Butyronitrile ester rubber and preparation method thereof

Abstract

The invention provides butyronitrile ester rubber and a preparation method thereof. The method comprises the following steps: S1, mixing 100 parts by weight of a first acrylate monomer, 1-10 parts by weight of a first initiator and an organic solvent, and reacting to obtain a surfactant HXJ; s2, mixing 1-10 parts by weight of a surfactant HXJ, 5-50 parts by weight of a vinyl nitrile monomer, 1-50 parts by weight of a second acrylate monomer, 40-80 parts by weight of a conjugated diene monomer, a chain transfer agent, 0.01-1 part by weight of a second initiator and water, and carrying out a polymerization reaction; the chain transfer agent comprises sulfydryl alkyl acid and / or salt of sulfydryl alkyl acid; and S3, when the conversion rate of the polymerization reaction is greater than or equal to 70%, terminating the reaction, and carrying out post-treatment to obtain the butyronitrile ester rubber. The preparation method is simple in post-treatment, and the obtained rubber is high in quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, and in particular to a nitrile ester rubber and a preparation method thereof. BACKGROUND

[0002] Nitrile ester rubber is a new variety of improved NBR prepared by emulsion polymerization of butadiene, acrylonitrile and acrylic ester. Compared with nitrile rubber, the ester group of nitrile ester rubber endows it with unique properties. The physical and mechanical properties of nitrile rubber and nitrile ester rubber are comparable, and the mechanical properties of nitrile ester rubber after thermal oxidation are more excellent, which may be due to the good thermal stability of the ester group in nitrile ester rubber. CN115785304A reports a method for preparing hydrogenated nitrile ester rubber using nitrile ester rubber as raw material, which has excellent low temperature resistance, and the glass transition temperature (Tg) is lower than -37.0℃, and even lower than -46.0℃, which is significantly better than the reported similar rubber products.

[0003] In the preparation process of nitrile ester rubber, emulsifiers play a key role, but emulsifiers are generally small hydrophilic molecules that do not participate in polymerization and need to be removed in the polymer post-processing stage, increasing the complexity of the post-processing process and production costs. In addition, it is difficult to completely remove the emulsifier small molecules in the post-processing stage, and they are easily migrated and adsorbed on the surface of the product, resulting in poor oil resistance. Since the ash content of nitrile ester rubber prepared by traditional polymerization method is difficult to reduce, it is difficult to expand its application in the fields of medicine, biology, electronics and other fields with high cleanliness requirements. At the same time, since the acrylic ester small molecule monomer is more prone to hydrolysis at the initial stage of polymerization, how to reduce the degree of hydrolysis of functional monomers during the polymerization process has always been a research focus.

[0004] Researchers found that using soap-free emulsion polymerization, the acrylic acid / methyl methacrylate copolymer emulsion is stable and has a white color. The research on soap-free emulsion polymerization has made great progress, but there are still few public reports on the preparation of nitrile ester rubber.

[0005] CN110684148A discloses a method for preparing a cationic ester-based soap-free emulsion polymer. The method uses cationic monomers and ester-based monomers as raw materials, and uses a pH regulator to control the pH value of the reaction environment at 8-8.5. A soap-free cationic hydrophilic monomer, a soap-free ester-based hydrophobic monomer and an initiator a are reacted to synthesize a soap-free polymer, and the soap-free polymer is further reacted with other raw materials to synthesize a polymer emulsion. This technology must use quaternary ammonium salt and quaternary phosphonium salt cationic hydrophilic monomers, which will have an adverse effect on the performance of the rubber when used in the nitrile rubber reaction system.

[0006] CN114507307A discloses that polyvinyl acetate is prepared by a soap-free emulsion polymerization method, and then the prepared polyvinyl acetate is alcoholized to obtain low degree of polymerization PVA. The reaction system is homopolymerization of reaction monomers, which cannot be simply applied to the multi-copolymerization system of nitrile rubber.

[0007] CN111234060A does not add any emulsifier in emulsion polymerization, but adds a plurality of insoluble block solids in the system. The plurality of insoluble block solids collide with each other under stirring, so that the polymer raw materials are well dispersed in the system. The polymer product prepared has high degree of polymerization and good performance. The reaction system is actually to increase the degree of turbulence to enhance mass transfer, but it is not suitable for emulsion radical polymerization system.

