JPH0739580B2 - Method for producing spinning pitch for carbon fiber - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a spinning pitch for carbon fiber, and more specifically, to a spinning pitch which gives a pitch-based carbon fiber having high strength and high elastic modulus. The present invention relates to a manufacturing method.

(Prior Art) As is well known, when carbonaceous raw materials such as heavy oil, tar, and pitch are heated to 350 to 500 ° C., these substances have an optical difference under polarized light with a particle size of several microns to several hundreds of microns. Small spheres that show direction are generated. Then, upon further heating, these small spheres grow and coalesce, and finally the whole becomes a state exhibiting optical anisotropy. This anisotropic structure is formed by stacking and orienting high molecular weight aromatic hydrocarbons produced by a thermal polycondensation reaction of a carbonaceous raw material in layers, and is regarded as a precursor of a graphite crystal structure.

Such a heat-treated product is melt-spun, infusibilized, carbonized, and optionally graphitized through a spinneret to obtain a Pitch-based high-performance carbon fiber having characteristics such as high strength and high elastic modulus. Proposed as a raw material.

Carbon fiber is a material with a high specific strength and a high specific elastic modulus, and has been the focus of attention as a filler fiber for high-performance composite materials. Among them, Pitch-based high-performance carbon fiber has a large yield in the carbonization process, It has various advantages over polyacrylonitrile-based carbon fiber such as high rate.

Conventionally, the Pitch-based high-performance carbon fiber is usually prepared by using a so-called mesophase-containing pitch as a spinning raw material, spinning a fibrous pitch from the mesophase-containing pitch, then infusibilizing and firing (carbonization, graphitization). Being manufactured.

In particular, when producing a spinning pitch containing a large amount of mesophases, silica contained in the carbonaceous raw material as disclosed in JP-A-58-18421, JP-A-58-214531, etc. It was a widely known technique to remove the infusible substance which is insoluble in quinoline in the form of carbon black or the like and then heat-treat it to produce a spinning pitch.

(Problems to be Solved by the Invention) However, in the conventional method, a paper or glass filter was used to remove such foreign matter, but in such a method, the foreign matter contained in the carbonaceous raw material was sufficiently removed. There is a problem in stably and uniformly producing spinning pitches that are difficult to remove, have excellent spinnability, and give high-performance pitch-based carbon fibers.

(Means for Solving Problems) Therefore, the inventors of the present invention have conducted diligent studies to solve the above problems, and as a result, in order to sufficiently remove foreign substances contained in the carbonaceous raw material, Recognizes that a material having a specific structure and a specific opening is important, and by using the specific material, it has been found that the foreign matter in the carbonaceous raw material can be sufficiently removed sufficiently, and the present invention is realized. Arrived

That is, an object of the present invention is to provide a method for stably and uniformly producing a spinning pitch which gives a pitch-based carbon fiber having high characteristics.

The purpose of the method is to heat the carbonaceous raw material to produce a spinning pitch for carbon fiber,
It is achieved by passing through a laminated wire mesh sintered filter layer having a mesh size of μ or less and then performing heat treatment.

Hereinafter, the present invention will be described in detail.

Examples of the carbonaceous raw material used to obtain the spinning pitch in the present invention include coal-based coal tar, coal tar pitch, coal liquefaction, petroleum-based heavy oil, tar, and pitch, and a benzene-insoluble content of 60% by weight. % Or less, preferably 50% by weight or less, more preferably 5 to 45% by weight, and quinoline-insoluble matter 20% by weight or less, preferably 15% by weight or less, more preferably 5% by weight or less.

If the benzene-insoluble matter and the quinoline-insoluble matter of the carbonaceous raw material exceed the above-mentioned ranges, the melt viscosity of the obtained spinning pitch becomes high, and accordingly, spinning must be performed at a high temperature.
Therefore, thermal deterioration of the spinning pitch is likely to occur during spinning, which is not preferable.

As the pretreatment, the carbonaceous raw material is heat-treated at 350 to 500 ° C. under atmospheric pressure to 10 kg / cm ² · G for about 0.5 to 20 hours to give an optically anisotropic portion of at least 30% or more, preferably 50. % Or more, and particularly preferably 70% or more, to obtain a heat-treated product, and then about 0.1 to 3 per 1 part by weight of this heat-treated product.
The soluble portion is obtained by bringing into contact with an aromatic oil having a boiling point or initial boiling point of 150 parts by weight or higher. As the aromatic oil, naphthalene oil, absorbing oil, creosote oil or anthracene oil is preferable.

