JPH08190902A - Film for thin battery sealing material and its manufacture - Google Patents

Abstract

PURPOSE: To enhance moisture resistance, heat resistance, and adhesive of a thin battery by a sealing material. CONSTITUTION: In order to seal a battery element placed between a pair of terminal boards in the peripheries of the terminal boards, a three-layer structure sealing material 5 comprising heat adhesive polyolefin layers 11, 13 on both outer layer sides for heat bonding a pair of terminal boards 1, 6, and a polyolefin interlayer 12 containing a filler, placed between the polyolefin layers 11, 13 is used. Modified polyolefin having hot melt adhesive property is contained in the heat adhesive polyolefin, and polypropylene is contained in the interlyaer 12. High adhesion with terminal boards 1, 6 is maintained by layers 11, 13, and thermal deformation temperature of the interlayer 12 is raised by adding the filler.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film for a sealing material for a thin battery such as a paper battery, a method for producing the film, a sealing material using the film, and a thin battery.

[0002]

2. Description of the Related Art Thin batteries such as paper batteries, paper lithium batteries and plate batteries are used as a power source for small electronic devices such as IC cards, memory cards, RAM cards, ID cards, card calculators and card clocks. ing. The paper lithium battery is, for example,
It has a structure in which a battery element (for example, a positive electrode mixture, a separator and a lithium negative electrode material) is sandwiched between a thin plate-shaped positive electrode terminal plate also serving as an electrode terminal and a negative electrode terminal plate.

Since such a paper lithium battery has a thickness of at most about 0.5 mm, its sealing structure is different from that of a button type alkaline battery in which an insulating gasket is sandwiched between terminal plates. different. That is, in a paper lithium battery, normally, a frame-shaped sealing material made of an insulating material such as polyolefin is arranged on the peripheral portions of the positive electrode terminal plate and the negative electrode terminal plate, and the peripheral portion of the battery element is heated and pressed. A sealing structure for heat-sealing the peripheral portion of the terminal plate with a sealing material is adopted.

The sealing material for such a thin battery is moisture-proof to prevent water from entering the battery element, has high thermal adhesiveness to the terminal plate, and is high even when the battery is exposed to a high temperature environment. Heat resistance is required to maintain the adhesive strength. Further, the adhesiveness is required to be not only the above heat-resistant adhesiveness but also the adhesiveness not to be lowered by the action of moisture or load. Furthermore, the sealing material is also required to have high chemical resistance to an electrolytic solution.

Japanese Unexamined Patent Publication (Kokai) No. 5-182649 discloses a thin battery using an exterior material having a heat-fusible layer such as modified polypropylene and a metal layer, and Japanese Unexamined Patent Publication No. 2-250257.
JP-A-2-234344 and JP-A-2-220
Japanese Patent No. 351 proposes to use a monolayer film of polyolefin, modified polyethylene, polyisobutylene modified polyethylene, or the like as a sealing material. These sealing materials show good thermal adhesive strength to the terminal board. However, among these sealing materials, modified polyethylene has a low Vicat softening point of about 60 to 70 ° C, and even modified polypropylene has a Vicat softening point of 110 to 130 ° C.
The heat resistance is inferior.

On the other hand, when a polymer having high heat resistance is used,
Thermal adhesiveness is reduced. Therefore, it is difficult to achieve both properties of heat resistance and thermal adhesiveness. For example, it is conceivable to use a polyamide hot melt adhesive film having a high melting point such as nylon 12 or nylon 6 in order to improve heat resistance. When the polyamide-based hot melt adhesive film is used, a battery having a high initial adhesive strength can be obtained. However, polyamide has high hygroscopicity and moisture permeability. Therefore, not only the adhesive strength is greatly reduced by the moisture, but also the invading moisture deteriorates the battery element, the electromotive force is significantly reduced, and the life of the battery is shortened.

When a film having a high melting point is used among the polyester hot melt adhesive films, the heat resistance can be improved, but the adhesive strength to the terminal board is small. Moreover, since the water vapor permeability of polyester is still high, it is difficult from a practical point of view to utilize the battery element in association with the terminal plate for sealing.

As described above, since the conventional sealing material is deteriorated in any of the moisture-proof property, the adhesive property and the heat resistance, there is a limit in improving the sealing property and greatly improving the battery life. .

[0009]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a film for a sealing material which can achieve all the properties of moisture resistance, adhesiveness and heat resistance, and a method for producing the film.

Another object of the present invention is to provide a film for a sealing material having high heat resistance despite the use of an olefin polymer and a method for producing the film.

Still another object of the present invention is to provide a sealing material having the above-mentioned excellent properties and a battery using the sealing material.

[0012]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventor found that when an intermediate layer of an olefin polymer containing a filler is formed between heat-adhesive olefin layers, The present invention has been completed by finding that heat resistance can be improved while maintaining the advantages.

