JP3482610B2 - Prepreg sheet for porous carbonaceous molded plate - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prepreg sheet made of carbon fiber and a solid phenol resin as main components, which is suitable for obtaining a porous carbonaceous molded plate for compression molding and firing.

[0002]

2. Description of the Related Art Porous carbonaceous molded plates are manufactured by various methods. For example, carbon fiber paper, felt,
A carbon fiber aggregate such as cloth is impregnated with a thermosetting resin and dried to form a prepreg in a semi-cured state (B stage), the prepreg is molded by compression molding or the like, and fired in an inert atmosphere. It can be obtained. Since the firing is performed in the final step in this way, the yield remaining after carbonization (residual coal rate)
Is preferably high, and a prepreg sheet using a phenol resin is generally used.

When carbon fibers are used in the form of continuous long fibers, particularly when producing a homogeneous thin plate, it is difficult to uniformly disperse the fibers, and discontinuous portions of the fiber density occur and there is no directionality. It is very difficult to form a thin sheet,
Usually, a short fiber aggregate of carbon fibers, that is, paper, non-woven fabric, needle-punched felt, or the like is used.

However, the short fiber aggregate of carbon fibers used for producing a homogeneous thin plate, that is, paper, non-woven fabric, or needle punched felt, has a small weight per unit area for its purpose, and its dynamics. Since the strength is weak, the resin ratio and B in the prepreg forming process
It is difficult to control stage formation, and quality and yield problems are likely to occur.

As one means for solving this problem, carbon fiber paper by a wet papermaking method using a phenol resin as a binder is considered. According to this method, a predetermined amount of phenol resin can be included in the carbon fiber paper as a binder in advance, and the prepreg step becomes unnecessary.

However, in most cases, the phenol resin contains free phenol and has a problem in wastewater treatment in wet papermaking, and it is practically impossible to make paper at the actual machine level.

On the other hand, the solid phenol resin may not contain free phenol, and papermaking on an actual machine level is possible without problems of wastewater treatment in the papermaking process.

[0008]

However, since the solid phenolic resin has a high viscosity when it is melted by heat, it is very difficult to form a homogeneous molded plate in the thermoforming process.
It has a drawback that the resin has poor dispersibility and a plate having poor surface smoothness is easily formed.

[0009]

As a result of intensive studies to solve these problems, the present inventors have found that a prepreg sheet made by adding a third component in addition to the main components of carbon fiber and solid phenolic resin is used. It was found that the above-mentioned drawbacks in the production of a porous carbonaceous molded body can be solved, and the present invention has been completed.

That is, the present invention is a sheet obtained by making paper using carbon fiber (A) and solid phenolic resin (B) as main components, which is subjected to compression molding and firing to form a porous carbonaceous molded plate. In a prepreg sheet for a porous carbonaceous molded plate, an epoxy resin (C) is used in combination with a resin (B) as an auxiliary component, and a prepreg sheet for a porous carbonaceous molded plate and the prepreg sheet are compression molded and fired. The present invention provides a porous carbonaceous molded plate.

The carbon fiber (A) used in the present invention is not particularly limited, but for example, PAN-based carbon fiber, pitch-based carbon fiber, carbon fiber starting from various organic fibers, or these. Any of the graphitized graphite fibers can be used. These fibers (A) are used alone or in combination depending on the purpose.

The fiber diameter of the fiber (A) is not particularly limited, but is preferably in the range of 5 to 25 μm in view of its strength and handleability. The aspect ratio (fiber length / fiber diameter) is, for example, 50 or more, preferably 50 to 10,000 in consideration of the strength of the sheet to be paper-made and the dispersibility in the paper-making process.

As the solid phenol resin (B) used in the present invention, any known and conventional solid phenol resin which is solid at room temperature can be used and is not particularly limited. Examples of heat-melting or heat-curing type resins include resole resins and novolac resins. The former is generally a self-curing type which can be thermoset with a resin alone, and the latter is not curable by itself, and therefore, a curing agent is generally used together. The resin (B) has a weight average molecular weight of 500 to 10
From the standpoint of the rate of residual coal, it is preferable that the amount is 10,000.

