JP2012111205A - Separator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator having a polylactic acid-based base material, in which a separator material is not melted or deformed even at temperatures exceeding 100°C and furthermore, during production and machining of the separator, there is no breakage or tearing when rolled in a roll or the like.SOLUTION: The base material of the separator comprises a polylactic acid-based film or sheet, where the separator base material contains polylactic acid (A) and 1-20 parts weight of a core shell-structured polymer (B) that has a graft layer on the outside of granular rubber, based on 100 parts weight of the polylactic acid (A), and which has ≥10 J/g melting endothermic value ΔHc' in a crystallized section thereof when the film or sheet is formed, the melting endothermic value being calculated by using formula (1): ΔHc'=ΔHm-ΔHc (wherein ΔHc is the exothermic value (J/g) associated with crystallization in the heating process of the film or sheet after film-forming and measured by using a DSC; and ΔHm is the endothermic value (J/g) associated with the melting thereafter).

Description

  The present invention relates to a separator, and more particularly, to a separator (release liner) based on a polylactic acid film or sheet that has excellent heat resistance and does not break or tear during production or processing. This separator is used for protecting the pressure-sensitive adhesive layer surface such as a pressure-sensitive adhesive tape, a pressure-sensitive adhesive sheet, and a label.

  Polylactic acid is a plant-derived biomass polymer and has attracted attention as a resin that replaces petroleum-derived polymers. However, polylactic acid has a slow crystallization rate and is hardly crystallized by ordinary film forming means. For this reason, a film made of a resin composition containing polylactic acid has a problem in that the film shape cannot be maintained due to thermal deformation at 60 ° C. or higher, which is the glass transition temperature of polylactic acid. Therefore, several methods have been proposed in the past in order to improve the heat resistance of the polylactic acid resin film.

  For example, a method of increasing the heat resistance of a polylactic acid-based resin film by forming a resin composition containing polylactic acid into a film by melt extrusion and then stretching and crystallizing by biaxial stretching is known. However, this method has an internal residual stress at the time of stretching, so that there is a disadvantage that the heat shrinkage becomes very large when the use temperature becomes high. Therefore, the temperature that can actually be used is at most about 100 ° C.

  Japanese Patent Application Laid-Open No. 11-116788 (Patent Document 1) proposes a method for improving heat resistance by blending a high melting point material with polylactic acid. However, in this method, the plant-derived component ratio (biomass degree) decreases.

  Japanese Patent Application Laid-Open No. 2010-106272 (Patent Document 2) discloses that a resin composition containing polylactic acid is heated from the crystallization temperature (Tc) + 15 ° C. during the temperature lowering process of the resin composition. The melting temperature in the process (Tm) −5 ° C. or after forming a melt film of a resin composition containing polylactic acid, the crystallization temperature in the process of lowering the temperature of the resin composition ( Tc) A method for producing a polylactic acid-based resin film or sheet characterized by cooling and solidifying after a step of promoting crystallization at a temperature of ± 10 ° C. is disclosed. However, although the polylactic acid-based resin film or sheet thus obtained has improved heat resistance, the film or sheet may be broken or torn at the time of production, processing, or winding into a roll. . Therefore, when such a film or sheet is used as a base material for a separator (release liner), the separator may be broken or torn during manufacturing or processing of the separator.

JP-A-11-116788 JP 2010-106272 A

  Therefore, the object of the present invention is that the base material is not melted or deformed even at a high temperature exceeding 100 ° C., and further, when the separator is manufactured or processed, when it is wound into a roll shape, it does not break or tear. Another object of the present invention is to provide a separator based on a polylactic acid film or sheet.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors set the melting endotherm at the time of film formation of the polylactic acid resin film or sheet used as the separator substrate to a specific value or more, and a specific value. The inventors have found that the above-mentioned problems can be solved by containing components, and have completed the present invention.

That is, the present invention is a separator having a release agent treatment layer on at least one surface of a separator base material, the separator base material containing polylactic acid (A), and 100 parts by weight of the polylactic acid (A) 1 to 20 parts by weight of the core-shell structure polymer (B) having a graft layer outside the particulate rubber, and the following formula (1)
ΔHc ′ = ΔHm−ΔHc (1)
[In the formula, ΔHc is a calorific value (J / g) accompanying crystallization in the temperature rising process of a film or sheet after film formation, as measured by DSC, and ΔHm is an absorption due to subsequent melting. The amount of heat (J / g)]
The separator is characterized by being composed of a polylactic acid film or sheet having a melting endothermic amount ΔHc ′ of 10 J / g or more at the time of film formation, which is obtained in (1).

  The polylactic acid film or sheet constituting the separator substrate may further contain 0.5 to 15 parts by weight of the fluoropolymer (C) with respect to 100 parts by weight of the polylactic acid (A). The fluoropolymer (C) may be a tetrafluoroethylene polymer.

  The polylactic acid film or sheet constituting the separator substrate may further contain 0.1 to 15 parts by weight of the crystallization accelerator (D) with respect to 100 parts by weight of the polylactic acid (A).

  The polylactic acid film or sheet constituting the separator substrate is further modified with an acidic functional group having an acid value of 10 to 70 mgKOH / g and a weight average molecular weight of 10,000 to 80,000 with respect to 100 parts by weight of polylactic acid (A). The olefin polymer (E) may be contained in an amount of 0.1 to 10 parts by weight.

  The polylactic acid film or sheet constituting the separator substrate may be a film or sheet formed by a melt film formation method, for example, a calendar method.

  The separator of the present invention has no melting or deformation of the base material even at a high temperature exceeding 100 ° C., and maintains the original rigidity of the base material while being rolled into a roll at the time of manufacturing or processing the separator. For example, even if tension is applied, it has a characteristic that it does not break or tear.

It is a schematic diagram which shows an example of the calendering machine used when manufacturing the base material (polylactic acid-type film or sheet) of the separator of this invention. It is a schematic diagram which shows an example of the polishing film-forming machine used when manufacturing the base material (polylactic acid-type film or sheet) of the separator of this invention.

[Separator substrate]
The polylactic acid film or sheet used as the base material (separator base material) of the separator of the present invention is a resin film or sheet containing polylactic acid (A). Since lactic acid, which is a raw material monomer for polylactic acid, has an asymmetric carbon atom, there are L and D isomers of optical isomers. The polylactic acid (A) used in the present invention is a polymer mainly composed of L-form lactic acid. The smaller the content of lactic acid in the D-form that is mixed as an impurity during production, the higher the crystallinity and the higher melting point of the polymer. Therefore, it is preferable to use the L-form purity as high as possible, and the L-form purity is 95%. It is more preferable to use the above. Moreover, polylactic acid (A) may contain other copolymerization components other than lactic acid.

  Examples of the other copolymer components include ethylene glycol, propylene glycol, 1,3-propanediol, butanediol, pentanediol, neopentylglycol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, 1 , 4-cyclohexanedimethanol, glycerin, pentaerythritol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, bisphenol A and other polyol compounds; oxalic acid, malonic acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, dodecanedione Acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, bis (p-carboxyphenyl) methane, anthracene Polycarboxylic acids such as carboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 5-sodium sulfoisophthalic acid, 5-tetrabutylphosphonium isophthalic acid; glycolic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid And hydroxycarboxylic acids such as hydroxybenzoic acid; lactones such as propiolactone, valerolactone, caprolactone, undecalactone, and 1,5-oxepan-2-one. These copolymerization components are preferably 0 to 30 mol%, more preferably 0 to 10 mol%, based on all monomer components constituting the polylactic acid (A).

