Introduction of optical brightening agents for textiles

There’re so many kinds of fluorescent brighteners for textiles, I’d like to introduce them from the textile types as follows:

1. Cellulose fiber

A linear polymer with more hydroxyl groups in the cellulose fiber molecule has better water solubility. For the whitening of cellulose fibers, anionic fluorescent whitening agents that are both water-soluble and direct to fibers are generally used. Their molecular weight is relatively large, and they all contain sulfonic acid groups, which are direct to fibers, but too high directness will lead to uneven whitening. In continuous processing (especially cloth or knitted fabric), low directivity is often used. Varieties; batch processing, often use fluorescent whitening agent varieties with medium or high directness; for fiber bleaching and whitening one-bath processing, it is also required to be resistant to chlorine bleaching and oxygen bleaching. VBL, 4BK, BA, BBU, MST, CXT, CBS-X are often used for cellulose fiber brightening.

2. Polyester and its blends

Polyester fiber has high crystallinity and is a kind of hydrophobic fiber. Non-ionic hydrophobic fluorescent whitening agent is required. Polyester dyeing is divided into high temperature (130 ° C), hot melt (180 ~ 210 ° C) and carrier method. In order to meet the requirements of heat resistance and diffusion, the generally applicable fluorescent whitening agents have small molecular weight and good heat resistance stability, and are distributed in various types of fluorescent whitening agents. Uvitex ERN, OB, OB-1, ER, EFR, EBL are commonly used.

3. Nylon fibre

Since nylon is a hydrophobic fiber, but also contains amino groups and carboxyl groups (end groups), in addition to the use of dispersed fluorescent whitening agents for whitening, fluorescent whitening agents for whitening protein fibers can also be used. Commercial fluorescent whitening agents for nylon can be divided into two categories according to ionic types: anionic (acid-resistant) type with water-soluble groups such as sulfonic acid groups and non-ionic dispersion type that is insoluble in water. Uvitex CF, Blankphor G/CC, Tinapol SWN/EF, Blankphor CA/DCB and Uvitex CF are commonly used.

4. Wool fiber

The wool itself is slightly yellow and must be bleached before it can be whitened. For even-colored wool products, in order to make the color bright, it is also necessary to use fluorescent whitening agents for brightening treatment. Whitening is generally carried out in an acid bath. Tinopal SWN/EF, Tinopal WG, CBS-X and NFW are commonly used.

5. Acrylic fiber

Because acrylic fiber is composed of 3 monomers, it is not only affected by the third monomer containing dye base, but also by the degree of polymerization, which brings certain complexity to the selection of fluorescent whitening agents. However, acrylic fiber itself has good whiteness and does not need bleaching before whitening. Therefore, the requirements for chlorine bleaching resistance and oxygen bleaching resistance of fluorescent whitening agents are relatively low. Generally speaking, most cationic fluorescent whitening agents are suitable, and some dispersed fluorescent whitening agents such as pyrazoline, coumarin, naphthalene Imides can also be used for whitening acrylic fibers.Because the acrylic dye base is an acidic group with negative charge, the whitening of acrylic fiber is mostly cationic fluorescent whitening agent. BAC, KCB, Blankphor ANB are commonly used.

6. Acetate fibre

Acetate cellulose has a very low swelling degree in water and has a strong negative charge. It cannot be whitened with a water-soluble anionic fluorescent whitening agent, and a non-ionic fluorescent whitening agent must be used for whitening. The whitening agent can be whitened by exhaustion in a neutral to weakly acidic bath at 60-80℃ or boiling temperature. DT, Tinopal PBS and AT are commonly used.