Metal fluoride production method

Abstract

The purpose of the present disclosure is to provide a production method that makes it possible to efficiently produce a metal fluoride via mechanochemical processing. The present disclosure is a metal fluoride production method comprising a step for obtaining a metal fluoride by performing mechanochemical processing of 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 conditions (a)-(c). (a) The mechanochemical processing is performed in the presence of a grinding aid having an old Mohs hardness of 5-8.5. (b) The size of the fluorine-containing compound is 0.002-0.15 times that of a grinding medium used in the mechanochemical processing, on a volume basis. (c) The mechanochemical processing is performed using two or more grinding media having differing sizes.

Description

Method for producing metal fluorides

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

[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).

[0003] Japanese Patent Application Laid-Open No. 2000-70401

[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.

[0006] The present disclosure (1) is a method for producing a metal fluoride, comprising the 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 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 volume of the grinding media used in the mechanochemical treatment; and (c) the mechanochemical treatment is carried out using two or more grinding media of different sizes.

[0007] The present disclosure (2) is the manufacturing 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 (a) to (c).

[0008] The present disclosure (3) is the manufacturing 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 of 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), wherein 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) comprises 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), wherein the grinding media in (c) include a first grinding medium having a three-dimensional length of 10 to 20 mm and a second grinding medium 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 any combination of the present disclosures (1) to (8), in which the metal oxide is calcium oxide.

[0015] The present disclosure (10) is a production method of any combination with any 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 with any of the present disclosures (1) to (10), wherein the fluorine-containing compound is a fluorine-containing low-molecular-weight compound having a molecular weight of 2000 or less.

[0017] The present disclosure (12) is a method for producing any 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.

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

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

[0021] The present disclosure relates to a method for producing a metal fluoride, comprising the 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 (a) to (c) below to obtain 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 volume of the grinding media used in the mechanochemical treatment. (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 produced efficiently 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 inorganic fluorine compounds other than calcium fluoride are not included. 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. In addition, the fluorine-containing compound is preferably solid at 25°C, in order to facilitate 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 allyl ether include vinyl fluoride [PVF], polydifluoroethylene (polyvinylidene fluoride [PVdF], poly(1,2-difluoroethylene), etc.), 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, TFE / perfluoroalkyl allyl ether copolymer, and the like, and these can be used alone or in combination. The perfluoroalkyl allyl ether is CF ２ =CFCF ２ -O-Rf １ (Rf １ is 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): CH ２ = CFRf ２ (1) (wherein, Rf ２ represents 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, still 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. From the viewpoint of reactivity, the fluorine-containing polymer is also preferably a fluororesin having a monomer unit having a C-H bond, more preferably at least one selected from the group consisting of polydifluoroethylene and ETFE, still more preferably at least one selected from the group consisting of PVdF and ETFE, and even more preferably PVdF.

[0032] The fluorine-containing compound does not have to be a polymer, and may be a fluorine-containing low-molecular-weight compound, so long as it is solid at 25° C. The fluorine-containing low-molecular-weight compound may have a molecular weight of 2000 or less. 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-containing telomer. Examples of the fluorine-containing telomer include those represented by the following formula: ２ F ５ (CF ２ CF ２ )ｎ -X (wherein X is a halogen atom and n is an integer of 5 or greater). 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 preferably an integer of 5 or greater and an integer of 10 or less.

[0034] The fluorine-containing low molecular weight compound is represented by the following general formula (I): Y—(CF ２ ) ｘ１ - (CH ２ ) ｙ１ -A (I) (wherein Y represents H or F, x1 represents an integer of 4 or more, y1 represents an integer of 0 to 3, and A represents -SO ３ M Ｉ or -COOM Ｉ indicates M Ｉ is H, NH ４ , Li, Na, Mg, Al, K or Ca), and a compound (I) represented by the following general formula (II): F—(CF ２ ) ｘ２ O(CFXCF ２ O) ｙ２ -CFX-A (II) (wherein x2 represents an integer of 1 or more, y2 represents an integer of 0 to 10, and X represents F or CF ３ A represents -SO ３ M ＩＩ or -COOM ＩＩ indicates M ＩＩ is H, NH ４ , Li, Na, Mg, Al, K or Ca.

[0035] Examples of the compound (I) include fluorocarboxylic acids and salts thereof, such as perfluorocarboxylic acids and salts thereof. Examples of salts include ammonium salts and sodium salts. Examples of the compound (I) also include fluorosulfonic acids and salts thereof, such as perfluorosulfonic acids and salts thereof. Examples of salts include 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 obtained by adsorbing the fluorine-containing low molecular weight compound 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 manufacturing method of the present disclosure, a composition containing the fluorine-containing compound and other components may be subjected to mechanochemical treatment. The other components may 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 adsorbents described above.

