Heat-resistant cable accessory silicone rubber compound and preparation method thereof

Abstract

The invention relates to a heat-resistant cable accessory silicone rubber compound and a preparation method thereof. The heat-resistant cable accessory silicone rubber compound comprises the following components in parts by weight: 100 parts of raw silicone rubber, 30-80 parts of white carbon black, 1-10 parts of polyvinyl silicone oil, 2-13 parts of transition metal oxide, 0.05-0.8 part of phenyl silicone oil, 5-18 parts of an anti-structuring agent, 0.5-3 parts of hydrogen-containing silicone oil and 0.1-0.3 part of an internal release agent. Based on the synergistic regulation and control mechanism of the polyvinyl silicone oil to the phenyl silicone oil and the transition metal oxide, the obtained silicone rubber can still maintain good mechanical properties under the long-term high-temperature working condition, and has good high-temperature aging resistance. By adopting a step-by-step processing technology, the dispersion performance of the transition metal oxide in the silicone rubber is improved, so that the transition metal oxide can be more easily and uniformly mixed with the silicone rubber, and the problem of performance reduction caused by non-uniform dispersion is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silicone rubber, in particular to a heat-resistant cable accessory silicone rubber compound and a preparation method thereof. BACKGROUND

[0002] The investment scale of China's power grid construction continues to expand, driving the power cable accessory market to grow significantly. Industry data shows that its market size has climbed from 3.91 billion yuan in 2019 to 5.54 billion yuan in 2023, and the demand for high-performance silicone rubber is increasingly urgent. However, domestic silicone rubber for cable accessories has obvious shortcomings in long-term high-temperature aging resistance, resulting in a high dependence on imports. This technical bottleneck is due to the special working conditions of cable accessories: in densely populated power transmission areas, the long-term operating temperature of cable joints can reach 130-160℃ due to limited heat dissipation, and transient overload such as short circuit fault can cause high temperature impact above 250℃. If the thermal and oxidative stability of silicone rubber is insufficient, it will induce sealing failure, moisture intrusion to form an electric tree channel, and even cause surface discharge or explosion accidents, so improving long-term heat resistance has become an important demand in the industry.

[0003] In the prior art, metal oxides have been widely used as heat-resistant additives for silicone rubber, and their heat-resistant mechanism is mainly based on the capture of free radicals generated during the thermal and oxidative aging process by the variable valence metal elements in the oxides, thereby effectively inhibiting the degradation of silicone rubber molecular chains. For example, patent CN102234427B discloses an implementation scheme using titanium dioxide as a heat-resistant component of silicone rubber.

[0004] Further, patent CN108102380A simultaneously uses metal oxides and phenyl silicone oil to improve the heat-resistant stability of silicone rubber. However, it still has a fundamental flaw: there is a lack of molecular-level synergistic effect between the physical barrier effect of phenyl silicone oil and the chemical quenching of metal oxides, resulting in a significant decline in free radical removal efficiency under long-term high temperature; at the same time, transition metal particles are prone to agglomeration and deactivation during thermal cycling, causing the protective effectiveness to rapidly decline with service time.

[0005] Currently, domestic silicone rubber cannot maintain good mechanical properties under long-term high-temperature working conditions, thus failing to meet the stringent requirements of the power system for the long-term service performance of key equipment. SUMMARY

[0006] In view of the deficiencies in the prior art, the main purpose of the present application is to provide a heat-resistant cable accessory silicone rubber compound based on the synergistic regulation mechanism of multi-vinyl silicone oil on phenyl silicone oil and transition metal oxides. The heat-resistant cable accessory silicone rubber compound can still maintain good mechanical properties under long-term high-temperature working conditions and has good high-temperature aging resistance. Another purpose of the present application is to provide a step-by-step preparation method to avoid the performance decline of silicone rubber caused by uneven dispersion of transition metal oxides.

[0007] To achieve the above technical effects, the specific technical solutions of the present application are as follows:

[0008] A kind of heat-resistant cable accessory silicone rubber mixing rubber, by weight parts includes: raw rubber 100 parts, white carbon black 30-80 parts, multi-vinyl silicone oil 1-10 parts, transition metal oxide 2-13 parts, phenyl silicone oil 0.05-0.8 parts, anti-structuring agent 5-18 parts, hydrogen-containing silicone oil 0.5-3 parts, internal release agent 0.1-0.3 parts.

[0009] The multi-vinyl silicone oil, phenyl silicone oil and transition metal oxide composite system constructed by the present application, which improves the core of high temperature aging resistance of silicone rubber is a multi-level, dynamic synergistic protection mechanism formed between the three. This synergistic effect profoundly affects the free radical chain reaction process and physical structure evolution of raw materials in high temperature oxidation environment.

[0010] The starting point of the synergistic effect of the system is the π-π conjugation effect formed between the vinyl group (-CH=CH2) in the multi-vinyl silicone oil and the benzene ring in the phenyl silicone oil. In high temperature or free radical initiated oxidation environment, vinyl group or benzene ring may become the initial site of free radical attack to form carbon-centered free radicals. At this time, the spatially adjacent vinyl double bond or benzene ring can effectively stabilize these newly generated free radical intermediates through its delocalized π-electron system. This stabilization does not occur in isolation, but due to the large number of vinyl and phenyl groups in the system, a widely and efficiently "free radical capture and stabilization network" is jointly constructed. The unique value of this network lies in that it significantly reduces the energy state of the captured free radicals (especially the destructive peroxyl radical ROO·), making it more prone to participate in subsequent quenching reactions.

