JP2012164565A - Laminate for battery outer packaging and secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-fusible laminate for a battery outer packaging, comprising a stainless steel sheet laminated with a heat-fusible resin layer, excellent in adhesion of the heat-fusible resin layer and less in environmental loads.SOLUTION: A laminate for a battery outer packaging is obtained by forming an organic/inorganic composite process layer on a surface of a stainless steel sheet, and then forming a heat-fusible polyolefin resin layer on the organic/inorganic composite process layer. The organic/inorganic composite process layer comprises a cured product of a resin composition containing a carboxyl group-containing resin, an oxazoline group-containing resin and a basic phosphate compound.

Description

  The present invention relates to a battery outer laminate and a secondary battery using the battery outer laminate.

  Secondary batteries such as nickel-cadmium batteries, nickel-hydrogen batteries, and lithium-ion batteries are widely used in electronic devices and electronic parts such as mobile phones, notebook personal computers, video cameras, electric vehicles, satellites, and social infrastructure components. Has been. In particular, since lithium ion secondary batteries are excellent in energy density and output characteristics, they are frequently used in mobile phones and mobile devices that are required to be small and lightweight. Conventionally, aluminum alloys have been used for the packaging members of these small batteries from the viewpoints of lightness, formability, and cost.

  In recent years, secondary batteries have also been adopted in large equipment such as electric vehicles, hybrid vehicles, and storage batteries for solar cells. In these batteries for large equipment, it is necessary to increase the amount of the electrolyte in order to improve the output capacity, and the battery size is also large. Such a large battery packaging member is required to have safety (fastness, durability, etc.) higher than that of the small battery packaging member.

  Conventionally, since aluminum alloys that have been used as battery packaging members have low rigidity, it has been necessary to increase the plate thickness in order to increase pressure resistance against an increase in pressure inside the battery. In addition, since the aluminum alloy is inferior in buckling resistance, an auxiliary bundling member is required when using the flange portion around the case when bundling and fixing the battery cells. Therefore, when an aluminum alloy is used as a battery packaging member, there is a limit to space saving and cost reduction of the battery. Furthermore, since the aluminum alloy has a large coefficient of thermal expansion, there is also a problem that a large thermal shock is applied to the packaging member due to heat generation during charging and discharging.

  As means for solving the above problems, it has been proposed to use a stainless steel plate as a battery packaging member (for example, see Patent Document 1). In Patent Document 1, a battery member (a positive electrode, a negative electrode, a separator, an electrolytic solution, etc.) is accommodated in a case member obtained by forming an austenitic stainless steel plate, and the case members are joined together by seam welding. And manufacturing a battery.

  Since the battery exterior material made of a stainless steel plate described in Patent Document 1 has high strength and a small coefficient of thermal expansion, the above problems can be solved. However, when a battery is manufactured using the battery exterior material described in Patent Document 1, since the battery member is welded in a state of being accommodated in the case, the battery member (particularly, a resin separator) is deteriorated by welding heat. There is a risk of it. In addition to the battery disclosed in Patent Document 1, in a battery using a case made of a metal such as a stainless steel plate, the internal pressure of the container may increase excessively during use and the container may burst. In order to prevent an excessive increase in the internal pressure of the container, a safety valve may be provided. However, since the safety valve has a complicated structure, the manufacturing cost increases.

  As a means for solving the problems of the welding heat and the manufacturing cost, it has been proposed to use a laminate of a stainless steel plate and a heat-fusible resin film for a battery packaging member (see, for example, Patent Document 2). . Patent Document 2 describes a resin-coated stainless steel plate in which an acid-modified polyolefin resin film is laminated on a chromate-treated stainless steel plate. A battery member is manufactured by housing a battery member (a positive electrode, a negative electrode, a separator, an electrolytic solution, etc.) inside a case member made of this resin-coated stainless steel plate, and joining the case members together by heat fusion. In the technique of Patent Document 2, since the case members are joined not by welding but by heat fusion, the battery member does not deteriorate due to welding heat. Moreover, the joint strength by heat fusion is much smaller than the joint strength by welding. Therefore, even if the internal pressure of the container rises excessively, the case member is separated at the heat-sealing surface, so that no safety valve is required.

JP 2004-52100 A JP 2007-168184 A

  In the resin-coated stainless steel plate described in Patent Document 2, a chromate treatment layer is formed in order to ensure adhesion of the heat-fusible resin film. This chromate treatment layer is formed using a treatment liquid containing hexavalent chromium which has a large environmental load. Therefore, the resin-coated stainless steel sheet described in Patent Document 2 has a problem that the environmental load is large.

  The present invention has been made in view of the above points, and is a heat-sealable laminate for battery exterior in which a heat-sealable resin layer is formed on a stainless steel plate, and the adhesion of the heat-sealable resin layer. An object of the present invention is to provide a battery exterior laminate that is excellent in environmental impact and has a low environmental impact.

  The present inventor forms an organic-inorganic composite treatment layer comprising a cured product of a resin composition containing a carboxyl group-containing resin, an oxazoline group-containing resin, and a basic phosphoric acid compound on the surface of a stainless steel plate, and heat-melted thereon. It has been found that the adhesiveness of the heat-fusible resin layer can be improved without using hexavalent chromium by forming the adhesive resin layer, and further studies have been made to complete the present invention.

