JP2007001839A - Manufacturing method of composition containing magnesia cement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of magnesia cement wherein although it is rich in resources and has many excellent points as compared with Portland cement, it has gradually dropped out of usage because stable and active magnesia required by the conventional technology is not supplied on a commercial scale and its usage is restricted to the flow-in method or the like. <P>SOLUTION: In this manufacturing method for a composition containing magnesia cement, which is based on new findings in the process of hardening of a magnesium cement, a magnesium salt and/or an aqueous solution which forms a magnesium salt are impregnated into a composition containing magnesium oxide and/or magnesium hydroxide. It enables the manufacture of various magnesia cement compositions using a wide range of feed materials. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a method for producing a magnesia cement composition, and more particularly to a method for producing a magnesia cement composition including a region not conventionally used.

  Magnesia cement composition is composed of active magnesia (or magnesium oxide) and magnesium salt aqueous solution such as magnesium chloride. The mixture is allowed to stand, and is allowed to react and cure over time. The method of use is very similar to the method of mixing Portland cement with water and aggregate and curing.

  Magnesia cement is stronger than Boltland cement and has higher strength, better adhesion to organic matter, finer grained hardened surface, white coloration, antibacterial and less prone to wrinkles have.

  However, it is difficult to obtain an active magnesia of a certain quality, and even when the composition is cured under the same reaction conditions, a phenomenon such as sedimentation occurs in the composition until it is cured, and a uniform cured product is obtained. Not only was it difficult, but in some cases, undesirable phenomena such as destruction of the cured product (called “abare”) and condensation (called “sweat”) were also observed. In order to prevent this, JIS A 6905 “Magnesia cement” was established to select active magnesia that can be used for magnesia cement. However, in spite of such efforts, versatility like Portland cement has not been obtained, and magnesia cement is currently rarely used, and JIS A 6905 has also been abolished.

In the idea of conventional magnesia cement, it is thought that magnesium oxide and magnesium chloride react directly, and unless magnesium oxide is produced, magnesia cement is not generated. In some cases, the magnesium oxide raw material partially reacted with moisture in the air during storage was discarded as a so-called cold. In addition, the compound is placed in a mold and allowed to stand, and after it is cured, it is demolded. Depending on changes in the activity of magnesia and the temperature at the time of curing, the time to demolding is long and short. However, it was difficult to carry out simple production.

Charles A. Sorrell and Charles R. Armstrong, J. Am. Ceram. Soc. [59] No. 1-2, 51-54 (1976)

  The method for producing a composition containing magnesia cement according to the present invention has corrected the direction of the conventional technique for obtaining magnesia having higher activity by a novel method based on the hardening process of magnesia cement. In addition, it has become possible to create magnesia cement products using magnesia cement as a hardener using a wide range of raw materials without being restricted by the activity of magnesia, and can also use the superior properties of magnesia cement more freely. .

The present invention changes the reaction process of magnesia cement to a more rational one, discloses a method for producing a composition including a region that has not been used in the past, and expands the application of magnesia cement having a number of advantages. It is.

Prior to this application, the present inventor published a report clarifying the reaction process of magnesia cement in Nikkan Kogyo Shuppan Production "Industrial Materials" Vol.53, No.2 pp88-91 2005. In this report, the present inventor has roughly divided the process of hardening magnesia cement, a process in which active magnesia reacts with water to change to magnesium hydroxide, a process in which magnesium hydroxide dissolves in a magnesium chloride solution, and this solution It was clarified that the process includes precipitation of magnesia cement minerals.

  From these processes, for the production of magnesia cement, it is not essential that active magnesia is used as a magnesia raw material, and it is recognized that magnesium hydroxide can be sufficiently cured. In this invention, it is a manufacturing method of the composition containing a magnesia cement using these facts.

  That is, this invention is a manufacturing method of the composition containing the magnesia cement which makes the composition containing magnesium oxide and / or magnesium hydroxide impregnate the magnesium salt and the aqueous solution which produces | generates a magnesium salt.