[0011] Especially critical is that this network constructed by organosilicon components creates favorable conditions for the intrinsic antioxidant activity of transition metal oxides. Transition metal oxides quench free radicals through their surface variable valence high valence metal ions, and the classic mechanism is that the electron transfer of free radicals is reduced to low valence state, and free radicals are converted into relatively inert products (such as ROOH). However, the efficiency of this process depends largely on the regeneration rate and energy barrier of the low valence metal ions being oxidized by oxygen to the high activity high valence state. The π-π conjugation network of multi-vinyl silicone oil and phenyl silicone oil greatly promotes the process of free radicals transferring electrons to high valence metal ions by stabilizing free radical intermediates, substantially reduces the energy barrier of transition metal ion regeneration cycle, so that it can play a free radical quenching role more quickly and more persistently, effectively breaking the chain reaction of oxidative degradation.

[0012] In maintaining the long-term activity of transition metal oxides, the polyvinyl silicone oil plays another indispensable role. Transition metal oxide nanoparticles are prone to agglomeration, especially during high-temperature and long-term use, leading to a sharp decrease in active specific surface area and a rapid decay in free radical quenching efficiency. The abundant vinyl functional groups on the polyvinyl silicone oil molecular chain provide a solution. The vinyl double bond is rich in π electrons, which can act as a Lewis base to form a coordination bond with the Lewis acidic high-valent metal ions on the surface of transition metal oxides. This coordination forms an organic "coating layer" on the surface of metal particles. This coating layer has two main synergistic effects: one is the steric hindrance effect, which physically hinders direct contact between metal particles; the other is the possible change in particle surface charge distribution, which increases the electrostatic repulsive force. The combined effect effectively suppresses the agglomeration tendency of transition metal oxide nanoparticles, ensuring their high dispersibility and stability in the silicone rubber matrix. This good dispersion state allows more active metal ion sites to be exposed and continuously participate in the redox cycle of free radical quenching, thereby ensuring that the aforementioned free radical capture network and metal ion quenching mechanism can operate efficiently and for a long time.

[0013] When the system is subjected to the severe test of continuous high temperature, the polyvinyl silicone oil exhibits its third protective ability of structural evolution. Under high-temperature aging environment, multiple vinyl groups suspended on the polyvinyl silicone oil molecular chain tend to undergo intramolecular cyclization reactions, such as Diels-Alder cycloaddition between adjacent vinyl groups, driven by thermal energy and / or initiated by trace amounts of free radicals in the system. This reaction generates rigid, polycyclic fused ring structures in situ within the silicone rubber matrix. These fused ring structures are firmly anchored to the siloxane backbone through covalent bonds, having a profound impact on the local microstructure of the material: they are equivalent to introducing new crosslinking points, increasing the local crosslinking density; their inherent rigidity significantly limits the thermal motion ability of the surrounding siloxane segments; the restriction of segment motion leads to a decrease in free volume within the polymer. The combined effects of these changes are to densify the silicone rubber matrix at high temperatures. This in-situ formed dense structure, especially the physical barrier formed by the fused ring structure, effectively hinders the dissolution and diffusion of oxygen molecules within the material. Since oxygen is a key reactant for initiating and maintaining high-temperature oxidative degradation, blocking its diffusion pathway is equivalent to suppressing the rate and depth of the oxidation reaction from the source, providing crucial physical protection support for the aforementioned chemical quenching mechanism.

[0014] The synergy of polyvinyl silicone oil, phenyl silicone oil and transition metal oxide is a dynamic coupling process in time and space, and is a process of layer by layer progress. The π-π conjugation of polyvinyl silicone oil and phenyl silicone oil builds an efficient free radical capture and transmission network, significantly improves the efficiency and persistence of transition metal ion quenching free radicals, and the core is to reduce the regeneration energy barrier of metal ion; the polyvinyl silicone oil stabilizes the transition metal oxide particles through coordination, prevents deactivation, and ensures the sustainability of chemical protection; and under the induction of high temperature, intramolecular cyclization reaction of polyvinyl silicone oil occurs, and a dense physical barrier is constructed in situ to block the penetration of oxygen, thereby delaying oxidation from the root. The three mechanisms of efficient chemical quenching, active center protection and stability, and physical diffusion barrier are not isolated, but interdependent and mutually reinforcing, and together form a powerful multi-level synergistic protection system, which ultimately enables the silicone rubber mixing rubber to maintain the integrity of its network structure to the greatest extent in a long-term high-temperature harsh environment, thereby significantly improving the retention rate of its mechanical properties.

[0015] The anti-structuring agent is used to promote the dispersion of white carbon black in the silicone rubber and reduce the agglomeration of white carbon black; the hydrogen-containing silicone oil is used as an auxiliary crosslinking agent to improve the mechanical properties; and the internal release agent effectively prevents the silicone rubber from being torn during demolding.

[0016] Preferably, the heat-resistant cable accessory silicone rubber mixing rubber comprises, by weight: 100 parts of raw silicone rubber, 35-70 parts of white carbon black, 2-8 parts of polyvinyl silicone oil, 4-12 parts of transition metal oxide, 0.08-0.6 parts of phenyl silicone oil, 6-16 parts of anti-structuring agent, and 0.6-2.5 parts of hydrogen-containing silicone oil.

[0017] More preferably, the heat-resistant cable accessory silicone rubber mixing rubber comprises, by weight: 100 parts of raw silicone rubber, 40-60 parts of white carbon black, 3-7 parts of polyvinyl silicone oil, 6-10 parts of transition metal oxide, 0.1-0.5 parts of phenyl silicone oil, 7-14 parts of anti-structuring agent, and 0.7-2 parts of hydrogen-containing silicone oil.

[0018] Preferably, the anti-structuring agent comprises hydroxyl silicone oil and methoxyl silicone oil, the amount of the hydroxyl silicone oil is 4-8 parts, and the amount of the methoxyl silicone oil is 3-6 parts.