That is, the first of the present invention relates to the following battery laminate.
[1] A stainless steel plate having a first surface and a second surface; a resin containing a carboxyl group-containing resin, an oxazoline group-containing resin, and a basic phosphate compound formed on the first surface of the stainless steel plate A laminate for battery exterior, comprising: an organic / inorganic composite treatment layer comprising a cured product of the composition; and a heat-fusible polyolefin resin layer having a thickness of 10 to 100 μm formed on the surface of the organic / inorganic composite treatment layer. .
[2] The organic-inorganic composite treatment layer contains 5 to 800 mg / m ² of the resin component of the cured product, and 0.1 to 100 mg / m ² of the phosphorus component of the cured product in terms of phosphorus. 1] The battery exterior laminate according to 1).
[3] The ratio of the oxazoline group-containing resin to the total amount of the carboxyl group-containing resin and the oxazoline group-containing resin in the resin composition is in the range of 2.0 to 50.0 mass%, [1 ] Or the battery outer laminate according to [2].
[4] The battery exterior laminate according to any one of [1] to [3], wherein the acid value of the carboxyl group-containing resin is 300 mgKOH / g or more in terms of resin solid content.
[5] The resin composition further contains a basic zirconium compound; the organic-inorganic composite treatment layer contains 0.5 to 60 mg / m ² of a zirconium component of the cured product in terms of zirconium [1] to The laminated body for battery exterior as described in any one of [4].
[6] The battery exterior laminate according to [1], further comprising an acid-modified polyolefin resin layer having a thickness of 10 to 100 μm between the organic-inorganic composite treatment layer and the heat-fusible polyolefin resin layer. body.
[7] The laminated body for battery exterior according to [1], wherein the stainless steel plate has a thickness in the range of 20 to 400 μm.
[8] The laminate for battery exterior according to [1], further including a resin layer formed on the second surface of the stainless steel plate.

The second of the present invention relates to the following secondary battery.
[9] A secondary battery having a case formed by heat-sealing a molded product of the battery exterior laminate according to [1].

  ADVANTAGE OF THE INVENTION According to this invention, the laminated body for battery exteriors excellent in the adhesiveness of the heat-fusible resin layer can be manufactured, without using hexavalent chromium. Therefore, according to this invention, the laminated body for battery exterior excellent in the adhesiveness of the heat-fusible resin layer can be manufactured with a smaller environmental load.

1. Battery exterior laminate The battery exterior laminate of the present invention is a laminate comprising a stainless steel plate, an organic-inorganic composite-treated layer, and a heat-sealable polyolefin resin layer. The organic-inorganic composite treatment layer is formed on the surface of the stainless steel plate. The heat-fusible polyolefin resin layer is directly bonded to the surface of the organic-inorganic composite treatment layer, or is bonded to the surface of the organic-inorganic composite treatment layer via an acid-modified polyolefin resin. In this specification, among the surfaces of the stainless steel plate, the surface on which the organic-inorganic composite treatment layer and the heat-fusible polyolefin resin layer are formed is referred to as “first surface”, and the opposite surface is referred to as “second surface”. The face of "." When the battery exterior laminate of the present invention is applied to a secondary battery, the first surface is an inner surface (electrolyte side surface), and the second surface is an outer surface (external surface side surface).

  Hereinafter, each component will be described.

(1) Stainless steel plate The type of stainless steel constituting the stainless steel plate is not particularly limited, such as austenitic, ferritic, and martensitic. Examples of the steel types include SUS304, SUS430, SUS316, and the like. Further, the type of surface finish of the stainless steel plate is not particularly limited. Examples of types of surface finish include BA, 2B, 2D, No. 4, HL, and the like.

  The plate thickness of the stainless steel plate can be appropriately set according to the required weight, required strength, required processing depth, etc., as the battery exterior material. From the viewpoint of reducing the weight of the battery exterior material, the thinner the plate thickness, the better. However, the thinner the plate thickness, the lower the strength and workability, and the manufacturing cost increases. From the viewpoint of securing the strength as the battery exterior material, the plate thickness is preferably 20 μm or more. Even when a deep drawing process of about 50 mm is performed, a thickness of 400 μm is sufficient. Considering generally required strength and processing depth of the battery outer packaging material, the thickness of the stainless steel plate is preferably in the range of 40 to 150 μm.

(2) Organic-inorganic composite treatment layer The organic-inorganic composite treatment layer is formed on the first surface of the stainless steel plate. The organic-inorganic composite treatment layer is made of a stainless steel plate and a heat-fusible polyolefin-based resin layer (or acid-modified polyolefin-based resin layer) firmly adhered to each other. Responsible for preventing deterioration.

  The organic / inorganic composite treatment layer is formed of a cured product of a resin composition containing a carboxyl group-containing resin (A), an oxazoline group-containing resin (B), and a basic phosphoric acid compound (C). The carboxyl group-containing resin (A), the oxazoline group-containing resin (B), and the basic phosphoric acid compound (C) form a three-dimensional network structure by coordination bonds and chemical bonds, and are bonded to each other. Bond or adhere firmly. Specifically, the basic phosphate compound (C) is firmly bonded or adhered to the stainless steel plate to form an inorganic treatment layer, and the carboxyl group of the resin (A) and the oxazoline group of the resin (B). It also functions as a reaction catalyst. As a result, an organic-inorganic composite treatment layer having high crosslink density and excellent chemical resistance derived from the three components of carboxyl group-containing resin (A), oxazoline group-containing resin (B) and basic phosphoric acid compound (C) is formed. Is done. Moreover, the polar group (carboxyl group, hydroxyl group, etc.) which resin (A) has improves the adhesiveness of an organic inorganic composite process layer and a heat-fusible polyolefin resin layer (or acid-modified polyolefin resin layer).

  The resin composition preferably further contains a basic zirconium compound (D). By containing a basic zirconium compound in the resin composition, the bond between the resins can be further strengthened by metal crosslinking. Further, the basic zirconium compound (D) reacts with the basic phosphoric acid compound (C) to form an insoluble zirconium phosphate salt and further improves the barrier property of the organic-inorganic composite treatment layer. The film-forming property and barrier property of the inorganic composite treatment layer, and the adhesion between the organic-inorganic composite treatment layer and the heat-fusible polyolefin resin layer (or acid-modified polyolefin resin layer) can be improved.

  The organic-inorganic composite treatment layer exhibits poor solubility in water, an acidic aqueous solution containing an acid component (such as hydrofluoric acid), an organic solvent, and the like. In the organic / inorganic composite treatment layer, the three components (A) to (C) or the four components (A) to (D) act synergistically, so that the liquid electrolyte and the solid organic electrolyte are deteriorated. It has excellent resistance to the electrolyte and can maintain strong adhesion between the organic-inorganic composite treatment layer and the heat-fusible polyolefin resin layer (or acid-modified polyolefin resin layer).