Of course, even in the case of the self-curing type, it is often practiced to add a curing agent or a curing aid as necessary to relax the curing conditions. As the curing agent, for example, hexamethylenetetramine or polyamide resin can be used.

Epoxy resin (C) used in the present invention
Is added for imparting plasticity to the resin (B), for example. In the present invention, examples of the epoxy resin which can be added to the basic component include bisphenol A epoxy resin, novolac epoxy resin, other glycidyl ether epoxy resins and modified products thereof. Among them, the resin (C) has a melting point of 60 ° C.
The temperature is preferably 200 ° C or higher and 200 ° C or lower, more preferably 80 ° C or higher and 150 ° C or lower.

The amount of the resin (C) used is not particularly limited, but for example, 5% by weight to 50% by weight relative to the amount of the resin (B) used.
It is desirable to use it so that it becomes the weight%. When added in this range, the plasticizing effect does not level off, and the strength of the molded plate obtained by firing described later is also good.

The total amount of the solid phenol resin (B) and the epoxy resin (C) used is usually 5% by weight to 90% by weight based on the total of the carbon fiber (A) and the solid phenol resin (B).
The range is 30% by weight, preferably 30% by weight to 70% by weight. Within these ranges, the strength of the prepreg sheet itself is sufficient and it is easy to mold. Within this range, the mechanical strength of the porous carbonaceous molded plate finally obtained from this prepreg sheet also becomes good.

In obtaining the prepreg sheet for a porous carbonaceous molded plate of the present invention, an organic fiber (D) is further added so that the gas permeability of the carbonaceous molded plate after firing becomes a sufficient value. Can also be used together.

As the fiber (D), any of known and commonly used fibers can be used and is not particularly limited, and examples thereof include rayon, polyester fiber, polypropylene fiber,
Polyethylene fiber, aramid fiber, etc. can be used. As the fiber (D), a non-fibrillated organic fiber that is not fibrillated is preferable. The fibrillated organic fiber, for example, wood pulp fiber, tends to form a film structure after carbonization when the prepreg sheet finally obtained by using the same is formed and fired, and the gas permeability decreases.

The fiber (D) is usually 10 to 60 parts by weight based on 100 parts by weight of the total weight of the carbon fiber (A) and the solid phenol resin (B), and in particular, 10 to 10 from the viewpoint of the molding pressure in the subsequent step. It is preferably 40 parts by weight.

These fibers (A) and (D) contain various inorganic fibers such as ceramic fibers, silicon carbide fibers and silicon nitride fibers, and graphite in order to further improve thermal properties and mechanical properties as required. It is also possible to add a filler such as powder.

The prepreg sheet of the present invention can be easily produced by making a paper using the fibers (A), the resins (B), the resins (C) and, if necessary, the fibers (D). As the papermaking method, either a dry method or a wet method is adopted, but the wet method is preferable from the viewpoint of uniformity.

In this wet papermaking method, for example, the fiber (A), the resin (B), the resin (C) and optionally the fiber (D), various fillers, and, if necessary, a dispersion aid are added. Add to the aqueous medium, disperse so as to be uniform, form a slurry, and strain with a slanted net to remove only the aqueous medium to obtain a wet nonwoven paper web, and dry it to obtain a prepreg sheet. The method can be adopted.

Further, for example, the fibers (A) and, if necessary, the fibers (D) are added to an aqueous medium to which a dispersion aid is added, if necessary, and dispersed uniformly to form a slurry. , A wet non-woven paper web is obtained by filtering with an inclined net to remove only the aqueous medium, and impregnating with a composition containing the resin (B) and the resin (C) as essential components, and then drying. The method can also be adopted.

As the dispersion aid, well-known and commonly used protective colloids, surfactants and the like can be used. For example, polyethylene oxide, polyoxyalkylene monophenol ether, metal alkylbenzene sulfonate, polyvinyl alcohol, self-emulsifying acrylic resin, A self-emulsifying epoxy resin or the like can be used.

Further, it is desirable to use various polymer fixing agents for the resin powder in order to improve the yield at the time of paper making. Examples of these fixing agents include polyacrylamide resin, aluminum sulfate, polyaluminum chloride and the like.

