Characteristics of Waste Streams Caused by Dyeing Knitted Fabrics

A large amount of waster streams or effluents is produced during dyeing knitted fabrics. Water streams produced in different sector of dyeing knitted fabrics pollute environment. Desizing, souring, bleaching, mercerizing, dyeing, printing, finishing, washing and other process can produce waste streams which contains harmful chemicals. For that, waste streams need to be purified before discharge to the environment.

Characteristics of waste streams: the followings are the characteristics of waste streams.

Desizing: Size materials are used on the surface of yarn during weaving. The process removing size materials form the fabric is called as desizing. Possible pollutant in water is Starch, Glucose, CMC, PVC, Resins, Fats, and Oils etc. Waste streams have high BOD (35-50%).

Scouring: Scouring can remove impurities of textile materials. Waste water contains NaOH, Na2CO3, Waxes, Grease, Fragments of cotton etc. Nature of waste water is strongly alkaline, dark color, high BOD (30%) of total.

Bleaching: Bleaching can remove natural color of the textile materials which also causes waste streams containing Na(0Ocl)Cl, NaOH, Cl2, H2O2, Na2O2, acids etc. Nature of waste stream is alkaline, BOD (5%) of the total.

Mercerizing: The process can improve the physical properties of the fiber, producing waste streams. Pollutant in water is NaOH, H2SO4, Na2CO3 etc. Nature of waste water is strongly alkaline, BOD (less than 1%).

Dyeing: The process can produce a large number of waste water. Possible pollutant is various types of dyes, salts, acids, alkalis, soap and detergent etc. Nature of waste streams is strongly colored, fair BOS (6%) of the total.

Printing: Printing forms carious types of decorous design. Possible pollutant is colors, pigments, gums, oils, acids, different salts and other auxiliaries. Waste water is highly colored, oily appearance, BOD (6 to 10%) of the total.

Finishing: Possible pollutant in water is Traces of Starch, Resins, Softeners, and Stiffeners etc. Nature of waste water is low BOD (2 to 4%) of the total.

Effluent treatment plant (ETP) should be set up for protecting the environment from the influence of the waster streams.

Objectives and Requirements of Soft Winding for Dyeing Knitted Fabrics

Dyeing knitted fabrics is quite special. Knitted fabrics must be packaged after having been packaged. Soft winding transfer knitted fabrics from paper cone to spring tube or plastic tube. Various winding machines are used for soft winding section. Different parameters having influence on dyeing process directly should be maintained.

Soft winding which is the first step for preparing yarn for dyeing plays a key role in yarn dyeing industry.

The following objectives should be gained during soft winding section

Making soft package (Density should lie between 0.300 and 0.350 gm/cc
Transferring yarn from cone to spring tube or plastic tube
Making free cone from yarn to facilities next process
Decreasing the density of package
Removing unwanted materials from the package
Facilities batching operation

Requirements of soft winding: Various parameters should be set based on requirements of package which is best for yarn dyeing. The followings are the requirements of soft winding.

Density lies between 0.30 and 0.35 gm/cc
Winding is on the basis of yarn count.
Tension of yarn must be kept strictly. More tension makes the package hard and less tension makes the package soft. Softness of package should be acceptable for better dyeing.
Winding floor must be kept neat and clean.
Winding parameter should be set wisely for different yarn count.
More tension can make hard yarn and low tension make soft package. For that tension must be accurate.

Selection of knitted fabric dyeing auxiliaries common quality problems

1. color fastness unqualified
Color fastness to light fastness, washing fastness, perspiration fastness, rubbing fastness, fastness to open China, ironing fastness, these fastness lies dye structural performance, but also with the fibers, dyes closely related to the concentration, dyeing and finishing processes, external conditions, so whether the target color fastness, the key is to choose the dye, followed by dyeing and auxiliaries applications.

When dyeing system permits must be based dyes, fibers and customer indicators reasonable assurance that the dye additives help, under certain conditions, as far as possible on the ground dye fastness fiber to make it fully fixed. For the additives, the first, a good choice and pro-dye leveling agent, the dye slowly and evenly, fully dyeing fibers; Second, plus a chelating agent to overcome the dye and metal ions from the water floating color, and reduce hydrolytic activity of the dye in the water; Third, choose good soaping, go to the net floating color, and anti-floating re-stain fabric;; fourth is to select the appropriate fixative, the current sublimation fastness, sun outside fastness is no ideal fixative for soaping fastness, perspiration fastness collapse, the indicators rubbing fastness, etc. are excellent fixative to choose from.

