In the eyes of the auxiliary factory, the printing and dyeing factory is “God”! Today, there are thousands of auxiliary factories in China. In order to compete for the market, auxiliary factories use various means to deliver samples door-to-door and find connections! As a result, the printing and dyeing factory faces south, and there are too many samples to make. The negative effect is that you develop a habit of looking at the sky from a well, without seeking to explore, and are used to choosing additives from the ones that come to your door! As everyone knows, the world is huge and good additives are emerging in endlessly, providing a good stage for improving product quality.
The first condition for printing and dyeing enterprises to select additives must be to improve the quality of finished printing and dyeing products as the main criterion!
Note Several questions
1. Technical personnel must master the basic knowledge of auxiliaries, which is the prerequisite for selecting printing and dyeing auxiliaries.
To use auxiliaries well, you must have a basic understanding of the basic concepts, basic structure, performance, and usage characteristics of printing and dyeing auxiliaries. If an abnormal situation is found, the cause can also be analyzed, dealt with in time, and the working principle, basic characteristics, structural classification, usage method, application detection method and precautions of this type of additive can be mastered. When using new printing and dyeing auxiliaries, the supplier must inform the structural category of the auxiliary. For example, the softener applied is an amino silicone oil softener, a hydroxy silicone oil softener, a fatty amide softener, or an imidazoline softener. , which type of fatty acid paraffin softener the application factory should know. Only in this way can we master its basic performance and prevent blind use.
2. It is necessary to have a basic understanding of the solubility properties of additives and their stability to hard water and metal ions.
For example, the solubility of anionic surfactants in alkaline is greater than that in acid, and the opposite is true for cationic surfactants; amphoteric surfactants have the characteristics of both anions and cations. Non-ionic surfactants have less influence; the solubility of the first three surfactants increases when the temperature rises, while the solubility of non-ionic surfactants decreases as the temperature rises, so a cloud point appears, and the cloud point must be Higher than the use temperature, otherwise it will lose its efficiency and cannot play the role of the additive.
The cloud point increases with the increase of EO number and the amount of incorporated anionic additives, but decreases with the increase of electrolyte content. 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 precipitation in the dye liquor. Not only will it not work, but it will condense the dye and cause Causes color spots.
Silicon defoamer is an emulsion made of methyl silicone oil or ethyl silicone oil emulsified with nonionic surfactant and white carbon black. If emulsifiers with low cloud points are used, the same problems mentioned above will occur, and auxiliary factories often do not pay attention to this problem, which causes great harm to printing and dyeing factories.
3. The acid and alkali resistance of printing and dyeing auxiliaries must be measured to understand whether the auxiliaries 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 best resistance to alkali. The worst acid resistance. Cationic surfactants are generally resistant to acids but not alkali. 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 appear turbid or precipitated during use according to process requirements. One factory used imported additives for underwater crawler bleaching, and it did not start. problem found. Subsequently, wrinkles continued to appear, and irregular color spots appeared on the cloth surface after dyeing. When I opened the box, I found that there were solids of different thicknesses on the guide rollers. It turned out to be the precipitates deposited by the additives that were not resistant to alkali and stuck to the cloth. On the other hand, color spots are formed during dyeing.
So, the alkali and acid resistance of additives must be measured. This should be paid more attention to during cold rolling, stacking and bleaching. Many additives will be hydrolyzed in alkaline and acidic media, and their measurement methods are as follows.
4. The ionic properties of printing and dyeing auxiliaries must be mastered
There are four types of auxiliaries: anionic, cationic, nonionic, and amphoteric. The first three are commonly used. Anions cannot be used in the same bath with cationic additives. When they are together, they will form a flocculent precipitate. Not only will they not work, but they will also cause dyeing defects. Non-ionic additives can be used in the same bath with cationic or anionic additives.
Everyone knows these principles, but they are often unconsciously ignored in actual production. For example, color-fixing agents are cationic and cannot interact with anionic additives. However, many factories use anionic soaping agents when washing after direct, acidic, and reactive dyeing, but do not wash the detergent afterwards. The fixing agent fixes the color. At this time, the fixing agent is combined with the lotion on the cloth. Not only is the fixing agent wasted and the fixing effect is reduced, but the precipitates of the soaping agent and the fixing agent also affect the soaping of the dye.and friction fastness.