That is, the film for a sealing material of the present invention is
A film for a sealing material for sealing a battery element interposed between a pair of terminal plates at a peripheral portion of the terminal plate, wherein both outer layers are heat-bonded for thermal bonding to the pair of terminal plates. Has at least a three-layer structure composed of a heat-resistant polyolefin layer and a polyolefin intermediate layer which is interposed between these heat-adhesive polyolefin layers and contains a filler.

The heat distortion temperature of the intermediate layer may be higher than that of the polyolefin of the intermediate layer by 15 ° C. or more. As the heat-adhesive polyolefin, a polyolefin having a high heat-adhesive strength, for example, 1.5 Kg / 15 mm or more, can be used as the heat-adhesive polyolefin, and often has hot-melt adhesiveness. The intermediate layer may be composed of a polyolefin such as polypropylene and a filler such as talc, mica and calcium carbonate. The polyolefin constituting the intermediate layer often has a higher softening point than the heat-adhesive polyolefin.

The thicknesses of the thermoadhesive polyolefin layer (A) and the intermediate layer (B) can be selected within a range that does not impair the adhesiveness, heat resistance, etc. For example, the thickness ta of the thermoadhesive polyolefin layers of both outer layers is ta. Is about 5 to 20 .mu.m, and the thickness ti of the intermediate layer is often ti = 2.times.ta.times.1.2 (.mu.m) or more.

Such a film for a sealing material is a method of laminating a hot-melt adhesive polyolefin layer, a polyolefin intermediate layer containing a filler, and a hot-melt adhesive polyolefin layer, which is higher than the intermediate polyolefin. It can be produced by a method of forming an intermediate layer using a resin composition having a heat distortion temperature.

The sealing material of the present invention is composed of the film formed in a frame shape. Further, the thin battery of the present invention, a battery element composed of a positive electrode mixture, a separator and a negative electrode material, a pair of terminal plates for holding the battery element, and the battery element at the peripheral portion of the terminal plate. A battery composed of a sealing material for sealing, wherein the sealing material is composed of a laminated body having at least a three-layer structure composed of the following A layer and B layer.

A layer: a heat-adhesive polyolefin layer constituting both outer layers B layer: a polyolefin intermediate layer which is interposed between A layers and contains a filler, and has a heat distortion temperature higher than that of the B layer polyolefin. Intermediate Layer In the present specification, “thermal adhesiveness” means melt adhesiveness in which adhesiveness is exhibited by melting or softening, and “adhesive strength” is measured according to JIS K 6854.
It means 0 ° peel strength. What is "heat distortion temperature"?
Load 4.2 Kg / cm ² according to IS K 7207
"Vicat softening point" means the softening point measured by the method specified in JIS K 7206. Also, "moisture permeability" means ASTM
Means a value measured by the method specified in F 1249,
It is a value when converted to a thickness of 25 μm. Further, the "film" means a two-dimensional structure sometimes called a sheet.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings as needed.

FIG. 1 is an exploded perspective view showing a paper lithium battery which is an example of the present invention. This battery includes a pair of terminal plates made of a conductive material such as stainless steel, that is, a positive electrode terminal plate 1 and a negative electrode terminal plate 6,
The battery element is interposed between the pair of terminal plates 1 and 6. The battery element is composed of a sheet-shaped positive electrode mixture 2 containing an anode active material, a separator 3 impregnated with an electrolytic solution, and a negative electrode material 4 made of lithium or the like. Then, the battery element is sealed at the peripheral edges of the terminal plates 1 and 6 with a frame-shaped sealing member 5 that can be heat-bonded between the pair of terminal plates 1 and 6.

The terminal plate is a conductive material that can be thinned,
In particular, it is often formed of a flexible conductive metal film having a large mechanical strength without being deteriorated by the electrolytic solution.
Such conductive metals include, for example, aluminum, copper, nickel, titanium, stainless steel, nickel plated stainless steel and the like. Of these conductive metals, nickel, stainless steel, nickel-plated stainless steel, etc. are often used. The thickness of the terminal plate corresponding to the conductive metal film is, for example, 0.01 mm to 0.1 mm, preferably 0.01 mm to 0.07 mm. If the thickness is less than 0.01 mm, the strength is low and defects are likely to occur,
If it exceeds 0.1 mm, the weight of the battery tends to increase.

The members constituting the battery element are not limited to the above, but can be selected according to the type of battery. The battery element will be described by taking the above paper lithium battery as an example. Examples of the positive electrode active material of the positive electrode mixture include TiS ₂ and Mo.
Metal chalcogenides having a layered structure such as S ₃ , NbSe ₃ , VSe ₂ ; CoO ₂ , Cr ₃ O ₅ , TiO ₂ ,
CuO, V ₃ O ₆ , Mo ₃ O, V ₂ O ₅ , V ₂ O ₅ (・
P ₂ O _5), metal oxides such as _{Mn 2 O (· Li 2 O} ); such a conjugated polymer having conductivity such as polyacetylene. Preferred anode active materials include V ₂ O
₅ , MnO _{2 and the} like are included. Such an anode active material can be used in combination with a binder such as a fluororesin (eg, polytetrafluoroethylene) or a conductive agent such as conductive carbon black.

