Preparation method of rubber

Abstract

The invention discloses a preparation method of rubber, and relates to the technical field of rubber preparation. The rubber prepared by the invention comprises modified natural rubber, butadiene styrene rubber, modified carbon black, sulfur, stearic acid, zinc oxide and zinc chloride. The modified natural rubber is obtained by reacting epoxidized natural rubber with 3-(6-bromopyridyl)-3-oxo ethyl propionate and then reacting with guanidine hydrochloride; the modified carbon black is obtained by reacting carboxyl carbon black with a phosphorus-containing monomer, reacting with nitrogen disulfide and chloroacetic acid, and reacting with sodium azide. The rubber prepared by the invention has good mechanical properties, flame retardancy and aging resistance.

Description

Technical Field

[0001] The invention relates to the technical field of rubber preparation, in particular to a method for preparing rubber. Background Art

[0002] Rubber is a highly elastic polymer material that can deform over a wide range and quickly return to its original shape after the external force is removed. According to the source and manufacturing process, rubber can be divided into two categories: natural rubber and synthetic rubber. Common synthetic rubbers include styrene-butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), etc. They have better performance than natural rubber in specific application fields, such as oil resistance, wear resistance and weather resistance. Rubber is widely used in tire manufacturing, seals, shock absorbers, conveyor belts, hoses, wire and cable coatings, etc., and is an indispensable and important material in modern industry.

[0003] However, the rubber in the prior art has some significant disadvantages. First, it is not resistant to aging. When exposed to air, sunlight, heat or mechanical stress for a long time, the rubber will undergo oxidative degradation, resulting in a decrease in physical properties, which manifests as hardening, brittleness or even loss of elasticity. Secondly, the toughness and strength are not enough. The rubber is prone to breakage or deformation and cannot meet the needs of certain high-performance application scenarios. Thirdly, it is not flame retardant. Ordinary rubber is extremely easy to burn when encountering open flames and releases toxic gases, posing a safety hazard to use. Therefore, in order to overcome these shortcomings, it is particularly important to develop a rubber that is resistant to aging, reinforced, toughened, and flame retardant. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing rubber to solve the problems existing in the prior art.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A method for preparing rubber comprises the following steps:

[0007] (1) reacting epoxidized natural rubber and ethyl 3-(6-bromopyridyl)-3-carbonylpropionate to obtain pre-modified natural rubber;

[0008] (2) reacting guanidine hydrochloride, ethanol, and potassium hydroxide to obtain a guanidine salt solution; reacting pre-modified natural rubber and the guanidine salt solution to obtain modified natural rubber;

[0009] (3) reacting 4-(diphenylphosphino)benzaldehyde and (3,4-diaminophenyl)-1-methylethanol to obtain a phosphorus-containing monomer; reacting carbon black and a nitric acid solution to obtain carboxyl carbon black; reacting carboxyl carbon black and a phosphorus-containing monomer to obtain pretreated carbon black;

[0010] (4) reacting pretreated carbon black, carbon disulfide and chloroacetic acid to obtain pre-modified carbon black;

[0011] (5) reacting pre-modified carbon black and sodium azide to obtain modified carbon black;

[0012] (6) Weigh the following components: 30-50 parts by mass of modified natural rubber, 50-70 parts by mass of styrene-butadiene rubber, 10-15 parts by mass of modified carbon black, 2-3 parts by mass of sulfur, 3-5 parts by mass of stearic acid, 1-3 parts by mass of zinc oxide, and 2-3 parts by mass of zinc chloride, and prepare a rubber compound by a two-stage mixing process; and then vulcanize the compound by a flat vulcanizer to obtain a rubber compound.

[0013] As an optimization, the preparation method of the pre-modified natural rubber in step (1) is: epoxidized natural rubber, 3-(6-bromopyridyl)-3-carbonylpropionic acid ethyl ester, N,N-dimethylformamide, and additives are mixed in a mass ratio of 1:(0.5-0.6):(10-12):0.4, stirred for 2 hours under nitrogen protection, 0.01 times the mass of epoxidized natural rubber of ethylene glycol dimethyl ether nickel bromide is added, stirred for 5-6 hours, after the reaction is completed, 3-4 times the mass of N,N-dimethylformamide of ethanol is added, filtered and washed with ethanol 3-4 times, and vacuum dried at 50°C to obtain pre-modified natural rubber.

[0014] As an optimization, the preparation method of the modified natural rubber described in step (2) is: guanidine hydrochloride, ethanol, and potassium hydroxide are mixed in a mass ratio of 1: (5-6): (0.5-0.6), heated to 85°C and refluxed for reaction for 5 minutes, then cooled to room temperature, filtered and retained the filtrate to obtain a guanidine salt solution; pre-modified natural rubber, toluene, guanidine salt solution, and tetrabutylammonium bromide are mixed in a mass ratio of 1: (10-12): (2-3): (0.2-0.3), heated to 100-110°C and refluxed for reaction for 5-6 hours, filtered and retained the filtrate, and the modified natural rubber is obtained by vacuum rotary evaporation.

