â–¶The common quality problems of knitting dyeing and finishing products and the selection of additives

The quality of pre-treatment (practice bleaching) is not only related to the quality of the finished product of bleaching, but also as a semi-product, it will directly affect the quality of dyeing, printing and finishing. Some experts said that 70% of the quality problems of dyeing and finishing products are caused by poor pre-treatment, which has certain reasons. The quality of dyeing and finishing is related to the grey fabric, related to the equipment condition and operation, related to the process technology and execution, related to the dye, and related to the auxiliary. We focus on the influence of the additive.

1.1 Whiteness and poor hair efficiency

Poor whiteness, including whiteness is not pure, uneven and the hair effect is less than 8~10cm/30min. This is related to the quality of knitted fabrics. For example, low-grade cotton has many contents, and often whiteness and hairiness are not easy to do. Of course, most The key is the process development and the selection of additives.

In the process development:

1 H202 and NaOH must be sufficient

H202: not only plays the role of bleaching pigment after pre-treatment, but also has de-doping effect (including de-cotton seed shell), the amount of H202 is insufficient (including decomposition too fast), whiteness is impossible to guarantee, NaOH not only provides H202 bleaching Alkalinity (PH), and with the scouring agent, the maximum degumming effect, the amount of NaOH is insufficient, the impurity is poor, the gross effect can not meet the requirements first, of course, the whiteness can not meet the requirements, so the amount of H202 and NaOH It can be said that it is the primary factor to ensure whiteness and gross effect;

2 use high quality scouring agent

The comprehensive effects of scouring agent such as washing, emulsifying, dispersing and infiltration must be excellent to ensure the removal of impurities and whiteness and wool effect. However, the quality of scouring agents on the market is uneven. We must choose products with excellent comprehensive effects. Not only the permeability and solid content are measured, but the penetration is only one aspect considered; 3 oxygen bleach stabilizer and chelating dispersant

These two additives are mainly used to improve water quality, adsorb and complex metal ions such as Fe3+ in water, and prevent metal ions from catalyzing the rapid and inefficient decomposition of H202. If H202 decomposes rapidly, its whiteness and gross effect will not be achieved. Requirements, at the same time will cause the fabric to be brittle or even broken, so to achieve whiteness and gross effect, oxygen bleach stabilizer should choose excellent varieties, in the selection should focus on the decomposition rate of H202. The addition of the chelating dispersing agent not only chelate iron or the like, but also can chelate various impurities in the water, so that the impurities do not re-stain the fabric, causing whiteness, darkening and ash, etc., so the chelating dispersing agent is not only Consider its chelation to metal ions and also consider its dispersing power;

4 Process conditions: It takes a certain time and temperature to react the auxiliary agent with the impurities. If the conditions are not enough, the pigment and impurities are not removed, and the whiteness and the gross effect can not be achieved:

5 Washing: It is very important to wash after bleaching. It is necessary to clean and remove the impurities to ensure whiteness and hairiness.

1.2 Cottonseed hull removal is not clean

The removal of cottonseed hulls mainly relies on the expansion and swelling of cottonseed hull under certain conditions, and then removes the cottonseed hulls by a certain mechanical washing power. The removal of uncleanness is mainly caused by insufficient temperature and time, so it must be sufficient at a certain temperature. Time can completely remove the cottonseed hulls. H202 and scouring agent can help the removal of cottonseed hulls. Therefore, there must be a certain temperature and time in the pretreatment to ensure the removal of cotton husks. At the same time, sodium bisulfite (NaHS03) or strontium can be added. A substance that helps remove cottonseed hulls.

1.3 Holes and fragility

The main reason is the presence of Fe3+, Cu2+ and other metal ions in the H202 bleaching bath or on the cloth surface, in addition to the singeing hole, the broken process during the processing, the original hole in the grey cloth, etc. Metal ions catalyze the decomposition of H202 for rapid decomposition, resulting in fiber brittleness. If metal ions (such as rust, etc.) are too concentrated in one place, the fibers and yarns are brittle and form holes. Therefore, H202 bleaching must select high-quality oxygen bleach stabilizers and chelating dispersants to complex, adsorb fabrics and bleach baths. The metal ions in the metal prevent the H202 from decomposing too quickly to cause holes or fragility. If the mercerizing base is used for bleaching, it is necessary to ensure that the alkali does not contain impurities such as rust.

