JPS59102883A - Manufacture of magnesia cement product - 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 method for manufacturing a magnesia cement molded body.

For Portland cement molded bodies, after molding and demolding,
Curing by underwater curing, in which the molded product is immersed in water, or moist air curing, in which it is cured in a high-humidity atmosphere, is widely used.4 However, for example, when the underwater curing method is applied to magnesia cement molded products, The unreacted magnesium chloride and magnesium sulfate in the magnesia cement molded body are eluted into the water, inhibiting hardening, and if the leaching continues, even the double salt crystals that make up the hardened magnesia cement body are dissolved. As it decomposes, its physical properties deteriorate significantly. In addition, in the case of humid air curing, magnesium salts are eluted at the dew condensation area, which deteriorates physical properties, causes whitening of the surface of the molded product, and also causes loss of surface gloss and warping, impairing product quality. .

The present invention has been made in view of the above, and is a novel curing process that provides a cured product with excellent strength by uniformly hardening and densifying the structure of the molded product, without warping or cracking, and with excellent surface properties. An object of the present invention is to provide a method for manufacturing a magnesia cement molded body containing the following.

The method for producing a magnesia cement molded body of the present invention includes activated magnesia, magnesium chloride or magnesia sulfate,
After molding and demolding the magnesia cement paste containing the above-mentioned magnesia cement, the molded product is immersed in an aqueous solution containing the same magnesium salt as that contained in the magnesia cement, and cured and hardened. .

In the method of the present invention, magnesia cement paste is cast into a mold, molded, and the magnesium salt contained in the magnesia cement is poured until the molded product is completely cured, preferably immediately after demolding. The molded body is immersed in a curing aqueous solution containing the same magnesium salt as above, and the molded body is cured and hardened.

That is, by immersion in this magnesium salt aqueous solution,
Suppressing the elution of ions from the molded body, and further supplying magnesium ions, chloride ions, or sulfate ions into the molded body,
It is possible to promote crystallization with unreacted magnesium ions in the molded body, and in this way, to harden the entire molded body C woven densely to obtain a hardened body with excellent strength. can. In addition, since double salt crystals that have already formed inside the molded body are kept in a stable state,
Improves the surface properties of the resulting molded product.

Therefore, the concentration of magnesium salt in the curing aqueous solution used is:
Although it depends on the amount of magnesium salt blended in the magnesia cement, as mentioned above, so that each ion is not eluted from the magnesium molded body when immersed in the curing aqueous solution and can be supplied into the molded body, In the case of an aqueous magnesium chloride solution, the content is preferably 20% by weight or more, and in the case of magnesium sulfate, the content is preferably 15% by weight or more. If the concentration of these magnesium salts in the curing aqueous solution is too low, ions will still be dissolved from the molded product when the molded product is immersed in it, making it impossible to achieve the desired hardening as described above. It is from.

In addition, when the magnesia cement molded body contains both magnesium chloride and magnesium sulfate, it is desirable that the curing aqueous solution also contains the above two types of magnesium salts in the above concentration range.

The magnesia cement paste used in the present invention is
As is generally well known, it is an aqueous composition prepared by blending activated magnesia with magnesium chloride and/or magnesium sulfate and water. In addition, this composition
As is known in the art, the tripolyphosphate may contain various hardening modifiers, fillers such as calcium carbonate and perlite, and reinforcing fibers such as organic fibers and non-V1 fibers. In particular, in the case of a magnesia cement molded body containing fibers, the method of the present invention uniformly densifies the structure of the molded body at the interface of the magnesia cement matrix surrounding the fibers, thereby significantly improving composite physical properties, especially flexural strength and elastic modulus. Improve.

As described above, according to the method of the present invention, after demolding a magnesia cement molded body, the molded body is cured by immersing it in a curing aqueous solution containing the same magnesium salt as that contained in the molded body. Ions are supplied from an aqueous solution to promote crystallization with unreacted ions in the molded body. Therefore, the obtained cured product has a dense structure as a whole and has excellent strength, and since it keeps the already formed double salt stable, there is no cracking or whitening phenomenon, and the surface quality is improved.

The present invention will be explained below with reference to Examples.

