JP6771351B2 - Stainless steel sheet carbon composite material and its manufacturing method - Google Patents

Description

The present invention relates to a stainless steel plate carbon composite material and a method for producing the same, and in particular, a carbon layer containing carbon powder and resin powder is laminated on the surface of a stainless steel plate-like base material, whereby, for example, a solid polymer. Conductivity and corrosion resistance that can be used for separators for fuel cells such as type fuel cells, current collectors for redox flow type secondary batteries, gaskets and packings for petrochemical refining, petrochemicals, etc. The present invention relates to a stainless steel plate carbon composite material having excellent flexibility and the like, and a method for producing the same.

In recent years, polymer electrolyte fuel cells have been attracting attention from the viewpoint of environmental protection. Examples of such a fuel cell and a separator for a fuel cell are shown in FIGS. 7 and 8 (a) and 8 (b).
Here, FIG. 7 is an exploded view showing the configuration of the unit cells constituting the fuel cell 16, and FIG. 8 is a diagram showing the configuration of the fuel cell separator 5 shown in FIG. 7. 8 (a) is a plan view, and FIG. 8 (b) is a cross-sectional view taken along the line XY of FIG. 8 (a).

The polymer electrolyte fuel cell 16 uses two MEA (membrane / electrode assembly) fuels, which are composed of a polymer electrolyte membrane 6, an anode (fuel electrode) 7, and a cathode (oxidizer electrode) 8. Dozens to hundreds of configurations 10 sandwiched between the battery separators 5 and the gasket 9 as a unit cell are laminated, and the fuel gas (hydrogen gas) which is a fluid is applied to the anode 7 and the fluid is applied to the cathode 8. By supplying the oxidative gas (oxygen gas), the current is taken out from the external circuit. As shown in FIGS. 8A and 8B, the fuel cell separator 5 has a plurality of gas supply / discharge grooves 11 and a gas supply / discharge groove 11 on one side or both sides of a thin plate-like body. It has a shape having an opening 12 for supplying fuel gas or oxidation gas to the fuel cell and a fixing hole 13 for arranging MEAs in parallel, and has a function of separating the fuel gas flowing in the fuel cell and the oxidation gas so as not to be mixed. In addition to having the above, it plays an important role of transferring the electric energy generated by the MEA to the outside and dissipating the heat generated by the MEA to the outside.

Therefore, the characteristics required for the separator for polymer electrolyte fuel cells are long-term durability (corrosion resistance) under the operating environment (high temperature, corrosiveness, low pH, etc.) in the fuel cell, and less power generation loss. In addition to the characteristics such as low electrical resistance and excellent conductivity, and gas impermeable to completely separate fuel gas and oxidation gas on both sides and supply them to the electrodes, assuming an in-vehicle use. It is required to have strength and flexibility (flexibility) that does not break even when bolted or vibrated during assembly.

In order to meet such demands, various efforts are being made as shown below.
That is, as a separator for a polymer electrolyte fuel cell, a carbon separator centered on glassy carbon has been conventionally studied, but such a carbon separator is extremely fragile and flexible. Practicality is lacking, and considering its use as an in-vehicle fuel cell, etc., it has poor gas barrier properties and airtightness, and also has problems such as difficulty in miniaturization and high processing cost. Is said to have a problem.

Therefore, attempts have been made to use a metal material instead of the carbon separator, and in particular, from the viewpoint of mechanical strength, workability, and cost, a separator made of stainless steel has been studied, but stainless steel is generally used. The steel surface has a relatively thick passivation film formed due to the manufacturing process or the like, and although it has excellent corrosion resistance, this passivation film has high electrical resistance and poor conductivity. Therefore, some reports have been made from the viewpoint of improving the conductivity (reducing the contact resistance) of the stainless steel separator as described above.

For example, Patent Document 1 proposes a fuel cell separator in which the surface of a stainless steel member is gold-plated to ensure conductivity and improve corrosion resistance. However, in this fuel cell separator, stainless steel is used. Since the surface of the manufacturing member is gold-plated, the manufacturing cost becomes too high, which makes it unsuitable industrially from an economical point of view.

Further, in Patent Document 2, the central portion in the thickness direction is C: 0.03% or less, Si: 0.01% or more and 1.5% or less, Mn: 0.01% or more and 2.5% or less in terms of mass%. , P: 0.035% or less, S: 0.01% or less, Cr: 16.0% or more and 30.0% or less, Ni: 6.0% or more and 30.0% or less, B: 0.01% or less , Al: 0.001% or more and 0.2% or less, N: 0.06% or more and 0.3% or less, Mo: 7.0% or less, and Cu: 5.0% or less, balance: Fe and impurities C: 0.03% or less, Si: 0.01% or more and 1.5% or less, Mn in terms of mass% of the surface portion up to a depth of 10% or less of the total thickness. : 0.01% or more and 2.5% or less, P: 0.035% or less, S: 0.01% or less, Cr: 16.0% or more and 30.0% or less, Ni: 12.0% or more and 50. 0% or less, B: 0.4% or more and 3.5% or less, Al: 0.001% or more and 0.2% or less, N: 0.01% or more and 0.1% or less, Mo: 7.0% or less , And Cu: 5.0% or less, the balance: a stainless steel having a chemical composition consisting of Fe and impurities, and having a chemical composition satisfying the relationship of 17.0 ≤ Cr + 3Mo-2.5B, 0.2%. Stainless steel for fuel cell separators having a withstand strength YS of 300 N / mm ² or more and a total elongation EI of 40% or more, and a separator for fuel cells using the same have been proposed. And, in this Patent Document 2, it is described that the contact resistance is lowered by finely dispersing a boride having excellent conductivity, but this boride is present in a relatively high concentration on the surface portion. When used as a separator, there is a problem that cracks are likely to occur due to boride having a high hardness when rolling or the like in order to make it thin.

Further, in Patent Document 3, stainless steel is immersed in a solution containing fluorine ions at a predetermined dissolution rate, and the passivation film on the surface contains fluorine to improve conductivity (low contact resistance). Stainless steel for energizing parts has been proposed, but in this stainless steel for energizing parts, since fluorine ions are present in the passivation coating, the stainless steel is liable to deteriorate, and as a result, it corrodes in the usage environment of the fuel cell. It is easy to use and deterioration during use is unavoidable.

Further, in Patent Document 4, it is obtained by treating the surface of austenite-based stainless steel with a first acid and a second acid to form a non-conductor coating having a large chromium oxide composition ratio on the surface. A stainless steel member for a solid polymer fuel cell separator has been proposed, which is said to have excellent corrosion resistance and low contact resistance. However, this stainless steel member has a large chromium oxide composition ratio and is non-conductor. Not only the resistance of the film is high, but also the surface is easily oxidized due to the excess nitric acid in the hydrofluoric acid and nitric acid (hereinafter, this may be referred to as "fluoric acid" etc.) solution. If only this stainless steel member is used as a separator, there is a problem that the contact resistance tends to change with time.

Further, in Patent Document 5, stainless steel containing 16% by mass of chromium is electrolyzed and then immersed in a solution containing fluorine such as hydrofluoric acid and fluoric acid to bring it into contact. Stainless steel for fuel cell separators, which has reduced resistance and excellent corrosion resistance, has been proposed. However, this stainless steel is also subjected to any treatment after the treatment for removing the passivation film. Therefore, surface oxidation is likely to occur, and if only this stainless steel member is used as a separator, there is a problem that the contact resistance tends to increase over time in the usage environment of the fuel cell.

As described above, it is difficult for the stainless steel separator to exhibit sufficient conductivity and corrosion resistance over time under the usage environment of the fuel cell, for example, and it is possible without cracks or cracks. So far, no stainless steel separator has been found that has excellent flexibility and satisfies them.
On the other hand, a coated metal in which a paint containing a mixed powder of a mixture of carbon powder and resin powder is applied to a metal base material to form a conductive coating film on the surface of the metal base material, or the above-mentioned It has also been studied to use a composite carbon plate in which a carbon plate obtained by molding a mixed powder is laminated on a metal base material as a separator for a fuel cell.

