Bleaching and dyeing; fluid treatment and chemical modification – Fluid treatment – Combined liquid and gas or vapor
Patent
1989-11-21
1991-04-30
Coe, Philip R.
Bleaching and dyeing; fluid treatment and chemical modification
Fluid treatment
Combined liquid and gas or vapor
8151, 8158, 68 5E, 68 9, 68 13R, D06B 312
Patent
active
050106120
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention concerns a method for continuous dyeing of tubular cotton knit fabrics with reactive dyes, in which method the fabric passes through a padding phase, optionally a swelling phase, a levelling phase, a steaming phase, and a washing out, and in which the tubular fabric is ballooned one or several times at least in the levelling phase.
BACKGROUND ART
A method for continuous dyeing of woven cotton fabrics has been known for a long time, in which method the fabric passes through a padding machine followed immediately by a steamer and is subsequently washed out.
Such a method cannot be used for cotton knot fabrics because a cut knit fabric is not sufficiently dimensionally stable, and because it is not possible to prevent the edges of the length of fabric from rolling up.
It is preferred to use uncut tubular fabric, but said fabric is encumbered with the drawback that the two edges resulting from the squeezing procedure in the padding machine absorb a great amount of dyestuff and therefore appear as dark stripes. In connection with vat dyeing attempts have been made to solve this problem by ballooning the tubular fabric one or several times during its passage through the steamer in which the fixation occurs, cf. German Offenlegungsschrift No. 3.422.759.
The present invention is based on the same technique, i.e. ballooning the tubular fabric one or several times during its passage through the steamer.
Dyeing with reactive dyes is, however, encumbered with a different problem than dyeing with vat dyes as the latter method requires a feeding of fixation chemicals. These fixation chemicals are very conveniently fed through the liquid locks forming the inlet and the outlet of the steamer. Fabrics dyed with reactive dyes do not require a feeding of fixation chemicals and can pass through the steamer directly from the padding or the swelling phase provided the ballooning technique is not used in the steamer. When the latter technique is used it is necessary that the length of fabric passes a lock such as a trap, in order to maintain the pressure inside the steamer. The latter procedure has, however, a damaging effect on the fabric dyed with reactive dyes because the dye is washed out by water.
DISCLOSURE OF THE INVENTION
According to the present invention the above problem has been solved by the length of fabric passing through a bath of a neutral, inert salt before each ballooning in the steamer and being squeezed to approximately the same moisture content as at the inlet to the salt bath after each ballooning, the squeezed off liquid being recirculated to the salt bath. In this manner the colour is preserved in the levelling phase at the same time as the salt consumption is minimized and the environment is not polluted by large amounts of salt.
However, as it cannot be avoided that the length of fabric absorbs some salt, the concentration of the salt bath is according to the invention suitably maintained by dosing salt.
The above dosing of salt is suitably carried out by the salt bath being kept in constant circulation to an outer vessel in which the concentration of salt is measured and the dosing of salt is carried out.
The measuring is suitably carried out by measuring the conductivity, but can also be carried out for instance by measuring the specific gravity.
The slat bath is a strong solution of a neutral, inert salt, such as common salt (NaCl), for instance in a concentration up to 250 g/l.
In addition to the concentration of the salt bath also the temperature of said bath affects the dye absorption, and therefore said temperature is suitable kept constant for instance in the range of 70.degree.-90.degree. C. This necessitates a heating of the salt bath at the beginning of the process and a cooling thereof later on in the process because the temperature inside the steamer must be kept at at least 100.degree. C. for instance by blowing in steam or by means of an evaporator situated below the length of fabric.
BRIEF DESCRIPTION OF DRAWING
The invention is described
REFERENCES:
patent: 3451077 (1969-06-01), Meier-Windhorst et al.
patent: 4747190 (1988-05-01), Koch
patent: 4843669 (1989-07-01), Koch et al.
Jensen Aage
Landberg Jakob
Stingsen Jeppe
Coe Philip R.
Vald. Henriksen A/S
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