Preparation method of nitrile rubber

Abstract

The invention discloses a preparation method of nitrile rubber, which comprises the following steps: (1) adding water, a vinyl nitrile monomer and an ionizable initiator into a polymerization kettle, stirring, heating, and cooling after the reaction is finished to obtain a reaction compound with an emulsification effect; (2) in the polymerization reaction, adding water, a cosolvent and the reaction compound obtained in the step (1), introducing nitrogen for replacement, then adding a deoxidant, a chain transfer agent with a surface activity function, conjugated diene and a vinyl nitrile monomer, heating, adding an ionizable initiator, and measuring the conversion rate of the reaction monomer in each period of time; and when the conversion rate is greater than 70%, adding a terminator and an anti-aging agent, stirring, degassing, adding a coagulant, flushing and drying to obtain the nitrile rubber. According to the preparation method, soap-free polymerization of nitrile rubber can be realized, the complexity of a post-treatment process is reduced, the environmental friendliness and economic benefits are improved, and the problem that the cleanliness of a product is difficult to improve is solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of emulsion polymerization rubber, and particularly relates to a method for preparing nitrile rubber by soap-free polymerization. BACKGROUND

[0002] Nitrile rubber is prepared by emulsion copolymerization of conjugated diene and vinyl cyanide monomers, and has good oil resistance, wear resistance, heat resistance and sealing property, and is mainly used for preparing oil-resistant rubber products, modifiers, adhesives and the like. At present, one of the key development directions of nitrile rubber is to improve product performance, reduce energy consumption and environmental pollution by studying polymerization process.

[0003] Emulsifiers play a key role in the emulsion polymerization process, but emulsifiers are generally small hydrophilic molecules and do not participate in the polymerization reaction, and need to be removed in the polymer post-treatment stage, which increases the complexity of the post-treatment process and the production cost; in addition, it is difficult to completely remove the emulsifier small molecules in the post-treatment stage, and the emulsifier small molecules are easy to migrate and adsorb on the surface of the product, resulting in poor oil resistance; since the ash content of the nitrile rubber prepared by the 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. Soap-free emulsion polymerization refers to an emulsion polymerization process in which no emulsifier is added or only a trace amount of emulsifier (the concentration of which is less than the critical micelle concentration) is added during the reaction process, and is also called emulsifier-free emulsion polymerization. The particle size of soap-free emulsion is uniform, the system is free of emulsifier, and the pollution of emulsifier to the environment is also eliminated, therefore, the soap-free emulsion polymerization technology has attracted wide attention.

[0004] Journal of Polymer Science 1977 "Mechanism of Emulsion Polymerization of Styrene in Soap-Free Systems" proposed the micellar nucleation mechanism of hydrophobic monomer soap-free emulsion polymerization, which made soap-free emulsion polymerization develop rapidly. "VPE initiated styrene soap-free emulsion polymerization research" in Chemical New Materials 2007 used azo polyethylene glycol macromolecular initiator (VPE) to initiate styrene soap-free emulsion polymerization, and prepared copolymer nanospheres with regular particle morphology and good monodispersity. The morphology, particle size and distribution of the microspheres were characterized by transmission electron microscopy (TEM) and laser light scattering (LLS), and the effect of the amount of macromolecular initiator VPE on the particle size of the polymer nanospheres and the viscosity of the polymer emulsion was investigated. The experimental results show that when the concentration of styrene is fixed at 0.385 mol / L, with the increase of the concentration of VPE from 1.2 mmol / L to 4.8 mmol / L, the particle size of the polymer nanospheres decreases from 178 nm to 70 nm, and the viscosity of the polymer emulsion increases from 1.93 mPa.s to 2.17 mPa.s, indicating that the particle size of the microspheres can be controlled within a certain range. "Study on styrene / hydroxymethyl acrylamide soap-free emulsion copolymerization" in Colloid and Polymer 2005 used styrene as the main monomer, N-hydroxymethyl acrylamide as the functional monomer, and potassium persulfate as the initiator to prepare styrene / N-hydroxymethyl acrylamide soap-free copolymer emulsion with high solid content and good stability, and discussed the effects of solid content, monomer ratio, reaction temperature, and initiator dosage on the stability of the emulsion and the particle size.

