Preparation method of high oil-resistant nitrile rubber

Abstract

This invention discloses a method for preparing high oil-resistant nitrile rubber. Based on 100 parts by weight of butadiene and acrylonitrile, the mixture includes 275 parts soft water, 50-55 parts butadiene, and 45-50 parts acrylonitrile. The emulsifier is a composite system of dodecylbenzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate sodium salt, with an emulsifier dosage of 2.5-5 parts. The initiator is a persulfate, with a dosage of 0.1-0.5 parts. Triethanolamine is 0.1 parts. A nitrile rubber paste is synthesized via a thermal polymerization process using a batch feeding method with the addition of a molecular weight regulator. A terminator and antioxidant are added, and the paste is then degassed, coagulated, washed, and dried to obtain a high-strength nitrile rubber product. This nitrile rubber exhibits a Mooney viscosity (ML). (1+4) 100℃ With a strength of 90-120, tensile strength ≥27.5MPa, and elongation at break ≥450%, it can meet the application requirements of automobiles, aerospace, gaskets and other fields.

Description

Technical Field

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

[0002] Due to its excellent oil resistance, benzene resistance, heat resistance, and physical and mechanical properties, nitrile rubber (NBR) is widely used in the automotive, aerospace, and gasket industries. These fields have even more stringent performance requirements for rubber, demanding higher levels of oil resistance, bound acrylonitrile content, and Mooney viscosity. Regarding polymerization processes, Zeon Corporation of Japan has developed NBR with an ML(1+4) concentration of 30–150°C at 100°C, a molecular weight distribution index of 5–8, a gel content of less than 5%, and a bound acrylonitrile content of 10%–45%, suitable for use in the rubber roller and other rubber product industries. However, in existing technologies, the bound acrylonitrile content in most NBRs is below 40%, failing to meet the requirements of the automotive, aerospace, and gasket industries. Furthermore, the monomer conversion rate during polymerization is only around 75%, which is insufficient. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing high oil-resistant nitrile butadiene rubber, which solves the problem of insufficient conversion rate due to acrylonitrile content of less than 40% in the prior art. This invention improves the polymerization conversion rate while ensuring that the rubber performance is not affected by the precise control of the pH value of the polymerization system. Based on the prior art, a high oil-resistant nitrile butadiene rubber with higher acrylonitrile content and better Mooney viscosity is prepared.

[0004] The technical solution adopted in this invention is a method for preparing high oil-resistant nitrile butadiene rubber. Butadiene and acrylonitrile are used as polymerization monomers, and the emulsion system uses a combination of sodium salt of dodecylbenzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate. The pH value of the polymerization system is controlled by sodium (potassium) hydroxide. The initiation system uses water-soluble initiators such as potassium persulfate and ammonium persulfate. Tertiary dodecyl mercaptan is selected as the molecular weight regulator. An intermittent feeding method with batch addition of the molecular weight regulator is used to synthesize nitrile butadiene rubber paste. Tertiary agents and antioxidants are added, and the paste is then degassed, coagulated, washed, and dried to obtain a high oil-resistant nitrile butadiene rubber, as detailed below:

[0005] Based on 100 parts by weight of butadiene and acrylonitrile, the mixture includes 275 parts of soft water, 50-55 parts of butadiene, and 45-50 parts of acrylonitrile; the emulsifier is a composite system of sodium salt of dodecylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate, with an emulsifier dosage of 2.5-5 parts; the initiator is a persulfate, with a dosage of 0.1-0.5 parts; triethanolamine 0.1 parts; and a molecular weight regulator, with an addition amount of 0.3-0.7 parts, added in three portions.

[0006] The above raw materials are mixed and a polymerization reaction is carried out. The pH value of the polymerization system is 10.0-11.0. 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 85-90%, the temperature is lowered to 20-25℃ and the material is discharged. Terminator and antioxidant are added, and the mixture is degassed, coagulated, washed and dried to obtain high-strength special nitrile rubber.

[0007] The invention is further characterized in that,

[0008] Preferably, the amount of dodecylbenzenesulfonic acid is 2 to 4.5 parts, and the amount of sodium salt of naphthalenesulfonic acid formaldehyde condensate is 0.5 to 1 part.

