JP7204334B2 - Polyolefin composition, laminate and packaging material for electrochemical cells - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyolefin composition, a laminate, and packaging materials for electrochemical cells using the same.

Lithium ion batteries, also referred to as lithium secondary batteries, include those that have a liquid, gel, or high-molecular polymer electrolyte, and whose positive and negative electrode active materials are made of polymers. In this lithium-ion battery, during charging, lithium atoms (Li) in the lithium transition metal oxide, which is the positive electrode active material, become lithium ions (Li ⁺ ) and enter the carbon layers of the negative electrode (intercalation), and during discharging, lithium A battery in which ions (Li ⁺ ) are deintercalated from carbon layers, move to the positive electrode, and become the original lithium compound, thereby progressing the charge-discharge reaction. It has excellent features such as high output voltage, high energy density, and no so-called memory effect, in which the apparent discharge capacity decreases due to repeated shallow discharge and recharge.

A lithium-ion battery is composed of a lithium-ion battery main body composed of a positive electrode current collector, a positive electrode active material layer, an electrolyte layer, a negative electrode active material layer, and a negative electrode current collector, and an outer package for packaging these, forming an outer package. Conventionally, as a packaging material for packaging, a can, which is formed by pressing a metal into a cylindrical or rectangular parallelepiped container, has been used. However, since the outer wall of the can is rigid, the shape of the battery itself is limited, and there is no degree of freedom in shape because the hardware side must be designed to match the battery. For this reason, there is a tendency in recent years to use multi-layer films as packaging materials in place of cans.

The manufacturing process of lithium-ion batteries that use multi-layer film as the packaging material (exterior) includes the process of filling the contents (lithium-ion battery body) inside the exterior and then heat-sealing to seal the contents. be Sealability is very important for safety in the case of the lithium ion battery. A packaging material made of this multilayer film is composed of at least a substrate layer, a metal foil, and a thermoadhesive resin layer, and an adhesive polyolefin layer may be provided between the metal foil and the thermoadhesive resin layer. The packaging material is formed into a bag to form a pouch-type exterior body for housing the battery body, or the packaging material is pressed to form a recess, and an embossed exterior body for housing the battery body in the recess is formed. be done. For example, in Patent Document 1, an unstretched polypropylene layer with a thickness of more than 10 μm and 60 μm or less, an acid-modified polyolefin layer with a thickness of 1 to 5 μm for bonding a metal foil and a heat-adhesive resin layer, and a coating amount of 5 to 30 mg. A packaging material has been proposed in which an aluminum foil layer having a thickness of 10 to 100 μm on which a first chemical conversion film layer of 1/m ² is formed and a synthetic resin layer are sequentially laminated.

Japanese Patent Application Laid-Open No. 2005-056729

Patent Literature 1 describes a mode in which a lithium ion battery main body is enclosed in an exterior body, and is sandwiched and packaged with the metal terminals of the battery main body projecting outward. However, if the fluidity of the thermoadhesive resin layer and the adhesive polyolefin layer, which serve as sealants, is high, the film thickness of these layers is greatly reduced during sealing, and there is a risk of short circuit. On the other hand, if the viscosity of the thermoadhesive resin layer and the adhesive polyolefin layer is increased in order to suppress the decrease in film thickness, molding defects such as film vibration and deterioration of film thickness accuracy occur in high-speed molding such as extrusion lamination molding. do. Patent Literature 1 does not describe such problems at all.

Therefore, in view of the above problems, the present invention provides an electrochemical cell packaging material used as an exterior body for sealingly housing electrochemical cells such as a lithium ion battery body, a capacitor, and an electric double layer capacitor, It is an object of the present invention to provide an electrochemical cell packaging material that suppresses reduction in film thickness and has excellent moldability, and a polyolefin composition that is useful for producing such an electrochemical cell packaging material.

The gist of the present invention is as follows.
[1]
A polyolefin composition containing a polyolefin and satisfying the following requirements (1) and (2).
(1) The ratio of shear viscosity η _12.16 measured at 230°C and shear rate 12.16 s ⁻¹ to shear viscosity η _243.2 measured at 230°C and shear rate 243.2 s ⁻¹ [η _12.16 / η _243.2 ] is 4 or more.
(2) Melt flow rate (230°C, 2.16 kg load) is 1 g/10 minutes or more and 8 g/10 minutes or less.

[2]
(A) 20 to 50% by mass of a polyolefin component having a melt flow rate (230°C, 2.16 kg load) of 0.1 g/10 minutes or more and less than 1.0 g/10 minutes
(B) 15 to 73% by mass of a polyolefin component having a melt flow rate (230°C, 2.16 kg load) of 1 g/10 minutes or more and less than 10 g/10 minutes
(C) 5 to 20% by mass of a polyolefin component having a melt flow rate (230°C, 2.16 kg load) of 10 g/10 minutes or more and less than 20 g/10 minutes, and (D) a melt flow rate (230°C, 2.16 2 to 15% by mass of polyolefin component whose (kg load) is 200 g/10 minutes or more
(where the total of polyolefin components (A) to (D) is 100% by mass).

[3]
The polyolefin composition of [2] above, wherein the polyolefin component (D) is a modified polyolefin modified with an unsaturated carboxylic acid or a derivative thereof.

[4]
At least one selected from the polyolefin components (A) to (D) has a melting point of 155° C. or more and 165° C. or less by differential scanning calorimetry, and at least one selected from the polyolefin components (A) to (D) The polyolefin composition of [2] or [3] above, wherein the melting point of the seed is 145°C or higher and lower than 155°C as measured by differential scanning calorimetry.