[0005] Preparation of polymers by soap-free emulsion polymerization of hydrophobic monomers has been widely studied, but there are few reports on the preparation of nitrile rubber by soap-free method. Since the conjugated diene and vinyl cyanide monomers in nitrile rubber are both hydrophobic monomers, and the polarity of the vinyl cyanide monomer is relatively large, it is difficult to prepare them by simple soap-free emulsion polymerization.

[0006] CN 114380948 A discloses a method for preparing nitrile rubber, which mainly includes polymerizing a raw material system containing butadiene, acrylonitrile, reactive antioxidant N-(4-(anilino)phenyl)methyl acrylamide, and part of the molecular weight regulator; when the reaction conversion rate reaches 55-60%, the remaining part of the molecular weight regulator is added; when the reaction conversion rate reaches 80-85%, the reaction is terminated to obtain nitrile rubber. This technology has obvious deficiencies: (1) a large amount of emulsifier is added to the reaction system, making the post-treatment process complex; (2) the post-treatment process is relatively complex and the ash content of the product is difficult to reduce.

[0007] CN 103755865 A discloses a soap-free polymerization acrylic emulsion and a preparation method, which contains methyl methacrylate, ethyl octyl acrylate, methacrylic acid, styrene, acrylamide as the composition monomer, ammonium persulfate or potassium persulfate as the initiator, alkylamide ethylene sulfonate sodium or dodecylbenzenesulfonic acid sodium as the emulsifier, ammonia as the pH regulator, and water, mainly composed of olefin monomer, emulsifier, initiator, pH regulator and water. The soap-free polymerization acrylic emulsion is prepared by pre-emulsification, seed polymerization and polymerization. The technology has obvious deficiencies: (1) the use of reactive emulsifier in the reaction system is difficult to apply to the preparation of nitrile rubber; (2) without additional addition of cosolvent, when used for conjugated diene non-water-soluble monomer, the reaction solid content is difficult to improve, resulting in lower economic benefit of the reaction.

[0008] CN 109535345 A discloses a method for preparing a polymer based on a semi-continuous feeding method. The water-soluble monomer, chain transfer agent, initiator and water are mixed uniformly, and the polymer solution is obtained by reaction; the monomer, initiator, water and polymer solution are mixed, argon gas is passed to remove oxygen, and then heated, the remaining monomer is added to the container by a micro-injection pump, the feeding time is 90-150 min; the soap-free polymer emulsion is obtained after the feeding is completed, and after freeze-drying, precipitation, standing, suction filtration and drying, the polymer is obtained. The technology has obvious deficiencies: the polymerization monomer used in the technology is water-soluble monomer, which is not suitable for the polymerization system of hydrophobic monomer.

[0009] CN116925288A discloses a preparation method of high-strength special nitrile rubber, specifically: with the addition amount of butadiene and acrylonitrile being 100 parts by weight, soft water 275 parts, butadiene 50-60 parts, acrylonitrile 40-50 parts; emulsifier 2.5-5 parts, sodium hydroxide 0.01-0.1 parts; initiator 0.2-1.0 parts; triethanolamine 0.1 parts; molecular weight regulator 0.4-0.6 parts, added in three equal portions; when the reaction conversion rate reaches 35-40%, add the second molecular weight regulator, when the reaction conversion rate reaches 50-55%, add the third molecular weight regulator, cool to 20-25℃, then discharge, add the terminating agent and antioxidant, and after degassing, coagulation, washing and drying, the high-strength special nitrile rubber is prepared. The technology has obvious deficiencies: the emulsifier which does not participate in the reaction needs to be added, which affects the cleanliness of the product. SUMMARY

