JP2006143541A - Polypropylene short fiber for concrete reinforcement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain polypropylene short fibers for concrete reinforcement having high adhesion to hydraulic compositions such as concrete and being excellent in the reinforcing effect of the mechanical strength of concrete and the like. <P>SOLUTION: The polypropylene short fibers 1 are formed by melt-spinning polypropylene being an extrusion and stretched grade and whose melt flow rate is 0.5-5.0 g/10 min and by stretching it highly. The polypropylene short fibers are almost flat monofilaments whose fineness is 1,000-10,000 dtex, whose fiber width is 1.0-1.5 mm, whose apparent thickness is 0.5-1.0 mm and whose length is 20-60 mm. The polypropylene short fibers 10 for concrete reinforcement comprise the polypropylene short fibers 1 whose fiber tensile strength is 450 MPa or more, where raised projection parts 2 embossed with the patterns of diamond lattices or partial patterns having a width almost equal to a fiber width on a surface 1a and a back surface 1b and where the raised projection parts 2, 2 on the surface and the back surface have a thickness of 10-18% of the fiber thickness. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a short polypropylene fiber for concrete reinforcement that is added to and mixed with a hydraulic composition such as concrete or mortar to reinforce the strength of the concrete.

  Conventionally, steel fibers have mainly been used for reinforcement of cracks in concrete and mortar and prevention of peeling, but in recent years, the use of non-steel fibers such as organic fibers and inorganic fibers has attracted attention. . This is because the organic fiber and the inorganic fiber are lighter than the steel fiber, so that the workability is improved, and since there is no generation of rust, the quality deterioration of the concrete structure can be reduced. Typical examples of inorganic fibers include glass fibers and carbon fibers. Examples of organic fibers include vinylon fibers and polypropylene fibers.

Among inorganic fibers, glass fibers have the disadvantage that they are deteriorated by alkali in the cement and the reinforcing effect gradually decreases with time. In addition, the carbon fiber has no problem in terms of durability, but has a disadvantage that the elongation at break is low and the fiber itself is damaged during kneading into concrete and the reinforcing effect is lowered.
In contrast, organic fiber has low tensile strength and elastic modulus, but has high elongation capacity, so when it is combined with concrete, it cracks in the concrete and reinforces even after the cracks have progressed greatly. It can be expected to retain the effect.

However, in the vinylon fiber, usually, a thin monofilament of about several tens of μ is simply focused and fixed, and in this state, its surface area does not increase specially, so it is somewhat higher than that of polypropylene fiber. Although it has hydrophilicity, when it is combined with concrete, it cannot be said that the adhesion strength between the concrete matrix is high. As a result, the reinforcing effect when using fiber reinforced concrete is insufficient.
For this reason, thick monofilament-like polypropylene fibers have attracted attention as concrete reinforcing fibers, and various proposals and studies have been made regarding their use, but at the present time they are still inadequate for practical use. Further improvements and developments are underway.

  For example, Japanese Patent Application Laid-Open No. 56-9269 discloses a method for producing a cement blend in which unevenness is imparted to the fiber surface in order to enhance the reinforcing effect of polypropylene fiber as a cement reinforcement blend. And the unevenness | corrugation provided to the fiber surface currently disclosed by this is illustrated by the simple thing which formed the unevenness | corrugation by changing the thickness repeatedly to the large diameter-small diameter along the length direction of a fiber. Therefore, further improvement of the reinforcing effect is desired.

  Japanese Patent Application Laid-Open No. 57-156363 discloses polypropylene as a reinforcing material mixed into a molded body formed by curing a hydraulic inorganic binder such as mortar or concrete. Synthetic resin fiber monofilaments are disclosed. And it is described that it is effective to give a concavo-convex pattern to the surface of the linear body of synthetic resin fiber monofilament in order to further enhance the reinforcing effect.

  The formation of the concavo-convex pattern is shown to be formed on the surface of a synthetic resin fiber monofilament using an embossing roll provided with a large number of two intersecting parallel concave stripes. However, in this proposal, it is only effective to give the surface of the synthetic resin fiber monofilament a concavo-convex pattern to improve the concrete reinforcing effect, and polypropylene fiber is used as a reinforcing material for concrete. It is still insufficient for practical use, and further investigation of physical components is necessary.

  Further, as a concrete reinforcing fiber, Japanese Patent Laid-Open No. 9-86984 discloses a short fiber of a continuous yarn shaped tape by connecting polypropylene short fibers in a separable manner without using individual monofilaments in the form of roses. It has been proposed to enhance the reinforcement effect of concrete, but there are problems in manufacturing and the problem of reproducibility of dispersion in concrete, so some have been put into practical use. However, it has not been widely put into practical use.

