JP5138915B2 - Reinforcing short fibers for cement-based moldings - Google Patents

Description

  The present invention relates to a synthetic resin reinforced short fiber for cement-based molded bodies. More specifically, cement-based molded bodies for civil engineering and construction work, particularly those related to reinforcing short fibers for cement-based molded bodies suitable for preventing cracking of concrete and preventing the separation and peeling of concrete fragments accompanying this. It is.

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.
Recently, polypropylene fibers have been attracting attention by taking advantage of the cost advantage that the mass ratio is the smallest in the cement molding because it does not rust, has excellent cement alkali resistance, and has the lowest specific gravity among the synthetic fibers. It has been used for tunnel lining concrete.
However, a reinforcing fiber made of polyolefin resin such as polypropylene has a problem that its adhesiveness with a cement paste is weak and it is difficult to obtain a sufficient reinforcing effect as it is. In order to overcome such problems, following the provision of strength properties by stretching, mechanically imparting irregularities to the fiber surface with a gear roll or press-molding roll, fixing to the cement molded body, and providing resistance during drawing The technique to do is proposed (refer patent document 1).
By using such a technology, it is possible to continuously fix the cement molded body by using a gear roll or a press-molding roll, which is simple in terms of the fiber manufacturing process and low in cost. Although it is advantageous in that it can be produced, it is not sufficient in terms of fixability to a cement molded body.

On the other hand, for the purpose of increasing the contact area with the cement paste, the present applicants have a cross-sectional shape that is a substantially polygonal shape having 3 to 6 protrusions, and at the tips of the protrusions, in the longitudinal direction of the fibers. A technique has been proposed in which a concave portion or a convex portion is shaped by a pair of parallel pattern concave and convex rollers (see Patent Document 2).
However, in this technique, the fixability with the cement paste can be improved. However, in the cross-sectional fiber having such a projection tip, the tensile stress is increased when the reinforcing fiber in the cement molded body is loaded. Since the protrusions are sequentially applied from the tip of the protrusion toward the center, the cross-sectional shape is such that stress is easily concentrated on the tip of the cross section of the fiber.
In addition, the tip is mechanically shaped with irregularities that can be called defects, which degrade the tensile properties of the fiber, and there is a problem that the fiber is likely to break starting from this part. The fixing property of the fiber and the tensile strength of the fiber cannot be achieved, and there is room for improvement as a reinforcing fiber for a cement molded body.

In addition, the reinforcing fiber should be introduced into various cement-based molded bodies represented by fuller concrete and opened in a short time and uniformly in consideration of the cement hardening time.
In general, manual opening or a machine opening machine such as a rotary blade type or a rotary pin type is used, and it is put into various cement-based molded bodies represented by Fluoresh concrete in a short time with an air flow. At this time, the fibers having irregularities on the fiber surface are not sufficiently opened due to the catching of the fibers, which may cause a problem in terms of uniform dispersion in the cement-based molded body.
Thus, a reinforced short fiber for a cement-based molded body that has been practically satisfactory for polyolefin fibers having advantages in alkali resistance, lightness, etc. has not yet been obtained.

JP-A-11-116297 Japanese Patent Laid-Open No. 2005-220498

  The present invention has been made to solve the above-mentioned problems, and has sufficient fixing power with cement paste as a reinforcing short fiber for cement-based molded articles for civil engineering, building construction, etc. It is an object of the present invention to provide a reinforcing short fiber for a cement-based molded body that sometimes provides good spreadability and good dispersibility in concrete.

The present inventors, when opening the fiber, in the portion where the fibers are in contact with each other, there is no unevenness that becomes an obstacle, and in order to ensure the fixability with the cement paste, the surface area of the fiber is increased, The shape which can remarkably increase the physical bond has been intensively studied. As a result, by forming recesses with embossing rollers at specific depths and at specific intervals on the sides or groove bottoms of roughly polygons with protrusions, they are put into various cement-based structures such as fuller concrete. It has been found that, at the same time, it is possible to achieve both a strong fixing property with a cement paste and a tensile strength of a fiber that can effectively develop a reinforcing effect.
That is, the present invention
(1) The polypropylene resin as a main component, a cross-sectional shape consists of X-shaped drawn fiber, fineness of 2,000～8,000Dtex, fiber length a cementitious molded body reinforcing short fibers 20~60mm ,
The respective grooves the cross-sectional shape is at least one opposing the X-shaped, a recess depth 100~200μm that formed by shape with continuously at intervals of 2~4mm along the longitudinal direction of the fiber Reinforced short fibers for cement-based molded products,
Is to provide.

