Textile fabric knowledge: dyeing and printing
There are two main methods for coloring fabrics. One is extensive coloring (conventional coloring), which mainly involves placing fabrics in chemical dye solutions. The other method is to use paint. The paint is made into tiny insoluble colored particles to adhere to the fabric (the coloring of fiber raw materials is not included in this). Dye is a relatively complex organic substance with many types. 1. Acid dyes are mostly suitable for protein fibers, nylon fibers and silk. It is characterized by bright color, but poor washing fastness and excellent dry cleaning fastness. It is widely used in natural dead coloring. 2. Cationic dyes (alkaline fuel), suitable for polyacrylonitrile fiber, polyester, nylon, cellulose and protein fibers. It is characterized by bright color and is very suitable for man-made fibers, but its fastness to washing and dyeing of natural cellulose and protein fabrics is very poor. 3. Direct dyes are suitable for cellulose fiber fabrics. The washing fastness is relatively poor and the fastness is different. However, the washing fastness of modified direct dyes will be greatly improved. 4. Disperse dyes are suitable for viscose, polyacrylonitrile fiber, nylon, polyester, etc. The washing fastness varies, with polyester being better and viscose being worse. 5. Azo fuel (Naftol dye) is suitable for cellulose fabrics with bright colors and is more suitable for bright colors. 6. Reactive dyes are mostly used in cellulose fiber fabrics and less often in proteins. It is characterized by bright color, durability, good washing and rubbing fastness. 7. Sulfur dyes are suitable for cellulose fiber fabrics. They are dark in color, mainly navy blue, black and brown. They have excellent durability and washing fastness, but poor chlorine bleaching fastness. Long-term storage of fabrics will damage the fibers. 8. Vat dyes are suitable for cellulose fiber fabrics. They have good durability and washing fastness, and are resistant to chlorine bleaching and other oxidative bleaching. 9. Coating is suitable for all fibers. It is not a dye, but adheres to fibers mechanically through resin. Dark fabrics will harden, but the color registration is very precise. Most of them have good finishing fastness and good washing fastness, especially It is medium or light color. Types of coloring Coloring of fabrics can be carried out at any stage, and can be done at different stages such as fibers, yarns, fabrics and ready-made garments. 1. Coloring of loose fibers. Before spinning, the fibers or loose fibers are put into a large dye vat and colored at an appropriate temperature. Color spinning mostly adopts the method of coloring loose fibers (it also has the effect of single dyeing of different fibers), and is often used in woolen fabrics. 2. Top coloring This is also the fiber coloring before the fibers are made into yarn. The purpose of coloring the loose fibers is the same as that of the loose fibers, which is to obtain a soft color mixing effect. Top coloring is generally used for combed wool yarn and wool fabrics. 3. Spinning yarn dyeing Before weaving, the spinning yarn is dyed. It is generally used for colored fabrics, sweaters, etc. or the spinning yarn (sewing thread, etc.) is used directly. Spinning yarn dyeing is the basis of dyeing and weaving. There are three methods for coloring conventional spinning yarns: ①Hank coloring–soaking loose skeins in a special dye vat, which is a high-cost coloring method; ②Pannel coloring-Pannel coloring The spinning yarn is wound on a bobbin with holes, and then many bobbins are put into the dyeing vat. The dye liquid circulates, and the loosening effect and softness are not as good as that of skein dyeing. ③ Warp beam coloring – it is a kind of large-scale package coloring. Before weaving, the warp beam (warping) must be made first, and the entire spinning yarn of the warp beam is colored, such as combined sizing and dyeing machines. Beam spun yarn bundles for coloring. Since it is a warp beam, it is mostly suitable for tatting and coloring. But with the emergence of warp beam doffing, we can turn the dyed spinning yarn on the warp beam into a cheese yarn. This kind of dyed spinning yarn has a wider range of applications. For example, most of the indigo dyeing uses reduction The coloring method can only be solved by using warp beam coloring. It is difficult to achieve without warp beam doffing. 