Drawing methods commonly used in Spunbonded Nonwovens

Spunbonded nonwovens are drafted by air flow. With the different drafting mechanism applied, the specific drafting mode varies according to the machine type. In the spinning-bonding system, there are three common drafting methods: wide slit suction (negative pressure) drafting, wide slit positive pressure drafting and circular tube drafting.

 

I. Wide slit suction (negative pressure) drafting

 

The wide slit suction draft (negative pressure) is characterized by closed spinning draft channel, air netting, positive pressure draft air and cooling air combined into one, with the negative pressure produced by the suction device of the netting machine to accelerate the air flow and realize the drawing of the fibers. Because the basic shape of the drawing channel is the gradual contraction of the upper and lower parts, the airflow in the channel is accelerated to realize the drawing of the fibers.

 

Wide slit suction drafting process is one of the most widely used processes in the world.

 

2. Positive Pressure Drawing with Wide Slit

 

Open spinning drafting channel is adopted for wide slit positive pressure drafting, air flow (static separator for some models) is netted, integral independent drafter is used, positive pressure air flow is used as drafting power, and spinning channel is fully open. However, the cooling air flow has no drafting function basically. Compressed air (pressure is generally less than 1 Mpa) is generally used to achieve the drafting of fibers.

 

According to the actual operation, the wide slit positive pressure drafter has higher drafting speed and better raw material adaptability, but because of the high outlet air velocity of the drafting device, it is difficult to control the uniformity of the netting.

 

3. Pipe Drawing

 

Tube-type drawing process is often referred to as "tube-type drawing". Open spinning drawing channel is adopted. Machinery (such as pendulum type) is used for filament separation and netting. Numerous independent tube-type drawing devices (diameter is about 8-16 mm, length can reach several meters) are used, and positive pressure air flow is used as drafting power. After the draft air (compressed air) enters the annular space of the drafter, it is injected downward from the guide chamber into the draft tube and ejected from the lower part. High-speed air produces negative pressure at the inlet of the tow and sucks the tow and ambient air into the tube. The tow is held and accelerated by air flow in the channel and drawn. In tubular drafting system, the drawing speed of fibers can reach 3000-5000m/min, so it can be used not only in PP spinning system, but also in PET spinning system requiring higher drafting speed.

 

This kind of circular tube drawing method can achieve a high drawing speed, and the silk speed can reach 5000-7000m/min. The drawing effect is ideal. The fiber drawing is also adequate. It is the main technology used in the production of polyester nonwovens in China at present.