WO2017065192A1 - Porous film - Google Patents

Porous film Download PDF

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Publication number
WO2017065192A1
WO2017065192A1 PCT/JP2016/080294 JP2016080294W WO2017065192A1 WO 2017065192 A1 WO2017065192 A1 WO 2017065192A1 JP 2016080294 W JP2016080294 W JP 2016080294W WO 2017065192 A1 WO2017065192 A1 WO 2017065192A1
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WO
WIPO (PCT)
Prior art keywords
porous film
weight
vinyl aromatic
film
stretching
Prior art date
Application number
PCT/JP2016/080294
Other languages
French (fr)
Japanese (ja)
Inventor
俊介 小井土
昌幸 瀬尾
根本　友幸
Original Assignee
三菱樹脂株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
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Application filed by 三菱樹脂株式会社 filed Critical 三菱樹脂株式会社
Publication of WO2017065192A1 publication Critical patent/WO2017065192A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/24—Rubbers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/26—Polyalkenes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/26—Polyalkenes
    • B01D71/261—Polyethylene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/26—Polyalkenes
    • B01D71/262—Polypropylene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/28—Polymers of vinyl aromatic compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/28—Polymers of vinyl aromatic compounds
    • B01D71/281—Polystyrene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
    • C08L23/04—Homopolymers or copolymers of ethene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L25/00—Compositions of, homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Compositions of derivatives of such polymers
    • C08L25/02—Homopolymers or copolymers of hydrocarbons
    • C08L25/04—Homopolymers or copolymers of styrene
    • C08L25/08—Copolymers of styrene
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a porous film.
  • the porous film of the present invention can be used as a packaging product, sanitary product, livestock product, agricultural product, building product, medical product, light diffusion plate, reflection sheet, battery separator, or separation membrane.
  • the porous film of the present invention is suitably used as a filtration membrane used in the food-related field, pharmaceutical / cosmetic field, chemical industry field, and electronics industry field.
  • the present invention also relates to a water treatment filter provided with the porous film.
  • Filtration operations using porous films such as microfiltration membranes and ultrafiltration membranes include automotive industry (electrodeposition paint collection and reuse system), semiconductor industry (ultra pure water production), pharmaceutical and food industry (sanitization, enzyme purification), etc. has been put to practical use in many fields. In particular, in recent years, it has been frequently used as a technique for producing drinking water and industrial water by turbidizing river water and the like.
  • a wide variety of materials such as cellulose, polyacrylonitrile, and polyolefin are used as the material of the membrane.
  • polyolefin polymers (polyethylene, polypropylene, polyvinylidene fluoride, etc.) are suitable as a material for aqueous filtration membranes because they are hydrophobic and have high water resistance, and are widely used.
  • polyolefin-based polymers it does not contain halogen elements that cause problems during disposal, and since there are few tertiary carbon atoms with high chemical reactivity, chemical degradation during film cleaning hardly occurs, and long-term durability can be expected.
  • Polyethylene which is inexpensive and inexpensive, is considered particularly promising in the future.
  • Patent Document 1 discloses that a porous film is obtained by biaxially stretching a sheet containing a polypropylene resin and a polyolefin / polystyrene elastomer.
  • Patent Document 2 discloses a method of obtaining a porous film by stretching a film made of a resin composition containing high molecular weight polyethylene, high density polyethylene and a filler.
  • Patent Document 3 a mixture containing a composition composed of ultrahigh molecular weight polyethylene and high-density polyethylene and a film-forming solvent is extruded and stretched, and then the film-forming solvent is extracted and removed with an organic solvent, and dried. A method for producing a porous film is disclosed.
  • Patent Document 4 a high-density polyethylene is filled with an inorganic filler at a high ratio, an elastomer component is added to improve stretchability, and a porous structure that achieves both moisture permeability and air permeability and liquid resistance by stretching.
  • a film is disclosed.
  • Patent Document 1 describes that a polypropylene resin is used as a film material, but from the value of the air permeability of the Examples of Patent Document 1, the air permeability of the obtained porous film is low, and as a filtration membrane When used, the filtration rate is significantly lower.
  • the porous film described in Patent Document 4 is a porous film stretched and peeled at the interface between the polyethylene resin and the inorganic filler, and since the inorganic filler is added at a high rate, when used as a filtration membrane, Desorption of the inorganic filler occurs and there is a concern about elution into the filtrate. Moreover, since it is a film considering liquid permeation resistance, the air permeation performance is low, and when used as a filtration membrane, the filtration rate is remarkably low.
  • the present invention has a high porosity, excellent air permeability, and is used in the automobile industry (electrodeposition paint recovery and reuse system), semiconductor industry (ultra pure water production), pharmaceutical / food industry (sanitization, enzyme purification), etc.
  • An object of the present invention is to provide a polyethylene porous film excellent in filtration speed, filtration life, and filtration accuracy that is useful as a filtration membrane to be used at low cost and with high productivity.
  • the gist of the present invention is as follows.
  • the first invention includes 55 to 85 parts by weight of a polyethylene resin (A) having a density of 0.955 to 0.970 g / cm 3 and 15 to 45 parts by weight of a vinyl aromatic elastomer (B) ( However, the total of the polyethylene resin (A) and the vinyl aromatic elastomer (B) is 100 parts by weight.),
  • the porosity is 50% or more, and the air permeability is 200 seconds / 100 ml or less.
  • a porous film characterized by
  • the second invention is a porous film according to the first invention, wherein the vinyl aromatic elastomer (B) has a melt flow rate (MFR) of 1 g / 10 min or less at a temperature of 230 ° C. and a load of 2.16 kg.
  • MFR melt flow rate
  • a third invention is the porous film according to the first or second invention, wherein the polyethylene resin (A) has a melt flow rate (MFR) of 0.1 to 10 g / 10 min at a temperature of 190 ° C. and a load of 2.16 kg, It is.
  • MFR melt flow rate
  • a fourth invention is a porous film having a thickness of 70 ⁇ m or more in any one of the first to third inventions.
  • the fifth invention provides a porous film which is a biaxially stretched film in any one of the first to fourth inventions.
  • 0% of the crystal nucleating agent (C) is added to 100 parts by weight of the total of the polyethylene resin (A) and the vinyl aromatic elastomer (B).
  • a porous film comprising 0.001 to 10 parts by weight is provided.
  • the styrene-ethylene in which the vinyl aromatic elastomer (B) has a content of structural units derived from the vinyl aromatic compound of 10 to 40% by weight is provided.
  • a liquid filter comprising the porous film according to any one of the first to seventh inventions.
  • the porous film of the present invention is useful as a filtration membrane used in the automobile industry (electrodeposition paint recovery and reuse system), semiconductor industry (ultra pure water production), pharmaceutical / food industry (sanitization, enzyme purification), etc. .
  • the main component in the present invention is a component that is contained in the largest amount, and is a component that is usually contained in an amount of 50% by weight or more, preferably 70% by weight or more, and more preferably 80% by weight or more.
  • the porous film of the present invention contains 55 to 85 parts by weight of polyethylene resin (A) having a density of 0.955 to 0.970 g / cm 3 and 15 to 45 parts by weight of vinyl aromatic elastomer (B). (However, the total of the polyethylene resin (A) and the vinyl aromatic elastomer (B) is 100 parts by weight.),
  • the porosity is 50% or more, and the air permeability is 200 seconds / 100 ml or less. .
  • the porous film of the present invention is obtained by, for example, stretching an unstretched sheet formed using a polyethylene resin composition mainly composed of a polyethylene resin (A) and a vinyl aromatic elastomer (B) in at least a uniaxial direction. It is manufactured by making it porous.
  • the polyethylene resin composition used for the production of the porous film of the present invention may be referred to as “the polyethylene resin composition of the present invention”.
  • the porous film of the present invention is a polyethylene resin (A) that is a sea part and an island part in the stretching process of a sheet in which the sea part is a polyethylene resin (A) and the island part is a vinyl aromatic elastomer (B). It is manufactured by concentrating stress on the interface of the vinyl aromatic elastomer (B) to form a void and making it porous. Since the porous film of the present invention has a large number of fine pores having a uniform pore diameter, it is easy to form communication holes, and as a result, the film has a high porosity and low air permeability and excellent air permeability.
  • the porous film produced by stretching an unstretched sheet containing a high proportion of inorganic fillers such as barium sulfate and calcium carbonate was stretched and peeled at the interface between the base resin and the inorganic filler. It is a porous film. For this reason, stretching unevenness occurs due to the aggregation of the inorganic filler, and it is considered that it is difficult to form the communication holes as compared with the porous film of the present invention due to the nonuniformity of the size of the holes and the variation of the hole formation. Therefore, it becomes a porous structure with a low rate of pore formation and a film with poor air permeability.
  • the porous film of the present invention is a biaxially stretched film
  • the porous structure can be controlled, the porosity is high, and the film has excellent air permeability.
  • the porous film of the present invention contains the crystal nucleating agent (C), it becomes easier to form a denser and more uniform porous structure, and the film tends to have a low air permeability and excellent air permeability by stretching.
  • C crystal nucleating agent
  • the polyethylene-based resin (A) is a polymer or copolymer mainly composed of a structural unit derived from ethylene (hereinafter sometimes referred to as “ethylene unit”).
  • ethylene unit a structural unit derived from ethylene
  • the ethylene unit is 90 wt% of all structural units. % Of polyethylene.
  • polyethylene-based resins do not contain halogen elements that cause problems during disposal, and do not contain highly reactive functional groups or atoms, so chemical degradation occurs during membrane cleaning. It is difficult to expect long-term use resistance.
  • the polyethylene resin (A) may be a homopolymer of ethylene, and is a structural unit derived from ⁇ -olefin and 90% by weight or more of ethylene units (hereinafter referred to as “ ⁇ -olefin unit”). It may be a copolymer of 10% by weight or less.
  • the ⁇ -olefin used when the polyethylene resin (A) is a copolymer is propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4- Examples thereof include one or more of methyl-1-pentene, 3-methyl-1-pentene and the like.
  • polyethylene resin (A) examples include ultra high molecular weight polyethylene, high density polyethylene, medium density polyethylene, branched low density polyethylene, and chain low density polyethylene.
  • High-density polyethylene is preferable from the viewpoints of crystallinity, mechanical strength, and economy.
  • Polyethylene resin (A) has a density and mandatory that the 0.955 ⁇ 0.970g / cm 3, is preferably 0.955 ⁇ 0.965g / cm 3.
  • the density of the polyethylene-based resin (A) is less than 0.955 g / cm 3 , the resulting porous film has few crystal parts, so that it is difficult to form a target porous structure, and excellent filtration performance is satisfied. A porous film having porosity cannot be formed.
  • the density of the polyethylene-based resin (A) exceeds 0.970 g / cm 3 , since there are too many crystal parts, a porous film with uneven stretching is obtained.
  • the melt flow rate (MFR) of the polyethylene resin (A) is not particularly limited, but usually the MFR is preferably 0.1 to 10 g / 10 minutes, and preferably 0.2 to 5 g / 10 minutes. More preferably. When the MFR of the polyethylene resin (A) is 0.1 g / 10 min or more, the polyethylene resin (A) has a sufficient melt viscosity at the time of molding and can ensure high productivity. When the MFR of the polyethylene resin (A) is 10 g / 10 min or less, a porous film having sufficient strength can be obtained.
  • the density of the polyethylene resin (A) is measured by an underwater substitution method in accordance with JIS K7112.
  • the MFR of the polyethylene resin (A) is measured in accordance with JIS K7210 under conditions of a temperature of 190 ° C. and a load of 2.16 kg.
  • the polyethylene-based resin (A) may be used alone or in combination of two or more types having different physical properties such as structural units, density, and MFR.
  • Vinyl aromatic elastomer (B) In the present invention, it is important that the vinyl aromatic elastomer (B) is contained in a predetermined ratio with respect to the polyethylene resin (A). By including the vinyl aromatic elastomer (B), a fine and highly uniform porous structure can be efficiently obtained, and the shape and diameter of the pores can be easily controlled.
  • the vinyl aromatic elastomer (B) is a kind of thermoplastic elastomer containing a structural unit derived from a vinyl aromatic compound such as styrene, and a soft component (for example, a structural unit derived from butadiene) and a hard component (for example, styrene). It is a copolymer consisting of a continuum with the derived structural unit.
  • copolymer examples include a random copolymer, a block copolymer, and a graft copolymer.
  • various block copolymers such as a linear block structure and a radial branched block structure are known. Any structure may be used in the present invention.
  • the vinyl aromatic elastomer (B) preferably has a melt flow rate (MFR) of 1 g / 10 min or less at a temperature of 230 ° C. and a load of 2.16 kg. This is because the vinyl aromatic elastomer (B) dispersed in the polyethylene resin composition of the present invention changes in shape due to the difference in viscosity from the polyethylene resin (A), but the MFR is below the above upper limit. This is because the shape tends to be spherical. Unlike the domain having a large aspect ratio, the spherically dispersed domain is preferable because the uniformity of the porous structure obtained by the subsequent stretching step tends to be high and the physical property stability is excellent.
  • MFR melt flow rate
  • the MFR is not more than the above upper limit, in the stretching step, stress tends to concentrate on the matrix interface having a high modulus of elasticity and the domain interface portion having a low modulus of elasticity.
  • the minimum of MFR of a vinyl aromatic elastomer (B) Usually, it is 0.01 g / 10min or more.
  • the MFR of the vinyl aromatic elastomer (B) is measured under conditions of a temperature of 230 ° C. and a load of 2.16 kg according to JIS K7210.
  • the content of structural units derived from a vinyl aromatic compound such as styrene is preferably 10 to 40% by weight, and more preferably 15 to 35% by weight. Domains are effectively formed in the polyethylene resin composition of the present invention by the content of structural units derived from vinyl aromatic compounds such as styrene in the vinyl aromatic elastomer (B) being 10% by weight or more. can do.
  • the content of the structural unit derived from the vinyl aromatic compound such as styrene in the vinyl aromatic elastomer (B) is 40% by weight or less, excessively large domain formation can be suppressed.
  • the specific type of vinyl aromatic elastomer (B) is not particularly limited, but styrene-butadiene block copolymer (SBR), hydrogenated styrene-butadiene block copolymer (SEB), and styrene-butadiene-styrene block copolymer.
  • SBR styrene-butadiene block copolymer
  • SEB hydrogenated styrene-butadiene block copolymer
  • styrene-butadiene-styrene block copolymer styrene-butadiene block copolymer
  • SBS Styrene-butadiene-butylene-styrene block copolymer
  • SEBS Styrene-ethylene-butadiene-styrene block copolymer
  • SIR Styrene-ethylene -Propylene block copolymer
  • SEP styrene-isoprene-styrene block copolymer
  • SIS styrene-ethylene-propylene-styrene block copolymer
  • SEEPS styrene-ethylene-ethylene-propylene-styrene block And a copolymer
  • the compatibility with the polyethylene resin (A) is high.
  • Those containing an ethylene component and a butadiene component are preferred.
  • styrene-ethylene-propylene block copolymer (SEP) styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-ethylene-butadiene- Styrene block copolymer (SEBS) is more preferred.
  • vinyl aromatic elastomer (B) one kind may be used alone, or two or more kinds having different physical properties such as the kind and ratio of the soft component and the hard component, the copolymer structure, and MFR may be mixed and used. Good.
  • Ratio of polyethylene resin (A) and vinyl aromatic elastomer (B) The ratio of polyethylene resin (A) and vinyl aromatic elastomer (B) contained in the porous film of the present invention is as follows. 85 parts by weight, vinyl aromatic elastomer (B) 15-45 parts by weight, preferably polyethylene resin (A) 60-80 parts by weight, vinyl aromatic elastomer (B) 20-40 parts by weight (provided that 100 parts by weight in total of the polyethylene resin (A) and the vinyl aromatic elastomer (B)).
  • the ratio of the polyethylene resin (A) and the vinyl aromatic elastomer (B) contained in the polyethylene resin composition of the present invention is 55 to 85 parts by weight of the polyethylene resin (A), the vinyl aromatic elastomer (B). 15 to 45 parts by weight, preferably 60 to 80 parts by weight of the polyethylene resin (A) and 20 to 40 parts by weight of the vinyl aromatic elastomer (B) (however, the polyethylene resin (A) and the vinyl aromatic elastomer) 100 parts by weight in total with (B)).
  • the polyethylene resin (A) is 85 parts by weight or less and the vinyl aromatic elastomer (B) is 15 parts by weight or more, porosity due to stretching is likely to occur, and by ensuring a sufficient air layer, air permeability An improvement in performance can be expected.
  • the polyethylene resin (A) is 55 parts by weight or more and the vinyl aromatic elastomer (B) is 45 parts by weight or less, the vinyl aromatic elastomers (B) in the polyethylene resin composition of the present invention aggregate together. It becomes easy to occur, and it becomes hard to produce the porosity by extending
  • porous film of the present invention and the polyethylene resin composition of the present invention include those other than the polyethylene resin (A) and the vinyl aromatic elastomer (B), as long as the effects of the present invention are not impaired. You may contain other resin other than a component, for example, polyethylene-type resin (A).
  • resins include polyolefin resins, polystyrene resins, polyvinyl chloride resins, polyvinylidene chloride resins, chlorinated polyethylene resins, polyester resins, polycarbonate resins, polyamide resins, polyacetal resins, acrylic resins.
  • Resin ethylene vinyl acetate copolymer, polymethylpentene resin, polyvinyl alcohol resin, cyclic olefin resin, polylactic acid resin, polybutylene succinate resin, polyacrylonitrile resin, polyethylene oxide resin, cellulose resin , Polyimide resin, polyurethane resin, polyphenylene sulfide resin, polyphenylene ether resin, polyvinyl acetal resin, polybutadiene resin, polybutene resin, polyamideimide resin, polyamide Sumerimide resin, polyarylate resin, polyetherimide resin, polyetheretherketone resin, polyetherketone resin, polyethersulfone resin, polyketone resin, polysulfone resin, aramid resin, fluorine resin, etc. Is mentioned. These may be used individually by 1 type and may be used in combination of 2 or more type.
  • the porous film of the present invention and the polyethylene resin composition of the present invention appropriately contain additives generally incorporated in the resin composition within a range that does not significantly impair the effects of the present invention. Also good.
  • the content thereof is preferably 0.0001 to 10.0 parts by weight with respect to 100 parts by weight in total of the polyethylene resin (A) and the vinyl aromatic elastomer (B). More preferably, it is 0.002 to 5.0 parts by weight.
  • Additives include recycled resins generated from trimming loss such as ears, pigments such as carbon black, crystal nucleating agents, etc., added for the purpose of improving and adjusting molding processability, productivity, and various physical properties of the porous film. Flame retardants, weather resistance stabilizers, heat stabilizers, antistatic agents, melt viscosity improvers, crosslinking agents, lubricants, plasticizers, anti-aging agents, antioxidants, light stabilizers, UV absorbers, neutralizing agents, Additives such as anti-fogging agents, anti-blocking agents, slip agents, colorants, molecular adsorbents and the like can be mentioned. Among these, it is preferable to further contain the crystal nucleating agent described below.
  • Crystal nucleating agent (C) The polyethylene resin composition of the present invention preferably further contains a crystal nucleating agent (C). By containing the crystal nucleating agent (C), the crystallization of the polyethylene-based resin (A) is promoted, and the crystal structure is made dense and uniform. Therefore, the polyethylene-based resin (A) in the resin composition before stretching is composed of densely uniform crystal parts and amorphous parts existing between the crystal parts, and the vinyl aromatic elastomer (B) is a polyethylene-based resin. Many are present in the amorphous part of the resin (A).
  • the porosity that occurs at the interface between the dense crystal part of the polyethylene resin (A) and the vinyl aromatic elastomer (B) by stretching is facilitated by the improvement of the elastic modulus accompanying the crystallization of the matrix, and the crystal Due to the precise homogenization, the resulting porous structure can easily form a dense and uniform porous structure.
  • the type of the crystal nucleating agent (C) is not particularly limited as long as the effect of improving the crystallinity of the polyethylene resin (A) is recognized.
  • dibenzylidene sorbitol (DBS) compound 1,3-O-bis (3,4 dimethylbenzylidene) sorbitol; dialkyl benzylidene sorbitol; diacetal of sorbitol having at least one chlorine or bromine substituent; di (methyl or ethyl substituted benzylidene) ) Sorbitol; bis (3,4-dialkylbenzylidene) sorbitol having a substituent that forms a carbocycle; aliphatic, alicyclic and aromatic carboxylic acids, dicarboxylic acids or polybasic polycarboxylic acids, corresponding Metal salts of organic acids such as anhydrides and metal salts; bicyclic dicarboxylic acids and salts such as cyclic bis-phenol phosphate, disodium bicycl
  • fatty acid amides such as oleic acid amide, erucic acid amide, stearic acid amide, and ariaic acid amide
  • fatty acid metal salts such as magnesium stearate, zinc stearate, and calcium stearate are particularly preferable.
  • crystal nucleating agent (C) the trade name “Gelall D” series of Shin Nippon Rika Co., Ltd., the product name “Adeka Stub” series of ADEKA Co., Ltd., the product name “Millad” series of Milliken Chemical Co., Ltd.
  • Examples include the “Hyperform” series and the BASF brand name “IRGACLEAR” series.
  • Examples of the master batch of the crystal nucleating agent include “Rike Master CN” series of Riken Vitamin Co., Ltd. and “HL3-4” of Milkenn Chemical.
  • the products with the highest effect of improving the transparency are the product names of Milliken Chemicals “HYPERFORM HPN-20E” and “HL3-4”, and the product names of Riken Vitamin Co., Ltd. “Rike Master CN-001” “Rike Master CN-002 ".
  • crystal nucleating agent (C) one type may be used alone, or two or more types may be used in combination.
  • the crystal nucleating agent (C) is preferably used in a proportion of 0.001 to 10 parts by weight, more preferably 0 to 100 parts by weight in total of the polyethylene resin (A) and the vinyl aromatic elastomer (B). 0.005 to 5 parts by weight.
  • the product names “Rike Master CN-001” and “Rike Master CN-002” of Riken Vitamin Co., Ltd. are 0.5 to 5 with respect to the polyethylene resin (A). It is preferable to use 0.0 parts by weight.
