Medium-voltage cable shielding layer rubber compound and preparation method thereof

Abstract

The invention relates to the technical field of rubber compounds for cables, and particularly discloses a medium-voltage cable shielding layer rubber compound and a preparation method thereof. The preparation method comprises the following steps: S1, crushing the ethylene propylene diene monomer in an internal mixer, adding the carbon black, the plasticizer, the anti-aging agent, the flowable agent, the kaolin and the activated zinc oxide, and mixing at 120-130 DEG C; blowing dust, adding stearic acid, a vulcanizing agent and an accelerant, and mixing at 120-130 DEG C to obtain a rubber compound; s2, putting the rubber compound into a double-roller open mill, and carrying out roller covering and roller passing for three times to obtain a medium-voltage cable shielding layer rubber compound; the rubber compound comprises the following raw materials in parts by mass: 100 parts of ethylene propylene diene monomer, 60-70 parts of carbon black, 10-20 parts of a plasticizer, 1-3 parts of an anti-aging agent, 3-4 parts of a flowable agent, 5-8 parts of kaolin, 2-4 parts of activated zinc oxide, 0.5-1 part of stearic acid, 1-4 parts of a vulcanizing agent and 0.5-1 part of an accelerant.

Description

Technical Field

[0001] The invention relates to the technical field of rubber mixes for cables, and specifically discloses a medium-voltage cable shielding layer rubber mix and a preparation method thereof. Background Art

[0002] With the development of industry, various industrial equipment and devices have emerged. Power supply is an indispensable source of power, and shielded cables play an indispensable role in special occasions.

[0003] Since there may be a gap at the contact point between the surface of the cable insulation layer and the sheath layer, cracks are likely to appear on the surface of the insulation layer when the cable is bent, causing partial discharge. Therefore, medium and high voltage power cables of 6kV and above generally need to add a shielding layer to avoid partial discharge.

[0004] In order to improve the performance of the shielding layer rubber, a variety of additives and fillers are often added to the formula, but due to problems such as compatibility and migration, the mechanical properties and life of the rubber are affected. Therefore, it is of great significance to study a medium-voltage cable shielding layer compound with good mechanical properties and good aging resistance and its preparation method. Summary of the invention

[0005] The object of the present invention is to provide a medium voltage cable shielding layer rubber compound and a preparation method thereof, so as to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for preparing a medium voltage cable shielding layer rubber compound, comprising the following steps:

[0007] S1: crush the EPDM rubber in an internal mixer for 30 to 40 seconds; add carbon black, plasticizer, antioxidant, flow agent, kaolin and active zinc oxide, and mix at 120 to 130°C; blow off the dust at the mouth of the internal mixer, the top bolt and the wall of the internal mixer, add stearic acid, vulcanizing agent and accelerator, and continue mixing to 120 to 130°C, and control the heating time to 1 minute to obtain a mixed rubber;

[0008] S2: Put the mixed rubber into a two-roll open mill until the rolls are wrapped, adjust the roll distance to 2 mm, and roll three times to obtain the mixed rubber for the shielding layer of the medium-voltage cable.

[0009] More optimally, the rubber mixture includes the following raw materials, calculated by mass: 100 parts of EPDM rubber, 60-70 parts of carbon black, 10-20 parts of plasticizer, 1-3 parts of antioxidant, 3-4 parts of flow agent, 5-8 parts of kaolin, 2-4 parts of active zinc oxide, 0.5-1 part of stearic acid, 1-4 parts of vulcanizing agent, and 0.5-1 part of accelerator.

