JPH0380141A - Production of extrusion-molded cement product - Google Patents

Abstract

PURPOSE:To prevent the shortening of the hardening time of inorg. matter due to the heat generation in a molding machine by adding (hydroxyalkyl) alkylcellulose to a mixture of blast furnace slag with cement, carrying out extrusion molding and then curing under pressure. CONSTITUTION:0.3-2wt.% (hydroxyalkyl)alkylcellulose and 2-20wt.% fibrous reinforcing material other than asbestos, e.g. carbon fibers are added to 100 pts.wt. mixture of 70-90wt.% blast furnace slag with 30-10wt.% cement or an alkali stimulant such as gypsum is further added to obtain a compsn. for extrusion molding. This compsn. is extrusion-molded into a desired shape, cured at >=100 deg.C in an autoclave and hardened.

Description

[Detailed Description of the Invention] (Prior Art) In recent years, a mixture of cement with about 20 parts by weight of asbestos fibers, aggregates, etc. added thereto, water added and kneaded, is extruded into a die shape of a desired shape. Cement boards and asbestos/cement boards made by
It is used for building exterior wall materials, roofing materials, flooring materials, etc.

When added as reinforcing fibers, the asbestos fibers used in the production of such undeformed products are extremely well dispersed in the kneaded material, and have excellent shape-retaining properties for extruded products, as well as water-retaining properties. . In addition, 1 is carried out in order to impart dimensional stability to such extruded products and to form the necessary strength.
Even during curing in a steam pressure cooker at a high temperature of 70° C. or higher, asbestos' heat resistance allows it to exhibit sufficient effects as a strength-reinforcing fiber.

Asbestos is a unique fiber that is especially suitable for extrusion molding as a fiber that simultaneously has the reinforcing fiber properties required for the production of extrusion moldings, such as dispersibility, shape retention, water retention, and heat resistance, as shown above. It is used as a reinforcing fiber.

However, in recent years, carcinogenicity, which is thought to be caused by the unique fiber shape of asbestos, has become a problem, and good extrusion molded products can be obtained by using systems that do not use asbestos, or that add as little amount of asbestos as possible. It is hoped that the technology will be perfected. Organic fibers have been considered as fibers to replace asbestos, but all of them have poor dispersibility and when extrusion molding is attempted in place of asbestos fibers, they generate more heat in the molding machine than when asbestos is used. Since the amount is large, the hardening of the cementitious material is accelerated and the cement hardens in the molding machine, often making molding impossible during the molding process.

On the other hand, even in the extrusion molding of cement containing asbestos, a lot of pressure is applied to the shaping composition during extrusion molding, and asbestos' water retention ability alone makes it difficult to uniformly retain water within the molded body and perform good extrusion molding. Since this is not possible, an organic binder is used in order to make the compositions adhere to each other until the extrudate is solidified and to maintain the shape of the molded product discharged from the extrusion molding die. As these binders, water-soluble cellulose ethers such as methylcellulose, hydroxypropylmethylcellulose, polyethylene oxide, hydroxyethylcellulose, and carboxydimethylhydroxyethylcellulose, sodium polyacrylate, and casein have been proposed as described in Japanese Patent Publication No. 43-7134, among others. Alkyl cellulose and/or hydroxyalkylalkyl cellulose are often used because they have excellent dispersion performance for cement, aggregate, etc., and excellent water retention performance and adhesiveness. Furthermore, it is stated in JP-A-55-19581 that the addition of these substances causes a delay in the setting time of cement, and that cellulose ether is used to prevent the molding composition from hardening during extrusion molding, making molding difficult. The use of has also been proposed. Therefore, it is well known that by adding these cellulose ethers, curing can be delayed to some extent and troubles caused by heat generation in the molding machine can be solved. Additionally, cement hardening retarders such as calsulam salt are added to delay the hardening time of cement.

(Problem to be solved by the invention) However, in extrusion molding using fibers other than asbestos where heat generation of 50°C or more is expected, these additives must be added to enable extrusion molding. It is necessary to add 1% or more of the agent, which is disadvantageous in terms of raw material cost, and it is undesirable for the durability of the molded product to have a large amount of organic matter mixed in with the hardened cement product, so these organic materials are not added as much as possible. It has been desired to complete a molding method that can delay curing time.