Of course, the cloth with alkali (not alkali) or with acid (de-acidized) can also cause brittleness. At the same time, in the case of high temperature with alkali, the fabric will be brittle in the presence of air, which can be prevented by adding a weak reducing agent such as NaHS03. In addition, the moisture and mildew of the fabric is one of the causes of brittleness and holes.

Color fastness has light fastness, soaping fastness, perspiration fastness, rubbing fastness, sublimation fastness, ironing fastness, etc. These fastnesses are mainly related to dye structure properties, but also with fiber and dye concentration. Dyeing and finishing processes, external conditions, etc. are closely related, so whether the color fastness is up to standard, the key is to choose dyes, followed by the dyeing process and the application of additives.

When the dyeing process is formulated, it must be reasonably determined according to the dyes, fibers and customer indexes, so that the dyes can be dyed as firmly as possible under the conditions of the additives, so that the fibers are fully fixed. For the additives, one is to select A good leveling agent and a dyeing agent make the dye slow, uniform and fully dyed; and a chelating agent, which overcomes the complexation of the dye with the metal ions in the water to form a floating color, and reduces the hydrolysis of the dye in water; The third is to choose an excellent soaping agent, to remove the floating color, and to prevent the floating color from re-staining the fabric; the fourth is to choose an appropriate fixing agent, and currently there is no ideal fixing agent for sublimation fastness and light fastness. For the soaping fastness, perspiration fastness, rubbing fastness and other indicators have excellent fixing agent.

The brittleness is manifested as a strong drop. In addition to the causes of brittleness or even holes caused by improper oxygen bleaching, etc., the brittleness caused by the dyeing stage generally has two reasons. One is the photosensitive brittleness caused by the dye such as sulfur black. Loss, need to use anti-brittle agent to improve, as well as strong reducing agent and strong oxidant such as vat dyeing, the brittleness of the fiber; second, the dyeing stage or neutralization stage of the acid is not appropriate, the neutralization of the general acid is glacial acetic acid However, some alternative acids are currently available on the market. Some of these alternative acids are organic buffer acids like BASF. They are free of strong inorganic acids such as sulfuric acid, hydrochloric acid and phosphoric acid. They are even better than acetic acid. These buffer acids also improve ice. Some of the drawbacks of acetic acid (such as glacial acetic acid in winter, inconvenient, irritating, residual acidity, combined with metal ions (such as Ca2+, Mg2+) in water and left on the fabric to cause dim light, etc.). Some substitute acids containing H2S04, HCl, H3P04, etc., not only cause dyeing color change, but also corrosive to dyeing and finishing equipment and pumps, and acid residue after neutralization may cause brittleness of the fabric under acidic conditions.

The main reasons for the occurrence are equipment reasons, the reasons for the amount of cloth loading, the reason of the bath ratio and the operation of the processing technology. The equipment is different, such as the amount of cloth installed, the pressure and friction between the cloth and the cloth, the pumping force and the strength. It affects the flatness of the fabric surface, and the bath ratio also affects the flatness of the cloth surface. In the process operation, too much auxiliary foam causes the fabric to float and the temperature rise and cool down during the process operation will cause fineness and sudden heat. Wrinkle phenomenon. In the current bath, the anti-wrinkle agent, the bath treasure, and the softener in the bath can all improve the fine wrinkles. However, if the equipment is not improved, the process control is not good, and the lubricant can not be completely avoided by the lubricant in the bath alone. produced.

