Patent ID: 6090166
Filing Date: 2000-07-18
Classification: D06B,D06P,Y10S

Abstract:
A process for dyeing a thread with indigo, characterized in that it comprises the following stages:a. pre-washing the thread (F) by passing it through a pre-wash system (1) composed of two or more vats (2) containng a pre-wash solution (10,15);b. subsequent dyeing of the thread by passing it through a dyeing system (30) composed of a series of eight vats (35), each one containing an indoxyl solution, and during the passage from one vat (35) to another, the thread undergoes oxidation by exposure to air, converting the indoxyl to indigo, which then dyes the thread by impregnation, the oxidation by exposure to air being performed in such a way that, during the passage from the first vat (35) to the eighth vat in succession, if a value x is given to the oxidation between the first vat (35) and the second, the following values will be obtained successively:oxidation value between 1st and 2nd vats=xoxidation value between 2nd and 3rd vats=2xoxidation value between 3rd and 4th vats=3xoxidation value between 4th and 5th vats=4xoxidation value between 5th and 6th vats=5xoxidation value between 6th and 7th vats=6xoxidation value between 7th and 8th vats=7xoxidation value after 8th vat=8x;c. washing and pre-drying the thread by passing it through a washing and pre-drying system (40) comprising a series of vats (41, 42, 43, 44 and 45), the first vat (41) containing water, vats (42, 43 and 44) containing acetic acid and vat (45) containing water, so that the pH in the last vat is between 6 and 7, and, at the exit from vat (45), the thread is pre-dried by passing it between rollers (50);d. sizing the indigo dye onto the thread by passing it through a sizing system (60) comprising a vat (62) containing a resin blend in order to form a transparent film on the thread fibres;e. drying the thread by passing it through a drying system (70) composed of rollers (71);f. collecting the thread by winding it onto the spool (72).