Process for the preparation of high strength specialty nitrile rubber

Abstract

The application discloses a preparation method of high-strength special nitrile rubber. The preparation method comprises the following steps: taking butadiene and acrylonitrile as polymerization monomers, adopting a dual-compound emulsifying system of dodecyl benzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate sodium salt, taking persulfate as an initiator, taking tertiary dodecyl mercaptan as a molecular weight regulator, adopting a batch supplementing mode of the molecular weight regulator, and adopting a hot polymerization process to synthesize nitrile rubber paste. A high-strength nitrile rubber product is prepared by adding a terminating agent and an antioxidant, and then performing degassing, condensation, washing and drying. The nitrile rubber has a Mooney viscosity MS (1+4) 100℃ 40-65, a tensile strength ≥27.5 MPa and an elongation at break ≥400%, and can meet the application requirements in the fields of automobiles, aerospace, sealing gaskets and the like.

Description

Technical Field

[0001] This invention belongs to the field of rubber preparation technology, specifically relating to a method for preparing high-strength special nitrile rubber. Background Technology

[0002] Nitrile rubber (NBR) has become the standard elastomer for oil-resistant rubber products due to its excellent oil resistance, benzene resistance, heat resistance, and physical and mechanical properties. It is widely used in the automotive, aerospace, oil extraction, petrochemical, textile, wire and cable, printing, and food packaging industries. For many years, countries around the world have continuously conducted research on the synthesis of NBR. Abroad, NBR polymerization reactions often use alkali metal salts of alkyl aryl sulfonic acids, alkali metal salts of fatty acids, rosin acid soaps, and their mixed soaps as emulsifiers. For example, Bayer AG in Germany uses a biodegradable emulsifier to produce a product called Krynac. XN's NBR products use biodegradable compounds instead of non-biodegradable aralkyl sulfonates as emulsifiers, which can significantly reduce the concentration of dissolved organic matter and reduce the COD value of discharged wastewater by about 90%, without requiring additional equipment. 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. Russia uses a mixture of polyethylene oxide-modified alkyl ether sodium sulfate, sodium dodecylbenzene sulfonate, and sodium alkenyl sulfonate as a composite emulsifier to prepare 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. In terms of polymerization process research, Stamicarbon BV of the Netherlands invented a continuous emulsion polymerization process for NBR with an acrylonitrile content of up to 50%. The process involves at least two polymerization reactors, preferably five. All acrylonitrile, a portion of butadiene, water, emulsifiers, initiators, and other additives are continuously added to the first reactor. The reaction is carried out at 10°C, with the initial polymerization conversion controlled at 24%. Butadiene is then continuously added to the second through fifth polymerization reactors at conversion rates of 40%, 56%, 72%, and 82%, respectively. After termination, degassing, coagulation, washing, and drying, a high-acrylonitrile NBR product with a bound acrylonitrile content of 47.2%, a Mooney viscosity of 48, a tensile strength of 15.6 MPa, an elongation of 385%, a 300% elongation stress of 12.1 MPa, and good environmental resistance is obtained. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing high-strength special nitrile rubber, which has high tensile strength and elongation at break.

[0004] The technical solution adopted in this invention is a method for preparing high-strength special nitrile rubber, specifically as follows: Based on 100 parts by weight of butadiene and acrylonitrile, 275 parts of soft water, 50-60 parts of butadiene, and 40-50 parts of acrylonitrile; 2.5-5 parts of emulsifier, 0.01-0.1 parts of sodium hydroxide; 0.2-1.0 parts of initiator; 0.1 parts of triethanolamine; and 0.4-0.6 parts of molecular weight regulator are added in three equal parts. When the reaction conversion rate reaches 35-40%, a secondary molecular weight regulator is added; when the reaction conversion rate reaches 50-55%, a tertiary molecular weight regulator is added. After cooling to 20-25℃, the material is discharged. A terminator and an antioxidant are added, and the mixture is then degassed, coagulated, washed, and dried to obtain high-strength special nitrile rubber.

[0005] The invention is further characterized in that,

[0006] The emulsifier is a complex system of sodium salt of dodecylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate.

[0007] The amount of dodecylbenzenesulfonic acid used is 2 to 4 parts, and the amount of sodium salt of naphthalenesulfonic acid formaldehyde condensate is 0.5 to 1 part.

[0008] The molecular weight regulator used is tert-dodecyl mercaptan.

[0009] The reaction temperature is 25–35℃.

[0010] When the reaction conversion rate reaches 80-85%, a terminator and an antioxidant are added.

