Process for preparing yellow pigment based on the complex of nickel cation, melamine and azobarbituric acid and novel crystalline modifications of the pigment prepared by this process

摘要

The present invention relates to a process for preparing yellow pigment based on the complex of nickel cation, melamine and azobarbituric acid of the general formula [NiLMim]in, wherein L represents anion of the azobarbituric acid Ci8Hi4Ni6Oi6, M denotes melamine Ci3Hi6Ni6, m = 0,1 to 2, n is greater than or equal to 2. The preparation process is characterized in that in the first step, there is prepared the complex of nickel chloride and melamine and this complex is then brought in the second step in the reaction with azobarbituric acid or a slat thereof. The invention further describes novel crystalline modifications of the above-indicated pigment prepared by the process as described herein.