Nitrile rubber, and preparation method therefor and use thereof

Abstract

The present invention relates to the technical field of synthetic rubbers, and specifically relates to a nitrile rubber, and a preparation method therefor and the use thereof. In the preparation method, a composite emulsifier system formed by compounding at least disproportionated rosin acid soap, a C10-C13 linear alkyl benzene sulfonic acid and a sodium salt of naphthalene sulfonic acid formaldehyde condensate, and a low-temperature emulsion polymerization process are used, and a reactive anti-aging agent is introduced into emulsion polymerization, such that specific groups are effectively bonded into polymer molecular chains, and the obtained nitrile rubber can be used in the field of oil-resistant sealing in high-temperature operation environments.

Description

Nitrile butadiene rubber and its preparation method and application

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese patent applications 202311506025.4 and 202311502026.1 filed on November 13, 2023, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of synthetic rubber, and in particular to a nitrile rubber, a preparation method of the nitrile rubber, and an application of the nitrile rubber. Background Art

[0004] Nitrile rubber (NBR) boasts excellent oil resistance, heat resistance, wear resistance, gas permeability resistance, high modulus of elongation, hardness, and tensile strength, making it widely used in oil-resistant hoses for hydraulic transmission systems. Nitrile rubber is a type of rubber produced primarily through emulsion polymerization of butadiene and acrylonitrile. Due to the presence of double bonds in NBR molecules, the α-hydrogen is very reactive and susceptible to degradation under the influence of heat and oxygen, causing changes in the material's molecular structure. Over time, NBR gradually ages, losing its elasticity and degrading its mechanical properties. This is primarily due to the high temperatures during use in hot oil, where the antioxidants added to the formula are extracted, rendering the physical and chemical protection ineffective.

[0005] Normally in some current schemes, the mode of adding antioxidant is delayed or suppressed the oxidized process of NBR, to stop its aging, improve the retention rate of properties such as mechanics in its use process, yet, the antioxidant added is easy to be extracted under the high temperature environment, thereby causes the invalidation of NBR physical protection and chemical protection. Because the increase of acrylonitrile content causes vulcanized rubber elasticity, anti-compression set poor, the aging process performance retention rate is low, causes long-term service life in hot oil or hot air greatly shortened. This is mainly because when using in hot oil, the antioxidant added in the formula is extracted at high temperature, thereby causes the invalidation of physical protection and chemical protection.

[0006] Reactive antioxidants are amine or phenolic compounds that have both anti-aging and polymerization monomer functions. During copolymerization, they can enter the main chain of diene rubber and become part of the polymer molecule. Therefore, this type of nitrile rubber product is stable under the conditions of use. The antioxidant will not be lost due to the effects of oil, solvent and heat, thereby extending the service life and can be used in more harsh environments. Its anti-aging effect is 3-4 times that of non-reactive antioxidants added after polymerization.

[0007] Polymer-stabilized nitrile rubber (PSN) was developed based on research into reactive antioxidants. PSN exhibits superior aging resistance. Goodyear Tire & Rubber Company in the United States pioneered research into the application of PSN, which has since found application in the U.S. automotive industry.

[0008] US4078091 discloses a polymer or copolymer of N-(3,5-disubstituted-4-hydroxyphenyl)maleimide; US4152319 discloses a copolymer prepared from N-(3,5-disubstituted-4-hydroxyphenyl)imide substituted with maleic acid, itaconic acid and citric anhydride; JP56139541 discloses a copolymer of N-(p-anilinophenyl)maleimide with acrylonitrile and butadiene; DE2025336 discloses a copolymer of the same N-substituted maleimide with isoprene; CA677494 discloses a reactive antioxidant 2,6-di-tert-butyl-4-(N-maleimidomethyl)phenol; US3767628 discloses a reactive antioxidant N-[4-(anilino)phenyl]maleimide; US3 US Pat. No. 956298 and US Pat. No. 4,066,616 both disclose an N-[2-hydroxy-3-(3-tert-butyl-4-hydroxy-5-methylphenyl)-propyl]maleimide reactive antioxidant; and US Pat. No. 4,138,389, US Pat. No. 4,857,596, and US Pat. No. 4,981,917 all disclose a polymer-bonded antioxidant, which utilizes an amide group or a diacyl hydrazide to bond the antioxidant group to the polymer molecular chain, and is prepared by reacting the hydrazide-substituted antioxidant with an acid anhydride compound contained in the polymer.

[0009] However, the above-mentioned existing technologies all have the following problems: the heat-resistant nitrile rubber has a low acrylonitrile content, faces a lot of fine particles during coagulation, and is difficult to wash and dry during post-processing. In addition, the heat-resistant nitrile rubber obtained cannot have excellent heat-resistant oxygen aging resistance and mechanical properties.

[0010] Summary of the Invention

[0011] The purpose of the present invention is to overcome the above-mentioned technical problems and provide a nitrile rubber, a preparation method of nitrile rubber, and an application of nitrile rubber. The preparation method adopts a ternary compounded emulsification system and a low-temperature polymerization process, combined with a reactive antioxidant, to bond specific antioxidant groups to the polymer molecular chain. The prepared nitrile rubber not only has high polymerization stability, but also has excellent resistance to heat and oxygen aging, and is particularly suitable for the field of sealing in high-temperature working environments.

[0012] In order to achieve the above object, the first aspect of the present invention provides a method for preparing nitrile rubber, the preparation method comprising: in the presence of an initiator, using butadiene and acrylonitrile as polymerization monomers, using a reactive antioxidant with an acrylamide group as a functional monomer; using a low-temperature emulsion polymerization method, a composite emulsifier containing at least disproportionated rosin acid soap, C 10 -C 13 Sodium salt of linear alkylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate and a molecular weight regulator are added once or multiple times to synthesize nitrile butadiene rubber mortar, a terminator is added, and the nitrile butadiene rubber is obtained after degassing, coagulation, washing and drying.

[0013] The present invention adopts a specific composite emulsifying system. The composite emulsifier is at least a mixture of disproportionated rosin acid soap, linear alkylbenzene sulfonic acid and sodium salt of naphthalenesulfonic acid formaldehyde condensate.

[0014] The amount of the composite emulsifier added in the present invention can be the amount of emulsifiers commonly used in the art, especially when anionic emulsifiers and nonionic emulsifiers are compounded. The amount of the composite emulsifier used in the present invention is preferably 2.8-6.5 parts by weight, preferably 3.2-6.5 parts by weight, more preferably 3.35-6 parts by weight, and more preferably 3.8-6 parts by weight.

[0015] The present invention requires that the disproportionated rosin acid soap added to the composite emulsifier be either potassium soap or sodium soap. The disproportionated rosin acid soap or sodium soap in the composite emulsifier system of the present invention cannot be replaced with other anionic emulsifiers such as sodium lauryl sulfate, potassium oleate, and potassium stearate. This is because the inventors have discovered that, in the specific emulsion polymerization system of the present invention, the addition of disproportionated rosin acid soap or sodium soap increases the polymer emulsion particle size due to a synergistic effect, which is particularly beneficial for the subsequent emulsion coagulation process after emulsion polymerization. The amount of disproportionated rosin acid soap and / or sodium soap added can be adjusted based on the desired polymer emulsion particle size, particularly the difficulty of the emulsion coagulation process after emulsion polymerization. Preferably, the amount of disproportionated rosin acid soap and / or sodium soap added is 2-4.5 parts by weight, preferably 2-4 parts by weight, and more preferably 2.5-4 parts by weight.