[0008] In summary, there is still an urgent need in the technical field for a method of soap-free emulsion polymerization of nitrile rubber without using emulsifiers, which can avoid the hydrolysis of acrylate monomers during polymerization. SUMMARY

[0009] In order to solve the problems in the prior art described above, the purpose of the present application is to provide a nitrile rubber and a preparation method thereof. The preparation method is a soap-free emulsion polymerization, the post-treatment process is simple, and the degree of hydrolysis of acrylate monomers during polymerization can be inhibited, the gel content is reduced, and thus the quality of the rubber is improved.

[0010] In order to achieve the above-mentioned purpose, according to the first aspect of the present application, a preparation method of nitrile rubber is provided, which comprises:

[0011] S1, 100 parts by weight of a first acrylate monomer, 1-10 parts by weight of a first initiator, and an organic solvent are mixed to obtain a surfactant HXJ by reaction;

[0012] S2, 1-10 parts by weight of the surfactant HXJ, 5-50 parts by weight of a vinyl nitrile monomer, 1-50 parts by weight of a second acrylate monomer, 40-80 parts by weight of a conjugated diene monomer, a chain transfer agent, 0.01-1 parts by weight of a second initiator, and water are mixed to perform a polymerization reaction; the chain transfer agent comprises a mercaptoalkyl acid and / or a salt of mercaptoalkyl acid;

[0013] S3, when the conversion rate of the polymerization reaction is ≥70%, the reaction is terminated, post-treatment is performed, and the nitrile rubber is obtained.

[0014] Compared with the traditional emulsion polymerization, the preparation method of the present application does not use the traditional emulsifier, thus it is not necessary to apply a complex post-treatment process to remove the emulsifier not involved in the reaction, and it will not produce a large amount of emulsifier-containing wastewater which is harmful to the environment, and the chain transfer agent selected by the present application has a surface active function, which is used together with the surfactant HXJ, which is also conducive to the stability of the polymerization system. At the same time, since the HXJ prepared by the early polymerization of the acrylate monomer is a molecule with a larger molecular weight relative to the single small molecule of the acrylate monomer, the hydrolysis degree of the functional monomer can be reduced, thereby the gel content can be reduced.

[0015] In some preferred embodiments of the present application, in S1, the reaction is carried out under the condition that the pH is 8-10.

[0016] In some preferred embodiments of the present application, in S1, the amount of the first acrylate monomer is 50-100 parts, and the amount of the first initiator is 1.5-9 parts.

[0017] In some preferred embodiments of the present application, in S2, the amount of the surfactant HXJ is 2-10 parts, the amount of the vinyl nitrile monomer is 20-35 parts, the amount of the second acrylate monomer is 10-25 parts, the amount of the conjugated diene monomer is 50-75 parts, and the amount of the second initiator is 0.2-1 part.

[0018] In some preferred embodiments of the present application, the weight average molecular weight of the surfactant HXJ is 200-2000. Preferably, it has a suitable molecular weight, which on the one hand can inhibit the hydrolysis degree of the acrylate monomer during the polymerization process, reduce the gel content, and thus improve the quality of the rubber, and on the other hand, its molecular weight will not be too large to lose the surface activity function.

[0019] In some preferred embodiments of the present application, the organic solvent is phenoxyethanol and / or diethylene glycol dimethyl ether. Preferably, the above-mentioned organic solvent is more conducive to controlling the molecular weight of the surfactant HXJ, and is also conducive to improving the reaction efficiency in S1.

[0020] More preferably, the amount of the organic solvent is 20-200 parts by weight.

[0021] Preferably, in S1, a buffer is used to adjust the pH. More preferably, the buffer is a mixture of sodium carbonate and sodium bicarbonate. After the reaction in S1 is completed, desalted water is preferably added for stirring to obtain the surfactant HXJ.

[0022] Preferably, in S2, a protective atmosphere is filled into the reaction container before the conjugated diene monomer is added.

[0023] Preferably, in S3, when the reaction conversion rate exceeds 70%, a terminating agent and an antioxidant are added, and after stirring, a degassing treatment is performed. Preferably, the post-treatment comprises adding a coagulating agent to the reaction latex, washing with desalted water, and then drying to obtain the nitrile rubber.

[0024] In some preferred embodiments of the present application, the first acrylate monomer and the second acrylate monomer each independently comprises one or a combination of two or more of acrylic acid, hydroxyethyl methacrylate, butyl acrylate, methyl methacrylate, and hydroxypropyl acrylate.