  • Porous film Preferred physical properties of the porous film of the present invention will be described.
  • the thickness of the porous film of the present invention is not particularly limited, but is preferably 70 ⁇ m or more, and more preferably 100 ⁇ m or more.
  • the thickness of the porous film of the present invention is preferably 300 ⁇ m or less, and more preferably 200 ⁇ m or less. If thickness is 70 micrometers or more, it can have sufficient intensity
  • the air permeability of the porous film of the present invention is 200 seconds / 100 ml or less.
  • the air permeability of the porous film of the present invention is preferably 1 second / 100 ml to 100 seconds / 100 ml, more preferably 5 seconds / 100 ml to 50 seconds / 100 ml. If the air permeability is within the above range, a porous film having both strength and porosity is preferable.
  • the value obtained by converting the air permeability of the porous film per 1 ⁇ m of the film thickness is preferably 0.01 seconds / 100 ml / ⁇ m or more and 0.35 seconds / 100 ml / ⁇ m or less, more preferably 0.02 seconds / 100 ml / ⁇ m or more. It is 0.30 second / 100 ml / ⁇ m or less. It is preferable for the air permeability per 1 ⁇ m thickness to be in the above range because a porous film having the following suitable filtration rate can be easily obtained.
  • the air permeability of the porous film is measured by the method described in the Examples section below.
  • Porosity is an important factor for defining the porous structure, and is a numerical value indicating the ratio of the space portion of the porous layer in the porous film of the present invention. In general, it is known that the higher the porosity, the better the filtration rate, and the porous film of the present invention has a porosity of 50% or more, preferably 60% or more, more preferably 65% or more. It is.
  • the porosity of the porous film of the present invention is preferably 98% or less, and more preferably 95% or less. When the porosity is 50% or more, a porous film excellent in air permeability and filtration rate is obtained. If the porosity is 98% or less, a practical strength can be obtained.
  • the porosity of the porous film is measured by the method described in the Examples section below.
  • the filtration rate of the porous film of the present invention is preferably 10 ml / min ⁇ cm 2 or more, more preferably 15 ml / min ⁇ cm 2 or more, and further preferably 20 ml / min ⁇ cm 2 or more.
  • the filtration rate of the porous film of the present invention is preferably 100 ml / min ⁇ cm 2 or less, more preferably 90 ml / min ⁇ cm 2 or less, still more preferably 80 ml / min ⁇ cm 2 or less.
  • the filtration life of the porous film of the present invention is preferably 1.00 g / cm 2 or more and 10 g / cm 2 or less, more preferably 5.0 g / cm 2 or less, and still more preferably 2.0 g. / Cm 2 or less.
  • the filtration life is within the above range, a porous film having good filtration efficiency is obtained.
  • the filtration life (g / cm 2 ) of the porous film was calculated by colloidal silica (product name: Snowtex MP-4540M, average particle size: 450 nm, solid content: 40% by weight, medium: water) manufactured by Nissan Chemical Co., Ltd. with a silica concentration of 4
  • the weight of the liquid which was diluted with water so as to be weight% and sufficiently dispersed uniformly in an ultrasonic stirrer, then passed through the porous film at a pressure of 0.09 MPa, and before filtration became impossible It is calculated by measuring W (g) and dividing by the effective filtration area A (cm 2 ) of the porous film.
  • the filtration accuracy of the porous film of the present invention is preferably 0.50% or less, more preferably 0.25% or less, and still more preferably 0.20% or less. If the filtration accuracy is less than or equal to the above upper limit, the porous film has good filtration accuracy.
  • Filtration accuracy was diluted with water so that the colloidal silica (product name: Snowtex MP-4540M, average particle size: 450 nm, solid content: 40% by weight, medium: water) manufactured by Nissan Chemical Co., Ltd. would have a silica concentration of 4% by weight. Then, after being sufficiently uniformly dispersed in an ultrasonic stirrer, the porous film is passed at a pressure of 0.07 MPa, and the concentration of the liquid before and after passing is measured by an absorbance method to determine the particle collection efficiency (%). It is calculated by.
  • the porous film of the present invention contains a polyethylene resin (A) having a density of 0.955 to 0.970 g / cm 3 and a vinyl aromatic elastomer (B) at a predetermined ratio, and the air permeability and pores described above. Has a rate.
  • the pore size distribution derived from the dispersion diameter of the vinyl aromatic elastomer in the film before stretching is suitable for water filtration, and satisfies the above filtration speed, filtration life, and filtration accuracy ranges.
  • the porous film obtained from the polypropylene resin and the vinyl aromatic elastomer has a poor air permeability per 1 ⁇ m of film thickness and has a filtration life compared to the porous film of the present invention. Film is inferior.
  • the manufacturing method of a porous film As a method of manufacturing the porous film of this invention, the following methods are mentioned. First, a polyethylene resin composition of the present invention containing a polyethylene resin (A), a vinyl aromatic elastomer (B), a crystal nucleating agent (C) blended as necessary, and other components is prepared. By melting and molding this polyethylene-based resin composition using an extruder or the like under a temperature condition not lower than the melting point of the polyethylene-based resin (A) and lower than the decomposition temperature, a non-porous film (unstretched sheet) is obtained. . The obtained unstretched sheet is uniaxially stretched or biaxially stretched.
  • a non-porous film unstretched sheet
  • the thickness, air permeability, and porosity of the porous film to be created can be easily changed by changing the composition of the unstretched sheet (the composition of the polyethylene resin composition), the thickness, and the stretch ratio. It can be adjusted and is preferable.
  • a method of forming an unstretched sheet includes T-die molding.
  • the temperature of the cast roll when forming the unstretched sheet while cooling the kneaded product of the polyethylene resin composition of the present invention is preferably 80 ° C. or higher, more preferably 90 ° C. or higher, still more preferably 100 ° C. or higher.
  • the upper limit of the temperature of the cast roll is lower than the melting temperature of the polyethylene resin composition, and is usually 115 ° C. or lower.
  • the obtained unstretched sheet is uniaxially stretched or biaxially stretched.
  • Uniaxial stretching may be longitudinal uniaxial stretching or transverse uniaxial stretching.
  • Biaxial stretching may be simultaneous biaxial stretching or sequential biaxial stretching.
  • Sequential biaxial stretching When using sequential biaxial stretching, it is necessary to select the stretching temperature in a timely manner according to the composition of the polyethylene-based resin composition to be used, the crystal melting peak temperature, the crystallinity, and the like. Sequential biaxial stretching has the advantage that the porous structure is relatively easy to control and can easily be balanced with other physical properties such as mechanical strength and shrinkage.
  • the unstretched sheet has a temperature of 0 ° C. or more and less than 60 ° C., preferably 10 ° C. or more and less than 40 ° C., and is 1.1 times or more and less than 3.0 times, preferably 1.2 times or more and less than 2.0 times in the machine direction.
  • Uniaxial stretching is performed in the MD direction within the range.
  • the film tends to break, and when stretched at 60 ° C. or higher, the resulting stretched film has a low porosity and a high air permeability.
  • the unstretched sheet obtained in the sheet forming step may be heat-treated for a certain time in a certain temperature range before the stretching step.
  • the stretched sheet obtained by the above-described low-temperature longitudinal stretching is at least 60.degree. C. and less than 160.degree. C., preferably 70.degree. C. to less than 130.degree.
  • Uniaxial stretching is performed in the range of 5 times to 5.0 times.
  • the film tends to break, and when stretched at 160 ° C. or higher, the porosity of the obtained stretched film tends to be low and the air permeability tends to be high.
  • a porous film having good physical properties suitable for various applications can be obtained by stretching in two or more stages under the conditions described above. If this longitudinal stretching step is one stage, the stretched film obtained may not satisfy the required physical properties.
  • the longitudinal stretching ratio can be arbitrarily selected, but the stretching ratio per uniaxial stretching (total of low temperature longitudinal stretching and high temperature longitudinal stretching) is preferably 1.7 to 15 times, more preferably 1.8 to 12 times. More preferably, it is 2.0 to 10 times.
  • the draw ratio per uniaxial drawing is preferably 1.7 to 15 times, more preferably 1.8 to 12 times. More preferably, it is 2.0 to 10 times.
  • the transverse stretching temperature is preferably 70 to 150 ° C, more preferably 80 to 140 ° C.
  • the pores generated during the longitudinal stretching can be expanded to increase the porosity, so that sufficient porosity can be obtained.
  • the transverse draw ratio can be arbitrarily selected, but is preferably 1.1 to 10 times, more preferably 1.5 to 9.0 times, and still more preferably 2.0 to 8.0 times.
  • heat treatment After performing the above-mentioned sequential biaxial stretching, heat treatment may be performed in order to improve dimensional stability.
  • the heat treatment is usually performed at 100 to 150 ° C. for about 1 second to 30 minutes.
  • porous film of the present invention is produced in this way, the surface processing such as corona treatment, plasma treatment, printing, coating, vapor deposition, etc., if necessary, as long as the effects of the present invention are not impaired. Perforation can be applied. Depending on the application, it is also possible to use several porous films of the present invention.
  • the porous film of the present invention does not use an organic solvent in the production process, it has an advantage that it does not contain an organic solvent, is low in cost, and has no concern about environmental impact and elution of residual solvent.
  • the liquid filter of the present invention comprises the porous film of the present invention.
  • the liquid filter of the present invention may have a single-layer structure of the porous film of the present invention or a laminated structure combined with other layers.
  • the liquid filter of the present invention is a filter for purifying an aqueous solvent such as water or acetone, a petroleum-based solvent such as halides, esters, ether, benzene, or toluene. It is useful as a microfiltration membrane for use in the application system), semiconductor industry (ultra pure water production), pharmaceutical / food industry (sanitization, enzyme purification) and the like.
  • a porous film When a porous film is incorporated into a filtration system, it can be in a state in which the porous film is wound concentrically (wind type) or in a state of being pleated and stored in a cylindrical container (cartridge filter). Can be easily incorporated into a filtration system.
  • porous film of the present invention will be described in more detail with reference to Examples and Comparative Examples.
  • the present invention is not limited to the following examples as long as the gist thereof is not exceeded.
  • MD The direction of drawing (flowing) the porous film
  • TD the direction perpendicular thereto
  • A-1 High density polyethylene (Hi-Zex 3600F, manufactured by Prime Polymer Co., Ltd., MFR (190 ° C., 2.16 kg): 1.0 g / 10 min, density: 0.958 g / cm 3 , melting point: 134 ° C., melting enthalpy ⁇ Hm: 207 J / g, crystallization temperature: 115 ° C., crystallization enthalpy ⁇ Hc: 210 J / g)
  • A-2 High density polyethylene (Hi-Zex 3300F, manufactured by Prime Polymer Co., Ltd., MFR (190 ° C., 2.16 kg): 1.1 g / 10 min, density: 0.950 g / cm 3 , melting point: 132 ° C., melting enthalpy ⁇ Hm: 188 J / g, crystallization temperature: 114 ° C., crystallization enthalpy ⁇ Hc: 189 J
  • A′-1 Homopolypropylene (Novatech PP FY6HA, manufactured by Nippon Polypro Co., Ltd., MFR (230 ° C., 2.16 kg): 2.4 g / 10 min, density: 0.9 g / cm 3 )
  • B-1 Styrenic thermoplastic elastomer (styrene-ethylene-propylene block copolymer, grade name: SEPTON 1001, manufactured by Kuraray Co., Ltd., weight average molecular weight Mw: 186,000, molecular weight distribution Mw / Mn: 1.07, MFR (230 ° C., 2.16 kg); 0.1 g / 10 min, styrene content; 35% by weight)
  • C Crystal nucleating agent master batch for polyethylene (grade name: Riquet Master CN-002, manufactured by Riken Vitamin Co., Ltd.)
  • C-2 Nucleating agent (sorbitol compound, grade name: Gelol MD-LM30G, manufactured by Shin Nippon Rika Co., Ltd.)
  • the measuring method of various physical properties of the manufactured porous film is as follows.
  • Thickness The porous film was measured unspecified in five places with a 1/1000 mm dial gauge, and the average was taken as the thickness.
  • Air permeability The air permeability of the porous film was measured in accordance with JIS P8117 in an air atmosphere at 25 ° C. As a measuring instrument, a digital type Oken type air permeability dedicated machine (Asahi Seiko Co., Ltd.) was used. The measured air permeability (second / 100 ml) was divided by the thickness of the porous film to calculate the air permeability (second / 100 ml / ⁇ m) per 1 ⁇ m thickness.
  • Filtration life Colloidal silica (product name: Snowtex MP-4540M, average particle size: 450 nm, solid content: 40% by weight, medium: water) manufactured by Nissan Chemical Co., Ltd. with water so that the silica concentration is 4% by weight. Dilute and disperse sufficiently in an ultrasonic stirrer, then pass through a porous film at a pressure of 0.09 MPa, and measure the weight W (g) of the liquid that has passed before filtration becomes impossible. The filtration life (g / cm 2 ) was calculated by dividing by the filtration area A (cm 2 ).
  • Example 1 70 parts by weight of polyethylene resin (A-1), 30 parts by weight of vinyl aromatic elastomer (B-1), and 2.5 parts by weight of crystal nucleating agent (C-1) I put it in the machine. After melt-kneading at a set temperature of 230 ° C., it was shaped into a strand with a strand die, then cut with a strand cutter and pelletized.
  • A-1 polyethylene resin
  • B-1 vinyl aromatic elastomer
  • C-1 crystal nucleating agent
  • the obtained pellets were put into a single screw extruder, melt-kneaded at a set temperature of 210 ° C, shaped into a sheet with a T-die, cooled and solidified with a cast roll set at 110 ° C, and a thickness of 500 ⁇ m
  • An unstretched sheet was obtained.
  • the unstretched sheet was subjected to low-temperature longitudinal stretching at a draw ratio of 100% (stretching ratio: 2.0 times) between a roll (X) set at 15 ° C. and a roll (Y) set at 20 ° C. Subsequently, between the roll (P) set at 120 ° C.
  • a draw ratio of 50% (stretch ratio 1.5 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was.
  • This MD stretched film was preheated at a preheating temperature of 90 ° C. and a preheating time of 12 seconds in a film tenter facility manufactured by Kyoto Machine Co., Ltd., and then stretched in the transverse direction at a stretching temperature of 90 ° C. and 3.0 times. Thereafter, heat treatment was performed at 110 ° C. for 12 seconds to obtain a biaxially stretched porous film.
  • Table 1 shows the evaluation results of the obtained film.
  • Example 2 An unstretched sheet was obtained in the same manner as in Example 1. The obtained unstretched sheet is subjected to low-temperature longitudinal stretching by applying a draw ratio of 200% (stretching ratio: 3.0 times) between the roll (X) set at 15 ° C. and the roll (Y) set at 20 ° C. It was. Subsequently, between the roll (P) set at 120 ° C. and the roll (Q) set at 120 ° C., a draw ratio of 50% (stretch ratio 1.5 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was. This MD stretched porous film was preheated at a preheating temperature of 90 ° C.
  • Table 1 shows the evaluation results of the obtained film.
  • Example 3 An unstretched sheet was obtained in the same manner as in Example 1. The obtained unstretched sheet is subjected to low-temperature longitudinal stretching by applying a draw ratio of 200% (stretching ratio: 3.0 times) between the roll (X) set at 15 ° C. and the roll (Y) set at 20 ° C. It was. Subsequently, between the roll (P) set at 120 ° C. and the roll (Q) set at 120 ° C., a draw ratio of 100% (stretching ratio: 2.0 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was. This MD stretched porous film was preheated at a preheating temperature of 90 ° C.
  • Table 1 shows the evaluation results of the obtained film.
  • Example 1 An unstretched sheet was obtained in the same manner as in Example 1. The obtained unstretched sheet is subjected to low-temperature longitudinal stretching with a draw ratio of 100% (stretching ratio: 2.0 times) between the roll (X) set at 15 ° C. and the roll (Y) set at 20 ° C. It was. Subsequently, between the roll (P) set at 120 ° C. and the roll (Q) set at 120 ° C., a draw ratio of 50% (stretch ratio 1.5 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was. This MD stretched porous film was preheated at a preheating temperature of 90 ° C.
  • Table 2 shows the evaluation results of the obtained film. Since the filtration speed of the porous film was small and it took time to evaluate, the filtration life and filtration accuracy were not evaluated.
  • Example 2 An unstretched sheet was obtained in the same manner as in Example 1. The obtained unstretched sheet is subjected to low-temperature longitudinal stretching by applying a draw ratio of 200% (stretching ratio: 3.0 times) between the roll (X) set at 15 ° C. and the roll (Y) set at 20 ° C. It was. Subsequently, between the roll (P) set at 120 ° C. and the roll (Q) set at 120 ° C., a draw ratio of 50% (stretch ratio 1.5 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was. This MD stretched porous film was preheated at a preheating temperature of 90 ° C.
  • Table 2 shows the evaluation results of the obtained film. Since the filtration speed of the porous film was small and it took time to evaluate, the filtration life and filtration accuracy were not evaluated.
  • the obtained pellets were put into a single screw extruder, melt-kneaded at a set temperature of 210 ° C, shaped into a sheet with a T-die, cooled and solidified with a cast roll set at 110 ° C, and a thickness of 500 ⁇ m
  • An unstretched sheet was obtained.
  • the unstretched sheet was subjected to low-temperature longitudinal stretching at a draw ratio of 100% (stretching ratio: 2.0 times) between a roll (X) set at 15 ° C. and a roll (Y) set at 20 ° C. Subsequently, between the roll (P) set at 120 ° C.
  • Example 2 a draw ratio of 50% (stretch ratio 1.5 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was.
  • This MD stretched film was preheated at a preheating temperature of 90 ° C. and a preheating time of 12 seconds in a film tenter facility manufactured by Kyoto Machine Co., Ltd., and then stretched in the transverse direction at a stretching temperature of 90 ° C. for 1.5 times. Thereafter, heat treatment was performed in the same manner as in Example 1 to obtain a biaxially stretched porous film.
  • Table 2 shows the evaluation results of the obtained film. Since the filtration rate was low and it took time to evaluate, the filtration life and filtration accuracy were not evaluated.
  • Table 2 shows the evaluation results of the obtained film. Since the filtration rate was low and it took time to evaluate, the filtration life and filtration accuracy were not evaluated.
  • the unstretched sheet was subjected to low-temperature longitudinal stretching with a draw ratio of 100% (stretching ratio: 2.0) between a roll (X) set at 20 ° C. and a roll (Y) set at 40 ° C. Subsequently, between the roll (P) set at 120 ° C. and the roll (Q) set at 120 ° C., a draw ratio of 50% (stretch ratio 1.5 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was. This MD stretched film was preheated at a preheating temperature of 90 ° C.
  • Table 2 shows the evaluation results of the obtained film. However, since the air permeability was remarkably large and the air permeation performance was inferior and the filtration rate was remarkably reduced, the filtration performance was not evaluated.
  • Table 2 shows the evaluation results of the obtained film. However, since the air permeability was remarkably large and the air permeation performance was inferior and the filtration rate was remarkably reduced, the filtration performance was not evaluated.
  • the unstretched sheet was subjected to low-temperature longitudinal stretching with a draw ratio of 100% (stretching ratio: 2.0) between a roll (X) set at 20 ° C. and a roll (Y) set at 40 ° C. Subsequently, between the roll (P) set at 120 ° C. and the roll (Q) set at 120 ° C., a draw ratio of 50% (stretch ratio 1.5 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was. This MD stretched film was preheated at a preheating temperature of 90 ° C.
  • Table 2 shows the evaluation results of the obtained film. However, since the air permeability was remarkably large and the air permeation performance was inferior and the filtration rate was remarkably reduced, the filtration performance was not evaluated.
  • Table 2 shows the evaluation results of the obtained film. However, since the air permeability was remarkably large and the air permeation performance was inferior and the filtration rate was remarkably reduced, the filtration performance was not evaluated.
  • the obtained pellets were put into a single screw extruder, melt kneaded at a set temperature of 200 ° C., shaped into a sheet with a T die, cooled and solidified with a cast roll set at 127 ° C., and a thickness of 230 ⁇ m.
  • An unstretched sheet was obtained.
  • the unstretched sheet was subjected to low-temperature longitudinal stretching at a draw ratio of 100% (stretching ratio: 2.0 times) between the roll (X) set at 20 ° C. and the roll (Y) set at 20 ° C. Subsequently, between the roll (P) set at 120 ° C.
  • the porous films obtained in Examples 1 to 3 have a porosity of 60% or more, an air permeability of 50 sec / 100 ml or less, and have a good filtration rate, filtration life, and filtration accuracy.
  • the density of the polyethylene resin (A-2) was small, the degree of crystallinity was low, and it was difficult for the origin of opening to occur at the interface with the vinyl aromatic elastomer (B-1).
  • the porosity is small compared to the example, and the air permeability is large compared to the example. As a result, the film is inferior in filtration speed and inferior in filtration performance.
  • the films obtained in Comparative Examples 5 to 6 have a lower porosity than the examples and a higher air permeability than the examples. As a result, the film is inferior in filtration speed and inferior in filtration performance. Possible reasons for this result are as follows. Since the cast roll temperature was low and a good crystal structure system was not achieved, the crystallinity was lowered as a result, and the crystallinity of the polyethylene resin (A-2) was lowered, so that the vinyl aromatic elastomer (B-1) It was difficult for the starting point of hole formation to occur at the interface with.
  • the films obtained in Comparative Examples 7 to 8 have a lower porosity than the examples and a higher air permeability than the examples. As a result, the film is inferior in filtration speed and inferior in filtration performance. Possible reasons for this result are as follows. Since the crystal nucleating agent (C) was not added, a good crystal structure system was not obtained, and as a result, the crystallinity was lowered, and the crystallinity of the polyethylene resin (A-2) was lowered. It was difficult for the origin of opening to occur at the interface with the elastomer (B-1).
  • Comparative Example 9 is inferior in air permeability per 1 ⁇ m of film thickness and slightly inferior in filtration life as compared with Examples 1 to 3.
  • the reason for such a result is considered as follows.
