Method for producing partially fluorinated polymers

Abstract

The present invention relates to hydrophilic vinylidene fluoride copolymers that contain repeat units derived from hydrophilic monomers, processes for preparing these copolymers, and their use to make articles characterized by improved performance.

Description

Technical Field

[0001] The present invention relates to hydrophilic vinylidene fluoride copolymers containing repeating units derived from hydrophilic monomers, processes for preparing these copolymers, and their use for making articles characterized by improved performance.

Background Art

[0002] Fluoropolymers such as vinylidene fluoride polymers (PVDF) are very useful in a wide range of applications where good interfacial adhesion between the fluoropolymer and metal surfaces is strongly required, such as automotive materials, pipes and joints, bearings, linings, and containers. However, fluoropolymers have poor adhesion to metals because of their very low surface energy.

[0003] Surface treatments of fluoropolymers aimed at improving adhesion to metals are known and established in the art.

[0004] Fluoropolymers in the form of sheets, films and molded articles are chemically treated, subjected to discharge using corona discharge and plasma, subjected to flame treatment, and subjected to physical treatments such as chemical adsorption procedures to improve their adhesion to metals.

[0005] Treatments applied to fluoropolymer particles to change the chemical functionality of the particle surface and thereby change the surface properties of the aforementioned fluoropolymer particles are also known in the art.

[0006] As an example, U.S. Patent No. 6300641 discloses a process of irradiating polymer surfaces of articles such as PVDF surfaces with energized ion particles to reduce the wetting angle of the aforementioned surface and increase its adhesion strength. Since the irradiation is carried out in the presence of a reactive gas that chemically reacts with the surface of the polymer, chemical modification occurs on the surface of the article.

[0007] Among other surface treatments, Japanese Patent No. 3269024 discloses a method for producing a surface-modified fluororesin, which includes irradiating the fluororesin with short-wavelength ultraviolet light. While the aforementioned method is preferably applied to fluororesins in film form, it can also be applied to powders. This type of treatment allows only the surface layer of the fluororesin to be hydrophilized. In related technologies, PVDF has been used as an electrode binder in non-aqueous electrolyte secondary batteries. Generally, PVDF homopolymers have poor adhesion to metals. Several solutions have been proposed to address this problem. For example, in International Publication No. 2008 / 129041, it has been demonstrated that including certain repeating units derived from (meth)acrylic monomers improves the adhesion of PVDF polymers to metals. However, depending on the active materials used, higher bonding properties between active materials are still desired. [Overview of the project]

[0008] The applicant recognized that there is still a need for fluoropolymers with improved adhesion to metals.

[0009] The applicant has discovered that, surprisingly, a particular fluoropolymer comprising repeating units derived from vinylidene fluoride (VDF) and repeating units derived from a hydrophilic monomer can be modified in such a way that, when subjected to low-intensity irradiation with ionizing radiation, the aforementioned fluoropolymer is modified to obtain a fluoropolymer characterized by much higher hydrophilicity and significantly improved adhesion to metals.

[0010] Accordingly, in a first aspect, the present invention relates to a process for preparing polymer (A), wherein the process includes irradiating polymer (F) with ionizing radiation at a dose of less than 70 kGy, and polymer (F) is (i) Repeating units derived from vinylidene fluoride (VDF), (ii) For concentrations between 0.02 mol% and 5.0 mol%, the following formula (I): [ka] (In the formula: -R1, R2, and R3 are either equal to or different from each other, and are independently selected from hydrogen atoms and C1-C3 hydrocarbon groups. -R X C1-C12 contains at least one functional group selected from hydroxyl, carboxyl, epoxide, ester, and ether groups. 20 A repeating unit derived from at least one hydrophilic monomer [monomer (MA)] of the hydrocarbon moiety, The aforementioned mole percentage refers to the total moles of the repeating units of the polymer (F).

[0011] The irradiation process of the present invention yields a novel vinylidene fluoride (VDF) copolymer [polymer (A)] having remarkably high hydrophilicity.

[0012] Therefore, in another embodiment, the present invention is (i) Repeating units derived from vinylidene fluoride (VDF), (ii) For concentrations between 0.02 mol% and 5.0 mol%, the following formula (I): [ka] (In the formula: -R1, R2, and R3 are either equal to or different from each other, and are independently selected from hydrogen atoms and C1-C3 hydrocarbon groups. -R X C1-C12 contains at least one functional group selected from hydroxyl, carboxyl, epoxide, ester, and ether groups. 20 The present invention provides a vinylidene fluoride (VDF) copolymer [polymer (A)] comprising a repeating unit derived from at least one hydrophilic monomer [monomer (MA)] of the hydrocarbon moiety, The aforementioned mole percent refers to the total moles of the repeating units of polymer (A). The aforementioned polymer (A) has a contact angle of less than 73°, preferably less than 70°, according to the method reported in the following description.

[0013] The polymer (A) as defined above is particularly useful as an electrode binder for non-aqueous electrolyte secondary batteries.

[0014] Therefore, in another aspect of the present invention, a) at least one electrode active material (AM), b) at least one binder (B) (in this case, binder (B) comprises at least one vinylidene fluoride (VDF) copolymer [polymer (A)] as defined above), c) An electrode-forming composition [composition (C)] comprising at least one solvent (S) is provided. [Modes for carrying out the invention]

[0015] The term “repeating unit derived from vinylidene fluoride” (commonly also referred to as vinylidene difluoride, 1,1-difluoroethylene, or VDF) is intended to refer to the repeating unit of the formula CF2=CH2.

[0016] In one embodiment, the monomer (MA) is a C1-C12 monomer in which Rx contains at least one carboxyl group. 20 It is a compound of formula (I) as defined above, with the hydrocarbon portion being the hydrocarbon part.