[0025] In some preferred embodiments of the present application, the vinyl nitrile monomer comprises acrylonitrile and / or methacrylonitrile.

[0026] In some preferred embodiments of the present application, the conjugated diene comprises butadiene and / or isoprene.

[0027] In some preferred embodiments of the present application, the chain transfer agent comprises sodium mercaptoacetate and / or mercaptopropionic acid. The preferred chain transfer agent described above has excellent surface activity, and when used together with the aforementioned surfactant HXJ in the polymerization system of the nitrile rubber, the stable operation of the polymerization system can be more favorably achieved.

[0028] In some preferred embodiments of the present application, in S2, an activator is also added, and the amount of the activator is 0.05-0.3 parts by weight. Preferably, the activator comprises one or a combination of two or more of dilauryl thiodipropionate, ferrous sulfate, and EDTA iron sodium salt.

[0029] In some preferred embodiments of the present application, the amount of the chain transfer agent is 0.05-1.0 parts by weight.

[0030] In some preferred embodiments of the present application, the first initiator comprises a mixture of an oxidative initiator and a reducing initiator. Preferably, the oxidative initiator comprises benzoyl peroxide and / or tert-butyl peroxybenzoate, and the reducing initiator comprises sodium thiosulfate. The amounts of the oxidative initiator and the reducing initiator can be selected as needed.

[0031] In some preferred embodiments of the present application, the second initiator comprises cumene hydroperoxide and / or diisopropylbenzene hydroperoxide.

[0032] In some preferred embodiments of the present application, the temperature of the reaction in S1 is 120-140°C, and the time is 3-5 h.

[0033] In some preferred embodiments of the present application, the temperature of the polymerization reaction in S2 is 5-30°C.

[0034] In some preferred embodiments of the present application, an oxygen scavenger is added in the polymerization reaction of S2, which includes one or more than two combinations of sodium hydrosulfite, dimethyl ketoxime, erythorbic acid, preferably sodium hydrosulfite, and the amount is preferably 0.005-0.2 parts by weight.

[0035] In some preferred embodiments of the present application, the terminator includes one or more than two combinations of NaNO2, hydroxylamine sulfate, diethyl hydroxylamine, 2,5-pentyl butyl phenol, preferably 0.05-1.0 parts by weight.

[0036] In some preferred embodiments of the present application, the antioxidant includes one or more than two combinations of tris(nonylphenyl) phosphite, diphenylamine derivative, polybutyl bisphenol, 2,6-di-tert-butyl-4-methylphenol, preferably diphenylamine derivative.

[0037] In some preferred embodiments of the present application, the coagulant includes one or more than two combinations of CaCl2, Al2(SO4)3, NaCl, which is generally formulated into a 1wt% solution, and the amount of addition is 0.01-0.3 parts by weight, more preferably 0.05-0.2 parts by weight, based on the 1wt% solution.

[0038] According to another aspect of the present application, there is also provided a nitrile rubber obtained by the preparation method as described above.

[0039] In some preferred embodiments of the present application, the ash content of the nitrile rubber is less than 0.5%, preferably 0.3-0.4%.

[0040] In some preferred embodiments of the present application, the gel content of the nitrile rubber is less than 2%, preferably 0.5-1.1%.

[0041] In some preferred embodiments of the present application, the nitrile rubber has a raw rubber combined with acrylonitrile of 10-50%, a Mooney viscosity ML 1+4 100℃ of 20-100, an ash content of ≦0.5%, and a gel content of ≦2%.

[0042] Compared with the prior art, the present application has at least the following beneficial technical effects:

[0043] 1. The present application overcomes the problem of easy hydrolysis of acrylate monomers in the polymerization process, and provides a soap-free emulsion polymerization method, which simplifies the post-treatment process and makes the preparation method more suitable for industrial production needs;

[0044] 2, The butyl nitrile ester rubber obtained by the method has excellent performance, including low ash content, low gel content, and suitable acrylonitrile content and viscosity, thereby having good application prospect. DETAILED DESCRIPTION

[0045] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present application, the technical solutions of the present application are described in detail as follows, but cannot be understood as limiting the implementable scope of the present application.

[0046] In the following examples and comparative examples, the parts and ratios referred to are by weight unless specifically stated. The raw materials are all commercially available products unless specifically stated.

