JP2016225316A - Method for producing laminate film for battery outer packaging - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminate film for battery outer packaging, high in seal strength and interlayer adhesive strength, excellent in heat resistance and electrolyte resistance, low in environmental load, and capable of being produced inexpensively.SOLUTION: A laminate film 10 for battery outer packaging includes at least a base material layer 1, a first adhesive layer 2, a barrier layer 3, a second adhesive layer 4, and a sealant layer 5 which are laminated in the order. The second adhesive layer 4 comprises a polyethylene resin containing linear low density polyethylene (LLPE) as main components, at least a part of the polyethylene resin being acid-modified. The second adhesive layer has an MFR of 0.1 g/10 min or more and 3 g/10 min or less, a density of 0.920 g/cmor more and 0.950 g/cmor less, and a tensile modulus of elasticity of 100 MPa or more and 1,000 MPa or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laminate film for battery exterior and a method for producing the same. More specifically, the present invention relates to a battery body having a liquid, gel polymer, or solid electrolyte in a battery such as a lithium battery (lithium primary or secondary battery), a lithium ion secondary battery, or a polymer battery. The present invention relates to a laminate film for battery exterior packaging and a method for producing the same. The present invention also relates to a battery using the laminate film for battery exterior.

  In recent years, lithium batteries, lithium ion secondary batteries, and the like have been developed as thin and small batteries used in mobile phones, personal computers, automobiles, and the like. Conventionally, a metal can type has been used as an exterior material of these batteries. However, in recent years, since the degree of freedom in design of the battery is high and the weight can be further reduced, the base material layer and the sealant layer are used. A polymer film is used for the barrier layer, a metal foil is used for the barrier layer, and a laminated film of the base material layer / barrier layer / sealant layer formed by laminating them together, and the sealant layers are heat sealed to form a bag or a case What has been processed to have been used.

Some battery exterior materials are called pouch type or embossed type depending on the packaging form of the battery body. The pouch type is a three-side seal, four-side seal, pillow type, or other bag-shaped type. On the other hand, the embossed type has a recess in one or both exterior materials, and the battery body is stored in this recess. There is a shape in which the buttocks are sealed by heat sealing.
The battery exterior laminate film constituting these battery exterior materials requires high sealing strength as a basic packaging member and strong puncture resistance against external stress, but for the following reasons: There is also a demand for excellent anti-electrolytic solution resistance, high sealing properties and interlayer adhesion in a high temperature environment.

That is, in a lithium battery, together with a positive electrode material and a negative electrode material as battery contents, a polar solvent such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate as an electrolyte solution, and LiPF ₆ and LiBF ₄ as electrolytes. What mix | blended lithium salts, such as these, is used. Since these electrolyte solvents have high penetrability into the polymer film, the adhesive strength of the seal portion decreases due to penetration of the solvent of the electrolyte into the laminated film of the exterior material, and the adhesive strength between the layers. Decline is a problem.
Furthermore, in the battery, a hydrolytic reaction occurs between a slight amount of moisture contained in the electrode, active material, electrolyte, etc., moisture entering from the outside through the cross section of the seal layer, and lithium salt of the electrolyte. Produces. This hydrofluoric acid penetrates into the sealant layer of the laminated film of the exterior material and causes metal corrosion of the barrier layer, further promoting the decrease in the adhesion between the sealant layer and the barrier layer and the decrease in the adhesive strength of the seal part. Will be allowed to.
In addition, the lithium battery is assumed to have been left in a car in midsummer, and even when left in a high temperature environment at 60 to 80 ° C., it needs heat resistance to maintain the sealing strength and the adhesive strength between the layers. It becomes.

  For this reason, the laminated film as a battery outer packaging material is required to be much better than other packaging materials in terms of the sealability between sealant layers and the adhesive strength between layers. Is done.

Conventionally, in order to impart corrosion resistance to hydrofluoric acid generated from an electrolytic solution, it has been proposed to subject the aluminum foil used for the barrier layer to a surface treatment.
For example, Patent Document 1 discloses a laminate composed of a base material layer, an adhesive layer, a chemical conversion treatment layer, aluminum, a chemical conversion treatment layer, an acid-modified PP film layer, and an innermost layer, and the chemical conversion treatment is a phosphoric acid chromate treatment. A polymer battery packaging material characterized by the above has been proposed.
Patent Document 2 proposes a laminate using an aluminum foil subjected to chemical conversion treatment with a chemical conversion treatment liquid composed of three components of a phenol resin, a chromium fluoride (trivalent) compound, and phosphoric acid.
Patent Document 3 proposes a battery packaging material using an aluminum foil that has been subjected to a chemical conversion treatment with a chemical conversion treatment solution containing an aminated phenol polymer, a trivalent chromium compound and a phosphorus compound.
However, the chemical conversion treatment performed in Patent Documents 1 to 3 is also referred to as a coating-type chemical conversion treatment, and the treatment liquid has an influence on the human body, has a large environmental load, and environmental pollution such as soil contamination is often a problem. Therefore, it is not preferable to apply such a chemical conversion treatment to the aluminum foil of the barrier layer.

  The following are further proposed as laminated films for battery exterior materials.

In Patent Document 4, in a laminate comprising an outermost layer / barrier layer / sand resin layer / sealant layer, a boehmite-treated aluminum foil is used as a barrier layer, the sealant layer has a density of 0.925 g / cm ³ or more and a heat of fusion. A battery exterior material using a layer made of an ethylene-α-olefin copolymer having a peak top of 115 ° C. or higher has been proposed. In Patent Document 4, a sandwich lamination method is employed for molding a sand resin layer as an adhesive layer.

  In Patent Document 5, as a laminate having excellent electrolytic solution resistance, a single layer of acid-modified olefin resin or a co-polymer of acid-modified olefin resin and olefin resin is formed on an aluminum foil provided with a chemical conversion treatment layer by phosphoric acid chromate treatment. A laminate having an extruded film bonded by a thermal lamination method has been proposed.

In Patent Documents 6 and 7, as a method of manufacturing a packaging material for a battery, a chemical conversion treatment is performed on both surfaces of aluminum with an aqueous solution composed of a phenol resin, a chromium fluoride (3) compound, and phosphoric acid, and a substrate is formed on one surface. A laminate obtained by dry laminating and then laminating a polyethylene film or polypropylene film as a heat-sealable film layer on the other surface by sandwich lamination using acid-modified polyethylene resin or acid-modified polypropylene resin as an adhesive resin. A manufacturing method is disclosed in which heating is performed at or above the softening point of the adhesive resin by post-heating.
In Patent Documents 8 and 9, as a method for producing a polymer battery packaging material, phosphoric acid chromate treatment is performed on both surfaces of aluminum, a base material is dry laminated on one surface, and then an adhesive resin and an innermost layer are coated on the other surface. A method is disclosed in which a resin (heat seal layer) is co-extruded to form a laminate and heated by post-heating under conditions equal to or higher than the softening point of the adhesive resin.

  Patent Document 10 discloses a laminated film for a battery formed of a laminate composed of a biaxially stretched polyester film layer, a biaxially stretched nylon film layer, a metal foil layer, and a thermoadhesive resin layer. In addition, those using linear low density polyethylene, medium density polyethylene, polypropylene, and acid-modified polypropylene have been proposed. In Patent Document 10, as a method of laminating a heat-adhesive resin layer and a metal foil layer, a heat-adhesive resin such as acid-modified polypropylene is used as a film between the metal foil layer and the film of the heat-adhesive resin layer. Extrude is described.

JP 2011-138789 A JP 2004-98409 A JP 2003-236980 A JP 2003-62932 A JP 2004-74419 A JP 2001-307684 A JP 2001-202927 A JP 2001-229887 A JP 2001-202928 A JP 2011-142091 A

  In the battery exterior material of Patent Document 4 using a layer made of an ethylene-α-olefin copolymer as the sealant layer, the heat seal strength of the laminate specifically produced in the example is about 6.5 N / 15 mm. It is weak and cannot be used as a battery exterior material. In addition, since the sandwich lamination method is used instead of the inflation molding method for forming the sand resin layer as the adhesive layer, a high fluidity resin with a high MFR must be selected, and the adhesive resin layer is not sealed when sealing. There is a problem that it becomes fluidized, the thickness is reduced, and the adhesive strength between the barrier layer and the aluminum foil is insufficient. That is, unlike the case where the resin extruded by the sandwich lamination method is extruded by the inflation method, the resin is usually extruded at a high temperature of 50 to 100 ° C. or higher than the melting point. This causes thermal degradation when extruding and deteriorates the seal strength and electrolyte resistance.

