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Title:
RECYCLING
Document Type and Number:
WIPO Patent Application WO/2010/086664
Kind Code:
A2
Abstract:
A method of recycling a contaminated article comprising: chopping and/or shredding the contaminated article; heating the shredded contaminated article to a temperature at a pressure to at least partially decontaminate the shredded contaminated article and/or to at least partially alter the physical form of the shredded contaminated article to provide a second article.The second article may be used in the manufacture of an end product such as a carrier bag.

Inventors:
CHIEFFO JUSTIN (GB)
CHIEFFO MICHELE (GB)
Application Number:
GB2010/050142
Publication Date:
August 05, 2010
Filing Date:
January 29, 2010
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
BE ECO UK LTD (GB)
CHIEFFO JUSTIN (GB)
CHIEFFO MICHELE (GB)
International Classes:
B29B17/02; C08J11/06
Domestic Patent References:
WO1993014915A21993-08-05
Foreign References:
JPH0892411A1996-04-09
GB2422609A2006-08-02
US20050259893A12005-11-24
GB1453851A1976-10-27
GB292213A1928-06-11
Other References:
None
Attorney, Agent or Firm:
HLBBSHAW (Merlin House, Falconry CourtBaker's Lane, Epping Essex CM16 5DQ, GB)
Download PDF:
Claims:
Claims

1. A method of recycling a contaminated article comprising: chopping and/or shredding the contaminated article; heating the shredded contaminated article to a temperature at a pressure to at least partially decontaminate the shredded contaminated article and/or to at least partially alter the physical form of the shredded contaminated article to provide a second article.

2. A method for recycling a contaminated plastics material comprising: providing a waste stream of contaminated plastics material; shredding the waste stream to provide shredded material; and heating the shredded material, preferably in an autoclave, at a first temperature and pressure for a first period of time.

3. The method according to Claim 1 or Claim 2, wherein the heating step comprises heating the contaminated article to a first temperature at a first pressure and to a second temperature at a second pressure.

4. The method according to Claim 3, wherein the first temperature is between 900C and 1400C.

5. The method according to any one of the preceding Claims, wherein the first pressure is between 0.15 MPa and 2 MPa, e.g. 0.3 MPa.

6. The method according to any one of the preceding Claims, wherein the article is held at the first temperature and the first pressure for up to 30 minutes.

7. The method according to Claim 3, wherein the second temperature is between 1400C and 1600C.

8. The method according to any preceding Claim, wherein the contaminants comprise fibrous materials such as paper or cardboard, food waste, adhesives, industrial, municipal or household waste and/or thermoset plastics materials.

9. The method according to any preceding Claim, wherein the contaminants are at least partially adhered to or at least partially contained within or entrained with a stream of the article.

10. The method according to any preceding Claim, wherein the heating step or steps are performed in the presence of water.

11. The method according to any preceding Claim, wherein the pressure is elevated with respect to ambient or atmospheric pressure.

12. The method according to any preceding Claim, wherein the contaminants which are adhered to the article are at least partially detached from the article during the heating step.

13. The method according to any preceding Claim, wherein the contaminants are separated from the article after the heating step or one of a plurality of heating steps.

14. The method according to Claim 13, wherein the separation is achieved by such means as air separation, screens and/or filters.

15. The method according to any preceding Claim, further comprising irradiating the article with infra-red and/or microwave radiation prior to or after the or a first heating step, as the or a first or second heating step, or after the or a second heating step.

16. The method according to any preceding Claim, wherein the or at least one of the heating steps is carried out in an autoclave.

17. The method according to Claim 16, wherein the autoclave is a rotary autoclave containing a plurality of particles for abrading the contaminants from the material.

18. The method according to Claim 17, wherein the particles are of irregular shape.

19. The method of Claim 16, Claim 17 or Claim 18, wherein a plurality of moisture- absorbent bodies is introduced into the autoclave.

20. The method according to any preceding Claim, wherein the article is dried after the heating step or steps.

21. The method according to any one of the preceding Claims, wherein liquid or moisture is removed, e.g. drained, from the shredded material prior to heating.

