Use of a hyperbranched vinylidene fluoride polymer in the processing of thin film articles

Abstract

The present application relates to application of hyperbranched polyvinylidene fluoride in film product processing, in particular, in the process of preparing film product by melt blending polyvinylidene fluoride and non-fluorine-containing polymer, the polyvinylidene fluoride comprises 0.1wt%-10wt% hyperbranched polyvinylidene fluoride and 90wt%-99.9wt% polyvinylidene fluoride, the weight average molecular weight of the hyperbranched polyvinylidene fluoride is 5000-500000, the melt viscosity is 5-60Pa.S, and the branching degree is 80-300 / 1000 carbon atoms. The hyperbranched polyvinylidene fluoride provided by the present application can effectively reduce the melt processing temperature and viscosity of polyvinylidene fluoride and non-fluorine-containing polymer.

Description

Technical Field

[0001] The present invention relates to the technical field of fluorine-containing polymers, and in particular to the application of a hyperbranched vinylidene fluoride polymer in the processing of film products. Background Art

[0002] Polyvinylidene fluoride (PVDF) has excellent resistance to high and low temperatures, chemical solvents, weather resistance, electrical insulation, mechanical properties and processing properties. It is currently widely used in the chemical, electronic and electrical, and mechanical fields.

[0003] Due to the relatively high cost of PVDF, it is often blended with non-fluoropolymers to reduce costs and balance various performance characteristics. When melt-blending PVDF with non-fluoropolymers, due to the high melting point of PVDF (usually between 160°C and 170°C), a higher processing temperature (between 210°C and 240°C) is required. This places high demands on the heat stability of the blended non-fluoropolymer and the compatibility of the additives.

[0004] If the melting temperature of polyvinylidene fluoride blends can be lowered, the processing temperature can be reduced, thereby lowering the thermal stability requirements of the non-fluorinated polymer blend and reducing energy consumption. However, simply lowering the processing temperature will increase the viscosity of the polymer melt, requiring a reduction in extrusion speed, which will reduce production efficiency. Otherwise, problems such as melt fracture may occur, affecting product quality.

[0005] In the prior art, the following methods are usually used to reduce the melt processing temperature of polyvinylidene fluoride blends:

[0006] Chinese patent CN102167836A discloses a method for preparing polyvinylidene fluoride film. This method uses a diluent to dissolve PVDF, thereby reducing processing temperatures. However, the dissolution process is time-consuming and requires subsequent de-volatilization using hot air (100-150°C), which is time-consuming and energy-intensive, and also poses environmental risks.

[0007] Chinese patent CN105085762A discloses a long-chain branched, high-molecular-weight polyvinylidene fluoride (PVDF) produced by emulsion polymerization at a temperature of 90°C or higher. This PVDF has a melting point of 157°C to 165°C and a melt viscosity of 120 to 190 ml / g, but still suffers from issues such as high melting temperature and high melt viscosity.

[0008] Chinese patent CN101305024A discloses a method for forming a branched fluoropolymer with long chain branches and little or no gel. The method involves preparing the branched fluoropolymer at a high temperature of 120°C to 150°C. However, due to the long chain branches and insufficient degree of branching, the branched fluoropolymer cannot effectively reduce the melting point and viscosity.

[0009] Therefore, developing a fluoropolymer processing aid and adding it to the polyvinylidene fluoride blend can effectively solve the above problems by reducing the melt processing temperature of the blend and also reducing the viscosity. Summary of the Invention

[0010] In order to solve the above problems, the present invention provides a hyperbranched vinylidene fluoride polymer as a fluoropolymer processing aid, which is added to a polyvinylidene fluoride blend to reduce not only the melt processing temperature of the blend but also the viscosity.

[0011] The present invention is achieved through the following technical solutions:

[0012] Disclosed is an application of a hyperbranched vinylidene fluoride polymer in the processing of a film product. Specifically, in the process of melt blending a vinylidene fluoride polymer and a non-fluorine-containing polymer to prepare a film product, the vinylidene fluoride polymer comprises 0.1 to 10 wt% of a hyperbranched vinylidene fluoride polymer and 90 wt% to 99.9 wt% of polyvinylidene fluoride.

