Abstract: A process for purifying p-phenylenediamine color developers in their free-base form. The process includes subjecting a solution containing p-phenylenediamine-type free base color developer to short path distillation which includes at least one of falling film evaporator, thin film evaporator, wiped film evaporator, or short-path evaporator. Another aspect is a method for preparing an acid salt from a p-phenylenediamine free base color developer. The method includes the steps of: a) dissolving a purified p-phenylenediamine free base derived from the short path distillation process in an organic solvent; b) contacting the dissolved free base distillate with an appropriate mineral acid; and c) crystallizing the color developer in the acid salt form.

Abstract: An improved method for making a p-phenylenediamine color developer concentrate in a free-base form wherein the sulfate or chloride salt of the color developer is contacted with an alkali metal hydroxide includes the steps of forming a liquid free-base layer and a water layer, separating the liquid free-base layer from the water layer; and mixing the liquid free-base with a water soluble hydroxy organic solvent, wherein the p-phenylenediamine color developer concentrate has at least 0.06 mol/l of a color developing agent in the free base form.

Abstract: A process for purifying p-phenylenediamine color developers in their free-base form. The process includes subjecting a solution containing p-phenylenediamine-type free base color developer to short path distillation which includes at least one of falling film evaporator, thin film evaporator, wiped film evaporator, or short-path evaporator.

Abstract: A process for purifying p-phenylenediamine color developers in their free-base form. The process includes subjecting a solution containing p-phenylenediamine-type free base color developer to short path distillation which includes at least one of falling film evaporator, thin film evaporator, wiped film evaporator, or short-path evaporator.

Abstract: A process for purifying p-phenylenediamine color developers in their free-base form. The process includes subjecting a solution containing p-phenylenediamine-type free base color developer to short path distillation which includes at least one of falling film evaporator, thin film evaporator, wiped film evaporator, or short-path evaporator. Another aspect is a method for preparing an acid salt from a p-phenylenediamine free base color developer. The method includes the steps of: a) dissolving a purified p-phenylenediamine free base derived from the short path distillation process in an organic solvent; b) contacting the dissolved free base distillate with an appropriate mineral acid; and c) crystallizing the color developer in the acid salt form.

Abstract: The present invention relates to a method of making purified monotertiarybutyl hydroquinone containing less than 0.2% (wt.) of 2,5 ditertiarybutyl hydroquinone. This method includes heating a composition of monotertiarybutyl hydroquinone and 2,5 ditertiarybutyl hydroquinone in a solvent mixture of a polar solvent and a non-polar solvent. During this step, the non-polar solvent is substantially stripped-off and at least part of the 2,5 ditertiarybutyl hydroquinone is solidified, which is separated from the non-solidified composition. The remaining non-solidified composition and polar solvent are mixed with a non-polar solvent of the same type as was previously stripped-off. The polar solvent, which contains the purified monotertiarybutyl hydroquinone, is separated from the non-polar solvent. This purified monotertiarybutyl hydroquinone is separated the from the polar solvent to produce purified monotertiarybutyl hydroquinone containing less than 0.2% (wt.) of 2,5 ditertiarybutyl hydroquinone.