Process for the preparation of an epoxy and dcp dual crosslinked eaa and ldpe cable material

Abstract

The present application relates to a kind of epoxy and DCP double crosslinking EAA and LDPE cable material preparation method, belong to high-voltage direct current cable material preparation technical field.The preparation method of cable material in the present application is as follows: with ethylene acrylic acid copolymer EAA and low-density polyethylene LDPE as matrix resin, biphenyl type small molecule epoxy compound 4,4'-biphenyldiol diglycidyl ether and dicumyl peroxide DCP are used as double crosslinking agent, and the double crosslinking EAA / LDPE high-voltage direct current cable material of biphenyl type small molecule epoxy and DCP is obtained in flat vulcanization machine by heating and pressurizing.The double crosslinking structure formed by biphenyl type small molecule epoxy and DCP double crosslinking EAA / LDPE material and the stable voltage segment introduced in situ effectively improve the direct current electrical resistance of cable material.The high-voltage direct current cable material prepared by the above method has simple preparation process, low cost, excellent mechanical properties and electrical properties.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of an epoxy and DCP double-crosslinking EAA and LDPE cable material and belongs to the technical field of high-voltage direct-current cable material preparation. BACKGROUND

[0002] With the rapid development of high-voltage conversion technology and high-power power electronic devices, countries around the world have paid more and more attention to the development of high-voltage direct-current transmission technology. Compared with an alternating current transmission system, a direct-current transmission system has the advantages of large transmission capacity, long transmission distance, more flexible power regulation, high system operation reliability and the like, and is widely applied to new energy grid connection, island power supply and cross-sea long-distance power transmission and the like. Among them, a high-voltage direct-current cable is a key equipment in high-voltage direct-current transmission, and the insulation reliability of the high-voltage direct-current cable plays a significant role in the stability of a high-voltage transmission network.

[0003] The breakdown characteristic of a high-voltage direct-current cable material is one of key electrical characteristics, and according to the breakdown field strength of a cable insulation material, the insulation characteristics and voltage resistance performance of the cable material can be evaluated. Generally, the breakdown of the cable material is a one-way and irreversible process, and after the breakdown of the cable material, a channel such as a hole or a crack that cannot be restored is left, and the insulation characteristics are also permanently damaged.

[0004] Crosslinked polyethylene is widely applied in the field of high-voltage direct-current cable materials due to its excellent electrical insulation performance, and researchers have carried out a large amount of research work on the improvement of the performance of crosslinked polyethylene insulation materials. At present, the main means include nano-doping modification, graft modification and chemical modification. Nano-doping modification is to introduce nano-sized fillers into the material through physical and chemical methods and surface modification and the like, so as to improve the electrical insulation performance of the polyethylene material; graft modification is a modification method for introducing functional side groups on the polyolefin molecular chain by using a free radical polymerization reaction; and chemical modification is a kind of modification method for changing atoms or atomic groups on the polymer molecular chain through a chemical reaction.

[0005] The application utilizes the characteristics that crosslinked ethylene acrylic acid copolymer EAA has good insulation performance and excellent mechanical performance, adopts a biphenyl type small molecule epoxy compound and DCP as a double-crosslinking agent to construct an XLPE and epoxy / EAA double-crosslinking system, and introduces functional groups such as benzene rings and carbonyl groups with voltage stabilizing effect into the system through the small molecule epoxy compound, so that the direct-current breakdown characteristic of the cable material is significantly improved. SUMMARY