[0010] In the preparation of synthetic rubber by traditional emulsion polymerization, a large amount of emulsifier is needed to form an emulsified system so as to dissolve hydrophobic monomers in micelles for free radical polymerization reaction, but the emulsifier does not actually participate in the reaction during the reaction and needs to be removed in the post-processing process, causing problems of high preparation cost, complex post-processing process and difficult improvement of product cleanliness. To solve the above technical problems, the present application uses ionizable initiator, chain transfer agent with surface activity function and cosolvent to jointly prepare nitrile rubber. The ionizable initiator is used to initiate the hydrophobic monomer with certain water solubility to obtain oligomers with emulsifier effect, and then cosolvent and chain transfer agent with surface activity function are introduced to realize soap-free polymerization of nitrile rubber, reduce the complexity of the post-processing process, improve the environmental friendliness and economic benefit, and break through the problem of difficult improvement of product cleanliness.

[0011] The present application provides a preparation method of nitrile rubber, which comprises the following steps:

[0012] (1) In the polymerization kettle, 100 parts of water, 1-10 parts of vinyl nitrile monomer and 0.1-5 parts of ionizable initiator are added based on 100 parts of water, and stirring, heating and cooling are carried out after the reaction is completed to obtain a reaction compound with emulsifying effect, which is marked as RHT;

[0013] (2) In the polymerization reaction, 100 parts of water, cosolvent, 1-10 parts of the reaction compound RHT obtained in step (1), nitrogen replacement, deoxidizing agent, chain transfer agent with surface activity function, 40-85 parts of conjugated diene and 14-51 parts of vinyl nitrile monomer are added based on 100 parts of monomer, heating is carried out, ionizable initiator is added, the conversion rate of reaction monomer is determined every time, when the conversion rate is greater than or equal to 70%, terminating agent and antioxidant are added, stirring, degassing, adding coagulating agent to the reaction latex, washing and drying are carried out to obtain nitrile rubber.

[0014] The ionizable initiator in the present application is a mixture of at least one of potassium persulfate and ammonium persulfate and at least one of potassium sulfite and ammonium sulfite.

[0015] In step (2) of the present application, the addition amount of the ionizable initiator is 0.01-5 parts by weight, and more preferably 0.01-2 parts by weight.

[0016] The cosolvent in the present application can be ethanol, acetone and other solvents that can be well miscible with water, and the addition amount is 0.1-4 parts by weight.

[0017] The conjugated diene in the present application is at least one of butadiene and isoprene.

[0018] The vinyl nitrile monomer is at least one of acrylonitrile and methacrylonitrile, preferably acrylonitrile.

[0019] The chain transfer agent with surface activity function is at least one of mercapto alkyl acid salts, such as sodium mercaptoacetate and mercapto propionic acid, and the adding amount is 0.05-5 parts by weight.

[0020] The oxygen scavenger is at least one of sodium hydrosulfite, dimethyl ketone oxime and erythorbic acid, and the preferred oxygen scavenger is sodium hydrosulfite, and the amount is the conventional amount in the art, and the adding amount is 0.005-0.02 parts by weight.

[0021] The terminating agent is at least one of NaNO2, hydroxylamine sulfate, diethyl hydroxylamine and 2,5-pentyl butyl phenol, and the amount is the conventional amount in the art, and the adding amount is 0.05-0.5 parts by weight.

[0022] The antioxidant is at least one of tris (nonylphenyl) phosphite, diphenylamine derivative, polybutyl bisphenol and 2,6-di-tert-butyl-4-methylphenol, and the preferred antioxidant is diphenylamine derivative, and the adding amount is 0.1-1 parts by weight.

[0023] The coagulating agent is at least one of CaCl2, Al2(SO4)3 and NaCl, and is generally prepared into a 1% solution, and the adding amount is 0.01-0.5 parts by weight, and more preferably 0.05-0.5 parts by weight.

