4. Experimental data

Some experiments were carried out to verify the effectiveness of the conditions for level dyeing induced from the concept of area exchange and circulation.

1) Dyeing polyester with disperse dye

Test method: The levelness was evaluated by the strength difference between c part and a part in the Dye-O-Meter test dyeing machine as shown in Figure 3.

Figure 3 Test dyeing apparatus

The dyeing recipe is as follows:

Material: polyester yarna: 2.5g, b: 5.0g, c: 2.5g
Package density: 0.35~0.42g/ml
Flux: 10~40 Ｌ/kg/min.
Dye: Sumikaron Blue E-FBL1.0%
Auxiliary: Sumipon TF (dispersing leveling agent) 1g/L
pH: 5.0
Liquor ratio: 1:20
Rate of temperature rise: 0.5~2.0°C/min.

The relation between the ratio of area exchange and levelness is investigated by varying the package density and/or flux.

The levelness is given by the following equation.

Levelness=strength of part a/strength of part c×100

Result: The relation between the ratio of area exchange and levelness is shown in Figure 4.

Figure 4 The relation between the ratio of area exchange and levelness

The ratio of area exchange corresponding to 100% levelness can be obtained by extrapolating the plotted line, and the value is 36%.

Then, k=0.143 is obtained by substituting the conditions (Vs(1)=2.58(%/min), T=2°C/min. and k=36) for the parameters in equation (17)

T=2(°C/min.)=kK/V=k×36/2.58
k=2(°C/min.)×2.58（％/°C）/36(%)=0.143

Further, other parameters such as package density=0.42g/ml, specific density of polyester=1.38g/ml, and gloss volume=200ml are put into equations (14), (15) and (16), the following values are obtained.

P(effective area)=volume of packaged area－volume of yarn=(10/0.42)－(10/1.38)=16.6ml
R(ratio of effective area)=P/Q=16.6/200=0.083
Dcrit=kR×100=0.143×0.083×100=1.19(%/circulation)

The rate of temperature rise for level dyeing is given by equation (17) by putting into parameters, flux=20 L/kg/min., liquor ratio=20 L/kg, Vs(1)= 2.585(measured value for Blue E-FBL) and k=0.143.

T=kAR/BVs(1)=0.143×20×8.3/20×2.58=0.46(°C/min.)

From this calculation result, when the rate of temperature rise is 0.46°C/min. , or less, level dyeing can be achieved.

The levelness in the experiment with the rate of temperature rise of 0.46°C/min. was 98.5% and then the calculation proved to be applicable to the practical dyeing.

2) Dyeing cotton with reactive dye

Test method: The levelness was evaluated by the strength difference between c part and a part in the Dye-O-Meter test dyeing machine using the same method as described in 1).

The dyeing recipe is as follows:

Material: cotton yarna: 2.5g, b: 5.0g, c: 2.5g
Package density: 0.33g/ml
Flux:5～40 L/kg/min.
Dye : C.I. Reactive Blue 191.0%
         C.I. Reactive Black 51.0%
         C.I. Reactive Yellow 1451.0%
Auxiliary: Glauber’ salt anhyd. 50g/L, Soda ash 20g/L
Liquor ratio: 1:20

The rate of the dyeing curve of C.I. Reactive Yellow 145 is shown in Figure 5. The rate of the exhaustion curve is employed for examining the rate of the dyeing curve of reactive dye.

Figure 5 Rate of dyeing curve of C.I. Reactive Yellow 145

Dyeingconditions such as package density=0.33g/ml, specific density of cotton=1.54g/ml, and gloss volume=200ml are put into equations (14), (15) and (16), and the following values are obtained.

P(effective area)=volume of packaged area－volume of yarn=(10/0.33)－(10/1.54)=23.8ml
R(ratio of effective area)=P/Q=23.8/200=0.119
Dcrit=kR×100=0.143×0.119×100=1.70(%/circulation)

The relation between the dye uptake in one circulation of dye liquor (D) and the levelness is shown in Figure 6.

From this result, level dyeing can be achieved when D<1.7 and the concept of area exchange is proved to be applicable to the reactive dye /cotton dyeing system.

Figure 6 Relation between the dye uptake in one circulation of dye liquor (D) and the levelness