22. A method for recycling contaminated material comprising heating the material to a first temperature at a first pressure then heating the material to a second higher temperature at a second higher pressure.

23. An article formed from an article recycled according to the method of any one of the preceding Claims.

24. A carrier bag formed from an article recycled according to the method of any one of Claims 1 to 22.

Description:
Recycling

The present invention relates to methods of recycling waste streams, for example, the recycling of such streams comprising or consisting of plastics and to recycling materials such as plastics and further relates to articles made from recycled materials.

The desire to recycle materials such as plastics, particularly such materials used as packaging, has become increasingly popular in recent years as concern about the earth's depleting resources and the problems associated with disposal by landfill have increased. Indeed, many states have introduced and escalated so-called "landfill taxes" in recent years in order to encourage citizens and businesses to waste less material and recycle more of their discarded waste.

Much of the waste plastics material that arrives at processing plants for recycling is, however, contaminated in some way by its previous use. For example, plastics that have been used in packaging are often contaminated with organic material such as paper or card, or food and other perishable material.

These contaminants are problematic in the recycling process because they are known to block flow paths in the process equipment and/or burn or char during heat treatments, potentially having a detrimental impact on product quality and/or reducing the efficiency of the recycling route.

Some known recycling processes require the contaminants to be removed by hand. Bales of material for recycling are typically opened upon arrival at a recycling plant to be visually inspected for contamination. Large and/or handlable contaminants may be removed from the plastic, which may then be passed on for processing. However, this step is expensive and time consuming. Moreover, where contaminants are legion or cannot be manually removed (or if it is too difficult to do so), the plastics material is deemed low-grade and is usually incinerated or sent to landfill.

It is known to recycle high grade plastics waste streams. Such high grade plastics waste may be melted as it is passed through an extruder and, as the stream of material emerges from the extruder, it is pelletised (i.e. it is cut into pellets).

These pellets may be used to form articles by melting and employing such processes as blowing or injection moulding. Alternatively, the pellets may be mixed with further materials and subjected to a second melt extrusion step to provide modified pellets for use in a blowing or injection moulding process.

The present invention provides a process for recycling low grade material which might otherwise be rejected by recyclers. Moreover, the present invention preferably removes the necessity to perform a manual inspection and sorting of material for recycling and seeks to further reduce downstream processing time. A further potential advantage is the reduction in time and/or energy required to process waste material and convert it to a commodity.

In a first aspect, the present invention provides a method of recycling a contaminated article comprising heating the contaminated article to a temperature at a pressure to at least partially decontaminate the article and at least partially alter the physical form of the article to provide a second article. Preferably, the heating step comprises heating the contaminated article to a first temperature at a first pressure and to a second temperature at a second pressure.

Preferably, the article is comprised of a plastics material.

The article may be contaminated by one or more contaminant.

A second aspect of the invention provides a method for recycling contaminated material comprising heating the material to a first temperature at a first pressure then heating the material to a second higher temperature at a second higher pressure.

Preferably, the first heating step is predominantly a decontamination and/or delamination step.

Preferably the second heating step is predominantly a form-altering, e.g. shrinkage, step. For example, thermoplastic materials may shrink, whereas thermoset materials may not, which may aid subsequent separation processes, especially if the contaminated material has all been shredded to a nominal, uniform, size prior to shrinkage.

The material is preferably a plastics material, such as that used in packaging and/or plastic carrier bags, polypropylene, PET, high density polyethylene (HDPE) or low density polyethylene (LDPE). The contaminants may include fibrous materials such as paper or cardboard, food waste, adhesives, industrial, municipal or household waste. The contaminants may also include thermoset plastics materials. The contaminants may be at least partially adhered to or at least partially contained within the material or entrained with a stream of the material. The methods of the present invention may be tolerant of a relatively wide variety of contaminated waste streams. The waste steam may comprise from 25% to 100% by volume, preferably from 50% to 90% by volume, more preferably from 55% to 85% by volume, most preferably from 60% to 80% by volume, of recyclable plastics material.

