Preparation method of flame-retardant rubber material for vehicles

Abstract

The invention discloses a preparation method of a flame-retardant rubber material for vehicles, and belongs to the technical field of flame-retardant rubber. Comprising the following raw materials in parts by weight: 60-70 parts of nitrile rubber, 22-30 parts of ethylene propylene diene monomer, 5-15 parts of a modifier, 3-5 parts of zinc oxide, 0.1-0.3 part of an initiator, 2-4 parts of a lubricant, 4-6 parts of sulfur and 0.5-1.5 parts of a vulcanization accelerator. Nitrile rubber is used as a matrix, so that the material is endowed with excellent oil resistance and good mechanical property; the oxidation resistance of the material can be enhanced by introducing the ethylene propylene diene monomer; wherein the modifier enhances the flame retardance, heat resistance, oxidation resistance and a certain degree of mechanical properties of the material, and the properties are long-lasting and stable; therefore, the prepared rubber material is high in oil resistance and good in mechanical property, has stable and efficient flame retardance, heat resistance and oxidation resistance, and has important application value in the technical field of flame-retardant rubber.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardant rubber, and in particular relates to a method for preparing a flame retardant rubber material for a vehicle. Background Art

[0002] In recent years, with the continuous development of the new energy field, new energy vehicles have occupied an increasingly larger proportion. In addition to tires, cars also have 200-300 kinds of rubber parts or sub-parts. Therefore, rubber materials are an important part of cars and play a vital role in ensuring the performance and safety of cars.

[0003] There are many types of automotive rubber materials, mainly including the following: nitrile rubber (NBR), chloroprene rubber (CR), acrylic rubber (ACM), silicone rubber (VMQ), fluororubber (FKM), butyl rubber (IIR), natural rubber (NR) and styrene-butadiene rubber (SBR). Among them, nitrile rubber is a copolymer formed by the polymerization of acrylonitrile and butadiene monomers. It is mainly produced by low-temperature emulsion polymerization. It has excellent oil resistance, high wear resistance, good heat resistance, and strong adhesion. Due to its excellent performance, it is often used to manufacture automotive parts such as oil seals, sealing rings, and oil pipes. However, the flame retardancy of nitrile rubber is very poor. In order to improve the flame retardancy of nitrile rubber, people usually use halogen flame retardants such as bromine compounds with high flame retardant efficiency or inorganic flame retardants as matching materials. However, the amount of smoke generated by the combustion of halogen flame retardants is large and toxic, which is not environmentally friendly; while inorganic flame retardants have poor compatibility with the rubber matrix and are unevenly dispersed in the rubber matrix. Therefore, it is urgent to solve the above problems and invent a halogen-free flame-retardant rubber material for automobiles to meet higher demands in the field of flame-retardant rubber technology. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a method for preparing a flame retardant rubber material for a vehicle.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A method for preparing a flame-retardant rubber material for a vehicle comprises the following steps: Add nitrile rubber and EPDM rubber into an open mill for the first mixing. After the mixing is completed, add a modifier, zinc oxide, an initiator and a lubricant for the second mixing. After the mixing is completed, put it into a flat vulcanizer and add sulfur and a vulcanization accelerator for vulcanization. After the vulcanization is completed, a flame retardant rubber material for automobiles is obtained.

[0006] Furthermore, the raw materials are calculated in parts by weight as follows: 60-70 parts of nitrile rubber, 22-30 parts of EPDM rubber, 5-15 parts of modifier, 3-5 parts of zinc oxide, 0.1-0.3 parts of initiator, 2-4 parts of lubricant, 4-6 parts of sulfur, and 0.5-1.5 parts of vulcanization accelerator.

[0007] Furthermore, the initiator is one of benzoyl peroxide and tert-butyl perbenzoate.

[0008] Furthermore, the lubricant is one of epoxidized soybean oil and paraffin.

[0009] Furthermore, the vulcanization accelerator is one of 2-mercaptobenzothiazole and tetramethylthiuram disulfide.

