Low-temperature resistant perfluoroether rubber and preparation method thereof

Abstract

The present invention discloses a low-temperature resistant perfluoroether rubber and a preparation method thereof. In parts by weight, the raw material components include: 80-120 parts of perfluoroether rubber polymer, 1-5 parts of additives, 10-30 parts of fillers, 1-3 parts of cross-linking agents, 1-4 parts of accelerators, 1-3 parts of processing aids, and 1-3 parts of acid absorbers. The present invention prepares a perfluoroether rubber polymer by a two-step polymerization method, and then prepares a low-temperature resistant perfluoroether rubber by mixing the perfluoroether rubber polymer with all mixed auxiliary materials. The perfluoroether rubber provided by the present invention not only has higher hardness, tensile strength, anti-extrusion deformation, shear resistance and low-temperature resistance, can meet the use demand of perfluoroether rubber at 40°C, and also has excellent plasma etching resistance, and can be applied to the semiconductor industry.

Description

Technical Field

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

[0002] Perfluoroelastomer (FFKM) is the most resistant of all elastic sealing materials, exhibiting the best resistance to high temperatures, strong acids and alkalis, and organic solvents. It is widely used in industries such as the chemical industry, nuclear industry, semiconductor industry, aerospace, deep-sea exploration, and ultra-deep well oilfield development. Currently, FFKM is primarily a copolymer of tetrafluoroethylene (TFE) and perfluoromethyl vinyl ether (PMVE) perfluorinated and curing monomers. However, the molecular chains of this composition are highly rigid and have poor flexibility, limiting its use to temperatures above -10°C and unable to meet lower temperature requirements. In the semiconductor field, various plasma gases are often used for micro-processing in semiconductor manufacturing processes, and plasma processing must be performed within a sealed reaction chamber. When FFKM is used as a sealing material and is directly or indirectly exposed to the plasma generated within semiconductor manufacturing equipment, the physical and chemical effects of the plasma can etch the FFKM, causing surface morphology changes, quality loss, and even cracks. This shortens the life of the sealing material. Therefore, it is necessary to provide a perfluoroether rubber with good low temperature resistance and plasma corrosion resistance to meet the needs.

[0003] CN117070043A discloses a low-temperature resistant perfluoroether elastomer composition and a preparation method thereof. This patent application uses a perfluoroether rubber latex and a PTFE latex to mix and coagulate to prepare the perfluoroether elastomer composition. However, since the two emulsions are prepared separately and then processed, the emulsions are mixed unevenly. The filler in the perfluoroether elastomer composition obtained during coagulation is unevenly dispersed and the filler is agglomerated. As a result, the perfluoroether elastomer composition has low tensile strength, low elongation, low tear strength, and large compression deformation. Summary of the Invention

[0004] In view of the above-mentioned defects of the prior art, the present invention provides a low-temperature resistant perfluoroether rubber and a preparation method thereof. The perfluoroether rubber provided by the present invention not only has high hardness, tensile strength, resistance to extrusion deformation, shear resistance and low-temperature resistance, which can meet the use requirements of perfluoroether rubber at -40°C, but also has excellent resistance to plasma etching.

[0005] To achieve the above object, the present invention provides a low-temperature resistant perfluoroether rubber, which comprises the following raw material components, calculated by weight: 80-120 parts of perfluoroether rubber polymer, 1-5 parts of additives, 10-30 parts of fillers, 1-3 parts of cross-linking agents, 1-4 parts of accelerators, 1-3 parts of processing aids, and 1-3 parts of acid absorbers;

[0006] Preferably, the additive is selected from one of reduced graphene oxide and modified graphene. Preferably, the preparation method of the modified graphene comprises the following steps, calculated in parts by weight:

[0007] a. Dissolve 0.25-0.35 parts of 2-azidoethanol in 2-4 parts of anhydrous dichloromethane, add 0.25-0.35 parts of dry triethylamine and 0.01-0.02 parts of 4-dimethylaminopyridine in sequence under argon, then add 1.5-2.5 parts of dichloromethane containing 0.25-0.3 parts of additives under ice-salt bath conditions, and continue stirring under argon conditions for 22-25 hours to obtain a mixture; then wash the mixture three times with 0.5-1 mol / L hydrochloric acid, then wash with water and sodium chloride aqueous solution, extract with ether 2-3 times, and then dry the organic phase with anhydrous magnesium sulfate, filter, remove dichloromethane under reduced pressure, and dry to obtain a modifier;

[0008] b. Under argon, add 0.04-0.06 parts of reduced graphene oxide to 8-9 parts of dry N,N-dimethylacetamide and ultrasonically disperse for 0.5-1.5 hours, then add 0.02-0.1 parts of the modifier obtained in step a, and continue stirring and reflux at 160-170° C. under argon for 22-25 hours to obtain a mixed solution; the mixed solution is cooled to room temperature, then filtered through a filter membrane, and repeatedly washed with acetone, dichloromethane and ethanol until the filtrate is colorless, and dried to obtain modified graphene.

[0009] Further preferably, the additive in step a is selected from one of 5,8-dihydroxy-9,10-dioxo-9,10-dihydroanthracene-2-carboxylic acid and 9,10-dioxo-9,10-dihydro-anthracene-2,6-dicarboxylic acid.

[0010] The present invention reacts an anthraquinone structure-containing additive with an azide-containing compound 2-azidoethanol to form a new CN bond, thereby introducing an azide group into the anthraquinone structure molecule to prepare an anthraquinone compound containing an azide group, namely a modifier. The modifier is then mixed with reduced graphene oxide under high temperature conditions. During this process, the azide group in the modifier structure can be decomposed to form a nitrene intermediate (RN=). The generated nitrene intermediate has high reactivity and can quickly undergo an insertion reaction with the C=C double bond in the reduced graphene oxide to form a stable CN bond, thereby fixing the modifier on the surface of the reduced graphene oxide through a covalent bond to obtain modified graphene.

