JP5253209B2 - Carbon molded body and method for producing the same - Google Patents

Description

  The present invention is, for example, a carbon molded body that can be suitably used as a magnetic head component, various molding dies, a jig, and the like, in addition to various conductive structures such as a separator for a fuel cell and a conductive material for an electrode. Regarding the method.

  Conventionally, a carbon molded body having excellent wettability with respect to an aqueous medium such as water in applications such as separators for fuel cells, various conductive structures such as electrode conductive materials, magnetic head parts, various molding dies, jigs, etc. Is required. For example, in an electrode plate for a secondary battery, hydrophilic carbon particles are used for the electrode active material layer so that the conductive material is easily dispersed in a solvent so that the conductive material is less likely to aggregate, and a large amount of conductive material is contained in the active material. It has been proposed to form an effective electron path by containing a material and efficiently disposing a conductive material on the surface of the active material particles (see Patent Document 1). In addition, in the fuel cell separator, for the purpose of producing a fuel cell separator imparted with hydrophilicity by a relatively easy and economical method, the surface of the fuel cell separator made of graphite powder and resin is treated with a flame to make the hydrophilicity. Giving (see Patent Document 2) and the like have been proposed.

JP 2007-103066 A JP 2002-313356 A

  For applications such as fuel cell separators that are expected to be used under high temperature conditions, the surface of the carbon molded body is required to maintain hydrophilicity not only near room temperature but also under high temperature conditions. However, under high-temperature conditions, particularly high-temperature and low-humidity conditions, wetting of the surface of the carbon molded body is likely to decrease due to evaporation of the aqueous solvent, etc., which is better due to the aqueous medium on the surface of the carbon molded body than when used near room temperature. There is a problem that it is difficult to ensure wetting.

  The present invention solves the above-mentioned problems, and a carbon molded body having good wettability to an aqueous medium, particularly water, not only when used near room temperature but also when used under high temperature conditions, particularly high temperature and low humidity conditions. And it aims at providing the manufacturing method.

  The present invention is a carbon molded body in which a hydrophilic coating film formed of a carbodiimide resin having a hydrophilic group in the molecule is provided on a carbon substrate, and the carbodiimide resin is modified with an organic acid. A carbon molded body is provided.

  The present invention also provides the carbon molded body, wherein the organic acid is at least one selected from the group consisting of propionic acid, lactic acid, malic acid, and tartaric acid.

  The present invention also provides the carbon molded body, wherein the carbon base material is a composite material containing carbon and a binder.

  Moreover, this invention provides the said carbon molded object in which the said hydrophilic coating film further contains a quaternary ammonium silicate.

  Moreover, this invention provides the said carbon molded object in which the said hydrophilic coating film further contains a silane coupling agent.

The present invention also provides an aqueous solution and / or aqueous dispersion of a carbodiimide resin having a hydrophilic group in the molecule on a carbon substrate, followed by drying, whereby the carbon substrate is coated on the carbon substrate. A resin application step of applying the carbodiimide resin;
An organic acid treatment step of treating the carbodiimide resin with an organic acid aqueous solution;
A water washing step of washing the treated carbon substrate;
The manufacturing method of the carbon molded object containing this is provided.

  The present invention also provides the method for producing the carbon molded body, wherein the organic acid is at least one selected from the group consisting of propionic acid, lactic acid, malic acid, and tartaric acid.

  Moreover, this invention provides the manufacturing method of the said carbon molded object whose said carbon base material is a composite material containing carbon and a binder.

  Moreover, this invention provides the manufacturing method of the said carbon molded object in which the said hydrophilic treatment liquid further contains a quaternary ammonium silicate.

  Moreover, this invention provides the manufacturing method of the said carbon molded object in which the said hydrophilic treatment liquid further contains a silane coupling agent.

  According to the present invention, there is provided a carbon molded body having a surface showing good hydrophilicity not only when used near room temperature but also when used under high temperature conditions, particularly high temperature and low humidity conditions, and a method for producing the same. Can do.

<Carbon molded body>
In the present invention, a hydrophilic coating film formed of a carbodiimide resin having a hydrophilic group in a molecule (hereinafter also referred to as “hydrophilic group-containing carbodiimide resin” in this specification) is provided on a carbon substrate. Provided is a carbon molded body, wherein the hydrophilic group-containing carbodiimide resin is modified with an organic acid. Here, the carbodiimide resin is a resin having a structure of -N = C = N- in the main chain.

