JP2009176647A - Battery case for secondary battery, and secondary battery having the battery case - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery case for a secondary battery which is superior in steam barrier performance and mechanical strength, and superior in durability, in particular, durability under a metal contact environment, and a secondary battery having this battery case. <P>SOLUTION: The battery case includes a resin composition which contains a polypropylene-based resin (A), phosphorous acid ester (B), and a heavy-metal deactivator (C). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a battery case for a secondary battery and a secondary battery having the battery case. More specifically, the present invention relates to a battery case for a secondary battery that is excellent in water vapor barrier properties and mechanical strength, and has excellent heat weldability, pressure resistance, and durability in a metal contact environment, and a secondary battery having the battery case. Is.

  Secondary batteries are widely used as power sources for automobiles, electrical products, industrial machines and the like. In particular, secondary batteries having nickel-metal hydride electrodes or lithium electrodes, which are high energy density, high capacity storage batteries, are used. With the demand for secondary batteries, it has become necessary to increase the size and weight of battery cases, diversify their designs, etc. The materials used for battery cases also have moldability, water vapor barrier properties, and gas barriers. , Durability, heat weldability and the like are required.

As a material used for the battery case of the secondary battery, for example, a resin composition made of polypropylene and a propylene-ethylene copolymer and having a crystallinity between 55% and 65% is disclosed (Patent Document). 1). Further, it is disclosed to use a resin composition comprising a polyphenylene ether resin, a specific crystalline polypropylene resin, and, if necessary, a block copolymer blended at a predetermined ratio (see Patent Document 2). ).
Japanese Patent Laid-Open No. 11-31483 JP 2002-63873 A

However, although the battery case manufactured using the resin composition disclosed in Patent Document 1 has improved gas barrier properties, it cannot be said that the durability and thermal weldability are necessarily sufficient. Moreover, although the battery case manufactured using the resin composition currently disclosed by patent document 2 improved mechanical strength and chemical resistance, it cannot be said that water vapor | steam barrier property is necessarily enough.
In view of the above problems, the present invention is a battery case for a secondary battery that is excellent in water vapor barrier properties and mechanical strength, and is excellent in durability, particularly durability in a metal contact environment, and a secondary battery having the battery case. The purpose is to provide.

The present inventor has found that the above-mentioned problems can be solved by using a resin composition having the following configuration, and has completed the present invention.
That is, the present invention comprises a resin composition containing a polypropylene resin (A), a phosphite ester (B), and a heavy metal deactivator (C). A battery case is provided.
Moreover, this invention provides the secondary battery which has the said battery case and a nickel metal hydride electrode or a lithium electrode.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the battery case for secondary batteries which is excellent in water vapor | steam barrier property and mechanical strength, and is excellent in durability, and a secondary battery which has this battery case.

  The battery case according to the present invention comprises a polypropylene resin (A) (hereinafter also referred to as component (A)), a phosphite (B) (hereinafter also referred to as component (B)), a heavy metal deactivator. (C) (hereinafter also referred to as the component (C)). This will be described in detail below.

(Resin composition)
<Polypropylene resin (A)>
The resin composition contains a polypropylene resin (A). Although the weight average molecular weight (polystyrene conversion weight average molecular weight calculated by gel permeation chromatography) of the polypropylene resin (A) is not particularly limited, it is preferably 650,000 to 1,000,000, more preferably 700,000. ~ 900,000. By setting the weight average molecular weight to 650000 or more, it is possible to prevent a decrease in the melt viscosity of the resin composition. Thereby, when welding and sealing a battery case main body and a lid | cover, it becomes possible to prevent that the welding layer thickness of a welding part becomes thin and the pressure resistance of the battery case after welding falls. Moreover, it becomes possible to prevent the raise of the melt viscosity of a resin composition by a weight average molecular weight being 1000000 or less. This makes it possible to improve the injection moldability of the resin composition.
The ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polypropylene resin (A) used in the present invention, that is, the molecular weight distribution is preferably 2 or more, more preferably 4 or more.
The molecular weight of the polypropylene resin (A) can be adjusted by adjusting the hydrogen concentration in the reaction vessel during polymerization. Generally, it is possible to reduce the molecular weight by increasing the hydrogen concentration. The molecular weight distribution can be adjusted depending on the type of catalyst used.

Examples of the polypropylene resin (A) include a propylene homopolymer, a propylene-ethylene random copolymer, or a block copolymer composed of a propylene homopolymer and a propylene-ethylene random copolymer.
As a manufacturing method of a propylene homopolymer or a propylene-ethylene random copolymer, the well-known manufacturing method using a polymerization catalyst is mentioned. Examples of the polymerization catalyst include Ziegler catalysts and metallocene catalysts. Examples of the polymerization method include slurry polymerization and gas phase polymerization.

  As a manufacturing method of the block copolymer which consists of a propylene homopolymer and a propylene-ethylene random copolymer, the well-known manufacturing method using a polymerization catalyst is mentioned. For example, the manufacturing method which consists of the 1st process of obtaining a propylene homopolymer, and the 2nd process of obtaining a propylene-ethylene random copolymer is mentioned.