  The weight average molecular weight of polylactic acid (A) is, for example, 10,000 to 400,000, preferably 50,000 to 300,000, and more preferably 80,000 to 150,000. Moreover, the melt flow rate [JIS K-7210 (test condition 4)] of polylactic acid (A) at 190 ° C. and a load of 21.2 N is, for example, 0.1 to 50 g / 10 minutes, preferably 0.2 to 20 g. / 10 minutes, more preferably 0.5 to 10 g / 10 minutes, and particularly preferably 1 to 7 g / 10 minutes. If the melt flow rate is too high, the mechanical properties and heat resistance of the film or sheet obtained by film formation may be inferior. On the other hand, if the value of the melt flow rate is too low, the load during film formation may become too high.

In the present invention, “weight average molecular weight” refers to that measured by gel permeation chromatography (GPC) (in terms of polystyrene). The measurement conditions of GPC are as follows.
Column: TSKgel SuperHZM-H / HZ2000 / HZ1000
Column size: 4.6 mm I.D. D. × 150mm
Eluent: Chloroform Flow rate: 0.3 ml / min
Detector: RI
Column temperature: 40 ° C
Injection volume: 10 μl

  The production method of polylactic acid is not particularly limited, but typical production methods include lactide method and direct polymerization method. In the lactide method, lactic acid is heated and dehydrated and condensed to give low molecular weight polylactic acid, which is then thermally decomposed under reduced pressure to obtain lactide, which is a cyclic dimer of lactic acid, and this lactide is converted into tin (II) octanoate or the like. In this method, high molecular weight polylactic acid is obtained by ring-opening polymerization in the presence of a metal salt catalyst. The direct polymerization method is a method in which polylactic acid is directly obtained by heating lactic acid in a solvent such as diphenyl ether under reduced pressure and polymerizing it while removing water in order to suppress hydrolysis.

  A commercially available product can be used as the polylactic acid (A). Commercially available products include, for example, trade names “LAISIA H-400”, “LAISIA H-100” (manufactured by Mitsui Chemicals, Inc.), trade names “TERRAMAC TP-4000”, “TERRAMAC TE-4000” (and above, Unitika Corporation). Manufactured) and the like. Of course, as polylactic acid (A), you may use what was manufactured by the well-known thru | or usual polymerization method (for example, emulsion polymerization method, solution polymerization method, etc.).

  The content of polylactic acid (A) in the polylactic acid film or sheet is usually 60% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, particularly preferably, from the viewpoint of increasing the degree of biomass. Is 85% by weight or more. Moreover, the upper limit of content of the said polylactic acid (A) is 97 weight%, for example, Preferably it is 95 weight%, More preferably, it is 93 weight%. Here, the biomass degree is the ratio of the dry weight of the used biomass to the dry weight of the film or sheet. Biomass is a renewable, organic organic resource that excludes fossil resources.

In the present invention, the polylactic acid film or sheet constituting the separator substrate is represented by the following formula (1).
ΔHc ′ = ΔHm−ΔHc (1)
[In the formula, ΔHc is a calorific value (J / g) accompanying crystallization in the temperature rising process of a film or sheet after film formation, as measured by DSC, and ΔHm is an absorption due to subsequent melting. The amount of heat (J / g)]
The melting endothermic amount ΔHc ′ of the crystallized portion at the time of film formation determined in the above is 10 J / g or more.

  ΔHc is the amount of heat generated by crystallization in the temperature raising process in the region where the film or sheet could not be crystallized during film formation, and ΔHm was generated in the crystallization part during film formation and in the temperature raising process. This is the amount of heat absorbed when the crystallization part melts. These values are measured in DSC (Differential Scanning Calorimetry) as the crystal exothermic peak area (calorie) and the melting endothermic peak area (calorie). ΔHc ′ is a value obtained by subtracting ΔHc from ΔHm, and corresponds to the melting endotherm of the crystallized portion generated during film formation. Therefore, ΔHc ′ is an index of the crystallinity of the polylactic acid film or sheet, and thus the heat resistance.

  A polylactic acid film or sheet having ΔHc ′ of 10 J / g or more is excellent in heat resistance, and the film or sheet does not melt or deform even at a high temperature exceeding 100 ° C. (for example, a temperature of 120 ° C. or higher). Therefore, processing at a high temperature is possible. ΔHc ′ is preferably 12 J / g or more, more preferably 14 J / g or more, and particularly preferably 15 J / g or more. The value of ΔHc ′ is preferably as high as possible from the viewpoint of heat resistance. However, if the value of ΔHc ′ is too high, the film or sheet becomes hard and the tear resistance may be lowered. Therefore, ΔHc ′ is preferably 40 J / g or less, more preferably 35 J / g or less, and particularly preferably 30 J / g or less.

  In the present invention, the fluorine-based polymer (C) may be used for the polylactic acid film or sheet constituting the separator substrate. The fluorine-based polymer (C) is used, for example, as a melt tension adjusting agent or a crystallization accelerator. Examples of the fluorine-based polymer (C) include tetrafluoroethylene-based polymers, polychlorotrifluoroethylene, polyvinylidene fluoride, and polyvinyl fluoride. The fluorine-based polymer (C) can be used alone or in combination of two or more. As the fluoropolymer (C), a tetrafluoroethylene polymer (C ′) can be particularly preferably used.

  The tetrafluoroethylene-based polymer (C ′) may be a tetrafluoroethylene homopolymer or a copolymer of tetrafluoroethylene and another monomer. Examples of the tetrafluoroethylene-based polymer (C ′) include polytetrafluoroethylene, perfluoroalkoxyalkane (copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether), and perfluoroethylene propene copolymer (tetrafluoroethylene and hexafluoro). Copolymer with propylene), ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-perfluorodioxole copolymer and the like. Among these, polytetrafluoroethylene is preferable. The tetrafluoroethylene-based polymer (C ′) can be used alone or in combination of two or more.

  The fluorine-based polymer (C) improves the melt tension of the polylactic acid (A) -containing resin composition, and enables, for example, orientation crystallization in a flow field during the melt film formation process, thereby allowing polylactic acid (A) Promotes crystallization. Further, when the fluoropolymer (C) is blended with the polylactic acid (A) -containing resin composition, the melt tension is improved and the melt viscosity is also increased. It is possible to prevent the occurrence of elongation and peeling failure when the formed resin composition leaves the roll. In particular, fluorine-based polymers such as tetrafluoroethylene-based polymer (C ′) also have a function as a crystal nucleating agent for polylactic acid (A), so that the temperature of the resin composition immediately after film formation is the crystallization temperature. By setting in the vicinity, crystallization of polylactic acid (A) can be further promoted. Thus, crystallization of polylactic acid (A) can be promoted by blending the fluoropolymer (C) [particularly tetrafluoroethylene polymer (C ′)], thereby increasing ΔHc ′ of the polylactic acid film or sheet. be able to.

  The function of the tetrafluoroethylene polymer (C ′) as a crystal nucleating agent for the polylactic acid (A) is considered to depend on the crystal structure of the tetrafluoroethylene polymer (C ′). As a result of wide-angle X-ray diffraction, the plane spacing of the polylactic acid crystal lattice was 4.8 angstroms, whereas that of the tetrafluoroethylene polymer (C ′) was 4.9 angstroms. From this, it is considered that the tetrafluoroethylene-based polymer (C ′) can act as a crystal nucleating agent for the polylactic acid (A) by having an epitaxy action. Here, the epitaxy action means that polylactic acid (A) grows on the surface of the tetrafluoroethylene polymer (C ′) and aligns with the crystal plane of the crystal surface of the tetrafluoroethylene polymer (C ′). This refers to the growth pattern in which lactic acid (A) is arranged.