[0024] In step (1), the temperature is raised to 70-90℃, and then is lowered to 10-30℃ after the reaction is completed.

[0025] In step (2), the temperature is raised to 70-90℃.

[0026] The "parts" not specially mentioned in the present application refer to parts by weight.

[0027] In step (2), 100 parts by weight of monomers refer to the total weight of the reaction compound RHT, conjugated diene and vinyl nitrile monomer.

[0028] The nitrile rubber produced by the method of the present application has a raw rubber combined with acrylonitrile of 12-50wt%, a Mooney viscosity ML 1+4 100℃: 20-95, ash content≦0.5wt%.

[0029] The present application has at least the following beneficial effects:

[0030] (1) Compared with the traditional emulsion, the soap-free emulsion polymerization of the present application does not contain emulsifiers, so it does not need a complex post-treatment process to remove emulsifiers that do not participate in the reaction, and also does not produce a large amount of emulsifier-containing wastewater that is harmful to the environment.

[0031] (2) Ionizable initiator refers to a compound that contains both a surface active group and a free radical group in the molecule. The chain transfer agent with surface activity is similar to the ionizable initiator, both of which can achieve the function of emulsifier. When the ionizable initiator is used to initiate the copolymerization of hydrophobic vinyl nitrile monomers, the generated oligomer radical does not directly precipitate from water. Due to the presence of the hydrophilic group of the initiator at one end, it exhibits hydrophilicity, and the other end is hydrophobic, which has the function of emulsifier. The oligomer radical self-assembles to form micelles, and the micelles aggregate to form primary ions. The ionizable initiator and the chain transfer agent with surface activity work together to play the role of emulsifier, realize soap-free emulsion polymerization, improve the cleanliness of the product, and make the ash content less than 1%, so that the product can be applied in the fields of medicine, biology, electronics and other fields with high cleanliness requirements.

[0032] (3) To improve the stability of the latex, a cosolvent that is highly miscible with water is added to the polymerization system to improve the stability of the system at high solid content and achieve high polymerization efficiency. DETAILED DESCRIPTION

[0033] Evaluation and analysis method: molecular weight and its distribution: high temperature gel chromatography analysis method (GPC) was used. The GPC instrument used in the experiment was GPCV2000 type high temperature gel chromatograph of WATERS company. With o-dichlorobenzene as the solvent, the sample was dissolved, placed and filtered at 135℃; the sample amount was 200μL / column, the flow rate was 1mL / min, and HT6, HT5, HT4, HT3 column group was used.

[0034] Mooney viscosity: Mooney viscosity instrument (GT-7082S2) produced by high iron detection instrument company was used to test the raw rubber according to GB / T1232.1-2016.

[0035] Combined with acrylonitrile: the raw rubber was tested by Kjeldahl nitrogen determination method according to SH / T 1157-2015.

[0036] Tensile strength, 300% modulus (MPa), elongation at break (%): the standard GB / T528-2009 was executed.

[0037] Ash content: the raw rubber was tested by GB / T 4498.1-2013A method.

[0038] Example 1

[0039] In a polymerization kettle, 100 parts of water, 2 parts of acrylonitrile, 0.2 parts of a mixture of ammonium persulfate and ammonium sulfite were added based on 100 parts of water, stirred and warmed to 75°C, and after the reaction was completed, cooled to 25°C to obtain a reaction compound having an emulsifying effect, labeled RHT.

[0040] In a polymerization reaction, 150 parts of water, 0.15 parts of ethanol, 3 parts of RHT were added based on 100 parts of monomer, replaced with nitrogen three times, then 0.01 parts of sodium hyposulfite, 1 part of sodium mercaptoacetate, 77 parts of butadiene, 20 parts of acrylonitrile were added, the temperature was raised to 75°C, 0.02 parts of a mixture of ammonium persulfate and ammonium sulfite were added, and the conversion rate of the reaction monomer was measured at each time interval. When the conversion rate reached 70%, a mixture of 0.1 parts of NaNO2 and hydroxylamine sulfate, 0.2 parts of a mixture of tris(nonylphenyl) phosphite and diphenylamine derivative was added, stirred for 30 minutes, then degassed, 0.1 parts of a mixture of CaCl2 and Al2(SO4)3 was added to the reaction latex, washed three times with desalted water, and finally dried to obtain butyl nitrile rubber.

