JP2015096578A - Metal-adhered conductive resin film and conductive resin-metal composite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal-adhered conductive resin film which is improved, compared with conventional resin films, by improving conductivity and enhancing adhesion of a single resin film to a metal member and a conductive resin-metal composite using the film.SOLUTION: A resin film is to be adhered to the surface of a metal member and is formed by mixing, with kneading, a substrate resin based on a thermoplastic acid-modified polyolefin resin with granular graphite and carbon nano-tube as a conductive carbon material and rolling to 100 μm or smaller. Another resin member is adhered to one side of the conductive resin film. A conductive resin-metal composite is formed by adhering the conductive resin film to the surface of a metal member.

Description

  The present invention relates to a metal-bonded conductive resin film and a conductive resin-metal composite, and more particularly to a resin film having good conductivity and good adhesion to a metal member and a conductive resin-metal composite using the same.

  Conventionally, since a resin material is an insulator, it has been used for metal insulation. On the other hand, the resin material has moldability and corrosion resistance. Furthermore, it is used for an extremely wide range of applications because of its advantage of being lightweight and easy to process and being easily fused with other resin materials. For example, in a fuel cell or the like, a metal member is used for a component such as a separator, and a resin member is also arranged in order to increase the resistance of the metal member. However, it has been regarded as a problem that the resin material alone has extremely low conductivity.

  In order to cope with this problem, a conductive film in which a carbon material is kneaded with a resin in advance to improve conductivity has been proposed (see Patent Documents 1, 2, 3, etc.). The films disclosed in these patent documents are attached to a metal plate. As a result, the conductivity of the film exhibits electrical conductivity not only on the metal member but also on the film side, and is expected to improve the efficiency of the fuel cell.

  However, the conductivity of the existing conductive resin film is still poor. That is, the resistance value is high. For this reason, when it is assumed that the fuel cell is used at a practical stage, the performance is not sufficient. It was one of the obstacles to overcome when aiming for further improvement in power generation efficiency in the future.

  In addition, the adhesion performance of the conductive resin film itself to a metal plate or the like is also important. There is also a need for a property that does not peel easily after bonding. Inadvertent peeling may cause corrosion of the metal member. Such properties of conductivity and strong adhesion are not limited to fuel cell applications, but are also demanded as materials for various high-performance batteries such as cation batteries such as lithium and other advanced electrical devices.

  From the above-mentioned circumstances, it is required to secure higher conductivity in the conductive resin film than ever. And the strong adhesion performance with a metal member is also requested | required. However, the adhesive strength with a metal member will fall if it is going to improve the electroconductivity in a resin film. On the contrary, if priority is given to adhesiveness with a metal member, the target conductivity will deteriorate. From such mutual contradiction, conductive resin films having suitable properties are under development. Thus, there is a strong demand for a conductive resin film that satisfies both of the contradictory properties and further satisfies the requirements alone.

International Publication Number WO 2005/027248 JP 2008-207404 A JP 2013-93334 A

  The present invention has been proposed in view of the above-described situation, and in the single resin film, it is possible to achieve both of the contradictory properties of improvement in conductivity and enhancement of adhesive strength with a metal member, and both properties are existing resins. Provided are a metal-bonded conductive resin film improved over the film, and a conductive resin-metal composite material using the film.

  That is, the invention of claim 1 is a resin film adhered to the surface of a metal member, the resin film comprising a base resin mainly composed of an acid-modified polyolefin resin, and granular graphite and carbon nanotubes as a conductive carbon material. It is related with the metal-bonding conductive resin film characterized by being a conductive resin film mixed and rolled while kneading.

  The invention of claim 2 relates to the metal-bonded conductive resin film according to claim 1, wherein the acid-modified polyolefin resin has thermoplasticity.

  The invention according to claim 3 relates to the metal-bonded conductive resin film according to claim 1 or 2, wherein the conductive carbon material further contains carbon fiber.

  Invention of Claim 4 concerns on the metal-bonding conductive resin film of any one of Claim 1 thru | or 3 whose thickness of the said conductive resin film is 100 micrometers or less.

  The invention according to claim 5 relates to the metal-bonded conductive resin film according to any one of claims 1 to 4, wherein another resin member is bonded to one surface side of the conductive resin film.

  A sixth aspect of the present invention relates to a conductive resin-metal composite characterized in that the metal-bonded conductive resin film according to any one of the first to fourth aspects is bonded to a surface of a metal member.

  A seventh aspect of the present invention is the conductive resin-metal composite, wherein the surface of the metal-bonded conductive resin film according to the fifth aspect to which the other resin member is not bonded is bonded to the surface of the metal member. Related to the material.

