Method for passivating end group of fluoroelastomer

Abstract

Provided in the present application is a method for passivating an end group of a fluoroelastomer, which method is applied to the technical field of fluoroelastomers. The method comprises: S1, subjecting a fluoroelastomer to a devolatilization treatment by using a liquid or a supercritical fluid; S2, subjecting the devolatilized fluoroelastomer to a passivation treatment, and removing a passivation medium; and S3, washing the fluoroelastomer with deionized water, dehydrating the fluoroelastomer, and then drying same to obtain a devolatilized and passivated fluoroelastomer. By passivating the fluoroelastomer after liquid or supercritical fluid devolatilization, the obtained fluoroelastomer has less volatile components; by controlling the concentration of the passivation medium and the passivation time so as to control and adjust the end group passivation degree or the end group stabilization degree, the passivated fluoroelastomer has good processability and storage stability, and does not change color when in contact with a high-temperature and oxidation environment during the subsequent processing and using processes; and in addition, partial active end groups are used for secondary vulcanization to form a network structure, such that the mechanical performance is good, the compression set is low, and a product of the fluoroelastomer can be applied to the manufacturing process of a high-cleanliness semiconductor.

Description

A method for passivating end groups of fluoroelastomers Technical Field

[0001] The present application relates to the technical field of fluoroelastomers, and in particular to a method for passivating end groups of fluoroelastomers. Background Art

[0002] Fluoroelastomer products are versatile and multipurpose sealing materials. In high-precision chip production, even the slightest impurity can significantly degrade product performance. Only ultra-clean, high-purity environments can meet the demands of the semiconductor industry. Therefore, fluoroelastomer products used in semiconductor manufacturing must not only exhibit excellent chemical resistance, thermal stability, and mechanical properties, but also exhibit low levels of extractables, low outgassing, and low permeability.

[0003] However, in actual applications, fluoroelastomers with the same chemical composition often have very different processing and application properties, and may even be unsuitable for practical applications. Factors that affect the processing and application properties of fluoroelastomers and the physical properties of finished products mainly include chemical composition, chemical structure, polymer physical form, and the end groups of the fluoroelastomer.

[0004] Whether the end group is stable is determined by its chemical structure, which depends on the polymerization chemistry and specific polymerization conditions. Depending on the polymerization conditions, such as the type of polymerization initiator and chain transfer agent used during polymerization, fluoroelastomers may produce not only the stable end group trifluoromethyl -CF3, but also unstable end groups such as carboxylic acid -COOH, acyl fluoride -COF, hydroxymethyl -CH2OH, and ester functional groups -COOCH3. These unstable end groups will decompose during subsequent high-temperature processing, and the released gases will produce bubbles, which will adversely affect the processing and physical properties of the product. When the prepared sealing products are used in semiconductor processes, the unstable end groups will slowly decompose, precipitating pollutants such as fluoride ions, which will contaminate the semiconductor process and affect the quality of semiconductor components.

[0005] In addition, the perfluoroether elastomer should also remove the initiator, chain transfer agent, emulsifier and other components added during the polymerization process. If the perfluoroether elastomer contains a small amount of residues of these components, it is very easy to cause oxidative yellowing during subsequent processing and use.

[0006] As we all know, in the production process of thermoplastic resin PFA (perfluoroalkoxy vinyl ether polymer), the aqueous phase is polymerized and then condensed. The powdered resin after condensation is washed with deionized water and dried and devolatilized at a temperature of up to 280°C to remove moisture, initiators, chain transfer agents, surfactants and small molecular polymers in the polymer. The resin after drying and devolatilization has good fluidity.

[0007] The thermal stability of end groups generally ranks in the following order: -CF3 > -CONH2 > -COOCH3 > -CH2OH > -COF. Therefore, end group passivation involves chemically converting unstable end groups into stable ones. For example, PFA resin is treated with 1-10% fluorine gas (nitrogen as the balance) for end group passivation (converting them into stable end groups -CF3) and / or 50% NH3 for amination (converting them into stable end groups -CONH2), ultimately yielding a transparent, process-stable PFA powder.

