JP3594849B2 - Battery packaging material - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
This invention relates to superior batteries packaging material corrosion resistance.
[0002]
[Prior art]
Conventionally, packaging materials using aluminum foil have been used mainly for packaging and packing foodstuffs, beverages, medicines, daily necessities, various parts, and the like. There has been a configuration in which an acrylonitrile resin or the like is laminated as a layer, but these resins are very expensive and are hardly popular as packaging materials. A configuration in which nylon or EVOH is laminated has also been proposed, but there is a limit in terms of performance. If the number of laminated layers is increased or the thickness is increased in order to improve corrosion resistance, the cost will eventually increase. On the other hand, a method of coating an aluminum foil with a silane coupling agent or a titanate-based treating agent has been proposed, but it has been practically used due to problems such as difficulty in uniform application and limited contents. Not converted. Until now, there have been few attempts to modify the surface of the aluminum foil itself in the field of packaging materials. Further, conventional resins laminated with aluminum foil, such as nylon and EVOH, have problems in adhesiveness and adhesive strength with aluminum foil, and have been difficult to withstand long-term use.
[0003]
[Problems of the Invention]
Therefore, an object of the present invention is to improve the corrosion resistance by modifying the surface of the aluminum foil itself by a simple method. Another object of the present invention is to provide a battery packaging material using an aluminum foil having improved corrosion resistance.
[0004]
[Means for solving the problem]
In order to solve the above-mentioned problems, the battery packaging material of the present invention has at least one surface thereof formed of at least one solution selected from phosphoric acid, phosphate, chromate, chromate, hydrofluoric acid, and hydrofluoric acid. The structure in which the treated aluminum foil and the random copolymer resin layer of polyethylene and polypropylene as the innermost layer of the thermal adhesive resin were laminated was adopted. It is preferable to further heat-treat the aluminum foil treated as described above.
[0005]
For laminating a random copolymer resin layer of the previous SL aluminum foil and polyethylene and polypropylene, a blend resin of polyethylene and random copolymers are not acid-modified polypropylene resins or acid-modified polypropylene and thermosetting epoxy resin, It is preferable to use any one or more of the above.
[0006]
Embodiment
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0007]
As shown in FIG. 1, an aluminum foil 1 for a battery packaging material of the present invention has a chemically treated film 3 formed on an aluminum substrate 2.
[0008]
Known aluminum foils and aluminum plates can be used for the aluminum substrate 2, and known components of pure aluminum and aluminum alloy can also be used. Specifically, it is preferable to use an aluminum foil having a thickness of about 15 to 150 μm. If the thickness is less than 15 μm, deformation or cracks may occur during the later-described process, and should be avoided. On the other hand, if the thickness exceeds 150 μm, it is not preferable in terms of cost, flexibility, moldability, and weight increase as a packaging material. In addition, the purity of aluminum is not particularly limited, and a known material such as pure aluminum for industrial use and alloys such as (JIS) 3003, 3004, 5052, 8021, and 8079 can be used. It can be used. As for the refining, any of an annealed material (O material), an as-rolled material (H material), and an intermediate material thereof (semi-hard material) can be applied, and can be appropriately selected according to required characteristics. Further, if necessary, washing may be performed with water, a detergent, an acid, an alkali or an organic solvent.
