JPH1140113A - Battery jar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery jar which has alkali resistance, toughness, and impact resistance in good balance and is durable for a long time use by using a composition containing propylene-ethylene block copolymer, having a specified ratio of isotactic pentad insoluble in boiled heptane and a specified ratio of the constituents which are insoluble in boiled heptane to the whole copolymer and a core-forming agent in specified ratio for making a main body container. SOLUTION: The composition used for making a main body container contains 100 pts.wt. of propylene-ethylene block copolymer having 0.970 or higher isotactic pentad insoluble in boiled heptane and 70-90 wt.% of constituent which are insoluble in boiled heptane and 0.01-3.0 pts.wt. of a core-forming agent. It is preferable for the block copolymer having 0.975 or higher isotactic pentad insoluble in boiled heptane. Further, the content of ethylene in the copolymer is preferably 2-7 wt.%, ad MFR is desirably 0.1-80 g/10 minute. The core- forming agent is aluminum benzoate, Al-p-butyl benzoate, etc., and the mixing ratio of the agent is preferably controlled to be 0.05-1.0 pts.wt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery case for an alkaline secondary battery used in an electric vehicle or the like. More specifically, it is a battery case for an alkaline secondary battery used in electric vehicles and the like, which has excellent alkali resistance and a good balance between rigidity and impact resistance against internal pressure.

[0002]

2. Description of the Related Art Nickel-metal hydride storage batteries are widely used as alkaline secondary batteries used for electric vehicles and the like. Nickel-metal hydride storage batteries have a battery case in which an electrode group formed by alternately stacking a plurality of nickel positive plates and a hydrogen storage alloy negative electrode via a resin separator is inserted into a main body container. After the injection of an alkaline electrolyte, a lid provided with a safety valve is welded. As the electrolytic solution, potassium hydroxide having a concentration of about 5 to 8 N is used.

Conventionally, an injection molded body of a resin such as engineering plastics or polypropylene is mainly used as a main body container constituting a battery case of an alkaline secondary battery used for an electric vehicle. Polypropylene is considered to be suitable for this application because it has relatively excellent alkali resistance and good mechanical properties. For example, JP-A-7-320
In the 775 gazette, polypropylene is used as a material for the battery case.

[0004]

However, no study has been made on the optimum polypropylene resin which satisfies the above-mentioned properties required in such applications, and there has been no study on the case. Had various problems to be solved.

[0005] For example, when a general-purpose propylene ethylene block copolymer is used as a resin constituting the main container of such a battery case to improve mechanical properties, long-term contact with an alkaline solution and temperature cycling during use are considered. As a result, deterioration of the inner surface of the battery case is likely to occur, and there is concern about long-term use. Further, the balance between rigidity and impact resistance for withstanding an increase in internal pressure and an external impact was still insufficient.

Accordingly, an object of the present invention is to provide an alkali-resistant
An object of the present invention is to provide a battery container of an alkaline secondary battery which has an excellent balance between rigidity and impact resistance and can withstand long-term use.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the above-mentioned problems, and as a result, a molded article of a resin composition comprising a specific polypropylene ethylene block copolymer and a nucleating agent has been required. The present invention has been found to be extremely useful as a main container constituting a battery case of an alkaline secondary battery, such as a nickel-metal hydride storage battery used in an electric vehicle or the like, and has completed the present invention.

That is, according to the present invention, the isotactic pentad fraction of the boiling heptane-insoluble component is 0.970 or more, and the proportion of the boiling heptane-insoluble component in the total polymer is 7%.
0 to 90% by weight of a propylene ethylene block copolymer (100 parts by weight) and a nucleating agent of 0.01 to 3.0%
A battery case for an alkaline secondary battery, wherein a main body container is constituted by a resin composition consisting of parts by weight.

In the present invention, the highly crystalline propylene ethylene block copolymer has an isotactic pentad fraction of 0.970% or more, more preferably 0.1%, in a boiling heptane-insoluble portion used as an index of the crystallinity of polypropylene. It is important to use more than 975 to achieve the objectives of the present invention. That is, the isotactic pentad fraction in the boiling heptane-insoluble portion was 0.970.
If it is less than 1, the creep resistance and the alkali resistance are inferior, and the battery case constituted by the molded main body container cannot withstand long-term use.

Here, the isotactic pentad fraction of the boiling heptane-insoluble portion refers to the boiling heptane-insoluble portion of polypropylene as defined by A.I. The method was announced by Zambelli et al (Macromolecules 6 9
25 1973) means the value obtained by measuring the fraction of propylene monomer units at the center of a chain in which five propylene monomer units are consecutively meso-bonded in pentad units in a polypropylene molecule.