For example, in Patent Document 6, a surface-coated metal separator material obtained by applying a water-dispersible paint containing a conductive agent composed of a mixed powder of graphite powder and carbon black and a polyolefin resin to the surface of a pickled stainless steel plate base material. It has been proposed that there are no coating defects and the adhesion and contact resistance of the coating are improved. However, in this surface-coated metal separator material, the passivation film on the stainless steel surface is removed by pickling. Although the method is used, the graphite cleaning that is specifically used is not sufficient, it becomes difficult to make contact with the conductive material, and the desired low contact resistance cannot be achieved. There is a problem that the flexibility is inferior when the material for forming the portion is a combination of graphite particles and carbon black.

Similarly, in Patent Document 7 using a coated metal, a conductive paint containing a conductive agent composed of a mixture of carbon black and graphite and a thermosetting resin composed of an epoxy resin or a phenol resin is applied to the surface of a stainless steel plate. Although a stainless steel plate has been proposed, this painted stainless steel plate is relatively weak against impact and easily cracked, and as a result, it is caused by vibration during use as a separator for a polymer electrolyte fuel cell for automobiles, for example. Therefore, there is a concern that the coating film on the surface may be cracked and corroded in the usage environment of the fuel cell, and the contact resistance between the stainless steel plate and the coating film may be significantly deteriorated.

Further, in Patent Document 8, expanded graphite powder and graphite powder are mixed as carbon powder in a specific ratio, and a carbon plate obtained by compression molding a specific amount of phenol resin containing no ammonia is used as a metal base material. Laminated composite carbon plates have been proposed, but in this composite carbon plate, the stainless steel, which is the metal base material used, has not been treated in any way, so there is a problem that the contact resistance is relatively high. is there. Further, since the carbon plate used in Patent Document 8 uses a large amount of expanded graphite powder of 30 wt% or more, the resin is embedded in expanded graphite having many voids in the particles. As a result, there is a concern that the adhesive force between the carbon plate and the metal foil will decrease and the contact resistance will increase.

Japanese Unexamined Patent Publication No. 10-228,914 Japanese Unexamined Patent Publication No. 2010-037614 Japanese Unexamined Patent Publication No. 2010-013684 Japanese Unexamined Patent Publication No. 2013-129896 WO 2012/098689 Japanese Unexamined Patent Publication No. 11-345618 Japanese Unexamined Patent Publication No. 2010-248474 WO 2014/148649

As described above, carbon, metal (stainless steel plate), or laminated carbon and metal have been proposed as separators for fuel cells, but all of them have the flexibility required for practical use (flexibility required for practical use). No one was found that satisfied all the properties such as flexibility), durability (corrosion resistance) and conductivity.
Therefore, as a result of diligent studies by the present inventors under such circumstances, the following findings were obtained. That is, it was found that even if the surface of the stainless steel is surface-treated with fluorine or the like, the contact resistance increases with time, but when the state of the stainless steel surface is analyzed in detail, the outermost surface is found. It was found that the larger the Si content present, the greater the contact resistance over time. As for stainless steel, which has a large change in contact resistance with time, it is not practical because it is necessary to take measures such as forming a carbon layer in a short time after surface treatment in view of industrial mass production. According to the study of, a stainless steel plate having a specific composition was used as the plate-shaped base material, the silicon concentration in the outermost surface layer of the plate-shaped base material was reduced as much as possible, and then through this surface layer. We have found that by laminating a carbon layer, a stainless steel plate carbon composite material having stable low contact resistance, good conductivity, and excellent corrosion resistance and flexibility can be obtained, and the present invention has been completed.

Therefore, an object of the present invention is, for example, a separator for a fuel cell such as a polymer electrolyte fuel cell, a current collector plate for a redox flow type secondary battery, and a gasket for petroleum refining, petrochemicals, etc. It is an object of the present invention to provide a stainless steel plate carbon composite material having excellent conductivity, corrosion resistance, flexibility and the like, which can also be used for packing and packing.
Another object of the present invention is to provide a method for producing a stainless steel plate carbon composite material having excellent conductivity, corrosion resistance, flexibility and the like.

That is, the gist of the present invention is as follows.
(1) A stainless steel plate carbon composite material in which a carbon layer containing carbon powder and a resin powder made of a thermoplastic resin or a thermosetting resin is laminated on at least one surface of a plate-shaped base material made of stainless steel.
The plate-like base material is a stainless steel plate having a silicon content of 1.0% by mass or less, and has a silicon concentration of 0.5 at% or less from the surface to a depth of 5 nm.
The carbon layer is a stainless steel plate carbon composite material having a volume ratio (C / R) of carbon powder (C) and resin powder (R) of 6/4 to 9/1.
(2) The stainless steel plate carbon composite material according to (1) above, wherein the silicon concentration from the surface of the plate-shaped base material to a depth of 5 nm is 0.01 at% or less.
(3) The stainless steel plate carbon composite material according to (1) or (2) above, wherein the plate-shaped base material is austenitic stainless steel or ferritic stainless steel.
(4) The resin powder composed of the thermoplastic resin is polypropylene resin, polyethylene resin, polyamide resin, polyphenylene sulfide resin, polymethylpentene resin, polyether ether ketone resin, polyphenylene ether resin, liquid crystal polymer resin, polyamideimide resin, polysulfone. Any one of the above (1) to (3), which is a resin powder composed of any one selected from the group consisting of a resin, a polyethylene terephthalate resin and a polybutylene terephthalate resin, or a mixture of two or more kinds. The stainless steel plate carbon composite material described in.
(5) The resin powder made of the thermosetting resin is a resin powder made of any one or a mixture of two or more selected from the group consisting of phenol resin and epoxy resin. The stainless steel plate carbon composite material according to any one of 1) to (3).
(6) Any of the above (1) to (5), wherein the surface of the plate-shaped base material and the carbon layer laminated on the surface are bonded via an adhesive layer. The stainless steel plate carbon composite material described in.
(7) A carbon layer containing carbon powder and a resin powder made of a thermoplastic resin or a thermosetting resin is laminated on at least one surface of a stainless steel plate-shaped base material having a silicon content of 1.0% by mass or less. It is a method of manufacturing stainless steel plate carbon composite material.
A hydrofluoric acid aqueous solution having a concentration of 1 to 10% by mass or a concentration ratio of hydrofluoric acid (HF) to nitric acid (HNO ₃ ) (HF /) on at least one surface of the plate-like substrate as a surface treatment liquid. A surface treatment step in which a hydrofluoric acid / nitric acid mixed aqueous solution having an HNO ₃ ) of 2 or more and an HF concentration of 2% by mass or more is brought into contact with each other.
A carbon layer having a volume ratio (C / R) of 6/4 to 9/1 of the carbon powder (C) and the resin powder (R) is laminated on the surface of the plate-shaped base material after the surface treatment. A method for producing a stainless steel plate carbon composite material, which comprises a laminating step.
(8) Prior to the surface treatment step, before contacting at least one surface of the plate-shaped substrate with an iron chloride-containing acid aqueous solution having an acid concentration of 25% by mass or more and an iron chloride concentration of 20% by mass or more as a pretreatment liquid. The method for producing a stainless steel plate carbon composite material according to (7) above, which comprises a treatment step.
(9) In the laminating step, a powder mixture containing the carbon powder and the resin powder is hot-pressed to form a carbon layer, and the obtained carbon layer is hot-pressed on the surface of the plate-shaped base material after surface treatment. The method for producing a stainless steel plate carbon composite material according to (7) or (8) above, which comprises laminating the materials.
(10) Prior to the laminating step, there is an adhesive layer forming step of applying an adhesive composition to the surface of the plate-shaped base material after surface treatment to form an adhesive layer, and this adhesive is used in the laminating step. The method for producing a stainless steel plate carbon composite material according to any one of (7) to (9) above, wherein a carbon layer is laminated on the surface of a plate-like base material after surface treatment via a layer.
(11) The resin powder made of the thermoplastic resin is polypropylene resin, polyethylene resin, polyamide resin, polyphenylene sulfide resin, polymethylpentene resin, polyether ether ketone resin, polyphenylene ether resin, liquid crystal polymer resin, polyamideimide resin, polysulfone. Any one of (7) to (10) above, which is a resin powder composed of any one or a mixture of two or more selected from the group consisting of a resin, a polyethylene terephthalate resin and a polybutylene terephthalate resin. A method for producing a stainless steel plate carbon composite material according to.
(12) The resin powder made of the thermosetting resin is a resin powder made of any one or a mixture of two or more selected from the group consisting of a phenol resin and an epoxy resin. The method for producing a stainless steel plate carbon composite material according to any one of 7) to (10).
(13) The method for producing a stainless steel plate carbon composite material according to any one of (7) to (12) above, wherein the plate-shaped base material is austenitic stainless steel or ferritic stainless steel.

