JP6727486B2 - Nylon fiber for reinforcing hydraulic material, method for producing nylon fiber for reinforcing hydraulic material, and hydraulic material using the same - Google Patents

Description

The present invention relates to a nylon fiber for reinforcing a hydraulic material, a method for manufacturing a nylon fiber for reinforcing a hydraulic material, and a hydraulic material using the same.

In order to strengthen the impact strength and flexural strength of various hydraulic materials such as cement mortar, concrete and cement board, short fibers obtained by cutting synthetic fibers such as nylon, polypropylene, vinylon, etc. to a prescribed fiber length are used as reinforcing fibers. Has been. Fibers having a high fiber strength are generally used as these reinforcing fibers, and polymers have been selected for this purpose.

For example, Patent Document 1 proposes to use a semi-aromatic polyamide fiber as a reinforcing fiber for cement, and Patent Document 2 proposes to use a nylon fiber as a reinforcing fiber for a plasterer material. Patent Document 3 proposes to use an acrylic fiber or a nylon fiber as a reinforcing fiber of a mortar composition. Patent Document 4 proposes to use a nylon fiber having a tensile strength, which is a stress when the fiber is broken, of 2.1 g/denier to 3.7 g/denier as a reinforcing fiber of cement.

JP, 09-256219, A JP, 2002-274903, A JP, 2001-220205, A Japanese Patent No. 4636693

However, conventionally proposed semi-aromatic polyamide fibers and wholly aromatic polyamide fibers such as aramid fibers have a problem of high production cost (for example, Patent Document 1), or a hydraulic material to which nylon fibers are added. There is a problem in strength and breaking energy (for example, Patent Documents 2 to 4), and further improvement has been required.

In order to solve the above-mentioned conventional problems, the present invention has a low manufacturing cost, and when added to various hydraulic materials, the fracture energy of the resulting hydraulic material is high. A hydraulic material using this is provided.

The nylon fiber for reinforcing hydraulic material of the present invention is a nylon fiber for reinforcing hydraulic material composed of short fibers, and the nylon fiber has a melt flow rate (MFR) at 270° C. of 10 to 70 g/10 min. It is a nylon fiber containing 66 as a main component, and is characterized by having a single fiber strength of 5.25 to 9.0 cN/dtex and a breaking elongation of 15 to 80%.

The method for producing a nylon fiber for reinforcing a hydraulic material of the present invention is such that nylon 66 having a melt flow rate at 270° C. of 10 to 70 g/10 min is melt-spun and wet-stretched in the presence of water at a temperature of 10 to 80° C. Then, by heat-setting at a dry heat temperature higher than the stretching temperature, a nylon fiber for reinforcing hydraulic material mainly composed of nylon 66 having a melt flow rate at 270° C. of 10 to 70 g/10 min is obtained. Characterize.

The hydraulic material of the present invention is a hydraulic material containing the above-mentioned nylon fiber, and is characterized by containing 0.01 to 5 Vol% of the nylon fiber when the hydraulic material is 100% by volume.

The hydraulic material-reinforcing nylon fiber of the present invention is a short fiber, and the nylon fiber is a nylon fiber whose main component is nylon 66 having a melt flow rate at 270° C. of 10 to 70 g/10 min. Strength is 5.25 to 9.0 cN/dtex and elongation at break is 15 to 80%, so that manufacturing cost is low, and nylon fiber for reinforcing hydraulic material has high fracture energy of hydraulic material. A hydraulic material can be provided. That is, since the nylon fiber has a high affinity with the hydraulic material, the fracture energy of the hydraulic material can be increased. Further, according to the method for producing a nylon fiber for reinforcing a hydraulic material of the present invention, the manufacturing cost is low, and the nylon 66 for reinforcing a hydraulic material is mainly composed of nylon 66 having a melt flow rate at 270° C. of 10 to 70 g/10 min. Fibers can be obtained.

FIG. 1 is a schematic front view showing the shape of a dumbbell and a tensile test device used in one embodiment of the present invention. FIG. 2 is an explanatory view showing the breaking energy shown in one embodiment of the present invention. FIG. 3 is a graph showing tensile stress-strain in one example of the present invention. FIG. 4 is a graph showing tensile stress-strain in another example of the present invention. FIG. 5 is a graph showing the tensile stress-strain of the comparative example.

