Preparation method of high-temperature-resistant perfluoroether elastomer composition

Abstract

The invention provides a preparation method of a high-temperature-resistant perfluoroether elastomer composition, which is applied to the technical field of perfluoroether elastomers and comprises the following steps: S1, cross-linking or grafting multi-walled carbon nanotube modified polyamide acid and a vulcanization point monomer to obtain cross-linked or grafted multi-walled carbon nanotube modified polyimide; s2, carrying out emulsion polymerization reaction on the cross-linked or grafted multi-walled carbon nanotube modified polyimide, a vulcanization point monomer and a copolymerized fluorine-containing monomer to obtain a perfluoroether elastomer composite emulsion; s3, condensing, washing and drying the perfluoroether elastomer composite emulsion to obtain a modified perfluoroether elastomer; s4, the modified perfluoroether elastomer is subjected to mixing, thin passing, compression molding and second-stage vulcanization, and the high-temperature-resistant perfluoroether elastomer composition is obtained. The polyamic acid and the copolymerized fluorine-containing monomer are fully combined in a cross-linking grafting manner, and the polyimide can effectively improve the high temperature resistance of the modified perfluoroether elastomer composition.

Description

Technical Field

[0001] The present application relates to the technical field of perfluoroether elastomers, and in particular to a method for preparing a high temperature resistant perfluoroether elastomer composition. Background Art

[0002] Fluorine is the element with the strongest electronegativity and the highest degree of oxidation of all known chemical elements. Perfluoroether elastomer contains tetrafluoroethylene (TFE) and other fluorinated monomer units, and all hydrogen atoms on its main chain or side chain are replaced by fluorine atoms. Therefore, perfluoroether elastomer has high chemical stability and is difficult to be oxidized and decomposed. It has the best media resistance among all elastomers. Its products are widely used in sealing and other harsh environments, as well as terminal applications requiring high purity.

[0003] As technology advances, the requirements for sealing materials are becoming more and more stringent. In the fields of aviation, downhole oil drilling, aerospace, semiconductors, and chemicals and pharmaceuticals, existing sealing materials continue to play a role in increasingly harsh chemical environments, but as the application environment temperature becomes higher and higher, such as above 300°C, the ability of perfluoroether elastomer compositions to withstand high temperature environments becomes increasingly important.

[0004] Typical fillers used in semiconductor and other industries to enhance mechanical properties while maintaining chemical and / or plasma resistance of perfluoroether elastomer compositions include carbon black, silica, alumina, TFE-based fluoroplastics, barium sulfate and other polymers. Sometimes, a mixture of one or more perfluoroether elastomer compositions is also used to achieve different properties, meeting higher heat resistance while maintaining chemical resistance, plasma resistance, and not sacrificing mechanical and sealing properties.

[0005] The use of fluoropolymer fillers limits the moldability and adhesion of perfluoroether elastomer compositions and has a relatively high negative impact on compression set, especially in end-use applications at higher temperatures (eg, above 300° C.).

[0006] For this purpose, various polymers with unique crosslinking systems have been developed to improve the heat resistance of perfluoroether elastomer compositions. For example, US6855774B2 discloses a crosslinking structure that helps improve heat resistance. US6878778B1 further develops crosslinking agents that give the terminal material excellent chemical resistance and mechanical strength as well as heat resistance at high temperatures.

[0007] Mixed perfluoroether elastomers have also been developed to achieve unique properties. US8367776B2 describes a composition of such a polymer and a composition with one or more additional perfluoroether elastomers, wherein the two perfluoroether elastomers in the composition differ in perfluoroalkyl vinyl ether (PAVE) monomer content by about 5 to about 25 mol%. Under certain conditions, these compositions can replace plastic fillers and in some cases are improvements over plastic filler materials. Such mixtures are crack resistant in the presence of harsh chemicals and have good heat and plasma resistance.

[0008] Some existing technologies attempt to prepare elastomer compositions suitable for high temperature environments by giving polymers certain specific functional groups through complex chemical reactions. Because the polymer is fixed during the synthesis stage, this method limits the ability to customize the crosslink density, and it is necessary to develop technologies with more flexibility to allow customization of terminal materials for different uses.

[0009] Based on this, it is necessary to provide a high temperature resistant fluoroelastomer material to meet application requirements. Summary of the invention

[0010] In view of this, the present specification provides a method for preparing a high temperature resistant perfluoroether elastomer composition to improve the high temperature resistance of the fluoroelastomer composition.

