Low-temperature-resistant perfluoroether rubber and preparation method thereof

Abstract

The invention discloses low-temperature-resistant perfluoroether rubber and a preparation method thereof, and the low-temperature-resistant perfluoroether rubber comprises the following raw material components in parts by weight: 80-120 parts of a perfluoroether rubber polymer, 1-5 parts of an additive, 10-30 parts of a filler, 1-3 parts of a cross-linking agent, 1-4 parts of an accelerant, 1-3 parts of a processing aid and 1-3 parts of an acid acceptor. The perfluoroether rubber polymer is prepared through a two-step polymerization method, and then the perfluoroether rubber polymer and all the mixed auxiliary materials are mixed and mixed to prepare the low-temperature-resistant perfluoroether rubber. The perfluoroether rubber provided by the invention not only has relatively high hardness, tensile strength, extrusion deformation resistance, shearing resistance and low temperature resistance, can meet the use requirement of the perfluoroether rubber at-40 DEG C, but also has excellent plasma etching resistance, and can be applied to the semiconductor industry.

Description

Technical Field

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

[0002] Perfluoroether rubber (FFKM) is the best rubber material in terms of high temperature resistance, strong acid and alkali resistance, and organic solvent resistance 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. At present, perfluoroether rubber is mainly copolymerized by tetrafluoroethylene (TFE) and perfluoromethyl vinyl ether (PMVE) perfluorinated and vulcanization point monomers, but the molecular chain of the perfluoroether rubber composed of this composition is rigid and has poor flexibility, which leads to the perfluoroether rubber of this structure can only be used above -10°C and cannot meet the use requirements of lower temperatures. In the semiconductor field, various plasma gases are often used for fine processing in the semiconductor manufacturing process, and the plasma treatment needs to be carried out in a sealed reaction chamber. When the perfluoroether rubber used as a sealing material is used to be directly or indirectly irradiated by the plasma generated in the semiconductor manufacturing device, the perfluoroether rubber is exposed to the plasma environment. Due to the physical and chemical effects of the plasma, the perfluoroether rubber will be etched, resulting in changes in its surface morphology and quality loss or even cracks, so there is a problem of short 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. The patent application adopts 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, and the fillers in the perfluoroether elastomer composition obtained during coagulation are unevenly dispersed and the fillers are agglomerated, resulting in low tensile strength, low elongation, low tear strength, and large compression deformation of the perfluoroether elastomer composition. 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 plasma etching resistance.

[0005] To achieve the above object, the present invention provides a low-temperature resistant perfluoroether rubber, which comprises the following raw material components 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 absorbents;

[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 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, continue stirring for 22-25 hours under argon conditions 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, 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 for ultrasonic dispersion for 0.5-1.5h, then add 0.02-0.1 parts of the modifier obtained in step a, and continue stirring and refluxing at 160-170°C and argon for 22-25h 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 invention allows an additive containing an anthraquinone structure to react with an azide-containing compound 2-azidoethanol to form a new CN bond, thereby introducing an azide group into an anthraquinone structure molecule to prepare an anthraquinone compound containing an azide group, namely a modifier; then, the modifier is mixed with reduced graphene oxide under high temperature conditions, during which the azide group in the modifier structure can be decomposed to generate a nitrene intermediate (RN=), and the generated nitrene intermediate has high reactivity and can rapidly undergo an insertion reaction with a 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 by 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, fluoro wax, low molecular weight polyethylene, zinc stearate, and palm wax.

