Modified amides for pigments and method for producing the same
A polyfunctional amine is reacted with both a polycarboxylic acid and a monocarboxylic acid to form relatively short chain polyamides in the molecular weight range from about 400 to about 2500, which are substantially linear and which have at least one carboxy group remaining on the majority of molecules, which permits a thermoplastic resin to be formed which is extremely friable and grindable, at the same time making it a durable and desirable matrix for incorporating dyes, particularly fluorescent dyes, to form a pigment characterized by exceptionally high heat stability. Light stability is also improved with some fluorescent dyes. Optionally, an epoxy resin may be included in the co-condensate, maintaining at least one carboxy group on most molecules of the co-condensate, without altering the thermoplastic nature of the resin. Alternatively, the monocarboxylic acid may be omitted, forming a modified polyamide with a polyfunctional amine and a polycarboxylic acid. Optionally, whether or not a monocarboxylic acid is used, a sufficient amount of stabilizing compound of an element from Groups IIA and IIB may be added to further stabilize the pigment.