Discussion on the technique of color and light mat

2022-07-25
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Discussion on the color and light symbol technology of exhaustion dyeing

Abstract: This paper systematically and concretely expounds the accuracy and stability of color and light symbol in exhaustion dyeing process. From the three aspects of small sample, enlarged sample and mass production, this paper analyzes the factors affecting the color light, and puts forward the precautions for operation in combination with practice

the requirements of exported clothing for the color light and color of dyed fabrics are becoming more and more stringent. Therefore, it is becoming more and more important to improve the accuracy and stability of the color light of export dyed fabrics and meet the requirements of customers. It is not only related to the economic benefits of enterprises, but also related to the reputation of enterprises. Therefore, some people call the accuracy and stability of color light as the soul of dyeing. The author talks about some practical experiences on how to improve the accuracy and stability of color light symbols in dip dyeing process

1 proofing and color imitation

1.1 the new color list issued by the business planning department must be carefully reviewed first. For example, the standard samples shall be complete, the light source shall be clear, the fabric texture specification shall be clear, the requirements for color fastness (soaping, friction, sunlight, chlorine resistance, dry cleaning, etc.) and finishing requirements (softness, waterproof, antibacterial, flame retardant, UV protection, etc.) shall be accurate, and the sample delivery time shall be reasonable. If any problem is found, it shall be recognized with the business planning department in a timely manner

1.2 before proofing, the quality of semi-finished products shall be uniformly identified with the production planning department. Such as mercerized cloth or non mercerized cloth; Ground or unglazed cloth; This white cloth or bleached cloth; Front setting cloth or rear setting cloth; Pre shrunk cloth or non shrunk cloth, etc. The principle is that the cloth used for proofing must be consistent with the cloth used for mass production in the future, so as to unify the process flow and process conditions, and should not be changed on the way after confirmation

1.3 before proofing, the production mode shall be determined by the production planning department in a unified manner with the production planning department in which the workshop type rough processing enterprises account for the majority. If the large-scale production is liquid jet dyeing or flat cylinder jigging dyeing, once it is determined, it should not be changed on the way. Because the proofing conditions of liquid flow dyeing and jigger dyeing are different, the dyes and additives used are also different. If it is changed, it can only be re proofed, and the proofing prescription must not be used in series

1.4 carefully select dyes according to the requirements of the customer's color sheet for dyeing depth, color brightness and color fastness. If the color is deep and thick, the dye with high strength, high deepening and high wet rubbing fastness shall be selected; For light color, use dyes with high levelness and high sun fastness; If there are requirements for chlorine bleaching fastness, chlorine resistant dyes shall be selected; If there are requirements for dry cleaning fastness, dyes resistant to organic solvents shall be selected; When dyeing cotton/polyamide or cotton/polyester blends, especially when dyeing white or shiny varieties, dyes with low mutual contamination must be selected. For polyamide cotton or cotton nylon elastic fabric, when dyeing nylon, it is necessary to match disperse dyes with neutral dyes or acid dyes to ensure freshness, color fastness and fabric evenness to meet customer requirements. It should be pointed out here that there is a big difference between the color absorption (depth and color) of nylon and spandex to disperse dyes. Dyeing nylon with disperse dyes alone has good levelness, but spandex often jumps out of the cloth as "different color silk", affecting the uniformity and color of the cloth

1.5 the original sample provided by the customer must be re identified before the approval sample is printed. The original samples provided by customers are usually in the following situations:

(1) the organizational specification of the original sample is different from that specified in the color sheet.

in this case, the color light of the small sample is difficult to be consistent with that of the original sample due to the different light absorption, reflection and transmission of the fabric. At this time, several small samples with different depths and colors should be made for customers to choose. Only when there is an arc-shaped transition zone with a radius of 75mm between the end and the working section of this type I sample, can the customer's acceptance rate be improved

(2) the original sample is not fabric, but printed paperboard

in this case, it is often difficult to match the color light of the dyed sample with the original sample under the irradiation of the specified light source because the surface of the paper sample is smooth and has strong luster, and the paper sample is a printing coating rather than a dye. At this time, only a few more samples with different depths and colors can be made for customers to choose

(3) when dyeing cotton brocade or cotton polyester interwoven fabric, if the original sample provided by the customer shows poor color depth and color uniformity of the two-component fiber, there is a double color phenomenon. At this point, there are usually two situations: the first is to retain the two-color effect; Second, do not double color effect, but uniform color. Therefore, the shade of bicomponent fiber should be leveled (in the original sample, the shade of bicomponent fiber is different, which is caused by poor dyeing uniformity). In this case, be sure to ask the customer clearly to avoid that the sample cannot be confirmed

(4) the original sample has certain fluorescence under the light source

in this case, special attention should be paid. Generally, there are two possibilities: first, the cloth should have fluorescent effect under a specific light source; Second, the fabric itself is not required to have fluorescence, but in order to brighten the dyeing, fluorescent brighteners are added. At this time, we must first understand the real requirements of the customer, and then we can make an approval sample according to the requirements

(5) the original sample is silk fabric or acrylic fabric (or acrylic yarn), while the small sample is made of pure cotton, cotton polyester, cotton brocade

in this case, the original sample is often dyed with acid dyes or cationic dyes, and the brightness is very good, so the small sample cannot meet the brightness requirements of the original sample. In this case, make an approximate sample for the customer's reference and explain the reason to the customer. If a fluorescent brightener is added for brightening, the consent of the customer must be obtained

