Preparation method of peroxide vulcanized fluororubber with high fluorine content and low compression deformation

Abstract

The invention discloses a preparation method of peroxide vulcanized fluororubber with high fluorine content and low compression deformation, and relates to the field of fluororubber synthesis. According to the method, vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene are used as mixed monomers to carry out polymerization reaction; wherein in the polymerization reaction process, a vulcanization point monomer is added. The peroxide vulcanized fluororubber which is high in fluorine content, resistant to a new energy battery medium and low in compression deformation is prepared by adjusting the component proportion of mixed monomers and uniformly and continuously adding vulcanization point monomers. According to the peroxide vulcanized fluororubber prepared by the method provided by the invention, the fluorine content is stabilized at 70-71%, the compressive deformation stability is less than or equal to 20%, the tensile strength is about 22MPa, and the elongation at break is greater than 180%; the problem of high compressive deformation of peroxide vulcanized fluororubber (especially peroxide vulcanized fluororubber with high fluorine content) applied to new energy batteries is effectively solved.

Description

Technical Field

[0001] The invention relates to the field of fluororubber synthesis, in particular to a method for preparing peroxide-cured fluororubber with high fluorine content and low compression deformation. Background Art

[0002] High fluorine content peroxide (or free radical) vulcanized fluororubber is obtained by copolymerization of vinylidene fluoride (VDF), tetrafluoroethylene (TFE), hexafluoropropylene (HFP) and vulcanization point monomers (CSM, CTA), and its fluorine mass fraction is 69% to 71%. In addition to the excellent properties of high temperature resistance and corrosion resistance unique to fluororubber, this type of rubber also has outstanding thermal tear resistance, resistance to superheated steam, resistance to organic media and other properties. Peroxide-cured fluororubber products have excellent resistance to hot air aging, methanol resistance, fuel resistance, ozone resistance and other properties, but their high pressure change limits their application; especially peroxide-cured fluororubber with a fluorine content greater than 69%, its pressure change value is 32 to 45%, which limits the application of high fluorine content peroxide-cured fluororubber.

[0003] CN202010620629 discloses a method for preparing a peroxide-cured fluororubber with low compression set. However, the vulcanization point of the peroxide-cured fluororubber cannot solve the problem that the addition of the vulcanization point monomer will terminate the molecular weight, resulting in less vulcanization point added during the reaction process, resulting in a compression set value of about 22%, and poor stability between batches, which is not conducive to industrial production.

[0004] CN108017746A discloses a method for preparing a peroxide-cured fluororubber with a high fluorine content and low compression set. However, the vulcanization points of the peroxide-cured fluororubber are unevenly distributed in the chain segments, and the vulcanization time is long or under-vulcanization occurs during processing, resulting in a compression set value of about 25%, and poor stability between batches, which is not conducive to industrial production.

[0005] CN1989202A discloses a fluorine-containing elastomer composition that can be vulcanized with peroxide, which mainly significantly improves the fluidity of the fluorine-containing elastomer composition that has disadvantages in productivity and improves processability. However, the number average molecular weight of the obtained fluorine-containing elastomer is only 30,000 to 70,000, the cross-linking density is insufficient, and the vulcanization time is relatively long, resulting in a relatively large compression permanent deformation value.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] The present invention provides a method for preparing peroxide-cured fluororubber with high fluorine content and low compression deformation, so as to solve the problem that the compression deformation of peroxide-cured fluororubber is relatively high.

[0008] In order to achieve the above-mentioned invention object, this method proposes the following solution:

[0009] A method for preparing high-fluorine content and low-compression deformation peroxide-cured fluororubber, the operating steps of which are:

[0010] a. In a high-pressure reactor, add 30-50 parts of deoxygenated deionized water, evacuate the reactor, then add 0.025-0.045 parts of dispersant and 0.01-0.03 parts of vulcanization point monomer CTA, stir evenly, heat the reactor to 80-100°C, introduce a mixed monomer 1 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene, make the pressure in the reactor 2.0-3.5MPa, then add 0.01-0.02 parts of initiator to initiate the polymerization reaction;

[0011] b. After the polymerization reaction is carried out, the pressure in the reactor is maintained constant by adding a mixed monomer 2 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene. When the mixed monomer begins to be added at a total amount of 5%, the vulcanization point monomer CTA and the vulcanization point monomer CSM are continuously added at a constant flow rate;

[0012] c. When the solid content of the emulsion in the reactor reaches 25-35wt%, the polymerization reaction is terminated, the unreacted monomers are recovered, and the emulsion is placed in a coagulation barrel, and after coagulation and drying, peroxide-cured fluororubber is obtained.

