Polyvinylidene fluoride resin, preparation method therefor and use thereof

Abstract

The present invention provides a method for preparing a polyvinylidene fluoride resin. The preparation method comprises: dissolving a polar monomer and a fluorine-containing monomer together in an organic solvent having specific solubility parameters, then adding a fluorine-containing organic amine to the solvent, continuously adding the prepared solvent to a vinylidene fluoride monomer-containing suspension polymerization system for a polymerization reaction, adding a certain amount of an acid to a kettle after the polymerization is complete, and then washing, filtering, and drying the polymerization product to obtain the polyvinylidene fluoride resin. The method for preparing a polyvinylidene fluoride resin according to the present invention solves the problem of uneven distribution of copolymer blocks caused by polymerization activity difference and polarity difference between the vinylidene fluoride monomer, a polar comonomer and a fluorine-containing comonomer, and can prepare a high-performance lithium-ion battery binder having high alkali resistance, high flexibility, high adhesiveness, and excellent heat resistance and chemical resistance.

Description

A polyvinylidene fluoride resin and its preparation method and use Technical Field

[0001] The present invention belongs to the field of polymers, and in particular relates to a polyvinylidene fluoride resin and a preparation method and application thereof. Background Art

[0002] Polyvinylidene fluoride resin is the second largest fluororesin after polytetrafluoroethylene resin. Due to its moderate fluorine content, it has excellent chemical corrosion resistance, high temperature resistance, oxidation resistance, weather resistance, UV resistance, and radiation resistance. It also has good processability and is widely used in semiconductors, electronics, chemicals, photovoltaics, lithium batteries and other fields.

[0003] New energy vehicles have developed rapidly in recent years, with significant progress made by Chinese new energy vehicle and lithium battery companies in particular. Simultaneously, demands for longer driving range in new energy vehicles, and correspondingly, higher energy density requirements for lithium batteries, have risen. Conventional lithium battery binders are no longer able to meet these requirements, placing higher demands on alkali resistance, heat resistance, adhesion, and flexibility. Homopolymer polyvinylidene fluoride resins have reached a performance bottleneck, and further improving resin performance requires the addition of modified comonomers. Typically, polar comonomers are added to enhance adhesion, while fluorinated comonomers are added to improve alkali resistance and flexibility.

[0004] Solvay patent CN101679563 discloses a vinylidene fluoride copolymer, which is prepared by copolymerizing a hydrophilic (meth)acrylic acid monomer, a fluorine-containing monomer and vinylidene fluoride to prepare a polyvinylidene fluoride resin. The vinylidene fluoride monomer and the fluorine-containing comonomer are added to the reactor as a bottom layer, and an aqueous solution of acrylic acid monomer is continuously added during the polymerization process to prepare the polyvinylidene fluoride resin.

[0005] Fonolin's patent WO2020 / 238246A1 discloses a vinylidene fluoride polymer for lithium-ion power battery binder and its preparation method, which includes three stages: the first stage: the vinylidene fluoride monomer is homopolymerized to obtain an ultra-high molecular weight vinylidene fluoride homopolymer resin; the second stage: the vinylidene fluoride monomer and the second monomer and the third monomer are copolymerized to obtain a high molecular weight vinylidene fluoride copolymer resin; the third stage: the vinylidene fluoride homopolymer resin and the copolymer resin are blended to obtain the vinylidene fluoride polymer.

[0006] The above patents use continuous feeding of comonomers or physical mixing of homopolymers and copolymers in order to improve the uniformity of the segment distribution of the copolymer product. However, due to the large differences in polymerization activity and polarity among the vinylidene fluoride monomer, polar comonomer, and fluorine-containing comonomer, the uniformity of the segment distribution of the copolymer product is still at a relatively low level.

[0007] In summary, how to solve the differences in polymerization activity and polarity between vinylidene fluoride monomer, polar comonomer and fluorine-containing comonomer and improve the uniformity of chain segment distribution of polyvinylidene fluoride resin copolymer products becomes the key.

