A rubber material for cold shrinkable cable accessories, a method for producing the same, and a cold shrinkable cable accessory

Abstract

The application relates to the technical field of insulating materials, and discloses a cold-shrink cable accessory rubber material, a preparation method thereof and a cold-shrink cable accessory. The cold-shrink cable accessory rubber material comprises the following components in mass fractions: 100 parts of ethylene-propylene-diene rubber, 40-70 parts of white carbon black, 10-30 parts of kaolin, 5-20 parts of mica powder, 1-5 parts of a silane coupling agent, 2-6 parts of a peroxide vulcanizing agent, 1-4 parts of a crosslinking agent, 5-20 parts of paraffin oil and 1-3 parts of an antioxidant. The specific-structure antioxidant is used in cooperation with fillers such as the white carbon black, the calcined kaolin and the mica powder, and the physical and chemical effects are combined to effectively resist ultraviolet and oxygen aging, significantly slow down discoloration and cracking of the material in a complex outdoor environment, maintain stable electrical performance, and prolong the service life of the material.

Description

Technical Field

[0001] This invention relates to the field of insulating materials technology, specifically to a rubber material for cold-shrinkable cable accessories, its preparation method, and the cold-shrinkable cable accessories themselves. Background Technology

[0002] In the field of prefabricated cable accessories, the performance of insulation materials is crucial. However, existing insulation materials have significant problems with UV and oxygen aging.

[0003] Ultraviolet (UV) aging occurs because the high energy of UV rays in sunlight easily breaks down the molecular chains of insulating materials. Prefabricated cable accessories are mostly used outdoors and are exposed to UV radiation for extended periods. This exposure causes photochemical reactions in the materials. For example, in polymers like EPDM rubber, the double bonds or benzene rings in the molecular chains readily absorb UV energy, triggering chain reactions that lead to discoloration and cracking. This, in turn, degrades electrical performance, such as reduced dielectric strength and insulation resistance, increasing the risk of cable accessory failures and impacting the stability of the power system.

[0004] Oxygen aging is also a significant concern. Oxygen is widely present in the environment and is chemically reactive, reacting with insulating materials through oxidation. During long-term operation, unsaturated bonds or active groups within the material combine with oxygen molecules, generating oxidation products such as peroxides. This leads to increased cross-linking density or molecular chain breakage, causing the material to harden, become brittle, and lose elasticity. This deterioration of physical properties reduces the material's wear resistance and impact resistance, shortening the service life of cable accessories.

[0005] While existing insulation materials employ methods such as adding anti-aging agents to delay aging, the effects are limited. Single anti-aging agents are insufficient to cope with complex aging environments, and in practical applications, they may migrate or volatilize, leading to accelerated material aging. Therefore, there is an urgent need for an insulation material for prefabricated cable accessories that can effectively resist ultraviolet and oxygen aging to improve the reliability and service life of cable accessories. Summary of the Invention

[0006] The present invention aims to provide a novel insulating material for prefabricated cable accessories. By optimizing the material formulation and preparation process, its resistance to ultraviolet radiation and oxidation aging is significantly improved, the service life of the material is extended, and the stability and reliability of cable accessories in complex environments are enhanced, thus meeting the high-performance requirements of modern power systems for insulating materials.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a rubber material for cold-shrink cable accessories, comprising an antioxidant with the structure shown in Formula 1:

[0008] Formula 1;

[0009] In Formula 1, R1 is selected from: methyl, ethyl, cyano, tert-butyl.

[0010] Furthermore, the rubber material for the cold-shrink cable accessory comprises the following components by weight: 100 parts EPDM rubber, 40-70 parts silica, 10-30 parts kaolin, 5-20 parts mica powder, 1-5 parts silane coupling agent, 2-6 parts peroxide vulcanizing agent, 1-4 parts crosslinking agent, 5-20 parts paraffin oil, and 1-3 parts antioxidant.

[0011] Furthermore, the silica is precipitated silica; the kaolin is calcined kaolin.

[0012] Furthermore, the mica powder is 325-800 mesh flake mica powder.

[0013] Furthermore, the silane coupling agent is γ-aminopropyltriethoxysilane.

[0014] Furthermore, the peroxide sulfiding agent is dicumyl peroxide.

[0015] Furthermore, the crosslinking agent is triallyl isocyanurate.

[0016] Furthermore, the antioxidant is any one of the compounds shown in the following structures:

[0017] ;

[0018] .

