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

1. The influence of technological process

Different fabrics have different dyeing and finishing processes:

Conventional plate fabric processing process is as follows:

Preparing cloth → refining → dyeing → post-treatment → dehydration → drying → setting → inspection

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

Preparing cloth → preshrinking → predetermined type → alkali reduction → washing → dyeing → post-treatment → dehydration and drying → setting → inspection

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

Preparing cloth → open width refining → Preshrinking → preshaping → dyeing → post-treatment → dehydration → drying → shaping → inspection

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

Prepare cloth → singeing → preshrinking → preordering → dyeing → post-treatment → dehydration → drying → Setting → pot steaming → inspection

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

2. The influence of processing process

① Prepare cloth

The main tasks of the cloth preparation process are embroidery, sewing and weighing. The length of parking time after rolling blank cloth, although has an effect on the fabric shrinkage, but this effect is weak. If the time of unwinding is too long, the shrinkage of grey fabric will increase. The shrinkage of the door width of the blank weft elastic fabric directly affects the finished door width. The contraction of the warp in the meridional elastic fabric will cause the weft yarn to become more zigzag and eventually lead to the narrowing of the weft width. The pressure on the top and bottom of the cloth is different after the cloth is prepared. No matter the elastic fabric or the strongly twisted fabric, if the grey fabric after unwinding is affected unevenly by the outside in the process of releasing the internal stress, it will lead to the uneven change of the door width of the whole cylinder grey fabric, and eventually lead to the non-uniformity of the pre-shrunk or predetermined back door width, which will bring bad influence to the subsequent processing. The storage time of polyester woven strong twist fabrics, especially elastic fabrics, should not be too long. If the time is too long, the door width of the pre-shrunk fabric will not be uniform, which will bring great influence to the next process.

② Refine

Refining includes rope refining and width refining. Rope scouring is the pre-treatment of common polyester woven fabric, its purpose is to remove the impurities on the fabric, without affecting the processing quality of the next process. The temperature rise rate, the maximum process temperature, the concentration of auxiliaries and the holding time are the most important process parameters. As a thermoplastic fiber, polyester always changes in hot and humid conditions. The higher the temperature, the faster the rate of warming, the more pronounced the change. In order to mitigate this change, the pretreatment temperature does not exceed the glass transition temperature of the polyester fiber. Therefore, rope scouring has little influence on the door width of ordinary flat polyester woven fabric.

For elastic fabrics, especially weft elastic fabrics and double elastic fabrics, in order to effectively control the shrinkage of the fabric width, it is necessary to refine the open width. Open - width scouring needs to be carried out in the open - width scouring machine. Multiple flat washing tanks in the open - width scouring machine can provide different scouring temperatures. First cold water, after warm water; The blank width of the weft elastic fabric can shrink more than 20% evenly after unloading. 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 realize slow and uniform shrinkage of polyester elastic fabric at low temperature. By using an open-width scouring machine to refine the wide-width plain elastic fabric, the internal stress of the fabric can be eliminated under mild moist and hot condition, 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 refining can be reduced. The blank cloth of 210cm weft projectile (double projectile) on the machine, the width of the door is generally about 180cm(including the cloth edge) after getting off the machine. If the door width is greater than 160mn after refining, it means that the speed of open width refining is too fast.

③ preshrink

The cylinder is carried on in rope shape, and the pre-shrinking temperature is higher than the scouring temperature and lower than the dyeing temperature. Pre-shrinkage is the pre-treatment under the condition of high temperature and humid heat. In addition to removing impurities such as slurry, oil and dirt on the fabric, the internal stress of the fabric should be eliminated as far as possible through high temperature and humid heat processing, and the door width of the fabric should ease the contraction. Under the condition of high temperature and humid heat, the orientation trend appeared in the region of high crystallinity and the orientation trend appeared in the region of low crystallinity. The orientation and disorientation in the thermoplastic fiber cause that the orientation of the whole fabric tends to be balanced, and the internal stress formed in the process of manufacturing and storage can be released. The end result is increased dimensional stability, a smoother surface and a more stable door width. Polyester woven fabric preshrink similar to cotton fabric mercerizing.

In the process of preshrinking, the warp tension of the fabric comes from the dye cylinder nozzle, and the warp force is large, while the weft force is relatively small. The pre-cut weft is shorter, and each weft bypasses only as many warp points as the warp points 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 warp shrinkage resistance is much greater than that of the weft yarn. At the same time, it is more difficult for the warp yarn to shrink under the effect of nozzle tension, which results in the non-elastic polyester fabric's weft contraction is greater than the warp contraction. In the same way that the warp around the weft is generally shortened by the thickened weft when the thermoplastic fibers contract at high temperature and humidity. After the end of the preshrinking, the door width and length of the fabric tend to be reasonable. Understanding the contraction of grey fabric with different twist, different raw materials and different organization in the process of weaving and dyeing is the basis of rational design of finished product width.