[0017] In another embodiment, the monomer (MA) is given by formula (Ia): [ka] (In the formula, -R1, R2, and R3 are either equal to or different from each other, and are independently selected from hydrogen atoms and C1-C3 hydrocarbon groups. -R H C1-C2 is a hydrogen atom or a C1-C2 containing at least one carboxyl group. 20 It is a compound of the hydrocarbon group.

[0018] Non-restrictive examples of monomers (MA) in formula (Ia) include, in particular, -Acrylic acid (AA) and -(meth)acrylic acid, and These mixtures are included.

[0019] In another embodiment, the monomer (MA) is given by the following formula (Ib): [ka] (In the formula: -R1, R2, and R3 are either equal to or different from each other, and are independently selected from hydrogen atoms and C1-C3 hydrocarbon groups. -R OH It is a compound (a C1-C5 hydrocarbon moiety containing at least one hydroxyl group).

[0020] Non-limiting examples of monomers (MA) of formula (Ib) include, in particular, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxyethylhexyl (meth)acrylate.

[0021] The monomer (MA) of formula (Ib) is more preferably selected from the following: -formula: [ka] Hydroxyethyl acrylate (HEA), -formula: [ka] Any of the following 2-hydroxypropyl acrylates (HPA), - and mixtures thereof.

[0022] The monomers (MA) are randomly distributed within the polymer (F) described above. It is essential that at least 40% of the monomers (MA) in the polymer (F) are randomly distributed within the polymer (F).

[0023] The expression "Percentage of randomly distributed monomers (HA)" is intended to represent the percentage ratio between the average number (%) of (HA) monomer sequences contained between two repeating units derived from VDF monomers and the total average number (%) of (MA) monomer repeating units, as shown by the following formula:

number

[0024] If each of the (MA) repeating units is separated, i.e., contained between two repeating units of the VDF monomer, the average number of (MA) sequences is equal to the average total number of (MA) repeating units, and therefore the percentage of randomly distributed units (MA) is 100%: this value corresponds to a completely random distribution of (MA) repeating units.

[0025] Therefore, the greater the number of isolated (MA) units relative to the total number of (MA) units, the higher the percentage of randomly distributed (MA) units, as described above.

[0026] The determination of the total average number of (MA) monomer repeating units in polymer (F) can be performed by any suitable method, with NMR being preferred.

[0027] The proportion of randomly distributed units (MA) is preferably at least 50%, more preferably at least 60%, and most preferably at least 70%.

[0028] The polymer (F) preferably contains at least 0.02 mol%, more preferably at least 0.2 mol%, of repeating units derived from the aforementioned monomer (MA).

[0029] The polymer (F) preferably contains repeating units derived from monomer (MA) in an amount of at most 5.0 mol%, more preferably at most 3.0 mol%, and even more preferably at most 1.5 mol%.

[0030] Excellent results have been obtained using a polymer (F) comprising repeating units derived from at least 70 mol% of VDF.

[0031] The polymer (F) can be an elastomer or a semi - crystalline polymer, preferably a semi - crystalline polymer.

[0032] As used herein, the term "semi - crystalline" means a fluoropolymer having at least one crystal melting point in addition to a glass transition temperature Tg in DSC analysis. For the purposes of the present invention, a semi - crystalline fluoropolymer is herein intended to advantageously denote a fluoropolymer having a heat of fusion measured according to ASTM D 3418 of at least 0.4 J / g, preferably at least 0.5 J / g, more preferably at least 1 J / g.

[0033] For the purposes of the present invention, the term "elastomer" is intended to denote a true elastomer or a polymer resin that serves as a base component for obtaining a true elastomer.

[0034] True elastomers are defined by ASTM, Special Technical Bulletin, Specification No. 184 as materials that can be stretched to twice their original length at room temperature and, when released after being held under tension for 5 minutes, return to within 10% of their initial length simultaneously.

[0035] Preferably, the intrinsic viscosity of the polymer (F) measured in dimethylformamide at 25 °C is included in the range of 0.1 l / g to 0.80 l / g, more preferably 0.15 l / g to 0.45 l / g, even more preferably 0.25 l / g to 0.35 l / g.

[0036] The polymer (F) used in the process of the present invention usually has a melting temperature (T m ) included in the range of 120 to 200 °C.

[0037] The melting temperature can be determined from the DSC curve obtained by differential scanning calorimetry (hereinafter also called DSC). If the DSC curve shows multiple melting peaks (endothermic peaks), the melting temperature (T m ) is determined based on the peak with the largest peak area.

[0038] The polymer (F) may further contain repeating units derived from one or more fluorinated comonomers (CF) different from VDF.

[0039] In this specification, the term "fluorinated comonomer (CF)" is intended to refer to an ethylenically unsaturated comonomer containing at least one fluorine atom.

[0040] Non-limiting examples of suitable fluorinated comonomers (CFs) include, among others: (a) C2-C8 fluoro and / or perfluoroolefins, for example, tetrafluoroethylene (TFE), hexafluoropropylene (HFP), pentafluoropropylene and hexafluoroisobutylene, (b) C2-C8 hydrogenated monofluoroolefins, e.g., vinyl fluoride, 1,2-difluoroethylene and trifluoroethylene, (c)Formula CH2=CH-R f0 (In the formula, R f0 (These are perfluoroalkylethylenes, which are C1-C6 perfluoroalkyl groups.) (d) Includes chlorotrifluoroethylene (CTFE) and / or bromo- and / or iodo-C2~C6 fluoroolefins.

[0041] In one preferred embodiment, the polymer (F) is semicrystalline and contains 0.1 to 15.0 mol%, preferably 0.3 to 5.0 mol%, and more preferably 0.5 to 3.0 mol%, of repeating units derived from the aforementioned fluorinated comonomer (CF).

