Preparation method and system of fluorine-containing polymer

Abstract

The invention belongs to the technical field of fluorine-containing polymers, and particularly relates to a preparation method and system of a fluorine-containing polymer. The invention provides a preparation method of a fluorine-containing polymer, which comprises the following steps: (1) adding high-purity water into a polymerization kettle, adding a surfactant with the concentration exceeding the critical micelle concentration into the high-purity water, and stirring at the rotating speed of 100-150rpm for micro-emulsification; (2) adding a gas-phase PAVE monomer into the polymerization kettle, and continuously stirring at the rotating speed of 100-150rpm, so that the PAVE monomer is adsorbed by the surfactant micelles; and (3) reducing the stirring speed to 30-50 rpm, adding a chain transfer agent and an initiator into the polymerization kettle, uniformly mixing the gas-phase PAVE monomer and the gas-phase TFE monomer, adding the mixture into the polymerization kettle, and carrying out a copolymerization reaction. According to the preparation method, the conversion rate of the PAVE monomer in the PFA polymerization reaction can be improved, and the production cost of the PFA is obviously reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fluoropolymers, and particularly relates to a preparation method and system of fluoropolymers. BACKGROUND

[0002] The fluorine chemical industry is a new industry developed in the middle of the 20th century, and is also a technology-intensive industry. It has the characteristics of multiple product varieties and brands, wide application, high technical content, high added value, and good economic benefits; and has the characteristics of complex production process, high equipment requirements, difficult production, and relatively small product scale. In the fluorine chemical industry, fluoropolymer products have excellent high and low temperature performance and chemical stability, as well as good insulation, non-adhesion, low friction, non-flammability, and lubricity, and are widely used in aerospace, petroleum and chemical industry, machinery, electronics, construction and other industrial departments, and become an indispensable main synthetic material in the industrial field.

[0003] The raw material cost of perfluoroalkyl ethylene (PAVE) is the main cost source in the production process of meltable polytetrafluoroethylene (PFA), and the conversion rate of PAVE needs to be excessively added during the reaction process,

[0004] Therefore, how to improve the conversion rate of PAVE in the PFA polymerization reaction to reduce the production cost of PFA has attracted more and more widespread attention. SUMMARY

[0005] The present application aims to at least solve one of the technical problems in the related art. To this end, an embodiment of the present application proposes a preparation method of fluoropolymers.

[0006] The preparation method of fluoropolymers of the present application embodiment comprises the following steps:

[0007] (1) After adding high-purity water in the polymerization kettle, a surfactant exceeding the critical micelle concentration is added to the high-purity water, and the stirring treatment is carried out at a speed of 100-150 rpm for microemulsification;

[0008] (2) The gas-phase PAVE monomer is added to the polymerization kettle, and the stirring treatment is continued at a speed of 100-150 rpm, so that the PAVE monomer is adsorbed by the surfactant micelles;

[0009] (3) The stirring speed is reduced to 30-50 rpm, the chain transfer agent and the initiator are added to the polymerization kettle, and the gas-phase PAVE monomer and the gas-phase TFE monomer are mixed uniformly and then added to the polymerization kettle for copolymerization reaction.

[0010] The preparation method of the fluorine-containing polymer has the following advantages and technical effects: 1. The method can improve the solubility and reaction speed of the PAVE monomer and reduce the addition amount of the PAVE monomer; 2. The method can increase the PAVE content in the micelle and improve the conversion rate of the PAVE in the subsequent copolymerization reaction process; and 3. The method can improve the uniformity of the monomer distribution and avoid the uneven distribution of the molecular weight and the PAVE content of the PFA product.

[0011] In some embodiments, the surfactant in step (1) includes at least one of ammonium perfluorooctanoate, ammonium perfluorooctylsulfonate, perfluorooctylsulfonamide, ammonium perfluorohexanoate, or ammonium perfluoro-2,5-dimethyl-3,6-dioxanonanoate.

[0012] In some embodiments, the mass ratio of the high-purity water to the surfactant in step (1) is (200-350):1.

[0013] In some embodiments, the stirring time in step (1) is 10-20 min.

[0014] In some embodiments, the mass ratio of the gaseous PAVE monomer to the surfactant in step (2) is (5-9):1.

[0015] In some embodiments, the PAVE in step (2) includes at least one of perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, or perfluoro-n-propyl vinyl ether.

[0016] In some embodiments, the stirring time in step (2) is 5-10 min.

