JPH10265246A - Polypropylene fiber for reinforcing cement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure improved dispersibility and affinity for cement by using short fibers of fales twisted yarn obtd. by splitting a uniaxially stretched continuous yarn tape of polypropylene or short fibers of fales twisted and crimpled yarn obtd. by crimpling the fales twisted yarn. SOLUTION: Polypropylene resin is melted, extruded from a die of a continuous yarn shape and spun as a continuous yarn tape having 5-100 dr size of single yarn, >=5 g/dr tensile strength and 200-3,000 dr total fineness. The tape is uniaxially stretched and partically split by temporary air twisting to form fales twisted yarn alternately twisted 30-200 times per 1 m. This yarn is further crimpled if necessary to form temporarily twisted and crimpled yarn, and short fibers of 3-30 mm fiber length are produced from the yarn to obtain the objective fibers for reinforcing cement. The fibers are added to cement by 0.1-20 wt.% based on the solid content of the cement. the temporarily twisted yarn, the temporarily twisted and crimpled yarn or a mixture of them is used in accordance with the purpose. A propylene homopolymer having an isotactic pentad fraction of >=0.95 and 0.1-50 g/10 min melt flow rate is used as the polypropylene resin as starting material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene fiber for cement reinforcement, and more particularly, to tensile strength,
As a reinforcing fiber to be incorporated into cement to obtain a cement molded product with improved bending strength, impact resistance, crack resistance, etc., affinity with cement by passing through specific spinning, defibration, crimping, and cutting processes The present invention relates to a polypropylene fiber for cement reinforcement having a special shape and excellent in properties and dispersibility.

[0002]

2. Description of the Related Art Conventionally, it has been widely attempted to blend ordinary polypropylene short fibers consisting of uniaxially drawn filaments as reinforcing fiber materials for cement molded products. However, the conventional polypropylene fiber does not have sufficient affinity with cement, and the shape of the short fiber is simple, so that the reinforcing effect is not sufficiently satisfied in that the polypropylene fiber easily comes out of the cement against stress. . Generally, a surface treatment agent or a coupling agent is often used for polypropylene fibers in order to increase the affinity between the polypropylene fibers and the cement, and for the purpose of improving the adhesiveness between the synthetic resin fibers and the cement. Method of using a fibrous material in which epoxy resin is blended with polypropylene
(JP-B-61-25669) and a method of increasing the interfacial bonding force by forming a metal coating layer on the surface of a fiber (JP-B-63-63504) are disclosed. Further, as a method of reducing the detachment by improving the shape of the short fiber, various methods of preventing the detachment of the fiber by changing the cross-sectional area of the spun yarn irregularly in the drawing direction have been attempted. Ori
No. 8-18343, Japanese Patent Publication No. 61-301, Japanese Patent Publication No. 62-4346, Japanese Patent Publication No. 62-28106, etc.) An application method (Japanese Patent Publication No. 61-26510) and a method using split fibers of a polypropylene film (Japanese Patent Publication No. 5-87460, Japanese Patent Application Laid-Open No. 4-59644) have also been tried.

However, none of these techniques is sufficient. For example, a method using a coupling agent or the like has a drawback that the compounding is complicated and troublesome, and that the reinforcing fibers are difficult to be uniformly dispersed in cement. In addition, the method of irregularly changing the cross-sectional area of the yarn has drawbacks such as difficulty in uniform winding in the manufacturing process and poor productivity. Also, in the method using split fibers of a polypropylene film, the number of steps for split splitting increases, and the split ends generated by split splitting cannot be expected to have much reinforcing effect in the cement, and the dispersion due to split split spots varies. It has the disadvantage of being.

[0004] It is also known that by imparting appropriate entanglement and bunching properties to short fibers to improve the dispersibility of cement and short fibers during kneading of cement, it contributes to the improvement of impact strength and bending strength of cement molded products. However, if the entanglement or bunching of the short fibers is too strong, the fibers will solidify and the dispersibility in cement will be insufficient.If the entanglement or bunching is insufficient, the fibers will not have the rigidity and the strength of the cement molding will not be obtained. There was a problem that was not.

