Vinylidene fluoride polymer as well as green preparation method and application thereof

Abstract

The invention discloses a vinylidene fluoride polymer as well as a green preparation method and application thereof. The green preparation method of the vinylidene fluoride polymer comprises the following steps: carrying out free radical polymerization on a comonomer in a polymerization medium under the action of an inorganic free radical initiator to form the vinylidene fluoride polymer, the comonomer comprises a vinylidene fluoride monomer and a polyethylene glycol acrylate macromonomer; the polymerization medium comprises water and a chain transfer agent. According to the method disclosed by the invention, the amphiphilic polyethylene glycol acrylate macromonomer and the vinylidene fluoride monomer are subjected to emulsion random copolymerization, so that the high-performance vinylidene fluoride polymer is efficiently and stably prepared under the condition that an emulsifier is not used.

Description

Technical Field

[0001] This invention relates to the field of fluoropolymer preparation, and more specifically, to a vinylidene fluoride polymer, its green preparation method, and its applications. Background Technology

[0002] Emulsion polymerization is a common method for preparing vinylidene fluoride (PVDF) polymers. This process requires the use of emulsifiers to maintain the stability of the emulsion system. Appropriate emulsifiers and dosages can improve polymerization efficiency and latex stability, but inevitably lead to environmental problems, and their residues can affect polymer purity and performance. For example, perfluorooctanoic acid (PFOA) and its derivatives are difficult to degrade, exhibit persistent bioaccumulation, and pose extremely adverse effects on human and environmental health; therefore, their use is gradually being banned in the production of fluoropolymers. Some PVDF polymers produced using non-fluorinated emulsifiers exhibit yellowing during processing. Furthermore, the use of emulsifiers increases production costs and the complexity of post-processing unit operations. Regardless of the number of washing processes, emulsifier residues will always remain, affecting the use of PVDF polymers in high-end applications.

[0003] With increasingly stringent environmental and performance requirements, developing a green preparation method for vinylidene fluoride polymers has become an important research direction in this field. In recent years, researchers have attempted to reduce or avoid the use of emulsifiers by using novel initiators or auxiliaries and improving polymerization processes. However, these methods suffer from low polymerization efficiency, high cost, and unstable product performance, failing to achieve large-scale industrial production. For example, Chinese patent CN115677902B proposes a method for preparing vinylidene fluoride copolymers through soap-free emulsion polymerization. This process requires intermittent addition of initiators and chain transfer agents, and strict control of temperature and pressure during the reaction, lacking feasibility for the industrial production of vinylidene fluoride polymers. Summary of the Invention

[0004] This invention is based on the inventors' findings and understanding of the following facts and problems: appropriate emulsifiers and dosages help improve polymerization efficiency and latex stability, but inevitably cause environmental problems, and their residues affect polymer purity and performance. Current related technologies reduce or avoid the use of emulsifiers by using novel initiators or auxiliaries, or by improving polymerization processes, but these methods suffer from low polymerization efficiency, high cost, and unstable product performance, failing to achieve large-scale industrial production.

[0005] Polyethylene glycol acrylate macromonomers are functionalized PEG compounds containing carbon-carbon double bonds. They are non-toxic, biocompatible, and possess good hydrophilic and lipophilic properties. Their acrylate groups exhibit high reactivity under free radical initiators, radiation, or heat, and have been reported for graft modification of polyvinylidene fluoride (PVDF) membrane surfaces to improve the membrane's hydrophilicity and antifouling properties; or for forming block copolymers with PVDF through controlled free radical polymerization to improve the compatibility of PEO segments and PVDF in lithium-ion battery solid polymer electrolytes.

[0006] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a vinylidene fluoride polymer, its green preparation method, and its application. This method involves emulsion random copolymerization of amphiphilic polyethylene glycol acrylate macromonomers with vinylidene fluoride monomers, achieving efficient and stable preparation of a high-performance vinylidene fluoride polymer without the use of emulsifiers.

[0007] This invention provides a green preparation method for vinylidene fluoride polymer, comprising: forming a vinylidene fluoride polymer by free radical polymerization of comonomers in a polymerization medium under the action of an inorganic free radical initiator; wherein the comonomers comprise vinylidene fluoride monomers and polyethylene glycol acrylate macromonomers; and wherein the polymerization medium comprises water and a chain transfer agent.

[0008] The advantages and technical effects of the green preparation method of vinylidene fluoride polymer in this invention are as follows: by performing emulsion random copolymerization of amphiphilic polyethylene glycol acrylate macromonomer (PEG Acrylate) and vinylidene fluoride (VDF) monomer, the use of emulsifiers is eliminated or greatly reduced, and high-performance vinylidene fluoride polymers can be prepared efficiently and stably with almost no or no emulsifiers.