[0011] This specification provides the following technical solution: a method for preparing a high temperature resistant perfluoroether elastomer composition, comprising:

[0012] S1, 9-12 parts by weight of multi-walled carbon nanotube-modified polyamic acid and 0.24-1.55 parts by weight of a vulcanization site monomer are cross-linked or grafted to obtain a cross-linked or grafted multi-walled carbon nanotube-modified polyimide;

[0013] S2, carrying out emulsion polymerization reaction of the cross-linked or grafted multi-walled carbon nanotube-modified polyimide with 0.24-1.55 parts by mass of a vulcanization point monomer and 100 parts by mass of a copolymerized fluorine-containing monomer to obtain a perfluoroether elastomer composite emulsion;

[0014] S3, coagulating, washing and drying the perfluoroether elastomer composite emulsion to obtain a modified perfluoroether elastomer;

[0015] S4, mixing, thin-passing, compression molding and two-stage vulcanization of the modified perfluoroether elastomer to obtain a high temperature resistant perfluoroether elastomer composition.

[0016] Optionally, the polyamic acid and the multi-walled carbon nanotubes undergo a dehydration reaction of -COOH under alkaline conditions to generate polyamic acid modified with the multi-walled carbon nanotubes.

[0017] Optionally, the method for preparing the multi-walled carbon nanotube-modified polyamic acid comprises:

[0018] The polyamic acid is generated by polycondensation reaction of pyromellitic anhydride and 4,4'-diaminodiphenyl ether in dimethylacetamide; and the polyamic acid reacts with multi-walled carbon nanotubes to generate polyamic acid modified by multi-walled carbon nanotubes.

[0019] Optionally, the S1 includes:

[0020] S1-1, the multi-walled carbon nanotube-modified polyamic acid undergoes a dehydration reaction of -COOH under alkaline conditions to generate a multi-walled carbon nanotube-modified polyimide; S1-2, the multi-walled carbon nanotube-modified polyimide sulfide monomers are cross-linked or grafted to obtain a cross-linked or grafted multi-walled carbon nanotube-modified polyimide.

[0021] Optionally, the cure site monomer is a crosslinkable compound containing a nitrile group and a fluorovinyl group.

[0022] Optionally, the sulfurization site monomer is perfluoro-8-cyano-5-methyl-3,6-dioxa-1-octene.

[0023] Optionally, the mass ratio of tetrafluoroethylene to perfluoromethyl vinyl ether in the copolymerized fluorine-containing monomer is (55-70):(30-45).

[0024] Optionally, the mass proportion of the multi-walled carbon nanotubes in the multi-walled carbon nanotube-modified polyamic acid is 1.5-10%.

[0025] Optionally, a carbon-containing filler is added during the mixing process, wherein the carbon-containing filler is 1-6 parts by mass.

[0026] Optionally, the carbon-containing filler is polyimide and / or multi-walled carbon nanotube.

[0027] Optionally, in S1, the multi-walled carbon nanotube-modified polyamic acid is cross-linked or grafted with a vulcanization point monomer via a catalyst, and the catalyst is 0.2-0.6 parts by mass.

[0028] Optionally, the catalyst is a weakly alkaline salt, and the catalyst is one of sodium bicarbonate, sodium carbonate, sodium sulfite, and ammonium sulfite.

[0029] Optionally, the aspect ratio of the multi-walled carbon nanotubes is 500-1000:1.

[0030] Optionally, the carboxyl content of the multi-walled carbon nanotube-modified polyamic acid is 0.5 wt %-3 wt %.

[0031] Compared with the prior art, the beneficial effects that can be achieved by at least one of the above technical solutions adopted in this specification include at least:

[0032] The carboxyl groups on the low-carboxyl polyamic acid and multi-walled carbon nanotubes of the present invention react with the nitrile group -CN in the vulcanization point monomer, and the vulcanization point monomer is further added to crosslink and vulcanize it with the copolymerized fluorine-containing monomer during emulsion polymerization, so that the multi-walled carbon nanotube-modified polyimide and the copolymerized fluorine-containing monomer are fully combined with each other in a cross-linking and grafting manner through the vulcanization point monomer, which can effectively improve the high temperature resistance of the modified perfluoroether elastomer composition. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0034] Figure 1 This is a process flow chart of a method for preparing a high temperature resistant perfluoroether elastomer composition of the present application;

[0035] Figure 2 The present invention discloses a reaction flow chart of a method for preparing a multi-walled carbon nanotube-modified polyimide. DETAILED DESCRIPTION

[0036] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0037] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0038] It should be noted that various aspects of the embodiments within the scope of protection of the present invention are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspect described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0039] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the examples can be practiced without these specific details.

