Perfluoroether fluororubber as well as preparation method and application thereof

Abstract

The invention relates to the technical field of rubber preparation, and particularly discloses perfluoroether fluororubber as well as a preparation method and application thereof. A polymer chain segment of the perfluoroether fluororubber is in an A-B-A block form. The preparation method comprises the following steps: (1) carrying out polymerization reaction on an early-stage polymerization monomer consisting of a segment A monomer and a cyano-containing compound vulcanization point monomer to form a chain segment A; the A-segment monomer comprises tetrafluoroethylene and perfluoroalkyl vinyl ether; (2) carrying out polymerization reaction on the A chain segment, a middle-term polymerization monomer consisting of a B segment monomer and a cyano-containing compound vulcanization point monomer to form an A-B chain segment; the section B monomer comprises tetrafluoroethylene; and (3) carrying out polymerization reaction on the A-B chain segment and a later-stage polymerization monomer consisting of the A-segment monomer and a cyano-containing compound vulcanization point monomer to form the perfluoroether fluororubber emulsion with an A-B-A block form. The method is high in production efficiency, and the obtained product is resistant to high temperature and good in processability.

Description

Technical Field

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

[0002] Perfluoroether fluororubber mainly uses tetrafluoroethylene (TFE) and perfluoroalkyl vinyl ether (PAVE) as the main copolymer monomers, and usually also contains perfluoro bromine, iodine, cyanide compounds or dienes and other vulcanization point monomers for copolymerization. The molar ratio of TFE / PAVE is (35~65): (35~65). The vulcanized products of perfluoroether fluororubber are favored by industries such as petrochemicals and semiconductor industries. The Tg of general perfluoroether rubber is about -4℃~2℃.

[0003] Existing Chinese patents CN107868163A and CN1120343A report the preparation method of perfluoroether elastomer, but they cannot meet the high temperature resistance performance. USP 4487903 relates to a fluorine-containing elastomer copolymer prepared from perfluorovinyl ether, using TFE and PAVE for copolymerization, but due to the addition of PAVE monomer to the polymerization system, the polymerization time is as long as 96h, which is very unfavorable for production. Chinese patent CN1120343A discloses a preparation method of low-temperature perfluoroether elastomer, using high molecular weight perfluoropolyether and perfluoroelastomer for blending to prepare modified perfluoroelastomer, but due to the addition of modified monomer perfluoropolyether during the polymerization process, the activity of the polymerization system is weakened, the polymerization time is long, which is not conducive to industrial production, and after the polymerization is completed, the perfluoropolyether remaining in the polymerization system cannot be recycled, which is not conducive to environmental protection.

[0004] Therefore, it is still necessary to develop a perfluoroether fluororubber material with high production efficiency and high temperature resistance. Summary of the invention

[0005] One of the purposes of the present invention is to provide a high-efficiency and high-temperature resistant perfluoroether fluororubber material.

[0006] The present invention provides a method for preparing perfluoroether fluororubber, wherein the polymer chain segment of the perfluoroether fluororubber is in the form of ABA block, and the preparation method comprises: (1) polymerizing the prepolymer monomers consisting of the A segment monomer and the cyanide compound-containing sulfurization point monomer to form the A segment; the A segment monomers include tetrafluoroethylene and perfluoroalkyl vinyl ether; (2) polymerizing the A segment with a mid-term polymerization monomer consisting of a B segment monomer and a cyanide compound-containing sulfurization point monomer to form an AB segment; the B segment monomer includes tetrafluoroethylene; (3) polymerizing the AB segment with the A segment monomer and the post-polymerization monomer consisting of a cyano compound-containing sulfurization point monomer to form an emulsion of a perfluoroether fluororubber having an ABA block morphology; In steps (1) and (3), the added mass of the cyanide compound-containing sulfurization point monomer is 8-12‰ of the mass of the A-stage monomer; In step (2), the added mass of the cyanide compound-containing sulfurization point monomer is 20-45‰ of the mass of the B-stage monomer.

