Method for improving elasticity of EVM rubber

Abstract

The invention discloses a method for improving the elasticity of ethylene-vinyl acetate rubber (EVM rubber). The method comprises the following steps: blending raw materials including an EVM raw rubber raw material and a flexible vulcanizing aid, and vulcanizing to prepare the EVM rubber, the invention also discloses an application of the EVM rubber. The EVM rubber prepared from the EVM raw rubber with the VA content of 70-80 wt% can meet the vulcanization safety and also has high elasticity; the sealing ring is suitable for the high-temperature oil-resistant sealing industry.

Description

Technical Field

[0001] The invention relates to EVM rubber, and in particular to a method for improving the elasticity of EVM rubber. Background Art

[0002] Ethylene-vinyl acetate rubber (EVM rubber) is the abbreviation of ethylene-vinyl acetate copolymer with a vinyl acetate (VA) content of 40%-80%. The EVM rubber obtained by vulcanization with it as the main raw material has excellent high temperature resistance (175℃), oil resistance (equivalent to nitrile rubber with an acrylonitrile ACN content of 26%-34%), aging resistance (second only to EPDM) and flame retardant properties. In recent years, it has been widely used in products such as cables, rubber rollers, household appliances and automotive rubber accessories, and has become an irreplaceable new material for some special rubber products. However, due to the high chain transfer constant of VA monomer during copolymerization of EVM rubber, it is difficult to obtain polymers with higher molecular weight, especially when the VA content is high (70-80%), which can generally only reach about 100,000, while the molecular weight of general synthetic rubber needs to be above one million in order to obtain higher elasticity. Therefore, the EVM rubber obtained by vulcanization of EVM rubber with high VA content usually has insufficient elasticity, which limits its application in the sealing field with high requirements for mechanical properties such as elasticity, and it is difficult to give full play to its advantages of oil resistance and high temperature resistance.

[0003] Chinese patent document CN103709570A discloses an ethylene vinyl acetate rubber / mesoporous silica composite material, the raw materials of which include the following components in parts by weight: 100 parts of ethylene vinyl acetate rubber, 0.1 to 10 parts of surface-modified mesoporous silica, and 2.0 to 3.0 parts of a vulcanizing agent; the tensile strength of the obtained ethylene vinyl acetate rubber composite material is ≥14.5 MPa, and the elongation at break is ≥429%; but the vinyl acetate content in the raw material ethylene vinyl acetate rubber used is 50 to 60 wt% to make the tensile strength and elongation at break of the obtained ethylene vinyl acetate rubber composite material good.

[0004] Chinese patent document CN102532680A discloses an EVM rubber composition for the outer layer of a fuel hose; including: the composition components and mass proportions are: 100 parts of EVA, 50-60 parts of reinforcing agent N330, 5-10 parts of plasticizer DOS, 2 parts of antioxidant RD, 2-3 parts of anti-hydrolysis agent P50, 0.5 parts of processing aid stearic acid, 2 parts of processing aid polyethylene wax, 2-3 parts of vulcanizing aid DCP and 1-3 parts of vulcanizing agent TAC; the invention effectively resists fuel corrosion and is more conducive to protecting the safe transportation of fuel.

[0005] The prior art has the following deficiencies: the EVM rubber composition can resist fuel corrosion, but the application field does not have high requirements for the elasticity of the rubber. If it is applied to the field of oil-resistant sealing, it will cause poor sealing due to insufficient elasticity. Summary of the invention

[0006] On the one hand, the present invention provides a method for preparing EVM rubber with good elasticity, wherein raw materials including EVM raw rubber and a flexible vulcanization aid are blended and then vulcanized to prepare the EVM rubber.

[0007] Furthermore, the tensile strength of the EVM rubber is ≥12Mpa and the elongation at break is ≥350%.

[0008] Furthermore, the content of vinyl acetate structural unit (VA) in the EVM raw rubber is 70-80wt%. Furthermore, the content of the flexible vulcanization aid is 1%-5% of the content of the EVM raw rubber raw material, calculated as a mass percentage.

[0009] Furthermore, the flexible vulcanization aid is one or more of acrylate derivatives.