In obtaining a dried prepreg sheet, methods such as hot air drying, far infrared ray irradiation, and microwave irradiation can be adopted. It is preferred to dry until the sheet itself is tack free. With a high degree of drying,
It becomes difficult to form a desired shape for the compression molding described later. When obtaining a dense carbonaceous molded plate, the drying conditions are carefully examined.

The prepreg sheet of the present invention may have any thickness, but is, for example, 0.2 to 1.2 mm. The weight per 1 m ² is usually 75 to 300 g.

The sheet thus obtained can be formed into, for example, a porous carbonaceous molded plate by compression-molding, shaping and then firing. In this compression molding, a well-known and commonly used mold is used, and heat is applied at the same time if necessary to perform molding. Of course, a vacuum compression molding method in which the inside of the mold is deaerated to a vacuum and then molded can be adopted.

In any of the methods, one sheet or a plurality of sheets are laminated and molded. At this time, different kinds of sheets may be laminated and molded according to the purpose.

Next, the molded plate obtained by the above-mentioned molding can be fired to form a carbonaceous and porous molded plate. The firing conditions are not particularly limited, but a carbonaceous shaped plate can be obtained by firing at a temperature of 1000 to 3000 ° C. in an atmosphere of an inert gas such as nitrogen or argon, or in vacuum. it can. Depending on the purpose, it may be graphitized by further firing at a temperature of 2000 to 3000 ° C.

The porous carbonaceous molded plate thus obtained can be used for various known and conventional uses. Specifically, it can be used as various electrode materials, separators, heat insulating materials and the like.

Using non-fibrillated organic fibers,
Epoxy resin weight to solid phenol resin weight,
The carbonaceous molded plate obtained by using the sheet of the present invention in which the ratio of the organic fiber to the carbon fiber is in the range of 5 to 50% by weight and the range of 5 to 50% by weight is It satisfies the surface smoothness, strength, gas permeability, etc. required for electrode plates, and is a very useful material for electrode plates. In particular, it agrees well with the specification value for a phosphoric acid fuel cell electrode plate.

It is pointless to say that the above-mentioned required performance is peculiar to the electrode plate and cannot be predicted directly from the molded plate obtained simply by molding. .

[0035]

EXAMPLES The present invention will now be described in detail with reference to Examples.
Hereinafter, "parts" and "%" are based on weight unless otherwise specified.

[Example 1] Pitch-based carbon fiber having an aspect ratio of 460 [DONACAR manufactured by Donac Co., fiber diameter 1
3.5 μm] and polybutylene terephthalate (PB
T) Fiber [1d × 3 mm] and ratio 4/6 (weight ratio)
With a total fiber concentration of 0.2%, dispersed in water, and with self-curing phenol resin (weight average molecular weight 12000),
A bisphenol A diglycidyl ether type epoxy resin (melting point 100 ° C., epoxy equivalent 950) was added to prepare a slurry.

The content of each component was 20% by weight of phenol resin powder.
Parts, 1 part of epoxy resin powder, 200 parts of carbon fiber, PBT
A sheet was made into 10 parts of fibers. At this time, the amount of the epoxy resin added to the phenol resin was 5% by weight, and the content of the organic fibers to the carbon fibers was 5% by weight.

In order to improve the yield of resin powder, cationic polyacrylamide was added to the above slurry in an amount of 0.3% based on the total amount of fibers to improve the fixing of the resin component to the fiber base material. The slurry was subjected to paper making by a tilted wire mesh nonwoven fabric manufacturing apparatus to obtain a wet web.

The web was dried with hot air at 140 ° C. for 4 minutes to obtain a non-adhesive 175 g / m ² prepreg sheet.

Two sheets of this sheet are stacked and compression molded (170
° C., the pressure 7 kg / cm ^2, 20 minutes) was further fired at 2000 ° C. in vacuo to obtain a graphite plate. The physical properties of the obtained graphite plate are shown in Table 1.

[Comparative Example 1] A prepreg sheet was obtained by papermaking under the same conditions as in Example 1 except that 1 part of epoxy resin powder was not used, and then baked under the same conditions to obtain a graphite plate. . The physical properties of the obtained graphite plate are shown in Table 1.

