A semi-conductive insulating shielding rubber and its preparation method

Abstract

This invention relates to the field of cables, specifically to a semi-conductive insulating shielding rubber and its preparation method. The semi-conductive insulating shielding rubber comprises the following components in parts by weight: 100 parts ethylene / octene copolymer elastomer, 5-9 parts activated zinc oxide, 5-6 parts methyl methacrylate, 1-1.2 parts bis(tert-butylperoxyisopropyl)benzene, and 0.2-0.5 parts 1,6-bis(N,N) / —Dibenzothiazole carbamoyl disulfide)-hexane, 2-3 parts dibasic lead stearate, 2-3 parts microcrystalline wax, 2-3 parts processing aids, 1-2 parts antioxidant RD, 1-2 parts antioxidant MB, 20-25 parts softener, 40-60 parts conductive carbon black, 15-18 parts nano-calcium carbonate. This invention utilizes inexpensive, high-quality, mechanically superior, and easily processable POE rubber. A multi-component vulcanization system consisting of ZDMA, BIPB, and WY98 was synthesized using an in-situ synthesis method, significantly improving the elasticity, mechanical strength, curl resistance, and dynamic fatigue resistance of the shielding rubber.

Description

Technical Field

[0001] This invention relates to the field of cables, and more specifically to a semi-conductive insulating shielding rubber and its preparation method. Background Technology

[0002] Currently, the semi-conductive insulating shielding rubber (hereinafter referred to as shielding rubber) used in dynamic cables such as 10kV-35kV ethylene propylene rubber insulated medium-voltage reel cables and torsion-resistant wind power cables is made of ethylene vinyl acetate (EVA) as the skeleton material. It is not only expensive and has poor processing performance (sticking to rollers), but also has poor elasticity, mechanical strength (tensile strength approximately 6MPa, elongation approximately 200%), bending resistance, and dynamic fatigue resistance. Under repeated bending and torsion conditions, the semi-conductive insulating shielding layer is prone to cracking and splitting, causing it to lose its shielding function, such as a uniform electric field and the formation of an equipotential body. This leads to increased insulation discharge, cable breakdown, and other problems, affecting the cable's service life. Summary of the Invention

[0003] The technical problem to be solved by the present invention is that the existing semi-conductive insulating shielding rubber for dynamic cables is not only expensive and has poor processing performance, but also has poor elasticity, mechanical strength, bending resistance and dynamic fatigue resistance. The purpose is to provide a semi-conductive insulating shielding rubber and its preparation method to solve the above problems.

[0004] This invention is achieved through the following technical solution:

[0005] A semi-conductive insulating shielding rubber comprises the following components in parts by weight: 100 parts ethylene / octene copolymer elastomer, 5-9 parts active zinc oxide, 5-6 parts methyl methacrylate, 1-1.2 parts bis(tert-butylperoxyisopropyl)benzene, 0.2-0.5 parts 1,6-bis(N,N′-dibenzothiazole carbamoyl dithio)hexane, 2-3 parts dibasic lead stearate, 2-3 parts microcrystalline wax, 2-3 parts processing aids, 1-2 parts antioxidant RD, 1-2 parts antioxidant MB, 20-25 parts softener, 40-60 parts conductive carbon black, and 15-18 parts nano calcium carbonate.

[0006] This invention uses ethylene / octene copolymer (POE) as the main raw material. Because POE has crystalline ethylene chains, amorphous ethylene and octene long chains, and a very narrow relative molecular mass distribution and short branching distribution, it possesses excellent physical and mechanical properties, with overall performance superior to EPDM (ethylene propylene diene monomer rubber). It exhibits high elasticity, high strength, thermal stability, excellent heat aging resistance, weather resistance and flexibility, high elongation, good low-temperature performance, and excellent flowability. Semi-conductive insulating shielding rubber prepared using POE possesses excellent flexibility, elasticity, mechanical strength, heat aging resistance, bending resistance, and dynamic fatigue resistance, thereby further ensuring the electrical performance of the cable and significantly extending the service life of dynamic cables.

[0007] This invention utilizes zinc methacrylate (ZDMA) synthesized in situ from active zinc oxide (ZnO) and methyl methacrylate (MAA) as a vulcanizing agent. During the compounding process, ZnO and MAA react in situ to generate ZDMA. In the presence of peroxides, ionic crosslinking bonds (-COO-Zn-OOC-) are formed on the POE backbone and side chains. These ionic bonds combine the heat resistance of -CC- bonds with the high mechanical strength, good flexibility, and excellent dynamic resistance of polysulfide bonds. This is crucial for semi-conductive shielding materials where excessive filler can degrade the flexibility and dynamic properties of the compound. Simultaneously, ZnO also acts as an antioxidant, neutralizing the hydroperoxides generated during POE oxidation, thereby improving the polymer's aging resistance.