[0007] The present invention provides a high temperature resistant perfluoroether fluororubber, whose polymer chain segment is a specific ABA polymer structure, wherein the two side A are TFE / PAVE obtained by ternary copolymerization, and the middle segment B is a PTFE high temperature resistant segment, and in order to make the material have the performance of resistant to 350°C high temperature after vulcanization, the present invention also adds a specific proportion of cyano compound vulcanization point monomers in different blocks during the polymerization process, and by connecting it to the polymer, the perfluoroether elastomer can be cross-linked and vulcanized using a triazine vulcanization system, which is beneficial to improve the processing performance of the high temperature resistant perfluoroether fluororubber to a certain extent. The final product is high temperature resistant, the compression permanent deformation value of the perfluoroether elastomer is ≤55% (350°C×24h), the tensile strength is greater than 20MPa, the elongation is about 200%, the hardness is low, and the medium resistance and processing performance are good.

[0008] In the A-stage monomer of the method of the present invention, the molar ratio of tetrafluoroethylene to perfluoroalkyl vinyl ether is (65-80): (20-35).

[0009] In the method of the present invention, the pre-polymerized monomers in step (1) account for 25% to 50% of the mass of the perfluoroether fluororubber; the mid-polymerized monomers in step (2) account for 19.5% to 40% of the mass of the perfluoroether fluororubber; and the late-polymerized monomers in step (3) account for 25% to 50% of the mass of the perfluoroether fluororubber.

[0010] Preferably, the early-stage polymerized monomers in step (1) account for 34-40% of the mass of the perfluoroether fluororubber; the mid-stage polymerized monomers in step (2) account for 19.5-32% of the mass of the perfluoroether fluororubber; and the late-stage polymerized monomers in step (3) account for 34-40% of the mass of the perfluoroether fluororubber.

[0011] In the polymerization process of the present invention, different mixed monomers and cyanide-containing compound sulfurization point monomers of different concentrations are added in three stages, thereby ensuring the structure and performance of the final product.

[0012] In the method of the present invention, the mass of the monomers polymerized in the early stage and the monomers polymerized in the late stage are the same; And / or, the proportions of the components in the early-stage polymerization monomers and the late-stage polymerization monomers are the same.

[0013] In the method of the present invention, the perfluoroalkyl vinyl ether is perfluoromethyl vinyl ether or perfluoropropyl vinyl ether; The cyano compound sulfurization point monomer includes CF2=CFO(CF2) n CF(CF3)OCF2CF2CN, CF2=CFO(CF2)CF(CF3) n OCF2CF2CN, CF2=CFO(CF2)CF(CF3)O(CF2) m One of CN, wherein n=1, 2 or 3; m=1, 2, 3, 4 or 5.

[0014] In the method of the present invention, the temperature of the polymerization reaction in steps (1) and (3) is 80-105° C. and the pressure is 2.8-3.5 MPa; the temperature of the polymerization reaction in step (2) is 70-95° C. and the pressure is 1.6-2.0 MPa; the temperature of the polymerization reaction in steps (1) and (3) is higher than the temperature of the polymerization reaction in step (2).

[0015] In order to make the cyano compound sulfurization point monomers evenly distributed in segment A and segment B, and the monomers in segment A and segment B evenly inlaid and distributed, while improving production efficiency, during the polymerization process, the present invention particularly adopts different polymerization process conditions in different production stages, which is beneficial to ensure the preparation effect of the product.

[0016] In the method of the present invention, the total polymerization time for preparing the perfluoroether fluororubber is 5 to 8 hours, preferably 6.5 to 7.5 hours.

[0017] In the method of the present invention, the reaction medium for preparing the perfluoroether fluororubber is water, and the oxygen content in the reaction system is ≤30ppm; the reaction medium is 2.5-4 times, preferably 2.5-3 times, the mass of the total monomers to be polymerized; When performing step (1), an initiator, an emulsifier and a chain transfer agent are also added to the reaction system; The initiator is one or more of ammonium persulfate, potassium persulfate, and potassium permanganate; preferably, the amount of the initiator added is 0.01-8% of the mass of water; The emulsifier is perfluorooctanoate (including its ammonium salt, sodium salt or potassium salt); preferably, the amount of the emulsifier added is 0.1-5% of the mass of water; The chain transfer agent is one or more of 1,2-diiodoperfluoroethane, 1,3-diiodoperfluoropropane, and 1,4-diiodoperfluorobutane; preferably, the amount of the chain transfer agent added is 0.025-15% of the total polymerization monomer mass, and the total polymerization monomer includes the early polymerization monomer, the mid-term polymerization monomer, and the late polymerization monomer.