[0019] A method for preparing a rubber material for cold-shrink cable accessories includes the following steps:

[0020] S1. Put the EPDM rubber, silica, kaolin, mica powder and silane coupling agent into a mixer and mix at 120-150℃ for 5-10 minutes;

[0021] S2. Cool to 80-100℃, add the antioxidant and paraffin oil, and mix for 3-5 minutes;

[0022] S3. Add peroxide vulcanizing agent and crosslinking agent, and mix at 70-85℃ for 2-4 minutes to obtain compound rubber;

[0023] S4. Place the compounded rubber in a mold and vulcanize it at 160-180℃ and 10-15MPa pressure for 10-30 minutes. Cool it to room temperature to obtain a rubber material for cold-shrinkable cable accessories.

[0024] Furthermore, S2 is performed under a nitrogen atmosphere.

[0025] A rubber material for cold-shrink cable accessories is used in cold-shrink cable accessories.

[0026] A cold-shrink cable accessory includes a stress cone, an insulation body, and a sealing structure, wherein the stress cone and / or the insulation body are made of the rubber material used in the aforementioned cold-shrink cable accessory.

[0027] Furthermore, the insulation material retains ≥85% of its elongation at break after aging in an air chamber at 135°C for 168 hours.

[0028] Furthermore, the Shore A hardness of the stress cone is ≤68.

[0029] Application of a cold-shrink cable accessory in the terminal and / or intermediate connection parts of 10-35kV cross-linked polyethylene cables.

[0030] The antioxidant of this invention, as a compound represented by Formula 1, has a core structure comprising a polyhydroxy group and a large conjugated aromatic ring system. It terminates the oxygen aging chain reaction through the free radical capture mechanism of the polyhydroxy structure, and is optimized for addition in step S2 to prevent hydroxyl oxidation failure. Furthermore, it enhances dispersibility and fixation in insulating materials through hydrogen bonding stabilization, reducing migration. Simultaneously, the large conjugated aromatic ring system absorbs ultraviolet light energy (especially in the UV-B and UV-A bands) by expanding the π-electron cloud and converts it into heat energy for dissipation, preventing ultraviolet light from attacking the photochemical reactions of the material's molecular chains. It also provides steric protection to shield sensitive sites and, in step S1, synergistically disperses with fillers to form a uniform barrier. The synergistic effect of the polyhydroxy structure against oxygen aging and the aromatic ring structure against ultraviolet aging is activated during the vulcanization process in step S4, significantly improving the durability and electrical properties of the insulating material. It is suitable for 10-35kV cable accessories, ensuring the maintenance of high flexibility and reliability in power system operation in complex outdoor environments.

[0031] The present invention provides elasticity and insulation properties based on EPDM rubber. A filler system is constructed through a synergistic formulation of silica, calcined kaolin, and mica powder: the porous structure of silica adsorbs free radicals and scatters ultraviolet light; the layered structure of kaolin and mica powder forms a physical barrier against oxygen and ultraviolet penetration; a silane coupling agent is activated in the S1 mixing step, bridging the filler and rubber matrix to ensure dispersion of each component and eliminate local weaknesses; the core component, an antioxidant, is added in the S2 step, whose polyhydroxyl groups capture oxygen aging free radicals to terminate chain reactions, and the aromatic ring structure undergoes π→π... *The transition absorbs ultraviolet light and converts it into heat energy; the steric hindrance effect of R1 shields sensitive sites in the rubber; paraffin oil is added simultaneously to assist in the diffusion of antioxidants and slightly inhibit oxygen; the vulcanization system forms a high-density cross-linked network after low-temperature mixing in S3 and vulcanization in S4, locking antioxidant molecules to reduce migration and eliminating uncross-linked areas. This results in a three-dimensional synergy: ① physical level (filler barrier, mica reflecting ultraviolet light) and chemical level (anti-aging through dual mechanisms of antioxidants) complement each other; ② process level (nitrogen pre-oxidation prevention, gradient temperature mixing, vulcanization to fix the network) ensures stable release of component functions; ③ molecular level (silane-enhanced interface, cross-linked network encapsulating antioxidant hydrogen bonds) achieves long-term protection, ultimately enabling the material to maintain an elongation at break of ≥85% and a hardness of ≤68 after aging at 135℃ for 168h, completely solving the problems of discoloration, cracking, hardening, and decreased electrical performance of outdoor cable accessories caused by ultraviolet / oxygen aging, and is suitable for 10-35kV power systems.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] 1. Significantly improved anti-aging performance: This invention uses an anti-aging agent with a specific structure, in conjunction with fillers such as silica, calcined kaolin, and mica powder, to work together from physical and chemical levels to effectively resist ultraviolet and oxygen aging, significantly slow down discoloration and cracking of materials in complex outdoor environments, maintain stable electrical performance, and extend the service life of materials.

