A perfluoroether rubber seal and preparation method thereof

Abstract

The present invention proposes a perfluoroether rubber seal and a preparation method thereof, the preparation method comprising: using tetrafluoroethylene and perfluoroalkyl vinyl ether as comonomers, and performing emulsion polymerization under the conditions of a vulcanization point monomer and a chain transfer agent to obtain a perfluoroether rubber raw rubber; mixing the perfluoroether rubber raw rubber with carboxyl fluorinated modified carbon nanotubes, fillers, a vulcanizing agent, and an accelerator, and then performing a first stage vulcanization and a second stage vulcanization to obtain the perfluoroether rubber seal. The perfluoroether rubber seal and the preparation method thereof proposed by the present invention improve the compression deformation resistance of the perfluoroether rubber seal by adding carboxyl fluorinated modified carbon nanotubes, thereby ensuring that the obtained seal meets the sealing requirements of semiconductor equipment.

Description

Technical Field

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

[0002] Perfluoroether rubber is a synthetic elastomer made by copolymerization of tetrafluoroethylene (TFE) and perfluoromethyl vinyl ether (PMVE) as the main raw materials, and is known as the "king of rubber". Perfluoroether rubber is widely used in many industries and sectors such as aerospace, petrochemical, atomic energy, semiconductor manufacturing, medicine, food and office equipment due to its excellent properties. However, due to its high price and the fact that most of it is made into rubber seals, the aerospace industry, petrochemical industry and semiconductor manufacturing industry, which have strict safety and maintenance requirements, are its main application industries.

[0003] Perfluoroether rubber seals are resistant to almost all media and high temperatures, and their ability to maintain elasticity and sealing at high temperatures is far superior to other elastomers. With the rapid development of industries such as semiconductors, the requirements for processing equipment are getting higher and higher. The perfluoroether rubber material used in seals not only needs to have media resistance, but also needs to have high and low temperature resistance and excellent compression deformation resistance.

[0004] At present, in order to improve the high temperature resistance, mechanical properties and processing properties of perfluoroether rubber seals, processing aids such as magnesium oxide, calcium hydroxide, lead oxide, etc. are usually added to the formula. The use of these processing aids introduces metals such as magnesium, calcium or lead, which will not only affect the success rate of the etching process, but also lead to a decrease in the process yield of sealing products in the semiconductor industry.

[0005] Patent CN106751257A discloses a perfluoroether rubber material, preparation method and application for high temperature and high pressure resistant seals, which improves the hardness, tensile strength, extrusion deformation resistance and shear resistance of the seals by adding a small amount of carbon nanotubes to the perfluoroether rubber polymer and optimizing the filler and vulcanization system. However, the seals prepared from the perfluoroether rubber material described in the patent have too high hardness and poor compression deformation resistance, which cannot meet the high requirements of the semiconductor industry for seals. Summary of the invention

[0006] Based on the technical problems existing in the background technology, the present invention proposes a perfluoroether rubber seal and a preparation method thereof, and improves the compression deformation resistance of the perfluoroether rubber seal by adding carboxyl fluorinated modified carbon nanotubes, thereby ensuring that the obtained seal meets the sealing requirements of semiconductor equipment.

[0007] The present invention provides a method for preparing a perfluoroether rubber seal, comprising the following steps:

[0008] S1, using tetrafluoroethylene and perfluoroalkyl vinyl ether as comonomers, and carrying out emulsion polymerization under the conditions of a vulcanization point monomer and a chain transfer agent to obtain a perfluoroether rubber raw rubber;

[0009] S2, hydroxylating the carbon nanotubes and subjecting them to a condensation reaction with dicarboxyl trithiocarbonate, and then subjecting them to a reversible addition-fragmentation chain transfer polymerization reaction with fluorinated acrylate to obtain carboxyl fluorinated modified carbon nanotubes;

[0010] S3, mixing the perfluoroether rubber raw rubber, carboxyl fluorinated modified carbon nanotubes, fillers, vulcanizing agents, and accelerators, and subjecting the mixture to first-stage vulcanization and second-stage vulcanization to obtain the perfluoroether rubber seal;

[0011] In step S2, the condensation reaction is carried out under the conditions of an activator and a dehydrating agent, the weight ratio of the carbon nanotubes to the dicarboxyl trithiocarbonate is 1:(0.02-0.08), and the temperature of the condensation reaction is 20-30°C; the polymerization reaction is carried out under the conditions of an initiator, the weight ratio of the carbon nanotubes to the fluorine-containing acrylate is 1:(0.1-0.5), and the temperature of the polymerization reaction is 80-100°C.