[0018] The method of the present invention further comprises the steps of coagulating, washing and drying the emulsion.

[0019] Coagulation, washing and drying are performed by methods known in the art. For example, coagulation is performed by adding a coagulant (such as salts such as MgCl2) to the emulsion, and washing is performed by washing with deionized water for multiple times.

[0020] As a specific embodiment, in the method of the present invention, in the early stage of the polymerization process, the monomer components for polymerization are TFE / PAVE, in the middle stage of the polymerization process, the early mixed monomers are quickly recovered, and TFE with a certain pressure is added to carry out polymerization reaction, and in the late stage of the polymerization process, the early mixed monomers are quickly recovered, and TFE / PAVE is added to carry out polymerization reaction. After the reaction is completed, the mixed gas is recovered and the dispersion is released. The dispersion is formed into a final product after condensation, washing, and drying.

[0021] The present invention also provides a perfluoroether fluororubber, which is prepared by the above method.

[0022] The present invention also provides the application of the above-mentioned perfluoroether fluororubber in the fields of automobile industry, aerospace, and electronic appliances.

[0023] The beneficial effects of the present invention are at least: The invention provides a high-temperature resistant perfluoroether fluororubber material, which can be used under 350°C working conditions. The obtained high-temperature resistant perfluoroether elastomer has a compression permanent deformation value of ≤55% (350°C×24h), a tensile strength of greater than 20MPa, an elongation of about 200%, a low hardness, and good medium resistance and processing performance. DETAILED DESCRIPTION

[0024] The preferred embodiments of the present invention will be described in detail below in conjunction with examples. It should be understood that the following examples are provided only for the purpose of illustration and are not intended to limit the scope of the present invention. Those skilled in the art may make various modifications and substitutions to the present invention without departing from the purpose and spirit of the present invention.

[0025] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples are commercially available or prepared according to conventional methods in the art unless otherwise specified.

[0026] Example 1 This embodiment provides a high temperature resistant perfluoroether fluororubber material, and the preparation method is as follows: Emulsion polymerization was carried out in a 50 L reactor. 30 L of deionized water was added to the reactor. The reactor was evacuated, and when the oxygen content was ≤30 ppm, 35 g of ammonium perfluorooctanoate was added, and the contents in the reactor were heated to 95°C.

[0027] In the early stage of the polymerization process, the monomers of stage A were added. The monomers of stage A were TFE and PMVE. The molar ratio of TFE / PMVE was 75:25. The pressure of the reactor was raised to 3.2 MPa. 15 g of potassium persulfate, 25 g of 1,2-diiodoperfluoroethane and 38 g of CF2=CFOCF2CF(CF3)OCF2CF2CN were added to start the polymerization reaction. The monomers of stage A were continuously added to keep the temperature in the kettle at 95°C and the pressure at 3.2 MPa. When the amount of monomer added to be reacted reached 4.5 kg, the unreacted monomers were recovered.

[0028] In the middle stage of polymerization, 65 g of B-stage monomers TFE and CF2=CFOCF2CF(CF3)OCF2CF2CN were added, the polymerization pressure was 1.8 MPa, and the polymerization temperature was adjusted to 75°C; the B-stage monomers were continuously added to maintain the polymerization pressure and temperature, and when the amount of reacted monomers added reached 2.8 kg, the unreacted monomers were recovered.

[0029] In the late stage of the polymerization process, the temperature was raised to 95°C, and the A-stage monomers were added. The A-stage monomers were TFE and PMVE, and the molar ratio of TFE / PMVE was 75:25. The reactor pressure was raised to 3.2MPa, and 38g of the high temperature resistant vulcanization point monomer CF2=CFOCF2CF (CF3) OCF2CF2CN was added. The A-stage monomers were continuously added to keep the temperature in the kettle at 95°C and the pressure at 3.2Mpa. When the amount of monomer added to be reacted reached 4.5kg, the reaction was terminated, the unreacted monomers were recovered, the emulsion was discharged into the coagulation barrel, and the coagulant (MgCl2) was added for coagulation, and then washed with deionized water. It was vacuum dried at about 100°C. The polymer produced was about 11.84kg, and the polymerization time was about 6.5h.

