A kind of high temperature resistant nitrile rubber and preparation method thereof

Abstract

The invention discloses a high temperature resistant nitrile rubber and a preparation method thereof, and belongs to the technical field of nitrile rubber. The invention comprises the following raw materials in parts by weight: 80-100 parts of nitrile rubber, 20-30 parts of ethylene propylene diene rubber, 3-7 parts of zinc oxide, 14-20 parts of modified magnesium hydroxide, 6-18 parts of modifier, 4-6 parts of lubricant, 3-5 parts of sulfur, and 0.5-1.5 parts of vulcanization accelerator. Among them, ethylene propylene diene rubber can enhance the aging resistance and a certain degree of heat resistance of nitrile rubber; wherein the modified magnesium hydroxide has good compatibility with nitrile rubber, and greatly enhances the flame retardant and smoke suppression performance of nitrile rubber; wherein the various groups in the modifier play a synergistic role, significantly enhances the heat resistance and flame retardant and smoke suppression performance of nitrile rubber, and has stable performance. Therefore, the nitrile rubber prepared by the invention has good aging resistance, stable and efficient heat resistance and flame retardant and smoke suppression performance, and has important application value in the technical field of nitrile rubber.

Description

Technical Field

[0001] The invention belongs to the technical field of nitrile rubber, and in particular relates to a high temperature resistant nitrile rubber and a preparation method thereof. Background Art

[0002] Nitrile rubber (NBR) is a copolymer formed by the polymerization of acrylonitrile and butadiene monomers. Because it contains acrylonitrile in its molecular chain, it has excellent oil resistance, which is better than that of natural rubber, chloroprene rubber and styrene-butadiene rubber. In addition, the high elasticity obtained by the cross-linked network structure of the rubber itself makes nitrile rubber widely used in various oil sealing fields.

[0003] In recent years, the automotive industry has been developing continuously, and higher requirements have been placed on vehicle safety and comfort. Therefore, the operating temperature and service life of automotive parts are getting higher and higher. For example, the temperature resistance requirement of rubber parts involved in automobile engines and surrounding areas has been increased to 150°C, and ordinary nitrile rubber cannot meet the requirement. Only acrylic rubber, fluororubber, hydrogenated nitrile rubber, etc. with better temperature resistance can be selected. However, the price of these rubbers is 4-10 times that of nitrile rubber, which greatly increases the cost. In addition, nitrile rubber has a low oxygen index and poor flame retardant properties, and there is a safety risk of combustion. Therefore, it is urgent to solve the above problems to meet the higher demands in the field of nitrile 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 high temperature resistant nitrile rubber and a preparation method thereof.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing high temperature resistant nitrile rubber comprises the following steps:

[0007] Put nitrile rubber, EPDM rubber, zinc oxide, modified magnesium hydroxide, modifier and lubricant into an internal mixer, mix at room temperature for 20 minutes, add into an open mixer and add sulfur (vulcanizing agent) and vulcanization accelerator, mix at 80°C for 10 minutes, discharge the rubber and obtain a rubber mixture; add the rubber mixture into a flat vulcanizer, and after primary vulcanization and secondary vulcanization, obtain a high temperature resistant nitrile rubber.

[0008] Furthermore, the raw materials are calculated in parts by weight as follows: 80-100 parts of nitrile rubber, 20-30 parts of EPDM rubber, 3-7 parts of zinc oxide, 14-20 parts of modified magnesium hydroxide, 6-18 parts of modifier, 4-6 parts of lubricant, 3-5 parts of sulfur, and 0.5-1.5 parts of vulcanization accelerator.

[0009] Furthermore, the lubricant is one of epoxidized soybean oil and stearic acid.

[0010] Furthermore, the vulcanization accelerator is one of tetraethylthiuram disulfide and tetramethylthiuram disulfide.

[0011] Furthermore, the conditions for the primary vulcanization are 162-170° C. for 10-20 minutes, and the conditions for the secondary vulcanization are 170-175° C. for 2-3 hours.

[0012] EPDM rubber has excellent aging resistance, which can not only enhance the aging resistance of nitrile rubber, but also enhance the heat resistance of nitrile rubber to a certain extent; adding a small amount of vulcanization accelerator can shorten the vulcanization time, lower the vulcanization temperature and reduce the amount of vulcanizing agent.

