Butadiene-acrylonitrile rubber and its preparation method and application

Abstract

The application relates to the technical field of synthetic rubber, in particular to a nitrile rubber, a preparation method and application thereof, wherein the preparation method adopts at least potassium saponification soap and / or sodium saponification soap of disulfated rosin acid, C 10 -C 13 A composite emulsifier system composed of linear alkyl benzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate sodium salt and a low-temperature emulsion polymerization process, and the obtained nitrile rubber can be used in the field of oil-resistant sealing in a hydraulic oil operation environment.

Description

Technical Field

[0001] This invention belongs to the field of synthetic rubber technology, and relates to nitrile rubber, its preparation method, and its applications. Background Technology

[0002] Nitrile rubber (NBR) possesses excellent oil resistance, heat resistance, abrasion resistance, gas permeability resistance, high elongation modulus, hardness, and tensile strength, making it widely used in oil-resistant hoses for hydraulic transmission systems. NBR is a type of rubber produced by emulsion polymerization of butadiene and acrylonitrile, primarily using this method. Due to the presence of double bonds in the NBR molecule, the α-hydrogen atoms are highly reactive and prone to degradation under heat and oxygen, leading to changes in the material's molecular structure. During use, the rubber gradually ages, resulting in loss of elasticity and a decline in mechanical properties.

[0003] For many years, countries around the world have been conducting research on the synthesis of nitrile butadiene rubber (NBR). Currently, alkali metal salts of alkyl aryl sulfonic acids, alkali metal salts of fatty acids, rosin acid soaps, and their mixed soaps are commonly used as emulsifiers in emulsion polymerization. For example, Idemitsu Petrochemical Co., Ltd. of Japan has developed a highly efficient dispersant for NBR emulsion polymerization, composed of maleic acid (anhydride) and styrene sulfonate. Using this dispersant can improve the dispersibility of monomers and the stability of NBR. JSR Corporation of Japan uses nonionic surfactants such as polyethylene oxide alkyl ethers, polyethylene oxide fatty acid esters, polyethylene oxide sorbitol fatty acid esters, and ethylene oxide / propylene oxide block copolymers as emulsifiers. Zeon Corporation of Japan, by appropriately adjusting the polymerization temperature, uses potassium persulfate as an initiator, potassium oleate, sodium dodecylbenzene sulfonate, and other anionic or nonionic surfactants such as polyethylene oxide alkyl ethers as emulsifiers, and dodecyl mercaptan as a regulator to prepare NBR emulsions. It has a temperature range of 30–150°C, a molecular weight distribution index of 5–8, a gel content of less than 5%, and a bound acrylonitrile content of 10%–45%, and is intended for use in the rubber products industry, such as rubber rollers.

[0004] CN103450399A discloses a method for preparing nitrile rubber by emulsion polymerization. The polymerization includes at least the following steps: adding a portion of acrylonitrile, a portion of emulsifier, a portion of regulator, and an initiator to a polymerization reactor; adding butadiene under vacuum; carrying out emulsion polymerization under stirring; adding a portion of emulsifier, crosslinking agent, and acrylonitrile to the polymerization reactor when the polymerization conversion rate reaches 25-40% in the middle stage of the reaction; and adding the remaining portion of emulsifier and regulator when the polymerization conversion rate reaches 60-75% in the later stage of the reaction. The crosslinking agent is one or more of the following: triallyl isocyanurate, triallyl cyanurate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, 1,4-butanediol diacrylate, and polyethylene glycol dimethacrylate; the amount of crosslinking agent added is 0.1-3.0 parts. The emulsifier is one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, potassium stearate, potassium oleate, and disproportionated rosin potassium soap. The resulting nitrile rubber has a high microgel content and low gel content, making it easy to form a three-dimensional structure during processing. This results in good physical and mechanical properties of the rubber product, increased Mooney viscosity, and consequently, improved tensile strength and 300% elongation stress. In the examples, the tensile strength is 19-24 MPa.

[0005] CN114380949A discloses a nitrile rubber, its preparation method, and its application. The preparation method includes: subjecting a raw material system containing butadiene, acrylonitrile, a reactive antioxidant N-(4-(aniline)phenyl)methylacrylamide, and a portion of a molecular weight regulator to a low-temperature polymerization reaction; adding the remaining molecular weight regulator when the reaction conversion reaches 50-55%; terminating the reaction when the reaction conversion reaches 70-75% to obtain nitrile rubber; the amount of acrylonitrile added is 31-33 parts; the emulsifier is a composite system composed of a sodium salt of a linear alkylbenzene sulfonic acid and a formaldehyde condensate. Using this preparation method, the Mooney viscosity (ML) of the obtained nitrile rubber is... With a temperature range of 40-60°C, this nitrile rubber exhibits good processing properties and excellent resistance to heat and oxygen aging.

