JP2000016855A - Production of inorganic board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an inorganic board, intended to improve the mechanical strength of a mat subjected to forming by dry process so as to ensure the mat not to get out of shape. SOLUTION: This method for producing an inorganic board comprises the following process: a stock mixture comprising a hydraulic material, a woody material and a powdered thermosetting resin is prepared without using any water and then subjected to forming on a mat followed by hot pressing to effect melt curing of mainly the powdered thermosetting resin; subsequently, such an amount of water as to be necessary for hardening the hydraulic material is fed to the resultant mixture followed by performing an autoclave curing; therefore, the alkaline component in the hydraulic material is not leached during the hot pressing process and the thermosetting resin is cured smoothly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an inorganic plate mainly used as a building plate.

[0002]

2. Description of the Related Art Conventionally, as a method for producing this type of building board, a raw material mixture mainly comprising a mixture of a hydraulic material such as cement and a woody material such as wood chips and pulp has been conventionally sprayed on a template. A dry method is employed in which the mat is formed by heating and pressing the mat in the presence of moisture to pre-cure the mat, and then the pre-cured mat is removed from the mold, cured naturally or autoclaved, and completely cured.

[0003]

The dry method is easier to mass-produce than the wet method, and is particularly advantageous when manufacturing a thick building plate. There is an advantage that various kinds of products can be obtained from products having a low specific gravity to products having a high specific gravity.

However, in the above-mentioned dry method, in order to heat-press the formed mat in the presence of moisture to obtain a pre-cured mat having sufficient strength, a considerably long heat-pressing time is required, and the pressing time is insufficient. Then, there is a problem that the pre-cured mat is liable to collapse or break when the mold is released.

In order to shorten the heating and pressing time, a method of adding a curing accelerator to a raw material mixture in advance has been used. As the curing accelerator, a chloride such as calcium chloride is used because of its easy handling and low cost. However, when chloride is used as a hardening accelerator, iron ions such as nails and pillars used as means for supporting and fixing building boards are corroded by chloride ions released from chloride. There is.

In the above-mentioned dry method, it has been proposed to add a formaldehyde resin precursor to a raw material mixture in order to improve the strength of a hardened cement (Japanese Patent No. 2704929). In this proposal, the formaldehyde-based resin precursor is condensed at the time of pressing to generate water and the cement is hardened by the water. However, in order to generate sufficient water for hardening the cement, the formaldehyde-based resin is required to be hardened. It is necessary to add a large amount of the resin precursor (for example, 15 to 25 parts by weight based on 100 parts by weight of hydraulic cement), so that the cost increases and there is a problem of environmental pollution due to release of formaldehyde.

[0007]

According to the present invention, as a means for solving the above-mentioned conventional problems, a raw material mixture containing a hydraulic substance, a woody material and a powdery thermosetting resin is prepared in a non-hydrolyzed state, The mixture is formed into a mat, and then heated and pressed to melt and harden the powder thermosetting resin, and then supply at least an amount of water necessary for hardening the hydraulic material, thereby performing autoclave curing. A method for manufacturing a plate is provided. Generally, the powder thermosetting resin is a formaldehyde resin, and the formaldehyde resin is a phenol resin.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Examples of the hydraulic material used in the present invention include cements such as Portland cement, blast furnace cement, silica cement, fly ash cement and alumina cement.

The woody material used in the present invention includes, for example, wood flour, woody fiber, pulp, woody fiber bundle, wood wool, wood chip, bamboo fiber, hemp fiber, coconut fiber, or herbs such as rice straw, reed and the like. There are fibers and the like.

As the powder thermosetting resin used in the present invention, for example, a phenol resin, a melamine resin, a urea resin, a benzoguanamine resin or the like is mainly used as a formaldehyde resin. Among the formaldehyde resins, a phenol resin is preferable in consideration of the effect of improving the strength of mats and products and the price. The above-mentioned formaldehyde resin is usually used in a state of an initial condensate.

Other than the above components, silica sand, silica stone powder, silica fume, silicate-containing substances such as blast furnace slag, fly ash, shirasu balloon, perlite, etc., magnesium chloride, magnesium sulfate, calcium chloride, sodium aluminate, aluminate Potassium, aluminum sulfate,
Hardening accelerators such as water glass, other dihydrate gypsum, hemihydrate gypsum,
Activated lime-containing substances such as anhydrous gypsum, slaked lime, quicklime, mineral powders such as vermiculite and bentonite, wax,
A water repellent such as paraffin or silicon, a reinforcing material, or the like may be added.