[0016] The present invention requires that C be added to the composite emulsifier 10 -C 13Linear alkylbenzene sulfonic acid. The linear alkylbenzene sulfonic acid and linear alkylbenzene sodium sulfonate have different effects. If only linear alkylbenzene sodium sulfonate is added without linear alkylbenzene sulfonic acid, its effect is different from that of the present invention. This is because sodium alkylbenzene sulfonate is a saponification product of alkylbenzene sulfonic acid. Due to the use of alkylbenzene sulfonic acid, some alkylbenzene sulfonic acid will not be completely saponified during its saponification process. A synergistic effect will occur between the two, which will improve the stability of the entire polymerization system and the efficiency of the polymerization reaction. Therefore, linear alkylbenzene sulfonic acid in the composite emulsification system of the present invention cannot be replaced by linear alkylbenzene sodium sulfonate. As an emulsifier, C 10 -C 13 The most commonly used linear alkylbenzenesulfonic acid is dodecylbenzenesulfonic acid. 10 -C 13 The linear alkylbenzene sulfonic acid is preferably added in an amount of 0.5-2 parts by weight, preferably 0.5-1.5 parts by weight, more preferably 1-1.5 parts by weight.

[0017] The present invention requires that the sodium salt of naphthalenesulfonic acid formaldehyde condensate and C 10 -C 13 The use of linear alkylbenzene sulfonic acid is also known in the art, and its amount is determined as needed and is not particularly limited in the present invention. Omission of this addition can lead to decreased stability of the polymer emulsion and increased risk of glue buildup during polymerization. The preferred amount of naphthalenesulfonic acid formaldehyde condensate sodium salt is 0.2-0.5 parts by weight, preferably 0.3-0.5 parts by weight, and more preferably 0.35-0.5 parts by weight.

[0018] The present invention does not exclude the addition of other anionic emulsifiers or nonionic emulsifiers to the composite emulsification system in addition to the disproportionated potassium or sodium soap of rosin acid, linear alkylbenzenesulfonic acid and sodium salt of naphthalenesulfonic acid formaldehyde condensate, such as at least one of sodium dodecylbenzenesulfonate, sodium lauryl sulfate, potassium oleate, potassium stearate, sorbitan tristearate and octylphenol polyoxyethylene ether.

[0019] The second aspect of the present invention provides a nitrile rubber prepared by the preparation method provided in the first aspect.

[0020] The third aspect of the present invention provides an application of the nitrile rubber provided in the second aspect in the field of oil-resistant sealing in a high-temperature working environment.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] The present invention provides a method for preparing heat-oxidative aging-resistant nitrile rubber with a simple process, which comprises the following steps: 10 -C 13A composite emulsifier system consisting of linear alkylbenzenesulfonic acid and sodium salt of naphthalenesulfonic acid formaldehyde condensate and a low-temperature emulsion polymerization process are used. Reactive antioxidants are introduced into the emulsion polymerization to effectively bond specific groups to the polymer molecular chains. This also solves the technical problems of large amounts of fine particles during coagulation and difficulty in washing and drying during the post-processing process.

[0023] At the same time, the preparation method provided by the present invention can effectively improve the heat-oxidative aging resistance of nitrile rubber, provide better tensile strength and elongation at break, and can be used in the field of oil-resistant sealing in high-temperature working environments.

[0024] The present invention also finds that adding acrylonitrile in batches multiple times, especially four times, can also reduce the glass transition temperature of the heat-resistant nitrile rubber, so that the polymer has excellent high-temperature and low-temperature resistance; the nitrile rubber produced using the method of the present invention has good heat-oxidative aging resistance, and the nitrile rubber meets the application requirements of oil-resistant seals in high-temperature working environments. DETAILED DESCRIPTION

[0025] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0026] The first aspect of the present invention provides a method for preparing nitrile rubber, the method comprising: in the presence of an initiator, using butadiene and acrylonitrile as polymerization monomers, using a reactive antioxidant with an acrylamide group as a functional monomer; using a low-temperature emulsion polymerization method, a composite emulsifier containing at least disproportionated rosin acid soap, C 10 -C 13 Sodium salt of linear alkylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate and a molecular weight regulator are added once or multiple times to synthesize nitrile butadiene rubber mortar, a terminator is added, and the nitrile butadiene rubber is obtained after degassing, coagulation, washing and drying.

[0027] Those skilled in the art know that, when a composite emulsification system is usually used for emulsion polymerization of nitrile rubber, its emulsifier includes a primary emulsifier and a secondary emulsifier. The primary emulsifier can be one or more anionic emulsifiers, such as at least one of potassium disproportionate rosin acid, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, potassium oleate and potassium stearate, or other anionic emulsifiers; the secondary emulsifier can be a nonionic emulsifier, such as at least one of sorbitan tristearate, sodium β-naphthalenesulfonate formaldehyde condensate and octylphenol polyoxyethylene ether, or other nonionic emulsifiers.

[0028] However, the present invention adopts a specific composite emulsification system, in which the composite emulsifier is at least selected from the group consisting of disproportionate potassium rosin acid soap and / or sodium soap, linear alkylbenzene sulfonic acid and sodium naphthalene sulfonate formaldehyde condensate, which has a synergistic effect and thus improves the stability of the latex in the nitrile rubber mortar. The respective addition amounts can be adjusted as needed. The addition amount of the composite emulsifier can be the addition amount of the composite emulsifier commonly used in the art, especially the amount used when anionic emulsifiers and non-ionic emulsifiers are used for compounding. Preferably, the amount of the disproportionate rosin acid soap is 2-4.5 parts by weight relative to 100 parts by weight of the polymerized monomer; preferably, the amount of the linear alkylbenzene sulfonic acid is 0.5-2 parts by weight; preferably, the amount of the sodium salt of the naphthalene sulfonic acid formaldehyde condensate is 0.2-0.5 parts by weight.

[0029] In some embodiments of the present invention, further preferably, the amount of the disproportionated rosin acid soap is 2-4 parts by weight relative to 100 parts by weight of the polymerized monomer, and the C 10 -C 13 The amount of linear alkylbenzenesulfonic acid used is 0.5-1.5 parts by weight, and the amount of naphthalenesulfonic acid formaldehyde condensate sodium salt used is 0.3-0.5 parts by weight.

[0030] In some embodiments of the present invention, more preferably, the amount of the disproportionated rosin acid potassium soap and / or sodium soap is 2.5-4 parts by weight relative to 100 parts by weight of the polymerized monomer; 10 -C 13 The amount of linear alkylbenzenesulfonic acid used is 1-1.5 parts by weight; the amount of naphthalenesulfonic acid formaldehyde condensate sodium salt used is 0.35-0.5 parts by weight.