[0010] More optimally, the carbon black is pre-modified to obtain modified carbon black, which is then introduced into the rubber mix. The modified carbon black specifically comprises the following steps: Step 1: Take 3-(2,3-epoxypropoxy)propyltrimethoxysilane, add it to water and ethanol, stir evenly, heat to 40-50°C and stir for 1-2h, add carbon black, keep stirring at 40-50°C for 4-6h, filter and take the solid, dry it, and obtain epoxidized carbon black;

[0011] Step 2: Take 2-mercaptobenzimidazole, add it to ethanol, heat it to 75-80°C and stir it evenly, add ethylamine hydrobromide ethanol solution dropwise, reflux for 24-25 hours, concentrate to obtain a solid, dissolve it in water, adjust the pH to 7-8 with sodium bicarbonate, extract it with dichloromethane, combine and concentrate the extracts to obtain an intermediate;

[0012] Step 3: Take epoxy soybean oil, diallylamine, 4,4'-diaminodiphenylamine, and octadecylamine, add them to dimethylformamide and stir evenly, react at 110-120℃ for 4-6h, add epoxidized carbon black, react at 110-120℃ for 35-40h, add intermediate and photoinitiator, stir and mix, 70-80mW / cm 2 Expose to light for 0.5 to 1 hour, remove the solvent, and obtain modified carbon black.

[0013] More optimally, the epoxidized carbon black includes the following raw materials, calculated by weight: 1 to 2 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and 10 to 15 parts of carbon black.

[0014] More optimally, the intermediate comprises the following raw materials, calculated by mass: 10 to 12 parts of 2-mercaptobenzimidazole, 80 to 100 parts of ethanol solution of bromoethylamine hydrobromide; in the ethanol solution of bromoethylamine hydrobromide, the mass ratio of bromoethylamine hydrobromide to ethanol is (4 to 5): (5 to 6).

[0015] More optimally, in the ethanol solution of bromoethylammonium hydrobromide, the mass ratio of bromoethylammonium hydrobromide to ethanol is 4:5.

[0016] More optimally, the modified carbon black includes the following raw materials, calculated by mass: 2 to 3 parts of epoxidized soybean oil, 1 to 2 parts of diallylamine, 3 to 4 parts of 4,4'-diaminodiphenylamine, 1 to 1.5 parts of octadecylamine, 30 to 50 parts of dimethylformamide, 70 to 80 parts of epoxidized carbon black, 3 to 4 parts of intermediates, and 0.1 to 0.2 parts of photoinitiator.

[0017] More optimally, the antioxidant includes one or more of antioxidant TMQ, antioxidant 4010NA, and antioxidant MB; the accelerator is a peroxide; and the plasticizer includes one or more of cycloalkanes and paraffin-based oils.

[0018] More optimally, the antioxidant is antioxidant MB; the accelerator is di-tert-butyl peroxide, CAS: 110-05-4; and the plasticizer is Topfine 3080 of Qingdao Taiyangsheng Chemical Co., Ltd.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: (1) the rubber compound produced by the present invention can be used for medium voltage cables and has good shielding function, and the mixing method is simple to operate and only requires one mixing stage, which greatly reduces the energy consumption of equipment, shortens the production cycle, and reduces the waste in the material transportation and storage process, and the raw materials are simple and easy to obtain, and the material cost is low;

[0020] (2) In order to improve the dispersibility of carbon black and inhibit the migration of additives such as plasticizers in the rubber mix to improve the performance of the rubber mix; the present invention adds modified carbon black: first, epoxy soybean oil, diallylamine, 4,4'-diaminodiphenylamine, and octadecylamine are used as raw materials to react for a period of time, and then epoxy carbon black is added to react for 35 to 40 hours to obtain a carbon black material with a hyperbranched structure; epoxy soybean oil is green, environmentally friendly, renewable, and has a plasticizing effect on rubber. The present invention uses epoxy soybean oil and 4,4'-diaminodiphenylamine as basic materials to prepare a hyperbranched structure. The structure can improve the dispersibility of carbon black in the rubber matrix, and it can be embedded in the rubber matrix and is not easy to migrate. Its network structure can also inhibit the migration of other additives. Since epoxidized soybean oil is a vegetable oil, its compatibility with cycloalkane and paraffin-based oil plasticizers needs to be improved. Therefore, octadecylamine is introduced to increase the affinity between the two and further improve the anti-migration property. The addition of diallylamine introduces a double bond that can participate in the next reaction, and the intermediate is introduced by the reaction with the thiol group. The intermediate has good anti-aging and antioxidant properties and good heat resistance.

