Vinylidene fluoride polymer with controllable particle size and high solid content as well as preparation method and application of vinylidene fluoride polymer

Abstract

The invention discloses a vinylidene fluoride polymer with controllable particle size and high solid content as well as a preparation method and application of the vinylidene fluoride polymer. According to the invention, mass and heat transfer and molecule mixing are enhanced through the supergravity reactor, so that the polymerization rate is effectively increased, and the solid content of polymer particles is increased; the particle size of the vinylidene fluoride polymer is horizontally regulated and controlled by supergravity and is uniformly distributed, meanwhile, the stability of a polymerization system is improved by high shear force provided by the supergravity reactor, and the use amount of a surfactant is greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of material preparation, and in particular to a vinylidene fluoride polymer with controllable particle size and high solid content, and a preparation method and application thereof. Background Art

[0002] Vinylidene fluoride polymer is a general term for vinylidene fluoride homopolymer and copolymers with other monomers. It is widely used in the fields of coatings, diaphragms, films and cables. The particle size and distribution of vinylidene fluoride polymer affect its dispersibility and compatibility in the above-mentioned application processing, and are key factors affecting its processing performance and product performance. At present, the suspension polymerization method and emulsion polymerization method are mostly used in the industrial preparation of vinylidene fluoride polymer. Compared with the suspension method, the emulsion method is the preferred method for producing vinylidene fluoride polymer particles with a primary particle size of 50-1000nm. The smaller particle size enables the vinylidene fluoride polymer to be quickly and stably dissolved in the solvent, which is conducive to improving production efficiency. However, the maintenance of the stability of the emulsion polymerization system and the regulation of the product particle size and particle size distribution often rely on the large-scale use of surfactants. Common surfactants include non-fluorinated surfactants, such as hexadecyltrimethylammonium bromide and polyethylene glycol octylphenyl ether; fluorinated surfactants, such as perfluorooctanoate and perfluoropolyether carboxylate. The addition of surfactants can reduce the interaction between polymer particles and improve the interfacial interaction between particles and the aqueous phase, thereby preventing the aggregation and sedimentation of emulsion particles under mechanical shear. However, non-fluorinated surfactants can reduce initiator efficiency, interfere with polymerization kinetics and reduce product yield through chain transfer; fluorinated surfactants can be directly incorporated into the structure of vinylidene fluoride polymers, resulting in adverse changes in physical and chemical properties. In addition, surfactants are difficult to completely remove after polymer aggregation, greatly increasing the burden of washing operations, and their well-known toxicity and possible potential release have also caused widespread concern. Therefore, it is very necessary to reduce the amount of surfactants used in the emulsion polymerization process.

[0003] In order to achieve this goal, those skilled in the art have tried to improve the polymerization formula to obtain a stable polymerization system, but there are still disadvantages. For example, U.S. Patent No. 5,453,477A uses a redox initiator system, but does not disclose the effect of the initiator system on the color of the final molten product. Chinese Patent CN111918882 discloses a high-solid fluorine-containing polymer without surfactant, but the preparation method requires a higher polymerization temperature than is usually used. The higher the polymerization reaction temperature, the more defective structures will be produced.

[0004] By choosing a suitable and efficient preparation process, it is also possible to obtain a stable emulsion polymerization system, achieve controllable particle size and particle size distribution, and increase the solid content of the product. In the emulsion polymerization process, the stirring speed of the polymerization kettle is also a key factor affecting the polymer particle size and the stability of the polymerization system. Sufficient stirring speed can increase the gas-liquid contact area, which is conducive to initiating free radical polymerization and promoting chain growth, and controlling the polymerization reaction rate; it can timely diffuse the heat generated in the center of the kettle, which is conducive to controlling the temperature of the reaction system and reducing the generation of gel. However, when the stirring speed is too fast, the stability of the emulsion may be destroyed, and demulsification may occur. In addition, considering that the fluorinated monomer is extremely hydrophobic, the mass transfer is very unsatisfactory. Summary of the invention

[0005] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0006] To this end, the embodiments of the present invention provide a vinylidene fluoride polymer with controllable particle size and high solid content, and a preparation method and application thereof. The present invention uses supergravity technology to strengthen the emulsion polymerization process, increase the polymerization rate and the solid content of polymer particles, and use the strong shearing effect in the supergravity field to maintain the stability of the polymerization system and regulate the particle size of the polymer particles while reducing the surfactant.