Although the meaning of this pretreatment is not completely clear, it is assumed by the present inventors that the relatively high molecular weight portion that cannot be restored to an appropriate substance again in the subsequent treatment is to be removed in advance. To be done. As a means for satisfying such a meaning, a carbonaceous raw material or the above aromatic oil-soluble component is easily combined with a hydrogen donating solvent of tetralin, decalin, tetrahydroquinoline, hydrogenated aromatic oil, or a hydrogen donating solvent. Solvents such as quinoline, naphthalene oil, and anthracene oil, which can be converted to, and iron-based compounds as catalysts, supported or unsupported catalysts containing Mo are added to the catalysts under hydrogen gas pressure.
A method is conceivable in which hydrogenation is carried out at 360 to 500 ° C., and if necessary, the solvent is removed by distillation or the like to obtain a residue.

In the present invention, the carbonaceous raw material which has been subjected to the above-mentioned pretreatment is 300 to 500 ° C., preferably 380 to 450 ° C., and reduced pressure to 10 kg / cm ^2.
G, preferably 10 mmHg to atmospheric pressure for 20 minutes to 10 hours, preferably 1 to 6 hours to obtain a spinning pitch. At that time, the carbonaceous raw material is a laminated wire mesh having openings of 5 μm or less. After passing through the sintered filter layer, it is important to perform heat treatment under the above-mentioned conditions.

The laminated wire net sintered filter layer used is a wire net made of metal such as stainless steel, titanium, nickel, etc., which is formed by laminating 2 to 10 layers, preferably 3 to 8 layers and sintering them to form an integrated structure. The wire mesh is thick to provide strength and has a large opening. On the other hand, it is preferable to use a thin wire mesh having a small opening and a small opening.

The shape of the filter layer is flat or cylindrical, and the layer thickness is 0.5 to 4 mm, preferably 1 to 3 mm.

The mesh size of the filter layer is the minimum mesh size of the wire mesh to be laminated and is usually 5 μm or less, preferably 2 μm or less.

With such a specific laminated wire mesh sintered filter layer, foreign substances in the carbonaceous raw material are sufficiently removed and heat treatment is performed.

Further, in the present invention, the carbonaceous raw material from which the foreign matter is removed may be subjected to a heat treatment while the inert gas is blown and the stirring is performed at the same time.

The inert gas is not particularly limited as long as it is not a gas that oxidizes the carbonaceous raw material to make it heavy during the heat treatment, and specifically, nitrogen, argon, carbon dioxide. , Helium, water vapor, hydrogen or carbon number 6
Hydrocarbons and the like of less than or equal to the number, and particularly preferably nitrogen,
It is preferable to use argon, hydrogen or the like.

Further, these inert gases may be used alone, or if necessary, two or more kinds of inert gases may be mixed and used.

In the present invention, the optically anisotropic phase is 40% or more, preferably 70 to 100%, particularly preferably 90 to 100%, and the quinoline insoluble content is 40% by weight or less, preferably 30.
It is necessary to select the above-mentioned heat treatment conditions so as to obtain a spin-spun pitch of not more than 25% by weight, particularly preferably not more than 25% by weight.

The content of the optically anisotropic phase of the spinning pitch in the present invention is a value obtained as the area ratio of the portion showing the optical anisotropy in the heat-treated product sample under a polarization microscope at room temperature.

Specifically, for example, a heat-treated product sample crushed into a few mm square is embedded with a sample piece on almost the entire surface of a resin having a diameter of about 2 cm according to a conventional method, and after polishing the surface, the entire surface is thoroughly covered. It is determined by observing under a polarizing microscope (100 magnification) and measuring the ratio of the area of the optically anisotropic phase to the total surface area of the sample.

According to a known method, the spinning pitch thus obtained is
Melt spinning, infusibilize and carbonize the resulting fibrous pitch,
In some cases, by further graphitizing, it is possible to obtain a high-performance pitch-based carbon fiber having improved strength and small variation in strength distribution.

(Effect) According to the present invention, foreign matter contained in the carbonaceous raw material can be efficiently and sufficiently removed by heating the carbonaceous raw material after passing the carbonaceous raw material through the laminated wire mesh sintered filter layer. Therefore, a spinning pitch having homogenized physical properties can be stably obtained, and a high-performance pitch-based carbon fiber can be produced by the spinning pitch.

