The quality of water not only has a great influence on the product quality of pretreatment and other processes, but also affects the consumption of dyeing and chemical materials and auxiliaries. In textile printing and dyeing industry, sodium hexametaphosphate is a good softener, which makes the dye or soap powder not precipitate or agglomerate.

The standard for distinguishing soft water from hard water is as follows: soft water 0-57ppm, slightly hard water 57-100ppm, hard water 100-280ppm, extremely hard water > 280ppm. Calcium and magnesium salts in hard water are unfavorable to printing and dyeing. For example, they react with soap to form insoluble calcium and magnesium soap, precipitate on fabric, and form insoluble scale in alkaline solution, which is attached to pretreatment equipment (such as groove inner wall, valve and guide roller), hindering normal production.

When the amount of iron and manganese salts in the water exceeds the specified limit, rust spots and catalytic oxidation of cotton fibers will be produced during scouring. When bleaching with oxidant, iron and manganese salts also play the role of catalytic decomposition of bleaching agent, making cotton fiber brittle.

To remove calcium and magnesium salts from natural water is called softening of hard water. There are many ways to soften, and appropriate methods can be adopted according to the needs.

Generally, the water used for pretreatment, dyeing and washing after printing will use sodium hexametaphosphate to complexing the metal ions in the water. The PH value of sodium hexametaphosphate is close to neutral, which will not cause serious surface dyeing phenomenon and affect the product quality like using soda soft water. Sodium hexametaphosphate can form complex with calcium ion in hard water, and block up calcium, so as to achieve the purpose of soft water.

The addition of sodium hexametaphosphate can also prevent the combination of iron, calcium, magnesium and other metal ions in the washing, printing and dyeing processes, which will affect the dye performance and dyeing brightness, and prevent printing defects such as dye spots. Because of its blocking effect on metal ions in water, it can effectively prevent the re adhesion of silicon spots, plankton or pollutants, and enhance the color fastness.

The general dosage of sodium hexametaphosphate is 10 ppm of hard water, about 10 grams of sodium hexametaphosphate is used for every hundred liters. The sodium hexametaphosphate produced by Chongqing Chuandong Chemical Group is produced by thermal process phosphoric acid, which has better effect on textile printing and dyeing.