[0006] CN111019046A relates to a method for preparing nitrile rubber, which includes the following steps: First, water, emulsifier, activator, acrylonitrile, and molecular weight regulator are added to a polymerization reactor. Then, under an inert atmosphere, an oxygen scavenger, butadiene, and an initiator are added to induce a polymerization reaction between acrylonitrile and butadiene. When the polymerization conversion rate reaches 45% or higher, a molecular weight regulator is added. Finally, when the polymerization conversion rate reaches 75% or higher, a terminator is added. The obtained nitrile latex is collected, coagulated, and dried to obtain nitrile rubber. The amount of acrylonitrile added is 40-50 parts. The emulsifier includes a primary emulsifier and a co-emulsifier, wherein: the primary emulsifier is selected from at least one of potassium disproportionated rosinate, sodium dodecylbenzene sulfonate, potassium oleate, and potassium stearate; the co-emulsifier is selected from at least one of sorbitan tristearate, polyoxyethylene sorbitan monolaurate, and sodium β-naphthalenesulfonate formaldehyde condensate. Using this preparation method, the resulting nitrile rubber has a bound acrylonitrile content of 38% to 41%, a Mooney viscosity range of 40 to 70, a tear strength > 40 KN / m, and a tensile strength > 25 MPa. This nitrile rubber has good properties, especially good oil resistance and high tear strength.

[0007] Existing technologies all suffer from problems such as long polymerization reaction time, high power consumption of reaction equipment, a large number of fine rubber particles during agglomeration of nitrile rubber, difficulty in washing and drying during post-processing, and the inability of the obtained nitrile rubber to possess both excellent oil resistance and physical and mechanical properties. Summary of the Invention

[0008] The purpose of this invention is to overcome the above-mentioned technical problems and provide a nitrile rubber, a method for preparing nitrile rubber, and an application of nitrile rubber. The preparation method uses a ternary compound emulsion system and a low-temperature polymerization process. The resulting nitrile rubber not only has high polymerization stability but also excellent low-temperature resistance, making it particularly suitable for sealing applications in low-temperature working environments.

[0009] To achieve the above objectives, a first aspect of the present invention provides a method for preparing nitrile rubber, comprising: using butadiene and acrylonitrile as polymerization monomers in the presence of an initiator, employing a low-temperature emulsion polymerization method, wherein the composite emulsifier contains at least potassium disproportionated rosinate soap and / or sodium soap, C 10 -C 13 Sodium salts of linear alkylbenzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate, with molecular weight regulators added once or multiple times, are used to synthesize nitrile rubber paste. A terminator is added, and the paste is then degassed, coagulated, washed, and dried to obtain nitrile rubber.

[0010] This invention employs a specific composite emulsification system, wherein the composite emulsifier is a combination of at least three substances: disproportionated rosin acid soap, linear alkylbenzene sulfonic acid, and sodium salt of naphthalene sulfonic acid formaldehyde condensate.

[0011] Unless otherwise specified, all parts by weight in this invention are based on 100 parts by weight of total polymerized monomers.

[0012] The amount of composite emulsifier added in this invention can be the general amount of emulsifier added in the art, especially the amount used when anionic emulsifier and nonionic emulsifier are compounded. The preferred amount of composite emulsifier used in this invention is 1.5-7.1 parts, more preferably 2.2-6.4 parts.

[0013] This invention requires the addition of disproportionated rosin acid soap, which can be either potassium or sodium soap, to the composite emulsifier. The potassium or sodium disproportionated rosin acid soap in the composite emulsion system of this invention cannot be replaced by other anionic emulsifiers such as sodium decaalkyl sulfate, potassium oleate, and potassium stearate. This is because the inventors have discovered that, in the specific emulsion polymerization system of this invention, due to a synergistic effect, the addition of potassium or sodium disproportionated rosin acid soap increases the particle size of the polymer emulsion, which is particularly beneficial to the subsequent emulsion coagulation process after emulsion polymerization. The amount added can be adjusted according to the desired polymer emulsion particle size, especially the ease of emulsion coagulation after emulsion polymerization. Generally, the amount of potassium and / or sodium disproportionated rosin acid soap is increased when the acrylonitrile content is low. The recommended amount of potassium and / or sodium disproportionated rosin acid soap is 0.5-3.3 parts, preferably 1.0-3.3 parts, and more preferably 1.2-2.5 parts.