[0040] Based on this, the present specification proposes a method for preparing a high temperature resistant perfluoroether elastomer composition: Figure 1 Shown, including

[0041] S1, 9-12 parts by weight of multi-walled carbon nanotube-modified polyamic acid and 0.24-1.55 parts by weight of a vulcanization site monomer are cross-linked or grafted to obtain a cross-linked or grafted multi-walled carbon nanotube-modified polyimide;

[0042] S2, carrying out emulsion polymerization reaction of the cross-linked or grafted multi-walled carbon nanotube-modified polyimide with 0.24-1.55 parts by mass of a vulcanization point monomer and 100 parts by mass of a copolymerized fluorine-containing monomer to obtain a perfluoroether elastomer composite emulsion;

[0043] The reaction system is an amine vulcanization system, which uses a nitrile-containing vulcanization point monomer, tetraphenyltin or 18-crown ether-6 (chemical name is hexaoxacyclooctadecane) as a vulcanization system catalyst;

[0044] S3, coagulating, washing and drying the perfluoroether elastomer composite emulsion to obtain a modified perfluoroether elastomer;

[0045] S4, mixing, thin-passing, compression molding and two-stage vulcanization of the modified perfluoroether elastomer to obtain a high temperature resistant perfluoroether elastomer composition;

[0046] A carbon-containing filler is added during the mixing process, wherein the carbon-containing filler is 1-6 parts by mass and is polyimide and / or multi-walled carbon nanotubes; the vulcanization point monomer is a cross-linkable compound containing a nitrile group and a fluorovinyl group; and the high temperature resistance refers to a temperature resistance higher than 330°C.

[0047] The carbon-containing filler in S4 includes at least one of carbon nanotubes, carbon black and graphene;

[0048] The high temperature resistant resin includes at least one of polyetherimide PEI, polybenzimidazole PBI, polyetheretherketone PEEK, polyphenylene sulfide PPS, polyimide PI and polyamide-imide PAI.

[0049] The carboxyl groups in the low-carboxyl polyamic acid provide reaction sites to react with the vulcanization point monomers, and the copolymerized fluorinated monomers are coupled and grafted together with the vulcanization point monomers, so that the polyamic acid and the copolymerized fluorinated monomers are fully combined in a cross-linked grafting manner, and the polyimide can effectively improve the high temperature resistance of the modified perfluoroether elastomer composition.

[0050] In S1, the vulcanization site monomer may be a cross-linkable compound containing a nitrile group and a fluorovinyl group. For example, the vulcanization site monomer is perfluoro-8-cyano-5-methyl-3,6-dioxa-1-octene. The mass proportion of multi-walled carbon nanotubes in the multi-walled carbon nanotube-modified polyamic acid is 1.5-10%.

[0051] The multi-walled carbon nanotube-modified polyamic acid undergoes a dehydration reaction of -COOH under alkaline conditions to generate a multi-walled carbon nanotube-modified polyimide; the multi-walled carbon nanotube-modified polyimide is cross-linked or grafted with a sulfurization point monomer to obtain a cross-linked or grafted multi-walled carbon nanotube-modified polyimide.

[0052] The copolymerized fluorine-containing monomer comprises TFE and PMVE, wherein the mass ratio of TFE to PMVE in the copolymerized fluorine-containing monomer is (55-70):(30-45), wherein TFE is tetrafluoroethylene and PMVE is perfluoromethyl vinyl ether.

[0053] In one embodiment, S1 includes the following steps:

[0054] S1-1, the multi-walled carbon nanotube-modified polyamic acid undergoes a dehydration reaction of -COOH under alkaline conditions to generate a multi-walled carbon nanotube-modified polyimide.

[0055] The thermal ring-closing imidization method can be used first, for example, thermal imidization is carried out at a temperature greater than 120°C. The main reaction equation is

[0056] S1-2, the multi-walled carbon nanotube-modified polyimide sulfuration point monomer is cross-linked or grafted to obtain a cross-linked or grafted multi-walled carbon nanotube-modified polyimide.

[0057] The reaction conditions for crosslinking or grafting can be 30-60° C. or 180-220° C. in the vulcanization stage, wherein tetraphenyltin or 18-crown ether-6 (chemical name: hexaoxacyclooctadecane) is used as a catalyst for the vulcanization system.

[0058] A carbon-containing filler is added during the mixing process, wherein the carbon-containing filler is 1-6 parts by mass, and the carbon-containing filler is polyimide and / or multi-walled carbon nanotubes. In one embodiment, when the carbon-containing filler is polyimide and multi-walled carbon nanotubes, the polyimide and multi-walled carbon nanotubes can be reacted to generate micropowders, and the mass of the multi-walled carbon nanotubes is 1.5-10% of the polyimide; and then the micropowders are directly mixed with the multi-walled carbon nanotubes / polyimide and added during the mixing process. In one embodiment, when the carbon-containing filler is polyimide and multi-walled carbon nanotubes, the polyimide and multi-walled carbon nanotubes can also be directly added during the mixing process, and at this time, there is no specific ratio between polyimide and multi-walled carbon nanotubes. Polyimide and multi-walled carbon nanotubes are reaction-coupled, and have better dispersibility than simple addition, and have good compatibility with elastomers.

[0059] In S1, the multi-walled carbon nanotube-modified polyamic acid is cross-linked or grafted with a sulfide point monomer through a catalyst, the catalyst is 0.2-0.6 parts by mass, the catalyst is a weakly alkaline salt, the catalyst is used to dehydrate the multi-walled carbon nanotube-modified polyamic acid, and the dehydration treatment can also be achieved by high-temperature heating treatment, and the catalyst is one of sodium bicarbonate, sodium carbonate, sodium sulfite, and ammonium sulfite.

