JPH0672223B2 - Method for producing hydrogenated 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, when further heated, these small spheres grow and coalesce, and finally the coalesce 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.

Particularly when producing a spinning pitch containing a large amount of mesophases, JP-A-58-18421 and JP-A-58-214531 are used.
It is widely known that, as disclosed in Japanese Unexamined Patent Publication, etc., silica or carbon black-like quinoline contained in a carbonaceous raw material is insoluble and infusible substances are removed, and then heat treatment is carried out to produce a spinning pitch. It was a technology.

(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 such a method sufficiently removes the foreign matter contained in the carbonaceous raw material. However, there is a problem in stably and uniformly producing spinning pitches which are difficult to produce and have excellent spinnability and 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, Found that the material having a specific structure and a specific opening is important, and found that the foreign material in the carbonaceous raw material can be efficiently and sufficiently removed by using the specific material, and arrived at the present invention.

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.

And, in the method of producing a hydrogenated pitch for carbon fiber by reacting the pitch with hydrogen in the presence of an organic solvent and a solid catalyst for hydrogenation, the hydrogenation reaction product is a nonwoven fabric of a heat resistant fiber or the nonwoven fabric. It is achieved by supplying to an extruder having a material layer made of a sintered body and removing the solid catalyst contained in the product.

Hereinafter, the present invention will be described in detail.

The pitch used to obtain the spinning pitch in the present invention includes a pitch obtained by solvent extraction treatment of coal or coal-based tar, a pitch obtained by hydrotreatment of coal, tar pitch, petroleum pitch and petroleum Pitches obtained from hydrocracking and heat treatment of residual oils, and their analogs, or mixtures thereof are used.

The hydrogenation of the pitch is usually carried out at a temperature of 150 to 600 ° C., a hydrogen pressure of normal pressure to 300 kg / cm ² G, in the presence of a solid catalyst for hydrogenation and an organic solvent, in a continuous system or a batch system.

As the solid catalyst for hydrogenation, a metal or alloy selected from at least one of iron, nickel, chromium, molybdenum, cobalt, zinc, copper, yttrium, lanthanide, tin, vanadium, manganese and tungsten, an oxide or sulfide thereof. Or a mixture of these is used. The amount of catalyst used is 0.1 to 1 with respect to the pitch used as the raw material.
It is selected from the range of 5% by weight, preferably 0.2-10% by weight.

Further, as the organic solvent, it is substantially soluble in toluene, has a boiling point of 200 to 550 ° C, and has an aromatic carbon ratio (fa) of 0.
Five or more aromatic hydrocarbon oils are used, such as coal liquefied oil, cracked oil, anthracene oil, absorption oil, naphthalene oil,
Examples thereof include alkali naphthalene and tetralin. It is also possible to use a small amount of an aromatic hydrocarbon such as kerosene mixed with these aromatic hydrocarbons. The hydrogenation reaction product itself can be partially recycled to be used as a solvent. In this case, the mixing ratio of the pitch and the organic solvent is usually 0.2 to 10 parts by weight, preferably 0.5 to 3 parts by weight per 1 part by weight of the pitch.

In the hydrogenation reaction product thus obtained, during the solid catalyst used in the hydrogenation reaction or in the production process, storage,
Solid components such as rust and foreign substances introduced during the process of transportation are usually contained as quinoline insoluble matter in an amount of 0.2 to 15% by weight.

The hydrogenation reaction product is then supplied to an excess device to remove solid components, and it is essential that the excess device uses a heat-resistant fiber nonwoven fabric or a material layer made of a sintered pair of the nonwoven fabric as a material layer. Is.

As the material layer, a heat-resistant fiber nonwoven fabric having a softening point of 100 ° C. or higher, preferably 300 ° C. or higher and a yarn diameter of 2 to 50 μm, preferably 3 to 40 μm, that is, these fibers are woven and formed into cotton. Needle punched and entangled to make a 3-20 mm thick felt-like material or cotton-like material, then compressed to a thickness of 0.3-10 mm and sintered to bond fibers to each other (porosity 40- 95%) is used.