The applicant previously proposed in Japanese Patent Application No. 7-249759 a polypropylene fiber for cement reinforcement consisting of short fibers of a continuous yarn tape in which individual filaments are separably connected. As shown in FIGS. 5 and 6, the short fibers are short fibers made of a continuous yarn tape 1 in which single filaments 2 are connected by a separable connecting portion 3. Therefore, the short fibers of the continuous yarn tape are appropriately separated at the time of kneading the cement, and as a result, have an appropriate convergence, so that the dispersibility with the cement is improved and the bending strength and impact strength of the cement molded product are remarkably increased. Improved. However, since the continuous yarn tape that is separably connected is only automatically separated by the kneading operation at the time of kneading the cement, it is somewhat difficult to adjust the bundling property according to the application, and the shape of the separated short fiber Because of the simplicity, the entanglement between short fibers is slightly insufficient, and in some cases, the effect of removing from the cement to form a continuous yarn is insufficient, and further improvement has been demanded.

[0006]

SUMMARY OF THE INVENTION In order to technically solve the above-mentioned problems, the present invention adjusts the short fibers of a continuous yarn tape formed using a polypropylene-based resin to an optimum convergence according to the application. An object of the present invention is to provide a polypropylene fiber for cement reinforcement which is possible and has improved dispersibility and affinity by improving the shape of short fibers.

[0007]

An object of the present invention is to provide a polypropylene fiber for cement reinforcement comprising short fibers of false twisted yarn obtained by disintegrating a polypropylene uniaxially drawn continuous yarn tape.

The method for producing the polypropylene fiber for cement reinforcement includes a step of melt-extruding a polypropylene-based resin from a continuous thread-shaped die having nozzle holes connected or adjacent to a series and spinning as a continuous thread tape; A step of subjecting the tape to a longitudinal uniaxial stretching treatment, a step of subjecting the stretched continuous tape to an air false twist nozzle to form a partially unwound false twisted yarn, and cutting the false twisted yarn to a predetermined length. It comprises the step of obtaining short fibers. Here, the defibration needs to be performed to such an extent that the continuous yarn structure remains, and the degree is set to a degree of defibration at which a preferable bunching property is obtained depending on the application. The degree of defibration is usually about 10 to 90%, preferably about 20 to 80%.

A solution for further improving the convergence is to provide a polypropylene fiber for cement reinforcement consisting of short fibers of a false twisted crimped yarn obtained by crimping a false twisted yarn obtained by unraveling a polypropylene uniaxially stretched continuous yarn tape. . That is, the false twisted yarn is supplied to, for example, a heated fluid extrusion nozzle to form a false twisted crimped yarn.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The polypropylene resin used as a raw material of the polypropylene fiber for cement reinforcement of the present invention is a known polypropylene copolymer such as a propylene homopolymer, an ethylene-propylene block copolymer or a random copolymer, or any of them. Among these, propylene homopolymer is desirable as a reinforcing material for cement molded articles requiring high strength and heat resistance, and those having an isotactic pentad fraction of 0.95 or more are particularly preferably used. Is done. What is the isotactic pentad fraction?
It is the isotactic fraction in pentad units in the polypropylene molecule measured using ¹³ C-NMR, as reported by Zambelli et al. In Macromolecules 6 925 (1973). The degree of conversion increases, and as a result, the rigidity and heat resistance of the molded body are improved. Further, the melt flow rate (MFR) is from 0.1 to 50 g / 10 min., Preferably from 1 to 40 g /
It is preferable to select from the range of 10 min., More preferably 5 to 30 g / 10 min.

The polypropylene-based resin may include an antioxidant, a lubricant, an ultraviolet absorber, an antistatic agent, an inorganic filler, and the like, within a range not departing from the spirit of the present invention depending on the purpose of use.
Additives such as an organic filler, a crosslinking agent, a foaming agent, and a nucleating agent may be blended.

Next, a method for producing the polypropylene fiber for cement reinforcement of the present invention will be described with reference to the drawings.
FIG. 3 is a schematic explanatory view showing an example of a process of forming a false twist yarn partially unwound from spinning of a continuous yarn tape.