[0031] In the composite emulsification system of the present invention, the disproportionated rosin acid soap is preferably used in an amount of 2-4.5 parts by weight, for example, 2 parts by weight, 2.5 parts by weight, 3 parts by weight, 3.5 parts by weight, 4 parts by weight, 4.5 parts by weight, and any value within a range consisting of any two of these values, preferably 2-4 parts by weight, and more preferably 2.5-4 parts by weight. The disproportionated rosin acid soap in the composite emulsification system of the present invention can be replaced with other anionic emulsifiers such as sodium lauryl sulfate, potassium oleate, and potassium stearate. This is because the inventors have discovered that in the specific emulsion polymerization system of the present invention, the addition of the disproportionated rosin acid soap increases the particle size of the polymer emulsion due to a synergistic effect, which is particularly beneficial to the emulsion coagulation process after the subsequent emulsion polymerization.

[0032] In some specific embodiments of the present invention, the disproportionated rosin acid soap is selected from disproportionated rosin acid potassium soap and / or disproportionated rosin acid sodium soap, that is, it can be selected from disproportionated rosin acid potassium soap, disproportionated rosin acid sodium soap, or disproportionated rosin acid potassium soap and disproportionated rosin acid sodium soap.

[0033] In the composite emulsification system of the present invention, preferably, the C 10 -C 13 The amount of linear alkylbenzene sulfonic acid is 0.5-2 parts by weight, for example, 0.5 parts by weight, 1 part by weight, 1.1 parts by weight, 1.3 parts by weight, 1.4 parts by weight, 1.5 parts by weight, 2 parts by weight, and any value in the range of any two values, preferably 0.5-1.5 parts by weight, more preferably 1-1.5 parts by weight. In the present invention, the effects of linear alkylbenzene sulfonic acid and linear alkylbenzene sodium sulfonate are different, and only adding C 10 -C 13 Sodium linear alkylbenzene sulfonate without adding C 10 -C 13 The role of linear alkylbenzene sulfonic acid differs from that of the present invention because sodium dodecylbenzene sulfonate is a saponification product of dodecylbenzene sulfonic acid. Due to the use of dodecylbenzene sulfonic acid, some dodecylbenzene sulfonic acid is not completely saponified during the saponification process. This creates a synergistic effect between the two, improving the stability of the entire polymerization system and the efficiency of the polymerization reaction. Therefore, sodium linear alkylbenzene sulfonate cannot be used to replace linear alkylbenzene sulfonic acid in the composite emulsification system of the present invention.

[0034] In some embodiments of the present invention, the C 10 -C 13 The linear alkylbenzenesulfonic acid is at least one selected from the group consisting of decanylbenzenesulfonic acid, undecylbenzenesulfonic acid, dodecylbenzenesulfonic acid and tridecylbenzenesulfonic acid, preferably dodecylbenzenesulfonic acid.

[0035] In the composite emulsification system of the present invention, the amount of the sodium salt of naphthalenesulfonic acid formaldehyde condensate is preferably 0.2-0.5 parts by weight, for example, 0.2 parts by weight, 0.3 parts by weight, 0.35 parts by weight, 0.4 parts by weight, 0.45 parts by weight, 0.5 parts by weight, and any value within a range consisting of any two of these values, preferably 0.3-0.5 parts by weight, and more preferably 0.35-0.5 parts by weight. If the sodium salt of naphthalenesulfonic acid formaldehyde condensate is not added, the stability of the polymer emulsion will be reduced, and glue will easily appear during the polymerization process.

[0036] In some specific embodiments of the present invention, the sodium salt of naphthalenesulfonic acid formaldehyde condensate includes but is not limited to sodium β-naphthalenesulfonate formaldehyde condensate and the like.

[0037] In the present invention, the composite emulsifier includes disproportionated rosin acid potassium soap and / or sodium soap, C 10 -C 13In addition to the sodium salt of linear alkylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate, the composite emulsifier also contains other anionic emulsifiers and nonionic emulsifiers. Preferably, the composite emulsifier also contains at least one of sodium dodecylbenzenesulfonate, sodium lauryl sulfate, potassium oleate, potassium stearate, sorbitan tristearate, and octylphenol polyoxyethylene ether.

[0038] In some embodiments of the present invention, preferably, the composite emulsifier is composed of disproportionated rosin acid potassium soap and / or sodium soap, C 10 -C 13 It is composed of linear alkylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate sodium salt.

[0039] In some embodiments of the present invention, preferably, relative to 100 parts by weight of the polymerized monomer, the amount of the composite emulsifier is 2.8-6.5 parts by weight, for example, 2.8 parts by weight, 3 parts by weight, 3.3 parts by weight, 3.35 parts by weight, 3.8 parts by weight, 4 parts by weight, 4.5 parts by weight, 5 parts by weight, 5.5 parts by weight, 6 parts by weight, 6.5 parts by weight, and any value in the range consisting of any two numerical values, preferably 3.2-6.5 parts by weight, more preferably 3.35-6 parts by weight, and more preferably 3.8-6 parts by weight.

[0040] In some embodiments of the present invention, preferably, relative to 100 parts by weight of the polymerized monomer, the amount of the reactive antioxidant is 0.5-3 parts by weight, for example, 0.5 parts by weight, 1 part by weight, 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, 3 parts by weight, and any value in the range consisting of any two numerical values, preferably 1-2.5 parts by weight, more preferably 1.5-2.5 parts by weight.

[0041] The reactive antioxidant selected in the present invention is a reactive antioxidant with an acrylamide group. In this technical field, reactive antioxidants with an amide group having an aniline phenyl group are generally used. The general formula is

[0042] Wherein, R1 and R2 represent hydrogen, chlorine, bromine or an alkyl group having 1-12 carbon atoms respectively; R3 represents hydrogen or an alkyl group having 1-4 carbon atoms; R4 represents hydrogen, or an alkyl group having 1-4 carbon atoms, or an aryl group having 6-12 carbon atoms, and R4 and R3 may be the same or different; preferably, this type of reactive antioxidant is selected from N-(4-anilinophenyl)acrylamide, N-(4-anilinophenyl)methacrylamide, N-(4-anilinophenyl)cinnamamide, N-(4-anilinophenyl)crotonamide, N-[4-(4-methylanilino)phenyl]acrylamide and N-[4-(4-methylanilino)phenyl]methacrylamide. The most typical types are N-[4-(anilino)phenyl]methacrylamide and N-[4-(anilino)phenyl]pivalamide. These are used as functional monomers in the polymerization reaction. Typically, when the reactive antioxidant is incorporated into the nitrile rubber at a concentration of 1-2 wt%, it exhibits excellent resistance to thermal oxidative aging, enabling its use in oil-resistant seals in high-temperature operating environments. Different types of acrylamide do not affect the unique effects of the present invention.

[0043] In some embodiments of the present invention, preferably, the reactive antioxidant is selected from N-[4-(anilino)phenyl]methacrylamide and N-[4-(anilino)phenyl]pivalamide.

[0044] The synthesis method of the nitrile rubber of the present invention is low-temperature emulsion polymerization. The polymerization temperature used for low-temperature emulsion polymerization commonly used in the art can be any polymerization temperature and is not particularly limited. Preferably, the conditions of the low-temperature emulsion polymerization include: a temperature of 5-15°C, preferably 5-12°C, more preferably 5-8°C; and a time of 10-30 hours, preferably 15-25 hours.

[0045] In the present invention, the low-temperature emulsion polymerization can be either batch polymerization or continuous polymerization.