[0009]
The corrosion-resistant aluminum foil 1 can be provided by forming the chemical treatment film 3 on at least a part or more, preferably on one or both sides of the aluminum substrate 2. When the treatment is performed on one side, the treatment may be performed on the side to be the inner surface of the container or the bag. As the treating agent, at least one selected from phosphoric acid, chromic acid, hydrofluoric acid, phosphate, chromate, and hydrofluoric acid is used. The concentration of the treating agent is preferably 0.02% by weight to 30% by weight, and the remainder may be a solvent. As the solvent, water, alcohol (methanol / ethanol / propanol / hexanol / pentanol) or the like can be used. If necessary, oxalic acid, sulfuric acid, water glass (silicic acid), heavy metal acids and their salts and compounds can also be added. Further, if necessary, an appropriate amount of a pH adjuster, a viscosity adjuster, or the like may be added. The treatment method and conditions may be appropriately determined according to the type and concentration of the treatment agent and the like, and the present invention is not limited thereto.For example, application by a roll coater, bar coater, doctor blade, etc., spray coating, brush coating, It can be treated by means such as immersion. The amount of coating and the treatment time are not particularly limited as long as the chemical film 3 is formed on the aluminum base material 2. However, in the case of the dipping method, it is preferably about 1 second to 600 seconds. (Weight) about 0.5 g to 50 g / m ² is appropriate. The processing temperature (solution temperature) is preferably from room temperature to about 90 ° C. After the treatment, water washing, natural drying, hot-air drying and the like may be performed as necessary.
[0010]
Although the corrosion resistance of the aluminum foil 1 is improved by the chemical film treatment, when the aluminum foil 1 is to be further improved, the treated aluminum foil may be dried and heat-treated at 120 to 300 ° C, preferably 150 to 250 ° C. If the temperature is lower than 120 ° C., the effect of heating is poor, and it is considered that the treating agent does not sufficiently react with the aluminum surface. On the other hand, even if heat treatment is performed at a temperature exceeding 300 ° C., the effect tends to be poor, and it is considered that the chemical treatment film 3 may be partially cracked due to overheating. The heating method may be either a continuous method or a batch method, and is not particularly limited. However, it is preferable that the heating is performed at a set temperature for about 10 seconds to 30 minutes. By the heat treatment, the chemically treated film 3 becomes stronger and the corrosion resistance and the film adhesion are improved. Note that the same effect can be obtained even if this heat treatment is performed during the later-described manufacturing process of the laminate.
[0011]
Although the above-mentioned aluminum foil 1 exhibits excellent corrosion resistance as a battery packaging material, it is necessary to consider a heat-adhesive resin (film) used for the innermost layer forming the package for more stable use over a long period of time. is there. Conventionally, homopolypropylene or block copolymer type resins have been used as the innermost layer of the heat-adhesive resin.However, these resins are cracked during molding or over time in the form of the final product, and the electrolytic solution Leaks may occur. In the present invention, as shown in FIG. 2, a random copolymer resin (film) layer 4 of polyethylene and polypropylene is formed and used as a packaging material 1a. By laminating the resin layer 4, stable use can be endured for a long time. In this case, the polypropylene resin may be an acid-modified polypropylene or a normal non-acid-modified polypropylene, but the former acid-modified polypropylene resin is more preferable. The thickness of the heat-adhesive resin layer (film) 4 is preferably from 10 to 70 μm, and if it is less than 10 μm, it is difficult to obtain a sufficient adhesive force. It does not need to be unnecessarily thick because it causes it. The heat sealing conditions can be appropriately selected depending on the lamination structure and lamination thickness, but are usually from 140 to 260 ° C. for about 1 to 3 seconds. In addition, a ring seal (also referred to as a line seal) in which the cross-sectional shape after sealing becomes concave can be implemented.
[0012]
As shown in FIG. 3, as an adhesive (anchor coating agent) layer 5 used for laminating the chemically treated aluminum foil 1 and the heat-adhesive resin layer (film) 4, (A) polyethylene was randomly copolymerized. An adhesive using at least one of an acid-modified polypropylene resin and (B) a blend resin of an acid-modified polypropylene and a thermosetting epoxy resin enhances flexibility and initial adhesion, and prevents cracking and resistance. The content properties can be improved. Preferred coating weight of the adhesive, with (weight after ^{drying) 0.1g / m 2 ~5g / m} 2, it is desirable to perform about 10 seconds to 30 minutes drying at 60 to 200 degree ℃ after application. The acid-modified polypropylene resin refers to a polypropylene modified with maleic anhydride, phthalic anhydride, citraconic anhydride, acrylic acid, itaconic acid, citraconic acid, or the like. The epoxy resin is an organic polymer compound having one or more epoxy groups in a molecule, for example, a bisphenol A type epoxy resin, a resole type epoxy resin, a glycerin triether type epoxy resin, and other so-called fats. It refers to a cyclic epoxy resin and the like, and further includes derivatives thereof. As the curing agent, any one or more of isocyanates, amines, acid anhydrides, polyamide resins, phenol resins, and butylated urea-formaldehyde resins can be used.
