Butyronitrile ester rubber as well as preparation method and application thereof

Abstract

The invention discloses butyronitrile ester rubber as well as a preparation method and application thereof. Polymeric monomers of the butyronitrile ester rubber comprise butadiene, acrylonitrile and itaconic acid diester. According to the preparation method disclosed by the invention, itaconic acid diester is used as an ester-containing monomer for copolymerization of butyronitrile ester rubber; the butyronitrile ester rubber with excellent performances of high and low temperature resistance, oil resistance and stability in multiple deformations is obtained by adopting low-temperature copolymerization and improving a feeding mode, a raw material ratio and the like.

Description

Technical Field

[0001] The invention relates to the technical field of modified nitrile rubber preparation, and in particular to nitrile ester rubber and a preparation method and application thereof. Background Art

[0002] With the continuous development of the economy, the demand for sealing materials in various fields is increasing, and due to the harsh application environment, higher requirements are placed on the low temperature resistance, heat resistance, friction resistance and other properties of sealing materials.

[0003] As a copolymer of butadiene and acrylonitrile, nitrile rubber is widely used in sealing products due to its excellent properties such as good oil resistance, wear resistance, solvent resistance, heat resistance and easy processing. However, due to the increasingly stringent application conditions of sealing materials, it is necessary to meet the requirements of application in complex environments such as high altitude and deep sea, which requires nitrile rubber to have more excellent performance. The existing technology mostly uses the method of introducing a third monomer copolymerization or mixing to modify nitrile rubber. At present, there are studies on products such as carboxyl nitrile rubber, end-functionalized nitrile rubber, fluorine-containing nitrile rubber and nitrile ester rubber. Among them, nitrile ester rubber, as a special rubber with excellent performance, has also attracted the attention of researchers. However, the current research on nitrile ester rubber is mostly focused on the performance of nitrile ester and subsequent modification research, and there are few reports on the synthesis and preparation of low-temperature copolymerized ester-functional monomer-modified nitrile rubber.

[0004] At present, the preparation of ester-containing monomers in nitrile rubber mainly adopts concentrated sulfuric acid to catalyze the dehydration of acrylic acid and alcohol to prepare acrylic acid. Due to the strong oxidizing property of concentrated sulfuric acid, the yield of the product is low and the color is dark. At the same time, the post-processing process is complicated, the equipment is seriously corroded, and the waste acid pollutes the environment. In view of this, the catalytic system based on ferric chloride, tin tetrachloride, aminosulfonic acid, and solid-supported heteropolyacid has achieved better esterification reaction results, but there are also defects such as catalyst loss, poor compatibility, complex post-processing, high cost and long reaction time to varying degrees.

[0005] CN104628955A discloses a method for producing chemically modified nitrile rubber, which uses butadiene, acrylonitrile and butyl acrylate as polymerization monomers, sodium oleate, tert-dodecyl mercaptan, sodium pyrophosphate, oleic acid, sodium sulfite, sodium hydroxide and the like as auxiliary agents, and the polymerization temperature is 35-45°C. The modified nitrile rubber is obtained by polymerization, degassing, coagulation and drying. However, the Mooney viscosity of the nitrile rubber obtained by this method is ML 1+4 100℃ The molecular weight of the polyol is 105-145, which is not easy to process subsequently, and no relevant data such as the ester content is indicated.

[0006] CN105294939A discloses a low-temperature hydrogenated nitrile rubber raw rubber and a preparation method thereof, which involves the synthesis of a butadiene-propylene-dibutyl fumarate copolymer. However, the method uses a one-time addition and reaction, and the main research key lies in the hydrogenation of the ester-containing nitrile rubber copolymer, and does not involve the performance of the ester-containing copolymer. The one-time addition method will affect the various properties of the copolymer and is difficult to stably regulate. At the same time, the ester used is an unsaturated ester. If it is not used for subsequent hydrogenation, the rubber performance will be greatly reduced.

[0007] CN110684252A discloses a carboxylated nitrile rubber and a preparation method thereof, and the technical scheme adopted is based on carboxylated nitrile rubber raw rubber, reinforcing agent, antioxidant, esterification vulcanizing agent, esterification dehydrating agent, and esterification accelerator as raw materials. Carboxylated nitrile rubber raw rubber is vulcanized using polyols, and the alcohol groups of the polyols react with the carboxyl groups of the carboxylated nitrile rubber raw rubber to form ester bonds, and finally a cross-linking system is formed through the ester bonds to complete the vulcanization of the carboxylated nitrile rubber raw rubber. The technical scheme is to introduce ester bonds into the carboxylated nitrile rubber in the vulcanization stage, rather than introducing them through copolymerization.

[0008] CN109517240A discloses a method for preparing a nitrile rubber with a dynamic crosslinking structure, which is prepared by reacting the cyano group on the nitrile rubber with an isocyanate crosslinking agent after oximation. Wherein, the crosslinking reaction of isocyanate and oximated nitrile rubber introduces a carbamate bond, which is a necessary condition for forming and maintaining the dynamic nitrile rubber structure. By regulating and controlling the nitrile rubber cyano content, the crosslinking agent structure and the relative amount of the crosslinking agent, a dynamic nitrile rubber of different properties can be prepared. In addition, due to the dynamic reversibility of the carbamate bond in the nitrile rubber crosslinking system without any catalyst, the novel nitrile rubber prepared has the ability to be recovered and reprocessed. This method is actually the modification of the nitrile rubber product, and is not to introduce an ester group in the copolymerization synthesis stage of the nitrile rubber.

[0009] CN103443188A discloses a highly saturated nitrile rubber composition and a rubber crosslinked product, wherein a highly saturated nitrile rubber (A1) containing carboxyl groups and containing 1 to 60 weight percent of α,β-ethylenically unsaturated dicarboxylic acid monoester monomer units and a highly saturated nitrile rubber (A2) containing 0.9wt% or less of α,β-ethylenically unsaturated dicarboxylic acid monoester monomer units are used in a specific ratio, wherein the rubber composition obtained by mixing with a polyamide resin (B) has excellent roller processability and can provide a rubber crosslinked product having excellent normal physical properties, oil resistance, fuel oil resistance, and tensile strength at high temperatures. The method provides corresponding reaction raw materials, uses α,β-ethylenically unsaturated dicarboxylic acid monoester monomers to prepare highly saturated nitrile rubber containing carboxyl groups, and uses them for subsequent high-temperature mixing, and the application point is completely different from the present invention.

[0010] CN112521551A discloses a tetrapolymer of itaconate, wherein a mixture of diethyl itaconate, butyl acrylate, ethyl acrylate and glycidyl methacrylate is poured into a flask, plugged with a glass stopper and stirred. After pre-emulsification at 20°C for 1 hour, an initiator, tert-butyl hydroperoxide, is injected into the flask to polymerize and obtain a latex. This invention is for laboratory small-batch production, and the application point is modified acrylate, and the emulsion polymerization is carried out by a one-time feeding method.

[0011] US4675436A reports a method for preparing acrylic esters by esterification of long-chain alcohols and unsaturated monocarboxylic acids, wherein strong acid concentrated sulfuric acid is used as a catalyst, thiophene azine and hydroquinone monomethyl ether are used as inhibitors, and air is used as a water-carrying agent to synthesize acrylic ester compounds containing long-chain (C6-C20) alcohols, and the conversion rate (about 75%) and selectivity (about 96%) both reach good levels. CN114369023A reports a method for preparing 2-aryl acrylic esters in high yield by reacting trifluoromethyl olefins with alcohols in alkali and organic solvents without the need for additional catalysts. The method has a high product yield (about 70%), good selectivity (about 90%), and the reaction is insensitive to water and air, and has good industrial application prospects, but the method has the disadvantage of a narrow scope of application of substrates.

