Chemistry of hydrocarbon compounds – Production of hydrocarbon mixture from refuse or vegetation – From synthetic resin or rubber
Reexamination Certificate
2000-01-31
2001-10-30
Yildirim, Bekir L. (Department: 1764)
Chemistry of hydrocarbon compounds
Production of hydrocarbon mixture from refuse or vegetation
From synthetic resin or rubber
C201S002500, C201S025000, C422S184100
Reexamination Certificate
active
06310264
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the processing of waste materials comprising combinations of aluminium and plastic. Such materials are used on a large scale, inter alia, in the packaging industry, for example in the packaging of drinks and the like. Known examples are the cans for soft drinks and beer; with bottles, too, such materials are used in the cap. These caps are made of aluminium and are internally coated with a plastic sealing layer.
BACKGROUND OF THE INVENTION
The caps are usually attached to the neck of the bottle by means of a screw thread. They can be provided with a safety strip which is broken when the bottle is opened. Such bottle caps produce a large amount of waste material which is difficult to reprocess. The plastic coating is quite firmly embedded in the cap and can be removed only with a great deal of effort. On the other hand, the plastic coating hinders the reprocessing of the aluminiun. The plastic residues would result in such contamination of the smelted aluminium as to make it unsuitable as a raw material.
The plastic coating in the bottle cap usually consists of PVC. This material, in contrast to many other plastics, does not affect the taste of the drink and can therefore not readily be replaced by some other substance which presents fewer problems during reprocessing.
On the other hand, the reprocessing of such materials, in particular bottle caps, has major advantages. First of all, the reprocessed aluminium constitutes an inexpensive raw material, in any case in comparison with production from bauxite. In the case of bottle caps, a closed cycle would be achievable, in which the aluminium can be continuously used for new bottle caps.
Account must also be taken of the fact that the fabrication of bottle caps makes use, as the starting material, of a plate or roll of aluminium which is printed beforehand with the desired lettering, designs and the like. From these plates the caps are then punched, waste material remaining behind which is partially printed. This material remaining behind when the caps are punched out would likewise have to be reprocessable at the same time, in order for a complete cycle to be achievable.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a method by means of which materials comprising combinations of aluminium and a plastic, in particular like those present in bottle caps, can be reprocessed into a usable raw material. To this end, the invention comprises the steps of:
pyrolysing the plastic in an inert atmosphere,
cracking or gasifying the gases or vapours which are released in the course of pyrolysis,
afterbuning the coke which remains behind on the aluminium in the course of pyrolysis.
The pyrolysis step is continued for a sufficiently long period to ensure that the HCl has been completely removed from the PVC of the coating in the bottle cap. The gases or vapours released in the process are recirculated and used as an inert, oxygen-free medium for creating the desired inert atmosphere during pyrolysis.
The gases or vapours released are then scrubbed to remove HCl and are used as an energy source for the pyrolysis process.
To supply the required energy to the pyrolysis process, the recirculated gases or vapours are heated.
In combination with the complete removal of the HCl, as cited above, pyrolysis is preferably carried out at an oxygen level of less than 0.2 vol % over a period of approximately 20 minutes.
For the purpose of complete removal of the coke formed during pyrolysis from the aluminium, the afterburning is preferably carried out at an oxygen level of 1.6% over a period of approximately 10 minutes.
The method according to the invention can be used to process not only PVC, but also materials comprising PE and/or PP. The material can also comprise paints and/or varnishes.
The method according to the invention is particularly suitable, as already stated, for processing bottle caps, wherein the material has a composition of approximately 70% Al, 20% PVC, 6% PE, 3% varnish and residues such as sugars.
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Alcoa Nederland B.V.
Yildirim Bekir L.
Young & Thompson
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