Abstract: There are many advantages of nylon/Lycra warp knitted fabrics, such as good tenacity and abrasion resistance due to the nylon, and excellent elastic recovery property due to the Lycra. The fabrics also have a fine moisture releasing, soft hand-feeling. Moreover, clothings, which are sewed with this kind of fabrics give people a feeling of pressure-free comfort, and help to build a perfect figure. However, there is a lot of silicone oil from the spinning of the synthetic fiber, especially the Lycra, which brings difficulties to process nylon/Lycra warp knitted fabrics. In general practice, the warp knitted fabric is pretreated under traditional batchwise method, dyed by long LR overflow machine, and heat set by high energy consumption stenter. Therefore, most customers are not satisfied with the fabric quality and high production cost. This article will introduce FONG'S Industries Group's eco-friendly machineries, GOLLER Sintensa Washing Range for oil removal, FONG'S ECO-88D Double Rope High Speed Dyeing Machine for dyeing, and MONFONGS 828 ES TwinAir Stenter Frame Range for pre-setting and heat setting, which are widely applied in the dyeing and finishing process of nylon/Lycra warp knitted fabric.
Nowadays, with obtaining of many new kinds of fiber and developing of application technology, due to the good performance, such as the excellent elastic recovery, fine moisture releasing, soft hand-feeling, the elastic fabric knitted with micro synthetic fiber and Lycra is widely used in lingerie, sports wear and shape wear and so on. These products can provide you a comfortable living. The clothings with Lycra has the end-using properties of comfort, smoothly-act, pressure-free to the body, which makes it popular in the warp knitting industries. Especially the elastic fabric with micro synthetic fiber and high percentage of Lycra is more popular and with much value added in apparel field. However, how to process this kind of fabric and how to choose the suitable equipments are of utmost importance in the production. FONG'S Industries Group, as the leader of dyeing and finishing equipment manufactures, has made remarkable progresses on it. FONG'S machineries are well received by the customers. This article will discuss the dyeing and finishing process and the key technology of nylon/Lycra warp knitted fabric on the machineries provided by Fong's Industries Group.
2.Materials and Machineries
Materials: Nylon/Lycra warp knitted fabric (Lycra 10~20%); Light acid dyestuff; Levelling agent; Lubricant; Acetic acid; Sodium acetic; Anionic fixing agent
Machineries: GOLLER Sintensa; MONFONGS 828 ES TwinAir stenter; FONG'S ECO-88D series
3.Process and the key technology on machineries of Fong's Industries Group
Prepare Fabric → Oil Removing → Pre-setting → Dyeing → Heat setting → Quality Control → Package
3.2 Oil Removing
Oil removing and washing of nylon/Lycra warp knitted fabric is better to be processed in continuous open-width equipment, which can remove the oil more efficiently without affecting the surface of the fabric. Oil removing is a process of removing silicone oil from the spinning of synthetic fiber, especially the Lycra. Most of the oil must be removed to ensure a satisfactory dyeing result. Please be reminded that it should be directly rinsed with warm water after oil removing instead of cold water, otherwise it will cause the emulsification oil adhered to the fabric again.
Sintensa is a good open-width washing equipment from GOLLER (the wholly owned subsidiary of FONG'S Industries Group) to process this kind of fabric, due to its outstanding features: installed with Loadcell tension adjustment device, which enables the fabric to keep low tension and excellent elasticity in the pretreatment; low fabric density in the store room and the constant water spray or pretreatment bath system, which effects the fabric without folded mark or abrasion mark; the special adjustable intensity via frequency regulated rotor device, which achieves intensive pretreatment and washing effect, and also low water consumption.
(Figure 1: GOLLER Sintensa Washing Range for oil removal)
Nylon/Lycra warp knitted fabrics must be pre-set before dyeing to enhance dimensional stability, otherwise it will cause selvage curling and crease mark during dyeing process. There is a lot of silicone oil in the spinning of Lycra. Although most of that was removed during pretreatment, but some of them can still come out from the fabric and form into smoke, which is easy to cause problems like making the fabric yellowish due to silicone spots, increasing difficulties of dyeing, and polluting the environment.