  The polypropylene resin (A) used in the present invention is preferably a polypropylene resin containing a propylene-ethylene random copolymer from the viewpoint of the mechanical strength (impact resistance) of the obtained molded product. And, the content of ethylene contained in this random copolymer is from 0.1% by mass to less than 1% by mass from the viewpoint of enhancing the mechanical strength and impact resistance of the battery case, more preferably, 0.1 mass% to 0.5 mass% (however, the total amount of the polypropylene resin (A) is 100 mass%).

  When the polypropylene resin (A) used in the present invention is a block copolymer composed of a propylene homopolymer and a propylene-ethylene random copolymer, the content of the propylene-ethylene random copolymer can be obtained. From the viewpoint of heat resistance of the molded product, 5% by mass to 40% by mass is preferable (provided that the total amount of the propylene homopolymer and the ethylene-propylene random copolymer is 100% by mass), propylene-ethylene random copolymer. The ethylene content contained in the coalescence is preferably 0.05% by mass to 20% by mass from the viewpoint of mechanical strength (provided that the total amount of the propylene-ethylene random copolymer is 100% by mass).

The melt viscosity at a temperature of 230 ° C. and a shear rate of 12 sec ⁻¹ of the polypropylene resin used in the present invention is 2000 to 7000 Pa · s from the viewpoint of improving the pressure resistance of the obtained battery case and the injection moldability of the resin composition. Preferably, it is 4000 to 6000 Pa · s.

〔式中、Ｒ¹、Ｒ²、Ｒ⁴及びＲ⁵はそれぞれ独立に水素原子、炭素数１〜８のアルキル基、炭素数５〜８のシクロアルキル基、炭素数６〜１２のアルキルシクロアルキル基、炭素数７〜１２のアルキル基又はフェニル基を表し、Ｒ³は水素原子又は炭素数１〜８のアルキル基を表す。Ｘは硫黄原子もしくは−ＣＨＲ⁶−基（Ｒ⁶は水素原子、炭素数１〜８のアルキル基又は炭素数５〜８のシクロアルキル基を示す。）を表し、ｎは０又は１である。Ａは炭素数２〜８のアルキレン基又は＊−ＣＯ（Ｒ⁷）_m−基（Ｒ₇は炭素数１〜８のアルキレン基を、＊は酸素原子との結合部位であることを示し、ｍは０又は１である。）を表す。Ｙ、Ｚは、そのいずれかの一方がヒドロキシル基、炭素数１〜８のアルコキシ基又は炭素数７〜１２のアルキルオキシ基を表し、他方が水素原子又は炭素数１〜８のアルキル基を表す。〕 <Phosphorous ester (B)>
The resin composition used in the present invention contains a phosphite (B) represented by the general formula P (OR) ₃ (wherein R represents an organic group). Specifically, the following general formula (B-1
It is preferable to use a compound represented by

[Wherein R ¹ , R ² , R ⁴ and R ⁵ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, or an alkylcycloalkyl having 6 to 12 carbon atoms. Group, an alkyl group having 7 to 12 carbon atoms or a phenyl group, and R ³ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. X represents a sulfur atom or a —CHR ⁶ — group (R ⁶ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms), and n is 0 or 1. A represents an alkylene group having 2 to 8 carbon atoms or * -CO (R ⁷ ) _m -group (R ₇ represents an alkylene group having 1 to 8 carbon atoms, * represents a bonding site with an oxygen atom, m Is 0 or 1. One of Y and Z represents a hydroxyl group, an alkoxy group having 1 to 8 carbon atoms or an alkyloxy group having 7 to 12 carbon atoms, and the other represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. . ]

In the phosphites (B), the substituents R ¹ , R ² , R ⁴ and R ⁵ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, An alkylcycloalkyl group having 6 to 12 carbon atoms, an alkyl group having 7 to 12 carbon atoms, or a phenyl group is represented.

  Here, examples of the alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a sec-butyl group, and a t-butyl group. , T-pentyl group, i-octyl group, t-octyl group, 2-ethylhexyl group and other linear or branched alkyl groups. Examples of the cycloalkyl group having 5 to 8 carbon atoms include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group. Examples of the alkylcycloalkyl group having 6 to 12 carbon atoms include 1-methylcyclopentyl group, 1-methylcyclohexyl group, 1-methyl-4-i-propylcyclohexyl group and the like. Examples of the alkyl group having 7 to 12 carbon atoms include benzyl group, α-methylbenzyl group, α, α-dimethylbenzyl group and the like.

R ¹ , R ² , and R ⁴ are preferably an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, and an alkyl cycloalkyl group having 6 to 12 carbon atoms. Among them, R ¹ and R ⁴ are more preferably a t-alkyl group such as a t-butyl group, a t-pentyl group, or a t-octyl group, a cyclohexyl group, and a 1-methylcyclohexyl group.
R ² is more preferably a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group, t-butyl group, t-pentyl group, etc. And an alkyl group having 1 to 5 carbon atoms, more preferably a methyl group, a t-butyl group, or a t-pentyl group.
R ⁵ is preferably a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms, more preferably a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, or i-propyl. Group, an n-butyl group, an i-butyl group, a sec-butyl group, a t-butyl group, a t-pentyl group and the like, and an alkyl group having 1 to 5 carbon atoms.

