Preparation method of nitrile rubber with improved thermo-oxidative aging resistance

Abstract

The invention discloses a preparation method of nitrile rubber with improved thermo-oxidative aging resistance, which comprises the following steps: butadiene and acrylonitrile are used as main polymerization monomers, and a reactive anti-aging agent with an amide group is used as a functional monomer; the total addition amount of butadiene and acrylonitrile is 100 parts by mass, and acrylonitrile is added in batches or continuously, preferably more than three times; a low-temperature emulsion polymerization method is adopted, and the compound emulsifier at least contains disproportionated rosin soap, C10-C13 linear alkyl benzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate sodium salt; the preparation method comprises the following steps of: adding a molecular weight regulator into a compound emulsifier, preferably 3.2-6.5 parts by weight, more preferably 3.8-6.0 parts by weight of the compound emulsifier, adding the molecular weight regulator once or multiple times, synthesizing butyronitrile rubber cement, adding a terminating agent, degassing, condensing, washing and drying to obtain the butyronitrile rubber. According to the invention, the nitrile rubber with good thermo-oxidative aging resistance is produced, wherein the content of bound acrylonitrile is 17-20%, and the binding amount of Mooney viscosity # imgabs0 # reactive anti-aging agent is 1-2%.

Description

Technical Field

[0001] The invention belongs to the technical field of rubber materials, and particularly relates to a method for preparing nitrile rubber with improved heat-oxidative aging resistance. 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. However, due to the increase in acrylonitrile content, the elasticity and compression permanent deformation 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 antioxidant added to the formula is extracted at high temperature, resulting in the failure of physical and chemical protection.

[0003] 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 to 4 times that of the non-reactive antioxidant added after polymerization.

[0004] Although reactive antioxidants have been used to prepare nitrile rubber, the current preparation process of nitrile rubber is complex, energy consumption is high, and the thermal and oxidative aging resistance is poor. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing nitrile rubber with simple process and good heat-oxidative aging resistance.

[0006] To achieve the purpose of this invention, the preparation method at least comprises:

[0007] Butadiene and acrylonitrile are used as main monomers for polymerization, and a reactive antioxidant with an amide group is used as a functional monomer; based on the total amount of butadiene and acrylonitrile added as 100 parts by weight, the acrylonitrile content is less than 25 parts, and acrylonitrile is added in batches or continuously, preferably more than three times; a low-temperature emulsion polymerization method is adopted, a composite emulsification system is used, and 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 composite emulsifier added is 3.2 to 6.5 parts, more preferably 3.8 to 6.0 parts, a molecular weight regulator is added once or multiple times, a nitrile rubber slurry is synthesized, a terminator is added, and a nitrile rubber is obtained after degassing, coagulation, washing and drying.

[0008] The present invention recommends a more preferred or typical composition ratio of the main monomers for polymerization: 80-83 parts of butadiene and 17-20 parts of acrylonitrile.

[0009] The acrylonitrile monomer of the present invention is added in batches or continuously into the low-temperature emulsion polymerization reaction, preferably three or more times, more preferably four times;

[0010] When the acrylonitrile is added in four times: when the reaction conversion rate reaches 30-35%, acrylonitrile is added for the first time; when the reaction conversion rate reaches 45-55%, acrylonitrile is added for the second time; when the reaction conversion rate reaches 60-65%, acrylonitrile is added for the third time; preferably, the amount of acrylonitrile monomer added for the first time is 30-50% of the total amount of acrylonitrile monomer added, and the amount of the remaining acrylonitrile monomer added is 50-70% of the total amount of acrylonitrile monomer added.

[0011] The synthesis scheme of the nitrile rubber of the present invention is low-temperature emulsion polymerization. The polymerization reaction temperature used in the low-temperature emulsion polymerization commonly used in the technical field can be any, and is not particularly limited. For example, the polymerization reaction temperature of the low-temperature emulsion polymerization is 5 to 15°C, and the preferred polymerization reaction temperature is 8 to 12°C.