[0046] In some embodiments of the present invention, preferably, the amount of the initiator used is 0.1-0.3 parts by weight relative to 100 parts by weight of the polymerizable monomer, for example, 0.1 parts by weight, 0.2 parts by weight, 0.25 parts by weight, 0.3 parts by weight, and any value within a range consisting of any two of these values, preferably 0.2-0.3 parts by weight. In the present invention, the amount of the initiator used is based on the organic hydroperoxide.

[0047] The present invention does not particularly limit the initiator, and any initiator commonly used in high-temperature emulsion polymerization of nitrile rubber can be used. Preferably, the initiator is selected from organic hydrogen peroxide-ferrous salt, and the organic hydrogen peroxide is diisopropylbenzene hydroperoxide. In the present invention, the initiator includes but is not limited to diisopropylbenzene hydroperoxide-ferrous salt, isopropylbenzene hydroperoxide-ferrous salt, etc.

[0048] The present invention also does not particularly limit the molecular weight regulator and the amount thereof, and any molecular weight regulator and amount thereof commonly used in acrylonitrile-butadiene rubber can be used. Preferably, the molecular weight regulator is selected from tert-dodecyl mercaptan and / or n-dodecyl mercaptan, preferably tert-dodecyl mercaptan.

[0049] In the present invention, the amount of the molecular weight regulator can be adjusted according to the product performance requirements and the type of molecular weight regulator. Preferably, the amount of the molecular weight regulator is 0.3-0.8 parts by weight, for example, 0.3 parts by weight, 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, and any value within a range consisting of any two of these values, preferably 0.5-0.8 parts by weight, relative to 100 parts by weight of the polymerizable monomer.

[0050] In the present invention, the molecular weight regulator is added once or multiple times during the low-temperature emulsion polymerization, and the amount can be selected based on the different product performance requirements. Preferably, the molecular weight regulator is added at least twice, with the initial addition amount being 40-60% of the total molecular weight regulator amount. More preferably, the molecular weight regulator is added at least twice, with the remaining molecular weight regulator added when the conversion rate of the low-temperature emulsion polymerization reaches 50-55% during the second addition.

[0051] The present invention does not particularly limit the timing of adding the terminator. The terminator can be selected to achieve different conversion rates of the nitrile butadiene rubber mortar according to product requirements. Preferably, the terminator is added when the conversion rate of the low-temperature emulsion polymerization reaches 70% or more; more preferably, the terminator is added when the conversion rate of the low-temperature emulsion polymerization reaches 70-76%.

[0052] In some embodiments of the present invention, preferably, the amount of the terminator added is 0.05-0.15 parts by weight relative to 100 parts by weight of the polymerizable monomer.

[0053] The present invention also does not particularly limit the type and amount of the terminator, and any common terminator can be used. Preferably, the terminator includes but is not limited to sodium nitrite, hydroxylamine sulfate, diethylhydroxylamine, etc.

[0054] The present invention does not exclude the addition of other commonly used additives for butyronitrile emulsion polymerization into the polymerization system, such as deionized water, electrolytes, reducing agents, chelating agents, etc., and the addition amount range is the general addition amount range.

[0055] In some embodiments of the present invention, preferably, at least one of deionized water, an electrolyte, a reducing agent, and a chelating agent is further added during the low-temperature emulsion polymerization process.

[0056] The present invention does not particularly limit the type and amount of the electrolyte; a general-purpose electrolyte and general-purpose amount can be used. Preferably, the electrolyte is used in an amount of 0.1-0.5 parts by weight per 100 parts by weight of the polymerized monomer. More preferably, the electrolyte is selected from at least one of potassium hydroxide, sodium pyrophosphate, and sodium carbonate.

[0057] The present invention does not particularly limit the type and amount of the reducing agent; a general reducing agent and a general amount can be used. Preferably, the reducing agent is used in an amount of 0.01-0.15 parts by weight per 100 parts by weight of the polymerizable monomer. More preferably, the reducing agent is selected from at least one of ferrous sulfate, sodium ferric ethylenediaminetetraacetate, and sodium thiosulfate.

[0058] The present invention does not particularly limit the type and amount of the chelating agent; a general-purpose chelating agent and a general-purpose amount can be used. Preferably, the chelating agent is used in an amount of 0.01-0.05 parts by weight per 100 parts by weight of the polymerizable monomers. More preferably, the chelating agent is selected from disodium ethylenediaminetetraacetate and / or tetrasodium ethylenediaminetetraacetate.

[0059] The present invention does not particularly limit the specific ratio of butadiene and acrylonitrile in the polymerization monomers, and adopts any proportioning commonly used in the prior art to prepare acrylonitrile-butadiene rubber (such as acrylonitrile content 15-50%). Because the increase of acrylonitrile content causes the vulcanized rubber elasticity and anti-compression set to be poor, the aging process performance retention rate is low, causing the long-term service life to be greatly shortened in hot oil or hot air. Therefore, during the polymerization of this type of acrylonitrile-butadiene rubber, the acrylonitrile monomer content is lower.

[0060] In some embodiments of the present invention, preferably, relative to 100 parts by weight of polymerized monomers, the amount of acrylonitrile is less than 30 parts by weight, preferably less than 25 parts by weight; further preferably, relative to 100 parts by weight of polymerized monomers, the amount of acrylonitrile is 17-20 parts by weight, and the amount of butadiene is 80-83 parts by weight. In the present invention, when the amount of acrylonitrile is 20 parts by weight, the amount of butadiene is 80 parts by weight. But if the amount of acrylonitrile is too low, the resulting powdering will be serious during coagulation, and the problem of being difficult to coagulate will occur. The inventors of the present invention have found that due to the use of disproportionated rosin acid potassium soap and / or sodium soap in the emulsifier, the synergistic effect of the three types of compounding of disproportionated rosin acid potassium soap and / or sodium soap, linear alkylbenzene sulfonic acid and sodium naphthalenesulfonate formaldehyde condensate increases the polymer emulsion particle size, which is particularly beneficial to the emulsion coagulation process after subsequent emulsion polymerization, and is particularly suitable for the preparation of acrylonitrile-butadiene rubber with low content of acrylonitrile.

[0061] In the present invention, unless otherwise specified, the acrylonitrile monomer may be added all at once, continuously, or in multiple additions of more than two times.

[0062] The present invention also provides a preferred method for preparing nitrile rubber, comprising the following steps: based on 100 parts by weight of butadiene and acrylonitrile, preparing a monomer composition comprising: 80-83 parts by weight of butadiene, 17-20 parts by weight of acrylonitrile, 1.5-2.5 parts by weight of a reactive antioxidant with an acrylamide group, and 200-230 parts by weight of deionized water; and preparing an emulsification system formed by compounding a composite emulsifier containing at least 2-4.5 parts by weight of disproportionated rosin acid soap, 0.5-2 parts by weight of linear alkylbenzene sulfonic acid, and 0.2-0.5 parts by weight of sodium salt of naphthalenesulfonic acid formaldehyde condensate; the initiator being selected from organic hydrogen peroxide-ferrous salt in an amount of 0.1-0.3 parts by weight; the molecular weight regulator being selected from tert-dodecyl mercaptan in an amount of 0.3-0.8 parts by weight; the initiator being added once; the monomers being added once or multiple times; and the molecular weight regulator being preferably added at least twice, and the polymerization temperature being 5-15°C. Preferably, the amount of the composite emulsifier is 2.8-6.5 parts by weight relative to 100 parts by weight of the polymerizable monomer. Preferably, acrylonitrile is added in three or more additions, preferably four additions.