  The surface spacing of the tetrafluoroethylene-based polymer (C ′) is governed by the crystal form of the tetrafluoroethylene portion even if it is a copolymer of tetrafluoroethylene and other monomers. Is the same. Accordingly, the amount of the other monomer component of the copolymer is not particularly limited as long as the crystal form of polytetrafluoroethylene can be maintained and the physical properties are not greatly changed. Usually, the tetrafluoroethylene polymer (C The ratio of the other monomer component in ′) is desirably 5% by weight or less.

  The tetrafluoroethylene polymer (C ′) may be obtained by any polymerization method, but is preferably obtained by emulsion polymerization. Since the tetrafluoroethylene polymer obtained by emulsion polymerization is easy to be fiberized, it becomes easier to form a network structure in polylactic acid (A), improving the melt tension of the resin composition containing polylactic acid (A) and melting. It is considered that it effectively acts to promote crystallization of polylactic acid (A) in a flow field during film formation.

  Further, in order to uniformly disperse the polylactic acid (A), the particles of the tetrafluoroethylene polymer (C ′) are compatible with the polylactic acid (A) such as a (meth) acrylic acid ester polymer. You may use what modified | denatured with the polymer with favorable property. Examples of such tetrafluoroethylene-based polymer (C ′) include acrylic-modified polytetrafluoroethylene.

  The weight average molecular weight of the fluorine-based polymer (C) [tetrafluoroethylene-based polymer (C ′) etc.] is not particularly limited, but is usually 1 million to 10 million, preferably 2 million to 8 million.

  Commercial products may be used as the fluorine-based polymer (C) [tetrafluoroethylene-based polymer (C ′) etc.]. For example, as a commercial product of polytetrafluoroethylene, trade names “Fluon CD-014”, “Fluon CD-1”, “Fluon CD-145” manufactured by Asahi Glass Co., Ltd. and the like can be mentioned. Examples of commercially available products of acrylic-modified polytetrafluoroethylene include Metabrene A series such as trade names “Metabrene A-3000” and “Metabrene A-3800” manufactured by Mitsubishi Rayon Co., Ltd.

  The content of the fluorine-based polymer (C) in the polylactic acid-based film or sheet [particularly, the content of the tetrafluoroethylene-based polymer (C ′)] is usually 0.5% relative to 100 parts by weight of the polylactic acid (A). From the viewpoints of obtaining 15 parts by weight, improving the melt tension and maintaining the degree of biomass, and obtaining a good surface state, it is preferably 0.7 to 10 parts by weight, and more preferably 1 to 5 parts by weight. When the content of the fluoropolymer (C) [particularly, the content of the tetrafluoroethylene polymer (C ′)] is less than 0.5 parts by weight, the effect of improving the melt tension is difficult to obtain, and exceeds 15 parts by weight. And the effect according to addition amount is not acquired, and the fall of a biomass degree becomes a problem.

  In the present invention, as a specific method for setting the ΔHc ′ of the polylactic acid type film or sheet to 10 J / g or more, for example, (1) a resin composition containing polylactic acid (A) is melt-formed by a calendar film forming method or the like. Examples include film formation using a film method, (2) film formation of a resin composition in which a polycrystallization is added to polylactic acid (A), and (3) combinations thereof. The melt film forming method will be described later.

  As the crystallization accelerator, those other than the fluorine-based polymer [for example, tetrafluoroethylene-based polymer (C ′), etc.] that can be used as the crystallization accelerator in the fluorine-based polymer (C) can be used. . Such a crystallization accelerator [may be referred to as crystallization accelerator (D)] is not particularly limited as long as an effect of promoting crystallization is recognized, but is a crystal lattice of polylactic acid (A). It is desirable to select a substance having a crystal structure having a face spacing close to the face spacing. This is because a substance having a crystal lattice spacing close to that of polylactic acid (A) is more effective as a crystal nucleating agent for polylactic acid (A). Examples of such a crystallization accelerator (D) include organic materials such as melamine polyphosphate, melamine cyanurate, zinc phenylphosphonate, calcium phenylphosphonate, magnesium phenylphosphonate, inorganic talc, clay. Etc. Of these, zinc phenylphosphonate is preferred because the face spacing is closest to the face spacing of polylactic acid (A), and a good crystallization promoting effect is obtained. The crystallization accelerator (C) can be used alone or in combination of two or more.

  A commercial item can be used as a crystallization promoter (D). For example, as a commercial product of zinc phenylphosphonate, a trade name “Eco Promote” manufactured by Nissan Chemical Co., Ltd. may be mentioned.

  The content of the crystallization accelerator (D) in the polylactic acid film or sheet is usually 0.1 to 15 parts by weight with respect to 100 parts by weight of the polylactic acid (A), and a better crystallization promotion effect and biomass degree. From the viewpoint of maintenance, it is preferably 0.3 to 10 parts by weight. When the content of the crystallization accelerator (D) is less than 0.1 parts by weight, the effect of promoting crystallization is difficult to obtain. When the content exceeds 15 parts by weight, the effect according to the amount added cannot be obtained. Decrease in biomass degree becomes a problem. When tetrafluoroethylene polymer (C ′) is used as the fluoropolymer (C) at a ratio of 0.5 to 15 parts by weight with respect to 100 parts by weight of polylactic acid (A), the crystallization accelerator (D) The content of is usually 0.1 to 5 parts by weight with respect to 100 parts by weight of polylactic acid (A), preferably 0.3 to 3 parts by weight from the viewpoint of better crystallization promoting effect and maintaining the degree of biomass. It is. In this case, if the content of the crystallization accelerator (D) is less than 0.1 parts by weight, the effect of promoting crystallization is difficult to obtain, and if it exceeds 5 parts by weight, the effect according to the amount added is obtained. In addition, a decrease in the degree of biomass becomes a problem.

  In the present invention, the polylactic acid film or sheet contains 1 to 20 parts by weight of the core-shell structure polymer (B) having a graft layer outside the particulate rubber with respect to 100 parts by weight of the polylactic acid (A). This is very important. When a polylactic acid film or sheet containing the core-shell structure polymer (B) having a graft layer outside the particulate rubber in the above range is used as the base material of the separator, When processing the separator, even if there is a step where tension is applied, no breakage or tearing occurs. Further, even when wound into a roll shape or subjected to a punching process or the like, no breakage or tearing occurs. The core-shell structure polymer (B) having a graft layer outside the particulate rubber can be used alone or in combination of two or more.

  In the core-shell structure polymer (B) having a graft layer outside the particulate rubber, examples of the particulate rubber constituting the core include acrylic rubber, butadiene rubber, and silicone / acrylic composite rubber. Can be mentioned. Examples of the polymer constituting the shell include styrene resins such as polystyrene and acrylic resins such as polymethyl methacrylate.

  The average particle diameter (aggregate of primary particles) of the core-shell structure polymer is, for example, 50 to 500 μm, preferably 100 to 250 μm. When this is blended with polylactic acid (A) and melt-kneaded, primary particles are dispersed. The average particle diameter of the primary particles is, for example, 0.1 to 0.6 μm.

  A commercial item can be used as said core-shell structure polymer. Examples of commercial products of the core-shell structure polymer include paraloid series (particularly, paraloid EXL series) such as trade name “Paraloid EXL2315” manufactured by Rohm and Haas Japan, and trade name “Metabrene” manufactured by Mitsubishi Rayon Co., Ltd. Metabrene S type such as “S-2001”, Metabrene W type such as “Metabrene W-450A”, Metabrene C type such as “Metabrene C-223A”, Metabrene E type such as “Metabrene E-901”, and the like.