[0010] Furthermore, the first mixing condition is 75° C.-85° C., and the mixing time is 1-5 min.

[0011] Furthermore, the second mixing condition is 120-150° C., and the mixing time is 5-10 min.

[0012] Furthermore, the vulcanization conditions are 150-170° C. and vulcanization time is 2-3 hours.

[0013] With nitrile rubber as the matrix, the material has excellent oil resistance and good mechanical properties; the addition of EPDM rubber can enhance the material's antioxidant properties; the addition of zinc oxide can increase the crosslinking density of the finished product and promote vulcanization; the vulcanization accelerator shortens the vulcanization time, lowers the vulcanization temperature, and reduces the amount of vulcanizer used.

[0014] Furthermore, the modifier is prepared by the following steps: S1. Mix 3,5-di-tert-butyl-4-hydroxybenzaldehyde, piperidine (condensation agent) and toluene in a three-necked flask equipped with a stirring device, heat to 35°C, stir until the solid is completely dissolved, add diethylenetriamine, continue to heat to 65°C, keep warm for 6 hours, and after the reaction is completed, cool naturally, filter, and remove the solvent by vacuum distillation. Wash with deionized water to remove the residual diethylenetriamine, and vacuum dry to obtain intermediate 1; the ratio of 3,5-di-tert-butyl-4-hydroxybenzaldehyde, piperidine, toluene and diethylenetriamine is 23.4g:15mL:100mL:12.7g; Under the action of the condensation agent, the amino group on diethylenetriamine condenses with the aldehyde group on 3,5-di-tert-butyl-4-hydroxybenzaldehyde to form an imine group (C=N Schiff base structure), and by controlling the molar ratio of the two to be close to 1:1 and a slight excess of diethylenetriamine, only one amino group on diethylenetriamine participates in the reaction to obtain intermediate 1; the specific reaction process is as follows: ; S2. Add 4,4'-sulfonyl dibenzoic acid and toluene to a three-necked flask equipped with a stirring device, mix, heat to 30°C and stir continuously, introduce nitrogen, add intermediate 1 and dicyclohexylcarbodiimide (DCC, dehydrating agent), mix and stir evenly, place in a water bath, control the reaction temperature to 55°C, keep warm and react for 3 hours. After the reaction is completed, filter, remove the solvent by vacuum distillation, wash with anhydrous ethanol 2-3 times, and vacuum dry to obtain intermediate 2; the ratio of 4,4'-sulfonyl dibenzoic acid, toluene, intermediate 1, and DCC is 33.5g:150mL:32.1g:20.6g; Under the action of DCC, the carboxyl group on 4,4'-sulfonyl dibenzoic acid and the amino group of intermediate 1 undergo an amidation reaction. By controlling the molar ratio of the two to be close to 1:1 and a slight excess of 4,4'-sulfonyl dibenzoic acid, only one carboxyl group on 4,4'-sulfonyl dibenzoic acid participates in the reaction to obtain intermediate 2. The specific reaction process is as follows: ; S3. At room temperature, in a three-necked flask equipped with a stirring device, mix the intermediate II, 6-chloro-1-hexene, toluene and triethylamine evenly under nitrogen protection, gradually heat to 80°C, keep warm for 4 hours, and after the reaction is completed, filter, distill under reduced pressure, and then purify by column chromatography (the eluent is a mixed solvent of benzene / ethyl acetate, the volume ratio of the two is 3:2), remove