  • the compatibility with the vinyl aromatic elastomer used varies depending on the polypropylene resin and the polyethylene resin as the base resin.
  • the polypropylene resin used in Comparative Example 9 has a low compatibility with the vinyl aromatic elastomer, and the dispersibility of the elastomer with respect to the base resin is low. Therefore, compared with Examples 1 to 3, there is a difference in the porous structure obtained in Comparative Example 9.
  • the porous film of the present invention is a polyethylene porous film having a large number of pore structures, low air permeability and excellent air permeability, and excellent filtration speed, filtration life and filtration accuracy.
  • the porous film of the present invention is a filter for purifying water, specifically, automotive industry (electrodeposition paint recovery and reuse system), semiconductor industry (ultra pure water production), pharmaceutical / food industry (sanitization, enzyme It is useful as a filtration membrane used in purification.

Abstract

The present invention provides, at a low cost and with excellent yield, a polyethylene porous film having a high porosity, superior air permeability, and an excellent filtration rate, filter life, and filter rating. This porous film includes 55–85 parts by weight of a polyethylene resin (A) having a density of 0.955–0.970 g/cm3 and 15–45 parts by weight of a vinyl aromatic elastomer (B) (provided there is a total of 100 parts by weight of the polyethylene resin (A) and the vinyl aromatic elastomer(B)), has a porosity of 50% or higher, and has an air permeability of 200 seconds/100 ml or lower. The melt flow rate (MFR) of the vinyl aromatic elastomer (B) at 230°C under a load of 2.16 kg is preferably no higher than 1 g/10 minutes, and the melt flow rate (MFR) of the polyethylene resin (A) at 190°C under a load of 2.16 kg is preferably 0.1–10 g/10 minutes.

Description

多孔フィルムPerforated film
　本発明は多孔フィルムに関する。本発明の多孔フィルムは、包装用品、衛生用品、畜産用品、農業用品、建築用品、医療用品、光拡散板、反射シート、電池用セパレーターまたは、分離膜として利用できる。特に本発明の多孔フィルムは、食品関連分野、製薬・化粧品分野、化学工業品分野、電子工業分野に利用される濾過膜として好適に用いられる。 The present invention relates to a porous film. The porous film of the present invention can be used as a packaging product, sanitary product, livestock product, agricultural product, building product, medical product, light diffusion plate, reflection sheet, battery separator, or separation membrane. In particular, the porous film of the present invention is suitably used as a filtration membrane used in the food-related field, pharmaceutical / cosmetic field, chemical industry field, and electronics industry field.
　本発明はまた、この多孔フィルムを備えた水処理用フィルターに関する。 The present invention also relates to a water treatment filter provided with the porous film.
　精密濾過膜や限外濾過膜等の多孔フィルムによる濾過操作は、自動車産業（電着塗料回収再利用システム）、半導体産業（超純水製造）、医薬・食品産業（除菌、酵素精製）などの多方面にわたって実用化されている。特に近年は河川水等を除濁して飲料水や工業用水を製造するための手法としても多用されている。膜の素材としては、セルロース系、ポリアクリロニトリル系、ポリオレフィン系等多種多様のものが用いられている。 Filtration operations using porous films such as microfiltration membranes and ultrafiltration membranes include automotive industry (electrodeposition paint collection and reuse system), semiconductor industry (ultra pure water production), pharmaceutical and food industry (sanitization, enzyme purification), etc. Has been put to practical use in many fields. In particular, in recent years, it has been frequently used as a technique for producing drinking water and industrial water by turbidizing river water and the like. A wide variety of materials such as cellulose, polyacrylonitrile, and polyolefin are used as the material of the membrane.
　中でもポリオレフィン系重合体（ポリエチレン、ポリプロピレン、ポリフッ化ビニリデン等）は、疎水性で耐水性が高いため、水系濾過膜の素材として適しており、多用されている。これらポリオレフィン系重合体の中でも、廃棄時に問題となるハロゲン元素を含まず、かつ化学反応性の高い３級炭素原子が少ないために膜洗浄時の薬品劣化が起こりにくく、長期使用耐性が期待でき、かつ安価であるポリエチレンが、今後特に有望と考えられる。 Among these, polyolefin polymers (polyethylene, polypropylene, polyvinylidene fluoride, etc.) are suitable as a material for aqueous filtration membranes because they are hydrophobic and have high water resistance, and are widely used. Among these polyolefin-based polymers, it does not contain halogen elements that cause problems during disposal, and since there are few tertiary carbon atoms with high chemical reactivity, chemical degradation during film cleaning hardly occurs, and long-term durability can be expected. Polyethylene, which is inexpensive and inexpensive, is considered particularly promising in the future.
　従来、この種の高分子よりなる膜に微細な連通孔を多数形成した多孔フィルムを作製する技術としては、下記に記載するような技術が提案されている。 Conventionally, techniques as described below have been proposed as a technique for producing a porous film in which a large number of fine communication holes are formed in a film made of this type of polymer.
　特許文献１には、ポリプロピレン系樹脂とポリオレフィン・ポリスチレン系エラストマーを含有するシートを二軸延伸して多孔フィルムを得ることが開示されている。 Patent Document 1 discloses that a porous film is obtained by biaxially stretching a sheet containing a polypropylene resin and a polyolefin / polystyrene elastomer.
　特許文献２には、高分子量ポリエチレンと高密度ポリエチレンと充填剤を含む樹脂組成物からなるフィルムを延伸して多孔フィルムを得る方法が開示されている。 Patent Document 2 discloses a method of obtaining a porous film by stretching a film made of a resin composition containing high molecular weight polyethylene, high density polyethylene and a filler.
　特許文献３には、超高分子量ポリエチレンと高密度ポリエチレンからなる組成物と製膜用溶剤とを含有する混合物を押出して延伸した後、製膜用溶剤を有機溶剤で抽出除去し、乾燥して多孔フィルムを製造する方法が開示されている。 In Patent Document 3, a mixture containing a composition composed of ultrahigh molecular weight polyethylene and high-density polyethylene and a film-forming solvent is extruded and stretched, and then the film-forming solvent is extracted and removed with an organic solvent, and dried. A method for producing a porous film is disclosed.
　特許文献４には、高密度ポリエチレンに無機充填剤を高い割合で充填し、延伸性の改良のためにエラストマー成分を添加し、延伸によって透湿性及び透気性と耐透液性を両立させた多孔フィルムが開示されている。 In Patent Document 4, a high-density polyethylene is filled with an inorganic filler at a high ratio, an elastomer component is added to improve stretchability, and a porous structure that achieves both moisture permeability and air permeability and liquid resistance by stretching. A film is disclosed.
特開２０１４－１０１４４５号公報JP 2014-101445 A 特開２００７－２９７５８３号公報JP 2007-297583 A 特開２０１３－１０８０４５号公報JP 2013-108045 A 国際公開第２０１４／０８８０６５号International Publication No. 2014/088065
　特許文献１には、フィルム材料としてポリプロピレン系樹脂を用いることが記載されているが、特許文献１の実施例の透気度の値から、得られる多孔フィルムの透気性能は低く、濾過膜として使用した場合、濾過速度が著しく低い。 Patent Document 1 describes that a polypropylene resin is used as a film material, but from the value of the air permeability of the Examples of Patent Document 1, the air permeability of the obtained porous film is low, and as a filtration membrane When used, the filtration rate is significantly lower.
　特許文献２では、ポリエチレン系樹脂の多孔フィルムを延伸によって作製しているが、特許文献２の実施例の透気度の値から、得られる多孔フィルムの透気性能は低く、濾過膜として使用した場合、濾過速度が著しく低い。特許文献２に記載の多孔フィルムは、硫酸バリウム、炭酸カルシウム等の充填剤が高い割合で添加されているため、この多孔フィルムを濾過膜として使用した場合、無機充填剤の脱離が起き、濾過液への溶出が懸念される。 In patent document 2, although the porous film of polyethylene-type resin is produced by extending | stretching, the air permeability performance of the obtained porous film is low from the value of the air permeability of the Example of patent document 2, It was used as a filtration membrane. The filtration rate is significantly lower. In the porous film described in Patent Document 2, since fillers such as barium sulfate and calcium carbonate are added at a high ratio, when this porous film is used as a filtration membrane, the inorganic filler is detached and the filtration is performed. There is concern about elution into the liquid.
　特許文献３に記載の方法では、製膜用溶剤の抽出処理に要するコストが大きい。また、抽出のための有機溶剤が大量に必要となり、環境への影響が懸念される。更には、特許文献３の実施例の透気度の値から、得られる多孔フィルムの透気性能は低く、濾過膜として使用した場合、濾過速度が著しく低い。 In the method described in Patent Document 3, the cost required for the extraction treatment of the film-forming solvent is high. In addition, a large amount of organic solvent is required for extraction, and there is a concern about the impact on the environment. Furthermore, from the value of the air permeability of the Example of patent document 3, the air permeability of the obtained porous film is low, and when used as a filtration membrane, the filtration rate is extremely low.
　特許文献４に記載の多孔フィルムは、ポリエチレン樹脂と無機充填剤との界面で延伸剥離された多孔フィルムであり、無機充填剤が高い割合で添加されているため、濾過膜として使用をした場合、無機充填剤の脱離が起き、濾過液への溶出が懸念される。また、耐透液性を考慮したフィルムであるため透気性能は低く、濾過膜として使用した場合、濾過速度が著しく低いものとなる。 The porous film described in Patent Document 4 is a porous film stretched and peeled at the interface between the polyethylene resin and the inorganic filler, and since the inorganic filler is added at a high rate, when used as a filtration membrane, Desorption of the inorganic filler occurs and there is a concern about elution into the filtrate. Moreover, since it is a film considering liquid permeation resistance, the air permeation performance is low, and when used as a filtration membrane, the filtration rate is remarkably low.
　本発明は、空孔率が高く、透気性能に優れ、自動車産業（電着塗料回収再利用システム）、半導体産業（超純水製造）、医薬・食品産業（除菌、酵素精製）などで使用される濾過膜として有用な、濾過速度、濾過寿命、濾過精度に優れたポリエチレン製多孔フィルムを安価にかつ生産性良く提供することを目的とする。 The present invention has a high porosity, excellent air permeability, and is used in the automobile industry (electrodeposition paint recovery and reuse system), semiconductor industry (ultra pure water production), pharmaceutical / food industry (sanitization, enzyme purification), etc. An object of the present invention is to provide a polyethylene porous film excellent in filtration speed, filtration life, and filtration accuracy that is useful as a filtration membrane to be used at low cost and with high productivity.
　本発明は、以下を要旨とする。 The gist of the present invention is as follows.
　第１の発明は、密度が０．９５５～０．９７０ｇ／ｃｍ３であるポリエチレン系樹脂（Ａ）５５～８５重量部とビニル芳香族エラストマー（Ｂ）１５～４５重量部の割合でそれぞれ含み（ただし、ポリエチレン系樹脂（Ａ）とビニル芳香族エラストマー（Ｂ）との合計で１００重量部となる。）、空孔率が５０％以上であり、透気度が２００秒／１００ｍｌ以下であることを特徴とする多孔フィルム、である。 The first invention includes 55 to 85 parts by weight of a polyethylene resin (A) having a density of 0.955 to 0.970 g / cm 3 and 15 to 45 parts by weight of a vinyl aromatic elastomer (B) ( However, the total of the polyethylene resin (A) and the vinyl aromatic elastomer (B) is 100 parts by weight.), The porosity is 50% or more, and the air permeability is 200 seconds / 100 ml or less. A porous film characterized by
　第２の発明は、第１の発明において、前記ビニル芳香族エラストマー（Ｂ）の温度２３０℃、荷重２．１６ｋｇにおけるメルトフローレート（ＭＦＲ）が１ｇ／１０分以下である多孔フィルム、である。 The second invention is a porous film according to the first invention, wherein the vinyl aromatic elastomer (B) has a melt flow rate (MFR) of 1 g / 10 min or less at a temperature of 230 ° C. and a load of 2.16 kg.
　第３の発明は、第１または２の発明において、ポリエチレン系樹脂（Ａ）の温度１９０℃、荷重２．１６ｋｇにおけるメルトフローレート（ＭＦＲ）が０．１～１０ｇ／１０分である多孔フィルム、である。 A third invention is the porous film according to the first or second invention, wherein the polyethylene resin (A) has a melt flow rate (MFR) of 0.1 to 10 g / 10 min at a temperature of 190 ° C. and a load of 2.16 kg, It is.
　第４の発明は、第１～３のいずれかの発明において、厚みが７０μｍ以上である多孔フィルム、である。 A fourth invention is a porous film having a thickness of 70 μm or more in any one of the first to third inventions.
　第５の発明は、第１～４のいずれかの発明において、二軸延伸フィルムである多孔フィルムが提供される。 The fifth invention provides a porous film which is a biaxially stretched film in any one of the first to fourth inventions.
　第６の発明によれば、第１～５のいずれかの発明において、ポリエチレン系樹脂（Ａ）とビニル芳香族エラストマー（Ｂ）との合計１００重量部に対し、結晶核剤（Ｃ）を０．００１～１０重量部含む多孔フィルムが提供される。 According to the sixth invention, in any one of the first to fifth inventions, 0% of the crystal nucleating agent (C) is added to 100 parts by weight of the total of the polyethylene resin (A) and the vinyl aromatic elastomer (B). A porous film comprising 0.001 to 10 parts by weight is provided.
　第７の発明によれば、第１～６のいずれかの発明において、ビニル芳香族エラストマー（Ｂ）がビニル芳香族化合物に由来する構成単位の含有量が１０～４０重量％の、スチレン－エチレン－プロピレンブロック共重合体、スチレン－エチレン－プロピレン－スチレンブロック共重合体、及びスチレン－エチレン－ブタジエン－スチレンブロック共重合体よりなる群から選ばれる１種又は２種以上である多孔フィルムが提供される。 According to the seventh invention, in any one of the first to sixth inventions, the styrene-ethylene in which the vinyl aromatic elastomer (B) has a content of structural units derived from the vinyl aromatic compound of 10 to 40% by weight. Provided is a porous film of one or more selected from the group consisting of a propylene block copolymer, a styrene-ethylene-propylene-styrene block copolymer, and a styrene-ethylene-butadiene-styrene block copolymer The
　第８の発明によれば、第１～７のいずれかの発明に係る多孔フィルムを備えた液体用フィルターが提供される。 According to the eighth invention, there is provided a liquid filter comprising the porous film according to any one of the first to seventh inventions.
　本発明によれば、空孔率が高く、透気度が小さく透気性能に優れ、濾過速度、濾過寿命、濾過精度に優れたポリエチレン多孔フィルムを安価にかつ生産性良く提供することが可能となる。 According to the present invention, it is possible to provide a polyethylene porous film with high porosity, low air permeability, excellent air permeability, excellent filtration speed, filtration life, and filtration accuracy at low cost and high productivity. Become.
　本発明の多孔フィルムは、自動車産業（電着塗料回収再利用システム）、半導体産業（超純水製造）、医薬・食品産業（除菌、酵素精製）などで使用される濾過膜として有用である。 The porous film of the present invention is useful as a filtration membrane used in the automobile industry (electrodeposition paint recovery and reuse system), semiconductor industry (ultra pure water production), pharmaceutical / food industry (sanitization, enzyme purification), etc. .
　以下に本発明の実施の形態を詳細に説明する。 Hereinafter, embodiments of the present invention will be described in detail.
　本発明における数値範囲の上限値及び下限値は、本発明が特性する数値範囲内から僅かに外れる場合であっても、当該数値範囲内と同様の作用効果を備えている限り本発明の均等範囲に包含される。 Even if the upper limit and lower limit of the numerical range in the present invention are slightly out of the numerical range characterized by the present invention, the equivalent range of the present invention is provided as long as the same effects as those in the numerical range are provided. Is included.
　本発明における主成分とは、最も多量に含有されている成分のことであり、通常５０重量％以上、好ましくは７０重量％以上、更に好ましくは８０重量％以上含有される成分である。 The main component in the present invention is a component that is contained in the largest amount, and is a component that is usually contained in an amount of 50% by weight or more, preferably 70% by weight or more, and more preferably 80% by weight or more.
　本発明の多孔フィルムは、密度が０．９５５～０．９７０ｇ／ｃｍ３であるポリエチレン系樹脂（Ａ）５５～８５重量部とビニル芳香族エラストマー（Ｂ）１５～４５重量部の割合でそれぞれ含み（ただし、ポリエチレン系樹脂（Ａ）とビニル芳香族エラストマー（Ｂ）との合計で１００重量部となる。）、空孔率が５０％以上であり、透気度が２００秒／１００ｍｌ以下である。 The porous film of the present invention contains 55 to 85 parts by weight of polyethylene resin (A) having a density of 0.955 to 0.970 g / cm 3 and 15 to 45 parts by weight of vinyl aromatic elastomer (B). (However, the total of the polyethylene resin (A) and the vinyl aromatic elastomer (B) is 100 parts by weight.), The porosity is 50% or more, and the air permeability is 200 seconds / 100 ml or less. .
　本発明の多孔フィルムは、例えば、ポリエチレン系樹脂（Ａ）とビニル芳香族エラストマー（Ｂ）を主成分とするポリエチレン系樹脂組成物を用いて製膜した未延伸シートを、少なくとも一軸方向に延伸して多孔化することにより製造される。 The porous film of the present invention is obtained by, for example, stretching an unstretched sheet formed using a polyethylene resin composition mainly composed of a polyethylene resin (A) and a vinyl aromatic elastomer (B) in at least a uniaxial direction. It is manufactured by making it porous.
　以下、本発明の多孔フィルムの製造に用いられるポリエチレン系樹脂組成物を「本発明のポリエチレン系樹脂組成物」と称す場合がある。 Hereinafter, the polyethylene resin composition used for the production of the porous film of the present invention may be referred to as “the polyethylene resin composition of the present invention”.
　本発明の多孔フィルムは、海部をポリエチレン系樹脂（Ａ）、島部をビニル芳香族エラストマー（Ｂ）としたシートの延伸工程の際に、海部であるポリエチレン系樹脂（Ａ）と島部であるビニル芳香族エラストマー（Ｂ）の界面に応力集中させてボイドを形成させ、多孔化させることにより製造される。本発明の多孔フィルムは微細で孔径が均一な孔が多数あるため連通孔を形成しやすく、結果として空孔率が高く、かつ、透気度が低く透気性能に優れたフィルムとなる。 The porous film of the present invention is a polyethylene resin (A) that is a sea part and an island part in the stretching process of a sheet in which the sea part is a polyethylene resin (A) and the island part is a vinyl aromatic elastomer (B). It is manufactured by concentrating stress on the interface of the vinyl aromatic elastomer (B) to form a void and making it porous. Since the porous film of the present invention has a large number of fine pores having a uniform pore diameter, it is easy to form communication holes, and as a result, the film has a high porosity and low air permeability and excellent air permeability.
　特許文献４のように、硫酸バリウム、炭酸カルシウム等の無機充填剤を高い割合で含む未延伸シートを延伸して製造される多孔フィルムは、ベース樹脂と無機充填剤との界面で延伸剥離された多孔フィルムである。このため、無機充填剤の凝集により延伸ムラが生じ、孔の大きさの不均一性及び孔形成のバラツキにより、本発明の多孔フィルムに比較して連通孔を形成し難いと考えられる。従って、空孔形成の割合が低い多孔構造となり、透気度も劣るフィルムとなる。 As in Patent Document 4, the porous film produced by stretching an unstretched sheet containing a high proportion of inorganic fillers such as barium sulfate and calcium carbonate was stretched and peeled at the interface between the base resin and the inorganic filler. It is a porous film. For this reason, stretching unevenness occurs due to the aggregation of the inorganic filler, and it is considered that it is difficult to form the communication holes as compared with the porous film of the present invention due to the nonuniformity of the size of the holes and the variation of the hole formation. Therefore, it becomes a porous structure with a low rate of pore formation and a film with poor air permeability.
　後述するように、本発明の多孔フィルムを二軸延伸フィルムとすることで、多孔構造の制御が可能となり、空孔率が高く、透気性能が優れたフィルムとすることができる。 As described later, when the porous film of the present invention is a biaxially stretched film, the porous structure can be controlled, the porosity is high, and the film has excellent air permeability.
　本発明の多孔フィルムが結晶核剤（Ｃ）を含有することにより、より緻密で均一な多孔構造を形成しやすくなり、延伸により透気度が低く透気性能が優れたフィルムとなりやすい。 When the porous film of the present invention contains the crystal nucleating agent (C), it becomes easier to form a denser and more uniform porous structure, and the film tends to have a low air permeability and excellent air permeability by stretching.
１．ポリエチレン系樹脂（Ａ）
　ポリエチレン系樹脂（Ａ）は、主としてエチレンに由来する構成単位（以下「エチレン単位」と称す場合がある。）からなる重合体又は共重合体であり、好ましくはエチレン単位が全構成単位の９０重量％以上であるポリエチレンである。 1. Polyethylene resin (A)
The polyethylene-based resin (A) is a polymer or copolymer mainly composed of a structural unit derived from ethylene (hereinafter sometimes referred to as “ethylene unit”). Preferably, the ethylene unit is 90 wt% of all structural units. % Of polyethylene.
　濾過膜としての使用を考慮した場合、ポリエチレン系樹脂は、廃棄時に問題となるハロゲン元素を含まず、かつ反応性の高い官能基や原子を含まない樹脂であるので膜洗浄時の薬品劣化が起こりにくく、長期使用耐性が期待できる。 When considering use as a filtration membrane, polyethylene-based resins do not contain halogen elements that cause problems during disposal, and do not contain highly reactive functional groups or atoms, so chemical degradation occurs during membrane cleaning. It is difficult to expect long-term use resistance.
　ポリエチレン系樹脂（Ａ）は、具体的には、エチレンの単独重合体であってもよく、エチレン単位９０重量％以上とα－オレフィンに由来する構成単位（以下「α－オレフィン単位」と称す場合がある。）１０重量％以下との共重合体であってもよい。 Specifically, the polyethylene resin (A) may be a homopolymer of ethylene, and is a structural unit derived from α-olefin and 90% by weight or more of ethylene units (hereinafter referred to as “α-olefin unit”). It may be a copolymer of 10% by weight or less.