4. Piece dyeing The method for coloring fabrics is piece dyeing. Commonly used methods include rope dyeing, jet dyeing, jig dyeing, pad dyeing (not tie dyeing) and warp beam dyeing. I won’t introduce them one by one here. 5. Coloring of garments: Put the garments into nylon bags, put a series of bags into the dye vat, and continue stirring in the dye vat (paddle type coloring machine). Garment coloring is mostly suitable for knitted socks, T-shirts and other knitted work clothes, sweaters, pants, shirts and other simple garments. Since the 1990s, high and new technologies have advanced by leaps and bounds, and a large number of new materials and new processes have appeared one after another. Moreover, printing and dyeing technology meets the requirements of Ecological Fabric Product Standard 100, catering to the current world fabric consumption trend, and the application prospects are very optimistic. Due to the successful application of new foreign polymer materials and the reduction of commercial costs, the new adhesives, combined with relevant pastes and additives, can be used to print and color large areas of silk fabrics in an appropriate way, and the finished product The feel and color brightness are similar to dye printing or coloring, truly achieving a super soft effect and expanding the range of applications. Special printing: The technology is further developed and improved, including foam station printing, gold and silver powder printing, bead printing, flash printing, imitation burnt-out printing, reverse paint printing, metal foil printing, paint overprint, night flower printing, Diamond Print���Color-changing printing, etc. Imitation burnout printing: a process developed abroad (Japan, Italy, Germany) that uses special pigment printing paste to print on fabrics to create a translucent effect. The main component of this printing paste is polyurethane. It can be used on Palis fabric, cotton waltz, nylon 66 and wool fabrics. It can be used on white ground or colored ground to increase the variety of fabrics. Metal foil printing: It has become very popular in domestic and foreign markets in recent years. It is often used to make women’s tops or skirts, Arab women’s headscarves, etc., with a sense of luxury and luxury. The process is not too complicated, except that a critical adhesive needs to be imported and is expensive. At present, the adhesive has been successfully trial-produced. The effect is similar to that of imported products, and the cost is only 2/3 of imported products. Paint cover printing: Also known as imitation discharge printing, it refers to a method in which paint is directly printed on colored fabrics to obtain a discharge-like printing effect. Paint overprinting is divided into white overprinting and color overprinting. The former has a more mature technology and has more applications. Although the latter has products on the market, it often has problems with the coverage of ground colors and the color development or feel when mixed with mixed paints. Problems such as this cannot be solved very well, especially the big red phase, which often suffers from distortion, that is, the yellowish red phase turns into a pinkish red phase. The solution is to use high-quality adhesives and base powder with low color distortion to make printing paste, which can print imitation discharge printing fabrics with soft feel and good fastness on dark ground-colored fabrics. Flash printing: printing patterns with a flashing metallic finish on fabrics. It can print a flashing metallic finish effect on some fleece fabrics or light fabrics, such as georgette fabrics. It is an ideal way to improve the additional properties of fabrics. A novel printing method with great value. New progress in paint coloring technology. In addition to the research and application of continuous coloring (pad dyeing) and paint dip dyeing (piece dyeing and garment coloring), some new processes suitable for fashion and market needs have been developed in recent years. That is, the one-step color fixing method of paint coloring and printing (i.e., paint coloring-drying-printing-baking) and the one-step finishing method after paint coloring (i.e., the fabric after coloring and drying is treated with resin, water-blocking, water-repellent, and fire-proof , PU coating and other finishing and then baking processes) can greatly shorten the process and save energy, which is very promising. Printing is usually described as the application of color to a local pattern. As mentioned in the previous chapters, obtaining interesting patterns on fabrics can be achieved by several methods, including variations in spinning threads (fancy threads), variations in weaving processes (dobby and jacquard looms) and weaving color effect. Other colored patterns can be obtained by printing patterns on woven, knitted or non-woven fabrics. Fabric printing and coloring use the same dyes or pigments that can be used to produce colored fabrics. The special dyes that have great affinity for fibers used in printing and coloring have the same dyeing principle and roughly the same dye fastness. characteristic. The pattern design of printed fabrics is an important part of the printing industry. For this kind of work in the fabric industry with high fashion requirements, novel patterns and patterns need to be constantly introduced. Fabric printing pattern designers can create patterns through two methods: manual drawing and computer-aided design (CAD). Dyes or pigments are usually applied in a water bath. When the same dye or pigment is used for printing, it must be thickened with gum or starch to prevent it from