Ultra-high temperature resistant perfluoroether rubber and preparation method thereof

Abstract

The present invention relates to the technical field of fluororubber preparation, specifically to an ultra-high temperature resistant perfluoroether rubber and a preparation method thereof. The preparation method of the ultra-high temperature resistant perfluoroether rubber comprises the following steps: using tetrafluoroethylene and perfluoroalkyl propenyl ether as copolymer monomers, using functionalized perfluoroolefin as a vulcanization point monomer, using halogenated perfluoroalkane as a chain transfer agent and an initiator through emulsion polymerization and emulsion post-treatment. The ultra-high temperature resistant perfluoroether rubber prepared by the present invention can be used for a long time in a high temperature environment of 330°C.

Description

Technical Field

[0001] The invention relates to the technical field of fluororubber preparation, in particular to an ultra-high temperature resistant perfluoroether rubber and a preparation method thereof. Background Art

[0002] Perfluoroether rubber (FFKM) is the rubber material with the best resistance to high temperature, strong acid and alkali, and organic solvents among all elastic sealing materials. It is widely used in chemical industry, nuclear industry, semiconductor, aerospace, deep sea exploration, ultra-deep well oil field development and other industries.

[0003] At present, perfluoroether rubber is mainly made of tetrafluoroethylene (TFE) and perfluoromethyl vinyl ether (PMVE) and vulcanization point monomer copolymerization. Due to the structural limitations of perfluoromethyl vinyl ether, CF 2 =CFOCF 3 The CO bond in the rubber will break at high temperatures, so that the perfluoroether rubber composed of tetrafluoroethylene and perfluoromethyl vinyl ether cannot be used for a long time at temperatures above 315°C, limiting the use of perfluoroether rubber at higher temperatures.

[0004] Due to the development needs of various industries, higher demands are placed on the heat resistance of perfluoroether rubber, but perfluoroether rubber composed of tetrafluoroethylene and perfluoromethyl vinyl ether cannot meet the ultra-high temperature resistance needs of various industries. Summary of the invention

[0005] In order to solve the defects of the prior art, the present invention provides an ultra-high temperature resistant perfluoroether rubber and a preparation method thereof.

[0006] The invention provides a method for preparing ultrahigh temperature resistant perfluoroether rubber, comprising the following steps: using tetrafluoroethylene and perfluoroalkyl propenyl ether as copolymer monomers, using functionalized perfluoroolefin as a vulcanization point monomer, using halogenated perfluoroalkane as a chain transfer agent and an initiator through emulsion polymerization and emulsion post-treatment to prepare the ultrahigh temperature resistant perfluoroether rubber.

[0007] Preferably, the method for preparing the ultrahigh temperature resistant perfluoroether rubber comprises the following steps:

[0008] Tetrafluoroethylene and perfluoroalkyl propenyl ether are introduced into the reaction kettle until the pressure inside the kettle reaches 3-4 MPa, and functionalized perfluoroolefin, halogenated perfluoroalkane and initiator are added, and the emulsion polymerization reaction is carried out at a kettle temperature of 80° C. to 120° C. for 10 h to 20 h to obtain an emulsion;

[0009] performing emulsion post-treatment on the emulsion;

[0010] The ultra-high temperature resistant perfluoroether rubber is obtained by plasticizing and molding.

[0011] Preferably, the method for preparing the ultrahigh temperature resistant perfluoroether rubber comprises the following steps:

[0012] Deionized water, pH buffer and emulsifier were added to the reactor, vacuum was drawn and nitrogen was used to control the oxygen content in the reactor to ≤20ppm, and the temperature of the reactor was raised to 80-120°C;

[0013] Tetrafluoroethylene and perfluoroalkyl propenyl ether are introduced into a reaction kettle, the pressure in the kettle is 3-4 MPa, functionalized perfluoroolefin, halogenated perfluoroalkane and initiator are added, and the emulsion polymerization reaction is carried out at a kettle temperature of 80° C.-120° C. for 10 h-20 h to obtain an emulsion;

[0014] The emulsion is coagulated with a coagulant aqueous solution, washed, and dried at 90° C.-120° C. for 24-48 hours to obtain a dry rubber powder;

[0015] The ultra-high temperature resistant perfluoroether rubber is obtained by plasticizing and molding.

