JP2604220B2 - Fiber reinforced cement molding - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to the improvement of fiber-reinforced cement moldings formed by conventional papermaking, extrusion or cast molding and then autoclaved.

[Conventional technology]

Conventionally, cement moldings have been used for interior and exterior wall materials and roofing materials as building materials, and polypropylene (PP) fibers, polyvinyl alcohol-based fibers, polyacrylic fibers, alkali-resistant fibers have been used as reinforcing fibers for such cemented products. Glass fiber or the like is used. In producing these conventional fiber-reinforced cement moldings, they are formed by sheet forming, extrusion or casting, and then naturally cured or steam cured or autoclaved to obtain products.

However, natural curing requires a long time of 20 to 30 days and is not efficient for industrial production. As an alternative, steam curing or autoclave curing, which is forced curing, has recently become more and more applied. In addition to shortening the curing period described above, especially in autoclave curing performed for the purpose of improving the strength characteristics of the cement molded product, at a temperature of at least 150 ° C, usually 160 ° C or more under strong alkaline conditions of cement matrix. The hardening treatment of cement moldings is carried out under severe conditions of about 10 hours or more, and more recently, the autoclave curing temperature has been further increased, and there is a tendency to improve the strength characteristics.

[Problems to be solved by the invention]

When the cement molded product is subjected to autoclave curing under the severe processing conditions described above under the strongly alkaline conditions of cement matrix, polyvinyl alcohol-based fibers, polyacrylic fibers, and ordinary type glass fibers used as reinforcing fibers Is completely embrittled and loses its function as a reinforcing fiber at all. For this reason, alkali-resistant glass fibers are currently mainly used, but even such alkali-resistant glass fibers undergo considerable damage when subjected to autoclave curing treatment under the conditions described above, and their function as reinforcing fibers is reduced by half. The reality is that they do it.

Carbon fibers and aramid fibers are reinforcing fibers that can withstand the severe autoclave curing conditions described above, but these are very expensive and are not practical as reinforcing fibers for general cement moldings for building materials.

On the other hand, PP fiber is very strong against the strong alkaline condition of cement matrix, and hardly becomes brittle under autoclave curing below 160 ° C, so it is the only practical reinforcing fiber for such applications. is there.

However, PP fiber, which is generally used as a reinforcing fiber of a cement molded product, has a draw ratio of less than 10 times,
The fineness is usually around 2 denier. Such PP fiber has a curing temperature of 160 in autoclave curing.
C is the limit, and if it exceeds this, even PP fibers become brittle and lose their function as reinforcing fibers. For this reason PP
If the diameter of the fiber is further increased, the curing temperature can be slightly increased (for example, 3 to 4 ° C.), but the fiber may slip out of the molded product, and the number of fibers contained. And the strength characteristics cannot be improved, which is not preferable.

As an alternative to the above-mentioned cement molding reinforced with PP fibers, the present inventor has specific shape characteristics, that is, the average fineness of the trunk fibers is 40 to 200 denier, and the aspect ratio of the trunk fibers is 40 to 200. The present invention provides a cement molded product reinforced with a fibrillated trunk filament-shaped chopped filament type PP filament fiber (see Japanese Patent Application No. 62-2805392), and further increases the draw ratio of the PP film fiber to increase the degree of orientation. It has been found that an increase in the temperature contributes to an improvement in the autoclave curing temperature of the molded article, and a cement molded article reinforced with a high-magnification turned-up filament type PP film fiber was provided (Japanese Patent Application No. 63-18638). No.).

In general, recent autoclave curing of cement moldings is carried out at 160 to 180 ° C for 8 to 15 hours. However, the strength characteristics of moldings made from a mixture of cement admixtures that react at high temperatures And / or further increasing the curing temperature (e.g., 180
℃ or more). However, under such severe conditions, a practical organic reinforcing fiber capable of sufficiently exhibiting the function as a strength fiber has not been obtained. ~ 160 ℃
For example, curing treatment must be carried out for a long time, for example, 10 hours or more, usually 15 to 20 hours, which is disadvantageous both economically and in terms of product characteristics.

