JPH0986984A - Polypropylene fiber for cement reinforcement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cement forming having improved tensile strength, bending strength, shock resistance, crack resistance, etc., by using propylene fibers produced by a specific forming method as a reinforcing material. SOLUTION: A propylene synthetic resin is extruded in a molten state from a linked yarn-shaped dice in which nozzle holes are linked in a series or adjacent to each other, and the extruded resin is subjected to a longitudinal uniaxial drawing treatment to form a linked yarn-shaped tape 1 in which filaments 2 are linked 3 in an individually separable manner. The linked yarn-shaped tape 1 is cut into a specified length, and the obtained short fibers are used as a cement reinforcing 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,
The present invention relates to a polypropylene fiber obtained by a specific molding method as a reinforcing fiber mixed in cement to obtain a cement molded product having improved flexural strength, impact resistance, crack resistance and the like.

[0002]

2. Description of the Related Art Conventionally, it has been widely tried to blend polypropylene fiber short fibers as a reinforcing fiber material for cement molded products. However, conventional polypropylene fibers do not have sufficient affinity with cement, and since the shape of short fibers is simple, their reinforcing effect is not sufficiently satisfactory in that they easily come out of cement in response to stress. It was Generally, a surface treatment agent or a coupling agent is often used for polypropylene fibers in order to increase the affinity between polypropylene fibers and cement, and the purpose is to improve the adhesion between synthetic resin fibers and cement. As a method of using a fiber in which an epoxy resin is mixed with polypropylene (Japanese Patent Publication No. 61-25669), a method of forming a metal coating layer on the fiber surface to increase the interfacial bonding force (Japanese Patent Publication No. 63-63504), etc. It is disclosed. Further, as a method of reducing the dropout by improving the shape of the short fiber, various methods have been tried in which the cross-sectional area of the spun yarn is irregularly changed in the drawing direction to prevent the dropout of the fiber ( (Japanese Patent Publication No. 58-18343, Japanese Patent Publication No. 61-301, Japanese Patent Publication No. 62-4346, Japanese Patent Publication No. 62-28106, etc.). Surface treatment method (Japanese Patent Publication No. 61-2651)
No. 0), a method using split fibers of polypropylene film (Japanese Patent Publication No. 5-87460, Japanese Patent Application Laid-Open No. 4-59644) and the like have been tried.

[0003]

However, none of these techniques are sufficient. For example, the method using a coupling agent is complicated and complicated, and the reinforcing fibers are uniformly dispersed in the cement. However, the method of irregularly changing the cross-sectional area of the yarn has drawbacks that it is difficult to uniformly wind the yarn in the manufacturing process and the productivity is poor. 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]

As a result of intensive studies to solve the above problems, the present invention provides a cement molded product having improved tensile strength, bending strength, impact resistance, crack resistance, etc. The purpose is to achieve the object by using polypropylene fiber obtained by a specific molding method as the reinforcing fiber material to be blended with.

That is, the polypropylene fiber for cement reinforcement is a polypropylene-based synthetic resin filament, which is a continuous fiber-shaped tape short fiber in which individual filaments are separably connected.

Specifically, polypropylene-based synthetic resin is melt-extruded from a continuous-thread-shaped die in which nozzle holes are connected in series or adjacent to each other and subjected to longitudinal uniaxial stretching treatment, and filaments formed by separate separation are connected to each other. A polypropylene fiber for cement reinforcement, which comprises short fibers obtained by cutting a continuous yarn-shaped tape into a predetermined length.

More specifically, a polypropylene-based synthetic resin is formed by melt-extruding polypropylene synthetic resin from a continuous yarn-shaped die in which 5 to 100 nozzle holes are connected in series or adjacent to each other and subjected to longitudinal uniaxial stretching treatment. A polypropylene fiber for cement reinforcement, characterized in that a continuous yarn-shaped tape having a total fineness of 200 to 3,000 dr in which filaments of up to 100 dr are separably connected is cut into a length of 3 to 30 mm.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The polypropylene synthetic resin used in the present invention means a propylene homopolymer, ethylene-
Known polypropylene copolymers such as propylene block copolymers or random copolymers or mixtures thereof, and among them, propylene homopolymer is a high strength, as a reinforcing material for cement molded articles required to have heat resistance, a propylene homopolymer. Desirable, especially with an isotactic pentad fraction of 0.
Those of 95 or more are preferably used. Isotactic Pentad Fraction is a macrolecule by A. Zambelli et al.
es 6 925 (1973), which means the isotactic fraction in the pentad unit in the polypropylene molecule measured by ¹³ C-NMR, the higher the value, the higher the crystallinity. As a result, the rigidity and heat resistance of the molded product are improved. Further, the melt flow rate (MFR) from the resin melt flow characteristics is 0.1 to 50 g / 10 min., Preferably 1 to 40 g / 10 min., And more preferably 5 to 30 g / 10.
It is better to select from the range of min.

