JP5078418B2 - Battery case - Google Patents

Description

  The present invention relates to a resin battery case.

  In recent years, the development of an electric vehicle using a battery as a power source or a hybrid vehicle using a combination of a battery and an engine as a power source has been remarkable. Although these automobiles show good fuel efficiency, with the development, attempts to reduce the weight of automobiles by replacing metal parts with resin have been actively conducted for the purpose of further improving fuel efficiency.

  The biggest problem in making resin is the provision of electromagnetic shielding properties. For example, electromagnetic waves generated from a power secondary battery case built in an automobile adversely affect audio and ECU (electronic control board unit), and cause noise and malfunction. For this reason, metals such as iron and aluminum are usually used in housings and casings of devices, devices, and the like that need countermeasures against electromagnetic wave shielding for the purpose of electromagnetic wave shielding.

  Substituting these metals with conductive resins to which carbon fiber, carbon, graphite or the like is added has been studied, but the magnetic shielding property in the low frequency band is remarkably low and has a practical problem. For example, since a reception band has a low frequency, a radio or the like is easily affected by a low frequency of 100 Hz or less. As an alternative to the conductive resin, there is a method of conductive coating or vacuum deposition and plating of Ni, Cu, or aluminum on the surface of the molded product. However, the conductive coating uses a resin for the binder even if it uses a conductive paint to which metal powder such as Ag, Ni, Cu, etc. is added. Difficult, uniform coating is difficult, and the coating film thickness is not uniform. On the other hand, vacuum deposition and plating satisfy performance, but have problems such as high production cost, poor productivity, and difficulty in applying large molded products, and are not practical.

  In Patent Document 1, as a method for efficiently imparting electromagnetic wave shielding properties, a conductive material obtained by performing metal plating on a knitted fabric before injection molding is inserted into a mold, and injection molding, compression molding, transfer molding, or the like is performed. A method for obtaining a molded article containing a conductive material has been proposed.

JP 62-224100 A

  However, it cannot be said that the electromagnetic wave shield molded article described in Patent Document 1 sufficiently satisfies the low frequency band magnetic field shielding property particularly required for battery cases for automobiles. In addition, as a result of earnest research, the present inventor found that a battery case mounted on a vehicle requires vibration suppression and heat resistance in addition to sufficiently shielding low-frequency magnetism, but satisfies these characteristics. The electromagnetic shielding molded product case to be performed is not described in Patent Document 1.

  Accordingly, an object of the present invention is to provide a battery case that is optimal for a battery case that requires electromagnetic shielding properties, particularly a magnetic shielding property in a low frequency band.

  As a result of earnest study on the production of a resin battery case that requires magnetic shielding properties in a low frequency band, the present inventor has a conductive knitted fabric covered with a metal layer and having a specific aperture ratio, and a specific resin. It has been found that the battery case having the above characteristics is excellent in low-frequency band magnetic field shielding properties, has vibration damping properties and heat resistance (high load deflection temperature), and can be mounted on a vehicle, and has completed the present invention.

  That is, the battery case of the present invention comprises a conductive knitted fabric having a porosity of 10 to 60%, which is covered with a metal layer, and a resin main body, and the resin main body is polypropylene (hereinafter abbreviated as PP). And an alloy of polyphenylene ether (hereinafter abbreviated as PPE) (hereinafter abbreviated as PP / PPE alloy), or an alloy of polyamide (hereinafter abbreviated as PA) and PPE (hereinafter abbreviated as PA / PPE alloy). It is characterized by.

  The battery case of the present invention has excellent electromagnetic shielding properties, particularly low frequency magnetic field shielding properties that are difficult to obtain with conductive compound resins such as carbon fiber, carbon, graphite, etc., and also has vibration damping properties and heat resistance. Yes.

  An example of the battery case of the present invention is shown in FIG. 1A is a schematic external view, and FIG. 1B is a cross-sectional view taken along the line A-A ′ of FIG.

