The varieties of velvet currently on the market include double-sided velvet and single-sided velvet. Printed velvet is divided into single-sided printed velvet and double-sided printed velvet. Although the flannel printing process includes paint direct printing, anti-printing process and discharge printing process, most printing is still based on reactive dye direct printing process. To improve the quality of printed flannel, we must combine the characteristics of “flannel” and take measures and countermeasures to overcome quality problems and difficulties that often occur during the production process, so that the physical quality level of finished printed flannel can be continuously improved to meet the needs of customers and consumers.
The production of flannel cloth has a long history in my country. Generally, gray cloth such as plain weave, twill weave, and squeak are used. The relative movement of the fluffing steel wire roller on the flannel machine produces fluffy fluff on the surface of the fabric, thereby enhancing the warmth retention of the fabric and making it soft to the touch. thick. The flannel printing and dyeing fabrics are processed by bleaching, dyeing, printing and finishing processes to make the flannel cloth more beautiful in appearance, which is very popular among consumers. Flannel is often used as winter underwear. After printing, it can also be used as outerwear for women and children in spring and autumn.
Common tissue specifications of flannel fabrics are:
21×14 64×72, 32×14 74×58, 24×15 67×70, 24×18 72×64 velvet;
20×10 40×42, 24×13 42×41, 21×12 44×44, 20×10 50×46, 20×16/2 46×46 double-sided velvet;
21×6 44×42, 21×4 40×40, 20×6 40×34 Beibei velvet;
21×14 64×72, 21×14 74×68 jacquard velvet.
The varieties of velvet currently on the market include double-sided velvet and single-sided velvet. Printed velvet is divided into single-sided printed velvet and double-sided printed velvet. Although the flannel printing process includes paint direct printing, anti-printing process and discharge printing process, most printing is still based on reactive dye direct printing process. To improve the quality of printed flannel, we must combine the characteristics of “flannel” and take measures and countermeasures to overcome quality problems and difficulties that often occur during the production process, so that the physical quality level of finished printed flannel can be continuously improved to meet the needs of customers and consumers.
1 Common problems in flannel printing
To ensure and improve the quality of printed flannel, efforts must be made in the following aspects;
(1) Ensure the velvety effect of printed flannelette;
(2) Printing defects such as white core, exposed bottom, incomplete color, and uneven color are prone to occur;
(3) Pay attention to improving the wet rubbing fastness.
2 Guarantee of fluff raising effect
The fluff raising effect is one of the key appearance quality indicators for finished flannel fabrics, and it is also one of the internal quality indicators of the product. A good fluff raising effect is closely related to a good printing effect, so a good fluff raising effect Effect has always been one of the goals pursued by velvet printed fabrics. In order to obtain good fluff raising effect for printed flannel fabric, attention must be paid to many aspects including raw yarn, pre-bleaching treatment, auxiliary finishing before fluffing, fluffing machine raising and the operation during the printing production process.
2.1 Requirements for raw materials and weft yarns
From the perspective of the raw material and weft yarn, the quality of the pile raising effect not only depends on the fabric weave design, but also depends on the quality of the raw yarn. Because the raising of flannel fabric mainly affects the weft yarns, in order to facilitate raising and increase the thickness of the flannel cloth, the warp and weft yarn number ratio of double-sided plain flannel fabric is generally about 1:2, and the ratio of single-sided creaking fleece is about 1:1.5-2 between. After the flannel fabric is brushed, its strength loss is relatively large, and the weft strength generally loses about 50%. In order to maintain the strength of the finished flannel fabric, the yarn strength must be increased accordingly. The pile yarn should have a more even yarn texture.
Practice has proven that when mixed with flannel yarn, 5-10% combed noils are generally added to have little effect on the fluffing. If too much combed noils or waste cotton are added, the yarn dryness will be affected. , causing too many cotton grains on the suede surface and insufficiently uniform fluff. Because there are too many short fibers and neps in the noil, the fiber strength is also poor, and the fibers are easily broken during the raising process. Weft twist coefficient, under the same raw cotton conditions, the smaller the twist, the better the fluffing effect, but the yarn strength is lower. In order to take into account the elasticity of the fabric, the twist coefficient of the weft yarn is generally within the range of 266-285. Practice has proved that this is beneficial to the raising effect and has little effect on the strength of the fabric.
