"RECOVERY OF PLASTICS MATERIAL FROM OPTICAL STORAGE
MEDIA"
TECHNICAL FIELD
The present invention relates to a method and apparatus for separation and recovery or reclamation of plastics material and in particular to an apparatus and method for separation and recovery of the components making up optical storage media products and plastic storage containers for such products.
BACKGROUND
Disk recording media, such as optical disks, have become the storage media of choice for recording music, images, information and software because of their capability of high-density recording. In particular, compact disks (CDs) and other optical disks in the CD family have been used on a large scale.
Generally a CD includes a polycarbonate substrate, an aluminium reflective film, and a protective layer deposited in that order.
Although CDs are not particularly fragile, they can be rendered unusable if the surface of the disc is scratched or marred, or a disc is otherwise chipped, cracked or broken. In order to prevent damage, it is important that a storage case be provided that will protect the disc during transportation to the consumer, and while in the possession of the consumer.
Several known compact disc storage cases exist, including the ones shown in Herr, et al., U.S. Pat. No. 5,445, 265; and Philosophe, U.S. Pat. No. 4,702,369. Currently the most popular type of storage case for use with an audio-containing compact disc is the so-called "jewel case" which comprises a cover member and a base member, both of which are commonly made from styrene (polystyrene). The cover and base are formed as two separate members, and are hingedly coupled together. These storage containers generally include an insert or label upon which is printed information and/or images relating to the contents of the CD. Generally the insert or label is a sheet-like material made of paper or the like.
Optical storage, media such as CDs have become so ubiquitous that they now present a disposal problem. On the other hand waste optical media also present a potentially valuable resource in terms of the plastic material from
which they are formed, and in the case of some forms of optical media (eg
DVDs and writeable and rewriteable CDs), the precious metal reflective layer. Apart from the waste issue, there is also need for secure destruction of optical storage media storing sensitive information to prevent unauthorised access and/or copying of the information. This information may be confidential information or it may be copyright information or both.
Various methods have been proposed to reclaim potentially valuable material from optical storage media. These involve chemical, mechanical or a combination of mechanical and chemical treatments. In many cases, chemical solutions to the problem simply replace the waste problem caused by the optical recording media with a waste, disposal problem in terms of the disposal of spent chemicals
As far as we are aware, none of the solutions proposed thus far provide means that result in the reclamation of material not only from the optical recording medium itself, but also from the plastic container used to house the optical storage medium.
We have devised a method that allows for the recovery of plastic material from the optical storage medium itself as well as plastic material from the storage container, which method does not necessarily require the optical storage medium to be physically separated from its container prior to the recovery of the plastics material.
Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.
SUMMARY OF THE INVENTION Accordingly, in a first aspect, the present invention provides a method for the recovery of plastic material from a combination of:
(a) at least one optical storage medium formed at least in part from a first plastics material;
(b) at least one storage container adapted for holding said optical storage medium, the storage container being formed at least in part from a second plastics material; and
(c) at least one insert, label, wrapper or the like, the method comprising:
(i) providing said optical storage medium and said storage container in the form of granules and said insert, label, wrapper or the like in the form of pieces or the like;
(ii) introducing (i) into a gas stream to separate said granules from said pieces in said gas stream; and
(iii) removing at least some of said pieces from said gas stream.
The "at least one insert, label, wrapper or the like" to which reference is herein made may be formed from any material conventionally used in optical disk labels, insert or packaging. The insert, label and/or wrapper may in the form of a sheet or a film. For example, the material may be paper sheet and/or plastic film.
The storage container may be a jewel case conventionally used to store CDs and the like, although it will be clear that the method of the present invention has application to any storage container formed from at least one plastics material.
Step (i) may be carried out at the same location as steps (ii) and (iii) or step (i) may be carried out at a remote location and transported to the site at which steps (ii) and (iii) are performed.
Accordingly, in a second aspect, the present invention provides a method for the recovery of plastic material from the combination of:
(a) at least one optical storage medium formed at least in part from a first plastics material; (b) at least one storage container adapted for holding said optical storage medium, the storage container being formed at least in part from a second plastics material; and
(c) at least one insert, label or the like, the method comprising:
(i) subjecting said optical storage medium, said storage container and said insert, label or the like to granulation to produce a granulated product comprising plastic granules and pieces of said insert, label or the like;
(ii) introducing said granulated product into a gas stream to separate said granules from said pieces in said gas stream; and
(iii) removing at least some of said pieces from said gas stream. Steps (ii) and (iii) may be repeated, preferably until substantially all the pieces are removed.