[0015] As an optimization, the preparation method of the pretreated carbon black in step (3) is: 4-(diphenylphosphino)benzaldehyde, p-toluenesulfonic acid, and ethanol are mixed in a mass ratio of 1:(0.01-0.02):(20-30), and 4-(diphenylphosphino)benzaldehyde and (3,4-diaminophenyl)-1-methylethanol in an equal molar ratio are added; the temperature is raised to 80°C and refluxed for 3-4 hours. After the reaction is completed, the mixture is filtered and washed with pure water for 3-4 times, and a phosphorus-containing monomer is obtained by vacuum rotary evaporation; carbon black and 50wt% nitric acid solution are mixed in a mass ratio of 1:(0.01-0.02):(20-30). 1:(50-60), heat to 80 ° C to react for 3-4h, filter after the reaction and wash with pure water 5-6 times, and dry at room temperature to obtain carboxyl carbon black; carboxyl carbon black, phosphorus-containing monomer, 4-dimethylaminopyridine, dicyclohexyl diimide, N, N-dimethylformamide are ultrasonically mixed in a mass ratio of 1:(0.8-1.0):(0.1-0.2):1:(20-30), react at room temperature for 24h, after the reaction, filter, wash with ethanol 3-4 times, and dry at room temperature to obtain pretreated carbon black.

[0016] As an optimization, the preparation method of the pre-modified carbon black in step (4) is: pre-treated carbon black, N,N-dimethylformamide, and carbon disulfide are mixed in a mass ratio of 1: (20-30): (0.5-0.6), and then 0.6-0.7 times the mass of the pre-modified carbon black is added with chloroacetic acid, and the reaction is carried out at room temperature for 12 hours. After the reaction is completed, the mixture is filtered and washed with pure water for 3-4 times, and dried at room temperature to obtain the pre-modified carbon black.

[0017] As an optimization, the preparation method of the modified carbon black in step (5) is: pre-modified carbon black and tetrahydrofuran are mixed in a mass ratio of 1: (20-30), cooled to -15°C, 0.1 times the mass of the pre-modified carbon black in acetyl chloride and 0.1 times the mass of the pre-modified carbon black in N-methylmorpholine are added, stirred for 20 minutes, 5 times the mass of the pre-modified carbon black in a 0.3 g / mL sodium azide aqueous solution are added, stirring is continued for 1 hour, filtered and washed with pure water for 3-4 times, and dried at room temperature to obtain the modified carbon black.

[0018] As an optimization, the two-stage mixing process of step (6) is as follows: the rotor speed of the first-stage mixing process is 70r / min, the initial temperature is 100°C, the modified natural rubber and styrene-butadiene rubber are put into the internal mixer and plasticized for 1 min, zinc oxide, zinc chloride and stearic acid are added and mixed for 1 min, then the modified carbon black is added and mixed for 4 min, the temperature is controlled at 140-150°C and maintained for 2 min, and the masterbatch is obtained by rubber removal; the rotor speed of the second-stage mixing process is 35r / min, the initial temperature is 70°C, the first-stage masterbatch is added and plasticized for 1 min, sulfur is added, mixed at 90°C for 2 min, the glue is removed, and then the sheet is loaded and unloaded on the open mill; the plate vulcanization process parameters are: vulcanization time is 40-50min, vulcanization temperature is 160°C, and vulcanization pressure is 10MPa; the sulfur model is IS7020.

[0019] As an optimization, the model of the epoxy natural rubber is ENR-25; the additive is obtained by mixing triethylamine hydrobromide, manganese powder, ethylene glycol dimethyl ether nickel bromide, 2,2'-bipyridine, and dichlorobis(pentylene)titanium in a mass ratio of 1:2:0.2:0.2:0.3.

[0020] As an optimization, the carbon black model is MA-100.

[0021] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0022] The rubber prepared by the invention comprises modified natural rubber, styrene-butadiene rubber, modified carbon black, sulfur, stearic acid, zinc oxide and zinc chloride; the modified natural rubber is obtained by reacting epoxidized natural rubber with ethyl 3-(6-bromopyridyl)-3-carbonylpropionate and then with guanidine hydrochloride; the modified carbon black is obtained by reacting carboxyl carbon black with a phosphorus-containing monomer and then with nitrogen disulfide and chloroacetic acid and then with sodium azide.

[0023] First, the epoxy group on the epoxy natural rubber and the bromine on the pyridine ring of 3-(6-bromopyridyl)-3-carbonyl propionate undergo an epoxy ring-opening reaction to graft ethyl pyridylcarbonyl propionate; then, guanidine hydrochloride and potassium hydroxide are neutralized in ethanol to generate guanidine in the form of a free base; the generated free base guanidine is subjected to a ring condensation reaction with ethyl pyridylcarbonyl propionate to generate an aminopyrimidone structure;

[0024] Secondly, 4-(diphenylphosphino)benzaldehyde and (3,4-diaminophenyl)-1-methylethanol in equal molar ratios are oxidized by air to generate benzimidazole derivatives in which triphenylphosphine is grafted onto benzimidazole functional groups. The conjugated planar structure in which benzimidazole and benzene ring are connected has good ultraviolet absorption performance, which can provide rubber with good anti-ultraviolet aging performance. In addition, the introduction of phosphorus element can also cooperate with nitrogen element to synergistically flame retardant and improve the flame retardant performance of rubber. Then, dithiocarbamate structures are generated by reacting with carbon disulfide and chloroacetic acid. In the vulcanization process, the carbamate structure can act as a promoter to provide more active groups, thereby providing higher reaction speed and activity. The carboxyl group on chloroacetic acid can generate an acyl azide structure by reacting with sodium azide. The acyl azide structure will rearrange to generate an isocyanate structure under heating, and the isocyanate structure and the aminopyrimidone structure on the modified natural rubber can generate a quadruple hydrogen bond.