[0016] The perfluoroalkyl propenyl ether has the following structure: CF 2 =CFCF 2 OR, wherein R is a perfluoroalkyl group of 1 to 6 carbon atoms. The structure of R is: -(CF 2 ) n CF 3 , where n is an integer from 0 to 5.

[0017] Preferably, the perfluoroalkyl propenyl ether is one or more of perfluoromethyl propenyl ether and perfluoropropyl propenyl ether.

[0018] The mass ratio of the comonomers tetrafluoroethylene and perfluoroalkyl propenyl ether is (35-70): (65-30).

[0019] The functionalized perfluoroolefin is one or more of brominated perfluoroolefin, iodinated perfluoroolefin and nitrile-containing perfluoroolefin.

[0020] Preferably, the brominated perfluoroolefin is at least one of bromotrifluoroethylene, perfluoroallyl bromide and perfluoroethoxyvinyl bromide.

[0021] Preferably, the iodinated perfluorovinyl ether is at least one of iodotrifluoroethylene, perfluoroallyl iodide, perfluoroiodoethyl vinyl ether and perfluoroiodoethoxy vinyl ether.

[0022] Preferably, the nitrile-containing perfluoroolefin is CF 2 =CF-O-(CF 2 ) 4 CN and / or CF 2 =CF-O-(CF 2 ) 5 CN.

[0023] The functionalized perfluoroolefin is CF 2 =CF-O-(CF 2 ) 5 A mixture of CN and perfluoroiodoethyl vinyl ether.

[0024] The added amount of the functionalized perfluoroolefin is 0.1-6% of the total mass of the tetrafluoroethylene.

[0025] The halogenated perfluoroalkane is a brominated perfluoroalkane and / or an iodinated perfluoroalkane.

[0026] Preferably, the halogenated perfluoroalkane is at least one of perfluorobutyl bromide, perfluorohexyl bromide, 1,6-dibromoperfluorohexane, perfluorobutyl iodide, perfluorohexyl iodide, perfluorooctyl iodide, 1,4-diiodoperfluorobutane and 1,6-diiodoperfluorohexane.

[0027] The amount of the halogenated perfluoroalkane added is 0.1-4% of the total mass of the tetrafluoroethylene.

[0028] The initiator is a combination of an oxidizing agent and a reducing agent.

[0029] The oxidant is a persulfate, preferably, the oxidant is at least one of ammonium persulfate, potassium persulfate and sodium persulfate.

[0030] The reducing agent is a sulfite, preferably, the reducing agent is at least one of ammonium sulfite, potassium sulfite, sodium sulfite and thiosulfate, and more preferably, the thiosulfate is at least one of ammonium thiosulfate, potassium thiosulfate and sodium thiosulfate.

[0031] The initiator is a composition of 30-70 wt % of an oxidant and 30-70 wt % of a reducing agent, and the added amount of the initiator is 0.1-1.5 % of the total mass of the deionized water.

[0032] The pH buffer is one or more of sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, ammonium sulfate, and ammonium bicarbonate. The pH buffer is used in an amount of 0.01-1% of the total mass of the deionized water.

[0033] The emulsifier is a perfluoropolyether carboxylate, preferably, the emulsifier is one of perfluoro-2-methyl-3-oxahexanoic acid ammonium and perfluoro-2,5-dimethyl-3,6-dioxahexanoic acid ammonium. The amount of the emulsifier is 0.1-5% of the total mass of the deionized water.

[0034] The mass ratio of tetrafluoroethylene to deionized water is (1-25):(99-75).

[0035] Preferably, the mass content of the coagulant in the coagulant aqueous solution is 0.1-10wt%, and the coagulant is one or more of magnesium chloride, magnesium sulfate, aluminum sulfate, alum, calcium chloride, ammonium nitrate, nitric acid, hydrochloric acid and sulfuric acid.