[0011] The surface functionalization of modified graphene helps to improve the dispersibility and compatibility of graphene in the perfluoroether rubber matrix, reduce the phase separation between the perfluoroether rubber matrix and the graphene, and help to improve the uniformity and overall performance of the perfluoroether rubber. The present invention finds that introducing modified graphene into the preparation process of perfluoroether rubber is beneficial to improving the mechanical properties, low-temperature resistance and plasma etching resistance of the perfluoroether rubber.

[0012] Preferably, the filler is one or both of carbon black and white carbon black.

[0013] Preferably, the accelerator is triallyl isocyanurate.

[0014] Preferably, the cross-linking agent is selected from one or more of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0015] Preferably, the processing aid is one or more of Tecnoflon FPA, HT290, liquid nitrile rubber, fluorowax, low molecular weight polyethylene, zinc stearate, and palm wax.

[0016] Further preferably, the processing aid is formed by mixing HT290 and liquid nitrile rubber in a weight ratio of 1-2:1.

[0017] Preferably, the acid scavenger is selected from one or more of zinc oxide, magnesium oxide, and calcium hydroxide.

[0018] Preferably, the preparation method of the perfluoroether rubber polymer comprises the following steps:

[0019] Water, pH buffer and emulsifier are added to the reactor, vacuumed and nitrogen is used to control the oxygen content in the reactor to ≤20ppm, and the temperature of the reactor is raised to 80-120°C; tetrafluoroethylene and perfluoroalkoxy vinyl ether are introduced into the reactor until the pressure in the reactor reaches 3-4MPa, functionalized perfluoroolefin, halogenated perfluoroalkane and initiator are added, and then the first step emulsion polymerization reaction is carried out at the reactor temperature of 80-120°C for 10h-20h, and unreacted monomers are recovered to obtain the first step emulsion; tetrafluoroethylene and perfluoropropyl vinyl ether are introduced into the reactor until the pressure in the reactor reaches 3-4MPa, and functionalized perfluoroolefin, halogenated perfluoroalkane and initiator are added, and then the first step emulsion polymerization reaction is carried out at the reactor temperature of 80-120°C for 10h-20h, and unreacted monomers are recovered to obtain the first step emulsion; tetrafluoroethylene and perfluoropropyl vinyl ether are introduced into the reactor until the pressure in the reactor reaches 3-4MPa The second step emulsion polymerization reaction is carried out at a pressure of 3-4 MPa, an initiator is added, and a kettle temperature of 80° C.-120° C. for 5 h-10 h, and unreacted monomers are recovered to obtain a second step emulsion; the second step emulsion obtained above is subjected to emulsion post-treatment, i.e., the emulsion is coagulated with an aqueous solution of a coagulant in an amount of 10%-50% of the total mass of the emulsion and 0.1-10 wt % thereof, washed with a detergent, and then dried at 90-120° C. for 24-48 h to obtain a dry rubber powder; and the dry rubber powder is plasticized and molded to obtain a perfluoroether rubber polymer.

[0020] Wherein, the perfluoroalkoxy vinyl ether has the following structure:

[0021] CF2=CFO(CF2) n O(CF2) m CF3, wherein n is an integer from 1 to 6, and m is an integer from 0 to 5;

[0022] The perfluoroalkoxy vinyl ether is perfluoromethoxy vinyl ether.

[0023] Preferably, the pH buffer is selected from at least one of sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, ammonium sulfate, and ammonium bicarbonate.

[0024] Preferably, the amount of the pH buffer is 0.01-1% of the total mass of the water.

[0025] Preferably, the emulsifier is a perfluoropolyether carboxylate; further preferably, the emulsifier is one of perfluoro-2-methyl-3-oxahexanoic acid ammonium and perfluoro-2,5-dimethyl-3,6-dioxaoctanoic acid ammonium.

[0026] Preferably, the amount of the emulsifier is 0.1-5% of the total mass of the water.

[0027] Preferably, the mass ratio of tetrafluoroethylene to water is 1-25:75-99.

[0028] Preferably, the mass ratio of tetrafluoroethylene to perfluoroalkoxy vinyl ether in the first emulsion polymerization reaction is 35-70:30-65.

[0029] Preferably, the mass ratio of tetrafluoroethylene to perfluoropropyl vinyl ether in the second step emulsion polymerization reaction is 80-99:1-20.

[0030] Preferably, the functionalized perfluoroolefin is selected from at least one of brominated perfluoroolefin, iodinated perfluoroolefin and nitrile-containing perfluoroolefin.

[0031] More preferably, the brominated perfluoroolefin is selected from at least one of bromotrifluoroethylene, perfluoroallyl bromide and perfluoroethoxyvinyl bromide.

[0032] More preferably, the iodinated perfluoroolefin is selected from at least one of trifluoroethylene iodide, perfluoroallyl iodide, perfluoroiodoethyl vinyl ether and perfluoroiodoethoxy vinyl ether.

[0033] Preferably, the amount of the functionalized perfluoroolefin added is 0.1-6% of the total mass of the tetrafluoroethylene.

[0034] Preferably, the halogenated perfluoroalkane is selected from at least one of brominated perfluoroalkane and iodinated perfluoroalkane.

[0035] More preferably, the halogenated perfluoroalkane is at least one selected from perfluorobutyl bromide, perfluorohexyl bromide, 1,6-dibromoperfluorohexane, perfluorobutyl iodide, perfluorohexyl iodide, perfluorooctyl iodide, 1,4-diiodoperfluorobutane and 1,6-diiodoperfluorohexane.