  The content of the core-shell structure polymer (B) having a graft layer outside the particulate rubber in the polylactic acid-based film or sheet is effective in improving the tear resistance with respect to 100 parts by weight of the polylactic acid (A). From the viewpoint, it is 1 part by weight or more, preferably 1.5 parts by weight or more, more preferably 2 parts by weight or more. In addition, if the amount of the core-shell structure polymer (B) having a graft layer outside the particulate rubber is too large, the degree of crystallization and the crystallization rate are liable to be lowered, and the heat resistance is liable to be lowered. The core-shell structure polymer (B) having a graft layer outside the rubber-like rubber may bleed out. From this point of view, the content of the core-shell structure polymer (B) having a graft layer outside the particulate rubber in the polylactic acid film or sheet is 20 parts by weight with respect to 100 parts by weight of the polylactic acid (A). It is not more than parts by weight, more preferably not more than 15 parts by weight, still more preferably not more than 12 parts by weight, and particularly preferably not more than 10 parts by weight.

  By including the core-shell structure polymer (B) having a graft layer outside the particulate rubber in the above range in the polylactic acid film or sheet, the tear strength of the polylactic acid film or sheet is greatly improved. . For example, the tear strength of the polylactic acid film or sheet can be 2.5 N / mm or more in both the flow direction (MD direction) and the width direction (TD direction). The tear strength can be measured using a tear strength tester according to JIS P 8116 paper-tear strength test method-Elmendorf tear tester method. A polylactic acid film or sheet having a tear strength of 2.5 N / mm or more in both the flow direction (MD direction) and the width direction (TD direction) is not only rolled during the production of the film or sheet. Since no breakage or tearing occurs at the time of processing, etc., various processing becomes possible, and the range of use is dramatically expanded.

  The tear strength is preferably 2.8 N / mm or more, more preferably 3.2 N / mm or more in both the flow direction (MD direction) and the width direction (TD direction). The higher the tear strength, the better. Although it does not specifically limit as an upper limit of tear strength, For example, 30 N / mm or less may be sufficient, 20 N / mm or less may be sufficient, and it is 15 N / mm or less normally.

  In the present invention, the polylactic acid film or sheet may contain an acidic functional group-modified olefin polymer (E) in addition to the above components. Roll lubricity can be imparted by blending the acidic functional group-modified olefin polymer (E) with polylactic acid (A). For this reason, when a polylactic acid film or sheet is melted by a calender film forming machine or the like and formed into a film by passing through a gap between the metal rolls, the film or sheet is easily peeled off from the surface of the metal roll, and smooth. It can be formed into a film. The acidic functional group-modified olefin polymer (E) can be used alone or in combination of two or more.

  Examples of the acidic functional group of the acidic functional group-modified olefin polymer (E) include a carboxyl group or a derivative group thereof. A derivative group of a carboxyl group is chemically derived from a carboxyl group, and examples thereof include an acid anhydride group, an ester group, an amide group, an imide group, and a cyano group of carboxylic acid. Among these, a carboxylic anhydride group is preferable.

  The acidic functional group-modified olefin polymer (E) is abbreviated as, for example, an unsaturated compound containing the above “acidic functional group” (hereinafter referred to as “acidic functional group-containing unsaturated compound”) in an unmodified polyolefin polymer. In some cases).

  Examples of the unmodified polyolefin polymer include high density polyethylene, medium density polyethylene, low density polyethylene, polypropylene, polybutene, poly-4-methylpentene-1, a copolymer of ethylene and α-olefin, and propylene and α-olefin. Polyolefins such as copolymers or oligomers thereof; ethylene-propylene rubber, ethylene-propylene-diene copolymer rubber, butyl rubber, butadiene rubber, low crystalline ethylene-propylene copolymer, propylene-butene copolymer, Polyolefin such as ethylene-vinyl ester copolymer, ethylene-methyl (meth) acrylate copolymer, ethylene-ethyl (meth) acrylate copolymer, ethylene-maleic anhydride copolymer, blend of polypropylene and ethylene-propylene rubber Series Lastmers; and mixtures of two or more of these. Among these, preferred are polypropylene, a copolymer of propylene and α-olefin, low density polyethylene and oligomers thereof, and particularly preferred is a copolymer of polypropylene, propylene and α-olefin and oligomers thereof. It is. Examples of the “oligomers” include those obtained from a corresponding polymer by a molecular weight degradation method by thermal decomposition. Oligomers can also be obtained by polymerization methods.

  Examples of the acidic functional group-containing unsaturated compound include a carboxyl group-containing unsaturated compound and a carboxyl group derivative-containing unsaturated compound. Examples of the carboxyl group-containing unsaturated compound include maleic acid, itaconic acid, chloroitaconic acid, chloromaleic acid, citraconic acid, and (meth) acrylic acid. Examples of the carboxyl group derivative-containing unsaturated compound include, for example, maleic anhydride, itaconic anhydride, chloroitaconic anhydride, chloromaleic anhydride, citraconic anhydride and other carboxylic anhydride group-containing unsaturated compounds; (Meth) acrylate, glycidyl (meth) acrylate, (meth) acrylic acid ester such as 2-hydroxyethyl (meth) acrylate; (meth) acrylamide, maleimide, (meth) acrylonitrile and the like. Among these, a carboxyl group-containing unsaturated compound and a carboxylic acid anhydride group-containing unsaturated compound are preferable, an acid anhydride group-containing unsaturated compound is more preferable, and maleic anhydride is particularly preferable.

  It is important that the weight average molecular weight of the acidic functional group-modified olefin polymer (E) is 10000 to 80000, preferably 15000 to 70000, more preferably 20000 to 60000. If this weight average molecular weight is less than 10,000, it tends to cause bleed-out after film or sheet molding, and if it exceeds 80000, it may separate from polylactic acid (A) during roll kneading. Here, bleed-out refers to a phenomenon in which a low molecular weight component appears on the film or sheet surface over time after the film or sheet is formed.

  The acidic functional group in the acidic functional group-modified olefin polymer (E) may be bonded to any position of the olefin polymer, and the modification ratio is not particularly limited, but the acidic functional group-modified olefin polymer (E). The acid value of is usually 10 to 70 mgKOH / g, preferably 20 to 60 mgKOH / g. If the acid value is less than 10 mgKOH / g, the effect of improving roll lubricity cannot be obtained, and if it exceeds 70 mgKOH / g, it tends to cause plate-out to the roll. Here, the plate-out to the roll means that when the resin composition is melt-formed using a metal roll, the components blended in the resin composition or the oxidized, decomposed, combined, or deteriorated product is a metal. Attaching or depositing on the surface of a roll. In addition, in this invention, an "acid value" means what is measured based on the neutralization titration method of JISK0070-1992.

  The acidic functional group-modified olefin polymer (E) is obtained by reacting an unmodified polyolefin polymer with an acidic functional group-containing unsaturated compound in the presence of an organic peroxide. As the organic peroxide, those generally used as an initiator in radical polymerization can be used. Such a reaction can be performed by either a solution method or a melting method. In the solution method, an acidic functional group-modified olefin polymer (E) is obtained by dissolving a mixture of an unmodified polyolefin polymer and an acidic functional group-containing unsaturated compound together with an organic peroxide in an organic solvent and heating. Can do. The reaction temperature is preferably about 110 to 170 ° C.