[0021] The addition amount of each raw material in the modified carbon black needs to be strictly controlled. The addition amount of epoxidized soybean oil and 4,4'-diaminodiphenylamine affects the degree of branching. If the degree of branching is low, the modification effect is not obvious, and if the degree of branching is too high, the processing performance is affected. The addition amount of octadecylamine affects the compatibility of the modified carbon black with the plasticizer and the base rubber. Diallylamine introduces double bonds that can participate in the next step of the reaction, so the addition amount should not be too low, but if it is too high, the double bonds may participate in the crosslinking during the vulcanization process, consume the accelerator, reduce the crosslinking density of the rubber matrix, and affect the mechanical properties.

[0022] In summary, the modified carbon black prepared by the present invention has good dispersibility, can improve the mechanical properties and anti-aging properties of the mixed rubber, and also has good anti-migration property, can inhibit the migration of other additives, and further improve the performance of the mixed rubber. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the SEM image of the medium voltage cable shielding layer compound of Example 1. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] The following parts are by mass unless otherwise specified;

[0026] Example 1: S1: 100 parts of EPDM rubber were crushed in an internal mixer for 30 seconds; 68 parts of carbon black, 17 parts of plasticizer, 3 parts of antioxidant, 3 parts of flow agent, 6 parts of kaolin and 2.5 parts of active zinc oxide were added, and the mixture was mixed to 120°C; the dust on the mouth of the internal mixer, the top bolt and the wall of the internal mixer was cleaned, 0.5 parts of stearic acid, 3.6 parts of vulcanizing agent and 0.8 parts of accelerator were added, and the mixture was mixed to 120°C, and the heating time was controlled to 1 minute to obtain a mixed rubber;

[0027] S2: Put the mixed rubber into a two-roll open mill until the rolls are wrapped, adjust the roll distance to 2 mm, and roll three times to obtain the mixed rubber for the shielding layer of the medium-voltage cable.

[0028] Example 2: S1: 100 parts of EPDM rubber were crushed in an internal mixer for 30 seconds; 68 parts of carbon black, 17 parts of plasticizer, 3 parts of antioxidant, 3 parts of flow agent, 6 parts of kaolin and 2.5 parts of active zinc oxide were added, and the mixture was mixed to 120°C; the dust on the mouth of the internal mixer, the top bolt and the wall of the internal mixer was cleaned, 0.5 parts of stearic acid, 3.6 parts of vulcanizing agent and 0.5 parts of accelerator were added, and the mixture was mixed to 120°C, and the heating time was controlled to 1 minute to obtain a mixed rubber;

[0029] S2: Put the mixed rubber into a two-roll open mill until the rolls are wrapped, adjust the roll distance to 2 mm, and roll three times to obtain the mixed rubber for the shielding layer of the medium-voltage cable.

[0030] Example 3: S1: 100 parts of EPDM rubber were crushed in an internal mixer for 30 seconds; 68 parts of carbon black, 17 parts of plasticizer, 3 parts of antioxidant, 3 parts of flow agent, 6 parts of kaolin and 3.5 parts of active zinc oxide were added, and the mixture was mixed to 120°C; the dust on the mouth of the internal mixer, the top bolt and the wall of the internal mixer was purged clean, 0.5 parts of stearic acid, 3.6 parts of vulcanizing agent and 0.8 parts of accelerator were added, and the mixture was mixed to 120°C, and the heating time was controlled to 1 minute to obtain a mixed rubber;

[0031] S2: Put the mixed rubber into a two-roll open mill until the rolls are wrapped, adjust the roll distance to 2 mm, and roll three times to obtain the mixed rubber for the shielding layer of the medium-voltage cable.