  As shown in FIG. 1, the battery case of the present invention includes a resin main body 1 and a conductive knitted fabric 2. It is preferable that the resin main body 1 and the conductive knitted fabric 2 are bonded (anchored) in a state where the resin enters the opening of the conductive knitted fabric 2. The conductive knitted fabric 2 preferably covers the inner surface of the resin body 1 uniformly and is exposed on the inner surface of the battery case. By providing the conductive knitted fabric 2 inside the resin main body 1, the appearance of the battery case is not affected, and the conductive knitted fabric 2 is less susceptible to external damage. Further, by exposing the conductive knitted fabric 2, the battery case can be easily grounded, and even if an opaque resin is used for the resin main body 1, damage or the like of the conductive knitted fabric 2 can be identified by appearance.

  The “battery case” in the present invention refers to a case that houses a plurality of battery cells such as a Ni-hydrogen secondary battery and a fuel cell.

Conductive knitted fabric is composed of a metal layer covering the knitted fabric, a knitted fabric, preferably 2 mm ² or more 30 mm ² or less, more preferably an opening of 3 mm ² or more 20 mm ² or less continuously. It is preferable that the aperture is large as long as the electromagnetic shielding properties are not impaired. The porosity of the conductive knitted fabric is 10% to 60%, preferably 20% to 50%. When the open area ratio exceeds 60%, the strength of the conductive knitted fabric and the electromagnetic wave shielding property are low, which is not preferable. Further, if the open area ratio is less than 10%, the stretchability is low and the anchoring effect is also weak, so that the conductive knitted fabric is easily peeled off from the resin.

The opening size of the conductive knitted fabric can be measured by taking an enlarged photograph (about 10 times) of the conductive knitted fabric. The hole area ratio is
Opening ratio = Area of opening part / (Area of opening part + Area of mesh part)
The area of the mesh portion and the opening portion can be measured and obtained using image analysis software (for example, MEDIA CYBERNETICS, product name: ImagePro).

  The thickness of the conductive knitted fabric is preferably 0.2 mm or more and 1.0 mm or less, more preferably 0.4 mm or more and 0.8 mm or less. If the thickness of the conductive knitted fabric is less than 0.2 mm, the strength of the conductive knitted fabric tends to be weak. On the other hand, when the thickness of the conductive knitted fabric exceeds 1.0 mm, the extensibility tends to deteriorate.

  The fiber material forming the knitted fabric is preferably a synthetic fiber such as polyester, polyamide, or polyurethane, and polyester fiber is most preferable from the viewpoint of cost and heat resistance. The knitting method of the knitted fabric is not limited, but a knitting method that achieves both stretchability and tensile properties is preferable. For example, tricot knitting, chain knitting, rubber knitting, and Melias knitting are preferably used.

  Examples of the metal forming the metal layer include Cu, Ni, Al, Ti, Cr, and Ag. From the viewpoint of cost and electromagnetic wave shielding properties, Ni and Cu are preferable, and Ni is the outermost layer, and at least one layer of Ni. A metal layer having a multilayer structure of Ni and Cu having a layer and a Cu layer is most preferable. The metal layer having a multilayer structure of Ni and Cu with Ni as the outermost layer has excellent magnetic field shielding properties and also has environmental resistance such as wet heat resistance.

  The thickness of the metal layer is preferably 0.2 μm or more and 3 μm or less, more preferably 0.5 μm or more and 2 μm or less. From the viewpoint of electromagnetic shielding properties, the thickness of the metal layer is preferably as thick as possible, but from the viewpoint of cost and productivity, it is preferable to set the minimum thickness that satisfies the electromagnetic shielding properties.

  Although the formation method of a metal layer is not specifically limited, A metal layer can be formed in a knitted fabric by electroless-plating method, vacuum evaporation, sputtering, thermal spraying, etc.

  The resin used for the resin body is made of PP as a matrix from the viewpoints of sound and vibration control, oil resistance, heat resistance (high load deflection temperature), mechanical strength (impact strength), and dimensional accuracy (low warpage). PP / PPE alloy or PA / PPE alloy with PA as matrix.

