Nano-silicon dioxide reinforced ethylene propylene diene monomer and preparation method and application thereof

Abstract

The invention particularly relates to nano silicon dioxide reinforced ethylene propylene diene monomer and a preparation method and application thereof, and belongs to the technical field of insulating rubber. The formula of the nano-silica reinforced ethylene propylene diene monomer provided by the invention comprises ethylene propylene diene monomer, nano-silica, a silane coupling agent, zinc oxide, stearic acid, an anti-aging agent, argil, paraffin oil, white carbon black, sulfur, an assistant crosslinker and a vulcanizing agent. The preparation method comprises the following steps: mixing for multiple times, plastifying, carrying out high-temperature heat treatment, carrying out thin-passing, vulcanizing and the like. According to the material, through doping modification of the nano silicon dioxide in the ethylene propylene diene monomer, the problems of accumulation and irregular distribution of space charges of the existing ethylene propylene diene monomer for high-voltage direct current are effectively solved, and the material has good mechanical properties and electrical properties and can meet the performance requirements of high-voltage direct-current cable accessories.

Description

Technical Field

[0001] The invention specifically relates to a nano-silicon dioxide reinforced ethylene propylene diene monomer rubber and a preparation method and application thereof, belonging to the technical field of insulating rubber. Background Art

[0002] Compared with AC transmission system, DC transmission system has the advantages of long transmission distance and large transmission capacity. Its high-voltage DC transmission line can be hundreds of kilometers long. In such a system, the use of cable joints to connect the lines is a crucial link. DC cable joints usually contain important components such as insulation layer, stress cone and shielding layer. The preparation of insulation material of cable joints is one of the key points.

[0003] Insulating materials used in the field of ultra-high voltage direct current are mostly composed of a variety of dielectric materials, which put forward higher requirements on the suppression performance of space charge inside the material. Affected by the use of multiple dielectric materials as a composite insulation structure, there will be differences in conductivity between different dielectric materials in the insulating material, resulting in serious uneven distribution of the electric field inside the material, which in turn leads to the appearance of space charge and interface charge. When the cable joint is subjected to operating shock or lightning impulse voltage, the superposition of space charge and impulse voltage will cause serious distortion of the surface electric field at the root of the stress cone and the interface of the insulating medium, resulting in a significant increase in the failure rate of the joint.

[0004] At present, ethylene propylene diene monomer (EPDM) has become a key insulating material for the preparation of cable connector accessories due to its advantages such as low loss, resistance to partial discharge, acid and alkali resistance and UV resistance. Modifying it to improve the material conductivity, improve the inhibition of internal space charge and mechanical properties is an important direction of effort to increase the service life of EPDM. Currently, filling conductive or semiconductor inorganic fillers and conductive polymer organic fillers into the EPDM matrix is ​​a major way to modify EPDM. Among them, the type and amount of conductive fillers are crucial, which directly affects the conductive effect and tear strength of EPDM, while the mechanical properties and inhibition of space charge of existing EPDM need to be improved. Summary of the invention

[0005] In view of the existing problems, the present invention provides a nano-silicon dioxide reinforced EPDM rubber and a preparation method and application thereof; the material is modified by doping nano-silicon dioxide in the EPDM rubber, which effectively improves the accumulation and irregular distribution problems of space charge of the existing EPDM rubber for high-voltage direct current, has good mechanical properties and electrical properties, and can meet the performance requirements of high-voltage direct current cable accessories.

[0006] The technical aspects of the present invention are as follows:

[0007] One of the purposes of the present invention is to provide a nano-silicon dioxide reinforced ethylene propylene diene rubber, comprising the following components in parts by weight: 100 parts of ethylene propylene diene rubber, 8-10 parts of nano-silicon dioxide, 1.5-4 parts of silane coupling agent, 4-6 parts of zinc oxide, 0.5-1.5 parts of stearic acid, 2-5 parts of antioxidant, 50-60 parts of clay, 3-5 parts of paraffin oil, 20-25 parts of white carbon black, 1-3 parts of sulfur, 3-4 parts of cross-linking agent and 4-5 parts of vulcanizing agent.