2. brittle damage
Brittle damage showed a strong decline in profit before oxygen bleaching due to improper handling and other processes cause damage or even brittle outer holes and other reasons, there are generally two types of brittle damage caused by dyeing reasons, one is brittle damage such as sulfur black dye caused required to improve the anti-brittle agent, as well as dyeing vat dyes and strong oxidizing agents strong reducing agents, such as damage to the fibers brittle; Second stage or the improper dyeing and stages with acid, and acetic acid is generally used, and currently on the market supply of some alternative acids, some of these alternative acids like BASF’s strong organic acid buffer, excluding sulfuric acid, hydrochloric acid, phosphoric acid, and even superior performance than acetic acid, the chemical company Ningbo Runhe buffer acid is also true these buffer acetic acid but also to improve some of the shortcomings (such as glacial acetic acid winter inconvenient to use, stimulating taste great, residual acidity, and metal ions in water such as Ca +2 Mg +2) remain in the fabric caused by the combination of dark shade wilt etc. etc.). Some with H2SO4, HCl, H3PO4 and other alternative acid, not only cause changes in dyeing shade, dyeing and finishing equipment and pumps for corrosive effect, but during and after the acid residues can also cause fabric damage brittle under acidic conditions.

3. Wrinkle Article
Wrinkles are generated mainly of equipment reasons, the amount of cloths has installed causes the bath ratio and the processing operation of the reasons and other reasons, the amount of fabric mounted equipment, the pressure and friction between the pump power and the tension of the fabric and the fabric are affected fabric cloth flatness; bath ratio will affect the size of the flatness of canvas; process operations caused by too much fabric floating foam additives and process skid heating and cooling operation appears cold and hot phenomenon will cause fine wrinkles of the phenomenon . The current bath lubrication wrinkle agent, bath treasure, bath softener can improve fine wrinkles of the phenomenon, but if the device does not improve, poor process control, plus bath lubricant alone can not completely avoid the fine wrinkles of produced.

4. Wind India
Air India has little to do with the additives, the key is to dye their own performance (acid resistance) and fabric with pH, acid gas air humidity and so on, such as direct dyes Fast Turquoise Blue GC, chrysophenine G, etc. in case of sour gas prone to wind and India; activity in Turquoise Blue KN-G, brilliant orange X-GN and other pH sensitive and easy to produce on wind India; dyes such as yellow RGFL in base-sensitive, but also easy to produce wind India . For aid, the middle and must do to make cloth as pH = 7. Therefore, attention must also breed and when acids and bases, as far as possible with glacial acetic acid or organic acid substitution, can never substitute acid containing H2SO4, HCl and other strong inorganic acids, bases with Cheung also choose to ease as much as possible Some.

5. color flowers (including color, color does not match the sample, etc.)
Flower color dyeing process is the most common, the most common quality problems, the causes are:
(1) the development and operation of process issues: developing technology to produce an unreasonable or improper operation flower color.
(2) equipment problems: If the disperse dye polyester heat-setting machine inside the oven temperature varies also easy to produce color-color flowers, dyed rope pump power shortage also cause colored flowers.
(3) Dye problem: dye aggregation prone, poor solubility, poor compatibility, temperature, pH is too sensitive and are easy to produce color flower color. Reactive Turquoise Blue KN-R as easy to produce colored flowers.
(4) water quality problems: poor water quality, causing the dye and metal ions or dyes and impurities caused by condensation flower color, light color, the color does not match the kind of phenomenon.