[0008] Patent document Japanese Patent Application Laid-Open No. 62-104822 describes a method for passivating PFA terminal groups, which includes contacting a specific TFE-PAVE copolymer with a fluorine-containing gas under temperature, time and pressure conditions sufficient to remove all unstable terminal groups, and purging the copolymer with an inert gas to remove the unstable terminal groups.

[0009] Patent document Japanese Patent Application Laid-Open No. 04-20507 describes another method for passivating PFA end groups, which comprises contacting a specific TFE-PAVE copolymer with fluorine gas to obtain a PFA end group passivation method. 6 The total number of -COF groups in each carbon atom is 7 to 40, and then the -COF groups are completely converted into -CONH2 groups using ammonia gas.

[0010] Patent document US7754821B2 provides a method for end-group passivation of fluorine-containing thermoplastic polymers under mild conditions.

[0011] Unlike thermoplastic resins such as PFA, fluoroelastomers such as perfluoroether elastomers (PFEEs) become viscous when dried at relatively low temperatures (e.g., 120°C). This causes particles to adhere to each other, resulting in a reduced porosity and increased pressure differential and mass transfer resistance. Consequently, the initiator, chain transfer agent, surfactant, and small molecule polymer trapped within the PFEEs cannot be completely removed, making effective devolatilization impossible, and subsequent effective end group passivation treatment impossible. This is reflected in the fact that currently produced PFEEs both domestically and internationally exhibit a yellow or amber color after high-temperature treatment.

[0012] Summary of the Invention

[0013] In view of this, an embodiment of this specification provides a method for passivating the end groups of a fluoroelastomer, wherein the fluoroelastomer is devolatilized using a liquid or a supercritical fluid, and then passivated, washed, and dried to obtain a devolatilized and passivated fluoroelastomer.

[0014] The embodiments of this specification provide the following technical solutions: A method for passivating the end groups of fluoroelastomers comprises:

[0015] S1. Devolatilizing a fluoroelastomer using a liquid or a supercritical fluid, wherein the fluoroelastomer is a perfluoroether elastomer or a fluoroelastomer containing vinylidene fluoride;

[0016] S2. passivating the devolatilized fluoroelastomer and removing the passivation medium;

[0017] S3. Washing the fluoroelastomer with deionized water, dehydrating it, and then drying it to obtain a devolatilized and passivated fluoroelastomer.

[0018] Optionally, before the fluoroelastomer is devolatilized, the fluoroelastomer emulsion prepared by polymerization in an aqueous medium is subjected to coagulation, washing and centrifugal dehydration treatments.

[0019] Optionally, in S1, before the devolatilization treatment, the fluoroelastomer is subjected to vacuum drying or freeze drying.

[0020] Optionally, in S1, the liquid or supercritical fluid is CO2.

[0021] Optionally, in S1, the liquid or supercritical fluid contains an entrainer, and the entrainer includes one or more of methanol, ethanol, isopropanol, acetone, chloroform, hexane, and trichloroethane.

[0022] Optionally, in S1, the amount of the entrainer is 0.5%-10.0% of the mass of CO2.

[0023] Optionally, in S2, the fluoroelastomer is passivated by fluorination, and the fluorinating agent includes one or more of F2, NF3, SF4, PF5, IF5, and IF7.

[0024] Optionally, in S2, the fluoroelastomer is passivated by amination, and the aminating agent includes one or more of NH3, ammonium carbonate, ammonium bicarbonate, ammonium carbamate, ammonium oxalate, ammonium sulfamate, ammonium formate, ammonium thiocyanate and ammonium sulfate.

[0025] Optionally, in S2, the fluoroelastomer is subjected to an amination treatment after the fluorination treatment.

