Patent Application
20130119171
Not Applicable.
Not applicable.
The present invention relates to an assembly and system for recycling plastic waste material. More specifically, the present invention relates to an apparatus and method for recycling plastic film and/or rigid plastic material that includes washing and purifying the recycled plastic to create extruded plastic pellets that may be used to manufacture plastic products, including consumer packaging products.
Popular use of plastic to manufacture consumer and industrial products results in a substantial amount of plastic waste being available for recycling into material for again manufacturing such products, but very little is recycled an used in this manner. Despite public interest in reclaiming materials form waste and the rise in plastic waste collection efforts, most plastic waste is buried in landfills and is never recycled. A main reason plastic recycling is not more widely practiced is that conventional recycling processes commercially viable for large volume of material do not yield plastic free of contaminants such that the plastic has the purity for universal use in manufacturing processes. For example, conventionally processed recycled plastic is not suitable for certain manufacturing processes such as the process for making plastic film products. Similarly, conventional recycled plastic is not suitable for use in manufacturing food packaging for which strict compliance with specific criteria must be met, including U.S. Food and Drug Administration guidelines and approval criteria. It is desirable for recycled plastic material to meet such guidelines and to be suitable to manufacture a variety of products without restriction. As a result of such limited applicability of conventional recycled material, there is generally less demand for the material.
Accordingly, it is desirable to avoid contaminants in recycled plastic material, such as cellulose (paper fiber) and adhesives (residual of glue). It is also desirable to avoid blends of different types of plastic polymers, such as contaminants of polystyrene in recycled polypropylene material. These types of contaminants are typical in plastic material generated from conventional recycling equipment and processes available today.
There have been attempts to address issues of the purity of recycled plastic material. For example, the U.S. Pat. No. 5,667,151 issued to Miura et al. discloses a process for collection of plastic waste that includes the steps of crushing the waste plastic and subjecting the crushed material to a heat and passing the material through a trough with a specific piping with a spiral shape. U.S. Pat. No. 6,588,597, issued to Arakane et al., discloses a system for treating plastic material that includes dry cleaning of the material, which includes crushing the plastic into small pieces and applying a mechanical impact force on the particles in an effort to clean the plastic of debris without the use of a wash liquid. Additionally, U.S. Pat. No. 5,143,308, issued to Halley et al. discloses a recycling system in which plastic material is separated by the type of plastic, and the material is ground and converted into flakes for processing to remove contaminants from the surface of the flakes. Finally, U.S. Pat. No. 5,894,996, issued to Williams, discloses a method for reclaiming plastic which includes the steps of fragmenting the plastic and “sizing” the fragments to remove certain size fragments prior to continuing with additional steps to loosen contamination from the selected fragments in a specifically structured vessel.
These methods and assemblies, however, have not resolved the need for a reliable and commercially feasible process and assembly that recycles plastic material into a versatile highly purified state. Thus, there remains a need for a plastic recycling system that is both economical and reliable for producing high volume of recycled plastic material that has the purity for use in manufacturing a variety of products, including food packaging products and the desire for such plastic material to meet FDA approval for food-contact packaging. These and other objectives are met with the invention disclosed herein, providing solutions heretofore unavailable.
It is an object of the present invention to provide an assembly for recycling plastic waste material that has an intake for introducing the waste material into a universal shredder having a shredder blade and an output for directing shredded plastic waste material toward a shredder conveyor apparatus that is configured to convey the shredded material toward a rigid plastic recycling line or to a plastic film recycling line. The rigid plastic recycling line has a rigid material grinding assembly and a water bath assembly for separating the rigid plastic material by density, and the rigid line also has at least one dryer apparatus for drying each type of separated rigid material. The film recycling line has a film grinding assembly and a hot washer apparatus and an agitation device for soaking the plastic film and mixing the plastic for additional washing, followed by a water bath for separating the debris and waste products from the plastic film. The assembly further has at least one extrusion assembly that is comprised of two extruders, each having a filtering mechanism to filter the extruded plastic material to further remove contaminants from the extruded plastic.
The invention also provides a universal shredding assembly with a universal shredding blade assembly, as an elongated shredding blade formed of a plurality of blade segments stacked together. Each blade segment has a central axis and an outer peripheral area with at least one cutter kerf extending to an outer edge of the peripheral area, the cutter kerf providing an exposed cutting edge. The cutting kerfs are arranged such that a kerf from one blade segment is aligned forward of a kerf of an adjacent blade segment, thus providing multiple sequential cutting edges along the blade length. These stacked blade segments combine to form a general spiral arrangement of cutter surfaces surrounding the axis of the assembly.
Another feature of the present invention is to provide a method of recycling plastic film material that includes shredding the plastic film and subsequently soaking and agitating the shredded film material and then subsequently separating debris and contaminants from the plastic in a water bath. This method provides highly washed and enhanced purity of the ground plastic being recycled.