The size of the granulated plastic material is preferably in the range of about 8 to 10 mm.
The first and second plastics material may be the same or different. The first plastics material may be a polycarbonate, which is conventionally used in optical disks, and the second plastics material may be a styrene polymer or copolymer and/or a ABS copolymer (acrylonitrile-butadiene-styrene) which is conventionally used in jewel cases. Conventionally optical disk storage containers comprise three types of plastics - polystyrene, high impact polystyrene with a minor proportion of ABS. The optical storage medium may be any optical recording medium eg
CD, CD-ROM, CD-R, CD-RW, CD-DA, CD-1 and DVD-ROM, DVD-R, DVD-RW and the like.
The gas stream may be an air stream.
We have further found that it is possible to separate a first plastics material from a second plastics material by submersing the two plastics materials in granulated form in a solution having a preselected specific gravity (SG).
Accordingly, the present invention provides, in a third aspect, a method for the recovery of plastics material from one or more material(s) containing at least two different plastics, the method comprising the steps of: granulating said one or more materials to produce granules of each of the different plastics materials; and submerging said granulated material in a liquid having a specific gravity equal to or falling between the specific gravity of one plastics material and selectively recovering one of the plastics materials.
The first plastics material may be an optical storage medium and the second plastics material may be a container therefor. The plastics may be laminated and the method may include a preliminary treatment to separate said laminate layers. In fourth and fifth aspects, the present invention provides a method in accordance with the first and second aspect respectively including as a further step, the method of the third aspect.
Accordingly, in another aspect, the present invention provides a method for the recovery of plastic material from a combination of: (a) at least one optical storage medium formed at least in part from a first plastics material;
(b) at least one storage container adapted for holding said optical storage medium, the storage container being formed at least in part from a second plastics material; and
(c) at least one insert, label, wrapper or the like, the method comprising:
(i) providing said optical storage medium and said storage container in the form of granules and said insert, label, wrapper or the like in the form of pieces or the like;
(ii) introducing (i) into a gas stream to separate said granules from said pieces in said gas stream; and
(iii) removing at least some of said pieces from said gas stream; wherein the method further comprises submerging said separated granules in a liquid having a specific gravity equal to >or falling between the specific gravity of one of said first and second plastics material and selectively recovering one of said plastics materials.
In another aspect, the present invention provides a method for the recovery of plastic material from the combination of:
(a) at least one optical storage medium formed at least in part from a first plastics material; (b) at least one storage container adapted for holding said optical storage medium, the storage container being formed at least in part from a second plastics material; and
(c) at least one insert, label or the like, the method comprising: (i) subjecting said optical storage medium, said storage container and said insert, label or the like to granulation to produce a granulated product comprising plastic granules and pieces of said insert, label or the like;
(ii) introducing said granulated product into a gas stream to separate said plastic granules from said pieces in said gas stream; and
(iii) removing at least some of said pieces from said gas stream; - wherein the method further comprises submerging said separated granulated product in a liquid having a specific gravity equal to or falling between the specific gravity of one of said first and second plastics material and selectively recovering one of said plastics materials.
The liquid used in the method of the foregoing aspects of the invention may be a solution. The solution used may be a salt solution. The salt may be sodium chloride. An advantage of using sodium chloride is that a conventional
dechlorinator (eg a swimming pool dechlorinator) may be used to treat the saline solution prior to disposing it to waste.
The solution may be contained in a settling tank or the like. The SG of the solution may fall in the range 1.02 to 1.2. The SG may be about 1.02.
The plastic material of the optical recording medium will usually comprise a metal film, which may be aluminium or a more valuable metal such as gold.
This metal film may be removed by subjecting granules of the first plastic to a metal recovery step. The optical recording medium may have printing thereon which may also be removed.
Accordingly, the present invention provides in further aspects respectively, a method of the fourth or fifth aspects, which further comprises a step in which a least a portion of metal associated with the separated granules of the first plastics material is recovered. The methods and apparatus of the invention extend to recovery of metals in addition to recovery of plastics.
