WO2003037597A1

WO2003037597A1 - A method of forming plastics material into a block

Info

Publication number: WO2003037597A1
Application number: PCT/NZ2002/000229
Authority: WO
Inventors: Peter Joseph Lelievre Lewis; Steven Russell Evans
Original assignee: Bale Fusion Limited
Priority date: 2001-11-02
Filing date: 2002-10-31
Publication date: 2003-05-08
Also published as: NZ515224A

Abstract

A method of forming an article from a stock material, such as plastic waste, including a thermoplastics binder. The stock material is compressed into a container. The container is heated within a moulding apparatus which supplies super heated steam to melt the thermoplastics so that it binds the stock material when cooled. The article is then released from the container. The compaction apparatus can have moveable walls or an auger. The super heated steam can be injected through holes in the container wall. The container can be transferred from the heating station to separate cooling chamber.

Description

A Method of Forming Plastics Material into a Block

Field of the Invention

The present invention relates to a method and apparatus for forming an article in which thermoplastics materials are used as the binding agent. The invention also relates to an article formed by the method or apparatus.

Background of the Invention

A major challenge facing many nations is dealing with the volumes of waste produced. Efforts have been made, in particular, in relation to the recycling of plastics and paper waste. Approaches to the recycling of plastics have focused upon processes where plastics are sorted into the various types and controlled proportions are utilised to produce recycled products.

A report entitled "Assessing the potential for post-use plastics waste recycling - predicting recovery in 2001 and 2006" produced by the Association of Plastics Manufacturers in Europe identitied the mam constraints for improving recycling rates for plastic as:

i/ the imbalance between the waste collectable and the potential end-markets for the recycled plastics ii/ the presence of large quantities of mixed plastics waste where the difficulties and energy consumed in separating into homogenous fractions and cleaning outweigh the environmental gain of mechanical recycling.

The report considered there to be an upper limit to potential demand for mechanically recycled plastics. This report reflects the common mind set of those in the industry that tightly control sorting is required to produce a valuable product. It also reflects the commonly held perception that there is a limited marked for the types of articles that may be produced.

In the report "SIRA International (1 999) . Australian Plastics Materials Recycling Survey - Report for Plastics and Chemicals Industries

Association. Canberra, Australia" the major problems facing recyclers were identified as:

• Separation of difficult plastics

• Contamination between polymers • Contaminated waste

• Plastics re-processing is highly labour intensive for low returns

• Demand is unbalanced with supply

• Not enough end users

• Collection and separation

Plastic recyclers currently recycle plastics into seven types as follows:

Code 1 : Polyethylene Terephthalate (PET or PETE)

Code 2: High Density Polyethylene (HDPE) Code 3: Vinyl (Polyvinyl Chloride or PVC)

Code 4: Low Density Polyethylene (LDPE)

Code 5: Polypropylene (PP)

Code 6: Polystyrene (PS)

Code 7: Other

Tightly controlled sorting is expensive and is a significant cost component in current recycling processes. Where tightly controlled sorting has been required it has been difficult to produce a marketable product economically. The characteristics of many products produced in such recycling processes have been considered to be inferior. There has also been a prejudice against the use of polyethylene film in recycling processes. In "Siegler, T. & Perkins, R. (1 999). Sorting Plastic Bottles for Recycling. Ascotney, Vermont: DSM Environmental Services for The American Plastics Council" the following points were noted:

"Acceptance of even small amounts of recyclables in plastic bags will significantly reduce equipment efficiency unless all of the film is removed with a film removal system at the front end."

and

"The composition of material delivered to the MRF (materials recovery facility) has a significant impact on processing efficiency. Contaminants entering MRFs 5, 6, and 7 represented between 3.7% and 6.7% of the incoming material. This seemingly small amount of incoming contamination was responsible for between 31 and 67% of sorting labour at these three MRFs. "

and

"Increased public education is necessary to better inform participating households which plastic containers are acceptable in the recycling program."

Rathje, W and Murphy, C. cite as one of the "Five Major Myths about

Garbage and Why They're Wrong" that:

"The biggest problem faced by recycling is not the technological process of turning one thing into another. Anything can be recycled - and would be if demand for what it could be recycled into were great enough. The key, then, is demand, and demand for many recyclables is often soft." To date the most commercially attractive recycling processes have been those utilising industrial waste. Industrial waste may typically consist of large batches of one type of plastics which avoids the need for any sorting process.

