Electret material, filter, and masterbatch

Abstract

The purpose of the present disclosure is to provide an electret material having excellent collection performance, a filter including the electret material, and a masterbatch for producing the electret material. This electret material comprises a thermoplastic resin and charge enhancers contained in the thermoplastic resin, wherein the charge enhancers comprise at least one fluorochemical charge enhancer selected from the group consisting of polytetrafluoroethylene and vinylidene fluoride polymers and at least one hydrocarbon-based charge enhancer.

Description

Electret materials, filters, and masterbatches

[0001] The present disclosure relates to electret materials, filters, and masterbatches.

[0002] It is known to use electret materials in meltblown fibers used in air filters and the like.

[0003] Patent Document 1 describes electret fibers containing additives such as polyvinylidene fluoride.

[0004] Patent Document 2 describes an electret fiber sheet containing a perfluoroalkyl compound such as an acrylic acid compound.

[0005] Patent Document 3 describes a method for forming n-C on the surface of a carrier. １０ F ２２ The document describes an electret to which a compound such as the above is attached by vapor deposition or the like.

[0006] Patent Documents 4 and 5 describe electret fibers containing fatty acid metal salts and hindered amine compounds.

[0007] Japanese Patent Application Laid-Open No. 5-049824 Japanese Patent Application Laid-Open No. 2018-071018 International Publication No. 2015 / 152207 Japanese Patent Application Laid-Open No. 63-123414 International Publication No. 2021 / 033700

[0008] An object of the present disclosure is to provide an electret material having excellent collection performance, a filter using the same, and a masterbatch for producing the electret material.

[0009] The present disclosure relates to an electret material comprising a thermoplastic resin and a charge enhancing agent contained in the thermoplastic resin, wherein the charge enhancing agent comprises at least one fluorine-based charge enhancing agent selected from the group consisting of polytetrafluoroethylene and vinylidene fluoride polymers, and at least one hydrocarbon-based charge enhancing agent.

[0010] Preferably, the fluorine-based charge enhancer is a low molecular weight polytetrafluoroethylene and vinylidene fluoride polymer.

[0011] The vinylidene fluoride polymer is preferably at least one selected from the group consisting of polyvinylidene fluoride and vinylidene fluoride / tetrafluoroethylene copolymer.

[0012] The hydrocarbon-based charge enhancer is preferably at least one selected from the group consisting of metal soaps, hindered amine compounds, triazine compounds, clarifying agents, and low-molecular-weight amide compounds.

[0013] The hydrocarbon-based charge enhancer is preferably a metal soap or a low-molecular-weight amide compound.

[0014] The metal soap is preferably a salt of a fatty acid with a metal of Group 2 of the periodic table.

[0015] The low molecular weight amide compound is preferably at least one selected from the group consisting of fatty acid amides and fatty acid bisamides.

[0016] The mass ratio of the fluorine-based charge enhancer to the hydrocarbon-based charge enhancer (fluorine-based / hydrocarbon-based) is preferably 1 / 99 to 99 / 1.

[0017] The thermoplastic resin is preferably a polyolefin resin.

[0018] The electret material preferably has a ratio (F / C) of the F element content to the C element content on the surface of the electret material measured by XPS (X-ray photoelectron spectroscopy) of 0.20% or less.

[0019] The total amount of the charge enhancer is preferably 0.01 to 5.0% by mass relative to the thermoplastic resin.

[0020] The electret material is preferably a fiber sheet.

[0021] The present disclosure also relates to a filter using the above electret material.

[0022] The filter is preferably for use in a dust mask.

[0023] The present disclosure also relates to a masterbatch for producing an electret material, comprising a thermoplastic resin and a charge enhancing agent contained in the thermoplastic resin, wherein the charge enhancing agent comprises at least one fluorine-based charge enhancing agent selected from the group consisting of polytetrafluoroethylene and vinylidene fluoride polymers, and at least one hydrocarbon-based charge enhancing agent, and the total amount of the charge enhancing agent is greater than 5.0% by mass and less than or equal to 50% by mass of the thermoplastic resin.

[0024] According to the present disclosure, it is possible to provide an electret material having excellent collection performance, a filter using the same, and a masterbatch for producing the electret material.

[0025] The present disclosure will be specifically described below.

[0026] The present disclosure relates to an electret material comprising a thermoplastic resin and a charge enhancer contained in the thermoplastic resin, the charge enhancer comprising at least one fluorine-based charge enhancer selected from the group consisting of polytetrafluoroethylene and vinylidene fluoride polymers, and at least one hydrocarbon-based charge enhancer. The electret material of the present disclosure exhibits excellent particle collection performance (e.g., PF value) for particles such as NaCl particles and PAO (polyalphaolefin) particles by using a specific fluorine-based charge enhancer in combination with the hydrocarbon-based charge enhancer.

[0027] Examples of the thermoplastic resin include polyolefin resins such as polyethylene and polypropylene; polyester resins such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polylactic acid; polycarbonate resins; polystyrene resins; polyphenylene sulfide resins; fluorine-based resins; thermoplastic elastomers such as polystyrene elastomers, polyolefin elastomers, polyester elastomers, polyamide elastomers, and polyurethane elastomers; and copolymers or mixtures thereof.

[0028] Among these, polyolefin resins are preferably used. Polyolefin resins have high volume resistivity and low water absorption, and therefore have strong chargeability and charge retention properties when fibrous, thereby achieving high collection efficiency.

[0029] Examples of polyolefin resins include homopolymers such as polyethylene, polypropylene, polybutene, and polymethylpentene. Copolymers obtained by copolymerizing different components with these homopolymers, and blends of two or more different polymers, can also be used. Among these, polypropylene and polymethylpentene are preferred from the viewpoint of charge retention. Furthermore, polypropylene is even more preferred from the viewpoint of low cost.

