Effects of a Multi Scouring Agent on the Pretreatment and Dyeing of different Cellulosic Knitted Fabrics

Two types of pretreatments were conducted in this experiment. Conventional pretreatment included regular industrial methods, whereas the experimental pretreatment involved the replacement of caustic soda, soda ash light, abd H₂O₂, H₂O₂ stabilizer with Viscobleach. The procedure followed in each type of pretreatment is given below:

From Table 1, it can be seen that for all pretreatment methods, the bath was set maintaining a 1:6 ratio with the required fabric at 60 °C, with a wetting agent (1 g/l), sequestering agent (1 g/l), and anticreasing agent (0.8 g/L).

For the cotton conventionally pretreated sample, caustic soda (1.5 g/l) was added at 60 °C with the auxiliaries, and the temperature was raised to 70°C. Then H₂O₂ (2 g/l) and H₂O₂ stabilizer (0.25 g/L) was added, and left for 5 minutes. The temperature was raised to 98 °C with 1.5 °C gradient and left for 60 minutes at pH 11; the bath was then cooled down to 60 °C and drained. Then one room temperature wash and one cold wash at 40 °C were done separately.

For viscose and linen conventionally pretreated sample (VCP and LCP), soda ash light (1.5 g/l) was added at 60 °C with the auxiliaries and raised temperature to 90 °C run for 20 minutes at pH 10.5, the bath was then cooled down to 60 °C and drained. Then one room temperature wash and one cold wash at 40 °C was done separately.

For the experimentally pretreated cotton, Viscose and Linen samples (CEP, VEP, LEP), a multiscouring agent (Viscobleach) (2 g/l) was added at 60 °C with the auxiliaries, the temperature raised to 80 °C, then they were left for 60 minutes at pH 9.5, the bath next cooled down to 60 °C and drained. Then one room temperature wash and one cold wash at 40 °C were done separately.

All the conventionally and experimentally pretreated samples were dyed at shades of 0.5 %, 1.5 % and 3 % according to the following recipe using a sample dyeing machine (Fong’s-China).

The dyeing bath was set maintaining an M:L ratio of 1:6 with the required fabric at 60 °C with a wetting agent (1 g/l) (Felosan NOF-Cht smart Chemistry / RH corporation), sequestering agent (1 g/l) (Lufibrol 2UD-Archroma Singapore Pte Ltd), anticreasing agent (0.8 g/L) (Ceranine WN SR-Archroma Singapore Pte Ltd), levelling agent (3 g/l) (sarabid MIP-cht Bezema/RH Corporation), acetic acid (1 g/l) (Narayanganj Dyes and Chem), and reactive dye (0.5 %, 1.5 % and 3 %) for light, medium and dark shades correspondingly. After that, 30 g/l salt, 35 g/l salt and 50 g/l salt were added for light, medium and dark shades, correspondingly. Then the temperature was raised to 80 °C for 10 minutes for migration and then lowered to 60 °C. After doing so, for the light shade 15 g/l of soda, for the medium shade 15 g/l of soda, and for the dark shade 20 g/l of soda were added and then left for 60 minutes. After which time, the bath was drained. Then, one room temperature wash and one hot at 80 °C were done.

Here, 3 types of dyed samples according to shade %, as shown in Table 2, were prepared from the CCP sample, which were CCP_L, CCP_M, and CCP_D. Accordingly, from the CEP sample, CEP_L, CEP_M, and CEP_D samples were prepared.

From the VCP sample, VCP_L, VCP_M, and VCP_D samples were prepared (Table 2). From the VEP sample, VEP_L, VEP_M, and VEP_D samples were prepared. From the LCP sample, LCP_L, LCP_M, and LCP_D samples were prepared (Table 2). From the LEP sample, LEP_L, LEP_M, and LEPD samples were prepared.

After that neutralization was done with acetic acid (1 g/l) and a sequestering agent (1 g/l) at 40 °C, the temperature raised to 55 °C, and it was left for 20 minutes. One cold wash was done at 40 °C for 10 minutes in a sample dyeing machine (Fong’s - China).

After neutralization, soaping was done at 95 °C for 20 minutes for all the dyed samples. Then it was followed by a hot wash at 80 °C for 10 minutes. After which, a rinse wash and two cold washes were done at 40 °C for 10 minutes. After the cold wash, softening treatment was done on the fabric at 55 C for 20 minutes, and then it was unloaded. Afterwards, treatment was carried out in a sample dyeing machine (Fong’s-China).

Fabric absorbency was checked using Direct Congo Red (Huntsman Singapore Pte Ltd) after scouring at the Wet Processing Lab, Bangladesh University of Textiles. Afterwards, AATCC 79. 0.1 % solution of Direct Congo Red was prepared with distilled water. Then the solution was dropped on different places of the fabric sample using a dropper at room temperature. After that, the absorption of the colored drop was observed carefully. Then the absorption time was noted by noticing the spread and different shapes of the drop, and they were compared to the standard shape.

Rubbing fastness (Dry and Wet) was measured using the ISO 105 X12 standard to determine the color fastness of the textile against abrasion.