the eluent by rotary evaporation, and vacuum dry to obtain the intermediate III; the ratio of the amount of the intermediate II, 6-chloro-1-hexene, toluene and triethylamine is 60.9g:11.8g:150mL:15mL; Triethylamine is used as an acid binding agent to remove the hydrogen chloride generated by the reaction, accelerate the reaction, and the intermediate 2 undergoes a nucleophilic substitution reaction with 6-chloro-1-hexene to obtain the intermediate 3. The specific reaction process is as follows: ; S4, in a three-necked flask equipped with a stirring device, amino POSS and tetrahydrofuran were mixed, stirred for 30 minutes, intermediate three, DCC and 4-dimethylaminopyridine (catalyst) were added and stirred evenly, the temperature was raised to 60 ° C, and the reaction was stirred for 8 minutes. After the reaction was completed, the solvent was removed by distillation under reduced pressure, washed with anhydrous ethanol 3-4 times, and vacuum dried to obtain a modifier; the ratio of amino POSS, tetrahydrofuran, intermediate three, DCC, and 4-dimethylaminopyridine was 138.5g:300mL:69.1g:20.6g:0.6g; Under the catalysis of DCC and 4-dimethylaminopyridine, the amino group on aminoPOSS undergoes amidation reaction with the carboxyl group on the intermediate trimer to obtain a modifier; the structure of the aminoPOSS used is shown below (R is isooctyl): ; The prepared modifier is mainly composed of cage-type polysilsesquioxane (POSS) and is grafted with an organic small molecule chain. POSS is an environmentally friendly organic-inorganic hybrid material. The skeleton of the material has a regular cage structure, and the skeleton is a silicon-oxygen skeleton structure with a certain rigidity, which makes POSS have relatively high thermal stability and mechanical properties. When heated, it will form a protective layer containing Si-O bonds and Si-C bonds that is more dense and stable than the conventional carbon layer, isolating the heat transfer and the escape of combustibles produced by the decomposition of the nitrile rubber matrix, while blocking the supply of oxygen, thereby enhancing the flame retardant, heat resistance and mechanical properties of the matrix. In addition, the modifier molecule also contains diphenyl sulfone, Schiff base, hindered phenol and carbon-carbon double bond. Among them, diphenyl sulfone can further enhance the heat resistance of the matrix, and the S element in the diphenyl sulfone structure generates SO during thermal desulfurization. 2 , sulfurous acid and water can promote the Fries rearrangement reaction of the matrix, accelerate the carbonization of the matrix, and further enhance the flame retardant properties of the matrix; not only that, the C=N double bond in the introduced Schiff base structure can generate a carbon-nitrogen six-membered ring at high temperature. This kind of six-membered ring structure enables the matrix to form a stable cross-linked network, which can synergize with diphenyl sulfone and POSS, significantly enhancing the flame retardant properties of the matrix; the introduced hindered phenol can provide active hydrogen atoms to capture peroxyl radicals, which can enhance the antioxidant properties of the matrix; finally, the carbon-carbon double bond in the modifier molecule can produce chemical bonding with the nitrile rubber matrix, thereby improving the stability of the modifier.