According to the present invention, it is possible to provide a stainless steel plate carbon composite material having excellent conductivity, corrosion resistance and flexibility.
Further, according to the present invention, it is possible to provide a method for producing a stainless steel plate carbon composite material having excellent conductivity, corrosion resistance and flexibility.

FIG. 1 is an explanatory view (photograph) showing a TEM observation cross section of a stainless steel plate-shaped base material and an oxide film formed on the surface thereof [(a) Hydrofluoric acid treatment (HF: 1% by mass, HNO ₃ : HNO ₃ :). 4% by mass) 30 days later, (b) Hydrofluoric acid treatment (HF: 4% by mass) 30 days later] Figure 2 shows a SUS316L steel plate treated with nitric acid (HF: 1% by mass, HNO ₃ : 4% by mass) and then stored in the air for 30 days, and hydrofluoric acid treatment (HF: 4). By XPS measurement using a sample that was stored in the air for 30 days after (mass%), the depth direction (nm) from the surface of the oxide film formed on the SUS surface and its Si concentration (at%) It is a graph which shows the relationship of. FIG. 3 shows a SUS316L steel sheet stored in the air for 30 days after being treated with fluoric acid (HF: 1% by mass, HNO ₃ : 4% by mass) and hydrofluoric acid treatment (HF: 4). Using the sample (b) stored in the air for 30 days after (mass%), the difference between these treatment solutions was measured by XPS measurement, and the bonding state of Si and oxygen in the oxide film formed on the SUS surface was observed. It is a graph which shows the difference of. FIG. 4 is a schematic explanatory view of a molding method for producing a carbon layer or a stainless steel plate carbon composite material. FIG. 5 is a schematic explanatory view of a method of laminating a carbon layer, an adhesive layer, and a plate-shaped base material made of stainless steel in the production of the stainless steel plate carbon composite material of the present invention. FIG. 6 is a schematic explanatory view of a method for measuring contact resistance. FIG. 7 is an exploded view showing the configuration of the unit cells constituting the fuel cell. FIG. 8A is a plan view showing an example of a fuel cell separator, and FIG. 8B is a cross-sectional view showing a cross section taken along line XY of FIG. 8A.

Hereinafter, the stainless steel plate carbon composite material of the present invention and a method for producing the same will be described in detail.
The stainless steel plate carbon composite material of the present invention is a stainless steel plate carbon in which a carbon layer containing carbon powder and a resin powder made of a thermoplastic resin or a thermosetting resin is laminated on at least one surface of a plate-shaped base material made of stainless steel. The plate-like base material is a composite material, which is a stainless steel plate having a silicon content (Si content) of 1.0% by mass or less, and is 5 nm from the surface of the surface layer formed on the SUS surface. The silicon concentration (Si concentration) to the depth of is 0.5 at% or less, and the carbon layer has a volume ratio (C / R) of carbon powder (C) and resin powder (R) of 6/4 to 9 It is characterized by a ratio of / 1.

In the present invention, the stainless steel constituting the plate-like base material is not particularly limited as long as its Si content is 1.0% by mass or less, preferably 0.8% by mass or less, but it is preferable. For example, SUS316L, SUS316, SUS304L, SU304 and the like can be exemplified as the austenitic stainless steel, and SUS430, SUS444, SUS434, SUS405, SUS429 and the like can be exemplified as the ferrite stainless steel, for example. Here, if the Si content exceeds 1.0% by mass, the corrosion resistance and weldability may be lowered, and coarse graining may be induced to deteriorate the cold workability. In addition, if the Si content is too small, the quality of the product may deteriorate due to a shortage of Si, which is an antacid, or it may be necessary to prepare high-quality raw materials from the beginning, leading to an increase in cost. Therefore, it is preferably 0.05% by mass or more.

Further, in the present invention, the surface layer of the plate-like base material is an oxide film formed after removing the passivation film on the surface of the stainless steel sheet, and the Si concentration thereof is the surface (that is, the surface layer). It needs to be 0.5 at% or less in the region of 5 nm from the outermost surface), preferably 0.01 at% or less, and preferably as small as possible. Here, the Si concentration (at%) in the present invention indicates the ratio (%) of the number of Si atoms to the total number of atoms at each depth from the outermost surface to the region of 5 nm. If the Si concentration in this region becomes higher than 0.5 at%, the ratio of SiO ₂ which is an oxide of Si becomes high, so that the conductivity may decrease. The thickness of the surface layer composed of this oxide film is usually 6 nm or more and 25 nm or less, preferably 10 nm or more and 20 nm or less. If the thickness of this surface layer is smaller than 6 nm, it is not stabilized and oxidation occurs for a while. As a result, the oxide film may be formed thicker, and conversely, if the thickness exceeds 25 nm, the conductivity may decrease.

Here, in the present invention, the Si concentration from the surface of the plate-shaped substrate to a depth of 5 nm can be measured by, for example, XPS (X-Ray photoelectron spectroscopy), and is obtained. It is obtained by performing calculation from spectral data. Specifically, the data in the depth direction is etched by irradiation with Ar ions or the like, and the spectrum data in an arbitrary depth direction is collected. Then, the quantitativeness in the depth direction can be calculated by converting from the value using SiO ₂ as the standard material as the reference for the irradiation time and the depth data. Then, the present inventors speculate about the Si concentration of this surface in the present invention as follows. That is, we have grasped the phenomenon that the contact resistance increases as Si becomes thicker near the surface in the surface layer of the plate-shaped base material, and from this, it is not Si in the base material of the plate-shaped base material, but The fact that the Si exposed up to 5 nm from the surface is oxidized to SiO ₂ and the contact resistance increases over time and loses conductivity greatly affects the conductivity of the surface of the plate-shaped substrate. I'm guessing it's influencing.

In the present invention, since the plate-shaped base material has such a surface state, the contact resistance thereof is preferably 10 mΩ · cm ² or less, more preferably 5 mΩ · cm ² or less. More preferably, it is 3 mΩ · cm ² or less, and its contact resistance does not substantially change even after 30 days have passed.

The thickness of the stainless steel plate-shaped base material is not particularly limited, but is usually 10 μm or more and 150 μm or less, preferably 20 μm or more and 70 μm or less. If the thickness is less than 10 μm, the mechanical strength may decrease, and conversely, if the thickness exceeds 150 μm, problems may occur in terms of flexibility and flexibility.

The carbon layer laminated on the surface of the plate-shaped base material contains carbon powder and a resin powder made of a thermoplastic resin or a thermosetting resin, and is a carbon powder (C) and a resin powder ( R) is contained in a volume ratio (C / R) of 6/4 to 9/1, preferably 7/3 to 8/2, and the thickness thereof is preferably 0.05 mm or more and 2.0 mm or less. Is 0.1 mm or more and 1.0 mm or less. Regarding the volume ratio (C / R) of the carbon powder (C) and the resin powder (R), if it becomes smaller than 6/4 and the ratio of the carbon powder decreases, the conductivity may decrease. If it is larger than 9/1, the ratio of the thermoplastic resin or the thermosetting resin is low, so that the flexibility, flexibility and corrosion resistance may be inferior. Regarding the thickness of the carbon layer, if it is thinner than 0.05 mm, corrosion may start from a slight crack in the carbon layer, and conversely, if it is thicker than 2.0 mm, it may adversely affect the flexibility. is there.

