Лако-красочные материалы — производство

Method 1. The cooled, solidified melt is pulverized and mixed in­timately with 1 per cent of its weight of soda ash which serves to prevent clumping in the sulfonation. 100 grams of the melt is added to 300 grams of 100 per cent sulfuric acid at any desired temperature. When solution is complete (about 1 hour), the mixture is cooled to 25°C. with con­tinuous stirring, and 200 grams of 66 per cent oleum is added, over a period of 1 hour, with good cooling and stirring, keeping the temperature below 30°. The mixture is stirred for 5 hours at 30°, and then the tem­perature is raised to 40° and held there until a test sample dissolves completely in dilute ammonia. This point is usually reached in 10 hours, but it is desirable to heat even longer since complete sulfonation facili­tates the subsequent filtration. The mixture is then poured into a mix­ture of 500 grams of ice and 500 cc. water and is filtered after 12 hours. The mixed sulfonic acids are washed thoroughly with cold water to re­move the greater part of the toluidine — and thiotoluidinesulfonic acids. When the wash water gives only a weak mineral acid reaction, the resi­due is dissolved in about 50 grams of 20 per cent aqueous ammonia and 800 cc. water, and the solution is heated to 80° and made up to 1200 cc. The difficultly soluble ammonium salt of dehydrothiotoluidinesulfonic acid separates out completely in the course of 2 days and is filtered off and washed with a small amount of 5 per cent ammonia solution. The mother liquor contains the primuline which is precipitated by adding salt (15 per cent by volume) to the boiling solution. The yield of the dried ammonium salt is about 25 grams, that of primuline about 80 grams of concentrated material.

Method 2. The finely pulverized melt is extracted with alcohol of at least 90 per cent strength. The toluidine, thiotoluidine, and dehydrothiotoluidine go into solution leaving a pure primuline base behind. The alcoholic extract is evaporated to dryness, and the toluidine and part of the thiotoluidine are driven off by heating to 250°C. Sulfonation of the primuline base is done with 25 per cent oleum.

Method 3. Sulfonation is carried out exactly as in the first method. The washed sulfonic acid is dissolved at 80°C. in 20 parts of water and the required amount of sodium hydroxide; sufficient salt is added to make an 8 per cent salt solution, and the mixture is filtered at 75°. The primuline remains behind, while the dehydro­thiotoluidine stavs in solution in the form of its soluble sodium sulfonate and is subsequently salted out.

phenols and amines to produce colors fast to washing. уЗ-Naphthol gives primuline red, a dye once used in enormous quantities. Its fastness to

Primuline, discovered by Green, was the first commercial yellow direct dye which could be diazotized on the fiber and coupled with washing is good, but its light fastness is unsatisfactory. Also, it is not discharged to a white, but only to a yellow, since the primuline base withstands all discharging agents.