[0030] The polypropylene has good spinnability and can produce a melt-blown nonwoven fabric having good mechanical strength such as tensile strength, and therefore preferably has a melt flow rate (MFR) of 600 g / 10 min or more, more preferably 800 g / 10 min or more, and even more preferably 1100 g / 10 min or more, and preferably 2500 g / 10 min or less, more preferably 1800 g / 10 min or less, and even more preferably 1500 g / 10 min or less. The MFR is measured in accordance with ASTM D-1238 at 230°C and a load of 2160 g.

[0031] The charge enhancer includes at least one fluorine-based charge enhancer selected from the group consisting of polytetrafluoroethylene (PTFE) and vinylidene fluoride (VdF) polymers. The fluorine-based charge enhancer has excellent heat resistance.

[0032] The PTFE is preferably a low molecular weight PTFE.

[0033] The low-molecular-weight PTFE has a melt viscosity of 1.0×10 at 380° C. ２ ~7.0 x 10 ５ In the present disclosure, "low molecular weight" means that the melt viscosity is within the above range. ３It is preferable that the viscosity is 3.0×10 Pa s or more. ５ It is preferable that the viscosity is 1.0×10 Pa·s or less. ５ It is more preferable that the viscosity is Pa·s or less.

[0034] The melt viscosity is a value measured in accordance with ASTM D 1238 using a flow tester (manufactured by Shimadzu Corporation) and a 2φ-8L die, with a 2 g sample preheated at 380°C for 5 minutes and maintained at the above temperature under a load of 0.7 MPa.

[0035] The low-molecular-weight PTFE preferably has a melting point of 320 to 340°C, more preferably 324°C or higher, and more preferably 336°C or lower.

[0036] The melting point is measured using a differential scanning calorimeter (DSC) by calibrating the temperature in advance using indium and lead as standard samples, placing about 3 mg of low-molecular-weight PTFE in an aluminum pan (crimp container), and raising the temperature at 10°C / min in a temperature range of 250 to 380°C under an air flow of 200 ml / min, and the minimum point of the heat of fusion in the above range is taken as the melting point.

[0037] The low molecular weight PTFE is preferably particles having an average particle size of 0.1 to 100 μm, in order to prevent clogging of the melt-blowing die. The average particle size is more preferably 50 μm or less, even more preferably 10 μm or less, particularly preferably 6 μm or less, and more preferably 0.5 μm or more, even more preferably 1.0 μm or more.

[0038] The average particle size is measured using a laser diffraction particle size distribution analyzer (HELOS & RODOS) manufactured by JEOL Ltd. without using a cascade and at a dispersion pressure of 1.0 bar, and is defined as being equal to the particle size corresponding to 50% of the integrated particle size distribution (volume basis).

[0039] The low-molecular-weight PTFE may be a TFE homopolymer consisting of only tetrafluoroethylene (TFE) units, or may be a modified PTFE containing TFE units and modified monomer units based on a modified monomer copolymerizable with TFE.

[0040] In the modified PTFE, the content of the modified monomer unit is preferably 0.001 to 1 mass% of the total monomer units, more preferably 0.01 mass% or more, more preferably 0.5 mass% or less, and even more preferably 0.1 mass% or less. In this specification, the modified monomer unit refers to a portion of the molecular structure of the modified PTFE that is derived from the modified monomer, and the total monomer units refers to portions derived from all monomers in the molecular structure of the modified PTFE. The content of the modified monomer unit can be determined by a known method such as Fourier transform infrared spectroscopy (FT-IR).

[0041] The above-mentioned modified monomer is not particularly limited as long as it can be copolymerized with TFE, and for example, can be listed perfluoroolefin such as hexafluoropropylene (HFP); chlorofluoroolefin such as chlorotrifluoroethylene (CTFE); hydrogen-containing fluoroolefin such as trifluoroethylene, vinylidene fluoride (VDF); perfluorovinyl ether; perfluoroalkylethylene; ethylene etc. The modified monomer used can be one kind or multiple kinds.

[0042] The perfluorovinyl ether is not particularly limited, and examples thereof include perfluorovinyl ethers represented by the following general formula (1): ２ ═CF—ORf (1) (wherein Rf represents a perfluoroorganic group). In this specification, the term "perfluoroorganic group" refers to an organic group in which all hydrogen atoms bonded to carbon atoms are substituted with fluorine atoms. The perfluoroorganic group may have an ether oxygen.

[0043] Examples of the perfluorovinyl ether include perfluoro(alkyl vinyl ether) [PAVE], in which Rf in the general formula (1) represents a perfluoroalkyl group having 1 to 10 carbon atoms. The number of carbon atoms in the perfluoroalkyl group is preferably 1 to 5.

[0044] Examples of the perfluoroalkyl group in the PAVE include perfluoromethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl, perfluoropentyl, and perfluorohexyl groups, and preferred is purpuro(propyl vinyl ether) [PPVE], in which the perfluoroalkyl group is a perfluoropropyl group.

[0045] The perfluorovinyl ether further includes those represented by the general formula (1) in which Rf is a perfluoro(alkoxyalkyl) group having 4 to 9 carbon atoms, and those represented by the following formula:

[0046]

[0047] (wherein m represents 0 or an integer of 1 to 4), and Rf is a group represented by the following formula:

[0048]

[0049] (wherein n represents an integer of 1 to 4).

[0050] The perfluoroalkylethylene is not particularly limited, and examples thereof include (perfluorobutyl)ethylene (PFBE), (perfluorohexyl)ethylene, and (perfluorooctyl)ethylene.

[0051] The modifying monomer in the modified PTFE is preferably at least one selected from the group consisting of HFP, CTFE, VDF, PPVE, PFBE, and ethylene, and more preferably at least one selected from the group consisting of PPVE, HFP, and CTFE.