[0026] Optionally, in S2, the fluorination treatment is followed by replacement with an inert medium, and the amination treatment is performed after the inert medium replacement, wherein the inert medium is N2 or CO2.

[0027] Optionally, the fluorination concentration is 1-10 wt %, and the balance gas is N2 or CO2.

[0028] Optionally, the concentration of the amination medium is 10-60 wt %, the balance gas of the gaseous amination medium is N 2 , and the solution of the liquid amination medium is an aqueous solution.

[0029] Optionally, the temperature of the fluorination passivation is 60°C-200°C.

[0030] Optionally, the amination passivation temperature is 0°C-100°C.

[0031] Optionally, the cumulative amount of the passivation medium introduced per unit mass of polymer is 1 g to 10 g / kg of polymer.

[0032] Compared with the prior art, the at least one technical solution adopted in the embodiments of this specification can achieve the following beneficial effects:

[0033] The present application performs liquid or supercritical fluid devolatilization on a fluoroelastomer and then passivates it, thereby obtaining a fluoroelastomer with low volatile matter. By controlling the concentration of the passivation medium and the passivation time, the degree of end group passivation or end group stabilization is controlled and adjusted. The fluoroelastomer does not change color when exposed to high temperature and oxidizing environments during subsequent processing and use. At the same time, some active end groups are used for secondary vulcanization to form a grid structure, which has good mechanical properties and low compression permanent deformation. The products thereof can be used in high-cleanliness semiconductor processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. 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 these drawings without any creative work.

[0035] FIG1 is a schematic flow chart of a method for passivating end groups of a fluoroelastomer according to the present invention. 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 embodiments 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 embodiments, 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 features in the following embodiments and embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of this application.

[0038] It should be noted that various aspects of the embodiments within the scope of the appended claims 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 this 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 an apparatus and / or practice a method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this apparatus and / or practice this method.

[0039] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The illustrations only show components related to the present application and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0040] Additionally, in the following description, specific details are provided to provide a thorough understanding of the examples, however, one skilled in the art will appreciate that the examples can be practiced without these specific details.

[0041] Fluoroelastomer products are versatile and multipurpose sealing materials. However, in high-precision chip production, even trace impurities can significantly degrade product performance. Only ultra-clean, high-purity environments can meet the demands of the semiconductor industry. Fluoroelastomer products used in semiconductor manufacturing must not only exhibit excellent chemical resistance, thermal stability, and mechanical properties, but also exhibit low levels of extractables, low outgassing, and low permeability.

[0042] The stability of fluoroelastomer end groups is determined by their chemical structure. These unstable end groups decompose during subsequent high-temperature processing, releasing gases that can create bubbles and adversely affect processing and the physical properties of the finished product. When used in semiconductor manufacturing, these unstable end groups can slowly decompose, releasing contaminants such as fluoride ions, which can contaminate the semiconductor process and affect the quality of semiconductor components. Fluoroether elastomers must also be free of initiators, chain transfer agents, emulsifiers, and other components added during polymerization. Even small amounts of these residues in perfluoroether elastomers can easily lead to oxidative yellowing during subsequent processing and use.

[0043] Fluoroelastomers include vinylidene fluoride-containing fluoroelastomers, perfluoroether elastomers, fluorosilicone elastomers, and fluorophosphazene elastomers. Common fluoroelastomers, represented by vinylidene fluoride-containing fluoroelastomers, contain hydrocarbon groups. Perfluoroether elastomers are primarily composed of tetrafluoroethylene and perfluoroalkyl vinyl ether (including perfluoromethyl vinyl ether (PMVE) and perfluoropropyl vinyl ether (PPVE)) as the primary monomers, copolymerized with a small amount of a third monomer with a vulcanization point. All hydrogen atoms on the carbon atoms in the polymer are replaced by fluorine atoms. These products possess a structure that is stable to high temperatures and chemicals. For example, they possess the high-temperature stability of polytetrafluoroethylene (PTFE) and are resistant to corrosion from over 1,600 chemicals. Their excellent performance helps maintain seal integrity and reduces maintenance.

