Novel cable semi-conductive buffer layer and preparation method therefor

Abstract

A cable semi-conductive buffer layer and a preparation method therefor, relating to the field of electrical materials. The semi-conductive buffer layer comprises a semi-conductive buffer tape and a rubber coating located on the surface of the semi-conductive buffer tape. The semi-conductive buffer tape is a semi-conductive water-blocking tape or a semi-conductive nylon tape. The rubber coating comprises butyl rubber, a conductive filler, a functional addictive, paraffin wax, and a vulcanizing agent. In order to mitigate the technical problem of poor water blocking performance of a cable semi-conductive buffer layer, a rubber coating is provided on the surface of a semi-conductive buffer tape, butyl rubber in the rubber coating has good air tightness, effectively preventing the permeation of water molecules, thus avoiding the risk of breakdown during long-term operation in a humid environment, such that electrical performance and tensile strength can be improved, and a conductive filler is also uniformly dispersed in the rubber coating, so that the volume resistivity and surface resistance of the buffer layer can be maintained or reduced, achieving good electrical conductivity and field intensity homogenization effect, thus meeting application requirements.

Description

A novel semiconductive buffer layer for cables and its preparation method

[0001] This application claims priority to Chinese Patent Application No. 202510183509.2, filed on February 19, 2025, entitled "A Novel Semiconductor Buffer Layer for Cables and Its Preparation Method", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of electrical materials, and in particular to a novel semiconductive buffer layer for cables and its preparation method. Background Technology

[0003] In the design of buffer layers for high-voltage cables, uneven distribution of electric field stress is a prominent issue. This uneven distribution often leads to ablation and white spots. The main function of the buffer layer is to evenly distribute electric field stress during cable operation, thereby preventing electrical breakdown and protecting the internal insulation layer from damage. Under harsh external conditions, such as when cables become damp, uneven distribution of electric field stress can easily occur. Some areas may experience excessively high electric field stress, leading to localized or overall breakdown, resulting in cable faults and damage. Therefore, improving the electrical performance of the buffer layer is particularly important.

[0004] Cable buffer layer materials, such as semi-conductive non-woven fabric, semi-conductive water-resistant tape, and semi-conductive nylon tape, play a crucial role in cable buffer layers. Their main functions include: achieving a uniform electric field distribution between the cable's insulation layer and metal sheath through the voltage equalization effect, significantly reducing the electric field gradient and thus lowering the risk of partial discharge and breakdown; they also extend cable life, reduce insulation aging caused by electric field stress, and improve cable reliability and durability. Currently, cable buffer tapes have poor moisture resistance; even with water-blocking powder, they are at risk of breakdown under prolonged moisture exposure, and the tensile strength of the buffer tape is not high enough. Therefore, improving the water resistance and tensile strength of buffer tapes while maintaining good electrical performance remains a challenge. Summary of the Invention

[0005] This application provides a novel semi-conductive buffer layer for cables and its preparation method, in order to solve the technical problems of poor water resistance and high risk of breakdown in humid environments in current cable buffer layer tapes. By coating the surface of the semi-conductive tape with a rubber coating containing conductive filler, the rubber coating has excellent water resistance, can simultaneously improve tensile strength, and is not easily broken down in humid environments, thus maintaining electrical performance.

[0006] To address the aforementioned technical problems, one objective of this application is to provide a novel semi-conductive buffer layer for cables, comprising a semi-conductive buffer tape and a rubber coating on the surface of the semi-conductive buffer tape. The semi-conductive buffer tape is a semi-conductive resistive water tape or a semi-conductive nylon tape. The rubber coating comprises the following components by weight: butyl rubber: 300 parts; conductive filler: 150-180 parts; functional additives: 13-30 parts; paraffin wax: 15-20 parts; vulcanizing agent: 4-7 parts.

[0007] The functional additives include zinc oxide, magnesium oxide and calcium oxide in a mass ratio of 4:(0.5-1):(0.5-1).