[0014] This invention requires the addition of C to the composite emulsifier. 10 -C 13 Linear alkylbenzene sulfonic acid. The function of linear alkylbenzene sulfonic acid differs from that of sodium linear alkylbenzene sulfonate. Adding only sodium linear alkylbenzene sulfonate without linear alkylbenzene sulfonic acid results in a different effect than in this invention. This is because sodium alkylbenzene sulfonate is a saponification product of alkylbenzene sulfonic acid. Due to the use of alkylbenzene sulfonic acid, some alkylbenzene sulfonic acid remains incompletely saponified during its saponification process. A synergistic effect occurs between the two, improving the stability of the entire polymerization system and increasing the polymerization efficiency. Therefore, linear alkylbenzene sulfonic acid in the composite emulsion system of this invention cannot be replaced by sodium linear alkylbenzene sulfonate. As an emulsifier, C 10 -C 13 The most commonly used linear alkylbenzene sulfonic acid is dodecylbenzene sulfonic acid. 10 -C 13 The preferred amount of linear alkylbenzene sulfonic acid is 0.7-3 parts, more preferably 0.9-2.5 parts.

[0015] This invention requires sodium salt of naphthalenesulfonic acid formaldehyde condensate and C 10 -C 13The simultaneous use of linear alkylbenzene sulfonic acid is a technique already existing in the art, and its usage is determined as needed; this invention does not impose any particular limitation. Failure to add it will lead to a decrease in the stability of the polymerization emulsion, and sludge formation may easily occur during polymerization. The preferred amount of sodium naphthalenesulfonic acid formaldehyde condensate is 0.3-0.8 parts, more preferably 0.3-0.6 parts.

[0016] This invention also does not exclude the addition of other anionic emulsifiers or nonionic emulsifiers in the composite emulsion system, in addition to potassium or sodium disproportionated rosinate soap, linear alkylbenzene sulfonic acid and sodium salt of naphthalene sulfonic acid formaldehyde condensate. For example, at least one of sodium dodecylbenzene sulfonate, sodium decaalkyl sulfate, potassium oleate, potassium stearate, sorbitan tristearate and octylphenol polyoxyethylene ether may also be added.

[0017] The second aspect of the present invention provides a nitrile rubber prepared by the preparation method provided in the first aspect.

[0018] The third aspect of this invention provides an application of the nitrile rubber provided in the second aspect in the field of oil-resistant sealing.

[0019] Compared with the prior art, the present invention has the following advantages: This invention provides a simple method for preparing low-temperature resistant nitrile rubber, which uses at least potassium disproportionated rosinate soap and / or sodium soap, C 10 -C 13 A composite emulsifier system composed of sodium salt of linear alkylbenzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate, along with a low-temperature emulsion polymerization process, improves the polymerization conversion rate, reduces the energy consumption of the polymerization reaction, and solves the technical problems of numerous fine particles during coagulation and the difficulty of washing and drying in the post-processing.

[0020] Meanwhile, the preparation method provided by this invention can provide good tensile strength and elongation at break, and can be used in the field of oil-resistant sealing. Detailed Implementation

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] The first aspect of this invention provides a method for preparing nitrile rubber, the method comprising: using butadiene and acrylonitrile as polymerization monomers in the presence of an initiator, employing a low-temperature emulsion polymerization method, wherein the composite emulsifier contains at least potassium disproportionated rosinate soap and / or sodium soap, C 10 -C 13Sodium salts of linear alkylbenzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate, with molecular weight regulators added once or multiple times, are used to synthesize nitrile rubber paste. A terminator is added, and the paste is then degassed, coagulated, washed, and dried to obtain nitrile rubber.

[0023] Those skilled in the art will know that when emulsion polymerization of nitrile butadiene rubber uses a composite emulsion system, the emulsifier includes a primary emulsifier and a co-emulsifier. The primary emulsifier can be one or more anionic emulsifiers, such as at least one of potassium disproportionated rosinate, sodium dodecylbenzene sulfonate, sodium decaalkyl sulfate, potassium oleate, and potassium stearate, or other anionic emulsifiers. The co-emulsifier can be a nonionic emulsifier, such as at least one of sorbitan tristearate, sodium β-naphthalenesulfonate formaldehyde condensate, and octylphenol polyoxyethylene ether, or other nonionic emulsifiers.

[0024] However, this invention employs a specific composite emulsification system. This composite emulsifier is selected from at least three types: potassium disproportionated rosinate soap and / or sodium soap, linear alkylbenzene sulfonic acid, and sodium naphthalene sulfonate formaldehyde condensate, which have a synergistic effect, thereby improving the stability of the latex in nitrile rubber. The amount of each can be adjusted as needed. The amount of composite emulsifier added can be the commonly used amount in this technical field, especially when using anionic and nonionic emulsifiers in combination. Preferably, the amount of composite emulsifier is 1.5-7.1 parts by weight, more preferably 2.2-6.4 parts by weight. Preferably, equivalent to 100 parts by weight of polymeric monomers, the amount of potassium disproportionated rosinate soap and / or sodium soap is 0.5-3.3 parts by weight; preferably, the amount of linear alkylbenzene sulfonic acid is 0.7-3 parts by weight; preferably, the amount of sodium naphthalene sulfonate formaldehyde condensate is 0.3-0.8 parts by weight.

