Semi-conductive shielding layer rubber compound and preparation method thereof

Abstract

The invention discloses a semiconductive shielding layer rubber compound and a preparation method thereof, and belongs to the technical field of semiconductive shielding layers. Comprising the following components: 100 to 110 parts of EPDM rubber, 40 to 60 parts of a reinforcing agent, 45 to 55 parts of a plasticizer paraffin oil, 5 to 8 parts of surface modified attapulgite, 4 to 6 parts of zinc oxide, 0.5 to 1.2 parts of stearic acid, 1.2 to 1.8 parts of an anti-aging agent, 0.8 to 1.5 parts of a silane coupling agent, 0.5 to 1.0 part of a processing aid, 3.0 to 4.0 parts of a vulcanizing agent peroxide and 1.5 to 2.5 parts of an assistant crosslinking agent. Through the introduction of the surface modified attapulgite and a silane grafting process, the interface affinity of the rubber material and the surface of a conductor is remarkably improved. Attapulgite is endowed with a porous structure and hydroxyl active sites through acid activation treatment, and an organic-inorganic interface transition layer is formed after a silane coupling agent is grafted, so that the spreading capacity of a sizing material melt on the surface of a stranded conductor is enhanced, and stranded gaps and microcosmic convex parts are effectively filled. According to the design, the problem of air gap residue caused by insufficient infiltration of a traditional rubber material is solved from the chemical level of a material interface, and the initial probability of partial discharge is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of semi-conductive shielding layers, in particular to a semi-conductive shielding layer rubber compound and a preparation method thereof. Background Art

[0002] Power cable conductors are composed of multiple strands of wire twisted together. The irregularities of their surface microstructure form a complex interface with the twist gaps, making it difficult for the shielding rubber compound to fully penetrate and fill the gaps. When the interfacial affinity between the rubber compound and the conductor surface is insufficient, air gaps are likely to remain in the twist gaps and protruding areas of the conductor. Under the action of an electric field, these air gaps become the starting point for localized discharges, gradually eroding the insulation layer and triggering dendritic discharges. The melt flowability and curing shrinkage characteristics of existing rubber compounds make it difficult to adapt to the deep groove structure formed by twisting large-cross-section conductors. This leads to microscopic defects in the interfacial bonding, which becomes a key hidden danger affecting the cable's resistance to electrical aging.

[0003] The rough surface of the conductor will trigger the wire effect, resulting in local electric field concentration. The semi-conductive shielding layer needs to reasonably control the conductive properties to form a uniform transition electric field distribution on the conductor surface. However, the dispersion uniformity of the conductive filler directly affects the stability of the conductivity of the shielding layer: if the conductive particles are unevenly dispersed, local conductive paths or insulating areas are easily formed, resulting in fluctuations in the electric field suppression effect. When the conductivity is too low, it is impossible to effectively reduce the peak field strength on the conductor surface; if the conductivity is too high, it may cause increased leakage current and heat generation problems. How to find a balance between conductive properties and insulation properties to achieve precise uniformity of the electric field on the conductor surface is the core technical bottleneck of existing shielding layer material design.

[0004] Based on this, the present invention designs a semi-conductive shielding layer compound and a preparation method thereof to solve the above problems. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the prior art, the present invention provides a semi-conductive shielding layer rubber compound comprising the following components in parts by weight:

[0006] 100-110 parts of EPDM rubber, 40-60 parts of reinforcing agent, 45-55 parts of plasticizer paraffin oil, 5-8 parts of surface-modified attapulgite, 4-6 parts of zinc oxide, 0.5-1.2 parts of stearic acid, 1.2-1.8 parts of antioxidant, 0.8-1.5 parts of silane coupling agent, 0.5-1.0 parts of processing aid, 3.0-4.0 parts of vulcanizing agent peroxide, 1.5-2.5 parts of cross-linking agent;

[0007] The reinforcing agent consists of N220 carbon black and conductive carbon black in a mass ratio of 3-5:1.