The reinforcing short fiber for cement-based molded article of the present invention has no irregularities that obstruct the fiber surface on the fiber surface where the fibers are in contact with each other. It has a unique polygonal cross-sectional shape that can be opened easily and has protrusions at the time of insertion into the groove, and concave portions are formed at specific depths and specific intervals at the bottom of the groove. The decrease in tensile properties of the fiber is small. As a result, it is possible to prevent the fiber from coming off after the cement has been cured, so that an extremely excellent reinforcing effect can be exhibited.
In addition, if a synthetic resin is a polyolefin resin, especially a polypropylene resin, it has excellent resistance to cement alkali, and the specific gravity is the lowest among the synthetic fibers. Reduction can be achieved.

The synthetic resin raw material used in the present invention is not particularly limited, but a polyolefin-based resin, a polyacetal resin, and the like are desirable from the viewpoint that cement alkali resistance is required. Particularly preferred resins include polypropylene, polyethylene, poly-4-methylpentene-1, etc. for polyolefin resins, and polyoxymethylene for polyacetal resins. These resins can be used alone or in combination of two or more.
Of these, polypropylene resin is particularly preferable.
As the polypropylene resin, a propylene homopolymer, a block or random copolymer of an α-olefin such as ethylene and propylene, or a mixture thereof can be used.
Furthermore, other polyolefins can be blended with the polypropylene resin, if necessary, at the raw material stage or at the time of spinning extrusion. Other polyolefins to be blended here include polyethylene resins such as high density polyethylene, linear low density polyethylene, low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-alkyl acrylate copolymer, polybutene-1 Etc.
Further, the melt flow rate (MFR) of the resin is 0.1 to 30 g / 10 minutes, preferably 0.1 to 20 g / 10 minutes, more preferably from the viewpoint of the balance between continuous stable productivity and fiber strength. 0.3-10 g / 10min is suitable.

  In addition, the synthetic resin has an antioxidant, a light stabilizer, an ultraviolet absorber, a neutralizer, a nucleating agent, an epoxy stabilizer, a lubricant, an antibacterial agent, a flame retardant, as long as the effects of the present invention are not hindered. In addition, additives such as an antistatic agent, an inorganic filler, an organic filler, a pigment, and a plasticizer can be appropriately added.

The reinforcing short fibers for cement-based molded bodies in the present invention (hereinafter sometimes simply referred to as “reinforcing short fibers”) are drawn fibers mainly composed of a synthetic resin, and the cross-sectional shape of the fibers is 3 or more. The protrusions are substantially polygonal having side portions or groove portions between adjacent protrusion portions, and concave portions are attached to the at least one side portion or the groove portions at predetermined intervals along the longitudinal direction of the fiber. The feature is that it is shaped.
More specifically, examples of the substantially polygonal cross section include an X shape, a Y shape, a cross shape, a substantially triangular shape, a substantially rectangular shape, and a star shape.
In the present invention, the side means a ridge line (real line) connecting adjacent protrusions (corners, vertices) in the fiber cross section.
More specifically, FIG. 1 is a perspective view schematically showing a reinforcing short fiber having a substantially square cross section, which has four protrusions (corner portions) 2 and four side portions S, and has two upper and lower portions. The case where the diamond-shaped recessed part 4 was continuously formed in the one side part S by the predetermined pitch is shown.
Moreover, in the reinforced short fiber of the present invention, the groove is a ridge line (real line) connecting adjacent protrusions (vertices) to a center side of the fiber cross section from a straight line (imaginary line) connecting adjacent protrusions For example, in the X-shaped cross section, it is a V-shaped or arc-shaped groove-shaped portion, and a recess formed continuously in the longitudinal direction of the fiber. means.