As the separator, for example, a polyolefin-based porous material having a liquid retaining property such as polypropylene nonwoven fabric can be used. As the negative electrode material, an alkali metal such as metallic lithium (for example, lithium foil), a carrier carrying an alkali metal, or the like can be used.

The solvent of the electrolytic solution is a non-aqueous solvent such as propylene carbonate, ethylene carbonate,
Aprotic solvents such as tetrahydrofuran, dioxolane, sulfolane, dimethoxyethane, dimethylsulfoxide, acetonitrile, N, N-dimethylformamide, diethylene glycol, dimethyl ether and the like can be mentioned. In a paper lithium battery, as the electrolytic solution, LiClO ₄ , LiBF ₄ , Li
_{ClF 4, LiAsF 6, LiSbF 6} , LiCl, L
A solvent in which a lithium salt such as iI is dissolved is often used.

As described above, the sealing material exhibits high adhesive strength by heat fusion to the positive and negative electrode terminal plates,
Prevent the permeation or permeation of water and protect the positive electrode mixture material and the lithium negative electrode material, that the adhesive strength does not decrease even when exposed to the use environment or the high temperature environment in the manufacturing process (high heat resistance adhesiveness), High chemical resistance to the electrolyte is required.

In order to meet these required performances, the sealing material of the present invention is not a single layer but a laminated body of a plurality of layers. That is, as shown in FIG. 2, the sealing material is a thermoadhesive polyolefin layer 11, 13 (hereinafter, simply referred to as A layer) that forms both outer layers for thermally adhering to the pair of terminal boards 1, 6. In some cases) and the intermediate layer 12 (hereinafter sometimes simply referred to as B layer) interposed between these heat-adhesive polyolefin layers, and has at least a three-layer structure (A layer / B layer / Layer A). The A layers 11 and 13 impart high adhesiveness, moisture resistance and chemical resistance, and the B layer 12 as an intermediate layer imparts high heat resistance, moisture resistance and chemical resistance. The sealing material 5 is obtained from a sealing material film having a laminated structure corresponding to the structure shown in FIG.

The heat-adhesive polyolefin constituting the layer A may be a homopolymer or copolymer of α-olefin. Examples of the α-olefin include ethylene, propylene, 1-butene, 4-methyl-1-butene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, and 1-hexene. -Octene, 1
-Decene, 1-dodecene, etc. are included.

Preferred heat-adhesive polyolefins include modified polyolefins obtained by modifying the above α-olefin homopolymers or copolymers. In the modified polyolefin, the α-olefin homopolymer or copolymer,
Homo- or copolymers of α-olefin having 2 to 6 carbon atoms, preferably about 2 to 4, such as polyethylene, polypropylene, ethylene-propylene copolymer, propylene-
Ethylene copolymer, ethylene-butene-1 copolymer, propylene-butene-1 copolymer, propylene-ethylene-butene-1 copolymer, ethylene-3-methylpentene-1 copolymer, ethylene-propylene- 3-methylpentene-1 copolymer, ethylene-4-methylpentene-1
A copolymer, an ethylene-propylene-4-methylpentene-1 copolymer, an ethylene-butene-1-3-methylpentene-1 copolymer and the like can be mentioned. The modified polyolefin is preferably modified polypropylene in order to enhance heat resistance.

The modified polyolefin can be composed of a copolymer of one or more kinds of the above α-olefin and a copolymerizable vinyl monomer. Examples of the copolymerizable vinyl monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, mesaconic acid and angelic acid; Ethylenically unsaturated carboxylic acid anhydrides such as maleic acid, citraconic anhydride, and itaconic anhydride; acrylic acid esters, methacrylic acid esters (eg, methyl (meth) acrylate, ethyl (meth) acrylate, (meth) acrylic acid) Butyl,
Hexyl (meth) acrylate, (meth) acrylic acid 2-
Ethylhexyl, alkyl (meth) acrylates such as octyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate, hydroxyl group-containing (meth) acrylates such as 2-hydroxypropyl (meth) acrylate, (meth) (Meth) acrylate having a functional group such as glycidyl group-containing (meth) acrylate such as glycidyl acrylate; carboxylic acid vinyl ester such as vinyl acetate and vinyl propionate; cyclic olefin such as norbornene and cyclopentadiene;
Chain conjugated diene such as 1,3-butadiene and isoprene, chain non-conjugated diene such as 1,4-hexadiene and 1,6-octadiene, cyclic non-conjugated such as dicyclopentadiene, methyltetrahydroindene and 5-vinylnorbornene Examples include dienes such as diene and cyclic conjugated dienes such as 2,3-diisopropylidene-5-norbornene. The copolymerizable monomer may be used alone or in combination of two or more.