Wind printing has little to do with additives. The key is the performance of the dye itself (acid and alkali resistance) and the acidity and alkalinity of the fabric, the humidity of the air and the acid gas, such as the light-resistant chlorophyll GC and the frozen yellow in the direct dye. G and so on are prone to wind and rain, active in the Cuilan KN-G, Yan Orange X-GN and other sensitive to acid and alkali are also easy to produce wind, disperse dyes such as yellow RGFL sensitive to alkali, but also easy to produce wind For the additives, the neutralization must be done so that the cloth surface is as PH<7 as possible. Therefore, it is necessary to pay attention to the acid and alkali varieties during neutralization. The acid should use glacial acetic acid or organic substitute acid as much as possible. With a substitute acid containing a strong inorganic acid such as H2S04 or HCl, the choice of base should also be moderated as much as possible."

Color flowers are the most common and most common quality problems in dyeing processes. The reasons for this are:

1 Process development and operation issues:
Unreasonable process or improper operation to produce color flowers;
2 Equipment problems:
Such as disperse dye dyed polyester after the heat setting machine oven temperature is not easy to produce color difference color flower, rope dyeing machine pumping power is also easy to cause color flowers.
3 Dye problem:
The dye is easy to aggregate, has poor solubility, and has poor compatibility. It is easy to produce color and color difference when it is too sensitive to temperature and pH. Such as active turquoise KN-R is easy to produce color flowers.
4 Water quality issues:
Poor water quality, causing the dye to combine with metal ions or dyes and impurities to cause color, color and color are not attached.
5 Auxiliary issues:
Among the auxiliaries, the auxiliaries related to color flowers mainly include penetrants, leveling agents, chelating dispersants, pH control agents, and the like. The penetrating agent has insufficient penetrating power, which is easy to cause uneven penetration of dyeing liquid, such as loose cotton dyeing, cheese dyeing, heavy fabric dyeing, and the role of penetrant can not be ignored. Some plant penetrants only believe in authentic JFC, but It is not considered that the cloud point of JFC is only 38 to 42 ° C. When it exceeds 42 ° C, its penetration force will not be exerted, which will cause quality problems. The leveling agent is used for polyester, cotton, wool nylon and acrylic fiber. The quality of the leveling agent must be mixed. The leveling agent must take into account the dispersing and solubilizing effect of the dye, slow dyeing and dyeing, and help the osmosis. Even for the complexation of metal ions in water, and must take into account the factors such as pH applicability, foaming, etc., the leveling agent is indispensable for improving the color, color point, etc. The leveling agent of the plant is only a solution of the diffusing agent N, but it is not thought that the anti-dye coagulation effect of the diffusing agent N is greatly reduced at high temperatures. Some plants use non-ionic surfactants, which are not suitable, resulting in the precipitation of non-ionic surfactants above the cloud point. The adsorption of dyes into tar-like substances is on the fabric equipment, which causes quality problems. The quality of the chelating dispersant is also related to the leveling problem. At present, in the case of poor water quality, the chelating dispersing agent should pay more attention to the leveling. The PH control problem is a problem that factories do not pay much attention to. Some plants have different PH values ​​for dyeing per cylinder. In addition, some plants use different types of substitute acids, such as phosphoric acid and phosphoric acid. There are differences, how can we control the uniform PH value? Some factories use PH slip agents, but do not grasp the relationship between temperature and time and the pH value generated by the slip agent. PH control is impossible to talk about, so the color flower, The phenomenon of chromatic aberration is constantly occurring.

There are many reasons for the color point, such as white spots, which may be the reason why the immature cotton does not dye the dye, or it may be that the solid such as soda ash is stained on the cloth to cause local staining. The main reasons for the color point are:
1 Dyes are not properly selected: the dye particles are too large or highly likely to produce agglomerated color points;
2 Poor dye dissolution: undissolved dye enters the dyeing liquid and stains on the fabric. 3 Poor water quality: Poor water quality causes dye condensation:
4 The equipment is not clean: the tar of the dyeing tank is dropped to cause a color point;
5 auxiliary reasons: the additives added during dyeing sometimes cause the dye to agglomerate and produce color points; the auxiliary foam is too much, the foam and the dye are combined into a colored foam, and the color point is formed on the fabric; the auxiliary precipitate is combined with the dye. On the fabric and equipment, the agglomerates on the equipment will turn on the fabric to create a color point.