The mixing weight ratio between the hydraulic substance and the woody material is usually in the range of 1: 1 to 8: 1. The powder thermosetting resin is usually 1 to 15% by weight in the raw material mixture.
Is added within the range. Further, when a silicic acid-containing substance is used, the mixing weight ratio of the hydraulic substance and the silicic acid-containing substance is usually in the range of 1: 1 to 5: 1. When a hardening accelerator of a hydraulic substance is added, it is usually added in the range of 1 to 10% by weight in the raw material mixture.

The raw materials are mixed in a non-hydrolyzed state to prepare a raw material mixture, and the raw material mixture is sprayed on a template and formed as a mat. The mat is then heated and pressed, usually with a template, and pre-cured. The pre-curing conditions are usually a pressing pressure of 15 to 30 kg / cm ² , a heating temperature of 140 to 300 ° C., and a pressing time of 5 to 30 minutes.

In the heating and pressing step, the powder thermosetting resin in the mat melts and hardens to reinforce the mat. At this time, since the raw material mixture is in a non-hydrolyzed state, the alkali is not substantially eluted from the hydraulic material such as cement, and therefore, the hardening of the thermosetting resin by the alkali does not occur. In general, thermosetting resins may discolor due to contact with alkali,
In the present invention, there is no such concern.

The mat preliminarily hardened by the above-mentioned heat pressing is reinforced by the cured product of the thermosetting resin, and as a result, the mat exhibits strength. Therefore, the pre-cured product is released from the pressure, released from the mold, hydrated and introduced into the autoclave curing step, but does not collapse or break when the mold is removed. For the above-mentioned water addition, a method of spraying water on a pre-cured body with a spray or dipping the pre-cured body in water is usually employed. The amount of water added is at least an amount sufficient to cure the hydraulic substance. In the autoclave curing step, the pre-cured product is removed from the template or cured together with the template. Curing conditions are temperature 160-180 ° C, relative humidity 70-95.
%, A pressure of 4 to 10 kg / cm ² , and a curing time of 6 to 15 hours. Due to the autoclave curing, the hydraulic substance in the pre-cured body is almost completely cured in the presence of water due to the above-mentioned water.

In this way, an inorganic plate useful for building boards and the like is manufactured. Since the inorganic plate is reinforced by a cured product of the thermosetting resin, even if it has low density and light weight, it has sufficient strength. Having.

[0017]

EXAMPLES Raw materials are mixed at the ratios shown in Table 1 to prepare a raw material mixture.

[0018]

[Table 1]

The raw material mixture is sprayed on a template to a thickness of 30 mm and formed into a mat. The mat is pressed together with the template at a pressure of 20 kg / cm ² and at 160 ° C.
Heat for 5 minutes. By such heating and pressing, the phenol resin precondensate in the mat melts and hardens. Water is added to the pre-cured body by spraying. The spray amount of the water is set at 3 kg per 1 m ² (surface area) of the pre-cured body. The hydrated precured product is then subjected to autoclave curing. Curing conditions are a temperature of 165 ° C., a relative humidity of 90%, and a curing time of 10 hours. Table 2 shows the physical properties of the thus obtained inorganic plate.

COMPARATIVE EXAMPLE As Comparative Example 1, a building board was prototyped under the same conditions as in Example 2, except that the mixing of the raw materials and the amount of supplied water were the same as in Example 2.
As Comparative Example 2, a building board was prototyped by adding a curing accelerator instead of the phenol resin powder.

[0021]

[Table 2]

According to Table 2, in each of Examples 1, 2, 3, and 4, a precured product and a final cured product having high mechanical strength can be obtained. In Comparative Example 1 in which water was supplied at the time of mixing the raw materials, although the reason is not clear, the pre-cured product was extremely fragile and was not in a state in which it could be handled as a plate, and it was impossible to measure physical properties. Further, in Comparative Example 2 in which the phenol resin powder was not added, the strengths of the pre-cured product and the final cured product were much smaller than those of the Examples, despite the addition of the curing accelerator.

[0023]

According to the present invention, since the precuring is performed by pressing and pressing the mat of the raw material mixture in a non-hydrous state under pressure, the curing of the thermosetting resin proceeds smoothly, and therefore the strength of the precured mat is improved and the autoclave is improved. Does not lose shape before curing. The product strength is also improved by the thermosetting resin.

Claims (3)

[Claims] 1. A raw material mixture containing a hydraulic substance, a woody material, and a powdered thermosetting resin is prepared in a non-hydrolyzed state, and the mixture is formed into a mat, and then heated and pressed to mainly form the powdered thermosetting resin. A method for producing an inorganic plate, comprising: melting and curing a resin; and then supplying at least an amount of water necessary for curing the hydraulic material, followed by autoclave curing. 2. The method according to claim 1, wherein the thermosetting resin is a formaldehyde resin. 3. The method according to claim 2, wherein the formaldehyde resin is a phenol resin.