Production process of rubber mould pressing foaming material

Abstract

The invention discloses a production process of a rubber mould pressing foaming material, and belongs to the technical field of rubber. The preparation method comprises the following steps: putting 100 parts of ethylene propylene diene monomer into an internal mixer, plastifying, adding 10-60 parts of a reinforcing agent, 10-40 parts of a softening agent, 0.5-1.5 parts of an accelerant, 2-8 parts of an active agent and 1-3 parts of an anti-aging agent, mixing, adding 2-10 parts of a foaming agent and 1-4 parts of a vulcanizing agent, discharging after mixing, and standing at room temperature to obtain a mixed rubber material; and carrying out vulcanization foaming molding on the rubber compound twice, and cooling to obtain the rubber mould pressing foaming material. The anti-aging agent disclosed by the invention contains a diaryl secondary amine structure, a benzotriazole structure and a coupling structure, and chemical action exists between the anti-aging agent and ethylene propylene diene monomer, so that the anti-aging agent disclosed by the invention is added into a rubber mould pressing foaming material, the protection efficiency of the material on heat, ultraviolet rays and the like can be effectively improved, and the service life of the material is prolonged. And meanwhile, the tensile strength, wear resistance and other properties of the material can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of rubber, and in particular relates to a production process of a rubber molded foaming material. Background Art

[0002] Rubber refers to a highly elastic polymer material with reversible deformation. It is elastic at room temperature and can produce a large deformation under a very small external force. It can return to its original shape after the external force is removed. Rubber foam material is also called porous rubber, sponge rubber or foam rubber. The characteristics of rubber foam material are light weight, good elasticity, shock absorption, sound insulation, heat insulation, a wide range of physical property adjustment, and high cost performance. It has been widely used in aviation, automobiles, instruments, meters, home appliances, packaging, shoemaking, sporting goods, etc. There are usually two molding methods for rubber foam materials: compression foaming and free foaming. The rubber compression foaming method must accurately control the speed and starting point of the two reactions of vulcanization and foaming to achieve mutual matching of the two processes of rubber vulcanization and foaming.

[0003] Chinese patent CN1760253A provides a foam rubber shock-absorbing product and a production method thereof, wherein the raw materials include 100 parts of EPDM rubber, 10-300 parts of filler, 10-200 parts of softener, 1-17 parts of vulcanization system and 1-15 parts of foaming agent by mass, and the foam rubber shock-absorbing product is obtained by two-step molding and foaming. The foam rubber product has good production stability, high product flatness, fine and uniform internal pore size, is not easy to absorb water, and has good shock-absorbing performance, but the foam rubber product has poor aging resistance, so as to prolong the use time, the foam rubber product is easy to turn yellow, powder or become brittle, thereby causing various performances to deteriorate and affecting the use.

[0004] The rubber molded foam materials in the prior art are also prone to aging under the influence of external conditions such as light, high temperature, and moisture, which in turn causes problems such as reduced strength. Therefore, it is urgent to produce and prepare a rubber molded foam product with strong anti-aging performance to meet market demand. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a production process of a rubber molded foam material.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A production process for a rubber molded foam material comprises the following steps: 100 parts of EPDM rubber are put into an internal mixer below 90° C. by weight, and plasticized for 2 minutes. Then, 10-60 parts of a reinforcing agent, 10-40 parts of a softening agent, 0.5-1.5 parts of an accelerator, 2-8 parts of an active agent, and 1-3 parts of an antioxidant are added, and the mixing is continued for 8 minutes. Finally, 2-10 parts of a foaming agent and 1-4 parts of a vulcanizing agent are added, and the material is discharged after mixing for 2 minutes, and placed at room temperature for 12 hours to obtain a mixed rubber material; the mixed rubber material is vulcanized at 140-180° C. for 5-20 minutes for primary vulcanization and foaming molding; then, the mixed rubber material is vulcanized at 120-180° C. for 10-30 minutes for secondary vulcanization and foaming molding, and a rubber molded foam material is obtained after cooling.

[0007] Furthermore, the reinforcing agent is one or more of carbon black, white carbon black, calcium carbonate, talcum powder, calcium silicate, aluminum hydroxide, and magnesium hydroxide.

[0008] Furthermore, the softener is paraffin oil.

[0009] Furthermore, the accelerator is one or more of N-cyclohexyl-2-benzothiazole sulfenamide, N-tert-butyl-2-benzothiazole sulfenamide, 2,2′-dibenzothiazole disulfide, tetramethylthiuram monosulfide, and tetramethylthiuram disulfide.