　ポリエチレン系樹脂（Ａ）が共重合体の場合に使用されるα－オレフィンとしては、プロピレン、１－ブテン、１－ペンテン、１－ヘキセン、１－オクテン、１－デセン、１－ドデセン、４－メチル－１－ペンテン、３－メチル－１－ペンテン等の１種又は２種以上が挙げられる。 The α-olefin used when the polyethylene resin (A) is a copolymer is propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4- Examples thereof include one or more of methyl-1-pentene, 3-methyl-1-pentene and the like.
　ポリエチレン系樹脂（Ａ）としては、超高分子量ポリエチレン、高密度ポリエチレン、中密度ポリエチレン、分岐状低密度ポリエチレンおよび鎖状低密度ポリエチレンが挙げられる。結晶性、機械強度、経済性の観点から、高密度ポリエチレンが好ましい。 Examples of the polyethylene resin (A) include ultra high molecular weight polyethylene, high density polyethylene, medium density polyethylene, branched low density polyethylene, and chain low density polyethylene. High-density polyethylene is preferable from the viewpoints of crystallinity, mechanical strength, and economy.
　ポリエチレン系樹脂（Ａ）は、密度が０．９５５～０．９７０ｇ／ｃｍ３であることを必須とし、０．９５５～０．９６５ｇ／ｃｍ３であることが好ましい。ポリエチレン系樹脂（Ａ）の密度が０．９５５ｇ／ｃｍ３未満であると、得られる多孔フィルムの結晶部分が少ないため、目的とする多孔構造の形成が困難となり、優れた濾過性能を満たすための空孔率を有する多孔フィルムを形成し得ない。一方、ポリエチレン系樹脂（Ａ）の密度が０．９７０ｇ／ｃｍ３を超えると結晶部分が多すぎるため、延伸ムラのある多孔フィルムとなる。 Polyethylene resin (A) has a density and mandatory that the 0.955 ~ 0.970g / cm 3, is preferably 0.955 ~ 0.965g / cm 3. When the density of the polyethylene-based resin (A) is less than 0.955 g / cm 3 , the resulting porous film has few crystal parts, so that it is difficult to form a target porous structure, and excellent filtration performance is satisfied. A porous film having porosity cannot be formed. On the other hand, when the density of the polyethylene-based resin (A) exceeds 0.970 g / cm 3 , since there are too many crystal parts, a porous film with uneven stretching is obtained.
　ポリエチレン系樹脂（Ａ）のメルトフローレート（ＭＦＲ）は特に制限されるものではないが、通常、ＭＦＲは０．１～１０ｇ／１０分であることが好ましく、０．２～５ｇ／１０分であることがより好ましい。ポリエチレン系樹脂（Ａ）のＭＦＲが０．１ｇ／１０分以上であると、成形加工時において十分な溶融粘度を有し、高い生産性を確保することができる。ポリエチレン系樹脂（Ａ）のＭＦＲが１０ｇ／１０分以下であると、十分な強度を有する多孔フィルムとすることができる。 The melt flow rate (MFR) of the polyethylene resin (A) is not particularly limited, but usually the MFR is preferably 0.1 to 10 g / 10 minutes, and preferably 0.2 to 5 g / 10 minutes. More preferably. When the MFR of the polyethylene resin (A) is 0.1 g / 10 min or more, the polyethylene resin (A) has a sufficient melt viscosity at the time of molding and can ensure high productivity. When the MFR of the polyethylene resin (A) is 10 g / 10 min or less, a porous film having sufficient strength can be obtained.
　ポリエチレン系樹脂（Ａ）の密度は、ＪＩＳ　Ｋ７１１２に従い、水中置換法で測定される。ポリエチレン系樹脂（Ａ）のＭＦＲはＪＩＳ　Ｋ７２１０に準拠して、温度１９０℃、荷重２．１６ｋｇの条件で測定される。 The density of the polyethylene resin (A) is measured by an underwater substitution method in accordance with JIS K7112. The MFR of the polyethylene resin (A) is measured in accordance with JIS K7210 under conditions of a temperature of 190 ° C. and a load of 2.16 kg.
　ポリエチレン系樹脂（Ａ）は、１種を単独で用いてもよく、構成単位や密度、ＭＦＲ等の物性の異なるものの２種以上を混合して用いてもよい。 The polyethylene-based resin (A) may be used alone or in combination of two or more types having different physical properties such as structural units, density, and MFR.
２．ビニル芳香族エラストマー（Ｂ）
　本発明においては、ポリエチレン系樹脂（Ａ）に対し、ビニル芳香族エラストマー（Ｂ）を所定の割合で含むことが重要である。ビニル芳香族エラストマー（Ｂ）を含むことにより、微細で均一性の高い多孔構造を効率的に得ることが可能となり、空孔の形状や孔径を制御し易くなる。 2. Vinyl aromatic elastomer (B)
In the present invention, it is important that the vinyl aromatic elastomer (B) is contained in a predetermined ratio with respect to the polyethylene resin (A). By including the vinyl aromatic elastomer (B), a fine and highly uniform porous structure can be efficiently obtained, and the shape and diameter of the pores can be easily controlled.
　ビニル芳香族エラストマー（Ｂ）とは、スチレン等のビニル芳香族化合物に由来する構成単位を含む熱可塑性エラストマーの１種で、軟質成分（例えばブタジエンに由来する構成単位）と硬質成分（例えばスチレンに由来する構成単位）との連続体からなる共重合体である。 The vinyl aromatic elastomer (B) is a kind of thermoplastic elastomer containing a structural unit derived from a vinyl aromatic compound such as styrene, and a soft component (for example, a structural unit derived from butadiene) and a hard component (for example, styrene). It is a copolymer consisting of a continuum with the derived structural unit.
　共重合体の種類については、ランダム共重合体、ブロック共重合体、グラフト共重合体が挙げられる。一般にブロック共重合体としては、線状ブロック構造や放射状枝分れブロック構造等種々のものが知られている。本発明ではいずれの構造のものを用いてもよい。 Examples of the type of copolymer include a random copolymer, a block copolymer, and a graft copolymer. In general, various block copolymers such as a linear block structure and a radial branched block structure are known. Any structure may be used in the present invention.
　ビニル芳香族エラストマー（Ｂ）は、温度２３０℃、荷重２．１６ｋｇにおけるメルトフローレート（ＭＦＲ）が１ｇ／１０分以下であることが好ましい。これは、本発明のポリエチレン系樹脂組成物中に分散したビニル芳香族エラストマー（Ｂ）は、ポリエチレン系樹脂（Ａ）との粘度差によってその形状が変化するが、ＭＦＲが上記上限以下のものであれば、その形状が球状になり易いからである。球状分散したドメインは、アスペクト比が大きなドメインとは異なり、その後の延伸工程によって得られる多孔構造の均一性が高くなり易く、物性安定性に優れるので好ましい。さらに、ＭＦＲが上記上限以下であれば、延伸工程において、高い弾性率を有するマトリックスと低い弾性率のドメイン界面部分に応力が集中しやすくなるため、開孔起点が生じやすく、多孔化し易い。ビニル芳香族エラストマー（Ｂ）のＭＦＲの下限については特に制限はないが、通常、０．０１ｇ／１０分以上である。 The vinyl aromatic elastomer (B) preferably has a melt flow rate (MFR) of 1 g / 10 min or less at a temperature of 230 ° C. and a load of 2.16 kg. This is because the vinyl aromatic elastomer (B) dispersed in the polyethylene resin composition of the present invention changes in shape due to the difference in viscosity from the polyethylene resin (A), but the MFR is below the above upper limit. This is because the shape tends to be spherical. Unlike the domain having a large aspect ratio, the spherically dispersed domain is preferable because the uniformity of the porous structure obtained by the subsequent stretching step tends to be high and the physical property stability is excellent. Furthermore, if the MFR is not more than the above upper limit, in the stretching step, stress tends to concentrate on the matrix interface having a high modulus of elasticity and the domain interface portion having a low modulus of elasticity. Although there is no restriction | limiting in particular about the minimum of MFR of a vinyl aromatic elastomer (B), Usually, it is 0.01 g / 10min or more.
　ビニル芳香族エラストマー（Ｂ）のＭＦＲはＪＩＳ　Ｋ７２１０に準拠して、温度２３０℃、荷重２．１６ｋｇの条件で測定される。 The MFR of the vinyl aromatic elastomer (B) is measured under conditions of a temperature of 230 ° C. and a load of 2.16 kg according to JIS K7210.
　ビニル芳香族エラストマー（Ｂ）は、スチレン等のビニル芳香族化合物に由来する構成単位の含有量が１０～４０重量％であることが好ましく、１５～３５重量％であることがより好ましい。ビニル芳香族エラストマー（Ｂ）中のスチレン等のビニル芳香族化合物に由来する構成単位の含有量が１０重量％以上であることにより、効果的に本発明のポリエチレン系樹脂組成物中にドメインを形成することができる。ビニル芳香族エラストマー（Ｂ）中のスチレン等のビニル芳香族化合物に由来する構成単位の含有量が４０重量％以下であることにより、過度に大きなドメイン形成を抑制することができる。 In the vinyl aromatic elastomer (B), the content of structural units derived from a vinyl aromatic compound such as styrene is preferably 10 to 40% by weight, and more preferably 15 to 35% by weight. Domains are effectively formed in the polyethylene resin composition of the present invention by the content of structural units derived from vinyl aromatic compounds such as styrene in the vinyl aromatic elastomer (B) being 10% by weight or more. can do. When the content of the structural unit derived from the vinyl aromatic compound such as styrene in the vinyl aromatic elastomer (B) is 40% by weight or less, excessively large domain formation can be suppressed.
　ビニル芳香族エラストマー（Ｂ）の具体的な種類については特に限定しないが、スチレン－ブタジエンブロック共重合体（ＳＢＲ）、水素添加スチレン－ブタジエンブロック共重合体（ＳＥＢ）、スチレン－ブタジエン－スチレンブロック共重合体（ＳＢＳ）、スチレン－ブタジエン－ブチレン－スチレンブロック共重合体（ＳＢＢＳ）、スチレン－エチレン－ブタジエン－スチレンブロック共重合体（ＳＥＢＳ）、スチレン－イソプレンブロック共重合体（ＳＩＲ）、スチレン－エチレン－プロピレンブロック共重合体（ＳＥＰ）、スチレン－イソプレン－スチレンブロック共重合体（ＳＩＳ）、スチレン－エチレン－プロピレン－スチレンブロック共重合体（ＳＥＰＳ）、スチレン－エチレン－エチレン－プロピレン－スチレンブロック共重合体（ＳＥＥＰＳ）などが挙げられる。 The specific type of vinyl aromatic elastomer (B) is not particularly limited, but styrene-butadiene block copolymer (SBR), hydrogenated styrene-butadiene block copolymer (SEB), and styrene-butadiene-styrene block copolymer. Polymer (SBS), Styrene-butadiene-butylene-styrene block copolymer (SBBS), Styrene-ethylene-butadiene-styrene block copolymer (SEBS), Styrene-isoprene block copolymer (SIR), Styrene-ethylene -Propylene block copolymer (SEP), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene block And a copolymer (SEEPS).
　本発明のポリエチレン系樹脂組成物中にビニル芳香族エラストマー（Ｂ）を効率的に分散させるためには、ビニル芳香族エラストマー（Ｂ）の中でも、ポリエチレン系樹脂（Ａ）との相溶性が高い、エチレン成分、ブタジエン成分が含有されているものが好ましく、中でも、スチレン－エチレン－プロピレンブロック共重合体（ＳＥＰ）、スチレン－エチレン－プロピレン－スチレンブロック共重合体（ＳＥＰＳ）、スチレン－エチレン－ブタジエン－スチレンブロック共重合体（ＳＥＢＳ）がより好ましい。 In order to efficiently disperse the vinyl aromatic elastomer (B) in the polyethylene resin composition of the present invention, among the vinyl aromatic elastomer (B), the compatibility with the polyethylene resin (A) is high. Those containing an ethylene component and a butadiene component are preferred. Among them, styrene-ethylene-propylene block copolymer (SEP), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-ethylene-butadiene- Styrene block copolymer (SEBS) is more preferred.
　ビニル芳香族エラストマー（Ｂ）は１種を単独で用いてもよく、軟質成分及び硬質成分の種類や割合、共重合構造や、ＭＦＲ等の物性の異なるものの２種以上を混合して用いてもよい。 As the vinyl aromatic elastomer (B), one kind may be used alone, or two or more kinds having different physical properties such as the kind and ratio of the soft component and the hard component, the copolymer structure, and MFR may be mixed and used. Good.
３．ポリエチレン系樹脂（Ａ）とビニル芳香族エラストマー（Ｂ）の割合
　本発明の多孔フィルムに含まれるポリエチレン系樹脂（Ａ）とビニル芳香族エラストマー（Ｂ）の割合は、ポリエチレン系樹脂（Ａ）５５～８５重量部、ビニル芳香族エラストマー（Ｂ）１５～４５重量部であり、好ましくはポリエチレン系樹脂（Ａ）６０～８０重量部、ビニル芳香族エラストマー（Ｂ）２０～４０重量部である（ただし、ポリエチレン系樹脂（Ａ）とビニル芳香族エラストマー（Ｂ）との合計で１００重量部）。 3. Ratio of polyethylene resin (A) and vinyl aromatic elastomer (B) The ratio of polyethylene resin (A) and vinyl aromatic elastomer (B) contained in the porous film of the present invention is as follows. 85 parts by weight, vinyl aromatic elastomer (B) 15-45 parts by weight, preferably polyethylene resin (A) 60-80 parts by weight, vinyl aromatic elastomer (B) 20-40 parts by weight (provided that 100 parts by weight in total of the polyethylene resin (A) and the vinyl aromatic elastomer (B)).
　従って、本発明のポリエチレン系樹脂組成物に含まれるポリエチレン系樹脂（Ａ）とビニル芳香族エラストマー（Ｂ）の割合も、ポリエチレン系樹脂（Ａ）５５～８５重量部、ビニル芳香族エラストマー（Ｂ）１５～４５重量部であり、好ましくはポリエチレン系樹脂（Ａ）６０～８０重量部、ビニル芳香族エラストマー（Ｂ）２０～４０重量部である（ただし、ポリエチレン系樹脂（Ａ）とビニル芳香族エラストマー（Ｂ）との合計で１００重量部）。 Therefore, the ratio of the polyethylene resin (A) and the vinyl aromatic elastomer (B) contained in the polyethylene resin composition of the present invention is 55 to 85 parts by weight of the polyethylene resin (A), the vinyl aromatic elastomer (B). 15 to 45 parts by weight, preferably 60 to 80 parts by weight of the polyethylene resin (A) and 20 to 40 parts by weight of the vinyl aromatic elastomer (B) (however, the polyethylene resin (A) and the vinyl aromatic elastomer) 100 parts by weight in total with (B)).
　ポリエチレン系樹脂（Ａ）が８５重量部以下でビニル芳香族エラストマー（Ｂ）が１５重量部以上であることによって、延伸による多孔化が生じやすくなり、十分な空気層を確保することで、透気性能の向上が期待できる。ポリエチレン系樹脂（Ａ）が５５重量部以上でビニル芳香族エラストマー（Ｂ）が４５重量部以下であることによって、本発明のポリエチレン系樹脂組成物中のビニル芳香族エラストマー（Ｂ）同士が凝集を生じやすくなり、延伸による多孔化が生じ難くなる。 When the polyethylene resin (A) is 85 parts by weight or less and the vinyl aromatic elastomer (B) is 15 parts by weight or more, porosity due to stretching is likely to occur, and by ensuring a sufficient air layer, air permeability An improvement in performance can be expected. When the polyethylene resin (A) is 55 parts by weight or more and the vinyl aromatic elastomer (B) is 45 parts by weight or less, the vinyl aromatic elastomers (B) in the polyethylene resin composition of the present invention aggregate together. It becomes easy to occur, and it becomes hard to produce the porosity by extending | stretching.
４．多孔フィルム中の他の成分
　本発明の多孔フィルム及び本発明のポリエチレン系樹脂組成物には、本発明の効果を損なわない範囲において、ポリエチレン系樹脂（Ａ）、ビニル芳香族エラストマー（Ｂ）以外の成分、例えばポリエチレン系樹脂（Ａ）以外の他の樹脂を含有してもよい。 4). Other components in the porous film The porous film of the present invention and the polyethylene resin composition of the present invention include those other than the polyethylene resin (A) and the vinyl aromatic elastomer (B), as long as the effects of the present invention are not impaired. You may contain other resin other than a component, for example, polyethylene-type resin (A).
　他の樹脂としては、ポリオレフィン系樹脂、ポリスチレン系樹脂、ポリ塩化ビニル系樹脂、ポリ塩化ビニリデン系樹脂、塩素化ポリエチレン系樹脂、ポリエステル系樹脂、ポリカーボネート系樹脂、ポリアミド系樹脂、ポリアセタール系樹脂、アクリル系樹脂、エチレン酢酸ビニル共重合体、ポリメチルペンテン系樹脂、ポリビニルアルコール系樹脂、環状オレフィン系樹脂、ポリ乳酸系樹脂、ポリブチレンサクシネート系樹脂、ポリアクリロニトリル系樹脂、ポリエチレンオキサイド系樹脂、セルロース系樹脂、ポリイミド系樹脂、ポリウレタン系樹脂、ポリフェニレンスルフィド系樹脂、ポリフェニレンエーテル系樹脂、ポリビニルアセタール系樹脂、ポリブタジエン系樹脂、ポリブテン系樹脂、ポリアミドイミド系樹脂、ポリアミドビスマレイミド系樹脂、ポリアリレート系樹脂、ポリエーテルイミド系樹脂、ポリエーテルエーテルケトン系樹脂、ポリエーテルケトン系樹脂、ポリエーテルスルホン系樹脂、ポリケトン系樹脂、ポリサルフォン系樹脂、アラミド系樹脂、フッ素系樹脂等が挙げられる。これらは１種を単独で用いてもよく、２種以上を組み合わせて用いてもよい。 Other resins include polyolefin resins, polystyrene resins, polyvinyl chloride resins, polyvinylidene chloride resins, chlorinated polyethylene resins, polyester resins, polycarbonate resins, polyamide resins, polyacetal resins, acrylic resins. Resin, ethylene vinyl acetate copolymer, polymethylpentene resin, polyvinyl alcohol resin, cyclic olefin resin, polylactic acid resin, polybutylene succinate resin, polyacrylonitrile resin, polyethylene oxide resin, cellulose resin , Polyimide resin, polyurethane resin, polyphenylene sulfide resin, polyphenylene ether resin, polyvinyl acetal resin, polybutadiene resin, polybutene resin, polyamideimide resin, polyamide Sumerimide resin, polyarylate resin, polyetherimide resin, polyetheretherketone resin, polyetherketone resin, polyethersulfone resin, polyketone resin, polysulfone resin, aramid resin, fluorine resin, etc. Is mentioned. These may be used individually by 1 type and may be used in combination of 2 or more type.
　本発明の多孔フィルム及び本発明のポリエチレン系樹脂組成物には、前述した成分のほか、本発明の効果を著しく阻害しない範囲内で、一般に樹脂組成物に配合される添加剤を適宜含有してもよい。これらの添加剤を含む場合、その含有量はポリエチレン系樹脂（Ａ）とビニル芳香族エラストマー（Ｂ）との合計１００重量部に対し、００．００１～１０．０重量部とすることが好ましく、０．００２～５．０重量部とするのがより好ましい。 In addition to the components described above, the porous film of the present invention and the polyethylene resin composition of the present invention appropriately contain additives generally incorporated in the resin composition within a range that does not significantly impair the effects of the present invention. Also good. When these additives are included, the content thereof is preferably 0.0001 to 10.0 parts by weight with respect to 100 parts by weight in total of the polyethylene resin (A) and the vinyl aromatic elastomer (B). More preferably, it is 0.002 to 5.0 parts by weight.
　添加剤としては、成形加工性、生産性および多孔フィルムの諸物性を改良・調整する目的で添加される、耳などのトリミングロス等から発生するリサイクル樹脂や、カーボンブラック等の顔料、結晶核剤、難燃剤、耐候性安定剤、耐熱安定剤、帯電防止剤、溶融粘度改良剤、架橋剤、滑剤、可塑剤、老化防止剤、酸化防止剤、光安定剤、紫外線吸収剤、中和剤、防曇剤、アンチブロッキング剤、スリップ剤、着色剤、分子吸着材などの添加剤が挙げられる。その中でも次に記載する結晶核剤を更に含有することが好ましい。 Additives include recycled resins generated from trimming loss such as ears, pigments such as carbon black, crystal nucleating agents, etc., added for the purpose of improving and adjusting molding processability, productivity, and various physical properties of the porous film. Flame retardants, weather resistance stabilizers, heat stabilizers, antistatic agents, melt viscosity improvers, crosslinking agents, lubricants, plasticizers, anti-aging agents, antioxidants, light stabilizers, UV absorbers, neutralizing agents, Additives such as anti-fogging agents, anti-blocking agents, slip agents, colorants, molecular adsorbents and the like can be mentioned. Among these, it is preferable to further contain the crystal nucleating agent described below.
