Silane crosslinked polyethylene cable insulation material and preparation method thereof

Abstract

The invention relates to a silane crosslinked polyethylene cable insulating material and a preparation method thereof, and relates to the technical field of insulating materials. The silane crosslinked polyethylene cable insulating material is prepared from the following raw materials in parts by mass: 0.2 to 2 parts of modified sepiolite, 30 to 50 parts of high-density polyethylene, 70 to 100 parts of linear low-density polyethylene, 1.2 to 2 parts of silane coupling agent, 1 to 3 parts of antioxidant, 0.5 to 1 part of catalyst, 0.2 to 0.8 part of initiator, 0.2 to 2 parts of heat-conducting filler and 0.5 to 3 parts of rheological master batch. According to the polytetrahydrofuran glycol, a series of tetrahydric alcohols are connected through ether bonds to form a flexible chain structure, the chain structure brings good flexibility to the polytetrahydrofuran glycol, and the chain structure of the polytetrahydrofuran glycol is entangled with a polyethylene macromolecule long chain, so that the polytetrahydrofuran glycol is formed. By adding the polytetrahydrofuran glycol, the cable material can resist brittle rupture caused by a low-temperature environment, so that the cable material has good low-temperature resistance.

Description

Technical Field

[0001] This invention belongs to the field of insulation materials technology, specifically relating to a silane cross-linked polyethylene cable insulation material and its preparation method. Background Technology

[0002] The development of power energy is crucial to national welfare and national security. With the sustained and rapid development of my country's economy and society, electricity demand has entered a period of rapid growth. Cross-linked polyethylene (XLPE) materials, due to their unique three-dimensional network structure composed of polyethylene polymer chains grafted with vinyl silane, possess excellent electrical and mechanical properties, leading to their widespread application in cable insulation materials. However, because the main molecular chains of the three-dimensional network structure of XLPE materials are polyethylene polymer chains, they inevitably lack low-temperature resistance and are prone to low-temperature brittleness. Furthermore, currently available silane-crosslinked polyethylene insulation materials have a long-term operating temperature of only 90℃, which limits their application for cables with higher temperature resistance requirements, such as wind power cables.

[0003] The invention patent with publication number CN111040333A discloses a high-temperature resistant polyvinyl chloride / nitrile rubber composite cable material. This high-temperature resistant polyvinyl chloride / nitrile rubber composite cable material contains the flame retardant sepiolite. Sepiolite has water absorption properties and has strong surface polarity and high surface energy, making it prone to agglomeration. Summary of the Invention

[0004] The first objective of this invention is to provide a silane cross-linked polyethylene cable insulation material to solve the technical problem of the limited application range of existing cross-linked polyethylene materials.

[0005] The second objective of this invention is to provide a method for preparing silane cross-linked polyethylene cable insulation material.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A silane cross-linked polyethylene cable insulation material, comprising the following raw materials by weight: 0.2-2 parts modified sepiolite, 30-50 parts high-density polyethylene, 70-100 parts linear low-density polyethylene, 1.2-2 parts silane coupling agent, 1-3 parts antioxidant, 0.5-1 part catalyst, 0.2-0.8 parts initiator, 0.2-2 parts thermally conductive filler, and 0.5-3 parts rheology masterbatch; the modified sepiolite is prepared by:

[0008] S1: Sepiolite is soaked in an epoxy silane coupling agent solution to obtain silane coupling agent modified sepiolite;

[0009] S2: Sepiolite modified with silane coupling agent, polytetrahydrofuran diol, catalyst, and solvent are mixed and heated to react. The solvent is then removed under vacuum to obtain the final product.

[0010] Furthermore, the epoxy silane coupling agent solution in S1 is an epoxy silane coupling agent ethanol solution, and the concentration of the epoxy silane coupling agent solution is 0.5-1 mmol / L; 5-8 mL of epoxy silane coupling agent solution is added for each g of sepiolite.

[0011] Furthermore, the mass ratio of the silane coupling agent-modified sepiolite to the polytetrahydrofuran diol is 1:1 to 1:1.2; the mass ratio of the silane coupling agent-modified sepiolite to the catalyst is 1:0.05 to 1:0.08; the catalyst is triethylamine, and the solvent is methanol.

[0012] Furthermore, the temperature for heating in S2 is 60–100°C, and the reaction time is 5–8 hours.

[0013] Furthermore, the thermally conductive filler is vitrified microspheres and silicon dioxide; the mass ratio of the vitrified microspheres to silicon dioxide is 1:1 to 1:1.2.

