Crosslinkable perfluoroelastomer as well as preparation method and application thereof

Abstract

The invention discloses a crosslinkable perfluoroelastomer and a preparation method and application thereof, the preparation method comprises the following steps: (1) mixing nitrile perfluoroalkyl vinyl ether, a fluorocarbon solvent, deionized water and an emulsifier, and emulsifying to obtain a nitrile perfluoroalkyl vinyl ether microemulsion; (2) adding raw materials containing the nitrile perfluoroalkyl vinyl ether microemulsion, perfluoromethyl vinyl ether, tetrafluoroethylene and an initiator into a high-pressure polymerization kettle, and carrying out a copolymerization reaction; (3) after the copolymerization reaction is finished, cooling, emptying the pressure of the polymerization kettle to normal pressure, and taking out the emulsion in the kettle; and (4) demulsifying, condensing, filtering, washing and drying the emulsion in the kettle to obtain the crosslinkable perfluoroelastomer. The copolymer has higher molecular weight and crosslinking degree, and can be used as a sizing material of the perfluoroether rubber to perform vulcanization reaction in a rubber system without a crosslinking agent or with peroxide as a crosslinking agent, and the obtained perfluoroether rubber has excellent high temperature resistance.

Description

Technical Field

[0001] The invention belongs to the field of synthesis of fluorine-containing polymers, and in particular relates to a cross-linkable perfluoroelastomer and a preparation method and application thereof. Background Art

[0002] Perfluoroether rubber (FFKM) has a high fluorine content and has superior physical and chemical properties compared to fluororubber (FKM). Selecting the right rubber for a specific application or equipment is critical to ensuring the long-term operation of the equipment. Since its successful development and application, FFKM is very suitable for use in highly corrosive chemical processing, semiconductor wafer production, pharmaceutical processing, oil and gas extraction and recovery, and aerospace. FFKM material combines the chemical resistance of tetrafluoroethylene (PTFE) with the flexibility and elasticity of traditional FKM. With the growing demand for more chemically resistant and high-temperature resistant polymers, the chemical structure of FFKM rubber before cross-linking (cross-linkable perfluoroelastomer) is posed with higher challenges. Summary of the invention

[0003] The object of the present invention is to provide a cross-linkable perfluoroelastomer and a preparation method thereof. The cross-linkable perfluoroelastomer is a terpolymer of tetrafluoroethylene-perfluoromethyl vinyl ether-nitrile perfluoroalkyl vinyl ether; the copolymer has a high molecular weight and a cross-linking degree. The copolymer is used as a rubber material for perfluoroether rubber (FFKM) and can be subjected to a vulcanization reaction in a rubber system without a cross-linking agent or with peroxide as a cross-linking agent. The obtained perfluoroether rubber (FFKM) has excellent high-temperature resistance and can be applied to ultra-high-temperature resistant sealing environments, such as seals for downhole equipment in oil wells 10,000 meters deep.

[0004] In order to achieve the above-mentioned object, in the first aspect, the present invention provides a cross-linkable perfluoroelastomer, which is a terpolymer obtained by polymerization of tetrafluoroethylene, perfluoromethyl vinyl ether and nitrile perfluoroalkyl vinyl ether, wherein the content of tetrafluoroethylene is 20-55 mol%, the content of perfluoromethyl vinyl ether is 40-60 mol%, and the content of nitrile perfluoroalkyl vinyl ether is 5-20 mol%.

[0005] Preferably, the content of tetrafluoroethylene is 38 mol %, the content of perfluoromethyl vinyl ether is 51 mol %, and the content of nitrile perfluoroalkyl vinyl ether is 11 mol %.

[0006] In a second aspect, the present invention provides a method for preparing a cross-linkable perfluoroelastomer as described above, comprising the following steps: (1) mixing and emulsifying a nitrile perfluoroalkyl vinyl ether, a fluorocarbon solvent, deionized water and an emulsifier to obtain a nitrile perfluoroalkyl vinyl ether microemulsion; (2) adding raw materials comprising a nitrile perfluoroalkyl vinyl ether microemulsion, perfluoromethyl vinyl ether, tetrafluoroethylene and an initiator to a high-pressure polymerization kettle to carry out a copolymerization reaction; (3) after the copolymerization reaction is completed, cooling the kettle, venting the pressure of the polymerization kettle to normal pressure, and taking out the emulsion in the kettle; (4) demulsifying and condensing the emulsion in the kettle, filtering, washing and drying the emulsion to obtain a cross-linkable perfluoroelastomer.