[0034] 2. Superior mechanical properties: The optimized formula and preparation process enable the material to perform well in mechanical properties such as tear resistance and hardness. It has high strength and moderate hardness in the initial stage, and its performance degradation after aging is small. It can better maintain flexibility, reduce the risk of material hardening and embrittlement, and improve the reliability and durability of cable accessories.

[0035] 3. More rational preparation process: The process of gradient temperature mixing and nitrogen atmosphere protection is refined to ensure that each component is fully dispersed and reacted, and to ensure that the functions of key components such as antioxidants are stable. At the same time, the vulcanization process forms a high-density cross-linked network, which locks in the antioxidants and reduces migration, thereby improving the stability and consistency of the overall performance of the material. Attached Figure Description

[0036] Figure 1 This is the NMR spectrum of the antioxidant 1 described in this invention.

[0037] Figure 2 This is a physical image of a cold-shrink cable accessory prepared in an application example of the present invention. Detailed Implementation

[0038] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Preparation Example 1

[0040] Preparation of antioxidant 1:

[0041] ;

[0042] Under a nitrogen atmosphere, 10.00 g of starting material 1, 10.36 g of starting material 2, 6.82 g of potassium carbonate, 0.08 g of target carbon, 0.32 g of triphenylphosphine, and 150 g of toluene were added to the reaction system. After stirring until homogeneous, the mixture was heated to 110 °C and refluxed for 12 h. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered using silica gel cake. 400 g of water was added to the organic phase, and the extraction was repeated three times. The organic phases were combined. The organic phase was dried over anhydrous magnesium sulfate, filtered, and evaporated to dryness. Silica gel column chromatography was performed using a mixture of petroleum ether and ethyl acetate as eluent. After evaporation to dryness, 9.26 g of intermediate 1 was obtained.

[0043] Intermediate structure identification: Mass spectrometry (M / Z-MS+H) + ): 674.

[0044] ;

[0045] Under a nitrogen atmosphere, 9.26 g of intermediate 1, 2.83 g of starting material 3, 3.94 g of potassium carbonate, 0.05 g of target carbon, 0.18 g of triphenylphosphine, and 150 g of toluene were added to the reaction system. After stirring until homogeneous, the mixture was heated to 110 °C and refluxed for 12 h. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered using silica gel cake. 400 g of water was added to the organic phase, and the extraction was repeated three times. The organic phases were combined. The organic phase was dried over anhydrous magnesium sulfate, filtered, and evaporated to dryness. Silica gel column chromatography was performed using a mixture of petroleum ether and ethyl acetate as eluent. After evaporation to dryness, 7.56 g of antioxidant 1 was obtained.

[0046] Structure identification of antioxidant 1: Mass spectrometry (M / Z-MS+H) + ): 759. NMR spectroscopy of antioxidant 1 (deuterated chloroform) is shown in [reference needed]. Figure 1 .

[0047] Preparation Examples 2 to 4

[0048] In Preparation Examples 2 to 4, antioxidants 2 to 4 were prepared sequentially, following the same preparation method as in Preparation Example 1, except that raw material 2 was replaced, while the rest remained the same. Specific structures of raw material 2, antioxidants 2 to 4, and mass spectrometry (M / Z-MS+H) were described. + The data is shown in Table 1.

[0049] Table 1

[0050]

[0051] Example 1

[0052] Preparation of a rubber material for cold-shrink cable accessories:

[0053] 1. Raw material components by weight:

[0054] 100 parts of EPDM rubber, 55 parts of silica (precipitated silica), 20 parts of kaolin (calcined kaolin), 12 parts of mica powder (325 mesh flake mica powder), 3 parts of silane coupling agent (γ-aminopropyltriethoxysilane), 4 parts of peroxide vulcanizing agent (diisopropylbenzene peroxide), 2.5 parts of crosslinking agent (triallyl isocyanurate), 12 parts of paraffin oil, and 2 parts of antioxidant (antioxidant 1 prepared in Preparation Example 1).

[0055] 2. Preparation method:

[0056] S1. Add EPDM rubber, silica, kaolin, mica powder and γ-aminopropyltriethoxysilane into a mixer and mix at 145°C for 7 minutes.

