JPS61264092A - Raw material pitch for carbon fiber - Google Patents

Abstract

PURPOSE:The titled pitch, having pyridine insolubles, mesophase content and softening point respectively within specific ranges, readily infusibilized, with a higher softening point than the infusibilizing temperature and good spinning properties and capable of giving carbon fibers having improved physical properties, e.g. tensile strength and elastic modulus. CONSTITUTION:A raw material pitch having 60-95wt%, preferably 82-93wt% pyridine insolubles, 95-100wt% mesophase content and 300-400 deg.C, preferably 310-350 deg.C softening point. Either one of coal and petroleum based pitches may be used as a starting pitch to be the raw material pitch and preferably the starting pitch has 35-60wt% benzene insolubles and 15-35wt% pyridine insolubles, and the above-mentioned starting pitch is mixed with a hydrogenation solvent at 1:1-4 weight ratio of the pitch to the solvent, and then hydrogenated at 410-450 deg.C for 10-240min. After distillation and drying, the hydrogenated pitch is heat-treated at 450-490 deg.C for 1-40min and then treated under reduced pressure for 1-20min to afford the aimed raw material pitch.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to carbon fibers and their raw material pitch. More specifically, the present invention relates to a carbon fiber having good spinnability and excellent physical properties, and a raw material pitch for the carbon fiber.

Conventional carbon fibers have excellent heat insulation properties, heat resistance, chemical resistance, 1゛rigidity, electrical conductivity, etc., and are used as insulation materials, sealing materials, various structural members, friction plates, carbon fibers, etc. As a result, its applications are expanding in fields such as aviation, space, electromechanical parts, and sporting goods.

Methods for producing such carbon fibers are broadly divided into methods of firing fibers such as acrylonitrile and methods of spinning and carbonizing pitch-like materials. Among these, molding from pitch-like materials has the advantage that the raw materials are cheap and easily available, but has the disadvantage that spinnability is insufficient and carbon fibers with excellent physical properties cannot be produced.

Various improvements have been made in the past regarding pitch for carbon fibers.
5625) and a method of hydrogenating pitch and then heat-treating the pitch to mold pre-mesophase pitch for carbon fibers (Japanese Patent Laid-Open No. 88923/1983).

However, many of the pitches made by these methods do not have sufficient spinnability, and furthermore, it is not easy to perform an infusible treatment before carbonizing the spinning pitches.

An object of the present invention is to provide a raw material pitch that yields carbon fibers having good spinnability and infusibility properties and poor physical properties from a pitch that is inexpensive and easily available.

That is, in the present invention, the pyridine insoluble content is 60 to 95%
, mesophase 95-100% and softening point 300℃
The present invention provides raw material pitch for carbon fibres, which can be used at temperatures exceeding 400°C and below 400°C, and carbon fibers and fibers obtained from the pitch.

The raw material pitch for carbon fibers of the present invention is obtained by subjecting the starting pitch to hydrogenation treatment, so that
Unlike the pitch disclosed in Japanese Patent Publication No. 59-98923, although it contains a large amount of pyridine insoluble matter, it is sufficiently bright and has good spinnability. These seven different compositions differ in that they do not require the presence of primesophase and have good spinnability despite having a high softening point.

In the raw material pitch for carbon fibers of the present invention, either coal-based pitch or petroleum-based pitch can be used as the starting pitch serving as the raw material.

The composition of these starting pitches is 30 to 90% benzene-insoluble.
% by weight, preferably 35 to 60% by weight, and 0 to 40% by weight of pyridine-insoluble matter, preferably 15 to 35% by weight.

In order to obtain the raw material pitch for carbon fibers of the present invention from such starting pitch, first, the starting pitch is hydrogenated using a hydrogenation solvent. Any solvent may be used as long as it can be used as a solvent, for example, tetrahydroquinoline, hydrogenated creosote oil, or pyridine as a solvent under hydrogen pressure F.
Any method such as hydrogenation using quinoline or creosote oil may be used. In the hydrogenation treatment, the starting pitch and the solvent are mixed at a p4 ratio of 1.1 to 1.4 at a reaction temperature of 380 to 470°C, preferably 410 to 450°C.
for 10 to 240 minutes under hydrogen atmosphere, and 10 to 250 minutes under hydrogen atmosphere.
1ψ/cd, 1 to 2 Or<9 in nitrogen atmosphere 1 to 14 gas
/ca in a pressurized reaction vessel.