The organic-inorganic composite treatment layer contains the resin component of the cured product of the resin composition (derived from the carboxyl group-containing resin (A) and the oxazoline group-containing resin (B)) within a range of 5 to 800 mg / m ^2. It is preferable that it is contained in the range of 12.5 to 400 mg / m ² . When the content of the resin component is less than 5 mg / m ² , strong adhesion between the organic-inorganic composite treatment layer and the heat-fusible polyolefin resin layer (or acid-modified polyolefin resin layer) cannot be maintained. On the other hand, even if the content of the resin component exceeds 800 mg / m ² , the effect of improving the adhesion is saturated, which is disadvantageous in terms of cost. In addition, content of the resin component in an organic inorganic composite treatment layer can be calculated | required from carbon amount (mg / m < ² >) obtained by analyzing an organic inorganic composite treatment layer with a fluorescent X-ray apparatus.

Moreover, the organic-inorganic composite treatment layer contains the phosphorus component of the cured product of the resin composition (derived from the basic phosphoric acid compound (C)) within a range of 0.1 to 100 mg / m ^{2 in} terms of phosphorus. It is preferable to contain in the range of 0.25-50 mg / m < ² >. Even when the phosphorus content of the phosphorus component is less than 0.1 mg / m ² , strong adhesion between the organic-inorganic composite treatment layer and the heat-fusible polyolefin resin layer (or acid-modified polyolefin resin layer) is obtained. It cannot be maintained. On the other hand, when the phosphorus content of the phosphorus component exceeds 100 mg / m ² , the adhesion between the organic-inorganic composite treatment layer and the heat-fusible polyolefin resin layer (or acid-modified polyolefin resin layer) is on the contrary. There exists a possibility that it may fall or the barrier property of an organic inorganic composite process layer may fall. In addition, content of the phosphorus component in an organic inorganic composite treatment layer can be calculated | required as phosphorus amount (mg / m < ² >) obtained by analyzing an organic inorganic composite treatment layer with a fluorescent X ray apparatus.

  The content of the resin component and the phosphorus component is adjusted by adjusting the concentrations of the three components (A) to (C) in the resin composition (organic-inorganic composite treatment liquid) applied when forming the organic-inorganic composite treatment layer. Or by adjusting the coating amount of the resin composition (organic-inorganic composite treatment liquid).

  In addition, in the resin composition (organic-inorganic composite treatment liquid) applied when forming the organic-inorganic composite treatment layer, the oxazoline group-containing resin relative to the total amount of the carboxyl group-containing resin (A) and the oxazoline group-containing resin (B) ( The proportion of B) is preferably in the range of 2.0 to 50.0% by mass as the solid content, and more preferably in the range of 5.0 to 40.0% by mass. By making the solid content mass ratio of the carboxyl group-containing resin (A) and the oxazoline group-containing resin (B) in the organic-inorganic composite treatment liquid within the above range, the carboxyl group and the oxazoline group in the organic-inorganic composite treatment layer The ratio can be in a suitable range. As a result, the crosslink density by the carboxyl group and oxazoline group in the organic-inorganic composite treatment layer can be increased, and the barrier property of the organic-inorganic composite treatment layer can be improved. Moreover, when the ratio of the carboxyl group-containing resin (A) is within an appropriate range, the adhesion between the stainless steel plate and the heat-fusible polyolefin resin layer can be maintained well. When the ratio of the oxazoline group-containing resin (B) is outside the above range, the adhesion of the organic-inorganic composite treatment layer to the stainless steel plate and the heat-fusible polyolefin resin layer (or acid-modified polyolefin resin layer) becomes insufficient. There is a fear.

When the resin composition also contains a basic zirconium compound (D), the organic-inorganic composite treatment layer is obtained by converting the zirconium component of the cured product of the resin composition (derived from the basic zirconium compound (D)) to 0. preferably it contains in the range of 5-60 mg / ^{m 2,} and more preferably contains in the range of 1.25~30mg / ^{m 2.} When the zirconium content of the zirconium component is less than 0.5 mg / m ^{2, the} film forming property and barrier property of the organic-inorganic composite treatment layer cannot be sufficiently improved. On the other hand, when the zirconium content of the zirconium component is more than 60 mg / m ² , the adhesion between the organic-inorganic composite treatment layer and the heat-fusible polyolefin resin layer (or acid-modified polyolefin resin layer) is reduced. The barrier property of the organic / inorganic composite treatment layer may be deteriorated. In addition, content of the zirconium component in an organic inorganic composite treatment layer can be calculated | required as a zirconium amount (mg / m < ² >) obtained by analyzing an organic inorganic composite treatment layer with a fluorescent X ray apparatus.

  The content of the zirconium component is adjusted by adjusting the concentration of the basic zirconium compound (D) in the resin composition (organic-inorganic composite treatment liquid) applied when forming the organic-inorganic composite treatment layer, or by adjusting the resin composition (organic It can be adjusted within the above range by adjusting the coating amount of the inorganic composite treatment liquid.

  Hereinafter, the components (A) to (D) included in the resin composition will be described.

[Carboxyl group-containing resin (A)]
The carboxyl group-containing resin (A) forms a cured product having a three-dimensional network structure together with the oxazoline group-containing resin (B), and includes a stainless steel plate and a heat-fusible polyolefin-based resin layer (or acid-modified polyolefin-based resin layer). Improve adhesion.

  For example, the carboxyl group-containing resin (A) is a polymer having a plurality of carboxyl groups obtained by polymerizing a carboxyl group-containing ethylenically unsaturated monomer. Examples of such a carboxyl group-containing resin (A) include a polymer obtained by radical polymerization of one or more monomers selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid. Examples thereof include a copolymer obtained by radical polymerization of the one or more monomers and one or more other ethylenically unsaturated monomers.

