The use of KAYACELON REACT Dyes needs high temperatures. These dyes are suitable for Tencel dyeing, which requires a high temperature crumpling process, and also for the one-bath dyeing of polyester/Tencel blended products.

In Tencel dyeing, fibrillation, alkali treatment and enzyme caustic treatment are carried out in order to produce special hands. The use of KAYACELON REACT Dyes can lead to the following advantages: fibrillation process can be carried out at the same time; and pH in an enzyme caustic treatment bath can be controlled easily because of non-use of alkali agents.

100% Tencel is sometimes dyed with atmospheric dyeing machines. The KAYACELON REACT CN-603 series will be appropriate for such processing since they have improved their detergency and atmospheric dyeing suitability at less than 100°C.

Leveling properties, reproducibility

KAYACELON REACT Dyes will be absorbed when inorganic salt (Glauber's salt) is added, however, level dyeing can be obtained through the migration of dyes absorbed, without relying on Glauber's salt for the control of absorption. As the temperature rises, the migration becomes more active, therefore, leveling properties are superior with low pH that inhibits dye fixation until the temperature becomes high.

For high fixation and superior reproducibility, pH should be high.

KAYASLIDE PH-509, which was developed at the same time as KAYACELON REACT CN-603 Dyes, can maintain a pH level that takes account of level dyeing when the temperature rises and smoothly slips, or 'slides', the dyebath pH into the appropriate range that promotes fixation when the temperature reaches the high range. KAYASLIDE PH-509 is a pH balancer mainly used for atmospheric dyeing (Figure 1).

Figure 1.Relations between dyebath pH and fixing ratio in the use of KAYACELON REACT Dyes

Table 1. Standard set up for dyeing temperature and time for KAYACELON REACT Dyes

Dyeing method

Table 1 shows relations between the high temperature range for atmospheric & high-pressure dyeing and fixing time.

For high temperature dyeing at more than 100°C, it is not necessary to slide into the appropriate range of pH, and superior fixation can be obtained through neutral dyeing (with KAYAKU BUFFER P-7).

For reduction in dyeing time, it is effective to raise dyeing temperature.

Dyeability of Tencel A-100

Surface concentration, build-up properties

Tencel A-100 can lead to high surface concentration and superior build-up properties.

When it is dyed, the surface concentration can be twice as high as cotton with no mercerization. Comparisons between cotton, rayon and Tencel are indicated in Figure 2.

Figure 2. Comparison between surface concentration and build-up properties of each cellulosic fiber

Absorption speed

At the initial stage of dyeing, Tencel A-100 shows absorption speed as fast as cotton, and it leads to considerably faster absorption when Glauber's salt is added, as well as to high absorptance. Figure 3 shows the absorption speed of KAYACELON REACT Dyes used on cellulose fibers at the initial stage of dyeing (the initial dyeing).

Figure 3. Absorption speed of KAYACELON REACT Dyes in cellulosic fiber dyeing

Migration properties

The migration properties of Tencel A-100 tend to be inferior to Tencel. When it absorbs reactive dyes, there is a high affinity between dyes and fiber. In the case of hot water treatment (80°C) without inorganic salt (Glauber's salt), their tends to be little migration into the dyebath.

Leveling properties

Tencel A-100 brings about considerably high absorption speed when Glauber's salt is added, and it is important to control absorption in order to obtain level dyeing since there is little migration of the dye absorbed. In such a case, it is effective to control the amount of Glauber's salt used or carry out portionwise addition of Glauber's salt taking account of level dyeing.

Figure 4 shows the results of checking the degree of leveling properties in dyeing with KAYACELON REACT Dyes. This is a test for checking the degree of leveling at the final stage of dyeing after causing absorption gaps on purpose in the initial stage of dyeing (putting 2 substrates into a dyebath at different times).

Figure 4. Leveling properties of KAYACELON REACT Dyes in cellulosic fiber dyeing and Glauber's salt influence

The larger the amount of Glauber's salt used, the more inferior leveling properties tend to become. This indicates that the amount of dye left in the dyebath and the dye's affinity can affect leveling properties (the leveling properties of KAYACELON REACT Dyes are superior).

COMET system, setting up the appropriate amount of Glauber's salt

The appropriate amount of Glauber's salt for reactive dyes

Inorganic salt (Glauber's salt) is a chemical that plays an important fixation (absorption) role in dip dyeing with reactive dyes.