[0013] The hyperbranched vinylidene fluoride polymer of the present invention effectively reduces the melt processing temperature and viscosity of the blend of the vinylidene fluoride polymer and the non-fluorine-containing polymer.

[0014] The hyperbranched vinylidene fluoride polymer of the present invention may be a vinylidene fluoride homopolymer or a vinylidene fluoride copolymer. When the hyperbranched vinylidene fluoride polymer comprises a vinylidene fluoride copolymer, in addition to vinylidene fluoride, the other comonomer is selected from at least one of vinyl fluoride, chlorotrifluoroethylene, tetrafluoroethylene, or hexafluoropropylene.

[0015] The weight average molecular weight of the hyperbranched vinylidene fluoride polymer of the present invention is 5000-500000, and the melt viscosity is 5-60 Pa.S (at 230°C, 100S -1 The branching degree is 80 to 300 / 1000 carbon atoms.

[0016] Preferably, the weight average molecular weight of the hyperbranched vinylidene fluoride polymer is 5000-100000, and the melt viscosity is 5-30 Pa.S (at 230°C, 100S -1 The branching degree is 150 to 300 / 1000 carbon atoms.

[0017] The preparation steps of the hyperbranched vinylidene fluoride polymer of the present invention are as follows: using vinylidene fluoride as a raw material, or using vinylidene fluoride and a second polymerizable monomer as raw materials, in the presence of a metal organic catalyst and a mixed solvent, a polymerization reaction is carried out to obtain the hyperbranched vinylidene fluoride polymer; the metal organic catalyst is a nickel-diimide-based or palladium-based metal coordination catalyst represented by the following formula (I):

[0018]

[0019] Wherein, M is selected from nickel or palladium; R is selected from hydrogen, methyl, ethyl, isopropyl, isobutyl or tert-butyl; R' is selected from methyl, tribromomethyl, pentabromophenyl, trifluoromethyl or pentafluorophenyl.

[0020] In the preparation process of the hyperbranched vinylidene fluoride polymer of the present invention, the metal organic catalyst is first dissolved in a mixed solvent to obtain a metal organic catalyst solution. The concentration of the metal organic catalyst solution is 0.1-1 g / L, preferably 0.2-0.8 g / L, and more preferably 0.2-0.6 g / L.

[0021] The mixed solvent is a mixture of a first organic solvent and a second organic solvent, wherein the volume ratio of the first organic solvent to the second organic solvent in the mixed solvent is 1:1 to 6:1; preferably, the volume ratio is 2:1 to 4:1; more preferably, the volume ratio is 2:1 to 3:1. The first organic solvent refers to an organic solvent capable of dissolving the metal organic catalyst; preferably, the first organic solvent is selected from at least one of carbon tetrachloride, chloroform, dichloromethane, or chlorobenzene, and the water content of the first organic solvent is less than 100 ppm. The second organic solvent refers to an organic solvent capable of dissolving polyvinylidene fluoride; preferably, the second organic solvent is selected from at least one of dimethylformamide (DMF), dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), triethyl phosphate (TEP), or nitrogen methyl pyrrolidone (NMP), and the water content of the second organic solvent is less than 100 ppm.

[0022] The second polymerizable monomer of the present invention is selected from at least one of vinyl fluoride, chlorotrifluoroethylene, tetrafluoroethylene or hexafluoropropylene, and the molar fraction of the vinylidene fluoride in the total amount of the polymerizable monomer is 60-100%; preferably, the molar fraction is 70-100%.

[0023] In the preparation process of the hyperbranched vinylidene fluoride polymer of the present invention, the reactor needs to be evacuated and replaced with nitrogen. When the oxygen content is less than 20 ppm, the polymerization monomer is added, and the polymerization reaction is carried out at a reaction temperature of 30° C. to 85° C., a reaction pressure of 0.1 to 5.0 MPa, a stirring rate of 100 to 500 rpm, and a polymerization reaction time of 2 to 72 hours to obtain a crude hyperbranched vinylidene fluoride polymer. Preferably, the stirring rate is 150 to 400 rpm and the polymerization reaction time is 8 to 24 hours.