The heating of the material under pressure at least partially removes the material from any contaminants that may be attached to it, thereby allowing for a separation of the material from the contaminants. Moreover, the contaminants are prevented from charring or burning, which can have a detrimental effect on the quality of the end product and/or reduce the efficacy of the recycling process.

Preferably, the heating step or steps are performed in the presence of water.

Preferably, the first pressure is elevated with respect to ambient or atmospheric pressure.

Preferably, any contaminants which are adhered to the material are at least partially detached from the material during the heating step.

Preferably, the contaminants are separated from the material after the heating step or one of the heating steps. This may be achieved by such means as air separation, flotation devices, vibrating screens and/or filters.

In some embodiments the material is divided, e.g. shredded prior to the heating step or one of the heating steps. Alternatively or additionally, the material may be divided, e.g. shredded, after the heating step. Shredding the contaminated material prior to heating may be especially advantageous, particularly in cases where the waste stream comprises carrier bags or other packaging materials, which may contain contaminants. For example, shredding such material may "open up" carrier bags to expose contaminants such as discarded receipts and food waste.

Further, shredding may be particularly beneficial in cases where the waste stream comprises thermoplastic as well as thermoset plastics materials. By shredding the waste stream to a nominal size, the differential shrinkage behaviour of the two plastics types during the subsequent heating step(s), will result in different pellet/particle sizes being produced. The larger (i.e. non-shrunken) thermoset bodies may be readily separated from the smaller thermoplastic bodies subsequently, e.g. using a vibrating screen.

Further, shredding may be particularly beneficial in cases where the waste stream comprises objects containing liquids, e.g. discarded plastic bottles or plastic containers of milk or the like which has passed its sell-by date, or has a large moisture content, as the liquid or moisture may be removed, e.g. drained, from the stream after shredding. More aggressive forms of moisture removal may additionally or alternative be deployed such as by crushing, squeezing or compressing, e.g. using one or more rollers or other suitable means. Should such a moisture removal step be employed, the stream may be subsequently agitated, preferably before heating, to at least partially reduce the density of the stream.

In any event, agitation of the stream before heating and/or irradiation may be utilised. Preferably, the material is irradiated with infra-red and/or microwave radiation prior to or after the or a first heating step, as the or a first or second heating step, or after the or a second heating step. The infra-red and/or microwave treatment has been found to shrink the material, e.g. the plastics material, which may increase the exposure of the contaminants to heat and pressure during the heating step.

The shrunken material may be separated from the contaminant, e.g. by filtration, following the irradiation step which results in a decontaminated material, and negates the need to carry out any further steps.

The or at least one of the heating steps is preferably carried out in an autoclave, for example a rotary autoclave. The autoclave may contain a plurality of particles for abrading the contaminants from the material.

These particles are preferably of irregular shape and may, for example, be formed from metal or any other substance which will remain hard and abrasive at the temperature of the heating step.

Preferably, the or at least one of the heating steps takes place in the presence of water.

For waste streams comprising substantially only plastics materials, a runaway effect may arise in the autoclave. Without wishing to be bound by any theory, it is thought that this may be caused by the heat balance of the treated materials. This problem can be mitigated against or mitigated by the addition of absorbent bodies. Beneficially, the contaminants, e.g. organic matter, may absorb moisture during heating in the autoclave. Preferably, the first temperature is between 90 0 C and 140 0 C and more preferably between 1 10 0 C and 140 0 C. Preferably, the first pressure is between 0.15 MPa and 2 MPa and more preferably between 0.2 MPa and 0.5 MPa, for example 0.3 MPa. Preferably, the material is held at the first temperature and the first pressure for up to 30 minutes. More preferably, the material is held at the first temperature and the first pressure for between 5 and 25 minutes, say, between 15 and 20 minutes.

Preferably, the second temperature is between 140 0 C and 200 0 C, and more preferably between 140 0 C and 160 0 C. Preferably, the second pressure is between 0.15 MPa and 2 MPa and more preferably between 0.2 MPa and 0.5 MPa, for example 0.3 MPa. Preferably, the material is held at the second temperature and the second pressure for up to 30 minutes. More preferably, the material is held at the second temperature and second pressure for between 5 and 25 minutes, say, between 10 and 15 minutes.