[0012] Ishihara et al. (Tetrahedron., 2002, 58(41): 8179-8188) reported that the use of inorganic metal Hf(IV) and Zr(IV) salts as esterification catalysts can achieve a direct dehydration reaction of acrylic acid and alcohol (C2-C8) in an equimolar ratio to prepare acrylic ester compounds with a yield of up to 99%. This method is simple, practical and highly efficient, but the catalyst used is relatively expensive, which limits the large-scale application of this method. Summary of the invention

[0013] The object of the present invention is to provide a nitrile rubber and a preparation method and application thereof. The preparation method of the present invention is practical, and itaconate diester is used as an ester-containing monomer for the copolymerization of nitrile rubber; low-temperature copolymerization is adopted, and a nitrile rubber with excellent properties of high and low temperature resistance, oil resistance, and multiple deformation stability is obtained by improving the feeding method and raw material ratio.

[0014] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0015] In one aspect, the present invention provides a nitrile rubber, wherein the polymerization monomers of the nitrile rubber include butadiene, acrylonitrile and itaconic acid diester; the structural formula of the itaconic acid diester is:

[0016]

[0017] In the formula, R is a C1-C12 alkyl group.

[0018] According to the nitrile rubber of the present invention, preferably, based on 100 parts by total weight of the butadiene, acrylonitrile and itaconic acid diester, the butadiene is 40 to 75 parts, the acrylonitrile is 19 to 34 parts, and the itaconic acid diester is 5.3 to 38 parts.

[0019] According to the nitrile rubber of the present invention, preferably, the nitrile rubber is prepared by emulsion copolymerization of butadiene, acrylonitrile and itaconate.

[0020] According to the nitrile rubber of the present invention, preferably, the content of itaconic acid diester structure in the nitrile rubber is ≥5wt%, more preferably 6wt% to 25wt%.

[0021] According to the nitrile rubber of the present invention, preferably, the Mooney viscosity ML 1+4 100℃ All are ≤80, more preferably 64-79; the tensile strength of the vulcanized rubber is ≥19MPa, more preferably 19-25MPa, the glass transition temperature is ≤-40℃, more preferably -56℃ to -40℃; the thermal weight loss temperature is ≥320℃, more preferably 320-350℃.

[0022] Another aspect of the present invention provides a method for preparing a nitrile rubber, comprising the following steps:

[0023] Based on 100 parts of the total weight of acrylonitrile, butadiene and itaconic acid diester, 240-315 parts of desalted water, 3-8 parts of emulsifier, 0.06-0.4 parts of reducing agent, 0.03-0.3 parts of chelating agent, 0.5-1 parts of pH buffer, 0.03-0.4 parts of diffusing agent, 0.1-1.2 parts of molecular weight regulator, 15-30 parts of acrylonitrile, 5-35 parts of itaconic acid diester and 0.05-0.2 parts of deoxidizer are added into a reaction container, and after the addition is completed, 40-75 parts of butadiene are added in a protective gas atmosphere, and the mixture is stirred for pre-emulsification, and then 0.02-0.1 parts of initiator are added for polymerization reaction;

[0024] When the monomer conversion rate of acrylonitrile, butadiene and itaconate diester reaches 20% to 25%, acrylonitrile is added once; when the monomer conversion rate reaches 40% to 50%, emulsifier, itaconate diester, initiator and molecular weight regulator are added; when the monomer conversion rate reaches 60% to 65%, acrylonitrile is added once; when the monomer conversion rate reaches 80% to 85%, 0.5 to 1 part of terminator is added to terminate the reaction, followed by degassing, condensation, washing and drying to obtain raw nitrile rubber.

[0025] According to the preparation method of the present invention, preferably, when the monomer conversion rate reaches 20% to 25%, 2 to 4 parts of acrylonitrile are added.

[0026] According to the preparation method of the present invention, preferably, when the monomer conversion rate reaches 40% to 50%, 1 to 5 parts of emulsifier, 0.3 to 3 parts of dibutyl itaconate, 0.001 to 0.003 parts of initiator, and 0.2 to 0.4 parts of molecular weight regulator are added.

[0027] According to the preparation method of the present invention, preferably, when the monomer conversion rate reaches 60% to 65%, 2 to 4 parts of acrylonitrile are added.

[0028] According to the preparation method of the present invention, preferably, the emulsifier is a composite emulsification system of anionic surfactant and nonionic surfactant, and the composite mass ratio is (3-4):1;

[0029] The anionic surfactant is a fatty alkyl sulfonate or a disproportionated rosin acid soap, and the fatty alkyl sulfonate is, for example, sodium dodecylbenzene sulfonate, sodium dodecyl sulfonate, etc.; the nonionic surfactant is a polyoxyethylene ether.

[0030] According to the preparation method of the present invention, preferably, the amount of the emulsifier used is 4 to 6 parts.

[0031] According to the preparation method of the present invention, preferably, the reducing agent is selected from but not limited to at least one of sodium formaldehyde sulfoxylate, ferrous sulfate, cuprous sulfate, EDTA sodium iron salt, EDTA sodium copper salt and the like.

[0032] According to the preparation method of the present invention, preferably, the amount of the reducing agent is 0.2 to 0.3 parts.

[0033] According to the preparation method of the present invention, preferably, the chelating agent is selected from at least one of but not limited to EDTA tetrasodium salt, glutamic acid diacetate sodium salt, etc.; more preferably EDTA tetrasodium salt.

[0034] According to the preparation method of the present invention, preferably, the amount of the chelating agent is 0.1 to 0.25 parts.

[0035] According to the preparation method of the present invention, preferably, the pH buffer is selected from but not limited to at least one of alkaline buffers such as sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium acetate, etc.; the pH needs to be adjusted to neutral or weak alkaline, and the pH buffer is more preferably sodium bicarbonate.

[0036] According to the preparation method of the present invention, preferably, the dosage of the pH buffer is 0.8 to 1 part.

[0037] According to the preparation method of the present invention, preferably, the dispersant is a sodium naphthalenesulfonate formaldehyde condensate, selected from but not limited to at least one of β-naphthalenesulfonate sodium formaldehyde condensate, methylnaphthalenesulfonate sodium formaldehyde condensate, benzylnaphthalenesulfonic acid formaldehyde condensate, etc.; more preferably, it is β-naphthalenesulfonate sodium formaldehyde condensate.

[0038] According to the preparation method of the present invention, preferably, the amount of the diffusing agent is 0.2 to 0.3 parts.

[0039] According to the preparation method of the present invention, preferably, the molecular weight regulator is selected from but not limited to at least one of dodecyl mercaptan, tert-dodecyl mercaptan, and 2,4-diphenyl-4-methyl-1-pentene; more preferably tert-dodecyl mercaptan or 2,4-diphenyl-4-methyl-1-pentene.

[0040] According to the preparation method of the present invention, preferably, the molecular weight regulator is used in an amount of 0.8 to 1.2 parts.

[0041] According to the preparation method of the present invention, preferably, the oxygen scavenger is selected from but not limited to at least one of sodium dithionite, dimethyl ketoxime, isoascorbic acid, etc.; more preferably, it is sodium dithionite.

[0042] According to the preparation method of the present invention, preferably, the amount of the deoxidizer is 0.1 to 0.15 parts.

[0043] According to the preparation method of the present invention, preferably, the initiator is an organic hydroperoxide, selected from but not limited to at least one of cumene hydroperoxide, diisopropyl hydroperoxide, isopropyl tert-butyl peroxide, etc.; more preferably, it is diisopropyl hydroperoxide.