[0025] Finally, modified natural rubber, styrene-butadiene rubber, modified carbon black, sulfur, stearic acid, zinc oxide and zinc chloride are mixed and vulcanized to obtain rubber. The pyridine structure on the modified natural rubber and the benzimidazole structure on the carbon black have ion coordination effect with the zinc ion added to the rubber, and there is hydrogen bond interaction between the quadruple hydrogen bonds generated by the isocyanate structure and the aminopyrimidone structure on the modified natural rubber. In addition to serving as additional physical cross-linking points in the rubber to increase the overall cross-linking degree, the ion coordination bonds and weak hydrogen bonds can also bear a certain load during the stress deformation process, thereby dissipating energy and inhibiting stress concentration; and the broken weak bonds continue to break and reconstruct during the stretching process, thereby achieving a good toughening effect. DETAILED DESCRIPTION

[0026] 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 making creative work are within the scope of protection of the present invention.

[0027] In the following examples and comparative examples, the epoxy natural rubber is of model ENR-25, purchased from Zhonghe Chemical Co., Ltd.; the carbon black is of model MA-100, purchased from Mitsubishi Corporation of Japan; the manganese powder has a particle size of 325 mesh; and the sulfur is of model IS7020.

[0028] Embodiment 1:

[0029] A method for preparing rubber, comprising the following steps:

[0030] (1) epoxidized natural rubber, ethyl 3-(6-bromopyridyl)-3-carbonylpropionate, N,N-dimethylformamide, and an additive are mixed in a mass ratio of 1:0.5:10:0.4, stirred for 2 hours under nitrogen protection, 0.01 times the mass of epoxidized natural rubber of ethylene glycol dimethyl ether nickel bromide is added, stirred for 6 hours, and after the reaction is completed, 3 times the mass of N,N-dimethylformamide of ethanol is added, filtered and washed with ethanol 4 times, and vacuum dried at 50° C. to obtain a pre-modified natural rubber;

[0031] (2) guanidine hydrochloride, ethanol, and potassium hydroxide are mixed in a mass ratio of 1:5:0.5, heated to 85°C for reflux reaction for 5 minutes, then cooled to room temperature, filtered and retained the filtrate to obtain a guanidine salt solution; pre-modified natural rubber, toluene, guanidine salt solution, and tetrabutylammonium bromide are mixed in a mass ratio of 1:10:2:0.2, heated to 110°C for reflux reaction for 6 hours, filtered and retained the filtrate, and subjected to reduced pressure rotary evaporation to obtain modified natural rubber;

[0032] (3) 4-(diphenylphosphino)benzaldehyde, p-toluenesulfonic acid, and ethanol are mixed in a mass ratio of 1:0.01:20, and (3,4-diaminophenyl)-1-methylethanol in an equal molar ratio of 4-(diphenylphosphino)benzaldehyde is added; the temperature is raised to 80°C and refluxed for reaction for 4 hours. After the reaction is completed, the mixture is filtered and washed with pure water three times, and the phosphorus-containing monomer is obtained by vacuum rotary evaporation; carbon black and 50wt% nitric acid solution are mixed in a mass ratio of 1:50, the temperature is raised to 80°C and the mixture is reacted for 4 hours. After the reaction is completed, the mixture is filtered and washed with pure water six times, and then dried at room temperature to obtain carboxyl carbon black; carboxyl carbon black, phosphorus-containing monomer, 4-dimethylaminopyridine, dicyclohexyl diimide, and N,N-dimethylformamide are ultrasonically mixed in a mass ratio of 1:0.8:0.1:1:20, and the mixture is reacted at room temperature for 24 hours. After the reaction is completed, the mixture is filtered, washed with ethanol three times, and dried at room temperature to obtain pretreated carbon black;

[0033] (4) Pretreated carbon black, N,N-dimethylformamide, and carbon disulfide were mixed in a mass ratio of 1:20:0.5, and then 0.6 times the mass of pre-modified carbon black was added with chloroacetic acid, and the mixture was reacted at room temperature for 12 hours. After the reaction was completed, the mixture was filtered and washed with pure water for 4 times, and dried at room temperature to obtain pre-modified carbon black;

[0034] (5) Pre-modified carbon black and tetrahydrofuran were mixed in a mass ratio of 1:20, cooled to -15°C, 0.1 times the mass of pre-modified carbon black in acetyl chloride and 0.1 times the mass of pre-modified carbon black in N-methylmorpholine were added, stirred for 20 minutes, 5 times the mass of pre-modified carbon black in a 0.3 g / mL sodium azide aqueous solution were added, stirring was continued for 1 hour, filtered and washed with pure water 3 times, and dried at room temperature to obtain modified carbon black;