The invention further provides an apparatus and method for processing recycled plastic in a multi-stage extruder apparatus that has a first extruder with a filter screen and a second extruder with a second filter screen. Further, the invention provides for the pressure of the multi-stage extruder apparatus to be at least partially adjusted by a hot melt pump in line with the extrusion apparatus.
Other features and advantages of the invention will be apparent from the following specification, taken in conjunction with the following drawings.
To understand the present invention, it will now be described by way of example, with reference to the accompanying drawings in which:
While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated.
The present invention provides an assembly and a system for recycling plastic waste products of different types, including plastic film, such as film made of polyethylene or polypropylene, or rigid plastic waste that includes polypropylene, polystyrene, and/or PET and which also often includes metal contaminants. A significant aspect of the invention is the ability to produce recycled plastic material that is highly pure and thereby very useful in manufacturing products, including consumer products such as food containers and the like. This has not been available with conventional processes and equipment. Another significant aspect of the invention is to provide an apparatus that is capable of processing either film or rigid material in a manner that utilizes a common initial grinding apparatus and a common water bath assembly. Thus, recycled plastic material produced according to the present invention has heretofore not existed and, thus, is an improvement over conventional recycled plastic material.
The apparatus 10 according the present invention, as shown in the Figures, preferably utilizes a single plastic waste intake 12 that introduces the waste material to an initial universal shredder 14. In the preferred form, the intake includes a conveyor belt 16 that extends at an incline to elevate the waste material W to be fed into an open top of the universal shredder 14. As the waste material W is shredded in the universal shredder 14, the shredded plastic material 18 is delivered to a conveyor assembly 20 positioned adjacent the shredder 14, preferably as a reversible conveyor belt 22 under the shredder 14. The reversible conveyor 22 is configured to move in a first direction toward a plastic film recycling line 24 and alternatively in a second direction toward a rigid plastic recycling line 26. This is a central feature of an aspect of the invention, wherein the plastic material W is processed into a recycling apparatus and method, by first shredding the waste material in an initial shredder 14, and wherein the conveyor transporting the shredded material 18 is connected to at least a plastic film recycling line or a rigid plastic recycling line. Thus, according to this aspect of the preferred embodiment, the waste material being recycled is subject to a pre-grinding process in which the waste material is shredded, and wherein the assembly performing the shredding is a universal shredding device 14 rather than requiring separate shredder assemblies for each type of plastic waste material W.
The universal shredder 14 has a shredder housing 30 with a rotational shredder blade assembly 32. The unique structure of this blade assembly 32 is configured to provide a blade design that is useful for shredding all types of plastic materials, including the plastic of film material and rigid material. As is shown in
Each blade segment 34 preferably is formed as a generally flat metal blade having an outer edge 50 such that the outer cutting teeth 46 extend to the outermost peripheral edge 52, preferably having all of the cutting teeth 46 reside in the same circumferential region of a circular outer peripheral edge 50. The cutting teeth 46 are formed as a cutting kerf 54 that includes an inward notch 56 and a protruding cutting edge 58. The outer edge 50 of the blade segments 34 also include a plurality of protruding blunt kerfs 60, preferably positioned between adjacent cutting kerfs 54 about the outer edge 50. The blunt kerfs 60 preferably do not extend to the outer peripheral edge and, thus, are configured to mix material being shredded in the shredder assembly 14 without acting as a shredding blade surface of the blade assembly 32.
Each blade segment 34 of the blade assembly 32 is preferably positioned in a rotational orientation relative to an adjacent blade segment 34, such as is shown in
The shredded material 18 exiting the shredder 14 is transported by a conveyor assembly 20, such as by dropping on the reversible conveyor belt 22, as shown in
It is advantageous for the rigid line 66 to also provide an in-line fines separator 82 to filter out the fine plastic material that includes dust of plastic material difficult to process in the recycling system because the particle size is too fine for conventional techniques. In the preferred form of the apparatus 10, the fines separator 82 is positioned directly in line with the rigid recycling process, and consists mainly of a blower assembly 84 and a fines filtration unit 86. Having this apparatus in line with the feed of the rigid material 66 provides an assembly 82 that positions the fines collector 86 in line with the air flow from the blower 84, which is also preferably in line with the direction of the material transported from the rigid material grinder 76 through the passageway 88 positioned below the grinder 76.
