agglomeration.

[0045] (6) The method for preparing the composite layer material for cable intermediate joints described in this invention employs a three-layer co-injection molding process. Specifically, the inner semiconductive layer, insulating layer, and outer semiconductive layer rubber materials are respectively mixed and plasticized in a Banbury mixer, and then sequentially injected into the same mold cavity using a three-layer co-injection molding machine. Each layer is not vulcanized immediately after injection, and pressure vulcanization is performed after all three layers have been injected. This process enables the three layers to crosslink synchronously under the shared vulcanization system. Combined with an interface compatibilizer to improve interlayer wettability and the hydrophobic properties imparted by trifluoropropyl cage-type silsesquioxane, a seamless integrated structure is achieved, significantly reducing interlayer defects and effectively inhibiting water vapor penetration. Detailed Implementation

[0046] The following are methods for preparing some of the raw materials used in the examples and comparative examples:

[0047] The method for preparing modified acetylene carbon black in the inner and outer semiconductive layers comprises the following steps: ① Mix anhydrous ethanol and deionized water evenly, then add acetic acid to adjust the pH of the system to 4.5, add KH-570 silane coupling agent and stir at room temperature for 40 min to prepare a hydrolysate; ② Add acetylene carbon black to the hydrolysate and ultrasonically disperse for 20 min, then mechanically stir for 20 min, and reflux at 80℃ for 4 h; ③ After the reaction is complete, filter, wash three times with anhydrous ethanol, vacuum dry at 80℃ for 12 h, and then grind through a 300-mesh sieve to prepare modified acetylene carbon black.

[0048] In step ① of the preparation method of modified acetylene carbon black, the mass ratio of KH-570 silane coupling agent, anhydrous ethanol, and deionized water is 5:90:10.

[0049] In step ② of the preparation method of modified acetylene carbon black, the mass ratio of KH-570 silane coupling agent to acetylene carbon black is 5:100.

[0050] The same vinyl hyperbranched polysiloxane is used in both the inner and outer semiconductive layers. The vinyl hyperbranched polysiloxane was prepared according to the following literature: Zhuang Mingyan, Wang Yandong, Xi Kai. Vinyl hyperbranched polysiloxane modified release coating and its properties [J]. Acta Polymerica Sinica, 2025, 56(11): 2058-2065.

[0051] The preparation method of vinyl hyperbranched polysiloxane described in the aforementioned literature is as follows: First, MTMS (0.9 mol, 122.6 g) and deionized water (0.9 mol, 16.2 g) are added to a round-bottom flask, and the co-hydrolysis reaction is carried out at room temperature for 4 h. Subsequently, VTMS (0.4 mol, 57.17 g), deionized water (0.9 mol, 16.2 g), and solvent are added. After adjusting the pH to acidic using HCl, the reaction is continued at elevated temperature for another 4 h. Subsequently, the monomer and solvent are removed by rotary evaporation under vacuum to obtain a product with a certain viscosity. Finally, the product is dried under vacuum to obtain HPSi (vinyl content approximately 9.73 wt%).

[0052] The preparation method of the modified nano-hydroxyapatite and nano-lithium saponite mixture in the insulating layer consists of the following steps: ① Mix anhydrous ethanol and deionized water evenly, then add acetic acid to adjust the pH of the system to 4.5, add hexadecyltrimethoxysilane and stir at room temperature for 3.5 h to prepare a hydrolysate; ② Add nano-hydroxyapatite and nano-lithium saponite to the hydrolysate simultaneously and disperse ultrasonically for 20 min, then stir mechanically for 30 min, and reflux at 80℃ for 3 h; ③ After the reaction is completed, filter, wash three times with anhydrous ethanol, vacuum dry at 100℃ for 12 h, and then grind through a 300-mesh sieve to prepare a mixture of modified nano-hydroxyapatite and nano-lithium saponite.

[0053] In step ①, the mass ratio of anhydrous ethanol, deionized water, and hexadecyltrimethoxysilane is 72:8:20.