  Japanese Patent Application Laid-Open No. 11-116297 discloses a short fiber having a concavo-convex shape formed on its surface by an embossing roll as a polypropylene fiber as a concrete reinforcing fiber. And in order to improve the reinforcing performance, a monofilament having a single yarn fineness of 200 to 10,000 dr and having an unevenness in the range of 2/1 to 7/1 in terms of the average flatness of the fiber cross section on the surface has a length of 5 to 60 mm. It is used after cutting. However, there is no specific disclosure regarding the degree of unevenness in the polypropylene fiber, and further development is desired in order to improve the reinforcing effect against the pulling of concrete.

  Furthermore, in the recently published Japanese Patent Application Laid-Open No. 2004-18352, a polypropylene fiber as a concrete reinforcing fiber is formed with an uneven shape on its surface by an embossing roll. The feature is the fineness of the fiber. When determining the fiber shape and size according to the depth of the concave and convex depressions, the reinforcing effect of the concrete mixed with this was further improved by forming the concave and convex shape within the range calculated based on a specific mathematical formula. Is.

As specific shapes of the concave and convex recesses, various fine container shapes such as a teacup shape, a tray shape, and a box shape are used, which are formed by pressing into the front and back of the fiber. And this container-shaped hollow is filled with concrete, and it is said that the anchor effect is exhibited. However, the use of an embossing roll having such a special shape causes inconvenience in uniformity and reproducibility in the production of delicate short fibers, and there is a problem in practical use of such short fibers.
JP-A-56-9269 JP 57-156363 A JP-A-9-86984 JP-A-11-116297 JP 2004-18352 A

  The present invention has been made in view of the above circumstances, eliminates the disadvantages of conventional reinforcing materials, and is added to and mixed with concrete and mortar to improve the adhesion between them and enhance the mechanical strength of concrete and mortar. It is an object of the present invention to provide a polypropylene short fiber for concrete reinforcement that is excellent in reinforcing effect and has high practicality.

To solve this problem,
The invention according to claim 1 is a polypropylene short fiber obtained by melt spinning and high-stretching polypropylene having an extrusion drawing grade having a melt flow rate of 0.5 to 5.0 g / 10 min., And having a fineness of 1000 to 10,000 dtex. The fiber width is 1.0 to 1.5 mm, the apparent thickness is 0.5 to 1.0 mm, the length is 20 to 60 mm, and the tensile strength is 450 MPa or more. A concrete reinforcement characterized by forming a raised convex portion by embossing a diamond lattice pattern or a partial pattern thereof having substantially the same width, and the height of the raised convex portion is 10 to 18% of the fiber thickness. Polypropylene short fiber.

  The invention according to claim 2 is characterized in that the raised convex portions are formed such that the positions of the diamond lattice pattern or the partial pattern thereof coincide with each other on the front and back surfaces. It is.

  According to a third aspect of the present invention, in the raised convex portion, the diamond lattice pattern of the raised convex portions on the front surface and the back surface is aligned and matched on one side on the front and back surfaces, and the other opposed side is displaced on the front and back surfaces. The short polypropylene fiber for concrete reinforcement according to claim 1, wherein

  According to a fourth aspect of the present invention, there is provided a diamond lattice pattern having a width substantially equal to the fiber width formed on the front and back surfaces of the polypropylene short fiber, or the raised convex portion of the partial pattern, and the rear surface within the raised convex portion of the front diamond lattice pattern 2. The polypropylene reinforcing short fiber for concrete reinforcement according to claim 1, wherein corners of the raised convex portions of the diamond lattice pattern are positioned.

  According to a fifth aspect of the present invention, there is provided a polypropylene short fiber formed by aligning and matching the diamond lattice pattern or its partial pattern on the front and back surfaces, and the raised protrusions of the rear diamond lattice pattern in the raised protrusions of the front diamond lattice pattern. 2. The short polypropylene fiber for concrete reinforcement according to claim 1, wherein the short staple polypropylene is arranged so that the corners of the portion are positioned and mixed at a ratio of 1: 1.

  In the invention according to claim 6, the diamond lattice pattern of the raised convex portions on the front surface and the back surface is a polypropylene short fiber in which one opposing side is aligned and matched on the front and back surfaces, and the other facing side is displaced on the front and back surfaces. In addition, polypropylene short fibers that are arranged so that the corners of the raised protrusions of the back diamond lattice pattern are positioned in the raised protrusions of the front diamond lattice pattern are mixed at a ratio of 1: 1. The polypropylene short fiber for concrete reinforcement according to claim 1.

  The concrete short polypropylene fiber for reinforcing concrete according to the present invention has a diamond lattice pattern having a predetermined thickness or a raised convex part of its partial pattern formed on the front and back surfaces of the polypropylene short fiber, thereby significantly improving the adhesion to concrete. At the same time, the anchor effect can be enhanced, and a polypropylene short fiber for concrete reinforcement having an extremely excellent reinforcing effect can be obtained.

