Source: He Liangzhen, Shao Jianqin
Keywords: dyeing and finishing; sanding; enzyme; cotton fabric
Abstract : The jeanette style dyeing and finishing of cotton fabrics includes many processes such as sanding, polishing and softening. The main factors affecting the grinding and polishing process, such as the selection of processing equipment and processing aids, and the formulation of process parameters, are described.
Key words : dyeing and finishing; sanding; enzyme; cotton fabric Peach skin processing of all cotton fabric
HE Liang-zhen, SHAO Gai-qin
Abstract: This paper covers wet processing of peach skin-like cotton fabric, including sanding, polishing, softening and so on. Main factors mi pacting on sanding and polishing qualities are processing machinery, auxiliaries and corresponding processing parameters.
Key words:dyeing and finishing; sanding; enzyme; cotton fabric
0 Foreword Lyocell fiber is sold under the trade name Tence, l Chinese trade name "Tiansi". The ordinary Lyocell fiber fabric is processed in a wet state, and the surface will have obvious fibrillation phenomenon, that is, the fiber is longitudinally split to produce microfibers having a diameter of less than 4 μm, and the microfibers are nearly transparent, forming a "frost" effect on the surface of the fabric. Also known as the peach skin style. Fibrillation not only imparts an aesthetic effect to the Tencel fabric, but also provides a special hand.
Cotton and Lyocell fiber belong to the same cellulose fiber. Through the well-designed dyeing and finishing process, the surface of the cotton woven fabric can also produce the peach skin style, also known as the “imitation sky†processing of cotton fabric. The cotton woven fabric with peach skin style is full, smooth, delicate, soft and warm. It is popular among consumers for fabrics and home textile fabrics.
Generally, the cotton woven fabric does not produce significant fibrillation during processing, and it needs to be ground and napped, and then cellulase is used to remove the plush on the surface of the fabric to form a peach skin style.
At present, the processing process of cotton woven fabric jeanette ("Imitation"): preparation cloth → singeing → bleaching → tenter drying → sanding → polishing → dyeing → shaping → soft → inspection packaging The specific operation of each process is described later.
1 Pre-treatment When singeing, the gas singeing machine is used to ensure the effectiveness of the bristle device and improve the singeing efficiency. The immersion of light alkali during singeing is beneficial to improve the efficiency of de-boiling.
Bleaching is mainly based on oxygen bleaching, and the process conditions should be soft to minimize the strong damage of the fabric. The whitening of the fabric can be achieved by bleaching the whitening agent by complex bleaching or shaping of the finished product to improve whiteness.
2 Grinding The sanding process of cotton woven fabric is the process of rubbing the surface of the fabric with the sandpaper coated on the sanding roller to produce the fluff. The sandpaper is coated with densely packed, sharp abrasives (metal abrasive or diamond grains). The sanding roller which rotates at a high speed during sanding is in close contact with the fabric, and the fiber is ground by the abrasive, the fiber is pulled out from the yarn, and cut into a single fiber of 1 to 2 mm in length to form a pile. As the sanding progresses, the length of the pile on the fabric tends to be uniform, forming a uniform, dense, flat suede. After the cotton woven fabric is ground, the surface of the fabric is provided with a short, dense, uniform and homogeneous fluffy velvet, which resembles the skin of the peach. The color is soft, the hand feels soft and full, the wet stagnation is strong, the touch is comfortable, and the fluffing phenomenon is reduced. The drape is greatly improved.