[0041] Example 2

[0042] In a polymerization kettle, 100 parts of water, 6 parts of acrylonitrile, 0.35 parts of a mixture of potassium persulfate and ammonium sulfite were added based on 100 parts of water, stirred and warmed to 85°C, and after the reaction was completed, cooled to 25°C to obtain a reaction compound having an emulsifying effect, labeled RHT.

[0043] In a polymerization reaction, 170 parts of water, 0.3 parts of acetone, 5 parts of RHT were added based on 100 parts of monomer, replaced with nitrogen three times, then 0.015 parts of dimethyl ketone oxime, 4.5 parts of mercaptopropionic acid, 70 parts of butadiene, 25 parts of acrylonitrile were added, the temperature was raised to 80°C, 4 parts of a mixture of ammonium persulfate and ammonium sulfite was added, and the conversion rate of the reaction monomer was measured at each time interval. When the conversion rate reached 75%, a mixture of 0.3 parts of NaNO2 and 2,5-pentyl hydroquinone was added, 0.6 parts of 2,6-di-tert-butyl-4-methylphenol, stirred for 30 minutes, then degassed, 0.2 parts of a mixture of CaCl2 and NaCl was added to the reaction latex, washed three times with desalted water, and finally dried to obtain butyl nitrile rubber.

[0044] Example 3

[0045] In a polymerization kettle, 100 parts of water, 9 parts of acrylonitrile, 4.5 parts of a mixture of potassium persulfate and ammonium sulfite were added based on 100 parts of water, stirred and warmed to 85°C, and after the reaction was completed, cooled to 25°C to obtain a reaction compound having an emulsifying effect, labeled RHT.

[0046] In the polymerization reaction, 170 parts of water, 0.3 parts of acetone, 5 parts of RHT were added to 100 parts of monomer, replaced with nitrogen three times, then 0.015 parts of dimethyl ketone oxime, 2.5 parts of mercapto propionic acid, 70 parts of butadiene, 25 parts of acrylonitrile were added, the temperature was raised to 80°C, 0.02 parts of ammonium persulfate and ammonium sulfite mixture was added, the conversion rate of the reaction monomer was measured at each time interval. When the conversion rate reached 75%, 0.45 parts of diethyl hydroxylamine and 2,5-pentyl butyl phenol mixture, 0.8 parts of diphenylamine derivative and polybutyl bisphenol mixture were added, stirred for 30 minutes, then degassed, 0.4 parts of CaCl2 and NaCl were added to the reaction latex, washed with desalted water three times, and finally dried to obtain butyl nitrile rubber.

[0047] Example 4

[0048] In the polymerization kettle, 100 parts of water, 4 parts of methacrylonitrile, 3 parts of a mixture of potassium persulfate and ammonium sulfite were added to 100 parts of water, stirred and heated to 80°C, and then cooled to 25°C after the reaction was completed to obtain a reaction compound with emulsifying effect, marked as RHT.

[0049] In the polymerization reaction, 170 parts of water, 4 parts of ethanol, 5 parts of RHT were added to 100 parts of monomer, replaced with nitrogen three times, then 0.02 parts of erythorbic acid, 2.5 parts of sodium mercaptoacetate, 70 parts of butadiene, 25 parts of methacrylonitrile were added, the temperature was raised to 80°C, 0.03 parts of ammonium persulfate and ammonium sulfite mixture was added, the conversion rate of the reaction monomer was measured at each time interval. When the conversion rate reached 70%, 0.45 parts of diethyl hydroxylamine and 2,5-pentyl butyl phenol mixture, 0.8 parts of diphenylamine derivative and polybutyl bisphenol mixture were added, stirred for 30 minutes, then degassed, 0.45 parts of CaCl2 and NaCl were added to the reaction latex, washed with desalted water three times, and finally dried to obtain butyl nitrile rubber.