[0010] Furthermore, the active agent is one or more of zinc oxide, zinc carbonate, stearic acid, zinc stearate, and polyethylene glycol.

[0011] Furthermore, the antioxidant is prepared by the following steps: (1) Add 2-chloro-1,3-propanediol, triethylamine and chloroform into a fully dried three-necked flask, stir evenly and then add ultraviolet absorber UV-327 (2,4-di-tert-butyl-6-(5-chloro-2H-benzotriazole-2-yl)phenol). After the addition is complete, heat to 35°C and keep warm for 24 hours. After the reaction is completed, cool to room temperature and then distill under reduced pressure to obtain intermediate 1. The amount ratio of ultraviolet absorber UV-327, 2-chloro-1,3-propanediol, triethylamine and chloroform is 43 g:10.9 mL:18.3 mL:200 mL. Under the action of triethylamine, the molar ratio of UV absorber UV-327 and 2-chloro-1,3-propylene glycol is controlled to be 1:1.05-1.1, then -Cl of UV absorber UV-327 and -OH of 2-chloro-1,3-propylene glycol undergo substitution reaction, and the reaction equation is as follows:

[0012] (2) Add p-aminodiphenylamine, triethylamine and ethanol to a fully dried three-necked flask, stir evenly and then add 4-chloro-1-butene. After the addition is complete, heat to 60°C and keep warm for 3 hours. After the reaction is completed, cool to room temperature and distill under reduced pressure to obtain intermediate 2. The dosage ratio of p-aminodiphenylamine, 4-chloro-1-butene, triethylamine and ethanol is 21.9 mL:12.1 mL:19.2 mL:200 mL. The molar ratio of p-aminodiphenylamine to 4-chloro-1-butene is controlled to be 1.05-1.1:1. Under heating, -NH2 of p-aminodiphenylamine and -Cl of 4-chloro-1-butene undergo nucleophilic substitution reaction, and triethylamine is used as an acid binding agent. The reaction process is as follows:

[0013] (3) Add intermediate 1, pyridine and dimethyl sulfoxide into a fully dried three-necked flask, stir evenly and then add intermediate 2. After the addition is complete, heat to 65°C and keep warm for 4 hours. After the reaction is completed, cool to room temperature and distill under reduced pressure to obtain intermediate 3. The amount ratio of intermediate 1, intermediate 2, pyridine and dimethyl sulfoxide is 43.2g:25.7g:8.9mL:240mL. Pyridine is an acid-binding agent, and the molar ratio of intermediate 1 to intermediate 2 is controlled to be 1:1.05-1.1. The -Cl of intermediate 1 and the -NH- of intermediate 2 undergo a nucleophilic substitution reaction under heating. The reaction process is as follows:

[0014] (4) Blow nitrogen gas through a dry three-necked flask for 30 minutes to expel air and moisture from the flask, then add intermediate 3, tetraisopropyl titanate and dimethyl sulfoxide, stir evenly and heat to 90°C, then slowly add bis-[3-(triethoxysilyl)propyl]-disulfide, keep warm for 24 hours after the addition is complete, cool to room temperature after the reaction is complete, distill under reduced pressure, purify by column chromatography (the eluent is a mixed solvent of chloroform and ether, the volume ratio of chloroform to ether is 9:1), and finally remove the eluent by distillation under reduced pressure to obtain an antioxidant; the amount ratio of intermediate 3, bis-[3-(triethoxysilyl)propyl]-disulfide, tetraisopropyl titanate and dimethyl sulfoxide is 50.7 g:41.3 g:0.7 mL:250 mL.

[0015] The molar ratio of intermediate 3 and bis-[3-(triethoxysilyl)propyl]-disulfide is controlled to be 1:1.05-1.1. Then, under the catalysis of tetraisopropyl titanate, the hydroxyl group of intermediate 3 and the siloxy group of bis-[3-(triethoxysilyl)propyl]-disulfide undergo the following chemical reaction. The reaction process is shown below:

[0016] The antioxidant of the present invention contains a diaryl secondary amine structure, which contains an active amine group. The amine group can react with active oxygen free radicals in the polymer material to generate a stable compound, thereby preventing the oxidative degradation of the polymer material. In addition, the structure also has the characteristics of a hydrogen atom donor and a free radical capture, which can improve the heat resistance and weather resistance of the polymer material. Therefore, the antioxidant containing the diaryl secondary amine structure is used in rubber molded foaming materials to effectively improve the material's protective performance against ozone cracking and flex fatigue.

