KR100343339B1 - Twist-form reinforcement-fiber and method of preparing the same - Google Patents

Abstract

The present invention relates to an organic synthetic fiber for reinforcing cement composites and a method of manufacturing the same, and more particularly, to a twist type synthetic resin reinforcing fiber exhibiting excellent reinforcing effect by adding to cement composites such as concrete and shotcrete, and a method for manufacturing the same. will be.

The present invention provides a twist-type polypropylene fiber for reinforcing cement composites having a fineness of 1000 to 10000 g / 9000 m (denier) and a twist degree of 40 times / m or more, and a method of manufacturing the same.

The twisted polypropylene fiber of the present invention does not cause the initial fiber ball phenomenon when mixed with cement composites such as concrete or shotcrete, and it is possible to fill the cement composite in the structure of the twist, so that the pulling phenomenon when breaking after curing It doesn't happen at all. In addition, it is a synthetic fiber having excellent elasticity and a large fineness, which can impart excellent toughness to the cement composite.

Description

Twist type reinforcing fiber and its manufacturing method {TWIST-FORM REINFORCEMENT-FIBER AND METHOD OF PREPARING THE SAME}

[Industrial use]

The present invention relates to an organic synthetic fiber for reinforcing cement composites and a method of manufacturing the same, and more particularly, to a twist type synthetic resin reinforcing fiber exhibiting excellent reinforcing effect by adding to cement composites such as concrete and shotcrete, and a method for manufacturing the same. will be.

[Prior art]

In the construction of cement molded products using conventional mortar or concrete, or the outer wall of a building, the inner wall of a tunnel, an inclined surface, etc., the molded products are relatively brittle, and thus the tensile strength, the bending strength, the bending strength, the impact resistance Insufficient physical properties may cause the wall to leak due to cracks or the outer wall may peel off or fall. Therefore, steel fiber, glass fiber, polyvinyl alcohol fiber (Japanese Patent Laid-Open No. 63-303837, 1-40786, 8-218220, etc.) are mixed and used for the purpose of reinforcing concrete.

In addition, in the shotcrete field to be sprayed, there is a case of shotcreting with bare skin, but in most shotcrete operations, suppression of plastic shrinkage crack, inherent defect of Portland cement concrete, supplementation of insufficient toughness, and adhesion to rock For this purpose, various reinforcement materials are used than ordinary concrete. The shotcrete reinforcement includes a wire mesh used mainly in the related art, followed by steel fiber, glass fiber, and polypropylene fiber, which is found to be superior in reinforcing function.

However, concrete mixed with steel fibers has a heavy specific gravity of 7.8%, making it difficult to transport or mix materials, and in shotcrete to be sprayed, there is a high risk of worker stepping on and injuring the steel fiber dropped by recoil when spraying. The problem is pointed out.

In addition, the glass fiber is damaged by the alkali of the cement, and its reinforcing function is lost in the long term, alkali-resistant fiber among the glass fiber is difficult to use because of the high price, it is difficult to supply.

In addition, the polyvinyl alcohol fibers have a water absorbency, and thus the fibers may be hydrolyzed by high temperature under alkali, and the slump tends to be remarkably reduced as compared with not mixing the fibers. In addition, in the case of shotcrete spraying, when polyvinyl alcohol fiber is used as reinforcing fiber, it is necessary to increase the unit quantity to secure the slump required for the spraying, and the ratio of unit quantity is increased to make the water: cement ratio constant. Increasing the amount of cement, there is a problem that mismatch occurs.

In addition, the method of installing the wire mesh is one step of installing the wire mesh to the work process of the shotcrete, there is a problem that affects the cycle of the process due to the large amount of work time for transporting or handling the material.

In addition, the steel fiber or wire mesh is inevitably corroded after a certain time has elapsed, and there is a problem that causes the lamination of the shotcrete parent by the expansion of the corroded material.

In order to solve such a problem, it has recently been attempted to use polyolefin fibers having good moldability, light weight, and low cost by replacing steel fibers or polyvinyl alcohol fibers (Japanese Patent Application Laid-Open No. 58-18343, 61-301, SO 61-26510, SO 62-4346, SO 62-28106, WO 9-86984, WO 11-116297, etc.).

