A type of ethylene propylene diene monomer (EPDM) rubber, its preparation method and application

Abstract

This invention discloses a EPDM rubber, its preparation method, and its applications. The raw materials for preparing the EPDM rubber include EPDM rubber base material, a vulcanizing agent, and polyethylene wax. The polyethylene wax has a softening point of 130-140℃. By using a polyethylene wax with a higher softening point, it is possible to ensure good mold release and overall rubber compound performance while avoiding poor pattern formation. This invention also discloses the preparation method and applications of the EPDM rubber, as well as the application of polyethylene wax in EPDM rubber.

Description

Technical Field

[0001] This invention relates to the field of rubber technology, and in particular to a EPDM rubber, its preparation method, and its applications. Background Technology

[0002] Ethylene propylene diene monomer (EPDM) rubber is a terpolymer of ethylene, propylene, and a non-conjugated diene. The non-conjugated diene has a saturated main chain with only a small number of unsaturated double bonds in the side chains. This structure endows EPDM rubber with excellent weather resistance, heat resistance, acid and alkali resistance, electrical insulation properties, and corona resistance, making it more suitable for use as insulation material for high-voltage and ultra-high-voltage AC cables.

[0003] In practical applications, EPDM rubber requires high-temperature vulcanization, which can easily lead to appearance defects such as uneven patterns. Currently, most factories use rapid cooling processes to overcome this problem, which not only consumes air and labor but also generates noise pollution. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes the application of polyethylene wax in ethylene propylene diene monomer (EPDM) rubber. EPDM rubber using this polyethylene wax can be processed through conventional vulcanization processes, avoiding appearance defects such as uneven texture, and exhibits excellent overall performance of the rubber compound.

[0005] The present invention also proposes a ternary ethylene propylene diene monomer (EPDM) rubber.

[0006] The present invention also proposes a method for preparing the above-mentioned EPDM rubber.

[0007] This invention also proposes applications of the aforementioned EPDM rubber.

[0008] The first aspect of the present invention relates to the application of polyethylene wax in ethylene propylene diene monomer (EPDM) rubber, wherein the polyethylene wax has a softening point of 130-140°C.

[0009] Polyethylene wax is a commonly used release agent in EPDM rubber. To ensure smooth demolding of rubber products, the softening point of the polyethylene wax used is usually relatively low, generally 90-120℃. This embodiment uses a polyethylene wax with a higher softening point, which can ensure the demolding effect and the overall performance of the rubber compound while avoiding pattern defects.

[0010] The second aspect of the present invention relates to a EPDM rubber, the raw materials for which include EPDM rubber base material, vulcanizing agent and polyethylene wax, wherein the softening point of the polyethylene wax is 130-140℃.

[0011] This embodiment uses polyethylene wax with a higher softening point, which can ensure the demolding effect and the overall performance of the rubber compound while avoiding the problem of poor pattern.

[0012] According to some embodiments of the present invention, the Mooney viscosity of the EPDM rubber base material is 20-25 under ML1+4 and 125°C conditions.

[0013] According to some embodiments of the present invention, the ethylene monomer content in the EPDM rubber base material is 55wt%-75wt%. Higher ethylene monomer content results in better electrical insulation and mechanical properties, but worse processing performance.

[0014] Using EPDM rubber base materials with the above-mentioned ethylene monomer content and Mooney viscosity range can better balance electrical properties, mechanical properties and molding properties.

[0015] According to some embodiments of the present invention, in the EPDM rubber base material, the third monomer is ethylene-ide norbornene (ENB, CAS: 16219-75-3). According to convention in the art, the third monomer refers to a monomer other than ethylene monomer and propylene monomer among the polymerizing monomers used to prepare the EPDM rubber base material.

[0016] According to some embodiments of the present invention, the content of the third monomer in the EPDM rubber base material is 2wt%-10wt%.

[0017] The vulcanizing agent is a peroxide vulcanizing agent. Commonly used vulcanizing agents for EPDM rubber are sulfur and peroxides. Peroxide vulcanization systems offer better insulation and are suitable for high-voltage and ultra-high-voltage cable insulation materials. However, the polysulfide bonds formed by sulfur vulcanization have lower bond energies than the carbon-carbon bonds formed by peroxide vulcanization, and these polysulfide bonds are also prone to reduction vulcanization. This results in poorer electrical stability and aging resistance at high temperatures, making sulfur vulcanization more suitable for medium- and low-voltage cable accessories insulation materials.