  In the present specification, the hydrophilic group means an atomic group that exhibits an affinity for water due to a weak bond with a water molecule by electrostatic interaction, hydrogen bonding, or the like. Examples of the hydrophilic group include a hydroxyl group, a carboxy group, an amino group, a carbonyl group, an acyl group, a sulfo group, a polar group such as a thiol group, and an ether bond.

  The hydrophilic group-containing carbodiimide resin can be, for example, a modified carbodiimide resin using a compound containing a hydrophilic group. Examples of such modification include PEG (polyethylene glycol) and PPG (polypropylene glycol). And the like by modification with a polyalkylene oxide such as The molecular weight of the carbodiimide resin to be modified is not limited to this. For example, the number average molecular weight is preferably in the range of 200 to 100,000, more preferably in the range of 500 to 50,000, and further preferably in the range of 2,000 to 6,000. it can. The number average molecular weight can be determined in terms of polystyrene using gel permeation chromatography (GPC).

  The hydrophilic group-containing carbodiimide resin exhibits good wettability with respect to an aqueous medium and also has good adhesion to a carbon substrate. The aqueous medium is typically water, and examples thereof include alcohols, ketones, ethers and the like. Without being bound by theory, the hydrophobic part due to the main chain of the hydrophilic group-containing carbodiimide resin and the hydrophilic part due to the hydrophilic group contribute to the adhesion to the carbon substrate and the wettability to the aqueous solvent, respectively. There is a possibility.

  More specific examples of hydrophilic group-containing carbodiimide resins include “Carbodilite SV-02”, “Carbodilite V-02”, “Carbodilite V-02-L2” and “Carbodilite” which are aqueous solutions having an active ingredient concentration of 40% by mass. V-04 ", and" Carbodilite E-01 "," Carbodilite E-02 "," Carbodilite E-03A "and" Carbodilite E-04 "(both Nisshinbo Co., Ltd.), which are aqueous dispersions having an active ingredient concentration of 40% by mass Koji Co., Ltd.). These can be used alone or in combination of two or more.

  In the hydrophilic coating film formed in the present invention, the hydrophilic group-containing carbodiimide resin is further modified with an organic acid. In this specification, an organic acid means an organic compound that acts as an electron pair acceptor. As the organic acid, aliphatic and aromatic carboxylic acids are preferable in that the reactivity with the carbodiimide resin is good. Specific examples of preferable organic acids include aliphatic monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid and isobutyric acid, aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid and glutaric acid, glycolic acid and lactic acid. , Aliphatic monohydroxymonocarboxylic acids such as hydroxybutyric acid, aliphatic monohydroxydicarboxylic acids such as malic acid, aliphatic dihydroxydicarboxylic acids such as tartaric acid, aliphatic monohydroxytricarboxylic acids such as citric acid and isocitric acid, gallic acid, etc. Aromatic trihydroxymonocarboxylic acid, and the like. For example, the type and combination of organic acids can be appropriately selected according to the purpose, such as adopting a polybasic acid for the purpose of improving warm water durability by crosslinking and increasing the molecular weight of the carbodiimide resin. It is preferable that the organic acid is at least one selected from the group consisting of propionic acid, lactic acid, malic acid, and tartaric acid in terms of reactivity with the hydrophilic group-containing carbodiimide resin, handling properties, and the like.

  The carbon substrate is typically a composite material containing carbon and a binder. Examples of carbon include particulate graphite, and examples of binder include resins such as epoxy resin and phenol resin, and pitch. More specifically, for example, the carbon: binder mass ratio is in the range of 50:50 to 95: 5.

  The hydrophilic coating film provided in the present invention may be formed substantially only from an organic acid-modified product of a hydrophilic group-containing carbodiimide resin, but other than the hydrophilic group-containing carbodiimide resin as long as the effects of the present invention are not impaired. These components may be contained as subcomponents. Moreover, this invention does not prevent that the mass ratio of a subcomponent exceeds the mass ratio of the hydrophilic group containing carbodiimide resin by which the organic acid modification was carried out in a hydrophilic coating film. Hereinafter, examples of subcomponents that can be used in forming the hydrophilic coating film will be described.