Preferred modified polyolefins are carboxylic acid modified polyolefins, acid anhydride modified polyolefins such as maleic anhydride, and (meth) acrylates such as ethyl acrylate.
In many cases, acrylate modified polyolefin, glycidyl modified polyolefin such as (meth) acrylic acid glycidyl ester, vinyl modified polyolefin such as vinyl acetate and the like.

The modified polyolefin as described above is, for example, manufactured by Mitsui Petrochemical Co., Ltd. under the trade name "Admer".
"Nukurel", product name "MODIC" from Mitsubishi Petrochemical Co., Ltd., product name "Novatech A" from Mitsubishi Kasei Co., Ltd.
P ”, trade name“ Rescue Pearl ”from Nippon Petrochemical Co., Ltd.
"N Polymer" is commercially available from Sumika Atokem Co., Ltd. under the trade name "Bondaine" and Sumitomo Chemical Co., Ltd. under the trade name "Bond Fast". Among these commercially available modified polyolefins, in order to improve heat resistance, modified polyolefins containing polypropylene as a main component (modified polypropylene), for example, "Admer" QF series, "Modik" P series, "Novatech AP" P series Are preferred.

The heat-adhesive strength of the heat-adhesive polyolefin constituting the layer A to the positive and negative electrode terminal plates may be within a range capable of preventing leakage of the electrolytic solution and deterioration of the battery element.
1.5 kg / 15 mm or more, preferably 2.0 kg / 1
It is 5 mm or more, more preferably 2.5 kg / 15 mm or more. If the adhesive strength is less than 1.5 kg / 15 mm, the battery may be broken depending on the environment in which the battery is used.

The Vicat softening point of the heat-adhesive polyolefin is often 70 ° C. or higher, preferably 160 ° C., and more preferably 90 to 150 ° C. in many cases. In order to improve the heat resistance of the sealing material, the heat-adhesive polyolefin is
Vicat softening point is 100 ° C or higher, preferably 110-1
The temperature is preferably 60 ° C (for example, 120 to 155 ° C), more preferably 125 to 150 ° C (for example, 125 to 145 ° C).

The adhesive strength of the heat-adhesive polyolefin to the positive electrode terminal plate and the negative electrode terminal plate is, for example, humidity,
Especially under high temperature and high humidity environment (for example, 40 ℃ 90% RH, 6
20 days or more, preferably 40 days under 0 ° C. 90% RH condition
It is required that it does not decrease over a day or more, more preferably 100 days or more) and that it does not decrease due to an electrolytic solution such as propylene carbonate. The thermoadhesive polyolefin used in the present invention can sufficiently withstand such required performance.

The outer layer of the film for sealing material and both outer layers of the sealing material may be composed of the same thermoadhesive polyolefin or different thermoadhesive polyolefins.

The feature of the present invention is that the sealing material film and the sealing material are composed of a laminate having a three-layer structure, and that the intermediate layer is composed of a polyolefin containing a filler, whereby high moisture resistance and The point is to increase heat resistance while maintaining chemical resistance.

The polyolefin constituting the B layer as the intermediate layer includes the α-olefin homopolymer or copolymer described in the section of the A layer, and the heat-adhesive polyolefin (modified polyolefin). A preferable polyolefin constituting the layer B is a homo- or copolymer of α-olefin, more preferably a homo- or copolymer of α-olefin having 2 or 3 carbon atoms, particularly a homo- or copolymer containing propylene as a main component. Is preferred.

The polypropylene constituting the B layer as the intermediate layer is a polyolefin containing propylene as a main component such as a propylene homopolymer or a random or block copolymer of propylene, particularly a polypropylene having a high melting point (eg isotactic). Polypropylene, highly crystalline polypropylene, etc.) are preferred.

Specific examples of the polyolefin that constitutes the preferable B layer include, for example, low density polyethylene (available from Mitsubishi Kasei Kogyo Co., Ltd. as “Mitsubishi Polyethylene LD”) and linear low density polyethylene (eg, "Sumikasen L" available from Sumitomo Chemical Co., Ltd., high-density polyethylene (eg, "HIZEX" available from Mitsui Petrochemical Co., Ltd.), polypropylene (eg "Ube Polypro" from Ube Industries Ltd.) , And highly crystalline polypropylene (available as "HCPP" from Chisso Corporation).

The Vicat softening point of the polyolefin constituting the layer B is not particularly limited as long as it does not impair heat resistance, but it is preferably at least equal to or higher than that of the heat-adhesive polyolefin of the layer A. In order to improve the heat resistance of the sealing material film and the sealing material, the Vicat softening point of the polyolefin forming the B layer is 3 ° C. or more than that of the thermoadhesive polyolefin of the A layer when measured according to JIS K 7206 ( (Eg, 3 to 75 ° C.), preferably 5
℃ or more (eg 5 to 60 ℃), more preferably 10
It is preferable that the temperature is higher than 0 ° C (for example, 10 to 50 ° C).