[0036] The detergent is one or more of deionized water, acetone, ethyl acetate, methanol, ethanol, and toluene.

[0037] The perfluoroether rubber prepared by the present invention has tetrafluoroethylene and perfluoroalkyl propenyl ether as main comonomers, and exhibits excellent high temperature resistance and long-term use stability. The perfluoroether rubber of the present invention exhibits good low compression permanent deformation rate and hot air aging performance in a high temperature environment of 330°C. Specifically, the compression permanent deformation rate is maintained between 40-45%, which is significantly lower than the 68-71% of conventional rubber, indicating that the perfluoroether rubber of the present invention has better deformation stability at high temperatures. In addition, the hot air aging test results show that the tensile strength changes by only -16% to -33%, while the tensile strength of conventional rubber changes by as much as -43% to -58%, further proving the superior thermal stability and mechanical strength retention ability of the material of the present invention. DETAILED DESCRIPTION

[0038] A method for preparing ultrahigh temperature resistant perfluoroether rubber comprises the following steps:

[0039] Deionized water, pH buffer and emulsifier were added to the reactor, vacuum was drawn and nitrogen was used to control the oxygen content in the reactor to ≤20ppm, and the temperature of the reactor was raised to 80-120°C;

[0040] Deionized water provides a pure reaction environment to prevent impurity ions from interfering with the reaction and ensure the high purity of the polymer; pH buffers maintain the pH stability of the reaction system, ensuring the activity of the initiator and the uniformity of the polymerization reaction; emulsifiers form stable emulsions during the reaction, promote the uniform dispersion of monomers in the aqueous phase, improve the conversion rate of monomers, and form polymer particles with uniform particle size, thereby improving polymer performance. Vacuum and replace with nitrogen to remove oxygen from the reaction system to prevent oxygen from inhibiting free radical polymerization, ensure polymerization efficiency and avoid side reactions; control the reactor temperature between 80-120°C to provide suitable conditions for the decomposition of the initiator and the polymerization of the monomers, thereby improving the molecular weight and performance of the polymer;

[0041] Tetrafluoroethylene and perfluoroalkyl propenyl ether are introduced into a reaction kettle, the pressure in the kettle is 3-4 MPa, functionalized perfluoroolefin, halogenated perfluoroalkane and initiator are added, and the emulsion polymerization reaction is carried out at a kettle temperature of 80° C.-120° C. for 10 h-20 h to obtain an emulsion;

[0042] Tetrafluoroethylene and perfluoroalkyl propene ether are used as the main comonomers to promote efficient free radical polymerization under high pressure conditions. Functionalized perfluoroolefins and halogenated perfluoroalkanes are used as vulcanization point monomers and chain transfer agents, respectively, to form a stable and highly heat-resistant molecular structure, enhancing the thermal stability and mechanical properties of the polymer. The initiator starts the polymerization reaction by generating free radicals, ensuring the progress of the reaction and the control of the polymer molecular weight. The reaction temperature range of 80℃-120℃ provides the best polymerization conditions, ensuring the efficient conversion of the monomer and the uniformity of the polymer.

[0043] The emulsion is coagulated with a coagulant aqueous solution, washed with a detergent, and dried at 90° C.-120° C. for 24-48 hours to obtain a dry rubber powder;

[0044] The coagulant in the aqueous solution of the coagulant, such as magnesium chloride or magnesium sulfate, can effectively neutralize the charge in the emulsion and promote the aggregation of polymer particles into blocks. Next, the coagulated polymer is washed with a detergent such as deionized water, acetone or ethyl acetate to remove residual emulsifiers, monomers and other impurities to ensure the purity of the final product. The washed polymer is then dried at a temperature of 90°C-120°C for 24-48 hours to remove moisture and solvent to obtain a dry rubber powder.

[0045] The ultra-high temperature resistant perfluoroether rubber is obtained by plasticizing and molding.

[0046] The perfluoroalkyl propenyl ether is one or more of perfluoromethyl propenyl ether (CAS No.: 67641-44-5) and perfluoropropyl propenyl ether (CAS No.: 91891-42-8).