[0025] In some embodiments of the present invention, more preferably, the amount of polymeric monomers, specifically potassium disproportionated rosinate soap and / or sodium soap, equivalent to 100 parts by weight, is 1.0-3.3 parts by weight; preferably C 10 -C 13 The amount of linear alkylbenzene sulfonic acid used is 0.9-2.5 parts by weight; preferably, the amount of sodium salt of naphthalene sulfonic acid formaldehyde condensate is 0.3-0.6 parts by weight.

[0026] In this invention, 1.0-3.3 parts by weight of disproportionated rosinate potassium soap and / or sodium soap are preferably added to the composite emulsion system, for example, 1.1 parts by weight, 1.5 parts by weight, 2 parts by weight, 3.5 parts by weight, 3 parts by weight, 3.2 parts by weight, and any value within any range of any two values, preferably 1.2-2.5 parts by weight. The disproportionated rosinate potassium soap and / or sodium soap in the composite emulsion system of this invention can be replaced by other anionic emulsifiers such as sodium decaalkyl sulfate, potassium oleate, and potassium stearate. This is because the inventors unexpectedly discovered in experiments that, in the specific emulsion polymerization system of this invention, due to a synergistic effect, the addition of disproportionated rosinate potassium soap and / or sodium soap, in addition to emulsification, can also increase the particle size of the polymer emulsion, which is particularly beneficial to the subsequent emulsion coagulation process after emulsion polymerization.

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

[0028] The present invention preferably adds C to the composite emulsion system. 10 -C 13 The linear alkylbenzene sulfonic acid is added in amounts of 0.7-3 parts by weight, for example, 0.6 parts by weight, 1 part by weight, 1.5 parts by weight, 2.2 parts by weight, 2.8 parts by weight, and any value within the range of any two of these values, preferably 0.9-2.5 parts by weight. In this invention, the linear alkylbenzene sulfonic acid and sodium linear alkylbenzene sulfonate have different functions; only C is added. 10 -C 13 Sodium linear alkylbenzene sulfonate without the addition of C 10 -C 13 Linear alkylbenzene sulfonic acid plays a different role than in this invention because sodium dodecylbenzene sulfonate is a saponification product of dodecylbenzene sulfonic acid. Due to the use of dodecylbenzene sulfonic acid, some dodecylbenzene sulfonic acid remains unsaponified during its saponification process. This results in a synergistic effect between the two, improving the stability of the entire polymerization system and increasing the polymerization efficiency. Therefore, linear alkylbenzene sulfonic acid in the composite emulsion system of this invention cannot be replaced by sodium linear alkylbenzene sulfonate.

[0029] In some specific embodiments of the present invention, C 10 -C 13 The linear alkylbenzene sulfonic acid is selected from at least one of decaalkylbenzene sulfonic acid, undecylbenzene sulfonic acid, dodecylbenzene sulfonic acid, and tridecylbenzene sulfonic acid, preferably dodecylbenzene sulfonic acid.

[0030] In this invention, 0.3-0.8 parts by weight of sodium naphthalenesulfonic acid formaldehyde condensate condensate is preferably added to the composite emulsion system. For example, 0.3 parts by weight, 0.35 parts by weight, 0.4 parts by weight, 0.6 parts by weight, 0.8 parts by weight, or any value within any range of two such values, are preferred. If sodium naphthalenesulfonic acid formaldehyde condensate condensate is not added, the stability of the polymer emulsion will decrease, and sludge formation will easily occur during polymerization.

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

[0032] In this invention, the composite emulsifier, in addition to disproportionated potassium rosinate soap and / or sodium soap, C 10 -C 13 In addition to sodium salts of linear alkylbenzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate, the compound emulsifier also contains other anionic and nonionic emulsifiers. Preferably, the compound emulsifier further contains at least one of sodium dodecylbenzene sulfonate, sodium decaalkyl sulfate, potassium oleate, potassium stearate, sorbitan tristearate, and octylphenol polyoxyethylene ether.

[0033] In some embodiments of the present invention, preferably, the composite emulsifier comprises potassium disproportionated rosinate soap and / or sodium soap, C 10 -C 13 It consists of sodium salt of linear alkylbenzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate.

[0034] In some embodiments of the present invention, preferably, the amount of composite emulsifier is 1.5-7.1 parts by weight relative to 100 parts by weight of polymeric monomer, for example, 2.0 parts by weight, 2.8 parts by weight, 3.5 parts by weight, 4.0 parts by weight, 5.3 parts by weight, 7 parts by weight, and any value within the range of any two values, preferably 2.2-6.4 parts by weight.