[0035] (6) Weigh the following components: 30 parts by mass of modified natural rubber, 50 parts by mass of styrene-butadiene rubber, 10 parts by mass of modified carbon black, 2 parts by mass of sulfur, 3 parts by mass of stearic acid, 1 part by mass of zinc oxide, and 2 parts by mass of zinc chloride, and prepare a rubber compound by a two-stage mixing process; then vulcanize the compound on a flat vulcanizer to obtain a rubber compound. The two-stage mixing process is as follows: in the first-stage mixing process, the rotor speed of the internal mixer is 70r / min, the initial temperature is 100°C, the modified natural rubber and styrene-butadiene rubber are put into the internal mixer for plasticizing for 1min, zinc oxide, zinc chloride and stearic acid are added for mixing for 1min, then the modified carbon black is added for mixing for 4min, the temperature is controlled at 150°C and maintained for 2min, and the masterbatch is obtained by rubber removal; in the second-stage mixing process, the rotor speed of the internal mixer is 35r / min, the initial temperature is 70°C, the first-stage masterbatch is added for plasticizing for 1min, sulfur is added, the mixture is mixed at 90°C for 2min, the rubber is removed, and the sheet is loaded and unloaded on the open mill; the plate vulcanization process parameters are as follows: the vulcanization time is 50min, the vulcanization temperature is 160°C, and the vulcanization pressure is 10MPa.

[0036] Embodiment 2:

[0037] A method for preparing rubber, comprising the following steps:

[0038] (1) epoxidized natural rubber, ethyl 3-(6-bromopyridyl)-3-carbonylpropionate, N,N-dimethylformamide, and an additive are mixed in a mass ratio of 1:0.55:11:0.4, stirred for 2 hours under nitrogen protection, 0.01 times the mass of epoxidized natural rubber of ethylene glycol dimethyl ether nickel bromide is added, stirred for 5.5 hours, and after the reaction is completed, 3.5 times the mass of N,N-dimethylformamide of ethanol is added, filtered and washed with ethanol for 3 times, and vacuum dried at 50° C. to obtain a pre-modified natural rubber;

[0039] (2) guanidine hydrochloride, ethanol, and potassium hydroxide are mixed in a mass ratio of 1:5.5:0.55, heated to 85°C and refluxed for 5 minutes, then cooled to room temperature, filtered and the filtrate is retained to obtain a guanidine salt solution; pre-modified natural rubber, toluene, guanidine salt solution, and tetrabutylammonium bromide are mixed in a mass ratio of 1:11:2.5:0.25, heated to 105°C and refluxed for 5.5 hours, filtered and the filtrate is retained, and the modified natural rubber is obtained by vacuum rotary evaporation;

[0040] (3) 4-(diphenylphosphino)benzaldehyde, p-toluenesulfonic acid, and ethanol are mixed in a mass ratio of 1:0.015:25, and (3,4-diaminophenyl)-1-methylethanol in an equal molar ratio of 4-(diphenylphosphino)benzaldehyde is added; the temperature is raised to 80°C and refluxed for reaction for 3.5 hours. After the reaction is completed, the mixture is filtered and washed with pure water three times, and the phosphorus-containing monomer is obtained by vacuum rotary evaporation; carbon black and 50wt% nitric acid solution are mixed in a mass ratio of 1:55, the temperature is raised to 80°C and the reaction is carried out for 3.5 hours. After the reaction is completed, the mixture is filtered and washed with pure water five times, and dried at room temperature to obtain carboxyl carbon black; carboxyl carbon black, phosphorus-containing monomer, 4-dimethylaminopyridine, dicyclohexyl diimide, and N,N-dimethylformamide are ultrasonically mixed in a mass ratio of 1:0.9:0.15:1:25, and the mixture is reacted at room temperature for 24 hours. After the reaction is completed, the mixture is filtered, washed with ethanol three times, and dried at room temperature to obtain pretreated carbon black;

[0041] (4) Pretreated carbon black, N,N-dimethylformamide, and carbon disulfide were mixed in a mass ratio of 1:25:0.55, and then 0.65 times the mass of pre-modified carbon black was added with chloroacetic acid, and the mixture was reacted at room temperature for 12 hours. After the reaction was completed, the mixture was filtered and washed with pure water for 3 times, and dried at room temperature to obtain pre-modified carbon black;

[0042] (5) Pre-modified carbon black and tetrahydrofuran were mixed in a mass ratio of 1:25, cooled to -15°C, 0.1 times the mass of pre-modified carbon black in acetyl chloride and 0.1 times the mass of pre-modified carbon black in N-methylmorpholine were added, stirred for 20 minutes, 5 times the mass of pre-modified carbon black in a 0.3 g / mL sodium azide aqueous solution were added, stirring was continued for 1 hour, filtered and washed with pure water 3 times, and dried at room temperature to obtain modified carbon black;

[0043] (6) Weigh the following components, by mass: 42 parts of modified natural rubber, 55 parts of styrene-butadiene rubber, 13 parts of modified carbon black, 2 parts of sulfur, 4 parts of stearic acid, 2 parts of zinc oxide, and 3 parts of zinc chloride, and prepare a rubber compound by a two-stage mixing process; then vulcanize the compound on a flat vulcanizer to obtain a rubber compound. The two-stage mixing process is as follows: in the first-stage mixing process, the rotor speed of the internal mixer is 70r / min, the initial temperature is 100°C, the modified natural rubber and styrene-butadiene rubber are put into the internal mixer for plasticizing for 1min, zinc oxide, zinc chloride and stearic acid are added for mixing for 1min, and then the modified carbon black is added for mixing for 4min, the temperature is controlled at 140°C and maintained for 2min, and the masterbatch is obtained by rubber removal; in the second-stage mixing process, the rotor speed of the internal mixer is 35r / min, the initial temperature is 70°C, the first-stage masterbatch is added for plasticizing for 1min, sulfur is added, the mixture is mixed at 90°C for 2min, the rubber is removed, and the sheet is loaded and unloaded on the open mill; the plate vulcanization process parameters are as follows: the vulcanization time is 45min, the vulcanization temperature is 160°C, and the vulcanization pressure is 10MPa.

