Nitrile rubber as well as preparation method and application thereof

Abstract

The invention relates to the technical field of synthetic rubber, in particular to nitrile rubber and a preparation method and application thereof. According to the preparation method, a composite emulsifier system at least containing disproportionated potassium abietate soap and / or sodium soap, C10-C13 linear alkyl benzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate sodium salt are compounded, a low-temperature emulsion polymerization process is adopted, and a reaction type anti-aging agent is introduced into emulsion polymerization, so that specific groups are effectively bonded into polymer molecular chains; the obtained nitrile rubber can be used in the field of oil-resistant sealing in a high-temperature working environment.

Description

Technical Field

[0001] The invention relates to the technical field of synthetic rubber, and in particular to a nitrile rubber, a method for preparing the nitrile rubber, and an application of the nitrile rubber. Background Art

[0002] Nitrile rubber has excellent oil resistance, heat resistance, wear resistance, gas permeability resistance, high modulus of elongation, hardness and tensile strength, so it is widely used in oil-resistant hoses in hydraulic transmission systems. Nitrile rubber is a type of rubber made from butadiene and acrylonitrile by emulsion polymerization, and is mainly produced by emulsion polymerization. Due to the presence of double bonds in nitrile rubber molecules, α hydrogen is very active and is prone to degradation reactions under the action of heat and oxygen, causing changes in the molecular structure of the material. During use, the rubber will gradually age, causing it to lose elasticity and mechanical properties to decline.

[0003] Some current solutions usually delay or inhibit the oxidation process of NBR by adding antioxidants to prevent its aging and improve the retention rate of mechanical properties during its use. However, the added antioxidants are easily extracted under high temperature conditions, resulting in the failure of physical and chemical protection of NBR. Due to the increase in acrylonitrile content, the elasticity and compression set resistance of the vulcanized rubber are poor, and the performance retention rate during the aging process is low, resulting in a greatly shortened service life in hot oil or hot air for a long time. This is mainly because when used in hot oil, the antioxidants added in the formula are extracted at high temperatures, resulting in the failure of physical and chemical protection.

[0004] 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 environments with more harsh conditions. Its anti-aging effect is 3-4 times that of the non-reactive antioxidant added after polymerization.

[0005] Polymer stabilized nitrile rubber (abbreviated as poly-stabilized nitrile) was developed based on the research of reactive antioxidants. Poly-stabilized nitrile has excellent aging resistance. Goodyear Tire & Rubber Company of the United States first made progress in the application research of poly-stabilized nitrile and applied it in the American automobile industry.

[0006] 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) imine 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-maleimide) US3767628 discloses a reactive antioxidant N-[4-(anilino)phenyl]maleimide; US3956298 and US4066616 both disclose a reactive antioxidant N-[2-hydroxy-3-(3-tert-butyl-4-hydroxy-5-methylphenyl)-propyl]maleimide; and US4138389, US4857596, and US4981917 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 anhydride compound contained in the polymer.

[0007] However, the above-mentioned prior arts all have the disadvantages of low acrylonitrile content in heat-resistant nitrile rubber, large amount of fine particles during coagulation, great difficulty in washing and drying during post-treatment, etc., and the heat-resistant nitrile rubber obtained cannot have excellent heat-resistant oxygen aging resistance, mechanical properties, etc. Summary of the invention

[0008] The purpose of the present invention is to overcome the above-mentioned technical problems and provide a nitrile rubber, a method for preparing 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.

[0009] In order to achieve the above object, 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 potassium soap and / or sodium 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.

[0010] The invention adopts a specific composite emulsifying system, wherein the composite emulsifier is at least a compound of three kinds of disproportionated rosin acid soap, linear alkylbenzene sulfonic acid and naphthalenesulfonic acid formaldehyde condensate sodium salt.

[0011] 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, more preferably 3.35-6 parts.

[0012] The present invention requires that the disproportionated rosin acid soap added to the composite emulsifier can be either potassium soap or sodium soap. The disproportionated rosin acid potassium soap or sodium soap in the composite emulsification system of the present invention cannot be replaced by other anionic emulsifiers such as sodium lauryl sulfate, potassium oleate and potassium stearate. This is because the inventors have found that in the specific emulsion polymerization system of the present invention, due to the synergistic effect, the particle size of the polymer emulsion increases after the addition of disproportionated rosin acid potassium soap or sodium soap, which is particularly beneficial to the emulsion coagulation process after the subsequent emulsion polymerization. The amount of addition can be adjusted according to the desired polymer emulsion particle size, especially the difficulty of the emulsion coagulation process after the emulsion polymerization. The recommended amount of disproportionated rosin acid potassium soap and / or sodium soap is 2-4.5 parts, more preferably 2-4 parts.