[0009] Preferably, the molecular weight regulator is tert-dodecyl mercaptan.

[0010] Preferably, the molecular weight regulator is added in three equal parts.

[0011] Preferably, the polymerization reaction temperature is controlled at 30–40°C.

[0012] Preferably, the initiator is potassium persulfate.

[0013] The nitrile rubber polymerization conversion rate of the present invention reaches 85-90%, which improves the primary utilization rate of monomers, reduces the energy consumption of monomer recovery, and increases the production capacity of polymerization equipment.

[0014] The beneficial effects of this invention are that it uses an emulsion system composed of dodecylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate sodium salt, and synthesizes high oil-resistant nitrile rubber through pH control of the polymerization system and a thermal batch emulsion polymerization process. The resulting rubber has an acrylonitrile content of 40-45% and a Mooney viscosity of [missing value - likely ML]. (1+4) 100℃ The tensile strength is ≥27.5MPa, and the elongation at break is ≥450%. The nitrile rubber produced using this invention meets the application requirements of the automotive, aerospace, and gasket industries. In addition, the polymerization process is stable and energy consumption is low when using this invention to synthesize the adhesive. Detailed Implementation

[0015] The present invention will now be described in detail with reference to specific embodiments.

[0016] This invention discloses a method for preparing high oil-resistant nitrile butadiene rubber. The method utilizes an emulsion system composed of a sodium salt of dodecylbenzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate. The method involves controlling the pH of the polymerization system and employing a thermal batch emulsion polymerization process. The specific details are as follows:

[0017] Butadiene and acrylonitrile were used as polymerization monomers, and the emulsion system employed a combination of sodium salts of dodecylbenzene sulfonic acid and naphthalene sulfonic acid formaldehyde condensate. The pH of the polymerization system was controlled by sodium (potassium) hydroxide. The initiation system used water-soluble initiators such as potassium persulfate and ammonium persulfate. Tertiary dodecyl mercaptan was selected as the molecular weight regulator. An intermittent feeding method with batch addition of the molecular weight regulator was used to synthesize nitrile butadiene rubber paste. Tertiary agents and antioxidants were added, and the paste was then degassed, coagulated, washed, and dried to obtain a high-oil-resistant nitrile butadiene rubber. Specifically:

[0018] The monomer composition (based on 100 parts by weight of butadiene and acrylonitrile, the same below) is: 50-55 parts butadiene, 45-50 parts acrylonitrile, 275 parts soft water; 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 2-4.5 parts, and naphthalenesulfonic acid formaldehyde condensate sodium salt dosage being 0.5-1 part; the initiator dosage is 0.1-0.5 parts; and triethanolamine dosage is 0.1 parts; the pH value of the polymerization system is 10.0-11.0. The monomer and initiator are added at once, and the molecular weight regulator is added in three stages, using a batch emulsion polymerization process at a polymerization temperature of 30-40℃.

[0019] After evacuating the polymerization reactor, soft water, emulsifier, some or all of the monomer, and triethanolamine are added. The temperature is raised to 30-40°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 85-90%, 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 a high oil-resistant nitrile rubber.

[0020] The high oil-resistant nitrile rubber produced using this invention has an acrylonitrile content of 40-45% and exhibits high tensile strength and elongation at break, meeting the application requirements of the automotive, aerospace, and gasket industries.

[0021] The testing methods for rubber are standard: total solids testing follows SH / T1154-92 standard; combined with acrylonitrile testing follows SH / T1157-1997 standard; Mooney viscosity (MS) (1+4)The 100℃ test adopts the GB / T1232.1-2000 standard; the tensile strength test adopts the GB / T528-1998 standard; the elongation at break test adopts the GB / T528-1998 standard.

[0022] Effects of the invention: The technology of this invention can produce products with a bound acrylonitrile content of 40-45% and a Mooney viscosity of ML. (1 +4) 100℃ The tensile strength is ≥27.5MPa, and the elongation at break is ≥450%. The nitrile rubber produced using this invention meets the application requirements of the automotive, aerospace, and gasket industries. In addition, the polymerization process is stable and energy consumption is low when using this patent for the synthesis of the adhesive.