[0044] Embodiment 3:

[0045] A method for preparing rubber, comprising the following steps:

[0046] (1) epoxidized natural rubber, ethyl 3-(6-bromopyridyl)-3-carbonylpropionate, N,N-dimethylformamide, and an additive are mixed in a mass ratio of 1:0.6:12:0.4, stirred for 2 hours under nitrogen protection, ethylene glycol dimethyl ether nickel bromide in an amount of 0.01 times the mass of the epoxidized natural rubber is added, stirred for 5 hours, and after the reaction is completed, ethanol in an amount of 4 times the mass of N,N-dimethylformamide is added, filtered, washed with ethanol 3 times, and vacuum dried at 50° C. to obtain a pre-modified natural rubber;

[0047] (2) guanidine hydrochloride, ethanol, and potassium hydroxide are mixed in a mass ratio of 1:6:0.6, heated to 85°C for reflux reaction for 5 minutes, then cooled to room temperature, filtered and retained the filtrate to obtain a guanidine salt solution; pre-modified natural rubber, toluene, guanidine salt solution, and tetrabutylammonium bromide are mixed in a mass ratio of 1:12:3:0.3, heated to 100°C for reflux reaction for 5 hours, filtered and retained the filtrate, and subjected to reduced pressure rotary evaporation to obtain modified natural rubber;

[0048] (3) 4-(diphenylphosphino)benzaldehyde, p-toluenesulfonic acid, and ethanol are mixed in a mass ratio of 1:0.02:30, and (3,4-diaminophenyl)-1-methylethanol in an equal molar ratio of 4-(diphenylphosphino)benzaldehyde is added; the temperature is raised to 80°C and refluxed for reaction for 3 hours. After the reaction is completed, the mixture is filtered and washed with pure water three times, and the phosphorus-containing monomer is obtained by rotary evaporation under reduced pressure; carbon black and 50wt% nitric acid solution are mixed in a mass ratio of 1:60, the temperature is raised to 80°C and the mixture is reacted for 4 hours. After the reaction is completed, the mixture is filtered and washed with pure water five times, and the mixture is dried at room temperature to obtain carboxyl carbon black; carboxyl carbon black, phosphorus-containing monomer, 4-dimethylaminopyridine, dicyclohexyl diimide, and N,N-dimethylformamide are ultrasonically mixed in a mass ratio of 1:1.0:0.2:1:30, and the mixture is reacted at room temperature for 24 hours. After the reaction is completed, the mixture is filtered, washed with ethanol three times, and dried at room temperature to obtain pretreated carbon black;

[0049] (4) Pretreated carbon black, N,N-dimethylformamide, and carbon disulfide were mixed in a mass ratio of 1:30:0.6, and then 0.7 times the mass of pre-modified carbon black was added with chloroacetic acid, and the mixture was reacted at room temperature for 12 hours. After the reaction was completed, the mixture was filtered and washed with pure water for 3 times, and dried at room temperature to obtain pre-modified carbon black;

[0050] (5) Pre-modified carbon black and tetrahydrofuran were mixed in a mass ratio of 1:30, cooled to -15°C, 0.1 times the mass of pre-modified carbon black in acetyl chloride and 0.1 times the mass of pre-modified carbon black in N-methylmorpholine were added, stirred for 20 minutes, 5 times the mass of pre-modified carbon black in a 0.3 g / mL sodium azide aqueous solution were added, stirring was continued for 1 hour, filtered and washed with pure water 3 times, and dried at room temperature to obtain modified carbon black;

[0051] (6) Weigh the following components, by mass: 0 parts of modified natural rubber, 70 parts of styrene-butadiene rubber, 15 parts of modified carbon black, 3 parts of sulfur, 5 parts of stearic acid, 3 parts of zinc oxide, and 3 parts of zinc chloride, and prepare a rubber compound by a two-stage mixing process; then vulcanize the compound on a flat vulcanizer to obtain a rubber compound. The two-stage mixing process is as follows: in the first-stage mixing process, the rotor speed of the internal mixer is 70r / min, the initial temperature is 100°C, the modified natural rubber and styrene-butadiene rubber are put into the internal mixer for plasticizing for 1 minute, zinc oxide, zinc chloride and stearic acid are added for mixing for 1 minute, and then the modified carbon black is added for mixing for 4 minutes, the temperature is controlled at 140°C and maintained for 2 minutes, and the masterbatch is obtained by rubber removal; in the second-stage mixing process, the rotor speed of the internal mixer is 35r / min, the initial temperature is 70°C, the first-stage masterbatch is added for plasticizing for 1 minute, sulfur is added, the mixture is mixed at 90°C for 2 minutes, the rubber is removed, and the sheet is loaded and unloaded on the open mill; the plate vulcanization process parameters are as follows: the vulcanization time is 40 minutes, the vulcanization temperature is 160°C, and the vulcanization pressure is 10MPa.