Accordingly, an object of the present invention is to provide a cement molded product which overcomes the various drawbacks caused by the conventional autoclave curing described above, and particularly to a cement molded product using a chopped filament type PP film fiber as a reinforcing fiber. The present invention is to provide a cement molded product having excellent strength properties and dimensional stability after autoclaving at a temperature of 165 ° C. or more.

[Means for solving the problem]

The present inventor has conducted various studies on a cement molded product cured by autoclaving, and by using a special PP film fiber described later as a reinforcing fiber, has sufficiently achieved the function as a reinforcing fiber even under high temperature curing conditions. I found here what I can do.

That is, the present invention is a fiber-reinforced cement molded product formed by papermaking, extrusion or cast molding, and then cured in an autoclave, containing a specific amount of an inorganic substance having a specific particle size described later as a reinforcing fiber, and further stretched uniaxially at a high magnification. And a fiber-reinforced cement molding using a chopped filament type PP film fiber produced from a polypropylene film having a high degree of orientation.

Chopped filament type PP used in the present invention
The film fiber has the formula [Wherein formula C is a numerical value representing the content (% by weight) of the inorganic substance, and S is a numerical value representing the stretching ratio (times) of the film].
It is a film fiber made from a film having a high degree of orientation by being drawn at a high magnification, ie, 12 times or more, in one direction.

As the inorganic substance contained in the film fiber used in the present invention, microsilica, ultrafine calcium carbonate, magnesium carbonate and barium sulfate can be used.

In the present invention, the average particle size of the inorganic substance contained in the PP film fiber has a high correlation with the content thereof and the stretching ratio of the film.
If the value is larger than the value calculated in the above, unless one or both of the content of the inorganic substance and the draw ratio is out of the range of the specific value, it becomes difficult to produce the intended film fiber, and therefore Curing at high temperatures, especially at high temperatures exceeding 180 ° C., cannot improve the strength characteristics or dimensional stability.

On the other hand, even if the particle size of the inorganic substance contained satisfies the formula (1), the content in the film is 30% by weight.
If the ratio exceeds 1, it is difficult to unidirectionally stretch the film by a factor of 12 or more, and a film with a draw ratio of less than 12 times cannot withstand the high-temperature curing, and the strength characteristics and dimensional stability of the cement molded product also deteriorate. If the content is less than 15% by weight, the stretch ratio can be increased to 12 times or more, but it cannot withstand the high-temperature curing temperature, and it is difficult to expect improvement in the strength characteristics of the cement molded product. Therefore, the content of the inorganic substance in the film is 15 to 30% by weight, preferably 20 to 25% by weight.

When the average particle size of the inorganic substance satisfies the above formula (1) and the content is 15 to 30% by weight, the draw ratio can be 12 times or more, and generally, the draw ratio can be increased. About
Although the film can withstand the above-mentioned high temperature curing temperature, however, if the stretching ratio is too large, for example, if it exceeds 22 times, the film breaks and it becomes difficult to produce the film. If the stretching ratio is less than 12 times, high temperature curing resistance cannot be obtained. In general, the stretching ratio is 12 to 22 times, preferably 15 to 20 times.

Chopped filament type PP used in the present invention
As described above, a PP film containing an inorganic substance having a particle size satisfying the formula (1) of 15 to 30% by weight is stretched in a uniaxial direction at least 12 times, and then split in a stretching direction by a usual method. It may be a thin strip-shaped chopped filament type PP film fiber, or a fibrillated chopped filament type PP film fiber, with the latter being more preferred.

Fibrillated chopped filament type PP
The methods of producing film fibers per se are known to those skilled in the art, for example, GB 1130612, U.S. Pat.
No. 4310475, a strip-shaped chopped filament type PP film fiber formed by slitting a film to a small width and then cutting the film to an appropriate length is also well known. In the present invention, those known film fibers containing the above-mentioned inorganic substance and drawn at a high magnification are used.

The strip-shaped or fibrillated chopped filament type PP film fiber used in the present invention has, as its shape characteristics, an average fineness of fiber or trunk fiber: 40 to 200 denier fiber or trunk fiber length: 3 It is preferable to use fibers having an aspect ratio of 1818 mm fiber or trunk fiber: 40-200.