[0042] Please understand that polymer (F) may contain chain ends, defects, or other types of impurities, but these do not impair its properties.

[0043] Polymer (F) is more preferably, -At least 80 mol%, preferably at least 85 mol%, of vinylidene fluoride (VDF), -0.1 mol% to 3.0 mol%, preferably 0.15 mol% to 1.5 mol%, more preferably 0.15 mol% to 1.0 mol%, of at least one monomer (MA) of formula (I) as defined above, -Optionally, a repeating unit derived from at least one fluorinated comonomer (CF) in an amount of 0.5 to 3.0 mol%, and a repeating unit derived from, The aforementioned mole percentage refers to the total moles of the repeating units of the polymer (F).

[0044] Polymer (F) can be obtained by polymerizing a VDF monomer, at least one monomer (MA), and optionally at least one comonomer (CF) in a suspension in an organic medium, for example, according to the procedure described in International Publication No. 2008129041, or in an aqueous emulsion, typically as described in the Art (see, for example, U.S. Patent No. 4,016,345, U.S. Patent No. 4,725,644, and U.S. Patent No. 6,479,591).

[0045] Polymer (F) is preferably obtained by suspension polymerization.

[0046] The procedure for preparing polymer (F) includes the step of polymerizing vinylidene fluoride (VDF) monomer, monomer (MA), and optionally comonomer (CF) in an aqueous medium in a reaction vessel in the presence of a radical initiator, and this process is - A process of continuously supplying an aqueous solution containing monomers (MA), - The process includes the step of maintaining the pressure inside the aforementioned reaction vessel above the critical pressure of vinylidene fluoride.

[0047] Throughout the polymerization process, the pressure is maintained above the critical pressure of vinylidene fluoride. Generally, the pressure is maintained at a value greater than 50 bar, preferably greater than 75 bar, and more preferably greater than 100 bar.

[0048] The expression "continuous supply" or "continuous supply" means that an aqueous solution of monomer (monomer (MA)) is slowly added in small amounts for most of the polymerization until at least 70 mol% of VDF is converted.

[0049] Generally, the process of the present invention is carried out at a temperature of at least 20°C, preferably at least 30°C, and more preferably at least 35°C.

[0050] When polymerization is carried out in a suspension state, the polymer (F) is typically provided in the form of a powder.

[0051] When polymerization to obtain polymer (F) is carried out in an emulsion state, polymer (F) is typically provided in the form of an aqueous dispersion (D) and can be used either directly by emulsion polymerization or after a concentration step. Preferably, the solids content of polymer (F) in the dispersion (D) is in the range of 20 to 50% by weight.

[0052] The polymer (F) obtained by emulsion polymerization can be isolated from the aqueous dispersion (D) by concentration and / or coagulation of the dispersion, and can be obtained in powder form by subsequent drying.

[0053] The polymer (F) in powder form can be optionally further extruded to obtain the polymer (F) in pellet form.

[0054] Extrusion is carried out appropriately in the extruder. The duration of extrusion is appropriately in the range of a few seconds to 3 minutes.

[0055] A solution (sol) of polymer (F) can be obtained by dissolving polymer (F) in any suitable organic solvent. Preferably, the solid content of polymer (F) in the solution (sol) is in the range of 2 to 30% by weight.

[0056] Non-limiting examples of organic solvents suitable for dissolving polymer (F) include N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphamide, dioxane, tetrahydrofuran, tetramethylurea, triethyl phosphate, and trimethyl phosphate, aliphatic ketones, alicyclic ketones, and alicyclic esters. These organic solvents can be used alone or in mixtures of two or more chemical species.

[0057] In the process of the present invention, the polymer (F) subjected to the ionization step is preferably in the form of a powder.

[0058] The step of irradiating polymer (F) can therefore be carried out using any ionizing radiation, which may be alpha rays, beta rays, gamma rays, or electron beams; however, from the viewpoint of safety and reactivity, beta rays, gamma rays, and electron beams are preferred.

[0059] Irradiation must be carried out in the presence of oxygen. Irradiation can be carried out in air.

[0060] In this field, it is known that irradiation treatment can lead to a decrease in the molecular weight of the irradiated polymer due to chain severance, the formation of double bonds along the polymer chain, and the formation of oxygen-containing polar groups (Adv Polym Sci (2005)) 184:127-211, pages 186-189). Polar groups are mainly generated by the decomposition of hydroperoxides formed by the reaction of oxygen and radicals in the main chain of the polymer chain. Subsequent decomposition of these can also lead to the formation of hydroxyl groups, which explains the increase in the hydrophilicity of the polymer.

[0061] Irradiation in the presence of oxygen can further promote the formation of the aforementioned hydroxyl group (Kongop Hwahak (2011), 22(4), 353-357).

[0062] The irradiation step of the process of the present invention is carried out such that the absorbed dose of the treated polymer is preferably 0.1 kGy to 70 kGy, more preferably 1 kGy to 40 kGy, and even more preferably 1 kGy to 20 kGy.

[0063] The applicant has surprisingly found that under such soft conditions, polymer (F) can be modified to become hydrophilic, while minimizing damage to the original main chain structure of polymer (F). Indeed, NMR and FT-IR analysis shows that monomers (MA) in polymer (F) remain substantially unchanged in polymer (A) obtained after irradiation. This is primarily due to the low-intensity radiation used. Thus, the monomer composition of polymer (A) and polymer (F) is substantially identical. At the same time, the low-intensity radiation used in the process of the present invention enables polymer (A) to become hydrophilic due to the presence of polar groups in the main chain of the polymer chain.

[0064] In the present invention, a decrease in the contact angle means the formation of hydrophilic groups on the surface of the polymer, and the formation of hydrophilic groups will mean a decrease in the contact angle. The term "contact angle" or "contact angle with respect to water" as used in the present invention is defined as the angle formed between the tangent of a water droplet placed on a surface and the surface on which the water droplet resides.

