JPH06104583B2 - Method for producing high strength carbon fiber reinforced cement material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention provides a reinforcing carbon fiber used in a high-strength carbon fiber reinforced cement material.

(Prior Art) In recent years, carbon fiber reinforced cement materials have been attracting attention as a material that has heat resistance, fire resistance, and water resistance, is lightweight and has high strength, and has been actively researched for use in construction and civil engineering. It is taking place. Looking at the conventional technology regarding the properties and physical properties of the reinforcing carbon fiber used, the tensile elastic modulus obtained by firing at a relatively low temperature mainly from petroleum-based or coal-based pitch is about 3 to 10 T / mm ^2. Pitch-based low-elasticity carbon fiber is used, and it is regarded as an application field unsuitable for so-called PAN-based fiber generally used in high-functionality fields.

On the other hand, carbon fibers, especially Pitch-based carbon fibers, have a drawback that they have poor adhesiveness (or adhesiveness) to cement as compared with asbestos and glass fibers that have been conventionally used for cement reinforcement. Conventionally, various measures have been taken to improve the adhesiveness and 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 cement are simultaneously cured (Japanese Patent Publication No. 58-19620). They are bound to each other with a water-soluble binder such as methyl cellulose. A method of orienting the deposited carbon fibers in the cement in one direction or in two directions intersecting with each other (JP-A-56-129657) A magnesia cement mixed with an inorganic cement surface-treated with an organic chelating agent (JP-A-57-129657) 56363) A method of stacking cement slurry layers through a carbon fiber sheet containing a water-soluble synthetic resin emulsion such as an acrylic emulsion (Japanese Patent Laid-Open No. 58-223659) Fibers used in the production of a reinforced cement material by the Hachiek-type papermaking method. Use a non-ionic or cationic polymer flocculant such as polyalkylamino acrylate attached to the surface (JP Patent 60-81052), and the like.

(Problems to be Solved by the Invention) However, in these conventional techniques, there are limitations on the form of carbon fiber to be used (method), there are limitations on construction method (methods), and Since there are inconveniences such as the type of cement being restricted and
There is a demand for carbon fibers that can be used without such limitations and that have good adhesion to cement and that can provide high-strength reinforced cement materials.

(Means for Solving Problems) In the present invention, carbon fibers made from a pitch containing an optically anisotropic phase as a raw material (hereinafter, referred to as ““ (Hereinafter referred to as "mesophase Pitch-based carbon fiber"), the adhesion between the carbon fiber and the cement matrix is increased, and as a result of diligent study to obtain a high-strength carbon fiber-reinforced cement material, a certain value or more Using mesophase Pitch-based carbon fiber having tensile modulus,
The present invention was completed by finding that a high-strength carbon fiber reinforced cement material can be obtained by oxidizing the surface of the fiber to a specific atomic ratio of oxygen and carbon (O / C) and then compounding it in cement. .

That is, an object of the present invention is to provide a novel carbon fiber reinforced cement material and a method for producing the same, and particularly to provide a high strength cement material and a method for producing the same.

Hereinafter, the present invention will be described in detail.

The mesophase Pitch-based carbon fiber used in the present invention is produced by a known method, for example, coal-based or petroleum-based pitch, coal liquefaction and the like containing a substance containing a condensed polycyclic aromatic compound, if necessary, solvent extraction. After pretreatment such as removal of impurities, heat treatment is carried out to obtain a mesophase pitch containing a phase (so-called mesophase phase) in which fused polycyclic aromatic compounds are laminated and exhibit optical anisotropy.

Then, the mesophase pitch is melt-spun, infusibilized, carbonized, and, if necessary, graphitized to obtain a mesophase pitch carbon fiber.

Compared with carbon fiber made from isotropic phase pitch, in which mesophase pitch carbon fiber does not show optical anisotropy, tensile strength and tensile modulus are remarkably high mainly because the raw material pitch has a graphite crystal structure. This is because the condensed polycyclic aromatic compound, which should be called a precursor, has a laminated structure and exhibits optical anisotropy, and the laminated structure is introduced into the obtained fiber to become a carbon fiber having a developed graphite structure. The mesophase pitch carbon fiber used in the present invention can be made from mesophase containing pitch having an optically anisotropic portion content of 30% or more, preferably 50% or more. It has higher strength and higher elasticity than carbon fiber made from pitch, and the resulting reinforced cement material can also have higher strength.

The content of the optically anisotropic portion of the mesophase pitch in the present invention is a value determined as the area ratio of the portion showing the optical anisotropy in the pitch under a polarization microscope at room temperature.

Specifically, for example, by crushing a mesophase pitch sample into a few mm square according to a conventional method, a sample piece is embedded in almost the entire surface of the resin having a diameter of about 2 cm, and after polishing the surface, the entire surface is cleaned. It is determined by visually observing under a polarizing microscope (100 magnification) throughout and measuring the ratio of the area of the optically anisotropic portion to the total surface area of the sample.