[0057] S2. Cool down to 90℃, add antioxidant 1 and paraffin oil under nitrogen atmosphere, and mix for 4 minutes;

[0058] S3. Add dicumyl peroxide and triallyl isocyanurate, and mix at 80°C for 3 minutes;

[0059] S4. Place the compounded rubber into a mold and vulcanize it at 170°C and 12MPa pressure for 20 minutes. Cool it to room temperature to obtain a rubber material for cold-shrinkable cable accessories.

[0060] Examples 2 to 4

[0061] The preparation of a rubber material for cold-shrinkable cable accessories is carried out by referring to the preparation method of Example 1, except that the antioxidant is replaced in sequence with antioxidant 2-antioxidant 4 prepared in Examples 2 to 4, and the rest is the same as in Example 1.

[0062] Comparative Example 1

[0063] The preparation of a rubber material for cold-shrink cable accessories is carried out according to the preparation method of Example 1, except that the antioxidant is replaced with comparative compound 1, and the rest is the same as in Example 1.

[0064] Comparative compound 1: Rubber antioxidant 445, CAS: 10081-67-1.

[0065] Comparative Example 2

[0066] The preparation of a rubber material for cold-shrink cable accessories is carried out according to the preparation method of Example 1, except that the antioxidant is replaced with comparative compound 2, and the rest is the same as in Example 1.

[0067] Comparative compound 2: .

[0068] Comparative Example 3

[0069] The preparation of a rubber material for cold-shrink cable accessories is the same as in Example 1, except that the antioxidant is not added.

[0070] Comparative Example 4

[0071] The preparation of a rubber material for cold-shrinkable cable accessories is carried out by referring to the preparation method of Example 1, except that the mass fraction of silica is replaced with 90 parts, and the rest remains the same as in Example 1.

[0072] Comparative Example 5

[0073] The preparation of a rubber material for cold-shrinkable cable accessories is carried out by referring to the preparation method of Example 1, except that the mass fraction of kaolin is replaced with 5 parts, and the rest remains the same as in Example 1.

[0074] Comparative Example 6

[0075] The preparation of a rubber material for a cold-shrinkable cable accessory is carried out according to the preparation method of Example 1, wherein step S2 is carried out in an air environment, and the rest is the same as in Example 1.

[0076] Performance testing:

[0077] 1. Tear resistance: The tear resistance of a cold-shrinkable cable accessory rubber material prepared in the examples and comparative examples was tested in accordance with GB / T 529 2008. The data are shown in Table 2.

[0078] 2. Aging tear strength test: The rubber material for cold-shrink cable accessories prepared in the examples and comparative examples was accelerated to 200 hours under hot air at 135°C, oxygen concentration of 35%, and UV-A lamp irradiation. The tear strength after accelerated aging was tested according to GB / T 529 2008. The data are shown in Table 2.

[0079] 3. Hardness test: The hardness of the rubber material for cold-shrink cable accessories prepared in the examples and comparative examples was tested according to GB / T531.1-2008. The data are shown in Table 2.

[0080] 4. Aging Hardness Test: The rubber material for cold-shrinkable cable accessories prepared in the examples and comparative examples was subjected to accelerated aging for 200 hours in hot air at 135°C, oxygen concentration of 35%, and UV-A lamp irradiation. The hardness after accelerated aging was tested according to GB / T531.1-2008, and the data are shown in Table 2.

[0081] Table 2

[0082]

[0083] Application examples

[0084] Preparation of a cold-shrink cable accessory:

[0085] S1. Component molding: The cold shrink cable accessory obtained in Example 1 is cut into pre-designed sizes using rubber material (mixed rubber) and placed into special molds to make stress cones and insulation bodies;

[0086] The mold design is based on standard 10-35kV cable specifications to ensure compatibility between accessories and cables;

[0087] Stress cone mold: The mold adopts a cone-shaped structure and the inner surface is coated with a release agent (paraffin).

[0088] Insulation main body mold: adopts a cylindrical hollow mold;

[0089] Molding temperature control: Preheat the mold to 80-90℃, then fill with the compound, apply an initial pressure of 5-10MPa, and hold for 1-2 minutes to ensure uniform material distribution and eliminate air bubbles.

[0090] S2. Vulcanization treatment: Transfer the mold filled with the compounded rubber into a flat vulcanizing machine and vulcanize for 15-25 minutes at 160-180℃ and 10-15MPa pressure; specific parameters are adjusted according to the thickness of the part.