Example 1 A magnesia cement paste consisting of 35 parts by weight of magnesium chloride (anhydrous salt), 97 parts by weight of water and 0.7 parts by weight of potassium tripolyphosphate was prepared using the sI Yokouchi method, each having a depth of 30 cm and a depth of 1. The mixture was poured into a mold, cured at 25° C. for 24 hours, and then removed from the mold.

After this, 1% by weight in an aqueous solution of magnesium chloride
After soaking and curing for 4 days, and then leaving it in the air for 14 days, according to the method specified in JIS Z-2113,
The bending strength and bending elastic modulus of the obtained molded body were measured.

The results are shown in the table. In addition, in the following, all measurements of bending strength and bending elastic modulus are based on this method.

Example 2 Cast molding was performed in exactly the same manner as in Example 1, except that magnesium chloride in the magnesia cement formulation was replaced with magnesium sulfate, and the curing aqueous solution was changed to a 30% by weight aqueous solution of magnesium sulfate. After demolding, the molded product was cured by immersion in a curing aqueous solution, and then left in the air, and the bending strength and bending elastic modulus of the obtained molded product were measured. The results are shown in the table.

Example 3 Chopped strand mat (#300) was laminated on the same magnesia cement paste as in Example 1 to give a concentration of 13% by volume.
After impregnation and curing at 25° C. for 24 hours, the mold was demolded.

Thereafter, in the same manner as in Example 1, the molded body was immersed in a 35% by weight aqueous solution of magnesium chloride for 14 days, and then left in the air for 14 days to obtain a molded body. The flexural strength and flexural modulus of this molded body are shown in the table.

Comparative Example 1 A magnesia cement paste having the same formulation as in Example 1 was cast and molded in the same manner as in Example 1, and after demolding, it was cured for 14 days in a constant temperature and humidity bath at a temperature of 30° C. and a relative humidity of 95%. Many cracks and warps were observed in the molded product after curing. After this curing, the molded article was left in the air for 14 days to obtain a molded article. The bending strength and bending modulus are shown in the table.

Comparative Example 2 After casting and demolding as in Example 3, the product was immersed in water for 14 days, and then left in air for 14 days. The molded product thus obtained turned white and a powder blowing phenomenon was observed. The flexural strength and flexural modulus of the molded body were measured. The results are shown in the table.

Comparative Example 3 A magnesia cement paste consisting of 30 parts by weight of magnesium chloride (anhydrous salt), 105 parts by weight of water and 1 part by weight of potassium tripolyphosphate was cast in the same manner as in Example 1 and hardened. After that, it was demolded. Thereafter, it was cured by immersing it in a 10% by weight aqueous solution of magnesium chloride for 14 days, and then left in the air for 14 days.

The flexural strength and flexural modulus of the obtained molded body are shown in the table.

Comparative Example 4 A magnesia cement paste having the same composition as in Example 2 was similarly cast and molded, and after demolding, 5% by weight of magnesium sulfate was added.
After curing by immersion in an aqueous solution for 14 days, the molded product was left in the air for 14 days to obtain a molded product. The flexural strength and flexural modulus of this molding are shown in the table.

As is clear from comparing Example 1 with Comparative Example 1, the method of the present invention significantly improves the physical properties and surface properties of the cured product compared to the underwater curing method. Comparing Example 3 with Comparative Example 2, it is found that the method of the present invention significantly improves the physical properties and surface properties of the fiber-reinforced molded product. Moreover, Comparative Examples 3 and 4 show cases where the concentration of magnesium salt in the curing aqueous solution is insufficient. In particular, when Example 2 and Comparative Example 4 are compared, it is clear that the method of the present invention is superior.

Patent applicant Sekisui Chemical Co., Ltd. Representative Mototoshi Fujinuma

Claims (1)

[Scope of Claims] (11) After molding and demolding a magnesia cement paste containing activated magnesia and magnesium chloride or magnesium sulfate, the molded product is dissolved in an aqueous solution containing the same magnesium salt as that contained in the magnesia cement. A method for manufacturing a magnesia cement molded body, which is characterized by immersing the molded body in a molded body and curing it. (2) The magnesium chloride aqueous solution has a concentration of 20% by weight or more. A method for manufacturing a magnesia cement molded body. (3) The method for manufacturing a magnesia cement molded body according to claim 1, wherein the concentration of the magnesium sulfate aqueous solution is 15% by weight or more.