[0047] Example 1

[0048] The present embodiment provides a preparation method of butyl nitrile ester, which comprises the following steps:

[0049] S1, 100 parts of acrylic acid and methacrylic acid hydroxyethyl ester, 50 parts of diethylene glycol dimethyl ether, 2 parts of a mixture of t-butyl peroxybenzoate and sodium thiosulfate (1:1 by weight) are weighed according to a weight ratio of 1:2, uniformly mixed, heated to 130℃ and reacted for 4 hours, then cooled, a buffer (a mixture of sodium carbonate and sodium bicarbonate with a mass ratio of 1:1) is added to adjust the pH to 8.5, and desalted water is added for stirring to obtain a surfactant HXJ with a weight average molecular weight of 1600 and a molecular weight distribution of 1.5.

[0050] S2, in a polymerization kettle, 200 parts of water, 5 parts of surfactant HXJ, 25 parts of acrylonitrile, 15 parts of a mixture of acrylic acid and methacrylic acid hydroxyethyl ester (1:1 by weight), 0.1 parts of a combination of dithio compound and ferrous sulfate (1.5:1 by weight), 0.3 parts of sodium mercaptoacetate, nitrogen gas is replaced three times, 0.1 parts of dimethyl ketone oxime, 55 parts of butadiene, 0.2 parts of cumene hydroperoxide are added for stirring, and the temperature is controlled at 10℃. The conversion rate of monomer is determined at intervals.

[0051] S3, when the conversion rate exceeds 70%, 0.5 parts of a combination of NaNO2 and hydroxylamine sulfate, 0.5 parts of a combination of polybutyl bisphenol and 2,6-di-tert-butyl-4-methylphenol (1:1.2 by weight) are added, stirred for 30 minutes, then degassed, 0.1 parts of a 1wt% NaCl solution (the mass concentration in the following examples and comparative examples is as follows) is added to the reaction latex, washed with desalted water for three times, and finally dried to obtain the final product.

[0052] Example 2

[0053] This embodiment provides a method for preparing butyric acid ester, which includes the following steps:

[0054] S1, weigh out 100 parts of butyl acrylate and methyl methacrylate, 100 parts of phenoxyethanol, and 5 parts of a mixture of benzoyl peroxide and sodium thiosulfate (by weight 0.5:1) in a 1:1 ratio. After mixing evenly, heat to 125℃ and react for 5 hours. Then cool down, add a buffer (a mixture of sodium carbonate and sodium bicarbonate in a mass ratio of 1:1.5) to adjust the pH to 9, add deionized water and stir to obtain surfactant HXJ with a weight average molecular weight of 1000 and a molecular weight distribution of 1.4.

[0055] S2, in a polymerization reactor, add a composition of 250 parts water, 8 parts surfactant HXJ, 30 parts acrylonitrile, 10 parts methyl methacrylate, 0.1 parts bleaching agent and ferrous sulfate (in a weight ratio of 2:3), add 0.1 parts mercaptopropionic acid, purge with nitrogen three times, then add 0.01 parts sodium dithionite, 52 parts isoprene, and 0.5 parts diisopropylbenzene hydrogen peroxide and stir. The temperature is controlled at 20°C, and the conversion rate of the reactants is measured at regular intervals.

[0056] S3, when the conversion rate exceeds 70%, add 0.9 parts of a composition of diethylhydroxylamine and 2,5-pentanebutylquinone (in a weight ratio of 1:1) and 0.6 parts of a composition of tris(nonylphenyl) phosphite and diphenylamino derivative (in a weight ratio of 1.2:1.5). Stir for 30 minutes and then degas. Add 0.5 parts of CaCl2 solution to the reaction latex, rinse three times with deionized water, and finally dry to obtain the final product.

[0057] Example 3

[0058] This embodiment provides a method for preparing butyric acid ester, which includes the following steps:

[0059] S1, weigh 100 parts of butyl acrylate, 80 parts of phenoxyethanol, and 9 parts of a mixture of benzoyl peroxide and sodium thiosulfate (at a weight ratio of 1:1.3). After mixing evenly, heat to 115℃ and react for 4 hours. Then cool down, add a buffer (a mixture of sodium carbonate and sodium bicarbonate at a mass ratio of 2:1) to adjust the pH to 8, add deionized water and stir to obtain surfactant HXJ with a weight average molecular weight of 300 and a molecular weight distribution of 1.6.