  As the substantially polygonal cross section, a shape having 3 or more, particularly 4 or more apexes is more preferable. By forming the shape of the fiber in this way, the apparent fiber thickness is increased as compared with a fiber having a conventional round cross-section or flat round cross-section, and the cross-sectional bending secondary moment of the fiber is improved. For this reason, even short fibers with a relatively small tensile Young's modulus are prevented from bending due to collision with coarse aggregates, fine aggregates, etc. during cement mixing, and are dispersed in a form effective for reinforcement. By exhibiting a fiber reinforcing effect, a large effect of improving physical properties of concrete can be exhibited.

Further, the reinforcing short fiber of the present invention requires that concave portions are formed at predetermined intervals along the longitudinal direction of the fiber at the bottom of at least one groove portion of the groove portion.
The recess at the bottom of the groove is preferably formed on 2 to 6 groove bottoms.
From the viewpoint of the reinforcing effect, the depth of the concave portion formed on the bottom of the groove portion of the fiber cross section is 50 to 250 μm, more preferably 100 μm to 200 μm, and the arrangement interval in the longitudinal direction is 1 to 5 mm, more preferably 2 mm to 4 mm. It is.
If the embossed roller has too deep recesses and the number thereof is too large, the fixing property with the cement paste is improved, but on the other hand, the tensile strength of the fiber is lowered, and sufficient reinforcement becomes difficult. On the other hand, when it is too shallow and when the number is small, the decrease in the tensile strength of the fiber is small, but the fixing property with the cement paste is lowered and the reinforcement becomes difficult. As the fiber tensile strength, according to the Japan Road Authority tunnel construction management guidelines (fiber reinforced concrete lining, September 2003), the fiber strength required for cement concrete reinforcement for tunnels is 450 N / mm ² or more. It is defined and needs to be satisfied, and the depth and the arrangement interval of the recesses are determined in consideration of these.

Examples of the method for forming the recess at the bottom of the groove include a method of continuously forming the recess by passing the drawn fiber between the pair of embossing rollers under an appropriate pressure following the drawing.
As a method of preventing the fiber strength from being lowered even if the concave portions having the depths and intervals as described above are formed, the embossing positions are not shifted to the same position in the length direction, but are formed in a shifted manner when embossing a plurality of grooves. It is desirable. This is possible by shifting the shaping positions of the pair of embossing rollers.
In the case of a fiber having a nominal thickness of 3,300 dtex, the surface shape of the embossing roller having such a concave shape is an embossing roller engraved with multiple rows of convex portions arranged linearly along the circumferential direction. The embossing has an interval between convex portions in the circumferential direction of 1 mm to 5 mm, a multi-row convex portion interval in the roller width direction of 0.7 mm to 0.8 mm, and an engraved convex portion height of about 0.5 mm to 1 mm. By using an embossing roller in which the tips of the projections are processed flat into a circular shape or a polygonal shape, and the tips of the multi-row projections are arranged in a staggered pattern, a large number of stretched strands (fibers) are continuous. Therefore, the recess can be processed only in the groove.
That is, since the convex part of the embossing roller is linearly arranged in the circumferential direction, each strand of the strand is coupled with the groove part of the fiber cross section and the convex part of the embossing roller. Only the bottom of the cross-sectional groove can be formed with a recess.

For the groove bottom recess processing of the fiber cross section, in the cross section with an even number of grooves, embossing rollers for shaping are used by placing a pair of rollers in the vertical direction, left and right direction, or diagonal direction, and sandwiching the fiber strand. This is advantageous for the production of reinforcing fibers.
In particular, when the fiber cross section is X-shaped, the number of grooves is 4, and a pair of rollers can form recesses in two opposing grooves, making it easy to produce stably.
In addition, embossing recessed part processing can also be given to an odd number of groove bottoms by making one of a pair of rollers into a flat roller.
Furthermore, a plurality of embossing rollers can be arranged in multiple stages within a range that does not adversely affect the physical properties of the fiber as the reinforcing fiber of the present invention, and the same groove or other grooves can be provided with a recess. In this case, the convex shape of each pair of embossing rollers is different from that of the previous stage, and different concave portions are formed in one groove or between the grooves to adjust the fixing property to the cement paste. You can also.