[0013] As an optional embodiment, in step a, the reactor is evacuated until the oxygen content is ≤20 ppm.

[0014] As an optional embodiment, the dispersant in step a is selected from a selenium-doped trimer dispersant, and the specific steps of its synthesis are:

[0015] T1: Add hexafluoropropylene trimer (molecular weight 150), 2,4,6-tripropyleneoxy-1,3,5-triazine (molecular weight 249), CAS: 25988-85-6, 4,4'-dimercaptodiphenyl sulfide (molecular weight 250) into a closed reactor in proportion, introduce nitrogen, add tetramethylguanidine under stirring, and react at 60-70°C for 3-7h under nitrogen protection;

[0016] T2: Add diallyl selenium (molecular weight 161) and react at 60-70° C. for 1-3 hours under nitrogen protection to obtain a selenium-doped trimer dispersant.

[0017] As an optional embodiment, the molar ratio of hexafluoropropylene trimer: 2,4,6-tripropyleneoxy-1,3,5-triazine: 4,4'-dimercaptodiphenyl sulfide: tetramethylguanidine: diallyl selenium is 1-1.2: 0.003-0.03: 1.5-2.5: 0.02-0.05: 0.0005-0.005.

[0018] As an optional embodiment, the vulcanization site monomer CTA in step a is an iodinated alkane, including perfluorobutyl iodide, perfluoropropyl diiodide, and perfluorodiiodoethane.

[0019] As an optional embodiment, in step a, the molar ratio of the mixed monomer 1 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene is (35-55): (15-32.5): (20-32.5).

[0020] As an optional embodiment, the initiator in step a is selected from at least one of ammonium persulfate, sodium persulfate and potassium persulfate.

[0021] As an optional embodiment, in step b, the molar ratio of the mixed monomers of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene is (35-55): (15-32.5): (20-32.5).

[0022] As an optional embodiment, the vulcanization site monomer CSM in step b is selected from at least one of trifluoroethylene bromide, difluoroethylene bromide, trifluoroethylene iodide, perfluoroalkyl iodide vinyl ether, perfluoroalkyl bromide vinyl ether, and 3,3,4,4-tetrafluoro-4-bromobut-1-ene.

[0023] Reaction mechanism:

[0024] 1. Effect of triazine: The nitrogen atoms in the triazine structure can form NC bonds with carbon cations in the polymer, thereby enhancing the crosslinking density and improving thermal stability.

[0025] 2. The role of phenylene sulfide: The sulfur atoms in phenylene sulfide form weak FS interactions with the fluorine atoms in the polymer, increasing the rigidity of the polymer chain and improving heat resistance.

[0026] 3. Contribution of selenium complexes: Selenium complexes act as catalysts or co-catalysts in polymerization reactions, accelerating the reaction and further functionalizing the polymer by forming chemical bonds such as SeC.

[0027] Technical effect:

[0028] 1. Improve thermal stability: The additional cross-linking points provided by triazine, the increased segment rigidity of phenylene sulfide, and the catalytic effect of selenium complexes jointly improve the thermal stability of the polymer.

[0029] 2. Enhanced chemical stability: These functional groups work together through different mechanisms to protect the polymer backbone from chemical attack, allowing it to maintain the integrity of its physical and chemical properties even under extreme conditions.