Polyolefin-based fibers generally have a single fiber of 0.01 to 100 dr fineness and a fiber length of about 0.5 to 50 mm, and short fibers of a focused yarn or split yarn. This fiber has a problem that low-density short fibers can produce a so-called "fiber ball" fiber mass, which makes it difficult to uniformly disperse them in a cement composite having a high specific gravity. In addition, when the fineness is increased in order to improve dispersibility, the adhesiveness with cement is inferior, and the curvature stress is lowered. When the cement matrix is broken by cutting, the so-called "pull-out" phenomenon occurs. It tends to be difficult to maintain cement metrics. In addition, low-fiber long fibers are often difficult to disperse in cement as they are connected to each other, or they often cause strength degradation in cement products when bent in cement.

On the other hand, since the polyolefin fibers are hydrophobic, which causes the fibers to float in the cement slurry, hydrophilicity is given to the polyolefin fibers to obtain good sedimentation properties. Thus, the fibers having improved dispersibility and cement are mixed homogeneously to give a predetermined fiber reinforcement effect. It is known to obtain (Korean Patent Publication No. 94-5541). Moreover, in the case of polypropylene fiber, the surface treatment is also performed with various surfactants in order to improve the focusability. However, in order to improve the pulling out of the cement composite, sand paper, plasma treatment, heating roll treatment (Japanese Patent Laid-Open No. 11-116297), etc., add irregularities to the surface of the fiber or chemical treatment with a coupling agent, etc. The surface modification method of did not completely improve the pulling phenomenon described above.

On the other hand, since the polyolefin fiber has a specific gravity of about 0.91, it is economical not to have a low specific gravity in order to mix the same volume of fibers with cement, but it is relatively difficult to uniformly disperse in concrete when the specific gravity is low and hydrophobic. Therefore, it is necessary to review the mixing method such as mixing order and mixing time of water and fibers.

In addition, when the concrete mixture containing polyolefin-based fibers is sprayed like shotcrete, the repulsion is relatively small, so it is easy to work, but the dispersibility of the fiber affects the slump. If the slump is large, the repulsion tends to increase.

Accordingly, an object of the present invention is to provide a polypropylene-based reinforcing fiber and a method of manufacturing the same, in which fiber ball does not occur at the beginning of mixing when mixing the cement composite in consideration of the problems of the prior art.

Another object of the present invention is to provide a polypropylene-based reinforcing fiber and a method of manufacturing the same to reinforce the cement composite without pulling phenomenon when the cement composite hardening after fracture.

Still another object of the present invention is to provide a polypropylene-based reinforcing fiber and a method of manufacturing the same, which can replace the steel fiber used as the reinforcing fiber of the shotcrete composition.

Still another object of the present invention is to provide a polypropylene-based reinforcing fiber and a method of manufacturing the same, which are easy to adjust the concrete slump.

Still another object of the present invention is to provide a polypropylene-based reinforcing fiber and a method of manufacturing the same that can be easily used in a construction site.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a twist type polypropylene fiber for reinforcing cement composite having a fineness of 1000 to 10000 g / 9000m (denier) and a twist degree of 40 times / m or more.

In addition, the present invention is a method for producing a twisted polypropylene fiber for reinforcing the cement composite,

a) Melt spinning the polypropylene resin in an extruder, and cooling the filament

Preparing a fiber;

b) drawing the filament fibers prepared in step a);

c) passing the stretched filament fibers of step b) through a heating zone

Twisting in the direction perpendicular to produce twisted fibers; And

d) cutting the twisted fiber of step c)

It provides a method for producing a twisted polypropylene-based fiber comprising a.

In addition, the present invention provides a method of the above,

e) performing the surface treatment selected from the group consisting of embossing or coupling agent chemical treatment of the stretched filament fibers of step b) may be further included.

Hereinafter, the present invention will be described in detail.

[Action]

The present invention is to use the twisted fiber as a reinforcing fiber of the cement composite so that when the cement composite is broken by external force after curing curing, the reinforcing fiber is broken only by the toughness of the reinforcing fiber without pulling out phenomenon.

That is, the twisted fiber of the present invention is an organic synthetic fiber, but when used as a reinforcing fiber of the cement composite, no pulling phenomenon occurs because the cement composite is filled in the twist structure. Therefore, it is possible to play a sufficient reinforcement role by showing the inherent toughness of organic synthetic fiber in the cement composite, and to break the cement composite after sufficiently enduring the tensile strength of the fiber without being pulled out even when destroyed by external force. In particular, it is possible to solve the problem of pulling out polypropylene fibers having a conventional fiber diameter having only irregularities on the fiber surface.

