JPH09255391A - Fiber reinforced cement molding - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide a fiber-reinforced cement molded product which is excellent in bending strength and impact strength by suppressing the loss and drop-off of reinforcing fibers. SOLUTION: A composite fiber such as a multi-layer split yarn or a core-sheath filament composed of a high melting point component and a low melting point component is mixed into a cement matrix and molded, followed by autoclave curing. A fiber-reinforced cement molded product obtained by melting a low melting point component of a composite fiber and fusing cross-contact portions of the fibers together.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a cement molded product reinforced with a synthetic resin fiber, and in particular, improved tensile strength, bending strength, impact resistance, crack resistance, etc. obtained by heat curing by incorporating a specific fiber. The present invention relates to cement molded products.

[0002]

2. Description of the Related Art Conventionally, polyolefin-based, polyamide-based, polyvinyl chloride-based fibers are used as reinforcing fibers for cement molded products.
It has been widely tried to blend short fibers such as polyacrylonitrile resin. However, conventional reinforcing fibers do not have sufficient affinity with cement, and because the shape of short fibers is simple, their reinforcing effect is sufficiently satisfied in that they can be easily pulled out from cement with respect to tensile stress and shrinkage stress. Was not.

Therefore, in order to increase the affinity between the reinforcing fiber and the cement, a surface treating agent or a coupling agent is often used for the reinforcing fiber, and the composite fiber is reinforced by adhering inorganic fine particles to the fiber surface. Material (JP-A-4-74741), a sheath-core type composite fiber having a sheath portion containing a substantially plate-like inorganic agent (JP-A-6-9254), and a sheath portion containing calcium carbonate fine powder. There is an attempt to improve the affinity by using a core-sheath composite fiber having an alkaline phosphate metal salt attached to its surface (JP-A-6-219797).

Further, many methods have been proposed to reduce the loss by improving the shape of the fiber. For example, the cross-sectional area of the spun yarn is irregularly changed with respect to the drawing direction to prevent the loss of the fiber. Various methods have been tried (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.), and further, on the surface of the fiber. A method of providing surface treatment with an electron beam on the surface having irregularities (Japanese Patent Publication No. 61-26510) or a method using split fibers of a film (Japanese Patent Publication No. 5-87460, Japanese Patent Laid-Open No. 4-59644).
Gazette) is also disclosed.

These reinforcing fibers are blended in a predetermined amount in a cement matrix and formed into a cement molded body by papermaking molding, extrusion molding, cast molding or the like, and are naturally cured or heat cured. As a method of this curing, natural curing requires long-term curing and is not efficient, and heating curing is performed as a method of shortening the curing time by forcibly heating and obtaining a cement compact with high strength. It is often seen.

However, the heating and curing is carried out in the autoclave.
It cures the cement compact by curing it at a temperature of 150 to 200 ° C for 8 to 20 hours, and the synthetic resin reinforcing fibers to be blended may undergo thermal deterioration. A low-fineness fiber such as a fiber is easily affected by heat, and there is a problem that the function of the reinforcing fiber is significantly reduced.

[0007]

Therefore, it is a molded product obtained by molding from a cement matrix containing a specific reinforcing fiber and curing by heating in a high temperature atmosphere, and the reinforcing fiber is hard to come off from the cement. The purpose of the present invention is to obtain a fiber-reinforced cement molded product having a sufficient reinforcing effect and having excellent strength.

[0008]

The present invention provides a composite fiber having a structure in which a high-melting-point component is a core layer and a low-melting-point component resin is present on at least a part of the surface of the core layer, and obtained by stretching and orientation. The fiber-reinforced cement molded product is characterized in that it is uniformly mixed with a matrix, molded, and then cured by heating and curing.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The cement molded product of the present invention contains a composite fiber as a reinforcing fiber material, and the resin constituting the core layer of the composite fiber can be spun.
Polyester-based, polyamide-based, acrylic-based, vinylon-based, olefin-based, etc. are examples of those that maintain high strength without causing thermal degradation even by heating curing, but since the cement matrix is alkaline, it has excellent alkali resistance. Polypropylene, which is inexpensive and easy to process, is preferable.

Of these polypropylene resins, fibers having particularly high strength and heat resistance are required. Therefore, those having an isotactic pentad fraction of 0.95 or more are preferably used. This isotactic pentad fraction refers to Macromolecules 6 925 (197) by A. Zambelli et al.
3), which means the isotactic fraction in the pentad unit in the polypropylene molecule measured by using ¹³ C-NMR, and the higher this number, the higher the crystallinity. As a result, the molded product has improved rigidity and heat resistance.