[0060] S2, in a polymerization reactor, add 280 parts water, 10 parts surfactant HXJ, 23 parts methacrylonitrile, 15 parts methyl methacrylate, 0.25 parts sodium iron EDTA and ferrous sulfate (in a weight ratio of 3:1), add 0.6 parts mercaptopropionic acid, purge with nitrogen three times, then add 0.15 parts isoascorbic acid, 52 parts butadiene, and 0.8 parts diisopropylbenzene hydrogen peroxide, stir and control the temperature at 5°C, and measure the conversion rate of the reaction monomers at regular intervals.

[0061] S3, when the conversion rate exceeds 70%, add 0.9 parts of a composition of hydroxylamine sulfate and diethylhydroxylamine (in a weight ratio of 1:1.5) and 0.9 parts of a composition of tris(nonylphenyl) phosphite and diphenylamine derivative (in a weight ratio of 1:1.5). Stir for 30 minutes and then degas. Add 0.05 parts of Al2(SO4)3 solution to the reaction latex, rinse three times with deionized water, and finally dry to obtain the final product.

[0062] Example 4

[0063] This embodiment provides a method for preparing butyric acid ester, which includes the following steps:

[0064] S1, weigh 100 parts of hydroxyethyl methacrylate, butyl acrylate, and methyl methacrylate, and 90 parts of phenoxyethanol in a ratio of 1:1:2. Then add 1.5 parts of a mixture of benzoyl peroxide and sodium thiosulfate (in a weight ratio of 1:2), mix well, heat to 138℃ and react for 4 hours, then cool down, add a buffer (a mixture of sodium carbonate and sodium bicarbonate in a mass ratio of 1:1.8) to adjust the pH to 9, add deionized water and stir to obtain surfactant HXJ with a weight average molecular weight of 1800 and a molecular weight distribution of 2.

[0065] S2, in a polymerization reactor, add 150 parts water, 2 parts HXJ, 35 parts methacrylonitrile, 20 parts methyl methacrylate, 0.25 parts sodium iron EDTA and ferrous sulfate (in a weight ratio of 2.5:1), add 0.6 parts mercaptopropionic acid, purge with nitrogen three times, then add 0.15 parts isoascorbic acid, 43 parts butadiene, and 0.8 parts diisopropylbenzene hydrogen peroxide, stir and control the temperature at 5°C, and measure the conversion rate of the reaction monomers at regular intervals.

[0066] S3, when the conversion rate exceeds 70%, add 0.9 parts of a composition of hydroxylamine sulfate and diethylhydroxylamine (in a weight ratio of 1:1) and 0.9 parts of a composition of tris(nonylphenyl) phosphite and diphenylamino derivative (in a weight ratio of 1:1). Stir for 30 minutes and then degas. Add 0.8 parts of NaCl solution to the reaction latex, rinse three times with deionized water, and finally dry to obtain the final product.

[0067] Example 5

[0068] This embodiment provides a method for preparing butyric acid ester, which includes the following steps:

[0069] S1, weigh 100 parts of methyl methacrylate, 20 parts of phenoxyethanol, and 7 parts of a mixture of tert-butyl peroxide and sodium thiosulfate (in a weight ratio of 1:3). After mixing evenly, heat to 130℃ and react for 4 hours. Then cool down, add a buffer (a mixture of sodium carbonate and sodium bicarbonate in a mass ratio of 1:2) to adjust the pH to 9, add deionized water and stir to obtain surfactant HXJ with a weight average molecular weight of 1700 and a molecular weight distribution of 1.5.

[0070] S2, in a polymerization reactor, add 100 parts water, 6 parts surfactant HXJ, 15 parts acrylonitrile, 25 parts methyl methacrylate, 0.25 parts sodium iron EDTA and ferrous sulfate (in a weight ratio of 1:2), add 0.6 parts mercaptopropionic acid, purge with nitrogen three times, then add 0.15 parts isoascorbic acid, 54 parts butadiene, and 0.8 parts diisopropylbenzene hydrogen peroxide, stir and control the temperature at 5°C, and measure the conversion rate of the reaction monomers at regular intervals.

[0071] S3, when the conversion rate exceeds 70%, add 0.9 parts of a composition of hydroxylamine sulfate and diethylhydroxylamine (in a weight ratio of 1:1) and 0.9 parts of a composition of tris(nonylphenyl) phosphite and diphenylamino derivative (in a weight ratio of 1:1). Stir for 30 minutes and then degas. Add 0.8 parts of NaCl solution to the reaction latex, rinse three times with deionized water, and finally dry to obtain the final product.

