- Preparation method of 3, 6-diethoxy fluorane yellow thermal dye
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The present invention relates to the field of heat-sensitive dyes, and particularly relates to a preparation method of a 3, 6-diethoxy fluorane yellow thermal dye. The method is as follows: (1) in a reaction vessel, adding fluorescein and a solvent, and dissolving with stirring at room temperature for 1 to 2 hours; (2) adding sodium hydroxide for reacting for 1 to 2 hours, and then adding sodium carbonate; wherein the molar ratio of sodium carbonate to sodium hydroxide to fluorescein is 2: 2: 1-4: 2: 1; (3) heating to 40-90 DEG C, at the time of 2 to 4 hours adding dibromoethane, wherein the molar ratio of dibromoethane to fluorescein is 3: 1 to 5: 1, and after the addition is complete, reacting for 6 to 16 hours at the temperature of 40-90 DEG C; (4) adding water to cool to room temperature, stirring, dispersing and precipitating for 8 to 10 hours, filtering and drying to obtain a crude product; and (5) recrystallizing the crude product with a mixed solvent of ethyl acetate and dimethyl carbonate to obtain the 3, 6-diethoxy fluorane yellow thermal dye. The method is simple in process and suitable for industrial mass production, and can be widely used in medical CT film production.
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Paragraph 0060; 0061
(2016/11/28)
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