５．結晶核剤（Ｃ）
　本発明のポリエチレン系樹脂組成物は、結晶核剤（Ｃ）を更に含有することが好ましい。結晶核剤（Ｃ）を含有することにより、ポリエチレン系樹脂（Ａ）の結晶化が促進され、結晶構造が緻密に均一化する。それゆえ、延伸前の樹脂組成物におけるポリエチレン系樹脂（Ａ）は緻密に均一化した結晶部と、該結晶部間に存在する非晶部とからなり、ビニル芳香族エラストマー（Ｂ）はポリエチレン系樹脂（Ａ）の非晶部に多く存在する。そのため、延伸によりポリエチレン系樹脂（Ａ）の緻密な結晶部とビニル芳香族エラストマー（Ｂ）との界面で生じる多孔化は、マトリックスの結晶化に伴う弾性率の向上によって容易になり、かつ、結晶の緻密な均一化によって、得られる多孔構造も緻密で均一な多孔構造を形成しやすくなる。 5). Crystal nucleating agent (C)
The polyethylene resin composition of the present invention preferably further contains a crystal nucleating agent (C). By containing the crystal nucleating agent (C), the crystallization of the polyethylene-based resin (A) is promoted, and the crystal structure is made dense and uniform. Therefore, the polyethylene-based resin (A) in the resin composition before stretching is composed of densely uniform crystal parts and amorphous parts existing between the crystal parts, and the vinyl aromatic elastomer (B) is a polyethylene-based resin. Many are present in the amorphous part of the resin (A). Therefore, the porosity that occurs at the interface between the dense crystal part of the polyethylene resin (A) and the vinyl aromatic elastomer (B) by stretching is facilitated by the improvement of the elastic modulus accompanying the crystallization of the matrix, and the crystal Due to the precise homogenization, the resulting porous structure can easily form a dense and uniform porous structure.
　結晶核剤（Ｃ）は、ポリエチレン系樹脂（Ａ）の結晶性を向上させる効果が認められれば、その種類を特に制限するものではない。例えばジベンジリデンソルビトール（ＤＢＳ）化合物；１，３－Ｏ－ビス（３，４ジメチルベンジリデン）ソルビトール；ジアルキルベンジリデンソルビトール；少なくとも一つの塩素または臭素置換基を有するソルビトールのジアセタール；ジ（メチルまたはエチル置換ベンジリデン）ソルビトール；炭素環を形成する置換基を有するビス（３，４－ジアルキルベンジリデン）ソルビトール；脂肪族、脂環族、及び、芳香族のカルボン酸、ジカルボン酸または多塩基性ポリカルボン酸、相当する無水物、及び、金属塩などの有機酸の金属塩化合物；環式ビス－フェノールホスフェート、２ナトリウムビシクロ［２．２．１］ヘプテンジカルボン酸などの二環式ジカルボン酸及び塩化合物；ビシクロ［２．２．１］ヘプタン－ジカルボキシレートなどの二環式ジカルボキシレートの飽和の金属または有機の塩化合物；１，３：２，４－Ｏ－ジベンジリデン－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（ｍ－メチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（ｍ－エチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（ｍ－イソプロピルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（ｍ－ｎ－プロピルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（ｍ－ｎ－ブチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（ｐ－メチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（ｐ－エチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（ｐ－イソプロピルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（ｐ－ｎ－プロピルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（ｐ－ｎ－ブチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（２，３－ジメチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（２，４－ジメチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（２，５－ジメチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（３，４－ジメチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（３，５－ジメチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（２，３－ジエチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（２，４－ジエチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（２，５－ジエチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（３，４－ジエチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（３，５－ジエチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（２，４，５－トリメチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（３，４，５－トリメチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（２，４，５－トリエチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（３，４，５－トリエチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（ｐ－メチルオキシカルボニルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（ｐ－エチルオキシカルボニルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（ｐ－イソプロピルオキシカルボニルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（ｏ－ｎ－プロピルオキシカルボニルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（ｏ－ｎ－ブチルベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（ｏ－クロロベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－（ｐ－クロロベンジリデン）－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－［（５，６，７，８,－テトラヒドロ－１－ナフタレン）－１－メチレン］－Ｄ－ソルビトール、１，３：２，４－ビス－Ｏ－［（５，６，７，８,－テトラヒドロ－２－ナフタレン）－１－メチレン］－Ｄ－ソルビトール、１，３－Ｏ－ベンジリデン－２，４－Ｏ－ｐ－メチルベンジリデン－Ｄ－ソルビトール、１，３－Ｏ－ｐ－メチルベンジリデン－２，４－Ｏ－ベンジリデン－Ｄ－ソルビトール、１，３－Ｏ－ベンジリデン－２，４－Ｏ－ｐ－エチルベンジリデン－Ｄ－ソルビトール、１，３－Ｏ－ｐ－エチルベンジリデン－２，４－Ｏ－ベンジリデン－Ｄ－ソルビトール、１，３－Ｏ－ベンジリデン－２，４－Ｏ－ｐ－クロルベンジリデン－Ｄ－ソルビトール、１，３－Ｏ－ｐ－クロルベンジリデン－２，４－Ｏ－ベンジリデン－Ｄ－ソルビトール、１，３－Ｏ－ベンジリデン－２，４－Ｏ－（２，４－ジメチルベンジリデン）－Ｄ－ソルビトール、１，３－Ｏ－（２，４－ジメチルベンジリデン）－２，４－Ｏ－ベンジリデン－Ｄ－ソルビトール、１，３－Ｏ－ベンジリデン－２，４－Ｏ－（３，４－ジメチルベンジリデン）－Ｄ－ソルビトール、１，３－Ｏ－（３，４－ジメチルベンジリデン）－２，４－Ｏ－ベンジリデン－Ｄ－ソルビトール、１，３－Ｏ－ｐ－メチル－ベンジリデン－２，４－Ｏ－ｐ－エチルベンジリデンソルビトール、１，３－ｐ－エチル－ベンジリデン－２，４－ｐ－メチルベンジリデン－Ｄ－ソルビトール、１，３－Ｏ－ｐ－メチル－ベンジリデン－２，４－Ｏ－ｐ－クロルベンジリデン－Ｄ－ソルビトール、及び、１，３－Ｏ－ｐ－クロル－ベンジリデン－２，４－Ｏ－ｐ－メチルベンジリデン－Ｄ－ソルビトールなどのジアセタール化合物；ナトリウム２，２’－メチレン－ビス－（４，６－ジ－ｔｅｒｔ－ブチルフェニル）ホスフェート、アルミニウムビス［２，２’－メチレン－ビス－（４－６－ジ－ｔｅｒｔ－ブチルフェニル）ホスフェート］、燐酸２，２－メチレンビス（４，６－ジ－ｔｅｒｔ－ブチルフェニル）ナトリウムや、カプロン酸、エナント酸、カプリル酸、ペラルゴン酸、カプリン酸、ウンデカン酸、ラウリン酸、トリデカン酸、ミリスチン酸、ペンタデカン酸、パルミチン酸、マーガリン酸、ステアリン酸、ノナデカン酸、アラキン酸、ベヘニン酸、モンタン酸等の脂肪酸；オレイン酸アミド、エルカ酸アミド、ステアリン酸アミド、及び、ヘベニン酸アミドなどの脂肪酸アミド；ステアリン酸マグネシウム、ステアリン酸亜鉛、及び、ステアリン酸カルシウム等の脂肪酸金属塩；シリカ、タルク、カオリン、及び、炭化カルシウム等の無機粒子；グリセロール、グリセリンモノエステルなどの高級脂肪酸エステル、及び類似物を挙げることができる。 The type of the crystal nucleating agent (C) is not particularly limited as long as the effect of improving the crystallinity of the polyethylene resin (A) is recognized. For example, dibenzylidene sorbitol (DBS) compound; 1,3-O-bis (3,4 dimethylbenzylidene) sorbitol; dialkyl benzylidene sorbitol; diacetal of sorbitol having at least one chlorine or bromine substituent; di (methyl or ethyl substituted benzylidene) ) Sorbitol; bis (3,4-dialkylbenzylidene) sorbitol having a substituent that forms a carbocycle; aliphatic, alicyclic and aromatic carboxylic acids, dicarboxylic acids or polybasic polycarboxylic acids, corresponding Metal salts of organic acids such as anhydrides and metal salts; bicyclic dicarboxylic acids and salts such as cyclic bis-phenol phosphate, disodium bicyclo [2.2.1] heptenedicarboxylic acid; bicyclo [ 2.2.1] Heptane-dicarboxyle Bicyclic dicarboxylate saturated metal or organic salt compounds such as 1,3: 2,4-O-dibenzylidene-D-sorbitol, 1,3: 2,4-bis-O— (m -Methylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (m-ethylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (m-isopropylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (mn-propylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (mn-butylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (p-methylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (p-ethylbenzylidene) -D-sorbitol 1,3: 2,4-bis-O (P-isopropylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (pn-propylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (p -N-butylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (2,3-dimethylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (2 , 4-Dimethylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (2,5-dimethylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O— (3 , 4-Dimethylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (3,5-dimethylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O— (2 , 3-Diethylbenzylidene) -D-sorby Tol, 1,3: 2,4-bis-O- (2,4-diethylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (2,5-diethylbenzylidene) -D- Sorbitol, 1,3: 2,4-bis-O- (3,4-diethylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (3,5-diethylbenzylidene) -D- Sorbitol, 1,3: 2,4-bis-O- (2,4,5-trimethylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (3,4,5-trimethylbenzylidene ) -D-sorbitol, 1,3: 2,4-bis-O- (2,4,5-triethylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (3,4, 5-triethylbenzylidene) -D-sorbitol, 1,3: 2 4-bis-O- (p-methyloxycarbonylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (p-ethyloxycarbonylbenzylidene) -D-sorbitol, 1,3: 2, 4-bis-O- (p-isopropyloxycarbonylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (on-propyloxycarbonylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (on-butylbenzylidene) -D-sorbitol, 1,3: 2,4-bis-O- (o-chlorobenzylidene) -D-sorbitol, 1,3: 2, 4-bis-O- (p-chlorobenzylidene) -D-sorbitol, 1,3: 2,4-bis-O-[(5,6,7,8, -tetrahydro-1-naphthalene) -1-methylene ] D-sorbitol, 1,3: 2,4-bis-O-[(5,6,7,8, -tetrahydro-2-naphthalene) -1-methylene] -D-sorbitol, 1,3-O-benzylidene -2,4-Op-methylbenzylidene-D-sorbitol, 1,3-Op-methylbenzylidene-2,4-O-benzylidene-D-sorbitol, 1,3-O-benzylidene-2,4 -Op-ethylbenzylidene-D-sorbitol, 1,3-Op-ethylbenzylidene-2,4-O-benzylidene-D-sorbitol, 1,3-O-benzylidene-2,4-Op -Chlorbenzylidene-D-sorbitol, 1,3-O-p-chlorobenzylidene-2,4-O-benzylidene-D-sorbitol, 1,3-O-benzylidene-2,4-O- (2,4- Zimechi Benzylidene) -D-sorbitol, 1,3-O- (2,4-dimethylbenzylidene) -2,4-O-benzylidene-D-sorbitol, 1,3-O-benzylidene-2,4-O- (3 , 4-Dimethylbenzylidene) -D-sorbitol, 1,3-O- (3,4-dimethylbenzylidene) -2,4-O-benzylidene-D-sorbitol, 1,3-Op-methyl-benzylidene- 2,4-Op-ethylbenzylidenesorbitol, 1,3-p-ethyl-benzylidene-2,4-p-methylbenzylidene-D-sorbitol, 1,3-Op-methyl-benzylidene-2,4 -Op-chlorobenzylidene-D-sorbitol and 1,3-Op-chloro-benzylidene-2,4-Op-methylbenzylidene-D-sorbitol Diacetal compounds of sodium 2,2′-methylene-bis- (4,6-di-tert-butylphenyl) phosphate, aluminum bis [2,2′-methylene-bis- (4-6-di-tert-butyl) Phenyl) phosphate], sodium 2,2-methylenebis (4,6-di-tert-butylphenyl) phosphate, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, Fatty acids such as myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, montanic acid; fatty acids such as oleic acid amide, erucic acid amide, stearic acid amide, and hebenic acid amide Amides; magnesium stearate, zinc stearate, and And fatty acid metal salts such as calcium stearate; inorganic particles such as silica, talc, kaolin, and calcium carbide; higher fatty acid esters such as glycerol and glycerin monoester, and the like.
　これらの中でも、オレイン酸アミド、エルカ酸アミド、ステアリン酸アミド、及び、ヘベニン酸アミドなどの脂肪酸アミド；ステアリン酸マグネシウム、ステアリン酸亜鉛、ステアリン酸カルシウム等の脂肪酸金属塩が特に好ましい。 Among these, fatty acid amides such as oleic acid amide, erucic acid amide, stearic acid amide, and hebenic acid amide; fatty acid metal salts such as magnesium stearate, zinc stearate, and calcium stearate are particularly preferable.
　結晶核剤（Ｃ）の具体例としては、新日本理化（株）の商品名「ゲルオールＤ」シリーズ、（株）ＡＤＥＫＡの商品名「アデカスタブ」シリーズ、ミリケンケミカル社の商品名「Ｍｉｌｌａｄ」シリーズ、「Ｈｙｐｅｒｆｏｒｍ」シリーズ、ＢＡＳＦ社の商品名「ＩＲＧＡＣＬＥＡＲ」シリーズ等が挙げられる。結晶核剤のマスターバッチとしては理研ビタミン（株）の商品名「リケマスターＣＮ」シリーズ、ミリケンケミカル社の商品名「ＨＬ３－４」等が挙げられる。この中でも特に透明性を向上する効果が高いものとして、ミリケンケミカル社の商品名「ＨＹＰＥＲＦＯＲＭ　ＨＰＮ－２０Ｅ」、「ＨＬ３－４」、理研ビタミン（株）の商品名「リケマスターＣＮ－００１」「リケマスターＣＮ－００２」が挙げられる。 As specific examples of the crystal nucleating agent (C), the trade name “Gelall D” series of Shin Nippon Rika Co., Ltd., the product name “Adeka Stub” series of ADEKA Co., Ltd., the product name “Millad” series of Milliken Chemical Co., Ltd., Examples include the “Hyperform” series and the BASF brand name “IRGACLEAR” series. Examples of the master batch of the crystal nucleating agent include “Rike Master CN” series of Riken Vitamin Co., Ltd. and “HL3-4” of Milkenn Chemical. Among these, the products with the highest effect of improving the transparency are the product names of Milliken Chemicals “HYPERFORM HPN-20E” and “HL3-4”, and the product names of Riken Vitamin Co., Ltd. “Rike Master CN-001” “Rike Master CN-002 ".
　結晶核剤（Ｃ）は１種を単独で用いてもよく、２種以上を併用してもよい。 As the crystal nucleating agent (C), one type may be used alone, or two or more types may be used in combination.
　結晶核剤（Ｃ）は、ポリエチレン系樹脂（Ａ）とビニル芳香族エラストマー（Ｂ）との合計１００重量部に対し、０．００１～１０重量部の割合で用いることが好ましく、より好ましくは０．００５～５重量部である。 The crystal nucleating agent (C) is preferably used in a proportion of 0.001 to 10 parts by weight, more preferably 0 to 100 parts by weight in total of the polyethylene resin (A) and the vinyl aromatic elastomer (B). 0.005 to 5 parts by weight.
　上記の結晶核剤（Ｃ）のうち、理研ビタミン（株）の商品名「リケマスターＣＮ－００１」「リケマスターＣＮ－００２」については、ポリエチレン系樹脂（Ａ）に対し、０．５～５．０重量部用いることが好ましい。 Among the above crystal nucleating agents (C), the product names “Rike Master CN-001” and “Rike Master CN-002” of Riken Vitamin Co., Ltd. are 0.5 to 5 with respect to the polyethylene resin (A). It is preferable to use 0.0 parts by weight.
６．多孔フィルム
　本発明の多孔フィルムの好適物性等について説明する。 6). Porous film Preferred physical properties of the porous film of the present invention will be described.
（１）厚み
　本発明の多孔フィルムの厚みは、特に制限されるものではないが、７０μｍ以上が好ましく、１００μｍ以上がより好ましい。本発明の多孔フィルムの厚みは３００μｍ以下が好ましく、２００μｍ以下がより好ましい。厚みが７０μｍ以上であれば、充分な強度を有することができる。厚みが３００μｍ以下であれば、小型化・軽量化が求められる用途に対しても使用が容易である。 (1) Thickness The thickness of the porous film of the present invention is not particularly limited, but is preferably 70 μm or more, and more preferably 100 μm or more. The thickness of the porous film of the present invention is preferably 300 μm or less, and more preferably 200 μm or less. If thickness is 70 micrometers or more, it can have sufficient intensity | strength. If the thickness is 300 μm or less, it can be easily used for applications that require reduction in size and weight.
（２）透気度
　本発明の多孔フィルムの透気度は、２００秒／１００ｍｌ以下である。本発明の多孔フィルムの透気度は、好ましくは１秒／１００ｍｌ以上１００秒／１００ｍｌ以下、より好ましくは５秒／１００ｍｌ以上５０秒／１００ｍｌ以下である。透気度が上記範囲であれば、強度と多孔性を両立した多孔フィルムとなるため好ましい。 (2) Air permeability The air permeability of the porous film of the present invention is 200 seconds / 100 ml or less. The air permeability of the porous film of the present invention is preferably 1 second / 100 ml to 100 seconds / 100 ml, more preferably 5 seconds / 100 ml to 50 seconds / 100 ml. If the air permeability is within the above range, a porous film having both strength and porosity is preferable.
　多孔フィルムの透気度をフィルム厚み１μｍあたりに換算した値は、好ましくは０．０１秒／１００ｍｌ／μｍ以上０．３５秒／１００ｍｌ／μｍ以下、より好ましくは０．０２秒／１００ｍｌ／μｍ以上０．３０秒／１００ｍｌ／μｍ以下である。厚さ１μｍあたりの透気度が上記の範囲であると、以下に示す好適な濾過速度を有する多孔フィルムとなり易いため好ましい。 The value obtained by converting the air permeability of the porous film per 1 μm of the film thickness is preferably 0.01 seconds / 100 ml / μm or more and 0.35 seconds / 100 ml / μm or less, more preferably 0.02 seconds / 100 ml / μm or more. It is 0.30 second / 100 ml / μm or less. It is preferable for the air permeability per 1 μm thickness to be in the above range because a porous film having the following suitable filtration rate can be easily obtained.
　多孔フィルムの透気度は、後掲の実施例の項に記載される方法で測定される。 The air permeability of the porous film is measured by the method described in the Examples section below.
（３）空孔率
　空孔率は多孔構造を規定するための重要な要素であり、本発明の多孔フィルムにおける多孔層の空間部分の割合を示す数値である。一般に空孔率が高いほど、優れた濾過速度を有することが知られており、本発明の多孔フィルムは、空孔率が５０％以上であり、好ましくは６０％以上、より好ましくは６５％以上である。本発明の多孔フィルムの空孔率は９８％以下が好ましく、９５％以下がより好ましい。空孔率が５０％以上であれば、透気性能及び濾過速度に優れた多孔フィルムとなる。空孔率が９８％以下であれば実用的な強度を得ることができる。 (3) Porosity The porosity is an important factor for defining the porous structure, and is a numerical value indicating the ratio of the space portion of the porous layer in the porous film of the present invention. In general, it is known that the higher the porosity, the better the filtration rate, and the porous film of the present invention has a porosity of 50% or more, preferably 60% or more, more preferably 65% or more. It is. The porosity of the porous film of the present invention is preferably 98% or less, and more preferably 95% or less. When the porosity is 50% or more, a porous film excellent in air permeability and filtration rate is obtained. If the porosity is 98% or less, a practical strength can be obtained.
　多孔フィルムの空孔率は、後掲の実施例の項に記載される方法で測定される。 The porosity of the porous film is measured by the method described in the Examples section below.
（４）濾過速度
　本発明の多孔フィルムの濾過速度は、好ましくは１０ｍｌ／ｍｉｎ・ｃｍ２以上、より好ましくは１５ｍｌ／ｍｉｎ・ｃｍ２以上、更に好ましくは２０ｍｌ／ｍｉｎ・ｃｍ２以上である。本発明の多孔フィルムの濾過速度は、好ましくは１００ｍｌ／ｍｉｎ・ｃｍ２以下、より好ましくは９０ｍｌ／ｍｉｎ・ｃｍ２以下、更に好ましくは８０ｍｌ／ｍｉｎ・ｃｍ２以下である。濾過速度が上記範囲であれば、強度と濾過効率を両立した多孔フィルムとなる。 (4) Filtration rate The filtration rate of the porous film of the present invention is preferably 10 ml / min · cm 2 or more, more preferably 15 ml / min · cm 2 or more, and further preferably 20 ml / min · cm 2 or more. The filtration rate of the porous film of the present invention is preferably 100 ml / min · cm 2 or less, more preferably 90 ml / min · cm 2 or less, still more preferably 80 ml / min · cm 2 or less. When the filtration rate is in the above range, a porous film having both strength and filtration efficiency is obtained.
　濾過速度は、２５℃の空気雰囲気下において、所定の体積Ｖ（ｍｌ）のアセトンが０．０７ＭＰａの圧力で、有効濾過面積Ａ（ｃｍ２）の多孔フィルムを通過する時間ｔ（ｓｅｃ）を測定し、下記式に基づき算出される。
　　　濾過速度［ｍｌ／ｍｉｎ・ｃｍ２］＝（Ｖ×６０）／（ｔ×Ａ） The filtration rate is a time t (sec) in which an acetone having a predetermined volume V (ml) passes through a porous film having an effective filtration area A (cm 2 ) at a pressure of 0.07 MPa in an air atmosphere at 25 ° C. And calculated based on the following formula.
Filtration rate [ml / min · cm 2 ] = (V × 60) / (t × A)
（５）濾過寿命
　本発明の多孔フィルムの濾過寿命は、好ましくは１．００ｇ／ｃｍ２以上、１０ｇ／ｃｍ２以下であり、より好ましくは５．０ｇ／ｃｍ２以下、更に好ましくは２．０ｇ／ｃｍ２以下である。濾過寿命が上記範囲であれば、濾過効率が良好な多孔フィルムとなる。 (5) Filtration life The filtration life of the porous film of the present invention is preferably 1.00 g / cm 2 or more and 10 g / cm 2 or less, more preferably 5.0 g / cm 2 or less, and still more preferably 2.0 g. / Cm 2 or less. When the filtration life is within the above range, a porous film having good filtration efficiency is obtained.
