Why can't we dye cotton first and then polyester?

Because cotton and polyester have different dyeing activities. Light cotton can only be dyed with reactive dyes, and polyester does not need to be dyed. Dark colors require both fibers to be dyed. This method can be one-liquid dyeing or two-liquid dyeing of polyester first and then cotton, and vice versa. The dyeing process includes pad dyeing and hot air high temperature fixation or steaming fixation after dip dyeing.

Relevant data of cotton dyeing

A method for dyeing cotton with food pigment at low temperature includes the following steps: dissolving food pigment and carboxymethyl chitosan in deionized water, adjusting the solution value to 5-6 with sodium hydroxide, heating to 50-60 degrees, adding laccase, and uniformly stirring to obtain cotton dyeing solution, wherein the dyeing bath ratio is 30:1-1.

Adde cotton, reacting for 4-5 hour, washing, and drying to obtain cotton dyed with edible pigment by enzyme. Compared with the traditional dyeing process, the patented technology reduces the use of chemical additives, uses environmental-friendly additives, reduces the cost, and the dyeing temperature is 50-60 degrees, greatly reducing the energy consumption.

The food pigments used in the patented technology of the present invention are natural food pigments, such as tea polyphenols extracted from tea leaves, or synthetic food pigments, such as carmine, brilliant blue and lemon yellow. The edible pigments used are all green, safe, harmless, energy-saving and environment-friendly.