[0009] Polypropylene-based synthetic resins include antioxidants, lubricants, ultraviolet absorbers, antistatic agents, inorganic fillers, organic fillers, cross-linking agents, and foams within the range not departing from the gist of the present invention depending on the purpose of use. You may mix | blend additives, such as an agent and a nucleating agent.

The method for producing the polypropylene fiber for cement reinforcement of the present invention is as follows. The polypropylene resin is extruded in a molten state from a continuous yarn-shaped die having a plurality of nozzle holes arranged substantially linearly in a molten state, and then cooled in the longitudinal direction. A continuous filament tape in which filaments are connected is formed by subjecting the filaments to a high-strength heat drawing treatment.

The continuous thread type die has a shape in which at least 5 to 100 nozzle holes are connected or adjacent to each other in a series, but usually has a shape in which 10 to 50, preferably 20 to 30 nozzles are connected. is there. The number of holes in the nozzle represents the number of filaments that make up the continuous yarn. It will be described later that the number of holes is less than 5, but it is easy to handle before cement mixing and a matrix due to the unevenness of the fiber surface when defibrated in cement. The reinforcing effect due to the increase in the contact area of the fiber is the same as the normal monofilament shape, while the number of holes is 100
If it exceeds the number, the width as a continuous yarn-shaped tape becomes wider and it becomes difficult to uniformly perform the necessary heat drawing, and even if it is mixed with cement, it does not defibrate and remains as a fiber lump and the surface of the cement molded product It causes problems such as degrading quality. The nozzle shape may be a circular shape, a triangular shape, a polygonal shape such as a quadrangle, or an irregular cross-sectional shape such as a Y shape or a star shape.

The unstretched continuous filament tape extruded from the die is subjected to hot stretching at a temperature below the melting point of the polypropylene-based synthetic resin and above the softening point. Any known technology such as hot plate type, infrared type, hot air type, etc. can be adopted. Among them, the hot plate type heated on a convex type hot plate electrically heated from the inside is high in productivity and stability. preferable. The continuous yarn-shaped tape heated at a predetermined temperature is stretched due to the difference in peripheral speed between the front and rear rolls. Here, the draw ratio is preferably 3 to 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.

The continuous continuous filament tape has a total fineness of 20.
It is preferably 0 to 3,000 dr. Those with a total fineness of less than 200dr have poor handleability as a fiber for cement reinforcement, and those with a total fineness of more than 3,000dr tend to form fiber lumps in the cement and become poorly dispersed when used in combination with cement,
Therefore, there is a problem that the reinforcing effect of the cement molded product is not sufficiently exhibited.

A continuous yarn-shaped tape having a predetermined total fineness is cut to have 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. As the method for cutting the fiber length to a constant length, all commonly used cutting methods are used, but a method in which the cutter blade needs to be heated or a method in which the cutter blade accumulates heat in continuous operation is preferable. Absent. That is, when the continuous yarn-shaped tape is cut, the filaments are heated by the cutter blade and partially melted, so that adjacent filaments are welded to each other to form a bundle of fibers, which is likely to cause poor dispersion.

The polypropylene fiber of the present invention thus obtained is used as a reinforcing fiber material by being mixed with hydraulic cement such as Portland cement, white Portland cement, alumina cement or cement such as gypsum, air-hardening cement such as lime, etc. To be The content of fibers in cement is usually 0.1 to 20% by weight based on the solid content of cement. Further, 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 cement slurry, and a spray-up method of simultaneously spraying cement and fibers and water are known. Any method can be used.

