JPS63162559A - Manufacture of carbon fiber reinforced hydraulic composite material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a composite material made of a hydraulic raw material reinforced with carbon fibers.

(Conventional technology) Hydraulic composite materials, which are made by adding carbon fiber as a reinforcing material to various cements such as Portland cement, blast furnace cement, and alumina cement, and hydraulic raw materials such as gypsum, are lightweight, strong, and tough. As a material with the following characteristics, carbon fiber is increasingly being used in the fields of architecture and civil engineering, etc. Carbon fiber has various superior characteristics compared to other reinforcing fibers.

For example, glass fiber has poor alkali resistance and therefore has poor durability in cement, whereas carbon fiber has excellent alkali resistance and is superior in durability. Synthetic fibers such as vinylon, polypropylene, and aramid have inferior heat resistance and chemical resistance compared to carbon fibers, and when producing hydraulic composite materials, they have disadvantages such as being unable to withstand the autoclave curing process at high temperatures. Furthermore, metal fibers such as steel fibers suffer from deterioration due to corrosion in the cement matrix.

(Problems to be Solved by the Invention) Although carbon fiber is excellent as a reinforcing material, it is difficult to uniformly mix and disperse short carbon fibers in hydraulic raw materials, so that its reinforcing performance cannot be sufficiently improved. There was a problem that made it difficult to perform.

For this reason, the following various studies have been attempted to achieve uniform mixing and dispersion, but they are still insufficient and have many problems. For example, ■ viscosity 000cpa ~
A method of cooling and mixing a mixture of 100,000 cpe water-based viscous material and carbon fiber into a hydraulic composition mainly composed of cement and aggregate.

(Japanese Patent Publication No. 1986-Dasi-Da-λ) According to this method, uniform mixing and dispersion may be possible, but as shown in the examples, it is expensive to mix and disperse methylcellulose in an aqueous viscous body such as a water bath liquid. The carbon fibers are mixed in advance using a special mixer ('Omni-mixer': there is no stirring blade, a readable rubber ball is attached to the oscillating plate, and mechanically, diffusion mixing is performed at the same time). Since the resulting mixture is then mixed with a hydraulic composition using a tilting concrete mixer, it is essential to use a thickener such as methylcellulose, and two types of mixers are used. There are problems that need to be improved in terms of economy and operability.

■ A method in which short fibers such as carbon fibers are loosely bound with a binder and mixed into unhardened cement, and the short fibers are untied and dispersed by stirring the unhardened cement.

(Japanese Unexamined Patent Publication No. 10-10-06) In this method, it is explained that the degree of binding is such that it can be easily untied when stirred with an ``omni mixer'', and even in a practical series, it is said that the degree of binding is such that it can be easily untied when mixed with an ``omni mixer.'' However, in addition to the inconvenience of using a special mixer, the amount of binder used is 5/S to 9// as a fiber/binder volume ratio.
However, there are disadvantages such as the disadvantage of using a large amount of binder, and the fact that it is expected that a large amount of stirring power will be required to mix and disperse fibers in a cement slurry with water added, which has a high viscosity compared to cement with water-based additions. There is also.

(Means for solving the problem) In order to improve the problems of the conventional technology, the method and state of the carbon fibers used, the mixing method for uniformly mixing and dispersing the carbon fibers in the hydraulic raw material, etc. The method and structure of the mixer, as well as the physical properties of the resulting hydraulic composite material, were investigated in depth. As a result, the short d1. Using fibrous carbon fiber bundles, dry mix (dry kneading) with hydraulic raw materials for a very short time in a general-purpose mixer normally used for mixing hydraulic raw materials, then add water and knead! We discovered that hydraulic composite materials with excellent physical properties can be manufactured using a practical and economical method.
The invention has been completed.

In other words, the present invention provides a method for manufacturing a composite material by mixing and dispersing carbon fibers in a hydraulic raw material, in which carbon fibers have a bulk density of 0.0597 m1 or more as measured by the following method, and are 30 to 1 ml, Using a short carbon fiber bundle in which seven monofilaments are bundled, the hydraulic raw material and the carbon fiber bundle are mixed in a mixer with a rotating outer shell and/or a mixer with stirring blades. The present invention relates to a method for producing a carbon FFL fiber-reinforced hydraulic composite material, which comprises dry mixing and then kneading the resulting mixture with water.