When preshrinking, the larger the nozzle tension, the more obvious the shrinkage of fabric door width. Nozzle diameter is too small, affect the fabric smoothly through the nozzle, easy to cause fabric poke, resulting in uneven fabric shrinkage. When the nozzle diameter is too large and the nozzle tension is too large, the fabric without the edge organization is easy to produce the phenomenon of edge leakage. It is difficult to carry out subsequent processing and fining after fabric edge draining. Although the fabric drain phenomenon can be improved by increasing the temperature of the fabric into the cylinder, it is easy to cause uneven fabric pre-shrinking when the water temperature in the cylinder is too high.

It is the main way to prolong the process time and ease the process conditions in the preshrinking process of the strong twist fabric by heating in stages and keeping heat in different stages. Prolonging time and easing conditions will make the effect of fabric preshrinking more obvious. Uniform shrinkage, stable size, flat cloth surface, is the main quality index 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 formulation of the preshrinking process. If the stage heating preshrinking process is adopted, it can be considered to properly reduce the pull of the nozzle and the circulation speed of the fabric, which can increase the impregnation time of the fabric in the cylinder preshrinking liquid. The fabric shrinks under the state of high temperature and humid heat relaxation, which is conducive to increasing the preshrinking effect.

④ make reservation

The reservation is carried out on the setting machine. For polyester woven fabric, the reservation is the continuation of the preshrinking, with the same purpose. The former is carried out in a state of damp heat, the latter is carried out in a state of dry heat. 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 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 meridional tension is, the wider the door width and the smoother the cloth surface. Increasing the warp tension increases the chance that the warp will be straightened, and the weft will become more tortuous, thus tending to decrease the width of the gate. The speed of the vehicle not only depends on the length of the drying room, but also depends on the thickness of the fabric, raw material properties, organizational structure and other aspects.

The predetermined door width is determined according to the pre-shrinkable door width, the flatness of the cloth before the fabric is predetermined and the finished door width. At the time of reservation, the amplitude of adjusting the predetermined door width should not be too large, nor should the fluctuation of qualitative temperature be too large. Otherwise, after reducing and dyeing, the front door width of finished fabric in the same cylinder will be too big 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 them, resulting in improved fabric feel. After alkali reduction, the fabric softens and the door widens slightly. The increased width is most closely related to raw materials and organizational structure, generally about 1cm wide. After the high temperature reduction in the dye VAT, the width of the fabric door will become more obvious. The washing before dyeing after reducing has no effect on the door width of the fabric.

⑥ dyeing

Like preshrinking, the dyeing process is also carried out at high temperature and humid heat. 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℃ higher than the pre-shrinking temperature, the thermoplastic property of the polyester fiber after high temperature and dry heat shaping during dyeing is that the width of the fabric door has slightly widened, and the increased width is generally about 1cm wider than the predetermined width of the door.

There are two main reasons for the width of the fabric door after reduction and dyeing. One is that the fabric keeps circulating in the equipment, and the circulating process is the process of mechanical softness. As the yarn softens, it becomes easier to slide between the yarns than before, making the fabric slightly wider. The other is the release of new stresses imposed on the fabric by the preshrinking and predetermined processes under the condition of heat and humidity, and the fabric widens slightly.

⑦ Post-treatment

The processing such as reduction cleaning and color fixing after dyeing of ordinary fabric, strong twist fabric and short fiber wool-like fabric has no effect on the width of fabric door. 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 cellulose fibers are dyed with active dyes and fixed 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 increase of fabric door width is too large, and finally lead to the finished product 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 opening here is 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, but some varieties of dehydration too dry, 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 above can be directly predetermined after opening without drying. As long as the length of the drying room of the setting machine is long enough, it can guarantee the predetermined effect of the fabric. Dehydration, opening and drying after dyeing have little effect on the door width of the fabric.

Although the loose drying equipment and tensioning drying equipment have a certain influence on the door width of the fabric after drying, but this effect occurs after the fabric dyeing, far less than the finished product styling effect on the door width of the fabric. Some special styles of fabric, such as bark crepe, pearl hemp and other fabrics, in order to maintain the fabric style, after dehydration and open need to loose drying. Most polyester woven fabrics can be shaped directly after opening.

⑨ Finished product setting

The final shaping of common flat polyester woven fabric has the greatest influence on dimensional stability. Whether it is common fabric, strong twist fabric, wool-like staple fiber fabric or elastic fabric, the door width of the finished product should be based on the width of the fabric itself before shaping. Although increasing the warp tension of the fabric is conducive to narrowing the width of the finished door, it is impossible to narrow the width of the door much by dyeing the fabric with too wide width of the back door through the finished shape. Similarly, it is impossible to increase the width of the door greatly by dyeing the fabric with too narrow width through the finished shape, even if it greatly reduces the warp tension of the fabric during the finished shape.

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 gram weight and feel of the fabric, but also affect the door width of the finished fabric. After the rubber blanket preshrinking machine, the door width of T/C class fabric will increase moderately. The door widens slightly after steaming the wool-like fabric pot. The width of the door will also be widened after washing the weft elastic fabric made of viscose staple fiber warp. The pin-plate setting machine is helpful to maintain the warp tension of the fabric in the final shape, which includes both the positive tensile tension and the negative preshrinking tension. Clip type setting machine is inferior to pin type setting machine in this respect.

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