[0008] Bis(tert-butylperoxyisopropyl)benzene (BIPB) serves as both an initiator and a vulcanizing agent. Firstly, BIPB homolytically cleaves at high temperatures to form two alkoxy radicals. These alkoxy radicals abstract hydrogen atoms from the polymer chain, and the radicals from two adjacent polymer chains combine to form carbon-carbon (-CC-) bonds, thus demonstrating the role of a vulcanizing agent. Secondly, under the influence of the alkoxy radicals generated by BIPB, ZDMA reacts to form polymerized ZDMA, which is then grafted onto the POE molecular chain, forming ionic crosslinks. This improves the flexibility, physical and mechanical properties, and dynamic fatigue resistance of POE.

[0009] 1,6-Bis(N,N′-dibenzothiazole carbamoyl dithio)-hexane (abbreviated as WY988) is a novel multifunctional and efficient crosslinking agent. It contains benzothiazole groups and thiohexyl groups for post-curing stability. This special structure can participate in crosslinking during the curing process of rubber compounds. When it works together with ZDMA, it forms a complex ionic long chain bond containing -SS- bonds, which connects POE molecules to form a stable crosslinking network, further improving the elasticity and softness of POE.

[0010] The four materials ZnO, MAA, BIPB, and WY988 form four interpenetrating network structures through synergy: ionic bonds, carbon-carbon bonds, disulfide bonds, and sulfur-containing ionic bonds. By fully utilizing the free rotational property of the -COO-Zn-OOC- bonds, the softness and elasticity of the rubber are significantly improved. Furthermore, the density and proportion of crosslinking bonds can be controlled by adjusting the amount and ratio of each component, thereby achieving the desired performance indicators.

[0011] Dibasic lead stearate, as a surfactant and lubricant, activates the surface of conductive carbon black, nano-fillers, etc., which helps disperse the fillers and makes the rubber properties more uniform. In addition, it has excellent lubricity, which can improve the processing fluidity and ensure a smooth and glossy rubber surface.

[0012] Microcrystalline wax is a refined synthetic wax with near-microcrystalline properties. It has good gloss, high melting point, and light color. Its compact structure acts as a lubricant and processing aid, which helps to improve the dispersion and extrusion processing performance of materials.

[0013] Antioxidant MB is a preventative antioxidant whose main function is to decompose hydroperoxides in the oxidation chain reaction process. It reacts with hydroperoxides to generate non-free stable compounds, preventing chain initiation and delaying the oxidation reaction. Antioxidant RD is a free radical scavenger. The NH functional group in antioxidant RD captures free radicals to terminate chain reactions, thereby preventing rubber aging. The synergistic effect of the two effectively improves the performance of rubber and can effectively inhibit oxidation, heat aging, and weather aging under harsh conditions.

[0014] Conductive carbon black increases the conductivity of rubber compounds. When the distance between conductive carbon black particles in the polymer is less than a few amperes (1A = 0.1nm), a voltage difference can be generated. This voltage difference causes the π electrons of the carbon black particles to move through the current via chain transmission. By adding a large amount of conductive carbon black, the distance between the carbon black particles can reach the conditions for conduction. At the same time, as a filler and reinforcing agent, it can effectively improve the physical and mechanical properties and aging resistance of the rubber compound, while also effectively increasing the volume of the rubber and reducing production costs.

[0015] Nano-calcium carbonate, as a reinforcing and modifying filler in rubber production, can increase the volume of rubber products and reduce the production cost of rubber, while also increasing the stability of structural dimensions and shape.

[0016] Furthermore, the processing aid is designated WB222. Processing aid WB222 improves the flowability, extrusion processing performance, and mold release properties of the rubber compound.

[0017] Furthermore, the ethylene / octene copolymer elastomer is designated as POE8150 or POE8100.

[0018] Furthermore, the softener is No. 500 paraffin oil. No. 500 paraffin oil, as a softener, has good heat resistance. When added to rubber, it can reduce the processing viscosity of the rubber compound, increase the flowability of the rubber compound, improve the rubber compounding and extrusion processing performance, improve the plasticity of the rubber compound, and improve the cold resistance.

[0019] The preparation method for the above-mentioned semiconductive insulating shielding rubber includes the following steps:

[0020] S1. Preparation of vulcanizing agent masterbatch: Weigh the vulcanizing agent bis(tert-butylperoxyisopropyl)benzene and 1,6-bis(N,N′-dibenzothiazolecarbamoyl dithio)-hexane according to the formula ratio, add 2-5 times the total weight of bis(tert-butylperoxyisopropyl)benzene and 1,6-bis(N,N′-dibenzothiazolecarbamoyl dithio)-hexane nano-calcium carbonate, stir and mix in a mixer for 10-15 minutes, and then put it into a batching bucket for use. The speed of the mixer should not exceed 50 rpm.

[0021] S2. In-situ synthesis of zinc methacrylate (ZDMA): After mixing ethylene / octene copolymer elastomer in a mixer for 1 min, add 0.7-1.0 times the amount of active zinc oxide equivalent to methyl methacrylate and mix for 1-1.5 min. Then add methyl methacrylate and mix for 3.5-5 min. During this mixing process, the temperature of the mixer is controlled at 80-95℃ and the speed is controlled at 25-28 rpm.