  In the laminate of Patent Document 5, in order to firmly bond the aluminum foil and the acid-modified resin, the chemical conversion treatment layer is heated above the softening point of the acid-modified olefin resin and below the melting point, and bonded by a thermal lamination method. After forming the laminate, it is necessary to perform a two-stage heat treatment in which the intermediate laminate is reheated so as to be equal to or higher than the melting point of the acid-modified olefin resin, which increases processing costs. Moreover, also in this patent document 5, similarly to patent documents 1-3, environmental pollution resulting from the chemical conversion process by a phosphoric acid chromate process becomes a problem.

  In the methods of Patent Documents 6 and 7, since the sandwich lamination method is adopted for forming the adhesive resin layer, the adhesive resin layer is fluidized at the time of sealing, and the thickness is reduced and the barrier layer aluminum foil is formed. There is a problem that the adhesive strength is insufficient, and there is a problem that the seal strength and the electrolytic solution resistance deteriorate due to thermal deterioration during extrusion at a high temperature.

  The methods of Patent Documents 8 and 9 are based on a so-called extrusion lamination method in which an adhesive resin is directly extruded onto an aluminum surface by a co-extrusion method. Similar to the sandwich lamination method, a high fluidity resin having a high MFR as an adhesive resin. The adhesive resin layer is fluidized at the time of sealing, the thickness becomes thin and the adhesive strength with aluminum is insufficient, and the sealing strength and electrolyte resistance deteriorate due to thermal deterioration during extrusion at high temperatures. There is a problem to do. In addition, as in Patent Documents 1 to 3, there is a problem of environmental pollution caused by the phosphoric acid chromate treatment.

  In Patent Document 10, since acid-modified polypropylene is used as the adhesion-strengthening resin layer, the electrolytic solution resistance is inferior.

As described above, conventionally, various laminated films have been proposed as battery exterior materials, but the optimum selection has not been made in the resin characteristics and film forming methods of the adhesive layer and the sealant layer, and also in the bonding processing method. For this reason, there is no actual product that has high sealing strength and interlayer adhesion strength, is excellent in electrolytic solution resistance and heat resistance, and has no problem of environmental pollution and can be manufactured at low cost.
The present invention solves the above-mentioned problems, and the object of the present invention is to produce a low cost by a method having high sealing strength and interlayer adhesion strength, excellent electrolytic solution resistance and heat resistance, and less environmental impact. The present invention provides a laminate film for battery exterior.

  As a result of intensive studies, the present inventors have found that in the laminate film for battery exterior, in which at least the base material layer, the first adhesive layer, the barrier layer, the second adhesive layer, and the sealant layer are laminated in this order, By using high-viscosity, high-density acid-modified polyethylene resin mainly composed of specific linear low-density polyethylene (LLPE) as the adhesive resin for the adhesive layer, the barrier layer is subjected to chemical treatment such as chromate treatment with a large environmental load. Electrolytic solution resistance, heat resistance, and high adhesive strength can be obtained without any treatment, and further, when an inflation molding method of extruding the film forming material from an annular die is used for forming the second adhesive layer. It is possible to obtain a uniform adhesive film with no difference in physical properties such as vertical and horizontal tensile strength and elongation, and this film is bonded to the metal foil of the barrier layer by the thermal lamination method. By causing I have found that it is possible to obtain by promoting the crystallinity of the acid-modified polyethylene resin electrolyte solution resistance, heat resistance, excellent laminate film for a battery case in interlayer adhesion.

  The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.

[1] A battery exterior laminate film in which at least a base material layer, a first adhesive layer, a barrier layer, a second adhesive layer, and a sealant layer are laminated in this order. It is made of a polyethylene resin mainly composed of linear low density polyethylene (LLPE), at least a part of the polyethylene resin is acid-modified, and has an MFR of 0.1 g / 10 min to 3 g / 10 min, and a density of 0.920 g / A laminate film for battery exterior having a cm ³ or more and 0.950 g / cm ³ or less and a tensile modulus of 100 MPa or more and 1000 MPa or less.

[2] The sealant layer may be composed mainly of LLPE, MFR0.1g / 10min or 3 g / 10min or less, characterized by having a layer consisting of a density 0.920 g / cm ³ or more 0.950 g / cm ³ or less of the resin The laminate film for battery exterior according to [1].

[3] The laminate film for battery exterior according to [1] or [2], wherein the sealant layer has a higher density layer than the second adhesive layer.

[4] The laminate film for battery exterior according to any one of [1] to [3], wherein the barrier layer is made of an aluminum foil that has not been subjected to chromium conversion treatment.

[5] The laminate film for battery exterior according to any one of [1] to [4], wherein the barrier layer is made of an aluminum foil having a boehmite film formed on a surface thereof.

[6] An inflation molding step of forming the second adhesive layer forming film by an inflation molding method in which the film forming material of the second adhesive layer is extruded from an annular die, and the second adhesive layer forming film The method for producing a laminate film for battery exterior according to any one of [1] to [5], further comprising: a thermal lamination step of bonding to the barrier layer by a thermal lamination method.

[7] In [6], in the inflation molding step, coextrusion inflation molding is performed in which the film forming material of the second adhesive layer is coextruded from an annular die together with the film forming material of the sealant layer. The manufacturing method of the laminated film for battery exterior of description.

[8] In the thermal lamination step, the temperature on the base material layer side of the laminate film for battery exterior obtained is less than 170 ° C., the temperature on the sealant layer side is 170 ° C. or higher, and the temperature on the base material layer side The method for producing a laminate film for battery exterior according to [6] or [7], wherein the temperature difference on the sealant layer side is 20 ° C. or more.

[9] In the thermal lamination step, when the barrier layer and the sealant layer are bonded together via the second adhesive layer, a heat resistant film having a melting point of 200 ° C. or higher is stacked on the non-bonded surface on the sealant layer side. The method for producing a laminate film for battery exterior according to any one of [6] to [8], wherein lamination is performed and then the heat-resistant film is peeled off from the sealant layer.

[10] A battery comprising the laminate film for battery exterior according to any one of [1] to [5].

  According to the present invention, there is provided a battery exterior laminate film that has high sealing strength, interlayer adhesion strength, excellent electrolytic solution resistance, heat resistance, and can be produced at low cost by a method with less environmental impact. The laminate film can be used to reduce the weight, thickness, and size of the battery, reduce costs, improve long-term durability, and improve reliability.

It is sectional drawing which shows embodiment of the laminate film for battery exteriors of this invention. It is the schematic of the thermal lamination process which shows an example of the manufacturing method of the laminated film for battery exteriors of this invention. It is a perspective view which shows an example of the battery exterior material using the laminate film for battery exteriors of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view showing an embodiment of a laminate film for battery exterior of the present invention, and FIG. 2 is a schematic view of a thermal lamination process showing an example of a method for producing a laminate film for battery exterior of the present invention. 3 is a perspective view showing an example of a battery exterior material using the laminate film for battery exterior of the present invention. However, FIGS. 1-3 shows an example of embodiment of this invention, The laminate film for battery exteriors of this invention, and a battery exterior material are not limited to what is shown in FIGS. . Moreover, the manufacturing method of the laminate film for battery exteriors of this invention is not limited to what passes through the thermal lamination process shown in FIG.

  In this specification, the tensile modulus of the resin or the resin composition is measured at 1 mm / min using a Tensilon tensile tester with a strip-like sample having a width of 15 mm based on ISO 1184-1970 with a distance between chucks of 100 mm. Value. Further, MFR (melt flow rate) was measured at 190 ° C. and a load of 2.16 kgf in the case of a polyethylene resin, an acid-modified polyethylene resin, or a resin composition containing these as a main component based on the JIS K7210A method. In the case of a polypropylene resin or a polypropylene resin composition, it is a value measured at 230 ° C. and a load of 2.16 kgf. The density of the resin is determined by the JISK7112A method (submersion method in water).

[Laminate film for battery exterior]
As shown in FIG. 1, the laminate film 10 for battery exterior of the present invention has at least a base layer 1, a first adhesive layer 2, a barrier layer 3, a second adhesive layer 4, and a sealant layer 5 laminated in this order. The second adhesive layer 4 is made of a polyethylene resin mainly composed of linear low density polyethylene (LLPE), at least a part of the polyethylene resin is acid-modified, and the MFR is 0. .1g / 10min or 3 g / 10min or less, density of 0.920 g / cm ³ or more 0.950 g / cm ³ or less, a tensile modulus is equal to or less than 1000MPa or more 100 MPa.