[0012] The present invention does not particularly limit the amount of disproportionated rosin acid soap added in the composite emulsifier. For example, based on 100 parts by weight of the total amount of butadiene and acrylonitrile added, the amount of disproportionated rosin acid soap in the composite emulsifier is 2.0 to 4.0 parts, preferably 2.5 to 4.0 parts.

[0013] The present invention does not particularly limit the C in the composite emulsifier. 10 ~C 13 The amount of linear alkylbenzene sulfonic acid added, such as the total amount of butadiene and acrylonitrile added is 100 parts by weight, C in the composite emulsifier 10 ~C 13 The amount of linear alkylbenzene sulfonic acid used is 1.0 to 2.0 parts, preferably 1.0 to 1.5 parts.

[0014] The present invention does not particularly limit the amount of naphthalenesulfonic acid formaldehyde condensate sodium salt added in the composite emulsifier, such as the amount of naphthalenesulfonic acid formaldehyde condensate sodium salt is 0.2 to 0.5 parts, preferably the amount of naphthalenesulfonic acid formaldehyde condensate sodium salt is 0.3 to 0.5 parts.

[0015] The present invention does not particularly limit the initiator system and the amount added. Generally, any initiator used for low-temperature emulsion polymerization of nitrile rubber can be used. For example, the initiator system used for the low-temperature emulsion polymerization can be an organic hydrogen peroxide-ferrous salt, and the organic hydrogen peroxide is preferably diisopropylbenzene hydroperoxide, and the preferred amount added is 0.1 to 0.3 parts; the preferred reducing agent used for the low-temperature emulsion polymerization is sodium ferric ethylenediaminetetraacetate, and the preferred amount added is 0.01 to 0.15 parts; the preferred chelating agent used for the low-temperature emulsion polymerization is disodium ethylenediaminetetraacetate, and the preferred amount added is 0.01 to 0.05 parts.

[0016] The present invention also does not particularly limit the molecular weight regulator and the amount thereof. The molecular weight regulator and the amount thereof commonly used in nitrile rubber are all acceptable. The common molecular weight regulator is one of tert-dodecyl mercaptan and n-dodecyl mercaptan, preferably tert-dodecyl mercaptan; the molecular weight regulator is preferably used in an amount of 0.3 to 0.8 parts, more preferably 0.5 to 0.8 parts; the preferred terminator is one of sodium nitrite, hydroxylamine sulfate, and diethylhydroxylamine; the terminator is preferably added in an amount of 0.05 to 0.15 parts.

[0017] The present invention does not particularly limit the timing of adding the terminator, but preferably the terminator is added when the reaction conversion rate reaches 70 to 76%.

[0018] The present invention also provides a preferred method for preparing the nitrile rubber, the preparation method comprising the following steps:

[0019] Based on 100 parts by mass of butadiene and acrylonitrile, the monomer composition is: 80-83 parts of butadiene, 17-20 parts of acrylonitrile, 1.5-2.5 parts of a reactive antioxidant with an amide group, 200-230 parts of deionized water, and a composite emulsifier including disproportionated rosin acid soap, C 10 ~C 13 The emulsifying system of linear alkylbenzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate sodium salt is prepared, the amount of the composite emulsifier is 3.2 to 6.5 parts, and the amount of disproportionate rosin acid soap is 2.0 to 4.0 parts, C 10 ~C 13 The dosage of linear alkylbenzene sulfonic acid is 1.0-2.0 parts, the dosage of naphthalenesulfonic acid formaldehyde condensate sodium salt is 0.2-0.5 parts; the initiator system is organic hydrogen peroxide-ferrous salt, and the dosage of organic hydrogen peroxide is 0.1-0.3 parts; the molecular weight regulator is tert-dodecyl mercaptan, and the dosage is 0.3-0.8 parts; acrylonitrile is added in more than 3 times; the polymerization reaction temperature is 5-15°C; and the preferred dosage of the composite emulsifier is 3.8-6.0 parts.