  In addition, when the thickness of the reinforcing fiber is changed, the multi-row convex spacing in the horizontal direction of the embossing roller and the height of the convex portion are adjusted as appropriate. It is necessary to make adjustments while increasing the interval and increasing the height of the convex portion in consideration of the balance between the deterioration of the physical properties of the fiber and the fixing property of the cement paste. It is important to shape continuously in the direction.

  In addition, the reinforced short fiber of this invention can use not only a single layer fiber but the composite fiber which uses a high melting component as a core layer, and uses a low melting component as a sheath layer. The manufacturing method of such a composite fiber is well-known.

  The manufacturing method of the reinforced short fiber of this invention is not specifically limited, A various method is employable. Usually, a synthetic resin is first used to melt and extrude from a nozzle having a shape corresponding to a desired protrusion shape, and after cooling and stretching, a single piece having a rectangular or fin-like protrusion that is continuous in the longitudinal direction of the fiber. A layer fiber or a composite fiber is formed. Next, an embossing roller having a convex portion corresponding to the concave shape is brought into contact with the groove portion existing between the fin-like projections, and the concave portion is formed in a predetermined groove, and further, a surfactant is attached. It can be manufactured by applying and finally cutting to a desired length. Below, the manufacturing method of a reinforced short fiber is demonstrated in detail.

The method for forming a single fiber having fin-like protrusions continuous in the longitudinal direction of the fiber is not particularly limited, and the cross section provided with the protrusions is a substantially polygonal shape having three or more protrusions. For example, any method may be used as long as it can be manufactured so as to form a substantially triangular shape, a substantially star polygon shape, a substantially complex polygon shape, or the like. For example, polyolefin resin is melt-extruded from a die using X-shaped, Y-shaped, cross-shaped, substantially triangular, substantially quadrangular, star-shaped nozzles, or these continuous yarn-shaped nozzles, cooled and solidified, and continuously unstretched Synthetic resin fibers can be obtained.
Next, the synthetic resin fiber obtained as described above is subjected to thermal stretching and, if necessary, thermal relaxation treatment. By this heat treatment, the rigidity of the fiber can be increased, and a fiber suitable for cement reinforcement having a small elongation can be obtained. Hot stretching is performed at a temperature below the melting point of the synthetic resin and above the softening point.
As the thermal stretching method, a heating method such as a hot roll method, a hot plate method, an infrared irradiation method, a hot air oven method, a hot water method, a water vapor method and the like can be adopted. The stretching operation may be one-stage stretching, two-stage stretching, or multi-stage stretching.

A method for forming a recess at the bottom of the groove is, for example, a method in which, following stretching, a pair of embossed rollers is inserted and sandwiched between the embossing rollers under appropriate pressure, and the indentation is continuously formed by heat applied during stretching. Since the concave portion can be shaped while the fiber is heated, it is efficient and economical.
As a method for preventing a decrease in fiber strength even when the concave portion is formed, in the case of multi-groove embossing, it is desirable that the embossed position between the multiple grooves is not the same position in the length direction but is formed by shifting. This is possible by shifting the shaping positions of the pair of embossing rollers.
In the case of a fiber having a nominal thickness of 3,300 dtex, the surface shape of the embossing roller having such a concave shape is an embossing roller engraved with multiple rows of convex portions arranged linearly along the circumferential direction. The embossing has an interval between convex portions in the circumferential direction of 1 mm to 5 mm, a multi-row convex portion interval in the roller width direction of 0.7 mm to 0.8 mm, and an engraved convex portion height of about 0.5 mm to 1 mm. By using an embossing roller in which the tips of the projections are processed flat into a circular shape or a polygonal shape, and the tips of the multi-row projections are arranged in a staggered pattern, a large number of stretched strands (fibers) are continuous. Therefore, the recess can be processed only in the groove.
That is, each strand of the embossing roller is linearly arranged in the circumferential direction on the embossing roller, so that the groove section of the fiber cross section and the embossing roller protrusion are coupled to each other, and fitted. Only the bottom of the cross-sectional groove can be formed with a recess.

