JP5619701B2 - Method for producing porous body - Google Patents

Description

The present invention relates to the production how the porous body, a porous body manufactured by the manufacturing method and packaging supplies, hygiene products, livestock supplies, agricultural supplies, building supplies, medical supplies, separation films, light diffusing plate, a reflective sheet or It can be used as a battery separator, and is particularly preferably used as a non-aqueous electrolyte battery separator such as a lithium ion secondary battery used as a power source for various electronic devices.

  The polymer porous body with many fine communication holes is used for separation membranes used for the production of ultrapure water, purification of chemicals, water treatment, waterproof and moisture-permeable films used for clothing and sanitary materials, and batteries. It is used in various fields such as battery separators.

Various techniques as described below have been proposed as techniques for creating a large number of fine communication holes in this type of polymer.
For example, Japanese Patent Application Laid-Open No. 5-25305 (Patent Document 1) proposes that a porous film can be obtained by kneading and sheeting ultrahigh molecular weight polyethylene and a solvent, extracting the solvent after stretching.
However, in this method, as described in paragraph 0045 and the like, the solvent contained in the entire porous membrane is removed by washing with an organic solvent for washing, so a large amount of organic solvent is required. This is not preferable from an environmental point of view.

In Japanese Patent No. 3166279 (Patent Document 2), a porous film or a continuous film is formed by inflation-molding a resin composition containing a polyolefin resin and a filler, and uniaxially stretching the obtained film or sheet in the take-up direction. It has been proposed that a sheet be obtained.
Similarly, in Japanese Patent Application Laid-Open No. 2004-95550 (Patent Document 3), a porous film used as a separator for a lithium secondary battery is stretched at least in a uniaxial direction from a sheet formed from a resin composition containing a thermoplastic resin and a filler. It is obtained by doing.
However, in the porous film or sheet obtained by these methods, since the mass (basis weight) per unit area increases due to the presence of the filler in all layers, there is room for improvement for weight reduction. is there.

In Japanese Patent Application Laid-Open No. 10-50286 (Patent Document 4), a high melting point polyolefin film and a low melting point polyolefin film are heat-treated to adjust birefringence and elastic recovery, respectively, and then subjected to thermocompression bonding to three or more layers. It is proposed to produce a porous film to be used as a battery separator by stretching the porous film in two stages, making it porous, and then heat setting.
In this method, which is generally referred to as an open-hole stretching method using a single polymer, an organic solvent is not required in the production process, and since no filler is present, the mass per unit area (basis weight) is also Don't get big. However, this method is very difficult to control crystals, and the conditions under which a preferred porous structure can be obtained under stretching conditions such as stretching temperature, stretching ratio, and multi-stage stretching are very narrow (columns 0025 to 0028, etc.). It is not preferable when considering process control when producing on a scale.

  As described above, although the porous films described in Patent Documents 1 to 4 have their respective characteristics, there are not particularly sufficient in terms of environmental aspects, light weight, and productivity with respect to the manufacturing method.

In addition, foaming techniques using subcritical or supercritical fluids are also known. Specifically, a polymer is impregnated with a subcritical or supercritical fluid to be saturated, and then a supersaturated state is created by a rapid pressure drop or the like, and supersaturated gas is foamed.
This method has the advantage that the load on the environment is extremely small if a subcritical or supercritical fluid of an inert gas such as carbon dioxide or nitrogen is used. Moreover, since the blending of the filler is not an essential requirement, the weight can be easily reduced.
However, since the micropores formed using the subcritical or supercritical fluid exist only in independent states, there is a problem that the application is limited. That is, for example, in applications such as battery separators, electrolytic capacitor membranes, various filters, reverse osmosis filtration membranes, ultrafiltration membranes or microfiltration membranes, it is necessary to allow fluids such as certain gases and liquids to permeate. If the micropores are in an independent state, they cannot be used for the above-mentioned purposes because they cannot exhibit permeability.

JP-A-5-25305 Japanese Patent No. 3166279 JP 2004-95550 A Japanese Patent Laid-Open No. 10-50286

The present invention has been made in view of the above problems, and uses a subcritical or supercritical fluid to produce a porous body that is a three-dimensional network of pores in which at least some of the micropores communicate with each other. Therefore, an object of the present invention is to provide a method for producing a porous body that can reduce the burden on the environment, has a high degree of freedom in production conditions, and is excellent in productivity .

In order to solve the above-mentioned problem, the present invention is a method for producing a porous body having a large number of micropores that open to the surface and have connectivity in the thickness direction,
Producing a laminate having at least a three-layer structure in which at least one intermediate layer made of a thermoplastic resin composition and an adhesive layer made of a resin composition containing an adhesive resin are laminated on both sides of the intermediate layer;
The obtained laminate is impregnated with a fluid in a supercritical state or subcritical state, and then released from the supercritical state or subcritical state to vaporize the fluid, whereby independent micropores and communicating micropores are obtained. Forming a micropore with a mixture of pores,
After the porosification step for forming the micropores, at least uniaxially stretching, and a stretching step for further communicating the micropores ;
The manufacturing method of the porous body including the process of peeling the said contact bonding layer after the said extending process is provided.

According to the manufacturing method, the fluid in the supercritical state or the subcritical state is impregnated into the laminate, and then released from the supercritical state or the subcritical state to vaporize the fluid, thereby not communicating with each other. Independent micropores and continuous micropores in which adjacent pores communicate with each other are formed as a whole so that the material can be made porous as a whole.
Furthermore, independent micropores can be communicated with each other by stretching after the porosity forming step, and pores in which the micropores are three-dimensionally communicated can be formed throughout the material.

The pore size of the micropores formed in the porous body produced by the above-described method varies greatly depending on the intended use of the porous body, and the type, thickness and density of the material, as well as the supercritical state or subcriticality impregnated in the material. The diameter of the micropores can be controlled by the pressure and time of the fluid in the state.
As described above, the pore size of the porous body is adjusted according to the application, but the packaging material, sanitary product, livestock product, agricultural product, building product, medical product, separation membrane, light diffusion plate, reflective sheet or battery separator In use, the average pore diameter is preferably about 0.001 to 600 μm. This is because if the average pore diameter is smaller than 0.001 μm, fluid such as gas or liquid is difficult to permeate the porous body, whereas if the average pore diameter is larger than 600 μm, the mechanical strength of the porous body may be too low. It depends. Specifically, when the porous body is used as a battery separator, the average pore diameter is more preferably 0.01 to 10 μm, and further preferably 0.01 to 2 μm.

In the method for producing a porous body of the present invention, the material to be impregnated with the fluid in the supercritical state or subcritical state is not particularly limited. Various materials can be used. Among them, a hard segment comprising a polypropylene resin even without least the thermoplastic resin composition of the intermediate layer in the present invention is preferably made of a thermoplastic resin composition having a soft segment.
The shape of the laminate when impregnating the fluid in the supercritical state or subcritical state is not particularly limited, and may have any shape. Specifically, for example, the average thickness is 1 μm or more and less than 250 μm. Examples include a film shape, a sheet shape having a thickness of 250 μm or more and less than several mm, a plate shape having a thickness of several mm or more, and a fiber shape.

When using the method for producing a porous body of the present invention, when impregnating a fluid in a supercritical state or a subcritical state and then causing a rapid pressure drop or the like to release from the supercritical state or the subcritical state, The supersaturated state does not occur in the vicinity of the surface, but gas is immediately released from the surface by diffusion / evaporation, and a nonporous layer having no micropores is formed on the outermost surface. Therefore, in order to provide the inner portion of the hole and communicating pores in the surface, it may be removed outermost surface layer of the peeling layer, such as non-porous.

  Delete

  Delete

In the method for producing a porous body, an adhesive layer in which a non-porous layer is formed is laminated on both sides of an intermediate layer to be made porous using a subcritical or supercritical fluid, and the surface of the intermediate layer is covered with an adhesive layer. By keeping the lid in a state where the laminate is impregnated with a subcritical or supercritical fluid and then a sudden pressure drop or the like is generated, a supersaturated state can be created on the surface of the intermediate layer. Micropores can also be formed on the surface .

  Delete

The method for producing the porous body will be described in detail below.
First, in the first step, an adhesive layer comprising at least one intermediate layer (A layer) made of a thermoplastic resin composition and comprising a resin composition containing an adhesive resin on both sides of the intermediate layer (A layer). A laminate having at least a three-layer structure in which (B layer) is laminated is produced.

As the thermoplastic resin composition constituting the A layer of the intermediate layer, a known thermoplastic resin can be used without particular limitation. One type of resin may be used alone, or two or more types of resins may be used in combination.
Especially, it is preferable to use the thermoplastic resin composition which has a hard segment and a soft segment as a thermoplastic resin composition which comprises A layer.
The hard segment serves to maintain the strength of the layer, and the soft segment serves to impregnate the subcritical or supercritical fluid. In order to ensure that each segment plays the role, it is preferable that the hard segment ratio is 5 to 95 mass% and the soft segment ratio is 95 to 5 mass%. If the hard segment ratio is less than 5% by mass, the A layer is too soft to maintain the strength, and the subcritical or supercritical fluid cannot remain in the A layer and is degassed. There is a possibility that it cannot be made porous. On the other hand, when the soft segment ratio is less than 5% by mass, the amount of subcritical or supercritical fluid impregnated decreases, making it difficult to obtain sufficient communication. More preferably, the hard segment ratio is 10 to 90% by mass, the soft segment ratio is 90 to 10% by mass, more preferably the hard segment ratio is 30 to 80% by mass, and the soft segment ratio is It is 70-20 mass%.

