The printing of knitted fabrics has developed rapidly in just ten years, but because of its dimensional stability, it is difficult to control during the processing, making it difficult to develop circular fabric printing of knitwear, especially cotton fabrics containing spandex, except for cotton knitted fabric itself. The size of the plasticity is large, and the drape weight of the cloth and the tension of the cloth feeding frame are also subjected to the tensile force of the speed change. The shape and size of the flower pattern are more difficult to control, and it is more difficult to maintain the flower shape when the geometric pattern is encountered. Some spirits are difficult to achieve satisfactory results. This requires the necessary control of the entire process to be resolved.
1 Printing process with spandex knitted fabric Weaving open film rolling → loose cloth → (steaming) → predetermined shape → pre-treatment → (dyeing) → printing → steaming → washing → dehydration → drying → setting.
2 Separation design of color separation design Computer color separation drawing, first of all, according to the variety of fabrics, the size of the elastic force, the pattern of the return, the number of sets, the printing method (direct printing, printing, anti-printing), deep and complex color, And scale the drawing to the specifications that meet production requirements.
2.1 Scaling of the printing size Under the condition of the return position, according to the size of the spandex content of different fabrics, the printing speed is set and the pattern shape after printing is maintained. When the spandex content of cotton spandex is between 3% and 5%, the warp direction of the pattern is enlarged by l3% to l8%, and the latitudinal direction can be reduced by about 3%; when the spandex content is between 6% and 15%, the pattern is The magnification is 20% to 26%, and the latitude is reduced by about 5%. The ratio of the warp magnification should take into account the speed of the printing speed. Therefore, the design of the drafting process must take into account the conditional design of the entire printing process. At the same time as the drafting, various parameters of the rotary screen printing have been formulated. The printing speed of the above data is controlled between 30 and 40 m/min. If the printing speed is above 50 m/min, the warp-like elongation ratio of the flower shape is required to be larger, but the general printing speed is below 40 rn/min, regardless of the flower shape. It is still easier to control in terms of quality.
2.2 Processing of complex color position in different printing processes during computer color separation Compared with woven fabrics, knitted fabrics are looser and have better permeability. Therefore, there is a slight difference between the draft and the woven fabric print. In the direct printing of dyeing of knitted fabrics, the permeability of the printing paste is relatively good, generally 8 to 16 filaments of complex color, in the case of the mechanical precision of the printing equipment, 8 filaments are good, ensuring the printing precision, while processing the stack When printing in color, try to reduce the three complex colors of the cover to prevent the printing paste; the anti-printing printing has the anti-activity and active anti-activity of the coating, and the anti-active process of the coating, because the edge of the printing printing is not easy to open, the printing of the coating is divided into The color draft, the size is drawn according to the requirements of the color draft, and the active flower is covered with the paint; when the active anti-active printing, the set of monochrome prints must be 8 to 16 silk, so that the printed pattern and color The draft conforms; when printing the print, the edge of the color that is connected to the bottom color must be 16~24 filaments. The color of the print should not be covered with each other as much as possible, but the white part can be covered in the whole. The color of the printed part can increase the color brightness of the colored part without the white edge caused by the printing. In terms of the processing of color separation, in addition to the above requirements related to the printing effect, the general principle of treatment is to conform to the original spirit, and the style of the flower is repeated on the cloth.
2.3 Considering the method of making the net, the size of the draft is also related to the method of making the net. At present, companies use more inkjet nets and wax-jet nets, and some still use film-made nets. Relatively speaking, the inkjet net is slightly less accurate than the wax-laid net, because the ink-jet net is to make the ink spray wet on the round surface at room temperature before exposure, and the ink has a process of spreading, which affects The accuracy of the draft, the reason for this part must be considered when scaling complex or monochrome edges. Of course, the temperature and humidity of the netting chamber must be kept constant.
