JPS63315613A - Production of carbon and graphite fiber - Google Patents

Abstract

PURPOSE:To obtain the titled fiber in the form of continuous filament, having extremely high strength and elastic modulus and good appearance, by applying a specific heat-resistant lubricant to a melt spun carbonaceous pitch fiber and subjecting the resultant fiber to infusibilizing, carbonizing and graphitizing treatment. CONSTITUTION:Carbonaceous pitch, such as coal tar pitch, is melt spun to provide a carbonaceous pitch fiber. A heat-resistant lubricant containing (A) a polyoxyalkylene-modified silicone based surfactant having <=60 deg.C boiling point (expressed in terms of atmospheric pressure) and (B) an alkylphenylpolysiloxane having 10-1,000cSt viscosity at 25 deg.C is applied to the above-mentioned fiber to form a fiber bundle, which is subsequently infusibilized, then subjected to carbonizing and graphitizing treatment in an inert gas atmosphere to afford the aimed fiber. Furthermore, the number-average molecular weight of the afore-mentioned component (A) is preferably <=1,500 and the component (B) preferably contains 1-80mol.% phenyl groups.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing carbon fibers and graphite fibers from carbonaceous pitch. More specifically, the present invention relates to a method for producing pitch fibers by spinning carbonaceous pitch, subjecting it to infusibility, carbonization, and graphitization, and using an oil suitable for obtaining long filament carbon fibers.

(Prior art) There has been a demand for the development of high-performance materials with properties such as light weight, high strength, and high modulus of elasticity in a wide range of technical fields related to automobiles, aircraft, and various other industrial fields. Carbon fiber or molded carbon materials are attracting attention. In particular, the method for producing carbon fiber from carbonaceous pitch is
It is regarded as an important method for producing carbon fiber with low cost and high performance.

However, depending on the conventional technology, pitch fibers have a small tensile strength of approximately 0.010 Pa and are brittle when scratched, so fiber bundles may be cut, fluffed, rolled around rollers, etc. during the infusibility process, carbonization process, etc. It was extremely difficult to obtain long filament-like fibers necessary to obtain high-performance products without a bundling oil (processing part).

For this reason, various sizing agents (oil agents) have been proposed as means for solving these problems.

Special Publication No. 51-12379, Japanese Patent Publication No. 54-131032
No. 1 and others disclose a method of using a silicone oil for flame-retardant treatment in the production of polyacrylonitrile-based carbon fibers, but even if this method is applied directly to pitch fibers, the desired effect cannot be obtained. During the infusibility process, fusion and adhesion occur significantly, and the decomposition of the oil agent disrupts the convergence and causes the fibers to become tattered, resulting in fiber bundles being cut, fluffed, and wrapped around guide rollers, making normal work difficult. .

On the other hand, as a binding oil agent for carbonaceous pitch fibers, a method using an aqueous solution of a water-soluble surfactant (Japanese Patent Publication No. 51-1274
No. 0) has been disclosed. Although this method improves the cohesiveness of the fibers during spinning, the infusibility process
When exposed to high temperatures, the surfactant decomposes, deteriorates, or turns into tar, resulting in severe adhesion, causing the fibers to become tattered and the fiber bundles to break.

Furthermore, as a binding oil agent for carbonaceous pitch fibers, a method of using silicone oil with a viscosity of 2 to 10,0000 cst at 25°C or diluting these silicone oils with a solvent (Japanese Patent Application Laid-Open No. 59-223315), 25°C A method using dimethyl polysiloxane (dimethyl silicone oil) with a viscosity of 0.5 to 500 cst (Japanese Patent Application Laid-open No. 60-88
No. 124), however, since it is diluted with a solvent or low-viscosity silicone oil, the threads are easily damaged due to the solubility of the solvent, and the fibers are easily damaged during the infusibility process. However, it has the disadvantage that it tends to cause fusion and sticking, and it tends to become fluffy. In addition, since a low boiling point solvent or silicone oil is used as a diluent, the diluent evaporates during work, which poses a major problem in terms of work and environmental protection, as well as high costs. .

In contrast, the present inventors have developed a process for producing carbon fibers and graphite fibers in which an oil agent is first applied to melt-spun carbonaceous pitch fibers to make them infusible, carbonized, and graphitized. Boiling point 600℃ obtained by distilling the agent under reduced pressure
Using a distillate with a boiling point below (atmospheric pressure equivalent) as an emulsifier,
proposed a method for producing carbon fibers and graphite fibers (Japanese Patent Application No. 273,823/1982), which is characterized by using a water emulsion oil emulsified with an alkylphenylpolysiloxane having a viscosity of 10 to 1000 cst.