2.1 Preparation of sanding After the fabric is pretreated, the degree of drying has a certain influence on the uniformity of warp density of the fabric during tentering. When the tenter is shaped, the curved weft yarn is straightened, which reduces the warp density. At this time, the weft yarn is less restricted by the warp yarn, and the elongation at both ends of the weft yarn is more obvious than that in the middle during the drawing, which tends to cause the phenomenon that the warp of the fabric after the tentering is larger than the two sides. Before the tentering, if the fabric maintains a certain moisture content, it is beneficial to slowly eliminate the internal stress of the fabric during the shaping, reduce the density difference between the edges, and improve the sanding quality. If the moisture content of the fabric is too low, the fabric will heat up too quickly when the web is stretched. At this time, if the density of the fabric is not uniform, the suede after sanding tends to produce warp marks. The greater the weight of the fabric, the higher the moisture content after drying. In production, the sample is sampled by a disc sampler, and the moisture content can be well controlled by simple weighing, drying and calculation. The actual production experience shows that the moisture content of the light-weight fabric and the medium-thick fabric after drying is controlled at 7% and 10%, respectively, and the uniformity of fabric density after tenter shaping is better.
2.2 Sanding equipment There are many sanding equipments, which are mainly divided into dry sanding equipment and wet sanding equipment. At present, the wet broaching machine is used to grind the cotton woven fabric less. Because it is dried after grinding, it is easy to cause the suede to fall down. Direct drying in the wet state will seriously affect the dimensional stability of the fabric. Conducive to the subsequent processing of the product. There are two main types of dry sanding equipment, one is horizontal and the other is planetary gear train. The domestic dry sanding machine is mainly horizontal, and the imported dry sanding machine is mainly planetary gear. At present, the development of carbon brush rolls for the development of knitted fabric bristles is very rapid, which has led to an increase in the application of planetary gear grinding equipment.
The sanding rolls of the horizontal sanding equipment are all round, and the sanding rolls of the planetary wheel sanding equipment have a hexagonal or eight diamond shape in addition to the circular shape. The core of the round sanding roller is mostly made of metal, and the surface is directly coated with sanding paper. The core of the planetary wheel-type sanding roller with a hexagonal or eight-diamond shape is also made of metal, but the diameter is fine. The outer backing wood is also hexagonal or eight-diamond, and is tightly fixed to the roller core by screws. When the grinding roller is in contact with the surface of the fabric, the grinding process can be started, and the impact force of the grinding roller on the surface of the sanding is larger, and the grinding efficiency is higher. When the contact pressure (sand tension) is fixed, the circular grinding roller has the least impact on the surface of the sanding, the impact of the six-diamond roller on the surface of the sanding is the greatest, and the impact of the eight-diamond roller on the surface of the sanding It is somewhere in between.
2.3 Abrasive process Al2O3 and SiC particles are lower in price and are commonly used as abrasive surface abrasive grains. Synthetic diamond particles are harder but more expensive. The size of the abrasive particles is usually expressed in terms of particle size, that is, the number of pores per square inch, and the larger the number of pores, the smaller the particle size of the abrasive grains. The number of holes per unit area is often referred to as the mesh number. The larger the number of sandpaper, the smaller the actual size of the abrasive grains, the finer the surface of the sanding paper, the finer and evener the pile, and the smaller the strength of the fabric. Generally, the number of sandpaper is selected according to the customer's sample and fabric specifications. Lightweight fabrics are suitable for high-grade sandpaper for short velvet, and low-weight sandpaper for heavy velvet for long velvet.
The greater the tension of the sanding, the tighter the contact between the fabric and the sanding roller, and the deeper the sand is embedded in the fabric, the more effective the number of sand grains, the better the sanding effect. However, the greater the tension of the sanding, the greater the degree of yarn damage and the tendency to produce wrinkles. Therefore, it is important to control the sanding tension reasonably. Thin fabrics have less tension when sanding, and thick fabrics have greater tension when sanding. When the fabric is sanded, the rotation speed of the sanding roller is much larger than the running speed of the fabric. The greater the speed difference, the easier it is to produce short, dense and even hair, and the suede is full, but the strength drop is more obvious. The speed of the sanding roller is faster when the medium-thick fabric is processed, and the rotation speed of the sanding roller is slower when the light-weight fabric is processed. The larger the coating angle of the fabric and the sanding roller, the larger the contact surface, and the better the sanding effect. When using new sandpaper, the wrap angle should be adjusted appropriately. As the sandpaper is used for a long time, the wrap angle should be adjusted until the sandpaper is replaced. The more the number of sanding rollers, the higher the sanding efficiency, the softer the fabric and the finer the suede. When the number of sanding is singular, it is not easy to cause unevenness of the inverted hair and the weft.
