There are two main purposes of bleaching in the washing process, one is to remove the residual dirt on the fabric that needs to be removed by oxidation or reduction, so that it can achieve the original color of the fabric itself, and the other is to improve the whiteness and brightness of the white fabric and the colored fabric, so that its color is more bright and gorgeous.
Fabrics (such as towels, sheets, tablecloths, etc.) in the washing process through washing, pre-washing and main washing process, in the case of reasonable program feeding, water-soluble dirt, oil-soluble dirt and some solid dirt and other general conditions can be removed. However, for some pigment dirt, special dirt that can only be removed by oxidation and reduction, conventional washing can not be completely removed, and bleaching procedures must be set in the washing process to achieve total removal of dirt.
The length of time in the bleaching process is related to the release time of the bleach. At the ideal bleaching temperature and the ideal pH of the lotion (pH 10.5), the bleach is basically evenly dissolved in the lotion when the bleach is added for one minute. At this time, the effective chlorine is released evenly, and the release of chlorine is basically complete in 6-8 minutes, and the concentration of effective chlorine in the solution is 10ppm. The available chlorine content should be less than 10ppm during drainage, so extending the bleaching time after the release of available chlorine is no longer effective.
In the bleaching process, the temperature is very important to the bleaching effect, in the bleaching process to choose oxygen bleaching or ammonia bleaching, according to the characteristics of the fabric and the color of the fabric to choose a reasonable use.
The temperature of bleaching is very important for chlorine bleaching. Increasing the temperature of bleaching liquid can improve the bleaching speed and shorten the bleaching time. Under normal circumstances, increasing the bleaching temperature by 10°C can shorten the bleaching time, such as the use of chlorine bleaching agent, the bleaching temperature is generally selected below 65°C, otherwise it will make the fabric yellow, fastness decline. If you use oxygen bleaching agent, you can choose 70°C~ 90%C
The pH value of the bleaching bath has a great influence on the fastness damage of the fabric. When the pH value of the bleaching bath is neutral 7, the damage to the fabric is more serious. Bleaching bath under acidic conditions bleaching speed is very fast, but the damage to the fiber is more serious, under normal circumstances is not recommended, the use of chlorine bleaching the best state pH value is about 10.2-10.5, in this case the bleaching speed is general, but the damage to the fiber is small, under normal circumstances can be the main washing and rinsing design at the same time, both to maintain the pH value and achieve bleaching effect.
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