Problem with colored flowers are mainly related to penetrant additives, leveling agents, chelating dispersant, pH value control agents penetrant penetration enough, could easily lead to uneven color dye penetration flowers, such as casual cotton dyeing, cheese dyeing effect, heavy fabric dyeing, penetrant can not be ignored, and some believe only authentic factory penetrant JFC, but did not take into account the cloud point JFC only 38-42 ℃, More than 42 ℃, its penetration force it to play out, will cause quality problems. There leveler with polyester, cotton with wool, nylon used, with all kinds of acrylic leveling agent, and the quality is uneven, leveler selection must take into account the effect of dispersing the dye solubilization, retarding migration effect, Help osmosis or complexation of metal ions in water, and must take into account various factors which PH applicability, foam and other effects on the rate of color. Leveler to improve the color of flowers, color point and so contributed, some plants leveler just solution diffusion agent N, but did not think the proliferation of agents N at a high temperature resistant dyes its unifying role greatly reduced; there the plant selection nonionic surfactants are not suitable, resulting in more than the cloud point nonionic surfactant itself precipitated dye adsorbed from tarry substance or apparatus into the fabric, but cause quality problems. Quality chelating dispersant leveling problems are related, in the current water quality is getting worse, the chelating dispersant leveling should help more attention. pH control problem is a problem of the plant too seriously, pH and some plants are not the same for each cylinder stained, with some plants using different acid substitution of quality, such as containing phosphate, pH phosphate are three ionization there are differences in how to control a uniform pH: pH slip agents using some plants, but not such as to grasp the relationship between the pH and the temperature and time generated between the slip agents, pH control of the question, so that the flower color, the phenomenon of color continue to produce.

6. color point (including white point)
The reason there are many color points generated, such as white spots, may be non-mature cotton is not the cause of the dye, it may be caused by the local soda ash and other solid stick and other reasons not to dye the cloth. Color point is the main reason:
(1) Dye inappropriate choice: dye particles are too large or easy to produce condensed color point;
(2) performing a dye dissolved: not dissolved dye into the fabric from sticking to the dye color point;
(3) water quality is poor: poor water quality caused by dye condensation;
(4) the device without a net: vat of tar-like substance under the swap cause color point;
(5) Auxiliary Reason: added in dyeing auxiliaries sometimes cause the dye to produce color point but agglutination; aids too much foam, foam with a colored dye binding bubbles stick to the fabric to form color point; additives and dyes precipitate combined with the device sticks to the fabric, and agglutinates will turn the device on the color point of the dip caused by the fabric.

About knitted fabric printing and dyeing entry-level knowledge

Knitted fabric printing definition:
The various colors of dye or paint made ​​of paste, applicator printed on the fabric pattern into the process, generally known as textile printing. Processing means for the completion of textile printing and the use of, Pan said printing process (printing is the use of printing paste containing the original delivery role, so that the dye or paint printed on the fabric into a flower pattern in the process).

Textile printing processes include:
Carving and flower patterns produced version, printing (proofing, paste modulation, printed pattern) after treatment in three parts. Detail, including both: graphic design, printing process selection, carving choice spendthrift carving (or flower plate production), imitation color proofing, paste modulation, fabric prepress processing (such as adding white, pre-shrinking, stenter , weft, dye etc.), printing, steaming or baking, washing plus soft and so on.

Difference dyeing and printing

The same principle of dyeing and printing dye and fiber combination; required for dye fixation external environment (ie, the process conditions) the same; same request with the fastness. However, in the printing of a color is applied only to the spendthrift sculptured spreads part of the fabric, properly processed, complete the process of dyeing fibers dye in the fabric have one or more color prints, so printing is a partial dyeing.

1, different media: water stain in general, printing paste generally have to add more paste to thicken and prevent infiltration of patterns;

2, dye concentration different: whether with dip dyeing, jigger, or tie-dye, the dye concentration is not high, the concentration of the dye printing paste is often high (due to the partial rationing, and dye transfer from the slurry to the fabric rate, the coloring is not high), need to add a co-solvent, urea, alcohol, etc.;

3, the fixing process is different: after printing to prevent bleeding of the dye, drying the paste film are required, the fixation of the dye to the printing by steaming, baking and other post-treatment to improve the diffusion of the dye, the final dyed fibers

4, to choose a different dyes: dyes suitable for dyeing may not apply to printing, similar reasoning applies to printing dyes do not necessarily apply to stain. As a reactive dye staining is available but not high solubility phenomenon highly colored points for printing color unevenness; Another example of a trend in the reduction of vat dyes large but slow reduction rate, and the steaming time and is easy to produce offshoot reaction, printing can not be but stained with a dry cylinder reduction, low temperature dyeing; Again the reaction rate is too fast under a high-temperature reactive dyes, highly uneven dyeing, and printing is available and more appropriate. Sometimes with a special stamp printing dyes, dye selectively;

5, to fight the case and process different materials: Requires little fight in recent fight, fight with a selected process conditions and staining Ingredient, while printing, often use different types of dyes, conducted jointly with the paste printing or printing, such as direct printing + anti / pull printing, as a calico paint on both active, as well as reduction, etc.;

6 different requirements for semi-finished products, calico high pre-treatment requirements:
a, semi-finished products for hair calico efficiency and barium values ​​demanding, requiring uniform instantaneous capillary effect and good capillary effect, namely uniform and fast surface finish of the fabric also higher;
b, semi-finished products for printing skew, width shrinkage and demanding, especially printed plaid, circles, stripes, squares, etc., and can be dyed after staining the whole;
c, different requirements for fabric: Printed fabric dyeing than hiding better, and spend more full blocks covering more chaotic the finer the better, but not dyed, printed fabric on fabric selection so critical as dyeing high.