  According to the metal-bonded conductive resin film of the first aspect of the invention, the resin film is bonded to the surface of the metal member, and the resin film includes a base resin mainly composed of an acid-modified polyolefin resin, and conductive carbon. Since it is a conductive resin film obtained by kneading and rolling granular graphite and carbon nanotubes as materials, the properties of the individual resin films are contrary to each other in improving conductivity and strengthening the adhesion to metal members. Both properties can be achieved and both properties can be improved over existing resin films.

  According to the metal-bonded conductive resin film according to the invention of claim 2, in claim 1, since the acid-modified polyolefin resin has thermoplasticity, it melts by heating to increase fluidity, and kneading or rolling with a conductive carbon material Convenient for processing.

  According to the metal-bonded conductive resin film of the third aspect of the present invention, in the first or second aspect, since the conductive carbon material further contains carbon fiber, the conductivity is improved and the structural strength is increased.

  According to the metal-bonded conductive resin film of the invention of claim 4, in any one of claims 1 to 3, since the thickness of the conductive resin film is 100 μm or less, it is possible to ensure good conductivity. it can.

  According to the metal-bonded conductive resin film according to the invention of claim 5, in any one of claims 1 to 4, since another resin member is bonded to one surface side of the conductive resin film, other than the acid-modified polyolefin resin The resin can be used.

  According to the conductive resin-metal composite material of the sixth aspect of the invention, since the metal-bonded conductive resin film according to any one of the first to fourth aspects is bonded to the surface of the metal member, the metal member and the metal member An integrated composite of conductive resin that adheres to the substrate can be easily produced.

  According to the conductive resin-metal composite material of the seventh aspect of the invention, the surface side of the metal-bonded conductive resin film of the fifth aspect, to which the other resin member is not bonded, is bonded to the surface of the metal member. In addition, a composite body in which the metal member and the conductive resin bonded to the metal member are integrated can be easily manufactured.

  The metal-bonded conductive film of the present invention is a resin film that is thermally fused and bonded to the surface of an appropriate metal member, and is useful when forming a composite of conductive resin and metal. As this application, fuel cell separators are promising. Of course, as long as the characteristics of the conductive resin can be utilized, the application is wide. The main part of the metal-bonded conductive film of the present invention is a conductive resin film.

  The conductive resin film that is the main body of the metal-bonded conductive film (A) of the first embodiment is formed of a base resin mainly composed of an acid-modified polyolefin resin. Then, a predetermined amount of conductive carbon material is blended in the base resin. Particulate graphite and carbon nanotubes are interspersed as conductive carbon materials in the base resin.

  The acid-modified polyolefin resin of the base resin is preferably a polyolefin-based resin modified with an unsaturated carboxylic acid or a derivative thereof. Examples of such an unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid. Acid, crotonic acid, itaconic acid, citraconic acid, and the like. These esters and anhydrides can also be used, and the derivatives include methyl acrylate, methyl methacrylate, ethyl acrylate, propyl acrylate, acrylic Examples include butyl acrylate, butyl methacrylate, vinyl acetate, glycidyl acrylate, glycidyl methacrylate, acrylamide, methacrylamide, and sodium acrylate.

  Examples of the polyolefin resin that can be used include polyethylene, polypropylene, polybutene, and copolymers thereof, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, and the like. The amount of the unsaturated carboxylic acid or derivative thereof contained in the polyolefin resin at this time is preferably 0.001 to 3% by weight, more preferably 0.01 to 1% by weight, and particularly preferably 0.03 to 3% by weight. 0.5% by weight. If the amount of modification in the modified product is small, the effect of improving the interlaminar adhesion is poor, and conversely if it is large, a crosslinking reaction is caused and the moldability is deteriorated. In addition, the adhesiveness of these adhesive resins can be improved by blending a rubber / elastomer component such as polyisobutylene or ethylene-propylene rubber, or a polyolefin resin different from the base polyolefin resin of the adhesive resin. It is useful.

  The acid-modified polyolefin resin is required to have thermoplasticity. This is because thermoplasticity is melted by heating to increase fluidity, and is suitable for processing such as kneading or rolling with a conductive carbon material.

  The acid-modified polyolefin resin alone has no conductivity. In this case, it is also possible to add a fine metal powder as a conductive material. However, common metals have corrosive problems. Metals such as gold and platinum have corrosion resistance, but the manufacturing cost increases. For this reason, it is extremely difficult to employ fine metal powder for the conductive film. Therefore, a conductive carbon material that is a good conductive material and excellent in corrosion resistance is used.