[0036] Preferably, the amount of the halogenated perfluoroalkane added is 0.1-4% of the total mass of the tetrafluoroethylene.

[0037] Preferably, the initiator is a composition of 30-70 wt% of an oxidizing agent and 30-70 wt% of a reducing agent.

[0038] More preferably, the oxidizing agent is persulfate; and the reducing agent is selected from at least one of sulfite and thiosulfate.

[0039] Preferably, the amount of the initiator added is 0.1-1.5% of the total mass of the water.

[0040] Further preferably, the coagulant is selected from at least one of magnesium chloride, magnesium sulfate, aluminum sulfate, alum, calcium chloride, ammonium nitrate, nitric acid, hydrochloric acid and sulfuric acid.

[0041] Preferably, the amount of the detergent is 1-5 times the total mass of the perfluoroether rubber polymer.

[0042] Preferably, the detergent is selected from at least one of water, acetone, ethyl acetate, methanol, ethanol, and toluene.

[0043] The present invention also provides a method for preparing the above-mentioned low-temperature resistant perfluoroether rubber, comprising the following steps:

[0044] (1) uniformly plasticizing a perfluoroether rubber polymer on a two-roll mill and rolling it, then pre-mixing an additive, a accelerator, a filler, a cross-linking agent, a processing aid, and an acid scavenger to obtain a mixed auxiliary material, and gradually adding the mixed auxiliary material into the mill to mix the perfluoroether rubber polymer with all the mixed auxiliary materials;

[0045] (2) After the perfluoroether rubber polymer and the mixed auxiliary materials are evenly mixed, the perfluoroether rubber mixture of the wrapped roller is cut 5-10 times on each side, the roller distance of the open mill is adjusted to the minimum, and the roll or triangle package is made 8-12 times. The entire mixing time is controlled between 15-20 minutes, and the temperature of the open mill roller is controlled below 80°C. After the perfluoroether rubber composite material is evenly mixed, a sheet is produced to obtain a perfluoroether rubber material mixed rubber;

[0046] (3) The prepared perfluoroether rubber compound is aged for 15-20 hours, and then re-refined 8-12 times by rolling or triangular packaging, and then produced into sheets for use, thereby obtaining low-temperature resistant perfluoroether rubber.

[0047] Beneficial effects of the present invention:

[0048] 1. Compared with the prior art, the present invention adopts a two-step polymerization method. In the first step, tetrafluoroethylene and perfluoroalkoxy vinyl ether are reacted as comonomers, functionalized perfluoroolefins are used as vulcanization site monomers, and halogenated perfluoroalkanes are used as chain transfer agents and initiators. In the second step, tetrafluoroethylene and perfluoropropyl vinyl ether are reacted as comonomers and initiators. The obtained emulsion is post-treated to prepare a perfluoroether rubber polymer. The introduction of perfluoroalkoxy vinyl ether during the preparation process introduces flexible ether bonds (-CF2-O-CF2-) into the side chains of the fluoroelastomer. These ether bonds increase the flexibility of the molecular chain and reduce its rigidity. This structural change helps maintain the mobility of the molecular chain at low temperatures, thereby improving the low-temperature resistance of the perfluoroether rubber and allowing the perfluoroether rubber to be used at -40°C. The perfluoroether rubber polymer prepared by the present invention is used as a rubber matrix and mixed with mixed auxiliary materials to prepare a low-temperature resistant perfluoroether rubber, which not only meets the requirements for use in a high-purity environment, but also maintains the excellent heat resistance, wide media resistance, low compression permanent deformation and strong sealing retention of the perfluoroether rubber, and can be used in the semiconductor industry.

[0049] 2. Compared with the existing technology, the present invention adds a small amount of modified graphene to perfluoroether rubber, which can improve the low-temperature resistance and plasma etching resistance of perfluoroether rubber without significantly affecting other properties of the rubber. Most importantly, it has almost no effect on the chemical resistance of the rubber composition. The present invention also reasonably optimizes the filler and the vulcanization system. While ensuring a high rubber content in the entire formula system, the low-temperature resistant perfluoroether rubber material provided by the present invention has high hardness, tensile strength, anti-extrusion deformation, anti-shear performance and low-temperature resistance, which can meet the use requirements of perfluoroether rubber at -40°C, and also has excellent plasma etching resistance. The present invention has a reasonable formula and a simple process. The various properties of the low-temperature resistant perfluoroether rubber material provided by the present invention can meet the sealing requirements in low-temperature environments. DETAILED DESCRIPTION

[0050] Parameters for specific chemical substances used, sources.

[0051] Perfluoro-2,5-dimethyl-3,6-dioxaoctanoic acid ammonium, CAS number: 510774-79-5;

[0052] Reduced graphene oxide, product number: CRG1210, from Angxing New Carbon Materials Changzhou Co., Ltd.

[0053] Liquid nitrile rubber: Brand: LNBR820E, sourced from Shandong Wang's Brothers Rubber and Plastic Technology Co., Ltd.