  Examples of the soft segment of the thermoplastic resin constituting the layer A include polyisoprene, polybutadiene, hydrogenated polybutadiene, hydrogenated polyisoprene, amorphous polyethylene, polyvinyl chloride, polyether, ethylene-propylene rubber, and isobutene-isoprene rubber. , Fluorine rubber or silicone rubber. Examples of the hard segment include polystyrene, polyethylene, polypropylene, polyurethane, polyester, polyamide, polybutylene terephthalate, or a fluororesin.

More specifically, examples of the thermoplastic resin composition constituting the A layer include styrene-based thermoplastic resins, polyester-based thermoplastic resins, polyamide-based thermoplastic resins, and olefin-based thermoplastic resins.
As the styrene-based thermoplastic resin, as a hard segment, a styrene derivative such as styrene or methylstyrene, indene or vinylnaphthalene, etc., preferably polystyrene is used, and a conjugated diene polymer such as polybutadiene or polyisoprene as a soft segment, or ethylene Styrene thermoplastic resins using polyolefin elastomers such as / butylene copolymer, ethylene / propylene copolymer or polyisobutene.

As the polyester-based thermoplastic resin, an aromatic polyester, an alicyclic polyester or a derivative thereof, or a mixture thereof is used as a hard segment, and a polytetramethylene glycol or poly (ethylene / propylene) block poly is used as a soft segment. And polyester-based thermoplastic resins using polyalkylene glycols such as glycols.
As the polyamide-based thermoplastic resin, polyamides such as polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 11 and polyamide 12 or copolymers thereof are used as hard segments, and polytetramethylene glycol or the like as soft segments. Examples thereof include polyamide-based thermoplastic resins using polyalkylene glycol such as poly (ethylene / propylene) block polyglycol.

As a hard segment constituting the olefin thermoplastic resin,
A homopolymer resin of ethylene, a copolymer resin having ethylene as a main component and an α-olefin having 3 or more carbon atoms as a minor component;
A homopolymer resin of propylene, a copolymer resin of propylene as a main component and ethylene or an α-olefin having 4 or more carbon atoms;
1-butene homopolymer resin, a copolymer resin of 1-butene as a main component and ethylene, propylene or an α-olefin having 5 or more carbon atoms;
· Homopolymer resin of 4-methyl-1-pentene, copolymer resin of 4-methyl-1-pentene as a main component and ethylene, propylene, 1-butene or α-olefin having 6 or more carbon atoms ;
・ Modified products of the above resins. Two or more of these may be mixed.

Examples of the soft segment constituting the olefin-based thermoplastic resin include diene rubber, hydrogenated diene rubber, olefin elastomer, and the like.
Examples of the diene rubber include isoprene rubber, butadiene rubber, butyl rubber, propylene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-isoprene rubber, and styrene-butadiene rubber.
The hydrogenated diene rubber is obtained by adding a hydrogen atom to at least a part of a double bond of a diene rubber molecule.
The olefin elastomer is an elastic copolymer obtained by adding at least one polyene copolymerizable with two or three or more olefins. As the olefin, an α-olefin such as ethylene or propylene is used. 1,4-hexadiene, cyclic diene, norbornene and the like are used. Preferred olefin elastomers include, for example, ethylene-propylene copolymer rubber, ethylene-propylene-diene rubber, ethylene-butadiene copolymer rubber and the like.

  The thermoplastic resin composition constituting the A layer is preferably an olefinic thermoplastic resin. Of these, olefin-based thermoplastic resins using polyethylene or polypropylene as the hard segment and ethylene-propylene rubber or ethylene-propylene-diene rubber, hydrogenated polybutadiene or hydrogenated polyisoprene as the soft segment are preferable.

As the thermoplastic resin composition, an olefin-based thermoplastic resin having a propylene-based resin as a hard segment and an ethylene-propylene rubber in a proportion of 5 to 95% by mass as a soft segment is particularly preferable.
The propylene resin as the hard segment includes homopolymers and copolymers, and the copolymers include random copolymers and block copolymers. Homopolymers are propylene homopolymers, which are isotactic or syndiotactic and polypropylene exhibiting various degrees of stereoregularity.
On the other hand, as a copolymer, propylene is a main component, and this and α such as ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene or 1-decene. -Copolymers with olefins are used. This copolymer may be a binary system, a ternary system, or a quaternary system, and may be a random copolymer or a block copolymer.
The propylene resin may be mixed with a resin having a lower melting point than that of the propylene homopolymer. Examples of such a resin having a low melting point include high-density or low-density polyethylene. It is preferable that the compounding quantity is 2-50 mass%.
The ethylene-propylene rubber as a soft segment includes a binary copolymer of ethylene and propylene and a terpolymer containing a small amount of a non-conjugated diene monomer as a third component. It may be used. Examples of the non-conjugated diene monomer include dicyclopentadiene, ethylidene norbornene, and hexadiene. As the ethylene-propylene rubber, an ethylene-propylene rubber having an ethylene content of 7 to 80% by mass relative to the whole rubber is preferable, and an ethylene-propylene rubber having 10 to 60% by mass is more preferable.
By adjusting the ethylene-propylene rubber content or the ethylene content in the ethylene-propylene rubber, the ethylene content with respect to the entire resin composition constituting the A layer is preferably 5 to 95% by mass.

As a classification by the manufacturing method of the thermoplastic resin composition constituting the A layer, a soft component such as ethylene-propylene rubber constituting a soft segment is added to a propylene resin constituting a hard segment like a twin screw extruder. There are compound polymers that are blended using a kneader and polymer polymers that directly polymerize ethylene or the like and propylene.
From the viewpoint of dispersibility of soft components such as ethylene-propylene rubber constituting the soft segment, it is preferable to use a polymerization type polymer.

Further, as a method for increasing the content of the soft segment, there is a method of blending a commercially available propylene copolymer with a soft component such as ethylene propylene rubber. In this case, the content of the soft segment can be easily increased by using a kneader such as a twin screw extruder.
Similarly, an olefinic thermoplastic resin having a preferable soft segment content can be obtained by blending propylene homopolymer with ethylene propylene rubber or polyethylene using a kneader such as a twin screw extruder.

  As the thermoplastic resin composition constituting the A layer, in addition to the above-mentioned olefin thermoplastic resin, a mixed resin composition of a polyester resin, an olefin thermoplastic elastomer, and a styrene thermoplastic elastomer should be cited as a suitable example. Can do. The mixing ratio of each component in the mixed resin is not particularly limited, but it is preferable to include 50% by mass or more of the polyester resin. The polyester resin is preferably a polyethylene terephthalate resin.

The olefin-based thermoplastic elastomer is not particularly limited as long as it contains an olefin unit in a molecular chain and exhibits rubbery elasticity.
Especially, as an olefin type thermoplastic elastomer, what shows rubber-like elasticity by copolymerizing monomers other than ethylene to an ethylene monomer is mentioned as a suitable example.
Examples of monomers other than ethylene include α-olefin, vinyl acetate (VA), ethyl acrylate (EA), and the like. Examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1 -Tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicocene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl -1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3 -Ethyl-1-hexene, 9-methyl-1-decene, 11-methyl-1-dodecene, 12-ethyl-1-tetradecene and combinations of two or more thereof Align, and the like. In addition to these ethylene monomers and α-olefin monomers, non-conjugated diene monomers such as cyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylene norbornene, ethylidene norbornene and the like were copolymerized. Olefin-based thermoplastic elastomers are also included. Among these, a copolymer of an ethylene monomer and an α-olefin monomer having 4 to 10 carbon atoms, particularly an ethylene monomer and propylene, 1-butene, 1-hexene, 1-octene and / or 1- A copolymer with a decene monomer, and a copolymer having an ethylene monomer / α-olefin monomer mass ratio of 90/10 to 50/50, preferably 80/20 to 60/40 However, it is rich in rubber-like elasticity, is easily available industrially, does not contain a double bond, and is excellent in weather resistance and is preferable.

Examples of the styrenic thermoplastic elastomer include a block copolymer of a polymer block (A) mainly composed of a styrene monomer and a block (B) mainly composed of a conjugated diene compound, and a conjugated diene polymer unit of the block copolymer. The hydrogenated product can be exemplified. Examples of the styrenic monomer include styrene, α-methyl styrene, vinyl toluene, and t-butyl styrene. These monomers may be used alone or in combination of two or more. Of these, styrene is preferable as the styrene monomer. Examples of the conjugated diene compound include butadiene, isoprene, chloroprene, and 2,3-dimethylbutadiene. These may be used alone or in combination of two or more.
Specific examples of styrenic thermoplastic elastomers include styrene-butadiene-styrene copolymer (SBS), styrene-isoprene-styrene copolymer (SIS), styrene-ethylene / butylene-styrene copolymer (SEBS), and styrene. -Ethylene / propylene-styrene copolymer (SEPS) or styrene-ethylene-ethylene / propylene-styrene copolymer (SEEPS).