The Vicat softening point of the polyolefin constituting the intermediate layer can be selected according to the softening point of the heat-adhesive polyolefin constituting the A layer within a range that does not impair the heat resistance, and is, for example, 80 to 170 ° C., preferably Is often about 90 to 160 ° C. The preferred polyolefin is 110
℃ or more (for example, 120 to 160 ℃), preferably 12
In many cases, the Vicat softening point is 0 ° C. or higher (for example, 125 to 160 ° C.), more preferably 130 ° C. or higher (for example, 135 to 155 ° C.), and particularly 140 ° C. or higher (for example, 140 to 155 ° C.).

As the filler, either an organic filler or an inorganic filler can be used as long as the heat distortion temperature is higher than that of the polyolefin. Examples of the organic filler include thermoplastic resins such as polyacetal, polycarbonate, polyamide, polyalkylene terephthalate such as polybutylene terephthalate, polyetherimide, polyether ether ketone, polyphenylene sulfide, polyphenylene oxide, polysulfone, and polyarylate; phenol resin. , Epoxy resin, melamine resin, urea resin, benzoguanamine resin, alkyd resin, unsaturated polyester resin, and silicone resin. The thermosetting resin can be used as an uncured resin, but a cured product is often used. The organic filler may be fibrous, but it is often powdery.

Examples of the inorganic filler include fibrous inorganic substances such as glass fiber, carbon fiber, ceramic fiber, boron fiber, asbestos and whiskers; calcium carbonate, magnesium carbonate, barium sulfate, silicon dioxide, and the like.
Titanium oxide, zinc oxide, iron oxide, highly dispersible silicic acid, alumina, aluminum hydroxide, talc, mica, diatomaceous earth, glass flakes, glass beads, quartz powder, silica sand,
Boron night light, silicon nitride, carbon black,
Examples include powdery inorganic substances such as graphite.

The fibrous filler has, for example, an average fiber diameter of 1 to
50 μm, preferably about 3 to 30 μm, average fiber length 1
00 μm to 1 mm, preferably 200 μm to 0.5 mm
It is often a degree. The average particle size of the powdery filler is, for example, 0.1 to 50 μm, preferably 1 to 25 μm.
It is often about μm.

Of these fillers, organic or inorganic fillers having high non-conductivity or electrical insulation, particularly inorganic fillers are often used. Preferred fillers from the viewpoint of economical efficiency and practicality, for example, fibrous inorganic substances such as glass fiber, talc, mica, calcium carbonate, barium sulfate, silicon dioxide, titanium oxide, alumina, glass flakes, quartz powder, Contains powdered inorganic substances such as silica sand,
Talc, mica, calcium carbonate, crow fiber, etc. are often used.

The content of the filler can be appropriately selected depending on the kind of the filler within the range that the moisture resistance and the chemical resistance are not impaired and the heat resistance can be enhanced. ˜50% by weight, preferably 8 to 40% by weight, more preferably 10 to 35% by weight. The B layer as an intermediate layer often contains about 10 to 50% by weight of an inorganic filler.

The heat distortion temperature can be appropriately adjusted depending on the kind and addition amount of the filler, but the heat distortion temperature of the B layer as the intermediate layer is measured with a load of 4.2 Kg by the method prescribed in JIS K 7207. Then, the temperature is 10 ° C or higher, preferably about 15 to 60 ° C, more preferably 20 to 50, as compared with the polyolefin of the intermediate layer to which the filler is not added.
It is preferable that the temperature is as high as ℃. The addition of the filler may increase the heat distortion temperature of the intermediate layer by 15 ° C. or higher, preferably 20 ° C. or higher (eg 20 to 50 ° C.), more preferably 25 ° C. or higher (eg 25 to 50 ° C.). Many.

In order to improve the heat resistance, it is possible to use a monolayer film in which a filler is added to modified polyethylene or modified polypropylene having a high thermal adhesive property. The adhesiveness is extremely reduced, or the filler is present at the adhesive interface between the film and the terminal plate, so that the moisture resistance is greatly reduced.

The heat-adhesive polypropylene layer (A layer) and the intermediate layer (B layer) may be added with a polyolefin or other polymer in the other layer as long as the adhesiveness and heat resistance are not impaired. Good. Further, the filler of the B layer may be added to the A layer constituting the surface layer, as long as the thermal adhesiveness is not impaired. In addition, a dispersant, a dispersion aid, or the like may be added to the layer containing the filler or the like in order to enhance the dispersibility of the filler.
Further, additives such as stabilizers such as antioxidants and ultraviolet absorbers, plasticizers, flame retardants, antistatic agents, colorants, tackifiers, etc. may be added to each layer.

The thickness of the film and sealing material of the present invention is
It can be selected within a range that does not impair heat adhesion, heat resistance, moisture resistance, chemical resistance, etc., and is, for example, 25 to 200 μm, preferably 40 to 150 μm, and more preferably 50 to 120 μm.
It is a degree. If the thickness of the film and the sealing material is too thin, the heat-adhesive polyolefin layer may partially adhere during heat-adhesion with the terminal board, resulting in poor adhesion.The heat-adhesive polyolefin layer is effectively used for heat-adhesion. If it becomes too thick and too thick, it becomes impossible to obtain a thin battery.