[5]
The polyolefin composition according to any one of [2] to [4], wherein the polyolefin component (B) further contains a propylene elastomer (B-1).

[6]
A laminate comprising an adhesive polyolefin layer containing the polyolefin composition according to any one of the above [1] to [5], and a metal foil layer.

[7]
Electrochemistry comprising a laminate obtained by laminating a substrate layer, a metal foil layer, an adhesive polyolefin layer made of the polyolefin composition according to any one of the above [1] to [5], and a thermoadhesive resin layer in this order Packaging material for cells.

By using the polyolefin composition of the present invention, it is possible to produce an electrochemical cell packaging material that suppresses reduction in film thickness during heat sealing and has excellent moldability.

FIG. 1 shows one aspect of the electrochemical cell packaging material according to the present invention. FIG. 2 shows one mode of usage of the electrochemical cell packaging material according to the present invention.

The polyolefin composition of the present invention and packaging materials for electrochemical cells using the same will be described in more detail below.
[Polyolefin composition]
The polyolefin composition according to the present invention is characterized by containing a polyolefin and satisfying the following requirements (1) and (2).
(1) Ratio of shear viscosity η _12.16 measured at 230°C and shear rate 12.16 s ⁻¹ to shear viscosity η _243.2 measured at 230°C and shear rate 243.2 s ⁻¹ [η _12.16 / η _243.2 ] ( hereinafter also referred to as "shear rate ratio") is 4 or more.
(2) Melt flow rate (230°C, 2.16 kg load) is 1 g/10 minutes or more and 8 g/10 minutes or less.
In addition, the said polyolefin composition shall also include the aspect containing only 1 type of said polyolefins.

《Requirements (1)》
The shear rate ratio of the polyolefin composition according to the present invention is 4 or more, and the upper limit thereof is preferably 20, more preferably 10, and even more preferably 5.
This shear rate ratio has the following technical significance.

The shear viscosity measured at a shear rate of 12.16 s ^-1 corresponds to the viscosity during processing with a small shear such as heat sealing, and the shear viscosity measured at a shear rate of 243.2 s ^-1 is the It corresponds to the viscosity at the time of rolling. That is, in order to suppress the decrease in film thickness during heat sealing, it is necessary to increase the shear viscosity measured at a shear rate of 12.16 s ^-1 . The shear viscosity measured at a shear rate of 243.2s ^-1 should be low. By using the polyolefin composition of the present invention having a shear rate ratio of 4 or more, it is possible to produce packaging materials for electrochemical cells that suppress reduction in film thickness during heat sealing and have excellent moldability. can. Further, when the shear rate ratio is equal to or less than the upper limit, the influence of variations in temperature during molding on the viscosity is small, and a molded product can be stably produced. On the other hand, if the shear rate ratio is less than 4, and the viscosity is increased to suppress the decrease in film thickness during heat sealing, the film thickness accuracy is significantly deteriorated, while the viscosity is decreased to improve the film thickness accuracy. In this case, the reduction in film thickness during heat sealing becomes large.
Said shear rate ratio can be increased or decreased, for example, by changing the molecular weight distribution of the composition.

《Requirement (2)》
The melt flow rate (according to ISO 1133, 230° C., 2.16 kg load) of the polyolefin composition according to the present invention is 1 to 8 g/10 minutes, preferably 1 to 5 g/10 minutes.

When the melt flow rate is within the above range, sufficient sealing strength can be ensured when the electrochemical cell packaging material using the polyolefin composition according to the present invention is heat-sealed at a normal sealing temperature (190 ° C.), and Thinning of the thickness of the seal portion can be suppressed.

On the other hand, if the melt flow rate is less than 1 g/10 min, molding defects such as film swaying and deterioration of film thickness accuracy may occur in extrusion lamination molding in which melt extrusion is performed at high speed. If is more than 8 g/10 minutes, the film thickness of the electrochemical cell packaging material at the time of heat sealing may be greatly reduced.

In order to satisfy the above requirements (1) and (2), the polyolefin composition of the present invention is an adhesive polyolefin layer for bonding a metal foil and a heat-adhesive resin layer in a packaging material for an electrochemical cell, which will be described later. It can be preferably used as a material.

It is important to design the polyolefin contained in the polyolefin composition of the present invention to have a wide molecular weight distribution.
A polyolefin component (A) having a melt flow rate (hereinafter also referred to as "MFR (230 ° C, 2.16 kg)" at 230 ° C. and a load of 2.16 kg) of 0.1 g / 10 minutes or more and less than 1.0 g / 10 minutes 50% by weight, preferably 25-45% by weight,
15 to 73% by mass, preferably 20 to 70% by mass of the polyolefin component (B) having an MFR (230°C, 2.16 kg) of 1 g/10 min or more and less than 10 g/10 min,
5 to 20% by mass, preferably 5 to 15% by mass of a polyolefin component (C) having an MFR (230°C, 2.16 kg) of 10 g/10 minutes or more and less than 20 g/10 minutes, and MFR (230°C, 2.16 kg) is 200 g/10 min or more polyolefin component (D) 2 to 15% by mass, preferably 2 to 10% by mass (however, polyolefin components (A), (B), (C) and (D) Let the total amount be 100% by mass.)
A polyolefin composition (hereinafter also referred to as "polyolefin composition (X)") containing the polyolefin is preferable.

In the polyolefin composition (X), the proportion of the polyolefin component having an MFR (230°C, 2.16 kg) of less than 0.1 g/10 min is 0 to 30% by mass, and the MFR (230°C, 2.16 kg) is 20 g/10 The proportion of the polyolefin component of 200 g/10 min or more is 0 to 30% by mass (provided that the total amount of polyolefin components (A), (B), (C) and (D) is 100% by mass) .).