[0047] The mass ratio of the comonomers tetrafluoroethylene and perfluoroalkyl propenyl ether is (35-70): (65-30).

[0048] The functionalized perfluoroolefin is one or more of a brominated perfluoroolefin, an iodinated perfluoroolefin and a nitrile-containing perfluoroolefin. The brominated perfluoroolefin is at least one of bromotrifluoroethylene (CAS No.: 598-73-2), perfluoroallyl bromide (CAS No.: 431-56-1) and perfluoroethoxyvinyl bromide (CAS No.: 85737-06-0). The iodinated perfluorovinyl ether is at least one of iodotrifluoroethylene (CAS No.: 359-37-5), perfluoroallyl iodide (CAS No.: 431-65-2), perfluoroiodoethyl vinyl ether (CAS No.: 378-82-5) and perfluoroiodoethoxy vinyl ether (CAS No.: 6037-91-8). The nitrile-containing perfluoroolefin is CF 2 =CF-O-(CF 2 ) 4 CN (CAS No.: 19237-73-1) and / or CF2 =CF-O-(CF 2 ) 5 CN (CAS No.: 120903-40-4).

[0049] Preferably, the functionalized perfluoroolefin is CF 2 =CF-O-(CF 2 ) 5 A mixture of CN and perfluoroiodoethyl vinyl ether, the CF 2 =CF-O-(CF 2 ) 5 The mass ratio of CN to perfluoroiodoethyl vinyl ether is (1-3):(1-3).

[0050] The added amount of the functionalized perfluoroolefin is 0.1-6% of the total mass of the tetrafluoroethylene.

[0051] The halogenated perfluoroalkane is at least one of perfluorobutyl bromide (CAS No.: 375-48-4), perfluorohexyl bromide (CAS No.: 335-56-8), 1,6-dibromoperfluorohexane (CAS No.: 918-22-9), perfluorobutyl iodide (CAS No.: 423-39-2), perfluorohexyl iodide (CAS No.: 355-43-1), perfluorooctyl iodide (CAS No.: 507-63-1), 1,4-diiodoperfluorobutane (CAS No.: 375-50-8) and 1,6-diiodoperfluorohexane (CAS No.: 375-80-4).

[0052] The amount of the halogenated perfluoroalkane added is 0.1-4% of the total mass of the tetrafluoroethylene.

[0053] The initiator is a combination of an oxidant and a reductant. The oxidant is a persulfate, preferably, the oxidant is at least one of ammonium persulfate, potassium persulfate and sodium persulfate. The reductant is at least one of ammonium sulfite, potassium sulfite, sodium sulfite and thiosulfate. Preferably, the thiosulfate is at least one of ammonium thiosulfate, potassium thiosulfate and sodium thiosulfate.

[0054] The initiator is a composition of 30-70 wt % of an oxidant and 30-70 wt % of a reducing agent, and the added amount of the initiator is 0.1-1.5 % of the total mass of the deionized water.

[0055] The pH buffer is one or more of sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, ammonium sulfate, and ammonium bicarbonate. The pH buffer is used in an amount of 0.01-1% of the total mass of the deionized water.

[0056] The emulsifier is a perfluoropolyether carboxylate, and the perfluoropolyether carboxylate is one of perfluoro-2-methyl-3-oxahexanoic acid ammonium (CAS No.: 62037-80-3) and perfluoro-2,5-dimethyl-3,6-dioxahexanoic acid ammonium (CAS No.: 510774-79-5). The amount of the emulsifier is 0.1-5% of the total mass of the deionized water.

[0057] The mass ratio of tetrafluoroethylene to deionized water is (1-25):(99-75).

[0058] The mass content of the coagulant in the coagulant aqueous solution is 0.1-10wt%, and the coagulant is one or more of magnesium chloride, magnesium sulfate, aluminum sulfate, alum, calcium chloride, ammonium nitrate, nitric acid, hydrochloric acid and sulfuric acid.