[0006] Low-density polyethylene (LDPE) is widely used in cable insulation material industry due to its good electrical insulation, processability, elongation and relatively low cost. Ethylene acrylic acid copolymer (EAA) is a kind of high molecular compound copolymerized by ethylene and acrylic acid, which has good adhesion, weather resistance and toughness, and is widely used in packaging, adhesives and other fields. The present application adopts two kinds of thermoplastic polymers (low-density polyethylene (LDPE) and ethylene acrylic acid copolymer (EAA) containing carboxyl monomer) as the base resin, adopts the method of melt blending, and adds diphenyl type small molecule epoxy compound and dicumyl peroxide (DCP) as double crosslinking agent. Under heating and pressurization, DCP decomposes to make LDPE crosslinking reaction to form XLPE, and the ring-opening crosslinking reaction of epoxy group and carboxyl in EAA forms crosslinked EAA structure, the double crosslinking system is fused with each other, and the crosslinked EAA effectively improves the mechanical strength of the material. In addition, the epoxy / EAA crosslinking network improves the mechanical strength of the cable material, compared with the commonly used crosslinked polyethylene in the market, the amount of DCP is reduced, and the generation of scorching and over-crosslinking phenomenon is effectively prevented.

[0007] The technical scheme of the present application:

[0008] One of the purposes of the present application is to provide a preparation method of epoxy and DCP double crosslinked EAA and LDPE cable material, characterized in that: the crosslinking agent dicumyl peroxide DCP accounts for 1.6 parts by weight of the weight of low-density polyethylene, and the diphenyl type small molecule epoxy compound / EAA / LDPE blended material includes, by weight parts: 73.80-93.45 parts of low-density polyethylene LDPE, 5-20 parts of ethylene acrylic acid copolymer EAA, and 1.55-6.20 parts of epoxy compound.

[0009] Further limited, EAA is ethylene acrylic acid copolymer with an acrylic acid content of 6-8%.

[0010] Further limited, the model of LDPE is BASF 2220H of Yangzi Petrochemical.

[0011] Further limited, the epoxy is 4,4'-diphenol diglycidyl ether (BEB).

[0012] The second purpose of the present application is to provide a preparation method of epoxy and DCP double crosslinked EAA and LDPE cable material, which comprises the following steps:

[0013] S1, melt blending: blend all raw materials uniformly to obtain LDPE / EAA / DCP / BEB blended composite material;

[0014] S2, processing molding: the LDPE / EAA / DCP / BEB blended composite material is pressed and molded in a flat vulcanizing machine, then pressure crosslinking, vacuum drying after cooling to obtain LEDB high voltage direct current cable material.

[0015] Further limited, S1 is specifically: first, low density polyethylene is added into the torque rheometer at 110 DEG C and 60 rpm for 5 minutes, then EAA and epoxy compound are added for 7 minutes, finally, DCP is added for not more than 3 minutes, and the LDPE / EAA / DCP / BEB blended material can be obtained after mixing uniformly.

[0016] Further limited, the pressing molding temperature in S2 is 110 DEG C, and the pressure is 15 MPa.

[0017] Further limited, the pressure crosslinking temperature in S2 is 175 DEG C, and the pressure is 15 MPa.

[0018] Further limited, the vacuum drying treatment temperature in S2 is 80 DEG C, and the time is 24 hours.

[0019] The third object of the present application is to provide an application of the above-mentioned cable material, specifically, the cable material is applied to the preparation of high voltage direct current cables.

[0020] The present application has the following beneficial effects:

[0021] (1) The present application uses DCP and biphenyl type small molecule epoxy compound as a double crosslinking agent, and constructs an XLPE and biphenyl type small molecule epoxy / EAA double crosslinking system, which greatly improves the direct current breakdown characteristics of the cable material.

[0022] (2) The double crosslinking network constructed by the present application not only can reduce the amount of crosslinking agent DCP while ensuring excellent mechanical properties, effectively prevent the occurrence of overcrosslinking phenomenon, but also can introduce deep traps (carbonyl electron-deficient groups) and voltage stabilizing fragments (biphenyl structure) in situ, without adding additional additives, which can improve the electric field distortion and improve the electrical properties of the cable material.