[0008] Furthermore, the average particle size of the nano-silicon dioxide is 20 to 50 nm.

[0009] Furthermore, the silane coupling agent is KH550; the auxiliary cross-linking agent is triallyl isocyanurate; the vulcanizing agent is BIBP; the antioxidant comprises antioxidant RD and antioxidant MB; and the mass ratio of the antioxidant RD to the antioxidant MB is 1:(5-7).

[0010] The second object of the present invention is to provide a method for preparing the above-mentioned nano-silicon dioxide reinforced EPDM rubber, comprising the following steps:

[0011] S1, premixing 40% to 60% of the formula amount of EPDM rubber, nano-silicon dioxide, and silane coupling agent, and then plasticizing the premix with the remaining formula amount of EPDM rubber, nano-silicon dioxide, and silane coupling agent to obtain a masterbatch;

[0012] S2, mixing the masterbatch obtained in step S1 with the formula amount of zinc oxide, stearic acid, and antioxidant for the first time, adding 40% to 60% of the formula amount of clay, paraffin oil, and white carbon black thereto for the second mixing, and then adding the remaining formula amount of clay, paraffin oil, and white carbon black for the third mixing to obtain a rubber material;

[0013] S3, cooling and parking the rubber material obtained in step S2 after heat treatment in an open mixing mill;

[0014] S4, subjecting the rubber material treated in step S3 to a first-stage thin-pass treatment, and then adding a formula amount of sulfur, a cross-linking agent and a vulcanizing agent to a second-stage thin-pass treatment, and then vulcanizing to obtain the nano-silica reinforced EPDM rubber.

[0015] Furthermore, in step S1, the roller temperature for premixing 40% to 60% of the EPDM rubber, nano-silicon dioxide and silane coupling agent is 35 to 55°C.

[0016] Furthermore, in step S3, the heat treatment temperature is 175-185° C., and the heat treatment time is 5-15 min.

[0017] Furthermore, in step S4, the temperature of the vulcanization treatment is 160-170° C., the time of the vulcanization treatment is 30-40 min, and the pressure of the vulcanization treatment is 12-15 MPa.

[0018] The third object of the present invention is to apply the above-mentioned nano-silicon dioxide reinforced EPDM rubber to the preparation of high-voltage DC cable accessories.

[0019] Different from the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention uses nano-silicon dioxide to modify EPDM rubber to obtain nano-silicon dioxide reinforced EPDM rubber, which is applied to the preparation of DC high-voltage cable accessories, which can effectively reduce the temperature gradient of the high-voltage DC cable accessories during normal operation, improve the conductivity of the DC high-voltage cable accessories, reduce the accumulation and irregular distribution of space charges in the cable accessories, make the electric field uniformly distributed to avoid the occurrence of field strength reversal, and greatly improve the overall electrical performance of the cable.

[0021] 2. Different from the existing EPDM rubber, the present invention efficiently utilizes the electrical conductivity and thermal conductivity of nano-silicon dioxide, ensuring the insulation of the rubber material and the high inhibition of space charge; the introduction of nano-silicon dioxide particles into the rubber matrix causes steric hindrance in the matrix, reduces the mobility of the rubber molecular segments and their side group segments, reduces the migration and aggregation of charges, thereby increasing the threshold field strength of space charge injection and improving the insulation performance of the rubber; at the same time, the addition of nano-silicon dioxide also introduces deep trap energy levels, which can improve the DC dielectric properties of the rubber, and can reduce the number of free charges by capturing charge carriers, thereby inhibiting the accumulation of space charges; the above characteristics make the nano-silicon dioxide reinforced EPDM rubber of the present invention more suitable for the preparation of DC high-voltage cable accessories.

