WO1997047450A1

WO1997047450A1 - Solid materials and method for manufacturing the same

Info

Publication number: WO1997047450A1
Application number: PCT/GB1997/001592
Authority: WO
Inventors: Roger Neil Ferguson
Original assignee: Ecobuild International Limited
Priority date: 1996-06-12
Filing date: 1997-06-12
Publication date: 1997-12-18
Also published as: AU3099597A; GB9612230D0

Abstract

Methods of manufacturing a solid material are described. The methods include the step of processing waste material, particularly fragmentation waste, and plastics material to form a mixture in which at least some of the plastics material is in a softened state. A solid material is then formed from the mixture.

Description

SOLID MATERIALS AND METHOD FOR MANUFACTURING THE SAME

The invention relates to solid materials and methods for manufacturing such materials. In particular, but not exclusively, this invention relates to a method for the continuous production of solid materials by combining plastics materials (e.g. waste plastics) with a waste material which it at least partially comprised of non-plastics materials.

Known solid materials such as concrete, cement, rock, plastics materials, wood and the like are relatively expensive.

It is one object of the invention to provide methods for manufacturing solid materials at least in part from waste material, and in particular from so-called fragmentation waste (sometimes referred to as "car-fluff, "shredder light fraction", "fragmentizer waste" or "ASR" (automobile shredder residue) ) . It is another object of the invention to provide solid material formed at least in part from waste material, and, in particular, from fragmentation waste.

Fragmentation waste is produced by comminuting, e.g. by shredding or pulverising, manufactured articles, e.g. car parts or white goods such as refrigerators, washing machines and the like, and removing metal fragments from the comminuted material.

The resulting fragmentation waste has a low relative bulk density, on average around 0.3, and typically contains fragments of plastics materials, glass, rubber, wood, fabrics and other materials derived from the comminuted articles. The fragmentation waste may also contain a small amount of residual metal. Typically fragmentation waste will contain from about 15% to 20% by weight of moisture and about 8% to 10% by weight of metals (ferrous and non-ferrous) .

Hitherto, there have been no acceptable uses of fragmentation waste, and its disposal by way of land fill, is relatively expensive due to its low relative bulk density.

According to a first aspect of the invention, there is provided a method of manufacturing a solid material including the steps of processing fragmentation waste and plastics material to form a mixture in which at least some of the plastics material is in a softened state and forming said solid material from said mixture.

According to a second aspect of the invention, there is provided a solid material formed from fragmentation waste and plastics material.

According to a third aspect of the invention, there is provided a method of manufacturing a solid material including the steps of processing plastics material and a waste material composed at least partially of non-plastics material to form a mixture in which at least some of the plastics material is in a softened state and forming said solid material from the mixture such that the softened plastics material solidifies to encapsulate the non-plastic material.

According to a fourth aspect of the invention, there is provided a solid material formed from plastics material and a waste material composed at least partially of non-plastics material, the non-plastics material being encapsulated by plastics material.

According to a fifth aspect of the invention, there is provided a solid material formed by either one of the first or third aspects of the invention.

According to a sixth aspect of the invention, there is provided a method for the continuous production of solid materials and in particular solid materials from a plastics material, and a waste material that comprises, at least partially, non-plastics material, which method comprises granulating said waste material, pulverising said plastics material, blending the granulated waste material and pulverised plastics material, heating and mixing the resulting blend of waste material and plastics material, under temperature controlled conditions resulting from the supply of external heat while said mixing is carried out, and extruding and pelletizmg the resulting mixture.

The following is a more detailed description, of exemplary methods of the invention.

In a first exemplary method, fragmentation waste, of the above-described form, and mixed waste plastics material recovered from household, industrial and commerical, refuse (without sorting of different types of plastics materials) are used as starting materials.