[0008] This application aims to improve the water resistance and tensile strength of cable buffer tapes. By applying a butyl rubber coating to a semi-conductive buffer tape, a waterproof layer can be formed. Its water resistance is mainly based on the excellent water resistance, resistance to polar liquids, and chemical structure of butyl rubber. The polymer structure of butyl rubber gives it good airtightness, effectively preventing the penetration of water molecules. There is no risk of breakdown during long-term operation in a humid environment, thus improving electrical performance. This results in a cable buffer layer material with superior tensile strength and water resistance. Furthermore, the rubber coating contains uniformly dispersed conductive fillers, which ensures that the buffer layer material still has low volume resistivity and surface resistance, guaranteeing the electrical performance of the buffer layer material.

[0009] As a preferred embodiment, the rubber coating further includes an antioxidant in the form of 3-9 parts by weight.

[0010] As a preferred embodiment, the rubber coating further includes 1-6 parts by weight of a vulcanization accelerator.

[0011] As a preferred embodiment, the vulcanization accelerator comprises 2-4 parts by weight of accelerator TMTD and 1-2 parts by weight of accelerator M.

[0012] As a preferred embodiment, the functional additives include zinc oxide, magnesium oxide and calcium oxide in a mass ratio of 4:0.5:0.5.

[0013] As a preferred embodiment, the conductive filler is at least one of carbon black, carbon nanotubes, graphene, graphite, and nano-metallic elements.

[0014] As a preferred embodiment, the antioxidant is N-cyclohexyl-N'-phenyl-p-phenylenediamine.

[0015] As a preferred embodiment, the vulcanizing agent is sulfur.

[0016] As a preferred embodiment, the thickness of the semiconductive buffer strip is 0.1-1 mm.

[0017] To address the aforementioned technical problems, a second objective of this application is to provide a novel method for preparing a semiconductive buffer layer for cables, comprising the following steps:

[0018] (1) Cut the butyl rubber composite compound into rubber granules, add No. 120 solvent oil, stir for 4-10 hours, then heat and stir in a water bath for 4-8 hours to obtain a rubber solution;

[0019] (2) A rubber solution is coated on the surface of the semi-conductive buffer strip, dried and vulcanized to form a rubber coating, thereby obtaining a buffer layer.

[0020] As a preferred embodiment, in step (1), the preparation method of the butyl rubber composite compound is as follows: butyl rubber is added to the open mill and plasticized evenly. Then, functional additives, antioxidants, and paraffin wax are added and mixed evenly. Subsequently, carbon black is added in several batches and mixed evenly. Finally, vulcanizing agent and vulcanization accelerator are added and mixed evenly. The roller gap is adjusted to pass through the rubber sheet and the sheet is cut to obtain the butyl rubber composite compound.

[0021] In this application, the prepared butyl rubber composite compound is dissolved by heating with No. 120 solvent oil, and then uniformly coated onto a semi-conductive buffer tape. After curing, a water-blocking layer is formed, which improves the water-blocking ability of the semi-conductive buffer tape. The rubber coating also has a certain elasticity and strength, which improves the overall tensile strength of the buffer layer. At the same time, after coating a relatively thin rubber coating, the buffer tape still maintains high conductivity, with low volume resistivity and surface resistance, verifying the feasibility of the scheme.

[0022] As a preferred option, in the preparation method of butyl rubber composite compound, the rotor speed of the open mill is adjusted to 20-40 r / min.

[0023] As a preferred option, in the preparation method of butyl rubber composite compound, the plasticizing time is 2-5 minutes.

[0024] As a preferred option, in the preparation method of butyl rubber composite compound, the total mixing time is 10-20 min.

[0025] As a preferred embodiment, in step (1), the mass ratio of the rubber material to No. 120 solvent oil is (10-20):(80-90).

[0026] As a preferred option, in step (1), the water bath heating temperature is 40-60℃.

[0027] As a preferred embodiment, in step (2), the coating thickness of the rubber solution is 0.02-0.08 mm.

[0028] As a preferred embodiment, in step (2), the drying temperature is 60-100℃ and the drying time is 5-15min.

[0029] As a preferred embodiment, in step (2), the vulcanization temperature is 150-180℃ and the vulcanization time is 5-15min.