[0023] (3) The cable material LEDE prepared by the present application has low raw material cost and is easy to obtain, and the production process is simple, which has good economic benefit and social benefit. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The infrared spectrum test result comparison curve of the cable material provided for different embodiments;

[0025] Figure 2 The thermal extension performance test diagram of the cable material provided for different embodiments;

[0026] Figure 3 Tensile test result curves of cable materials provided for different embodiments;

[0027] Figure 4 Weibull distribution plots of DC breakdown field strength of cable materials provided for different embodiments, where a is the experimental group and b is the control group;

[0028] Figure 5 Comparison plots of conductivity test curves of cable materials provided for different embodiments, where a is the experimental group and b is the control group. DETAILED DESCRIPTION

[0029] The experimental methods used in the following examples are all conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained by commercial channels by those skilled in the art.

[0030] DCP and epoxy compound 4,4'-diphenol diglycidyl ether (BEB) were selected as crosslinking agents in the following examples.

[0031] Example 1:

[0032] The process for preparing the LEDB cable material in this example is as follows:

[0033] (1) Melt blending: 37.38 g of LDPE was added to a torque rheometer and melted at 110°C with a rotation speed of 60 r / min. After mixing for 5 min, 2 g of EAA and 0.62 g of 4,4'-diphenol diglycidyl ether (hereinafter referred to as BEB) were added and mixed for another 7 min. Finally, 0.6 g of DCP was added and mixed for 3 min to obtain a blended composite material.

[0034] (2) Processing and molding: the blended composite material was placed in a flat vulcanizing machine at a temperature of 110°C and a pressure of 15 MPa for compression molding. Then, crosslinking was completed by compression molding at a temperature of 175°C and a pressure of 15 MPa for 30 min to obtain LEDB cable material LE5D. 1.6 B high-voltage DC cable material.

[0035] Example 2:

[0036] (1) Melt blending: 34.76 g of LDPE was added to a torque rheometer and melted at 110°C with a rotation speed of 60 r / min. After mixing for 5 min, 4 g of EAA and 1.24 g of BEB were added and mixed for another 7 min. Finally, 0.56 g of DCP was added and mixed for 3 min to obtain a blended composite material.

[0037] (2) Processing and molding: the blended composite material is placed in a flat vulcanizing machine with a temperature of 110 ℃ and a pressure of 15 MPa for pressing and molding, and then is pressed for 30 min under the condition of a temperature of 175 ℃ and a pressure of 15 MPa to complete crosslinking, to obtain LE 10 D 1.6 B high-voltage direct-current cable material.

[0038] Example 3:

[0039] (1) Melt blending: 32.14 g of LDPE is added to a torque rheometer and melted at 110 ℃, with a rotation speed of 60 r / min, and then 6 g of EAA and 1.86 g of BEB are added and mixed for 7 min, and finally 0.51 g of DCP is added and mixed for 3 min, to obtain a blended composite material.

[0040] (2) Processing and molding: the blended composite material is placed in a flat vulcanizing machine with a temperature of 110 ℃ and a pressure of 15 MPa for pressing and molding, and then is pressed for 30 min under the condition of a temperature of 175 ℃ and a pressure of 15 MPa to complete crosslinking, to obtain LE 15 D 1.6 B high-voltage direct-current cable material.

[0041] Example 4:

[0042] (1) Melt blending: 29.52 g of LDPE is added to a torque rheometer and melted at 110 ℃, with a rotation speed of 60 r / min, and then 8 g of EAA and 2.48 g of BEB are added and mixed for 7 min, and finally 0.47 g of DCP is added and mixed for 3 min, to obtain a blended composite material.

[0043] (2) Processing and molding: the blended composite material is placed in a flat vulcanizing machine with a temperature of 110 ℃ and a pressure of 15 MPa for pressing and molding, and then is pressed for 30 min under the condition of a temperature of 175 ℃ and a pressure of 15 MPa to complete crosslinking, to obtain LE 20 D 1.6 B high-voltage direct-current cable material.

[0044] Example 5:

[0045] (1) Melt blending: 34.76 g of LDPE is added to a torque rheometer and melted at 110 ℃, with a rotation speed of 60 r / min, and then 4 g of EAA and 1.24 g of BEB are added and mixed for 10 min, to obtain a blended composite material.