The thermoplastic resin composition constituting the A layer of the intermediate layer may contain a filler. In addition, when it is set as the structure which does not contain a filler, the porous body with small mass per unit area can be provided.
When mix | blending the said filler, any filler of an inorganic filler and an organic filler can be used, and it can use 1 type or in combination of 2 or more types.
Examples of inorganic fillers include carbonates such as calcium carbonate, magnesium carbonate and barium carbonate; sulfates such as calcium sulfate, magnesium sulfate and barium sulfate; chlorides such as sodium chloride, calcium chloride and magnesium chloride; calcium oxide, magnesium oxide, Examples thereof include oxides such as zinc oxide, titanium oxide and silica; silicates such as talc, clay and mica. Among these, calcium carbonate or barium sulfate is preferable.
In order to improve the dispersibility in the resin, the inorganic filler may be hydrophobized by coating the surface of the inorganic filler with a surface treatment agent. Examples of the surface treatment agent include higher fatty acids such as stearic acid or lauric acid, or metal salts thereof.

As the organic filler, resin particles having a melting point higher than the melting point of the thermoplastic resin constituting the A layer are preferable so that the filler does not melt under the temperature condition of the treatment involving heating such as stretching treatment, and the gel content is 4 to 4 More preferably, about 10% crosslinked resin particles.
Examples of the organic filler include ultra high molecular weight polyethylene, polystyrene, polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polytetrafluoroethylene, polyimide, and polyetherimide. , Thermoplastic resins such as melamine and benzoguanamine, and thermosetting resins. Among these, cross-linked polystyrene and the like are particularly preferable.

  The average particle size of the filler is about 0.01 to 25 μm, preferably 0.05 to 7 μm, and more preferably 0.1 to 5 μm. When the average particle size is less than 0.01 μm, the dispersibility decreases due to the aggregation of fillers. Moreover, even if the average particle diameter exceeds 25 μm, it is difficult to mix uniformly.

  When blending a filler, it is preferable to blend a plasticizer for the purpose of enhancing the dispersibility of the filler in the resin.

Examples of the plasticizer include ester compounds, amide compounds, alcohol compounds, amine salts, amine compounds (excluding amine salts), epoxy compounds, ether compounds, mineral oil, fats and oils, paraffin wax, liquid silicone, fluorine oil, and liquid polyether. , Liquid polybutenes, liquid polybutadienes, long chain fatty acids, carboxylates, carboxylic acid compounds (excluding carboxylates), sulfonates, sulfone compounds (excluding sulfonates), fluorine compounds, etc. Can be mentioned.
Specifically, plastic compounding agents (published by Taiseisha Co., Ltd., November 30, 1987, second edition) P31 to P64, P83, P97 to P100, P154 to P158, P178 to P182, P271 to P275, P283 to 294 And the like. More specifically, the plasticizers (TCP, TOP, PS, ESBO, etc.) described in the items of plasticizers P29 to P64 and listed in Tables 4 to 49 and P6 to P54 are listed. It can be used. Further, the surfactant compounds listed in the new introduction to surfactants (published by Sanyo Kasei Kogyo Co., Ltd., August 1992, third edition) can also be suitably used as plasticizers.

  The blending amount of the plasticizer is preferably about 1 to 30 parts by weight, more preferably 1 to 15 parts by weight, with respect to 100 parts by weight of the thermoplastic resin constituting the A layer. Is particularly preferred. When the amount of the plasticizer is less than 1 part by mass, the effect of blending the plasticizer is difficult to express, and when the amount of the plasticizer exceeds 30 parts by mass, defects in the process such as resin burning during the production of the laminate It becomes easy to cause.

  Furthermore, if it is in a range that does not impair the purpose of the present invention and the properties of the intermediate layer, additives generally blended into the resin composition in the thermoplastic resin composition constituting the A layer, such as antioxidants, heat Stabilizers, light stabilizers, ultraviolet absorbers, neutralizers, antifogging agents, antiblocking agents, antistatic agents, slip agents, coloring agents, and the like may be blended.

The B layer of the adhesive layer laminated on the outer layers on both sides of the A layer serving as the intermediate layer is mainly composed of an adhesive resin. By adhering and laminating the adhesive layer (B layer) on both sides of the intermediate layer (A layer), air pockets are not generated on the outer surfaces of both sides of the intermediate layer.
In this way, the outer surface of the intermediate layer is sealed by the adhesive layer, so that the supercritical state or the subcritical state is caused by causing a sudden pressure drop after impregnating the fluid in the supercritical state or the subcritical state. In order to prevent the fluid from being easily vaporized when released from the inside, micropores equivalent to the inside are reliably formed near the surface of the intermediate layer, and the micropores formed inside and on the surface are made uniform. be able to.

The adhesive resin used for the B layer serving as the adhesive layer is mainly composed of at least one copolymer or resin selected from the group consisting of the following (a), (b), and (c). Is preferred. More specifically, it preferably contains 50% by mass or more of the following polymer or resin, preferably 70% by mass or more, more preferably 90% by mass or more, and still more preferably 100% by mass.
(A) a copolymer comprising at least one comonomer selected from the group consisting of vinyl acetate, (meth) acrylic acid, ethyl (meth) acrylate, methyl (meth) acrylate, maleic anhydride and glycidyl methacrylate and ethylene. Polymer (hereinafter referred to as “ethylene copolymer”) (b) Copolymer of soft aromatic hydrocarbon and conjugated diene hydrocarbon or hydrogenated derivative thereof (c) Modified polyolefin resin

First, the ethylene-based copolymer (a) will be described.
Examples of the ethylene copolymer include ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) ethyl acrylate copolymer, ethylene- (meth) acrylic acid methyl copolymer. Polymer, ethylene-vinyl acetate-maleic anhydride terpolymer, ethylene-ethyl acrylate-maleic anhydride terpolymer, ethylene-glycidyl methacrylate copolymer, ethylene-vinyl acetate-glycidyl methacrylate terpolymer Examples thereof include an original copolymer and an ethylene-ethyl acrylate-glycidyl methacrylate terpolymer. Among these, an ethylene-vinyl acetate copolymer, an ethylene- (meth) acrylic acid copolymer, an ethylene- (meth) ethyl acrylate copolymer, and an ethylene-methyl (meth) acrylate copolymer can be suitably used.

  The ethylene copolymer has an ethylene unit content of 30% by mass to 90% by mass, preferably 40% by mass to 80% by mass. If the content rate of an ethylene unit is 30 mass% or more, the rigidity of the whole laminated body can be favorably maintained, which is preferable. On the other hand, when the ethylene unit content is 90% by mass or less, delamination can be suppressed when stress is applied to the laminate.

  The ethylene copolymer having a melt flow rate (MFR) of 0.1 g / 10 min to 10 g / 10 min, preferably 0.5 g / 10 min to 8.0 g / 10 min is suitably used. It is done. If the MFR is 0.1 g / 10 min or more, the extrudability can be maintained satisfactorily. On the other hand, if the MFR is 10 g / 10 min or less, the thickness of the laminate and the mechanical strength are hardly lowered. MFR is measured according to JIS K 7210 under conditions of a temperature of 190 ° C. and a load of 21.18N.

  The ethylene-based copolymer is “bondin” (manufactured by Sumitomo Chemical Co., Ltd.), ethylene-glycidyl methacrylate copolymer, ethylene-vinyl acetate-glycidyl methacrylate triethylene as an ethylene-vinyl acetate-maleic anhydride copolymer. “Bond First” (manufactured by Sumitomo Chemical Co., Ltd.) and the like are commercially available as an original copolymer, an ethylene-ethyl acrylate-glycidyl methacrylate terpolymer.

Next, the copolymer (b) and its hydrogenated derivative will be described.
As the aromatic hydrocarbon constituting the copolymer of the soft aromatic hydrocarbon and the conjugated diene hydrocarbon, styrene is preferably used, and styrene homologues such as α-methylstyrene can also be used. . Examples of conjugated diene hydrocarbons include 1,3-butadiene, 1,2-isoprene, 1,4-isoprene, 1,3-pentadiene, and the like, and these may be hydrogenated derivatives. These may be used alone or in admixture of two or more.

  The copolymer of aromatic hydrocarbon and conjugated diene hydrocarbon or its hydrogenated derivative has an aromatic hydrocarbon content of 5% by mass or more, preferably 7% by mass or more of the total amount of the copolymer. More preferably, it is a soft copolymer of 10% by mass or more and 50% by mass or less, preferably 40% by mass or less, more preferably 35% by mass or less. If the content of the aromatic hydrocarbon is 5% by mass or more, the rigidity of the entire film can be maintained satisfactorily. On the other hand, when the content of the aromatic hydrocarbon is 50% by mass or less, delamination can be suppressed when stress is applied to the film. The polymerization form of the copolymer is not particularly limited, and may be any form of a block copolymer, a random copolymer, and a graft copolymer, but includes a pure structure, a random structure, or a tapered structure. Block copolymers are preferred.