The groove bottom recess processing of the fiber cross section can be used by sandwiching the fiber strand by arranging a pair of embossing rollers for shaping in the vertical direction, the horizontal direction, or the diagonal direction in a cross section having an even number of grooves. Therefore, it is convenient for the production of reinforcing fibers.
When the fiber cross section is X-shaped, the number of grooves is 4, and a pair of rollers can form recesses in two opposing grooves, making it easy to produce stably.

Further, in the reinforcing fiber of the present invention, the single yarn fineness is preferably 1,000 to 9,000 dtex from the viewpoints of the reinforcing effect, mixing workability, dispersibility, shape of the concave portion in the groove, and the like. 8,000 to 8,000 dtex is particularly preferred.
If it is 1,000 dtex or more, it is possible to form a recess at the groove bottom with an embossing roller, and if it is 9,000 dtex or less, the contact area of the fiber with the cement admixture decreases, and the amount of blended fiber In adjusting with (capacity%), there is no problem that the reinforcing effect is inferior.

The reinforcing fiber can be subjected to various treatments before or after cutting to make short fibers. For example, the surface of the fiber may be treated with a surfactant, a dispersant, a coupling agent, etc., or in the case of a polyolefin resin fiber or surface activated or crosslinked by corona discharge treatment, ultraviolet irradiation, electron beam irradiation, etc. You may perform the process of. In particular, it is preferable to perform a surface hydrophilization treatment with a surfactant or the like from the viewpoint of enhancing dispersibility when blended in a cement-based molded body.
The surfactant is selected according to the synthetic resin used for the fiber. In the case of polyolefin fiber, a hydrophilic interface is used to improve the affinity between the hydrophobic polyolefin fiber and the cement paste. It is preferred to use an activator. Dispersibility is improved by imparting hydrophilicity to the polyolefin fiber, and fiber reinforcing effect is improved by uniformly mixing the fiber and the cement paste.
As the hydrophilic surfactant, it can be used without any particular limitation. Among them, a polyethylene glycol alkyl ester nonionic surfactant, an alkyl phosphate anionic surfactant, a polyhydric alcohol type amide nonionic surfactant Etc. 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 preferred 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 air bubbles are generated in various cement-based molded products represented by the time-fresh concrete, and the physical properties such as compressive strength and bending strength of the cement-based molded products may be lowered. In order to suppress the generation of bubbles, an antifoaming agent can be used in combination with the surfactant treatment on the fiber.

  The method for attaching the surface treatment agent to the polyolefin fiber is not particularly limited, and any of a dipping method, a spray method, and a coating method can be employed. After the surface treatment agent is applied to the fiber, it can be penetrated into the fiber assembly using a squeeze roll or the like, if necessary.

The reinforcing synthetic fiber thus obtained is cut to a predetermined length and used as a cement reinforcing short fiber. From the viewpoint of improving the cracking resistance (toughness) of the cement-based molded body, the short fiber has a smaller thickness (fiber diameter D) and a longer length (fiber length L), that is, an aspect of the short fiber. The higher the ratio (L / D), the better. However, the reinforcing short fiber of the present invention has a shorter fiber length as long as the short fiber diameter is the same, even if the aspect ratio is smaller than that of the conventional product. Is also characterized by a large reinforcing effect.
The short fiber for reinforcement of the present invention has a short fiber length (apparent length) of 10 to 80 mm, preferably 15 to 70 mm, and more preferably 20 to 60 mm. If the fiber length is 10 mm or more, it is difficult for the cement to come off from the cement, and if it is within 80 mm, the dispersibility does not become poor.