[0007] In a first aspect, the present invention provides a method for preparing a vinylidene fluoride polymer with controllable particle size and high solid content, comprising the following steps:

[0008] (a) dissolving a surfactant and a chain transfer agent in deionized water, pumping the water into a high gravity reactor and deoxygenating the water;

[0009] (b) raising the temperature to the reaction temperature, pumping in comonomers including vinylidene fluoride to the reaction pressure, pumping in an initiator, and performing a free radical emulsion polymerization reaction under supergravity conditions while maintaining a constant pressure;

[0010] (c) After the polymerization reaction is completed, the obtained emulsion is coagulated, washed and dried to obtain vinylidene fluoride polymer powder.

[0011] In step (a), deoxygenation can be achieved by introducing an inert gas, wherein the inert gas can be nitrogen or argon. In step (b), the pressure in the high gravity reactor is maintained constant by adding vinylidene fluoride and other possible monomers.

[0012] Furthermore, the surfactant includes one or more of a fluorine-containing surfactant and a non-fluorine-containing surfactant.

[0013] In some embodiments, the surfactant is a perfluoropolyether carboxylate, such as ammonium perfluoropolyether carboxylate, sodium perfluoropolyether carboxylate, etc.; or the surfactant is nonylphenol polyoxyethylene ether, sodium dodecylbenzene sulfonate.

[0014] Furthermore, the amount of the surfactant is 0.01% to 0.05% of the total mass of the comonomer.

[0015] The amount of surfactant used can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05% of the total mass of the comonomer or a value within the range of any two values. The present invention adopts a high-gravity emulsion polymerization process. The high shear force provided by the high-gravity reactor improves the stability of the polymerization system and greatly reduces the amount of surfactant used, thereby reducing the adverse effects of surfactants interfering with free radical polymerization reactions through chain transfer or the deterioration of thermal stability caused by incorporation into polymer chains.

[0016] Furthermore, the high gravity reactor includes one or more of a high gravity rotating packed bed, a high gravity rotating spiral channel, a high gravity rotating disc, and a stator-rotor type high gravity rotating device.

[0017] In some embodiments, the high gravity reactor is a high gravity rotating packed bed.

[0018] Furthermore, the hypergravity level of the hypergravity reactor is 10 to 800 g, wherein g is the acceleration due to gravity.

[0019] In some embodiments, the hypergravity level of the hypergravity reactor is 50-500 g.

[0020] The hypergravity level of the hypergravity reactor may be 10 g, 20 g, 50 g, 100 g, 150 g, 200 g, 250 g, 500 g, 600 g, 700 g, 800 g, or a value within a range consisting of any two of these values.

[0021] In the present invention, the particle size of the vinylidene fluoride polymer is regulated by regulating the supergravity level. It is understood that the higher the supergravity level, the smaller the particle size of the primary particles of the prepared vinylidene fluoride polymer.

[0022] Furthermore, the chain transfer agent includes one or more of oxygen-containing compounds and short-chain hydrocarbons, wherein oxygen-containing compounds include alcohols, ketones, esters and ethers; and short-chain hydrocarbons include ethane, propane and cyclohexane.

[0023] Furthermore, the amount of the chain transfer agent is 0.15% to 2.0% of the total mass of the comonomer. If too little chain transfer agent is added, the polymer molecular weight and molecular weight distribution cannot be effectively controlled and the polymer chain branching and cross-linking cannot be reduced; if too much chain transfer agent is added, the normally growing linear polymer chain is forced to terminate, resulting in a decrease in molecular weight.