Knitted fabric printing method

Divided by technology: direct printing, discharge printing, resist printing, anti-paste printing

By equipment of:

First, type edition printing
Type edition printing advantages:
1, flexible, easy carving, suitable for small batch production
2, pattern size, chromatic unrestricted, gaudy printed products.
Disadvantages:
1, stamped outline is not clear enough, the pattern due to the fine;
2, printed straight (bar) registering the pattern, no measures are taken can not be printed hollow circular pattern;
3, chromatic spend more difficult;
4, low labor productivity.

Second, copper roll printing
Roller printing is pulling flowers engraved on copper spendthrift, storage in the recessed portion spendthrift paste, paste printing process is transferred to the fabric.
Advantages: clear pattern, rich layers, high production efficiency, speed up to 100 m / min.
Cons: limited chromatic printing, unit size of the pattern and fabric width is limited; spendthrift pattern printed by the first printing on fabric extrusion, resulting in mass color affect color vividness, and (due to compression) color not full; fabric by tension, suitable for light books and deformation fabric printing. 70s roller printing machine is the widely used printing equipment, is now gradually being replaced by screen printing.

Third, screen printing
1, flat screen printing: screen frame is first prepared in a pattern on the screen frame where the mesh was hollow, no pattern of the mesh smear. When printing paste was printed onto fabric and mesh scratched up.
There are flat screen printing machine from the degree of automation
(1) manual – Box-action hand platen (of course there are semi-automatic type);
Advantages: Flower back, trapping unrestricted pattern outline a clear, rich and gaudy colors, fabric tension by small, suitable for small batch production.
Disadvantages: large area, high labor intensity, low productivity, flower, uneven squeegee, then printed version is a common flaw, and straight, Montreal and other patterns can not accept version.
Application: used for fabrics, garments and pieces printed, knitted printing.
(2) automatic flat screen printing machine – cloth-action.
Printing Process: cloth travel guide – the conduction band to stop running – Screen decline – squeegee – screen upgrade – reincarnation
Pros: small footprint and labor intensity, trapping more and spend unlimited back, the color is more nuanced, fabric by little tension.
Disadvantages: Similar to frame acting, the printing type is restricted.
Application: suitable for small volume, variety, easily deformed, light book upscale fabric, used for printing sheets, silk, knitted fabric.

2, rotary screen printing machine
The flat screen be made ​​of a cylindrical screen printing on continuous operation with a roller printing features.
Advantages: high efficiency, low labor intensity, easy operation, small footprint, multi-color printing, color was not as gaudy degree heat platen screen printing, but better than the drum, flowers and flat screen flexible back though, but better than the big drum, no contact with the printed version of the drum as a problem.
Disadvantages: subject to certain restrictions flower printing, roller printing pattern level is better, especially printed moire effects, color transition difficulties, high nickel net cost.

Fourth, transfer printing
Printing with the dye ink printed on paper made​​, the pattern was printed on paper (referred to as transfer paper); positive after the transfer paper is printed on the front fabric with the close fit at a certain temperature, pressure, squeezing a certain time, so that the dye sublimation transfer paper on the dyed fabric to be printed up, which is called sublimation thermal transfer method or the transfer method.
Advantages: transfer paper for long-term storage, you can always transfer as needed, to facilitate the production, do small batches (tens of meters can be made​​), product defects rarely printing on fabric prepress requirements low, due to the need to deal , colorful patterns, levels, and can significantly Photos prototype.

Disadvantages: fiber used dyes narrow range, a large number of current use is mainly polyester fabric dyes on heat transfer, and applies mostly low temperature disperse low sublimation fastness, color yield are all too apparent color.

Fifth, multicolor printing dye leaching method
Rationale: When the dye solution before absorption of water or a color of the fabric, will be able to produce “anti-pollution effects,” leaving another color dye stain blocking solution. Using this principle, different color dye can be sprayed on the fabric, although the patched-color mixing these colors the dye, but the color of the fabric, but there are different dye from the fabric coming down, mostly single topped to color, is also part of two colors mixed colors, resulting in the formation of color patterns….