bleeding through the pattern. This thickened solution, approximately equivalent to the consistency of thick skim milk, is called printing paste. Some dyes cannot be used in printing pastes due to poor solubility and low coloring capacity. Fabric printing factory is a professional department of the fabric industry that produces printed fabrics. They may be a production department of a large fabric joint company, or they may be its entrusted finishing factory. Finishing and printing mills, like knitting and knitting mills (see Chapter 6), can perform the steps of printing on fabrics that are lacking in large fabric combines. Likewise, they are not responsible for the selection of patterns and colors for printed fabrics. The selection of printing patterns and colors is usually the responsibility of design companies or natural cotton shippers (such as fabric wholesalers, import agents, private producers). There are several methods for printing fabrics, among which there are two commercially important printing methods: screen printing and roller printing. The third method is thermal transfer printing, which is of relatively low importance. Other printing methods that are rarely used in fabric production include: wood template printing, wax valerian (i.e. wax-proof) printing, spun tie-dye printing and resist-dye printing. Many fabric printing factories use screen printing and roller printing to print fabrics. Most thermal transfer printing performed by printing factories is also printed using this method. 1. Screen printing Screen printing includes the design of printing screens. Printing screens (the screens used in the printing process were once made of fine silk, this process is called screen printing. After the silk screen has been completed No longer used, but the name screen printing is still commonly used in the printing process. Made of nylon, polyester or wire fabric with a fine mesh stretched tightly over a wooden or metal frame. The screen fabric should be coated with an opaque, non-porous film. Where there are patterns, the opaque film should be removed, leaving a screen with fine mesh. This area is where the pattern will be printed. Most commercial screen fabrics are first coated with a finishing coatA flexible film is applied, and then the film in the patterned area is removed through the induction method to reveal the pattern. Place a screen on the fabric to be printed for printing. Pour the printing paste into the printing frame and use a scraper (a tool similar to a wiper on a car windshield) to force it through the mesh of the screen. Each color in the printing pattern requires a separate screen, in order to print different colors separately. Example: 3-color printing requires 3 screen frames to print 3 colors on the fabric respectively. In addition, each color pattern in the pattern must be accurately positioned on the screen so that the pattern position is accurate after printing, to avoid the phenomenon that the green stem of a rose is printed in the middle of the red petals. Printing is an industrial term that refers to the precise printing of all pattern colors on fabrics. There are three methods to achieve screen printing, and the application principles of each method are basically the same. The first is hand screen printing, which was very common in the 1920s and is still widely used today. Manual screen printing was the only screen printing method until the mid-1950s, when modern technology enabled automation of the process. The second method is called automatic screen printing (also known as flat screen printing and automatic flat screen printing). In the mid-1960s, there was further progress, and the shape of the screen changed from manual and automatic flat screens to round screen shapes. The third method is called circular screen printing or rotary screen printing, which is currently the most widely used screen printing method. 2. Manual screen printing Manual screen printing is commercially produced on a long platen (the platen is up to 60 yards long). The printed cloth roll is spread smoothly on the table, and the surface of the table is pre-coated with a small amount of sticky substance. The printer then moves the frames by hand continuously along the entire platen, printing one frame at a time, until all the fabric is printed. Each screen frame corresponds to a printing color. The production speed of this method is 50-90 yards per hour. Commercial hand screen printing is also widely used to print cut garments. In the garment printing process, the garment making process and the printing process are arranged together. Customized or unique patterns are printed on the pieces before they are sewn together. Because hand screen printing can produce large screen frames for large flower patterns, fabrics such as beach towels, novel printed aprons, curtains and shower curtains can also be printed using this printing method. Hand screen printing is also used to print limited edition, highly fashionable women’s workwear and small batches of products for market exploration. The manual screen printing method is shown in Figure 9-3. 