[0024] Furthermore, in step (b), the reaction temperature is 70-90° C., the reaction pressure is 2.0-4.0 MPa, and the polymerization reaction time is 1-2 h.

[0025] The polymerization reaction temperature can be 70°C, 75°C, 80°C, 85°C, 90°C or a value within a range consisting of any two values. The present invention utilizes ultra-gravity technology to enhance heat transfer. Therefore, the reaction temperature does not need to be very high. At the same time, it is beneficial to control the temperature of the reaction system, prevent overheating to produce gel, and increase the solid content of the polymer particles.

[0026] The reaction pressure may be 2.0 MPa, 2.5 MPa, 3.0 MPa, 3.5 MPa, 4.0 MPa or a range consisting of any two of these values.

[0027] The polymerization reaction time can be 1h, 1.5h, 2h or a value within a range consisting of any two numerical values. The present invention utilizes ultra-gravity technology to enhance mass transfer, which can timely break the "cage effect" of the free radical initiator, and make the polymerization reaction rate controlled by the polymerization process instead of the mass transfer process; increase the contact area between the gas phase monomer and the water phase, improve the problem of slow reaction rate caused by poor water solubility of the monomer in the early stage of polymerization, further increase the polymerization rate, and shorten the reaction time.

[0028] Furthermore, the molar content of the vinylidene fluoride in the comonomer is 60% to 100%, and the molar content of other monomers that may exist in the comonomer except the vinylidene fluoride is 0 to 40%.

[0029] Furthermore, the comonomers also include one or more of trifluoroethylene, tetrafluoroethylene, hexafluoropropylene and chlorotrifluoroethylene.

[0030] Further, the initiator comprises one or more of inorganic peroxides and organic peroxides. When the initiator is pumped in step (b), an emulsion or emulsion of the initiator is pumped in.

[0031] Among them, inorganic peroxides include sodium persulfate, potassium persulfate, ammonium persulfate and potassium permanganate; organic peroxides include diethyl peroxydicarbonate, dipropyl peroxydicarbonate, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, tert-butyl peroxypivalate and dibenzoyl peroxide.

[0032] Furthermore, the amount of the initiator is 0.05% to 0.5% of the total mass of the comonomer. If the initiator is too little, the polymerization reaction rate is extremely slow; if the initiator is too much, the number of initial free radicals is too large, which will lead to a very low molecular weight and a wide molecular weight distribution, and if the initiator concentration is too high, the reaction will be violent. If the reaction heat cannot be removed in time, it will cause implosion or even explosion problems.

[0033] In a second aspect, the present invention provides a vinylidene fluoride polymer with controllable particle size and high solid content prepared by the method proposed in the first aspect of the present invention.

[0034] Furthermore, the primary particle size of the vinylidene fluoride polymer is 50 to 1000 nm, and the solid content is 30 wt% to 35 wt%.

[0035] The present invention adopts a supergravity emulsion polymerization process. The supergravity technology strengthens mass transfer. The highly enhanced molecular mixing is conducive to forming a uniform monomer and latex particle concentration field in the reactor, thereby improving product quality. The high shear force provided by the supergravity field can regulate the particle size of the primary polymer particles.

[0036] In a third aspect, the present invention provides the use of the vinylidene fluoride polymer prepared by the method provided in the first aspect or the vinylidene fluoride polymer provided in the second aspect in coatings, diaphragms, films, and cables.

[0037] The present invention prepares a vinylidene fluoride polymer with a primary particle size in the range of 50-1000 nm by adjusting the gravity level, which can meet different application requirements in industries such as coatings, diaphragms, films and cables.

[0038] Compared with the prior art, the beneficial effects of the present invention are:

[0039] The present invention utilizes an ultra-gravity reactor to enhance mass transfer, which can timely break the "cage effect" of the free radical initiator and make the polymerization reaction rate controlled by the polymerization process instead of the mass transfer process; it increases the contact area between the gas phase monomer and the water phase, improves the problem of slow reaction rate caused by poor water solubility of the monomer in the early stage of polymerization, and further increases the polymerization rate.