[0011] The beneficial effect of this invention is that it synthesizes nitrile rubber using a compound emulsion system of sodium salt of dodecylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate and a thermal emulsion polymerization process, achieving a Mooney viscosity of MS. (1+4) 100℃ The tensile strength is ≥27.5 MPa, and the elongation at break is ≥400%. The nitrile rubber prepared by the method of this invention meets the application requirements of automobiles, aerospace, gaskets and other fields; in addition, the polymerization process is stable and energy consumption is low when synthesizing the adhesive. Detailed Implementation

[0012] The present invention will now be described in detail with reference to specific embodiments.

[0013] The present invention discloses a method for preparing high-strength special nitrile butadiene rubber, which uses butadiene and acrylonitrile as polymerizing monomers, employs a combination of dodecylbenzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate sodium salt in the emulsion system, uses persulfate salts such as potassium persulfate and ammonium persulfate as water-soluble initiators in the initiation system, contains 0.01-0.1% free alkali in the aqueous phase system, and selects tert-dodecyl mercaptan as the molecular weight regulator. The method employs an intermittent feeding method in which monomers and initiators are added at once, and the molecular weight regulator is added in batches to synthesize nitrile butadiene rubber paste. Terminating agents and antioxidants are added, and the paste is then degassed, coagulated, washed, and dried to obtain high-strength special nitrile butadiene rubber.

[0014] Specifically, the monomer composition is as follows (based on 100 parts by weight of butadiene and acrylonitrile, the same below): 275 parts soft water, 50-60 parts butadiene, and 40-50 parts acrylonitrile; the emulsifier is a composite system of dodecylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate sodium salt, with the emulsifier dosage being 2.5-5 parts, dodecylbenzenesulfonic acid dosage being 2-4 parts, and naphthalenesulfonic acid formaldehyde condensate sodium salt dosage being 0.5-1 parts; sodium hydroxide dosage being 0.01-0.1 parts; initiator dosage being 0.2-1.0 parts; triethanolamine dosage being 0.1 parts; and molecular weight regulator dosage being 0.4-0.6 parts.

[0015] After evacuating the polymerization reactor, soft water, emulsifier, sodium hydroxide, butadiene, acrylonitrile, triethanolamine, and 1 / 3 part of molecular weight regulator are added. The reaction temperature is raised to 25-35°C, and an initiator is added. When the reaction conversion rate reaches 35-40%, a secondary molecular weight regulator is added. When the reaction conversion rate reaches 50-55%, a tertiary molecular weight regulator is added. When the reaction conversion rate reaches 80-85%, the temperature is lowered to 20-25°C, and the material is discharged. A terminator and antioxidant are added, and the mixture is degassed, coagulated, washed, and dried to obtain high-strength special nitrile rubber.

[0016] Example 1

[0017] The preparation method of the high-strength special nitrile rubber of the present invention is as follows:

[0018] A 10L polymerization reactor was evacuated and purged with nitrogen to a vacuum level of -0.1 MPa. Then, 275 parts soft water, 55 parts butadiene, 45 parts acrylonitrile, emulsifier (including 2.5 parts dodecylbenzenesulfonic acid and 0.5 parts sodium naphthalenesulfonic acid formaldehyde condensate), 0.03 parts sodium hydroxide, 0.1 parts triethanolamine, and 0.5 parts tert-dodecyl mercaptan (added in three equal parts) were added sequentially. The temperature was raised, and when the reaction temperature reached 30°C, 0.3 parts potassium persulfate initiator were added. When the reaction conversion rate reached 35%, a secondary molecular weight regulator was added. When the reaction conversion rate reached 55%, a tertiary molecular weight regulator was added. When the reaction conversion rate reached 80%, the temperature was lowered to 20°C, and the material was discharged. A terminator and antioxidant were added, and the mixture was degassed, coagulated, washed, and dried to obtain high-strength special nitrile rubber.

[0019] Example 2

[0020] The preparation method of the high-strength special nitrile rubber of the present invention is as follows:

[0021] A 10L polymerization reactor was evacuated and purged with nitrogen to a vacuum level of -0.1 MPa. Then, 275 parts soft water, 52 parts butadiene, 48 parts acrylonitrile, emulsifier (including 2 parts dodecylbenzenesulfonic acid and 0.5 parts sodium naphthalenesulfonic acid formaldehyde condensate), 0.03 parts sodium hydroxide, 0.1 parts triethanolamine, and 0.5 parts tert-dodecyl mercaptan (added in three equal parts) were added sequentially. The temperature was raised, and when the reaction temperature reached 30°C, 0.3 parts potassium persulfate initiator were added. When the reaction conversion rate reached 35%, a secondary molecular weight regulator was added. When the reaction conversion rate reached 54%, a tertiary molecular weight regulator was added. When the reaction conversion rate reached 85%, the temperature was lowered to 25°C, and the material was discharged. A terminator and antioxidant were added, and the mixture was degassed, coagulated, washed, and dried to obtain high-strength special nitrile rubber.