The obtained pitch is further filtered, distilled, and vacuum dried. The softening point of the pitch obtained by such hydrogenation treatment is 40 to 60°C.

Next, the pitch was adjusted to 450 to 490 in a nitrogen atmosphere.
A mesophase pitch having a 100% flow structure is obtained by heat treatment at 1 to 40 minutes at a temperature of 1 to 40 minutes and further treatment at reduced pressure 2 for 1 to 20 minutes.

The thus obtained mesophase pitch, which is a raw material for carbon fibers, has a pyridine-insoluble content of 60 to 95% by weight, preferably 82 to 93% of heavy acid, and an area ratio of 6% under a polarizing microscope to a mesophase pitch of 95 to 100%. %, and has a softening point of 300 to 400°C, preferably 310 to 350°C, as determined by hot stage microscopic observation.

The raw material pitch for carbon fibers of the present invention can be spun using any conventionally known method, such as spinning, melt spinning, extrusion spinning, or blow spinning. The spun pitch is further made infusible and carbonized or graphitized to form carbon fibers according to a small method.

Effects of the Invention According to the raw material pitch for carbon fibers of the present invention, it is particularly easy to make it infusible, and its softening point is higher than the 7 degrees of infusibility.
It is possible to make it infusible under all conditions such as rapid temperature rise. Furthermore, good spinnability of 300 m/min or more is obtained, and the obtained carbon fiber has a tensile strength of 200 Kp/- to
9/+i to 350, tensile modulus 40t/mtN~95
It showed excellent physical properties of /-.

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. In addition, unless otherwise specified below, all % means city m%.

Example 1 Coal-based pitch (softened at 97°C, pyridine insoluble content 27%,
Charge benzene insoluble matter (40tfo) 60F and tetrahydroquinoline 1807 into an autoclave. After nitrogen substitution, hydrogenation was carried out by holding at 450° C. for 30 minutes. Next, filter this, lOO12g9 precepts IF ■, 2
After distillation at 70°C, the tetrahydroquinoline was removed by vacuum drying. The obtained hydrogenated pyridine has a softening point of 57°C
Met.

Further, the pyridine was heat-treated at 470°C for 20 minutes under a nitrogen atmosphere of 1η, and then heated under reduced pressure of F (1000Hg) at 470°C.
After treatment at 0° C. for 5 minutes, a mesophase pyridine having a 100% (area percentage) flow structure was obtained. The pyridine softened at 330° C., and had a pyridine insoluble content of 85% and a benzene insoluble content of 90%.

This mesophase pitch is spun into a melt spinning device (nozzle diameter: 0.
5 mu, extrusion weight 0.25~/c-J, spinning temperature 40
When spinning was carried out at 0° C.), good spinnability of 3201 n/min was obtained.

The obtained fibers were made infusible at 300°C and graphitized at 2650°C to obtain carbon fibers. f The obtained carbon fiber has a fiber diameter of 14 μm, a tensile strength of 230 g/body, and an elastic modulus of 45 [/
- It had excellent physical properties.

Comparison example 1 Reduced hydrogenated pitch (softening point 57℃) in purchase example 1
The pitch was heat-treated at 460° C. for 1 minute at T:, F (10 mmHg) to obtain a pitch with a softening point of 230° C., a pyridine insoluble content of 58%, and a benzene insoluble content of 75%.

When the pitch was spun in the same manner as in Example 1, the spinning speed was as low as 5 Qm, z min or less, and the tensile strength of the carbon fiber obtained by processing it in the same manner as in Example 1 was 130 k/m. It was Td.

Claims (2)

[Claims] (1) Pyridine insoluble content 60-95% by weight, mesophase 95-100% and softening point exceeding 300°C and 400°C
A raw material pitch for carbon fiber characterized by the following: (2) Pyridine insoluble content 60-95% by weight, mesophase 95-100% and softening point exceeding 300°C and 400°C
A carbon fiber characterized by spinning the following raw material pitch for carbon fiber.