[0012] In the present invention, tetrafluoroethylene and perfluoroalkyl vinyl ether are used as main copolymer monomers, and after emulsion polymerization is carried out under the conditions of vulcanization point monomers and chain transfer agents, carboxyl fluorinated modified carbon nanotubes are added for modification, thereby giving full play to the mechanical improvement effect of carbon nanotubes on perfluoroether rubber materials, so that the tensile strength, compression permanent deformation resistance and hot air aging resistance of the obtained perfluoroether rubber seal are further improved.

[0013] Preferably, in step S1, the perfluoroalkyl vinyl ether is at least one of perfluoromethyl vinyl ether, perfluoroethyl vinyl ether or perfluoropropyl vinyl ether;

[0014] Preferably, the mass ratio of tetrafluoroethylene to perfluoroalkyl vinyl ether is 1: (0.8-1).

[0015] Preferably, the comonomer further comprises an organic fluorine aryl vinyl ether;

[0016] Preferably, the general structural formula of the organic fluorinated aryl vinyl ether is as shown in the following structure:

[0017] n is 1-5;

[0018] Preferably, the mass ratio of tetrafluoroethylene to organic fluorine aromatic vinyl ether is 1:(0.05-0.2).

[0019] In the present invention, the organic fluorine aryl vinyl ether is a rigid monomer, and the organic fluorine aryl vinyl ether is introduced to participate in the copolymerization, thereby achieving the effect of modifying the structure of the perfluoroether rubber to improve its high and low temperature resistance.

[0020] Preferably, in step S1, the vulcanization site monomer is at least one of 4-bromo-3,3,4,4-tetrafluorobutene, 1-bromo-2,2-difluoroethylene, ethyl vinyl bromide or trifluoroethylene bromide; the chain transfer agent is at least one of 1,2-diiodoethane, iodoethane, iodoform or iodomethane;

[0021] Preferably, the mass ratio of tetrafluoroethylene, vulcanization site monomer and chain transfer agent is 1: (0.01-0.05): (0.01-0.03).

[0022] Preferably, in step S2, the dicarboxy trithiocarbonate is bis(carboxymethyl) trithiocarbonate; the fluorine-containing acrylate is at least one of trifluoroethyl methacrylate, hexafluorobutyl methacrylate, dodecafluoroheptyl methacrylate or tridecafluorooctyl methacrylate; the activator is N-hydroxysuccinimide; the dehydrating agent is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide; and the initiator is azobisisobutyronitrile.

[0023] In the present invention, the carboxyl fluorinated modified carbon nanotubes are prepared by hydroxylating the carbon nanotubes and then reacting them with dicarboxyl trithiocarbonate to graft a carboxyl chain transfer agent onto the surface of the carbon nanotubes. The carbon nanotubes are then subjected to a reversible addition-fragmentation chain transfer polymerization reaction with fluorinated acrylates to graft carboxyl fluorinated polyacrylates onto the surface of the carbon nanotubes.

[0024] On the one hand, based on similar compatibility, the carboxyl fluorinated polyacrylate can promote the effective dispersion of carbon nanotubes in perfluoroether rubber raw rubber to ensure the subsequent reinforcement effect. On the other hand, the carboxyl fluorinated polyacrylate also contains carboxyl groups, which not only can play a good anti-scorch effect during vulcanization, but also makes the main chain of perfluoroether rubber raw rubber contain ionic groups, the chain segment distance becomes larger, the vulcanization time is shortened, the compression permanent deformation value can be reduced, and the tensile strength is increased.

[0025] Preferably, in step S3, the filler is at least one of carbon black N550, carbon black N660, carbon black N774 or carbon black N990; the vulcanizing agent is at least one of dicumyl peroxide, benzoyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane or di-tert-butylperoxyisopropylbenzene; and the accelerator is triallyl isocyanurate.

[0026] Preferably, in step S3, the mass ratio of the perfluoroether rubber raw rubber and the carboxyl fluorinated modified carbon nanotubes, filler, vulcanizing agent and accelerator is 100:(1-5):(5-10):(1-3):(0.5-2).

[0027] Preferably, in step S1, the emulsion polymerization is carried out under the conditions of a pH buffer and an emulsifier;

[0028] Preferably, the pH buffer is disodium hydrogen phosphate or dipotassium hydrogen phosphate, and the emulsifier is ammonium perfluorooctanoate;

[0029] Preferably, the initiator of the emulsion polymerization is potassium persulfate or ammonium persulfate;

[0030] Preferably, the temperature of the emulsion polymerization is 70-90°C.

[0031] Preferably, in step S3, the first stage vulcanization temperature is 150-190°C, the time is 5-15 min, and the vulcanization pressure is 10-20 MPa; the second stage vulcanization temperature is 200-240°C, and the time is 12-24 h.

[0032] The present invention also provides a perfluoroether rubber seal, which is prepared by the above preparation method.