[0030] Compared with the prior art, this application has the following beneficial effects:

[0031] This application addresses the technical problem of poor water-blocking performance of semi-conductive buffer layers in cables by applying a rubber coating to the surface of the semi-conductive buffer tape. The rubber coating contains butyl rubber, whose polymer structure provides excellent airtightness, effectively preventing water molecule penetration. It eliminates the risk of breakdown during long-term operation in humid environments, improving electrical performance. Furthermore, the rubber coating provides a certain strength to the semi-conductive buffer tape, increasing the overall tensile strength of the buffer layer. The rubber coating also contains uniformly dispersed conductive fillers with excellent conductivity, which does not affect the conductivity of the semi-conductive buffer tape. It can maintain or reduce the volume resistivity and surface resistance of the buffer layer, resulting in good conductivity and field strength homogenization, meeting application requirements. Attached Figure Description

[0032] Figure 1: A statistical chart showing the volume resistivity of the semiconductive buffer layer of the cable in Comparative Example 7-11 of this application as a function of temperature.

[0033] Figure 2: Cross-sectional scanning electron microscope image of the butyl rubber composite compound prepared in Example 3 of this application (Note: scale bar 10 μm);

[0034] Figure 3: Cross-sectional scanning electron microscope image of the butyl rubber composite compound prepared in Example 3 of this application (Note: scale bar 5 μm). Detailed Implementation

[0035] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0036] It should be understood that the terminology used in this application is merely for describing particular implementations and is not intended to limit the application. Furthermore, for numerical ranges in this application, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this application. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0037] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art described herein. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this application. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0038] As used in this article:

[0039] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0040] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0041] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically inventing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether such range is invented individually. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0042] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0043] "Parts by mass" is a basic unit of measurement that expresses the proportional relationship between the masses of multiple components. One part can represent any unit mass. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike the number of parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0044] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0045] In the description of this application, it should be understood that the terms "upper", "lower", "left", "right", "top", "bottom", etc., indicating the orientation or positional relationship, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0046] To further illustrate this application, the following detailed description is provided in conjunction with embodiments, but these should not be construed as limiting the scope of protection of this application. Unless otherwise specified, the raw materials used in the following embodiments and comparative examples are commercially available, and the same raw materials were used in parallel experiments.

[0047] Preparation Example 1

[0048] A butyl rubber composite compound comprises 300g butyl rubber raw rubber, 16g zinc oxide, 2g magnesium oxide, 2g calcium oxide, 6g N-cyclohexyl-N'-phenyl-p-phenylenediamine, 18g paraffin wax, 150g carbon black, 5.625g sulfur, 3.75g accelerator TMTD and 1.5g accelerator M. Its preparation method includes the following steps:

[0049] Add butyl rubber raw material to the open mill, adjust the rotor speed to 30 r / min, and after the rubber is plasticized evenly for about 3 minutes, add zinc oxide, stearic acid, N-cyclohexyl-N'-phenyl-p-phenylenediamine, and paraffin wax and mix for 3 minutes. Then add carbon black in two batches and mix for 3 minutes. After the carbon black is evenly dispersed, add sulfur, accelerator TMTD, and accelerator M and mix for 3 minutes. Adjust the roller gap and pass the rubber sheet through. After 7 minutes, the sheet is removed to obtain the butyl rubber composite compound.

[0050] Preparation Example 2

[0051] A butyl rubber composite compound comprises 300g butyl rubber raw rubber, 16g zinc oxide, 2g magnesium oxide, 2g calcium oxide, 6g N-cyclohexyl-N'-phenyl-p-phenylenediamine, 18g paraffin wax, 165g carbon black, 5.625g sulfur, 3.75g accelerator TMTD and 1.5g accelerator M. Its preparation method includes the following steps:

[0052] Add butyl rubber raw material to the open mill, adjust the rotor speed to 30 r / min, and after the rubber is plasticized evenly for about 3 minutes, add zinc oxide, stearic acid, N-cyclohexyl-N'-phenyl-p-phenylenediamine, and paraffin wax and mix for 3 minutes. Then add carbon black in two batches and mix for 3 minutes. After the carbon black is evenly dispersed, add sulfur, accelerator TMTD, and accelerator M and mix for 3 minutes. Adjust the roller gap and pass the rubber sheet through. After 7 minutes, the sheet is removed to obtain the butyl rubber composite compound.