The nylon fiber for reinforcing hydraulic material of the present invention is a fiber containing nylon 66 as a main component and having a melt flow rate at 270° C. of 10 to 70 g/10 min. In the following, unless otherwise specified, nylon 66 means nylon 66 having a melt flow rate at 270° C. of 10 to 70 g/10 min. The fiber containing nylon 66 as the main component in the present invention means that nylon 66 occupies 50% by mass or more when the total mass of the hydraulic material reinforcing fiber is 100% by mass. Nylon 66 consists primarily of polyhexamethylene adipamide. Polyhexamethylene adipamide refers to an aliphatic polyamide composed of hexamethylene diamine and adipic acid and having a melting point of 250° C. or higher. However, the nylon fiber for reinforcing hydraulic materials of the present invention has a melting point of less than 250° C. Nylon 6, Nylon 6I, Nylon 610, Nylon 6T, etc. may be copolymerized or blended to the extent that they do not occur. The hydraulic material-reinforcing nylon fiber of the present invention contains 50% by mass or more of nylon 66 when the mass of the fiber is 100% by mass, preferably 70% by mass or more, more preferably 80% by mass or more, Particularly preferably, the thermoplastic resin that constitutes the fiber for reinforcing the hydraulic material is a fiber made of nylon 66. In the nylon fiber for reinforcing hydraulic material of the present invention, nylon 66 may be contained in any part of the fiber, but preferably nylon 66 occupies at least a part of the fiber surface. If it is a single fiber, a fiber whose nylon 66 occupies at least a part of the fiber surface can be manufactured by melt spinning a raw material containing nylon 66 as a main component. A composite fiber composed of two or more kinds of resin components, for example, a core-sheath composite fiber having a concentric cross section, a core-sheath composite fiber having an eccentric structure, a side-by-side composite fiber, a split composite fiber, and a sea-island composite fiber. In the case of, the resin component containing nylon 66 is preferably exposed on the fiber surface. More specifically, in the case of a core-sheath type composite fiber having a concentric cross section or a core-sheath type composite fiber having an eccentric structure, it is preferable to use a resin component containing nylon 66 as a sheath component. It is preferable that the resin component containing is a sea component.

In the nylon fiber for reinforcing hydraulic material (hereinafter, also simply referred to as nylon fiber) of the present invention, nylon 66 contained as the main component of the fiber has a melt flow rate at 270° C. of 10 to 70 g/10 minutes. The preferred melt flow rate is 20 to 70 g/10 minutes, the more preferred melt flow rate is 40 to 70 g/10 minutes, the particularly preferred melt flow rate is 50 to 70 g/10 minutes, and the most preferred melt flow rate is It is 55 to 67 g/10 minutes. When the nylon 66 has an MFR satisfying the above range, yarn breakage and fusion between fibers are less likely to occur in melt spinning, and a stretching process at a high magnification in the stretching step can be performed with a reduced frequency of yarn breakage, In addition, since the heat setting process can be performed efficiently, it can be manufactured at low manufacturing costs, and when used as a reinforcing fiber for hydraulic materials, nylon has a high affinity with hydraulic materials and a high reinforcing effect can be obtained. Become a fiber.

In the present invention, the melt flow rate of nylon 66 is measured according to JIS K 7210 at 270° C. or 280° C. and a load of 21.2 N. More specifically, the MFR measured by the following method is used as the MFR of nylon 66 in the present invention. First, a nylon 66 sample (resin pellet or manufactured fiber) whose MFR is to be measured is held for 5 hours in a constant temperature dryer set at 100° C. to be sufficiently dried. Next, the extruding plastometer according to JIS K 7210 is heated to a predetermined temperature, held for 20 minutes after the temperature reaches the predetermined temperature to stabilize the temperature, and then 3 to 8 g of a dried sample is filled. Then, the measurement of the melt flow rate is started 360 seconds after the filling of the sample. The same measurement was repeated twice, and the average value was taken as the melt flow rate of nylon 66.

