Causes and avoidance methods of fabric wind printing

Windprint generally refers to a dyeing defect produced during the drying and storage of textiles after printing and dyeing. Compared with the normal dyed blank, the wind print will have a white or shaded gray stripe in the latitude of almost the entire width of the door. This defect is not visible before the setting, and will be produced after the setting.

Polyester fabrics are less prone to windprints during continuous production (long-distance production lines), while batch production (when high-temperature and high-pressure overflow dyeing) is prone to windprinting. Most of the polyester fabrics are produced after the dewatering of the fabrics and before the shaping, and appear in the reciprocating folding of the stacker. In severe cases, there will be dozens of latitudes in the latitudinal direction, and the spacing is exactly the spacing of the fabrics.

Reasons for the production of wind-printed polyester-free woven or knitted fabrics

During the unfolding of such fabrics after opening, the reciprocating folds are exposed to the air, and the flow of air causes the moisture of these parts to first evaporate and dry. Free water from other parts of the capillary effect will flock to the reciprocating fold. However, there are still a small amount of antistatic agents, lubricants, leveling agents and detergents added during spinning and weaving, which remain in the free water carried by fabrics and fabrics, and most of these additives It is a non-ionic additive. As with the principle of dye migration, when free water surges toward the reciprocating fold, residual auxiliaries dissolved in free water also flock to the reciprocating fold.

As the moisture is further volatilized, the concentration of the auxiliary agent at the reciprocating fold is much larger than other parts. During the high-temperature setting process, the thor-mo-migration of the disperse dye produced by the reciprocating folded portion is significantly larger than other parts. The reason for the thermal mobility of the disperse dye is that the auxiliary agent of the outer layer of the fiber can dissolve at a high temperature, and the dye migrates from the inside of the fiber through the capillary to the surface layer of the fiber, causing the dye to accumulate on the surface of the fiber, causing a series of effects. Such as color change, friction, washing, sweat, dry cleaning, light fastness and other color fastness. But the fatal effect is the difference in the color shade between the reciprocating fold and other normal parts, namely the wind print.

Reasons for sizing of polyester woven fabrics

Compared with the pulp-free polyester woven fabric or knitted fabric, the sizing polyester woven fabric has a long dyeing and finishing process, and most of the additives used in spinning and weaving have been removed. However, there may still be a small amount of auxiliaries used in the dyeing and post-treatment process remaining in the fabric and the free water it carries. In addition, although the hot washing and the first pickling have been carried out after desizing, the caustic soda used in the desizing may still remain in a small amount inside the monofilament of the polyester fiber or even inside the amorphous region.

In the same way, in the process of stacking the fabric before the mold is set, the free water can carry the residual alkali and the auxiliary agent to the reciprocating fold. At this time, the pH value of the reciprocating fold is significantly higher than other parts of the fabric, which is also confirmed by the universal indicator, and the concentration of the auxiliary agent is also larger than other parts. During the high-temperature setting process of the fabric, the polyester macromolecular chain moves violently, and the OH-ion can be instantaneously drilled into the amorphous region to react with the disperse dye with the water molecules.

Disperse dyes are stable under acidic conditions (pH 5). Under alkaline conditions, there are generally two effects on disperse dyes: alkaline conditions can dissociate certain dye structures. This reaction is reversible and neutral. The undissociated structure reappears in the slightly acidic structure.

The base can hydrolyze some of the disperse dyes. After hydrolysis, the dye not only changes color, but also has different affinity. Therefore, the base can permanently destroy some of the disperse dyes.

Therefore, the color change of the sizing polyester woven fabric at the reciprocating fold is caused by the excessive pH, the hydrolysis or dissociation of the disperse dye, and the combined effect of the auxiliary agent on the thermal migration of the disperse dye.

Avoid the way to produce polyester fabrics

If the above two fabrics can be dehydrated, opened, and shaped in time after being discharged from the cylinder, generally no windscreen will be produced. If you leave it for a period of time (about 30 hours), it will be easy to produce a wind print. In order to solve the wind print fundamentally, we must start with the mechanism of producing the wind print and minimize the factors that cause the wind print.

The reasons for the production of textiles are mainly related to dyes. In general, a small number of vat dyes, naltrex dyes and some vinyl sulfone type reactive dyes and most direct dyes can produce wind marks due to the poor fastness of the dye itself to sunlight and oxidation. Some reactive dyes have strong sensitivity to alkali. If the surface alkali is not cleaned after dyeing, it is easy to produce wind marks when the pH value is greater than 8 (such as active Cuilan KN-G, reactive brilliant orange G, etc.).

The pattern is found to have a wind print, and the remaining unformed fabric has a high concentration of auxiliary or OH-ion at the reciprocating fold, but is physically adsorbed on the surface of the fiber, and the dye which cannot dissolve the amorphous region without the high-temperature setting aid, OH-ion It is also impossible to enter the amorphous region of the fiber to react with the disperse dye. Therefore, after washing with water or pickling, the high concentration of the auxiliary agent and the OH-root ions at the reciprocating fold have been diluted, and the weathering can be avoided by timely setting.