[0022] 3. The present invention achieves the purpose of pre-treating the nano-silica in advance by premixing the silane coupling agent with the nano-silica, so that the nano-silica is evenly distributed in the prepared nano-silica reinforced EPDM rubber, and the agglomeration problem of the nano-silica is solved. The bending strength and bending modulus of the prepared rubber material and the interface properties of the EPDM rubber / nano-silica are significantly improved, and the electrical properties and mechanical properties are also improved. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with preferred embodiments. The embodiments provided are only for illustrating the present invention, but not for limiting the scope of the present invention.

[0024] Unless otherwise specified, the materials, reagents, etc. used in the following examples can be obtained from commercial sources; the methods in the following examples are conventional methods unless otherwise specified.

[0025] Example 1

[0026] The present embodiment provides a nano-silicon dioxide reinforced EPDM rubber. The component formula of the nano-silicon dioxide reinforced EPDM rubber is as follows: 100 parts of EPDM rubber, 10 parts of nano-silicon dioxide, 2 parts of silane coupling agent, 5 parts of zinc oxide, 1 part of stearic acid, 3.5 parts of antioxidant, 60 parts of clay, 5 parts of paraffin oil, 25 parts of white carbon black, 2 parts of sulfur, 4 parts of cross-linking agent, and 4.5 parts of vulcanizing agent.

[0027] The average particle size of the nano-silicon dioxide is 40 nm; the silane coupling agent is KH550; the auxiliary cross-linking agent is triallyl isocyanurate TAIC; the vulcanizing agent is BIBP; and the antioxidant contains 0.5 parts of antioxidant RD and 3 parts of antioxidant MB.

[0028] The preparation method of the nano-silicon dioxide reinforced EPDM rubber comprises the following steps:

[0029] S1. Premix 50% of the formula amount of EPDM rubber (50 parts), silane coupling agent (1 part) and nano silicon dioxide (5 parts), with the roller temperature at 40°C and the roller distance at 0.5-1mm. After reaching the required plasticity, let it stand for 2 hours, and then plasticize with the remaining formula amount of EPDM rubber (50 parts), silane coupling agent (1 part) and nano silicon carbide (5 parts) for 8 minutes to prepare a masterbatch;

[0030] S2, adding the masterbatch obtained in step S1 and the formula amount of zinc oxide, stearic acid, antioxidant RD and antioxidant MB into a pressure mixer for the first mixing, mixing for 3 minutes; then adding 50% of the formula amount of clay (30 parts), white carbon black (12.5 parts) and paraffin oil (2.5 parts) thereto for the second mixing, mixing for 3 minutes; then adding the remaining clay (30 parts), white carbon black (12.5 parts) and paraffin oil (2.5 parts) in the component formula for the third mixing, mixing for 4 minutes;

[0031] S3, placing the rubber obtained in step S2 in an open mixer, heat treating at 180°C for 10 min, cooling to 25°C, and standing for 24 h;

[0032] S4, putting the rubber material treated in step S3 into an open mill and thinning it twice, then adding the formulated amount of sulfur, co-crosslinking agent TAIC and vulcanizing agent BIBP into the open mill, thinning it 10 times, and then vulcanizing and film-making, wherein the vulcanization temperature is 165°C, the vulcanization time is 35min, and the vulcanization pressure is 14MPa, to obtain the nano-silica reinforced EPDM rubber.

[0033] Example 2

[0034] The present embodiment provides a nano-silicon dioxide reinforced EPDM rubber. The component formula of the nano-silicon dioxide reinforced EPDM rubber is as follows: 100 parts of EPDM rubber, 8 parts of nano-silicon dioxide, 1.5 parts of silane coupling agent, 4 parts of zinc oxide, 0.5 parts of stearic acid, 2 parts of antioxidant, 55 parts of clay, 4 parts of paraffin oil, 22 parts of white carbon black, 1 part of sulfur, 3.5 parts of cross-linking agent, and 4 parts of vulcanizing agent.

[0035] The average particle size of the nano-silicon dioxide is 30 nm; the silane coupling agent is KH550; the auxiliary cross-linking agent is triallyl isocyanurate; the vulcanizing agent is BIBP; and the antioxidant contains 0.35 parts of antioxidant RD and 1.65 parts of antioxidant MB.

