Denim-Types

3 types

Since the late 1970s, denim has undergone several major developments in China and has become an important producer of denim in the world. A large number of relatively advanced denim and denim clothing enterprises have basically reached international standards in terms of quality and variety, initially reversing the concept that Chinese denim products are "low-grade products" in the international market.
Although the development and production of denim products in China started relatively late, they started at a relatively high level, with air spinning, automatic winding, ball warp dyeing, and shuttleless looms (a large number of them are rapiers, followed by projectiles, and air jets again). , Heavy-duty pre-shrinking and finishing machines and other advanced equipment, thus creating good conditions for the development of denim varieties and improving the quality level. However, for a long time, some equipment with excellent performance and complete functions, such as the functions of electronic dobby, multi-color, uneven winding, quick change of varieties and unmanned operation of rapier looms, have not attracted enough attention, resulting in waste of functions. This situation needs to be resolved urgently in order to better serve the development of varieties, improvement of quality and labor productivity.
Bamboo
When designing slub yarns with different yarn numbers, different slub thicknesses (ratio to base yarn), slub lengths and pitches, use slub yarns in single warp direction or single weft direction, and both warp and weft directions are equipped with slub yarns. A variety of slub denim fabrics can be produced when normal yarns of different sizes or sizes are properly proportioned and arranged, and various hazy or clear striped denim styles can be formed after garment washing. , and is welcomed by groups with individual consumer needs. Early slub denim was almost always made of ring-spun slub yarn, because it can be spun into slub yarn with shorter length, smaller pitch and relatively higher density, which is easy to form a denser embellishment effect on the cloth surface, and The meridian bamboo joints are the main ones. With the development of market consumption demand, especially the two-way slub denim products with weft elasticity are very popular in domestic and foreign markets. For some varieties, as long as the organizational structure is well designed, a single variety of ring-spun yarn can be used in the warp direction, and a proper proportion of slub yarn can be used in the weft direction, and the effect of bidirectional slub denim in warp and weft can also be achieved.
Ring yarn
With the development and application of new technology equipment such as high-speed ring spinning, large package, fine-bonding, and knot-free yarn, the shortcomings of short spinning length, low production efficiency, and many knots of coarse-count yarn have been solved. The situation that denim yarn is being replaced by air-jet yarn is changing rapidly, and ring-spun yarn is likely to make a comeback. Because ring-spun denim is superior to some properties of air-laid yarn, such as hand feeling, drape, tear strength, etc., but also due to the influence of people's psychological return to nature and the pursuit of the original developed denim style, the more important reason is that ring-spun denim After grinding and washing, the surface of spindle-spun denim will show a hazy slub style, which is in line with the individual needs of today's denim. The ring spun slub can be spun into shorter and denser slubs, which also promotes the development momentum of ring spun denim.
Weft stretch
The use of spandex elastic yarn has developed the denim variety into a new field, which can make the denim clothing close to the body and comfortable, and with bamboo or different colors, the denim products are more suitable for fashion and personalized consumer demand. Great potential for development. The elastic elongation is generally 20% to 40%. The elastic elongation depends on the weave design of the fabric. The smaller the warp and weft weave tightness on the loom, the greater the elasticity. Next, the greater the tightness of the elastic yarn in the weft direction, the smaller the elasticity. When the weft tightness reaches a certain level, it may even lose its elasticity. In addition, the prominent problem of elastic denim finished fabrics is that the weft shrinkage rate is too large, generally more than 10%, and some even reach more than 20%. Unstable fabric width brings great difficulties to garment production. The first solution is not to make the elastic stretch too large in product design. Generally, 20% to 30% is used, that is, to maintain a certain warp and weft weave tightness, and in the During the pre-shrinking finishing, the method of appropriately increasing the tension is adopted to make the cloth have a larger shrinkage, so as to obtain a lower residual shrinkage in the weft direction of the finished fabric; another solution is to heat-set the stretch denim after pre-shrinking , so that a more uniform cloth width and a more stable and lower weft shrinkage can be obtained, which can meet the requirements of garment processing and production.
chromatography
In order to increase the color and shade of indigo denim varieties. For example, indigo over-dyed sulfur black, indigo over-dyed sulfur grass green, sulfur black green, sulfur blue, etc., to meet the individual needs of the market. At the same time, the denim production factories have their own new denim varieties with patent characteristics to improve the competitiveness of the market. What needs to be paid attention to in this regard is to control the concentration of the mother liquor as much as possible to prevent the excessive overflow of the dye liquor and cause the waste of dyes and expand the pollution to the environment.
special color
Because the garments made of super indigo dyed or extra deep indigo dyed denim can obtain the special effect of rich and bright color after washing, they are widely welcomed by consumers. "Super indigo" dyed denim has two characteristics: particularly deep dyeing depth and particularly good color fastness to washing. The former refers to the amount of indigo dye dyed on the yarn per unit weight (generally expressed as the percentage of the dye in the dry weight of the yarn, referred to as the dyeing depth %) is particularly large, for example, the indigo dyeing depth of conventional denim warp yarns is 1% to 3%. , while the dyeing depth of "super indigo" needs to reach more than 4% before it can be called super indigo or extra deep indigo. The latter means that "super indigo" dyed denim needs to withstand repeated grinding and washing for more than 3 hours, and its color can still reach or exceed the color depth of conventional dyed denim without grinding, and its shade is better than that of conventional dyed denim. Much richer and brighter. The rubbing fastness of indigo-dyed denim depends essentially on the degree of penetration of the dye to the yarn, rather than the rubbing fastness of the dye itself (wet rubbing fastness of indigo is only grade 1), that is, through the core The better the degree, the better the color fastness to grinding and washing.
In the past, the so-called "indigo dyeing fast washing process" actually made the indigo dye penetrate the core of the fiber very shallowly during the yarn dyeing process. After the first layer of dye is rubbed off, more white yarn cores are exposed, which makes the color lighten quickly, so as to achieve the effect of fading immediately after a short period of grinding and washing. The "Super Indigo" dyeing process is on the contrary. It requires the dye to penetrate the core very well, so that the denim garment can obtain a deep and bright color after grinding.
Since the dyeing depth of "super indigo" dyed denim products is more than 60% higher than that of conventional traditional denim dyeing, the indigo concentration in the dyeing solution will also increase exponentially, even reaching 3-4g/L, and it is possible to obtain deeper Strong color. In this way, the viscosity of the dye solution increases and the fluidity becomes poor, which affects the penetration ability of the leuco dye, reduces the color fastness to washing of denim, and fails to meet the final depth requirements of garment production. Therefore, some enterprises adopt the design of increasing the dyeing depth again, so that the concentration of indigo in the dye solution increases again, and the permeability becomes worse. In this way, a vicious circle is formed, and the requirement of "super indigo" color is still not met. The higher the concentration of indigo in the dyeing solution, the heavier the red light of the dyed product, the darker the color, and there will be no "super indigo" effect. This difficult problem can be solved by increasing the number of staining passes. For example, increasing the number of dyeing processes to 8, or even 10, not only increases the investment cost, the consumption of dyes and chemicals, but also increases the difficulty of operation, and increases the pollution to the environment. A better way to solve this contradiction is to appropriately reduce the proportioning dosage of sodium hydrosulfite or caustic soda, especially the control of the dosage of caustic soda, so that the pH value of the dyeing solution is stable between 11 and 12, the dyeing rate is the highest and the color is stable, and at the same time Appropriately reduce the dyeing tension of warp yarn pieces, so as to obtain better "super indigo" dyeing effect.