[0072] Example 6

[0073] This embodiment provides a method for preparing butyric acid ester, which includes the following steps:

[0074] S1, weigh 100 parts of hydroxyethyl methacrylate and 50 parts of phenoxyethanol, then add 1.5 parts of a mixture of benzoyl peroxide and sodium thiosulfate (by weight ratio 2:1), mix well, heat to 130℃ and react for 4.5 hours, then cool down, add a buffer (a mixture of sodium carbonate and sodium bicarbonate by mass ratio 1:1) to adjust the pH to 9, add deionized water and stir to obtain surfactant HXJ with a weight average molecular weight of 1800 and a molecular weight distribution of 1.6.

[0075] S2, in a polymerization reactor, add 180 parts water, 3 parts surfactant HXJ, 15 parts methacrylonitrile, 10 parts methyl methacrylate, 0.25 parts sodium iron EDTA and ferrous sulfate (in a weight ratio of 1:1), add 0.6 parts mercaptopropionic acid, purge with nitrogen three times, then add 0.15 parts isoascorbic acid, 72 parts butadiene, and 0.7 parts diisopropylbenzene hydrogen peroxide, stir and control the temperature at 5°C, and measure the conversion rate of the reaction monomers at regular intervals.

[0076] S3, when the conversion rate exceeds 70%, add 0.9 parts of a composition of hydroxylamine sulfate and diethylhydroxylamine (in a weight ratio of 1:1) and 0.9 parts of a composition of tris(nonylphenyl) phosphite and diphenylamino derivative (in a weight ratio of 1:1). Stir for 30 minutes and then degas. Add 0.8 parts of NaCl solution to the reaction latex, rinse three times with deionized water, and finally dry to obtain the final product.

[0077] The performance tests of the nitrile butadiene rubber obtained in the above examples are shown in Table 1.

[0078] Table 1

[0079]

[0080]

[0081] Comparative Example 1

[0082] The implementation conditions were the same as in Example 1, except that the surfactant HXJ was not prepared or applied. The polymerization method included:

[0083] In a polymerization reactor, add 200 parts water, 25 parts acrylonitrile, 15 parts a mixture of acrylic acid and hydroxyethyl methacrylate (in a 1:1 weight ratio), 0.1 parts a composition of bleaching agent and ferrous sulfate (in a 1.5:1 weight ratio), add 0.3 parts sodium mercaptoacetate, purge with nitrogen three times, then add 0.1 parts dimethyl ketoxime, 55 parts butadiene, and 0.2 parts...

[0084] The reaction mixture was stirred at 10°C, and the conversion rate of the reactants was measured at regular intervals. The reaction system became unstable when the conversion rate exceeded 40%.

[0085] Comparative Example 2

[0086] Unlike Example 2, no chain transfer agent was added. The preparation method of its butyronitrile ester is as follows:

[0087] S1, weigh out 100 parts of butyl acrylate and methyl methacrylate, 100 parts of phenoxyethanol, and 5 parts of a mixture of benzoyl peroxide and sodium thiosulfate (by weight 0.5:1) in a 1:1 ratio. After mixing evenly, heat to 125℃ and react for 5 hours. Then cool down, add a buffer (a mixture of sodium carbonate and sodium bicarbonate in a mass ratio of 1:1.5) to adjust the pH to 9, add deionized water and stir to obtain surfactant HXJ with a weight average molecular weight of 1000 and a molecular weight distribution of 1.4.

[0088] S2, in a polymerization reactor, add a composition of 250 parts water, 8 parts surfactant HXJ, 30 parts acrylonitrile, 10 parts methyl methacrylate, 0.1 parts bleaching agent and ferrous sulfate (in a weight ratio of 2:3), purge with nitrogen three times, then add 0.01 parts sodium dithionite, 52 parts isoprene, and 0.5 parts diisopropylbenzene hydrogen peroxide and stir. The temperature is controlled at 20°C, and the conversion rate of the reactants is measured at regular intervals.

[0089] S3, when the conversion rate exceeds 70%, add 0.9 parts of a composition of diethylhydroxylamine and 2,5-pentanebutylquinone (in a weight ratio of 1:1) and 0.6 parts of a composition of tris(nonylphenyl) phosphite and diphenylamino derivative (in a weight ratio of 1.2:1.5). Stir for 30 minutes and then degas. Add 0.5 parts of CaCl2 solution to the reaction latex, rinse three times with deionized water, and finally dry to obtain the final product.