[0054] In step ①, the mass of hexadecyltrimethoxysilane accounts for 3% of the combined mass of nano-hydroxyapatite and nano-lithium saponite in step ②.

[0055] In step ②, the mass ratio of nano-hydroxyapatite to nano-lithium saponite is 2:1.

[0056] The composite layer material for cable intermediate joints described in this embodiment 1 is composed of an inner semiconductive layer, an insulating layer, and an outer semiconductive layer. The inner semiconductive layer, by weight, is composed of the following raw materials: 65 parts methyl vinyl silicone rubber, 27 parts vinyl hyperbranched polysiloxane, 8 parts trifluoropropyl methyl vinyl silicone rubber, 23 parts modified acetylene black, 1.0 part vulcanizing agent, 1.8 parts co-crosslinking agent, 0.4 parts accelerator, 0.9 parts interface compatibilizer, and 0.9 parts anti-aging agent.

[0057] The insulating layer, by weight, is composed of the following raw materials: 87 parts methyl vinyl silicone rubber, 7 parts methyl phenyl vinyl silicone rubber, 6 parts trifluoropropyl methyl vinyl silicone rubber, 1.0 part vulcanizing agent, 1.8 parts co-crosslinking agent, 0.4 parts accelerator, 3 parts diphenylsilanediol, 0.9 parts anti-aging agent, 6 parts trifluoropropyl cage-type silsesquioxane, and 16 parts a mixture of modified nano hydroxyapatite and nano lithium saponite.

[0058] The outer semiconductive layer, by weight, is composed of the following raw materials: 55 parts methyl vinyl silicone rubber, 10 parts methyl phenyl vinyl silicone rubber, 25 parts vinyl hyperbranched polysiloxane, 10 parts trifluoropropyl methyl vinyl silicone rubber, 30 parts modified acetylene black, 1.0 part vulcanizing agent, 1.8 parts co-crosslinking agent, 0.4 parts accelerator, 0.9 parts interface compatibilizer, 0.7 parts release agent, and 0.9 parts anti-aging agent.

[0059] in:

[0060] The inner and outer semiconductive layers use the same interface compatibilizer, which is vinyltris(2-methoxyethoxy)silane.

[0061] The release agent in the outer semiconductive layer is zinc stearate.

[0062] The modified acetylene black in the inner semiconductive layer is the same as that in the outer semiconductive layer.

[0063] The vulcanizing agent in the inner semiconducting layer, the insulating layer and the outer semiconducting layer is the same, which is 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0064] The crosslinking agent used in the inner semiconductive layer, insulating layer, and outer semiconductive layer is the same, which is triallyl isocyanurate.

[0065] The accelerator is the same in the inner semiconductive layer, the insulating layer, and the outer semiconductive layer. The accelerator is N,N'-m-phenylenebismaleimide.

[0066] The anti-aging agent in the inner semiconductive layer, insulating layer and outer semiconductive layer is the same, which is 4,4'-bis(α,α-dimethylbenzyl)diphenylamine.

[0067] The method for preparing the composite layer material for cable intermediate joints described in Example 1 comprises the following steps:

[0068] (1) The inner semiconductive layer raw material, the insulating layer raw material and the outer semiconductive layer raw material are respectively added to the internal mixer for mixing and plasticizing to prepare the inner semiconductive layer rubber compound, the insulating layer rubber compound and the outer semiconductive layer rubber compound;

[0069] (2) Add the inner semiconductive layer rubber, the insulating layer rubber and the outer semiconductive layer rubber to the three plasticizing barrels of the three-layer injection molding machine for plasticizing. Then, inject the rubber into the same mold cavity from the three barrels in the order of inner semiconductive layer, insulating layer and outer semiconductive layer. After all three layers are injected, perform pressure vulcanization.

[0070] (3) After vulcanization, the composite material semi-finished product for cable intermediate joint is prepared by depressurization, cooling and demolding.

[0071] (4) The composite material semi-finished product for cable intermediate joint is placed in an oven for two-stage vulcanization to prepare the composite layer material for cable intermediate joint.

[0072] Wherein: in step (1), the mixing temperature of the inner semiconductive layer raw material in the internal mixer is 96℃ and the mixing time is 16min.