Object and Statement of the Invention

It is an object of the present invention to provide a method and apparatus for forming an article from mixed plastics waste which overcomes these problems or at least provides the public with a useful choice.

There is thus provided a method of forming an article from a stock material containing a sufficient amount of thermoplastics material to bind the material together when formed, the method comprising the steps of: compressing the material and retaining it within a container; transferring the container to a heating apparatus; supplying sufficient energy to melt sufficient thermoplastics material substantially throughout the stock material to bind the stock material together when cooled; and releasing an article produced from the container.

Preferably the stock material includes shredded thermoplastics material. This may include or consist entirely of waste plastics material. The stock material preferably includes sufficient polyethylene and/or PETE to bind the stock material together when formed. Preferably 80% or more, more preferably 90% or more, of the stock material is thermoplastics material. The stock material is preferably shredded into strips of about 6 to 20 mm in width. The strips may have rough edges.

Stock material may be compressed between movable walls. Preferably between 3 pairs of movable walls which move in directions transverse to each other. Alternatively, the stock material may be compressed using an augur.

In a first embodiment, the stock material may be heated by the injection of superheated steam. Preferably the stock material is exposed to superheated steam having a manifold temperature of between 200 to

400 °C at a manifold pressure of between 5 to 100 psi for a period of between 10 to 5 minutes, more preferably 260 to 320°C at 5 to 60 psi for 10 to 60 seconds, most preferably 280 to 300°C at 10 to 20 psi for 10 to 20 seconds. The superheated steam is preferably injected into the stock material by tubes inserted into it. Superheated steam may also be applied to the surrounding container.

Alternatively, the energy to melt the thermoplastics material may be supplied by a microwave radiation source. In this case it is desirable for a sufficient water to be present in the stock material to generate sufficient steam to melt the thermoplastics material. After processing the article may be cooled by the introduction of a cooling fluid which may be evacuated by a vacuum.

There is further provided a compacting apparatus including: a chamber formed by a plurality of walls including at least one movable wall for compressing stock material therein; and a wall opposite the moveable wall provided with an opening therein and means for securing a container having an opening therein so that the openings are aligned.

The chamber may include up to three pairs of walls which are sequentially moved together in directions transverse to each other.

There is further provided a compacting apparatus including: an augur having an inlet end for receiving stock material and an outlet end adapted to engage with a container for receiving compacted stock material therein.

5 The outlet end may include a transfer chamber including a blade which may be moved to position in which an opening between the outlet end and the augur is closed and a transfer means for transferring the compacted stock material to a container.

1 0 There is also provided a moulding apparatus including: a chamber adapted to accommodate a perforated container containing material to be formed; a plurality of tubes movable relative to the chamber from a rest position in which the tubes are outside of a region for accommodating a 1 5 container to an operating position in which the tubes are introduced into the region for accommodating the container such that, in use, they pass though perforations in a container to enable steam to be delivered substantially throughout the container; and a steam source for supplying superheated steam to the tubes.

^'20

The apparatus preferably includes a superheated steam source for supplying steam at a manifold temperature of between 200 to 400 °C at a pressure of between 5 to 1 00 psi for a period of between 1 0 seconds to 5 minutes.

25

There is also provided an apparatus for cooling an article comprising: a chamber having movable walls that may be moved apart to allow a container to be introduced there within and move together to contain the container therewithin; 30 a cooling fluid supply for supplying cooling fluid to the chamber; and a vacuum for evacuating the chamber. There is further provided an article forming container comprising: a receptacle having an opening for the introduction of stock material to the receptacle and apertures in one or more walls adapted to receive steam injection tubes; a lid adapted to cover the opening of the receptacle; and locking means for securing the lid to the container.

The receptacle may be provided with latches around its upper edges to retain the lid. Formations may be provided in the lid and bottom of the receptacle to produce corresponding formations in the article produced.

There is also provided an article formed by the method or apparatus of the invention.

Brief Description of the Drawings

The invention will now be described by the way of example with reference to the accompanying drawings in which:

Figure 1 . : shows an apparatus for shredding washing and drying stock material.