In addition, the twisted fiber of the present invention is a twisted type, unlike the general single yarn synthetic fiber when mixed in the cement composite, the fiber ball phenomenon does not occur fundamentally. That is, since the fineness is about 1000 denier to 10,000 denier, the fiber diameter is larger than that of conventional synthetic reinforcing fibers, and the fiber length is not longer than that of the conventional fiber. Also, the twisted structure does not bend when mixing the fibers in the cement composite because of its structure. Because of this, the fiber ball phenomenon does not occur at all. In addition, since the fiber diameter is large, it can be dispersed in the cement composite (including slurry) as it is without floating when dispersed in the cement composite.

Hereinafter, the present invention will be described in more detail.

In the twisted fiber of the present invention, the polypropylene resin used as the fiber raw material can use a polypropylene copolymer such as a propylene homopolymer, an ethylene-propylene block copolymer or a lanthanum copolymer or a mixture thereof. Among these, a propylene homopolymer is preferable for cement reinforcement which requires high strength and heat resistance. In addition to the polypropylene resin, olefins such as nylon, polyvinyl alcohol, polyester, polyacrylonitrile, polyethylene, and the like are applicable. However, polypropylene is most preferred when considering cement composites. The melt index (MFR) of polypropylene is preferably selected in the range of 0.1 to 20 g / 10 min, more preferably in the range of 1 to 5 g / 10 min for continuous and stable production.

The polypropylene fibers of the present invention are in the form of short fibers cut after twisting a monofilament having a relatively large fiber shape, and the manufacturing method thereof is not particularly limited, but the filaments are formed from round, elliptical, mold release, or other twisted dies. The extruded manufacturing technology is adopted.

The cross-section of the twisted reinforcing fiber of the present invention may have various shapes such as triangle, rectangle, circle, oval, cross, etc., in the case of multifilament as well as monofilament, two or more concentric circles when rotated in one central axis Any shape that appears can be used as a cross section. In addition, when extruding, when two or more adjacently connected slots are installed and extruded, two or more monofilaments may be attached and extruded and twisted in the form of multifilaments. However, it is preferable to twist the monofilament or twist the multifilament extruded by two to three strands rather than twisting the fiber of low fineness in consideration of using it as reinforcing fiber of cement composite. Do.

Spun mono or multifilaments are subjected to thermal stretching and thermal relaxation treatments. In this heat treatment, a polypropylene monofilament suitable for cement reinforcement having a small elongation which is advantageous in increasing the rigidity of the filament is obtained. This hot drawing is performed at a temperature below the melting point of the polypropylene and above the softening point. Usually, the stretching temperature is 90 to 150 캜, the stretching ratio is usually 5 to 12 times, and more preferably 7 to 9 times. As the hot drawing method, methods such as hot roll type, hot plate type, infrared irradiation type, hot air oven type and hot water type can be adopted.

The single yarn fineness of the polypropylene monofilament to be formed is important to be 1000 to 10,000 denia, more preferably 2000 to 7000 denier. If the single yarn fineness is less than 1000 denier, the fiber is thin and the dispersibility in the concrete blend is uneven, so it is easy to form a fiber ball, and there is a problem of workability or reinforcement; on the other hand, if the single yarn fineness is more than 10000, the concrete blend of fiber It is not good to reduce the reinforcing effect because the contact area with is decreased and the repulsion against the bending stress is increased.

In addition, in the case of multifilament, the sum of single yarn fineness of each monofilament is preferably 1000 to 10,000 denia. In particular, when the fineness of each monofilament is less than 200 denia, the twisting effect is halved, and the pulling phenomenon may occur in the cement composite.

The tensile strength (yield point) of the polypropylene filament is preferably 2000 kgf / cm 2 or more, and more preferably 3000 kgf / cm 2 or more. If it exceeds this range, the toughness as a polypropylene fiber for cement reinforcement is insufficient, and it is not good.

The polypropylene filaments of the present invention may be surface treated with an outer surface of the reinforcing fibers to increase their adhesion with cement before twisting. Such surface treatments include embossing and chemical treatment with a coupling agent.