[0019] The present application uses hydroxyl silicone oil and methoxyl silicone oil as a silicone rubber anti-structuring agent. This scheme retains the hydroxyl silicone oil to improve the dispersion of white carbon black and the process flowability of silicone rubber, and uses the more complex structure of methoxyl silicone oil to optimize the crosslinking density of the three-dimensional network of silicone rubber, thereby significantly improving the tensile strength and elongation at break of silicone rubber. In addition, the small molecules contained in the methoxyl silicone oil have lower volatility than the hydroxyl silicone oil, which helps to further improve the heat resistance of the silicone rubber.

[0020] Preferably, the raw silicone rubber is a vinyl-terminated methyl vinyl raw rubber with a vinyl content of 0.03-0.3% and a molecular weight of 50-70w.

[0021] Preferably, the silica is fumed silica with a specific surface area of ​​200-300 m². 2 / g.

[0022] Preferably, the vinyl content of the polyvinyl silicone oil is 3.0-10.0%.

[0023] Preferably, the transition metal oxide is one or more of cerium oxide, titanium oxide, and iron oxide.

[0024] Preferably, the hydrogen content of the hydrogen-containing silicone oil is 1.0-3.0%.

[0025] Preferably, the internal release agent is any one of zinc stearate, stearic acid, and C16.

[0026] This invention further provides a method for preparing a silicone rubber compound for heat-resistant cable accessories, the method comprising the following steps:

[0027] S1: The aforementioned parts by weight of raw silicone rubber, transition metal oxide, and phenyl silicone oil are put into a kneader for intensive mixing, degassing, and cooling to obtain a paste-like heat resistant agent;

[0028] S2: The aforementioned parts by weight of raw silicone rubber, silica, polyvinyl silicone oil, methoxy silicone oil, hydroxyl silicone oil, hydrogen-containing silicone oil, and internal release agent are put into a kneader for intensive mixing, blending, degassing, and cooling to obtain silicone rubber base rubber.

[0029] S3: Mix the aforementioned paste-like heat-resistant agent with silicone rubber base;

[0030] S4: Add 1.6% of bis(2,4) vulcanizing agent, mix evenly, and vulcanize at 115°C for 300s in a flat vulcanizing machine to obtain heat-resistant cable accessory silicone rubber compound.

[0031] This invention employs a step-by-step processing technique. First, a pre-mixing process is used to initially disperse the raw silicone rubber, phenyl silicone oil, and transition metal oxides. Then, through repeated refining processes, the dispersion uniformity of the transition metal oxides is significantly improved, effectively overcoming the problem of easy agglomeration of metal oxides in traditional methods and avoiding performance degradation caused by uneven dispersion.

[0032] Preferably, the mixing conditions include a temperature of 30-90°C and a time of 1-8 hours.

[0033] Preferably, the mixing conditions include: a temperature of 70-155℃ and a time of 0.5-3 hours.

[0034] Preferably, the degassing conditions include: a vacuum degree of -0.03 to -0.08 MPa, a degassing temperature of 100-160°C, and a degassing time of 0.5-3 hours.

[0035] Preferably, the mixing conditions include a temperature of 15-30°C and a time of 0.5-1 hour.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] This invention achieves long-term stability of silicone rubber under harsh high-temperature environments, especially ensuring the durability of key mechanical properties, thereby significantly improving the long-term operational reliability and lifespan of cable accessories.

[0038] High-content dispersions of transition metal oxides can simultaneously quench UV free radicals, giving silicone rubber UV resistance and expanding its application scenarios in outdoor cable accessories. Detailed Implementation

[0039] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0040] Comparative Example 1

[0041] Preparation of paste-like heat resistant agent: Weigh 400g of 101 raw rubber, transition metal oxides (133g of cerium oxide, 133g of titanium oxide, 133g of iron oxide), and 15g of phenyl silicone oil and add them to a 2L vacuum kneader. Stir at 70℃ for 1.5 hours, raise the temperature to 80℃, degas under vacuum for 1 hour, vacuum degree -0.06MPa, and cool to room temperature to obtain paste-like heat resistant agent.

[0042] Preparation of silicone rubber base: Weigh 800g of 110 raw rubber (vinyl content 0.08%), 158g of 110 raw rubber (vinyl content 0.23%), and 550g of fumed silica (fumed silica, specific surface area 200m²). 2 95g of hydroxyl silicone oil, 10g of hydrogen-containing silicone oil (hydrogen content 1.0%), and 1.5g of zinc stearate were sequentially added to a 5L vacuum kneader and stirred at 90°C for 2 hours; the temperature was then raised to 120°C and stirred for another hour; the temperature was then raised to 155°C and stirred for another hour; the temperature was maintained and the mixture was degassed under vacuum for 1 hour at a vacuum degree of -0.06MPa; the mixture was then cooled to below 80°C to obtain the silicone rubber base.

[0043] Take 3g of the above-mentioned paste-like heat resistant agent and 100g of silicone rubber base, and repeatedly refine them evenly on a two-roll mill. Then add 1.6% of the bis(2,4) vulcanizing agent and refine them evenly again. Finally, vulcanize them at 115℃ for 300s in a flat vulcanizing machine to obtain heat-resistant cable accessory silicone rubber. Test the performance, and the test results are shown in Table 2.

[0044] Comparative Example 2

[0045] Preparation of paste-like heat resistant agent: Weigh 400g of 101 raw rubber, transition metal oxides (133g of cerium oxide, 133g of titanium oxide, 133g of iron oxide), and 15g of phenyl silicone oil and add them to a 2L vacuum kneader. Stir at 70℃ for 1.5 hours, raise the temperature to 80℃, degas under vacuum for 1 hour, vacuum degree -0.06MPa, and cool to room temperature to obtain paste-like heat resistant agent.