[0030] Example 2 This embodiment provides a high temperature resistant perfluoroether fluororubber material, and the preparation method is as follows: Emulsion polymerization was carried out in a 50L reactor. 30L of deionized water was added to the reactor. The reactor was evacuated, and when the oxygen content was ≤30ppm, 30g of sodium perfluorooctanoate was added, and the contents in the reactor were heated to 80°C.

[0031] In the early stage of the polymerization process, the monomers of stage A were added. The monomers of stage A were TFE and PPVE. The molar ratio of TFE / PPVE was 65:35. The pressure of the reactor was raised to 3.5 MPa. 3 g of ammonium persulfate, 3 g of 1,3-diiodoperfluoropropane and 44.5 g of CF2=CFO(CF2)CF(CF3)2OCF2CF2CN were added to start the polymerization reaction. The monomers of stage A were continuously added to keep the temperature in the kettle at 80°C and the pressure at 3.5 MPa. When the amount of monomer added to be reacted reached 3.7 kg, the unreacted monomers were recovered.

[0032] In the middle stage of polymerization, 68 g of B-stage monomers TFE and CF2=CFO(CF2)CF(CF3)2OCF2CF2CN were added, the polymerization pressure was 2.0 MPa, and the polymerization temperature was adjusted to 70°C; the B-stage monomers were continuously added to maintain the polymerization pressure and temperature, and when the amount of reacted monomers added reached 3.4 kg, the unreacted monomers were recovered.

[0033] In the late stage of the polymerization process, the temperature was raised to 80°C, and the monomers of stage A were added. The monomers of stage A were TFE and PPVE, and the molar ratio of TFE / PPVE was 65:35. The pressure of the reactor was raised to 3.5MPa, and 44.5g of the high temperature resistant vulcanization point monomer CF2=CFOCF2CF (CF3) OCF2CF2CN was added. The monomers of stage A were continuously added to keep the temperature in the kettle at 80°C and the pressure at 3.5Mpa. When the amount of monomer added to be reacted reached 3.7kg, the reaction was terminated, the unreacted monomers were recovered, the emulsion was discharged into the coagulation barrel, the coagulant (MgCl2) was added for coagulation, and then washed with deionized water. It was vacuum dried at about 100°C. The polymer produced was about 10.85kg, and the polymerization time was about 6.8h.

[0034] Example 3 This embodiment provides a high temperature resistant perfluoroether fluororubber material, and the preparation method is as follows: Emulsion polymerization was carried out in a 50L reactor. 30L of deionized water was added to the reactor. The reactor was evacuated, and when the oxygen content was ≤30ppm, 1500g of potassium perfluorooctanoate was added, and the contents in the reactor were heated to 105°C.

[0035] In the early stage of the polymerization process, the A-stage monomers were added. The A-stage monomers were TFE and PPVE, and the molar ratio of TFE / PPVE was 80:20. The pressure of the reactor was raised to 2.8 MPa, and 2400 g of potassium permanganate, 1500 g of 1,4-diiodoperfluorobutane and 33 g of CF2=CFO(CF2)CF(CF3)O(CF2)3CN were added to start the polymerization reaction. The A-stage monomers were continuously added to keep the temperature in the kettle at 105°C and the pressure at 2.8 MPa. When the amount of monomers added to be reacted reached 4.08 kg, the unreacted monomers were recovered.

[0036] In the middle stage of polymerization, 91.8 g of B-stage monomer TFE and CF2=CFO(CF2)CF(CF3)O(CF2)3CN were added, the polymerization pressure was 1.6 MPa, and the polymerization temperature was adjusted to 95°C; the B-stage monomer was continuously added to maintain the polymerization pressure and temperature, and when the amount of reacted monomer added reached 2.04 kg, the unreacted monomer was recovered.

