Method For Preparing Benzoxazine By Using Water Based Solvent
A technology of benzoxazine and organic solvent, which is applied in the field of preparing benzoxazine with aqueous solvent, can solve problems such as unsatisfactory, reduced total yield, increased time, labor and cost, etc.
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Embodiment 1
[0085] 6 g (0.2 mol) of paraformaldehyde, 20 ml of ethanol, and 0.1 g of NaOH were reacted at 40° C. for 1 hour until the solution became transparent. The mixture was cooled to 14°C. 20 ml of toluene and 9.98 g (0.05 mol) of MDA were added, and reacted at 15° C. for 1 hour. Then 20 ml of toluene and 9.4 g (0.1 mol) of phenol were added, and the mixture was heated to 80° C. and refluxed for 5 hours. After cooling, the phases were separated. Remove the upper aqueous layer. A pale yellow benzoxazine-toluene solution was obtained. Its percent ring closure is >70%. (see CN94111852.5)
Embodiment 2
[0087] 52 g of phenol, 55 g of MDA, 39 g of paraformaldehyde, 234 g of water and 10 g of ethyl acetate were added to the reaction vessel at room temperature. A small amount of catalytic base (NaOH) was added and the reaction mixture was kept at a temperature of 90-95° C. for 4 hours. Thus, about 60% by weight of water and 3% by weight of ethyl acetate are used. The crude product was poured into cold water and precipitated in powder form. The resulting powder was washed several times with warm water and dried in a vacuum oven. Analysis: monomer 33.2%; phenol 1.1%; ring closure rate 77%; volatile matter 0.57%; DSC initial temperature is 202°C; DSC peak temperature is 223°C.
[0088] Monomer structure:
[0089]
Embodiment 3
[0091] 95 g of paraformaldehyde, 150 g of MDA and 211 g of water were added to the reactor vessel at room temperature. The reaction was kept at room temperature for 3 hours using a small amount of catalytic base (NaOH) as catalyst. Then 30 g of ethyl acetate were added and the mixture was warmed to 55°C. 138 g of phenol were added and the reaction was maintained at 85-90°C for 4 hours. Thus, about 34% by weight of water and 5% by weight of ethyl acetate are used. The crude product was poured into cold water and precipitated in powder form. The resulting powder was washed several times with warm water and dried in a vacuum oven. Analysis: monomer 40.5%; phenol 1.45%; ring closure rate 80%; volatile matter 0.92%; DSC initial temperature is 211°C; DSC peak temperature is 226°C.
[0092] Monomer structure:
[0093]
PUM
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