  In the melting method, an acidic functional group-modified olefin polymer (E) is obtained by mixing a mixture of an unmodified polyolefin polymer and an acidic functional group-containing unsaturated compound with an organic peroxide, and melt-mixing and reacting them. be able to. Melt mixing can be performed with various mixers such as an extruder, a plastic bender, a kneader, and a Banbury mixer, and the kneading temperature is usually in the temperature range of the melting point to 300 ° C. of the unmodified polyolefin polymer.

  The acidic functional group-modified olefin polymer (E) is preferably maleic anhydride-modified polypropylene. As the acidic functional group-modified olefin polymer (E), a commercially available product can be used. For example, trade name “Yumex 1010” (maleic anhydride group-modified polypropylene, acid value: 52 mgKOH / g, manufactured by Sanyo Chemical Industries, Ltd.) (Weight average molecular weight: 32000, modification ratio: 10% by weight), “Yumex 1001” (maleic anhydride group-modified polypropylene, acid value: 26 mg KOH / g, weight average molecular weight: 49000, modification ratio: 5% by weight), “Yumex 2000 (Maleic anhydride group-containing modified polyethylene, acid value: 30 mg KOH / g, weight average molecular weight: 20000, modification ratio: 5% by weight) and the like.

  The content of the acidic functional group-modified olefin polymer (E) in the polylactic acid film or sheet is not particularly limited, and is usually 0.1 to 10 parts by weight per 100 parts by weight of the polylactic acid (A). From the viewpoint of sustaining the roll slip effect without plate-out and maintaining the degree of biomass, the amount is preferably 0.1 to 5 parts by weight, particularly preferably 0.3 to 3 parts by weight. If the content of the acidic functional group-modified olefin polymer (E) is less than 0.1 parts by weight, the effect of improving roll lubricity is difficult to obtain, and if it exceeds 10 parts by weight, the effect according to the amount added cannot be obtained. In addition, a decrease in biomass degree becomes a problem.

  In this invention, the polylactic acid-type film or sheet | seat may contain various additives as needed in the range which does not impair the effect of this invention. Such additives include antioxidants, ultraviolet absorbers, plasticizers, stabilizers, mold release agents, antistatic agents, colorants (white pigments, etc.), anti-drip agents, flame retardants, hydrolysis inhibitors, A foaming agent, a filler, etc. are mentioned.

  In the present invention, the polylactic acid film or sheet constituting the separator substrate has a high degree of crystallization, and therefore has excellent solvent resistance. For example, the degree of swelling of the polylactic acid film or sheet is, for example, 2.5 or less, preferably 2.0 or less, with respect to any solvent of ethyl acetate and toluene. The degree of swelling was determined by immersing a film or sheet sample (50 mm × 50 mm × 0.05 mm thickness) in a solvent for 15 minutes, removing the solvent on the surface of the taken film or sheet sample with a waste cloth, and immersing the weight after immersion. Can be measured by dividing by previous weight.

Moreover, the polylactic acid-type film or sheet which comprises a separator base material in this invention can maintain a high level also about mechanical characteristics, such as rigidity, and an elastic characteristic. For example, the initial elastic modulus of the polylactic acid film or sheet in the present invention is usually 1000 MPa or more, preferably 1500 MPa or more in the flow direction (MD direction). The upper limit of the initial elastic modulus is generally about 3500 MPa (for example, about 3000 MPa) in the flow direction (MD direction). The breaking strength of the polylactic acid film or sheet in the present invention is usually 30 MPa or more, preferably 35 MPa or more in the flow direction (MD direction). The upper limit of the breaking strength is generally about 150 MPa (for example, about 120 MPa). Furthermore, the elongation of the polylactic acid film or sheet in the present invention is usually 2.5% or more, preferably 3.5% or more in the flow direction (MD direction). The upper limit of elongation is generally about 15% (for example, about 12%) in the flow direction (MD direction). The initial elastic modulus, breaking strength, and elongation were measured using a tensile tester according to the plastic-tensile property test method of JIS K 7161.
Apparatus: Tensile tester (Autograph AG-20kNG, manufactured by Shimadzu Corporation)
Sample size: thickness 0.05 mm x width 10 mm x length 100 mm (note that the direction parallel to the length direction is the flow direction (MD) during film formation)
Measurement condition:
Distance between chucks: 50mm
Tensile speed: 300 mm / min

  Although the thickness of the polylactic acid-type film or sheet which comprises a separator base material in this invention is not specifically limited, Usually, 10-500 micrometers, Preferably it is 20-400 micrometers, More preferably, it is 30-300 micrometers.

[Manufacture of separator substrate (polylactic acid film or sheet)]
A method for producing a polylactic acid film or sheet used as a separator substrate in the present invention is not particularly limited, but a method for forming a resin composition containing polylactic acid (A) by a melt film formation method. Is preferred. When the melt film formation method is employed, the melting endotherm ΔHc ′ of the crystallized portion during film formation can be easily set to 10 J / g or more.

  For example, a polylactic acid film or sheet is a polylactic acid in which each component is uniformly dispersed by a continuous melt kneader such as a twin screw extruder or a batch type melt kneader such as a pressure kneader, a Banbury mixer, or a roll kneader. (A) A containing resin composition is prepared, and this can be produced by film formation and cooling and solidification by an extrusion method such as a T-die method or an inflation method, a calendar method, a polishing method, or the like. The melt film formation method is preferably a technique in which a molten resin composition is formed into a desired thickness by passing through a gap between two metal rolls, and particularly preferably a calendar method. This is a polishing method.

  When the polylactic acid (A) -containing resin composition is formed by a melt film formation method, the temperature of the resin composition at the time of melt film formation (hereinafter referred to as the resin temperature at the time of melt film formation) is not particularly limited, The temperature is preferably between the crystallization temperature (Tc) + 15 ° C. in the temperature lowering process of the resin composition and the melting temperature (Tm) −5 ° C. in the temperature rising process. By setting to such temperature, crystallization of polylactic acid (A) is promoted, and the separator base material (film or sheet) in the present invention easily obtains heat resistance.

  For example, when the resin composition is melt-formed by a calendering method, the temperature of the resin composition at the time of calender roll rolling (corresponding to the resin temperature at the time of melt film-forming) is reduced in the temperature-decreasing process of the resin composition. Is set to a temperature between the crystallization temperature (Tc) + 15 ° C. and the melting temperature (Tm) −5 ° C. in the heating process. By rolling at a temperature below the melting point in this way, oriented crystallization is promoted. This effect of promoting orientation crystallization is markedly improved when the resin composition contains a tetrafluoroethylene-based polymer (C ′). The tetrafluoroethylene-based polymer (C ′) is considered to promote oriented crystallization by fibrillating and networking in the resin composition and synergistic effect of its effect as a crystal nucleating agent. Therefore, by rolling in the above temperature range, the separator base material (film or sheet) in the present invention can realize good heat resistance due to the orientation crystallization promoting effect as well as the smooth surface state.

  In producing a polylactic acid-based film or sheet, in order to make the crystallization promoting effect of the tetrafluoroethylene-based polymer (C ′) more effective, a step of suppressing the temperature condition after the melt film formation may be provided. Good. Specifically, the melt-formed resin composition is temporarily held from the temperature of crystallization temperature (Tc) -25 ° C. in the temperature-decreasing process of the resin composition to the crystallization temperature (Tc) + 10 ° C. And may be cooled and solidified after undergoing a step of promoting crystallization (hereinafter sometimes simply referred to as “crystallization promoting step”). In other words, the crystallization promoting step refers to the temperature of the resin composition in the process of lowering the temperature of the resin composition from the temperature of crystallization temperature (Tc) -25 ° C. to the crystallization temperature (Tc) + 10 ° C. This is a step of exposing to a temperature-controlled state, and a step of promoting crystallization of the resin composition while maintaining a smooth surface state after melt film formation. The temperature control method is not particularly limited, and examples thereof include a method in which the resin composition that has been melt-formed is brought into direct contact with a roll or belt that can be heated to a predetermined temperature.