[0030] 3. The peroxide-cured fluororubber prepared by the method provided by the present invention has a fluorine content that is stable at 70-71%, a compression deformation that is stable at ≤20%, a tensile strength of about 22 MPa, and an elongation at break that is greater than 180%. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The TGA spectrum of the peroxide-cured fluororubber prepared in Example 1;

[0032] Figure 2 The TGA spectrum of the peroxide-cured fluororubber prepared in Example 2;

[0033] Figure 3 This is the solid-state NMR spectrum of the peroxide-cured fluororubber prepared in Example 1. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0035] Example 1

[0036] A method for preparing high-fluorine content and low-compression deformation peroxide-cured fluororubber, the operating steps of which are:

[0037] a. In a high-pressure reactor, add 3kg of deoxygenated deionized water, evacuate the reactor, add 0.025kg of dispersant and 0.01kg of vulcanization point monomer CTA, stir evenly, heat the reactor to 100°C, introduce a mixed monomer 1 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene, make the pressure in the reactor 2.0MPa, then add 0.01kg of initiator to initiate the polymerization reaction;

[0038] b. After the polymerization reaction is carried out, the pressure in the reactor is maintained constant by adding a mixed monomer 2 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene. When the mixed monomer begins to be added at a total amount of 5%, the vulcanization point monomer CTA and the vulcanization point monomer CSM are continuously added at a constant flow rate;

[0039] c. When the solid content of the emulsion in the reactor reaches 25wt%, the polymerization reaction is terminated, the unreacted monomers are recovered, and the emulsion is placed in a coagulation barrel, and after coagulation and drying, peroxide-cured fluororubber is obtained.

[0040] In the step a, the reactor is evacuated until the oxygen content is ≤20 ppm.

[0041] The dispersant in step a is selected from a selenium-doped trimer dispersant, and the specific steps of its synthesis are:

[0042] T1: Hexafluoropropylene trimer (molecular weight 150), 2,4,6-tripropyleneoxy-1,3,5-triazine (molecular weight 249), CAS: 25988-85-6, 4,4'-dimercaptodiphenyl sulfide (molecular weight 250) were added into a closed reactor in proportion, nitrogen was introduced, tetramethylguanidine was added under stirring, and the reaction was carried out at 60°C for 3 hours under nitrogen protection;

[0043] T2: Diallyl selenium (molecular weight 161) was added, and the mixture was reacted at 60° C. for 1 h under nitrogen protection to obtain a selenium-doped trimer dispersant.

[0044] The molar ratio of the hexafluoropropylene trimer: 2,4,6-tripropyleneoxy-1,3,5-triazine: 4,4'-dimercaptodiphenyl sulfide: tetramethylguanidine: diallyl selenium is 1: 0.003: 1.5: 0.02: 0.0005.

[0045] In the step a, the vulcanization point monomer CTA is an iodinated alkane selected from perfluorobutyl iodide.

[0046] In the step a, the molar ratio of the mixed monomer 1 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene is 35:32.5:32.5.

[0047] In the step a, the initiator is selected from ammonium persulfate.

[0048] In the step b, the molar ratio of the mixed monomers of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene is 35:32.5:32.5.

[0049] In the step b, the vulcanization point monomer CSM is selected from trifluoroethylene bromide.

[0050] Example 2

[0051] A method for preparing high-fluorine content and low-compression deformation peroxide-cured fluororubber, the operating steps of which are:

[0052] a. In a high-pressure reactor, add 40kg of deoxygenated deionized water, evacuate the reactor, add 0.035kg of dispersant and 0.02kg of vulcanization point monomer CTA, stir evenly, heat the reactor to 90°C, introduce a mixed monomer 1 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene, make the pressure in the reactor 2.5MPa, then add 0.01kg of initiator to initiate the polymerization reaction;

[0053] b. After the polymerization reaction is carried out, the pressure in the reactor is maintained constant by adding a mixed monomer 2 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene. When the mixed monomer begins to be added at a total amount of 5%, the vulcanization point monomer CTA and the vulcanization point monomer CSM are continuously added at a constant flow rate;

[0054] c. When the solid content of the emulsion in the reactor reaches 30wt%, the polymerization reaction is terminated, the unreacted monomers are recovered, and the emulsion is placed in a coagulation barrel, and the peroxide-cured fluororubber is obtained after coagulation and drying.

[0055] In the step a, the reactor is evacuated until the oxygen content is ≤20 ppm.

