Method for producing metal fluoride

Abstract

To provide a production method capable of efficiently producing a metal fluoride by mechanochemical treatment.SOLUTION: A method for producing a metal fluoride, comprising a step of mechanochemically treating a fluorine-containing compound and at least one metal oxide selected from the group consisting of alkali metal oxides and alkaline earth metal oxides under at least one condition selected from the group consisting of the following (a) to (c) to obtain a metal fluoride: (a) The mechanochemical treatment is performed in the presence of a grinding aid having an old Mohs hardness of 5 to 8.5. (b) The size of the fluorine-containing compound is 0.002 to 0.15 times the size of the grinding medium used in the mechanochemical treatment on a volume basis. (c) The mechanochemical treatment is performed using two or more types of grinding media having different sizes.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing metal fluorides. [Background technology]

[0002] A method for defluorinating polyethylene fluoride by mechanochemical treatment using a planetary ball mill in the presence of calcium oxide is known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-70401 Summary of the Invention [Problem to be solved by the invention]

[0004] However, there is room for further improvement in the efficiency of conventional methods.

[0005] An object of the present disclosure is to provide a production method that can efficiently produce metal fluorides by mechanochemical treatment. [Means for solving the problem]

[0006] The present disclosure (1) is a method for producing a metal fluoride, comprising a step of mechanochemically treating a fluorine-containing compound and at least one metal oxide selected from the group consisting of alkali metal oxides and alkaline earth metal oxides under at least one condition selected from the group consisting of the following (a) to (c), thereby obtaining a metal fluoride: (a) The mechanochemical treatment is carried out in the presence of a grinding aid having a Mohs hardness of 5 to 8.5. (b) The size of the fluorine-containing compound is 0.002 to 0.15 times the size of the grinding media used in the mechanochemical treatment on a volume basis. (c) The mechanochemical treatment is carried out using two or more grinding media of different sizes.

[0007] The present disclosure (2) is the production method according to the present disclosure (1), in which mechanochemical treatment is carried out under at least two conditions selected from the group consisting of the above (a) to (c).

[0008] The present disclosure (3) is the production method according to the present disclosure (1) or (2), wherein the grinding aid in (a) is titanium oxide.

[0009] The present disclosure (4) is a manufacturing method for any combination with any of the present disclosures (1) to (3), in which the grinding aid in (a) is particles having an average particle size of 5 to 10 μm.

[0010] The present disclosure (5) is a production method for any combination with any of the present disclosures (1) to (4), in which the amount of the grinding aid used in (a) is 0.1 to 1 equivalent per equivalent of the fluorine-containing compound.

[0011] The present disclosure (6) is a production method for any combination with any of the present disclosures (1) to (5), in which the size of the fluorine-containing compound in (b) is 0.002 to 0.08 times the volume of the grinding medium used in the mechanochemical treatment.

[0012] The present disclosure (7) is a method for producing any combination of any of the present disclosures (1) to (6), wherein the grinding media in (c) include a first grinding media and a second grinding media that is smaller than the first grinding media and has a length of more than 1 mm in at least one dimension.

[0013] The present disclosure (8) is a method for producing any combination of any of the present disclosures (1) to (7), in which the grinding media in (c) include a first grinding media having a three-dimensional length of 10 to 20 mm and a second grinding media having a three-dimensional length of more than 1 mm and less than 5 mm.

[0014] The present disclosure (9) is a method for producing an arbitrary combination with any of the present disclosures (1) to (8), in which the metal oxide is calcium oxide.

[0015] The present disclosure (10) is a production method for any combination of the present disclosures (1) to (9), in which the amount of the metal oxide used is 1 to 3 equivalents per equivalent of the fluorine-containing compound.

[0016] The present disclosure (11) is a method for producing an arbitrary combination of the present disclosures (1) to (10), in which the fluorine-containing compound is a low-molecular-weight fluorine-containing compound having a molecular weight of 2,000 or less.

[0017] The present disclosure (12) is a method for producing an arbitrary combination of the present disclosures (1) to (10) in which the fluorine-containing compound is a fluorine-containing polymer.

[0018] The present disclosure (13) is a method for producing any combination of the present disclosures (1) to (10), in which the fluorine-containing compound is at least one selected from the group consisting of polytetrafluoroethylene, polydifluoroethylene, ethylene / tetrafluoroethylene copolymer, and fluorine-containing telomer. [Effects of the Invention]

[0019] According to the present disclosure, it is possible to provide a manufacturing method that can efficiently manufacture metal fluorides by mechanochemical treatment. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present disclosure will be specifically described below.

[0021] The present disclosure relates to a method for producing a metal fluoride, comprising a step of obtaining a metal fluoride by mechanochemically treating a fluorine-containing compound and at least one metal oxide selected from the group consisting of alkali metal oxides and alkaline earth metal oxides under at least one condition selected from the group consisting of the following (a) to (c): (a) The mechanochemical treatment is carried out in the presence of a grinding aid having a Mohs hardness of 5 to 8.5. (b) The size of the fluorine-containing compound is 0.002 to 0.15 times the size of the grinding media used in the mechanochemical treatment on a volume basis. (c) The mechanochemical treatment is carried out using two or more grinding media of different sizes.

[0022] In the production method of the present disclosure, a mechanochemical treatment is carried out under specific conditions, and therefore, a metal fluoride can be efficiently produced by the mechanochemical treatment.

[0023] The fluorine-containing compound used in the production method of the present disclosure may be any compound having a fluorine atom, but does not include inorganic fluorine compounds other than calcium fluoride. The fluorine-containing compound may be a compound having a fluorine atom bonded to a carbon atom, and is preferably an organic compound having a fluorine atom bonded to a carbon atom. The fluorine-containing compound is preferably a solid at 25° C., since this facilitates mechanochemical treatment.