[Method of measuring bulk density]

A carbon fiber bundle λθ1 with a length of 10rrs! The fiber bundle is placed in a glass graduated cylinder with a capacity of 00 ml, and the volume of the fiber bundle is measured after falling by repeatedly turning the graduated cylinder 5 times from a height of 3 crn on a wooden stand to determine the bulk density.

The present invention will be explained in detail below.

In the present invention, various inorganic hydraulic raw materials commonly used for building materials and civil engineering materials can be used, such as Portland cement, blast furnace cement, alumina cement, calcium silicate, natural gypsum, and synthetic gypsum.

The carbon fiber used in the present invention is not particularly limited as long as it is a known carbon fiber. For example, carbon fibers made from coal tar pitch, petroleum pitch, liquefied coal, polyacrylonitrile, cellulose, polyvinyl alcohol, etc. Fibers can be used.

Among them, carbon fiber made from pitch containing an optically anisotropic phase, that is, mesophase pitch carbon fiber, is a type of carbon fiber made from pitch containing an isotropic phase, which is conventionally mainly used as a reinforcing material for hydraulic raw materials. Since the tensile strength and tensile modulus of the fibers themselves are greater than those of the negative pinch type carbon fibers, it is preferable that when used in the present invention, a hydraulic composite material having greater strength and rigidity can be obtained.

In particular, when a mesophase pitch carbon fiber having a tensile strength of /00 Kg/wm2 or more and/or a tensile modulus of /00 Kg/wm2 or more is used, the physical properties of the resulting hydraulic composite material are even more excellent.

Regarding these carbon fibers, various methods are possible to produce the focused carbon fiber bundles having the desired bulk density for use in the present invention.

For example, after the raw material fibers obtained by spinning the above-mentioned raw materials are attached with a sizing agent and bundled to obtain a raw fiber bundle, this is treated to be infusible or flameproof, carbonized, and if necessary graphitized. It is possible to obtain a charcoal 2 flt fiber bundle. In this case, a carbon fiber bundle having a desired bulk density can be obtained by appropriately selecting and determining the type of sizing agent, amount of sizing agent, amount of sizing agent, and method of adhesion.

In addition, in the present invention, a graphitized fiber bundle obtained by graphitization treatment is also considered to be a carbon fiber bundle.

A variety of substances can be used as the above-mentioned sizing agent, such as polydimethylsiloxane derivatives such as polydimethylsiloxane and amine-modified polydimethylsiloxane, polyalkylene glycol derivatives such as polyethylene glycol and polypropylene/glycol, machine oil, turbine oil, One type of mineral oil such as kerosene, a fatty acid ester compound, a sulfide group-containing compound, a perfluoroalkyl group-containing compound, or a mixture of two or more thereof is used.

The sizing agent can be used alone or with a sizing agent as its main component and known antistatic agents, smoothing agents, and surfactants added.Furthermore, the sizing agent can be used to uniformly adhere to the fibers and to In order to reduce the resistance, instead of applying the focusing agent straight, it may be diluted with a known diluent such as water, kerosene, or dimethyl silicon dimer.

The amount of the binding agent attached to the raw material fibers is usually in the range of 0.1 to 20% by weight, particularly preferably 0.2 to lθ weight f%.

If the adhesion amount is less than 0.1% by weight, the obtained carbon fiber bundle will easily come apart, the desired bulkiness will not be obtained, and the monofilaments will become entangled when mixed with the hydraulic raw material.
This causes the inconvenience that fluff-like fiber balls are formed and uniform mixing and dispersion is not possible.

In addition, if the OM fit is 1 or more, the sizing agent that adhered during the infusibility treatment or flameproofing treatment will not be sufficiently volatilized and will remain on the fibers, causing inhibition of the reaction of the infusibility treatment or flameproofing treatment. Otherwise, the low molecular weight gases generated from the fibers cannot be sufficiently dispersed, which may actually cause deterioration of the physical properties of the carbon fibers.

As a method for attaching the sizing agent to the raw material fibers, a method of spraying it, a method of attaching it to a roller or a guide and bringing it into contact with it, a method of dipping it, etc. are used.

The bundle of raw material fibers to which the sizing agent has been attached is subjected to infusibility treatment or flameproofing treatment and carbonization treatment according to well-known methods. Infusibility treatment or flameproofing treatment is performed by subjecting the raw fiber to an oxidizing atmosphere such as oxygen, ozone, air, nitrogen oxides, halogen, sulfur dioxide gas, etc. This is carried out by heating at a temperature of 0 to 700°C for about 10 minutes to 10 hours.