  Examples of other ethylenically unsaturated monomers are not particularly limited. For example, 1) 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) Ethylenically unsaturated monomers containing hydroxyl groups such as acrylate, allyl alcohol, methacryl alcohol, adducts of 2-hydroxyethyl (meth) acrylate and ε-caprolactone; 2) containing carboxyl groups such as half amides and half thioesters 3) (Meth) acrylamide, N-methylol (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-dibutyl (meth) acrylamide, N, N-dioctyl (meth) Acrylamide, N-monobutyl Ethylenically unsaturated monomers containing amide groups such as (meth) acrylamide and N-monooctyl (meth) acrylamide; 4) methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl (meth) acrylate, lauryl methacrylate, phenyl acrylate, isobornyl (meth) acrylate, cyclohexyl methacrylate, t-butylcyclohexyl (meth) acrylate, dicyclopentadienyl (meth) acrylate, dihydrodicyclo (Meth) acrylate ester monomers such as pentadienyl (meth) acrylate; 5) styrene, α-methylstyrene, vinyl ketone, t-butylstyrene, parachlorostyrene 6) Polymerizable nitriles such as acrylonitrile and methacrylonitrile; 7) α-olefins such as ethylene and propylene; 8) Vinyl esters such as vinyl acetate and vinyl propionate; 9 ) Dienes such as butadiene and isoprene. Among these, it is preferable that the ethylenically unsaturated monomer containing a hydroxyl group is contained as another ethylenically unsaturated monomer.

  The weight average molecular weight of the carboxyl group-containing resin (A) is preferably in the range of 1000 to 500000. When the weight average molecular weight of the carboxyl group-containing resin (A) is less than 1,000, the film-forming property of the organic-inorganic composite treatment layer is insufficient, and as a result, the chemical resistance may be insufficient. On the other hand, when the mass average molecular weight of the carboxyl group-containing resin (A) is more than 500,000, the viscosity of the resin composition (organic-inorganic composite treatment liquid) for forming the organic-inorganic composite treatment layer increases, and the workability decreases. There is a fear. The mass average molecular weight of the carboxyl group-containing resin (A) can be calculated from the measurement result of gel permeation chromatography (GPC) using polystyrene as a standard.

  As the carboxyl group-containing resin (A), a commercially available product may be used. For example, as the carboxyl group-containing resin (A), Aron A30 (polyammonium acrylate; Toagosei Co., Ltd.), Jurimer AC-10L (polyacrylic acid; Nippon Seiyaku Co., Ltd.), PIA728 (polyitaconic acid; Iwata Chemical Industries) Co., Ltd.), Aquaric HL580 (polyacrylic acid; Nippon Shokubai Co., Ltd.) can be used.

  As the carboxyl group-containing resin (A), it is preferable to use a resin in which (meth) acrylic acid or a (meth) acrylic acid derivative or a combination thereof is used in an amount of 50 mol% or more based on the whole monomer. More preferably, all are composed of acrylic monomers such as (meth) acrylic acid and (meth) acrylic acid derivatives.

  The acid value of the carboxyl group-containing resin (A) is 300 mgKOH / g or more in terms of resin solids from the viewpoint of maintaining the reactivity with the oxazoline group-containing resin, basic phosphate compound and basic zirconium compound described later. It is preferable. When the acid value of the carboxyl group-containing resin (A) is less than 300 mgKOH / g, the reactivity of the carboxyl group-containing resin (A) is lowered, and the adhesion and corrosion resistance may be lowered. The upper limit of the acid value of the carboxyl group-containing resin (A) is 779 mgKOH / g in terms of resin solid content.

  A resin composition (organic-inorganic composite treatment liquid) containing a carboxyl group-containing resin (A), an oxazoline group-containing resin (B) and a basic phosphate compound (C) (and a basic zirconium compound (D) as an optional component) From the viewpoint of improving the temporal stability, the carboxyl group of the carboxyl group-containing resin (A) is preferably neutralized with a basic neutralizing agent. As a basic neutralizer, it is difficult to remain in the organic-inorganic composite treatment layer, and carboxyl group-containing resin (A) and oxazoline group-containing resin (B), basic phosphate compound (C) or basic zirconium compound (D) It is preferable to use volatile amine, ammonia, or the like that is less likely to inhibit the crosslinking reaction. Examples of volatile amines include monoethanolamine, ethylethanolamine, dimethylethanolamine, trimethylamine, triethylamine, morpholine and the like.

[Oxazoline group-containing resin (B)]
The oxazoline group-containing resin (B) forms a three-dimensional network structure cured product together with the carboxyl group-containing resin (A), and includes a stainless steel plate and a heat-fusible polyolefin resin layer (or acid-modified polyolefin resin layer). Improve adhesion.

  The oxazoline group-containing resin (B) is not particularly limited as long as the main chain is an acrylic skeleton and has a plurality of oxazoline groups.

  The number of oxazoline groups in the oxazoline group-containing resin (B) can be defined by an oxazoline value (gsolid / eq.). “Oxazoline number” means the mass of polymer per mole of oxazoline group. When the number of oxazoline groups in the polymer is large, the oxazoline value becomes small. On the other hand, when the number of oxazoline groups in the polymer is small, the oxazoline value increases.

  The oxazoline value of the oxazoline group-containing resin (B) is preferably in the range of 40 to 1000 g solid / eq., More preferably in the range of 120 to 240 g solid / eq. When the oxazoline value is less than 40 g solid / eq., The viscosity of the oxazoline group-containing resin (B) increases, and the workability when forming the organic-inorganic composite treatment layer may be reduced. On the other hand, when the oxazoline value exceeds 1000 g solid / eq., The reaction with the carboxyl group-containing resin (A) becomes insufficient, and as a result, chemical resistance may be insufficient.

  The mass average molecular weight of the oxazoline group-containing resin (B) is preferably in the range of 1,000 to 500,000. When the mass average molecular weight of the oxazoline group-containing resin (B) is less than 1000, the film-forming property of the organic-inorganic composite treatment layer is insufficient, and as a result, the chemical resistance may be insufficient. On the other hand, when the mass average molecular weight of the oxazoline group-containing resin (B) is more than 500,000, the viscosity of the resin composition (organic-inorganic composite treatment liquid) for forming the organic-inorganic composite treatment layer increases, and the workability decreases. There is a fear. The mass average molecular weight of the oxazoline group-containing resin (B) can be calculated from the measurement result of gel permeation chromatography (GPC) using polystyrene as a standard.