[0036] The preparation method of the nano-silicon dioxide reinforced EPDM rubber comprises the following steps:

[0037] S1. Premix 40% of the formula amount of EPDM rubber (40 parts), silane coupling agent (0.6 parts) and nano silicon dioxide (4 parts), with the roller temperature at 35°C and the roller distance at 0.5-1mm. After reaching the required plasticity, let it stand for 3 hours, and then plasticize with the remaining formula amount of EPDM rubber (60 parts), silane coupling agent (0.9 parts) and nano silicon carbide (4 parts) for 8 minutes to prepare a masterbatch;

[0038] S2, adding the masterbatch obtained in step S1 and the formula amount of zinc oxide, stearic acid, antioxidant RD and antioxidant MB into a pressure mixer for the first mixing, mixing for 3 minutes; then adding 40% of the formula amount of clay (22 parts), white carbon black (8.8 parts) and paraffin oil (1.6 parts) thereto for the second mixing, mixing for 3 minutes; then adding the remaining clay (33 parts), white carbon black (13.2 parts) and paraffin oil (2.4 parts) in the component formula for the third mixing, mixing for 4 minutes;

[0039] S3, placing the rubber material obtained in step S2 in an open mixer, heat treating at 175°C for 15 min, cooling to 25°C, and standing for 24 h;

[0040] S4, putting the rubber material treated in step S3 into an open mill and thinning it twice, then adding the formulated amount of sulfur, co-crosslinking agent TAIC and vulcanizing agent BIBP into the open mill, thinning it 10 times, and then vulcanizing and film-making, wherein the vulcanization temperature is 160°C, the vulcanization time is 30 minutes, and the vulcanization pressure is 15 MPa, to obtain the nano-silica reinforced EPDM rubber.

[0041] Example 3

[0042] The present embodiment provides a nano-silicon dioxide reinforced EPDM rubber. The component formula of the nano-silicon dioxide reinforced EPDM rubber is as follows: 100 parts of EPDM rubber, 9 parts of nano-silicon dioxide, 4 parts of silane coupling agent, 6 parts of zinc oxide, 1.5 parts of stearic acid, 5 parts of antioxidant, 50 parts of clay, 3 parts of paraffin oil, 20 parts of white carbon black, 3 parts of sulfur, 3 parts of cross-linking agent, and 5 parts of vulcanizing agent.

[0043] The average particle size of the nano-silicon dioxide is 20 nm; the silane coupling agent is KH550; the auxiliary cross-linking agent is triallyl isocyanurate TAIC; the vulcanizing agent is BIBP; and the antioxidant contains 0.8 parts of antioxidant RD and 4.2 parts of antioxidant MB.

[0044] The preparation method of the nano-silicon dioxide reinforced EPDM rubber comprises the following steps:

[0045] S1. Premix 60% of the formula amount of EPDM rubber (60 parts), silane coupling agent (2.4 parts) and nano silicon dioxide (5.4 parts), with the roller temperature at 55°C and the roller distance at 0.5-1mm. After reaching the required plasticity, let it stand for 4 hours, and then plasticize with the remaining formula amount of EPDM rubber (40 parts), silane coupling agent (1.6 parts) and nano silicon carbide (3.6 parts) for 8 minutes to prepare a masterbatch;

[0046] S2, adding the masterbatch obtained in step S1 and the formula amount of zinc oxide, stearic acid, antioxidant RD and antioxidant MB into a pressure mixer for the first mixing, mixing for 3 minutes; then adding 60% of the formula amount of clay (30 parts), white carbon black (12 parts) and paraffin oil (1.8 parts) thereto for the second mixing, mixing for 3 minutes; then adding the remaining clay (20 parts), white carbon black (8 parts) and paraffin oil (1.2 parts) in the component formula for the third mixing, mixing for 4 minutes;

[0047] S3, placing the rubber material obtained in step S2 in an open mixer, heat treating at 185°C for 15 min, cooling to 25°C, and standing for 24 h;

[0048] S4, putting the rubber material treated in step S3 into an open mill and thinning it twice, then adding the formulated amount of sulfur, co-crosslinking agent TAIC and vulcanizing agent BIBP into the open mill, thinning it 10 times, and then vulcanizing and film-making, wherein the vulcanization temperature is 170°C, the vulcanization time is 40min, and the vulcanization pressure is 12MPa, to obtain the nano-silica reinforced EPDM rubber.