[0046] Preparation of silicone rubber base: Weigh 800g of 110 raw rubber (vinyl content 0.08%), 158g of 110 raw rubber (vinyl content 0.23%), and 550g of fumed silica (fumed silica, specific surface area 200m²). 2 55g of hydroxyl silicone oil, 40g of methoxy silicone oil, 10g of hydrogen-containing silicone oil (hydrogen content 1.0%), and 1.5g of zinc stearate were sequentially added to a 5L vacuum kneader and stirred at 90°C for 2 hours; the temperature was then raised to 120°C and stirred for another hour; the temperature was then raised to 155°C and stirred for another hour; the temperature was maintained and the mixture was degassed under vacuum for 1 hour at a vacuum degree of -0.06MPa; the mixture was then cooled to below 80°C to obtain the silicone rubber base.

[0047] Take 3g of the above-mentioned paste-like heat resistant agent and 100g of silicone rubber base, and repeatedly refine them evenly on a two-roll mill. Then add 1.6% of the bis(2,4) vulcanizing agent and refine them evenly again. Finally, vulcanize them at 115℃ for 300s in a flat vulcanizing machine to obtain heat-resistant cable accessory silicone rubber. Test the performance, and the test results are shown in Table 2.

[0048] Comparative Example 3

[0049] Preparation of paste-like heat resistant agent: Weigh 400g of 101 raw rubber, 400g of transition metal oxide (cerium oxide), and 15g of phenyl silicone oil and add them to a 2L vacuum kneader. Stir at 70℃ for 1.5 hours, raise the temperature to 80℃, degas under vacuum for 1 hour at a vacuum degree of -0.06MPa, and cool to room temperature to obtain paste-like heat resistant agent.

[0050] Preparation of silicone rubber base: Weigh 800g of 110 raw rubber (vinyl content 0.08%), 158g of 110 raw rubber (vinyl content 0.23%), and 550g of fumed silica (fumed silica, specific surface area 200m²). 255g of hydroxyl silicone oil, 40g of methoxy silicone oil, 10g of hydrogen-containing silicone oil (hydrogen content 1.0%), and 1.5g of zinc stearate were sequentially added to a 5L vacuum kneader and stirred at 90°C for 2 hours; the temperature was then raised to 120°C and stirred for another hour; the temperature was then raised to 155°C and stirred for another hour; the temperature was maintained and the mixture was degassed under vacuum for 1 hour at a vacuum degree of -0.06MPa; the mixture was then cooled to below 80°C to obtain the silicone rubber base.

[0051] Take 3g of the above-mentioned paste-like heat resistant agent and 100g of silicone rubber base, and repeatedly refine them evenly on a two-roll mill. Then add 1.6% of the bis(2,4) vulcanizing agent and refine them evenly again. Finally, vulcanize them at 115℃ for 300s in a flat vulcanizing machine to obtain heat-resistant cable accessory silicone rubber. Test the performance, and the test results are shown in Table 2.

[0052] Comparative Example 4

[0053] Preparation of paste-like heat resistant agent: Weigh 400g of 101 raw rubber, 400g of transition metal oxide (titanium oxide), and 15g of phenyl silicone oil and add them to a 2L vacuum kneader. Stir at 70℃ for 1.5 hours, raise the temperature to 80℃, degas under vacuum for 1 hour at a vacuum degree of -0.06MPa, and cool to room temperature to obtain paste-like heat resistant agent.

[0054] Preparation of silicone rubber base: Weigh 800g of 110 raw rubber (vinyl content 0.08%), 158g of 110 raw rubber (vinyl content 0.23%), and 550g of fumed silica (fumed silica, specific surface area 200m²). 2 55g of hydroxyl silicone oil, 40g of methoxy silicone oil, 10g of hydrogen-containing silicone oil (hydrogen content 1.0%), and 1.5g of zinc stearate were sequentially added to a 5L vacuum kneader and stirred at 90°C for 2 hours; the temperature was then raised to 120°C and stirred for another hour; the temperature was then raised to 155°C and stirred for another hour; the temperature was maintained and the mixture was degassed under vacuum for 1 hour at a vacuum degree of -0.06MPa; the mixture was then cooled to below 80°C to obtain the silicone rubber base.

[0055] Take 3g of the above-mentioned paste-like heat resistant agent and 100g of silicone rubber base, and repeatedly refine them evenly on a two-roll mill. Then add 1.6% of the bis(2,4) vulcanizing agent and refine them evenly again. Finally, vulcanize them at 115℃ for 300s in a flat vulcanizing machine to obtain heat-resistant cable accessory silicone rubber. Test the performance, and the test results are shown in Table 2.

[0056] Comparative Example 5

[0057] Preparation of paste-like heat resistant agent: Weigh 400g of 101 raw rubber, 400g of transition metal oxide (iron oxide), and 15g of phenyl silicone oil and add them to a 2L vacuum kneader. Stir at 70℃ for 1.5 hours, raise the temperature to 80℃, degas under vacuum for 1 hour, vacuum degree -0.06MPa, and cool to room temperature to obtain paste-like heat resistant agent.

[0058] Preparation of silicone rubber base: Weigh 800g of 110 raw rubber (vinyl content 0.08%), 158g of 110 raw rubber (vinyl content 0.23%), and 550g of fumed silica (fumed silica, specific surface area 200m²). 2 55g of hydroxyl silicone oil, 40g of methoxy silicone oil, 10g of hydrogen-containing silicone oil (hydrogen content 1.0%), and 1.5g of zinc stearate were sequentially added to a 5L vacuum kneader and stirred at 90°C for 2 hours; the temperature was then raised to 120°C and stirred for another hour; the temperature was then raised to 155°C and stirred for another hour; the temperature was maintained and the mixture was degassed under vacuum for 1 hour at a vacuum degree of -0.06MPa; the mixture was then cooled to below 80°C to obtain the silicone rubber base.

