Process for the preparation of glycidyl ether ester and dcp dual crosslinked eaa and ldpe cable material

Abstract

The present application relates to a kind of 4-(4-epoxy methoxyl phenyl) benzoic acid glycidyl ester and DCP double crosslinking EAA and LDPE high-voltage direct current cable material preparation method, belong to high-voltage direct current cable material field.4-(4-epoxy methoxyl phenyl) benzoic acid glycidyl ester and DCP double crosslinking EAA and LDPE high-voltage direct current cable material preparation method in the present application is: with ethylene acrylic acid copolymer EAA and low-density polyethylene LDPE as matrix, using small molecule epoxy compound 4-(4-epoxy methoxyl phenyl) benzoic acid glycidyl ester and DCP as crosslinking agent, obtain double crosslinking high-voltage direct current cable material on flat curing press with heating and pressurization.The double crosslinking high-voltage direct current cable material prepared by the present application preparation method is simple, significantly improves the direct current breakdown performance and tensile property of high-voltage cable material.

Description

Technical Field

[0001] The invention relates to a preparation method of a glycidyl ether ester and DCP double-crosslinked EAA and LDPE cable material, belonging to the technical field of high-voltage direct current cable material preparation. Background Art

[0002] Power cables not only provide a reliable power supply for homes and businesses, but also support the normal operation of multiple fields such as industry, transportation, and communications. The current mainstream high-voltage cable insulation material is based on low-density polyethylene (LDPE) and is prepared by adding various small molecule additives such as voltage stabilizers and antioxidants. Among them, low-density polyethylene is the most important component that exerts the insulation performance of the material. However, the mechanical properties of low-density polyethylene itself are poor, and it is necessary to add a peroxide crosslinking agent DCP to form cross-linked polyethylene (XLPE) to make its mechanical properties meet basic usage requirements. In order to meet the use standards of cable insulation materials, traditional cross-linked polyethylene will add functional additives such as voltage stabilizers and co-crosslinking agents to improve the material's voltage rating and mechanical strength. However, after the small molecule voltage stabilizer is mixed with XLPE, problems such as migration and phase separation will occur. Therefore, the present invention proposes a novel XLPE cross-linking method. While introducing polyolefin polymer substances into the system, the voltage stabilizing segment is introduced into the insulation material in a "click reaction" manner, thereby achieving the purpose of improving mechanical and electrical properties.

[0003] The present invention adds two crosslinking agents, DCP and 4-(4-epoxymethoxyphenyl) benzoic acid glycidyl ester, to LDPE and EAA, so that LDPE and EAA undergo free radical crosslinking and nucleophilic addition crosslinking simultaneously, and simultaneously introduces voltage-stabilizing fragments and electron deep traps in situ, thereby improving the mechanical and electrical properties of the cable material without adding unnecessary small molecule additives. Summary of the Invention

[0004] A method for preparing a high-voltage direct current cable material comprising 4-(4-epoxymethoxyphenyl) benzoic acid glycidyl ester and DCP double-crosslinked EAA and LDPE is characterized in that a certain amount of low-density polyethylene (LDPE), small molecule 4-(4-epoxymethoxyphenyl) benzoic acid glycidyl ester, ethylene acrylic acid copolymer (EAA), and dicumyl peroxide (DCP) are added into a torque rheometer for melt blending to obtain a mixed material; the mixed material is press-formed in a flat vulcanizer, then heated for cross-linking, and cooled to obtain a high-voltage direct current cable material having significantly improved breakdown strength and tensile properties, referred to as LEED.

[0005] Furthermore, the amount of DCP is 1.4% of the mass of LDPE, and the blend of 4-(4-epoxymethoxyphenyl) benzoic acid glycidyl ester, EAA, and LDPE contains: 1%-7% by mass of EAA, 91.72%-98.82% by mass of LDPE, and 0.18%-1.26% by mass of 4-(4-epoxymethoxyphenyl) benzoic acid glycidyl ester.