[0022] S3. Mixing: After step 2 is completed, continue to add the remaining active zinc oxide, dibasic lead stearate, conductive carbon black, softener, nano calcium carbonate, antioxidant RD, antioxidant MB, microcrystalline wax, and processing aids to the internal mixer. Mix for 3-4 minutes and then discharge the glue. The speed of the internal mixer is controlled at 30-35 r / min, the mixing temperature is 130-140℃, and the discharge temperature is controlled below 140℃.

[0023] S4. Filtering impurities: Filter the rubber compound after S3 mixing using a 100-mesh stainless steel filter to remove impurities;

[0024] S5. Sheeting: The filtered rubber material is rolled into sheets using a three-roll calender and stored for 24 hours.

[0025] S6. Vulcanization: The film formed in step 5 is added to the vulcanizing agent masterbatch prepared in step S1 and then mixed. The mixing time is 0.8 to 1 min, the internal mixer rotor speed is 25 to 30 r / min, and the mixing temperature is 100 to 120℃.

[0026] S7, Slicing: The rubber compound after S6 is mixed is rolled by a three-roll calender to form strips of rubber with a thickness of 0.8-1mm and a width of 150-160mm.

[0027] Furthermore, in step S7, the strip rubber is placed for 24 hours before being used for extrusion molding.

[0028] After the strip rubber formed in step S7 is left to stand for a longer period of time, on the one hand, the vulcanizing agent, activator, accelerator, antioxidant and other additives in the rubber will be further dispersed evenly; on the other hand, the stress generated during the mixing process can be eliminated, which is beneficial to molding and processing and performance improvement.

[0029] In step 3, the internal mixer rotor speed is 30-35 r / min and the mixing temperature is 130-140℃. Mixing at this speed and temperature can remove moisture and small molecule volatiles from the material.

[0030] In step 6, the internal mixer rotor speed is 25-30 r / min and the mixing temperature is 100-120℃. Within this speed and temperature range, scorching of the rubber compound can be prevented, ensuring the quality of the rubber compound. This invention ensures the mixing and compounding of raw materials by setting the basic parameters of the internal mixer, thereby ensuring the quality of rubber production.

[0031] This invention is based on formulation innovation. By using inexpensive and high-quality ethylene / octene copolymer elastomer (POE) to replace ethylene vinyl acetate (EVA) as the skeleton material, the compound's mixing and processing performance is improved and the cost is greatly reduced.

[0032] This invention uses active zinc oxide (ZnO) and methyl methacrylate (MAA) to synthesize ZDMA in situ at a temperature of 80-95℃ as a vulcanizing agent. The ionic crosslinking bonds generated during vulcanization combine the heat resistance of rigid -CC- bonds with the advantages of high mechanical strength, good flexibility, and excellent dynamic resistance of polysulfide bonds, thereby improving the lifespan of dynamic cables.

[0033] This invention uses bis(tert-butylperoxyisopropyl)benzene (BIPB) as both an initiator and a vulcanizing agent. It exhibits higher and better initiation effects and vulcanization efficiency than the commonly used dicumyl peroxide (DCP). The BIPB initiator enables ZDMA to generate more ionic bonds with higher efficiency. At the same time, by adjusting the amount of BIPB, a suitable ratio of ionic bonds to carbon-carbon covalent bonds can be obtained to achieve better overall performance.

[0034] This invention will incorporate 1,6-bis(N,N) / —Dibenzothiazole carbamoyl dithiohexane (WY988) is used as a crosslinking agent. It contains benzothiazole groups and thiohexyl groups for post-curing stability. This special structure can participate in crosslinking during the curing process of rubber. After working together with ZDMA, it forms a complex ionic long chain bond to connect POE molecules, forming a stable crosslinking network, which further improves the elasticity and softness of POE.

[0035] This invention improves the formulation of anti-aging agents. On the one hand, anti-aging agent RD can work synergistically with anti-aging agent MB to improve the anti-aging properties of rubber. On the other hand, anti-aging agent MB can work synergistically with dibasic lead stearate to achieve protection against vapor.

[0036] This invention uses nano-calcium carbonate, which acts as both a rubber reinforcing agent and a rubber filler. On the one hand, it improves the performance of the rubber, and on the other hand, it increases the volume of the rubber, thus greatly reducing production costs.

[0037] The present invention, through a related preparation method, can achieve thorough mixing of rubber raw materials, ensuring the realization of the above-mentioned rubber functions, and is simple and convenient to operate.

[0038] This invention ensures the quality of rubber compounding and guarantees the performance of rubber by using vulcanizing agent masterbatch and conductive carbon black masterbatch sheets, and by multiple mixing and rolling processes.

[0039] This invention ensures the performance of the rubber by allowing it to stand for a period of time before extruding, thereby further guaranteeing the vulcanization of the rubber.