Typically, the plastics material will include about 50% to about 65% by weight polyolefines, as well as PVC, polystyrene and some heat resistant plastics materials having very high softening temperatures. The plastics material may contain sheet, film, fragments of articles and even whole articles, and typically has a relative bulk density of about 0.3.

Furthermore, a sample of raw mixed waste plastics will usually contain from about 11% to 15% by weight of moisture and from about 2.5% to 3% by weight of metals (ferrous and non-ferrous) , and have a baled density of from 450 to 520 kg/m³.

Initially, the plastics material in baled form, is passed through a Metpro (Trade Mark) shredder to separate the component pieces of the bale. The fragments are passed in close proximity to overband and rare earth magnets to extract contaminating metal.

The fragmentation waste is passed through a granulator to give a maximum fragment size of approximately 6mm, and these fragments are also passed in close proximity to overband and rare earth magnets to extract residual metal .

The shredded plastics material and fragmentation waste are then simultaneously mixed and heated in an agglomerator. An agglomerator has a mixing drum and a number of rotatable blades disposed within the drum, and is used to comminute and then agglomerate a charge of material. Agglomeration is caused by frictional heat generated by the action of the blades.

Additionally, some agglomerators are adapted for the injection of a relatively cold quenching agent (a liquid or a gas) , to cool and fracture the hot agglomerated material so as to produce small pieces of the material. An example of a suitable agglomerator is described in GB 2 030 472.

The fragmentation waste and the plastics material (after shredding and metal extraction as described above) are loaded into the agglomerator in the proportion, by weight, of 50%:50% until the optimum load for the agglomerator has been added. Optionally, if the colour of the final product is important, a small amount of a colouring agent, such as carbon black, may also be added.

The agglomerator is then operated. Initially the action of the blades further reduces the size of the fragments of fragmentation waste and plastics material. Additionally, friction between the fragments, and between the fragments and the drum and blades of the agglomerator causes the temperature of the fragmentation waste and the plastics material steadily to increase, and this process is continued until at least some of the plastics material has softened and a plastic, viscous, generally homogenous mixture has been formed. In this example the agglomerator is operated for approximately 6 minutes and the temperature reached is 185°C.

If the fragmentation waste contains plastics material it is believed that at least some of the plastics material may also be softened by the action of the agglomerator and will assist in the formation of the mixture.

After the mixture has been formed, it is discharged from the agglomerator into a mold and, before the mixture cools significantly, it is subjected to a pressure of 20 bar in the mold for a period of 3 to 6 hours. During this time the mixture cools and solidifies to form a block of solid material. The pressure is then released and the block is removed from the mold and is ready for use.

Blocks formed in this way are all found to have a smooth surface and are substantially impervious to water. Furthermore, when the blocks are submerged in water only minimal leaching of the components of the fragmentation waste occurs. For example, the degree of leaching of heavy metals, traces of which are retained in the fragmentation waste, is very low and well below the relevant Environmental Quality Standards of the Environmental Agency.

On sectioning the blocks, the material appears substantially homogeneous with few if any gas pockets The material has a relative density of between about 1.1 to about 1.4.

It is believed that the solidified plastics material forms a matrix which, in effect, encapsulates the fragmentation waste and unsoftened plastics material.

The afore-mentioned molding step ensures that the formed solid has a required shape and satisfactory surface properties. Additionally, the molding step tends to eliminate gas pockets and improves the water imperviousness of the solid material. The molding pressure of 20 bar has been found to be the optimum pressure with regard to the structural properties of the resultant material. No significant improvement of the material's properties is achieved when the mixture is compressed at higher pressures. If the surface properties, homogeneity and water-imperviousness are not critical a block of a required shape may be molded without the application of pressure.

Certain aspects of the above-described first exemplary method may be varied. For example, different relative proportions of the fragmentation waste and the plastics material may be used. It has been found that the minimum proportion, by weight, of plastics material required for the formation of a satisfactory solid material is about 30% (although this figure may vary depending on the composition of the plastics material) . Below this, the fragmentation waste and the plastics material do not bind together sufficiently to form an acceptable material, and the quality of the material is found to improve as the proportion of the plastics material is increased. The 50%:50% proportions used in the exemplary method described above give a relatively inexpensive material having excellent qualities of water-imperviousness and strength.

