Secondary polyethylene granules – what it is, how they are produced, use

The production of pellets from polyethylene waste is one of the most profitable from the point of profitability and ecology of the business. Secondary granules LDPE or HDPE can reduce the cost of production of new goods without compromising their quality. Many products made from recycled materials are not inferior in quality to products made from primary raw materials.

What is a secondary granule of polyethylene

This is a fine-grained bulk material consisting of spherical or cylindrical grains with a diameter of from 0.2 to 0.5 mm. It is made from high pressure polyethylene (LDPE). There are also granules of low pressure polyethylene – HDPE, and some other less commonly used types of this polymeric material. Primary polyethylene is produced from petroleum, the reserves of which are not infinite. Therefore, the production of secondary granules LDPE and HDPE every year becomes more and more economic value. The color of the granules depends on the color of the raw material. They are mostly whitish-translucent. The recycling plant sorts recycled materials by color, so green bottles and bags, for example, are processed separately from transparent ones.

Where does the secondary polyethylene come from

Producers of HDPE and LDPE granules replenish stocks of raw materials, buying used plastic containers – bottles of any colors and volumes, stretch film, etc. The company sorts raw materials by color. </ P> <p> Secondary low-density polyethylene is obtained first turn thanks to recycling plastic bottles. The volumes of their daily discharge to the dump in large cities are enormous, they amount to tens of tons, despite the ease of raw materials. Recycling of plastic crates, pipes and other such waste is also used. Recycled waste nonwoven covering material, shrink film, some types of construction waste, etc.

For the “secondary” production of PVD granules, waste of primary, synthesized high-density polyethylene is also used. At the same time it is only necessary to ensure that the third recycling cycle is not allowed. It is impossible to recycle polymers for the third time – the quality of goods deteriorates dramatically.

Processing technology

Polyethylene granules are obtained from PVD agglomerate – polyethylene chips. The processing process consists of the following steps:

Sorting. It is made on a garbage dump or directly at the overworking enterprise. Raw materials are sorted by type – bottles, packages, insulation of wires, etc., by size, according to the degree of contamination. Too dirty raw materials are not used or are thoroughly rinsed.
– Grinding of raw materials to sizes that are able to process the machines of the enterprise – on average from 0.5 to 15 mm.
– Washing in special washing chambers. It is necessary, since dirty raw materials will give turbid, low-quality granulated polyethylene. The quality of the product obtained directly depends on the quality and purity of the raw materials.
– Blowing in centrifuges to remove excess moisture.
– Pre-drying.
– Agglomeration – partial melt of washed and dried chips, followed by sintering. Produced under pressure. Preliminary stage before obtaining polyethylene granulate.
– Granulation; processing of polyethylene into granules. In modern enterprises, it is carried out simultaneously with agglomeration in plastcompactor installations. On the equipment of the previous generation was a separate stage of the process.

The LDPE granulator is an apparatus that heats the polyethylene mass simultaneously with its last, final filtration from possible inclusions of metals and other impurities. After melting (polyethylene mass is heated to a temperature of 200 degrees Celsius), it is fed under pressure to a die plate – a fine-meshed frame. Passing through it, the semi-fluid melt takes the form of thin sausages, which are cut into auger knives in a split second. Next, the resulting polyethylene granules are sent for cooling and packaging.
At this stage, the production of polyethylene pellets ends.

What is made of secondary granules?

Secondary polyethylene granule has been used in the manufacture of:
– packaging (secondary stretch film, technical film, plastic bags);
– large bottles for non-alcoholic or low-alcohol liquids;
– disposable tableware;
– decor items;
– materials for hydro and thermal insulation;
– water pipes (used in low pressure systems);
– polymer tiles;
– plastic garden furniture;
– any other products that during the work should not withstand significant physical and electrical loads. This means that insulation for electrical cables, for example, is no longer made of pure “secondary” HDPE.

But in some cases it is used in the form of additives – up to 50% by weight, in order to reduce the cost of production.

Fittings and pipes, car parts, hoses, non-woven material, cable insulation, roofing material and polymer tiles, housings for various machines and mechanisms are made of secondary LDPE.

Why is the recycling of HDPE and LDPE

Polyethylene recycling is one of the most profitable types of modern ecological business.

Buying HDPE in granules is much cheaper than using primary polyethylene. Oil is necessary for its synthesis; the synthesis process is technologically complex. It is easier to produce secondary polyethylene, therefore it costs several times less than primary.
Secondary polyethylene granules, packaged in any container (usually used bags; “big run”), can be stored in the warehouse for several years. He is not afraid of either high humidity or other adverse conditions.

Enterprises engaged in recycling of recycled polyethylene have a high percentage of profitability, because their raw material costs are minimal, the technological process is not complex and does not require expensive equipment, and the demand for end products is high and constant.

With the active use of recycling plastic bottles, bags and other packaging materials, it is possible to significantly reduce the area allocated for landfills for disposal of used packaging, and to improve the environmental situation in the city, country and world. Decomposing (decomposition term is about 300 years), polyethylene emits harmful substances into the atmosphere. Given the volume of its production, in the future this could be a serious problem.

Polyethylene recycling is a profitable and environmentally friendly business. It allows you to use existing resources for production, which significantly saves mineral reserves on the planet and reduces the cost of the resulting polymer products