[0009] In this embodiment of the invention, an aqueous emulsion polymerization process is employed, and no emulsifier is used during polymerization under the action of an inorganic free radical initiator. In the structure of polyethylene glycol acrylate macromonomers, one end is an acrylate, which provides polymerization sites, and the other end is a polyethylene glycol chain, which possesses emulsifying capabilities. VDF monomers copolymerize with amphiphilic polyethylene glycol acrylate macromonomers to form polymer chains with self-emulsifying effects, ultimately yielding a stable polymer emulsion.

[0010] In some embodiments, the polyethylene glycol acrylate macromonomer includes at least one of the monomers represented by the following chemical formulas:

[0011] Wherein, R1 is selected from hydrogen atom or hydrocarbon group; R2 is selected from hydrogen atom, C1-C5 straight chain or branched alkylene group, wherein when R2 is selected from hydrogen atom, the chemical formula does not contain R3; R3 is selected from carboxyl group, amino group, mercapto group, acrylic group, acrylate group, and n is an integer from 2 to 200.

[0012] In some embodiments, the polyethylene glycol acrylate macromonomers include at least one of polyethylene glycol acrylate, polyethylene glycol methacrylate, polyethylene glycol diacrylate, carboxylated polyethylene glycol acrylate, and amino polyethylene glycol acrylate. And / or, the mass of the polyethylene glycol acrylate macromonomer is at least 0.1% of the total mass of the comonomer; And / or, the polyethylene glycol acrylate macromonomers are added in full before the polymerization reaction, and / or, added in stages during the polymerization reaction, and / or, added continuously throughout the entire polymerization reaction.

[0013] In some embodiments, in the green preparation method of the vinylidene fluoride polymer, the amount of emulsifier used is 0, or the mass of the emulsifier is less than 0.02% of the total mass of the comonomer.

[0014] In some embodiments, the comonomer may further include other monomers, which may include at least one of other fluorinated monomers and other non-fluorinated monomers.

[0015] In some embodiments, the other fluorinated monomers include at least one of trifluoroethylene, tetrafluoroethylene, hexafluoropropylene, trifluorochloroethylene, and perfluoroalkyl vinyl ethers; And / or, the other fluorine-free monomers include at least one of acrylic acid and its derivatives, acrylates and their derivatives, maleic acid and its derivatives, maleimide and its derivatives, and acrylamide and its derivatives; And / or, the mass of the other monomers is 0 to 20% of the total mass of the comonomers.

[0016] In some embodiments, the inorganic free radical initiator includes at least one of persulfate, permanganate, redox system formed by persulfate, and redox system formed by permanganate; And / or, the mass of the inorganic free radical initiator is 0.05% to 2.0% of the total mass of the comonomer; And / or, the chain transfer agent comprises at least one of acetone, methanol, mercaptoethanol, isopropanol, cyclohexane, diethyl ether, methyl tert-butyl ether, ethyl acetate, methyl propionate, ethyl propionate, diethyl malonate, diethyl succinate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. And / or, the chain transfer agent has a mass of 0.05% to 2.0% of the total mass of the comonomer.

[0017] In some embodiments, the polymerization pressure of the free radical polymerization is 2.0~6.0 MPa, preferably 2.5~5.0 MPa; And / or, the polymerization temperature of the free radical polymerization is 30~100℃, preferably 40~90℃; And / or, the reaction time for the free radical polymerization is 3 to 10 hours, preferably 4 to 8 hours.

[0018] This invention provides a vinylidene fluoride polymer, which is prepared using the green preparation method for vinylidene fluoride polymer described in this invention.

[0019] In this embodiment of the invention, amphiphilic polyethylene glycol acrylate macromonomers are subjected to emulsion random copolymerization with vinylidene fluoride monomers to achieve efficient and stable preparation of high-performance vinylidene fluoride polymers with almost no or no emulsifiers.

[0020] In some embodiments, the vinylidene fluoride polymer comprises: (1) a repeating unit containing at least 50% of vinylidene fluoride monomer on a molar basis; and (2) a repeating unit containing 0.01%-20% of polyethylene glycol acrylate macromonomer on a molar basis. And / or, it also includes repeating units of other monomers, said other monomers including at least one of other fluorinated monomers and other non-fluorinated monomers.

[0021] This invention provides an application of vinylidene fluoride polymer for use as a battery binder, separator, sensor, coating and impregnation, and water treatment membrane.

[0022] In this embodiment of the invention, vinylidene fluoride polymer has broad application prospects and can be used as a battery binder, separator, or in the fields of energy conversion and storage, sensing, coating, impregnation, and water treatment membranes. Attached Figure Description

[0023] Figure 1 These are physical images of the vinylidene fluoride polymer emulsions in the embodiments and comparative examples of the present invention. Detailed Implementation

[0024] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0025] An embodiment of the present invention provides a green preparation method for a vinylidene fluoride polymer, comprising: forming a vinylidene fluoride polymer by free radical polymerization of comonomers in a polymerization medium under the action of an inorganic free radical initiator; wherein the comonomers comprise vinylidene fluoride monomers and polyethylene glycol acrylate macromonomers; and wherein the polymerization medium comprises water and a chain transfer agent.