[0040] This invention divides the rubber compound mixing process into three stages: The first stage involves masterbatch preparation, primarily preparing the vulcanizing agent masterbatch, which ensures more uniform dispersion of the vulcanizing agent. The second stage involves in-situ synthesis and mixing: firstly, POE and ZnO / MAA are added to an internal mixer to synthesize ZDMA in situ under specific process conditions; then, materials other than the vulcanizing agent masterbatch are added according to process requirements for mixing, filtering, calendering, and slicing followed by cooling and standing for 24 hours. The third stage involves vulcanization: the mixed rubber from the second stage is added to an internal mixer and mixed for 2-3 minutes, followed by mixing with the vulcanizing agent masterbatch. The multi-stage mixing method increases the viscosity of the rubber compound during cooling and standing, improving the shear and dispersion mixing effect during mixing, enhancing the dispersion of fillers and compounding agents such as carbon black, and improving the physical and mechanical properties of the vulcanized rubber, thereby improving the quality of the mixed rubber.

[0041] Further, in step S2, zinc methacrylate (ZDMA) is synthesized in situ: ethylene / octene copolymer elastomer is added to a mixer and mixed for 1 min, then 0.8 to 0.9 times the amount of methyl methacrylate equivalent of active zinc oxide is added and mixed for 1 to 1.5 min, then methyl methacrylate is added and mixed for 3.5 to 5 min. During this mixing process, the temperature of the mixer is controlled at 85-90℃ and the rotation speed is controlled at 26 to 27 rpm.

[0042] Further, in step S5, the filtered rubber material is rolled into a sheet with a thickness of 1.2-1.5 mm using a three-roll calender and stored for 24 hours.

[0043] Furthermore, in step 7, the thickness of the strip rubber is 0.9–1.0 mm, more preferably 0.8–0.9 mm, and the width is 155–160 mm.

[0044] Furthermore, the processing aid in S3 is WB222, the ethylene / octene copolymer elastomer is POE8150 or POE8100, and the softener is No. 500 paraffin oil.

[0045] To address the problems of existing semi-conductive insulating shielding rubber for 10kV-35kV ethylene propylene insulated medium-voltage dynamic cables, such as high price, poor processing performance (sticking to rollers), and poor elasticity, mechanical strength, bending resistance, and dynamic fatigue resistance, which easily crack and split after repeated bending and twisting under operating conditions, leading to cable scrapping, this invention provides a semi-conductive insulating shielding rubber and its preparation method. Through new materials, a new formulation system, and a preparation process, the cost is reduced, the processing performance is improved, and the problems of poor elasticity, mechanical strength, bending resistance, and dynamic fatigue resistance of the semi-conductive insulating shielding rubber are solved, thereby improving its dynamic fatigue resistance and extending the service life of the cable.

[0046] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0047] 1. The present invention provides a semi-conductive insulating shielding rubber by using inexpensive and high-quality ethylene / octene copolymer elastomer (POE) instead of ethylene vinyl acetate (EVA) as the skeleton material, which improves the mixing and processing performance of the rubber compound and greatly reduces the cost.

[0048] 2. This invention discloses a semi-conductive insulating shielding rubber that uses bis(tert-butylperoxyisopropyl)benzene (BIPB) as both an initiator and a vulcanizing agent. It exhibits higher and better initiation effects and vulcanization efficiency than commonly used dicumyl peroxide (DCP). The BIPB initiator enables ZDMA to generate more ionic bonds with higher efficiency. Furthermore, by adjusting the amount of BIPB, a suitable ratio of ionic bonds to carbon-carbon covalent bonds can be obtained to achieve better overall performance.

[0049] 3. This invention provides a semi-conductive insulating shielding rubber through an improved formulation of anti-aging agents. On one hand, anti-aging agent RD can synergistically work with anti-aging agent MB to improve the rubber's anti-aging properties. On the other hand, anti-aging agent MB can synergistically work with dibasic lead stearate to achieve protection against vapor.

[0050] 4. The present invention provides a semi-conductive insulating shielding rubber using nano-calcium carbonate, which acts as both a rubber reinforcing agent and a rubber filler. On the one hand, it improves the performance of the rubber, and on the other hand, it increases the volume of the rubber, thus greatly reducing the production cost.

[0051] 5. The present invention provides a method for preparing a semi-conductive insulating shielding rubber by using active zinc oxide (ZnO) and methyl methacrylate (MAA) and adding ZnO in stages to synthesize ZDMA in situ as a vulcanizing agent. The ionic crosslinking bonds generated during vulcanization have the advantages of both the heat resistance of the rigid -CC- bond and the high mechanical strength, good flexibility, and excellent dynamic resistance of the polysulfide bond, thereby improving the life of dynamic cables.