[0006] One of the objects of the present invention is to provide a method for preparing the composite material, the method comprising the following steps:

[0007] S1, melt blending; blending all raw materials uniformly to obtain a DCP / epoxy / EAA / LDPE blended composite insulation material;

[0008] S2, processing and molding; the DCP / epoxy / EAA / LDPE blended composite insulation material is pressed and molded in a flat vulcanizer, and then cross-linked under pressure, cooled and vacuum dried to obtain the high-voltage DC cable material LEED.

[0009] Further defined, S1 is specifically: first add low-density polyethylene to a torque rheometer at 115°C and a rotation speed of 50 rpm and mix for 5 minutes, then add EAA and epoxy compound and mix for 10 minutes, and finally add DCP and mix for no more than 3 minutes. After mixing evenly, the DCP / epoxy / EAA / LDPE blend material can be obtained.

[0010] It is further defined that the pressing temperature in S2 is 115° C. and the pressure is 15 MPa.

[0011] It is further defined that the pressurized cross-linking temperature in S2 is 175° C. and the pressure is 15 MPa.

[0012] It is further defined that the vacuum drying treatment temperature in S2 is 80° C. and the time is 24 h.

[0013] A second object of the present invention is to provide an application of the composite material, specifically, the composite material is used to manufacture a high-voltage DC cable.

[0014] The present invention has the following beneficial effects:

[0015] (1) The small molecule epoxy compound designed in the present invention can be cross-linked with a polymer containing a carboxyl group. After cross-linking, EAA and XLPE can form a double cross-linking system, which can significantly improve the tensile properties of the material.

[0016] (2) The aromatic compound in the present invention can play a voltage stabilizing role, and the electron trap formed in situ can effectively capture electrons, significantly enhancing the DC breakdown performance of the high-voltage DC cable material.

[0017] (3) The LEED composite insulation material prepared by the present invention has a simple preparation process, low cost, and easy-to-obtain materials, and has prospects for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Infrared spectrum test charts of LEED high-voltage DC cable materials provided by different embodiments;

[0019] Figure 2 Thermal elongation diagram of LEED high-voltage DC cable materials provided by different embodiments;

[0020] Figure 3 Tensile test result curves of LEED high-voltage DC cable materials provided by different embodiments;

[0021] Figure 4 Weibull distribution diagram of DC breakdown field strength of LEED high-voltage DC cable materials provided by different embodiments. DETAILED DESCRIPTION

[0022] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods, and instruments used are conventional in the art and can be obtained commercially by those skilled in the art unless otherwise specified.

[0023] Embodiment 1:

[0024] The process of preparing LEED modified composite materials in this example is as follows:

[0025] (1) Melt blending: 39.53 g of LDPE was added to a torque rheometer, melted at 115 °C, with a rotation speed of 50 r / min, and mixed for 5 min. Then, 0.4 g of EAA and 0.07 g of epoxy compound 4-(4-epoxymethoxyphenyl) benzoic acid glycidyl ester (hereinafter referred to as E) were added and mixed for 10 min. Finally, 0.55 g of DCP was added and mixed for 3 min to obtain LE. 1.0 ED 1.4 Blended composite materials.

[0026] (2) Processing and molding: LE 1.0 ED 1.4 The blended composite material was pressed in a flat vulcanizer at a temperature of 115°C and a pressure of 15 MPa, and then pressed for 30 minutes at a temperature of 175°C and a pressure of 15 MPa to complete crosslinking and obtain LE 1.0 ED 1.4 High voltage DC cable materials.

[0027] Example 2:

[0028] (1) Melt blending: 38.58 g of LDPE was added to a torque rheometer, melted at 115 °C, with a rotation speed of 50 r / min, and mixed for 5 min. Then, 1.2 g of EAA and 0.22 g of epoxy compound 4-(4-epoxymethoxyphenyl) benzoic acid glycidyl ester were added and mixed for 10 min. Finally, 0.54 g of DCP was added and mixed for 3 min to obtain LE 3.0 ED 1.4 Blended composite materials.

[0029] (2) Processing and molding: LE 3.0 ED 1.4 The blended composite material was pressed in a flat vulcanizer at a temperature of 115°C and a pressure of 15 MPa, and then pressed for 30 minutes at a temperature of 175°C and a pressure of 15 MPa to complete crosslinking and obtain LE 3.0 ED 1.4 High voltage DC cable materials.