 Further, the diamond grid pattern formed by embossing on the front and back surfaces of the polypropylene short fibers or the raised convex portions of the partial pattern are further reinforced by changing the arrangement and the depth of the unevenness between the front and back surfaces. It is possible to obtain polypropylene short fibers for concrete reinforcement that increase the effect.

  Further, a polypropylene short fiber formed by changing the arrangement and the depth of the unevenness on the front and back surfaces of the diamond lattice pattern formed by embossing on the front surface and the back surface or a raised convex portion of the partial pattern, and the diamond The bending toughness coefficient of concrete can be improved by mixing the arrangement of the raised protrusions of the lattice pattern or the partial pattern thereof with the polypropylene short fibers formed on the front and back surfaces as a reinforcing material.

  For this reason, by using the polypropylene short fiber for concrete reinforcement of the present invention, the concrete significantly exceeding the standard value of the bending toughness coefficient in the fiber reinforced tunnel lining concrete quality control standard of the tunnel construction management guidelines established by the Japan Highway Public Corporation. It is possible to build up the cracks of concrete and mortar, and to prevent peeling off.

  As the polypropylene used in the polypropylene fiber for reinforcing concrete according to the present invention, first, a propylene homopolymer represented by isotactic polypropylene, then a block copolymer of propylene and an α-olefin other than propylene, a random copolymer And copolymers such as graft copolymers. Examples of α-olefins other than propylene include ethylene, butene-1, pentene-1, and hexene-1. The copolymerization ratio of these α-olefins is preferably 10 mol% or less in order to exhibit the rigidity of polypropylene.

  Further, as the polypropylene in the present invention, the above-mentioned homopolymers and copolymers of propylene can also be used. Further, a mixture obtained by adding a small amount of the above-mentioned various α-olefin homopolymers other than polypropylene can be used. Among these, isotactic polypropylene which is a propylene homopolymer having a narrow molecular weight distribution and excellent stereoregularity is particularly preferable.

  Moreover, a small amount of various additive components can be added to the polypropylene used in the present invention, if necessary. Examples of these components include lubricants, antistatic agents, surfactants, organic fillers, inorganic fillers, pigments and other colorants, nucleating agents, antioxidants and various other stabilizers.

The concrete reinforcing polypropylene short fibers of the present invention are made of polypropylene short fibers obtained by melt-spinning and stretching high-stretched polypropylene having a melt flow rate of 0.5 to 5.0 g / min. is there.
Here, when the polypropylene has a melt flow rate of less than 0.5 g / 10 min., It is difficult to extrude and stretch, and polypropylene exceeding 15 g / 10 min. Insufficient strength. More preferred is polypropylene having a melt flow rate of 1 to 3 g / 10 min.

Polypropylene having a fineness of 1000 to 10000 dtex is obtained by drawing such a grade of polypropylene at a high draw ratio of 10 to 15 times during drawing to a tensile strength of 450 MPa or more. Then, this polypropylene fiber is embossed to form a tape-like fiber in which raised protrusions made of diamond lattice patterns or diamond lattice partial patterns are formed on the front and back surfaces, and this is cut into a predetermined length for reinforcement. Polypropylene short fibers.
The concrete reinforcing polypropylene short fibers of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view for explaining a first embodiment of a short polypropylene fiber for concrete reinforcement according to the present invention, and FIG. 2 is a perspective view for explaining a modification of the first embodiment.
In FIG. 1, in the concrete reinforcing polypropylene short fiber 10 of this example, the width of the polypropylene short fiber 1 having a tape-like appearance is 1 to 1.5 mm, and the apparent thickness is 0.5 to 1.0 mm. Thus, a flat shape formed by cutting the length to 20 to 60 mm is exhibited.

  On the front surface 1a and back surface 1b of such a tape-like polypropylene short fiber 1, a raised projection 2 having a fine diamond lattice pattern is continuously formed along the longitudinal direction with a width substantially equal to the fiber width by embossing. ing. And the height of this protruding convex part 2 is 10 to 18% of the apparent thickness of the polypropylene short fiber 1.

  This height is related to the adhesion to concrete and the like, and if the height is less than 10%, the adhesion when the polypropylene short fiber 1 is dispersed in a hydraulic composition such as concrete is low. It becomes. On the other hand, if it exceeds 18%, the thickness of the short fiber 1 becomes relatively small, resulting in a shortage of the tensile strength of the short fiber 1 itself. The size of the diamond lattice pattern depends on the width of the short fiber 1 of polypropylene, the apparent thickness, etc., but the vertical dimension is 1.0 to 3.0 mm and the horizontal dimension is 1.0 to 1.5 mm. It is preferable to make it.