[0024] The fluorine-containing compound is preferably a fluorine-containing polymer compound, more preferably a fluorine-containing polymer. The molecular weight of the fluorine-containing polymer compound is usually more than 2000, and can be measured by a known method depending on the type of compound.

[0025] The fluoropolymer preferably contains polymerization units based on at least one monomer selected from the group consisting of tetrafluoroethylene [TFE], difluoroethylene, chlorotrifluoroethylene [CTFE], hexafluoropropylene [HFP], trifluoroethylene and monofluoroethylene, more preferably contains polymerization units based on at least one monomer selected from the group consisting of TFE, difluoroethylene and CTFE, further preferably contains polymerization units based on at least one monomer selected from the group consisting of TFE and VdF, and still more preferably contains polymerization units based on TFE. Examples of the difluoroethylene include vinylidene fluoride [VdF] and 1,2-difluoroethylene.

[0026] The fluorine-containing polymer may be a fluororesin or a fluororubber.

[0027] Examples of the fluororesin include polytetrafluoroethylene [PTFE], tetrafluoroethylene [TFE] / perfluoro(alkyl vinyl ether) [PAVE] copolymer [PFA], TFE / hexafluoropropylene [HFP] copolymer [FEP], ethylene [Et] / TFE copolymer [ETFE], Et / TFE / HFP copolymer [EFEP], polychlorotrifluoroethylene [PCTFE], chlorotrifluoroethylene [CTFE] / TFE copolymer, CTFE / TFE / PAVE copolymer, Et / CTFE copolymer, polyfluoro Examples of the perfluoroalkyl aryl ether include vinyl fluoride [PVF], polydifluoroethylene (such as polyvinylidene fluoride [PVdF] and poly(1,2-difluoroethylene)), vinylidene fluoride [VdF] / TFE copolymer, VdF / HFP copolymer, VdF / TFE / HFP copolymer, VdF / HFP / (meth)acrylic acid copolymer, VdF / CTFE copolymer, VdF / pentafluoropropylene copolymer, VdF / PAVE / TFE copolymer, and TFE / perfluoroalkyl aryl ether copolymer, which can be used alone or in combination. The perfluoroalkyl aryl ether is CF2=CFCF2-O-Rf 1 (Rf 1 is a monomer represented by a perfluoroalkyl group having 1 to 5 carbon atoms.

[0028] The fluororesin may be a fluororesin having a monomer unit having a C-H bond, or may be a perhalopolymer, preferably a perfluoropolymer, in which halogen atoms are bonded to all of the carbon atoms constituting the main chain of the polymer.

[0029] Examples of the fluororubber include vinylidene fluoride [VdF]-based fluororubbers, tetrafluoroethylene [TFE] / propylene [Pr]-based fluororubbers, TFE / Pr / VdF-based fluororubbers, ethylene [Et] / hexafluoropropylene [HFP]-based fluororubbers, Et / HFP / VdF-based fluororubbers, Et / HFP / TFE-based fluororubbers, fluorosilicone-based fluororubbers, and fluorophosphazene-based fluororubbers, and these may be used alone or in combination.

[0030] Examples of the VdF-based fluororubbers include VdF / HFP copolymer, VdF / TFE / HFP copolymer, VdF / chlorotrifluoroethylene [CTFE] copolymer, VdF / CTFE / TFE copolymer, VdF / perfluoro(alkyl vinyl ether) [PAVE] copolymer, VdF / TFE / PAVE copolymer, VdF / HFP / PAVE copolymer, VdF / HFP / TFE / PAVE copolymer, VdF / TFE / Pr copolymer, VdF / Et / HFP copolymer, and VdF / copolymer of a fluorine-containing monomer represented by the following formula (1): Formula (1): CH2=CFRf 2 (1) (In the formula, Rf 2 is a linear or branched fluoroalkyl group having 1 to 12 carbon atoms)

[0031] The fluorine-containing polymer is preferably a fluororesin, more preferably at least one selected from the group consisting of PTFE, polydifluoroethylene, and ETFE, even more preferably at least one selected from the group consisting of PTFE and polydifluoroethylene, even more preferably at least one selected from the group consisting of PTFE and PVdF, and particularly preferably PTFE. As the fluorine-containing polymer, from the viewpoint of reactivity, a fluororesin having a monomer unit having a C-H bond is also preferred, at least one selected from the group consisting of polydifluoroethylene and ETFE is more preferred, at least one selected from the group consisting of PVdF and ETFE is even more preferred, and PVdF is even more preferred.

[0032] The fluorine-containing compound does not have to be a polymer as long as it is solid at 25°C, and may be a fluorine-containing low-molecular-weight compound. The fluorine-containing low molecular weight compound may have a molecular weight of not more than 2000. The molecular weight of the fluorine-containing low molecular weight compound can be determined by calculation from the chemical formula.

[0033] The fluorine-containing low molecular weight compound is preferably a fluorine-based telomer. Examples of the fluorine-based telomer include those represented by the following formula: C2F5(CF2CF2) n -X (wherein X is a halogen atom, and n is an integer of 5 or more) is exemplified. In the above formula, X may be a halogen atom other than a fluorine atom, and is preferably a chlorine atom, a bromine atom, or an iodine atom, more preferably a bromine atom or an iodine atom, and even more preferably an iodine atom. In the above formula, n is an integer of 5 or more and preferably an integer of 10 or less.

[0034] The fluorine-containing low molecular weight compound is represented by the following general formula (I): Y-(CF2) x1 -(CH2) y1 -A (I) (In the formula, Y represents H or F, x1 represents an integer of 4 or more, y1 represents an integer of 0 to 3, and A represents -SO3M I or -COOM I indicates M I represents H, NH4, Li, Na, Mg, Al, K or Ca), and a compound (I) represented by the following general formula (II): F-(CF2) x2 O(CFXCF2O) y2 -CFX-A (II) (In the formula, x2 represents an integer of 1 or more, y2 represents an integer of 0 to 10, X represents F or CF3, A represents -SO3M II or -COOM II indicates M IIrepresents H, NH4, Li, Na, Mg, Al, K or Ca.

