Brightening Treatment Of Light Colored Cashmere Knitwear

　　 For light colors Cashmere knitwear In the process of dyeing, adding brightening agent, brightening agent and optimized finishing process were studied to improve the brightness of light colored cashmere products. Using wool reactive dyes and different brightening auxiliaries, the effects of brightening agents and brightening agents on the dyeing process of wool fabrics were studied, and the influence of different finishing methods on the dyeing process was optimized. Cashmere fiber The brightness of the fabric is improved, and the appearance quality of the fabric is improved. Textile The changing rule of sunlight fastness.

In the process of dyeing wool or cashmere, in order to increase the freshness, it is commonly used in the selection of dyes. For example, medium and light colors are often used with reactive dyes. If additives are not up to date, auxiliaries will also be helpful. For example, adding ammonium sulphate in washing and dyeing bath can increase the brightness of wool. The addition of ammonium sulphate in the process of washing wool keeps the acid condition of water bath. At the same time, it does not affect the washing effect due to the decrease of pH value. Ammonium sulfate is added in dyeing, and its action principle is that ammonium sulfate decomposes in a small amount of water in high temperature. Another way to brighten the dyed bath is to add fluorescent brighteners. The molecular structure of the 2 whitening agents Tinopal WG and Uvitex NFW used in this experiment is shown in Figure 1.

Fig. 1 molecular structure of whitening agent

The molecules of fluorescent brighteners must contain a long conjugated double bond system and are basically in the same plane. Molecules can contain groups, such as hydroxyl, amino and heterocycles containing oxygen and nitrogen atoms, but there will be no electron withdrawing groups, such as nitro and azo groups. The fluorescent whitening agent adsorbs on the surface of the fiber and absorbs near ultraviolet light with a wavelength of about 350 nm, which makes the pigment molecules enter the excited state, intensifies the molecules and then returns to the lower energy ground state, and radiates the excess energy in the form of light. In this process, the energy loss is longer than that of the absorption wavelength, and the blue light is about 450 nm. The yellow of yellowing fabric can be corrected by the blue light reflected by the fluorescent whitening agent, and the yellow and blue light complement each other. Because the intensity of reflected light exceeds the original intensity of visible light projected onto the whitened fabric, the whitening effect is slightly colored. The whitening of fluorescent whitening agents is an optical complementary function. Therefore, fluorescent whitening agents are also called optical brighteners.

1 Experiment

1.1 materials

This white has no plush (14.7 m, whiteness 65.7) and its 41.7 tex * 2 cashmere sweater, Lanasol wool reactive dyes (Hunsman company), brightening agent Lanalbine B (Clarient Clarient), whitening agent Tinopal WG (Foshan Yuyang Textile Chemical Co., Ltd.) and Uvitex NFW (NFW company). ORIENT color matching colorimeter (Italy Orintex company), standard light box, Magasso 500 fastness tester.

1.2 experimental method

1.2.1 staining experiment

Light blue, light powder and light green were selected in large scale production. Lanasol reactive dyes were added to wool, and brightening agents were added with different brighteners to dye them. Dye formulation: dye X% (OWF), levelling agent 1% (OWF), brightening auxiliaries 0.2 to 2% (OWF) (in actual use as standard), sodium sulfate 10% (OWF), ammonium sulfate 2% (OWF), dyeing 5.5 pH, bath ratio 1: 30. Mix the dye solution with the prescription, put it in the dyed cup, adjust the dye bath pH value with acetic acid, dye 5 g cashmere fiber at 40 degrees, add sodium sulfate and ammonium sulfate, 10 min, then heat up to 60 degrees at 1 /min, heat up 15 min, then heat up to 1 degrees /min and continue to dye 30min at 98 degrees.

Optimization of finishing process for 1.2.2

As the cashmere fiber is acid and alkali resistant, the acid and alkali content of the finishing water has a certain effect on the freshness of the fabric. Soft finishing with different color numbers under the same conditions at different pH values is adopted to select the best finishing process. The FK-220B2 is 5% (OWF), 40 degrees x 30 min, the bath ratio is 1: 20, and the pH value is adjusted by acetic acid and soda ash.

2 results and discussion

2.1 effect of brighteners / brighteners on the brightness

The effect of brightener / Brightener on the brightness is shown in Table 1. The experimental data in Table 1 show that adding brightening agent or brightener in dye bath can obviously improve the brilliance of cashmere fiber, and the difference between brightening agent and whitening agent is not very significant. The effect of whitening agent Uvitex NFW is slightly better than that of Tinopal WG, which may be related to their molecular structure. The number of planar conjugated systems in the structure of Uvitex NFW is much more than that of Tinopal WG molecules, indicating that Uvitex NFW is a fluorescent brightener with good properties in cashmere.

Table 1 Effect of brightener / brightening agent on brightness

2.2 effect of brighteners / brightening agents on the fastness to sunlight

The effect of whitening agent / brightening agent on the fastness to sunlight is shown in Table 2. From table 2, it can be found that adding fluorescent whitening agent to dye bath has a significant effect on the fastness of the final fiber products, and will reduce the fastness to sunlight. During the test of sunlight fastness, the whitening agent is introduced to the excited state due to the action of ultraviolet radiation, and its molecules are gradually destroyed.

Table 2 Effect of brighteners / brighteners on light fastness

Effect of 2.3 finishing process on brightness

Table 3 Effect of finishing process on brightness

Wool fiber will be yellowed to some extent under alkaline conditions. It is mainly caused by the change of some amino acids in the fiber under the action of alkali agents, and the handle of the fiber is also bad. Therefore, soft treatment is better in weak acid bath, and it is more advantageous to the protection of fibers. Moreover, the components of softeners in this condition are of good stability and are not prone to demulsification.

3 conclusion

　　 When wool is dyed with reactive dyes, adding brighteners or fluorescent brighteners in the bath can significantly enhance the fabric's final brilliance. Compared with the different brightening methods, the brightening agent is better, and the fluorescent fastness will reduce the fastness of the products. When the cashmere sweater is ready for finishing, it is better to use the weak acid (pH value 5~6) condition to keep the fabric brightly bright, and to protect the fiber better. 。