[0040] The present invention utilizes the supergravity reactor to enhance heat transfer, which is beneficial to controlling the temperature of the reaction system, preventing gelation or agglomeration caused by overheating, and increasing the solid content of polymer particles.

[0041] The invention utilizes a supergravity reactor to carry out highly enhanced molecular mixing, which is beneficial to forming a uniform monomer and latex particle concentration field in the reactor, thereby improving product quality.

[0042] The high shear force provided by the supergravity field of the present invention improves the stability of the polymerization system, which is beneficial to reducing the amount of surfactant used, thereby reducing the adverse effects caused by their interference with free radical polymerization reactions through chain transfer or the deterioration of thermal stability caused by incorporation into polymer chains. The variable shear strength can also regulate the particle size of the primary polymer particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0044] Figure 1 The process flow chart of the preparation method of the vinylidene fluoride polymer with controllable particle size and high solid content of the present invention;

[0045] Figure 2 This is a diagram of a device for preparing a vinylidene fluoride polymer with controllable particle size and high solid content according to the present invention;

[0046] Description of reference numerals:

[0047] Surfactant and chain transfer agent solution storage tank 1, vinylidene fluoride storage tank 2, other comonomer storage tank 3, initiator liquid storage tank 4, supergravity reactor 5. DETAILED DESCRIPTION

[0048] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0049] The process flow and device for preparing the vinylidene fluoride polymer of the present invention are as follows: Figure 1 and Figure 2 As shown, Figure 1 The preparation process shown is not described here in detail. Figure 2 As shown, surfactant and chain transfer agent solutions are stored in surfactant and chain transfer agent solution storage tank 1, vinylidene fluoride is stored in vinylidene fluoride storage tank 2, other comonomers are stored in other comonomer storage tank 3, initiator solution is stored in initiator solution storage tank 4, and the required substances are pumped into gravity reactor 5 by a pressure pump.

[0050] The following is a detailed description with reference to the examples and comparative examples. Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0051] Example 1

[0052] 0.5g of ammonium perfluoropolyether carboxylate and 20g of ethyl acetate were dissolved in 4000g of deionized water. After complete dissolution, they were pumped into a supergravity rotating packed bed reactor and nitrogen was passed into the reactor for 30 minutes for deoxygenation. Then the air was evacuated, the supergravity level was adjusted to 20g, the water feed in the reactor was heated to the required reaction temperature of 85°C, and vinylidene fluoride monomer was added. The reactor pressure was increased to 3MPa by the addition of vinylidene fluoride. After the reactor pressure stabilized, 100ml of 1.5wt% aqueous emulsion of diisopropyl peroxydicarbonate was pumped in to initiate a free radical polymerization reaction. Subsequently, the pressure in the reactor was maintained by adding vinylidene fluoride monomer until a cumulative amount of about 2500g of vinylidene fluoride monomer was introduced into the reaction mass and the feeding was stopped. The reaction was stopped after 1.5h, the reactor was vented and the emulsion was collected, and the obtained emulsion was condensed, washed and dried to obtain polyvinylidene fluoride powder.

[0053] Example 2

[0054] The difference from Example 1 is that the hypergravity level is 100 g.

[0055] Example 3

[0056] The difference from Example 1 is that the hypergravity level is 250 g.

[0057] Example 4

[0058] The difference from Example 1 is that the hypergravity level is 500 g and the reaction time is 1 h.

[0059] Example 5

[0060] The difference from Example 2 is that the amount of ammonium perfluoropolyether carboxylate used is 0.25 g and the reaction time is 2 h.