The polypropylene fiber of the present invention in such a use state has a continuous yarn shape composed of a plurality of filaments, and since it is subjected to a longitudinal uniaxial stretching treatment at a high magnification, orientation is imparted in the longitudinal direction, The connection between them is easily broken by external force. For this reason, the polypropylene fiber of the present invention is a tape-shaped fiber having a total fineness of about 200 to 3,000 dr, which has a good handleability similar to that of the bundled fiber in the preceding stage of being mixed with cement,
By kneading with cement, the fibers are appropriately separated and defibrated into fibers having good dispersibility. The disentangled tape shape has some monofilament fibers,
Most of them are a plurality of bundled fibers, and since the filaments have a cross section in which a large number of filaments are connected by a connecting part, irregularities are formed on the surface or the whole of the fibers, and these irregularities physically affect the cement. It significantly improves the physical coupling.

The filament of the continuous yarn has a single yarn fineness of 5 to 100 dr, preferably 10 to 60 dr, and a single yarn fineness of 5 d.
If it is less than r, the fiber is too thin, and even if several fibers are bundled, the dispersion becomes non-uniform and the effect as a reinforcing fiber material is remarkably reduced, and if the single yarn fineness exceeds 100 dr, contact with cement occurs. The area is reduced and the reinforcing effect is inferior. The tensile strength of the filament is preferably 5 g / dr or more, more preferably 7 g / dr or more. If the tensile strength is less than 5 g / dr, the reinforcing effect as a cement-reinforced fiber may be insufficient.

The polypropylene fiber of the present invention may be subjected to various treatments before being mixed with 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 of the present invention in an appropriate amount is molded according to a known molding method such as a paper-forming molding method, an extrusion molding method, an injection molding method, etc., and left in the air or water at room temperature for several tens of days. Natural cure or 2
After being left at room temperature for 3 days, it is cured by an autoclave curing method in which it is treated at a temperature of 100 to 200 ° C. to be a cement molded product. The applications of fiber-reinforced cement molded products are all cement products, but for example, wall materials for buildings, concrete floor materials, finished mortar, waterproof concrete, roof materials, etc. It can be used for sleepers, benches, flower pots, etc. as pavements for runways, road signs, road members such as gutters, sewer pipes, pipes such as cable ducts, fishing reefs, revetment blocks, tetrapots, etc.

[0020]

Example: Polypropylene resin (isotactic pentad fraction 0.96, MFR = 5.0 g / 10 min.) Was supplied to an extruder,
At a melting temperature of 230 ℃, extrude from a continuous yarn shape nozzle with 2mmφ × 25 holes and cool, then draw at a draw temperature of 130 by hot plate contact drawing method.
℃, annealing temperature 135 ℃, longitudinal uniaxial stretching at a draw ratio of 12 times, to form a continuous thread-shaped tape with a total fineness of 500 dr in which filaments with a single-thread fineness of 20 dr are connected in the width direction and cut into about 6 mm length with a cutter blade. The polypropylene fiber of this example was obtained.

When the polypropylene fiber of this example was mixed with cement to form a specimen, 100 parts by weight of Portland cement and 200 parts by weight of standard sand were sufficiently mixed,
5 parts by weight of the above-mentioned polypropylene fiber was added and mixed by stirring, and 65 parts by weight of tap water was further added and kneaded so that the whole was uniform. When the shape of the fiber was confirmed in this state,
Some are slightly separated into single fibers, but most of them are 2 to
It was in a state in which it was divided into about 5 continuous yarns and uniformly dispersed in the cement mixture. FIG. 1 is a plan view sketched from the micrograph and the magnification is 8 times. FIG. 2 is a sectional view of the same, and the magnification is 60 times. It can be clearly seen that the continuous yarn-shaped tape 1 is a continuous body of the single yarn filaments 2, and the individual single yarn filaments 2 are appropriately separated from the connecting portion 3.

The cement mixture was poured into a mold,
Leave it in the air at room temperature for 48 hours and then in an autoclave.
After curing at 165 ° C for 20 hours, a plate material having a thickness of 5 mm and a length and width of 500 mm was prepared.

As Comparative Example 1, an ordinary monofilament-shaped polypropylene fiber is taken up. This is a polypropylene resin (isotactic pentad fraction 0.9
6, MFR = 5.0g / 10min.) Is fed to the extruder and melt temperature 230
After being extruded from a 2 mmφ circular nozzle at ℃ and cooled, the drawing temperature is 130 ℃ and the annealing temperature is 135 by the hot plate contact drawing method.
A uniaxial longitudinal stretching was performed at a temperature of 7 ° C and a draw ratio of 7 to form a monofilament having a fineness of 20dr, which was cut into about 6mm length by a cutter blade to obtain a polypropylene fiber.

