These problems exist in 90% of printing and dyeing factories:
Dyeing and finishing definition dyeing and finishing is a modern printing and dyeing technology, which is a scientific definition after chemical finishing into the printing and dyeing industry. Including the general name of bleaching, dyeing, printing, finishing, washing, etc. Dyeing and finishing synergistic spinning, weaving and knitting production are combined to form the whole process of fabric production and processing.
The importance of dyeing and finishing determines the quality and quality of textiles. Dyeing and finishing is the key technology in the industry chain to drive the grades of fiber, spinning, weaving, clothing and home textiles, and the added value.
Dyeing and finishing products not only reflect the technical problems of dyeing and finishing, but also reflect the comprehensive problems of fiber raw materials, spinning, weaving, dyeing materials and additives. The advantages and disadvantages of dyeing and finishing products are not only the comprehensive expression of the technical level, production level, management level and equipment level of the dyeing factory, but also the comprehensive expression of the quality of the upstream grey cloth and yarn, and the quality of the intermediate dyeing materials and additives.
It is the general name for singeing, scouring and bleaching before dyeing and bleaching. It is also a general term for the processing of desizing, scouring, bleaching and mercerizing. The purpose of bleaching is to apply chemical and physical mechanical action to remove impurities, oil stains and stains on the yarn and fabric, making it white and soft, with good hair effect and uniform permeability. Provides qualified pre-processed semi-finished products for dyeing, printing, and finishing.
Practicing bleaching is a colorless treatment and is not taken seriously. In fact, more than 60% of the quality problems of dyed products come from pre-treatment. The quality of dyeing and finishing products is related to various factors, such as the quality of the grey cloth, the condition of the equipment, the process technology, the implementation status, the operation status, whether the dye is correct, the quality of the dyeing materials and additives, and so on.
Pre-processing FAQ
1. The whiteness is not good and the gross effect is not good.
(1) Poor whiteness: mainly manifested in insufficient whiteness, unevenness, impureness, and opacity.
(2) Causes: First, the rough cloth is seriously stained and the impurities are oily. The quality of the oil used in the loom cannot be removed by emulsification. The amount of degreaser used during bleaching is not enough. Second, the amount or concentration of hydrogen peroxide is not enough, the pH value of the working fluid is improperly controlled, the oxygen bleaching temperature is too low, the decomposition time is not enough, the amount of the hydrogen peroxide stabilizer is too large, or the stabilizer storage time is too long to fail. The third is the addition of caustic soda or soda ash, not only to provide the pH required for the decomposition of hydrogen peroxide, but also to key substances in combination with emulsifiers and refining agents to remove impurities. Insufficient dosage will affect the whiteness, the miscellaneous, the poor hair, the unevenness, and the rough feel.
2. Solution (1) Ensure the best ratio of hydrogen peroxide and alkaline agent.
(2) Select a high-quality refining agent with a comprehensive effect of cleansing, emulsifying, dispersing, infiltrating, and anti-sticking.
(3) Select high-quality hydrogen peroxide stabilizer and chelating dispersant to control the decomposition rate of hydrogen peroxide, adsorb iron and other metal ions in the working fluid, prevent the decomposition of hydrogen peroxide and the fabric brittleness and holes caused by iron ions. , strong decline, weight loss and so on.
3. Stressed measures
(1) The main reason for the uncleanness of cottonseed hulls and impurities is that the time for caustic soda to swell the cottonseed hull, the boiling temperature, the amount of alkali agent and the amount of refining agent are not enough.
(2) When the cottonseed hull is severe, the addition of sodium bisulfite (NaHS03) helps to remove impurities and cottonseed hulls.
(3) The reason for the hole and the strength drop is not only the singeing hole, the weaving, the repairing and repairing of the hole, but also the reason for the broken hole. The main reason for the hole generated during the bleaching is that the working fluid or the cloth has Iron ions, copper ions, magnesium ions, and the like. As we all know, metal ions are catalysts for hydrogen peroxide, which can promote the rapid decomposition of hydrogen peroxide in the surface of the fabric, resulting in local fiber brittleness, strong decline or formation of holes. Secondly, the fabric with alkali or with acid (de-alkali or deacidification) storage time is too long, water loss and air drying, the occurrence of macula is also the cause of brittle damage.
4. Mistakes in the selection of additives (1) Some operators lack basic basic chemical knowledge, and do not understand the effects of penetrants, emulsifiers, detergents, stabilizers, complexing agents, and chelating agents.