  As a hydrogenated derivative of a copolymer of an aromatic hydrocarbon and a conjugated diene hydrocarbon, a hydrogenated derivative of a styrene-conjugated diene random copolymer can be preferably used. The details of the hydrogenated derivative of the styrene-conjugated diene random copolymer and the production method thereof are disclosed in JP-A-2-158443, JP-A-2-305814 and JP-A-3-72512. ing.

  Commercially available products of aromatic hydrocarbon-conjugated diene hydrocarbon copolymer include styrene-butadiene block copolymer elastomer as “Tufprene” (manufactured by Asahi Kasei Chemicals), styrene-butadiene block copolymer. Trade name “Tuftec H” (manufactured by Asahi Kasei Chemicals Co., Ltd.), trade name “Clayton G” (manufactured by Kraton Polymer Japan Co., Ltd.), and hydrogenated derivative of styrene-butadiene random copolymer. "Dynalon" (manufactured by JSR Corporation), trade name "Septon" (manufactured by Kuraray Co., Ltd.) as a hydrogenated derivative of a styrene-isoprene block copolymer, trade name "HIBLER" as a styrene-vinylisoprene block copolymer elastomer (Made by Kuraray Co., Ltd.) and the like.

Moreover, the copolymer of the aromatic hydrocarbon and the conjugated diene hydrocarbon or the hydrogenated derivative thereof can further improve the interlayer adhesion with the A layer by introducing a polar group.
Examples of polar groups to be introduced include acid anhydride groups, carboxylic acid groups, carboxylic acid ester groups, carboxylic acid chloride groups, carboxylic acid amide groups, carboxylic acid groups, sulfonic acid groups, sulfonic acid ester groups, and sulfonic acid chloride groups. Sulfonic acid amide group, sulfonic acid group, epoxy group, amino group, imide group, oxazoline group, hydroxyl group and the like.

Copolymers of styrene compounds having a polar group and a conjugated diene or hydrogenated derivatives thereof include maleic anhydride-modified styrene-ethylene / butylene-styrene copolymer (SEBS), maleic anhydride-modified styrene-ethylene / propylene -Typical examples include styrene copolymer (SEPS), epoxy-modified SEBS, and epoxy-modified SEPS. These copolymers can be used alone or in admixture of two or more.
Specifically, trade names “Tuftec M” (manufactured by Asahi Kasei Co., Ltd.), “Epofriend” (manufactured by Daicel Chemical Industries, Ltd.) and the like are commercially available.

Next, the modified polyolefin resin (c) will be described.
The modified polyolefin resin refers to a resin mainly composed of an unsaturated carboxylic acid or a derivative thereof, or a polyolefin modified with a silane coupling agent.
Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, citraconic acid, and itaconic acid. Examples of the unsaturated carboxylic acid derivative include acid anhydrides, acid halides, amides, imides, and esters of the unsaturated carboxylic acid, and examples thereof include maleic anhydride, citraconic anhydride, and itaconic anhydride. Anhydrides are preferred. In addition, there are ester compounds of monoepoxy compounds of the unsaturated carboxylic acids or their anhydrides and the acids, reaction products of acids and polymers having groups capable of reacting with these acids in the molecule, etc. Can be mentioned. These metal salts can also be used. Among these, maleic anhydride is more preferably used. Moreover, these copolymers can be used individually or in mixture of 2 or more types, respectively.
Examples of the silane coupling agent include vinyltriethoxysilane, methacryloyloxytrimethoxysilane, and γ-methacryloyloxypropyltriacetyloxysilane.

  In order to produce the modified polyolefin resin, for example, these modified monomers can be copolymerized in the stage of polymerizing the polymer in advance, or these modified monomers can be graft copolymerized with the polymer once polymerized. For modification, these modified monomers are used alone or in combination, and those having a content in the range of 0.1 mass% or more and 5 mass% or less are preferably used. Of these, those that have been graft-modified are preferably used.

  As the modified polyolefin resin, specifically, trade names “Admer” (Mitsui Chemicals), “Modic” (Mitsubishi Chemical) are commercially available.

  In the resin composition constituting the B layer of the adhesive layer, additives that are generally blended in the resin composition in addition to the adhesive resin, as long as the object of the present invention and the characteristics of the B layer are not impaired May be blended.

If the laminate produced in the first step of the present invention comprises at least three layers of the above-described intermediate layer A layer and B layer of two non-porous adhesive layers located on both sides of the A layer, in particular, Its structure is not limited .
For example, A layer may be constituted of a plurality of layers having different compositions. Specifically, the case where the layer which does not contain a filler and the layer containing a filler are laminated | stacked alternately, or the case where the layer which does not contain a filler is laminated | stacked continuously is mentioned.
One or both of the two B layers present on both sides of the A layer may be composed of a plurality of layers having different compositions. The composition or structure of each of the two B layers may be the same or different .

In the laminate produced in the first step of the present invention, the ratio tra (= ta / t) of the thickness ta of the A layer to the thickness t of all layers is 0.05 to 0.95, preferably 0.1 to 0.1. It is adjusted to 0.90, more preferably 0.1 to 0.60.
If tra is larger than 0.95, the substantial thickness of the B layer becomes extremely thin, and it becomes difficult to remove the B layer . Further, if the thickness of the B layer is extremely thin, it does not serve as a lid. That is, when impregnated with a fluid in a supercritical state or subcritical state and then deviates from the supercritical state or subcritical state, gas is released from the surface of the A layer through the thin B layer by diffusion / evaporation. For this reason, there is a possibility that a region where foaming does not occur in the A layer, that is, a so-called non-porous layer, is not preferable. On the other hand, if tra is smaller than 0.05, the A layer becomes extremely thin. Also in this case, it becomes difficult to peel off the B layer .
Furthermore, arbitrary proportion trb thickness tb of B layer to the thickness t of all layers (= tb / t) is preferable to be 0.01 to 0.1.
In the present invention, when the stretching process is performed in any step, the tra and tr b are calculated from the measured values after the stretching process. Further, when the A layer or the B layer is composed of a plurality of layers, ta or tb represents the sum of the layers.

A known technique may be used as a method for manufacturing the laminate. For example, it can be created by the following method.
First, the components constituting each layer may be mixed and granulated once using a powder mixer such as a Henschel mixer or a kneader such as a uniaxial or biaxial kneader or a kneader.
The said laminated body is produced using the resin composition or granulated material which comprises each layer. Examples of the method for producing the laminate include a thermal bonding method, an extrusion lamination method, a dry lamination method, and a coextrusion method. Among these, a co-extrusion method using a T-die molding method or an inflation molding method is particularly preferably used .

In the method for producing a porous body of the present invention, as described above, as the second step, the laminate obtained in the first step is impregnated with a fluid in a supercritical state or a subcritical state, and then the supercritical state is obtained. The fluid is vaporized by releasing from the state or subcritical state.
Since the B layer of the adhesive layer has a so-called lid on the surface of the A layer of the intermediate layer, it is possible to create a supersaturated state on the surface of the A layer, and the thickness without causing a skin layer on the surface of the A layer. Micropores having communication in the direction can be formed.
In this step, micropores are formed when the fluid impregnated in the supercritical state or subcritical state in the B layer as well as the A layer is released from this state.

Gases that can be used as subcritical or supercritical fluids are not limited to the following, but include, for example, carbon dioxide, nitrogen, nitrous oxide, ethylene, ethane, tetrafluoroethylene, perfluoroethane, tetrafluoromethane, trifluoromethane, 1 , 1-difluoroethylene, trifluoroamide oxide, cis-difluorodiazine, trans-difluorodiazine, nitrogen difluoride, trideuterated phosphorus, dinitrogen tetrafluoride, ozone, phosphine, nitrosyl fluoride, three Nitrogen fluoride, deuterium chloride, hydrogen chloride, xenon, sulfur hexafluoride, fluoromethane, perfluoroethane, tetrafluoroethane, pentafluoroethane, tetrafluoromethane, trifluoromethane, 1,1-difluoroethene, ethyne, diborane , Water, tetrafluorohy Rajin, silane, silicon tetrafluoride, four germanium hydride, boron trifluoride, carbonyl fluoride, chlorotrifluoromethane, bromotrifluoromethane and vinyl fluoride, and the like.
Among them, preferable gases include carbon dioxide, nitrogen, nitrous oxide, ethylene, ethane, tetrafluoroethylene, perfluoroethane, tetrafluoromethane, trifluoromethane, and 1,1-difluoroethylene. Of these, carbon dioxide and nitrogen, which are inert gases, are particularly preferred in that they are non-flammable and non-toxic, are fairly inexpensive, and are non-reactive with most polymers.