[0056] The dispersant in step a is selected from a selenium-doped trimer dispersant, and the specific steps of its synthesis are:

[0057] T1: Hexafluoropropylene trimer (molecular weight 150), 2,4,6-tripropyleneoxy-1,3,5-triazine (molecular weight 249), CAS: 25988-85-6, 4,4'-dimercaptodiphenyl sulfide (molecular weight 250) were added into a closed reactor in proportion, nitrogen was introduced, tetramethylguanidine was added under stirring, and the reaction was carried out at 65°C for 5 hours under nitrogen protection;

[0058] T2: Add diallyl selenium (molecular weight 161) and react at 65° C. for 2 h under nitrogen protection to obtain a selenium-doped trimer dispersant.

[0059] The molar ratio of the hexafluoropropylene trimer: 2,4,6-tripropyleneoxy-1,3,5-triazine: 4,4'-dimercaptodiphenyl sulfide: tetramethylguanidine: diallyl selenium is 1.1: 0.01: 2: 0.02: 0.001.

[0060] In the step a, the vulcanization point monomer CTA is an iodinated alkane selected from perfluoropropyl diiodide.

[0061] In the step a, the molar ratio of the mixed monomer 1 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene is 40:30:30.

[0062] In the step a, the initiator is selected from sodium persulfate.

[0063] In the step b, the molar ratio of the mixed monomers of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene is 40:30:30.

[0064] In the step b, the vulcanization point monomer CSM is selected from difluoroethylene bromide.

[0065] Example 3

[0066] A method for preparing high-fluorine content and low-compression deformation peroxide-cured fluororubber, the operating steps of which are:

[0067] a. Add 40kg of deoxygenated deionized water into a high-pressure reactor, evacuate the reactor, add 0.035kg of dispersant and 0.02kg of vulcanization point monomer CTA, stir evenly, heat the reactor to 90°C, introduce a mixed monomer 1 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene, make the pressure in the reactor 3MPa, then add 0.02kg of initiator to initiate the polymerization reaction;

[0068] b. After the polymerization reaction is carried out, the pressure in the reactor is maintained constant by adding a mixed monomer 2 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene. When the mixed monomer begins to be added at a total amount of 5%, the vulcanization point monomer CTA and the vulcanization point monomer CSM are continuously added at a constant flow rate;

[0069] c. When the solid content of the emulsion in the reactor reaches 30wt%, the polymerization reaction is terminated, the unreacted monomers are recovered, and the emulsion is placed in a coagulation barrel, and the peroxide-cured fluororubber is obtained after coagulation and drying.

[0070] In the step a, the reactor is evacuated until the oxygen content is ≤20 ppm.

[0071] The dispersant in step a is selected from a selenium-doped trimer dispersant, and the specific steps of its synthesis are:

[0072] T1: Hexafluoropropylene trimer (molecular weight 150), 2,4,6-tripropyleneoxy-1,3,5-triazine (molecular weight 249), CAS: 25988-85-6, 4,4'-dimercaptodiphenyl sulfide (molecular weight 250) were added into a closed reactor in proportion, nitrogen was introduced, tetramethylguanidine was added under stirring, and the reaction was carried out at 65°C for 5 hours under nitrogen protection;

[0073] T2: Add diallyl selenium (molecular weight 161) and react at 65° C. for 2 h under nitrogen protection to obtain a selenium-doped trimer dispersant.

[0074] The molar ratio of the hexafluoropropylene trimer: 2,4,6-tripropyleneoxy-1,3,5-triazine: 4,4'-dimercaptodiphenyl sulfide: tetramethylguanidine: diallyl selenium is 1.1: 0.02: 2: 0.03: 0.003.

[0075] In the step a, the vulcanization point monomer CTA is an iodinated alkane selected from perfluoropropyl diiodide.

[0076] In the step a, the molar ratio of the mixed monomer 1 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene is 45:25:30.

[0077] In the step a, the initiator is selected from sodium persulfate.

[0078] In the step b, the molar ratio of the mixed monomers of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene is 45:25:30.

[0079] In the step b, the vulcanization site monomer CSM is selected from iodotrifluoroethylene.