[0063] The present invention also provides a more preferred method for preparing nitrile rubber, comprising the following steps: based on 100 parts by weight of butadiene and acrylonitrile, the monomer composition comprises: 80-83 parts by weight of butadiene, 17-20 parts by weight of acrylonitrile, 1.5-2.5 parts by weight of a reactive antioxidant with an acrylamide group, 200-230 parts by weight of deionized water, and the composite emulsifier comprises at least 2-4.5 parts by weight of disproportionated rosin acid potassium soap and / or sodium soap, 0.5-1.5 parts by weight of linear alkylbenzenesulfonic acid, 0. The emulsifier is prepared by mixing 3-0.5 parts by weight of the composite emulsifier; the initiator is selected from organic hydrogen peroxide-ferrous salt, and the amount thereof is 0.1-0.3 parts by weight; the molecular weight regulator is selected from tert-dodecyl mercaptan, and the amount thereof is 0.5-0.8 parts by weight; the initiator is added once; the monomer is added once or multiple times; the molecular weight regulator is added at least twice, and the polymerization temperature is 5-8°C; preferably, the amount of the composite emulsifier is 2.8-6.5 parts by weight, more preferably 3.35-6 parts by weight, relative to 100 parts by weight of the polymerized monomer.

[0064] The present invention does not particularly limit the timing of adding the terminator, which can be determined according to the performance requirements of different products. Preferably, the terminator is added when the conversion rate of the low-temperature emulsion polymerization reaches 70-76%.

[0065] The present invention also provides a most preferred method for preparing nitrile rubber, comprising the following steps: after evacuating a polymerization kettle, adding deionized water, an emulsifier, a reducing agent, an electrolyte, a chelating agent, all polymerization monomers, and 40-60% of a molecular weight regulator; after controlling the temperature to 5-8° C., adding the initiator; when the conversion rate of the low-temperature emulsion polymerization reaches 50-55%, adding the remaining molecular weight regulator; when the conversion rate of the low-temperature emulsion polymerization reaches 70-76%, adding the terminator; discharging the material; and performing degassing, coagulation, washing, and drying to obtain the nitrile rubber.

[0066] The present invention also provides another preferred method for preparing nitrile rubber, which comprises at least: using butadiene and acrylonitrile as polymerization monomers, and using a reactive antioxidant with an acrylamide group as a functional monomer; based on the total amount of butadiene and acrylonitrile added as 100 parts by weight, wherein the acrylonitrile content is less than 25 parts by weight, and the acrylonitrile is added in batches or continuously, preferably more than three times; using a low-temperature emulsion polymerization method, using a composite emulsifying system, wherein the composite emulsifier contains at least disproportionated rosin acid soap, C 10 -C 13 Sodium salt of linear alkylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate; preferably, the amount of the composite emulsifier added is 3.2-6.5 parts by weight, more preferably 3.8-6 parts by weight, the molecular weight regulator is added once or multiple times, the nitrile rubber slurry is synthesized, a terminator is added, and the nitrile rubber is obtained after degassing, coagulation, washing and drying.

[0067] In the present invention, when the amount of acrylonitrile is less than 25 parts by weight relative to 100 parts by weight of the polymerizable monomer, acrylonitrile is added continuously or in batches, preferably more than three times, especially four times, which significantly improves the distribution of acrylonitrile in the molecular chain segments, significantly reduces the glass transition temperature of the polymer, and makes the polymer have excellent high and low temperature resistance.

[0068] In some embodiments of the present invention, it is further preferred that the acrylonitrile is added in four batches: when the conversion rate of the low-temperature emulsion polymerization reaches 30-35%, acrylonitrile is added in the first batch; when the conversion rate of the low-temperature emulsion polymerization reaches 45-55%, acrylonitrile is added in the second batch; when the conversion rate of the low-temperature emulsion polymerization reaches 60-65%, acrylonitrile is added in the third batch.

[0069] In some embodiments of the present invention, more preferably, the amount of acrylonitrile added for the first time is 30-50% of the total amount of acrylonitrile added.

[0070] The present invention also provides another more preferred method for preparing nitrile rubber, comprising the following steps: based on 100 parts by weight of butadiene and acrylonitrile, the monomer composition is: 80-83 parts by weight of butadiene, 17-20 parts by weight of acrylonitrile, 1.5-2.5 parts by weight of a reactive antioxidant with an acrylamide group, 200-230 parts by weight of deionized water, the composite emulsifier comprising disproportionated rosin acid soap, C 10 -C 13 A linear alkylbenzenesulfonic acid, naphthalenesulfonic acid formaldehyde condensate sodium salt composite emulsification system, the composite emulsifier is used in an amount of 3.2-6.5 parts by weight, and the disproportionated rosin acid soap is used in an amount of 2-4 parts by weight, C 10 -C 13 The amount of linear alkylbenzenesulfonic acid is 1-2 parts by weight, the amount of naphthalenesulfonic acid formaldehyde condensate sodium salt is 0.2-0.5 parts by weight; the initiator is organic hydrogen peroxide-ferrous salt, the amount of which is 0.1-0.3 parts by weight; the molecular weight regulator is tert-dodecyl mercaptan, the amount of which is 0.3-0.8 parts by weight; acrylonitrile is added in three or more times; the polymerization reaction temperature is 5-15° C.; and the amount of the composite emulsifier is preferably 3.8-6 parts by weight.

[0071] The present invention also provides another most preferred method for preparing nitrile butadiene rubber, comprising the following steps: after vacuuming a polymerization kettle, adding deionized water, a composite emulsifier, a reducing agent, an electrolyte, a chelating agent, butadiene, a first acrylonitrile, and a molecular weight regulator; after controlling the temperature to 8-12°C, adding an initiator; when the conversion rate of the low-temperature emulsion polymerization reaches 30-35%, adding a second acrylonitrile; when the conversion rate of the low-temperature emulsion polymerization reaches 45-55%, adding a third acrylonitrile; when the conversion rate of the low-temperature emulsion polymerization reaches 60-65%, adding a fourth acrylonitrile; when the conversion rate of the low-temperature emulsion polymerization reaches 70-76%, adding a terminator, discharging the material, and performing degassing, coagulation, washing, and drying to obtain the nitrile butadiene rubber.

[0072] The second aspect of the present invention provides a nitrile rubber prepared by the preparation method provided in the first aspect.

[0073] In some embodiments of the present invention, preferably, based on the total content of the nitrile rubber, the content of combined acrylonitrile is ≥17wt%, preferably 17-20wt%, for example, 17wt%, 18wt%, 18.5wt%, 19wt%, 19.5wt%, 20wt%, and any value in the range of any two numerical values; the content of combined reactive antioxidant is ≥1wt%, preferably 1-2wt%, for example, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2wt%, and any value in the range of any two numerical values.

[0074] In some embodiments of the present invention, preferably, by adopting the method of the present invention, a nitrile rubber with a latex particle size of ≥100 nm, preferably 100-130 nm, can be obtained.

[0075] In some embodiments of the present invention, preferably, the Mooney viscosity can be obtained by using the method of the present invention. The tensile strength is 20-30MPa, preferably 20-25MPa of nitrile rubber.