The raised protrusions 2 of the diamond lattice pattern are formed on the surfaces 1a and 1b of the polypropylene short fibers 1, but in this first embodiment, the positions of the diamond lattice patterns on the front surface 1a and the back surface 1b are aligned and matched. Has been placed.
The raised protrusions 2 having such a diamond lattice pattern increase the adhesion with concrete due to the fine unevenness, and increase the frictional resistance and flexibility. In addition, by forming the raised protrusions 2 on both the front and back surfaces, these effects are further increased and effectively act to reinforce the mechanical strength of the concrete.

FIG. 2 shows a concrete reinforcing polypropylene short fiber 15 obtained by deforming the concrete reinforcing polypropylene short fiber 10 of the first embodiment. The concrete reinforcing polypropylene short fibers 15 are obtained by shifting the raised protrusions 2 of the diamond lattice pattern formed on the front surface 1a and the back surface 1b of the polypropylene short fibers 1 in the first embodiment along the width direction. is there. Then, the raised convex portions 12 of the diamond lattice partial pattern are arranged and formed in a manner matching the front surface 1a and the back surface 1b, and the rest has the same configuration as in the first embodiment.
The deformed concrete reinforcing polypropylene short fibers 15 also have the same effects as the concrete reinforcing polypropylene short fibers 10 of the first embodiment.

  Next, a concrete reinforcing polypropylene short fiber according to a second embodiment of the present invention and a concrete reinforcing polypropylene short fiber according to a third embodiment will be described. The feature of these embodiments is that the diamond lattice pattern formed on the polypropylene short fiber 1 or the raised protrusions of the partial pattern of the diamond lattice are formed in different arrangement states on the front surface 1a and the back surface 1b, and mechanical mechanical properties of concrete The strength reinforcement effect is further improved. These will be described below with reference to the drawings.

  FIG. 3 is a plan view for explaining a concrete reinforcing polypropylene short fiber according to the second embodiment. FIG. 3 (A) is a plan view of the front surface, and FIG. 3 (B) is a perspective plan view of the back surface. The concrete reinforcing polypropylene short fiber 20 of the second embodiment is substantially equal to the width of the polypropylene short fiber on the surface 1a of the polypropylene short fiber 1 as in the concrete reinforcing polypropylene short fiber 10 of the first embodiment. The raised protrusions 2 of a diamond lattice pattern with a small width are formed by embossing.

  On the other hand, on the back surface 1b, the opposite sides 2a-2c of the four sides 2a, 2b, 2c, 2d of the diamond lattice pattern at the raised projections 2 of the diamond lattice pattern on the front surface 1a, and the diamond lattice pattern of the back surface 1b Of the four raised edges 3a, 3b, 3c, and 3d of the four sides 3a, 3b, 3c, and 3d, and the other raised edges 2b-2d of the diamond lattice pattern raised protrusion 2 on the surface 1a. The raised convex part 3 of a fine diamond lattice pattern is shaped by the arrangement position and the raised convex part of the opposing sides 3b-3d provided in a displaced manner.

  As described above, the concrete reinforcing polypropylene short fibers 20 according to the second embodiment have the raised convex portions 2 and 3 of each diamond lattice pattern formed on the front surface 1a and the back surface 1b of the polypropylene short fibers 1 facing each other. The opposite side 2a-2c of the front surface 1a and the opposite side 3a-3c of the back surface 1b are aligned and matched, and the other opposing side, that is, the opposing side 2b-2d of the front surface 1a and the back side 1b This is a polypropylene short fiber formed on the front and back surfaces by disposing 3b-3d at a displaced position, thereby enhancing the reinforcing effect of the strength of the concrete.

Next, a concrete reinforcing polypropylene short fiber according to a third embodiment will be described with reference to FIG.
FIG. 4 is a plan view of a concrete reinforcing polypropylene short fiber according to the third embodiment. In the figure, a solid line indicates a raised convex portion 2 of a diamond lattice pattern arranged on the surface 1a of the polypropylene short fiber 1, Moreover, the dotted line has shown the protruding convex part 4 of the diamond lattice pattern arrange | positioned at the back surface 1b. The concrete reinforcing polypropylene short fiber 30 of this embodiment is characterized in that the raised convex portions 2 and 4 of the diamond lattice pattern having a width substantially equal to the fiber width formed on the front surface 1a and the back surface 1b of the polypropylene short fiber 1 are displaced. Is formed.

  That is, the raised convex portion of the displaced diamond lattice pattern formed on the front surface 1a and the rear surface 1b of the polypropylene short fiber 1 is replaced with the raised convex portion 4 of the diamond lattice pattern formed on the rear surface 1b of the polypropylene short fiber 1. The corner portions 4e, 4f, 4g, and 4h of the diamond lattice pattern are arranged so as to be positioned within the enclosure of the raised convex portions 2 of the diamond lattice pattern formed on the surface 1a. is there. As a result, the adhesion to the concrete is improved, the number of obstacles due to the raised protrusions is increased, the anchor effect and the frictional resistance are increased, and the effect of reinforcing the mechanical strength of the hand concrete is enhanced.

