Patent ID: 6123741
Filing Date: 2000-09-26
Classification: D06B,D06M,D06P,Y10S

Abstract:
A Process for dyeing a thread with indigo, characterized in that the process comprises the following steps:a. prewashing the thread (F) by passing it through a prewash arrangement (1) comprising two or more prewash tanks (2) containing a prewash solution (10, 15);b. then dyeing the thread by passing it through a dyeing arrangement (30) comprising a series of dyeing tanks (35) each containing a solution of reduced indigo, and when passing from one dyeing tank (35) to another the thread is subjected to oxidation by exposure to the air transforming the reduced indigo into indigo, which then dyes the thread by impregnation, the oxidation by exposure to the air being achieved in such a way that when passing from the first dyeing tank (35) to the eighth in succession, if the value x is given to the oxidation between the first and second dyeing tanks, the successive result will be:Between the 1st and 2nd tanks the oxidation value=xBetween the 2nd and 3rd tanks the oxidation value=2xBetween the 3rd and 4th tanks the oxidation value=3xBetween the 4th and 5th tanks the oxidation value=4xBetween the 5th and 6th tanks the oxidation value=5xBetween the 6th and 7th tanks the oxidation value=6xBetween the 7th and 8th tanks the oxidation value=7xAfter the 8th tank the oxidation value=8x;c. washing and initial drying the thread by passing it through a washing and initial drying arrangement (40) comprising a series of washing tanks (41, 42, 43, 44 and 45) including a first washing tank, at least one middle washing tank, and a last washing tank; the first washing tank (41) containing water, the at least one middle washing tank (42, 43 and 44) containing acetic acid, and the last washing tank (45) containing water such that the pH in the last tank will be between 6 and 7, and upon exit from the last washing tank (45), the thread is pre-dried by passing it between drying rollers (50);d. sizing the indigo dye on the thread by passing it through a sizing arrangement (60) comprising a sizing tank (62) containing a mixture of resins to form a transparent film on the fibers of the thread;e. drying the thread by passing it through a drying arrangement (70) comprising drying rollers (71); andf. collecting the thread by rolling it on a drum (72).