[0020] The present invention also provides a more preferred method for preparing nitrile rubber, the preparation method comprising the steps of:

[0021] After the polymerization kettle is evacuated, deionized water, composite emulsifier, reducing agent, electrolyte, chelating agent, part of monomers and molecular weight regulator are added, and after the temperature is controlled to 8-12 DEG C, an initiator is added. When the reaction conversion rate reaches 30-35%, acrylonitrile is added for the second time; when the reaction conversion rate reaches 45-55%, acrylonitrile is added for the third time; when the reaction conversion rate reaches 60-65%, acrylonitrile is added for the fourth time; when the reaction conversion rate reaches 70-76%, a terminator is added, the material is discharged, and a nitrile rubber is obtained after degassing, condensation, washing and drying.

[0022] The present invention does not particularly limit the type of reactive antioxidant, which may be a currently existing reactive antioxidant with an amide group. The technical field of the present invention is generally a reactive antioxidant with an amide group of aniline phenyl. The present invention is not particularly limited. For example, the reactive antioxidant with an amide group is a reactive antioxidant with an amide group of aniline phenyl, and the general formula is:

[0023]

[0024] 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, 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.

[0025] The present invention does not particularly limit C 10 ~C 13 The type of linear alkylbenzene sulfonic acid, as described in C 10 ~C 13 The linear alkylbenzenesulfonic acid may be dodecylbenzenesulfonic acid.

[0026] Compared with the prior art, the embodiments of the present invention have at least the following advantages: an emulsification system and a low-temperature emulsion polymerization process containing disproportionated rosin acid soap, dodecylbenzenesulfonic acid, and naphthalenesulfonic acid formaldehyde condensate are used to introduce a reactive antioxidant into the emulsion polymerization, so that the antioxidant group is effectively bonded to the polymer molecular chain, and the technical problems of a large number of fine particles during coagulation and difficulty in washing and drying during the post-treatment process due to the low acrylonitrile content of the heat-resistant nitrile rubber are solved; at the same time, the present invention finds that the glass transition temperature of the heat-resistant nitrile rubber can be reduced by adding acrylonitrile in batches for multiple times, especially four times, so that the polymer has excellent high temperature and low temperature resistance; the nitrile rubber produced by 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; in addition, when the method of the present invention is used to synthesize the mortar, the polymerization process is stable and the energy consumption is low; it can be seen from the best production scheme in the embodiment that the technology of the present invention can produce a nitrile rubber with a combined acrylonitrile content of 17-20% and a Mooney viscosity of 1. The nitrile rubber with good heat-oxidative aging resistance and a reactive antioxidant combined with a content of 1 to 2% can be used in the field of oil-resistant sealing in high-temperature working environments.

[0027] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The invention discloses a method for preparing a nitrile rubber with improved heat-oxidative aging resistance, comprising:

[0030] Butadiene and acrylonitrile are used as main monomers for polymerization, and a reactive antioxidant with an amide group is used as a functional monomer; based on the total amount of butadiene and acrylonitrile added as 100 parts by weight, the acrylonitrile content is less than 25 parts, and acrylonitrile is added in batches or continuously, preferably more than three times; a low-temperature emulsion polymerization method is adopted, a composite emulsification system is used, and the composite emulsifier contains at least disproportionated rosin acid soap, C 10 ~C 13Sodium salt of linear alkylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate, wherein 2.0 to 4.0 parts, preferably 2.5 to 4.0 parts, of disproportionated rosin acid soap, C 10 ~C 13 The linear alkylbenzene sulfonic acid is used in an amount of 1.0 to 2.0 parts, preferably 1.0 to 1.5 parts, the sodium salt of naphthalenesulfonic acid formaldehyde condensate is used in an amount of 0.2 to 0.5 parts, and the sodium salt of naphthalenesulfonic acid formaldehyde condensate is more preferably used in an amount of 0.3 to 0.5 parts, a molecular weight regulator is added once or multiple times, a nitrile rubber is synthesized, a terminator is added, and a nitrile rubber is obtained after degassing, coagulation, washing and drying. It should be noted that the parts in this application are all calculated by mass.