As can be appreciated by the Figures, including
In the preferred embodiment of this aspect of the invention, as shown in
The hot water soak apparatus 102 preferably includes a mixing operation with the introduction of hot water, such as is achieved with a screw-type drive mechanism 104 inside a washer housing 106 of the washer apparatus 102. In this manner, the plastic material 72 passes from the film grinder 94 through a transport duct 108 to a washer in-feed 110. Once inside the washer apparatus 102, heated water, preferably to a temperature in the range of 150 to 100 degrees Fahrenheit is introduced into the housing 106 to mix with the material 72. The screw mechanism 104 then turns the wet material 72 inside the housing 106, causing the heated water to mix with the material for a thorough wash of the plastic with the heated water. In a preferred form of the invention, the housing 106 of the hot washer 102 includes an outer drum 105 which rotates at an opposite direction from the inner drive 104. Preferably, the outer drum 105 rotates at a slow speed in the range of approximately 6 revolutions per minute and the inner drive 104 rotates at a more rapid speed of approximately 40 revolutions per minute. This rotation of the components of the washer 102 enhances the mixing operation within the hot washer to assure the plastic material 72 is thoroughly soaked with the hot water.
The next step of the water wash process 100 is for the material 72 exiting the hot washer 102 to be mixed in an agitation process 110 in a high-speed mixer apparatus 112. The plastic film material 72 is preferably transported from the hot washer 102 to the mixer 112 via a wet material conveyor system 114 that has a hosing 116 with an internal conveyor (not shown). The wet-material conveyor 114 transfers the material from an end of the washer housing 106 to an in-feed hopper 118 of the mixer 112. The wet material 72 then enters the body 120 of the mixer which houses a mixing drive 122.
In the preferred form of the invention, the mixing drive 122 includes an elongated central drive shaft 124 and a plurality of angular surfaces 126 along an extent of the drive shaft 124. As shown in
The next step of the film line 70 is for the film material 72 exiting the water wash process 100 (the hot washer 102 and the agitation by the mixer 112) is inserting the material into the water tank 90 at a first end 92. The film material 72 inside the water tank 90, because of its density properties, floats in the top area of the water in the tank 90. Contaminants in the film material, such as paper which has been saturated by the water wash process and the time in the water tank, sinks to the bottom of the tank 90, towards the bottom transfer mechanism which, in the preferred embodiment, is an elongated screw drive mechanism 138 located near the bottom of the water tank to capture and move the sinking material along the length of the tank 90. Preferably, the screw drive 138 rotates in a direction to force the material within the screw drive back toward the first end 92 of the tank 90. The film material 72, which has them been rid of contaminants by the water soaking, agitation and time spent in the water bath tank 90, is then transferred from the water tank 90 into the remainder of the process, as described herein. Significantly, this combination of processes of the water wash 100 and the time passing through the water bath tank 90 is one of the key aspects of the present invention, as the purity of the plastic material created by the process is much greater than achieved through conventional recycling processes and equipment.
When the apparatus 10 is processing rigid plastic 68 instead of film material 72, such that the rigid line 66 is operational, the rigid material 68 is introduced into the tank at the first end 92 of the tank 90. In the tank 90 of water, the less dense plastic material floats near the top of the tank 90, whereas the dense plastic material sinks to the bottom toward the screw drive assembly 138. Thus, the rigid plastic that is inserted into the water bath tank 90 separates according the density of the material, with plastics such as polypropylene and polyethylene rising to the top and material such as polystyrene and PET sinking to the bottom. In this manner, the less dense plastic material 68A remains at the top of the water and separately the dense plastic material 68B will sink to the bottom, such that the two are independently purified as the process continues and the two are separately transferred from the water bath tank 90 as described herein. As shown in
The water bath tank 90 includes a skimming apparatus 140 which resides at the top of the water tank 90 to urge the floating plastic material along the length of the tank 90. In the preferred form of the invention shown in the Figures, the skimming apparatus 140 is comprised of a series of paddle wheels 142, each having a length that spans substantially the width of the tank 90. The paddle wheels 142 are configured such that a first paddle wheel 144 is positioned adjacent the first end 92 of the tank 90, shown as the left side of the tank in the Figures. The paddle wheels 142 in this arrangement rotate counter-clockwise such that a leading face 146 of each paddle segment 148 pushes into the water and along the upper surface of the water in the tank 90. As the paddle wheels are preferably partially submerged in the water of the tank 90, the material is moved along the length of the tank 90 with minimal resistance. In the preferred form of the assembly 10, the first group of paddle segments 148 passing through the water at the first end 92 are generally solid and flat surfaces, such as shown in
In the preferred embodiment, the paddle segments at the terminal end 152 of the bath tank 90 include a plurality of outwardly-extending stems 154 which collectively are configured as a rake structure 156 protruding from the outer portion of the paddles 148 along at least an extent of the length of the paddles 148. Additionally, the paddles of the final paddle wheel assembly at the terminal end 152 preferably has many perforations 150 to provide an even greater amount of the paddle being open for water to pass through relative the other paddles, thus being configured to move the floating plastic without causing much turbulence to the water. This arrangement of numerous openings in the surface of the paddle wheels 142 that reside near the terminal end 152 of the tank 90 provides structural features that increase the ability for the paddles to move material through the final part of the tank 90 and into the hopper 160 at the end of the bath tank 90. The hopper 160, therefore, receives the less dense rigid plastic material that floats in the water bath tank 90 when the rigid line 66 is in operation, or it receives the plastic film material 72 that has been washed and separated from contaminants such as paper in the water bath tank 90 when the plastic film line 70 is in operation.