[0052] 6. The preparation method of the semi-conductive insulating shielding rubber of the present invention ensures the mixing quality of the rubber and ensures the performance of the rubber by using vulcanizing agent masterbatch and conductive carbon black masterbatch sheet, and multiple mixing and rolling processes. Attached Figure Description

[0053] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0054] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0056] This invention provides a semi-conductive insulating shielding rubber, comprising the following components in parts by weight: 100 parts ethylene / octene copolymer elastomer, 5-9 parts active zinc oxide, 5-6 parts methyl methacrylate, 1-1.2 parts bis(tert-butylperoxyisopropyl)benzene, 0.2-0.5 parts 1,6-bis(N,N′-dibenzothiazole carbamoyl dithio)hexane, 2-3 parts dibasic lead stearate, 2-3 parts microcrystalline wax, 2-3 parts processing aids, 1-2 parts antioxidant RD, 1-2 parts antioxidant MB, 20-25 parts softener, 40-60 parts conductive carbon black, and 15-18 parts nano-calcium carbonate.

[0057] Preferably, the processing aid is of type WB222.

[0058] Preferably, the ethylene / octene copolymer elastomer is of type POE8150 or POE8100.

[0059] Preferably, the softener is No. 500 paraffin oil.

[0060] Another aspect of the present invention provides a method for preparing the above-mentioned semiconductive insulating shielding rubber, such as... Figure 1 The steps shown are as follows:

[0061] Step 1: Preparation of vulcanizing agent masterbatch: Weigh the crosslinking agents BIPB and WY988 according to the formula ratio, add them to 2 to 5 times the total weight of nano calcium carbonate in a high-speed mixer and mix for 10 to 15 minutes until uniform. Then, put them into a mixing tank for use.

[0062] In some embodiments, in the above preparation method of the present invention, the weight of nano-calcium carbonate is preferably 2 to 5 times the total weight of BIPB and WY988, and the mixing time is preferably 10 to 15 min.

[0063] In some embodiments, in the above preparation method of the present invention, the weight of nano-calcium carbonate is preferably 2.5 to 3.5 times the total weight of BIPB and WY988, and the mixing time is preferably 11 to 14 min;

[0064] In some embodiments, the weight of nano-calcium carbonate is preferably 2 to 3 times the total weight of BIPB and WY988, and the mixing time is preferably 12 to 13 minutes.

[0065] Step 2: In-situ synthesis of ZDMA: Add POE to the internal mixer and mix for 1 min. Then add 0.7-1.0 times the MAA equivalent of ZnO and mix for 1-1.5 min. Then add an equivalent amount of MAA and mix for 3.5-5 min. During this period, the temperature of the internal mixer should be controlled at 80-95℃ and the speed should be controlled at 25-28 rpm. Pay attention to the temperature of the mixing chamber of the internal mixer during mixing to ensure the quality of the in-situ synthesized ZDMA.

[0066] In some embodiments, in the preparation method of the present invention, the amount of ZnO added is 0.8 to 0.9 times the MAA equivalent, the temperature of the internal mixer is controlled at 85-90℃, and the rotation speed is controlled at 26 to 27 rpm.

[0067] Step 3: After step 2 is completed, continue to add the remaining ZnO, dibasic lead stearate, conductive carbon black, paraffin oil, nano calcium carbonate, antioxidant, microcrystalline wax, and WB222. Mix for 3.0 to 4 minutes and then discharge the glue. Control the speed at 30-35 rpm and the discharge temperature below 140℃.

[0068] In some embodiments, in the preparation method of the present invention, after mixing for 3.5 to 4 minutes, the glue is discharged, the rotation speed is controlled at 32-34 rpm, and the discharge temperature is 135-140℃.

[0069] Step 4: Filter the mixed material through a 100-mesh stainless steel filter to remove impurities;

[0070] Step 5: Use a three-roll calender to roll the filtered rubber compound into a sheet with a thickness of 1.2-1.5mm;

[0071] In some embodiments, the thickness of the rolling process described above is preferably 1.3-1.4 mm.

[0072] Step 6: Add the film formed in step 5 to the vulcanizing agent masterbatch and then perform a second mixing. The mixing time is 0.8 to 1 minute.

[0073] In some embodiments, the mixing time in step 6 above is preferably 0.9 to 1.0 min;

[0074] In some embodiments, the mixing time in step 6 above is preferably 0.8 to 0.9 min.

[0075] Step 7: Roll the secondary mixed rubber compound through a three-roll calender to form strips of rubber with a thickness of 0.8-1mm and a width of 150-160mm.

[0076] In some embodiments, the thickness of the strip rubber in step 7 of the present invention is preferably 0.9 to 1.0 mm;

[0077] In some embodiments, the thickness of the strip rubber in step 7 of the present invention is preferably 0.8 to 0.9 mm;

[0078] In some embodiments, the width of the strip rubber in step 7 of the present invention is preferably 155-160 mm;

[0079] In some embodiments, the width of the strip rubber in step 7 of the present invention is preferably 152-158 mm.