The resin having a low melting point component is a resin having a melting point or difficulty point lower than that of the high melting point component by 10 ° C. or more, more preferably 20 ° C. or more, and examples thereof include low density polyethylene, medium density polyethylene, high density polyethylene, Linear low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-propylene copolymer, low melting point polyolefin and the like can be mentioned.

The synthetic resin used for these composite fibers has a melt flow rate (MFR) of 0.1 to 50 g / 10 min., Preferably 1 to 40 g / 10 min because of the melt flow characteristics of the resin in stable and good moldability. ., More preferably from 5 to 30 g / 10 min.

A publicly known technique can be adopted as the method for producing the composite fiber, and the specific structure thereof is a core-sheath type having a high melting point component as a core and a low melting point component as a sheath, or a core part and a sheath part in parallel type. Filament extruded from a nozzle is stretched, a two-layer structure film having a high melting point component as a core layer and a low melting point component laminated on the surface, and a low melting point component laminated on both outer layers of the high melting point component core layer. For example, a split yarn having a trunk-branch shape obtained by slitting a film having a three-layer structure, stretching the film, and then splitting the film through a cloth roll.

As described above, the unstretched fibers extruded from the die are imparted with high strength by the hot stretching treatment. The stretching methods are hot roll type, hot plate type, infrared type and hot air type. Any known technique such as the above can be adopted.
The draw ratio is 3 to 20 times, more preferably 5 to 12 times so that the fiber resin can be sufficiently oriented and exert sufficient strength, and by this drawing treatment, a fiber having high rigidity and high strength can be formed. Moreover, since the stretched and oriented composite fibers are composed of components having different heat shrinkage rates, shrinkage or curling is likely to occur during heat curing in the cement matrix, which is effective for linear drawing. Can be expected.

The fineness of the composite fiber is 1 to 80 dr for the filament single yarn and 10 for the split stem fiber as the reinforcing fiber material.
~ 80dr is preferred. If the cut fiber length is too long, the dispersibility deteriorates, and if it is too short, the reinforcing effect is not exhibited. Therefore, a fiber length of 3 to 30 mm, preferably 5 to 15 mm is used.

The composite fiber thus obtained is used as a reinforcing fiber material by blending it with hydraulic cement such as Portland cement, white Portland cement, alumina cement, blast furnace slag cement, etc.
Various treatments may be performed. For example, the fiber surface may be treated with a surfactant, a dispersant, a coupling agent, or the like,
Alternatively, surface activation or cross-linking treatment may be performed by corona discharge treatment, ultraviolet ray irradiation, electron beam irradiation, or the like.

In the production of the cement molded product of the present invention, the composite fiber is blended in the cement matrix and uniformly mixed by a mixer or the like, and molded by a known paper forming molding, extrusion molding, cast molding method or the like. However, the content of the fibers in the cement matrix is usually 0.5 to 10% by weight based on the cement solid content.

The compact was then placed in an autoclave for 15 minutes.
It is heated and cured at a temperature of 0 to 200 ° C. for 7 to 18 hours to give a hardened cement molded product. In the fiber reinforced cement molded product of the present invention, a composite fiber containing a low melting point component is blended. As a result, the composite fiber dispersed in the cement matrix has the low melting point component in the contact portion between the folded, entangled, and crossed fibers melted and fused by heating. Therefore, the fusion bonding between the composite fibers acts to prevent the fibers from slipping off or falling off, and the strength of the cement molded product is improved.

[0019]

【Example】

Example 1 Polypropylene resin (isotactic pentad fraction
0.96, MFR = 5.0g / 10min., Melting point 170 ° C) as core resin, ethylene-propylene copolymer (MFR = 8.0g / 10min., Melting point 1)
(42 ° C) is used as the outer layer resin and is supplied to each of two series of extruders, and is extruded in an amorphous state from a circular die by a multi-layer inflation molding method and cooled to obtain a three-layer film (layer ratio).
1: 8: 1), and then cut into tapes, uniaxially stretched longitudinally at a draw ratio of 5.5 times by the hot plate contact type stretching method, and then splitting through a cloth roll that rotates at high speed. Fine trunk fineness 50dr
The split yarn was prepared and bundled, and a composite fiber having a fiber length of about 9 mm was obtained by a cutter.