  The damping effect required for the battery case is defined by the numerical value of the loss factor η. The loss factor is the ratio of energy lost per cycle to vibration energy, expressed as a percentage (%), and the greater the value, the greater the damping performance. The loss factor is measured by fixing a short rail-shaped test piece at one end, applying vibration to the test piece from the free end with an electromagnetic shaker, and measuring the response speed and displacement of the test piece from the other end with a frequency response function. Analyzed and determined by the ratio of the energy lost per cycle to the vibration energy given inside the specimen. A resin molded body having vibration damping properties has a vibration damping effect and a sound damping effect, and has the effect of dampening vibrations, reducing noise, and reducing interference sound with other parts. Since a secondary battery case for a hybrid vehicle contains a plurality of battery cells, it suppresses the resonance noise of the secondary battery case caused by the vibration of the vehicle, and the wind noise of the fan and the motor noise for cooling the battery. Etc. are required. The loss factor of PP (homopolymer) is 8 to 10%, the highest among thermoplastic resins, and the loss factor of hygroscopic PA is as high as PP. These alloys are required for secondary battery cases. It will fully satisfy the vibration and sound control properties.

  However, PP and PA alone satisfy the required characteristics of the battery case, such as noise suppression, vibration suppression and oil resistance, but heat resistance (high load deflection temperature), mechanical strength (impact strength), and dimensional accuracy. (Warpage) is not satisfied and is not preferable.

  PP / PPE and PA / PPE alloys that use PP and PA as crystalline resins as a matrix phase and PPE as an amorphous resin as a dispersed phase used in the present invention retain the characteristics of PP and PA as they are. However, the presence of PPE (the dispersed phase PPE acts as an organic filler having a high heat resistance (glass transition temperature of about 210 ° C.)) significantly improves the high load heat distortion temperature, impact strength, and dimensional accuracy (warpage), and the battery. It is preferable as a material for the case.

  As PP used for PP / PPE alloy, resin generally called PP can be used. For example, a random or block polymer with a small amount of ethylene or α-olefin is included.

  Moreover, as PPE, the homopolymer which consists of at least 1 sort (s) from which a structural unit is chosen from General formula (1) and (2), or a copolymer can be used.

(In the formula, R1, R2, R3, R4, R5, and R6 are monovalent residues such as an alkyl group having 1 to 4 carbon atoms, an aryl group, halogen, and hydrogen, and R5 and R6 are not hydrogen at the same time.)

  Representative examples of PPE homopolymers include poly (2,6-dimethyl-1,4-phenylene) ether, poly (2-methyl-6-ethyl-1,4-phenylene) ether, poly (2,6 -Diethyl-1,4-phenylene) ether, poly (2-ethyl-6-n-propyl-1,4-phenylene) ether, poly (2,6-di-n-propyl-1,4-phenylene) ether Poly (2-methyl-6-n-butyl-1,4-phenylene) ether, poly (2-ethyl-6-isopropyl-1,4-phenylene) ether, poly (2-methyl-6-chloroethyl-1) , 4-phenylene) ether, poly (2-methyl-6-hydroxyethyl-1,4-phenylene) ether, and poly (2-methyl-6-chloroethyl-1,4-phenylene) ether Include homopolymers and the like.

  The copolymer of PPE is a copolymer of 2,6-dimethylphenol and 2,3,6-trimethylphenol, a copolymer of 2,6-dimethylphenol and o-cresol, or 2,6-dimethyl. It includes polyphenylene ether copolymers mainly composed of a polyphenylene ether structure, such as a copolymer of phenol, 2,3,6-trimethylphenol and o-cresol.

  The PPE preferably has a reduced viscosity (0.5 g / dl, chloroform solution, measured at 30 ° C.) in the range of 0.10 to 2.0. In addition to the above, maleic acid, maleic anhydride A modified polyphenylene ether resin modified with an α, β-unsaturated carboxylic acid such as acid, fumaric acid, itaconic acid, acrylic acid, acrylic ester, methacrylic acid or methacrylic ester or a derivative thereof may be used.

  The method for producing such PPE is not particularly limited as long as it is a known method. For example, a complex of cuprous salt and amine by Hay described in U.S. Pat. No. 3,306,874 is used as a catalyst. -It can be easily produced by oxidative polymerization of xylenol. In addition, the specifications of U.S. Pat. Nos. 3,306,875, 3,257,357 and 3,257,358, JP-B-52-17880 and JP-A-50-51197 are disclosed. And it can manufacture easily by the method described in each gazette etc. of 63-152628.