[0073] In step (1), the mixing temperature of the insulating layer raw material in the internal mixer is 104℃ and the mixing time is 22min.

[0074] In step (1), the mixing temperature of the outer semiconductive layer raw material in the internal mixer is 96℃ and the mixing time is 16min.

[0075] In step (2), the mold used for injection is preheated to 173°C and evacuated to a pressure of -0.09MPa.

[0076] In step (2), the three plasticizing cylinders are plasticized at the same temperature when they are plasticized independently, which is 80°C.

[0077] In step (2), the injection pressure of the inner semiconductive layer material is 90 MPa, the injection time is 7 s, and the mold temperature is 173 ℃.

[0078] In step (2), the injection pressure of the insulating layer adhesive is 110 MPa, the injection time is 13 s, and the mold temperature is 173 ℃.

[0079] In step (2), the injection pressure of the outer semiconductive layer material is 90 MPa, the injection time is 7 s, and the mold temperature is 173 ℃.

[0080] In step (2), each layer is not vulcanized separately after injection. All three layers are vulcanized under pressure after injection. The pressure of the pressure vulcanization is 105MPa, the pressure vulcanization time is 20min, and the mold temperature is 173℃.

[0081] In step (3), the temperature is cooled to 86°C at a rate of 8°C / min before the mold is opened and the mold is removed.

[0082] In step (4), the temperature for the second stage of vulcanization is 200℃ and the vulcanization time is 5h.

[0083] Example 2

[0084] The composite layer material for the cable intermediate joint described in this embodiment 2 is composed of an inner semiconductive layer, an insulating layer, and an outer semiconductive layer. The inner semiconductive layer, by weight, is composed of the following raw materials: 64 parts of methyl vinyl silicone rubber, 26 parts of vinyl hyperbranched polysiloxane, 10 parts of trifluoropropyl methyl vinyl silicone rubber, 22 parts of modified acetylene black, 1.0 part of vulcanizing agent, 1.8 parts of crosslinking agent, 0.4 parts of accelerator, 0.8 parts of interface compatibilizer, and 0.8 parts of anti-aging agent.

[0085] The insulating layer, by weight, is composed of the following raw materials: 86 parts methyl vinyl silicone rubber, 6 parts methyl phenyl vinyl silicone rubber, 8 parts trifluoropropyl methyl vinyl silicone rubber, 1.0 part vulcanizing agent, 1.8 parts co-crosslinking agent, 0.4 parts accelerator, 2 parts diphenylsilanediol, 0.8 parts anti-aging agent, 5 parts trifluoropropyl cage-type silsesquioxane, and 15 parts a mixture of modified nano hydroxyapatite and nano lithium saponite.

[0086] The outer semiconductive layer, by weight, is composed of the following raw materials: 54 parts methyl vinyl silicone rubber, 11 parts methyl phenyl vinyl silicone rubber, 24 parts vinyl hyperbranched polysiloxane, 11 parts trifluoropropyl methyl vinyl silicone rubber, 29 parts modified acetylene black, 1.0 part vulcanizing agent, 1.8 parts co-crosslinking agent, 0.4 parts accelerator, 0.8 parts interface compatibilizer, 0.6 parts release agent, and 0.8 parts anti-aging agent.

[0087] in:

[0088] The inner and outer semiconductive layers use the same interface compatibilizer, which is vinyltris(2-methoxyethoxy)silane.

[0089] The release agent in the outer semiconductive layer is zinc stearate.

[0090] The modified acetylene black in the inner semiconductive layer is the same as that in the outer semiconductive layer.

[0091] The vulcanizing agent in the inner semiconducting layer, the insulating layer and the outer semiconducting layer is the same, which is 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0092] The crosslinking agent used in the inner semiconductive layer, insulating layer, and outer semiconductive layer is the same, which is triallyl isocyanurate.

[0093] The accelerator is the same in the inner semiconductive layer, the insulating layer, and the outer semiconductive layer. The accelerator is N,N'-m-phenylenebismaleimide.

