Commonly Used Drafting Methods For Spunbonded Nonwovens

Spunbonded nonwovens achieve draft drafting by air draft. With the drafting mechanism applied, the specific drafting methods vary with the type.

In spunbonded systems, the commonly used drafting methods include three types: wide slot suction (negative pressure) drafting, wide slit positive draft and circular tube drafting.

1. Wide slot suction (negative pressure) drafting.

The characteristics of wide slot suction (negative pressure) drafting are the use of closed spinning drafting passageways, airflow net forming, positive pressure draft air flow and cooling air flow into one, and the negative pressure generated by the suction device of the net forming machine accelerates the air flow and realizes drafting of fibers.

Because the basic shape of the draft channel is the gradual contraction of the upper, the lower and the smaller, the air flow in the passageway is accelerated, and the draft of the fiber is realized.

Wide slot suction draft technology is currently the most widely used technology in the world.

Two. Wide slit positive draft.

The wide slit positive pressure drafting adopts an open spinning drafting channel. The airflow (some models are made of static wire separator), and the integral independent drafting device is used. The positive pressure airflow is used as the drafting power, and the spinning channel is a fully open type.

The cooling air flow basically has no draft function, generally using compressed air (pressure is generally less than 1Mpa) to achieve fiber drafting.

According to the actual operation situation, the wide slit positive draft drafting machine has higher draft speed and better raw material adaptability, but because of the high speed of the exit air flow of the drafting device, the difficulty of controlling the evenness of the laying net is increased.

Three. Round tube drafting

The circular tube drawing process is often referred to as "tubular draft". It adopts open spinning drafting channel, mechanical (such as pendulum type) wire splitting and mesh forming, and uses a large number of independent round tube type (diameter 8 ~ 16mm, length up to several meters) drafting device, using positive pressure airflow as traction power.

The draft air (compressed air) enters the annular space of the drafting unit, and then flows down from the diversion chamber to the draft tube and ejected from the lower part.

High speed airflow generates negative pressure at the inlet of the tow and suck the tow and ambient air into the tube. The tow is accelerated by the airstream and drafted in the channel.

In pipe drafting system, the drafting speed of fiber can reach 3000 ~ 5000m/min, so it can be applied to PP spinning system as well as PET spinning system requiring higher drafting speed.

This tube drawing method can achieve higher drafting speed. The wire speed can reach 5000 to 7000m/min. The draft effect is ideal, and the draft of the fiber is also sufficient. It is the main technology used in polyester nonwovens production in China.