[0010] Furthermore, the flexible vulcanization aid is selected from one or more of tripropylene glycol diacrylate, polyethylene glycol dimethacrylate and ditrihydroxypropane tetraacrylate.

[0011] Furthermore, the EVM rubber is prepared by blending the following raw materials in parts by weight and then vulcanizing them: based on 100 parts of EVM raw rubber raw materials, it includes 1.5-8.5 parts of active agent, 1-5 parts of anti-hydrolysis agent, 10-60 parts of reinforcing filler, 5-10 parts of plasticizer, 1-3 parts of vulcanizing agent and 1-3 parts of vulcanization aid.

[0012] Furthermore, the vulcanizing agent is selected from one or both of diisopropylbenzene peroxide and di-tert-butyl diisopropylbenzene peroxide.

[0013] Furthermore, the vulcanization aid is selected from one or both of triallyl isocyanurate and triallyl cyanurate.

[0014] In a second aspect, the present invention provides the application of the EVM rubber prepared by the method of the present invention in the oil-resistant sealing industry.

[0015] The present invention has the following beneficial effects.

[0016] (1) The EVM rubber obtained by vulcanizing EVM raw rubber with a high VA content (70-80wt%) usually has insufficient elasticity. The present invention can make the tensile strength of the EVM rubber made from EVM raw rubber with a VA content of 70-80wt% ≥12Mpa and the elongation at break ≥350% by adding a specific flexible vulcanization aid. Therefore, the EVM rubber made from EVM raw rubber with a VA content of 70-80wt% has an extremely excellent elongation at break while ensuring the qualified tensile strength, thereby meeting the higher elasticity requirements under specific needs.

[0017] (2) The present invention adds a specific flexible vulcanization aid, which can prolong the scorch time, improve the vulcanization safety of EVM rubber made from EVM raw rubber with a VA content of 70-80wt%, and improve the elongation at break and tensile strength, so that it can meet the higher elasticity requirements under specific needs; thus, it is suitable for oil-resistant sealing scenarios; DETAILED DESCRIPTION The examples are provided to better illustrate the content of the present invention, but the content of the present invention is not limited to the examples. Therefore, those skilled in the art can make non-essential improvements and adjustments to the implementation scheme according to the above content of the invention, which still fall within the protection scope of the present invention.

[0018] Preferably, the EVM raw rubber is an ethylene-vinyl acetate copolymer, and the vinyl acetate content thereof is 70-80wt%. The EVM raw rubber with a specific vinyl acetate content of 70-80wt% used in the embodiment of the present invention is provided by Chongqing Chuanwei Chemical Co., Ltd. of China Petrochemical Corporation.

[0019] Preferably, the active agent is selected from one or both of stearic acid and zinc oxide.

[0020] Preferably, the anti-hydrolysis agent is selected from polycarbodiimide or its derivatives.

[0021] Preferably, the reinforcing filler is selected from one or both of carbon black and white carbon black; and its content is more preferably 20-40 parts (based on 100 parts of EVM rubber).

[0022] Preferably, the plasticizer is selected from one or both of dioctyl sebacate (DOS) and trioctyl trimellitate (TOTM).

[0023] Detection method: Scorch time (t 10 ): Rotorless rheometer manufactured according to national standard GB / T16584; Tensile strength and elongation at break: universal testing machine; Example 1.

[0024] A method to improve the elasticity of EVM rubber: The following materials were added in sequence on a double-roll mill and fully blended to obtain a rubber compound; the mass fractions of the materials were as follows: EVM raw rubber (VA content is 80wt%) 100g, stearic acid 1g, zinc oxide 5g, polycarbodiimide 3g, carbon black 20g, dioctyl sebacate 6g, diisopropylbenzene peroxide 2g, triallyl isocyanurate 2g, tripropylene glycol diacrylate 2 / 3g; A small amount of the mixed rubber was cut and placed in a rotorless vulcanizer to measure its vulcanization characteristics. The mixed rubber was vulcanized for 40 minutes at 150°C and 10MPa using a flat vulcanizer to obtain the vulcanized rubber, and its mechanical properties were tested. The sample with 2 parts of tripropylene glycol diacrylate (TPGDA) added to the formula was recorded as T2, and the sample with 3 parts of TPGDA added to the formula was recorded as T3; Comparative example 1.