The thickness of the heat-adhesive polyolefin layer constituting both outer layers and the filler-containing polyolefin layer as the intermediate layer can be selected within a range that does not impair the heat-adhesiveness and heat resistance. The thickness ta of the heat-adhesive polyolefin layers of both outer layers is
The thickness is 3 to 25 μm, preferably 5 to 20 μm, and more preferably 7 to 15 μm. Further, the thickness ti of the intermediate layer is often larger than the thickness of both outer layers in order to impart heat resistance to the film and the sealing material. Therefore, the thickness ti of the intermediate layer can be selected within a range capable of imparting high heat resistance to the sealing agent according to the thicknesses of both outer layers.
ti = 2 × ta × 1.2 (μm) or more, preferably 2 ×
In many cases, ta × 1.5 ≦ ti ≦ 2 × ta × 5 (μm) and 2 × ta × 1.7 ≦ ti ≦ 2 × ta × 3 (μm). The thickness ti of the intermediate layer is usually 10
˜150 μm, preferably 20 to 100 μm, more preferably about 30 to 80 μm.

The ratio (ti / t) of the thickness ti of the intermediate layer to the total thickness t of the film or the sealing material is 5
It is 0 to 95%, preferably 60 to 90%, more preferably 65 to 85%. When the ratio of the thickness of the outer layer (A layer) to the intermediate layer (B layer) is large, the heat resistance decreases,
If it is too small, the adhesion to the terminal board will decrease.

Since the film and the sealing material of the present invention have a layered structure composed of an outer layer containing a polyolefin having a low moisture permeability and an intermediate layer, even if the intermediate layer contains a filler, it is moisture-proof. Is high. In addition, since both outer layers and the intermediate layer are olefin-based polymers having high adhesiveness and affinity with each other, the adhesive strength between the A layer and the B layer is high even with a three-layer structure. Therefore, using the film and the sealing material,
The deterioration of the battery can be prevented for a long time.

The moisture permeability of the film for sealing material and the sealing material, when measured according to ASTM F1249, is 60 g / m ² · day or less in terms of thickness of 25 μm (for example, 1
~ 50 g / m ² · day), preferably 40 g / m ² ·
Day or less (e.g., 1 to 35 g / m of about ² · day), more preferably not more than ² per day 30 g / m (e.g., 5 to 30 g
/ M about ² · day), in particular 20 g / m ² · day or less (e.g., 5 to 20 g / m of about ² · day). If the sealing material has a high water vapor transmission rate, the battery element is deteriorated by moisture and the battery life is shortened.

The film and the sealing material of the present invention are
It suffices that it has at least the above-mentioned three-layer structure, that is, A layer and B
It may have a multilayer structure in which other layers such as an adhesive layer, a laminate layer, and a barrier layer are interposed between the layers. For example, when a vinylidene chloride-based polymer layer is formed between the A layer and the B layer, the moisture resistance can be further enhanced. Further, when the content of the filler in the B layer is large, the flexibility and the adhesive strength between the A layer and the B layer may decrease. In such a case, by forming a polyolefin layer having a small filler content between the A layer and the B layer, A
You may raise the adhesive strength of a layer and B layer. In addition, A layer and B
It is possible to form a conductive metal layer between the layers, but this is not preferable because it may cause a short circuit. When joining the A layer and the B layer with an adhesive or a laminating agent, A
Depending on the thickness of the layer (heat-adhesive polyolefin layer), the adhesive or the like may be eroded by the electrolytic solution of the battery.

The film and the sealing material of the present invention are obtained by sequentially laminating a thermoadhesive polyolefin layer (A layer), a polyolefin intermediate layer (B layer) containing a filler, and a thermoadhesive polyolefin layer (A layer). Can be manufactured by undergoing various laminating steps to obtain a laminated body having at least a three-layer structure. At that time, the intermediate layer may be formed by using a resin composition having a heat distortion temperature higher than that of the polyolefin of the intermediate layer.

A preferred method includes a film forming method, particularly a melt forming method (for example, an extrusion forming method such as a T-die method or an inflation method) in order to improve the workability of lamination and the production efficiency of the sealing material. In the extrusion molding method, a dry laminating method using a laminating agent may be adopted, but in order to avoid erosion by an electrolytic solution, a thermal laminating method of sequentially laminating film-like melts without using a laminating agent, particularly The coextrusion method is preferred.

In the coextrusion molding method, the resin compositions corresponding to the A layer and the B layer are melted and kneaded by an extruder and merged in a die to have at least a three-layer structure (A layer / B).
Layer / A layer) in a molten state, and extruded from a die to form a film. The obtained film may be stretched, but in many cases, it is not stretched in order to prevent heat shrinkage during heat bonding. If necessary, the obtained film may be subjected to a surface treatment process such as corona discharge treatment.

The film thus obtained is often processed into a shape (for example, a frame shape) corresponding to the sealing material. The frame-shaped sealing material can be obtained by subjecting the film to a punching process or the like.