In addition, the carbonization treatment is performed by adding nitrogen to the fibers obtained through the above treatment.
Under an inert gas atmosphere such as argon, jθO-co000℃
at a temperature of 0. ! This is done by heating for about r minutes to 10 hours.

Furthermore, when graphitizing treatment is performed, 20θO~300
It may be heated to a temperature of 0° C. for about 1 second to 1 hour.

Another method is to attach a sizing agent to the raw material fiber bundle of the present invention, perform an infusible treatment or a flame resistant treatment, and then re-adhere a sizing agent to the resulting infusible or flame resistant fibers and bundle them. The desired carbon fiber bundle can be obtained by carbonization and, if necessary, graphitization.

The specific type, amount, and method of applying the sizing agent to these infusible or flame-resistant fibers can be carried out in the same manner as for the raw material fibers described above. It can be implemented in the same way as in the case.

Still another method is to produce a bundle of carbon fibers produced by attaching a sizing agent to the raw material fibers and/or the infusible or flame-resistant fibers in the process of the present invention, or by a conventional method. By attaching a sizing agent to carbon fibers, the desired focused carbon fiber bundle can be obtained, and the type of sizing agent, amount of attachment, attachment method, etc. can be adjusted as appropriate.
As a result, a bundle of carbon fibers having a desired bulk density can be obtained.

Specific sizing agents include polyvinyl alcohol (PTA) based unsaponified polyvinyl acetate, partially saponified PVA, completely saponified PVA, and modified PVA such as itaconic acid modified, 7-tar acid modified, and acrylic acid modified. P
There is a VA.

Also, vinyl acetate and ethylene, maleic acid, crotonic acid,
Alternatively, copolymers with acrylic acid, cellulose derivatives such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose, and hydroxyethyl cellulose, starch derivatives such as corn starch and soluble starch, and acrylic polymers such as sodium polyacrylate and polyacrylamide may also be used.

Furthermore, rubber latex, epoxy resin with a softening point of 90° C. or higher, and polyurethane that do not contain a hardening agent can also be used. Among these polymers, those exhibiting cationic properties are particularly effective in improving adhesion with cement, such as cation-modified PTA, cationic polyvinyl acetate,
Cationic pumice latex, cationized polyurethane, etc. are used.

The above sizing agents are attached to carbon fibers in the form of an aqueous solution, an emulsion, or a solution dissolved in a solvent, as one type or a mixture of two or more, and then dried or desolventized.
A focused carbon fiber bundle is obtained.

The amount of sizing agent attached to carbon fiber is usually 0.1 to 2.
It is 0% by weight. 0. / If it is less than 100%, the convergence will be insufficient, the desired bulk density will not be obtained, and uniform mixing and dispersion in the hydraulic raw material will not be possible. In addition, if it exceeds 20% by weight, the bundle becomes too strong, the degree of dispersion in the hydraulic original is poor, the physical properties of the hydraulic composite material deteriorate, and the fiber bundles may be attached to the roller during sizing treatment. There are disadvantages such as the fact that it is difficult to manufacture because it is difficult to manufacture. Furthermore, a more appropriate range of adhesion amount is selected depending on the type of sizing agent. For example, unsaponified polyvinyl alcohol (PVA)-based poly I! rll:
C role vinyl, partially saponified P''JA, fully saponified PVA,
and cationic modified products thereof are preferably 9.
3 to 70% by weight, more preferably Fio, 5-23% by weight.

The sizing agent can be applied by spraying, by attaching it to a roller or guide, or by dipping it.

Furthermore, the carbon-silver fibers that can be used in the present invention include those that have been carbonized or graphitized according to the method described above, and then subjected to surface treatment such as oxidation or electrolytic treatment in the gas phase or liquid phase, and those that have been further treated with a sizing agent. Processed products can also be used.

In the present invention, the number of monofilaments constituting the thus obtained focused carbon fiber bundle is 30 to 1,000.
Suitably a book, preferably 50~b, o o
It is desirable that the number of books is o.

If there are fewer than 30 fibers, there are problems such as poor productivity when producing a bundled fiber bundle, while if there are more than θθθ fibers, it may be difficult to bundle them into a single bundle, or it may be difficult to bundle them in hydraulic raw materials. This is disadvantageous because the dispersibility of the liquid may deteriorate.