[0035] The compound (I) may be a fluorocarboxylic acid or a salt thereof, such as a perfluorocarboxylic acid or a salt thereof, for example, an ammonium salt or a sodium salt. Compound (I) also includes fluorosulfonic acid and its salts, such as perfluorosulfonic acid and its salts, including ammonium salts and sodium salts. Examples of the compound (II) include perfluoroethercarboxylic acids and salts thereof, such as 2,3,3,3-tetrafluoro-2-[1,1,2,3,3,3-hexafluoro-2-(trifluoromethoxy)propoxy]-propanoic acid.

[0036] The fluorine-containing low molecular weight compound may be adsorbed onto an adsorbent. In this embodiment, the solid in which the fluorine-containing low molecular weight compound is adsorbed onto the adsorbent may be subjected to mechanochemical treatment. The adsorbent is not limited as long as it is a solid capable of adsorbing the fluorine-containing low-molecular-weight compound, but is preferably at least one selected from the group consisting of activated carbon, silica gel, clay, metal-organic framework (MOF), and zeolite.

[0037] The fluorine-containing compound may be calcium fluoride, in which case a metal fluoride different from calcium fluoride is obtained by the mechanochemical treatment.

[0038] In the production method of the present disclosure, a composition containing the fluorine-containing compound and other components may be subjected to mechanochemical treatment. The other components can be used within a range that does not impair the effects of the manufacturing method of the present disclosure. Examples of the other components include general fillers, polymers, and the above-mentioned adsorbents.

[0039] Examples of the common filler include inorganic fillers such as glass fiber, glass beads, carbon fiber, spherical carbon, carbon black, graphite, silica, alumina, mica, silicon carbide, boron nitride, aluminum nitride, titanium oxide, bismuth oxide, cobalt oxide, magnesium oxide, molybdenum disulfide, bronze, gold, silver, copper, nickel, aluminum fluoride, carbon fluoride, and carbon black.

[0040] Examples of the common polymers include polyolefin resins such as polyethylene and polypropylene; polyamide (PA) resins such as nylon 6, nylon 11, nylon 12, nylon 46, nylon 66, nylon 610, nylon 612, and nylon MXD6; polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyarylate, aromatic polyesters (including liquid crystal polyesters), and polycarbonate (PC); polyacetal (POM) resins; polyether resins such as polyphenylene oxide (PPO), modified polyphenylene ether, and polyether ether ketone (PEEK); polyamide-imide (PAI) resins such as polyaminobismaleimide; polysulfone resins such as polysulfone (PSF) and polyethersulfone (PES); vinyl polymers such as ABS resin and poly-4-methylpentene-1 (TPX resin), as well as polyphenylene sulfide (PPS), polyketone sulfide, polyetherimide, polyimide (PI), and epoxy resins. The nylon MXD6 is a crystalline polycondensate obtained from metaxylenediamine (MXD) and adipic acid. The general polymers may be non-fluorinated polymers.

[0041] The content of the above other components may be 50% by mass or less, preferably 30% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, relative to the composition, and may be 0% by mass or more, 0.01% by mass or more, 0.1% by mass or more, or 1% by mass or more.

[0042] The fluorine-containing compound (or the composition when the other components are present; the same applies hereinafter) may be in the form of a powder, a molded product, or waste material from the manufacturing process or after use of a product. It may also be one that has been heated once to above its melting point. If necessary, the fluorine-containing compound may be pulverized before use.

[0043] The shape of the fluorine-containing compound is not particularly limited and may be in the form of a powder, sheet, block, pellet, flake, or the like. From the viewpoint of reaction efficiency, the fluorine-containing compound is preferably in the form of a sheet, block, pellet, or flake, more preferably in the form of a sheet, block, or pellet, even more preferably in the form of a sheet or block, and even more preferably in the form of a block.

[0044] Although the size of the fluorine-containing compound is not particularly limited, it has been found that a certain degree of size increase in reaction efficiency. This finding is unexpected because, in general, the smaller the size, the higher the reaction efficiency tends to be. Of the three dimensions that represent the size of the fluorine-containing compound, the length of at least one dimension may be 0.001 mm or more, preferably 0.010 mm or more, more preferably 0.100 mm or more, even more preferably 1.0 mm or more, even more preferably 2.0 mm or more, and particularly preferably 3.0 mm or more, and is preferably 20 mm or less, more preferably 10 mm or less, even more preferably 5.0 mm or less, and even more preferably 4.0 mm or less. Of the three dimensions that represent the size of the fluorine-containing compound, the length of the shortest dimension is preferably within the above range. Furthermore, it is more preferable that the length of at least two of the three dimensions that represent the size of the fluorine-containing compound is within the above range, and it is even more preferable that the length of the third dimension is within the above range. The length of the dimension indicating the size of the fluorine-containing compound is measured with a micrometer or vernier calipers.

[0045] When the fluorine-containing compound is in powder form, the average particle size can also be used as an index of size. When the fluorine-containing compound is in powder form, the average particle size may be 10 μm or more, preferably 30 μm or more, more preferably 100 μm or more, and even more preferably 200 μm or more, and is preferably 4000 μm or less, more preferably 2000 μm or less, and even more preferably 1000 μm or less. The average particle size of the fluorine-containing compound is measured in a dry state at a vacuum pressure of 20 mH2O using a laser diffraction / scattering particle size distribution analyzer manufactured by Nikkiso Co., Ltd., and is defined as being equal to the particle size corresponding to 50% of the integrated particle size distribution (volume basis).

