JP2018058757A - Reinforcing fiber for cement-based molded body, method for producing the same, and fiber-reinforced cement-based molded body using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel technique capable of producing a polyolefin-based reinforcing fiber having high affinity with a cement slurry and excellent adhesion to a cement composition; and to provide a fiber-reinforced cement-based molded body using the fiber.SOLUTION: A reinforcing fiber for a cement-based molded body is formed by coating a surface of a polyolefin fiber with a layer comprising at least: a carbonate of an alkaline earth metal; and a binder which consists of a different composition from that of a polymer used in the polyolefin fiber.SELECTED DRAWING: None

Description

The present invention relates to a reinforcing fiber for a cement-based molded body. More specifically, for cement-based molded products for civil engineering and construction work, especially for cement-based molded products suitable for prevention of cracking of concrete, peeling of concrete fragments accompanying this, prevention of peeling, and concrete secondary products. The present invention relates to a polyolefin-based reinforcing fiber.

Conventionally, organic fibers such as steel fibers, vinylon, and polypropylene are known as reinforcing fibers for cement-based molded bodies such as mortar and concrete. Polyolefins such as polypropylene taking advantage of cost merit that they do not rust in recent years, are excellent in alkali resistance to cement, and have the lowest specific gravity among synthetic fibers, resulting in the lowest mass ratio in the cement-based molded product. Fiber has attracted attention, and its use has been progressing especially for tunnel lining concrete.

However, a reinforcing fiber made of polyolefin resin such as polypropylene has a problem that adhesion to a cement composition is weak and it is difficult to obtain a sufficient reinforcing effect as it is. In order to overcome such problems, a technique has been proposed in which irregularities are mechanically imparted to the fiber surface, fixing to a cement molded body, and resistance during drawing (see Patent Document 1). These methods are advantageous in that they are relatively simple and can be produced at low cost, but are not sufficient in adhesion to cement-based molded bodies.

On the other hand, Patent Documents 2 and 3 propose techniques for improving adhesion to a cement composition by performing corona treatment, plasma treatment, ozone treatment, and the like under specific conditions. In addition, a technology that improves the dispersibility of fibers in cement and improves strength by surface treatment (coating) using carboxyl-modified polyolefin-based low molecular weight materials or polyethylene-based elastomer and maleic acid-modified polyethylene wax. And Patent Documents 4 and 5. However, these techniques are not sufficient from the viewpoint of improving adhesion.

Further, Patent Documents 6 and 7 propose techniques for improving dispersibility in a cement slurry by producing fibers using polypropylene kneaded with calcium carbonate. In these methods, it is mentioned that calcium ions derived from calcium carbonate form chemical bonds with each component constituting the cement matrix, and as a result, the bending strength of the cement-based molded body is remarkably improved. . However, these methods have a problem that when the calcium carbonate is kneaded in the entire fiber, the strength of the fiber itself is reduced, and the calcium carbonate is kneaded only in the sheath portion of the core-sheath composite fiber. When producing polypropylene fibers, it is necessary to use a relatively complicated technique called multi-layer spinning, which leaves a problem in terms of production cost.

JP-A-11-116297 JP 2001-058858 A JP 2003-089559 A JP 2000-034146 A JP 2005-239512 A Japanese Patent Laid-Open No. 06-219797 Japanese Patent Laid-Open No. 06-248506

An object of the present invention is to provide a new technology capable of producing a polyolefin-based reinforcing fiber having high affinity with a cement slurry and excellent adhesion to a cement composition. Another object of the present invention is to provide a fiber-reinforced cement-based molded body using the above-mentioned fibers.

The inventors of the present invention have made extensive studies on a technique capable of improving adhesion without kneading into the polyolefin fiber itself, while paying attention to improving adhesion with a cement composition using a carbonate of an alkaline earth metal such as calcium carbonate. Repeated. As a result, it has been found that the adhesion between the fiber and the cement composition is greatly improved by coating the surface of the polyolefin fiber with a layer containing at least an alkaline earth metal carbonate and a binder. It came to be completed.
That is, the present invention relates to the following matters.

1. A cement-based molded body characterized in that a layer containing at least a carbonate of an alkaline earth metal and a binder having a composition different from the polymer used for the polyolefin fiber is coated on the surface of the polyolefin fiber. Reinforcing fiber.

2. Item 2. The reinforcing fiber for a cement-based molded article according to Item 1, wherein the alkaline earth metal carbonate is calcium carbonate particles.

