The use of PET recycled plastics: PET plastic recycled pellet technology refers to the used PET industrial waste, food packaging containers, waste beverage bottles, etc., after crushing, cleaning, high vacuum drying, heating plasticizing, drawing, cooling, making Granules, PET pellets produced after processing, for re-formation of PET-related products, such as chemical fiber textile raw materials, PET sheet raw materials, engineering plastic injection molding materials. At present, the supporting technologies at home and abroad are relatively perfect, and the only weak link is the thickening technology of PET recycled particles, and whether the viscosity can be increased is directly related to the performance of recycled PET particles. The technology of this project completely broke through this technical bottleneck and opened up the space for the value of recycled PET pellets. The core equipment of PET recycled particle reactive polycondensation and extrusion equipment is φ90mmPET recycled particle reactive polycondensation extruder. Its main feature is to solve the problem of molecular chain degradation and intrinsic viscosity reduction of polyester chips during recycling. And the problem of unreasonable input and output ratio. The equipment uses a series of high-tech, can fully increase the intrinsic viscosity of PET during recycling, improve the quality of recycled particles, and meet the relevant standards of PET new materials. According to the characteristics of the physical and chemical methods, the degraded molecules are chain-extended by adding a chain extender in a molten state, and the chains are re-chained into macromolecules, thereby significantly improving the performance of the regenerated PET particles. The main innovations are: a. Using a high aspect ratio reaction extruder, the intrinsic viscosity of the polyester bottle material can be significantly improved; b. High vacuum reaction polycondensation reaction and material melting in the screw extruder Mixing at the same time, greatly saving energy consumption; c. Low pollution, continuous production, large processing capacity, and objective economic benefits. Here we will discuss "PP woven bags recycling", waste refers to plastic waste suitable for the production of woven bags. This is a single type of waste utilization, the requirements are relatively high, can not be mixed with other varieties of plastic, and can not contain sediment, sundries, mechanical impurities, etc., its melt index is required to be 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 production process of PP woven bags; the other is the recycling of discarded pp bags, such as fertilizer bags, feed bags, salt bags and so on. So what are their regeneration methods?
1. Regeneration method It mainly has two kinds of molten pellet method and extrusion granulation method, and most of them adopt extrusion granulation method. The flow of the two methods is as follows.
(1), molten pellet method Waste - material selection and washing - drying - cutting - high-speed pellets (feeding - heat shrinking - water spray - pellets) discharge packaging.
(2), extrusion granulation method Waste - material selection - washing - drying - cutting - heating extrusion - cooling granulation - packaging. The equipment used in the extrusion process is a self-made two-stage extruder. To exclude the gas generated in the extrusion of the waste, a vented extruder can also be used. In order to eliminate the debris in the waste, a screen of 80-120 mesh must be used at the discharge end of the extruder.
2, the use of recycled materials and the impact on the performance of pp bags due to the thermal aging of plastic processing has a considerable impact on performance, especially the recycling of "" bags after two or even multiple thermal processes, plus in use before recycling The UV aging has a significant decrease in performance.
3, the use of recycled materials adjustment of the drawing process due to multiple thermal processing of pp plastics resulting in heat aging and long-term use of ultraviolet radiation aging, resulting in the pp recycled material melt index with increasing processing times and increased. Therefore, after adding a large amount of recycled materials in the new material, in the control of the process temperature, the temperature of the extruder, the temperature of the head, and the temperature of the stretching and setting should be appropriately adjusted relative to the new material. The adjustment amount should pass the test. The melt index of the mixture is determined. On the other hand, since the recycled material is processed a plurality of times, the molecular weight is lowered, a large number of short molecular chains are present, and a plurality of stretching orientations are performed. Therefore, in the production process, the draw ratio is also lower than the same new material. Generally, the draw ratio of the new material is 4--5 times, and after adding 40% of the recycled material, it is usually 3--4 times. Also, due to the increase of the melt index of the recycled material, the viscosity is lowered and the extrusion rate is increased. Therefore, under the same screw rotation speed and temperature conditions, the drawing speed of the wire drawing is also slightly accelerated. In the compounding of new and old raw materials, it is worth noting that it should be mixed evenly; at the same time, raw materials with similar melt indexes should be selected as much as possible. The melt index differs greatly and the melting temperature differs greatly. In plasticizing extrusion, the two raw materials cannot be plasticized at the same time, which will seriously affect the extrusion drawing speed, resulting in high scrap rate and even impossible production.
4. Conclusions As mentioned above, the recycling and recycling of PP woven bags is completely feasible as long as it is carefully selected, properly formulated, and controlled by reasonable and precise process conditions. Will not affect the quality of the product, and the economic benefits are very obvious. The unit cost of the woven bag produced after adding 40% of the recycled material can be reduced.