[0060] The aspect ratio of the multi-walled carbon nanotubes is 500-1000:1.

[0061] The carboxyl content of the polyamic acid modified by the multi-walled carbon nanotubes is 0.5wt%-3.5wt%. Part of the carboxyl groups from the polyamic acid and the multi-walled carbon nanotubes react with the vulcanization point monomer, and the vulcanization point monomer is further added in the next step to make it cross-link with the fluorine-containing monomers TFE and PMVE. The vulcanization point monomer added in S1 improves the binding property of the multi-walled carbon nanotube-modified polyimide and the perfluoroether elastomer and the dispersibility of the multi-walled carbon nanotubes in the modified polyimide, thereby effectively improving the high temperature resistance of the perfluoroether elastomer composition.

[0062] In one embodiment, a method for preparing a polyamic acid modified with multi-walled carbon nanotubes comprises the following steps:

[0063] Step 1: Carboxylation-modified multi-walled carbon nanotubes modified by pyromellitic dianhydride undergo condensation reaction with 4,4'-diaminodiphenyl ether in dimethylacetamide to generate polyamic acid, and then remove water to generate multi-walled carbon nanotube 4-aminodiphenyl ether.

[0064]

[0065]

[0066] Step 2: 4-aminodiphenyl ether pyromellitic dianhydride (PMDA) and 4,4'-diaminodiphenyl ether (ODA) can be polycondensed in dimethylacetamide (DMAc) at room temperature to generate polyamic acid. The specific reaction formula can be: the polyamic acid and multi-walled carbon nanotubes react to generate multi-walled carbon nanotube-modified polyamic acid.

[0067] The polyamic acid and multi-walled carbon nanotubes can react at 30-80°C for 2-6 hours to generate polyamic acid modified with multi-walled carbon nanotubes. The specific reaction equation is:

[0068]

[0069] In one embodiment, Figure 2 As shown in S1, g-MWNTs -H -PI is synthesized by the following steps,

[0070] Step a), carboxylate high aspect ratio multi-walled carbon nanotubes (MWNTs -COOH-H ) was ultrasonically dispersed in a polar solvent containing a water absorbent, diaminodiphenyl ether (ODA) and p-phenylenediamine (p-PDA) were added, and then dianhydride pyromellitic dianhydride (PMDA) was added stepwise according to a certain molar ratio, and stirred at no more than 25°C for a certain period of time to obtain polyamic acid PAA (MWNTs) modified with high aspect ratio multi-walled carbon nanotubes. -H The polar solvent may be at least one of N,N-dimethylacetamide (DMAC), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO).

[0071] The sum of the amine moles of ODA and p-PDA is m1;

[0072] PMDA and MWNTs -COOH-H The sum of the moles of anhydride and carboxyl -COOH is m2;

[0073] m1:m2=1:1.02-1.06.

[0074] Step b), diluting MWNTs with polar solvent -H -PAA solution, filtering to remove the water absorbent, spray granulation, forming microparticles in a precipitant, washing, and vacuum drying; heating the dried product to control the dehydration temperature to about 110°C to partially close the ring imidization, and naturally cooling to room temperature to obtain low-carboxyl high aspect ratio multi-walled carbon nanotube modified PAA (MWNTs- H -PAA- COOH-L). The water absorbent may be a 4A molecular sieve or a 3A molecular sieve. The precipitant may be at least one of water, ethanol and methanol. Before spraying, the solution is diluted with a polar solvent to a solid content of 5-15%; the spray granulation pressure is 0.5-10MPa; the PAA particle size range is 0.01μm-0.1μm. In one embodiment, the vacuum drying temperature is lower than 80°C, and then the temperature is raised to 110°C and dried for 4h. The drying temperature is controlled to be lower than 120°C. The purpose is to retain some of the -COOH functional groups of PAA, that is, to form PAA containing a low carboxyl group (PAA-COOH-L), which is used to form a cross-linking reaction with the third monomer for synthesizing the perfluoroether elastomer.

[0075] Step c), PAA (MWNTs containing low carboxyl groups) is catalyzed by ammonium sulfite in DMAC solution. -H -PAA -COOH-L ) is cross-linked and / or grafted with the vulcanization site monomer of the synthetic perfluoroether elastomer to generate a hydrophobic cross-linked high aspect ratio multi-walled carbon nanotube modified polyimide PI (g-MWNTs -H -PI) particles (A). The amount of the vulcanization point monomer is not only used for grafting perfluoroether elastomer, but also for catalytic reaction with PAA-COOH-L to complete the dehydration ring-closing imidization of PAA.

[0076] The catalyst is one of sodium bicarbonate, sodium carbonate, sodium sulfite and ammonium sulfite.

[0077] The acid absorber is one of zinc oxide, magnesium oxide and calcium oxide, or no acid absorber is added.