[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 polyamino bismaleimide; 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 polymer may be a non-fluorine-containing polymer.

[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 or 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] The size of the fluorine-containing compound is not particularly limited, but it has been found that a larger size to a certain extent improves the reaction efficiency. Generally, the smaller the size, the higher the reaction efficiency tends to be, so this finding is unexpected. Of the three dimensions indicating 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, particularly preferably 3.0 mm or more, and 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 indicating the size of the fluorine-containing compound, it is preferable that the length of the shortest dimension is within the above range. Furthermore, it is more preferable that the lengths of at least two of the three dimensions indicating the size of the fluorine-containing compound are 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 using 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 using a laser diffraction / scattering particle size distribution analyzer manufactured by Nikkiso Co., Ltd., under a vacuum pressure of 20 mH. ２ Measurement is carried out at 0°C and is considered to be equal to the particle diameter corresponding to 50% of the integrated particle size distribution (volume basis).

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

[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, 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 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, shaking, etc., to activate the reactant and impart structural change, phase transition, reactivity, adsorptivity, catalytic activity, etc. The method of mechanochemical treatment is not particularly limited, and examples include a compression 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 indicating the size of the grinding medium may be 5 mm or more, preferably 10 mm or more, and 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 indicating the size of the grinding medium, it is preferable that the length of the shortest dimension is within the above range. Furthermore, it is more preferable that the lengths of at least two of the three dimensions indicating the size of the grinding medium are within the above range, and it is even more preferable that the length of the third dimension is within the above range. When the grinding medium is spherical, it is preferable that the diameter is within the above range. By using grinding media of such 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 medium 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 may 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 amount of 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 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. The material of the reaction vessel may be the same as or different from the grinding medium.

[0056] From the viewpoint of reaction efficiency, the filling rate of the grinding medium 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, preferably under at least two conditions selected from the group consisting of (a) to (c), and more preferably under all of (a) to (c). The mechanochemical treatment is also preferably carried out under at least condition (b), more preferably under at least conditions (a) and (b), or more preferably under at least conditions (b) and (c), and even more preferably under at least 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, it is also possible to suppress wear on the grinding media and reaction vessel. The Mohs hardness is preferably 5.5 or higher, and more preferably 8 or lower, and more preferably 7.5 or lower. The Mohs hardness is measured using a Mohs hardness scale.

[0059] The grinding aid may be titanium oxide (TiO ２ ), quartz (SiO ２ ), zirconia (ZrO ２ ), 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, with titanium oxide being more preferred. Note that, due to differences in crystal structure and other factors, grinding aids of the same type (name) may have different old Mohs hardnesses. The grinding aids exemplified above are grinding aids whose old Mohs hardness is within the above-mentioned range and whose types are as described above.

[0060] The grinding aid is preferably in the form of particles. 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 analyzer 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 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, 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 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. This allows high energy to be applied to the material to be treated, improving reaction efficiency. The two or more grinding media of different sizes preferably have different volumes. The two or more grinding media of different sizes also preferably have different lengths in at least one dimension of the three dimensions that represent 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 of different sizes, it is preferable to use at least a first grinding medium and a second grinding medium smaller than the first grinding medium. The second grinding medium preferably has a smaller volume than the first grinding medium. Of the three dimensions representing the size of the grinding medium, it is preferable that at least one dimension of the second grinding medium is shorter than the first grinding medium, more preferably at least two dimensions of the second grinding medium are shorter than the first grinding medium, and even more preferably the third dimension of the second grinding medium is shorter 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 in the same range as the amount of the grinding medium normally used in the mechanochemical treatment.

[0066] The size of the second grinding medium is preferably at least 0.01 times, more preferably at least 0.05 times, and even more preferably at least 0.1 times, the volume of the first grinding medium, 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 preferably has a length of at least one dimension of 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 indicating the size of the second grinding medium, it is preferable that the length of the shortest dimension is within the above range. Furthermore, it is more preferable that the lengths of at least two of the three dimensions indicating the size of the grinding medium are within the above range, and even more preferable that the length of the third dimension is within the above range. When the second grinding medium is spherical, it is preferable that the diameter is within the above range. By using a grinding medium having the above size as the second grinding medium, the reaction efficiency can be further improved. Furthermore, by having a certain size, the second grinding medium 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 medium may be the same as those described above for the grinding medium (first grinding medium) 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 or different in shape and material.