[0053] Preparation Example 3

[0054] A butyl rubber composite compound comprises 300g of butyl rubber raw rubber, 16g of zinc oxide, 2g of magnesium oxide, 2g of calcium oxide, 6g of N-cyclohexyl-N'-phenyl-p-phenylenediamine, 18g of paraffin wax, 180g of carbon black, 5.625g of sulfur, 3.75g of accelerator TMTD and 1.5g of accelerator M. Its preparation method includes the following steps:

[0055] Add butyl rubber raw material to the open mill, adjust the rotor speed to 30 r / min, and after the rubber is plasticized evenly for about 3 minutes, add zinc oxide, stearic acid, N-cyclohexyl-N'-phenyl-p-phenylenediamine, and paraffin wax and mix for 3 minutes. Then add carbon black in two batches and mix for 3 minutes. After the carbon black is evenly dispersed, add sulfur, accelerator TMTD, and accelerator M and mix for 3 minutes. Adjust the roller gap and pass the rubber sheet through. After 7 minutes, the sheet is removed to obtain the butyl rubber composite compound.

[0056] Comparative Preparation Example 1

[0057] A butyl rubber composite compound comprises 300g of butyl rubber raw rubber, 16g of zinc oxide, 2g of magnesium oxide, 2g of calcium oxide, 6g of N-cyclohexyl-N'-phenyl-p-phenylenediamine, 18g of paraffin wax, 120g of carbon black, 5.625g of sulfur, 3.75g of accelerator TMTD and 1.5g of accelerator M. Its preparation method includes the following steps:

[0058] Add butyl rubber raw material to the open mill, adjust the rotor speed to 30 r / min, and after the rubber is plasticized evenly for about 3 minutes, add zinc oxide, stearic acid, N-cyclohexyl-N'-phenyl-p-phenylenediamine, and paraffin wax and mix for 3 minutes. Then add carbon black in two batches and mix for 3 minutes. After the carbon black is evenly dispersed, add sulfur, accelerator TMTD, and accelerator M and mix for 3 minutes. Adjust the roller gap and pass the rubber sheet through. After 7 minutes, the sheet is removed to obtain the butyl rubber composite compound.

[0059] Comparative Preparation Example 2

[0060] A butyl rubber composite compound comprises 300g of butyl rubber raw rubber, 16g of zinc oxide, 2g of magnesium oxide, 2g of calcium oxide, 6g of N-cyclohexyl-N'-phenyl-p-phenylenediamine, 18g of paraffin wax, 135g of carbon black, 5.625g of sulfur, 3.75g of accelerator TMTD and 1.5g of accelerator M. Its preparation method includes the following steps:

[0061] Add butyl rubber raw material to the open mill, adjust the rotor speed to 30 r / min, and after the rubber is plasticized evenly for about 3 minutes, add zinc oxide, stearic acid, N-cyclohexyl-N'-phenyl-p-phenylenediamine, and paraffin wax and mix for 3 minutes. Then add carbon black in two batches and mix for 3 minutes. After the carbon black is evenly dispersed, add sulfur, accelerator TMTD, and accelerator M and mix for 3 minutes. Adjust the roller gap and pass the rubber sheet through. After 7 minutes, the sheet is removed to obtain the butyl rubber composite compound.

[0062] Comparative preparation example 3

[0063] A butyl rubber composite compound comprises 300g butyl rubber raw rubber, 20g zinc oxide, 3g magnesium oxide, 3g calcium oxide, 6g N-cyclohexyl-N'-phenyl-p-phenylenediamine, 8g paraffin wax, 180g carbon black, 2.5g sulfur, 2g accelerator TMTD, and 1.5g accelerator M. Its preparation method includes the following steps:

[0064] Add butyl rubber raw material to the open mill, adjust the rotor speed to 30 r / min, and after the rubber is plasticized evenly for about 3 minutes, add zinc oxide, stearic acid, N-cyclohexyl-N'-phenyl-p-phenylenediamine, and paraffin wax and mix for 3 minutes. Then add carbon black in two batches and mix for 3 minutes. After the carbon black is evenly dispersed, add sulfur, accelerator TMTD, and accelerator M and mix for 3 minutes. Adjust the roller gap and pass the rubber sheet through. After 7 minutes, the sheet is removed to obtain the butyl rubber composite compound.