- preferable for dispersion in

Next, in the present invention, the bundled carbon fiber bundles are made into short fibers and mixed with the hydraulic raw material, but the method for producing the fiber bundles is to cut the bundled long fiber bundles, or to cut the bundles that have already been made into short fibers. Any of the things that are focused can be used.

The method of shortening the strands can be a commonly used method, for example,
Can be cut using a guillotine cutter, roving cutter, or direct spray machine nozzle gun.

When cutting a long fiber bundle that has already been bundled, it is desirable to prevent the bundle from becoming too loose by using an excessive cutting screen or the like.

It is preferable that the length of the bundle of short fibers is 1100 rrr. / If the temperature is less than 1100 r, the dispersibility during mixing with hydraulic raw materials is good, but sufficient reinforcing performance cannot be obtained.
On the contrary, if it exceeds r, reinforcing properties can be obtained, but the dispersibility is poor and a uniform product cannot be obtained.

One important aspect of the present invention is that the bulk density of the short carbon fiber bundle obtained as described above is 0.0! -11/
rnl1 or more, preferably θ, 071//m1 or more.

The bulk density is jt0 of carbon fiber bundle 201/ with length 10tts
The sample is placed in a glass measuring cylinder with a capacity of 0 ml, and the volume (VmJ) after the cylinder is repeatedly dropped from a height of 3 cnt j times on a wooden stand is measured, and the volume (VmJ) is determined by the calculation: U0/V.

Bulk density is 0.0! If it is less than 11/m1, when mixed with hydraulic raw materials by the method of the present invention, the fibers may come apart in the form of monofilaments, become entangled, or form fluff-like fiber balls, which are then dispersed uniformly. The resulting product may have poor physical properties or be non-uniform.

The short carbon fibers that have been used in the past have a flocculent shape or are poorly focused, so they have a low bulk density. However, in the present invention, the bulk density is reduced by devising a focusing method.
By combining the use of fiber bundles of , o sy ~ or more and the use of an inexpensive and large-capacity mixer that is commonly used for mixing with hydraulic raw materials, it is possible to mix and disperse in a very short time. In particular, there is a #f sign.

The mixer used in the present invention may be a general-purpose mixer such as the following by Kozo, which has a rotating outer jacket and/or a stirring blade.

Mixing machines with rotating cylindrical, double conical, and regular cubic shells include tilting concrete mixers and rotating drum mixers.Also, paddle type, propeller type, tower type, turbine type, and pan type. , ribbon type, screw type, Warner type, kneader type or the like having a 1W stirring blade is used.

Furthermore, a pan-rotating forced mixer, an Eirich type mixer, and the like having a rotating outer shell and stirring blades are also used.

These mixers used in the present invention mainly perform convection and/or assisted mixing in terms of mixing mechanism.

Next, when mixing the carbon fiber bundle and the hydraulic raw material,
It is important to first mix without adding water, then add water and knead.

If water is added from the beginning, the hydraulic raw material becomes a viscous slurry, which is disadvantageous because it requires a large stirring power or takes a long time to disperse the fiber bundles.

In contrast, in the present invention, dry mixing is performed without adding water, so
The stirring power is low and mixing can be done in a short time, for example, paddle type mixing 8! (J-Ko S R3 CoO/standard cement mixing iso), it can be mixed in an extremely short time of 70 seconds to several minutes, and the productivity is superior, and the physical properties of the resulting hydraulic composite material are better than those of a special mixer. It is as good as or better than the one using .

Carbon fiber content t in hydraulic composite material is usually 0, / ~ 20
If it is less than 0.1%, the reinforcing effect will be poor, while if it exceeds 0%, it will be difficult to mix or uniformly disperse, which is undesirable.

Further, it is desirable to mix aggregates such as sand, silica sand, gravel, crushed stone, shirasu balloons, fly ash, and ultrafine silica in advance during this dry mixing to facilitate mixing with the hydraulic raw materials.

The resulting mixture of hydraulic raw materials and carbon fibers is then kneaded with water, for example, by directly adding water to the resulting mixture in a mixer and then kneading it, or by mixing the mixture for the first time. A method in which hydraulic raw materials and carbon fibers are continuously supplied to a machine, and the resulting mixture and water are continuously supplied to a metal mixer to perform cross-mixing, or from one end of a horizontally long cylindrical mixer. Possible methods include continuously supplying hydraulic raw materials, carbon fibers, and water from the center, respectively, mixing at the front stage of the mixer and kneading at the rear stage.