[0049] Example 4

[0050] This embodiment provides a nano-silicon dioxide reinforced EPDM rubber, which is different from the embodiment 3 in that:

[0051] The particle size of the nano-silicon dioxide in the component formula of the nano-silicon dioxide reinforced EPDM rubber is 50 nm.

[0052] The dosage of the remaining components is the same as that in Example 1. The preparation steps of the nano-silicon dioxide reinforced EPDM rubber are the same as those in Example 1, which will not be repeated here.

[0053] Comparative Example 1

[0054] This comparative example provides an EPDM rubber, which is different from Example 1 in that:

[0055] The component formula of the nano-silicon dioxide reinforced EPDM rubber does not contain nano-silicon dioxide components.

[0056] The method for preparing nano-silicon dioxide reinforced EPDM rubber is different from that in Example 1 in that:

[0057] The premixing and mixing in step S1 do not include the addition of nano silicon dioxide;

[0058] The dosage of the remaining components is the same as that in Example 1, and the remaining preparation steps are the same as those in Example 1, which will not be repeated here.

[0059] Comparative Example 2

[0060] This comparative example provides a nano-silicon dioxide reinforced EPDM rubber. The preparation method of the nano-silicon dioxide reinforced EPDM rubber is different from that of Example 1 in that:

[0061] In step S1, 50% of the formula amount of EPDM rubber (50 parts) and nano silicon dioxide (5 parts) are premixed, the roller temperature is 40° C., the roller distance is 0.5-1 mm, and after reaching the required plasticity, they are left to stand for 2 hours, and then plasticized with the remaining formula amount of EPDM rubber (50 parts) and nano silicon carbide (5 parts) for 8 minutes to prepare a masterbatch;

[0062] In step S2, the masterbatch obtained in step S1 and the formulated amount of silane coupling agent, zinc oxide, stearic acid, antioxidant RD and antioxidant MB are added to a pressure mixer for first mixing, and the mixing is performed for 3 minutes;

[0063] The remaining steps are the same as those in Example 1, and the formula amounts of each component are the same as those in Example 1, which will not be repeated here.

[0064] Performance Testing

[0065] The mechanical properties and electrical properties of the nano-silica reinforced EPDM rubber described in Examples 1 to 3 are shown in Table 1. Under the doping modification of nano-silica, the nano-silica reinforced EPDM rubber with different average particle sizes described in Examples 1 to 4 all exhibit good mechanical properties, higher positive / negative electrode DC breakdown strength and lower space charge density. The average particle size of the nano-silica can be 20 to 50 nm.

[0066] Table 1 Mechanical and electrical properties of nano-silica reinforced EPDM rubber

[0067]

[0068] Compared with Example 1, Example 2 adds less nano-silica and silane coupling agent. Through experimental data, it can be found that due to the reduction in the amount of nano-silica added, the overall volume resistivity of the EPDM rubber in Example 2 is significantly improved, and the mechanical properties and the ability to suppress space charge decrease to a certain extent.

[0069] Compared with Example 1, the composition of Comparative Example 1 does not contain nano-silica filler. Through experimental data, it can be found that the mechanical properties of the EPDM rubber in Comparative Example 1 do not change significantly, and the hardness, tear strength, tensile strength and elongation at break of the rubber do not have significant differences. However, since no nano-silica filler is added to the formula, its volume resistivity is significantly increased, and the space charge suppression performance is significantly reduced. It can be seen that the doping of nano-silica is of great significance to the improvement of the electrical properties of EPDM rubber, and can significantly improve the space charge suppression ability of the rubber.