[0065] The irradiation process causes modification of polymer (F) in the main chain of the VDF copolymer by the formation of polar groups, mainly hydroxyl groups, thereby obtaining polymer (A) that is hydrophilic with a contact angle to water of less than 73°.

[0066] A smaller contact angle means that the water droplet spreads widely and thinly across the material surface, which increases the surface's ability to attract water, i.e., its hydrophilicity.

[0067] The polymer (A) obtained by the process of the present invention is a novel product.

[0068] Therefore, in another aspect of the present invention, (i) Repeating units derived from vinylidene fluoride (VDF), (ii) For concentrations between 0.02 mol% and 5.0 mol%, the following formula (I): [ka] (In the formula: -R1, R2, and R3 are either equal to or different from each other, and are independently selected from hydrogen atoms and C1-C3 hydrocarbon groups. -R X C1-C12 contains at least one functional group selected from hydroxyl, carboxyl, epoxide, ester, and ether groups. 20 A vinylidene fluoride (VDF) copolymer [polymer (A)] is provided, comprising a repeating unit derived from at least one hydrophilic monomer [monomer (MA)] of the hydrocarbon moiety, The aforementioned mole percent refers to the total moles of the repeating units of polymer (A). The aforementioned polymer (A) has a contact angle of less than 73°, preferably less than 70°, according to the method described below.

[0069] The definition of polymer (F) given above applies here to polymer (A).

[0070] Therefore, the monomer (MA) as defined above is randomly distributed in polymer (A). It is essential that at least 40% of the monomer (MA) in polymer (A) is randomly distributed within polymer (A) as described above.

[0071] The proportion of randomly distributed units (MA) in polymer (A) is preferably at least 50%, more preferably at least 60%, and most preferably at least 70%.

[0072] The polymer (A) preferably contains at least 0.1 mol%, more preferably at least 0.2 mol%, of repeating units derived from the aforementioned monomer (MA).

[0073] The polymer (A) preferably contains repeating units derived from a monomer (MA) in an amount of at most 5.0 mol%, more preferably at most 3.0 mol%, and even more preferably at most 1.5 mol%.

[0074] Excellent results were obtained using polymer (A) containing at least 70 mol% repeating units derived from VDF.

[0075] Polymer (A) may be an elastomer or a semicrystalline polymer, and is preferably a semicrystalline polymer.

[0076] Preferably, the intrinsic viscosity of polymer (A), measured with dimethylformamide at 25°C, is contained within 0.1 l / g to 0.80 l / g, more preferably 0.15 l / g to 0.45 l / g, and even more preferably 0.25 l / g to 0.35 l / g.

[0077] The polymer (A) of the present invention typically has a melting temperature (T) that falls within the range of 120 to 200°C. m ) has.

[0078] Polymer (A) may further contain repeating units derived from one or more fluorinated comonomers (CF) different from VDF.

[0079] In this specification, the term "fluorinated comonomer (CF)" is intended to refer to an ethylenically unsaturated comonomer containing at least one fluorine atom.

[0080] Non-limiting examples of suitable fluorinated comonomers (CFs) include, among others: (a) C2-C8 fluoro and / or perfluoroolefins, for example, tetrafluoroethylene (TFE), hexafluoropropylene (HFP), pentafluoropropylene and hexafluoroisobutylene, (b) C2-C8 hydrogenated monofluoroolefins, e.g., vinyl fluoride, 1,2-difluoroethylene and trifluoroethylene, (c)Formula CH2=CH-R f0 (In the formula, R f0 (These are perfluoroalkylethylenes, which are C1-C6 perfluoroalkyl groups.) (d) Includes chlorotrifluoroethylene (CTFE) and / or bromo- and / or iodo-C2~C6 fluoroolefins.

[0081] In one preferred embodiment, the polymer (F) is semicrystalline and contains 0.1 to 10.0 mol%, preferably 0.3 to 5.0 mol%, and more preferably 0.5 to 3.0 mol%, of repeating units derived from the aforementioned fluorinated comonomer (CF).

[0082] It is understood that chain ends, defects, or other impurity types may be present in polymer (A) without impairing the polymer's properties.

[0083] Polymer (A) is more preferably, -At least 80 mol%, preferably at least 85 mol%, of vinylidene fluoride (VDF), -0.1 mol% to 3.0 mol%, preferably 0.15 mol% to 1.5 mol%, more preferably 0.15 mol% to 1.0 mol%, and at least one monomer (MA) of formula (I) as defined above, -Optionally, a repeating unit derived from at least one fluorinated comonomer (CF) in an amount of 0.5 to 3.0 mol%, and a repeating unit derived from, The aforementioned mole percentage refers to the total moles of the repeating units of polymer (A).

[0084] To measure the contact angle of polymer (A) in powder form, surface treatment is required. A film of polymer (A) can be prepared by any known process starting from polymer (A) in powder form, for example, by treating the polymer (A) composition in a suitable solvent by casting it onto an inert support, preferably a glass support, and then properly drying it to remove the solvent. The contact angle with water can then be measured on the side of the film exposed to the substrate.

[0085] More specifically, the contact angle with respect to water is appropriately performed on polymer films cast from an NMP solution on a glass surface at room temperature using a Contact Angle System (OCA20) instrument (DataPhysics Instruments GmbH). Droplets of Milli-Q water are automatically deposited on the film surface exposed to the glass substrate during film preparation. The contact angle is determined as the average of 10 measurements.

[0086] As mentioned above, polymer (A) as defined above is particularly useful as an electrode binder for non-aqueous electrolyte secondary batteries.