Here, the carbon powder forming the carbon layer is selected from, for example, natural graphite powder, artificial graphite powder, expanded graphite powder, expanded graphite powder, scaly graphite powder, spheroidal graphite powder, and the like. One type or a mixture of two or more types can be mentioned, and it is preferable to include at least expanded graphite powder and / or expanded graphite powder from the viewpoint of flexibility and conductivity. In that case, the content of the expanded graphite powder and / or the expanded graphite powder is preferably 4% by volume or more and less than 51% by volume, more preferably 5% by volume or more and less than 21% by volume in the mixed powder of the carbon powder and the resin powder. preferable. If it is less than 4% by volume, the flexibility may be lowered, while if it is 51% by volume or more, the resin that originally contributes to the adhesion between the particles or between the particles and the metal plate can function well. Instead, the contact resistance may increase. In this range, the mass content of the expanded graphite powder and / or the expanded graphite powder in the carbon powder is such that the true specific gravity of the expanded graphite powder and / or the expanded graphite powder is 2.2 g / g, which is the same as that of other graphite powders. It can be calculated as cm ³ , preferably 5% by mass or more and less than 73% by mass, and more preferably 7% by mass or more and less than 30% by mass.
The particle size of this carbon powder is represented by the value of D ₅₀ (cumulative 50% by volume) calculated by a particle size counter such as a laser diffraction type particle size distribution measuring device (for example, "Mastersizer 2000" manufactured by Malvern). The average particle size to be formed is usually 4 μm or more and 200 μm or less, preferably 10 μm or more and 30 μm or less, and if it is smaller than 4 μm, the specific surface area is large, so that it is difficult for the resin to be used for adhesion between particles or a SUS plate. The flexibility may be inferior, and conversely, if it is larger than 200 μm, it is difficult to obtain a smooth surface when forming the carbon layer, and the defect rate may increase.

Further, the resin powder forming the carbon layer may be a thermoplastic resin or a thermosetting resin, and the thermoplastic resin can be selected according to the intended use. Although not particularly limited, polypropylene resin (PP), polyethylene resin (PE), polyamide resin (PA), polyphenylene sulfide resin (PPS), polymethylpentene resin (PMP), polyetheretherketone resin ( Selected from the group consisting of PEEK), polyphenylene ether resin (PPE), liquid crystal polymer resin (LCP), polyamideimide resin (PAI), polysulfone resin (PSU), polyethylene terephthalate resin (PET) and polybutylene terephthalate resin (PBT). Any one or a mixture of two or more thereof can be mentioned, and the thermosetting resin can be selected according to the intended use and is not particularly limited, but is preferably phenol. Examples thereof include any one or a mixture of two or more selected from the group consisting of resins and epoxy resins.

Here, as for the polyolefin resin such as PP, PE, PMP, it is also possible to use a modified polyolefin resin in which a part or all of the unsaturated carboxylic acid or a derivative thereof is grafted on the polyolefin resin. .. By using such a modified polyolefin resin, it is possible to improve the flexibility of the carbon layer and the stainless steel plate carbon composite material provided with the carbon layer, and to improve the adhesion to SUS and the adhesion to carbon particles. Expected, which is preferable as it reduces contact resistance. The amount of graft (graft ratio) in the entire modified polyolefin resin is usually preferably 0.05 to 15% by mass, more preferably 0.1 to 10% by mass, and further preferably 0.1 to 3%. It is said to be% by mass. Specific examples of the unsaturated carboxylic acid or its derivative used for grafting to the polyolefin resin before modification include acrylic acid, methacrylic acid, maleic acid, itaconic acid, citraconic acid, mesaconic acid, and maleic anhydride. , Hymic anhydride, 4-methylcyclohexe-4-ene-1,2-dicarboxylic acid anhydride, α-ethylacrylic acid, fumaric acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, endocis-bicyclo [2,2 1] Hept-5-ene-2,3-dicarboxylic acid (nagic acid [trademark]), bicyclo [2.2.2] octo-5-ene-2,3-dicarboxylic acid anhydride, 1,2,3 , 4,5,8,9,10-Octahydronaphthalene-2,3-dicarboxylic acid anhydride, 2-octa-1,3-diketospiro [4.4] non-7-ene, bicyclo [2.2. 1] Hept-5-ene-2,3-dicarboxylic acid anhydride, maleopimaric acid, tetrahydrophthalic acid anhydride, x-methyl-bicyclo [2.2.1] hept-5-ene-2,3-dicarboxylic acid Anhydride, x-methyl-norbornen-5-ene-2,3-dicarboxylic acid anhydride (x indicates the substitution position of the methyl group), norborn-5-ene-2,3-dicarboxylic acid anhydride, etc. Can be used. In addition, derivatives such as acid halide, amide, imide, and ester of the unsaturated carboxylic acid can also be used. Among these, unsaturated dicarboxylic acids or acid anhydrides thereof are preferable, and maleic anhydride or hymic anhydride is particularly preferable. Such an unsaturated carboxylic acid or a derivative thereof may be used alone, or a combination of two or more thereof may be used. As the halogen group, chlorine or bromine can be preferably used.

The average particle size of the above-mentioned resin powder is usually 5 μm or more and 300 μm or less, preferably 20 μm or more and 200 μm or less, and if it is smaller than 5 μm, agglomeration of resin particles may occur, and conversely, 300 μm. If it becomes larger, the resin flow during warm compression molding (hot pressing) becomes poor, and there is a risk that a problem may occur in the formation of the carbon layer. The average particle size is defined in the same manner as in the case of the carbon powder.

In the present invention, the surface of the stainless steel plate-like base material and the carbon layer laminated on the surface may be bonded via an adhesive layer of usually 0.1 μm or more and 10 μm or less. The adhesive composition for forming such an adhesive layer is not particularly limited, but preferably a modified polyolefin resin in which a part or all of an unsaturated carboxylic acid or a derivative thereof is grafted on the polyolefin resin. (For example, refer to Japanese Patent Application Laid-Open No. 2005-146,178), specifically, an adhesive composition containing an adhesive polyolefin resin (trade name: Admer manufactured by Mitsui Chemicals, Inc.), unsaturated. Examples thereof include an adhesive composition containing a modified polyolefin resin graft-modified with a carboxylic acid (trade name: Unistor, manufactured by Mitsui Chemicals, Inc.). An adhesive composition containing a modified polyolefin resin graft-modified with halogen (trade name: Toyo Tuck Co., Ltd.) can also be used, and a 5 wt% -phenol resin adhesive composition (solvent: Isopropyl alcohol, phenol resin: Lignite Co., Ltd. trade name: AH-1148), epoxy resin adhesive composition (Nippon Steel & Sumikin Chemical Co., Ltd. trade name: YSLV-80XY) and the like can also be used. If the layer thickness of the adhesive layer is less than 0.1 μm, the adhesive strength may decrease, and if it exceeds 10 μm, the conductivity of the produced stainless steel plate carbon composite material may decrease.

Regarding the method for producing a carbon composite material of a stainless steel plate of the present invention, carbon powder and a thermoplastic resin or thermosetting property are formed on at least one surface of a plate-shaped base material made of stainless steel having a silicon content of 1.0% by mass or less. When a carbon layer containing a resin powder made of a resin is laminated to produce a stainless steel plate carbon composite material, preferably, a surface treatment liquid having a concentration of 1 to 10% by mass is applied to at least one surface of the plate-shaped base material. hydrogen acid aqueous solution, or a hydrofluoric acid (HF) and nitric acid (HNO ₃₎ and the concentration ratio (HF / HNO ₃₎ is 2 or more in a by HF concentration of 2 mass% or more hydrofluoric acid-nitric acid The volume ratio (C / R) of the carbon powder (C) and the resin powder (R) is 6/4 to 9 on the surface treatment step of bringing the mixed aqueous solution into contact and the surface of the plate-shaped base material after the surface treatment. It is preferable to use a method having a laminating step of laminating carbon layers having a ratio of 1/1. At this time, more preferably, chloride having an acid concentration of 25% by mass or more and an iron chloride concentration of 20% by mass or more as a pretreatment liquid on at least one surface of the plate-shaped substrate prior to performing the surface treatment step. A pretreatment step of contacting the iron-containing acid aqueous solution may be performed.