[0008] Summary of the Invention

[0009] Experimental studies have found that polar comonomers can improve the bonding properties of polyvinylidene fluoride resins, and fluorine-containing comonomers can improve the alkali resistance and flexibility of polyvinylidene fluoride resins. Therefore, high-performance lithium battery binders are usually prepared by copolymerizing vinylidene fluoride monomers, polar comonomers, and fluorine-containing comonomers. However, the chain segment distribution uniformity of the copolymerization product is not good, mainly because: on the one hand, the polarity of the polar comonomer is quite different from that of the vinylidene fluoride monomer and the fluorine-containing comonomer. The polar comonomer has a high polarity and is easily soluble in water. During the reaction process, it is easy to polymerize in the aqueous phase and is not easy to enter the suspended oil droplets to undergo polymerization reaction with the vinylidene fluoride monomer and the fluorine-containing comonomer. On the other hand, the polar comonomer has high polymerization activity, while the fluorine-containing comonomer has low polymerization activity, which makes the chain segment composition inconsistent and easy to form self-polymers of the polar comonomer.

[0010] Due to differences in polymerization activity and polarity, the final product chain segment distribution is not uniform. Due to the uneven distribution of polar comonomers, the resin adhesion is not sufficiently improved. The uneven distribution of fluorinated comonomers results in poor alkali resistance of the resin. At the same time, the product's polar comonomer self-polymerization leads to poor heat resistance.

[0011] The inventors have discovered that by adding an organic solvent in which vinylidene fluoride monomer, polar comonomer, and fluorine-containing comonomer are all soluble to the copolymerization reaction system to provide a place for common reaction, the problem that polar comonomers are easily polymerized in the aqueous phase and fluorine-containing comonomers are easily polymerized in suspended oil droplets due to polarity differences can be solved, making it impossible for both to form a uniform block copolymer with the vinylidene fluoride monomer.

[0012] The inventors also discovered that adding a fluorinated organic amine to an organic solvent containing a polar comonomer and a fluorinated comonomer can reduce the polymerization activity of the polar comonomer, thereby preventing it from forming self-polymers due to excessive polymerization activity. At the same time, the introduction of the fluorinated organic amine increases the compatibility of the polar comonomer with the fluorinated comonomer and the vinylidene fluoride monomer, thereby improving the uniformity of the chain segment distribution of the copolymer product.

[0013] In view of the shortcomings of the prior art, the present invention aims to provide a method for preparing a polyvinylidene fluoride resin. The polyvinylidene fluoride resin prepared by the method has high alkali resistance, high flexibility, high adhesion, and excellent heat resistance and chemical resistance.

[0014] To achieve the above-mentioned object, the technical solution of the preparation method of polyvinylidene fluoride resin provided by the present invention is as follows:

[0015] A method for preparing polyvinylidene fluoride resin comprises the following steps:

[0016] (1) adding a polar comonomer and a fluorine-containing comonomer together into an organic solvent, then adding an organic amine into the organic solvent, and mixing the mixture uniformly for later use;

[0017] (2) adding deionized water, a dispersant, and an initiator into the reactor, and then adding vinylidene fluoride monomer into the reactor;

[0018] (3) continuously or intermittently adding the solution prepared in step (1) into the reactor until the reaction is completed;

[0019] (4) After the reaction is completed, acid is added to the reactor, and the polymer product is filtered, washed, and dried to obtain polyvinylidene fluoride resin.

[0020] According to the preparation method of the present invention, in step (1), the solubility parameter of the organic solvent is 7.5-9.8.

[0021] According to the preparation method of the present invention, in step (1), the organic solvent is selected from one or more of diethyl ether, butyl acetate, cyclohexane, isobutyl acetate, ethyl acetate, methyl acetate, methyl propyl ketone, p-xylene, and acetone; preferably, the organic solvent is selected from one or more of diethyl ether and butyl acetate.