The single fiber strength of the nylon fiber is 5.25 to 9.0 cN/dtex, preferably 5.3 to 8.5 cN/dtex, more preferably 5.4 to 8.0 cN/dtex, and particularly It is preferably 5.4 to 7.5 cN/dtex. The breaking elongation is 15 to 80%, preferably 20 to 70%. If the single fiber strength and the elongation at break are in the above ranges, the balance between the strength and the elongation is good, the affinity with the hydraulic material is high, and the melt spinning, drawing, and heat setting can be efficiently performed, and the manufacturing cost is low. it can. If the single fiber strength of the nylon fiber is less than 5.25 cN/dtex or the elongation at break exceeds 80%, the strength of the fiber itself is low, so that the reinforcing effect is not imparted to the hydraulic material. For example, in hydraulic materials cured by adding these fibers, various fracture strengths such as compressive strength, tensile strength, bending strength are improved compared to hydraulic materials cured without adding various reinforcing fibers. May not be expected. If the single fiber strength of the nylon fiber exceeds 9.0 cN/dtex or the elongation at break is less than 15%, the reinforcing effect of the hydraulic material, especially in the hydraulic material containing the nylon fiber of the present invention, the fracture In addition to not being able to expect further improvement in energy, it is necessary to manufacture at a higher temperature and a higher draw ratio when manufacturing nylon fibers, which may lead to an increase in manufacturing cost.

Although the fineness of the nylon fiber is not particularly limited, the fineness is preferably 0.3 to 30 dtex, more preferably 0.5 to 25 dtex, and particularly preferably 0.7 to 20 dtex. The fiber length of the nylon fiber is also not particularly limited, but the fiber length is preferably 1 to 50 mm, more preferably 2 to 30 mm, and particularly preferably 3 to 20 mm. When the fineness and the fiber length are within the above ranges, the miscibility with the hydraulic composition is good.

The cross-sectional shape of the nylon fiber is not particularly limited, and in addition to circular cross-sections, non-circular cross-sections, for example, polygonal cross-sections such as triangles and quadrilaterals, multi-lobed cross-sections, multi-lobed cross-sections, etc. It may have any cross-sectional shape such as a cross section, a Y-shape, a W-shape, or a well-shape. In addition, these cross-sectional shapes may be solid fibers that do not include hollow portions, or as hollow fibers having one or more continuous hollow portions or discontinuous hollow portions in the fiber length direction in the fiber. Good. In the nylon fiber for reinforcing hydraulic material of the present invention, the fiber cross section is preferably a solid and round cross section. If it is solid and has a round cross section, it can be manufactured at low cost. The round cross section includes various circles such as circles, ellipses, and ellipses. The cross-sectional structure of the nylon fiber for reinforcing hydraulic material of the present invention is not particularly limited and may be a single resin component, that is, a single fiber composed of a resin component containing nylon 66 as a main component, or a plurality of fibers. May be a composite fiber composed of the resin component of, for example, a core-sheath composite fiber having a concentric cross section, a core-sheath composite fiber having an eccentric structure, a side-by-side composite fiber, a split composite fiber, or a sea-island composite fiber. ..

The method for producing the nylon fiber for reinforcing the hydraulic material of the present invention will be described. In the method for producing nylon fiber of the present invention, nylon 66 having a melt flow rate at 270° C. of 10 to 70 g/10 min is melt-spun, wet-stretched in the presence of water at a temperature of 10-80° C., and then stretched. Heat set at a dry heat temperature higher than the temperature. First, the process of melt spinning in the method for producing nylon fiber of the present invention will be described. In the step of melt spinning, nylon 66 satisfying the melt flow rate is charged into an extruder, melted in a spinning temperature range of 260 to 300° C., extruded from a spinning nozzle, and drawn at a take-up speed of 200 to 2000 m/min to obtain nylon. A bundle of undrawn fibers containing 66 as a main component and having a fineness of 1.5 to 100 dtex (also referred to as undrawn tow) is obtained.

The spinning temperature in the melt spinning process will be described. In the method for producing a nylon fiber for reinforcing a hydraulic material of the present invention, the spinning temperature is 260 to 300°C. When the spinning temperature is less than 260° C., when nylon 66 is melted, its melt viscosity is high, and the spinning property may be extremely deteriorated due to frequent yarn breakage. When the spinning temperature exceeds 300° C., the melt viscosity of nylon 66 is excessively lowered, so that not only fusion of unstretched fibers occurs, but also thermal decomposition of nylon 66 may start during melt spinning. In the method for producing the nylon fiber of the present invention, the preferred spinning temperature is 270°C to 295°C, and the particularly preferred spinning temperature is 270 to 290°C.