[0059] The detergent is one or more of deionized water, acetone, ethyl acetate, methanol, ethanol, and toluene.

[0060] The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0061] In the following embodiments, the detection methods of various performance indicators are as follows

[0062] 1. Mooney viscosity of perfluoroether rubber raw rubber: Tested according to the method specified in GB / T 1232.1-2016 Determination of unvulcanized rubber by disc shear viscometer Part 1: Determination of Mooney viscosity.

[0063] 2. Density of raw perfluoroether rubber: Tested according to the method specified in GB / T 533-2008 Determination of density of vulcanized rubber or thermoplastic rubber.

[0064] 3. Perfluoroether rubber vulcanizate formula

[0065] Use bromine or iodine-containing sulfur-site monomers according to the following formula

[0066]

[0067] Use nitrile-containing vulcanization point monomers according to the following formula

[0068]

[0069] 4. Vulcanized rubber hardness: Test according to the method specified in GB / T 531.1-2008 Test method for indentation hardness of vulcanized rubber or thermoplastic rubber Part 1: Shore durometer method (Shore hardness)

[0070] 5. Testing of tensile strength and elongation at break of vulcanized rubber: Testing shall be carried out according to the method specified in GB / T 528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber.

[0071] 6. Detection of compression set of vulcanized rubber: Detection shall be carried out according to the method specified in GB / T 7759.1-2015 Determination of compression set of vulcanized rubber or thermoplastic rubber Part 1: At room temperature and high temperature conditions.

[0072] 7. Testing of hot air aging performance of vulcanized rubber: Testing shall be carried out according to the method specified in GB / T 3512-2014 Hot air accelerated aging and heat resistance test for vulcanized rubber or thermoplastic rubber.

[0073] Example 1

[0074] 6000g of deionized water, 9g of disodium hydrogen phosphate, and 30g of perfluoro-2-methyl-3-oxahexanoic acid ammonium were added to a 10L autoclave, and the autoclave was evacuated and replaced with nitrogen to make the oxygen content in the autoclave ≤20ppm. The autoclave temperature was raised to 90°C. 1375g of tetrafluoroethylene and 1125g of perfluoromethylpropene ether were introduced into the reaction vessel until the pressure in the autoclave reached 3.5MPa, and 30g of CF 2 =CF-O-(CF 2 ) 5 -CN, 10g perfluorohexyl iodide, 10g ammonium persulfate and 10g ammonium sulfite, and emulsion polymerization was carried out at a kettle temperature of 90°C. The pressure in the kettle was maintained at 3.5MPa, and the reaction lasted for 12 hours to obtain an emulsion. The emulsion obtained after the above emulsion polymerization reaction was condensed with 3000g of 5wt% magnesium chloride aqueous solution, then washed with deionized water, dried in a drying oven at 110°C for 24 hours, and the dried rubber was plasticized to obtain perfluoroether rubber.

[0075] The properties of the prepared perfluoroether rubber were tested, and the results are shown in Table 1.

[0076] Example 2

[0077] 6000g of deionized water, 9g of disodium hydrogen phosphate, and 30g of perfluoro-2-methyl-3-oxahexanoic acid ammonium were added to a 10L autoclave, and the autoclave was evacuated and replaced with nitrogen to make the oxygen content in the autoclave ≤20ppm. The autoclave temperature was raised to 90°C. 1375g of tetrafluoroethylene and 1125g of perfluoropropyl propenyl ether were introduced into the reaction vessel until the pressure in the autoclave reached 3.5MPa, and 30g of CF 2 =CF-O-(CF 2 ) 5-CN, 10g perfluorohexyl iodide, 10g ammonium persulfate and 10g ammonium sulfite, and emulsion polymerization was carried out at a kettle temperature of 90°C. The pressure in the kettle was maintained at 3.5MPa, and the reaction lasted for 12 hours to obtain an emulsion. The emulsion obtained after the above emulsion polymerization reaction was condensed with 3000g of 5wt% magnesium chloride aqueous solution, then washed with deionized water, dried in a drying oven at 110°C for 24 hours, and the dried rubber was plasticized to obtain perfluoroether rubber.

