AU2003101075A4 - Recycling Process for Waste Expanded Polystyrene (EPS) and Waste Wood to produce Composites of Polystyrene/Wood - Google Patents

Description

Innovation Patent Application O Version 301003 OApplicant: Polyloop Unit Trust SRecycling Process for Waste of Expanded Polystyrene (EPS) and Waste Wood to produce Composites of Polystyrene/Wood.

O Description Scope This invention relates to a process methods which can be applied in isolation or in combination as set out in this invention to produce a Opolystyrene(PS)/wood composite from expanded polystyrene (EPS) waste 2and waste of forest wood or industrial/post consumer wood products.

Waste Material Preparation eThe process as the preferred set up consists of a chipping process for Opreparing EPS feedstock of crushed waste EPS or compressed EPS billets to N free flowing flakes of approximately 10 mm to 15 mm dimension. This is typically achieved by knifemill granulation commercially applied. As the preferred set up the preparation plant for waste wood feedstock supplied in form of wood chips or sawdust consists of commercially available single disc, double disc or turbo type high velocity wood flour mills capable of producing a woodflour of fiber length in the range of 1.0 mm to 0.1 mm and with a residual moisture content of less than 1.0 Both composite feedstock preparation lines are as the preferred set up placed in parallel to feed the prepared waste feedstock into a weighing hopper for direct feed to the densifier for plastic phase agglomeration. The weighing hopper may optionally be suitable to receive preweight or proportionally metered compound additives as per compound composition. Should it be necessary metal detection and removal devices may be installed at the appropriate points of the material delivery lines to the blender.

The feedstock preparation, as an optional combination, may be set up to produce the EPS waste and/or the wood waste as separate lines and to store the feedstock in appropriate containers to ensure the retention of free flow and maximum permissible moisture content Plastic Phase Agglomeration The blended EPS/Wood compound material or EPS/Wood concentrate is automatically metered into a plastic phase densifier for agglomeration. This process is in the preferred instance conducted by a plant equipment that generates mixing shear by choice of configuration of disc plates to a level controlled by the temperature limits set for the appropriate compound. The process temperature is in the preferred instance to be held within the 1100 C to 1600 C depending on throughput and properties of compound additives when specified. The agglomerated compound/concentrate is in the preferred instance dry pelletised on exit from the agglomeration machine.

Alternatively, if the pelletisation produces inadequate pellet shapes, the agglomerated material can be directly delivered hot into a short length extrusion line with hot face dry pelletisation facility or into a hot melt granulator. The pellets/granules are then cooled and metered in a typical plant equipment used for this purpose for storage in bags, bulk bags or silos.

The agglomeration can in the second instance also be conducted by any continuous mixing/extrusion equipment suitable to provide sufficient mixing 4 shear under controlled temperature condition within the limits of 1100 C to O 1600 C and with the ability to remove any residual moisture and gas from the ocompound during the mixing operation.

EPS Waste Material Coverage The waste EPS applicable for this invention consists in the first instance of clean expanded polystyrene packaging in form of boxes, containers, coverings, cups and irregularly shaped blocks used as packaging fillers.

o Contaminants of paper labels or PE shrink-wrap in combination of less than 1 is acceptable. Origin or specific grade of EPS is unlimited. The EPS waste collection stream may in the second instance also contain solid polystyrene, but must be free of chemicals, fluids of any kind, food and oorganic matter. When EPS is densified is converted to polystyrene The 2origin grades of EPS may be consists of high or medium impact modified polystyrene (HIPS, MIPS) and further modified to impart flame retardance.

For the purpose of this invention EPS and PS covers all the polystyrene types ovariations.

N Wood Waste Material Coverage The wood waste applicable for this invention consists in the first instance of wood waste generated during sawmilling operations of forest wood either green or dry falling on as saw dusts or chips from wood off-cuts. The wood waste must not be contaminated with chemicals for treatments of any kind.

Waste wood may in the second instance consist of post industrial untreated wood waste with the same limitations regarding chemical treatment. The waste wood stream is to be distinguished between softwood and hardwood or preferably by their specific wood type. All types of wood waste regarded suitable for this invention is below the moisture level of 20 bw.

PS/Wood Compound and PS/Wood Concentrate Coverage The process of this invention relates to producing as outcome either PS/Wood concentrates suitable to be used as a base compound for producing product specific compounds or PS/Wood composite compounds as ready to use compound for conversion by common plastics fabrication methods.

The PS/Wood concentrate consists of two components polystyrene and woodflour in the ration of: Densified Polystyrene: 20 to 80 bw Woodflour: 20 to 80 bw PS/Wood composition may contain in the first instance further components and are then regarded as PS/Wood compounds. Compounds suitable to be produced by this process may contain as third components one or more processing aids, as fourth component one or more antidegradation additives and as fifth component one or more colourants common in the art of designing polystyrene/wood compositions. The ratio of PS to woodflour for compound are the same as covered under PS/Wood concentrates.

The PS/wood compound compositions may in the second instance be specifically formulated to meet specific end application requirements with additives to modify impact, flame retardance and thermal characteristics.

Claims (4)

1. The process of converting selective EPS plastics waste from the packaging waste streams and selective waste wood from forest and industrial waste generation by simultaneous mixing the two waste materials to a range of PS/Wood composites provides a low energy omethod to produce an economical, readily usable PS/Wood plastics compound and concentrate with useful properties.

2. The use of the in-line woodflour preparation from woodchips and/or sawdust by high velocity milling enables the production of a low omoisture content woodflour. The immediate incorporation into opolystyrene ensures to produce a wood composite with low moisture content and consequently a technically useful compound or wood/polystyrene concentrate for further processing.

3. The use of the temperature controlled high shear plastic phase i agglomeration of incorporation the woodflour and densifying the EPS under graded disc densification conditions enables the residual gas and entrapped air of the EPS to escape to produce a polystyrene/wood composite with good interfacial contact between wood fibers and polymer.

4. The production process of applying the stated inline size reduction and agglomeration technique is also suitable to incorporate any other cellulose short fiber material into polystyrene producing compounds with specific properties. This invention demonstrates that EPS waste and wood waste by parallel size preparation and then densifying the blend by temperature controlled shear agglomeration results in compounds that: can be reprocessed by extrusion and moulding into products (ii) are suitable to be used as recyclate plastics with good structural properties of small deviations where the EPS returns to void free PS and the wood fibers are encapsulated as particulate. (iii) allow to be mixed into additional compounds by further incorporation of fibrous or polymeric particulate, fillers and additives typically applied for designing compounds with specific properties as common for plastics for achieving end application processes and characteristics.