[0013] Further, the modified magnesium hydroxide is prepared by the following steps:

[0014] Magnesium hydroxide and ethanol aqueous solution were added to a three-necked flask and stirred magnetically for 2 hours to make the magnesium hydroxide evenly dispersed. Vinyltrimethoxysilane was added and stirred for reaction at 80°C for 3 hours. After the reaction was completed, the residue was filtered out, vacuum dried, and ground to obtain modified magnesium hydroxide.

[0015] Furthermore, the ratio of magnesium hydroxide, ethanol aqueous solution and vinyltrimethoxysilane is 1 g:100 mL:3.6 g.

[0016] Vinyltrimethoxysilane is used to modify magnesium hydroxide to form an organic layer on its surface, which can improve the interfacial compatibility between magnesium hydroxide and the nitrile rubber matrix, thereby promoting the uniform dispersion of the modified magnesium hydroxide in the matrix, reducing the agglomeration phenomenon, and making the flame retardant and smoke suppression properties of magnesium hydroxide fully exerted, while reducing the amount of magnesium hydroxide used and reducing its influence on mechanical properties.

[0017] Furthermore, the modifier is prepared by the following steps:

[0018] S1. Add 4,4'-diaminodiphenyl sulfone and N,N-dimethylformamide (DMF) to a three-necked flask equipped with a stirring device, mix, heat to 30°C and stir continuously until the solid is completely dissolved, introduce nitrogen to exclude air, add diethylphosphoacetic acid and dicyclohexylcarbodiimide (DCC, dehydrating agent), mix and stir evenly, heat to 50°C, keep warm and react for 135 minutes. 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 1; the ratio of 4,4'-diaminodiphenyl sulfone, N,N-dimethylformamide, diethylphosphoacetic acid, and dicyclohexylcarbodiimide is 26.6g:150mL:19.6g:20.6g;

[0019] The amino group on 4,4'-diaminodiphenyl sulfone and the carboxyl group of diethylphosphoacetic acid undergo an amidation reaction. Under the action of DCC, the reaction can be carried out under relatively mild conditions. By controlling the molar ratio of the two to be close to 1:1 and a slight excess of 4,4'-diaminodiphenyl sulfone, only one amino group on 4,4'-diaminodiphenyl sulfone participates in the reaction to obtain intermediate 1. The specific reaction process is shown below:

[0020] ;

[0021] S2. In a three-necked flask equipped with a stirring device, the intermediate 1, 4-pentenal, piperidine (condensing agent) and N,N-dimethylformamide were mixed, and the mixture was stirred continuously until the solid was completely dissolved. The reaction temperature was controlled to 70°C, and the mixture was kept warm for 6 hours. After the reaction was completed, part of the solvent was removed by distillation under reduced pressure, and then purified by column chromatography (the eluent was a mixed solvent of ethyl acetate / benzene in a volume ratio of 2:3), the eluent was removed by rotary evaporation, and the mixture was dried in vacuo to obtain the intermediate 2; the ratio of the amount of the intermediate 1, 4-pentenal, piperidine and N,N-dimethylformamide was 42.6 g:8.4 g:15 mL:100 mL;

[0022] Under the action of the condensation agent, the amino group on the intermediate 1 condenses with the aldehyde group on the 4-pentenal to form an imine group (C=N Schiff base structure) to obtain the intermediate 2; the specific reaction process is as follows:

[0023] ;

[0024] S3. Add hydrogenated silicone oil, N,N-dimethylformamide and Speier catalyst to a three-necked flask equipped with a stirring reflux device, stir at room temperature for 30 minutes, add intermediate 2, raise the temperature to 80°C, keep the reaction for 8 hours, stop heating, wait for the device to cool to room temperature, stir for 5 hours, filter and rotary evaporate to remove the solvent to obtain a modifier; the ratio of hydrogenated silicone oil, N,N-dimethylformamide, Speier catalyst and intermediate 2 is 10g:100mL:0.5mL:18.6g;

[0025] Under the catalysis of Speier catalyst, hydrogen-containing silicone oil and intermediate 2 undergo a hydrosilylation reaction to obtain a modifier; the specific reaction process is as follows:

[0026] ;

