Method and apparatus of recycling previously used agricultural plastic film mulch

A method and apparatus for recycling previously used agricultural plastic film mulch in which the plastic film mulch is fed by a conveyor along a predetermined path of travel, while being agitated and shaken on the conveyor to dislodge and remove dirt and debris therefrom, shredding the plastic film mulch into discreet pieces in a shredder while removing additional dirt and debris therefrom, conveying the shredded plastic film mulch through a vertical separator along a second, tortuous path of travel, while drying the shredded plastic mulch by heated air and agitating the plastic film mulch by projections extending into the second path of travel to dislodge and remove still further dirt and debris therefrom, and extruding the cleaned and shredded plastic film mulch into a reusable form in an extruder, which melts the plastic film mulch, screens solids from the molten plastic, and extrudes the molten plastic into a reusable form, such as pellets.

FIELD OF THE INVENTION 
This invention relates generally to the recycling of plastic films and more 
particularly to a method and apparatus for recycling plastic webs 
previously used as mulch in agricultural fields. 
BACKGROUND OF THE INVENTION 
It is very common in many agricultural fields and with many different 
agricultural crops, such as vegetables, to use plastic film webs as mulch 
covering the rows or seed beds. Plastic webs preserve moisture, inhibit 
weed growth and permit fumigation of the soil. 
The rows or seed beds are prepared to have a planting surface above the 
level of the ground between the rows. The raised beds are covered by a web 
of plastic film and the opposite side edges of the plastic web are held 
down by a small amount of soil placed thereon. The crop is planted in the 
rows or seed beds by punching or cutting holes in the plastic webs at 
spaced intervals and setting plants or seedlings in the seed beds through 
such holes. 
The plastic webs inhibit weed growth and conserve moisture. In addition, 
the crops may be irrigated by percolating water from below into the seed 
beds, with such percolation being assisted by plastic webs. A plastic web 
generally can be used for two successive crops and sometimes even more 
before it must be removed and replaced. 
Upon removal of the used plastic webs from the agricultural field, disposal 
of such used plastic webs is a distinct problem. Heretofore, it has been 
common to dispose of such agricultural plastic mulch by depositing the 
same in landfills. Such landfills usually charge for the disposal of such 
agricultural plastic mulch by volume and weight and, accordingly, such 
disposal has been very expensive. 
In more recent times, landfills are refusing to accept agricultural plastic 
mulch for disposal. Accordingly, users of such agricultural plastic mulch 
have few, if any, disposal options currently available to them. The used 
plastic film mulch simply accumulates in large mounds or stacks at the 
ends of the agricultural fields from which such agricultural mulch has 
been removed, or at other equally unacceptable locations. 
In Applicant's application, Ser. No. 08/213,688, filed Mar. 16, 1994, now 
U.S. Pat. No. 5,452,652, there is disclosed an apparatus for removing and 
baling plastic mulch when it is desired to remove the same from the seed 
beds on which the plastic film mulch has been used. While such an 
apparatus effectively removes the plastic mulch and compacts and bales the 
same into compact form, the users of plastic mulch still are faced with 
the same disposal problems that existed with other forms of plastic mulch 
removal. 
Disposal options, other than burying in landfills, for the agricultural 
mulch are further limited by the significant amounts of dirt, debris and 
the like which adhere to the used plastic film mulch after it is removed 
from the seed beds. Heretofore, the only effective means for removing the 
dirt, debris and the like from the used agricultural film mulch has been 
to wash the plastic mulch with water. The use of water on the plastic 
mulch is highly undesirable because of the volume of water required, the 
disposal of the contaminated water and the difficulty in drying the 
plastic mulch so that it may be further processed. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a method and 
apparatus for recycling plastic film mulch from agricultural fields which 
solves the problems previously attendant to disposal of such agricultural 
film mulch. 
It is a more specific object of the present invention to provide a method 
and apparatus for recycling previously used agricultural plastic film 
mulch in which dirt, debris and the like are removed from the previously 
used agricultural film mulch, the agricultural film mulch is shredded into 
relatively small pieces and the shredded plastic film mulch is extruded 
into a reusable form. 
The foregoing objects of this invention are accomplished by a method and 
apparatus in which the previously used agricultural film mulch is formed 
into a relatively loose, linear mass by being either unrolled from the 
roll in which it was formed during removal or by breaking down the bales 
formed by the apparatus disclosed in Applicant's co-pending application. 
The loose mass of plastic film mulch is then transported or conveyed along 
a predetermined path of travel during which significant portions of the 
dirt, debris and the like adhering thereto are removed by agitating or 
shaking the plastic film mulch to dislodge the dirt and debris therefrom. 