As described above, the sealing material obtained in this manner is a battery element (for example, a thin-walled terminal plate made of a metal film or the like) interposed between a pair of terminal plates in a thin battery as described above. , Positive electrode mixture, separator and negative electrode material). That is, a battery can be obtained by arranging a battery element between a pair of terminal plates, arranging a sealing material on a peripheral portion of the terminal plate, and thermally bonding an outer layer of the sealing material to the pair of terminal plates. it can.

[0061]

Since the film for a sealing material of the present invention comprises both outer layers composed of a heat-adhesive polyolefin and an intermediate layer composed of a polyolefin containing a filler, it is moisture-proof, adhesive and heat-resistant. It has both excellent properties and high chemical resistance. Further, the heat resistance can be improved even though both outer layers and the intermediate layer contain the olefin polymer. Therefore, when the sealing material formed of the film is used, a thin battery having high moisture resistance, chemical resistance, adhesiveness and heat resistance can be obtained.

In the method of the present invention, the film for a sealing material having the above-mentioned excellent properties can be produced by a simple operation by undergoing the laminating step.

[0063]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited by these examples.

Examples 1 to 10 The following polymer for layer A and resin composition for layer B were melted in an extruder to obtain T
A layer / B layer / by the three-layer coextrusion molding method of extruding from a die
A layer = 12/50/12 (μm) film (thickness 74
μm) was obtained. The extrusion molding is performed at a temperature of 200 to 250.
Performed at ° C.

[Polymer for Layer A] (A1) Thermal Adhesive Polyethylene: Mitsui Petrochemical Co., Ltd.
Admer NF550 (A2) Thermal Adhesive Polypropylene: Mitsui Petrochemical Co., Ltd.
Made by Admer QF550 (A3) Thermal adhesive polypropylene: Mitsubishi Kasei Co., Ltd., Novatec AP197P (A4) Thermal adhesive polypropylene: Mitsubishi Kasei Co., Novatec AP030P (A5) Thermal adhesive polypropylene: Mitsubishi Kasei ), Novatec AP021P [B layer resin composition] (B1) Talc-filled high-density polyethylene: This resin composition contains 70 parts by weight of high-density polyethylene (Hi-Zex 3300F, manufactured by Mitsui Petrochemical Co., Ltd.) and talc (Pfizer). A mixture with 30 parts by weight of TALCORN-MP44-26 manufactured by MSP Co., Ltd. was pelletized using a twin-screw extruder.

(B2) Talc-filled polypropylene: This resin composition comprises 70 parts by weight of polypropylene (Ube Polypro YK121 manufactured by Ube Industries, Ltd.) and 30 parts by weight of talc (TALCORN-MP44-26 manufactured by Pfizer MSP). The mixture was made by pelletizing using a twin screw extruder.

(B3) Filler (talc) filled polypropylene: Sumitomo Chemical Co., Ltd., Noblene BWH14,
Talc content 30% by weight (B4) Filler (glass fiber) filled polypropylene: Sumitomo Chemical Co., Ltd., Noblen GHH43, glass fiber content 30% by weight (B5) Filler (talc-mica type) filled polypropylene: Ube Industries Ube Polypro CJ104, talc-mica-based filler content of 30% by weight, Comparative Examples 1-8, in place of the B layer resin composition, the A layer heat adhesive polyolefin or the following fillers are included. A single-layer or three-layer structure film (thickness: 74 μm) was obtained in the same manner as in Example 1 except that no polyolefin was used.

(C1) High-density polyethylene: manufactured by Mitsui Petrochemical Co., Ltd., Hi-Zex 3300F (C2) Polypropylene: manufactured by Ube Industries Ltd., Ube Polypro YK121 The frame obtained from the films obtained in the above Examples and Comparative Examples. Of the positive electrode and negative electrode terminal plate (SUS30).
4, film with a thickness of 0.3 mm), 190 ° C
Paper lithium battery (thickness: 0.5 mm x width: 1 mm)
6.5 mm × length 34.5 mm) was produced.

When the following characteristics were evaluated, the results shown in the table were obtained.

[Vicat Softening Point and Thermal Deformation Temperature] The Vicat softening point of the polyolefin of the A layer and the polyolefin of the B layer are measured according to JIS K 7206, and the thermal deformation temperature of the resin composition of the B layer is JIS K 72.
In accordance with No. 07, the load was measured at 4.2 Kg / cm ² .

[Adhesive Strength] The adhesive strength (kg / 15 mm) between the sealing material and the terminal plate was measured as 180 ° peel strength according to JIS K 6854.

[Humidity resistance and chemical resistance] After being stored at 40 ° C. and 90% relative humidity (RH) for 40 days, the state of the adhesive surface and the electrolytic solution resistance of the sealing material were examined.

[Heat Resistance] In order to evaluate the heat resistance, the temperature at which the sealing material was melted and exuded from the battery was examined by applying a load of 5 kg / cm ² to the battery and raising the temperature.