[0078] The properties of the prepared perfluoroether rubber were tested, and the results are shown in Table 1.

[0079] Example 3

[0080] Add 6000g of deionized water, 9g of disodium hydrogen phosphate, and 30g of perfluoro-2-methyl-3-oxahexanoic acid ammonium to a 10L autoclave, evacuate and replace with nitrogen to make the oxygen content in the autoclave ≤20ppm, and raise the temperature of the autoclave to 90°C. Pass 1375g of tetrafluoroethylene and 1125g of perfluoromethyl propylene ether into the reaction vessel until the pressure in the autoclave is 3.5MPa, add 30g of perfluoro iodoethyl vinyl ether, 10g of perfluorohexyl iodide, 10g of ammonium persulfate and 10g of ammonium sulfite, and carry out emulsion polymerization at a temperature of 90°C. Keep the pressure in the autoclave at 3.5MPa, and react for 12h to obtain an emulsion. The emulsion obtained after the above emulsion polymerization reaction is condensed with 3000g of a 5wt% magnesium chloride aqueous solution, then washed with deionized water, dried in a drying oven at 110°C for 24 hours, and the dried rubber is plasticized to obtain a perfluoroether rubber.

[0081] The properties of the prepared perfluoroether rubber were tested, and the results are shown in Table 1.

[0082] Example 4

[0083] 6000g of deionized water, 9g of disodium hydrogen phosphate, and 30g of perfluoro-2-methyl-3-oxahexanoic acid ammonium were added to a 10L autoclave, and the autoclave was evacuated and replaced with nitrogen to make the oxygen content in the autoclave ≤20ppm. The autoclave temperature was raised to 90°C. 1375g of tetrafluoroethylene and 1125g of perfluoromethylpropenyl ether were introduced into the reaction vessel until the pressure in the autoclave reached 3.5MPa, and 15g of CF 2 =CF-O-(CF 2 ) 5-CN, 15g perfluoro iodoethyl vinyl ether, 10g perfluorohexyl iodide, 10g ammonium persulfate and 10g ammonium sulfite, and emulsion polymerization was carried out at a kettle temperature of 90°C. The pressure in the kettle was maintained at 3.5MPa, and the reaction lasted for 12h to obtain an emulsion. The emulsion obtained after the above emulsion polymerization reaction was condensed with 3000g of 5wt% magnesium chloride aqueous solution, then washed with deionized water, dried in a drying oven at 110°C for 24 hours, and the dried rubber was plasticized to obtain perfluoroether rubber.

[0084] The properties of the prepared perfluoroether rubber were tested, and the results are shown in Table 1.

[0085] Comparative Example 1

[0086] 6000g of deionized water, 9g of disodium hydrogen phosphate, and 30g of perfluoro-2-methyl-3-oxahexanoic acid ammonium were added to a 10L autoclave, and the autoclave was evacuated and replaced with nitrogen to make the oxygen content in the autoclave ≤20ppm. The autoclave temperature was raised to 90°C. 1375g of tetrafluoroethylene and 1125g of perfluoromethyl vinyl ether were introduced into the reaction vessel until the pressure in the autoclave reached 3.5MPa, and 30g of CF 2 =CF-O-(CF 2 ) 5 -CN, 10g perfluorohexyl iodide, 10g ammonium persulfate and 10g ammonium sulfite, and emulsion polymerization was carried out at a kettle temperature of 90°C. The pressure in the kettle was maintained at 3.5MPa, and the reaction lasted for 12 hours to obtain an emulsion. The emulsion obtained after the above emulsion polymerization reaction was condensed with 3000g of 5wt% magnesium chloride aqueous solution, then washed with deionized water, dried in a drying oven at 110°C for 24 hours, and the dried rubber was plasticized to obtain perfluoroether rubber.

[0087] The properties of the prepared perfluoroether rubber were tested, and the results are shown in Table 1.