[0027] The prepared modifier is mainly composed of polysiloxane chains, and the main chain of polysiloxane is composed of silicon-oxygen bonds (Si-O bonds). The bond energy of this bond is relatively high, which can greatly enhance the heat resistance of the nitrile rubber matrix. In addition, the modifier molecule also contains diphenyl sulfone, phosphate and Schiff base structures. The diphenyl sulfone structure contains two benzene rings, which can further enhance the heat resistance of the matrix. The S element in the diphenyl sulfone structure generates SO2, sulfurous acid and water during thermal desulfurization, which can promote the Fries rearrangement reaction of the matrix and accelerate the carbonization of the matrix, which can effectively enhance the flame retardant and smoke suppression properties of the matrix. In addition, the phosphate also has good flame retardant properties. Not only that, the C=N double bond in the Schiff base structure can generate a carbon-nitrogen six-membered ring at high temperature. This type of six-membered ring structure enables the matrix to form a stable cross-linked network, which can synergize with diphenyl sulfone and phosphate to greatly enhance the flame retardant properties of the matrix. Finally, the prepared modifier is a macromolecule, which is not easy to migrate and seep out compared with small molecule modifiers, and its performance is more stable.

[0028] Beneficial effects of the present invention:

[0029] 1. EPDM rubber is added to the nitrile rubber prepared by the present invention to enhance the aging resistance and heat resistance of the nitrile rubber to a certain extent;

[0030] 2. By modifying magnesium hydroxide, compared with ordinary magnesium hydroxide, it has better compatibility with nitrile rubber, reduces agglomeration, and greatly enhances the flame retardant and smoke suppression properties of nitrile rubber;

[0031] 3. The various groups in the prepared modifier molecules work synergistically, significantly enhancing the heat resistance and flame retardant and smoke suppression properties of nitrile rubber, and the performance is stable and not easy to fall off;

[0032] Therefore, the nitrile rubber prepared by the present invention has good aging resistance, stable and efficient heat resistance and flame retardant and smoke suppression properties, and has important application value in the technical field of nitrile rubber. DETAILED DESCRIPTION

[0033] 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.

[0034] Embodiment 1

[0035] Preparation of modifier:

[0036] S1. Add 26.6 g of 4,4'-diaminodiphenyl sulfone and 150 mL of N,N-dimethylformamide to a three-necked flask equipped with a stirring device, mix, heat to 30°C and stir continuously until the solid is completely dissolved, introduce nitrogen to exclude air, add 19.6 g of diethylphosphoacetic acid and 20.6 g of dicyclohexylcarbodiimide, mix and stir evenly, heat to 50°C, keep warm and react for 135 minutes, filter after the reaction, remove the solvent by distillation under reduced pressure, wash 3 times with anhydrous ethanol, and vacuum dry to obtain intermediate 1;

[0037] S2, in a three-necked flask equipped with a stirring device, 42.6g of intermediate 1, 8.4g of 4-pentenal, 15mL of piperidine and 100mL of N,N-dimethylformamide were mixed, and the mixture was stirred continuously until the solid was completely dissolved. The reaction temperature was controlled to 70°C, and the mixture was kept warm for 6h. After the reaction was completed, part of the solvent was distilled off under reduced pressure, and then purified by column chromatography (the eluent was a mixed solvent of ethyl acetate / benzene in a volume ratio of 2:3), the eluent was removed by rotary evaporation, and the mixture was dried in vacuo to obtain intermediate 2;

[0038] S3. Add 10 g of hydrogenated silicone oil, 100 mL of N,N-dimethylformamide and 0.5 mL of Speier catalyst into a three-necked flask equipped with a stirring reflux device, stir at room temperature for 30 min, then add 18.6 g of intermediate 2, raise the temperature to 80°C, keep the reaction warm for 8 h, stop heating, wait for the device to cool to room temperature, stir for 5 h, filter and rotary evaporate to remove the solvent to obtain a modifier; wherein the Speier catalyst is prepared by dissolving 0.1 g of chloroplatinic acid in 100 mL of isopropanol and stirring at room temperature.