[0087] Therefore, the present invention is a) at least one electrode active material (AM), b) at least one binder (B) (binder (B) comprises at least one vinylidene fluoride (VDF) copolymer [polymer (A)] as defined above), c) Provides an electrode-forming composition [composition (C)] comprising at least one solvent (S).

[0088] The electrode-forming composition (C) of the present invention comprises one or more electroactive materials (AMs). For the purposes of the present invention, the term “electroactive material” is intended to refer to a compound that can incorporate or insert alkali or alkaline earth metal ions into its structure and substantially release them therefrom during the charging and discharging phases of an electrochemical device. Preferably, the electroactive material can incorporate or insert lithium ions and release them.

[0089] The properties of the electroactive material in the electrode-forming composition of the present invention depend on whether the aforementioned composition is used to manufacture a positive or negative electrode.

[0090] When forming a positive electrode for a lithium-ion secondary battery, the electroactive compound may include a lithium-containing compound.

[0091] In one preferred embodiment, the lithium-containing compound may be a metal chalcogenide of formula LiMQ2.

[0092] In one preferred embodiment, the lithium-containing compound may be a metal chalcogenide of formula LiMQ2, where M is at least one metal selected from transition metals such as Co, Ni, Fe, Mn, Cr, and V, or metals such as Al and mixtures thereof, and Q is a chalcogen such as O or S. Among these, it is preferable to use a lithium-based composite metal oxide of formula LiMO2 (wherein M is the same as defined above). Preferred examples include LiCoO2, LiNiO2, and LiNi x Co 1-x O2(0 <x<1)、LiNi a Co b Al c This may include O2(a+b+c=1) and LiMn2O4 with a spinel structure. In another embodiment, when forming a positive electrode for a lithium-ion secondary battery, the electroactive compound may be of the formula M1M2(JO4) f E 1-fThe formula may include a lithified or partially lithified transition metal oxyanion-based electroactive material, where M1 is lithium, which can be partially substituted with another alkali metal in the proportion of less than 20% of the M1 metal; M2 is a transition metal with an oxidation level of +2, selected from Fe, Mn, Ni, or mixtures thereof, which can be partially substituted with one or more further metals with oxidation levels between +1 and +5, in the proportion of less than 35% of the M2 metal; JO4 is any oxyanion where J is P, S, V, Si, Nb, Mo, or a combination thereof; E is a fluoride, hydroxide, or chloride anion; and f is the mole fraction of the JO4 oxyanion, which is generally between 0.75 and 1.

[0093] M1M2(JO4) as defined above f E 1-f The electroactive material is preferably a phosphate-based material and may have a regular or modified olivine structure.

[0094] More preferably, the electroactive compound used to form the positive electrode is of formula Li 3-x M' y M'' 2-y (JO4)3 (wherein 0≦x≦3, 0≦y≦2, M' and M'' are the same or different metals, at least one of which is a transition metal, JO4 is preferably PO4 which can be partially substituted with another oxyanion, where J is any of S, V, Si, Nb, Mo or a combination thereof). More preferably, the electroactive compound has the formula Li(Fe x Mn 1-x )PO4 (wherein 0≦x≦1, where x is preferably 1 (i.e., lithium iron phosphate of the formula LiFePO4)) is a phosphate-based electroactive material.

[0095] In the most preferred embodiment, the electroactive material for the positive electrode is of general formula (III) LiRing x M1 y M2 z Y2(III) Selected from lithium-containing composite metal oxides (wherein M1 and M2 are the same or different from each other, transition metals selected from Co, Fe, Mn, Cr, and V, 0.5 ≤ x ≤ 1, where y + z = 1 - x, and Y preferably represents a chalcogen selected from O and S).

[0096] The electroactive material in this embodiment is preferably a compound of formula (III) where Y is O. In a further preferred embodiment, M1 is Mn and M2 is Co, or M1 is Co and M2 is Al.

[0097] Examples of such active materials include LiNi x Mn y Co z O2 (hereinafter referred to as NMC in this specification), and LiNi x Co y Al z It contains O2 (hereinafter referred to as NCA in this specification).

[0098] Specifically, LiNa x Mn y Co z Regarding O2, the power and energy performance of the battery can be adjusted by varying the content ratio of manganese, nickel, and cobalt.

[0099] In a particularly preferred embodiment of the present invention, compound AM is a compound of formula (III) as defined above (wherein 0.5 ≤ x ≤ 1, 0.1 ≤ y ≤ 0.5, and 0 ≤ z ≤ 0.5).

[0100] Non-limiting examples of suitable electroactive materials for the positive electrode of equation (III) include, among others: LiRing 0.5 Mn 0.3 Co 0.2 O2, LiRing 0.6 Mn 0.2 Co 0.2 O2, LiRing 0.8 Mn 0.1 Co 0.1 O2, LiRing 0.8 Co 0.15 Al 0.05 O2, LiRing 0.8 Co 0.2 O2, LiRing 0.8 Co 0.15 Al 0.05 O2, LiRing 0.6 Mn 0.2 Co 0.2 O2, LiRing 0.8 Mn 0.1 Co 0.1 O2, LiRing 0.9 Mn 0.05 Co 0.05 O2 It includes.

[0101] Compound: LiRing 0.8 Co 0.15 Al 0.05 O2, LiRing 0.6 Mn 0.2 Co 0.2 O2, LiRing 0.8 Mn 0.1 Co 0.1 O2, LiRing 0.9 Mn 0.05 Co 0.05 O2 That is particularly preferable.

[0102] When forming a negative electrode for a lithium-ion secondary battery, the electroactive compound may preferably include one or more carbon-based materials and / or one or more silicon-based materials.

[0103] In some embodiments, the carbon-based material can be selected from graphite such as natural or artificial graphite, graphene, carbon black, and carbon nanotubes (CNTs).

[0104] These materials can be used individually or as a mixture of two or more of them.

[0105] The carbon-based material is preferably graphite.