  The “supercritical state” refers to a state where the temperature (critical temperature) and pressure (critical pressure) at which gas and liquid can coexist are exceeded. “Subcritical state” means a state where the pressure or temperature is in the vicinity of the critical pressure or temperature. Preferably, assuming that the critical temperature is Tc and the critical pressure is Pc, the temperature is 0.5 Tc or higher and / or the pressure is 0.5 Pc or higher (except when the temperature is Tc or higher and the pressure is Pc or higher. ). In particular, it is more preferable that either the pressure or the temperature exceeds the critical pressure or the critical temperature.

A fluid in a supercritical state or a subcritical state is a special fluid having properties different from those of ordinary gases and liquids, and has a very high impregnation property. Therefore, when the supercritical or subcritical fluid is brought into contact with the laminate obtained in the first step, the laminate is impregnated with the fluid.
A specific method for impregnating the laminate with a fluid in a supercritical state or a subcritical state may be a known method.
For example, the laminate is placed in a pressure-resistant container such as an autoclave, and a gaseous or liquid substance to be impregnated into the laminate is made into a fluid as exemplified above. Next, the temperature or / and pressure in the pressure vessel is increased to create a supercritical state or a subcritical state. That is, the temperature in the pressure vessel is raised to 0.5 Tc or higher, preferably higher than the critical temperature, or / and the pressure in the pressure vessel is raised to 0.5 Pc or higher, preferably higher than the critical pressure. In particular, it is more preferable to raise the temperature in the pressure vessel to a critical temperature or higher and raise the pressure to a critical pressure or higher.

Specifically, for example, when carbon dioxide is used, the critical temperature of carbon dioxide is 304.3 K and the critical pressure is 7.38 MPa.
When nitrogen is used, the critical temperature of nitrogen is 126.2 K and the critical pressure is 3.40 MPa. Therefore, it is preferable that the pressure is 3 MPa or more while maintaining the temperature at room temperature.
When nitrous oxide is used, since the critical temperature of nitrous oxide is 309.6K and the critical pressure is 7.24 MPa, it is preferable that the pressure is 7 MPa or more while keeping the temperature at room temperature.
When ethylene is used, since the critical temperature of ethylene is 282.4K and the critical pressure is 5.04MPa, it is preferable to set the temperature to 283.2K or more and the pressure to 5MPa or more.
When ethane is used, since the critical temperature of ethane is 305.2K and the critical pressure is 4.88 MPa, it is preferable that the pressure is 4.5 MPa or more while maintaining the temperature at room temperature.

  The time for impregnating the fluid in the supercritical state or the subcritical state varies depending on the composition of the resin constituting the A layer of the intermediate layer, the target air permeability and porosity, etc. The above is preferable. This is because if the time is less than 1 minute, the fluid A cannot be sufficiently impregnated into the A layer. The upper limit value is 10 hours or less, preferably 5 hours or less, more preferably 2 hours or less from the viewpoint of production efficiency.

Next, the laminate is made porous by releasing (deviating) from the supercritical state or subcritical state to vaporize the fluid.
At this time, the temperature or pressure may be rapidly returned to normal temperature or normal pressure, or may be gradually decreased. Alternatively, the temperature may be lowered to a temperature below normal temperature or a pressure below normal pressure and then returned to normal temperature or normal pressure.

  Delete

  Delete

  Delete

The stretching treatment may be either uniaxial stretching or biaxial stretching, but biaxial stretching is preferred from the viewpoint of isotropic property. Biaxial stretching may be simultaneous biaxial stretching or sequential biaxial stretching in which the film is stretched in the longitudinal direction (longitudinal direction) and then in the transverse direction. As a stretching method, a method using a general apparatus such as a roll stretching machine or a tenter stretching machine may be used. As a draw ratio, it is at least 2 times by area magnification, Preferably it is 4-25 times, More preferably, it is 4-16 times.
The stretching temperature is not particularly limited, but the stretching is preferably performed at a temperature lower than the melting point of the thermoplastic resin constituting each layer, preferably at 30 ° C. or less from the melting point .

Further, if necessary, measures such as heat shrinkage and dimensional stability may be taken by performing heat fixation near the melting point or relaxation after stretching.
These treatments can be performed by known methods. For example, the heat treatment can be performed by any known method such as contact heating with a heating roll or heating in air in an oven. Moreover, it is also possible to divert the above-mentioned extending | stretching apparatus. The heat treatment temperature can be any temperature below the melting point of the thermoplastic resin constituting each layer constituting the laminate, but is preferably 100 ° C. or higher and lower than the melting point of the resin, more preferably 110 ° C. or higher and 130 ° C. It is as follows.

Porous body manufactured in the method of the present invention (hereinafter, abbreviated as the porous body of the present invention) the physical properties of the type of the resin constituting the A layer of the intermediate layer, the conditions for impregnating the subcritical or supercritical fluids, stretching It can be freely adjusted depending on conditions (stretch ratio, stretch temperature, etc.).

  The porous body of the present invention preferably has an air permeability, which is an index of communication, in the range of 1 to 10,000 seconds / 100 ml. This means that if the air permeability is greater than 10,000 seconds / 100 ml, the numerical value of the air permeability will be obtained in the measurement, but it means that the structure is quite poorly connected. It may be equal to not. The air permeability is preferably 1 to 5,000 seconds / 100 ml, more preferably 50 to 4,000 seconds / 100 ml, and particularly preferably 100 to 2,000 seconds / 100 ml. . The air permeability is measured in accordance with JIS P 8117.

  In the porous body of the present invention, the porosity is also an important factor for limiting the porous structure. Although the measuring method of a porosity is mentioned later, it is preferable to make the porosity of the porous body of this invention into the range of 5 to 80%. If the porosity is less than 5%, it is difficult to substantially obtain communication. Moreover, if the porosity is higher than 80%, handling becomes difficult from the viewpoint of strength, which is not preferable. The porosity is more preferably 20 to 70%, and particularly preferably 40 to 60%.

Since the range required for the air permeability and the porosity differs depending on the application, the air permeability and the porosity are appropriately adjusted according to the application.
For example, when used for sanitary products such as diapers and sanitary products, the air permeability is preferably 1 to 2,000 seconds / 100 ml.
When used as a battery separator, the air permeability is preferably 1 to 500 seconds / 100 ml.

The air permeability and porosity are, for example, the content of the soft segment in the thermoplastic resin constituting the A layer of the intermediate layer, the time for impregnating the fluid in the supercritical state or subcritical state, the supercritical state or the subcritical state It can be controlled by adjusting the temperature or pressure when impregnating the fluid.
For example, if the content of the soft segment in the thermoplastic resin constituting the A layer is increased, the fluid in the supercritical state or the subcritical state is easily impregnated, so that the permeability and the porosity are increased. Further, even if the time for impregnating the fluid in the supercritical state or the subcritical state is extended, the permeability and the porosity can be increased.

The porous body of the present invention preferably has a mass per unit area (referred to as a weight) of 10 to 30 g / m ² and more preferably 10 to 25 g / m ² when converted to a thickness per 25 μm. . By reducing the weighing, it is possible to reduce the weight of the device on which the porous body of the present invention is mounted. In order to show a certain range of weighing, even if the layer A does not contain a filler or a filler is added, the ratio of the mass of the filler to the total mass of the porous body of the present invention, that is, the filler content is 40% by mass. Hereinafter, it is more preferably suppressed to 30% by mass or less.

In the porous body of the present invention, when the A layer of the intermediate layer is composed of a polypropylene resin composition, higher heat resistance can be exhibited than a conventional porous film made of only a polyethylene resin. That is, the shape can be maintained even when exposed to high temperatures.
As an index of heat resistance, the porous body of the present invention preferably has a thermal shrinkage of 25% or less, more preferably 15% or less, and particularly preferably 10% or less. When the thermal shrinkage rate is larger than 25%, when the porous body of the present invention is used as a battery separator, there is a concern that the positive electrode and the negative electrode come into contact with each other at the end of the porous body, causing a short circuit.

The thickness or shape of the porous body of the present invention is not particularly limited. For example, the porous body of the present invention may be any of a film shape having an average thickness of 1 μm or more and less than 250 μm, a sheet shape having a thickness of 250 μm or more and less than several mm, and a molded product having a thickness of several mm or more. It can be appropriately selected depending on the situation.
Especially, it is preferable that the porous body of this invention exhibits a film form. That is, the average thickness of the porous body is 1 to 250 μm, preferably 10 to 200 μm, and more preferably 10 to 150 μm.
Note that the average thickness is a value obtained by measuring five in-plane positions in an unspecified manner with a 1/1000 mm dial gauge and calculating the average.

The porous body of the present invention having the above characteristics can be applied to various uses that require air permeability. Battery separators; Sanitary materials such as disposable paper diapers and sanitary items such as pads or bed sheets for absorbing body fluids; Medical materials such as surgical clothing or base materials for warm compresses; Materials for clothing such as jumpers, sportswear or rainwear ; Building materials such as wallpaper, roof waterproofing material, heat insulating material, sound absorbing material; desiccant; moisture-proofing agent; oxygen scavenger; disposable body warmer; can be used very suitably as a material for packaging materials such as freshness preservation packaging or food packaging .
Especially, the porous body of this invention is used suitably as a separator for nonaqueous electrolyte batteries, such as a lithium ion secondary battery utilized as power supplies, such as various electronic devices.