2.2 Control and mastery of pre-bleaching treatment
(1) Mastering the wool effect of semi-finished fabrics
The wool effect of the semi-finished fabric surface can directly reflect the fat and wax content of the semi-finished fabric surface, which is closely related to the fluffing effect of the semi-finished fabric. If the wool efficiency of the cloth surface is low, the fat and wax content on the cloth surface will be high, which is conducive to fabric raising, but the whiteness of the fabric will be poor, and some even have seed shells, which will affect the physical appearance quality; conversely, if the wool efficiency of the cloth surface is high, the fabric surface will be It contains less fat and wax, which is not conducive to the raising of the fabric. Therefore, it is necessary to ensure the raising effect of the semi-finished product. As a semi-finished product before raising, it is necessary to remove the slurry and cottonseed shells and have good whiteness. And maintain the appropriate wax content.
In order to achieve the above purposes and requirements, currently driftingPretreatment generally uses the following methods:
The first is to adopt the pre-treatment process of “heavy desizing, light scouring, and appropriate bleaching”. Carefully control and master the process flow, process conditions and process operations, so that a proper amount of fat and wax remains on the processed semi-finished products. This method is a traditional flannel bleaching pre-treatment process. This method has high requirements on process conditions and process operations. Fluctuations in process conditions and changes in operations will affect the removal of impurities from the fabric and the amount of fat and wax remaining in the fabric. So as to affect the flannel fluffing effect.
The second is to use the conventional scouring process of cotton fabrics for production, without considering the preservation of fabric fats and waxes, only the removal of fabric fiber symbionts. Before the fabric is raised, a waxing process is used to ensure the raising effect of the fabric, so that the velvet semi-finished product obtains the necessary amount of fat and wax. The wool efficiency of the pile blank treated by the former scouring pre-treatment process is relatively low, while the wool blank processed by the second scouring pre-treatment process has a relatively high wool efficiency, and the operation is relatively easy to master.
(2) Comparison between rope bleaching and open width bleaching
There are two types of flannel pre-treatment: rope scouring and flat scouring. The process selection should be determined based on the enterprise’s equipment conditions, fabric characteristics and processing requirements. Rope blanching is superior to open-width blanching in terms of desizing effect, penetration effect and hand feel. However, the rope blanching process is more complicated and can easily cause weft skew defects. For denser and thicker flannel, irregular warp wrinkles will easily occur after drying using this process, and wrinkle defects will still exist even after fluffing. For this reason, if the equipment conditions of the enterprise permit, it is more reasonable to use rope bleaching for velvet fabrics with loose fabric structures, such as 20×10 40×42 double-sided velvet fabrics, and for those with tighter and thicker fabric structures. For example, 21×14 74×68 flannel fabric, it is better to use open width processing.
2.3 Auxiliary workers before pile raising
(1) Pay attention to and attach importance to the role of fat-containing wax additives in assisting fleece
For semi-finished products to be raised that are heavily scoured and have high wool efficiency, as well as semi-finished products to be raised that are prone to dense and uneven defects during the raising process due to thin pile blanks, they should be padded with fat-containing wax to help Agent to avoid the situation where the fluff raising effect does not meet the satisfactory requirements. We call this process the “waxing process”.
Commonly used fat-containing wax additives include paraffin, stearic acid, softener 101, etc. Among them, softener 101 has a more ideal effect and can achieve the requirements of short, dense and even pile during the raising process. The dosage of softener 101 is 10-20 g/L, and the temperature is 60-65 ℃. The temperature should not exceed 80 ℃ for a long time to avoid wax precipitation. The prepared padding liquid should be in the shape of white soap bubbles. If it is turmeric-yellow and viscous, it means that the emulsification is incomplete and stains are likely to occur on the fabric during padding.
(2) Tentting the fabric before raising is beneficial to the uniformity of the pile surface
After pre-bleaching treatment, the fabric width of the raised semi-finished product shrinks, and the warp and weft yarns are arranged closely. After rolling and drying, the yarns become flat. After the fabric is tentered, the width of the fabric increases, so that the contact surface with the wire roller of the pile machine increases. At the same time, the yarn slightly recovers its roundness, which is beneficial to pile raising. In addition, the width of the fabric after tentering is relatively close to the width of the finished flannel fabric. The uniformity of the flannel cloth after the new width is better, so that the width will not be narrow when the pile is raised, and the fabric will be widened during the finished product, causing the fabric to be dense and uneven. Even defects.