The molten resin extruded from the spinning nozzle under the spinning temperature condition is taken up at a take-up speed of 200 to 2000 m/min. If the take-up speed is less than 200 m/min, not only the nylon 66 fibers constituting the bundle of unstretched fibers are too thick, but also the take-up rollers are likely to be entangled during the production, which may reduce the productivity. If the take-up speed is higher than 2000 m/min, the unstretched fibers of nylon 66 are likely to be broken during take-up, which may also reduce the productivity. In the method for producing the nylon fiber of the present invention, the take-up speed of the undrawn fiber is preferably 300 to 1800 m/min, more preferably 350 to 1500 m/min, and particularly preferably 400 to 1200 m/min.

Nylon 66 is melt-spun at the spinning temperature and the take-up speed to obtain an unstretched tow, which is a bundle of unstretched fibers. The fineness of the nylon fiber constituting the undrawn tow, that is, the fineness of the nylon fiber before the drawing step is 1.5 to 100 dtex. When the fineness of the unstretched fiber containing nylon 66 as a main component exceeds 100 dtex, it is difficult to obtain a fiber suitable as a fiber for reinforcing hydraulic material even after the stretching step. When the fineness of the unstretched fiber containing nylon 66 as the main component is less than 1.5 dtex, yarn breakage is likely to occur during melt spinning, resulting in poor productivity and a low draw ratio in the stretching step. The fiber strength of the obtained nylon fiber tends to be low. In the method for producing a nylon fiber of the present invention, the fineness of the nylon fiber after melt spinning is preferably 2 to 60 dtex, more preferably 3 to 50 dtex, and particularly preferably 3.5 to 45 dtex.

The unstretched tow containing nylon 66 as a main component obtained by the above-mentioned method is subjected to a stretching step and a heat setting step, and then cut into a desired fiber length, and the nylon for reinforcing hydraulic material of the present invention. Fibers are obtained. In the method for producing a nylon fiber of the present invention, as a drawing step, drawing is performed using hot water at 10 to 80°C, and then heat setting is performed in a dry state at 100 to 200°C (hereinafter, also referred to as a dry heat setting). First, the stretching process using hot water at 10 to 80°C will be described. In this stretching step, the unstretched tow containing nylon 66 as a main component is wet-stretched with warm water at 10 to 80°C. It is not clear why the nylon fibers could be efficiently stretched by performing wet stretching with warm water adjusted to the above temperature range, but the secondary transition point (glass transition point) of nylon is 40 to 50°C in the dry state. However, it is known to be −20 to 0° C. in a hygroscopic state (“Encyclopedia of Fiber”, page 793, left column, lines 2 to 14, March 25, 2002, Maruzen), and the above. It is presumed that the unstretched nylon fiber can be efficiently stretched by performing wet stretching in a warm water tank adjusted to the above range. A preferable water temperature for the wet stretching is 15 to 70°C, and a particularly preferable water temperature is 20 to 70°C.

In the wet stretching, the stretching ratio is preferably 2 to 6 times, more preferably 2.5 to 5.5 times, and particularly preferably 2.8 to 5.2 times. By performing wet drawing at the draw ratio, the undrawn nylon fiber can be sufficiently drawn within the temperature range of the wet drawing, and the obtained nylon fiber is sufficient as a fiber for reinforcing hydraulic material. Not only does it have single fiber strength, but the frequency of yarn breakage is also suppressed in the drawing process. When the draw ratio of the wet drawing is less than 2 times, the drawing is not sufficiently performed, and thus the obtained nylon fiber has low single fiber strength and is hardened when used as a reinforcing fiber for a hydraulic material. Strength may not improve much. In the wet drawing step, if the draw ratio exceeds 6 times, yarn breakage will occur frequently, and productivity may decrease.

Next, the dry heat setting step performed after the wet stretching step will be described. In the method for producing a nylon fiber of the present invention, the dry heat setting step is performed for the purpose of promoting crystallization. By applying heat to the amorphous portion of the wet-stretched nylon fiber, crystallization is further promoted and stronger dimensional stability can be imparted. The dry heat setting step can be performed using a known dry stretching apparatus. As an example, a dry stretching process in which a stretching process is performed in dry air whose atmosphere temperature is adjusted to 100 to 200° C., or a dry stretching process using a metal roll whose temperature is adjusted to 100 to 200° C. Examples include stretching. In the method for producing a nylon fiber for reinforcing a hydraulic material of the present invention, the heat treatment temperature when performing dry heat setting is preferably 100 to 200°C, more preferably 120°C to 160°C or more, and further preferably 130 to It is 150°C. As a result, strong heat fixation can be achieved and dimensional stability can be obtained.