[0033] The present invention provides a perfluoroether rubber seal and a preparation method thereof, which have at least the following technical effects:

[0034] (1) After perfluoroether rubber raw rubber is obtained by emulsion polymerization of tetrafluoroethylene and perfluoroalkyl vinyl ether as main copolymer monomers under the conditions of vulcanization point monomer and chain transfer agent, carboxyl fluorinated modified carbon nanotubes are added for filling; since the surface of the carboxyl fluorinated modified carbon nanotubes is grafted with carboxyl fluorinated polyacrylate, on the one hand, the carboxyl fluorinated polyacrylate can promote the effective dispersion of carbon nanotubes in the perfluoroether rubber raw rubber based on similar compatibility, thereby ensuring the subsequent reinforcement effect; on the other hand, the carboxyl fluorinated polyacrylate also contains carboxyl groups, which not only can play a good anti-scorching effect during vulcanization, but also makes the main chain of the perfluoroether rubber raw rubber contain ionic groups, the segment distance becomes larger, the vulcanization time is shortened, the compression permanent deformation value becomes smaller, and the tensile strength becomes larger.

[0035] (2) By selecting organic fluoroaryl vinyl ether as the comonomer of perfluoroether rubber raw rubber, organic fluoroaryl vinyl ether is a rigid monomer, and by introducing organic fluoroaryl vinyl ether to participate in the copolymerization, the structure of perfluoroether rubber is modified to improve its high and low temperature resistance.

[0036] (3) The present invention adds carboxyl fluorinated carbon nanotubes to perfluoroether rubber raw rubber and rationally optimizes the molecular chain structure of the perfluoroether rubber. The obtained perfluoroether rubber seal has excellent tensile strength, compression deformation resistance and high and low temperature resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a product schematic diagram of the perfluoroether rubber seal described in Example 1 of the present invention;

[0038] Figure 2 This is a schematic diagram of the structure of the carboxyl fluorinated modified carbon nanotubes described in Example 1 of the present invention. DETAILED DESCRIPTION

[0039] The technical solutions of the present invention are described in detail below through specific embodiments. However, it should be clearly stated that these embodiments are for illustration only and are not to be construed as limiting the scope of the present invention.

[0040] The present invention provides a perfluoroether rubber seal, the preparation process of which includes three steps:

[0041] Step 1, preparing perfluoroether rubber raw rubber: firstly, adding a pH regulator and an emulsifier into water to form a microemulsion, then at a certain temperature, introducing a comonomer of tetrafluoroethylene and perfluoroalkyl vinyl ether to a certain pressure, then adding an initiator to initiate a polymerization reaction of the comonomer, after a period of reaction, adding a vulcanization point monomer and a chain transfer agent to react, and continuously introducing a comonomer of tetrafluoroethylene and perfluoroalkyl vinyl ether during the whole reaction process until the reaction is completed, and the emulsion after the reaction is completed is condensed, washed, and dried to obtain a perfluoroether rubber raw rubber;

[0042] Step 2, preparing carboxyl fluorinated carbon nanotubes: first acidify the carbon nanotubes to obtain hydroxylated carbon nanotubes; disperse the hydroxylated carbon nanotubes in a solvent, add an activator and a dehydrating agent, and then add dicarboxyl trithiocarbonate, and a condensation reaction occurs between the hydroxyl groups on the surface of the hydroxylated carbon nanotubes and the carboxyl groups of the dicarboxyl trithiocarbonate to generate corresponding esters, and after filtering, washing, and drying, carboxyl thiocarbonate-modified carbon nanotubes are obtained; the carboxyl thiocarbonate-modified carbon nanotubes are dispersed in a solvent, and a fluorinated acrylate and an initiator are added to undergo a reversible addition-fragmentation chain transfer radical polymerization (RAFT) reaction at a certain temperature, wherein the trithiocarbonate group on the carboxyl thiocarbonate-modified carbon nanotubes serves as a RAFT chain transfer agent, so that the fluorinated acrylate is polymerized to form a fluorinated acrylate and grafted on the surface of the carbon nanotubes, and after filtering, washing, and drying, the carboxyl fluorinated carbon nanotubes are obtained;

[0043] Step 3, preparing a perfluoroether rubber seal: first add the perfluoroether rubber raw rubber, carboxyl fluorinated modified carbon nanotubes and fillers, vulcanizing agents, and accelerators prepared above into an open mill and mix them evenly, then place the obtained rubber composition into a flat vulcanizer for a first-stage compression vulcanization to obtain a first-stage vulcanized product, and place the obtained first-stage vulcanized product in an oven for a second-stage vulcanization to obtain the perfluoroether rubber seal. Example 1

[0044] A method for preparing a perfluoroether rubber seal comprises the following steps:

[0045] (1) Water, disodium hydrogen phosphate and ammonium perfluorooctanoate were added to a reactor and stirred to mix evenly. The mass ratio of water, disodium hydrogen phosphate and ammonium perfluorooctanoate was 100:0.2:0.1. After replacing the air in the reactor with nitrogen, the temperature was raised to 85°C. A mixed gas consisting of tetrafluoroethylene and perfluoromethyl vinyl ether in a mass ratio of 1:0.9 was compressed into the reactor using a diaphragm compressor. The pressure in the reactor was raised to 3.5 MPa. A potassium persulfate aqueous solution (5 wt%) was added under stirring. During the stirring reaction, tetrafluoroethylene in a mass ratio of 1:0.9 was continuously compressed into the reactor. A mixed gas consisting of tetrafluoroethylene and perfluoromethyl vinyl ether is introduced to keep the pressure constant, and 4-bromo-3,3,4,4-tetrafluorobutene and iodine are added, and the mixture is stirred and reacted at 85°C until the predetermined amount of feed is reached, and the mass ratio of tetrafluoroethylene, 4-bromo-3,3,4,4-tetrafluorobutene, iodine and potassium persulfate is 1:0.03:0.02:0.002. After cooling to room temperature, the polymerization reaction is stopped, and the obtained latex is coagulated by adding a magnesium chloride aqueous solution (2wt%), filtered, washed with deionized water, and vacuum dried to obtain a perfluoroether rubber raw rubber;

[0046] (2) Add carbon nanotubes (multi-walled carbon nanotubes) to a nitric acid aqueous solution (65 wt%) and disperse them uniformly by ultrasonication. Stir the reaction at 80° C. for 4 h. After cooling to room temperature, filter, wash, and dry to obtain hydroxylated carbon nanotubes. Add the hydroxylated carbon nanotubes to N,N-dimethylformamide and disperse them uniformly by ultrasonication. Add N-hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide in sequence and stir to obtain a uniform mixture. The mass ratio of carbon nanotubes, N-hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide is 1:0.05:0.08. Then, add N,N-dimethylformamide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide to obtain a hydroxylated carbon nanotube. , N-dimethylformamide solution, the mass ratio of carbon nanotubes and bis(carboxymethyl) trithiocarbonate is 1:0.05, after stirring at room temperature for 24 hours, filtering, washing, and drying to obtain carboxyl thiocarbonate-modified carbon nanotubes, the carboxyl thiocarbonate-modified carbon nanotubes are added back into N, N-dimethylformamide for ultrasonic dispersion, and under nitrogen protection, methacrylate tridecafluorooctyl ester and azobisisobutyronitrile are added, the weight ratio of carbon nanotubes, methacrylate tridecafluorooctyl ester and azobisisobutyronitrile is 1:0.3:0.001, heated to 90°C and stirred for 6 hours, filtered, washed, and dried to obtain carboxyl fluorinated carbon nanotubes, such as Figure 2 As shown;

[0047] (3) Add the above-mentioned perfluoroether rubber raw rubber into an open training mill, and then add the above-mentioned carboxyl fluorinated modified carbon nanotubes, carbon black N990, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane and triallyl isocyanurate, wherein the weight ratio of the perfluoroether rubber raw rubber, carboxyl fluorinated modified carbon nanotubes, carbon black N990, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane and triallyl isocyanurate is 100:3:8:2:1, mix them evenly at 80°C and form a sheet, put it into a mold, and place the mold in a flat vulcanizer for a first stage of vulcanization at a pressure of 15 MPa, a temperature of 170°C, and a time of 10 minutes. After completion, put the first stage vulcanized product into an oven for a second stage of vulcanization at a vulcanization temperature of 220°C and a time of 18 hours, thereby obtaining the perfluoroether rubber seal, such as Figure 1 shown. Example 2

[0048] A method for preparing a perfluoroether rubber seal comprises the following steps:

[0049] (1) Prepare a perfluoroether rubber raw rubber according to the method described in Example 1;

[0050] (2) Add carbon nanotubes (multi-walled carbon nanotubes) to a nitric acid aqueous solution (65 wt%) and disperse them uniformly by ultrasonication. Stir the reaction at 80°C for 4 h. After cooling to room temperature, filter, wash, and dry to obtain hydroxylated carbon nanotubes. Add the hydroxylated carbon nanotubes to N,N-dimethylformamide and disperse them uniformly by ultrasonication. Add N-hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide in sequence and stir to obtain a mixture uniformly. The mass ratio of carbon nanotubes, N-hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide is 1:0.03:0.06. Then, add bis(carboxymethyl) trithiocarbonate. N, N-dimethylformamide solution, the mass ratio of carbon nanotubes and bis(carboxymethyl) trithiocarbonate is 1:0.02, after stirring at room temperature for 24 hours, filtering, washing, and drying to obtain carboxyl thiocarbonate-modified carbon nanotubes, the carboxyl thiocarbonate-modified carbon nanotubes are added back into N, N-dimethylformamide for ultrasonic dispersion, trifluoroethyl methacrylate and azobisisobutyronitrile are added under nitrogen protection, the weight ratio of carbon nanotubes, trifluoroethyl methacrylate and azobisisobutyronitrile is 1:0.1:0.001, the temperature is raised to 80°C and stirred for 6 hours, filtered, washed, and dried to obtain carboxyl fluorinated carbon nanotubes;