In addition, an electromagnetic device attracts and removes any metal 
pieces that might be lodged in the loose mass of plastic film mulch. 
Thereafter, the plastic film mulch is shredded to reduce the form thereof 
into relatively small pieces or particles while removing additional 
amounts of dirt, debris and the like therefrom. 
After being shredded, the plastic film pieces are fed through an additional 
cleaning and moisture removal step. More specifically, the shredded 
plastic mulch is fed through a tortuous path of travel within a cleaning 
device which also has heaters associated therewith to dry the plastic film 
pieces and remove any residual moisture therefrom. Because of the 
agitation of the plastic film pieces within the cleaning device, 
substantially all of the residual dirt, debris and the like are dislodged 
from the plastic pieces and fall downwardly by gravity into collection 
areas. 
Following cleaning and drying, the plastic film pieces are fed into a 
holding area wherein the same are accumulated and then fed to one or more 
extruders which melt the plastic film pieces, screen any solid particles 
therefrom, and extrude the same into suitable containers in the form of 
pellets which are suitable for reuse to form other plastic products.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT 
Referring now more particularly to the drawings and specifically to FIG. 1, 
the preferred embodiment of the present invention will now be described. 
The used agricultural film mulch may be received and processed in any 
initial form, such as manually rolled into large rolls as has previously 
been the custom or in compacted bales as disclosed in Applicant's 
co-pending application. For illustration purposes, the used plastic film 
mulch is shown as being received in baled form. 
In the initial stage of the method and apparatus of the present invention, 
the used plastic mulch is removed from its compacted form either by 
unrolling the rolls or by breaking down or de-baling the bales B into a 
relatively loose, linear form wherein the webs of plastic film are 
extended and not compacted to any appreciable extent. Such de-baling is 
generally referred to at 20 in FIG. 1. The next step in the method of the 
present invention is the removal of as much dirt, debris and the like from 
the loose mass of plastic mulch as possible and this step is generally 
referred to at 30. 
Following the major cleaning step, the used plastic film mulch is shredded 
into pieces of predetermined size, which is generally referred to at 50. 
After shredding, there is a final cleaning step which is generally 
referred to at 80. The cleaned and shredded plastic film mulch is 
delivered to an accumulation or holding area generally referred to at 100. 
Finally, the cleaned and shredded plastic film mulch is delivered to an 
extruder-pelletizer generally referred to at 120. 
The apparatus of the present invention is more particularly shown in FIGS. 
2A, 2B and 2C. Referring first to FIG. 2A, the receiving and de-baling 
area 20 includes a floor space which functions as the receiving area where 
palletized bales B of plastic mulch are received. The bales B are removed 
from the pallets manually and placed on a de-baling platform 21. The 
de-baling platform 21 includes a plurality of vertical posts 22 supporting 
a work platform 23 at the top thereof. A worker supporting platform 24 is 
mounted on the vertical posts 22 at a point intermediate the floor and the 
work platform 23 such that a worker can comfortably stand on the platform 
24 and loosen or de-bale the plastic mulch. 
Once the plastic mulch is de-baled or loosened into a generally loose mass, 
the cleaning step 30 can then commence. In this regard, during the 
de-baling process the operator can manually remove any large items of 
debris, such as stakes, stalks or other large items and deposit such 
debris in a waste bin (not shown). The loosened plastic webs are deposited 
on the upper run of a cleaning conveyor generally indicated at 31. The 
cleaning conveyor 31 includes an endless belt or similar conveying means 
32 which is supported at opposite ends by drive rollers 33, 34. At least 
one of the drive rollers 33 and 34, and preferably both, are driven by a 
drive means (not shown). The belt 32 is foraminous, such that dirt, debris 
and the like dislodged from the plastic mulch can fall by gravity through 
the belt 32 downwardly. The belt 32 may consist of spaced interconnected 
slats or wire mesh or any other suitable material which will convey the 
plastic mulch while permitting the removed dirt, debris, and the like to 
pass therethrough. 
Underneath the top run of the conveyor belt 32, there is disposed a 
plurality of rollers 35 which are mounted eccentrically on shafts 35a. 
Shafts 35a are interconnected by gears 35b and 35c (FIGS. 3 and 4) and are 
driven by a drive means (not shown). The eccentric rollers 35 are 
positioned closely together and are disposed along the full length of the 
upper run of conveyor belt 32. Due to the eccentric nature of the rollers 
35, the upper run of the belt 32 is moved upwardly and downwardly in an 
undulating rapid manner to shake or agitate the plastic mulch in such a 
manner as to loosen or dislodge any dirt, debris or the like thereon and 
cause the same to fall downwardly through the foraminous belt 32. 