[0044] According to the preparation method of the present invention, preferably, the amount of the initiator is 0.04 to 0.08 parts.

[0045] According to the preparation method of the present invention, preferably, the polymerization reaction temperature is 20-30°C, more preferably 20-25°C.

[0046] According to the preparation method of the present invention, preferably, the terminator is selected from but not limited to at least one of sodium nitrite, hydroxylamine sulfate, diethylhydroxylamine, hydroquinone, p-aminoazobenzene, etc.; more preferably, sodium nitrite or diethylhydroxylamine.

[0047] According to the preparation method of the present invention, preferably, the amount of the terminator is 0.5 to 0.8 parts.

[0048] In the preparation method of the present invention, the degassing is preferably carried out in a degassing tower, more preferably for 4 to 5 hours, and the nitrile rubber latex is obtained after degassing; and the nitrile rubber raw rubber is obtained after coagulation, washing and drying. Coagulation, washing and drying are all conventional techniques in the preparation of nitrile rubber raw rubber, and the present invention does not limit this. "Protective gas" is, for example, nitrogen, argon, etc.

[0049] According to the preparation method of the present invention, preferably, the itaconate diester is prepared by the following reaction formula, which specifically comprises the following steps:

[0050]

[0051] Itaconic acid, fatty alcohol R-OH, a dehydrating agent and a catalyst are added to a reaction container, and the temperature is raised to carry out an esterification reaction. During the reaction, the generated water and the dehydrating agent are continuously evaporated. When the amount of separated water no longer increases and reaches the theoretical calculated amount, the reaction is stopped, the reaction system is filtered to obtain a filter cake, and the filter cake is distilled under reduced pressure to obtain the itaconic acid diester.

[0052] The fatty alcohol is the alcohol corresponding to R in the structural formula of itaconate diester, that is, R-OH, wherein R is a C1-C12 alkyl group.

[0053] In the preparation process of itaconic acid diester of the present invention, preferably, the temperature of the esterification reaction is 100-110° C., and the reaction time is 24-30 hours. The reaction temperature specifically depends on the azeotropic temperature of the dehydrating agent and water, and the reaction temperature should be higher than the azeotropic temperature.

[0054] In the preparation process of itaconic acid diester of the present invention, preferably, the molar ratio of itaconic acid to fatty alcohol is 1:(2-2.5), more preferably 1:(2-2.2).

[0055] In the preparation process of itaconate diester of the present invention, preferably, the dehydrating agent is selected from at least one of toluene, xylene, p-toluene and ethylbenzene, more preferably toluene or xylene.

[0056] In the preparation process of itaconic acid diester of the present invention, preferably, the added amount of the dehydrating agent is twice the total mass of itaconic acid and fatty alcohol.

[0057] In the preparation process of itaconate diester of the present invention, preferably, the catalyst is an organic sulfonic acid selected from but not limited to at least one of methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and 2-naphthalenesulfonic acid; more preferably, it is benzenesulfonic acid or p-toluenesulfonic acid.

[0058] In the preparation process of itaconic acid diester of the present invention, preferably, the amount of the catalyst used is 0.3 wt% to 1 wt% of the total mass of itaconic acid and fatty alcohol, and more preferably 0.5 wt% to 0.8 wt%.

[0059] In the preparation process of itaconate diester of the present invention, preferably, the evaporated dehydrating agent is separated and then refluxed into the reaction container to continue the reaction; or the dehydrating agent is added during the reaction, and the amount added is consistent with the amount evaporated.

[0060] The synthesis method of itaconic acid diester in the present invention is different from the current industrial production using concentrated sulfuric acid as a catalyst. The present invention uses organic sulfonic acid as a catalyst, a dehydrating agent as a solvent, and removes water generated in the esterification reaction in an azeotropic manner, thereby improving the esterification reaction efficiency. The yield of itaconic acid diester obtained in this way can reach more than 90%, and the price of itaconic acid diester raw materials is much higher than itaconic acid and fatty alcohol. Therefore, the production cost can be greatly reduced by adopting this method, and there is no concentrated sulfuric acid as a catalyst, which can reduce the corrosion to the equipment and realize the self-sufficiency of the ester monomer raw materials when preparing nitrile rubber. It is a green, efficient and large-scale production ester monomer synthesis method.

[0061] In another aspect, the present invention provides a nitrile rubber obtained by the above preparation method. Preferably, the content of itaconic acid diester structure in the nitrile rubber is ≥5wt%, more preferably 6wt% to 25wt%.

[0062] Preferably, the Mooney viscosity ML of the nitrile rubber is 1+4 100℃ All are ≤80, more preferably 64-79; the tensile strength of the vulcanized rubber is ≥19MPa, more preferably 19-25MPa, the glass transition temperature is ≤-40℃, more preferably -56℃ to -40℃; the thermal weight loss temperature is ≥320℃, more preferably 320-350℃.

[0063] The preparation method of the nitrile rubber provided by the invention utilizes a method of adding acrylonitrile, emulsifier, ester monomer and molecular weight regulator in multiple stages, thereby improving the uniform distribution problem of nitrile groups and ester groups in the nitrile rubber. By introducing itaconate diester monomer, the alkoxy carbon chain in the rubber polymer improves the flexibility of the chain segment, improves the low temperature resistance of the rubber polymer, improves the stability of multiple deformations, and the ester group structure improves the heat resistance and ozone stability of the polymer, improves the mechanical properties, etc., and obtains a nitrile rubber product with a dibutyl itaconate content of ≥5wt%, a Mooney viscosity of ≤80, a vulcanized rubber tensile strength of ≥18MPa, a glass transition temperature of ≤-40°C, and a thermal weight loss temperature of ≥320°C, so that the nitrile rubber product can be applied to special rubber sealing products.

[0064] Another aspect of the present invention provides the use of the above nitrile rubber in special rubber sealing products. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 This is the NMR spectrum of dibutyl itaconate prepared in Example 2.

[0066] Figure 2 This is the NMR spectrum of the nitrile rubber prepared in Example 2. DETAILED DESCRIPTION

[0067] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. It should be understood by those skilled in the art that the following specific description is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0068] All numerical specifications herein (e.g., temperature, time, concentration, and weight, etc., including ranges for each thereof) are generally approximate values ​​that may be appropriately varied (+) or (-) in increments of 0.1 or 1.0. All numerical specifications may be understood as being preceded by the term "about."

[0069] Example 1

[0070] This embodiment prepares a nitrile rubber, which specifically includes the following steps:

[0071] S1: At room temperature, itaconic acid (130g, 1mol), n-butanol (148g, 2mol) and benzenesulfonic acid (1.39g, 0.5wt%) were dissolved in a reactor containing 556g toluene. The reaction was carried out at 100°C for 24 hours. During the reaction, the water and dehydrating agent generated in the reaction were continuously evaporated, the water was separated, and the dehydrating agent was added. The amount of dehydrating agent added was consistent with the amount of dehydrating agent evaporated. After the amount of separated water reached the theoretical value, the reaction was stopped, the feed liquid was filtered to obtain a filter cake, the filter cake was added to the reactor, and the dehydrating agent toluene was removed by reduced pressure distillation at 50°C and 0.2MPa, and then the final dibutyl itaconate 221.9g was obtained by reduced pressure distillation at 72°C and 0.4MPa, with a yield of 91.6%.