[0022] Example 3

[0023] The preparation method of the high-strength special nitrile rubber of the present invention is as follows:

[0024] A 10L polymerization reactor was evacuated and purged with nitrogen to a vacuum level of -0.1 MPa. Then, 275 parts soft water, 56 parts butadiene, 44 parts acrylonitrile, emulsifier (including 2.5 parts dodecylbenzenesulfonic acid and 0.8 parts sodium naphthalenesulfonic acid formaldehyde condensate), 0.05 parts sodium hydroxide, 0.1 parts triethanolamine, and 0.5 parts tert-dodecyl mercaptan (added in three portions) were added sequentially. The temperature was raised, and when the reaction temperature reached 30°C, 0.3 parts potassium persulfate initiator were added. When the reaction conversion rate reached 40%, a second molecular weight regulator was added. When the reaction conversion rate reached 55%, a third molecular weight regulator was added. When the reaction conversion rate reached 85%, the temperature was lowered to 25°C, and the material was discharged. A terminator and antioxidant were added, and the mixture was degassed, coagulated, washed, and dried to obtain high-strength special nitrile rubber.

[0025] Example 4

[0026] The preparation method of the high-strength special nitrile rubber of the present invention is as follows:

[0027] A 10L polymerization reactor was evacuated and purged with nitrogen to a vacuum level of -0.1 MPa. Then, 275 parts soft water, 57 parts butadiene, 43 parts acrylonitrile, emulsifier (including 3.5 parts dodecylbenzenesulfonic acid and 0.8 parts sodium naphthalenesulfonic acid formaldehyde condensate), 0.03 parts sodium hydroxide, 0.1 parts triethanolamine, and 0.5 parts tert-dodecyl mercaptan (added in three portions) were added sequentially. The temperature was raised, and when the reaction temperature reached 30°C, 0.3 parts potassium persulfate initiator were added. When the reaction conversion rate reached 36%, a second molecular weight regulator was added. When the reaction conversion rate reached 50%, a third molecular weight regulator was added. When the reaction conversion rate reached 82%, the temperature was lowered to 25°C, and the material was discharged. A terminator and antioxidant were added, and the mixture was degassed, coagulated, washed, and dried to obtain high-strength special nitrile rubber.

[0028] Example 5

[0029] The preparation method of the high-strength special nitrile rubber of the present invention is as follows:

[0030] A 10L polymerization reactor was evacuated and purged with nitrogen to a vacuum level of -0.1 MPa. Then, 275 parts soft water, 52 parts butadiene, 48 parts acrylonitrile, emulsifier (including 2.5 parts dodecylbenzenesulfonic acid and 0.8 parts sodium naphthalenesulfonic acid formaldehyde condensate), 0.03 parts sodium hydroxide, 0.1 parts triethanolamine, and 0.5 parts tert-dodecyl mercaptan (added in three portions) were added sequentially. The temperature was raised, and when the reaction temperature reached 30°C, 0.3 parts potassium persulfate initiator were added. When the reaction conversion rate reached 35%, a second molecular weight regulator was added. When the reaction conversion rate reached 55%, a third molecular weight regulator was added. When the reaction conversion rate reached 85%, the temperature was lowered to 20°C, and the material was discharged. A terminator and antioxidant were added, and the mixture was degassed, coagulated, washed, and dried to obtain high-strength special nitrile rubber.

[0031] Comparative Example 1

[0032] A 10L polymerization reactor was evacuated and purged with nitrogen to a vacuum level of -0.1 MPa. Then, 275 parts soft water, 55 parts butadiene, 45 parts acrylonitrile, emulsifier (including 6 parts dodecylbenzenesulfonic acid and 0.5 parts sodium naphthalenesulfonic acid formaldehyde condensate), 0.03 parts sodium hydroxide, 0.1 parts triethanolamine, and 0.5 parts tert-dodecyl mercaptan (molecular weight regulator) were added sequentially. The temperature was raised, and when the reaction temperature reached 30°C, 0.3 parts potassium persulfate initiator was added. After cooling to 20°C, the material was discharged. Terminator and antioxidant were added, and the mixture was degassed, coagulated, washed, and dried to obtain nitrile rubber.