Figure 2. : shows the shredding section of the apparatus of figure 1 .

Figure 3. : shows the washing and tumble drying section of the apparatus of figure 1 .

Figure 4. : shows the drying and storage section of the apparatus of figure 1 .

Figure 5.: shows the arrangement for transferring stock material from the storage hopper for further processing. Figures 6a-9b: show the various stages of compression of the stock material utilising a compressing means according to a first embodiment.

Figures 10 and 1 1 : show the operation of a heating means according to one embodiment of the invention.

Figures 1 2-1 6.: show the stages of operation of a cooling apparatus.

Figure 1 7-22: show the operation of a compressing apparatus utilising an augur.

Figure 23: shows a cross-sectional view of a container for use in the method of the invention.

Detailed Description of Preferred Embodiment

According to the present invention stock material including a sufficient proportion of thermoplastics material is compressed and retained in a conTalTTer, the container is transferred to a^" heating-mean-r and-then cooled.

Referring now to figures 1 to 5 a method for pre-processing the stock material will be described. Stock material 1 is supplied to hopper 2 and conveyed by conveyor 3 to hopper 4. Stock material will typically be substantially unsorted plastics waste. Some rough sorting may be performed to exclude large undesirable components or unsuitable materials. Generally, however, a relatively random mixture of waste plastics may be employed providing a sufficient quantity of thermoplastics material such as polyethylene or PETE is included to bind the article together after processing. The material provided to hopper 4 passes through shredder 5 and is shredded into strips of about 6 to 20 mm width. The strips are then supplied to a rotary drum 7 via chute 6. Water from water tank 8 is pumped via pump 9 and sprayed onto the material in chute 6. Drum 7 includes a first solid section having a partial augur about the peripheral walls to advance the water and plastic strips therethrough followed by perforated sections having drip trays 1 0 for collecting waste water which may filtered by filter 1 1 and pumped by pump 1 2 back to water tank 8.

The material output from drum 7 is supplied to output hopper 13 and conveyed to a drying cyclone 14. Hot air is supplied to inlets 1 5 to dry the stock material. Stock material from the drying cyclone 14 is supplied to storage hopper 1 6. A controllable gate 1 7 allows a measured amount of stock material 1 8 to be delivered to a batch container 20. A load cell 1 9 may weigh the amount of stock material 21 within container 20 and control the operation of controllable gate 1 to deliver the required amount of stock material.

Figure 6a shows a side cross-sectional view of compacting apparatus according to first embodiment. Figure 6b shows a top view oτ tne compacting apparatus of figure 6a. In each pair of figures 6a to 9b the "a" drawing is a side view and the "b" drawing is top view. The compacting apparatus includes a first movable wall 23 which may be driven inwards by ram 23a, a second movable wall 24 which may be driven inwards by ram 24a and a third movable wall 25 which may be driven inwards by ram 25a.

The chamber thus consists of three pairs of movable walls which may be sequentially driven inwardly to compress stock material therein. Rams 23a and 25a may be driven by a programmable logic controller controlling valves to the respective rams.

A container 26 having an open top is engaged with the bottom face of chamber 22 and aligned with an opening 25b in the lower wall 25c. A cross-sectional view of container 26 and lid 27 is shown in figure 23. Container 26 consists of four side walls with an open top. A plurality of spring loaded catches 70 are provided around the upper rim of the side walls of container 26. Catches 70 have ramped faces 71 so that as lid 27 is forced downwardly the catches spring back and then lock lid 27 in place. Apertures 74 are provided in one side wall to allow tubes to be inserted into the container 26. A protrusion 72 may be provided in the base of container 26 and a recess 73 in lid 27 to produce formations in the article produced. When the article is a block such protrusions and recesses in the article may be used to locate blocks relative to one another (as with

LEGO™ blocks). Although this description is given in relation to a block it will be appreciated that a variety of article forms may be produced depending upon the shape of the container cavity.