[0072] S2: In a 15L polymerization kettle, 240 parts of desalted water, 3 parts of emulsifier (compounded mass ratio of disproportionated rosin acid soap and polyoxyethylene ether is 3:1), 0.03 parts of sodium formaldehyde sulfoxylate, 0.03 parts of ferrous sulfate, 0.03 parts of EDTA tetrasodium salt, 0.5 parts of sodium bicarbonate, 0.03 parts of sodium β-naphthalenesulfonate formaldehyde condensate, 0.1 parts of tert-dodecyl mercaptan, 20 parts of acrylonitrile, 7.7 parts of dibutyl itaconate and 0.05 parts of sodium dithionite were added. After the addition was completed, nitrogen was replaced three times, 68 parts of butadiene were added, and then 0.02 parts of diisopropylbenzene hydroperoxide were added at 20°C for polymerization reaction.

[0073] When the monomer conversion rate of acrylonitrile, butadiene and dibutyl itaconate reaches 20%, 2 parts of acrylonitrile monomer are added; when the monomer conversion rate reaches 40%, 1 part of emulsifier, 0.3 parts of dibutyl itaconate, 0.001 parts of diisopropylbenzene hydroperoxide and 0.2 parts of tert-dodecyl mercaptan are added; when the monomer conversion rate reaches 60%, 2 parts of acrylonitrile are added; when the monomer conversion rate reaches 80%, 0.5 parts of sodium nitrite are added to terminate the reaction and discharge the material; after discharge, the material is degassed in a degassing tower for 4 hours to obtain a nitrile rubber latex; after coagulation, washing and drying, the nitrile rubber raw rubber is obtained.

[0074] Example 2

[0075] This embodiment prepares a nitrile rubber, which specifically includes the following steps:

[0076] S1: At room temperature, itaconic acid (130g, 1mol), n-butanol (185g, 2.5mol) and benzenesulfonic acid (3.15g, 1wt%) were dissolved in a reactor containing 630g toluene. The reaction was carried out at 110°C for 30 hours. During the reaction, the water and dehydrating agent generated in the reaction were continuously evaporated, the water was separated, and the dehydrating agent was added. The amount of dehydrating agent added was consistent with the amount of dehydrating agent evaporated. After the amount of separated water reached the theoretical value, the reaction was stopped, the feed liquid was filtered to obtain a filter cake, the filter cake was added to the reactor, and the dehydrating agent toluene was removed by reduced pressure distillation at 50°C and 0.2MPa, and then the final dibutyl itaconate 228.4g was obtained by reduced pressure distillation at 72°C and 0.4MPa, with a yield of 94.3%.

[0077] S2: In a 15L polymerization kettle, 315 parts of desalted water, 8 parts of emulsifier (4:1 mass ratio of disproportionated rosin acid soap and polyoxyethylene ether), 0.2 parts of sodium formaldehyde sulfoxylate, 0.2 parts of ferrous sulfate, 0.3 parts of EDTA tetrasodium salt, 1 part of sodium bicarbonate, 0.4 parts of sodium β-naphthalenesulfonate formaldehyde condensate, 1.2 parts of tert-dodecyl mercaptan, 22 parts of acrylonitrile, 12 parts of dibutyl itaconate and 0.2 parts of sodium dithionite were added. After the addition was completed, nitrogen was replaced three times, 55 parts of butadiene were added, and then 0.1 parts of diisopropylbenzene hydroperoxide were added at 30°C to carry out polymerization reaction.

[0078] When the monomer conversion rate of acrylonitrile, butadiene and dibutyl itaconate reaches 25%, 4 parts of acrylonitrile monomer are added; when the monomer conversion rate reaches 40%, 3 parts of emulsifier, 3 parts of dibutyl itaconate, 0.003 parts of diisopropylbenzene hydroperoxide and 0.4 parts of tert-dodecyl mercaptan are added; when the monomer conversion rate reaches 65%, 4 parts of acrylonitrile are added; when the monomer conversion rate reaches 85%, 1 part of sodium nitrite is added to terminate the reaction and discharge the material; after discharge, the material is degassed in a degassing tower for 5 hours to obtain a nitrile rubber latex; after coagulation, washing and drying, the nitrile rubber raw rubber is obtained.

[0079] Example 3

[0080] This embodiment prepares a nitrile rubber, which specifically includes the following steps:

[0081] S1: At room temperature, itaconic acid (130g, 1mol), methanol (64g, 2mol) and benzenesulfonic acid (0.97g, 0.5wt%) were dissolved in a reactor containing 388g toluene. The reaction was carried out at 100°C for 28 hours. During the reaction, the water and dehydrating agent generated in the reaction were continuously evaporated, the water was separated, and the dehydrating agent was added. The amount of dehydrating agent added was consistent with the amount of dehydrating agent evaporated. After the amount of separated water reached the theoretical value, the reaction was stopped, the feed liquid was filtered to obtain a filter cake, the filter cake was added to the reactor, and the dehydrating agent toluene was removed by reduced pressure distillation at 50°C and 0.2MPa, and then the final dimethyl itaconate of 142.6g was obtained by reduced pressure distillation at 72°C and 0.4MPa, with a yield of 90.3%.

[0082] S2: In a 15L polymerization kettle, 270 parts of desalted water, 5 parts of emulsifier (compounded mass ratio of sodium dodecylbenzene sulfonate and polyoxyethylene ether is 3:1), 0.06 parts of sodium formaldehyde sulfoxylate, 0.3 parts of sodium ferric EDTA, 0.12 parts of sodium glutamate diacetate, 0.8 parts of sodium bicarbonate, 0.25 parts of benzylnaphthalenesulfonic acid formaldehyde condensate, 0.4 parts of tert-dodecyl mercaptan, 15 parts of acrylonitrile, 28 parts of dimethyl itaconate and 0.1 parts of dimethyl ketoxime were added. After the addition was completed, nitrogen was replaced three times, 51 parts of butadiene were added, and then 0.06 parts of diisopropylbenzene hydroperoxide were added at 25°C to carry out polymerization reaction.

[0083] When the monomer conversion rate of acrylonitrile, butadiene and dimethyl itaconate reaches 20%, 2 parts of acrylonitrile monomer are added; when the monomer conversion rate reaches 40%, 1 part of emulsifier, 2 parts of dimethyl itaconate, 0.002 parts of diisopropylbenzene hydroperoxide and 0.3 parts of tert-dodecyl mercaptan are added; when the monomer conversion rate reaches 60%, 2 parts of acrylonitrile are added; when the monomer conversion rate reaches 80%, 0.6 parts of hydroxylamine sulfate are added to terminate the reaction and discharge the material; after discharge, the material is degassed in a degassing tower for 4 hours to obtain a nitrile rubber latex; after coagulation, washing and drying, the nitrile rubber raw rubber is obtained.

[0084] Example 4

[0085] This embodiment prepares a nitrile rubber, which specifically includes the following steps:

[0086] S1: At room temperature, itaconic acid (130g, 1mol), ethanol (115g, 2.5mol) and benzenesulfonic acid (2.45g, 1wt%) were dissolved in a reactor containing 490mL toluene. The reaction was carried out at 110°C for 28 hours. During the reaction, the water and dehydrating agent generated in the reaction were continuously evaporated, the water was separated, and the dehydrating agent was added. The amount of dehydrating agent added was consistent with the amount of dehydrating agent evaporated. After the amount of separated water reached the theoretical value, the reaction was stopped, the feed liquid was filtered to obtain a filter cake, the filter cake was added to the reactor, and the dehydrating agent toluene was removed by vacuum distillation at 50°C and 0.2MPa, and then the final diethyl itaconate of 173.2g was obtained by vacuum distillation at 72°C and 0.4MPa, with a yield of 93.1%.

