JP3220983B2 - Method for producing carbon fiber reinforced carbon material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a high-strength carbon fiber reinforced carbon material having excellent physical properties such as heat resistance, chemical resistance, abrasion resistance and light weight. .

(Prior Art) Methods of producing carbon fiber reinforced carbon materials using prepregs are roughly classified into a resin impregnated carbonization method and a CVD method, and many improved methods have been proposed (Japanese Patent Application Laid-Open No. 53-4011, Kosho 58-90
70, JP-B-58-48485, JP-A-58-79806, JP-A-62-21
2263).

In the resin impregnation carbonization method, a thermosetting resin such as a furan resin or a phenol resin or a thermoplastic resin represented mainly by pitch is used as a carbon raw material serving as a matrix of a carbon fiber reinforced carbon material. In this manufacturing process, a carbon fiber aggregate as a reinforcing agent (aggregate) is impregnated with these resins, heated and cured to form a prepreg, and the prepreg is laminated at about 1000 ° C. in an inert atmosphere. A method of carbonizing a matrix resin by heat treatment is widely used.

In this resin impregnation carbonization method, an extremely slow heating rate is required in a temperature region where the resin (including pitch) is molten and carbonized, and the carbonization yield of the resin is as low as 40 to 60%. There is a problem that a complicated secondary treatment such as re-impregnation, carbonization and compression of the resin is repeated to generate the resin.

On the other hand, in the CVD method, low-carbon hydrocarbons such as methane and propane and an inert gas such as argon are introduced into a CVD apparatus as a matrix material, and the pressure is reduced to about 800 to 1500 ° C.
This is a method of directly depositing the carbon reacted in the above. Since the CVD method deposits pyrolytic carbon directly on the substrate in the gas phase, a dense and homogeneous matrix can be created. This is extremely disadvantageous in terms of aspects. For this reason, usually it is often used for secondary densification treatment in combination with the resin impregnation carbonization method.

(Problems to be Solved by the Invention) The manufacturing process of a carbon / carbon composite material that combines a carbon fiber and a matrix is complicated. That is, in the method for producing a carbon fiber reinforced carbon material according to the above-described conventional technology, in order to impart denseness, a complicated post-treatment such as repetition of CVD treatment or resin re-impregnation and firing is required, and it is extremely expensive. . For this reason, its use is currently limited,
It hinders its use in a wide range of fields.

An object of the present invention is to provide a method for producing a high-strength carbonized fiber reinforced carbon material having excellent properties such as heat resistance, chemical resistance, abrasion resistance, and light weight by a simple method in a short time. That is.

(Means for Solving the Problems) The inventors paid attention to the characteristics of the mesoface pitch, and as a result of intensive studies to achieve the above object, as a result, the impregnation was high.
Using a female face pitch with a high carbonization yield for the matrix, high tackiness was obtained by heat treatment, and it was found that a high-performance carbon fiber reinforced carbon material could be obtained by a simple method without using a binder. Invented the invention.

That is, the present invention, when producing a carbon fiber reinforced carbon material obtained by laminating a plurality of prepregs using a carbon fiber aggregate, the temperature at which the viscosity becomes 80 poise at the softening point 350 ° C. or less in the carbon fiber aggregate is 400 A carbon fiber reinforced carbon material characterized by laminating a prepreg pre-heat treated by melting and impregnating a mesoface pitch having a carbonization yield of not less than 70 ° C and a carbonization yield of 70% or more at 600 ° C, followed by pressing and firing. .

The carbon fiber aggregate used in the present invention includes PAN
A variety of carbon fibers such as a carbon fiber and a pitch fiber are used. The carbon fiber aggregate may be any one of a unidirectional fiber, a two-dimensional woven fabric, and a nonwoven fabric sheet, or may be a combination thereof, and is determined according to the use and required characteristics. In general, it is preferable to use the carbon fiber aggregate as a reinforcing material after performing a surface treatment such as an oxidation treatment.

The mesoface pitch used as the matrix must be at least 80% optically anisotropic by polarization microscopy
Or more, preferably 90% or more, more preferably substantially 10% or more.
Desirably, it is 0%. This mesoface pitch needs to have impregnating properties for the carbon fiber aggregate, and the impregnation varies depending on the shape of the carbon fiber aggregate, etc.
Generally, a pitch having a lower softening point has a higher impregnation property, and the softening point of the mesoface pitch in the present invention is 350 ° C. or lower, preferably 300 ° C. or lower. The pitch must have a temperature of 400 ° C. or less at which the viscosity becomes 80 poise. The softening point is measured by a differential scanning calorimeter, and the viscosity is measured by a flow tester. When a mesoface pitch having a temperature at which the softening point and the viscosity become 80 poise is higher than these values is used, the fluidity is low and the impregnating property is reduced, so that a dense and homogeneous matrix cannot be formed, and the high strength carbon No material available.