[0008] A method for preparing the semi-conductive shielding layer rubber compound comprises the following steps:

[0009] S1: Acid activation treatment: soak the attapulgite in hydrochloric acid solution, stir to react, filter, wash and dry;

[0010] S2: Silane grafting modification: the acid-activated attapulgite is mixed with a silane coupling agent, a mixture of ethanol and water is added, ultrasonic treatment is performed, centrifugation is performed, and drying is performed to a constant weight to obtain surface-modified attapulgite;

[0011] S3: Pre-disperse the composite conductive filler by mixing the surface-modified attapulgite with F500B conductive carbon black and ball milling to obtain a uniform composite conductive filler;

[0012] S4: First mixing: preheat the internal mixer, add EPDM rubber, zinc oxide, stearic acid, antioxidant KY-405, processing aid HAFTOLAT / P and N220 carbon black in sequence, mix, add composite conductive filler and paraffin oil P500, mix, clean the top plug and continue mixing to produce sheet A rubber;

[0013] S5: The second mixing step is to put rubber A into an internal mixer, add vulcanizing agent F40P-SP2 and co-crosslinking agent TAIC-70, mix, clean and mix again, and then take off the sheet to obtain the semi-conductive shielding layer mixed rubber.

[0014] Furthermore, S1 is specifically as follows: attapulgite with a diameter of 20-50 nm is soaked in a hydrochloric acid solution with a concentration of 1-1.5 mol / L, stirred at 75-85°C at a rate of 200-300 rpm, reacted for 1.0-2.0 hours, filtered, washed with deionized water to a pH of 6.5-7.0, and dried at 110-130°C to a moisture content of ≤0.5%.

[0015] Furthermore, S2 is specifically as follows: mixing the acid-activated attapulgite with the silane coupling agent A-172, adding a mixture of ethanol and water, ultrasonically treating the mixture at a frequency of 40-50 kHz and a temperature of 55-65° C. for 50-70 minutes, centrifuging and drying at 100-120° C. to constant weight to obtain surface-modified attapulgite.

[0016] Furthermore, S3 is specifically as follows: mixing the surface modified attapulgite with F500B conductive carbon black, adding the mixture into a ball mill with a ball-to-material ratio of 8-12:1, a rotation speed of 200-250 rpm, and ball milling for 25-35 minutes to obtain a uniform composite conductive filler.

[0017] Furthermore, the ball milling medium in S3 is zirconia ceramic balls with a particle size of 3-5 mm. The ball mill is protected by inert gas with an oxygen content of ≤0.5%.

[0018] Furthermore, S4 is specifically as follows: preheating the internal mixer to 70-80°C, adding EPDM rubber, zinc oxide, stearic acid, antioxidant KY-405, processing aid HAFTOLAT / P and N220 carbon black in sequence, mixing time 60-70s, rotor speed 40-50rpm, adding composite conductive filler and paraffin oil P500, mixing time 85-95s, cleaning the top bolt and continuing mixing for 145-155s, controlling the rubber temperature ≤110°C, and producing sheet A rubber.

[0019] Furthermore, S5 is specifically as follows: put rubber A into an internal mixer, add vulcanizer F40P-SP2 and co-crosslinking agent TAIC-70, mix for 75-85s, rotor speed 30-40rpm, mix for a second time for 35-45s after cleaning, control the rubber temperature ≤100℃, and place at room temperature for 24 hours after unloading to obtain a semi-conductive shielding layer mixed rubber.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. This invention significantly improves the interfacial compatibility between the rubber compound and the conductor surface through the introduction of surface-modified attapulgite and a silane grafting process. Acid activation treatment imparts a porous structure and hydroxyl active sites to the attapulgite. Silane coupling agent grafting forms an organic-inorganic interface transition layer, enhancing the ability of the rubber compound melt to spread across the stranded conductor surface, effectively filling the strand gaps and microscopic protrusions. This design addresses the problem of residual air gaps caused by insufficient wetting in conventional rubber compounds through the material interface chemistry, reducing the probability of partial discharge initiation and improving the cable's resistance to treeing.