  As a modification of the concrete reinforcing polypropylene short fiber according to the third embodiment, as shown in the plan view of FIG. 5, the polypropylene short fiber 1 in which the raised protrusions 2 and 4 of the partial pattern of the diamond lattice are formed on the front and back surfaces is concrete. It can also be set as the polypropylene short fiber 35 for reinforcement. This is because the fine diamond lattice pattern formed on the front surface 1a and the back surface 1b of the polypropylene short fiber 1 in the concrete reinforcing polypropylene short fiber 30 of the third embodiment shown in FIG. In the form shifted along the width direction, the raised protrusions 2 on the front surface 1a and the raised protrusions 4 on the back surface 1b are formed by embossing.

  In this case, these raised protrusions 2 and 4 are formed in the shape of a diamond lattice partial pattern, but the raised protrusions 4 of the diamond lattice pattern formed on the back surface 1b are the corner portions 4e and 4f of the diamond lattice pattern. 4g and 4h are arranged and formed so as to be positioned in the enclosure of the raised protrusions 2 of the diamond lattice pattern formed on the surface 1a, as in the concrete reinforcing polypropylene short fibers of the third embodiment. is there. Of course, this concrete reinforcing polypropylene short fiber 35 has the same effect as the concrete reinforcing polypropylene short fiber 30 of the third embodiment.

  Further, in the concrete reinforcing polypropylene short fibers of the present invention, the concrete reinforcing polypropylene short fibers 10 or 15 of the first embodiment, the concrete reinforcing polypropylene short fibers 20 of the second embodiment, and the third implementation are provided. If the concrete reinforcing polypropylene short fibers 30 or 35 are mixed in an appropriate ratio and mixed with concrete, the reinforcing effect of the concrete can be further improved.

  For example, the above-described concrete reinforcing polypropylene short fibers 10 or 15 of the first embodiment and the concrete reinforcing polypropylene short fibers 20 of the second embodiment may be mixed at a weight ratio of 1: 1, or the first The concrete reinforcing polypropylene short fibers 10 or 15 of the embodiment and the concrete reinforcing polypropylene short fibers 30 or 35 of the third embodiment can be mixed in a weight ratio of 1: 1, and the mixing ratio thereof is as follows. It can be changed appropriately depending on the application.

Next, the manufacturing method of the concrete short polypropylene fiber for concrete reinforcement of this invention is demonstrated.
First, among isotactic polypropylene used for fibers, yarns, strings, bands, etc., the melt flow rate is 0.5 to 5.0 g / 10 min. (According to JIS K 7210, measurement temperature 230 ° C., load 2. 16 kg) of pellets called extrusion stretch grade is fed to an extruder and extruded as a monofilament from a nozzle having a melt temperature of 230 ° C. and an opening diameter of 2 mm.

  Next, the extruded monofilament is rapidly cooled by a cooling device such as a cooling bath, and then fed into a stretching device. In the stretching apparatus, the monofilament is stretched at a temperature not lower than the melting point of the polypropylene and not higher than the melting point, for example, 50 to 150 ° C. Since the magnification at this time affects the tensile strength of the obtained short fiber 1, it is preferably made 10 to 15 times, and a polypropylene monofilament having a tensile strength of 450 MPa or more is obtained by stretching.

Next, the monofilament after stretching described above is fed into an embossing machine and embossed on the front and back surfaces.
This embossing is performed by a method in which two metal embossing rolls face each other and rotated in opposite directions, a plurality of monofilaments are passed between the embossing rolls, and the monofilaments are crushed. On the peripheral surface of each embossing roll, there are raised convex portions 2, 3, and 4 having a delicate diamond lattice pattern formed on the polypropylene short fibers of the above-described concrete reinforcing polypropylene short fibers according to the first to third embodiments. Corresponding recesses are engraved. And by maintaining an embossing roll at the temperature of 80-120 degreeC, a monofilament will be in a semi-molten state, and the protruding convex parts 2, 3, and 4 will be formed easily.

By this embossing, the monofilament is compressed, and the monofilament having a circular cross section is changed to a monofilament having a rectangular cross section as shown in FIGS.
In addition, the two embossing rolls have a mechanism in which the position of one of the rolls can be easily adjusted, and can be moved in the traverse direction of the roll or the flow direction of the monofilament. Front and back surfaces of polypropylene short fibers such as the concrete reinforcing polypropylene short fibers of the first to third embodiments shown in FIGS. 1 to 5 by easily adjusting the arrangement positional relationship of the raised protrusions of the lattice pattern. It is possible to emboss by changing the arrangement of the raised protrusions of the diamond lattice pattern.