[0052] Comparative Example 1:

[0053] The difference between the preparation method of the rubber of Comparative Example 1 and that of Example 2 is that the method does not contain steps (1) to (2), and step (6) is modified as follows: weigh the following components: 42 parts by mass of epoxidized natural rubber, 55 parts by mass of styrene-butadiene rubber, 13 parts by mass of modified carbon black, 2 parts by mass of sulfur, 4 parts by mass of stearic acid, 2 parts by mass of zinc oxide, and 3 parts by mass of zinc chloride, and prepare the above components into a mixed rubber by a two-stage mixing process; and then vulcanize the rubber by a flat vulcanizer. The two-stage mixing process is as follows: in the first-stage mixing process, the rotor speed of the internal mixer is 70r / min, the initial temperature is 100°C, the modified natural rubber and styrene-butadiene rubber are put into the internal mixer for plasticizing for 1min, zinc oxide, zinc chloride and stearic acid are added for mixing for 1min, and then the modified carbon black is added for mixing for 4min, the temperature is controlled at 140°C and maintained for 2min, and the masterbatch is obtained by rubber removal; in the second-stage mixing process, the rotor speed of the internal mixer is 35r / min, the initial temperature is 70°C, the first-stage masterbatch is added for plasticizing for 1min, sulfur is added, the mixture is mixed at 90°C for 2min, the rubber is removed, and the sheet is loaded and unloaded on the open mill; the plate vulcanization process parameters are as follows: the vulcanization time is 45min, the vulcanization temperature is 160°C, and the vulcanization pressure is 10MPa.

[0054] Comparative Example 2:

[0055] The difference between the preparation method of the rubber of Comparative Example 2 and that of Example 2 is that steps (3) to (5) are not included, and step (6) is modified as follows: the following components are weighed: 42 parts by mass of modified natural rubber, 55 parts of styrene-butadiene rubber, 13 parts of carbon black, 2 parts of sulfur, 4 parts of stearic acid, 2 parts of zinc oxide, and 3 parts of zinc chloride; the above components are prepared into a mixed rubber by a two-stage mixing process; and then the rubber is vulcanized on a flat vulcanizer to obtain the rubber. The two-stage mixing process is as follows: in the first-stage mixing process, the rotor speed of the internal mixer is 70r / min, the initial temperature is 100°C, the modified natural rubber and styrene-butadiene rubber are put into the internal mixer for plasticizing for 1min, zinc oxide, zinc chloride and stearic acid are added for mixing for 1min, and then the modified carbon black is added for mixing for 4min, the temperature is controlled at 140°C and maintained for 2min, and the masterbatch is obtained by rubber removal; in the second-stage mixing process, the rotor speed of the internal mixer is 35r / min, the initial temperature is 70°C, the first-stage masterbatch is added for plasticizing for 1min, sulfur is added, the mixture is mixed at 90°C for 2min, the rubber is removed, and the sheet is loaded and unloaded on the open mill; the plate vulcanization process parameters are as follows: the vulcanization time is 45min, the vulcanization temperature is 160°C, and the vulcanization pressure is 10MPa.

[0056] Comparative Example 3:

[0057] The difference between the preparation method of the rubber of Comparative Example 3 and that of Example 2 is that steps (4) to (5) are not included, and step (6) is modified as follows: by weight, 42 parts of modified natural rubber, 55 parts of styrene-butadiene rubber, 13 parts of pretreated carbon black, 2 parts of sulfur, 4 parts of stearic acid, 2 parts of zinc oxide, and 3 parts of zinc chloride are prepared into a mixed rubber by a two-stage mixing process; and then the rubber is vulcanized on a flat vulcanizer to obtain the rubber. The two-stage mixing process is as follows: in the first-stage mixing process, the rotor speed of the internal mixer is 70r / min, the initial temperature is 100°C, the modified natural rubber and styrene-butadiene rubber are put into the internal mixer for plasticizing for 1min, zinc oxide, zinc chloride and stearic acid are added for mixing for 1min, and then the modified carbon black is added for mixing for 4min, the temperature is controlled at 140°C and maintained for 2min, and the masterbatch is obtained by rubber removal; in the second-stage mixing process, the rotor speed of the internal mixer is 35r / min, the initial temperature is 70°C, the first-stage masterbatch is added for plasticizing for 1min, sulfur is added, the mixture is mixed at 90°C for 2min, the rubber is removed, and the sheet is loaded and unloaded on the open mill; the plate vulcanization process parameters are as follows: the vulcanization time is 45min, the vulcanization temperature is 160°C, and the vulcanization pressure is 10MPa.

[0058] Test Example 1:

[0059] Flame retardant performance test:

[0060] Test method: According to the test method specified in GB / T 2406.2-2009 "Determination of combustion behavior by oxygen index method Part 2: Room temperature test", the limiting oxygen index of the rubber prepared in the examples and comparative examples was tested. The results are shown in Table 1.

[0061] Table 1

[0062] Limiting oxygen index (%) Limiting oxygen index (%) Example 1 32.7 Comparative Example 1 31.8 Example 2 32.9 Comparative Example 2 26.1 Example 3 33.2 Comparative Example 3 31.7

[0063] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 3 in Table 1, it can be found that the rubber prepared by the present invention has good flame retardant properties.