[0025] A method to improve the elasticity of EVM rubber: The following formula materials were added in sequence on a double-roll mill and fully blended to obtain a rubber compound. The mass fractions of the formula materials are as follows: EVM raw rubber (VA content is 80wt%) 100g, stearic acid 1g, zinc oxide 5g, polycarbodiimide 3g, carbon black 20g, dioctyl sebacate 6g, diisopropylbenzene peroxide 2g, triallyl isocyanurate 2g; A small amount of the mixed rubber was cut and placed in a rotorless vulcanizer to measure its vulcanization characteristics. The mixed rubber was vulcanized for 40 minutes at 150°C and 10 MPa using a flat vulcanizer to obtain the vulcanized rubber, and its mechanical properties were tested.

[0026] Table 1 serial number <![CDATA[Scorch time (t 10 ).]]> Tensile Strength Elongation at break <![CDATA[Example 1 - T2]]> 3 minutes 37 seconds 13.74 MPa 403.43% <![CDATA[Example 1 - T3]]> 3 minutes 38 seconds 12.26 MPa 425.49% Comparative Example 1 3 minutes 14 seconds 10.45 MPa 304.30% The tensile strength of Example 1 is 12.26-13.74 MPa, the elongation at break is 403.43%-425.49%, and the scorch time (t 10 ) is 3 minutes 37 seconds - 3 minutes 38 seconds; the tensile strength of comparative example 1 is 10.45 MPa, the elongation at break is 304.30%, and the scorch time (t 10) is 3 minutes and 14 seconds; it can be seen that the EVM rubber prepared by using EVM raw rubber with a VA content of 80wt% in Example 1 of the present invention has a significantly improved elongation at break while improving the tensile strength, and has an extremely excellent elongation at break, thereby proving that the EVM rubber prepared by using EVM raw rubber with a VA content of 80wt% in the present invention has a higher elastic effect and meets the requirements under specific needs; and the scorch time of the present invention is better than that of Comparative Example 1, which further improves the vulcanization safety; therefore, while improving the vulcanization safety, Example 1 of the present invention meets the higher elasticity requirements under specific needs, and is suitable for the scene of oil-resistant sealing: Example 2.

[0027] A method to improve the elasticity of EVM rubber: The following formula materials were added in sequence on a double-roll mill and fully blended to obtain a rubber compound. The mass fractions of the formula materials are as follows: EVM raw rubber (VA content is 80wt%) 100g, stearic acid 1g, zinc oxide 5g, polycarbodiimide 3g, carbon black 20g, dioctyl sebacate 6g, diisopropylbenzene peroxide 2g, triallyl isocyanurate 2g, polyethylene glycol dimethacrylate 2g; A small amount of the mixed rubber was cut and placed in a rotorless vulcanizer to measure its vulcanization characteristics. The mixed rubber was vulcanized for 40 minutes at 150°C and 10 MPa using a flat vulcanizer to obtain the vulcanized rubber, and its mechanical properties were tested.

[0028] Table 2 serial number <![CDATA[Scorch time (t 10 ).]]> Tensile Strength Elongation at break Example 2 8 minutes 34 seconds 12.34 MPa 363.63% Comparative Example 1 3 minutes 14 seconds 10.45 MPa 304.30% The tensile strength of Example 2 is 12.34 MPa, the elongation at break is 363.63%, and the scorch time (t 10 ) is 8 minutes and 34 seconds; the tensile strength of comparative example 1 is 10.45MPa, the elongation at break is 304.30%, the scorch time (t 10 ) is 3 minutes and 14 seconds; it can be seen that Example 2 significantly prolongs the scorch time, greatly improves the vulcanization safety, and improves the tensile strength while the elongation at break is increased by 59.33%. Therefore, the EVM rubber prepared by Example 2 of the present invention using EVM raw rubber with a VA content of 80wt% meets the vulcanization safety while meeting the higher elasticity requirements under specific needs, and is suitable for oil-resistant sealing scenarios: Example 3.