  The granular graphite, which is one of the components constituting the conductive carbon material, is a substantially spherical graphite having a diameter (particle diameter) of 5 μm or more, preferably 10 to 30 μm. The granular graphite occupies 30 to 60% by weight of the total weight of the conductive resin film. Therefore, granular graphite becomes arrangement | positioning which adjoins or contacts in a conductive resin film, and the electroconductivity of the whole conductive resin film improves.

  Carbon nanotubes, which are the second component constituting the conductive carbon material, are carbon compounds composed of only carbon atoms having a diameter of 10 nm to 150 nm. Carbon nanotubes occupy 15 to 30% by weight of the total weight of the conductive resin film. By including the carbon nanotube in the base resin, the conductor is bridged between the granular graphites in the base resin. For this reason, electroconductivity increases further.

  When producing a conductive resin film, the acid-modified polyolefin resin, which is a base resin, is heated and melted, and a predetermined amount of granular graphite and carbon nanotubes are charged therein, and are sufficiently kneaded and uniformly dispersed in the resin. . In kneading, a known kneading apparatus such as a blender or kneader that can be heated and melted is used. Thereafter, the kneaded product of the base resin containing the conductive carbon material is passed through a rolling roller or the like and rolled until it reaches a predetermined thickness. Thus, a conductive resin film is completed.

  The thickness of the conductive resin film is adjusted at the rolling stage. Which thickness is adopted depends exclusively on the use of the conductive resin film. However, if it is too thick, the conductivity deteriorates. On the other hand, if the thickness is too thin, the protection performance of the metal surface is lowered. Therefore, the thickness of the conductive resin film is set to 100 μm or less, more preferably about 20 to 50 μm.

  The conductive resin film that is the main body of the metal-bonded conductive film (B) of the second embodiment is also formed of a base resin mainly composed of an acid-modified polyolefin resin. Then, a predetermined amount of conductive carbon material is blended in the base resin. Particulate graphite and carbon nanotubes are interspersed as conductive carbon materials in the base resin. Furthermore, carbon fiber is also added as a conductive carbon material. The characteristic of the conductive resin film is that it contains three types of carbon materials having different forms as the conductive carbon material.

  Carbon fiber, which is the third component constituting the conductive carbon material, is a fibrous material obtained by carbonizing resin fibers, and has a diameter of 5 μm to 30 μm. The carbon fiber occupying the total weight of the conductive resin film is 5 to 30% by weight.

  In addition to the granular graphite and carbon nanotubes as the conductive carbon material, carbon fiber is further added to the inside of the base resin to further improve the conductivity. Moreover, when the carbon fiber is dispersed in the conductive resin film, a complicated network structure is generated in the film. This increases the structural strength of the base resin and increases the rigidity of the conductive resin film.

  In the production of the conductive resin film, similarly to the above-described conductive resin film, the granular carbon, carbon nanotube, and carbon fiber, which are conductive carbon materials, are weighed by a predetermined amount and are heated and melted by a blender or kneader. Kneaded. Thereafter, the base resin kneaded material containing the conductive carbon material is passed through a rolling roller or the like and rolled until it reaches a predetermined thickness.

  In the metal-bonded conductive film of the third embodiment, the other resin member (C) is bonded to one surface side of the above-described conductive resin film by heat fusion. As combinations, “metal-bonded conductive film (A) | resin member (C)”... {P}, “metal-bonded conductive film (B) | resin member (C)”. An appropriate resin is used for the resin member depending on the use of the metal-bonded conductive film. Therefore, the resin member may be a conductive resin or may be a nonconductor. The resin member does not assume direct adhesion to the surface of the metal member. Therefore, it is not necessarily limited to the above-mentioned acid-modified polyolefin resin. Therefore, inexpensive polyethylene and polypropylene can be used. In selection, properties such as compatibility with the acid-modified polyolefin resin are taken into consideration.

  In order to increase the conductivity of a resin member that is separately bonded, granular graphite and carbon nanotubes are blended inside the resin. Since these conductive carbon materials are common, description is omitted. Furthermore, carbon fiber can also be added here. The weight ratio of each conductive carbon material contained in the resin depends on strength, use, and the like. In general, for the convenience of kneading and rolling the resin, it has the same composition as the conductive resin film described above.

  A series of metal-bonded conductive films are bonded to the surface of the target metal member (D) to form a conductive resin-metal composite. Specific combinations are “metal member (D) | metal-bonded conductive film (A)”... {X}, “metal member (D) | metal-bonded conductive film (B)”... {Y}.

  Furthermore, the surface side where the other resin member in the metal-bonded conductive film is not bonded is bonded to the surface of the metal member. The specific combination is “metal member (D) | metal adhesive conductive film (A) | resin member (C)”... {Z}, “metal member (D) | metal adhesive conductive film (B) | resin Member (C) "... {W}.