<Base material layer>
The base material layer 1 in the present invention reinforces the barrier layer 3 to prevent damage to the barrier layer 3 due to external force due to piercing or the like, and the battery outer laminate film itself during processing of the battery outer laminate film. It is a layer for preventing breakage and may be a single layer or a laminate of two or more layers.
The base material layer 1 is required to be excellent in mechanical strength and heat resistance, and is preferably made of a resin film having a high tensile elastic modulus.

  Preferred resins used for the base material layer 1 include polyamide (PA), polyamideimide (PAI), polyimide (PI), polyacetal (POM), polyarylate (Par), polycarbonate (PC), polyethylene terephthalate (PET), Polyalkylene terephthalate (PAT) such as polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), polymethyl methacrylate (PMMA), polyphenylene oxide (PPE) , Polyethersulfone (PES), polymethylpentene (TPX), polyoxybenzylene (POB), liquid crystalline polyester, polysulfone (PSF), polyphenylene sulfide (PP ), Poly bisamide triazole, polyaminobismaleimide, polyether imide (PEI), polyetheretherketone (PEEK), include one or more mixtures of these thermoplastic resins such as acrylic.

  Among these, polycarbonate (PC), polybutylene terephthalate (PBT), polyalkylene terephthalate (PAT) such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), polyamide (PA), Polyphenylene sulfide (PPS), polyamideimide (PAI), and polyimide (PI) are preferable.

  Although the base material layer 1 may be an unstretched film or a stretched film, it is preferably a stretched film from the viewpoint of mechanical strength and heat resistance, and particularly preferably a biaxially stretched film. In particular, a biaxially stretched polyethylene terephthalate film, a biaxially stretched polyethylene naphthalate film or a biaxially stretched polyamide film is preferable because it has a high tensile elastic modulus and is inexpensive.

  The base material layer 1 has a role for preventing pinhole generation of the barrier layer 2 due to deformation such as external piercing during assembly as a battery, and press processing generally performed when pouching or embossing. In order to play a role in preventing damage to the laminate film for battery exterior during the overhanging process, a certain degree of elastic modulus and thickness are required.

  The tensile elastic modulus of the base material layer 1 is usually 2000 MPa or more, preferably 2200 MPa or more, and particularly preferably 2400 MPa or more. The upper limit of the tensile elastic modulus is not particularly defined, but the tensile elastic modulus of the preferred resin as described above is usually 6000 MPa or less.

  Moreover, the thickness of the base material layer 1 is preferably 10 μm or more and 50 μm or less. When the thickness of the base material layer 1 is larger than 50 μm, the laminate film for battery exterior becomes too high in rigidity and not only is difficult to process such as press working, but also the surface density tends to increase and the weight cannot be reduced. . Moreover, when the thickness of the base material layer 1 is less than 10 μm, the puncture resistance may be affected. The thickness of the base material layer 1 is particularly preferably 12 μm or more and 30 μm or less.

  When the battery exterior laminate film is an embossed exterior material as illustrated in FIG. 3, the base material layer 1 also needs to be slidable with the mold during press molding. It is preferable to improve the slipperiness by applying a lubricant to the surface (the outermost surface of the laminate film for battery exterior) or providing unevenness.

  However, when a lubricant is used, there is a concern about the problem of mold contamination due to the lubricant. Therefore, it is particularly preferable that the surface of the base material layer 1 is uneven to reduce the coefficient of friction with the mold. . In this case, the unevenness of the surface of the base material layer 1 is a surface measured in an area of 40 μm × 40 μm using a laser microscope VK8500 manufactured by Keyence Co., Ltd. under the measurement conditions of lens 100 times, pitch 0.01 μm, shutter speed AUTO, gain 835. The average value obtained by measuring the roughness Ra at four points is preferably 0.3 μm or more and 1.0 μm or less. If Ra is smaller than the lower limit, the slipping property tends to be insufficient, and if Ra is larger than the upper limit, dust tends to adhere to the unevenness. A preferable surface roughness Ra of the base material layer 1 is not less than 0.35 μm and not more than 0.70 μm.

<First adhesive layer>
The first adhesive layer 2 is a layer for adhering the base material layer 1 and the barrier layer 3. When the base material layer 1 and the barrier layer 3 are bonded together by a dry lamination method, the first adhesive layer 2 is used for dry lamination. Adhesive, for example, aliphatic polyester, aromatic polyester, polyethyleneimine, polyether, cyanoacrylate, urethane, organic titanium, polyetherurethane, epoxy, polyesterurethane, imide, isocyanate Various adhesives such as those based on polyolefin, polyolefin, silicone, and acrylic can be used.
Among these adhesives, aromatic polyester-based, polyolefin-based, and acrylic-based adhesives are preferable because of their excellent resistance to electrolytic solution.

  When further electrolytic solution resistance is required, the base material layer 1 and the barrier layer 3 may be bonded together by a thermal lamination method using an acid-modified resin film for the first adhesive layer 2.

  Although the thickness of the 1st contact bonding layer 2 is not limited, Usually, it is about 1-10 micrometers.

<Barrier layer>
The barrier layer 3 is a layer for preventing (barrier) the entry of moisture from the outside into the battery, has no pinhole, and has a high tensile strength as a laminate film for battery exterior. It is required to have crack resistance against deformation and elongation during embossing and pouching.

As the barrier layer 3, a metal foil (metal layer) is preferable, and an aluminum foil is particularly preferable. Further, from the viewpoint of crack resistance during press working or embossing, an aluminum foil excellent in extensibility is preferable, and an aluminum foil containing 0.3 wt% or more and 3.0 wt% or less of iron is preferable. If the iron content is less than this range, the elongation tends not to be sufficient. If the iron content is more than this range, the problem of corrosion of the barrier layer 3 due to hydrofluoric acid generated from the electrolytic solution tends to occur. . The preferable iron content of the aluminum foil is not less than 0.5% by weight and not more than 1.7% by weight.
Moreover, although hard aluminum foil and soft aluminum foil exist in aluminum foil, since the soft aluminum foil which performed annealing treatment has a softness | flexibility, it is preferable.

The thickness of the barrier layer 3 such as an aluminum foil is preferably 9 μm or more and 60 μm or less, and particularly preferably 20 μm or more and 50 μm or less in order to achieve both thinning and barrier properties.
In addition, although the metal foil (metal layer) shape | molded previously is normally used for the barrier layer 3, the aspect which forms the barrier layer 3 by a vapor deposition method or the apply | coating method is also included, for example.

<Surface treatment of aluminum foil>
The surface of the aluminum foil suitable as a barrier layer in the present invention may be subjected to a surface treatment for imparting corrosion resistance. However, in the present invention, the surface treatment of the aluminum foil is not necessarily required.
That is, in the present invention, as will be described later, a film formed by an inflation molding method using an acid-modified polyethylene resin having specific physical properties as a film forming material for the second adhesive layer is heated with a temperature gradient. By laminating to the aluminum foil by the lamination method, the second adhesive layer can be firmly adhered to the aluminum foil that has not been surface-treated, and sufficient resistance to electrolyte and corrosion can be secured. Therefore, in the present invention, the surface treatment of the aluminum foil is not necessarily required, and in particular, it is preferable not to perform a surface treatment having a problem of environmental pollution such as a chromium-based chemical conversion treatment described later.

  When surface treatment is performed on an aluminum foil as a barrier layer, a known treatment is used as the surface treatment. For example, chromate chromate treatment, phosphoric acid chromate treatment, phosphoric acid-chromate treatment, chromate treatment, alkali Examples thereof include chromium-based chemical conversion treatment such as chromate treatment and coating-type chromate treatment, coating-type non-chromium treatment such as zirconium, titanium, and zinc phosphate, boehmite treatment, and anodizing treatment. In addition to these treatments, corona treatment, plasma treatment, flame treatment, and other treatments for imparting polar groups to the surface of the aluminum foil are performed to enhance corrosion resistance by enhancing adhesion to the second adhesive layer. May be. Two or more of these processes may be combined. However, it is preferable not to perform the chromium-based chemical conversion treatment as described above.

Among the above surface treatments, boehmite treatment that has a low environmental burden and can be surface treated at low cost is preferable.
The boehmite treatment is a treatment for forming an aluminum hydrated oxide film (boehmite film) having a boehmite crystal structure on the surface of the aluminum foil by holding the aluminum foil in high-temperature boehmite-treated water for a certain period of time.