Additionally, the operating time of the agglomerator may be altered with the result that the mixture attains a different temperature. However, the agglomerator must be operated for a time period sufficient to form the mixture and, in practice, it has been found that this time period corresponds to a temperature of about 180°C. Acceptable solid materials may be produced using temperatures up to 250°C. However, at temperatures over 210°C, large quantities of pollutant gases such as HCl, HF and volatile organic compounds are evolved. Although technology exists for the removal of these gases, this adds to the cost and complexity of the process. If the mixture is formed at temperatures over 185°C, the mixture is preferably cooled to about 185°C before molding.

Current designs of agglomerator known to the applicant have an maximum capacity of about 1100 kg. However, for many purposes it is desirable to manufacture blocks of 20,000 kg or more. By operating several agglomerators in a staggered, cyclic manner it is possible to supply the hot mixture of fragmentation waste and plastics material at an acceptable rate to a mold suitable for forming such a block. For example, if it is desired to prepare the fragmentation waste/plastics material mixture as described above in respect of the first exemplary method, a bank of 12 agglomerators may be used. In any particular cycle, each agglomerator would be in operation for about 8 minutes; 1 minute to load the agglomerator, 6 minutes to form the mixture and 1 minute to unload. By staggering the operations of the 12 agglomerators such that there is an interval of 1 minute between their successive operations it is possible to produce a substantially continuous stream of mixture at a rate of 66,000 kg/hour (assuming an agglomerator load of 1100 kg per operation) from which blocks may be formed.

This rate of supply is believed to be sufficient for supplying 20,000 kg to a mold such that no significant cooling of the mixture occurs while the mold is being filled.

Alternatively, if fewer agglomerators are used, the mixture may be fed to a holding tank provided with heating and stirring means for maintaining the mixture at a desired temperature. Once the amount of the mixture that has been accumulated in the tank is sufficient to fill the mold, the mixture is transferred to the mold to form a block.

In a second exemplary method, now described, the temperature required to produce a solid material is modified by mixing the fragmentation waste and the plastics material with a small quantity of a molten bituminous material, such as roofing bitumen.

In this second exemplary method, fragmentation waste and mixed waste plastics material are shredded and metals extracted, as described above in respect of the first exemplary method. Roofing bitumen is heated to a temperature of 150°C causing the bitumen to liquify. The fragmentation waste, the plastics material and the liquified bitumen are then introduced into the agglomerator in the respective proportions 45%:50%:5%, by weight. The agglomerator is operated until at least some of the plastics material has softened and a viscous, generally homogeneous mixture has formed. In this example, the temperature of the mixture will be approximately 190°C.

The agglomerator is then emptied into a mold and a block of solid material is formed as described above for the first exemplary method.

Blocks manufactured in this way are substantially identical to blocks prepared by the first exemplary method, with the exception that they are slightly more prone to leaching of components of the fragmentation waste. Additionally, a small amount of the bituminous material may leach from the block. The bituminous material enables a suitable mixture to be formed in the agglomerator more quickly and at a correspondingly lower temperature; however, the mechanism by which this is achieved is not fully understood. It is believed that the bituminous agent may wet the fragments of fragmentation waste (and possibly also fragments of the plastics material) causing them to stick together and thereby assisting heat transfer between the fragments.

When 5%, by weight, of roofing bitumen is added as described above, it has been found that the minimum temperature in the agglomerator for the production of a satisfactory material is about 180°C.

The invention is not limited to the manufacture of blocks of solid material. In a third exemplary method, a quenching agent (e.g. water) is added to the mixture of fragmentation waste, plastics material and optionally bituminous material in the agglomerator. The quenching agent causes the mixture to solidify rapidly and to break up into small irregular pieces, which are then discharged from the agglomerator.