[0035] The synthesis scheme of nitrile rubber of the present invention is low-temperature emulsion polymerization. The polymerization temperature used in low-temperature emulsion polymerization commonly used in this technical field is not particularly limited. Preferably, the conditions for low-temperature emulsion polymerization include: temperature of 5-12℃, preferably 5-10℃; and time of 5-25h, preferably 7-20h.

[0036] In this invention, low-temperature emulsion polymerization can be either batch polymerization or continuous polymerization.

[0037] In some embodiments of the present invention, preferably, the amount of initiator is 0.1-0.5 parts by weight relative to 100 parts by weight of the polymerizing monomer, for example, 0.1 parts by weight, 0.25 parts by weight, 0.35 parts by weight, 0.5 parts by weight, and any value within a range of any two of these values, preferably 0.2-0.5 parts by weight. In the present invention, the amount of initiator is based on organic hydrogen peroxide.

[0038] This invention does not particularly limit the initiator; any initiator commonly used in the low-temperature emulsion polymerization of nitrile rubber is acceptable. Preferably, the initiator is selected from organic hydrogen peroxide-ferrous salt, and the organic hydrogen peroxide is dicumyl peroxide. In this invention, the initiator includes, but is not limited to, dicumyl peroxide-ferrous salt, cumyl peroxide-ferrous salt, etc.

[0039] This invention does not particularly limit the molecular weight regulator or its amount; generally, any molecular weight regulator and its amount used for nitrile rubber are acceptable. Preferably, the molecular weight regulator is selected from tert-dodecyl mercaptan and / or n-dodecyl mercaptan, with tert-dodecyl mercaptan being more preferred.

[0040] In this invention, the amount of molecular weight regulator can be adjusted according to the product performance requirements and the type of molecular weight regulator. Preferably, the amount of molecular weight regulator relative to 100 parts by weight of polymeric monomer is 0.3-0.8 parts by weight, for example 0.3 parts by weight, 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, and any value within any range of any two values, preferably 0.4-0.7 parts by weight.

[0041] In this invention, the molecular weight regulator is added once or multiple times during low-temperature emulsion polymerization, depending on the different performance requirements of the product. Preferably, the molecular weight regulator is added at least twice, with the first addition being 40-60% of the total molecular weight regulator amount; more preferably, the molecular weight regulator is added at least twice, with the remaining molecular weight regulator added when the conversion rate of the low-temperature emulsion polymerization reaches 50-55%.

[0042] This invention does not particularly limit the type and amount of the terminator; any commonly used terminator may be used. Preferably, the terminator includes, but is not limited to, sodium nitrite, hydroxylamine sulfate, diethylhydroxylamine, etc.

[0043] In some embodiments of the present invention, preferably, the amount of the terminator added is 0.05-0.15 parts by weight relative to 100 parts by weight of the polymeric monomer.

[0044] This invention does not specifically limit the timing of adding the terminator; the desired conversion rate of the nitrile butadiene rubber paste can be selected according to product requirements. Preferably, the terminator is added when the conversion rate of the low-temperature emulsion polymerization reaches 80% or more; more preferably, the terminator is added when the conversion rate of the low-temperature emulsion polymerization reaches 80-85%.

[0045] This invention also does not exclude the addition of other commonly used auxiliaries for nitrile emulsion polymerization, such as deionized water, electrolytes, reducing agents, chelating agents, etc., to the polymerization system, provided that the addition amount is within the general addition range.

[0046] This invention does not particularly limit the type or amount of electrolyte; a general electrolyte and a general amount are acceptable. Preferably, the amount of electrolyte is 0.01-0.05 parts by weight relative to 100 parts by weight of polymer monomer; more preferably, the electrolyte is selected from at least one of potassium hydroxide, sodium pyrophosphate, and sodium carbonate.

[0047] This invention does not particularly limit the type and amount of reducing agent; a general reducing agent and a general amount are acceptable. Preferably, the amount of reducing agent is 0.01-0.15 parts by weight relative to 100 parts by weight of polymeric monomer; more preferably, the reducing agent is selected from at least one of ferrous sulfate, sodium ferric ethylenediaminetetraacetate, and sodium thiosulfate.

[0048] This invention does not particularly limit the type and amount of chelating agent; a general chelating agent and a general amount are acceptable. Preferably, the amount of chelating agent is 0.01-0.05 parts by weight relative to 100 parts by weight of polymeric monomer; more preferably, the chelating agent is selected from disodium ethylenediaminetetraacetate and / or tetrasodium ethylenediaminetetraacetate.

[0049] This invention does not specifically limit the exact ratio of butadiene to acrylonitrile in the polymer monomers; any ratio commonly used in the preparation of nitrile rubber in existing technologies can be used (e.g., acrylonitrile content 15-60%). Increasing the acrylonitrile content results in poor elasticity and compression set resistance of the vulcanized rubber, and a low performance retention rate during aging, leading to a significantly shortened service life when polymerized in hot oil or hot air. Therefore, the acrylonitrile monomer content is relatively low during the polymerization of this type of nitrile rubber.