[0080] Example 4

[0081] A method for preparing high-fluorine content and low-compression deformation peroxide-cured fluororubber, the operating steps of which are:

[0082] a. Add 50kg of deoxygenated deionized water into a high-pressure reactor, evacuate the reactor, add 0.045kg of dispersant and 0.03kg of vulcanization point monomer CTA, stir evenly, heat the reactor to 100°C, introduce a mixed monomer 1 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene, make the pressure in the reactor 3.5MPa, then add 0.02kg of initiator to initiate the polymerization reaction;

[0083] b. After the polymerization reaction is carried out, the pressure in the reactor is maintained constant by adding a mixed monomer 2 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene. When the mixed monomer begins to be added at a total amount of 5%, the vulcanization point monomer CTA and the vulcanization point monomer CSM are continuously added at a constant flow rate;

[0084] c. When the solid content of the emulsion in the reactor reaches 35wt%, the polymerization reaction is terminated, the unreacted monomers are recovered, and the emulsion is placed in a coagulation barrel, and after coagulation and drying, peroxide-cured fluororubber is obtained.

[0085] In the step a, the reactor is evacuated until the oxygen content is ≤20 ppm.

[0086] The dispersant in step a is selected from a selenium-doped trimer dispersant, and the specific steps of its synthesis are:

[0087] T1: Hexafluoropropylene trimer (molecular weight 150), 2,4,6-tripropyleneoxy-1,3,5-triazine (molecular weight 249), CAS: 25988-85-6, 4,4'-dimercaptodiphenyl sulfide (molecular weight 250) were added into a closed reactor in proportion, nitrogen was introduced, tetramethylguanidine was added under stirring, and the reaction was carried out at 70°C for 7 hours under nitrogen protection;

[0088] T2: Diallyl selenium (molecular weight 161) was added, and the mixture was reacted at 70° C. for 3 h under nitrogen protection to obtain a selenium-doped trimer dispersant.

[0089] The molar ratio of the hexafluoropropylene trimer: 2,4,6-tripropyleneoxy-1,3,5-triazine: 4,4'-dimercaptodiphenyl sulfide: tetramethylguanidine: diallyl selenium is 1.2: 0.03: 2.5: 0.05: 0.005.

[0090] In the step a, the vulcanization point monomer CTA is an iodinated alkane, including perfluorodiiodoethane.

[0091] In the step a, the molar ratio of the mixed monomer 1 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene is 45:32.5:22.5.

[0092] In the step a, the initiator is selected from potassium persulfate.

[0093] In the step b, the molar ratio of the mixed monomers of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene is 45:32.5:22.5.

[0094] In the step b, the vulcanization site monomer CSM is selected from perfluoroalkyl bromide vinyl ether.

[0095] Comparative Example 1

[0096] A method for preparing high-fluorine content and low-compression deformation peroxide-cured fluororubber, the operating steps of which are:

[0097] a. In a high-pressure reactor, add 3kg of deoxygenated deionized water, evacuate the reactor, add 0.025kg of dispersant and 0.01kg of vulcanization point monomer CTA, stir evenly, heat the reactor to 100°C, introduce a mixed monomer 1 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene, make the pressure in the reactor 2.0MPa, then add 0.01kg of initiator to initiate the polymerization reaction;

[0098] b. After the polymerization reaction is carried out, the pressure in the reactor is maintained constant by adding a mixed monomer 2 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene. When the mixed monomer begins to be added at a total amount of 5%, the vulcanization point monomer CTA and the vulcanization point monomer CSM are continuously added at a constant flow rate;

[0099] c. When the solid content of the emulsion in the reactor reaches 25wt%, the polymerization reaction is terminated, the unreacted monomers are recovered, and the emulsion is placed in a coagulation barrel, and after coagulation and drying, peroxide-cured fluororubber is obtained.

[0100] In the step a, the reactor is evacuated until the oxygen content is ≤20 ppm.