[0031] The content of acrylonitrile monomer in the present invention is relatively low, less than 25 parts, and the polymerization formula can be adjusted according to product needs. Too high acrylonitrile content easily leads to poor elasticity and compression permanent deformation of the vulcanized rubber, low performance retention rate during aging, and greatly shortened service life in hot oil or hot air for a long time. The present invention recommends a more preferred or more typical monomer composition ratio of 80-83 parts of butadiene and 17-20 parts of acrylonitrile for the synthesis of acrylonitrile rubber.

[0032] The acrylonitrile monomer of the present invention is added into the polymerization reaction in batches or continuously, preferably more than 3 times, more preferably 4 times; preferably, the amount of acrylonitrile monomer added for the first time is 30-50% of the total amount of acrylonitrile monomer added.

[0033] When acrylonitrile monomer is added to the polymerization reaction four times, the preferred method is: when the reaction conversion rate reaches 30-35%, acrylonitrile is added for the first time; when the reaction conversion rate reaches 45-55%, acrylonitrile is added for the second time; when the reaction conversion rate reaches 60-65%, acrylonitrile is added for the third time.

[0034] It is recommended that the amount of acrylonitrile monomer added for the first time is 30-50% of the total amount of acrylonitrile monomer added, and the amount of the remaining acrylonitrile monomer added is 50-70% of the total amount of acrylonitrile monomer added.

[0035] The present invention finds that when the amount of acrylonitrile monomer added is less than 25 parts, if the acrylonitrile monomer is added in batches for multiple times or continuously, especially if the acrylonitrile monomer is added four times, the distribution of acrylonitrile in the molecular chain segments is significantly improved, so that the glass transition temperature of the polymer is significantly reduced.

[0036] The synthesis scheme of the nitrile rubber of the present invention is low-temperature emulsion polymerization. The polymerization temperature used in the low-temperature emulsion polymerization commonly used in the technical field can be any, and is not particularly limited, such as 5 to 15° C., and preferably the polymerization reaction temperature is controlled at 8 to 12° C. It can be intermittent polymerization or continuous polymerization.

[0037] The present invention does not particularly limit the initiator system and the amount added. Any initiator commonly used in low-temperature emulsion polymerization of nitrile rubber can be used. For example, the initiator system can adopt an organic hydrogen peroxide-ferrous salt redox initiator system, such as diisopropylbenzene hydrogen peroxide-ferrous salt, isopropylbenzene hydrogen peroxide-ferrous salt and other initiator systems. The amount added is usually 0.1 to 0.3 parts.

[0038] The present invention also does not particularly limit the type and amount of the terminator, and any common terminator may be used, such as sodium nitrite, hydroxylamine sulfate, and diethylhydroxylamine. The terminator is usually added in an amount of 0.05 to 0.15 parts.

[0039] The present invention does not particularly limit the timing of adding the terminator, and the desired nitrile rubber mortar can be selected to achieve different ranges of conversion rates according to product requirements. The present invention preferably adds the terminator when the reaction conversion rate reaches more than 70%, and more preferably adds the terminator when the reaction conversion rate reaches 70-76%.

[0040] The present invention also does not particularly limit the molecular weight regulator and the amount thereof. The molecular weight regulator and the amount thereof commonly used in acrylonitrile-butadiene rubber can be used. Common molecular weight regulators include tert-dodecyl mercaptan, n-dodecyl mercaptan, etc., and tert-dodecyl mercaptan is preferably used as the molecular weight regulator. The molecular weight regulator is usually used in an amount of 0.3 to 0.8 parts, more preferably 0.5 to 0.8 parts, and the amount thereof can be adjusted according to the product performance requirements and the type of molecular weight regulator.

[0041] In the present invention, the molecular weight regulator is added once, multiple times or continuously in the emulsion polymerization, and can be selected according to different requirements of product performance.

[0042] The reactive antioxidant selected in the present invention is a reactive antioxidant with an amide group. In the art, reactive antioxidants with an amide group of aniline phenyl are generally used, and the general formula is:

[0043]

[0044] 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 antioxidant is 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)tivalamide, which are used as functional monomers to participate in the polymerization reaction. Usually, when the binding amount of reactive antioxidants in nitrile rubber reaches 1-2%, it can show good resistance to heat and oxygen aging and can be used in the field of oil-resistant sealing in high-temperature working environments.