[0024] Furthermore, the hyperbranched vinylidene fluoride polymer crude product is diluted with a third organic solvent, and after filtering to remove excess metal organic catalyst, the product is precipitated with a fourth organic solvent, and finally filtered and dried to obtain a hyperbranched vinylidene fluoride polymer.

[0025] The third organic solvent is an organic solvent capable of dissolving polyvinylidene fluoride. Preferably, the third organic solvent is selected from at least one of dimethylformamide (DMF), dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), triethyl phosphate (TEP), or nitrogen methyl pyrrolidone (NMP), and the amount of the third organic solvent used is 1 to 3 times that of the mixed solvent.

[0026] The fourth type of organic solvent is an organic solvent capable of precipitating polyvinylidene fluoride. Preferably, the fourth type of organic solvent is selected from at least one of methanol, ether, n-hexane or petroleum ether, and the amount of the fourth type of organic solvent used is 3 to 5 times that of the third type of organic solvent.

[0027] The level of branch content in the hyperbranched vinylidene fluoride polymer of the present invention has a very significant impact on the crystalline morphology of the final product. This impact is mainly due to the shortening of the segment length between the branches as the degree of branching increases, the resistance to the regular arrangement of the polymer segments in the molten state increases, the crystallization ability and wafer thickness decrease, and the melting point and melting enthalpy decrease, and DSC often cannot detect the existence of the melting point. At room temperature, the hyperbranched vinylidene fluoride polymer exists in the form of an elastomer, which can effectively reduce the melt processing temperature and viscosity of the polyvinylidene fluoride and non-fluoropolymer blend.

[0028] The film product of the present invention is a solar cell photovoltaic backplane film product.

[0029] The present invention also provides a method for preparing a hyperbranched vinylidene fluoride polymer, which comprises: using vinylidene fluoride as a raw material, or using vinylidene fluoride and a second polymerizable monomer as raw materials, in the presence of a metal organic catalyst and a mixed solvent, performing a polymerization reaction to obtain the hyperbranched vinylidene fluoride polymer.

[0030] Specifically, the method for preparing a hyperbranched vinylidene fluoride polymer comprises the following steps:

[0031] (1) dissolving the metal organic catalyst in a mixed solvent in a reactor to obtain a metal organic catalyst solution;

[0032] (2) evacuating the reactor and replacing the atmosphere with nitrogen, and when the oxygen content is less than 20 ppm, adding the polymerization monomer, and carrying out the polymerization reaction for 2 to 72 hours at a reaction temperature of 30° C. to 85° C., a reaction pressure of 0.1 to 5.0 MPa, and a stirring rate of 100 to 500 rpm to obtain a crude hyperbranched vinylidene fluoride polymer;

[0033] (3) diluting the crude hyperbranched vinylidene fluoride polymer in step (2) with a third organic solvent, filtering to remove excess metal organic catalyst, and then settling with a fourth organic solvent, and finally filtering and drying to obtain a hyperbranched vinylidene fluoride polymer.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The hyperbranched vinylidene fluoride polymer of the present invention has a low melting point, low viscosity and good fluidity, and can be used as a processing aid to effectively reduce the melt processing temperature and viscosity of the blend of polyvinylidene fluoride and non-fluorine-containing polymer.

[0036] 2. The method for preparing the hyperbranched vinylidene fluoride polymer of the present invention has simple process, mild reaction conditions and is easy to industrialize. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all possible alternatives, improvements and equivalents within the scope of the claims.

[0038] The polymer properties of the examples and comparative examples of the present invention were tested using the following methods:

[0039] Molecular weight and distribution width test: DMF was used as the mobile phase and Agilent Technologies PL-GPC 50 was used to test the weight-average molecular weight and distribution width.

[0040] Melting point test: The melting point of the polymer was tested using a PerKinElmer Diamond DSC differential scanning calorimeter in the test range of 50-220°C and a heating rate of 10°C / min. The peak temperature during the second melting was recorded as the melting point of the polymer.