[0091] Stress cone: vulcanize at 160℃ and 12MPa for 20 minutes;

[0092] Insulation body: vulcanized at 170℃ and 15MPa for 25 minutes;

[0093] After vulcanization, cool the mold to room temperature, then demold and remove the stress cone and the main insulating component. The surface of the component should be smooth and free of defects, cracks, or deformation.

[0094] S3. Attachment Assembly: Assemble the vulcanized stress cone and insulating main body components with the prefabricated sealing structure (such as silicone rubber sealing rings):

[0095] First, fit the insulation body onto the cable conductor, ensuring a tight fit;

[0096] Next, a stress cone is installed at the end of the cable shield to provide electric field control;

[0097] Finally, a sealing structure is added to the end of the accessory, which shrinks at room temperature using a cold shrinkage technology (using an expandable mandrel) to form a sealing barrier to prevent moisture and contaminants from entering.

[0098] After assembly, check the accessories (see) Figure 2 Perform visual and dimensional checks to ensure all parts are aligned correctly, without gaps or stress concentration points.

[0099] Performance verification:

[0100] The prepared cold-shrink cable accessories were subjected to accelerated aging tests: aged for 168 hours in hot air at 135℃, oxygen concentration of 35%, and UV-A lamp irradiation (simulating long-term outdoor environment); the elongation at break retention rate was ≥85%, indicating that the material still maintains high flexibility after aging, without hardening or embrittlement.

[0101] Electrical performance testing: According to GB / T 16927.1 standard, the insulation resistance of the accessory is ≥10 Ω under 10kV power frequency voltage. 14 The dielectric strength was ≥25kV / mm, with no breakdown or leakage, which verified that the synergistic effect of the antioxidant and filler system effectively resisted ultraviolet / oxygen aging and maintained insulation stability.

[0102] After being installed on a 10kV cross-linked polyethylene cable terminal, the accessory showed no discoloration, cracking, or malfunction after 12 months of operation, extending its service life by more than 30%, highlighting the reliability of this invention in power systems.

[0103] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A rubber material for cold-shrink cable accessories, characterized in that, Antioxidants including those with the structure shown in Formula 1: Formula 1; R1 in Formula 1 is selected from: methyl, ethyl, cyano, tert-butyl.

2. The rubber material for cold-shrink cable accessories according to claim 1, characterized in that, The rubber material for the cold-shrink cable accessory comprises the following components by weight: 100 parts EPDM rubber, 40-70 parts silica, 10-30 parts kaolin, 5-20 parts mica powder, 1-5 parts silane coupling agent, 2-6 parts peroxide vulcanizing agent, 1-4 parts crosslinking agent, 5-20 parts paraffin oil, and 1-3 parts antioxidant.

3. The rubber material for cold-shrink cable accessories according to claim 2, characterized in that, The silica is precipitated silica; the kaolin is calcined kaolin.

4. The rubber material for cold-shrink cable accessories according to claim 2, characterized in that, The mica powder is 325-800 mesh flake mica powder.

5. The rubber material for cold-shrink cable accessories according to claim 2, characterized in that, The silane coupling agent is γ-aminopropyltriethoxysilane.

6. The rubber material for cold-shrink cable accessories according to claim 2, characterized in that, The peroxide sulfiding agent is dicumyl peroxide; The crosslinking agent is triallyl isocyanurate.

7. A method for preparing a rubber material for cold-shrink cable accessories according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Add EPDM rubber, silica, kaolin, mica powder and silane coupling agent into a mixer and mix at 120-150℃ for 5-10 minutes; S2. Cool to 80-100℃, add antioxidant and paraffin oil, and mix for 3-5 minutes; S3. Add peroxide vulcanizing agent and crosslinking agent, and mix at 70-85℃ for 2-4 minutes to obtain compound rubber; S4. Place the compounded rubber in a mold and vulcanize it at 160-180℃ and 10-15MPa pressure for 10-30 minutes. Cool it to room temperature to obtain a rubber material for cold-shrinkable cable accessories. The antioxidant has the structure of the compound shown in Formula 1 of claim 1.

8. A method for preparing a rubber material for cold-shrink cable accessories according to claim 7, characterized in that, The S2 process is carried out under a nitrogen atmosphere.

9. The application of a rubber material for cold-shrinkable cable accessories as described in any one of claims 1-6 in cold-shrinkable cable accessories.

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