Do you know the technological process and matters needing attention of waste plastic granulation?
September 18, 2019
With the development of industry, all kinds of plastic products have entered thousands of households, and with the increasingly plastic waste also waste plastic granulation process and matters needing attention do you know?More.All kinds of plastic packaging, plastic containers, plastic toys and stationery, plastic shoes, plastic home appliances shell, car bumpers, plastic pipes, industrial waste and so on, can be seen everywhere, causing great environmental pollution.Recycling of waste plastics is beneficial to environmental protection and resource saving.They are recycled and granulated, or modified and granulated again, and can be used again to make plastics.
I. characteristics of waste plastics
Waste plastics can be divided into three types according to the occasions in which they are produced:
1. The scrap produced in the production process, which is relatively clean, less polluting and contains impurities, such as substandard film production, cutting edge, lead material or unqualified products in the production of pipe and profile, incomplete parts in the injection production, etc.;
2. Used plastic wastes with single material system, such as disassembled pipes, doors and Windows, packaging materials or other waste plastic products that are strictly sorted according to resin types;
3. Mixed waste plastics that are difficult to distinguish or cannot be separated at all, such as multilayer co-extruded composite films, plastic products with coating, composite products of plastics and other materials, etc.
Different types of waste plastics have different characteristics. Do you know about the pelleting process and matters needing attention for impurities and waste plastics?Do you know the technological process and matters needing attention of granulation of waste plastics?Less than 0.Do you know the technological process and matters needing attention for granulation of leftover materials and other used products containing waste plastics that have been piled up for a certain period of time?To zero.1% ~ 0.5%.And mixed with aluminum, cloth and paper compound waste plastic impurities containing waste plastic granulation process and matters needing attention do you know?It tends to be more than 10%.
For used waste plastic products, according to the use of different conditions, will contain ultraviolet radiation, heat, oxygen aging effects, pollutants produced by the impact.Different shapes of waste plastics, after the crushing of the bulk density of the material has a great difference, film, sheet, flat wire crushing material volume density is small, this is in the waste plastic recycling granulation feeding process must be considered.
Second, waste plastic pretreatment
Waste packaging materials from the waste, such as packaging bags, shopping bags, bottles, cans, boxes and waste agricultural film plastic, before granulation to be processed.The pretreatment process mainly includes classification, cleaning, crushing and drying.
The job of classification is to classify the various kinds of waste plastic products according to the type of raw materials and the shape of the products.Sorting according to the type of raw materials requires skilled knowledge of identifying plastic varieties. The purpose of sorting is to avoid the poor performance of recycled materials caused by the incompatibility of different types of polymers.According to the shape of the product classification is to facilitate the waste plastic crushing process can be carried out smoothly, because the film, flat silk and fabric used by the crushing equipment and some thick wall, hard products between the crushing equipment often can not replace each other.
There are three processes for cleaning and crushing before granulation.
1.Cleaning before crushing process
Large waste plastic products without serious pollution and complex structure should be cleaned first and then broken, such as car bumpers, dashboards, recycling boxes, plates, etc.
First soak with detergent water, then rinse with clean water, remove and air dry.Due to the large size and can not be put into the crusher hopper of the larger parts, should be coarse broken and then fine broken, in order to be prepared for extrusion granulator feeding.Do you know the granulation process and matters needing attention for quality waste plastics to ensure recycled granule?, should be dried after fine crushing, often using a rotating dryer with heating interlayer, interlayer into the superheated steam, while being heated while rotating, high drying efficiency.
2.Rough wash - crushing - fine wash - drying process
For the contaminated profile, waste agricultural film, packaging bags, should first carry out coarse washing, remove sand, stone and metal and other foreign bodies, to prevent damage to the crusher.Waste plastic products after rough washing centrifuge dehydration, and then sent to the crusher broken.After crushing, it is further cleaned to remove the impurities contained in it.Do you know the granulation process and precautions for waste plastics if they contain oil?Soak in concentrated alkaline water or warm washing solution, and then generate friction and collision between waste plastic blocks (pieces) by stirring, remove dirt, rinse and then dehydrate and dry.
Before the waste plastic enters the cleaning equipment, it is crushed in a dry or wet crushing equipment. After drying, it is blown into a storage bin. Then the waste plastic is crushed by a screw feeder to set the granulation process of waste plastic and matters for attention.Enter into the cleaning tank.Two counter-rotating paddle shafts slowly transport the material through the wash tank, creating a vortex that rinses away the dirt on the plastic.The dirt sinks to the bottom of the tank and is removed at regular intervals.The cleaned waste floats up and is discharged by a screw conveyor.Most of the water was removed.Do you know the process and matters needing attention of granulation of waste plastics for crushing materials with screw input?Feed into the drying system.The drying system consists of a rotating dryer and a hot air dryer.The residual moisture from the drying system accounts for 1 % ~ 2 %.The cleaned material is sent to the storage bin, and then sent to the extrusion granulator to make granule.
Three, waste plastic extrusion granulation process
Waste plastics in performance with the new resin is different, this is because they experience the forming process of heat and shear history, and experienced in the process of using heat, oxygen, light, climate and a variety of media, as a result, the mechanical properties of recycled materials, including tensile strength and impact performance than the original resin, cracks caused by surface structure change, the appearance quality, and the waste plastic granulating technological process and matters needing attention, you know?Also greatly inferior to before, color hair is yellow, diaphaneity drops.The properties of different materials vary.The variation of polyolefin is relatively small.Do you know the relative molecular waste plastic granulation process and matters needing attention due to processing, especially multiple processing?The reduction can be compensated by the crosslinking reaction, so the processing property can be kept constant to a certain extent.The situation of styrene copolymer is different, every time after processing, the tensile properties are reduced.After about four processes, the toughness reduction is very serious.In addition, the effectiveness of rubber phase impact modifier has been reduced due to cross-linking. Although it is high impact polystyrene, its impact toughness is no better than that of general purpose polystyrene.
The properties of waste plastics can be improved by mixing new materials or adding specific stabilizers and additives, such as antioxidant and heat stabilizer, which can reduce the adverse effects of heat and oxygen during the pelleting process of waste plastics.In some mixed waste plastics, compatibilizer can also be appropriately added, such as polyethylene and polypropylene mixed waste plastics EP D M or E V A.In the waste plastic recycling granulation can also be filled modified, such as PP waste film at the same time to add 10% ~ 35% of the filling material, 3% ~ 6% of the lubricant, 2% ~ 4% of the color masterbatch.The regenerated material prepared with CaC O 3 filler is used in injection products, which can effectively shorten the molding cycle, improve the rigidity of products, increase the temperature of thermal deformation and reduce shrinkage.
The lubricant improves the fluidity of the melt.In the recycling of some engineering plastics, filling and granulating process of waste plastics can also be carried out and matters needing attention do you know?Strong and alloyed.For some materials that are easy to absorb moisture, such as PA, PET, etc., water will cause degradation in the process, making the relative molecular waste plastic granulation process and matters needing attention do you know?Decrease, melt viscosity decreases, physical properties decrease.Do you know that water in waste plastics should be removed and fully dried before processing, so as to ensure the quality waste plastics granulation process of recycled materials and matters needing attention?.