As the hydrofluoric acid used as the surface treatment liquid in the surface treatment step, an aqueous hydrofluoric acid solution having a concentration of 1% by mass or more and 10% by mass or less, preferably 3% by mass or more and 8% by mass or less is used. Here, if the hydrofluoric acid concentration of the hydrofluoric acid aqueous solution used as the surface treatment liquid is lower than 1% by mass, the Si concentration in the oxide film on the stainless steel surface may not be within a predetermined concentration range. On the contrary, when it is higher than 10% by mass, the stainless steel of the base material is largely eluted, the thickness of the oxide film formed on the surface thereof is increased, and the contact resistance may be increased.
When a mixed aqueous solution of hydrofluoric acid and nitric acid is used as the surface treatment liquid, the concentration ratio (HF / HNO ₃ ) of hydrofluoric acid (HF) and nitric acid (HNO ₃ ) is preferably 2 or more. Is 2.5 or more, and the HF concentration is 2% by mass or more, preferably 3% by mass or more. When the concentration ratio (HF / HNO ₃ ) of hydrofluoric acid (HF) and nitric acid (HNO ₃ ) is less than 2, the Si concentration in the above-mentioned surface region becomes high and the contact resistance becomes larger than 10 mΩ · cm ^2. In addition, when the HF concentration is less than 2% by mass, the Si concentration in the surface region may increase and the contact resistance may become larger than 10 mΩ · cm ² . Even when used as a mixed aqueous solution, the upper limit concentration of hydrofluoric acid is 10% by mass or less, preferably 8% by mass or less, as described above. Regarding the treatment temperature, the plate-like substrate is immersed under the treatment conditions of a temperature of 30 ° C. or higher and 60 ° C. or lower and a time of 1 minute or longer and 20 minutes or lower, and then washed with pure water or the like.

Here, in the pretreatment step that may be performed prior to the surface treatment, iron chloride such as FeCl ₃ is dissolved in a non-oxidizing acid aqueous solution such as hydrochloric acid or hydrofluoric acid as a pretreatment solution. A pretreatment is performed in which a plate-like base material is immersed in the iron chloride-containing acid aqueous solution, and then washed with pure water or the like. Here, the iron chloride-containing acid aqueous solution varies depending on the type of acid used and the type of iron chloride, but the acid concentration is usually 25% by mass or more, preferably 30% by mass or more and 40% by mass or less, and also. Those having an iron chloride concentration of usually 20% by mass or more, preferably 20% by mass or more and 30% by mass or less are used, and the pretreatment conditions for immersing the plate-shaped base material in the iron chloride-containing acid aqueous solution are usually used. The treatment is carried out under the treatment conditions of a temperature of 30 ° C. or higher and 60 ° C. or lower and a time of 30 seconds or longer and 3 minutes or shorter. By this pretreatment, pitting corrosion is formed in advance on the relatively thick oxide film formed on the stainless steel surface in the annealing step performed in the stainless steel manufacturing process, or the oxide film is thinned to form a thin film on the subsequent surface. It is preferable because it becomes easy to control the structure of the oxide film in the treatment step.

Then, in the laminating step of laminating the carbon layer on the surface of the plate-shaped base material after the surface treatment, the carbon layer containing the carbon powder and the resin powder is laminated on the surface of the plate-shaped base material after the surface treatment. The method of laminating the carbon layer is not particularly limited, and for example, a method of filling the surface of a plate-shaped base material with a powder mixture containing carbon powder and resin powder and hot-pressing, resin powder and carbon powder An example is a method in which a slurry obtained by dispersing the above in a solvent is applied to a stainless steel surface using a doctor blade or the like, and then hot-pressed after drying. However, a powder mixture containing carbon powder and resin powder is preferably warmly compressed. It is preferable to use a hot press method in which a carbon layer is formed in advance by molding (hot pressing), and the obtained carbon layer is hot-pressed again on the surface of the plate-shaped base material after surface treatment and laminated. By forming the carbon layer by this hot press method and laminating the carbon layer, there is an advantage that the carbon layer can be continuously formed on the surface of the plate-like base material after the surface treatment.

In the production method of the present invention, prior to the laminating step, the adhesive composition is applied to the surface of the plate-shaped base material after surface treatment, and an adhesive layer is applied to the surface of the plate-shaped base material after surface treatment. The adhesive layer forming step to be formed may be carried out, and in the laminating step, the carbon layer is laminated via the adhesive layer. By carrying out the adhesive layer forming step prior to the laminating step, the adhesion between the plate-shaped base material and the carbon layer is improved, and the stainless steel surface of the plate-shaped base material is covered with the adhesive layer. For example, when used as a polymer electrolyte fuel cell, it has the advantage of improving durability against a corrosive environment.

The stainless steel plate carbon composite material of the present invention obtained by the method of the present invention has a compressive strength of 3 MPa or more, a bending strain of 0.8% or more, no cracks, and a contact resistance of 10 mΩ · cm ² or less. It is preferably 5 mΩ · cm ² or less, more preferably 3 mΩ · cm ² or less, and the contact resistance is in an environment corresponding to the usage environment of the fuel cell (for example, the implementation described later). It is preferable that the material does not change substantially even in the durability test) in which the material is immersed in an acid solution containing fluorine ions as shown in the example.
The stainless steel plate carbon composite material of the present invention is not only excellent in flexibility, flexibility, compressive strength, moldability, airtightness, etc., but also excellent in both conductivity (low contact resistance) and corrosion resistance. For example, it is suitably used in applications such as fuel cell separators for polymer electrolyte fuel cells, current collectors for redox flow type secondary batteries, gaskets and packings for petroleum refining and petroleum chemistry.

Hereinafter, the stainless steel plate carbon composite material of the present invention, a method for producing the same, and each performance evaluation will be specifically described based on Examples and Comparative Examples.

<Examples 1 to 8>
1. 1. Preparation of stainless steel plate-shaped base material [Stainless steel plate-shaped base material]
In each of the following examples and comparative examples, SUS430 stainless steel sheet (Si content 0.47% by mass, hereinafter referred to as "M1"), SUS444 stainless steel sheet (Si content 0.75% by mass, hereinafter referred to as "M2"). , SUS316L stainless steel sheet (Si content 0.75% by mass, hereinafter referred to as "M3"), and SUS447J1 stainless steel sheet (Si content 0.1% by mass, hereinafter referred to as "M4") 50 μm thickness × width 100 mm × A plate-shaped base material (M1 to M4) having a size of 100 mm in length was used.

[Surface treatment process of plate-like substrate: formation of surface layer]
For the plate-shaped substrates (M1 to M4) obtained above, 4% by mass hydrofluoric acid aqueous solution was used as the surface treatment liquid as shown in Table 1, and 50 ° C. and 10 were used in the surface treatment liquid, respectively. Plate-shaped base material (M1 to M4) after surface treatment in which a surface layer consisting of an oxide film is formed on the surface of the plate-shaped base material after immersion under the treatment conditions for 1 minute and then cleaning the surface with ultrapure water. Was prepared.

[Measurement of surface layer thickness]
For the plate-shaped base material (M1 to M4) after surface treatment, using a focused ion beam processing device (SMI3050SE manufactured by Hitachi High-Tech Science), a Mo mesh, and a carbon depot film as a surface protective film, FIB- A thin film cross-sectional sample for TEM observation was prepared by the microsampling method.
For TEM observation, an electrolytic emission type transmission electron microscope (JEM-2100F manufactured by JEOL Ltd.) is used to measure the thickness of the oxide film at any three locations per field and average the thickness to obtain the oxide film. The thickness of the surface layer was measured (Fig. 1).

[Measurement of Si concentration]
For the plate-shaped substrates (M1 to M4) after surface treatment, use an X-ray photoelectron spectrometer (Quantum 2000 type XPS manufactured by PHI) under the conditions of X-ray output of 15 kV, 25 W, and measurement area of 300 x 300 μm. Sputtering was performed under the conditions of an accelerating voltage of 2 kV and an irradiation range of 2 mm × 2 mm using argon as an ion species, and the Si concentration in the depth direction from the surface of the plate-shaped substrate (M1 to M4) was measured (Fig.). 2). The spatter rate is based on SiO ₂ , and the thickness is calculated by converting from the time when the surface of the surface treatment material is sputtered. In addition, MultiPak V.80 (analysis software manufactured by Ulvac-phi) was used for data analysis.
In XPS, a chemical shift (peak shift) occurs depending on the chemical state. For example, the 2p orbital spectrum of Si alone has a peak around 98.8eV to 99.5eV, whereas the oxide of Si has a peak of 102eV ~. Since the peak appears near 104 eV, it is possible to identify the state of Si. From FIG. 3, the peaks of Si and Si oxides cannot be observed in the case of HF treatment (concentration 4% by mass), whereas Si in the case of fluoride nitric acid treatment (HF concentration 1% by mass, HNO ₃ concentration 4% by mass). From the fact that the peak of the oxide can be confirmed, it can be inferred that the contact resistance increased for a while because the Si remaining near the surface was oxidized and the contact resistance value increased.
The results obtained are shown in Table 2 below.