[0039] Embodiment 2

[0040] Preparation of modifier:

[0041] S1. Add 53.2 g of 4,4'-diaminodiphenyl sulfone and 300 mL of N,N-dimethylformamide to a three-necked flask equipped with a stirring device, mix, heat to 30°C and stir continuously until the solid is completely dissolved, introduce nitrogen to exclude air, add 39.2 g of diethylphosphoacetic acid and 41.2 g of dicyclohexylcarbodiimide, mix and stir evenly, heat to 50°C, keep warm and react for 135 min. After the reaction is completed, filter, remove the solvent by distillation under reduced pressure, wash twice with anhydrous ethanol, and vacuum dry to obtain intermediate 1;

[0042] S2, in a three-necked flask equipped with a stirring device, 85.2g of intermediate 1, 16.8g of 4-pentenal, 30mL of piperidine and 200mL of N,N-dimethylformamide were mixed, and the mixture was stirred continuously until the solid was completely dissolved. The reaction temperature was controlled to 70°C, and the mixture was kept warm for 6h. After the reaction was completed, part of the solvent was distilled off under reduced pressure, and then purified by column chromatography (the eluent was a mixed solvent of ethyl acetate / benzene, and the volume ratio of the two was 2:3), the eluent was removed by rotary evaporation, and the mixture was dried in vacuo to obtain intermediate 2;

[0043] S3. Add 20 g of hydrogenated silicone oil, 200 mL of N,N-dimethylformamide and 1 mL of Speier catalyst into a three-necked flask equipped with a stirring reflux device, stir at room temperature for 30 min, then add 37.2 g of intermediate 2, raise the temperature to 80°C, keep the reaction warm for 8 h, stop heating, wait for the device to cool to room temperature, stir for 5 h, filter and rotary evaporate to remove the solvent to obtain a modifier; wherein the Speier catalyst is prepared by dissolving 0.1 g of chloroplatinic acid in 100 mL of isopropanol and stirring at room temperature.

[0044] Embodiment 3

[0045] Add 1 g of magnesium hydroxide and 100 mL of ethanol aqueous solution into a three-necked flask, stir magnetically for 2 h to evenly disperse the magnesium hydroxide, then add 3.6 g of vinyltrimethoxysilane, stir and react at 80 °C for 3 h. After the reaction is complete, filter out the residue, vacuum dry it, and grind it to obtain modified magnesium hydroxide.

[0046] Embodiment 4

[0047] 80g of nitrile rubber, 20g of EPDM rubber, 3g of zinc oxide, 14g of modified magnesium hydroxide prepared in Example 3, 6g of the modifier prepared in Example 1 and 4g of epoxidized soybean oil were put into an internal mixer, mixed at room temperature for 20min, added into an open mixer and 3g of sulfur and 0.5g of tetraethylthiuram disulfide were added, mixed at 80°C for 10min, and discharged to obtain a mixed rubber; the mixed rubber was added into a flat vulcanizer, vulcanized at 162°C for 10min to complete primary vulcanization, and vulcanized at 170°C for 2h to complete secondary vulcanization to obtain a high temperature resistant nitrile rubber.

[0048] Embodiment 5

[0049] 90g of nitrile rubber, 25g of EPDM rubber, 5g of zinc oxide, 17g of modified magnesium hydroxide prepared in Example 3, 12g of the modifier prepared in Example 2 and 5g of stearic acid were put into an internal mixer, mixed at room temperature for 20min, added into an open mixer and 4g of sulfur and 1g of tetramethylthiuram disulfide were added, mixed at 80°C for 10min, and discharged to obtain a rubber mixture; the rubber mixture was added into a flat vulcanizer, vulcanized at 166°C for 15min to complete primary vulcanization, and vulcanized at 172°C for 2.5h to complete secondary vulcanization to obtain a high temperature resistant nitrile rubber.

[0050] Embodiment 6

[0051] 100g of nitrile rubber, 30g of EPDM rubber, 7g of zinc oxide, 20g of the modified magnesium hydroxide prepared in Example 3, 18g of the modifier prepared in Example 2 and 6g of stearic acid were put into an internal mixer, mixed at room temperature for 20min, added into an open mixer and 5g of sulfur and 1.5g of tetramethylthiuram disulfide were added, mixed at 80°C for 10min, and discharged to obtain a rubber mixture; the rubber mixture was added into a flat vulcanizer, vulcanized at 170°C for 20min to complete primary vulcanization, and vulcanized at 175°C for 3h to complete secondary vulcanization to obtain a high temperature resistant nitrile rubber.

[0052] Comparative Example 1

[0053] The modifier in Example 6 is replaced by a commercially available phosphorus-based flame retardant of equal quality, and the remaining steps are the same as those in Example 6 to obtain a high-temperature resistant nitrile rubber.