[0018] According to some embodiments of the present invention, the vulcanizing agent is at least one of dicumyl peroxide and 2,5-dimethyl-2,5-di-tert-butylperoxyhexane.

[0019] According to some embodiments of the present invention, the amount of the vulcanizing agent is 3wt%-5wt% of the EPDM rubber base material.

[0020] According to some embodiments of the present invention, the amount of the polyethylene wax is 2wt%-4wt% of the EPDM rubber base material.

[0021] According to some embodiments of the present invention, the raw materials for preparing the EPDM rubber also include a crosslinking agent, which can accelerate the vulcanization speed and improve the vulcanization efficiency.

[0022] According to some embodiments of the present invention, the co-crosslinking agent is at least one selected from triallyl isocyanurate, 2-mercaptobenzothiazole, and sulfur. When the co-crosslinking agent contains sulfur, insoluble sulfur is preferred to avoid blooming.

[0023] According to some embodiments of the present invention, the amount of the crosslinking agent is 1wt%-2wt% of the EPDM rubber base material.

[0024] According to some embodiments of the present invention, the raw materials for preparing the EPDM rubber also include an activator.

[0025] According to some embodiments of the present invention, the activator is at least one of zinc oxide and stearic acid.

[0026] According to some embodiments of the present invention, the activator is a combination of zinc oxide and stearic acid.

[0027] Furthermore, the mass ratio of zinc oxide to stearic acid is 4-6:1, and more specifically 5:1.

[0028] According to some embodiments of the present invention, the amount of the activator is 4wt%-6wt% of the EPDM rubber base.

[0029] According to some embodiments of the present invention, the raw materials for preparing the EPDM rubber also include an antioxidant to improve the heat and oxygen aging resistance of the rubber compound.

[0030] According to some embodiments of the present invention, the antioxidant is antioxidant RD.

[0031] According to some embodiments of the present invention, the amount of antioxidant is 1wt%-2wt% of the EPDM rubber base material.

[0032] According to some embodiments of the present invention, the raw materials for preparing the EPDM rubber also include reinforcing agents.

[0033] According to some embodiments of the present invention, the reinforcing agent is at least one of clay and talc.

[0034] Furthermore, the particle size of the clay is not coarser than 5000 mesh.

[0035] Furthermore, the particle size of the talc powder is not coarser than 1250 mesh.

[0036] According to some embodiments of the present invention, the amount of the reinforcing agent is 50wt%-70wt% of the EPDM rubber base material.

[0037] According to some embodiments of the present invention, the raw materials for preparing the EPDM rubber also include a silane coupling agent, which can improve the compatibility and dispersibility of the filler in the rubber and enhance the reinforcing effect of the filler.

[0038] According to some embodiments of the present invention, the silane coupling agent is at least one of bis-(γ-triethoxysilylpropyl)tetrasulfide (CAS: 40372-72-3) and vinyltris(β-methoxyethoxy)silane (CAS: 1067-53-4).

[0039] According to some embodiments of the present invention, the amount of the silane coupling agent is 2wt%-4wt% of the EPDM rubber base material.

[0040] According to some embodiments of the present invention, the raw materials for preparing the EPDM rubber also include plasticizers. Plasticizers can improve processing and molding performance, reduce aging shrinkage, decrease appearance defects, and lower costs.

[0041] According to some embodiments of the present invention, the plasticizer is at least one of paraffin oil and naphthenic oil.

[0042] According to some embodiments of the present invention, the amount of plasticizer used is 10wt%-15wt% of the EPDM rubber base material.

[0043] According to some embodiments of the present invention, the raw materials for preparing the EPDM rubber also include a binder for improving the bonding performance.

[0044] According to some embodiments of the present invention, the adhesive is xylene-formaldehyde resin.

[0045] According to some embodiments of the present invention, the amount of the adhesive is 2wt%-4wt% of the EPDM rubber base material.

[0046] It is understood that the above embodiments can be applied individually or in combination, and all fall within the protection scope of this invention.