To remove any magnetic-responsive materials, such as metals that are 
subject to magnetic attraction, an electromagnet 36 is disposed above the 
terminal end portion of the conveyor belt 32. Magnet 36 is positioned 
sufficiently close to the plastic mulch being conveyed to attract and 
remove metallic objects therefrom. Also, magnet 36 is of a width 
substantially the same as conveyor belt 35. 
As shown in FIG. 3, the magnet 36 is disposed immediately adjacent the 
lower run of a waste conveyor belt 37 which is supported at opposite ends 
by rollers 38 and 39. At least one of the rollers 38 and 39 is driven by a 
drive means (not shown). Preferably, the conveyor belt 37 has spaced apart 
dividers 37a mounted thereon which extend across the full width of the 
conveyor belt 37. The conveyor belt 37 is of a length to extend beyond the 
width of electromagnet 36. Accordingly, any metallic objects attracted to 
the electromagnet 36 will be held on the lower surface of the bottom run 
of the conveyor belt 37 by the magnet 36 until the belt 37 clears the side 
of the magnet 36. Then, the metallic objects, which had been held on the 
lower surface of the conveyor belt 37, will fall by gravity from the belt 
37 into a waste bin 41 disposed beneath the belt 37 and outwardly of the 
conveyor belt 35. To isolate the magnet from other areas of the plant, a 
non-magnetic cover 42 is mounted in covering relation to the magnet 36 and 
the conveyor belt 37. The cover 42 has an open bottom but a closed top, 
sides and ends. 
Mounted beneath the conveyor belt 35 in a recessed area in the floor of the 
plant is a waste removal conveyor belt 43 which is supported by a 
plurality of rollers 44 at spaced points along the length thereof. The 
lower run of the conveyor belt 43 is supported by idler rollers 45 at 
spaced apart points along the length thereof. At least one of the rollers 
44 is driven by a drive means (not shown). Any dirt, debris or other waste 
falling through the conveyor belt 35 will fall onto the waste removal 
conveyor belt 43 and be transported by the upper run thereof to the 
discharge end of the conveyor belt 43 on the outside of the plant where 
the same is deposited in a waste receptacle (not shown). 
When the plastic mulch leaves the discharge end of conveyor belt 32, it is 
delivered to a conveyor means, generally referred to at 51, which forms a 
part of the shredding section 50. Conveyor means 51 includes a lower 
conveyor belt 52 supported at opposite ends by rollers 53, 54 and idler 
rollers 55 which are disposed at the upper end of the conveyor belt 52. 
Conveyor means 51 also includes an upper conveyor belt 56 which is 
disposed above the conveyor belt 52 and has the lower run thereof disposed 
closely adjacent to the upper run of belt 52 to positively grip the 
plastic film waste therebetween. The conveyor belt 56 is supported at 
opposite ends by rollers 57 and an idler roller 58. Conveyor belts 52 and 
56 are driven by suitable drive means (not shown) such that the upper run 
of belt 52 and the lower run of belt 56 travel in the same direction. 
Preferably, the conveyor belts 52 and 56 are angled upwardly and terminate 
at their upper ends above the initial shredder means, generally indicated 
at 60. 
Shredder means 60 includes a hopper 61 in which the plastic mulch is 
deposited by the conveyor means 51. The lower end of the hopper 61 is open 
and has a pair of feed rolls 61a and 61b disposed immediately adjacent 
thereto. The feed roll 61a is positively driven by a first synchronous 
motor 62, the output of which is connected directly to the shaft of the 
feed roll 61a. Feed roll 61a is connected to the feed roll 61b by a gear 
box 62a. The outer surfaces of the feed rolls 61a, 61b are preferably 
knurled to provide a positive grip on the plastic mulch being fed thereby. 
A first pair of shredding rolls 6a, 63b is mounted beneath the feed rolls 
61a, 61b and has the axis thereof generally parallel to the feed rolls 
61a, 61b. The shredding roll 63a is positively driven by a second 
synchronous motor 64 and roll 63a is connected to roll 63b by a gear box 
64a such that the shredding rolls 63a, 63b are driven in synchronism with 
the feed rolls 61a, 61b. 