[0070] Compared with Example 1, the positive and negative DC breakdown strengths of Comparative Example 2 are significantly reduced, and the space charge density is significantly increased. This can be attributed to the change in the preparation method of Comparative Example 2. The preparation method does not add silane coupling agent in the masterbatch premixing stage, and cannot achieve the purpose of pretreating the nano-silica, which leads to agglomeration inside the rubber material, reducing its ability to suppress space charge. It can be seen that the preparation method of nano-silica reinforced EPDM rubber provided by the present invention can significantly improve the material's suppression of space charge.

Claims

1. A nano-silicon dioxide reinforced EPDM rubber, characterized in that: The invention comprises the following components in parts by weight: 100 parts of EPDM rubber, 8-10 parts of nano silicon dioxide, 1.5-4 parts of silane coupling agent, 4-6 parts of zinc oxide, 0.5-1.5 parts of stearic acid, 2-5 parts of antioxidant, 50-60 parts of clay, 3-5 parts of paraffin oil, 20-25 parts of white carbon black, 1-3 parts of sulfur, 3-4 parts of cross-linking agent and 4-5 parts of vulcanizing agent.

2. The nano-silicon dioxide reinforced EPDM rubber according to claim 1, characterized in that: The average particle size of the nano silicon dioxide is 20 to 50 nm.

3. The nano-silicon dioxide reinforced EPDM rubber according to claim 1, characterized in that: The silane coupling agent is KH550; the auxiliary cross-linking agent is triallyl isocyanurate; the vulcanizing agent is BIBP; and the antioxidants include antioxidant RD and antioxidant MB.

4. The nano-silicon dioxide reinforced EPDM rubber according to claim 1, characterized in that: The mass ratio of the antioxidant RD to the antioxidant MB is 1:(5-7).

5. A method for preparing nano-silicon dioxide reinforced EPDM rubber as claimed in any one of claims 1 to 4, characterized in that: The preparation method thereof comprises the following steps: S1, premixing 40% to 60% of the formula amount of EPDM rubber, nano-silicon dioxide, and silane coupling agent, and then plasticizing the premix with the remaining formula amount of EPDM rubber, nano-silicon dioxide, and silane coupling agent to prepare a masterbatch; S2, mixing the masterbatch obtained in step S1 with the formula amount of zinc oxide, stearic acid, and antioxidant for the first time, adding 40% to 60% of the formula amount of clay, paraffin oil, and white carbon black thereto for the second mixing, and then adding the remaining formula amount of clay, paraffin oil, and white carbon black thereto for the third mixing to obtain a rubber material; S3, cooling and parking the rubber material obtained in step S2 after heat treatment in an open mixing mill; S4, subjecting the rubber material treated in step S3 to a first-stage thin-pass treatment, and then adding a formula amount of sulfur, a cross-linking agent and a vulcanizing agent to a second-stage thin-pass treatment, and then vulcanizing to obtain the nano-silica reinforced EPDM rubber.

6. The method for preparing nano-silicon dioxide reinforced EPDM rubber according to claim 5, characterized in that: In step S1, the roller temperature for premixing 40% to 60% of the EPDM rubber, nano-silicon dioxide and silane coupling agent is 35 to 55°C.

7. The method for preparing nano-silicon dioxide reinforced EPDM rubber according to claim 5, characterized in that: In step S3, the heat treatment temperature is 175-185° C., and the heat treatment time is 5-15 minutes.

8. The method for preparing nano-silicon dioxide reinforced EPDM rubber according to claim 5, characterized in that: In step S4, the temperature of the vulcanization treatment is 160-170° C., the time of the vulcanization treatment is 30-40 min, and the pressure of the vulcanization treatment is 12-15 MPa.

9. Use the nano-silica reinforced EPDM rubber according to any one of claims 1 to 4 or the nano-silica reinforced EPDM rubber prepared by the method according to any one of claims 5 to 8 in the preparation of high-voltage DC cable accessories.

Images