[0090] Comparative Example 3

[0091] Compared to Example 3, the surfactant HXJ was replaced with a mixture of potassium fatty acid soap and sodium dodecyl sulfate, while the other operating conditions remained unchanged. The preparation method of its butyronitrile ester is as follows:

[0092] S1. In a polymerization reactor, add 280 parts water, 10 parts potassium fatty acid soap and sodium dodecyl sulfate (in a weight ratio of 1:3), 23 parts methacrylonitrile, 15 parts methyl methacrylate, 0.25 parts sodium iron EDTA and ferrous sulfate (in a weight ratio of 3:1), and 0.6 parts mercaptopropionic acid. Purge the reactor three times with nitrogen gas. Then add 0.15 parts isoascorbic acid, 52 parts butadiene, and 0.8 parts diisopropylbenzene hydrogen peroxide. Stir the mixture and control the temperature at 5°C. Measure the conversion rate of the reactants at regular intervals.

[0093] S2, when the conversion rate exceeds 70%, add 0.9 parts of a composition of hydroxylamine sulfate and diethylhydroxylamine, and 0.9 parts of a composition of tris(nonylphenyl) phosphite and diphenylamino derivative. Stir for 30 minutes and then degas. Add 0.05 parts of Al2(SO4)3 solution to the reaction latex, rinse three times with deionized water, and finally dry to obtain the final product.

[0094] Comparative Example 4

[0095] Compared to Example 4, dodecyl mercaptopropionic acid was used instead of thiopropionic acid, while all other conditions remained unchanged. The preparation method of its butyronitrile ester is as follows:

[0096] S1, weigh 100 parts of hydroxyethyl methacrylate, butyl acrylate, and methyl methacrylate, and 90 parts of phenoxyethanol in a ratio of 1:1:2. Then add 1.5 parts of a mixture of benzoyl peroxide and sodium thiosulfate (in a weight ratio of 1:2). After mixing evenly, heat to 138℃ and stir to react. After reacting for 4 hours, start cooling and add a buffer (a mixture of sodium carbonate and sodium bicarbonate in a mass ratio of 1:1.8) to adjust the pH to 9. Add deionized water and stir to obtain surfactant HXJ with a weight average molecular weight of 1800 and a molecular weight distribution of 2.

[0097] S2, in a polymerization reactor, add 150 parts water, 2 parts HXJ, 35 parts methacrylonitrile, 20 parts methyl methacrylate, 0.25 parts sodium iron EDTA and ferrous sulfate (in a weight ratio of 2.5:1), add 0.6 parts dodecyl mercaptan, purge with nitrogen three times, then add 0.15 parts isoascorbic acid, 43 parts butadiene, and 0.8 parts diisopropylbenzene hydrogen peroxide, stir and control the temperature at 5°C, and measure the conversion rate of the reaction monomers at regular intervals.

[0098] S3, when the conversion rate exceeds 65%, some precipitation occurs in the reaction system. When the conversion rate exceeds 70%, 0.9 parts of a composition of hydroxylamine sulfate and diethylhydroxylamine (in a weight ratio of 1:1) and 0.9 parts of a composition of tris(nonylphenyl) phosphite and diphenylamine derivative (in a weight ratio of 1:1) are added. After stirring for 30 minutes, degassing is performed. 0.8 parts of NaCl solution are added to the reaction latex, and the mixture is washed three times with deionized water. Finally, the product is dried to obtain the final product.

[0099] Comparative Example 5

[0100] Compared to Example 5, distilled water was used as the solvent in preparing the surfactant, while all other conditions remained unchanged. A portion of the prepared surfactant precipitated out; the precipitate was filtered before use.

[0101] S1, weigh 100 parts of methyl methacrylate, 20 parts of distilled water, and 7 parts of a mixture of tert-butyl peroxide and sodium thiosulfate (in a weight ratio of 1:3). After mixing evenly, heat to 130℃ and react for 4 hours. Then cool down, add a buffer (a mixture of sodium carbonate and sodium bicarbonate in a mass ratio of 1:2) to adjust the pH to 9, add deionized water and stir to obtain surfactant DB with a weight average molecular weight of 600 and a molecular weight distribution of 3.5.