[0041] Melt viscosity test: at 230℃, 100S -1 The MCR72 Anton Paar rotational rheometer measures the polymer melt viscosity at a frequency of .

[0042] Degree of branching test: Deuterated DMSO was used as solvent and Bruker AVANCE III HD 600 MHz NMR spectrometer was used. 19 The degree of branching of the polymer was measured by F-NMR.

[0043] 1. Preparation of Hyperbranched Vinylidene Fluoride Polymers

[0044] Example 1

[0045] (1) 0.4 g of diimine metal palladium catalyst (R is isopropyl and R' is methyl in the structure of the catalyst) was dissolved in 400 mL of mixed solvent of chloroform and DMF in a 5 L stainless steel reaction kettle, and the volume ratio of chloroform and DMF was 2:1;

[0046] (2) After vacuumizing and replacing with nitrogen for 3 times, when the oxygen content was less than 20 ppm, the temperature was increased to 60℃, and vinylidene fluoride monomer was introduced, the rotation speed of the reaction kettle was 150 rpm, and the pressure was maintained at 0.1 MPa, and the reaction was carried out for 72 h;

[0047] (3) 1.2 L of DMF was used for product dissolution, the catalyst was removed by filtration, and the product was precipitated in 5 times the volume of methanol in DMF, and then vacuum filtration was performed, and the product was dried in a vacuum oven at 65℃ until the weight was constant, to obtain the hyperbranched vinylidene fluoride polymer.

[0048] The prepared hyperbranched vinylidene fluoride polymer was tested for performance, and the test results were as follows: the weight average molecular weight (Mw) of the hyperbranched vinylidene fluoride polymer was 55000; the dispersity index (PDI) was 2.12; it was an elastomer without melting point; the melt viscosity was 20 Pa.S; and the degree of branching was 210 / 1000 carbon atoms.

[0049] Example 2

[0050] (1) 0.1 g of diimine metal nickel catalyst (R is methyl and R' is pentafluorophenyl in the structure of the catalyst) was dispersed in 1000 mL of mixed solvent of carbon tetrachloride and DMAC in a 5 L stainless steel reaction kettle, and the volume ratio of carbon tetrachloride and DMAC was 6:1;

[0051] (2) After vacuumizing and replacing with nitrogen for 3 times, when the oxygen content was less than 20 ppm, the temperature was increased to 85℃, and a mixture of vinylidene fluoride and fluoroethylene monomers was introduced, wherein the molar ratio of vinylidene fluoride was 60%, the rotation speed of the reaction kettle was 200 rpm, and the pressure was maintained at 5.0 MPa, and the reaction was carried out for 2 h;

[0052] (3) 1 L of DMAC was used for product dilution, the catalyst was removed by filtration, and the product was precipitated in 5 times the volume of diethyl ether in DMAC, and then vacuum filtration was performed, and the product was dried in a vacuum oven at 65℃ until the weight was constant, to obtain the hyperbranched vinylidene fluoride polymer.

[0053] The prepared hyperbranched vinylidene fluoride polymer was tested for performance, and the performance test results were as follows: Mw was 155000; PDI was 2.5; it was an elastomer without melting point; melt viscosity was 35 Pa.S; and the degree of branching was 156 / 1000 carbon atoms.

[0054] Example 3

[0055] (1) In a 5 L stainless steel reactor, 1.0 g of diimine metal palladium catalyst (R is isobutyl and R' is pentafluorophenyl in the catalyst structure) was dispersed in 1000 mL of a mixed solvent of dichloromethane and NMP, with a volume ratio of dichloromethane to NMP of 4:1;

[0056] (2) Evacuate and replace with nitrogen three times. When the oxygen content is less than 20 ppm, heat to 30°C and introduce a mixed monomer of vinylidene fluoride and hexafluoropropylene, wherein the molar ratio of vinylidene fluoride to hexafluoropropylene is 7:3. The speed of the reactor is 300 rpm, the pressure is maintained at 0.1 MPa, and the reaction is carried out for 12 hours.