Since the spinning pitch of the present invention is homogenized and does not contain a gelled substance and the like, it is excellent in spinnability, and the industrial properties of the present invention are great together with the high characteristics of the obtained fiber.

Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to the following Examples unless it exceeds the gist.

Example 1 100 parts by weight of tar-based pitch (toluene-insoluble content 35.4%, quinoline-insoluble content 13.7%) and tar-based heavy oil (b.p22) as a solvent
(0-280 ℃) 170 parts by weight of hydride is treated in an autoclave with a stirrer at 450 ℃ for 1 hour, and at 130 ℃ under normal pressure.
After cooling down to 5.6 kg (5.0 liters), a stainless steel wire mesh sintered filter (cylindrical filter, over-area 200 cm ² ) with a minimum opening of 0.5μ was laminated.
After passing at a speed of 5l / Hr, the final pressure was 3.3kg / cm ² G, and the liquid was 5.0kg (quinoline insoluble content 0.01% or less).
0.6 kg (quinoline insoluble matter 39.3%) was obtained. After backwashing with a solvent, this operation was repeated 10 times or more, but almost no increase in material resistance was observed.

This liquid was distilled under the conditions of 10 mmHg and 300 ° C. to remove the solvent and light boiling oil. The hydrotreated product (pitch) thus obtained was heat-treated at 450 ° C. for 50 minutes while passing nitrogen at a rate of ³ Nm ³ / Hr per 1 kg of the pitch under normal pressure. The optically anisotropic phase of the obtained mesophase pitch was 100%.

This mesophase pitch was melt-spun at a liquid temperature of 340 ° C, and the obtained pitch fiber with a diameter of 10μ was heated to 300 ° C from 150 ° C in air.
After incubating while raising the temperature to ℃ for 1 hour,
A carbon fiber was obtained by carrying out a two-step carbonization treatment in which it was heated in argon at 1000 ° C. for 30 minutes and then at 2000 ° C. for 5 minutes.
The tensile strength and tensile elastic modulus of this carbon fiber were measured and found to be 350 kg / mm ² and 50.7 ton mm / ² .

Example 2 Example 1 except that a wire mesh having an opening of 1 μ is used in place of the wire mesh having an opening of 0.5 μ of the filter in Example 1.
A carbon fiber was obtained in exactly the same manner as. The tensile strength and tensile elastic modulus of this carbon fiber were measured and found to be 320 kg / mm ²
And 49.0 ton / mm ² .

Examples 3 to 4 Carbon fibers were obtained in the same manner as in Example 1 except that the mesh size of the wire mesh and the temperature and time of the carbonization treatment in Example 1 were changed as shown in Table 1. Tensile strength And the tensile elastic modulus was measured. The obtained results are shown in Table 1 together with the results of Examples 1 and 2.

Comparative Example 1 A carbon fiber was obtained in the same manner as in Example 1 except that a glass filter having an opening of 10 to 15 μ was used in place of the laminated wire mesh sintered filter having an opening of 0.5 μ in Example 1. However, the carbonization is 1000 ℃, 30 minutes plus 2000 ℃, 5 minutes and 10 minutes.
The temperature was set to 00 ° C. and two 35 minutes. The tensile strength and tensile elastic modulus of this carbon fiber were measured. The results obtained are shown in Table 2.

As is clear from Table 2, when a glass filter with a mesh opening of 10 to 15 μ was used, it did not depend on the difference in the carbonization conditions,
In each case, only carbon fiber having poor strength can be obtained.

Comparative Example 2 Distillation and heat treatment were carried out in the same manner as in Example 1 without passing through the hydrotreatment liquid obtained in the same manner as in Example 1. The optically anisotropic phase of the obtained mesophase pitch was 100%. When this mesophase pitch was melt-spun at 340 ° C, the spinning duration with a yarn diameter of 10μ was about 20 seconds at the maximum, and stable spinning could not be performed. The pitch fibers obtained were slightly infusibilized and carbonized in the same manner as in Example 1. The carbon fibers obtained had a tensile strength and a tensile elastic modulus of 94 kg / mm ² and 45.0 tom / mm ² . It was inferior.

Claims (2)

[Claims] 1. A method for producing a spinning pitch for carbon fibers by heat-treating a carbonaceous raw material, which is heat-treated after passing the carbonaceous raw material through a laminated wire mesh sintered filter layer having openings of 5 μm or less. A method for producing a spinning pitch for carbon fiber, which comprises: 2. The opening of the laminated wire mesh sintered filter layer is 2 μm.
The method according to claim 1, characterized in that: