Reactive Printing and Crease Resistance Finishing of Cotton Fabrics-Effects of Fixation Modes by 2.4 Mixed Factorial Design

A single step fixation for reactive printing and crease resistance finishing of cotton fabric has been exp lored in this research work using an experimental design technique (DOE).2.4 mixed factorial design have been conducted to efficiently identify the act ive set of factors and their interaction. A ll of the three factors namelychroma, concentration of crease resistant and fixation conditions were found to be significant.The results further show that apart from the influence of individual factors, the said properties of cotton fabric are also reliant on the interaction effect of the significant factors. The influence of individual factors and their interactions on color yield (K/S) and Dry Crease Recovery Angle (DCRA) has been critically examined using software Design Expert 7.0.The results showed that combination of the Econtrol* process at 130 ̊C without urea has been verified experimentally to be the best selection for the single step fixation of reactive printing and crease resistance finishing for the cotton fabric using the pad-dry-print-fix method. The uncertainty analyses for measurements shows that the predicted values are in good agreement with experimental data and are sufficiently accurate.


Introduction
Modern text ile processes have high demand for development of a combined application of crease resistance fin ishing and reactive printing. A number o f experimental and numerical studies on simultaneous fixation of reactive dyeing and crease resistance finishing have become availab le in recent years. However, some studies have reported on combined application of reactive printing and crease resistance finishing that probably due to contradictory application and fixation conditions of both processes, it is difficult to develop an acceptable combination.
There are nu merous factors that influence the printing process of cotton fabric with react ive dyes. A nu mber of theoretical and experimental studies exist providing detailed informat ion about the effect of process parameters and operating conditions [1][2][3][4][5][6][7][8][9]. Since the 1950s many researchers [10][11][12][13][14][15] have attempted to combine reactive dyeing and crease resistance finishing processes into one step to capture the potential time, energy, and other savings associated with the combined process.
So me research [16] was conduct ed on co mb in ing CR fin ishing and pigment p rinting. Such co mbined application of finish and print, may not be favourable due to the differential finish effects resulting from the localisation of paste to an area of print design on the treated substrate.In summary, most prior studies did not experimentally evaluate the single step fixation process of reactive printing and crease resistance finishing. To make this technology practical, a new approach needs to be developed that gives high dye fixation, excellent crease recovery in a one step process.

Fabric
Co mmercially singed, desized, scoured, bleached and mercerized cotton fabric with satin weave structure, 40x40 s, 130 ends/inch x 73 picks/inch, and an area density of approximately 136 g/m 2 .
The reactive dye used was Drimarine Red P2B (Clariant), based on the MCT reactive group. Other chemicals used were co mmercially available thickener Lamitex HP (sodium alginate), sodium b icarbonate, urea, reduction inhibitor (RevatolS) and sodium hexametaphosphate as a sequestrant.

Methods
Print-finish paste manufacture A concentration of 2.50-3.00% w/w(30g/kg) o f thickener Lamitex HP (to maintain the 60-65 dPa viscosity range) was added to produce stock paste with continuous high speed stirring to the required volume of water. This was followed by the gradual addition of urea 200 g/kg, sodium b icarbonate 30 g/kg, Revatol S 10 g m/ kg and sodiu m hexametaphosphate 5 g m/ kg with continuous stirring g iving a final stock paste viscosity of 60-65dPa. Ho wever, urea is not added in the stock paste manufactured for the experiments conducted using the Econtrol without urea method for fixation. The printing pastes of different concentrations were prepared with Drimarine Red P2B as outlined in Table 1. During stock and print paste preparation a vigorous high speed stirring for 10 min was required to obtain a homogenous paste after adding all reagents. The viscosities of all types of pastes were measured using a Brookfield Viscometer (Type LV). The CR finishing liquor was prepared by using Magnesium Chloride 25% of CR but not greater than 30 g/l, So lusoft MW 20g/l, Ceranine-L 20g/l and Imercol PCLF 1g/l. The final finish bath was prepared with Arkofix NEC as outlined in Table 1. Print-finish Procedure The CPF process was carried out as fo llo ws: In the first stage the fabric was immersed in an aqueous solution of CR fin ish liquor, and then squeezed to obtain a 70% wet pickup. The wet fabric was then dried at 100°C for 1 min. In the second stage the treated fabric was printed by the lab scale Rotary Printing machine (Zimmer). The printed fabric going to be fixed though steaming and curing process was again dried at 100℃ for 1 min. Ho wever, the printed fabrics fixed through the Econtrol process was not dried. In the third stage, the print-fin ish fabric was fixed. The preparat ion of fin ish bath, printing recipe and fixation method and temperature were emp loyed in accordance with the experimental design arrangement as stated in Table 1 and 2. The fixed samples were finally washed in 1g/l non-ionic detergent until all unreacted dyes and chemicals were removed fro m the fabric surface.