[0064] By comparison, the limiting oxygen index of Examples 1 to 3 is greater than that of Comparative Example 2, indicating that 4-(diphenylphosphino)benzaldehyde and (3,4-diaminophenyl)-1-methylethanol in equal molar ratios are oxidized by air to generate benzimidazole derivatives in which triphenylphosphine is grafted onto benzimidazole functional groups. The introduction of phosphorus element can synergistically flame retardant with nitrogen element to improve the flame retardant properties of rubber.

[0065] Test Example 2:

[0066] Mechanical properties test:

[0067] Test method: According to standard ASTM D 412, the rubber prepared in the examples and comparative examples was tested for tensile properties on a tensile testing machine, the rubber was cut into dumbbell shapes, the tensile rate was 500 mm / min, and the tensile strength was recorded. The results are shown in Table 2.

[0068] Test of anti-ultraviolet aging performance:

[0069] Test method: Use QUV type ultraviolet accelerated aging tester, and select UVA-340 lamp for test according to GB / T14522-2008 test method, the test time is 300h, and the tensile strength before and after ultraviolet aging is tested according to the mechanical properties test method, and the tensile strength retention rate is calculated. The results are shown in Table 2.

[0070] Table 2

[0071] Tensile strength(MPa) Tensile strength retention rate (%) Example 1 17.21 94.37 Example 2 17.47 94.66 Example 3 17.96 95.01 Comparative Example 1 11.73 93.41 Comparative Example 2 8.31 74.16 Comparative Example 3 10.26 93.25

[0072] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 3 in Table 2, it can be found that the rubber prepared by the present invention has good mechanical properties and anti-ultraviolet aging properties.

[0073] The tensile strength of Examples 1 to 3 is greater than that of Comparative Examples 1 to 3, and the tensile strength retention rate of Examples 1 to 3 is greater than that of Comparative Example 2, indicating that 4-(diphenylphosphino)benzaldehyde and (3,4-diaminophenyl)-1-methylethanol in an equal molar ratio are oxidized by air to generate benzimidazole derivatives in which triphenylphosphine is grafted onto benzimidazole functional groups, wherein the conjugated planar structure in which benzimidazole and the benzene ring are connected has good ultraviolet absorption performance, and can provide rubber with good anti-ultraviolet aging performance; and then react with carbon disulfide and chloroacetic acid to generate a dithiocarbamate structure, and the carboxyl group on the chloroacetic acid can react with sodium azide to generate an acyl azide structure, and the acyl azide structure will rearrange to generate an isocyanate structure under the action of heating, and the isocyanate structure The cyanate structure and the aminopyrimidone structure on the modified natural rubber can generate quadruple hydrogen bonds; the modified natural rubber, styrene-butadiene rubber, modified carbon black, sulfur, stearic acid, zinc oxide and zinc chloride are mixed and vulcanized to obtain rubber, the pyridine structure on the modified natural rubber and the benzimidazole structure on the carbon black have ion coordination effects with the zinc ions incorporated into the rubber, and the quadruple hydrogen bonds generated by the isocyanate structure and the aminopyrimidone structure on the modified natural rubber have hydrogen bond interactions, and the ion coordination bonds and weak hydrogen bonds can not only act as additional physical cross-linking points in the rubber to improve the overall cross-linking degree, but also bear a certain load during the stress deformation process, and play the role of dissipating energy and inhibiting stress concentration; and the broken weak bonds are continuously broken and reconstructed during the stretching process, thereby playing a good toughening effect.

[0074] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and scope of the equivalent elements of the claims be included in the invention. Any marking in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for preparing rubber, characterized in that: The method comprises the following preparation steps: (1) reacting epoxidized natural rubber and ethyl 3-(6-bromopyridyl)-3-carbonylpropionate to obtain pre-modified natural rubber; (2) reacting guanidine hydrochloride, ethanol, and potassium hydroxide to obtain a guanidine salt solution; reacting pre-modified natural rubber and the guanidine salt solution to obtain modified natural rubber; (3) reacting 4-(diphenylphosphino)benzaldehyde and (3,4-diaminophenyl)-1-methylethanol to obtain a phosphorus-containing monomer; reacting carbon black and a nitric acid solution to obtain carboxyl carbon black; reacting carboxyl carbon black and a phosphorus-containing monomer to obtain pretreated carbon black; (4) reacting pretreated carbon black, carbon disulfide and chloroacetic acid to obtain pre-modified carbon black; (5) reacting pre-modified carbon black and sodium azide to obtain modified carbon black; (6) Weigh the following components: 30-50 parts by mass of modified natural rubber, 50-70 parts by mass of styrene-butadiene rubber, 10-15 parts by mass of modified carbon black, 2-3 parts by mass of sulfur, 3-5 parts by mass of stearic acid, 1-3 parts by mass of zinc oxide, and 2-3 parts by mass of zinc chloride, and prepare a rubber compound by a two-stage mixing process; and then vulcanize the compound by a flat vulcanizer to obtain a rubber compound.