[0047] According to some embodiments of the present invention, the raw materials for preparing the EPDM rubber include: EPDM rubber base material, activator, antioxidant, plasticizer, reinforcing agent, silane coupling agent, vulcanizing agent, crosslinking agent and the polyethylene wax.

[0048] Furthermore, it also includes adhesives.

[0049] According to some embodiments of the present invention, the raw materials for preparing the EPDM rubber include, by weight:

[0050] EPDM rubber base material: 100 parts

[0051] Surfactant: 4-6 parts

[0052] Anti-aging agent: 1-2 parts,

[0053] Plasticizer: 10-15 parts

[0054] Reinforcing agent: 50-70 parts

[0055] Silane coupling agent: 2-4 parts,

[0056] Adhesive: 2-4 parts

[0057] Vulcanizing agent: 3-5 parts,

[0058] Crosslinking agent: 1-2 parts

[0059] The polyethylene wax: 2-4 parts.

[0060] The third aspect of the present invention relates to a method for preparing EPDM rubber, comprising the step of mixing the raw materials for preparing EPDM rubber.

[0061] The present invention does not have any particular limitation on the mixing process, and conventional mixing methods can be used, such as first plasticizing the EPDM rubber base material and then mixing it evenly with the other components.

[0062] When the raw materials for preparing the EPDM rubber include EPDM rubber base material, vulcanizing agent, polyethylene wax, activator, antioxidant, plasticizer, reinforcing agent, silane coupling agent, co-crosslinking agent, and binder, the preparation method is as follows:

[0063] S1. The EPDM rubber base material is plasticized, and then activator, antioxidant and polyethylene wax are added for the first mixing.

[0064] S2. Add binder, part of reinforcing agent, part of plasticizer and all of silane coupling agent to the rubber compound obtained in step S1, and perform a second mixing. Then add the remaining reinforcing agent and remaining plasticizer, and perform a third mixing.

[0065] S3. Filter the adhesive material obtained in step S2;

[0066] S4. Add vulcanizing agent and crosslinking agent to the filtered rubber compound, and vulcanize after thin-passing.

[0067] The preparation method of this embodiment can balance processing efficiency and rubber performance. Filtering the rubber can remove impurities, improve dispersibility, and further improve the appearance and overall performance of the product.

[0068] According to some embodiments of the present invention, in step S1, the temperature of the first mixing is 70-90°C.

[0069] According to some embodiments of the present invention, in step S1, the first mixing time is 2-4 minutes.

[0070] According to some embodiments of the present invention, in step S1, the plasticizing temperature is 60-75°C.

[0071] According to some embodiments of the present invention, in step S1, the plasticizing time is 5-10 minutes.

[0072] According to some embodiments of the present invention, in step S2, the mass ratio of the partial reinforcing agent to the remaining reinforcing agent is 1:1-1.5.

[0073] According to some embodiments of the present invention, in step S2, the mass ratio of the partial plasticizer to the remaining plasticizer is 1:1-1.5.

[0074] According to some embodiments of the present invention, in step S2, the temperature of the second mixing is 90-115°C.

[0075] According to some embodiments of the present invention, in step S2, the second mixing time is 3-5 minutes.

[0076] According to some embodiments of the present invention, in step S3, the temperature of the third mixing is 120-140°C.

[0077] According to some embodiments of the present invention, in step S2, the third mixing time is 3-5 minutes.

[0078] According to some embodiments of the present invention, in step S3, the mesh size of the filter is not less than 130 mesh.

[0079] According to some embodiments of the present invention, in step S3, the filtration is a two-stage filtration, wherein the mesh size of the first stage filter is not less than 100 mesh, and the mesh size of the second stage filter is not less than 130 mesh. Staged filtration can improve filtration efficiency and avoid screen clogging.

[0080] According to some embodiments of the present invention, in step S3, the filtration temperature is 170-190°C.

[0081] According to some embodiments of the present invention, in step S3, the filtered material is allowed to stand. Further, the standing temperature is room temperature, and the standing time can be 16-24 hours.

[0082] According to some embodiments of the present invention, in step S4, the vulcanization temperature is 155-160°C, the time is 25-35 min, and the pressure is 10-14 MPa.

[0083] According to some embodiments of the present invention, in step S4, the thin-passing is performed 8 times or more. Thin-passing can improve the uniformity of dispersion, and to better balance production efficiency and material properties, the number of thin-passing passes can be selected as 8-10 times.