[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. It is also preferable that the energy is 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 improved, and it becomes easier to carry out the mechanochemical treatment using equipment 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 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. (In the formula, E ｗ is the total collision energy (J / s / g), m is the mass of the grinding media (g), v ｊ is the relative velocity (m / s), W is the total mass (g) of the object to be treated introduced into the container, t ｓrepresents the simulation time (s). The relative velocity is the relative velocity between the grinding media or between the grinding media and the inner wall of the reaction vessel when they collide, and can be adjusted, for example, by the mass of the powder media, the vibration frequency, or the rotation speed of the device. The simulation time is the time input based on the estimated processing time.

[0072] In the mechanochemical treatment, the ratio of the material to be treated 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 ratio of the material to be treated is the total ratio of all raw materials to be mechanochemically treated, such as the fluorine-containing compound, the metal oxide, and the grinding aid.

[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 a ball mill, rod mill, jet mill, rotary mill, vibration mill, SAG mill, and planetary mill; grinders such as rotary stone mills and crushers; (horizontal axis rotation) container rotation type mixers such as horizontal cylindrical, V-type, double cone type, square cube type, S-type, and continuous V-type; (baffle blade equipped) container rotation type mixers such as horizontal cylindrical, V-type, double cone type, and ball mill type; (rotational vibration) container rotation type mixers such as rocking type and cross rotary type; 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 type; (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 that can impart high energy, it is also a device that generates a large amount of wear powder derived 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 powder may interfere with the use of the product after reaction. The manufacturing method of the present disclosure can react a fluorine-containing compound under conditions that are less likely to generate wear powder derived from the device. In addition, methods that use general-purpose equipment such as a ball mill or vibration mill rather than a planetary mill 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. The metal fluoride may be at least one selected from the group consisting of alkali metal fluorides and alkaline earth metal fluorides, and is preferably an alkaline earth metal fluoride, such as calcium fluoride (CaF ２ ) is more preferable.

[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 metal fluorides from organic fluorine compounds by using an 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 using the amount of organic fluorine (by mass) in the mechanochemically treated product described below using 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) × 100. The amount of fluorine in the organic fluorine compound before the mechanochemical treatment can be measured by known techniques 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. "Substantially no organic fluorine" in the mechanochemically treated product 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. The amount of organic fluorine in the mechanochemically treated product can be measured by the following method. A 0.5 g sample of the mechanochemically treated product is subjected to ultrasonic extraction treatment with 10 mL of methanol for 2 hours at 60°C to extract the organic fluorine compounds in the sample, thereby obtaining an extract. The methanol in the obtained extract 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. Using the fluorine ion mass measured above, the amount of organic fluorine is calculated using the following formula: Amount of organic fluorine in mechanochemically treated product (ppm by mass) = ((mass of detected fluorine ions) / 0.5 g) x 10 ６Amount of organic fluorine in mechanochemically treated product (mol ppm)=((mass of detected fluorine ions) / 0.5 g / 19 / (number of fluorines in monomer units 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 having 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.

[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 Compound> (Flake-like) The thickness (mm) of 20 or more fluorine-containing compounds was measured using a micrometer, and the average value was taken as the thickness. The long side (mm) and short side (mm) of the fluorine-containing compound were measured using images taken with a Keyence VHX5000 video microscope for 90 or more flakes, and the average values ​​were taken as the long side and short side. (Block-like) The three sides (mm) of the fluorine-containing compound were measured using a micrometer or vernier calipers. (Pellet-like) The long side (mm), short side (mm) and height (mm) of the fluorine-containing compound were measured using a micrometer or vernier calipers. (Powder-like) The long side (mm), short side (mm) and height (mm) of the fluorine-containing compound were measured using a laser diffraction / scattering particle size distribution analyzer manufactured by Nikkiso Co., Ltd. in a dry state at a vacuum pressure of 20 mH ２ The measurement was carried out at 0°C and was set 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 Medium)> 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 carried out using a laser diffraction / scattering particle size distribution measuring device manufactured by Nikkiso Co., Ltd.

[0092] <Collision Energy> Based on the method described in AIChE Journal, Vol. 52, No. 10, 2006, pp. 3421-3426, collision energy was calculated using the following formula using simulation software KIK DEM (Tohoku University) or UX-DEM (JX Metals). (In the formula, E ｗ is the total collision energy (J / s / g), m is the mass of the grinding media (g), v ｊ is the relative velocity (m / s), W is the total mass (g) of the object to be treated introduced into the container, t ｓ represents the simulation time (s).