[0046] The metal oxide used in the production method of the present disclosure is at least one selected from the group consisting of alkali metal oxides and alkaline earth metal oxides. The alkali metal oxides include lithium oxide, sodium oxide, potassium oxide, etc., and one or more of these can be used. The alkaline earth metal oxides include calcium oxide, strontium oxide, barium oxide, etc., and one or more of these can be used. As the metal oxide, from the viewpoint of reactivity, alkaline earth metal oxides are preferred, at least one selected from the group consisting of calcium oxide and strontium oxide is more preferred, and calcium oxide (CaO) is even more preferred.

[0047] The amount of the metal oxide used in the mechanochemical treatment is preferably 0.01 equivalents or more, more preferably 0.05 equivalents or more, even more preferably 0.1 equivalents or more, even more preferably 0.5 equivalents or more, and particularly preferably 1 equivalent or more, relative to 1 equivalent (molar equivalent) of the fluorine-containing compound, and is preferably 10 equivalents or less, more preferably 8 equivalents or less, even more preferably 5 equivalents or less, and even more preferably 3 equivalents or less. When the fluorine-containing compound is a fluorine-containing polymer, the equivalent weight is calculated based on the monomers constituting the fluorine-containing polymer.

[0048] The mechanochemical treatment is a treatment method in which mechanical energy is applied to a reactant (preferably a solid reactant) by methods such as shearing, compression, stretching, grinding, friction, kneading, mixing, dispersing, crushing, and shaking, thereby activating the reactant and imparting structural change, phase transition, reactivity, adsorption, catalytic activity, and the like. The mechanochemical treatment method is not particularly limited, and examples thereof include a compressive shear treatment method, an impact treatment method, and a mixed shear friction method, with the impact treatment method being preferred.

[0049] The energy in the mechanochemical treatment is mechanically applied energy, which is a mechanical phenomenon in which the position of an object is changed or deformed by the action of force, and includes potential energy, kinetic energy, etc. Among mechanical energies, energy that performs work is called collision energy, shear energy, vibration energy, etc. From the viewpoint of being able to apply high energy to the object to be treated, collision energy applied by a planetary mill, vibration mill, etc. is preferred, but any energy applied to the reactants will do, and is not limited to collision energy.

[0050] The mechanochemical treatment is usually carried out using a grinding medium. The grinding medium is preferably not connected to the reaction vessel. The grinding medium may be used in combination with a member connected to the reaction vessel, such as a stirring member.

[0051] The shape of the grinding medium is not particularly limited, and may be spherical, ellipsoidal, cylindrical, cylindrical, bale-shaped, tea canister-shaped, etc., but from the viewpoint of reaction efficiency, it is preferably spherical, ellipsoidal, or cylindrical, more preferably spherical or ellipsoidal, and even more preferably spherical.

[0052] From the viewpoint of reaction efficiency, the length of at least one dimension of the three dimensions that represent the size of the grinding medium may be 5 mm or more, preferably 10 mm or more, and is preferably 100 mm or less, more preferably 70 mm or less, even more preferably 50 mm or less, even more preferably 40 mm or less, and may be 30 mm or less, or may be 20 mm or less. Of the three dimensions that represent the size of the grinding medium, it is preferable that the length of the shortest dimension be within the above range. Furthermore, it is more preferable that at least two of the three dimensions that represent the size of the grinding media are within the above range, and it is even more preferable that the three-dimensional length is within the above range. When the grinding media are spherical, it is preferable that the diameter is within the above range. By using grinding media having the above-mentioned sizes, the energy in the mechanochemical treatment can be further increased, and the reaction efficiency can be further improved.

[0053] The material of the grinding media is not particularly limited, and examples thereof include steels such as carbon steel, stainless steel, and chromium steel, zirconia, tungsten carbide, agate, silicon nitride, alumina, and polyamide, and one or more of these can be used. Among these, steels and zirconia are preferred, steels are more preferred, and carbon steel and stainless steel are even more preferred.

[0054] From the viewpoint of reaction efficiency, the amount of the grinding medium used is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, relative to the fluorine-containing compound, and is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 83% by mass or less.

[0055] The material of the reaction vessel used in the mechanochemical treatment is not particularly limited, and examples include steels such as carbon steel, stainless steel, and chromium steel, zirconia, tungsten carbide, agate, silicon nitride, alumina, and polyamide, and one or more of these can be used. Among these, steels and zirconia are preferred, steels are more preferred, and carbon steel and stainless steel are even more preferred. The material of the reaction vessel may be the same as or different from that of the grinding medium.

[0056] From the viewpoint of reaction efficiency, the filling rate of the grinding media relative to the internal volume of the reaction vessel is preferably 0.05% by volume or more, more preferably 0.1% by volume or more, more preferably 0.3% by volume or more, and even more preferably 1.0% by volume or more, and is preferably 20% by volume or less, more preferably 10% by volume or less, and even more preferably 6.0% by volume or less.

[0057] The mechanochemical treatment is carried out under at least one condition selected from the group consisting of (a) to (c) described above, but is preferably carried out under at least two conditions selected from the group consisting of (a) to (c), and more preferably under all of the conditions (a) to (c). The mechanochemical treatment is preferably carried out under at least the conditions (b), more preferably under at least the conditions (a) and (b), or under at least the conditions (b) and (c), and even more preferably under at least the conditions (a) and (b). By carrying out the mechanochemical treatment under these specific conditions, the reaction efficiency can be further improved.

[0058] Under condition (a), the mechanochemical treatment is carried out in the presence of a grinding aid with a Mohs hardness of 5 to 8.5. By using a grinding aid with a Mohs hardness within the above range, high energy can be applied to the material to be treated, improving reaction efficiency. Furthermore, because the grinding aid does not have too high a hardness, wear on the grinding media and reaction vessel can also be suppressed. The Mohs hardness is preferably 5.5 or more, and is preferably 8 or less, and more preferably 7.5 or less. The above-mentioned old Mohs hardness is measured by a Mohs hardness scale.