First, the above-mentioned polypropylene resin is charged into an extruder 11 and melt-kneaded, and is extruded in a molten state from a continuous thread-shaped die 12 having a plurality of nozzle holes arranged substantially linearly.
It is cooled and solidified by the cooling roll 13 and spun as a continuous yarn-shaped tape, and the spun continuous yarn tape is heated by a stretching machine 17 to be vertically elongated by a peripheral speed difference between the first stretching roll 14 and the second stretching roll 15. After performing a uniaxial stretching process and performing annealing by passing through a heat treatment machine 18, it is supplied to a false twist nozzle 19 to partially open the continuous yarn tape to form a false twist yarn A, which is wound via a take-off roll 16. Taken. The extruder 11 is not particularly limited, and any of a known single-screw extruder and a twin-screw extruder can be used.

A continuous thread-shaped die 12 for obtaining a continuous thread tape
Has a shape in which at least 5-100 nozzle holes are connected or adjacent to the series, usually 10-50,
Preferably, the shape is such that 20 to 30 nozzles are connected. The number of holes in the nozzle represents the number of filaments constituting the continuous yarn, and if the number of holes is less than 5, it will be described later. The reinforcement effect due to the increase in the contact area of the fibers will not be different from that of the normal monofilament shape, while if the number of holes exceeds 100, the width as a continuous yarn tape will be wide and the necessary thermal drawing will be uniform In addition, even if it is subjected to false twisting, it is difficult to properly disintegrate it, and even if it is mixed with cement, it does not disintegrate but remains as a fiber mass and roughens the surface of the cement molded product. Cause problems. The nozzle shape may be a circular shape, a polygonal shape such as a triangle or a quadrangle, or a modified cross-sectional shape such as a Y shape or a star shape. Therefore, although the obtained continuous yarn tape changes variously depending on the type of the continuous yarn shape dies, any of them can be used for the intermediate of the present invention.

The undrawn continuous yarn tape extruded from the continuous yarn die 12 is guided to a drawing machine 17 and subjected to a hot drawing process at a temperature below the melting point and above the softening point of the polypropylene-based synthetic resin. However, as a heating method, a hot roll type,
Any of known techniques such as a hot plate contact type and a hot oven type can be adopted. The continuous yarn tape heated at a predetermined temperature is subjected to a stretching treatment by a peripheral speed difference between the first stretching roll 14 and the second stretching roll 15. Here, the stretching ratio is preferably 3 to
It is 20 times, more preferably 10 to 15 times. By this drawing treatment, a filament having a high rigidity and a small elongation can be formed, and more importantly, since the film is drawn in the longitudinal direction, it is oriented so that it is easily broken in the longitudinal direction, so that the continuous yarn can be easily separated. That is. This heating stretching process is not limited to one stage, and a plurality of stages of stretching processes are also possible.

The fineness of the single yarn constituting the drawn continuous yarn tape is 5 to 100 dr, preferably 10 to 60 dr. In other words, if the single-fiber fineness is less than 5dr, the fibers are too thin, and even if several fibers are bundled, the dispersion becomes uneven and the effect as a reinforcing fiber material is significantly reduced. The area of contact with the cement is reduced and the reinforcing effect is poor, and the appearance of the cement molded product is also poor. At the same time, the tensile strength per single yarn is preferably 5 g / dr or more, and 7 g / dr.
More preferably, it is dr or more. That is, the tensile strength is 5
If it is less than g / dr, the reinforcing effect as a cement reinforcing fiber is insufficient. And the total fineness of the stretched continuous yarn tape is 20
It is from 0 to 3,000dr, preferably from 500 to 2,000dr. In other words, those with a total fineness of less than 200dr have poor handleability as fibers for cement reinforcement, and those with a total fineness of more than 3,000dr tend to form a fiber mass in the cement when used in combination with the cement, resulting in poor dispersion, In addition, if the defibration treatment is performed in the next step described later, the degree of defibration varies greatly, which causes a problem that the reinforcing effect of the cement molded product is not sufficiently exhibited.