3. Item 3. The reinforcing fiber for a cement-based molded article according to any one of Items 1 or 2, wherein the binder is a polymer-based binder.

4). Item 4. The reinforcing fiber for a cement-based molded article according to Item 3, wherein the polymer binder is a primer resin for polyolefin.

5. Item 5. The reinforcing fiber for a cement-based molded article according to item 4, wherein the polyolefin primer resin is an aqueous emulsion resin.

6). Item 6. The reinforcing fiber for a cement-based molded article according to any one of Items 2 to 5, wherein the calcium carbonate particles have a particle size of 10 nm to 1000 µm.

7). Item 7. The reinforcing fiber for a cement-based molded article according to any one of Items 2 to 6, wherein the addition amount of the calcium carbonate particles is 10 to 300% by mass with respect to the binder.

8). Item 8. The reinforcing fiber for a cement-based molded article according to any one of Items 1 to 7, wherein the polyolefin fiber is mainly composed of polypropylene and / or polyethylene.

9. A method for producing a reinforcing fiber for a cement-based molded article, wherein a binder solution or emulsion in which at least an alkaline earth metal carbonate is dispersed is applied to a polyolefin fiber, followed by heat drying.

10. A fiber-reinforced cement-based molded body to which the reinforcing fiber for cement-based molded body according to any one of Items 1 to 8 is added.

According to the present invention, it is possible to obtain a reinforcing fiber for a cement-based molded body having high affinity with a cement slurry and excellent adhesion to a cement composition. Since the reinforcing fiber for a cement-based molded article of the present invention has a high affinity with cement slurry, the fiber can be easily opened when it is put into the cement-based fresh, and the fibers can be uniformly dispersed in the cement-based fresh. In addition, since the reinforcing fibers for cement-based molded bodies have high affinity with cement slurry and excellent adhesion to cement compositions, a high bending toughness coefficient can be obtained in concrete molded products after cement hardening, which is extremely excellent. Reinforcing effect can be expressed.

The present invention will be described in detail below.

In the reinforcing fiber for cement-based molded article of the present invention, the surface of the polyolefin fiber is coated with a layer containing at least an alkaline earth metal carbonate and a binder different from the polymer used for the polyolefin fiber. It is characterized by.

<Polyolefin fiber>
The polyolefin fiber used in the present invention is a polyolefin polymer such as polyethylene, polypropylene, polymethylpentene, polybutene-1, or a polyolefin copolymer such as ethylene-acrylic acid copolymer or ethylene-vinyl acetate copolymer. It can be used, and those mainly composed of polypropylene or polyethylene can be suitably used from the viewpoint of cement alkali resistance, fiber properties, low cost, reinforcement efficiency, and the like. Among them, the surface of the cement reinforcing fiber is exposed to a high temperature by autoclave curing at the time of cement molding, and therefore, a fiber using a resin composed of a component having a high melting point as much as possible is preferable, and polypropylene is particularly preferably used. As the polypropylene resin, a propylene homopolymer, a block or random copolymer of an α-olefin such as ethylene and propylene, or the like can be used. These polyolefins may be used alone or as a mixture. The fiber form of the polyolefin fiber of the present invention may be either a single type fiber or a composite type fiber. In the case of a composite type fiber, any of a core-sheath type, an eccentric type, a parallel type, and a split type may be used.

Although the single fiber fineness of the polyolefin-type fiber used for this invention is not specifically limited, 100-10,000 dtex are preferable, More preferably, it is 500-9000 dtex. When the single fiber fineness is less than 100 dtex, the fibers are too thin and dispersed as short fibers in the cement slurry, the dispersion becomes uneven and easily becomes fiber balls, which is not preferable in terms of workability and reinforcement. On the other hand, if the single fiber fineness exceeds 10,000 dtex, the contact area of the fiber with the cement slurry decreases, and the reinforcing effect is inferior.

The form of the polyolefin-based fiber used in the present invention is appropriately selected depending on the application, and it may be a short fiber or a woven or non-woven fiber. In the present invention, a short fiber-like polyolefin fiber is particularly preferably used. When short fibers are used, the fiber length is preferably 5 to 80 mm, more preferably 5 to 60 mm, and even more preferably 5 to 50 mm. If the fiber length is less than 5 mm, it is easy for the cement to come off, and if it exceeds 80 mm, the dispersibility may be unfavorable.