As indicated below, these small irregular pieces may be used directly without further processing. Alternatively, they may be subjected to further processing to give solid products in different forms, for example as follows.

The pieces are fed, via a suitable holding container if required, to a continuous mixer. Continuous mixers are well known in the art and use one or more rotating screws to propel material through a heating chamber - the action of the screw or screws simultaneously causing mixing of the material. One particularly suitable continuous mixer, is marketed as part of a unit also incorporating a dump extruder by Farrel Limited (Rochdale, UK) , under the Trade Mark CP Compact Compounder.

The pieces are passed through the continuous mixer using machine settings chosen so that the pieces form a second, plastic, viscous, generally homogeneous mixture in which at least part of the plastics material is softened.

It has been found that the temperature at which a second mixture, satisfactory for subsequently forming solid products, can be formed from the pieces in a continuous mixer, is lower than the temperature required to form the initial mixture from which the pieces are formed, as described above.

Preferably, the continuous mixer settings (e.g. controlling the heating chamber temperature and residence time in the chamber) are chosen such that the final temperature of the second mixture is between 160°C and 180°C. At temperatures in this range a satisfactory second mixture is formed and very little if any gas (such as HCl, HF or volatile organic compounds) is evolved from the second mixture - the absence of significant gas evolution facilitating the subsequent production of solid products.

The second mixture can now be processed in several ways to produce solid products having a desired form.

For example, if pellets are required, the second mixture may be passed directly to a dump extruder and through the extruder to a die face pelletizer. The dump extruder comprised in Farrel Limited's CP Compact Compounder (Trade Mark) has been found to be particularly suitable and has a propelling screw provided in a heating barrel with four temperature controlled regions disposed sequentially along the barrel - the temperature of each region being independently controllable.

The temperature of the dump extruder is adjusted so that the second mixture is maintained in the plastic, viscous state as it passes through the extruder. For example, the temperatures of the four regions of the Farrel extruder in sequence from the first region encountered by the second mixture to the region adjacent the pelletizer, may be set to 155°C, 165°C, 175°C and 185°C respectively.

The temperature of the die of the pelletizer is set such that the second mixture starts to solidify as it passes through the die.

Alternatively, pellets may be formed using a dump extruder in combination with a strand pelletizer.

Instead of the using the dump extruder to produce pellets, the second mixture may be extruded in conventional ways to produce solid products having a desired shape. For example, the second mixture maybe extruded to form pipes.

If the desired final product is a block having a required shape, the second mixture may be fed to a suitably shaped mold. This is ideally done by feeding the second mixture directly from the continuous mixer into a dump extruder and using the dump extruder to propel the second mixture into the mold. However, the second mixture may be fed to the mold in other ways .

The second mixture may also be used to form sheets of predetermined thickness . To do this the second mixture can be passed from the mixer to a calendering machine.

Solid products produced as described above from the second mixture generally have a more homongeneous internal consistency compared to the blocks produced by the first or second exemplary methods described above.

Although a continuous mixer is used to form the second mixture in the example described above, other mixers may be used. Preferably, alternative mixers will be of a type which allows the second mixture to be formed at temperatures lower than 180°C.

In a fourth exemplary embodiment, now described, a continuous mixer is used to form a plastic, viscous generally homongeneous mixture from fragmentation waste and plastics material after firstly processing the plastics material alone in an agglomerator.

The plastics material is firstly passed through a shredder, and metals removed, as described above. A charge of the plastics material is then introduced into an agglomerator and the agglomerator is operated until at least some of the plastics material has softened and a plastic, viscous, generally homogeneous mixture has formed. A quenching agent is then added to the mixture to form small irregular pieces, as described above .

The fragmentation waste is granulated and metals extracted, as described above.