[0050] Example 5

[0051] In the polymerization kettle, 100 parts of water, 4 parts of methacrylonitrile, 4.5 parts of a mixture of potassium persulfate and ammonium sulfite were added to 100 parts of water, stirred and heated to 80°C, and then cooled to 10°C after the reaction was completed to obtain a reaction compound with emulsifying effect, marked as RHT.

[0052] In the polymerization reaction, 200 parts of water, 4 parts of acetone, 5 parts of RHT were added to 100 parts of monomer, replaced with nitrogen three times, then 0.02 parts of erythorbic acid, 2.5 parts of sodium mercaptoacetate, 60 parts of isoprene, 35 parts of methacrylonitrile were added, the temperature was raised to 80°C, 0.03 parts of ammonium persulfate and ammonium sulfite mixture was added, the conversion rate of the reaction monomer was measured at each time interval. When the conversion rate reached 75%, 0.45 parts of diethylhydroxylamine and 2,5-pentylbenzenediol mixture, 0.8 parts of diphenylamine derivative and polybutyl bisphenol mixture were added, stirred for 30 minutes, then degassed, 0.35 parts of Al2(SO4)3 and NaCl were added to the reaction latex, washed with desalted water three times, and finally dried to obtain nitrile rubber.

[0053] Example 6

[0054] In the polymerization kettle, 100 parts of water, 4 parts of methacrylonitrile, 4.5 parts of a mixture of potassium persulfate and ammonium sulfite were added to 100 parts of water, stirred and heated to 80°C, and then cooled to 30°C after the reaction was completed to obtain a reaction compound with emulsifying effect, marked as RHT.

[0055] In the polymerization reaction, 200 parts of water, 4 parts of acetone, 8 parts of RHT were added to 100 parts of monomer, replaced with nitrogen three times, then 0.02 parts of erythorbic acid, 2.5 parts of sodium mercaptoacetate, 60 parts of butadiene, 32 parts of methacrylonitrile were added, the temperature was raised to 80°C, 0.05 parts of ammonium persulfate and ammonium sulfite mixture was added, the conversion rate of the reaction monomer was measured at each time interval. When the conversion rate reached 70%, 0.45 parts of diethylhydroxylamine and 2,5-pentylbenzenediol mixture, 0.8 parts of diphenylamine derivative and polybutyl bisphenol mixture were added, stirred for 30 minutes, then degassed, 0.35 parts of Al2(SO4)3 and NaCl were added to the reaction latex, washed with desalted water three times, and finally dried to obtain nitrile rubber.

[0056] Table 1 Performance test of examples

[0057]

[0058] Comparative Example 1

[0059] Compared with Example 1, the other implementation conditions are the same, no RHT is added, 3 parts of RHT in Example 1 is replaced with 3 parts of acrylonitrile and added with 20 parts of acrylonitrile, and the rest of the implementation conditions remain unchanged.

[0060] In the polymerization reaction, 150 parts of water, 0.15 parts of ethanol, 0.01 parts of sodium hyposulfite, 1 part of sodium mercaptoacetate, 77 parts of butadiene, and 23 parts of acrylonitrile were added to 100 parts of monomers, and the temperature was raised to 75°C. The conversion rate of the monomers was measured at each time interval. The reaction system was unstable, and the reaction was terminated.

[0061] Comparative Example 2

[0062] In comparison with Example 2, no cosolvent was added, and the remaining conditions were unchanged.