In most cases, establishing the amount of Glauber's salt used is crucial for reproducibility in dyeing.

Taking account of reproducibility only, in many cases, exceeding the amount of Glauber's salt used is not going to be a problem. Thus, many dyeing factories establish the appropriate amount of Glauber's salt for dyeing concentration stage by stage.

For dyeing factories' dyeing & finishing, reproducibility (color difference, lot variation) is vital, however, levelness (uneven dyeing), workability and cost for dyeing chemicals are, at the same time, important factors.

It is important to decide the amount of Glauber's salt used taking into full consideration the above factors (Figure 5).

(Note) At certain dyeing concentration & bath ratio, the fixing ratio is determined by the surface concentration of the cloth, compared to the surface concentration that has reached the equilibrium of fixed amounts and is taken as 100. Figure 5. Concept figure for appropriate amount of Glauber's salt

Appropriate dyes

It is rare that a single dye is used in a normal dyeing process. In order to obtain target colors, in most cases, combination dyeing is carried out.

In combination dyeing, the affinity of each dye for combination should match other dyes' affinities in order to decide (figure out) the appropriate amount of Glauber's salt.

The dyeing properties of reactive dyes in combination dyeing, when these affinities vary, greatly vary due to the difference between dyes' combination ratios or total concentrations. Practically speaking it is impossible to understand all the movements, for which we would need huge amounts of data.

With the three primary colors of KAYACELON REACT Dyes and KAYACION E-CM, E-LE conc. Dyes, it is possible to figure out the appropriate amount of Glauber's salt (COMET system).

COMET system

The COMET system requires personal computers that can figure out the appropriate amount of Glauber's salt during dyeing with reactive dyes and the coefficients for bath ratios where there is variation.

For figuring out the appropriate amount of Glauber's salt using the COMET system, the following calculations are possible by entering the types of fiber, the types of alkali agent used, dyeing concentrations and bath ratios:

Calculating the standard amount of Glauber's salt (the standard method): the amount of Glauber's salt for the fixing ratio in consideration of dyeing reproducibility

Calculating the amount of Glauber's salt for level dyeing (the level dyeing method): the amount of Glauber's salt that leads to 50% absorption in relation to the amount of dye used

Calculating the economical amount of Glauber's salt (the economical method): the amount of Glauber's salt that leads to lower total costs for dyes and Glauber's salt used to obtain a certain degree of concentration

Designating fixing ratio: designating the most suitable fixing ratio for dyeing based on the above information, in order to figure out the amount of Glauber's salt

Figure 6 shows the relation between the standard amount of Glauber's salt and KAYACELON REACT Dyes used with either cotton or Tencel.

Figure 6. The relation of the standard amount of Glauber's salt used in cotton or Tencel dyeing to KAYACELON REACT Dyes

Right now, the amount of Glauber's salt used in Tencel dyeing is almost the same as in rayon dyeing, which is generally 3/4 of the amount for cotton. When this amount is considered to be the standard, the fixing ratio (where fixing ratio that has reached the equilibrium is considered to be 100 in the use of a large amount of Glauber's salt) comes to 85% in the case of cotton and 80% in the case of Tencel. However, the fixing ratio in Tencel's case is the standard, and the fixing ratio that has reached the equilibrium is so much higher than cotton, therefore, the ratio for the effective use of dyes and the surface concentration of dyed materials is high.

Reduction in Glauber's salt

Taking a close look at an example of the standard amount of Glauber's salt, Figure 7 shows the comparison between the amount established stage by stage and the amount figured out by the COMET system.

Figure 7. Figuring out the standard amount of Glauber's salt and reduction in Glauber's salt through the COMET system--comparing Glauber's salt amounts figured out by the COMET system and the amounts established stage by stage

Since the amount of Glauber's salt for reactive dye dyeing can be figured out in detail according to dyeing concentration and bath ratio, considerable reduction in the amount of Glauber's salt is possible compared with when the amount of Glauber's salt is established stage by stage.

In establishing the amount of Glauber's salt stage by stage, a great amount of Glauber's salt can be wasted due to Glauber's salt dyeing concentrations, and furthermore the amount used badly affects level dyeing.