  The preferred boehmite-treated water contains deionized water and an alkali such as triethanolamine and ammonia in an amount of 0.1 wt% to 2 wt%, preferably 0.3 wt% to 1 wt%, more preferably 0. The boehmite treatment is performed by heating such boehmite-treated water to 90 to 100 ° C., and the aluminum foil for 20 seconds to 5 minutes, preferably 20 seconds. It can be performed by immersing for 1 minute.

  By such boehmite treatment, an aluminum foil having a boehmite film having a thickness of preferably 0.1 μm or more and 1 μm or less, more preferably 0.1 μm or more and 0.8 μm or less, and further preferably 0.2 μm or more and 0.4 μm or less. If it exists, in the heat lamination with the acid-modified polyethylene resin layer of the second adhesive layer, strong adhesiveness can be obtained, and a laminate film for battery exterior excellent in electrolytic solution resistance can be obtained. If the thickness of the boehmite film is thinner than the above range, the effect of improving the adhesiveness by the boehmite treatment cannot be sufficiently obtained, and if it is thicker than the above range, the boehmite crystal is easily detached from the interface with the aluminum foil, which is not preferable. .

<Second adhesive layer>
The second adhesive layer 4 is a layer for adhering the barrier layer 3 and the sealant layer 5, and in the present invention contains a polyethylene resin mainly composed of linear low density polyethylene (LLPE), and Has specific physical properties. In the present invention, the second adhesive layer 4 may contain components other than the polyethylene resin as long as the above conditions are satisfied.

  Polyethylene resin is a polymer whose melting point is lower than that of polypropylene resin, but is a polymer in which molecules are cross-linked by repeated application of heat. It is difficult to cut molecules and has better long-term heat resistance than polypropylene.

Furthermore, polyethylene has a high melt tension, flexibility, resistance to deformation when processed as a battery exterior material, hardly whitening during deformation, and excellent cold resistance. In addition, polyethylene has a higher density than polypropylene and has high resistance to moisture from the outside and a carbonate-based solvent that is a polar solvent for the electrolytic solution.
Such polyethylene acid-modified resin is excellent in adhesion to metal foil such as aluminum foil constituting the barrier layer, and is subjected to chromium-based chemical conversion treatment or phosphorus-based chemical conversion treatment that causes environmental pollution to the aluminum foil. Even if it is not, a strong adhesive force can be obtained.

In the present invention, among polyethylene resins, a polyethylene resin mainly composed of linear low density polyethylene (LLPE) is used because it has moderate flexibility and excellent adhesion to a barrier layer such as an aluminum foil. .
The main component as used herein refers to a component that is contained most in the compounded material in a material formed by compounding a plurality of components.

  In the present invention, linear low density polyethylene (LLPE) means a copolymer of ethylene and an α-olefin having about 4 to 20 carbon atoms, and is a specific example of a branched side chain composed of an α-olefin. Include various comonomers such as butene-1, hexene-1, 4-methylpentene-1, octene-1, decene-1, tetracene-1, and octadecene-1. Two or more of these α-olefins may be used in combination. Further, if an α-olefin having about 4 to 20 carbon atoms is used as a comonomer, propylene may be further used as a comonomer. Any linear low density polyethylene (LLPE) may be used as long as the MFR, density and tensile elastic modulus of the second adhesive layer can be in a specific range. Among these, linear low density polyethylene having at least one side chain of butene-1, hexene-1, and octene-1 is preferable because it has appropriate flexibility. Although the manufacturing method of linear low density polyethylene (LLPE) is not limited, The well-known method of manufacturing polyolefin resin is employable.

  The polyethylene resin in the present invention can also be blended with polyethylene resins other than linear low density polyethylene (LLPE). Polyethylene resins other than linear low density polyethylene (LLPE) are not limited, and specific examples include high density polyethylene (HDPE), medium density polyethylene, and low density polyethylene (LDPE). Here, the low-density polyethylene (LDPE) does not include the above-mentioned linear low-density polyethylene (LLPE), and usually includes what is called a high-pressure method low-density polyethylene. The manufacturing method of high density polyethylene (HDPE), medium density polyethylene, and low density polyethylene (LDPE) is not limited, and a known method can be adopted, but it is usually preferable to manufacture with a Ziegler catalyst or the like.

  A preferred acid-modified polyethylene resin is an acid-modified polyethylene resin that is a blend material of linear low-density polyethylene (LLPE) and high-density polyethylene (HDPE), and this blend material has an LLPE of 50 wt% or more and 98 wt% or less. HDPE is preferably 2% by weight or more and 50% by weight or less in view of heat resistance and resistance to electrolyte solution penetration. Furthermore, in order to impart inflation molding stability, low density polyethylene (LDPE) may be blended as the third component. In this case, the blending ratio is LLPE 50% to 95% by weight, HDPE 5% to 40% by weight. % Or less, preferably 1% by weight or more and 30% by weight or less of LDPE.

The polyethylene resin used in the present invention is at least partially acid-modified. Such an acid-modified polyethylene resin is produced, for example, by modifying an unsaturated carboxylic acid and / or a derivative thereof into a polyethylene resin by graft polymerization. can do.
The unsaturated carboxylic acid and the derivative of the unsaturated carboxylic acid are not particularly limited. For example, dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, and mesaconic acid; acrylic acid and methacrylic acid And unsaturated monocarboxylic acids such as crotonic acid; dicarboxylic acid anhydrides such as maleic anhydride, fumaric anhydride, itaconic anhydride, mesaconic anhydride, and derivatives such as amide, imide, and ester. Among these, maleic acid, maleic anhydride, acrylic acid, and methacrylic acid are preferably used, and maleic anhydride is particularly preferable.

  The method for modifying the polyethylene resin is not particularly limited. For example, a solution method in which a polyethylene resin is dissolved in an organic solvent and reacted with an acid (such as maleic anhydride) in the presence of a radical generator, polyethylene Examples thereof include a melting method in which a resin is heated and melted and reacted with an acid (such as maleic anhydride) in the presence of a radical generator.

The acid-modified polyethylene resin may be a linear low-density polyethylene (LLPE) as a main component, or other polyethylene resin that can be used in combination with this, for example, high-density polyethylene (HDPE). Or low density polyethylene (LDPE). Furthermore, an acid-modified polyethylene resin and a non-acid-modified polyethylene resin can be appropriately blended and used.
In addition, when other polyethylene resins are used together with linear low density polyethylene (LLPE), these polyethylene resins may be acid-modified in a mixed or coexisting state, or at least one of the polyethylene resins may be It may be previously modified with an acid, and this may be mixed with another polyethylene resin that has not been modified with an acid.

If the modification rate of the acid-modified polyethylene resin (content of acid groups in the acid-modified polyethylene resin) is too small, the effect of improving adhesiveness due to acid modification may not be obtained sufficiently. Since the heat resistance of the modified polyethylene resin tends to decrease, it is preferably 0.05% by weight or more and 10% by weight or less, particularly preferably 0.2% by weight or more and 5% by weight or less. Here, the modification rate of the acid-modified polyethylene resin can be confirmed by means such as infrared absorption spectrum analysis (IR) or titration. In addition, in the case of blending and using an acid-modified polyethylene resin and a non-acid-modified polyethylene resin, the modification rate refers to the modification rate in all polyethylene resins including a polyethylene resin not acid-modified. Shall mean.
In addition, as an acid-modified polyethylene resin, a commercial item can also be used. For example, it corresponds to the above from Mitsubishi Chemical Corporation, Modic (trade name) series, Mitsui Chemicals, Admer (trade name), etc. What is to be selected can be appropriately selected and used.

  The second adhesive layer 4 may contain a resin other than the polyethylene resin as long as the effects of the present invention are not impaired. The resin other than the polyethylene resin is not limited. For example, an ethylene-based resin obtained by copolymerizing ethylene and a comonomer other than an α-olefin, such as an ethylene-vinyl acetate copolymer or an ethylene-vinyl alcohol copolymer; a propylene-based resin Vinyl chloride resin, polyamide resin, polyester resin, polycarbonate resin and the like. In addition, when the resin other than the polyethylene resin is contained in a large amount as the second adhesive layer 4, since the effect of using the above-described polyethylene resin may be impaired, these resins are used in the second adhesive layer. It is preferable to use in the range of 20% by weight or less, preferably 15% by weight or less.