Further, in the present invention, the proportion of the boiling heptane-insoluble content in the total polymer is 70 to 90% by weight, more preferably 75 to 85% by weight. If the proportion is less than 70% by weight, the creep resistance and alkali resistance are inferior. If it exceeds 90%, sufficient impact resistance cannot be obtained.

In the present invention, the boiling heptane-insoluble portion of the polypropylene is obtained by completely dissolving the polymer in boiling xylene, lowering the temperature to 20 ° C., and allowing it to stand still.
It is obtained by separating and filtering the insoluble portion, drying the insoluble portion, and performing boiling heptane extraction with a Soxhlet extraction tube.

In the present invention, the ethylene content of the highly crystalline propylene ethylene block copolymer is from 1 to 10 in order to achieve a good balance between rigidity and impact resistance.
%, Preferably 2 to 7% by weight.

The propylene ethylene block copolymer is copolymerized with an α-olefin such as 1-butene, 1-pentene, 4-methylpentene-1 and the like within a range not to impair the effects of the present invention. It doesn't matter.

In the present invention, the fluidity of the highly crystalline propylene ethylene block copolymer is not particularly limited. However, in consideration of moldability, rigidity and impact resistance, melt flow rate (hereinafter, MFR) is considered. Abbreviated) is 0.1 to 8
It is preferably 0 g / 10 minutes (min). here,
This melt flow rate is a value at a cylinder temperature of 230 ° C. according to JIS K7210.

In the present invention, the highly crystalline propylene ethylene block copolymer having such properties may be obtained by any method. JP-A-1-126355 and JP-A-7-4841 disclose methods for producing a highly crystalline propylene ethylene block copolymer.
7 publications and the like. Generally, it is a Ziegler-Natta type stereospecific catalyst, and a catalyst comprising a titanium compound supported on magnesium chloride or a titanium trichloride compound and an organic aluminum compound is used.

As the titanium compound, known compounds used for olefin polymerization can be used without any limitation.
In particular, a titanium compound containing titanium, magnesium and halogen as components and having a high catalytic activity and capable of obtaining a highly crystalline polymer is preferable. Examples of such a titanium compound include titanium halides, particularly titanium tetrachloride supported on various magnesium compounds. As a method for producing this catalyst, a known method is employed without any limitation. For example, a method of co-grinding titanium tetrachloride with a magnesium compound such as magnesium chloride, alcohol, ether,
Examples thereof include a method of co-grinding a titanium halide and a magnesium compound in the presence of an electron donor such as an ester, a ketone or an aldehyde, and a method of contacting a titanium halide, a magnesium compound and an electron donor in a solvent.

Next, as the organoaluminum compound,
Known compounds used for olefin polymerization can be used without any limitation. For example, alkyl aluminums such as trimethyl aluminum, triethyl aluminum and tri-n-propyl aluminum; and halogen-containing alkyl aluminums such as ethyl aluminum sesquichloride and diethyl aluminum chloride can be used.

Further, in order to enhance the crystallinity of the obtained polymer, it is preferable to use an electron donor in addition to the above titanium compound and organic aluminum compound. Examples of the electron donor include ether, amine, amide, sulfur-containing compound, nitrile, carboxylic acid, acid amide, acid anhydride, acid ester, and organosilicon compound. Of these, organosilicon compounds are most preferred.

The polymerization may be carried out in a gas phase or in a liquid phase. The polymerization may be carried out in an inert liquid or an inert solvent with respect to the catalyst.The polymerization may be carried out by introducing hydrogen during polymerization, or the obtained polymer may be prepared by a molecular weight regulator such as an organic peroxide. Degraded ones may be used. Further, the polymerization can be carried out by any of batch, semi-batch and continuous methods.

The polymerization conditions are not particularly limited as long as the effects of the present invention are recognized, and known conditions can be employed. For example, the polymerization temperature is 20-200 ° C., preferably 5
The range is 0 to 150 ° C. Further, the polymerization can be carried out in two or more stages under different conditions.

In the present invention, the above-mentioned highly crystalline propylene ethylene block copolymer constituting the main container is:
You may mix and use with other resin within the range which does not impair the effect of this invention remarkably. Such other resins include, in addition to ordinary polypropylene, homopolymers of α-olefins such as ethylene, 1-butene, 1-pentene and 4-methylpentene-1, or block copolymers of these α-olefins and propylene. Polymers or random copolymers are preferred. In this case, such another resin is suitably blended in a proportion of 40 parts by weight or less, preferably 25 parts by weight or less based on 100 parts by weight of the highly crystalline propylene ethylene block copolymer.