[0052] The VdF polymer is preferably at least one selected from the group consisting of polyvinylidene fluoride (PVdF) and a VdF / TFE copolymer.

[0053] The PVdF may be a homopolymer consisting of only polymerization units based on VdF, or may be a homopolymer consisting of polymerization units based on VdF and polymerization units based on a monomer (α) copolymerizable with VdF.

[0054] The monomer (α) may have an ethylenically unsaturated double bond. Specific examples of the monomer (α) include fluorine-containing monomers [e.g., vinyl fluoride (VF), trifluoroethylene (TrFE), hexafluoropropene (HFP), 1-chloro-1-fluoroethylene (1,1-CFE), 1-chloro-2-fluoroethylene (1,2-CFE), 1-chloro-2,2-difluoroethylene (CDFE), chlorotrifluoroethylene (CTFE), trifluorovinyl monomer, 1,1,2-trifluorobutene-4-bromo-1-butene, 1,1,2-trifluorobutene-4-silane-1-butene, perfluoropropyl vinyl ether, fluorine-containing monomers [e.g., α-olefins (e.g., ethylene, propylene); unsaturated dicarboxylic acids or derivatives thereof (e.g., maleic acid, maleic anhydride); vinyl ethers (e.g., ethyl vinyl ether); allyl ethers (e.g., allyl glycidyl ether); vinyl esters (e.g., vinyl acetate); acrylic acid or esters thereof; methacrylic acid or esters thereof], and combinations of one or more of these.

[0055] The PVdF may contain repeating units derived from the monomer (α) in an amount of, for example, 10 mol % or less, preferably 5 mol % or less, and preferably 0.01 mol % or more, of the repeating units derived from all monomers.

[0056] The PVdF preferably has a weight average molecular weight (polystyrene equivalent) of 50,000 to 2,000,000. The weight average molecular weight is more preferably 80,000 or more, and more preferably 1,900,000 or less. The weight average molecular weight can be measured by gel permeation chromatography (GPC) at 50°C using N,N-dimethylformamide as a solvent.

[0057] The PVdF preferably has a number average molecular weight (polystyrene equivalent) of 150,000 to 1,400,000. The number average molecular weight is more preferably 200,000 or more, and more preferably 1,300,000 or less. The number average molecular weight can be measured by gel permeation chromatography (GPC) at 50°C using N,N-dimethylformamide as a solvent.

[0058] In the VdF / TFE copolymer, the repeating unit (—CH ２ -CF ２ -) and repeating units derived from TFE (-CF ２ -CF ２ -) molar ratio ((-CH ２ -CF ２ -) / (-CF ２ -CF ２ Although not limited thereto, the molar ratio can be, for example, within the range of 50 / 50 to 99 / 1. The molar ratio is preferably 55 / 45 or more, more preferably 60 / 40 or more, and even more preferably 70 / 30 or more, and is preferably 97 / 3 or less, more preferably 95 / 5 or less, and even more preferably 90 / 10 or less.

[0059] The VdF / TFE copolymer may be a copolymer consisting of only VdF and TFE, or may be a copolymer consisting essentially of VdF and TFE. The VdF / TFE copolymer may also contain repeating units derived from a monomer (β) copolymerizable with VdF and TFE.

[0060] Examples of the monomer (β) include the same monomers as the monomer (α) described for PVdF.

[0061] The VdF / TFE copolymer may contain repeating units derived from the monomer (β) in an amount of, for example, 10 mol % or less, preferably 5 mol % or less, and preferably 0.01 mol % or more, of the repeating units derived from all monomers.

[0062] The VdF / TFE copolymer preferably has a weight average molecular weight (polystyrene equivalent) of 50,000 to 2,000,000. The weight average molecular weight is more preferably 80,000 or more, and even more preferably 100,000 or more, and is more preferably 1,950,000 or less, and even more preferably 1,500,000 or less. The weight average molecular weight can be measured by gel permeation chromatography (GPC) at 50°C using N,N-dimethylformamide as a solvent.

[0063] The VdF / TFE copolymer preferably has a number average molecular weight (polystyrene equivalent) of 10,000 to 1,400,000. The number average molecular weight is more preferably 16,000 or more, and even more preferably 20,000 or more, and is more preferably 1,300,000 or less, and even more preferably 1,200,000 or less. The number average molecular weight can be measured by gel permeation chromatography (GPC) at 50°C using N,N-dimethylformamide as a solvent.

[0064] The VdF polymer is preferably the VdF / TFE copolymer.

[0065] The VdF polymer may also be a mixture of the PVdF and the VdF / TFE copolymer, in which case the mass ratio [(VdF / TFE copolymer) / PVdF] is preferably 5 / 95 or more, more preferably 10 / 90 or more, and even more preferably 20 / 80 or more, and is preferably 90 / 10 or less, and more preferably 85 / 15 or less.

[0066] The fluorine-based electrostatic charge enhancer is preferably the PTFE and the VdF polymer, more preferably the low-molecular-weight PTFE and the VdF polymer, and even more preferably the low-molecular-weight PTFE, the PVdF, and the VdF / TFE copolymer.

[0067] When the fluorine-based charge enhancer is the PTFE and the VdF polymer, the mass ratio of the PTFE to the VdF polymer (PTFE / VdF polymer) is preferably 1 / 99 to 70 / 30, from the viewpoint of further improving collection performance. The mass ratio is more preferably 5 / 95 or more, even more preferably 10 / 90 or more, and particularly preferably 15 / 85 or more. The mass ratio is also more preferably 60 / 40 or less, even more preferably 50 / 50 or less, even more preferably 40 / 60 or less, and particularly preferably 30 / 70 or less.