  The PPE to be used in the present invention can be used even with the above-mentioned PPE component of 100% by weight, but in the present invention, PPE / styrene resin = 1 to 99% by weight / 99 to 1% by weight. It can be preferably used, and it is more preferable to use at a ratio of 20 to 80% by weight / 80 to 20% by weight.

  Such a styrene resin is a rubber polymer dispersed in the form of a homopolymer of a styrene compound, a copolymer of two or more styrene compounds and a polymer of a styrene compound. Examples thereof include rubber-modified styrene resin (high impact polystyrene). Examples of the styrenic compound that gives these polymers include styrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, α-methylstyrene, ethylstyrene, α-methyl-p-methylstyrene, 2,4- Examples thereof include dimethyl styrene, monochloro styrene, and p-tert-butyl styrene.

  A copolymer obtained by using two or more of these styrenic compounds may be used, but among them, polystyrene obtained by polymerization using styrene alone is preferable. As these polymers, polystyrene having a stereoregular structure such as atactic polystyrene and syndiotactic polystyrene can be effectively used.

  The mixing ratio of PP and PPE is PP / PPE = 95 to 40 wt% / 5 to 60 wt%, and preferably PP / PPE = 90 to 50 wt% / 10 to 50 wt%.

  An alloy in which PP is uniformly dispersed as a matrix phase and PPE as a dispersed phase is obtained by using, for example, a hydrogenated styrene butadiene block polymer (SEBS) compatible with both PP and PPE as a compatibilizing agent, and heat-treating PP and PPE. It is obtained by kneading.

  Specific examples of PP / PPE alloys using PP as a matrix include “Zylon EV102” manufactured by Asahi Kasei Chemicals Corporation, “Noryl PPX” series manufactured by GE Plastics Japan, and the like.

  Examples of PA used in the PA / PPE alloy include polycondensates of dibasic acids and diamines, cyclic lactam ring-opening polymers, polycondensates of aminocarboxylic acids, and copolymers and blends thereof. More specifically, polyamide 66, polyamide 46, polyamide 612, polyamide 610, polyamide 6, polyamide 11, polyamide 12 and other aliphatic amide resins, polymetaxylene adipamide (polyamide MXD6), polyhexamethylene terephthalamide Examples thereof include aliphatic and aromatic polyamide resins such as (polyamide 6T) and polyhexamethylene isophthalamide (polyamide 6I), and copolymers and blends thereof. Of these, polyamide 66, polyamide 6, polyamide 66/6, and polyamide 66 / 6I are particularly preferably used from the viewpoints of heat resistance and mechanical properties.

  Moreover, as PPE, PPE similar to the PP / PPE alloy mentioned above is used.

  The mixing ratio of PA and PPE is PA / PPE = 80 to 40% by weight / 20 to 60% by weight, and preferably PA / PPE = 70 to 50% by weight / 30 to 50% by weight.

  The PA / PPE alloy has at least one carbon-carbon double bond or triple bond and at least one carboxylic acid group, acid anhydride group, amino group, hydroxyl group, or glycidyl group in the molecular structure. It can be obtained by heat-kneading PA and PPE using the above modified compound as a compatibilizer. Among these compatibilizers, maleic acid, maleic anhydride, and citric acid are preferably used.

  Specific examples of PA / PPE alloys include “Zylon A0210” manufactured by Asahi Kasei Chemicals Corporation, “Noryl GTX” series manufactured by GE Plastics, Inc., and “Remalloy” series manufactured by Mitsubishi Engineering Plastics Co., Ltd. .

  PP / PPE alloy and PA / PPE alloy have other resins and additives, for example, elastomers, plasticizers, stabilizers, antistatic agents, ultraviolet absorbers, flame retardants, colorants, as long as the invention is not impaired. Release agents and fibrous reinforcing agents such as glass fibers, potassium titanate whiskers, and zinc oxide whiskers, and fillers such as glass beads, glass flakes, mica, calcium carbonate, and talc can be added.