Embossing is a method in which the twisted fibers produced are passed through a heated press mold or a heated roller in which the irregularities are carved. The fibers thus treated have embossed surfaces. The heating temperature is preferably 60 to 150 ° C., the fiber shrinks when the temperature is 150 ° C. or higher, and it is difficult to form embossing when the temperature is 60 ° C. or lower.

Chemical treatment is produced by the process of depositing and drying these fibers in a solution containing a coupling agent selected from the group consisting of silanes, zirconaluminates, or titanates. great.

Preferred coupling agents include γ-methacryloxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-glycidyloxypropyltrimethoxysilane, γ-mercitopropyl trimethoxy silane and methacryloxy Group-containing zircoaluminates, isopropyl tristearoyl titanate, and the like.

The embossing treatment and the chemical treatment may both be performed in parallel.

In the method for producing the twisted polypropylene-based fiber of the present invention, the twisting method is achieved by twisting the mono or multifilament fibers vertically in the longitudinal direction while transporting them from the drawing axis to the heating zone. The temperature of the heating zone is 80 to 150 ° C, the feed rate may vary depending on the temperature. The formation of a twist occurs only in the heating zone, and no twist is formed before and outside the heating zone. It uses the heat deflection temperature of polypropylene, where the heated portion is twisted and the unheated portion acts as one axis. In particular, the degree of twist is more than 40 times per meter. Less than 40 short fibers are difficult to improve the pulling phenomenon in the cement composite. In consideration of productivity, 100 to 300 times are preferable.

The twisted polypropylene fiber produced as described above is cut into predetermined lengths to become short fibers for cement reinforcement. The length of the short fibers is 4 to 70 mm, preferably 12 to 60 mm. If the length of the fiber is less than 4 mm, there is no molding effect in the twisted shape, so that the phenomenon of pulling out from the cement molded body may occur, and if the length exceeds 70 mm, the length is long, which is not good because dispersibility may be poor. These sizes are set to be advantageous for the development of strength, such as flexural strength, compressive strength, and the collection of cement particles when included in various cement composites, and can be adjusted if necessary.

The twisted polypropylene fiber for cement composite reinforcement of the present invention is a chemically stable fiber which solves the corrosion problem or the alkali damage problem, and is the most economical concrete or shotcrete reinforcement material. In addition, the fiber is twisted form of the fiber is not pulled phenomenon or fiber ball is formed.

On the other hand, in the shotcrete operation, the fibers of the present invention can be effectively used in both the wet method and the dry method. In particular, in the dry process, conventional low-density polypropylene fibers are lost without about 15% of the fibers flying into the air and added to the shotcrete. This is because when the fibers leave the nozzle, they are actually dry and there is no time for all to adhere to the mixture. However, the twisted fiber of the present invention has a high fineness, and the twisted space has a large adhesive area, so that the loss is small.

The present invention will be described in more detail with reference to the following examples and comparative examples. However, the examples are only for illustrating the present invention and are not limited thereto.

EXAMPLE

Example 1

(Manufacture of Twist Type Reinforcement Fiber by Extrusion-Monofilament)

Polypropylene resin (H5300 manufactured by Hyundai Petrochemical Co., Ltd .; MFR = 3.4 g / 10min, softening point 152 ° C., heat deformation temperature 104 ° C.) was extruded and spun at a temperature of 240 ° C. through a die having one rectangular slot by a conventional extrusion method. Monofilament fibers were prepared.

After cooling, stretching was performed at a hot drawing temperature of 115 ° C., a hot delay temperature of 120 ° C., and a draw ratio of 6 times.

The filament fibers were fixed at both ends of the jig on both axes, and twisted 40 times per meter while rotating one axis of the jig while passing through an oven at a temperature of 105 ° C., and then naturally cooled after passing through the oven.

Twist-type reinforcing fibers were prepared by press cutting the prepared twisted fibers in units of 50 mm. The cross section of the fiber produced was square and the front face was observed to be circular.

In addition, the fiber had a tensile strength of 3600 kg / cm 2 according to ASTM D1280, and the fineness at this time showed 2170 g / 9000 m (denier).

Example 2

(Manufacture of Twist Type Reinforcement Fiber by Extrusion-Multifilament)

A twist-type reinforcing fiber was prepared in the same manner as in Example 1, but the monofilament fiber was manufactured by extrusion spinning through a die having two square slots during extrusion. Square slots were used with one vertex of each square slot.

This fiber had a tensile strength of 5000 kg / cm 2 according to ASTM D1280, with a fineness of 5000 g / 9000 m (denier).