[0022] According to the preparation method of the present invention, in step (1), the polar comonomer is selected from one of acrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, acrylonitrile, methyl acrylate, methyl methacrylate, and isooctyl acrylate; preferably, the polar comonomer is selected from one of acrylic acid, hydroxyethyl acrylate, and hydroxyethyl methacrylate.

[0023] According to the preparation method of the present invention, in step (1), the fluorine-containing comonomer is selected from one of hexafluoropropylene, chlorotrifluoroethylene, trifluoroethylene, and tetrafluoroethylene; preferably, the fluorine-containing comonomer is selected from one of hexafluoropropylene and chlorotrifluoroethylene.

[0024] According to the preparation method of the present invention, in step (1), the organic amine is a fluorine-containing organic amine, and the fluorine-containing organic amine is selected from one or more of 2,4-difluoroaniline, 2,3,4-trifluoroaniline, o-fluoroaniline, m-fluoroaniline, and p-fluoroaniline; preferably, the organic amine is selected from one or more of 2,4-difluoroaniline and 2,3,4-trifluoroaniline.

[0025] According to the preparation method of the present invention, in step (1),

[0026] The polar comonomer is added in an amount of 0.3 wt% to 2.2 wt% of the vinylidene fluoride monomer;

[0027] The amount of the fluorine-containing comonomer added is 1.2 wt% to 5.6 wt% of the vinylidene fluoride monomer;

[0028] The amount of the organic solvent added is 25wt%-36wt% of the vinylidene fluoride monomer;

[0029] The amount of the organic amine added is 108 wt% to 135 wt% of the amount of the polar comonomer added.

[0030] According to the preparation method of the present invention, in step (2), optionally, a certain amount of the solution prepared in step (1) is first added to the bottom of the reactor, the amount added not exceeding 18% of the total amount prepared, and the temperature is raised to start the polymerization reaction.

[0031] According to the preparation method of the present invention, in step (2), the dispersant is selected from one or more of hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose and sodium carboxymethyl cellulose.

[0032] According to the preparation method of the present invention, in step (2), the initiator is selected from one or more of diethyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di-tert-butyl peroxide and tert-butyl peroxypivalate.

[0033] According to the preparation method of the present invention, in step (2),

[0034] The dispersant is added in an amount of 0.04wt%-0.26wt% of the vinylidene fluoride monomer;

[0035] The amount of the initiator added is 0.07wt%-0.36wt% of the vinylidene fluoride monomer;

[0036] The amount of deionized water added is 105 wt% to 170 wt% of the vinylidene fluoride monomer.

[0037] According to the preparation method of the present invention, in step (3), the pressure of the polymerization reaction is 4 MPaG-14 MPaG, preferably 8 MPaG-13 MPaG.

[0038] According to the preparation method of the present invention, in step (3), the polymerization reaction temperature is 38°C-65°C, preferably 45°C-56°C.

[0039] According to the preparation method of the present invention, in step (3), the polymerization reaction time is 3-9 hours, preferably 4-6 hours.

[0040] According to the preparation method of the present invention, in step (4), the added acid is selected from one or more of hydrochloric acid, sulfuric acid, and phosphoric acid; preferably, the added acid is hydrochloric acid; more preferably, the added acid is 35% hydrochloric acid.

[0041] According to the preparation method of the present invention, in step (4), the molar amount of the acid added is 108-125% of the molar amount of the organic amine added in step (1).

[0042] According to the preparation method of the present invention, in step (4), the solvent used for washing is deionized water.

[0043] Another object of the present invention is to provide a polyvinylidene fluoride resin, which is prepared according to the above method.

[0044] According to the polyvinylidene fluoride resin of the present invention, the polyvinylidene fluoride resin has the following performance parameters:

[0045] Bond strength is 78-106N / m;

[0046] Yellow index is 2.7-3.4;

[0047] The crystallinity is 40%-45%.