[0013] The present invention requires that C be added to the composite emulsifier 10 -C 13 Linear alkylbenzene sulfonic acid. The linear alkylbenzene sulfonic acid and the linear alkylbenzene sodium sulfonate have different effects. If only linear alkylbenzene sodium sulfonate is added without linear alkylbenzene sulfonic acid, the effect is different from that of the present invention. This is because sodium alkylbenzene sulfonate is the saponification product of alkylbenzene sulfonic acid. Due to the use of alkylbenzene sulfonic acid, some alkylbenzene sulfonic acid will not be completely saponified during the saponification process. A synergistic effect will be generated between the two, which will improve the stability of the entire polymerization system and the efficiency of the polymerization reaction. Therefore, the 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 alkylbenzene sulfonic acid is dodecylbenzene sulfonic acid. 10 -C 13 The linear alkylbenzene sulfonic acid is preferably added in an amount of 0.5-1.5 parts, preferably 1-1.5 parts.

[0014] The present invention requires that the sodium salt of naphthalenesulfonic acid formaldehyde condensate and C 10 -C 13The linear alkylbenzene sulfonic acid is used at the same time. This technology is already available in the prior art. Its usage amount is determined according to the needs and is not particularly limited in the present invention. If it is not added, the stability of the polymer emulsion will decrease and glue sticking will easily occur during the polymerization process. The preferred usage amount of naphthalenesulfonic acid formaldehyde condensate sodium salt is 0.3-0.5 parts, more preferably 0.35-0.5 parts.

[0015] The present invention also does not exclude the addition of other anionic emulsifiers and nonionic emulsifiers in addition to disproportionated rosin acid potassium soap or sodium soap, linear alkylbenzene sulfonic acid and naphthalenesulfonic acid formaldehyde condensate sodium salt in the composite emulsification system, such as sodium dodecylbenzene sulfonate, sodium lauryl sulfate, potassium oleate, potassium stearate, sorbitan tristearate and octylphenol polyoxyethylene ether.

[0016] The second aspect of the present invention provides a nitrile rubber prepared by the preparation method provided in the first aspect.

[0017] 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.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] The present invention provides a method for preparing heat-resistant oxygen aging nitrile rubber with a simple process, which comprises at least disproportionate rosin acid potassium soap and / or sodium soap, C 10 -C 13 A composite emulsifier system and low-temperature emulsion polymerization process consisting of linear alkylbenzene sulfonic acid and sodium salt of naphthalenesulfonic acid formaldehyde condensate are used, and a reactive antioxidant is introduced into the emulsion polymerization to effectively bond specific groups to the polymer molecular chains. The technical problems of large amounts of fine particles during coagulation and difficulty in washing and drying during post-treatment are solved.

[0020] 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. DETAILED DESCRIPTION

[0021] The endpoints and any values ​​of the ranges disclosed in this article 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 endpoint values ​​of each range, the endpoint values ​​of each range and the 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 as specifically disclosed in this article.

[0022] 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 potassium soap and / or sodium 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.

[0023] Those skilled in the art know that, when a composite emulsification system is used for emulsion polymerization of nitrile rubber, its emulsifier includes a primary emulsifier and an auxiliary emulsifier. The primary emulsifier may be one or more anionic emulsifiers, such as at least one of potassium disproportionate rosin acid, sodium dodecylbenzene sulfonate, sodium lauryl sulfate, potassium oleate and potassium stearate, or other anionic emulsifiers; the auxiliary emulsifier may 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.