[0017] In some embodiments, the chain transfer agent in step (3) includes a straight-chain alkane, and the molecular formula of the straight-chain alkane is CnH2n+2, where n=1-4. n H 2n+2 The mass ratio of the chain transfer agent to TFE is 1 / 15000-1 / 1000.

[0018] In some embodiments, the initiator in step (3) includes at least one of a potassium persulfate aqueous solution or an ammonium persulfate aqueous solution, the mass ratio of the initiator to TFE is 1 / 30000-1 / 3000, and the concentration of the potassium persulfate aqueous solution or the ammonium persulfate aqueous solution is 0.1-3%.

[0019] In some embodiments, in the step (3), the mass ratio of the gas-phase PAVE monomer and the gas-phase TFE monomer is 1:(8-25), and the mass ratio of the TFE and the high-purity water is 1:(2-3.5).

[0020] In some embodiments, in the step (3), the temperature of the copolymerization reaction is 60-120°C, the pressure of the copolymerization reaction is 1.5-5.0 MPa, and the time of the copolymerization reaction is 90-240 min.

[0021] The embodiments of the present application also provide a system for implementing the above method for preparing the fluorine-containing polymer, which comprises a PAVE metering pump, a PAVE heater, a gas mixer and a polymerization kettle, wherein the liquid outlet of the PAVE metering pump is connected with the liquid inlet of the PAVE heater, the gas outlet of the PAVE heater is connected with the gas inlet of the gas mixer, and the gas outlet of the gas mixer is connected with the gas inlet of the polymerization kettle. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 FIG. 1 is a schematic diagram of a system for preparing a fluorine-containing polymer according to an embodiment of the present application;

[0023] In the figure, 1 represents a PAVE metering pump, 2 represents a PAVE heater, 3 represents a gas mixer, and 4 represents a polymerization kettle. DETAILED DESCRIPTION

[0024] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0025] The method for preparing the fluorine-containing polymer according to an embodiment of the present application comprises the following steps:

[0026] (1) After adding high-purity water into a polymerization kettle, a surfactant in excess of a critical micelle concentration is added into the high-purity water, and the stirring treatment is carried out at a stirring speed of 100-150 rpm to perform microemulsification;

[0027] (2) A gas-phase PAVE monomer is added into the polymerization kettle, and the stirring treatment is continuously carried out at a stirring speed of 100-150 rpm to enable the PAVE monomer to be adsorbed by the surfactant micelles;

[0028] (3) The stirring speed is reduced to 30-50 rpm, a chain transfer agent and an initiator are added into the polymerization kettle, and the gas-phase PAVE monomer and the gas-phase TFE monomer are mixed uniformly and then added into the polymerization kettle to perform a copolymerization reaction.

[0029] The preparation method of the fluorine-containing polymer of the embodiment can improve the solubility and reaction speed of the PAVE monomer, and reduce the addition amount of the PAVE monomer; in the method, the gaseous PAVE monomer is first added and adsorbed by micelles, so that the content of the PAVE in the dissolved monomers in the micelles is increased, and the conversion rate of the PAVE is increased in the subsequent copolymerization reaction process with TFE; in the embodiment, the PAVE and TFE monomers are added in the gaseous phase, so that the uniformity of the monomers is improved, and the non-uniformity of the molecular weight distribution and the content of the PAVE in the PFA product is avoided.

[0030] In some embodiments, preferably, at least one of the surfactants in step (1) is ammonium perfluorooctanoate, ammonium perfluorooctylsulfonate, ammonium perfluorooctylsulfonamide, ammonium perfluorohexanoate, or ammonium perfluoro-2,5-dimethyl-3,6-dioxanonanoate.

[0031] In some embodiments, preferably, the mass ratio of the high-purity water to the surfactant in step (1) is (200-350):1.

[0032] In some embodiments, preferably, the stirring treatment time in step (1) is 10-20 min.

[0033] In some embodiments, preferably, the mass ratio of the gaseous PAVE monomer to the surfactant in step (2) is (5-9):1.

[0034] In some embodiments, preferably, the PAVE in step (2) includes at least one of perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, and perfluoro-n-propyl vinyl ether.

[0035] In some embodiments, preferably, the stirring treatment time in step (2) is 5-10 min.

[0036] In some embodiments, preferably, the chain transfer agent in step (3) includes a straight-chain alkane, and the molecular formula of the straight-chain alkane is CnH2n+2, where n=1-4. n H 2n+2 The mass ratio of the chain transfer agent to TFE is 1 / 15000-1 / 1000.