The substituent R ³ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Examples of the alkyl group having 1 to 8 carbon atoms include the same alkyl groups as described above. Preferably they are a hydrogen atom or a C1-C5 alkyl group, More preferably, they are a hydrogen atom or a methyl group.

X is a sulfur atom or —CHR ⁶ — group (R ⁶ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms). And when n is 0, it represents that the group which has two phenoxy group frame | skeletons has couple | bonded directly, and when n is 1, it is a sulfur atom, a C1-C8 alkyl group, or C5-C8. Represents a methylene group which may be substituted by the cycloalkyl group. Here, examples of the alkyl group having 1 to 8 carbon atoms and the cycloalkyl group having 5 to 8 carbon atoms substituted on the methylene group include the same alkyl groups and cycloalkyl groups as described above. As the substituent X, n is preferably 0 and a group having two phenoxy group skeletons is directly bonded, or n is 1, and a methylene group, a methyl group, an ethyl group, or an n-propyl group , I-propyl group, n-butyl group, i-butyl group, t-butyl group and the like are substituted methylene groups.

A is an alkylene group having 2 to 8 carbon atoms or * —CO (R ⁷ ) _m — group, wherein R ⁷ is an alkylene group having 1 to 8 carbon atoms, and * is a bonding site with an oxygen atom. M is 0 or 1. ] Is represented.
Here, examples of the alkylene group having 2 to 8 carbon atoms include ethylene group, propylene group, butylene group, pentamethylene group, hexamethylene group, octamethylene group, 2,2-dimethyl-1,3-propylene group and the like. Preferably, it is a propylene group. The * -COR ⁷ - * in group indicates that the carbonyl group is a moiety that binds to the oxygen atom of the phosphite group. Examples of the alkylene group having 1 to 8 carbon atoms in R ⁷ include a methylene group, an ethylene group, a propylene group, a butylene group, a pentamethylene group, a hexamethylene group, an octamethylene group, and 2,2-dimethyl-1,3- A propylene group etc. are mentioned. * —CO (R ⁷ ) _m — group is preferably * —CO— group in which m is 0, or m is 1, and R ⁷ is ethylene * —CO (CH ₂ CH ₂ ) — It is a group.

One of Y and Z represents a hydroxyl group, an alkoxy group having 1 to 8 carbon atoms or an alkyloxy group having 7 to 12 carbon atoms, and the other represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. .
Here, examples of the alkyl group having 1 to 8 carbon atoms include the same alkyl groups as described above. As a C1-C8 alkoxy group, the alkoxy group whose alkyl part is the same alkyl as the said C1-C8 alkyl is mentioned, for example. Moreover, as a C7-12 alkyloxy group, the alkyloxy group whose alkyl part is the same alkyl as the said C7-12 alkyl, for example is mentioned.

  The phosphites (B) used in the present invention are preferably compounds represented by the following structural formula, and particularly preferably the compound (B-1-1).

Compound (B-1-1):
2,4,8,10-tetra-tert-butyl-6- [3- (3-methyl-4-hydroxy-5-tert-butylphenyl) propoxy] dibenzo [d, f] [1,3,2] Dioxaphosphepine

Compound (B-1-2):
2,10-dimethyl-4,8-di-t-butyl-6- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propoxy] -12H-dibenzo [d, g] [1 , 3,2] dioxaphosphocin,

Compound (B-1-3):
2,4,8,10-tetra-t-butyl-6- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propoxy] dibenzo [d, f] [1,3,2] Dioxaphosphepine,

Compound (B-1-4):
2,4,8,10-Tetra-t-pentyl-6- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propoxy] -12-methyl-12H-dibenzo [d, g] [1,3,2] dioxaphosphocin,

Compound (B-1-5):
2,10-dimethyl-4,8-di-t-butyl-6- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -12H-dibenzo [d, g] [ 1,3,2] dioxaphosphocin,

Compound (B-1-6):
2,4,8,10-tetra-t-pentyl-6- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -12-methyl-12H-dibenzo [d, g ] [1,3,2] dioxaphosphocin,

Compound (B-1-7):
2,4,8,10-tetra-t-butyl-6- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -dibenzo [d, f] [1,3 2] dioxaphosphepine,

Compound (B-1-8):
2,10-dimethyl-4,8-di-t-butyl-6- (3,5-di-t-butyl-4-hydroxybenzoyloxy) -12H-dibenzo [d, g] [1,3,2 Dioxaphosphocin,

Compound (B-1-9):
2,4,8,10-tetra-tert-butyl-6- (3,5-di-tert-butyl-4-hydroxybenzoyloxy) -12-methyl-12H-dibenzo [d, g] [1,3 , 2] dioxaphosphocin,

Compound (B-1-10):
2,10-dimethyl-4,8-di-tert-butyl-6 [3- (3-methyl-4-hydroxy-5-tert-butylphenyl) propoxy] -12H-dibenzo [d, g] [1, 3,2] dioxaphosphocin,

Compound (B-1-11):
2,4,8,10-tetra-t-butyl-6- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propoxy] -12H-dibenzo [d, g] [1,3 , 2] dioxaphosphocin,

Compound (B-1-12):
2,10-diethyl-4,8-di-t-butyl-6 [3- (3,5-di-t-butyl-4-hydroxyphenyl) propoxy] -12H-dibenzo [d, g] [1, 3,2] dioxaphosphocin,

Compound (B-1-13):
2,4,8,10-tetra-tert-butyl-6- [2,2-dimethyl-3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propoxy] -dibenzo [d, f] [1,3,2] Dioxaphosphepine.