The mesoface pitch used in the present invention has a carbonization yield of 70% or more, preferably 80% or more. The carbonization yield is the carbonization yield when gradually raising the temperature to 600 ° C. in an inert gas stream and maintaining the temperature for about 2 hours.
When using low mesophase pitch with low carbonization yield,
Voids are easily generated in the product due to volatile fractions, and the strength of the obtained carbon fiber reinforced carbon material is reduced.

As an example of a mesoface pitch that satisfies these conditions, the mesoface pitch described in JP-A-1-13621, JP-A-1-254796 and Japanese Patent Application No. 1-309842 is preferable. The mesophase pitch is a pitch obtained by condensed polycyclic aromatic hydrocarbons and polymerized in the presence of HF-BF _3, to obtain a high carbonization yield, softening point lower 20
It shows good impregnation at 0-350 ° C.

This mesoface pitch is set at a temperature higher than the softening point,
For example, it is heated and melted at 200 to 390 ° C. to impregnate the carbonized fiber aggregate. In order to appropriately adjust the impregnation amount, an operation of squeezing out an excessive pitch as necessary for the impregnation property is performed.

The pitch impregnated carbon fiber aggregate thus obtained is then subjected to a preheating treatment. The pre-heating treatment is to the extent that the mesoface pitch soaked between the fibers is not completely carbonized,
It is necessary to select appropriate heating conditions that do not lose the tackiness and that can further improve the carbonization yield. The preheating conditions vary depending on the properties of the mesoface pitch, the impregnation ratio, etc., but are generally 2 to 10 ° C. in a non-oxidizing atmosphere.
Short-time heating to 350 to 490 ° C. at a heating rate of / min is performed. The pressure in the preheating treatment is not particularly limited, and may be normal pressure, increased pressure, or reduced pressure.

If the preheating treatment is insufficient, expansion and foaming due to volatile gas are likely to occur in the next lamination carbonization step, and a high-performance carbon material cannot be obtained. However, if the oxidation treatment is performed by blowing a small amount of air during or immediately before the preheating treatment step, these expansion and foaming can be suppressed. Further, with respect to a slight expansion during the preheating treatment, it is possible to densify without losing the adhesiveness by performing high filling by a roll or a press during the preheating treatment step.

On the other hand, excessive preheating treatment hinders the fusibility of the prepreg, which is likely to cause delamination, and a carbon fiber reinforced carbon material having a desired strength may not be obtained. That is, by appropriately performing the preheating treatment, the gas generated in the carbonization step can be excluded as much as possible while maintaining the adhesiveness of the mesoface pitch, and a single baking can provide a high density,
A high-strength carbon fiber reinforced carbon material can be obtained.

Next, the prepregs maintaining the adhesiveness are laminated and pressed. At this time, no binder is required, and the shape of the laminate can be freely selected to a desired shape such as a plate shape or a cylindrical shape according to the purpose, application, and required performance. The pressing needs to be performed in a pressure range where the carbon fiber structure of the reinforcing material is not destroyed and the initial strength is not lost. In the pressing step, a high-strength carbon material can be obtained at room temperature in a non-oxidizing atmosphere. However, if necessary, the strength of the carbon material can be further improved by raising the temperature to about 300 to 600 ° C.

The desired carbon fiber reinforced carbon material is manufactured by successively firing the laminate obtained by pressing. The firing step is performed by heating the laminate to a temperature of 600 to 1500 ° C. and carbonizing under a non-oxidizing atmosphere, and further includes a step of heating the carbide to a temperature of 2000 to 3000 ° C. to graphitize. Can also.

(Effects of the Invention) In the present invention, carbonization,
Since a mesoface pitch which is easy to graphitize and has a high carbonization yield is used, sintering can be achieved in a short time, and a sufficient high density can be obtained by only one sintering. Further, by performing the preheating treatment of the present invention using a mesoface pitch having a high impregnation property, a high tackiness can be obtained, so that a binder is not particularly required. Further, the matrix derived from the mesoface pitch has an optically anisotropic structure, and is highly dense and highly pure, so that a high-strength carbon fiber reinforced carbon material can be obtained.