[0068] The charge enhancing agent includes at least one hydrocarbon-based charge enhancing agent, which may be a non-fluorine-based charge enhancing agent.

[0069] Examples of the hydrocarbon-based charge enhancer include metal soaps, hindered amine compounds, triazine compounds, clarifying agents, and low molecular weight amide compounds.

[0070] The metal soap may be a fatty acid metal salt, which is believed to effectively trap charges that arrive on the thermoplastic resin composition from, for example, an ion flow emitted from a corona electrode when the thermoplastic resin composition is electretized.

[0071] The number of carbon atoms of the fatty acid in the fatty acid metal salt is preferably 10 to 50, more preferably 12 or more, even more preferably 16 or more, and more preferably 30 or less, even more preferably 22 or less. Examples of the fatty acid include linear saturated fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid; and linear unsaturated fatty acids such as oleic acid and erucic acid. Of these, linear saturated fatty acids are preferred, and stearic acid is more preferred.

[0072] Examples of the metal in the fatty acid metal salt include metals in Group 2 of the periodic table such as magnesium and calcium, metals in Group 12 of the periodic table such as zinc, and metals in Group 13 of the periodic table such as aluminum. Of these, metals in Group 2 of the periodic table are preferred, magnesium or calcium are more preferred, and magnesium is even more preferred.

[0073] The melting point of the fatty acid metal salt is preferably 80° C. or higher, more preferably 100° C. or higher, and may be 300° C. or lower. The thermal decomposition temperature is preferably 200° C. or higher, and may be 300° C. or lower.

[0074] The number of fatty acid chains bound to the metal may be one to three, but two is preferred.

[0075] The metal soap is preferably a Group 2 metal salt of a fatty acid, more preferably a Group 2 metal salt of a linear saturated fatty acid, even more preferably a magnesium salt or calcium salt of a linear saturated fatty acid, even more preferably magnesium stearate or calcium stearate, and particularly preferably magnesium stearate. The metal soap is also preferably a fatty acid magnesium salt.

[0076] Examples of the hindered amine compound include poly[(6-(1,1,3,3-tetramethylbutyl)imino-1,3,5-triazine-2,4-diyl)((2,2,6,6-tetramethyl-4-piperidyl)imino)hexamethylene((2,2,6,6-tetramethyl-4-piperidyl)imino)] (e.g., "Chimassorb" (registered trademark) 944LD, manufactured by BASF Japan Ltd.), dimethyl succinate-1-(2 2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonate bis(1,2,2,6,6-pentamethyl-4-piperidyl) (e.g., TINUVIN (registered trademark) 144, manufactured by BASF Japan Ltd.) and the like.

[0077] The hindered amine compound is preferably one having a triazine structure, and more preferably poly[(6-(1,1,3,3-tetramethylbutyl)imino-1,3,5-triazine-2,4-diyl)((2,2,6,6-tetramethyl-4-piperidyl)imino)hexamethylene((2,2,6,6-tetramethyl-4-piperidyl)imino)] (for example, "Chimassorb" (registered trademark) 944LD, manufactured by BASF Japan Ltd.).

[0078] Examples of the triazine-based compound include poly[(6-(1,1,3,3-tetramethylbutyl)imino-1,3,5-triazine-2,4-diyl)((2,2,6,6-tetramethyl-4-piperidyl)imino)hexamethylene((2,2,6,6-tetramethyl-4-piperidyl)imino)] (e.g., Chimassorb (registered trademark) 944LD, manufactured by BASF Japan Ltd.), and 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-((hexyl)oxy)-phenol (e.g., Tinuvin (registered trademark) 1577FF, manufactured by BASF Japan Ltd.). The triazine-based compound may not have a hindered amine structure.

[0079] The clarifying agent may be a crystal nucleating agent, such as a sorbitol-based nucleating agent, a nonitol-based nucleating agent, a xylitol-based nucleating agent, a phosphoric acid-based nucleating agent, a triaminobenzene derivative nucleating agent, or a metal carboxylate nucleating agent.

[0080] Examples of the sorbitol-based nucleating agent include dibenzylidene sorbitol (DBS), monomethyldibenzylidene sorbitol (e.g., 1,3:2,4-bis(p-methylbenzylidene)sorbitol (p-MDBS)), dimethyldibenzylidene sorbitol (e.g., 1,3:2,4-bis(3,4-dimethylbenzylidene)sorbitol (3,4-DMDBS)), 1,3:2,4-bis-O-(4-methylbenzylidene)-D-sorbitol, and commercially available products thereof include "Millad" (registered trademark) 3988 (manufactured by Milliken Japan Co., Ltd.) and "Gelall" (registered trademark) E-200 (manufactured by New Japan Chemical Co., Ltd.).

[0081] Examples of the nonitol-based nucleating agent include 1,2,3-trideoxy-4,6:5,7-bis-[(4-propylphenyl)methylene]-nonitol, and examples of commercially available products include "Millad" (registered trademark) NX8000 (manufactured by Milliken Japan Co., Ltd.).

[0082] Examples of the xylitol-based nucleating agent include bis-1,3:2,4-(5',6',7',8'-tetrahydro-2-naphthaldehyde benzylidene) 1-allyl xylitol.

[0083] Examples of the phosphoric acid-based nucleating agent include aluminum-bis(4,4',6,6'-tetra-tert-butyl-2,2'-methylenediphenyl-phosphate)-hydroxide, and commercially available products thereof include "ADK STAB" (registered trademark) NA-11 (manufactured by ADEKA CORPORATION) and "ADK STAB" (registered trademark) NA-21 (manufactured by ADEKA CORPORATION).

[0084] Examples of the triaminobenzene derivative nucleating agent include 1,3,5-tris(2,2-dimethylpropanamido)benzene, and examples of commercially available products include "Irgaclear" (registered trademark) XT386 (manufactured by BASF Japan Ltd.).