[0059] Take 3g of the above-mentioned paste-like heat resistant agent and 100g of silicone rubber base, and repeatedly refine them evenly on a two-roll mill. Then add 1.6% of the bis(2,4) vulcanizing agent and refine them evenly again. Finally, vulcanize them at 115℃ for 300s in a flat vulcanizing machine to obtain heat-resistant cable accessory silicone rubber. Test the performance, and the test results are shown in Table 2.

[0060] Comparative Example 6

[0061] Weigh out 15g of 101 raw rubber, 496g of 110 raw rubber (vinyl content 0.08%), 98g of 110 raw rubber (vinyl content 0.23%), transition metal oxides (5g of cerium oxide, 5g of titanium oxide, and 5g of iron oxide), 0.5g of phenyl silicone oil, and 310g of fumed silica (fumed silica with a specific surface area of ​​200m²). 2 34g of hydroxyl silicone oil, 25g of methoxy silicone oil, 6g of hydrogen-containing silicone oil (hydrogen content 1.0%), and 0.9g of zinc stearate were sequentially added to a 5L vacuum kneader and stirred at 90℃ for 2 hours; the temperature was raised to 120℃ and stirred for another hour; then the temperature was raised to 155℃ and stirred for another hour; the temperature was maintained and the mixture was degassed under vacuum for 1 hour at a vacuum degree of -0.06MPa; the mixture was cooled to below 80℃, and a bis(2,4)-dichloroforming agent was added at a ratio of 1.6% and the mixture was repeatedly kneaded until uniform. The mixture was then vulcanized at 115℃ for 300s in a flat vulcanizing machine to obtain heat-resistant cable accessory silicone rubber. The performance was tested, and the test results are shown in Table 2.

[0062] Comparative Example 7

[0063] Weigh out 15g of 101 raw rubber, 496g of 110 raw rubber (vinyl content 0.08%), 98g of 110 raw rubber (vinyl content 0.23%), 15g of transition metal oxide (cerium oxide), 0.5g of phenyl silicone oil, and 310g of fumed silica (fumed silica with a specific surface area of ​​200m²). 234g of hydroxyl silicone oil, 25g of methoxy silicone oil, 6g of hydrogen-containing silicone oil (hydrogen content 1.0%), and 0.9g of zinc stearate were sequentially added to a 5L vacuum kneader and stirred at 90℃ for 2 hours; the temperature was raised to 120℃ and stirred for another hour; then the temperature was raised to 155℃ and stirred for another hour; the temperature was maintained and the mixture was degassed under vacuum for 1 hour at a vacuum degree of -0.06MPa; the mixture was cooled to below 80℃, and a bis(2,4)-dichloroforming agent was added at a ratio of 1.6% and the mixture was repeatedly kneaded until uniform. The mixture was then vulcanized at 115℃ for 300s in a flat vulcanizing machine to obtain heat-resistant cable accessory silicone rubber. The performance was tested, and the test results are shown in Table 2.

[0064] Comparative Example 8

[0065] Weigh out 15g of 101 raw rubber, 496g of 110 raw rubber (vinyl content 0.08%), 98g of 110 raw rubber (vinyl content 0.23%), 15g of transition metal oxide (titanium oxide), 0.5g of phenyl silicone oil, and 310g of fumed silica (200m² specific surface area). 2 34g of hydroxyl silicone oil, 25g of methoxy silicone oil, 6g of hydrogen-containing silicone oil (hydrogen content 1.0%), and 0.9g of zinc stearate were sequentially added to a 5L vacuum kneader and stirred at 90℃ for 2 hours; the temperature was raised to 120℃ and stirred for another hour; then the temperature was raised to 155℃ and stirred for another hour; the temperature was maintained and the mixture was degassed under vacuum for 1 hour at a vacuum degree of -0.06MPa; the mixture was cooled to below 80℃, and a bis(2,4)-dichloroforming agent was added at a ratio of 1.6% and the mixture was repeatedly kneaded until uniform. The mixture was then vulcanized at 115℃ for 300s in a flat vulcanizing machine to obtain heat-resistant cable accessory silicone rubber. The performance was tested, and the test results are shown in Table 2.

[0066] Comparative Example 9

[0067] Weigh out 15g of 101 raw rubber, 496g of 110 raw rubber (vinyl content 0.08%), 98g of 110 raw rubber (vinyl content 0.23%), 15g of transition metal oxide (iron oxide), 0.5g of phenyl silicone oil, and 310g of fumed silica (200m² specific surface area). 2 34g of hydroxyl silicone oil, 25g of methoxy silicone oil, 6g of hydrogen-containing silicone oil (hydrogen content 1.0%), and 0.9g of zinc stearate were sequentially added to a 5L vacuum kneader and stirred at 90℃ for 2 hours; the temperature was raised to 120℃ and stirred for another hour; then the temperature was raised to 155℃ and stirred for another hour; the temperature was maintained and the mixture was degassed under vacuum for 1 hour at a vacuum degree of -0.06MPa; the mixture was cooled to below 80℃, and a bis(2,4)-dichloroforming agent was added at a ratio of 1.6% and the mixture was repeatedly kneaded until uniform. The mixture was then vulcanized at 115℃ for 300s in a flat vulcanizing machine to obtain heat-resistant cable accessory silicone rubber. The performance was tested, and the test results are shown in Table 2.