2.4 Selection of nickel mesh network The mesh of nickel mesh is selected according to the fineness of the pattern and the permeability of different fabrics. The nickel mesh is an indispensable material for printing. Currently, the commonly used nickel mesh has 40, 60 mesh. , 80, 105, 125, 155, etc. The permeability of nickel mesh is an important indicator. Of course, the actual amount of slurry is related to the viscosity of the slurry, the size and pressure of the scraper or magnet, the printing speed, and the fabric. However, compared with the woven fabric, the knitted fabric has a rougher texture, so the same pattern is printed, and the selected mesh on the knitted fabric can be larger than the woven fabric. 50 mesh is mainly decorated with gold and silver grain, 60 mesh is used for large-area background printing, 80 mesh is used for thicker and large-sized printing of glue, water slurry, etc., l05 mesh is mainly used for fine fabrics. The color, 125 mesh, and l55 mesh are mainly used for printing particularly fine patterns. If it is a plush or velvet print of the terry cloth, the fineness of the printing will be affected by the texture of the cloth surface. The high mesh size is difficult to reflect the effect of printing the fine pattern, mainly considering the permeability of the printing. the Lord. Therefore, the choice of nickel mesh network is mainly determined according to the specific conditions of each plant.
3 Pretreatment methods for spandex fabrics 3.1 Predetermined shape In order to improve the running performance during spinning, silicone oil lubricants and other additives are used in the weaving process. These additives naturally degrade over time causing the fibers to yellow and the elasticity of the fabric to decrease. At the same time, the spandex-containing fabric will form a "cold shape" during long-term storage, which causes the fabric to produce permanent wrinkles that cannot be eliminated in the post-processing. Therefore, in addition to reducing the storage time, the spandex-containing knitted fabric is more importantly, after the weaving, the flat-width package is opened immediately after opening. Avoid the chance of creases.
In the spandex-containing knitted fabric, the spandex inside the fiber after the machine has a certain internal stress formed during weaving. Therefore, the purpose of preheating and setting is to eliminate the stress through the process of fabric relaxation, to make the size of the fabric sufficiently stable, and to eliminate the permanent crease of the fabric in the post processing. If the coil formed during the weaving of the cylinder, the second coil is on the left side of the first coil, then the direction of the cloth should be 7% to 10% (relative width) in front of the front when the shape is predetermined, so that the twist of the finished product be consistent.
Therefore, the optimal pre-formation scheme is: relaxation → steaming (80 ° C hot water without steaming conditions) → super-feeding shape → (into the fabric pre-treatment → shaping → printing). Most dyeing plants directly roll into the shape because there is no steaming equipment. When the temperature is below 10 degrees (winter), the fabric is prone to creases. After the fabric is relaxed by the steamer, it will be shaped and will receive satisfactory results. The heat setting temperature is preferably between 85 and 190 ° C, and the setting time is 45 to 60 s. If the setting temperature is too high, the fabric will be yellowed. At the same time, if the impurities and auxiliaries on the fabric are partially degraded by the influence of the baking, and the degradation substances migrate to the inside of the fiber to cause the marks, the stains are difficult to remove in the subsequent processing, and the oil spots inside the fibers during dyeing. The dye will be absorbed first, and in the process of heat preservation and dyeing, it will not be able to run out in time to form a deep spot. Even if it is further dyed and dyed, it will remain on the fabric. Therefore, avoid the high temperature of 195 °C or above. It also affects the spandex fastness. When the shape is set, the width is 10% to 15% wider than that of the blank, so that it has a sufficient recovery in the dyeing cylinder before the treatment, so that the internal stress of the fabric is completely eliminated.
3.2 Pre-treatment The knitted fabrics to be printed should also be pre-treated to remove cotton stains and grease wax, etc., to increase the whiteness of the fabric and improve the wetting and water absorption properties of the fabric, so as to achieve a good printing effect. The pretreatment process can be divided into two categories, namely traditional alkali treatment and modern biological enzyme treatment. The biological enzyme treatment meets the requirements of environmental protection processing, but at present, fabrics with high requirements for whitening or bleaching are difficult to meet the requirements, so conventional The alkali treatment process is still widely used, and it is necessary to gradually cool down the water washing after the pretreatment of the spandex fabric to prevent the fiber from shrinking and causing creases due to sudden cooling.