(Means for Solving the Problems) The inventors of the present invention have made extensive studies in view of these facts, and have found that, using a material mixed with a blast furnace slag/cement weight ratio of 70/30-90710, and based on 100 parts by weight of this mixed material, Extrusion molding using 03-2% by weight of alkyl cellulose and/or hydroxyalkylalkyl cellulose and curing in an autoclave at a temperature of 10,000 or higher allows extrusion molding containing alternative fibers other than asbestos to exceed 50 °C. We have completed the present invention by discovering that even with excessive heat generation, hardening does not occur in the molding machine and a strong molded product can be produced.

A mixture of blast furnace slag and water is generally known as an inorganic material that hardens in the presence of alkaline stimulants to develop the necessary strength. Generally, it is said that unless the ratio of blast furnace slag to cement is 70% or less, a hardened product with the necessary strength cannot be obtained. As a result of studying this blast furnace slag/cement ratio, the present inventors found that even in a blast furnace slag/cement mixed material in which the amount of blast furnace slag is 70% to 90%, alkyl cellulose/and hydroxyalkyl alkyl cellulose can be added. It has been found that by molding and curing under pressure in an autoclave at a temperature of 100°C or higher, a molded product with sufficient strength can be produced.

If the amount of blast furnace slag is less than 70%, the object of the present invention will not be achieved because there will be too little delay in curing time when the compact is heated in the molding machine to 50° C. or higher.

On the other hand, the use of an appropriate amount of an alkaline stimulant such as gypsum, preferably in the range of 1050%, in order to obtain the initial strength of the molded product immediately after molding does not impede the object of the present invention.

As the alkylcellulose and/or hydroxyalkylalkylcellulose used in the present invention, any water-soluble cellulose such as methylcellulose, ethylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, and hydroxyethylethylcellulose can be used. The amount of these cellulose ethers added is 0 to 100 parts by weight of the blast furnace slag/cement mixture.
3-2% by weight is desirable. If it is less than 0.03%, the molded product will not have sufficient water retention properties and will be difficult to mold. Moreover, exceeding 2% by weight is not only disadvantageous in terms of cost, but also
This is not preferable because the strength of the molded product may become weak.

As the asbestos substitute fiber used in the present invention, fibers such as carbon fiber, alkali-resistant glass fiber, aramid fiber, and rock wool, which have a high heat resistance temperature, are preferable. Examples include pulverized pulp fibers, polypropylene fibers, and polyhinyl alcohol fibers that have low heat resistance. The amount added is preferably 2-20% by weight.

The present invention is also useful when only asbestos is added in a large amount, resulting in high heat generation during molding.

(Example) The present invention will be explained below with reference to Examples and Comparative Examples.

Examples 1 to 4 and Comparative Example 1.2 The mixtures according to the formulations in Table 1 were kneaded using a double-arm kneader,
Width 75m from Y-22 type vacuum extrusion molding machine manufactured by Ishikawa Toki Co., Ltd.
A sheet with a thickness of 6 mm was extrusion molded, and the moldability was compared.

Binder 1) 90SH-100000 hydroxypropyl methylcellulose (HPMC, manufactured by Shin-Etsu Chemical Co., Ltd.) 2) 5M-8000 methylcellulose (MC, manufactured by Shin-Etsu Chemical Co., Ltd.) Examples 1 to 4 corresponding to the present invention are Comparative Example 1. For 2,
Good extrusion moldability was obtained without causing any hardening of the extruded product even when the temperature inside the molding machine was as high as 50° C. or higher.

(Effects of the Invention) According to the extrusion molding method of the present invention, in non-asbestos extrusion molding using asbestos substitute fibers with poor dispersion, the acceleration of the inorganic curing time due to heat generation in the molding machine is minimized, and the inorganic curing time is minimized. It is possible to eliminate troubles in which extrusion cannot be performed due to blockages.

Claims (1)

[Claims] 1. In extrusion molding containing reinforcing fiber materials other than asbestos, the blast furnace slag/cement weight ratio is 70/30-90.
An extrusion molding composition containing 0.3-2% by weight of alkylcellulose and/or hydroxyalkylalkylcellulose based on 100 parts by weight of this mixed material was extruded into a desired shape. A method for producing a cement extruded product, which is then cured under pressure in an autoclave at a temperature of 100°C or higher to harden the extruded product.