The present invention relates to a method and a device for making shaped articles from thermoplastic plastics, particularly non-cleaned, non-sorted plastic refuse.
With methods and devices of the type under consideration plastic refuse is plasticized in a roller extruder and fed into molds in which pressure is applied to the plastic filling the molds which are afterwards cooled and from which shaped objects are thereafter removed.
Methods and devices for a repeated use of plastic refuse or plastic trash have been not, however, known until now.
It is known that plastic refuse which was cleaned, sorted and re-granulated was treated together with a new plastic to produce plastic articles. Since the cleaning and sorting involves a manual work and the plastic refuse or trash is a garbage-like or trash-like non-homogeneous substrate no working forces are normally available in the economy to do this kind of work; and when such forces are found this kind of work is too expensive. A remarkable portion of new plastic does not solve the problem because the product consisted of such re-granulated material cannot be successfully marketed due to its quality and is a so-called second choice. It is particularly difficult to use this re-granulate due to high costs of production.
Re-granulates are as a rule plasticized for processing in worm-type extruders.
The solution of the problem has been found in the field of elimination of industry and household thermoplastic refuse and trash in the utilization of roller extruders disclosed, for example, in DE-PS No. 27 00 846. The roller extruder is so robust that it not only is able to process non-cleaned, non-sorted thermoplastic trash or refuse but also rock and metal particles included in the plastic trash or refuse so that the plasticized thermoplastic plastic remains homogeneous and has no quality deficiencies. The plasticized material pushed from the nozzle of the roller extruder, however, has been until now, calibrated into pieces of suitable size by hand, cut and fed into respective molds in which the plastic was pressed by suitable devices. The objects formed of plastic normally had the weight of less than one kilogram.
Despite the homogenizing and high pressures used for producing shaped articles such articles are of pure quality and no market exists for such articles. Such articles can be relatively expensive when there is a chance of amortization of initial costs; they should however not be expensive on the market where a consumer is found.
The thermoplastic refuse material plasticized in the roller extruder can result in the material which is acid-resistant, weather-resistant and resistant to insects and further damaging factors and which would have high rigidity.
In order to solve the problem of increasing amounts of collected plastic refuse or trash the elimination of which by burning is costly and problematic it has been suggested to introduce this refuse into the economical circuit as a worthwhile crude product which would find a consumer. It has been found that such product pallets should consist of articles which are large and heavy not only because a great deal of plastic refuse is consumed but also because heavy articles, for example having weight of 100 or many hundred kilograms are not of a third choice as it concerns their quality, but their properties, which affect quality of small products, can be utilized.
Three groups of shaped objects were selected as preferable product pallets, namely universal plates, solid profiles and hollow bodies. The solid profiles can be utilized similarly to bricks for making palisades; they can form non-prismatic shaped table plates, warning signal pedestals or the like.
In the production of these objects which has been carried out by methods as described herein above, such objects are always too expensive to be on the market, and practically it has been impossible to find consumers for such objects.