In this case, since there is no deterioration of the oil agent, it is possible to extremely easily handle fragile fibers during the firing process of pitch fibers, such as focusing during spinning, infusibility, preliminary carbonization, carbonization, and graphitization. Since this oil is a water emulsion type oil, it improves the working environment, and also reduces fusion and agglutination between fibers (thus preventing yarn damage and fluffing caused by the use of solvents). This method is excellent in that continuous filament carbon fibers and graphite fibers can be obtained.

(Problems to be Solved by the Invention) However, depending on the carbonaceous pitch fiber [6], in order to improve the infusibility rate, the carbonaceous pitch fiber cannot be heated at high temperatures of 300 to 350°C or in a strongly oxidizing gas atmosphere. There are cases where it is necessary to perform infusibility under harsh conditions, and when producing carbon fibers and graphite fibers under such harsh infusibility conditions,
Even if the above-mentioned oil is used, decomposition or deterioration of the oil may occur during infusibility, and pitch fibers may be cut. What is needed is a method of manufacturing carbon fibers and graphite fibers that does not involve cutting.

Furthermore, since the nonionic surfactant added as an emulsifier to the oil agent needs to be distilled under reduced pressure during the production of the oil agent, there is also the problem that the production of the oil agent is complicated.

Therefore, the first object of the present invention is to prevent the decomposition and deterioration of the oil agent even when infusible under harsh conditions (to ensure smooth production of long filament carbon fibers and graphite fibers). An object of the present invention is to provide a method for producing carbon fibers and graphite fibers that can be produced.

A second object of the present invention is to provide an oil agent that can withstand harsh conditions when producing carbon fiber from pitch.

(Means for Solving the Problems) The above-mentioned aspects of the present invention include melt-spun carbonaceous pitch fibers, a polyoxyalkylene-modified silicone surfactant with a boiling point of 600°C or less (in terms of atmospheric pressure), and 25 1 in °C
This was achieved by a method for producing carbon fibers and graphite fibers, which is characterized by using a heat-resistant oil agent containing alkylphenylpolysiloxane having a viscosity of 0 to 1000 cst, and carrying out infusibility, carbonization, and graphitization treatments.

a) Carbonaceous pitch The carbonaceous pitch used in the present invention is not particularly limited, and includes coal tar pitch obtained by dry distilling coal;
Coal-based pitches such as coal liquefied products, petroleum-based pitches such as atmospheric distillation residues and vacuum distillation residues, synthetic pitches obtained by decomposing synthetic resins, and various pitches such as hydrogen,
Those hydrogenated with a hydrogen donor, those modified by heat treatment, solvent extraction, etc. can also be used.

The carbonaceous pinch of the present invention may be an isotropic pitch or an optically anisotropic pitch, and can also be applied to pitches called neomesoface and brimesoface, but their softening point is approximately The temperature is preferably from 30°C to about 320°C, and it is particularly preferred to use an optically anisotropic pitch.

b) Oil agent The polyoxyalkylene-modified silicone surfactant used in the oil agent in the present invention has a boiling point of 600°C or lower (based on atmospheric pressure), preferably 500°C or lower, and a number average molecular weight of 1500 or lower. suitable. The alkylene group of the polyoxyalkylene-modified silicone surfactant is preferably an ethylene group or a propylene group, and those having the same or two different groups selected from these are used. Among them, those in which the alkylene group is an ethylene group are preferable, and in the oil agent of the present invention, an alkylphenyl polysiloxane having a viscosity of 10 to 1000 cst at 25°C is used in combination with the above surfactant. As the alkylphenylpolysiloxane, those containing 2 to 80 mol% of phenyl groups are preferred, and those containing 5 to 30 mol% are particularly preferred.

Further, as the alkyl group constituting the alkylphenylpolysiloxane, methyl group, ethyl group, and propyl group are preferable.

