Patent Publication Number: US-2018029088-A1

Title: Method and apparatus for film treatment

Description:
RELATED APPLICATIONS 
     This application claims priority of provisional U.S. patent application 62/366,915, filed Jul. 26, 2016, which is incorporated by reference. 
    
    
     TECHNICAL FIELD 
     This technology relates to the removal of undesirable coatings from polymeric films in preparation for recycling. 
     BACKGROUND 
     Polymeric films to be recycled may have coatings that are undesirable in the recycled material. For example, such coatings may include inks, labels, adhesives, metallic films, and the like, as used in packaging or manufacture of personal care products such as diapers and diaper packaging. It may be desirable to process the polymeric films to remove the undesirable coatings prior to further uses of the films, such as recycled feed stocks for remanufactured plastics. 
     SUMMARY 
     Each of the following summary paragraphs describes an example of how the invention may be implemented as a combination of structural or method elements disclosed by the detailed description that follows. Any one or more of the elements of each summary paragraph may be utilized with any or more of the distinct elements of another. 
     In a given example, a method forms comminuted material by comminuting a coated polymeric film. The method advances the comminuted material between successive processing stations in a coating removal system. This is accomplished by conveying the comminuted material in a stream of conveyance fluid driven through a conduit reaching between the successive processing stations. 
     The method may comprise blowing the comminuted material through a conduit, discharging the comminuted material from the conduit into a milling device containing an aqueous solution for removing coating material from the comminuted material, and mixing the comminuted material with the aqueous solution in the milling device. 
     Additional processing may comprise pumping a mixture of the comminuted material and the aqueous solution through a conduit from the milling device to a straining device, pumping the mixture further through a conduit from the straining device to a washing device, and pumping a mixture of water and comminuted material from the washing device to a dryer. 
     An apparatus may thus comprise means for forming comminuted material by comminuting coated polymeric film, and means for advancing the comminuted material between successive processing stations in a coating removal system by conveying the comminuted material in a stream of conveyance fluid reaching between the successive processing stations. 
     In a given example, the apparatus includes a milling device containing an aqueous solution for removing coating material from the comminuted material. A conduit has an inlet configured to receive the comminuted material, and has an outlet configured to discharge the comminuted material into the milling device. A blower is coupled to the conduit to provide a stream of conveyance air for conveying the comminuted material through the conduit. 
     The apparatus may further include means for straining a mixture of the comminuted material and the aqueous solution, and means for pumping the mixture from the milling device to the straining means. 
     Additional elements may include means for washing and rinsing the aqueous solution from the mixture, means for pumping the mixture from the straining means to the washing means, and means for pumping a mixture of water and comminuted material from the washing means to a dryer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of components of a system for the treatment of coated plastic film material. 
         FIG. 2  is a schematic showing additional components of the system of  FIG. 1 . 
         FIG. 3  also is a schematic showing additional components of the system of  FIG. 1 . 
         FIG. 4  is a detailed schematic view of a component shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The system illustrated in the drawings can be operated as recited in the method claims, and has components that are examples of the elements recited in the apparatus claims. The illustrated system thus includes examples of how a person of ordinary skill in the art can make and use the claimed invention. It is described here to meet the enablement and best mode requirements of the patent statute without imposing limitations that are not recited in the claims. 
     As shown in  FIGS. 1-3 , a system  10  is provided for the treatment of coated polymeric film material  12 . The system  10  has components arranged as successive processing stations at which the film material  12  is treated. These include a comminuting device  20  at one end of the system  10 , as shown in  FIG. 1 , and an extruder  22  at the opposite end of the system  10 , as shown in  FIG. 3 . Intermediate processing stations are defined by a mill tank  24  ( FIGS. 1 and 2 ), as well as a dump tank  26 , a washer  28 , and a dryer  30  ( FIG. 2 ). The components  20 - 30  may be interconnected to operate under the control of a PLC  32  with a monitor  34 . 
     A conveyance subsystem  40  reaches through the system  10  to advance the film material  12  between successive processing stations, also under control of the PLC  32 . As further shown in the drawings, the conveyance subsystem  40  includes conduits and pumps that convey the film material  12  between successive processing stations in streams of conveyance fluid. 
     The coated polymeric film material  12  is obtained from a manufacturer or other source of recyclable material, and is typically provided in bales of separate pieces, such as bags, or in rolls of continuous pieces. The film material  12  may also be provided as a collection of separate pieces of scrap material having a range of differing sizes and shapes. In each case, the film material  12  is inherently flexible and tends to deform, such as by crimping or tangling, more easily than relatively thick-walled plastic pieces such as bottles and the like. Accordingly, the film material  12  is shredded, granulated, or otherwise comminuted in the comminuting device  20  before being advanced further through the system  10 . This reduces the sizes of separate pieces of the film material  12 , and also renders them more uniformly sized and shaped, so that the comminuted film material  12  is flowable through the system without becoming tangled or jammed. 