[0054] Comparative Example 2

[0055] Commercially available nitrile rubber was used.

[0056] Embodiments 4, 5, 6 and comparative examples 1 and 2 were made into corresponding shapes according to different test standards and the following performance tests were performed:

[0057] The tensile strength is measured using the national standard GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber";

[0058] 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%;

[0059] The smoke density is measured using the national standard GB / T 8627-2007;

[0060] 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 4, 5, 6 and Comparative Example 1 was measured again after being left to stand at room temperature for 180 days;

[0061] The measured results are shown in the following table:

[0062] ;

[0063] It can be seen from the above table that the heat resistance and flame retardant and smoke suppression properties of the nitrile rubber prepared in the embodiment of the present invention are higher than those of the control example, and with the continuous increase in the amount of modified magnesium hydroxide, the effect on the mechanical properties of the nitrile rubber is relatively small, and the flame retardant properties of the embodiment are long-term and stable, and have important application value in the field of nitrile rubber technology.

[0064] 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.

[0065] 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 method for preparing a high temperature resistant nitrile rubber, characterized in that: The following steps are involved: Putting nitrile rubber, EPDM rubber, zinc oxide, modified magnesium hydroxide, a modifier and a lubricant into an internal mixer, mixing at room temperature, adding them into an open mixer and adding sulfur and a vulcanization accelerator, mixing again, draining the rubber, and obtaining a mixed rubber; adding the mixed rubber into a flat vulcanizer, and obtaining a high temperature resistant nitrile rubber after primary vulcanization and secondary vulcanization; Wherein, the modifier is prepared by the following steps: S1. Mix 4,4'-diaminodiphenyl sulfone and N,N-dimethylformamide, heat to 30°C and stir continuously until the solid is completely dissolved, introduce nitrogen, add diethylphosphoacetic acid and dicyclohexylcarbodiimide, mix and stir evenly, heat to 50°C, keep warm and react for 135 minutes, filter, evaporate under reduced pressure, wash, and dry in vacuum to obtain intermediate 1; S2, mixing the intermediate 1, 4-pentenal, piperidine and N,N-dimethylformamide, stirring continuously until the solid is completely dissolved, and reacting at 70°C for 6 hours. After the reaction is completed, distilling under reduced pressure, purifying by column chromatography, rotary evaporation, and vacuum drying to obtain the intermediate 2; S3. Add hydrogenated silicone oil, N,N-dimethylformamide and Speier catalyst to a three-necked flask equipped with a stirring reflux device, stir at room temperature for 30 minutes, add intermediate 2, raise the temperature to 80°C, keep the reaction for 8 hours, stop heating, wait for the device to cool to room temperature, stir for 5 hours, filter, and remove the solvent by rotary evaporation to obtain a modifier; Wherein, in step S1, the ratio of 4,4'-diaminodiphenyl sulfone, N,N-dimethylformamide, diethylphosphoacetic acid, and dicyclohexylcarbodiimide is 26.6g:150mL:19.6g:20.6g; in step S2, the ratio of intermediate 1, 4-pentenal, piperidine, and N,N-dimethylformamide is 42.6g:8.4g:15mL:100mL; in step S3, the ratio of hydrogen-containing silicone oil, N,N-dimethylformamide, Speier catalyst, and intermediate 2 is 10g:100mL:0.5mL:18.6g; Wherein, the modified magnesium hydroxide is prepared by the following steps: Add magnesium hydroxide and ethanol aqueous solution into a three-necked flask, stir magnetically for 2 hours to make the magnesium hydroxide evenly dispersed, then add vinyltrimethoxysilane, stir and react at 80°C for 3 hours. After the reaction is completed, filter out the residue, vacuum dry, and grind to obtain modified magnesium hydroxide; the ratio of magnesium hydroxide, ethanol aqueous solution, and vinyltrimethoxysilane is 1g:100mL:3.6g; The raw materials are calculated in parts by weight as follows: 80-100 parts of nitrile rubber, 20-30 parts of EPDM rubber, 3-7 parts of zinc oxide, 14-20 parts of modified magnesium hydroxide, 6-18 parts of modifier, 4-6 parts of lubricant, 3-5 parts of sulfur, and 0.5-1.5 parts of vulcanization accelerator.

2. A high temperature resistant nitrile rubber, characterized in that: Prepared according to the method of claim 1.