In some embodiments, the material is dried after the heating steps. This may be performed by, for example, irradiating the material with infra-red and/or microwave radiation. In certain embodiments, the material may be ground to aid removal of residual moisture.

Preferably, some or all of the contaminants removed from the material are themselves recycled. For example, organic material may be used as biomass.

Preferably, the method comprises using the material after the heating step to form new products. The products may be, for example, pellets of material for further processing, as may be formed by extrusion of the material. Advantageously, however, the material may be used to form end products without any further processing such as extruding. For example, the material may be introduced to a blower for melting and forming into bags.

Optionally, the end products may be manufactured from a mixture of recycled and virgin material, for example, a 50:50 mixture. Preferably, the amount of virgin material used may be minimised, e.g. end products of satisfactory quality may be made from a

90:10 mixture of recycled and virgin material, or from pure recycled material (together with e.g. colourants and other appearance modifiers where required). The pellets of the recycled material may be processed before forming into end products, e.g. the pellets may be chopped, ground or sliced. This may be done to provide pellets within a narrow or at least narrower size distribution.

In a third aspect, the invention provides an article formed from material recycled according to the method described herein.

In a fourth aspect, the invention provides a carrier bag formed from material recycled according to the method described herein.

In a further embodiment, the present invention provides a method for recycling a contaminated material comprising heating the material to a first temperature at a first pressure.

In a yet further embodiment, the present invention provides a method of recycling a contaminated article comprising heating and/or irradiating the article to at least partially decontaminate the article, wherein the heating and/or the irradiation steps at least partially alter the physical form of the article and/or the contaminant thereof. The method may further comprise a separation step, e.g. filtration or screening.

In a yet further embodiment, the present invention provides a method for recycling a contaminated plastics material comprising providing a waste stream of contaminated plastics material and treating the stream to at least partially alter the physical characteristics of the plastics component of the stream relative to those of the contaminants to cause separation, or at least start to separate, the plastics material from the contaminant.

A further aspect of the invention provides a method for recycling a contaminated plastics material comprising: providing a waste stream of contaminated plastics material; shredding the waste stream to provide shredded material; and heating the shredded material, preferably in an autoclave, at a first temperature and pressure for a first period of time. Preferably, the shredded material may then be heated at a second temperature and pressure for a second period of time, the second temperature being higher than the first temperature.

In order that the invention may be more fully appreciated, it will now be disclosed by way of example only with reference to the accompanying drawings, in which:

Figure 1 displays a flow chart of steps of a prior art recycling process.

Figure 2 displays a flow chart of steps of a recycling method according to the invention.

Figure 3 shows a schematic drawing of the apparatus of the invention.

The present invention provides an efficient process for recycling materials, such as plastics materials. In a preferred embodiment, a consignment of waste polyethylene material is obtained. This material might comprise such articles as used plastic carrier bags and pallet wrap. Such waste polyethylene material is typically contaminated with other waste materials, including food waste, say, from food once held within or packaged by the material, and paper and cardboard which may have been used as labelling or come from discarded receipts and the like.

Prior art processes, as shown schematically in Figure 1 , have required this contaminant material to be separated from the polyethylene by hand, which is time consuming and expensive. Moreover, if contaminant material is too difficult or expensive to remove from a portion of polyethylene, that portion is discarded, often being sent to landfill or for incineration rather than being recycled. That material which is suitable for recycling is then typically shredded, then melt-extruded. The pellets produced by the melt extrusion step often need to be mixed with further additives before a second melt extrusion step yields usable pellets.

In the present process, however, contaminated polyethylene may be processed without a manual removal of the contaminants, as is demonstrated schematically in Figure 2. In fact, the contaminants may be processed such that they may be themselves recycled or used, inter alia, as fuel, rather than being charred or removed for incineration.

The obtained consignment of polyethylene is shredded to produce an easily processable material stream and ensuring that at least some of the contaminant material is at least partially exposed and/or is not trapped within the polyethylene during the one or more further treatment steps. The shredded polyethylene is then placed on a conveyor belt which is passed under a source of infra-red radiation. The polyethylene shrinks when exposed to the infra-red radiation and residual water evaporates.