[0061] Example 6

[0062] 0.4g sodium dodecylbenzene sulfonate and 20g ethyl acetate were dissolved in 4000g deionized water. After complete dissolution, they were pumped into a supergravity rotating packed bed reactor and nitrogen was passed into the reactor for 30 minutes for deoxygenation. Then the air was evacuated, the supergravity level was adjusted to 200g, the water feed in the reactor was heated to the required reaction temperature of 80°C, and vinylidene fluoride monomer was added. The reactor pressure was increased to 3.8MPa by the addition of vinylidene fluoride. After the reactor pressure stabilized, 100ml of 2wt% aqueous emulsion of diisopropyl peroxydicarbonate was pumped in to initiate free radical polymerization. Subsequently, the pressure in the reactor was maintained by adding vinylidene fluoride monomer until a cumulative amount of about 2500g of vinylidene fluoride monomer was introduced into the reaction mass and the feeding was stopped. The reaction was stopped after 1.5h, the reactor was vented and the emulsion was collected, and the obtained emulsion was condensed, washed and dried to obtain polyvinylidene fluoride powder.

[0063] Example 7

[0064] 0.6g of nonylphenol polyoxyethylene ether and 20g of ethyl acetate were dissolved in 4000g of deionized water. After complete dissolution, they were pumped into a supergravity rotating packed bed reactor and nitrogen was passed into the reactor for 30 minutes for deoxygenation. Then the air was evacuated, the supergravity level was adjusted to 500g, the water feed in the reactor was heated to the required reaction temperature of 82°C, 500g of hexafluoropropylene monomer and a certain amount of vinylidene fluoride monomer were added, and the reactor pressure was increased to 4.0MPa by the addition of the two monomers. After the reactor pressure stabilized, 100ml of 1wt% of diisopropyl peroxydicarbonate aqueous emulsion was pumped in to initiate free radical polymerization. Subsequently, the pressure in the reactor was maintained by adding vinylidene fluoride monomer until a cumulative amount of about 2000g of vinylidene fluoride monomer was introduced into the reaction mass and the feeding was stopped. The reaction was stopped after 2h, the reactor was vented and the emulsion was collected, and the obtained emulsion was condensed, washed and dried to obtain polyvinylidene fluoride powder.

[0065] Comparative Example 1

[0066] Dissolve 0.5g of ammonium perfluoropolyether carboxylate and 20g of ethyl acetate in 4000g of deionized water. After complete dissolution, pump into a 5L vertical reactor and pass nitrogen into the reactor for 30 minutes for deoxidation. Then evacuate, adjust the stirring blade speed to 500rpm, heat the water feed in the reactor to the required reaction temperature of 87°C, start adding vinylidene fluoride monomer, and increase the reactor pressure to 3.5MPa by adding vinylidene fluoride. After the reactor pressure stabilizes, pump in 100ml of 1.5wt% diisopropyl peroxydicarbonate aqueous emulsion to initiate free radical polymerization. Subsequently, the pressure in the reactor is maintained by adding vinylidene fluoride monomer until a total of about 2500g of vinylidene fluoride monomer is introduced into the reaction mass and the feeding is stopped. The reaction is stopped after 1.5h, the reactor is vented and the emulsion is collected, and the obtained emulsion is condensed, washed, and dried to obtain polyvinylidene fluoride powder.

[0067] Comparative Example 2

[0068] The difference from Comparative Example 1 is that the reaction time is 3 h.

[0069] Comparative Example 3

[0070] The difference from Comparative Example 1 is that the amount of ammonium perfluoropolyether carboxylate used is 2.5 g and the reaction time is 3.5 h.

[0071] Comparative Example 4

[0072] The difference from Comparative Example 1 is that 5 g of sodium dodecylbenzene sulfonate and 20 g of ethyl acetate are dissolved in 4000 g of deionized water, the speed of the stirring paddle is 300 rpm, the cumulative amount of vinylidene fluoride monomer is about 2000 g, and the reaction time is 4 hours.

[0073] After the polymerization reaction is completed, observe whether agglomerates or gels are generated in the chambers of the reactors of Examples 1 to 7 and Comparative Examples 1 to 4. The average particle size and particle size distribution of the samples prepared in Examples 1 to 7 and Comparative Examples 1 to 4 are analyzed using a Malvern laser particle size analyzer. The results are shown in Table 1.