[0085] Examples of the metal carboxylate nucleating agent include sodium benzoate and calcium salt of 1,2-cyclohexanedicarboxylate.

[0086] The clarifying agent is preferably at least one selected from the group consisting of sorbitol-based nucleating agents, nonitol-based nucleating agents, xylitol-based nucleating agents, phosphoric acid-based nucleating agents, triaminobenzene derivative nucleating agents, and metal carboxylate nucleating agents, more preferably at least one selected from the group consisting of sorbitol-based nucleating agents and phosphoric acid-based nucleating agents, still more preferably a sorbitol-based nucleating agent, and particularly preferably 1,3:2,4-bis-O-(4-methylbenzylidene)-D-sorbitol.

[0087] The low molecular weight amide compound preferably has a molecular weight of 100 to 1,000, more preferably 200 or more, even more preferably 500 or more, and more preferably 800 or less, even more preferably 700 or less. The molecular weight can be determined from the molecular structure (chemical formula).

[0088] Examples of the low molecular weight amide compound include fatty acid amides and fatty acid bisamides.

[0089] The number of carbon atoms of the fatty acid in the fatty acid amide and fatty acid bisamide is preferably 8 to 60, more preferably 10 or more, even more preferably 20 or more, and particularly preferably 30 or more, and is more preferably 50 or less, even more preferably 40 or less. Examples of the fatty acid include linear saturated fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid; branched saturated fatty acids such as isostearic acid; and linear unsaturated fatty acids such as oleic acid and erucic acid. Of these, linear saturated fatty acids are preferred, and stearic acid is more preferred.

[0090] Examples of the fatty acid amide include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, N-lauryllauric acid amide, N-palmitylpalmitic acid amide, N-stearylstearic acid amide, N-stearyl-hydroxystearic acid amide, oleic acid amide, etc. Among these, stearic acid amide is preferred.

[0091] Examples of the fatty acid bisamides include methylene bisstearic acid amide, methylene bislauric acid amide, methylene bishydroxystearic acid amide, ethylene biscaprylic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bisisostearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene Examples thereof include bishydroxystearic acid amide, butylene bishydroxystearic acid amide, N,N'-distearyl adipamide, N,N'-distearyl sebacic acid amide, methylene bisoleic acid amide, ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipamide, N,N'-dioleyl sebacic acid amide, m-xylylene bisstearic acid amide, and N,N'-distearyl isophthalic acid amide. Among these, alkylene bisfatty acid amides such as ethylene bisstearic acid amide are preferred.

[0092] The low molecular weight amide compound is preferably at least one selected from the group consisting of fatty acid amides and fatty acid bisamides, more preferably fatty acid bisamides, even more preferably alkylene bisfatty acid amides, and particularly preferably ethylene bisstearic acid amides.

[0093] The hydrocarbon-based charge enhancer is preferably at least one selected from the group consisting of a metal soap, a hindered amine compound, a triazine compound, a clarifying agent, and a low-molecular-weight amide compound, more preferably at least one selected from the group consisting of a metal soap, a hindered amine compound, a clarifying agent, and a low-molecular-weight amide compound, even more preferably at least one selected from the group consisting of a metal soap and a low-molecular-weight amide compound, and particularly preferably at least one selected from the group consisting of a metal soap and a hindered amine compound, a clarifying agent, and a low-molecular-weight amide compound. Also preferred is at least one selected from the group consisting of a metal soap and a hindered amine compound, a clarifying agent, and a low-molecular-weight amide compound.

[0094] When the hydrocarbon-based charge enhancer is the metal soap and the low-molecular-weight amide compound, the mass ratio of the metal soap to the low-molecular-weight amide compound (metal soap / low-molecular-weight amide) is preferably 30 / 70 to 99 / 1, in order to further improve collection performance. This mass ratio is more preferably 40 / 60 or more, even more preferably 50 / 50 or more, even more preferably 60 / 40 or more, and particularly preferably 70 / 30 or more. This mass ratio is also more preferably 95 / 5 or less, even more preferably 90 / 10 or less, and particularly preferably 85 / 15 or less. When the hydrocarbon-based charge enhancer is the metal soap and the hindered amine compound, the mass ratio of the metal soap to the hindered amine compound, and when the hydrocarbon-based charge enhancer is the metal soap and the clarifying agent, the mass ratio of the metal soap to the clarifying agent are also preferably within the above-mentioned ranges.

[0095] In the electret material of the present disclosure, the mass ratio (fluorine / hydrocarbon) of the fluorine-based charge enhancer to the hydrocarbon-based charge enhancer is preferably 1 / 99 to 99 / 1, in order to further improve collection performance. The mass ratio is more preferably 10 / 90 or more, even more preferably 20 / 80 or more, even more preferably 30 / 70 or more, and particularly preferably 40 / 60 or more. The mass ratio is also more preferably 90 / 10 or less, even more preferably 80 / 20 or less, even more preferably 70 / 30 or less, and particularly preferably 60 / 40 or less.

[0096] In the electret material of the present disclosure, in order to further improve collection performance, the total amount of the charge enhancers, i.e., the total amount of the fluorine-based charge enhancer and the hydrocarbon-based charge enhancer, is preferably 0.01 to 5.0% by mass relative to the thermoplastic resin. This total amount is more preferably 0.10% by mass or more, even more preferably 0.20% by mass or more, even more preferably 0.30% by mass or more, and particularly preferably 0.40% by mass or more. This total amount is also more preferably 1.0% by mass or less, even more preferably 0.8% by mass or less, even more preferably 0.7% by mass or less, and particularly preferably 0.6% by mass or less.

