CH293880A - Process for the production of an azo pigment. - Google Patents

Description

  

  Process for the production of an azo pigment. It has been found that a valuable azo pigment is obtained if diazotized 4-chloro-2-methyl-1-aminobenzene is coupled with 2-oxynaphthalene-3-carboxylic acid N-benzyl anilide.



  After recrystallizing from benzene, the new pigment has a bright scarlet color and shows red fluorescence.



  The coupling is conveniently carried out in a weakly acidic, e.g. B. acetic acid and buffered with alkali acetate medium vorgenom men, in which the serving as a coupling component carboxylic acid arylide is present in finely divided form as possible.

   In order to achieve a sufficiently fine distribution, the carboxylic acid arylide is advantageously first dissolved in hot water with the addition of alkali metal hydroxide as an alkali compound. and then precipitated again in the cold by adding acetic acid, whereupon it is advisable to add a small amount of Turkish red oil before precipitating.



  <I> Example: </I> 18.57 parts of 2-Oxynaphth.halin-3-carboxylic acid-N-benzylanilide are stirred into a solution of 18.68 parts of 30% sodium hydroxide solution in 240 parts of water and 175 parts Entered ethanol at 80 to 90, the 2-oxynaphthalene-3-carboxylic acid arylide gradually dissolving with a yellow-brown color.

   The clear and still warm solution is allowed to flow below level within 1.5 minutes into a mixture of 10 parts of glacial acetic acid, 50 parts of water, 66.7 parts of crushed ice and 2.5 parts by volume of a commercially available lime-resistant turkey red oil, with very good stirring. the temperature between 5 and 10 must be kept. Stirring is then continued for 2 to 21 1/2 hours, the yellowish, fine arylide suspension being allowed to gradually reach room temperature. Before the coupling starts, 14.2 parts of crystallized sodium acetate are added and the homogeneous, easily stirrable suspension is heated to 30.



  A clear solution, protected from light, of diazotized 4-chloro-2-methyl-1-aminobenzene, which consists of 9.36 parts of 4-chloro-2-methyl-l-aminobenzene chlorohydrate, 20 parts of water, 10 parts by volume 30 11 / oiger hydrochloric acid and 12.5 parts by volume of 4N-N atriumnitr itlösung was obtained,

   is allowed to drop within 3 hours with vigorous stirring below the level of the arylide suspension. The coupling mixture is gradually heated from 50 to 65, and after all of the diazolösimg have been added, stirring is continued at 65 for an hour.



  Thereafter, to redissolve any unreacted carboxylic acid or arylide, 24.5 parts of 30% sodium hydroxide solution are added dropwise, so that a clear and lasting alkaline reaction to phenolphthalein occurs. The mixture is stirred for 30 minutes at 50, then suction filtered while still warm and washed with hot water until the filtrate is colorless and neutral. The pigment obtained is dried in vacuo at 80 to 95 hours. It can be recrystallized from 350 parts by volume of benzene.



  The 2-oxynaphthalene-3-carboxylic acid-N-benzylanilide can, for. B. be prepared as follows In a reaction vessel equipped with a stirring thermometer and reflux condenser, 194 parts of 2-oxynaphthalene-3-carboxylic acid, 800 parts by volume of toluene previously dried over calcium chloride and 30 parts by volume of phosphorus trichloride are stirred for 30 minutes at 30 to 35. Within 30 minutes 183,

  24 parts of N-benzyl aniline were added dropwise, a lot of hydrochloric acid escaping.



  The reaction temperature is brought to 90 to 95 within 30 minutes and the mixture is stirred for a further hour at this temperature. It will now be within. 10 minutes further 10 parts by volume of phosphorus trichloride were added dropwise and the reaction mixture with. heated to boiling in an oil bath on a reflux condenser for 15 hours. The initially strong hydrochloric acid development gradually subsides completely.



  After cooling, the toluene is made by adding 40 parts. crystallized sodium acetate and 20 parts of sodium bicarbonate are completely driven off with steam (until about 4000 parts by volume of distillate are driven over). The aqueous layer on top is decanted. still hot and dissolves. the yellow residue obtained for the purpose of crystallization with 600 parts by volume of glacial acetic acid on a boiling water bath. When allowed to cool slowly, a yellow crystal mass forms, from which the solvent is separated off by suction filtration.

   You see the filter first. a little glacial acetic acid and then a lot of hot water and then dry it in a vacuum for 12 hours at 60 to 70.



  The 2-oxynaphthalene-3-carbonic acid-N-benzylanilide is obtained as a yellow crystalline powder with a melting point of 160.5 to 161. After repeated recrystallization from glacial vinegar, the melting point is 161.5 to 162.

 

Claims (1)

PATENT CLAIM A process for the production of an azo pigment, characterized in that diazotized 4-chloro-2-methyl-1-aminobenzene is coupled with 2-oxynaphthalene-3-carboxylic acid-N-ben7.yl-a.nilide. After recrystallizing from benzene, the new pigment has a bright scarlet color and shows red fluorescence.