In the present invention, a water emulsion type oil can also be prepared using the above-mentioned surfactant and alkylphenyl polysiloxane. When this water emulsion type oil is used in the method of the present invention, during infusibility, There is very little decomposition or deterioration of the oil agent, and the fiber bundles are well bundled, so there is no breakage of the fiber bundles during infusibility, and there is little fuzz.In contrast, dimethyl polysiloxane (dimethyl silicone oil), fatty acid ester Oils, mineral oils, etc. can be emulsified with ordinary surfactants, but compared to when alkylphenyl polysiloxane is used, severe decomposition and deterioration of the oil and fiber bundles occur during infusibility, making thread handling extremely difficult. Therefore, these cannot be used in the present invention.

In the present invention, antioxidants such as amines, selenium compounds, and phenols may be added to the oil agent in order to further improve the heat resistance of the oil agent.

As these antioxidants, phenyl-α-naphthylamine, dilaurylselenide, phenothiazine, iron octolate, etc. are used.

The oil may be applied by any method such as roller contact, spray application, foam application, etc.

In the present invention, the amount of oil attached to the fibers is 0°01 to 1
0% by weight, preferably 0.05-5% by weight.

ii) Infusibility of pitch fibers The pitch fibers to which the oil agent has been applied and bundled can be infusible by a known method.

The temperature of the infusibility step is 150° C. to 400° C., preferably 200° C. to 350° C., and the temperature is increased stepwise or gradually, and the treatment is usually carried out for 10 minutes to 5 hours. The treatment time may be as long as 1 to 3 days so that the infusibility reaction proceeds sufficiently and uniformly.

Infusibility can be performed using air, oxygen, a mixed gas of air and oxygen or nitrogen, or the like.

In the present invention, halogen and N
Sufficient infusibility can be obtained by treating for a single hour in an atmosphere containing an oxidizing agent such as O2 or ozone, or at a temperature 30 to 50 degrees Celsius lower than the softening point of pitch, i.e., 150 to 240 degrees Celsius, in an oxygen gas atmosphere. It is preferable to hold the mixture for 10 minutes to 1 hour until the mixture is obtained, and then raise the temperature to about 300° C. if necessary to complete the infusibility. The latter method is particularly preferred because it is easy and simple.

iii) Heat treatment process Next, the carbonaceous pinch fibers that have become infusible are heated for 1 time in a chemically inert atmosphere such as argon gas or nitrogen gas.
Carbon fibers are obtained by raising the temperature to a temperature in the range of 000 to 2000°C and carbonizing, and graphite fibers are obtained by raising the temperature to a temperature in the range of 2000 to 3000°C and proceeding to graphitization treatment.

In the present invention, the details of the carbonization and graphitization methods are not particularly limited, and generally known methods can be used.

Also, during the infusibility, carbonization, and graphitization treatments, to prevent scratches from rubbing against the furnace wall and furnace bottom, to avoid shrinkage and deformation of the yarn, or to obtain carbon fibers and graphite fibers with good appearance and high physical properties. ,
When processing a fiber bundle coated with an oil agent, it is also possible to apply a load or tension to the fiber bundle.

(Effect of the invention) In the present invention, a polyoxyalkylene-modified silicone surfactant with a boiling point of 600°C or less (in terms of atmospheric pressure), and 25
Since an oil agent containing alkylphenyl polysiloxane having a viscosity of 10 to 1000 cst at °C is used, the
There is no decomposition or deterioration of the oil agent even when infusibility is performed under harsh conditions such as high temperatures of up to 350°C or in a strongly oxidizing gas atmosphere.Therefore, there is no decomposition or deterioration of the oil agent. In addition to making it possible to extremely easily handle fragile fibers in the pitch fiber firing process of melting, pre-carbonization, carbonization, and graphitization, it is also possible to shorten the infusibility time.

In addition, when the above-mentioned nonionic surfactant is used as an emulsifier in a water emulsion oil, it is possible to not only improve the working environment, but also to further reduce fusion and adhesion between fibers, and to reduce the amount of solvent used. It is possible to prevent yarn damage and fuzz caused by the use of carbon fibers, and it is possible to obtain continuous filament carbon fibers and graphite fibers. In particular, when optically anisotropic carbonaceous pitch is used as the carbonaceous pitch, continuous filament carbon fibers and graphite fibers with extremely high strength, high elastic modulus, and good appearance can be produced.

(Examples) Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1° A carbonaceous pitch containing approximately 55% of an optically anisotropic phase and having a softening point of 235° C. was used as a precursor pitch. This precursor pitch was separated using a cylindrical centrifugal separator at 370° C. to obtain a pitch containing a large amount of optically anisotropic phase. The obtained optically anisotropic pitch contained 98% of the optically anisotropic phase and had a softening point of 265°C.