[0037] In some embodiments, preferably, the initiator in step (3) includes at least one of a potassium persulfate aqueous solution or an ammonium persulfate aqueous solution, the mass ratio of the initiator to TFE is 1 / 30000-1 / 3000, and the concentration of the potassium persulfate aqueous solution or the ammonium persulfate aqueous solution is 0.1-3%.

[0038] In some embodiments, preferably, in step (3), the mass ratio of the gaseous PAVE monomer to the gaseous TFE monomer is 1:(8-25), and the mass ratio of the TFE to high-purity water is 1:(2-3.5).

[0039] And / or, in step (3), the temperature of the copolymerization reaction is 60-120°C, the pressure of the copolymerization reaction is 1.5-5.0 MPa, and the time of the copolymerization reaction is 90-240 min.

[0040] like Figure 1 As shown, this embodiment of the invention also provides a system for implementing the above-described method for preparing fluoropolymers, comprising: a PAVE metering pump 1, a PAVE heater 2, a gas mixer 3, and a polymerization reactor 4;

[0041] The liquid outlet of PAVE metering pump 1 is connected to the liquid inlet of PAVE heater 2, the gas outlet of PAVE heater 2 is connected to the gas inlet of gas mixer 3, and the gas outlet of gas mixer 3 is connected to the gas inlet of polymerization reactor 4.

[0042] PAVE liquid is delivered to PAVE heater 2 via PAVE metering pump 1. Hot water or steam is introduced into the shell side of PAVE heater 2 to heat and vaporize the PAVE liquid. The gaseous PAVE is then delivered to polymerization reactor 4 via gas mixer 3 for stirring. After the PAVE monomer is adsorbed by surfactant micelles, the gaseous PAVE and gaseous TFE are mixed evenly in gas mixer 3 and then enter polymerization reactor 4 for reaction.

[0043] The technical solution of the present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0044] Example 1

[0045] (1) After adding 4000 kg of water to the polymerization reactor, add 100 kg of 20% perfluoro-2,5-dimethyl-3,6-dioxanonate ammonium solution and stir at 100 rpm for 20 min to microemulsify the micelles.

[0046] (2) 160 kg of perfluoroethyl vinyl ether (PEVE) monomer was initially added and pressurized by a metering pump. Before entering the polymerization reactor, the PEVE liquid was vaporized by a steam heat exchanger and then the gaseous PEVE was added into the polymerization reactor. The mixture was stirred at 100 rpm for 6 min to allow the PAVE monomer to be adsorbed by surfactant micelles.

[0047] (3) After the addition of PEVE gas phase is completed, the stirring speed of the polymerizer is reduced to 30 rpm, 1 kg of C2H6 chain transfer agent and 0.5 kg of 0.7% potassium persulfate aqueous solution initiator are added, and 200 kg of PEVE gas phase monomer and 2000 kg of TFE gas phase monomer are mixed through a gas mixer and then added into the polymerizer. The copolymerization reaction is carried out at 100°C and 2.0 MPa for 200 min.

[0048] Example 2

[0049] (1) After 4000 kg of water is added into the polymerizer, 60 kg of 20% concentration of perfluoro-2,5-dimethyl-3,6-dioxanonanoic acid ammonium solution is added, and the stirring speed is 120 rpm. The micelles are micro-emulsified for 15 min;

[0050] (2) 108 kg of perfluoro-n-propyl vinyl ether (PPVE) monomer is initially added into the polymerizer through a metering pump with pressure boosting. The PPVE liquid is vaporized through a steam heat exchanger before entering the polymerizer, and then the gas phase PPVE is added into the polymerizer. The stirring speed is 120 rpm, and the PPVE monomer is adsorbed by the micelles of the surfactant for 5 min;

[0051] (3) After the addition of PPVE is completed, the stirring speed of the polymerizer is restored to 50 rpm, 0.3 kg of C3H8 chain transfer agent and 0.24 kg of 2% ammonium persulfate aqueous solution initiator are added, and 60 kg of PPVE gas phase monomer and 1200 kg of TFE gas phase monomer are mixed through a gas mixer and then added into the polymerizer. The copolymerization reaction is carried out at 120°C and 4.0 MPa for 150 min.

[0052] Comparative Example 1

[0053] The preparation method of the comparative example is the same as that of Example 1, except that in step (1), no stirring treatment is performed; and in step (2), the stirring speed is 30 rpm.

[0054] Comparative Example 2

[0055] The preparation method of the comparative example is the same as that of Example 1, except that in steps (2) and (3), PEVE and TFE are both added in liquid form.