[0037] In the late stage of the polymerization process, the temperature was raised to 105°C, and the monomers of stage A were added. The monomers of stage A were TFE and PPVE, and the molar ratio of TFE / PPVE was 80:20. The pressure of the reactor was raised to 2.8MPa, and 33g of the high temperature resistant vulcanization point monomer CF2=CFOCF2CF (CF3) OCF2CF2CN was added. The monomers of stage A were continuously added to keep the temperature in the kettle at 105°C and the pressure at 2.8Mpa. When the amount of monomer added to be reacted reached 4.08kg, the reaction was terminated, the unreacted monomers were recovered, the emulsion was discharged into the coagulation barrel, the coagulant (MgCl2) was added for coagulation, and then washed with deionized water. It was vacuum dried at about 100°C. The polymer produced was about 10.25kg, and the polymerization time was about 7.5h.

[0038] Comparative Example 1 This comparative example provides a perfluoroether fluororubber, and the preparation method is as follows: (1) Add 30 L of deionized water to a 50 L reactor, evacuate the reactor until the oxygen content is ≤30 ppm, add 35 g of ammonium perfluorooctanoate, and heat the contents in the reactor to 85° C.

[0039] (2) adding prepolymer monomers composed of I(CF2)2OCF=CF2, TFE, and perfluoromethyl vinyl ether in a molar ratio of 1:60:39, raising the reactor pressure to 3.0 MPa, adding 15 g of potassium persulfate and 25 g of 1,2-diiodoperfluoroethane to start a prepolymerization reaction, and when the amount of prepolymer monomers added reaches 2.5 kg, recovering unreacted monomers; (3) introducing into the reactor a mid-term polymerization monomer consisting of I(CF2)2OCF=CF2, TFE, and perfluoromethyl vinyl ether in a molar ratio of 0.1:35:64.9, adjusting the polymerization pressure to 2.0 MPa to carry out a mid-term polymerization reaction, and when the amount of mid-term polymerization monomer added reaches 3.3 kg, recovering the unreacted monomer; (4) continuing to feed the reactor with a late polymerization monomer composed of I(CF2)2OCF=CF2, TFE, and perfluoromethyl vinyl ether in a molar ratio of 1:60:39, raising the reactor pressure to 3.0 MPa, and when the amount of late polymerization monomer added reaches 2.5 kg, terminating the reaction, recovering the unreacted monomer, and obtaining an emulsion containing perfluoroether fluororubber; (5) The emulsion was mechanically coagulated and washed, and vacuum dried at 100° C. to obtain about 7.5 kg of a perfluoroether fluororubber product.

[0040] Comparative Example 2 This comparative example provides a perfluoroether fluororubber material, and its preparation method is the same as that of Example 1, except that the B-stage monomer is changed to TFE and PMVE with a molar ratio of 75:25 in the middle stage of polymerization.

[0041] Comparative Example 3 This comparative example provides a perfluoroether fluororubber material, and its preparation method is the same as that of Example 1, except that the amount of CF2=CFOCF2CF(CF3)OCF2CF2CN added in steps (1) and (3) is increased to 15‰ of the total mass of the reaction monomers (tetrafluoroethylene and perfluoroalkyl vinyl ether).

[0042] Experimental example In this experimental example, the rubber of each embodiment and comparative example was vulcanized, and then its performance was tested, as follows: The curing formula is shown in Table 1: Table 1 Vulcanization conditions: first stage vulcanization at 170℃×30min, second stage vulcanization: 290℃×(8+16)h.

[0043] The test items are as follows, and the results are shown in Table 2: 1. Mooney viscosity, test method refers to GB / T 1232-1992; 2. Fluorine content, the test method refers to F-NMR; 3. Compression set value (350℃×24h), test method refers to GB / T7759.1-1996; 4. Tensile strength, test method refers to GB / T528-2009; 5. Elongation, test method refers to GB / T528-2009; 6. Hardness, test method refers to GB / T 531.1-2008; 7. Medium resistance performance, test method refers to GB / T 1690-2010.