2. Carbon layer laminating process [adhesive layer forming process]
Examples of the adhesive composition for forming the adhesive layer include thermoplastic resins [polypropylene resin (PP), polyethylene resin (PE), polyamide resin (polypropylene resin (PP), polyethylene resin (PE), polyamide resin) as resin powders, including the cases of Examples and Comparative Examples described later. PA), polyphenylene sulfide resin (PPS, polymethylpentene resin (PMP), polyether ether ketone resin (PEEK), polyphenylene ether resin (PPE), liquid crystal polymer resin (LCP), polyamideimide resin (PAI), polysulfone resin (PA) When using PSU), polyethylene terephthalate resin (PET), polypropylene terephthalate resin (PBT)], a modified polyolefin resin adhesive (manufactured by Mitsui Kagaku Co., Ltd., Unistor) is used, and heat curing is performed as a resin powder. When using a sex resin, if the thermosetting resin is a phenol resin (PF), a phenol resin adhesive in which the phenol resin is dissolved in isopropyl alcohol so as to be 5 wt% (phenol resin manufactured by Lignite Co., Ltd.). , Product name: AH-1148), while using an epoxy resin adhesive (trade name: YSLV-80XY manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd.) when the thermosetting resin is epoxy resin (EP). There was.
Then, the adhesive composition was applied to the surface of the plate-shaped substrate (M1 to M4) 30 days after the surface treatment obtained above using a tabletop coater so as to have a coating thickness of 10 μm, and at room temperature. It was dried for 10 minutes to form an adhesive layer, and plate-like substrates (M1 to M4) with the adhesive layer were obtained.

[Formation of carbon layer]
As the carbon powder, spheroidal graphite (trade name: SG-BH manufactured by Ito Graphite Co., Ltd., average particle size: 20 μm) and expanded graphite (trade name: EC100, average particle size: 160 μm manufactured by Ito Graphite Co., Ltd.) were used.
In addition, as the resin powder, including the cases of Examples and Comparative Examples described later, as the thermoplastic resin, polypropylene resin (PP) (trade name: Flowbren HP-8522 manufactured by Sumitomo Seika Co., Ltd.) and polyethylene resin (PE). ) (Sumitomo Seika Co., Ltd. product name: Frosen UF-20S), polyamide resin (PA) (Toray Co., Ltd. product name: TR-2), polyphenylene sulfide resin (PPS) (Toray Co., Ltd. product name: A900) ), Polymethylpentene resin (PMP) (trade name: MX002 manufactured by Mitsui Chemicals, Inc.), modified polymethylpentene resin (m-PMP) [developed product, modified with maleic anhydride (modification amount: 1.0% by mass)] , Polyether ether ketone resin (PEEK) (Quadrant Polypenco Japan Co., Ltd. product name: Ketron 1000), Polyphenylene ether resin (PPE) (Asahi Kasei Chemicals Co., Ltd. product name: Zylon 300H), Liquid crystal polymer resin (LCP) ( JX Nikko Nisseki Energy Co., Ltd. Product name: Zider NX-101), Polyamiimide resin (PAI) (Toray Co., Ltd. product name: TI-5013), Polysulfone resin (PSU) (BASF product name: Ultrazone) S2010), polyethylene terephthalate resin (PET) (manufactured by Teijin Co., Ltd .: TRN-MTJ), and polybutylene terephthalate resin (PBT) (trade name: Novaduran 5010R5 manufactured by Mitsubishi Engineering Plastics Co., Ltd.) are used and heat-cured. As the sex resin, phenol (PF) resin (trade name: AH-1148 manufactured by Lignite Co., Ltd.) and epoxy (EP) resin (trade name: YSLV-80XY manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd.) were used.

Then, the above carbon powder and resin powder were mixed at the ratios shown in Table 1 to obtain a powder mixture, and 1.6 g of this powder mixture was made of stainless steel with an adhesive layer as shown in FIG. 4 (in this case, made of stainless steel with an adhesive layer). The plate-shaped base material 4 is not used.) Put it evenly into a female mold with a volume of 50 x 50 x 20 mm of a press device (desktop hot press MP-SCL manufactured by Toyo Seiki Seisakusho Co., Ltd.) and pre-press. The carbon layer 3 (thickness: 0.4 mm) was obtained by hot pressing [pressure: 2 MPa, temperature: 180 ° C. (PP), 80 ° C. (PF)]. Next, as shown in FIGS. 4 and 5, the obtained carbon layer 3 and the plate-shaped base material 4 with the adhesive layer prepared above are superposed, and the heating temperature is 180 ° C. (PP) or 150 ° C. (PF). ) (T) and a pressure of 5 MPa (P) (main press, molding time 10 minutes) to obtain a stainless steel plate carbon composite material 15.

Stainless steel plate carbon composite produced using the plate-shaped base material after the surface treatment (immediately after and after 30 days) according to Examples 1 to 8 obtained above and the plate-shaped base material after 30 days after the surface treatment. The materials were evaluated as follows.

[Contact resistance measurement method]
FIG. 6 shows a method for measuring contact resistance. First, each plate-shaped base material immediately after surface treatment is processed into a test piece S having a length of 17 to 20 mm and a width of 3 to 5 mm, and this and standard carbon paper (trade name: TGP- of Toray Industries, Inc.) are used. H-120) 301 was overlapped. Then, this is sandwiched between two gold-plated copper metal fittings 302, and a test piece S / carbon paper contact area value (unit: cm ² ) is applied between the two gold-plated copper metal fittings with a compressive stress of 0.9 MPa (P') applied. Contact resistance value (unit: mΩ · cm ²⁾ obtained by measuring the voltage drop that occurs at the connection part of the gold-plated copper metal fitting 302 / carbon paper 301 / test piece S by passing a direct current (unit A) of the same value as ) Confirmed. The measurement was performed at 10 points, and the average value of 8 points excluding the maximum value and the minimum value was used as the measured value. Further, the contact resistance of each plate-shaped base material (S') 30 days after the surface treatment and the stainless steel plate carbon composite material (S'') produced by using the plate-shaped base material in the same manner. Was measured.
The results obtained are shown in Table 2 below.

[Durability test method]
In the durability test, the test piece S'' (stainless steel plate carbon composite material) was previously immersed in a sulfuric acid solution containing 20 ppm of fluorine (F) ions at 80 ° C. and pH 3 for 4 days, and then treated. The test piece S'' was washed with ultrapure water, dried, and then the contact resistance value (unit: mΩ · cm ² ) was measured by the same method as described above. Durability (corrosion resistance) was evaluated by evaluating the change in contact resistance before and after immersion.
The results obtained are shown in Table 2 below.

[Flexibility evaluation (bending strength evaluation)]
From each of the stainless steel plate carbon composite materials S'' obtained in Examples 1 to 8, each was cut out as a test piece having a size of 50 mm × 5 mm × 0.6 mm, and each of these test pieces was made in accordance with JIS K7171. Measure the Stress-Strain curve with a universal testing machine (AUTOGRAPH AG-IS type manufactured by Shimadzu Corporation) and visually check whether or not each test piece is broken (cracked) when the strain is 1.5% or 0.8%. Was observed and evaluated according to the following criteria.
The results obtained are shown in Table 2 below.
⊚: When not destroyed by 1.5% distortion ○: When not destroyed by 0.8% distortion ×: When destroyed by 0.8% distortion

<Examples 9 to 13, Comparative Example 1>
Using the plate-shaped base material (M1), first, hydrochloric acid (special grade manufactured by Kanto Chemical Co., Inc.) and iron chloride (FeCl ₃ ) (special grade manufactured by Kanto Chemical Co., Inc.) are dissolved as pretreatment solutions at a concentration of 30% by mass. Using an iron chloride-containing acid solution, the surface was washed with ultrapure water at 50 ° C. for 1 minute under the treatment conditions, and the plate-like substrate (M1) after the pretreatment was performed. Was prepared.

