JPH0153362B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing carbon fiber.

In recent years, approaches to shape have become more prominent in order to improve carbon fibers that take advantage of the many advantages of carbon, such as heat resistance and chemical resistance. The most important example is hollow carbon fiber, which makes it possible to reduce weight and improve heat insulation.

However, conventional methods for producing hollow carbon fibers have had several drawbacks. For example, a method in which a phenolic resin whose main component is novolac is melt-spun, then partially cured, and then the uncured portion is eluted with a solvent to form hollow fibers, which are then carbonized (Japanese Patent Publication No. 51-5090). , by contacting the fibers made of organic polymer with sulfuric anhydride or chlorosulfonic acid, the inner core is left untreated and the surface is treated, and then this is heated to a temperature higher than the thermal decomposition temperature of the organic polymer and fired. (Japanese Unexamined Patent Publication No. 49-101618), polyacrylonitrile fibers are heated in an oxidizing atmosphere to
A method of carbonizing the flame-resistant fibers obtained by heating to 300℃ and heating them to 500℃ or higher in a non-oxidizing atmosphere ( Although it is disclosed that hollow carbon fibers can be obtained using known methods such as JP-A No. 50-142819), the treatment of the fibers before heat treatment is insufficiently controlled, and the fibers during heat treatment are If the shrinkage becomes too large, the shape of the hollow portion of the obtained carbon fiber becomes substantially uncontrollable.

The present invention has been made in view of the above-mentioned points, and includes an organic substance A having a high carbon yield through calcination,
Fibers made of organic matter B, which also has a low carbon yield, and/or inorganic matter that is vaporized in the process of heat treatment up to the calcination temperature or removed by chemical treatment, are processed without causing the disappearance of the organic matter B or the inorganic matter. The gist of the present invention is a method for producing carbon fibers, which comprises subjecting organic substance A to flame-retardant treatment, and then heat-treating the organic substance A to a firing temperature and removing the inorganic substance by chemical treatment as necessary. .

First, to explain the materials used in the present invention, organic substances A include chlorine-containing resins such as polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, chlorinated polyvinyl chloride, and chlorinated polyethylene. In addition to various synthetic resins such as furan resins and polyacrylonitrile, examples include pitch, such as dry distillation of polyvinyl chloride in a non-oxidizing atmosphere, cellulose derivatives, lignin derivatives, gum arabic, and polyvinyl alcohol. Examples include polyethylene, polypropylene, polybutadiene, polyisobutylene, polystyrene, nylon, polymethyl methacrylate, polyethyl methacrylate, poly-α-methylstyrene, polymetamethylstyrene, trifluorostyrene, poly-α-deuterostyrene, Examples include polyester, natural rubber, butyl rubber, polytetrafluoroethylene, rosin, salicylic acid, anthraquinone, naphthacene, etc., but complete classification is by no means necessary. That is,
Powders and organic complex salts of metals (including alloys) such as chromium, manganese, iron, cobalt, nickel, zinc, and copper, and their oxides and carbides, as well as emulsions and dispersions as appropriate. This is because the carbon yield can be increased by using together with a substance that acts as a carbonization accelerator while being used in a small amount. Therefore, organic matter A and organic matter B are in the form of fibers and are mixed with other materials so that the carbon yield is high or low (including zero) by heat treatment up to the firing temperature described below. It also shows compounds that have been made into compounds. In addition, inorganic substances include aluminum, zinc, cadmium, copper, cadmium oxide, barium oxide, calcium carbonate, sodium carbonate,
Examples include sodium chloride and zinc sulfide.
Any material may be used as long as it is vaporized during the heat treatment up to the firing temperature or removed by chemical treatment.
Typical examples of chemical treatment include dissolution and removal using an aqueous acid or alkali solution or water.

Inorganic substances have the same basic purpose of use as organic substance B. However, there are differences in the ranges that are preferably used. Inorganic materials generally have poor moldability; for example, considerable ductility is required to form them into thin wires, or they are subject to size restrictions, such as whiskers. Comparatively, organic matter B costs
It is superior to inorganic materials in terms of moldability, but inferior in thermal stability. Therefore, in order to obtain hollow carbon fibers, it is generally more advantageous to use organic material B that is easy to fiberize and whose cross section is polygonal, such as a star, or circular, and to obtain dispersed porous carbon fibers. Then, particleization,
It is generally advantageous to use inorganic materials since they are easier to powder.

Moreover, the combination of inorganic substance and organic substance B produces various advantages. For example, hollow and dispersed porous carbon fibers, which are preferred as filter materials, can be easily obtained by combining the above-mentioned materials, and the advantages of both can be obtained by using, for example, organic material B whose surface is plated with metal. .

Next, it consists of one or more types of each of the above-mentioned organic substance A, organic substance B, and inorganic substance, as well as a plasticizer, a solvent, a stabilizer, etc., which are used as necessary.
The carbon fiber treatment of the fibers, which are bundled, twisted, etc. as necessary, will be explained.