[0063] In the polymerization reactor, 100 parts of water, 6 parts of acrylonitrile, and 0.35 parts of a mixture of potassium persulfate and hyposulfite were added to 100 parts of water, and the temperature was raised to 85°C. After the reaction was completed, the temperature was lowered to 25°C to obtain a reaction compound having an emulsifying effect, which was labeled as RHT.

[0064] In the polymerization reaction, 170 parts of water, 5 parts of RHT, 0.015 parts of dimethyl ketone oxime, 4.5 parts of mercapto propionic acid, 70 parts of butadiene, and 25 parts of acrylonitrile were added to 100 parts of monomers, and the temperature was raised to 80°C. The conversion rate of the monomers was measured at each time interval. When the conversion rate reached 60%, precipitates were generated. When the conversion rate reached 70%, a mixture of 0.3 parts of NaNO2 and 2,5-dicumyl hydroquinone, and 0.6 parts of 2,6-di-tert-butyl-4-methylphenol were added, and the mixture was stirred for 30 minutes. Then, the reaction latex was degassed, and a mixture of 0.2 parts of CaCl2 and NaCl was added. The mixture was washed three times with desalted water, and finally dried to obtain a butadiene-acrylonitrile rubber.

[0065] Comparative Example 3

[0066] In comparison with Example 3, mercapto propionic acid was replaced with an alkyl mercaptan, and the remaining conditions were unchanged.

[0067] In the polymerization reactor, 100 parts of water, 9 parts of acrylonitrile, and 4.5 parts of a mixture of potassium persulfate and hyposulfite were added to 100 parts of water, and the temperature was raised to 85°C. After the reaction was completed, the temperature was lowered to 25°C to obtain a reaction compound having an emulsifying effect, which was labeled as RHT.

[0068] In the polymerization reaction, 170 parts of water, 0.3 parts of acetone, 5 parts of RHT were added, replaced by nitrogen three times, then 0.015 parts of dimethyl ketone oxime, 2.5 parts of dodecyl mercaptan, 70 parts of butadiene, 25 parts of acrylonitrile were added, the temperature was increased to 80℃, 0.02 parts of ammonium persulfate and ammonium sulfite mixture was added, the conversion rate of the reaction monomer was measured every time. When the conversion rate reached 70%, a small amount of solid was precipitated from the system, when the conversion rate exceeded 75%, 0.45 parts of diethyl hydroxylamine and 2,5-pentyl butyl phenol mixture, 0.8 parts of diphenylamine derivative and polybutyl bisphenol mixture were added, stirring for 30 minutes, then degassing, 0.4 parts of CaCl2 and NaCl were added to the reaction latex, washed with desalted water three times, and finally dried to obtain butyl nitrile rubber.

[0069] Comparative Example 4

[0070] Compared with Example 4, in the preparation of the reaction compound in the reaction system, conjugated diene hydrocarbon was added instead of vinyl nitrile monomer, and the polymer preparation reaction was directly carried out, and the rest of the operation conditions were unchanged.

[0071] In the polymerization kettle, 100 parts of water, 4 parts of butadiene, 3 parts of a mixture of potassium persulfate and ammonium sulfite were added, stirring and heating to 80℃, and then the reaction was completed. After cooling to 25℃, a reaction compound was obtained, labeled as A1.

[0072] In the polymerization reaction, 170 parts of water, 4 parts of ethanol, 5 parts of A1 were added, replaced by nitrogen three times, then 0.02 parts of erythorbic acid, 2.5 parts of sodium mercaptoacetate, 70 parts of butadiene, 25 parts of methacrylonitrile were added, the temperature was increased to 80℃, 0.03 parts of ammonium persulfate and ammonium sulfite mixture was added, the conversion rate of the reaction monomer was measured every time. When the conversion rate reached 70%, 0.45 parts of diethyl hydroxylamine and 2,5-pentyl butyl phenol mixture, 0.8 parts of diphenylamine derivative and polybutyl bisphenol mixture were added, stirring for 30 minutes, then degassing, 0.45 parts of CaCl2 and NaCl were added to the reaction latex, washed with desalted water three times, and finally dried to obtain solid particles.