It is preferable to add a dispersant at the time of mixing and/or cross-wiring, and specifically, cellulose derivatives such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose, and hydroxyethyl cellulose, polyamide mold,
Cationic surfactants such as polyamine type, alkylpicolinium salt type, water-soluble acid type of alkylamine, alkylamine oxide type nonionic surfactant, alkylglycine type, alkylalanine type, alkylbetaine type,
One type or a mixture of two or more amphoteric surfactants such as alkylimidacillin type surfactants are added.

The amount of dispersant added is usually 0.1 to 10% based on the hydraulic raw material.
If it is less than o, i%, the dispersion effect is poor, and 1
Even if it is added in excess of 0%, no particular effect will be obtained.

In addition to the dispersant, admixtures such as a water reducing agent, a foaming agent, and an antifoaming agent can also be added as appropriate.

The bundled a,re fiber-like carbon fiber bundle used in the present invention is
Not only can it be used alone in hydraulic raw materials, but it can also be used in combination with other reinforcing materials other than those of the present invention, such as carbon fibers, asbestos, glass fibers, metal fibers, organic fibers, and iron-based reinforcing materials.

The hydraulic raw material containing carbon and basic fibers of the present invention is molded by various commonly used molding methods, such as molding, extrusion, centrifugal molding, and paper molding, and is then cured, solidified, and branched. Hydraulic composite materials can be manufactured in various shapes such as circular, tubular, and columnar.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example: A seven-novel filament obtained by melt-spinning coal tar pitch-based meso 7Aze Vinci (1 gO raw material fibers) using polydimethylsiloxane with a viscosity of 10 centistokes (25°C) as a guide. By the method of attaching and contacting, five pieces of rice cake were attached to the raw material fibers and bundled. This focused coolant fiber bundle is heated in air from 170°C to θ0°C while being infusible, and then in an argon atmosphere from room temperature to /1t00'c. Carbonization treatment was carried out over a period of 0.5 hours while increasing the temperature to obtain a carbon fiber bundle, the properties of which are shown in Table 1. Next, the carbon fiber bundle was cut with a chironan cutter to a length of 1
A short fiber bundle of 0 m length was obtained and the bulk density measured by the method described above is shown in Table 1. Subsequently, the short fiber bundle, early strength Portland cement <1003iK Hanto), silica sand (jOJ
kt part) and methylcellulose (0,3 parts) were put into a cement mixer (Mortar Mixer 1-1Q-/, 3gA type, made by Maruto Seisaku FDr) of J-Ko S R1,2θ/standard, and mixed for 30 seconds. After mixing the entire mixture in which short fibers were sufficiently dispersed, water (qsTL parts) was added for 7 minutes, and an antifoaming agent was added and kneaded for 30 seconds. A carbon fiber-reinforced cement material containing carbon fibers with a carbon fiber content of 43 mm was obtained by shaking with a kW of 4' m and a thickness of 1 cm) and curing in air (temperature 20°C, relative humidity A5%). The bending strength of the test piece J
The average k and Atsushi WJ lO values are shown in the first column.

Example A water emulsion of polydimethylsiloxane (emulsion IAK 3.3%) was attached to a guide and contacted with a raw material fiber having seven filaments (the number of which is θ) obtained by melt-spinning cocoal tar pitch-based meso 7Aze pinch. By this method, 10% of the fibers were adhered to the raw material fibers and bundled. This focused raw material fiber bundle was placed in the air at 730°C for 30 minutes.
It took 2.7 hours to raise the temperature to IO'C, held it at 310°C for 5 hours to make it infusible, and then heated it from room temperature to 7100°C in an argon atmosphere in 4.3 hours. The temperature was raised at 7100° C. for 7 hours to carry out carbonization treatment.

The properties of the obtained carbon fibers are shown in Table 1.

Next, the carbon fibers were continuously immersed in the form of long fibers in an aqueous solution (concentration θ0g%) of polyvinyl alcohol (sizing agent) with a saponification degree of 0%, and dried at 7gθ℃, so that the sizing agent was coated with gz. A focused carbon fiber bundle with e4 deposition was obtained.

Table 1 shows the bulk density of short fiber bundles obtained from this carbon fiber bundle in the same manner as in Example 1.

Subsequently, Table 1 shows the bending strength of a test piece of carbon fiber reinforced cement material obtained using this short fiber bundle in the same manner as in Example.