  Further, the second adhesive layer 4 has an ethylene-propylene copolymer, an ethylene-butene copolymer, a propylene-butene copolymer, and an ethylene-butene-propylene copolymer as long as the effects of the present invention are not impaired. Olefin elastomers such as ethylene-propylene-diene copolymers, various elastomer components such as styrene elastomers, polyester elastomers, polyamide elastomers, antioxidants, thermal stabilizers, various plasticizers, light stabilizers, ultraviolet rays Various additives such as an absorbent, a neutralizing agent, a lubricant, an antifogging agent, an antiblocking agent, a crosslinking agent, a crosslinking aid, a colorant, a flame retardant, and a dispersing agent can be added.

The second adhesive layer, MFR0.1g / 10min or 3 g / 10min or less, density of 0.920 g / cm ³ or more 0.950 g / cm ³ or less, or less than the tensile modulus of 100 MPa 1000 MPa.

  If the MFR of the second adhesive layer 4 is larger than 3 g / 10 min, the fluidity is too high, and flow due to melting of the resin occurs at the time of sealing. There is not preferable. Furthermore, the molecular weight is lowered, the permeability to hydrofluoric acid generated from the electrolytic solution is increased, and the barrier layer is corroded. The preferred MFR of the second adhesive layer 4 is 2 g / 10 min or less, more preferably 1.5 g / 10 min or less. The lower limit of the MFR of the second adhesive layer 4 is preferably 0.1 g / 10 min or more, particularly 0.3 g / min, since it is preferably at a level that does not cause a problem in film forming properties when the film is formed by an inflation molding method. If it is 10 min or more, it is preferable because high-speed moldability and high seal strength in inflation molding can be maintained.

Further, the density of the second adhesive layer 4 needs to be 0.920 g / cm ³ or more. If the density is smaller than this, the solvent resistance and the electrolytic solution resistance deteriorate. In order to block moisture from the outside and to increase resistance to hydrofluoric acid generated by hydrolysis of the electrolytic solution and moisture, the density of the second adhesive layer 4 should be high, and the lower limit of the preferred density is a 0.923 g / cm ³ or more, and particularly preferably 0.925 g / cm ³ or more. The upper limit of the density of the second adhesive layer 4 is not particularly limited as long as the flexibility of the polyethylene resin is not impaired. Usually, the upper limit of the density is 0.950 g / cm ³ or less, and In consideration of adhesiveness, acid resistance to hydrogen fluoride, and resistance to whitening in pressing or overhanging, the upper limit of the density is preferably 0.945 g / cm ³ or less.
The means for setting the density of the second adhesive layer 4 in the above range is not limited. In addition to the optimization of the polyethylene resin used for acid modification and the modification rate, as described above, the polyethylene resin not acid-modified is used. In addition, a resin other than polyethylene resin or the like is used in combination, and the mixing ratio thereof is optimized.

  In addition, the tensile elastic modulus of the second adhesive layer 4 is 100 MPa or more because it tends to cause material destruction when an external force such as deformation is applied if too much flexibility is applied, and on the contrary, it tends to become brittle if it becomes too hard. Since it becomes easy to peel at the interface with the barrier layer, it is 1000 MPa or less. The tensile elastic modulus of the second adhesive layer 4 is more preferably 130 MPa to 800 MPa, and particularly preferably 180 MPa to 600 MPa.

  The values of MFR, density, and tensile modulus described above indicate the characteristics of the material constituting the second adhesive layer 4, and when a plurality of polyethylene resins are used in combination as the polyethylene resin, a resin other than the polyethylene resin is used. In the case of containing, it means a value as a resin composition.

  The thickness of the second adhesive layer 4 is preferably 3 μm or more and 50 μm or less, more preferably 10 μm or more and 40 μm or less, and particularly preferably 12 μm or more and 35 μm or less. If the thickness of the second adhesive layer 4 is thinner than the above range, it may not be possible to obtain sufficient adhesive strength for the adhesion between the barrier layer 3 and the sealant layer 5, and if thicker than the above range, The thickness must be reduced and the electrolytic solution resistance may be inferior.

<Sealant layer>
The sealant layer 5 is required to have heat sealability during processing as a battery exterior material and resistance to electrolyte. Although the material which comprises the sealant layer 5 is not limited, It is preferable to consist of an acid-modified polyolefin resin having a lower modification rate than the acid-modified polyethylene resin of the second adhesive layer 4 or a non-acid-modified polyolefin resin layer. The sealant layer may be a single layer or a laminate of two or more layers.

Acid-modified resins have lower heat resistance compared to non-acid-modified resins, and low molecular weight components may precipitate during the film formation by the sand lamination method or the extrusion lamination method, especially when the film is formed at a high temperature. . When such a layer is used as the innermost layer, that is, a layer that is in direct contact with the electrolytic solution, from the portion where the low molecular weight component is deposited, to the inner layer of hydrofluoric acid generated by the solvent of the electrolytic solution or the hydrolysis of the electrolytic solution This may accelerate the penetration of the electrolyte and may cause a problem in the resistance to the electrolyte. Therefore, the sealant layer 5 is preferably an acid-modified polyolefin resin having a low modification rate or a polyolefin resin layer that is not acid-modified.
Here, “low modification rate” specifically means a modification rate of 0.1% by weight or less, preferably 0.05% by weight or less.

  As a constituent material of the sealant layer 5, any polyolefin resin can be used without any problem. Low density polyethylene (LDPE), medium density polyethylene, high density polyethylene (HDPE), linear low density polyethylene (LLPE), One kind of polyolefin resin such as random copolymerized polypropylene with ethylene, block copolymerized polypropylene with ethylene, or homopolypropylene, or a mixture of two or more of these polyolefin resins can be used.

  A preferable constituent material of the sealant layer 5 is a linear low density polyethylene (LLPE) or a blend material of LLPE and high density polyethylene (HDPE), particularly LLPE 50 wt% or more and 100 wt% or less, HDPE 0 wt% or more 50 A weight percent or less of LLPE alone or a blend material is preferred in terms of heat resistance and electrolyte solution penetration. Furthermore, low density polyethylene (LDPE) may be blended as the third component in order to impart inflation molding stability. In that case, the blending ratio is 50% to 95% by weight of LLPE, 5% to 40% by weight of HDPE. Hereinafter, the LDPE content is preferably 1% by weight or more and 30% by weight or less.

  As described above, linear low-density polyethylene includes copolymers obtained by copolymerizing various comonomer species such as butene-1, hexene-1, 4-methylpentene-1, and octene-1 as branched side chains. There is no particular limitation as long as it satisfies the density and MFR described below suitable as a layer, and a straight chain having at least one side chain of hexene-1 and octene-1 is particularly preferable among them. 50% by weight or more of a low-density polyethylene, and such a linear low-density polyethylene is further blended with a high-density polyethylene and / or a low-density polyethylene in an amount of 2 to 50% by weight, Electrolytic solution resistance, adhesiveness with tab seal layer, inflation moldability, heat resistance during thermal lamination, adhesiveness with second adhesive layer, acid resistance to hydrogen fluoride Superior in whitening resistance, etc. in the press or overhanging working, preferred.

In the present invention, since a specific acid-modified polyethylene resin layer is used for the second adhesive layer 4, the electrolyte solution resistance can be maintained with this acid-modified polyethylene resin layer alone. The layer 5 preferably has at least one layer mainly composed of linear low-density polyethylene that is not acid-modified (hereinafter, this layer may be referred to as “high-density layer”). the resin constituting the can, MFR is below 0.1 g / 10min or higher 3 g / 10min, or less density of 0.920 g / cm ³ or more 0.950 g / cm ^3, higher than the acid-modified polyethylene resin of the second adhesive layer It is preferable that there is a density. When the density of the high density layer is smaller than the above range, the solvent resistance and the electrolytic solution resistance are deteriorated. In order to block moisture from the outside and increase the resistance to hydrofluoric acid generated by hydrolysis of the electrolyte and moisture, a higher density is preferable, and the lower limit of the density of the high-density layer is more preferable. It is 0.923 g / 10 min or more, more preferably 0.925 g / 10 min or more, particularly preferably 0.935 g / 10 min or more. Further, the upper limit of the density of the high-density layer is not particularly limited as long as the tensile elastic modulus is 1200 MPa or less without impairing the flexibility of the polyethylene, and the preferable upper limit of the density is 0.95 g / 10 min. In consideration of adhesiveness to the second adhesive layer 4, acid resistance to hydrogen fluoride, and resistance to whitening in pressing or overhanging, the upper limit of the more preferable density is 0.945 g / 10 min or less.