[Surface treatment process of plate-like substrate: formation of surface layer]
For each of the plate-shaped base materials (M1) after the pretreatment obtained above, a hydrofluoric acid aqueous solution having the concentration shown in Table 1 was used as the surface treatment liquid, and the surface treatment liquid was charged at 50 ° C. for 10 minutes. After immersion under the treatment conditions, the surface was washed with ultrapure water to prepare a plate-shaped base material (M1) after surface treatment in which a surface layer composed of an oxide film was formed on the surface of the plate-shaped base material.

Then, for each of the obtained plate-shaped base materials (M1) after the surface treatment, the thickness, Si concentration, and contact resistance value of the surface layer of the base material were measured in the same manner as in Examples 1 to 8 described above, and also. Similarly, an adhesive layer and a carbon layer (PP is used as a resin powder) are laminated on a plate-like base material 30 days after the surface treatment to obtain a stainless steel plate carbon composite material, and the contact resistance value is measured and durability is obtained. A sex test and a flexibility evaluation were performed.
The results obtained are shown in Table 2 below.

<Examples 14 to 18, Comparative Examples 2 to 4>
In Examples 9 to 13, nitric acid (special grade manufactured by Kanto Chemical Co., Ltd.) and hydrofluoric acid (special grade manufactured by Kanto Chemical Co., Ltd.) were used as the surface treatment liquid instead of the hydrofluoric acid aqueous solution used as the surface treatment liquid. A plate-like base material (M1) after pretreatment and surface treatment was prepared in the same manner as in Examples 9 to 13 except that the hydrofluoric acid / nitric acid mixed aqueous solution contained in the above ratio was used. In addition, the thickness, Si concentration, and contact resistance value of the surface layer of the base material were measured, and similarly, the adhesive layer and the carbon layer were laminated on the plate-shaped base material 30 days after the surface treatment to form a stainless steel plate. A carbon composite material was obtained, and the contact resistance value was measured, the durability test and the flexibility evaluation were performed.
The results obtained are shown in Table 2 below.

<Examples 19 to 40>
Plate-like groups pretreated and surface-treated in the same manner as in Examples 9 to 13 except that the concentration of the hydrofluoric acid aqueous solution used as the surface treatment liquid was 4% by mass in Examples 9 to 13. A material (M1) was prepared, and the thickness of the surface layer of the substrate, the Si concentration and the contact resistance value were measured in the same manner. Then, instead of the resin powder used in Examples 9 to 13, as shown in Table 1, the resin powder was used as PE, PA, PPS, PMP, m-PMP, PEEK, PSU, LCP, PET, PAI, PPE, respectively. , PBT, PF or EP, and the pre-press temperature for forming the carbon layer is 130 ° C (PE), 250 ° C (PA, PBT, PPE, m-PMP), 300 ° C (PPS, PET, respectively. A carbon layer was formed in the same manner as in Examples 9 to 13 except that the temperature was PAI), 350 ° C (LCP), 400 ° C (PEEK, PSU), 250 ° C (PMP) and 80 ° C (PF and EP). Similarly, the adhesive layer and the carbon layer are laminated on the plate-like base material 30 days after the surface treatment to obtain a stainless steel plate carbon composite material, and the contact resistance value is measured, the durability test and the flexibility evaluation are performed. Was performed. The temperatures of this press when a carbon layer with an adhesive layer is laminated on a plate-like base material 30 days after the surface treatment to obtain a stainless steel plate carbon composite material are 130 ° C (PE) and 250 ° C (, respectively). PA, PBT, PPE, m-PMP), 300 ° C (PPS, PET, PAI), 350 ° C (LCP), 400 ° C (PEEK, PSU), 150 ° C (PF and EP).
The results obtained are shown in Table 2 below.

<Examples 41 to 43, Comparative Examples 5 to 6>
Plate-like groups pretreated and surface-treated in the same manner as in Examples 9 to 13 except that the concentration of the hydrofluoric acid aqueous solution used as the surface treatment liquid was 4% by mass in Examples 9 to 13. A material (M1) was prepared, and the thickness, Si concentration and contact resistance value of the surface layer of the base material were measured in the same manner. Then, the carbon layer was formed in the same manner as in Examples 9 to 13, except that the blending ratios of the carbon powder and the resin powder used in Examples 9 to 13 were set to the ratios shown in Table 1, and similarly, after the surface treatment. After 30 days, the adhesive layer and the carbon layer were laminated on the plate-shaped base material to obtain a stainless steel plate carbon composite material, and the contact resistance value was measured, the durability test and the flexibility evaluation were performed.
The results obtained are shown in Table 2 below.

<Examples 44 to 47>
Plate-like groups pretreated and surface-treated in the same manner as in Examples 9 to 13 except that the concentration of the hydrofluoric acid aqueous solution used as the surface treatment liquid was 4% by mass in Examples 9 to 13. A material (M1) was prepared, and the thickness, Si concentration and contact resistance value of the surface layer of the base material were measured in the same manner. Then, a carbon layer was formed in the same manner as in Examples 9 to 13, except that the blending ratio of the carbon powders used in Examples 9 to 13 was set to the ratio shown in Table 1, and similarly, 30 days after the surface treatment had passed. An adhesive layer and a carbon layer were laminated on the plate-shaped base material of No. 1 to obtain a stainless steel plate carbon composite material, and a contact resistance value was measured, a durability test and a flexibility evaluation were performed.
The results obtained are shown in Table 2 below.

<Examples 48 to 54>
In Examples 9 to 13, an iron chloride-containing acid solution in which hydrochloric acid and iron chloride (FeCl ₃ ) were dissolved at the concentrations shown in Table 1 was used as the pretreatment liquid, and was used as the surface treatment liquid. A plate-shaped base material (M1) which had been pretreated and surface-treated by the same method as in Examples 9 to 13 except that the concentration of the hydrofluoric acid aqueous solution was 4% by mass was prepared, and the base material was similarly prepared. The thickness of the surface layer, the Si concentration and the contact resistance value were measured. Then, as in Examples 9 to 13, the adhesive layer and the carbon layer are laminated on the plate-like base material 30 days after the surface treatment to obtain a stainless steel plate carbon composite material, and the contact resistance value is measured and the durability is measured. A sex test and a flexibility evaluation were performed.
The results obtained are shown in Table 2 below.

<Comparative Example 7>
Using the plate-shaped substrate (M3), this is immersed in 2% by mass sulfuric acid (manufactured by Kanto Chemical Co., Inc.), and at a temperature of 30 ° C., + 2A / dm ² × 1 second, -2A / dm ² × 1 Electrolysis treatment (pretreatment) was performed in the order of seconds, + 2A / dm ² × 1 second, -2A / dm ² × 1 second, and + 2A / dm ² × 1 second (+ is the anode electrode and-is the cathode electrode). Next, a 5% by mass hydrofluoric acid aqueous solution was used as the surface treatment liquid, the plate-shaped base material after the electrolysis treatment was immersed under the treatment conditions of 55 ° C. and 90 seconds, and then the surface was washed with ultrapure water. Then, a plate-shaped base material (M3) after surface treatment in which a surface layer composed of an oxide film was formed on the surface of the plate-shaped base material was prepared.
Then, with respect to the obtained plate-shaped base material (M3) after the surface treatment, the thickness of the surface layer of the base material, the Si concentration and the contact resistance value were measured in the same manner as in Examples 1 to 8 described above. Durability test and flexibility evaluation are performed using the same method as in Examples 1 to 8 without laminating the adhesive layer and the carbon layer and leaving each plate-like base material (M3) after the surface treatment as it is. Was done.
The results obtained are shown in Table 2 below.