[0051] (3) Referring to the method described in Example 1, the above-mentioned carboxyl fluorinated carbon nanotubes are added to prepare the perfluoroether rubber seal. Example 3

[0052] A method for preparing a perfluoroether rubber seal comprises the following steps:

[0053] (1) Prepare a perfluoroether rubber raw rubber according to the method described in Example 1;

[0054] (2) Add carbon nanotubes (multi-walled carbon nanotubes) to a nitric acid aqueous solution (65 wt%) and disperse them uniformly by ultrasonication. Stir the reaction at 80° C. for 4 h. After cooling to room temperature, filter, wash, and dry to obtain hydroxylated carbon nanotubes. Add the hydroxylated carbon nanotubes to N,N-dimethylformamide and disperse them uniformly by ultrasonication. Add N-hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide in sequence and stir to obtain a uniform mixture. The mass ratio of carbon nanotubes, N-hydroxysuccinimide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide is 1:0.05:0.1. Then, add N,N-dimethylformamide and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide to obtain a hydroxylated carbon nanotube. , N-dimethylformamide solution, the mass ratio of carbon nanotubes and bis(carboxymethyl)trithiocarbonate is 1:0.08, after stirring at room temperature for 24 hours, filtering, washing, and drying to obtain carboxyl thiocarbonate-modified carbon nanotubes, the carboxyl thiocarbonate-modified carbon nanotubes are added back into N, N-dimethylformamide for ultrasonic dispersion, and under nitrogen protection, dodecafluoroheptyl methacrylate and azobisisobutyronitrile are added, the weight ratio of carbon nanotubes, dodecafluoroheptyl methacrylate and azobisisobutyronitrile is 1:0.5:0.001, the temperature is raised to 100°C and stirred for 6 hours, filtered, washed, and dried to obtain carboxyl fluorinated carbon nanotubes;

[0055] (3) Referring to the method described in Example 1, the above-mentioned carboxyl fluorinated carbon nanotubes are added to prepare the perfluoroether rubber seal. Example 4

[0056] A method for preparing a perfluoroether rubber seal comprises the following steps:

[0057] (1) Water, disodium hydrogen phosphate and ammonium perfluorooctanoate were added to a reactor and stirred to mix evenly. The mass ratio of water, disodium hydrogen phosphate and ammonium perfluorooctanoate was 100:0.2:0.1. After replacing the air in the reactor with nitrogen, the temperature was raised to 85°C. A mixed gas consisting of tetrafluoroethylene and perfluoroethyl vinyl ether in a mass ratio of 1:0.8 was compressed into the reactor using a diaphragm compressor. The pressure in the reactor was raised to 3.5 MPa. A potassium persulfate aqueous solution (5 wt%) was added under stirring. During the stirring reaction, tetrafluoroethylene in a mass ratio of 1:0.8 was continuously added. A mixed gas consisting of tetrafluoroethylene and perfluoroethyl vinyl ether is introduced to keep the pressure constant, and 4-bromo-3,3,4,4-tetrafluorobutene and iodine are added, and the mixture is stirred and reacted at 90°C until a predetermined amount of the feed is reached, and the mass ratio of tetrafluoroethylene, 4-bromo-3,3,4,4-tetrafluorobutene, iodine and potassium persulfate is 1:0.05:0.03:0.002. After cooling to room temperature, the polymerization reaction is stopped, and the obtained latex is coagulated by adding a magnesium chloride aqueous solution (2wt%), filtered, washed with deionized water, and vacuum dried to obtain a perfluoroether rubber raw rubber;

[0058] (2) preparing carbon nanotubes (multi-walled carbon nanotubes) by the method described in Example 1 to obtain carboxyl fluorinated carbon nanotubes;

[0059] (3) Add the above-mentioned perfluoroether rubber raw rubber into an open mill, and then add the above-mentioned carboxyl fluorinated modified carbon nanotubes, carbon black N774, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane and triallyl isocyanurate, wherein the weight ratio of the perfluoroether rubber raw rubber, carboxyl fluorinated modified carbon nanotubes, carbon black N774, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane and triallyl isocyanurate is 100:1:10:1:2, mix them evenly at 80°C and form a sheet, put it into a mold, and place the mold in a flat vulcanizer for one-stage vulcanization at a pressure of 10 MPa, a temperature of 190°C, and a time of 5 minutes. After completion, put the first-stage vulcanized product into an oven for two-stage vulcanization at a vulcanization temperature of 240°C and a time of 12 hours, thereby obtaining the perfluoroether rubber seal. Example 5

[0060] A method for preparing a perfluoroether rubber seal comprises the following steps:

[0061] (1) Add water, disodium hydrogen phosphate and ammonium perfluorooctanoate into a reactor and stir to mix evenly. The mass ratio of water, disodium hydrogen phosphate and ammonium perfluorooctanoate is 100:0.2:0.1. After replacing the air in the reactor with nitrogen, the temperature is raised to 85°C, and a mixed gas consisting of tetrafluoroethylene and perfluoropropyl vinyl ether in a mass ratio of 1:1 is compressed into the reactor using a diaphragm compressor. The pressure in the reactor is raised to 3.5 MPa. Potassium persulfate aqueous solution (5 wt%) is added under stirring. During the stirring reaction, tetrafluoroethylene and perfluoropropyl vinyl ether in a mass ratio of 1:1 are continuously compressed into the reactor. A mixed gas composed of fluoropropyl vinyl ether is introduced to keep the pressure constant, and 1-bromo-2,2-difluoroethylene and 1,2-diiodoethane are added, and the mixture is stirred and reacted at 80°C until a predetermined amount of the feed is reached, and the mass ratio of tetrafluoroethylene, 1-bromo-2,2-difluoroethylene, 1,2-diiodoethane and potassium persulfate is 1:0.01:0.01:0.002. After cooling to room temperature, the polymerization reaction is stopped, and the obtained latex is coagulated by adding a magnesium chloride aqueous solution (2wt%), filtered, washed with deionized water, and vacuum dried to obtain a perfluoroether rubber raw rubber;

[0062] (2) preparing carbon nanotubes (multi-walled carbon nanotubes) by the method described in Example 1 to obtain carboxyl fluorinated carbon nanotubes;

[0063] (3) Add the above-mentioned perfluoroether rubber raw rubber into an open mill, and then add the above-mentioned carboxyl fluorinated modified carbon nanotubes, carbon black N550, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane and triallyl isocyanurate, wherein the weight ratio of the perfluoroether rubber raw rubber, carboxyl fluorinated modified carbon nanotubes, carbon black N550, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane and triallyl isocyanurate is 100:5:5:3:0.5, mix them evenly at 80°C and form a sheet, put it into a mold, and place the mold in a flat vulcanizer for one-stage vulcanization at a pressure of 20 MPa, a temperature of 150°C, and a time of 15 minutes. After completion, put the first-stage vulcanized product into an oven for two-stage vulcanization at a vulcanization temperature of 200°C and a time of 24 hours, thereby obtaining the perfluoroether rubber seal. Example 6

[0064] A method for preparing a perfluoroether rubber seal comprises the following steps:

[0065] (1) Water, disodium hydrogen phosphate and ammonium perfluorooctanoate were added to a reactor and stirred to mix evenly. The mass ratio of water, disodium hydrogen phosphate and ammonium perfluorooctanoate was 100:0.2:0.1. Organic fluorinated aromatic vinyl ether was then added and stirred to mix evenly. After replacing the air in the reactor with nitrogen, the temperature was raised to 85°C. A mixed gas consisting of tetrafluoroethylene and perfluoromethyl vinyl ether in a mass ratio of 1:0.9 was compressed into the reactor using a diaphragm compressor. The pressure in the reactor was raised to 3.5 MPa. A potassium persulfate aqueous solution (5 wt%) was added under stirring. During the stirring reaction, tetrafluoroethylene in a mass ratio of 1:0.9 was continuously added. A mixed gas composed of fluoroethylene and perfluoromethyl vinyl ether is introduced to keep the pressure constant, and 4-bromo-3,3,4,4-tetrafluorobutene and iodine are added, and the mixture is stirred and reacted at 85°C until a predetermined amount of materials are added, and the mass ratio of tetrafluoroethylene, organic fluorine aryl vinyl ether, 4-bromo-3,3,4,4-tetrafluorobutene, iodine and potassium persulfate is 1:0.1:0.03:0.02:0.002. After cooling to room temperature, the polymerization reaction is stopped, and the obtained latex is coagulated by adding a magnesium chloride aqueous solution (2wt%), filtered, washed with deionized water, and vacuum dried to obtain a perfluoroether rubber raw rubber;

[0066] The above-mentioned organic fluorine aryl vinyl ether is prepared by the following method: adding perfluorobutyl carbinol to N, N-dimethylformamide to dissolve completely, then adding an equimolar amount of sodium hydride, stirring and reacting at room temperature for 3 hours, and adding the obtained solution dropwise to the N, N-dimethylformamide solution of pentafluorophenoxyethyl vinyl ether in an ice-water bath. After the reaction is completed, stirring and reacting at room temperature for 24 hours, adding water and separating the liquids, extracting with petroleum ether, drying, and rotary evaporation to obtain the organic fluorine aryl vinyl ether. The structural formula of the organic fluorine aryl vinyl ether is as follows: Its structural characterization data are as follows: 1H NMR (400 MHz, CDCl 3 ) δ 6.43 (m, 1H), 4.52 (m, 2H), 4.30 (m, 1H), 4.21 (m, 2H), 4.12 (dd, 1H), 4.06 (m, 2H);