[0057] (3) Dissolve the product in 1 L of NMP, remove the catalyst by filtration, and precipitate with methanol in an amount 5 times the volume of NMP. Filter and dry in a vacuum oven at 65° C. to constant weight to obtain a hyperbranched vinylidene fluoride polymer.

[0058] The prepared hyperbranched vinylidene fluoride polymer was subjected to performance testing, and the performance test results were: Mw was 5000; PDI was 3.12; it was an elastomer with no melting point; the melt viscosity was 5 Pa.S; and the branching degree was 300 / 1000 carbon atoms.

[0059] Example 4

[0060] (1) In a 5 L stainless steel reactor, 0.4 g of diimine metal palladium catalyst (R is ethyl and R' is trifluoromethyl in the catalyst structure) was dispersed in 800 mL of a mixed solvent of chlorobenzene and DMAC, with a volume ratio of chlorobenzene to DMAC of 3:1;

[0061] (2) Evacuate and replace with nitrogen three times. When the oxygen content is less than 20 ppm, heat to 70°C and introduce a mixed monomer of vinylidene fluoride and chlorotrifluoroethylene, wherein the molar ratio of vinylidene fluoride to chlorotrifluoroethylene is 9:1. The speed of the reactor is 500 rpm, the pressure is maintained at 3.0 MPa, and the reaction is continued for 24 hours.

[0062] (3) The product was dissolved in 1.5 L of DMAC, the catalyst was removed by filtration, and the product was precipitated with methanol in an amount 5 times the volume of DMAC. The product was filtered and dried in a vacuum oven at 65° C. to a constant weight to obtain a hyperbranched vinylidene fluoride polymer.

[0063] The prepared hyperbranched vinylidene fluoride polymer was subjected to performance testing, and the performance test results were: Mw was 16500; PDI was 3.25; it was an elastomer with no melting point; the melt viscosity was 16 Pa.S; and the branching degree was 265 / 1000 carbon atoms.

[0064] Example 5

[0065] (1) 0.4 g of diimine metal nickel catalyst (R is hydrogen and R' is methyl in the structure of the catalyst) was dispersed in 1000 mL of mixed solvent of chlorobenzene and DMF in a 5 L stainless steel reaction kettle, and the volume ratio of chlorobenzene and DMF was 5:1;

[0066] (2) After vacuumizing and replacing with nitrogen for 3 times, when the oxygen content was less than 20 ppm, the temperature was increased to 35℃, and the mixed monomers of vinylidene fluoride and tetrafluoroethylene were introduced, wherein the molar ratio of vinylidene fluoride and tetrafluoroethylene was 19:1, the rotation speed of the reaction kettle was 200 rpm, the pressure was maintained at 2.0 MPa, and the reaction was carried out for 48 h;

[0067] (3) 2 L of DMF was used for product dissolution, the catalyst was removed by filtration, and the product was precipitated in 5 times the volume of methanol, and then vacuum filtration was performed, and the product was dried in a vacuum oven at 65℃ until the weight was constant, to obtain the hyperbranched vinylidene fluoride polymer.

[0068] The prepared hyperbranched vinylidene fluoride polymer was tested for performance, and the performance test results were as follows: Mw was 500000; PDI was 2.87; it was an elastomer without melting point; the melt viscosity was 60 a.S; the degree of branching was 80 / 1000 carbon atoms.

[0069] Example 6

[0070] (1) 0.2 g of diimine metal palladium catalyst (R is isobutyl and R' is methyl in the structure of the catalyst) was dispersed in 1000 mL of mixed solvent of carbon tetrachloride and DMF in a 5 L stainless steel reaction kettle, and the volume ratio of carbon tetrachloride and DMF was 1:1;

[0071] (2) After vacuumizing and replacing with nitrogen for 3 times, when the oxygen content was less than 20 ppm, the temperature was increased to 60℃, and the vinylidene fluoride monomer was introduced, the rotation speed of the reaction kettle was 100 rpm, the pressure was maintained at 2.0 MPa, and the reaction was carried out for 48 h;

[0072] (3) 2.5 L of DMF was used for product dissolution, the catalyst was removed by filtration, and the product was precipitated in 5 times the volume of methanol, and then vacuum filtration was performed, and the product was dried in a vacuum oven at 65℃ until the weight was constant, to obtain the hyperbranched vinylidene fluoride polymer.