[0050] In this invention, unless otherwise specified, acrylonitrile monomer can be added in one go, continuously, or in two or more additions, preferably in two to five additions.

[0051] The present invention also provides a preferred method for preparing nitrile rubber, comprising the following steps: based on 100 parts by weight of butadiene and acrylonitrile, the monomer composition is: 35-85 parts by weight of butadiene, 15-65 parts by weight of acrylonitrile, 200-250 parts by weight of deionized water; the composite emulsifier contains at least 0.5-3.3 parts by weight of potassium disproportionated rosin acid soap and / or sodium soap, 0.7-3 parts by weight of linear alkylbenzene sulfonic acid, and 0.3-0.8 parts by weight of sodium salt of naphthalene sulfonic acid formaldehyde condensate; the initiator is selected from organic hydrogen peroxide-ferrous salt, and its dosage is 0.1-0.5 parts by weight; the molecular weight regulator is selected from tert-dodecyl mercaptan, and its dosage is 0.3-0.8 parts by weight; the initiator is added at once; the monomer is added once or multiple times; the molecular weight regulator is added at least twice; and the polymerization temperature is 5-12℃. Preferably, the amount of composite emulsifier is 1.5-7.1 parts by weight relative to 100 parts by weight of polymeric monomer, and more preferably 2.2-6.4 parts by weight.

[0052] The present invention does not specifically limit the timing of adding the terminator, but can be determined according to the performance requirements of different products. It is preferred to add the terminator when the conversion rate of low-temperature emulsion polymerization reaches 80-85%.

[0053] The present invention also provides an optimal method for preparing nitrile rubber, comprising the following steps: after evacuating the polymerization reactor, deionized water, emulsifier, reducing agent, electrolyte, chelating agent, all monomers, and 40-60% of molecular weight regulator are added; after controlling the temperature to 5-12°C, an initiator is added; when the conversion rate of low-temperature emulsion polymerization reaches 50-55%, the remaining molecular weight regulator is added; when the conversion rate of low-temperature emulsion polymerization reaches 80-85%, a terminator is added; the material is discharged, and degassed, coagulated, washed, and dried to obtain nitrile rubber.

[0054] The second aspect of the present invention provides a nitrile rubber prepared by the preparation method provided in the first aspect.

[0055] In some embodiments of the present invention, preferably, based on the total content of nitrile rubber, the acrylonitrile content is ≥17wt%, preferably 17-50wt%, for example, 18wt%, 25.5wt%, 33wt%, 40.5wt%, 50wt%, and any value within the range of any two values.

[0056] In some embodiments of the present invention, preferably, the method of the present invention can be used to obtain nitrile rubber with a latex particle size ≥100nm, preferably 110-130nm.

[0057] In some embodiments of the present invention, preferably, the Mooney viscosity ML can be obtained using the method of the present invention. ℃The strength is 40-80; the tensile strength is ≥18MPa, preferably 18-30MPa, of nitrile rubber.

[0058] In this invention, unless otherwise specified, the total solids content is measured according to SH / T1154-92; the acrylonitrile content is measured according to SH / T1157-1997; and the Mooney viscosity (ML) is... ℃ The tests were conducted according to GB / T1232-2000; the tensile strength test was conducted according to GB / T528-1998; and the elongation at break test was conducted according to GB / T528-1998.

[0059] The third aspect of the present invention provides an application of the nitrile rubber provided in the second aspect in oil-resistant products, preferably in the field of oil-resistant sealing in hydraulic oil working environments.

[0060] The nitrile rubber produced by the method of this invention not only has excellent polymerization stability, but also produces nitrile rubber with balanced oil resistance and physical and mechanical properties, meeting the application requirements of oil-resistant seals in hydraulic oil working environments; in addition, when using this preparation method to synthesize the adhesive, the polymerization process is stable and the energy consumption is low.

[0061] As can be seen from the optimal production scheme in the examples, the preparation method of the present invention can produce a product with a bound acrylonitrile content of 17-50 wt% and a Mooney viscosity of ML. ℃ Nitrile rubber with a strength of 40-80 has excellent oil resistance and physical and mechanical properties, making it suitable for use in oil-resistant sealing applications in hydraulic oil working environments.

[0062] The present invention will be described in detail below through embodiments.

[0063] Total solids were measured according to SH / T1154-92; Mooney viscosity ML ℃ The test was conducted according to GB / T1232-2000; The acrylonitrile content was determined using SH / T1157-1997. Tensile strength was measured according to GB / T528-1998; The elongation at break was measured according to GB / T 528-1998.

