Process for separating components of aluminium cladding

Abstract

The present invention relates to a process for separating metal-polymer laminate into a metal component and a polymer component, the process comprising the steps of subjecting the laminate to mechanical force such as deformation by crimping; applying thermal stress to the deformed laminate; and separating the metal from the polymer.

Description

PROCESS FOR SEPARATING COMPONENTS OF ALUMINIUM CLADDINGFIELD OF INVENTION

[0001] The present invention relates to the field of processing materials for downstream applications such as recycling.

[0002] In one form, the invention relates to separating the components of building cladding into components for recycling.

[0003] In one particular aspect, the present invention is suitable for use in separating the components of metal composite panels having a sandwich structure comprising a core of polymer, such as polyethylene located between two aluminium sheets.

[0004] It will be convenient to hereinafter describe the invention in relation to separating the components of aluminium cladding for the purpose of recycling, however it should be appreciated that the present invention is not limited to that use only and the components may be used for a wide range of purposes.BACKGROUND ART

[0005] It is to be appreciated that any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the present invention. Further, the discussion throughout this specification comes about due to the realisation of the inventor and / or the identification of certain related art problems by the inventor. Moreover, any discussion of material such as documents, devices, acts or knowledge in this specification is included to explain the context of the invention in terms of the inventor’s knowledge and experience and, accordingly, any such discussion should not be taken as an admission that any of the material forms part of the prior art base or the common general knowledge in the relevant art in Australia, or elsewhere, on or before the priority date of the disclosure and claims herein.

[0006] Aluminium cladding laminate is a material which is used on external surfaces of buildings due to its strength, durability and light weight. It is typically supplied in the form of panels of sheets. The panels and sheets are lightweight, compared with brick, timber or weatherboards. The panels and sheets are easy to transport and install, are durable and can be manufactured in a wide range of surface styles and appearances.

[0007] Aluminium cladding panels (ACPs) for buildings normally comprises a polymeric core between two thin panels of aluminium. The core typically comprises composite polyethylene (PE), that is, polyethylene combined with additives that improve mechanical properties, such as tensile strength, tensile modulus and flexural strength of the PE. In accordance with fire safety rules, the additives should include fire retardant to resist deformation or delamination of the cladding during building fires. In the past, ACPs that were non-compliant with fire safety rules have been used on buildings but are being progressively removed from buildings during rectification works or demolition. Combustible cladding waste is managed as industrial waste and in the past has often been dumped as landfill.

[0008] However, the aluminium and polymeric core are relatively valuable materials and ACPs that have been removed as part of rectification works, demolition or building renovation can be recycled and reused. This is preferable to having the ACPs sent to landfill, given that they are not biodegradable and do not break down. Recycled material can be used to offset virgin material used in the production for aluminium and polyethylene products. This contributes to lowering energy consumption and greenhouse gas emissions.

[0009] In the simplest form of ACPs processing, the panels are shredded into smaller pieces which are then separated into the component materials, aluminium and polymer composite, typically comprising polyethylene (PE) including high density polyethylene (HDPE) or low density polyethylene (LDPE). Other metals - typically ferrous metals - and mixed residuals may also be separated. The mixed residuals, such as caulking paint, adhesives and other miscellaneous materials are converted into waste-to-energy and used as a coal offset. The different materials are separately bagged and distributed to be recycled by manufacturers.

[0010] Optimally, 100% of the ACPs are recycled and nothing goes to waste. Typically, the separated aluminium is sent to a smelter to be incorporated into building materials or other products. The separated polyethylene may go to plastic manufacturers to be incorporated into manufacture of items such as plant pots, concrete bar chairs, pipes and bottles.

[0011] In another form of recycling, the ACPs are reduced to a crumb comprising both aluminium and polymer composite, however this is not a form that is preferred by recyclers.

[0012] In another method of ACP recycling, a crusher uses claw knives to cut pieces of ACP into flakes no bigger than 1 cm. The flaked ACP is then sent to a grinder where it is pulverized into pieces measuring less than a millimetre. The pulverized ACP is then sieved on a vibrating screen to separate pieces of less than 20 mesh. Any pieces greater in size than 20 mesh are sent back to the grinder for further pulverization. A cooling system keeps the pulveriser cool to stop the pieces burning and to stop overheating.

[0013] In the final step the metal and plastics are electrostatically separated by virtue of their conductive differences. The aluminium particles are attracted to an electrode and fall into a conductor pile, thus separating the aluminium from the nonconducting polyethylene.