[0054] Example 1

[0055] A low-temperature resistant perfluoroether rubber, the preparation method of which comprises the following steps:

[0056] (1) 95 kg of perfluoroether rubber polymer was uniformly plasticized on a two-roll mill and rolled, and then 3 kg of reduced graphene oxide, 25 kg of carbon black N660, 3 kg of triallyl isocyanurate, 2 kg of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 1.5 kg of processing aid and 1.5 kg of zinc oxide were pre-mixed to obtain a mixed auxiliary material, and the mixed auxiliary material was gradually added to the mill to mix the perfluoroether rubber polymer with all the mixed auxiliary materials;

[0057] (2) After the perfluoroether rubber polymer and the mixed auxiliary materials are evenly mixed, the perfluoroether rubber mixture of the wrapped roller is cut 9 times on each side, the roller distance of the open mill is adjusted to the minimum, and the roll or triangle package is made 10 times. The entire mixing time is controlled between 18 minutes, and the temperature of the open mill roller is controlled below 80°C. After the perfluoroether rubber composite material is evenly mixed, a sheet is produced to obtain a perfluoroether rubber material mixed rubber;

[0058] (3) The prepared perfluoroether rubber compound is aged for 16 hours, and then re-refined 10 times by rolling or triangular packaging, and then produced into sheets for use, thereby obtaining a low-temperature resistant perfluoroether rubber.

[0059] The processing aid in step (1) is a mixture of HT290 (STRUKTOL, Germany) and liquid nitrile rubber in a weight ratio of 2:1;

[0060] The preparation method of the perfluoroether rubber polymer in step (1) comprises the following steps:

[0061] 80 kg of water, 0.4 kg of disodium hydrogen phosphate and 2.4 kg of perfluoro-2,5-dimethyl-3,6-dioxaoctanoic acid ammonium were added to a reactor, vacuumed and the oxygen content in the reactor was controlled to ≤20 ppm by nitrogen, and the temperature of the reactor was raised to 110° C. 11 kg of tetrafluoroethylene and 11 kg of perfluoromethoxyvinyl ether were introduced into the reactor until the pressure in the reactor reached 3.5 MPa, 0.6 kg of trifluoroiodoethylene, 0.4 kg of perfluorobutyl bromide and 0.6 kg of initiator were added, and then the first step of emulsion polymerization was carried out at a reactor temperature of 110° C. for 15 hours, and the unreacted monomers were recovered to obtain a first step emulsion; the reaction was carried out. 9 kg of tetrafluoroethylene and 1 kg of perfluoropropyl vinyl ether were introduced into the kettle until the pressure inside the kettle reached 3.5 MPa, 0.6 kg of initiator was added, and a second-step emulsion polymerization reaction was carried out at a kettle temperature of 110° C. for 8 hours, and unreacted monomers were recovered to obtain a second-step emulsion; the second-step emulsion obtained above was subjected to emulsion post-treatment, namely, coagulation of the emulsion with a 5 wt % magnesium chloride aqueous solution, which was 30% of the total mass of the emulsion, and washing with water 4 times the total mass of the perfluoroether rubber polymer, and then drying at 100° C. for 36 hours to obtain a dry rubber powder; and the dry rubber powder was plasticized and molded to obtain a perfluoroether rubber polymer.

[0062] The initiator is a composition of 50 wt% potassium persulfate and 50 wt% potassium thiosulfate.

[0063] Example 2

[0064] A method for preparing low-temperature resistant perfluoroether rubber differs from Example 1 in that 3 kg of reduced graphene oxide in step (1) is replaced by 3 kg of modified graphene. The method for preparing modified graphene comprises the following steps:

[0065] 0.3 kg of 2-azidoethanol was dissolved in 3 kg of anhydrous dichloromethane, and 0.3 kg of dry triethylamine and 0.015 kg of 4-dimethylaminopyridine were added in sequence under argon conditions, and then 2 kg of anhydrous dichloromethane containing 0.27 kg of 9,10-dioxo-9,10-dihydro-anthracene-2,6-dicarboxylic acid was added under ice-salt bath conditions, and stirring was continued under argon conditions for 24 hours to obtain a mixture; the mixture was then washed three times with 1 mol / L hydrochloric acid, washed with water and a sodium chloride aqueous solution, extracted three times with diethyl ether, and then the organic phase was dried over anhydrous magnesium sulfate, filtered, and dichloromethane was removed under reduced pressure, and dried to obtain a modifier;

[0066] b. Under argon, 0.05 kg of reduced graphene oxide was added to 8.5 kg of dry N, N-dimethylacetamide, and ultrasonically dispersed for 1 h. Then, 0.08 g of the modifier obtained in step a was added, and the mixture was stirred and refluxed at 165 ° C. under argon for 24 h to obtain a mixed solution; the mixed solution was cooled to room temperature, then filtered through a filter membrane (0.22 μm), and repeatedly washed with acetone, dichloromethane, and ethanol until the filtrate was colorless, and dried to obtain modified graphene.

[0067] Example 3

[0068] A method for preparing low-temperature resistant perfluoroether rubber differs from Example 1 in that 3 kg of reduced graphene oxide in step (1) is replaced by 3 kg of modified graphene. The method for preparing modified graphene comprises the following steps:

[0069] a. Dissolve 0.3 kg of 2-azidoethanol in 3 kg of anhydrous dichloromethane, add 0.3 kg of dry triethylamine and 0.015 kg of 4-dimethylaminopyridine in sequence under argon, then add 2 kg of anhydrous dichloromethane containing 0.27 kg of 5,8-dihydroxy-9,10-dioxo-9,10-dihydroanthracene-2-carboxylic acid under ice-salt bath, and continue stirring under argon for 24 hours to obtain a mixture; then wash the mixture three times with 1 mol / L hydrochloric acid, then wash with water and sodium chloride aqueous solution, extract with ether three times, and then dry the organic phase over anhydrous magnesium sulfate, filter, remove dichloromethane under reduced pressure, and dry to obtain a modifier;

[0070] b. Under argon, 0.05 kg of reduced graphene oxide was added to 8.5 kg of dry N, N-dimethylacetamide, and ultrasonically dispersed for 1 h. Then, 0.08 g of the modifier obtained in step a was added, and the mixture was stirred and refluxed at 165 ° C. under argon for 24 h to obtain a mixed solution; the mixed solution was cooled to room temperature, then filtered through a filter membrane (0.22 μm), and repeatedly washed with acetone, dichloromethane, and ethanol until the filtrate was colorless, and dried to obtain modified graphene.