[0088] Comparative Example 2

[0089] Add 6000g of deionized water, 9g of disodium hydrogen phosphate, and 30g of perfluoro-2-methyl-3-oxahexanoic acid ammonium to a 10L autoclave, evacuate and replace with nitrogen to make the oxygen content in the autoclave ≤20ppm, and raise the temperature of the autoclave to 90°C. Pass 1375g of tetrafluoroethylene and 1125g of perfluoromethyl vinyl ether into the reaction vessel until the pressure in the autoclave is 3.5MPa, add 30g of perfluoroethyl iodide vinyl ether, 10g of perfluorohexyl iodide, 10g of ammonium persulfate and 10g of ammonium sulfite, and carry out emulsion polymerization at a temperature of 90°C. Keep the pressure in the autoclave at 3.5MPa, and react for 12h to obtain an emulsion. The emulsion obtained after the above emulsion polymerization reaction is condensed with 3000g of a 5wt% magnesium chloride aqueous solution, then washed with deionized water, dried in a drying oven at 110°C for 24 hours, and the dried rubber is plasticized to obtain a perfluoroether rubber.

[0090] The properties of the prepared perfluoroether rubber were tested, and the results are shown in Table 1.

[0091] Table 1 Perfluoroether rubber performance test results

[0092]

[0093] As can be seen from Table 1, the high temperature performance of the perfluoroether rubber prepared from tetrafluoroethylene and perfluoroalkyl vinyl ether in this invention is better than that of the perfluoroether rubber prepared from tetrafluoroethylene and perfluoromethyl vinyl ether.

[0094] The heat resistance of Example 1 is better than that of Comparative Example 1, and the heat resistance of Example 3 is better than that of Comparative Example 2, which indicates that the heat resistance of the perfluoroether rubber prepared by using perfluoromethylpropylene ether as a comonomer is better than that of the perfluoroether rubber prepared by using perfluoromethylvinyl ether. Due to the presence of the propylene group in perfluoromethylpropylene ether, a higher steric hindrance effect and a stronger conjugation effect are introduced into its structure, which can effectively disperse heat energy, thereby improving the heat resistance of the material. Therefore, the prepared perfluoroether rubber has better heat resistance indicators such as compression permanent deformation rate at high temperature and change in tensile strength and elongation after hot air aging.

[0095] In addition, the heat resistance of Example 1 is better than that of Example 3. 2 =CF-O-(CF 2 ) 5 -CN is used as the vulcanization point monomer, and the formed vulcanization structure is a triazine group, which has excellent thermal stability; Example 3 uses perfluoroiodoethyl vinyl ether as the vulcanization point monomer, and the formed vulcanization structure has a small amount of CH bonds with worse heat resistance. Therefore, at high temperatures, the vulcanization structure of Example 1 exhibits better high temperature resistance, which is specifically manifested in a lower compression permanent deformation rate and smaller changes in tensile strength and elongation after hot air aging.

[0096] The compression set (330°C x 70hr, 25%) of Example 4 was 36%. The change in tensile strength after hot air aging (330°C x 70hr) was -14%. Compared with Example 1 and Example 3, it showed better high temperature resistance, which is attributed to the fact that CF 2 =CF-O-(CF 2 ) 5 -CN and perfluoroethyl iodide vinyl ether. 2 =CF-O-(CF 2 ) 5 -CN forms a triazine group during the vulcanization process. This structure has high thermal stability and can effectively resist molecular chain breakage caused by high temperature. Perfluoro iodoethyl vinyl ether participates in the vulcanization reaction through its iodine atom, thus showing good stability at high temperature. The introduction of these free radicals helps to alleviate the concentration of thermal stress and reduce the compression permanent deformation rate of the material. The combination of the two not only enhances the chemical stability of the material at high temperature, but also ensures the mechanical stability of the material in high temperature environment by forming a more stable and flexible vulcanization network.

Claims

1. A method for preparing ultrahigh temperature resistant perfluoroether rubber, characterized in that: The method comprises the following steps: using tetrafluoroethylene and perfluoroalkyl propenyl ether as copolymer monomers, using functionalized perfluoroolefin as vulcanization point monomer, using halogenated perfluoroalkane as chain transfer agent and initiator, performing emulsion polymerization and emulsion post-treatment.

