GB2467528A

GB2467528A - Recycling materials such as plastics

Info

Publication number: GB2467528A
Application number: GB0901461A
Authority: GB
Inventors: Justin Chieffo; Michelle Chieffo
Original assignee: BE ECO UK Ltd
Current assignee: BE ECO UK Ltd
Priority date: 2009-01-29
Filing date: 2009-01-29
Publication date: 2010-08-11
Also published as: WO2010086664A2; WO2010086664A3; GB0901461D0

Abstract

A method of recycling a contaminated article such as carrier bags or pallet wrap comprises heating the contaminated article to a temperature at a pressure to at least partially decontaminate and at least partially alter the physical form to provide a second article. The second article may be used to produce end products such as carrier bags. A waste plastics consignment such as polyethylene is shredded to ensure contaminants are not trapped and placed on a conveyor and passed under a source of infra-red and/or microwave radiation to shrink it and evaporate water. Alternatively the shredded material may be deposited into a rotary autoclave containing irregular sized abrasive metal particles having an average size of 10cm to 100cm and exposed to steam or water. The autoclave is first heated to a temperature of 90-140 degrees centigrade at a pressure of 0.15-2.0 MPa for up to 30 minutes and then heated to a higher temperature and pressure for a period of time. Both processes may be used. Contaminants and plastics are separated by filtration, air or floatation. Recycled plastics may be formed into pellets. Contaminant may be pulped for use in making recycled paper or may be used as biomass for heat or electricity generation.

Description

Recycling The present invention relates to methods of recycling materials such as plastics and further relates to articles made from recycled materials.

The recycling of 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 when the plastic is melted, 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 the 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 incinerated or sent to landfill.

When it is possible to separate the material from the contaminants, the so-separated material is typically shredded or ground and then melted as it is passed through an extruder. 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 step.

Preferably the second heating step is predominantly a form-altering step.

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 be at least partially adhered to or at least partially contained within the material or entrained with a stream of the 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, floatation devices 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.

Preferably, the material is irradiated with infra-red and/or microwave radiation prior to the or a first 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.

Preferably, the first temperature is between 90°C and 140°C and more preferably between 110° and 140°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°C and 200°C, and more preferably between 140°C and 160°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 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.

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

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.

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.

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 a/ia, 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. :l1

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.

Examrle 1 A bale of used supermarket carrier bags were 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 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°C at 0.2 MPa for 15 minutes. The temperature was then increased to 160°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 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 infra-red lamp until dry. The plastic pellets were subsequently blown into new carrier bags 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 a conveyor and exposed to infra-red radiation by passing under an JR 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.

The isolated plastics material was subsequently formed into new pallet wrap without further treatment.

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.

Claims

Claims 1. 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 to at least partially alter the physical form of the article to provide a second article.
2. The method according to Claim 1, wherein the heating step comprises exposing the contaminated article to infra-red radiation.
3. The method according to Claim 1, 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 90°C and 140°C.
5. The method according to any one of Claim 3 or Claim 4, 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 Claims 3 to 5, wherein the article is held at the first temperature and the first pressure for up to 30 minutes.
7. The method according to any preceding Claim, wherein the article is a plastics material.
8. The method according to any preceding Claim, wherein the contaminants are fibrous materials such as paper or cardboard, food waste, adhesives, industrial, municipal or household waste.
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 the heating steps.
14. The method according to Claim 13, wherein the separation is achieved by such means as air separation and/or filters.
15. The method according to any preceding Claim, comprising the initial step of shredding the article.
16. The method according to any preceding Claim, further comprising irradiating the article with infra-red and/or microwave radiation prior to the or a first heating step.
17. The method according to any preceding Claim, wherein the or at least one of the heating steps is carried out in an autoclave.
18. The method according to Claim 17, wherein the autoclave is a rotary autoclave containing a plurality of particles for abrading the contaminants from the material.
19. The method according to Claim 18, wherein the particles are of irregular shape.
20. The method according to any preceding Claim, wherein the article is dried after the heating step or steps.
21. 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.
22. An article formed from an article recycled according the method described herein.
23. A carrier bag formed from an article recycled according to the method described herein.
24. A method as described hereinbefore and with reference to the accompanying figures.
25. An article as described hereinbefore.
26. A carrier bag as described hereinbefore.Amendments to the claims have been filed as follows: Claims 1. A method of recycling a contaminated article comprising: the initial step of shredding the contaminated article; and heating the contaminated article to a temperature at a pressure to at least partially decontaminate the article and to at least partially alter the physical form of the article to provide a second article.2. The method according to Claim 1, wherein the heating step comprises exposing the contaminated article to infra-red radiation.3. The method according to Claim 1, 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 90°C and 140°C.5. The method according to any one of Claim 3 or Claim 4, 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 Claims 3 to 5, wherein the article is held at the first temperature and the first pressure for up to 30 minutes.7. The method according to any preceding Claim, wherein the article is a plastics material.8. The method according to any preceding Claim, wherein the contaminants are fibrous materials such as paper or cardboard, food waste, adhesives, industrial, municipal or household waste.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. (\J11. 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 the heating steps.14. The method according to Claim 13, wherein the separation is achieved by such means as air separation and/or filters.16. The method according to any preceding Claim, further comprising irradiating the article with infra-red and/or microwave radiation prior to the or a first heating step.17. The method according to any preceding Claim, wherein the or at least one of the heating steps is carried out in an autoclave.18. The method according to Claim 17, wherein the autoclave is a rotary autoclave containing a plurality of particles for abrading the contaminants from the material.19. The method according to Claim 18, wherein the particles are of irregular shape.20. The method according to any preceding Claim, wherein the article is dried after the heating step or steps.21. 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.22. An article formed from an article recycled according the method described herein.23. A carrier bag formed from an article recycled according to the method described herein. a)24. A method as described hereinbefore and with reference to the accompanying figures.25. An article as described hereinbefore.26. A carrier bag as described hereinbefore.