  As a method for producing phosphites (B), for example, as described in JP-A-10-273494, a bisphenol having a predetermined structure, phosphorus trihalide and a hydroxy compound are reacted. The method of letting it be mentioned.

  The content of the phosphites (B) used in the present invention is 0.15 to 2 parts by mass with respect to 100 parts by mass of the polypropylene resin (A). Preferably it is 0.22-2 mass parts, More preferably, it is 0.25-1.5 mass parts. By setting the content of the phosphites (B) to 0.15 mass or more, it becomes possible to further improve the durability in a metal contact environment. Moreover, it becomes possible to prevent that phosphorous acid ester (B) precipitates on the surface of a battery case, and the external appearance of a molded article deteriorates by making content into 2 mass parts or less.

<Heavy metal deactivator (C)>
The heavy metal deactivator (C) used in the present invention has a function of chelating metal ions, and thermal oxidation degradation of the polymer material by the metal proceeds in an environment where the polymer material is in contact with the metal. It is a compound having the action of preventing the above. By adding the heavy metal deactivator (C) to the resin composition together with the phosphites (B), a battery case having excellent durability, particularly durability in a metal contact environment can be produced. It becomes possible.
A known heavy metal deactivator can be used as the heavy metal deactivator (C). For example, "New development of polymer additive (76-85 pages (Nikkan Kogyo Shimbun))", a benzotriazole derivative disclosed in JP-A-8-302331, a group represented by -CO-NH- (For example, oxalic acid derivatives, salicylic acid derivatives, hydrazide derivatives, hydroxybenzoic acid anilide derivatives), sulfur-containing phosphites, and the like.

Benzotriazole derivatives include benzotriazole, 2,4,6-triamino-1,3,5-triazine, 3,9-bis [2- (3,5-diamino-2,4,6-triazaphenyl) Ethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, ethylenediamine-tetraacetic acid and the like.
Examples of compounds having one or more groups represented by —CO—NH— include alkali metal salts (Li, Na, K) of ethylenediamine-tetraacetic acid, N, N′-disalicylidene-ethylenediamine, N, N′-disalicylidene-1,2-propylenediamine, N, N ″ -disalicylidene-N′-methyl-dipropylenetriamine, 3- (N-salicyloyl) amino-1,2,4-triazole, decamethylenedicarboxy Rick acid-bis (N′-salicyloylhydrazide), nickel-bis (1-phenyl-3-methyl-4-decanoyl-5-pyrazolate), 2-ethoxy-2′-ethyloxanilide, 5-t -Butyl-2-ethoxy-2'-ethyloxanilide, N, N-diethyl-N ', N'-diphenyloxamide, N, N'-die Ru-N, N′-diphenyloxamide, oxalic acid-bis (benzylidenehydrazide), thiodipropionic acid-bis (benzylidenehydrazide), isophthalic acid-bis (2-phenoxypropionylhydrazide), bis (salicylo) Ylhydrazine), N-salicylidene-N′-salicyloylhydrazone, 2 ′, 3-bis [[3- [3,5-di-t-butyl-4-hydroxyphenyl] propionyl]] propionohydrazide and the like Can be mentioned.

  Sulfur-containing phosphites include tris [2-t-butyl-4-thio (2′-methyl-4′-hydroxy-5′-t-butyl) phenyl-5-methyl] -phenyl phosphite, bis [ 2-t-butyl-4-thio (2′-methyl-4′-hydroxy-5′-t-butylphenyl) -5-methylphenyl] -pentaerythritol-diphosphite, tetrakis [2-t-butyl- 4-thio (2′-methyl-4′-hydroxy-5′-t-butylphenyl) -5-methylphenyl] -1,6-hexamethylene-bis (N-hydroxyethyl-N-methylsemicarbazide) -di Phosphite, tetrakis [2-t-butyl-4-thio (2′-methyl-4′-hydroxy-5′-t-butylphenyl) -5-methylphenyl] -1,10-de Methylene-di-carboxylic acid-di-hydroxyethylcarbonylhydrazide-diphosphite, tetrakis [2-tert-butyl-4-thio (2'-methyl-4'-hydroxy-5'-tert-butylphenyl)- 5-methylphenyl] -1,10-decamethylene-di-carboxylic acid-di-salicyloylhydrazide-diphosphite, tetrakis [2-tert-butyl-4-thio (2′-methyl-4′-hydroxy) -5'-t-butylphenyl) -5-methylphenyl] -di (hydroxyethylcarbonyl) hydrazide-diphosphite, tetrakis [2-t-butyl-4-thio (2'-methyl-4'-hydroxy-) 5′-t-butylphenyl) -5-methylphenyl] -N, N′-bis (hydroxyethyl) oxami - diphosphite, 2,2' Okisamidobisu [ethyl 3- (3, 5-t-butyl-4-hydroxyphenyl) propionate] and the like.