(3) Pay attention to the dry humidity of the fabric before fleece and the heat and cold of the fabric
The fabric before fluffing must have a certain moisture content, about 5-6%. Fabrics that are too dry will not fluff easily. The moisture content must be controlled so that no steam can be seen when the fabric passes through a drying cylinder after passing through the dryer. Evaporate as well. In addition, when the fabric is heated during raising, the yarn count of the fabric can be loosened and expanded, which is beneficial to the insertion of the needle tip, which is beneficial to the raising. In winter, it is an effective method to spray a small amount of steam on the cloth at the cloth outlet of the pile machine, which can not only moisturize the fabric but also eliminate static electricity on the cloth.
2.4 Raising machine raising operations and precautions
The raising of the fleece machine is a key process to ensure the fleece effect of the flannel cloth. Pay attention to the precautions for the fleece raising machine and play an important role in the fleece of the fabric. The main issues in raising the fleece machine are: first, we must understand the factors that affect the fleece effect of the fleece machine, so we first start with the fleece mechanism and function.
(1) The raising mechanism and function of the raising machine
There are 36 raising rollers installed on the large roller bracket of the main shaft of the raising machine. There are two types of pile needle rollers: clockwise rollers and counter-needle rollers. The needle points point in the direction of fabric movement and rotate with the large roller. The needle rollers have clockwise rollers, commonly known as push needle rollers. The needle points point in the direction of fabric movement and do not rotate with the large roller. The needle roller is called a counter-needle roller, commonly known as a thorn needle roller. The two types of needle rollers are a set, that is, 36 pile needle rollers mounted on the large roller bracket. There are 18 groups in total, with 18 needle rollers and 18 counter-needle rollers. During the raising process of the fleece machine, the running direction of the fabric on the needle tip of the needle roller is consistent with the rotation direction of the main shaft large drum, and runs in a clockwise direction. Both clockwise and counter-needle rollers rotate counterclockwise, and the needle tip contacts the fabric. Due to the linear speed difference between the fabric and the needle roller in the relative motion, the needle tip lifts one end of the surface fiber of the weft yarn to form a suede surface.
(2) Clockwise roller and counter-needle roller�The fluffing effect
The raising effects of the above two types of needle rollers are different. From the practice of raising production, the nap of the counter-needle roller is longer and thinner than that of the counter-needle roller: the nap of the counter-needle roller is shorter and denser than that of the counter-needle roller. In addition, the raising of the clockwise roller is gentler than that of the counter-needle roller, with less fiber breakage and less strength damage to the fabric; the counter-needle roller is more violent than the clockwise roller, causing more fiber breakage and greater strength damage to the fabric. During the raising production process, it is necessary to pay attention to the length of different needle rollers and overcome the shortcomings to ensure a good raising effect.
(3) The relationship between running speed and raising
There are three speeds for fabric raising on the raising machine, namely:
① The revolution speed of the main shaft large roller is U, and it runs clockwise;
② The rotation speed of the clockwise and counterclockwise rollers is U, and they run counterclockwise;
③ The fabric running speed is U cloth, clockwise.
During raising, there are three situations in which the linear speed difference between the relative movement of the fabric and the needle roller affects the raising effect.
① U male-U self>U cloth, the clockwise roller is for raising, the counter-needle roller is for carding;
② U male-U self-cloth, the counter-needle roller is for raising, the clock-needle roller is for carding;
③ U public – U self = U cloth, the algebraic sum of the linear velocities of the needle tip and the fabric is equal to zero, that is, no relative motion occurs, and then,
The counter-needle roller neither naps nor combs the fabric. This state is called zero point. The “zero point” is of great significance during raising, as it is the benchmark for adjusting the raising force.
(4) Various factors affecting the raising effect of the raising machine
As far as the raising machine is concerned, the quality of raising is related to the adjustment of the raising force, fabric tension, elasticity of the steel needle, sharpness of the needle tip, etc. The domestic M301 raising machine also needs to consider the sliding factors of the belt drive, etc. .