[0026] The green preparation method of vinylidene fluoride polymer in this invention involves emulsion random copolymerization of amphiphilic polyethylene glycol acrylate macromonomer (PEG Acrylate) and vinylidene fluoride (VDF) monomer, eliminating or greatly reducing the use of emulsifiers, and achieving efficient and stable preparation of high-performance vinylidene fluoride polymers with almost no or no emulsifiers.

[0027] In this embodiment of the invention, an aqueous emulsion polymerization process is employed, and no emulsifier is used during polymerization under the action of an inorganic free radical initiator. In the structure of polyethylene glycol acrylate macromonomers, one end is an acrylate, which provides polymerization sites, and the other end is a polyethylene glycol chain, which possesses emulsifying capabilities. VDF monomers copolymerize with amphiphilic polyethylene glycol acrylate macromonomers to form polymer chains with self-emulsifying effects, ultimately yielding a stable polymer emulsion.

[0028] In some embodiments, the polyethylene glycol acrylate macromonomer includes at least one of the monomers represented by the following chemical formulas:

[0029] Wherein, R1 is selected from hydrogen atoms or hydrocarbon groups; optionally, the hydrocarbon group includes methyl. R2 is selected from hydrogen atoms, C1-C5 straight-chain or branched alkylene groups; R3 is selected from carboxyl, amino, mercapto, acrylic, or acrylate groups; when R2 is selected from hydrogen atoms, the chemical formula does not contain R3. n is an integer from 2 to 200, specifically, for example, 2, 3, 4, 5, 10, 20, 50, 100, 150, 200, preferably an integer from 3 to 100, more preferably an integer from 4 to 50; Preferably, the polyethylene glycol acrylate macromonomer includes at least one of polyethylene glycol acrylate (PEG AC), polyethylene glycol methacrylate (PEGMA), polyethylene glycol diacrylate (PEGDA), carboxylated polyethylene glycol acrylate (AC-PEG-COOH), and amino polyethylene glycol acrylate (AC-PEG-NH2); More preferably, the polyethylene glycol acrylate macromonomer includes at least one of the following monomers: Polyethylene glycol acrylate (PEG AC):

[0030] Polyethylene glycol methacrylate (PEGMA):

[0031] Carboxylated polyethylene glycol acrylate (AC-PEG-COOH): ; More preferably, the polyethylene glycol acrylate macromonomers include polyethylene glycol acrylate (PEGAC), polyethylene glycol methacrylate (PEGMA), and mixtures thereof.

[0032] In this embodiment of the invention, by selecting polyethylene glycol acrylate macromonomers, high-performance vinylidene fluoride polymers can be prepared efficiently and stably without the use of emulsifiers. The integer n, ranging from 2 to 200, is beneficial for achieving efficient and stable preparation of high-performance vinylidene fluoride polymers without emulsifiers. However, excessively high n may lead to complete demulsification.

[0033] In some embodiments, the mass of the polyethylene glycol acrylate macromonomer is at least 0.1% of the total mass of the comonomer, specifically, for example, 0.1%, 0.5%, 1%, 2%, 3%, 5%, 10%, preferably at least 1% of the total mass of the comonomer, more preferably at least 2% of the total mass of the comonomer.

[0034] In this embodiment of the invention, the vinylidene fluoride polymer contains at least 0.1% polyethylene glycol acrylate macromonomers by mass of the total comonomers to obtain a stable polymer emulsion. This facilitates the efficient and stable preparation of high-performance vinylidene fluoride polymers without the need for emulsifiers. If the amount of polyethylene glycol acrylate macromonomers is too low, complete demulsification may occur; if the amount is too high, the reaction rate may be slowed down.

[0035] In some embodiments, the polyethylene glycol acrylate macromonomers are added entirely before the polymerization reaction, and / or added in stages during the polymerization reaction, and / or added continuously throughout the polymerization reaction. There are no particular restrictions on the staged or continuous addition method in this invention. For example, optionally, continuous addition throughout the polymerization reaction means adding continuously at a target flow rate throughout the entire reaction, or adding a portion before the polymerization reaction and then continuously adding the remaining portion at the target flow rate. Alternatively, staged addition during the polymerization reaction means adding at target intervals during the reaction, or adding a portion before the polymerization reaction and then adding the remaining portion at target intervals during the reaction.

[0036] In this embodiment of the invention, the addition method of polyethylene glycol acrylate macromonomers can be adjusted to achieve efficient and stable preparation of high-performance vinylidene fluoride polymers.

[0037] In some embodiments, in the green preparation method of the vinylidene fluoride polymer, the amount of emulsifier used is 0 (no emulsifier is used), or the amount of emulsifier used is extremely low, for example, the mass of the emulsifier is less than 0.02% or even less than 0.01% of the total mass of the comonomer.

[0038] In this embodiment of the invention, high-performance vinylidene fluoride polymers can be prepared efficiently and stably with little or no emulsifiers, avoiding the environmental problems caused by emulsifiers and the impact of emulsifier residues on polymer purity and performance.