  Next, the reinforcing short fiber of the present invention is used 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 is compounded and used, and it can be set as cement-type molded objects, 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. Examples of fine aggregates include river sand, sea sand, mountain sand, quartz sand, glass sand, iron sand, ash sand, and other artificial sand. Coarse aggregates include reki, gravel, crushed stone, slag, and various artificial light weights. Examples include aggregates. 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 blending amount of the reinforcing short fibers with respect to the cement is usually 0.05 to 2% by volume with respect to the volume of the cement-based molded body. From the viewpoints of uniform dispersibility of fibers at the time of cement blending, fluidity of blended cement, workability, and improvement in physical properties of cement-based molded products, the blending amount of reinforcing short fibers is preferably 0.1 to 1.5 volumes. %, More preferably in the range of 0.3 to 1% by volume.

When the short fiber for reinforcement of the present invention is used for the production of a cement-based molded body, the reinforcing short fiber is dispersed in a cement-based powder, a cement-based flash or a slurry to form a cement-based mixture, and this is 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 or the like as base concrete, and after kneading the base concrete, the reinforcing short 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 is appropriate for the mixing of the base concrete, and the range of 45 to 90 seconds is appropriate for the kneading after the reinforcing short fibers are added.

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.
As a concrete product, it can also be used for sheet piles formed by molding, concrete pulp, piles, poles, etc. of hollow cylindrical products. As road concrete, it can be used for sidewalk concrete flat plates, reinforced concrete U-shaped, concrete guardrails and the like. In addition, it can also be used for plastering mortars, exterior materials and roofing materials as building-related members, and wall materials, reliefs, flooring materials, ceiling materials as interior materials.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.

Example 1
Using a single-screw melt extruder equipped with a nozzle with 16 holes and an X-shaped hole, melt an isotactic polypropylene resin (WF464N; manufactured by Sumitomo Chemical Co., Ltd.) with an MFR = 2 g / 10 min at an extrusion temperature of 255 ° C. The extruded resin was put into a cooling water tank and solidified by being put in a cooling water tank, and was taken up at a constant speed by five parallel stretching rollers. The taken-up fiber strand was continuously put into a warm water heated drawing tank at 95 ° C. and drawn 6.9 times with a second drawing roller. Further, this was continuously put into a steam heating stretching tank at 120 ° C., stretched by 1.74 times with a third stretching roller, and a two-stage stretching of 12 times was performed.
Next, this stretched strand was made into a pair of upper and lower file embossing rollers (φ 101 mm, width 160 mm, circumferential spacing of protrusions 2.93 mm, spacing in the width direction of projections 1.33 mm, and the height of the projections of 0.2 mm. 9mm, the tip shape of the convex part is a rhombus shape with a short diagonal length of 0.35 mm x long diagonal line length of 0.625 mm, the convex part tip clearance of the upper and lower pair of rollers is adjusted to 0.2 mm, and the surface speed is the speed of the strand And a concave shape was added to the upper and lower groove bottoms of the X section.
After that, alkyl phosphate amine salt surfactant diluted with water (manufactured by Takemoto Yushi) is attached to the strand so that it is equivalent to about 0.05% by mass by spraying, and cut to a constant length of 40 mm with a fan type cutter. Thus, a short fiber made of polypropylene was obtained.
The shape of the reinforcing short fiber 1 made of polypropylene is such that the upper and lower surfaces of the four groove portions 3 between the four protrusions 2 are schematically shown in FIG. 1 (C). The rhombus-shaped recesses 4 are formed in the two rows of grooves, and as shown in FIG. 1A, the interval x is 2.9 mm, and the maximum depth of the embossed recesses is 150 μm on average.
In addition, as shown in the plane photograph of FIG. 2, the tendency for the fin-like protrusion 2 to swell in the width direction of the fiber corresponding to the recess 4 was recognized.
As shown in Table 1, the physical properties were a fineness of 3,305 dtex, a tensile strength of 509 N / mm ² , and a fiber length of 40 mm.

Comparative example The embossed roller of the stretched strand is a parallel pattern uneven gear roller (φ100 mm, width 160 mm, gear tip radius 0.5 mm, gear tip interval 2.90 mm, the height of the gear tip is perpendicular to the traveling direction of a pair of upper and lower strands. 0.9 mm), a pair of upper and lower gear tip clearances was adjusted to 0.5 mm, and a polypropylene short fiber was obtained in the same manner as in Example 1, except that only the projection tip portion of the fiber X cross section was unevenly shaped. It was.
This polypropylene short fiber has an X cross section, the embossed recess is formed only at the tip of the four cross-sectional protrusions, the recess spacing in the fiber direction is 2.9 mm, and the physical properties are fineness of 3,310 dtex, tensile strength It was 487 N / mm ² and the fiber length was 40 mm.

