Technology | What should we pay attention to when selecting additives? Ultra-comprehensive analysis!


1. Technical personnel must master the basic knowledge of auxiliaries.
This is the precondition for selecting proper additives. In order to make good use of auxiliaries, we must have a basic understanding of the basic concepts, basic structures, properties and characteristics of auxiliaries. If abnormal conditions are found, we can also analyze the reasons and deal with them in time. When using new additives, suppliers must inform the type of structure of the additives. For example, the softeners used belong to amino silicone oil softener, hydroxyl silicone oil softener, aliphatic amide softener, imidazoline softener, fatty acid paraffin softener, which kind of softener should be known by the application factory. Only in this way can we master its basic performance and prevent blind use.
2. Basic understanding of solubility of additives and their stability to hard water and metal ions
For example, the solubility of anionic surfactants in alkaline solution is greater than that in acidic solution, whereas that of cationic surfactants, amphoteric surfactants have both anionic and cationic characteristics, while non-ionic surfactants have less influence. The solubility of the first three surfactants increases with the increase of temperature, while the solubility of non-ionic surfactants decreases with the increase of temperature. Therefore, there is a cloud point, which must be higher than the use temperature, otherwise its efficiency will be lost and the role of assistants will not be played. The cloud point increases with the increase of EO number. It increases with the amount of anionic additives added. However, it decreased with the increase of electrolyte content. If leveling agent or dispersant is used in high temperature and high pressure dyeing, it will fold out in dyeing solution because the temperature is much higher than its cloud point (usually about 75 C). On the contrary, it will agglomerate dyes and cause color points. Silicone defoamer is a kind of emulsion made of methyl silicone oil or ethyl silicone oil emulsified with non-ionic surfactant and white carbon black. If the emulsifier of low cloud point is used, the same problems will appear, and auxiliary factories often do not pay attention to this problem, which will cause great harm to printing and dyeing factories.
3. The acid and alkali resistance of additives must be determined.
It is convenient to know whether the additives can meet the technological requirements. There are great differences in acid and alkali resistance of additives. Anionic surfactants are generally alkali and acid resistant, among which phosphate esters are the best, while carboxylic acids are the worst. Cationic surfactants are generally acid and alkali resistant. Non-ionic surfactants can resist weak alkali and weak acid, but not strong acid and strong alkali. Printing and dyeing factories must first test the presence of turbidity or precipitation in the use of additives according to technological requirements. One factory used imported additives to scour and bleach the underwater tracked track. At first, no problems were found, then wrinkles continued to appear, and irregular color dots were scattered on the distribution surface after dyeing. Open the box and see that the thickness of knots on the guide roll was not. The same solids were originally precipitates deposited by additives which were not alkali-resistant. When they were adhered to the cloth, they formed colour spots during dyeing. Therefore, the alkali and acid resistance of the additives must be determined. This should be paid more attention in cold pad batch scouring and bleaching.
4. The ionicity of auxiliaries must be mastered
There are four kinds of auxiliaries: anion, cation and non-ion, and amphoteric. The first three kinds of auxiliaries are commonly used. Anions can not be used in the same bath with cationic auxiliaries. When they are together, they will form flocculent precipitation, not only will they not play a role, but also will form defects. This ion can be used in the same bath with cationic or anionic auxiliaries. These principles are well known to all, but they are often unconsciously ignored in actual production. For example, fixing agents are cationic and cannot meet anionic auxiliaries. But many factories use anionic soaping agents to wash after dyeing with direct, acidic and reactive dyes, and then fix fixing agents without washing them. At this time, the fixing agent is bound with the lotion on the cloth, which not only wastes the fixing agent to reduce its fixing effect, but also affects the soaping and abrasion fastness of the dyes due to the precipitates of the soaping agent and fixing agent.
5. Don't reduce the dosage of auxiliaries at will
The components of printing and dyeing auxiliaries can be roughly divided into two categories: functional auxiliaries and auxiliaries of surfactant complexes. The former uses different compounds to play a functional role in processing, such as oxygen bleaching stabilizer, fixing agent, color fixing agent, defoamer, softener, green agent, water and oil repellent finishing agent, flame retardant, crease repellent finishing agent, etc. They can achieve the desired effect only when a certain amount of them is used. The other is that surfactants are used as auxiliaries for printing and dyeing, such as penetrating agent, detergent, leveling agent, scouring agent, foaming agent, dispersant, emulsifier, etc. Their effects are in fact to play the role of wetting, emulsifying, dispersing and solubilizing of surfactants, which is the specific manifestation of their comprehensive or single effects. Now, the theory of surfactant is completely in line with the theory of surfactant, so we need to learn the knowledge of surfactant. Surfactant can form micelles in the solution. The concentration of micelles is called cumulative micelle concentration, referred to as C.M.C. The number of micelles whose concentration exceeds C.M.C increases and the micelles become larger. The wetting effect of surfactants can occur below C.M.C. The emulsifying, solubilizing, dispersing and cleaning effects of micelles are all in effect. Therefore, it must be above C.M.C. in order to be effective. In general, the C.M.C value of pure surfactants is not more than 0.2g/L, while the amount of surfactants in most commodities is only 15-20%, and the total solid content is 40%, so the C.M.C of precipitated commodities is not more than 1g/L. In other words, when the concentration of additives is at least more than 0.5g/L, micelles begin to form, which is large. At this concentration, the amount of micelles increases, and the effect is remarkable. Therefore, the amount of additives can not be reduced at will, especially the cheap detergents sold in the market. The effective ingredients are only 5% in competition, a large number of them are sodium bicarbonate powder and so on. The washing effect can not be achieved with less use. The amount of soap used in soaping fastness test according to the national standard and ISO standard is 3 g./ That's the truth. The wetting penetration is not a function of micelles, but of monomolecular surfactants, so it can be below C.M.C. and the concentration of the processing fluid does not need to exceed 1g/L.
6. Auxiliaries must be dissolved and diluted before being added to the processing fluid.
Because of the different proportion of raw materials and the different solubility, the compounded additives often form different components in the upper and lower layers in the commercial additives solution, which will affect the effect. After a long storage time or when the weather is cold, turbidity or even stratification will be formed due to the change of solubility. As long as it is not emulsion, this phenomenon can be allowed. But before using the material, it must be strict with the operator to stir the mixture first, then weigh it. If it is emulsion, it will not allow turbidity and stratification. This indicates that the emulsion has been demulsified and can no longer be used or must be emulsified by rapid agitation. The centrifuge test shows that it can be used when it is still in use and must not be used by hand stirring.
Solid auxiliaries should be dissolved in hot water and used thoroughly. Liquid auxiliaries must be diluted with warm water before they are used. Auxiliaries with high viscosity must be diluted gradually by adding water slowly in stirring conditions. Auxiliaries that are easy to mildew, such as fat softeners and slurries, can be skimmed from the upper layer as long as they are not diluted and there are few mildew spots. Use, thinner, return.
Dissolved and diluted auxiliaries should be added to the treatment bath according to the technological requirements. Generally, before the fabric enters the treatment bath, they are added to the treatment solution, and then introduced into the fabric after the solution is circulated uniformly. If leveling agent is added, the fabric runs in leveling agent for several minutes before the dyeing solution is added.
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