[0046] (2) Processing and molding: The blended composite material was pressed in a flat vulcanizer at a temperature of 110°C and a pressure of 15 MPa, and then pressed at a temperature of 175°C and a pressure of 15 MPa for 30 minutes to complete crosslinking and obtain LE 10 B High voltage DC cable material.

[0047] Example 6:

[0048] (1) Melt blending: 36 g of LDPE was added to a torque rheometer and melted at 110 °C at a speed of 60 r / min. After mixing for 5 min, 4 g of EAA was added and mixing continued for 7 min. Finally, 0.58 g of DCP was added and mixed for 3 min to obtain a blended composite material.

[0049] (2) Processing and molding: The blended composite material was pressed in a flat vulcanizer at a temperature of 110°C and a pressure of 15 MPa, and then pressed at a temperature of 175°C and a pressure of 15 MPa for 30 minutes to complete crosslinking and obtain LE 10 D 1.6 High voltage DC cable materials.

[0050] Example 7:

[0051] (1) Melt blending: 36 g of LDPE was added to a torque rheometer and melted at 110 °C at a speed of 60 r / min. After mixing for 5 min, 4 g of EAA was added and mixing was continued for 10 min to obtain a blended composite material.

[0052] (2) Processing and molding: The blended composite material is placed in a flat vulcanizer at a temperature of 110°C and a pressure of 15 MPa to obtain LE 10 High voltage DC cable materials.

[0053] Effect example:

[0054] The performance of LEDB high-voltage DC cable materials prepared in different formulation ratios in Examples 1 to 4 above was tested. The specific test process and results are as follows:

[0055] (1) The molecular structure of the above cable materials was tested, analyzed and characterized by Fourier transform infrared spectrometer (FT / IR-6100) to verify whether the epoxy compound BEB successfully participated in the cross-linking reaction.

[0056] Depend on Figure 1 It can be seen that compared with LE and LED cable materials, LEDB cable materials are -1 A new absorption peak appears at 1705cm, which corresponds to the characteristic absorption peak of hydroxyl groups generated in the cable material after the epoxy compound is cross-linked with EAA. -1a sharp red shift to 1730 cm -1 , and became a wide peak, corresponding to the characteristic peak of the conversion of carboxyl group to ester group after the crosslinking of epoxy compound and EAA in cable material. This shows that the epoxy compound BEB successfully reacted with the carboxylic acid monomer in EAA, and the crosslinking reaction was successfully carried out.

[0057] (2) The above cable material was tested by RYS-III type thermal extension tester according to national standard GB / T2951.21-2008. The test box temperature was set to 200℃, and after the sample was placed in the test box for 15 min, the distance between the two mark lines was observed through the observation window, and the thermal elongation rate of the sample was calculated. Each material was tested 3 times, and the average value was taken, and the results are shown in Figure 2

[0058] According to the requirements of GB / T12527-2008, the thermal elongation rate of XLPE insulation cable under load should not be higher than 175%. As can be seen from Figure 2 , the thermal elongation rate of LEDB cable material meets the requirements of the test standard, and the crosslinking degree has met the use standard of crosslinked polyethylene. With the increase of EAA content, the thermal elongation rate of the cable material has a downward trend, because the performance of the cable material to resist external stress at high temperature will become better with the increase of EAA / BEB crosslinking network, and when the EAA content is 20%, the thermal elongation rate can reach 62.5%.

[0059] (3) The above cable material was tested by SUNS UTM2203 type universal testing machine according to national standard GB / T528-2009. According to the test method required in the standard, the above LEDB cable material sample was cut into dumbbell-shaped sample with thickness of 1mm, total length of 75mm and effective test part width of 4±0.2mm, and the surface was smooth without visible defects, and the mark line with 20mm interval was marked on the narrow part by using marking pen. The clamp distance was set to 20mm, and the tensile speed was 250mm / min, and each material was tested 5 times.