  In any case, the adhesion to the surface of the resin member is heat-sealed, so that it adheres firmly to the metal. Adhesion becomes strong due to the influence of the ionic bond between the polar group of the acid-modified resin and the metal atom. For example, a metal member and a metal-bonded conductive film are carried between a heating panel and a heating roller, and heat fusion is performed. For this reason, it becomes possible to easily manufacture an integrated product of the metal member and the conductive resin bonded thereto. In particular, since one surface side of the metal-bonded conductive film is a resin surface, appropriate processing is easy.

The inventor made the metal-bonded conductive films of Prototype Examples 1 to 13 based on the formulations disclosed in Tables 1 to 3 below using the following raw materials. And about the film of each prototype, thickness (micrometer), penetration resistance (mohm * cm < ² >), volume resistance (ohm * cm), and adhesiveness (%) were measured according to the description in a table | surface.

[Raw materials]
The following was used as the acid-modified polyolefin resin.
Maleic anhydride-modified low-density polyethylene (Mitsubishi Chemical Co., Ltd., Modic M504, melting point 121 ° C.) (referred to as modified LL in the table)
Maleic anhydride-modified polypropylene (manufactured by Mitsubishi Chemical Corporation, Modic P555, melting point 168 ° C.) (referred to as modified PP in the table)
The following were used as other resins used.
Low density polyethylene (Ube Maruzen Polyethylene Co., Ltd., Umerit 4540F, melting point 134 ° C.) (referred to as LL in the table)
Homopolypropylene (Nippon Polypro Co., Ltd., Novatec FL100A, melting point 161 ° C.) (in the table, PP)
For each base resin, resin pellets were freeze-ground and used as powder.

The following was used for the conductive carbon material.
Carbon nanotube: VGCF-X (fiber diameter: 10 to 15 nm) manufactured by Showa Denko KK (referred to as CNT in the table)
Granular graphite: manufactured by Nippon Carbon Co., Ltd., Nikabeads P25B-ZG (average particle diameter: 25 μm, true density: 2.17 g / cm ³ ) (referred to as SG in the table)
Carbon fiber: manufactured by Mitsubishi Plastics Co., Ltd., DIALEAD K223HE (fiber diameter: 11 μm, true density: 2.0 g / cm ³ ) (referred to as CF in the table)

  The notation of the blending ratio (wt%) in the table indicates the respective weight% (total 100 wt%) in the order of “base resin / CNT / SC / CF”. The blank is not compounded. The “carbon material weight ratio” is the weight of the total conductive carbon material when the weight of the base resin is “100”. “Resin ratio” is the volume ratio (vol%) of the resin component in the total volume of the metal-bonded conductive film.

[Creation of prototype examples 1 to 11]
Resins (modified LL, modified PP, LL) and various conductive carbon materials listed in the table were weighed at the blending ratios described in the table, and kneaded while melting the resin to obtain a resin kneaded product. The resin kneaded product of each trial example was formed into a film by rolling it to 100 μm or less through a calender roll machine heated to a temperature 1 ° C. to 5 ° C. lower than the melting point of the resin used at a linear pressure of about 2 t / cm.

  The completed conductive resin film was placed on a mirror-finished stainless steel plate and bonded by heating and pressing from above and below. The pressing temperature at this time was set to 20 ° C. to 50 ° C. higher than the melting point of the resin used. The press pressure was 30 MPa.

[Creation of prototype examples 12 and 13]
As another resin member that adheres to the conductive resin film, a film-like material was separately prepared based on the formulation shown in Table 3. These production methods are the same as those in the above-described prototype examples 1 to 11. The other resin members (conductive film-like materials) of Prototype Examples 12 and 13 were placed on the conductive resin film of Prototype Example 2, and the conductive resin film side of Prototype Example 2 was mirror-finished stainless steel. It was placed on a plate and bonded by heating and pressing from above and below. The press temperature and pressure were the same.

[Measurement of thickness]
Citizen Watch Co., Ltd .: MEI-10 A JIS paper thickness measuring machine was used to measure the thickness of 10 sheets of each prototype, and the thickness (μm) per sheet was calculated.

[Measurement of volume resistivity]
In accordance with JIS K 7194 (1994) {Resistivity testing method using conductive plastic 4-probe method}, low resistivity meter Loresta GP MCP-T610, manufactured by Mitsubishi Chemical Analytech Co., Ltd., using a PSP probe The rate (Ω · cm) was measured.
[Measurement of penetration resistance]
A low resistivity meter, Loresta GP MCP-T610, manufactured by Mitsubishi Chemical Analytech Co., Ltd., is used to sandwich the film of the sample to be measured from the thickness direction with a gold-plated plate with a diameter of 30 mm and pressurize at 1 MPa. The resistance in the thickness direction (mΩ · cm ² ) was measured.