The resistance capability of the color of the dyed fabric against washing is known as colorfastness to washing. The ISO 105 C06 B₂S method was used for the testing.

In this test, as shown in Figure 1, the whiteness index is higher for conventionally pretreated cotton sample (CCP) than for the experimented one (CEP) (the sample identification of pretreated samples is shown in Table 1). This may be because NaOH is known for its ability to remove various impurities from cotton, whereas mild alkali present in the multiscouring agent was too mild to eliminate all the natural waxes, oils, pectins and other impurities. The whiteness index of the viscose sample was more increased for the experimental sample (VEP) than for the conventionally pretreated sample (VCP). This maybe because soda ash only removes natural impurities, while Viscobleach targets a wide range of impurities. For example, sulfur content is eliminated when applied to viscose pretreatment. Thus, this could be the reason for the better whiteness index of the multiscouring agent treated fabric [1]. Also, it can be seen in Figure 1, that the whiteness index value slightly increased for linen with multiscouring treatment, which could be attributed to the fact that it eliminates a wide range of impurities, as compared to soda ash [4].

Fig. 1.

The absorbency of pretreated samples CCP, CEP, VCP, VEP, LCP and LEP is shown in Table 3. From Figure 2 it is observed that the absorbency of the cotton experimentally pretreated sample (CEP) was quite poor as it took much time to absorb, and the shape was uneven, as compared with the conventionally pretreated sample (CCP). The decreased absorbency of cotton with multiscouring agents compared to sodium hydroxide may be due to the presence of mild alkali in the multiscouring agent, which is unable to effectively remove that full range of waxes and impurities, hindering the cotton’s ability to properly absorb liquids [4,5]. But the viscose and linen showed a good result in the case of both conventional samples (VCP, LCP) and experimental samples (VEP, LEP).

Fig. 2.

Color strength (K/S) is the most important parameter to test the quality of a sample in terms of the depth of the color-dyed fabric. A comparison of the K/S value between the conventional and experimental methods is presented here. It was observed that the peak value at 520 nm was almost similar for all of the samples.

The result of the color strength of all dyed fabric samples is shown in Figure 3., from which it is observed that the K/S value increased more for the experimental cotton sample (CEP_L, CEP_M, CEP_D) than for the conventional sample (CCP_L, CCP_M, CCP_D). The high K/S value observed in cotton can be attributed to the fact that the multiscouring agent (Viscobleach) may have modified the surface characteristics of the fabrics, which improved dye diffusion, retention and binding capability, resulting in enhanced color intensity.

Fig. 3.

In some cases, like for medium and dark shades of viscose and linen, the K/S value increased.. This could be attributed to the fact that multiscouring agents are specially formulated to target a wide range of impurities, both natural and synthetic. They prove to be particularly effective for viscose since Viscobleach removed sulfur from it, which might result in stronger surface binding of the reactive dye to the surface of the fabric.

The rubbing fastness results of all the dyed samples are shown in Table 4. From which, it can be seen that for cotton, the experimental samples (CEP_L, CEP_M, CEP_D) showed better rubbing fastness (wet and dry) than the conventional method sample (CCP_L, CCP_M, CCP_D). The increase in rubbing fastness in the cotton sample can be attributed to the fact that the multiscouring agent is formulated to provide a milder treatment while still achieving effective cleaning with traditional scouring, high pH and aggressive action, which can potentially damage cotton fibers during scouring and reduce rubbing fastness [13].

From Table 4, it is observed that for viscose, the conventional method samples (VCP_M, VCP_D) showed better rubbing fastness (wet) for medium and dark shades. Rubbing fastness (dry) was the same for all samples.

It is observed that for the linen sample, the rubbing fastness (dry and wet) result was the same, 4 - 5 for both the conventional method samples (LCP_L, LCP_M, LCP_D) and experimental samples (LEP_L, LEP_M, LEPD).

In Table 5 results of the wash fastness of the dyed samples (staining and fading) are shown. And the test results are shown in Figure 4. From Table 5 for the cotton samples, the wash fastness result was the same for both the experimental (CEP_L, CEP_M, CEP_D) and conventional method samples (CCP_L, CCP_M, CCP_D ).Even the result was better for the medium and dark shade samples of the experimental method. This better performance in wash fastness can be attributed to the fact that Viscobleach uses lower temperature and mild alkali, which does not weaken cellulosic fabric and results in better wash fastness [13,14]. Even the result was better for medium and dark shade samples of the experimental method. The wash fastness rating was almost good to excellent for all samples.

Fig. 4.

It is observed for viscose that the wash fastness result was the same for both the experimental (VEP_L, VEP_M, VEP_D) and conventional method samples (VCP_L, VCP_M, VCP_D) And the rating was good to excellent for both the staining and color change of the samples.

For linen fabric, the wash fastness result was the same for both the experimental (LEP_L, LEP_M, LEP_D) and conventional method samples (LCP_L, LCP_M, LCP_D) And the rating was good to excellent for both the staining and color change of the samples.