[0059] Examples of the grinding aid include titanium oxide (TiO2), quartz (SiO2), zirconia (ZrO2), magnesium oxide (MgO), etc., and one or more of these can be used. Among these, at least one selected from the group consisting of titanium oxide and quartz is preferred, and titanium oxide is more preferred. Note that grinding aids of the same type (name) may have different old Mohs hardnesses due to differences in crystal structure, etc. The grinding aids exemplified above are grinding aids whose old Mohs hardnesses are within the above-mentioned ranges and whose types are as described above.

[0060] The grinding aid is preferably in the form of particles, and the average particle size of the grinding aid is preferably 1 μm or more, more preferably 5 μm or more, and is preferably 5 mm or less, more preferably 1 mm or less, even more preferably 500 μm or less, even more preferably 100 μm or less, even more preferably 50 μm or less, even more preferably 30 μm or less, and particularly preferably 10 μm or less. The average particle size of the grinding aid is measured using a laser diffraction / scattering particle size distribution measuring device manufactured by Nikkiso Co., Ltd.

[0061] The amount of the grinding aid used is preferably 0.01 equivalents or more, more preferably 0.05 equivalents or more, even more preferably 0.1 equivalents or more, even more preferably 0.3 equivalents or more, and particularly preferably 0.5 equivalents or more, relative to 1 equivalent (molar equivalent) of the fluorine-containing compound, and is preferably 5 equivalents or less, more preferably 3 equivalents or less, even more preferably 1 equivalent or less, and even more preferably 0.8 equivalents or less.

[0062] Under condition (b), the size of the fluorine-containing compound is set to 0.002 to 0.15 times the volume of the grinding medium used in the mechanochemical treatment, and the mechanochemical treatment is carried out. By using a fluorine-containing compound that is relatively large in size, the reaction efficiency can be improved. The size of the fluorine-containing compound is preferably 0.005 times or more, more preferably 0.010 times or more, more preferably 0.040 times or more, more preferably 0.050 times or more, and particularly preferably 0.060 times or more, and is more preferably 0.12 times or less, more preferably 0.10 times or less, and even more preferably 0.08 times or less, of the grinding medium.

[0063] Under condition (c), the mechanochemical treatment is carried out using two or more grinding media of different sizes, which allows high energy to be applied to the material to be treated, improving the reaction efficiency. The two or more grinding media having different sizes preferably have different volumes. The two or more grinding media having different sizes preferably have different lengths in at least one dimension of the three dimensions representing the size of the grinding media, more preferably have different lengths in at least two dimensions, and even more preferably have different lengths in three dimensions.

[0064] As the two or more types of grinding media having different sizes, it is preferable to use at least a first grinding medium and a second grinding medium that is smaller than the first grinding medium. The second grinding medium preferably has a smaller volume than the first grinding medium. Of the three dimensions that represent the size of the grinding medium, the second grinding medium preferably has a shorter length in at least one dimension than the first grinding medium, more preferably has a shorter length in at least two dimensions than the first grinding medium, and even more preferably has a shorter length in three dimensions than the first grinding medium.

[0065] The first grinding medium may be the same as the grinding medium normally used in the mechanochemical treatment. The amount of the first grinding medium used may be within the same range as the amount of the grinding medium normally used in the mechanochemical treatment.

[0066] The size of the second grinding media is preferably at least 0.01 times, more preferably at least 0.05 times, and even more preferably at least 0.1 times, of the first grinding media on a volume basis, and is preferably less than 1.0 times, more preferably at most 0.5 times, and even more preferably at most 0.3 times.

[0067] The second grinding medium has a length in at least one dimension of the three dimensions that represent the size of the grinding medium, preferably greater than 1 mm, more preferably 1.5 mm or greater, even more preferably 2 mm or greater, even more preferably 2.5 mm or greater, and preferably less than 30 mm, more preferably less than 25 mm, even more preferably less than 20 mm, even more preferably less than 15 mm, particularly preferably less than 10 mm, and may even be less than 5 mm. Of the three dimensions that represent the size of the second grinding medium, the length of the shortest dimension is preferably within the above range. Furthermore, it is more preferable that at least two of the three dimensions that represent the size of the grinding media are within the above range, and it is even more preferable that the three-dimensional length is within the above range. If the second grinding media is spherical, it is preferred that the diameter is within the above range. By using the second grinding media having the above-mentioned size, the reaction efficiency can be further improved. In addition, since the second grinding media have a certain size, they can be easily separated from the product after the reaction using a sieve or the like.

[0068] The shape and material of the second grinding media may be the same as those described above for the grinding media (first grinding media) normally used in the mechanochemical treatment, and the preferred forms are also the same. The first grinding medium and the second grinding medium may be the same in shape and material, or may be different.

[0069] From the viewpoint of reaction efficiency, the amount of the second grinding medium used is preferably 20% by volume or more, more preferably 30% by volume or more, and even more preferably 40% by volume or more, relative to the internal volume of the reaction vessel, and is preferably 70% by volume or less, more preferably 60% by volume or less, and even more preferably 50% by volume or less.

[0070] The mechanochemical treatment may be carried out by applying energy of 1.5 J / s / g or more. From the viewpoint of reaction efficiency, the energy is preferably 1.8 J / s / g or more, more preferably 2.0 J / s / g or more, and even more preferably 2.5 J / s / g or more, and is preferably 30.0 J / s / g or less, more preferably 15.0 J / s / g or less, even more preferably 10.0 J / s / g or less, and even more preferably 5.0 J / s / g or less. By applying energy within the above range, the reaction efficiency can be further increased, and it becomes easier to carry out the mechanochemical treatment using an apparatus that is easy to industrialize. The energy to be applied is not particularly limited, but collision energy is particularly preferred.