Furthermore, the important factor in the mesophase Pitch-based carbon fiber used in the present invention is the tensile elastic modulus.
When it is 12 T / mm ² or more, it is preferable because a higher strength reinforced cement material can be obtained, and such a carbon fiber has a content of the optically anisotropic portion of the spinning pitch, spinning conditions and carbonization or graphitization. It can be manufactured by appropriately selecting the temperature and the like.

That is, according to the study of the present inventors, in the case of carbon fiber having a low tensile elastic modulus as conventionally used, there is little meaning to how the adhesiveness with cement is devised, and the cement obtained essentially is obtained. For example, the bending strength of the molded body is 150 kg / cm ² or more,
Further, it was difficult to achieve a high level such as 200 kg / cm ² , but when using carbon fiber as specified in the present invention, it is necessary to use a fiber to maintain the strength of the cement molded product at such a high level. It has been found that the compatibility with cement becomes extremely important, and in order to secure this property, the present invention proposes to subject the surface of such high-performance Pitch-based carbon fiber to an oxidation treatment.

The method of the oxidation treatment is not particularly limited as long as it is a known method usually carried out for carbon fibers, and for example, in an electrolytic solution such as an aqueous solution of caustic soda, a method of electrolytically oxidizing carbon fibers as an anode, concentrated nitric acid. A liquid phase oxidation method in which carbon fibers are brought into contact with an oxidizing liquid such as, and a gas phase oxidation method in which carbon fibers are brought into contact with an oxidizing gas such as ozone or oxygen are possible.

Among them, the electrolytic oxidation treatment is advantageous in that each filament can be uniformly oxidized in a short time, and is a method having a high practicality. When the surface-oxidized mesophase Pitch-based carbon fiber is used, the physical properties of the reinforced cement material are improved as compared with those when the surface-oxidized one is not used. Although the reason for this improvement effect is not yet clear enough, the oxidation functional group formed on the fiber surface by surface oxidation enhances the hydrophilicity of the carbon fiber surface, which is originally hydrophobic, and a cement slurry containing water. It is presumed that the physical properties of the reinforced cement material are improved as a result of increasing the binding force of the carbon fiber and strengthening the adhesion between the carbon fiber and the cement.

The oxidized functional groups of the surface-oxidized carbon fiber can be analyzed by known chemical means, for example, X-ray photoelectron spectroscopy (Electron Spe
The method of measuring the value of the atomic ratio of oxygen atoms to carbon atoms (hereinafter abbreviated as "O / C") in the surface layer of the carbon fiber is used by the ctroscopy for Chemical Analysis hereinafter "ESCA" method. In this case, taking the O / C of the mesophase pitch-based carbon fiber of the present invention as an example, the O / C is increased by at least 0.02 before and after the oxidation treatment. It is necessary that the value of about 0.06 to 0.08 before the surface oxidation treatment is increased to 0.1 to 0.4 after the surface oxidation treatment. The addition of the oxidation functional group by such a surface oxidation treatment can be carried out by appropriately selecting the conditions according to the method of the surface oxidation treatment.
In a 20wt% aqueous solution of caustic soda, etc., use carbon fiber as the anode, and current density per carbon fiber surface area 0.01 to 5mA / cm
^{2. The} electrolysis time can be selected from the processing conditions of 5 seconds to 10 minutes. Thus, a mesophase Pitch-based carbon fiber whose surface has been subjected to oxidation treatment for the purpose of cement reinforcement is obtained, and if necessary, post-treatment such as attaching a sizing agent, a sizing agent, a water-soluble binder, etc. is added. It can also be used for cement reinforcement.

Conventional knowledge, eg "Carbon fiber and carbon fiber reinforced cement / concrete technical data" (issued by Information Development) No. 205-2
According to page 09, generally, in order to improve the adhesiveness between the carbon material and cement, a carbon flat plate mirror baked at 1000 ° C is
The surface oxidation treatment with ClO was mixed with cement, and the impact peeling energy was measured. As a result, there was no effect on the improvement of adhesion, and the carbon flat plate mirror surface was used as a model of the carbon fiber surface. It is said that it is not always appropriate to consider such irregularities. From this knowledge, as in the present invention, carbon fiber,
In particular, the purpose of obtaining a high-strength carbon fiber reinforced cement material by using a mesophase Pitch-based carbon fiber and subjecting its surface to an oxidation treatment is completely unexpected, therefore, the present invention is a great advance. It brings about sexuality.

(Effect of the present invention) As described above, in the present invention, mesophase Pitch-based carbon fiber having high strength and elasticity is used, and its surface is oxidized as compared with the conventional carbon fiber made of isotropic phase Pitch. By blending the treated material in cement, an effect of obtaining a high-strength carbon fiber reinforced cement agent is brought about.

And, when the carbon fiber of the present invention is used for cement reinforcement, there is no limitation on the fiber form and construction method as in the prior art, and depending on the manufacturing method of the reinforced cement agent, short fiber shape, long fiber (or strand). ), Sheet, non-woven fabric, woven fabric, etc., and has the advantage that it can be applied by various methods such as direct spray method, premix method, impregnation method (or handlay-up method), and papermaking method. Further, it can be mixed with various hydraulic cements such as Portland cement, blast furnace cement, alumina cement and calcium silicate to produce carbon fiber reinforced cement materials of various shapes such as plate, tube and column.