  Among these, at least one compound selected from compounds having one or more groups represented by —CO—NH— (for example, oxalic acid derivatives, salicylic acid derivatives, hydrazide derivatives) and sulfur-containing phosphites is used. It is preferable to use a compound having the following structural formula. These can be used alone or in combination of two or more.

Compound (C-1-1):
Adeka Stub CDA-1, CDA-1M: 3- (N-salicyloyl) amino-1,2,4-triazole manufactured by Asahi Denka Kogyo Co., Ltd.

Compound (C-1-2):
Adeka Stub CDA-6 manufactured by Asahi Denka Kogyo Co., Ltd .: Decamemethylene dicarboxyl acid-bis (N'-salicyloyl hydrazide)

Compound (C-1-3):
Inhibitor OABH manufactured by Eastman: Oxalic acid-bis (benzylidene hydrazide)

Compound (C-1-4):
Irganox MD1024: 2 ′, 3-bis [[3- [3,5-di-tert-butyl-4-hydroxyphenyl] propionyl]] propionohydrazide manufactured by Ciba Specialty Chemicals

Compound (C-1-5):
Sauishi Calcium Co., Ltd. Naugard XL-1: 2,2′-oxamidobis [ethyl 3- (3,5-t-butyl-4-hydroxyphenyl) propionate]

Compound (C-1-6):
Hostalnox OSP-1 manufactured by Clariant Japan Co., Ltd .: Tris [2-t-butyl-4-thio (2′-methyl-4′-hydroxy-5′-t-butyl) phenyl-5-methyl] -phenylphos Fight

The content of the heavy metal deactivator (C) is 0.21 to 3 parts by mass, preferably 0.22 with respect to 100 parts by mass of the polypropylene resin (A) containing a propylene-ethylene random copolymer. It is -3 mass parts, More preferably, it is 0.25-2.5 mass parts.
By setting the content of the heavy metal deactivator (C) to 0.21 part by mass or more, it becomes possible to further improve the durability in a metal contact environment. Moreover, it becomes possible to prevent that a heavy metal deactivator (C) precipitates on the surface of a battery case, and the external appearance of a molded article deteriorates by making content into 3 mass parts or less.

<Antioxidant (D)>
Moreover, it is preferable that the resin composition used by this invention contains antioxidant (D) (henceforth (D) component). Examples of the antioxidant (D) include phenol-based antioxidants, phosphorus-based antioxidants and sulfur-based antioxidants.

  Examples of phenolic antioxidants include 2,6-di-t-butyl-4-methylphenol, tetrakis [methylene-3 (3 ′, 5′-di-t-butyl-4-hydroxyphenyl) propionate] methane, Octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 3,9-bis [2- {3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyl Oxy} -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5 · 5] undecane, 1,3,5-tris2 [3 (3,5-di-tert-butyl- 4-hydroxyphenyl) propionyloxy] ethyl isocyanate, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, Lis (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanurate, pentaerythris Lityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], triethylene glycol-N-bis-3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) ) Propionate, 1,6-hexanediol bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,2-thiobis-diethylene bis [3- (3,5-di-) t-butyl-4-hydroxyphenyl) propionate], 2,2′-methylene-bis- (4-methyl-6-tert-butylphenol), 2,2 ′ Methylene-bis- (4-ethyl-6-tert-butylphenol), 2,2′-methylene-bis- (4,6-di-tert-butylphenol), 2,2′-ethylidene-bis- (4,6 -Di-t-butylphenol) (cheminox 1129), 2,2'-butylidene-bis- (4-methyl-6-t-butylphenol), 4,4'-butylidenebis (3-methyl-6-t-butylphenol) And tocopherols.

  In addition, phosphorus antioxidants include triphenyl phosphite, tris (nonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, trilauryl phosphite, trioctadecyl phosphite, di Stearyl pentaerythritol diphosphite, diisodecyl pentaerythritol diphosphite, bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite, bis (2,4-dicumylphenyl) pentaerythritol diphosphite, bis (2,4-di-t-butyl-6-methylphenyl) pentaerythritol diphosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, bis (2,4 , 6-Tri-t-butylphenyl) penta Lithritol diphosphite, tristearyl sorbitol triphosphite, tetrakis (2,4-di-t-butylphenyl) -4,4′-diphenylenediphosphonite, 2,2′-methylenebis (4,6-di-) t-butylphenyl) 2-ethylhexyl phosphite, 2,2′-ethylidenebis (4,6-di-t-butylphenyl) fluorophosphite, bis (2,4-di-t-butyl-6-methylphenyl) ) Ethyl phosphite, bis (2,4-di-t-butyl-6-methylphenyl) methyl phosphite, 2- (2,4,6-tri-t-butylphenyl) -5-ethyl-5-butyl 1,3,2-oxaphosphorinane, 2,2 ′, 2 ″ -nitrilo [triethyl-tris (3,3 ′, 5,5′-tetra-t-butyl-1,1′- Phenyl-2,2'-diyl) phosphite and mixtures thereof and the like.

  Examples of the sulfur-based antioxidant include dilauryl 3,3′-thiodipropionate, tridecyl 3,3′-thiodipropionate, dimyristyl 3,3′-thiodipropionate, distearyl 3,3′-. Thiodipropionate, laurylstearyl 3,3′-thiodipropionate, neopentanetetrayltetrakis (3-laurylthiopropionate), bis [2-methyl-4- (3-n-alkyl (C12-C14) ) Thiopropionyloxy) -5-tert-butylphenyl] sulfide and the like.