[0071] In the case of collision energy, for example, the energy is the collision energy per unit mass, and is calculated using simulation software according to the following formula, based on the method described in AIChE Journal, Vol. 52, No. 10, 2006, pp. 3421-3426. The simulation software is not limited as long as it can perform calculations based on the above method, and for example, KIK DEM manufactured by Tohoku University or UX-DEM manufactured by JX Metals can be used.

number

[0072] In the above mechanochemical treatment, the ratio of the material to the internal volume of the reaction vessel is preferably 0.1 g / L or more, more preferably 1.0 g / L or more, and even more preferably 10.0 g / L or more, from the viewpoint of reaction efficiency, and is preferably 150.0 g / L or less, more preferably 100.0 g / L or less, even more preferably 50.0 g / L or less, even more preferably 30.0 g / L or less, and particularly preferably 25.0 g / L or less. The proportion of the material to be treated is the total proportion of all raw materials to be mechanochemically treated, such as the fluorine-containing compound, the metal oxide, the grinding aid, etc.

[0073] The apparatus for carrying out the mechanochemical treatment is not particularly limited as long as it is an apparatus capable of adding energy by the above-mentioned method, and known pulverizers and mixers can be used. For example, pulverizers such as ball mills, rod mills, jet mills, rotary mills, vibration mills, SAG mills, and planetary mills; grinders such as rotary stone mills and crushers; (horizontal axis rotation) container rotation type mixers such as horizontal cylindrical, V-type, double cone, square cube, S-type, and continuous V-type; (baffle blade equipped) container rotation type mixers such as horizontal cylindrical, V-type, double cone, and ball mills; (rotation vibration) container rotation type mixers such as rocking and cross rotary types; ribbon type, paddle type, single-shaft rotor type, and bag mill type. (horizontal axis rotation) fixed vessel type mixers; (vertical axis rotation) fixed vessel type mixers such as ribbon type, screw type, planetary type, turbine type, high speed fluid type, rotating disk type and Mahler type; (vibration) fixed vessel type mixers such as vibration mill type and sieve; (fluidization) fluid motion type mixers such as heterogeneous fluidized bed, swirling fluidized bed, type with riser and Jot pump type; (gravity) fluid motion type mixers such as gravity type and static mixer; and kneaders such as twin-screw kneaders, single-screw kneaders, mixers, roll mills, etc.

[0074] As the apparatus for carrying out the mechanochemical treatment, a rotary mill, a vibration mill, or a planetary mill is preferred, and in terms of ease of industrialization, a rotary mill or a vibration mill is more preferred, and a vibration mill is even more preferred.

[0075] The mechanochemical treatment can be carried out using a planetary mill, but is also preferably carried out without a planetary mill. While a planetary mill is a device capable of applying high energy, it also generates a large amount of wear debris from the device (see, for example, J.Soc.Powder Technol.,Japan,44,186-190(2007)[https: / / www.jstage.jst.go.jp / article / sptj1978 / 44 / 3 / 44_3_186 / _pdf / -char / ja]). The inclusion of wear debris can interfere with the use of the reaction product. The production method of the present disclosure can react a fluorine-containing compound under conditions that are less likely to generate wear debris from the device. Furthermore, methods using general-purpose devices such as ball mills and vibration mills, rather than planetary mills, also have the advantage of being easily industrialized.

[0076] The temperature of the mechanochemical treatment is preferably 5°C or higher, more preferably 10°C or higher, even more preferably 15°C or higher, even more preferably 20°C or higher, and is preferably 300°C or lower, more preferably 250°C or lower, even more preferably 200°C or lower, even more preferably 160°C or lower.

[0077] In particular, when the fluorine-containing compound is a fluorine-containing polymer compound that does not contain hydrogen, the reaction is accelerated by heating, so it is preferable to carry out the reaction at room temperature (25° C.) or above.

[0078] The time for the mechanochemical treatment can be determined depending on the equipment used, the amount of material to be treated, etc., but may be, for example, 0.1 hours or more, 0.5 hours or more, 1 hour or more, or 100 hours or less, 50 hours or less, 30 hours or less, or 10 hours or less.

[0079] The mechanochemical treatment may be carried out in any atmosphere, for example, in air, in an inert gas, in vacuum, etc. From the viewpoint of low cost, it is preferably carried out in air.

[0080] The mechanochemical treatment is preferably carried out in a dry manner, which means that the amount of liquid in the reaction system is 5% by mass or less, preferably 1% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0.01% by mass or less.

[0081] The mechanochemical treatment can cause the fluorine-containing compound to react, which may be a reaction that produces fluoride ions, and is preferably a defluorination reaction.

[0082] The mechanochemical treatment produces a metal fluoride, which may be at least one selected from the group consisting of alkali metal fluorides and alkaline earth metal fluorides, preferably an alkaline earth metal fluoride, and more preferably calcium fluoride (CaF).

[0083] The production method of the present disclosure also preferably includes a step of purifying the crude product obtained by the mechanochemical treatment to recover the metal fluoride. The purification method is not particularly limited, and any known method can be used.

[0084] The production method of the present disclosure can be used not only for producing metal fluorides but also for decomposing (defluorinating) fluorine-containing compounds. The production method of the present disclosure can also obtain a metal fluoride from an organic fluorine compound by using the organic fluorine compound as the fluorine-containing compound. The reaction rate of the organic fluorine compound is preferably 30% or more, more preferably 50% or more, even more preferably 90% or more, most preferably 99% or more, and may be 100% or less. The reaction rate of the organic fluorine compound can be calculated by the following formula using the amount of organic fluorine (by mass) in the mechanochemically treated product, which will be described later. Reaction rate of organic fluorine compound = ((amount of fluorine in organic fluorine compound before mechanochemical treatment - amount of organic fluorine in mechanochemically treated product) / amount of fluorine in organic fluorine compound before mechanochemical treatment) x 100 The amount of fluorine in the organic fluorine compound before the mechanochemical treatment can be measured by a known method such as combustion ion chromatography or IR.