If necessary, the polyolefin fiber used in the present invention can be processed by imparting mechanical irregularities to the fiber surface or making the fiber cross-sectional shape irregular using a known method. By these processes, the contact area between the fiber and the cement slurry can be increased, thereby improving the affinity, dispersibility, and adhesion of the cement, and the effect of improving the pulling resistance due to the catching of the cement and the fiber. .

Furthermore, in the polyolefin fiber used in the present invention, other synthetic resins and modified resins, antioxidants, light stabilizers, nucleating agents, antibacterial agents, flame retardants, antistatic agents, as long as the effects of the present invention are not hindered. Pigments, plasticizers, and other inorganic / organic fillers can be appropriately added.

<Alkaline earth metal carbonate>
Examples of the alkaline earth metal carbonate used in the present invention include calcium carbonate, magnesium carbonate, strontium carbonate, and the like, and calcium carbonate particles are most preferable from the viewpoint of cost and adhesion to the cement composition.

The particle size of the calcium carbonate particles is preferably 10 nm to 1000 μm, and more preferably 100 nm to 300 μm. When the particle size of the calcium carbonate particles is less than 10 nm, it is not preferable because a large cost is required for the production of the particles. When the particle size exceeds 1000 μm, it is difficult to fix together with the binder, and it becomes easy to detach. It is not preferable.

The addition amount of the calcium carbonate particles used in the present invention is preferably 5 to 80% by mass and more preferably 10 to 50% by mass with respect to the coating solution. When the amount is less than 5% by mass, the adhesion to the cement composition may not be sufficient, which is not preferable. When the amount exceeds 80% by mass, the adhesion of the fiber surface with the binder becomes insufficient, and it is not preferable because it tends to be detached. .

The addition amount of the calcium carbonate particles used in the present invention is preferably 10 to 300% by mass and more preferably 50 to 200% by mass with respect to the binder. When the amount is less than 10% by mass, the adhesion to the cement composition may not be sufficient, which is not preferable. When the amount exceeds 300% by mass, the adhesion of the fiber surface with the binder becomes insufficient, and it is not preferable because it tends to be detached. .

<Binder>
The binder used in the present invention is a binder having a composition different from that of the polymer used in the polyolefin fiber, and the modified polyolefin also has a different composition. The material is not particularly limited as long as it has a suitable adhesion to the polyolefin fiber and the alkaline earth metal carbonate. For example, a polymer binder, an inorganic binder, and the like are used. In the present invention, from the viewpoint of adhesion to polypropylene, a polymer-based binder is more preferable, and a primer resin for polyolefin is particularly preferable.

As the primer resin for polyolefin, a known primer resin for polyolefin can be appropriately selected as necessary, and examples thereof include ethylene-vinyl acetate copolymer, polyolefin elastomer, and modified polyolefin such as acid-modified polyolefin and chlorine-modified polyolefin. . Further, for the purpose of improving adhesion, a novolac type phenolic resin, an epoxy resin, and other adhesion improving components may be added as necessary.

The polyolefin primer may be a solution type resin dissolved in an organic solvent or an aqueous emulsion type resin dispersed in water, but from the viewpoint of workability and VOC emission suppression, it should be an aqueous emulsion resin. Is particularly preferred. These binders may be used alone or as a mixture of two or more.

<Method for producing reinforcing fiber for cement-based molded article>
The reinforcing fiber for a cement-based molded article of the present invention can be produced by applying a binder solution or emulsion in which at least an alkaline earth metal carbonate is dispersed to a polyolefin fiber, followed by heat drying. More specifically, an alkaline earth metal carbonate is mixed with a binder solution or emulsion, and diluted with an organic solvent and / or water as necessary to prepare a coating solution. Cement-based molding with good adhesion to the cement composition by applying this coating solution to polyolefin fibers, followed by heat drying to dry the organic solvent and / or water and fix the binder to the polyolefin fiber surface. A body reinforcing fiber is obtained.

The method for applying the coating solution to the polyolefin fiber is not particularly limited, and any of dipping, spraying, and coating methods can be employed. Moreover, the method of apply | coating continuously, when spinning a fiber, and the method of apply | coating after processing into shapes, such as a short fiber, a textile fabric, and a nonwoven fabric, may be sufficient. In consideration of work and cost, a method of applying continuously when spinning the fiber is more preferable.