[0071] Comparative Example 1

[0072] A method for preparing a low-temperature resistant perfluoroether rubber is different from that of Example 1 in that reduced graphene oxide is not added in step (1), that is, step (1) is: 95 kg of perfluoroether rubber polymer is uniformly plasticized on a two-roll mill and rolled, and then 25 kg of carbon black N660, 3 kg of triallyl isocyanurate, 2 kg of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 1.5 kg of processing aid and 1.5 kg of zinc oxide are pre-mixed to obtain a mixed auxiliary material, and the mixed auxiliary material is gradually added into the mill to mix the perfluoroether rubber polymer with all the mixed auxiliary materials;

[0073] The processing aid in step (1) is a mixture of HT290 (STRUKTOL, Germany) and liquid nitrile rubber in a weight ratio of 2:1;

[0074] The preparation method of the perfluoroether rubber polymer in step (1) is consistent with that in Example 1.

[0075] Comparative Example 2

[0076] A method for preparing a low-temperature resistant perfluoroether rubber is different from that of Example 1 in that 3 kg of reduced graphene oxide in step (1) is replaced with 3 kg of graphene oxide, that is, step (1) is: 95 kg of perfluoroether rubber polymer is uniformly plasticized on a double-roll mill and rolled, and then 3 kg of graphene oxide, 25 kg of carbon black N660, 3 kg of triallyl isocyanurate, 2 kg of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 1.5 kg of processing aid and 1.5 kg of zinc oxide are pre-mixed to obtain a mixed auxiliary material, and the mixed auxiliary material is gradually added into the mill to mix the perfluoroether rubber polymer with all the mixed auxiliary materials;

[0077] The processing aid in step (1) is a mixture of HT290 (STRUKTOL, Germany) and liquid nitrile rubber in a weight ratio of 2:1;

[0078] The preparation method of the perfluoroether rubber polymer in step (1) is consistent with that in Example 1.

[0079] Comparative Example 3

[0080] The difference between the preparation method of low-temperature resistant perfluoroether rubber and Example 1 is that the processing aid in step (1) is HT290 (STRUKTOL, Germany).

[0081] Test Example 1

[0082] Performance Testing

[0083] Preparation of perfluoroether rubber vulcanization specimens: The low-temperature resistant perfluoroether rubbers prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to a first-stage vulcanization at 180°C, a vulcanization time of 10 minutes, and a mold closing pressure of 20 MPa. The perfluoroether rubber mix was compression-vulcanized into a standard rubber test piece. The first-stage vulcanized product was then placed in an oven for a second-stage vulcanization, maintained at 200°C for 2 hours, then heated to 220°C and maintained for 10 hours, cooled to 25°C, and taken out to obtain a perfluoroether rubber vulcanization specimen for later use.

[0084] The prepared perfluoroether rubber vulcanized samples of each embodiment and comparative example were subjected to perfluoroether rubber performance test according to the standard:

[0085] Mechanical properties: Hardness: Hardness test is carried out in accordance with the national standard GB / T531.1-2008; Tensile strength and elongation at break: Tensile test is carried out at room temperature using a universal testing machine in accordance with GB / T528-2009 Vulcanized rubber or thermoplastic rubber - Determination of tensile stress and strain properties;

[0086] Low temperature resistance: The low temperature resistance compression coefficient was determined according to the standard "HG / I3866-2008 Determination of the Cold Resistance Coefficient of Compression of Vulcanized Rubber". The test temperatures were -40°C, -50°C, and -55°C. The low temperature resistance of the perfluoroether rubber in each embodiment and comparative example was analyzed. The test parameters were: maintain the low temperature for 5 minutes, remove the pressure within 10 seconds, and read the data after 3 minutes of recovery. The formula for the cold resistance compression coefficient is as follows:

[0087] k c =(h2-h1) / (h0-h1)

[0088] Where h o h1 is the original height of the sample before compression, in millimeters (mm); h2 is the height of the sample after compression, in millimeters (mm); the test results are taken as the arithmetic mean, and the allowable deviation is ±10%;

[0089] The specific test results are shown in Table 1 below:

[0090] Table 1

[0091]

[0092]

[0093] As can be seen from Table 1, by comparing Examples 1-3 and Comparative Example 1-3, it is found that compared with the perfluoroether rubber material of Comparative Example 1 without adding graphene, the hardness of Examples 1-3 and Comparative Example 3 increases, and the hardness of Example 2 decreases; the tensile strength of Examples 1-3 and Comparative Example 2-3 increases, among which the increase in Comparative Example 2 is smaller; the elongation at break of Examples 1-3 and Comparative Example 2-3 decreases, among which the decrease in Examples 2-3 and Comparative Example 2 is smaller; it shows that the addition of reduced graphene oxide and modified graphene is beneficial to improving the hardness and tensile strength of perfluoroether rubber, but is not conducive to elongation at break. The addition of graphene oxide leads to a decrease in hardness while the tensile strength and elongation at break are significantly smaller. The present invention finds that the coordinated use of modified graphene and liquid nitrile rubber is beneficial to eliminating the adverse effects of the addition of modified graphene on the elongation at break of perfluoroether rubber, and is beneficial to obtaining a perfluoroether rubber material with higher hardness, tensile strength, anti-extrusion deformation and shear resistance. Analysis suggests that the reason may be that after liquid nitrile rubber enters the perfluoroether rubber system, it can effectively provide free volume for the molecular segments on the rubber surface, increase the mobility of its molecular segments, and weaken the interaction between the molecular chains, thereby reducing the difficulty of relative slip between the molecular chains during stretching, thereby increasing the elongation at break of the perfluoroether rubber. When modified graphene and liquid nitrile rubber are used in conjunction, the active groups on the surface of the modified graphene may covalently cross-link with the double bonds of the liquid nitrile rubber, further increasing the free volume between the perfluoroether rubber molecules, increasing the mobility of the segments, and improving the elongation at break of the perfluoroether rubber. In addition, the liquid nitrile rubber molecular structure contains flexible nitrile segments with good flexibility and adhesion, which can improve the compatibility of the modified graphene with the perfluoroether rubber matrix, making the internal structure of the perfluoroether rubber form a more uniform dispersed phase, thereby more evenly dispersing the internal stress when the perfluoroether rubber is stretched, reducing stress concentration, and further improving the elongation at break.