The shredding roll 63a has a plurality of cutting disks 63c mounted in 
spaced apart relation and having outer sharpened peripheries which will 
cut through the plastic mulch as the shredding roll 63a rotates. The 
cutting disks 63c are maintained in the proper spaced apart relationship 
by spacers 63d. The shredding roll 63b is an anvil roll which is mounted 
closely adjacent to the cutting roll 63a and has an equal number of spaced 
apart grooves 63e in the outer periphery thereof for receipt of the 
cutting edges of the cutting disks 63c therein. The shredding rolls 63a 
and 63b cut the plastic mulch longitudinally into strips of a width equal 
to the spacing between the cutting disks 63c on cutting roll 63a. 
A second pair of shredding rolls 65a, 65b are mounted below the first pair 
of shredding rolls 63a, 63b with the axes of the shredding rolls 65a, 65b 
perpendicular to the axes of the shredding rolls 63a, 63b. The shredding 
roll 65a includes a plurality of axially extending cutting blades 65c 
which are mounted in spaced apart relation around the circumference of the 
shredding roll 65a and extend the full length of the shredding roll 65a. 
The shredding roll 65b has an equal number of circumferentially spaced 
grooves 65d in the periphery thereof for receipt of the outer cutting 
edges of the blades 65c. The shredding roll 65a is driven by a third 
synchronous motor 66, the output of which is connected to the shaft of the 
shredding roll 65a. The shaft of the shredding roll 65a is connected to 
the shaft of the anvil roll 65b by a gear box 67. (FIG. 8). 
In this manner, the plastic mulch is first cut into longitudinal strips by 
the shredding rolls 63a, 63b and then these strips are cut transversely by 
the shredding rolls 65a, 65b into pieces of a predetermined size. The cut 
or shredded pieces of the plastic mulch fall downwardly from the shredding 
rolls 65a, 65b onto the upper run of a conveyor belt 70 which is supported 
at opposite ends by rollers 71a, 71b. Roller 71a is driven by a 
synchronous motor 72. Preferably, the conveyor belt 70 is also foraminous 
such that any dirt, debris or the like that is dislodged from the plastic 
mulch during the initial shredding operation will fall downwardly through 
the conveyor belt 70 and onto the waste removal conveyor belt 43 which 
extends from the cleaning section 30 also underneath the shredding section 
50. 
One shredding apparatus 60 may be sufficient to reduce the size of the 
pieces of plastic waste material to that suitable for feeding to the 
extruding section 120. However, under most circumstances, it will be 
desirable to pass the initially shredded plastic through at least one 
additional shredding apparatus. In that event, the discharge end of the 
conveyor belt 70 feeds a second conveyor means 51' which includes a lower 
conveyor belt 52' and an upper conveyor belt 56'. The conveyor means 51' 
is identical to conveyor means 51 and will not be described again. 
The discharge end of the conveyor means 51' feeds a second shredding 
apparatus 60' which has a hopper 61', feed rolls 62a', 62b', first 
shredding rolls 63a', 63b' and second shredding rolls 65a', 65b'. A second 
conveyor means 70' is disposed below the second shredding rolls 65a', 65b' 
for receipt of the shredded particles of plastic mulch which are shredded 
to a finer size than the particles being delivered from the first 
shredding means 60. 
Insofar as particle size is concerned, two shredding apparatus will 
generally and usually be sufficient. However, for especially dirty plastic 
mulch, additional shredding apparatus may be desirable for additional 
cleaning purposes. 
The conveyor belt 70' has the discharge end thereof disposed within the 
second cleaning section 80 which preferably is in the form of a vertical 
separator. The vertical separator 80 includes an outer housing 81 and a 
plurality of vertical dividers 82, 83 and 84 therein. The vertical divider 
82 extends from the bottom of the housing 81 upwardly for a predetermined 
distance and terminates in a free upper end in spaced relation to the top 
of the housing 81. The vertical divider 83 extends downwardly from the top 
of the housing 81 and terminates in a bottom free end in spaced relation 
to the bottom of the housing 81. Finally, the divider 84 extends upwardly 
from the bottom of the housing 81 and terminates in a free end in spaced 
relation to the top of the housing 81. Accordingly, a serpentine or 
tortuous path of travel for the shredded plastic mulch is provided with 
the vertical separator 80. Preferably, the walls of the housing 81 and the 
dividers 82-84 have projections 85 extending outwardly therefrom and into 
the path of the shredded plastic mulch traveling through the vertical 
separator 80 to increase further the agitation of the shredded plastic 
mulch to enhance the cleaning effect. 