[0048] According to the polyvinylidene fluoride resin of the present invention, the weight average molecular weight of the polyvinylidene fluoride resin is 800,000-1,350,000, preferably 1,000,000-1,350,000, and the molecular weight distribution index (PDI) is 1.4-2.4.

[0049] Another object of the present invention is to provide a use of polyvinylidene fluoride resin in the preparation of lithium battery binders. Beneficial effects

[0050] The present invention provides a method for preparing a polyvinylidene fluoride resin. By dissolving a polar comonomer and a fluorine-containing comonomer in a co-soluble organic solvent, the polarity difference between the two is improved, and a site for a common reaction is provided. This method can solve the problem that the polar comonomer is easily polymerized in the aqueous phase due to the polarity difference, and the fluorine-containing comonomer is easily polymerized in suspended oil droplets, making it impossible for the polar comonomer and the polyvinylidene fluoride monomer to form a uniform block copolymer.

[0051] The present invention adds a fluorine-containing organic amine to an organic solvent in which a polar comonomer and a fluorine-containing comonomer are dissolved, thereby reducing the polymerization activity of the polar comonomer, preventing the formation of self-polymers due to excessively high polymerization activity, and improving the difference in polymerization activity between the polar comonomer and the fluorine-containing comonomer. At the same time, the introduction of the fluorine-containing organic amine increases the compatibility of the polar comonomer with the fluorine-containing comonomer and the vinylidene fluoride monomer, thereby improving the uniformity of block distribution of the copolymer product.

[0052] The method of the present invention solves the problem of uneven distribution of copolymer blocks caused by differences in polymerization activity and polarity between vinylidene fluoride monomers and polar comonomers and fluorine-containing comonomers, and produces a high-performance lithium battery binder with high alkali resistance, high flexibility, high adhesion, and excellent heat resistance and chemical resistance. DETAILED DESCRIPTION

[0053] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0054] The described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art are within the scope of protection of the present invention.

[0055] The main test methods are as follows:

[0056] Bond strength

[0057] The bonding strength of the polymer after it is prepared into an electrode is measured according to the ISO4624 standard (adhesion pull-off test). The preparation process of the electrode is as follows: At room temperature, 1g of the resin produced in the embodiment or comparative example is dissolved in 50g of NMP under mechanical stirring. Add 2g of conductive carbon black and 30g of lithium cobalt oxide (LiCoO2) while stirring, and mix thoroughly to ensure uniformity. The mixture is then degassed under vacuum and spread on aluminum foil with a scraper. Finally, the aluminum foil spread with the electrode material mixture is placed in a vacuum oven and heated to 60°C and dried for 12 hours to finally prepare an electrode sheet. The bonding strength of the electrode material on the electrode sheet is measured using an INSTRON tensile testing machine.

[0058] Thermal stability

[0059] Approximately 200g of polymer powder was extruded and pelletized using a twin-screw extruder, maintaining a barrel temperature of 200°C at all sections and a screw speed of 50 rpm. An appropriate amount of PVDF polymer pellets was then molded into 4mm thick plates, which were then heated in a 250°C oven for 1 hour. The plates were then tested using a HunterLab CQX3576 yellowness meter, using a yellowness index (YID1925) to indicate the degree of yellowing. A lower YID indicates better thermal stability.

[0060] crystallinity

[0061] The test was carried out using a METTLERDSC-1 differential scanning calorimeter.

[0062] Molecular weight and its distribution

[0063] The molecular weight and distribution of the polymers were determined using Shimadzu gel permeation chromatography (GPC).