(2) The hydrophilicity and lipophilicity of the surfactant are not known.
(3) Do not know which are cationic, anionic or nonionic additives.
(4) Workers are afraid of problems, and mistakenly adopt a more beneficial method. It is believed that the more varieties and dosages of additives added to the working fluid, the better, which causes the ionic additives to react with each other and cancel each other. On fabric or yarn.
(5) On-site management is not strict. Because it is colorless, the amount of additives added during operation is very random and random. Holding an indifferent attitude not only causes unnecessary waste, but also causes a large amount of surfactant, foam, and washing. The unclean night remains on the cloth.
Mercerizing problems and the choice of auxiliaries are pure cotton, hemp or its blended, interwoven fabrics, or their yarns, padded in high concentration caustic soda, at room temperature or temperature below 40 °C tension, for a certain period of time, then Washed with hot water, washed with water, neutralized with acid to obtain a permanent gloss. The mercerized product is stable in size, enhances the absorption capacity of the dye, and has a bright color and a long-lasting gloss after dyeing, which increases the added value of the product.
1. The problem of poor mercerizing effect
(1) The gloss is not good because the alkali concentration is not enough, the mercerizing penetrant is not good or the amount is insufficient, and the expansion tension is insufficient.
(2) The mercerizing fabric is slanted because the grey fabric is skewed when it is sewn and the fabric is inclined when it is fed.
(3) Mercerized scratches are caused by improper operation. Check the equipment for the gusset, guide roller, needle plate and fabric for burr scratching or rubbing.
(4) Folding, the reason is that the amount of water is insufficient when the spray is washed, and the friction coefficient between the mercerized cloth and the spreader is increased.
(5) The mercerized fabric feels rough and hard, because the residual alkali concentration in the washing tank is high, the washing temperature is too high, and the pH value is more than ≥8 when the temperature is dropped or dropped.
2. Solution
(1) According to the process requirements, adjust the concentration of mercerized alkali, use special penetrating agent for mercerizing, and adjust the size and tension of the expanded gusset.
(2) The seams must be flush and flush.
(3) Ensure the integrity of the equipment and avoid abrasion on the fabric.
(4) Check if the spray hole is blocked, ensure the water pressure and water volume of the spray hole, and clean the debris in the working fluid tank in time.
3. Stressed measures
(1) During the production process, the alkali concentration of the washing tank must be checked frequently to prevent the concentration of concentrated alkali from being introduced. (2) When picking up the cloth during pickling, it is necessary to check the PH value of the cloth surface in batches. It should be weakly acidic to prevent alkali precipitation during storage and form alkali spots and chloasma.
4. Mistakes in the selection of additives
(1) The penetrants and auxiliaries used in mercerizing are the same as those used in boiling and bleaching.
(2) Attention must be paid to the use of special mercerizing penetrants, dispersants and other additives that have good alkali resistance.
Dyeing problems and selection of additives
1. Poor dyeing effect
(1) The color fastness is unsatisfactory because the selected dye, dyeing agent, leveling agent, chelating agent, and fixing agent are not suitable.
(2) Chromatic color flower, because the selected dye combination is not good, the formula is unreasonable, the dyeing time is not enough, and the pH value of the dye and the regulating working fluid is unstable.
(3) The jump light and the left-right color difference are due to poor compatibility of the dye chromophore group, mismatch of hue, and abnormal operation of the equipment.
(4) Color points, color blocks, color stains and stains, because the dye solubility is not good, the dye particles are too large to produce coagulation, the additives are not good, the equipment is not clean, the contaminated tar falls, boiled and bleached The semi-product has poor hair effect, uneven working fluid, and high water quality. The added additives cause the dye to agglomerate, the auxiliary foam is too much, and the dye forms a coated colored foam, which forms a color point and halo after being broken.
(5) Uneven color, the reason is that the yarn is not dry well, the surface finish is poor, and the impurities are not cleaned before cooking and bleaching, resulting in uneven dyeing.
(6) Dyeing is not deeply dyed, the selected dyes are not enough, the amount of dyes is not enough, and the pretreatment fabrics are covered with impurities or oil stains.
2. Solution
(1) Color fastness mainly includes soap fastness, washing fastness, dry and wet rubbing fastness, light fastness fastness, light fastness, chlorine fastness (or salt fastness) , color fastness, perspiration fastness, sublimation fastness, ironing fastness and special seawater fastness, UV fastness, salic fastness, etc. These fastness are key to dye structure and performance . Therefore, the choice of dye is very important, followed by the application of dyeing process, technical parameters and additives.