[0044] Unlike thermoplastic resins such as PFA, fluoroelastomers such as perfluoroether elastomers (PFEEs) become viscous when dried at relatively low temperatures (e.g., 120°C). This causes particles to adhere to each other, resulting in a reduced porosity and increased pressure differential and mass transfer resistance. Consequently, the initiator, chain transfer agent, surfactant, and small molecule polymer trapped within the PFEEs cannot be completely removed, making effective devolatilization impossible, and subsequent effective end group passivation treatment impossible. This is reflected in the fact that currently produced PFEEs both domestically and internationally exhibit a yellow or amber color after high-temperature treatment.

[0045] Based on this, the embodiment of this specification proposes a method for passivating the end groups of fluoroelastomers, as shown in Figure 1, comprising the following steps:

[0046] Step S1: Coagulating, washing, and centrifuging a fluoroelastomer emulsion prepared by polymerization in an aqueous medium to granulate the coagulated dispersion while preventing agglomeration. The resulting polymer particles are approximately 0.01 mm to 1 mm in size, thereby facilitating the removal of free water and some bound water contained in the fluoroelastomer and preventing most particles from adhering to each other. The fluoroelastomer is vacuum dried or freeze-dried, and then devolatilized using liquid or supercritical CO2. The fluoroelastomer is specifically a perfluoroether elastomer or a fluoroelastomer containing vinylidene fluoride.

[0047] Step S2, passivating the devolatilized fluoroelastomer, introducing a passivation medium at a cumulative rate of 1 g to 10 g per kg of polymer, and removing the passivation medium;

[0048] Step S3: washing the fluoroelastomer with deionized water, dehydrating it, and then drying it to obtain a devolatilized and passivated fluoroelastomer.

[0049] In step S1, the fluoroelastomer prepared by polymerization in an aqueous medium is a perfluoroether elastomer and / or a fluoroelastomer containing vinylidene fluoride.

[0050] In step S1, the liquid or supercritical fluid CO2 contains an entrainer, which includes one or more of methanol, ethanol, isopropanol, acetone, chloroform, hexane, and trichloroethane, with the entrainer dosage ranging from 0.5% to 10.0% of the CO2 mass. The entrainer enhances the selectivity, solubility, and efficiency of the CO2 extraction process. The entrainer is miscible with the fluid solvent and has a volatility between that of the extracted substance and the supercritical component, thereby improving its selectivity and solubility for the extracted component.

[0051] In step S2, the fluoroelastomer is passivated by fluorination, using a fluorinating agent selected from one or more of F2, NF3, SF4, PF5, IF5, and IF7. The concentration of the fluorinating agent is 1-10 wt %, with the balance gas being N2 or CO2. The fluorination passivation temperature is 60°C to 200°C.

[0052] In step S2, the fluoroelastomer is subjected to fluorination treatment and then an amination treatment. After the fluorination treatment, the fluoroelastomer is replaced with an inert medium, and then the amination treatment is performed. The inert medium is N2 or CO2. The fluoroelastomer is passivated by amination. The aminating agent includes one or more of NH3, ammonium carbonate, ammonium bicarbonate, ammonium carbamate, ammonium oxalate, ammonium sulfamate, ammonium formate, ammonium thiocyanate, and ammonium sulfate. The concentration of the amination medium is 10-60wt%, the balance gas of the gaseous amination medium is nitrogen, and the solution of the liquid amination medium is an aqueous solution. The amination passivation temperature is 0°C-100°C.

[0053] Example 1

[0054] 10 L of a perfluoroether elastomer emulsion (approximately 28% solids content), prepared by aqueous polymerization, was diluted to 15 L with deionized water (conductivity 0.1-1.0 μs / cm; 25°C). MgCl₂, an electrolyte with a solids content of 1.5 wt%, was added while stirring to initiate coagulation. Vigorous stirring was used to prevent agglomeration. The particles were 0.01-1 mm in size. The mixture was repeatedly washed and soaked in deionized water, centrifuged for dehydration, and dried in a rotary vacuum oven at 40°C for 24 hours at an absolute pressure of 0.01 MPa. The resulting dry polymer powder had a mass of w₁.