At the beginning of a cycle the walls 23, 24 and 25 are in their retracted position as shown in figure 6a. Stock material 21 is supplied from container 20 into chamber 22. The walls 23, 24 and 25 are then sequentially driven inwardly. As shown in figures 7a and 7b wall 23 is the first to be driven inwardly by ram 23a. As shown in figures 8a and 8b wall 24 is f fieri driven inwardly By ram 24a. As shown^' in figures 9 aland 9tJ wall 25 is then driven downwardly to force the stock material 21 into container 26 and force lid 27 into engagement with container 26 to securely seal the compressed stock material therein. Wall 25 may then be retracted by ram 25a and container 26 removed for processing at the next stage. Another lid is then secured to wall 25. By utilising 3 compaction stages in transverse directions a relatively omnidirectional orientation of stock material may be achieved. This results in similar mechanical properties of an article formed in all directions.

Referring now to figure 1 0 a heating apparatus according to a first embodiment is shown in cross-sectional plan view. Chamber 30 has a lid 31 that may be opened to allow a container 26 to be placed therein. The lid 31 may then be closed to seal the container. Superheated steam may be supplied to inlet 39 and controlled via valves 34a to 34c to selectively allow the introduction of steam into the region of the chamber surrounding container 26 and to tubes 33. Steam supplied to manifold 32 passes through tubes 33. Tubes 33 are sealed at their ends and formed to a point. Apertures of about 2 mm diameter are provided at 20 mm spacings.

In use a container 26 is placed within chamber 30 which is then sealed by lid 31 . Valves 34a and 34c are controlled so that superheated steam is supplied to the regions surrounding container 26 to heat container 26.

Ram 29 is advanced to insert tubes 33 through apertures' 4 in a side wall of container 26 to the position shown in figure 1 1 . In this position valve 34a is controlled so that superheated steam is injected into container 26 so as to melt sufficient thermoplastics material substantially throughout the stock material so as to bind the stock material together when cooled.

Pressure control valve 35 ensures that the required pressure is maintained within the chamber. Superheated steam is removed via line 38.

The superheated steam preferably has a manifold temperature of between 200 to 400°C at a manifold pressure of between 5 to 100 psi. The superheated steam preferably supplied by tubes 33 and to the area surrounding container 26 for a period of between 1 0 seconds to 5 minutes. The superheated steam preferably has a manifold temperature of between 260 to 320°C and a manifold pressure of between 5 to 60 psi and is supplied for a period of 1 0 to 60 seconds. More preferably the superheated steam has the manifold temperature of between 280 to 300 °C and a manifold pressure of between 10 to 20 psi and is supplied for ^• a period of between 10 to 20 seconds.

Valves 34a to 34c are then closed and ram 29 is then retracted to withdraw tubes 33. Chamber 30 is then opened and the container is removed for cooling. The container is then preferably cooled by a cooling fluid.

Referring now to figures 1 2 to 1 6 a cooling method and apparatus are shown (top views for figures 1 2 and 1 3 are shown above). The cooling chamber consists of two adjacent side .walls 44a, a base 44c, a pair of adjacent movable side walls 44b and a movable lid 43. A container 26 is placed within the chamber when it is open. Walls 44b are then moved inwardly to close the side walls and lid 43 is then moved down to form a closed chamber. Valve 42 is then opened as shown in figure 14 to allow the introduction of cooling fluid from line 41 through lid 43 into the interior of the chamber. Cooling fluid is removed by vacuum pump 46 connected by line 45 to the base of the chamber. Cooling fluid from vacuum pump 46 is ejected via line 47.

Valve 42 is then closed as shown in figure 1 5 whilst vacuum pump 46 continues to extract cooling fluid from the chamber. When the pressure within the chamber drops below a predetermined level vacuum release valve opens to allow air to flow though the chamber. Vacuum pump 46 is then stopped as shown in figure 1 6 and the chamber is opened to the configuration shown in figure 1 2 so that the cooled container may be removed. Lid 27 is then removed from container 26 to allow an article 21 formed therein to be removed.

Referring now to figures 1 7-22 an alternative compressing means to that shown in figure 6a to 9b is shown. Hopper 50 receives stock material and supplies it to an augur 51 . Augur 51 is driven by a suitable motor, such as an hydraulic motor, to compress the stock material into an outlet chamber 52. Chamber 52 is shown without its closed top surface for ease of explanation. Chamber 52 has an opening 53 at one end and grooves 54 for receiving flanges 55 of container 26. At the beginning of the cycle flanges 55 of container 26 are engaged with grooves 54 as shown in figure 18. The top of chamber 52 is closed so that a closed chamber is defined with a single opening adjacent the augur. Material is then supplied to hopper 50 and augur 51 is driven to force material into chamber 52 and container 26.

