JP2756068B2 - Carbon fiber and cement composite for cement reinforcement - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon fiber for reinforcing cement and a cement composite using the same.
More specifically, the present invention provides a carbon fiber for cement reinforcement that has excellent adhesion to cement, has good processability with a direct spray gun, and has good convergence, and is particularly suitable for the direct spray method. And a cement composite having high flexural strength using the same.

[0002]

2. Description of the Related Art In recent years, carbon fibers have excellent characteristics such as high strength, high elastic modulus and light weight. Therefore, carbon fibers are used in various fields such as aircraft parts, automobile parts and sports equipment. Demand for such materials as resin reinforcing materials and cement reinforcing materials is increasing remarkably.

Also, kneaded materials using hydraulic powders of cements are widely used in various building materials, civil engineering materials and the like. In order to reinforce such a kneaded material and prevent crack generation, a fiber material has conventionally been blended. However, the use of asbestos as a reinforcing fiber is not preferable from the viewpoint of carcinogenicity, and has the disadvantage that the strength of the glass fiber itself is deteriorated in the cement because the glass fiber has poor alkali resistance. For this reason, various organic fibers and alkali-resistant glass fibers are used as reinforcing materials.However, organic fibers have a problem in terms of fire resistance. In this case, there is a problem that the strength is reduced when used for a long time. Accordingly, attention has been paid to carbon fibers which are excellent in heat resistance and chemical resistance, and have high strength and high elastic modulus.

However, when carbon fibers are added to and mixed with cement, the adhesiveness (or adhesion) to cement is inferior to that of asbestos or glass fibers, so that there is a problem that a sufficient effect as a reinforcing material cannot be exhibited. Therefore, various devices have been devised to increase the adhesion of carbon fiber to cement and to increase the strength of the obtained carbon fiber reinforced cement material. For example, a method in which a carbon fiber strand impregnated with a hydrophobic liquid resin such as an epoxy resin is stretched in cement and the resin and the cement are simultaneously cured (Japanese Patent Publication No. 58-19620), a water-soluble binder such as methylcellulose. (Japanese Patent Application Laid-Open No. 56-129657) in which carbon fibers bonded to each other are oriented in one direction or two directions crossing each other in cement, and a water-soluble synthetic resin emulsion such as an acrylic emulsion is included. A method in which a cement slurry layer is overlapped via a carbon fiber sheet (Japanese Patent Application Laid-Open No. 58-223659), a nonionic property such as polyalkylaminoacrylate or the like on the fiber surface when a reinforced cement material is manufactured by the Hachiek-type papermaking method, A method of attaching a cationic polymer flocculant (JP-A-60-81052), a carbon fiber Surface cationic rubber latex the deposited cement reinforcing fiber material (JP 62-108755 JP) have been proposed.

[0005] However, these conventional techniques have problems such as a limitation in the form of the carbon fiber used, a limitation in the construction method, a limitation on the type of cement to be applied, and insufficient adhesion to the cement. Which is not always satisfactory. By the way, recently
In the production of concrete composites using various fibers as reinforcements, the direct spray method, which can use longer fibers (25 to 30 mm or more) and sufficiently exhibit mechanical properties, has attracted attention. Has been Further, in a fiber manufacturing process, a proposal is made to apply pitch-based carbon fibers having improved sizing properties by using a special sizing agent to a direct spray method (Japanese Patent Laid-Open No. 62-300).
No. 08), but it is difficult to apply to carbon fibers in general because the production method and the form of carbon fibers are limited. Furthermore, when this direct spray method is applied, the reinforcing carbon fiber has good adhesiveness to cement and has excellent processability to the direct spray gun, that is, low friction between the carbon fiber and the metal, and is slippery. This is very important.

[0006]

SUMMARY OF THE INVENTION Under such circumstances, the present invention provides excellent adhesiveness to cement, good processability with a direct spray gun, and good convergence. In particular, it is an object of the present invention to provide a carbon fiber for cement reinforcement suitable for a direct spray method and a cement composite having high bending strength using the carbon fiber.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, by applying a sizing agent composed of a polyetherester to the surface of carbon fiber, The carbon fiber for cement reinforcement is excellent in the adhesiveness of the carbon fiber, and has good processability to the direct spray gun, and has good convergence. The carbon fiber has a specific length and a specific ratio. The cement composite was found to have a high flexural modulus. The present invention has been made based on such findings. That is, the present invention provides a carbon fiber for cement reinforcement, characterized in that a sizing agent made of polyetherester is applied to the surface of the carbon fiber. The present invention also provides a cement composite having a flexural strength of 300 kgf / cm ² or more, which is obtained by cutting the carbon fiber into a fiber length of 10 to 50 mm and containing the carbon fiber at a volume mixing ratio of 1 to 5% with respect to a cement matrix. To provide.