Example 3

(Embossing treatment of twisted reinforcing fiber)

The filament stretched after extrusion prepared in Example 1 was passed through a roller heated to 100 ° C. having a stepped 0.5 mm unevenness, to prepare a monofilament having emboss on the surface, and twisted as in the method of Example 1 Twist type reinforcing fibers were prepared.

This fiber had a tensile strength of 3000 kg / cm 2 according to ASTM D1280, with a fineness of 2100 g / 9000 m (denier).

Example 4

(Chemical Treatment of Twist Type Reinforcing Fiber)

1.0 wt% of γ-methacryloxypropyltrimethoxysilane as a coupling agent using the filament stretched after extrusion prepared in Example 1, 0.2 wt% of benzene peroxide as an oxidizing agent, 0.3 wt% of acetic acid as a pH adjuster, and a nonionic interface After dipping for 1 minute in a coupling agent solution having a composition of 0.2% by weight of the active agent, 15% by weight of methanol, and 83.3% by weight of water, it was taken out and distilled, and dried at 95-110 ° C. for 20 minutes to prepare a surface-modified monofilament. , Twisted as in the method of Example 1 to prepare a twist type reinforcing fiber.

This fiber had a tensile strength of 3330 kg / cm 2 according to ASTM D1280, with a fineness of 2350 g / 9000 m (denier).

Example 5

(Shotcrete composition preparation)

Each twist type reinforcing fibers of Examples 1 to 4 were mixed for 5 minutes at a speed of 30 rpm in a rotating drum mixer as in the mixing ratio of the shotcrete composition shown in Table 1 below.

division Reinforcing fiber 1 seed cement Fine aggregate (10 mm) Sand (1-3 mm) Formulation water Glidants Water / cement ratio Concrete (1 ㎥) Quantity 400 kg 530 kg 1240 kg 194 kg 0.2% by weight of cement 48.5 wt%

(Slump evaluation)

The shotcrete composition was added so that the amount of reinforcing fibers was 0.9 and 3 kg / m 3, and the slough test was performed before adding reinforcing fibers and after adding reinforcing fibers and fluidizing agents according to the slump test method of KSF 2402. The results are shown in Table 2.

(Compressive strength evaluation)

After the shotcrete composition prepared above was added so that the amount of reinforcing fiber was 3, 6 kg / m 3, injection molding into a cylinder mold having a diameter of 10 cm and a height of 20 cm and demolding after 1 day, in a constant temperature water bath at 21 ° C. Cured in water for 28 days, and tested according to the test method of compressive strength of ASTM C42-87. The results are shown in Table 3 below.

(Bending strength evaluation)

After the shotcrete composition prepared above was added so that the amount of reinforcing fiber was 3, 6 kg / m 3, injection molded into a mold of 15 x 15 x 450 mm, and demolded after 1 day, in a constant temperature water bath at 21 ° C. for 7 days, Cured in water for 28 days and tested according to the flexural strength test method of KSF 2408. The results are shown in Table 3 below.

(Toughness index assessment)

Toughness index, one of the fiber reinforcing properties, is the energy absorbed up to a given displacement divided by the energy absorbed up to the first cracking displacement. The higher the value, the higher the resistance to fracture.

The shotcrete composition prepared above was injected into a mold of 10 × 10 × 35 cm, respectively, molded and demolded after 1 day, and then cured in water for 7 days and 28 days in a constant temperature water bath at 21 ° C., and tested for toughness of ASTM C1018 I ₅ and I ₁₀ values were measured according to the method. The results are shown in Table 3 below.

Comparative Example 1

In the same manner as in Example 5 except for using a general mesh type polypropylene fiber (manufactured by SS industry; length 38 mm) having a fineness of 50 dr as a reinforcing fiber and changing the amount added to the shotcrete to 3, 6 kg / m 3. Shotcrete compositions were prepared, and slump evaluation, compressive strength evaluation, flexural strength evaluation, and toughness index evaluation were performed.