Examples of the polyolefin components (A) to (D) each independently include ethylene homopolymers, propylene homopolymers, ethylene/α-olefin copolymers, propylene/α-olefin copolymers, and modifications thereof. These may be used singly or in combination of two or more. Examples of the α-olefin include ethylene, propylene, 1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-tetradecene and 1-octadecene. and α-olefins having 2 to 20 carbon atoms, preferably 4 to 10 carbon atoms. These α-olefins may be used singly or in combination of two or more. The ratio of the structural units derived from the α-olefin to the total structural units contained in the copolymer is preferably 0.5 to 50 mol%, more preferably 0.5 to 30 mol%.

The types of the polyolefin components (A) to (D) may all be the same, some may be the same, or all may be different from each other. Examples of combinations of different types of polyolefin components (A) to (D) include propylene/α-olefin copolymers and polyolefin mixtures (for example, propylene homopolymers and propylene/α-olefin copolymers ( For example, a mixture with a propylene-based elastomer (B-1)) described later), an ethylene/α-olefin copolymer, and a graft-modified polyolefin may be combined.

The polyolefin component (B) preferably contains a propylene elastomer (B-1) described later. The propylene-based elastomer (B-1) further improves the flexibility and durability of the packaging material for an electrochemical cell described below, improves bending resistance, and prevents cracks during molding.

The proportion of the propylene-based elastomer (B-1) in the polyolefin composition (X) is preferably 3 to 35% by mass.
From the viewpoint of adhesion between the metal foil and the adhesive polyolefin layer in the electrochemical cell packaging material, the polyolefin component (D) is preferably a modified polyolefin grafted with an unsaturated carboxylic acid or a derivative thereof. The grafting amount is preferably 0.01 to 10% by mass, more preferably 0.1 to 5% by mass. With such a graft amount, the adhesion of the adhesive polyolefin to the metal foil is good.

Examples of the unsaturated carboxylic acid or derivative thereof include acrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, nadic acid (trade name) (endosys-bicyclo[2,2 ,1]hept-5-ene-2,3-dicarboxylic acid), or derivatives thereof such as acid halides, amides, imides, anhydrides, esters and the like. Among these, unsaturated dicarboxylic acids and their acid anhydrides are preferred, and maleic acid, nadic acid and their acid anhydrides are particularly preferred. Various conventionally known methods can be employed to produce the component (D) by graft copolymerizing the unsaturated carboxylic acid or its derivative with the polyolefin. For efficient graft copolymerization of the graft monomer, the graft reaction is preferably carried out in the presence of a radical initiator. The grafting reaction is usually carried out at a temperature of 60-350°C. The ratio of the radical initiator to be used is usually 0.001 to 1 part by mass per 100 parts by mass of polyolefin.

Examples of radical initiators include organic peroxides, organic peresters, azo compounds, especially dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy). Hexyne-3, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 1,4-bis(tert-butylperoxyisopropyl)benzene and the like are preferred.

At least one selected from the polyolefin components (A) to (D) has a melting point of 155° C. or more and 165° C. or less by differential scanning calorimetry, and at least one selected from the polyolefin components (A) to (D) The melting point of the seed by differential scanning calorimetry is preferably 145° C. or more and less than 155° C. (preferably 154° C. or less). This melting point was measured by differential scanning calorimetry (DSC), about 10 mg of the sample was packed in an aluminum pan, (i) the temperature was raised from room temperature to 230 ° C. at 500 ° C./min and held at 230 ° C. for 10 minutes, and (ii ) the temperature is lowered to room temperature at 10°C/min, and then (iii) the temperature is raised to 230°C at 10°C/min. is the temperature at which the highest endothermic peak is observed.

In order to obtain the adhesive polyolefin composition of the present invention, for example, the components (A) to (D) are mixed in the above ranges by various known methods such as Henschel mixer, v-blender, ribbon blender, tumble blender, and the like. Alternatively, after mixing, the mixture is melt-kneaded with a single-screw extruder, twin-screw extruder, kneader, Banbury mixer, or the like, and then granulated or pulverized. In addition to the components described above, the composition of the present invention may optionally contain process stabilizers, heat stabilizers, weather stabilizers, etc., as long as the objects of the present invention are not impaired.

[Packaging materials for electrochemical cells]
The packaging material for an electrochemical cell according to the present invention comprises a laminate in which a substrate layer, a metal foil layer, an adhesive polyolefin layer and a thermoadhesive resin layer are laminated in this order, preferably a lithium ion battery. used as an exterior body for

Materials constituting each layer of the electrochemical cell packaging material according to the present invention will be described with reference to FIG. As shown in FIG. 1, an electrochemical cell packaging material (armor) 7 according to the present invention comprises a substrate layer 3, a thermoadhesive resin layer 2, and a metal foil layer 4 disposed therebetween. , the thermoadhesive resin layer 2 and the metal foil layer 4 are adhered via the adhesive polyolefin layer 1 . A chemical conversion treatment layer 4a may be provided on the surface of the metal foil layer 4. By providing the chemical conversion treatment layer 4a, the interlayer adhesive strength between the base material layer 3 and the thermoadhesive resin layer 2 and the metal foil layer 4 is further stabilized. Moreover, a protective layer 5 may be formed on the surface of the base material layer 3 . A different layer may be interposed between each layer.