[0085] It is preferable that the produced mechanochemically treated product (product containing metal fluoride) contains substantially no organic fluorine. The mechanochemically treated product contains substantially no organic fluorine, which means that the amount of organic fluorine in the mechanochemically treated product is 1000 ppm by mass or less. The amount of organic fluorine in the mechanochemically treated product may be 500 ppm by mass or less, preferably 100 ppm by mass or less, and may be 0 ppm by mass or more, or may be an amount below the detection limit or more. The amount of organic fluorine in the mechanochemically treated product can be measured by the following method. 0.5 g of a sample of the mechanochemically treated product is subjected to ultrasonic extraction with 10 mL of methanol for 2 hours at 60°C to extract the organic fluorine compounds in the sample, obtaining an extract. The methanol in the extract obtained is concentrated and analyzed by combustion ion chromatography to measure the mass of fluorine ions derived from the organic fluorine compounds detected in the extract. The amount of organic fluorine is calculated using the fluorine ion mass measured above using the following formula. Amount of organic fluorine in mechanochemically treated material (ppm by mass) = ((mass of detected fluorine ions) / 0.5g) x 10 6 Amount of organic fluorine in mechanochemically treated material (mol ppm) = ((mass of detected fluorine ions) / 0.5g / 19 / (number of fluorines in the monomer unit of fluorine-containing compound)) × 10 6 The number of fluorine atoms in the monomer unit of the fluorine-containing compound can be determined from the chemical formula of the monomer, and for example, in the case of TFE, it is 4. When two or more monomers with different numbers of fluorine atoms are contained, the number is determined from the number of fluorine atoms in the monomer unit with the largest content.

[0086] Although the embodiments have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the claims. [Example]

[0087] The present disclosure will now be described in more detail with reference to examples, but the present disclosure is not limited to these examples.

[0088] Each value was determined by the following method.

[0089] <Size of fluorine-containing compounds> (flakes) The thickness (mm) of the fluorine-containing compound was measured using a micrometer on 20 or more flakes, and the average value was used as the thickness. The long and short sides (mm) of the fluorine-containing compound were measured using images taken with a Keyence VHX5000 video microscope on 90 or more flakes, and the average values ​​were used as the long and short sides. (Block-shaped) The three sides (mm) of the fluorine-containing compound were measured using a micrometer or vernier calipers. (pellet form) The long side (mm), short side (mm) and height (mm) of the fluorine-containing compound were measured using a micrometer or vernier calipers. (powder) Measurements were carried out dry at a vacuum pressure of 20 mH2O using a laser diffraction / scattering particle size distribution analyzer manufactured by Nikkiso Co., Ltd., and the particle size was determined to be equal to the particle diameter corresponding to 50% of the integrated particle size distribution (volume basis).

[0090] <Size of fluorine-containing compound (volume ratio to grinding media)> The volume was calculated from the measured size of the fluorine-containing compound, and the volume was calculated from the size of the powder medium, and the ratio (volume of fluorine-containing compound / volume of powder medium) was calculated.

[0091] <Average particle size of grinding aid> Measurement was performed using a laser diffraction / scattering particle size distribution analyzer manufactured by Nikkiso Co., Ltd.

[0092] <Collision energy> Based on the method described in AIChE Journal, Vol. 52, No. 10, 2006, pp. 3421-3426, the calculation was carried out using the following formula using simulation software KIK DEM (made by Tohoku University) or UX-DEM (made by JX Metals).

number

[0093] <Yield of metal fluoride> A mixture of CaF2 and CaO reagents in a specified mass ratio was measured using X-ray diffraction (XRD), and a calibration curve was created based on the quantitative values ​​calculated by analysis (RIR method). After processing, the sample was measured using XRD, and the amount of CaF2 was calculated from the calibration curve, and the yield of CaF2 (metal fluoride) was calculated.

[0094] <Reaction rate of organic fluorine compounds> A 0.5 g sample of the mechanochemically treated product (product containing metal fluoride) obtained in the example was subjected to ultrasonic extraction with 10 mL of methanol at 60°C for 2 hours to extract the organic fluorine compounds in the sample, and an extract was obtained. The methanol in the resulting extract was concentrated and analyzed by combustion ion chromatography to measure the mass of fluorine ions derived from the organic fluorine compounds detected in the extract. Using the mass of fluorine ions measured above, the amount of organic fluorine in the mechanochemically treated product was calculated according to the following formula. Amount of organic fluorine in mechanochemically treated material (ppm by mass) = ((mass of detected fluorine ions) / 0.5g) x 10 6 Amount of organic fluorine in mechanochemically treated material (mol ppm) = ((mass of detected fluorine ions) / 0.5g / 19 / (number of fluorines in the monomer unit of fluorine-containing compound)) × 106 In addition, the reaction rate of the organic fluorine compound was calculated using the amount of organic fluorine (by mass) in the mechanochemically treated product calculated above, according to the following formula. Reaction rate of organic fluorine compound = ((amount of fluorine in organic fluorine compound before mechanochemical treatment - amount of organic fluorine in mechanochemically treated product) / amount of fluorine in organic fluorine compound before mechanochemical treatment) x 100 The amount of fluorine in the organofluorine compound before the mechanochemical treatment was measured by combustion ion chromatography.