[0094] The anti-aging agent in the inner semiconductive layer, insulating layer and outer semiconductive layer is the same, which is 4,4'-bis(α,α-dimethylbenzyl)diphenylamine.

[0095] The method for preparing the composite layer material for cable intermediate joints described in Example 2 consists of the following steps:

[0096] (1) The inner semiconductive layer raw material, the insulating layer raw material and the outer semiconductive layer raw material are respectively added to the internal mixer for mixing and plasticizing to prepare the inner semiconductive layer rubber compound, the insulating layer rubber compound and the outer semiconductive layer rubber compound;

[0097] (2) Add the inner semiconductive layer rubber, the insulating layer rubber and the outer semiconductive layer rubber to the three plasticizing barrels of the three-layer injection molding machine for plasticizing. Then, inject the rubber into the same mold cavity from the three barrels in the order of inner semiconductive layer, insulating layer and outer semiconductive layer. After all three layers are injected, perform pressure vulcanization.

[0098] (3) After vulcanization, the composite material semi-finished product for cable intermediate joint is prepared by depressurization, cooling and demolding.

[0099] (4) The composite material semi-finished product for cable intermediate joint is placed in an oven for two-stage vulcanization to prepare the composite layer material for cable intermediate joint.

[0100] Wherein: in step (1), the mixing temperature of the inner semiconductive layer raw material in the internal mixer is 95℃ and the mixing time is 15min.

[0101] In step (1), the mixing temperature of the insulating layer raw material in the internal mixer is 103℃ and the mixing time is 21min.

[0102] In step (1), the mixing temperature of the outer semiconductive layer raw material in the internal mixer is 95℃ and the mixing time is 15min.

[0103] In step (2), the mold used for injection is preheated to 173°C and evacuated to a pressure of -0.09MPa.

[0104] In step (2), the three plasticizing cylinders are plasticized at the same temperature when they are plasticized independently, which is 80°C.

[0105] In step (2), the injection pressure of the inner semiconductive layer material is 90 MPa, the injection time is 7 s, and the mold temperature is 173 ℃.

[0106] In step (2), the injection pressure of the insulating layer adhesive is 110 MPa, the injection time is 13 s, and the mold temperature is 173 ℃.

[0107] In step (2), the injection pressure of the outer semiconductive layer material is 90 MPa, the injection time is 7 s, and the mold temperature is 173 ℃.

[0108] In step (2), each layer is not vulcanized separately after injection. All three layers are vulcanized under pressure after injection. The pressure of the pressure vulcanization is 105MPa, the pressure vulcanization time is 20min, and the mold temperature is 173℃.

[0109] In step (3), the temperature is cooled to 85°C at a rate of 8°C / min before the mold is opened and the mold is removed.

[0110] In step (4), the temperature for the second stage of vulcanization is 200℃ and the vulcanization time is 5h.

[0111] Example 3

[0112] The composite layer material for the cable intermediate joint described in this embodiment 3 is composed of an inner semiconductive layer, an insulating layer, and an outer semiconductive layer. The inner semiconductive layer, by weight, is composed of the following raw materials: 66 parts of methyl vinyl silicone rubber, 28 parts of vinyl hyperbranched polysiloxane, 6 parts of trifluoropropyl methyl vinyl silicone rubber, 24 parts of modified acetylene black, 1.0 part of vulcanizing agent, 1.8 parts of crosslinking agent, 0.4 parts of accelerator, 1.0 part of interface compatibilizer, and 1.0 part of anti-aging agent.

[0113] The insulating layer, by weight, is composed of the following raw materials: 88 parts of methyl vinyl silicone rubber, 8 parts of methyl phenyl vinyl silicone rubber, 4 parts of trifluoropropyl methyl vinyl silicone rubber, 1.0 part of vulcanizing agent, 1.8 parts of crosslinking agent, 0.4 parts of accelerator, 4 parts of diphenylsilanediol, 1.0 part of anti-aging agent, 7 parts of trifluoropropyl cage-type silsesquioxane, and 14 parts of a mixture of modified nano-hydroxyapatite and nano-lithium saponite.