  A commercially available oxazoline group-containing resin (B) may be used. For example, as the oxazoline group-containing resin (B), Epocros WS-300, Epocros WS-500, Epocros WS-700 (all of which are Nippon Shokubai Co., Ltd.), NK Linker FX (Shin Nakamura Chemical Co., Ltd.) may be used. it can.

[Basic Phosphate Compound (C)]
The basic phosphoric acid compound (C) is firmly bonded or adhered to the stainless steel plate to form an inorganic treatment layer. The basic phosphoric acid compound (C) also functions as a reaction catalyst for the carboxyl group of the resin (A) and the oxazoline group of the resin (B), and the carboxyl group-containing resin (A) and the oxazoline group-containing resin. It is an essential component for forming an organic-inorganic composite treatment layer having a high crosslinking density and excellent chemical resistance derived from the three components (B) and the basic phosphate compound (C).

  It is essential that the phosphoric acid compound (C) is basic. If an acidic phosphoric acid compound is added to the resin composition (organic inorganic treatment liquid) containing the carboxyl group-containing resin (A) and the oxazoline group-containing resin (B), the resin component will be gelled. Absent.

  A well-known thing can be widely used for the basic phosphoric acid compound (C). Examples of basic phosphate compounds (C) that are soluble in an alkaline aqueous solution include sodium tripolyphosphate, sodium hexametaphosphate, potassium pyrophosphate, sodium pyrophosphate, potassium dihydrogen phosphate, triammonium phosphate, hydrogen phosphate Examples include diammonium, trisodium phosphate, and disodium hydrogen phosphate. These may be used alone or in combination of two or more.

[Basic Zirconium Compound (D)]
The basic zirconium compound (D) adheres to the polyolefin-based resin layer (or acid-modified polyolefin-based resin layer) of the organic / inorganic composite treatment layer by forming a metal bridge between the resins. Improve sex more. In addition, when a basic zirconium compound is added to the resin composition (organic / inorganic treatment liquid) applied when forming the organic / inorganic composite treatment layer, the zirconium bonds to each other through oxygen to increase the molecular weight. The barrier property of the inorganic composite treatment layer is further improved. Further, the basic zirconium compound (D) reacts with the basic phosphoric acid compound (C) to form an insoluble zirconium phosphate salt, thereby further improving the barrier property of the organic-inorganic composite treatment layer.

  It is essential that the zirconium compound (D) is basic like the basic phosphate compound (C). If an acidic zirconium compound is added to the resin composition (organic inorganic treatment liquid) containing the carboxyl group-containing resin (A) and the oxazoline group-containing resin (B), the resin component will gel, which is not preferable. .

  A well-known thing can be widely used for a basic zirconium compound (D). Examples of the basic zirconium compound (D) include ammonium zirconium carbonate, lithium zirconium carbonate, sodium zirconium carbonate, potassium zirconium carbonate, zirconium hydroxide and the like. These may be used alone or in combination of two or more.

  The organic-inorganic composite treatment liquid is obtained by dispersing or dissolving a carboxyl group-containing resin (A), an oxazoline group-containing resin (B), and a basic phosphoric acid compound (C) in an aqueous solvent. A basic zirconium compound (D) may be further added to the organic-inorganic composite treatment liquid. The density | concentration of each component of said (A)-(D) is adjusted so that it may become above-mentioned content, when an organic inorganic composite membrane | film | coat is formed. The aqueous solvent is usually water, but an alcohol may be added to adjust the physical properties of the organic-inorganic composite treatment liquid. Known alcohols can be widely used as alcohols that can be added to the aqueous solvent. Examples of the alcohol that can be added include alcohols having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, isopropyl alcohol, and n-butyl alcohol. The addition amount of these alcohols should just be 20 mass% or less with respect to water, and about 1-5 mass% is preferable. In addition, the pH of the organic / inorganic composite treatment liquid is preferably neutral to alkaline at 7 or more. If the pH is less than 7, the resin component gels with time and the desired quality cannot be obtained. The pH of the treatment liquid can be adjusted by applying basic compounds such as alkali, alkaline earth metal oxides and hydroxides, alkalis, alkaline earths, and ammonium salts, ammonia, amines, among others. , A volatile amine, ammonia, etc. that are less likely to inhibit the crosslinking reaction between the carboxyl group-containing resin (A) and the oxazoline group-containing resin (B), the basic phosphate compound (C), or the basic zirconium compound (D) Is preferably used. Examples of volatile amines include monoethanolamine, ethylethanolamine, dimethylethanolamine, trimethylamine, triethylamine, morpholine and the like.

  The method for forming the organic-inorganic composite treatment layer is not particularly limited. For example, an organic-inorganic composite treatment liquid containing a carboxyl group-containing resin (A), an oxazoline group-containing resin (B), a basic phosphoric acid compound (C), and an aqueous solvent is applied to the surface of a stainless steel plate and dried by heating. That's fine.

  When the organic / inorganic composite treatment liquid is applied to the surface of the stainless steel plate, the surface of the stainless steel plate is preferably cleaned. The method for cleaning the surface of the stainless steel plate is not particularly limited, and a known method can be widely used. Examples of cleaning methods include pure water cleaning, alkali cleaning, acid cleaning, detergent cleaning, solvent cleaning, and corona discharge treatment. Two or more of these methods may be combined.

  The method for applying the organic-inorganic composite treatment liquid is not particularly limited, and a known method can be widely used. Examples of the application method include a dipping method, a spray method, a roll coating method, a bar coating method, and a pouring treatment method. From the viewpoint of strictly controlling the coating amount, the roll coating method and the bar coating method are particularly preferable.

  The heat drying is performed to evaporate the aqueous solvent in the organic-inorganic composite treatment liquid and to promote the reaction of the components (A) to (D) to insolubilize the organic-inorganic composite treatment layer. As a drying method, a known method such as heating with an electric oven or heating with an infrared oven can be widely used. The heating temperature is preferably in the range of 80 to 300 ° C, and more preferably in the range of 120 to 250 ° C. The heating time may be appropriately adjusted according to the heating temperature and the coating amount of the organic / inorganic composite treatment liquid.

