1. Field of the Invention
This apparatus provides a mechanism for continuously removing labels and similar contaminants from granulated material prior to its reclamation into a manufactured product. Primarily, the apparatus is used to remove adhesive backed product labels from granulated plastic containers prior to their reprocessing into plastic pellets. The need for this process is particularly acute with blow molded plastic containers which have paper and plastic labels affixed to large areas of their surface.
Because this apparatus is continuous in operation, it can be placed in line with other automatic processing equipment such as granulators, washers, classifiers, dryers, and extruders.
2. Description of the Prior Art
Within present plastic material reclamation technology, much attention is being given to the needs of increasing the quality of the end product. Removing contamination from the material prior to pelletizing in an extruder is now recognized as a mandatory step in this direction. A significant step in contamination elimination is the removal of product labels and the accompanying adhesive from blow molded containers.
To date, most processes specializing in fiber removal from granulated plastic have used one of two technologies. In some cases, separation is done directly after granulation with air classification systems where the granulated material falls through a labyrinth with a counter air flow which entrains the light materials. (See references to air classification in Tomaszek, U.S. Pat. No. 4,728,045.) Though this will effectively remove fibrous materials which are physically separated from the plastic granules, it can do nothing with the label material yet affixed to the plastic base.
A second, and most commonly used process, involves baths of aqueous solutions in which the label contaminated material is either soaked or agitated at high energy levels. Most notable among these processes are those by Hannigan et al. (U.S. Pat. No. 4,830,188), Nowicki et al. (U.S. Pat. No. 4,379,525), and Beck (U.S. Pat. No. 3,833,178). Though effective in removing labels from granulated plastic containers, these methods often result in complex batching apparatus and a high degree of complexity in clean-up to avoid cross-contamination in subsequent batches.
Other label removal technics have also been used. In one technology heat is used to deform the container prior to further label removal. (Refer to Baldyga, U.S. Pat. No. 4,033,804.) These processes consume relatively high input levels of energy in the form of radiant heat. They will also require additional separation methods as noted above.
A final process addressing the need to further remove the label and adhesive material is a batch process which subjects the material to repeated impact from rotating members. Though effective, these attempts are batch processes and lack the advantages of a continuous process. In general, batch methods are less adaptable to the requirements of other continuous production technologies, and often involve more complex and costly equipment.
The technology of this invention is a significant advancement over the prior art in that it has achieved an effective apparatus for removing adhesive and label contaminants from granulated plastic containers. Further, it has achieved this end with a continuous process.