The raising force is controlled by adjusting the rotation speed of the clockwise and counter-needle rollers, and the raising amount is adjusted by the running speed of the fabric. If the fabric runs faster, the number of contacts between the needle tip and the fabric will be reduced, and the raising amount will be reduced; otherwise , the amount of fluff increases.
Finding the “zero point” is the benchmark for adjusting the pile force. It is not easy to calculate the “zero point” in theory, and there is a gap between it and the reality. It is of practical value to find an approximate “zero point” in the actual production process. When the fabric is running on the machine, adjust the speed changer and adjust the speed ratio to achieve the desired fluffing effect.
On the basis of the summary of production practice, the company determines the total number of raising passes for each fleece product, the requirements for the fleece effect of each pass, the speed ratio of the clockwise and counterclockwise rollers, the cloth traveling speed, the speed of the clockwise and counterclockwise rollers, and the door. The percentage of amplitude shrinkage, zonal strength loss, etc. are clearly defined. In fabric fleece production, the prescribed operating process must be strictly implemented to ensure the fleece effect. For napping machines driven by belts, the fixed sliding movement often changes due to changes in the load on the needle roller. For example, the yarn count of the fabric remains unchanged but the width changes; another example is that in single-width raising and double-width raising, the load of the raising needle roller is different. In the raising operation, the rotation speed of the needle roller must be adjusted as necessary. . In addition, the tightness of the belt driving the needle roller on the large gear should also be checked frequently.
(5) Control of fabric tension during raising
The tension of the fabric during raising will affect the raising effect. If the tension is large, the vertical pressure of the fabric on the needle tip will be large, the resistance of the needle roller will also be large, the raising force will be small, and the velvet will be shorter; conversely, if the tension is small, Then the pile force is strong and uneven, and the pile is long.
The tension of the fabric during raising is generated by the front resistance and rear pulling. The actual tension is controlled on the M301 fleece machine, using the force and elastic device of the cloth outlet roller and the cloth inlet roller. The cloth outlet teeth are 98T, and the cloth feed teeth are in four gears: 98T, 97T, 96T, 95T. , 20×10 40×42 pile blank, generally use 98T out and 97T in, the tension is moderate, and the raising effect is generally better. If it is inconvenient to adjust the latching teeth, you can fix a kind of latching force. The elastic frame at the cloth feeding position is not controlled and is in a relaxed state. You can also adjust the elastic frame to control the tension during operation.
(6) Control the length and density of villi
The pile blanks used for printing should have a short, dense and even pile on the front. During the production process, the following operating precautions should be paid attention to:
① Multiple passes of light pulling should be used to raise the fabric. Taking 20×10 40×42 double-sided flannel as an example, there should generally be eight passes, four passes on the front, then two passes on the reverse, and then two passes on the front. .
② During the raising process, if the pile is long but not dense, the length of the pile indicates that the counter-needle roller cannot play a good raising role; the long and uneven pile indicates that the clockwise roller is playing a raising role; the density is insufficient. It means that the amount of fluff is not enough. To make the counter-needle roller have a good fluffing effect, the rotation speed of the needle roller must be increased so that U public – U self < U cloth.
Especially when the speed of the counter-needle roller is increased, the amount of pile must be increased, and the running speed of the pile fabric must be slowed down to increase the number of contacts between the needle tip and the fabric. When the needle pile is long and not dense during production, the usual measures are: increase the speed of the counter-needle and clock-needle rollers, especially the speed of the counter-needle roller, reduce the cloth speed by one gear, and add a little tension appropriately.�, to make the fluff shorter. If the pile is not long enough and not dense, it means that the needle roller should be used to raise the pile, and the needle roller should be slowed down, especially the clock roller; the tension should be relaxed to increase the length of the pile; if it is not dense, it means that the pile is not dense enough. The amount of pile should be increased, and the cloth speed of the fabric to be piled should be slowed down.
③ If the needle roller is driven by a flat belt, check whether the belt is loose to prevent it from affecting the raising effect.
(7) Causes and methods of overcoming lint or unevenness
There are generally three reasons for the occurrence of uneven or uneven fuzz:
① The blank to be raised does not meet the requirements for fabric raising. For example, the semi-finished products after pretreatment are unevenly cooked, the fabric is unevenly dried, the fabric surface is uneven, and the wax content on the fabric surface is too low, etc. Whenever you encounter severe fabric suction by the needle roller during pile raising, severe beating of the fabric at the entry point, pulling at the exit point, or fabric fluff that cannot come out, you should stop raising the pile and re-measure the left and middle sides of the pile blank. , right wool effect, if the wool effect is high, the fabric should be waxed again, and if necessary, the fabric with uneven raw and cooked semi-finished products should be re-bleached.