The granulated fragmentation waste and the pieces of plastics material are then loaded, in the desired ratio, into a continuous mixer and fed through the mixer under conditions chosen such that at least part of the plastics material softens and a plastic, viscous, generally homogeneous mixture is formed. The final temperature of the mixture is preferably 160°C to 180°C.

The mixture may then be used to form solid products.

For example, pellets, blocks or sheets may be produced as described above for the third exemplary method.

Because of the heat generated internally of the agglomerator by the mechanical action of the knives it can be difficult to control its operating temperature. For example, an agglomerator, operating in a batch process, must be operated for sufficient time to raise the temperature to around 200°C in order to produce sufficient softening, and in some instances the temperature may be higher. However, as has been previously stated, excessively high temperatures, for instance those over 225 to 230°C, can result in the generation of corrosive and hazardous breakdown products from plastics materials, e.g. hydrogen chloride, hydrogen fluoride and volatile organic materials.

Accordingly, a fifth exemplary method comprises granulating the waste material, pulverizing the plastics material, blending the granulated waste material and pulverised plastics material, heating and mixing the resulting blend of waste material and plastics material, under temperature-controlled conditions resulting from the supply of external heat while the mixing is carried out, and extruding and pelletizing the resulting mixture.

This fifth exemplary method will be further described with reference to the accompanying drawing, which is a schematic flow diagram of the process involved. It will be understood that the drawing is not to be taken as indicating all components and apparatus intended for forming the final materials. Details such as air purification systems, power supply, etc. can be provided as desired or required by statutory regulations or health and safety considerations.

Referring now to the drawing, fragmentization waste 1 and plastics materials 6 are passed separately at first through a series zones, wherein certain operations are carried out on them, and then combined and passed through further zones for further operations to be carried out. In general, it is convenient to employ pneumatic conveyors for transferring material from zone to zone, but other transport means can be employed if desired. It is to be understood that reference to a zone for carrying out a particular operation does not imply that only a single machine is necessarily used in that zone. If desired, two or more machines, operating in series or in parallel, can be used to produce the desired result. The use of two or more machines in parallel has the advantage that there need be no complete shut down of the process during necessary maintenance. Also, it makes it possible to expand or reduce the throughput of material, depending on the availability of fragmentation waste and plastics materials.

The fifth exemplary method involves bringing fragmentation waste 1 on site, where it can be stored 2 before being sent by conveyor 3 into a granulation zone 4. Since such waste often contains a considerable amount of metals, these are conveniently removed from conveyor 3 e.g. by magnetic separation as previously mentioned and/or manually. Granulated material is passed from granulation zone 4 to a storage facility 5 for further use as described below. A typical granulation zone 1 will contain a pair of granulators, operating in parallel. Each will have rotary and fixed knives whose combined effect will size reduce the fragmentation waste to such a size as to pass a 6mm screen, thereby producing a fine earth-like material. The frictional heat generated by the knives will raise the temperature of the fragmentation waste, driving off moisture. Advantageously the loss of this heat can be avoided by using ducted cladding when conveying the material from zone to zone, thereby reducing the energy needed in later stages of the process. Furthermore, ferrous metals can be recovered magnetically, e.g. by an overband magnet over the conveyor transporting the granulated material from the granulation zone 4 to the storage facility 5.

Plastics materials 6 are brought on site and stored 7. Depending upon the nature of the plastics material, it is passed directly or indirectly to a pulverizing zone 10, and the resulting pulverized material is passed to a suitable plastics storage facility 11. If the plastics material is in the form of bales of material, it can be passed from the feed storage 7 through a shredding zone 8 and hence to the pulverizing zone 10. A typical shredder will reduce mixed waste plastics to a size able to pass a 150mm screen. Any metals present in the plastics material can be removed magnetically in a metals separation step 9, e.g. by an overband magnet over a conveyor transferring the shredded plastics to the pulverizing zone 10. Alternatively, if the plastics material 6 is already in an agglomerated state, it can be passed directly 19 from the feed hopper 7 to the pulverizing zone 10.