  In particular, from the viewpoint of always controlling to a predetermined temperature, it is desirable to bring the resin composition formed into a melt into contact with a metal roll having a predetermined surface temperature. Therefore, it is desirable to make the polylactic acid (A) -containing resin composition easily peelable from the metal roll also in this step. From this viewpoint, the addition of the acidic functional group-modified olefin polymer (E) is desirable. preferable.

  The time for the crystallization promoting step is preferably as long as possible, and ultimately depends on the degree of crystallization of the resin composition, so it cannot be specified unconditionally, but usually 2 to 10 seconds, preferably 3 to 8 seconds. It is.

  In the crystallization promotion step, even if the crystallization temperature (Tc) in the temperature-decreasing process of the resin composition changes due to the addition of another crystal nucleating agent or the like, the measurement is performed in advance with a differential scanning calorimeter (DSC). By carrying out and grasping the maximum temperature of the exothermic peak accompanying the crystallization in the temperature lowering process, it is possible to always obtain the optimum temperature condition for the crystallization promoting step. At that time, the shape change of the film or sheet obtained by heating at the temperature hardly needs to be considered, but it is preferably a temperature at which the heat deformation rate of the obtained film or sheet is 40% or less. .

  The method for producing a polylactic acid film or sheet used as a separator substrate in the present invention is preferably a method comprising forming a polylactic acid (A) -containing resin composition by a melt film formation method. The temperature of the resin composition at the time of melt film formation (resin temperature at the time of melt film formation) is melted in the temperature rising process from the temperature of crystallization temperature (Tc) + 15 ° C. in the temperature lowering process of the resin composition. The resin composition that has a temperature (Tm) of −5 ° C. and / or is melt-deposited from the temperature of the crystallization temperature (Tc) of −25 ° C. The method is characterized by cooling and solidifying after a crystallization promoting step at a crystallization temperature (Tc) + 10 ° C.

  In the method for producing a polylactic acid film or sheet including the crystallization promotion step, the resin composition was cooled and solidified after the crystallization promotion step in the crystallization promotion step. It does not cause extreme heat shrinkage when using the film or sheet. Therefore, the highly crystallized film or sheet formed by the above production method can maintain the shape up to the vicinity of the melting point of polylactic acid, and can be sufficiently used even in applications requiring heat resistance that could not be used so far. . Furthermore, since the inefficient process of heating once again after cooling and solidification becomes unnecessary, the above manufacturing method can be said to be a very useful method in terms of economy and productivity. In addition, you may give a uniaxial or biaxial stretching process (preferably biaxial stretching process) before and / or after a crystallization promotion process. In some cases, the crystallization can be further improved by performing the stretching treatment. The extending | stretching process temperature is 60-100 degreeC, for example.

  As a method for producing a polylactic acid-based film or sheet including the crystallization promotion step, a method of continuously performing from the melt film formation step to the crystallization promotion step and the cooling and solidification step shortens the processing time. This is desirable. Examples of such a method include a method using a calendar film forming machine, a polishing film forming machine, and the like.

[Calendar film formation]
FIG. 1 shows a schematic diagram of an example of a calendar film forming machine used in such a manufacturing method. In the following, FIG. 1 will be described in detail.

  The resin composition in a molten state is rolled between four calender rolls of the first roll 1, the second roll 2, the third roll 3, and the fourth roll 4, and gradually thinned. It adjusts so that it may become desired thickness when passing between the roll 3 and the 4th roll 4. FIG. In the case of calendar film formation, the film formation of the resin composition in the first roll 1 to the fourth roll 4 corresponds to the “melt film formation process”. Further, the take-off roll 5 that is set from the temperature of crystallization temperature (Tc) -25 ° C. to the temperature of crystallization temperature (Tc) + 10 ° C. in the temperature lowering process of the resin composition, The roll group which contacts first is shown, is comprised of one or two or more (three in FIG. 1) roll groups, and plays the role of peeling the resin composition 8 in the molten state from the fourth roll 4. Thus, when the take-off roll 5 is composed of a plurality of rolls and the temperature of each roll can be adjusted, the temperature of each roll is preferably the same, but if within the desired temperature range, May be different. The larger the number of take-off rolls 5, the longer the isothermal crystallization time, which is advantageous for promoting crystallization. In the case of calendar film formation, the take-off roll 5 accelerates the crystallization of the resin composition 8 that has been melt-formed, and thus the process of passing the resin composition 8 through the take-off roll 5 is the “crystallization promotion process”. It corresponds to.

  The two cooling rolls 6 and 7 serve to cool and solidify the resin composition 8 by passing the resin composition 8 between them, and to mold the surface of the resin composition 8 into a desired shape. Therefore, one roll (for example, the cooling roll 6) is usually a metal roll, and the roll surface is designed to bring out the surface shape of the resin composition 8, and the other roll (for example, the cooling roll 7). ) Rubber rolls are used. In addition, the arrow in a figure shows the rotation direction of a roll. 9 is a bank (resin pool).

[Polishing film formation]
FIG. 2 shows a schematic diagram of an example of a polishing film forming machine used in such a manufacturing method. In the following, FIG. 2 will be described in detail.

  An extruder tip 10 of an extruder (not shown) is disposed between the heated second roll 2 and third roll 3, and the second roll 3 and third roll 3 are set at a preset extrusion speed. In the meantime, the molten resin composition 8 is continuously extruded. The extruded resin composition 8 is rolled and thinned between the second roll 2 and the third roll 3, and finally has a desired thickness when it passes between the third roll 3 and the fourth roll 4. It is adjusted to become. In the case of polishing film formation, film formation of the resin composition 8 on the second roll 4 to the fourth roll 4 corresponds to a “melt film formation process”. Thereafter, the resin composition 8 passes through three take-off rolls 5 set to a crystallization temperature (Tc) + 10 ° C. from a temperature of crystallization temperature (Tc) −25 ° C. in the temperature lowering process, and finally a cooling roll By passing through 6) and 7, a solidified film or sheet is produced. In the case of polishing film formation, the process of passing through the take-off roll 5 corresponds to the “crystallization promoting process”.

[Release agent treatment layer]
The separator of the present invention has a release agent treatment layer on at least one surface of the separator substrate.

  The release agent (release agent) used for forming the release agent treatment layer is not particularly limited, and examples thereof include silicone release agents, fluorine release agents, long-chain alkyl release agents, polyolefin release agents, and the like. Can be used. The release agents can be used alone or in combination of two or more.

  Further, the release agent is not particularly limited as long as it can form a film on the separator substrate, and the film exhibits an appropriate release property according to the application and does not adversely affect the adhesive. However, for example, from the viewpoint of exhibiting excellent peeling characteristics with respect to an adhesive surface such as an adhesive tape or a sheet, the peeling force on the adhesive surface is about 0 to 25 N / 50 mm (preferably about 0.1 to 10 N / 50 mm). That which can form the film which becomes) is preferable.

  Among the release agents, a silicone release agent is preferable from the viewpoint of release performance. Although it does not specifically limit as a silicone type release agent, The thermosetting addition type silicone type release agent (thermosetting addition type polysiloxane type release agent) is mentioned as the typical thing.