  As a method for producing the battery case of the present invention, a method in which a conductive knitted fabric is bonded by injection molding in a mold, or a two-layer sheet laminated with a conductive knitted fabric is formed by vacuum forming, and thermoformed by vacuum / pressure air. Examples thereof include a method, and a method of thermally forming a two-layer sheet laminated with a conductive knitted fabric by compression molding. Of these, injection molding is particularly preferably used. In injection molding, in order to obtain a battery case in which a conductive knitted fabric is uniformly laminated inside the resin body, before injecting the resin into the mold, on the mold surface forming the inside of the battery case It is important to arrange the conductive knitted fabric uniformly. For example, by providing protrusions such as pins at the required locations in the mold cavity that forms the product, the conductive knitted fabric forms the inside of the battery case by the action of the protrusions automatically when the mold closes. A mold structure that can be uniformly pressed against the mold surface is preferable.

  Hereinafter, the present invention will be described in more detail by way of examples.

<Resin>
Resins used in the examples are as follows.

PP / PPE alloy: "Zylon EV102" manufactured by Asahi Kasei Chemicals Corporation
PA / PPE alloy: “Zylon A0210” manufactured by Asahi Kasei Chemicals Corporation
PP: “NOVATEC EA9BT” manufactured by Nippon Polypro Co., Ltd.
Conductive modified PPE: “Zylon X8600” manufactured by Asahi Kasei Chemicals Corporation

<Measurement method>
The measuring method in an Example is as follows.

(1) Opening ratio of conductive knitted fabric A 10-fold enlarged photograph of the conductive knitted fabric was taken and measured using image analysis software (trade name: ImagePro, manufactured by MEDIA CYBERNETICS). The hole area ratio was obtained by dividing the area of the hole part by (the area of the hole part + the area of the mesh part) and expressing the value as a percentage.

(2) Electromagnetic wave shielding property A 150 mm square plate was cut out from the battery case and measured by the Advantest method.

(3) Damping property The loss factor η was determined by the cantilever method according to ASTM-E756-83. The loss factor was measured at the secondary resonance frequency. The measuring machine used was a 2032 type 2-channel FFT analyzer (distributor: Song Trading Equipment Company).

(4) Heat resistance From the battery case, cut out a tuna-shaped test piece having a width of 12.7 mm and a length of 130 mm and applying a bending stress of 1.82 MPa to the test piece in accordance with ASTM-D648. It was immersed and heated at a rate of 120 ° C./hr), and the temperature (high load deflection temperature) when the bending deflection reached 0.254 mm was measured.

(5) Izod impact strength (notched)
From the battery case, a tuna-shaped test piece having a width of 12.7 mm and a length of 130 mm was cut out, and a V-notch defined by ASTM-D256 was inserted to measure the Izod impact strength.

(6) Oil resistance From the battery case, cut out a tuna-shaped test piece with a width of 12.7 mm and a length of 130 mm, fix the test piece along the bending bar, and apply hydraulic oil to the surface of the test piece. It was left to stand at room temperature for one day, and it was measured whether cracks occurred on the surface of the test piece. It was determined that the oil resistance was poor when cracking occurred at a strain of 0.2 or less. Even when the strain was 0.8 or more, the sample that did not crack and did not generate cracks was judged to have good oil resistance.

(7) Dimensional accuracy The amount of internal warpage of the long side surface portion of the injection molded product was measured.

(8) Formability The conductive knitted fabric is almost uniformly bonded to the surface of the molded product without breakage, and the adhesion strength is obtained when the conductive knitted fabric at the end of the molded product is grasped by hand and a peel test is performed. A sufficient one was judged to have good moldability. Those in which partial breakage of the conductive knitted fabric was observed or those in which the conductive knitted fabric easily peeled off from the molded product were determined to have poor moldability.

<Example 1>
The battery case shown in FIG. 1 was manufactured.