[0073] The prepared hyperbranched vinylidene fluoride polymer was tested for performance, and the performance test results were as follows: Mw was 35500; PDI was 2.85; it was an elastomer without melting point; the melt viscosity was 18 Pa.S; the degree of branching was 182 / 1000 carbon atoms.

[0074] Comparative Example 1

[0075] The operation of Comparative Example 1 is the same as that of Example 1, except that 0.4 g of diimine metal palladium catalyst (R is isopropyl and R' is methyl in the catalyst structure) is dissolved in 400 mL of chloroform instead of in 400 mL of a mixed solvent of chloroform and DMF.

[0076] During the reaction, the reactor pressure did not drop, and the remaining monomers were vented. After opening the reactor, no hyperbranched PVDF polymer was found. This shows that a mixed solvent is required to obtain a hyperbranched vinylidene fluoride polymer.

[0077] Comparative Example 2

[0078] The PVDF resin is prepared by an emulsion polymerization method (using the method of Chinese patent CN101305024A).

[0079] 18 kg of pure water, 200 g of a 5% sodium perfluorooctanoate solution, and 80 g of paraffin wax (melting point: 60°C) were placed in a reactor. The reactor was evacuated with nitrogen to remove oxygen, reducing the oxygen content to less than 20 ppm. The stirring speed was adjusted to 400 rpm / min, and the reactor temperature was raised to 125°C. Vinylidene fluoride (VDF) was added until the reactor pressure reached 5.0 MPa. 1.2 g of phenoxyethyl peroxydicarbonate was added to initiate the polymerization reaction. Additional VDF was then added to maintain the reactor pressure at 4.5 MPa. 0.0096 g of initiator was added intermittently every 10 minutes. Chain transfer agent HFC-4310 was added in four batches of 5 g each at 20%, 40%, 60%, and 80% conversion. A total of 5 kg of VDF monomer was added to the reaction, and the reaction was continued until the pressure dropped to 4.0 MPa. The reaction was then vented and the reaction was completed for 160 minutes. The polyvinylidene fluoride resin is dried after filtering to remove wax, coagulating and breaking emulsions, washing, and dehydrating. The polyvinylidene fluoride resin obtained by drying is sampled and analyzed.

[0080] The prepared polyvinylidene fluoride resin was subjected to performance testing, and the performance test results were: Mw was 671000; PDI was 3.05; melting point was 158.6°C; melt viscosity was 700 Pa.S; and branching degree was 3.9 / 1000 carbon atoms.

[0081] 2. Application of Hyperbranched Vinylidene Fluoride Polymers

[0082] Application Example 1

[0083] 70 parts of PVDF resin (melting temperature of 168°C), 30 parts of PMMA resin, 25 parts of titanium dioxide, 3 parts of light stabilizer, 1 part of heat stabilizer, and 5 parts of the polymers prepared in Examples 1 to 6 and Comparative Example 2 were pre-dried and added to a high-speed mixer and stirred at high speed for 45 minutes to obtain a special dry blend.

[0084] The obtained dry blend is extruded and granulated in a twin-screw extruder to prepare a special masterbatch.

[0085] The obtained masterbatch was added to a single-screw extruder, and the three-stage temperature of the single-screw extruder was adjusted until a smooth film was obtained. At this time, the three-stage temperature of the single-screw extruder was shown in Table 1 below.

[0086] Table 1. Film processing temperature data using polymer additives from Examples and Comparative Examples

[0087]

[0088] It can be seen from this that the addition of hyperbranched PVDF resin can effectively reduce the melt processing temperature during the preparation of solar photovoltaic backplane film, while the addition of long-chain branched PVDF resin requires a higher melt processing temperature.

[0089] Application Example 2

[0090] The melt viscosity values ​​of 70 parts of PVDF resin (melt viscosity of 400 Pa.S) and 5 parts of the polymers prepared in Examples 1 to 6 and Comparative Example 2 after blending are shown in Table 2 below.