[0094] The present invention uses low-temperature compression coefficient as the main basis for measuring its low-temperature performance. According to national standards, a low-temperature compression coefficient higher than 0.2 indicates that the rubber has excellent low-temperature resistance. As can be seen from Table 1, the low-temperature compression coefficients of Examples 1-3 and Comparative Example 1-3 are both higher than 0.2 at -40°C, indicating that there is recovery ability at -40°C, indicating that the addition of the perfluoroether rubber polymer prepared by the present invention can give the perfluoroether rubber good low-temperature resistance; when the temperature drops from -50°C to -55°C, the low-temperature compression coefficient of Comparative Example 1-2 drops to below 0.2 until it is 0, and the rebound performance is gradually lost, indicating that when the temperature is further reduced, the low-temperature resistance of Comparative Example 1-2 deteriorates, while the low-temperature compression coefficients of Examples 1-3 and Comparative Example 3 can still be maintained above 0.2, having good low-temperature resistance; By comparing Examples 1-3 and Comparative Example 3, it can be found that the mass loss rate of Examples 2-3 is lower than that of Examples 1 and Comparative Example 3, among which the low-temperature compression coefficient of Example 3 at -55°C is 0.32, and its low-temperature resistance is the best, indicating that the synergistic use of modified graphene and liquid nitrile rubber is more conducive to improving the low-temperature resistance of perfluoroether rubber. Analysis suggests that the reason for this may be that the graphene sheets have a very large specific surface area and contain a conjugated π-electron system, which can form π-π interactions with the fluorine atoms and other polar functional groups in the perfluoroelastomer polymer. Furthermore, the surface-functionalized modified graphene increases its dispersibility and compatibility in the perfluoroelastomer matrix, enabling it to contact and interact with more rubber chains within the rubber matrix. Furthermore, the presence of hydroxyl groups or other polar functional groups on the modified graphene surface can form hydrogen bonds with the fluorine atoms in the perfluoroelastomer polymer, further enhancing the interaction between the modified graphene and the perfluoroelastomer chains. The enhanced interaction between the modified graphene and the perfluoroelastomer chains due to the introduction of the modified graphene may not only alter the original interactions between the perfluoroelastomer chains but also improve the molecular dispersion, thereby increasing the perfluoroelastomer chain compliance. This increased compliance helps lower the glass transition temperature of the perfluoroelastomer, thereby improving its performance under low-temperature conditions. At the same time, the introduction of modified graphene may increase the free volume of the perfluoroether rubber molecular chain, that is, the space between the molecular chains is larger, which reduces the difficulty of the movement of the perfluoroether rubber molecular chain segments, allowing the molecular chain segments to still maintain a certain degree of activity at low temperatures, which helps to further improve the low-temperature resistance of perfluoroether rubber.The present invention introduces liquid nitrile rubber and uses modified graphene in conjunction to prepare perfluoroether rubber. During the preparation process, active groups on the surface of the modified graphene may be covalently cross-linked with double bonds of the liquid nitrile rubber, which not only increases the free volume between molecules and helps to further reduce the difficulty of the movement of perfluoroether rubber molecular segments at low temperatures, making the segments easier to move at low temperatures and improving low-temperature resistance, but also improves the stress distribution inside the perfluoroether rubber, so that when the perfluoroether rubber is subjected to external force, the stress can be more evenly distributed between the modified graphene sheets and the liquid nitrile rubber molecular chains, reducing local stress concentration and improving the low-temperature resistance of the perfluoroether rubber material.

[0095] Test Example 2

[0096] Perfluoroether rubber vulcanized samples of Examples 1-3 and Comparative Examples 1-3 were prepared according to the method of Test Example 1. The samples of each Example and Comparative Example were cut into 23 mm × 15 mm × 2 mm rubber sheets. A plasma etching test was then performed to measure the plasma etching resistance of the perfluoroether rubber vulcanized samples using the plasma etching mass loss rate.

[0097] Test method:

[0098] The rubber sheet was placed in an ultrasonic cleaning machine for 30 minutes, and then placed in an 80°C oven to dry. After the surface of the rubber sheet was free of liquid, the mass was weighed on an analytical balance as m1. The cleaned rubber sheet was placed on the reaction table of an ICP etcher (plasma etcher; Beijing Tongjia Hongrui Technology Co., Ltd.) and plasma etched for 1 hour. During etching, the rubber sheet was placed in the center of the cavity (stretching rate was 0), the test temperature was 200°C, the power was 1kW, the gas was NF3 and O2, the flow rates were 135sccm and 35sccm respectively, the vacuum was 170mTorr, and the etching time was 60 minutes. After etching, the rubber sheet was placed in an ultrasonic cleaning agent again for 30 minutes to remove surface particles, and placed in an 80°C oven. After the surface of the rubber sheet was free of liquid, it was weighed again on an analytical balance as m2. The mass loss rate of perfluoroether rubber plasma etching was calculated based on the mass change of the rubber sheet before and after plasma etching. The calculation formula is as follows:

[0099] Mass loss rate = (m1-m2) / m1×100%

[0100] The specific test results are shown in Table 2 below;

[0101] Table 2

[0102]

[0103]

[0104] Comparing Examples 1-3 with Comparative Examples 1-3, it can be found that the mass loss rates of Examples 2-3 and Comparative Example 3 are significantly lower than those of Examples 1 and Comparative Example 1-2, indicating that the introduction of modified graphene is more conducive to improving the plasma etching resistance of perfluoroether rubber compared to graphene oxide and reduced graphene oxide. Comparing Examples 2-3 with Comparative Example 3, it can be found that the mass loss rates of Examples 2-3 are lower than those of Comparative Example 3, with the mass loss rate of Example 3 being only 2.61%, indicating that the synergistic use of modified graphene and liquid nitrile rubber is more conducive to improving the plasma etching resistance of perfluoroether rubber. Analysis suggests that this may be because the two-dimensional sheet structure of the modified graphene can form a physical barrier on the surface of the perfluoroether rubber. This barrier can prevent particles in the plasma from directly contacting the rubber matrix, and the graphene portion of the modified graphene has high chemical stability, so it can act as a protective layer to protect the rubber matrix, thereby reducing plasma erosion of the rubber matrix. At the same time, the carbonyl C=O is connected to the benzene ring in the surface functionalized modified graphene structure, and the C=O bond energy is low and the activity is large and easy to react, which can absorb the free radicals in part of the plasma, so that the plasma first attacks the carbonyl in the modified graphene structure, reduces the attack of the -CF2- bond in the rubber macromolecular chain by the plasma, protects the polymer, and thus reduces the etching of the rubber by the plasma. At the same time, the present invention introduces liquid acrylonitrile-butadiene rubber and modified graphene to prepare perfluoroether rubber in collaboration, and the liquid acrylonitrile-butadiene rubber has good flexibility and adhesion, can better fill the gap between the modified graphene layers, improves the interface interaction, strengthens the physical barrier effect of the modified graphene, reduces the direct erosion of the rubber matrix by the plasma, and the nitrile group in the liquid acrylonitrile-butadiene rubber may not only interact with the graphene surface to form a stronger chemical bond, further improve the chemical stability of the composite material, but also may react with the free radicals in the plasma, further reduce the attack of the -CF2- bond in the rubber macromolecular chain by the free radicals, protect the polymer, and improve the plasma etching resistance of the perfluoroether rubber.

[0105] Comparing Example 2 and Example 3, the additive 5,8-dihydroxy-9,10-dioxo-9,10-dihydroanthracene-2-carboxylic acid used in the graphene modification process, the plasma etching resistance of Example 3 is better than that of the additive 9,10-dioxo-9,10-dihydro-anthracene-2,6-dicarboxylic acid Example 2 used in the graphene modification process, indicating that compared with 9,10-dioxo-9,10-dihydro-anthracene-2,6-dicarboxylic acid, 5,8-dihydroxy-9,10-dioxo-9,10-dihydroanthracene-2-carboxylic acid is more conducive to improving the modified graphene to absorb free radicals in the plasma, protect the fluororubber macromolecular chain, and reduce the ability of the plasma to etch the rubber. Analysis shows that the reason may be that 5,8-dihydroxy-9,10-dioxo-9,10-dihydroanthracene-2-carboxylic acid contains two hydroxyl groups. The hydroxyl groups have a higher electron density and may provide additional active sites, making them more likely to react with free radicals, thereby more effectively absorbing free radicals in the plasma. In addition, hydroxyl groups are generally more likely to lose hydrogen atoms to form free radicals than carboxyl groups, which makes 5,8-dihydroxy-9,10-dioxo-9,10-dihydroanthracene-2-carboxylic acid-modified graphene more active when reacting with free radicals in the plasma, enabling the modified graphene to more effectively neutralize free radicals in the plasma and reduce etching of rubber.

Claims

1. A low-temperature resistant perfluoroether rubber, characterized in that: Calculated by weight, it includes the following raw material components: 80-120 parts of perfluoroether rubber polymer, 1-5 parts of additives, 10-30 parts of fillers, 1-3 parts of cross-linking agents, 1-4 parts of accelerators, 1-3 parts of processing aids, and 1-3 parts of acid absorbents; The additive is modified graphene; The preparation method of the modified graphene comprises the following steps, calculated by weight: a. Dissolve 0.25-0.35 parts of 2-azidoethanol in 2-4 parts of anhydrous dichloromethane, add 0.25-0.35 parts of dry triethylamine and 0.01-0.02 parts of 4-dimethylaminopyridine in sequence under argon, then add 1.5-2.5 parts of dichloromethane containing 0.25-0.3 parts of additives under ice-salt bath conditions, and continue stirring under argon conditions for 22-25 hours to obtain a mixture; then wash the mixture three times with 0.5-1 mol / L hydrochloric acid, then wash with water and sodium chloride aqueous solution, extract with ether 2-3 times, and then dry the organic phase with anhydrous magnesium sulfate, filter, remove dichloromethane under reduced pressure, and dry to obtain a modifier; b. Under argon, 0.04-0.06 parts of reduced graphene oxide were added to 8-9 parts of dry N,N-dimethylacetamide and ultrasonically dispersed for 0.5-1.5 hours, and then 0.02-0.1 parts of the modifier obtained in step a were added, and the mixture was stirred and refluxed at 160-170° C. under argon for 22-25 hours to obtain a mixed solution; the mixed solution was cooled to room temperature, filtered through a filter membrane, and repeatedly washed with acetone, dichloromethane, and ethanol until the filtrate was colorless, and dried to obtain modified graphene; The additive in step a is selected from one of 5,8-dihydroxy-9,10-dioxo-9,10-dihydroanthracene-2-carboxylic acid and 9,10-dioxo-9,10-dihydro-anthracene-2,6-dicarboxylic acid; The processing aids are HT290 and liquid nitrile rubber.