[0014] Furthermore, the melt index of the high-density polyethylene is 2.0 to 10.0 g / 10 min; the melt index of the linear low-density polyethylene is 10 to 30 g / 10 min.

[0015] Furthermore, the silane coupling agent is one or more of vinyltrimethoxysilane and vinyltriethoxysilane; the initiator is one or more of dicumyl peroxide, di-tert-butyl peroxide, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane; the antioxidant is one or more of antioxidant 264, antioxidant 2246, and antioxidant 1010; and the catalyst is one or more of dibutyltin dilaurate, dibutyltin diacetate, and dibutyltin dioctanoate.

[0016] A method for preparing a silane cross-linked polyethylene cable insulation material includes the following steps:

[0017] S1: Mix the high-density polyethylene, silane coupling agent, modified sepiolite, initiator, thermally conductive filler and 20-25 parts of linear low-density polyethylene evenly, and then extrude and granulate them using a twin-screw extruder to obtain component A.

[0018] S2: Mix the rheology masterbatch, catalyst, antioxidant and the remaining linear low-density polyethylene in the formula evenly, and then add it to a twin-screw extruder for extrusion granulation to obtain component B;

[0019] S3: Mix components A and B, extrude them into a mold, and then crosslink them to obtain the final product.

[0020] Furthermore, the crosslinking is carried out in water at 90–100°C.

[0021] Furthermore, the temperatures of each stage of the twin-screw extruder described in S1 and S2 are as follows: feed section 120-140℃, compression section 150-190℃, plasticizing section 205-225℃, flange 170-180℃, neck 170-180℃, die head 210-230℃, and die 230-240℃.

[0022] The beneficial effects of this invention are:

[0023] Polytetrahydrofuran diol is a flexible chain structure formed by a series of tetraols linked by ether bonds. This chain structure gives polytetrahydrofuran diol good flexibility. The chain structure of polytetrahydrofuran diol is entangled with the long chain of polyethylene polymer. The addition of polytetrahydrofuran diol can make the cable material resist brittle fracture caused by low temperature environment, so that the cable material has good low temperature resistance.

[0024] Sepiol has a very strong surface polarity and high surface energy, making it prone to particle agglomeration. This invention addresses this by grafting polytetrahydrofuran diol onto sepiol. The chain structure of polytetrahydrofuran diol extends around the sepiol, increasing its steric hindrance and preventing agglomeration.

[0025] Sepiolite is hygroscopic. This invention reduces its hygroscopicity by forming a coating layer on the surface of sepiolite using anhydrous ethanol, ammonia, and tetraethyl orthosilicate. Sepiolite exhibits high thermal stability and does not deform at temperatures below 350°C. Vitrified microspheres and silica both have high thermal conductivity, and thermally conductive fillers can play a temperature-regulating role in cable materials. The composite of sepiolite, vitrified microspheres, and silica in this invention can effectively reduce the heating rate of cable materials in high-temperature environments and improve their high-temperature stability. This invention significantly broadens the application range of silane cross-linked polyethylene cable insulation materials. Detailed Implementation

[0026] The present invention will be further described below with reference to embodiments thereof.

[0027] Example 1

[0028] The silane cross-linked polyethylene cable insulation material of Example 1 comprises the following raw materials: 0.2g modified sepiolite, 35g high-density polyethylene, 70g linear low-density polyethylene, 1.2g silane coupling agent, 1.5g antioxidant, 0.5g catalyst, 0.2g initiator, 0.2g thermally conductive filler, and 0.5g rheology masterbatch. The thermally conductive filler comprises 0.1g vitrified microspheres and 0.1g silica. The melt index of the high-density polyethylene is 8g / 10min; the melt index of the linear low-density polyethylene is 13g / 10min. The silane coupling agent is vinyltrimethoxysilane; the initiator is dicumyl peroxide; the antioxidant is antioxidant 264; and the catalyst is dibutyltin dilaurate.

[0029] The preparation method of modified sepiolite is as follows:

[0030] S1: 1g of sepiolite powder was mixed with 20mL of anhydrous ethanol, 1mL of ammonia water and 1.2mL of tetraethyl orthosilicate and reacted at 10℃ to obtain coated sepiolite.

[0031] S2: The coated sepiolite was soaked in an ethanol solution of 6 mL of 0.5 mmol / L epoxy silane coupling agent to obtain sepiolite modified with silane coupling agent.

[0032] S3: Sepiolite modified with silane coupling agent, 1.1 g of polytetrahydrofuran diol, 0.06 g of triethylamine, and 3 mL of methanol were mixed and reacted at 60 °C for 7 h. Then, the methanol was removed under vacuum to obtain the final product.