[0095] <Wear amount of grinding media> The mass of the grinding media was measured before treatment (mechanochemical treatment), and after treatment, the media was washed in water for 15 minutes while stirring at 500 rpm, and the mass of the grinding media after drying was measured. The mass was calculated from the ratio of the difference using the following formula. Wear amount (%) = (mass of grinding media before treatment - mass of grinding media after treatment) / (mass of grinding media before treatment)

[0096] In each experimental example, the following materials (all solid at 25° C.) were used. <Fluorine-containing compounds> PTFE (1): Powder of PTFE M18 manufactured by Daikin Industries, Ltd. was compression molded under conditions of 30 MPa for 1 minute and then baked at 370°C for 3 hours to obtain a molded product. The molded product obtained was then cut and crushed to produce flakes with an average thickness of 129 μm, an average long side of 2.4 mm, and an average short side of 0.9 mm, or the product was further crushed and crushed in an impact crusher to produce powdered secondary particles with a D50 of 208 μm. PTFE (2-1): Powder of PTFE M18 manufactured by Daikin Industries, Ltd. is compression molded at 30 MPa for 1 minute, and then baked at 370°C for 3 hours to obtain a molded product, which is then cut into a cubic block shape with three sides of approximately the same length. PTFE (2-2): TFE homopolymer, Daikin Industries, Ltd. M18 (unsintered), powder form ETFE:Et / TFE copolymer, Daikin Industries, Ltd. EP521, pellet form PVdF: VdF homopolymer, Daikin Industries, Ltd. VP832, powder form Fluorine-based telomer: C2F5 (CF2CF2) n -I(5≦n≦10), powder <Metal oxides> CaO: CaO obtained by firing CaCO3 at 1000°C <Grinding aid> TiO2: Titanium dioxide IV manufactured by Wako Pure Chemical Industries, Ltd., anatase type, old Mohs hardness 6, average particle size 5.8 μm Al2O3: Aluminum oxide (special reagent grade) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Mohs hardness 9, average particle size 54.9 μm

[0097] Example 1 The raw materials (fluorine-containing compound, metal oxide, and grinding aid) shown in Table 1 were weighed. The raw materials and zirconia balls serving as grinding media (first grinding media) were placed in the pot of a planetary mill. A lid was attached to the pot, and the pot was placed in the planetary mill body and started to rotate. After mechanochemical treatment for a predetermined time, a product containing metal fluoride (CaF2) was removed. The yield of metal fluoride and the wear amount of the grinding media were determined using the above methods. The results are shown in Table 1. The planetary mill used for the mechanochemical treatment is as follows: Equipment: Fritsch Pulverisette planetary ball mill P-7 Grinding tube: Zirconia pot (volume 45 mL, diameter 40 mm) Grinding media (first grinding media): zirconia balls (φ15 mm), 7 pieces, filling rate 80% by volume

[0098] Example 2 The mechanochemical treatment was carried out in the same manner as in Example 1, except that 38.75 g (435 pieces) of φ3 mm zirconia balls were used as second grinding media instead of the grinding aid. The results are shown in Table 1.

[0099] Examples 3 to 10 and Comparative Examples 1 to 5 The mechanochemical treatment was carried out in the same manner as in Example 1, except that the raw materials and treatment conditions were changed as shown in Tables 1 and 2. The results are shown in Tables 1 and 2. In Comparative Example 1, in which alumina was used as the grinding aid, the grinding media and reaction vessel were subjected to considerable wear. The amount of organic fluorine in the mechanochemically treated product obtained in Example 5 was 60 ppm by mass, 0.79 ppm by mole. The amount of organic fluorine in the mechanochemically treated product obtained in Example 7 was 2.1 ppm by mass, 27 ppb by mole. The reaction rate of the organic fluorine compound in Example 5 was 99.96%. The reaction rate of the organic fluorine compound in Example 7 was 99.999%.

[0100] [Table 1]

[0101] [Table 2]

[0102] "Sample size" in each table indicates the average particle size if the sample is in powder form, the average value of the three sides if the sample is in block form, and the average value of the long side, short side, and height if the sample is in pellet form.

Claims

1. A method for producing a metal fluoride, comprising: a step of mechanochemically treating a fluorine-containing compound and at least one metal oxide selected from the group consisting of alkali metal oxides and alkaline earth metal oxides under at least one condition selected from the group consisting of the following (a) to (c), thereby obtaining a metal fluoride: (a) The mechanochemical treatment is carried out in the presence of a grinding aid having a Mohs hardness of 5 to 8.

5. (b) The size of the fluorine-containing compound is 0.002 to 0.15 times the size of the grinding medium used in the mechanochemical treatment on a volume basis. (c) The mechanochemical treatment is carried out using two or more grinding media of different sizes.

2. 2. The method according to claim 1, wherein the mechanochemical treatment is carried out under at least two conditions selected from the group consisting of (a) to (c).

3. 3. The method according to claim 1, wherein the grinding aid in (a) is titanium oxide.

4. 3. The method according to claim 1, wherein the grinding aid in (a) is a particle having an average particle size of 5 to 10 μm.

5. 3. The method according to claim 1, wherein the amount of the grinding aid used in (a) is 0.1 to 1 equivalent per equivalent of the fluorine-containing compound.

6. 3. The method according to claim 1, wherein the size of the fluorine-containing compound in (b) is 0.002 to 0.08 times the size of the grinding medium used in the mechanochemical treatment on a volume basis.

7. 3. The method of claim 1 or 2, wherein the grinding media in (c) comprises a first grinding media and a second grinding media that is smaller than the first grinding media and has at least one dimension greater than 1 mm in length.

8. 3. The method of claim 1 or 2, wherein the grinding media in (c) comprise a first grinding media having a three-dimensional length of 10 to 20 mm and a second grinding media having a three-dimensional length of more than 1 mm but less than 5 mm.

9. 3. The method according to claim 1, wherein the metal oxide is calcium oxide.

10. 3. The method according to claim 1, wherein the amount of the metal oxide used is 1 to 3 equivalents per equivalent of the fluorine-containing compound.

11. 3. The method according to claim 1, wherein the fluorine-containing compound is a low-molecular-weight fluorine-containing compound having a molecular weight of 2,000 or less.

12. 3. The method according to claim 1, wherein the fluorine-containing compound is a fluorine-containing polymer.

13. 3. The method according to claim 1, wherein the fluorine-containing compound is at least one selected from the group consisting of polytetrafluoroethylene, polydifluoroethylene, ethylene / tetrafluoroethylene copolymer, and fluorine-containing telomer.

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