In the method for producing a nylon fiber for reinforcing a hydraulic material according to the present invention, the heat setting is performed at a stretching ratio such that a filament of the nylon fiber (fiber tow containing nylon 66 as a main component) does not sag during processing. Long heat setting is preferable, more preferably a draw ratio of 0.85-1.5 times, particularly preferably 0.9-1.4 times, and most preferably 0.95-1.2 times. It is preferable to perform the constant length set while satisfying the above temperature range. As a result, the crystal structure of the nylon fiber whose crystallization inside the fiber has progressed by the wet heat drawing treatment can be firmly fixed by heat, and dimensional stability and high single fiber strength can be obtained.

(Hydraulic material)
The hydraulic material of the present invention is added to the hydraulic composition so that the hydraulic material-reinforcing nylon fiber obtained by the above-mentioned method is contained at a constant ratio, and a proper amount of water is added and sufficiently kneaded and then cured. Or by adding it to a hydraulic material slurry in which a hydraulic composition and water have already been mixed, sufficiently kneading, and then curing. The hydraulic composition contained in the hydraulic material of the present invention includes various cements, fine aggregates, and if necessary, coarse aggregates, admixtures and admixtures. As the cement that constitutes the hydraulic composition, it is possible to use various cements such as ordinary Portland cement, early strength Portland cement, super early strength Portland cement, moderate heat Portland cement, low heat Portland cement and sulfate resistant Portland cement. it can. The fine aggregate and coarse aggregate constituting the hydraulic composition include silica sand, river sand, sea sand, beach sand, crushed stone, and various slags such as blast furnace slag, ferronickel slag, copper slag, and electric furnace oxidation slag. Can be used, and the particle size of the aggregate can be selected from these depending on the application of the hydraulic material to be used as a fine aggregate or a coarse aggregate. As the admixture contained in the hydraulic composition, fly ash, silica stone powder, silica fume, blast furnace slag fine powder, ettringite and various known expansive materials can be used. Examples of the admixture contained in the hydraulic composition include an AE agent, an AE water reducing agent, a highly functional AE water reducing agent, a fluidizing agent, a curing accelerator, a rust preventive agent, a setting retarder, a quick setting agent, and a shrinkage reducing agent. The various admixtures described below can be appropriately selected and used according to the purpose and application.

The hydraulic material of the present invention contains 0.01 to 5 Vol% of the nylon fiber for reinforcing the hydraulic material. That is, in a hydraulic material, it is externally divided with respect to the hydraulic material, in other words, among the hydraulic materials, various cement, fine aggregate, coarse aggregate, water and other components excluding nylon fiber for reinforcing the hydraulic material Of 100% by volume, and 0.01 to 5% by volume of the nylon fiber for reinforcing the hydraulic material. The hydraulic material of the present invention preferably contains 0.03 to 3 Vol% of the nylon fiber for reinforcing hydraulic material, more preferably 0.05 to 2.5 Vol%. The fracture energy of the hydraulic material obtained by curing the hydraulic composition can be increased by adding the nylon fiber for reinforcing the hydraulic material of the present invention to the hydraulic material in the above proportion. When the ratio of the nylon fiber for reinforcing hydraulic material of the present invention contained in the hydraulic material is less than 0.01 Vol %, the fracture energy of the hydraulic material is small because the amount of fibers contained in the hydraulic material is small. However, there is a possibility that the magnitude of fracture energy will not be much different from that of a hydraulic material to which no nylon fiber for reinforcing a hydraulic material is added, that is, a nylon fiber for reinforcing a hydraulic material is not added. .. If the ratio of the nylon fiber for reinforcing the hydraulic material of the present invention contained in the hydraulic material exceeds 5% by volume, not only the cost increases but also various mechanical strengths such as compressive strength and tensile strength of the hydraulic material may decrease. ..

The hydraulic material of the present invention, that is, the hydraulic material containing the hydraulic material-reinforcing nylon fiber of the present invention in a proportion of 0.01 to 5 Vol% has a strain within a range of 0 to 4% in its tensile stress test. Comparing the maximum value (A) of the tensile stress of (1) and the tensile stress value (B) when the strain is 4%, B is preferably 30% or more of A, and more preferably 40% or more. Within the above range, the tensile stress (strength) of the hydraulic material can be kept high even if the strain increases.