[0039] In some embodiments, the comonomer further includes other monomers, which include at least one of other fluorinated monomers and other non-fluorinated monomers; Optionally, the other fluorinated monomers include other fluoroolefin unsaturated monomers capable of participating in free radical polymerization reactions; the other fluorinated monomers include at least one of trifluoroethylene, tetrafluoroethylene, hexafluoropropylene, trifluorochloroethylene, and perfluoroalkyl vinyl ethers; preferably, the other fluorinated monomers include at least one of trifluoroethylene, tetrafluoroethylene, hexafluoropropylene, trifluorochloroethylene, and perfluoromethyl vinyl ethers. Optionally, the other fluorine-free monomers include other fluorine-free alkenyl unsaturated polar monomers capable of participating in free radical polymerization reactions; the other fluorine-free monomers include at least one of acrylic acid and its derivatives, acrylates and their derivatives, maleic acid and its derivatives, maleimide and its derivatives, and acrylamide and its derivatives; preferably, the other fluorine-free monomers include at least one of acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, maleic acid, and maleimide; more preferably, the other fluorine-free monomers include at least one of acrylic acid, methacrylic acid, and hydroxyethyl acrylate. Optionally, the mass of the other monomers is 0-20% of the total mass of the comonomers, specifically, for example, 0, 1%, 2%, 5%, 8%, 10%, 15%, 20%; Optionally, the other monomers may be added all before the polymerization reaction, or added in stages during the polymerization reaction, or added continuously throughout the polymerization reaction, or added together with the vinylidene fluoride monomer.

[0040] In this embodiment of the invention, other fluorinated monomers or fluorine-free monomers may also participate in the copolymerization reaction to prepare high-performance vinylidene fluoride polymers.

[0041] In some embodiments, in a polymerization medium under the action of an inorganic free radical initiator, comonomers are free radical polymerized to form vinylidene fluoride polymers; Optionally, the inorganic free radical initiator includes at least one of persulfate, permanganate, a redox system formed by persulfate, and a redox system formed by permanganate; optionally, the persulfate includes at least one of ammonium persulfate, sodium persulfate, and potassium persulfate; the permanganate includes potassium permanganate; preferably, the inorganic free radical initiator includes at least one of ammonium persulfate, potassium persulfate, a redox system formed by ammonium persulfate, and a redox system formed by potassium persulfate; optionally, the redox system formed by potassium persulfate includes potassium persulfate and sodium bisulfite; Optionally, the mass of the inorganic free radical initiator is 0.05% to 2.0% of the total mass of the comonomer, specifically, for example, 0.05%, 0.1%, 0.2%, 0.5%, 1.0%, 1.5%, 2.0%; Optionally, an inorganic free radical initiator may be added after the target temperature and pressure for polymerization have been reached.

[0042] In some embodiments, the polymerization medium includes water and a chain transfer agent; Optionally, the chain transfer agent includes at least one of acetone, methanol, mercaptoethanol, isopropanol, cyclohexane, diethyl ether, methyl tert-butyl ether, ethyl acetate, methyl propionate, ethyl propionate, diethyl malonate, diethyl succinate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; preferably, the chain transfer agent includes at least one of mercaptoethanol and ethyl acetate. Optionally, the chain transfer agent is 0.05% to 2.0% of the total mass of the comonomers, specifically, for example, 0.05%, 0.1%, 0.2%, 0.5%, 1.0%, 1.5%, 2.0%; Optionally, the chain transfer agent may be added entirely before the polymerization reaction, or added in stages during the polymerization reaction, or added continuously throughout the entire polymerization reaction.

[0043] In some embodiments, the polymerization medium includes water and a chain transfer agent; the present invention does not impose any special restrictions on the amount of water used in the polymerization medium, and can achieve the free radical polymerization of comonomers in the polymerization medium under the action of inorganic free radical initiators to obtain vinylidene fluoride polymers.

[0044] In some embodiments, water is first added to the polymerization reactor, and then nitrogen is used to replace the oxygen in the reactor three times to ensure that the oxygen content in the reactor is below 10 ppm.

[0045] In some embodiments, the polymerization pressure of the free radical polymerization is 2.0~6.0 MPa, specifically, for example, 2.0 MPa, 2.5 MPa, 2.6 MPa, 3.0 MPa, 3.8 MPa, 4.0 MPa, 5.0 MPa, 6.0 MPa, preferably, the polymerization pressure is 2.5~5.0 MPa; the polymerization temperature of the free radical polymerization is 30~100℃, specifically, for example, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 86℃, 90℃, 100℃, preferably, the polymerization temperature is 40~90℃; the reaction time of the free radical polymerization is 3~10h, specifically, for example, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, preferably, the reaction time is 4~8h; optionally, the free radical polymerization reaction is stirred, optionally, the stirring speed is 200 rpm.

[0046] In this embodiment of the invention, the polymerization temperature is determined based on the inorganic free radical initiator and the redox system it forms.