5. Do not reduce the dosage of printing and dyeing auxiliaries at will
The components of printing and dyeing auxiliaries can be roughly divided into two categories: functional auxiliaries and surfactant compound auxiliaries.
The former uses different compounds to play a functional role during processing, such as: oxygen bleach stabilizer, color fixing agent, color corrector, defoaming agent, softener, color stripping agent Agents, water-repellent and oil-repellent finishing agents, flame retardants, anti-wrinkle finishing agents, etc.; they can achieve the desired effect only 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, and emulsifiers. etc.; their effect is actually to play the role of wetting, emulsifying, dispersing, solubilizing, etc. of surfactants, which is the comprehensive effect of its functions or the specific manifestation of a single effect, so it is completely consistent with the theory of surfactants, and it is also So learn about surfactants.
Surfactant will form micelles in the solution, and the concentration at which micelles appear is called the critical micelle concentration, referred to as C. m. C. The concentration exceeds C. m. When C, the number of micelles increases and the micelles become larger. The wetting effect of surfactants can be found in C. m. Only C or above can be effective.
Generally pure surfactant C. m. The C value does not exceed 0.2g/L, and the amount of surfactant actives in most products is only 15-20%. Together with other auxiliary materials, the total solid content is 40%, so it is converted into a product with C. m. C probably does not exceed 1g/L. In other words, the additive concentration must exceed at least 0.5g/L before micelles begin to be produced. When the concentration is greater than this concentration, the amount of micelles increases and the effect is significant. Therefore, the additives The dosage cannot be reduced at will, especially the cheap detergents on the market, which have only 5% active ingredients, and a large amount of them are Yuanming powder, etc.; if you use too little, the cleaning effect will not be achieved at all. National and ISO standards do This is why the amount of soap used in the soaping fastness test is stipulated at 3g/L. Wetting and penetration is not done by micelles but by single-molecule surfactants, so it can be done in C. m. C or less, the concentration in the machining fluid does not need to exceed lg/L.
6. Printing and dyeing auxiliaries must first be dissolved and diluted before being added to the processing fluid
Due to different proportions of raw materials and different solubilities, compound auxiliaries are often found in commercial auxiliary solutions. The composition of the upper and lower layers is not exactly the same, which affects the effect. After long storage time or in cold weather, turbidity or even stratification may form due to changes in solubility. This phenomenon is still allowed as long as it is not an emulsion. However, 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 broken emulsification and cannot be used anymore, or it must be first Re-emulsify with rapid stirring. It can be used only after it has been proved by high-speed centrifugal separation test that it can still be used. It can never be used by manual stirring.
Solid printing and dyeing auxiliaries must be thoroughly dissolved with hot water before use. Liquid auxiliaries must be diluted with warm water before use. Additives with high viscosity must be gradually diluted with water while stirring. As long as the auxiliaries that are prone to mildew, such as fatty softeners and slurry, have not become thinned and there are not many mildew spots, the upper layer can be skimmed off, and the printing and dyeing auxiliaries below can still be used. If they become thinner, they will be returned.
When adding the dissolved and diluted printing and dyeing auxiliaries 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. The solution is circulated to make it uniform before being introduced into the fabric. If it is a leveling agent, the fabric is first run in the leveling agent solution before the dye solution is added. Add more dye solution after a few minutes. It is not uncommon for some factories to lack strict operating procedures and cause dyeing defects.
7. It is necessary to change passive selection to active selection
In the eyes of auxiliary manufacturers, printing and dyeing factories are “gods”. Printing and dyeing companies are accustomed to selecting auxiliaries from the auxiliaries that come to their doorsteps, but they do not know that the world The market is so big that good additives emerge in endlessly, providing a good stage for improving product quality. Therefore, printing and dyeing factories must change this situation and seek affordable, high-quality additives for their own selection. Today, as the level of informatization continues to increase, it is very It’s easy to find the samples you need.
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