     As shown in greater detail  FIG. 4 , the comminuting device  20  in the given example includes both a shredder  42  and a granulator  44 . The film material  12  is placed on a conveyor  46  that takes the film material  12  to the shredder  42 , or the film material may alternatively be placed directly into the shredder  42 . The shredder  42  cuts the film material  12  into smaller pieces, and dumps the cut film material  12  onto another conveyor  48  that takes it to the granulator  44 . 
     Once the cut film material is in the granulator  44 , it is size-reduced to a specified size based on the material and application. Different size screens in the granulator  44  allow the cut film material  12  to be reduced to different sizes. The screens sort the granulated film material  12  and allow it to fall into receptacles  50  such as boxes or bags, or into a pump, once it is reduced to the size needed. 
     Referring again to  FIG. 1 , a box  50  of the granulated film material  12  is loaded into a box dumper  56 , which dumps the granulated film material  12  into a receptacle  60 . The conveyance subsystem  40  includes a light material feed pump  62  in a conduit  64 . The conduit  64  has an inlet  66  at the receptacle  60 , and has an outlet  68  at the mill tank  24 . The pump  62  drives a stream of conveyance air that blows the granulated film material  12  through the conduit  64  from the receptacle  60  into the mill tank  24 . 
     The mill tank  24  contains an aqueous solution for removing coating material from the granulated film material  12 . The aqueous solution may have any suitable composition known in the art, and may alternatively have a composition as described in any one or more of the following U.S. Patent Applications, each of which is incorporated by reference: 
     U.S. patent application Ser. No. 14/830,529, filed Aug. 19, 2015. 
     U.S. patent application Ser. No. 14/830,639, filed Aug. 19, 2015. 
     U.S. patent application Ser. No. 14/830,626, filed Aug. 19, 2015. 
     U.S. patent application Ser. No. 14/830,614, filed Aug. 19, 2015. 
     U.S. patent application Ser. No. 15/049,105, filed Feb. 21, 2016. 
     U.S. patent application Ser. No. 15/049,106, filed Feb. 21, 2016. 
     U.S. patent application Ser. No. 15/049,107, filed Feb. 21, 2016. 
     The aqueous solution in the mill tank  24  is preferably heated before the granulated film material  12  is inserted. The mill tank  24  has an agitator, such as a shaft with three blades, that stir and mix the contents. This provides heat, friction, and chemicals that together remove the coating material from the granulated film material  12 . 
     Samples of the granulated film material  12  are taken out of the mill tank  24  periodically to perform a contaminant count, to determine parts per million of coating on the plastic, until the material passes inspection. Usually the initial sample is weighed, then the coated pieces are pulled out and reweighed. Then a calculation using both weights is performed to determine the parts per million that are still coated. 
     As shown in  FIG. 2 , the conveyance subsystem  40  in the illustrated example further includes a conduit  70  with an inlet  72  at the mill tank  24  and an outlet  74  at the dump tank  26 . Once the granulated film material  12  passes inspection at the mill tank  24 , it is conveyed through the conduit  70  from the mill tank  24  to the dump tank  26 . A pump  76  uses the aqueous fluid in the mill tank  24  as the conveyance fluid for this movement of the granulated film material  12 . 
     The dump tank  26  strains the aqueous solution from the granulated film material  12 . Specifically, the granulated film material  12  goes across a screen where the water and chemicals drain into a separate section of the dump tank  26 . Once the material goes across the screen it falls into a larger section of the dump tank  26 . 
     There are a few ways to feed the material through the dump tank  26  into the next phase of the process. One way is to use an auger to push the material through the bottom of the tank. Also a rotary valve can be used with the auger system to help push material through the tank. If the auger is used, water is sprayed onto the auger and material to keep the plastic wet, to allow the auger to push the material. Another way to move the material through the dump tank  26  is to remove the rotary valve at the bottom of the tank, and have the operator use a manual slide to regulate the flow rate of the material. 
     Once the granulated film material  12  is pumped out of the dump tank  26 , it goes into the washer  28 , which washes all the chemicals off the plastic and rinses it with water. In the illustrated example, the conveyance subsystem  40  includes a conduit  80  having an inlet  82  in the dump tank  26 , an outlet  84  at the washer  28 , and a pump  86  for driving the granulated film material  12  through the conduit  80 . 
     Next, a pump  90  drives the granulated film material  12  through a conduit  90  having an inlet  92  at the washer  28  and an outlet  94  at the dryer  30 . Finally, the cleaned and dried granulated film material is pushed out of the dryer  30  and into receptacles  50  for transportation to the extruder  22 . 
     The extrusion phase is started by pumping the cleaned, dried granulated film material  12  out of the receptacles  50  and into a hopper  96  at the extruder  22 . In the illustrated example, this is accomplished by a pump  100  in a conduit  102  in substantially the same manner that the coated granulated film material  12  is delivered to the mill tank  24  by the pump  62  and conduit  64  described above with reference to  FIG. 1 . Once the material is loaded into the hopper  96 , it is fed into the extruder  22 . The material is extruded using the appropriate speeds and temperature for the material. As the material is extruded, it is made into small round pellets using an underwater pelletizer. The pellets are then pumped through pipes into a drying system and then into boxes, ready for inspection. 
     This written description sets for the best mode of carrying out the invention, and describes the invention so as to enable a person of ordinary skill in the art to make and use the invention, by presenting examples of the elements recited in the claims. The detailed descriptions of those elements do not impose limitations that are not recited in the claims, either literally or under the doctrine of equivalents.