JPH02221199A - Graphite whisker manufacturing method - Google Patents

Abstract

PURPOSE:To obtain graphite whiskers having high tensile strength and satisfactory wettability with plastics by bringing a mixture of an org. substance generating H2 and C by thermal decomposition with carbon black and a metal catalyst into a reaction at a prescribed temp. CONSTITUTION:A metal catalyst selected among Fe, Ni, Co, Cr, Mn, Mo, V, W and Ti is prepd. An org. substance generating H2 and C by thermal decomposition is also prepd. The org. substance is mixed with the metal catalyst and carbon black. This mixture is brought into a reaction at 1,400-2,000 deg.C to grow graphite crystals.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing graphite whiskers,
More specifically, the present invention relates to an improved manufacturing method for graphite whiskers, which are most suitable as fiber reinforcing materials mixed into FRP.

[Background of the Invention] In recent years, lightweight and strong fiber reinforced plastics (FRP) have been used in large quantities mainly in the space and aviation industries.

Carbon fibers, glass fibers, alumina fibers, and the like are known as fibers mixed into plastics as reinforcing materials.

However, since all of the fibers are polycrystalline fibers, the maximum strength of the material cannot be utilized, and the manufacturing cost is extremely high.

In order to overcome these drawbacks, the use of graphite whiskers as a reinforcing material for FRP has recently attracted attention. A representative example of the method for producing graphite whiskers is Japanese Patent Publication No. 57-8762. Here, graphite whiskers are grown by treating carbon black fine particles of a predetermined particle size alone in a non-oxidizing atmosphere at a temperature of about 2000° C. or higher.

As a result of repeated research into improving the production of graphite whiskers, the applicant has found that by using carbon black in combination with an organic substance that thermally decomposes to generate hydrogen and carbon, it has been possible to produce graphite whiskers with properties superior to those of conventional techniques. We discovered this and arrived at the present invention.

[Object of the Invention] An object of the present invention is to provide an improved method for producing graphite whiskers having excellent properties suitable as a reinforcing material for FRP.

[Means for achieving the object] In order to achieve the above object, the present invention uses carbon black, Fe5Ni, Co5Cr, and MnSMo.

At least one metal catalyst selected from the group consisting of V, W, and T1 and at least one organic substance that generates N3 and C by thermal decomposition are mixed, and this mixture is heated to 1
This is achieved by reacting at a temperature of 400 to 2000°C to grow graphite crystals.

[Embodiments] The carbon black used in the method of the present invention is well known in the art, and is not particularly limited, but preferably has a particle size of 100 Å or less, particularly preferably a particle size of about 50 Å. .

The metal catalysts used are Fe, N15 (:o, Cr.

MnSMo, VSW, Ti, etc. are selected from group Ⅰ and group Ⅰ metals, and one or both of them are selected.
More than one species can be used in combination.

Further, as the organic substance that can be used in the present invention, any organic substance can be used as long as it is thermally decomposed to generate N2 and C (including those that generate H2 and CO). However, from the viewpoint of hydrocarbons and especially ease of handling, polyvinyl alcohol C-CH,・CH(OH)
-1 is preferred. Further, it is desirable that the organic substance does not contain sulfur and has a low oxygen content.

According to the method of the present invention, graphite whiskers can theoretically be generated even in the absence of carbon black, but if only organic substances are used alone, the amount of free carbon will be excessive and the purity of the whiskers will decrease. have a tendency to

On the other hand, when using carbon black alone, the temperature required for the reaction becomes too high (see, for example, Japanese Patent Publication No. 578762).
. Therefore, the combination of carbon black and organic substances is recommended.

Regarding the reaction temperature, if it is about 1000°C or higher, the dehydrogenation reaction (described below) that is essential to the method of the present invention will occur, so there is no particular limitation, but in consideration of production efficiency,
The temperature range is preferably from 00 to 2000°C. The reaction pressure is about 50
It is preferred to maintain the pressure above atmospheric pressure, especially about 80 atmospheres.

An inert gas atmosphere, particularly an Ar gas atmosphere, is suitable as the reaction atmosphere. The reaction time can be appropriately selected depending on the length of the whisker and the like.

According to the method of the present invention, for example, when polyvinyl alcohol is used as the organic substance, the following formulas (1) and (2
) graphite whiskers are generated according to That is, polyvinyl alcohol is first thermally decomposed under high temperature conditions according to the following formula (1).

nC+ (-CH2-CH) ,,→CO+H2+CH
2+C2H6+C3H4+...OH (1) Next, C H2 generated by thermal decomposition is dehydrogenated in accordance with the following formula [2] in a high temperature N2 atmosphere and in the presence of a metal catalyst such as Cr.

CH2-” C (act) +H.

[Here, C (act) means an activated carbon atom]

Thus, the reaction proceeds from the left side to the right side of equation (2), and the activated carbon atoms form a single crystal graphite whisker.

[Example] The invention will now be explained by way of non-limiting examples.

Example 1 Carbon black with a particle size of 50 mm and a small amount of powdered Cr as a catalyst were kneaded with polyvinyl alcohol, and this was mixed with A
Temperature 1700℃ and pressure 80℃ in a reactor with r atmosphere
Maintained at atmospheric pressure.

In this way, single-crystal graphite whiskers were produced according to the reactions of formulas (1) and (2) above. The obtained graphite whiskers were analyzed for various properties by conventional methods, and the following results were obtained.

Tensile strength: 2000kg/mm' specific gravity
:2.2 Wettability: Good for plastics [Effects of the invention] As described above, the graphite whisker produced by the method of the present invention is a single crystal, and has a weight of 2000 kg/
It has extremely high tensile strength of mm2,
Its specific gravity is 2.2, compared to 3.18 for SiC, and its wettability with plastic materials is extremely good, making it extremely suitable as a reinforcing fiber for FRP.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited thereto. For example, organic substances such as hydrocarbons other than polyvinyl alcohol may be used alone or in combination, or Cr may be used as a metal catalyst. It goes without saying that metals from Groups 1 and 2 of the Periodic Table may be used alone or in combination. Accordingly, various modifications can be made without departing from the spirit and scope of the invention.

Claims (2)

[Claims] (1) Carbon black and Fe, Ni, Co, Cr, M
At least one metal catalyst selected from the group consisting of n, Mo, V, W, and Ti and at least one organic substance that generates H_2 and C by thermal decomposition are mixed, and this mixture is heated to A method for producing graphite whiskers, which comprises causing graphite crystal growth by reacting at a temperature of 2000°C. (2) A method for producing graphite whiskers according to claim 1, wherein the organic substance is polyvinyl alcohol.