[0047] In some embodiments, after the free radical polymerization reaction is completed, the temperature is lowered, the emulsion is collected, and then coagulated, washed, and dried to obtain vinylidene fluoride polymer powder. Specifically, after the free radical polymerization reaction is completed, the reactor is cooled and vented, the collected emulsion is coagulated with calcium chloride, and then washed with alternating hot and cold water and dried to obtain vinylidene fluoride polymer powder.

[0048] An embodiment of the present invention provides a vinylidene fluoride polymer, wherein the vinylidene fluoride polymer is prepared using the green preparation method of the vinylidene fluoride polymer described in the embodiment of the present invention.

[0049] In this embodiment of the invention, amphiphilic polyethylene glycol acrylate macromonomers are subjected to emulsion random copolymerization with vinylidene fluoride monomers to achieve efficient and stable preparation of high-performance vinylidene fluoride polymers with almost no or no emulsifiers.

[0050] In some embodiments, the vinylidene fluoride polymer comprises: (1) A repeating unit containing at least 50% (relative to the comonomer (repeating unit)) of vinylidene fluoride monomer, specifically, for example, 50%, 60%, 70%, 80%, 90%, 99%, 99.99%; Optionally, it also includes repeating units of other monomers, which include at least one of other fluorinated monomers and other non-fluorinated monomers; the mass of the other monomers is 0 to 20% of the total mass of the comonomers, specifically, for example, 0, 1%, 2%, 5%, 8%, 10%, 15%, 20%; (2) The repeating unit of polyethylene glycol acrylate macromonomers comprises 0.01%-20% (relative to the comonomer (repeating unit)) on a molar basis, specifically, for example, 0.01%, 0.02%, 0.05%, 0.1%, 1%, 5%, 10%, 15%, 20%; preferably, the vinylidene fluoride polymer comprises at least 0.02% on a molar basis, more preferably at least 0.05%, more preferably at least 0.1% of repeating units from polyethylene glycol acrylate macromonomers.

[0051] In this embodiment of the invention, the vinylidene fluoride polymer contains a certain amount of polyethylene glycol acrylate macromonomers in order to obtain a stable polymer emulsion.

[0052] An application of a vinylidene fluoride polymer according to an embodiment of the present invention is used in at least one of battery binders, separators, energy conversion and storage, sensing, coatings, impregnation, coatings, and water treatment membranes.

[0053] In this embodiment of the invention, vinylidene fluoride polymer has broad application prospects and can be used as a battery binder, separator, or in the fields of energy conversion and storage, sensing, coating and impregnation, water treatment membranes, etc.

[0054] In some embodiments, the vinylidene fluoride polymer is used to coat and / or impregnate to form a coating.

[0055] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0056] Example 1 A green preparation method for vinylidene fluoride polymer, comprising: Add 3500g of deionized water to a 5L polymerization reactor equipped with a double-layered two-bladed inclined paddle, and replace the oxygen in the reactor three times with nitrogen to ensure that the oxygen content in the reactor is below 10ppm.

[0057] Add 1g of polyethylene glycol to the polymerization reactor (Mw=400) Acrylate and 5g of ethyl acetate were added, and the stirrer was turned on at 200 rpm. The reactor was heated, and the pressure was increased using vinylidene fluoride monomer. The temperature reached 86°C and the pressure reached 3.8 MPa. Then, 5.5g of ammonium persulfate initiator was added to the reactor to begin the polymerization reaction. The pressure inside the reactor was maintained constant by adding vinylidene fluoride monomer until approximately 1000g of vinylidene fluoride monomer was introduced into the reaction system, at which point the polymerization reaction was terminated.

[0058] After cooling and venting the reactor, the collected emulsion was coagulated with calcium chloride, and after alternating washing with hot and cold water and drying, vinylidene fluoride polymer powder was obtained.

[0059] Example 2 A green preparation method for vinylidene fluoride polymer, comprising: Add 3500g of deionized water to a 5L polymerization reactor equipped with a double-layered two-bladed inclined paddle, and replace the oxygen in the reactor three times with nitrogen to ensure that the oxygen content in the reactor is below 10ppm.

[0060] Add 20g of polyethylene glycol to the polymerization reactor. (Mw=1000) Methacrylate and 4g of ethyl acetate were added, and the stirrer was turned on at 200 rpm. The reactor was heated, and the pressure was increased using vinylidene fluoride monomer. The temperature reached 86°C and the pressure reached 3.8 MPa. Then, 5g of potassium persulfate initiator was added to the reactor to begin the polymerization reaction. The pressure inside the reactor was maintained constant by adding vinylidene fluoride monomer until approximately 1000g of vinylidene fluoride monomer was introduced into the reaction system, at which point the polymerization reaction was terminated.

[0061] After cooling and venting the reactor, the collected emulsion was coagulated with calcium chloride, and after alternating washing with hot and cold water and drying, vinylidene fluoride polymer powder was obtained.