In the present invention, pitch-based, PAN-based and rayon-based carbon fibers can be used.
Spinning, infusibility (flame resistance), carbonization,
If the graphitized tensile strength is 150 kgf / mm ² or more,
Those having a tensile modulus of 10 × 10 ³ kgf / mm ² or more can be preferably used. In addition, mesophase pitch-based carbon fibers, which easily exhibit an elastic modulus compared to the cost, can be particularly preferably used.

In the present invention, a sizing agent is applied to the surface of the carbon fiber. The sizing agent may be applied directly to the surface of the carbon fiber or, if desired, the surface of the carbon fiber may be coated by a known method. For example, it may be applied after being processed by a liquid phase oxidation method using an oxidant, a heat cleaning method, a gas phase oxidation method, a whiskering method, an electrolytic oxidation method, or the like. As the sizing agent, a polyether ester is used. Suitable examples of the polyetherester include those obtained by subjecting a dicarboxylic acid component and a glycol component to a polycondensation reaction in the presence of a catalyst, and those obtained by polycondensing dimethyl terephthalate, ethylene glycol adipate and ethylene glycol. Is exemplified. The sizing agent composed of the polyether ester may be used alone or in combination of two or more.

The method for applying the sizing agent is not particularly limited, and a solution dissolved in an appropriate solvent or an emulsion emulsified in an aqueous medium is prepared, and a carbon fiber strand is contacted or immersed in the solution. The surface of the carbon fiber is coated with a sizing agent by desolvation by a known method, for example, hot air drying, infrared drying, microwave drying, or the like. The amount of the sizing agent applied is preferably in the range of 0.5 to 10% by weight based on the carbon fiber. When the amount is less than 0.5% by weight, the effect of the present invention is not sufficiently exerted. When the amount is more than 10% by weight, the convergence becomes excessively strong, the degree of dispersion in cement is poor, and the physical properties of the cement composite deteriorate. There is a tendency. The number of monofilaments constituting the carbon fiber bundle thus treated is 30 to
It is desirable that the number be 12,000, preferably 50 to 6,000. Those having less than 30 monofilaments are inferior in productivity when producing bundled fiber bundles,
When the number exceeds 000, it becomes difficult to bundle them in a bundle, or the dispersibility in cement becomes poor. The carbon fiber for cement reinforcement obtained in this way has excellent adhesion to cement, low friction with metal, and is slippery. Good, especially suitable for direct spray method.

In the cement composite of the present invention, the carbon fiber for cement reinforcement is cut to a fiber length of 10 to 50 mm, and a volume mixing ratio of 1 to 5% with respect to a cement matrix.
In the ratio of There is no particular limitation on the method of cutting the carbon fiber, and the cutting can be performed using, for example, a guillotine-type cutter, a roving cutter, or a nozzle gun for direct spraying. When the fiber length is less than 10 mm, the dispersibility at the time of mixing with the cement is good, but sufficient reinforcing performance cannot be obtained, and the fiber length is 50 m.
If it exceeds m, the reinforcing property can be obtained, but the dispersibility is reduced, and it is difficult to obtain a uniform product. Further, when the mixing ratio of the carbon fiber to the cement matrix is less than 1% by volume, the reinforcing effect is not sufficiently exhibited. When the mixing ratio is more than 5%, it is difficult to mix or cannot be uniformly dispersed. Invite no situation.

There is no particular limitation on the method for forming the cement composite by incorporating the carbon fibers into cement,
Various methods conventionally used, for example, a direct spray method or a premix method can be used,
In the present invention, the direct spray method is particularly preferably used. The direct spray method is a method in which a roving of carbon fiber is blown out from a nozzle of a compressed air gun while being continuously cut, and simultaneously blown with a cement slurry blown out from another nozzle to form the roving. The cement slurry used at this time is not particularly limited, and those conventionally used in the production of carbon fiber reinforced cement composites can be used. Examples of the cement slurry include hydraulic cements such as Portland cement, blast furnace cement, and alumina cement.
Aggregates such as sand, silica sand, perlite, vermiculite, shirasu balloon, fly ash, and ultrafine silica are mixed with admixtures such as dispersants, water reducing agents, and defoamers, and water is added to form a mixed slurry. Can be mentioned. The mixing ratio such as the water / cement ratio or the aggregate / cement ratio in the slurry is appropriately selected according to the form of the carbon fiber used, the moldability of the cement composite to be produced, and the workability. The uncured molded body thus obtained is cured by a known method such as underwater curing, air curing, or steam curing, and then solidified to produce a desired carbon fiber reinforced cement composite. . The thus-produced cement composite of the present invention has a high flexural strength of 300 kgf / cm ² or more and is suitably used for various applications in the fields of construction and civil engineering.