[0068] Example 1

[0069] Preparation of paste-like heat resistant agent: Weigh 400g of 101 raw rubber, transition metal oxides (133g of cerium oxide, 133g of titanium oxide, 133g of iron oxide), and 15g of phenyl silicone oil and add them to a 2L vacuum kneader. Stir at 70℃ for 1.5 hours, raise the temperature to 80℃, degas under vacuum for 1 hour, vacuum degree -0.06MPa, and cool to room temperature to obtain paste-like heat resistant agent.

[0070] Preparation of silicone rubber base: Weigh 800g of 110 raw rubber (vinyl content 0.08%), 158g of 110 raw rubber (vinyl content 0.23%), and 550g of fumed silica (fumed silica, specific surface area 200m²). 2 35g of polyvinyl silicone oil (vinyl content 3%), 95g of hydroxyl silicone oil, 10g of hydrogen-containing silicone oil (hydrogen content 1.0%), and 1.5g of zinc stearate were sequentially added to a 5L vacuum kneader and stirred at 90°C for 2 hours; the temperature was raised to 120°C and stirred for another hour; then the temperature was raised to 155°C and stirred for another hour; the temperature was maintained and the mixture was degassed under vacuum for 1 hour at a vacuum degree of -0.06MPa; the mixture was then cooled to below 80°C to obtain the silicone rubber base.

[0071] Take 3g of the above-mentioned paste-like heat resistant agent and 100g of silicone rubber base, and repeatedly refine them evenly on a two-roll mill. Then add 1.6% of the bis(2,4) vulcanizing agent and refine them evenly again. Finally, vulcanize them at 115℃ for 300s in a flat vulcanizing machine to obtain heat-resistant cable accessory silicone rubber. Test the performance, and the test results are shown in Table 2.

[0072] Example 2

[0073] Preparation of paste-like heat resistant agent: Weigh 400g of 101 raw rubber, transition metal oxides (133g of cerium oxide, 133g of titanium oxide, 133g of iron oxide), and 15g of phenyl silicone oil and add them to a 2L vacuum kneader. Stir at 70℃ for 1.5 hours, raise the temperature to 80℃, degas under vacuum for 1 hour, vacuum degree -0.06MPa, and cool to room temperature to obtain paste-like heat resistant agent.

[0074] Preparation of silicone rubber base: Weigh 800g of 110 raw rubber (vinyl content 0.08%), 158g of 110 raw rubber (vinyl content 0.23%), and 550g of fumed silica (fumed silica, specific surface area 200m²). 235g of polyvinyl silicone oil (vinyl content 3%), 55g of hydroxyl silicone oil, 40g of methoxy silicone oil, 10g of hydrogen-containing silicone oil (hydrogen content 1.0%), and 1.5g of zinc stearate were sequentially added to a 5L vacuum kneader and stirred at 90°C for 2 hours; the temperature was raised to 120°C and stirred for another hour; then the temperature was raised to 155°C and stirred for another hour; the temperature was maintained and the mixture was degassed under vacuum for 1 hour at a vacuum degree of -0.06MPa; the mixture was then cooled to below 80°C to obtain the silicone rubber base.

[0075] Take 3g of the above-mentioned paste-like heat resistant agent and 100g of silicone rubber base, and repeatedly refine them evenly on a two-roll mill. Then add 1.6% of the bis(2,4) vulcanizing agent and refine them evenly again. Finally, vulcanize them at 115℃ for 300s in a flat vulcanizing machine to obtain heat-resistant cable accessory silicone rubber. Test the performance, and the test results are shown in Table 2.

[0076] Example 3

[0077] Preparation of paste-like heat resistant agent: Weigh 400g of 101 raw rubber, 400g of transition metal oxide (cerium oxide), and 15g of phenyl silicone oil and add them to a 2L vacuum kneader. Stir at 70℃ for 1.5 hours, raise the temperature to 80℃, degas under vacuum for 1 hour at a vacuum degree of -0.06MPa, and cool to room temperature to obtain paste-like heat resistant agent.

[0078] Preparation of silicone rubber base: Weigh 800g of 110 raw rubber (vinyl content 0.08%), 158g of 110 raw rubber (vinyl content 0.23%), and 550g of fumed silica (fumed silica, specific surface area 200m²). 2 35g of polyvinyl silicone oil (vinyl content 3%), 55g of hydroxyl silicone oil, 40g of methoxy silicone oil, 10g of hydrogen-containing silicone oil (hydrogen content 1.0%), and 1.5g of zinc stearate were sequentially added to a 5L vacuum kneader and stirred at 90°C for 2 hours; the temperature was raised to 120°C and stirred for another hour; then the temperature was raised to 155°C and stirred for another hour; the temperature was maintained and the mixture was degassed under vacuum for 1 hour at a vacuum degree of -0.06MPa; the mixture was then cooled to below 80°C to obtain the silicone rubber base.

[0079] Take 3g of the above-mentioned paste-like heat resistant agent and 100g of silicone rubber base, and repeatedly refine them evenly on a two-roll mill. Then add 1.6% of the bis(2,4) vulcanizing agent and refine them evenly again. Finally, vulcanize them at 115℃ for 300s in a flat vulcanizing machine to obtain heat-resistant cable accessory silicone rubber. Test the performance, and the test results are shown in Table 2.

[0080] Example 4

[0081] Preparation of paste-like heat resistant agent: Weigh 400g of 101 raw rubber, 400g of transition metal oxide (titanium oxide), and 15g of phenyl silicone oil and add them to a 2L vacuum kneader. Stir at 70℃ for 1.5 hours, raise the temperature to 80℃, degas under vacuum for 1 hour at a vacuum degree of -0.06MPa, and cool to room temperature to obtain paste-like heat resistant agent.