[0067] (2) preparing carbon nanotubes (multi-walled carbon nanotubes) by the method described in Example 1 to obtain carboxyl fluorinated carbon nanotubes;

[0068] (3) Add the above-mentioned perfluoroether rubber raw rubber into an open mill, and then add the above-mentioned carboxyl fluorinated modified carbon nanotubes, carbon black N990, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane and triallyl isocyanurate, wherein the weight ratio of the perfluoroether rubber raw rubber, carboxyl fluorinated modified carbon nanotubes, carbon black N990, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane and triallyl isocyanurate is 100:3:8:2:1, mix them evenly at 80°C and form a sheet, put it into a mold, and place the mold in a flat vulcanizer for one-stage vulcanization at a pressure of 15 MPa, a temperature of 170°C, and a time of 10 minutes. After completion, put the first-stage vulcanized product into an oven for two-stage vulcanization at a vulcanization temperature of 220°C and a time of 18 hours, thereby obtaining the perfluoroether rubber seal.

[0069] Comparative Example 1

[0070] A method for preparing a perfluoroether rubber seal comprises the following steps:

[0071] (1) Water, disodium hydrogen phosphate and ammonium perfluorooctanoate were added to a reactor and stirred to mix evenly. The mass ratio of water, disodium hydrogen phosphate and ammonium perfluorooctanoate was 100:0.2:0.1. After replacing the air in the reactor with nitrogen, the temperature was raised to 85°C. A mixed gas consisting of tetrafluoroethylene and perfluoromethyl vinyl ether in a mass ratio of 1:0.9 was compressed into the reactor using a diaphragm compressor. The pressure in the reactor was raised to 3.5 MPa. A potassium persulfate aqueous solution (5 wt%) was added under stirring. During the stirring reaction, tetrafluoroethylene in a mass ratio of 1:0.9 was continuously compressed into the reactor. A mixed gas consisting of tetrafluoroethylene and perfluoromethyl vinyl ether is introduced to keep the pressure constant, and 4-bromo-3,3,4,4-tetrafluorobutene and iodine are added, and the mixture is stirred and reacted at 85°C until the predetermined amount of feed is reached, and the mass ratio of tetrafluoroethylene, 4-bromo-3,3,4,4-tetrafluorobutene, iodine and potassium persulfate is 1:0.03:0.02:0.002. After cooling to room temperature, the polymerization reaction is stopped, and the obtained latex is coagulated by adding a magnesium chloride aqueous solution (2wt%), filtered, washed with deionized water, and vacuum dried to obtain a perfluoroether rubber raw rubber;

[0072] (2) Add the above-mentioned perfluoroether rubber raw rubber into an open mill, and then add carbon nanotubes (multi-walled carbon nanotubes), carbon black N990, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane and triallyl isocyanurate, wherein the weight ratio of the perfluoroether rubber raw rubber, carbon nanotubes, carbon black N990, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane and triallyl isocyanurate is 100:3:8:2:1, mix them evenly at 80°C and form a sheet, put it into a mold, and place the mold in a flat vulcanizer for one-stage vulcanization at a pressure of 15 MPa, a temperature of 170°C, and a time of 10 minutes. After completion, put the first-stage vulcanized product into an oven for two-stage vulcanization at a vulcanization temperature of 220°C and a time of 18 hours, thereby obtaining the perfluoroether rubber seal.

[0073] The perfluoroether rubber seals obtained in the above examples and comparative examples were prepared and tested according to standard test specimens, and the performance test results are shown in Table 1 below.

[0074] Shore A hardness: Tested in accordance with GB / T 531.1-2008 "Test method for indentation hardness of vulcanized rubber or thermoplastic rubber Part 1: Shore durometer method (Shore hardness)";

[0075] Tensile strength and elongation at break: tested in accordance with GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber";

[0076] Compression set: Tested in accordance with ASTM D395-03 "Standard test methods for rubber property-Compression Set", sample size: AS568-214 O-ring, test conditions: 204℃, 70h;

[0077] Hot air aging resistance: Tested in accordance with GB / T3512-2014 "Hot air aging and heat resistance test for vulcanized rubber or thermoplastic rubber", test conditions: 300℃, 72h;

[0078] Table 1 Test results of the perfluoroether rubber materials obtained in the examples and comparative examples

[0079]

[0080] It can be seen from the results in the above table that the present invention provides a perfluoroether rubber seal and a preparation method thereof, by adding carboxyl fluorinated carbon nanotubes to perfluoroether rubber raw rubber and rationally optimizing the molecular chain structure of the perfluoroether rubber, the obtained perfluoroether rubber seal has excellent tensile strength, compression deformation resistance and high and low temperature resistance.