The cleaned/separated plastic material that is loaded into the end hopper 160 is ready for the next stage of the process—the drying process that precedes extrusion of the plastic. The drying process preferably includes the steps of first straining water from the plastic material in the hopper 160, spinning the material to remove additional water, and then subjecting the material to air drying for final removal of moisture on the surface of the plastic. Keeping with the objective of the invention to practice a method of creating a highly purified recycled plastic material by thorough washing and separation of the plastic material form other materials, the present invention provides a complete drying step to result in a final ground recyclable material that is substantially free of moisture. As shown in
The blower passageway 170 is preferably a substantially closed system that includes partial ventilation along its path through its length, and terminates at a final location for collecting the plastic material. Along that path of the elongated blower passageway 170, different arrangements of the passageway are included to mix the material being dried, including bends and undulations of the passageway 170, such as with the coil segments 174 shown in
The material passing through the blower passageway 170 exits the terminal end 178 and, depending on the material being processed, is collected for the final step of the recycling process—extrusion. When the film line 70 is in operation, as shown in
This is a significant aspect of the invention in that, while the rigid line 66 is operational, a separate simultaneous extruder process is carried out for both the less dense material that is dried in the blower passageway 170 and the dense material from one output of the color separator 184. Specifically,
The extrusion step of the recycling processes of the apparatus 10 utilizes an extruder assembly 200 that preferably has two extrusion lines, a first extrusion line 202 and a second extrusion line 204, as shown in
In the preferred form of the invention, each extruder line 202, 204 included multiple, preferably two, extruders 206 that are unified in line together as a continuous extrusion process. Each of the extrusion lines 202, 204 are substantially identical in components, each including an in-feed hopper 208 for receiving the cleaned plastic material and inserted into a first in-line extruder 210. The plastic material is heated and extruded into the first inline extruder 210, preferably as a twin-screw extruder, with conventional technique and extruder equipment. The material is passed from the first extruder 210 to a second in-line extruder 212, which is preferably positioned transverse to the first extruder 210, such that the two extruders are being generally transverse to one another as shown in the Figures. Significantly, the extrusion process through each extruder line 202, 204 includes at least one, and preferably two, screen filtration steps 216. Each screen filtration step 216 is a process in which the material form an extruder 210, 212 passes through a screen filtration device 218, which, as shown in
As shown in the Figures, each extrusion line 202, 204 preferably has two dual-screen changer apparatus, one located after each of the two in-line extruders 210, 212. In the preferred embodiment, each extrusion line 202, 204 also includes components for monitoring and adjusting the pressure in the extruder, such as utilizing a pressure gauge and joining a hot-melt pump 226 in communication with the extruder. This assembly for pressure regulation assist with the consistency and flow control of the material being extruded. This arrangement of multiple screen filtration 216 with each filtration step associated with an inline extruder 210, 212 is configured to filter contaminants from the plastic material being extruded and to enhance mixing of the extrusion material. This is a significant aspect of the process and apparatus of the invention, providing increased purity and uniformity of the recycled plastic end product. This end product is harvested by the final operation of pelletizing 228 the material in a pelletizer apparatus 230 associated with each extrusion line 202, 204. The pelletizer 230 utilizes conventional techniques for such devices, using water to cool the pellets and subjecting the pellets to a drying operation in a dryer assembly, and the resulting dried pellets are then transported to a finished product storage container 234.
The resulting harvested recycled pellets derived from the process steps disclosed herein have a remarkably high purity as compared with conventional recycling processes, primarily due to the unique washing process and multiple in-line extruders 210, 212 with screen filtration 216. In the case of the film line 70 in operation, the water wash process 100, which preferably includes use of a hot water washer 102 and a high speed mixer apparatus 112, is a process that results in high purity of the plastic material for extrusion because an increased amount of separation of contaminant debris is achieved in the water bath tank 90. This results in overall surprising levels of purity of the final extruded product. Further, with regard to both recycling lines 66, 70, the unique arrangements of multiple in-line extruders with intermediate filtration processes 216 provides a high purity of the final extruded pellet product.
One advantage of the method and apparatus of the present invention is the efficiency of providing numerous components of a recycling process with a generally closed system for water use and purification. This aspect of the apparatus and process provides conservation of resources to operate a recycling process, increased efficiency and lessens waste produced as a by-product of the process. In a preferred form of the invention, several of the components of the system are interconnected to a single water purification assembly 240. As shown in
In the embodiment shown in