When the composite fiber is mixed with the cement to form a specimen, 100 parts by weight of Portland cement and 200 parts by weight of standard sand are thoroughly mixed to prepare 5 parts of the above-mentioned composite fiber.
Then, 65 parts by weight of tap water was added, and the mixture was kneaded with a rotary drum mixer so that the whole was uniform. This cement mixture is made into paper by the Fourdrinier method and the
By pressure molding for 1 minute at a pressure of kg / cm ² , thickness 5 mm, length and width 35
0 mm plate shape, this plate shape after 12 hours of room temperature curing,
Curing was carried out in an autoclave at a temperature of 165 ° C. for 12 hours to obtain a fiber-reinforced cement molded product of Example 1.

Comparative Example 1 Polypropylene resin (isotactic pentad ratio of 0.
94, MFR = 3.0g / 10min., Melting point 168 ℃) to the extruder,
A single layer inflation molding method extrudes from a circular die in an amorphous state to cool and form a film, which is then shredded into a tape shape, and a draw ratio of 5.5 by a hot plate contact drawing method.
Uniaxially stretched in the longitudinal direction, and then splitting and splitting through a cloth roll that rotates at high speed to form a split yarn with a trunk fineness of 50dr, which is bundled and a single layer fiber is made with a cutter to a fiber length of about 9 mm. Obtained. Thereafter, papermaking was carried out in the same manner as in Example 1, and the autoclave curing was carried out at room temperature to obtain a fiber-reinforced cement molded product of Comparative Example 1.

Example 2 Polypropylene resin (isotactic pentad fraction
0.96, MFR = 5.0g / 10min., Melting point 170 ° C) as core resin, ethylene-propylene copolymer (MFR = 8.0g / 10min., Melting point 1)
(42 ° C) is used as the sheath layer resin, supplied to each of two series of extruders, extruded in an amorphous state from the multilayer nozzle and cooled to form a core-sheath filament (weight ratio = core layer 8: sheath layer 2). , A filament having a fineness of 20dr, which was longitudinally uniaxially stretched at a draw ratio of 6.5 times by a hot air oven type stretching method, was bundled,
A composite fiber having a fiber length of about 6 mm was obtained by a cutter. Thereafter, papermaking was carried out in the same manner as in Example 1, and normal temperature and autoclave curing were carried out to obtain a fiber-reinforced cement molded product of Example 2.

Comparative Example 2 Polypropylene resin (isotactic pentad ratio of 0.
94, MFR = 3.0g / 10min., Melting point 168 ℃) to the extruder,
A single layer nozzle is extruded in an amorphous state and cooled to spin the filament, and then the draw ratio is 6.
Form a filament with a fineness of 20dr that is uniaxially stretched 5 times,
This was bundled and a single layer fiber was obtained by a cutter with a fiber length of about 6 mm. Thereafter, papermaking was carried out in the same manner as in Example 1, and the autoclave curing was carried out at room temperature to obtain a fiber-reinforced cement molded product of Comparative Example 2.

The physical properties of the fiber-reinforced cement molded products of Examples and Comparative Examples were measured, and the results are summarized in Table 1. From these results, comparing Example 1 which is a branch-branch-shaped split fiber and Comparative Example 1, the composite fiber of Example 1 has a bending strength and impact strength of about 10% as compared with the single-layer fiber of Comparative Example 1. It was confirmed to have improved. Further, in the comparison between the filament-shaped fibers of Example 2 and Comparative Example 2, it was similarly confirmed that the composite fiber was superior.

[0025]

[Table 1]

[0026]

INDUSTRIAL APPLICABILITY The present invention is a fiber-reinforced cement molded product obtained by mixing composite fibers composed of a high-melting point component and a low-melting point component and curing by heating curing, and heating by autoclave curing or the like. Because the low melting point component of the composite fiber is melted and the fibers are fused to each other, loss or dropping of the fiber is suppressed, and the high melting point component does not cause thermal deterioration and the strength of the fiber itself is not impaired. Bending strength and impact strength can be improved.

Claims (1)

[Claims] 1. A structure having a high melting point component as a core layer and a low melting point component resin present on at least a part of the surface thereof,
A fiber-reinforced cement molded product, characterized in that the composite fiber obtained by stretching and orientation is uniformly mixed with a cement matrix, molded, and then cured by heating and curing.