[0091] Table 2 Melt viscosity values ​​of polymer additives and PVDF resin blends in Examples and Comparative Examples

[0092]

[0093] It can be seen that the present invention can effectively reduce the melt processing viscosity by adding the hyperbranched vinylidene fluoride polymer as a processing aid to polyvinylidene fluoride, while when long-chain branched PVDF resin is added, the melt viscosity is increased.

Claims

1. Application of a hyperbranched vinylidene fluoride polymer in the processing of film products, characterized in that: In the process of melt blending a vinylidene fluoride polymer and a non-fluorine-containing polymer to prepare a film product, the vinylidene fluoride polymer contains 0.1wt% to 10wt% of a hyperbranched vinylidene fluoride polymer and 90wt% to 99.9wt% of polyvinylidene fluoride, the hyperbranched vinylidene fluoride polymer has a weight average molecular weight of 5000 to 500000, a melt viscosity of 5 to 60 Pa.S, and a branching degree of 80 to 300 / 1000 carbon atoms.

2. The use of the hyperbranched vinylidene fluoride polymer according to claim 1 in the processing of film products, characterized in that: The vinylidene fluoride polymer comprises 2.0 wt% to 9.8 wt% of a hyperbranched vinylidene fluoride polymer and 90.2 wt% to 98.0 wt% of polyvinylidene fluoride.

3. The use of the hyperbranched vinylidene fluoride polymer according to claim 1 or 2 in the processing of film products, characterized in that: The hyperbranched vinylidene fluoride polymer has a weight average molecular weight of 5,000 to 100,000, a melt viscosity of 5 to 30 Pa.s, and a branching degree of 150 to 300 / 1,000 carbon atoms.

4. The use of the hyperbranched vinylidene fluoride polymer according to claim 1 in the processing of film products, characterized in that: The preparation steps of the hyperbranched vinylidene fluoride polymer are as follows: using vinylidene fluoride as a raw material, or using vinylidene fluoride and a second polymerizable monomer as raw materials, in the presence of a metal organic catalyst and a mixed solvent, a polymerization reaction is carried out to obtain the hyperbranched vinylidene fluoride polymer; the metal organic catalyst is a nickel-diimide-based or palladium-based metal coordination catalyst represented by the following formula (I): Wherein, M is selected from metal nickel or palladium; R is selected from hydrogen, methyl, ethyl, isopropyl, isobutyl or tert-butyl; R' is selected from methyl, tribromomethyl, pentabromophenyl, trifluoromethyl or pentafluorophenyl.

5. The use of the hyperbranched vinylidene fluoride polymer according to claim 4 in the processing of film products, characterized in that: During the preparation process, the metal organic catalyst is dissolved in a mixed solvent to obtain a solution with a concentration of 0.1 to 1 g / L.

6. Use of the hyperbranched vinylidene fluoride polymer according to claim 4 or 5 in the processing of film products, characterized in that: The mixed solvent is a mixed solvent formed by a first type organic solvent and a second type organic solvent in a volume ratio of 1:1 to 6:1, the first type organic solvent is selected from at least one of carbon tetrachloride, chloroform, dichloromethane or chlorobenzene; the second type organic solvent is selected from at least one of dimethylformamide, dimethylacetamide, dimethyl sulfoxide, triethyl phosphate or nitrogen methyl pyrrolidone.

7. The use of the hyperbranched vinylidene fluoride polymer according to claim 6 in the processing of film products, characterized in that: The water content of the first organic solvent and the second organic solvent is less than 100 ppm.

8. The use of the hyperbranched vinylidene fluoride polymer according to claim 4 in the processing of film products, characterized in that: The second polymerizable monomer is selected from at least one of vinyl fluoride, chlorotrifluoroethylene, tetrafluoroethylene and hexafluoropropylene, and the molar fraction of the vinylidene fluoride in the total amount of the polymerizable monomer is 60 to 100%.

9. The use of the hyperbranched vinylidene fluoride polymer according to claim 1 in the processing of film products, characterized in that: The film product is a photovoltaic backplane film for solar cells.

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