[0087] S2: In a 15L polymerization kettle, 265 parts of desalted water, 4 parts of emulsifier (compounded mass ratio of sodium dodecyl sulfate and polyoxyethylene ether is 3:1), 0.1 parts of sodium formaldehyde sulfoxylate, 0.2 parts of EDTA copper sodium salt, 0.15 parts of EDTA tetrasodium salt, 0.7 parts of sodium acetate alkaline buffer, 0.16 parts of sodium β-naphthalenesulfonate formaldehyde condensate, 0.6 parts of 2,4-diphenyl-4-methyl-1-pentene, 17 parts of acrylonitrile, 20.5 parts of diethyl itaconate and 0.05 parts of dimethyl ketone oxime were added. After the addition was completed, nitrogen was replaced three times, 56 parts of butadiene were added, and then 0.02 parts of diisopropylbenzene hydroperoxide were added at 20°C to carry out polymerization reaction.

[0088] When the monomer conversion rate of acrylonitrile, butadiene and diethyl itaconate reaches 25%, 2 parts of acrylonitrile monomer are added; when the monomer conversion rate reaches 40%, 2 parts of emulsifier, 2.5 parts of diethyl itaconate, 0.001 parts of diisopropylbenzene hydroperoxide and 0.3 parts of 2,4-diphenyl-4-methyl-1-pentene are added; when the monomer conversion rate reaches 65%, 2 parts of acrylonitrile are added; when the monomer conversion rate reaches 80%, 0.8 parts of diethylhydroxylamine are added to terminate the reaction and discharge the material; after discharge, the material is degassed in a degassing tower for 4 hours to obtain a nitrile rubber latex; after coagulation, washing and drying, the nitrile rubber raw rubber is obtained.

[0089] Example 5

[0090] This embodiment prepares a nitrile rubber, which specifically includes the following steps:

[0091] S1: At room temperature, itaconic acid (130g, 1mol), ethanol (110.4g, 2.4mol) and benzenesulfonic acid (1.2g, 0.5wt%) were dissolved in a reactor containing 480.8mL toluene. The reaction was carried out at 100°C for 24 hours. During the reaction, the water and dehydrating agent generated in the reaction were continuously evaporated, the water was separated, and the dehydrating agent was added. The amount of dehydrating agent added was consistent with the amount of dehydrating agent evaporated. After the amount of separated water reached the theoretical value, the reaction was stopped, the feed liquid was filtered to obtain a filter cake, the filter cake was added to the reactor, and the dehydrating agent toluene was removed by reduced pressure distillation at 50°C and 0.2MPa, and then the final diethyl itaconate of 170.6g was obtained by reduced pressure distillation at 72°C and 0.4MPa, with a yield of 91.7%.

[0092] S2: In a 15L polymerization kettle, 300 parts of desalted water, 7 parts of emulsifier (4:1 mass ratio of disproportionated rosin acid soap and polyoxyethylene ether), 0.2 parts of sodium formaldehyde sulfoxylate, 0.15 parts of cuprous sulfate, 0.25 parts of sodium glutamate diacetate, 0.6 parts of sodium acetate alkaline buffer, 0.32 parts of benzylnaphthalenesulfonic acid formaldehyde condensate, 1 part of tert-dodecyl mercaptan, 19 parts of acrylonitrile, 24 parts of diethyl itaconate and 0.05 parts of isoascorbic acid were added. After the addition was completed, nitrogen was replaced three times, 50 parts of butadiene were added, and then 0.08 parts of isopropyl tert-butyl peroxide were added at 25°C for polymerization.

[0093] When the monomer conversion rate of acrylonitrile, butadiene and diethyl itaconate reaches 25%, 2 parts of acrylonitrile monomer are added; when the monomer conversion rate reaches 40%, 4 parts of emulsifier, 3 parts of diethyl itaconate, 0.001 parts of isopropyl tert-butyl peroxide and 0.3 parts of tert-dodecyl mercaptan are added; when the monomer conversion rate reaches 65%, 2 parts of acrylonitrile are added; when the monomer conversion rate reaches 80%, 0.7 parts of hydroquinone are added to terminate the reaction and discharge the material; after discharge, the material is degassed in a degassing tower for 4 hours to obtain a nitrile rubber latex; after coagulation, washing and drying, the nitrile rubber raw rubber is obtained.

[0094] Example 6

[0095] This embodiment prepares a nitrile rubber, which specifically includes the following steps:

[0096] S1: At room temperature, itaconic acid (130g, 1mol), methanol (80g, 2.5mol) and benzenesulfonic acid (1.05g, 0.5wt%) were dissolved in a reactor containing 420mL toluene. The reaction was carried out at 110°C for 24 hours. During the reaction, the water and dehydrating agent generated in the reaction were continuously evaporated, the water was separated, and the dehydrating agent was added. The amount of dehydrating agent added was consistent with the amount of dehydrating agent evaporated. After the amount of separated water reached the theoretical value, the reaction was stopped, the feed liquid was filtered to obtain a filter cake, the filter cake was added to the reactor, and the dehydrating agent toluene was removed by vacuum distillation at 50°C and 0.2MPa, and then the final dimethyl itaconate of 142.5g was obtained by vacuum distillation at 72°C and 0.4MPa, with a yield of 90.2%.

[0097] S2: In a 15L polymerization kettle, 290 parts of desalted water, 6 parts of emulsifier (compounded mass ratio of disproportionated rosin acid soap and polyoxyethylene ether is 3:1), 0.08 parts of sodium formaldehyde sulfoxylate, 0.12 parts of ferrous sulfate, 0.09 parts of EDTA tetrasodium salt, 0.7 parts of sodium hydroxide, 0.19 parts of sodium methylnaphthalene sulfonate formaldehyde condensate, 0.3 parts of 2,4-diphenyl-4-methyl-1-pentene, 30 parts of acrylonitrile, 13 parts of dimethyl itaconate and 0.08 parts of sodium dithionite were added. After the addition was completed, nitrogen was replaced three times, 48 ​​parts of butadiene were added, and then 0.02 parts of cumene hydroperoxide were added at 20°C to carry out polymerization reaction.

[0098] When the monomer conversion rate of acrylonitrile, butadiene and dimethyl itaconate reaches 25%, 4 parts of acrylonitrile monomer are added; when the monomer conversion rate reaches 40%, 3 parts of emulsifier, 1 part of dimethyl itaconate, 0.003 parts of isopropylbenzene hydroperoxide and 0.2 parts of 2,4-diphenyl-4-methyl-1-pentene are added; when the monomer conversion rate reaches 65%, 4 parts of acrylonitrile are added; when the monomer conversion rate reaches 80%, 0.7 parts of sodium nitrite are added to terminate the reaction and discharge the material; after discharge, the material is degassed in a degassing tower for 4 hours to obtain a nitrile rubber latex; after coagulation, washing and drying, the nitrile rubber raw rubber is obtained.

[0099] Structural characterization and performance testing

[0100] In order to characterize the structural characteristics of the obtained nitrile rubber and its ester monomer, the dibutyl itaconate and nitrile rubber obtained in Example 2 were subjected to nuclear magnetic resonance analysis. The test results are as follows: Figure 1 and Figure 2 shown.