[0014] One of the drawbacks of existing processes for ACP separation is that there can be significant amounts of cross contamination. In other words, the separation of the aluminium from the polymer is not ‘clean’. This can restrict the potential recycling applications and the value of the product to recyclers.SUMMARY OF INVENTION

[0015] An object of the present invention is to provide a more efficient process for reducing ACPs into constituent materials.

[0016] A further object of the present invention is to alleviate at least one disadvantage associated with the related art.

[0017] It is an object of the embodiments described herein to overcome or alleviate at least one of the above noted drawbacks of related art systems or to at least provide a useful alternative to related art systems.

[0018] In its broadest aspect, the process of the present invention comprises subjecting metal-polymer laminate to thermomechanical stress to recover the metal component separate from the polymer component. Typically, the thermomechanical stress comprises the application of the mechanical stress, such as a deformation force, and thermal stress.

[0019] In a first aspect of embodiments described herein there is provided a process for separating metal-polymer laminate, such as ACP, into a metal component and a polymer component, the process comprising the steps of:- optionally cutting the laminate into pieces,- subjecting the laminate to deformation force such as crimping,- applying heat to the deformed laminate, and- separating the metal from the polymer.

[0020] Typically, as a pre-processing step, the ACPs are cleaned, then sorted and classified according to various physical parameters such as their thickness and size. The classification determines the relevant processing parameters. The process heating temperatures and processing times need to be adjusted based on the classification of the ACPs.

[0021] Preferably, the ACPs are cut into pieces, such as by a hydraulic cutting machine. For example, suitable average sample size maybe less than about 35 x 50 cm2(length x width) with an average sample thickness of about 3 to 5 mm.

[0022] The pieces are subjected to deformation forces, such as the force imparted by a crimping machine, to break the internal bonding between the Al sheet and the polymer.

[0023] The deformed pieces are subjected to thermal stress, such as in a furnace. In a preferred embodiment the pieces of ACP are subjected to a temperature of between 400 and 450 °C for 30 to 180 secs, more preferably 50 to 70 seconds. The exact processing time may vary depending on the size and thickness of the deformed pieces, with thicker pieces requiring longer heating times.

[0024] The main product stream emerging from the furnace consists of aluminium and polymer. At this point substantially all of the aluminium and polymer have separated due to the thermo-mechanical stresses applied to the pieces of ACP.

[0025] The aluminium may be compressed into a convenient form such as sheets that can be readily stored and transported for further processing, such as recycling as a feed into a smelter. The polymer may be reduced to any convenient form such as ground particles that can be readily stored and transported for further processing, such as recycling. Both the aluminium and the polymer have a purity equivalent to their original production grade.

[0026] In another aspect of embodiments described herein there is provided a process for separating a metal-polymer laminate comprising a metal component and a polymer component, the process comprising:- a first step of cutting the laminate to provide a stream of pieces,- a second step of subjecting the pieces to deformation force such as crimping to provide a stream of deformed pieces,- a third step of applying heat to the deformed pieces to provide a thermally treated stream comprising metal that has been thermally separated from the polymer, and- a fourth step of separating the thermally treated stream into (i) a first substream comprising the metal and the polymer, and (ii) a second sub-stream comprising recyclable and non-recyclable materials.

[0027] The recyclable material from the second stream may be fed back into the third step for further processing.

[0028] In yet a further aspect of embodiments described herein there is provided metal, preferably aluminium, and polymer separated from ACPs according to the process of the present invention.

[0029] Other aspects and preferred forms are disclosed in the specification and / or defined in the appended claims, forming a part of the description of the invention.

[0030] In essence, embodiments of the present invention stem from the realization that applying a combination of mechanical and thermal stress to ACPs provided a substantially cleaner separation of ACPs into constituent parts when compared to the chemical separation processes of the prior art.

[0031] Further scope of applicability of embodiments of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure herein will become apparent to those skilled in the art from this detailed description.BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Further disclosure, objects, advantages and aspects of preferred and other embodiments of the present application may be better understood by those skilled in the relevant art by reference to the following description of embodiments taken in conjunction with the accompanying drawings, which are given by way of illustration only, and thus are not limitative of the disclosure herein, and in which:- Figure 1 is a schematic diagram of one embodiment of the process of the present invention for separating ACPs for recycling; and- Figure 2 is a schematic diagram of a further embodiment of the process of the present invention.

[0033] List of partsDETAILED DESCRIPTION

[0034] The present invention is primarily a thermo mechanical process for separating aluminium composite panels into their constituents. The thermomechanicalprocess ensures better output quality compared to chemical processes of the prior art. The thermomechanical process has the advantage of ensuring that the material quality of the separated components remain intact, whereas thermochemical process tend to degrade the material properties of the components.