[0078] The sources of the reagents in the above steps are as follows:

[0079] BIPB, Hubei Mackays Fine Chemical Technology Co., Ltd.;

[0080] TAIC, Shanghai Tuojing New Materials Technology Co., Ltd.;

[0081] Nano ZnO, Shanghai Yaotian New Materials Technology Co., Ltd.;

[0082] 4,4′-Diaminodiphenyl ether (ODA): industrial grade, Nantong Huishun Chemical Co., Ltd.; used after purification;

[0083] Pyromellitic dianhydride (PMDA): industrial grade, Rugao Leheng Chemical Co., Ltd.; used after purification;

[0084] 3,3′,4,4′-Biphenyltetracarboxylic dianhydride (BPDA): industrial grade, Shijiazhuang Haili Refining Chemical Co., Ltd.; used after purification;

[0085] Carboxylated long multi-walled carbon nanotubes (MWNTs -COOH-L): carboxyl content 2%, diameter 20-30nm, length 10-30μm, purity>98%, Chengdu Organic Chemistry Co., Ltd., Chinese Academy of Sciences; aspect ratio is about 850;

[0086] N,N′-Dimethylacetamide (DMAc): analytical grade, Tianjin Yongda Chemical Reagent Co., Ltd.

[0087] Example 1

[0088] S1: 119 g of multi-walled carbon nanotube-modified polyamic acid and 10.2 g of a sulfurization point monomer are cross-linked or grafted to obtain a cross-linked or grafted multi-walled carbon nanotube-modified polyimide.

[0089] S2: The cross-linked or grafted multi-walled carbon nanotube-modified polyimide is subjected to emulsion polymerization with 4.5 g of a vulcanization point monomer and a copolymerized fluorine-containing monomer to obtain a perfluoroether elastomer composite emulsion, wherein the copolymerized fluorine-containing monomer includes 695.0 g of TFE and 290.5 g of PMVE.

[0090] S3, coagulating, washing and drying the perfluoroether elastomer composite emulsion to obtain a modified perfluoroether elastomer;

[0091] S4, mixing the modified perfluoroether elastomer with 48g of carbon-containing filler, thin-passing, compression molding and two-stage vulcanization to obtain a high-temperature resistant perfluoroether elastomer composition.

[0092] The vulcanization point monomer is perfluoro-8-cyano-5-methyl-3,6-dioxa-1-octene, the carbon-containing filler includes polyimide and multi-walled carbon nanotubes, and the mass of the multi-walled carbon nanotubes is 3.5% of that of the polyimide.

[0093] In S1, the polyamic acid modified with multi-walled carbon nanotubes is cross-linked or grafted with a sulfurization point monomer by sodium bicarbonate catalysis, and the mass of the sodium bicarbonate is 6 g. The mass proportion of the multi-walled carbon nanotubes in the polyamic acid modified with multi-walled carbon nanotubes is 4.0%. The carboxyl content of the polyamic acid modified with multi-walled carbon nanotubes is 2.92wt%.

[0094] The aspect ratio of multi-walled carbon nanotubes is 500-1000:1.

[0095] Example 2

[0096] S1: crosslinking or grafting 119 g of multi-walled carbon nanotube-modified polyamic acid with 9.6 g of a sulfurization point monomer to obtain a crosslinked or grafted multi-walled carbon nanotube-modified polyimide;

[0097] S2: The cross-linked or grafted multi-walled carbon nanotube-modified polyimide is subjected to emulsion polymerization with 15.0 g of a vulcanization point monomer and a copolymerized fluorine-containing monomer to obtain a perfluoroether elastomer composite emulsion, wherein the copolymerized fluorine-containing monomer includes 663.9 g of TFE and 336.1 g of PMVE.

[0098] S3, coagulating, washing and drying the perfluoroether elastomer composite emulsion to obtain a modified perfluoroether elastomer;

[0099] S4, mixing the modified perfluoroether elastomer with 60g of carbon-containing filler, thin-passing, compression molding and two-stage vulcanization to obtain a high-temperature resistant perfluoroether elastomer composition.

[0100] The vulcanization point monomer is perfluoro-8-cyano-5-methyl-3,6-dioxa-1-octene, the carbon-containing filler includes polyimide and multi-walled carbon nanotubes, and the mass of the multi-walled carbon nanotubes is 8% of that of the polyimide.

[0101] In S1, the polyamic acid modified with multi-walled carbon nanotubes is cross-linked or grafted with a sulfurization point monomer by sodium bicarbonate catalysis, and the mass of the sodium bicarbonate is 6 g. The mass proportion of the multi-walled carbon nanotubes in the polyamic acid modified with multi-walled carbon nanotubes is 10.0%. The carboxyl content of the polyamic acid modified with multi-walled carbon nanotubes is 2.92 wt%.

[0102] The aspect ratio of multi-walled carbon nanotubes is 500-1000:1.