[0062] Example 3 A green preparation method for vinylidene fluoride polymer, comprising: Add 3500g of deionized water to a 5L polymerization reactor equipped with a double-layered two-bladed inclined paddle, and replace the oxygen in the reactor three times with nitrogen to ensure that the oxygen content in the reactor is below 10ppm.

[0063] Add 10g of polyethylene glycol to the polymerization reactor. (Mw=1000) Methacrylate and 2g mercaptoethanol were added, and the stirrer was turned on at 200 rpm. The reactor was heated while simultaneously pressurizing it using vinylidene fluoride monomer. The temperature reached 86°C and the pressure reached 3.8 MPa. Then, 5g of potassium persulfate initiator was added to the reactor to begin the polymerization reaction. Subsequently, vinylidene fluoride monomer was added to maintain a constant pressure inside the reactor, and 10g of polyethylene glycol was continuously added during the polymerization process. (Mw=1000) The polymerization reaction continues until approximately 1000g of vinylidene fluoride monomer is introduced into the reaction system, at which point the polymerization reaction ends.

[0064] After cooling and venting the reactor, the collected emulsion was coagulated with calcium chloride, and after alternating washing with hot and cold water and drying, vinylidene fluoride polymer powder was obtained.

[0065] Example 4 A green preparation method for vinylidene fluoride polymer, comprising: Add 3500g of deionized water to a 5L polymerization reactor equipped with a double-layered two-bladed inclined paddle, and replace the oxygen in the reactor three times with nitrogen to ensure that the oxygen content in the reactor is below 10ppm.

[0066] Add 20g of polyethylene glycol to the polymerization reactor. (Mw=2000) Methacrylate and 5g of ethyl acetate were added, and the stirrer was turned on at 200 rpm. The reactor was heated while simultaneously pressurizing it using vinylidene fluoride monomer and hexafluoropropylene monomer. Once the temperature reached 50°C and the pressure reached 2.6 MPa, 6g of potassium persulfate and 4g of sodium bisulfite were added to initiate the polymerization reaction. The pressure inside the reactor was subsequently maintained by adding vinylidene fluoride monomer and hexafluoropropylene monomer, and 10g of polyethylene glycol was added in stages during the polymerization process. (Mw=2000) The polymerization reaction continued until approximately 900g of vinylidene fluoride monomer and 300g of hexafluoropropylene monomer were introduced into the reaction system, at which point the polymerization reaction ended.

[0067] After cooling and venting the reactor, the collected emulsion was coagulated with calcium chloride, and after alternating washing with hot and cold water and drying, vinylidene fluoride polymer powder was obtained.

[0068] Example 5 A green preparation method for vinylidene fluoride polymer, comprising: Add 3500g of deionized water to a 5L polymerization reactor equipped with a double-layered two-bladed inclined paddle, and replace the oxygen in the reactor three times with nitrogen to ensure that the oxygen content in the reactor is below 10ppm.

[0069] Add 8g of polyethylene glycol to the polymerization reactor. (Mw=600) Acrylic acid ester, 1.5g mercaptoethanol, then the stirrer was turned on at 200 rpm, and the reactor was heated while simultaneously pressurizing it using vinylidene fluoride monomer. The polymerization reaction was initiated when the temperature reached 80°C and the pressure reached 3.5 MPa, and then 5g of potassium persulfate was added to the reactor. Subsequently, vinylidene fluoride monomer was added to maintain a constant pressure inside the reactor, and 0.5g of acrylic acid and 17g of polyethylene glycol were continuously added during the polymerization process. (Mw=600) The polymerization reaction continues until approximately 1200g of vinylidene fluoride monomer is introduced into the reaction system, at which point the polymerization reaction ends.

[0070] After cooling and venting the reactor, the collected emulsion was coagulated with calcium chloride, and after alternating washing with hot and cold water and drying, vinylidene fluoride polymer powder was obtained.

[0071] Comparative Example 1 A method for preparing a vinylidene fluoride polymer, comprising: Add 3500g of deionized water to a 5L polymerization reactor equipped with a double-layered two-bladed inclined paddle, and replace the oxygen in the reactor three times with nitrogen to ensure that the oxygen content in the reactor is below 10ppm.

[0072] Add 0.1g of polyethylene glycol to the polymerization reactor. (Mw=400) Acrylate and 5g of ethyl acetate were added, and the stirrer was turned on at 200 rpm. The reactor was heated, and the pressure was increased using vinylidene fluoride monomer. The temperature reached 86°C and the pressure reached 3.8 MPa. Then, 5.5g of ammonium persulfate initiator was added to the reactor to begin the polymerization reaction. The pressure inside the reactor was maintained constant by adding vinylidene fluoride monomer until approximately 1000g of vinylidene fluoride monomer was introduced into the reaction system, at which point the polymerization reaction was terminated.

[0073] After cooling and venting the reactor, the collected emulsion was coagulated with calcium chloride, and after alternating washing with hot and cold water and drying, vinylidene fluoride polymer powder was obtained.