According to the method of the present invention, at least some of the micropores formed using the subcritical or supercritical fluid are in communication with the adjacent micropores. Therefore, for example, it is possible to provide a porous body that can be used for applications that require the passage of a certain gas or liquid such as a battery separator, an electrolytic capacitor diaphragm, various filters, or various filtration membranes. .
In the present invention, a subcritical or supercritical fluid is used as a means for making a porous material, and an organic solvent is not used in a large amount unlike the invention described in the prior art document 1, so that the burden on the environment can be reduced. In particular, if a non-toxic inert gas such as carbon dioxide or nitrogen is used as a subcritical or supercritical fluid, the burden on the environment can be further reduced.
Furthermore, the method for producing a porous body of the present invention has an advantage that the production conditions are wide and process management is easy.
Further, in the method of making porous by removing the plasticizer and the solvent, the plasticizer and the solvent may remain without being removed, but in the present invention, the subcritical or supercritical fluid is used. Such a problem of remaining does not occur, and a porous body with fewer impurities can be produced.

  When porous using a subcritical or supercritical fluid, the surface does not become supersaturated and gas is immediately released from the surface by diffusion / evaporation, resulting in the formation of a non-porous layer that does not have micropores. . However, an adhesive layer (B layer) made of a resin composition containing an adhesive resin is provided on both sides of an intermediate layer (A layer) to be made porous using a subcritical or supercritical fluid, and a so-called surface is formed on the surface of the intermediate layer. By covering the laminate, it is possible to create a supersaturated state on the surface of the intermediate layer when the laminate is impregnated with a subcritical or supercritical fluid and then a sudden pressure drop occurs. Micropores can be formed. Therefore, by using the method of the present invention, it is possible to prevent a non-porous layer from being formed on at least a part of the surface in the porosity using a subcritical or supercritical fluid.

  The porous body of the present invention obtained by the above production method is characterized by having uniform communication holes throughout and having a small mass per unit area. Therefore, the porous body of the present invention can be particularly suitably used as a battery separator, and in this case, a non-aqueous electrolyte secondary battery having good electrolyte retention and high safety without greatly increasing the battery weight is provided. can do.

It is a general | schematic process drawing for demonstrating the manufacturing method of the reference 1st Embodiment of this invention. It is a partially broken perspective view of a nonaqueous electrolyte battery accommodating the porous body produced as the non-aqueous electrolyte battery separator. It is a schematic process drawing for demonstrating the manufacturing method of 1st Embodiment of this invention . Reference embodiments are shown, in which (A) and (B) are schematic process diagrams, and (C) are a two-dimensional schematic diagram and a three-dimensional schematic diagram showing the structure of the manufactured porous body.

Hereinafter, embodiments of the present invention will be described.
It shows a schematic process diagram of a reference to the first embodiment of the method for manufacturing a porous member of the present invention.
Method of manufacturing a multi-hole body 11, first, the A layer 2 made of an intermediate layer comprising a thermoplastic resin composition, consisting of two adhesive layers made of a resin composition comprising an adhesive resin on both sides of the A layer 2 B Layers 3-1 and 3-2 are stacked, and further, three types and five layers are formed by stacking C layers 4-1 and 4-2, which are release layers, on each of the two B layers 3-1 and 3-2. A first step of producing a laminated body 1 having a structure;
A second step of impregnating the laminate 1 obtained in the first step with a fluid in a supercritical state or a subcritical state, and then releasing the fluid from the state to vaporize the fluid;
A third step of stretching the obtained laminate in at least a uniaxial direction;
It consists of a fourth step of peeling the two B layers 3-1 and 3-2 and the two C layers 4-1 and 4-2.

As the thermoplastic resin composition constituting the A layer 2 serving as the intermediate layer, as a first aspect, a polypropylene resin composition in which an ethylene-propylene rubber is blended with a polypropylene homopolymer is used.
The ethylene-propylene rubber content is preferably 5 to 95% by mass, more preferably 15 to 75% by mass, and further preferably 30 to 60% by mass.
As the ethylene-propylene rubber, an ethylene-propylene rubber having an ethylene content of 30 to 55% by mass based on the whole rubber is particularly preferable.
By adjusting the ethylene-propylene rubber content and the ethylene content in the ethylene-propylene rubber, the ethylene content with respect to the entire polypropylene resin composition constituting the A layer is preferably 5 to 70% by mass. It is more preferably ˜50 mass%, and particularly preferably 10 to 30 mass%.

A modified polyolefin resin is used as the adhesive resin contained in the B layers 3-1 and 3-2 of the adhesive layer.
As the thermoplastic resin constituting the C layers 4-1 and 4-2 of the release layer, it is preferable to use polyethylene terephthalate resin, ethylene-vinyl alcohol copolymer or nylon, particularly 6 nylon.

In the first step, the thermoplastic resin constituting the A layer 2, the adhesive resin composition constituting the B layers 3-1, 3-2, and the thermoplastic constituting the C layers 4-1, 4-2. A film obtained by laminating a resin and five layers by coextrusion is extruded. More specifically, lamination is performed under a temperature condition of 150 to 250 ° C, preferably 190 to 220 ° C, using an inflation die or T die for multilayer molding.
In the laminated body thus obtained, the ratio tra (= ta / t) of the thickness ta of the A layer to the thickness t of all layers is 0.1 to 0.5, and the ratio trb (= tb / t) of the thickness tb of the B layer. ) Is 0.01 to 0.1, and the ratio trc (= tc / t) of the thickness tc of the C layer is adjusted to 0.1 to 0.5.
In addition, when the resin composition which comprises each layer contains 2 or more components, it is preferable to mix and pelletize beforehand.

The laminate obtained in the first step is placed in a pressure vessel, and carbon dioxide gas or nitrogen gas is sealed in the pressure vessel. The pressure in the pressure vessel is increased to bring carbon dioxide or nitrogen into a supercritical or subcritical state.
More specifically, when carbon dioxide is used, the pressure is increased to 7 Mpa or more, preferably 10 Mpa or more. When nitrogen is used, the pressure is increased to 3 Mpa or more, preferably 10 Mpa or more. The temperature in the pressure vessel may be room temperature, but can be heated.

By maintaining the pressure and temperature in the pressure vessel, carbon dioxide or nitrogen in a supercritical state or a subcritical state is impregnated into the laminate. The impregnation time is 10 minutes to 2 hours, preferably 20 minutes to 2 hours.
Thereafter, the impregnated carbon dioxide or nitrogen is vaporized by returning the pressure or temperature in the pressure vessel to normal pressure or normal temperature. The pressure or temperature in the pressure vessel may be gradually decreased, or may be returned to normal pressure or room temperature at once.
In this step, the insides of the A layer 2, the B layers 3-1, 3-2 and the C layers 4-1, 4-2 are made porous, but the surfaces of the C layers 4-1, 4-2 are impregnated. The gas is released from the outer surface and no holes are formed, so-called non-porous layer 5 is formed.

The laminate obtained in the above step is stretched.
By stretching the micropores generated by the subcritical or supercritical fluid, the adjacent independent micropores can be communicated with each other, and in the A layer 2, the connectivity in the thickness direction is ensured. Can do.
The stretching method in this step is preferably sequential biaxial stretching in which the film is stretched in the longitudinal direction (longitudinal direction) and then stretched in the transverse direction. The draw ratio is 4 to 16 times, preferably 4 to 9 times in terms of area magnification. The stretching temperature is preferably 40 to 80 ° C.

  Furthermore, after the stretching step, heat treatment may be performed as needed to impart thermal dimensional stability to the porous body. The heat treatment can be performed by any known method such as contact heating with a heating roll or heating in the air in an oven. The heat treatment temperature can be any temperature below the melting point of the thermoplastic resin constituting the A layer 2, the B layers 3-1, 3-2 and the C layers 4-1, 4-2, but preferably 100. It is set to not less than the melting point of the resin and more preferably not less than 110 ° C. and not more than 130 ° C.

  About the laminated body which performed the extending | stretching process, the B layer 3-1 of an adhesive layer, the C layer 4-1 of a peeling layer, and similarly 3-2 and 4-2 are each teared and peeled together as a force. Thereby, the porous body 11 which consists of A layer 2 of the intermediate | middle layer which has communication property in the thickness direction is obtained.

The porous body 11 manufactured as described above has an air permeability, which is an index of communication, of 50 to 5,000 seconds / 100 ml, preferably 100 to 1,000 seconds / 100 ml. The porosity is 30 to 70%, preferably 40 to 60%.
Moreover, when A layer 2 consists of polypropylene resin, heat resistance higher than the porous film which consists only of the conventional polyethylene resin can be exhibited.