The hydrophilic coating film may further contain a quaternary ammonium silicate for the purpose of improving hydrophilicity. As the quaternary ammonium silicate, for example, the following general formula:
(R ₃ N) ₂ O · nSiO ₂
(In the formula, R represents an alkyl group having 1 or more carbon atoms, and n represents an integer of 1 or more.)
The thing shown by is mentioned. More specific examples of the quaternary ammonium silicate include dimethylethanolammonium silicate, monomethyltripropanolammonium silicate, dimethyldipropanolammonium silicate, monoethyltripropanolammonium silicate and the like. As a more specific example of the quaternary ammonium silicate, “Ceramica MS85” (dimethylethanolammonium silicate) (manufactured by Nippon Sheet Laboratory Co., Ltd.) and the like can be mentioned.

  When a quaternary ammonium silicate is used, it is preferable to further combine a silane coupling agent. In this case, there is an effect that the quaternary ammonium silicate is difficult to fall off from the hydrophilic coating film even during long-term use. Examples of silane coupling agents include amino silane coupling agents such as 3-aminopropyltriethoxysilane, epoxy silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, and vinyl silanes such as vinyltrimethoxysilane. Examples include coupling agents and methacrylic silane coupling agents such as methacryloxypropyltrimethoxysilane.

In addition, the hydrophilic coating film in this invention may be formed as a continuous layer on the carbon substrate surface, and may be formed as a discontinuous deposit. The basis weight of the hydrophilic coating film in the carbon molded body of the present invention can be, for example, 0.1 to 5 g, more preferably 0.2 to ² g, per 1 m ² of the carbon substrate surface area.

  The carbon molded body provided by the present invention can be used, for example, for various molding structures, magnetic head components, jigs, etc., in addition to various conductive structures such as a separator for a fuel cell and a conductive material for an electrode. The shape of the carbon molded body can be appropriately designed depending on the application, and examples thereof include various shapes formed using particles, thin films, flat plates, and molds.

<Method for producing carbon molded body>
The present invention also provides a resin that imparts a carbodiimide resin on a carbon substrate by applying an aqueous solution and / or aqueous dispersion of a carbodiimide resin having a hydrophilic group in the molecule to the carbon substrate and then drying the solution. Granting process;
An organic acid treatment step of treating the carbodiimide resin with an organic acid aqueous solution;
A water washing step of washing the treated carbon substrate;
The manufacturing method of the carbon molded object containing this is provided.

[Resin application process]
In the resin application step, an aqueous solution and / or aqueous dispersion of a hydrophilic group-containing carbodiimide resin is applied onto the carbon substrate. The preferred embodiments of the hydrophilic group-containing carbodiimide resin and the carbon substrate to be used are as described above in the section <Carbon molded product>. The hydrophilic group-containing carbodiimide resin used for the coating only needs to be in the state of an aqueous solution and / or an aqueous dispersion at the use temperature at the time of coating. Here, the dispersion size of the hydrophilic group-containing carbodiimide resin is, for example, It means that it is 10 μm or less. Examples of the application method include dipping, spraying, curtain flow coating, roll coating and the like. For example, when dipping is employed, it is preferable to remove excess aqueous solution and / or dispersion liquid on the surface of the carbon substrate by air blowing or the like after dipping. Immersion may be performed under normal pressure, or may be performed under pressure or under reduced pressure. After the application, the coated surface is dried to remove water. Drying can be performed, for example, at 100 ° C. for about 1 hour. The hydrophilic group containing carbodiimide resin can be provided on the carbon substrate by the above procedure.

  The concentration of the hydrophilic group-containing carbodiimide resin in the hydrophilization treatment liquid is preferably in the range of 1 to 40% by mass, and more preferably in the range of 2 to 20% by mass. When the concentration is 1% by mass or more, the effect of imparting hydrophilicity to the carbon substrate is better, and when it is 40% by mass or less, the liquid viscosity is low and the coating property on the carbon substrate is better.

  The hydrophilization treatment liquid preferably further contains a quaternary ammonium silicate for the purpose of improving the hydrophilicity of the hydrophilic coating film formed in the present invention. Preferred specific examples of the quaternary ammonium silicate are as described above in the section <Carbon molded product>. When the quaternary ammonium silicate is contained, the amount of the quaternary ammonium silicate in the hydrophilization treatment liquid is more than 0 parts by weight and less than 1900 parts by weight with respect to 100 parts by weight of the hydrophilic group-containing carbodiimide resin. When the amount is 1900 parts by mass or less, it is advantageous in that uneven coating can be reduced. The amount of the quaternary ammonium silicate is more preferably in the range of 1 to 1900 parts by mass, and when it is 1 part by mass or more, it is advantageous in that the effect of improving hydrophilicity is improved. The amount is more preferably in the range of 2 to 400 parts by mass.