[0033] Comparative Example 2

[0034] A 10L polymerization reactor was evacuated and purged with nitrogen to a vacuum level of -0.1 MPa. Then, 275 parts soft water, 52 parts butadiene, 48 parts acrylonitrile, emulsifier (including 3 parts sodium dodecyl sulfate and 0.5 parts sodium naphthalenesulfonic acid formaldehyde condensate), 0.03 parts sodium hydroxide, 0.1 parts triethanolamine, and 0.5 parts tert-dodecyl mercaptan (added in three portions) were added sequentially. The temperature was raised, and when the reaction temperature reached 30°C, 0.3 parts potassium persulfate initiator was added. When the reaction conversion rate reached 35%, a second molecular weight regulator was added. When the reaction conversion rate reached 55%, a third molecular weight regulator was added. When the reaction conversion rate reached 85%, the temperature was lowered to 20°C, and the material was discharged. A terminator and antioxidant were added, and the mixture was degassed, coagulated, washed, and dried to obtain nitrile rubber.

[0035] Comparative Example 3

[0036] A 10L polymerization reactor was evacuated and purged with nitrogen to a vacuum level of -0.1 MPa. Then, 275 parts soft water, 52 parts butadiene, 48 parts acrylonitrile, emulsifier (including 3.5 parts sodium dodecyl sulfate and 0.5 parts sodium naphthalenesulfonic acid formaldehyde condensate), 0.03 parts sodium hydroxide, 0.1 parts triethanolamine, and 0.5 parts tert-dodecyl mercaptan (added in three portions) were added sequentially. The temperature was raised, and when the reaction temperature reached 30°C, 0.3 parts potassium persulfate initiator was added. When the reaction conversion rate reached 35%, a second molecular weight regulator was added. When the reaction conversion rate reached 55%, a third molecular weight regulator was added. When the reaction conversion rate reached 85%, the temperature was lowered to 20°C, and the material was discharged. A terminator and antioxidant were added, and the mixture was degassed, coagulated, washed, and dried to obtain nitrile rubber.

[0037] The nitrile rubber produced using this invention has high tensile strength and elongation at break, which can meet the application requirements of automobiles, aerospace, gaskets and other fields.

[0038] The testing methods for rubber are standard: total solids test follows SH / T1154-92 standard; Mooney viscosity (MS) (1+4) 100℃ The tests were conducted according to GB / T1232.1-2000 standard; the tensile strength test was conducted according to GB / T528-1998 standard; the elongation at break test was conducted according to GB / T528-1998 standard; and the acrylonitrile test was conducted according to SH / T1157-1997 standard.

[0039] The properties of the high-strength special nitrile rubber prepared in Examples 1-5 and the nitrile rubber in Comparative Examples 1-3 were tested, and the test results are shown in Table 1 below. As can be seen from the table, the nitrile rubber synthesized using a compound emulsion system of dodecylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate sodium salt and a hot emulsion polymerization process has a Mooney viscosity of MS. (1+4)100℃ 40~65, tensile strength ≥27.5Mpa, elongation at break ≥400%.

[0040] Table 1. Test results of physical properties of nitrile rubber

[0041]

Claims

1. A method for preparing high-strength special nitrile butadiene rubber, characterized in that, Specifically, based on 100 parts by weight of butadiene and acrylonitrile, the following are added: 275 parts of soft water, 50-60 parts of butadiene, 40-50 parts of acrylonitrile; 2.5-5 parts of emulsifier, 0.01-0.1 parts of sodium hydroxide; 0.2-1.0 parts of initiator; 0.1 parts of triethanolamine; a molecular weight regulator is added. When the reaction conversion rate reaches 35-40%, a secondary molecular weight regulator is added. When the reaction conversion rate reaches 50-55%, a tertiary molecular weight regulator is added. When the reaction conversion rate reaches 80-85%, the temperature is lowered to 20-25℃ and the material is discharged. A terminator and an antioxidant are added, and the mixture is degassed, coagulated, washed, and dried to obtain high-strength special nitrile rubber. The emulsifier is a composite system of dodecylbenzenesulfonic acid and sodium salt of naphthalenesulfonic acid formaldehyde condensate; the amount of dodecylbenzenesulfonic acid is 2 to 4 parts, and the amount of sodium salt of naphthalenesulfonic acid formaldehyde condensate is 0.5 to 1 part; the molecular weight regulator is tert-dodecyl mercaptan.

2. The method for preparing high-strength special nitrile rubber according to claim 1, characterized in that, The molecular weight regulator is added in an amount of 0.4 to 0.6 parts, divided into three equal parts.

3. The method for preparing high-strength special nitrile rubber according to claim 1, characterized in that, The reaction temperature is 25–35℃.

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