2. The method for preparing rubber according to claim 1, characterized in that: The preparation method of the pre-modified natural rubber in step (1) is as follows: epoxidized natural rubber, 3-(6-bromopyridyl)-3-carbonylpropionic acid ethyl ester, N,N-dimethylformamide, and an auxiliary agent are mixed in a mass ratio of 1:(0.5-0.6):(10-12):0.4, stirred for 2 hours under nitrogen protection, 0.01 times the mass of epoxidized natural rubber of ethylene glycol dimethyl ether nickel bromide is added, stirred for 5-6 hours, after the reaction is completed, 3-4 times the mass of N,N-dimethylformamide of ethanol is added, filtered and washed with ethanol 3-4 times, and vacuum dried at 50°C to obtain the pre-modified natural rubber.

3. The method for preparing rubber according to claim 1, characterized in that: The preparation method of the modified natural rubber in step (2) is as follows: guanidine hydrochloride, ethanol and potassium hydroxide are mixed in a mass ratio of 1:(5-6):(0.5-0.6), heated to 85°C for reflux reaction for 5 minutes, then cooled to room temperature, filtered and retained the filtrate to obtain a guanidine salt solution; pre-modified natural rubber, toluene, guanidine salt solution and tetrabutylammonium bromide are mixed in a mass ratio of 1:(10-12):(2-3):(0.2-0.3), heated to 100-110°C for reflux reaction for 5-6 hours, filtered and retained the filtrate, and subjected to reduced pressure rotary evaporation to obtain the modified natural rubber.

4. The method for preparing rubber according to claim 1, characterized in that: The preparation method of the pretreated carbon black in step (3) is as follows: 4-(diphenylphosphino)benzaldehyde, p-toluenesulfonic acid, and ethanol are mixed in a mass ratio of 1:(0.01-0.02):(20-30), and 4-(diphenylphosphino)benzaldehyde and (3,4-diaminophenyl)-1-methylethanol in an equal molar ratio are added; the temperature is raised to 80°C and refluxed for 3-4 hours. After the reaction is completed, the mixture is filtered and washed with pure water for 3-4 times, and a phosphorus-containing monomer is obtained by vacuum rotary evaporation; carbon black and 50wt% nitric acid solution are mixed in a mass ratio of 1:(0.01-0.02):(20-30). (50-60) are mixed, the temperature is raised to 80°C for reaction for 3-4h, after the reaction is completed, the mixture is filtered and washed with pure water for 5-6 times, and dried at room temperature to obtain carboxyl carbon black; carboxyl carbon black, phosphorus-containing monomer, 4-dimethylaminopyridine, dicyclohexyl diimide, and N,N-dimethylformamide are ultrasonically mixed in a mass ratio of 1:(0.8-1.0):(0.1-0.2):1:(20-30), and the mixture is reacted at room temperature for 24h. After the reaction is completed, the mixture is filtered, washed with ethanol for 3-4 times, and dried at room temperature to obtain pretreated carbon black.

5. The method for preparing rubber according to claim 1, characterized in that: The preparation method of the pre-modified carbon black in step (4) is: pre-treated carbon black, N,N-dimethylformamide, and carbon disulfide are mixed in a mass ratio of 1: (20-30): (0.5-0.6), and then 0.6-0.7 times the mass of the pre-modified carbon black is added with chloroacetic acid, reacting at room temperature for 12 hours. After the reaction is completed, filter and wash with pure water for 3-4 times, and dry at room temperature to obtain the pre-modified carbon black.

6. The method for preparing rubber according to claim 1, characterized in that: The preparation method of the modified carbon black in step (5) is as follows: pre-modified carbon black and tetrahydrofuran are mixed in a mass ratio of 1: (20-30), cooled to -15°C, 0.1 times the mass of the pre-modified carbon black in acetyl chloride and 0.1 times the mass of the pre-modified carbon black in N-methylmorpholine are added, stirred for 20 minutes, 5 times the mass of the pre-modified carbon black in a 0.3 g / mL sodium azide aqueous solution are added, stirring is continued for 1 hour, filtered and washed with pure water for 3-4 times, and dried at room temperature to obtain the modified carbon black.

7. The method for preparing rubber according to claim 1, characterized in that: The two-stage mixing process of step (6) is as follows: the rotor speed of the first-stage mixing process is 70r / min, the initial temperature is 100°C, the modified natural rubber and styrene-butadiene rubber are put into the internal mixer and plasticized for 1min, zinc oxide, zinc chloride and stearic acid are added and mixed for 1min, then the modified carbon black is added and mixed for 4min, the temperature is controlled at 140-150°C and maintained for 2min, and the masterbatch is obtained by rubber removal; the rotor speed of the second-stage mixing process is 35r / min, the initial temperature is 70°C, the first-stage masterbatch is added and plasticized for 1min, sulfur is added, mixed at 90°C for 2min, and then the rubber is removed, and then the sheet is loaded and unloaded on the open mill; the plate vulcanization process parameters are as follows: vulcanization time is 40-50min, vulcanization temperature is 160°C, and vulcanization pressure is 10MPa; the sulfur model is IS7020.

8. The method for preparing rubber according to claim 2, characterized in that: The model of the epoxy natural rubber is ENR-25; the auxiliary agent is obtained by mixing triethylamine hydrobromide, manganese powder, ethylene glycol dimethyl ether nickel bromide, 2,2'-bipyridine, and dichlorobis(pentyl)tantalum in a mass ratio of 1:2:0.2:0.2:0.

3.

9. The method for preparing rubber according to claim 4, characterized in that: The carbon black model is MA-100.