Next, the stretched continuous yarn tape is subjected to a heat treatment machine.
After passing through 18 and performing annealing, it is supplied to the false twist nozzle 19. In the false twist nozzle 19, the compressed air pressure is 1 to 7 kg / c
The false twisting treatment is performed under the conditions of m ² , preferably 3 to 5 kg / cm ² . By this air false twisting process, the continuous yarn tape is in a state where it is easily defibrated, or becomes a false twist yarn in a state where it is partially defibrated and peeled. In other words, the dispersibility in the cement is improved, and the reinforcing effect is enhanced, for example, the unevenness of the fiber surface or the branched shape makes the fiber more familiar with the matrix and makes it difficult for fibers to come off. Here, before entering the false twisting nozzle 19, the continuous yarn was twisted in one direction, and then twisted in the opposite direction when passing through the false twisting nozzle 19, so that S-shaped and Z-shaped alternate twists were applied. It is preferable to use a false twisted yarn in a state in order to express a good defibration state. The number of alternate twists is usually set to about 30 to 200 pieces / m, preferably about 50 to 100 pieces / m. Short fibers of the false twisted yarn directly cut to a predetermined length from the state of the false twisted yarn are effective as cement reinforcing fibers.

As the polypropylene fiber for cement reinforcement of the present invention, short fibers of false-twisted crimped yarn obtained by further crimping the false-twisted yarn of the continuous yarn tape and cutting the same are also useful. The specific structure will be described based on a manufacturing method.

FIG. 4 is an explanatory view showing a step of performing a crimping process to obtain a crimped yarn. The false twisted yarn A obtained by the manufacturing process shown in FIG. 3 is fed out by an appropriate method, and supplied to the heating fluid pushing nozzle 21 via the supply roll 25. This heating fluid pushing nozzle 21 is
2. It is composed of a deposition unit 23 and a cooling unit 24. False twist yarn A
Is supplied to the jet nozzle unit 22 in a relaxed state, and is sent to the deposition unit 23 at high speed by a high-pressure heating fluid having a propulsive force in the same direction as the traveling direction of the false twist yarn. In the stacking section 23, the sent false twist yarn rapidly stalls, and due to the sudden loosening of the false twist yarn due to this stall and the turbulent flow created by the high-pressure heating fluid, the slack or entanglement is formed to form a three-dimensional crimp. Then, the crimped state is fixed by the cooling unit 24 to form a false twisted crimped yarn B,
It is wound up via a take-up roll 26. Here, the heating fluid is sent in from an introduction port 27 in the jet nozzle section 22 and is discharged from a suction port 28 in the deposition section 23.

In this crimping step, air or steam is used as the high-pressure heating fluid, and its temperature and pressure are not particularly limited. The pressure is preferably in the range of 1 to 5 kg / cm ² at 120 to 160 ° C.

In the fiber production method of the present invention, the false twisted yarn A obtained in the step shown in FIG. 3 or the false twisted crimped yarn B obtained in the step shown in FIG. 4 is cut into a predetermined length by a cutting method (not shown). And a cutting step for making short fibers.

As the method of cutting into short fibers, any ordinary cutting method can be used, but it is necessary to heat the cutter blade or the cutter blade may accumulate heat in continuous operation. The method is not preferred. That is,
When the continuous yarn tape is cut, the fibers are heated by the cutter blade and partially melted, so that adjacent fibers are welded to each other to form a bundle of fibers, which tends to cause poor dispersion.

The short fiber as the cement reinforcing fiber has a fiber length of 3 to 30 mm, preferably 5 to 15 mm. If the fiber length is less than 3 mm, it tends to come off from the cement when blended with the cement, and if it exceeds 30 mm, the dispersibility tends to be poor, which is not preferable.