[Fiber physical property test method]
-The measurement of the fineness of the fiber and the tensile test were carried out according to JIS-L-1013.
・ Groove bottom embossing ・ Depression depth measurement: Using a surface roughness measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd .: Surfcom E-MD-S138A type), the concave depth in the longitudinal direction of the fiber in the measurement range of 6 mm to 8 mm Further, 50 cut fibers were measured in the same manner, and the average value was defined as the recess depth.
-Embossed recess spacing: The number of recesses per cut fiber length was measured, and the fiber length / number of recesses was calculated. This was similarly measured with 100 cut fibers, and the average value was taken as the emboss interval.
Fiber length: The fiber length of 100 cut fibers was measured, and the average value was defined as the fiber length.

Cement fixability test Next, the reinforcing fiber of Example 1 and Comparative Example 1 was used as a measure to indicate the fixability with cement paste. Were subjected to a compression test and a bending test (measurement of bending strength and bending toughness coefficient).
[Fiber pulling resistance value]
About 15 mm of fiber was embedded in cement mortar filled in a polyvinyl chloride pipe with a pipe inner diameter of 53 mm and a depth of 20 mm. After curing at room temperature for 28 days, the fiber was pulled out from cement at a rate of 2 mm / min with Tensilon. The stress at the time (drawing resistance value) was measured. The cement used was ordinary portland cement (manufactured by Taiheiyo Cement Co., Ltd.), and the sand was land sand. The water / cement ratio was 57%.
The specific mixing ratio is as follows.
Cement: 359 g, sand: 831 g, water: 205 (total amount: 1395 g) was collected in a 2 L stainless steel vat, and electric mortar was inserted into the mortar.
In comparing the drawing resistance value between the fibers, the measured embedment length of each fiber measurement sample was measured, and this was proportionally converted to the embedment length per 15 mm to obtain the drawing resistance value. (See Table 1)

[Compression and bending property test of fiber blended concrete]
(Manufacture of concrete test specimens)
Using the 50L forced biaxial mixer, so that the total volume of 40L, cement 350 kg / m ^3, fine aggregates 870 kg / m ^3, coarse aggregate 901kg / m ^3, water 175 kg / m ^3, high AE water reducing agent The mixture was kneaded in advance for 90 seconds at a blending ratio of 2.8 kg / m ³ . Next, the fibers of Example 1 and Comparative Example 1 were added at a blending ratio of 2.73 kg / m ³ , respectively, and further kneaded for 45 seconds.
Using the obtained fresh concrete, a specimen for a bending test was prepared in accordance with the Japan Highway Public Corporation Tunnel Construction Management Guidelines (Fiber-Reinforced Lining Concrete Edition, September 2003).
The specimens were subjected to room temperature curing for 24 hours, then released from the mold, and then cured in water for 6 days. The specimens were then cured at room temperature in the atmosphere until the age of 28 days.
Materials used:
・ Cement: Normal portland cement (specific gravity: 3.16, made by Taiheiyo Cement)
-Fine aggregate: land sand, surface dry specific gravity 2.60 (maximum particle size 5mm)
-Coarse aggregate: crushed stone, surface dry specific gravity 2.67 (maximum particle size 20mm)
・ Water: City water ・ High-performance AE water reducing agent: SP8SV (manufactured by NMB)

(Concrete property test method)
The bending strength and bending toughness tests were in accordance with the bending toughness test method (JHS 730-2003) of fiber reinforced lining concrete.
-Compressive strength: According to JHS-G551-1999.
-Slump test: According to JIS A1101.
-Air quantity test: JIS A 1128 was followed.