[0033] The preparation method of the silane cross-linked polyethylene cable insulation material in Example 1 includes the following steps:

[0034] S1: Mix the high-density polyethylene, silane coupling agent, modified sepiolite, initiator, thermally conductive filler and 20g of linear low-density polyethylene evenly, and then extrude and granulate them using a twin-screw extruder to obtain component A.

[0035] S2: After the rheology masterbatch, catalyst, antioxidant and the remaining linear low-density polyethylene are mixed evenly, they are added to a twin-screw extruder for extrusion granulation to obtain component B;

[0036] S3: Mix components A and B, extrude them, and crosslink them in water at 90°C to obtain the final product.

[0037] The temperatures of each stage of the twin-screw extruders S1 and S2 are as follows: feed section 120℃, compression section 150℃, plasticizing section 205℃, flange 170℃, neck 170℃, die head 210℃, and die 230℃.

[0038] Example 2

[0039] The silane cross-linked polyethylene cable insulation material of Example 2 comprises the following raw materials: 1 kg of modified sepiolite, 50 kg of high-density polyethylene, 100 kg of linear low-density polyethylene, 2 kg of silane coupling agent, 3 kg of antioxidant, 1 kg of catalyst, 0.8 kg of initiator, 1 kg of thermally conductive filler, and 1.5 kg of rheology masterbatch. The thermally conductive filler comprises 0.45 kg of vitrified microspheres and 0.55 g of silica. The melt index of high-density polyethylene is 10 g / 10 min; the melt index of linear low-density polyethylene is 20 g / 10 min. The silane coupling agent is vinyltrimethoxysilane; the initiator is 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane; the antioxidant is antioxidant 2246; and the catalyst is dibutyltin dioctanoate.

[0040] The preparation method of modified sepiolite is as follows:

[0041] S1: 1 kg of sepiolite powder was mixed with 15 L of anhydrous ethanol, 0.8 L of ammonia water and 1 L of tetraethyl orthosilicate and reacted at 20 °C to obtain coated sepiolite.

[0042] S2: The coated sepiolite was immersed in an ethanol solution of epoxy silane coupling agent with a concentration of 8L and 0.8mmol / L to obtain sepiolite modified with silane coupling agent.

[0043] S3: Sepiolite modified with silane coupling agent, 1.2 kg of polytetrahydrofuran diol, 0.08 kg of triethylamine, and 3 L of methanol were mixed and reacted at 100 °C for 8 h. The methanol was then removed under vacuum to obtain the final product.

[0044] The preparation method of the silane cross-linked polyethylene cable insulation material in Example 2 includes the following steps:

[0045] S1: Mix the high-density polyethylene, silane coupling agent, modified sepiolite, initiator, thermally conductive filler and 25 kg of linear low-density polyethylene evenly, and then extrude and granulate them using a twin-screw extruder to obtain component A.

[0046] S2: Mix the rheology masterbatch, catalyst, antioxidant and the remaining linear low-density polyethylene in the formula evenly, and then add it to a twin-screw extruder for extrusion granulation to obtain component B;

[0047] S3: Mix components A and B, extrude them, and crosslink them at 100°C to obtain the final product.

[0048] The temperatures of each stage of the twin-screw extruders S1 and S2 are as follows: feed section 135℃, compression section 170℃, plasticizing section 210℃, flange 180℃, neck 170℃, die head 220℃, and die 235℃.

[0049] Example 3

[0050] The silane cross-linked polyethylene cable insulation material of Example 3 comprises the following raw materials: 2 kg of modified sepiolite, 50 kg of high-density polyethylene, 90 kg of linear low-density polyethylene, 1.8 kg of silane coupling agent, 2 kg of antioxidant, 0.8 kg of catalyst, 0.8 kg of initiator, 2 kg of thermally conductive filler, and 2 kg of rheology masterbatch. The thermally conductive filler comprises 0.95 kg of vitrified microspheres and 1.05 kg of silica. The melt index of the high-density polyethylene is 10 g / 10 min; the melt index of the linear low-density polyethylene is 30 g / 10 min. The silane coupling agent is vinyltriethoxysilane, the initiator is di-tert-butyl peroxide, the antioxidant is antioxidant 1010, and the catalyst is dibutyltin diacetate.

[0051] The preparation method of modified sepiolite is as follows:

[0052] S1: 2 kg of sepiolite powder was mixed with 25 L of anhydrous ethanol, 1.2 L of ammonia water and 1.2 L of tetraethyl orthosilicate and reacted at 15 °C to obtain coated sepiolite.