[0064] The main raw material information is as follows:

[0065] Vinylidene fluoride: Wanhua Chemical Group Co., Ltd., industrial products;

[0066] Acrylic acid: Wanhua Chemical Group Co., Ltd., industrial product;

[0067] Hydroxyethyl acrylate: Wanhua Chemical Group Co., Ltd., industrial product;

[0068] Chlorotrifluoroethylene: Aladdin, analytical grade;

[0069] Hexafluoropropylene: Aladdin, analytical grade;

[0070] Ether: Sigma, analytical grade;

[0071] Butyl acetate: Beijing Yinuokai, analytical grade;

[0072] 2,4-Difluoroaniline: Shanghai Hanxiang Biological, analytical grade;

[0073] 2,3,4-Trifluoroaniline: Shanghai Hanxiang Biological, analytical grade;

[0074] Hydroxyethyl cellulose: Beijing Yinuokai, analytical grade;

[0075] Hydroxypropyl cellulose: Beijing Yinuokai, analytical grade;

[0076] Diethyl peroxydicarbonate: Zibo Hongtai Chemical Co., Ltd., analytical grade;

[0077] Diisopropyl peroxydicarbonate: Zibo Hongtai Chemical Co., Ltd., analytical grade;

[0078] 35% hydrochloric acid: Changzhou Qinghong Chemical, industrial product.

[0079] Example

[0080] Example 1

[0081] Add 20.8g of acrylic acid and 43.2g of hexafluoropropylene to 464g of organic solvent ether, stir and mix until evenly mixed, then add 22.7g of 2,4-difluoroaniline for later use.

[0082] After the 5L high-pressure reactor was filled with nitrogen and vacuum-displaced, 1940g of deionized water was added, and after stirring, 1.92g of dispersant hydroxyethyl cellulose and 1.28g of initiator diethyl peroxydicarbonate were added to the reactor. Then, 1600g of vinylidene fluoride monomer was added, and the temperature was raised to 51°C to start the polymerization reaction. The prepared solution was continuously added to the reactor, and the pressure in the reactor was maintained at 11MPaG. After the reaction was completed, the temperature in the reactor was lowered to room temperature, 19.8g of 35% hydrochloric acid was added to the reactor, and the polymerization product was filtered, washed, and dried to obtain polyvinylidene fluoride resin.

[0083] Example 2

[0084] 5.6 g of hydroxyethyl acrylate and 88 g of chlorotrifluoroethylene were added to 400 g of butyl acetate as an organic solvent, and the mixture was stirred and mixed thoroughly, and then 6.9 g of 2,3,4-trifluoroaniline was added for later use.

[0085] After nitrogen was filled and vacuumed in a 5L high-pressure reactor, 1940 g of deionized water was added. After stirring, 0.8 g of hydroxypropyl cellulose as a dispersant and 3.84 g of diisopropyl peroxydicarbonate as an initiator were added to the reactor. 40.04 g of a prepared solution (a mixed solution of hydroxyethyl acrylate, chlorotrifluoroethylene and 2,3,4-trifluoroaniline) was added to the reactor, and 1600 g of vinylidene fluoride monomer was added. The temperature was raised to 45°C to start a polymerization reaction. The prepared solution was continuously added to the reactor, and the pressure in the reactor was maintained at 8.5 MPaG. After the reaction was completed, the temperature in the reactor was lowered to room temperature. 6.1 g of 35% hydrochloric acid was added to the reactor, and the polymer product was filtered, washed, and dried to obtain polyvinylidene fluoride resin.

[0086] Example 3

[0087] 33.6 g of acrylic acid and 20.8 g of hexafluoropropylene were added to 544 g of organic solvent ether, stirred and mixed until uniform, and then 44.7 g of 2,4-difluoroaniline was added for later use.

[0088] After nitrogen filling and vacuum replacement, a 5L high-pressure reactor was filled with nitrogen and evacuated, 1940g of deionized water was added, and after stirring, 4g of dispersant hydroxyethyl cellulose and 5.76g of initiator diethyl peroxydicarbonate were added to the reactor. Then, 1600g of vinylidene fluoride monomer was added, and the temperature was raised to 55°C to start the polymerization reaction. The prepared solution was continuously added to the reactor, and the pressure in the reactor was maintained at 13MPaG. After the reaction was completed, the temperature in the reactor was lowered to room temperature, 42.2g of 35% hydrochloric acid was added to the reactor, and the polymerization product was filtered, washed, and dried to obtain polyvinylidene fluoride resin.