[0097] The charge enhancer is contained in the thermoplastic resin. Since an electret material having such a configuration can be produced by mixing the thermoplastic resin and the charge enhancer, there is no need to attach the charge enhancer by post-processing such as vapor deposition or impregnation, which simplifies the production process. It is also possible to prevent a decrease in collection performance due to peeling of the charge enhancer from the surface. The charge enhancer may be dispersed in the thermoplastic resin.

[0098] In the electret material of the present disclosure, the ratio of the F element content to the C element content (F / C) on the surface of the electret material measured by XPS (X-ray photoelectron spectroscopy) is preferably 0.20% or less, more preferably 0.10% or less, and even more preferably 0.03% or less, and is preferably 0.0005% or more, more preferably 0.0006% or more, and even more preferably 0.0008% or more. The fact that the ratio (F / C) is within the above range indicates that the charge enhancer is contained in the thermoplastic resin (the charge enhancer is not attached to the surface by post-processing). The ratio (F / C) can be calculated using the value obtained by XPS (X-ray photoelectron spectroscopy) measurement using the following method: Ratio (F / C) = A / B A: Peak area value of F element B: Peak area value of C element

[0099] The electret material of the present disclosure may contain other components within a range that does not impair the effects. Examples of the other components include matting agents, pigments, mildew inhibitors, antibacterial agents, flame retardants, heat stabilizers, weather resistance agents, and polymerization inhibitors.

[0100] The electret material of the present disclosure can be produced by mixing the thermoplastic resin, the charge enhancer, and, if necessary, other components to prepare a resin composition, and then subjecting the resin composition to an electret treatment. The thermoplastic resin and the charge enhancer may be mixed by mixing a masterbatch containing the thermoplastic resin and the charge enhancer with the thermoplastic resin. The masterbatch will be described later. The resin composition may be processed into a desired shape before and / or after the electret treatment.

[0101] The method for mixing the thermoplastic resin and the charge enhancer is preferably melt-kneading. When the masterbatch is used, it is preferable to melt-knead the masterbatch and the thermoplastic resin. The melt-kneading may be carried out by a known method, for example, using a single-screw or twin-screw extruder, an open roll, a kneader, a Banbury mixer, or the like. The melt-kneading temperature is preferably higher than the melting point of the thermoplastic resin, and more preferably 5°C or more higher than the melting point of the thermoplastic resin.

[0102] The electret treatment method can be arbitrarily selected from known charging methods such as corona charging, liquid contact charging, friction charging, electric field charging, hot electric field charging, electron beam irradiation, etc. Specific electretization methods that can be preferably used include those based on electrical action such as polarization by high voltage, collision of charged ions, injection of charged particles, etc.; those based on interaction with solids such as friction and collision; and those utilizing contact and collision with a liquid.

[0103] The shape of the electret material of the present disclosure is not particularly limited, and may be fibrous, sheet-like, film-like, particle-like, rod-like, pipe-like, or the like.

[0104] The electret material of the present disclosure is preferably in the form of fibers, and more preferably in the form of a fiber sheet.

[0105] The average fiber diameter of the fibers constituting the fiber sheet is preferably 0.001 μm or more, more preferably 0.1 μm or more, even more preferably 0.2 μm or more, and particularly preferably 0.5 μm or more. It is also preferably 100 μm or less, more preferably 20 μm or less, even more preferably 10 μm or less, and particularly preferably 5 μm or less. If the average fiber diameter of the fibers is thicker than 100 μm, it is difficult to achieve a practical collection efficiency, and the efficiency decreases significantly during charge decay. If the average fiber diameter of the fibers is thinner than 0.001 μm, it is difficult to produce a charged electret. The average fiber diameter is measured as follows. An arbitrary 25 μm × 20 μm region is observed in an electron micrograph taken at 5000x magnification using a scanning electron microscope (product name: SU8020, manufactured by Hitachi Corporation), and lines intersecting vertically and horizontally are drawn. The diameters of all fibers crossing each line are measured with a ruler and converted to a scale to determine the fiber diameter (μm). Next, the cumulative frequency distribution of the determined fiber diameters is plotted in a log-normal manner on a logarithmic probability paper, with fiber diameter on the horizontal axis and cumulative frequency on the vertical axis. The value at which the cumulative frequency is 50% is defined as the average fiber diameter (median diameter).

[0106] The fiber sheet may be a homogeneous product made from a single manufacturing method and material, or may be a mixture made from two or more materials that are different in manufacturing method, material, and fiber diameter.

[0107] The basis weight of the fiber sheet is set to 3 g / m from the viewpoint that an electret fiber sheet excellent in breathability and collection properties can be obtained. ２ It is preferable that the content is 5 g / m or more. ２ More preferably, it is 10 g / m or more. ２ It is more preferable that the density is 100 g / m or more. ２ Preferably, it is 70 g / m or less. ２ More preferably, it is 50 g / m or less. ２ It is more preferable that:

[0108] The thickness of the fiber sheet is preferably 0.01 mm or more, more preferably 0.05 mm or more, and even more preferably 0.1 mm or more, from the viewpoint of obtaining an electret fiber sheet having excellent breathability and collection properties, and is preferably 1.0 mm or less, more preferably 0.7 mm or less, and even more preferably 0.5 mm or less.

[0109] The fiber sheet is preferably a nonwoven fabric. Methods for obtaining the nonwoven fabric include sheeting short fibers such as single-component fibers, composite fibers such as core-sheath fibers and side-by-side fibers, and split fibers using carding, airlaid, wet papermaking, etc., and sheeting continuous fibers using spunbonding, melt-blowing, electrospinning, force spinning, etc. Among these, melt-blowing, electrospinning, and force spinning are preferred, as they can easily obtain dense and fine fibers from the viewpoint of effectively utilizing the mechanical collection mechanism. The melt-blowing, melt electrospinning, and melt force spinning are more preferred, and the melt-blowing method is even more preferred, as they do not require treatment of residual solvents. The fiber sheet is preferably a melt-blown nonwoven fabric.

