Hefty fluorescent brighteners (EFR) synthesis

(1) process flow:

(3) operation:
 
1) chloride: fan 120 kg and 140 kg thionyl chloride added to the reaction kettle, stirring, cooled to 0 ~ 5 ℃, then add 4 kg anhydrous aluminium trichloride, heating up to 15 ~ 18 ℃, 5 h at this temperature reaction. Then vacuum distillation, collect about pressure of 1.3 kPa under 190 ~ 215 ℃ fraction, namely get 4, 5 - dichloro fan.
 
(2) oxidation: 4, 5-dichlorofen added to 400kg of chlorobenzene, add 500kg of dichromate potassium, in the stir drop add concentrated sulfuric acid 500kg and gradually heated up to the reflux, reflux reaction for 8h, and then steam distillation steam out chlorobenzene, cooling, filtering, get yellow slurry of 4, 5-dichloro-1,
 
8 - naphthalene anhydride.
 
(3) N - methylation: 4, 5, 8 - dichloro - 1 - naphthalene anhydride join has been equipped with 1500 kg of methanol in the reaction kettle, adding 30 kg40 % aqueous methylamine, return 2 h at 65 ℃. After cooling, filtration and recovery of methanol, the filter cake was recrystallized with benzene to obtain n-methyl 1, 4, 5-dichloro-1.
 
8 - naphthalene imide crystallization, its melting point is 245 ~ 248 ℃.
 
(4) ethoxylation: add 235 in reaction kettle kg25 % sodium ethoxide ethanol solution, then add in N - methyl 4, 5, 8 - dichloro - 1 - naphthyl imide and small amount of anhydrous sodium acetate, in the condition of 80 ℃ reflux reaction 4 ~ 5 h. After the reaction, part of the ethanol was evaporated, cooled and filtered, and the fluorescent whitening agent EFR crude product was obtained.
 
(5) refining: the fluorescence brightener EFR crude product added to 8 times the amount of about acetic acid, heating solution, recrystallization, cooling precipitation out of the yellow-green needle crystal, filtered brightener refined products.
 

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