The obtained optically anisotropic pitch was passed through a spinning machine having a spinneret with 500 holes, and extruded and spun at 355° C. under a nitrogen gas pressure of 200 mmHg.

The spun pitch fibers are wound onto a bobbin that rotates at high speed provided at the bottom of the nozzle, and the fibers are wound at a winding speed of approximately 500 m/min.
Spinning was carried out for 0 minutes. At this time, the spun yarn was substantially converged by an air sucker and guided to an oiling roller, and a convergence oil was applied thereto.

As the oil agent, a polyoxyethylene-modified silicone surfactant (decamethyltetrasiloxane with pendant oxyethylene added) having a number average molecular weight of 1000 and a boiling point of 500°C (atmospheric pressure equivalent boiling point) or less is used. Methylphenylpolysiloxane (phenyl group content 25
A water emulsion type oil agent emulsified with mol %) was applied.

The above number average molecular weight was calculated using gel permeation chromatography LCO8 (manufactured by Japan Analytical Industry ■).
This is the value obtained by measuring with a column and converting it to standard polystyrene molecular weight.

The concentration of the water emulsion oil agent was 0.5mff1%, and the amount applied was 0.2% by weight based on the yarn.

A portion of the pitch fiber bundle thus obtained was taken out and infusible while being heated in air from 150°C to 330''C for 60 minutes.

The tension applied to the fiber bundle at this time is 0 per filament.
．． It was 0.007g.

During infusibility, there was no breakage of the fiber bundle and no fluffing was observed. The fiber bundle after infusibility was flexible and easy to handle.

This infusible pitch fiber was heated for 1 hour in an inert gas atmosphere.
The temperature was raised to 500°C to obtain carbon fibers. The obtained carbon fiber had a thread diameter of 10.0 μm and a tensile strength of a .8 μm, tensile strength was 3.0 GPa, and tensile modulus was 7°0 GPa.

Comparative Example 1 The same as Example 1 except that the number average molecular weight of the polyoxyethylene-modified silicone surfactant used in Example 1 was changed from 1000 to 2000 and a substance containing a component with a boiling point of 600°C or higher was used. The same oil was used and the treatment was carried out in the same manner as in Example 1.

In this case, during the infusibility treatment in air, the fiber bundles were significantly stuck together, and the fiber bundles were cut during the infusibility treatment.

Claims (1)

[Scope of Claims] 1) Melt-spun carbonaceous pitch fibers, a polyoxyalkylene-modified silicone surfactant with a boiling point of 600°C or less (in terms of atmospheric pressure), and an alkylphenyl having a viscosity of 10 to 1000 cst at 25°C. A method for producing carbon fibers and graphite fibers, which comprises using a heat-resistant oil agent containing polysiloxane and performing infusible, carbonized, and graphitized treatments. 2) The method for producing carbon fibers and graphite fibers according to claim 1, wherein the polyoxyalkylene-modified silicone surfactant has a number average molecular weight of 1,500 or less. 3) The method for producing carbon fibers and graphite fibers according to claim 1, wherein the polyoxyalkylene-modified silicone surfactant is a polyoxyethylene-modified silicone surfactant. 4) Alkylphenylpolysiloxane has 1 phenyl group
Claim 1 containing from mol% to 80 mol%
A method for producing carbon fibers and graphite fibers according to any one of items 1 to 3. 5) The alkyl group of the alkylphenylpolysiloxane includes any one of a methyl group, an ethyl group, a propyl group, or two or more same or different groups selected from these. The method for producing carbon fibers and graphite fibers according to any one of Item 4. 6) The method for producing carbon fibers and graphite fibers according to any one of claims 1 to 5, wherein the heat-resistant oil agent contains an antioxidant such as amines, organic selenium compounds, and phenols. . 7) Claim 6, characterized in that the antioxidant is one or a mixture of two or more selected from phenyl-α-naphthylamine, dilaurylselenide, phenothiazine, and iron octolec. The method for producing carbon fiber and graphite fiber described in . 8) Claims 1 to 7, wherein the carbonaceous pitch is an optically anisotropic pitch that contains about 95% or more of an optically anisotropic phase and has a softening point of 230 to 320°C. The method for producing carbon fibers and graphite fibers according to any one of the above.