The metal may be recovered by subjecting the separated first plastics material to wet mechanical agitation.
Preferably the wet mechanical agitation is carried out in the presence of a granular abrasive material, eg sand, to assist in the removal of printing from the surface of the granules.
The wet mechanical agitation may be performed in a hammer mill or the like.
In a further aspect, the present invention provides any plastics material and/or metal recovered by a method in accordance with the present invention. A particular advantage of the present invention is that it avoids the use of chemicals (apart from salt) in the process and so avoids the production of chemical waste that must be disposed of.
In a further aspect, the present invention provides an apparatus for the recovery of plastic material from the combination of: (a) at least one optical storage medium formed at least in part from a first plastics material;
(b) at least one storage container adapted for holding said optical storage medium, the storage container being formed at least in part from a second plastics material; and (c) at least one insert, label or wrapper, the apparatus comprising:
(i) granulation means for granulating said first and second plastics material and for forming pieces of said paper or the like;
(ii) at least one column provided with a means for providing a flow of gas and means for removal of paper from the column; and (iii) a settling tank or the like containing a liquid of preselected specific gravity.
Preferably the granulation means has a set of knives or the like on a rotary stator. An example of a suitable granulator is an Olmar granulator. Preferably the granulator is equipped with a vacuum chamber below the rotary knives to prevent the paper from clogging up the screen of the granulator.
Preferably, the flow of air through the at least one column is controllable by means of a valve. Preferably the apparatus of the present invention is equipped with a plurality of columns, each of the columns communicating at or adjacent their base with an adjacent column to allow granulated plastics material to pass therebetween. Each column may be provided with an opening adjacent the top of the column to allow paper to be blown out of the column into a collection point.
The means for providing a flow of air may be at least one fan, blower or compressor or it each column may have an associated fan or blower. In one particularly preferred embodiment, a single blower provides a flow of air in each column, with the flow of air being controlled by means of a valve. An alternative to using valves is to control air flow by using columns of different diameters. For example, a 100 mm diameter pipe could be used for the first column and pipes of diameter of about 300mm could be used for the other pipes. A combination of metering valves and column diameters may be employed.
In a further aspect, the present invention provides a settling tank, the settling tank having a sloping floor, the settling tank including skimmer means for skimming off granular material floating on a liquid contained in the settling tank and screw conveyer means or the like for conveying granular material from the floor of the tank to a location above the floor of the tank.
The skimmer means may be a set of paddles or the like connected by a set of mechanically driven circular chains to provide continual skimming of the liquid surface.
Whilst the present invention has been described with particular reference to optical recording media, it also has application in the treatment of other material(s), provided those materials can be granulated.
In order that the present invention may be more readily understood, we provide the following non-limiting embodiments
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a block diagram showing the various stages of an embodiment of a method in accordance with the invention; Figure 2 is a detailed schematic drawing of an embodiment of the granulation/paper separation stage of Figure 1 ;
Figure 3 is a detailed schematic drawing of an embodiment of the plastics separation stage of Figure 1 ;
Figure 4 is a detailed schematic drawing of the separation vessel; and Figure 5 is a detailed schematic drawing of the metal recovery section of the apparatus in accordance with the invention.
Embodiments
This particular embodiment is described with particular reference to the reclamation of plastics from CDs contained in jewel cases containing paper labelling/inserts.
Referring to Figure 1 , the CDs/jewel cases/paper inserts are subjected to a "plastic granulation/paper separation" stage 10. The plastic granules, substantially free of paper, are passed to a plastics separation stage 20 in which granules of the plastic material forming the CD (polycarbonate) are separated from granules of plastic forming the jewel case (polystyrene/ABS). The polycarbonate granules are transferred to a metal separation" stage 30 in which metal and printing are separated from the polycarbonate granules.
Figure 2, shows the plastic granulation/paper separation stage shown in Figure 1. In this stage, CDs, their jewel cases and paper labelling/inserts are fed into granulator 50. Granulator 50 granulates the plastic content of the CDs and cases and tears/shreds the paper inserts/labelling into pieces.