  The hydrophilization treatment liquid preferably contains a silane coupling agent in combination with a quaternary ammonium silicate. In this case, the quaternary ammonium silicate is removed from the hydrophilic coating film even during long-term use. There is an effect that it becomes difficult to do. Preferred specific examples of the silane coupling agent are as described above in the section <Carbon molded product>. The amount of the silane coupling agent is preferably in the range of 0.1 to 5 parts by mass, more preferably in the range of 0.2 to 2 parts by mass with respect to 100 parts by mass of the quaternary ammonium silicate. In the case where the amount is 0.1 parts by mass or more, the above effect can be obtained more remarkably. Moreover, even if the said amount exceeds 5 mass parts, since the said effect by the mixing | blending of a silane coupling agent does not change a lot, it is economically preferable to set it as 5 mass parts or less.

[Organic acid treatment process]
In the organic acid treatment step, the hydrophilic group-containing carbodiimide resin is treated with an organic acid aqueous solution. The preferred kind of organic acid to be used is as described above in the section <Carbon molded product>, and is preferably at least one selected from the group consisting of propionic acid, lactic acid, malic acid and tartaric acid. From the viewpoint of satisfactorily imparting the effect of improving wettability to aqueous media under high-temperature use conditions obtained by organic acid treatment, the concentration of organic acid in the aqueous organic acid solution is large relative to the amount of hydrophilic group-containing carbodiimide resin applied. It is preferable to make it excessive, for example, it is preferable to be in the range of 0.1 to 5% by mass, more typically about 1% by mass.

  The organic acid treatment can be carried out, for example, by immersing the carbon base material provided with the hydrophilic group-containing carbodiimide resin in an organic acid aqueous solution. The dipping conditions are that the organic acid aqueous solution temperature is room temperature to 100 ° C. and the dipping time is in the range of 5 minutes to 24 hours, more typically the organic acid aqueous solution temperature is about 80 ° C. and the dipping time is about 12 hours. Can be.

[Washing process]
In the water washing step, for example, washing with running water is performed for about 10 seconds to wash away excess organic acid on the carbon substrate. After washing with water, for example, drying is appropriately performed at 100 ° C. for about 1 hour.

  With the above method, the carbon molded body according to the present invention can be obtained.

  EXAMPLES Hereinafter, although an Example is given and this invention is further demonstrated, this invention is not limited to this.

A fuel cell separator material (“G347B” (manufactured by Tokai Carbon Co., Ltd.)) (size: 100 mm × 100 mm × 3 mm) was used as the carbon substrate. Moreover, the hydrophilic treatment liquid of the composition shown in Table 1 was each prepared using the hydrophilic group containing carbodiimide resin liquid shown in Tables 2-5. The symbols in the table are shown below.
SV-02 is “Carbodilite SV-02” manufactured by Nisshinbo Co., Ltd. (carbodiimide equivalent = 430, aqueous solution having an active ingredient concentration of 40% by mass), and the hydrophilization treatment liquid produced using this is an aqueous solution.
V-02-L2 is “Carbodilite V-02-L2” (carbodiimide equivalent = 385, aqueous solution having an active ingredient concentration of 40% by mass) manufactured by Nisshinbo Industries, Ltd. It is an aqueous solution.
E-03A is “Carbodilite E-03A” (carbodiimide equivalent = 365, aqueous dispersion having an active ingredient concentration of 40% by mass) manufactured by Nisshinbo Industries, Ltd. It is a liquid.

[Examples 1 to 17]
After immersing the carbon base material in the above-mentioned hydrophilization treatment solution at room temperature for 5 seconds, the excess hydrophilization treatment solution is blown off by air blow and then dried at 100 ° C. for 1 hour, and the hydrophilic group-containing carbodiimide is formed on the carbon base material. Resin was applied ("After impregnation" in the table). Next, the impregnated carbon base material was immersed in a 1% by weight aqueous solution of an organic acid at 80 ° C. for 12 hours, then washed with running water for about 10 seconds, and further dried at 100 ° C. for 1 hour (Table). "After acid treatment").

