CADAUTA

Process for the reuse of mixed plastic wastes

The Rivive system is a process for the reuse of heterogeneous waste plastics materials by recycling and making products from them. It is ecologically beneficial, energy-saving, and has economic advantages. The system reduces pollution, recovers energy from materials which otherwise would be dispersed, and offers economic and socially desirable benefits. The process homogenizes waste plastics materials from various sources, such as HDPE, LDPE, LLDPE, PP, BOPP, PP+A1, CPP, PS, shock-proof PS, rigid PVC, flexible PVC, ABS, AM, PET, polyurethane, PA6 and PA11. There is no need to pre-sort the various polymers, even if they are mixed with paper and board, aluminium foil or vegetable or mineral dusts, provided that these are present at reasonable percentages and that the water content is minimal. A compound is obtained which has average properties in relation to those of the raw materials, but which is usable and can be given the properties required in the end-products. Revive can supply units of different capacities or repeat orders as required by processors or producers of waste materials.

REUSABLE WASTES

Usable waste plastics materials are usually in the form of urban or industrial refuse, the average composition is:

65% polyolefins – plastic sheet, photographic films, articles containing HDPE, LDPE or PP;

10% polyvinyl chlorides – bottles, photographic films, containers, rigid and flexible PVC;

15% polystyrene – trays and packaging materials;

5% PET, bottles;

5% other.

These waste materials can be recycled without washing if the impurities are in low percentages and are free from foreign bodies such as pieces of iron, glass, stone or organic matter, etc. As stated above, the various polymers can be homogenized without sorting, but there is a limit to the proportion of PVC items mixed with PET which can be recycled. However, a high proportion of PVC mixed with polyolefins can be handled.

Obviously, there must be selective collection of urban waste materials upstream, otherwise the plastic waste will have to be removed from the rest.

The waste materials must not be excessively moist, a 5% water content being the absolute limit.

The industrial plastic waste, this comes from manufacturing processes, shaping processes, rejects, composite materials, etc. In general, these wastes are not contaminated and the composition of one mixture of the different polymer types does not change.

These mixture can be recycled without any sorting. Their polymer content may be variable according to their origin.

PROCESS

THE MAIN PHASES OF THE PROCESS ARE:

Solid state, mixed composition

In this phase the waste materials are stored under cover and sorted by type and by state. Metal or other heavy objects are extracted, and the waste materials are then fed into a crusher and a grinder which reduces them to pieces 5 to 8 mm in size. The materials are then stored;

Solid state, homogeneous composition

In this phase the materials may be mixed, and then dried and injected;

Molten state, homogeneous composition

In this phase the mixed polymers are homogenized in a chamber with special rotors, wich operate at low temperature gradients and ranger of mechanical stress and are then extruded through a special head;

Relaxed state, ready for production

This involves three production lines, used either alternately or in combination:

line 1: Batch feeling and compacting of products which are very thick and have a simple shape in a vertical press;

line 2: Shaping: continuous feed to rolling mill or extrusion of various sections or sheet;

line 3: Granulation into chips for injection moulding of various products, including sheet.