② During raising, the fabric tension is too high, the resistance to the needle roller is large, and the sliding between the needle roller drive wheel and the belt of the raising machine using a flat belt to drive the needle roller increases, resulting in no nap on the surface of the fabric. The way to overcome this problem is to lower the four-speed gear by one gear, relax the fabric feeding elastic device, and reasonably adjust the fabric tension.
③ The steel wire card cloth has been used for a long time, the steel needle is round and blunt, the steel wire card cloth is not wrapped well, the needle roller is displaced from the seam during use, or the needle roller is bent, resulting in uneven needle rollers. In addition, the needle roller is wrapped with yarn ends, cilia, etc. It will cause the fluff to be unreliable or uneven.
In order to prevent fluffing or unevenness caused by the above reasons, the following measures should be taken:
① Carry out regular cleaning and maintenance work. This includes insisting on refueling the relevant parts of the machine once every shift, and doing a more thorough cleaning job once a week, paying special attention to and removing the yarn ends and cilia wrapped around the needle roller.
② Prevent the fabric from breaking when raising pile. Because once the end is broken, the cloth will be entangled on the counter-needle roller, and a pulling phenomenon will occur on the needle roller. The cloth will be pulled to pieces and the steel needle will be damaged.
③ Pay attention to the sharpening of the needle roller. The sharpness and dullness of the needle tip of the needle roller have a certain impact on the fluffing, so the sharpening of the needle roller is essential. The needle roller of the new card clothing package needs to be sharpened before use. This is mainly because the new card clothing is sharp and the area around the needle tip is rough. Although the pile is strong, it is easy to break the fluff and produce waste hair. The needle roller of the new card clothing package needs to be sharpened. The purpose is to smooth the needle tip of the new card clothing. For a pile needle roller that has been used for a period of time, the needle tip will be dull and affect the pile, so it must be sharpened regularly. The general cycle is six months. It may be shortened or extended in special circumstances.
④ Pay attention to the replacement and use of the grinding needle roller. The needle rollers used in the first and second raising machines have greater wear after use. After grinding, they can be adjusted to be used in the third and fourth raisings or subsequent raisings. In this way, the service life of the needle roller card clothing can be extended.
⑤ Pay attention to the quality of the card clothing wrapping. The quality of the card clothing wrapping is related to the service life and pile quality of the card clothing. It is not only important that the card clothing wraps around the needle roller, but also that the card clothing does not stretch or loosen during use. Therefore, before wrapping the card clothing, apply a layer of anti-rust paint on the surface of the steel pipe roller, and tightly wrap the card clothing while the paint is still wet. The effect is generally good.
(8) After the fleece machine is raised, the wool should be smoothed during the printing and dyeing production process
After the pile fabric is raised by the pile machine, all the pile will fall in the forward direction of the fabric. If the pile continues to be piled on this surface, it should also be kept in the forward direction, that is, the running direction of the fabric is consistent with the direction of the pile inversion, otherwise it will cause the pile to fall off. , uneven suede and other phenomena. The smoothing operation during the raising process has been clearly stipulated in the raising operation and cloth threading route, so there will not be a big problem in the raising process. The problem must also be achieved during the printing and dyeing production process. Due to the long production process, the cloth needs to be turned over in the cloth box, and management needs to be strengthened to ensure perseverance.
The pre-press flat cleaning and post-printing flat cleaning of the printed pile blank must be carried out along the wool. In other processing processes, all machines passing through expansion boards or rollers should be carried out along the wool, which is conducive to maintaining the suede surface. , to prevent hair loss. There should be no dead rolls during the production process, and spray pipes should not be used for flat washing rolling fluid to avoid damage to the suede.