<<Base material layer>>
The substrate layer 3 is generally a film made of oriented polyester or nylon. Examples of polyester include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolyester, polycarbonate and the like. Examples of nylon include polyamide resins such as nylon 6, nylon 6,6, copolymers of nylon 6 and nylon 6,6, nylon 6,10, and polymetaxylylene adipamide (MXD6).

In addition, the base layer 3 is a single-layer polyester film or nylon film or a laminate of films of different materials in order to improve pinhole resistance and insulation when used as a battery exterior. There may be. The thickness of the substrate layer composed of a single-layer film is usually 6 μm or more, preferably 6 to 25 μm. The laminated substrate layer 3 includes two or more resin layers, each layer having a thickness of 6 μm or more, preferably 6 to 25 μm. An example of a combination of layers of the laminated base material layer is a combination of an oriented polyethylene terephthalate layer and an oriented nylon layer.

The electrochemical cell packaging material of the present invention has mechanical suitability (stability of transportation in packaging machines and processing machines), surface protective properties (heat resistance, electrolyte resistance), or secondary processing for lithium ion batteries When the exterior body 7 is an embossed type, the substrate is used for the purpose of reducing the frictional resistance between the mold and the substrate layer 3 during embossing, or from the viewpoint of protecting the substrate layer 3 when the electrolyte adheres. The layer 3 is multi-layered, and a protective layer 5 (see FIG. 1) such as a fluorine-based resin layer, an acrylic resin layer, a silicone-based resin layer, a polyester-based resin layer, and a blend layer thereof is formed on the surface of the base material layer 3. It is preferable to provide
A similar effect can be obtained when stretched polybutylene terephthalate or polyethylene naphthalate is used instead of the stretched polyethylene terephthalate.

《Metal foil layer》
The metal foil layer 4 is a layer for preventing water vapor from entering the inside of the lithium ion battery from the outside. As the metal foil layer 4, a metal such as aluminum or nickel having a thickness of 15 μm or more, or an inorganic compound such as, for example, A film obtained by depositing silicon oxide, alumina, or the like can be mentioned, and conventionally, an aluminum foil having a thickness of 20 to 80 μm is used.

In addition, in order to improve the generation of pinholes and to prevent the generation of cracks in the embossing when the type of the exterior body of the lithium ion battery is embossed, the material of the aluminum used as the metal foil layer 4 is selected. , the iron content is 0.3 to 9.0% by mass, preferably 0.7 to 2.0% by mass.

As a result, compared to aluminum that does not contain iron, aluminum has good malleability, less occurrence of pinholes due to bending as an exterior body, and easy formation of side walls when packaging materials are embossed. can. If the iron content is less than 0.3% by mass, the effects of preventing pinholes and improving embossability are not observed, and the iron content of aluminum exceeds 9.0% by mass. In this case, the flexibility of aluminum is hindered, and the bag-making properties of the packaging material deteriorate.

In addition, aluminum produced by cold rolling changes its flexibility, stiffness, and hardness depending on the annealing (so-called annealing treatment) conditions, but the aluminum used in the present invention is less than hard-treated products that are not annealed. , slightly or fully annealed aluminum which tends to be soft.

That is, the annealing conditions may be appropriately selected according to the processability (pouching, embossing). For example, to prevent wrinkles and pinholes during embossing, annealed soft aluminum can be used depending on the degree of forming.

《Chemical conversion layer》
By subjecting the metal foil layer 4 to chemical conversion treatment, the bonding strength of the metal foil layer 4 with the adhesive 6 or the adhesive polyolefin layer 1 is improved.
As shown in FIG. 1, the chemical conversion treatment layer 4a is formed at least on the surface of the metal foil layer 4 on the thermoadhesive resin layer 2 side. The chemical conversion treatment layer 4 a can stably bond the adhesive polyolefin layer 1 and the metal foil layer 4 and prevent delamination of the metal foil layer 4 and the heat-adhesive resin layer 2 . Moreover, the chemical conversion treatment layer 4a prevents the metal foil layer 4 from corroding.

Specifically, by forming an acid-resistant film of phosphate, chromate, fluoride, triazinethiol compound, or the like on the surface of the metal foil layer 4, that is, a chemical conversion treatment layer 4a, the metal foil layer at the time of embossing is formed. Prevent delamination between 4 and the heat-adhesive resin layer 2, and dissolve and corrode the surface of the metal foil by hydrogen fluoride generated by the reaction between the electrolyte and moisture of the lithium ion battery, especially the metal foil When is an aluminum foil, it can prevent the aluminum oxide present on the surface from dissolving and corroding, and improve the adhesiveness (wettability) of the metal foil surface.

As a method for forming the chemical conversion treatment layer 4a, the metal foil layer 4 may be subjected to chromium-based chemical conversion treatments such as chromic acid chromate treatment, phosphoric acid chromate treatment, and coating-type chromate treatment, or non-chromium-based treatments such as zirconium, titanium, and zinc phosphate. (Coating-type) chemical conversion treatment and the like can be mentioned, but from the viewpoint that continuous treatment is possible and the treatment cost can be reduced without the need for a water washing step, coating-type chemical conversion treatments, especially aminated phenol polymers, Treatment with a treatment solution containing a trivalent chromium compound and a phosphorus compound is most preferred.

As a method for applying the treatment liquid when forming the chemical conversion treatment layer 4a, known application methods such as a bar coating method, a roll coating method, a gravure coating method, and an immersion method can be selected. Also, before forming the chemical conversion layer 4a, the surface of the metal foil layer 4 may be treated in advance by a well-known degreasing treatment method such as an alkali dipping method, an electrolytic cleaning method, an acid cleaning method, an acid activation method, or the like. , the function of the chemical conversion treatment layer 4a can be maximized and maintained for a long period of time.