Hereinafter, a test piece was molded by mixing with cement in the same manner as in Example. The polypropylene fiber of Comparative Example 1 had a single yarn fineness similar to that of Example, but was finely separated before use. It was difficult to handle, and the dispersability was poor because the single fibers separated in the cement were entangled with each other. The difference in fiber morphology can be understood by comparing FIGS. 1 and 2.

As Comparative Example 2, a trunk-branch-shaped polypropylene fiber obtained by splitting and splitting a film is taken. this is,
Polypropylene resin (isotactic pentad fraction
0.94, MFR = 3.0 g / 10 min.) Is fed to the extruder, and is extruded in an amorphous state from a circular die at a melting temperature of 230 ° C by the inflation method, cooled to form a film, and then chopped into tapes. Uniaxially stretching at a drawing temperature of 130 ° C., an annealing temperature of 135 ° C., and a draw ratio of 5 times by a hot plate contact method, and makes a cut by splitting the fiber by contacting with a high-speed rotary blade roll to split the trunk fiber. A split yarn having a trunk-branch shape with an average fineness of 60 dr is formed and cut into about 6 mm long with a cutter blade to obtain polypropylene fiber. FIG. 3 is a plan view sketched from the micrograph and the magnification is 8 times. FIG. 4 is the same cross-sectional view (60 times), and only the random splits 5 are formed in the conventional flat yarn 4.

Hereinafter, the sample was molded by mixing it with cement in the same manner as in Example. However, the polypropylene fiber of Comparative Example 2 was in a bundled state before use due to the characteristic trunk-branch shape, and was easy to handle. However, the presence of split ends in the cement made the fibers bulky and difficult to disperse uniformly.

Table 1 shows the results of measuring the physical properties of the reinforced cement molded products obtained by blending the polypropylene fibers of Example 1 and Comparative Examples 1 and 2 described above.

[0028]

[Table 1]

Examples 2 to 5 The polypropylene resin used in Example 1 was melt extruded from different continuous yarn shape nozzles, and the drawn filaments were cut to prepare various continuous yarn shape tapes shown in Table 2. In the same manner as in 1, the physical properties of the cement board were measured. The results are summarized in Table 1.

[0030]

[Table 2]

[0031]

As described in detail above, in the polypropylene fiber of the present invention, 5 to 100 shortly cut filaments having a single yarn fineness of 5 to 100 dr have a continuous yarn shape and are separable connecting portions. Since they are joined, they are easy to put into cement and have good handleability, and when kneaded in cement, they are easily separated into a small number of continuous yarns and are therefore uniformly dispersed. Further, most of them are a small number of continuous yarns, so that unevenness is formed on the surface or the whole of the fiber, and it is possible to increase the contact area between the fiber and the cement and increase the physical binding force to the cement. Thus, the cement molded product containing the polypropylene fiber of the present invention as a reinforcing fiber material can be improved in tensile strength, bending strength, impact strength and the like.

[Brief description of drawings]

FIG. 1 is a plan view sketched from a micrograph (8 times) of a polypropylene fiber for cement reinforcement of the present invention (Example 1).

FIG. 2 is a cross-sectional view sketched from a micrograph (60 times) of a polypropylene fiber for cement reinforcement of the present invention (Example 1).

FIG. 3 is a plan view sketched from a microscope photograph (8 times) of a conventional (Comparative Example 2) polypropylene fiber for cement reinforcement.

FIG. 4 is a sectional view sketched from a microscope photograph (60 times) of a conventional (Comparative Example 2) polypropylene fiber for cement reinforcement.

[Explanation of symbols]

 1 Continuous yarn shape tape 2 Single yarn filament 3 Connection part 4 Flat yarn 5 Split

Claims (2)

[Claims] 1. A polypropylene fiber for cement reinforcement, which is a polypropylene-based synthetic resin filament and is composed of short fibers of a continuous yarn-shaped tape in which individual filaments are separably connected. 2. A continuous thread shape in which polypropylene synthetic resin is melt extruded from a continuous thread shape die in which nozzle holes are connected in series or adjacent to each other and subjected to longitudinal uniaxial stretching treatment, and filaments formed in such a manner that they can be individually separated. Polypropylene fiber for cement reinforcement, which consists of short fibers obtained by cutting a tape to a specified length.