As the heat-resistant fiber and heat-resistant powder, metal such as stainless steel, titanium, nickel, and aluminum, and glass, and fibers such as ceramics such as alumina, silica, titia, and silicon carbide are preferably used. When the filtration is carried out at a relatively low temperature, synthetic fibers which are insoluble in the hydrogenation reaction product such as polyester or polypropylene can be used.

Various material layers such as a pleated cylinder, a flat cylinder, a circular, a donut shape, a rectangular or a square disk, or a leaf disk in which a plurality of donut-shaped disks are stacked with a gap therebetween are formed by laminating about 1 to 5 layers. However, as shown in FIGS. 2 and 3, it is desirable to provide one or both layers of protective wire mesh of about 60 to 200 mesh on one surface or both surfaces of the material layer. FIG. 2 is an enlarged vertical sectional view of an example of a flat-shaped cylindrical filter element, and FIG. 3 is a sectional view taken along the line AA ′ of FIG. 2. The filter element has a wire mesh on the outer surface of a cylindrical material layer. One layer is provided with a perforated tube on the inner surface through one layer of wire mesh, and the tip is closed by a cap. The liquid that has passed through the material layer is taken out from the inside of the perforated pipe in the direction of the arrow. FIG. 4 is an enlarged cross-sectional view of an example of a pleated cylindrical filter element, and FIG. 5 is a cross-sectional view taken along the line BB ′ of FIG. 4, in which the outer surface of the perforated tube is provided with a single wire mesh on the inner surface thereof. Material is provided. The liquid that has passed through the material passes through the gap and is taken out from the inner tube of the perforated tube.

Various well-known type operating units are used which are operated by a pressurizing system or a depressurizing system, but are of a candle type using a pleated cylindrical or flat cylindrical filter element as shown in FIG. Those having a large excess area are preferable and the clogging material layer can be easily regenerated by backwashing.

FIG. 1 is an explanatory view of an example of a candle type passing device, in which a plurality of filter elements are suspended in a rigid casing.

Next, the case where the hydrogenation reaction product of pitch is passed by using the passing device shown in FIG. 1 will be described. The hydrogenation reaction product is supplied from the conduit into the casing, and the solid components such as the solid catalyst separated by the filter element are deposited on the surface of the filter element. It is also possible to pre-coat the surface of the filter element with a solid component, a diatomaceous earth or the like as an auxiliary agent prior to the filtration. The hydrogenation reaction product from which the solid components have been removed is taken out from the rear surface side of the filter element via a conduit.

Overpressure has an overspeed of 1 × 10 ^-6 to 1 × 10 ^-2 / mm ・ c
It is desirable to control so that m ² is preferably 1 × 10 ⁻⁵ to 1 × 10 ⁻³ / mm · cm ^2, and the differential pressure of the overlayer is usually 20.
It is appropriately selected from the range not exceeding kg / cm ² G.

The overtemperature is advantageous from the viewpoint of overspeed because the higher the temperature, the lower the year of the liquid, but if the temperature is too high, the pitch may be thermally polymerized. Is used about 100 ℃ lower temperature. For example, it is selected from the range of about 100 to 480 ° C.

There are constant speed overpressure and constant pressure overpressure as overflow methods. In the former case, the overpressure rises due to clogging of solid components as the overspeed progresses. When the pressure rises to about 5 kg / cm ³ G, it is preferable to regenerate the material layer by backwashing.

The backwashing of the material layer stops the supply of the hydrogenation reaction product to the conduit and supplies the solvent from the conduit. The supplied solvent passes from the inside of the filter element to the outside, and is dropped into the casing except for the solid components trapped inside the material layer and the solid components adhering to the surface of the material layer. The mixture of solvent and solid components is withdrawn from the conduit. After the backwashing, the filtration apparatus is repeatedly used to filter the hydrogenation reaction product in the same manner as described above.