[0042]

[Table 1]

The actual measurement conditions for these evaluation items are as follows. Basis weight: Measured according to JIS P8124. Density: Measured according to JIS P8118. Thickness: Measured using a micrometer. Bulk density: Measured according to JIS R7212. Bending strength: same as above. Surface condition (surface smoothness): visually determined. Gas permeability (excess): Measured by a modified Gurley method.

As can be seen from the comparison between Example 1 and Comparative Example 1, the prepreg of Example 1 uses the epoxy resin in combination, and due to its plasticizing effect, the dispersibility of the resin component during thermoforming Good flowability and a homogeneous molded plate are obtained. Therefore, it is understood that the graphite plate obtained by firing the graphite plate also has excellent surface smoothness.

[Examples 2 to 3] Slurries as shown in Table 2 were prepared in the same manner as described above, and papermaking was performed under the same conditions as in Example 1 except that the prepreg sheets were obtained. Then, firing was performed under similar conditions to obtain a graphite plate. The physical properties of the obtained graphite plate are shown in Table 2.

The same phenolic resin, epoxy resin and carbon fiber as used in Example 1 were used, while Daiwa Bo Rayon (1d × 3 mm) manufactured by Daiwa Boshoku Co., Ltd. was used as rayon fiber. As the wood pulp fiber, bleached pulp (hardwood kraft pulp, freeness 600 cc) was used.

[0047]

[Table 2]

The graphite plate of Example 3 had gas permeability, but it was insufficient as a phosphoric acid fuel cell electrode plate.

[Examples 4 to 5] Slurries as shown in Table 3 were prepared as described above, and papermaking was carried out under the same conditions as in Example 1 except that the prepreg sheets were obtained. Then, firing was performed under similar conditions to obtain a graphite plate. The physical properties of the obtained graphite plate are shown in Table 3.

The same phenolic resin, epoxy resin and carbon fiber as used in Example 1 were used, and the same rayon fiber was used in Example 2 while polypropylene (PP ) As fiber, 1d x 3m
m was used.

[0051]

[Table 3]

[0052]

EFFECTS OF THE INVENTION In the present invention, when a prepreg sheet for a porous carbonaceous molded plate is obtained, an epoxy resin is used in combination with a phenol resin which is a conventional resin component. It is possible to obtain a particularly excellent carbonaceous molded plate.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayuki Mine 29-15 Minamitomioka, Nara, Nara (56) References JP-A-4-100851 (JP, A) JP-A-57-129814 (JP, A) ) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08J 5/24

Claims (8)

(57) [Claims] 1. A sheet obtained by making paper from carbon fiber (A) and solid phenolic resin (B) as main components, which is subjected to compression molding and firing to form a porous carbonaceous molded plate. A prepreg sheet for a porous carbonaceous molded plate, characterized by using an epoxy resin (C) as a subcomponent together with the resin (B) in the prepreg sheet for a porous molded plate. 2. The prepreg sheet according to claim 1, further comprising an organic fiber (D) in combination with the epoxy resin (C). 3. The prepreg sheet according to claim 1, wherein the carbon fiber (A) is a pitch-based carbon fiber. 4. The prepreg sheet according to claim 1, wherein the solid phenol resin (B) has a weight average molecular weight of 500 to 100,000. 5. The prepreg sheet according to claim 2, wherein the organic fiber (D) is an organic fiber which is not fibrillated. 6. The prepreg sheet according to claim 1, wherein the weight of the epoxy resin (C) relative to the weight of the solid phenol resin (B) is in the range of 5 to 50% by weight. 7. Organic fiber (D) to carbon fiber (A)
The prepreg sheet according to claim 2, wherein the ratio is 5% by weight to 50% by weight. 8. A sheet obtained by making paper from carbon fiber (A) and solid phenol resin (B) as main components, which is subjected to compression molding and firing to form a porous carbonaceous molded plate. A prepreg sheet for a phosphoric acid fuel cell electrode plate, characterized in that, in a prepreg sheet for a quality molded plate, an epoxy resin (C) is used in combination with a resin (B) as an auxiliary component.