[0065] Comparative preparation example 4

[0066] A butyl rubber composite compound comprises 300g of butyl rubber raw rubber, 20g of stearic acid, 6g of N-cyclohexyl-N'-phenyl-p-phenylenediamine, 18g of paraffin wax, 180g of carbon black, 5.625g of sulfur, 3.75g of accelerator TMTD and 1.5g of accelerator M, and its preparation method includes the following steps:

[0067] Add butyl rubber raw material to the open mill, adjust the rotor speed to 30 r / min, and after the rubber is plasticized evenly for about 3 minutes, add zinc oxide, stearic acid, N-cyclohexyl-N'-phenyl-p-phenylenediamine, and paraffin wax and mix for 3 minutes. Then add carbon black in two batches and mix for 3 minutes. After the carbon black is evenly dispersed, add sulfur, accelerator TMTD, and accelerator M and mix for 3 minutes. Adjust the roller gap and pass the rubber sheet through. After 7 minutes, the sheet is removed to obtain the butyl rubber composite compound.

[0068] Example 1

[0069] A novel method for preparing a semiconductive buffer layer for cables includes the following steps:

[0070] (1) The butyl rubber composite compound of Preparation Example 3 was cut into rubber particles and then placed in a beaker. No. 120 solvent oil was added. The rubber particles accounted for 14 wt% of the total mass fraction of the system. The beaker was placed in a magnetic stirrer and the speed was set to 800 r / min. The stirring was carried out for 6 hours and the dissolution was observed. Then, the beaker was placed in a water bath and heated and stirred for 6 hours. The water bath heating temperature was 50℃ to obtain a rubber solution.

[0071] (2) Take a 0.3mm thick semiconducting resistance water tape and lay it flat on an automatic coating machine. Pour in the rubber solution and adjust the coating thickness to 0.05mm. Automatically coat the rubber solution at a low speed. Then put the prepared semiconducting buffer layer into an 80℃ oven to dry for 10min. Then put it into a 170℃ oven to vulcanize for 10min to form a rubber coating and obtain the buffer layer.

[0072] Example 2

[0073] A novel method for preparing a semiconductive buffer layer for cables includes the following steps:

[0074] (1) The butyl rubber composite compound of Preparation Example 3 was cut into rubber particles and then placed in a beaker. No. 120 solvent oil was added. The rubber particles accounted for 14 wt% of the total mass fraction of the system. The beaker was placed in a magnetic stirrer and the speed was set to 800 r / min. The stirring was carried out for 6 hours and the dissolution was observed. Then, the beaker was placed in a water bath and heated and stirred for 6 hours. The water bath heating temperature was 50℃ to obtain a rubber solution.

[0075] (2) Take a 0.114mm thick semi-conductive nylon tape and lay it flat on an automatic coating machine. Pour in the rubber solution and adjust the coating thickness to 0.05mm. Automatically coat the rubber solution at a low speed. Then put the prepared semi-conductive buffer layer into an 80℃ oven to dry for 10min. Then put it into a 170℃ oven to vulcanize for 10min to form a rubber coating and obtain the buffer layer.

[0076] Comparative Example 1

[0077] A novel method for preparing a semiconductive buffer layer for cables includes the following steps:

[0078] (1) The butyl rubber composite compound of Preparation Example 3 was cut into rubber particles and then placed in a beaker. No. 120 solvent oil was added. The rubber particles accounted for 14 wt% of the total mass fraction of the system. The beaker was placed in a magnetic stirrer and the speed was set to 800 r / min. The stirring was carried out for 6 hours and the dissolution was observed. Then, the beaker was placed in a water bath and heated and stirred for 6 hours. The water bath heating temperature was 50℃ to obtain a rubber solution.