The high-density layer is preferably a layer having a higher density than the acid-modified polyethylene resin that constitutes the second adhesive layer 4, and is higher than the density of the acid-modified polyethylene resin that constitutes the second adhesive layer 4. 001G / cm ³ or more, preferably it is a high density of 0.002 g / cm ³ or more, solvent resistance, preferred in view of electrolytic solution resistance. This density difference is usually 0.060 g / cm ³ or less.

  Further, if the MFR of the high-density layer is larger than 3 g / 10 min, the fluidity is too high and a flow due to the melting of the resin occurs at the time of sealing, and the thickness of the seal portion is insufficient, which may cause a decrease in the sealing strength. . Furthermore, the molecular weight is lowered, the permeability to hydrofluoric acid generated from the electrolytic solution is increased, and the barrier layer 3 may be corroded. A more preferable MFR of the high-density layer is 2 g / 10 min or less, and further preferably 1.5 g / 10 min or less. On the other hand, the lower limit of the MFR is not particularly limited, and when the film is formed by inflation molding, the lower limit of the MFR is preferably 0.1 g / 10 min or more. .3 g / 10 min or more is preferable because high-speed moldability and high seal strength can be maintained during film formation by inflation molding.

  Moreover, even if the innermost layer (surface opposite to the second adhesive layer) of the sealant layer is mainly composed of linear low density polyethylene, the seal member used for the electrode tab portion is random polypropylene. There is no problem because sufficient sealing strength can be obtained, but if the sealing property with the tab is low, the sealant layer has a multilayer structure, a layer mainly composed of linear low density polyethylene, and a random polypropylene layer Or it is good also as a laminated structure with the outermost layer of block polypropylene.

The thickness of the sealant layer 5 is preferably 10 μm or more, particularly preferably 15 μm or more for the above-described high-density layer in terms of solvent resistance, electrolyte resistance, and the like. However, the thickness of the high-density layer is preferably 80 μm or less, and particularly preferably 60 μm or less, because appropriate flexibility of the sealant layer 5 can be obtained and flexibility as a laminate film for battery exterior can be obtained.
Also in the case of a sealant layer having a multilayer laminated structure, it is preferable that the total thickness falls within the above range.

  In addition, like the base material layer 1, the sealant layer 5 is formed on the surface (the surface opposite to the second adhesive layer 4) which is the outermost surface of the laminate film for battery exterior in order to improve the slipping property at the time of embossing. It is preferable to provide unevenness because a lubricant having a problem of mold contamination can be dispensed with. In this case, the surface roughness Ra of the unevenness imparting surface of the sealant layer 5 is preferably about 0.02 to 0.08 μm, particularly about 0.03 to 0.07 μm. Here, the surface roughness Ra of the sealant layer 5 is a value measured in the same manner as the surface roughness Ra of the substrate layer 1 described above. This surface irregularity can be imparted by a thermal lamination process described later.

[Method for producing laminated film for battery exterior]
Although there is no restriction | limiting in particular as a manufacturing method of the laminate film for battery exteriors of this invention, About at least 2nd contact bonding layer, it forms into a film by the inflation molding method, Then, it bonds together with a barrier layer and a sealant layer by the thermal lamination method. It is preferable.
In addition, a laminated film of the second adhesive layer and the sealant layer is formed in advance by the coextrusion inflation molding method (multilayer inflation molding method), and then the metal foil / second adhesive layer / sealant layer is formed by the thermal lamination method. A laminated film may be formed, or the second adhesive layer and the sealant layer may be separately formed in advance, and these may be bonded together at the time of thermal lamination to form a laminated film of metal foil / second adhesive layer / sealant layer. In any case, if a high density and low MFR resin is selected, the film can withstand high temperature thermal lamination, the crystallinity of the film is increased, and the crystal lamella of the acid-modified polyethylene resin of the second adhesive layer is increased. It becomes easy to penetrate the metal foil surface of the barrier layer, and high adhesive strength, heat resistance, and electrolyte resistance are obtained.

  In addition, the metal foil of the barrier layer used for thermal lamination should be used as a laminated film in which a base material layer is bonded in advance through a first adhesive layer by a dry lamination method or the like. This is preferable because the side is cooled more slowly, crystallization proceeds, and a laminate film for battery exterior having excellent heat resistance and electrolytic solution resistance can be obtained.

  Hereinafter, a first adhesive layer, preferably a laminated film of the first adhesive layer and a sealant layer, is formed by an inflation molding method, and this is subjected to thermal lamination to form a barrier layer, preferably a base material layer, with the first adhesive layer. A method for producing the laminated film for battery exterior of the present invention by bonding to the bonded barrier layer will be described.

<Inflation molding>
Inflation molding is a method in which air or the like is placed in a melting tube made of a film forming material extruded from an annular die, inflated larger than the diameter of the annular die, and continuously taken and filmed while being cooled and solidified by air cooling or water cooling. Extrusion method.

  In the inflation molding method, the molten resin extruded from the extruder is formed into a tube shape, and the molten resin flows through an annular flow path using an inflation die. This flow path is between the outer die and the inner mandrel. Immediately after the molten resin film exits the annular die, air pressure is applied inside the tube to expand it. The expanded tube is configured to be tightened with a nip roll to maintain air pressure. The expanded tube (bubble) is cooled with air from the cooling ring above the die exit.

  Since the bubble grows in the extrusion direction (MD direction) and the circumferential direction (TD direction), the film speed at the nip roll must be much faster than the tube speed at the die exit. The film is stretched in the MD direction and expanded in the TD direction. The stretch ratio is expressed as the ratio between the final film speed and the initial speed, and the blow-up ratio is expressed as the ratio between the final tube diameter and the initial diameter (annular die diameter). The size of the blow-up ratio is from 1: 1 to 10: 1. A range is preferred, with a range of 1.3: 1 to 5: 1 being particularly preferred.

In general, polypropylene is often used as the resin for the battery exterior film from the viewpoint of heat resistance, and in order to emphasize low cost, it is manufactured by an extrusion lamination method, a sand lamination method, or a casting method. Often filmed polypropylene is used. However, since all of these films are formed by cooling the molten resin extruded from a T-shaped mold (strip-shaped resin discharge port), physical properties such as tensile strength, elongation, and tensile modulus in the MD and TD directions are obtained. Differences are likely to occur. Therefore, when used as a battery exterior film, at the time of press working or overhanging, wrinkles at the time of working tend to occur due to the difference in mechanical properties depending on the direction.
Further, as described above, since the highly elastic film of the base material layer is usually stretch-molded with a T-die, the difference in the MD / TD direction is likely to occur.

  For this reason, in the present invention, the second adhesive layer, and further the sealant layer, is difficult to produce a difference in physical properties in the MD / TD direction by inflation molding, and has a balance with the physical properties of the base material layer. In view of the above, it is preferable that the laminated film for battery exterior is formed by adjusting the blow-up ratio within the above range so as to eliminate anisotropy.

  As described above, the film formed by the inflation molding method is unlikely to have a difference in mechanical properties between the extrusion direction (MD direction) and the circumferential direction (TD direction) perpendicular to the extrusion direction, and is subjected to press processing and overhang processing. The laminated film has an advantage that wrinkles during processing are less likely to occur because there is little difference in mechanical properties depending on the direction.

  In addition, the resin raw material suitable for the inflation molding method requires characteristics such as a low MFR, a high molecular weight, a high melt tension, and a low processing temperature during film formation. The properties are different from those of resins used in extrusion laminating or sandwich laminating methods that are molded at high temperatures and require high MFR, high flow resin properties. For this reason, in the present invention, the above-mentioned low MFR resin is used as the acid-modified polyethylene resin of the second adhesive layer and the resin of the sealant layer, but these resins have low MFR property and high melt tension property. Therefore, there is an advantage that high seal strength can be easily obtained.

  In the present invention, in order to impart various properties such as mechanical properties, sealing properties, heat resistance, moldability, etc. as a battery exterior film while taking advantage of the low anisotropy of the film by the inflation molding method, By paying attention to the resin characteristics used in the method, and constructing the second adhesive layer having the specific resin and specific physical properties described above, the aluminum foil that is the barrier layer is made of aluminum without being subjected to chromium conversion treatment. A battery exterior laminate film having excellent adhesion to the foil, preventing the ingress of moisture, having excellent resistance to electrolyte solution and high sealing strength can be obtained.

<Thermal lamination method>
In the present invention, a second adhesive layer (second adhesive layer forming film) formed by an inflation method, preferably a laminated film of the second adhesive layer and a sealant layer is thermocompression bonded by a thermal lamination method. Adhesion with the barrier layer is important for improving the resistance to electrolytic solution.

