Denim is an important part of clothing fabrics for garment accessories and denim of indigo blue is popular globally and known by everyone.Because of its popular appearances in cotton denim,dye of indigo blue maybe the only dye known by people.
In 1980S,the output of denim in America accounted for 50% of global output,but in recent decade,a great deal of denim fabric product factory were built in China ,Indian,Pakistan,Malaysia,Turkey and Mexico,the production center of denim of America and even the whole world has shift to Asian counties with low labor cost.In 2000, the output of denim in China was2424t around, the import of indigo blue dye was 759t.While in 2001,the output of denim raised to 2717t and the import of reduced to 702t.
In the market of denim fabric,althought cotton is undeniably important,still there are series of blend fabrics like those of cotton fabric and dion fabric（50/50）,cotton and other fibres such as Tencel,fiberflax,and even jute and wool yarn.
Different from most products in denim fabric market,such denim products offer customers products design of high level and clothes of high added value.The use of denim of optical filament elasticity and ring spinning yarn has also improve the value of products.Some companies has invested in such sectors.Ring spinning yarn has higher strength property ,softer touching sense and some appearance of slub yarn in cotton denim.
The output of ball denim exceeds 2 billion meters which is one quite high quantity for garment accessories products, there are two kinds of it namely yarn of air spinning or ring spinning.In the past, America produced elastic denim of mainly zonal level,while Europe meridional level.Nowadays,human is continually studying denim with fashionable changes and getting new appearances, touching sense and property by dyeing and rearranging.
Cotton denim with high thickness is used as fabric in pants and jackets,but in 1990s, the requirements of customers on material’s softy,comfort and nursing quality improved,so arrangers must response to such changes.
The study on improving denim appearance through various chemical processing and such effects like flocking embroidery and paint-coat is continuing all the time.Besides, the developed new products include indigo blue jacquard,knitted or woven fabric of linum and cotton, laser hollow on denim that is characterized by dark brightness pattern and personalized.
Types of Denim
Introduction to Denim
Since 1970S, great development on denim has took place in China ,it is estimated that the annual output of denim is over 1.5billions.China has become an important denim manufacturer. A great deal of advanced entreprises of denim and cowboy clothing has basically come up the international level in quality and types, which primarily turn the concept around that Chinese denim products belong to inferior goods in international market.
Although the beginning of exploring and producing denim products is late ,but it began from a high place and it has advanced equipment like rotor spinning , automatic winding, ball dyed, shuttleless loom (a large number of rapier, followed by projectile, then jet） heavy pre-shrinkage finishing machine,all of which offer sound condition for developimg denim products and improving its quality.But for a long time,some functions of some high quality and complete function equipment like rapier loom has not been valued enough,including electronic dobby, multicolor, uneven coiling, quick variety change and unattended operation,so this ignorance causes functional wears.It need to be dealt immediately to serve for better quality and productivity.
Nowadays,some popular denim types mainly include ring yarn denim, warp and weft zigzag denim, superindigo dyed denim, colour denim, colored denim, weft elastic denim, etc. which are used well by clothing manufacturers
Ring Yarn Denim
With the development and application of ring yarn’s new technics like high speed, large package, fine winding, no knot yarn, etc,some problems like short spinning length, low production efficiency and many knot defects from coarse yarn have been handled.The situation that yarn that is used in denim is being taken place by rotor spinning is changing ,the face is that ring yarn is expected to come back to the market.The reasons lie in some properties of ring yarn denim like touch feeling,drape, tear strength are better than those of rotor spinning yarn ,in that people has psychologically come back to nature so they chase the influence of primitive denim style, and more importantly ,after being processed,this clothing’s surface will show a hazy bamboo-shaped style,which right meets the need of modern individuation.Nowadays,the bamboo shaped clothing is very popular in market.Meanwhile, ring bamboo can weave those short and thin one ,so it facilities the development of ring yarn denim.