(6) customers' color lists often have "white" color numbers, such as natural white, ivory white and pearl white, but there is no physical standard sample. In this case, it is necessary to make clear in advance whether the so-called "color light" in the color list refers to the original white, bleaching or whitening. If the customer is confused about this and it is difficult to identify it, the customer should first make three samples of whitening, bleaching and whitening for the customer's approval. If it is identified as whitening, the customer should generally provide three small samples of yellow light, red light and blue light for the customer to confirm. This situation must be taken seriously. Otherwise, it is easy to have color and light differences with customers during the acceptance of large goods, or even rework and repair

(7) for cotton brocade, cotton polyester, polyamide polyester, polyester viscose and other interwoven or blended fabrics, the original samples provided by customers are sometimes flash samples (that is, the two fiber components have different colors, which has a flash effect). For the flash color sample, it is necessary to determine exactly which fiber is which color, which can not be changed generally. If the color is reversed, two situations will generally occur: first, the overall effect of the cloth surface is mostly inconsistent; Second, if the blending proportion is equal and the weaving specification is appropriate, the overall effect of the cloth surface is basically similar, giving people an illusion, but leaving a potential problem, that is, once the customer finds that the fiber color is wrong, he will refuse to receive the goods and must be re dyed. Therefore, the flash color samples should be taken very seriously and should not be sloppy

(8) nylon and polyester contained in cotton brocade or cotton polyester fabrics are not all matte silk, and sometimes there are glossy silk. The lustre of nylon and polyester has a great influence on the brightness and brilliance of the dyed fabric. Therefore, it is necessary to determine whether the nylon or polyester contained in the original sample provided by the customer is glossy or matte. If it is glossy, it should be proofed with the same fabric. If it is proofed with matte fabric, the color and light must be inconsistent. If fluorescent brightener is used for brightening, the customer usually does not accept it. Therefore, it must be approved by the customer in advance, and it is not allowed to make its own decision

(9) the nylon component in the cotton nylon interweave is usually nylon 6, but also nylon 66. Because the amino content of nylon 6 is more than twice as high as that of nylon 66, nylon 6 has great affinity for anionic dyes, good dyeing depth, and is easy to dye deep color. Nylon 66, due to its low amino content, is only suitable for medium light color dyeing. Therefore, before proofing, first, try to ask the weaving factory about the category of nylon. Second, try to use nylon 6 blank to dye deep color. If nylon 66 blank is used for deep color dyeing, even if acid bath and ultra-high temperature (100 ℃) saturation dyeing are used, it is often difficult to meet the depth requirements. Even if the small sample reaches the depth, the reproducibility of the large sample is often very poor. In addition, there are still problems of low color fastness and serious sewage

(10) for twill fabrics with front and back sides, generally the twill side is the front, and sometimes there are exceptions. The reverse side is the front. Therefore, the original samples provided by customers should be carefully reviewed. If you find that the color board in the color list is facing up, you must make clear whether the opposite side is facing up or the customer pastes the color board upside down. Do not change it without authorization. Otherwise, it is a trivial matter to reprint the sample. If it is put into production, it will be a big mistake

(11) sometimes in the color list provided by the customer, there are both the original sample (usually different from the required texture in the color list) and the approved sample (usually the first approved sample produced by another factory entrusted, and its texture is generally the same as the requirements in the color list), but there is usually a certain difference in color light or depth between the two. At this time, there are generally two kinds of customer requirements: one is to take the original sample as the standard and re print the approved sample; The other is to re proofing based on the first approved sample provided. In this regard, it is important to understand the customer's intention and not to make subjective assumptions

1.6 in the proofing color sheet provided by customers, there are generally clear light source requirements, such as natural light, daylight light, D65 light (artificial sunlight), tl84 light (white light of European department stores), CWF light (white light of American department stores), f/a light (indoor tungsten light), UV light (ultraviolet light), etc. In the actual work of the factory, there are the following problems:

1.6.1 standard light box

(1) there are many brands of standard light boxes and tubes used. Different brands of light boxes and tubes have certain differences in color light

(2) improper use of standard light box. For example, the color card sample card is placed on the gray bottom plate of the light box, and even the prescription paper and color sample plate are pasted on the gray inner wall of the light box, which will have a certain impact on the color and light of the color. Thus, when the standard light box is used for color matching, the color and light in the factory light box are consistent, while the color and light deviation in the light box of the customer company is generated, resulting in the difficulty in the recognition of the color and light of the small sample and the large sample

therefore, the standard lamp box, especially the lamp tube, must select products that meet international standards, and the lamp tube must be used correctly, so as to eliminate the non-standard standard of the standard lamp box caused by the non-standard light source of the lamp tube and the improper use of the lamp box, resulting in color differences

1.6.2 D65 light source

d65 light source is an artificial daylight source. Compared with the natural light source, their response to the color light automatically printed by the dyeing printer on the 18 sample data is not completely consistent. Some customers confuse the two and think that D65 light is natural light. Therefore, the proofing color list is often specified as D65 color matching, while the acceptance of small samples (or large samples) uses natural light color matching. Therefore, there are often differences between the factory and the customer. In this regard, we must communicate with customers, unify our understanding and eliminate misunderstandings

1.6.3 different light sources

some customers require that two different light sources should be used to eliminate burrs by using synchronous counter circuits. They even require that the two light sources be turned on at the same time and mixed light sources be used for color matching. In this case, there is usually an obvious light skipping problem. That is, different colored lights are produced under different light sources

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