[0080] To further improve the tensile strength and elongation of the rubber, refine and improve the rubber formula, and better ensure the service life of the cable, the strip rubber in step S7 is placed for 24 hours before being extruded to form the corresponding shape. By placing the rubber for a period of time before extrusion, the vulcanization of the rubber can be further guaranteed, thus ensuring the performance of the rubber.

[0081] This invention utilizes inexpensive, high-quality POE rubber with excellent mechanical properties and easy processing. A multi-component vulcanization system consisting of ZDMA (ZnO / MAA), BIPB, and WY988 is synthesized in situ, resulting in different vulcanization mechanisms and processes, and the formation of various chemical bonds. These bonds synergistically significantly improve the elasticity, mechanical strength, curl resistance, and dynamic fatigue resistance of the shielding rubber, thereby ensuring a uniform electric field distribution in medium-voltage cables, preventing electric field distortion, and improving cable quality and service life. Furthermore, the semi-conductive insulating shielding rubber described in this invention possesses excellent conductivity and quality stability, making it suitable not only for cables but also for other fields, demonstrating significant practical value and application prospects. In addition, the preparation method provided by this invention is simple, readily available, and operates under mild conditions, making it suitable for large-scale industrial production.

[0082] Experiments show that the shielding rubber produced by this invention has a volume resistivity ≤50Ω·m, tensile strength TB≥10.0MPa, elongation at break EB≥350%, and the shielding rubber test piece passed 2 million flexural tests without cracks or damage on the sample surface.

[0083] Example 1

[0084] The following ingredients were selected: 1000g POE, 50g active zinc oxide, 50g methyl methacrylate, 10g bis(tert-butylperoxyisopropyl)benzene, 3g 1,6-bis(N,N′-dibenzothiazole carbamoyl dithio)-hexane (abbreviated as WY988), 30g dibasic lead stearate, 20g microcrystalline wax, 20g processing aid WB222, 15g antioxidant RD, 10g antioxidant MB, 200g No. 500 paraffin oil, 500g conductive carbon black, and 150g nano calcium carbonate.

[0085] According to the above-mentioned method for preparing a semi-conductive insulating shielding rubber, 10g of bis(tert-butylperoxyisopropyl)benzene, 3g of 1,6-bis(N,N′-dibenzothiazole carbamoyl dithio)-hexane (abbreviated as WY988) and 2.5 times the amount of nano-calcium carbonate are mixed for 10 minutes to prepare a masterbatch; then POE is kneaded for 1 minute, 0.7-1.0 times the amount of MAA equivalent of ZnO is added, and kneaded for 1-1.5 minutes, followed by the addition of MAA and kneading for 3.5-5 minutes. During this period, the temperature is controlled at 80-95℃ and the rotation speed is controlled at 25-28 rpm; the remaining ZnO, dibasic lead stearate, conductive carbon black, and stone are then added. Wax oil, nano calcium carbonate, antioxidant, microcrystalline wax, and WB222 are mixed for 3.0-4 minutes and then discharged at a speed of 30-35 rpm and a discharge temperature below 140℃. The mixed mixture is then filtered through a 100-mesh stainless steel filter to remove impurities. The filtered rubber compound is then rolled into sheets with a thickness of 1.2-1.5 mm using a three-roll calender and stored for 24 hours. The rubber sheets are then mixed a second time with vulcanizing masterbatch for 0.8-1 minutes. The second-mixed rubber compound is then rolled through a three-roll calender to form strips of rubber with a thickness of 0.8-1 mm and a width of 150-160 mm.

[0086] Experiments show that the semiconductive rubber produced by this invention has a volume resistivity of 43 Ω·m, a tensile strength of TB of 11.5 MPa, and an elongation at break of EB of 440%. The shielding rubber test piece passed 2 million flexural tests, and the sample surface showed no cracks or damage.

[0087] Example 2

[0088] The following ingredients were selected: 1000g POE, 70g active zinc oxide, 55g methyl methacrylate, 11g bis(tert-butylperoxyisopropyl)benzene, 4g 1,6-bis(N,N′-dibenzothiazole carbamoyl dithio)-hexane (abbreviated as WY988), 25g dibasic lead stearate, 25g microcrystalline wax, 25g processing aid WB222, 10g antioxidant RD, 12g antioxidant MB, 220g No. 500 paraffin oil, 550g conductive carbon black, and 160g nano calcium carbonate.