《Adhesive polyolefin layer》
The adhesive polyolefin layer 1 is made of the above-described polyolefin composition according to the present invention, and is a layer provided for bonding the metal foil layer 4 and the thermoadhesive resin layer 2 together.
The thickness of the adhesive polyolefin layer 1 is usually 10-50 μm, preferably 20-40 μm.

《Thermal Adhesive Resin Layer》
The thermoadhesive resin layer 2 functions as an innermost layer and as a sealant layer when an electrochemical cell such as a lithium ion battery main body 8 is packaged with the electrochemical cell packaging material 7 according to the present invention.

The thickness of the thermoadhesive resin layer 2 is usually 10-50 μm, preferably 20-40 μm.
The thermoadhesive resin layer 2 may be a single-layer or multi-layer film of polypropylene, a single-layer or multi-layer film of linear low-density polyethylene or medium-density polyethylene, or a single-layer or multi-layer mixture of linear low-density polyethylene and medium-density polyethylene. Among them, polypropylene monolayer or multilayer films are preferred.

Examples of polypropylene include random polypropylene, homopolypropylene, block polypropylene and the like. These may be used individually by 1 type, and may be used in mixture of 2 or more types. When the multilayer film made of polypropylene has a layer of polypropylene containing the propylene-based elastomer (B-1) described below, physical properties such as durability, flexibility, and whitening resistance of the heat-adhesive resin layer 2 can increase

The polypropylene containing the propylene-based elastomer (B-1) has a particle size of 10 nm to 10 nm, unlike an ethylene/propylene random copolymer in which the resin is dispersed in a sea-island pattern with the amorphous portion as the sea and the crystal portion as the islands. It is preferable to have a structure in which "islands", which are helical crystal parts on the order of 50 nm, are connected to each other to form a net-like structure and cover the entire amorphous part. Due to this network structure, the polypropylene containing the propylene elastomer (B-1) has excellent sealing strength, durability, heat resistance and flexibility.

Since the polypropylene containing the propylene-based elastomer (B-1) has such a structure, the heat-adhesive resin layer 2 has a polypropylene layer containing the propylene-based elastomer (B-1). In addition, the molding limit of the packaging material can be increased, and cracking of the thermoadhesive resin layer 2 due to press molding can be prevented.

This is because the crystal part of the polypropylene containing the propylene-based elastomer (B-1) has a "mesh" structure, so the polypropylene layer containing the propylene-based elastomer (B-1) melts and solidifies once during heat sealing. This is thought to be due to the fact that the "net" structure remains even when solidified uniformly.

When the propylene-based elastomer (B-1) is contained in the polypropylene in a proportion of 3% by mass or more and 35% by mass or less, the physical properties and functions of the polypropylene layer can be most improved.

The propylene-based elastomer (B-1) is a copolymer comprising propylene-derived structural units and α-olefin (excluding propylene)-derived structural units having 2 to 20 carbon atoms. 50 mol% or more (where the total of propylene-derived structural units and α-olefin-derived structural units having 2 to 20 carbon atoms is 100 mol%) and satisfies the following (a) to (d) .
(a) Shore A hardness (ASTM D2240) measured by the method described later is 65-90, preferably 65-85, more preferably 72-85.
(b) a melting point of 130 to 170°C, preferably 130 to 150°C, as measured by the method described later;
(c) a density (ASTM D1505) of 860-875 kg/m ³ , preferably 860-872 kg/m ³ ;
(d) The glass transition temperature is -25°C to -35°C, preferably -26°C to -33°C, as measured by the method described later.

Examples of α-olefins having 2 to 20 carbon atoms (excluding propylene) constituting the propylene-based elastomer (B-1) include ethylene, 1-butene, 1-pentene, 1-hexene, and 4-methyl-1-pentene. , 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene and the like.

The propylene-based elastomer (B-1) is preferably a copolymer comprising propylene-derived structural units, ethylene-derived structural units, and α-olefin-derived structural units having 4 to 10 carbon atoms.

The content of structural units derived from propylene is 50 mol% or more when the total content of structural units derived from propylene and α-olefins having 2 to 20 carbon atoms (excluding propylene) is 100 mol%. It is 99 mol % or less, preferably 60 mol % or more and 99 mol % or less.

The propylene-based elastomer (B-1) preferably satisfies the above (a), (b), (c), and (d) and also satisfies one of the following (e) or (f). ) and (f) are more preferably satisfied.
(e) Haze (internal haze) is less than 15%, preferably less than 10%.
(f) a melt flow rate (measured according to ASTM D1238 at 230° C. and a load of 2.16 kg) of 3 to 15 g/10 min, preferably 5 to 10 g/10 min;

The methods for measuring the physical properties shown in (a) to (f) will be described in order.
The Shore A hardness of (a) was determined by leaving a press sheet with a thickness of 2 mm obtained by molding under the following press molding conditions at 23 ° C. for 72 hours, and then using a rubber hardness tester (Shore A type). The scale was read immediately after the sheets were stacked and brought into contact with the indentor (according to ASTM D2240).
Press molding conditions: temperature 190°C, heating and pressurization time 7 minutes, cooling with a 15°C chiller

The melting point (Tm) of (b) was determined by differential scanning calorimetry (DSC), in which about 10 mg of the sample was packed in an aluminum pan, (i) the temperature was raised to 200°C at 100°C/min, and the temperature was maintained at 200°C for 5 minutes. After (ii) the temperature was lowered at 10°C/min to -150°C, and then (iii) the temperature was raised at 10°C/min to 200°C, the temperature of the endothermic peak observed in (iii) was measured. be.