In the pulverizing zone, which can typically contain two pulverizers operating in parallel, the shredded plastics material from the shredding zone 8, or agglomerated material passed directly from the feed hopper 7 are size reduced to below 3mm, for example to a size of 1-2 mm so that it may pass through a 2mm screen.

Granulated waste from storage 5, and pulverized plastics from storage 11 are blended, typically in a 50/50 weight ratio and preferably with at least 30% by weight of plastics, in a blending zone 12 and passed to a mixing zone 14 , to be described in more detail below. This blended material can be passed directly from the blending zone 12 to the mixing zone 14, or can be held in an intermediate blend buffer storage 13, from which it is supplied to the mixing zone as needed.

The mixing zone 14 conveniently comprises two continuous mixers, designed to mix and melt the blend, and transfer this via a gravity pusher-assisted feed system to a dump extruder 15. A controlled heat input from the heated barrel of each mixer raises the blend to a temperature of 160 to 175°C, preventing HCl and HF evolution. The use of pulverized small particles in the blend helps to ensure a more homogeneous output from the mixers.

The extruder maintains the heat and pressurises the molten plastic to give a consistent feed to a water cooled die plate, which has a number of holes, conveniently having a diameter of about 10mm. As the plastic passes through the holes, it is cut into pre-determined lengths by a series of rotating knives contained within an underwater pelletizer mounted directly to the die plate and extruder.

In this cut form, the pellets are initially shock-cooled in the underwater pelletizer 17 and transferred using the same water as a transport means to a water separator. The water is advantageously passed through a heat exchanger to collect and utilise recovered heat within the upstream pneumatic transport system, thus maintaining as much heat energy in the material being processed as possible.

The pelletized product is fed into a fluidised bed system, designed to allow air to pass between the pellets and lower their temperature to a point where each pellet will maintain its integrity, without sticking together.

The remaining heat contained in the pellets allows final drying to take place during and after the material is transported via a pneumatic transport system to an aggregate bunker storage 18, ready for shipment of the product .

The output of the continuous mixers may alternatively be fed to moulds and cooled to form large constructional blocks.

There are many constructional uses for the solid materials produced by the exemplary methods described above. The uses described below are by way of example only.

Blocks of solid material made by the first and second exemplary methods may be formed in any required shape and may have a wide range of uses. For example, the blocks may be used as structural elements for building sea or river defences. A plurality of blocks may be connected together by a steel framework to form a wall for the reinforcement or repair of regions of coast or riverbank susceptible to flooding or erosion.

Alternatively, suitably shaped blocks may be used in the construction of central reservation barriers on motorways.

The small irregular pieces produced by the third exemplary method also finds a wide range of applications. For example, this material may be used in place of gravel; for example, the material may be used as a packing material around pipes laid in trenches .

It will be appreciated that a number of modifications may be made to the exemplary methods described above. For example, instead of using mixed waste plastics material as described above, fragmentation waste may be mixed with a single type of waste plastics material, for example a polyolefin sorted from refuse. Alternatively, a single virgin plastics material or a mixture of virgin plastics materials may be used.

It is not essential to granulate the fragmentation waste and the plastics material before introducing these materials into the agglomerator. They may be introduced directly into the agglomerator, though a longer operating time may then be needed. Nor is it essential to remove contaminating or residual metals from the starting materials.

It is not essential that an agglomerator is used to mix and heat the fragmentation waste and the plastics material. Nor is it essential that mixing and heating are performed simultaneously. For example, fragmentation waste may be mixed with plastics material at ambient temperature using any suitable mixing device and the mixture could be subsequently heated using superheated steam.

Where it is desirable that the solid material has a relative density greater than 1.4, a relatively dense filler material may be added to the mixture from which the material is to be formed. For example, crushed limestone aggregate may be added. Blocks having a relative density of about 2 or greater are particularly useful for the manufacture of sea defences, as they are resistant to movement by wave action.