[0089] According to the above-mentioned method for preparing a semi-conductive insulating shielding rubber, 11g of bis(tert-butylperoxyisopropyl)benzene, 4g of 1,6-bis(N,N′-dibenzothiazole carbamoyl dithio)-hexane (abbreviated as WY988) and 2.5 times the amount of nano-calcium carbonate are mixed for 10 minutes to prepare a masterbatch; then POE is kneaded for 1 minute, 0.7-1.0 times the amount of MAA equivalent of ZnO is added, and kneaded for 1-1.5 minutes. Then MAA is added and kneaded for 3.5-5 minutes. During this period, the temperature is controlled at 80-95℃ and the rotation speed is controlled at 25-28 rpm. The remaining ZnO, dibasic lead stearate, conductive carbon black, and paraffin are then added. Oil, nano-calcium carbonate, antioxidant, microcrystalline wax, and WB222 are mixed and kneaded for 3.0–4 minutes, then discharged at a speed controlled at 30–35 rpm and a discharge temperature controlled below 140℃. The mixed material is then filtered through a 100-mesh stainless steel filter to remove impurities. The filtered rubber compound is then rolled into sheets with a thickness of 1.2–1.5 mm using a three-roll calender and stored for 24 hours. The rubber sheets are then mixed a second time with vulcanizing agent masterbatch for 0.8–1 minute. The second-mixed rubber compound is then rolled through a three-roll calender to form strips of rubber with a thickness of 0.8–1 mm and a width of 150–160 mm.

[0090] Experiments show that the semiconductive rubber produced by this invention has a volume resistivity of 36 Ω·m, a tensile strength of TB of 12.0 MPa, and an elongation at break of EB of 435%. The shielding rubber test piece passed 2 million flexural tests, and the sample surface showed no cracks or damage.

[0091] Example 3

[0092] The following ingredients were selected: 1000g POE, 90g active zinc oxide, 60g methyl methacrylate, 12g bis(tert-butylperoxyisopropyl)benzene, 5g 1,6-bis(N,N′-dibenzothiazole carbamoyl dithio)-hexane (abbreviated as WY988), 30g dibasic lead stearate, 30g microcrystalline wax, 30g processing aid WB222, 15g antioxidant RD, 15g antioxidant MB, 250g No. 500 paraffin oil, 600g conductive carbon black, and 180g nano calcium carbonate.

[0093] According to the above-mentioned method for preparing a semi-conductive insulating shielding rubber, 12g of bis(tert-butylperoxyisopropyl)benzene, 5g of 1,6-bis(N,N′-dibenzothiazole carbamoyl dithio)-hexane (abbreviated as WY988) and 2.5 times the amount of nano-calcium carbonate are mixed for 10 minutes to prepare a masterbatch; then POE is kneaded for 1 minute, 0.7-1.0 times the amount of MAA equivalent of ZnO is added, and kneaded for 1-1.5 minutes. Then MAA is added and kneaded for 3.5-5 minutes. During this period, the temperature is controlled at 80-95℃ and the rotation speed is controlled at 25-28 rpm. The remaining ZnO, dibasic lead stearate, conductive carbon black, and stone are then added. Wax oil, nano calcium carbonate, antioxidant, microcrystalline wax, and WB222 are mixed for 3.0-4 minutes and then discharged at a speed of 30-35 rpm and a discharge temperature below 140℃. The mixed material is then filtered through a 100-mesh stainless steel filter to remove impurities. The filtered rubber compound is then rolled into sheets with a thickness of 1.2-1.5 mm using a three-roll calender. After 24 hours, the rubber sheets are mixed again with vulcanizing masterbatch for 0.8-1 minutes. The second-mixed rubber compound is then rolled through a three-roll calender to form strips of rubber with a thickness of 0.8-1 mm and a width of 150-160 mm. Experiments show that the semiconductive rubber produced by this invention has a volume resistivity of 24 Ω·m, a peel strength of 25.5 N / cm, a tensile strength of TB of 13.0 MPa, and an elongation at break of EB of 422%. The shielding rubber test piece passed 2 million flexural tests, and the sample surface showed no cracks or damage.

[0094] Test case

[0095] The volume resistivity, tensile strength and elongation at break of the strip rubber prepared in Examples 1-3 were measured according to existing technology, and the surface condition of the strip rubber specimens after passing 2 million flexural tests was examined. The results are shown in Table 1.

[0096] Table 1 shows the test results for strip-shaped rubber.

[0097] Volume resistivity Tensile strength (TB) Elongation at break (EB) Sample surface Example 1 43Ω·m 11.5MPa 440％ No cracks, no damage Example 2 36Ω·m 12.0MPa 435％ No cracks, no damage Example 3 24Ω·m 13.0MPa 422％ No cracks, no damage

[0098] As shown in Table 1, with the simultaneous increase of the amount of each component in the semi-conductive insulating shielding rubber, the elongation at break (EB) of the semi-conductive insulating shielding rubber will decrease relatively, the tensile strength (TB) will increase relatively, and the volume resistivity will decrease relatively. Based on the elongation at break, tensile strength, and volume resistivity of the semi-conductive insulating shielding rubber, this invention optimizes the proportion range of each component in the semi-conductive insulating shielding rubber. The semi-conductive insulating shielding rubber obtained within this range has better overall performance compared with the prior art, and solves the problems that the existing semi-conductive insulating shielding rubber for dynamic cables is not only expensive and has poor processing performance, but also has poor elasticity, mechanical strength, bending resistance, and dynamic fatigue resistance.