  Next, a cycle of immersion in warm water at 80 ° C. for a predetermined time (the time shown in Tables 2 to 6) and heating at 95 ° C. for 4 hours (in a heater under absolutely dry conditions) was repeated, and contact at each time point The corner was measured. For example, Table 2 shows the following conditions: 80 ° C. warm water immersion for 24 hours, 95 ° C. absolute dry heating for 4 hours, 80 ° C. warm water immersion for 291 hours, 95 ° C. absolute dry heat for 4 hours, 80 ° C. hot water immersion for 2151 hours, 95 ° C. It shows that the contact angle was measured by repeating the cycle of immersion and heating in order, and the same applies to Tables 3 to 6 (however, Table 6 shows the continuation of Table 5). After soaking in warm water, the water was lifted from the warm water and allowed to stand at room temperature for 15 minutes. After heating, after being removed from the heater and allowed to stand at room temperature for 15 minutes, the contact angle of water with respect to the carbon substrate was measured. . The contact angle of water was determined by using a contact angle meter (“DM500” manufactured by Kyowa Interface Science Co., Ltd.), dropping water onto the carbon substrate at room temperature, and setting the contact angle after 30 seconds to the θ / 2 method. Measured. Each sample was measured at 5 points on the front and back, a total of 10 positions, and an average value of 10 points was adopted as a measured value.

[Reference Examples 1-3]
The contact angle of water was measured in the same manner as in each example except that the treatment up to the “after impregnation” was not performed.

[Reference Examples 4 to 12]
After the above “after impregnation”, the contact angle of water was measured by performing the same operation as in each Example except that the sample was not immersed in an organic acid, washed with water and dried.

[Comparative Examples 1 and 2]
The contact angle of water was measured in the same manner as in each of the above examples except that the treatment up to the “after acid treatment” was not performed.

  The measurement results of the contact angle of water in each of the above Examples, Reference Examples and Comparative Examples are shown in Tables 2-6.

  From the above results, in each example that is an example of the present invention, the carbon base material was treated with a hydrophilic group-containing carbodiimide resin and an organic acid, so that none of these treatments were performed, and It can be seen that, compared with each reference example in which only this is performed, the hydrophilicity is particularly excellent after heating under absolutely dry conditions, that is, under high temperature and low humidity conditions.

  The carbon molded body and the method for producing the same according to the present invention are suitable for various molding structures, parts for magnetic heads, jigs, etc., in addition to various conductive structures such as separators for fuel cells and conductive materials for electrodes. Applicable to.

Claims (10)

  A carbon molded body in which a hydrophilic coating film formed of a carbodiimide resin having a hydrophilic group in a molecule is provided on a carbon substrate, wherein the carbodiimide resin is modified with an organic acid. .   The carbon molded body according to claim 1, wherein the organic acid is at least one selected from the group consisting of propionic acid, lactic acid, malic acid, and tartaric acid.   The carbon molded body according to claim 1 or 2, wherein the carbon base material is a composite material containing carbon and a binder.   The carbon molded object in any one of Claims 1-3 in which the said hydrophilic coating film further contains a quaternary ammonium silicate.   The carbon molded body according to claim 4, wherein the hydrophilic coating film further contains a silane coupling agent. An aqueous solution and / or aqueous dispersion of a carbodiimide resin having a hydrophilic group in the molecule is applied on a carbon substrate and then dried to give the carbodiimide resin on the carbon substrate. A resin application step,
An organic acid treatment step of treating the carbodiimide resin with an organic acid aqueous solution;
A water washing step of washing the treated carbon substrate;
The manufacturing method of the carbon molded object containing this.   The method for producing a carbon molded body according to claim 6, wherein the organic acid is at least one selected from the group consisting of propionic acid, lactic acid, malic acid, and tartaric acid.   The method for producing a carbon molded body according to claim 6 or 7, wherein the carbon base material is a composite material containing carbon and a binder.   The method for producing a carbon molded body according to any one of claims 6 to 8, wherein the hydrophilization treatment liquid further contains a quaternary ammonium silicate.   The method for producing a carbon molded body according to claim 9, wherein the hydrophilic treatment liquid further contains a silane coupling agent.