[0106] The silicon-based compound may be one or more selected from the group consisting of chlorosilane, alkoxysilane, aminosilane, fluoroalkylsilane, silicon, silicon chloride, silicon carbide, and silicon oxide. More specifically, the silicon-based compound may be silicon oxide or silicon carbide.

[0107] When present in an electroactive compound, the silicon-based compound is contained in an amount ranging from 1 to 60% by weight, preferably 5 to 20% by weight, relative to the total weight of the electroactive compound.

[0108] The electrode-forming composition of the present invention comprises at least one solvent (S).

[0109] The solvent in the cathode-forming composition comprises one or more organic solvents, preferably polar solvents, and examples include: N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphamide, dioxane, tetrahydrofuran, tetramethylurea, triethyl phosphate, and trimethyl phosphate. These organic solvents can be used alone or in mixtures of two or more chemical species.

[0110] The electrode-forming composition of the present invention typically contains 0.5% to 10% by weight, preferably 0.7% to 5% by weight, of polymer (A). This composition also contains 80% to 99% by weight of electroactive material. All percentages are weight percentages of the total "solids content". "Solids content" means "all the raw materials of the electrode-forming composition of the present invention, excluding the solvent".

[0111] Generally, in the electrode-forming compositions of the present invention, the solvent is 10% to 90% by weight of the total amount of the composition. In particular, in the case of anode-forming compositions, the solvent is preferably 25% to 75% by weight, more preferably 30% to 60% by weight of the total amount of the composition. In the case of cathode-forming compositions, the solvent is preferably 5% to 60% by weight, more preferably 15% to 40% by weight of the total amount of the composition.

[0112] The electrode-forming composition of the present invention may further contain one or more optional conductive agents to improve the conductivity of electrodes obtained from the composition of the present invention. Conductive agents for batteries are known in the art.

[0113] These examples may include carbonaceous materials such as carbon black, graphite powder, carbon nanotubes (CNTs), graphene, or fibers, or fine powders or fibers of metals such as nickel or aluminum. Any conductive agent is preferably carbon black. Carbon black is available, for example, under the brand names Super P® or Ketjenblack®.

[0114] If present, the conductive agent is different from the carbon-based material mentioned above.

[0115] The amount of any conductive agent is preferably 0 to 30% by weight of the total solids in the electrode-forming composition. In particular, in the case of a cathode-forming composition, the amount of any conductive agent is typically 0% to 10% by weight, more preferably 0% to 5% by weight of the total solids in the composition.

[0116] In the case of anode-forming compositions that do not contain silicon-based electroactive compounds, the amount of any conductive agent is typically 0% to 5% by weight, more preferably 0% to 2% by weight, of the total solid content in the composition. However, in the case of anode-forming compositions that contain silicon-based electroactive compounds, it has been found to be beneficial to introduce a larger amount of any conductive agent, typically 5% to 20% by weight, of the total solid content in the composition.

[0117] The electrode-forming composition of the present invention can be used in an electrode manufacturing process, and the aforementioned process is (i) A step of providing a metal substrate having at least one surface, (ii) A step of providing the electrode-forming composition (C) defined above, (iii) A step of applying the composition (C) provided in step (ii) to at least one surface of the metal substrate provided in step (i), thereby providing an assembly comprising the metal substrate coated with the aforementioned composition (C) on at least one surface, (iv) A step of drying the assembly provided in step (iii) at a temperature in the range of 50°C to 200°C, preferably 80°C to 180°C, for 5 minutes to 48 hours, preferably 30 minutes to 24 hours.

[0118] Metal substrates are generally foils, meshes, or nets made from metals such as copper, aluminum, iron, stainless steel, nickel, titanium, or silver.

[0119] In step (iii) of the process of the present invention, the electrode-forming composition is typically applied to at least one surface of a metal substrate by any suitable procedure such as casting, printing, and roll coating.

[0120] Optionally, step (iii) may be repeated typically one or more times by applying the electrode-forming composition provided in step (ii) to the assembly provided in step (iv).

[0121] The assembly obtained in step (iv) can undergo further compression processes, such as calendering, to achieve the target porosity and density of the electrodes.

[0122] Preferably, the assembly obtained in step (iv) is hot-pressed, and the temperature during the compression step is in the range of 25°C to 130°C, preferably about 90°C.

[0123] The preferred target porosity for the resulting electrode is within the range of 15% to 40%, preferably 25% to 30%. The porosity of the electrode is calculated as the one's complement of the ratio between the measured density and the theoretical density of the electrode, where, - The density to be measured is given by dividing the mass by the volume of the circular portion of the electrode having a diameter equal to 24 mm and a measured thickness. - The theoretical density of the electrode is calculated as the sum of the products of the densities of the electrode components multiplied by their volume ratios in the electrode mixture.

[0124] In further cases, the present invention relates to electrodes obtained by the process of the present invention.

[0125] Therefore, the present invention is - Metal substrate and, - At least one layer, (a) at least one vinylidene fluoride (VDF) copolymer [polymer (A)], (i) Repeating units derived from vinylidene fluoride (VDF), (ii) comprising a repeating unit derived from at least one hydrophilic monomer [monomer (MA)] of formula (I) as defined above, Polymer (A) comprises at least one vinylidene fluoride (VDF) copolymer [polymer (A)] having a contact angle of less than 73°, preferably less than 70°, by the method reported herein, (b) The present invention relates to an electrode comprising at least one layer, which is directly bonded to at least one surface of the aforementioned metal substrate, comprising a composition comprising at least one electroactive material (AM).

[0126] The electrode-forming composition (C) of the present invention is particularly suitable for the manufacture of positive electrodes for electrochemical devices.

[0127] The electrode of the present invention is particularly suitable for use in electrochemical devices including the aforementioned electrode, especially in secondary batteries.