[0082] Preparation of silicone rubber base: Weigh 800g of 110 raw rubber (vinyl content 0.08%), 158g of 110 raw rubber (vinyl content 0.23%), and 550g of fumed silica (fumed silica, specific surface area 200m²). 2 35g of polyvinyl silicone oil (vinyl content 3%), 55g of hydroxyl silicone oil, 40g of methoxy silicone oil, 10g of hydrogen-containing silicone oil (hydrogen content 1.0%), and 1.5g of zinc stearate were sequentially added to a 5L vacuum kneader and stirred at 90°C for 2 hours; the temperature was raised to 120°C and stirred for another hour; then the temperature was raised to 155°C and stirred for another hour; the temperature was maintained and the mixture was degassed under vacuum for 1 hour at a vacuum degree of -0.06MPa; the mixture was then cooled to below 80°C to obtain the silicone rubber base.

[0083] Take 3g of the above-mentioned paste-like heat resistant agent and 100g of silicone rubber base, and repeatedly refine them evenly on a two-roll mill. Then add 1.6% of the bis(2,4) vulcanizing agent and refine them evenly again. Finally, vulcanize them at 115℃ for 300s in a flat vulcanizing machine to obtain heat-resistant cable accessory silicone rubber. Test the performance, and the test results are shown in Table 2.

[0084] Example 5

[0085] Preparation of paste-like heat resistant agent: Weigh 400g of 101 raw rubber, 400g of transition metal oxide (iron oxide), and 15g of phenyl silicone oil and add them to a 2L vacuum kneader. Stir at 70℃ for 1.5 hours, raise the temperature to 80℃, degas under vacuum for 1 hour, vacuum degree -0.06MPa, and cool to room temperature to obtain paste-like heat resistant agent.

[0086] Preparation of silicone rubber base: Weigh 800g of 110 raw rubber (vinyl content 0.08%), 158g of 110 raw rubber (vinyl content 0.23%), and 550g of fumed silica (fumed silica, specific surface area 200m²). 2 35g of polyvinyl silicone oil (vinyl content 3%), 55g of hydroxyl silicone oil, 40g of methoxy silicone oil, 10g of hydrogen-containing silicone oil (hydrogen content 1.0%), and 1.5g of zinc stearate were sequentially added to a 5L vacuum kneader and stirred at 90°C for 2 hours; the temperature was raised to 120°C and stirred for another hour; then the temperature was raised to 155°C and stirred for another hour; the temperature was maintained and the mixture was degassed under vacuum for 1 hour at a vacuum degree of -0.06MPa; the mixture was then cooled to below 80°C to obtain the silicone rubber base.

[0087] Take 3g of the above-mentioned paste-like heat resistant agent and 100g of silicone rubber base, and repeatedly refine them evenly on a two-roll mill. Then add 1.6% of the bis(2,4) vulcanizing agent and refine them evenly again. Finally, vulcanize them at 115℃ for 300s in a flat vulcanizing machine to obtain heat-resistant cable accessory silicone rubber. Test the performance, and the test results are shown in Table 2.

[0088] Example 1 used only hydroxyl silicone oil as an anti-structuring agent. Example 2, based on Example 1, modified the process by using a mixture of hydroxyl silicone oil and methoxyl silicone oil as the anti-structuring agent.

[0089] The difference between Examples 2-5 is that the types of transition metal oxides used are different; Example 2 uses a composite formulation of cerium oxide, titanium oxide, and iron oxide; Example 3 uses only cerium oxide; Example 4 uses only titanium oxide; and Example 5 uses only iron oxide.

[0090] Comparative Examples 1-5 were designed to examine the effect of not adding polyvinyl silicone oil, and they correspond one-to-one with Examples 1-5 (i.e., Comparative Example 1 corresponds to Example 1, Comparative Example 2 corresponds to Example 2, and so on). Specifically, each comparative example did not add polyvinyl silicone oil (vinyl content 3%) compared to its corresponding example, while the remaining components and conditions remained completely identical.

[0091] Comparative Examples 6-9 were designed to examine the effects of not employing a step-by-step processing method. They correspond one-to-one with Examples 2-5 (i.e., Comparative Example 6 corresponds to Example 2, Comparative Example 7 corresponds to Example 3, and so on). Specifically, the only difference between each comparative example and its corresponding example is the processing method: the paste-like heat-resistant agent component is mixed simultaneously with the silicone rubber base during the initial mixing stage (one-step method). The remaining formulation components are exactly the same as those in the corresponding examples.

[0092] Table 1 Sample Design Table

[0093]

[0094] The performance of the silicone rubber samples prepared in the embodiments and comparative examples of this invention was tested according to national standards. The specific test items and methods are as follows: hardness test was conducted according to GB / T 531.1-2008; tensile strength and elongation test were conducted according to GB / T528-2009; hot air aging test was conducted according to GB / T 3512-2014 / ISO 188:2011 standard, with test conditions set at 250℃ and aging for 14 days.

[0095] Table 2 Comparison of Mechanical Properties Before and After Hot Air Aging Test

[0096]

[0097] Experimental data from Examples 1-5 show that the polyvinyl silicone oil synergistic with phenyl silicone oil and transition metal oxide formulation of the present invention can give silicone rubber superior high-temperature aging resistance. After accelerated aging tests at 250℃ for 14 days, the changes in tensile strength and elongation of the sample samples were generally controlled within 20%.

[0098] Comparing the heat aging test data of Examples 2-5, it was found that Example 3 (using cerium oxide) exhibited the best heat resistance stability: its mechanical property degradation rate after aging was significantly lower than that of Example 2 (cerium oxide / titanium oxide / iron oxide composite formulation), Example 4 (titanium oxide), and Example 5 (iron oxide). This result indicates that cerium oxide has a better effect on improving the high-temperature aging resistance of silicone rubber than other transition metal oxides.