[0056] The properties of the polymers prepared in Examples 1-2 and Comparative Examples 1-2 are characterized, and the results are shown in Table 1.

[0057] Table 1

[0058]

[0059] Note: The volatile matter refers to the mass loss rate of the polymer after being placed at 380°C for 30 min.

[0060] In this disclosure, the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" mean that a particular feature, structure, material, or characteristic is included in at least one embodiment or example of the present disclosure. The illustrative appearances of the above-mentioned terms in various places in the specification are not necessarily referred to the same embodiment or example. Moreover, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples. Furthermore, the terms "comprising", "containing", "having" and "including" and their derivatives, are not intended to exclude other features, structures, materials, or characteristics not expressly mentioned. The terms "comprising", "containing", "having" and "including" and their derivatives are intended to be equivalent to the terms "consisting of" and "consisting essentially of" and their derivatives.

[0061] Although the above-mentioned embodiments have been shown and described, it is understood that the above-mentioned embodiments are exemplary, and cannot be understood as limiting the present disclosure, and the changes, modifications, replacements and variations of the above-mentioned embodiments made by those skilled in the art are within the protection scope of the present disclosure.

Claims

1. A method for preparing a fluoropolymer, characterized in that, Includes the following steps: (1) After adding high-purity water to the polymerization reactor, a surfactant exceeding the critical micelle concentration is added to the high-purity water, and microemulsification is carried out by stirring at a speed of 100-150 rpm. (2) Add gaseous PAVE monomer to the polymerization reactor and continue stirring at a speed of 100-150 rpm to allow the PAVE monomer to be adsorbed by surfactant micelles. (3) Reduce the stirring speed to 30-50 rpm, add chain transfer agent and initiator to the polymerization reactor, and add gas phase PAVE monomer and gas phase TFE monomer after mixing evenly to the polymerization reactor for copolymerization reaction.

2. The method for preparing the fluoropolymer according to claim 1, characterized in that, In step (1), the surfactant includes at least one of ammonium perfluorooctanoate, ammonium perfluorooctyl sulfonate, perfluorooctyl sulfonamide, ammonium perfluorohexanoate, or ammonium perfluoro-2,5-dimethyl-3,6-dioxanonate.

3. The method for preparing the fluoropolymer according to claim 1 or 2, characterized in that, In step (1), the mass ratio of the high-purity water to the surfactant is (200-350):

1.

4. The method for preparing the fluoropolymer according to claim 3, characterized in that, In step (1), the stirring time is 10 to 20 minutes.

5. The method for preparing the fluoropolymer according to claim 1, characterized in that, In step (2), the mass ratio of the gas-phase PAVE monomer to the surfactant is (5-9):1; And / or, in step (2), the PAVE includes at least one of perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, and perfluoropropyl vinyl ether.

6. The method for preparing the fluoropolymer according to claim 1 or 5, characterized in that, In step (2), the stirring time is 5 to 10 minutes.

7. The method for preparing the fluoropolymer according to claim 1, characterized in that, In step (3), the chain transfer agent includes a straight-chain alkane with the molecular formula C1. n H 2n+2 Where n = 1 to 4; the mass ratio of the chain transfer agent to TFE is 1 / 15000 to 1 / 1000.

8. The method for preparing the fluoropolymer according to claim 1, characterized in that, In step (3), the initiator includes at least one of potassium persulfate aqueous solution or ammonium persulfate aqueous solution, and the mass ratio of the initiator to TFE is 1 / 30000 to 1 / 3000; the concentration of the potassium persulfate aqueous solution or ammonium persulfate aqueous solution is 0.1% to 3%.

9. The method for preparing the fluoropolymer according to claim 1, characterized in that, In step (3), the mass ratio of the gaseous PAVE monomer to the gaseous TFE monomer is 1:(8-25), and the mass ratio of the TFE to high-purity water is 1:(2-3.5). And / or, in step (3), the temperature of the copolymerization reaction is 60-120°C, the pressure of the copolymerization reaction is 1.5-5.0 MPa, and the time of the copolymerization reaction is 90-240 min.

10. A system for implementing the method for preparing a fluoropolymer according to any one of claims 1 to 9, characterized in that, include: PAVE metering pump, PAVE heater, gas mixer and polymerization reactor, The liquid outlet of the PAVE metering pump is connected to the liquid inlet of the PAVE heater, the gas outlet of the PAVE heater is connected to the gas inlet of the gas mixer, and the gas outlet of the gas mixer is connected to the gas inlet of the polymerization reactor.

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