[0102] S2, in a polymerization reactor, add 100 parts water, 6 parts surfactant DB, 15 parts acrylonitrile, 25 parts methyl methacrylate, 0.25 parts sodium iron EDTA and ferrous sulfate (in a weight ratio of 1:2), add 0.6 parts mercaptopropionic acid, purge with nitrogen three times, then add 0.15 parts isoascorbic acid, 54 parts butadiene, and 0.8 parts diisopropylbenzene hydrogen peroxide, stir and control the temperature at 5°C, and measure the conversion rate of the reaction monomers at regular intervals.

[0103] S3, when the conversion rate exceeds 60%, polymerization instability occurs and a large amount of precipitation occurs.

[0104] The performance tests of the nitrile butadiene rubber obtained from the above comparative examples are shown in Table 2.

[0105] Table 2

[0106]

[0107] A comparison of the data in Tables 1 and 2 shows that the nitrile butadiene rubber of the present invention has low ash content and low gel content, and also has suitable bound acrylonitrile content and suitable viscosity, thus showing good application prospects.

[0108] The test methods used in the above embodiments, comparative examples, and test cases are as follows:

[0109] Mooney viscosity: Raw rubber was tested according to GB / T1232.1-2016 using a Mooney viscometer (GT-7082S2) manufactured by High-speed Rail Testing Instruments Co., Ltd.

[0110] Combined with acrylonitrile: Raw rubber was tested using the Kjeldahl method according to SH / T 1157-2015.

[0111] Ester group content: determined by nuclear magnetic resonance.

[0112] Tensile strength, stress at 300% elongation (MPa), elongation at break (%): Compliant with standard GB / T528-2009.

[0113] Ash content: Test raw rubber according to GB / T 4498.1-2013A.

[0114] Gel content: Raw rubber was tested according to SH / T 1050.

Claims

1. A method for preparing nitrile butadiene rubber, characterized in that, include: S1, 100 parts by weight of a first acrylate monomer, 1 to 10 parts by weight of a first initiator and an organic solvent are mixed and reacted to obtain surfactant HXJ; S2, 1-10 parts by weight of the surfactant HXJ, 5-50 parts by weight of the vinyl nitrile monomer, 1-50 parts by weight of the second acrylate monomer, 40-80 parts by weight of the conjugated diene monomer, chain transfer agent, 0.01-1 parts by weight of the second initiator, and water are mixed to carry out a polymerization reaction; the chain transfer agent includes mercaptoalkyl acid and / or salts of mercaptoalkyl acid; S3, when the polymerization conversion rate is ≥70%, the reaction is terminated and post-processing is performed to obtain the acrylonitrile rubber.

2. The preparation method according to claim 1, characterized in that, The surfactant HXJ has a weight-average molecular weight of 200 to 2000.

3. The preparation method according to claim 1, characterized in that, The organic solvent is phenoxyethanol and / or diethylene glycol dimethyl ether.

4. The preparation method according to claim 1, characterized in that, The first acrylate monomer and the second acrylate monomer each independently include one or more combinations of acrylic acid, hydroxyethyl methacrylate, butyl acrylate, methyl methacrylate, and hydroxypropyl acrylate.

5. The preparation method according to claim 1, characterized in that, The vinyl nitrile monomers include acrylonitrile and / or methacrylonitrile.

6. The preparation method according to claim 1, characterized in that, The conjugated diene includes butadiene and / or isoprene.

7. The preparation method according to claim 1, characterized in that, The amount of the chain transfer agent is 0.05 to 1.0 parts by weight.

8. The preparation method according to claim 1, characterized in that, The first initiator comprises a mixture of an oxidizing initiator and a reducing initiator.

9. The preparation method according to claim 1, characterized in that, The second initiator includes cumene hydroperoxide and / or dicumene hydroperoxide.

10. The preparation method according to claim 1, characterized in that, The reaction described in S1 is carried out at a temperature of 120–140°C for 3–5 hours.

11. The preparation method according to claim 1, characterized in that, The polymerization reaction described in S2 is carried out at a temperature of 5–30°C.

12. A type of nitrile butadiene rubber, characterized in that, The preparation method according to any one of claims 1 to 11 is used.

13. The nitrile butadiene rubber according to claim 12, characterized in that, The ash content of the nitrile butadiene rubber is less than 0.5%.

14. The nitrile butadiene rubber according to claim 12, characterized in that, The gel content of the nitrile butadiene rubber is less than 2%.

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