[0110] The electret material of the present disclosure, preferably the fiber sheet, has excellent collection performance and can be suitably used in filters. The present disclosure also relates to a filter using the electret material of the present disclosure. The filter of the present disclosure can be used for purposes such as dust collection, protection, and ventilation in dust masks, various air conditioning elements, air purifiers, cabin filters, and various devices. In particular, it can be suitably used in dust masks.

[0111] The present disclosure also relates to a masterbatch for producing an electret material, comprising a thermoplastic resin and a charge enhancing agent contained in the thermoplastic resin, wherein the charge enhancing agent comprises at least one fluorine-based charge enhancing agent selected from the group consisting of polytetrafluoroethylene and vinylidene fluoride polymers, and at least one hydrocarbon-based charge enhancing agent, and the total amount of the charge enhancing agent is greater than 5.0% by mass and less than or equal to 50% by mass of the thermoplastic resin.

[0112] As the thermoplastic resin in the masterbatch of the present disclosure, the same thermoplastic resins that can be used in the electret material of the present disclosure can be used.

[0113] The charge enhancer in the masterbatch of the present disclosure can be the same as the charge enhancer that can be used in the electret material of the present disclosure. In addition, the preferred combination of charge enhancers and the preferred ratio when combining them can also be the same as those in the electret material of the present disclosure.

[0114] In the masterbatch of the present disclosure, the total amount of the charge enhancer is more than 5.0% by mass and not more than 50% by mass, more preferably not less than 10% by mass, even more preferably not less than 15% by mass, and more preferably not more than 40% by mass, even more preferably not more than 30% by mass, relative to the thermoplastic resin.

[0115] The masterbatch of the present disclosure may contain other components as needed. Examples of other components include the same components as those that can be contained in the electret material of the present disclosure.

[0116] The masterbatches of the present disclosure may be non-electret, but may also be electret.

[0117] The masterbatch of the present disclosure can be produced by mixing the thermoplastic resin, the charge enhancer, and other components as needed, using a single-screw or twin-screw extruder, an open roll, a kneader, a Banbury mixer, or the like.

[0118] The masterbatch of the present disclosure may be in any form, such as powder, granules, or pellets, but is preferably in the form of pellets obtained by melt-kneading, in that the charge-enhancing agent is maintained in a finely dispersed state in the thermoplastic resin. The melt-kneading temperature is preferably higher than the melting point of the thermoplastic resin, and more preferably 5°C or more higher than the melting point of the thermoplastic resin.

[0119] The masterbatch of the present disclosure is used to produce an electret material. The masterbatch may be used to produce an electret material containing a thermoplastic resin and a charge-enhancing agent contained in the thermoplastic resin, and is preferably used to produce the electret material of the present disclosure described above.

[0120] The present disclosure will now be described in more detail with reference to examples, but the present disclosure is not limited to these examples.

[0121] In the examples and comparative examples, the following raw materials were used.

[0122] <Thermoplastic resin> Polypropylene (PP) (MFR: 1500 g / 10 min)

[0123] <Fluorine-based electrostatic charge enhancer> PTFE: low molecular weight PTFE (average particle size: 4 μm, melt viscosity: 5.0×10 ４ Pa s, melting point: 329°C. VdF polymer 1: VdF / TFE copolymer (VdF / TFE (molar ratio) = 81 / 19, weight average molecular weight: 1,300,000). VdF polymer 2: A mixture of PVdF (weight average molecular weight: 1,850,000) and VdF / TFE copolymer (VdF / TFE (molar ratio) = 81 / 19, weight average molecular weight: 1,300,000) in a mass ratio of 75 / 25.

[0124] <Hydrocarbon-based electrostatic charge enhancer> Metal soap 1: magnesium stearate (StMg) Metal soap 2: calcium stearate Low-molecular-weight amide compound 1: ethylene bisstearylamide (EBS) Low-molecular-weight amide compound 2: stearic acid amide Hindered amine compound: poly[(6-(1,1,3,3-tetramethylbutyl)imino-1,3,5-triazine-2,4-diyl)((2,2,6,6-tetramethyl-4-piperidyl)imino)hexamethylene((2,2,6,6-tetramethyl-4-piperidyl)imino)] Clarifying agent: 1,3:2,4-bis-O-(4-methylbenzylidene)-D-sorbitol

[0125] Various physical properties were measured by the following methods.

[0126] <Surface Measurement by XPS (X-ray Photoelectron Spectroscopy)> The surface of the obtained electret fiber sheet was measured by XPS (X-ray Photoelectron Spectroscopy) using the following method. For the measurement, an ESCA3400 (manufactured by Shimadzu Corporation) was used. MgKα radiation (1253.6 eV) was used as the radiation source, and the measurement was performed under the conditions of a measurement area diameter of approximately 3 mm and a detection depth of approximately 7 nm (photoelectron take-off angle 90°). [Ratio (F / C)] This was calculated using the values ​​obtained by XPS (X-ray Photoelectron Spectroscopy) measurement using the following method. Ratio (F / C) = A / B A: Peak area value of F element B: Peak area value of C element

