JPH01192753A - Fiber reinforced cement molded article - Google Patents

Abstract

PURPOSE:To prevent reduction in strength of molded article resulting from brittleness in producing fiber-reinforced cement molded article through autoclave curing process, by using polypropylene film fibers produced by a specific method as reinforcing fibers. CONSTITUTION:A polypropylene film is drawn in a high ratio in the unidirection and provided with high degree of orientation. Then the film is cleft in the drawing direction to produce polypropylene film fibers of chopped filament type. The shape characteristics of the fibers are preferably 40-200denier average size, 3-18mm fiber length and 40-200 aspect ratio of fibers. Then a cement matrix is blended with the fibers as reinforcing fibers, made into a sheetlike material, extruded or subjected to cast molding. Then the molded article is cured in an autoclave to give fiber reinforced cement molded articles having excellent flexural strength, impact strength, toughness, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to improvements in cement moldings formed by conventional papermaking, extrusion or casting, and then autoclaved.

[Prior art] Cement moldings have traditionally been used as building materials for interior and exterior wall materials, roofing materials, etc., and reinforcing fibers for such cement moldings include polypropylene (PP) fibers, polyvinyl alcohol fibers, and polyacrylic fibers. type fibers, alkali-resistant glass fibers, etc. are used. In producing these conventional fiber-reinforced cement molded products, the products are made by paper-forming, extrusion molding, or cast molding, followed by natural curing or autoclave curing.

However, natural curing requires a long period of 20 to 30 days and is not efficient for industrial production.

As an alternative to this, autoclave curing, which is forced curing, has recently been increasingly applied. In this autoclave curing, the cement matrix under strongly alkaline conditions is at least 130°C, usually 160°C.
Cement molded products are cured under severe conditions for about 10 hours or more at temperatures above ℃.

Problem 1 to be Solved by the Invention When a cement molded product is autoclaved under the strong alkaline conditions of the cement matrix and under the severe treatment conditions described above, polyvinyl alcohol fibers used as reinforcing fibers, polyacrylic fibers Fibers and ordinary type glass fibers become completely brittle and lose their function as reinforcing fibers.For this reason, alkali-resistant glass fibers are currently mainly used; The reality is that if the fiber is subjected to autoclave curing under the conditions described above, it will be severely damaged and its function as a reinforcing fiber will be halved.

Carbon fibers or aramid fibers are examples of reinforcing fibers that can withstand the above-mentioned severe autoclaving conditions, but these are very expensive and are not practical as reinforcing fibers for cement moldings for boat-related building materials.

On the other hand, PP fibers are extremely resistant to the strong alkaline conditions of the cement matrix and hardly become brittle when autoclaved at temperatures below 160'C, making them the only practical reinforcing fibers for such applications. be.

However, PP fibers, which are generally used as reinforcing fibers for cement moldings, have a stretching ratio of less than 10 times.
Further, the fineness is usually around 2 denier. The steam temperature limit for this stiff PP fiber during autoclave curing is 160°C, and if this temperature is exceeded, even the PP fiber becomes brittle and loses its function as a reinforcing fiber. For this reason, if the diameter of the PP fiber is made larger,
This is not preferable as it may cause the molded product to slip out completely.

Generally, in recent autoclave curing of cement molded products, treatment conditions of 8 to 15 hours at 160 to 180°C are desired, but under such harsh conditions, the function as reinforcing fibers cannot be fully demonstrated and is not practical. Organic reinforcing fibers have not been obtained, and for this reason, in the case of such organic reinforcing fibers, it is necessary to lower the temperature to, for example, 140 to 150°C, and perform a curing treatment for a long time, for example, 15 to 20 hours. However, it is inevitable that it will be disadvantageous from an industrial perspective.

Therefore, an object of the present invention is to provide a cement molded product which overcomes the various drawbacks caused by the conventional autoclave curing mentioned above, and in particular, to provide a cement molded product which has excellent strength even after autoclave curing for 8 to 15 hours at a temperature of 160 to 180°C. Our goal is to provide molded products.

[Means for Solving the Problems] The present inventor has conducted various studies on cement molded products cured in an autoclave, and has found that the function as reinforcing fibers can be sufficiently achieved by using special PP film fibers as reinforcing fibers. I found it here.

That is, the present invention provides a fiber-reinforced cement molded product formed by papermaking, extrusion, or cast molding, and then cured in an autoclave, in which a polypropylene film, which is uniaxially stretched at a high magnification and given a high degree of orientation, is used as a reinforcing fiber. This is a fiber-reinforced cement molded product using chopped filament type PP film fibers manufactured by

Chopped filament type PP used in the present invention
The film fibers are PP film fibers made from a film that has been uniaxially stretched at a high magnification, that is, 15 times or more, and has been given a high degree of orientation.