[0013]

Next, the present invention will be described in more detail by way of examples. Example 1 Dimethyl terephthalate (0.20 molar ratio), adipic acid ethylene glycol ester (0.78 molar ratio), 5-sulfoneso disophthaldimethyl (0.02 molar ratio),
Preparing an aqueous emulsion solution containing 2 wt% of a polyetherester having a molecular weight of 8,000 to 12,000 obtained by subjecting polyethylene glycol (0.15 mol ratio) to a polycondensation reaction with an excess of ethylene glycol in the presence of a catalyst; In this solution, the strand tensile modulus is 21 × 10 ³ kgf / mm.
2000 with a ² and tensile strength of 216kgf / mm ²
A mesophase pitch-based carbon fiber strand composed of a filament was immersed and then dried to prepare a carbon fiber for cement reinforcement coated with 1.0% by weight of polyetherester. Meanwhile, a cement mortar having a cement / sand weight ratio of 1.33, a water / cement weight ratio of 0.35, and a cement admixture / cement weight ratio of 0.008 was prepared. The carbon fiber bundle for cement reinforcement was cut to a length of 25 mm and sprayed simultaneously with the cement mortar by a spray gun used in a direct spray method to obtain a carbon fiber reinforced cement concrete molded body. At this time, the supply amount of the carbon fiber was adjusted to be 3 vol%. This molded body is room temperature 7 days old 250mm long, 50mm wide,
A 10-mm-thick bending test specimen was cut out and subjected to a three-point bending test at a distance between supporting points of 200 mm. As a result, the bending strength was 305 kgf / cm ² . When the same molded body was tested in the same manner at room temperature for 28 days, the flexural strength was 320 kgf / cm ² .

COMPARATIVE EXAMPLE 1 In an emulsion type epoxy sizing agent containing Epicoat 828 and a curing agent SE-11, the same strand tensile modulus as in Example 1 was used, ie, 21 × 10 ³ kgf /
20 having a tensile strength of 216 kgf / mm ² and a tensile strength of 216 kgf / mm ²
A mesophase pitch-based carbon fiber strand composed of 00 filaments was immersed and dried to prepare a carbon fiber for cement reinforcement coated with 1.0% by weight of an epoxy sizing agent. On the other hand, cement / sand weight ratio 1.33,
A cement mortar having a water / cement weight ratio of 0.35 and a cement admixture / cement weight ratio of 0.008 was prepared. Hereinafter, it carried out similarly to Example 1. As a result, the flexural strength of a material having a room temperature material age of 7 days was 187 kgf / cm ² .

[0015]

The carbon fiber for reinforcing cement of the present invention is:
It has excellent adhesion to cement, has good processability with a direct spray gun, and has good convergence, and is particularly suitable for the direct spray method. Further, the cement composite containing carbon fibers for cement reinforcement has a high flexural strength and is suitably used for various applications in the fields of construction and civil engineering.

──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Yoshikazu Nagata 4th Towada, Kamisu-cho, Kashima-gun, Ibaraki Pref. Inside Petka Co., Ltd. In the laboratory (72) Inventor Toshio Yonezawa 2-5-14 Minamisuna, Koto-ku, Tokyo Takenaka Corporation Technical Research Laboratory (72) Inventor Junichi Toda 5-2101, Hara, Tenpaku-ku, Nagoya-shi, Aichi (72) Inventor Masaki Iwata 29-11 Tatsumicho, Minato-ku, Nagoya-shi, Aichi (56) References JP-A-4-65338 (JP, A) JP-A-61-252365 (JP, A) JP-A-3-150241 (JP, A (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) C04B 14/38 C04B 28/00-28/36 D06M 15/53 D06M 101: 40 EPAT ( QUESTEL)

Claims (3)

(57) [Claims] 1. A carbon fiber for cement reinforcement, characterized in that a sizing agent comprising a polyetherester is applied to the surface of the carbon fiber. 2. The carbon fiber for cement reinforcement according to claim 1, wherein the amount of the sizing agent applied is 0.5 to 10% by weight based on the carbon fiber. 3. A bending strength of 300 kgf / cm, wherein the carbon fiber for cement reinforcement according to claim 1 or 2 is cut to a fiber length of 10 to 50 mm and contained in a cement matrix at a volume mixing ratio of 1 to 5%. cm ² or more of the cement complex.