[0089] Comparative Example

[0090] Comparative Example 1

[0091] After nitrogen was filled into a 5L high-pressure reactor and vacuum-displaced, 1940g of deionized water was added. After stirring was started, 1.92g of hydroxyethyl cellulose as a dispersant and 1.28g of diethyl peroxydicarbonate as an initiator were added to the reactor. Then, 1600g of vinylidene fluoride monomer, 20.8g of acrylic acid and 43.2g of hexafluoropropylene were added. The temperature was then raised to 51°C to start a polymerization reaction. The pressure in the reactor was 11MPaG. After the reaction was completed, the temperature in the reactor was lowered to room temperature. The polymerization product was filtered, washed and dried to obtain polyvinylidene fluoride resin.

[0092] Comparative Example 2

[0093] Add 20.8 g of acrylic acid and 43.2 g of hexafluoropropylene to 464 g of organic solvent ether, start stirring and mix well for later use.

[0094] After nitrogen filling and vacuum replacement, 1940 g of deionized water was added to the 5 L high-pressure reactor. After stirring, 1.92 g of hydroxyethyl cellulose as a dispersant and 1.28 g of diethyl peroxydicarbonate as an initiator were added to the reactor. Then, 1600 g of vinylidene fluoride monomer was added. The temperature was raised to 51° C. to start the polymerization reaction. The prepared solution was continuously added to the reactor while maintaining the pressure in the reactor at 11 MPaG. After the reaction was completed, the temperature in the reactor was lowered to room temperature. The polymerization product was filtered, washed, and dried to obtain polyvinylidene fluoride resin.

[0095] Comparative Example 3

[0096] 20.8 g of acrylic acid and 43.2 g of hexafluoropropylene were mixed evenly, and then 22.7 g of 2,4-difluoroaniline was added for later use.

[0097] After the 5L high-pressure reactor was filled with nitrogen and vacuum-displaced, 1940g of deionized water was added, and after stirring, 1.92g of dispersant hydroxyethyl cellulose and 1.28g of initiator diethyl peroxydicarbonate were added to the reactor. Then, 1600g of vinylidene fluoride monomer was added, and the temperature was raised to 51°C to start the polymerization reaction. The prepared solution was continuously added to the reactor, and the pressure in the reactor was maintained at 11MPaG. After the reaction was completed, the temperature in the reactor was lowered to room temperature, 19.8g of 35% hydrochloric acid was added to the reactor, and the polymerization product was filtered, washed, and dried to obtain polyvinylidene fluoride resin.

[0098] Test Case

[0099] The properties of the polyvinylidene fluoride resins obtained in the above examples and comparative examples are shown in Table 1 below:

[0100] Table 1 Performance parameters of examples and comparative examples

[0101] As can be seen from the table, the present invention improves the polarity difference between the polar comonomer and the fluorine-containing comonomer by dissolving them in a co-soluble organic solvent, and improves the polymerization activity difference between the two by adding a fluorine-containing organic amine, thereby ultimately solving the problem of uneven distribution of polyvinylidene fluoride resin block copolymerization. It is possible to prepare a lithium battery binder with high alkali resistance, high flexibility, high adhesion, and excellent heat resistance and chemical resistance.

[0102] Those skilled in the art will appreciate that, based on the teachings of this specification, some modifications or adjustments may be made to the present invention, and such modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for preparing a polyvinylidene fluoride resin, characterized in that: The steps include: (1) adding a polar comonomer and a fluorine-containing comonomer together into an organic solvent, then adding an organic amine into the organic solvent, and mixing the mixed solution for later use; (2) adding deionized water, a dispersant, and an initiator into a reactor, and then adding vinylidene fluoride monomer into the reactor; (3) continuously or intermittently adding the solution prepared in step (1) into the reactor until the reaction is completed; (4) After the reaction is completed, an acid is added into the reactor, and the polymerized product is filtered, washed, and dried to obtain a polyvinylidene fluoride resin.