[0032] Example 4: S1: Take 1.5 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, add it to 60 parts of water and 60 parts of ethanol, stir evenly, heat to 50°C, stir for 2 hours, add 10 parts of carbon black, maintain 50°C, stir for 5 hours, filter out the solid, and dry to obtain epoxidized carbon black;

[0033] S2: Take 10 parts of 2-mercaptobenzimidazole, add 30 parts of ethanol, heat to 77°C, dropwise add 90 parts of ethyl bromoamine hydrobromide ethanol solution, reflux for 24 hours, concentrate to obtain a solid, dissolve in water, adjust the pH to 8 with sodium bicarbonate, extract with dichloromethane, combine and concentrate the extracts to obtain an intermediate;

[0034] S3: Take 3 parts of epoxidized soybean oil, 1.8 parts of diallylamine, 3.5 parts of 4,4'-diaminodiphenylamine, and 1.2 parts of octadecylamine, add to 40 parts of dimethylformamide, stir evenly, react at 120℃ for 5h, add 75 parts of epoxidized carbon black, react at 120℃ for 40h, add 4 parts of intermediate, 0.1 parts of photoinitiator, stir and mix, 75mW / cm 2 After irradiation for 0.5 h, the solvent was removed to obtain modified carbon black;

[0035] S4: Crush 100 parts of EPDM rubber in an internal mixer for 30 seconds; add 68 parts of modified carbon black, 17 parts of plasticizer, 3 parts of antioxidant, 3 parts of flow agent, 6 parts of kaolin and 3.5 parts of active zinc oxide, and mix to 120°C; blow off the dust on the mouth of the internal mixer, the top bolt and the wall of the internal mixer, add 0.5 parts of stearic acid, 3.6 parts of vulcanizing agent and 0.8 parts of accelerator, and continue to mix to 120°C, and control the heating time to 1 minute to obtain a mixed rubber;

[0036] S5: Put the mixed rubber into a two-roll open mill until the rolls are wrapped, adjust the roll distance to 2 mm, and pass the rolls three times to obtain the mixed rubber for the shielding layer of the medium voltage cable.

[0037] Comparative Example 1 (changing the amount of 4,4'-diaminodiphenylamine added in the modified carbon black, and the other method steps are consistent with Example 4): S1: Take 1.5 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, add it to 60 parts of water and 60 parts of ethanol, stir evenly, heat to 50°C, stir for 2h, add 10 parts of carbon black, maintain 50°C, stir for 5h, filter and take the solid, and dry it to obtain epoxidized carbon black;

[0038] S2: Take 10 parts of 2-mercaptobenzimidazole, add 30 parts of ethanol, heat to 77°C, dropwise add 90 parts of ethyl bromoamine hydrobromide ethanol solution, reflux for 24 hours, concentrate to obtain a solid, dissolve in water, adjust the pH to 8 with sodium bicarbonate, extract with dichloromethane, combine and concentrate the extracts to obtain an intermediate;

[0039] S3: Take 3 parts of epoxidized soybean oil, 1.8 parts of diallylamine, 2.5 parts of 4,4'-diaminodiphenylamine, and 1.2 parts of octadecylamine, add to 40 parts of dimethylformamide, stir evenly, react at 120℃ for 5h, add 75 parts of epoxidized carbon black, react at 120℃ for 40h, add 4 parts of intermediate, 0.1 parts of photoinitiator, stir and mix, 75mW / cm 2 After irradiation for 0.5 h, the solvent was removed to obtain modified carbon black;

[0040] S4: Crush 100 parts of EPDM rubber in an internal mixer for 30 seconds; add 68 parts of modified carbon black, 17 parts of plasticizer, 3 parts of antioxidant, 3 parts of flow agent, 6 parts of kaolin and 3.5 parts of active zinc oxide, and mix to 120°C; blow off the dust on the mouth of the internal mixer, the top bolt and the wall of the internal mixer, add 0.5 parts of stearic acid, 3.6 parts of vulcanizing agent and 0.8 parts of accelerator, and continue mixing to 120°C to obtain a mixed rubber;

[0041] S5: Put the mixed rubber into a two-roll open mill until the rolls are wrapped, adjust the roll distance to 2 mm, and pass the rolls three times to obtain the mixed rubber for the shielding layer of the medium voltage cable.