[0013]
As described above, the aluminum foil 1, the heat-adhesive resin layer 4, and the adhesive layer 5 which have been subjected to the chemical film treatment are the main components of the battery packaging material 1a. One or more intermediate resin films may be further laminated between the resin film or the aluminum foil 1 subjected to the chemical film treatment and the heat-adhesive resin layer 4 as long as the effects of the present invention are not impaired.
[0014]
As the exterior resin film / intermediate resin film, a resin film having a thickness of 9 μm or more, preferably 12 to 50 μm, specifically, one or more of polyamide, high-density polyethylene, polypropylene, PET (polyethylene terephthalate) and the like can be used. . The method of laminating and bonding the exterior resin film / intermediate resin film is not particularly limited, and is a known method, for example, dry lamination using a two-component curable urethane-based adhesive, coextrusion, extrusion coating, anchoring. A method such as heat lamination using a coating agent can be employed.
[0015]
If necessary, an anchor coat layer, a print layer, a decorative layer, an overcoat layer, an adhesive layer, and the like may be further formed on an arbitrary layer.
[0016]
After laminating the above components, a final heat treatment may be performed, if necessary, to further improve the adhesive strength of each layer. In this case, the processing temperature is about 60 to 180 ° C., and preferably about 10 seconds to 10 minutes.
[0017]
When the packaging material 1a of the present invention is formed into a container, a known press machine, for example, a hydraulic press, a mechanical (crank) press, a hydraulic press, a manual press, or the like can be used, and is not particularly limited. Usually, it is preferable to press-mold using a mold, a wooden mold, a resin mold and the like. The shape and size of the molded container are appropriately set according to the application and purpose. On the other hand, when used as a bag, it can be formed into a known form, for example, a flat bag, a square bag, a self-standing bag, a gusset bag, a pillow bag, or the like.
[0018]
The aluminum foil 1 and the packaging material 1a of the present invention are particularly useful as containers and bags for batteries such as organic electrolyte batteries.
[0019]
[Examples and Comparative Examples]
Chemical coating treatment on the entire surface of a 50 μm thick raw aluminum foil (1N30: manufactured by Toyo Aluminum Co., Ltd.) using a 0.2% by weight aqueous solution of the treatment agent described in the table by an immersion method (weight before drying: 10 g / m ² applied). Was given. After the treatment, the substrate was kept at the drying temperature shown in FIG. 4 for 30 seconds, and was subjected to drying and heat treatment. The adhesive shown in FIG. 4 was roll-coated on one surface of the treated aluminum foil to a weight of 2 g / m ² after drying. After the drying treatment (holding time: 30 seconds) at the temperature shown in FIG. 4, the heat-adhesive resin (thickness: 50 μm) shown in FIG. On the other side of the treated aluminum foil, after drying the adhesive for dry lamination (manufactured by Toyo Morton Co., Ltd.), apply a weight of about 4 g / m ^2, and apply a 15 μm thick nylon film (manufactured by Toyo Boseki Co., Ltd.) to the outer protective resin. And bonded together. After the production of the laminated material by the above steps, a final heat treatment (holding time: 30 seconds) was performed at the temperature shown in FIG. 4 as necessary, to produce a battery packaging material.