[0024] However, the present invention adopts a specific composite emulsification system, and the composite emulsifier is at least selected from three kinds of disproportionate rosin acid potassium soap and / or sodium soap, linear alkylbenzene sulfonic acid and sodium naphthalene sulfonate formaldehyde condensate for compounding, which has a synergistic effect, thereby improving 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 technical field, especially the amount used when anionic emulsifiers and non-ionic emulsifiers are compounded. Preferably, the amount of the composite emulsifier is 2.8-6.5 parts by weight, and more preferably 3.35-6 parts by weight. Preferably, the amount of the disproportionate rosin acid potassium soap and / or sodium soap is 2-4.5 parts by weight, equivalent to 100 parts by weight of the polymerized monomer; preferably, the amount of the linear alkylbenzene sulfonic acid is 0.5-1.5 parts by weight; preferably, the amount of the sodium salt of the naphthalene sulfonic acid formaldehyde condensate is 0.3-0.5 parts by weight.

[0025] In some embodiments of the present invention, further preferably, the amount of the disproportionated rosin acid potassium soap and / or sodium soap is 2-4 parts by weight, equivalent to 100 parts by weight of the polymerized monomer; preferably, the C 10 -C 13 The amount of linear alkylbenzene sulfonic acid used is 1-1.5 parts by weight; preferably, the amount of naphthalenesulfonic acid formaldehyde condensate sodium salt used is 0.35-0.5 parts by weight.

[0026] In the composite emulsification system of the present invention, 2-4.5 parts by weight of disproportionate rosin acid potassium soap and / or sodium soap are preferably added, 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 in the range of any two values, preferably 2-4 parts by weight. The disproportionate rosin acid potassium soap and / or sodium soap in the composite emulsification system of the present invention can be replaced by other anionic emulsifiers such as sodium lauryl sulfate, potassium oleate and potassium stearate, because the inventors have found that in the specific emulsion polymerization system of the present invention, due to the synergistic effect, the particle size of the polymer emulsion increases after the addition of disproportionate rosin acid potassium soap and / or sodium soap, which is particularly beneficial to the emulsion coagulation process after the subsequent emulsion polymerization.

[0027] In some specific embodiments of the present invention, the disproportionate rosin acid potassium soap and / or sodium soap can be selected from disproportionate rosin acid potassium soap, disproportionate rosin acid sodium soap, or disproportionate rosin acid potassium soap and disproportionate rosin acid sodium soap.

[0028] In the composite emulsification system, C is preferably added 10 -C 13 0.5-1.5 parts by weight of linear alkylbenzene sulfonic acid, 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, and any value in the range of any two values, 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. Only adding C 10 -C 13 Sodium linear alkylbenzene sulfonate without adding C 10 -C 13 The effect of linear alkylbenzene sulfonic acid is different 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, part of the dodecylbenzene sulfonic acid will not be completely saponified during its saponification process, and a synergistic effect will be generated between the two, so that the stability of the entire polymerization system is improved and the polymerization reaction efficiency is improved. Therefore, the linear alkylbenzene sulfonic acid in the composite emulsification system of the present invention cannot be replaced by sodium linear alkylbenzene sulfonate.

[0029] In some specific embodiments of the present invention, 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.

[0030] In the present invention, 0.3-0.5 parts by weight of naphthalenesulfonic acid formaldehyde condensate sodium salt is preferably added to the composite emulsification system, for example, 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 in the range of any two values, preferably 0.35-0.5 parts by weight. If the naphthalenesulfonic acid formaldehyde condensate sodium salt is not added, the stability of the polymer emulsion will be reduced, and the phenomenon of glue hanging will easily occur during the polymerization process.

[0031] In some specific embodiments of the present invention, the naphthalenesulfonic acid formaldehyde condensate sodium salt includes but is not limited to sodium β-naphthalenesulfonate formaldehyde condensate and the like.

[0032] In the present invention, the composite emulsifier includes disproportionate rosin acid potassium soap and / or sodium soap, C 10 -C 13 In addition to the sodium salt of linear alkylbenzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate, it also contains other anionic emulsifiers and nonionic emulsifiers. Preferably, the composite emulsifier also contains at least one of sodium dodecylbenzene sulfonate, sodium lauryl sulfate, potassium oleate, potassium stearate, sorbitan tristearate and octylphenol polyoxyethylene ether.

[0033] In some embodiments of the present invention, 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.

[0034] 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, 3.35 parts by weight, 3.8 parts by weight, 4 parts by weight, 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 3.35-6 parts by weight.