[0007] Preferably, the weight ratio of the nitrile perfluoroalkyl vinyl ether to the fluorocarbon solvent is 1:5-10.

[0008] Preferably, the fluorocarbon solvent is a linear or cyclic fluorocarbon compound.

[0009] Preferably, the fluorocarbon solvent is a cyclic oxyfluorocarbon compound having 4-12 carbon atoms; the cyclic oxyfluorocarbon compound is one or a combination of perfluorotetrahydropyran, perfluoromethyltetrahydrofuran and perfluorobutyltetrahydrofuran.

[0010] Preferably, the emulsifier is one or a combination of ammonium perfluorooctanoate, ammonium perfluorononanoate, ammonium perfluorohexylacetate and perfluoro-2,6-dimethyl-4,8-dioxadecanoic acid.

[0011] Preferably, the initiator is one or a combination of ammonium persulfate, potassium persulfate, sodium persulfate, disuccinic anhydride peroxide, diacetyl peroxide, dipropionyl peroxide, tert-butyl peroxyacetate, tert-butyl peroxypivalate, dibenzoyl peroxide and diglutaric acid peroxide.

[0012] In a third aspect, the present invention provides a sulfide comprising the crosslinkable perfluoroelastomer described above or the crosslinkable perfluoroelastomer obtained by the preparation method described above.

[0013] Preferably, it also contains rubber, vulcanizing agent, inorganic filler, co-vulcanizing agent and carbon black.

[0014] In a fourth aspect, the present invention provides an application of sulfide for use in equipment seals in deep oil wells.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) The cross-linkable perfluoroelastomer of the present application is a terpolymer of tetrafluoroethylene-perfluoromethyl vinyl ether-nitrile perfluoroalkyl vinyl ether, and the content of the third monomer nitrile perfluoroalkyl vinyl ether is at least 5 mol%, which is higher than 0.1-3 mol% of the ordinary polymerization method, thereby improving the comprehensive properties of the material such as high temperature resistance.

[0017] (2) The present application pre-emulsifies the third monomer nitrile perfluoroalkyl vinyl ether to make its microemulsion particle size less than 200 nm, thereby improving the conversion rate of nitrile perfluoroalkyl vinyl ether in emulsion polymerization; the study found that using fluorocarbon solvent as an emulsifier for nitrile perfluoroalkyl vinyl ether can reduce the particle size of the nitrile perfluoroalkyl vinyl ether microemulsion, help to improve the reaction interface of emulsion polymerization, and facilitate tetrafluoroethylene and perfluoromethyl vinyl ether to enter the emulsion and copolymerize with nitrile perfluoroalkyl vinyl ether. The obtained cross-linkable perfluoroelastomer has a higher molecular weight and improved high temperature resistance.

[0018] (3) The perfluoroether rubber using the cross-linkable perfluoroelastomer as the rubber material has high temperature resistance. According to the test of GB / T1040.1-2018, the tensile strength exceeds 140MPa and the elongation exceeds 400% at 240°C. DETAILED DESCRIPTION

[0019] In order to make the above-mentioned objects, features and advantages of the invention more obvious and easy to understand, the specific embodiments of the invention are described in detail below.

[0020] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0021] A first method for preparing a crosslinkable perfluoroelastomer comprises the following steps:

[0022] (1) mixing a nitrile perfluoroalkyl vinyl ether, a fluorocarbon solvent, deionized water and an emulsifier, and emulsifying the mixture under high-speed stirring to obtain a nitrile perfluoroalkyl vinyl ether microemulsion; wherein the weight ratio of the fluorocarbon solvent, the nitrile perfluoroalkyl vinyl ether, the deionized water and the emulsifier is 1:(5-10):(20-60):(0.1-0.3);

[0023] (2) adding deionized water and an emulsifier into a high-pressure polymerization autoclave, stirring evenly, and adding the nitrile perfluoroalkyl vinyl ether microemulsion and perfluoromethyl vinyl ether of step (1) in proportion to obtain a primary reaction emulsion; the weight ratio of the nitrile perfluoroalkyl vinyl ether microemulsion, perfluoromethyl vinyl ether, deionized water, and emulsifier is 1:(0.1-0.2):(8-12):(0.05-0.15);

[0024] (3) adding tetrafluoroethylene to the reactor to reach the reaction pressure, wherein the reaction pressure is 2-3 MPa;