The polypropylene fiber of the present invention obtained by such a production method is blended as a reinforcing fiber material with a hydraulic cement such as Portland cement, white Portland cement or alumina cement or a cement such as a plaster or a lime or the like with an air-hardened cement. Used. Depending on the application, the short fibers of the false twisted yarn A and the false twisted crimped yarn B of the continuous yarn tape are used alone or in combination. In addition to the short fibers of the false twisted yarn A and the false twisted crimped yarn B, the use of a mixture of the short fibers of the continuous yarn tape as an intermediate is not hindered. The amount of fiber in cement is usually 0.1 to 20% by weight based on the solid content of cement.
It is. A more preferred amount is 1 to 5% by weight. Also, as a method of mixing polypropylene fibers with cement, known methods such as a method of dispersing fibers in cement powder, a premix method of dispersing fibers in a cement slurry, a spray-up method of simultaneously spraying cement, fibers and water. A method can be used.

The polypropylene fiber in such a use state has a continuous yarn shape in which a plurality of fibers are appropriately defibrated, and thus has irregularities formed on the surface or the whole.
In addition, the surface shape of the fiber is displaced due to the provision of false twist or crimp, and the fiber has a characteristic that it does not easily come off from the cement slurry. Further, since the longitudinal uniaxial stretching treatment is performed at a high magnification, the orientation is given in the longitudinal direction, and the connecting portion between the fibers is easily broken by an external force. For these reasons, the polypropylene fiber produced by the production method of the present invention has an appropriate convergence and dispersibility when blended with cement, and significantly improves physical bonding with cement.

The polypropylene fiber for cement reinforcement of the present invention may be subjected to various treatments before compounding the cement. For example, the fiber surface may be treated with a surfactant, a dispersant, a coupling agent, or the like, or may be subjected to a treatment such as surface activation or cross-linking by corona discharge treatment, ultraviolet irradiation, electron beam irradiation, or the like. Good.

The cement mixture containing the polypropylene fiber for cement reinforcement of the present invention in an appropriate amount is molded according to a known molding method such as a papermaking molding method, an extrusion molding method, or an injection molding method depending on the intended use. It is cured by a natural curing method in which it is left in water or an autoclave curing method in which it is treated at a temperature of 100 to 200 ° C. after being left at a temperature of 2 to 3 days, and a cement molded product is obtained. The applications of fiber-reinforced cement moldings include all types of cement products, for example, building wall materials, floor concrete, finishing mortar, waterproof concrete, roofing materials, etc. It can be used for pavements such as runways, road signs, road members such as gutters, pipes such as sewer pipes and cable ducts, fishing reefs, seawall blocks, tetrapots, and other various structures such as sleepers, benches and flower pots.

[0028]

【Example】

Example 1 Polypropylene resin (isotactic pentad ratio 0.9
6, MFR = 5.0g / 10min.) To the extruder, extruded in a molten state from a continuous yarn nozzle of 0.6mmφ × 25 holes, cooled, and then stretched at 130 ° C by annealing with hot air oven, annealing temperature Uniaxial longitudinal drawing was performed at 135 ° C. and a draw ratio of 12 to form a continuous yarn tape having a total fineness of 500 dr, in which filaments having a single yarn fineness of 20 dr were connected in the width direction.

Next, the continuous yarn tape is supplied to an air false twist nozzle using air at a compressed air pressure of 3.5 kg / cm ² and alternately twisted at 80 yarns / m 2.
Was given as false twisted yarn A. This false twisted yarn A was cut into a length of about 6 mm by a cutter blade to obtain a polypropylene fiber.
The degree of defibration was about 70%.

In mixing the polypropylene fiber of the present example with the cement to form a specimen, 100 parts by weight of Portland cement and 200 parts by weight of standard sand are sufficiently mixed, and 5 parts by weight of the polypropylene fiber is added and stirred. Mix,
Further, 65 parts by weight of tap water was added and kneaded so that the whole became uniform. In this state, when the shape of the fiber was confirmed, there was one that was slightly separated into single fibers, but most of the fibers were separated into 2 to 5 continuous yarns and uniformly dispersed in the cement mixture. there were. The cement mixture was poured into a mold, left in the air at room temperature for 48 hours, and then cured in an autoclave at 165 ° C. for 20 hours, and was 5 mm thick, 500 mm long and 500 mm wide.
mm plate material.