[0084] According to some embodiments of the present invention, in step S4, before adding the vulcanizing agent and the crosslinking agent, the rubber compound is subjected to a thin pass through the rubber compound. The number of thin passes through the rubber compound can be multiple times, for example, 2-5 times.

[0085] It is understood that the process parameters in the above embodiments can be applied individually or in combination, and all of them fall within the protection scope of this invention.

[0086] The fourth aspect of the present invention relates to the application of the EPDM rubber in the preparation of insulating products or cables.

[0087] According to some embodiments of the present invention, the insulating product is a cable accessory.

[0088] In the description of this invention, room temperature refers to 23±2℃.

[0089] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Detailed Implementation

[0090] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0091] In the following examples and comparative examples, the EPDM rubber base material was Kumho KEP510 from South Korea, with an ethylene content of 71%, an ENB content of 5.7%, and a Mooney viscosity of 23 (ML1+4, 125°C); the polyethylene wax was purchased from Qingdao Sainuo New Materials Co., Ltd., with a softening point of 130°C; the clay particle size was -5000 mesh; and the remaining components were all commercially available conventional raw materials.

[0092] Example 1

[0093] This embodiment prepares a EPDM rubber, the raw materials of which are as follows by weight:

[0094] EPDM rubber base material: 100 parts

[0095] Zinc oxide: 5 parts

[0096] Stearic acid: 1 part

[0097] Anti-aging agent RD: 1 part

[0098] Paraffin oil: 12 parts

[0099] Clay: 60 parts

[0100] bis-(γ-triethoxysilylpropyl)tetrasulfide: 3 parts

[0101] Xylene-formaldehyde resin: 3 parts

[0102] Polyethylene wax: 3 parts

[0103] Dicumyl peroxide: 3 parts

[0104] Insoluble sulfur: 0.5 parts

[0105] 2-Mercaptobenzothiazole: 0.5 parts,

[0106] Triallyl isocyanurate: 1 part.

[0107] Its preparation method is as follows:

[0108] S1. Put the formulated amount of EPDM rubber base material into a pressure mixer and break it apart by plasticizing at 70°C for 8 minutes.

[0109] S2. Add the zinc oxide, stearic acid, antioxidant RD and polyethylene wax in the formula to a pressure mixer and mix at 80°C for 3 minutes.

[0110] S3. Add the following ingredients: xylene-formaldehyde resin, 1 / 2 clay, 1 / 2 paraffin oil, and all of the bis-(γ-triethoxysilylpropyl)tetrasulfide. Mix at 100°C for 3 minutes. Then add the remaining clay and paraffin oil and mix at 130°C for 4 minutes.

[0111] S4. The mixed rubber compound is filtered in two stages. The filtration temperature is 190℃. The first filtration uses a 100-mesh filter and the second filtration uses a 130-mesh filter. After filtration, the mixture is left to stand at room temperature for 24 hours.

[0112] S5. After cooling and resting, put the material into the open mill and pass it through twice. Then add the formula amount of dicumyl peroxide, 2-mercaptobenzothiazole, triallyl isocyanurate and insoluble sulfur into the open mill and pass it through 10 times. Then vulcanize and make sheets: the vulcanization temperature is 160℃, the vulcanization time is 35min, and the vulcanization pressure is 14MPa.

[0113] Comparative Example 1

[0114] EPDM rubber was prepared using the same method as in Example 1, except that the polyethylene wax was replaced with an equal amount of conventional polyethylene wax with a softening point of 110°C.

[0115] Comparative Example 2

[0116] EPDM rubber was prepared using the same method as in Example 1, except that 2 / 3 of the polyethylene wax was replaced with conventional polyethylene wax with a softening point of 110°C.

[0117] Comparative Example 3

[0118] EPDM rubber was prepared using the same method as in Example 1, except that step S4 was omitted, i.e., after step S3 was completed, the process proceeded directly to step S5.

[0119] Comparative Example 4

[0120] EPDM rubber was prepared using the same method as in Example 1, except that in step S4, only the first filtration was performed, and the filter mesh size was 100 mesh.

