Hebei Messi Biology Co., Ltd. stated that the preparation method of composite magnesium oxide powder for dental alginate impression materials includes the following specific steps:
a. Select magnesium hydroxide powder raw material, magnesium hydroxide content is 97.3%, CaO is 1.3%, SO4 is 0.3%, Cl is 0.10%, heavy metals are 9ppm, As is 3ppm, acid insoluble matter is 0.08%; ignition weight loss is 31%, laser particle size D50 is 1.8μm, and glycoside whiteness is 96.
b. Add the raw material magnesium hydroxide powder to the rotary kiln calcining furnace, control the temperature range from the front part to the back part of the rotary kiln to 575℃～625℃, and the residence time of the material in the calcining furnace is controlled to 1.5h. The magnesium oxide powder after calcination is passed through a vibrating screen to obtain a magnesium oxide powder product a with 325 meshes fully passed. The chemical detection of magnesium oxide a showed that the reaction activity of citric acid value was in the range of 136s, the bulk density was 0.31g/cm3, and the whiteness was 94. After packaging, the bagged magnesium oxide powder product a was obtained;
c. Select light magnesium carbonate powder raw material, wherein the magnesium oxide content was 43.5%, the CaO content was 0.07%, the SO4 content was 0.035%, the Cl content was 0.03%, the heavy metal content was 6ppm, the As content was 3ppm, the acid insoluble matter was 0.045%, the ignition weight loss was 53.5%, the laser particle size D50 was 1.7μm, and the whiteness was 95;
d. Add the light magnesium carbonate powder raw material to the rotary kiln calcining furnace, control the temperature range from the front part to the rear part of the rotary kiln to 900℃～1050℃, and control the residence time of the material in the calcining furnace to 1.8h. The magnesium oxide powder after calcination was passed through a vibrating screen to obtain a magnesium oxide powder product b with 325 meshes fully passed. The chemical detection shows that the reaction activity of magnesium oxide a is in the range of 76s, the bulk density is 0.15g/cm3, and the whiteness is 94. After packaging, the bagged magnesium oxide powder product b is obtained;
e. When preparing the dental alginate impression material, the bagged magnesium oxide powder product a and the bagged magnesium oxide powder product b are opened, and the magnesium oxide powder product a and the magnesium oxide powder product b are mixed according to the weight ratio of 2.0 to 0.5:1.0 to obtain a dental alginate impression material with an activity value of 120s to 85s, that is, a composite magnesium oxide powder product. The solidification time is an important parameter of the impression material. The length of the solidification time of the impression material depends on the reactivity of the reactants in the impression material, especially the reactivity of magnesium oxide. The higher the reactivity of magnesium oxide, the shorter the solidification time of the impression material. The composite magnesium oxide powder is a ready-to-use powder obtained by mixing two magnesium oxide powders of different qualities, wherein the magnesium oxide powder product a obtained by calcining the raw material magnesium hydroxide has a lower activity and a longer solidification time when used alone; the magnesium oxide powder product b obtained by calcining the raw material light magnesium carbonate has a higher activity and a shorter solidification time when used alone. When in use, according to the solidification time requirements of the impression material, by changing the different ratios of the magnesium oxide powder product a and the magnesium oxide powder product b, the ready-to-use magnesium oxide powder with the required solidification time is obtained. At the same time, the bulk density of the two is also different. Through different ratios, ready-to-use composite magnesium oxide powder c with different bulk densities can also be obtained.
The composite magnesium oxide powder for dental alginate impression material of the present invention has the following outstanding advantages:
(1) The composite magnesium oxide powder makes the target solidification time of the dental alginate impression material more accurate;
(2) The uniform compounding of the two magnesium oxide powders increases the success rate of the impression material molding;
(3) After the impression material obtained by the product is molded, the impression is complete, clear, smooth and easy to demold.