[0053] S2: The coated sepiolite was soaked in an ethanol solution of epoxy silane coupling agent with a concentration of 8L and 1mmol / L to obtain sepiolite modified with silane coupling agent.

[0054] S3: Sepiolite modified with silane coupling agent, 2.4 kg of polytetrahydrofuran diol, 0.16 kg of triethylamine, and 5 L of methanol were mixed and reacted at 100 °C for 6 h. The methanol was then removed under vacuum to obtain the final product.

[0055] The preparation method of the silane cross-linked polyethylene cable insulation material in Example 3 includes the following steps:

[0056] S1: Mix the high-density polyethylene, silane coupling agent, modified sepiolite, initiator, thermally conductive filler and 25 kg of linear low-density polyethylene evenly, and then extrude and granulate them using a twin-screw extruder to obtain component A.

[0057] S2: Mix the rheology masterbatch, catalyst, antioxidant and the remaining linear low-density polyethylene in the formula evenly, and then add it to a twin-screw extruder for extrusion granulation to obtain component B;

[0058] S3: Mix components A and B, extrude them, and crosslink them at 100°C to obtain the final product.

[0059] The temperatures of each stage of the twin-screw extruders S1 and S2 are as follows: feed section 140℃, compression section 190℃, plasticizing section 225℃, flange 180℃, neck 180℃, die head 220℃, and die 235℃.

[0060] Comparative Example 1

[0061] The silane cross-linked polyethylene cable insulation material of Comparative Example 1 is largely the same as that of Example 2. The difference between the silane cross-linked polyethylene cable insulation material of Comparative Example 1 and Example 2 is that the modified sepiolite in Comparative Example 1 is replaced with an equal mass of sepiolite.

[0062] Comparative Example 2

[0063] The silane cross-linked polyethylene cable insulation material of Comparative Example 2 is largely the same as that of Example 2. The difference between the silane cross-linked polyethylene cable insulation material of Comparative Example 2 and Example 2 is that the modified sepiolite of Comparative Example 2 is prepared by mixing 1 kg of sepiolite powder with 15 L of anhydrous ethanol, 0.8 L of ammonia water and 1 L of tetraethyl orthosilicate and reacting at 20 °C to obtain the product.

[0064] Comparative Example 3

[0065] The silane cross-linked polyethylene cable insulation material of Comparative Example 3 is largely the same as that of Example 2. The difference between the silane cross-linked polyethylene cable insulation material of Comparative Example 3 and Example 2 is that the preparation method of the modified sepiolite in Comparative Example 3 is as follows:

[0066] S1: Soak 1 kg of sepiolite powder in an ethanol solution of epoxy silane coupling agent with a concentration of 8 L and a concentration of 0.8 mmol / L to obtain sepiolite modified with silane coupling agent.

[0067] S2: Sepiolite modified with silane coupling agent, 1.2 kg of polytetrahydrofuran diol, 0.08 kg of triethylamine, and 3 L of methanol were mixed and reacted at 100 °C for 8 h. The methanol was then removed under vacuum to obtain the final product.

[0068] Experimental Example 1

[0069] The cable materials prepared in Example 1 and Comparative Examples 1-3 were used to make test samples:

[0070] 1. Mechanical performance tests shall be conducted in accordance with GB / T 1040.3-2006;

[0071] 2. Long-term high temperature resistance performance test was conducted according to GB / T2951.12~2008. Test conditions: 145℃, 6 months.

[0072] 3. Conduct low-temperature resistance tests according to GB / T 5470;

[0073] The test results are shown in Table 1.

[0074] Table 1. Test results of cable material performance in Example 1 and Comparative Examples 1-3

[0075]

[0076] As shown in Table 1, Example 1 exhibits good high-temperature and low-temperature resistance, indicating that the cable material of Example 1 has a wide range of applications. However, the sepiolite in Comparative Examples 1 and 2 agglomerates, resulting in uneven distribution and affecting the high-temperature resistance of the cable materials. Furthermore, the absence of polytetrahydrofuran glycol in Comparative Examples 1 and 2 negatively impacts their low-temperature resistance.

[0077] Experimental Example 2

[0078] The cable materials prepared in Example 1 and Comparative Examples 1-3 were used to make test samples:

[0079] 1. Use a contact angle tester to measure the static contact angle of the cable material surface. The volume of the water droplet is about 5μL. The average value of the contact angle at 5 different points on the cable material surface is used as the measurement result.