[Fiber opening test]
Using a fiber opening grid (outside dimensions: 490 mm x 700 mm; grid square spacing: 75 mm constant, grid material: φ2.5 SUS rod) installed in the input hopper of the fiber input machine to the agitator car, manually The time for passing 3 kg of fiber was measured 5 times each.
-Example fiber: 44, 36, 43, 40, 35 seconds (average: 40 seconds)
Comparative fibers: 56, 47, 50, 49, 51 seconds (average: 51 seconds)
As a result, the fibers of the examples were able to easily open the fiber mass (each one piece apart) in a short time. This was able to suppress the fullness of the flesh concrete due to the time for fiber input at the time of implementation, and was superior to the fibers of the comparative example. Contributes to the improvement of workability (workability) in subsequent concrete placement.

[Fiber concrete dispersibility test]
12.7 kg (equivalent to 0.3 vol%) of the fiber of the example was put into an agitator vehicle loaded with 4.5 m ³ of fresh concrete in about 3 minutes using the above-mentioned feeder equipped with a φ75 mm opening grid. Thereafter, the mixture was kneaded for 2 minutes. In accordance with JSCE-F554-1999 (Testing method for mixing steel fibers in steel fiber reinforced concrete), the fresh concrete was measured to 7L for concrete from the beginning, middle and end of the concrete. Then, the PP fibers of the present invention separated by floating in water (floating in water) were collected separately, and the dry mass was measured.
・ Start: 19.0 g, middle: 19.3 g, final: 19.0 g
・ Theoretical value (0.3 vol%): 19.1 g
As a result, it was confirmed that the spreadability and dispersibility from fiber feeding to concrete kneading were good.
The above measurement results are summarized in Table 1.

As is clear from Table 1, the reinforcing short fiber of Example 1 of the present invention has a higher tensile strength and a pulling resistance value that is about 1.8 times larger than that of the fiber of Comparative Example 1, and has a fixing property with cement paste. It was very good.
In addition, the reinforcing short fibers of Example 1 of the present invention were superior to the reinforcing short fibers of the comparative example in terms of workability for feeding fibers into an agitator vehicle and dispersibility in concrete.
And the concrete molding using the fiber of an Example had a larger bending toughness coefficient than the concrete using the fiber of a comparative example, and was excellent in the reinforcement effect.

The reinforcing short fiber for cement-based molded article of the present invention has no irregularities that obstruct the fiber surface on the fiber surface where the fibers are in contact with each other. Since the recesses are shaped at a specific depth and at specific intervals at the bottom of the groove having a specific cross-sectional shape of a substantially polygonal shape having protrusions that can be easily opened at the time of insertion into the fiber, The decrease in tensile properties is small, and it has a high resistance to drawing with cement. As a result, an extremely excellent reinforcing effect can be expressed in the concrete molded product after cement hardening.
Further, if the polyolefin resin, particularly polypropylene resin, is used as the synthetic resin, the short fiber for reinforcement excellent in workability and workability when it is transported and mixed with concrete because the specific gravity of the polypropylene short fiber is light can be provided.
As described above, the reinforcing short fiber for cement-based molded product of the present invention is excellent in the charging work and workability when blended with concrete and has a high fiber reinforcing effect, so it is effective as a reinforcing short fiber for cement molded product. Available.

It is a perspective view of one embodiment of the reinforcing short fiber for cement-based molded article of the present invention. It is a schematic diagram of other embodiment of the reinforcing short fiber for cement-type molded objects of this invention. (A) Schematic plan view, (B) YY sectional view, (C) ZZ side view 2 is a top view photograph of a reinforcing short fiber for cement-based molded article of the present invention obtained in Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Short fiber for reinforcement 2 Protrusion part S Side part 3 Groove part 4, 4 'Concave part

Claims (1)

It is a reinforcing short fiber for cement-based molded bodies having a polypropylene resin as a main component , made of drawn fibers having an X-shaped cross section , a fineness of 2,000 to 8,000 dtex, and a fiber length of 20 to 60 mm,
The respective grooves the cross-sectional shape is at least one opposing the X-shaped, a recess depth 100~200μm that formed by shape with continuously at intervals of 2~4mm along the longitudinal direction of the fiber A reinforced short fiber for cement-based molded products.

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