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

[0017] Preferably, the acid absorber 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, vacuuming and controlling the oxygen content in the reactor to ≤20ppm with nitrogen, 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 is carried out at a reactor temperature of 80°C-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 is carried out at a reactor temperature of 80°C-120°C for 10h-20h, and unreacted monomers are recovered to obtain the first step emulsion; The second step emulsion polymerization reaction is carried out at a pressure of 3-4 MPa, an initiator is added, and the kettle temperature is 80°C-120°C for 5h-10h, and the unreacted monomers are recovered to obtain a second step emulsion; the second step emulsion obtained above is subjected to emulsion post-treatment, that is, 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 0.1-10wt%, washed with a detergent, and then dried at 90-120°C for 24-48h to obtain a dry rubber powder; 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 pH buffer is used in an amount of 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-dioxahexanoic 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 step of emulsion polymerization 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] Further 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] Further preferably, the oxidant 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 used 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, an accelerator, a filler, a cross-linking agent, a processing aid and an acid absorbent to obtain a mixed auxiliary material, and gradually adding the mixed auxiliary material to 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 wrapped on the roller is cut 5-10 times on each side, the roller distance of the mixing mill is adjusted to the minimum, and the rolling or triangle packing is performed 8-12 times. The entire mixing time is controlled between 15-20 minutes, and the roller temperature of the mixing mill 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 for 8-12 times by rolling or triangle packing, and then produced into sheets for standby use, thereby obtaining a 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 used as comonomers, functionalized perfluoroolefin is used as a vulcanization point monomer, and halogenated perfluoroalkane is used as a chain transfer agent to react with an initiator. In the second step, tetrafluoroethylene and perfluoropropyl vinyl ether are used as comonomers to react with an initiator. The obtained emulsion is post-treated to prepare a perfluoroether rubber polymer. In the preparation process, perfluoroalkoxy vinyl ether is introduced, and flexible ether bonds (-CF2-O-CF2-) are introduced into the side chains of the fluoroelastomer. These ether bonds increase the flexibility of the molecular chain and reduce the rigidity of the molecular chain. This structural change helps to maintain the activity of the molecular chain at low temperatures, thereby improving the low temperature resistance of the perfluoroether rubber, so that the perfluoroether rubber can 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 use requirements 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 prior art, 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, resistance to extrusion deformation, shear resistance 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 a low-temperature environment. 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 & 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 roller temperature of the open mill is controlled below 80°C. After the perfluoroether rubber composite material is mixed evenly, 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 standby 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 reaction kettle, vacuumed and the oxygen content in the reaction kettle was controlled to be ≤20 ppm by nitrogen, and the temperature of the reaction kettle was raised to 110° C. 11 kg of tetrafluoroethylene and 11 kg of perfluoromethoxyvinyl ether were introduced into the reaction kettle until the pressure in the kettle 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 kettle temperature of 110° C. for 15 hours, and the unreacted monomers were recovered to obtain the first step of emulsion; the reaction kettle was reacted 9 kg tetrafluoroethylene and 1 kg perfluoropropyl vinyl ether are introduced into the kettle until the pressure in the kettle reaches 3.5 MPa, 0.6 kg initiator is added, and the second step emulsion polymerization reaction is carried out at a kettle temperature of 110° C. for 8 hours, and unreacted monomers are recovered to obtain a second step emulsion; the second step emulsion obtained above is subjected to emulsion post-treatment, that is, the emulsion is condensed with a 5wt% magnesium chloride aqueous solution of 30% of the total mass of the emulsion, and the emulsion is washed with water of 4 times the total mass of the perfluoroether rubber polymer, and then dried at 100° C. for 36 hours to obtain a dry rubber powder; the dry rubber powder is 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 is different from that in Example 1 in that 3 kg of reduced graphene oxide in step (1) is replaced by 3 kg of modified graphene, and 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 for 24 hours under argon conditions to obtain a mixture; then the mixture was washed three times with 1 mol / L hydrochloric acid, and then washed with water and sodium chloride aqueous solution, extracted with ether three times, and then the organic phase was dried with anhydrous magnesium sulfate, filtered, dichloromethane was removed under reduced pressure, and dried to obtain a modifier;

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

[0067] Example 3

[0068] A method for preparing low-temperature resistant perfluoroether rubber is different from that in Example 1 in that 3 kg of reduced graphene oxide in step (1) is replaced by 3 kg of modified graphene, and 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, continue stirring for 24 hours under argon 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, then dry the organic phase with anhydrous magnesium sulfate, filter, remove dichloromethane under reduced pressure, and dry to obtain a modifier;

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

[0071] Comparative Example 1

[0072] The 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 the step (1), that is, the step (1) is: 95 kg of perfluoroether rubber polymer is plasticized evenly on a double-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 evenly 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 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 by 3 kg of graphene oxide, that is, step (1) is: 95 kg of perfluoroether rubber polymer is plasticized evenly 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 evenly to obtain mixed auxiliary materials, and the mixed auxiliary materials are 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 method for preparing 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 test sample: The low-temperature resistant perfluoroether rubber prepared in Examples 1-3 and Comparative Examples 1-3 were respectively subjected to a first-stage vulcanization at 180°C, a vulcanization time of 10 min and a mold pressure of 20 MPa, and the perfluoroether mixed rubber was molded and vulcanized into a standard rubber test piece, and then the first-stage vulcanized product was placed in an oven for a second-stage vulcanization, maintained at 200°C for 2h, then heated to 220°C and maintained for 10h, cooled to 25°C, taken out, and a perfluoroether rubber vulcanization test sample was obtained for standby 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: According to GB / T528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber, tensile tests are carried out at room temperature using a universal testing machine;

