In the eyes of auxiliary factories, printing and dyeing factories are “gods”. There are thousands of auxiliary factories in China today. In order to compete for the market, auxiliary factories use various means to deliver samples door-to-door and find ways to connect, causing problems in printing and dyeing factories. Sitting facing south, there are too many samples and there is no time to make them. The negative effect is that you develop a habit of sitting in a well and looking at the sky without seeking to explore. You are used to choosing additives from the ones that come to your door. Little do you know that the world is big and good additives emerge in endlessly, which is very helpful for improving product quality. A good stage.
The first condition for printing and dyeing companies to select additives must be to improve the quality of printed and dyed finished products as the main criterion.
Pay attention to several issues
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 any abnormality is found, you can also analyze the reasons. , handle it in time, and master the working principle, basic characteristics, structural classification, usage method, application detection method and precautions of this type of auxiliary. When using new printing and dyeing auxiliaries, the supplier must inform the structure of the auxiliary. Category, for example, the application factory should know which category of amino silicone oil softener, hydroxy silicone oil softener, fatty amide softener, imidazoline softener, and fatty acid paraffin softener the applied softener belongs to. 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, while 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, increases with the amount of anionic additives, but decreases with the increase of electrolyte content. If Pingping is added It is used as a leveling agent or dispersant in high-temperature and high-pressure dyeing. Because the use temperature greatly exceeds its cloud point (usually around 75~C), it will cause precipitation in the dye liquor. Not only does it not work, but it will condense the dye and cause color spots. .
Silicone defoamer is an emulsion 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 mentioned above will also 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. The problem was discovered, and wrinkles continued to appear. There were also irregular color spots scattered on the cloth surface after dyeing. When I opened the box, I found that there were solids with different thicknesses on the guide rollers. It turned out to be precipitates deposited by the additives that were not resistant to alkali. If it sticks to the cloth, it will form color spots when it is dyed.
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 ionicity 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 as cationic auxiliaries. They are together. When used, a flocculent precipitate will be formed, which will not only fail to work, but will also cause dyeing defects. Non-ionic additives can be used in the same bath as cationic or anionic additives.
Everyone knows these truths, but they are often unconsciously ignored in actual production. For example, color fixing agents are cationic and cannot meet anionic additives, but many factories use direct, acidic . Use anionic soaping agent when washing after dyeing with reactive dyes, but then use the fixing agent to fix the color without washing the detergent. At this time, the fixing agent is combined with the detergent on the cloth, which is not only wasted. Fixing agent will reduce the fixing effect, and the precipitate of soaping agent and fixing agent will affect the soaping and rubbing fastness of the dye.
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 perform functional functions during processing, such as: oxygen bleach stabilizers, color fixing agents, color correcting agents, defoaming agents, softeners, and color stripping agents.�Water-repellent, oil-repellent finishing agents, flame retardants, anti-wrinkle finishing agents, etc., 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, emulsifiers, etc. Their effects are practical. The above is to play the role of wetting, emulsifying, dispersing, solubilizing, etc. 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 surfactants. knowledge.
Surfactant will form micelles in the solution, and the concentration at which micelles appear is called the critical micelle concentration, or C for short. 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 less, the washing effect will not be achieved at all. National and ISO standards for soap making This is why the dosage of soap used in the wash 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 liquid
Due to different proportions and different solubilities of raw materials, compound auxiliaries often form upper and lower layers with different compositions in commercial auxiliary liquids. They are exactly the same, so as to affect the effect. After long storage time or in cold weather, turbidity or even stratification may be formed due to changes in solubility. As long as it is not an emulsion, this phenomenon is still allowed, but the operator must be strictly required to weigh the material before use. Stir evenly first, and then weigh the ingredients. If it is an emulsion, no turbidity or stratification is allowed. This means that the emulsion has been broken and cannot be used anymore, or it must be quickly stirred and then re-emulsified. This has been proven by high-speed centrifugal separation tests. Use only when still ready for use and never by hand mixing.
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 slowly 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 the dissolved and diluted printing and dyeing auxiliaries are added to the treatment bath, it must be determined according to the process requirements. Generally, it is added to the treatment solution before the fabric enters the treatment bath, and the solution is circulated to make it uniform. Then introduce the fabric into the fabric. If it is a leveling agent, before adding the dye solution, the fabric should run in the leveling agent solution for a few minutes and then add the dye solution. 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. Little do they know that the world is big and good auxiliaries 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, with the increasing level of informatization, it is easy to find what you need. sample. </p