[0079] (2) Take a 0.31mm thick semi-conductive non-woven fabric and lay it flat on an automatic coating machine. Pour in the rubber solution and adjust the coating thickness to 0.05mm. Automatically coat the rubber solution at a low speed. Then put the prepared semi-conductive buffer layer into an 80℃ oven to dry for 10min. Then put it into a 170℃ oven to vulcanize for 10min to form a rubber coating and obtain the buffer layer.

[0080] Comparative Example 2

[0081] A semi-conductive buffer layer for cables, wherein the buffer layer is a semi-conductive non-woven fabric tape with a thickness of 0.31 mm.

[0082] Comparative Example 3

[0083] A semi-conductive buffer layer for cables, wherein the buffer layer is a semi-conductive resistive water tape with a thickness of 0.3 mm.

[0084] Comparative Example 4

[0085] A semi-conductive buffer layer for cables, wherein the buffer layer is a semi-conductive nylon tape with a thickness of 0.114 mm.

[0086] Comparative Example 5

[0087] A novel method for preparing a semiconductive buffer layer for cables includes the following steps:

[0088] (1) Cut the butyl rubber composite compound of Comparative Preparation Example 3 into rubber particles, then put them into a beaker, add No. 120 solvent oil, the rubber particles account for 14 wt% of the total mass fraction of the system, place the beaker in a magnetic stirrer, set the speed to 800 r / min, stir for 6 h, observe the dissolution, then put it in a water bath heating pot and heat and stir for 6 h, the water bath heating temperature is 50℃, to obtain a rubber solution;

[0089] (2) Take a 0.3mm thick semiconducting resistance water tape and lay it flat on an automatic coating machine. Pour in the rubber solution and adjust the coating thickness to 0.05mm. Automatically coat the rubber solution at a low speed. Then put the prepared semiconducting buffer layer into an 80℃ oven to dry for 10min. Then put it into a 170℃ oven to vulcanize for 10min to form a rubber coating and obtain the buffer layer.

[0090] Comparative Example 6

[0091] A novel method for preparing a semiconductive buffer layer for cables includes the following steps:

[0092] (1) Cut the butyl rubber composite compound of Comparative Preparation Example 4 into rubber particles, then put them into a beaker, add No. 120 solvent oil, the rubber particles account for 14 wt% of the total mass fraction of the system, place the beaker in a magnetic stirrer, set the speed to 800 r / min, stir for 6 h, observe the dissolution, then put it in a water bath heating pot and heat and stir for 6 h, the water bath heating temperature is 50℃, to obtain a rubber solution;

[0093] (2) Take a 0.3mm thick semiconducting resistance water tape and lay it flat on an automatic coating machine. Pour in the rubber solution and adjust the coating thickness to 0.05mm. Automatically coat the rubber solution at a low speed. Then put the prepared semiconducting buffer layer into an 80℃ oven to dry for 10min. Then put it into a 170℃ oven to vulcanize for 10min to form a rubber coating and obtain the buffer layer.

[0094] Comparative Example 7

[0095] A novel method for preparing a semiconductive buffer layer for cables includes the following steps:

[0096] (1) Cut the butyl rubber composite compound of Comparative Preparation Example 2 into rubber particles, then put them into a beaker, add No. 120 solvent oil, the rubber particles account for 14 wt% of the total mass fraction of the system, place the beaker in a magnetic stirrer, set the speed to 800 r / min, stir for 6 h, observe the dissolution, then put it in a water bath heating pot and heat and stir for 6 h, the water bath heating temperature is 50℃, to obtain a rubber solution;

[0097] (2) Take a 0.3mm thick semiconducting resistance water tape and lay it flat on an automatic coating machine. Pour in the rubber solution and adjust the coating thickness to 0.05mm. Automatically coat the rubber solution at a low speed. Then put the prepared semiconducting buffer layer into an 80℃ oven to dry for 10min. Then put it into a 170℃ oven to vulcanize for 10min to form a rubber coating and obtain the buffer layer.