[0060] According to the requirements of standard GB / T22078.1-2008, the tensile strength and elongation at break of XLPE material for high voltage cable should not be less than 12.5MPa and 200% respectively. As can be seen from Figure 3 , under the same experimental conditions, the mechanical properties of LEDB cable material increase first and then decrease with the increase of EAA / BEB content. Among them, the mechanical properties of LEDB cable material are the best, the elongation at break reaches 1070.3%, the tensile strength reaches 27.3MPa, the elongation at break is 5.35 times higher than the standard, and the tensile strength is 2.18 times higher than the standard. 10 D 1.6 B​

[0061] (4) The DC breakdown field strength of the above-mentioned cable material was tested at room temperature using a cylindrical electrode, with a voltage rise rate of 1 kV / s and a sample thickness of 50 um. The sample and electrode were immersed in transformer oil throughout the test. Fifteen groups of samples were selected for repeated experiments under each experimental condition, and ten groups of effective data were selected.

[0062] The Weibull distribution of the DC breakdown strength of the above-mentioned cable material is shown in Figure 4 .

[0063] As can be seen from Figure 4 , with the increase of the amount of BEB / EAA, the DC breakdown field strength shows a trend of first increasing and then decreasing. Among them, the LE 10 D 1.6 B high-voltage DC cable material has the highest DC characteristic breakdown strength, reaching a maximum value of 453.6 kV / mm, which is 46.65%, 34.36%, 20.10%, and 18.34% higher than the blank test LDPE, LE 10 , LE 10 B, LE 10 D 1.6 , respectively. The LEDB cable material with this content has excellent DC breakdown characteristics.

[0064] (5) According to the electric field strength and temperature of the insulation layer of the high-voltage DC cable in operation, the electric conductivity current of the above-mentioned cable material was tested at room temperature at a field strength of 5 kV-40 kV on a 200 um sample to obtain its E-σ curve, as shown in Figure 3 , and the polarization time was set to 2h.

[0065] As can be seen from Figure 5 , under the same experimental conditions, the conductivity of the LEDB high-voltage DC cable material is significantly lower than that of LDPE. Similar to the DC breakdown test results, the conductivity of the LE 10 D 1.6 B cable material is the lowest, with a conductivity of only 2.14 x 10 -12 S / m at 20KV / mm, which is only 1.1% of the conductivity of pure LDPE. This indicates that the construction of the interpenetrating structure of the double crosslinked network and the introduction of the functional group effectively inhibit the accumulation of space charge in the material, which greatly improves the DC withstand performance of the LEDB cable material compared with traditional crosslinked polyethylene.

[0066] The above-mentioned is only a preferred embodiment of the present application. Since those skilled in the art can make appropriate changes and modifications to the above-mentioned embodiments, the present application is not limited to the specific embodiments described above. Some modifications and changes of the present application should also fall within the protection scope of the claims of the present application.

Claims

1. A process for the preparation of an epoxy and DCP dual crosslinking EAA and LDPE cable material, characterized in that: The preparation method is: low-density polyethylene (LDPE), ethylene acrylic acid copolymer (EAA), 4,4'-diphenylol diglycidyl ether and dicumyl peroxide (DCP) are added into a torque rheometer for melt blending to obtain a blended material; the blended material is pressed into a shape in a flat curing machine, crosslinked by heating, and cooled to obtain a cable material (LEDB) with significantly improved breakdown strength; The mass of the EAA is 5%-20% of the total mass of the LDPE, the EAA and the 4,4'-diphenylol diglycidyl ether; The mass of the LDPE is 73.80-93.45% of the total mass of the LDPE, the EAA and the 4,4'-diphenylol diglycidyl ether; The mass of the 4,4'-diphenylol diglycidyl ether is 1.55%-6.20% of the total mass of the LDPE, the EAA and the 4,4'-diphenylol diglycidyl ether; The amount of the DCP is 1.6% of the mass of the LDPE.

2. Use of the epoxy and DCP dual crosslinking EAA and LDPE cable material prepared by the method of claim 1, characterized by: A high-voltage direct-current cable material is prepared.

3. Use according to claim 2, characterized in that: The direct-current breakdown strength of the high-voltage direct-current cable material can reach 453.6 kV / mm.

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