[0035] The process of the present invention is suitable for all thicknesses of available cladding. The heating temperature and processing speed needs to be adjusted for different thicknesses and sizes.

[0036] The process comprises the following steps:

[0037] Step 1 . ACPs are cleaned, then sorted and classified according to various physical parameters such as their thickness and size. The classification determines the relevant processing parameters. The process heating temperatures, processing times need to be adjusted based on the classification of the ACPs.

[0038] Step 2. The ACPs are fed (1 ) to a hydraulic cutting machine (101 ) where they are cut to the required size and shape. For example, suitable average sample size maybe less than about 35 x 50 cm2 (length x width) with an average sample thickness of about 3 to 5 mm.

[0039] Step 3. The feed of cut pieces (2) passes to a crimping machine (102) where they are crimped to break the internal bonding between the aluminium cover sheets and polymer composite to accelerate subsequent thermal separation.

[0040] Step 4. The feed of crimped ACP pieces (3) passes to the main furnace (103) via a feed conveyor belt (104a) associated with a first fume hood (122). A product conveyor belt (104b) associated with a second fume hood (123) connects to the main furnace (103) outlet and conveys the thermally treated feed (4) to the next process steps. Upon exit from the furnace substantially all the polymer and aluminium have separated due to the thermo-mechanical stress applied to the ACP pieces.

[0041] In a preferred embodiment the main furnace is of rectangular box shape and the conveyor belt (104) passes therethrough from an inlet to an outlet and betweena top heating surface / coil and a bottom heating surface / coil. The heating may be at least 300°C. The top heating surface / coil is typically at 420-460 °C, more typically about 450°C. The bottom heating surface / coil is typically at 380-420 °C, more typically about 400°C. The residence time of the crimped pieces in the furnace is typically 30 to 180 secs, more preferably 50 to 70 seconds.

[0042] The exact processing time may vary depending on the size and thickness of the deformed pieces, with thicker pieces requiring longer heating times. For example, a crimped piece of ACP of 3 to 4 mm thickness may require a residence time of 50-60 secs while a crimped piece of ACP of similar length and width, but of 4-5 mm thickness, may require a residence time of 60-70 secs.

[0043] A controller (109) maintains the top and bottom surface / coil of the furnace (103) within the desired residence time and temperature parameters.

[0044] Gas emissions (5) from the furnace are vented or redirected to other processes or captured as a by-product. One possible treatment step for the gas emissions is described in further detail with reference to Fig. 2.

[0045] Step 5. The feed (6) of thermally treated pieces (4) exiting the furnace divides into two streams (7, 8). Division into two streams may be carried out manually, or by automated means. One stream (7) consists of separated (recyclable) products. The other stream (8) comprises non-separated products.

[0046] The stream (8) of non-separated products divides into two sub-streams (9 & 10).

[0047] One sub-stream (9) comprises non-separated ACP pieces. Products are returned to the feed stream to be re-processed until finally successfully separated. The non-separated ACP pieces are added back into the main feed stream of crimped ACP pieces (3) for further heating and full separation. (In other words, stream 9 is fed into stream 4 and re-emerges from the furnace in stream 6).

[0048] The other sub-stream (10) comprises pieces of ACP panel that resist separation even after they have been re-processed 2 or 3 times. This non-recyclable material is fed to a holding tank (1 10) prior to its removal to a landfill site or supplied to downstream processing for other applications. This sub-stream of discarded ‘incompatible’ products (10) comprised 2-5% by weight of material exiting the furnace. These ‘incompatible’ crimped pieces of ACP are generally partially separated (~1 to 10% separated) or unchanged after exiting the furnace.

[0049] Step 6. The main product stream (7) emerging from the furnace is a mixture of pure aluminium (1 1 ) and polymer (13). The Al stream (11 ) is compressed by a compressor (105) and converted to compacted Al sheet (12) that drops into an open Al storage tank (107).

[0050] Step 7. The polymer stream (13) composite is further processed by a grinding machine (106) and converted to a stream of ground particles (14) that passes to an open storage tank (108).Optimised Separation process

[0051] Figure 2 is a schematic diagram of a further embodiment of the process of the present invention.

[0052] This process includes the basic process scheme outlined in Fig. 1 , adapted to include processing of gaseous emissions from the furnace to meet legislated gas concentration and quality standards.

[0053] These include two fume hood covers (122, 123) that feed their respective gas emissions (5a, 5b) into an overhead gas absorption unit. The gas emitted from the inlet loop (16) and outlet loops (17) of the furnace flow to an air compressor (11 1 ) and then to a separator (1 12) that filters out particles and dumps them in a particle storage tank (1 13).