Next, the embossed monofilament is annealed at a temperature near the crystallization temperature of polypropylene until its length is reduced by 5%, and then this is cut into a predetermined length to obtain a polypropylene short fiber for concrete reinforcement. Polypropylene short fibers are obtained which are formed with raised protrusions having a predetermined diamond lattice pattern on the front and back surfaces.
If this annealing is not performed, the produced short fibers curl over time and are not uniformly dispersed in concrete, mortar, etc., and so-called fiber balls are formed.

The concrete short polypropylene fibers for reinforcing concrete thus obtained are stretched at a high draw ratio, so that their tensile strength is high and the value is 450 MPa or more. Satisfies non-steel fiber quality standards for tunnel lining concrete in construction management guidelines, and also satisfies quality control standards for fiber reinforced concrete lining concrete.
In addition, the polypropylene short fiber obtained by the above method may contain a small amount of raised protrusions having an arrangement different from the arrangement of the embossed diamond lattice pattern specified at the time of production. Absent.

  Moreover, in the polypropylene short fiber for concrete reinforcement of this invention, in the range which does not inhibit the objective of this invention, it does not prevent applying the various physical and chemical processes to the surface as desired. The purpose of the present invention is to prevent the fibers of the present invention from agglomerating and floating and separating in an aqueous slurry of concrete, to disperse uniformly and stably in the aqueous slurry, and to impart resistance to the strong alkalinity of cement. For example, corona discharge treatment, flame or hot air treatment, infrared radiation, electron beam or other radiation irradiation, immersion in a surfactant solution, surface coating with various stabilizer coatings, etc. are exemplified.

  These surface treatments can be performed within a range that does not impair the object of the present invention, before and after embossing the diamond lattice pattern on the fiber surface. In addition, when surface isomerization is performed by forming a core-sheath structure by forming a core-sheath structure by forming a coating layer of a different polymer or the like on the outer peripheral surface of polypropylene fiber as a core, embossing in the present invention is performed on the outer surface of the sheath I will not prevent it.

Example 1
In order to confirm the performance of the concrete reinforcing polypropylene short fibers of the present invention, the concrete reinforcing polypropylene short fibers 10 of the first embodiment described above, the concrete reinforcing polypropylene short fibers 20 of the second embodiment, and the third The short polypropylene fiber 30 for concrete reinforcement of the embodiment was produced.

  An isotactic polypropylene homopolymer having a melt flow rate of 2 g / 10 min. Is used as a raw material, and this is put into an extruder and extruded from a nozzle hole having an opening diameter of 2 mm at a melting temperature of 230 ° C. Monofilament was used. This was rapidly cooled to 30 ° C. and then stretched by a stretching apparatus at a temperature of 80 ° C. and a stretching ratio of 10 times.

  Subsequently, this was sent to the embossing machine and embossed at a temperature of 100 ° C. As a result, the fineness is 4000 dtex, the width is 1.2 mm, the embossed apparent thickness is 0.60 mm, and the front and back surfaces are applied in the first to third embodiments shown in FIGS. The height of the embossed convex part to be formed is 16.7% (about 0.1 mm) of the apparent thickness, the width of the embossed convex part is about 0.2 mm at the base, the horizontal dimension is 1.2 mm, and the vertical dimension is 2 A monofilament having raised protrusions of a diamond lattice pattern of .64 mm. This was annealed at a temperature of 110 ° C. until the length decreased by 5%, and then cut to a length of 30 mm to obtain a predetermined polypropylene short fiber.

By this method, the concrete reinforcing polypropylene short fibers of the first to third embodiments shown in FIGS. 1 to 5 were produced as Sample I, Sample II, and Sample III below.
Sample I: Polypropylene short fibers in which the positions of the raised protrusions 2 of the diamond lattice pattern formed on the front surface 1a and the back surface 1b coincide with each other (the polypropylene short fibers 10 for reinforcing concrete in the first embodiment shown in FIG. 1). Equivalent).

Sample II: Polypropylene short fibers in which the diamond lattice pattern of the raised protrusions on the front surface 1a and the back surface 1b has one opposing side aligned and matched on the front and back surfaces and the other facing side displaced on the front and back surfaces (see FIG. 3). This corresponds to the concrete reinforcing polypropylene short fiber 20 of the second embodiment shown in the figure).
Sample III: Polypropylene short fibers (third embodiment shown in FIG. 4) in which the corners of the raised protrusions 4 of the diamond lattice pattern on the back surface 1b are positioned in the raised protrusions 2 of the diamond lattice pattern on the front surface 1a. Corresponding to the form of concrete reinforcing polypropylene short fiber 30).

  The tensile strength of each reinforcing material of sample I, sample II and sample III was measured in the state of long fibers according to JIS L1013. The tensile strength was 486 MPa for sample I, 482 MPa for sample II, and 488 MPa for sample III, and it was confirmed that there was no difference in tensile strength between the types of diamond lattice patterns.