[0025] (4) preparing an initiator solution and adding it into a high-pressure polymerization reactor, and heating it to 50-80° C.;

[0026] (5) when the pressure in the autoclave begins to decrease, adding tetrafluoroethylene gas to maintain the reaction pressure in the autoclave until the tetrafluoroethylene is consumed; the weight ratio of the tetrafluoroethylene to the perfluoromethyl vinyl ether is 7:(2-4);

[0027] (6) Stop stirring, cool to below 40°C, vent the polymerization kettle to normal pressure, and take out the emulsion in the kettle;

[0028] (7) breaking the emulsion, coagulating, filtering, washing and drying to obtain a cross-linkable perfluoroelastomer.

[0029] A second method for preparing a crosslinkable perfluoroelastomer comprises the following steps:

[0030] (1) mixing a nitrile perfluoroalkyl vinyl ether, a fluorocarbon solvent, deionized water and an emulsifier, and emulsifying the mixture under high-speed stirring to obtain a nitrile perfluoroalkyl vinyl ether microemulsion; wherein the weight ratio of the fluorocarbon solvent, the nitrile perfluoroalkyl vinyl ether, the deionized water and the emulsifier is 1:(5-10):(500-600):(3-7);

[0031] (2) adding 10% of the total amount of the nitrile perfluoroalkyl vinyl ether microemulsion prepared in step (1) and 10% of the total amount of perfluoromethyl vinyl ether into a high-pressure polymerization vessel to obtain a reaction primary emulsion;

[0032] (3) adding tetrafluoroethylene gas into the kettle;

[0033] (4) preparing an initiator solution and adding it into a high-pressure polymerization reactor, raising the temperature to 50-80° C., sealing and maintaining the pressure, and when the reaction pressure in the reactor reaches the reaction pressure and begins to drop, adding the remaining nitrile perfluoroalkyl vinyl ether microemulsion, perfluoromethyl vinyl ether and tetrafluoroethylene gas in proportion to maintain the reaction pressure in the reactor until all the materials are consumed.

[0034] (5) Stop stirring, cool to below 40°C, vent the polymerization kettle to normal pressure, and take out the emulsion in the kettle;

[0035] (6) breaking the emulsion, coagulating, filtering, washing and drying to obtain a cross-linkable perfluoroelastomer.

[0036] In one embodiment of the present invention, the fluorocarbon solvent is a linear or cyclic fluorocarbon compound, preferably a cyclic oxyfluorocarbon compound with a carbon number of 4-12; the cyclic oxyfluorocarbon compound is preferably one or a combination of perfluorotetrahydropyran, perfluoromethyltetrahydrofuran and perfluorobutyltetrahydrofuran.

[0037] In one embodiment of the present invention, the emulsifier is one or a combination of ammonium perfluorooctanoate, ammonium perfluorononanoate, ammonium perfluorohexylacetate and perfluoro-2,6-dimethyl-4,8-dioxadecanoic acid.

[0038] In one embodiment of the present invention, the initiator is one or a combination of ammonium persulfate, potassium persulfate, sodium persulfate, disuccinic anhydride peroxide, diacetyl peroxide, dipropionyl peroxide, tert-butyl peroxyacetate, tert-butyl peroxypivalate, dibenzoyl peroxide and diglutaric acid peroxide.

[0039] The cross-linkable perfluoroelastomer of the present invention and its preparation method and application are described in detail below by way of examples. Main raw materials and equipment used: Unless otherwise specified, the raw materials and equipment of each embodiment and comparative example are the same; materials without specific models or types are purchased from the market or commonly available through common channels, and are not specifically limited.

[0040] Example 1

[0041] (I) Preparation of polymer elastomers

[0042] (1) 300 g of nitrile perfluoroalkyl vinyl ether, 50 g of perfluoromethyltetrahydrofuran, 2 kg of deionized water, and 10 g of ammonium perfluorooctanoate were mixed and emulsified under high-speed stirring to obtain a nitrile perfluoroalkyl vinyl ether microemulsion. The particle size of the obtained microemulsion was 160-170 nm as measured by a laser particle size analyzer.