[0114] The outer semiconductive layer, by weight, is composed of the following raw materials: 56 parts methyl vinyl silicone rubber, 9 parts methyl phenyl vinyl silicone rubber, 26 parts vinyl hyperbranched polysiloxane, 9 parts trifluoropropyl methyl vinyl silicone rubber, 31 parts modified acetylene black, 1.0 part vulcanizing agent, 1.8 parts co-crosslinking agent, 0.4 parts accelerator, 1.0 part interface compatibilizer, 0.8 parts release agent, and 1.0 part anti-aging agent.

[0115] in:

[0116] The inner and outer semiconductive layers use the same interface compatibilizer, which is vinyltris(2-methoxyethoxy)silane.

[0117] The release agent in the outer semiconductive layer is zinc stearate.

[0118] The modified acetylene black in the inner semiconductive layer is the same as that in the outer semiconductive layer.

[0119] The vulcanizing agent in the inner semiconducting layer, the insulating layer and the outer semiconducting layer is the same, which is 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0120] The crosslinking agent used in the inner semiconductive layer, insulating layer, and outer semiconductive layer is the same, which is triallyl isocyanurate.

[0121] The accelerator is the same in the inner semiconductive layer, the insulating layer, and the outer semiconductive layer. The accelerator is N,N'-m-phenylenebismaleimide.

[0122] The anti-aging agent in the inner semiconductive layer, insulating layer and outer semiconductive layer is the same, which is 4,4'-bis(α,α-dimethylbenzyl)diphenylamine.

[0123] The method for preparing the composite layer material for cable intermediate joints described in Example 3 consists of the following steps:

[0124] (1) The inner semiconductive layer raw material, the insulating layer raw material and the outer semiconductive layer raw material are respectively added to the internal mixer for mixing and plasticizing to prepare the inner semiconductive layer rubber compound, the insulating layer rubber compound and the outer semiconductive layer rubber compound;

[0125] (2) Add the inner semiconductive layer rubber, the insulating layer rubber and the outer semiconductive layer rubber to the three plasticizing barrels of the three-layer injection molding machine for plasticizing. Then, inject the rubber into the same mold cavity from the three barrels in the order of inner semiconductive layer, insulating layer and outer semiconductive layer. After all three layers are injected, perform pressure vulcanization.

[0126] (3) After vulcanization, the composite material semi-finished product for cable intermediate joint is prepared by depressurization, cooling and demolding.

[0127] (4) The composite material semi-finished product for cable intermediate joint is placed in an oven for two-stage vulcanization to prepare the composite layer material for cable intermediate joint.

[0128] Wherein: in step (1), the mixing temperature of the inner semiconductive layer raw material in the internal mixer is 97℃ and the mixing time is 17min.

[0129] In step (1), the mixing temperature of the insulating layer raw material in the internal mixer is 105℃ and the mixing time is 23min.

[0130] In step (1), the mixing temperature of the outer semiconductive layer raw material in the internal mixer is 97°C and the mixing time is 17 min.

[0131] In step (2), the mold used for injection is preheated to 173°C and evacuated to a pressure of -0.09MPa.

[0132] In step (2), the three plasticizing cylinders are plasticized at the same temperature when they are plasticized independently, which is 80°C.

[0133] In step (2), the injection pressure of the inner semiconductive layer material is 90 MPa, the injection time is 7 s, and the mold temperature is 173 ℃.

[0134] In step (2), the injection pressure of the insulating layer adhesive is 110 MPa, the injection time is 13 s, and the mold temperature is 173 ℃.

[0135] In step (2), the injection pressure of the outer semiconductive layer material is 90 MPa, the injection time is 7 s, and the mold temperature is 173 ℃.

[0136] In step (2), each layer is not vulcanized separately after injection. All three layers are vulcanized under pressure after injection. The pressure of the pressure vulcanization is 105MPa, the pressure vulcanization time is 20min, and the mold temperature is 173℃.

[0137] In step (3), the temperature is cooled to 88°C at a rate of 8°C / min before the mold is opened and the mold is removed.