The hydrogenation reaction product from which the fixed components have been removed is then subjected to meso-mechanization after removing the organic solvent according to a conventional method to form a spinning pitch.

The conditions of the meso-formation are usually 350 to 500 ° C., preferably 400 to 450 ° C., while blowing nitrogen gas or the like, the reaction time (in the case of continuous reaction, the average residence time of the reactor) is 1 to 7 hours, It is preferably about 3 to 5 hours. In addition, the properties of mesopitches obtained by mesomorphization are as follows:
i) 90 to 100%, quinoline insoluble matter (Qi) is 10 to 30%, and optical anisotropy is about 70 to 100%.

According to a conventional method, the spinning pitch is melt-spun (spinning temperature 300 to 380 ° C.) in a gas phase under drawing conditions to form pitch fibers. High strength carbon fibers can be obtained by subjecting the Pitch fibers to infusibilization treatment in an oxidizing gas atmosphere, followed by carbonization treatment in an inert gas atmosphere and, if necessary, graphitization treatment.

According to the present invention, the hydrogenation reaction product containing a solid component such as a solid catalyst is contained in the hydrogenation reaction product by a simple operation of supplying the hydrogenation reaction product having a specific material layer to a filtration apparatus having a specific material layer. Since the solid component can be set to an extremely small amount of 10 ppm or less, a high-strength carbon fiber can be easily obtained by spinning, infusibilizing and carbonizing the obtained hydrogenated pitch after mesomorphization.

When the metal remains in the pitch fiber, the metal acts as an oxidation catalyst in the infusibilization treatment, or forms a metal carbide in the carbonization process. It is considered that the metal itself also gives various defects to the carbon fiber as a foreign matter, and causes the strength of the fiber to decrease.

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

Example 1 A mixture of 100 parts by weight of a tar-based pitch, 170 parts by weight of a tar-based heavy oil (bp 220 to 280 ° C.) as an organic solvent and 5 parts by weight of an iron-based catalyst in an autoclave with a stirrer at a hydrogen pressure of 120 kg / cm.
^{It was} treated at ² G and 450 ° C. for 1 hour and cooled to 130 ° C. under normal pressure.
5.6 kg (5.0) of the obtained hydrogenation reaction product was fibrillated from stainless fibers with a yarn diameter of 4 μm to form a cotton shape, which was then compressed to a thickness of 2 mm and sintered (shape: cylindrical, porosity :about
70%, excess area 76 cm ² ) and passed at a speed of 5 / Hr, the overpressure was 3.3 kg / cm ² G, liquid 1.0 kg (quinoline insoluble content 0.01% or less) G and slag 0.12 kg ( Quinoline insoluble matter (39.3%) was obtained. After backwashing with solvent, perform this operation 10
Almost no increase in material resistance was observed even after repeated times.

This liquid was distilled under the conditions of 10 mmHg and 300 ° C. to remove the solvent and light boiling oil. The solid component contained in the obtained hydrogenated pitch was 8 ppm. The hydrogenated pitch was blown with nitrogen at a rate of ³ Nm ³ / Hr per 1 kg of pitch under normal pressure at 450 ° C.
And heat treated for 50 minutes. The optically anisotropic phase of the obtained mesophase pitch was 100%. Liquid temperature of this mesophase pitch is 340
Melt-spin at ℃, the obtained Pitch fiber with a diameter of 10μ was infusibilized by distillation in air from 150 ℃ to 300 ℃ for 1 hour, then at 1000 ℃ in Argon.
A carbon fiber was obtained by carrying out a two-step carbonization treatment of heating for 30 minutes and then at 2000 ° C. for 5 minutes. The physical properties of this carbon fiber are JIS-
As a result of measurement according to the single fiber tensile test method specified in R-7601, the tensile strength and the tensile elastic modulus are 370 kg / mm ²
And 52 ton / mm ² .

