In the process of processing, the control of fabric door width is one of the very important indicators. In fact, the impact of fabric design on the finished door width is the most direct. The door width of the blank cloth, the type of reed, the size of the raw material, the organization structure of the fabric, the warp and weft density of the blank cloth, etc., have a direct impact on the finished door width. Taking polyester woven fabric as an example, the common woven fabric mainly includes: conventional flat fabric, strong twist imitation silk finishing fabric, elastic fabric and short fiber blended wool-like fabric and so on. The dyeing and finishing process also has a great influence on the door width of the fabric.

01、The impact of the process flow

Different types of fabrics have different dyeing and finishing processes, the conventional flat fabric processing process is as follows:

Preparation → scouring → dyeing → post-treatment → dehydration → drying → Setting → inspection

The dyeing and finishing process of strong twist imitation silk fabric is as follows:

Preparation → pre-shrink → pre-type → alkali reduction → washing → dyeing → post-treatment → dehydration and drying → setting → inspection

The dyeing and finishing process of elastic fabric is as follows:

Preparation → open-width scouring → Pre-shrink → preform → dyeing → post-treatment → dehydration → drying → Setting → inspection

The dyeing and finishing process of blended wool-like fabric is as follows:

Preparation → singeing → preshrinking → preordering → dyeing → post-treatment → dehydration → drying → Setting → steaming → inspection

Based on the above processing processes of different varieties, the main processes of dyeing and finishing of common polyester woven fabrics include: cloth preparation, (open width) refining, pre-shrinking, predetermined type, alkali reduction, dyeing, post-treatment, dehydration, drying, styling, steaming and inspection 12 processes.

02、The effect of processing

1 Prepared Cloth

The main tasks of the cloth preparation process are embroidery, sewing and weighing. Although the length of parking time after rolling grey cloth has an effect on the shrinkage of grey cloth, this effect is weak. Warp elastic fabric, weft elastic fabric and warp and weft two-way elastic fabric after unwinding time is too long, the fabric shrinkage will increase. The shrinkage of the door width of the grey weft elastic fabric directly affects the finished door width. The contraction of the warp of the warp elastic fabric will cause the weft to become more tortuous, and eventually lead to the narrowing of the weft width. The pressure on the top and bottom of the fabric is different after preparation. Whether it is elastic fabric or strongly twisted fabric, if the grey cloth after unwinding is unbalanced by external influences during the process of releasing internal stress, it will lead to uneven changes in the door width of the whole cylinder grey cloth, and eventually lead to non-uniformity of the pre-shrunk or predetermined back door width, which will bring adverse effects on subsequent processing. The storage time should not be too long after the polyester woven strong twist fabric is withdrawn from the cylinder, especially the elastic fabric. If the time is too long, the door width of the pre-shrunk fabric will not be uniform, which will have a greater impact on the later process.

2 Refinement

Scouring includes rope scouring and width scouring. Rope scouring is the pre-treatment of ordinary polyester woven fabric, its purpose is to remove the impurities on the fabric, without affecting the processing quality of the subsequent process. The temperature rise rate, maximum process temperature, additive concentration and holding time of pre-treatment process are the most important process parameters. Under hot and humid conditions, polyester as a thermoplastic fiber always changes. The higher the temperature, the faster the rate of warming, the more obvious this change. In order to mitigate this change, the pre-treatment temperature does not exceed the glass transition temperature of the polyester fiber. Therefore, rope scouring has little effect on the finished door width of ordinary flat polyester fabric.

For elastic fabrics, especially weft elastic fabrics and double-elastic fabrics, in order to effectively control the shrinkage of the blank fabric width, it is necessary to open width scouring. Open-width scouring needs to be carried out in an open-width scouring machine. Multiple flat washing tanks in the open-width scouring machine can provide different scouring temperatures. First cold water, then warm water; The door width of the weft elastic fabric can be shrunk by more than 20% after the machine is off, while the open width is refined and the width is expanded continuously. Slow and uniform shrinkage is the basis and key to keep the finished cloth flat. Open-width scouring is a simple and effective process to achieve slow and uniform shrinkage of polyester elastic fabric at low temperature. By using an open-width scouring machine to refine wide-width plain elastic fabric, the internal stress of the fabric can be eliminated under mild moist and hot conditions, and the chance of wrinkles in the fabric surface during subsequent processing can be reduced. If the door width shrinks too much, the speed of open-width scouring can be reduced. The weft shot (double shot) blank cloth of 210cm on the machine, the door width is generally about 180cm(including cloth edge) after getting off the machine. If the door width is greater than 160mn after scouring, it means that the open-width scouring speed is too fast.

3 Preshrink

The cylinder is carried out in a rope shape, and the pre-shrinking temperature is higher than the scouring temperature but lower than the dyeing temperature. Pre-shrinkage is the pre-treatment under high temperature and humid heat state, in addition to removing the slurry, oil, stains and other impurities on the fabric, but also through high temperature and humid heat processing to eliminate the internal stress of the fabric as far as possible, and the door width of the fabric alleviates the contraction. Under the condition of high temperature and humid heat, the orientation trend appears in the region with high crystallinity and the orientation trend appears in the region with low crystallinity. The orientation and disorientation in the thermoplastic fiber cause the orientation of the whole fabric to be balanced, and the internal stress formed in the manufacturing and storage process of the fabric can be released. The end result is an increased dimensional stability of the fabric, a smoother fabric surface, and a more stable door width. Polyester woven fabric preshrink similar to cotton fabric mercerization.

In the process of preshrinking, the warp force of the fabric comes from the dye cylinder nozzle, and the warp force is larger, but the weft force is relatively smaller. The weft is shorter when preshrunk, and the number of warp threads bypassed by each weft is only equal to the tip of the warp of the fabric. The number of weft bypassed by each warp is equal to the weft density of the fabric multiplied by the length of the piece. Therefore, the resistance encountered by the warp contraction is much greater than that of the weft yarn. At the same time, it is more difficult for the warp to shrink under the action of nozzle tension, and the weft contraction of non-elastic polyester woven fabric is greater than the warp contraction. When the thermoplastic fiber shrinks under high temperature and humidity, the thickened weft will shorten the warp wrapped around the weft overall, and the warp will also shorten the weft overall. After the end of the preshrinking, the door width and piece length of the fabric tend to be reasonable. Understanding the shrinkage of grey cloth with different twist, different raw materials and different organization during weaving and dyeing and finishing is the basis of rational design of finished door width.

When pre-shrinking, the larger the nozzle tension, the more obvious the fabric door width shrinkage. The aperture of the nozzle is too small, which affects the smooth flow of the fabric through the nozzle, easy to cause the fabric poke, resulting in uneven shrinkage of the fabric. When the nozzle diameter is too large and the nozzle tension is adjusted too large, the fabric without fabric fabric is easy to produce edge leakage phenomenon. It is difficult to carry out subsequent processing and finished product shaping after fabric trimming. Although the fabric drain phenomenon can be improved by increasing the temperature of the fabric entering the cylinder, it is easy to cause uneven fabric pre-shrinking when the water temperature in the cylinder is too high.

Stage heating and heat preservation at different heating stages are the main ways to prolong the process time and ease the process conditions in the pre-shrinking process of strong-twist fabrics. Prolonging time and easing conditions will make the effect of fabric preshrinking more obvious. Uniform shrinkage, stable size and flat cloth surface are the main quality indicators of pre-shrinkage. Sometimes the width of the back door of the strong twist fabric is too wide, and the splitting phenomenon of the fabric surface is caused by the improper preparation of the preshrinking process. If the segmentialized temperature pre-shrinking process is used, it can be considered to properly reduce the nozzle tension and the fabric circulation speed, which can increase the impregnation time of the fabric in the pre-shrinking liquid in the cylinder, and the fabric shrinks in the state of high temperature and humid heat relaxation, which is conducive to increasing the pre-shrinking effect.

4 Reserve

The reservation is carried out on the molding machine, and for the polyester woven fabric, the reservation is the continuation of the preshrinking, with the same purpose. The former is carried out in a hot and humid state, while the latter is carried out in a hot and dry state. The result of slow precontraction under hot and humid conditions requires predetermined consolidation and strengthening under hot and dry conditions. Temperature, door width, tension and speed are the main parameters of the predetermined process. The predetermined temperature is slightly higher than that of the finished product, which is beneficial to the dimensional stability of the predetermined fabric. The predetermined door width should be slightly smaller than the finished door width. The larger the warp tension, the wider the door width and the smoother the cloth surface. Increasing the warp tension increases the chance of the warp being straightened, the weft will become more tortuous, and then the door width has a tendency to become smaller. The speed of the speed depends not only on the length of the drying room, but also on the thickness of the fabric, the nature of the raw material, the organizational structure and many other aspects.

The predetermined door width is determined according to the pre-shrunk door width, the flatness of the cloth before fabric booking and the finished door width. When booking, the amplitude of adjusting the predetermined door width should not be too large, and the fluctuation of qualitative temperature should not be too large, otherwise, after reducing and dyeing, the front door width of the finished fabric in the same cylinder will be too large to finalize the finished product.

5 Alkali decrement

The purpose of the reduction is to make the strong twist polyester filament thinner. Thinner yarns are less rigid and have more space to move between yarns, resulting in improved fabric feel. After the alkali reduction, the fabric becomes soft and the door width will be slightly wider. The increased width is most closely related to the raw material and organizational structure, and is generally about 1cm wide. After the high temperature in the dyeing tank is reduced, the phenomenon of the width of the fabric door will be more obvious. The washing before dyeing after reducing has no effect on the door width of the fabric.

6 Dye

Like preshrinking, the dyeing process is also carried out in a state of high temperature and humidity. The difference is that the dyeing temperature is higher than the pre-shrinking temperature, which is the second wet heat setting of the fabric. After the first wet heat setting and the first dry heat setting, the door width of the fabric is basically stable. Although the dyeing temperature is about 10 ° C higher than the pre-shrink temperature, the thermoplastic characteristics of the polyester fiber after high temperature and dry heat setting during dyeing are that the fabric door width is slightly wider, and the increased width is generally about 1cm wider than the predetermined door width.

There are two main reasons for the width of the fabric door after reduction and dyeing, one is that the fabric is constantly circulating in the equipment, and the cycle process is the process of mechanical softness. As the yarn softens, sliding between the yarns becomes easier than before the preorder, making the fabric slightly wider. The other is that the new stress imposed on the fabric by the pre-shrinking and predetermined processes is released under the hot and humid state, and the fabric becomes slightly wider.

7 Post-Processing

The processing of ordinary fabric, strong twist fabric and short fiber wool-like fabric after dyeing, such as reduction cleaning and fixing color, has no effect on the fabric width. Elastic fabrics, especially the weft elastic fabrics of blended raw materials, when the cellulose fibers are dyed with sulfide dyes and then oxidized with oxidants for color development, or when the reactive dyes are dyed with cellulose fibers for color fixing with soda ash, the process conditions should not be too harsh and the process time should not be too long. Otherwise, the spandex elastic damage is too large, it will cause the fabric door width to increase too much, and finally lead to the finished door width is too wide, and the fabric weft elasticity disappears.

8 Dehydration, opening and drying

Dehydration and opening after preshrinking and dyeing have little effect on the reservation itself. The open width here refers to the use of equipment or hand to flatten the rope fabric without winding, easy to dry or shape. Although the moisture content of the fabric after dehydration will affect the drying efficiency, some varieties are too dry, and the fabric surface will produce new creases and other defects. In most cases, in order to improve processing efficiency, the conventional varieties of polyester woven fabrics mentioned earlier can be directly predetermined after opening without drying procedures. As long as the drying length of the molding machine is long enough, the predetermined effect of the fabric can be fully guaranteed. Dehydration, opening and drying after dyeing have little effect on the fabric door width.

Although the loose drying equipment and the tensioning drying equipment have a certain impact on the door width after the fabric is dried, this impact occurs after the fabric is dyed, and the impact on the fabric door width is much less than that of the finished product. Some special styles of fabric, such as bark crepe, pearl hemp and other fabrics, in order to maintain the style of cloth, dehydration after the need for loose drying. Most polyester woven fabrics can be set directly after opening.

9 Finished product shaping

The final shape of ordinary flat polyester woven fabric has the greatest influence on dimensional stability. Whether it is ordinary fabric, strong twist fabric, wool-like staple fabric or elastic fabric, the finished door width should be based on the door width of the fabric itself before the setting. Although it is possible to increase the warp tension of the fabric to narrow the width of the finished door, it is impossible to narrow the width of the door by dyeing the fabric with too wide width through the finished shape. In the same way, it is impossible to increase the width of the door through the finished shape of the fabric that is too narrow, even if it greatly reduces the warp tension when the fabric is finished.

The tension adjustment of the finished product is more important than the warp tension adjustment of the fabric. By adjusting the tension bar, tightener, expanding roller and overfeeding device at the front end of the setting machine, the warp tension of the finished fabric can be adjusted, which can not only affect the weight of the fabric, feel, but also affect the door width of the finished fabric. After the rubber blanket pre-shrinking machine is pre-shrunk, the door width of T/C class fabric will increase moderately. After steaming the wool-like fabric pot, the door width will be slightly wider. The width of the door will also be widened when the fabric of imitation cowboy weft made of viscose staple fiber is washed. The pin-plate molding machine is conducive to maintaining the warp tension of the fabric in the final shape, which includes both the positive tensile tension and the negative preshrinking tension. The function of the clip setting machine in this respect is inferior to that of the pin-plate setting machine.

The final door width of the fabric does not depend on the finished door width, but depends on the characteristics of the fabric itself and the entire dyeing and finishing process. Reasonable design and careful processing, the final door of the fabric will fully reflect the characteristics of the fabric itself, and the size of the door will be stable.