  The said antioxidant (D) can be used individually or in combination of 2 or more types. Among them, it is preferable to use a combination of a phenol-based antioxidant and a sulfur-based antioxidant, and among them, 3,9-bis [2- (3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyl (Oxy) -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5 · 5] undecane and dimyristyl 3,3′-thiodipropionate are preferably used in combination.

  Content of antioxidant (D) used for this invention is 0.41-3 mass parts with respect to 100 mass parts of polypropylene resin (A) containing a propylene-ethylene random copolymer. Preferably it is 0.42-3 mass parts, More preferably, it is 0.45-2.5 mass parts. By setting the content of the antioxidant (D) to 0.4 parts by mass or more, it becomes possible to improve the antioxidant performance. Moreover, it becomes possible to prevent that antioxidant (D) precipitates on the surface of a battery case and an external appearance deteriorates by making content into 3 mass parts or less.

<Other ingredients>
Moreover, it is preferable that the said polypropylene resin (A) is a polypropylene resin with which the nucleating agent was mix | blended. Examples of the nucleating agent include benzoic acid metal salts, sorbitol compounds, rosin-based alkali metal salts or alkaline earth metal salts. You may use these individually or in combination of 2 or more types.
Examples of the benzoic acid metal salt include sodium 2,2′-methylenebis (4,6-di-t-butylphenyl) phosphate, [phosphoric acid-2,2′-methylenebis (4,6-di-t-butylphenyl) Dihydrooxyaluminum, bis [phosphate-2,2′-methylenebis (4,6-di-t-butylphenyl)] hydroxyaluminum, tris [phosphate-2,2′-methylenebis (4,6-di) -T-butylphenyl)] aluminum, sodium bis (4-t-butylphenyl) phosphate, sodium benzoate, aluminum pt-butylbenzoate and the like.
Examples of the sorbitol compound include 1,3: 2,4-bis (o-benzylidene) sorbitol, 1,3: 2,4-bis (o-methylbenzylidene) sorbitol, 1,3: 2,4-bis (o- Ethylbenzylidene) sorbitol, 1,3-o-3,4-dimethylbenzylidene-2,4-o-benzylidenesorbitol, 1,3-o-benzylidene-2,4-o-3,4-dimethylbenzylidenesorbitol, 1 , 3: 2,4-bis (o-3,4-dimethylbenzylidene) sorbitol, 1,3-op-chlorobenzylidene-2,4-o-3,4-dimethylbenzylidenesorbitol, 1,3-o -3,4-dimethylbenzylidene-2,4-op-chlorobenzylidenesorbitol, 1,3: 2,4-bis (op-chlorobenzylidene) sol Tall and mixtures thereof.
Specific examples of rosin-based alkali metal salts or alkaline earth metal salts include rosin lithium salts, sodium salts, potassium salts, calcium salts, magnesium salts, aluminum salts, and the like.

  In addition, the polypropylene resin (A) used in the present invention, if necessary, other thermoplastic resins, impact resistance improvers, inorganic fillers, antioxidants, ultraviolet absorbers, pigments, antistatic agents, You may add additives, such as a copper harm prevention agent, a flame retardant, a neutralizing agent, a foaming agent, a plasticizer, an anti-bubble agent, a crosslinking agent, and a lubricant.

The resin composition constituting the battery case according to the present invention is obtained by adding and mixing the components (A) to (C) and other components such as the above-described nucleating agent as necessary, and kneading. It is done.
Examples of the apparatus used for kneading include a single screw extruder, a twin screw extruder, a Banbury mixer, a hot roll, and the like. The kneading temperature is 170 to 300 ° C., preferably 180 to 270 ° C., and the kneading time is usually 1 to 20 minutes, preferably 1 to 15 minutes. Moreover, kneading | mixing of a polypropylene resin (A) and the said nucleating agent and / or various additives may be performed simultaneously, and you may carry out by dividing | segmenting. In the case of dividing and kneading, the kneading order may be arbitrarily determined as appropriate.

[Battery and secondary battery]
The secondary battery which concerns on this invention is equipped with the battery case obtained by shape | molding the resin composition obtained by said method, an electrode, etc.
The molding method of the battery case is not particularly limited, and a known molding method such as injection molding or extrusion molding can be used. Among these, it is preferable to use an injection molding method. Moreover, it is preferable that the temperature of injection molding is 220-300 degreeC.

  The battery case for the secondary battery according to the present invention is a battery case used for a secondary battery that can be repeatedly charged and discharged used in various industrial fields such as the electric / electronic field and the automobile field. It is not particularly limited. In this invention in this invention, the battery case for secondary batteries means what is comprised by the 1 or 2 or more molded product shape | molded using the said resin composition. For example, a lid is also included in addition to a battery case body for storing electrodes and electrolyte. As a typical battery cell drawing, there is a battery case described in JP-A-2007-059062.