[0138] In step (4), the temperature for the second stage of vulcanization is 200℃ and the vulcanization time is 5h.

[0139] Comparative Example 1

[0140] The preparation method of the composite layer material for cable joints described in Comparative Example 1 is the same as that in Example 1, and the composition of the inner and outer semiconductive layer raw materials is also the same as in Example 1. The only difference is that the composition of the insulating layer raw materials of the composite layer material for cable joints is different. The insulating layer, by weight, is composed of the following raw materials: 87 parts of methyl vinyl silicone rubber, 7 parts of methyl phenyl vinyl silicone rubber, 6 parts of trifluoropropyl methyl vinyl silicone rubber, 1.0 part of vulcanizing agent, 1.8 parts of crosslinking agent, 0.4 parts of accelerator, 3 parts of diphenylsilanediol, and 0.9 parts of anti-aging agent.

[0141] Comparative Example 2

[0142] The preparation method of the composite layer material for cable joints described in Comparative Example 2 is the same as that in Example 1, and the composition of its insulation layer raw materials and outer semiconductive layer raw materials is also the same as that in Example 1. The only difference is that the composition of the inner semiconductive layer raw materials of the composite layer material for cable joints is different. The inner semiconductive layer, by weight, is composed of the following raw materials: 65 parts of methyl vinyl silicone rubber, 23 parts of modified acetylene black, 1.0 part of vulcanizing agent, 1.8 parts of crosslinking agent, 0.4 parts of accelerator, 0.9 parts of interface compatibilizer, and 0.9 parts of anti-aging agent.

[0143] Comparative Example 3

[0144] The preparation method of the composite layer material for cable joints described in Comparative Example 3 is the same as that in Example 1, and the composition of its insulation layer raw materials and inner semiconductive layer raw materials is also the same as in Example 1. The only difference is that the composition of the outer semiconductive layer raw materials of the composite layer material for cable joints is different. The outer semiconductive layer, by weight, is composed of the following raw materials: 55 parts methyl vinyl silicone rubber, 30 parts modified acetylene black, 1.0 part vulcanizing agent, 1.8 parts co-crosslinking agent, 0.4 parts accelerator, 0.9 parts interface compatibilizer, 0.7 parts release agent, and 0.9 parts anti-aging agent.

[0145] Comparative Example 4

[0146] The preparation method of the composite layer material for cable joints described in Comparative Example 4 is the same as that in Example 1, and the composition of the inner and outer semiconductive layer raw materials is also the same as in Example 1. The only difference is that the composition of the insulating layer raw materials of the composite layer material for cable joints is different. The insulating layer, by weight, is composed of the following raw materials: 87 parts of methyl vinyl silicone rubber, 1.0 part of vulcanizing agent, 1.8 parts of crosslinking agent, 0.4 parts of accelerator, 3 parts of diphenylsilanediol, 0.9 parts of anti-aging agent, 6 parts of trifluoropropyl cage-type silsesquioxane, and 16 parts of a mixture of modified nano-hydroxyapatite and nano-lithium saponite.

[0147] The cable joints prepared in Examples 1-3 and Comparative Examples 1-4 were fabricated into standard specimens using composite layer materials. Elongation at break was tested according to ASTM D412 (tensile rate 500 mm / min), tear strength was tested according to ASTM D624 (tensile rate 500 mm / min), and peel strength was tested according to ASTM D903 (peel rate 152 mm / min). The average peel strength of the two interfaces was used as the interlayer bond strength index. The water contact angle of the outer and inner semiconductive layers was tested according to GB / T30693. The results are shown in Table 1 below.

[0148] Table 1. Performance test results of composite layer materials for cable joints

[0149]

[0150] As shown in Table 1, the performance of the composite layer materials for cable joints prepared in Examples 1-3 is significantly better than that in Comparative Examples 1-4. The properties of the composite layer materials for cable joints prepared in Comparative Examples 1-4 are greatly reduced due to the lack of filler in the insulation layer, the inner semiconductive layer, the outer semiconductive layer, and the change in the matrix resin in the insulation layer.