[0055] Supercritical CO2 is used as the extraction agent, and ethanol entrainer is added by a plunger pump, the mass of which is about 8% of the mass of CO2.

[0056] The vacuum-dried powder was placed in a stainless steel inner cylinder. The cylinder was sieved with a 2000-mesh stainless steel screen (Tyler mesh, about 6.5 microns). The inner cylinder was placed in an extraction device. The gap between the inner cylinder and the extraction device was sealed with a PTFE gasket.

[0057] The supercritical CO2 temperature and pressure were 85°C and 12 MPa, respectively, with a superficial CO2 velocity of 0.05 m / s. GC-MS (Agilent 8860-5977B) was used to measure the organic matter concentration in the exhaust gas. The devolatilization process was terminated when the organic matter concentration was less than 0.01 mg / kg. The pressure was released and purged, and the stainless steel inner cylinder was removed to obtain the mass w2 of the polymer micropowder after devolatilization.

[0058] Fluorination treatment was performed at atmospheric pressure. First, N2 was introduced, followed by 3.0 wt% and then 8.0 wt% (balanced with N2) fluorine gas. The fluorination temperature was 100°C and the flow rate was 0.2 L / min. After the fluorination treatment, N2 was replaced to purge and remove the fluorine-containing gas in the interstitial space, thereby obtaining a devolatilized and fluorinated perfluoroether elastomer. The cumulative amount of fluorine gas introduced per unit mass of polymer was approximately 1.5-4.1 g / kg of polymer.

[0059] The perfluoroether elastomer product was washed in pure water at 90°C, centrifuged and then dried in a vacuum drying oven to obtain a devolatilized fluorinated perfluoroether elastomer product mass w3. The functional groups on the fluoroelastomer surface were detected by microscopy-infrared (Shimadzu ATM9000).

[0060] Example 2

[0061] The difference between this embodiment and embodiment 1 is that during the extraction and devolatilization process, the fluoroelastomer is a fluoroelastomer containing vinylidene fluoride, the entraining agent is methanol, and during the fluorination and passivation process, the fluorinating agent is SF4, N2 is the balance gas, and the fluorination temperature is 120°C to obtain a devolatilized and fluorinated fluoroelastomer containing vinylidene fluoride.

[0062] Example 3

[0063] The difference between this embodiment and embodiment 1 is that during the extraction and devolatilization process, the entraining agent is methanol, and during the fluorination and passivation process, the fluorinating agent is IF7, N2 is the balance gas, and the fluorination temperature is 70°C to obtain a devolatilized and fluorinated perfluoroether elastomer.

[0064] Example 4

[0065] The difference between this embodiment and embodiment 1 is that during the extraction and devolatilization process, the entraining agent is ethanol, and during the fluorination and passivation process, the fluorinating agent is NF3, CO2 is the balance gas, and the fluorination temperature is 120°C to obtain a devolatilized and fluorinated perfluoroether elastomer.

[0066] The functional groups on the surface of the fluoroelastomer were detected by microscopy-infrared (Shimadzu ATM9000) and deionized water leaching experiments. The fluoride ion content was measured by a fluoride ion electrode (Mettler, SD50 F-ionKid), the number of end groups after fluorination was measured by FTIR (Shimadzu), and the weight loss was measured by a balance (Shimadzu, accuracy 0.1 mg).

[0067] Table 1 Performance test results of Examples 1-4 (fluorine-containing gas flow rate 0.2 L / min)

[0068] The fluorinated and passivated fluoroelastomers of Examples 1-4 were further subjected to amination treatment, and the corresponding examples were Examples 5-8 respectively.