When the uniaxial stretching ratio of the film is less than 15 times,
Under curing conditions at a temperature of 60 to 180°C, the PP film fibers become brittle, making it impossible to obtain a cement molded product having the desired strength. Furthermore, it is not preferable to use a film that has been stretched in two axial directions, since a cement molded product having the desired strength cannot be obtained.

Chopped filament type PP used in the present invention
The film fibers may be ordinary chopped filament type PP film fibers made by splitting a PP film uniaxially stretched at a high ratio in the stretching direction using a conventional method, as described above, or chopped filament type PP film fibers having a trunk and branch shape. It may also be a pud filament type PP film fiber, with the latter being preferred.

The method for producing the trunk-branch-shaped chopped filament type PP film fibers is described, for example, in British Patent No. 11306.
No. 12, U.S. Patent Sections 4,261,754 and 4310
It is described in No. 475.

When using the above-mentioned normal chopped filament type PP film fiber, its shape characteristics are as follows: Average fineness of fiber: 40-20 denier Fiber length = 3-18 mm Fiber aspect ratio: 40-200 It is preferable to use If the average fineness of the fiber is less than 40 denier, the heat resistance during autoclave curing tends to be poor, and if it exceeds 200 denier, the heat resistance is good but it is too thick and cannot be used as a reinforcing fiber for thin cement moldings. Undesirable. Moreover, if the length is less than 3 mm, the reinforcing function will be poor, and if it exceeds 18 mm, the moldability and workability of thin cement molded products will deteriorate, which is not preferable.

Also, if the aspect ratio is less than 40, the enhancement function will be lower.
Moreover, if it exceeds 200, the moldability and workability of thin cement molded products will deteriorate, which is not preferable.

In addition, when using chopped filament type PP film fibers with trunk and branch shapes, the shape characteristics of the trunk fibers are as follows: Average fineness of the trunk fibers: 40 to 60 denier Length of the trunk fibers:
It is preferable to use a fiber having an aspect ratio of 3 to 18 mm and a trunk fiber of 40 to 200. A cement molded product using trunk-branch-shaped chopped filament type PP film fibers having the above-mentioned shape characteristics as reinforcing fibers was disclosed in a previous application filed by the inventor on November 6, 1988.
It is described in Japanese Patent Application No. 1982-280392 filed on 1983. The specification of this earlier application is hereby incorporated by reference.

However, in this earlier application, natural curing, for example, long-term curing of 28 days, was used for the molding, and autoclave curing was not used.

The present inventors used chopped filament type PP film fibers of the core shape in the invention of the earlier application,
It has been found that fiber-reinforced cement molded products with sufficient strength cannot be obtained when curing molded products made by papermaking, extrusion, or cast molding in an autoclave, for example, at 160 to 180°C for 8 to 15 hours. Ta. For this reason, not only chopped filament type PP film fibers with a trunk and branch shape but also regular chopped filament type PP film fibers can be used.
We studied film fibers and used chopped filament type PP film fibers made from films that had been uniaxially stretched at a high ratio, that is, 15 times or more, to give a high degree of orientation to the PP film before fiber production. It was found that even when processed under the above-mentioned severe autoclave curing conditions, the strength characteristics could be maintained, and a cement molded product having the desired strength could be obtained.

As mentioned above, for normal PP fibers, the temperature condition for autoclave curing is limited to 160°C, and if this temperature is exceeded, PP fibers will deteriorate.
However, according to the present invention, the fibers can be cured even at a high temperature of 180°C.

According to the present invention, the mixing ratio of the above-mentioned normal and trunk-branch chopped filament type PP film fibers into the cement matrix is usually 0.3 to 5.
It is preferable to use it at 0% by volume.

Furthermore, the molded product before autoclave curing can be produced by conventional paper forming, extrusion, or cast molding.

The autoclave curing after molding can be carried out in a conventional manner, for example, at 160-180°C for 8-15 hours, preferably at 165-170°C for 8-10 hours.

[Function] The reason why the regular and trunk-branch shaped chopped filament type PP film fibers used in the present invention do not deteriorate under the above-mentioned severe autoclave curing conditions and provide a cement molded product having sufficient strength. Although it is not clear, by stretching the PP film 15 times or more in the uniaxial direction prior to making chopped filament type PP film fibers, a cement molded product with excellent strength properties that does not deteriorate even after autoclave curing can be obtained. [Example J] The present invention will be described below with reference to Examples and Comparative Examples.