3 Causes and solutions to common defects in the printing process
Printed flannel cloth has a lot of fluff and cilia on the surface, which will affect the clarity of the printing outline during printing. During the printing process, it is easy to produce printing defects such as broken threads, clogging, white core white spots, and dew points. In order to overcome the above-mentioned defects and improve the quality of velvet fabric production, the traditional method is to wash the velvet blank to be printed and then sizing it, and then print it. This method plays a certain role in improving the quality of flannel printing and overcoming printing defects. Therefore, using this method for production has become a classic method. However, this method exposes the following problems in the production process of flannel printing:
3.1 Problems with the traditional process of sizing flannel first and then printing
(1) The fluff and cilia on the surface of the fabric are not very effectiveIdeal
Part of the hair and cilia can be removed by washing, but the effect is not ideal, and a considerable amount of hair and cilia cannot be removed. During washing, there are quite a lot of fluff and cilia on the surface of the flannel cloth that cannot be washed off by water, or the fluff and cilia that have been washed down are adhered to the surface of the fabric during the flat washing and rolling process. The fluff on the fabric is closely connected with the yarn on the fabric, and these fluff and cilia are not actually “rooted” in the fabric. Some of them have a certain degree of cohesion with the fabric fibers, and even have a certain twist with the fluff yarn. However, they are not firmly attached to the fabric; some are simply free from the fabric yarns and float in the fabric fluff. These hairs and cilia slip or fall from the fabric, which will affect the quality of the printed flannel fabric. Due to the poor color quality, printing defects such as screen blocking, white core, unclear outline of printed lines, and broken lines are prone to occur during printing.
(2) Sizing affects the penetration and color giving amount of printing paste
From the perspective of production practice, what kind of sizing should be used for sizing? Sodium alginate paste has good washability, but its cohesion ability is not strong. The fluff and cilia on the cloth surface are not easy to cohere and can be worn flatly. Synthetic dragon glue paste has poor washability and the paste should be used after printing. It is difficult to remove the material, and the fabric feels hard. Starch paste is cheap. After printing, it needs to be washed at a higher temperature or kneaded with amylase to desize. Generally, it can be removed and the fabric can be softer. Therefore, starch paste is currently used for sizing before flannel printing. However, starch paste covers the surface of the fabric, affecting the direct contact between the dye and the fabric fiber, stitching, and sizing. In addition, the starch molecular structure contains reactive genes that can react with the dye for stitching, affecting the penetration and color amount of the fabric.
(3) Sizing cannot effectively prevent the shedding and adhesion of hairs and cilia
The purpose of sizing is to make the upright fluff on the fabric lean to one side and adhere to the cloth surface to form a smooth plane, thereby reducing the shedding and sticking of the fluff and cilia during printing. However, from production practice, the method of washing the pile blanks and then sizing them cannot effectively prevent the fluff and cilia from falling off and being stuck. This is mainly because considering the permeability of the printing paste and the amount of color given, it is impossible to use a thicker paste amount when sizing, and only light paste can be used for sizing. These light slurries cannot effectively prevent the shedding of fluff and cilia. In addition, the sized fleece is adhered to by the wet pulp during printing. After being pressed by the printing net, the fluff and cilia on the fleece are still easily adhered. , so the sized fleece will still cause many problems and printing defects during printing.
3.2 Overcoming methods
Measures can be taken to increase the coloring amount of printed flannel, increase the permeability of the fabric, and reduce and prevent printing defects such as white cores, white spots, net plugging, exposed bottoms, and broken threads.
(1) Pre-bleaching treatment strives to remove fiber impurities more thoroughly
The impurity removal of fabric fibers is relatively thorough, which is beneficial to improving the permeability of printing paste and improving the color yield. The specific method is to carry out desizing, scouring and bleaching according to the general cotton fabric pre-treatment process, and the wool effect is controlled at 7-8cm. As for the flannel raising effect, it can generally be solved by applying softener before brushing. The advantage of this is that it can not only ensure the fleece effect and quality of the flannel cloth, but also have good washing performance. When the fabric is fluffed and printed, the softener can be easily removed from the fabric.
(2) Before printing, the fabric is brushed and washed without sizing
The advantage of this is that it is conducive to the coating and sewing of the dye and the fabric. It is not necessary to print the printing paste on the sizing film first, and then react with the fiber through the sizing film to sew and dye the fiber. At the same time, it reduces the loss of sizing slurry. The amount of printing paste increases the amount of color given. What should I do if the pre-press fabric is not sizing and there are a lot of fluff and cilia on the fabric? To this end, brushing and washing can be used. Brushing can be carried out on a brushing machine. The newly brushed velvet blanks are brushed, and the excess velvet and cilia on the fabric are scraped off with a brush (brushing is more effective at removing short velvet and cilia than simply washing the velvet) (much more), and then wash the fabric to remove the softener and part of the fluff and cilia on the fabric, which greatly facilitates printing.