Solid materials may also be manufactured from combinations of plastics material, fragmentation waste and other waste materials or exclusively from plastics material and the other waste materials, the other waste materials being at least partly composed of a non-plastics material. An example, of a suitable alternative waste material is cement kiln dust or incinerator flue dust. Flue dust is a material comprising compounds of zinc, collected in scrubbing systems provided in the flues of iron and steel manufacturing plants.

Solid materials may be manufactured from combinations of flue dust and mixed waste plastics material with or without fragmentation waste essentially as described above in respect of the first, second, third, fourth and fifth exemplary embodiments - the flue dust being partly or wholly substituted for fragmentation waste.

Claims

CLAIMS ;

1. Method of manufacturing a solid material including the steps of processing plastics material and a waste material composed at least partially of non-plastics material to form a first mixture in which at least some of the plastics material is in a softened state and forming said solid material from said first mixture.

2. Method according to claim 1, wherein the plastics material comprises two or more plastics materials.

3. Method according to claim 2, wherein said two or more plastics materials are waste plastics materials.

4. Method according to claim 3, wherein said two or more waste plastics materials include approximately 60% or more by weight of polyolefines .

5. Method according to any preceding claim, wherein said processing includes passing the plastics material through a shredder prior to said softening at least some plastics material.

6. Method according to any preceding claim, wherein said at least some of the plastics material is softened by heating the plastics material during said processing step.

7. Method according to claim 6, wherein the processing includes simultaneously mixing together and heating the waste material and the plastics material, thereby causing said softening and forming said first mixture.

8. Method according to claim 7, wherein the processing includes mechanically comminuting and heating the waste material and plastics material in an agglomerator to form said first mixture.

9. Method according to any one of claims 6 to 8 , wherein the forming step includes applying pressure to the first mixture in a mold and allowing the first mixture to cool to form a block of said solid material.

10. Method according to claim 9, wherein the pressure applied to the mixture is about 20 bar.

11. Method according to claim 8, wherein the forming step includes adding a quenching agent to the first mixture in the agglomerator to solidify and fragment the first mixture whereby to form said material as a plurality of irregularly shaped pieces.

12. Method according to claim 11, wherein the quenching agent is a liquid, preferably water.

13. Method according to claim 11, comprising the further steps of heating the irregularly shaped pieces so as to produce a second mixture in which at least some of the plastics material is in a softened state, and forming a further solid material from said second mixture .

14. Method according to claim 13, wherein the pieces are subjected to mixing during said heating thereof.

15. Method according to claim 14, wherein the final temperature attained by the second mixture is in the range of 160°C to 180°C.

16. Method according to claim 14 or claim 15, wherein the heating and the mixing of the pieces is carried out in a continuous mixer.

17. Method according to any one of claims 13 to 16, wherein said forming of the further material includes passing the second mixture through an extruder to a pelleting means.

18. Method according to any one of claims 13 to 16, wherein said forming of the further material includes molding the second mixture.

19. Method according to claim 18, wherein the second mixture is passed through an extruder to a mold.

20. Method according to any one of claims 13 to 16, wherein said forming of the further material includes calendering the second mixture to form a sheet .

21. Method according to any one of claims 1 to 20, wherein the waste material is fragmentation waste.

22. Method according to any one of claims 1 to 20, wherein the waste material is flue dust or kiln dust.

23. Method according to any one of claims 1 to 22, wherein said processing involves processing plastics material, fragmentation waste and one or both of flue dust and kiln dust such that said first mixture comprises plastics material, fragmentation waste and one or both of flue dust and kiln dust.

24. Method according to claim 21, wherein the proportion by weight of the plastics material in the first mixture is at least 30%.

25. Method according to claim 24, wherein the proportion by weight of the plastics material in the first mixture is no greater than 90%.