[0042] Comparative Example 2 (changing the amount of diallylamine and octadecylamine added in the modified carbon black, and the other method steps are consistent with Example 4): S1: Take 1.5 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, add it to 60 parts of water and 60 parts of ethanol, stir evenly, heat to 50°C, stir for 2h, add 10 parts of carbon black, maintain 50°C, stir for 5h, filter and take the solid, and dry it to obtain epoxidized carbon black;

[0043] S2: Take 10 parts of 2-mercaptobenzimidazole, add 30 parts of ethanol, heat to 77°C, dropwise add 90 parts of ethyl bromoamine hydrobromide ethanol solution, reflux for 24 hours, concentrate to obtain a solid, dissolve in water, adjust the pH to 8 with sodium bicarbonate, extract with dichloromethane, combine and concentrate the extracts to obtain an intermediate;

[0044] S3: Take 3 parts of epoxidized soybean oil, 2.8 parts of diallylamine, 3.5 parts of 4,4'-diaminodiphenylamine, and 0.6 parts of octadecylamine, add them to 40 parts of dimethylformamide, stir evenly, react at 120℃ for 5h, add 75 parts of epoxidized carbon black, react at 120℃ for 40h, add 4 parts of intermediate, 0.1 parts of photoinitiator, stir and mix, 75mW / cm 2 After irradiation for 0.5 h, the solvent was removed to obtain modified carbon black;

[0045] S4: Crush 100 parts of EPDM rubber in an internal mixer for 30 seconds; add 68 parts of modified carbon black, 17 parts of plasticizer, 3 parts of antioxidant, 3 parts of flow agent, 6 parts of kaolin and 3.5 parts of active zinc oxide, and mix to 120°C; blow off the dust on the mouth of the internal mixer, the top bolt and the wall of the internal mixer, add 0.5 parts of stearic acid, 3.6 parts of vulcanizing agent and 0.8 parts of accelerator, and continue mixing to 120°C to obtain a mixed rubber;

[0046] S5: Put the mixed rubber into a two-roll open mill until the rolls are wrapped, adjust the roll distance to 2 mm, and pass the rolls three times to obtain the mixed rubber for the shielding layer of the medium voltage cable.

[0047] Comparative Example 3 (changing the amount of epoxidized carbon black added in the modified carbon black, and the other method steps are consistent with Example 4): S1: Take 1.5 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, add it to 60 parts of water and 60 parts of ethanol, stir evenly, heat to 50°C, stir for 2h, add 10 parts of carbon black, maintain 50°C, stir for 5h, filter and take the solid, and dry it to obtain epoxidized carbon black;

[0048] S2: Take 10 parts of 2-mercaptobenzimidazole, add 30 parts of ethanol, heat to 77°C, dropwise add 90 parts of ethyl bromoamine hydrobromide ethanol solution, reflux for 24 hours, concentrate to obtain a solid, dissolve in water, adjust the pH to 8 with sodium bicarbonate, extract with dichloromethane, combine and concentrate the extracts to obtain an intermediate;

[0049] S3: Take 3 parts of epoxidized soybean oil, 1.8 parts of diallylamine, 3.5 parts of 4,4'-diaminodiphenylamine, and 1.2 parts of octadecylamine, add to 40 parts of dimethylformamide, stir evenly, react at 120℃ for 5h, add 60 parts of epoxidized carbon black, react at 120℃ for 40h, add 4 parts of intermediate, 0.1 parts of photoinitiator, stir and mix, 75mW / cm 2 After irradiation for 0.5 h, the solvent was removed to obtain modified carbon black;

[0050] S4: Crush 100 parts of EPDM rubber in an internal mixer for 30 seconds; add 68 parts of modified carbon black, 17 parts of plasticizer, 3 parts of antioxidant, 3 parts of flow agent, 6 parts of kaolin and 3.5 parts of active zinc oxide, and mix to 120°C; blow off the dust on the mouth of the internal mixer, the top bolt and the wall of the internal mixer, add 0.5 parts of stearic acid, 3.6 parts of vulcanizing agent and 0.8 parts of accelerator, and continue mixing to 120°C to obtain a mixed rubber;

[0051] S5: Put the mixed rubber into a two-roll open mill until the rolls are wrapped, adjust the roll distance to 2 mm, and pass the rolls three times to obtain the mixed rubber for the shielding layer of the medium voltage cable.