The secondary battery according to the present invention is formed by adhering (welding) the battery case body and the lid after putting the electrode and the electrolyte into the battery case body. Examples of the welding method include hot plate welding, vibration welding, ultrasonic welding and the like. Although it does not specifically limit about welding conditions, It is preferable that the welding part surface temperature at the time of welding is 170-300 degreeC, More preferably, it is 200-250 degreeC.
In addition, a nickel-metal hydride electrode, a lithium electrode, or the like is preferable because of its high electric capacity as a battery.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention more concretely, this invention is not limited to these Examples.
The measuring method of the physical property of the test piece used by the Example and the comparative example was shown below.
(1) Melt flow rate (MFR, unit: g / 10 minutes)
Based on ASTM D1238, the melt flow rate (MFR) at 230 ° C. and 21 N load was measured.

(2) Melt viscosity at a measurement temperature of 230 ° C. and a shear rate of 12 sec ⁻¹ (unit: Pa · s)
Using a capillary rheometer (model: Capillograph IB (manufactured by Toyo Seiki Seisakusho)), the melt viscosity was measured under the conditions of a measurement temperature of 230 ° C. and a shear rate of 12 sec-1. In addition, as the capillary, the one having a flow part length of 4 mm and a diameter of 1 mm was used.

(3) Intrinsic viscosity ([η], unit: dl / g)
Using a Ubbelohde viscometer, reduced viscosities were measured at three concentrations of 0.1, 0.2 and 0.5 g / dl. Intrinsic viscosity is calculated according to the calculation method described in “Polymer Solution, Polymer Experiments 11” (published by Kyoritsu Shuppan Co., Ltd.), page 491. That is, the reduced viscosity is plotted against the concentration and extrapolated to zero. Obtained by extrapolation. Polypropylene was evaluated at a temperature of 135 ° C. using tetralin as a solvent.

(4) Proportion of propylene-ethylene block copolymer in the propylene-ethylene random copolymer portion with respect to the total amount of propylene-ethylene block copolymer (X, mass%) and propylene in the propylene-ethylene block copolymer Ethylene content of ethylene random copolymer portion [(C2 ′) EP, mass%] and ethylene content in propylene-ethylene block copolymer [(C2 ′), mass%]
It calculated | required based on the report (Macromolecules 1982, 15, 1150-1152) of Kakugo et al. From the ¹³ C-NMR spectrum measured on condition of the following.
A sample was prepared by uniformly dissolving about 200 mg of propylene-ethylene block copolymer in 3 ml of orthodichlorobenzene in a 10 mmφ test tube, and the ¹³ C-NMR spectrum of the sample was measured under the following conditions.
Measurement temperature: 135 ° C
Pulse repetition time: 10 seconds Pulse width: 45 °
Integration count: 2500 times

［η］Ｐ：プロピレン単独重合体部分の固有粘度（ｄｌ／ｇ）
［η］Ｔ：ブロック共重合体全体の固有粘度（ｄｌ／ｇ）
なお、プロピレン−エチレンブロック共重合体中のプロピレン単独重合体部分の固有粘度［η］Ｐは、その製造時に、第一工程であるプロピレン単独重合体部分の製造後に重合槽内より取り出し、取り出されたプロピレン単独重合体からその固有粘度［η］Ｐを求めた。 (5) Intrinsic viscosity of propylene-ethylene random copolymer portion in propylene-ethylene block copolymer ([η] EP, unit: dl / g)
The intrinsic viscosity [η] EP of the propylene-ethylene random copolymer portion in the propylene-ethylene block copolymer is the intrinsic viscosity [η] P of the propylene homopolymer portion and the intrinsic viscosity [η] of the propylene-ethylene block copolymer. It was calculated from the following equation by measuring T.

[Η] P: Intrinsic viscosity of the propylene homopolymer part (dl / g)
[Η] T: Intrinsic viscosity of the entire block copolymer (dl / g)
In addition, the intrinsic viscosity [η] P of the propylene homopolymer portion in the propylene-ethylene block copolymer is taken out from the polymerization tank after the production of the propylene homopolymer portion, which is the first step, during the production. The intrinsic viscosity [η] P was determined from the propylene homopolymer.

(6) Heavy metal resistance Evaluation of heavy metal made by contacting a copper plate (disk shape, diameter: 15 mm, thickness: 1 mm) with the surface of a flat test piece (length 20 mm × width 2 mm, thickness 3 mm) in a gear oven Evaluation was performed based on JIS K7212, except that heat treatment was performed. A gear oven manufactured by Toyo Seiki Seisakusho was used for the heat treatment. The test piece was heat-treated in an oven set at 150 ° C. and 160 ° C., and the time until the surface of the test piece was cracked due to heavy metal deterioration was visually evaluated every day.

