Revealing the factors that cause chicken paw prints in the dyeing workshop! The most troublesome problem for the masters of the printing and dyeing factory is that after a vat of cloth is finalized, they find that there are “chicken paw prints” on the cloth! This is not your mouth-watering delicacy! Instead, folds appeared on the cloth! The boss knows and must tell us! According to the interpretation of industry technical circles, when various fiber fabrics are dyed on an overflow machine, whether at normal temperature (100°C) or high temperature and high pressure (130°C/0.19 MPa), they may form “chicken paw prints” (hereinafter referred to as folding marks). print). What to do? Check out the in-depth analysis below!
Potential factors in spinning and weaving
For example, uneven yarn lines and differences in twist and shrinkage after twisting, tension and density differences during weaving, especially high-count and high-density fabrics, will directly affect subsequent processes.
During the moist heat treatment process, the shrinkage of the fiber (yarn) is often Different to form folds. Therefore, to overcome folding, it is best for the fabric to undergo mercerization and preshrinking treatment. Especially after mercerization, the cotton fiber molecules are rearranged and the crystallinity is increased to reduce folding caused by spinning and weaving.
Inconsistent heat shrinkage
The thermal shrinkage of two or more fibers in the blended fabric is inconsistent
Sometimes the fabric is pre-shaped after pre-treatment, but sometimes there is still residual stress, especially when heat shrinks at 130°C. Sexual differences are even more pronounced. Therefore, two or more fiber components will form folds due to their different thermal shrinkage rates. Although pre-shaped, sometimes it does not help (see the figure below).
1-boiling water shrinkage; 2-hot air shrinkage [190℃×15 min); 3-saturated steam shrinkage (nylon 6 is 125℃×3 min, nylon 66 and polyester are 130℃×3 min)
The author believes that pre-shaping before dyeing is one way. However, practice has proved that the pre-setting temperature is higher than the post-setting temperature and the effect is better. In addition, if conditions are met, comprehensive processing of flat width, rope shape and flat width can be adopted, and the effect will be better.
The dyeing bath ratio is too small
When dyeing on a domestic overflow machine, the liquor ratio is generally controlled at 1:12~15. For example, if a T/C (65:35) blended fabric with a mass of 280g1112 can dye a 100 kg tube, a pure polyester fabric with similar thickness, density and width is often only about 180g/m2, and can only dye 65 kg/tube.
In short, the length of each tube of fabric should be controlled at 350-400 as much as possible ITI, its operating cycle is roughly consistent with the theoretical number (i.e. 1r/min). The design capacity and circulation function of the machine are sometimes inconsistent. Most dyeing machines are generally o. About 5 r/rain. If it is l r/(3~4) rain, it is obvious that the liquor ratio is too small. Not only is it easy to dye flowers, but it is also easier to form folds, especially light and high-density fabrics, such as polyester and pongee. .
The heating/cooling speed is too fast
Dyeing on an overflow machine, heating and cooling will directly affect the shrinkage rate of the fiber , thus forming a fold. For thermoplastic fibers such as nylon, once folds are formed, they are irreversible. Therefore, when dyeing, special attention should be paid to the need to slowly raise/lower the temperature within 10°C before and after the fiber glass transition temperature. Generally, a speed of 1°C/rain is appropriate.
Of course, the temperature rise and fall can generally be increased beyond 10°C before and after the glass transition temperature. speed to shorten processing time. Sometimes in order to speed up the heating and cooling speed but also prevent folding, in addition to adding leveling agent during dyeing, you can also add 2-3 g/L of anti-wrinkle agent or bath softener in the bath to reduce the rigidity of the fabric and improve the softness. , reducing the chance of creases during dyeing. For example, for thick leather-like fabrics made of polyester/cotton and polyester/polyester microfibers, in addition to selecting the ANOCRON microfiber-specific disperse dye series, in order to prevent folding during overflow dyeing, you can Add the above two auxiliaries to the dye bath.
There are many varieties of this type of additives, so pay attention to the following when selecting them: span>
① Affinity and miscibility with dyes; dyers can edit without borders
② Low or no foaming is required to prevent Block the cloth or consume too much defoaming agent;
③ It must be resistant to high temperatures and weakly acidic media;
④ It needs to be selected after testing.
Cannot be cooled instantly
Attention! Fabrics after heat treatment cannot be cooled instantly
Practice has proven that no matter what kind of fabric, From the beginning of pre-treatment to the end of dyeing, the machine must not be shut down to discharge the residual liquid after each heat treatment, and then replaced with cold water for cleaning, otherwise it will accumulate in the machine.Fabrics that are constantly hot will form fold marks when exposed to cold for a moment, especially synthetic fibers and their blended fabrics. Edited and compiled by No Borders.
Therefore, do not rush to drain the liquid after terminating dyeing, but wait until the fabric is running First, gradually add cold water until it overflows the dyeing machine, then wash with running water for a while, wait until the temperature of the fabric and the machine body has dropped before draining the liquid, or even changing the liquid for cleaning. This method can also reduce the occurrence of “pine board printing” if used in jigger dyeing machines. Hot and cold buffering facilitates the dyeing process.
Reasonable selection of processing equipment
Fabrics that can be processed by open-width equipment, such as nylon, polyester taffeta, cotton high count and high density fabrics, etc. , try not to use an overflow machine. In fact, the dyeing and finishing processing of various fabrics has its own suitable equipment, which should be selected according to the performance and end use of the fabric.
A friend said, wouldn’t the problem be solved by softening it first and then dyeing it? So, fellow printing and dyeing factory masters, what do you think?
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