JPH0823089B2 - Method for producing pitch-based carbon fiber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing carbon fiber from pitches such as coal pitch, petroleum pitch, and polymer fired pitch. The present invention relates to a method for obtaining a high-quality carbon fiber which is easy to handle and is free from adhesion or fusion between fibers.

[Conventional technology]

Pitch-based carbon fibers are usually produced by melt-spinning raw material pitch and subjecting the obtained pitch fibers to infusibilization treatment and carbonization treatment. Pitch-based carbon fibers have the advantage of being industrially advantageous in high yield compared to polyacrylonitrile-based carbon fibers, but pitch fibers are extremely fragile, making them difficult to handle by infusibilizing treatment or carbonization treatment. In these steps, fiber fluffing, winding around the guide roller, yarn breakage, etc. are likely to occur. Further, there is a problem that the pitch fibers are adhered or fused to each other during the infusibilizing treatment and the carbonizing treatment, and the obtained carbon fibers are easily damaged.

Therefore, various studies have been made on a method capable of stably producing a high-quality pitch-based carbon fiber by solving the problems inherent in the pitch-based carbon fiber, and a method using a silicone oil / water emulsion as a treating agent (JP-A-61). No. 70017), this treatment agent has solved the problems of fiber fluffing, winding around guide rollers, yarn breakage, etc. in the spin focusing process, but at about 100 ° C. in an oxidizing atmosphere. In order to sufficiently eliminate fusion and adhesion between fibers in the infusibilizing treatment performed in a heating zone of about 400 ° C or in the carbonizing treatment following the infusibilizing treatment at a temperature of at least 400 ° C or more in an inert atmosphere. Still had room for improvement.

It has been found that the cause of such a phenomenon of fusion or adhesion is that a part of the surfactant contained in the treating agent is decomposed or tarified during the heat treatment such as the infusibilizing treatment or the carbonizing treatment. .

[Problems to be solved by the invention]

Therefore, the present inventors have investigated and studied the effect of such a surfactant on fibers, and as a result, among various surfactants,
It has been found that the aliphatic carboxylic acid alkanolamide or the aliphatic carboxylic acid amine salt does not cause fusion or sticking between fibers during heat treatment such as infusibilization treatment or carbonization treatment. However, when an aqueous emulsion of a silicone oil obtained by using an aliphatic carboxylic acid alkanolamide or / and an aliphatic carboxylic acid amide salt is attached to fibers to be bundled, the sizing property is not sufficient, and the process passes. However, some problems such as fluffing of fibers, wrapping around guide rollers, and thread breakage remain, and these problems become more noticeable when the fibers to which the sizing agent is attached are stored for several days to one week. was there.

On the other hand, a silicone oil / water emulsion using polyoxyethylene alkyl ether, which is often used as a surfactant for conventional sizing agents, has excellent sizing properties, and fiber fluffing, winding around guide rollers, and yarn breakage are very small. Moreover, although the performance deterioration of the fiber to which the sizing agent is attached is stored for about one week, there is a problem that fusion or gluing of the fiber occurs during heat treatment in the infusibilizing treatment or the carbonizing treatment.

[Means for solving problems]

Therefore, the present inventors have conducted extensive studies to solve these problems, and as a result, the surfactant is composed of a plurality of components, at least one component is a polyoxyethylene alkyl ether, the other component is an aliphatic The inventors have found that the above problems can be solved by using a silicone oil-water emulsion that is a carboxylic acid alkanolamide or / and an aliphatic carboxylic acid amine salt, and have reached the present invention.

That is, the gist of the present invention is that after pitch fibers obtained by melt-spinning a spinning pitch in a gas phase are bundled by using a water emulsion of silicone oil, infusibilization treatment, carbonization treatment, and further graphitization as necessary. In the method for producing a pitch-based carbon fiber by performing treatment, the surfactant in the water emulsion is composed of a plurality of components, at least one component is polyoxyethylene alkyl ether, and the other component is an aliphatic carboxylic acid alkanol. An amide or / and an amine salt of an aliphatic carboxylic acid, which is a method for producing a pitch-based carbon fiber.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail, as the spinning pitch used in the present invention, coal tar pitch, coal pitch such as coal liquefaction, atmospheric distillation residual oil of crude oil, vacuum distillation residual oil, or heat-treated product thereof. Examples thereof include petroleum-based pitches such as heat-treated products of thermal decomposition by-product tar of naphtha, and polymer calcined pitches obtained by carbonization of synthetic resins and natural resins.