[0127] <Evaluation of Collection Performance> After storing the electret fiber sheet in a thermo-hygrostat (temperature 38°C, humidity 85%) for 25 hours, the collection performance was evaluated under the following conditions. (Pressure Loss) A measurement sample of the electret fiber sheet was placed on a sheet having an effective area of ​​65 cm ２The fiber sheet was set in a filter holder, the inlet side was pressurized with a compressor, and the air flow rate was adjusted to 9.6 cm / sec using a flow meter. The pressure loss at this time was measured with a manometer. (Collection Efficiency of NaCl Particles with a Particle Diameter of 0.3 μm) According to the method described in JIS B9928, Appendix 5 (Regulations), "Method for Generating NaCl Aerosol (Pressure Spray Method)," NaCl particles generated by an atomizer were classified to a particle diameter of 0.3 μm using an electrostatic classifier (TSI). After neutralizing the particle charge with americium-241, the flow rate was adjusted to 9.6 cm / sec. The particle counts before and after the fiber sheet (measurement sample) were determined using a particle counter (TSI, CNC), and the collection efficiency was calculated using the following formula. The initial collection efficiency was measured using a fiber sheet that had not yet been used. Transmittance (%) = (CO / CI) x 100 Collection efficiency (%) = 100 - transmittance (%) CO = number of 0.3 µm NaCl particles counted on the downstream side of the measurement sample (rear side of the fiber sheet) CI = number of 0.3 µm NaCl particles counted on the upstream side of the measurement sample (front side of the fiber sheet) (PF Value of NaCl Particles with a Particle Diameter of 0.3 µm) Using NaCl particles with a particle diameter of 0.3 µm, the PF value was calculated from the pressure loss and collection efficiency (collection efficiency of NaCl particles with a particle diameter of 0.3 µm) of the electret fiber sheet according to the following formula: PF value = {-log((100 - collection efficiency (%)) / 100)} / (pressure loss (Pa) / 1000)

[0128] Examples 1 to 18 [Preparation of Masterbatch] PP and the charge enhancer shown in Table 1 or 2 were mixed so that the total amount of charge enhancer was 10 mass % relative to the PP, and the mixture was put into a twin-screw extruder (Labo Plastomill 30C150, manufactured by Toyo Seiki Seisaku-sho, Ltd.) and melt-kneaded to obtain masterbatch pellets. [Preparation of electret fiber sheet] PP and the master batch prepared above were mixed so that the charge enhancer was blended in the amount shown in Table 1 or 2 relative to 100 parts by mass of PP, and the mixture was charged into the raw material hopper of a spinning machine. Using a die (hole pitch: 0.9 mm, number of holes: 275 holes, width: 250 mm) in which every other nozzle hole with a diameter of 0.2 mm was arranged in a straight line, the mixture was sprayed by a melt-blowing method under the conditions of a polymer discharge rate of 500 g / hour, a nozzle temperature of 220°C, and an air pressure of 0.15 MPa, and the collection conveyor speed was adjusted to obtain an electret fiber sheet having a basis weight of 25 g / m ２ A nonwoven fabric sheet of the above formula was obtained. The obtained melt-blown nonwoven fabric sheet was subjected to a corona charging treatment to obtain an electret fiber sheet. The obtained electret fiber sheet was evaluated by the above-mentioned methods. The results are shown in Tables 1 and 2.

[0129] Comparative Example 1 An electret fiber sheet was prepared using only PP in the same manner as in Example 1, and evaluated. The results are shown in Table 1.

[0130] Comparative Examples 2 to 5 Electret fiber sheets were prepared and evaluated in the same manner as in the Examples, except that the charge enhancers shown in Table 1 were used. The results are shown in Table 1.

[0131]

[0132]

Claims

1. An electret material comprising a thermoplastic resin and a charge enhancing agent contained in the thermoplastic resin, The electret material includes a fluorine-based charge enhancer that is a polytetrafluoroethylene and vinylidene fluoride polymer, and at least one hydrocarbon-based charge enhancer.

2. 2. The electret material of claim 1, wherein the fluorine-based charge enhancing agent is a low molecular weight polytetrafluoroethylene and vinylidene fluoride polymer.

3. 3. The electret material according to claim 1, wherein the vinylidene fluoride polymer is at least one selected from the group consisting of polyvinylidene fluoride and vinylidene fluoride / tetrafluoroethylene copolymer.

4. The electret material according to claim 1 or 2, wherein the hydrocarbon-based charge enhancer is at least one selected from the group consisting of metal soaps, hindered amine compounds, triazine compounds, clarifying agents, and low molecular weight amide compounds.

5. The electret material according to claim 1 or 2, wherein the hydrocarbon-based charge enhancing agent is a metal soap or a low molecular weight amide compound.

6. The electret material according to claim 4 , wherein the metal soap is a salt of a metal in Group 2 of the Periodic Table of fatty acids.

7. The electret material according to claim 4 , wherein the low molecular weight amide compound is at least one selected from the group consisting of fatty acid amides and fatty acid bisamides.

8. 3. The electret material according to claim 1, wherein the mass ratio of the fluorine-based charge enhancer to the hydrocarbon-based charge enhancer (fluorine-based / hydrocarbon-based) is 1 / 99 to 99 / 1.

9. The electret material according to claim 1 or 2, wherein the thermoplastic resin is a polyolefin resin.

10. 3. The electret material according to claim 1 or 2, wherein the ratio (F / C) of the F element content to the C element content on the surface of the electret material measured by XPS (X-ray photoelectron spectroscopy) is 0.20% or less.

11. 3. The electret material according to claim 1, wherein the total amount of the charge enhancer is 0.01 to 5.0% by mass relative to the thermoplastic resin.

12. 3. The electret material according to claim 1, which is a fiber sheet.

13. A filter using the electret material according to claim 1 or 2.

14. 14. The filter according to claim 13, which is for a dust mask.

15. A masterbatch for producing an electret material, comprising: A thermoplastic resin and a charge enhancing agent contained in the thermoplastic resin, the charge enhancer includes a fluorine-based charge enhancer that is a polytetrafluoroethylene and vinylidene fluoride polymer, and at least one hydrocarbon-based charge enhancer; The total amount of the electrostatic charge enhancer is more than 5.0% by mass and not more than 50% by mass relative to the thermoplastic resin.