[0015] Beneficial effects of the present invention: 1. The rubber material prepared by the present invention is based on nitrile rubber, which gives the material excellent oil resistance and good mechanical properties; 2. The introduction of EPDM rubber can enhance the material's antioxidant properties; 3. The prepared modifier molecules contain various functional groups and can play a synergistic role, significantly enhancing the flame retardancy, heat resistance, oxidation resistance and a certain degree of mechanical properties of the material, and the performance is long-term and stable; Therefore, the rubber material prepared by the present invention has strong oil resistance, good mechanical properties, stable and efficient flame retardancy, heat resistance and oxidation resistance, and has important application value in the field of flame retardant rubber technology. DETAILED DESCRIPTION

[0016] 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.

[0017] Embodiment 1

[0018] Preparation of modifier: S1. In a three-necked flask equipped with a stirring device, 23.4 g of 3,5-di-tert-butyl-4-hydroxybenzaldehyde, 15 mL of piperidine and 100 mL of toluene were mixed, the temperature was raised to 35°C, and the mixture was stirred until the solid was completely dissolved. 12.7 g of diethylenetriamine was added, and the temperature was continued to be raised to 65°C. The mixture was kept warm for 6 hours. After the reaction was completed, the mixture was naturally cooled, filtered, and the solvent was removed by distillation under reduced pressure. The residual diethylenetriamine was removed by washing with deionized water, and the mixture was dried in vacuo to obtain an intermediate 1. S2. Add 33.5 g of 4,4'-sulfonyldibenzoic acid and 150 mL of toluene to a three-necked flask equipped with a stirring device, mix, heat to 30°C and stir continuously, introduce nitrogen, add 32.1 g of intermediate 1 and 20.6 g of DCC, mix and stir evenly, place in a water bath, control the reaction temperature to 55°C, keep warm and react for 3 hours. After the reaction is completed, filter, remove the solvent by vacuum distillation, wash 3 times with anhydrous ethanol, and vacuum dry to obtain intermediate 2; S3. At room temperature, in a three-necked flask equipped with a stirring device, 60.9 g of intermediate 2, 11.8 g of 6-chloro-1-hexene, 150 mL of toluene and 15 mL of triethylamine were mixed evenly under nitrogen protection, and the temperature was gradually raised to 80°C. The reaction was kept warm for 4 hours. After the reaction was completed, the mixture was filtered, evaporated under reduced pressure, and purified by column chromatography (the eluent was a mixed solvent of benzene / ethyl acetate in a volume ratio of 3:2). The eluent was removed by rotary evaporation and dried in vacuo to obtain intermediate 3. S4. In a three-necked flask equipped with a stirring device, 138.5 g of amino POSS and 300 mL of tetrahydrofuran were mixed, and after stirring for 30 min, 69.1 g of intermediate tris, 20.6 g of DCC and 0.6 g of 4-dimethylaminopyridine were added and stirred evenly. The temperature was raised to 60°C, and the reaction was stirred for 8 min. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the mixture was washed with anhydrous ethanol for 3 times and dried in vacuo to obtain a modifier.

[0019] Embodiment 2

[0020] Preparation of modifier: S1. In a three-necked flask equipped with a stirring device, 46.8 g of 3,5-di-tert-butyl-4-hydroxybenzaldehyde, 30 mL of piperidine and 200 mL of toluene were mixed, the temperature was raised to 35° C., and the mixture was stirred until the solid was completely dissolved. 25.4 g of diethylenetriamine was added, and the temperature was continued to be raised to 65° C. The mixture was kept warm for 6 h. After the reaction was completed, the mixture was naturally cooled, filtered, and the solvent was removed by distillation under reduced pressure. The residual diethylenetriamine was removed by washing with deionized water, and the mixture was dried in vacuo to obtain an intermediate 1. S2. Add 67.0 g of 4,4'-sulfonyldibenzoic acid and 300 mL of toluene to a three-necked flask equipped with a stirring device, mix, heat to 30°C and stir continuously, introduce nitrogen, add 64.2 g of intermediate 1 and 41.2 g of DCC, mix and stir evenly, place in a water bath, control the reaction temperature to 55°C, keep warm and react for 3 hours. After the reaction is completed, filter, remove the solvent by vacuum distillation, wash 3 times with anhydrous ethanol, and vacuum dry to obtain intermediate 2; S3, at room temperature, in a three-necked flask equipped with a stirring device, 121.8 g of intermediate 2, 23.6 g of 6-chloro-1-hexene, 300 mL of toluene and 30 mL of triethylamine were mixed evenly under nitrogen protection, and the temperature was gradually raised to 80°C, and the reaction was kept warm for 4 hours. After the reaction was completed, the mixture was filtered, evaporated under reduced pressure, and purified by column chromatography (the eluent was a mixed solvent of benzene / ethyl acetate in a volume ratio of 3:2), the eluent was removed by rotary evaporation, and vacuum dried to obtain intermediate 3; S4. In a three-necked flask equipped with a stirring device, 277.0 g of amino POSS and 600 mL of tetrahydrofuran were mixed, and after stirring for 30 min, 138.2 g of intermediate tris, 41.2 g of DCC and 1.2 g of 4-dimethylaminopyridine were added and stirred evenly. The temperature was raised to 60°C, and the reaction was stirred for 8 min. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the mixture was washed with anhydrous ethanol for 3 times and dried in vacuo to obtain a modifier.