(2) When selecting dyes, attention must be paid to the compatibility, solubility, directness of dyes, ease of aggregation of dye molecules, sensitivity to temperature and pH, and requirements for water quality.
(3) Pay attention to the flatness of the cloth surface, the uniformity of the hair effect and whiteness, the degree of cleanliness of removing impurities and removing stains.
(4) If the chemical method is proper, be sure to dry the cloth evenly, first add the auxiliary agent and then add the dye solution.
(5) Check the integrity of the equipment at any time, and the equipment must not be “sick†to work and operate.
(6) The poor quality of dyeing is also an important problem that causes dyes to combine with metal ions or agglomerates with impurities, resulting in color, light color, uneven color, color mismatch, and poor reproducibility. Therefore, water resources are guaranteed to be dyed successfully. The essential.
3. Stressed measures
(1) There are many dyeing aids currently dyed, and dyeing is the most important process in all dyeing factories. However, the more important it is, the place that is most prone to problems, the more additives and varieties that are not added during the dyeing process.
(2) Some companies only believe in the commonly used JFC penetrant, and apply it to all products as a universal additive. It does not take into account that the cloud point (cloud point) of JFC is only 38-42 ° C, and its penetration will exceed 43 ° C. Loss of effect causes quality problems.
(3) Habitually, a leveling agent is used on all cotton, wool, hemp, silk, and chemical fiber. It is not known that all fiber properties are different, and suitable leveling agents are also different.
(4) The main cause of wrinkles and fuzzing is equipment problems, large loading, too small bath ratio or operational problems. When the amount of cloth is too large, it is easy to cause the pressure, tension and friction between the cloth and the cloth to increase, and the pump pressure and the pump are more difficult to lift the fabric, which affects the flatness of the cloth surface and causes wrinkles and cloth fluffing.
(5) The relationship between wind printing and additives is not big. The key is the acid and alkali resistance of the dye itself, the acidity and alkalinity of the semi-product fabric, the air humidity of the workshop and the sour gas. For example, active Cuilan KN-G and Brilliant Orange X-GN are sensitive to acid and alkali, and the yellow RGFL is sensitive to alkali and is also prone to windprint.
(6) Dye selection must take into account the dual effects of dispersion and solubilization, osmosis and complexation of metal ions in water, pH adaptability, foaming, etc., which have an impact on the dye uptake rate.
(7) It must be emphasized that the normal dry rubbing fastness is better than the wet rubbing fastness. When we encounter wet rubbing fastness and the dry rubbing fastness is unqualified, we must first check whether the temperature is too high when drying and high temperature setting. It can be said that some dye sublimation or high temperature dye molecules are destroyed. In particular, disperse dyes sublimate dyes under high temperature conditions, resulting in low dry rubbing fastness and common problems such as color matching between color-dyed fabrics/
4. Mistakes in the selection of additives
(1) Some dyeing and finishing plants are worried about color flowers, and will not be considered for similar compatibility, but will be penetrant, leveling agent, chelating dispersant, anti-smudge agent, pH control agent, lubricating anti-wrinkle agent, soft in bath. Agents, bath treasures, etc. are all added to the working fluid, resulting in "mutual killing" reaction between various additives, internal consumption and functionality.
(2) Levelling agent works well for improving color and color points. However, it should be known that it is also a retarding agent. It also has the function of dyeing and preventing dye dyeing while leveling, and the amount of addition is less than the leveling effect. Dyeing the dyeing seat, but not dyed deep color.
(3) The diffusing agent N is a commonly used dispersing agent, however, its anti-dye cohesion is greatly reduced at high temperatures.
(4) When the selected nonionic surfactant is not suitable, the nonionic surfactant above itself is precipitated or decomposed above the cloud point, and the dye is adsorbed to the tar-like substance to adhere to the fabric or equipment, causing quality problems.
(5) The quality of the chelating dispersant also affects the leveling problem. Companies with good water quality do not necessarily add chelating agents.
(6) The pH of the working fluid is often not taken seriously, and there is no actual measurement and monitoring during dyeing. Substituted acid substitute bases are used to provide a pH-like, better dye-assisted, like buffer. In fact, the market is extremely confusing because there is no uniform product standard. It is recommended that when the ingredients are not known, it is better to use the suitable glacial acetic acid or organic acid directly. Never use the substitute acid of H2S04 and HCI inorganic strong acid.
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