JPS6088124A - Method for infusibilizing pitch fiber - Google Patents

Abstract

PURPOSE:To prevent the sticking between pitch fibers and obtain carbon fibers having improved dividing property, by applying a dimethylpolysiloxane having a specific viscosity to pitch fibers, and infusibilizing the resultant pitch fibers in the atmosphere of an oxidizing gas. CONSTITUTION:A carbonaceous pitch, e.g. petroleum pitch, having preferably 260-300 deg.C softening point is melt spun to give pitch fibers. A dimethylpolysiloxane of the formula having 0.5-500cSt, preferably 1.0-25cSt at 25 deg.C in an amount of 0.1-25wt% is applied to the pitch fibers, and the resultant fibers are then infusibilized in the atmosphere of an oxidizing gas, e.g. oxygen or air, preferably at 200-350 deg.C, carbonized, and graphitized to afford the aimed carbon fibers.

Description

[Detailed description of the invention] The present invention relates to a method for making pitch fibers infusible.

Pitch-based carbon fibers are produced by subjecting pitch fibers obtained by completely melt-spinning carbonaceous pitch to infusibility, carbonization, or further graphitization. The infusibility treatment of pitch fibers is usually carried out at temperatures below 400°C in the presence of oxidizing gases such as air, oxygen, ozone, nitrogen oxides, halogens, or sulfur dioxide gas. The pitch fibers coalesce into each other, albeit very slightly,
When the mutually bonded infusible fibers are carbonized or further graphitized, the splitting properties of the resulting carbon fibers are reduced.

An object of the present invention is to prevent coalescence between pitch fibers and to produce carbon fibers with excellent splitting properties.

The object of the present invention is to provide a method in which pitch fibers obtained by melt-spinning carbonaceous pitch are rendered infusible in an oxidizing gas atmosphere, such that the pitch fibers have a viscosity of 0.25%.
This is achieved by applying dimethylpolysiloxane having a strength of 5 to 500 cSt and then making it infusible.

It is known that pitch fibers are treated to be infusible after being coated with an oil agent; for example, a technique has been reported in which pitch fiber bundles are bundled using an aqueous solution of a water-soluble surfactant (Japanese Patent Publication No. 1986-- No. 12740). However, when these water-soluble surfactants are used, although the convergence of the fiber bundles is improved, when they are treated to make them infusible, the surfactants and pitch fibers interact with each other at high temperatures, resulting in fiber splitting. Decreases sex.

On the other hand, there are reports that silicone oils are effective in thermally stabilizing polyacrylonitrile precursors (JP-A-54-131032, JP-B-Sho 51-127).
No. 39), excellent effects cannot be obtained even if this method is applied to pitch fibers as is. The present inventors have found that a silicone compound with a limited structure and limited viscosity is extremely suitable for infusible pitch fibers, and that the obtained infusible fibers have good splitting properties. A friend who was able to discover and complete the present invention.

The present invention will be explained in detail below.

The carbonaceous pitch used in the present invention includes various pitches such as coal tar pitch, coal-based pitch such as SRC, petroleum-based pitch such as ethylene tar pitch, and decant oil pitch, or synthetic pitch, but petroleum-based pitch is particularly preferred. .

The above pitch is modified, for example, treated with a hydrogen donor such as tetralin, hydrogenated under a hydrogen pressure of 20 to 350/d, modified by heat treatment, or modified by these methods as appropriate. Various modified pitches, such as those modified in combination, are also carbonaceous pitches as used in the present invention.

In other words, the carbonaceous pitch of the present invention is used to collectively refer to precursor pitch that can form pitch fibers.

The carbonaceous pitch of the present invention may be an optically isotropic pitch or an optically anisotropic pitch.

When the pitch is optically isotropic, the reflectance is 9.0~
11. Those exhibiting values within the range of - are preferred. Here, the reflectance is measured by embedding pitch in a resin such as acrylic resin, polishing it, and measuring it in air using a reflectance measuring device.

Optically anisotropic pitch means that the pitch is usually heated to 340 to
It is a pitch containing an optically anisotropic phase (so-called membrane phase) obtained by heat treatment at 450C, and one having a membrane phase content of 5 to 100 degrees is particularly preferable.

The carbonaceous pitch used in the present invention has a softening point of 240 to 400.
℃ is preferable, and 260 to 300℃ is particularly preferable.

The pitch fibers can be obtained by melt-spinning the carbonaceous pitch using a known method. For example, carbonaceous pitch is melted at a temperature 30 to 80°C higher than its softening point and extruded through a nozzle with a diameter of 0.1 to 0.5.
A machined pitch fiber is obtained by winding at ~2000 m/min.

A dimethylpolysiloxane having a viscosity of 0.5 to 500 cst at 25°C is applied to the pitch fiber thus obtained. The dimethylpolysiloxane mentioned here has the following structure 5-, and preferably has a viscosity of 1 at 25°C.
．． 0-100 cst, more preferably 1.0-25
It is from cst.

The viscosity of dimethylpolysiloxane is extremely important;
If the viscosity is high within the above range, the infusibility reaction will be hindered and the infusibility rate will decrease. On the other hand, if the viscosity is less than the above range, the splitting properties of the infusible fibers will decrease, and the effects of the present invention cannot be expected.

Further, in the case of a mixture of two or more types of dimethylpolysiloxane, those whose viscosity as a mixture is within the above range can be used.

Other known silicone-based materials include methylphenyl polysiloxane, methylhydrodiene polysiloxane, polyether-modified products (with increased solubility in water), fluorine-modified products, and 6-amino-modified products. However, it has become clear that all of these interact with pitch fibers during infusibility, resulting in a total decrease in fiber splitting properties. Further, even if dimethylpolysiloxane has a viscosity within the same range as that of the present invention, emulsifying it is not preferable because it causes deterioration in line segmentability.

The amount of dimethylpolysiloxane applied is 0.01 to 50% by weight, preferably 0.1 to 2% by weight based on the pitch fiber.
It is 5% by weight. Further, the application method is not particularly limited, and known techniques such as oiling roller 1 application, dipping, and spraying can be used.

The pitch fibers coated with dimethylpolysiloxane are then treated to be infusible in an oxidizing gas atmosphere. The infusibility treatment is usually carried out at a temperature of 400°C or lower, preferably 150°C or lower.
The temperature is 380°C, preferably 200 to 350°C. If the processing temperature is too low, the processing time will be longer;
Furthermore, if the processing temperature is too high, it is not preferable because it may cause fusing or consumption of the pitch fibers. As the oxidizing gas, oxidizing gases such as oxygen, ozone, air, nitrogen oxides, sulfur dioxide gas, or halogen are usually used.
A species or two or more species are used.

The infusible pitch fibers are then subjected to carbonization treatment or further graphitization treatment in an inert gas atmosphere to obtain carbon fibers.

Carbonization treatment is usually carried out at a temperature of 800 to 2000°C, and the treatment time generally required for carbonization is 0.1 minute to 10 hours. When further graphitizing, the temperature is 2000 to 350.
It is usually carried out for 1 second to 1 hour at 0°C. In addition, during carbonization or graphitization, if necessary, a slight load or tension Th1-
You can also leave it there.

EXAMPLES The present invention will be specifically explained below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1: Contains 80 wt% in the optically anisotropic phase and has a softening point of 280°C
The petroleum-based precursor pitch is melt-spun, and the average yarn diameter is 13
μ pitch fibers were obtained. This pitch fiber has a viscosity of 4.0
cst @ 25℃ dimethylpolysiloxane 10w
tq6tl-coated and treated in oxygen at 250°C for 30 minutes to obtain infusible fibers. The obtained infusible fiber had extremely excellent splitting properties.

Comparative Examples 1 to 6 The pitch fibers in Example 1 were applied with 10wt16f of various silicone oils shown in Table 1, and treated in oxygen at 250°C for 30 minutes to obtain infusible fibers.

Table 1 Comparative Example 1 Dimethylpolysiloxane 1ρ00cSt
△12 1 100ρ0OcSt X 〃 3 Methylphenyl polysiloxa 7 500cSt
xl 4 Amino modified siloxane 1,200cSt
xI 5 Fluorine modified siloxane 300 cst x
l 6 Dimethylpolysiloxane emulsion 40cSt
X9- Comparative Examples 1 and 2 are dimethylpolysiloxane with high viscosity, Comparative Examples 3 and 5 are modified silicone, and Comparative Example 6 is a dimethylpolysiloxane emulsion, and in each case, a nonwoven material with excellent fibrillation properties is used. No fused fibers were obtained.

Examples 2 to 6 Optically isotropic petroleum precursor pitch having a reflectance of 10.3% and a softening point of 260'C was melt-spun to obtain pitch fibers with an average yarn diameter of 12μ. Dimethylpolysiloxane shown in Table 2 was added to this pitch fiber, and the pitch fiber was heated at 280 °C/m in oxygen.
The temperature was raised to t: to obtain infusible fibers. Table 2 also shows the splitting properties of these infusible fibers.

In Tables 1 and 2, ◯ means excellent, △ means average, and × means poor.

10-

Claims (1)

[Claims] In a method of infusibleizing pitch fibers obtained by melt-spinning carbonaceous pitch in an oxidizing gas atmosphere, after imparting dimethylpolysiloxane having a viscosity of 0.5 to 500 cSt at 25° C. to pitch fibers, A method for making pitch fiber infusible, characterized by making it infusible.