[0023] Example 1

[0024] The 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 3 parts dodecylbenzenesulfonic acid and 0.5 parts sodium formaldehyde condensate of naphthalenesulfonic acid), 0.1 parts triethanolamine, and 0.15 parts molecular weight regulator were added sequentially, maintaining the pH of the polymerization system at 10.3. The temperature was then raised to 30°C, and 0.2 parts potassium persulfate initiator was added. When the reaction conversion rate reached 35–40%, a secondary molecular weight regulator was added. When the conversion rate reached 50–55%, a tertiary molecular weight regulator was added. When the conversion rate reached 88%, the temperature was lowered to 20–25°C, and the material was discharged. A terminator and antioxidant were added, and the mixture was degassed, coagulated, washed, and dried to obtain a highly oil-resistant nitrile rubber.

[0025] Example 2

[0026] The 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 salt of naphthalenesulfonic acid formaldehyde condensate), 0.1 parts triethanolamine, and 0.15 parts molecular weight regulator were added sequentially, maintaining the pH of the polymerization system at 10.5. The temperature was then raised to 30°C, and 0.2 parts potassium persulfate initiator was added. When the reaction conversion rate reached 35–40%, a secondary molecular weight regulator was added. When the conversion rate reached 50–55%, a tertiary molecular weight regulator was added. When the conversion rate reached 88%, the temperature was lowered to 20–25°C, and the material was discharged. A terminator and antioxidant were added, and the mixture was degassed, coagulated, washed, and dried to obtain a highly oil-resistant nitrile rubber.

[0027] Example 3

[0028] The 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 formaldehyde condensate of naphthalenesulfonic acid), 0.1 parts triethanolamine, and 0.15 parts molecular weight regulator were added sequentially, maintaining the pH of the polymerization system at 10.5. The temperature was then raised to 30°C, and 0.2 parts potassium persulfate initiator was added. When the reaction conversion rate reached 35–40%, a secondary molecular weight regulator was added. When the conversion rate reached 50–55%, a tertiary molecular weight regulator was added. When the conversion rate reached 86%, the temperature was lowered to 20–25°C, and the material was discharged. A terminator and antioxidant were added, and the mixture was degassed, coagulated, washed, and dried to obtain a highly oil-resistant nitrile rubber.

[0029] Example 4

[0030] The 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 formaldehyde condensate of naphthalenesulfonic acid), 0.1 parts triethanolamine, and 0.15 parts molecular weight regulator were added sequentially, maintaining the pH of the polymerization system at 10.6. The temperature was then raised to 30°C, and 0.2 parts potassium persulfate initiator was added. When the reaction conversion rate reached 35–40%, a secondary molecular weight regulator was added. When the conversion rate reached 50–55%, a tertiary molecular weight regulator was added. When the conversion rate reached 88%, the temperature was lowered to 20–25°C, and the material was discharged. A terminator and antioxidant were added, and the mixture was degassed, coagulated, washed, and dried to obtain a highly oil-resistant nitrile rubber.

[0031] Example 5

[0032] The 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 formaldehyde condensate of naphthalenesulfonic acid), 0.1 parts triethanolamine, and 0.15 parts molecular weight regulator were added sequentially, maintaining the pH of the polymerization system at 10.8. The temperature was then raised to 30°C, and 0.2 parts potassium persulfate initiator was added. When the reaction conversion rate reached 35–40%, a secondary molecular weight regulator was added. When the conversion rate reached 50–55%, a tertiary molecular weight regulator was added. When the conversion rate reached 90%, the temperature was lowered to 20–25°C, and the material was discharged. A terminator and antioxidant were added, and the mixture was degassed, coagulated, washed, and dried to obtain a highly oil-resistant nitrile rubber.

[0033] Comparative Example 1

[0034] 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 0.05 parts sodium formaldehyde condensate of naphthalenesulfonic acid), 0.1 parts triethanolamine, and 0.5 parts molecular weight regulator were added sequentially, maintaining the pH of the polymerization system at 10.3. The temperature was then raised to 30°C, and 0.2 parts potassium persulfate initiator was added. When the reaction conversion rate reached 35-40%, a secondary molecular weight regulator was added. When the conversion rate reached 50-55%, a tertiary molecular weight regulator was added. When the conversion rate reached 92%, the temperature was lowered to 20-25°C, and the material was discharged. A terminator and antioxidant were added, and the mixture was degassed, coagulated, washed, and dried to obtain a highly oil-resistant nitrile rubber.