Claims

1. A composite layer material for cable joints, characterized in that: It is composed of an inner semiconductive layer, an insulating layer, and an outer semiconductive layer. The inner semiconductive layer, by weight, is composed of the following raw materials: 64-66 parts of methyl vinyl silicone rubber, 26-28 parts of vinyl hyperbranched polysiloxane, 6-10 parts of trifluoropropyl methyl vinyl silicone rubber, 22-24 parts of modified acetylene black, 1.0 part of vulcanizing agent, 1.8 parts of co-crosslinking agent, 0.4 parts of accelerator, 0.8-1.0 parts of interface compatibilizer, and 0.8-1.0 parts of anti-aging agent. The insulating layer, by weight, is composed of the following raw materials: 86-88 parts of methyl vinyl silicone rubber, 6-8 parts of methyl phenyl vinyl silicone rubber, 4-8 parts of trifluoropropyl methyl vinyl silicone rubber, 1.0 part of vulcanizing agent, 1.8 parts of co-crosslinking agent, 0.4 parts of accelerator, 2-4 parts of diphenylsilanediol, 0.8-1.0 parts of anti-aging agent, 5-7 parts of trifluoropropyl cage-type silsesquioxane, and 14-16 parts of a mixture of modified nano-hydroxyapatite and nano-lithium saponite; The outer semiconductive layer, by weight, is composed of the following raw materials: 54-56 parts of methyl vinyl silicone rubber, 9-11 parts of methyl phenyl vinyl silicone rubber, 24-26 parts of vinyl hyperbranched polysiloxane, 9-11 parts of trifluoropropyl methyl vinyl silicone rubber, 29-31 parts of modified acetylene black, 1.0 part of vulcanizing agent, 1.8 parts of co-crosslinking agent, 0.4 parts of accelerator, 0.8-1.0 parts of interface compatibilizer, 0.6-0.8 parts of release agent, and 0.8-1.0 parts of anti-aging agent.

2. The composite layer material for cable joints according to claim 1, characterized in that: The interface compatibilizer in the inner semiconducting layer is the same as that in the outer semiconducting layer, which is vinyltris(2-methoxyethoxy)silane. The release agent in the outer semiconductive layer is zinc stearate; The inner semiconducting layer, the insulating layer and the outer semiconducting layer use the same vulcanizing agent, which is 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane; The crosslinking agent in the inner semiconducting layer, insulating layer and outer semiconducting layer is the same, which is triallyl isocyanurate. The inner semiconducting layer, insulating layer and outer semiconducting layer contain the same accelerator, which is N,N'-m-phenylenebismaleimide; The anti-aging agent in the inner semiconductive layer, insulating layer and outer semiconductive layer is the same, which is 4,4'-bis(α,α-dimethylbenzyl)diphenylamine.

3. The composite layer material for cable joints according to claim 1, characterized in that: The modified acetylene black in the inner and outer semiconductive layers is the same. The preparation method of the modified acetylene black consists of the following steps: ① Mix anhydrous ethanol and deionized water evenly, then add acetic acid to adjust the pH of the system to 4.5, add KH-570 silane coupling agent and stir at room temperature for 40 min to prepare a hydrolysate; ② Add acetylene black to the hydrolysate and ultrasonically disperse for 20 min, then mechanically stir for 20 min, and reflux at 80℃ for 4 h; ③ After the reaction is complete, filter, wash three times with anhydrous ethanol, vacuum dry at 80℃ for 12 h, and then grind through a 300-mesh sieve to prepare the modified acetylene black.

4. The composite layer material for cable joints according to claim 3, characterized in that: In step ① of the preparation method of modified acetylene black, the mass ratio of KH-570 silane coupling agent, anhydrous ethanol, and deionized water is 5:90:

10. In step ② of the preparation method of modified acetylene carbon black, the mass ratio of KH-570 silane coupling agent to acetylene carbon black is 5:

100.