[0021] Embodiment 3

[0022] 60 g of nitrile rubber and 22 g of EPDM rubber were added to an open mill and kneaded at 75° C. for 1 min. After kneading, 5 g of the modifier prepared in Example 1, 3 g of zinc oxide, 0.1 g of benzoyl peroxide and 2 g of epoxy soybean oil were added and kneaded at 120° C. for 5 min. After kneading, the mixture was put into a flat vulcanizer and 4 g of sulfur and 0.5 g of 2-mercaptobenzothiazole were added and vulcanized at 150° C. for 2 h. After vulcanization, a flame retardant rubber material for a vehicle was obtained.

[0023] Embodiment 4

[0024] 65g of nitrile rubber and 26g of EPDM rubber were added to an open mill and kneaded at 80°C for 3min. After kneading, 10g of the modifier prepared in Example 1, 4g of zinc oxide, 0.2g of tert-butyl perbenzoate and 3g of paraffin were added and kneaded at 135°C for 7.5min. After kneading, the mixture was put into a flat vulcanizer and 5g of sulfur and 1g of tetramethylthiuram disulfide were added and vulcanized at 160°C for 2.5h. After vulcanization, a flame retardant rubber material for a vehicle was obtained.

[0025] Embodiment 5

[0026] 70g of nitrile rubber and 30g of EPDM rubber were added to an open mill and kneaded at 85°C for 5min. After kneading, 15g of the modifier prepared in Example 1, 5g of zinc oxide, 0.3g of tert-butyl perbenzoate and 4g of paraffin were added and kneaded at 150°C for 10min. After kneading, the mixture was put into a flat vulcanizer and 6g of sulfur and 1.5g of tetramethylthiuram disulfide were added and vulcanized at 170°C for 3h. After vulcanization, a flame retardant rubber material for automobile was obtained.

[0027] Comparative Example 1 The modifier in Example 5 was replaced by a commercially available organosilicon flame retardant of equal quality, and the remaining steps were the same as those in Example 5 to obtain a rubber material.

[0028] Comparative Example 2 Commercially available nitrile rubber was used.

[0029] Embodiments 3, 4, 5 and comparative examples 1 and 2 were made into corresponding shapes according to different test standards and subjected to the following performance tests: The tensile strength is determined using the national standard GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber"; The national standard GB / T 3512-2001 "Hot air accelerated aging and heat resistance test for vulcanized rubber or thermoplastic rubber" was used to measure the tensile strength of the sample before and after aging (GB / T 528-2009), and the tensile strength retention rate was calculated; tensile strength retention rate = tensile strength after test / tensile strength before test × 100%; The induction time was determined using the national standard GB / T 19466.6-2009; The smoke density is measured using the national standard GB / T 8627-2007; The limiting oxygen index of the sample was measured according to the national standard GB / T 10707-2008 "Determination of Rubber Combustion Performance", and then the limiting oxygen index of Examples 3, 4, 5 and Comparative Example 1 was measured again after standing at room temperature for 200 days; and the limiting oxygen index retention rate was calculated; limiting oxygen index retention rate = limiting oxygen index after test / limiting oxygen index before test × 100%; The measured results are shown in the following table: ; It can be seen from the above table that the mechanical properties, flame retardancy, heat resistance and oxidation resistance of the rubber material prepared in the embodiments of the present invention are higher than those of the comparative example. As the content of the modifier continues to increase in Examples 3, 4 and 5, the various properties of the rubber are also improved to a certain extent. Moreover, after standing for 200 days, the limiting oxygen index of the embodiments can still be maintained. Therefore, the present invention has important application value in the field of flame retardant rubber technology.

[0030] 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.

[0031] The above contents are merely examples and explanations of the present invention. Any modifications or additions made by technicians in the technical field to the described specific embodiments or replacements with similar methods shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing a flame-retardant rubber material for a vehicle, characterized in that: The following steps are involved: Add nitrile rubber and EPDM rubber into an open mill for the first mixing. After the mixing is completed, add a modifier, zinc oxide, an initiator and a lubricant for the second mixing. After the mixing is completed, put it into a flat vulcanizer and add sulfur and a vulcanization accelerator for vulcanization. After the vulcanization is completed, a flame retardant rubber material for automobiles is obtained.

