1. Dye liquor circulation and leveling
This theory is based on the idea that the capacity of a dyeing machine to
give level dyeing (leveling capacity of the dyeing machine) is evaluated by the
amount of absorbed dye per one circulation of dye liquor, from which the physical
conditions of dyeing (mechanical operation) are reasonably determined.
In a practical dyeing system, the relation between dye liquor circulation and
leveling is known to be the following;
F=E/C
=100/CD
=100B/AD ..... (1)
E=100/D ..... (2)
C=A/B ..... (3)
where
F: minimal dyeing time (min.)
E: necessary number of circulations until the end of dyeing (times)
A: flux (L/kg/min.)
B: liquor ratio (L/kg)
C: number of circulations of dye liquor or fabric per minute (times/min.)
D: amount of absorbed dye per one circulation (%/time)
A or B depends on the capacity of the dyeing machine, and D represents the
leveling capacity of the dyeing machine. If the flux and the liquor ratio are
adjusted according to equations (1) and (2) to obtain D value corresponding to
the capacity of the dyeing machine, level dyeing can be practically achieved.
The experimental value of D is shown in Table 1.
Table 1 Experimental value of D
| Dyeing machine |
Experimental value of D |
| Cheese |
1~2（%/time) |
| Beam |
1~2（%/time) |
| Loose stock |
2~4（%/time) |
| Jet |
5~10（%/time) |
In a dyeing system where the rate of dyeing can be controlled by regulating
the rate of temperature rise, such as in the dyeing of polyester with disperse
dye, the following consideration can be made.
When the rate of dyeing is V (%/min, temperature rise is at 1°C/min.)
and the rate of temperature rise is T (°C/min.), the dye uptake per one minute
is presented as VT and dye uptake per one circulation is presented as VT/C, then,
equation (4) may be given.
D=VT/C ..... (4)
Level dyeing can be achieved by adjusting C using equation (4) to give D value
corresponding to the dyeing machine given in Table 1.
Combining equations (3) and (4), equation (5) is given.
T=CD/V=AD/BV ..... (5)
In the case of a dyeing machine with dye liquor circulation such as a cheese,
beam or loose stock dyeing machine, equation (5) can be directly applied.
However, in the case of a dyeing machine with fabric circulation such as a
winch or jet dyeing machine, modified equation (6) can be applied.
C'=M/N ..... (3')
T=MD/VN ..... (6)
where
N: loop length per one flow (m)
M: fabric speed (m/min.)
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