When considering the organic substance A as the main component, carbon fiber treatment can be roughly divided into flame resistance and carbonization. Flame-retardant treatment increases the proportion of carbon in organic substance A, which has the effect of maintaining shape and improving product strength.
There are methods such as low-temperature heat treatment, such as around 300℃, and chemical treatment, but from an industrial perspective, heat treatment is preferred because it allows production of relatively large items and mass production, and has excellent quality stability. suitable. The only problem in heat treatment is to be careful not to cause organic matter B and inorganic matter to disappear due to depolymerization, sublimation, etc. during heat treatment. Of course, even in the case of chemical treatment, it is necessary to pay attention to the disappearance of organic matter B and inorganic matter. If organic matter B and inorganic matter disappear before organic matter A becomes sufficiently flame resistant and the remaining organic matter A fibers are carbonized, the hollow or pore portions will become uncontrollable due to large fiber shrinkage, as in the conventional technology. will occur. Therefore, in the case of heat treatment, preferable examples of the organic substance B used include those having a high decomposition temperature, such as nylon and polytetrafluoroethylene. In addition, materials with a high decomposition temperature generally have high softening and melting points, and for example, when vinyl chloride is used as organic substance A to obtain hollow carbon fibers, they act as the main character of the shaped fiber during heat treatment. It may also be possible. It goes without saying that flame-resistant vinyl chloride can maintain its shape by itself.

Carbonization treatment is heat treatment of organic matter A until it is sufficiently carbonized and, in some cases, graphitized. In the present invention, this is referred to as heat treatment up to the firing temperature, but it may also be treated in a reducing atmosphere such as a nitrogen atmosphere, or in a reducing atmosphere such as a nitrogen atmosphere. 500℃ in what is generally called a non-oxidizing atmosphere such as a vacuum atmosphere
This is done by heating to about 3000℃. It graphitizes at high temperatures. In this process, most or all of the organic matter B disappears, and the inorganic matter also disappears. As described above, inorganic substances that do not disappear are appropriately removed in advance and/or further by chemical treatment.

In some cases, not all inorganic substances are actively removed. Either no chemical treatment is applied, or even after chemical treatment some inorganic matter remains. For example, when obtaining hollow carbon fibers, organic material B is made into a thin wire, the surface is covered with metal plating, etc., and the fiber with organic material A present on its outer periphery is further heat-treated to remove only organic material B. Then, a carbon fiber having metal in the hollow wall portion is obtained. There is no need to remove metal when there is a need for improved conductivity or metallic elasticity.

Example 1 A 6.6 nylon fiber with a thickness of 3 mils was immersed in a solution of polyacrylonitrile and 30% dimethylformamide, passed through a 0.3 mmφ die, and immediately dried.
6.6 A fiber made of nylon whose outer periphery was substantially uniformly covered with polyacrylonitrile was obtained, and this was subjected to flameproofing treatment at 200°C for 10 hours in an air atmosphere, and then heated to 500°C at a rate of 20°C/hour in a nitrogen atmosphere. Warm and then
Hollow carbon fibers were obtained by increasing the temperature to 1300°C at a rate of 100°C/hour and heat treating the fibers at 1300°C for 1 hour.

Example 2 Polytetrafluoroethylene fibers with a thickness of 6 mils were extruded using an extruder using a crosshead in the same manner as for covering electric wires so that vinylidene chloride-acrylonitrile copolymer was distributed around the outer periphery of polytetrafluoroethylene fibers with a thickness of 10 mils. This was subjected to flameproofing treatment at 230°C for 3 hours in an oxygen atmosphere (in this case, the vinylidene chloride-acrylonitrile copolymer undergoes a dehydrochloric acid reaction), and then
In a vacuum atmosphere, the temperature was raised to 700°C at a rate of 20°C/hour, then the temperature was raised to 1500°C at a rate of 100°C/hour, and the fibers were heat-treated at 1500°C for 1.5 hours to obtain hollow carbon fibers.

Example 3 A mixture of 70% by weight of polyvinyl chloride, 25% by weight of zinc oxide powder, and 5% by weight of a plasticizer (dioctyl phthalate) was placed in the cylinder of a ram extruder, and heated to 120°C to form a thin wire of 0.1 mmφ. It was pushed out. This was flame-resistant treated at 230℃ for 5 hours in an air atmosphere.
Next, heat treatment was performed in a nitrogen atmosphere at a rate of 30°C/hour to 1100°C and maintained at 1100°C for 30 minutes to obtain dispersed porous carbon fibers.

Example 4 Everything was the same as in Example 1, except that the nylon fibers had a nickel film formed in advance by electroless plating and electroplating thereon.

Example 5 In Example 3, the flame-retardant fibers were heat-treated up to 700°C in a nitrogen atmosphere to the firing temperature.
The procedure was the same as in Example 3 except that the temperature was increased at 20°C/hour and the heat treatment was maintained at 700°C for 1 hour, and further,
It was treated in a 10% aqueous hydrochloric acid solution for 10 hours in an ultrasonic cleaning manner.

As described above, including each embodiment shown as an example, the present invention uses a substance that should be carbonized and a substance that should not be carbonized together, brings the substance that should be carbonized to a state where it should be sufficiently carbonized, and then carbonizes the substance. It is based on the idea of removing substances that should not be carbonized and carbonizing substances that should be carbonized.
It is possible to obtain the desired carbon fiber according to the shape of the substance to be removed, and also to obtain fibers with good dimensional accuracy regardless of the thickness of the fiber, for example, 1 μm is 1 mm. This not only improves the functional quality of conventional applications such as liquid filter materials and insulation materials, but also enables the expansion of applications such as electrical fields.

Claims (1)

[Claims] 1 An organic substance (A) with a high carbon yield through calcination,
Similarly, fibers made of organic matter (B) with a low carbon yield and/or inorganic matter that is vaporized during the heat treatment process up to the calcination temperature or removed by chemical treatment are used to reduce the disappearance of the organic matter (B) and inorganic matter. Production of carbon fibers, characterized in that the organic substance (A) is flame-resistant treated without generation, and then the inorganic substance is removed by heat treatment up to the firing temperature of the organic substance (A) and, if necessary, chemical treatment. Method.