Example 2 Instead of the filter used in Example 1, stainless fiber having a thread diameter of 8 μm was defibrated into a cotton shape, and a felt compressed to a thickness of 5 mm was sandwiched by a wire mesh of 100 mesh to form a filter (shape). : Cylindrical, porosity about 80%, over-area 76cm ² )
A hydrogenated pitch and a carbon fiber were obtained in exactly the same manner as in Example 1 except that was used. The solid content of this hydrogenated pitch is 20ppm, and the tensile strength and tensile modulus of carbon fiber are 320kg.
/ mm ² and 49.0 ton / mm ² .

COMPARATIVE EXAMPLE 1 Instead of the filter in Example 1, the mesh size was 10 to 15 μm.
A carbon fiber was obtained in exactly the same manner as in Example 1 except that the graph filter of m was used. However, the carbonization treatment was performed at 1000 ° C. for 30 minutes plus, 2000 ° C. for 5 minutes, and 1000 ° C. for 35 minutes.
The tensile strength and tensile elastic modulus of this carbon fiber were measured. The results obtained are shown in Table 1.

As is clear from Table 1, when a glass filter having an opening of 10 to 15 μm is used, only carbon fibers having inferior strength can be obtained regardless of the difference in carbonization conditions.

Comparative Example 2 Distillation and heat treatment were performed in the same manner as in Example 1 without passing the hydrogenation reaction product obtained in the same manner as in Example 1. The optically anisotropic phase of the obtained mesophase pitch was 100%. When melt spinning was performed at 340 ° C. in this mesophase pitch, the duration of spinning with a yarn diameter of 10 μm was about 20 seconds at the maximum, and stable spinning was not possible. The obtained pitch fibers were slightly infusibilized and carbonized in the same manner as in Example 1. The carbon fibers obtained had inferior tensile strengths and tensile elastic moduli of 94 kg / mm ² and 45.0 ton / mm ^2. It was a thing.

(Effects of the Invention) According to the present invention, the solid component such as the solid catalyst contained in the hydrogenation reaction product can be made to an extremely small amount of 10 ppm or less by a simple operation. After spinning,
High-strength carbon fiber can be easily obtained by infusibilizing and carbonizing.

[Brief description of drawings]

FIG. 1 is an explanatory view of an example of a passing device used in the present invention, FIG. 2 is an enlarged vertical sectional view of an example of a filter element, FIG. 3 is a sectional view taken along line AA of FIG. 2, and FIG. 4 is a filter. FIG. 5 is an enlarged vertical sectional view of another example of the element, and FIG. 5 is a sectional view taken along the line BB in FIG. 2: Casing 3: Filter element 7: Material layer 8, 9: Wire mesh 10: Perforated pipe

Claims (6)

[Claims] 1. A method for producing a hydrogenated pitch for carbon fibers by reacting the pitch with hydrogen in the presence of an organic solvent and a solid catalyst for hydrogenation, wherein the hydrogenation reaction product is a nonwoven fabric of a heat resistant fiber or the nonwoven fabric. A method for producing a hydrogenated pitch for carbon fiber, which comprises supplying to a heating apparatus having a material layer made of a sintered body to remove a solid catalyst contained in the product. 2. The method for producing a hydrogenated pitch according to claim 1, wherein the heat resistant fiber has a softening point of 100 ° C. or higher. 3. The method for producing a hydrogenated pitch according to claim 1, wherein the heat-resistant fiber has a yarn diameter of 2 to 50 μm. 4. The method for producing a hydrogenated pitch according to claim 1, wherein the heat resistant fiber is a metal fiber or a ceramic fiber. 5. The method for producing a hydrogenated pitch as claimed in claim 1, wherein the persever is a candle type persever. 6. The method for producing a hydrogenated pitch according to claim 1, wherein the particle size of the solid catalyst for hydrogenation is 1 to 500 μm.