In the present invention, known nucleating agents can be used without any limitation. Specifically, metal carboxylate such as aluminum benzoate, potassium benzoate, sodium benzoate, lithium benzoate, Al-p-butylbenzoate, sodium β-naphthoate, sodium cyclohexanecarboxylate, sodium cyclopentanecarboxylate, etc. -Based compound: sodium bis (4-t-butylphenyl) phosphate, lithium bis (4-t-butylphenyl) phosphate, aluminum bis (4-t-butylphenyl) phosphate, bis (4-t -Butylphenyl) phosphate, magnesium bis (4-t-butylphenyl) phosphate, sodium 2,2′-methylene-bis (4,6-di-t-butylphenyl) phosphate, 2,2 ′ -Methylene-bis (4,6-di-t
-Butylphenyl) phosphate, aluminum 2,2′-methylene-bis (4,6-di-t-butylphenyl) phosphate, 2,2′-methylidene-bis (4,6
-Di-t-butylphenyl) phosphate calcium salt, 2,
Magnesium 2'-methylidene-bis (4,6-di-t-butylphenyl) phosphate, 2,2'-ethylidene-
Bis (4,6-di-t-butylphenyl) phosphate sodium salt, 2,2′-ethylidene-bis (4,6-di-t
-Butylphenyl) phosphate, aluminum 2,2'-ethylidene-bis (4,6-di-t-butylphenyl) phosphate, bis- (4-t-butylphenyl)
Aromatic metal phosphate compounds such as calcium phosphate and magnesium bis- (4-t-butylphenyl) phosphate; dibenzylidenesorbitol, 1.3, 2.4-
Di (methylbenzylidene) sorbitol, 1.3, 2.
4-di (ethylbenzylidene) sorbitol, 1.3
2.4-di (butylbenzylidene) sorbitol, 1.
3,2.4-di (methoxybenzylidene) sorbitol, 1.3,2.4-di (ethoxybenzylidene) sorbitol, 1.3-chlorobenzylidene, 2.4-methylbenzylidenesorbitol, mono (methyl) dibenzylidenesorbitol And the like; and inorganic compounds such as silica, titanium dioxide, carbon black, fine powder talc, mica, alum, and pigments. Of these, Al-pt-butyl benzoate, 2,2'-methylene-bis (4,6-
The use of a metal salt of di-t-butylphenyl) phosphate or the like is most preferable for achieving the object of the present invention.

In the present invention, the compounding amount of the nucleating agent is
It is 0.01 to 3.0 parts by weight based on 100 parts by weight of the highly crystalline propylene ethylene block copolymer, and among them, 0.05 to 1.0 part by weight is particularly preferable. That is, if the nucleating agent is less than 0.01 part by weight, the manifestation of creep resistance and alkali resistance is insufficient, and if it exceeds 3.0 parts by weight, the effect will level off and it will not be economical.
The above nucleating agents may be used alone or in combination of two or more.

The above-mentioned highly crystalline propylene ethylene block copolymer composition used in the present invention contains, in addition to the above components, an inorganic filler such as talc, wollastonite, barium sulfate, calcium carbonate, glass, etc. Barium may be blended. Here, two or more fillers may be used in combination. The amount of the inorganic filler is preferably 0.1 to 15 parts by weight based on 100 parts by weight of the highly crystalline propylene ethylene block copolymer.

The resin composition of the present invention further comprises:
Various additives can be appropriately blended to the extent that the effects of the invention are not impaired. Specifically, phenol-based, organic phosphite-based, phosphite-based organic phosphorus-based, thioether-based antioxidants; hindered amine-based heat stabilizers; benzophenone-based, benzotriazole-based, benzoate-based ultraviolet absorbers, etc. Nonionic, cationic, anionic and other antistatic agents; bisamide, wax, and organic metal salt dispersants; alkaline earth metal carboxylate and hydrotalcite-based chlorine scavengers; Amide-based, wax-based, organic metal salt-based, ester-based lubricants; oxide-based, hydrotalcite-based, etc. decomposers; hydrazine-based, amine-based, etc. metal deactivators; Flame retardants such as antimony, antimony trioxide, magnesium hydroxide, red phosphorus; organic pigments; inorganic pigments; foaming agents; organic fillers; Antibacterial agents, and the like.

In the present invention, the above-mentioned components can be blended by any ordinary method which is carried out by mixing resins without any limitation. For example, after adding a nucleating agent and optionally other additive components to a powder or pellet-like high-crystalline propylene ethylene block copolymer and mixing them with a tumbler or Henschel mixer, an extruder is used. A method of melt-kneading to form pellets or the like is preferable. The order of addition of each component is not particularly limited, and each component may be mixed in a different order from the above method. Furthermore, a masterbatch in which each component is concentrated and blended at a high concentration can be prepared and mixed and used.

As a method for molding the main body container, any method such as injection molding, press molding, extrusion molding, stampable molding and the like may be adopted. Usually, it is generally formed by injection molding. This injection molding is a single axis injection,
It may be carried out by any method such as multi-axis injection, high pressure injection, low pressure injection, gas assist injection, melt core molding, insert molding, core back molding, and two-color molding.

In the present invention, known specifications may be employed without particular limitation for the shape, structure, and the like of the main container of the battery case made of the above resin composition.

For example, FIG. 1 is a perspective view showing a typical structure of a main body container constituting a battery case of the alkaline secondary battery of the present invention.

In the main container, the dimensions of each part are not particularly limited, but the thickness e of the side wall is 1.5 × 10 ^-5 S ₁ to the total side wall area (2ac + 2bc: S ₁ ).
In the range of 3 × 10 ⁻⁵ S ₁ , the thickness d of the bottom is 4 × 10 ⁻⁴ S _{2 to} 12 × 10 ⁻⁴ S with respect to the bottom area (ab: S ₂ ).
By determining to be ₂ , the balance between product strength and product weight is improved, which is particularly preferable. Also, in order to further increase the strength of the battery case and enhance the heat radiation efficiency when the battery is assembled, an appropriate number of ribs may be provided on the side wall of the battery case.

In the battery case of the alkaline secondary battery of the present invention, other configurations, for example, types and arrangements of electrodes, diaphragms, and the like, are not particularly limited and known modes are adopted. FIG. 2 is a perspective view showing a typical embodiment of the battery case of the alkaline secondary battery of the present invention. That is, the battery case is provided with a nickel positive plate through a diaphragm (4) made of a polypropylene nonwoven fabric or the like in a main container. It is constituted by arranging (3) and the hydrogen storage alloy negative electrode (5) in an overlapping manner. Further, the battery case is filled with an alkaline aqueous solution obtained by adding lithium hydroxide (0.5 to 1 normal) to potassium hydroxide (5 to 8 normal) as an electrolytic solution, and then the electrode terminal (2) and the safety valve (6) The cover (7) provided with is attached by means such as welding to complete. The material of the lid is not particularly limited as long as it has resistance to the electrolytic solution, but in order to improve the fusion property with the main container, preferably, the material of the polyolefin resin, more preferably, the material of the polypropylene resin is used. used. Of course, the highly crystalline propylene ethylene block copolymer of the present invention, and furthermore, its resin composition can also be used.

[0033]

According to the battery case of the present invention, the main container is made of a resin composition comprising the above-mentioned specific propylene ethylene block copolymer and a nucleating agent, whereby alkali resistance, rigidity and impact resistance are improved. It is possible to exhibit extremely excellent characteristics in balance.

Therefore, according to the present invention, the deterioration of the inner surface of the battery case is small even by long-term contact with an alkaline solution and temperature cycling during use, and it has sufficient strength against internal pressure and external impact. It is possible to provide a battery case for an alkaline secondary battery that is optimal for installation in an electric vehicle or the like.

[0035]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

(1) The proportion of the boiling heptane-insoluble portion in the total polymer and the isotactic pentad fraction of the boiling heptane-insoluble portion After completely dissolved in boiling xylene, the temperature was lowered to 20 ° C.
After standing for a while, the insoluble portion was separated and filtered, the insoluble portion was dried, and boiling heptane was extracted with a Soxhlet extraction tube for 8 hours. The dry weight of the obtained insoluble portion was measured, and the total polymer amount was measured. Was calculated. Next, the insoluble matter obtained by the above-mentioned operation was The method was announced by Zambelli et al (Macromolecules 6 9
25 1973), the fraction of propylene monomer units at the center of a chain of five meso-bonded propylene monomer units in pentad units in a polypropylene molecule was determined.

(2) Ethylene content Calculated using a chart of ¹³ C-NMR spectrum.
That is, the ratio of monomer units based on ethylene is first determined by P
The assignment of peaks was determined by the method described in Orymer Vol. 29, paragraph 1848 (1988).
Acromolecules Volume 10, Section 773 (19
77).

(3) MFR Measurement was performed at 230 ° C. according to JIS K7210.

(4) Impact resistance (drop weight impact test of battery case) According to JIS K7211, a low surface of the battery case weighs 1 kg.
Was dropped, and the 50% breaking height was measured.

(5) Rigidity A lid made of polypropylene was welded to the opening of the battery case, and the hole for the electrode was sealed. Next, after filling the inside of the battery case with water, connect the hole of the safety valve to the manual pump, pressurize with the pump,
When the internal pressure was 0.2 MPa, the maximum value of the displacement of the interval between the side walls including the long side of the opening was measured.

(6) Alkali Resistance A container is filled with a 7N aqueous solution of potassium hydroxide, and the opening is covered so as not to volatilize the solution.
After standing for a month, the inner surface of the bottom of the battery case was observed with a scanning electron microscope. The degree of surface roughness was evaluated on the following three levels.

；: Little change from before test.

Δ: Slight skin roughness is observed.

X: remarkable rough skin is observed.

Example 1 The isotactic pentad fraction of the boiling heptane-insoluble portion was 0.975%, the proportion of the boiling heptane-insoluble portion in the total polymer was 85%, the ethylene content was 3.3 wt%, and the MF was MF.
100 parts by weight of a highly crystalline propylene ethylene block copolymer having an R of 17 g / 10 min, 0.2 parts by weight of Al-p-butyl benzoate, tetrakis [methylene (3,
5-di-t-butyl-4-hydroxyhydrocinnamate)] 0.04 parts by weight of methane, tris (2,4-di-
0.04 parts by weight of (t-butylphenyl) phosphite and 0.07 parts by weight of calcium stearate were blended and sufficiently mixed with a Henschel mixer.

Thereafter, the mixture was melt-kneaded by an extruder having a cylinder temperature set at 230 ° C. to obtain pellets of a highly crystalline propylene ethylene block copolymer composition. MF of this highly crystalline propylene ethylene block copolymer composition
R was measured, and the results are shown in Table 1.

Next, injection molding was performed using the above-mentioned highly crystalline propylene ethylene block copolymer composition to prepare a main container of a battery case as shown in FIG. The main container has a length a of 110 mm, a width b of 35 mm, and a height c.
Is 145 mm, and the thickness d of the bottom plate and the thickness e of the periphery are all 3 mm. Alkali resistance test using the obtained battery case,
A creep test and an impact resistance test were performed. The results are also shown in Table 1.

Example 2, Comparative Examples 1 and 3 In Example 1, the isotactic pentat fraction of the boiling heptane-soluble portion of the highly crystalline propylene ethylene block copolymer composition and the total weight of the boiling heptane-insoluble portion were obtained. A main container was molded and tested in the same manner as in Example 1 except that the proportion of the coalescent, the amount of ethylene, and the MFR were changed as shown in Table 1. The results are shown in Table 1.

Comparative Example 2 A main container was molded and tested in the same manner as in Example 1 except that a high-crystal homopolypropylene was used instead of the high-crystal propylene ethylene block copolymer. The results are shown in Table 1.

Examples 3 to 5 A body container was formed and tested in the same manner as in Example 1, except that the type and amount of the nucleating agent were changed as shown in Table 1. The results are shown in Table 1.

Comparative Example 4 A main container was molded and tested in the same manner as in Example 1 except that no nucleating agent was added. The results are shown in Table 1.

[0052]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a perspective view showing a typical shape of a battery case main body container of the present invention.

FIG. 2 is a perspective view showing a typical embodiment of a battery case of the alkaline secondary battery of the present invention.

[Explanation of symbols]

 a: Length of main container b: Width of main container c: Height of main container d: Thickness of bottom of main container e: Thickness around main container 1; Gate position 2: Electrode 3: Nickel positive electrode plate 4: Diaphragm 5: Hydrogen storage metal negative electrode plate 6: Safety valve 7: Lid

Claims (1)

[Claims] 1. A propylene ethylene block having a boiling heptane-insoluble fraction having an isotactic pentad fraction of at least 0.970 and a proportion of the boiling heptane-insoluble content in the total polymer of 70 to 90% by weight. A battery case for an alkaline secondary battery, wherein a main container is constituted by a resin composition comprising 100 parts by weight of a copolymer and 0.01 to 3.0 parts by weight of a nucleating agent.