How to choose a refining agent?

1. Refining agents

Refining agents are mainly divided into two categories:

(1) Used for cotton and linen textiles, their function is to assist caustic soda in removing symbiotic substances (pectin, wax, lignin, pigments, cottonseed shells, etc.) in cotton or linen fibers;

(2) Used for silk and tussah silk, their function is to remove sericin from silk fibers. The requirements and ingredients of these two types of refining agents are different and cannot be substituted for each other, but they are both made of a combination of multiple surfactants.

2. Refining agents must have the following properties:

(1) Ability to reduce the surface tension of the solution and the interfacial tension between the solution and the fabric, so that the refining solution can quickly wet the fabric;

(2) Ability to emulsify and disperse symbiotic substances (such as sericin, cotton wax, etc.) on the fabric;

(3) Ability to synthesize water-soluble complexes of metal ions such as calcium and magnesium and remove them from the fabric;

(4) Meet the requirements of environmentally friendly additives, with high safety, good biodegradability and low toxicity

The content of environmental hormones, heavy metal ions and formaldehyde must not exceed the standard. The symbiotic components of cellulose fibers, such as oil wax, pectin, lignin, pigment, cottonseed shell, etc., are mainly removed by boiling with caustic soda at high temperature. In order to reduce energy consumption and improve efficiency, a one-step boiling process, a one-step boiling and bleaching process, a one-step boiling and bleaching process, or a new low-temperature pre-treatment process such as cold rolling and stacking have been adopted. For this reason, a large number of matching refining agents have emerged.

3. Composition of refining agents

Refining agents are a combination of surfactants used for cooking and refining aids. Due to differences in equipment, processes, fabrics and fibers, their preparation methods are also very different. Surfactants are the main components that determine the performance of refining agents. The surfactants used in refining agents are mainly anionic surfactants and nonionic surfactants. The function of refining aids is to fully disperse the decomposed impurities and emulsified oil wax to prevent re-contamination. Refining aids include anti-fouling agents, chelating dispersants, foam suppressants and fiber protectors.

(1) Anionic surfactants

Anionic surfactants are composed of hydrophobic groups and hydrophilic groups, commonly known as lipophilic groups and hydrophilic groups. The influence of the hydrophilic group is greater than that of the hydrophobic group. The hydrophilic groups of the anionic surfactants commonly used in refining agents include carboxylates (RCOO·Na), sulfonates (RSO3·Na), sulfates (ROSO3·Na), phosphates [RO-(ONa)2], and fatty acid chloride and protein hydrolysis condensation products (RCONHR1COONa).

(2) Nonionic surfactants

The hydrophilic groups of nonionic surfactants used in refining agents are composed of a certain number of oxygen-containing groups (hydroxyl groups, polyoxyethylene chains). The types of hydrophobic groups in polyethylene glycol can be divided into: 

(1) fatty alcohol polyoxyethylene ether [R-O(CH2CH2O)nH], which has good emulsification, wetting, penetration, dispersion and solubilization capabilities;

 (2) alkylphenol polyoxyethylene ether [R-O(CH2CH2O)n] is highly toxic and has poor biodegradability, and is banned in printing and dyeing auxiliaries; 

(3) fatty acid polyoxyethylene ester [R-COO(CH2CH2O)nH] has good biodegradability and low foaming properties, and can be used as oil, antistatic agent, softener, etc.; 

(4) polyoxyethylene alkylamine [RNH(CH2CH2O)nH]; 

(5) polyoxyethylene alkylolamine [or RCONH(CH2CH2O)nH], which has strong foaming and foam stabilization effects, as well as good solubilization, cleaning and thickening effects.

 2. Auxiliary agents

The scouring power of the coagulant itself is very small or has no scouring effect at all, but adding it to the coagulant can significantly improve the scouring effect, reduce the amount of surfactant, or protect the fiber from damage. Coagulants have the following four functions: (1) chelating effect on metal ions; (2) alkaline buffering effect; (3) dispersing effect to prevent re-contamination of decomposition products; (4) preventing fiber brittleness. Common coagulant aids include sodium tripolyphosphate, sodium silicate, zeolite, chelating dispersant, fiber protectant, defoaming agent, sodium silicate powder, CMC, etc.

3. Pulping enzyme

Enzyme is a highly efficient and specific biocatalyst. Undyed and unfinished cotton fibers contain many natural impurities such as pectin, oil wax, nitrogen-containing substances, cottonseed hulls, pigments, etc., so pulping enzyme is a complex enzyme. The application of pulping enzyme...