(3) Using double flower screen printing
For larger-area patterns, especially those with deep and rich colors, due to the existence of downy hairs and cilia, it is easier for the cylindrical surface to adhere to a large number of hairs and cilia, or because the hairs and cilia are stuck together. ; Or due to the blocking of the net, regular blocking and white core white spots are formed on the cloth surface; or irregular fluff and cilia are adhered to the white core and white spots. In addition, insufficient amount of paste is applied during rotary screen printing, which can easily cause printing defects such as bottom exposure and lack of full color. The use of double screens can allow the same printed pattern to receive secondary paste placement in an instant, thus improving the color of the pattern. Full; secondly, the white core and white spots left by the first floral tube are immediately compensated by the same color ink of the second floral tube with the same pattern, making the white core, white spots, and exposed bottom defects produced during printing larger. for reduction.
4 Wet rubbing fastness
4.1 Reasons for low wet rubbing fastness
Floating color on fabrics printed with reactive dyes causes unqualified wet rubbing fastness.The main reasons for floating color include: dyes that have been adsorbed on the fiber but have not participated in the covalent reaction of the fiber, hydrolyzed dyes, and vinyl alum dyes after eliminating sulfate esters. The specific reasons for floating color on printed and dyed fabrics are as follows:
(1) Improper selection of dyes
As reactive dyes for printing, the solubility of the dye should be high, the substantivity should be small, the diffusivity should be high, the fixation rate should be high, etc. If the dye is more direct, hydrolyzed dyes and dyes that have not participated in the covalent reaction will not be easily washed away, and the floating color on the fabric surface will increase; if the dye diffusion performance is poor, the dye will not be fully diffused into the fiber in a short period of time. Fully react, resulting in low color yield and increased floating color on the fabric surface; low dye fixation rate, resulting in incomplete reaction between dye and fiber, increased floating color on the fabric surface, and reduced wet rubbing fastness.
(1) High dye concentration
The fiber’s adsorption of dyes has a limit value, that is, the dyeing saturation value. Generally, it cannot exceed 10% of the dyeing saturation value. Excessive dye cannot be dyed and fixed, and accumulates on the surface of the fabric, affecting the wet rubbing fastness of the printed matter. This can also explain that the wet rubbing fastness does not meet the requirements and mostly occurs in dark and dense colors. The main reason is color.
(3) Gray cloth quality factors
Smooth and clean, with reduced fiber length, can reduce the friction force during wet rubbing fastness testing, reduce the shedding of colored linters, help reduce the floating color transfer and mechanical friction transfer of water-soluble dyes, and help improve the wet rubbing fastness. Printed flannelette has a low wet rubbing fastness, which is more prominent due to the fact that the surface of the fabric is covered with rough velvet and has many short fibers.
(4) Pre-press bleaching and pre-processing factors
The pre-treatment of cotton fiber bleaching is not in place, the fiber symbionts cannot be completely removed, and the high content is difficult to dye and finish, which affects the adsorption, penetration and coloring of the dye, which in turn affects the wet rubbing fastness, etc. The pre-treatment of the printed fleece is generally not mercerized. When scouring, the fleece raising time is often considered to retain the wax on the fabric, resulting in low wool efficiency of the fabric. Incomplete treatment before blanching is also one of the reasons for the unqualified wet rubbing fastness of printed flannel.
4.1.5 The printing paste is not carried out according to the operating regulations and stored for too long
How to prevent the hydrolysis of reactive dyes during the preparation process and storage of printing paste is an issue that should be paid attention to. The pH value of printing paste directly affects the color fixation of reactive dyes. If the pH value is too low, it will not work, but if the pH value is too high, it will not work if the alkalinity is too strong. The number of hydrolyzed dyes will increase, which will affect the dye fixation rate. In addition, if the prepared color paste is stored for too long, it will also cause hydrolysis of the reactive dyes, which will affect the color fixation of the reactive dyes and lead to unqualified wet and rubbing fastness.