Examples 1 to 3 and Comparative Examples 1 to 3 The materials used in these Examples and Comparative Examples are shown below.

MXi! Ji) Mi support ■ L/J) 1 mouse 1u) Cement
15.0 3.3 4.55 Microsilica 6.0 2.2
2.73* Mighty 150 0.3 1
．． 0 0.3 Vibe 0.21
1.4 0.15 #8 silica sand? , 5
2.2 3.41Wed 3.0
1.0 3.0*? (T-150 + Glidifier (Kao product) ** Reinforcing fiber: These will be described later.

Using an experimental omnimixer with a capacity of 30 I2, add 15.0 kg of cement, 6.0 g of microsilica, 3.0 g of water, and 0.3 g of Mighty 150 and mix for 300 r.
pm for 1 minute. Next, 0.41 kg of each of the reinforcing fibers described below were added and kneaded for 5 minutes. Finally #8
7.5 kg of silica sand was added to form a mortar.

Next, this mortar was extruded onto a flat plate having a thickness of 10 mm and a width of 316 mm using an experimental extruder, and the plates were cut into pieces having a length of 316 mm, and each plate was cured in an autoclave under the conditions shown in Table 1.

Table 1 shows the measurement results of the bending strength, impact strength, and toughness of each of the obtained cement molded products.

In Table 1, the bending strength was measured using a test piece cut into a size of 5 cm x 25 cm. Also, the impact strength is 4cm x 8
A test piece cut to a size of cm was used. Toughness was determined by measuring the area S of the strength and strain curves obtained in the bending strength test using a branimeter.

Reinforcing fibers used: In Example 1, chopped filament type PP film fibers in a trunk and branch shape made from a film stretched 16 times, with a trunk fiber fineness of 60 denier, a length of 12 mm, and an aspect ratio of 120 were used.

In Example 2, normal strip-shaped chopped filament type PP film fibers made from a film stretched 16 times, with a fineness of 160 denier, a length of 12 mm, and an aspect ratio of 80, were used. In Example 3, the same ordinary chopped filament type PP film fiber as in Example 2 was used.

In Comparative Example 1, a trunk-branch shaped chopped filament type PP film fiber made from a film stretched 8 times was used, and the trunk fiber had a fineness of 60 denier, a length of 12 mm, and an aspect ratio of 120.

In Comparative Example 2, a chopped filament type PP film fiber of a normal shape made from a film stretched 8 times, with a fineness of 160 denier, a length of 12 mm, and an aspect ratio of 80 was used.

In Comparative Example 3, a general PP fiber having a fineness of 2 denier and a length of 10 mm was used.

Table-m-”.

[Effects of the Invention] As is clear from the data of the above Examples and Comparative Examples, cement molded products made using chopped filament type PP film fibers made from highly stretched films according to the present invention were not cured in an autoclave. It also has excellent strength properties.

Claims (1)

[Claims] 1. In a fiber-reinforced cement molded product formed by papermaking, extrusion or cast molding, and then cured in an autoclave, the reinforcing fibers are uniaxially stretched at a high magnification to give a high degree of orientation. A fiber-reinforced cement molded product characterized by using chopped filament type polypropylene film fibers manufactured from polypropylene film. 2. The cement molded article according to claim 1, wherein the chopped filament type polypropylene film fibers have the following properties: average fineness of fibers: 40 to 200 denier length of fibers: 3 to 18 mm; and aspect ratio of fibers: 40 to 200. 3. The chopped filament type polypropylene film fiber is a chopped filament type polypropylene film fiber with a trunk and branch shape, and its shape characteristics are: Average fineness of the trunk fiber: 40-60 denier Length of the trunk fiber: 3-18 mm Aspect of the trunk fiber The cement molded article according to claim 1, which has a ratio of 40 to 200. 4. Claim 1, wherein the stretching ratio in the uniaxial direction is 15 times or more.
Cement molded article according to 2 or 3. 5. Add chopped filament type polypropylene film fibers to the cement matrix at a ratio of 0.3 to 5.
The cement molded product according to any one of claims 1 to 4, which contains 0% by volume. 6. Autoclave curing at a temperature of 160-180℃ 8.
The cement molded article according to any one of claims 1 to 5, wherein the cement molding time is 15 hours. 7. The cement molded product according to any one of claims 1 to 6, wherein the cement molded product is a cement molded product made by papermaking, extrusion, or cast molding.