2. The low-temperature resistant perfluoroether rubber according to claim 1, characterized in that: The filler is one or both of carbon black and white carbon black; the crosslinking agent is selected from one or more of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane; the accelerator is triallyl isocyanurate; and the acid scavenger is selected from one or more of zinc oxide, magnesium oxide, and calcium hydroxide.

3. The low-temperature resistant perfluoroether rubber according to claim 1, characterized in that: The preparation method of the perfluoroether rubber polymer comprises the following steps: Water, pH buffer and emulsifier are added to a reactor, vacuumed and nitrogen is used to control the oxygen content in the reactor to ≤20ppm, and the temperature of the reactor is raised to 80-120°C; tetrafluoroethylene and perfluoroalkoxy vinyl ether are introduced into the reactor until the pressure in the reactor reaches 3-4MPa, functionalized perfluoroolefin, halogenated perfluoroalkane and initiator are added, and then the first step emulsion polymerization reaction is carried out at a reactor temperature of 80-120°C for 10h-20h, and unreacted monomers are recovered to obtain the first step emulsion; tetrafluoroethylene and perfluoropropyl vinyl ether are introduced into the reactor until the pressure in the reactor reaches 3 -4MPa, adding an initiator, and conducting a second-step emulsion polymerization reaction at a kettle temperature of 80°C-120°C for 5h-10h, recovering unreacted monomers to obtain a second-step emulsion; performing emulsion post-treatment on the second-step emulsion obtained above, i.e., coagulating the emulsion with an aqueous solution of a coagulant in an amount of 10%-50% of the total mass of the emulsion and a mass content of 0.1-10wt%, washing the emulsion with a detergent, and then drying the emulsion at 90-120°C for 24-48h to obtain a dry rubber powder; and plasticizing and molding the dry rubber powder to obtain a perfluoroether rubber polymer; Wherein, the perfluoroalkoxy vinyl ether has the following structure: CF2=CFO(CF2) n O(CF2) m CF3, wherein n is an integer of 1-6, and m is an integer of 0-5.

4. The low-temperature resistant perfluoroether rubber according to claim 3, characterized in that: The pH buffer is selected from at least one of sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, ammonium sulfate, and ammonium bicarbonate; the amount of the pH buffer is 0.01-1% of the total mass of the water; the emulsifier is perfluoropolyether carboxylate; the amount of the emulsifier is 0.1-5% of the total mass of the water.

5. The low-temperature resistant perfluoroether rubber according to claim 3, characterized in that: The mass ratio of tetrafluoroethylene to water is 1-25:75-99; the mass ratio of tetrafluoroethylene to perfluoroalkoxy vinyl ether in the first emulsion polymerization reaction is 35-70:30-65; the mass ratio of tetrafluoroethylene to perfluoropropyl vinyl ether in the second emulsion polymerization reaction is 80-99:1-20.

6. The low-temperature resistant perfluoroether rubber according to claim 3, characterized in that: The functionalized perfluoroolefin is selected from at least one of brominated perfluoroolefins, iodinated perfluoroolefins and nitrile-containing perfluoroolefins; the added amount of the functionalized perfluoroolefin is 0.1-6% of the total mass of the tetrafluoroethylene; the halogenated perfluoroalkane is selected from at least one of brominated perfluoroalkanes and iodinated perfluoroalkanes; the added amount of the halogenated perfluoroalkane is 0.1-4% of the total mass of the tetrafluoroethylene.

7. The low-temperature resistant perfluoroether rubber according to claim 3, characterized in that: The initiator is a composition of 30-70 wt% of an oxidant and 30-70 wt% of a reducing agent; the oxidant is a persulfate; the reducing agent is selected from at least one of a sulfite and a thiosulfate; the amount of the initiator added is 0.1-1.5% of the total mass of the water; the coagulant is selected from at least one of magnesium chloride, magnesium sulfate, aluminum sulfate, alum, calcium chloride, ammonium nitrate, nitric acid, hydrochloric acid and sulfuric acid; the amount of the detergent is 1-5 times the total mass of the perfluoroether rubber polymer; and the detergent is selected from at least one of water, acetone, ethyl acetate, methanol, ethanol and toluene.

8. The method for preparing the low-temperature resistant perfluoroether rubber according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) The perfluoroether rubber polymer is plasticized evenly on a two-roll mill and rolled, and then the additives, accelerators, fillers, cross-linking agents, processing aids and acid absorbents are pre-mixed to obtain mixed auxiliary materials, and the mixed auxiliary materials are gradually added to the mill to mix the perfluoroether rubber polymer with all the mixed auxiliary materials; (2) After the perfluoroether rubber polymer and the mixed auxiliary materials are evenly mixed, the perfluoroether rubber mixture of the wrapped roller is cut 5-10 times on each side, the roller distance of the open mill is adjusted to the minimum, and the roll or triangle package is made 8-12 times. The entire mixing time is controlled between 15-20 minutes, and the temperature of the open mill roller is controlled below 80°C. After the perfluoroether rubber composite material is evenly mixed, the sheet is produced to obtain the perfluoroether rubber material mixed rubber; (3) The prepared perfluoroether rubber compound is aged for 15-20 hours, and then re-refined 8-12 times by rolling or triangle packing, and then the sheet is produced for use to obtain low-temperature resistant perfluoroether rubber.

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