[0064] Example 1 A 10L polymerization reactor was evacuated and purged with nitrogen to a vacuum level of -0.1 MPa. Then, 230 parts by weight of deionized water, 84 parts by weight of butadiene, 16 parts by weight of acrylonitrile, a composite emulsifier (2.2 parts by weight of potassium disproportionated rosinate soap, 1.3 parts by weight of dodecylbenzenesulfonic acid, and 0.5 parts by weight of sodium naphthalenesulfonic acid formaldehyde condensate), and 0.4 parts by weight of tert-dodecyl mercaptan were added sequentially. The temperature was then controlled, and when the reaction temperature reached 7°C, 0.1 parts by weight of dicumyl peroxide was added.

[0065] When the reaction conversion rate reaches 50%, 0.3 parts by weight of tert-dodecyl mercaptan, a secondary molecular weight regulator, is added; when the reaction conversion rate reaches 77%, sodium nitrite is added, the material is discharged, and after degassing, coagulation, washing and drying, nitrile rubber S1 is obtained.

[0066] The physical properties of the aforementioned nitrile rubber S1 are listed in Table 3.

[0067] Examples 2-8 Following the method of Example 1, except that the amounts of each component and the polymerization conditions were as shown in Table 1, nitrile rubbers S2-S8 were obtained respectively.

[0068] The physical properties of the aforementioned nitrile rubbers S2-S8 are listed in Table 3.

[0069] Comparative Examples 1-8 Following the method of Example 1, except that the amount of each component and the polymerization conditions were as shown in Table 2, nitrile rubbers DS1-DS8 were obtained respectively.

[0070] The physical properties of the aforementioned nitrile rubbers DS1-DS8 are listed in Table 4.

[0071] Table 1

[0072] Table 2

[0073] Table 3

[0074] Table 4

[0075] As shown in Tables 1-4, compared to Comparative Examples 1-8, the preparation method provided by this invention can yield a bound acrylonitrile content of 17-50 wt% and a Mooney viscosity of ML. ℃ Selected from 40-80 nitrile rubber with a tensile strength ≥18MPa.

[0076] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing nitrile rubber, characterized in that, The preparation method includes at least the following steps: using butadiene and acrylonitrile as polymerization monomers in the presence of an initiator, employing a low-temperature emulsion polymerization method, wherein the composite emulsifier contains at least potassium disproportionated rosinate soap and / or sodium soap, C 10 -C 13 Sodium salt of linear alkylbenzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate, with a molecular weight regulator added once or multiple times, is used to synthesize nitrile rubber paste. A terminator is added, and the paste is then degassed, coagulated, washed, and dried to obtain nitrile rubber. Based on a total addition of butadiene and acrylonitrile of 100 parts by weight, the amount of the composite emulsifier is preferably 1.5-7.1 parts by weight, more preferably 2.2-6.4 parts by weight.

2. The method for preparing nitrile rubber according to claim 1, characterized in that, Relative to 100 parts by weight of polymeric monomers, the amount of potassium disproportionated rosinate soap and / or sodium disproportionated rosinate soap in the composite emulsifier is 0.5-3.3 parts by weight, preferably 1.0-3.3 parts by weight, and more preferably 1.2-2.5 parts by weight.

3. The method for preparing nitrile rubber according to claim 1, characterized in that, Relative to 100 parts by weight of the polymeric monomer, in the composite emulsifier, C 10 -C 13 The amount of linear alkylbenzene sulfonic acid used is 0.7-3 parts by weight, preferably C. 10 -C 13 The amount of linear alkylbenzene sulfonic acid used is 0.9-2.5 parts by weight; And / or, the C 10 -C 13 The linear alkylbenzene sulfonic acid is selected from at least one of decaalkylbenzene sulfonic acid, undecylbenzene sulfonic acid, dodecylbenzene sulfonic acid, and tridecylbenzene sulfonic acid, preferably dodecylbenzene sulfonic acid.

4. The method for preparing nitrile rubber according to claim 1, characterized in that, Relative to 100 parts by weight of the polymeric monomer, the amount of sodium naphthalenesulfonic acid formaldehyde condensate in the composite emulsifier is 0.3-0.8 parts by weight, preferably 0.3-0.6 parts by weight. And / or, the sodium salt of the naphthalenesulfonate formaldehyde condensate is selected from the sodium β-naphthalenesulfonate formaldehyde condensate.

5. The method for preparing nitrile rubber according to claim 1, characterized in that, The composite emulsifier also contains at least one of sodium dodecylbenzenesulfonate, sodium decaalkyl sulfate, potassium oleate, potassium stearate, sorbitan tristearate, and octylphenol polyoxyethylene ether.

6. The method for preparing nitrile rubber according to any one of claims 1-5, characterized in that, The conditions for the low-temperature emulsion polymerization include a temperature of 5-12℃, preferably 5-10℃.