MONFONGS 828 ES TwinAir stenter can effectively eliminate above problems. It adopts the integrated exhaust heat recovery (H/R) system, which ensures reduction of energy consumption by 18% or above subject to technical condition and impurities can be condensed after heat-exchanger. It brings notable economic benefit to the customers, and is a true "Energy saving, Environmental friendly" equipment.
Figure 2: MONFONGS 828 ES TwinAir Stenter Frame Range for pre-setting and heat setting)
There are different types of dyeing machines to can be applied in nylon/Lycra warp knitted fabric, such as beam dyeing machines, airflow dyeing machines, and overflow dyeing machines. The overflow dyeing machine to process this kind of fabric should be with features,like low tension, high fabric speed, few crease marks. The overflow dyeing machine of ECO-88D series, developed by FONG'S, has made remarkable progresses to process light to medium weight woven and knitted fabric made from synthetic and blend fiber, especially that is sensitive to temperature and the formation of crease marks, because of its design superiority as below:
---Long kier: the fabric spreads over the entire length of the kier so that fabric is not subject to high stack loading, thus reducing the formation of crease mark
---Low fabric tension: since the height of the fabric lifting from the chamber to the lifter reel is very low, the fabric lifting tension is very low, which helps to maintain the elasticity of the fabric
---High fabric speed: the fabric speed can go up to 500~600m/min to allow an optimum short fabric cycle time for sensitive fabric
---Conveyance tube: down-running mode, fabric immerse in the conveyance tube to complete the dyestuff exchange for evenness and reduce the formation of crease mark
---HydroSki supporting system: the Teflon rods chamber provides smoothest contact surface and good fabric quality
(Figure 3: FONG'S ECO-88D Double Rope High Speed Dyeing Machine for dyeing)
The dyeing recipe and process curve are as follow:
Dyeing: Light acid dyestuff X%
Levelling agent 1~3%
Sodium acetic 1g/L
Adjust pH value to 4~6 by Acetic acid
Fixing: Anionic fixing agent 2~3%
Adjust pH value to 4~5 by Acetic acid
Liquid ratio 1:7~10
As we all know, the nylon warp knitted fabric is easy to have claw marks or other dye defects. Based on it, we should choose excellent dyestuff and levelling agent to minimize barre in dyeing. Moreover, it is very important to use the same lot of yarn in knitting. In order to get good levelness and to reduce formation of crease mark, we should strictly control the heating and cooling gradient within 1.5℃/min, and the temperature of drain bath less than 60℃. Recommended holding time is 45~60min to maximize migration of dyestuff. Lubricant agent is widely used in dyeing of this kind sensitive fabric, which helps to increase the smoothness between fabric or fabric and machine, and eliminate the mechanic abrasion during running. Medium or dark shade must have fixation to be done in order to obtain get good color fastness.
3.5 Heat setting
Heat setting provides dimensional stability. Setting the width and weight of the fabric is the most important process for Lycra blend fabric. MONFONGS 828 ES TwinAir stenter is the prime choice for heat setting of the warp knitting elastic fabric. It is equipped with vertical padder, TwinAir system which is the patented system registered by Monforts Germany and air volume controlled by frequency inverter, which are all ideal for delicate fabric. Appropriate temperature and contact time are required as extended process time or highly set temperature could stress the relaxed Lycra fabric or damage its stretchability.
Feedbacks from the customers on FONG'S environmental solution to dyeing and finishing of nylon/Lycra warp knitted fabric are exciting. The highly efficient oil removal and low water consumption in the pretreatment with GOLLER Sintensa, the excellent dyeing levelness and short LR in FONG'S ECO-88D series as compared with the traditional long LR machines, and the heat setting effect and low energy consumption of MONFONGS 828 ES TwinAir stenter, all demonstrate that the FONG'S solution is the best choice for the treatment of this kind of sensitive fabric.
The challenge of dyeing and finishing application is becoming more severely with the innovation and development of micro fiber and warp knitting technology, which inevitably demands a critical selection of auxiliaries, dyestuff, process and equipments. Moreover, it is most important to apply efficient equipment to reduce water and energy consumption and protect environment in the production process. In the textile industry, the concept of environmental protection and the efforts in green production have brought new values to textile products. To meet the market needs for eco-friendly products and technologies, the innovative dyeing and finishing solution from Fong's Industries Group to Nylon/Lycra Warp Knitted Fabrics is our response to growing demand for quality dyes and global environmental concerns.
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