[0101] from Figure 1 The hydrogen nuclear magnetic spectrum shows that: 1HNMR (400MHz, CDCl3) δ6.33~6.29 (m, CH2=CH-, 1H), 5.68 (q, J=1.2Hz, CH2=CH-, 1H), 4.15 (t, J=6.6Hz, -CH2-C(CH2)-COO-CH2 -, 2H), 4.09 (t, J=6.7Hz, -C(CH2)-CH2-COO-CH2-(CH2)2CH3, 2H), 3.35~3.30 (m, -C(CH2)-CH2-COO-CH2-(CH2)2CH3, 2H), 1.68 -1.54 (m, -OCH2(CH2)2CH3, 4H), 1.46-1.29 (m, -OCH2(CH2)2CH3, 4H), 0.93 (td, J=7.3, 5.9Hz, -OCH2(CH2)2CH3, 6H). All of them correspond to the characteristic peaks of dibutyl itaconate, thus indicating that dibutyl itaconate has been successfully prepared. The remaining embodiments are not listed here one by one, and the yield is maintained at more than 90%. Different from the laboratory synthesis stage, this method can be used for industrial synthesis amplification.

[0102] from Figure 2 The hydrogen nuclear magnetic spectrum shows that: 1 HNMR (400MHz, CDCl3) The peak at δ2.55 (1) is CN-CH- next to the nitrile group, and the peak at δ4.05 (2) is -COO-CH2- next to the ester group, which proves that the dibutyl itaconate-modified nitrile rubber is successfully prepared.

[0103] In order to characterize the basic properties of the obtained nitrile rubber, the corresponding properties of the nitrile rubber prepared in Examples 1 to 6 were measured. Among them, the acrylonitrile content and the ester content were combined to obtain the results by nuclear magnetic area integration; the glass transition temperature was measured by DMA according to GB / T 29611-2013, with a heating rate of 5°C / min, a frequency of 10Hz, and a temperature range of -70 to 60°C; the Mooney viscosity was measured by Mooney viscometer (GT-7082S2) according to GB / T 1232.1-2016; the thermal weight loss temperature was measured by thermogravimetric analyzer at a heating rate of 20°C / min from 20°C to 650°C in a nitrogen atmosphere according to GB / T14837.2; the temperature at which the mass retention rate was reduced to 90wt% was the thermal weight loss temperature; the tensile strength was measured according to GB / T 528-2009. The test results are shown in Table 1.

[0104] Table 1

[0105] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Combined acrylonitrile content, wt% 22.6 28.5 18.3 19.9 22.1 35.9 Itaconate diester structure content, wt% 6.3 13.7 25.6 19.4 23.8 10.1 <![CDATA[Mooney viscosity ML 1+4 100℃ > 69.4 73.1 78.7 64.6 72.5 64.3 Vulcanized rubber tensile strength, MPa 20.1 23.1 19.4 21.6 20.9 24.5 Glass transition temperature, °C -42 -52 -49 -53 -56 -45 Thermal weight loss temperature, ℃ 322 339 329 343 346 335

[0106] It can be seen from Table 1 that the content of dibutyl itaconate in the nitrile rubbers prepared in Examples 1 to 6 is ≥5wt%, and the Mooney viscosity is ≤80; the tensile strength of the vulcanized rubber is ≥19MPa, and the glass transition temperature is ≤-40°C; the thermal weight loss temperature is ≥320°C, indicating that the obtained nitrile rubber has good low temperature resistance, heat resistance and mechanical properties.

[0107] In order to verify the influence of factors such as ester monomer synthesis and multi-point addition on the ester monomer yield and the performance of nitrile rubber, Example 2 was used as a reference to compare relevant data with the comparative examples under different conditions. The comparative example preparation method is as follows.

[0108] Comparative Examples 1 to 4

[0109] During the reaction of S1, only the temperature in Example 2 was changed to 40°C, 60°C, 80°C and 120°C, respectively, and other reaction conditions remained unchanged. The final yields of dibutyl itaconate were shown in Table 2.

[0110] Table 2

[0111] Yield of dibutyl itaconate (%) Example 2 94.3 Comparative Example 1 33.7 Comparative Example 2 46.2 Comparative Example 3 72.5 Comparative Example 4 79.3

[0112] From the data in Table 2, it can be seen that when the temperature is below 100°C, as the reaction temperature increases, the yield of the reaction has a relatively obvious growth trend. When the temperature is higher than 120°C, the higher temperature causes a dehydration reaction between n-butanol molecules to generate a by-product ether, which is not conducive to the reaction. Therefore, the temperature in this reaction should not exceed 120°C, so the reaction temperature is selected to be 100-110°C.

[0113] Comparative Example 5

[0114] Compared with Example 2, Comparative Example 5 adopts a one-time feeding method, and the specific S2 is as follows:

[0115] In a 15L polymerization kettle, 315 parts of desalted water, 8 parts of emulsifier (4:1 mass ratio of disproportionated rosin acid soap and polyoxyethylene ether), 0.2 parts of sodium formaldehyde sulfoxylate, 0.2 parts of ferrous sulfate, 0.3 parts of EDTA tetrasodium salt, 1 part of sodium bicarbonate, 0.4 parts of sodium β-naphthalenesulfonate formaldehyde condensate, 1.2 parts of tert-dodecyl mercaptan, 30 parts of acrylonitrile, 15 parts of dibutyl itaconate and 0.2 parts of sodium dithionite were added. After the addition was completed, nitrogen was replaced three times, 55 parts of butadiene were added, and then 0.1 parts of diisopropylbenzene hydroperoxide were added at 30°C for polymerization.

[0116] When the monomer conversion rate reaches 40%, 3 parts of emulsifier, 0.003 parts of diisopropylbenzene hydroperoxide and 0.4 parts of tert-dodecyl mercaptan are added. When the monomer conversion rate reaches 85%, 1 part of sodium nitrite is added to terminate the reaction and discharge the material. After discharge, the material is degassed in a degassing tower for 5 hours to obtain nitrile rubber latex, and the nitrile rubber raw rubber can be obtained after coagulation, washing and drying.

[0117] Comparative Example 6

[0118] Compared with Example 2, Comparative Example 6 adopts a one-time addition of initiator. The specific S2 is as follows:

[0119] In a 15L polymerization kettle, 315 parts of desalted water, 8 parts of emulsifier (compounded mass ratio of disproportionated rosin acid soap and polyoxyethylene ether 4:1), 0.2 parts of sodium formaldehyde sulfoxylate, 0.2 parts of ferrous sulfate, 0.3 parts of EDTA tetrasodium salt, 1 part of sodium bicarbonate, 0.4 parts of sodium β-naphthalenesulfonate formaldehyde condensate, 1.2 parts of tert-dodecyl mercaptan, 22 parts of acrylonitrile, 12 parts of dibutyl itaconate and 0.2 parts of sodium dithionite were added. After the addition was completed, nitrogen was replaced three times, 55 parts of butadiene were added, and then 0.103 parts of diisopropylbenzene hydroperoxide were added at 30°C for polymerization.

[0120] When the monomer conversion rate of acrylonitrile, butadiene and dibutyl itaconate reaches 25%, 4 parts of acrylonitrile monomer are added; when the monomer conversion rate reaches 40%, 3 parts of emulsifier, 3 parts of dibutyl itaconate and 0.4 parts of tert-dodecyl mercaptan are added; when the monomer conversion rate reaches 65%, 4 parts of acrylonitrile are added; when the monomer conversion rate reaches 85%, 1 part of sodium nitrite is added to terminate the reaction and discharge the material; after discharge, the material is degassed in a degassing tower for 5 hours to obtain nitrile rubber latex; after coagulation, washing and drying, the nitrile rubber raw rubber is obtained.