[0093] <Yield of metal fluoride> CaF ２ A mixture of CaF and CaO reagents in a predetermined mass ratio was measured by X-ray diffraction (XRD), and a calibration curve was created based on the quantitative values ​​calculated by analysis (RIR method). After the treatment, the sample was subjected to XRD measurement, and the CaF ２ The amount was calculated and ２ The yield of (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 examples was 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 obtained 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 using the following formula: Amount of organic fluorine in mechanochemically treated product (mass ppm) = ((mass of detected fluorine ions) / 0.5 g) x 10 ６ Amount of organic fluorine in mechanochemically treated product (mol ppm)=((mass of detected fluorine ions) / 0.5 g / 19 / (number of fluorines in monomer units of fluorine-containing compound))×10 ６The amount of organic fluorine (by mass) in the mechanochemically treated product determined above was used to determine the reaction rate of the organic fluorine compound 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 organic fluorine 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 wear amount was calculated from the ratio of the difference between the masses 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 baked at 370 ° C. for 3 hours to obtain a molded product, and the obtained molded product was cut and then pulverized to form 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 further pulverized and further pulverized in an impact pulverizer to form powdery secondary particles with a D50 of 208 μm. PTFE (2-1): Powder of PTFE M18 manufactured by Daikin Industries, Ltd. was compression-molded under conditions of 30 MPa for 1 minute and baked at 370 ° C. for 3 hours to obtain a molded product, and the obtained molded product was cut into a cubic block shape with three sides of approximately the same length. PTFE (2-2): TFE homopolymer, M18 (unsintered) manufactured by Daikin Industries, Ltd., powder form ETFE: Et / TFE copolymer, EP521 manufactured by Daikin Industries, Ltd., pellet form PVdF: VdF homopolymer, VP832 manufactured by Daikin Industries, Ltd., powder form Fluorine-based telomer: C ２ F ５ (CF ２ CF ２ ) ｎ -I (5≦n≦10), powder form <Metal oxide> CaO: CaCO ３ CaO obtained by firing at 1000°C <Grinding aid> TiO２ Titanium oxide IV, anatase type, Mohs hardness 6, average particle size 5.8 μm, manufactured by Wako Pure Chemical Industries, Ltd. ２ O ３ 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 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 rotation was started. After mechanochemical treatment for a predetermined time, a metal fluoride (CaF ２ ) was taken out. The yield of metal fluoride and the wear amount of the grinding media were determined by the above method. The results are shown in Table 1. The planetary mill used for the mechanochemical treatment is as follows. Apparatus: Pulverisette planetary ball mill P-7 manufactured by Fritsch Grinding tube: Zirconia pot (internal volume 45 mL, φ40 mm) Grinding media (first grinding media): Zirconia balls (φ15 mm), 7 balls, packing 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 3 mm diameter 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 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, significant wear of the grinding media and reaction vessel occurred. The amounts of organic fluorine in the mechanochemically treated product obtained in Example 5 were 60 ppm by mass and 0.79 mol ppm. The amounts of organic fluorine in the mechanochemically treated product obtained in Example 7 were 2.1 ppm by mass and 27 mol ppb. 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]

[0101]

[0102] "Sample size" in each table indicates the average particle size if the sample is in powder form, the average value of 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 the 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 (a) to (c) below to obtain 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 volume of the grinding media used in the mechanochemical treatment; and (c) the mechanochemical treatment is carried out using two or more types of grinding media of different sizes.

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

3. The manufacturing method according to claim 1 or 2, wherein the grinding aid in (a) is titanium oxide.

4. A manufacturing method according to any one of claims 1 to 3, wherein the grinding aid in (a) is a particle having an average particle size of 5 to 10 μm.

5. The method according to any one of claims 1 to 4, wherein the amount of the grinding aid used in (a) is 0.1 to 1 equivalent per equivalent of the fluorine-containing compound.

6. A method according to any one of claims 1 to 5, wherein 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.

7. A method according to any one of claims 1 to 6, 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. A method according to any one of claims 1 to 7, 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. The method according to any one of claims 1 to 8, wherein the metal oxide is calcium oxide.

10. The method according to any one of claims 1 to 9, wherein the amount of the metal oxide used is 1 to 3 equivalents per equivalent of the fluorine-containing compound.

11. The method according to any one of claims 1 to 10, wherein the fluorine-containing compound is a low-molecular-weight fluorine-containing compound having a molecular weight of 2,000 or less.

12. The method according to any one of claims 1 to 10, wherein the fluorine-containing compound is a fluorine-containing polymer.

13. The method according to any one of claims 1 to 10, 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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