[0044] Table 2 Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing perfluoroether fluororubber, characterized in that: The polymer chain segment of the perfluoroether fluororubber is in the form of ABA block, and the preparation method comprises: (1) polymerizing the prepolymer monomers consisting of the A segment monomer and the cyanide compound-containing sulfurization point monomer to form the A segment; the A segment monomers include tetrafluoroethylene and perfluoroalkyl vinyl ether; (2) polymerizing the A segment with a mid-term polymerization monomer consisting of a B segment monomer and a cyanide compound-containing sulfurization point monomer to form an AB segment; the B segment monomer includes tetrafluoroethylene; (3) polymerizing the AB segment with the A segment monomer and the post-polymerization monomer consisting of a cyano compound-containing sulfurization point monomer to form an emulsion of a perfluoroether fluororubber having an ABA block morphology; In steps (1) and (3), the added mass of the cyanide compound-containing sulfurization point monomer is 8-12‰ of the mass of the A-stage monomer; In step (2), the added mass of the cyanide compound-containing sulfurization point monomer is 20-45‰ of the mass of the B-stage monomer.

2. The method according to claim 1, characterized in that In the A-stage monomer, the molar ratio of tetrafluoroethylene to perfluoroalkyl vinyl ether is (65-80): (20-35).

3. The method according to claim 1 or 2, characterized in that: The pre-polymerized monomers in step (1) account for 25% to 50% of the mass of the perfluoroether fluororubber; the mid-polymerized monomers in step (2) account for 19.5% to 40% of the mass of the perfluoroether fluororubber; the late-polymerized monomers in step (3) account for 25% to 50% of the mass of the perfluoroether fluororubber; Preferably, the early-stage polymerized monomers in step (1) account for 34-40% of the mass of the perfluoroether fluororubber; the mid-stage polymerized monomers in step (2) account for 19.5-32% of the mass of the perfluoroether fluororubber; and the late-stage polymerized monomers in step (3) account for 34-40% of the mass of the perfluoroether fluororubber.

4. The method according to claim 3, characterized in that The mass of the early polymerization monomer and the late polymerization monomer is the same; And / or, the proportions of the components in the early-stage polymerization monomers and the late-stage polymerization monomers are the same.

5. The method according to any one of claims 1 to 4, characterized in that: The perfluoroalkyl vinyl ether is perfluoromethyl vinyl ether or perfluoropropyl vinyl ether; The cyano compound sulfurization point monomer includes CF2=CFO(CF2) n CF(CF3)OCF2CF2CN, CF2=CFO(CF2)CF(CF3) n OCF2CF2CN, CF2=CFO(CF2)CF(CF3)O(CF2) m One of CN, wherein n=1, 2 or 3; m=1, 2, 3, 4 or 5.

6. The method according to any one of claims 1 to 5, characterized in that: The polymerization reaction temperature in steps (1) and (3) is 80-105°C and the pressure is 2.8-3.5 MPa; the polymerization reaction temperature in step (2) is 70-95°C and the pressure is 1.6-2.0 MPa; the polymerization reaction temperature in steps (1) and (3) is higher than the polymerization reaction temperature in step (2); And / or, the total polymerization time for preparing the perfluoroether fluororubber is 5 to 8 hours, preferably 6.5 to 7.5 hours.

7. The method according to any one of claims 1 to 6, characterized in that: The reaction medium for preparing the perfluoroether fluororubber is water, and the oxygen content in the reaction system is ≤30ppm; The reaction medium is 2.5-4 times the mass of the total monomers in the polymerization; When performing step (1), an initiator, an emulsifier and a chain transfer agent are also added to the reaction system; The initiator is one or more of ammonium persulfate, potassium persulfate, and potassium permanganate; preferably, the amount of the initiator added is 0.01-8% of the mass of water; The emulsifier is perfluorooctanoate; preferably, the amount of the emulsifier added is 0.1-5% of the mass of water; The chain transfer agent is one or more of 1,2-diiodoperfluoroethane, 1,3-diiodoperfluoropropane, and 1,4-diiodoperfluorobutane; preferably, the amount of the chain transfer agent added is 0.025-15% of the total polymerization monomer mass, and the total polymerization monomer includes the early polymerization monomer, the mid-term polymerization monomer, and the late polymerization monomer.

8. The method according to any one of claims 1 to 7, characterized in that The method also includes the steps of coagulating, washing and drying the emulsion.

9. A perfluoroether fluororubber, characterized in that: Prepared by the method according to any one of claims 1 to 8.

10. Application of the perfluoroether fluororubber according to claim 9 in the automotive industry, aerospace, and electronic and electrical fields.

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