[0043] (2) In a 35L stainless steel high-pressure polymerization reactor, 24kg of deionized water and 240g of ammonium perfluorooctanoate were added in advance, stirring was started and the temperature was raised to 60°C, and the nitrile perfluoroalkyl vinyl ether microemulsion of step (1) and 350g of perfluoromethyl vinyl ether were added, and stirred for 0.5 hours at a stirring rate of 300 rpm;

[0044] (3) adding tetrafluoroethylene gas until the pressure in the kettle reaches 2.4 MPa;

[0045] (4) preparing a 12.5 wt % aqueous solution of ammonium persulfate and adding it into a high-pressure polymerization reactor, and when the pressure in the reactor begins to drop, adding tetrafluoroethylene gas to maintain the pressure in the reactor at 2.4 MPa until 152 g of tetrafluoroethylene is consumed;

[0046] (5) Stop stirring, cool to below 40°C, vent the polymerization kettle to normal pressure, and take out the emulsion in the kettle;

[0047] (6) demulsifying and coagulating with 20% nitric acid, filtering, washing and drying to obtain 612 g of polymer powder;

[0048] The test showed that the polymer powder had a tetrafluoroethylene content of 38 mol%, a perfluoromethyl vinyl ether content of 51 mol%, a nitrile perfluoroalkyl vinyl ether content of 11 mol / %, a Mooney viscosity of 19.0 Pa.S@121°C, and a glass transition temperature of -20°C.

[0049] (II) Preparation of vulcanized sheets

[0050] (1) Weigh 100 g of polymer powder, 3 parts of vulcanizing agent Luperco@101-XL45, 55 g of white carbon black, 4 g of trienoyl isocyanurate and 25 g of carbon black (N990), and mix them on a two-roll rubber mill to obtain a mixture.

[0051] (2) After the mixture is pressed out of the mill, a sheet with a thickness of about 1.8 mm is obtained, and the sheet is cut into rectangular pieces of 75×150 mm, and then hot-pressed in a hot press at a temperature of 160° C. for 10 minutes to obtain a preformed sheet;

[0052] (3) The preformed sheet is placed in an oven and baked at 180° C. for 2 hours to complete vulcanization and obtain a vulcanized sheet.

[0053] The tensile properties of the vulcanized sheet at high temperature were tested according to GB / T 1040.1-2018: the tensile strength was 154 MPa at 240°C and the elongation at break was 450%.

[0054] Example 2

[0055] (I) Preparation of polymer elastomers

[0056] (1) 300 g of nitrile perfluoroalkyl vinyl ether, 50 g of perfluoromethyltetrahydrofuran, 26 kg of deionized water and 250 g of ammonium perfluorooctanoate were mixed and emulsified under high-speed stirring to obtain a nitrile perfluoroalkyl vinyl ether microemulsion. The particle size of the obtained microemulsion was 180-200 nm as measured by a laser particle size analyzer.

[0057] (2) In a 35L stainless steel high-pressure polymerization reactor, add 10% of the total amount of the nitrile perfluoroalkyl vinyl ether microemulsion prepared in step (1) and 10% of the total amount of perfluoromethyl vinyl ether, and stir for 0.5 hours at a stirring rate of 300 rpm;

[0058] (3) adding tetrafluoroethylene gas into the kettle;

[0059] (4) preparing a 12.5 wt % aqueous solution of ammonium persulfate and adding it into a high-pressure polymerization reactor, raising the temperature to 60° C., sealing and maintaining the pressure, and when the pressure in the reactor begins to drop, adding tetrafluoroethylene gas to maintain the pressure in the reactor at 2.4 MPa until 152 g of tetrafluoroethylene is consumed;

[0060] (5) Stop stirring, cool to below 40°C, vent the polymerization kettle to normal pressure, and take out the emulsion in the kettle;

[0061] (6) demulsifying and coagulating with 20% nitric acid, filtering, washing and drying to obtain 605 g of polymer powder;

[0062] The test showed that the polymer powder had a tetrafluoroethylene content of 39 mol%, a perfluoromethyl vinyl ether content of 52 mol%, a nitrile perfluoroalkyl vinyl ether content of 9 mol / %, a Mooney viscosity of 18.5 Pa.S@121°C, and a glass transition temperature of -25°C.

[0063] (II) Preparation of vulcanized sheets

[0064] Similar to Example 1, the tensile properties of the vulcanized sheet at high temperature were tested according to GB / T 1040.1-2018: the tensile strength was 140 MPa at 240° C., and the elongation at break was 430%.

[0065] Comparative Example 1

[0066] (I) Preparation of polymer elastomers

[0067] The same procedures as in Example 1 were used except that perfluoromethyltetrahydrofuran was not used. The obtained polymer powder was tested to have a tetrafluoroethylene content of 41.4 mol%, a perfluoromethyl vinyl ether content of 56 mol%, a nitrile perfluoroalkyl vinyl ether content of 2.6 mol / %, a Mooney viscosity of 17.1 Pa.S@121°C, and a glass transition temperature of -12°C.