[0020]
Each packaging material shown in FIG. 4 was cut into 150 × 150 mm, and a recess having a size of 80 × 80 × 5 mm in depth was press-formed at the center thereof to obtain a container. 30 ml of the following solvent and electrolyte were injected into the recess, and the container having the same configuration was heat-sealed (square sealing) at 160 ° C. for 1 second using the same container as a lid, and then dried at 60 ° C. (dry state) at 40 ° C. and 90% humidity for 7 days. After standing, the package was opened and the inner surface of the laminate was observed.
[0021]
The solvent used was a mixture of diethyl carbonate and ethylene carbonate at a volume ratio of 1: 1. As the electrolyte (electrolyte solution), a solution prepared by dissolving 1 mol / liter of electrolyte lithium hexafluorophosphate (LiPF6) in the solvent was used. . In addition, the laminate strength of the packaging material was inspected. That is, the peel strength between the aluminum foil and the heat-adhesive resin layer (film) was determined before and after the standing (test) by a T-type peel test (JIS K 6854, where the test piece had a width of 15 mm, and was not particularly described in this specification. The pretreatment was not performed.).
[0022]
In the evaluation in FIG. 4, the case where no corrosion of the aluminum foil was observed and the decrease in the laminate strength was 30% or less was evaluated as ○, and the case where the decrease in the laminate strength exceeded 30% and 50% or less was evaluated as Δ. A part was corroded (discolored) or a decrease in laminate strength of more than 50% was evaluated as x.
[0023]
In FIG. 4, the phosphorus / chromium system is a mixture of phosphoric acid and chromic acid at a weight ratio of 1: 1 and the chromium / hydrofluoric acid system is a mixture of chromic acid and hydrofluoric acid at a weight ratio of 1: 1. The acid-modified PP was a random copolymer resin of polyethylene and acid-modified polypropylene (manufactured by Mitsui Chemicals, Inc.), and the epoxy / PP was a blend of a thermosetting epoxy resin and acid-modified polypropylene (solid content ratio 2: 1). , Blended by Toyo Aluminum Co., Ltd.), random PP is a random copolymer resin of polyethylene and polypropylene (manufactured by Tosero Corporation), and homo PP is a homopolypropylene manufactured by Tosero Corporation.
[0024]
【effect】
Batteries packaging material of the present invention, improves the corrosion resistance by a simple process without the use of special films, etc., it can be maintained for a long time laminate strength close to the initial state, to provide a long battery life be able to. In addition, there is no significant difference in cost from conventional packaging materials, and there is an advantage that it can be easily manufactured without requiring special equipment.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of an aluminum foil for a battery packaging material of the present invention. FIG. 2 is a cross-sectional view showing an example of a battery packaging material. FIG. 3 is a cross-sectional view showing another example of a battery packaging material. Table showing the laminated structure and test results of the examples and comparative examples.
DESCRIPTION OF SYMBOLS 1 Aluminum foil for packaging materials 1a Battery packaging material 2 Aluminum base material 3 Chemical treatment film 4 Thermal adhesive resin 5 Adhesive layer

Claims (3)

At least one surface of the aluminum foil treated with at least one solution selected from phosphoric acid, phosphate, chromate, chromate, hydrofluoric acid, and hydrofluoric acid, and polyethylene as the innermost layer of a thermo-adhesive resin. Battery packaging material laminated with a random copolymer resin layer with polypropylene . At least one surface is treated with at least one solution selected from phosphoric acid, phosphate, chromate, chromate, hydrofluoric acid, and hydrofluoric acid, and further heat-treated with an aluminum foil and an innermost layer having a thermal adhesive property. A battery packaging material in which a random copolymer resin layer of polyethylene and polypropylene is laminated as a resin. 3. An adhesion between the aluminum foil according to claim 1 and a random copolymer resin layer of polyethylene and polypropylene, and an acid-modified polypropylene resin randomly copolymerized with polyethylene, or an acid-modified polypropylene resin and a thermosetting epoxy resin. Battery packaging material using any one or more of blended resins.

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