[0121] Test case

[0122] Observe the appearance of the rubber in each example and comparative example, and record whether there are any defects in the pattern. The mechanical properties, electrical properties, aging resistance and Mooney viscosity of the EPDM rubber prepared in Example 1 and Comparative Example 2 were tested, and the results are shown in Tables 1 and 2.

[0123] Table 1. Appearance of EPDM rubber prepared in Example 1 and Comparative Examples 1-4

[0124] Number of test pieces Number of poorly patterned blocks Poor pattern percentage Example 1 40 0 0 Comparative Example 1 40 30 75％ Comparative Example 2 40 15 37.5％ Comparative Example 3 40 5 12.5％ Comparative Example 4 40 2 5％

[0125] Table 2 Properties of EPDM rubber prepared in Example 1 and Comparative Example 2

[0126]

[0127]

[0128] The results above show that the embodiments of the present invention do not exhibit pattern defects, and the overall mechanical, electrical, and aging resistance of the rubber is superior. Compared with Example 1, Comparative Example 1 used conventional polyethylene wax, resulting in a pattern defect rate as high as 75%. Comparative Example 2 added some conventional polyethylene wax, yet still showed a pattern defect rate of 37.5%, indicating that adding conventional polyethylene wax has a significant impact on the appearance of the rubber. This problem can be effectively solved by using polyethylene wax with a high softening point. Furthermore, Comparative Example 2 shows that using conventional polyethylene wax has a certain impact on the overall performance of the rubber compound, possibly because conventional polyethylene wax has high fluidity and is more prone to generating internal stress. Compared with the formulation of Example 1, Comparative Example 3 did not undergo filtration, yet still showed a pattern defect rate of 12.5%, indicating that filtration is beneficial for improving appearance defects. Compared with Example 1, Comparative Example 4 only underwent one 100-mesh filter filtration, resulting in a pattern defect rate of 5%, indicating that two filtration operations can further improve appearance defects.

[0129] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A EPDM rubber, characterized in that, The raw materials for its preparation include EPDM rubber base, vulcanizing agent and polyethylene wax, wherein the softening point of the polyethylene wax is 130-140℃; The raw materials used in the preparation also include activators, antioxidants, plasticizers, reinforcing agents, silane coupling agents, crosslinking agents, and binders; The EPDM rubber base material has a Mooney viscosity of 20-25 under ML1+4 and 125℃ conditions, an ethylene monomer content of 55wt%-75wt%, and a third monomer, ENB, with a content of 2wt%-10wt%. The vulcanizing agent is at least one of dicumyl peroxide and 2,5-dimethyl-2,5-di-tert-butylperoxyhexane; The crosslinking agent is insoluble sulfur; The activator is at least one of zinc oxide and stearic acid; The reinforcing agent is at least one of clay and talc; The silane coupling agent is at least one of bis-(γ-triethoxysilylpropyl)tetrasulfide and vinyltris(β-methoxyethoxy)silane; The plasticizer is at least one of paraffin oil and naphthenic oil; The adhesive is xylene-formaldehyde resin; Based on the weight of the EPDM rubber base material, the following amounts are used: polyethylene wax 2wt%-4wt%; vulcanizing agent 3wt%-5wt%; crosslinking agent 1wt%-2wt%; activator 4wt%-6wt%; antioxidant 1wt%-2wt%; reinforcing agent 50wt%-70wt%; silane coupling agent 2wt%-4wt%; plasticizer 10wt%-15wt%; and binder 2wt%-4wt%. The method for preparing EPDM rubber includes the following steps: S1. The EPDM rubber base material is plasticized, and then activator, antioxidant and polyethylene wax are added for the first mixing. S2. Add binder, part of reinforcing agent, part of plasticizer and all of silane coupling agent to the rubber compound obtained in step S1, and perform a second mixing. Then add the remaining reinforcing agent and remaining plasticizer, and perform a third mixing. S3. Filter the adhesive material obtained in step S2; S4. Add vulcanizing agent and crosslinking agent to the filtered rubber compound, and vulcanize after thin-passing.

2. The EPDM rubber according to claim 1, characterized in that, The filtration is a two-stage filtration, wherein the mesh size of the first stage filter is not less than 100 mesh, and the mesh size of the second stage filter is not less than 130 mesh.

3. The application of EPDM rubber as described in claim 1 or 2 in the preparation of insulating products or cables.

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