[0017] The antioxidant contains a benzotriazole structure, which can strongly absorb 300-400 mm ultraviolet rays, with the highest absorption peak at 353 nanometers. It also has good chemical stability, low volatility, high temperature resistance, and good thermal stability. Therefore, applying an antioxidant containing a benzotriazole structure to rubber molded foaming materials can effectively improve the material's protection against ultraviolet rays.

[0018] The antioxidant also contains a coupling structure, which can not only improve the elastic modulus and tensile strength of the rubber, significantly improve the wear resistance and compression performance of the rubber, but also reduce the viscosity of the rubber and save processing energy. In addition, the coupling structure can also improve the dispersion of the reinforcing agent, so that it can be evenly dispersed in the rubber molded foaming material, thereby improving the strength of the material and reducing production costs.

[0019] The carbon-carbon double bonds in the antioxidant can produce a chemical reaction with the carbon-carbon double bonds in the side chain of EPDM rubber under the action of the vulcanizer, and then the antioxidant is grafted onto the EPDM macromolecular chain and exists stably in the material, thereby giving the material excellent and stable heat aging resistance, UV aging resistance and strength.

[0020] Furthermore, the foaming agent is one or more of azodicarbonamide, 4,4′-oxybisbenzenesulfonylhydrazide, N,N′-dinitrosopentamethylenetetramine, sodium bicarbonate, and ammonium bicarbonate.

[0021] Furthermore, the vulcanizing agent is one or more of sulfur, dicumyl peroxide, and dibenzoyl peroxide.

[0022] The beneficial effects of the present invention are as follows: the antioxidant of the present invention contains a diaryl secondary amine structure, a benzotriazole structure and a coupling structure, and there is a chemical reaction between the antioxidant and the EPDM rubber. Therefore, adding the antioxidant of the present invention to the rubber molded foam material can effectively improve the material's protection against heat, ultraviolet rays, etc., and can also improve the material's tensile strength, wear resistance and other properties. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Example 1, preparation of antioxidant, the specific steps are as follows: (1) Add 10.9 mL of 2-chloro-1,3-propanediol, 18.3 mL of triethylamine and 200 mL of chloroform into a 500 mL fully dried three-necked flask, stir evenly and then add 43 g of UV absorber UV-327. After the addition is complete, heat to 35°C and keep warm for 24 hours. After the reaction is completed, cool to room temperature and then distill under reduced pressure to obtain intermediate 1. (2) Add 21.9 mL of p-aminodiphenylamine, 19.2 mL of triethylamine and 200 mL of ethanol into a 500 mL fully dried three-necked flask, stir evenly and then add 12.1 mL of 4-chloro-1-butene. After the addition is complete, heat to 60°C and keep the temperature to react for 3 h. After the reaction is completed, cool to room temperature and distill under reduced pressure to obtain intermediate 2. (3) Add 43.2 g of intermediate 1, 8.9 mL of pyridine and 240 mL of dimethyl sulfoxide into a 500 mL fully dried three-necked flask, stir evenly and then add 25.7 g of intermediate 1. After the addition is complete, heat to 65 °C and keep the temperature for 4 h. After the reaction is completed, cool to room temperature and distill under reduced pressure to obtain intermediate 3. (4) Nitrogen was blown into a 500 mL dry three-necked flask for 30 min to expel air and moisture from the flask. Then, 50.7 g of intermediate 3, 0.7 mL of tetraisopropyl titanate and 250 mL of dimethyl sulfoxide were added. The mixture was stirred evenly and the temperature was raised to 90 °C. Then, 41.3 g of bis-[3-(triethoxysilyl)propyl]-disulfide was slowly added. After the addition was completed, the mixture was kept warm for 24 h. After the reaction was completed, the mixture was cooled to room temperature and distilled under reduced pressure. The mixture was purified by column chromatography (the eluent was a mixed solvent of chloroform and ether, with a volume ratio of chloroform to ether of 9:1). Finally, the eluent was removed by distillation under reduced pressure to obtain an antioxidant.

[0025] Example 2, preparing a rubber molded foam material, the specific steps are as follows: 100 parts of EPDM rubber by weight were put into an internal mixer below 90° C. and plasticized for 2 minutes. Then, 10 parts of white carbon black, 10 parts of paraffin oil, 0.5 parts of N-cyclohexyl-2-benzothiazole sulfonamide, 2 parts of zinc oxide, and 1 part of the antioxidant prepared in Example 1 were added, and mixing was continued for 8 minutes. Finally, 2 parts of azodicarbonamide and 1 part of diisopropylbenzene peroxide were added, and the material was discharged after mixing for 2 minutes. The material was placed at room temperature for 12 hours to obtain a mixed rubber material; the mixed rubber material was vulcanized at 140° C. for 20 minutes for primary vulcanization foaming molding; then, it was vulcanized at 180° C. for 30 minutes for secondary vulcanization foaming molding, and a rubber molded foam material was obtained after cooling.