The melt spinning of the spinning pitch can be performed in the same manner as the dry method melt spinning of synthetic fibers, and there is no particular limitation, and the method of extruding the melted spinning pitch from the downward spinneret into the gas phase and cooling and solidifying is adopted. . As the spinneret, one having a discharge hole diameter of about 0.1 to 0.5 mm is used. The temperature of the spinneret depends on the kind of the raw material pitch and is determined by taking into consideration the melt viscosity suitable for spinning, but normally the range of 250 to 350 ° C is suitable. It is effective to stabilize the spinning state by providing a heat insulation tube below the spinneret.

In the present invention, a treating agent in which silicone oil is dispersed in water by a surfactant, which is used by attaching to pitch fibers spun by the above method, is used. It is important to use those in which one component is a polyoxyethylene alkyl ether and the other component consists of an aliphatic carboxylic acid alkanolamide or / and an aliphatic carboxylic acid amine salt.

Examples of the polyoxyethylene alkyl ether which is a component of such a surfactant include animal and plant alcohols such as lauryl, cetyl, oleyl and beef fatty alcohol, synthetic alcohols such as oxo alcohol and gerbet alcohol, and aliphatic alcohols such as resin alcohol. Examples thereof include those obtained by addition-polymerizing ethylene, and are represented by the general formula RO (CH ₂ CH ₂ O) _n H (wherein R is a C _{8 to} C ₂₀ optionally substituted alkyl group or alkenyl group, and n is 1 to 1). 20 integer).

On the other hand, as the aliphatic carboxylic acid alkanolamide, capric acid, lauric acid, coconut fatty acid, myristic acid,
Condensation products such as stearic acid and aliphatic carboxylic acids such as oleic acid and monoethanolamine, diethanolamine, monoisopropanolamine, diisopropanolamine and the like can be mentioned, and general formula R ¹ CONH (R ² O) _n H or (However, R ¹ is a C _{8 to} C ₂₂ optionally substituted alkyl group or alkenyl group, R ² and R ³ are C _{1 to} C ₄ optionally substituted alkylene groups, and n and m are It represents an integer of 1 to 20).

Commercially available alkanolamides include those having a ratio of alkanolamine to aliphatic carboxylic acid of 2: 1 type and those of 1: 1 type depending on the production method, and either of them can be used.

The aliphatic carboxylic acid amine salt has a general formula (R ¹ is a C _{6 to} C ₂₀ optionally substituted alkyl group, an alkenyl group, R ² , R ³ , R ⁴ are each optionally substituted C _{1 to} C ₁₀ alkyl group, an alkenyl group, It is represented by a salt of an aliphatic carboxylic acid represented by a hydroxyalkyl group, a polyoxyalkyl group or a hydrogen atom) and a primary to tertiary amine. Specifically, the aliphatic carboxylic acids include octanoic acid, decanoic acid, lauric acid, palmitic acid, stearic acid, etc., and the amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, tripropylamine, monoethanol. Amine, diethanolamine, triethanolamine, morpholine, dimethylaminopropylamine,
Examples include monoisopropylamine, diisopropylamine, triisopropylamine, butyldiethanolamine, dibutylethanolamine, aminoethylethanolamine, pentyldiethanolamine and the like.

Examples of the silicone oil include dimethylpolysiloxane, methylphenylpolysiloxane and various modified polysiloxanes, and preferably the viscosity (at 25 ° C) is
0.65 to 1,000,000 cst, more preferably 1 to 1000 cst, is preferably used. Moreover, you may use the mixture of 2 or more types of silicone oil.

The total amount of surfactant used for silicone oil is 1w
t% to 25 wt% is preferable. If it is less than 1 wt%, a stable water emulsion of silicone oil cannot be obtained, and if it exceeds 25 wt%, the properties of the fiber after infusibilization or carbonization may be adversely affected. Of the surfactants, the amount of polyoxyethylene alkyl ether is preferably 0.1 w relative to silicone oil.
t% to 6 wt%, more preferably 0.2 wt% to 2 wt%. If the amount is too small, the bundling property is not sufficient, and if the amount is too large, the fiber properties after infusibilization or carbonization may be adversely affected.