The porous body 11 has a film shape and has an average thickness of 1 to 250 μm, preferably 10 to 200 μm, more preferably 10 to 100 μm, and is prepared according to the use of the porous body. This average thickness is a value obtained by measuring five locations in a plane unspecified with a 1/1000 mm dial gauge and calculating the average.
Furthermore, by not adding a filler to the A layer 2, the porous body 11 has a mass per unit area (referred to as a weight) of 10 to 30 g / m ² , preferably 10 to 20 g / m when converted to a thickness per 25 μm. m ² and are lighter.

The above-described porous body 11 can be used for various applications that require air permeability, and among them, it is preferably used as a battery separator.
When the porous body 11 of the present invention is used as a battery separator, the air permeability is set to 50 to 500 seconds / 100 ml. This is because when the air permeability is less than 50 seconds / 100 ml, the electrolyte solution retainability is lowered and the capacity of the secondary battery is lowered or the cycle performance is lowered. On the other hand, if the air permeability exceeds 500 seconds / 100 ml, the ion conductivity is lowered and sufficient battery characteristics cannot be obtained. Preferably, it is 100 to 300 seconds / 100 ml.
Moreover, the porosity is set to 30 to 70%. This is because if the porosity is less than 30%, the ion permeability is low and it is difficult to obtain sufficient battery performance, whereas if the porosity exceeds 70%, it is not preferable from the viewpoint of battery safety. More preferably, it is 35 to 65%.

  As a battery separator, a porous film composed mainly of a polyethylene resin is used because of the necessity of shutdown characteristics. However, by using a polypropylene resin composition for the A layer, the dimensional stability after shutdown is improved and the battery is not suitable. It can be made difficult to fall into a stable state.

Next, the pre-Symbol porous body 11 for non-aqueous electrolyte battery that accommodates a battery separator 10, will be described with reference to FIG.
Both electrodes of the positive electrode plate 21 and the negative electrode plate 22 are wound in a spiral shape so as to overlap each other via the separator 10, and the outside is stopped with a winding tape to form a wound body. When winding in this spiral shape, the separator 10 preferably has a thickness of 5 to 40 μm, and more preferably 5 to 30 μm. This is because when the thickness is less than 5 μm, the separator is easily broken, and when it exceeds 40 μm, the battery area is reduced and the battery capacity is reduced when wound in a predetermined battery can as a battery separator.

  A wound body in which the positive electrode plate 21, the separator 10 and the negative electrode plate 22 are integrally wound is housed in a bottomed cylindrical battery case and welded to the positive and negative electrode lead bodies 24 and 25. Next, the electrolyte is injected into the battery can, and after the electrolyte has sufficiently penetrated into the separator 10 or the like, the positive electrode lid 27 is sealed to the periphery of the opening of the battery can via the gasket 26, and precharging and aging are performed. Type non-aqueous electrolyte battery.

As the electrolytic solution, an electrolytic solution in which a lithium salt is used as an electrolytic solution and is dissolved in an organic solvent is used. The organic solvent is not particularly limited. For example, propylene carbonate, ethylene carbonate, butylene carbonate, γ-butyrolactone, γ-valerolactone, esters such as dimethyl carbonate, methyl propionate or butyl acetate, and nitriles such as acetonitrile. 1,2-dimethoxyethane, 1,2-dimethoxymethane, dimethoxypropane, 1,3-dioxolane, ethers such as tetrahydrofuran, 2-methyltetrahydrofuran or 4-methyl-1,3-dioxolane, or sulfolane These may be used alone or in combination of two or more.
Among them, an electrolyte obtained by dissolving lithium hexafluorophosphate (LiPF ₆₎ at a rate of 1.4 mol / L in a solvent obtained by mixing 2 parts by mass of methyl ethyl carbonate relative to ethylene carbonate 1 part by weight is preferred.

As the negative electrode, an alkali metal or a compound containing an alkali metal integrated with a current collecting material such as a stainless steel net is used. Examples of the alkali metal include lithium, sodium, and potassium. Examples of the compound containing an alkali metal include an alloy of an alkali metal and aluminum, lead, indium, potassium, cadmium, tin or magnesium, a compound of an alkali metal and a carbon material, a low potential alkali metal and a metal oxide, and the like. Or a compound with a sulfide or the like.
When a carbon material is used for the negative electrode, the carbon material may be any material that can be doped and dedoped with lithium ions, such as graphite, pyrolytic carbons, cokes, glassy carbons, a fired body of an organic polymer compound, Mesocarbon microbeads, carbon fibers, activated carbon and the like can be used.

As a negative electrode, a carbon material having an average particle size of 10 μm is mixed with a solution in which vinylidene fluoride is dissolved in N-methylpyrrolidone to form a slurry, and this negative electrode mixture slurry is passed through a 70-mesh net to remove large particles. After that, uniformly apply to both sides of a negative electrode current collector made of a strip-shaped copper foil having a thickness of 18 μm and dry, and then compression-mold with a roll press machine and cut into a strip-shaped negative electrode plate. Used.
As the positive electrode, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, manganese dioxide, metal oxide such as vanadium pentoxide or chromium oxide, metal sulfide such as molybdenum disulfide, etc. are used as active materials. , These positive electrode active materials are combined with conductive additives and binders such as polytetrafluoroethylene as appropriate, and finished with a current collector material such as a stainless steel mesh as a core material. It is done.
The positive electrode uses a positive electrode plate of the strip which is produced as follows. In other words, lithium graphite oxide (LiCoO ₂ ) was mixed with phosphorous graphite as a conductive additive at a mass ratio of 90: 5, and this mixture was mixed with a solution in which polyvinylidene fluoride was dissolved in N-methylpyrrolidone. To make a slurry. The positive electrode mixture slurry is passed through a 70 mesh net to remove large particles, and then uniformly applied to both sides of a positive electrode current collector made of an aluminum foil having a thickness of 20 μm and dried. After compression molding, it is cut into a strip-like positive electrode plate.

FIG. 3 shows the manufacturing method of the first embodiment of the present invention . The difference from the reference first embodiment shown in FIG. 1 is that the B layer 3-1 of the adhesive layer is formed on both outer surfaces of the A layer 2 of the intermediate layer, 3-2 is laminated, but the release layer is not provided on the outer surface of the B layer.
In this case, the release layer is not provided on the surface of the B layers 3-1 and 3-2 of the adhesive layer, but the adhesive layers are laminated on both outer surfaces of the intermediate layer and are in close contact with each other without causing air accumulation. Thus, the adhesive layer serves as a lid for the intermediate layer.
After laminating the A layer 2 of the intermediate layer and the B layers 3-1 and 3-2 of the adhesive layers on both outer surfaces, the laminate is impregnated with a fluid in a supercritical state or a subcritical state, as in the first embodiment. Then, the fluid is vaporized by releasing from the state, and micropores are formed in the A layer 2 of the intermediate layer.
Then, after extending | stretching and making a micropore communicate, B layer 3-1, 3-2 of the contact bonding layer of a both-sides outer layer is peeled.
In a state where the B layer of the adhesive layer is peeled off, the porous body can be manufactured in which the micropores are opened on the surface of the first embodiment and communicated with the internal micropores.
Even if the B layers 3-1 and 3-2 are not peeled off, micro-holes are also formed on the surfaces of the B layers 3-1 and 3-2, so that they open to the surface and communicate in the thickness direction. It can be set as the porous body in which the micropore to do exists.

Figure 4 (A) (B) ( C) shows the reference implementation form, not by laminating adhesive layer and a release layer on both sides of the A layer 2.
That is, as shown in FIG. 4A, the A layer 2 is impregnated with a fluid in a supercritical state or a subcritical state as in the first and second embodiments, and then released from the state. The fluid is vaporized. In this state, as shown in FIG. 4B, the A layer 2 is formed with a mixture of independent micro holes 2a and communication micro holes 2b in which adjacent micro holes communicate with each other. In addition, the non- porous skin layer 2 c remains on the outer surfaces on both sides of the A layer 2.
In this state, by performing the stretching process, the independent microholes 2a and the connected microholes 2b are further communicated, and the microholes 2a and 2b communicated in a three-dimensional network form shown in FIG. 4C. Holes can be formed. In FIG. 4C, the hatched portion indicates the resin portion, and the blank portion indicates the minute hole.

It will be described below Reference Example of a multi-hole body.
Example, the porous body (porous film) was produced by the method of Reference first embodiment. In addition, the structure of the porous body of the reference example without the peeling layer and the adhesive layer manufactured by the method of the first embodiment and the porous body without the adhesive layer manufactured by the method of the first embodiment of the present invention is equivalent. It is.

( Reference Example 1)
As a thermoplastic resin composition constituting the A layer of the intermediate layer, a thermoplastic elastomer in which ethylene propylene rubber is contained in polypropylene (“Zelas 5013” manufactured by Mitsubishi Chemical Corporation),
Adhesive resin [manufactured by Mitsui Chemicals, Admer QF551] as the resin composition constituting the B layer of the adhesive layer,
A polyester resin (polyethylene terephthalate resin, “Easter PETG6763” manufactured by Eastman Chemical) was prepared as a thermoplastic resin composition constituting the C layer of the release layer.