[Moisture Proof] The moisture permeability of the films of Examples and Comparative Examples was measured by the method specified in ASTM F 1249, and converted into moisture permeability per 25 μm thickness.

[0075]

[Table 1] As is clear from the table, the sealing materials of Examples have high moisture resistance, adhesiveness, chemical resistance and heat resistance. In particular, the sealing materials of the examples have higher heat resistance than the sealing materials of the comparative examples.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a paper lithium battery which is an example of the present invention.

FIG. 2 is a schematic cross-sectional view of the sealing material shown in FIG.

[Explanation of Codes] 1, 6 ... Terminal plate 2 ... Positive electrode mixture material 3 ... Separator 4 ... Negative electrode material 5 ... Sealing material 11, 13 ... Thermal adhesive polyolefin layer 12 ... Intermediate layer

Claims (16)

[Claims] 1. A battery element interposed between a pair of terminal plates,
A film for a sealing material for sealing in the peripheral portion of the terminal plate, wherein the heat-adhesive polyolefin layers on both outer layers for thermally adhering to the pair of terminal plates, and these heat-adhesive polyolefin layers A film for a sealing material for a thin battery, which has at least a three-layer structure of a polyolefin intermediate layer containing a filler and a polyolefin intermediate layer. 2. The film for a sealing material according to claim 1, wherein the heat distortion temperature of the intermediate layer is higher than that of the polyolefin of the intermediate layer by 15 ° C. or more. 3. The film for a sealing material according to claim 1, wherein the heat-adhesive polyolefin has a heat-bonding strength of 1.5 kg / 15 mm or more with respect to the terminal plate. 4. The film for a sealing material according to claim 1, wherein the Vicat softening point of the heat-adhesive polyolefin is 120 ° C. or higher. 5. The film for a sealing material according to claim 1, wherein the polyolefin forming the intermediate layer is polypropylene. 6. The film for a sealing material according to claim 1, wherein the polyolefin constituting the intermediate layer has a Vicat softening point higher than that of the heat-adhesive polyolefin by 3 ° C. or more. 7. The film for a sealing material according to claim 1, wherein the polyolefin constituting the intermediate layer has a Vicat softening point of 135 ° C. or higher. 8. The moisture permeability is 60 g in terms of thickness of 25 μm.
The film for a sealing material according to claim 1, which is not more than / m ² · day. 9. The film for a sealing material according to claim 1, wherein the filler of the intermediate layer is talc, mica, calcium carbonate or glass fiber. 10. The content of the filler is 5 to 5 of the whole intermediate layer.
The film for a sealing material according to claim 1, which is 50% by weight. 11. The thermal adhesive polyolefin layers on both outer layers have a thickness ta of 3 to 25 .mu.m and an intermediate layer thickness ti of at least ti = 2.times.ta.times.1.2 (.mu.m). The film for a sealing material according to 1. 12. A film for a sealing material for sealing a battery element interposed between a pair of terminal plates at a peripheral portion of the terminal plate, which has thermal adhesiveness on both outer layer sides having a Vicat softening point of 125 ° C. or higher. A modified polyolefin layer (A) and an intermediate layer (B) of a propylene-based polymer containing 10 to 50% by weight of an inorganic filler interposed between these heat-adhesive modified polyolefin layers, and the entire film. Of the intermediate layer thickness ti to the thickness t of the intermediate layer (t
i / t) is a film for a sealing material for thin batteries, which is 50 to 95%. 13. The sealing material for a thin battery according to claim 12, wherein the polyolefin of the intermediate layer has a Vicat softening point of 145 ° C. or higher and the heat deformation temperature of the intermediate layer is 20 ° C. or higher than that of the polyolefin of the intermediate layer. the film. 14. A frame-shaped sealing material for sealing a battery element interposed between a pair of terminal plates at a peripheral edge portion of the terminal plates, the outer layer being heat-bonded to the pair of terminal plates. A sealing material for a thin battery having at least a three-layer structure composed of a heat-adhesive polyolefin layer on the side and a polyolefin intermediate layer containing a filler interposed between these heat-adhesive polyolefin layers. 15. A method of laminating a polyolefin layer having a hot melt adhesive property, a polyolefin intermediate layer containing a filler, and a polyolefin layer having a hot melt adhesive property, wherein the heat deformation temperature is higher than that of the polyolefin of the intermediate layer. A method for producing a film for a sealing material, which comprises forming an intermediate layer using the resin composition having: 16. A battery element composed of a positive electrode mixture material, a separator and a negative electrode material, a pair of terminal plates for holding the battery element, and a battery element for sealing the battery element at a peripheral portion of the terminal plate. A thin battery comprising a sealing material, wherein the sealing material is composed of a laminated body having at least a three-layer structure including the following A layer and B layer. A layer: a heat-adhesive polyolefin layer constituting both outer layers B layer: a polyolefin intermediate layer which is interposed between A layers and contains a filler, and which has a higher heat distortion temperature than the polyolefin of the B layer.