3.3 The setting of semi-finished products requires the shaping of semi-products to be carried out according to the original design process. Generally, the width of the fixed-form width is about 3% to 5% wider than the width of the finished product, and the warp reduction ratio is controlled within the shrinkage rate required by the finished product. The elongation of the patch is equal to the magnification of the draft. If it is a single-faced knitted fabric, then the paddle trimming and the optimal twist control are required to reduce the printing weft caused by the twist. The width of the pulp edge is about 1 cm, and the slurry is broken. It should not be too thin or too thick, too thin to function as it should be. Too thick will affect the printing effect of the near cloth edge. Paint printing, because the solid slurry staying on the cloth surface will increase the square gram mass of the fabric relatively, so under the condition of the width and the shrinkage rate, the gram quality can be lighter.
4 Operation method of rotary screen printing 4.1 When sewing the seam head, first check the front and back of the fabric. Before the seam, cut the edge along the weaving thread, and align the two sides. The fabric after the seaming machine is neatly arranged. Machine printing.
4.2 Feeding and printing speed According to the performance of the spandex-containing knitted fabric, choose the heat-shrinkable resin or the patch cloth, adjust the cloth edger, the stripper, the vacuum cleaner, adjust the tension of the cloth, and include the spandex knitted cloth patch. The tension is reduced to the minimum, and the width of the cloth is reduced by 3% to 5%. The vacuum cleaner is turned off. When the cloth is fed, the tension is uniform and the cloth surface is flat to prevent the weft. The spandex printing of spandex-containing knitted fabrics is affected not only by the tension of the patch but also by the speed of the fabric. Therefore, even if the tension of the patch is almost no, the instantaneous pulling force due to the change of the speed of the car will cause different elongation of the fabric. According to the practice test, when the printing speed is below 20 m/min, the width of the patch is reduced by 1% to 2 %, warp direction elongation 3% to 5%: when the printing speed is 20~25 m/min, the width after patching is reduced by about 2%, and the warp direction is extended by 5% to 10%: the printing speed is 30~35 m/ When min, the width of the patch is reduced by 2 to 4%, the warp direction is extended by l2% to l8%; when the printing speed is 35 to 45 m/min, the width of the patch is 4% to 6%, and the warp is elongated. 18% to 25%; when the vehicle speed is greater than 45m/min, the width of the patch is reduced by more than 7%. Of course, as the width is reduced, the warp direction is extended by a certain proportion. Therefore, the rotary screen printing of spandex-containing knitted fabrics is suitable for printing speeds of 30 to 40 m/min. The excessively fast speed is not conducive to the control of product quality. What's more, the pattern return of the rotary screen printing is subject to certain restrictions. Unlike the flat screen printing, the return of the rotary screen printing is fixed length. The speed must be strictly controlled according to the proportion that has been enlarged. Otherwise, due to the variability of the size of the knitted cloth patch, the pattern size of the printed product is deformed, even different from the horse, so the printing speed has been determined at the time of the rotary net production. It cannot be changed arbitrarily in future operations.
4.3 The pressure of the rotary screen printing and the selection of the magnetic bar (scraper). When the printing is done, the slurry in the net barrel is moderately high and low, and the thin stem and small area flower are less stored, and the large piece of surface flower is stored a little more. The carved sample is steamed once every two to three hours to check the quality of the print. It is also possible to indirectly white cloth in a certain amount of grey cloth to regularly check the printing quality of the engraving and the quality of the rotary screen. According to the sizing amount required by the fabric, the pressure and the magnetic bar (scraper) are controlled, the thin stem and the small-area flower type are selected as the magnetic bar No. 10 or l2, the scraper is 45 to 50 cm; the block-shaped pattern is selected as the magnetic bar 15-20 No., scraper 50cm; large block print selection magnetic bar No. 25, scraper 55cm. The size of the pressure varies from small to large depending on the pattern from the thin stem to the block surface. In short, according to the performance of the rotary screen printing machine to adjust the amount of pulp and penetration.
Due to the speed of the rotary screen printing, and the color printing of the engraved printing is difficult to see with the dark cloth, the discharge printing of more than three sets of colors is generally carried out on the flat screen printing machine, only one or two sets are not available. The engraved print shape with color precision can be printed on a circular screen.