The temperature at which the heat drying treatment is performed is appropriately determined according to the type of binder, the type of solvent, the heat resistance of the polyolefin fiber, and the like. For example, when polypropylene fiber is used as the polyolefin fiber, about 90 ° C to 150 ° C is preferable. It is. When the temperature is lower than 90 ° C., the solvent and / or water may be insufficiently dried, or the binder may be insufficiently fixed to the polyolefin fiber. On the other hand, when it exceeds 150 ° C., there is a concern that the strength of the polyolefin fiber is lowered, which is not preferable.

<Other processing>
The reinforcing fiber for a cement-based molded body of the present invention can be subjected to various other treatments as necessary. For example, the fiber surface may be treated with a surfactant, a dispersant, a coupling agent, or the like, or may be subjected to surface activation or crosslinking treatment by corona discharge treatment, ultraviolet irradiation, electron beam irradiation, or the like. . These treatments may be performed before or after the formation of the coating layer composed of the alkaline earth metal carbonate and the binder. In particular, after forming the coating layer, it may be possible to improve the dispersibility in the cement slurry by further treatment with a surfactant or the like.

As the surfactant, any surfactant can be used as long as it does not adversely affect the cement hydration reaction. Among them, polyethylene glycol alkyl ester nonionic surfactants, alkyl phosphate anionic surfactants, polyhydric alcohols can be used. Type amide nonionic surfactants can be preferably used.

As the polyethylene glycol alkyl ester, those in which the long-chain aliphatic alkyl group constituting the polyethylene glycol alkyl ester has 6 to 18, preferably 8 to 16 carbon atoms are preferable from the viewpoint of the stability of the aqueous dispersion and the fiber adhesion. Specific examples of preferable polyethylene glycol alkyl esters include polyethylene glycol laurate, polyethylene glycol oleate, and polyethylene glycol stearate. The alkyl phosphate is a phosphate having an average carbon number of 18 or less, preferably 6 to 16, more preferably 8 to 14 alkyl groups in one molecule, preferably 1 and an alkali metal salt as a salt. , Alkaline earth metal salts, ammonium salts, and amine salts. Specific examples of preferable alkyl phosphates include salts of higher alcohol phosphates such as octyl phosphate, lauryl phosphate, stearyl phosphate, such as sodium, potassium, magnesium, calcium, and amine salts. The neutralization is preferably 50% or more of the free hydroxyl group, particularly a completely neutralized product. As the polyhydric alcohol type amido nonion, an addition reaction product of an alkylamine having 4 to 18 carbon atoms and polyglycerin having 3 to 13 hydroxyl groups is used, preferably an alkylamine having 11 to 17 carbon atoms and 3 Addition reactants with polyglycerin having ˜6 hydroxyl groups are used.

Other preferable surfactants include polyoxyalkylene alkylphenyl ether phosphate esters and polyoxyalkylene fatty acid esters. Specific examples of the polyoxyalkylene alkyl phenyl ether phosphate ester include polyoxyethylene nonyl phenyl ether phosphate ester, polyoxyethylene dodecyl phenyl ether phosphate ester, and specific examples of the polyoxyalkylene fatty acid ester include Examples thereof include polyoxyethylene oleate and polyoxyethylene stearate. These surfactants can be used singly or in combination of two or more.

The amount of the surfactant attached to the fiber is not particularly limited, but it is usually used in the range of 0.05 to 2% by mass with respect to the total fiber from the viewpoint of suppressing the generation of bubbles when blending cement. If the adhesion amount to the fiber is less than 0.05% by mass with respect to the total fiber, the polyolefin fiber may not be sufficiently hydrophilic, and if it exceeds 2% by mass, the hydrophilicity will reach its peak, and the fiber kneading will be performed. It is not preferable because bubbles are generated in various cement-based molded bodies represented by fresh concrete at the time, and the physical property values such as compressive strength and bending strength of the cement-based molded bodies may be lowered. The adhesion of 0.5% by mass or more affects the fresh properties (air amount) of the cement system, so it is necessary to adjust with a known air conditioner when blending the fibers.