2. The method for preparing ultrahigh temperature resistant perfluoroether rubber according to claim 1, characterized in that: The steps include: Tetrafluoroethylene and perfluoroalkyl propenyl ether are introduced into the reaction kettle until the pressure inside the kettle reaches 3-4 MPa, functionalized perfluoroolefin, halogenated perfluoroalkane and initiator are added, and the emulsion polymerization reaction is carried out at a kettle temperature of 80°C-120°C for 10h-20h to obtain an emulsion; performing emulsion post-treatment on the emulsion; The ultra-high temperature resistant perfluoroether rubber is obtained by plasticizing and molding.

3. The method for preparing the ultrahigh temperature resistant perfluoroether rubber according to claim 2, characterized in that: The steps include: Deionized water, pH buffer and emulsifier were added to the reactor, vacuum was drawn and nitrogen was used to control the oxygen content in the reactor to ≤20ppm, and the temperature of the reactor was raised to 80-120°C; Tetrafluoroethylene and perfluoroalkyl propenyl ether are introduced into a reaction kettle, the pressure in the kettle is 3-4 MPa, functionalized perfluoroolefin, halogenated perfluoroalkane and initiator are added, and the emulsion polymerization reaction is carried out at a kettle temperature of 80° C.-120° C. for 10 h-20 h to obtain an emulsion; The emulsion is coagulated with a coagulant aqueous solution, washed, and dried at 90° C.-120° C. for 24-48 hours to obtain a dry rubber powder; The ultra-high temperature resistant perfluoroether rubber is obtained by plasticizing and molding.

4. The method for preparing the ultrahigh temperature resistant perfluoroether rubber according to any one of claims 1 to 3, characterized in that: The perfluoroalkyl propenyl ether has the following structure: CF2=CF CF2OR, wherein R is a perfluoroalkyl group with 1 to 6 carbon atoms. The structure of R is: -(CF2) n CF3, wherein n is an integer from 0 to 5.

5. The method for preparing ultrahigh temperature resistant perfluoroether rubber according to claim 4, characterized in that: The perfluoroalkyl propenyl ether is one or more of perfluoromethyl propenyl ether and perfluoropropyl propenyl ether.

6. The method for preparing ultrahigh temperature resistant perfluoroether rubber according to claim 4, characterized in that: The mass ratio of the comonomers tetrafluoroethylene and perfluoroalkyl propenyl ether is (35-70): (65-30).

7. The method for preparing the ultrahigh temperature resistant perfluoroether rubber according to any one of claims 1 to 3, characterized in that: The functionalized perfluoroolefin is one or more of brominated perfluoroolefin, iodinated perfluoroolefin and nitrile-containing perfluoroolefin.

8. The method for preparing the ultrahigh temperature resistant perfluoroether rubber according to any one of claims 1 to 3, characterized in that: The added amount of the functionalized perfluoroolefin is 0.1-6% of the total mass of the tetrafluoroethylene.

9. The method for preparing the ultrahigh temperature resistant perfluoroether rubber according to any one of claims 1 to 3, characterized in that: The halogenated perfluoroalkane is a brominated perfluoroalkane and / or an iodinated perfluoroalkane, and the added amount of the halogenated perfluoroalkane is 0.1-4% of the total mass of the tetrafluoroethylene.

10. The method for preparing the ultrahigh temperature resistant perfluoroether rubber according to any one of claims 1 to 3, characterized in that: The initiator is a combination of an oxidizing agent and a reducing agent; The oxidant is at least one of ammonium persulfate, potassium persulfate and sodium persulfate; The reducing agent is at least one of ammonium sulfite, potassium sulfite, sodium sulfite and thiosulfate, and the thiosulfate is at least one of ammonium thiosulfate, potassium thiosulfate and sodium thiosulfate; The initiator is a composition of 30-70 wt % of an oxidant and 30-70 wt % of a reducing agent, and the added amount of the initiator is 0.1-1.5 % of the total mass of the deionized water.

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