[0045] Usually, when emulsion polymerization of nitrile rubber uses a composite emulsification system, its emulsifier includes a primary emulsifier and an auxiliary emulsifier, among which:

[0046] 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;

[0047] 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.

[0048] The compounding of anionic emulsifier and nonionic emulsifier can play a synergistic role and improve the stability of latex.

[0049] The invention adopts a specific composite emulsifying system, wherein the composite emulsifier is at least composed of three kinds of disproportionated rosin acid soap, linear alkylbenzene sulfonic acid and naphthalenesulfonic acid formaldehyde condensate sodium salt.

[0050] The amount of the compound emulsifier added in the present invention can be the amount of emulsifiers used in the general technology in the art, especially when anionic emulsifiers and nonionic emulsifiers are compounded. The amount of the compound emulsifier used in the present invention is preferably 3.2 to 6.5 parts, more preferably 3.8 to 6.0 parts.

[0051] The present invention requires that the disproportionated rosin acid soap added to the compound 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 emulsion polymerization. The recommended amount of disproportionated rosin acid soap is 2.0 to 4.0 parts, and more preferably 2.5 to 4.0 parts.

[0052] 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 1.0 to 2.0 parts.

[0053] The present invention requires that the sodium salt of naphthalenesulfonic acid formaldehyde condensate and C 10 ~C 13 The linear alkylbenzene sulfonic acid is used at the same time, and its usage amount is determined according to the needs, and the present invention does not particularly limit it. If it is not added, the stability of the polymer emulsion will decrease, and the phenomenon of glue hanging will easily occur during the polymerization process. The preferred usage amount of the sodium salt of naphthalenesulfonic acid formaldehyde condensate is 0.2 to 0.5 parts, and more preferably 0.3 to 0.5 parts.

[0054] The present invention also does not exclude the addition of other anionic emulsifiers and nonionic emulsifiers in the composite emulsification system in addition to disproportionate rosin acid potassium soap or sodium soap, linear alkylbenzene sulfonic acid and naphthalenesulfonic acid formaldehyde condensate sodium salt, such as potassium oleate, potassium stearate, etc.

[0055] 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.

[0056] The present invention does not particularly limit the type and amount of electrolyte added. General electrolytes and general amounts can be used, such as potassium hydroxide, sodium pyrophosphate, sodium carbonate, etc., and the amount added can be 0.1 to 0.5 parts.

[0057] 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, such as ferrous sulfate, sodium ferric ethylenediaminetetraacetate, sodium thiosulfate, etc., and the amount added can be 0.01 to 0.15 parts.

[0058] The present invention does not particularly limit the type and amount of the chelating agent, and general chelating agents and general amounts can be used, such as disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, etc., and the amount added can be 0.01 to 0.05 parts.

[0059] Unless otherwise specified, the parts mentioned in the present invention refer to 100 parts by mass of the total amount of the main monomers to be polymerized, and the percentages are by mass percentages.

[0060] The present invention also provides a more preferred method for preparing nitrile rubber, comprising the steps of:

[0061] The monomer composition is (based on 100 parts by mass of butadiene and acrylonitrile, the same below) 80-83 parts of butadiene, 17-20 parts of acrylonitrile, 1.5-2.5 parts of a reactive antioxidant with an amide group, 200-230 parts of deionized water, and a composite emulsifier including disproportionated rosin acid soap, C 10 ~C 13 The emulsifying system of linear alkylbenzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate sodium salt is prepared, the amount of the composite emulsifier is 3.2 to 6.5 parts, and the amount of disproportionated rosin acid soap is 2.0 to 4.0 parts, C 10 ~C 13 The dosage of linear alkylbenzene sulfonic acid is 1.0-2.0 parts, the dosage of naphthalenesulfonic acid formaldehyde condensate sodium salt is 0.2-0.5 parts; the initiator system is organic hydrogen peroxide-ferrous salt, and the dosage of organic hydrogen peroxide is 0.1-0.3 parts; the molecular weight regulator is tert-dodecyl mercaptan, and the dosage is 0.3-0.8 parts; acrylonitrile is added in more than 3 times; the polymerization temperature is 5-15°C; and the preferred dosage of the composite emulsifier is 3.8-6.0 parts.