[0069] Example 5

[0070] First, an inert medium, N2, was introduced. Amination was then performed by switching between concentrations of 30 wt% and then 50 wt% ammonia. The balance gas was nitrogen. The amination temperature was 50°C, and the flow rate was 0.2 L / min. The cumulative amount of ammonia introduced per unit mass of polymer (mass flow meter; snier) was 5 g / kg to 8 g / kg of polymer. After amination, N2 was replaced by a purge to remove the ammonia-containing gas in the interstitial space, yielding a fluorinated and aminated fluoroelastomer.

[0071] The fluoroelastomer product is washed in deionized water, centrifuged and then dried in a vacuum environment to obtain an aminated dried fluoroelastomer product of mass w4. In a specific embodiment of the present invention, the deionized water temperature is 80-98°C and the washing and soaking time is 18 hours.

[0072] Example 6

[0073] The difference between this embodiment and embodiment 5 is that during the amination passivation process, the inert medium is deionized water, the aminating agent is ammonium carbonate, the amination temperature is 80°C, and after amination, the deionized water is replaced to remove the ammonium carbonate solution in the gaps to obtain a fluorinated-aminated fluoroelastomer.

[0074] Example 7

[0075] The difference between this embodiment and embodiment 5 is that during the amination passivation process, the inert medium is deionized water, the aminating agent is ammonium oxalate, the amination temperature is 70°C, and after amination, the deionized water is replaced to remove the ammonium oxalate solution in the gaps to obtain a fluorinated-aminated fluoroelastomer.

[0076] Example 8

[0077] The difference between this embodiment and embodiment 5 is that during the amination passivation process, the inert medium is deionized water, the aminating agent is ammonium sulfate, the amination temperature is 80°C, and after amination, the deionized water is replaced to remove the ammonium sulfate solution in the gaps to obtain a fluorinated-aminated fluoroelastomer.

[0078] Functional groups on the fluoroelastomer surface were detected by microscopy and infrared spectroscopy (Shimadzu ATM9000), and fluoride ion concentration was measured by deionized water leaching. The experiments were conducted in a 100 ml PTFE-lined autoclave (Iceberg) and maintained at a constant temperature for 48 hours in a constant temperature oven (Shanghai Yiheng BPG-9106B). Fluoride ion content was measured using a fluoride ion electrode (Mettler, SD50 F-ion Kid).

[0079] Table 2 Performance test results of Examples 5-8

[0080] Comparative Example 1 is a perfluoroether elastomer without devolatilization and passivation treatment

[0081] 10 L of a perfluoroether elastomer emulsion prepared by aqueous polymerization, with a solids content of approximately 28%, was diluted to 15 L with deionized water (conductivity of 0.1-1.0 μs / cm; 25°C). MgCl2 electrolyte with a solids content of 1.5 wt% was added while stirring to coagulate the emulsion. Vigorous stirring was used to prevent agglomeration. The particles were sized at 0.01 mm to 1 mm. The emulsion was repeatedly washed and soaked in deionized water, centrifuged, and then dried directly in a rotary vacuum drying oven at different temperatures for 24 hours. The drying temperature was 120°C and the absolute pressure of the drying oven was 0.01 MPa. The resulting dried agglomerated polymer had an apparent density of 1.030-1.052, approximately half its true density.

[0082] Functional groups on the fluoroelastomer surface were detected by microscopy and infrared spectroscopy (Shimadzu ATM9000), and fluoride ion concentration was measured by deionized water leaching. The experiments were conducted in a 100 ml PTFE-lined autoclave (Iceberg) in a constant temperature oven (Shanghai Yiheng BPG-9106B) for 48 hours. Fluoride ion content was measured using a fluoride ion electrode (Mettler, SD50 F-ion Kid).