[0073] Table 2 Comparative Example Performance Test

[0074]

[0075] As can be seen from the results of Table 1 and Table 2, the butyl nitrile rubber prepared by the preparation method of the present application has higher tensile strength and lower ash content, realizes soap-free emulsion polymerization, and improves the cleanliness of the product.

[0076] Of course, the present application can have other various embodiments, and those skilled in the art can make various corresponding changes and modifications according to the present application without departing from the spirit and essence of the present application, and these corresponding changes and modifications shall all belong to the protection scope of the claims of the present application.

Claims

1. A method for preparing nitrile rubber, characterized in that, Includes the following steps: (1) In a polymerization reactor, add 100 parts of water, 1-10 parts of vinyl nitrile monomer and 0.1-5 parts of ionizable initiator, stir, heat up, and cool down after the reaction is completed to obtain a reaction compound with emulsifying effect. (2) In the polymerization reaction, water, co-solvent, and 1-10 parts of the reaction compound obtained in step (1) are added based on 100 parts by weight of monomer. Nitrogen gas is introduced for purging, followed by the addition of an oxygen scavenger, a chain transfer agent with surface activity, 40-85 parts of conjugated diene, and 14-51 parts of vinyl nitrile monomer. The temperature is raised, and an ionizable initiator is added. The conversion rate of the reaction monomer is measured at regular intervals. When the conversion rate is greater than or equal to 70%, a terminator and an antioxidant are added, the mixture is stirred, degassed, and a coagulant is added to the reaction latex. The mixture is then rinsed and dried to obtain nitrile rubber.

2. The preparation method according to claim 1, characterized in that, The ionizable initiator is a mixture of at least one of potassium persulfate and ammonium persulfate with at least one of potassium sulfite and ammonium sulfite.

3. The preparation method according to claim 1, characterized in that, In step (2), the amount of the ionizable initiator added is 0.01-5 parts by weight.

4. The preparation method according to claim 1, characterized in that, The co-solvent is at least one of ethanol and acetone, and the amount added is 0.1-4 parts by weight.

5. The preparation method according to claim 1, characterized in that, The conjugated diene is at least one of butadiene and isoprene.

6. The preparation method according to claim 1, characterized in that, The vinyl nitrile monomer is at least one of acrylonitrile and methacrylonitrile.

7. The preparation method according to claim 1, characterized in that, The chain transfer agent with surface-active function is a mercaptoalkyl acid salt compound, and the amount added is 0.05-5 parts by weight.

8. The preparation method according to claim 7, characterized in that, The mercaptoalkyl acid salt compound is at least one of sodium mercaptoacetate and mercaptopropionic acid.

9. The preparation method according to claim 1, characterized in that, The oxygen scavenger is at least one of sodium dithionite, dimethyl ketoxime, and isoascorbic acid, and the amount added is 0.005-0.02 parts by weight.

10. The preparation method according to claim 1, characterized in that, The terminator is at least one of NaNO2, hydroxylamine sulfate, diethylhydroxylamine, and 2,5-pentanebutylquinone, and is added in an amount of 0.05-0.5 parts by weight.

11. The preparation method according to claim 1, characterized in that, The antioxidant is at least one of tris(nonylphenyl) phosphite, diphenylamino derivative, polybutyl bisphenol, and 2,6-di-tert-butyl-4-methylphenol, and is added in an amount of 0.1-1 parts by weight.

12. The preparation method according to claim 1, characterized in that, The coagulant is at least one of CaCl2, Al2(SO4)3, and NaCl, and the amount added is 0.01-0.5 parts by weight.

13. The preparation method according to claim 1, characterized in that, The raw rubber of the nitrile rubber prepared by the method has a raw rubber bond of 12-50 wt% acrylonitrile and a Mooney viscosity of ML. 1+4 100℃: 20~95, ash content ≤0.5wt%.

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