[0035] The reactive antioxidant selected in the present invention is a reactive antioxidant with an acrylamide group. In the art, reactive antioxidants with an amide group of aniline phenyl are generally used, and the general formula is

[0036]

[0037] Wherein, R1 and R2 represent hydrogen, chlorine, bromine or an alkyl group having 1 to 12 carbon atoms respectively; R3 represents hydrogen or an alkyl group having 1 to 4 carbon atoms; R4 represents hydrogen, or an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 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. Among them, the most typical types are N-[4-(anilino)phenyl]methacrylamide and N-[4-(anilino)phenyl]pivalamide, which are used as functional monomers to participate in polymerization reactions. Usually, when the amount of reactive antioxidant in the nitrile rubber reaches 1-2wt%, it can show good heat-oxidative aging resistance and can be used in the field of oil-resistant sealing in high-temperature working environments. Different types of acrylamide do not affect the unique effects of the present invention.

[0038] 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.

[0039] The synthesis scheme of the nitrile rubber of the present invention is low-temperature emulsion polymerization, and the polymerization temperature used for low-temperature emulsion polymerization commonly used in the technical field can be used without special limitation. Preferably, the conditions of the low-temperature emulsion polymerization include: temperature of 5-12°C, preferably 5-8°C; time of 10-30h, preferably 15-25h.

[0040] In the present invention, the low-temperature emulsion polymerization may be batch polymerization or continuous polymerization.

[0041] In some embodiments of the present invention, preferably, the amount of the initiator 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 in the range of any two values, preferably 0.2-0.3 parts by weight. In the present invention, the amount of the initiator is based on organic hydroperoxide.

[0042] 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.

[0043] 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 may be used. Preferably, the molecular weight regulator is selected from tert-dodecyl mercaptan and / or n-dodecyl mercaptan, preferably tert-dodecyl mercaptan.

[0044] In the present invention, the amount of the molecular weight regulator can be adjusted according to the product performance requirements and the type of the molecular weight regulator. Preferably, relative to 100 parts by weight of the polymerized monomer, the amount of the molecular weight regulator is 0.3-0.8 parts by weight, such as 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 in the range of any two values, preferably 0.5-0.8 parts by weight.

[0045] In the present invention, the molecular weight regulator is added once or multiple times in the low-temperature emulsion polymerization, and can be selected according to different requirements of product performance. Preferably, 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; further preferably, 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 two additions, the remaining molecular weight regulator is added.

[0046] 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.

[0047] 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.

[0048] The present invention does not particularly limit the timing of adding the terminator, and the required nitrile rubber mortar can be selected to achieve different ranges of conversion rates according to product requirements. Preferably, the terminator is added when the conversion rate of the low-temperature emulsion polymerization reaches more than 70%; more preferably, the terminator is added when the conversion rate of the low-temperature emulsion polymerization reaches 70-76%.

[0049] The present invention also 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.

[0050] The present invention does not particularly limit the type and amount of the electrolyte, and a general electrolyte and a general amount can be used. Preferably, the amount of the electrolyte is 0.1-0.5 parts by weight relative to 100 parts by weight of the polymerized monomer; further preferably, the electrolyte is selected from at least one of potassium hydroxide, sodium pyrophosphate and sodium carbonate.

[0051] The present invention does not particularly limit the type and amount of the reducing agent, and a general reducing agent and a general amount can be used. Preferably, the amount of the reducing agent is 0.01-0.15 parts by weight relative to 100 parts by weight of the polymerized monomer; further preferably, the reducing agent is selected from at least one of ferrous sulfate, sodium ferric ethylenediaminetetraacetate and sodium thiosulfate.

[0052] The present invention does not particularly limit the type and amount of the chelating agent, and a general chelating agent and a general amount of addition are sufficient. 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; further preferably, the chelating agent is selected from disodium ethylenediaminetetraacetate and / or tetrasodium ethylenediaminetetraacetate.

[0053] The present invention does not particularly limit the specific ratio of butadiene and acrylonitrile in the polymerization monomer, and the commonly used ratio for preparing acrylonitrile-butadiene rubber in the prior art can be adopted (such as acrylonitrile content of 15-50%). Due to the increase of acrylonitrile content, the elasticity and compression set resistance of the vulcanized rubber are poor, and the performance retention rate during the aging process is low, resulting in a greatly shortened service life in hot oil or hot air for a long time. Therefore, when this type of acrylonitrile-butadiene rubber is polymerized, the acrylonitrile monomer content is relatively low.

