Training And Bleaching of Cotton Knitted Fabrics

1、 Co organisms of cotton fibers

1. The purpose of bleaching is to remove various harmful impurities from the fabric, in order to facilitate smooth dyeing and finishing processes and improve its wearability.

2. Symbiotic: A small amount of impurities contained in cotton fibers.

2.1 Fruit gum: It has a significant impact on the wetting properties of fibers, has strong anti dyeing properties, and is prone to yellowing when made into special white cloth. (Hot alkali or high-temperature acid washing)

2.2 Nitrogen containing substances: In actual production, about 50% of nitrogen containing substances can be removed by treating with 100 ℃ hot water. If a dilute alkali solution is used for steaming, 90% of nitrogen containing substances can be removed

2.3 Wax like substances: Wax like substances left on fibers will affect their water absorption, but retaining a portion of the wax like substances is beneficial as it can make the fabric shiny and soft to the touch, especially for preventing needle holes when sewing knitted fabrics.

2.4 Ash content: generally composed of different inorganic salts

2.5 Pigments: Colored substances in cotton fibers

2.6 Lignin: Lignin contained in cottonseed hulls.

2、 Refining and bleaching of cotton knitted fabrics

1. There are two types of refined equipment: one is the atmospheric pressure cloth boiling pot and the high-pressure cloth boiling pot; Another type is continuous steam refining machine.

2. Bleach: The purpose of bleaching is to remove pigments and give fabrics the necessary whiteness, but to avoid significant loss of fibers.

3. Process conditions for sodium hypochlorite bleaching

3.1 The pH value of the bleaching solution is 9-11 of the actual pH value in production

3.2 Temperature of bleaching solution: above 35 ℃.

3.3 Concentration of bleaching solution: Increasing the concentration can improve the whiteness of the fabric, but once the concentration reaches a certain level, the whiteness does not increase significantly. On the contrary, the damage to the fibers is exacerbated.

3、 Whitening of cotton knitted fabrics

1. Upper Blue: The blue dye substance applied to the fabric can absorb the yellow color of the fabric and fade it, making the whiteness of the fabric appear whiter.

2. Fluorescent whitening agent whitening: Fluorescent whitening agent is a colorless dye that can absorb ultraviolet light and emit blue fluorescence. VBL

4、 Waxing of cotton knitted fabrics

1. The purpose of waxing is to soften the fabric without creating "needle holes" during sewing.

2. The requirements for softeners are colorless, odorless, non-toxic, non corrosive, easily soluble in water, and have no discoloration on the treated fabric, while not affecting the strength of the fibers. Paraffin emulsion. Example: Softener CY-4415.

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