26. Method according to claim 25, wherein the first mixture comprises 50% by weight of the fragmentation waste and 50% by weight of the plastics material.

27. Method according to claim 21, when claim 21 is dependent on claim 8, wherein the agglomerator is operated such that the first mixture attains a maximum temperature in the range from 180°C to 250°C.

28. Method according to claim 27, wherein the maximum temperature is in the range from 185°C to 210°C.

29. Method according to claim 28, wherein the maximum temperature is 185°C.

30. Method according to claim 8, wherein said processing includes passing the plastics material through a shredder prior to introducing the plastics material into the agglomerator.

31. Method according to claim 21, wherein said processing includes granulating the fragmentation waste.

32. Method according to claim 21, when claim 21 is dependent on claim 8, wherein said processing includes granulating the fragmentation waste prior to introducing the fragmentation waste into the agglomerator.

33. Method according to claim 8, including operating a plurality of said agglomerators cyclically, in sequence, and discharging the mixture from each agglomerator into a mold or a heated storage vessel.

34. Method according to any preceding claim, wherein said forming of the solid material is such that the softened plastics material solidifies to encapsulate the non-plastics material.

35. Method according to claim 2, wherein said processing involves the steps of mechanically comminuting and heating the plastics material in an agglomerator to form a plastics mixture in which at least some of the plastics material is in a softened state, adding a quenching agent to the plastics mixture in the agglomerator to solidify and fragment the plastics mixture whereby to form irregularly shaped pieces of the plastics material, simultaneously mixing together and heating the pieces and the waste material to form said first mixture.

36. Method according to claim 35, wherein the waste material is fragmentation waste.

37. Method according to claim 36, wherein the said simultaneous mixing together and heating is performed in a continuous mixer.

38. Method according to any one of claims 1 to 10 or 21 to 37, wherein the mixture includes a wetting agent for wetting the waste material to assist heat transfer within the mixture.

39. Method according to claim 38, wherein the said wetting agent is a bituminous material.

40. Method according to claim 39, wherein the waste material, plastics material and wetting agent are introduced into the agglomerator and the agglomerator is operated such that the mixture formed therein attains a maximum temperature in the range from 180°C to 204°C.

41. Method according to claim 40, wherein the maximum temperature is 190°C.

42. Method according to any one of claims 39 to 41 wherein the proportion by weight of bituminous material in the mixture is about 5%.

43. Method according to claim 42, wherein the proportions of the plastics material and the waste material by weight in the mixture are about 50% and about 45% respectively.

44. Method according to any one of claims 39 to 43 wherein the bituminous material is roofing bitumen.

45. A solid material formed from plastics material and a waste material composed at least partially of non-plastics material.

46. A material according to claim 45, wherein fragments of the non-plastics material are encapsulated within a matrix of plastics material.

47. A material according to claim 45 or claim 46, which is impervious to water.

48. A material according to any one of claims 45 to 47, which has a relative density of 1.1 or greater.

49. A material according to any one of claims 45 to 48, further including a relatively dense filler material.

50. A material according to claim 49, wherein the filler material is crushed limestone aggregate.

51. A material according to any one of claims 45 to 50, wherein the waste material is fragmentation waste.

52. A material according to any one of claims 45 to 50, wherein the waste material is flue dust or kiln dust .

53. A material according to any one of claims 45 to 52, in the form of a block.

54. A material according to any one of claims 45 to 52 consisting of irregularly shaped pieces.

55. A material according to any one of claims 45 to 52, in the form of particles or pellets.

56. A method of manufacturing a solid material including the steps of heating said material as claimed in claim 55 or irregularly shaped pieces produced by the method of claim 11 so as to produce a mixture in which at least some of the plastics material is in a softened state, and forming said solid material from said mixture.

57. A solid material formed by the method of any one of claims 1 to 44 or claim 56.

58. A method of manufacturing a solid material substantially as hereinbefore described.

59. A solid material substantially as hereinbefore described.