[0054] 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. However, if the amount of acrylonitrile is too low, the resulting powdering will cause serious problems during condensation and it is not easy to condense. 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 compounding three kinds of disproportionated rosin acid potassium soap and / or sodium soap, linear alkylbenzene sulfonic acid and sodium naphthalene sulfonate formaldehyde condensate makes the polymer emulsion particle size increase, which is particularly beneficial to the emulsion condensation process after subsequent emulsion polymerization, and is particularly suitable for the preparation of acrylonitrile-butadiene rubber with low content of acrylonitrile.

[0055] In the present invention, unless otherwise specified, the acrylonitrile monomer may be added once, continuously, or more than twice, multiple times, preferably 2-5 times.

[0056] 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.

[0057] The present invention also provides a preferred method for preparing nitrile rubber, comprising the following steps: based on 100 parts by weight of the added amount 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, preferably 3.35-6 parts by weight.

[0058] 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%.

[0059] The present invention also provides a most preferred method for preparing nitrile rubber, comprising the following steps: after the polymerization kettle is evacuated, deionized water, emulsifier, reducing agent, electrolyte, chelating agent, all monomers, and 40-60% of molecular weight regulator are added; after 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 performed to obtain the nitrile rubber.

[0060] The second aspect of the present invention provides a nitrile rubber prepared by the preparation method provided in the first aspect.

[0061] In some embodiments of the present invention, preferably, based on the total content of the nitrile rubber, the content of acrylonitrile is ≥18wt%, preferably 18-20wt%, for example, 18wt%, 18.5wt%, 19wt%, 19.5wt%, 20wt%, and any value in the range composed of any two numerical values; the content of the combined reactive antioxidant is ≥1wt%, preferably 1-2wt%, for example, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2wt%, and any value in the range composed of any two numerical values.

[0062] 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.

[0063] 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.

[0064] 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; and the elongation at break test was conducted in accordance with GB / T 528-1998.

[0065] 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.

[0066] The nitrile rubber produced by 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 stable and the energy consumption is low.

[0067] 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 18-20wt% and a Mooney viscosity of The nitrile rubber with good heat-oxidative aging resistance and a reactive antioxidant combined with 1-2 wt% can be used in the field of oil-resistant sealing in high-temperature working environments.

[0068] The present invention will be described in detail below through examples.

[0069] The total solids test was measured using SH / T 1154-92;

[0070] Mooney viscosity The test was conducted according to GB / T 1232-2000;

[0071] The combined acrylonitrile content test was measured using SH / T 1157-1997;

[0072] The tensile strength test was measured using GB / T 528-1998;

[0073] The elongation at break test is measured using GB / T 528-1998.

[0074] 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.

[0075] The nitrile rubber obtained in Example 8 was subjected to a heat oxidation resistance test.

[0076] Aging performance (100h oxygen absorption test (100℃)): (1) The rubber sample was purified by Soxhlet extraction method; (2) The purified rubber sample was dissolved in 2-3% toluene solution, and a film was prepared on a glass sheet by coating method, and the coated rubber was weighed. The mass of the rubber sample was about 0.1g; (3) The oxygen absorption test was carried out for 100h in a 100℃ hot oxygen aging box under normal pressure. The test result was based on the change in mass as the test standard, with an accuracy of 1×10 -4 g. The result of the 100h oxygen absorption test (100°C) is 0.242%. This indicates that the nitrile rubber obtained by using the reactive antioxidant with acrylamide group as the functional monomer has good heat-oxidation resistance and can be used in the field of oil-resistant sealing in high-temperature working environments.

[0077] Example 1

[0078] A 10L polymerization kettle was evacuated and replaced with nitrogen until the vacuum reached -0.1MPa, and 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 in sequence. Then the temperature was controlled, and when the reaction temperature reached 8°C, 0.15 parts by weight of diisopropylbenzene hydroperoxide were added.

[0079] 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 after degassing, condensation, washing and drying, nitrile rubber S1 is obtained.

[0080] The physical properties of the nitrile rubber S1 are listed in Table 3.

[0081] Embodiment 2-8

[0082] According to the method of Example 1, the difference is that

[0083] 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.