4.1.6 Insufficient flat washing and poor water quality after printing
The final fabric must be fully washed, and flat washing after printing is very important. Flat washing can clean the floating colors on the fabric, which is beneficial to improving the wet rubbing fastness. If the flat washing is rough and insufficient, and the water used during the flat washing process has high hardness, the dye will form a lake with the calcium and magnesium ions in the water, causing the wet rubbing fastness to fail.
What methods and measures can be taken to improve the wet rubbing fastness? It is impossible to achieve perfection in the actual production process. In the actual operation process, many things have been objectively stipulated for us. For example, the printed gray fabric should have a cloth surface. Smooth and clean, short fibers are reduced, but in actual operation, the customer’s gray fabric is a foregone conclusion. If the customer’s requirements for the fastness of the finished printed fabric are not reduced, it is the color blank. Taking into account the production cost, it is impossible to buy or cannot buy the ideal gray fabric at all. In the production of printed flannel and fabric velvet, short hair cannot be short; and if the amount of dye is large, the wet rubbing fastness of dark and dense colors is poor. The customer’s samples are dark and dense colors, and it is impossible to change them all to light colors. During production, the dye It is impossible to reduce the dosage; and pre-treatment of printing blanks, flat washing after printing steaming, etc. are closely related to the company’s management operations and equipment conditions. When we are discussing the issue of improving wet rubbing fastness today, we should take targeted and effective approaches and methods while seeing the objective problems, and strive to do it well subjectively.
4.2 Ways and measures to improve wet rubbing fastness
4.2.1 What to do when selecting dyes
It is necessary to constantly select dyes with high solubility, low substantivity, high diffusibility and high fixation rate for printing to reduce floating colors on the fabric surface.
4.2.2 It is necessary to continuously improve and improve the production process of each printing variety
The printing variety production technology is continuously improved and improved. This provides factories and enterprises with clear indicators for strengthening production management and production technology, and provides a basis for strict management and technical standardization. The relevant production process regulations must be strictly followed during the production process. In order to ensure that fabric bleaching, pre-printing, printing paste preparation, printing operation, post-printing, and finishing processing are in place, it is conducive to dye adsorption, penetration and diffusion, greatly reducing floating color on the fabric surface, and improving printing. Wet rubbing fastness of fabric.
4.2.3 Brushing the fleece blank before printing
Brushing the printed velvet blank before printing is generally not used in the traditional floral velvet production process. Seal�The use of brush bristles has considerable benefits in improving the wet rubbing fastness of printed flannel fabrics. Brushing bristles can remove those fluff, cilia and other floating hairs that are not “rooted” on the fabric, which is beneficial to the short, even and dense fluff. In order to reduce the shedding of colored fluff during testing of finished printed flannel fabrics, the wet rubbing fastness is improved.
4.2.4 Vigorously strengthen the flat washing of fabrics after printing and steaming
The fixation rate of reactive dyes is not high, generally only 60-70%. Even dyes with higher fixation rates are only about 80%. Therefore, attention must be paid to sufficient water washing of printed steamed wrinkle fabrics to remove floating colors and related colors. It can be washed with a large amount of water, which has practical significance for improving the wet rubbing fastness. The actual production experience of flat washing after reactive dye printing is generally as follows: first, pay attention to using a large amount of flowing cold water to wash away the floating color and paste from the fabric; second, use hot and cold horizontal washing before soaping to run multiple tanks. In order to remove more paste, etc., if the hot and cold horizontal washing is sufficient, soaping will easily cause white staining and floating colors on the fabric, which are difficult to wash away; third, soaping should be sufficient, and it should be washed flat on a continuous flat washing machine. Medium and dark colored printed fabrics generally need to be washed twice; fourth, pay attention to the water quality of flat washing to prevent dyes from forming lakes with calcium and magnesium ions.
4.2.5 Excellent wet rubbing fastness improving agent
Currently commonly used wet rubbing fastness enhancers generally include: polyamine polymer color fixing agents, silicone wet rubbing enhancers, polyurethane wet rubbing fastness enhancers, etc. Polyamine polymer color-fixing agents mainly enlarge the dye by combining with the dye to form a water-insoluble salt.
Author: Hu Musheng, Dyeing and Finishing Professional Committee of China Textile Engineering Society
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