7. The method for preparing nitrile rubber according to claim 6, characterized in that, The amount of the initiator relative to 100 parts by weight of the polymerizable monomer is 0.1-0.5 parts by weight, preferably 0.2-0.5 parts by weight; And / or, the initiator is selected from organic hydrogen peroxide-ferrous salt, wherein the organic hydrogen peroxide is dicumyl peroxide.

8. The method for preparing nitrile rubber according to claim 7, characterized in that, The amount of the molecular weight regulator relative to 100 parts by weight of the polymeric monomer is 0.3-0.8 parts by weight, preferably 0.4-0.7 parts by weight; And / or, the molecular weight regulator is selected from tert-dodecyl mercaptan and / or n-dodecyl mercaptan, preferably tert-dodecyl mercaptan; And / or, the molecular weight regulator is added at least twice, with the first addition being 40-60% of the total molecular weight regulator amount; And / or, the molecular weight regulator is added at least twice, with the remaining molecular weight regulator added when the conversion rate of the low-temperature emulsion polymerization reaches 50-55%.

9. The method for preparing nitrile rubber according to claim 8, characterized in that, When the conversion rate of the low-temperature emulsion polymerization reaches 80% or more, preferably 80-85%, the terminator is added; And / or, relative to 100 parts by weight of the polymerizing monomer, the amount of the terminator added is 0.05-0.15 parts by weight; And / or, the terminating agent is selected from at least one of sodium nitrite, hydroxylamine sulfate, and diethylhydroxylamine.

10. The method for preparing nitrile rubber according to claim 9, characterized in that, The low-temperature emulsion polymerization process also involves the addition of at least one of electrolytes, reducing agents, and chelating agents. Preferably, the amount of electrolyte used is 0.01-0.05 parts by weight relative to 100 parts by weight of polymer monomer; preferably, the electrolyte is selected from at least one of potassium hydroxide, sodium pyrophosphate and sodium carbonate; Preferably, the amount of the reducing agent is 0.01-0.15 parts by weight relative to 100 parts by weight of the polymerizing monomer; preferably, the reducing agent is selected from at least one of ferrous sulfate, sodium ferric ethylenediaminetetraacetate, and sodium thiosulfate. Preferably, the amount of the chelating agent is 0.01-0.05 parts by weight relative to 100 parts by weight of the polymerizing monomer; preferably, the chelating agent is selected from disodium ethylenediaminetetraacetate and / or tetrasodium ethylenediaminetetraacetate.

11. The method for preparing nitrile rubber according to claim 1 or 2, characterized in that, The amount of acrylonitrile used is 65 parts by weight or less, preferably 60 parts by weight or less, relative to 100 parts by weight of polymerizing monomer. More preferably, the amount of acrylonitrile used is 15-60 parts by weight and the amount of butadiene is 40-85 parts by weight relative to 100 parts by weight of polymeric monomers.

12. The method for preparing nitrile rubber according to claim 11, characterized in that, The preparation method includes the following steps: Based on 100 parts by weight of butadiene and acrylonitrile, the monomer composition is: 35-85 parts by weight of butadiene, 15-65 parts by weight of acrylonitrile, and 200-250 parts by weight of deionized water. The composite emulsifier contains at least 0.5-3.3 parts by weight of potassium disproportionated rosinate soap and / or sodium soap, 0.7-3 parts by weight of linear alkylbenzene sulfonic acid, and 0.3-0.8 parts by weight of sodium salt of naphthalene sulfonic acid formaldehyde condensate to form an emulsion system. The initiator is selected from organic hydrogen peroxide-ferrous salt, and its dosage is 0.1-0.5 parts by weight. The molecular weight regulator is selected from tert-dodecyl mercaptan, and its dosage is 0.3-0.8 parts by weight. The initiator is added at once; the monomer is added once or multiple times; the molecular weight regulator is added at least twice, and the polymerization temperature is 5-12℃. Preferably, the amount of the composite emulsifier is 1.5-7.1 parts by weight, more preferably 2.2-6.4 parts by weight, relative to 100 parts by weight of the polymeric monomer.

13. The method for preparing nitrile rubber according to claim 12, characterized in that, The preparation method includes the following steps: after evacuating the polymerization reactor, deionized water, emulsifier, reducing agent, electrolyte, chelating agent, all monomers, and 40-60% of molecular weight regulator are added. After controlling the temperature to 5-12℃, the initiator is added. When the conversion rate of the low-temperature emulsion polymerization reaches 50-55%, the remaining molecular weight regulator is added. When the conversion rate of the low-temperature emulsion polymerization reaches 80-85%, the terminator is added. The material is discharged, and degassing, coagulation, washing, and drying are performed to obtain the nitrile rubber.

14. The nitrile rubber prepared by the method of claim 13.

15. The application of the nitrile rubber according to claim 14 in oil-resistant products for hydraulic oil working environments, preferably in the field of oil-resistant sealing for hydraulic oil working environments.

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