When the direction of rotation of the sanding roller is consistent with the running direction of the fabric, the grinding efficiency is low, but the suede surface is soft; when the running direction is opposite, the sanding effect is better, but the fabric strength is obviously decreased, the operation is difficult, and the crease is easy to occur. . In order to improve the utilization rate of the sandpaper, the direction of the sanding roller can be uniformly changed during the maintenance of the equipment. In order to improve the suede effect, the fabric should be prevented from violently shaking during sanding. Before the end of the fabric grinding, the fluff which has been broken inside the suede should be removed as much as possible by the bristles to reduce the influence on the subsequent processing.
3 Polishing By cellulase treatment, the uniformity of the suede surface of cotton wool fabric is further improved, and the processing of fabric hand feeling is improved, which is generally called "polishing" processing of cellulose fiber products. Cellulase has a significant and specific degradation effect on cellulose fibers. The surface of the cotton sanded fabric has a large amount of fluff, and the fluff has a larger specific surface area than the fabric itself, so the surface fluff of the ground cotton fabric has a much greater chance of contact with the cellulase in the polishing fluid than the fabric itself. The prominent longer fluff is first degraded by cellulase and detached from the surface of the fluff, making the entire suede more uniform. In addition, the yarn below the suede will be degraded to a certain extent under the action of cellulase, and the yarn moving space is correspondingly increased, so that the fabric feels softer.
3.1 Selection of additives There are many kinds of biological enzyme preparations for polishing, and cellulase has the best effect. Polishing is carried out in a weakly acidic medium, usually with acetic acid. In order to prevent the residual cellulase from continuing to degrade the cotton fiber in the subsequent processing, the cellulase needs to be inactivated before the end of the polishing, and usually the two methods of heating the enzyme and the alkaline agent are used. In order to reduce the surface abrasion caused by the rope polishing method, the softener in the bath can be used during processing. However, since the fibrillation phenomenon of cotton fibers is significantly lower than that of ordinary Lyocell fibers, whether or not the softener is added to the bath during polishing is not the main cause of the surface abrasion of the textured fabric.
3.2 Polishing equipment Intermittent rope overflow dyeing equipment is the main equipment for polishing cotton wool fabric products. The nozzle diameter of the overflow dyeing equipment is too small, which may result in the smooth processing of the rope fabric. Usually, the J-cylinder is more suitable for the enzymatic polishing of cellulose fiber-finished products than the O-cylinder. The airflow dyeing cylinder has a better polishing effect on the cotton woven fabric. The M2 airflow softening equipment produced by ICBT of France is also very suitable for the biological enzymatic polishing of cotton woven fabrics.
Keeping the processing equipment clean during polishing is the key to avoiding the poisoning of biological enzymes. Avoiding the residue of heavy metal ions is the basis for keeping the processing equipment clean. After each polishing process, the filter of the joint between the material tank and the dyeing tank is cleaned in time, which not only improves the processing efficiency, but also reduces the amount of cellulase.
3.3 Polishing process Generally, the polishing process of the ground cotton fabric is: temperature 55 ° C, pH 5.5, holding time 55 min, cellulase dosage 1.5% (owf), bath ratio 1:15. The process temperature has the greatest effect on the polishing effect, followed by the pH of the processing fluid. If the temperature is too high or the pH is too high, the polishing efficiency and effect will be significantly reduced. In the polishing process, if the fabric weight is reduced by more than 5%, the fabric strength is very obvious, so the amount of cellulase must be cautious. When processing new products, it is possible to add cellulase in batches or reduce the amount of initial addition to avoid excessive reduction in fabric strength.