[0128] For the purposes of this invention, the term "secondary battery" is intended to refer to a rechargeable battery. The secondary battery of this invention is preferably an alkaline secondary battery or an alkaline earth secondary battery. The secondary battery of this invention is more preferably a lithium-ion secondary battery. The electrochemical device according to this invention can be prepared by standard methods known to those skilled in the art.

[0129] The main intended applications of the polymer (A) of the present invention and the composition (C) containing the aforementioned polymer (A) are the manufacture of binders and electrodes for secondary batteries.

[0130] Polymer (A) is also particularly suitable for the preparation of films and membranes, especially porous membranes, such as those described in Journal of Membrane Science 178 (2000) 13-23. It is particularly suitable for the preparation of porous membranes for water filtration.

[0131] Polymer (A) in the dispersion is particularly suitable for preparing battery components such as binders for electrodes and layers used as separator coatings, for example, in the applications described in U.S. Patent Application Publication No. 201503906 (ARKEMA Inc.), August 19, 2014.

[0132] The present invention will be described here with reference to the following examples, but the purpose is merely illustrative and not intended to limit the scope of the invention.

[0133] Experiment Section raw materials Polymer (F-1): A VDF-AA (0.9 mol%) polymer obtained as described in International Publication No. 2008 / 129041, having an intrinsic viscosity of 0.292 l / g in DMF at 25°C and a T2f at 162°C.

[0134] Determination of the intrinsic viscosity of polymers The intrinsic viscosity (η) [dl / g] is calculated using an Ubbelhode viscometer, based on the dropping time at 25°C for a solution obtained by dissolving the polymer in N,N-dimethylformamide at a concentration of approximately 0.2 g / dl, using the following formula:

number

[0135] DSC analysis DSC analysis is performed according to ASTM D 3418 standard, and the melting point (T f2 The temperature was determined by a heating rate of 10°C / minute.

[0136] Determination of the contact angle with water: Film preparation and measurement of the contact angle. Preparation of PVDF film: Prepare a polymer solution in 1.10 wt% NMP. Dissolve at room temperature overnight with magnetic stirring. 2. The polymer solution is cast onto the glass substrate using doctor blade technology. The blade height is set so that the final film thickness reaches approximately 40 μm. Dry the film overnight at 90°C with a dry air flow rate of 3.10 l / min. 4. Remove the film from the glass substrate.

[0137] Measurement of the contact angle with water: The contact angle with respect to water was measured at room temperature on the glossy side of the film (the side exposed to the glass substrate during film preparation). The following instrument was used: Contact Angle System OCA20 (DataPhysics Instruments GmbH). Solvent: MilliQ water Measurement settings: Droplet deposition: Automatic mode Dripping amount=2ml-speed=0.5ml / sec θM = average of 10 drops Laboratory temperature: 23℃

[0138] General preparation of electrodes using NMC active material A cathode having a final composition of 96.5% by weight NMC, 1.5% by weight polymer, and 2% by weight conductive additive was prepared as follows.

[0139] The first dispersion was prepared by pre-mixing 34.7 g of a polymer solution in 6% by weight NMP, 33.8 g of NMC, 2.8 g of SC-65, and 8.8 g of NMP in a centrifugal mixer for 10 minutes. Next, the mixture was mixed at 2000 rpm for 50 minutes using a high-speed disc impeller. Subsequently, an additional 7.2 g of NMP was added to the dispersion and further mixed at 1000 rpm for 20 minutes using a butterfly impeller. The resulting composition was cast onto a 15 μm thick Al foil using a doctor blade, and the coated layer was dried in a vacuum oven at 90°C for approximately 50 minutes to obtain the cathode. The thickness of the dried coating layer was approximately 110 μm.

[0140] Method for determining the adhesive peel force between aluminum and electrodes To evaluate the adhesion of the dried coating layer to the aluminum foil, a 180° peel test was performed at a speed of 300 mm / min at 20°C, according to the settings described in standard ASTM D903.

[0141] Preparation of Polymer A-1 Polymer (F-1) was treated with 0.6 Mrad electron beam (beta radiation). The properties of polymer A-1 are shown in Table 1.

[0142] Preparation of Polymer A-2 Polymer (F-1) was treated with 2.4 Mrad electron beam radiation (beta radiation). The properties of polymer A-2 are shown in Table 1.

[0143] Preparation of Polymer A-3 Polymer (F-1) was treated with 0.6 Mrad of gamma radiation. The properties of polymer A-3 are shown in Table 1.

[0144] [Table 1]

[0145] Electrodes were prepared using polymers F-1, A-1, A-2, and A-3 according to the procedure described above, and the results regarding peel adhesion strength are shown in Table 2.

[0146] [Table 2]

[0147] Surprisingly, the results show that electrodes prepared using polymers A-1, A-2, or A-3 as binders exhibit higher adhesion to metal foil, even at much lower intrinsic viscosities, than electrodes obtained with polymer F-1 that have not been treated with ionizing radiation such as beta or gamma rays.

Claims

1. (i) Repeating units derived from vinylidene fluoride (VDF), (ii) For concentrations between 0.1 mol% and 5.0 mol%, the following formula (Ia): (In the formula, -R1, R2, and R3 are equal to or different from each other, and are independently selected from a hydrogen atom and a C1-C3 hydrocarbon group. -R H is a hydrogen atom or a C1-C5 hydrocarbon moiety containing at least one carboxyl group. A vinylidene fluoride (VDF) copolymer [polymer (A)] comprising repeating units derived from at least one hydrophilic monomer [monomer (MA)], Mole percent is relative to the total moles of repeating units of polymer (A). Polymer (A) is a vinylidene fluoride (VDF) copolymer [polymer (A)] having a contact angle of less than 73°, preferably less than 70°, according to the following method. Determining the contact angle with water: Film preparation and measurement of the contact angle Film preparation: Prepare a polymer solution in 1.10 wt% NMP. Dissolve at room temperature overnight with magnetic stirring.