[0030] Example 3

[0031] (1) Melt blending: 37.64 g of LDPE was added to a torque rheometer, melted at 115 °C, with a rotation speed of 50 r / min, and mixed for 5 min. Then, 2 g of EAA and 0.36 g of epoxy compound 4-(4-epoxymethoxyphenyl) benzoic acid glycidyl ester were added and mixed for 10 min. Finally, 0.53 g of DCP was added and mixed for 3 min to obtain LE. 5.0 ED 1.4 Blended composite materials.

[0032] (2) Processing and molding: LE 5.0 ED 1.4 The blended composite material was pressed in a flat vulcanizer at a temperature of 115°C and a pressure of 15 MPa, and then pressed for 30 minutes at a temperature of 175°C and a pressure of 15 MPa to complete crosslinking and obtain LE 5.0 ED 1.4 High voltage DC cable materials.

[0033] Embodiment 4:

[0034] (1) Melt blending: 36.69 g of LDPE was added to a torque rheometer, melted at 115 °C, with a rotation speed of 50 r / min, and mixed for 5 min. Then, 2.8 g of EAA and 0.51 g of epoxy compound 4-(4-epoxymethoxyphenyl) benzoic acid glycidyl ester were added and mixed for 10 min. Finally, 0.51 g of DCP was added and mixed for 3 min to obtain LE. 7.0 ED 1.4 Blended composite materials.

[0035] (2) Processing and molding: LE7.0 ED 1.4 The blended composite material was pressed in a flat vulcanizer at a temperature of 115°C and a pressure of 15 MPa, and then pressed for 30 minutes at a temperature of 175°C and a pressure of 15 MPa to complete crosslinking and obtain LE 7.0 ED 1.4 High voltage DC cable materials.

[0036] The performance tests were conducted on the LEED high-voltage DC cable materials with different contents prepared in Examples 1 to 4 above. The specific test results are as follows:

[0037] (1) The molecular structures of the above four materials were tested, analyzed and characterized by Fourier transform infrared spectrometer (FT / IR 6100) to verify whether they successfully participated in the cross-linking reaction. The sample thickness selected in the experiment was 200 μm thin slices, and the test spectrum wave number range was 500-4000 cm -1 , scanning accuracy is 2cm -1 , the number of scans is 30, and the results are as follows Figure 1 shown.

[0038] Depend on Figure 1 It can be seen that compared with EAA / LDPE blends, the modified high voltage DC cable material has a high thermal conductivity at 3482cm -1 A new absorption peak appeared near the composite material, corresponding to the absorption peak of hydroxyl groups, and at 1700 cm -1 The peak red-shifted to 1726 cm -1 , and turned into a broad peak, corresponding to the characteristic peak of the ester group in the composite material, indicating that the cross-linking was successful.

[0039] (2) Prepare dumbbell specimens and measure cross-sectional area according to the test method specified in GB / T 2951.11-2008. Cut the prepared modified high-voltage DC cable material sample into a dumbbell-shaped specimen with a thickness of 1 mm using a cutter. Its total length is 75 mm and the effective test portion width is 4 ± 0.2 mm. Its surface is smooth and free of defects visible to the naked eye. Marking lines with a spacing of 20 mm are marked on the narrow section with a marker pen. The test is carried out in a 200℃ natural ventilation oven. The specimen is suspended from the upper chuck and clamped with the lower chuck. A weight is added to the lower chuck. The weight = 20.4 × specimen thickness × specimen width (including clamps, support rods and weights). The specimen is kept at 200℃ in the oven. After 15 minutes, the distance between the marking lines is measured and the elongation is calculated.

[0040] According to GB / T 12527-2008, the thermal elongation of XLPE insulated cables should not exceed 175%. Figure 2It can be seen that the cable materials prepared in the present invention meet the standards, and the thermal elongation decreases significantly with the increase of EAA. When the EAA content is 7%, the thermal elongation is the lowest, which is only 59.50%.