When the polishing temperature exceeds 80 ° C, or the pH of the processing liquid is greater than 9, the cellulase is inactivated. After polishing, it usually needs to be washed before it can be dyed. Regardless of the rope-like or flat-width dyeing method, in order to keep the polishing equipment clean, a cylinder-changing method should be adopted. When the water is washed at room temperature, if the pH of the washing liquid is increased by soda ash, not only the amount of steam and the amount of water can be saved, but also the washing time can be shortened. If dyed with vat dye or reactive dye, the water washing after polishing does not need to over-emphasize the residual amount of soda ash on the fabric surface. As long as the water washing after dyeing is strengthened, the residual amount of soda ash on the surface of the fabric can be guaranteed.
If the amount of cellulase added is too large, the holding time is too long, and when the grinding process is too sufficient, the fabric will be significantly damaged. Keeping the fabric stronger is more important than removing the long fluff from the fabric surface. When polishing, when the fabric is strongly damaged and the surface of the fabric is still too much, it can only be remedied by the dry tapping of the subsequent process.
4 Dyeing long-distance rolling can maximize the polishing effect, improve the production efficiency and ensure the color accuracy, but it is easy to cause the fabric to feel the knot, lack of resilience, so the dyeing of cotton imitation Tencel woven fabric is still processed intermittently. Mainly. Uniform low tension during dyeing is the key to maintaining and maintaining the feel of the fabric. Intermittent flat-panel dyeing maintains the polishing effect, improves the fabric feel, and improves dimensional stability, eliminating the need for pre-shrinking of the rubber blanket. At present, the dyeing process of medium-thick cotton imitation Tencel woven fabrics also adopts the long-car padding method, but it is mainly used to process jackets, jackets and bedding products. Because such fabrics are pre-shrinked by a rubber blanket, the feel and gloss of the fabric can be improved by loosening finishing and light calendering of the airflow softening device.
5 Shaped When the cotton sanding and polishing fabric is tenter shaped, the drying temperature is 150~160°C, and the speed is 30~40m/min. When the number of drying chambers of the needle plate type hot air tenter setting machine is less than 9 knots, the setting efficiency is lowered. The tension and overfeed size should be such that the cloth surface is flat and the needle is quickly placed. When the cloth is dropped, the cloth surface temperature should not be too high, so as to avoid dead pleats. If necessary, a large package can be used to keep the cloth flat and maintain the uniform tension of the cloth.
6 Soft Soft finishing is divided into chemical and mechanical methods. Commonly used silicone softeners are fluffy, slippery and hydrophilic, which can meet the different requirements of customers for the feel of sanded cotton fabric. The amount of softener added is based on the product not drawn. It is softly finished by padding, and is more efficient than the softening process by dipping.
Dry tapping is a common mechanical soft processing method, also known as "sand loose" finishing. The main purpose of the loosening finishing is to rub the longer fluff of the fabric surface which has not been treated by cellulase, and the new long fluff of the surface of the rope dyed fabric, while improving the fabric feel. At present, the common equipment for loosening finishing is M2 airflow soft machine and AIRO1000 airflow soft machine. In the airflow soft machine, the repeated suction and ejection of the high-speed air causes the sanded cotton fabric to collide with the inner wall of the soft machine multiple times, the rigidity of the warp and weft yarn is gradually reduced, and the fabric feel is further improved. In order to improve the loosening finishing effect, a small amount of moist hot steam can be applied to the machine if necessary.
7 Product development is to fully reflect the style of cotton imitation Tencel woven fabrics. Common light and thin fabrics are: warp and weft yarns are more than 18.45tex single yarn; warp and weft density is not less than 524 roots/10cm × 299 roots/10cm; 2 The upper ones have more twill, the upper ones have fewer twill, and the plain and satin are few. As far as fabrics are concerned, there are many light and light-colored summer casual trousers with high and high density, and thick and dark coat fabrics are gradually increasing in autumn and winter. In addition, if a slight calendering finish is added after polishing, the surface of the fabric can be given a natural soft gloss. The combined processing of sanding, polishing and calendering has become a new feature in the processing of cotton apparel fabrics in winter 2008. The variety and number of plain-woven home textile cotton-knitted fabrics of higher density and various colors are also increasing.
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