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

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

[0088] In the formula, h o is the original height value of the sample before compression, in millimeters (mm); h1 is the height value of the sample after compression, in millimeters (mm); h2 is the height value of the sample after the compression load is removed, 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 Examples 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, wherein the increase in Comparative Example 2 is smaller; the elongation at break of Examples 1-3 and Comparative Example 2-3 decreases, wherein the decrease in Examples 2-3 and Comparative Example 2 is smaller; it indicates that the addition of reduced graphene oxide and modified graphene is beneficial to improving the hardness and tensile strength of perfluoroether rubber, but not to the elongation at break, and 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 anti-shear properties. The reason may be that after the liquid nitrile rubber enters the perfluoroether rubber system, it can effectively provide free volume for the molecular chain segments on the rubber surface, increase the mobility of its molecular chain segments, and weaken the interaction between the molecular chains, so that the relative slip difficulty between the molecular chains is reduced during the stretching process, which leads to an increase in the elongation at break of the perfluoroether rubber. When the 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, which can further increase the free volume between the molecules of the perfluoroether rubber, increase the mobility of the chain segments, and improve 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, so that the internal structure of the perfluoroether rubber forms a more uniform dispersed phase, so that the internal stress can be more evenly dispersed when the perfluoroether rubber is stretched, reducing stress concentration, which is conducive to 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 Examples 1-3 are both higher than 0.2 at -40°C, indicating that there is still recovery ability at -40°C, indicating that adding 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 gradually loses its resilience, 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 coordinated use of modified graphene and liquid nitrile rubber is more conducive to improving the low-temperature resistance of perfluoroether rubber. The reason 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 fluorine atoms and other polar functional groups in perfluoroether rubber polymers, and the surface functionalized modified graphene has increased dispersion and compatibility in the perfluoroether rubber matrix, which enables them to contact and interact with more rubber molecular chains in the rubber matrix. At the same time, there are hydroxyl groups or other polar functional groups on the surface of modified graphene, which can form hydrogen bonds with fluorine atoms in perfluoroether rubber polymers, which is conducive to further enhancing the interaction between modified graphene and perfluoroether rubber molecular chains. Due to the introduction of modified graphene, the enhanced interaction between it and the perfluoroether rubber molecular chain may not only change the original interaction between the perfluoroether rubber molecular chains, but also improve the dispersion of the molecular chain, thereby increasing the flexibility of the perfluoroether rubber molecular chain. This increase in flexibility helps to reduce the glass transition temperature of perfluoroether rubber, 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 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 coordination 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, but also helps to further reduce the difficulty of 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 sheet and the liquid nitrile rubber molecular chain, reducing local stress concentration and improving the low-temperature resistance of the perfluoroether rubber material.

[0095] Test Example 2

[0096] According to the method of Test Example 1, the perfluoroether rubber vulcanized samples of Examples 1-3 and Comparative Examples 1-3 were prepared; the samples of each Example and Comparative Example were cut into rubber sheets of 23 mm×15 mm×2 mm respectively; and then a plasma etching test was performed to detect the plasma etching resistance of the perfluoroether rubber vulcanized samples by 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 rubber sheet surface was free of liquid, the mass was weighed in an analytical balance as m1. The rubber sheet with a clean surface was placed on the reaction table of an ICP etcher (plasma etcher; Beijing Tongjia Hongrui Technology Co., Ltd.) for 1 hour of plasma etching; wherein, 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 60min; after the etching was completed, the rubber sheet was placed in an ultrasonic cleaning agent again for 30min to remove surface particles, and placed in an 80°C oven. After the rubber sheet surface was free of liquid, it was weighed for the second time in 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, and 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] By comparing Examples 1-3 and Comparative Examples 1-3, it can be found that the mass loss rates of Examples 2-3 and Comparative Examples 3 are significantly lower than those of Examples 1 and Comparative Examples 1-2, indicating that the introduction of modified graphene is more conducive to improving the plasma etching resistance of perfluoroether rubber than graphene oxide and reduced graphene oxide; by comparing Examples 2-3 and Comparative Example 3, it can be found that the mass loss rate of Examples 2-3 is lower than that of Comparative Example 3, wherein the mass loss rate of Example 3 is only 2.61%, indicating that the coordinated use of modified graphene and liquid nitrile rubber is more conducive to improving the plasma etching resistance of perfluoroether rubber. The reason for the analysis may be that the two-dimensional sheet structure of modified graphene can form a physical barrier on the surface of perfluoroether rubber, which can prevent particles in the plasma from directly contacting the rubber matrix, and the graphene part in the modified graphene has a high chemical stability, so it can be used as a protective layer to protect the rubber matrix, thereby reducing the erosion of the rubber matrix by plasma. At the same time, in the surface functionalized modified graphene structure, the carbonyl C=O is connected to the benzene ring, 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 plasma on the -CF2- bond in the rubber macromolecular chain, protects the polymer, and thus reduces the etching of the rubber by the plasma. At the same time, the present invention introduces liquid nitrile rubber and modified graphene to prepare perfluoroether rubber in coordination, and the liquid nitrile 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 nitrile 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 free radicals on the -CF2- bond in the rubber macromolecular chain, 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 process of modifying graphene, the plasma etching resistance of Example 3 is better than that of Example 2 of the additive 9,10-dioxo-9,10-dihydro-anthracene-2,6-dicarboxylic acid used in the process of modifying graphene, 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 plasma, protect the fluororubber macromolecular chain, and reduce the ability of plasma to etch 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 in its structure. 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 than carboxyl groups to form free radicals, which makes 5,8-dihydroxy-9,10-dioxo-9,10-dihydroanthracene-2-carboxylic acid-modified graphene more active when reacting with free radicals in 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: 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 crosslinking agents, 1-4 parts of accelerators, 1-3 parts of processing aids, and 1-3 parts of acid absorbents; The additive is selected from one of reduced graphene oxide and modified graphene.