[0101] The dispersant in step a is selected from a selenium-doped trimer dispersant, and the specific steps of its synthesis are:

[0102] T1: Hexafluoropropylene trimer (molecular weight 150), 2,4,6-tripropyleneoxy-1,3,5-triazine (molecular weight 249), CAS: 25988-85-6, 4,4'-dimercaptodiphenyl sulfide (molecular weight 250) were added into a closed reactor in proportion, nitrogen was introduced, tetramethylguanidine was added under stirring, and the reaction was carried out at 60°C for 3 hours under nitrogen protection;

[0103] T2: Diallyl selenium (molecular weight 161) was added, and the mixture was reacted at 60° C. for 1 h under nitrogen protection to obtain a selenium-doped trimer dispersant.

[0104] The molar ratio of the hexafluoropropylene trimer: 4,4'-dimercaptodiphenyl sulfide: tetramethylguanidine: diallyl selenium is 1:1.5:0.02:0.0005.

[0105] In the step a, the vulcanization point monomer CTA is an iodinated alkane selected from perfluorobutyl iodide.

[0106] In the step a, the molar ratio of the mixed monomer 1 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene is 35:32.5:32.5.

[0107] In the step a, the initiator is selected from ammonium persulfate.

[0108] In the step b, the molar ratio of the mixed monomers of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene is 35:32.5:32.5.

[0109] In the step b, the vulcanization point monomer CSM is selected from trifluoroethylene bromide.

[0110] Comparative Example 2

[0111] A method for preparing high-fluorine content and low-compression deformation peroxide-cured fluororubber, the operating steps of which are:

[0112] a. In a high-pressure reactor, add 3kg of deoxygenated deionized water, evacuate the reactor, add 0.025kg of dispersant and 0.01kg of vulcanization point monomer CTA, stir evenly, heat the reactor to 100°C, introduce a mixed monomer 1 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene, make the pressure in the reactor 2.0MPa, then add 0.01kg of initiator to initiate the polymerization reaction;

[0113] b. After the polymerization reaction is carried out, the pressure in the reactor is maintained constant by adding a mixed monomer 2 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene. When the mixed monomer begins to be added at a total amount of 5%, the vulcanization point monomer CTA and the vulcanization point monomer CSM are continuously added at a constant flow rate;

[0114] c. When the solid content of the emulsion in the reactor reaches 25wt%, the polymerization reaction is terminated, the unreacted monomers are recovered, and the emulsion is placed in a coagulation barrel, and after coagulation and drying, peroxide-cured fluororubber is obtained.

[0115] In the step a, the reactor is evacuated until the oxygen content is ≤20 ppm.

[0116] The dispersant in step a is selected from a selenium-doped trimer dispersant, and the specific steps of its synthesis are:

[0117] T1: Hexafluoropropylene trimer (molecular weight 150), 2,4,6-tripropyleneoxy-1,3,5-triazine (molecular weight 249), CAS: 25988-85-6, 4,4'-dimercaptodiphenyl sulfide (molecular weight 250) were added into a closed reactor in proportion, nitrogen was introduced, tetramethylguanidine was added under stirring, and the reaction was carried out at 60°C for 3 hours under nitrogen protection;

[0118] T2: Diallyl selenium (molecular weight 161) was added, and the mixture was reacted at 60° C. for 1 h under nitrogen protection to obtain a selenium-doped trimer dispersant.

[0119] The molar ratio of the hexafluoropropylene trimer: 2,4,6-tripropyleneoxy-1,3,5-triazine: tetramethylguanidine: diallyl selenium is 1: 0.003: 0.02: 0.0005.

[0120] In the step a, the vulcanization point monomer CTA is an iodinated alkane selected from perfluorobutyl iodide.

[0121] In the step a, the molar ratio of the mixed monomer 1 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene is 35:32.5:32.5.

[0122] In the step a, the initiator is selected from ammonium persulfate.

[0123] In the step b, the molar ratio of the mixed monomers of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene is 35:32.5:32.5.

[0124] In the step b, the vulcanization point monomer CSM is selected from trifluoroethylene bromide.