[0022] 2. This invention utilizes a gradient composite system of N220 carbon black and conductive carbon black, combined with a ball mill pre-dispersion process, to achieve uniform dispersion of the conductive filler and optimize the conductivity gradient. The specific carbon black combination ensures conductivity while avoiding leakage current caused by excessive conduction. The pre-dispersion process eliminates conductive particle agglomeration, forming a continuous and stable conductive network within the shielding layer. This design creates a uniform and transitional electric field distribution on the conductor surface, effectively suppressing the field concentration caused by the wire effect, and resolving the problem of unstable electric field control caused by conductivity fluctuations in existing materials.

[0023] 3. The present invention's internal mixing process utilizes segmented temperature control and optimized rotor speed to ensure uniform filler dispersion while preventing overheating and degradation of the rubber compound. The optimized ratio of the vulcanization system and co-crosslinking agent enhances the interfacial bond strength of the rubber compound after curing. This approach, through the coordinated optimization of material formulation and preparation process, not only addresses interfacial air gaps and electric field concentration, but also simultaneously improves the rubber compound's processing fluidity and aging resistance, meeting the shielding conformability and long-term reliability requirements of large-cross-section cables. DETAILED DESCRIPTION

[0024] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0025] Example 1: This example provides a semi-conductive shielding layer rubber compound, which comprises the following components in parts by weight:

[0026] 100 parts of EPDM rubber, 40 parts of reinforcing agent, 45 parts of plasticizer paraffin oil, 5 parts of surface-modified attapulgite, 4 parts of zinc oxide, 0.5 parts of stearic acid, 1.2 parts of antioxidant, 0.8 parts of silane coupling agent, 0.5 parts of processing aid, 3.0 parts of vulcanizing agent peroxide, 1.5 parts of co-crosslinking agent;

[0027] The reinforcing agent consists of N220 carbon black and conductive carbon black in a mass ratio of 3:1.

[0028] The method for preparing the semi-conductive shielding layer rubber compound comprises the following steps:

[0029] S1: Acid activation treatment: attapulgite with a diameter of 20 nm was immersed in a 1 mol / L hydrochloric acid solution at 75°C and a stirring rate of 200 rpm for 1.0 h. After filtering, it was washed with deionized water to a pH of 6.5 and dried at 110°C to a moisture content of ≤0.5%;

[0030] S2: Silane grafting modification: The acid-activated attapulgite was mixed with silane coupling agent A-172, and a mixture of ethanol and water (volume ratio 9:1) was added. The mixture was ultrasonically treated at a frequency of 40 kHz and a temperature of 55°C for 50 min. After centrifugation, it was dried at 100°C to constant weight to obtain surface-modified attapulgite.

[0031] S3: Pre-disperse the composite conductive filler by mixing the surface-modified attapulgite and F500B conductive carbon black, adding them into a ball mill with a ball-to-material ratio of 8:1 and a rotation speed of 200 rpm for 25 minutes to obtain a uniform composite conductive filler. The ball milling medium is zirconia ceramic balls with a particle size of 3 mm. The ball mill is protected by inert gas with an oxygen content of ≤0.5%;

[0032] S4: First mixing: preheat the internal mixer to 70°C, add EPDM rubber, zinc oxide, stearic acid, antioxidant KY-405, processing aid HAFTOLAT / P and N220 carbon black in sequence, mix for 60 seconds, rotor speed 40 rpm, add composite conductive filler and paraffin oil P500, mix for 85 seconds, clean the top bolt and continue mixing for 145 seconds, control the rubber temperature ≤110°C, and produce rubber A;

[0033] S5: Second mixing: put rubber A into internal mixer, add vulcanizing agent F40P-SP2 and co-crosslinking agent TAIC-70, mix for 75s, rotor speed 30rpm, mix for 35s after cleaning, control the rubber temperature ≤100℃, and place at room temperature for 24h after unloading to obtain semi-conductive shielding layer rubber mix.