When a desired amount of material has been supplied to chamber 52 and container 26, blade 56 is driven downwardly by ram 57 to close the opening between the chamber 52 and augur 51 . The desired amount of stock material may be determined either by delivering the required amount to hopper 50 or by monitoring the torque required to drive augur 51 to force material into chamber 52. When it reaches a predetermined torque level augur 51 may be stopped.

Figure 20 is an end on view showing a container 26 secured to chamber 52 with blade 56 in its raised position. Once the desired amount of stock material has been forced into chamber 52 by augur 51 blade 56 is lowered to the position shown in figure 21 to close chamber 52. Ram 58 then drives wall 59 to the position shown in figure 22 so that the stock material within chamber 52 is forced into container 26. Lid 27 is provided adjacent wall 59 so that as the stock material is forced within container 26 lid, 27 is forced to a position such as to contain the compressed material within container 26. As shown in figure 23 lid 27 is forced past catchers 71 so as to contain the compressed material 21 within container 26. Ram 58 is then retracted and a new lid placed adjacent wall 59. Container 26 may then be removed to a heating means as previously described for further processing.

In an alternative embodiment the heating means may be a microwave radiation source. The stock material should contain sufficient water to produced sufficient steam to melt the thermoplastics. In this case the container 26 and lid 27 will need to be formed of a non-metallic material that is suitable for prolonged exposure to microwave radiation without rapid degradation. Suitable plastics materials may be employed for this purpose. The microwave radiation source may be a suitable commercial microwave heating device.

It will thus be seen that the present invention provides a method and . apparatus for producing articles from plastic waste material suitable for use in construction, insulation, acoustic barriers etc. The method of the invention enables substantially unsorted plastics waste to be processed into viable products. The use of mixed plastics materials without sorting provides significant economies over prior methods. The apparatus of the invention is relatively simple and can be constructed at relatively low cost.

Products formed by the method of the invention have good shock resistance and absorption characteristics. The products formed by the method of the invention also have good thermal insulation and acoustic isolation properties making them suitable for use in certain building applications.

By separating processing into separate stages each stage can be performed at optimum efficiency and simple apparatus may be employed.

Although this invention has been described by way of example it is to be appreciated that improvements and/or modifications may be made thereto without departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMS:

1 . A method of forming an article from a stock material containing a sufficient amount of thermoplastics material to bind the material together when formed, the method comprising the steps of: compressing the material and retaining it within a container; transferring the container to a heating apparatus; supplying sufficient energy to melt sufficient thermoplastics material substantially throughout the stock material to bind the stock material together when cooled; and releasing an article produced from the container.

2. A method as claimed in claim 1 wherein the stock material includes shredded thermoplastics material.

3. A method as claimed in claim 1 or claim 2 wherein the thermoplastics material includes mixed waste plastics.

4. A method as claimed in any proceeding claim wherein the stock material includes sufficient polyethylene and/or PETE^" to bind the stock material together.

5. A method as claimed in any preceding claim wherein the stock material includes 80% or more thermoplastics material.

6. A method as claimed in any one of claims 1 to 4 wherein the stock material includes 90% or more thermoplastics material.

7. A method as claimed in any proceeding claim wherein the thermoplastics material is in the form of strips.

8. A method as claimed in claim 7 wherein the strips are between 6 to 20 mm in width.

9. A method as claimed in claim 7 or claim 8 wherein the strips have rough edges.

1 0. A method as claimed in any preceding claim wherein the stock material is compressed between movable walls.

1 1 .A method as claimed in claim 10 wherein one pair of walls compresses the stock material in a first direction and a second pair of walls compresses the stock material in second direction transverse to the first direction.

1 2. A method as claimed in claim 1 1 wherein a third pair of walls compresses the stock material in a direction transverse to the first and second directions.

1 3. A method as claimed in any one of claims 1 to 9 wherein the stock material is compressed using an augur.

1 . A method as claimed in any preceding claim wherein energy to melt the thermoplastic material is provided by the injection of superheated steam.

1 5. A method as claimed in claim 14 wherein the stock material is exposed to superheated steam having a manifold temperature of between 200 to 400 °C at a manifold pressure of between 5 to 100 psi for a period of between 10 seconds to 5 minutes.