[0125] Comparative Example 3

[0126] A method for preparing high-fluorine content and low-compression deformation peroxide-cured fluororubber, the operating steps of which are:

[0127] a. In a high-pressure reactor, add 3kg of deoxygenated deionized water, evacuate the reactor, add 0.025kg of dispersant and 0.01kg of vulcanization point monomer CTA, stir evenly, heat the reactor to 100°C, introduce a mixed monomer 1 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene, make the pressure in the reactor 2.0MPa, then add 0.01kg of initiator to initiate the polymerization reaction;

[0128] b. After the polymerization reaction is carried out, the pressure in the reactor is maintained constant by adding a mixed monomer 2 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene. When the mixed monomer begins to be added at a total amount of 5%, the vulcanization point monomer CTA and the vulcanization point monomer CSM are continuously added at a constant flow rate;

[0129] c. When the solid content of the emulsion in the reactor reaches 25wt%, the polymerization reaction is terminated, the unreacted monomers are recovered, and the emulsion is placed in a coagulation barrel, and after coagulation and drying, peroxide-cured fluororubber is obtained.

[0130] In the step a, the reactor is evacuated until the oxygen content is ≤20 ppm.

[0131] The dispersant in step a is selected from a selenium-doped trimer dispersant, and the specific steps of its synthesis are:

[0132] T1: Hexafluoropropylene trimer (molecular weight 150), 2,4,6-tripropyleneoxy-1,3,5-triazine (molecular weight 249), CAS: 25988-85-6, 4,4'-dimercaptodiphenyl sulfide (molecular weight 250) were added into a closed reactor in proportion, nitrogen was introduced, tetramethylguanidine was added under stirring, and the reaction was carried out at 60°C for 3 hours under nitrogen protection;

[0133] T2: Diallyl selenium (molecular weight 161) was added, and the mixture was reacted at 60° C. for 1 h under nitrogen protection to obtain a selenium-doped trimer dispersant.

[0134] The molar ratio of the hexafluoropropylene trimer: 2,4,6-tripropyleneoxy-1,3,5-triazine: 4,4'-dimercaptodiphenyl sulfide: tetramethylguanidine is 1: 0.003: 1.5: 0.02.

[0135] In the step a, the vulcanization point monomer CTA is an iodinated alkane selected from perfluorobutyl iodide.

[0136] In the step a, the molar ratio of the mixed monomer 1 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene is 35:32.5:32.5.

[0137] In the step a, the initiator is selected from ammonium persulfate.

[0138] In the step b, the molar ratio of the mixed monomers of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene is 35:32.5:32.5.

[0139] In the step b, the vulcanization point monomer CSM is selected from trifluoroethylene bromide.

[0140] Evaluation of the embodiment:

[0141] 1. Determination of fluorine content

[0142] Weigh an appropriate amount of vulcanized fluororubber sample, crush it and mix it evenly.

[0143] The oxygen bomb combustion method (oxygen bomb combustion coulometer) is adopted, and the specific steps are as follows:

[0144] 1) Place the rubber sample in an oxygen bomb and burn it in a high-pressure oxygen environment.

[0145] 2) The combustion products are absorbed by the absorption liquid.

[0146] 2. Compression deformation measurement

[0147] Prepare rubber specimens of standard size, usually cylindrical (12.5 mm in diameter and 6.3 mm in height).

[0148] The test was carried out at 70°C.

[0149] 1) Place the sample in a compression device and keep it at a compression rate of 25% for 24 hours.

[0150] 2) After the test, remove the sample from the compression device and return it to room temperature for 30 minutes.

[0151] 3) Measure the height after recovery.

[0152] 3. Tensile strength determination

[0153] Standard dumbbell-shaped rubber specimens were prepared, and their dimensions were in accordance with GB / T 528-2009 (ISO 37:2005) standard.

[0154] The test was carried out at room temperature.

[0155] 1) Use a universal material testing machine to perform a tensile test at a constant tensile speed (such as 500 mm / min).

[0156] 2) Record the maximum tensile force of the specimen.

[0157] 4. Determination of elongation at break

[0158] Dumbbell-shaped rubber specimens are the same as those used for tensile strength determination.

[0159] The test was carried out at room temperature.

[0160] 1) Using a universal material testing machine, continue stretching until the specimen breaks.

[0161] 2) Record the elongation at break of the specimen.

[0162] 5. Thermal stability test

[0163] Thermogravimetric analysis (TGA)

[0164] 1) Take an appropriate amount of vulcanized fluororubber sample and make it into a suitable size so that it can be placed in the thermogravimetric analyzer.