[0026] Example 3, preparing a rubber molded foam material, the specific steps are as follows: 100 parts of EPDM rubber were put into an internal mixer at a temperature below 90°C by weight, and plasticized for 2 minutes. Then, 10 parts of carbon black, 10 parts of white carbon black, 10 parts of calcium carbonate, 10 parts of talcum powder, 10 parts of calcium silicate, 10 parts of aluminum hydroxide, 40 parts of paraffin oil, 0.5 parts of N-cyclohexyl-2-benzothiazole sulfenamide, 0.5 parts of N-tert-butyl-2-benzothiazole sulfenamide, 0.5 parts of 2,2′-dibenzothiazole disulfide, 3 parts of zinc carbonate, 2 parts of stearic acid, 3 parts of zinc stearate, 10 parts of ethyl acetate and 10 parts of ethyl acetate were added. The antioxidant prepared in Example 1 was added, and the mixing was continued for 8 minutes. Finally, 5 parts of azodicarbonamide, 2 parts of 4,4′-oxybisbenzenesulfonylhydrazide, 3 parts of sodium bicarbonate, 3.5 parts of sulfur, and 0.5 part of diisopropylbenzene peroxide were added. The mixture was discharged after mixing for 2 minutes, and the mixture was placed at room temperature for 12 hours to obtain a mixed rubber material. The mixed rubber material was vulcanized at 180°C for 5 minutes for primary vulcanization foaming molding; then, the mixed rubber material was vulcanized at 180°C for 10 minutes for secondary vulcanization foaming molding, and the rubber molded foam material was obtained after cooling.

[0027] Example 4, preparing a rubber molded foam material, the specific steps are as follows: 100 parts of EPDM rubber by weight were put into an internal mixer below 90° C. and plasticized for 2 minutes. Then, 5 parts of carbon black, 10 parts of talc, 10 parts of calcium silicate, 15 parts of white carbon black, 10 parts of magnesium hydroxide, 30 parts of paraffin oil, 0.5 parts of tetramethylthiuram monosulfide, 0.5 parts of tetramethylthiuram disulfide, 3 parts of zinc carbonate, 3 parts of zinc stearate, and 2 parts of the antioxidant prepared in Example 1 were added, and mixing was continued for 8 minutes. Finally, 3 parts of azodicarbonamide, 3 parts of N,N′-dinitrosopentamethylenetetramine, 2.9 parts of sulfur, and 0.1 part of dibenzoyl peroxide were added. After mixing for 2 minutes, the material was discharged and placed at room temperature for 12 hours to obtain a mixed rubber material. The mixed rubber material was vulcanized at 150° C. for 10 minutes for primary vulcanization foaming molding; then it was vulcanized at 160° C. for 15 minutes for secondary vulcanization foaming molding, and a rubber molded foam material was obtained after cooling.

[0028] Comparative Example 1: preparing a rubber molded foam material, the specific steps are as follows: The remaining steps remain unchanged, only the antioxidant in Example 2 is removed to prepare the rubber molded foam material.

[0029] Comparative Example 2, preparing a rubber molded foam material, the specific steps are as follows: The remaining steps remained unchanged, except that the antioxidant in Example 2 was replaced with 0.4 parts of antioxidant 4020, 0.3 parts of ultraviolet absorber UV-531, and 0.3 parts of 3-aminopropyltriethoxysilane to prepare a rubber molded foam material.

[0030] Performance Testing The rubber molded foam materials prepared in Examples 2-4 and Comparative Examples 1-2 were tested for tensile strength and elongation at break according to ASTM D412; the rubber molded foam materials prepared in Examples 2-4 and Comparative Examples 1-2 were tested for tensile strength and elongation at break by dry heat aging at 105°C for 120h; the rubber molded foam materials prepared in Examples 2-4 and Comparative Examples 1-2 were tested for tensile strength and elongation at break by UV aging at room temperature, vertical irradiation distance of 20cm, under 30W UV lamp, for 120h. The test results of all items are shown in the following table:

[0031] It can be seen from the above test results that the rubber molded foam materials prepared in Examples 2-4 of the present invention have more excellent heat aging resistance and UV aging resistance.