  The thermal lamination method uses two or more rolls, sandwiches two or more films between the rolls, moves the film while rotating at least one roll, and heats the film while heating at least one roll. Is a laminating method in which the material is heated and bonded. In this method, the line speed is slower than in the dry lamination and extrusion lamination methods, but since the cooling process is not rapid, it is easy to create processing conditions that promote crystallization of the resin.

  In the present invention, an acid-modified polyethylene resin mainly composed of a high-density, high-crystalline linear low-density polyethylene is used for the second adhesive layer, and the second adhesive layer is melted by a thermal lamination method. By adopting the pressure bonding method, the second adhesive layer is crystallized, and further, the crystallized lamellar developed in the second adhesive layer is formed into a barrier layer by promoting crystallization by slowly cooling in the cooling process. As a result of producing strong adhesion to the metal foil, the adhesive strength is increased and the crystallization of the second adhesive layer is promoted, thereby improving the electrolytic solution resistance and heat resistance of the adhesive layer. Is obtained. The crystal lamella of the second adhesive layer particularly enters the pores of the boehmite film of the aluminum foil on which the boehmite film is formed, and realizes higher adhesive strength and electrolyte resistance.

FIG. 2 shows a laminated film 14 of a second adhesive layer and a sealant layer by a thermal lamination method, and a base material layer / barrier layer laminated film 12 in which the base material layer is laminated and integrated with the barrier layer in advance by the first adhesive layer. The second adhesive layer / sealant layer laminated film 14 and the base material layer / barrier layer fed from the wound body 13 of the second adhesive layer / sealant layer laminated film The base layer / barrier layer laminated film 12 fed from the laminated film wound body 11 and the heat resistant film 16 fed from the heat resistant film wound body 15 are heated and pressurized between the heating rolls 17A and 17B. Thus, the second adhesive layer side 14A of the second adhesive layer / sealant layer laminated film 14 and the barrier layer side 12A of the base material layer / barrier layer laminated film 12 are thermally laminated.
The heat-laminated laminate film 10 for battery exterior passes between the feed rolls 18A and 18B and is taken up by the take-up roll 20.
On the other hand, the heat-resistant film 16 is peeled off from the battery exterior laminate film 10 and wound up on a winding roll 19.

  In such a thermal lamination method, the heating temperature between the rolls 17A and 17B can be arbitrarily set at a temperature that reaches the temperature at which the second adhesive layer melts, but the heating temperature in the thermal lamination is the second temperature. The temperature of the adhesive layer side, that is, the temperature of the heating roll 17A and the temperature of the barrier layer side, that is, the temperature of the heating roll 17B, is the difference between the acid-modified polyethylene resin crystals of the second adhesive layer. This is preferable because the orientation is further enhanced, crystal growth in the thickness direction is promoted, and the barrier layer is more strongly bonded. In this case, the temperature on the second adhesive layer side, that is, the temperature of the heating roll 17A is 170 ° C. or higher, for example, 200 ° C. or higher and 260 ° C. or lower, and the temperature on the barrier layer side, that is, the temperature of the heating roll 17B is less than 170 ° C. For example, it is desirable that the temperature be 120 ° C. or higher and 165 ° C. or lower, and a temperature difference of 20 ° C. or higher, preferably 25 ° C. or higher and 70 ° C. or lower is applied to both. If the temperature of the heating rolls 17A and 17B is too low, sufficient adhesion cannot be performed. However, if the temperature is too high, the resin deteriorates or melts and flows to reduce the thickness of the adhesive layer, resulting in sufficient adhesion. There is a tendency to disappear. Moreover, if the temperature difference between the two is too small, the effect of promoting crystal growth by providing the temperature difference cannot be sufficiently obtained, and excessively increasing this temperature difference is the setting temperature of each heating roll. It is difficult to meet the conditions.

In addition, when thermal lamination is performed at such a high temperature, the resin of the sealant layer may be welded to the heating roll. The purpose of preventing this welding is to promote the growth of the crystal lamella of the second adhesive layer on the surface of the barrier layer and the growth of the crystal lamella to the second adhesive layer of the sealant layer, thereby further strengthening the adhesion between the layers. For the purpose, it is preferable to overlap the heat resistant film 16 on the further outer side (non-bonded surface) of the sealant layer as shown in FIG. 2 and to peel off the heat resistant film 16 after thermal lamination.
At this time, when a heat-resistant film having a surface roughness Ra of 0.1 μm or more and 1 μm or less, preferably 0.25 μm or more and 0.75 μm or less by matting or the like is used on at least the side of the heat-resistant film that comes into contact with the sealant layer. The heat-resistant film irregularities are thermally transferred to the sealant layer during thermal lamination, and appropriate irregularities are imparted to the surface of the sealant layer, which is preferable because the slipperiness with the mold necessary for embossing can be obtained.

  As the heat-resistant film 16, a film having heat resistance capable of withstanding the heating temperature during thermal lamination, for example, a film having a melting point of 200 ° C. or higher, preferably 220 to 350 ° C. is used. The same thermoplastic resin film as that of the base material layer can be used. The thickness of the heat-resistant film 16 is usually 25 μm or more and 125 μm or less. If the heat-resistant film is too thin, the crystal lamellae growth promoting effect due to the provision of the heat-resistant film may not be sufficiently obtained, and if it is too thick, the heating efficiency at the time of thermal lamination tends to deteriorate.

[Battery exterior materials]
The laminated film for battery exterior of the present invention can be processed into a battery exterior material according to a conventional method.
The battery exterior material forms an exterior body that wraps the battery body, and there are a pouch type and an emboss type depending on the type.

  FIG. 3 shows an embodiment of an embossed type exterior material. The first exterior material 31 is formed with a recess that serves as a housing portion 31b of the battery body 30, and a flange (flange) 31a is formed at the periphery of the opening. Has been. The second exterior material 32 is a lid material that covers the opening of the first exterior material 31. As for the 1st exterior material 31, the inner wall side of the accommodating part 31b becomes a sealant layer, and as for the 2nd exterior material 32, the contact surface side to the 1st exterior material 31 becomes a sealant layer. The battery is assembled by covering the second exterior member 32 with the first exterior member 31 with the electrode tabs 30A and 30B pulled out, and heat-sealing the periphery.

In addition to the embossed type exterior material having the recesses formed on one side in this way, there is a type in which the recesses are formed on both exterior materials. In addition, there is a type in which a lid piece portion corresponding to the second exterior material extends from the flange on one side of the first exterior material.
On the other hand, the pouch type has a bag shape such as a three-side seal type, a four-side seal type, and a pillow type.

  The laminate film for battery exterior of the present invention can be used as various battery exterior materials including embossed type, pouch type and the like.

[battery]
The battery of the present invention is one in which a battery body is enclosed in an exterior material made of the laminate film for battery exterior of the present invention, and in various batteries such as lithium batteries and fuel cells, it is light, thin, small, and low in cost. In addition, long-term durability and reliability can be improved.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

In the following examples and comparative examples, the materials used for forming the second adhesive layer and the sealant layer are as follows.
In any of the acid-modified LLPE-1 to LLPE-4 used as the second adhesive layer, the main component LLPE having butene-1 as a side chain was used.

[Examples 1-9, Comparative Examples 1-3]
A laminate film for battery exterior was produced by the following method.
As the barrier layer, a JIS 8079-O material (soft aluminum foil containing 1.0% by weight of iron) having a thickness of 40 μm subjected to boehmite treatment was used.
Boehmite treatment was performed by immersing the aluminum foil in 95 ° C boehmite treated water in which triethanolamine was added to deionized water at a concentration of 0.5% by weight for 1 minute. A needle-like crystal film was formed.

  Next, as a base material layer, a biaxially stretched polyamide film (tensile elastic modulus: 2500 MPa) having a thickness of 25 μm and a surface roughness Ra of 0.03 μm and subjected to a single-sided corona treatment is used. One side of the aluminum foil and the corona-treated side of the biaxially stretched polyamide film were bonded to each other through an adhesive layer (first adhesive layer) for a two-component mixed dry dry with isocyanate.

  The film of the second adhesive layer and the sealant layer is made of the material shown in Table 2, and the second adhesive layer is extruded from an extruder having a diameter (barrel inner diameter) of 75 mm, and the sealant layer is extruded from an extruder having a diameter of 55 mm. Using a layer coextrusion inflation molding machine, extrusion molding was performed from a spiral annular die having an annular die diameter of 300 mm and a die gap of 3 mm so that the second adhesive layer would be on the outside of the tube, a tube diameter of 560 mm, a blow-up ratio of 1.87, The second adhesive layer / sealant layer is adjusted while adjusting the extrusion amount so that the second adhesive layer and the sealant layer have the predetermined thicknesses shown in Table 1, respectively. A two-layer laminated film was formed.