The fracture energy obtained from the tensile stress and displacement area of the hydraulic material is preferably 1.4 times or more higher than that of the hydraulic material of the present invention which does not contain the nylon fiber for reinforcing the hydraulic material. Within the above range, the tensile stress (strength) of the hydraulic material can be maintained high even when the strain is increased, and the hydraulic material is hardly broken.

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

<Measurement method>
(1) Melt flow rate (MFR)
The melt flow rate of nylon 66 was measured according to JIS K 7210 at 270° C. and a load of 21.2N. Specifically, a nylon 66 sample (resin pellet or manufactured fiber) whose melt flow rate is to be measured is held for 5 hours in a constant temperature dryer set at 100° C. to be sufficiently dried. Next, the extruding plastometer according to JIS K 7210 is heated to 270° C., and after it reaches 270° C., the temperature is held for 20 minutes to stabilize the temperature, and then 3 to 8 g of a dried sample is filled. Then, the measurement of the melt flow rate is started 360 seconds after the filling of the sample. The same measurement was repeated twice, and the average value was taken as the melt flow rate of nylon 66 at 270°C.
(2) Single Fiber Strength and Elongation at Break In accordance with JIS L 1015, a tensile tester was used to measure the load value and the elongation at the time of fiber cutting when the gripping interval of the sample was set to 20 mm. The strength and the elongation at break were used.
(3) Tensile test of molded product of hydraulic composition Uniaxial tensile test using dumbbell-shaped test body 1 shown in Fig. 1 having a length of 330 mm, a grip width of 60 mm, a thickness of 30 mm, a constricted portion width of 30 mm, and a length of 80 mm. The tensile stress and strain were measured by. This tensile test is based on JIS K6301. The test apparatus 10 fixes the test body 1 with the chucks 2a and 2b, then pulls it in the vertical direction to measure the tensile stress and also the strain with the displacement gauges 3a and 3b. In the right diagram of FIG. 1, the numerical value is the dimension (unit: mm) of the dumbbell test piece.

(Examples 1 to 4, Comparative Examples 1 to 5)
Nylon 66 (Ny66) was used as a raw material polymer, melt-spun, drawn, and heat set to obtain a fiber. The conditions and results are summarized in Table 1.

As is clear from Tables 1 and 2, Examples 1 to 4 had high single fiber strength and good production efficiency. On the other hand, Comparative Examples 1 to 5 had the problems as described in the remarks column.

(Examples 5-7, Comparative Examples 6-7)
A cement mortar placing test was conducted using the fiber made of nylon 66 prepared in Example 4. In Examples 5 to 7, fibers made of nylon 66 of Example 4 (hereinafter, also referred to as “nylon 66 fibers”) were used, and in Comparative Example 6, commercially available polypropylene (PP) reinforcing fibers (fiber length: 6 mm), Comparative Example 7 is a commercially available low monofilament strength nylon 66 reinforcing fiber (monofilament strength: 3.25 cN/dtex, breaking elongation: 86%, fiber length: 12 mm; 66 fiber"). Table 3 shows the materials used.

Using the materials shown in Table 3, cement 70 parts by mass, fly ash 30 parts by mass, fine aggregate 40 parts by mass, thickener 0.2 parts by mass, water reducing agent 0.9 parts by mass, water 39.1 parts by mass. And the reinforcing fibers in the amounts shown in Table 4 were uniformly mixed to prepare a hydraulic material slurry. The fiber content (Vol%) of the reinforcing fiber shown in Table 4 is the volume ratio of the fiber to the total volume of 100% of cement, fly ash, fine aggregate, thickener, water reducing agent and water excluding the reinforcing fiber. .. The mixing method is as follows: cement, fly ash and fine aggregate powder are first kneaded for 1 minute, then water, a water reducing agent and a thickener are added and mixed for 3 minutes, and then reinforcing fibers are added. Mixed 5 minutes x 2 times. The hydraulic material slurry thus obtained was put into a mold and cured in water to prepare a dumbbell shown in FIG. Using this dumbbell, a tensile test was conducted to obtain initial crack strength and fracture energy. As shown in FIG. 2, the breaking energy can be expressed as stress degree×displacement=breaking energy amount. The evaluation results are summarized in Table 4.