The reinforcing fiber for cement molding of the present invention is blended as a reinforcing fiber material in cement, fine aggregate, coarse aggregate, water and an appropriate amount of concrete admixture, or cement, fine aggregate, water and an appropriate amount of mortar admixture. It can be used as a cement-based molded body such as concrete and mortar. Here, as the cement, it is possible to use ordinary portland cement, blast furnace cement, silica cement, fly ash cement, hydraulic cement such as white portland cement, alumina cement, or cement such as plaster, air-cement cement such as lime. it can. Fine aggregates include river sand, sea sand, mountain sand, quartz sand, glass sand, iron sand, ash sand, and other artificial sand. Coarse aggregates include gravel, gravel, crushed stone, slag, Various artificial lightweight aggregates can be mentioned. As the admixture, an air entraining agent (AE agent), a fluidizing agent, a water reducing agent, a thickening agent, a water retention agent, a water repellent, a swelling agent and the like can be mixed and used.

The compounding amount of the reinforcing fiber with respect to the cement is usually 0.05 to 5% by volume with respect to the volume of the cement-based molded body. From the viewpoint of the uniform dispersibility of the fiber when blended with cement, the fluidity of the blended cement, the workability, and the effect of improving the physical properties of the cement-based molded body, the blending amount of the reinforcing fiber is preferably 0.1 to 3% by volume, more preferably Is in the range of 0.3 to 1% by volume.

When the reinforcing fiber for a cement molded body of the present invention is used for the production of a cement-based molded body, the reinforcing fiber is dispersed in a cement-based powder, a cement-based flash or a slurry to obtain a cement-based mixture, which is formed by a wet papermaking molding method. After molding into a predetermined shape by extrusion molding or cast molding, various cement-based molded bodies can be produced by natural curing, steam curing, autoclave curing, or the like. More specifically, it is preferable to use a concrete mixture made of cement, fine aggregate, coarse aggregate, water, and the like as base concrete, and after kneading the base concrete, the reinforcing fibers are subsequently added and kneaded. Although the kneading time varies depending on the amount of mixing per one time, generally, the range of 45 to 90 seconds for kneading the base concrete and the range of 45 to 90 seconds for kneading after the reinforcing fibers are added are appropriate.

The cement-based molded body thus obtained is particularly suitable as a concrete molded body for civil engineering and construction work. For example, in the concrete road pavement field, it is possible to reduce the amount of reinforcing bars to improve the bending strength by fiber reinforcement, and to reduce the thickness of the concrete plate, which is effective for shortening the construction period and saving raw materials. In addition, when used in the tunnel inner wall spraying method, the fibers are flexible and elastic, hydrophilic and light, so there is little flaking of aggregates and fibers during spraying, less falling of concrete, and yield safety. It is effective in terms.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to these examples.

Samples used in the following examples are as follows.

Polyolefin fiber A: Polypropylene short fiber
Fineness: 2050 dtex Length: 30 mm
With surface irregularity processing
(Ube Eximo Co., Ltd.)
Polyolefin fiber B: Simlock SX (short polypropylene fiber)
Fineness: 1000 dtex Length: 20 mm
With surface irregularity processing
(Ube Eximo Co., Ltd.)
Polyolefin fiber C: Simlock MX (polypropylene short fiber)
Fineness: 2000 dtex Length: 30 mm
With surface irregularity processing
(Ube Eximo Co., Ltd.)
Polyolefin fiber D: Simlock LX (polypropylene short fiber)
Fineness: 3300dtex Length: 48mm
With surface irregularity processing
(Ube Eximo Co., Ltd.)
Polyolefin fiber E: Valchip MK (polypropylene short fiber)
Fineness: 7100dtex Length: 40mm
With surface irregularity processing
(Made by Ebara Industry Co., Ltd.)
Polyolefin fiber F: Valchip JK (polypropylene short fiber)
Fineness: 3500 dtex Length: 48mm
With surface irregularity processing
(Made by Ebara Industry Co., Ltd.)
U primer 45: ethylene vinyl acetate copolymer aqueous emulsion (manufactured by Ube Industries) Solid content concentration 45%
PP primer GX1073: modified polyolefin aqueous emulsion (manufactured by Kyoyo Chemical Co., Ltd.) solid content concentration 23%
Super Clone 930: Acid-modified chlorinated polyolefin / toluene solution (manufactured by Nippon Paper Group) Solid content 20%
HARDREN EH801: Chlorinated polyolefin / water-based emulsion (Toyobo Co., Ltd.) Solid content concentration 30%
Calcium carbonate: Median diameter (d50) 9.33 μm (made by Wako Pure Chemical Industries, Ltd., reagent grade) The median diameter (d50) is measured using a laser diffraction scattering type particle size distribution measuring device (Malvern, Mastersizer 3000). It was measured.