  Using the two-layer laminated film of the second adhesive layer / sealant layer obtained by the method described above, the biaxially stretched nylon film so that the surface of the second adhesive layer is on the aluminum foil side as shown in FIG. / Laminated laminate film of aluminum foil and thermal lamination method. In this thermal lamination, the temperature of the heating roll 17A on the second adhesive layer / sealant layer laminated film side was 230 ° C., and the temperature of the heating roll 17B on the biaxially stretched nylon film / aluminum foil laminated film side was 160 ° C. As the heat-resistant film 16, a 75 μm thick PET film (melting point: 260 ° C.) was used. The surface of the PET film in contact with the sealant layer has irregularities with a surface roughness Ra of 0.06 μm.

The laminate film for battery exterior obtained in this way was evaluated for laminate strength, sealant strength, and electrolytic solution resistance by the following methods, and the results are shown in Table 2.
In addition, the unevenness | corrugation of surface roughness Ra0.06micrometer was formed in the sealant layer surface of the obtained laminate film for battery exteriors by the surface unevenness | corrugation of PET film used as a heat resistant film.

<Lamination strength>
For the laminate strength between the aluminum foil and the second adhesive layer, a sample cut into a strip shape with a width of 15 mm was used, and the 180 ° peel strength at the interface between the aluminum foil and the second adhesive layer was measured using a Tensilon tensile test. It measured on the conditions of the tension speed of 50 mm / min using the machine, and this value was made into laminate strength.

<Seal strength>
The sealant layers of the two laminate films for battery exterior that were cut in advance to 65 mm × 65 mm were used at 220 ° C. over a seal width of 10 mm and a length of 65 mm using a heat sealer “OPL-200-10” with a single-side heater manufactured by Fuji Impulse. Then, heat sealing was performed under the conditions of a sealing pressure of 0.15 MPa and a heat sealing time of 5 seconds, and then the sealing portion was cut into a strip having a width of 15 mm to obtain a sample for measuring the sealing strength.
The seal strength was measured at a tensile speed of 300 mm / min using a Tensilon tensile tester so as to peel off the sealant layers of the sample for measuring the seal strength.

<Electrolytic solution resistance (laminate strength and seal strength after immersion in electrolytic solution)>
Using ethylene carbonate: diethyl carbonate: dimethyl carbonate = 1: 1: 1 (volume ratio) as a mixed solvent, 1 mol of lithium hexafluorophosphate was dissolved in this mixed solvent, and 1 mol / L of lithium hexafluorophosphate was dissolved. A solution electrolyte was prepared.
This electrolytic solution is put into a blow bottle made of PFA (perfluoroalkoxy fluororesin), and the above-mentioned seal strength measurement sample and unsealed laminate strength measurement sample are put in the electrolytic solution, and the lid is closed. The heat cycle of leaving in a constant temperature water bath at 80 ° C. for 12 hours and then returning to room temperature and returning to room temperature for 12 hours is repeated three times (total 80 ° C. for 36 hours and room temperature for 36 hours), then the sample is taken out, washed with water, Similarly, laminate strength and seal strength were measured.

From Table 2, the laminate film for battery exterior having the second adhesive layer made of the acid-modified polyethylene resin satisfying the MFR, density, and tensile modulus defined in the present invention has interlayer adhesion, sealability, heat resistance, and resistance. It turns out that it is excellent in electrolyte solution property. In contrast, Comparative Examples 1 to 3 in which the second adhesive layer is made of polypropylene are inferior in heat resistance and electrolytic solution resistance.
In Table 2, “Comprehensive evaluation” was determined based on the following criteria as a battery exterior laminate film.
○: Laminate strength and seal strength are excellent.
Δ: Laminate strength and seal strength are at a usable level.
X: Laminate strength and seal strength are insufficient.

DESCRIPTION OF SYMBOLS 1 Base material layer 2 1st contact bonding layer 3 Barrier layer 4 2nd contact bonding layer 5 Sealant layer 10 Laminate film for battery exterior 12 Base material layer / barrier layer laminated film 14 2nd adhesion layer / sealant layer laminated film 16 Heat resistance Films 17A, 17B Heating roll 30 Battery body 31 First exterior material 32 Second exterior material

[1] at least a base material layer, a first adhesive layer, a barrier layer, a second adhesive layer, a sealant layer is a method for producing a battery exterior laminate film which are stacked in this order, the barrier layer and the and a sealant layer comprising a heat lamination step of laminating by thermal lamination through the second adhesive layer, the heat lamination process, repeated melting point 200 ° C. or more heat-resistant film to the non-bonding surface of the sealant layer side heat lamination Te, then, the production method of the laminate film for that electrostatic Ikegaiso be characterized by for peeling the heat-resistant film from the sealant layer.
[2] In the thermal lamination step, the temperature on the base material layer side of the laminate film for battery exterior obtained is less than 170 ° C., the temperature on the sealant layer side is 170 ° C. or higher, and the temperature on the base material layer side The method for producing a laminate film for battery exterior according to [1], wherein the temperature difference on the sealant layer side is 20 ° C. or more.
[3] An inflation molding step of forming a second adhesive layer forming film by an inflation molding method in which the film forming material of the second adhesive layer is extruded from an annular die, and in the thermal lamination step, The method for producing a laminate film for battery exterior according to [1] or [2], wherein the adhesive layer-forming film is bonded to the barrier layer by a thermal lamination method.
[4] In [3], in the inflation molding step, coextrusion inflation molding is performed in which the film forming material of the second adhesive layer is coextruded from an annular die together with the film forming material of the sealant layer. The manufacturing method of the laminated film for battery exterior of description.

Claims (10)

At least a base material layer, a first adhesive layer, a barrier layer, a second adhesive layer, and a sealant layer are laminated in this order, and the second adhesive layer is a linear low It consists of a polyethylene resin whose main component is density polyethylene (LLPE), at least a part of the polyethylene resin is acid-modified, and has an MFR of 0.1 g / 10 min or more and 3 g / 10 min or less, and a density of 0.920 g / cm ³ or more. A laminate film for battery exterior having 0.950 g / cm ³ or less and a tensile elastic modulus of 100 MPa or more and 1000 MPa or less. Wherein the sealant layer to main component LLPE, MFR0.1g / 10min or 3 g / 10min or less, characterized by having a layer made of a density 0.920 g / cm ³ or more 0.950 g / cm ³ or less of the resin Item 2. A laminated film for battery exterior according to Item 1.   The laminate film for battery exterior according to claim 1 or 2, wherein the sealant layer has a higher density layer than the second adhesive layer.   The battery barrier laminate film according to any one of claims 1 to 3, wherein the barrier layer is made of an aluminum foil that is not subjected to chromium-based chemical conversion treatment.   5. The laminated film for battery exterior according to claim 1, wherein the barrier layer is made of an aluminum foil having a boehmite film formed on a surface thereof.   An inflation molding step of forming the second adhesive layer forming film by an inflation molding method in which the film forming material of the second adhesive layer is extruded from an annular die, and thermal lamination of the second adhesive layer forming film A method for producing a laminated film for battery exterior according to any one of claims 1 to 5, further comprising a thermal lamination step of bonding to the barrier layer by a method.   The battery according to claim 6, wherein in the inflation molding step, coextrusion inflation molding is performed in which the film forming material of the second adhesive layer is coextruded from an annular die together with the film forming material of the sealant layer. A method for producing a laminate film for exterior use.   In the thermal lamination step, the temperature of the base material layer side of the laminate film for battery exterior obtained is less than 170 ° C., the temperature of the sealant layer side is 170 ° C. or more, and the temperature of the base material layer side and the sealant layer side The method for producing a laminate film for battery exterior according to claim 6 or 7, wherein the temperature difference is 20 ° C or more.   In the thermal lamination step, when the barrier layer and the sealant layer are bonded through the second adhesive layer, a heat-resistant film having a melting point of 200 ° C. or higher is laminated on the non-bonded surface on the sealant layer side, and heat lamination is performed. Thereafter, the heat-resistant film is peeled from the sealant layer. The method for producing a laminate film for battery exterior according to any one of claims 6 to 8.   A battery comprising the laminate film for battery exterior according to any one of claims 1 to 5.

Images