[0121] Comparative Example 7

[0122] Compared with Example 2, Comparative Example 7 adopts a one-time addition of acrylonitrile. The specific S2 is as follows:

[0123] In a 15L polymerization kettle, 315 parts of desalted water, 8 parts of emulsifier (4:1 mass ratio of disproportionated rosin acid soap and polyoxyethylene ether), 0.2 parts of sodium formaldehyde sulfoxylate, 0.2 parts of ferrous sulfate, 0.3 parts of EDTA tetrasodium salt, 1 part of sodium bicarbonate, 0.4 parts of sodium β-naphthalenesulfonate formaldehyde condensate, 1.2 parts of tert-dodecyl mercaptan, 30 parts of acrylonitrile, 12 parts of dibutyl itaconate and 0.2 parts of sodium dithionite were added. After the addition was completed, nitrogen was replaced three times, 55 parts of butadiene were added, and then 0.1 parts of diisopropylbenzene hydroperoxide were added at 30°C for polymerization.

[0124] When the monomer conversion rate reaches 40%, 3 parts of emulsifier, 3 parts of dibutyl itaconate, 0.003 parts of diisopropylbenzene hydroperoxide and 0.4 parts of tert-dodecyl mercaptan are added. When the monomer conversion rate reaches 85%, 1 part of sodium nitrite is added to terminate the reaction and discharge the material. After discharge, the material is degassed in a degassing tower for 5 hours to obtain nitrile rubber latex, and after coagulation, washing and drying, the nitrile rubber raw rubber is obtained.

[0125] Comparative Example 8

[0126] Compared with Example 2, Comparative Example 8 adopts a one-time addition method of dibutyl itaconate. The specific S2 is as follows:

[0127] In a 15L polymerization kettle, 315 parts of desalted water, 8 parts of emulsifier (4:1 mass ratio of disproportionated rosin acid soap and polyoxyethylene ether), 0.2 parts of sodium formaldehyde sulfoxylate, 0.2 parts of ferrous sulfate, 0.3 parts of EDTA tetrasodium salt, 1 part of sodium bicarbonate, 0.4 parts of sodium β-naphthalenesulfonate formaldehyde condensate, 1.2 parts of tert-dodecyl mercaptan, 22 parts of acrylonitrile, 15 parts of dibutyl itaconate and 0.2 parts of sodium dithionite were added. After the addition was completed, nitrogen was replaced three times, 55 parts of butadiene were added, and then 0.1 parts of diisopropylbenzene hydroperoxide were added at 30°C for polymerization.

[0128] When the monomer conversion rate of acrylonitrile, butadiene and dibutyl itaconate reaches 25%, 4 parts of acrylonitrile monomer are added; when the monomer conversion rate reaches 40%, 3 parts of emulsifier, 0.003 parts of diisopropylbenzene hydroperoxide and 0.4 parts of tert-dodecyl mercaptan are added; when the monomer conversion rate reaches 65%, 4 parts of acrylonitrile are added; when the monomer conversion rate reaches 85%, 1 part of sodium nitrite is added to terminate the reaction and discharge the material; after discharge, the material is degassed in a degassing tower for 5 hours to obtain a nitrile rubber latex; after coagulation, washing and drying, the nitrile rubber raw rubber is obtained.

[0129] Comparative Example 9

[0130] Compared with Example 2, no dibutyl itaconate was added in Comparative Example 9. The specific S2 is as follows:

[0131] In a 15L polymerization kettle, 315 parts of desalted water, 8 parts of emulsifier (compounded mass ratio of disproportionated rosin acid soap and polyoxyethylene ether 4:1), 0.2 parts of sodium formaldehyde sulfoxylate, 0.2 parts of ferrous sulfate, 0.3 parts of EDTA tetrasodium salt, 1 part of sodium bicarbonate, 0.4 parts of sodium β-naphthalenesulfonate formaldehyde condensate, 1.2 parts of tert-dodecyl mercaptan, 22 parts of acrylonitrile and 0.2 parts of sodium dithionite were added. After the addition was completed, nitrogen was replaced three times, 70 parts of butadiene were added, and then 0.1 parts of diisopropylbenzene hydroperoxide were added at 30°C for polymerization.

[0132] When the monomer conversion rate of acrylonitrile and butadiene reaches 25%, 4 parts of acrylonitrile monomer are added; when the monomer conversion rate reaches 40%, 3 parts of emulsifier, 0.003 parts of diisopropylbenzene hydroperoxide and 0.4 parts of tert-dodecyl mercaptan are added; when the monomer conversion rate reaches 65%, 4 parts of acrylonitrile are added; when the monomer conversion rate reaches 85%, 1 part of sodium nitrite is added to terminate the reaction and discharge the material; after discharge, the material is degassed in a degassing tower for 5 hours to obtain a nitrile rubber latex; after coagulation, washing and drying, the nitrile rubber raw rubber is obtained.

[0133] Comparative Example 10

[0134] Compared with Example 2, Comparative Example 10 replaces dibutyl itaconate with butyl acrylate as the ester monomer. The specific S2 is as follows:

[0135] In a 15L polymerization kettle, 315 parts of desalted water, 8 parts of emulsifier (compounded mass ratio of disproportionated rosin acid soap and polyoxyethylene ether 4:1), 0.2 parts of sodium formaldehyde sulfoxylate, 0.2 parts of ferrous sulfate, 0.3 parts of EDTA tetrasodium salt, 1 part of sodium bicarbonate, 0.4 parts of sodium β-naphthalenesulfonate formaldehyde condensate, 1.2 parts of tert-dodecyl mercaptan, 22 parts of acrylonitrile, 12 parts of butyl acrylate and 0.2 parts of sodium dithionite were added. After the addition was completed, nitrogen was replaced three times, 55 parts of butadiene were added, and then 0.1 parts of diisopropylbenzene hydroperoxide were added at 30°C for polymerization.

[0136] When the monomer conversion rate of acrylonitrile, butadiene and butyl acrylate reaches 25%, 4 parts of acrylonitrile monomer are added; when the monomer conversion rate reaches 40%, 3 parts of emulsifier, 3 parts of butyl acrylate, 0.003 parts of diisopropylbenzene hydroperoxide and 0.4 parts of tert-dodecyl mercaptan are added; when the monomer conversion rate reaches 65%, 4 parts of acrylonitrile are added; when the monomer conversion rate reaches 85%, 1 part of sodium nitrite is added to terminate the reaction and discharge the material; after discharge, the material is degassed in a degassing tower for 5 hours to obtain a nitrile rubber latex; after coagulation, washing and drying, the nitrile rubber raw rubber is obtained.

[0137] The properties of the nitrile rubbers prepared in Comparative Examples 5 to 9 are compared with those in Example 2 and are shown in Table 3.

[0138] Table 3

[0139]

[0140]

[0141] Comparative Example 5 Compared with Example 2, it can be found that the combined acrylonitrile content and ester content are correspondingly reduced, and the tensile strength is only 17.7MPa. This is because the one-time feeding method is adopted, resulting in an excessive initial acrylonitrile feed in the polymerization reaction, and the acrylonitrile reactivity ratio is too large, resulting in accelerated polymerization of acrylonitrile in the early stage of the polymerization reaction, thereby making the nitrile unit on the polymer chain unevenly distributed, and causing the ester monomer binding rate to decrease, resulting in a decrease in its temperature resistance and mechanical properties.

[0142] By comparing Comparative Example 6 with Example 2, it can be found that the content of acrylonitrile and dibutyl itaconate are reduced accordingly. This is because the initiator is added once, which leads to a faster reaction in the early stage of the polymerization reaction and a slower reaction in the later stage. According to field tests, it is found that the time required for the monomer conversion rate of Comparative Example 6 to reach 60% is much longer than that of Example 2.