Comparative example/ Early strength Portland cement (100 layers), silica sand (
50 parts by weight), and methylcellulose (o, r heavy parts)
was put into the same cement mixer as in Example 1, mixed for 30 seconds, water (+5 parts) was added for 30 seconds, and then the same short fiber bundle as in Example 1 was added (3 volume t%). ) for 1 minute, then an antifoaming agent was added and kneaded for 30 seconds.

Subsequently, Table 1 shows the bending strength of test pieces of carbon fiber reinforced cement materials obtained in the same manner as in Example 1.

Comparative Example - Short fiber bundles produced by the implementation side, early strength Portland cement (10
0 parts by weight), silica sand (25 parts by weight), and methylcellulose (0.5 parts by weight) were placed in an 'Omnimixer' (Chiyoda Giken OM-/θE type IOT capacity) and dry mixed for 7 minutes. , then water C'l! After kneading for a total of 77 minutes, adding the remaining silica sand (23 parts by weight) and kneading for 3 minutes, the remaining silica sand (23 parts by weight) was added and kneaded for 3 minutes.
Table 1 shows the bending strength of test pieces of carbon fiber reinforced cement material obtained in the same manner as above.

Comparative Example 3 Without sizing the carbon fiber of Example 3,
Table 1 shows the bulk density of the short spruce fibers cut in the same manner as in Example 1. However, since this short fiber is cotton-like and bulky, the fil and fiber amount for bulk density measurement were set to 109. When mixed in the same manner as in Example 1 using short fibers of
The fiber poles were not evenly dispersed due to entanglement or fluffy fiber poles, and the bending strength shown in Table 1 had a small average value and was significantly inferior during fluctuation.

(Effects of the Invention) According to the present invention, a bundle of short carbon fibers having a bulk density greater than a predetermined limit is dry mixed with a hydraulic raw material, and then water is added and kneaded. These mixing and kneading can be carried out in a very short time using a general-purpose, simple mixer and are highly practical.

With conventional carbon fibers, it is difficult to mix and disperse them uniformly, and in order to improve mixability, it is difficult to mix and disperse them, and the disadvantages of using an expensive and special mixer for a considerable amount of time can be overcome.

In addition, the obtained hydraulic composite material has good dispersion of carbon fibers, so the quality is uniform, and the adhesion effect between the fibers and the hydraulic raw material is good, so it has excellent physical properties such as strength, toughness, and crack resistance.

Sender: Mitsubishi Chemical Industries, Ltd. Representative Patent Attorney Naga Kagawa - Others/names

Claims (7)

[Claims] (1) In a method of manufacturing a composite material by mixing and dispersing carbon fibers in a hydraulic raw material, the carbon fibers have a bulk density of 0.05 g/ml or more as measured by the following method,
A short carbon fiber bundle containing 30 to 12,000 monofilaments is used to mix the hydraulic raw material and the mixture in a mixer with a rotating outer shell and/or a mixer with stirring blades. A method for producing a carbon fiber-reinforced hydraulic composite material, which comprises dry mixing carbon fiber bundles and then kneading the resulting mixture with water. [Method for measuring bulk density] 20 g of a carbon fiber bundle with a length of 10 mm was placed in a glass measuring cylinder with a capacity of 500 ml, and the measuring cylinder was repeatedly dropped from a height of 3 cm 5 times on a wooden stand. Measure the capacity of the fiber bundle and determine the bulk density. (2) The method according to claim 1, wherein the length of the carbon fiber bundle is 1 to 100 mm. (3) The method according to any one of claims 1 to 2, wherein the diameter of the monofilament constituting the carbon fiber bundle is 3 to 50 microns. (4) When the carbon fiber bundle bundles the raw material fibers, a binding agent is attached to the carbon fiber bundle, and then an infusible treatment or flameproofing treatment is performed,
The method according to any one of claims 1 to 3, which is obtained by further performing carbonization treatment. (5) Any one of claims 1 to 3, wherein the carbon fiber bundle is obtained by subjecting raw fibers to infusibility treatment or flameproofing treatment, then adhering a sizing agent, and then carbonization treatment. Method described in Crab. (6) The carbon fiber bundle is obtained by subjecting raw material fibers to infusibility treatment or flameproofing treatment, followed by carbonization treatment, and then adhering a sizing agent and bundling. Claim 1
The method described in any one of Items 1 to 5. (7) When mixing and/or kneading the hydraulic raw material and the carbon fiber bundle, one or a mixture of two or more of cellulose derivatives or cationic, nonionic, or amphoteric surfactants is added as a dispersant. Claim 1
The method described in any one of Items 1 to 6.