[0076] In the present invention, unless otherwise specified, the total solid content is measured using SH / T 1154-92; the acrylonitrile content is measured using SH / T 1157-1997; the Mooney viscosity is The test was conducted in accordance with GB / T 1232-2000; the tensile strength test was conducted in accordance with GB / T 528-1998; the elongation at break test was conducted in accordance with GB / T 528-1998; and the reactive antioxidant content parameters were tested using a nuclear magnetic resonance spectrometer with a frequency of 400mHz and a magnetic field strength of 9.40T.

[0077] The third aspect of the present invention provides an application of the nitrile rubber provided in the second aspect in the field of oil-resistant seals in high-temperature working environments, preferably in oil-resistant products in high-temperature working environments.

[0078] The nitrile rubber produced using the method of the present invention not only has good polymerization stability, but also can produce nitrile rubber with high heat-oxidative aging resistance, meeting the application requirements of oil-resistant seals in high-temperature working environments; in addition, when the preparation method is used to synthesize the mortar, the polymerization process is smooth and the energy consumption is low.

[0079] It can be seen from the best production scheme in the embodiment that the preparation method of the present invention can produce acrylonitrile with a content of 17-20 wt% and a Mooney viscosity of The nitrile rubber with a molecular weight of 40-70 and a reactive antioxidant content of 1-2 wt% and good heat-oxidative aging resistance can be used in the oil-resistant sealing field in high-temperature working environments.

[0080] The present invention will be described in detail below through examples.

[0081] Total solids test was measured using SH / T 1154-92;

[0082] Mooney viscosity The test was conducted according to GB / T 1232-2000;

[0083] The acrylonitrile content was determined using SH / T 1157-1997.

[0084] The tensile strength test was conducted using GB / T 528-1998;

[0085] The elongation at break test was measured using GB / T 528-1998.

[0086] The binding amount of the reactive antioxidant was tested using a nuclear magnetic resonance spectrometer at a frequency of 400 mHz and a magnetic field strength of 9.40 T.

[0087] The nitrile rubbers obtained in Examples 8 and 12 were subjected to a heat oxidation resistance test.

[0088] Aging performance (100h oxygen absorption test (100℃)): (1) The rubber sample was purified by Soxhlet extraction; (2) The purified rubber sample was dissolved in 2-3% toluene solution and coated on a glass slide by film coating. The coated rubber was weighed. The mass of the rubber sample was 0.1g; (3) The oxygen absorption test was carried out in a 100℃ hot oxygen aging chamber at normal pressure for 100h. The test results were based on the change in mass as the test standard with an accuracy of 1×10 -4 The nitrile rubber S8 of Example 8 showed a 100-hour oxygen absorption test (100°C) of 0.242%, while the nitrile rubber S12 of Example 12 showed a 100-hour oxygen absorption test (100°C) of 0.238%. This indicates that the nitrile rubber obtained by using the reactive antioxidant containing acrylamide groups as a functional monomer of the present invention has excellent thermal oxidation resistance and is suitable for use in oil-resistant sealing applications in high-temperature operating environments.

[0089] Example 1

[0090] A 10L polymerization kettle was evacuated and replaced with nitrogen until the vacuum reached -0.1 MPa. Then, 220 parts by weight of deionized water, 80 parts by weight of butadiene, 20 parts by weight of acrylonitrile, 1.5 parts by weight of N-[4-(anilino)phenyl]methacrylamide, a composite emulsifier (3.5 parts by weight of disproportionated rosin acid potassium soap, 1 part by weight of dodecylbenzenesulfonic acid, 0.35 parts by weight of naphthalenesulfonic acid formaldehyde condensate sodium salt), and 0.4 parts by weight of tert-dodecyl mercaptan were added. The temperature was then controlled, and when the reaction temperature reached 8°C, 0.15 parts by weight of diisopropylbenzene hydroperoxide (specific components are shown in Table 1) were added.

[0091] When the reaction conversion rate reaches 50%, 0.4 parts by weight of tert-dodecyl mercaptan, a secondary molecular weight regulator, is added; when the reaction conversion rate reaches 72%, sodium nitrite is added, the material is discharged, and degassed, coagulated, washed and dried to obtain nitrile rubber S1.

[0092] The physical properties of the nitrile rubber S1 are listed in Table 5.

[0093] Examples 2-8

[0094] According to the method of Example 1, the difference is that

[0095] The amount of each component and the polymerization conditions were in accordance with the data in Table 1, and nitrile rubbers S2-S8 were obtained respectively.

[0096] The physical properties of the nitrile rubbers S2-S8 are listed in Table 5.

[0097] Example 9

[0098] A 10 L polymerization kettle was evacuated and replaced with nitrogen until the vacuum degree reached -0.1 MPa. 215 parts by weight of deionized water, 80 parts by weight of butadiene, 11 parts by weight of acrylonitrile, 2.3 parts by weight of N-[4-(anilino)phenyl]methacrylamide, a composite emulsifier (2.8 parts by weight of disproportionated rosin acid potassium soap, 1.1 parts by weight of dodecylbenzenesulfonic acid, 0.38 parts by weight of naphthalenesulfonic acid formaldehyde condensate sodium salt), 0.11 parts by weight of sodium ferric ethylenediaminetetraacetate, 0.04 parts by weight of disodium ethylenediaminetetraacetate, and 0.6 parts by weight of tert-dodecyl mercaptan were added in sequence (specific components are shown in Table 2).

[0099] Then the temperature was controlled, and when the reaction temperature reached 7° C., 0.2 parts by weight of diisopropylbenzene hydroperoxide as an initiator was added.

[0100] When the reaction conversion rate reaches 30%, 3 parts by weight of secondary acrylonitrile are added; when the reaction conversion rate reaches 50%, 3 parts by weight of tertiary acrylonitrile are added; when the reaction conversion rate reaches 60%, 3 parts by weight of quadruple acrylonitrile are added; when the reaction conversion rate reaches 73%, 0.07 parts by weight of sodium nitrite as a terminator is added, the material is discharged, and after degassing, condensation, washing and drying, nitrile rubber S9 is obtained.

[0101] The physical properties of the nitrile rubber S9 are listed in Table 5.

[0102] Examples 10-16

[0103] The method of Example 9 is followed, except that

[0104] The amount of each component and the polymerization conditions were in accordance with the data in Table 2, and nitrile rubbers S10-S16 were obtained respectively.

[0105] The physical properties of the above-mentioned nitrile rubbers S10-S16 are listed in Table 5.

[0106] Comparative Examples 1-8

[0107] According to the method of Example 1, the difference is that

[0108] The amount of each component and the polymerization conditions were in accordance with the data in Table 3 to obtain nitrile rubbers DS1-DS8 respectively.

[0109] The physical properties of the nitrile rubbers DS1-DS8 are listed in Table 5.

[0110] Comparative Examples 9-16

[0111] The method of Example 9 is followed, except that

[0112] The amount of each component and the polymerization conditions were in accordance with the data in Table 4, and nitrile rubbers DS9-DS16 were obtained respectively.

[0113] The physical properties of the above-mentioned nitrile rubbers DS9-DS16 are listed in Table 5.