[0034] Example 2: This example provides a semi-conductive shielding layer rubber compound, which includes the following components in parts by weight:

[0035] 110 parts of EPDM rubber, 60 parts of reinforcing agent, 55 parts of plasticizer paraffin oil, 8 parts of surface-modified attapulgite, 6 parts of zinc oxide, 1.2 parts of stearic acid, 1.8 parts of antioxidant, 1.5 parts of silane coupling agent, 1.0 part of processing aid, 4.0 parts of vulcanizing agent peroxide, 2.5 parts of co-crosslinking agent;

[0036] The reinforcing agent consists of N220 carbon black and conductive carbon black in a mass ratio of 5:1.

[0037] The method for preparing the semi-conductive shielding layer rubber compound comprises the following steps:

[0038] S1: Acid activation treatment: attapulgite with a diameter of 50 nm was immersed in a 1.5 mol / L hydrochloric acid solution at 85°C and a stirring rate of 300 rpm for 2.0 h. After filtering, it was washed with deionized water to a pH of 7.0 and dried at 130°C to a moisture content of ≤0.5%;

[0039] S2: Silane grafting modification: The acid-activated attapulgite was mixed with silane coupling agent A-172, and a mixture of ethanol and water (volume ratio 9:1) was added. The mixture was ultrasonically treated at a frequency of 50 kHz and a temperature of 65°C for 70 min. After centrifugation, the mixture was dried at 120°C to constant weight to obtain surface-modified attapulgite.

[0040] S3: Pre-disperse the composite conductive filler by mixing surface-modified attapulgite with F500B conductive carbon black, adding the mixture into a ball mill with a ball-to-material ratio of 12:1 and a rotation speed of 250 rpm for 35 minutes to obtain a uniform composite conductive filler. The ball milling medium is zirconia ceramic balls with a particle size of 5 mm. The ball mill is protected by inert gas with an oxygen content of ≤0.5%.

[0041] S4: First mixing: preheat the internal mixer to 80°C, add EPDM rubber, zinc oxide, stearic acid, antioxidant KY-405, processing aid HAFTOLAT / P and N220 carbon black in sequence, mix for 70 seconds, rotor speed 50 rpm, add composite conductive filler and paraffin oil P500, mix for 95 seconds, clean the top bolt and continue mixing for 155 seconds, control the rubber temperature ≤110°C, and produce rubber A;

[0042] S5: Second mixing: put rubber A into internal mixer, add vulcanizing agent F40P-SP2 and co-crosslinking agent TAIC-70, mix for 85s, rotor speed 40rpm, mix for a second time for 45s after cleaning, control the rubber temperature ≤100℃, and place at room temperature for 24h after unloading to obtain semi-conductive shielding layer rubber mix.

[0043] Example 3: This example provides a semi-conductive shielding layer rubber compound, which includes the following components in parts by weight:

[0044] 105 parts of EPDM rubber, 48 parts of reinforcing agent, 52 parts of plasticizer paraffin oil, 7 parts of surface-modified attapulgite, 5 parts of zinc oxide, 1.1 parts of stearic acid, 1.5 parts of antioxidant, 0.9 parts of silane coupling agent, 0.8 parts of processing aid, 3.4 parts of vulcanizing agent peroxide, 2.2 parts of co-crosslinking agent;

[0045] The reinforcing agent consists of N220 carbon black and conductive carbon black in a mass ratio of 4:1.

[0046] The method for preparing the semi-conductive shielding layer rubber compound comprises the following steps:

[0047] S1: Acid activation treatment: attapulgite with a diameter of 40 nm was immersed in a 1.2 mol / L hydrochloric acid solution at 82°C and a stirring rate of 240 rpm for 1.5 h. After filtering, it was washed with deionized water to a pH of 6.8 and dried at 123°C to a moisture content of ≤0.5%;

[0048] S2: Silane grafting modification: The acid-activated attapulgite was mixed with silane coupling agent A-172, and a mixture of ethanol and water (volume ratio 9:1) was added. The mixture was ultrasonically treated at a frequency of 45 kHz and a temperature of 58°C for 63 min. After centrifugation, the mixture was dried at 107°C to constant weight to obtain surface-modified attapulgite.