  The thermosetting addition-type silicone release agent essentially comprises a polyorganosiloxane containing an alkenyl group as a functional group in the molecule (alkenyl group-containing silicone) and a polyorganosiloxane containing a hydrosilyl group as a functional group in the molecule. Ingredients.

  As the polyorganosiloxane containing an alkenyl group as a functional group in the molecule, a polyorganosiloxane having two or more alkenyl groups in the molecule is preferable. Examples of the alkenyl group include a vinyl group (ethenyl group), an allyl group (2-propenyl group), a butenyl group, a pentenyl group, and a hexenyl group. The alkenyl group is usually bonded to a silicon atom (for example, a terminal silicon atom or a silicon atom inside the main chain) of the polyorganosiloxane forming the main chain or skeleton.

  Examples of the polyorganosiloxane forming the main chain or skeleton include polyalkylalkylsiloxanes (polydialkylsiloxanes) such as polydimethylsiloxane, polydiethylsiloxane, and polymethylethylsiloxane, and polyalkylarylsiloxanes. In addition, a copolymer [for example, poly (dimethylsiloxane-diethylsiloxane) or the like] in which a plurality of silicon atom-containing monomer components are used may be used. Of these, polydimethylsiloxane is preferred. That is, as the polyorganosiloxane containing an alkenyl group as a functional group in the molecule, specifically, polydimethylsiloxane having a vinyl group, hexenyl group or the like as a functional group is preferably exemplified.

  The polyorganosiloxane crosslinking agent containing a hydrosilyl group as a functional group in the molecule is a polyorgano having a hydrogen atom bonded to a silicon atom (particularly a silicon atom having a Si-H bond) in the molecule. Polyorganosiloxane which is siloxane and has 2 or more silicon atoms having Si—H bond in the molecule is particularly preferable. The silicon atom having the Si-H bond may be either a silicon atom in the main chain or a silicon atom in the side chain, that is, may be contained as a constituent unit of the main chain, or It may be contained as a constituent unit of the side chain. The number of silicon atoms in the Si—H bond is not particularly limited as long as it is 2 or more. Specific examples of the polyorganosiloxane crosslinking agent containing a hydrosilyl group as a functional group in the molecule are polymethylhydrogensiloxane and poly (dimethylsiloxane-methylhydrogensiloxane).

  In the release agent in the present invention, a reaction inhibitor may be used in order to impart storage stability at room temperature. For example, when a thermosetting addition type silicone release agent is used as the release agent, specifically, for example, 3,5-dimethyl-1-hexyn-3-ol, 3-methyl-1-pentene- 3-ol, 3-methyl-3-penten-1-in, 3,5-dimethyl-3-hexen-1-in and the like can be mentioned.

  Moreover, the peeling control agent etc. may be used for the peeling agent other than the said component as needed. For example, when a thermosetting addition type silicone release agent is used as the release agent, specifically, a release control agent such as MQ resin, a polyorganosiloxane having no alkenyl group or hydrosilyl group (trimethylsiloxy group terminal) Sealed polydimethylsiloxane and the like) may be added. The content of these components in the thermosetting addition-type silicone release agent is not particularly limited, but is preferably 1 to 30% by weight.

  Furthermore, various additives may be used for the release agent as necessary. Examples of the additive used as necessary include a filler, an antistatic agent, an antioxidant, an ultraviolet absorber, a plasticizer, and a colorant (dye, pigment, etc.).

  The release agent-treated layer can be formed by a known or conventional method. For example, the method etc. which apply | coat the release agent composition containing a release agent on a separator base material (when an intermediate layer exists on a separator base material) are mentioned. The coating can be performed by a coater, an extruder, a printing machine or the like generally used for forming a release treatment layer.

  The thickness of the release agent treatment layer can be appropriately selected depending on the application and the like, and is, for example, about 0.02 to 1 μm, preferably 0.05 to 0.7 μm, and more preferably about 0.1 to 0.5 μm. .

  The separator of the present invention may have another layer (intermediate layer) between the separator substrate and the release agent-treated layer as necessary.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. The present invention is not limited by these. In addition, evaluation in an Example etc. was performed as follows.

  The materials used in the examples are shown below.

<Polylactic acid (A)>
A1: Trade name “Terramac TP-4000” (manufactured by Unitika)
<Core-shell structure polymer (B) having graft layer outside particulate rubber>
B1: Core-shell structure polymer (acrylic rubber / polymethyl methacrylate-styrene core-shell structure polymer, trade name “Paraloid EXL2315”, manufactured by Rohm and Haas Japan)
<Fluoropolymer (C)>
C1: Acrylic-modified polytetrafluoroethylene (trade name “METABREN A-3000”, manufactured by Mitsubishi Rayon Co., Ltd.)
<Crystal Accelerator (D)>
D1: zinc phenylphosphonate (trade name “Eco Promote”, manufactured by Nissan Chemical Industries, Ltd.)
<Acid functional group-modified olefin polymer (E)>
E1: Maleic anhydride group-containing modified polypropylene (weight average molecular weight 32000, acid value 52 mg KOH / g, trade name “Yumex 1010”, manufactured by Sanyo Chemical Industries)

Example 1
A resin composition was prepared at the blending ratio shown in Table 1 below, melted and kneaded with a Banbury mixer, and then formed into a calendar film so as to have a thickness of 50 μm with an inverted L-shaped four calendar (melting process). Membrane process). Next, as shown in FIG. 1, immediately after the melt film formation step, three rolls (take-off rolls) that can be heated to an arbitrary temperature are arranged so that the melt-formed resin composition can pass alternately up and down. This promoted crystallization (crystallization promoting step). Thereafter, the resin composition was solidified by passing through a cooling roll to produce a film. The temperature of the resin composition in the melt film formation step (resin temperature at the time of melt film formation) was the surface temperature of the roll corresponding to the fourth roll 4 in FIG. Moreover, about the temperature of the resin composition in a crystallization promotion process, the surface temperature of the three take-off rolls 5 of FIG. 1 was made substantially the same, and the temperature was made into the crystallization promotion temperature. The film formation rate was 5 m / min, and the substantial crystallization promotion step time (take-off roll passage time) was about 5 seconds.

  On the other hand, 100 parts by weight of thermosetting addition silicone (trade name “KS-847T”), manufactured by Shin-Etsu Chemical Co., Ltd., 30 wt% toluene solution), platinum catalyst (trade name “PL-50T”, Shin-Etsu Chemical Co., Ltd.) Manufactured, toluene solution) 1 part by weight and 3000 parts by weight of heptane were added, mixed and dissolved to prepare a release agent composition. This release agent composition was applied onto the film (separator base material) obtained above and dried (after curing) so as to have a thickness of 0.2 μm, and dried by heating to obtain a separator.

Comparative Example 1
A resin composition was prepared at a blending ratio shown in Table 1 below, a film (base material) of Comparative Example 1 was produced by the same operation as in Example 1, and a separator was obtained in the same manner as in Example 1.

  Measurement of physical properties of the separator substrate and evaluation of the pressure-sensitive adhesive sheet were performed as follows.

[Measurement of physical properties of separator substrate]
<Melting temperature (° C)>
The temperature at the top of the endothermic peak that accompanies the melting in the re-heating process of the resin composition after film formation, measured by DSC (differential scanning thermal analyzer), is the melting temperature (Tm; also referred to as crystal melting peak temperature). It was.

<Crystallization temperature (℃)>
The temperature at the peak top of the exothermic peak accompanying the crystallization of the resin composition after film formation, measured by DSC, during the temperature lowering process from 200 ° C. was defined as the crystallization temperature (Tc; also referred to as crystallization peak temperature). .