The density of (c) is measured by a method according to ASTM D1505 after leaving a press sheet with a thickness of 2 mm obtained under the same press molding conditions as the Shore A hardness measurement sample at 23° C. for 72 hours. is.

The glass transition temperature (Tg) of (d) is measured by differential scanning calorimetry (DSC), packing about 10 mg of the sample in a special aluminum pan, (i) heating from 30 ° C. to 200 ° C. at 200 ° C./min, After holding at 200° C. for 5 minutes, (ii) decreasing the temperature from 200° C. to −100° C. at 10° C./min, holding at −100° C. for an additional 5 minutes, and then (iii) increasing the temperature at 10° C./min. do. It is obtained from the DSC curve in this case (iii).

The haze (internal haze) of (e) is obtained by leaving a pressed sheet of s2 mm compressed under the same press molding conditions as the Shore A hardness measurement sample at 23 ° C. for 72 hours. Co., Ltd. Digital turbidity meter (NDH-2000) or equivalent turbidity meter is used to measure the diffuse transmitted light amount by C light source and the total transmitted light amount by C light source in cyclohexanol solution, and the following formula Haze (internal haze) is measured.
Haze (%) = 100 x (amount of diffuse transmitted light)/(amount of total transmitted light)

The melt flow rate of (f) is measured according to ASTM D1238 at 230° C. and a load of 2.16 kg.

The content of each structural unit in the propylene elastomer (B-1) was measured using ¹³ C-NMR.
The propylene-based elastomer (B-1) is not particularly limited as long as it satisfies the physical properties described above, but it may be a commercially available product. Examples of commercially available products include "Tafmer (registered trademark)" manufactured by Mitsui Chemicals, Inc.

Corona Surface activation treatment such as treatment, blasting treatment, oxidation treatment, and ozone treatment may be applied.

(Lamination method)
The electrochemical cell packaging material of the present invention can be produced by a conventionally known method, except that the adhesive polyolefin layer 1 is formed from the polyolefin composition of the present invention.

In the electrochemical cell packaging material of the present invention, for example, the substrate layer 3 and the metal foil layer 4 are first laminated together with the adhesive layer 6 using a dry lamination method, and then the adhesive polyolefin is attached to the resulting laminate. It can be manufactured by laminating the layer 1 and the thermoadhesive resin layer 2 .

As a method for laminating the adhesive polyolefin layer 1 and the thermoadhesive resin layer 2 on the laminate, a coextruded film composed of the adhesive polyolefin layer 1 and the thermoadhesive resin layer 2 is thermally laminated to the metal foil layer 4. A lamination method and a sandwich lamination method in which a molten adhesive polyolefin layer 1 is sandwiched between a metal foil layer 4 and a thermoadhesive resin layer 2 and laminated.

Specifically, in the thermal lamination method, the surface of the adhesive polyolefin layer 1 of the coextruded film composed of the adhesive polyolefin layer 1 and the thermal adhesive resin layer 2 is chemically treated, and the metal foil layer 4 such as aluminum is chemically treated. The sandwich lamination method is a method in which an adhesive polyolefin layer 1 is extruded as an adhesive resin onto the chemical conversion treatment layer 4a of the metal foil layer 4 and adhered to the thermoadhesive resin layer 2. . Here, when extrusion laminating the adhesive polyolefin layer 1, the obtained laminate is heated to a softening point of the adhesive polyolefin or higher (post-heating), or the aluminum surface is adhered in the extrusion process of the adhesive polyolefin. By heating above the softening point of the polyolefin (preheating), the packaging material can be laminated as an outer packaging material with adhesive strength to withstand contents resistance and moldability.

As this heating method, there are methods such as a hot roll contact method, a hot air method, and a near- or far-infrared method. It is good if it can be heated to

An exterior body for enclosing an electrochemical cell such as a lithium ion battery main body is produced, for example, by first bending the electrochemical cell packaging material of the present invention so that the thermoadhesive resin layer 2 is on the inside, or by folding two sheets or the present invention. The electrochemical cell packaging materials are placed face to face with the thermoadhesive resin layer 2 on the inside, and then heat-sealed around the electrochemical cell except for the inserting portion. An electrochemical cell is enclosed in the outer package thus produced, and the opening of the outer package is sealed. When the electrochemical cell is a lithium-ion battery body, the lithium-ion battery body is enclosed in the outer packaging, and the metal terminals of the battery body protrude outward and the opening of the packaging is sealed. will be For example, as shown in FIG. 2, when the lithium ion battery body 8 is enclosed in the outer package 7 and the metal terminal 9 of the battery body is sandwiched and sealed in a state of protruding to the outside, the melt-extruded adhesive polyolefin Since the fluidity of the layer 1 and the thermoadhesive resin layer 2 is high, the opening of the exterior body 7 can be hermetically sealed so as to cover the entire holding portion of the metal terminal 9 . Therefore, it is possible to block external water vapor permeating from the sandwiched portion of the metal terminal 9 and suppress the generation of hydrofluoric acid due to the reaction between the electrolyte and water vapor.