[0098] Performance testing

[0099] 1. The butyl rubber composite compounds prepared in Preparation Examples 1-3 and Comparative Preparation Examples 1-2 were respectively placed in a 70℃ flat vulcanizing machine for 30 min to melt, and then crosslinked and molded in a 15MPa, 170℃ flat vulcanizing machine for 10 min to obtain rubber sheets with a thickness of 1 mm. The sheets were cut into 5cm*11cm samples, and the volume resistivity at 25-100℃ was tested using a semiconducting rubber and plastic resistance tester according to the national standard GB-3048.3-2007. The test results are shown in Figure 1.

[0100] 2. The cross-section of the butyl rubber composite compound prepared in Example 3 above was observed using a scanning electron microscope. The observed SEM images are shown in Figure 2-3. It can be found that the carbon black component is uniformly distributed and the filler in the material is well dispersed.

[0101] 3. The volume resistivity and surface resistance of the semiconductive buffer layers prepared in Examples 1-2 and Comparative Examples 1-7 were tested. The volume resistivity of the buffer layer was required to be within 1*10⁻⁶. 5 The surface resistivity is required to be below 1000Ω·cm, and the test standard is T / CEEIA 610—2022 "Semi-conductive wrapping tape for buffer layer of power cable with rated voltage of 110kV and above". The test results are shown in Table 1 below.

[0102] 4. The semiconductive buffer layers prepared in Examples 1-2 and Comparative Examples 1-7 were tested for maximum breaking force and elongation at break. The test standard was T / CEEIA 610—2022 "Semiconductive wrapping tape for buffer layers of power cables with rated voltage of 110kV and above". The test results are shown in Table 1 below.

[0103] Table 1 - Performance test results of the semiconductive buffer layers prepared in the embodiments and comparative examples of this application

[0104] As shown in Figure 1 and Table 1, the butyl rubber composites of Preparation Examples 1-3 and Comparative Preparation Examples 1-2 were vulcanized to form rubber sheets. It can be found that the volume resistivity is between 10-90 Ω·cm, which is relatively small. Moreover, the volume resistivity gradually decreases with the increase of carbon black content. The volume resistivity of the rubber sheet prepared in Preparation Example 3 has been reduced to near the threshold and has good conductivity. However, the volume resistivity of the rubber sheet prepared in Comparative Preparation Examples 1-2 is relatively high. When coated on the surface of the semi-conductive buffer tape, it is easy to affect the overall volume resistivity of the buffer layer, resulting in a high volume resistivity of the buffer layer and a decrease in the mechanical strength of the buffer layer.

[0105] As shown in Table 1, Example 1 uses a semiconducting resistive water tape as the substrate and coats it with a rubber coating, while Example 2 uses a semiconducting nylon tape as the substrate and coats it with a rubber coating. The volume resistivity of the prepared buffer layer is less than 1*10⁻⁶. 5 The volume resistivity of the buffer layer is Ω·cm, and the surface resistivity is less than 1000Ω, exhibiting good conductivity and field strength homogenization effect; while Comparative Example 1 uses semi-conductive nonwoven fabric as the substrate and coats the surface with a rubber coating, resulting in a buffer layer with a volume resistivity higher than 1.5*10 Ω·cm. 5 The surface resistance is Ω·cm and the surface resistance is higher than 3000Ω, indicating poor conductivity and inability to meet high electrical performance requirements. This suggests that semi-conductive resistive water tape and semi-conductive nylon tape are more suitable as the substrate for cable buffer layers.

[0106] As shown in Table 1, the buffer layers of Comparative Examples 2-4 were made of uncoated semi-conductive nonwoven fabric, semi-conductive resistive water tape, and semi-conductive nylon tape. Compared with Examples 1-2 and Comparative Example 1, the buffer layers of Comparative Examples 2-4 had lower tensile strength, indicating that the tensile properties of the cable buffer layers were significantly improved after coating with butyl rubber composite material. Moreover, the buffer layers prepared using semi-conductive nylon tape had significantly better tensile properties, indicating that semi-conductive nylon tape was more suitable as the basic material for cable buffer tape. In addition, the semi-conductive resistive water tape of Comparative Example 3 had higher volume resistivity and surface resistivity than the uncoated rubber-coated Example 1.