[0074] Table 1:

[0075]

[0076] By comparing Examples 1 to 4, it can be seen that as the hypergravity level increases, the primary particle diameter of the prepared sample decreases and the uniformity of the particle size distribution improves. The present invention can regulate the particle size and particle size distribution of the sample by adjusting the gravity level.

[0077] By comparing Examples 1 to 4 and Comparative Examples 1 to 2, it can be seen that when the same amount of surfactant is used, the primary particle size of the samples prepared in the Examples is significantly lower than that in the Comparative Examples; by comparing Example 3, Example 6, Comparative Example 3 and Comparative Example 4, it can be seen that when samples with the same level of primary particle size are obtained, the amount of surfactant used in Comparative Examples 3 and 4 is significantly increased. The reason is that the high shear force provided by the supergravity field improves the stability of the polymerization system, thereby reducing the amount of surfactant used.

[0078] By comparing Examples 1 to 7 and Comparative Examples 1 to 4, it can be seen that after the polymerization reaction of Examples 1 to 7 is completed, there is no agglomerate or gel in the reaction chamber, and after the polymerization reaction of Comparative Examples 1 to 4 is completed, there is agglomerate or gel in the reaction chamber. Compared with the comparative examples, the stability of the emulsion polymerization system of the embodiments is higher, because the high shear force provided by the supergravity field of the present invention improves the stability of the polymerization system.

[0079] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms may be for different embodiments or examples. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0080] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0081] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for preparing a vinylidene fluoride polymer with controllable particle size and high solid content, characterized in that: The following steps are involved: (a) dissolving a surfactant and a chain transfer agent in deionized water, pumping the water into a high gravity reactor and deoxygenating the water; (b) raising the temperature to the reaction temperature, pumping in comonomers including vinylidene fluoride to the reaction pressure, pumping in an initiator, and performing a free radical emulsion polymerization reaction under supergravity conditions while maintaining a constant pressure; (c) After the polymerization reaction is completed, the obtained emulsion is coagulated, washed and dried to obtain vinylidene fluoride polymer powder.

2. The method according to claim 1, characterized in that The surfactant includes one or more of a fluorine-containing surfactant and a non-fluorine-containing surfactant. The amount of the surfactant used is 0.01% to 0.05% of the total mass of the comonomer.

3. The method according to claim 1, characterized in that The supergravity reactor includes one or more of a supergravity rotating packed bed, a supergravity rotating spiral channel, a supergravity rotating disc, and a stator-rotor supergravity rotating device. The supergravity level of the supergravity reactor is 10 to 800g, wherein g is the acceleration of gravity.

4. The method according to claim 1, characterized in that The chain transfer agent includes one or more of oxygen-containing compounds and short-chain hydrocarbons, and the amount of the chain transfer agent is 0.15% to 2.0% of the total mass of the comonomer.

5. The method according to claim 1, characterized in that In step (b), the reaction temperature is 70-90° C., the reaction pressure is 2.0-4.0 MPa, and the polymerization reaction time is 1-2 h.

6. The method according to claim 1, characterized in that The molar content of the vinylidene fluoride in the comonomer is 60% to 100%.

7. The method according to claim 6, characterized in that The comonomer also includes one or more of trifluoroethylene, tetrafluoroethylene, hexafluoropropylene and chlorotrifluoroethylene.

8. The method according to claim 1, characterized in that The initiator includes one or more of inorganic peroxides and organic peroxides, and the amount of the initiator is 0.05% to 0.5% of the total mass of the comonomer.

9. A vinylidene fluoride polymer with controllable particle size and high solid content, characterized in that: Prepared by the method described in any one of claims 1 to 8, the primary particle size of the vinylidene fluoride polymer is 50 to 1000 nm and the solid content is 30 wt% to 35 wt%.

10. Use of the vinylidene fluoride polymer prepared by the method according to any one of claims 1 to 8 or the vinylidene fluoride polymer according to claim 9 in coatings, diaphragms, films and cables.

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