[0165] 2) Place the sample in a thermogravimetric analyzer and set the temperature range from room temperature to 600°C at a heating rate of 10°C / min.

[0166] Test results:

[0167]

[0168]

[0169] Through the above detailed testing methods, the excellent performance of the peroxide-cured fluororubber provided by the present invention can be comprehensively evaluated.

[0170] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing high fluorine content and low compression deformation peroxide-cured fluororubber, the operating steps of which are: a. In a high-pressure reactor, add 30-50 parts of deoxygenated deionized water, evacuate the reactor, then add 0.025-0.045 parts of dispersant and 0.01-0.03 parts of vulcanization point monomer CTA, stir evenly, heat the reactor to 80-100°C, introduce a mixed monomer 1 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene, make the pressure in the reactor 2.0-3.5MPa, then add 0.01-0.02 parts of initiator to initiate the polymerization reaction; b. After the polymerization reaction is carried out, the pressure in the reactor is maintained constant by adding a mixed monomer 2 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene. When the mixed monomer begins to be added at a total amount of 5%, the vulcanization point monomer CTA and the vulcanization point monomer CSM are continuously added at a constant flow rate; c. When the solid content of the emulsion in the reactor reaches 25-35wt%, the polymerization reaction is terminated, the unreacted monomers are recovered, and the emulsion is placed in a coagulation barrel, and after coagulation and drying, peroxide-cured fluororubber is obtained.

2. The method for preparing a high fluorine content and low compression set peroxide-cured fluororubber according to claim 1, characterized in that: In the step a, the reactor is evacuated until the oxygen content is ≤20 ppm.

3. The method for preparing a high fluorine content and low compression set peroxide-cured fluororubber according to claim 1, characterized in that: The dispersant in step a is selected from a selenium-doped trimer dispersant, and the specific steps of its synthesis are: T1: Add hexafluoropropylene trimer, 2,4,6-tripropyleneoxy-1,3,5-triazine, and 4,4'-dimercaptodiphenyl sulfide into a closed reactor in proportion, introduce nitrogen, add tetramethylguanidine under stirring, and react at 60-70°C for 3-7h under nitrogen protection; T2: Add diallyl selenium and react at 60-70° C. for 1-3 hours under nitrogen protection to obtain a selenium-doped trimer dispersant.

4. The method for preparing a high fluorine content and low compression set peroxide-cured fluororubber according to claim 3, characterized in that: The molar ratio of the hexafluoropropylene trimer: 2,4,6-tripropyleneoxy-1,3,5-triazine: 4,4'-dimercaptodiphenyl sulfide: tetramethylguanidine: diallyl selenium is 1-1.2: 0.003-0.03: 1.5-2.5: 0.02-0.05: 0.0005-0.

005.

5. The method for preparing a high fluorine content and low compression set peroxide-cured fluororubber according to claim 1, characterized in that: In the step a, the vulcanization point monomer CTA is an iodinated alkane, including perfluorobutyl iodide, perfluoropropyl diiodide, and perfluorodiiodoethane.

6. The method for preparing a high fluorine content and low compression set peroxide-cured fluororubber according to claim 1, characterized in that: In the step a, the molar ratio of the mixed monomer 1 of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene is (35-55): (15-32.5): (20-32.5).

7. The method for preparing a high fluorine content and low compression set peroxide-cured fluororubber according to claim 1, characterized in that: In step a, the initiator is selected from at least one of ammonium persulfate, sodium persulfate and potassium persulfate.

8. The method for preparing a high fluorine content and low compression set peroxide-cured fluororubber according to claim 1, characterized in that: In the step b, the molar ratio of the mixed monomers of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene is (35-55): (15-32.5): (20-32.5).

9. The method for preparing a high fluorine content and low compression set peroxide-cured fluororubber according to claim 1, characterized in that: In the step b, the vulcanization site monomer CSM is selected from at least one of trifluoroethylene bromide, difluoroethylene bromide, trifluoroethylene iodide, perfluoroalkyl iodide vinyl ether, perfluoroalkyl bromide vinyl ether, and 3,3,4,4-tetrafluoro-4-bromobut-1-ene.

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