As is clear from Table 4, Examples 5 to 7 had high breaking energy. On the other hand, Comparative Examples 6 to 7 had low breaking energy. It is speculated that this is because the reinforcing material for the hydraulic material made of nylon 66 used in Nylon Examples 5 to 7 has a high single fiber strength and a high affinity with the hydraulic composition.

(Examples 8-9, Comparative Example 8)
A cement mortar placing test was conducted in the same manner as in Examples 5 and 6. Example 8 was a test in which the addition amount of the fiber made of nylon 66 (fiber length 10 mm) used in Example 5 was changed to 1.25 to 2.25 Vol%, and Example 9 was changed from nylon 66 used in Example 5. The test in which the added amount of the fiber (fiber length 20 mm) was changed to 1.25 to 2.25 Vol%, Comparative Example 8 added the polypropylene fiber (fiber length 6 mm) used in Comparative Example 6 to the amount of 1.25 to 2 The test was conducted by shaking to 25 Vol%. The results of Example 8 are shown in FIG. 3, the results of Example 9 are shown in FIG. 4, and the results of Comparative Example 8 are shown in FIG. Further, the relationship between the maximum value (A) of the tensile stress within the range of 0 to 4% strain and the tensile stress value (B) at the strain of 4% is shown in Table 5 for Example 8 and Table 6 for Example 9. Comparative Example 8 is as shown in Table 7, and it can be seen that the B/A values of Examples 8 and 9 are high.

As is clear from FIGS. 3 to 5 and Tables 5 to 7, it is understood that Examples 8 to 9 have a high tensile stress at a strain of 4%, a high B/A value, and a high fracture energy (toughness).

The hydraulic material-reinforcing fiber containing nylon 66 as a main component of the present invention is useful as a reinforcing fiber for hydraulic materials such as cement mortar, concrete and cement board. In addition, the method for producing nylon fibers of the present invention can efficiently produce nylon 66 fibers having a single fiber strength and elongation suitable for reinforcing fibers of hydraulic materials at low cost.

1 Test piece 2a, 2b Chuck 3a, 3b Displacement meter 10 Test device

Claims (9)

A nylon fiber for reinforcing a hydraulic material composed of short fibers,
The nylon fiber is a nylon fiber whose main component is nylon 66 having a melt flow rate (MFR) at 270° C. of 10 to 70 g/10 min.
A nylon fiber for reinforcing a hydraulic material, which has a single fiber strength of 5.25 to 9.0 cN/dtex and a breaking elongation of 15 to 80%. The nylon fiber for reinforcing a hydraulic material according to claim 1, wherein the nylon fiber has a fineness of 0.3 to 30 dtex and a fiber length of 1 to 50 mm. The nylon fiber for reinforcing a hydraulic material according to claim 1 or 2, wherein the nylon fiber is solid and has a round cross section. A method for manufacturing a nylon fiber for reinforcing a hydraulic material, comprising:
Nylon 66 having a melt flow rate (MFR) at 270° C. of 10 to 70 g/10 min is melt-spun and wet-stretched in the presence of water at a temperature of 10 to 80° C., and then at a dry heat temperature higher than the stretching temperature. A method for producing a nylon fiber for reinforcing a hydraulic material, characterized in that a nylon fiber mainly composed of nylon 66 having a melt flow rate (MFR) at 270° C. of 10 to 70 g/10 min is obtained by heat setting. The method for producing a nylon fiber for reinforcing a hydraulic material according to claim 4, wherein the draw ratio in the wet drawing is 2 to 6 times. The method for producing a nylon fiber for reinforcing a hydraulic material according to claim 4 or 5, wherein the heat set is a fixed length set. The dry heat temperature of the said heat set is 100-200 degreeC, The manufacturing method of the nylon fiber for hydraulic material reinforcement in any one of Claims 4-6. A hydraulic material comprising the nylon fiber according to claim 1,
When the hydraulic material is 100% by volume, the nylon fiber is contained in an amount of 0.01 to 5% by volume. In the tensile stress test of the hydraulic material, when the maximum value (A) of the tensile stress in the range of strain of 0 to 4% and the tensile stress value (B) at the strain of 4% are compared, B is A The hydraulic material according to claim 8, which is 30% or more.

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