As described above, a cement molded product using a chopped filament type PP film fiber having the above-mentioned shape characteristics as a reinforcing fiber is described in Japanese Patent Application No. 62-280392, Autoclave curing is not used for molding, but natural curing, for example, long-term curing for 28 days is used. As an improvement of the present invention, as described above, in Japanese Patent Application No. 63-18638, a film as a raw material for producing a chopped filament type PP film fiber is highly oriented to impart autoclave curing properties. However, using the chopped filament type PP film fiber in Japanese Patent Application No. 63-18638, the molded product obtained by papermaking, extrusion or casting was cured.
It has been found that when the autoclave curing is performed at a temperature of 175 ° C. or more for 10 hours or more, a fiber-reinforced cement molded product having sufficient strength properties cannot be obtained depending on the use. For this reason, as described above, not only the fibrillated trunk-branched chopped filament type but also a thin strip-shaped chopped filament type PP film fiber, as described above, an inorganic substance satisfying the formula (1), for example, an average particle size. But
When using a selected filament type PP film fiber made from a film having a specific orientation containing 0.3 μm or less and stretched 12 times or more to give a high degree of orientation, it is treated under the severe autoclave curing conditions described above. Thus, a cement molded product which can maintain strength characteristics and has good dimensional stability can be obtained.

If the average fineness of the film fiber is less than 40 denier, the heat resistance in autoclave curing tends to be inferior, and if it exceeds 200 denier, the heat resistance improves but the cement molding is too thick and thin. It is not preferable as a reinforcing fiber of the material. If the length is less than 3 mm, the reinforcing function is inferior. If the length is more than 18 mm, the dispersibility and workability of a thin cement molding are poor, which is not preferable. If the aspect ratio is less than 40, the enhancement function will be lower, and 200
Exceeding this is not preferable because workability and dispersibility deteriorate.

According to the present invention, the mixing ratio of the above-mentioned chopped filament type PP film fiber to the cement matrix is preferably 0.3 to 4.5% by weight as usual.

The molded product before curing in an autoclave can be produced by ordinary papermaking, extrusion or cast molding. The autoclave curing after molding is different from the conventional one, and is performed under the condition that has recently been generally performed.
The reaction may be performed in a time of 185 ° C. for 6 hours.

(Operation)

Chopped filament type PP used in the present invention
It is not clear why the film fiber does not deteriorate under the severe autoclave curing conditions described above and provides a cement molded product having sufficient strength, but it is not clear that the PP film prior to the production of the chopped filament type PP film fiber. The autoclave curing at a high temperature of 170 ° C. or more, especially 185 ° C. by containing 15 to 30% by weight of an inorganic substance having a particle size satisfying the above-mentioned formula (1) and stretching it in a uniaxial direction 12 times or more. However, it is possible to obtain a cement molded product having little deterioration and excellent strength characteristics and dimensional stability.

〔Example〕

 Hereinafter, the present invention will be described with reference to examples.

Manufacture of chopped filament type PP film fiber for test: Production Example 1 Kneaded with 60 parts by weight of microsilica having an average particle size of 0.23 μm and a master batch resin consisting of 40 parts by weight of PP resin (MI: 30). I got it.

37 parts by weight of the master batch resin is further added to the PP resin (MI: 3
0) Mix with 63 parts by weight, extrude through a normal extruder ring die by the inflation method with a melting temperature of 220 ° C and a blow ratio of 1: 1. After air cooling, stretch in an air oven at 180 ° C with a draw ratio of 17 times. Then, a film having a thickness of 30 μm was made. The microsilica content of this film was 22.2%.

Next, the film was subjected to a corona discharge treatment by a usual method, and then split and split in the axial direction through a porcupine roller having a needle density of 170 needles / cm ² and a surface speed of three times the film speed. Next, a polyoxyethylene glycol ester-based surfactant was applied and then cut into 6 mm to produce a chopped filament type PP film fiber.

 The special characteristics of the PP film fiber thus produced are shown below.