　多孔フィルムの濾過寿命（ｇ／ｃｍ２）は、日産化学社製コロイダルシリカ（製品名：スノーテックスＭＰ－４５４０Ｍ、平均粒子径：４５０ｎｍ、固形分：４０重量％、媒体：水）をシリカ濃度４重量％になるように水で希釈し、超音波攪拌機中で十分に均一分散させた後、０．０９ＭＰａの圧力で多孔フィルムを通過させ、濾過が不可能になるまでに通過させた液体の重量Ｗ（ｇ）を測定し、多孔フィルムの有効濾過面積Ａ（ｃｍ２）で除算することによって算出される。 The filtration life (g / cm 2 ) of the porous film was calculated by colloidal silica (product name: Snowtex MP-4540M, average particle size: 450 nm, solid content: 40% by weight, medium: water) manufactured by Nissan Chemical Co., Ltd. with a silica concentration of 4 The weight of the liquid which was diluted with water so as to be weight% and sufficiently dispersed uniformly in an ultrasonic stirrer, then passed through the porous film at a pressure of 0.09 MPa, and before filtration became impossible It is calculated by measuring W (g) and dividing by the effective filtration area A (cm 2 ) of the porous film.
（６）濾過精度
　本発明の多孔フィルムの濾過精度は、好ましくは０．５０％以下、より好ましくは０．２５％以下、更に好ましくは０．２０％以下である。濾過精度が上記上限以下であれば、濾過精度が良好な多孔フィルムとなる。 (6) Filtration accuracy The filtration accuracy of the porous film of the present invention is preferably 0.50% or less, more preferably 0.25% or less, and still more preferably 0.20% or less. If the filtration accuracy is less than or equal to the above upper limit, the porous film has good filtration accuracy.
　濾過精度は、日産化学社製コロイダルシリカ（製品名：スノーテックスＭＰ－４５４０Ｍ、平均粒子径：４５０ｎｍ、固形分：４０重量％、媒体：水）をシリカ濃度４重量％になるように水で希釈し、超音波攪拌機中で十分に均一分散させた後、０．０７ＭＰａの圧力で多孔フィルムを通過させ、吸光度法により通過前後の液の濃度を測定し、粒子の捕集効率（％）を求めることで算出される。 Filtration accuracy was diluted with water so that the colloidal silica (product name: Snowtex MP-4540M, average particle size: 450 nm, solid content: 40% by weight, medium: water) manufactured by Nissan Chemical Co., Ltd. would have a silica concentration of 4% by weight. Then, after being sufficiently uniformly dispersed in an ultrasonic stirrer, the porous film is passed at a pressure of 0.07 MPa, and the concentration of the liquid before and after passing is measured by an absorbance method to determine the particle collection efficiency (%). It is calculated by.
　本発明の多孔フィルムは、密度が０．９５５～０．９７０ｇ／ｃｍ３であるポリエチレン系樹脂（Ａ）とビニル芳香族エラストマー（Ｂ）を所定の割合で含み、上記の透気度、空孔率を有するものである。この多孔フィルムは、延伸前のフィルム中のビニル芳香族エラストマーの分散径に由来する孔径分布が水濾過に適しており、上記の濾過速度、濾過寿命、及び、濾過精度の範囲を満たす。 The porous film of the present invention contains a polyethylene resin (A) having a density of 0.955 to 0.970 g / cm 3 and a vinyl aromatic elastomer (B) at a predetermined ratio, and the air permeability and pores described above. Has a rate. In this porous film, the pore size distribution derived from the dispersion diameter of the vinyl aromatic elastomer in the film before stretching is suitable for water filtration, and satisfies the above filtration speed, filtration life, and filtration accuracy ranges.
　これに対して、前述の特許文献４のように、硫酸バリウム、炭酸カルシウム等の無機充填剤を高い割合で含む未延伸シートを延伸して製造される多孔フィルムは、無機充填剤の凝集により延伸ムラが生じ、孔の大きさの不均一性及び孔形成のバラツキにより、本発明の多孔フィルムに比較して連通孔を形成がし難くなると考えられる。従って、空孔形成の割合が低い多孔構造となり、透気度も劣るフィルムとなる。空孔形成の割合が低い多孔構造となり、透気度が上記の範囲を満たすことができず、強度と多孔性を両立した多孔フィルムとするのは困難である。 On the other hand, as in the above-mentioned Patent Document 4, a porous film produced by stretching an unstretched sheet containing a high proportion of an inorganic filler such as barium sulfate or calcium carbonate is stretched by aggregation of the inorganic filler. It is considered that unevenness occurs and it is difficult to form communication holes as compared with the porous film of the present invention due to non-uniformity in the size of the holes and variations in hole formation. Therefore, it becomes a porous structure with a low rate of pore formation and a film with poor air permeability. It becomes a porous structure with a low rate of pore formation, the air permeability cannot satisfy the above range, and it is difficult to obtain a porous film having both strength and porosity.
　一方、ポリプロピレン系樹脂とビニル芳香族エラストマーから得られる多孔フィルムは、後述する比較例９に示す通り、フィルム厚み１μｍあたりの透気度が劣り、かつ濾過寿命が、本発明の多孔フィルムと比較して劣るフィルムとなる。 On the other hand, as shown in Comparative Example 9 described later, the porous film obtained from the polypropylene resin and the vinyl aromatic elastomer has a poor air permeability per 1 μm of film thickness and has a filtration life compared to the porous film of the present invention. Film is inferior.
７．多孔フィルムの製造方法
　本発明の多孔フィルムを製造する方法としては、次のような方法が挙げられる。
　まず、ポリエチレン系樹脂（Ａ）、ビニル芳香族エラストマー（Ｂ）、及び、必要に応じて配合される結晶核剤（Ｃ）、その他の成分を含む本発明のポリエチレン系樹脂組成物を調製する。このポリエチレン系樹脂組成物をポリエチレン系樹脂（Ａ）の融点以上、分解温度未満の温度条件下で押出機等を用いて溶融・成形することによって、無孔膜状物（未延伸シート）を得る。得られた未延伸シートを一軸延伸又は二軸延伸する。この方法であれば、未延伸シートの組成（ポリエチレン系樹脂組成物の組成）、厚み、および延伸倍率を変更することにより、作成される多孔フィルムの厚み、透気度、空孔率を容易に調整することができ、好ましい。 7). The manufacturing method of a porous film As a method of manufacturing the porous film of this invention, the following methods are mentioned.
First, a polyethylene resin composition of the present invention containing a polyethylene resin (A), a vinyl aromatic elastomer (B), a crystal nucleating agent (C) blended as necessary, and other components is prepared. By melting and molding this polyethylene-based resin composition using an extruder or the like under a temperature condition not lower than the melting point of the polyethylene-based resin (A) and lower than the decomposition temperature, a non-porous film (unstretched sheet) is obtained. . The obtained unstretched sheet is uniaxially stretched or biaxially stretched. With this method, the thickness, air permeability, and porosity of the porous film to be created can be easily changed by changing the composition of the unstretched sheet (the composition of the polyethylene resin composition), the thickness, and the stretch ratio. It can be adjusted and is preferable.
　未延伸シートの成形方法として、より具体的にはＴダイ成形が挙げられる。 More specifically, a method of forming an unstretched sheet includes T-die molding.
　本発明のポリエチレン系樹脂組成物の混練物を冷却しながら未延伸シートを成形する際のキャストロールの温度は８０℃以上が好ましく、より好ましくは９０℃以上、更に好ましくは１００℃以上である。本発明ではポリエチレン系樹脂（Ａ）の結晶部分と非晶部分での延伸工程時による開孔によっても、良好な空孔構造を形成することが可能である。従って、キャストロールの温度を１００℃以上とし、高い結晶化度の未延伸シートを得ることが好ましい。キャストロールの温度の上限は、ポリエチレン系樹脂組成物の溶融温度より低く、通常１１５℃以下である。 The temperature of the cast roll when forming the unstretched sheet while cooling the kneaded product of the polyethylene resin composition of the present invention is preferably 80 ° C. or higher, more preferably 90 ° C. or higher, still more preferably 100 ° C. or higher. In the present invention, it is possible to form a favorable pore structure even by opening the polyethylene resin (A) in the crystal part and the amorphous part during the stretching step. Therefore, it is preferable to obtain a non-stretched sheet having a high crystallinity by setting the temperature of the cast roll to 100 ° C. or higher. The upper limit of the temperature of the cast roll is lower than the melting temperature of the polyethylene resin composition, and is usually 115 ° C. or lower.
　次いで、得られた未延伸シートについて一軸延伸、又は二軸延伸を行う。一軸延伸は縦一軸延伸であってもよいし、横一軸延伸であってもよい。二軸延伸は同時二軸延伸であってもよいし、逐次二軸延伸であってもよい。 Next, the obtained unstretched sheet is uniaxially stretched or biaxially stretched. Uniaxial stretching may be longitudinal uniaxial stretching or transverse uniaxial stretching. Biaxial stretching may be simultaneous biaxial stretching or sequential biaxial stretching.
　本発明で目的とする、空孔率が高く、透気性能に優れた多孔フィルムを作製するには、各延伸工程で延伸条件を選択でき、多孔構造を制御し易い逐次二軸延伸を行うことがより好ましい。
　膜状物の流れ方向（ＭＤ）への延伸を「縦延伸」といい、流れ方向に対して垂直方向（ＴＤ）への延伸を「横延伸」という。 In order to produce a porous film having a high porosity and excellent air permeability, which is an object of the present invention, it is possible to select stretching conditions in each stretching step, and perform sequential biaxial stretching that makes it easy to control the porous structure. Is more preferable.
Stretching in the flow direction (MD) of the film-like material is referred to as “longitudinal stretching”, and stretching in the direction perpendicular to the flow direction (TD) is referred to as “lateral stretching”.
　逐次二軸延伸を用いる場合、延伸温度を、用いるポリエチレン系樹脂組成物の組成、結晶融解ピーク温度、結晶化度等によって適時選択する必要がある。逐次二軸延伸は多孔構造の制御が比較的容易であり、機械強度や収縮率など他の諸物性とのバランスがとりやすいという利点がある。 When using sequential biaxial stretching, it is necessary to select the stretching temperature in a timely manner according to the composition of the polyethylene-based resin composition to be used, the crystal melting peak temperature, the crystallinity, and the like. Sequential biaxial stretching has the advantage that the porous structure is relatively easy to control and can easily be balanced with other physical properties such as mechanical strength and shrinkage.
　逐次二軸延伸を用いる場合、以下の手順で縦延伸及び横延伸を行うことが好ましい。 When using sequential biaxial stretching, it is preferable to perform longitudinal stretching and lateral stretching in the following procedure.
＜縦延伸工程＞
（低温縦延伸工程）
　縦延伸を行う際は、延伸による開孔をし易くする理由から、高温縦延伸の前に以下の低温縦延伸工程を行うことが好ましい。 <Vertical stretching process>
(Low-temperature longitudinal stretching process)
When performing longitudinal stretching, it is preferable to perform the following low-temperature longitudinal stretching step before high-temperature longitudinal stretching for the purpose of facilitating opening by stretching.
　未延伸シートを０℃以上６０℃未満、好ましくは１０℃以上４０℃未満の温度で、機械方向に１．１倍以上３．０倍未満、好ましくは１．２倍以上２．０倍未満の範囲でＭＤ方向に一軸延伸する。ここで、０℃未満で延伸した場合はフィルムが破断する傾向があり、６０℃以上で延伸した場合は、得られる延伸フィルムの空孔率が低く、透気度が高くなる傾向がある。 The unstretched sheet has a temperature of 0 ° C. or more and less than 60 ° C., preferably 10 ° C. or more and less than 40 ° C., and is 1.1 times or more and less than 3.0 times, preferably 1.2 times or more and less than 2.0 times in the machine direction. Uniaxial stretching is performed in the MD direction within the range. Here, when stretched at less than 0 ° C., the film tends to break, and when stretched at 60 ° C. or higher, the resulting stretched film has a low porosity and a high air permeability.
　得られる多孔フィルムの透気性能が向上することから、上記延伸工程を実施する前に、シート成形工程で得られた未延伸シートを一定の温度範囲で一定時間熱処理しても良い。 Since the air permeation performance of the resulting porous film is improved, the unstretched sheet obtained in the sheet forming step may be heat-treated for a certain time in a certain temperature range before the stretching step.
（高温縦延伸工程）
　次いで、上記の低温縦延伸で得られた延伸シートを６０℃以上１６０℃未満、好ましくは７０℃以上１３０℃未満の温度でＭＤ方向に１．５倍以上６．０倍未満、好ましくは１．５倍以上５．０倍の範囲で一軸延伸する。ここで、６０℃未満で延伸した場合はフィルムが破断する傾向があり、１６０℃以上で延伸した場合は、得られる延伸フィルムの空孔率が低く、透気度が高くなる傾向がある。 (High-temperature longitudinal stretching process)
Next, the stretched sheet obtained by the above-described low-temperature longitudinal stretching is at least 60.degree. C. and less than 160.degree. C., preferably 70.degree. C. to less than 130.degree. Uniaxial stretching is performed in the range of 5 times to 5.0 times. Here, when stretched at less than 60 ° C., the film tends to break, and when stretched at 160 ° C. or higher, the porosity of the obtained stretched film tends to be low and the air permeability tends to be high.
　上記したような条件で２段階以上で延伸することで、各種用途に好適な良好な物性の多孔フィルムを得ることができる。この縦延伸工程を１段階とすると、得られる延伸フィルムが、要求された物性を満たさない場合がある。 A porous film having good physical properties suitable for various applications can be obtained by stretching in two or more stages under the conditions described above. If this longitudinal stretching step is one stage, the stretched film obtained may not satisfy the required physical properties.
　縦延伸倍率は、任意に選択することができるが、一軸延伸（低温縦延伸と高温縦延伸の合計）あたりの延伸倍率は１．７～１５倍が好ましく、より好ましくは１．８～１２倍であり、さらに好ましくは２．０～１０倍である。一軸延伸あたりの延伸倍率を１．７倍以上とすることで白化が進行して、延伸による多孔化が十分起こる。一軸延伸あたりの延伸倍率を１０倍以下とすることで、空孔の変形は抑制され、十分に白化した多孔フィルムを得ることができる。 The longitudinal stretching ratio can be arbitrarily selected, but the stretching ratio per uniaxial stretching (total of low temperature longitudinal stretching and high temperature longitudinal stretching) is preferably 1.7 to 15 times, more preferably 1.8 to 12 times. More preferably, it is 2.0 to 10 times. By setting the draw ratio per uniaxial drawing to 1.7 times or more, whitening proceeds and sufficient porosity is obtained by drawing. By setting the draw ratio per uniaxial stretch to 10 times or less, deformation of pores is suppressed, and a sufficiently whitened porous film can be obtained.
＜横延伸工程＞
　横延伸温度は、好ましくは７０～１５０℃であり、より好ましくは８０～１４０℃である。横延伸温度がこの範囲内であることによって、縦延伸時に生じた空孔が拡大されて空孔率を増加することができ、十分な多孔性を有することができる。 <Horizontal stretching process>
The transverse stretching temperature is preferably 70 to 150 ° C, more preferably 80 to 140 ° C. When the transverse stretching temperature is within this range, the pores generated during the longitudinal stretching can be expanded to increase the porosity, so that sufficient porosity can be obtained.
　横延伸倍率は、任意に選択できるが、好ましくは１．１～１０倍、より好ましくは１．５～９．０倍、更に好ましくは２．０～８．０倍である。この範囲の横延伸倍率で延伸することによって、縦延伸時に生じた空孔を変形させることなく、十分な空孔率を有する多孔フィルムを得ることができる。 The transverse draw ratio can be arbitrarily selected, but is preferably 1.1 to 10 times, more preferably 1.5 to 9.0 times, and still more preferably 2.0 to 8.0 times. By stretching at a transverse stretching ratio in this range, a porous film having a sufficient porosity can be obtained without deforming pores generated during longitudinal stretching.
＜熱処理＞
　上記の逐次二軸延伸を行った後は、寸法安定性の向上のために、熱処理を行ってもよい。熱処理は、通常１００～１５０℃で１秒～３０分程度実施される。 <Heat treatment>
After performing the above-mentioned sequential biaxial stretching, heat treatment may be performed in order to improve dimensional stability. The heat treatment is usually performed at 100 to 150 ° C. for about 1 second to 30 minutes.
　本発明の多孔フィルムは、このようにして多孔フィルムを作製した後、本発明の効果を損なわない範囲で、必要に応じてコロナ処理、プラズマ処理、印刷、コーティング、蒸着等の表面加工、更にはミシン目加工などを施すことができる。用途に応じて本発明の多孔フィルムを数枚重ねて使用することも可能である。 After the porous film of the present invention is produced in this way, the surface processing such as corona treatment, plasma treatment, printing, coating, vapor deposition, etc., if necessary, as long as the effects of the present invention are not impaired. Perforation can be applied. Depending on the application, it is also possible to use several porous films of the present invention.
　多孔フィルムを製造する際、前述の特許文献３のように、製膜溶剤を有機溶媒によって抽出することによる手法では、抽出処理に要するコストが大きく、環境への影響がある。製造された多孔フィルムに微量の有機溶媒を含む可能性もあるため、多孔フィルムの性能として溶媒の溶出などが懸念される用途に用いる場合に不利である。 When manufacturing a porous film, as described in Patent Document 3 described above, the technique of extracting a film-forming solvent with an organic solvent requires a large cost for the extraction process and has an environmental impact. Since the manufactured porous film may contain a trace amount of an organic solvent, it is disadvantageous when used for applications in which the elution of the solvent is a concern as the performance of the porous film.
　本発明の多孔フィルムは製造過程では有機溶媒を用いないため、有機溶媒を含まず、低コストで、環境への影響及び残存溶媒の溶出の懸念がない利点を有する。 Since the porous film of the present invention does not use an organic solvent in the production process, it has an advantage that it does not contain an organic solvent, is low in cost, and has no concern about environmental impact and elution of residual solvent.
８．液体用フィルター
　本発明の液体用フィルターは、本発明の多孔フィルムを備えるものである。本発明の液体用フィルターは、本発明の多孔フィルムの単層構造であってもよく、他の層と組み合わせた積層構造であってもよい。本発明の液体用フィルターは、水あるいはアセトンといった水系溶媒、ハロゲン化物、エステル類、エーテル、ベンゼン、トルエンといった石油系溶剤を精製するためのフィルター、具体的には、自動車産業（電着塗料回収再利用システム）、半導体産業（超純水製造）、医薬・食品産業（除菌、酵素精製）などにおいて使用される精密濾過膜として有用である。 8). Liquid filter The liquid filter of the present invention comprises the porous film of the present invention. The liquid filter of the present invention may have a single-layer structure of the porous film of the present invention or a laminated structure combined with other layers. The liquid filter of the present invention is a filter for purifying an aqueous solvent such as water or acetone, a petroleum-based solvent such as halides, esters, ether, benzene, or toluene. It is useful as a microfiltration membrane for use in the application system), semiconductor industry (ultra pure water production), pharmaceutical / food industry (sanitization, enzyme purification) and the like.
　多孔フィルムを濾過システムに組み込む場合、多孔フィルムを同心状に巻き付けた状態（ワインド型）や、プリーツ加工を施し円筒の容器に収納した状態（カートリッジフィルター）とすることが可能であり、このカートリッジフィルターを、簡便に濾過システムに組み込むことができる。 When a porous film is incorporated into a filtration system, it can be in a state in which the porous film is wound concentrically (wind type) or in a state of being pleated and stored in a cylindrical container (cartridge filter). Can be easily incorporated into a filtration system.
　以下に、実施例および比較例を挙げて、本発明の多孔フィルムについて更に詳細に説明する。本発明はその要旨を超えない限り、以下の実施例に限定されるものではない。 Hereinafter, the porous film of the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to the following examples as long as the gist thereof is not exceeded.
　多孔フィルムの引き取り（流れ）方向を「ＭＤ」、その直角方向を「ＴＤ」と記載する。 The direction of drawing (flowing) the porous film is described as “MD”, and the direction perpendicular thereto is described as “TD”.
［多孔フィルム原材料］
　多孔フィルムの製造に用いた原材料は以下の通りである。 [Raw film raw material]
The raw materials used for the production of the porous film are as follows.
＜ポリエチレン系樹脂（Ａ）＞
・Ａ－１；高密度ポリエチレン（ハイゼックス３６００Ｆ、プライムポリマー社製、ＭＦＲ（１９０℃、２．１６ｋｇ）：１．０ｇ／１０分、密度：０．９５８ｇ／ｃｍ３、融点：１３４℃、融解エンタルピーΔＨｍ：２０７Ｊ／ｇ、結晶化温度：１１５℃、結晶化エンタルピーΔＨｃ：２１０Ｊ／ｇ）
・Ａ－２；高密度ポリエチレン（ハイゼックス３３００Ｆ、プライムポリマー社製、ＭＦＲ（１９０℃、２．１６ｋｇ）：１．１ｇ／１０分、密度：０．９５０ｇ／ｃｍ３、融点：１３２℃、融解エンタルピーΔＨｍ：１８８Ｊ／ｇ、結晶化温度：１１４℃、結晶化エンタルピーΔＨｃ：１８９Ｊ／ｇ） <Polyethylene resin (A)>
A-1: High density polyethylene (Hi-Zex 3600F, manufactured by Prime Polymer Co., Ltd., MFR (190 ° C., 2.16 kg): 1.0 g / 10 min, density: 0.958 g / cm 3 , melting point: 134 ° C., melting enthalpy ΔHm: 207 J / g, crystallization temperature: 115 ° C., crystallization enthalpy ΔHc: 210 J / g)
A-2: High density polyethylene (Hi-Zex 3300F, manufactured by Prime Polymer Co., Ltd., MFR (190 ° C., 2.16 kg): 1.1 g / 10 min, density: 0.950 g / cm 3 , melting point: 132 ° C., melting enthalpy ΔHm: 188 J / g, crystallization temperature: 114 ° C., crystallization enthalpy ΔHc: 189 J / g)
＜ポリプロピレン系樹脂（Ａ’）＞
・Ａ’－１；ホモポリプロピレン（ノバテックＰＰ ＦＹ６ＨＡ、日本ポリプロ株式会社製、ＭＦＲ（２３０℃、２．１６ｋｇ）：２．４ｇ／１０ｍｉｎ、密度：０．９ｇ／ｃｍ３） <Polypropylene resin (A ')>
A′-1: Homopolypropylene (Novatech PP FY6HA, manufactured by Nippon Polypro Co., Ltd., MFR (230 ° C., 2.16 kg): 2.4 g / 10 min, density: 0.9 g / cm 3 )
＜ビニル芳香族エラストマー（Ｂ）＞
・Ｂ－１；スチレン系熱可塑性エラストマー（スチレン－エチレン－プロピレンブロック共重合体、グレード名；ＳＥＰＴＯＮ１００１、クラレ社製、重量平均分子量Ｍｗ；１８６，０００、分子量分布Ｍｗ／Ｍｎ；１．０７、ＭＦＲ（２３０℃、２．１６ｋｇ）；０．１ｇ／１０分、スチレン含有量；３５重量％） <Vinyl aromatic elastomer (B)>
B-1: Styrenic thermoplastic elastomer (styrene-ethylene-propylene block copolymer, grade name: SEPTON 1001, manufactured by Kuraray Co., Ltd., weight average molecular weight Mw: 186,000, molecular weight distribution Mw / Mn: 1.07, MFR (230 ° C., 2.16 kg); 0.1 g / 10 min, styrene content; 35% by weight)
＜結晶核剤（Ｃ）＞
・Ｃ－１；ポリエチレン用結晶核剤マスターバッチ（グレード名：リケマスターＣＮ－００２、理研ビタミン社製）
・Ｃ－２：核剤（ソルビトール系化合物、グレード名：ゲルオールＭＤ－ＬＭ３０Ｇ、新日本理化社製） <Crystal nucleating agent (C)>
C-1: Crystal nucleating agent master batch for polyethylene (grade name: Riquet Master CN-002, manufactured by Riken Vitamin Co., Ltd.)