[0035] Comparative Example 2

[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, 0.5 parts sodium naphthalenesulfonic acid formaldehyde condensate emulsifier, 0.1 parts triethanolamine, and 0.5 parts molecular weight regulator were added sequentially, maintaining the pH of the polymerization system at 9.5. The temperature was then raised to 30°C, and 0.2 parts potassium persulfate initiator was added. When the reaction conversion rate reached 35-40%, a secondary molecular weight regulator was added. When the conversion rate reached 50-55%, a tertiary molecular weight regulator was added. When the conversion rate reached 92%, the temperature was lowered to 20-25°C, and the material was discharged. A terminator and antioxidant were added, and the mixture was degassed, coagulated, washed, and dried to obtain a highly oil-resistant nitrile rubber.

[0037] Comparative Example 3

[0038] 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, 0.1 parts sodium naphthalenesulfonic acid formaldehyde condensate emulsifier, 0.1 parts triethanolamine, and 0.5 parts molecular weight regulator were added sequentially, maintaining the pH of the polymerization system at 9.5. The temperature was then raised, and when it reached 30°C, 0.2 parts potassium persulfate initiator was added. When the reaction conversion rate reached 35-40%, a secondary molecular weight regulator was added. When the conversion rate reached 50-55%, a tertiary molecular weight regulator was added. When the conversion rate reached 70%, the temperature was lowered to 20-25°C, and the material was discharged. A terminator and antioxidant were added, and the mixture was degassed, coagulated, washed, and dried to obtain a highly oil-resistant nitrile rubber.

[0039] 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.

[0040] Table 1 shows a comparison of the experimental conditions for the high oil-resistant special nitrile rubber prepared in Examples 1-5 and Comparative Examples 1-3. The test results for the properties of the nitrile rubber are shown in Table 2 below. Table 2 shows that 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 (ML). (1 +4) 100℃ 90~120, tensile strength ≥27.5MPa, elongation at break ≥450%.

[0041] Table 1

[0042]

[0043]

[0044] Table 2

[0045]

[0046] In this invention, as the polymerization conversion rate increases, the acrylonitrile content in the rubber increases and the Mooney viscosity increases. However, as the conversion rate increases, the rubber properties deteriorate. This invention achieves improved polymerization conversion rate while ensuring that the rubber properties are not affected by precise control of the pH value of the polymerization system.

Claims

1. A method for preparing high oil-resistant nitrile butadiene rubber, characterized in that, Specifically as follows: Based on 100 parts by weight of butadiene and acrylonitrile, the mixture includes 275 parts of soft water, 50-55 parts of butadiene, and 45-50 parts of acrylonitrile; the emulsifier is a composite system of sodium salt of dodecylbenzenesulfonic acid and naphthalenesulfonic acid formaldehyde condensate, with an emulsifier dosage of 2.5-5 parts; the initiator is a persulfate, with a dosage of 0.1-0.5 parts; triethanolamine 0.1 parts; and a molecular weight regulator, with an addition amount of 0.3-0.7 parts, added in three portions. The above raw materials are mixed and a polymerization reaction is carried out. The pH value of the polymerization system is controlled at 10.0-11.0 by sodium hydroxide or potassium hydroxide. 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 85-90%, the temperature is lowered to 20-25℃ and the material is discharged. Terminator and antioxidant are added, and the material is degassed, coagulated, washed and dried to obtain high oil-resistant special nitrile rubber. The amount of dodecylbenzenesulfonic acid used is 2 to 4.5 parts, and the amount of sodium salt of naphthalenesulfonic acid formaldehyde condensate used is 0.5 to 1 part; The molecular weight regulator is selected as tert-dodecyl mercaptan.

2. The method for preparing high oil-resistant nitrile rubber according to claim 1, characterized in that, The molecular weight regulator was added in three equal parts.

3. The method for preparing high oil-resistant nitrile rubber according to claim 1, characterized in that, The polymerization reaction temperature is controlled at 30–40℃.

4. The method for preparing high oil-resistant nitrile rubber according to claim 1, characterized in that, The initiator is potassium persulfate.

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