[0062] More preferred:

[0063] After the polymerization kettle is evacuated, deionized water, composite emulsifier, reducing agent, electrolyte, chelating agent, part of monomers and molecular weight regulator are added, and after the temperature is controlled to 8-12 DEG C, an initiator is added. When the reaction conversion rate reaches 30-35%, acrylonitrile is added for the second time; when the reaction conversion rate reaches 45-55%, acrylonitrile is added for the third time; when the reaction conversion rate reaches 60-65%, acrylonitrile is added for the fourth time; when the reaction conversion rate reaches 70-76%, a terminator is added, the material is discharged, and a nitrile rubber is obtained after degassing, condensation, washing and drying.

[0064] The invention develops a method for preparing a nitrile rubber with a simple process, adopts an emulsification system composed of a compound of disproportionated rosin acid soap, dodecylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate sodium salt and a low-temperature emulsion polymerization process, introduces a reactive antioxidant into the emulsion polymerization, effectively bonds the antioxidant group to the polymer molecular chain, and solves the technical problems of many fine particles of rubber during coagulation and great difficulty in washing and drying during the post-treatment process due to the low acrylonitrile content of the heat-resistant nitrile rubber. At the same time, the invention finds that when acrylonitrile is added in batches for multiple times, especially four times, the glass transition temperature of the heat-resistant nitrile rubber can be reduced, so that the polymer has excellent high-temperature resistance and low-temperature resistance performance.

[0065] The nitrile rubber produced by the method of the present invention has excellent heat-oxidative aging resistance, and the nitrile rubber meets the application requirements of oil-resistant seals in high-temperature working environments; in addition, when the present application is used to synthesize the mortar, the polymerization process is stable and the energy consumption is low.

[0066] It can be seen from the best production scheme in the embodiment that the technology of the present invention can produce acrylonitrile content of 17-20% and Mooney viscosity The nitrile rubber with good heat-oxidative aging resistance and a reactive antioxidant combined with a content of 1 to 2% can be used in the field of oil-resistant sealing in high-temperature working environments.

[0067] The test method of nitrile rubber uses the conventional test method: the total solid test adopts the SH / T1154-92 standard; the Mooney viscosity The test adopts GB / T1232-2000 standard; the test of acrylonitrile content adopts SH / T1157-1997 standard; the tensile strength test adopts GB / T528-1998 standard; the elongation at break test adopts GB / T528-1998 standard.

[0068] 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.

[0069] The nitrile rubber obtained in Example 4 was subjected to a heat and oxygen aging resistance test.

[0070] 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.

[0071] The result of the 100h oxygen absorption test (100°C) is 0.238%, which indicates that the nitrile rubber obtained by using the reactive antioxidant with amide groups as the functional monomer has good heat-oxidation resistance.

[0072] Example 1

[0073] A 10L polymerization kettle was evacuated and replaced with nitrogen until the vacuum degree reached -0.1Mpa. 215 parts of deionized water, 80 parts of butadiene, 11 parts of acrylonitrile, 2.3 parts of N-(4-(anilino)phenyl)methacrylamide, a composite emulsifier (including 2.8 parts of disproportionated rosin acid potassium soap, 1.1 parts of dodecylbenzenesulfonic acid, 0.38 parts of naphthalenesulfonic acid formaldehyde condensate sodium salt), 0.11 parts of sodium ferric ethylenediaminetetraacetate, 0.04 parts of disodium ethylenediaminetetraacetate, and 0.6 parts of tert-dodecyl mercaptan were added in sequence (specific components are shown in Table 1).

[0074] Then the temperature was controlled, and when the reaction temperature reached 7°C, 0.2 parts of diisopropylbenzene hydroperoxide as an initiator was added.