<Comparative Example 8>
Using the plate-shaped substrate (M3), this is immersed in a sodium orthosilicate solution having a concentration of 5% by mass and a liquid temperature of 60 ° C. as a pretreatment, and anode electrolytic degreasing is carried out at a current density of 5 A / dm ² for 10 seconds. After that, for neutralization treatment, pickling with hydrochloric acid at a concentration of 5% by mass and room temperature was carried out for 10 seconds. Then, it is immersed in 15 mass% FeCl ₃ (manufactured by Kanto Chemical Co., Inc.) at a temperature of 50 ° C., and the anode current density is 3.0 kA / m ² , the cathode current density is 0.5 kA / m ² , and the alternating cycle is 2.5 Hz. The electrolytic treatment was carried out for 60 seconds, and then the surface was washed with ultrapure water.
Then, with respect to the obtained plate-shaped base material (M3) after the electrolytic treatment, the thickness of the surface layer of the base material, the Si concentration and the contact resistance value were measured in the same manner as in Examples 1 to 8 described above. On the other hand, phenolic resin (trade name: AH-1148 manufactured by Lignite Co., Ltd.), natural graphite powder (trade name: SG-BH8 manufactured by Ito Graphite Co., Ltd.) and carbon black (trade name: ECP-600JD manufactured by Lion Co., Ltd.) 3 g, 6 g or 1 g (mass ratio 3: 6: 1), respectively, and an isocyanate cross-linking agent (trade name: MF-B60X manufactured by Asahi Kasei Chemicals Co., Ltd.) was added to the mixture three times the mass of the phenol resin. The amount was added and this was kneaded. Ethylene glycol monobutyl ether acetate is added to this to form a slurry, which is then applied to the electrolytically treated plate-like base material (M3) with a bar coater, and baked at 275 ° C. for 60 seconds to form a stainless steel plate carbon composite material. did. The thickness of the coating layer after drying was 6 μm. Then, the obtained stainless steel plate carbon composite material was subjected to a contact resistance value measurement, a durability test and a flexibility evaluation in the same manner as in Examples 1 to 8.
The obtained results are shown in Table 2 below (for Comparative Example 8, "immediately after surface treatment" in Table 2 should be read as "immediately after electrolytic treatment", and "30 days after surface treatment" should be read as "electrolytic treatment". It shall be read as "30 days later").

<Comparative Example 9>
The thickness, Si concentration, and contact resistance value of the surface layer of the base material were measured in the same manner as in Example 1 described above, except that the surface treatment was not performed using the plate-shaped base material (M1). Similarly, after 30 days have passed, an adhesive layer and a carbon layer (PP is used as the resin powder) are laminated on the plate-like base material to obtain a stainless steel plate carbon composite material, and the contact resistance value is measured and the durability test is performed. And flexibility evaluation was performed (Note that, in this Comparative Example 9, no surface treatment was performed, but "immediately after the surface treatment" in Table 2 was read as "before 30 days passed", and "surface treatment 30" was performed. "After 30 days" shall be read as "after 30 days").

1 ... oxide film layer, 2 ... stainless steel plate-like base material layer, 3 ... carbon layer, 4 ... stainless steel plate-like base material with adhesive layer, 5 ... fuel cell separator, 6 ... solid polymer electrolyte membrane , 7 ... Anode (fuel electrode), 8 ... Cathode (oxidizer electrode), 9 ... Gasket, 10 ... Unit cell, 11 ... Gas supply / discharge groove, 12 ... Opening, 13 ... Fixing hole, 14 ... Adhesive layer , 15 ... Stainless steel plate carbon composite material, 16 ... Solid polymer fuel cell, 100 ... Press device, 101 ... Male mold, 102 ... Female mold, 103 ... Mold, 104 ... Machine frame, 105 ... Hydraulic cylinder, 301 ... Carbon paper, 302 ... Copper metal fittings, 303 ... Measuring device

Claims (13)

A stainless steel plate carbon composite material in which a carbon layer containing carbon powder and a resin powder made of a thermoplastic resin or a thermosetting resin is laminated on at least one surface of a stainless steel plate-shaped base material.
The plate-like base material is a stainless steel plate having a silicon content of 1.0% by mass or less, and has a silicon concentration of 0.5 at% or less from the surface to a depth of 5 nm.
The carbon layer is a stainless steel plate carbon composite material having a volume ratio (C / R) of carbon powder (C) and resin powder (R) of 6/4 to 9/1. The stainless steel plate carbon composite material according to claim 1, wherein the silicon concentration from the surface of the plate-shaped base material to a depth of 5 nm is 0.01 at% or less. The stainless steel plate carbon composite material according to claim 1 or 2, wherein the plate-shaped base material is an austenitic stainless steel or a ferritic stainless steel. The resin powder made of the thermoplastic resin is a polypropylene resin, a polyethylene resin, a polyamide resin, a polyphenylene sulfide resin, a polymethylpentene resin, a polyether ether ketone resin, a polyphenylene ether resin, a liquid crystal polymer resin, a polyamideimide resin, a polysulfone resin, and polyethylene. The stainless steel plate carbon according to any one of claims 1 to 3, which is a resin powder composed of any one or a mixture of two or more selected from the group consisting of a terephthalate resin and a polybutylene terephthalate resin. Composite material. Claims 1 to 3 characterized in that the resin powder made of the thermosetting resin is a resin powder made of any one or a mixture of two or more selected from the group consisting of a phenol resin and an epoxy resin. The stainless steel plate carbon composite material described in any of. The stainless steel plate carbon according to any one of claims 1 to 5, wherein the surface of the plate-shaped base material and the carbon layer laminated on the surface are bonded via an adhesive layer. Composite material. A stainless steel plate in which a carbon layer containing carbon powder and a resin powder made of a thermoplastic resin or a thermosetting resin is laminated on at least one surface of a stainless steel plate-like base material having a silicon content of 1.0% by mass or less. It is a method of manufacturing carbon composite material.
A hydrofluoric acid aqueous solution having a concentration of 1 to 10% by mass or a concentration ratio of hydrofluoric acid (HF) to nitric acid (HNO ₃ ) (HF /) on at least one surface of the plate-like substrate as a surface treatment liquid. A surface treatment step in which a hydrofluoric acid / nitric acid mixed aqueous solution having an HNO ₃ ) of 2 or more and an HF concentration of 2% by mass or more is brought into contact with each other.
A carbon layer having a volume ratio (C / R) of 6/4 to 9/1 of the carbon powder (C) and the resin powder (R) is laminated on the surface of the plate-shaped base material after the surface treatment. A method for producing a stainless steel plate carbon composite material, which comprises a laminating step. Prior to the surface treatment step, a pretreatment step of contacting at least one surface of the plate-shaped base material with an iron chloride-containing acid aqueous solution having an acid concentration of 25% by mass or more and an iron chloride concentration of 20% by mass or more as a pretreatment liquid is performed. The method for producing a stainless steel plate carbon composite material according to claim 7, wherein the material is provided. In the laminating step, a powder mixture containing the carbon powder and the resin powder is hot-pressed to form a carbon layer, and the obtained carbon layer is hot-pressed and laminated on the surface of a plate-shaped base material after surface treatment. The method for producing a carbon composite material of a stainless steel plate according to claim 7 or 8. Prior to the laminating step, there is an adhesive layer forming step of applying an adhesive composition to the surface of the plate-shaped base material after surface treatment to form an adhesive layer, and in the laminating step, the adhesive layer is used. The method for producing a stainless steel plate carbon composite material according to any one of claims 7 to 9, wherein a carbon layer is laminated on the surface of the plate-like base material after surface treatment. The resin powder made of the thermoplastic resin is a polypropylene resin, a polyethylene resin, a polyamide resin, a polyphenylene sulfide resin, a polymethylpentene resin, a polyether ether ketone resin, a polyphenylene ether resin, a liquid crystal polymer resin, a polyamideimide resin, a polysulfone resin, and polyethylene. The stainless steel plate carbon according to any one of claims 7 to 10, which is a resin powder composed of any one or a mixture of two or more selected from the group consisting of a terephthalate resin and a polybutylene terephthalate resin. Method of manufacturing composite material. Claims 7 to 10 characterized in that the resin powder made of the thermosetting resin is a resin powder made of any one or a mixture of two or more kinds selected from the group consisting of a phenol resin and an epoxy resin. The method for producing a stainless steel plate carbon composite material according to any one of. The method for producing a stainless steel plate carbon composite material according to any one of claims 7 to 12, wherein the plate-shaped base material is an austenitic stainless steel or a ferritic stainless steel.

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