When we need design bamboo denim with different dye and thickness, length and distance of bamboo,whatever we adopt ,be it warp direction ,zonal one or even both of them, we can use the normal yarns of the same size or different sizes that are properly proportioned and arranged, various kinds of bamboo-shaped denim can be produced. After washing and processing of clothing, various kinds of different denim with hazy or clearer stripe and lattice style can be formed. It is welcomed the consumer personalized demand group. In the early years, almost all of the denim were made of annular slub yarn, because of its short spinning length, small pitch and relatively high density, all of which made it easy to form a dense embellishment effect on the fabric surface, and main direction was warp.With the development of market consumption demand, ward and weft bidirectional denim,especially double directional bamboo denim products with warp elasticity sells very well in domestic and international market . Besides,some products can also achieve the effect of warp and weft bidirectionalas bamboo denim as long as the structure of some varieties is well designed if the warp direction can adopt a single variety of ring yarn, and the weft direction adopt a proper proportion of bamboo yarn.
Weft Elastic Denim
With the adoption of spandex elastic yarn, the variety of denim has stepped into a new field, which enables the denim suit both close and comfortable.Besides, quipped with bamboo section or different color ,the denim products more adoptable to the Desmond of fashion and personalization,increasing developmental potential. At present, the elastic denim is mostly weft elastic with the elastic elongation generally reach to 20% to 40%. The elastic extension depends on fabric structure design. The smaller the warp and weft tightness on the fabric machine, the greater the elasticity, and vice versa,under the condition that the warp fabric tightness is fixed, the greater the tightness of the warp elastic yarn, the smaller the elasticity, the higher the weft tightness, and even the loss of elasticity.In addition, the striking problem of the finished elastic denim is that big washing shinkage, which is usually above 10%,some even exceed 20%.Production difficulties comes from unstable cloth width.One way to solve this problem is not to stretch out too much elasticity in product design, but generally take 20 or 30%, that is to say, to maintain a certain warp and weft tightness. The method of increasing tension is adopted in pre-shrinkage finishing to increase the width of cloth shrink so as to obtain the low residual washing shrinkage rate of finished cloth in weft direction.Another solution is that the elastic denim is treated by heat setting after pre-shrinkage finishing, which can obtain more uniform cloth width and lower weft shrinkage rate, meeting the requirements of clothing processing and producing by clothing suppliers.
It is widely welcomed because it can get special effects of bright and thick color after the super indigo or deep indigo made clothing get grinded and washed. Superindigo dyeing denim has two characteristics: special depth of dyeing and excellent fastness to wash.The former means that the amount of indigo dyestuff dyed on the yarn per unit weight (generally expressed as%, the dry weight of the yarn, referred to as the dyeing depth) is particularly large. For example, conventional denim warp indigo dyeing depth is 1 / 3, while “super indigo” dyeing depth reach more than 4% to be called super indigo or extra deep indigo.The latter means that the denim dyed by “super indigo” need to undergo repeated wear and wash for more than 3 hours, and its color can still reach or exceed normal depth of color as the denim is not polished, and its color is much brighter than that of the conventional dyed denim. For indigo dyed denim, the essence of the fastness depends on the degree of penetration of dyestuff to yarn, not the fastness of dyestuff itself (the fastness of indigo wet grinding is only 1 grade), that is, the better the degree of penetration, the better the fastness to washing and washing.In the past, the so-called “Indigo Dyeing fast washing process” is actually in the yarn dyeing process, deliberately making the indigo dye core of the fiber very shallow, so when washing and processing , a thin layer of dyestuff on the yarn surface is worn out and It exposes more white yarn core, so that the color and lustre quickly fade. After washing and worning in a short time , the effect of color fading immediately. But the “super indigo” dyeing process is the opposite. It requires that the penetration of the dye be very good, so that the denim clothing can get both deep and bright color after washing and processing.Because the dyeing depth of denim products is more than 60% higher than that of conventional denim dyeing,to obtain deep and dense color, the indigo concentration of dyeing solution will increase exponentially, even up to 3 g / l.In this way, the viscosity of dyeing solution increases, the fluidity becomes worse, the penetration ability of dyestuff is affected, the color fastness of denim is reduced, and the final depth of garment production is not reached. As a result, some enterprises adopted the design of increasing dyeing depth again, so that the concentration of indigo increased again, and the permeability became worse, thus forming a vicious circle, which still could not meet the requirements of “super indigo” color.The higher the concentration of indigo in the dye, the heavier the red light of the dye, the darker the color, the less the “ultra indigo” effect.As a result, there are many factories nowdays are preparing to transform the dyed equipment and increase the number of stains to solve this problem. For example, increasing the number of dyestuff to 8, or even 10, which not only increases the investment cost, the consumption of dyestuff, and the difficulties in operation, but also the environmental pollution .The better way to solve this contradiction is to reduce the proportion of the insurance powder or caustic soda, especially the amount of caustic soda, so that the pH value of the dye solution is between 11-12, the dye uptake rate is in highest level and the color is stable. At the same time, the dyeing tension of warp sheet is reduced properly, so as to obtain better dyeing effect of “super indigo”.