[0049] S3: Pre-disperse the composite conductive filler by mixing surface-modified attapulgite with F500B conductive carbon black, adding the mixture into a ball mill with a ball-to-material ratio of 10:1 and a rotation speed of 210 rpm for 30 minutes to obtain a uniform composite conductive filler. The ball milling medium is zirconia ceramic balls with a particle size of 4 mm. The ball mill is protected by inert gas with an oxygen content of ≤0.5%;

[0050] S4: First mixing: preheat the internal mixer to 76°C, add EPDM rubber, zinc oxide, stearic acid, antioxidant KY-405, processing aid HAFTOLAT / P and N220 carbon black in sequence, mix for 64 seconds, rotor speed 48 rpm, add composite conductive filler and paraffin oil P500, mix for 88 seconds, clean the top bolt and continue mixing for 151 seconds, control the rubber temperature ≤110°C, and produce rubber A;

[0051] S5: Second mixing: put rubber A into internal mixer, add vulcanizing agent F40P-SP2 and co-crosslinking agent TAIC-70, mix for 83s, rotor speed 39rpm, mix for a second time for 41s after cleaning, control the rubber temperature ≤100℃, and keep it at room temperature for 24h after unloading to obtain semi-conductive shielding layer rubber mix.

[0052] Comparative Example 1: This comparative example differs from Example 3 in that the surface of the attapulgite is not modified.

[0053] Comparative Example 2: This comparative example differs from Example 3 in that no vulcanizing agent peroxide is added.

[0054] Experimental Example: The prepared semi-conductive shielding layer rubber compound was tested according to the following method:

[0055] Hardness (Shore A): GB / T 531.1-2008 "Rubber, vulcanized or thermoplastic — Test method for indentation hardness — Part 1: Shore A durometer method (Shore hardness)"

[0056] Tensile strength, elongation at break, 300% modulus of tensile stress: GB / T 528-2009 "Rubber, vulcanized or thermoplastic — Determination of tensile stress-strain properties";

[0057] Partial discharge test: in accordance with GB / T 3048.12-2007 "Electrical performance test methods for wires and cables Part 12: Partial discharge test";

[0058] Volume resistivity: GB / T 40719-2021 “Rubber, vulcanized or thermoplastic — Determination of volume and / or surface resistivity”;

[0059] The experimental results are as follows:

[0060]

[0061]

[0062] As can be seen from the above table, the present invention effectively reduces the residual air gaps on the interface by modifying the surface of attapulgite, thereby significantly reducing the amount of partial discharge of the rubber compound;

[0063] The volume resistivity is effectively improved by adding the vulcanizing agent peroxide.

[0064] In summary, the present invention significantly improves the interfacial affinity between the rubber compound and the conductor surface through the introduction of surface-modified attapulgite and a silane grafting process. Acid activation treatment imparts a porous structure and hydroxyl active sites to the attapulgite, while silane coupling agent grafting forms an organic-inorganic interface transition layer, enhancing the ability of the rubber compound melt to spread across the surface of the stranded conductor, effectively filling the strand gaps and microscopic protrusions. This design addresses the problem of residual air gaps caused by insufficient wetting in traditional rubber compounds at the material interface chemistry level, reducing the probability of partial discharge initiation and improving the cable's resistance to tree discharge.

[0065] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A semi-conductive shielding layer rubber compound, characterized in that: The following components are included in parts by weight: 100-110 parts of EPDM rubber, 40-60 parts of reinforcing agent, 45-55 parts of plasticizer paraffin oil, 5-8 parts of surface-modified attapulgite, 4-6 parts of zinc oxide, 0.5-1.2 parts of stearic acid, 1.2-1.8 parts of antioxidant, 0.8-1.5 parts of silane coupling agent, 0.5-1.0 parts of processing aid, 3.0-4.0 parts of vulcanizing agent peroxide, 1.5-2.5 parts of cross-linking agent; The reinforcing agent consists of N220 carbon black and conductive carbon black in a mass ratio of 3-5:

1.