Samples used in Examples or Comparative Examples are shown below.
Propylene-ethylene block copolymer (A) (component (A))
A propylene-ethylene copolymer comprising a propylene homopolymer and a propylene-ethylene random copolymer portion was used. This propylene-ethylene block copolymer was produced using a catalyst described in JP-A-10-212319, and details thereof were as follows.
A propylene-ethylene block copolymer that satisfies the following requirements (i) to (v) was used. This propylene-ethylene block copolymer has a weight average molecular weight (Mw) of 750,000, a weight average molecular weight (Mw) to number average molecular weight (Mn) ratio (Mw / Mn) of 5.0, and a measurement temperature of 230 ° C. The melt viscosity at a shear rate of 12 sec ⁻¹ was 4940 Pa · s.
(I) MFR (230 ° C.) 0.5 g / 10 min (ii) Intrinsic viscosity of propylene homopolymer part ([η] P) 3.0 dl / g
(Iii) Intrinsic viscosity of propylene-ethylene random copolymer portion ([η] EP) ... 3.0 dl / g
(Iv) Mass ratio of propylene-ethylene random copolymer portion to propylene-ethylene block copolymer: 20% by mass
(V) Ethylene content in ethylene-propylene random copolymer portion: 1% by mass (ethylene content in propylene-ethylene block copolymer is 0.2% by mass)

Phosphites (B) (component (B))
Trademark: Sumilizer GP: Chemical formula manufactured by Sumitomo Chemical Co., Ltd .: 2,4,8,10-tetra-t-butyl-6- [3- (3-methyl-4-hydroxy-5-t-butylphenyl) propoxy] Dibenzo [d, f] [1,3,2] dioxaphosphine

Heavy metal deactivator (C)
(1) Heavy metal deactivator 1 (component (C-1))
Trademark: Irganox MD1024: Chemical formula manufactured by Ciba Specialty Chemicals Co., Ltd .: 2 ′, 3-bis [[3- [3,5-di-t-butyl-4-hydroxyphenyl] propionyl]] propionohydrazide]
(2) Heavy metal deactivator 2 (component (C-2))
Trademark: ADK STAB ZS19: Made by ADEKA

Antioxidant (D)
(1) Phenolic antioxidant 1 (component (D-1))
Trademark: Sumilizer GA80: Sumitomo Chemical Co., Ltd. Chemical formula: 3,9-bis [2- (3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy) -1,1-dimethylethyl ] -2,4,8,10-tetraoxaspiro [5.5] undecane

(2) Sulfur-based antioxidant 2 (component (D-2))
Trademark: Sumilizer TPM: manufactured by Sumitomo Chemical Co., Ltd.)
Chemical formula: Dimyristyl 3,3′-thiodipropionate

Crystal nucleating agent (E)
Trademark: ADK STAB NA-11: Asahi Denka Kogyo Co., Ltd. Chemical formula: 2,2′-methylenebis (4,6-di-t-butylphenyl) phosphate

[Example 1]
Each component having the content shown in Table 1 was mixed and charged from a hopper of a twin-screw kneader (manufactured by Nippon Steel Works, TEX44) set at a cylinder temperature of 200 ° C. and a screw speed of 200 rpm, and then melted. The kneaded product was strand cut to obtain a pellet-shaped resin composition. The obtained pellets were set at a cylinder temperature of 260 ° C. and a mold temperature of 50 ° C. using an injection molding machine (IS150E manufactured by Toshiba Machine), and each test piece was molded. Using the obtained test piece, bending elastic modulus, bending strength, and Izod impact strength at 23 ° C. or 80 ° C. were measured. Moreover, the battery case main body and the lid were molded by an injection molding machine set at a cylinder temperature of 250 ° C. These molded articles were used to evaluate heat weldability. The results are shown in Table 1.

[Examples 2 to 4]
It implemented like Example 1 except having used each component of content shown in Table 1. FIG. The results are shown in Table 1.

[Comparative Examples 1-2]
It implemented like Example 1 except having used each component of content shown in Table 1. FIG. The results are shown in Table 1.

Claims (7)

  A battery case for a secondary battery comprising a resin composition containing a polypropylene resin (A), a phosphite (B), and a heavy metal deactivator (C). The battery case for a secondary battery according to claim 1, wherein the phosphite ester (B) is a compound represented by the following general formula (B-1).

^{Wherein, R 1, R 2, R} 4 and R ⁵ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, cycloalkyl group having 5 to 8 carbon atoms, alkylcycloalkyl having 6 to 12 carbon atoms An alkyl group, an aralkyl group having 7 to 12 carbon atoms, or a phenyl group is represented, and R ³ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. X represents a sulfur atom or a —CHR ⁶ — group (R ⁶ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms), and n is 0 or 1. A represents an alkylene group having 2 to 8 carbon atoms or * -CO (R ⁷ ) _m -group (R ₇ represents an alkylene group having 1 to 8 carbon atoms, * represents a bonding site with an oxygen atom, m Is 0 or 1. One of Y and Z represents a hydroxyl group, an alkoxy group having 1 to 8 carbon atoms or an aralkyloxy group having 7 to 12 carbon atoms, and the other represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. . ]   3. The battery case for a secondary battery according to claim 1, wherein a content of the phosphorous ester (B) is 0.12 to 2 parts by weight with respect to 100 parts by mass of the polypropylene resin (A).   4. The secondary battery according to claim 1, wherein a content of the heavy metal deactivator (C) is 0.21 to 3 parts by weight with respect to 100 parts by mass of the polypropylene resin (A). Battery case.   The battery case for a secondary battery according to any one of claims 1 to 4, wherein the polypropylene resin (A) has a weight average molecular weight in terms of polystyrene of 650000 to 1000000.   A secondary battery comprising the battery case according to claim 1 and a nickel-metal hydride electrode.   A secondary battery comprising the battery case according to claim 1 and a lithium electrode.