1 6. A method as claimed in claim 14 wherein the stock material is exposed to superheated steam having a manifold temperature of between 260° to 320°C at a manifold pressure of between 5 to 60 psi for a period of between 10 to 60 seconds.

17. A method as claimed in claim 14 wherein the stock material is exposed to superheated steam having a manifold temperature of between 280 to 300°C at a manifold pressure of between 10 to 20 psi for a period of between 10 to 20 seconds.

1 8. A method as claimed in any one of claims 14 to 1 7 wherein the superheated steam is injected into the stock material via tubes inserted into the stock material.

1 9. A method as claimed in claim 1 8 wherein superheated steam is supplied to an area surrounding the container.

20. The method as claimed in any one of claims 1 to 1 3 wherein the energy to melt the thermoplastics material is supplied by a microwave radiation source.

21 . A method as claimed in any one of the preceding claims wherein the article is cooled by a cooling fluid.

22. A compacting apparatus including: a chamber formed by a plurality of walls including at least one movable wall for compressing stock material therein; and a wall opposite the moveable wall provided with an opening therein and means for securing a container having an opening therein so that the openings are aligned.

23. An apparatus as claimed in claim 22 including first and second pairs of walls which can be driven together in directions transverse to one another.

24. An apparatus as claimed in claim 23 including a third pair of walls which may be driven together in a third direction transverse the first and second directions.

25. An apparatus as claimed in any one of claims 22 to 24 wherein the means for securing a container includes means for receiving flanges along upper edges of a container.

26. A compacting apparatus including: an augur having an inlet end for receiving stock material and an outlet end adapted to engage with a container for receiving compacted stock material therein.

27. An apparatus as claimed in claim 26 wherein the outlet end includes a transfer chamber including a blade which may be moved to a position in which an opening between the outlet end and the augur is closed and a transfer means for transferring the compacted stock material to a container.

28. A moulding apparatus including: a chamber adapted to accommodate a perforated container containing material to be formed; a plurality of tubes movable relative to the chamber from a rest position in which the tubes are outside of a region for accommodating a container to an operating position in which the tubes are introduced into the region for accommodating the container such that, in use, they pass though perforations in a container to enable steam to be delivered substantially throughout the container; and a steam source for supplying superheated steam to the tubes.

29. An apparatus as claimed in claim 28 wherein the steam source supplies superheated steam to a region of the chamber surrounding the region for accommodating a container.

30. An apparatus as claimed in claim 28 or claim 29 wherein the superheated steam is supplied at a manifold temperature between 200 to 400°C.

31 . An apparatus as claimed in any one of claims 28 to 30 wherein the chamber is sealed sufficiently to maintain a pressure of between 5 to

1 00 psi during introduction of the superheated steam.

32. An apparatus as claimed in any one of claims 28 to 31 including a timer for controlling the supply of superheated steam to the moulding apparatus for a period of between 10, seconds to 5 minutes.

33. An apparatus for cooling an article comprising: a chamber having movable walls that may be moved apart to allow a container to be introduced there within and move together to contain the container therewithin; a cooling fluid supply for supplying cooling fluid to the chamber; and a vacuum for evacuating the chamber.

34. An article forming container comprising: ^" a receptacle having an opening for the introduction of stock material to the receptacle and apertures in one or more walls adapted to receive steam injection tubes; a lid adapted to cover the opening of the receptacle; and locking means for securing the lid to the container.

35. A container as claimed in claim 34 wherein the locking means are the form of latches provided around the upper edges of the side walls of the receptacle.

36. A container as claimed in claim 34 and 35 wherein formations are provided in the lid to form recesses or protrusions in the article formed.

37. A container as claimed in any one of claims 34 to 36 wherein formations are provided in the base of the receptacle for forming protrusions or recesses in the article formed.

38. An article formed by the method or apparatus of any one of the proceeding claims.

39. A method of forming an article from a stock material containing a sufficient amount of thermoplastics material to bind the material together when formed, the method comprising the steps of: compressing the material and retaining it within a container; supplying sufficient energy to melt sufficient thermoplastics material substantially throughout the stock material to bind the stock material together when cooled; and releasing an article produced from the container.