[0074] Comparative Example 2 A method for preparing a vinylidene fluoride polymer, comprising: Add 3500g of deionized water to a 5L polymerization reactor equipped with a double-layered two-bladed inclined paddle, and replace the oxygen in the reactor three times with nitrogen to ensure that the oxygen content in the reactor is below 10ppm.

[0075] Add 1g of polyethylene glycol to the polymerization reactor (Mw=20000) Acrylate and 5g of ethyl acetate were added, and the stirrer was turned on at 200 rpm. The reactor was heated, and the pressure was increased using vinylidene fluoride monomer. The temperature reached 86°C and the pressure reached 3.8 MPa. Then, 5.5g of ammonium persulfate initiator was added to the reactor to begin the polymerization reaction. The pressure inside the reactor was maintained constant by adding vinylidene fluoride monomer until approximately 1000g of vinylidene fluoride monomer was introduced into the reaction system, at which point the polymerization reaction was terminated.

[0076] After cooling and venting the reactor, the collected emulsion was coagulated with calcium chloride, and after alternating washing with hot and cold water and drying, vinylidene fluoride polymer powder was obtained.

[0077] Comparative Example 3 A method for preparing a vinylidene fluoride polymer, comprising: Add 3500g of deionized water to a 5L polymerization reactor equipped with a double-layered two-bladed inclined paddle, and replace the oxygen in the reactor three times with nitrogen to ensure that the oxygen content in the reactor is below 10ppm.

[0078] Add 0.1g of polyethylene glycol 400 and 5g of ethyl acetate to the polymerization reactor. Then, turn on the stirrer at 200 rpm and begin heating the reactor while simultaneously pressurizing it using vinylidene fluoride monomer. Once the temperature reaches 86°C and the pressure reaches 4.0 MPa, add 5.5g of ammonium persulfate initiator to the reactor to begin the polymerization reaction. Subsequently, maintain a constant pressure inside the reactor by adding vinylidene fluoride monomer until approximately 1000g of vinylidene fluoride monomer has been introduced into the reaction system, at which point the polymerization reaction is complete.

[0079] After cooling and venting the reactor, the collected emulsion was coagulated with calcium chloride, and after alternating washing with hot and cold water and drying, vinylidene fluoride polymer powder was obtained.

[0080] Table 1 Comparison of Polyvinylidene Fluoride Polymer Emulsion Conditions

[0081] As demonstrated in Examples 1-5, the present invention utilizes amphiphilic polyethylene glycol acrylate macromonomers, vinylidene fluoride monomers, and optional other monomers for emulsion random copolymerization, enabling the efficient and stable preparation of high-performance vinylidene fluoride polymers without the need for emulsifiers. Actual images of the vinylidene fluoride polymer emulsions in the examples and comparative examples are shown below. Figure 1 As shown, the vinylidene fluoride polymer emulsions of Examples 1-5 are stable, with macromolecular monomer residues of less than 20 ppm.

[0082] As can be seen from Examples 2-4, continuously adding or adding polyethylene glycol acrylate macromonomers in stages during the polymerization reaction is beneficial to further improve the stability of vinylidene fluoride polymer emulsions.

[0083] As can be seen from Example 1 and Comparative Example 1, in Example 1, the presence of polyethylene glycol acrylate macromonomers at least 0.1% of the total mass of the comonomers in the vinylidene fluoride polymer is necessary to obtain a stable polymer emulsion. This facilitates the efficient and stable preparation of high-performance vinylidene fluoride polymers without the need for emulsifiers. In Comparative Example 1, the amount of polyethylene glycol acrylate macromonomers is relatively low, such as... Figure 1 As shown, the emulsion is unstable at this point and has completely broken down.

[0084] As can be seen from Example 1 and Comparative Example 2, the polyethylene glycol acrylate macromonomers used in Example 1 must contain polyethylene glycol segments with 2-200 repeating units (n) to obtain a stable polymer emulsion. This is beneficial for the efficient and stable preparation of high-performance vinylidene fluoride polymers without the need for emulsifiers. In Comparative Example 2, the number of repeating units in the polyethylene glycol segments is too high, resulting in excessive hydrophilicity, a decrease in the hydrophilic-hydrophobic balance, and reduced emulsion stability. Figure 1 As shown, the emulsion is unstable at this point and has completely broken down.

[0085] As can be seen from Example 1 and Comparative Example 3, the use of polyethylene glycol acrylate macromonomers in Example 1 is necessary to obtain a stable polymer emulsion, which is beneficial for the efficient and stable preparation of high-performance vinylidene fluoride polymers without the need for emulsifiers. In the structure of polyethylene glycol acrylate macromonomers, one end is an acrylate, which provides polymerization sites, and the other end is a polyethylene glycol chain, which has emulsifying capabilities. VDF monomers copolymerize with amphiphilic polyethylene glycol acrylate macromonomers to form polymer chains with self-emulsifying effects, ultimately resulting in a stable polymer emulsion. Comparative Example 3 uses polyethylene glycol 400 as an emulsifier, but in a smaller amount, such as... Figure 1 As shown, the emulsion is unstable at this point, and demulsification is severe.