Example 2 The false-twisted crimped yarn B in Example 1 was subsequently subjected to crimping at a heating temperature of 135 ° C. and a pressure of 4.5 kg / cm ² to obtain a false-twisted crimped yarn B. B was cut into a length of about 6 mm with a cutter blade to obtain a polypropylene fiber. Thereafter, a cement specimen was prepared in the same manner as in Example 1.

Example 3 A polypropylene fiber obtained by blending the short fibers of the false twisted yarn A obtained in Example 1 and the short fibers of the false twisted crimped yarn B obtained in Example 2 at a ratio of 1: 1 was used. A cement specimen was prepared in the same manner as in Example 1.

Example 4 About 6 mm of the short fiber of the false twisted yarn A obtained in Example 1, the false twisted crimped yarn B obtained in Example 2, and the continuous yarn tape before the false twisting treatment.
Cement specimens were prepared by mixing polypropylene fibers composed of long short fibers at a ratio of 2: 2: 1 in the same manner as in Example 1. In this mixture, the entanglement between the crimped yarns was alleviated, and the dispersibility in the cement was good.

Comparative Example 1 In the state of the continuous yarn tape in Example 1, it was immediately cut into a length of about 6 mm by a cutter blade to obtain a polypropylene fiber. Thereafter, a cement specimen was prepared in the same manner as in Example 1.

Comparative Example 2 A polypropylene multifilament having a single yarn fineness of 20 dr was cut into a length of about 6 mm by a cutter blade to obtain a polypropylene fiber. Thereafter, a cement specimen was prepared in the same manner as in Example 1.

Evaluation As a physical property evaluation of the cement specimens prepared as Examples and Comparative Examples, the bending strength was measured in accordance with JIS-A1408, and the Charpy impact strength was measured in accordance with JIS-B7722. Show.

[0037]

[Table 1]

[0038]

As described above, the polypropylene fiber for cement reinforcement of the present invention has a continuous yarn shape in which a plurality of fibers are appropriately defibrated, so that the surface or the entire surface has irregularities, and The surface shape of the fiber is displaced due to the provision of false twist or crimp, and the fiber has a characteristic that it does not easily come off from the cement slurry. In addition, since the fiber is uniaxially stretched at a high magnification, orientation is imparted in the longitudinal direction, and the connecting portion between the fibers is easily broken by an external force. And good dispersibility and good physical bonding with cement. As a result, a cement molded product containing this polypropylene fiber as a reinforcing fiber material can significantly improve tensile strength, bending strength, impact strength and the like.

[Brief description of the drawings]

Fig. 1 Micrograph (50x) of false twisted short fibers of continuous yarn tape
It is the top view sketched from FIG.

FIG. 2 is a plan view sketched from a micrograph (× 50) of a false twisted crimped yarn short fiber obtained by further crimping a false twisted yarn of a continuous yarn tape.

FIG. 3 is a schematic explanatory view showing an example of a process from spinning to false twisting in the polypropylene fiber for cement reinforcement of the present invention.

FIG. 4 is a schematic explanatory view showing an example of a crimping step in the polypropylene fiber for cement reinforcement of the present invention.

FIG. 5 is a plan view sketched from a micrograph (8 ×) of a short fiber of a continuous yarn tape in which filaments are separably connected.

FIG. 6 is a cross-sectional view sketched from a micrograph (× 60) of a short fiber of a continuous yarn tape in which filaments are separably connected.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Continuous yarn tape 2 Single yarn filament 3 Connecting part 11 Extruder 12 Continuous yarn shape die 17 Drawing machine 18 Heat treatment machine 19 False twist nozzle 21 Heating fluid pushing nozzle A False twisted yarn B False twisted crimped yarn

Claims (2)

[Claims] 1. A polypropylene fiber for cement reinforcement comprising false-twisted short fibers obtained by disintegrating a polypropylene uniaxially drawn continuous yarn tape. 2. A polypropylene fiber for cement reinforcement comprising short fibers of a false twisted crimped yarn obtained by crimping a false twisted yarn obtained by disintegrating a polypropylene uniaxially stretched continuous yarn tape.