C-2: Nucleating agent (sorbitol compound, grade name: Gelol MD-LM30G, manufactured by Shin Nippon Rika Co., Ltd.)
［物性の測定方法］
　製造された多孔フィルムの各種物性の測定方法は以下の通りである。 [Measurement method of physical properties]
The measuring method of various physical properties of the manufactured porous film is as follows.
（１）厚み
　多孔フィルムを１／１０００ｍｍのダイアルゲージにて、面内を不特定に５箇所測定しその平均を厚みとした。 (1) Thickness The porous film was measured unspecified in five places with a 1/1000 mm dial gauge, and the average was taken as the thickness.
（２）透気度
　２５℃の空気雰囲気下にて、ＪＩＳ　Ｐ８１１７に準拠して多孔フィルムの透気度を測定した。測定機器は、デジタル型王研式透気度専用機（旭精工社製）を用いた。
　測定された透気度（秒／１００ｍｌ）を多孔フィルムの厚さで除して、厚さ１μｍあたりの透気度（秒／１００ｍｌ／μｍ）を算出した。 (2) Air permeability The air permeability of the porous film was measured in accordance with JIS P8117 in an air atmosphere at 25 ° C. As a measuring instrument, a digital type Oken type air permeability dedicated machine (Asahi Seiko Co., Ltd.) was used.
The measured air permeability (second / 100 ml) was divided by the thickness of the porous film to calculate the air permeability (second / 100 ml / μm) per 1 μm thickness.
（３）空孔率
　多孔フィルムの実質量Ｗ１を測定し、多孔フィルムの製造に用いたポリエチレン系樹脂組成物の密度と厚みから空孔率０％の場合の質量Ｗ０を計算した。下記式に基づき空孔率を算出した。
　　　空孔率（％）＝{（Ｗ０－Ｗ１）／Ｗ０}×１００ (3) Porosity The substantial amount W1 of the porous film was measured, and the mass W0 when the porosity was 0% was calculated from the density and thickness of the polyethylene resin composition used for the production of the porous film. The porosity was calculated based on the following formula.
Porosity (%) = {(W0−W1) / W0} × 100
（４）濾過速度
　２５℃の空気雰囲気下において、体積Ｖ（ｍｌ）のアセトンが０．０７ＭＰａの圧力で、有効濾過面積Ａ（ｃｍ２）の多孔フィルムを通過する時間ｔ（ｓｅｃ）を測定した。下記式に基づき濾過速度を算出した。
　　　濾過速度（ｍｌ／ｍｉｎ・ｃｍ２）＝（Ｖ×６０）／（ｔ×Ａ） (4) Filtration rate In an air atmosphere at 25 ° C., the time t (sec) during which the volume V (ml) of acetone passed through the porous film having an effective filtration area A (cm 2 ) at a pressure of 0.07 MPa was measured. . The filtration rate was calculated based on the following formula.
Filtration rate (ml / min · cm 2) = (V × 60) / (t × A)
（５）濾過寿命
　日産化学社製コロイダルシリカ（製品名：スノーテックスＭＰ－４５４０Ｍ、平均粒子径：４５０ｎｍ、固形分：４０重量％、媒体：水）をシリカ濃度４重量％になるように水で希釈し、超音波攪拌機中で十分に均一分散させた後、０．０９ＭＰａの圧力で多孔フィルムを通過させ、濾過が不可能になるまでに通過した液体の重量Ｗ（ｇ）を測定し、有効濾過面積Ａ（ｃｍ２）で除算することによって濾過寿命（ｇ／ｃｍ２）を算出した。 (5) Filtration life Colloidal silica (product name: Snowtex MP-4540M, average particle size: 450 nm, solid content: 40% by weight, medium: water) manufactured by Nissan Chemical Co., Ltd. with water so that the silica concentration is 4% by weight. Dilute and disperse sufficiently in an ultrasonic stirrer, then pass through a porous film at a pressure of 0.09 MPa, and measure the weight W (g) of the liquid that has passed before filtration becomes impossible. The filtration life (g / cm 2 ) was calculated by dividing by the filtration area A (cm 2 ).
（６）濾過精度
　日産化学社製コロイダルシリカ（製品名：スノーテックスＭＰ－４５４０Ｍ、平均粒子径：４５０ｎｍ、固形分：４０重量％、媒体：水）をシリカ濃度４重量％になるように水で希釈し、超音波攪拌機中で十分に均一分散させた後、０．０７ＭＰａの圧力で多孔フィルムを通過させ、吸光度法により通過前後の液の濃度を測定し、粒子の捕集効率（％）を算出した。 (6) Filtration accuracy Colloidal silica (product name: Snowtex MP-4540M, average particle size: 450 nm, solid content: 40% by weight, medium: water) manufactured by Nissan Chemical Co., Ltd. with water so that the silica concentration is 4% by weight. After diluting and dispersing sufficiently in an ultrasonic stirrer, the porous film is passed at a pressure of 0.07 MPa, the concentration of the liquid before and after passing is measured by the absorbance method, and the particle collection efficiency (%) is measured. Calculated.
［実施例１］
　ポリエチレン系樹脂（Ａ－１）を７０重量部、ビニル芳香族エラストマー（Ｂ－１）を３０重量部、結晶核剤（Ｃ－１）を２．５重量部の割合で配合し、二軸押出機に投入した。設定温度２３０℃で溶融混練後、ストランドダイにてストランド状に賦形した後、ストランドカッターにて裁断し、ペレット化した。 [Example 1]
70 parts by weight of polyethylene resin (A-1), 30 parts by weight of vinyl aromatic elastomer (B-1), and 2.5 parts by weight of crystal nucleating agent (C-1) I put it in the machine. After melt-kneading at a set temperature of 230 ° C., it was shaped into a strand with a strand die, then cut with a strand cutter and pelletized.
　得られたペレットを単軸押出機に投入し、設定温度２１０℃で溶融混練後、Ｔダイにてシート状に賦形した後、１１０℃に設定したキャストロールにて冷却固化を行い、厚み５００μｍの未延伸シートを得た。この未延伸シートを、１５℃に設定したロール（Ｘ）と２０℃に設定したロール（Ｙ）間において、ドロー比１００％（延伸倍率２．０倍）を掛けて低温縦延伸を行った。次いで、１２０℃に設定したロール（Ｐ）と１２０℃に設定したロール（Ｑ）間において、ドロー比５０％（延伸倍率１．５倍）を掛けて高温縦延伸を行い、ＭＤ延伸フィルムを得た。このＭＤ延伸フィルムを、京都機械社製フィルムテンター設備にて、予熱温度９０℃、予熱時間１２秒間で予熱した後、延伸温度９０℃、３.０倍横方向に延伸した。その後、１１０℃で１２秒熱処理を行い、二軸延伸多孔フィルムを得た。 The obtained pellets were put into a single screw extruder, melt-kneaded at a set temperature of 210 ° C, shaped into a sheet with a T-die, cooled and solidified with a cast roll set at 110 ° C, and a thickness of 500 µm An unstretched sheet was obtained. The unstretched sheet was subjected to low-temperature longitudinal stretching at a draw ratio of 100% (stretching ratio: 2.0 times) between a roll (X) set at 15 ° C. and a roll (Y) set at 20 ° C. Subsequently, between the roll (P) set at 120 ° C. and the roll (Q) set at 120 ° C., a draw ratio of 50% (stretch ratio 1.5 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was. This MD stretched film was preheated at a preheating temperature of 90 ° C. and a preheating time of 12 seconds in a film tenter facility manufactured by Kyoto Machine Co., Ltd., and then stretched in the transverse direction at a stretching temperature of 90 ° C. and 3.0 times. Thereafter, heat treatment was performed at 110 ° C. for 12 seconds to obtain a biaxially stretched porous film.
　得られたフィルムの評価結果を表１に示す。 Table 1 shows the evaluation results of the obtained film.
［実施例２］
　実施例１と同様に未延伸シートを得た。得られた未延伸シートを、１５℃に設定したロール（Ｘ）と２０℃に設定したロール（Ｙ）間において、ドロー比２００％（延伸倍率３．０倍）を掛けて低温縦延伸を行った。次いで、１２０℃に設定したロール（Ｐ）と１２０℃に設定したロール（Ｑ）間において、ドロー比５０％（延伸倍率１．５倍）を掛けて高温縦延伸を行い、ＭＤ延伸フィルムを得た。このＭＤ延伸多孔フィルムを、京都機械社製フィルムテンター設備にて、予熱温度９０℃、予熱時間１２秒間で予熱した後、延伸温度９０℃、３．０倍横方向に延伸した。その後、実施例１と同様に熱処理を行い、二軸延伸多孔フィルムを得た。 [Example 2]
An unstretched sheet was obtained in the same manner as in Example 1. The obtained unstretched sheet is subjected to low-temperature longitudinal stretching by applying a draw ratio of 200% (stretching ratio: 3.0 times) between the roll (X) set at 15 ° C. and the roll (Y) set at 20 ° C. It was. Subsequently, between the roll (P) set at 120 ° C. and the roll (Q) set at 120 ° C., a draw ratio of 50% (stretch ratio 1.5 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was. This MD stretched porous film was preheated at a preheating temperature of 90 ° C. and a preheating time of 12 seconds using a film tenter facility manufactured by Kyoto Machine Co., Ltd., and then stretched in the transverse direction at a stretching temperature of 90 ° C. and 3.0 times. Thereafter, heat treatment was performed in the same manner as in Example 1 to obtain a biaxially stretched porous film.
　得られたフィルムの評価結果を表１に示す。 Table 1 shows the evaluation results of the obtained film.
［実施例３］
　実施例１と同様に未延伸シートを得た。得られた未延伸シートを、１５℃に設定したロール（Ｘ）と２０℃に設定したロール（Ｙ）間において、ドロー比２００％（延伸倍率３．０倍）を掛けて低温縦延伸を行った。次いで、１２０℃に設定したロール（Ｐ）と１２０℃に設定したロール（Ｑ）間において、ドロー比１００％（延伸倍率２.０倍）を掛けて高温縦延伸を行い、ＭＤ延伸フィルムを得た。このＭＤ延伸多孔フィルムを、京都機械社製フィルムテンター設備にて、予熱温度９０℃、予熱時間１２秒間で予熱した後、延伸温度９０℃、３．０倍横方向に延伸した。その後、実施例１と同様に熱処理を行い、二軸延伸多孔フィルムを得た。 [Example 3]
An unstretched sheet was obtained in the same manner as in Example 1. The obtained unstretched sheet is subjected to low-temperature longitudinal stretching by applying a draw ratio of 200% (stretching ratio: 3.0 times) between the roll (X) set at 15 ° C. and the roll (Y) set at 20 ° C. It was. Subsequently, between the roll (P) set at 120 ° C. and the roll (Q) set at 120 ° C., a draw ratio of 100% (stretching ratio: 2.0 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was. This MD stretched porous film was preheated at a preheating temperature of 90 ° C. and a preheating time of 12 seconds using a film tenter facility manufactured by Kyoto Machine Co., Ltd., and then stretched in the transverse direction at a stretching temperature of 90 ° C. and 3.0 times. Thereafter, heat treatment was performed in the same manner as in Example 1 to obtain a biaxially stretched porous film.
　得られたフィルムの評価結果を表１に示す。 Table 1 shows the evaluation results of the obtained film.
［比較例１］
　実施例１と同様に未延伸シートを得た。得られた未延伸シートを、１５℃に設定したロール（Ｘ）と２０℃に設定したロール（Ｙ）間において、ドロー比１００％（延伸倍率２．０倍）を掛けて低温縦延伸を行った。次いで、１２０℃に設定したロール（Ｐ）と１２０℃に設定したロール（Ｑ）間において、ドロー比５０％（延伸倍率１．５倍）を掛けて高温縦延伸を行い、ＭＤ延伸フィルムを得た。このＭＤ延伸多孔フィルムを、京都機械社製フィルムテンター設備にて、予熱温度９０℃、予熱時間１２秒間で予熱した後、延伸温度９０℃、１．５倍横方向に延伸した。その後、実施例１と同様に熱処理を行い、二軸延伸多孔フィルムを得た。 [Comparative Example 1]
An unstretched sheet was obtained in the same manner as in Example 1. The obtained unstretched sheet is subjected to low-temperature longitudinal stretching with a draw ratio of 100% (stretching ratio: 2.0 times) between the roll (X) set at 15 ° C. and the roll (Y) set at 20 ° C. It was. Subsequently, between the roll (P) set at 120 ° C. and the roll (Q) set at 120 ° C., a draw ratio of 50% (stretch ratio 1.5 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was. This MD stretched porous film was preheated at a preheating temperature of 90 ° C. and a preheating time of 12 seconds in a film tenter facility manufactured by Kyoto Machine Co., Ltd., and then stretched in the transverse direction at a stretching temperature of 90 ° C. for 1.5 times. Thereafter, heat treatment was performed in the same manner as in Example 1 to obtain a biaxially stretched porous film.
　得られたフィルムの評価結果を表２に示す。多孔フィルムの濾過速度が小さく評価に時間を要するため、濾過寿命、濾過精度の評価は行わなかった。 Table 2 shows the evaluation results of the obtained film. Since the filtration speed of the porous film was small and it took time to evaluate, the filtration life and filtration accuracy were not evaluated.
［比較例２］
　実施例１と同様に未延伸シートを得た。得られた未延伸シートを、１５℃に設定したロール（Ｘ）と２０℃に設定したロール（Ｙ）間において、ドロー比２００％（延伸倍率３．０倍）を掛けて低温縦延伸を行った。次いで、１２０℃に設定したロール（Ｐ）と１２０℃に設定したロール（Ｑ）間において、ドロー比５０％（延伸倍率１．５倍）を掛けて高温縦延伸を行い、ＭＤ延伸フィルムを得た。このＭＤ延伸多孔フィルムを、京都機械社製フィルムテンター設備にて、予熱温度９０℃、予熱時間１２秒間で予熱した後、延伸温度９０℃、１．５倍横方向に延伸した。その後、実施例１と同様に熱処理を行い、二軸延伸多孔フィルムを得た。 [Comparative Example 2]
An unstretched sheet was obtained in the same manner as in Example 1. The obtained unstretched sheet is subjected to low-temperature longitudinal stretching by applying a draw ratio of 200% (stretching ratio: 3.0 times) between the roll (X) set at 15 ° C. and the roll (Y) set at 20 ° C. It was. Subsequently, between the roll (P) set at 120 ° C. and the roll (Q) set at 120 ° C., a draw ratio of 50% (stretch ratio 1.5 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was. This MD stretched porous film was preheated at a preheating temperature of 90 ° C. and a preheating time of 12 seconds in a film tenter facility manufactured by Kyoto Machine Co., Ltd., and then stretched in the transverse direction at a stretching temperature of 90 ° C. for 1.5 times. Thereafter, heat treatment was performed in the same manner as in Example 1 to obtain a biaxially stretched porous film.
　得られたフィルムの評価結果を表２に示す。多孔フィルムの濾過速度が小さく評価に時間を要するため、濾過寿命、濾過精度の評価は行わなかった。 Table 2 shows the evaluation results of the obtained film. Since the filtration speed of the porous film was small and it took time to evaluate, the filtration life and filtration accuracy were not evaluated.
［比較例３］
　ポリエチレン系樹脂（Ａ－２）を７０重量部、ビニル芳香族エラストマー（Ｂ－１）を３０重量部、結晶核剤（Ｃ－１）を２．５重量部の割合で配合し、２軸押出機に投入した。設定温度２３０℃で溶融混練後、ストランドダイにてストランド状に賦形した後、ストランドカッターにて裁断し、ペレット化した。 [Comparative Example 3]
70 parts by weight of polyethylene resin (A-2), 30 parts by weight of vinyl aromatic elastomer (B-1), and 2.5 parts by weight of crystal nucleating agent (C-1) I put it in the machine. After melt-kneading at a set temperature of 230 ° C., it was shaped into a strand with a strand die, then cut with a strand cutter and pelletized.
　得られたペレットを単軸押出機に投入し、設定温度２１０℃で溶融混練後、Ｔダイにてシート状に賦形した後、１１０℃に設定したキャストロールにて冷却固化を行い、厚み５００μｍの未延伸シートを得た。この未延伸シートを、１５℃に設定したロール（Ｘ）と２０℃に設定したロール（Ｙ）間において、ドロー比１００％（延伸倍率２．０倍）を掛けて低温縦延伸を行った。次いで、１２０℃に設定したロール（Ｐ）と１２０℃に設定したロール（Ｑ）間において、ドロー比５０％（延伸倍率１．５倍）を掛けて高温縦延伸を行い、ＭＤ延伸フィルムを得た。このＭＤ延伸フィルムを、京都機械社製フィルムテンター設備にて、予熱温度９０℃、予熱時間１２秒間で予熱した後、延伸温度９０℃、１．５倍横方向に延伸した。その後、実施例１と同様に熱処理を行い、二軸延伸多孔フィルムを得た。 The obtained pellets were put into a single screw extruder, melt-kneaded at a set temperature of 210 ° C, shaped into a sheet with a T-die, cooled and solidified with a cast roll set at 110 ° C, and a thickness of 500 µm An unstretched sheet was obtained. The unstretched sheet was subjected to low-temperature longitudinal stretching at a draw ratio of 100% (stretching ratio: 2.0 times) between a roll (X) set at 15 ° C. and a roll (Y) set at 20 ° C. Subsequently, between the roll (P) set at 120 ° C. and the roll (Q) set at 120 ° C., a draw ratio of 50% (stretch ratio 1.5 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was. This MD stretched film was preheated at a preheating temperature of 90 ° C. and a preheating time of 12 seconds in a film tenter facility manufactured by Kyoto Machine Co., Ltd., and then stretched in the transverse direction at a stretching temperature of 90 ° C. for 1.5 times. Thereafter, heat treatment was performed in the same manner as in Example 1 to obtain a biaxially stretched porous film.
　得られたフィルムの評価結果を表２に示す。濾過速度が小さく評価に時間を要するため、濾過寿命、濾過精度の評価は行わなかった。 Table 2 shows the evaluation results of the obtained film. Since the filtration rate was low and it took time to evaluate, the filtration life and filtration accuracy were not evaluated.
［比較例４］
　比較例３と同様に未延伸シートを得た。得られた未延伸シートを、１５℃に設定したロール（Ｘ）と２０℃に設定したロール（Ｙ）間において、ドロー比３００％（延伸倍率４．０倍）を掛けて低温縦延伸を行った。次いで、１２０℃に設定したロール（Ｐ）と１２０℃に設定したロール（Ｑ）間において、ドロー比５０％（延伸倍率１．５倍）を掛けて高温縦延伸を行い、ＭＤ延伸フィルムを得た。このＭＤ延伸多孔フィルムを、京都機械社製フィルムテンター設備にて、予熱温度９０℃、予熱時間１２秒間で予熱した後、延伸温度９０℃、１．５倍横方向に延伸した。その後、実施例１と同様に熱処理を行い、二軸延伸多孔フィルムを得た。 [Comparative Example 4]
An unstretched sheet was obtained in the same manner as in Comparative Example 3. The obtained unstretched sheet is subjected to low-temperature longitudinal stretching by applying a draw ratio of 300% (stretching ratio: 4.0 times) between the roll (X) set at 15 ° C. and the roll (Y) set at 20 ° C. It was. Subsequently, between the roll (P) set at 120 ° C. and the roll (Q) set at 120 ° C., a draw ratio of 50% (stretch ratio 1.5 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was. This MD stretched porous film was preheated at a preheating temperature of 90 ° C. and a preheating time of 12 seconds in a film tenter facility manufactured by Kyoto Machine Co., Ltd., and then stretched in the transverse direction at a stretching temperature of 90 ° C. for 1.5 times. Thereafter, heat treatment was performed in the same manner as in Example 1 to obtain a biaxially stretched porous film.
　得られたフィルムの評価結果を表２に示す。濾過速度が小さく評価に時間を要するため、濾過寿命、濾過精度の評価は行わなかった。 Table 2 shows the evaluation results of the obtained film. Since the filtration rate was low and it took time to evaluate, the filtration life and filtration accuracy were not evaluated.