  Next, two rectangular parallelepiped containers with a length of 30 mm, a width of 16 mm, and a height of 11 mm are used, and cement is used so that 15 mm is embedded from one end of the short fiber in the center of one 16 mm × 11 mm surface. The kneaded material was packed. The other end of the short fiber was treated in the same manner, and the central portion where the two cement kneaded materials contacted each other was separated with a thin release film material so that the uncured cement kneaded material did not contact.

In this way, three types of samples were treated in the same manner, and after 7 days of solidification, the resistance to pull-out was examined with a tensile tester with the rectangular solid portion of the cement solidified being held by the chuck. .
This test method is similar to Experimental Example 1 described in Japanese Patent Application Laid-Open No. 2004-18352, which has been cited as the prior art.
Further, the blend of the cement kneaded mixture was 60 wt% of water with respect to the cement and the weight ratio of cement to sand of 1: 2 of the blend which is usually employed without particular description in this type of test.

As a result, the pull-out resistance was as follows.
Sample I 165N
Sample II 168N
Sample III 176N
This result greatly exceeded the value of 14.97 kg (about 147 N) for the short fiber of 4400 dtex, which is the maximum value of the pull-out resistance shown by the short fiber described in JP-A-2004-18352.

(Example 2)
In the same manner as in Example 1, three types of samples I, II, and III having different diamond lattice patterns were produced. However, the length was 45 mm.
These three kinds of samples were mixed at the ratios shown in Table 1 to conduct a bending toughness test of the reinforced concrete solidified material obtained by mixing a certain amount of polypropylene short fibers for concrete reinforcement, and short fibers having different diamond lattice patterns. The difference in the degree of reinforcement of the solidified concrete due to the difference in the blending ratio was compared.

The flexural toughness test of the solidified concrete is based on JHS 730-2003 “Bending toughness test method of fiber reinforced lining concrete”, and the blending of the concrete is JSCE-F552 and JSCE-G552. according to, ordinary Portland cement 340 kg / ^{m 3,} water 175 kg / ^{m 3,} sand 842kg / ^{m 3,} gravel 869kg / ^{m 3,} the dimensions of the reinforcing material mixed ratio of 0.3% by volume, the bending test concrete trial body Was 150 × 150 × 530 mm. The test results are displayed in Table 2.

As apparent from Table 2, the reinforcing material 10 of the first embodiment of the present invention, the reinforcing material 20 of the second embodiment, and the third embodiment shown by mixing 1, mixing 2, and mixing 3 are shown. For both the reinforcing material 30 and the bending toughness coefficient of each concrete using these, the bending toughness coefficient of 1.40 N / mm ^2, which is a standard value determined by the Japan Highway Public Corporation, is shown, and the reinforcing material of the present invention is concrete. It was confirmed that the reinforcing effect of the steel was remarkably improved.

  Furthermore, the reinforcing material 10 according to the first embodiment of the present invention, the reinforcing material 20 according to the second embodiment, and the reinforcing material according to the third embodiment, which are indicated by mixing 4, mixing 5, mixing 6, and mixing 7. It was confirmed that the bending toughness coefficient of concrete was further improved by using 30 as a reinforcing material for concrete by mixing 30 at an appropriate mixing ratio.

  In particular, the bending toughness coefficient of the concrete using the mixture 6 made of the mixture of the concrete reinforcing polypropylene short fibers 20 of the second embodiment and the concrete reinforcing polypropylene short fibers 30 of the third embodiment is different from that of other mixed reinforcing materials. Although the bending toughness coefficient was significantly exceeded, a significant improvement in the reinforcing effect was observed.

(Comparative example)
For comparison, Examples 1 and 2 were tested on commercially available short reinforcing fibers.
Commercially available products are polypropylene fibers manufactured by A (presumably a reinforcing material described in JP-A-11-116297 disclosed as a prior art), vinylon fibers manufactured by B, and polyethylene / polypropylene fibers manufactured by C. The polyethylene contained in the reinforcing material manufactured by Company C is presumed to be high-density polyethylene, but the mixing ratio is unknown, and its specific gravity is 0.92 from the catalog.
Table 3 shows the product specifications of these commercial products.

In addition, since the test body was a short fiber, the test of the tensile strength could not be performed by a method according to JIS L1013, and was performed by changing the gripping tool interval to 10 mm and the tensile speed to 10 mm / min. In this method, since the specimen is damaged by the gripping tool, the strength tends to decrease due to the influence.
By this method, the tensile strength of each sample in Example 1 decreased to 472 MPa for Sample I, 467 MPa for Sample II, and 470 MPa for Sample III, respectively.
The test results are also shown in Table 3.

  From the results in Table 3, the pull-out resistance of the commercially available products was lower than the values of Samples I, II, and III. This is because the texture is not applied, or even if the texture is applied, an effective texture is not applied, and the improvement effect by the diamond lattice pattern in the present invention becomes clear.