A method for measuring the characteristics used in the following examples is shown below.

[Evaluation of cement adhesion of reinforcing fibers]
A cement paste was obtained by kneading 150 g of commercially available quick-hardening cement (trade name: Instant Cement, manufactured by Keiji Kagaku Kogyo Co., Ltd.) and 30 g of water for 120 seconds. After kneading, the mixture was allowed to stand for 5 minutes, poured into a mold having a length of 5 mm, a width of 10 mm, and a height of 20 mm, and defoamed by applying vibration. Subsequently, the reinforcing fibers for cement molded bodies obtained in the examples and comparative examples were inserted vertically into the central portion of the mold so that the insertion depth was 15 mm, and vibrations were applied again to cause the air existing between the fibers and the cement. Was degassed. Then, it was cured for 3 days in a thermostatic chamber at 23 ° C., cured, and removed from the mold to obtain a sample for evaluating cement adhesion. The cement side of the obtained sample for evaluating cement adhesion was fixed to a pedestal of a tensile tester (EZtestCE manufactured by Shimadzu Corporation), the fiber side was gripped and pulled out at a speed of 2 mm / min, and displacement and test force were observed. The maximum adhesion force during extraction (kgf) and the extraction energy (mJ) were used for the cement adhesion evaluation index of the reinforcing fiber. The drawing energy was defined by the following formula as an integral value of energy required from the start of drawing of the fiber until the fiber was completely pulled out.
(Extraction energy [mJ]) = Σ {(displacement [mm]) × (test force [kgf]) × (standard gravity acceleration [m / sec 2])}

[Particle size of alkaline earth metal carbonate]
The particle diameter of the alkaline earth metal carbonate was measured using a master sizer 3000 manufactured by Malvern, based on the JIS Z8825 dry method.

[Example 1]
10 g of U primer 45, 4.5 g of calcium carbonate, and 8.0 g of ion-exchanged water were mixed in a sample bottle to prepare a coating solution containing 20% by mass of binder and 20% by mass of calcium carbonate. The polyolefin fiber A was immersed in this coating solution for 30 seconds, then pulled up at 1 cm / second, and immediately heated and dried in a hot air oven at 100 ° C. for 30 minutes to obtain a reinforcing fiber for a cement-based molded body. Table 1 shows the results of evaluation of cement adhesion of the obtained fibers. The maximum adhesion force and extraction energy were both high, indicating good adhesion to the cement molded body.

[Example 2]
A coating solution containing 18% by mass of binder and 30% by mass of calcium carbonate was prepared in the same manner as in Example 1 except that 7.5 g of calcium carbonate was used, and then a reinforcing fiber for cement-based molded body was obtained. . Table 1 shows the results of evaluation of cement adhesion of the obtained fibers. The maximum adhesion force and extraction energy were both high, indicating good adhesion to the cement molded body.

Example 3
A coating solution comprising 18% by mass of binder and 20% by mass of calcium carbonate was prepared in the same manner as in Example 1 except that PP primer GX1073 was used instead of U primer 45 as a binder, and then cement-based molding was performed. Body reinforcing fibers were obtained. Table 1 shows the results of evaluation of cement adhesion of the obtained fibers. The maximum adhesion force and extraction energy were both high, indicating good adhesion to the cement molded body.

Example 4
A coating solution comprising 16% by mass of binder and 20% by mass of calcium carbonate was prepared in the same manner as in Example 1 except that Super Clone 930 was used instead of U primer 45 as a binder, and then a cement-based molded body Reinforcing fiber was obtained. Table 1 shows the results of evaluation of cement adhesion of the obtained fibers. Even when a solvent-based binder was used, the maximum adhesion force and the drawing energy were both high, and good adhesion to the cement molded article was exhibited.

Example 5
A coating liquid consisting of 24% by mass of binder and 20% by mass of calcium carbonate was prepared in the same manner as in Example 1 except that HARDLEN EH801 was used instead of U primer 45 as the binder, and then reinforcement for cement-based molded bodies Fiber was obtained. Table 1 shows the results of evaluation of cement adhesion of the obtained fibers. The maximum adhesion force and extraction energy were both high, indicating good adhesion to the cement molded body.

