JPS5913657A - Asbestos cement product forming composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composition for molding asbestos-cement products containing asbestos and cement as main raw materials, specifically a composition for molding asbestos-cement products to which polyethylene oxide (hereinafter referred to as PEO) is added. It relates to a molding composition, and its content is a molding composition for asbestos cement products with good explosion resistance.

Traditionally, asbestos cement products have been made mainly from Portland cement and asbestos, in addition to siliceous raw materials and water-soluble polymers such as natural cellulose derivatives methylcellulose, hydroxyethylcellulose, and hydroxyglobil methylcellulose as plasticizers. is added and made into a plastic kneaded product with water, which is then subjected to injection molding, extrusion molding, continuous molding on a belt, discontinuous molding, and coating processing on a substrate, followed by humid air curing and steaming. It has been hardened and manufactured by curing or high temperature autoclave curing. Among these manufacturing methods, the vacuum extrusion method is usually adopted in the extrusion molding method, in which the above-mentioned plastic kneaded material is extruded while being vacuum degassed.As a result, the product has a uniform structure, a webbing, low water absorption, and high strength. Due to its excellent durability, it is being used as a siding material for general buildings and as a wall for building construction.

However, when asbestos cement products manufactured in this manner are subjected to rapid heating due to fire or the like, an explosion phenomenon similar to that observed in PC concrete boards and asbestos slate may occur. When an explosion phenomenon occurs, asbestos-cement products are used as wall materials, etc., making a loud explosion sound and part of them scattering as car debris 14, which may pose a problem for firefighting efforts.

The mechanism of the explosion phenomenon is that due to rapid heating, a large amount of water vapor is generated at once due to dehydration from free water in the capillaries inside the hardened body or from cement bound water, etc., and as a result, the internal water vapor pressure exceeds the tensile strength of the sake bottle. Therefore, in this case, if the volume of the capillary void inside the cured product is large, the water vapor generated will permeate the capillary void and dissipate to the outside, resulting in an increase in water vapor pressure.
The rise will be moderated and the explosiveness will be reduced.

Conventionally, in order to greatly reduce the explosiveness of the capillary voids, methods include increasing the blended water ratio, adding light aggregates such as perlite, diatomaceous earth, and vermiculite, and adding cellulose-based organic fibers. However, in the former case, the strength of the product decreases and the water absorption rate increases, and in the latter case, the combustible substances cause a decrease in its performance as a noncombustible material, and both methods reduce the important performance as a building material. As a result, no building material with excellent overall properties including explosion resistance has yet emerged.

The present inventor conducted extensive studies on the mechanism of explosion of asbestos-cement products, and found that the natural cellulose derivative polymer used as an iJ plasticizer for asbestos-cement kneaded products was It was discovered that during curing and drying, the natural cellulose derivative polymer precipitates and accumulates in the capillary voids, blocking the voids and impeding vapor permeability, thereby promoting explosive properties. The present invention was completed based on the finding that by replacing with PEO, which is a polymer, the explosion resistance is improved without impeding vapor permeability.

That is, the present invention is based on the findings described in section 1-1 and provides a composition suitable for producing asbestos cement products with good explosion resistance by using at least PEO as a plasticizer.

The PEO used in the present invention is not particularly limited as long as it is water-soluble, but it is preferably one with a uniform molecular weight of J000,000 to 5,000,000 that has a molding property of -14.

In addition, the usage is selected appropriately depending on the molding method, but usually,
It is preferable to use 05 to 15 parts of Portland cement. If less than 0.5 parts of Portland cement is used, the effect of plasticization and explosion resistance will not be sufficiently exhibited, and conversely, if it exceeds 15 parts of The contribution rate to moldability does not improve, and in some cases, the explosion resistance even decreases.

The present invention will be explained below using Examples and Comparative Examples.

Examples/Comparative Examples A mixture consisting of (ordinary Portland cement) 100 (heavy chewing part) 6 class asbestos 20 plasticizer Thickness 1
Continuously extruded from a die with 2wn slits,
After leaving the obtained plate-shaped molded product indoors for 12 hours and curing it,
A cured product was obtained by steam curing at 60° C. for 10 hours.

After air-drying this cured product indoors for 3 months, J000Qi
A 000 mm plate-shaped test specimen was constructed, set directly in a square oil burner furnace with an opening of 1 m on a side, and
ISA]:((14) The surface of the test piece was heated with direct flame of a burner until it reached 1000°C according to the heating curve, and the presence or absence of explosion was observed.

Furthermore, in order to evaluate the water vapor permeability of the test specimen, JIS
Water permeability was measured by the method of Afi910.

As plasticizers, in addition to PEO according to the present invention, conventionally known methylcellulose (MC) and hydroxyethylcellulose (HEC) were used alone or in combination (Tables 1 and 2). .

As is clear from Tables 1 and 2, the use of PEO greatly increases water permeability to 1. At the same time, the explosion phenomenon disappeared. Furthermore, in this case, the explosion was eliminated by reducing hydration (Example 4).

Also, in the case of a combination of PEO and MC, PE07
It can be seen that when the molded area becomes J'0.5 or less, the surface 1 explosive property begins to decrease.

In the case of only MC, explosion will occur regardless of whether or not a heavy MC is used to ensure good moldability. Although the water permeability is slightly improved by increasing the hydration, the moldability deteriorates, which is a problem.

A phenomenon similar to MC can also be seen in HEC.

In the above Examples and Comparative Examples, ordinary Portland cement was used as the cement, and the asbestos/cement ratio was 1.
00720, the curing conditions were 601:
Even if 27 powder, inorganic minerals such as serpentine, and various inorganic fibers are added as reinforcement, the effects of the present invention will not change in any way.

Patent applicant: Showa Denko Co., Ltd. Agent: Patent attorney Sei Kikuchi

Claims (1)

[Claims] Composition for molding asbestos cement products with addition of polyethylene oxide