[0103] Example 3

[0104] S1: crosslinking or grafting 95 g of multi-walled carbon nanotube-modified polyamic acid with 15.0 g of a vulcanization point monomer to obtain a crosslinked or grafted multi-walled carbon nanotube-modified polyimide;

[0105] S2: The cross-linked or grafted multi-walled carbon nanotube-modified polyimide is subjected to emulsion polymerization with 15.0 g of a vulcanization point monomer and a copolymerized fluorine-containing monomer to obtain a perfluoroether elastomer composite emulsion, wherein the copolymerized fluorine-containing monomer includes 656.1 g of TFE and 343.9 g of PMVE.

[0106] S3, coagulating, washing and drying the perfluoroether elastomer composite emulsion to obtain a modified perfluoroether elastomer;

[0107] S4, mixing the modified perfluoroether elastomer with 15g of carbon-containing filler, thin-passing, compression molding and two-stage vulcanization to obtain a high-temperature resistant perfluoroether elastomer composition.

[0108] The vulcanization point monomer is perfluoro-8-cyano-5-methyl-3,6-dioxa-1-octene, the carbon-containing filler includes polyimide and multi-walled carbon nanotubes, and the mass of the multi-walled carbon nanotubes is 3.5% of that of the polyimide.

[0109] In S1, the polyamic acid modified with multi-walled carbon nanotubes is cross-linked or grafted with a sulfurization point monomer by sodium bicarbonate catalysis, wherein the mass of the sodium bicarbonate is 5 g. The mass proportion of the multi-walled carbon nanotubes in the polyamic acid modified with multi-walled carbon nanotubes is 2.0%, and the carboxyl content of the polyamic acid modified with multi-walled carbon nanotubes is 2.92 wt%.

[0110] The aspect ratio of multi-walled carbon nanotubes is 500-1000:1.

[0111] Example 4

[0112] S1: crosslinking or grafting 119 g of multi-walled carbon nanotube-modified polyamic acid with 1.2 g of a sulfurization point monomer to obtain a crosslinked or grafted multi-walled carbon nanotube-modified polyimide;

[0113] S2: The cross-linked or grafted multi-walled carbon nanotube-modified polyimide is subjected to emulsion polymerization with 4.5 g of a vulcanization point monomer and a copolymerized fluorine-containing monomer to obtain a perfluoroether elastomer composite emulsion, wherein the copolymerized fluorine-containing monomer includes 573.4 g of TFE and 426.6 g of PMVE.

[0114] S3, coagulating, washing and drying the perfluoroether elastomer composite emulsion to obtain a modified perfluoroether elastomer;

[0115] S4, mixing, thin-passing, compression molding and two-stage vulcanization of the modified perfluoroether elastomer to obtain a high-temperature resistant perfluoroether elastomer composition.

[0116] The curing site monomer is perfluoro-8-cyano-5-methyl-3,6-dioxa-1-octene.

[0117] In S1, the polyamic acid modified with multi-walled carbon nanotubes is cross-linked or grafted with a sulfide monomer by sodium bicarbonate catalysis, and the mass of the sodium sulfite is 6 g. The mass proportion of the multi-walled carbon nanotubes in the polyamic acid modified with multi-walled carbon nanotubes is 6.0%, and the carboxyl content of the polyamic acid modified with multi-walled carbon nanotubes is 2.92 wt%.

[0118] The aspect ratio of multi-walled carbon nanotubes is 500-1000:1.

[0119] Example 5

[0120] S1: crosslinking or grafting 95 g of multi-walled carbon nanotube-modified polyamic acid with 1.2 g of a sulfurization point monomer to obtain a crosslinked or grafted multi-walled carbon nanotube-modified polyimide;

[0121] S2: The cross-linked or grafted multi-walled carbon nanotube-modified polyimide is subjected to emulsion polymerization with 1.2 g of a vulcanization point monomer and a copolymerized fluorine-containing monomer to obtain a perfluoroether elastomer composite emulsion, wherein the copolymerized fluorine-containing monomer includes 567.1 g of TFE and 432.9 g of PMVE.

[0122] S3, coagulating, washing and drying the perfluoroether elastomer composite emulsion to obtain a modified perfluoroether elastomer;

[0123] S4, mixing, thin-passing, compression molding and two-stage vulcanization of the modified perfluoroether elastomer to obtain a high temperature resistant perfluoroether elastomer composition.

[0124] The vulcanization point monomer is perfluoro-8-cyano-5-methyl-3,6-dioxa-1-octene, the carbon-containing filler includes polyimide and multi-walled carbon nanotubes, and the mass of the multi-walled carbon nanotubes is 2.5% of that of the polyimide.

[0125] In S1, the polyamic acid modified with multi-walled carbon nanotubes is cross-linked or grafted with a sulfurization point monomer by sodium bicarbonate catalysis, and the mass of the sodium bicarbonate is 3 g. The mass proportion of the multi-walled carbon nanotubes in the polyamic acid modified with multi-walled carbon nanotubes is 8.0%. The carboxyl content of the polyamic acid modified with multi-walled carbon nanotubes is 2.92 wt%.