According to the present invention, a high-density and high-strength carbon fiber reinforced carbon material having excellent physical properties such as heat resistance, chemical resistance, abrasion resistance, and light weight can be easily produced in a short time and at a low cost for the above reasons. Therefore, the present invention has great industrial significance.

(Examples) Hereinafter, the present invention will be described more specifically with reference to examples.
However, the present invention is not limited by these examples.

Example 1 PAN-based carbon fiber woven fabric (trade cloth # 6, manufactured by Toray Industries, Inc.)
After a 343) was washed with acetone, HF-BF ₃ was polymerized in the presence of naphthalene-obtained mesophase pitch (softening point 21
8 ° C, the temperature at which the viscosity becomes 80 poise is about 300 ° C, the carbonization yield 85% when heated to 600 ° C) is impregnated at 300 ° C under reduced pressure,
Excess pitch was squeezed out through a hot roll.

Next, as a pre-heating treatment, the impregnated material was heated at a rate of 5 ° C.
The temperature was raised to 370 ° C. at a rate of 370 ° C./min, and the temperature was maintained for 20 minutes to prepare a prepreg having a carbon fiber content of 50 wt% and having fusibility.

The prepregs thus obtained were laminated without adding a binder, and pressed in a nitrogen atmosphere to 500 ° C. using a hot press (temperature rising rate: 1 ° C./min, maximum press pressure: 200 kgf / cm ² ). Thereafter, the press pressure was released, and the temperature was raised to 1300 ° C. at a rate of 1 ° C./min in an argon atmosphere to obtain a carbide having a diameter of 60 mm and a thickness of 10 mm.

Example 2 The carbide obtained in Example 1 was further added under an argon atmosphere.
The temperature was raised to 2500 ° C. to obtain a graphitized product.

Example 3 The same prepreg as in Example 1 was laminated without adding a binder, and molded at normal temperature into a diameter of 60 mm and a thickness of 10 mm (molding pressure: 200 kgf / cm ² ). Thereafter, the temperature was raised to 1300 ° C. under an atmosphere of normal pressure argon to obtain a carbide.

Example 4 The carbide obtained in Example 3 was further added under an argon atmosphere.
The temperature was raised to 2500 ° C. to obtain a graphitized product.

Example 5 Sizing agent carbon fiber nonwoven fabric obtained by removing (Kureha Chemical Industry Co., Kureka Paper E-20) to, HF-BF ₃ was polymerized in the presence of naphthalene-obtained mesophase pitch (softening point 285 ℃, the temperature at which the viscosity becomes 800 poise is about 380
At 380 ℃ under normal pressure
And the excess pitch was squeezed out through a hot roll.

Next, as a pre-heating treatment, the impregnated material was heated at a rate of 5 ° C.
The temperature was raised to 430 ° C. at a rate of / min and maintained for 10 minutes to prepare a prepreg having a carbon fiber content of about 50% by weight and having fusibility.

Laminate this prepreg without adding binder, 100k
After hot pressing at 500 ° C. under a pressure of gf / cm ² , carbonization was performed at 1300 ° C. under normal pressure to obtain a carbide having a diameter of 60 mm and a thickness of 10 mm.

Example 6 The carbide obtained in Example 5 was subjected to 2,500 under an argon atmosphere.
The temperature was raised to ° C to obtain a graphitized product.

 The evaluation results of the carbide obtained in each example are shown below.

Claims (4)

(57) [Claims] When producing a carbon fiber reinforced carbon material in which a plurality of prepregs using a carbon fiber aggregate are laminated, a temperature at which the carbon fiber aggregate has a softening point of 350 ° C. or less and a viscosity of 80 poise is 400 ° C. Production of carbon fiber reinforced carbon material characterized by laminating prepregs pre-heat-treated by melting and impregnating mesoface pitch having a carbonization yield of 70% or higher at 600 ° C or lower and pressing, followed by firing. Method 2. The preheating step is performed in a non-oxidizing atmosphere.
The method for producing a carbon fiber reinforced carbon material according to claim 1, which is performed at a temperature of 0 to 490 ° C. 3. The pressing step is performed at 300 to 600 ° C. in a non-oxidizing atmosphere.
2. The method for producing a carbon fiber reinforced carbon material according to claim 1, wherein 4. The method according to claim 1, wherein the firing step comprises a step of carbonizing the pressed laminate at a temperature of 600 to 1500 ° C. in a non-oxidizing atmosphere or a step of further graphitizing at a temperature of 2000 to 3000 ° C. Method for producing carbon fiber reinforced carbon material