[0052] Comparative Example 4 (the preparation method of modified carbon black is changed, and the other method steps are consistent with Example 4): S1: Take 1.5 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, add 60 parts of water and 60 parts of ethanol, stir evenly, heat to 50°C, stir for 2h, add 10 parts of carbon black, maintain 50°C, stir for 5h, filter and take the solid, dry, and obtain epoxidized carbon black;

[0053] S2: Take 10 parts of 2-mercaptobenzimidazole, add 30 parts of ethanol, heat to 77°C, dropwise add 90 parts of ethyl bromoamine hydrobromide ethanol solution, reflux for 24 hours, concentrate to obtain a solid, dissolve in water, adjust the pH to 8 with sodium bicarbonate, extract with dichloromethane, combine and concentrate the extracts to obtain an intermediate;

[0054] S3: Take 3 parts of epoxy soybean oil, 1.8 parts of diallylamine, 3.5 parts of 4,4'-diaminodiphenylamine, and 1.2 parts of octadecylamine, add them to 40 parts of dimethylformamide and stir evenly, react at 120℃ for 45h, add 4 parts of intermediate and 0.1 parts of photoinitiator, stir and mix, 75mW / cm 2 After irradiation for 0.5 h, 75 parts of epoxidized carbon black were added, stirred evenly, and the solvent was removed to obtain modified carbon black;

[0055] S4: Crush 100 parts of EPDM rubber in an internal mixer for 30 seconds; add 68 parts of modified carbon black, 17 parts of plasticizer, 3 parts of antioxidant, 3 parts of flow agent, 6 parts of kaolin and 3.5 parts of active zinc oxide, and mix to 120°C; blow off the dust on the mouth of the internal mixer, the top bolt and the wall of the internal mixer, add 0.5 parts of stearic acid, 3.6 parts of vulcanizing agent and 0.8 parts of accelerator, and continue mixing to 120°C to obtain a mixed rubber;

[0056] S5: Put the mixed rubber into a two-roll open mill until the rolls are wrapped, adjust the roll distance to 2 mm, and pass the rolls three times to obtain the mixed rubber for the shielding layer of the medium voltage cable.

[0057] Comparative Example 5 (2-mercaptoimidazole is used instead of the intermediate, and the other method steps are consistent with Example 4): S1: Take 1.5 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, add it to 60 parts of water and 60 parts of ethanol, stir evenly, heat to 50°C, stir for 2h, add 10 parts of carbon black, maintain 50°C, stir for 5h, filter and take the solid, and dry to obtain epoxidized carbon black;

[0058] S2: Take 3 parts of epoxidized soybean oil, 1.8 parts of diallylamine, 3.5 parts of 4,4'-diaminodiphenylamine, and 1.2 parts of octadecylamine, add them to 40 parts of dimethylformamide, stir evenly, react at 120℃ for 5h, add 75 parts of epoxidized carbon black, react at 120℃ for 40h, add 4 parts of 2-mercaptoimidazole and 0.1 parts of photoinitiator, stir and mix, 75mW / cm 2After irradiation for 0.5 h, the solvent was removed to obtain modified carbon black;

[0059] S3: Crush 100 parts of EPDM rubber in an internal mixer for 30 seconds; add 68 parts of modified carbon black, 17 parts of plasticizer, 3 parts of antioxidant, 3 parts of flow agent, 6 parts of kaolin and 3.5 parts of active zinc oxide, and mix to 120°C; blow off the dust on the mouth of the internal mixer, the top bolt and the wall of the internal mixer, add 0.5 parts of stearic acid, 3.6 parts of vulcanizing agent and 0.8 parts of accelerator, and continue mixing to 120°C to obtain a mixed rubber;

[0060] S4: Put the mixed rubber into a two-roll open mill until the rolls are wrapped, adjust the roll distance to 2 mm, and pass the rolls three times to obtain the mixed rubber for the shielding layer of the medium voltage cable.