[0126] The aspect ratio of multi-walled carbon nanotubes is 500-1000:1.

[0127] In S1 of Examples 1 to 5, g-MWNTs -H -PI is synthesized by the following steps:

[0128] Step a), carboxylate high aspect ratio multi-walled carbon nanotubes (MWNTs -COOH-H ) was ultrasonically dispersed in a DMAC solvent containing 4A molecular sieves, diaminodiphenyl ether (ODA) and p-phenylenediamine (p-PDA) were added, and then dianhydride pyromellitic dianhydride (PMDA) was added stepwise according to a certain molar ratio, and stirred at no more than 25°C for a certain period of time to obtain polyamic acid PAA (MWNTs) modified with high aspect ratio multi-walled carbon nanotubes. -H -PAA) solution;

[0129] Assume that the sum of the amine moles of ODA and p-PDA is m1, PMDA and MWNTs -COOH-H The sum of the moles of anhydride and -COOH groups is m2, then m1:m2=1:1.05.

[0130] The two-step method is a relatively mature method for preparing polyimide. First, dianhydride and diamine monomers react in a non-protonic solvent (DMAC or NMP, etc.) to form polyamic acid PAA, and then heat treatment or addition of catalysts to obtain polyimide through chemical cyclization. However, since polyamic acid is unstable, sensitive to water vapor, and easily decomposed, its viscosity decreases, affecting the molecular weight, and finally having a certain impact on the performance, so the drugs and experimental instruments must be pre-treated before the experiment.

[0131] Since dimethylformamide is unstable in the presence of strong bases such as sodium hydroxide or strong acids such as hydrochloric acid or sulfuric acid (especially at high temperatures), and is hydrolyzed into formic acid and dimethylamine, a room temperature catalytic reaction is adopted, and the catalyst is a weak alkaline inorganic salt, such as sodium bicarbonate, sodium carbonate, sodium sulfite, and ammonium sulfite.

[0132] The present invention selects diamine 4,4'-diaminodiphenyl ether (ODA), p-phenylenediamine (p-PDA) and dianhydride pyromellitic dianhydride (PMDA) as copolymer monomers. The second diamine is introduced to destroy the molecular structure symmetry and repeat regularity of polyimide and improve its elasticity.

[0133] Step b), diluting MWNTs with polar solvent -H -PAA solution, filter to remove the water absorbent, spray granulate, precipitate in an aqueous solution containing 50% ethanol to form microparticles, filter and wash, vacuum dry at 80°C; heat to 110°C and dry for 4h to partially close the ring imidization, and cool naturally to room temperature;

[0134] Step c), PAA (MWNTs containing low carboxyl groups) is catalyzed by ammonium sulfite in a polar solution. -H -PAA -COOH-L ) is cross-linked and / or grafted with the curing point monomer 8-CNVE of the synthetic perfluoroether elastomer to generate a hydrophobic cross-linked high aspect ratio multi-walled carbon nanotube modified polyimide (g-MWNTs -H -PI) microparticles (A).

[0135] Comparative Example 1

[0136] S1: subjecting copolymerized fluorinated monomers to emulsion polymerization to obtain a perfluoroether elastomer composite emulsion, wherein the copolymerized fluorinated monomers include 687.3 g of TFE and 297.6 g of PMVE, and 2.4 g of a vulcanization point monomer.

[0137] The curing site monomer is perfluoro-8-cyano-5-methyl-3,6-dioxa-1-octene.

[0138] S2, coagulating, washing and drying the perfluoroether elastomer composite emulsion to obtain a modified perfluoroether elastomer;

[0139] S3, mixing the modified perfluoroether elastomer with 65g of carbon-containing filler, thin-passing, compression molding and two-stage vulcanization to obtain a high-temperature resistant perfluoroether elastomer composition. The carbon-containing filler includes polyimide and multi-walled carbon nanotubes, and the mass of the multi-walled carbon nanotubes is 2.5% of the mass of the polyimide.

[0140] Comparative Example 2

[0141] S1: The copolymerized fluorinated monomers are subjected to emulsion polymerization to obtain a perfluoroether elastomer composite emulsion, wherein the copolymerized fluorinated monomers include 634.3 g TFE and 336.1 g PMVE, and 2.4 g vulcanization point monomer.

[0142] The curing site monomer is perfluoro-8-cyano-5-methyl-3,6-dioxa-1-octene.

[0143] S2, coagulating, washing and drying the perfluoroether elastomer composite emulsion to obtain a modified perfluoroether elastomer;

[0144] S3, mixing, thin-passing, compression molding and two-stage vulcanization of the modified perfluoroether elastomer to obtain a high-temperature resistant perfluoroether elastomer composition.

[0145] Table 1 Main test results of the examples and comparative examples of this application

[0146]

[0147] During the compression set experiments in Comparative Examples 1 and 2, the elastomers were broken under high-temperature extrusion conditions, resulting in experimental failure.