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example 1 A coal tar pitch was hydrogenated and heat-treated to obtain a mesophase pitch having a content of the optically anisotropic portion of 90%.

According to a conventional method, the mesophase pitch is melt-spun at 330 ° C. to obtain a pitch fiber, the pitch fiber is infusible at 400 ° C. under an air atmosphere, and further carbonized at 1600 ° C. under an argon atmosphere,
A mesophase pitch-based carbon fiber was obtained.

Then, the carbon fiber is treated with an aqueous electrolyte solution (0.2% caustic soda).
Current density per fiber surface area is 2.9m
Electrolytic oxidation treatment was performed under conditions of A / cm ² and electrolysis time of 1 minute, washed with water, and thought.

The surface-oxidized mesophase Pitch-based carbon fiber thus obtained showed a single-yarn diameter of 10 μ, a single-yarn tensile strength of 205 kg / mm ² , a single-yarn tensile elastic modulus of 22 T / mm ² , and was analyzed by the ESCA method. O / C
Was 0.13.

Subsequently, after the surface-oxidized mesophase Pitch-based carbon fiber was cut to a length of 10 mm, in accordance with a conventional method of the pre-mitch method which is a method for producing a reinforced cement material, water 45 to 100 parts by weight of cement,
Kneading in an omni mixer together with cement slurry consisting of 50 parts of aggregate (silica sand) and 2.5 parts by weight of admixture, forming a plate-shaped test piece, curing in air (temperature 20 ° C, relative humidity)
65%) to obtain a carbon fiber reinforced cement material having a carbon fiber volume content of 3%. Its bending strength is 7 days, 263kg / cm ²
(Average value of 3 pieces of test pieces having a length of 16 cm, a width of 4 cm and a thickness of 1.2 cm, a three-point bending test method).

Comparative Example 1 The physical properties of single filament of the mesophase Pitch-based carbon fiber obtained in Example 1 after carbonization and not subjected to surface oxidation treatment are 10 μm in diameter,
The tensile strength was 213 kg / mm ² , the tensile elastic modulus was 22 T / mm ² , and the O / C was 0.06.

The bending strength of the carbon fiber reinforced cement material obtained in the same manner as in Example 1 using the fiber not subjected to the oxidation treatment is
It was 230 kg / cm ² , which was clearly inferior to the oxidization treatment of Example 1.

Example 2 The content of the optically anisotropic portion of the mesophase pitch is 70%,
Except for carbonizing at 1100 ° C., exactly the same as in Example 1, single yarn diameter 15 μ, single yarn tensile strength 155 kg / mm ² , single yarn tensile elastic modulus 19T
A surface-oxidized mesophase pitch-based carbon fiber having an O / C of 0.30 / mm ² was obtained.

Then, using this fiber, bending strength was set to 19 in the same manner as in Example 1.
A carbon fiber reinforced cement material of 4 kg / cm ² was obtained.

Comparative Example 2 The mesophase Pitch-based carbon fiber obtained in Example 2 after carbonization and not subjected to surface oxidation treatment has a single yarn diameter of 15 μ, a single yarn tensile strength of 159 kg / mm ² , and a single yarn tensile elastic modulus of 19 T / a mm ^2, O / C 0.08, the bending strength of the carbon fiber-reinforced cement material obtained from the fibers was clearly Retsutsu compared to 158 kg / cm ² as in example 2.

Comparative Example 3 Using commercially available Pitch-based carbon fiber Kurekato, which has a tensile elastic modulus of 3 T / mm ² , T-101T cut into a fiber length of 10 mm,
The bending strength of the carbon fiber reinforced cement material obtained by the same method as in Example 1 was only 132 kg / cm ² , which was significantly inferior to that in Example 1.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hiromichi Sakai 1-2447 Fujita, Hachimansai-ku, Kitakyushu, Fukuoka Prefecture Mitsubishi Kasei Kogyo Co., Ltd. Kurosaki Plant (56) References JP 62-13330 (JP, A) )

Claims (3)

[Claims] 1. A pitch system having a tensile elastic modulus of 12 T / mm ² or more obtained by subjecting pitch fibers obtained by spinning an optically anisotropic phase-containing pitch to infusibilization treatment, carbonization treatment, and, if necessary, graphitization treatment. Obtained by oxidizing the surface of the carbon fiber, the value of the atomic ratio O / C of oxygen and carbon in the surface layer O-C is 0.1 ~ 0.4 high characterized by compounding into the cement carbon fiber pitch A method for producing a strong carbon fiber reinforced cement material. 2. The high-strength carbon fiber reinforced cement according to claim 1, wherein the pitch containing the optically anisotropic phase contains 30% or more of the optically anisotropic phase. Method of manufacturing wood. 3. The production of a high-strength carbon fiber reinforced cement material according to claim 1 or 2, wherein the oxidation treatment is an anodic oxidation treatment method by electrolysis. Method.