How to Recycle PP Woven Bags

1 What is discussed here is ""recycling of bags," "plastic wastes that are suitable for the production of "bags." This is a single species of waste, which requires a relatively high demand, cannot be mixed with other varieties of plastics, and can not contain sediment, impurities, mechanical impurities, etc., and its melt index requirement is in the range of 2--5 (not any PP plastics are available). There are two main sources of it, one is the "" waste in the bag production process; the second is the waste pp bag of recycled products, such as fertilizer bags, feed bags, salt bags and so on.

2 Regeneration method

It mainly consists of melt granulation method and extrusion granulation method. Most of them adopt extrusion granulation method. The flow of the two methods is as follows.

2.1 Molten pellet method

Waste - the choice of materials and washed - dry - cutting - high-speed pellets (feed - heat shrink - spray - pellets) out of the packaging.

2.2 Extrusion granulation

Waste--selected material--washed--dry--crop--heated-extruded--cooled and pelletized--packed.

The equipment used in the extrusion method is a self-made two-stage extruder, and a vented extruder can also be used to exclude the gas generated during the extrusion of the waste. To eliminate impurities in the waste, an 80-120 mesh screen must be used at the discharge end of the extruder.

3. The use of recycled materials and the impact on the performance of pp bags Because the heat aging of plastic processing has a considerable impact on the performance, especially the recovery of "" bags after two or more thermal processes, plus before recovery in use UV aging, performance has significantly decreased.

4. The use of recycled materials for the adjustment of the drawing process due to heat aging caused by multiple thermal processing of pp plastics and ultraviolet radiation aging in long-term use, resulting in the melt index of pp regrind increases with the increasing number of processing (see Table 2) . Therefore, after a large amount of recycled material is added to the new material, relative to the new material, the temperature of the extruder, the temperature of the head, and the temperature of the stretching and forming should all be adjusted down properly. The amount of adjustment should pass the test. The melt index of the mix is ​​determined.

On the other hand, since the recycled material is processed many times, the molecular weight is reduced, a large number of short molecular chains exist, and after multiple stretching orientations. Therefore, in the production process, the draw ratio is also lower than the same brand new material. Generally, the new material has a stretching ratio of 4- to 5-fold, and generally 4 to 4 times after adding 40% of the recycled material. Also due to the increase of the melt index of the recycled material, the viscosity is reduced and the extrusion rate is increased. Therefore, under the same screw speed and temperature conditions, the drawing speed of the wire drawing is also slightly faster. In the mixing of old and new raw materials, it is worth noting that they should be mixed evenly; at the same time, they should try their best to match raw materials with similar melt index. Melt index difference, a large difference in melting temperature. In plasticizing and extruding, two kinds of raw materials cannot be plasticized at the same time, which will seriously affect the extrusion and drawing speed, resulting in high reject rate and even failure to produce.

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