Wool non-woven fabric

In non-woven processing, the fiber is directly converted into a fabric through a continuous process. The input wool is usually similar to that used in the roving process, that is, the fiber is shorter than that in the worsted process, and usually has no grass, thus Carbonized wool and short tops are used in non-woven processing. Short wool refers to shorter wool that has been combed to remove grass, very short fibers and knots, which are more expensive than carbonized wool. Like woollen processing, If the fabric is made of low-grass wool, it is also possible to carbonize the fabric, but this is less common, and if the nonwoven is not designed specifically for this type of processing, the grass may also Other problems are caused by the equipment. Wool and synthetic fibers can also be blended, and a wide range of fiber blends are commonly used in nonwoven processing.
Although non-woven fabrics have some appeal because of their lower cost, non-woven fabrics have some inherent physical limitations, which indicates that weaving and knitting processing will continue to be popular for some time.
Woven fabrics and knitwear
- Wool yarn interior: tight fiber contact - strength and elasticity
- Between the yarns: looser contact, yarn curling
- Drapable, bulky, feels good, flexible nonwoven
- Fiber contact is required throughout the process to provide strength and fiber stability, which results in:
Stiffness, poor hand feel, poor drapability, elastic recovery, the strength and elasticity of the fabric and knitted fabric are provided by the yarn, the yarn curl and the yarn arrangement, so the internal strength of the yarn is higher, the fiber stability is good, and the loose connection between the yarns makes the fabric It has elasticity and flexibility. The non-woven fabric can't easily imitate this effect, because in the whole non-woven fabric, the strength and fiber stability are caused by filament winding. At present, this disadvantage makes the application of non-woven fabric only Limited to a certain area, including industrial fabrics, medical cloth and protective clothing, but some clothing products are very suitable for the use of non-woven fabrics, research continues to overcome these limitations, broaden the application of non-woven fabrics.
1 Non-woven production Non-woven production can be divided into the following stages:
- Fiber web formation
- Fiber mesh bonding
- sort out
- Coloring The formation of the web is usually done by a carding process, or it can also be airlaid, such as Fehrer and Danweb.
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Figure 1. Basic nonwoven carding machine (the most common method of web formation)
Figure 1 shows the formation of a carded web, which may be chemically impregnated for bonding after carding. The method is to spray an emulsion or foamed adhesive onto the fibers and then continuously dry and solidify through a drying oven. The fibers stick together. This type of processing is very common in making thin disposable wipes, but it is also used in the manufacture of wool-blend hanging curtains, usually with stitching, as described below. If the fabric is light, the web is produced. The bonding process can be carried out directly. If the fabric is heavy, several carding machines can be arranged in a row to mix the webs. The direction of the fibers leaving the card is usually the same as the machine direction, even at the outlet. The same is true for the scorpion roller. This will make the strength along the "machine direction" (MD) larger, while the "machine-horizontal" (CMD) is less powerful, ie the MD/CMD ratio is higher, which is for some Application is not suitable, such as wool clothing. The scorpion roller is a pair of rollers behind the doffer, covered with a special card clothing, the card clothing can reduce the speed to a uniform. Each roller is slower than the previous roller, so the fiber The net is stuffed into the card clothing of the back roller. This changes the orientation of the fiber. This effect has the additional effect of speeding up the doffer while maintaining a consistent front and rear speed of the carding machine. Higher doffer speeds allow each rotation of the main cylinder. In the middle, the doffer takes more fibers, so the card has less total fiber load and faster production. In order to improve the quality while improving the productivity, the three-way non-woven carding machine came into being. It improves the speed of fiber removal from the main cylinder, increases the production volume, and further equalizes the irregular changes of the fiber web to improve the quality.
Main cylinder pre-rolling roller work roller doffer feeding part output fiber mesh
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Figure 2. Schematic representation of a typical non-woven carding machine with a purlin roller (eg Thibeau, Spinnbau, FOR)
One of the latest developments has been the development of an irregular carding machine. A roller with a special clothing is added between the doffer and the main cylinder of the carding machine. See the picture below. The roller and the main cylinder are rotated in opposite directions. And partially stripping the cylinders. This fiber transfer is said to be mostly done by airflow.
And the orientation is more irregular, it is said that the MD/CMD will drop to 3:1, and the scorpion roller will reduce the MD/CMD to 1.5:1.
Figure 3 Irregular carding machine with an additional anti-rotation roller between the cylinder and the doffer
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2 Cross (folding) paving In order to produce a heavy fabric with a carding machine, a folding paving machine is used. This equipment layeres the lightweight web so that the carding machine can comb the layered web. The folding and laying machine is at an angle of 90 degrees to the direction of the carding machine. The ratio of the speed of the carding machine to the output of the laminating machine determines the number and weight of the laying layer. At this time, the dominant direction of the fiber becomes the intersection with the fabric, ie The MD/CMD ratio is less than 1. This heavier web can be drawn or stretched to pull the fiber in the direction of the machine. In this way, the MD/CMD ratio can be achieved close to 1. by folding the net and Acupuncture can change the width density of the fabric. The newly designed non-woven "carding - folding paving machine" system uses computer control.