**4.1. Dyeing cotton fabric with UMP**

In order to improve the dyeability with UMP, the cationic pretreatment of fabric is used. It can introduce positively charged sites on cotton fabric. Without pigment modification, there are two inhibiting factors. Firstly, pigments are insoluble and have no affinity for cotton and, secondly, the surfaces of pigment particles are usually negatively charged. UMP dyeing has several noticeable advantages compared to dyes. This method is a short process, simple operation, saving energy consumption and low costs, and matching intui‐ tive easy color imitation, steady color hue, hiding power. Because UMP particles have no affinity for fibers, the UMP dyeing fibers does not exist the selective problem and is appro‐ priate for all spices.

There are many reports on cationic modification of cotton. Karrer researched the cationic pretreatment to the cellulose fiber [44]. Guthrie studied the cationic pretreatment of cellulose fiber and dyed it with acidic dye [45]. The chemical modification of cotton to promote dyea‐ bility, light fastness and washing fastness has been researched by Cai [12]. Wang investigat‐ ed chemical modification of cotton to promote fiber dyeability [46]. Burkinshaw analysized cationic pretreatment of cellulose fiber to improve the dye reactivity [47]. Hauser examined the dyeing behavior of cotton that had been rendered cationic by reaction with 2,3-epoxy propyltrimethylammonium chloride and the result showed that excellent dye yields and color fastness properties were obtained without the use of electrolytes, multiple rinsings or fixation agents [48].

**Figure 5.** Effect of cationic reactant concentration on pigment exhaustion and the K/S value

During exhaustion dyeing process, the dyeing uptake of cotton fabric without modification was very low. Via cationic reagent modification, the uptake of the cationic fabric was in‐ creased significantly. Cationic reagent with higher proportions increased the number of pos‐ itive charges on the cotton fiber, in turn increased pigment uptake.

nesses of cationic silk increased greatly. This was probably due to the fastness improving re‐

 2 1-2 2 4 4 2-3 2 3-4 4-5 4 3 3 4 4-5 4 3-4 3 4 4-5 4-5 4 3-4 4 4-5 4-5

Cationic pretreatment depended on the extents of reaction between cationic reagent and silk. This might affect the physical properties of the treated fabrics. The tensile strength and elongation at break of fabrics changed with the increase of pH. It was clear that the reaction between cationic reagent and silk took place significantly when pH of the pretreatment solu‐ tion increased. The tensile strength decreased with the peptide chain hydrolyzation when the pH increased. Also the elongation at break kept slightly decreasing. This revealed that the cationic pretreatment has little effect on the physical properties. The bending rigidity and hysteresis of cationization silk had no change compared with untreated silk. It revealed that the cationization treatment had no impact on the soft properties of fabrics. The handle of fabric decreased a little after dyeing, it might be due to the action of fastness improving

The wool fabric was modified by cationic reagent and dyed with UMP which was pre‐ pared with anionic polymer disperser via exhaust method [55]. The influence of pretreat‐ ment conditions such as concentration of cationic reagent, pH value of the bath, temperature and duration of treatment on the dyeing property of the fabric was of impor‐ tance to the drying properties. With the increase of the cationic content, the K/S value en‐ hanced sharply and then kept a constant value when the content on cationic reagent was higher than 10% (Figure 6). The dry and wet rubbing fastness of the wool fabric dyed with UMP via exhaustion was gray scale ratings of 3-4 and 4, respectively. The tensile strength and elongation at break decreased slightly with the increase of bath pH value. The test results of bending rigidity and hysteresis of bending revealed that the wool fab‐

**Rubbing fastness (Grade) Washing fastness (Grade)**

Preparation, Characterization and Application of Ultra-Fine Modified Pigment in Textile Dyeing

http://dx.doi.org/10.5772/53489

91

**Dry Wet Color change Stain cotton Stain silk**

agent acting as the binder between UMP and silk fabric [53].

**Table 1.** Color fastness at different cationic reagent concentration

**Fastness improving reagent conc. (g/L)**

reagent.

**4.3. Dyeing wool fabric with UMP**

ric had soft handle and good elasticity.

For example, the cationic polymerization modifier was used to modify the charge of cotton fiber, and this could enhance the uptake of UMP and K/S value with different cationic re‐ agent concentration (Figure 5). The application of cationic polymerization modifier on fibers for cationic modification could reduce the production cost, reduce dyeing temperature, shorten the dyeing process and improve production efficiency [49].