Furthermore, aliphatic carboxylic acid alkanolamide or /
Also, the amine salt of aliphatic carboxylic acid is preferably about 0.1 wt% to 24 wt% with respect to the silicone oil.

Further, for various purposes, it is possible to contain conventionally known emulsifiers, antistatic agents, rust preventives, antibacterial agents, etc. within a range that does not impair the effects of the present invention.

The treating agent having the above composition is usually used as a water emulsion with an oil content (total amount of silicone oil and surfactant) of 0.1 wt% to 30 wt%, but the amount of impregnation on pitch fibers is 0.02 wt% to 15 wt%. %, Preferably 0.2 wt
% To 5 wt% is recommended. If it is less than 0.02% by weight, the bundling property cannot be obtained, and if it exceeds 15% by weight, the fiber properties after infusibilization or carbonization may be adversely affected.

The method of attaching the treatment agent to the fiber can be appropriately selected from a method of spraying the running yarn coming out of the spinneret by spraying, a method of contacting with a roller and a method of contacting with a crow's mouth, and the like.

The pitch fiber bundled with the treatment agent is subjected to infusibilization treatment and carbonization treatment according to known methods. For example, the infusibilizing treatment is carried out by treating the fibers in an oxidizing atmosphere such as oxygen, ozone, air, nitrogen oxide, halogen, and sulfurous acid gas at 150 to 3
It is carried out by heating to a temperature of 60 ° C. for 5 minutes to 10 hours.

The carbonization treatment is carried out by heating the fibers at a temperature of 400 to 2000 ° C. for 0.5 to 10 hours in an atmosphere of an inert gas such as nitrogen or argon.

Further, when the graphitization treatment is performed, the temperature may be kept at 2000 to 3500 ° C. for about 1 second to 1 hour.

In addition, during infusibilization, carbonization or graphitization, it is also possible to apply tension to the object to be treated for the purpose of preventing shrinkage, deformation or the like.

The carbon fiber or the graphitized fiber thus obtained is optionally surface-treated or / and sized,
Used for each purpose.

(Examples) Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist.

Examples 1 to 4 Tar-based raw material pitch (mesophase pitch with 100% optical anisotropy) was melt-spun into the gas phase at a spinneret temperature of 340 ° C.,
The treating agents shown in Table 1 were attached to the obtained pitch fiber of 10 μm and 1000 filament pitch fibers by using an oiling guide and then bundled. Then, the temperature was raised from 150 ° C. to 350 ° C. over 2 hours and 40 minutes, and then the temperature was maintained for 30 minutes for infusibilization treatment. Then, in argon, from room temperature
It took 2 hours and 20 minutes to reach 1400 ° C., and then the temperature was maintained for 1 hour to carry out carbonization treatment to obtain carbon fibers. In the carbon fiber manufacturing process, the bundled state of the yarn, the property of the infusible fiber, and the fused state of the single yarn were observed. The results are shown in Table 1 (% indicates wt%).

Comparative Examples 1 to 4 Table 1 shows the results of the same procedure as in Example 1 except that the sizing agent type was changed.

The excellent performances of the treating agent according to the present invention are apparent from the results shown in Table 1.

[Effects of the Invention] As described in detail above, in the present invention, by using a treatment agent for carbon fibers obtained by dispersing silicone oil in water with a specific surfactant, it is possible to handle brittle fibers with a simple operation. Pitch-based carbon fibers having good properties can be produced in the form of continuous filaments under industrially advantageous conditions while facilitating the easiness and preventing the mutual adhesion and fusion of the fibers.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location D06M 13/419 15/643

Claims (1)

[Claims] 1. A pitch fiber obtained by melt-spinning a raw material pitch in a gas phase is bundled with a water emulsion of silicone oil, and then subjected to infusibilization treatment, carbonization treatment and, if necessary, graphitization treatment. In the method for producing a pitch-based carbon fiber according to the above, the surfactant in the water emulsion is composed of a plurality of components, at least one component is a polyoxyethylene alkyl ether, and the other component is an aliphatic carboxylic acid alkanolamide or / And a method for producing a pitch-based carbon fiber, which is an aliphatic carboxylic acid amine salt.