［比較例５］
　ポリエチレン系樹脂（Ａ－２）を７０重量部、ビニル芳香族エラストマー（Ｂ－１）を３０重量部、結晶核剤（Ｃ－１）を２．５重量部の割合で配合し、設定温度２１０℃に設定した同方向二軸押出機に投入して溶融混練した。溶融混練後、Ｔダイにてシート状に賦形した後、９０℃に設定したキャストロールにて冷却固化して厚み２５０μｍの未延伸シートを得た。 [Comparative Example 5]
70 parts by weight of the polyethylene resin (A-2), 30 parts by weight of the vinyl aromatic elastomer (B-1), and 2.5 parts by weight of the crystal nucleating agent (C-1) are blended, and the set temperature is 210. The mixture was put into a same-direction twin screw extruder set at ° C. and melt kneaded. After melt-kneading, it was shaped into a sheet with a T-die and then cooled and solidified with a cast roll set at 90 ° C. to obtain an unstretched sheet having a thickness of 250 μm.
　この未延伸シートを、２０℃に設定したロール（Ｘ）と４０℃に設定したロール（Ｙ）間において、ドロー比１００％（延伸倍率２．０倍）を掛けて低温縦延伸を行った。次いで、１２０℃に設定したロール（Ｐ）と１２０℃に設定したロール（Ｑ）間において、ドロー比５０％（延伸倍率１．５倍）を掛けて高温縦延伸を行い、ＭＤ延伸フィルムを得た。このＭＤ延伸フィルムを、京都機械社製フィルムテンター設備にて、予熱温度９０℃、予熱時間１２秒間で予熱した後、延伸温度９０℃、１．５倍横方向に延伸した。その後、実施例１と同様に熱処理を行い、二軸延伸多孔フィルムを得た。 The unstretched sheet was subjected to low-temperature longitudinal stretching with a draw ratio of 100% (stretching ratio: 2.0) between a roll (X) set at 20 ° C. and a roll (Y) set at 40 ° C. Subsequently, between the roll (P) set at 120 ° C. and the roll (Q) set at 120 ° C., a draw ratio of 50% (stretch ratio 1.5 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was. This MD stretched film was preheated at a preheating temperature of 90 ° C. and a preheating time of 12 seconds in a film tenter facility manufactured by Kyoto Machine Co., Ltd., and then stretched in the transverse direction at a stretching temperature of 90 ° C. for 1.5 times. Thereafter, heat treatment was performed in the same manner as in Example 1 to obtain a biaxially stretched porous film.
　得られたフィルムの評価結果を表２に示す。ただし、透気度が著しく大きく透気性能に劣り、濾過速度も著しく小さくなるため、濾過性能評価は行わなかった。 Table 2 shows the evaluation results of the obtained film. However, since the air permeability was remarkably large and the air permeation performance was inferior and the filtration rate was remarkably reduced, the filtration performance was not evaluated.
［比較例６］
　比較例５と同様に未延伸シートを得た。得られた未延伸シートを、２０℃に設定したロール（Ｘ）と４０℃に設定したロール（Ｙ）間において、ドロー比３００％（延伸倍率４．０倍）を掛けて低温縦延伸を行った。次いで、１２０℃に設定したロール（Ｐ）と１２０℃に設定したロール（Ｑ）間において、ドロー比５０％（延伸倍率１．５倍）を掛けて高温縦延伸を行い、ＭＤ延伸フィルムを得た。このＭＤ延伸フィルムを、京都機械社製フィルムテンター設備にて、予熱温度９０℃、予熱時間１２秒間で予熱した後、延伸温度９０℃、１．５倍横方向に延伸した。その後、実施例１と同様に熱処理を行い、二軸延伸多孔フィルムを得た。 [Comparative Example 6]
An unstretched sheet was obtained in the same manner as in Comparative Example 5. The obtained unstretched sheet is subjected to low-temperature longitudinal stretching by applying a draw ratio of 300% (stretching ratio: 4.0 times) between the roll (X) set at 20 ° C. and the roll (Y) set at 40 ° C. It was. Subsequently, between the roll (P) set at 120 ° C. and the roll (Q) set at 120 ° C., a draw ratio of 50% (stretch ratio 1.5 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was. This MD stretched film was preheated at a preheating temperature of 90 ° C. and a preheating time of 12 seconds in a film tenter facility manufactured by Kyoto Machine Co., Ltd., and then stretched in the transverse direction at a stretching temperature of 90 ° C. for 1.5 times. Thereafter, heat treatment was performed in the same manner as in Example 1 to obtain a biaxially stretched porous film.
　得られたフィルムの評価結果を表２に示す。ただし、透気度が著しく大きく透気性能に劣り、濾過速度も著しく小さくなるため、濾過性能評価は行わなかった。 Table 2 shows the evaluation results of the obtained film. However, since the air permeability was remarkably large and the air permeation performance was inferior and the filtration rate was remarkably reduced, the filtration performance was not evaluated.
［比較例７］
　ポリエチレン系樹脂（Ａ－２）を７０重量部、ビニル芳香族エラストマー（Ｂ－１）を３０重量部の割合で配合し、設定温度２１０℃に設定した同方向二軸押出機に投入して溶融混練した。溶融混練後、Ｔダイにてシート状に賦形した後、９０℃に設定したキャストロールにて冷却固化して厚み２５０μｍの未延伸シートを得た。 [Comparative Example 7]
70 parts by weight of polyethylene resin (A-2) and 30 parts by weight of vinyl aromatic elastomer (B-1) are blended and put into a co-axial twin screw extruder set at a set temperature of 210 ° C. and melted. Kneaded. After melt-kneading, it was shaped into a sheet with a T-die and then cooled and solidified with a cast roll set at 90 ° C. to obtain an unstretched sheet having a thickness of 250 μm.
　この未延伸シートを、２０℃に設定したロール（Ｘ）と４０℃に設定したロール（Ｙ）間において、ドロー比１００％（延伸倍率２．０倍）を掛けて低温縦延伸を行った。次いで、１２０℃に設定したロール（Ｐ）と１２０℃に設定したロール（Ｑ）間において、ドロー比５０％（延伸倍率１．５倍）を掛けて高温縦延伸を行い、ＭＤ延伸フィルムを得た。このＭＤ延伸フィルムを、京都機械社製フィルムテンター設備にて、予熱温度９０℃、予熱時間１２秒間で予熱した後、延伸温度９０℃、１．５倍横方向に延伸した。その後、実施例１と同様に熱処理を行い、二軸延伸多孔フィルムを得た。 The unstretched sheet was subjected to low-temperature longitudinal stretching with a draw ratio of 100% (stretching ratio: 2.0) between a roll (X) set at 20 ° C. and a roll (Y) set at 40 ° C. Subsequently, between the roll (P) set at 120 ° C. and the roll (Q) set at 120 ° C., a draw ratio of 50% (stretch ratio 1.5 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was. This MD stretched film was preheated at a preheating temperature of 90 ° C. and a preheating time of 12 seconds in a film tenter facility manufactured by Kyoto Machine Co., Ltd., and then stretched in the transverse direction at a stretching temperature of 90 ° C. for 1.5 times. Thereafter, heat treatment was performed in the same manner as in Example 1 to obtain a biaxially stretched porous film.
　得られたフィルムの評価結果を表２に示す。ただし、透気度が著しく大きく透気性能に劣り、濾過速度も著しく小さくなるため、濾過性能評価は行わなかった。 Table 2 shows the evaluation results of the obtained film. However, since the air permeability was remarkably large and the air permeation performance was inferior and the filtration rate was remarkably reduced, the filtration performance was not evaluated.
［比較例８］
　比較例７と同様に未延伸シートを得た。得られた未延伸シートを、２０℃に設定したロール（Ｘ）と４０℃に設定したロール（Ｙ）間において、ドロー比３００％（延伸倍率４．０倍）を掛けて低温縦延伸を行った。次いで、１２０℃に設定したロール（Ｐ）と１２０℃に設定したロール（Ｑ）間において、ドロー比５０％（延伸倍率１．５倍）を掛けて高温縦延伸を行い、ＭＤ延伸フィルムを得た。このＭＤ延伸フィルムを、京都機械社製フィルムテンター設備にて、予熱温度９０℃、予熱時間１２秒間で予熱した後、延伸温度９０℃、１．５倍横方向に延伸した。その後、実施例１と同様に熱処理を行い、二軸延伸多孔フィルムを得た。 [Comparative Example 8]
An unstretched sheet was obtained in the same manner as in Comparative Example 7. The obtained unstretched sheet is subjected to low-temperature longitudinal stretching by applying a draw ratio of 300% (stretching ratio: 4.0 times) between the roll (X) set at 20 ° C. and the roll (Y) set at 40 ° C. It was. Subsequently, between the roll (P) set at 120 ° C. and the roll (Q) set at 120 ° C., a draw ratio of 50% (stretch ratio 1.5 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was. This MD stretched film was preheated at a preheating temperature of 90 ° C. and a preheating time of 12 seconds in a film tenter facility manufactured by Kyoto Machine Co., Ltd., and then stretched in the transverse direction at a stretching temperature of 90 ° C. for 1.5 times. Thereafter, heat treatment was performed in the same manner as in Example 1 to obtain a biaxially stretched porous film.
　得られたフィルムの評価結果を表２に示す。ただし、透気度が著しく大きく透気性能に劣り、濾過速度も著しく小さくなるため、濾過性能評価は行わなかった。 Table 2 shows the evaluation results of the obtained film. However, since the air permeability was remarkably large and the air permeation performance was inferior and the filtration rate was remarkably reduced, the filtration performance was not evaluated.
［比較例９］
　ポリプロピレン系樹脂（Ａ’－１）を７０重量部、ビニル芳香族エラストマー（Ｂ－１）を３０重量部、結晶核剤（Ｃ－２）を０．１重量部の割合で配合し、二軸押出機に投入し、設定温度２３０℃で溶融混練後、ストランドダイにてストランド状に賦形した後、ストランドカッターにて裁断し、ペレット化した。 [Comparative Example 9]
70 parts by weight of the polypropylene resin (A′-1), 30 parts by weight of the vinyl aromatic elastomer (B-1), and 0.1 part by weight of the crystal nucleating agent (C-2) are blended in a biaxial manner. The mixture was put into an extruder, melt-kneaded at a set temperature of 230 ° C., shaped into a strand with a strand die, cut with a strand cutter, and pelletized.
　得られたペレットを単軸押出機に投入し、設定温度２００℃で溶融混練後、Ｔダイにてシート状に賦形した後、１２７℃に設定したキャストロールにて冷却固化を行い、厚み２３０μｍの未延伸シートを得た。この未延伸シートを、２０℃に設定したロール（Ｘ）と２０℃に設定したロール（Ｙ）間において、ドロー比１００％（延伸倍率２．０倍）を掛けて低温縦延伸を行った。次いで、１２０℃に設定したロール（Ｐ）と１２０℃に設定したロール（Ｑ）間において、ドロー比５０％（延伸倍率１．５倍）を掛けて高温縦延伸を行い、ＭＤ延伸フィルムを得た。このＭＤ延伸フィルムを、京都機械社製フィルムテンター設備にて、予熱温度１４５℃、予熱時間１２秒間で予熱した後、延伸温度１４５℃、３.０倍横方向に延伸した。その後、１５５℃で１２秒熱処理を行い、二軸延伸多孔フィルムを得た。
　得られたフィルムの評価結果を表２に示す。 The obtained pellets were put into a single screw extruder, melt kneaded at a set temperature of 200 ° C., shaped into a sheet with a T die, cooled and solidified with a cast roll set at 127 ° C., and a thickness of 230 μm. An unstretched sheet was obtained. The unstretched sheet was subjected to low-temperature longitudinal stretching at a draw ratio of 100% (stretching ratio: 2.0 times) between the roll (X) set at 20 ° C. and the roll (Y) set at 20 ° C. Subsequently, between the roll (P) set at 120 ° C. and the roll (Q) set at 120 ° C., a draw ratio of 50% (stretch ratio 1.5 times) is applied to perform high-temperature longitudinal stretching to obtain an MD stretched film. It was. This MD stretched film was preheated at a preheating temperature of 145 ° C. and a preheating time of 12 seconds in a film tenter facility manufactured by Kyoto Machine Co., Ltd., and then stretched in the transverse direction at a stretching temperature of 145 ° C. and 3.0 times. Thereafter, heat treatment was performed at 155 ° C. for 12 seconds to obtain a biaxially stretched porous film.
The evaluation results of the obtained film are shown in Table 2.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　実施例１～３で得られた多孔フィルムは、空孔率が６０％以上、透気度は５０ｓｅｃ／１００ｍｌ以下であり、良好な濾過速度、濾過寿命、濾過精度を有する多孔フィルムである。 The porous films obtained in Examples 1 to 3 have a porosity of 60% or more, an air permeability of 50 sec / 100 ml or less, and have a good filtration rate, filtration life, and filtration accuracy.
　比較例１～２で得られたフィルムは、横方向への延伸倍率が小さく形成される空孔の割合が低くなっているため、空孔率が実施例と比較して小さく、透気度が実施例と比較して大きい。その結果、濾過速度に劣り、濾過性能に劣るフィルムとなっている。 In the films obtained in Comparative Examples 1 and 2, since the ratio of the pores formed with a small stretching ratio in the transverse direction is low, the porosity is small compared to the examples and the air permeability is low. Larger than the examples. As a result, the film is inferior in filtration speed and inferior in filtration performance.
　比較例３～４で得られたフィルムは、ポリエチレン系樹脂（Ａ－２）の密度が小さく結晶化度が低くビニル芳香族エラストマー（Ｂ－１）のとの界面で開孔起点が生じにくかったため、空孔率が実施例と比較して小さく、透気度が実施例と比較して大きい。その結果、濾過速度に劣り、濾過性能に劣るフィルムとなっている。 In the films obtained in Comparative Examples 3 to 4, the density of the polyethylene resin (A-2) was small, the degree of crystallinity was low, and it was difficult for the origin of opening to occur at the interface with the vinyl aromatic elastomer (B-1). The porosity is small compared to the example, and the air permeability is large compared to the example. As a result, the film is inferior in filtration speed and inferior in filtration performance.
　比較例５～６で得られたフィルムは、空孔率が実施例と比較して小さく、透気度が実施例と比較して大きい。その結果、濾過速度に劣り、濾過性能に劣るフィルムとなっている。この様な結果となる理由として以下が考えられる。キャストロール温度が低く、良好な結晶構造系に至らなかったため、結果として結晶化度が低くなり、ポリエチレン系樹脂（Ａ－２）の結晶化度が低下したため、ビニル芳香族エラストマー（Ｂ－１）のとの界面で開孔起点が生じにくかった。 The films obtained in Comparative Examples 5 to 6 have a lower porosity than the examples and a higher air permeability than the examples. As a result, the film is inferior in filtration speed and inferior in filtration performance. Possible reasons for this result are as follows. Since the cast roll temperature was low and a good crystal structure system was not achieved, the crystallinity was lowered as a result, and the crystallinity of the polyethylene resin (A-2) was lowered, so that the vinyl aromatic elastomer (B-1) It was difficult for the starting point of hole formation to occur at the interface with.
　比較例７～８で得られたフィルムは、空孔率が実施例と比較して小さく、透気度が実施例と比較して大きい。その結果、濾過速度に劣り、濾過性能に劣るフィルムとなっている。この様な結果となる理由として以下が考えられる。結晶核剤（Ｃ）を添加していないため、良好な結晶構造系に至らず、結果として結晶化度が低くなり、ポリエチレン系樹脂（Ａ－２）の結晶化度が低下したため、ビニル芳香族エラストマー（Ｂ－１）のとの界面で開孔起点が生じにくかった。 The films obtained in Comparative Examples 7 to 8 have a lower porosity than the examples and a higher air permeability than the examples. As a result, the film is inferior in filtration speed and inferior in filtration performance. Possible reasons for this result are as follows. Since the crystal nucleating agent (C) was not added, a good crystal structure system was not obtained, and as a result, the crystallinity was lowered, and the crystallinity of the polyethylene resin (A-2) was lowered. It was difficult for the origin of opening to occur at the interface with the elastomer (B-1).
　比較例９では、実施例１～３に比較して、フィルム厚み１μｍあたりの透気度が劣り、かつ濾過寿命もわずかながら劣る。この様な結果となる理由は以下の通り考えられる。用いたビニル芳香族エラストマーとの相溶性が、ベース樹脂であるポリプロピレン系樹脂とポリエチレン系樹脂によって異なる。ポリエチレン系樹脂と比較して、比較例９で用いたポリプロピレン系樹脂はビニル芳香族エラストマーとの相溶性が小さく、ベース樹脂に対するエラストマーの分散性が低くなっている。従って、実施例１～３と比較して、比較例９では得られる多孔構造にも差が生じている。 Comparative Example 9 is inferior in air permeability per 1 μm of film thickness and slightly inferior in filtration life as compared with Examples 1 to 3. The reason for such a result is considered as follows. The compatibility with the vinyl aromatic elastomer used varies depending on the polypropylene resin and the polyethylene resin as the base resin. Compared with the polyethylene resin, the polypropylene resin used in Comparative Example 9 has a low compatibility with the vinyl aromatic elastomer, and the dispersibility of the elastomer with respect to the base resin is low. Therefore, compared with Examples 1 to 3, there is a difference in the porous structure obtained in Comparative Example 9.
　本発明の多孔フィルムは、多数の空孔構造を有し、透気度が小さく透気性能に優れ、濾過速度、濾過寿命、濾過精度に優れたポリエチレン製多孔フィルムである。本発明の多孔フィルムは、水を精製するためのフィルター、具体的には、自動車産業（電着塗料回収再利用システム）、半導体産業（超純水製造）、医薬・食品産業（除菌、酵素精製）などにおいて使用される濾過膜として有用である。 The porous film of the present invention is a polyethylene porous film having a large number of pore structures, low air permeability and excellent air permeability, and excellent filtration speed, filtration life and filtration accuracy. The porous film of the present invention is a filter for purifying water, specifically, automotive industry (electrodeposition paint recovery and reuse system), semiconductor industry (ultra pure water production), pharmaceutical / food industry (sanitization, enzyme It is useful as a filtration membrane used in purification.
　本発明を特定の態様を用いて詳細に説明したが、本発明の意図と範囲を離れることなく様々な変更が可能であることは当業者に明らかである。
　本出願は、２０１５年１０月１３日付で出願された日本特許出願２０１５－２０１７２１に基づいており、その全体が引用により援用される。 Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2015-201721 filed on Oct. 13, 2015, which is incorporated by reference in its entirety.

Claims (8)

  1. 　密度が０．９５５～０．９７０ｇ／ｃｍ３であるポリエチレン系樹脂（Ａ）５５～８５重量部とビニル芳香族エラストマー（Ｂ）１５～４５重量部の割合でそれぞれ含み（ただし、ポリエチレン系樹脂（Ａ）とビニル芳香族エラストマー（Ｂ）との合計で１００重量部となる。）、空孔率が５０％以上であり、透気度が２００秒／１００ｍｌ以下である多孔フィルム。 The polyethylene resin (A) having a density of 0.955 to 0.970 g / cm 3 is contained in an amount of 55 to 85 parts by weight and the vinyl aromatic elastomer (B) in a ratio of 15 to 45 parts by weight (however, the polyethylene resin ( A) and the vinyl aromatic elastomer (B) in total are 100 parts by weight.) A porous film having a porosity of 50% or more and an air permeability of 200 seconds / 100 ml or less.
  2. 　前記ビニル芳香族エラストマー（Ｂ）の温度２３０℃、荷重２．１６ｋｇにおけるメルトフローレート（ＭＦＲ）が１ｇ／１０分以下である請求項１に記載の多孔フィルム。 The porous film according to claim 1, wherein the vinyl aromatic elastomer (B) has a melt flow rate (MFR) of 1 g / 10 min or less at a temperature of 230 ° C and a load of 2.16 kg.
  3. 　ポリエチレン系樹脂（Ａ）の温度１９０℃、荷重２．１６ｋｇにおけるメルトフローレート（ＭＦＲ）が０．１～１０ｇ／１０分である請求項１または２に記載の多孔フィルム。 3. The porous film according to claim 1, wherein the polyethylene resin (A) has a melt flow rate (MFR) of 0.1 to 10 g / 10 min at a temperature of 190 ° C. and a load of 2.16 kg.
  4. 　厚みが７０μｍ以上である請求項１～３のいずれかに記載の多孔フィルム。 4. The porous film according to claim 1, wherein the thickness is 70 μm or more.
  5. 　二軸延伸フィルムである請求項１～４のいずれかに記載の多孔フィルム。 The porous film according to any one of claims 1 to 4, which is a biaxially stretched film.
  6. 　ポリエチレン系樹脂（Ａ）とビニル芳香族エラストマー（Ｂ）との合計１００重量部に対し、結晶核剤（Ｃ）を０．００１～１０重量部含む請求項１～５の何れかに記載の多孔フィルム。 The porous material according to any one of claims 1 to 5, comprising 0.001 to 10 parts by weight of the crystal nucleating agent (C) with respect to 100 parts by weight of the total of the polyethylene resin (A) and the vinyl aromatic elastomer (B). the film.
  7. 　ビニル芳香族エラストマー（Ｂ）がビニル芳香族化合物に由来する構成単位の含有量が１０～４０重量％の、スチレン－エチレン－プロピレンブロック共重合体、スチレン－エチレン－プロピレン－スチレンブロック共重合体、及びスチレン－エチレン－ブタジエン－スチレンブロック共重合体よりなる群から選ばれる１種又は２種以上である請求項１～６のいずれかに記載の多孔フィルム。 A styrene-ethylene-propylene block copolymer, a styrene-ethylene-propylene-styrene block copolymer, wherein the vinyl aromatic elastomer (B) has a content of structural units derived from a vinyl aromatic compound of 10 to 40% by weight, The porous film according to any one of claims 1 to 6, which is one or more selected from the group consisting of a styrene-ethylene-butadiene-styrene block copolymer.
  8. 　請求項１～７のいずれかに記載の多孔フィルムを備えた液体用フィルター。 A liquid filter comprising the porous film according to any one of claims 1 to 7.
PCT/JP2016/080294 2015-10-13 2016-10-13 Porous film WO2017065192A1 (en)

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US20030235681A1 (en) * 2002-06-21 2003-12-25 3 M Innovative Properties Company Biaxially-oriented ink receptive medium
JP2005145998A (en) * 2003-11-11 2005-06-09 Chisso Corp Thermoplastic resin porous film
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