[0061] In the above examples, the test methods used are conventional methods unless otherwise specified; the raw materials used are commercially available unless otherwise specified, and the sources of the raw materials are as follows: 3-(2,3-epoxypropoxy)propyltrimethoxysilane (CAS: 2530-83-8); ethanol (CAS: 64-17-5); carbon black (rubber carbon black Cabot Carbon Black N550); 2-mercaptobenzimidazole (S48637, Shanghai Yuanye); 2-mercaptoimidazole (S68535, Shanghai Yuanye); ethyl bromide hydrobromic acid Salt (CAS: 2576-47-8); epoxidized soybean oil (epoxy value 6.0-6.2, Wuhan Jiyesheng Chemical Co., Ltd.); diallylamine (CAS: 124-02-7); 4,4'-diaminodiphenylamine (CAS: 537-65-5); octadecylamine (CAS: 124-30-1); dimethylformamide (DMF, CAS: 68-12-2); photoinitiator (photoinitiator 1173, CAS: 7473-98-5); ethylene propylene diene monomer (Dow Nordel EPDM IP 4760, Herun Plastics Shenzhen Co., Ltd.); flow agent (RF-70, Jiangsu Ruiba); kaolin (S30588, Shanghai Yuanye); activated zinc oxide (Article No.: 032563, Hubei Shiteng Chemical Technology Co., Ltd.); stearic acid (CAS: 57-11-4); vulcanizing agent (rubber-specific sulfur powder, Shandong Yuanju Chemical Co., Ltd.).

[0062] Experiment (1): The test method was carried out in accordance with GB / T528-2009 and GB / T529-2008 (tensile rate 500 mm / min), and the basic properties of the medium voltage cable shielding layer compound rubber prepared in Examples 1 to 3 were tested; the specific results are shown in Table 1;

[0063] Table 1:

[0064]

[0065] (2) Take the medium voltage cable shielding layer rubber mixes prepared in Examples 3 to 4 and Comparative Examples 1 to 5; test the tensile strength; conduct a heat aging test with reference to GB / T3512-2014, at a temperature of 120°C, an air flow rate of 1m / s, and an air replacement rate of 3 times / h, and test the tensile strength again after 12 days; test the volume resistivity; see Table 2 for specific data;

[0066] Table 2:

[0067]

[0068] Conclusion: In comparative example 1, the amount of 4,4'-diaminodiphenylamine added in the modified carbon black is reduced, the branched structure is changed, and the performance is reduced; in comparative example 2, the amount of diallylamine added in the modified carbon black is increased and the amount of octadecylamine added is reduced, and the performance is reduced. From comparative examples 1 and 2, it can be seen that the change of the raw materials of the modified carbon black will lead to the reduction of performance, which shows the importance of controlling the amount of each raw material added; in comparative example 3, the amount of epoxidized carbon black added in the modified carbon black is reduced, and the performance is reduced due to the decrease in the proportion of solid fillers; in comparative example 4, the preparation method of the modified carbon black is changed: epoxy soybean oil, diene After propylamine, 4,4'-diaminodiphenylamine and octadecylamine are compounded, an intermediate and a photoinitiator are added, ultraviolet light is irradiated, and then epoxidized carbon black is added and stirred evenly, and the solvent is removed to obtain modified carbon black; the epoxidized carbon black is not compounded with the above raw materials in advance, so the dispersibility and other properties are deteriorated, resulting in a decrease in performance; Comparative Example 5 uses 2-mercaptoimidazole instead of the intermediate, and the performance is not as good as the embodiment; in summary, the medium-voltage cable shielding layer compound rubber prepared by the present invention has good mechanical properties and excellent heat aging resistance, and the modified carbon black can effectively reduce the migration of additives to improve its compound rubber performance.