4.4 The development of the printing process The prescription of the printing process depends on the dyeing performance of the dye on different fabrics. For example, direct printing of reactive dyes requires a slurry (sodium alginate), a reactive dye, an alkaline agent (baking soda or soda ash), and a moisture absorbent (urea) in the formulation. The amount of alkali agent and moisture absorbent is crucial, which is related to the ability and effect of dye coloring and coloring fibers. Therefore, depending on the fabric, the amount of additives selected will vary. In general, cotton or mercerized cotton is a little more amorphous than human cotton, modal, bamboo fiber, etc., dyes are easy to enter the fiber, especially the amount of urea is 3% to 6%; and human cotton, modal, bamboo The crystallization area of ​​fibers such as fibers is much more than that of cotton fibers, so the amount of urea needs to be up to 25%, so that the required water can be absorbed during steaming to achieve normal color development and good color yield. K-type reactive dyes are also relatively limited in their ability to color modal fibers, which does not achieve the richness of color, and P-type or PX-type reactive dyes can achieve good coloring performance.
4.4.1 Spandex printing fabric active process table 1
Formulated K-type dye Puschian PX/P Ciba clone P/PT
Adapted to varieties cotton cotton cotton cotton, modal,
Bamboo fiber cotton cotton, modal, bamboo fiber alginate paste (4%) 500
Thickener (2%) 200
Reactive dye X
Anti-staining salt S 10 10 10 10 10 10
Urea 30～60 150～250 30～60 150～250 30～60 150～250
Baking soda 10～30 20～30 10～30 10～20 10～30 10～20
Soda ash 0.5 5~lO 5~lO
Water Y
Total 1000
4.4.2 Discharge printing process a. Preparation and operation steps of the pulping
Engraving whiteness /% 12 14 16 18 20
Starch ether pulp / g 330 320 320 290 270
Sodium alginate (5%) / g 350 340 320 330 330
Carved white powder / g 120 140 160 180 200
Soda ash / g 60 60 60 60 60
Sodium hexametaphosphate / g 10 10 10 lO 10
Salt / g 20 20 20 20 20
Water / g XXXXX
Total / g 1000 1000 1000 1000 1000
Operation steps: Mix the starch ether slurry and the sodium alginate slurry according to the prescription, add sodium hexametaphosphate, salt, water, etc., and stir for 30 to 60 minutes. Add soda ash powder and sculpt white powder until evenly. The prepared diluted pulp was quantitatively analyzed for whiteness by iodine droplet method and recorded. In order to mix properly when mixing. Each factory prepares several kinds of dilute pulp with different ratios of whiteness as needed to create convenient conditions for the preparation of printing paste.
b. Process prescriptions and operation steps for various types of white pulp
Carved white pulp carving whiteness /% 12 14 16 18 20
White pulp (white dextrin) / g 700 680 660 640 620
Carved white powder / g 120 140 160 180 200
Water / g 140 140 140 140 140
Sodium hexametaphosphate / g 5 5 5 5 5
Soda ash / g 60 60 60 60 60
Brightener / g 2 ~ 3 2 ~ 3 2 ~ 3 2 ~ 3 2 ~ 3
The chemical is too white / g 2 ~ 3, depending on the need, or not.
Flat plus O/g 15, increase the slipperiness of the print, can not add the total amount / g 10OO
If neutral whitening is used, the amount of soda ash in the prescription can be reduced to 2%. The pure cotton knitwear vat dyeing white pulp process prescription is used for the white color of the base color, and the white pulp for the base pulp can guarantee the whiteness, because the starch ether and the sodium alginate pulp both contain yellow pigment, which will affect The whiteness of the base color will be used to obtain the expected effect, but many printing factories have no cooking pot, so if you use starch ether or sodium alginate directly, you will not be able to achieve white dextrin. The whiteness of the base pulp, the whitening agent in the white pulp must be a reducing agent and an electrolyte.
The specific printing process has been elaborated in the previous article "Production Practices of Reactive Dye Printing and Discharging Processes for Cotton Knitted Fabrics" and will not be repeated here.