[0041] (3) The above four materials were tested using a SUNS UTM2203 electronic universal testing machine in accordance with the national standard GB / T528-2009. According to the test method required by the standard, the modified LEED composite material specimens were cut into dumbbell-shaped specimens with a thickness of 1 mm using a cutter. The total length was 75 mm, the effective test portion width was 4 ± 0.2 mm, and the surface was smooth without visible defects. Marking lines with a spacing of 20 mm were marked on the narrow section using a marker pen. The clamp spacing was set to 20 mm, the tensile rate was set to 250 mm / min, and each material was tested 5 times.

[0042] According to the requirements of standard GB / T 22078.1-2008, the tensile strength and elongation at break of XLPE materials used in high-voltage power cables should be no less than 12.5MPa and 200% respectively. Figure 3 It can be seen that under the same experimental conditions, the tensile properties of the modified high-voltage DC cable material meet the required standards, with its elongation at break reaching 1378.82% and its tensile strength reaching 28.54 MPa. The elongation at break is 6.89 times higher than the standard, and the tensile strength is 2.28 times higher than the standard.

[0043] (4) The DC breakdown field strength test of the four materials was conducted at 30°C using a cylindrical electrode, with a voltage ramp rate of 1 kV / s and a sample thickness of 50 μm. The samples and electrodes were immersed in transformer oil throughout the entire process. Ten groups of samples were selected for repeated testing under each experimental condition.

[0044] The two-parameter Weibull distribution is used to perform statistics on the DC breakdown strength experimental data, which is described as follows:

[0045] P(E)=1-exp(-(E / E b ) β )

[0046] Where: P(E) is the cumulative failure probability, E is the measured breakdown field strength, E b is the characteristic breakdown field strength when the breakdown probability is 63.2%, and β is the shape parameter.

[0047] The Weibull distribution of DC breakdown strength of the above four materials is as follows: Figure 4 shown.

[0048] Depend on Figure 4It can be seen that the DC breakdown strength of the four modified high-voltage DC cable materials is improved to varying degrees compared to the unmodified ones. After the addition of epoxy compounds, the breakdown field strength of each content is significantly improved. The DC breakdown strength of the modified high-voltage DC cable material reaches a maximum of 476.3kV / mm at 3% EAA content, which is 57.51% higher than that of pure LDPE. The breakdown strength of the commonly available XLPE is 377kV / mm, and the LE 3.0 ED 1.4 The HVDC cable material with this content has good electrical resistance.

[0049] The above description is merely a preferred embodiment of the present invention. Given that those skilled in the art can make appropriate changes and modifications to the above embodiments, the present invention is not limited to the specific embodiments described above. Some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a high-voltage DC cable material of 4-(4-epoxymethoxyphenyl) benzoic acid glycidyl ester and DCP double crosslinked EAA and LDPE, characterized in that: Low-density polyethylene (LDPE), 4-(4-epoxymethoxyphenyl) glycidyl benzoate, ethylene acrylic acid copolymer (EAA), and dicumyl peroxide (DCP) are melt-blended in a torque rheometer to obtain a mixed material. The mixed material is then press-formed in a flat-plate vulcanizer, heated for cross-linking, and cooled to obtain a high-voltage DC cable material with significantly improved breakdown strength and tensile properties. The mass of EAA is 1%-7% of the total mass of 4-(4-epoxymethoxyphenyl) benzoic acid glycidyl ester, EAA, and LDPE; The mass of LDPE is 91.72%-98.82% of the total mass of 4-(4-epoxymethoxyphenyl) benzoic acid glycidyl ester, EAA, and LDPE; The mass of 4-(4-epoxymethoxyphenyl) benzoic acid glycidyl ester is 0.18%-1.28% of the total mass of 4-(4-epoxymethoxyphenyl) benzoic acid glycidyl ester, EAA, and LDPE; The mass of DCP is 1.4% of the mass of LDPE.

2. The preparation method according to claim 1, wherein: The DC breakdown strength of the prepared high-voltage DC cable material can reach 476.3 kV / mm, and the tensile elongation at break can reach 1130%-1378%.

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