1. Technical personnel must master the basic knowledge of additives
This is a good choice Prerequisites for additives. To make good use of additives, you must have a basic understanding of the basic concepts, basic structure, performance, and usage characteristics of additives. If an abnormality is discovered, you can also analyze the cause and handle it in time.
When each factory uses a new additive, the supplier must inform the structural category of the additive. For example, the softener applied is an amino silicone oil softness or a hydroxy silicone oil. The application factory should know which type of softener, fatty amide softener, imidazoline softener, and fatty acid paraffin softener. Only in this way can we master its basic performance and prevent blind use.
2. Have a basic understanding of the solubility properties of additives and their stability to hard water and metal ions
For example, anionic surfactants in alkali The solubility in acid is greater than that in acid, and vice versa for cationic surfactants. Ampholytic surfactants have both anionic and cationic characteristics, while nonionic surfactants have less influence.
The solubility of the first three surfactants increases when the temperature rises, while the solubility of the non-ionic surfactant decreases as the temperature rises, so a cloud point appears, and the cloud point must be higher than the one used. temperature, otherwise it will lose its efficiency and will not be able to play its role as an additive. The cloud point increases with increasing EO number. Increases with the amount of anionic additive incorporated. But it decreases as the electrolyte content increases. If Pingpingjia is used as a leveling agent or dispersant in high-temperature and high-pressure dyeing, the use temperature will greatly exceed its cloud point (usually around 75°C), which will cause it to fold out in the dye liquor. Not only will it not work, but it will condense the dye. And cause color spots. Silicone defoaming agent is an emulsion made of methyl silicone oil or ethyl silicone oil emulsified with nonionic surfactant and white carbon black. If an emulsifier with a low cloud point is used, the same problems as above will occur, and the additive factory This problem is often not paid attention to, which causes great harm to the printing and dyeing factory.
3. The acid and alkali resistance of the additives must be measured
This makes it easier to understand whether the additives can meet the needs of the process. The acid and alkali resistance of additives vary greatly. Anionic surfactants are generally resistant to alkali but not acid. Among them, phosphate esters have the best alkali resistance, while carboxylic acids have the worst acid resistance.
Cationic surfactants are generally acid-resistant but not alkali-resistant. Nonionic surfactants can withstand weak bases and weak acids, but cannot withstand strong acids and alkalis.
Printing and dyeing factories must first test whether the additives used will cause turbidity or precipitation when used according to process requirements. One factory used imported additives for underwater track bleaching. No problems were found at first, but then they continued to appear. Wrinkles and irregular color spots scattered on the cloth surface after dyeing. Open the box and see that there are solid substances with different thicknesses on the guide roller. It turns out that the additives are not resistant to alkali and are deposited. If they stick to the cloth, they will be dyed. Color dots are formed. Therefore, the alkali and acid resistance of additives must be measured. This should be paid more attention to during cold rolling, stacking and bleaching.
4. The ionicity of additives must be mastered
There are four types of additives: anionic, cationic, nonionic, and amphoteric. The first three are commonly used. Kindly, anions cannot be used in the same bath as cationic additives. When they are together, they will form a flocculent precipitate. Not only will they not work, but they will also cause dye defects. This ion can be used in the same bath as cationic or anionic additives. Everyone knows these principles, but they are often unconsciously ignored in actual production. For example, fixing agents are cationic and cannot meet anionic additives. However, many factories use direct, acidic, and reactive dyes when washing after dyeing. Soaping with an anionic soaping agent, but then without washing the lotion, the color-fixing agent is used to fix the color. At this time, the color-fixing agent is completely combined with the lotion on the cloth, which not only wastes the color-fixing agent and reduces its fixation The color effect is also affected by the precipitates of soaping agent and color-fixing agent that affect the soaping and rubbing fastness of the dye.
5. Do not reduce the dosage of auxiliaries arbitrarily
The components of printing and dyeing auxiliaries can be roughly divided into two categories, namely Additive for functional additives and surfactant compounds. The former uses different compounds to play a functional role during processing, such as: oxygen bleach stabilizer, color fixing agent, color correction agent, defoaming agent, softener, green agent, water-repellent and oil-repellent finishing agent, flame retardant, Anti-wrinkle finishing agents, etc., they can only achieve the desired effect when used in a certain amount.
The other type is surfactants used as printing and dyeing auxiliaries, such as penetrating agents, cleaning agents, leveling agents, scouring agents, foaming agents, dispersants, emulsifiers, etc. Their effects are practical. The above is to exert the wetting, emulsifying, dispersing, solubilizing and other functions of surfactants. It is the comprehensive effect of its functions or the specific manifestation of a single effect. Therefore, it is completely consistent with the theory of surfactants, and therefore it is necessary to learn the functions of surfactants. Knowledge. Surfactants will form micelles in the solution, and the concentration at which micelles appear is called the critical micelle concentration, or c.m.c. The number of micelles with a concentration exceeding c.m.c increases and the micelles become larger. The wetting effect of surfactants can occur below the c.m.c concentration, and emulsification, solubilization, dispersion, and cleaning are all performed by micelles, so it must It can only be effective if it is c.m.c or above. Generally, the c.m.c value of pure surfactants does not exceed 0.2g/L, and most products contain surfactant activity.The amount of ? L begins to produce micelles. When the concentration is greater than this, the amount of micelles increases and the effect is significant. Therefore, the dosage of additives cannot be reduced at will, especially the cheap detergents on the market, which have only 5% active ingredients. , a large amount of Yuan Ming powder, etc., if used too little, the washing effect will not be achieved at all. This is the reason why the dosage of soap is 3g/L when doing soaping fastness tests according to national and ISO standards. Wetting and penetration is not played by micelles but by single-molecule surfactants, so it can be below c.m.c., and the concentration in the processing fluid does not need to exceed 1g/L.
6. The additives must be dissolved and diluted before being added to the processing fluid
Due to the different specific gravity of the raw materials, the solubility of the compound additives varies. In commercial additive liquids, the upper and lower layers often have different compositions, which affects the effect. After long storage time or in cold weather, turbidity or even stratification may form due to changes in solubility. As long as it is not an emulsion, this phenomenon is still allowed. , but when weighing materials before use, the operator must be strictly required to stir evenly before weighing the materials. If it is an emulsion, turbidity and stratification are not allowed. This means that the emulsion has been demulsified and cannot be used again, or it must be re-emulsified by rapid stirring. It can only be used after it is proved to be usable by high-speed centrifugal separation tests. It must not be used by manual stirring.
Solid additives must be dissolved in hot water before use. Liquid additives must be diluted with warm water before use. Additives with high viscosity must be slowly diluted with water while stirring, as they are prone to mildew. As long as the additives, such as fatty softeners and slurries have not become thinned and there are not many mold spots, the upper layer can be skimmed off and the additives below can still be used. If they become thinner, return them.
When adding the dissolved and diluted additives to the treatment bath, it should be determined according to the process requirements. Generally, it is added to the treatment solution before the fabric enters the treatment bath, and then introduced after the solution is circulated to make it uniform. For fabrics, if it is a leveling agent, before adding the dyeing liquid, the fabric should be run in the leveling agent for a few minutes before adding the dyeing liquid. </p