Hereinafter, the present invention will be described more specifically based on examples.
Raw materials used in Examples and the like are shown below.
・Polyolefin component (A)
rPP-1: propylene/ethylene random copolymer (melt flow rate (230°C, 2.16 kg load) 0.5 g/10 min, density 0.90 g/cm ³ , ethylene content 6.0 mol%, melting point 145°C) )
- Polyolefin component (B)
hPP-1: Propylene homopolymer (melt flow rate (230°C, 2.16 kg load) 3.5 g/10 minutes, density 0.90 g/cm ³ , melting point 160°C)
hPP-2: Propylene homopolymer (melt flow rate (230°C, 2.16 kg load) 7.0 g/10 minutes, density 0.90 g/cm ³ , melting point 160°C)
(B-1) component
PN-1: Toughmer (registered trademark) PN-2070 (manufactured by MITSUI ELASTOMERS SINGAPORE PTE LTD)
(Melt flow rate (230°C, 2.16 kg load) 7.0 g/10 minutes, density 0.87 g/cm ³ , Shore A hardness 75, melting point 138°C, glass transition temperature -29°C, haze 7%)
・Polyolefin component (C)
PE-1: low density polyethylene (melt flow rate (230°C, 2.16 kg load) 15 g/10 minutes, density 0.92 g/cm ³ , melting point 103°C)
・Polyolefin component (D)
MAH-PP-1: Maleic anhydride-modified polypropylene (melt flow rate (230°C, 2.16 kg load) 200 g/10 minutes, density 0.90 g/cm ³ , melting point 158°C)
・Thermal adhesive resin
rPP-2: propylene/ethylene random copolymer (melt flow rate (230°C, 2.16 kg load) 10.0 g/10 min, density 0.90 g/cm ³ , ethylene content 4.0 mol%)

[Example 1]
(Polyolefin composition)
30% by mass of hPP-1, 30% by mass of rPP-1, 20% by mass of PN-1, 10% by mass of PE-1, and 10% by mass of MAH-PP-1 were mixed in a twin-screw kneader (Nippon Steel The adhesive polyolefin composition (1) was obtained by melt-kneading at 230° C. using TEX-30). The resulting composition had a melt flow rate of 3.8 g/10 minutes and a density of 0.90 g/cm ³ . Table 1 shows the ratio of the viscosity under a shear rate of 12.16 s ^-1 to the viscosity under a shear rate of 243.2 s ^-1 (η _12.16 /η _243.2 ). The viscosity under the above shear rate was measured at 230° C. using a capillary rheometer.

(packaging materials for electrochemical cells)
A metal foil layer made of aluminum foil (40 μm thick) with chemical conversion treatment on both sides was laminated by a dry lamination method on a substrate layer made of a biaxially oriented nylon film (25 μm thick). Specifically, a two-component urethane adhesive (polyester-based main agent and isocyanate-based curing agent) was applied to one surface of the aluminum foil to form an adhesive layer (4 μm thick) on the metal foil layer. Next, after the adhesive layer on the metal foil layer and the base layer are laminated under pressure and heat, an aging treatment is performed at 60° C. for 24 hours to form a laminate of the base layer/adhesive layer/metal foil layer. manufactured. In addition, the chemical conversion treatment of the aluminum foil used as the metal foil layer was carried out by applying a treatment solution consisting of phenolic resin, chromium fluoride compound, and phosphoric acid so that the coating amount of chromium was 10 mg/m ² (dry weight). Both surfaces of the aluminum foil were coated by a coating method and baked for 20 seconds under the condition that the coating temperature was 180° C. or higher.

Next, the adhesive polyolefin (1) and the thermal adhesive resin were laminated on the metal foil layer by a coextrusion method. Thus, an electrochemical cell packaging material (1) consisting of a laminate in which base layer/adhesive layer/metal foil layer/adhesive polyolefin layer/thermoadhesive resin layer were laminated in this order was obtained. The thicknesses of the adhesive polyolefin layer and the heat adhesive resin layer were 20 μm and 20 μm, respectively.
The electrochemical cell packaging material (1) was evaluated by the following methods. Table 1 shows the evaluation results.

[Moldability]
Film thickness accuracy in the TD direction when co-extrusion of adhesive polyolefin and thermal adhesive resin on a metal foil layer (specifically, the difference in thickness between the maximum thickness and minimum thickness of the co-extruded film. Keyence (measured with a digital microscope VH-5500 manufactured by Fujikura Ltd.) was evaluated according to the following criteria.
○: The difference between the thickness of the thickest part and the thickness of the thinnest part in the TD direction is less than 25% of the thickness of the thickest part ×: The thickness of the thickest part in the TD direction and the thickness of the thinnest part difference is 25% or more with respect to the thickness of the maximum thickness part

[Remaining film thickness]
A packaging material for an electrochemical cell was cut into a sheet piece of 60 mm (MD direction) x 60 mm (TD direction), and this sheet piece was horizontally folded in the TD direction so that the thermoadhesive resin layer was on the inside. , Heat-sealing was performed under the following conditions with a width of 7 mm in the TD direction, the film thickness before and after heat-sealing was measured, and the film thickness residual rate was calculated by the following equation.
Heat sealing conditions: surface pressure 1.0 MPa, sealing temperature 190° C., sealing time 3.0 seconds Film thickness residual rate (%)
= film thickness after heat sealing / film thickness before heat sealing × 100

[Presence or absence of whitening]
A packaging material for an electrochemical cell was deep-drawn using a mold with an engagement depth of 5 mm, and the presence or absence of whitening on the wall surface was visually confirmed.

[Example 2]
(Preparation of polyolefin composition)
50% by mass of hPP-1, 30% by mass of rPP-1, 10% by mass of PE-1, and 10% by mass of MAH-PP-1 using a twin-screw kneader (manufactured by Japan Steel Works, TEX-30) The mixture was melt-kneaded at 230° C. to obtain an adhesive polyolefin composition (2). The resulting composition had a melt flow rate of 3.4 g/10 minutes and a density of 0.90 g/cm ³ . Table 1 shows the ratio of the viscosity under a shear rate of 12.16 s ^-1 to the viscosity under a shear rate of 243.2 s ^-1 (η _12.16 /η _243.2 ).