[0099] The comparison between Comparative Example 1 and Comparative Example 2, and Example 1 and Example 2 shows that the silicone rubber using the hydroxyl silicone oil / methoxy silicone oil compound system (Comparative Example 2, Example 2) has better high-temperature aging resistance than the silicone rubber using only hydroxyl silicone oil (Comparative Example 1, Example 1).

[0100] By comparing the experimental data of Comparative Examples 1-5 with those of the corresponding Examples 1-5, it was found that the comparative sample without added polyvinyl silicone oil (transition metal oxide + phenyl silicone oil), after aging under the same conditions, generally showed a change rate of tensile strength and elongation at break exceeding 30%. This result verifies the synergistic anti-aging effect of polyvinyl silicone oil, phenyl silicone oil, and transition metal oxide, which is significantly better than the binary component system (transition metal oxide + phenyl silicone oil).

[0101] Comparing the experimental data of Comparative Examples 6-9 with those of Examples 2-5 revealed that the examples employing a stepwise processing method (i.e., first preparing a paste-like heat-resistant agent containing phenyl silicone oil and transition metal oxides separately, and then mixing them) exhibited a higher performance retention rate after aging than the one-step mixing method (Comparative Examples 5-8). This performance difference indicates that the stepwise processing method can improve the high-temperature aging resistance of silicone rubber. Analysis suggests that this improvement is mainly due to the stepwise process enabling a more uniform dispersion of the heat-resistant agent components (including phenyl silicone oil and transition metal oxides) within the silicone rubber matrix.

Claims

1. A heat-resistant cable accessory silicone rubber compound, characterized in that, By weight, it includes: 100 parts of raw silicone rubber, 30-80 parts of silica, 1-10 parts of polyvinyl silicone oil, 2-13 parts of transition metal oxides, 0.05-0.8 parts of phenyl silicone oil, 5-18 parts of anti-structuring agent, 0.5-3 parts of hydrogen-containing silicone oil, and 0.1-0.3 parts of internal release agent.

2. The silicone rubber compound for heat-resistant cable accessories according to claim 1, characterized in that, By weight, it includes: 100 parts of raw silicone rubber, 35-70 parts of silica, 2-8 parts of polyvinyl silicone oil, 4-12 parts of transition metal oxides, 0.08-0.6 parts of phenyl silicone oil, 6-16 parts of anti-structuring agent, and 0.6-2.5 parts of hydrogen-containing silicone oil.

3. The silicone rubber compound for heat-resistant cable accessories according to claim 1, characterized in that, By weight, it includes: 100 parts of raw silicone rubber, 40-60 parts of silica, 3-7 parts of polyvinyl silicone oil, 6-10 parts of transition metal oxides, 0.1-0.5 parts of phenyl silicone oil, 7-14 parts of anti-structuring agent, and 0.7-2 parts of hydrogen-containing silicone oil.

4. The silicone rubber compound for heat-resistant cable accessories according to any one of claims 1 to 3, characterized in that, The anti-structural agent includes hydroxyl silicone oil and methoxy silicone oil, wherein the amount of hydroxyl silicone oil is 4-8 parts and the amount of methoxy silicone oil is 3-6 parts.

5. The silicone rubber compound for heat-resistant cable accessories according to any one of claims 1 to 3, characterized in that, The silicone rubber raw material is vinyl-terminated methyl vinyl raw material with a vinyl content of 0.03-0.3% and a molecular weight of 50-70w; the silica is fumed silica with a specific surface area of ​​200-300m². 2 / g.

6. The silicone rubber compound for heat-resistant cable accessories according to any one of claims 1 to 3, characterized in that, The vinyl content of the polyvinyl silicone oil is 3.0-10.0%.

7. The heat-resistant cable accessory silicone rubber compound according to any one of claims 1 to 3, characterized in that, The transition metal oxide is one or more of cerium oxide, titanium oxide, and iron oxide.

8. The silicone rubber compound for heat-resistant cable accessories according to any one of claims 1 to 3, characterized in that, The hydrogen content of the hydrogen-containing silicone oil is 1.0-3.0%; the internal release agent is any one of zinc stearate, stearic acid, and C16.

9. A method for preparing a heat-resistant cable accessory silicone rubber compound according to any one of claims 1-8, characterized in that, The preparation method includes the following steps: S1: The aforementioned parts by weight of raw silicone rubber, transition metal oxide, and phenyl silicone oil are put into a kneader for intensive mixing, degassing, and cooling to obtain a paste-like heat resistant agent; S2: The aforementioned parts by weight of raw silicone rubber, silica, polyvinyl silicone oil, methoxy silicone oil, hydroxyl silicone oil, hydrogen-containing silicone oil, and internal release agent are put into a kneader for intensive mixing, blending, degassing, and cooling to obtain silicone rubber base rubber. S3: Mix the aforementioned paste-like heat-resistant agent with silicone rubber base; S4: Add 1.6% of the 24-dichlorodiphenyl ether vulcanizing agent, mix evenly, and vulcanize at 115°C for 300 seconds in a flat vulcanizing machine.

10. The method for preparing the heat-resistant cable accessory silicone rubber compound according to claim 9, characterized in that, The mixing conditions include: a temperature of 30-90℃ and a time of 1-8 hours; the blending conditions include: a temperature of 70-155℃ and a time of 0.5-3 hours; the degassing conditions include: a vacuum degree of -0.03~-0.08MPa, a degassing temperature of 100-160℃, and a degassing time of 0.5-3 hours; the mixing conditions include: a temperature of 15-30℃ and a time of 0.5-1 hour.

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