Low temperature dyeing of acrylic polymers

Claim 1

A LOW TEMPERATURE METHOD OF PRODUCING A MODIFIED AND DYED ACRYLONITRILE COPOLYMER FIBER CONTAINING (A) AT LEAST 70% BY WEIGHT OF POLYMERIZED ACRYLONITRILE AND (B) FROM ABOUT 0.5 TO ABOUT 30% BY WEIGHT OF AT LEAST ONE COPOLYMERIZED BASIC NITROGEN CONTAINING COMONOMER, SAID COPOLYMER BEFORE TREATMENT BEING CHARACTERIZED BY THE PRESENCE OF ELECTROSTATICALLY NEUTRAL NITROGEN ATOMS SUCH AS OCCUR IN PYRIDINE AND AS ARE DETERMINABLE BY INFRARED SPECTROSCOPY, SAID METHOD COMPRISING: TREATING SAID COPOLYMER, AT TEMPERATURES IN THE RANGE FROM ABOUT 65*F. TO ABOUT THE BOILING POINT AT ATMOSPHERIC PRESSURE, IN FROM ABOUT 10 TO ABOUT 300 PARTS BY WEIGHT PER PART OF COPOLYMER FIBERS OF AN AQUEOUS ACIDIC BATH CONTAINING (1) AN ACID CONTENT NOT LESS THAN THAT AT PH 6 AT ALL TIMES, AND (2) AT LEAST 0.1 PART BY WEIGHT PER PART OF COPOLYMER FIBERS OF AN ANIONIC-TYPE SURFACE-ACTIVE AGENT, AND SAID BATH BEING FREE FROM HYPOHALIDE-TYPE BLEACHING AGENTS; AND CONTINUING SAID TREATMENT FOR A PERIOD RANGING FROM ABOUT 10 HOURS AT SAID 65*F. TO ABOUT 10 MINUTES AT SAID BOILING POINT, WHEREBY SAID FIBERS UNDERGO SUBSTANTIALLY NO PHYSICAL DISTURBANCE BUT BECOME SUBSTANTIALLY FREE OF SAID ELECTROSTICALLY NEUTRAL NITROGEN ATOM; FORMING AN ACID DYE BATH OF ANY CONVENTIONAL DYESTUFF CAPABLE OF BEING DYED FROM AN ACIDIC MEDIUM, ADDING TO SAID DYE BATH FROM ABOUT 2 TO ABOUT 50 PARTS BY WEIGHT PER PART OF SAID ANIONIC SURFACE-ACTIVE AGENT OF A DYEING ASSISTANT, SAID ASSISTANT COMPRISING A LOWER ALKYL ESTER OF A CARBOCYCLIC AROMATIC CARBOXYLIC ACID HAVING NOT MORE THAN TWO CARBOCYCLIC RINGS, AND SUBJECTING THE TREATED FIBERS TO THE ACTION OF RESULTANT DYE BATH AT TEMPERATURES IN THE RANGE FROM ABOUT AMBIENT TEMPERATURE TO ABOUT 150*F.