2. The polymer solution is cast onto the glass substrate using doctor blade technology. The blade height is set so that the final film thickness reaches approximately 40 μm.

3. Dry the film overnight at 90°C with a dry air flow rate of 3.10 l / min.

4. Remove the film from the glass substrate. Measuring the contact angle relative to water: The contact angle with water was measured at room temperature on the glossy side of the film (the side exposed to the glass substrate during film preparation). The following instrument was used: Contact Angle System OCA20 (DataPhysics Instruments GmbH). Solvent: Milli-Q water Measurement settings: Droplet deposition: Automatic mode Dripping amount = 2ml Speed ​​= 0.5ml / sec θM = average of 10 drops Laboratory temperature: 23°C

2. The polymer (A) according to claim 1, wherein the at least one monomer (MA) of formula (Ia) is selected from acrylic acid (AA), (meth)acrylic acid, and mixtures thereof.

3. The polymer (A) according to claim 1 or 2, wherein at least 40% of the monomers (MA) are randomly distributed in the polymer (A).

4. Polymer (A) is (a) C ２ ~C ８ Fluoro and / or perfluoroolefins, for example, tetrafluoroethylene (TFE), hexafluoropropylene (HFP), pentafluoropropylene, and hexafluoroisobutylene. (b) C ２ ~C ８ Hydrogenated monofluoroolefins, for example, vinyl fluoride, 1,2-difluoroethylene and trifluoroethylene, (c) formula CH ２ = CH-R ｆ０ (wherein, R ｆ０ is C １ ~ C ６ a perfluoroalkyl group) perfluoroalkyl ethylene, (d) Chloro, and / or bromo, and / or iodo-C ２ ~C ６ Fluoroolefins, for example, chlorotrifluoroethylene (CTFE) The polymer (A) according to any one of claims 1 to 3, which may further comprise repeating units derived from one or more fluorinated comonomers (CFs) different from VDFs selected from the group consisting of the above.

5. The polymer (A) according to claim 4, wherein the polymer (A) is semi-crystalline and contains 0.1 to 15.0 mol%, preferably 0.3 to 5.0 mol%, and more preferably 0.5 to 3.0 mol%, of one or more repeating units derived from fluorinated comonomers (CF).

6. The process includes irradiating polymer (F) with ionizing radiation at a dose of less than 70 kGy, and polymer (F) (i) Repeating units derived from vinylidene fluoride (VDF), (ii) For concentrations between 0.1 mol% and 5.0 mol%, the following formula (Ia): (In the formula, -R1, R2, and R3 are equal to or different from each other, and are independently selected from a hydrogen atom and a C1-C3 hydrocarbon group. -R H is a hydrogen atom or a C1-C5 hydrocarbon moiety containing at least one carboxyl group. A repeating unit derived from at least one hydrophilic monomer [monomer (MA)], comprising A method for preparing polymer (A) according to any one of claims 1 to 5, wherein the mole percent is relative to the total moles of repeating units of polymer (F).

7. The method according to claim 6, wherein the step of irradiating the polymer (F) is carried out by ionizing radiation selected from beta rays, gamma rays, and electron beams.

8. The method according to claim 6 or 7, wherein the irradiation is carried out in the presence of oxygen.

9. The method according to any one of claims 6 to 8, wherein the irradiation is performed at a dose of 0.1 kGy to 70 kGy, preferably 1 kGy to 40 kGy, and more preferably 1 kGy to 20 kGy.

10. An electrode-forming composition [composition (C)], a) At least one electrode active material (AM), b) at least one binder (B), wherein the binder (B) comprises at least one polymer (A) according to any one of claims 1 to 5, c) An electrode-forming composition [composition (C)] comprising at least one solvent (S).

11. - Metal substrate and, - At least one layer, (a) at least one vinylidene fluoride (VDF) copolymer [polymer (A)] (i) Repeating units derived from vinylidene fluoride (VDF), (ii) For concentrations between 0.1 mol% and 5.0 mol%, the following formula (Ia): (In the formula, -R1, R2, and R3 are equal to or different from each other, and are independently selected from a hydrogen atom and a C1-C3 hydrocarbon group. -R H is a hydrogen atom or a C1-C5 hydrocarbon moiety containing at least one carboxyl group. A repeating unit derived from at least one hydrophilic monomer [monomer (MA)], comprising Mole percent is relative to the total moles of repeating units of polymer (A). Polymer (A) comprises at least one vinylidene fluoride (VDF) copolymer [polymer (A)] having a contact angle of less than 73°, preferably less than 70°, by the following method, (b) at least one electroactive material (AM), A composition comprising at least one layer directly bonded to at least one surface of the metal substrate, An electrode containing an electrode. Determining the contact angle with water: Film preparation and measurement of the contact angle Film preparation: Prepare a polymer solution in 1.10 wt% NMP. Dissolve at room temperature overnight with magnetic stirring.

2. The polymer solution is cast onto the glass substrate using doctor blade technology. The blade height is set so that the final film thickness reaches approximately 40 μm.

3. Dry the film overnight at 90°C with a dry air flow rate of 3.10 l / min.

4. Remove the film from the glass substrate. Measuring the contact angle relative to water: The contact angle with water was measured at room temperature on the glossy side of the film (the side exposed to the glass substrate during film preparation). The following instrument was used: Contact Angle System OCA20 (DataPhysics Instruments GmbH). Solvent: Milli-Q water Measurement settings: Droplet deposition: Automatic mode Dripping amount = 2ml Speed ​​= 0.5ml / sec θM = average of 10 drops Laboratory temperature: 23°C

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