A conductive knitted fabric with a thickness of 0.33 mm (mesh size: 3 to 4 mm ² , open pores) obtained by applying a multilayer plating of Ni and Cu, the outermost layer being Ni, to a mesh knitted fabric made of polyester fibers. (Rate: 30%) was inserted into a box-shaped mold, and PP / PPE alloy was injection molded under molding conditions of a cylinder temperature of 260 ° C. The obtained battery case was 3 mm in thickness, and the conductive knitted fabric was visually recognized on the inner surface of the battery case. The evaluation results are shown in Table 1.

  As shown in Table 1, the characteristics required for battery cases, low frequency magnetic field shielding, vibration damping, heat resistance (high deflection temperature), mechanical strength (impact strength), and dimensional accuracy (low warpage) are sufficient. We were satisfied with.

<Example 2>
After inserting the same conductive knitted fabric as in Example 1 into the box-shaped mold except that it has the mesh size and the open area shown in Table 1, PA / PPE alloy was injected under the molding conditions of a cylinder temperature of 270 ° C. Molded. The obtained battery case was 3 mm in thickness, and the conductive knitted fabric was visually recognized on the inner surface of the battery case.

  Since PA is a hygroscopic resin, it was evaluated after conditioning the molded product under the assumption that the molded product is actually used in an automobile (23 ° C., 50% RH equilibrium). The results are shown in Table 1.

  As shown in Table 1, the characteristics required for battery cases, low frequency magnetic field shielding, vibration damping, heat resistance (high deflection temperature), mechanical strength (impact strength), and dimensional accuracy (low warpage) are sufficient. We were satisfied with.

<Example 3, Comparative Examples 1-3>
A battery case was obtained in the same manner as in Example 1 except that the conductive knitted fabric similar to that in Example 1 was used except that the resin shown in Table 1 and the mesh size and porosity shown in Table 1 were used. The obtained battery case was 3 mm in thickness, and the conductive knitted fabric was visually recognized on the inner surface of the battery case. The evaluation results are shown in Table 1.

As shown in Table 1, Example 3 sufficiently satisfied the performance required for the battery case as in Example 1.
In Comparative Example 1, although the low-frequency magnetic field shielding property was satisfied, the conductive knitted fabric was partially damaged, and the adhesion strength to the molded product was weak.

  In Comparative Example 2, the magnetic field shielding property at 10 MHz was not satisfactory.

  Comparative Example 3 satisfied the low frequency magnetic field shielding properties and vibration damping properties, but did not satisfy the heat resistance (high load deflection temperature), mechanical strength (impact strength), and dimensional accuracy (low warpage).

<Comparative example 4>
A battery case was obtained in the same manner as in Example 1 except that the conductive knitted fabric was not used and the conductive modified PPE added with carbon fiber was used and the cylinder temperature was set to 270 ° C. The obtained battery case was 3 mm thick. The evaluation results are shown in Table 1.

  As shown in Table 1, the vibration damping property was low, and there was almost no magnetic field shielding property at 10 MHz.

<Comparative Example 5>
A battery case was obtained in the same manner as in Example 1 except that the conductive knitted fabric was not used. The obtained battery case was 3 mm thick. Next, a conductive paint (Nihon Acetin Co., Ltd., nickel-coated conductive paint “JEF-606”) was applied to the inner surface of the battery case with a thickness of 10 μm and then evaluated. The results are shown in Table 1.

  Similar to Comparative Example 3, there was almost no magnetic field shielding property at 10 MHz.

  The battery case of the present invention is excellent in magnetic field shielding properties and vibration damping properties, and sufficiently satisfies the characteristics required for an automobile battery case.

It is a figure which shows an example of the battery case of this invention.

Explanation of symbols

1 Conductive knitted fabric 2 Resin body

Claims (3)

  A conductive knitted fabric having a porosity of 10 to 60% covered with a metal layer and a resin main body, and the resin main body is made of an alloy of polypropylene and polyphenylene ether, or an alloy of polyamide and polyphenylene ether. A battery case characterized by that.   The battery case according to claim 1, wherein the metal layer includes a Ni plating layer and a Cu plating layer, and the Ni plating layer is an outermost layer.   The battery case according to claim 1, wherein the conductive knitted fabric is exposed on an inner surface of the battery case.

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