(3) Heat-sealable polyolefin resin layer As described above, the heat-sealable polyolefin resin layer is directly bonded to the organic-inorganic composite treatment layer formed on the first surface of the stainless steel plate or is organic. It joins to the organic inorganic composite treatment layer through the below-mentioned acid-modified polyolefin resin formed on the inorganic composite treatment layer. The heat-sealable polyolefin resin layer has a function of blocking the inside of the battery from the outside air to form a sealed system. That is, when a battery is manufactured using the laminate of the present invention, the heat-sealable polyolefin resin layer of one laminate is used as the heat-sealable polyolefin resin layer or metal electrode of the other laminate and the heat. By fusing, the inside of the battery is shielded from the outside air, and the leakage of the electrolyte is prevented. In particular, when external steam gas enters the battery, the electrolyte in the electrolyte is hydrolyzed and hydrofluoric acid is generated, which not only deteriorates the secondary battery itself but also corrodes the stainless steel plate. There is also a possibility that the heat-fusible polyolefin resin layer has a function of improving the corrosion resistance of the stainless steel plate against the electrolytic solution.

  The kind of the heat-fusible polyolefin resin constituting the heat-fusible polyolefin resin layer is not particularly limited, and can be appropriately selected from known ones. Examples of heat-sealable polyolefin resins include low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, ethylene-α-olefin copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid. Examples include acid copolymers, ethylene-acrylic acid ester copolymers, ethylene-methacrylic acid ester copolymers, ethylene-vinyl acetate copolymers, ionomers, polypropylene, and ethylene-propylene copolymers. Among these, polypropylene is particularly preferable.

  The thickness of the heat-fusible polyolefin resin layer is preferably in the range of 10 to 100 μm, and more preferably in the range of 20 to 80 μm. When the thickness is less than 10 μm, it cannot be heat-sealed with sufficient strength. Further, even if the thickness exceeds 100 μm, no improvement in the strength of heat fusion is recognized, which is disadvantageous in terms of cost. On the other hand, if the thickness exceeds 100 μm, the workability may be reduced.

  The method for disposing the heat-fusible polyolefin resin layer on the organic / inorganic composite treatment layer is not particularly limited, and can be appropriately selected from known methods. For example, a heat-sealable polyolefin resin film may be laminated on the organic-inorganic composite treatment layer (lamination method), or a heat-sealable polyolefin resin composition may be applied on the organic-inorganic composite treatment layer. (Coating method). Examples of the lamination method include a thermal lamination method and a sand lamination method. Moreover, a commercially available heat-sealable polyolefin resin film may be used, or may be produced using a T-die extruder or the like. The heat-fusible polyolefin resin film may be unstretched or uniaxially or biaxially stretched. On the other hand, examples of the coating method include a method in which a resin composition is melted and coated with a bar coater or a roll coater, a method in which a stainless steel plate having an organic-inorganic composite treatment layer formed thereon is immersed in the melted resin composition, a resin composition And a method in which the coating is dissolved in a solvent and applied by a bar coater, a roll coater, spin coating or the like.

(4) Acid-modified polyolefin resin layer The laminate of the present invention comprises an acid-modified polyolefin resin layer between an organic-inorganic composite treatment layer and a heat-fusible polyolefin resin layer formed on the first surface of a stainless steel plate. You may have a resin layer. The acid-modified polyolefin resin layer further improves the adhesion between the organic-inorganic composite treatment layer and the polyolefin resin layer.

  The kind of polyolefin resin which comprises an acid-modified polyolefin resin layer is not specifically limited, It can select suitably from a well-known thing. Examples of the acid-modified polyolefin resin include an olefin resin graft-modified with an unsaturated carboxylic acid, a copolymer of ethylene or propylene and acrylic acid or methacrylic acid, a metal-crosslinked olefin resin, and the like. Among these, an olefin resin graft-modified with an unsaturated carboxylic acid is particularly preferable from the viewpoint of heat resistance.

  The thickness of the acid-modified polyolefin resin layer is preferably in the range of 10 to 100 μm, and more preferably in the range of 15 to 50 μm. When thickness is less than 10 micrometers, there exists a possibility that adhesiveness to an organic inorganic composite process layer cannot fully be ensured. Further, even if the thickness exceeds 100 μm, improvement in adhesion to the organic-inorganic composite treatment layer is not recognized, which is disadvantageous in cost. On the other hand, if the thickness exceeds 100 μm, the workability may be reduced.

  The method for disposing the acid-modified polyolefin resin layer is not particularly limited, and can be appropriately selected from known methods. For example, an acid-modified polyolefin resin film may be laminated between the organic / inorganic composite treatment layer and the heat-fusible polyolefin resin layer (lamination method), or before the heat-fusible polyolefin resin layer is formed. In addition, an acid-modified polyolefin resin composition may be applied on the organic / inorganic composite treatment layer (application method). As the acid-modified polyolefin resin film, a commercially available one may be used, or a T-die extruder may be used. The acid-modified polyolefin resin film may be unstretched or uniaxially or biaxially stretched. On the other hand, examples of the coating method include a method in which a resin composition is melted and coated with a bar coater or a roll coater, a method in which a stainless steel plate having an organic-inorganic composite treatment layer formed thereon is immersed in the melted resin composition, a resin composition And a method in which the coating is dissolved in a solvent and applied by a bar coater, a roll coater, spin coating or the like.

(5) Outer resin layer The laminate of the present invention may have a resin layer (hereinafter also referred to as “outer resin layer”) on the second surface side of the stainless steel plate. The outer resin layer can improve processability, designability, puncture resistance, insulation, and the like required for battery exterior materials.

  The type of resin constituting the outer resin layer is not particularly limited, and can be appropriately selected from known ones according to required properties (workability, design properties, puncture resistance, insulation, etc.). Further, the thickness of the outer resin layer is not particularly limited, and can be appropriately set according to required characteristics. Further, the outer resin layer may be a single layer or a multilayer of two or more layers.