(packaging materials for electrochemical cells)
A packaging material for an electrochemical cell was produced and evaluated in the same manner as in Example 1, except that the adhesive polyolefin composition (1) was changed to the adhesive polyolefin composition (2).

[Comparative Example 1]
(Polyolefin composition)
99% by mass of hPP-1 and 1% by mass of MAH-PP-1 are melt-kneaded at 230 ° C. using a twin-screw kneader (manufactured by Japan Steel Works, TEX-30) to give an adhesive polyolefin composition (3 ). The adhesive polyolefin composition (3) had a melt flow rate of 3.6 g/10 minutes and a density of 0.90 g/cm ³ . Table 1 shows the ratio of the viscosity under a shear rate of 12.16 s ^-1 to the viscosity under a shear rate of 243.2 s ^-1 (η _12.16 /η _243.2 ).

(packaging materials for electrochemical cells)
An electrochemical cell packaging material was produced and evaluated in the same manner as in Example 1, except that the adhesive polyolefin composition (1) was changed to the adhesive polyolefin composition (3).

[Comparative Example 2]
(Preparation of polyolefin composition)
30% by mass of hPP-1, 30% by mass of hPP-2, 20% by mass of PN-1, 10% by mass of PE-1, and 10% by mass of MAH-PP-1 were mixed in a twin-screw kneader (Nippon Steel The adhesive polyolefin composition (4) was obtained by melt-kneading at 230° C. using TEX-30). The resulting composition had a melt flow rate of 8.3 g/10 minutes and a density of 0.90 g/cm ³ . Table 1 shows the ratio of the viscosity under a shear rate of 12.16 s ^-1 to the viscosity under a shear rate of 243.2 s ^-1 (η _12.16 /η _243.2 ).

(packaging materials for electrochemical cells)
An electrochemical cell packaging material was produced and evaluated in the same manner as in Example 1, except that the adhesive polyolefin composition (1) was changed to the adhesive polyolefin composition (4).

As shown in Table 1, in the electrochemical cell packaging materials of Examples in which the adhesive polyolefin layer was formed from the polyolefin composition according to the present invention, both moldability and reduction in film thickness reduction during heat sealing were achieved. did it. Moreover, whitening resistance was improved by adding a propylene-based elastomer.

On the other hand, when the melt flow rate of the polyolefin composition forming the adhesive polyolefin layer is higher than 8 g/10 minutes as in Comparative Example 2, the moldability is good, but the film thickness retention rate after heat sealing is low.

1: Adhesive polyolefin layer 2: Thermal adhesive resin layer 3: Base material layer 4: Metal foil layer 4a: Chemical conversion layer 5: Protective layer 6: Adhesive layer 7: Packaging material for electrochemical cell (exterior body)
8: Lithium ion battery body 9: Metal terminal

Claims (6)

contains polyolefin,
The polyolefin is
Propylene/ethylene copolymer (A) having a melt flow rate (230°C, 2.16 kg load) of 0.5 g/10 minutes, a density of 0.90 g/cm ³ , an ethylene content of 6.0 mol%, and a melting point of 145°C ;
Propylene homopolymer (B) having a melt flow rate (230°C, 2.16 kg load) of 3.5 g/10 minutes, a density of 0.90 g/cm ³ and a melting point of 160°C ,
an ethylene homopolymer (C) having a melt flow rate (230°C, 2.16 kg load) of 15 g/10 minutes, a density of 0.92 g/cm ³ and a melting point of 103° C;
Modified polypropylene modified with maleic anhydride (D) having a melt flow rate (230°C, 2.16 kg load) of 200 g/10 minutes, a density of 0.90 g/cm ³ and a melting point of 158°C
contains
A polyolefin composition that satisfies the following requirements (1) and (2).
(1) Ratio of shear viscosity η _12.16 measured at 230° C. and shear rate 12.16 s ⁻¹ to shear viscosity η _243.2 measured at 230° C. and shear rate 243.2 s ⁻¹ [η _12.16 /η _243.2 ] is 4 or more.
(2) Melt flow rate (230° C., 2.16 kg load) is 1 g/10 minutes or more and 8 g/10 minutes or less. Melt flow rate (230°C, 2.16 kg load) 7.0 g/10 minutes, density 0.87 g/cm ³ , a Shore A hardness of 75, a melting point of 138° C., a glass transition temperature of −29° C. and a haze of 7%. The content of the propylene/ethylene copolymer (A) is 30% by mass,
The content of the propylene homopolymer (B) is 50% by mass,
The content of the ethylene homopolymer (C) is 10% by mass,
The polyolefin composition according to claim 1, wherein the content of the maleic anhydride-modified polypropylene (D) is 10% by mass. The content of the propylene/ethylene copolymer (A) is 30% by mass,
The content of the propylene homopolymer (B) is 30% by mass,
The content of the propylene-based elastomer (B-1) is 20% by mass,
The content of the ethylene homopolymer (C) is 10% by mass,
3. The polyolefin composition according to claim 2, wherein the content of the maleic anhydride-modified polypropylene (D) is 10% by mass. A laminate comprising an adhesive polyolefin layer containing the polyolefin composition according to any one of claims 1 to 4 and a metal foil layer. An electrical system comprising a laminate obtained by laminating a substrate layer, a metal foil layer, an adhesive polyolefin layer made of the polyolefin composition according to any one of claims 1 to 4 , and a thermoadhesive resin layer in this order. Packaging materials for chemical cells.

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