  A conventional method for producing a composition containing magnesia cement is a composition containing magnesia cement, which contains a mixture of active magnesia and a magnesium salt solution, and is filled with a filler, poured into a mold, demolded after curing. The way to get it was done normally. In this method, the time required for the mouldia cement to harden in the mold is fixed, and the use efficiency of the mold decreases accordingly. Further, the magnesium salt aqueous solution has an action of corroding metals, and problems such as restrictions on the material used for the mold are pointed out.

  In the present invention, a raw material or composition containing magnesium oxide and / or magnesium hydroxide is prepared in advance, and this raw material or composition is impregnated with an aqueous solution that produces a magnesium salt and / or magnesium salt. Molding and granulation can be carried out without using a mold, and the above-mentioned problems of the material for the mold are almost improved. Further, unlike casting, the molding can be performed in a free shape, so that, of course, when the method of the present invention is applied to a pressure molded product containing magnesium oxide, for example, a magnesia cement mineral generated in the molded product. Fills the voids present in the molding, so that a dense magnesia cement composition can finally be made.

  Further, when forming a composition containing magnesium oxide, water can be used as a binder. In this case, the blended magnesium oxide may react with water and change to magnesium hydroxide, which may delay the curing of the magnesia cement composition but does not hinder the curing itself. Furthermore, in the present invention, a large amount of water can be used if necessary for molding. For example, when making a magnesia cement composition in which plant fibers are bonded with magnesia cement, a large amount of water can be used to disperse the fibers. In the conventional method of using magnesia cement, the solution portion of the magnesia cement is washed away during dehydration for molding, or the magnesia cement is hardened by excessive water. In this case, if only magnesium oxide or magnesium hydroxide is dispersed in the raw material of the molded product in advance, these products have extremely low solubility in water, so that they are not lost in the mechanical dehydration molding process. If the magnesium salt and / or the aqueous solution that forms the magnesium salt are impregnated after necessary drying, almost the entire amount of the raw material can be used.

  When the method of the present invention is used, a high-density magnesia cement composition that is difficult to obtain by the conventional method can be easily obtained. For example, when magnesium oxide powder is pressed into a magnesium oxide powder and cured, a semitransparent cured product is obtained, and then the entire cured product expands and there are fine cracks that appear to penetrate inside. Many are observed. This is because the specific gravity of the magnesia cement mineral is small compared to the specific gravity of the magnesium oxide, and after filling the pores contained in the molded product during the curing reaction, fine cracks enter to ease further expansion. Understood. From this, it is shown that if a magnesium oxide molded product taking this into consideration is prepared in advance, a magnesia cement composition having a preset density as well as a high density can be produced.

  20g of light-burned magnesia made in China is molded at a pressure of 300kg square centimeter, and the resulting molding is impregnated with a solution of 20g of industrial magnesium chloride hexahydrate in 10g of water and heated in an oven at 60 ° C for 3 hours. did. The obtained magnesia cement composition cured product was brown translucent and had a bulk specific gravity of 2.1.

  29 g of magnesium hydroxide obtained in the manufacturing process of domestic seawater magnesia is molded at a pressure of 300 kg square centimeter, and the resulting molding is impregnated with a solution of 20 g of industrial magnesium chloride hexahydrate in 10 g of water. Heated in an oven at 60 ° C. for 6 hours. The obtained cured magnesia cement composition was white and had a bulk specific gravity of 1.8.

600 g of water was added to 20 g of newspaper, and 30 g of light-burned magnesia made in China was added to and mixed with the slurry, and then commercially available coconut shell fibers were mixed. This mixture was put into a 10 cm × 10 cm molding frame and pressed by hand to mold while removing excess water. This molded product was dried in an oven at 80 ° C. The obtained dried product was impregnated with a solution prepared by dissolving 30 g of industrial magnesium chloride hexahydrate with 30 g of water and cured by heating in an oven at 60 ° C. for 3 hours. The obtained magnesia cement composition had a size of 10 cm × 10 cm × 3 cm and a bulk specific gravity of 0.4.

Claims (1)

The manufacturing method of the composition containing the magnesia cement which impregnates the aqueous solution which produces | generates a magnesium salt and / or a magnesium salt in the composition containing magnesium oxide and / or magnesium hydroxide.