Colored Denim Based on Indigo
In order to increase the color and changes of brightness of indigo denim ,all kinds of colored denim varieties are very popular. Such as indigo black, green,blue, and so on, which meet the needs of the market. At the same time, it also facilities denim manufacturers have their own new varieties of denim with patent characteristics to improve the market competitiveness.In this respect, it is necessary to control the concentration of mother liquor as much as possible to prevent excessive overflow of dye, resulting in the waste of dyes and the expansion of pollution to the environment.
Such denim mainly includes the bromine indigo denim and black vulcanized denim, those coffee, green, gray, khaki, sulphide blue denim with sulphide dyes, and a small amount of bright red peach red, concubine denim with Naftol or reactive dyes .Although the output of such denim is not large, but there are always urgent market demand that can not be meet.The main problems are that the color and lightness are not stable, dyeing attention is also poor, and the clothing manufacturers are not satisfied. This is of course related to the small quantity of production and the excessive variety of color, but it is also influenced by the problems like big production difficulties, high consumption and budget and sewage handling of colored varieties by the dyeing and pulp combined machine .The first solution is to gain stable dyeing effect by reducing the number of colors as much as possible to two colors or no more than three colors, or other more stable dye varieties to adapt to the production traits of the on-line dyeing station. Second, the more thoroughout solution is to produce colored denim by dyeing yarns of yarns in yarns with large capacity and warping by stripe and warping.
The specification of traditional and coloured denim
Denim is made of interwoven between pure cotton indigo dyed warp yarn and original weft yarn in three top down right twill textures way, generally it is divided into three sizes： light, medium and heavy light denim weight 200-340 g / square meter /(6-10 ounces / square yard), medium cloth weight of 340-450 g / square yard (10-13 ounces / square yard) heavy cloth weight more than 450 grams.Yarn thickness of fine yarn: heavy weight is 7 × 6, medium is 10 × 10, light is above 12×12 .Mostly,the width of the denim is between 114 – 152 cm . Besides the above – mentioned tradtional products , there is also the colored denim ;
1 . Adopt Colored Denim of Different Raw Material Structure
( 1 ) adopt elastic denim using small proportion spandex yarns ( about 3 – 4 percent of the weight of the yarn ) as the elastic warp yarns or the weft yarns of the warp yarns
( 2 ) adopt snowflakes denim blending with low – scale polyester and cotton as warp yarns and produce a white – white – effect after dyeing
( 3 ) high – grade denim made of cotton and cotton wool blended yarn .
( 4 ) adopt denim weaven with medium – length fiber ( T / R ) .
2.Adopt Colored Denim Made by Different Handicrafts
(1)Bark crepe denim made of high twisting weft
(2) when warp dyeing, underlay indigo denim with vulcanized or haichanlan dyes before dyeing indigo blue
(3)Embed colored denim into indigo blue warp yarn
(4) Hang white or printe indigo denim.
The unit of weight of denim is (g / m2, that is, g / m2), the unit of yarn weight is (English cotton yarn number, S)
Lightweight denim weighing between 6 and 10 ounces / square yard of 200-340g/, weave more than 12 x 12s
Medium denim weighing between 10-13 ounces / square yard of 340-450g/, weave 10 × 10 S
Heavy denim weighting more than 450g/, weave 7 × 6S