3. Automatic screen printing Automatic screen printing (or flat screen printing) is the same as manual screen except that the process is automated, so it is faster. The printed fabric is conveyed to the screen via a wide rubber belt, rather than being placed on a long table (as in manual screen printing). Like manual screen printing, automatic screen printing is an intermittent process rather than a continuous process. In this process, the fabric moves under the screen and then stops, and the scraper on the screen scrapes (automatic scraping). After printing, the fabric continues to move under the next screen frame, with a production speed of approximately 500 yards per hour. Automatic screen printing can only be used for the entire roll of fabric, and cut pieces of clothing are generally not printed using this method. As a commercial production process, the output of automatic screen printing (flat screen printing) is declining due to the preference for rotary screen printing with higher production efficiency. 4. Rotary screen printing Rotary screen printing has several important aspects that are different from other screen printing methods. Rotary screen printing, like the roller printing to be described in the next section, is a continuous process. The printed fabric is transported through a wide rubber belt to the bottom of the rotating rotary screen tube. Among screen printing, rotary screen printing has the fastest production speed, greater than 3,500 yards per hour. Use seamless perforated metal or plastic mesh. The circumference of a large rotary screen is greater than 40 inches, so the size of a large flower return is also greater than 40 inches. Rotary screen printing machines with more than 20 colors have also been produced. This printing method is gradually replacing roller printing. 5. Roller printing. Roller printing is like newspaper printing. It is a high-speed process that can produce more than 6,000 yards of printed fabric per hour. This method is also called mechanical printing. In roller printing, the pattern is printed on an engraved copper roller (or roller). on the fabric. The copper roller can be engraved with very delicate fine lines that are closely arranged, so it can print very detailed and soft patterns. For example, the fine, dense Perisli scroll tweed print is a type of pattern printed by roller printing. The flower tube engraving should be completely consistent with the design drawings of the pattern designer. Each color requires an engraving roller. (In specific printing finishing in the fabric industry, five-roller printing, six-roller printing, etc. are often used to refer to five-color or six-color roller printing. Roller printing is a mass printing production method that uses less, and the output continues to decrease every year. If each type of printing is produced The batch size of the pattern is not particularly large, so this method is not economical. In most cases, the cost and time required for roller preparation and equipment adjustment make printing using this method uneconomical. However, roller printing is often used for printing applications. Prints with very fine line patterns such as paisley tweed are the main prints that are printed in large quantities in many seasons. The size of the engraving tube depends on the printing machine and the printing pattern. Most printing machines can be configured with a maximum circumference of 16. inch flower tube, that is to say, the printing pattern isRing size cannot exceed 16 inches. The width of the floral tube should be slightly larger than the width of the printed fabric so that the fabric, including the edges, can be completely printed with the pattern. Once prepared, the printing cylinder can be used almost unlimitedly, and millions of yards of fabric can generally be printed with no problem. Color fixation after screen printing and roller printing Once the fabric has been screen or roller printed, the color is positioned on the cloth and requires further processing to fix the color. The dyes used as printing colorants must be able to combine with fibers. The printed fabric can be solidified by placing it in steam with a temperature close to or sometimes exceeding the boiling point of water (high-pressure steaming); this step is called steaming. After steaming, the fabric is passed through a soap bath to remove the printing paste and other substances used in the color paste formulation. Finally, the fabric goes through several washing and drying processes. A large amount of water and heat energy are consumed in the printing process. If pigments instead of dyes are used in printing, the fabric needs to be subjected to dry heat treatment of up to about 210°C to solidify the resin of the fixative coating. This step is called baking and no further treatment is required. Printing with pigments instead of dyes saves a lot of water and energy. In the fabric industry, fabrics printed with dyes are usually called wet printed fabrics, while fabrics printed with pigments are called dry printed fabrics. This is because wet calico requires steaming, and subsequent washing as part of the overall process. Printed fabrics on the other hand are simply dry-heat baked as part of the coloring process and do not require washing. 