[0114] Table 1

[0115] Table 2

[0116] Table 3

[0117] Table 4

[0118] Table 5

[0119] Table 5

[0120] Table 5

[0121] Table 5

[0122] As shown in Table 1-5, compared with Comparative Examples 1-16, the preparation method provided by the present invention can produce acrylonitrile content ≥17wt%, a reactive antioxidant content ≥1wt%, and a Mooney viscosity The nitrile rubber with a tensile strength of 40-70 and a tensile strength of 20-30 MPa can be used in the field of oil-resistant sealing in high-temperature working environments.

[0123] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing nitrile rubber, It is characterized in that The preparation method at least comprises: in the presence of an initiator, using butadiene and acrylonitrile as polymerization monomers, using a reactive antioxidant with an acrylamide group as a functional monomer; using a low-temperature emulsion polymerization method, a composite emulsifier containing at least disproportionated rosin acid soap, C 10 -C 13 Sodium salt of linear alkylbenzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate, a molecular weight regulator is added once or multiple times to synthesize nitrile rubber, a terminator is added, and the nitrile rubber is obtained after degassing, coagulation, washing and drying.

2. The preparation method according to claim 1, It is characterized in that Relative to 100 parts by weight of the polymerized monomer, the amount of the composite emulsifier is 2.8-6.5 parts by weight, preferably 3.2-6.5 parts by weight, more preferably 3.35-6 parts by weight, and more preferably 3.8-6 parts by weight.

3. The preparation method according to claim 1 or 2, It is characterized in that Relative to 100 parts by weight of the polymerized monomer, the amount of the disproportionated rosin acid soap in the composite emulsifier is 2-4.5 parts by weight, preferably 2-4 parts by weight, and more preferably 2.5-4 parts by weight; And / or, the disproportionated rosin acid soap is selected from disproportionated rosin acid potassium soap and / or disproportionated rosin acid sodium soap; And / or, relative to 100 parts by weight of the polymerizable monomer, in the composite emulsifier, C 10 -C 13 The amount of linear alkylbenzene sulfonic acid is 0.5-2 parts by weight, preferably 0.5-1.5 parts by weight, more preferably 1-1.5 parts by weight; and / or, the C 10 -C 13 The linear alkylbenzene sulfonic acid is at least one selected from the group consisting of decanylbenzene sulfonic acid, undecylbenzene sulfonic acid, dodecylbenzene sulfonic acid and tridecylbenzene sulfonic acid, preferably dodecylbenzene sulfonic acid; and / or, relative to 100 parts by weight of the polymerized monomer, the amount of the sodium salt of naphthalenesulfonic acid formaldehyde condensate in the composite emulsifier is 0.2-0.5 parts by weight, preferably 0.3-0.5 parts by weight, and more preferably 0.35-0.5 parts by weight; And / or, the naphthalenesulfonic acid formaldehyde condensate sodium salt is selected from sodium β-naphthalenesulfonate formaldehyde condensate.

4. The preparation method according to any one of claims 1 to 3, It is characterized in that The composite emulsifier further contains at least one of sodium dodecylbenzene sulfonate, sodium lauryl sulfate, potassium oleate, potassium stearate, sorbitan tristearate and octylphenol polyoxyethylene ether; Preferably, the composite emulsifier is composed of disproportionate rosin acid potassium soap and / or sodium soap, C 10 -C 13 It is composed of linear alkylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate sodium salt.

5. The preparation method according to any one of claims 1 to 4, It is characterized in that Relative to 100 parts by weight of the polymerized monomer, the amount of the reactive antioxidant is 0.5-3 parts by weight, preferably 1-2.5 parts by weight, and more preferably 1.5-2.5 parts by weight; And / or, the reactive antioxidant is a reactive antioxidant having an acrylamide group with an aniline phenyl group, and the general formula is Among them, R 1 and R 2 R represents hydrogen, chlorine, bromine or an alkyl group having 1 to 12 carbon atoms; 3 represents hydrogen or an alkyl group having 1 to 4 carbon atoms; R 4 represents hydrogen, or an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 12 carbon atoms; R 4 With R 3 Can be the same or different; And / or, the reactive antioxidant is preferably selected from one of N-(4-anilinophenyl)acrylamide, N-(4-anilinophenyl)methacrylamide, N-(4-anilinophenyl)cinnamamide, N-(4-anilinophenyl)crotonamide, N-[4-(4-methylanilino)phenyl]acrylamide, N-[4-(4-methylanilino)phenyl]methacrylamide, N-[4-(anilino)phenyl]methacrylamide and N-[4-(anilino)phenyl]tivalamide.

6. The preparation method according to any one of claims 1 to 5, It is characterized in that The temperature of the low-temperature emulsion polymerization is 5-15°C, preferably 5-12°C, and more preferably 5-8°C.

7. The preparation method according to any one of claims 1 to 6, It is characterized in that Relative to 100 parts by weight of the polymerizable monomer, the amount of the initiator is 0.1-0.3 parts by weight, preferably 0.2-0.3 parts by weight; And / or, the initiator is selected from organic hydrogen peroxide-ferrous salt, and the organic hydrogen peroxide is diisopropylbenzene hydroperoxide.

8. The preparation method according to any one of claims 1 to 7, It is characterized in that Relative to 100 parts by weight of the polymerizable monomer, the amount of the molecular weight regulator is 0.3-0.8 parts by weight, preferably 0.5-0.8 parts by weight; and / or, the molecular weight regulator is selected from tert-dodecyl mercaptan and / or n-dodecyl mercaptan, preferably tert-dodecyl mercaptan; And / or, the molecular weight regulator is added at least twice, and the first addition amount is 40-60% of the total molecular weight regulator addition amount; And / or, the molecular weight regulator is added at least twice, and when the conversion rate of the low-temperature emulsion polymerization reaches 50-55% during the second addition, the remaining molecular weight regulator is added.

9. The preparation method according to any one of claims 1 to 8, It is characterized in that When the conversion rate of the low-temperature emulsion polymerization reaches 70% or more, preferably 70-76%, adding the terminator; and / or, relative to 100 parts by weight of the polymerizable monomer, the amount of the terminator added is 0.05-0.15 parts by weight; And / or, the terminator is selected from at least one of sodium nitrite, hydroxylamine sulfate and diethylhydroxylamine.

10. The preparation method according to any one of claims 1 to 9, It is characterized in that During the low-temperature emulsion polymerization, at least one of deionized water, electrolyte, reducing agent and chelating agent is added; Preferably, the amount of the electrolyte is 0.1-0.5 parts by weight relative to 100 parts by weight of the polymerized monomer; Preferably, the electrolyte is selected from at least one of potassium hydroxide, sodium pyrophosphate and sodium carbonate; Preferably, the amount of the reducing agent is 0.01-0.15 parts by weight relative to 100 parts by weight of the polymerizable monomer; Preferably, the reducing agent is selected from at least one of ferrous sulfate, sodium ferric ethylenediaminetetraacetate and sodium thiosulfate; Preferably, the amount of the chelating agent is 0.01-0.05 parts by weight relative to 100 parts by weight of the polymerized monomer; Preferably, the chelating agent is selected from disodium ethylenediaminetetraacetate and / or tetrasodium ethylenediaminetetraacetate.

11. The preparation method according to any one of claims 1 to 10, It is characterized in that The amount of acrylonitrile is less than 30 parts by weight, preferably less than 25 parts by weight, relative to 100 parts by weight of the polymerizable monomer; More preferably, relative to 100 parts by weight of the polymerizable monomer, the amount of acrylonitrile used is 17-20 parts by weight, and the amount of butadiene used is 80-83 parts by weight.

