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4 warp-knitted finishing process
- Jul 04, 2018 -

The general process of warp knitting finishing is: white blank → initial setting → raising → shearing → opening → dyeing → heat setting → sanding → finished product inspection → rolling.


Since the white fabric is not flat and the width of the door is different, it is necessary to carry out the pre-formation treatment before the raising, and the temperature cannot be too high when the heat setting is performed, and only the various wrinkles of the cloth surface are removed, so that the cloth surface is flat and the width is Consistent. Otherwise, the microfibers are affected by high temperature, and the structure changes and it is difficult to fluff. Generally, the temperature is preferably between 155 and 165 ° C, and the setting temperature after the raising is suitably higher, usually 185 to 195 ° C. The speed of the car is 30m/min. The grey fabric is directly subjected to napping finishing, and the suede fluffing effect is relatively good and uniform, and the color is bright and the color is good after being dyed and finished.


Several important finishing techniques are discussed below.


4.1 Fiber opening process


The island-type ultrafine fiber dissolves the sea component after the fabric is formed, leaving the island component to form a continuous microfiber fabric. Therefore, the solubility of the sea component is critical to the effect of warp-knitted suede. The dissolution of COPET in water is consistent with the law of dissolution after swelling first. The composition, structure, molecular weight and external conditions of COPET have a certain influence on the dissolution. The influence of external conditions on the dissolution of COPET is shown in Fig. 2. Curve 1 is the dissolution of the water soluble polyester in hot water at 95 °C. It is mainly dissolved first; curve 2 is the dissolution of water-soluble polyester in 95% NaOH aqueous solution at 95 ° C, it also has a swelling and dissolution process, but the swelling is slow, and there is still residue after dissolution, which may be Due to the presence of Na+ and OH- ions, the dissolution equilibrium of the polymer is destroyed, the dissolution rate becomes slower, and NaOH also reacts with some components in the polymer to form a precipitate, and curve 3 is a water-soluble polymer. The solubility of the ester in the aqueous solution containing 0.5% NaOH and 1g/L 1227 accelerator at 95 ° C. Since the 1227 surfactant is added to the water, the water-soluble polyester is hydrolyzed while being swollen. The small molecule promotes the progress of hydrolysis and accelerates the dissolution rate. And the percentage of NaOH can be adjusted according to different conditions to control the dissolution rate.


The fiber opening process is carried out in an alkaline solution, which is advantageous for the complete dissolution of the sea component, but also has a hydrolysis effect on the conventional PET island fiber. Therefore, the sea island fiber needs to achieve complete dissolution of the sea component, and its weight loss rate. It is slightly larger than the proportion of sea components. If the sea component ratio is 20%, the weight loss rate of the island fiber is generally controlled at 22-26%, and the sea component can be completely dissolved. The general open fiber process curve is shown in Figure 3.


4.2 Dyeing process


After the fabric is opened, it must be thoroughly washed before dyeing. The amount of water should be large. In order to fully neutralize the alkali solution on the fabric, first wash it in a solution containing 1g/L of acetic acid at 70 ° C for 10 minutes, then use water. Rinse to a pH in the range of 6.5 to 7. If the water is not enough, the residual alkali and fiber impurities are retained on the cloth, which is easy to cause staining. In addition to dyeing the dyeing process, the dyeing process has a great influence on the shrinkage of the fabric, which is related to the density of the fabric and the subsequent process.


Among the influencing factors of the dyeing process, the first is the effect of dyeing temperature on the suede. Generally, polyester fiber is affected by heat, and its shrinkage changes with temperature, and a significant effect can be obtained between 80 and 100 °C. The dyeing temperature is between 120 and 130 °C. This is advantageous for increasing the shrinkage of the fabric and increasing the density and bulkiness.


The second is the effect of tension on the suede during the dyeing process. The ideal state of the fabric during the dyeing process is uniform longitudinal and lateral forces, but in fact the longitudinal tension is greater than the transverse direction due to the longitudinal movement of the fabric in the dyeing machine.


In some cases, in the solvent-based polyurethane finishing, the solvent has a certain stripping effect on the disperse dye, that is, the color becomes light, and the general color difference is about 0.5 to 1.5. Therefore, when determining the color and dyeing process, it can be increased by 5-10% on the basis of the normal dosage. In addition, the heating rate (60-130 °C) should be strictly controlled, and the holding time should be no less than 45 min, preferably 60 min. It can now be finished with a water-soluble polyurethane resin.


4.3 Grinding process


The sanding finishing is to enter the sanding zone under the control of a certain tension and pressure and the feeding speed under the control of a certain tension and pressure and the feeding speed. Under the action of the high-speed rotating sanding roller or the abrasive belt, the fabric raising surface coil is broken and formed. a layer of fluff with directional lodging. The sanding finishing is an important processing procedure for the production of suede, which has a great influence on the simulation of the fabric suede. The length and coverage density of the fluff are mainly affected by the following six factors: the length of the back of the front needle, the speed of the cloth, the speed of the sanding roller, the contact mode of the fabric with the sanding roller, and the shape and specifications of the sandpaper sanding material. ; the distance between the pressure roller and the sand roller