  As described above, the laminate of the present invention has a resin composition containing a carboxyl group-containing resin, an oxazoline group-containing resin, and a basic phosphate compound between the surface of the stainless steel plate and the heat-fusible polyolefin resin layer. Since it has an organic-inorganic composite treated layer made of a cured product, the adhesiveness of the heat-fusible polyolefin resin layer is excellent.

2. Secondary Battery The laminate of the present invention can be suitably used as an exterior material (case) for a secondary battery. The shape of the secondary battery is not particularly limited, such as a rectangular parallelepiped rectangular tube shape or a cylindrical shape. The type of secondary battery is not particularly limited, such as a lithium ion battery, a lithium polymer battery, a nickel metal hydride battery, or a nickel cadmium battery.

  When the laminate of the present invention is used as an exterior material (case) for a secondary battery, it is preferable that the laminates of the present invention are bonded together and sealed. At this time, the molded laminates may be bonded together, or only one of the laminates may be molded. The method for forming and processing the laminate of the present invention is not particularly limited, and can be appropriately selected from known methods such as pressing, handling, and drawing. As a method for laminating the laminate of the present invention, a method in which the first surfaces (surfaces coated with the polyolefin resin layer) of the laminate of the present invention are combined and bonded by heat fusion is preferable.

  In order to manufacture a secondary battery using the laminate of the present invention, a battery element such as a positive electrode, a negative electrode, a separator, and a battery content portion such as an electrolyte solution are formed on a case obtained by molding the laminate of the present invention. It can be accommodated and bonded by heat fusion.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail with reference to an Example, this invention is not limited by these Examples.

  As a test stainless steel plate, SUS304 (BA material) having a thickness of 0.1 mm was prepared. After each stainless steel plate is degreased with alkali (pH 12, liquid temperature 60 ° C., immersion time 1 minute), a treatment solution (organic-inorganic composite treatment solution, organic treatment solution or inorganic treatment solution) is applied to the surface of each stainless steel plate using a bar coater. This was applied and dried in an oven at 160 ° C. for 45 seconds to form a treatment layer (organic / inorganic composite treatment layer, organic treatment layer or inorganic treatment layer) on the surface of each stainless steel plate.

  In Examples 1 to 3, an organic-inorganic composite treatment liquid containing a carboxyl group-containing resin (A), an oxazoline group-containing resin (B), and a basic phosphate compound (C) was applied as the treatment liquid. In Examples 4 to 11, an organic-inorganic composite treatment containing a carboxyl group-containing resin (A), an oxazoline group-containing resin (B), a basic phosphate compound (C), and a basic zirconium compound (D) as the treatment liquid. The liquid was applied (see Table 1).

  On the other hand, in Comparative Example 1, an organic treatment liquid containing a carboxyl group-containing resin (A) and an oxazoline group-containing resin (B) was applied as the treatment liquid. In Comparative Example 2, an organic-inorganic composite treatment liquid containing a carboxyl group-containing resin (A), an oxazoline group-containing resin (B), and a basic zirconium compound (D) was applied as the treatment liquid. In Comparative Example 3, an inorganic treatment liquid containing a basic phosphate compound (C) and a basic zirconium compound (D) was applied as the treatment liquid (see Table 1).

  The carboxyl group-containing resin (A) was prepared by the following procedure. First, 775 parts by mass of ion-exchanged water was charged into a four-necked vessel having a heating device and a stirring device, and the ion-exchanged water was heated to 80 ° C. while stirring and refluxing with nitrogen. Next, while heating, stirring and refluxing with nitrogen, a mixed monomer solution of 120 parts by mass of acrylic acid, 20 parts by mass of ethyl acrylate and 60 parts by mass of 2-hydroxyethyl methacrylate, 1.6 parts by mass of ammonium persulfate, and ion exchange A mixed solution of 23.4 parts by mass of water was dropped over 3 hours using a dropping funnel. Even after completion of the dropwise addition, heating, stirring and nitrogen reflux were continued for 2 hours. Thereafter, heating and nitrogen reflux were stopped, and the content liquid was cooled to 30 ° C. while stirring. Subsequently, 113 mass parts of 25 mass% ammonia water and 887 mass parts of ion-exchange water were added. After stirring for 20 minutes, the mixture was filtered using a 200-mesh sieve to obtain an aqueous solution of a colorless and transparent carboxyl group-containing resin (A). The nonvolatile content of the aqueous solution of the obtained carboxyl group-containing resin (A) was 10% by mass. Moreover, the acid value of carboxyl group-containing resin (A) was 467 mgKOH / g in conversion of solid content. The mass average molecular weight of the carboxyl group-containing resin (A) was 58,000.

  As the oxazoline group-containing resin (B), Epocros WS-300 (B1) (oxazoline value: 120 g solid / eq., Mass average molecular weight: 120,000; Nippon Shokubai Co., Ltd.) was used. As the basic phosphate compound (C), sodium dihydrogen phosphate was used. The basic zirconium compound (D) used sodium zirconium carbonate and had a pH of 8.5.

Table 1 shows the content of each component per 1 m ² of the coating layer when each treatment liquid (organic-inorganic composite treatment liquid, organic treatment liquid, or inorganic treatment liquid) is applied to the surface of the stainless steel plate. About content of a basic phosphoric acid compound (C) and a basic zirconium compound (D), in the stainless steel plate which apply | coated each processing liquid using the fluorescent-X-ray-analysis apparatus (AXIS-NOVA; Shimadzu Corporation). The amount of phosphorus and the amount of zirconium per 1 m ^{2 of the} coating layer were measured. Moreover, about the total amount of (A) + (B) of the resin component, the amount of carbon per 1 m ² of the coating layer in the stainless steel plate coated with each treatment liquid was measured using a fluorescent X-ray analyzer, and the conversion coefficient was calculated. It calculated | required by converting from carbon amount as 2 times.

