There are many reasons for the formation of white spots during dyeing, such as water spots in the dyeing base machine and water spots in the reduction steamer. If the water spots in these places are whiter, they appear in the front position, and if they are lighter, they occur in the back position; the water spots are rounder. The long water spots are produced in places with a small height difference in the distribution route or splashed on them. The long water spots are generated in places with a large height difference in the distribution route.
There are some white spots, such as woven bag strips rolled on the mercerizing machine, which will cause white spots when dyeing here. If there is cotton wool on the mercerizing machine, dark spots will form here when dyeing. Other causes of white spots include wax spots, alkali mud, rotten cotton spots, etc.
Fabric quality treatment
During production, if the quality of the gray fabric is good, the dyeing rate will be high, the dyeing depth will be good, and the cloth surface will be smooth, uniform and plump; if the quality of the gray fabric is poor, the dyeing white stars and fabric stripes will be serious. Therefore, when encountering gray fabrics containing dead cotton and a lot of impurities, it is necessary to strengthen the pre-treatment process. While ensuring the safety and reliability of production, the cotton impurities should be treated as cleanly as possible, and the dead cotton should be cooked thoroughly to improve the dye uptake rate and the quality of the dyed fabric products.
Many companies are now using cold pile pre-treatment of fabrics because of its energy saving. However, the effect of cold pile on removing cotton impurities and slurry is poor, and the fabric is relatively stiff, so it is easy to wrinkle during dyeing, and the cloth guide roller is easy to get dirty and cause stains. stains, so less viscous additives should be added during dyeing production, such as: anti-migration agent, whitening agent NT-2, etc.
Processing of thick fabrics such as polyester brushed fabrics and pure cotton
When producing thick fabrics such as polyester-cotton brushed fabrics or pure cotton, if the rinsing and cleaning effect is poor and the cotton wool is not cleaned properly, some fine cotton wool will stick to the cloth surface, which will be more difficult to remove after rolling and rolling. White spots form. Some dyed white spots are not obvious after using the machine, but if you rub the cloth surface with your hands in reverse, the cotton wool will fall off and many white spots will be exposed. There are also tiny lints stuck to the cloth surface that are very difficult to remove and difficult to detect even after continuous dyeing. However, when it is necessary to add anti-wrinkle, rainproof, cross-linking agents and other viscous additives during tentering, the lint will stick down and be exposed. White spots.
Therefore, the white spots caused by cotton wool should not be underestimated. When producing sanded products, attention should be paid to diligently cleaning the cotton wool in the sanding machine blower, exhaust fan, and bristle roller to prevent it from adhering to the cloth surface and making it difficult to wash off after being rolled by the cloth rolling machine. . If the cotton wool is still not clean after cleaning on both sides, you can brush it again with a bristle roller on the sanding machine, and then dye the cotton wool and it will be clean.
Poor quality fabric treatment
For fabrics with a lot of cotton and dead cotton, increasing the alkali concentration (220g/L) during mercerization can effectively improve the surface quality of colored fabrics and reduce white stars and fabric stains.
During the production process of sanded fabrics, you must pay attention to aurora marks, because once there are aurora marks, white spots will form during dyeing. Therefore, during mercerization and alkali washing after sanding, hard objects should not be stuck on the pads and cloth guide rollers. Frequent inspections are required. White spots with aurora prints found during dyeing should be treated first and then dyed.
When dyeing polyester-cotton brushed fabrics (disperse/reactive dye two-bath method), we have encountered that white spots were found during the production of disperse dyeing, but we did not pay enough attention to them. We waited until the white spots were very serious during the over-dyeing and then tried to deal with them. The only way to deal with the aurora print on brushed cloth is at the expense of the sanding effect of the brushed cloth. Use a higher alkali concentration and then mercerize, so that the rough texture of the cloth surface outside the aurora print is the same as that of the aurora print, so that the dyed white spots caused by the aurora print will no longer appear. .
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