Categories of Knitted Fabrics

Knitting means that utilizing needles to make yarns bend to circle, bunching and overlapping into textiles. The difference between knitted fabrics and tatted fabrics is that the different structure of yarns in textiles. The categories of knitted fabrics are classified into weft knitted fabric and warp knitted fabric. For the moment, knitted fabrics being widely utilized for clothing fabrics, inner fabrics and home textiles, are welcomed by customers.

Weft knitted fabric is made of low flexible polyester silk, polyamide yarns, cotton yarns, wool yarns, etc. adopting plain stitch, changing plain stitch, plain rib stitch, interlock plain rib stitch, jacquard stitch, terry stitch. The fabric is knitted by using weft knitting machine. Weft knitted fabrics has various categories, good flexibility and extensibility, softness, fastness and creasing resistance, strong sense. It is washable and can be dried quickly. However, weft knitted fabric has bad hygroscopicity. Textile is not crisp enough.

1.Knitted polyester fabric: Knitted polyester fabric has various colors, beauty, harmonious color bending, tight and solid texture, clear weave grain, strong sense. The style of fancy suit is similar to wool fabric. The fabric is mainly used for clothes, suits, coats, skirts and children’s clothing.
2.Knitted polyester labor fabric: Knitted polyester labor fabric has tight and solid texture, good fastness and wearing resistance, flexibility. It can be knitted into jeans with spandex, having good flexibility. It is mainly used for trousers.
3.Knitted polyester wick fabric: The fabric has clear concave-convex, solid feelings, good flexibility and heat retention. It is ideal materials for clothes, suits, coats, skirts and children’s clothing.
4.Knitted polyester cotton fabric: Knitted polyester cotton fabric is used as raw materials for shirts, jackets, and sport wears. The fabric has crisp, crease resistance, fastness and abrasion resistance. The face next to skin has moisture absorption and breathability to feel comfortable.
5.Knitted fake fur fabric: The fabric has solid feeling, softness, good heat retention. It is mainly used for coats, lining, neck and caps.

Knitting Fabrics Introduction

Knitting fabrics have soft texture, hygroscopicity, breathability, good elasticity and elongation. Using knitting fabrics can make people feel comfortable, close and show body curve fully. Currently knitting fabrics have various colors. New type knitting fabrics with different texture effects and functions have been developed, bringing unprecedented sensory and visual sense.

Categories of knitting fabrics:
Acetel fiber: Acetel fiber has the same characteristics as silk. Acetel fiber has bright gloss, colors, good drapability and feelings. Knitting fabrics made of acetel fiber is welcomed by consumers for its slippery feeling, good hygroscopicity and breathability, light weight, low moisture regain and anti-static electricity.
Modal fiber: Modal fiber is a new type environment friendly fiber, combining with comfort of cotton, drapability of rayon, strength of polyester and feelings. Even can softness and bright gloss be maintained when modal fiber is washed for several times. Single or double knitting fabrics made of modal fiber and spandex by using circular knitting machine have slippery feelings, softness, elasticity, bright gloss, hygroscopicity and breathability. Clothes made of the fabrics can show body curve, sexy and fascinating female body fully. It is raw materials for high-grade knitted dresses.
Overtwisted combed yarn: Knitting fabrics made of overtwisted combed yarn have the feelings of yarn, coolness, hygroscopicity. Otherwise, overtwisted have stable sizes and good wearing resistance, being ideal fabrics for high-grade business attires and casual clothes.
Coolmax fiber: Coolmax fiber has four grooves which exclude sweats caused by activities to surface of clothes so that sweats can be evaporated. Knitted fabrics made of coolmax fiber and cotton fiber have good moisture conductivity, widely utilized as raw materials for T-shirt and sport shirt.
Lyocell fiber: Knitting fabrics made of Lyocell fiber, tencel and spandex have soft texture, smooth surface and good elasticity. It is ideal high grade fabric for strait jacket, casual clothes and sport shirt.
Shining knitting fabrics: Shining knitting fabrics are always welcomed by designer. Shining knitting fabrics are made of spun gold, filamentary silver and other materials by using circular knitting machine. The surface of fabric adopts strong reflective short and gilding. So glitters of various patterns are shown on the surface of clothes. Shining knitting fabrics have bright future.