  In Examples 1 and 3, an unstretched polypropylene film (pyrene film CT, P1128; Toyobo Co., Ltd.) having a film thickness of 30 μm was laminated on the surface of a stainless steel plate on which an organic / inorganic composite treatment layer was formed by a thermal lamination method. (See Table 2). Specifically, the stainless steel plate on which the organic / inorganic composite treatment layer is formed is heated in an oven so that the substrate temperature becomes 100 ° C., and then an unstretched polypropylene film is temporarily laminated on the surface with a pressure roll, The laminated steel sheet was heated in an oven at 160 ° C. for 60 seconds to produce a laminate.

Moreover, in Examples 2, 4 to 11 and Comparative Examples 1 to 3, the acid-modified polypropylene film and the above-mentioned were formed on the surface of the stainless steel plate on which the treatment layer (organic-inorganic composite treatment liquid, organic treatment liquid or inorganic treatment liquid) was formed. Two unstretched polypropylene films were stacked and laminated by the above-mentioned thermal lamination method to produce a laminate (see Table 2). The acid-modified polypropylene film was prepared by extruding acid-modified polypropylene (Modic, P553A; Mitsubishi Chemical Corporation) at a thickness of 30 μm using a T-die extruder.

  A test piece (15 mm × 100 mm) was cut out from each of the obtained laminates (Examples 1 to 11 and Comparative Examples 1 to 3), and an adhesion test was performed at a pulling speed of 300 mm / min in accordance with JIS K6854-3. . The case where the adhesive strength of the unstretched polypropylene film (Examples 1 and 3) or the acid-modified polypropylene film (Examples 2 and 4 to 11 and Comparative Examples 1 to 3) to the organic-inorganic composite treatment layer is 15 N / 15 mm or more is The case of 10 N / 15 mm or more and less than 15 N / 15 mm was evaluated as “◯”, and the case of less than 10 N / 15 mm was evaluated as “x”.

Moreover, the test piece (35 mm x 35 mm) was newly cut out from each obtained laminated body (Examples 1-11, Comparative Examples 1-3), and the electrolyte solution test was done. First, after immersing each test piece in an electrolyte solution at 85 ° C. for 7, 14, 21, or 28 days in a sealable Teflon (registered trademark) container, each test piece is washed with ethanol and dried. I let you. The electrolytic solution was prepared by adding lithium hexafluorophosphate (LiPF ₆ ) to a mixed liquid (1: 1) of ethylene carbonate and diethyl carbonate so as to be 1 mol / liter. Subsequently, after attaching a cellophane tape to the film of each test piece, the cellophane tape was peeled off and the film adhesion state was evaluated. “◎” indicates that the film did not peel after the cellophane tape peel test, “○” indicates that the film did not peel before the cellophane tape peel test, but “○” indicates that the film peeled after the test. What peeled was evaluated as "x".

Table 3 shows the results of the adhesion test and the electrolytic solution resistance test. “-” Indicates that the test was abandoned.

  The laminated body of Examples 1-11 is an organic inorganic composite process layer which consists of a hardened | cured material of the resin composition containing carboxyl group-containing resin (A), oxazoline group-containing resin (B), and basic phosphoric acid compound (C). Since the film was formed densely, good evaluation was obtained for film adhesion and electrolyte resistance. In particular, the laminates of Examples 2 and 4 to 11 including an acid-modified polypropylene film were better evaluated for film adhesion and electrolytic solution resistance. In addition, the laminates of Examples 4 to 11 in which the organic-inorganic composite treatment layer also contains the basic zirconium compound (D) have improved film-forming properties, barrier properties, and film adhesion of the organic-inorganic composite treatment layer. Therefore, favorable evaluation was obtained about electrolyte solution resistance.

  On the other hand, the laminates of Comparative Examples 1 to 3 are organic materials composed of a cured product of a resin composition containing a carboxyl group-containing resin (A), an oxazoline group-containing resin (B), and a basic phosphate compound (C). Since the inorganic composite treatment layer was not formed, good evaluation was not obtained for film adhesion and electrolyte resistance.

  Since the laminate of the present invention is excellent in the adhesion and electrolyte solution resistance of the heat-sealable polyolefin resin layer, it can be suitably used as a battery exterior material.

Claims (9)

A stainless steel plate having a first surface and a second surface;
An organic-inorganic composite treatment layer formed of a cured product of a resin composition containing a carboxyl group-containing resin, an oxazoline group-containing resin, and a basic phosphoric acid compound, formed on the first surface of the stainless steel plate;
A heat-fusible polyolefin resin layer having a thickness of 10 to 100 μm formed on the surface of the organic-inorganic composite treatment layer;
A laminate for battery exterior, comprising: The organic-inorganic composite treatment layer contains 5 to 800 mg / m ² of the resin component of the cured product, and 0.1 to 100 mg / m ² of the phosphorus component of the cured product in terms of phosphorus. The laminated body for battery exterior of description.   The ratio of the oxazoline group-containing resin to the total amount of the carboxyl group-containing resin and the oxazoline group-containing resin in the resin composition is in the range of 2.0 to 50.0% by mass. Item 3. A laminated body for battery exterior according to Item 2.   The laminated body for battery exteriors as described in any one of Claims 1-3 whose acid value of the said carboxyl group-containing resin is 300 mgKOH / g or more in conversion of resin solid content. The resin composition further contains a basic zirconium compound,
The organic-inorganic composite treatment layer contains 0.5 to 60 mg / m ² of a zirconium component of the cured product in terms of zirconium.
The laminated body for battery exteriors as described in any one of Claims 1-4.   The laminate for battery exterior according to claim 1, further comprising an acid-modified polyolefin resin layer having a thickness of 10 to 100 µm between the organic-inorganic composite treatment layer and the heat-fusible polyolefin resin layer.   The laminated body for battery exterior according to claim 1, wherein a thickness of the stainless steel plate is in a range of 20 to 400 µm.   The laminated body for battery exteriors of Claim 1 which further has the resin layer formed in the 2nd surface of the said stainless steel plate.   A secondary battery having a case formed by heat-sealing a molded article of the battery exterior laminate according to claim 1.