Comparative Example 2

Same as Example 5 except that corrugated type steel fiber (50 mm in length) having a fiber diameter of 1 mm was used as the reinforcing fiber, and the amount added to the shotcrete was changed to 40 and 60 kg / m 3. The shotcrete composition was prepared, and compressive strength evaluation, flexural strength evaluation, and toughness index evaluation were performed.

division Example 5 Comparative Example 1 Type of fiber Twisted fiber of Example 1 (length 50mm) Mesh type polypropylene fiber (38mm in length) Fiber amount (kg / ㎥) 0.9 3 3 6 Slump (mm / min) Before adding fiber 65 65 65 65 After adding fiber and glidant 140 120 110 70 Air volume (%) 2.5 2.8 2.8 3.5

division Example 5 Comparative Example 1 Comparative Example 2 Type of fiber Twisted fiber of Example 1 (length 50 mm) Mesh polypropylene fiber (38 mm length) Corrugated steel fiber (length 50 mm) Fiber amount (kg / ㎥) 3 6 3 6 40 60 Rebirth (Sun) 7 28 7 28 7 28 7 28 7 28 7 28 Compressive strength (mPa) 47.8 55.3 52.9 66.7 36.0 49.6 36.2 45.7 48.3 66.6 44.7 66.1 Flexural strength (mPa) 5.0 5.8 5.5 7.1 4.8 5.4 4.4 4.8 4.8 6.7 4.6 5.9 Toughness Index (I ₁₀ ) 3.5 3.4 3.6 3.5 1.9 2.0 2.9 2.8 3.4 2.2 3.4 3.4 Toughness Index (I ₅ ) 5.0 4.9 5.7 5.5 3.0 3.1 5.2 4.7 5.2 3.2 5.2 5.2

The twisted polypropylene fiber of the present invention does not cause the initial fiber ball phenomenon when mixed with cement composites such as concrete or shotcrete, and it is possible to fill the cement composite in the structure of the twist, so that the pulling phenomenon when breaking after curing It doesn't happen at all. In addition, it is a synthetic fiber having excellent elasticity and a large fineness, which can impart excellent toughness to the cement composite.

Claims (15)

Twisted polypropylene fiber for reinforcing cement composites having a fineness of 1000 to 10000 g / 9000 m (denier) and a twist degree of 40 times / m or more. The method of claim 1, Twisted polypropylene fiber, wherein the fiber is a monofilament. The method of claim 1, Twisted polypropylene fiber, wherein the fiber is a multifilament. The method of claim 1, Twisted polypropylene fiber of the cement composite is shotcrete. In the manufacturing method of twisted polypropylene fiber for cement composite reinforcement, a) melt spinning the polypropylene resin in an extruder and cooling to filament Preparing a fiber; b) drawing the filament fibers prepared in step a); c) passing the stretched filament fibers of step b) through a heating zone Twisting in the direction perpendicular to produce twisted fibers; And d) cutting the twisted fiber of step c) Method for producing a twisted polypropylene-based fiber comprising a. The method of claim 5, e) embossing the stretched filament fibers of step b), or coupling agent chemistry Surface treatment selected from the group consisting of step Method for producing a twist-type polypropylene fiber further comprising. The method of claim 6, A method for producing a twisted polypropylene-based fiber in which the embossed stretched filament fiber is passed through a press mold or a roller heated to a temperature of 60 to 150 ° C. in which irregularities are carved, to form irregularities on the fiber surface. The method of claim 6, Γ-methacryloxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-glycidyloxypropyltrimethoxysilane and γ-mercetopropyl trimethoxy Preparation of twisted polypropylene-based fiber which is dipped in a solution containing a coupling agent selected from the group consisting of oxy silane, zircoaluminate containing methacryloxy group, and isopropyl tristearoyl titanate and then dried Way. The method according to claim 5 or 6, Method for producing a twisted polypropylene fiber, wherein the filament of step a) is monofilament or multifilament. The method of claim 9, A method for producing a twisted polypropylene fiber, wherein the number of monofilaments of the multifilament is 2 or 3. The method of claim 9, The multifilament is a method of producing a twisted polypropylene fiber is a sum of the fineness of each monofilament 1000 to 10,000 denia. The method according to claim 5 or 6, Method for producing a twisted polypropylene fiber having a fineness of 1000 to 10,000 denia of the drawn fiber of step b). The method according to claim 5 or 6, Method for producing a twist-type polypropylene fiber having a twist degree of step c) is more than 40 times per meter. The method according to claim 5 or 6, Method for producing a twist-type polypropylene fiber of the heating zone of step c) is 80 to 150 ℃. The method according to claim 5 or 6, Method for producing a twisted polypropylene fiber having a cutting length of step d) of 4 to 70 mm.