[0068] (II) Preparation of vulcanized sheets

[0069] Except that the polymer powder in step (i) replaces the polymer powder in Example 1, the rest is the same as Example 3. The tensile properties of the vulcanized sheet at high temperature are tested according to GB / T 1040.1-2018: the tensile strength at 240°C is 90 MPa, and the elongation at break is 480%.

[0070] It can be seen from the data of the embodiments and comparative examples that the polymer elastomer of the embodiment of the present invention uses a fluorocarbon solvent as an emulsifier during the preparation process, and a microemulsion with a smaller particle size can be obtained, which is beneficial to improving the polymerization effect. The polymer elastomer has a higher content of the third monomer nitrile perfluoroalkyl vinyl ether, and the vulcanized sheet using the polymer elastomer as the rubber material has a higher high temperature resistance.

[0071] Although some specific embodiments of the present invention have been described in detail by way of example, it will be appreciated by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present invention. It will be appreciated by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A cross-linkable perfluoroelastomer, characterized in that: The invention is a terpolymer obtained by polymerizing tetrafluoroethylene, perfluoromethyl vinyl ether and nitrile perfluoroalkyl vinyl ether, wherein the content of tetrafluoroethylene is 20-55 mol%, the content of perfluoromethyl vinyl ether is 40-60 mol% and the content of nitrile perfluoroalkyl vinyl ether is 5-20 mol%.

2. The method for preparing a crosslinkable perfluoroelastomer according to claim 1, characterized in that: The following steps are involved: (1) mixing and emulsifying a nitrile perfluoroalkyl vinyl ether, a fluorocarbon solvent, deionized water and an emulsifier to obtain a nitrile perfluoroalkyl vinyl ether microemulsion; (2) adding raw materials including nitrile perfluoroalkyl vinyl ether microemulsion, perfluoromethyl vinyl ether, tetrafluoroethylene and initiator into a high-pressure polymerization kettle to carry out copolymerization reaction; (3) After the copolymerization reaction is completed, the temperature is lowered, the pressure of the polymerization kettle is vented to normal pressure, and the emulsion in the kettle is taken out; (4) Demulsifying and coagulating the emulsion in the kettle, filtering, washing and drying to obtain a cross-linkable perfluoroelastomer.

3. The method for preparing the compound as claimed in claim 2, characterized in that: The weight ratio of the fluorocarbon solvent to the nitrile perfluoroalkyl vinyl ether is 1:5-10.

4. The method for preparing a crosslinkable perfluoroelastomer as claimed in claim 2, characterized in that: The fluorocarbon solvent is a linear or cyclic fluorocarbon compound.

5. The method for preparing a crosslinkable perfluoroelastomer as claimed in claim 2, characterized in that: The fluorocarbon solvent is a cyclic oxyfluorocarbon compound with a carbon number of 4-12; the cyclic oxyfluorocarbon compound is one or a combination of perfluorotetrahydropyran, perfluoromethyltetrahydrofuran and perfluorobutyltetrahydrofuran.

6. The method for preparing a crosslinkable perfluoroelastomer as claimed in claim 2, characterized in that: The emulsifier is one or a combination of ammonium perfluorooctanoate, ammonium perfluorononanoate, ammonium perfluorohexylacetate and perfluoro-2,6-dimethyl-4,8-dioxadecanoic acid.

7. The method for preparing a crosslinkable perfluoroelastomer as claimed in claim 2, characterized in that: The initiator is one or a combination of ammonium persulfate, potassium persulfate, sodium persulfate, disuccinic anhydride peroxide, diacetyl peroxide, dipropionyl peroxide, tert-butyl peroxyacetate, tert-butyl peroxypivalate, dibenzoyl peroxide and diglutaric acid peroxide.

8. A sulfide, characterized in that: The invention comprises the cross-linkable perfluoroelastomer according to claim 1 or the cross-linkable perfluoroelastomer obtained by the preparation method according to any one of claims 2 to 7.

9. The sulfide according to claim 6, characterized in that It also contains rubber, vulcanizing agent, inorganic filler, co-vulcanizing agent and carbon black.

10. Use of the sulfide according to claim 8 or 9, characterized in that: Equipment seals used in deep oil wells.