Using these resins, using a T-die for multilayer molding while adjusting the layer ratio to be C layer / B layer / A layer / B layer / C layer = 25/5/40/5/25 Molding was performed at a temperature of 200 ° C. to obtain a laminate of three types and five layers.
The obtained laminate was charged into a pressure vessel, and carbon dioxide as an inert gas was sealed in the pressure vessel at room temperature. Next, the pressure was increased to 15 MPa to bring carbon dioxide into a subcritical state or supercritical state, and this state was maintained for 1 hour, and the laminate was impregnated with carbon dioxide in the subcritical state or supercritical state. Thereafter, the pressure vessel valve was fully opened to release the pressure in the vessel.
The resulting laminate is stretched with a stretcher at a stretching temperature of 70 ° C. at a stretching ratio of 2.5 times in the longitudinal direction (longitudinal direction) and 2 times in the transverse direction, and then heat set at 125 ° C. It was.
Then, B layer and C layer were peeled and the porous film of Example 1 was obtained.

( Reference Examples 2 to 6)
A porous film was obtained in the same manner as in Reference Example 1, except that the resin used, the layer ratio, the fluid impregnation conditions, and the stretching conditions were changed as shown in Table 1.

The detail of the component described in the table | surface is shown below.
“Zelas 5013”; a polymerization type polypropylene resin composition containing ethylene-propylene rubber in a polypropylene homopolymer (“Zelas 5013” manufactured by Mitsubishi Chemical Corporation, density 0.88 g / cm ³ , melt flow rate 0.8 g / 10 minutes)
“Zelas 7023”; a polymerization type polypropylene resin composition containing ethylene-propylene rubber in a polypropylene homopolymer (“Zelas 7023” manufactured by Mitsubishi Chemical Corporation, density 0.88 g / cm ³ , melt flow rate 0.8 g / 10 minutes)
“F104A”: polypropylene homopolymer (“F104A” manufactured by Sumitomo Mitsui Polyolefin Co., Ltd., density 0.9 g / cm ³ , melt flow rate 3.2 g / 10 min))
“T310V”; ethylene-propylene rubber (“T310V” manufactured by Idemitsu Kosan Co., Ltd., density 0.88 g / cm ³ )
“PETG”; polyester resin (Easterman Chemical “Easter PETG6763”)
"EG8200"; olefinic thermoplastic elastomer (specifically, a copolymer of ethylene and 1-octene) ("Engage 8200" manufactured by Dow Chemical)
“8630P”; hydrogenated styrene-butadiene elastomer (“Dynalon 1320P” manufactured by JSR Corporation)
“QF551”; modified polyolefin resin (“Admer QF551” manufactured by Mitsui Chemicals, Inc.),
"Novamid"; nylon resin ("Novamid 1022" manufactured by Mitsubishi Engineering Plastics Co., Ltd.)
“EVAL”; ethylene-vinyl alcohol copolymer (“EVAL SP292” manufactured by Kuraray Co., Ltd., density: 1.13 g / cm ³ , melt flow rate: 2.2 g / 10 minutes)

(Comparative Example 1)
In Comparative Example 1, a porous film was prepared by the method described in Example 1 of JP-A-5-25305 of Patent Document 1.
That is, 20% by mass of ultra high molecular weight polyethylene (UHMWPE) having a weight average molecular weight of 2.0 × 10 ⁶ , 66.7% by mass of high density polyethylene (HDPE) having a weight average molecular weight of 3.9 × 10 ⁵ , 15 parts by mass of a raw material resin mixed with 13.3% by mass of low density polyethylene (LDPE) 2.0 g / 10 min of an index (190 ° C., 2.16 kg load) and 85 parts by mass of liquid paraffin (64 cst / 40 ° C.) Were mixed to prepare a polyethylene composition solution.
Next, 100 parts by mass of this polyethylene composition solution was added 0.125 parts by mass of 2,5-di-t-butyl-p-cresol (“BHT”, manufactured by Sumitomo Chemical Co., Ltd.) and tetrakis [methylene -3- (3,5-di-t-butyl-4-hydroxylphenyl) -propionate] methane ("Irganox 1010", Ciba Geigy) 0.25 part by mass was added as an antioxidant. This mixed solution was filled in an autoclave equipped with a stirrer and stirred at 200 ° C. for 90 minutes to obtain a uniform solution. This solution was extruded from a T die by an extruder having a diameter of 45 mm, and a gel-like sheet was formed while being taken up by a cooling roll.
The obtained sheet was set in a biaxial stretching machine, and simultaneous biaxial stretching was performed 5 × 5 times at a temperature of 115 ° C. and a stretching speed of 0.5 m / min. The obtained stretched membrane was washed with methylene chloride to extract and remove the remaining liquid paraffin, and then heat-set at 100 ° C. for 30 seconds to obtain a polyethylene microporous membrane.

(Comparative Example 2)
In Comparative Example 2, a porous film was prepared by the method described in Example 1 of JP-A-2004-95550 of Patent Document 3.
High density polyethylene (“HI-ZEX7000FP” manufactured by Prime Polymer Co., Ltd., density: 0.956 g / cm ³ , melt flow rate: 0.04 g / 10 min) 100 parts by mass, soft polypropylene (“PER R110E manufactured by Idemitsu Petrochemical Co., Ltd.) 15.6 parts by mass, hardened castor oil (“HY-CASTOR OIL” manufactured by Toyokuni Oil Co., Ltd., molecular weight 938), 9.4 parts by mass, barium sulfate (“B-55”, Sakai Chemical Co., Ltd.) 187.5 parts by mass Were blended and compounded. Next, inflation molding was performed at a temperature of 210 ° C. using the obtained compound to obtain a raw sheet.
Next, the obtained raw fabric sheet was sequentially stretched at 70 ° C. in the longitudinal direction (MD) of the sheet at 1.23 times, and then at 11.5 ° C. in the transverse direction (TD) at 2.86 times to obtain a porous film. It was.

The following physical properties of the porous films obtained in the reference examples and comparative examples were measured.

(Measurement 1; thickness)
With a 1/1000 mm dial gauge, five in-plane measurements were made unspecified, and the average was taken as the thickness.
(Measurement 2: Air permeability (Gurley value))
The air permeability (second / 100 ml) was measured according to JIS P 8117.
(Measurement 3: Porosity)
The porosity is a numerical value indicating the proportion of the space portion in the porous body. The porosity is calculated by measuring the substantial amount W1 of the porous body, calculating the mass W0 when the porosity is 0% from the density and thickness of the resin composition, and calculating the following from the difference from the substantial amount of the porous body: The porosity is calculated based on the formula.
Porosity Pv (%) = {(W0−W1) / W0} × 100
(Measurement 4; basis weight)
The basis weight is a numerical value representing the mass per unit area. The measuring method cuts a porous body into 10 cm square, and measures the mass. Since the dependence on the thickness is large, this time was converted to a thickness per 25 μm, this operation was repeated three times, and the average was defined as the basis weight.

The results of the above measurements are shown in the following table.

From Reference Examples 1 to 6, a sub-critical or supercritical fluid can be used to produce a porous film having properties comparable to those of the conventional porous film represented by Comparative Example 1, and the production method of the present invention. As in the invention described in Comparative Example 1, it was found that an organic solvent such as methylene chloride is not required in the production process, and the burden on the environment can be greatly reduced.
In the porous film of Comparative Example 2, since the filler is present in all layers, the basis weight becomes as heavy as 33 g / m ^2. However, in the porous films of Reference Examples 1 to 6, the basis weight is 10 to 12 g. It was found that the weight could be reduced as small as / m ² .

Porous materials produced by the production method of the present invention include battery separators, sanitary products such as diapers, packaging materials, agricultural and livestock products, building products, medical products, separation membranes, light diffusion plates, reflective sheets, etc. It can be suitably used.

DESCRIPTION OF SYMBOLS 1 Laminated body 2 A layer 3-1, 3-2 of an intermediate | middle layer B layer 4-1, 4-2 of an adhesive layer C layer 10 of a peeling layer Separator 11 Porous body 20 Nonaqueous electrolyte battery 21 Positive electrode plate 22 Negative electrode plate

Claims (3)

A method for producing a porous body having a large number of micropores that open to the surface and have communication in the thickness direction,
Producing a laminate having at least a three-layer structure in which at least one intermediate layer made of a thermoplastic resin composition and an adhesive layer made of a resin composition containing an adhesive resin are laminated on both sides of the intermediate layer;
The obtained laminate is impregnated with a fluid in a supercritical state or subcritical state, and then released from the supercritical state or subcritical state to vaporize the fluid, whereby independent micropores and communicating micropores are obtained. Forming a micropore with a mixture of pores,
After the porosification step for forming the micropores, at least uniaxially stretching, and a stretching step for further communicating the micropores ;
The manufacturing method of the porous body including the process of peeling the said contact bonding layer after the said extending process . The method for producing a porous body according to claim 1, wherein the thermoplastic resin composition of the intermediate layer comprises a hard segment containing at least a polypropylene resin and a thermoplastic resin composition having a soft segment.   The method for producing a porous body according to claim 1 or 2, wherein the fluid impregnated in the supercritical state or subcritical state is carbon dioxide or nitrogen.

Images