Recycling of 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 cannot contain silt, impurities, mechanical impurities, etc. The melt index requirement is within 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 and extrusion granulation, and most of them use extrusion granulation. 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 pellets--packaging.
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 of the thermal aging of the plastic processing has a considerable impact on the performance, especially the recovery of the "" bag 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 the thermal aging of pp plastics and heat aging of long-term use, the melt index of pp regrind increases with the number of processing times. 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 setting should be appropriately adjusted downwards. 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 pulling speed of the wire drawing is 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, the two raw materials cannot be plasticized at the same time, which will seriously affect the extrusion and drawing speed, resulting in a high scrap rate and even failure to produce.

Reprinted from: China Plastic Packaging Network