[Evaluation of adhesion]
The stainless steel plate to which the film of each prototype was adhered was placed in distilled water. This was carried into an oven set at 100 ° C. and heated for 24 hours. The cellophane tape was affixed with respect to the surface of the film which took out here after a heating and affixed on the stainless steel plate. Then, the cellophane tape was peeled off. The area of the conductive resin film remaining on the stainless steel plate after peeling of the cellophane tape was measured, and the degree of peeling from the beginning was shown as a percentage. If there is no peeling, 100% remains. If the peeling is half the area, it is 50%.

[Results and discussion of Tables 1 and 2]
In Prototype Example 1, the base resin decreased relatively due to the effect of increasing the conductive carbon material. Therefore, although the resistance value is low, the decrease in adhesiveness is remarkable. On the other hand, for Prototype Examples 10 and 11, the conductivity decreased because the amount of the conductive carbon material was reduced. According to Prototype Example 9, it is a use other than acid-modified polyolefin resin and has no adhesiveness. From this result, it is essential to use an acid-modified polyolefin resin as long as the purpose is direct adhesion to a metal member. In Prototype Examples 2 to 8, the quantitative balance between the conductive carbon material and the base resin is good, and both the conductivity and adhesion indices are very good. For conductive carbon materials, both granular graphite (SG) and carbon nanotubes (CNT) are essential. And it was also clarified that the performance improvement progresses further by adding carbon fiber (CF).

[Results and discussion of Table 3]
The other resin members in Prototype Examples 12 and 13 correspond to simple conductive resins in Prototype Example 9 and the like. However, by interposing the metal-bonded conductive film of Prototype Example 2, it was possible to bond well with the metal member. In particular, Prototype Example 12 had a penetration resistance comparable to the other prototype examples. The penetration resistance in Prototype Example 13 is considered to be due to the thickness. In addition, good adhesion was ensured from the point of compatibility between the resins. Accordingly, the metal-bonded conductive film can be a single conductive resin film or a laminate of the conductive resin film and another resin member, and has a very high degree of freedom.

[Evaluation of change of metal member type]
Next, the metal member used as the adhesion object of a metal adhesion conductive film was changed, penetration resistance was measured, and adhesiveness was also evaluated. As the metal member, a gold-plated stainless steel plate (Prototype Example 14), a copper plate (Prototype Example 15), an aluminum plate (Prototype Example 16), and an iron plate coated with diamond-like carbon (Prototype Example 17) were used. In the evaluation, the metal-bonded conductive film of Prototype Example 2 was used. The bonding method was the same as described above. It is as Table 4.

[Results of changing the type of metal parts]
In any case, the adhesiveness is good. In addition, since the surface of Prototype Example 17 was not a metal, it did not peel off. The difference in penetration resistance for each prototype is considered to be the influence of the resistance of the metal member itself. From this result, the metal-bonded conductive film can be bonded to various metal members. Furthermore, it can respond to a wide range of uses as a conductive resin-metal composite material.

  The metal-bonded conductive film and conductive resin-metal composite material of the present invention have both good conductivity and metal adhesion, and are suitable for applications where metal is coated and conductivity is required. For example, it is promising for separator applications such as fuel cells. Of course, besides this, it can be used for various applications that require the characteristics of the present invention.

Claims (7)

A resin film adhered to the surface of a metal member,
The resin film is a conductive resin film obtained by mixing and rolling a base resin mainly composed of an acid-modified polyolefin resin and granular graphite and carbon nanotubes as a conductive carbon material while kneading. Metal adhesive conductive resin film.   The metal-bonded conductive resin film according to claim 1, wherein the acid-modified polyolefin resin has thermoplasticity.   The metal-bonded conductive resin film according to claim 1, wherein the conductive carbon material further contains carbon fiber.   The metal-bonded conductive resin film according to any one of claims 1 to 3, wherein the conductive resin film has a thickness of 100 µm or less.   5. The metal-bonded conductive resin film according to claim 1, wherein another resin member is bonded to one surface side of the conductive resin film.   5. A conductive resin-metal composite material, wherein the metal-bonded conductive resin film according to claim 1 is bonded to a surface of a metal member.   6. A conductive resin-metal composite material, wherein a surface of the metal-bonded conductive resin film according to claim 5 to which the other resin member is not bonded is bonded to the surface of the metal member.