In this particular embodiment use was made of an Olmar granulator having rotary knives supported on a rotor. The granulator was modified to include a vacuum chamber 52. An air blower 70, connected to the vacuum chamber by means of pipe 56, reduces the pressure in vacuum chamber 52
whilst transferring plastic granules/paper pieces produced in the granulator to vertical pipe 60, the first of a series of vertical pipes. Application of a vacuum to the vacuum chamber prevents paper pieces from collecting on the screen of the granulator. We have found that this arrangement allows processing of input material containing up to about 60% paper.
The paper pieces are removed from the plastic granules in a series of vertical pipes 60 to 68 which have an opening 80 feeding into an air pervious collector 85. The first pipe 60 has a diameter of 100 mm, whereas the remaining pipes 62-68 have each have a larger diameter of 300mm. Each vertical pipe communicates with an adjacent vertical pipe via a blower (72, 74, 76, 78) and pipe (73). As can be seen from Figure 2, each vertical pipe is in fluid communication with an upstream blower and a downstream blower. For example, first vertical pipe 60 is in fluid communication with upstream blower 70 and downstream blower 72. Each upstream blower provides a positive airflow to produce an airstream in the associated downstream vertical pipe. The air speed of this airstream is adjusted by means of metering valve 77, which controls the negative airflow created by the associated downstream blower. The air speed in each vertical pipe is adjusted so that only the paper pieces are entrained in the air stream and transferred to paper collector 85, whilst the plastic granules fall to the bottom of the vertical pipe. The plastic granules freed with reduces paper content are transferred to the adjacent downstream vertical pipe by means of the associated downstream blower. In this arrangement the amount of paper removed decreases progressively from the first vertical pipe to the last pipe, with most paper being removed from the first pipe and very little being removed from the last pipe.
The plastics separation section is shown in Figure 3. Plastic granules leaving the last vertical pipe 68 contain little or no paper contamination. These granules are transferred to distributor 101 by means of air flow created by blower 80. Distributor 101 is in the form of a cyclone which removes entrained air from the granulated product. The air-free granules are gravity fed to a mixing vessel or bowl 103, which is located against a side of settling tank 200. Tank 200 contains a saline solution of SG 1.02. The mixing bowl 103 is in fluid communication with the interior of the separation vessel and permits saline solution on one side of a partition (not shown) to pass into the mixing bowl and mix with the plastic granules.
The mixture of plastic granules and saline is pumped by pump 123 into the settling tank via conduit 125. The SG of polystyrene is about 1.05 and that of polycarbonate is about 1.2. The polystyrene granules, being less dense than the saline solution, float to the top of the solution whilst the denser polycarbonate granules sink to the bottom of the tank.
The polystyrene granules floating on the saline solution are "grabbed" by a series of paddles 127 supported on a pair of driven circular chains 130 and moved towards outlet 140 after being sprayed with fresh water from sprayer 139 (see Figure 4). The rinsed polystyrene granules are transferred to a dryer 143 where they are dried and thereafter the dried granules are transferred to bulk storage container 145.
The denser polycarbonate granules settle on the sloping floor 160 of the settling tank and move towards well 162. The polycarbonate granules are raised by screw conveyer 164 to the top of the settling tank and the wet granules are transferred to the metal removal section as shown in Figure 4. At least some of the polycarbonate granules have thin film of a metal such as aluminium. Some of granules also have printing which has to be removed.
The wet polycarbonate is metered into a water/sand mixture contained in vessel 300 enclosing hammermill 302. The action of the hammermill removes the metal film while the sand assists in abrading the printing from the polycarbonate granules. Polycarbonate granules free of metal film and printing are removed from vessel 300 and transferred to storage container 306.
A portion of the water/sand mixture containing metal film and printing residue is pumped by pump 309 via conduit 308 to water cyclone 320, which separates out wet sand at the base of the cyclone (see Figure 5). The water/sand mixture is returned to vessel 300 by means of pump 322 via conduit 324. The metal film and printing removed by the treatment in vessel 300 floats to the top of the water cyclone and passes into collecting vessel 324 where the metal and printing are retained. Water is removed from vessel 324 and transferred to vessel 326. Water from vessel 326 is recycled by pump 328 to vessel 300 via conduit 400.
The polycarbonate and polystyrene recovered by the method described may be recycled.
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not
the exclusion of any other element, integer or step, or group of elements, integers or steps.
It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.