JPS6232149B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to hydraulic magnesia cement compositions. Magnesia cement is made of activated magnesia and magnesium chloride or magnesium sulfate, and its slurry is almost neutral.It has advantages such as higher bending strength and hardness than other cements, and a relatively short curing time. However, the shrinkage rate during curing is high, and soluble salts are eluted after curing, resulting in poor water resistance, and its uses are extremely limited. Many reports have been made to overcome the above drawbacks, but none have been satisfactory.
For example, USP 3320077 proposes curing by adding polyphosphate. However, although water resistance improves when polyphosphate is added and cured, the slurry before curing is strongly acidic and difficult to handle, the container and agitator are oxidized and the service life is shortened, and there are concerns about pollution. There is also a problem. Furthermore, it has the disadvantage that curing time is long and productivity is poor. The object of the present invention is to have the advantages of conventional magnesia cement, which are that the PH of the slurry is almost neutral, the curing time is relatively short, and the cured product has high bending strength and hardness. An object of the present invention is to provide a hydraulic magnesia cement composition which has a small shrinkage rate during hardening and has improved water resistance of a hardened product. That is, the gist of the present invention resides in a magnesia cement comprising a hydraulic magnesia cement comprising activated magnesia and magnesium chloride or magnesium sulfate, and an organic chelating agent comprising a dicarboxylic acid, an amine, a derivative thereof, or a diketone. The hydraulic magnesia cement used in the present invention is obtained by adding magnesium chloride or magnesium sulfate to activated magnesia, and the activated magnesia preferably has a relatively high activity.
Activated magnesia can be easily obtained by firing magnesium hydroxide, magnesium carbonate, etc. at 400 to 1000°C, but it is preferably fired at 600 to 900°C. The organic chelating agent used in the present invention is an organic compound having a nitrogen, oxygen or sulfur ligand in its molecule, such as oxalic acid, malonic acid,
Succinic acid, glutaric acid, maleic acid, fumaric acid,
Dicarboxylic acids such as citraconic acid, itaconic acid, phthalic acid, ethylenediamine, tetramethylenediamine, triethylenediamine, pyridine, diethylenetriamine, ethylenediaminetetraacetic acid,
Examples include amines such as N,N'-ethylenediaminediacetic acid and N-butylethylenediaminetriacetic acid, and derivatives thereof, and diketones such as acetylacetone and benzoylacetone. Dicarboxylic acids are preferably used, and maleic acid is particularly preferably used. Ru. Also, the amount added is not particularly limited, but
It is preferable to add 0.1 to 10 parts by weight per 100 parts by weight of the activated magnesia. In the present invention, a magnesia cement composition can be easily obtained by adding and mixing the organic chelating agent to the hydraulic magnesia cement. The magnesia cement compositions of the present invention are used in the same manner as conventional cements. Further, when used, conventionally used additives such as inorganic fibers, organic fibers, silica powder, calcium carbonate, perlite, glass balloons, and pigments may be added. The structure of the magnesia cement composition of the present invention is as described above, and it can be easily obtained by adding and mixing an organic chelating agent to magnesia cement, and the pH of the slurry of the obtained magnesia cement composition is approximately medium. It is easy to use, and the curing time is relatively short, with no difference from conventional magnesia cement. Further, the shrinkage rate during curing is small, the water resistance of the cured product is good, the weight loss due to water immersion is small, and the decrease in bending strength is small. Further, when maleic acid is used as an organic chelating agent, a cured product with extremely high bending strength can be obtained.
Therefore, the magnesia cement composition of the present invention is suitably used as building materials, structural materials, etc. Next, examples of the present invention will be described. Note that the term "parts" hereinafter simply means "parts by weight." Examples 1 to 6, Comparative Examples 1 to 3 Magnesium chloride (hexahydrate) 100 parts Activated magnesia (calcined at 800°C for 3 hours) 100 parts Water 30 parts The compositions shown in Table 1 were added to the formulations having the above compositions. A predetermined amount of organic chelating agent is added, mixed and dispersed, and the resulting mixture is supplied to a volumenometer and heated at 20°C.
The volumetric shrinkage rate was measured 1 day and 7 days after storage in a constant temperature room. The results are shown in Table 1. Further, the above mixture was cured in a constant temperature room at 200° C. for 28 days to obtain a cured product. The bending strength of the obtained cured product was measured according to JISA-1408 "Bending test method for architectural boards." Furthermore, during curing, a setting test was conducted in accordance with JIS R-5201 "Physical Test Methods for Cement" to measure the initial and final setting times. Furthermore, after immersing the obtained cured body in water at 20℃ for 24 hours, it was dried in a dryer at 80℃.
After drying for 24 hours, the bending strength and weight loss rate after soaking were measured according to JISA-1408 "Bending test method for architectural boards." The results are shown in Table 1. In addition, for comparison, measurements were made in the same manner on samples to which no organic chelating agent was added and samples to which orthophosphoric acid or sodium hexametaphosphate was added instead of the organic chelating agent, and the results are shown in Table 1.

[Table] Examples 7 to 8, Comparative Example 4 Magnesium sulfate (hexahydrate) 100 parts Activated magnesia (calcined at 800°C for 3 hours) 100 parts Water 30 parts The formulation having the above composition was added as shown in Table 2. A predetermined amount of organic chelating agent was added, and the volume shrinkage rate, bending strength, bending strength after immersion in water, weight loss rate, and starting time and ending time by setting test were measured in the same manner as in Example 1. The results are shown in Table 2. For comparison, the same measurements were performed without adding an organic chelating agent, and the results are shown in Table 2.

【table】

Claims (1)

[Scope of Claims] 1. A magnesia cement composition comprising a hydraulic magnesia cement comprising activated magnesia and magnesium chloride or magnesium sulfate, and an organic chelating agent comprising a dicarboxylic acid, an amine, a derivative thereof, or a diketone. 2 The amount of organic chelating agent added is active magnesia
The composition according to claim 1, wherein the amount is 0.1 to 10 parts by weight per 100 parts by weight. 3. The composition according to claim 1, wherein the organic chelating agent is a dicarboxylic acid. 4. The composition according to claim 2, wherein the dicarboxylic acid is maleic acid.