[0099] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A semi-conductive insulating shielding rubber, characterized in that, It is composed of the following components in parts by weight: 100 parts ethylene / octene copolymer elastomer, 5-9 parts active zinc oxide, 5-6 parts methyl methacrylate, 1-1.2 parts bis(tert-butylperoxyisopropyl)benzene, 0.2-0.5 parts 1,6-bis(N,N′-dibenzothiazole carbamoyl dithio)hexane, 2-3 parts dibasic lead stearate, 2-3 parts microcrystalline wax, 2-3 parts processing aids, 1-2 parts antioxidant RD, 1-2 parts antioxidant MB, 20-25 parts softener, 40-60 parts conductive carbon black, and 15-18 parts nano calcium carbonate; Zinc methacrylate was synthesized in situ as a vulcanizing agent using an active zinc oxide and methyl methacrylate with the stepwise addition of ZnO. A multi-component vulcanization system is formed by three materials: zinc methacrylate, bis(tert-butylperoxyisopropyl)benzene, and 1,6-bis(N,N′-dibenzothiazole carbamoyl disulfide)-hexane.

2. The semi-conductive insulating shielding rubber according to claim 1, characterized in that, The processing aid is designated as WB222.

3. The semiconductive insulating shielding rubber according to claim 1, characterized in that, The ethylene / octene copolymer elastomer is designated as POE8150 or POE8100.

4. The semi-conductive insulating shielding rubber according to claim 1, characterized in that, The softener is No. 500 paraffin oil.

5. A method for preparing the semiconductive insulating shielding rubber according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Preparation of vulcanizing agent masterbatch: Weigh the vulcanizing agent bis(tert-butylperoxyisopropyl)benzene and 1,6-bis(N,N′-dibenzothiazolecarbamoyl disulfide)-hexane according to the formula ratio, add 2-5 times the total weight of nano-calcium carbonate of bis(tert-butylperoxyisopropyl)benzene and 1,6-bis(N,N′-dibenzothiazolecarbamoyl disulfide)-hexane, stir and mix in a mixer for 10-15 minutes, and then put it into a batching bucket for use. The speed of the mixer should not exceed 50 rpm. S2. In-situ synthesis of zinc methacrylate: After mixing ethylene / octene copolymer elastomer in a mixer for 1 min, add 0.7-1.0 times the amount of active zinc oxide equivalent to methyl methacrylate and mix for 1-1.5 min. Then add methyl methacrylate and mix for 3.5-5 min. During this mixing process, the temperature of the mixer is controlled at 80-95℃ and the speed is controlled at 25-28 rpm. S3. Mixing: After step 2 is completed, continue to add the remaining active zinc oxide, dibasic lead stearate, conductive carbon black, softener, nano calcium carbonate, antioxidant RD, antioxidant MB, microcrystalline wax, and processing aids to the internal mixer. Mix for 3-4 minutes and then discharge the glue. The speed of the internal mixer is controlled at 30-35 r / min, the mixing temperature is 130-140℃, and the discharge temperature is controlled below 140℃. S4. Filtering impurities: Filter the rubber compound after S3 mixing using a 100-mesh stainless steel filter to remove impurities; S5. Sheeting: The filtered rubber material is rolled into sheets using a three-roll calender and stored for 24 hours. S6. Vulcanization: The film formed in step 5 is added to the vulcanizing agent masterbatch prepared in step S1 and then mixed. The mixing time is 0.8 to 1 min, the internal mixer rotor speed is 25 to 30 r / min, and the mixing temperature is 100 to 120℃. S7, Slicing: The rubber compound after S6 is mixed is rolled by a three-roll calender to form strips of rubber with a thickness of 0.8-1mm and a width of 150-160mm.

6. The method for preparing a semiconductive insulating shielding rubber according to claim 5, characterized in that, In step S7, the strip rubber is placed for 24 hours before being used for extrusion molding.

7. The method for preparing a semiconductive insulating shielding rubber according to claim 5, characterized in that, In step S2, zinc methacrylate is synthesized in situ: ethylene / octene copolymer elastomer is added to a mixer and mixed for 1 min. Then, 0.8 to 0.9 times the amount of methyl methacrylate equivalent of active zinc oxide is added and mixed for 1 to 1.5 min. Finally, methyl methacrylate is added and mixed for 3.5 to 5 min. During this mixing process, the temperature of the mixer is controlled at 85-90℃ and the rotation speed is controlled at 26 to 27 rpm.

8. The method for preparing a semiconductive insulating shielding rubber according to claim 5, characterized in that, In step S5, the filtered rubber material is rolled into a sheet with a thickness of 1.2-1.5 mm using a three-roll calender and stored for 24 hours.

9. The method for preparing a semiconductive insulating shielding rubber according to claim 5, characterized in that, In step 7, the thickness of the strip rubber is 0.9-1.0 mm and the width is 155-160 mm.

10. The method for preparing a semiconductive insulating shielding rubber according to claim 5, characterized in that, The processing aid in S3 is WB222, the ethylene / octene copolymer elastomer is POE8150 or POE8100, and the softener is No. 500 paraffin oil.

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