[0081] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a perfluoroether rubber seal, characterized in that: The steps include: S1, using tetrafluoroethylene and perfluoroalkyl vinyl ether as comonomers, and carrying out emulsion polymerization under the conditions of a vulcanization point monomer and a chain transfer agent to obtain a perfluoroether rubber raw rubber; S2, hydroxylating the carbon nanotubes and subjecting them to a condensation reaction with dicarboxyl trithiocarbonate, and then subjecting them to a reversible addition-fragmentation chain transfer polymerization reaction with a fluorinated acrylate to obtain carboxyl fluorinated modified carbon nanotubes; S3, mixing the perfluoroether rubber raw rubber, carboxyl fluorinated modified carbon nanotubes, fillers, vulcanizing agents, and accelerators, and subjecting the mixture to first-stage vulcanization and second-stage vulcanization to obtain the perfluoroether rubber seal; In step S2, the condensation reaction is carried out under the conditions of an activator and a dehydrating agent, the weight ratio of the carbon nanotubes to the dicarboxyl trithiocarbonate is 1:(0.02-0.08), and the temperature of the condensation reaction is 20-30°C; the polymerization reaction is carried out under the conditions of an initiator, the weight ratio of the carbon nanotubes to the fluorine-containing acrylate is 1:(0.1-0.5), and the temperature of the polymerization reaction is 80-100°C.

2. The method for preparing the perfluoroether rubber seal according to claim 1, characterized in that: In step S1, the perfluoroalkyl vinyl ether is at least one of perfluoromethyl vinyl ether, perfluoroethyl vinyl ether or perfluoropropyl vinyl ether; The mass ratio of tetrafluoroethylene to perfluoroalkyl vinyl ether is 1:(0.8-1).

3. The method for preparing the perfluoroether rubber seal according to claim 1 or 2, characterized in that: In step S1, the comonomer further comprises an organic fluorine aryl vinyl ether; The general structural formula of the organic fluorine aryl vinyl ether is as follows: n is 1-5; The mass ratio of tetrafluoroethylene to organic fluorine aromatic vinyl ether is 1:(0.05-0.2).

4. The method for preparing the perfluoroether rubber seal according to claim 1 or 2, characterized in that: In step S1, the vulcanization site monomer is at least one of 4-bromo-3,3,4,4-tetrafluorobutene, 1-bromo-2,2-difluoroethylene, ethyl vinyl bromide or trifluoroethylene bromide; the chain transfer agent is at least one of 1,2-diiodoethane, iodoethane, iodoform or iodomethane; The mass ratio of tetrafluoroethylene, vulcanization point monomer and chain transfer agent is 1: (0.01-0.05): (0.01-0.03).

5. The method for preparing the perfluoroether rubber seal according to claim 1 or 2, characterized in that: In step S2, the dicarboxyl trithiocarbonate is bis(carboxymethyl) trithiocarbonate; the fluorine-containing acrylate is at least one of trifluoroethyl methacrylate, hexafluorobutyl methacrylate, dodecafluoroheptyl methacrylate or tridecafluorooctyl methacrylate; the activator is N-hydroxysuccinimide; the dehydrating agent is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide; and the initiator is azobisisobutyronitrile.

6. The method for preparing the perfluoroether rubber seal according to claim 1 or 2, characterized in that: In step S3, the filler is at least one of carbon black N550, carbon black N660, carbon black N774 or carbon black N990; the vulcanizing agent is at least one of diisopropylbenzene peroxide, benzoyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane or di-tert-butylperoxyisopropylbenzene; and the accelerator is triallyl isocyanurate.

7. The method for preparing the perfluoroether rubber seal according to claim 1 or 2, characterized in that: In step S3, the mass ratio of the perfluoroether rubber raw rubber, carboxyl fluorinated modified carbon nanotubes, filler, vulcanizing agent and accelerator is 100:(1-5):(5-10):(1-3):(0.5-2).

8. The method for preparing the perfluoroether rubber seal according to claim 1 or 2, characterized in that: In step S1, the emulsion polymerization is carried out under the conditions of a pH buffer and an emulsifier; The pH buffer is disodium hydrogen phosphate or dipotassium hydrogen phosphate, and the emulsifier is ammonium perfluorooctanoate; The initiator of the emulsion polymerization is potassium persulfate or ammonium persulfate; The temperature of the emulsion polymerization is 70-90°C.

9. The method for preparing the perfluoroether rubber seal according to claim 1 or 2, characterized in that: In step S3, the first stage vulcanization temperature is 150-190°C, the time is 5-15 minutes, and the vulcanization pressure is 10-20 MPa; the second stage vulcanization temperature is 200-240°C, and the time is 12-24 hours.

10. A perfluoroether rubber seal, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 9.

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