7. Thermal transfer printing The principle of thermal transfer printing is somewhat similar to the transfer printing method. During thermal transfer printing, patterns are first printed on paper with disperse dyes and printing inks, and then the printing paper (also called transfer paper) is stored for use in fabric printing factories. When the fabric is printed, it passes through a thermal transfer printing machine (as shown in Figure 9-10), so that the transfer paper and the unprinted paper are pasted face to face, and pass through the machine at about 210°C (400T). Under such high temperature, The dye on the transfer paper sublimates and transfers to the fabric, completing the printing process and requiring no further processing. The process is relatively simple and does not require the expertise required in roller printing or rotary screen printing production. Disperse dyes are the only dyes that can sublime, and in a sense they are the only dyes that can be used for thermal transfer printing. Therefore, this process can only be used on fabrics composed of fibers that have an affinity for such dyes, including acetate fiber, acrylic fiber, etc. Nitrile fiber, polyamide fiber (nylon) and polyester. When doing thermal transfer printing, fabric printing factories must purchase this kind of printing paper from highly specialized printing paper manufacturers. Transfer paper can be printed according to the requirements of pattern designers and customers (ready-made patterns can also be used for transfer paper printing). Thermal transfer printing can be used to print garment parts (such as edge printing, breast pocket embroidery, etc.). In this case very designed patterns are used. Thermal transfer printing stands out from the printing process as a complete fabric printing method, thus eliminating the need for large and expensive dryers, steamers, washers and tenters. Since the printing paper can be inspected before printing, inaccurate registration and other defects can be eliminated. Therefore, defects in thermal transfer printed fabrics are rare. The production speed of continuous thermal transfer printing is approximately 250 yards per hour. 8. Jet printing and its development prospects Jet printing is to spray small droplets of dye and stay on the precise position of the fabric. The nozzles and pattern formation used to spray the dye solution can be controlled by computers, and complex patterns and precise patterns can be obtained. Trick loop. Jet printing eliminates the delays and cost increases caused by engraving drums and making screens, which is a competitive advantage in the fast-changing fabric market. The jet printing system is sensitive and fast, and can quickly switch from one pattern to another. The printed fabric is not under tension (that is, it does not stretch to cause the pattern to become distorted), and the surface of the fabric is not rolled over, thus eliminating potential problems such as fabric fuzzing or fuzzing. However, this process cannot print fine patterns, and the outline of the pattern is blurred. Nowadays, the jet printing method is almost always used for carpet printing and is not an important process for printing workwear fabrics. However, with research and advances in mechanical and electronic manipulation technology, this may change. At present, several jet printing machines have been put into fabric printing production, including the Millitron liquid jet printing machine developed by Millilin and its company. Relevant contents of “Defects in Colored Fabrics”: 1. Printing drag paste (colordrag) Printing paste is stained due to friction before drying. 2. Color splash (colorsplatter) The printing color paste is not poured smoothly on the fabric, but splashed or splashed on the fabric, causing color spots or splashes. 3. Fuzzy pattern: The edges of the pattern are not perfect and the lines are unclear. Most of these are often caused by improper singeing or improper color paste concentration. 4. Inaccurate pattern alignment (off-register): Due to the misalignment of the longitudinal arrangement of the printing roller or screen, the front and rear pattern alignment is inaccurate. This defect is also called inaccurate color registration or pattern shift. 5. Stopmark: Because the printing machine suddenly stops during the printing process and then restarts, color bars are produced on the fabric. 6. Partial embrittlement (tenderspots) On printed fabrics, there is a…�A variety of colored areas are often damaged, usually due to excessive use of damaging chemicals in the printing paste. This problem can also be found in the discharge areas of discharge-dyed printed fabrics.
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