Methoxidation of Calcium Hydroxide and Characteristics of Its Compound

Abstract

In an attempt t o e l u c i id d a a tt e e u n _ a m e n t a l problems for synthetic step, and to improve properties of inorganic composite materials by the interaction between inorganic and organic su b stances, the hydrate of CaO-H₂O-CH₂OH system was prepared by immersing CaO and Ca (OH)₂ in methanol, and formation mechanism and characteristics of the hydrate were investigated.
Firstly the methoxidation of CaO and Ca (OH)₂ in methanol was compared; Both hydration and methoxidation occurred simultaneously in the former case, and Ca (OH)₂ and Ca (OCH₃)₂ formed after reacting for 5 h, but in the latter 4 days was necessary to achieve th e same state. However there is not any difference betwen the two cases to reach almost equilibr ium state after reacting for 7 days. The (001) spacing of Ca (OH)₂ and Ca (OCH₃)₂, for med in the early stage of immersion, increased or decreased. This fact suggested that the hydrate w as mixed with calcium hydroxide methoxides through mutual substitution of OH↔CH₃O group between the both layer of layer structured Ca (OH)₂ and Ca(OCH₃)₂ of CdI₂ type. From X-ray diffractometric analysis, these phases were expressed as formulae of Ca (OH)_1.5 (OCH₃)_0.5 and Ca (OH)_0.3(OCH₃)_1.7.
The h y drate crystal containing Ca-OCH₃ bond became thin hexagonal plate-like shape with particle size of 2 μ m (specific surface area being 2.1 m2/g) as a result of friction of (001)plane in layer structure by immersing in methanol. Moreover, it was proved that carbona tion of the hydrate under humidity at 80% was remarkably controlled by the bonded CH₃O group on the crystal surface. Also the group was stable at around 300°Cby heating. The hy d rate of CaO-H₂O-CH₃OH system fairly dispersed in several organic solvents and then its s urface was changed into lipophilic. The hydrate containing Ca-OCH₃ bond could be expec t ed as inorganic filler for plastics, rubber and paper.