[0107] As shown in Table 1, in Preparation Example 3 of this application, zinc oxide, magnesium oxide, and calcium oxide react with hydrogen sulfide generated during the vulcanization of butyl rubber, thus preventing hydrogen sulfide from destroying the disulfide bonds in the rubber. After the rubber solution is vulcanized, a rubber coating is formed on the semiconductive buffer tape, which can improve the overall mechanical strength of the buffer layer. In contrast, in Preparation Example 1, due to insufficient zinc oxide, magnesium oxide, and calcium oxide and excessive sulfur addition, more disulfide bonds in the rubber coating formed after vulcanization were destroyed by hydrogen sulfide, resulting in a decrease in the overall mechanical strength of the buffer layer.

[0108] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit the scope of protection of this application. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application for those skilled in the art.

Claims

1. A novel semi-conductive buffer layer for cables, characterized in that, The device includes a semi-conductive buffer tape and a rubber coating on the surface of the semi-conductive buffer tape. The semi-conductive buffer tape is a semi-conductive resistive water tape or a semi-conductive nylon tape. The rubber coating comprises the following components in parts by weight: butyl rubber: 300 parts. Conductive filler: 150-180 parts; Functional additives: 13-30 parts; Paraffin wax: 15-20 parts; Vulcanizing agent: 4-7 parts; The functional additives include zinc oxide, magnesium oxide and calcium oxide in a mass ratio of 4:(0.5-1):(0.5-1).

2. The novel cable semiconductive buffer layer as described in claim 1, characterized in that, The rubber coating also includes an antioxidant in the form of 3-9 parts by weight; And / or, the rubber coating further includes 1-6 parts by weight of a vulcanization accelerator.

3. The novel cable semiconductive buffer layer as described in claim 2, characterized in that, The vulcanization accelerator comprises 2-4 parts by weight of accelerator TMTD and 1-2 parts by weight of accelerator M.

4. The novel cable semiconductive buffer layer as described in claim 1, characterized in that, The functional additives include zinc oxide, magnesium oxide and calcium oxide in a mass ratio of 4:0.5:0.

5.

5. The novel cable semiconductive buffer layer as described in claim 1, characterized in that, The conductive filler is at least one of carbon black, carbon nanotubes, graphene, graphite, and nano-metallic elements.

6. The novel cable semiconductive buffer layer as described in claim 2, characterized in that, The antioxidant is N-cyclohexyl-N'-phenyl-p-phenylenediamine; And / or, the vulcanizing agent is sulfur.

7. The novel cable semiconductive buffer layer as described in claim 1, characterized in that, The thickness of the semi-conductive buffer strip is 0.1-1 mm.

8. A method for preparing a novel cable semiconductive buffer layer as described in any one of claims 1-7, characterized in that, Includes the following steps: (1) Cut the butyl rubber composite compound into rubber granules, add No. 120 solvent oil, stir for 4-10 hours, then heat and stir in a water bath for 4-8 hours to obtain a rubber solution; (2) Coat the substrate surface with a rubber solution, dry and vulcanize to form a rubber coating, and obtain a buffer layer.

9. The method for preparing the novel cable semiconductive buffer layer as described in claim 8, characterized in that, In step (1), the preparation method of the butyl rubber composite compound is as follows: butyl rubber is added to the open mill and plasticized evenly. Then, functional additives, antioxidants and paraffin wax are added and mixed evenly. Then, carbon black is added in several batches and mixed evenly. Finally, vulcanizing agent and vulcanization accelerator are added and mixed evenly. The roller gap is adjusted to pass through the thin rubber sheet and the sheet is cut to obtain the butyl rubber composite compound.

10. The method for preparing the novel cable semiconductive buffer layer as described in claim 8, characterized in that, In step (1), the mass ratio of the rubber material to No. 120 solvent oil is (10-20):(80-90); And / or, in step (1), the water bath heating temperature is 40-60℃; And / or, in step (2), the coating thickness of the rubber solution is 0.02-0.08 mm; And / or, in step (2), the drying temperature is 60-100℃ and the drying time is 5-15min; And / or, in step (2), the vulcanization temperature is 150-180℃ and the vulcanization time is 5-15min.

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