2. The preparation method according to claim 1, characterized in that: In step (1), the solubility parameter of the organic solvent is 7.5-9.8; the organic solvent is selected from one or more of diethyl ether, butyl acetate, cyclohexane, isobutyl acetate, ethyl acetate, methyl acetate, methyl propyl ketone, p-xylene, and acetone; preferably, the organic solvent is selected from one or more of diethyl ether and butyl acetate.

3. The preparation method according to claim 1 or 2, characterized in that: In step (1), The polar comonomer is selected from one of acrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, acrylonitrile, methyl acrylate, methyl methacrylate, and isooctyl acrylate; preferably, the polar comonomer is selected from one of acrylic acid, hydroxyethyl acrylate, and hydroxyethyl methacrylate; The fluorine-containing comonomer is selected from one of hexafluoropropylene, chlorotrifluoroethylene, trifluoroethylene and tetrafluoroethylene; preferably, the fluorine-containing comonomer is selected from one of hexafluoropropylene and chlorotrifluoroethylene; The organic amine is a fluorine-containing organic amine, and the fluorine-containing organic amine is selected from one or more of 2,4-difluoroaniline, 2,3,4-trifluoroaniline, o-fluoroaniline, m-fluoroaniline, and p-fluoroaniline; preferably, the organic amine is selected from one or more of 2,4-difluoroaniline and 2,3,4-trifluoroaniline.

4. The preparation method according to claim 1 or 2, characterized in that: In step (1), The polar comonomer is added in an amount of 0.3wt%-2.2wt% of the vinylidene fluoride monomer; The amount of the fluorine-containing comonomer added is 1.2wt%-5.6wt% of the vinylidene fluoride monomer; The amount of the organic solvent added is 25wt%-36wt% of the vinylidene fluoride monomer; The amount of organic amine added is 108 wt%-135 wt% of the amount of polar comonomer added.

5. The preparation method according to claim 1 or 2, characterized in that: In step (2), The dispersant is selected from one or more of hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose and sodium carboxymethyl cellulose; the amount of the dispersant added is 0.04wt%-0.26wt% of the vinylidene fluoride monomer; The initiator is selected from one or more of diethyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di-tert-butyl peroxide and tert-butyl peroxypivalate; the added amount of the initiator is 0.07wt%-0.36wt% of the vinylidene fluoride monomer.

6. The preparation method according to claim 1 or 2, characterized in that: In step (3), the polymerization reaction pressure is 4MPaG-14MPaG, preferably 8MPaG-13MPaG; the polymerization reaction temperature is 38°C-65°C, preferably 45°C-56°C; the polymerization reaction time is 3-9 hours, preferably 4-6 hours.

7. The preparation method according to claim 1 or 2, characterized in that: In step (4), the added acid is selected from one or more of hydrochloric acid, sulfuric acid, and phosphoric acid; preferably, the added acid is hydrochloric acid; more preferably, the added acid is 35% hydrochloric acid; the molar amount of the added acid is 108-125% of the molar amount of the organic amine added in step (1).

8. A polyvinylidene fluoride resin, characterized in that The polyvinylidene fluoride resin is prepared according to the method according to any one of claims 1-7.

9. The polyvinylidene fluoride resin according to claim 8, characterized in that The polyvinylidene fluoride resin has the following performance parameters: Bond strength is 78-106N / m; The yellow index is 2.7-3.4; Crystallinity is 40%-45%; The weight average molecular weight of the polyvinylidene fluoride resin is 800,000-1,350,000, and the molecular weight distribution index PDI is 1.4-2.

4.

10. Use of polyvinylidene fluoride resin in preparing lithium battery binder, characterized in that: The polyvinylidene fluoride resin is prepared according to the method according to any one of claims 1 to 7, or as described in claim 8 or 9.

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