5. The composite layer material for cable joints according to claim 1, characterized in that: The preparation method of the modified nano-hydroxyapatite and nano-lithium saponite mixture in the insulating layer consists of the following steps: ① Mix anhydrous ethanol and deionized water evenly, then add acetic acid to adjust the pH of the system to 4.5, add hexadecyltrimethoxysilane and stir at room temperature for 3.5 h to prepare a hydrolysate; ② Add nano-hydroxyapatite and nano-lithium saponite to the hydrolysate simultaneously and disperse ultrasonically for 20 min, then stir mechanically for 30 min, and reflux at 80℃ for 3 h; ③ After the reaction is completed, filter, wash three times with anhydrous ethanol, vacuum dry at 100℃ for 12 h, and then grind through a 300-mesh sieve to prepare a mixture of modified nano-hydroxyapatite and nano-lithium saponite.

6. The composite layer material for cable joints according to claim 5, characterized in that: In the preparation method of the mixture of modified nano-hydroxyapatite and nano-lithium saponite, the mass ratio of anhydrous ethanol, deionized water and hexadecyltrimethoxysilane in step ① is 72:8:

20. In the preparation method of the mixture of modified nano-hydroxyapatite and nano-lithium saponite, the mass of hexadecyltrimethoxysilane in step ① accounts for 3% of the total mass of nano-hydroxyapatite and nano-lithium saponite in step ②. In step ② of the preparation method of the mixture of modified nano-hydroxyapatite and nano-lithium saponite, the mass ratio of nano-hydroxyapatite to nano-lithium saponite is 2:

1.

7. A method for preparing the composite layer material for cable intermediate joints according to claim 1, characterized in that: It consists of the following steps: (1) The inner semiconductive layer raw material, the insulating layer raw material and the outer semiconductive layer raw material are respectively added to the internal mixer for mixing and plasticizing to prepare the inner semiconductive layer rubber compound, the insulating layer rubber compound and the outer semiconductive layer rubber compound; (2) Add the inner semiconductive layer rubber, the insulating layer rubber and the outer semiconductive layer rubber to the three plasticizing barrels of the three-layer injection molding machine for plasticizing. Then, inject the rubber into the same mold cavity from the three barrels in the order of inner semiconductive layer, insulating layer and outer semiconductive layer. After all three layers are injected, perform pressure vulcanization. (3) After vulcanization, the composite material semi-finished product for cable intermediate joint is prepared by depressurization, cooling and demolding. (4) The composite material semi-finished product for cable intermediate joint is placed in an oven for two-stage vulcanization to prepare the composite layer material for cable intermediate joint.

8. The method for preparing the composite layer material for cable intermediate joints according to claim 7, characterized in that: In step (1), the mixing temperature of the inner semiconductive layer raw material in the internal mixer is 95-97℃, and the mixing time is 15-17min. In step (1), the mixing temperature of the insulating layer raw material in the internal mixer is 103-105℃, and the mixing time is 21-23min; In step (1), the mixing temperature of the outer semiconductive layer raw material in the internal mixer is 95-97℃, and the mixing time is 15-17min.

9. The method for preparing the composite layer material for cable intermediate joints according to claim 7, characterized in that: In step (2), the mold used for injection is preheated to 173°C and evacuated to a pressure of -0.09MPa. In step (2), the three plasticizing cylinders have the same plasticizing temperature when they are plasticized independently, which is 80°C. In step (2), the injection pressure of the inner semiconductive layer material is 90 MPa, the injection time is 7 s, and the mold temperature is 173 ℃. In step (2), the injection pressure of the insulating layer adhesive is 110 MPa, the injection time is 13 s, and the mold temperature is 173 ℃. In step (2), the injection pressure of the outer semiconductive layer material is 90 MPa, the injection time is 7 s, and the mold temperature is 173℃. In step (2), the pressure of the pressure holding vulcanization is 105 MPa, the pressure holding vulcanization time is 20 min, and the mold temperature is 173℃.

10. The method for preparing the composite layer material for cable intermediate joints according to claim 7, characterized in that: In step (3), the temperature is cooled to 85-88℃ at a rate of 8℃ / min before mold opening and demolding. In step (4), the temperature for the second stage of vulcanization is 200℃ and the vulcanization time is 5h.

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