[0069] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A method for preparing a medium voltage cable shielding layer rubber compound, characterized in that: The following steps are involved: S1: crush the EPDM rubber in an internal mixer for 30 to 40 seconds; add carbon black, plasticizer, antioxidant, flow agent, kaolin and active zinc oxide, and mix at 120 to 130°C; blow off dust, add stearic acid, vulcanizer and accelerator, and continue mixing at 120 to 130°C to obtain a mixed rubber; S2: Put the mixed rubber into a two-roll open mill until the rolls are wrapped, adjust the roll distance to 2 mm, and roll three times to obtain the mixed rubber for the shielding layer of the medium-voltage cable.

2. The method for preparing a medium voltage cable shielding layer rubber compound according to claim 1, characterized in that: The rubber compound comprises the following raw materials, calculated by weight: 100 parts of EPDM rubber, 60-70 parts of carbon black, 10-20 parts of plasticizer, 1-3 parts of antioxidant, 3-4 parts of flow agent, 5-8 parts of kaolin, 2-4 parts of active zinc oxide, 0.5-1 part of stearic acid, 1-4 parts of vulcanizing agent and 0.5-1 part of accelerator.

3. The method for preparing a medium voltage cable shielding layer rubber compound according to claim 1, characterized in that: The carbon black is pre-modified to obtain modified carbon black, which is then introduced into the rubber mix. The modified carbon black specifically comprises the following steps: Step 1: Take 3-(2,3-epoxypropoxy)propyltrimethoxysilane, add it to water and ethanol, stir evenly, heat to 40-50°C and stir for 1-2h, add carbon black, keep stirring at 40-50°C for 4-6h, filter and take the solid, dry it, and obtain epoxidized carbon black; Step 2: Take 2-mercaptobenzimidazole, add it to ethanol, heat it to 75-80°C and stir it evenly, add ethylamine hydrobromide ethanol solution dropwise, reflux for 24-25 hours, concentrate to obtain a solid, dissolve it in water, adjust the pH to 7-8 with sodium bicarbonate, extract it with dichloromethane, combine and concentrate the extracts to obtain an intermediate; Step 3: Take epoxy soybean oil, diallylamine, 4,4'-diaminodiphenylamine, and octadecylamine, add to dimethylformamide and stir evenly, react at 110-120°C for 4-6 hours, add epoxidized carbon black, react at 110-120°C for 35-40 hours, add intermediates and photoinitiators, stir and mix, irradiate with ultraviolet light, remove the solvent, and obtain modified carbon black.

4. The method for preparing a medium voltage cable shielding layer rubber compound according to claim 3, characterized in that: The epoxidized carbon black comprises the following raw materials, calculated by weight: 1 to 2 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane and 10 to 15 parts of carbon black.

5. The method for preparing a medium voltage cable shielding layer rubber compound according to claim 3, characterized in that: The intermediate comprises the following raw materials, calculated by mass: 10 to 12 parts of 2-mercaptobenzimidazole and 80 to 100 parts of ethanol solution of bromoethylamine hydrobromide; in the ethanol solution of bromoethylamine hydrobromide, the mass ratio of bromoethylamine hydrobromide to ethanol is (4 to 5): (5 to 6).

6. The method for preparing a medium voltage cable shielding layer rubber compound according to claim 3, characterized in that: The modified carbon black comprises the following raw materials, calculated by mass: 2-3 parts of epoxy soybean oil, 1-2 parts of diallylamine, 3-4 parts of 4,4'-diaminodiphenylamine, 1-1.5 parts of octadecylamine, 30-50 parts of dimethylformamide, 70-80 parts of epoxy carbon black, 3-4 parts of intermediates, and 0.1-0.2 parts of photoinitiator.

7. The method for preparing a medium voltage cable shielding layer rubber compound according to claim 1, characterized in that: The antioxidant includes one or more of antioxidant TMQ, antioxidant 4010NA, and antioxidant MB; the accelerator is peroxide; and the plasticizer includes one or more of cycloalkanes and paraffin-based oils.

8. A medium voltage cable shielding layer rubber compound prepared according to the method for preparing a medium voltage cable shielding layer rubber compound according to any one of claims 1 to 7.

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