4.5 Drying after printing Strictly control the temperature of the drying room. The paint printing is better at l40～150°C. When the drying is done, the adhesive is partially crosslinked; the active printing is about l35°C, and the two sides are evenly dried. The degree is different, so there will be left and right chromatic aberration after steaming. Green, gray and other sensitive colors are more obvious; vat dye printing printing 125 ~ 130 ° C, not only to prevent drying and color, but also consider the temperature is too high to reduce the dying dye early to affect the color. The engraving and printing will follow the steaming. If it is piled up for a long time, it will cause the dye on the surface of the cloth exposed to the air to be oxidized first, resulting in permanent color difference. For the printing of polyester fabric with smooth surface, although there is solid content comparison High paste, but it does not rule out the possibility that the pulp layer is easy to be towed. After printing, it can not be squeezed, dragged or displaced, and naturally falls into piles, and then steamed into a steaming machine. In the case of reactive dye printing of fabrics such as modal and human cotton, it is best to spray the wet before the steaming machine to make the temperature of the fabric uniform at room temperature, and maintain the consistency and integrity of the color.
4.6 Steaming and Washing The spandex knitted fabric is more steamed than the cylindrical steamer by the continuous steaming machine, because if it is steamed in the cylinder steamer, the hanging spandex knitted fabric will not only latitude in the wet heat steaming Long deformation, and some drag to the bottom of the box, magnified the disadvantages of the cylinder steamer easy to produce up and down depth, resulting in uneven steaming color. When the long-ring steaming machine is steamed, it is also necessary to pay attention to the tension of the cloth to be fed, as long as the cloth can be driven into the steaming machine. The cloth should be leveled, especially the engraved printing, the cloth surface can not be folded, otherwise it will produce color, drag and so on during the steaming process. K-type reactive dyes have a steaming time of 10 to 14 minutes, a temperature of 102 ° C, a saturated steam inlet pressure of 0.4 to 0.5 MPa, and P-type and PX-type reactive dyes for 5 to 8 minutes of steaming, a temperature of 102 ° C, and saturated steam. The steam pressure is 0.4-0.5 Mpa; the disperse dye evaporation time is 7 min, and the temperature is 175 °C.
Washing with spandex-containing knitted fabrics should pay more attention to the warp force of the whole washing process. The rope-shaped pull cylinder is the most traditional washing equipment, which is more suitable for washing knitted fabrics. However, when it encounters the printed printed fabric, it will show the shortcoming that the fabric is always in a rope state, and inevitably will produce color. Therefore, the use of loose flat and loose rope continuous water washing is currently a good knitting washing machine, the flat state of the knitted fabric by spraying water, can easily puff the fabric on the fabric, wash off the fabric The alkaline agent and a part of the floating color enter a rope-like soaping or reduction cleaning process, and a good water washing effect is obtained.
4.7 After the finished product is shaped with water, the spandex knitted fabric is much smaller than the finished product. The soft setting on the setting machine often fails to meet the expected requirements. It needs to be dried in a loose dryer to allow it to naturally shrink. After super-feeding, the shaping speed is controlled at about 20 m/min, allowing the fabric to have sufficient time for overfeeding. Too fast a set speed will cause the fabric to be tight on both sides and loose in the middle. The setting temperature is 135-160 °C, because the finished shape is stabilized on the basis of the predetermined shape. The too high setting temperature will not only make the fabric yellow or yellow part of the softener, but also lose the partial elasticity of the spandex. Bad effect.
5 Conclusions 5.1 The circular screen printing of spandex-containing knitted fabrics, especially the discharge printing, has always been a production exclusion zone, which is related to the slightest process from the processing of the color draft to the printing process. The dimensional stability and torsion Problems such as latitude and skew, which caused irreparable damage. Through our practice, this problem has now been solved, and the rotary screen printing machine can completely print elastic knitted fabrics containing spandex.
5.2 In the processing of spandex-containing knitted fabrics, the most important thing is to grasp the problem of no wrinkles in each process, which is to start every step from weaving.
5.3 The requirements for the quality, width, shrinkage and torsion of the final product containing spandex knitted fabrics must be grasped from the predetermined shape in addition to the requirements for weaving. Otherwise, the same weaving specifications, due to different processing methods, will produce different grams of mass, width, shrinkage and twist. The predetermined width control and temperature and speed play a decisive role.