Moreover, although the bending toughness coefficient of the commercial product exceeds 1.40 N / mm ² which is a standard value, the bending toughness coefficient of the present invention product based on the mixing 1 to 7 in Example 1 is The value was greatly exceeded.
From this, the difference in the material, the magnitude of the tensile strength imparted to the fiber and the presence or absence of graining, and the difference in the shape of the grain that is formed, can bring about the concrete reinforcing effect in the present invention. Became clear.

  The polypropylene short fiber for concrete reinforcement of the present invention is effectively used for cracking restraint and flaking prevention of concrete and mortar. It is effectively used to prevent cracks and flaking due to surface aging as well as general enhancement of. In addition, the concrete and mortar that make up the inner wall of tunnels (straight roads) such as roads and railways are prevented from cracking and peeling off the surface of the concrete and mortar, thereby ensuring safety in the construction and civil engineering fields and increasing their reliability. Used effectively.

The perspective view explaining the polypropylene staple fiber for concrete reinforcement of the 1st Embodiment of this invention. The perspective view explaining the deformation | transformation of the polypropylene short fiber for concrete reinforcement of the 1st Embodiment of this invention. It is a top view explaining the polypropylene short fiber for concrete reinforcement of the 2nd Embodiment of this invention, FIG.3- (A) is a top view of the surface, FIG.3- (B) is a see-through | perspective plan view of a back surface. The top view explaining the polypropylene short fiber for concrete reinforcement of the 3rd Embodiment of this invention. The top view explaining a deformation | transformation of the polypropylene staple fiber for concrete reinforcement of the 3rd Embodiment of this invention.

Explanation of symbols

10, 15, 20, 30, 35 ... polypropylene short fibers for reinforcing concrete,
DESCRIPTION OF SYMBOLS 1 ... Polypropylene short fiber, 1a ... Polypropylene short fiber surface, 1b ... Polypropylene short fiber back surface, 2 ... Diaphragm pattern raised convex part, 2a, 2b, 2c, 2d ... Diamond grid pattern raised convex part 2 Sides 3, 4... Raised projections of diamond lattice pattern embossed on the back side of polypropylene short fibers, 3a, 3b, 3c, 3d... 4 sides of raised projections 3 of diamond lattice pattern, 4e, 4f, 4g, 4h: Each corner of the four corners of the raised protrusion 4 of the diamond lattice pattern

Claims (6)

  Polypropylene short fibers obtained by melt-spinning an extrusion-stretched grade polypropylene having a melt flow rate of 0.5 to 5.0 g / 10 min. And highly drawn, having a fineness of 1000 to 10,000 dtex and a fiber width of 1. 0 to 1.5 mm, apparent thickness of 0.5 to 1.0 mm, length of 20 to 60 mm, tensile strength of 450 MPa or more, and a diamond lattice pattern having a width substantially equal to the fiber width on the front and back surfaces or Embossing of the partial pattern is performed to form a raised convex portion, and the height of the raised convex portion is 10 to 18% of the fiber thickness.   2. The polypropylene reinforcing short fiber for reinforcing concrete according to claim 1, wherein the raised convex portions are formed such that the positions of the diamond lattice pattern or the partial pattern thereof coincide on the front and back surfaces.   In the raised protrusions, the diamond lattice pattern of the raised protrusions on the front surface and the back surface is such that one opposing side is aligned and matched on the front and back surfaces, and the other facing side is displaced on the front and back surfaces. Item 1. A polypropylene short fiber for reinforcing concrete according to Item 1.   The raised protrusions of the diamond lattice pattern having a width substantially equal to the width of the fibers formed on the front and back surfaces of the polypropylene short fiber or the partial pattern thereof are the raised protrusions of the rear diamond lattice pattern within the raised protrusions of the front diamond lattice pattern. The short polypropylene fiber for concrete reinforcement according to claim 1, wherein the short fiber is disposed so that the corners thereof are located.   Polypropylene short fibers formed by matching and matching the diamond lattice pattern or its partial pattern on the front and back surfaces, and the corners of the raised convex portions of the rear diamond lattice pattern are located within the raised convex portions of the front diamond lattice pattern The polypropylene short fiber for concrete reinforcement according to claim 1, wherein the polypropylene short fiber is mixed at a ratio of 1: 1. The diamond lattice pattern of the raised protrusions on the front and back surfaces is a polypropylene short fiber in which one opposing side is aligned and matched on the front and back surfaces, and the other opposing side is displaced on the front and back surfaces, and the raised surface of the diamond lattice pattern on the front surface 2. The concrete according to claim 1, wherein polypropylene short fibers arranged so that the corners of the raised convex portions of the back diamond lattice pattern are located in the convex portions are mixed at a ratio of 1: 1. Polypropylene short fiber for reinforcement.

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