Quinacridone pigment and a process for preparation thereof

A process for preparing Quinacridone pigment comprising 2,9-bis(isopropyl)quinacridone of Formula (I);

• said process comprising the following steps:
• i) condensing 4-isopropylaniline (II) and dimethyl succinylsuccinate (III) in at least one first fluid medium, in the presence of at least one mineral acid catalyst, at a pressure in the range of 0.5 kg/cm2 , and at a temperature in the range of 65 to 90° C. for a first predetermined time period to produce Dimethyl 2,5-bis(4-isopropylphenylamino)cyclohexa-1,4-diene-1,4-dicarboxylate (IV), heating said Dimethyl 2,5 -bis(4-isopropylphenylamino)cyclohexa-1,4-diene-1,4-dicarboxylate (IV), at a temperature in the range of 108 to 115° C., and at a pressure in the range of 1.0 to 4.0 kg/cm2 , in the presence of resist salt, at least one alkali, and water to obtain alkali metal salt of 2,5-bis(4-isopropylphenylamino)benzene-1,4-dioic acid, which on acidifying provides crude 2,5-bis(4-isopropylphenylamino)benzene-1,4-dioic acid (V) and optionally, purifying said crude 2,5-bis(4-isopropylphenylamino)benzene-1,4-dioic acid (V) by washing with a second fluid medium to obtain 2,5-bis(4-isopropylphenylamino)benzene-1,4-dioic acid (V);
• ii) cyclizing said 2,5-bis(4-isopropylphenylamino)benzene-1,4-dioic acid (V) in the presence of predetermined amount of polyphosphoric acid at a temperature in the range of 90 to 150° C., for a predetermined time period to obtain crude 2,9-bis(isopropyl)quinacridone (VI);
• and
• iii) washing said crude 2,9-bis(isopropyl)quinacridone (VI) with at least one third fluid medium, and drying to obtain 2,9-bis(isopropyl)quinacridone (I).