Average particle size of microsilica: 0.23 μm Microsilica content (C): 22.2% Film stretching ratio (S): 17 Value of equation (1): 0.31 Fineness of trunk fiber: 52 denier Length of trunk fiber: 6 mm stem Fiber aspect ratio: 67 Production Example 2 (Comparative Example 1) In the above Production Example 1, 17 parts by weight of the master batch and PP
A chopped filament type PP film fiber was prepared in the same manner as in Production Example 1 except that 83 parts of the resin was used and the film was drawn at a draw ratio of 20 times.

 The special characteristics of the PP film fiber thus produced are shown below.

Average particle size of micro-silica: 0.23 μm Micro-silica content (C): 10.2% Stretch ratio of film (S): 20 Value of formula (1): 0.49 Incidentally, film thickness, fiber and length of trunk fiber and aspect The ratio was the same as in Production Example 1.

Production Example 3 (Comparative Example 2) In the above Production Example 1, PP was used without using a master batch.
A chopped filament type PP film fiber was prepared in the same manner as in Production Example 1 except that only the resin was used and the film was drawn at a draw ratio of 24.

Production Example 4 (Comparative Example 3) In the above Production Example 1, 47 parts by weight of the master batch and PP
A chopped filament type of resin was prepared in the same manner as in Production Example 1 except that the resin was stretched at a stretching magnification of 8 times using 53 parts by weight.
Made PP film fiber.

 The special characteristics of the PP film fiber thus produced are shown below.

Average particle size of microsilica: 0.23 µm Microsilica content (C): 28.2% Stretch ratio (S) of film: 8 Value of formula (1): 1.11 Film thickness, trunk fiber, length and aspect The ratio was the same as in Production Example 1.

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

Portland cement 100 parts by weight No. 7 silica sand 50 parts by weight Micro silica 30 parts by weight Mighty 150 (plasticizer, manufactured by Kao Corporation) 2 parts by weight Water 50 parts by weight Based on the total solid content of each PP film fiber of Production Examples 1-4 1% by weight in an omni mixer with water and mighty 150 and Production Example 1
The PP fibers produced in each of No. 4 were mixed and stirred, cement was immediately added and kneaded for 2 minutes, and then microsilica and silica sand were added and kneaded for 3 minutes.

Next, the kneaded mortar was poured into a 316 mm × 316 mm × 10 mm mold, subjected to vibration molding, and then left to cure for about 4 hours.

The cured molded product was released from the mold, subjected to autoclave curing at 180 ° C. for 8 hours, and allowed to stand in a room for 1 week to be naturally dried.

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 at a span of 200 mm and a speed of 2 mm / min using a test piece cut into a size of 250 mm x 50 mm x 10 mm using a compression tester (manufactured by Shimadzu Corporation) having a capacity of 2 tons. The impact strength was measured at a span of 60 mm using a test piece cut into a size of 80 mm × 40 mm × 10 mm using a Charpy impact tester (manufactured by Shimadzu Corporation). The toughness was determined by measuring the integral (area) of the strength / strain in the strength / strain curve obtained by the bending strength test with a planimeter and performing toughness.

[Effects of the Invention] As is clear from the data of the above-mentioned Examples and Comparative Examples, the cement molded product of the present invention has excellent strength characteristics despite severe curing conditions under autoclave curing, that is, curing under temperature, Strength required by the elderly
It has excellent characteristics of 120 kg / cm ² or more and toughness of 50 kg · cm / cm ² or more, and has an excellent effect of greatly reducing the curing time.

Claims (1)

(57) [Claims] Claims: 1. Formed by papermaking, extrusion or cast molding,
Then, in a fiber-reinforced cement molded product that has been autoclaved, as a reinforcing fiber, the formula [Wherein C is a numerical value representing the content (% by weight) of the inorganic substance, and S is a numerical value representing the stretching ratio (times) of the film].
A fiber reinforced cement comprising a chopped filament type polypropylene film fiber produced from a polypropylene film containing and having a high degree of orientation at least 12 times stretched in one direction to impart a high degree of orientation. Moldings.