[0080] 2. The test was conducted on a GIW-50kV computer-controlled voltage breakdown tester, using DC breakdown mode, with the voltage ramp rate set to 1.0kV / mm. The value of the high voltage DC breakdown strength was taken as the average of 5 tests.

[0081] The test results are shown in Table 2.

[0082] Table 2. Test results of cable material performance in Example 1 and Comparative Examples 1-3

[0083]

[0084] As can be seen from Table 2, Example 1 has a larger contact angle and good hydrophobicity, while the contact angles of Comparative Examples 1 and 3 are reduced, which is due to the water absorption of sepiolite. Example 1 forms a coating layer on the surface of sepiolite, reducing its water absorption, thus improving the contact angle of the silane cross-linked polyethylene cable insulation material.

Claims

1. A silane cross-linked polyethylene cable insulation material, characterized in that, The raw materials, calculated by weight, include: 0.2-2 parts modified sepiolite, 30-50 parts high-density polyethylene, 70-100 parts linear low-density polyethylene, 1.2-2 parts silane coupling agent, 1-3 parts antioxidant, 0.5-1 part catalyst, 0.2-0.8 parts initiator, 0.2-2 parts thermally conductive filler, and 0.5-3 parts rheology masterbatch; the preparation method of the modified sepiolite is as follows: S1: Sepiolite is soaked in an epoxy silane coupling agent solution to obtain silane coupling agent modified sepiolite; S2: Sepiolite modified with silane coupling agent, polytetrahydrofuran diol, catalyst, and solvent are mixed and heated to react. The solvent is then removed under vacuum to obtain the final product.

2. The silane cross-linked polyethylene cable insulation material according to claim 1, characterized in that, The epoxy silane coupling agent solution mentioned in S1 is an epoxy silane coupling agent ethanol solution, and the concentration of the epoxy silane coupling agent solution is 0.5-1 mmol / L; 5-8 mL of epoxy silane coupling agent solution is added for each g of sepiolite.

3. The silane cross-linked polyethylene cable insulation material according to claim 1, characterized in that, The mass ratio of the silane coupling agent-modified sepiolite to the polytetrahydrofuran diol is 1:1 to 1:1.2; the mass ratio of the silane coupling agent-modified sepiolite to the catalyst is 1:0.05 to 1:0.08; the catalyst is triethylamine, and the solvent is methanol.

4. The silane cross-linked polyethylene cable insulation material according to claim 1, characterized in that, The temperature for heating in S2 is 60–100 °C, and the reaction time is 5–8 h.

5. The silane cross-linked polyethylene cable insulation material according to claim 1, characterized in that, The thermally conductive filler is vitrified microspheres and silicon dioxide; the mass ratio of the vitrified microspheres to silicon dioxide is 1:1 to 1:1.

2.

6. The silane cross-linked polyethylene cable insulation material according to claim 1, characterized in that, The melt index of the high-density polyethylene is 2.0 to 10.0 g / 10 min; the melt index of the linear low-density polyethylene is 10 to 30 g / 10 min.

7. The silane cross-linked polyethylene cable insulation material according to claim 1, characterized in that, The silane coupling agent is one or more of vinyltrimethoxysilane and vinyltriethoxysilane; the initiator is one or more of dicumyl peroxide, di-tert-butyl peroxide, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane; the antioxidant is one or more of antioxidant 264, antioxidant 2246, and antioxidant 1010; and the catalyst is one or more of dibutyltin dilaurate, dibutyltin diacetate, and dibutyltin dioctanoate.

8. A method for preparing the silane cross-linked polyethylene cable insulation material as described in claim 1, characterized in that, Includes the following steps: S1: Mix the high-density polyethylene, silane coupling agent, modified sepiolite, initiator, thermally conductive filler and 20-25 parts of linear low-density polyethylene evenly, and then extrude and granulate them using a twin-screw extruder to obtain component A. S2: Mix the rheology masterbatch, catalyst, antioxidant and the remaining linear low-density polyethylene in the formula evenly, and then add it to a twin-screw extruder for extrusion granulation to obtain component B; S3: Mix components A and B, extrude them into a mold, and then crosslink them to obtain the final product.

9. The method for preparing silane cross-linked polyethylene cable insulation material according to claim 8, characterized in that, The crosslinking is carried out in water at 90–100 °C.

10. The method for preparing silane cross-linked polyethylene cable insulation material according to claim 8, characterized in that, The temperatures of each stage of the twin-screw extruder described in S1 and S2 are as follows: feed section 120-140 ℃, compression section 150-190 ℃, plasticizing section 205-225 ℃, flange 170-180 ℃, and neck 170-180 ℃.

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