12. The preparation method according to claim 1, It is characterized in that The preparation method comprises the following steps: based on 100 parts by weight of butadiene and acrylonitrile, the monomer composition is: 80-83 parts by weight of butadiene, 17-20 parts by weight of acrylonitrile, 1.5-2.5 parts by weight of a reactive antioxidant with an acrylamide group, 200-230 parts by weight of deionized water, the composite emulsifier contains at least 2-4.5 parts by weight of disproportionated rosin acid soap, 0.5-2 parts by weight of linear alkylbenzene sulfonic acid, and 0.2-0.5 parts by weight of naphthalenesulfonic acid formaldehyde condensate sodium salt to form an emulsification system; the initiator is selected from organic hydrogen peroxide-ferrous salt, and the amount thereof is 0.1-0.3 parts by weight; the molecular weight regulator is selected from tert-dodecyl mercaptan, and the amount thereof is 0.3-0.8 parts by weight; the initiator is added once; the monomer is added once or multiple times; preferably, the molecular weight regulator is added at least twice, and the polymerization temperature is 5-15°C; Preferably, the amount of the composite emulsifier is 2.8-6.5 parts by weight relative to 100 parts by weight of the polymerized monomer; Preferably, acrylonitrile is added in 3 or more times, preferably in 4 times.

13. The preparation method according to claim 1 or 12, It is characterized in that The preparation method comprises the following steps: based on 100 parts by weight of butadiene and acrylonitrile, the monomer composition is: 80-83 parts by weight of butadiene, 17-20 parts by weight of acrylonitrile, 1.5-2.5 parts by weight of a reactive antioxidant with an acrylamide group, 200-230 parts by weight of deionized water, the composite emulsifier contains at least 2-4.5 parts by weight of disproportionated rosin acid potassium soap and / or sodium soap, 0.5-1.5 parts by weight of linear alkylbenzene sulfonic acid, and 0.3-0.5 parts by weight of naphthalenesulfonic acid formaldehyde condensate sodium salt to form an emulsification system; the initiator is selected from organic hydrogen peroxide-ferrous salt, and its dosage is 0.1-0.3 parts by weight; the molecular weight regulator is selected from tert-dodecyl mercaptan, and its dosage is 0.5-0.8 parts by weight; the initiator is added once; the monomer is added once or multiple times; the molecular weight regulator is added at least twice, and the polymerization temperature is 5-8°C; Preferably, relative to 100 parts by weight of the polymerized monomer, the amount of the composite emulsifier is 2.8-6.5 parts by weight, more preferably 3.35-6 parts by weight.

14. The preparation method according to any one of claims 1 and 12-13, It is characterized in that The preparation method comprises the following steps: after the polymerization kettle is evacuated, deionized water, a composite emulsifier, a reducing agent, an electrolyte, a chelating agent, all polymerization monomers and 40-60% of a molecular weight regulator are added, the temperature is controlled to 5-8°C, the initiator is added, when the conversion rate of the low-temperature emulsion polymerization reaches 50-55%, the remaining molecular weight regulator is added, when the conversion rate of the low-temperature emulsion polymerization reaches 70-76%, the terminator is added, the material is discharged, and the degassing, coagulation, washing and drying are carried out to obtain the nitrile rubber.

15. The preparation method according to claim 1, It is characterized in that The preparation method at least comprises: using butadiene and acrylonitrile as polymerization monomers, using a reactive antioxidant with an acrylamide group as a functional monomer; taking the total amount of butadiene and acrylonitrile added as 100 parts by weight, wherein the content of acrylonitrile is less than 25 parts by weight, and adding acrylonitrile in batches or continuously, preferably more than three times; adopting a low-temperature emulsion polymerization method, using a composite emulsification system, wherein the composite emulsifier contains at least disproportionated rosin acid soap, C 10 -C 13 Sodium salt of linear alkylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate; preferably, the amount of the composite emulsifier added is 3.2-6.5 parts by weight, more preferably 3.8-6 parts by weight, the molecular weight regulator is added once or multiple times, the nitrile rubber is synthesized, the terminator is added, and it is degassed, condensed, washed and dried to obtain the nitrile rubber.

16. The preparation method according to claim 15, It is characterized in that The acrylonitrile is added in four times: when the conversion rate of the low-temperature emulsion polymerization reaches 30-35%, acrylonitrile is added for the first time; when the conversion rate of the low-temperature emulsion polymerization reaches 45-55%, acrylonitrile is added for the second time; when the conversion rate of the low-temperature emulsion polymerization reaches 60-65%, acrylonitrile is added for the third time; Preferably, the amount of acrylonitrile added for the first time is 30-50% of the total amount of acrylonitrile added.

17. The preparation method according to any one of claims 1 and 15-16, It is characterized in that The preparation method comprises the following steps: based on 100 parts by weight of butadiene and acrylonitrile, the monomer composition comprises: 80-83 parts by weight of butadiene, 17-20 parts by weight of acrylonitrile, 1.5-2.5 parts by weight of a reactive antioxidant with an acrylamide group, and 200-230 parts by weight of deionized water; the composite emulsifier comprises disproportionated rosin acid soap, C 10 -C 13 A linear alkylbenzene sulfonic acid and naphthalenesulfonic acid formaldehyde condensate sodium salt composite emulsifier system, wherein the composite emulsifier is used in an amount of 3.2-6.5 parts by weight, and the disproportionate rosin acid soap is used in an amount of 2-4 parts by weight, C 10 -C 13 The amount of linear alkylbenzene sulfonic acid is 1-2 parts by weight, and the amount of naphthalenesulfonic acid formaldehyde condensate sodium salt is 0.2-0.5 parts by weight; the initiator is organic hydrogen peroxide-ferrous salt, and its amount is 0.1-0.3 parts by weight; the molecular weight regulator is tert-dodecyl mercaptan, and its amount is 0.3-0.8 parts by weight; acrylonitrile is added in more than 3 times; the polymerization reaction temperature is 5-15°C; preferably, the amount of composite emulsifier is 3.8-6 parts by weight.

18. The preparation method according to any one of claims 1 and 15-17, It is characterized in that The preparation method comprises the following steps: after vacuuming a polymerization kettle, deionized water, a composite emulsifier, a reducing agent, an electrolyte, a chelating agent, butadiene, the first acrylonitrile and a molecular weight regulator are added, and after the temperature is controlled to 8-12 DEG C, an initiator is added; when the conversion rate of the low-temperature emulsion polymerization reaches 30-35%, the second acrylonitrile is added; when the conversion rate of the low-temperature emulsion polymerization reaches 45-55%, the third acrylonitrile is added; when the conversion rate of the low-temperature emulsion polymerization reaches 60-65%, the fourth acrylonitrile is added; when the conversion rate of the low-temperature emulsion polymerization reaches 70-76%, a terminator is added, the material is discharged, and the degassing, condensation, washing and drying are performed to obtain the nitrile rubber.

19. A nitrile rubber obtained by the preparation method described in any one of claims 1 to 18.

20. Use of the nitrile rubber according to claim 19 in the field of oil-resistant seals in high-temperature working environments, preferably in oil-resistant products in high-temperature working environments.

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