The conveyor deposits the polyethylene material into a rotary autoclave, which contains a plurality of irregular sided stainless steel abrasion balls. Water is added to the autoclave, which is sealed and then held at a first temperature and a first pressure for up to 30 minutes. As the autoclave turns, the abrasion balls abrade the polyethylene, cleaning off firmly attached contaminants. Moreover, the heat and moisture help to break down the contaminants. Paper based contaminants, for example, are broken down to fibrous form.

The autoclave is then held at a second temperature and a second pressure for a period (for example, up to 15 minutes). At this stage, the polyethylene forms agglomerate particles, apart from the broken-down contaminant material.

The contents of the autoclave are then removed and the agglomerate particles may be separated from the broken-down contaminant material, which may be in the form of a sludge. This is performed by a separation stage, e.g. by filtration, an air separation system, flotation or otherwise.

In some embodiments, however, it may be sufficient to carry out only certain stages of the process. For example, the contaminated material may first be shredded to an easily processable material stream. The material may be either exposed to infra-red radiation in order to shrink the plastics material or deposited into a rotary autoclave to reduce the size of the contaminant material. The choice of step depends on the nature of the material stream. For example, a decision may be influenced by the percentage and/or nature of the contaminant.

The mixture may then be separated, for example, by filtration.

The contaminant material may be reserved for other uses. If a consignment of polyethylene is known to be contaminated predominantly with paper, for example, the broken down contaminant may be pulped for use in making recycled paper. Alternatively, the contaminant may be used as biomass for generating heat and/or electricity.

The agglomerate particles of polyethylene are loaded onto a second conveyor for further drying under infra-red radiation. In some circumstances, if moisture is present within the agglomerate particles themselves, they may be cut, shredded or milled prior to exposure to infra-red and/or microwave radiation.

The dried agglomerates are suitable for moulding and/or blowing directly into new articles, without any need for further extrusion or other processing. Moreover, their pellet-like size and appearance ensures ease of handling by manufacturers used to dealing in raw materials supplied as pellets.

In some embodiments, however, it may be desirable to extrude the agglomerates to produce pellets, such as pellets of a particular dimension as may be required for certain processes. In fact, the size of the agglomerates typically allows for smooth running of extrusion equipment.

Figure 3 shows schematically an example of an apparatus according to the invention. The apparatus comprises a shredder 1 , a rotary autoclave 2, a first conveyor belt 3a, a second conveyor belt 3b, a first vibrating screen 4 and a second vibrating screen 5.

In use, a steam of contaminated waste material WS is introduced to the shredder 1. The shredder 1 shreds contaminated waste material supplied thereto into pieces of a nominal size. The shredded material is then transferred by the first conveyor belt 3a to the rotary autoclave 2, in which it is subjected to a heat treatment in accordance with the invention.

Before the shredded material is transferred on to the first conveyor belt 3a, moisture of liquid may be removed, e.g. drained, from it. For instance, liquid may be drained off before the shredded material is removed from the shredder. This step may be particularly advantageous, where the waste stream includes containers of liquid which has passed its sell-by date.

After being allowed to dry, the treated pieces of material are transferred by the second conveyor belt 3b to the first vibrating screen 4.

The materal may be irradiated with infra-red radiation IR1 , IR2 while on the first conveyor belt 3a and/or the second conveyor belt 3b.

The first vibrating screen 4 comprises holes (not shown) therethrough. The dimensions of the holes are selected so that pieces of material, which did not shrink in the rotary autoclave 2, e.g. pieces of thermoset plastics materials cannot pass through the first vibrating screen 4. The material that passes through the first vibrating screen 4 will comprise pieces of thermoplastic materials that shrunk in the rotary autoclave 2 and smaller contaminants, e.g. organic materials. This material passes on to the second vibrating screen 5. The second vibrating screen 5 comprises holes (not shown) therethrough. The dimensions of the holes are selected so that the thermoplastic materials which shrunk in the autoclave 2 cannot pass through. The contaminants, which tend to be smaller, will pass through the holes in the second vibrating screen 5.

