Patent GB-612323-A (GB)
Title: Improvements in or relating to refining of phenothiazine
Filed: 1946-01-02
Abstract: <PICT:0612323/III/1> Phenothiazine in comminuted and purified form having enhanced insecticidal and parasiticidal properties is produced by vaporizing it in the presence of a sweep fluid and passing the mixture into a condensation zone where the vapours are shock-cooled by direct contact with water to condense the phenothiazine to the solid phase, thereby forming an aqueous slurry containing at least 20 lbs. of water per lb. of phenothiazine.  Steam and alkyl alcohols, e.g. methyl, ethyl and propyl alcohols, are suitable sweep fluids. Diphenylamine and sulphur in stoichiometric quantities react in a vessel 2 in presence of a catalyst such as iodine.  The molten products flow via an adsorption percolator 13 to a steam distillation kettle 15 to which superheated steam from superheater 22 is delivered by pipe 30.  The vapours pass by pipe 36 to a condensing column 40 in which an annular baffle 42, shaped as shown, is located just above the vapour entry point.  Water from nozzle 44 produces a slurry of condensed phenothiazine which is circulated in the base of the column by pump 66 and pipe 68.  A minimum of 20 lbs. of water per lb. of phenothiazine is necessary.  The slurry is withdrawn by pipes 70, 74 to filter-type thickeners 76 and thence to tank 84 from which it flows to a rotary filter 90, the dewatered product being dried in pans 94 in a vacuum drier 96.  A decolorized product may be obtained by treatment with alumina in the percolator 13 or the kettle 15, or mildly alkaline or reducing agents may be used as washing media, for example sodium, potassium or lithium carbonate, or sodium sulphide, sulphite or hydrosulphite in aqueous solution.  Such agents may be added to the water used in column 40.  In examples, reaction mixtures are heated at temperatures ranging from 148 DEG  to 190 DEG  C., steam distilled under pressures of 21 to 25 ins. of mercury with superheated steam at 201 DEG  to 220 DEG  C., and cooled by water. Ratios of steam to phenothiazine are at least 5 : 1 by weight and of water to steam at least 12 : 1.  The first portion of the steam distillate is decolorized with aqueous sodium carbonate or hydrosulphite.  The majority of the particles are of less than 4 microns diameter.ALSO:<PICT:0612323/IV(b)/1> Phenothiazine in comminuted and purified form having enhanced insecticidal and parasiticidal properties is produced by vaporizing it in the presence of a sweep fluid and passing the mixture into a condensation zone where the vapours are shock-cooled by direct contact with water to condense the phenothiazine to the solid phase, thereby forming an aqueous slurry containing at least 20 lbs. of water per lb. of phenothiazine.  Steam and alkyl alcohols, e.g. methyl, ethyl and propyl alcohols, are suitable sweep fluids.  Diphenylamine and sulphur in stoichiometric quantities react in a vessel 2 in presence of a catalyst such as iodine.  The molten product flows via an adsorption percolator 13 to a steam distillation kettle 15 to which superheated steam from superheater 22 is delivered by pipe 30.  The vapours pass by pipe 36 to a condensing column 40 in which an annular baffle 42, shaped as shown, is located just above the vapour entry point.  Water from nozzle 44 produces a slurry of condensed phenothiazine which is circulated in the base of the column by pump 66 and pipe 68.  A minimum of 20 lbs. of water per lb. of phenothiazine is necessary.  The slurry is withdrawn by pipes 70, 74 to filter-type thickeners 76 and thence to tank 84 from which it flows to a rotary filter 90, the de-watered product being dried in pans 94 in a vacuum drier 96.  A decolorized product may be obtained by treatment with alumina in the percolator 13 or the kettle 15, or mildly alkaline or reducing agents may be used as washing media, for example sodium, potassium or lithium carbonate, or sodium sulphide, sulphite or hydrosulphite in aqueous solution.  Such agents may be added to the water used in column 40, examples, reaction mixtures are heated at temperatures ranging from 148 DEG  to 190 DEG  C., steam-distilled under pressures of 21 to 25 ins. of mercury with superheated steam at 201 DEG  to 220 DEG  C., and cooled by water. Ratios of steam to phenothiazine are at least 5 : 1 by weight and of water to steam at least 12 : 1.  The first portion of the steam distillate is decolorized with aqueous sodium carbonate or hydrosulphite.  The majority of the particles are of less than 4 microns diameter.