[0054] The flow of filtered gas (19) is scrubbed by gas absorption in an absorber column (1 15). Toxic gas solutes are removed from the filtered gas (19) by dissolutionin a flow of absorbent solvent (20) passing down the absorber column (1 15) from a solvent tank (1 14).

[0055] The main solvents preferred for absorption include amines and activated alkanolamines (such as monethanolamine, diethanolamine, N-methyl diethanolamine or piperazine).

[0056] The flow of scrubbed gas then passes through a heat exchanger (1 17) to a stripper disrober column (1 16) associated with a reboiler (1 18) fed by water-air flow (23), and a condenser (1 19).

[0057] Streams of sweet gasses (21 , 22) from the absorber column (115) and disrober column (1 16) respectively, are collected.

[0058] While this invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modification(s). This application is intended to cover any variations uses or adaptations of the invention following in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth.

[0059] As the present invention may be embodied in several forms without departing from the spirit of the essential characteristics of the invention, it should be understood that the above described embodiments are not to limit the present invention unless otherwise specified, but rather should be construed broadly within the spirit and scope of the invention as defined in the appended claims. The described embodiments are to be considered in all respects as illustrative only and not restrictive.

[0060] Various modifications and equivalent arrangements are intended to be included within the spirit and scope of the invention and appended claims. Therefore, the specific embodiments are to be understood to be illustrative of the many ways in which the principles of the present invention may be practiced. In the following claims, means-plus-function clauses are intended to cover structures as performing thedefined function and not only structural equivalents, but also equivalent structures. For example, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface to secure wooden parts together, in the environment of fastening wooden parts, a nail and a screw are equivalent structures.

[0061] When a Markush group or other grouping is used herein, all individual members of the group and all combinations and sub-combinations possible of the group members are intended to be individually included in the disclosure. Every combination of components described or exemplified herein can be used to practice the invention, unless otherwise stated.

[0062] Whenever a range is given in the specification, for example, a temperature range, a time range, or a composition or concentration range, all intermediate ranges and subranges, as well as all individual values included in the ranges given are intended to be included in the disclosure. It will be understood that any subranges or individual values in a range or subrange that are included in the description herein can be excluded from the claims herein.

[0063] As used herein, "comprising" is synonymous with "including," "containing," or "characterized by," and is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. As used herein, "consisting of excludes any element, step, or ingredient not specified in the claim element. As used herein, "consisting essentially of does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claim. The broad term "comprising" is intended to encompass the narrower "consisting essentially of and the even narrower "consisting of." Thus, in any recitation herein of a phrase "comprising one or more claim element" (e.g., "comprising A”), the phrase is intended to encompass the narrower, for example, "consisting essentially of A" and "consisting of A". Thus, the broader word "comprising" is intended to provide specific support in each use herein for either "consisting essentially of or "consisting of." The invention illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations which is not specifically disclosed herein.

[0064] One of ordinary skill in the art will appreciate that materials and methods, other than those specifically exemplified can be employed in the practice of the invention without resort to undue experimentation. All art-known functional equivalents, of any such materials and methods are intended to be included in this invention. The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention that in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by examples, preferred embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims.

[0065] Each reference cited herein is incorporated by reference herein in their entirety. Such references may provide sources of materials; alternative materials, details of methods, as well as additional uses of the invention.

Claims

CLAIMSThe claims defining the invention are as follows:1 . A process for separating metal-polymer laminate into a metal component and a polymer component, the process comprising the steps of:- subjecting the laminate to mechanical force such as deformation by crimping, and- applying thermal stress to the deformed laminate; and- separating the metal from the polymer.

2. A process for separating metal-polymer laminate, such as ACP, into a metal component and a polymer component, the process comprising the steps of:- optionally cutting the laminate into pieces,- subjecting the laminate to deformation force such as crimping,- applying heat to the deformed laminate, and- separating the metal from the polymer.

3. A process for separating a metal-polymer laminate comprising a metal component and a polymer component, the process comprising:- a first step of cutting the laminate to provide a stream of pieces,- a second step of subjecting the pieces to deformation force such as crimping to provide a stream of deformed pieces,- a third step of applying thermal energy to the deformed pieces to provide a thermally treated stream comprising a metal component separated from the polymer, and- a fourth step of separating the thermally treated stream into (i) a first substream comprising the metal and the polymer, and (ii) a second substream comprising recyclable and non-recyclable materials.

4. A process according to claim 3, wherein the recyclable materials are returned to the third step for re-processing.

5. A process according to any one of the preceding claims wherein the metal is aluminium.

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