[0148] The compression set is not much different at a low temperature of 200°C, and the range of Examples 1-5 is 19%-25%; but when the temperature is increased to 250°C, the corresponding range of change increases to 22%-33%; and when the temperature continues to increase to 300°C, Examples 4 and 5 fail, indicating that the filler plays a great role in promoting the compression set to a certain extent, and the corresponding range of change of Examples 1-3 is 28%-33%.

[0149] By comparing the example in Table 1 with the comparative example 1, it can be seen that the present application adds the vulcanization point monomer in stages, which can effectively improve the high temperature resistance of the copolymerized fluorine-containing monomer.

[0150] In this specification, the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the embodiments described later, the description is relatively simple, and the relevant parts can be referred to the partial description of the previous embodiments.

[0151] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for preparing a high temperature resistant perfluoroether elastomer composition, characterized in that: include S1, 9-12 parts by weight of multi-walled carbon nanotube-modified polyamic acid and 0.24-1.55 parts by weight of a vulcanization site monomer are cross-linked or grafted to obtain a cross-linked or grafted multi-walled carbon nanotube-modified polyimide; S2, carrying out emulsion polymerization reaction of the cross-linked or grafted multi-walled carbon nanotube-modified polyimide with 0.24-1.55 parts by mass of a vulcanization point monomer and 100 parts by mass of a copolymerized fluorine-containing monomer to obtain a perfluoroether elastomer composite emulsion; S3, coagulating, washing and drying the perfluoroether elastomer composite emulsion to obtain a modified perfluoroether elastomer; S4, mixing, thin-passing, compression molding and two-stage vulcanization of the modified perfluoroether elastomer to obtain a high temperature resistant perfluoroether elastomer composition; Polyamic acid and multi-walled carbon nanotubes undergo a dehydration reaction of -COOH under alkaline conditions to generate polyamic acid modified with multi-walled carbon nanotubes; the high temperature resistance refers to a temperature resistance higher than 330°C; the vulcanization point monomer is a cross-linkable compound containing a nitrile group and a fluorovinyl group; a carbon-containing filler is added during the mixing process, the carbon-containing filler is 1-6 parts by mass, and the carbon-containing filler is polyimide and / or multi-walled carbon nanotubes.

2. The method for preparing a high temperature resistant perfluoroether elastomer composition according to claim 1, characterized in that: The method for preparing the multi-walled carbon nanotube-modified polyamic acid comprises: The polyamic acid is produced by polycondensation of pyromellitic anhydride and 4,4'-diaminodiphenyl ether in dimethylacetamide; The polyamic acid and the multi-walled carbon nanotubes react to generate polyamic acid modified by the multi-walled carbon nanotubes.

3. The method for preparing a high temperature resistant perfluoroether elastomer composition according to claim 2, characterized in that: The S1 includes: S1-1, the multi-walled carbon nanotube-modified polyamic acid undergoes a dehydration reaction of -COOH under alkaline conditions to generate a multi-walled carbon nanotube-modified polyimide; S1-2, the multi-walled carbon nanotube-modified polyimide is cross-linked or grafted with a sulfurization point monomer to obtain a cross-linked or grafted multi-walled carbon nanotube-modified polyimide.

4. The method for preparing a high temperature resistant perfluoroether elastomer composition according to claim 1, characterized in that: The sulfurization site monomer is perfluoro-8-cyano-5-methyl-3,6-dioxa-1-octene.

5. The method for preparing a high temperature resistant perfluoroether elastomer composition according to claim 1, characterized in that: The mass ratio of tetrafluoroethylene to perfluoromethyl vinyl ether in the copolymerized fluorine-containing monomer is (55-70):(30-45).

6. The method for preparing a high temperature resistant perfluoroether elastomer composition according to claim 1, characterized in that: The mass proportion of the multi-walled carbon nanotubes in the polyamic acid modified with the multi-walled carbon nanotubes is 1.5-10%.

7. The method for preparing a high temperature resistant perfluoroether elastomer composition according to claim 1, characterized in that: In S1, the multi-walled carbon nanotube-modified polyamic acid is cross-linked or grafted with a sulfurization point monomer via a catalyst, and the catalyst is 0.2-0.6 parts by mass.

8. The method for preparing a high temperature resistant perfluoroether elastomer composition according to claim 7, characterized in that: The catalyst is a weakly alkaline salt, and the catalyst is one of sodium bicarbonate, sodium carbonate, sodium sulfite and ammonium sulfite.

9. The method for preparing a high temperature resistant perfluoroether elastomer composition according to claim 1, characterized in that: The aspect ratio of the multi-walled carbon nanotubes is 500-1000:

1.

10. The method for preparing a high temperature resistant perfluoroether elastomer composition according to claim 1, characterized in that: The carboxyl content of the polyamic acid modified by the multi-walled carbon nanotubes is 0.5 wt % to 3 wt %.

Images