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 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; the processing aid is one or more of Tecnoflon FPA, HT290, fluorowax, liquid nitrile rubber, low molecular weight polyethylene, zinc stearate, and palm wax; and the acid absorber is 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: The steps of adding water, pH buffer and emulsifier into a reaction kettle, evacuating the reactor and controlling the oxygen content in the reactor to ≤20ppm with nitrogen, raising the temperature of the reactor to 80-120°C; introducing tetrafluoroethylene and perfluoroalkoxy vinyl ether into the reactor until the pressure in the reactor reaches 3-4MPa, adding functionalized perfluoroolefin, halogenated perfluoroalkane and initiator, and then carrying out the first step of emulsion polymerization at a reactor temperature of 80-120°C for 10h-20h, recovering unreacted monomers, and obtaining the first step of emulsion; introducing tetrafluoroethylene and perfluoropropyl vinyl ether into the reactor until the pressure in the reactor reaches 3 -4MPa, adding an initiator, and carrying out 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; carrying out an 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 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 from 1 to 6, and m is an integer from 0 to 5; The perfluoroalkoxy vinyl ether is perfluoromethoxy vinyl ether.

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 perfluoroolefin, iodinated perfluoroolefin and nitrile-containing perfluoroolefin; 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 perfluoroalkane and iodinated perfluoroalkane; 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 30-70wt% oxidant and 30-70wt% reductant; the oxidant is persulfate; the reductant is selected from at least one of sulfite and thiosulfate; the added amount of the initiator 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; the detergent is selected from at least one of water, acetone, ethyl acetate, methanol, ethanol and toluene.

8. The low temperature resistant perfluoroether rubber according to claim 1, characterized in that: The preparation method of the modified graphene comprises the following steps, measured 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 0.25-0.3 parts of additives under ice-salt bath conditions, continue stirring for 22-25 hours under argon conditions 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, then dry the organic phase with anhydrous magnesium sulfate, filter, remove dichloromethane under reduced pressure, and dry to obtain a modifier; b. Under argon, add 0.04-0.06 parts of reduced graphene oxide to 8-9 parts of dry N,N-dimethylacetamide for ultrasonic dispersion for 0.5-1.5h, then add 0.02-0.1 parts of the modifier obtained in step a, and continue stirring and refluxing at 160-170°C and argon for 22-25h 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.

9. The low temperature resistant perfluoroether rubber according to claim 8, characterized in that: In the step a, the additive 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.

10. The method for preparing the low-temperature resistant perfluoroether rubber according to any one of claims 1 to 9, characterized in that: The following steps are involved: (1) uniformly plasticizing a perfluoroether rubber polymer on a two-roll mill and rolling it, then pre-mixing an additive, an accelerator, a filler, a cross-linking agent, a processing aid and an acid absorbent to obtain a mixed auxiliary material, and gradually adding the mixed auxiliary material 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 wrapped on the roller is cut 5-10 times on each side, the roller distance of the mixing mill is adjusted to the minimum, and the rolling or triangle packing is performed 8-12 times. The entire mixing time is controlled between 15-20 minutes, and the roller temperature of the mixing mill 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; (3) The prepared perfluoroether rubber compound is aged for 15-20 hours, and then re-refined for 8-12 times by rolling or triangle packing, and then produced into sheets for standby use, thereby obtaining a low-temperature resistant perfluoroether rubber.

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