[Comparative Example 1]
Cement adhesion was evaluated using untreated polyolefin fibers that were not immersed in the coating solution. The results of cement adhesion evaluation are shown in Table 1. Compared with Example 1, both the maximum adhesion force and the drawing energy were low, indicating that the adhesion to the cement molded article was poor.

[Comparative Example 2]
A reinforcing fiber for a cement-based molded body was obtained in the same manner as in Example 1 except that the coating liquid was prepared by adjusting the amount of ion-exchanged water so that the binder was 20% by mass without adding calcium carbonate. . Table 1 shows the results of evaluation of cement adhesion of the obtained fibers. Compared with Example 1, both the maximum adhesion force and the drawing energy were low, indicating that the adhesion to the cement molded article was poor.

[Comparative Example 3]
Reinforcing fibers for cement-based molded bodies were obtained in the same manner as in Example 3, except that calcium carbonate was not added and PP primer GX1073 was used as the coating liquid. Table 1 shows the results of evaluation of cement adhesion of the obtained fibers. Compared to Example 3, both the maximum adhesion force and the drawing energy were low, indicating that the adhesion to the cement molded article was poor.

[Comparative Example 4]
Reinforcing fibers for cement-based molded bodies were obtained in the same manner as in Example 4, except that calcium carbonate was not added and Supercron 930 was used as the coating liquid. Table 1 shows the results of evaluation of cement adhesion of the obtained fibers. Compared to Example 4, both the maximum adhesion force and the drawing energy were low, indicating that the adhesion to the cement molded article was poor.

Example 6
A reinforcing fiber for a cement-based molded body was obtained in the same manner as in Example 1 except that the polyolefin fiber B was used. The maximum adhesion force and extraction energy were both high, indicating good adhesion to the cement molded body.

Example 7
A reinforcing fiber for cement-based molded body was obtained in the same manner as in Example 1 except that the polyolefin fiber C was used. The maximum adhesion force and extraction energy were both high, indicating good adhesion to the cement molded body.

Example 8
A reinforcing fiber for a cement-based molded body was obtained in the same manner as in Example 1 except that the polyolefin fiber D was used. The maximum adhesion force and extraction energy were both high, indicating good adhesion to the cement molded body.

Example 9
A reinforcing fiber for a cement-based molded body was obtained in the same manner as in Example 1 except that the polyolefin fiber E was used. The maximum adhesion force and extraction energy were both high, indicating good adhesion to the cement molded body.

Example 10
A reinforcing fiber for a cement-based molded body was obtained in the same manner as in Example 1 except that the polyolefin fiber F was used. The maximum adhesion force and extraction energy were both high, indicating good adhesion to the cement molded body.

The reinforcing fiber for cement-based molded article of the present invention has excellent adhesion to the cement composition, so that it is used for various civil engineering applications such as tunnel lining, road flooring, viaducts, construction applications, and concrete secondary products. It can be effectively used as a reinforcing fiber for a molded body.

Claims (10)

  A cement-based molded body characterized in that a layer containing at least a carbonate of an alkaline earth metal and a binder having a composition different from the polymer used for the polyolefin fiber is coated on the surface of the polyolefin fiber. Reinforcing fiber.   The reinforcing fiber for a cement-based molded article according to claim 1, wherein the alkaline earth metal carbonate is calcium carbonate particles.   The reinforcing fiber for a cement-based molded article according to claim 1, wherein the binder is a polymer-based binder.   The reinforcing fiber for a cement-based molded article according to claim 3, wherein the polymer binder is a polyolefin primer resin.   The reinforcing fiber for a cement-based molded article according to claim 4, wherein the polyolefin primer resin is a water-based emulsion resin.   The reinforcing fiber for a cement-based molded body according to any one of claims 2 to 5, wherein the calcium carbonate particles have a particle size of 10 nm to 1000 µm.   The reinforcing fiber for a cement-based molded article according to any one of claims 2 to 6, wherein the addition amount of the calcium carbonate particles is 10 to 300 mass% with respect to the binder.   The reinforcing fiber for a cement-based molded article according to any one of claims 1 to 7, wherein the polyolefin fiber is mainly composed of polypropylene and / or polyethylene.   A method for producing a reinforcing fiber for a cement-based molded article, wherein a binder solution or emulsion in which at least an alkaline earth metal carbonate is dispersed is applied to a polyolefin fiber, followed by heat drying. A fiber-reinforced cement-based molded body to which the reinforcing fiber for cement-based molded body according to any one of claims 1 to 8 is added.