2. The method for preparing a flame-retardant rubber material for a vehicle according to claim 1, characterized in that: The modifying agent is prepared by the following steps: S1. Mix 3,5-di-tert-butyl-4-hydroxybenzaldehyde, piperidine and toluene, heat to 35°C, stir until the solid is completely dissolved, add diethylenetriamine, continue to heat to 65°C, keep the temperature for 6 hours, and after the reaction is completed, cool naturally, filter, distill under reduced pressure, wash, and vacuum dry to obtain intermediate 1; S2, 4,4'-sulfonyldibenzoic acid and toluene were mixed, heated to 30°C and stirred continuously, nitrogen was introduced, intermediate 1 and dicyclohexylcarbodiimide were added, mixed and stirred evenly, placed in a water bath, reacted at 55°C for 3h, and after the reaction was completed, filtered, distilled under reduced pressure, washed, and dried in vacuo to obtain intermediate 2; S3, at room temperature, under nitrogen protection, the intermediate II, 6-chloro-1-hexene, toluene and triethylamine were mixed evenly, and the temperature was gradually raised to 80°C, and the reaction was kept at this temperature for 4 hours. After the reaction was completed, the intermediate III was filtered, distilled under reduced pressure, purified by column chromatography, rotary evaporated, and dried in vacuo to obtain the intermediate III; S4. Mix amino cage polysilsesquioxane and tetrahydrofuran, stir for 30 minutes, add intermediate tri-dicyclohexylcarbodiimide and 4-dimethylaminopyridine and stir evenly, heat to 60°C, stir and react for 8 minutes. After the reaction is completed, distill under reduced pressure, wash, and vacuum dry to obtain a modifier.

3. The method for preparing a flame-retardant rubber material for a vehicle according to claim 2, characterized in that: In step S1, the ratio of 3,5-di-tert-butyl-4-hydroxybenzaldehyde, piperidine, toluene and diethylenetriamine is 23.4 g: 15 mL: 100 mL: 12.7 g.

4. The method for preparing a flame-retardant rubber material for a vehicle according to claim 2, characterized in that: In step S2, the ratio of the amount of 4,4'-sulfonyldibenzoic acid, toluene, and the intermediate mono- and dicyclohexylcarbodiimide is 33.5 g: 150 mL: 32.1 g: 20.6 g.

5. The method for preparing a flame-retardant rubber material for a vehicle according to claim 2, characterized in that: In step S3, the ratio of the intermediate dichlorobenzene, 6-chloro-1-hexene, toluene and triethylamine is 60.9 g:11.8 g:150 mL:15 mL.

6. The method for preparing a flame-retardant rubber material for a vehicle according to claim 2, characterized in that: In step S4, the ratio of the amount of amino cage polysilsesquioxane, tetrahydrofuran, intermediate tris-dicyclohexylcarbodiimide, and 4-dimethylaminopyridine is 138.5 g: 300 mL: 69.1 g: 20.6 g: 0.6 g.

7. The method for preparing a flame-retardant rubber material for a vehicle according to claim 1, characterized in that: The raw materials are calculated in parts by weight as follows: 60-70 parts of nitrile rubber, 22-30 parts of EPDM rubber, 5-15 parts of modifier, 3-5 parts of zinc oxide, 0.1-0.3 parts of initiator, 2-4 parts of lubricant, 4-6 parts of sulfur, and 0.5-1.5 parts of vulcanization accelerator.

8. The method for preparing a flame-retardant rubber material for a vehicle according to claim 1, characterized in that: The first mixing condition is 75° C.-85° C., and the mixing time is 1-5 min.

9. The method for preparing a flame-retardant rubber material for a vehicle according to claim 1, characterized in that: The second mixing condition is 120-150° C., and the mixing time is 5-10 min.

10. The method for preparing a flame-retardant rubber material for a vehicle according to claim 1, characterized in that: The vulcanization conditions are 150-170° C. and vulcanization for 2-3 hours.