[0075] When the reaction conversion rate reaches 30-35%, 3 parts of secondary acrylonitrile are added; when the reaction conversion rate reaches 45-55%, 3 parts of tertiary acrylonitrile are added; when the reaction conversion rate reaches 60-65%, 3 parts of quadruple acrylonitrile are added; when the reaction conversion rate reaches 73%, 0.07 parts of sodium nitrite as a terminator is added, the material is discharged, and a nitrile rubber is obtained after degassing, condensation, washing and drying.

[0076] The preparation methods of Examples 2-8 are the same as that of Example 1, except for the differences shown in Table 1.

[0077] The preparation methods of Comparative Examples 1-8 are the same as those of Example 1, except for the differences shown in Table 2.

[0078] The performance of the nitrile rubber prepared in Examples 1-8 was tested, and the specific test results are shown in Table 3.

[0079] The performance of the nitrile rubber prepared in Comparative Examples 1-8 was tested, and the specific test results are shown in Table 4.

[0080] Table 1 Composition of Examples

[0081]

[0082]

[0083] Table 2 Components of Comparative Examples

[0084]

[0085]

[0086] Table 3 Example nitrile rubber performance test results

[0087]

[0088]

[0089] Table 4 Comparative Example Nitrile Rubber Performance Test Results

[0090]

[0091] As can be seen from Tables 3 and 4, the technology of the present invention can produce acrylonitrile content of 17-20% and Mooney viscosity The nitrile rubber with good heat-oxidative aging resistance and a reactive antioxidant combined with a content of 1 to 2% can be used in the field of oil-resistant sealing in high-temperature working environments.

[0092] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a nitrile rubber having improved heat-oxidative aging resistance, characterized in that: The preparation method at least comprises: Butadiene and acrylonitrile are used as main monomers for polymerization, and a reactive antioxidant with an amide group is used as a functional monomer; based on the total amount of butadiene and acrylonitrile added as 100 parts by weight, the acrylonitrile content is less than 25 parts, and acrylonitrile is added in batches or continuously, preferably more than three times; a low-temperature emulsion polymerization method is adopted, a composite emulsification system is used, and 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 composite emulsifier added is 3.2 to 6.5 parts, more preferably 3.8 to 6.0 parts, a molecular weight regulator is added once or multiple times, a nitrile rubber slurry is synthesized, a terminator is added, and a nitrile rubber is obtained after degassing, coagulation, washing and drying.

2. The method for preparing nitrile rubber according to claim 1, wherein The main monomer composition ratio of the polymerization is: 80-83 parts of butadiene and 17-20 parts of acrylonitrile.

3. The method for preparing acrylonitrile-butadiene rubber according to claim 1 or 2, wherein The acrylonitrile is added in four times: when the reaction conversion rate reaches 30-35%, acrylonitrile is added for the first time; when the reaction conversion rate reaches 45-55%, acrylonitrile is added for the second time; when the reaction conversion rate reaches 60-65%, acrylonitrile is added for the third time; preferably, the amount of acrylonitrile monomer added for the first time is 30-50% of the total amount of acrylonitrile monomer added, and the amount of the remaining acrylonitrile monomer added is 50-70% of the total amount of acrylonitrile monomer added.

4. The method for preparing nitrile rubber according to claim 1, wherein The polymerization reaction temperature of the low-temperature emulsion polymerization is 5 to 15°C, and the preferred polymerization reaction temperature is 8 to 12°C.

5. The method for preparing nitrile rubber according to claim 1, wherein Based on 100 parts by weight of the total amount of butadiene and acrylonitrile added, the amount of disproportionated rosin acid soap in the composite emulsifier is 2.0 to 4.0 parts, preferably 2.5 to 4.0 parts.

6. The method for preparing acrylonitrile-butadiene rubber according to claim 1 or 5, wherein: Based on the total amount of butadiene and acrylonitrile added as 100 parts by mass, the C 10 ~C 13 The amount of linear alkylbenzene sulfonic acid used is 1.0 to 2.0 parts, preferably 1.0 to 1.5 parts.