[0143] Comparative Example 7 is compared with Example 2, and it can be found that the content of acrylonitrile is reduced. The reason is similar to that of Comparative Example 5. However, since dibutyl itaconate is added in stages, the uniform distribution of dibutyl itaconate chain segments in the polymer chain is improved, so the ester content does not decrease significantly.

[0144] Comparative Example 8 Compared with Example 2, it can be found that the bound acrylonitrile content is not significantly reduced, but the dibutyl itaconate content is greatly reduced. This is because the reactivity ratio of dibutyl itaconate is weaker than that of acrylonitrile and butadiene. Therefore, adding dibutyl itaconate at one time will cause the dibutyl itaconate chain segments to be unevenly distributed in the polymer molecular chain and the binding rate to be reduced, thereby resulting in a decrease in the bound ester content.

[0145] Comparative Example 9 compares Example 2 and finds that the acrylonitrile content of ordinary nitrile rubber without the addition of dibutyl itaconate is similar to that of Example 2, but the glass transition temperature is -27°C, which is much higher than -52°C of Example 2, and the thermal decomposition temperature is 293°C, which is much lower than 339°C of Example 2, indicating that the high and low temperature resistance of Example 2 is much better than that of Comparative Example 9. Therefore, the ester-containing nitrile rubber has a better application prospect.

[0146] The properties of the nitrile rubber prepared in Comparative Example 10 are compared with those in Example 2 and are shown in Table 4.

[0147] Table 4

[0148] Example 2 Comparative Example 10 Combined acrylonitrile content, wt% 28.5 28.3 Mooney viscosity ML1+4100℃ 73.1 70.6 Vulcanized rubber tensile strength, MPa 23.1 17.7 Glass transition temperature, °C -52 -38 Thermal weight loss temperature, ℃ 339 319

[0149] Comparative Example 10 Compared with Example 2, it can be found that the nitrile rubber to which dibutyl itaconate is added has a lower glass transition temperature and a higher thermal weight loss temperature than the nitrile rubber with butyl acrylate as the ester monomer. This is because at the same addition amount, dibutyl itaconate has two ester structures, and the amount of ester groups introduced is higher than that of butyl acrylate. At the same time, it also contains alkyl flexible segments. Therefore, its low temperature resistance and heat resistance are better than those of traditional nitrile rubber.

[0150] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A nitrile rubber, wherein: The polymerizable monomers of the nitrile rubber include butadiene, acrylonitrile and itaconic acid diester; the structural formula of the itaconic acid diester is: In the formula, R is a C1-C12 alkyl group; Based on 100 parts by total weight of the butadiene, acrylonitrile and itaconic acid diester, the butadiene accounts for 40 to 75 parts, the acrylonitrile accounts for 19 to 34 parts, and the itaconic acid diester accounts for 5.3 to 38 parts.

2. The nitrile rubber according to claim 1, wherein The nitrile rubber is prepared by emulsion copolymerization of butadiene, acrylonitrile and itaconate.

3. The nitrile rubber according to claim 1, wherein The content of itaconate diester structure in the nitrile rubber is 6wt% to 25wt%; The Mooney viscosity ML of the nitrile rubber 1+4 100℃ The tensile strength of the vulcanized rubber is 19-25MPa; the glass transition temperature is -56℃ to -40℃; and the thermal weight loss temperature is 320-350℃.

4. A method for preparing the nitrile rubber according to any one of claims 1 to 3, wherein: The preparation method comprises the following steps: Based on 100 parts of the total weight of acrylonitrile, butadiene and itaconic acid diester, 240-315 parts of desalted water, 3-8 parts of emulsifier, 0.06-0.4 parts of reducing agent, 0.03-0.3 parts of chelating agent, 0.5-1 parts of pH buffer, 0.03-0.4 parts of diffusing agent, 0.1-1.2 parts of molecular weight regulator, 15-30 parts of acrylonitrile, 5-35 parts of itaconic acid diester and 0.05-0.2 parts of deoxidizer are added into a reaction container, and after the addition is completed, 40-75 parts of butadiene are added in a protective gas atmosphere, and the mixture is stirred for pre-emulsification, and then 0.02-0.1 parts of initiator are added for polymerization reaction; When the monomer conversion rate of acrylonitrile, butadiene and itaconate diester reaches 20% to 25%, acrylonitrile is added once; when the monomer conversion rate reaches 40% to 50%, emulsifier, itaconate diester, initiator and molecular weight regulator are added; when the monomer conversion rate reaches 60% to 65%, acrylonitrile is added once; when the monomer conversion rate reaches 80% to 85%, 0.5 to 1 part of terminator is added to terminate the reaction, followed by degassing, condensation, washing and drying to obtain raw nitrile rubber.

5. The preparation method according to claim 4, wherein When the monomer conversion rate reaches 20% to 25%, add 2 to 4 parts of acrylonitrile; When the monomer conversion rate reaches 40% to 50%, 1 to 5 parts of emulsifier, 0.3 to 3 parts of dibutyl itaconate, 0.001 to 0.003 parts of initiator, and 0.2 to 0.4 parts of molecular weight regulator are added; When the monomer conversion rate reaches 60% to 65%, add 2 to 4 parts of acrylonitrile.

6. The preparation method according to claim 4 or 5, wherein: The emulsifier is a composite emulsifying system of anionic surfactant and nonionic surfactant, and the composite mass ratio is (3-4):1; wherein the anionic surfactant is fatty alkyl sulfonate or disproportionated rosin acid soap, and the nonionic surfactant is polyoxyethylene ether; The reducing agent is selected from at least one of sodium formaldehyde sulfoxylate, ferrous sulfate, cuprous sulfate, EDTA sodium iron salt, and EDTA sodium copper salt; The chelating agent is selected from at least one of EDTA tetrasodium salt and glutamic acid diacetate sodium salt; The pH buffer is selected from at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, and sodium acetate alkaline buffers; The diffusant is selected from at least one of β-naphthalenesulfonate sodium formaldehyde condensate, methylnaphthalenesulfonate sodium formaldehyde condensate, and benzylnaphthalenesulfonic acid formaldehyde condensate; The molecular weight regulator is selected from at least one of dodecyl mercaptan, tert-dodecyl mercaptan, and 2,4-diphenyl-4-methyl-1-pentene; The deoxidizer is selected from at least one of sodium dithionite, dimethyl ketoxime and isoascorbic acid; The initiator is selected from at least one of cumene hydroperoxide, diisopropyl hydroperoxide, and isopropyl tert-butyl peroxide; The terminator is selected from at least one of sodium nitrite, hydroxylamine sulfate, diethylhydroxylamine, hydroquinone, and p-aminoazobenzene.

7. The preparation method according to claim 4, wherein The itaconate diester is prepared by the following steps: Itaconic acid, fatty alcohol R-OH, a dehydrating agent and a catalyst are added to a reaction container, and the temperature is raised to carry out an esterification reaction. During the reaction, the generated water and the dehydrating agent are continuously evaporated. When the amount of separated water no longer increases and reaches the theoretical calculated amount, the reaction is stopped, the reaction system is filtered to obtain a filter cake, and the filter cake is distilled under reduced pressure to obtain the itaconic acid diester.

8. The preparation method according to claim 7, wherein: The molar ratio of itaconic acid to fatty alcohol is 1:(2-2.5).

9. The preparation method according to claim 7, wherein: The dehydrating agent is selected from at least one of toluene, xylene, p-toluene and ethylbenzene; The catalyst is selected from at least one of methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid and 2-naphthalenesulfonic acid.

10. Use of the nitrile rubber according to any one of claims 1 to 3 in special rubber sealing products.

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