<Film formation results>
(1) Plate out to roll: Evaluate the surface of the roll by visual inspection, and determine that there is no contamination on the surface of the roll as "O" (None) and that the surface of the roll is dirty as "X" (Yes). did.
(2) Peelability: Evaluated by the peelability of the melt-formed resin composition from the fourth roll 4 in FIG. 1, “○” (good) indicates that the take-off roll 5 can be taken off, and the take-off roll 5 The state where it was not possible to pick up was determined as “x” (defective).
(3) Film surface state: The obtained film surface is visually observed, and the film surface is smooth and smooth, “◯” (good), bank mark (unevenness due to uneven flow of resin) and shark skin The state with a pinhole was determined as “x” (defective).

<The melting endotherm ΔHc ′ (J / g) of the crystallized portion during film formation>
From the calorific value ΔHc (J / g) of the exothermic peak accompanying the crystallization in the temperature rising process of the film sample after film formation measured by DSC, and the calorific value ΔHm (J / g) accompanying the subsequent melting, the following It calculated using Formula (1).
ΔHc ′ = ΔHm−ΔHc (1)

The DSC and measurement conditions used in the measurement of the melting temperature (Tm), the crystallization temperature (Tc), and the melting endotherm ΔHc ′ of the crystallization part during film formation are as follows.
Device: DSC6220 manufactured by SII Nano Technology
conditions:
Measurement temperature range: 20 ° C. → 200 ° C. → 0 ° C. → 200 ° C. (In other words, following the measurement in the temperature increasing process from 20 ° C. to 200 ° C., the measurement in the temperature decreasing process from 200 ° C. to 0 ° C. is performed. Finally, we measured in the process of re-heating from 0 ° C to 200 ° C)
Temperature increase / decrease rate: 2 ° C / min
Measurement atmosphere: under nitrogen atmosphere (200 ml / min)
In addition, since there was no exothermic peak due to crystallization in the reheating process, it was determined that the crystallizable region crystallized 100% at a temperature decreasing rate of 2 ° C./min. The validity of the calculation formula for the melting endotherm was confirmed.

<Tear strength (N / mm)>
It was measured in accordance with JIS P 8116 paper-tear strength test method-Elmendorf tear tester method. The measurement apparatus and measurement conditions used are as follows.
Equipment: Elmendorf-type tear tester manufactured by Tester Sangyo Co., Ltd. Conditions: Sample size: Thickness of about 0.25 mm (5 layers of 0.05 mm film) x width 76 mm x length 63 mm
In addition, it cut out so that the direction parallel to a length direction might turn into the flow direction (henceforth MD direction) at the time of film film-forming, and a direction opposite to a flow direction (henceforth TD direction).
Tear strength calculation method: calculated using the following formula (2).
T = (A × p) / (n × t × 1000) (2)
T: Tear strength (N / mm)
A: Reading of scale (mN)
p: Number of test specimens to be used as a reference for the scale of the pendulum (16 in this apparatus)
n: number of test pieces torn simultaneously t: average thickness (mm) per test piece

<Swelling degree>
A film or sheet sample (50 mm × 50 mm × thickness 0.05 mm) was immersed in a solvent for 15 minutes, the solvent on the surface of the sample taken out was removed with a waste cloth, and the weight after immersion was measured by dividing by the weight before immersion. .
In addition, the solvent used was two types, toluene and ethyl acetate.
Acceptance / rejection determination: 2.0 or less is accepted.

<Initial elastic modulus (MPa), breaking strength (MPa), elongation (%)>
It was measured according to the test method for plastic-tensile properties of JIS K 7161.
The measurement apparatus and measurement conditions used are as follows.
Apparatus: Tensile tester (Autograph AG-20kNG, manufactured by Shimadzu Corporation)
Sample size: thickness 0.05 mm x width 10 mm x length 100 mm (note that the direction parallel to the length direction is the flow direction (MD) during film formation)
Measurement condition:
Distance between chucks: 50mm
Tensile speed: 300 mm / min

[Evaluation of separator]
<Heat resistance test>
Both ends of a separator sample cut out to a width of 200 mm and a length of 300 mm are sandwiched between clips and placed in an oven at 100 ° C. for 1 minute. Thereafter, when the original shape was kept when it was taken out, it was judged as “◯” (good), and when the original shape could not be kept as “x” (bad).

<Workability test>
A sample cut into a thickness of 0.05 mm, a width of 20 mm, and a length of 100 mm is fixed using the above tensile tester so that the stress is 25 N / mm ² . Thereafter, a 1 mm cut is given with a razor so that the center part between the chucks is perpendicular to the MD direction. At that time, those that did not break were judged as “◯” (good), and those that broke were judged as “x” (bad). The measurement apparatus and measurement conditions used are as follows.
Apparatus: Tensile tester (Autograph AG-20kNG, manufactured by Shimadzu Corporation)
Sample size: thickness 0.05 mm x width 20 mm x length 100 mm (note that the direction parallel to the length direction is the flow direction (MD) during film formation)
Measurement condition:
Distance between chucks: 50mm
Tensile speed: 50 mm / min (stops when 25 N / mm ² is reached)

  The evaluation results of Example 1 and Comparative Example 1 are shown in Table 1.

  From the evaluation results shown in Table 1, it can be seen that the separator of Example 1 according to the present invention is excellent in heat resistance and workability. On the other hand, the separator of Comparative Example 1 was inferior in workability.

DESCRIPTION OF SYMBOLS 1 1st roll 2 2nd roll 3 3rd roll 4 4th roll 5 Take off roll 6 Cooling roll 7 Cooling roll 8 Resin composition 9 Bank (resin pool)
10 Extruder tip

Claims (7)

A separator having a release agent treatment layer on at least one surface of a separator base material, the separator base material containing polylactic acid (A), and in a particulate form with respect to 100 parts by weight of the polylactic acid (A) 1 to 20 parts by weight of the core-shell structure polymer (B) having a graft layer on the outside of the rubber, and the following formula (1)
ΔHc ′ = ΔHm−ΔHc (1)
[In the formula, ΔHc is a calorific value (J / g) accompanying crystallization in the temperature rising process of a film or sheet after film formation, as measured by DSC, and ΔHm is an absorption due to subsequent melting. The amount of heat (J / g)]
A separator characterized by comprising a polylactic acid film or sheet having a melting endothermic amount ΔHc ′ of 10 J / g or more at the time of film formation determined in (1).   The separator according to claim 1, wherein the polylactic acid film or sheet constituting the separator substrate further contains 0.5 to 15 parts by weight of the fluoropolymer (C) with respect to 100 parts by weight of the polylactic acid (A).   The separator according to claim 2, wherein the fluorine-based polymer (C) is a tetrafluoroethylene-based polymer.   The polylactic acid film or sheet constituting the separator substrate further contains 0.1 to 15 parts by weight of the crystallization accelerator (D) with respect to 100 parts by weight of the polylactic acid (A). A separator according to any of the above items.   The polylactic acid film or sheet constituting the separator substrate is further modified with an acidic functional group having an acid value of 10 to 70 mgKOH / g and a weight average molecular weight of 10,000 to 80,000 with respect to 100 parts by weight of polylactic acid (A). The separator according to any one of claims 1 to 4, comprising 0.1 to 10 parts by weight of the olefin polymer (E).   The separator according to any one of claims 1 to 5, wherein the polylactic acid film or sheet constituting the separator substrate is a film or sheet formed by a melt film formation method.   The separator according to claim 6, wherein the melt film-forming method is a calendar method.

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