[0029] A method to improve the elasticity of EVM rubber: The following formula materials were added in sequence on a double-roll mill and fully blended to obtain a rubber compound. The mass fractions of the formula materials are as follows: EVM raw rubber (VA content is 80wt%) 100g, stearic acid 1g, zinc oxide 5g, polycarbodiimide 3g, carbon black 20g, dioctyl sebacate 6g, diisopropylbenzene peroxide 2g, triallyl isocyanurate 2g, ditrihydroxypropane tetraacrylate 2g; A small amount of the mixed rubber was cut and placed in a rotorless vulcanizer to measure its vulcanization characteristics. The mixed rubber was vulcanized for 40 minutes at 150°C and 10 MPa using a flat vulcanizer to obtain the vulcanized rubber, and its mechanical properties were tested.

[0030] Table 3 serial number <![CDATA[Scorch time (t 10 ).]]> Tensile Strength Elongation at break Example 3 3 minutes 58 seconds 12.43MPa 369.11% Comparative Example 1 3 minutes 14 seconds 10.45 MPa 304.30% The tensile strength of Example 3 is 12.43 MPa, the elongation at break is 369.11%, and the scorch time (t 10 ) is 3 minutes and 58 seconds; the tensile strength of comparative example 1 is 10.45MPa, the elongation at break is 304.30%, the scorch time (t 10 ) is 3 minutes and 14 seconds; it can be seen that Example 3 prolongs the scorch time by 44 seconds, improves the vulcanization safety, and improves the tensile strength while increasing the elongation at break by 64.81%. Therefore, the EVM rubber prepared by Example 3 of the present invention using EVM raw rubber with a VA content of 80wt% meets the vulcanization safety while meeting the higher elasticity requirements under specific needs, and is suitable for oil-resistant sealing scenarios.

[0031] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for improving the elasticity of EVM rubber, characterized in that: The EVM rubber is prepared by blending raw materials including EVM raw rubber raw materials and flexible vulcanization aids and then vulcanizing them.

2. The method for improving EVM rubber elasticity according to claim 1, characterized in that: The tensile strength of the EVM rubber is ≥12Mpa and the elongation at break is ≥350%.

3. The method for improving EVM rubber elasticity according to claim 1 or 2, characterized in that: The content of vinyl acetate structural units (VA) in the EVM raw rubber is 70-80wt%.

4. The method for improving the rubber elasticity of EVM according to any one of claims 1 to 3, characterized in that: The content of the flexible vulcanization aid is 1%-5% of the content of the EVM raw rubber material, calculated as a percentage by mass.

5. The method for improving the elasticity of EVM rubber according to any one of claims 1 to 4, characterized in that: The flexible vulcanization aid is one or more of acrylate derivatives.

6. The method for improving EVM rubber elasticity according to claim 5, characterized in that: The flexible vulcanization aid is selected from one or more of tripropylene glycol diacrylate, polyethylene glycol dimethacrylate and ditrihydroxypropane tetraacrylate.

7. The method for improving the rubber elasticity of EVM according to any one of claims 1 to 6, characterized in that: The EVM rubber is prepared by vulcanizing and blending the following raw materials in parts by weight: based on 100 parts of EVM raw rubber raw materials, the following include 1.5-8.5 parts of active agent, 1-5 parts of anti-hydrolysis agent, 10-60 parts of reinforcing filler, 5-10 parts of plasticizer, 1-3 parts of vulcanizing agent and 1-3 parts of vulcanization aid.

8. The method for improving EVM rubber elasticity according to claim 7, characterized in that: The vulcanizing agent is selected from one or both of diisopropylbenzene peroxide and di-tert-butyl diisopropylbenzene peroxide.

9. The method for improving EVM rubber elasticity according to claim 7 or 8, characterized in that: The vulcanization aid is selected from one or both of triallyl isocyanurate and triallyl cyanurate.

10. Application of the EVM rubber prepared by the method described in any one of claims 1 to 9 in the oil-resistant sealing industry.