How to clean the blocked spinneret?

2020-09-07 | 466Hit

Melt-jet cloth is a kind of polypropylene with high melting index, which is made of many criss-cross fibers laminated in a random direction. The diameter of the fibers ranges from 0.5 to 10 microns, and the diameter of the fibers is about one thirtieth of a hair. The diameter of the molten spray is only one-tenth of the diameter of the outer fiber of the mask.

Melting spray principle: Molten polypropylene, driven by pressure and air flow, forms tiny fibers, which are then sprayed onto the object and bonded into cloth.

The production of melt spraying cloth mainly goes through six procedures, namely melt preparation, filtration, metering, melt extrusion from spinneret hole, melt trickle draft, cooling and mesh forming. And the key part of melting and spraying equipment is melting and spraying die head and mould.

Spinneret plate is the core part of melt spraying equipment. There are many spinneret holes for melt to go through on the mold. Its production and processing are very important, which is related to the production efficiency and quality of melt spraying cloth. More than 300~2000 microholes are distributed in different mold sizes. According to the different level of melting spray, the size of the micropore diameter is also different. For N95 masks, the aperture should be 0.2mm or less.

It is easy to plug holes and difficult to clean the molten spray mould, which will greatly affect the production efficiency and increase the production cost. Therefore, the cleaning of the molten spray mold will directly affect the efficiency of the entire production line and the quality of the mask. What if the die head is blocked?

Find the spinneret, also known as the spinneret. The key point to deal with the blocked die is to clean up the blocked hole of the spinneret. The traditional method of mold cleaning is mainly manual method, with steel wire brush, sandpaper and chemical cleaner to deal with, but time and effort. Newly developed new methods include:

1. Vacuum calcining method

The average polymer melts below 300 degrees Celsius, so when the temperature is high, the polymer melts. And as the temperature rises further, the polymer breaks down, and if you run a vacuum pump, you suck up the broken gas, and the broken residue, it can be washed away by the spray water. The disadvantage of vacuum calcining method is that the time is long and the treatment is not clean when the pinhole carbon is heavy.

2. Ultrasonic cleaning

The action of ultrasonic wave in the liquid causes the liquid to move and produce a large number of tiny bubbles. The tiny bubbles (cavitation nuclei) in the cleaning fluid vibrate under the action of the sound field. When the sound pressure reaches a certain value, the bubbles increase rapidly and then suddenly close. When the bubble is closed, a shock wave creates thousands of atmospheric pressures around it, destroying insoluble stains and dispersing them in the cleaning solution. The disadvantages of ultrasonic cleaning method need to cooperate with special solvent, and ultrasonic leakage will cause certain body damage.

3. Dry ice cleaning

Dry ice cleaning method is based on the compressed air as power and the carrier, to dry ice particles are accelerated particles, through a dedicated spray cleaner spray to the cleaning surfaces, by using high speed movement of the solid momentum change of dry ice particles (Δ mv), sublimation, melt, such as energy conversion, make the surface to be cleaned of dirt, oil, residual impurities such as quick freezing, and condensation, embrittlement, stripped, and at the same time with the clear air.

Dry ice is crushed and dispersed in high-pressure air, then accelerated through a high-speed nozzle and impinged on the cleaned surface. High pressure air waves, plus the dry ice particles in them, blow away the residue on the mold surface. The polymer becomes brittle at low temperatures and shrinks and separates from the mold. The dry ice particles sublimate on impact, changing from solid to gas, expanding hundreds of times, further generating impact force, thus achieving a fast and efficient cleaning effect.
The biggest advantage of dry ice cleaning method is its high efficiency. Other methods take more than ten hours, while dry ice cleaning method can clean it in 2-3 hours. And the operation is convenient, can carry on the field operation.