[0032] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0033] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A production process for a rubber molded foam material, characterized in that: The following steps are involved: 100 parts of EPDM rubber are put into an internal mixer at a temperature below 90° C. by weight, and plasticized for 2 minutes. Then, 10-60 parts of a reinforcing agent, 10-40 parts of a softening agent, 0.5-1.5 parts of an accelerator, 2-8 parts of an active agent, and 1-3 parts of an antioxidant are added, and the mixing is continued for 8 minutes. Finally, 2-10 parts of a foaming agent and 1-4 parts of a vulcanizing agent are added, and the material is discharged after mixing for 2 minutes, and placed at room temperature for 12 hours to obtain a mixed rubber material; the mixed rubber material is vulcanized at 140-180° C. for 5-20 minutes for primary vulcanization foaming molding; then, the mixed rubber material is vulcanized at 120-180° C. for 10-30 minutes for secondary vulcanization foaming molding, and a rubber molded foam material is obtained after cooling; Wherein, the antioxidant is prepared by the following steps: (1) Add 2-chloro-1,3-propanediol, triethylamine and chloroform into a flask, stir and then add ultraviolet absorber UV-327, heat to 35°C, react for 24 hours, cool, and distill under reduced pressure to obtain intermediate 1; (2) Add p-aminodiphenylamine, triethylamine and ethanol into a flask, stir and then add 4-chloro-1-butene, heat to 60°C, react for 3 hours, cool, and distill under reduced pressure to obtain intermediate 2; (3) Add intermediate 1, pyridine and dimethyl sulfoxide into a flask, stir and then add intermediate 2, heat to 65°C, react for 4 hours, cool, and distill under reduced pressure to obtain intermediate 3; (4) After nitrogen is purged into the flask, intermediate 3, tetraisopropyl titanate and dimethyl sulfoxide are added, the temperature is raised to 90°C after stirring, bis-[3-(triethoxysilyl)propyl]-disulfide is added, the reaction is carried out for 24 hours, the mixture is cooled, distilled under reduced pressure, purified by column chromatography, and distilled under reduced pressure to obtain an antioxidant.

2. The production process of a rubber molded foam material according to claim 1, characterized in that: The amount ratio of the ultraviolet absorber UV-327, 2-chloro-1,3-propanediol, triethylamine and chloroform in the step (1) is 43 g: 10.9 mL: 18.3 mL: 200 mL.

3. The production process of a rubber molded foam material according to claim 1, characterized in that: The amount ratio of p-aminodiphenylamine, 4-chloro-1-butene, triethylamine and ethanol in the step (2) is 21.9 mL: 12.1 mL: 19.2 mL: 200 mL.

4. The production process of a rubber molded foam material according to claim 1, characterized in that: The usage ratio of intermediate 1, intermediate 2, pyridine and dimethyl sulfoxide in step (3) is 43.2 g:25.7 g:8.9 mL:240 mL.

5. The production process of a rubber molded foam material according to claim 1, characterized in that: The amount ratio of the intermediate 3, bis-[3-(triethoxysilyl)propyl]-disulfide, tetraisopropyl titanate and dimethyl sulfoxide in step (4) is 50.7 g:41.3 g:0.7 mL:250 mL.

6. The production process of a rubber molded foam material according to claim 1, characterized in that: The reinforcing agent is one or more of carbon black, white carbon black, calcium carbonate, talcum powder, calcium silicate, aluminum hydroxide, and magnesium hydroxide; and the softening agent is paraffin oil.

7. The production process of a rubber molded foam material according to claim 1, characterized in that: The accelerator is one or more of N-cyclohexyl-2-benzothiazole sulfenamide, N-tert-butyl-2-benzothiazole sulfenamide, 2,2'-dibenzothiazole disulfide, tetramethylthiuram monosulfide, and tetramethylthiuram disulfide.

8. The production process of a rubber molded foam material according to claim 1, characterized in that: The active agent is one or more of zinc oxide, zinc carbonate, stearic acid, zinc stearate, and polyethylene glycol; the foaming agent is one or more of azodicarbonamide, 4,4'-oxybisbenzenesulfonyl hydrazide, N,N'-dinitrosopentamethylenetetramine, sodium bicarbonate, and ammonium bicarbonate.

9. The production process of a rubber molded foam material according to claim 1, characterized in that: The vulcanizing agent is one or more of sulfur, dicumyl peroxide and dibenzoyl peroxide.

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