[0084] Among them, the physical properties of the above-mentioned nitrile rubbers S2-S8 are listed in Table 3.

[0085] Comparative Examples 1-8

[0086] According to the method of Example 1, the difference is that

[0087] The amount of each component and the polymerization conditions are in accordance with the data in Table 2 to obtain nitrile rubbers DS1-DS8 respectively.

[0088] Among them, the physical properties of the above-mentioned nitrile rubbers DS1-DS8 are listed in Table 3.

[0089] Table 1

[0090]

[0091]

[0092] Table 2

[0093]

[0094] Table 3

[0095]

[0096]

[0097] Table 3

[0098]

[0099] According to the data in Table 1-2, compared with Comparative Examples 1-8, the preparation method provided by the present invention can produce acrylonitrile with a content of ≥18wt%, a reactive antioxidant with a content of ≥1wt%, and a Mooney viscosity of The tensile strength is selected from nitrile rubber with a value of 40-70 and a tensile strength of 20-30 MPa.

[0100] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing nitrile rubber, 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, the composite emulsifier at least contains disproportionated rosin acid potassium soap and / or sodium soap, C 10 -C 13 Sodium salt of linear alkylbenzene sulfonic acid and naphthalenesulfonic acid formaldehyde condensate, a molecular weight regulator is added once or multiple times to synthesize nitrile rubber slurry, a terminator is added, and the nitrile rubber is obtained after degassing, coagulation, washing and drying; preferably, the amount of the composite emulsifier is 2.8-6.5 parts by weight, preferably 3.35-6 parts by weight.

2. The preparation method according to claim 1, characterized in that: Relative to 100 parts by weight of the polymerized monomer, the amount of disproportionated rosin acid potassium soap and / or sodium soap in the composite emulsifier is 2-4.5 parts by weight, preferably 2-4 parts by weight.

3. The preparation method according to claim 1, characterized in that: 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 used is 0.5-1.5 parts by weight, preferably C 10 -C 13 The amount of linear alkylbenzene sulfonic acid is 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.

4. The preparation method according to claim 1, characterized in that: Relative to 100 parts by weight of the polymerized monomer, in the composite emulsifier, the amount of the sodium salt of naphthalenesulfonic acid formaldehyde condensate is 0.3-0.5 parts by weight, preferably the amount of the sodium salt of naphthalenesulfonic acid formaldehyde condensate is 0.35-0.5 parts by weight; And / or, the naphthalenesulfonic acid formaldehyde condensate sodium salt is selected from sodium β-naphthalenesulfonate formaldehyde condensate.

5. The preparation method according to claim 1, 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.

6. The preparation method according to claim 1, 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 / or, the reactive antioxidant is a reactive antioxidant having an acrylamide group with an aniline phenyl group, and the general formula is wherein R1 and R2 represent hydrogen, chlorine, bromine or an alkyl group having 1 to 12 carbon atoms; R3 represents hydrogen or an alkyl group having 1 to 4 carbon atoms; R4 represents hydrogen, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 12 carbon atoms; R4 and R3 may 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.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The conditions of the low-temperature emulsion polymerization include: a temperature of 5-12°C, preferably 5-8°C.

8. The preparation method according to any one of claims 1 to 7, 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.

9. The preparation method according to any one of claims 1 to 8, 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 two additions, the remaining molecular weight regulator is added.

10. The preparation method according to any one of claims 1 to 9, 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.

11. The preparation method according to any one of claims 1 to 10, 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 electrolyte is used in an amount of 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 polymerized 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.

12. The preparation method according to claim 1 or 2, 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.

13. The preparation method according to any one of claims 1 to 12, characterized in that: The preparation method comprises the following steps: Taking the addition amount of butadiene and acrylonitrile as 100 parts by weight, 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 usage is 0.1-0.3 parts by weight; the molecular weight regulator is selected from tert-dodecyl mercaptan, and its usage 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, preferably 3.35-6 parts by weight.

14. The preparation method according to claim 1 or 13, characterized in that: The preparation method comprises the following steps: after the polymerization kettle is evacuated, deionized water, an emulsifier, a reducing agent, an electrolyte, a chelating agent, all 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 performed to obtain the nitrile rubber.

15. A nitrile rubber obtained by the preparation method described in any one of claims 1 to 14.

16. Use of the nitrile rubber according to claim 15 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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