2. A method for preparing a semi-conductive shielding layer rubber compound according to claim 1, characterized in that: The following steps are involved: S1: Acid activation treatment: soak the attapulgite in hydrochloric acid solution, stir to react, filter, wash and dry; S2: Silane grafting modification: the acid-activated attapulgite is mixed with a silane coupling agent, a mixture of ethanol and water is added, ultrasonic treatment is performed, centrifugation is performed, and drying is performed to a constant weight to obtain surface-modified attapulgite; S3: Pre-disperse the composite conductive filler by mixing the surface-modified attapulgite with F500B conductive carbon black and ball milling to obtain a uniform composite conductive filler; S4: First mixing: preheat the internal mixer, add EPDM rubber, zinc oxide, stearic acid, antioxidant KY-405, processing aid HAFTOLAT / P and N220 carbon black in sequence, mix, add composite conductive filler and paraffin oil P500, mix, clean the top plug and continue mixing to produce sheet A rubber; S5: The second mixing step is to put rubber A into an internal mixer, add vulcanizing agent F40P-SP2 and co-crosslinking agent TAIC-70, mix, clean and mix again, and then take off the sheet to obtain the semi-conductive shielding layer mixed rubber.

3. The method for preparing a semi-conductive shielding layer rubber compound according to claim 2, characterized in that: S1 specifically comprises: soaking attapulgite with a diameter of 20-50 nm in a hydrochloric acid solution with a concentration of 1-1.5 mol / L, reacting at 75-85° C. and a stirring rate of 200-300 rpm for 1.0-2.0 h, filtering, washing with deionized water to a pH of 6.5-7.0, and drying at 110-130° C. to a moisture content of ≤0.5%.

4. The method for preparing a semi-conductive shielding layer rubber compound according to claim 2, characterized in that: S2 is specifically as follows: mixing the acid-activated attapulgite with the silane coupling agent A-172, adding a mixture of ethanol and water, ultrasonically treating the mixture at a frequency of 40-50 kHz and a temperature of 55-65° C. for 50-70 minutes, centrifuging and drying the mixture at 100-120° C. to a constant weight to obtain surface-modified attapulgite.

5. The method for preparing a semi-conductive shielding layer rubber compound according to claim 2, characterized in that: S3 is specifically as follows: the surface modified attapulgite and F500B conductive carbon black are mixed, added into a ball mill, the ball-to-material ratio is 8-12:1, the rotation speed is 200-250 rpm, and the ball milling is performed for 25-35 minutes to obtain a uniform composite conductive filler.

6. The method for preparing a semi-conductive shielding layer rubber compound according to claim 5, characterized in that: The ball milling medium in S3 is zirconia ceramic balls with a particle size of 3-5 mm. The ball mill is protected by inert gas with an oxygen content of ≤0.5%.

7. The method for preparing a semi-conductive shielding layer rubber compound according to claim 2, characterized in that: S4 is specifically as follows: preheat the internal mixer to 70-80℃, add EPDM rubber, zinc oxide, stearic acid, antioxidant KY-405, processing aid HAFTOLAT / P and N220 carbon black in sequence, the mixing time is 60-70s, the rotor speed is 40-50rpm, add composite conductive filler and paraffin oil P500, the mixing time is 85-95s, clean the upper push pin and continue mixing for 145-155s, control the rubber temperature ≤110℃, and produce sheet A rubber.

8. The method for preparing a semi-conductive shielding layer rubber compound according to claim 2, characterized in that: S5 is specifically as follows: put rubber A into an internal mixer, add vulcanizing agent F40P-SP2 and co-crosslinking agent TAIC-70, mix for 75-85s, rotate the rotor at 30-40rpm, mix for a second time for 35-45s after cleaning, control the rubber temperature ≤100℃, and place at room temperature for 24 hours after unloading to obtain a semi-conductive shielding layer mixed rubber.

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