[0083] Table 3 shows the direct drying of perfluoroether elastomers without devolatilization and fluorination (absolute pressure is 0.01 MPa)

[0084] A comparison of Tables 1, 2, and 3 demonstrates that, due to the low operating temperature, the weight loss of low-molecular-weight polymers in the perfluoroether elastomer is minimal despite the long devolatilization time. Fluorination reduces the number of unstable end groups by over 90%. End group passivation, particularly amination, essentially eliminates the unstable -COF end groups, resulting in stable -CONH2 end groups. The degree of passivation can be adjusted by adjusting the passivation time and / or the concentration of the passivation medium and / or the passivation temperature.

[0085] 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.

[0086] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for passivating end groups of fluoroelastomers, characterized in that: include, S1. Devolatilizing a fluoroelastomer using a liquid or a supercritical fluid, wherein the fluoroelastomer is a perfluoroether elastomer or a fluoroelastomer containing vinylidene fluoride; S2, passivating the devolatilized fluoroelastomer and removing the passivation medium; S3. Washing the fluoroelastomer with deionized water, dehydrating it and then drying it to obtain a devolatilized and passivated fluoroelastomer.

2. The method for passivating the end groups of a fluoroelastomer according to claim 1, characterized in that: Before the fluoroelastomer is devolatilized, the fluoroelastomer emulsion prepared by polymerization in an aqueous medium is subjected to coagulation, washing and centrifugal dehydration treatment.

3. The method for passivating the end groups of a fluoroelastomer according to claim 1, characterized in that: In S1, the fluoroelastomer is subjected to vacuum drying or freeze drying before the devolatilization treatment.

4. The method for passivating the end groups of a fluoroelastomer according to claim 1, characterized in that: In S1, the liquid or supercritical fluid is CO2.

5. The method for passivating the end groups of a fluoroelastomer according to claim 4, characterized in that: In S1, the liquid or supercritical fluid contains an entrainer, and the entrainer includes one or more of methanol, ethanol, isopropanol, acetone, chloroform, hexane, and trichloroethane.

6. The method for passivating the end groups of a fluoroelastomer according to claim 5, characterized in that: In S1, the amount of the entrainer is 0.5%-10.0% of the mass of CO2.

7. The method for passivating the end groups of a fluoroelastomer according to claim 1, characterized in that: In S2, the fluoroelastomer is passivated by fluorination, and the fluorination agent includes one or more of F2, NF3, SF4, PF5, IF5, and IF7.

8. The method for passivating the end groups of a fluoroelastomer according to claim 1, characterized in that: In S2, the fluoroelastomer is passivated by amination, and the aminating agent includes one or more of NH3, ammonium carbonate, ammonium bicarbonate, ammonium carbamate, ammonium oxalate, ammonium sulfamate, ammonium formate, ammonium thiocyanate and ammonium sulfate.

9. The method for passivating the end groups of a fluoroelastomer according to claim 1, characterized in that: In S2, the fluoroelastomer is subjected to amination treatment after fluorination treatment.

10. The method for passivating the end groups of a fluoroelastomer according to claim 9, characterized in that: In S2, the fluorination treatment is followed by replacement with an inert medium, and the replacement with the inert medium is followed by an amination treatment, wherein the inert medium is N2 or CO2.

11. The method for passivating the end groups of a fluoroelastomer according to claim 7, characterized in that: The concentration of the fluorination is 1-10wt%, and the balance gas is N2 or CO2.

12. The method for passivating the end groups of a fluoroelastomer according to claim 8, characterized in that: The concentration of the amination medium is 10-60 wt %, the balance gas of the gaseous amination medium is N2, and the solution of the liquid amination medium is an aqueous solution.

13. The method for passivating the end groups of a fluoroelastomer according to claim 7, characterized in that: The temperature of the fluorination passivation is 60°C-200°C.

14. The method for passivating the end groups of a fluoroelastomer according to claim 8, characterized in that: The amination passivation temperature is 0°C-100°C.

15. The method for passivating the end groups of a fluoroelastomer according to claim 7 or 8, characterized in that: The cumulative amount of passivation medium introduced per unit mass of polymer is 1g-10g / kg polymer.

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