Evaluation of Fabric Properties
Color yield measurement The printed fabrics were conditioned (at temperature 25±1 C and relative hu midity 65±1%) before color yield measurement with a Tex-Flash spectrophotometer. The condition for measurement was set under specular excluded with large aperture. The fabric was folded twice to ensure opacity.
The color yield (k/s value) was calculated for wavelengths 400-700n m at 20n m intervals within the visible spectrum. The k/s was calculated according to Eqn 1: (1) Where, kis the absorption coefficient, s is the scattering coefficient and R is the reflectance of the colored samples. The higher the k/s value is, the greater the color yield and dye uptake.

Evaluation of Crease Recovery Angle
The print-finish fabrics were conditioned (at temperature 25±1C and relative hu midity 65 ±1%) before the measurement of easy-care properties imparted by the CR fin ish. The dry crease recovery angle (DCRA) of the fabric was measured using AATCC test method 66-1990, using Shirley Crease recovery tester. The wider the DCRA is, the higher the crease recovery.

Results and Discussion
The results from the experiment suggest that all of three factors and two interactions were significant. The significant interactions are chroma and fixat ion conditions and concentration of crease resistant and fixat ion conditions. The experimental results, ANOVA for K/S and DCRA are shown in Table 2, 3 and 4 respectively. Fixation M odes by 2 2 .4 1 M ixed Factorial Design

Influence of Chro ma and fixation conditions
The interaction of chro ma and fixat ion condition found to be significant for both the responses K/S and DCRA. The interaction plots of Figure 1and Figure 2clearly illustrate that the Econtrol without urea process give highest K/S and DCRA as co mpared any other fixation method.
Increasing the chroma results in a radical increment of K/S ( Figure 2) shows that by increasing the concentration of dye, DCRA also increases in the case of Econtrol without urea and steaming process of fixat ion. This is highly probable when covalent bonding of reactive dye results in entrapping of crease resistant in the fiber system.

Influence of concentration of CR and fixation conditions
The interaction of the concentration of CR and fixat ion conditions was found to be significant for DCRA. As was observed earlier, the Econtrol without urea process yields the best results. Figure 3 illustrates with the increase in concentration of crease resistant, the increment in DCRA is highest in the Econtrol process as compared to other fixation methods.

Assessment of the Significant Factors
Influence of chro ma The main factor plot of chro ma is shownin Figure 4 wh ich reveals that as chroma increases, K/S increases while other factors are kept at average values.
Influence of concentration of CR The main factor plots of concentration of CR are shown in Figure 5 and 6. Figure 5 showed that as the concentration of CR increases, K/S decreases keeping other factors at average values. However, Figure 6 illustrates that as the concentration of CR increases, DCRA increases keeping other factors at average values.
Influence of fixation condition The main factor plots of fixation conditions are shown in Figure 7 and 8. The p lots of fixat ion condition showed that the final colour y ield and DCRA attained the maximu m value for the Econtrol without urea process.

Conclusions
The statistical analysis of the influential factors revealed the interaction effect of each factor on the response variables of reactive printing and crease resistance finishing process. For both the responses K/S and DCRA, the Econtrol without urea process yields the most favorable results as compared to any other fixation method for the CPF process.
The high values of coefficient of determination as indicated in Table 3 and 4 implied that the models effect ively explained the comb ined process. The interaction graphs forchro ma& fixation conditions and concentration of CR & fixation conditionsdemonstrate that the Econtrol method of fixation at 130°C using the pad-dry-print-fix-wash method provides an efficient system for imparting single step fixation of reactive printing and crease resistance finishing.
The graphical analyses of factors revealed the significant effect of chro ma, concentration of crease resistant, fixation condition on the comnbined process. Based on the experimental design study, it has been further confirmed that each factor had an interaction effect with other factors. Furthermore, the models have been tested for adequacy and found that the assumption of normality and independency are not violated. R 2 values were very high, suggesting that models accounted for most of the variability.