7. The method for preparing acrylonitrile-butadiene rubber according to claim 1, 5 or 6, wherein: The amount of the sodium salt of naphthalenesulfonic acid formaldehyde condensate is 0.2 to 0.5 parts, and the preferred amount of the sodium salt of naphthalenesulfonic acid formaldehyde condensate is 0.3 to 0.5 parts.

8. The method for preparing nitrile rubber according to claim 1, wherein The initiating system used in the low-temperature emulsion polymerization is an organic hydrogen peroxide-ferrous salt, the organic hydrogen peroxide is preferably diisopropylbenzene hydroperoxide, and the preferred addition amount is 0.1 to 0.3 parts; the reducing agent used in the low-temperature emulsion polymerization is preferably sodium ferric ethylenediaminetetraacetate, and the preferred addition amount is 0.01 to 0.15 parts; the chelating agent used in the low-temperature emulsion polymerization is preferably disodium ethylenediaminetetraacetate, and the preferred addition amount is 0.01 to 0.05 parts.

9. The method for preparing nitrile rubber according to claim 1, wherein The molecular weight regulator is one of tert-dodecyl mercaptan and n-dodecyl mercaptan, preferably tert-dodecyl mercaptan; the molecular weight regulator is preferably used in an amount of 0.3 to 0.8 parts, more preferably 0.5 to 0.8 parts; the terminator is preferably one of sodium nitrite, hydroxylamine sulfate, and diethylhydroxylamine; the terminator is preferably added in an amount of 0.05 to 0.15 parts.

10. The method for preparing acrylonitrile-butadiene rubber according to claim 1 or 9, characterized in that: When the reaction conversion rate reaches 70-76%, the terminator is added.

11. The method for preparing nitrile rubber according to claim 1, wherein The preparation method comprises the following steps: Based on 100 parts by mass of butadiene and acrylonitrile, the monomer composition is: 80-83 parts of butadiene, 17-20 parts of acrylonitrile, 1.5-2.5 parts of a reactive antioxidant with an amide group, 200-230 parts of deionized water, and a composite emulsifier including disproportionated rosin acid soap, C 10 ~C 13 The emulsifying system of linear alkylbenzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate sodium salt is prepared, the amount of the composite emulsifier is 3.2 to 6.5 parts, and the amount of disproportionate rosin acid soap is 2.0 to 4.0 parts, C 10 ~C 13 The dosage of linear alkylbenzene sulfonic acid is 1.0-2.0 parts, the dosage of naphthalenesulfonic acid formaldehyde condensate sodium salt is 0.2-0.5 parts; the initiator system is organic hydrogen peroxide-ferrous salt, and the dosage of organic hydrogen peroxide is 0.1-0.3 parts; the molecular weight regulator is tert-dodecyl mercaptan, and the dosage is 0.3-0.8 parts; acrylonitrile is added in more than 3 times; the polymerization reaction temperature is 5-15°C; and the preferred dosage of the composite emulsifier is 3.8-6.0 parts.

12. The method for preparing acrylonitrile-butadiene rubber according to claim 1 or 11, characterized in that: The preparation method comprises the following steps: After the polymerization kettle is evacuated, deionized water, composite emulsifier, reducing agent, electrolyte, chelating agent, part of monomers and molecular weight regulator are added, and after the temperature is controlled to 8-12 DEG C, an initiator is added. When the reaction conversion rate reaches 30-35%, acrylonitrile is added for the second time; when the reaction conversion rate reaches 45-55%, acrylonitrile is added for the third time; when the reaction conversion rate reaches 60-65%, acrylonitrile is added for the fourth time; when the reaction conversion rate reaches 70-76%, a terminator is added, the material is discharged, and a nitrile rubber is obtained after degassing, condensation, washing and drying.

13. The method for preparing acrylonitrile-butadiene rubber according to claim 1 or 11, characterized in that: The reactive antioxidant with an amide group is a reactive antioxidant with an amide group of aniline phenyl, and the general formula is: 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, 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.

14. The method for preparing acrylonitrile-butadiene rubber according to claim 1, 6 or 11, characterized in that: The C 10 ~C 13 The linear alkylbenzenesulfonic acid is dodecylbenzenesulfonic acid.

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