The applications of surfactants in textile processing are as follows.
1. Pre-treatment Auxiliaries
The scouring agent used in the scouring of pure acrylic fabrics is generally non-ionic detergent or anionic detergent.
If the size on the fabric is water-soluble chemical size such as polyvinyl alcohol, polyacrylic acid and carboxymethyl fiber, it will be removed in the scouring process. Starch size is desized with amylase.
Cationic additives are not as effective as nonionic or anionic additives in scouring and degreasing. However, the fabric has better hand feeling and luster, and is suitable for clean pure spinning acrylic fiber.
Acrylic fiber does not contain natural impurities and has good whiteness. If you want to further improve the whiteness and remove the impurities on the fabric, you can go through bleaching and fluorescent whitening treatment. Sodium chlorite is used as bleaching agent in bleaching, and it has desizing effect.
Dispersive fluorescent brighteners and cationic fluorescent brighteners are mainly used in fluorescent whitening of acrylic fiber.
Fluorescent whitening agent (FWA) is an optical whitening effect. It absorbs invisible ultraviolet rays in the daylight spectrum and reflects them as visible blue or violet-blue fluorescence. Thereby counteracting the yellowish tone on the acrylic fiber and ensuring that the acrylic fiber fabric has a good clean and white feeling. As the reflected light is enhanced, the brightness is also generally increased.
The affinity of cationic brighteners to acrylic fiber is large, the absorption rate is fast, and the migration is poor. Generally, the addition of levelling agents such as alkylaryl quaternary ammonium salts can slow down the absorption rate of cationic whitening agents, improve the migration of whitening agents, and achieve uniform whitening.
2. Dyeing Auxiliaries
Acrylic fiber dyeing needs more attention than cotton, wool and other chemical fibers. Especially with cationic dyes. Special dyeing auxiliaries mainly include cationic and anionic auxiliaries. Sometimes some inorganic salts and organic compounds can also be used as dyeing AIDS.
2.1 Cationic additives
It is an important levelling agent for acrylic fiber dyeing with cationic dyes. Some cationic auxiliaries can delay the dyeing of cationic dyes in the dyeing bath, also known as slow dyeing leveling agent.
The cationic auxiliaries used in acrylic fiber dyeing are alkyl quaternary ammonium salt, alkylaryl quaternary ammonium salt and alkyl amide quaternary ammonium salt. These three cationic levelling agents are mainly retarding agents, and have a certain effect of moving dyeing.
Some quaternary ammonium compounds as levelling agents mainly have the effect of moving dyeing, but the slow dyeing effect is weak. Some aryl or alkyl pyridine cationic compounds can also be used as levelling agents for acrylic fiber dyeing. Some cationic – non – ionic amphoteric AIDS can also be used as acrylic fiber dyeing levelling agent, such as octadecyl dimethyl polyvinyl oxide ammonium chloride.
Cationic levelling agents contain cationic groups, which have a relative affinity for acrylic fiber. When cationic levelling agent is present in the dyeing bath, competition between the levelling agent and dye will occur for dyeing position on the fiber. However, due to the low affinity of levelling agent to acrylic fiber, the position occupied by levelling agent can be partially replaced by cationic dye in boiling dyeing process. So as to achieve the purpose of slow dyeing.
2.2 Anionic additives
When acrylic is dyed with cationic and basic dyes, suitable anionic auxiliaries can be selected as leveling agents. Anion auxiliaries form complexes with dye cations in dyeing bath. At a certain temperature stage, this complex is similar to a disperse dye and is in a suspended state. Therefore, when using anionic additives, it is necessary to use non-ionic dispersants. This keeps the complex in a good suspension.
2.3 Non-ionic auxiliary
When acrylic fibers are dyed with cationic and basic dyes, only some non-ionic auxiliaries can be added. The nonionic additive mainly play that roles of diffusion, infiltration and clean. Generally, there is no retarding effect. Nonionic auxiliaries are suitable for acrylic fibers containing only weak acid groups with slow dyeing rate.
2.4 Some Organic and Inorganic Salts Dyeing AIDS
When acrylic fiber is dyed with cationic and basic dyes, some organic compounds and inorganic salts can be used as dyeing AIDS.
The following are commonly used.
1) Urea. It mainly plays the role of three aspects: dye co-solvent; Leveling agent; Ph regulator.
2) Sodium sulfate. Sodium sulfate can be used as a certain retarding agent. This is because the sodium ions delay the dyeing process by interacting with the acidic groups on the fiber, and the sulfate ions (may) interact with the cations of the dye.
3) Ammonium sulfate. Acrylic fiber dyeing is generally slow in low temperature area, fast in high temperature area, which is easy to cause dyeing failure, especially some dark colors, such as indigo. The addition of ammonium sulfate can alleviate the dyeing in high temperature area, which is beneficial to obtain uniform dyeing.
3. Printing auxiliaries
In order to get good effect of bleaching printing of acrylic fabric dyed with dispersive dyes, it is necessary to add bleaching agent. The whitening agent can increase the whiteness of the white printing by adding the whitening agent in the white drawing slurry.
When printing with cationic dyes, tartaric acid or citric acid is added to the printing pulp mainly to prevent in printing and drying, due to acetic acid volatilization, so that the pH value increases, resulting in some cationic dye damage discoloration. Because both are non-volatile organic acids with high melting point and high boiling point, the pH value of acrylic fabric can be kept in the acidic range after printing and steaming.
4. Finishing Aids
Anti-pilling finish of pure acrylic fabric. The finishing agent is acrylate copolymer emulsion and organic silicon. After the treated fabric is dried, the acrylate copolymer binds the fibers in the form of punctiform particles. Under the action of external force, the possibility that the fiber slips out to the surface of the fabric is reduced, so that the fuzzing and pilling property can be improved.
The organosilicon reagent forms a fine elastic film-like substance on the surface of the small particles and fibers of the acrylate copolymer, thereby improving the anti-pilling property.
The fuzzing and pilling properties of acrylic fabrics can also be obviously improved by treating with DMF. The softener used in the softening treatment of pure acrylic fabrics is generally cationic.