Three material streams emerge from the vibrating screens 4, 5. A first stream 6 comprises thermoset plastics materials, which can be re-used or disposed of appropriately. A second stream 7 comprises thermoplastic materials, which can be used in the manufacture of recycled articles such as carrier bags or pallet wrap. A third stream 8 comprises organic contaminants, which can be used as biomass for energy generation.

Example 1

A bale of used supermarket carrier bags was obtained and shredded in a shredder, e.g. a shredder of the type used for shredding film material, without prior cleaning or removal of contaminants. The bale contains contaminants such as organic matter, food waste or scraps, paper, cardboard, stickers, liquids, gunk and leaves, which may be contained within the carrier bags, adhered to the inside or outside of the carrier bags or located between the carrier bags. The carrier bags make up around 70% to 80% by volume of the bale. The material was then introduced to a rotary autoclave containing irregular sided abrasive metal particles having an average diameter of between 10cm and 100cm. Either steam was pumped into the autoclave or clean water was introduced and heated. The autoclave was rotated while held at 130 0 C at 0.2 MPa for 15 minutes. The temperature was then increased to 160 0 C at 0.4 MPa for a further 10 minutes, after which the system was allowed to cool.

Upon opening the autoclave it was found that the plastic material had separated from 5 the contaminant material, which had formed a sludge at the bottom of the autoclave. This sludge was washed from the autoclave.

The plastic material had formed pellets which were removed and placed under an infrared lamp until dry. The plastic pellets were subsequently blown into new carrier bags o without further treatment.

Example 2

A bale of used pallet-wrap was shredded in a shredder to a uniform size without prior cleaning or removal of contaminants. The resulting shredded material was placed on a5 conveyor and exposed to infra-red radiation by passing under an IR lamp set to a wavelength so the plastic material shrivelled and separated from the contaminant material. The material was then introduced to a filter to remove the larger contaminant material from the plastics material. 0 The isolated plastics material was subsequently formed into new pallet wrap without further treatment.

Example 3

A bale of mixed plastics waste, including thermoplastic and thermoset components and5 organic contaminants at about 25% w/w, was shredded in a shredder to a uniform size, nominally 50mm x 50mm, without prior cleaning or removal of contaminants. The shredded material was then introduced to a rotary autoclave containing irregular sided abrasive metal particles having an average diameter of from 10cm to 100cm and, optionally, additional absorbent matter if required.

Either steam was pumped into the autoclave or clean water was introduced and heated. The autoclave was rotated while held at 130 0 C and 0.2 MPa for 15 minutes. The temperature and pressure were then increased to 160 0 C and 0.4 MPa respectively, at which conditions the autoclave was held for a period of 10 minutes. The system was then allowed to cool.

The material was removed from the autoclave and dried, before being separated using vibrating screens. A first screen having a nominal mesh size of 2cm x 2cm was used to separate out the shredded thermoset component which were mostly unaffected by the heat treatment. In contrast, the shredded thermoplastic component shrinks in the autoclave, typically into the form of pellet-like bodies having dimensions which will pass through the first screen. For instance, the pellet-like bodies may have dimensions of from less than 2cm x 2cm, e.g. about 1.5cm x 0.5cm to 0.25 x 0.25cm. In this instance, the pellets had an average size of about 1.2cm x 0.6cm.

A second screen having a hole size through which the thermoplastic pellet-like bodies cannot pass, say 1 cm x 1 cm, separates the thermoplastic component from the contaminants, e.g. organic materials. The organic materials are partially digested.

The thermoplastic pellet-like bodies were subsequently used with some virgin material to produce new products through extrusion or moulding. A 90:10 mixture of pellets of recycled and virgin material was extruded. The contaminants, e.g. organic materials, can be used as biomass for energy generation.

Any of the features disclosed herein may be omitted and/or replaced with similar means able to perform the requisite task and/or any combination of any of the features disclosed herein is envisaged without departing from the scope of the invention.