[0086] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0087] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A green process for the preparation of a vinylidene fluoride polymer, characterized in that, The application relates to a green preparation method of a vinylidene fluoride polymer. The copolymerization monomers are formed into the vinylidene fluoride polymer through free radical polymerization under the action of an inorganic free radical initiator in a polymerization medium; the copolymerization monomers comprise vinylidene fluoride monomers and polyethylene glycol acrylate macromonomers; and the polymerization medium comprises water and a chain transfer agent.

2. The green process for the preparation of vinylidene fluoride polymers according to claim 1, characterized in that, The polyethylene glycol acrylate macromonomer comprises at least one of monomers shown in the following formula: wherein R1 is selected from a hydrogen atom or a hydrocarbon group; R2 is selected from a hydrogen atom, a C1-C5 straight chain or branched chain alkylene group, when R2 is selected from a hydrogen atom, R3 is not contained in the formula; R3 is selected from a carboxyl group, an amino group, a mercapto group, an acrylic acid group, an acrylate group, and n is an integer of 2-200.

3. The green process for the preparation of vinylidene fluoride polymers according to claim 2, characterized in that, The polyethylene glycol acrylate macromonomer comprises at least one of polyethylene glycol acrylate, polyethylene glycol methacrylate, polyethylene glycol diacrylate, carboxyl polyethylene glycol acrylate and amino polyethylene glycol acrylate; And / or, the mass of the polyethylene glycol acrylate macromonomer is at least 0.1% of the total mass of the copolymerization monomers; And / or, the polyethylene glycol acrylate macromonomer is added in whole before the polymerization reaction, and / or is added in stages during the polymerization reaction, and / or is continuously added during the whole polymerization reaction.

4. The green process for the preparation of vinylidene fluoride polymers according to claim 1, characterized in that, In the green preparation method of the vinylidene fluoride polymer, the amount of the emulsifier is 0, or the mass of the emulsifier is less than or equal to 0.02% of the total mass of the copolymerization monomers.

5. The green process for the preparation of vinylidene fluoride polymers according to claim 1, characterized in that, The copolymerization monomers further comprise other monomers, and the other monomers comprise at least one of other fluorine-containing monomers and other non-fluorine-containing monomers.

6. The green process for the preparation of vinylidene fluoride polymers according to claim 5, characterized in that, The other fluorine-containing monomers comprise at least one of trifluoroethylene, tetrafluoroethylene, hexafluoropropylene, trifluorochloroethylene and perfluoroalkyl vinyl ether; And / or, the other non-fluorine-containing monomers comprise at least one of acrylic acid and derivatives thereof, acrylate and derivatives thereof, maleic acid and derivatives thereof, maleimide and derivatives thereof, and acrylamide and derivatives thereof; And / or, the mass of the other monomers is 0-20% of the total mass of the copolymerization monomers.

7. The green process for the preparation of vinylidene fluoride polymers according to claim 1, characterized in that, The inorganic free radical initiator comprises at least one of persulfate, permanganate, a redox system formed by persulfate and a redox system formed by permanganate; And / or, the mass of the inorganic free radical initiator is 0.05%-2.0% of the total mass of the copolymerization monomers; And / or, the chain transfer agent comprises at least one of acetone, methanol, mercaptoethanol, isopropyl alcohol, cyclohexane, ethyl ether, methyl tert-butyl ether, ethyl acetate, methyl propionate, ethyl propionate, diethyl malonate, diethyl succinate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate; And / or, the mass of the chain transfer agent is 0.05%-2.0% of the total mass of the copolymerization monomers.

8. The green process for the preparation of vinylidene fluoride polymers according to claim 1, characterized in that, The polymerization pressure of the free radical polymerization is 2.0-6.0 MPa, preferably the polymerization pressure is 2.5-5.0 MPa; And / or, the polymerization temperature of the free radical polymerization is 30-100 DEG C, preferably the polymerization temperature is 40-90 DEG C; And / or, the reaction time of the free radical polymerization is 3-10 h, preferably the reaction time is 4-8 h.

9. A vinylidene fluoride polymer, characterized in that, The vinylidene fluoride polymer is prepared by the green preparation method of the vinylidene fluoride polymer according to any one of claims 1-8.

10. The vinylidene fluoride polymer according to claim 9, characterized in that, The vinylidene fluoride polymer comprises: (1) repeat units containing at least 50% by mole of vinylidene fluoride monomer; (2) repeat units containing 0.01%-20% by mole of polyethylene glycol acrylate macromonomer; And / or, further comprising repeat units of other monomers, which include at least one of other fluorine-containing monomers, other non-fluorine-containing monomers.

11. Use of a vinylidene fluoride polymer prepared according to the process of any one of claims 1 to 8 or of a vinylidene fluoride polymer according to claim 9 or 10, characterized in that, For battery binders, separators, sensors, coatings, impregnation, water treatment membranes.

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