A venturi suction means, generally referred at 86, is disposed on the 
discharge end of the vertical separator 80 and includes a blower 87 
connected to a venturi 88. The inlet end 89 of venturi 88 is connected to 
the outlet of the vertical separator 80 and the discharge end 90 thereof 
is connected to a conduit 91. The venturi means 86 creates a suction in 
the vertical separator 80 which causes an airflow from the inlet end 
thereof upwardly through the first section of the vertical separator to 
entrain the shredded plastic mulch therein and cause the shredded plastic 
mulch to travel upwardly to the top of the initial section of the vertical 
separator 80. As the shredded plastic mulch travels upwardly, some of the 
particles will strike the projections 85 and will be deflected thereby 
causing the particles to be agitated or shaken within the moving 
airstream. 
At the top of the housing 81, the airstream and entrained plastic waste 
will change direction and move downwardly to the bottom of the housing 81 
while being agitated and shaken by the projections 85. When the airstream 
and entrained plastic waste reach the bottom of divider 83 they will again 
change direction and move upwardly between the dividers 83 and 84 to the 
top of the housing 81. Again, the airstream and entrained plastic mulch 
will change direction and move downwardly between the divider 84 and the 
outer wall of the housing 81 to the discharge end of the separator and the 
inlet end 89 of the venturi 86. To remove any residual moisture that may 
be collected on the plastic waste, a plurality of heaters 92 are mounted 
on the outer wall of the housing 81 and communicate with the interior of 
the housing 81 through screened openings 93 in the walls of the housing 
81. The heaters 92 include motor driven fans 92a for forcing heated air 
through the screened openings 93 into the interior of the housing 81. 
Any dirt, debris or other contaminants that are dislodged from the shredded 
plastic mulch within the housing 81 falls downwardly and passes through 
screened openings 94 in the bottom of the housing 81 and collect in 
removable waste pans 95 disposed below the screened openings 94. 
Periodically, the waste pans 95 may be removed and emptied. 
Depending upon the cleanliness of the shredded plastic mulch exiting the 
vertical separator 80, further processing may or may not be desirable 
before feeding the plastic mulch to the recycling extruder 120. Additional 
separators 80 may be used as necessary to remove substantially all of the 
dirt, debris and the like from the shredded plastic mulch. 
Four samples of used plastic mulch film were tested to determine the 
effectiveness of the cleaning process. The first sample was of uncleaned 
plastic mulch. The second sample was of shredded plastic mulch that had 
been passed through a single vertical separator 80. The third sample was 
of shredded plastic mulch that had been passed through the vertical 
separator 80 twice. The fourth sample was like samples two and three, 
except it was passed through the vertical separator 80 three times. 
The samples were analyzed by ashing and by washing followed by weighing to 
evaluate the effectiveness of the cleaning thereof. The following table 
sets forth the results of this evaluation: 
______________________________________ 
Weight Moisture 
Number of 
before Weight after 
and Dirt 
Cleanings 
washing (g) washing (g) 
content (%) 
______________________________________ 
0 37.11 23.70 36 
1 7.24 6.07 16 
2 8.10 7.97 1.6 
3 20.87 20.59 1.3 
______________________________________ 
An additional, perhaps less scientific, evaluation was performed by 
starting with 80 pounds of used plastic mulch which was passed through the 
shredding apparatus 60 three times. The resultant shredded plastic mulch 
was then passed through the vertical separator 80 five times and was 
weighed after each pass. After the first pass, the shredded plastic mulch 
weighed 35 pounds. After the second pass, the shredded plastic mulch 
weighed 31 pounds; after the third, 28 1/2 pounds; after the fourth pass, 
27 1/2 pounds; and after the fifth pass, 27 pounds. Accordingly, from the 
80 pounds of used plastic mulch, 53 pounds of dirt, debris and moisture 
were removed. 
The cleaned shredded plastic mulch is delivered by the conduit 91 to the 
accumulating or holding area 100 which preferably comprises a mobile truck 
101. Truck 101 includes a foraminous body 102 in the form of screen wire 
or the like forming the side end and top walls. Preferably, the truck 101 
includes wheels 103 such that the same may be removed when full of plastic 
mulch and an empty truck put in its place. To that end, the conduit 91 has 
an easily removable connector 91a which mates with a connector 104 on the 
top wall of the body 102 of the truck 101. A motor driven fan 105 is 
disposed in one of the end walls of the body 102 of the truck 101 adjacent 
the inlet 104 to blow the shredded plastic mulch to the far end of the 
body 102 to ensure that the body 102 is completely filled with plastic 
mulch before the inlet 104 becomes clogged. 
The accumulator or holding truck 101 includes a discharge conduit 106 which 
extends from an outlet 107 at the top downwardly to an inlet end 108 at 
the bottom thereof. The outlet 107 has a releasable connector 107a to 
which a supply conduit 109 can be easily connected and disconnected. The 
supply conduit 109 supplies the shredded plastic mulch to the extruder 
120. 
The extruder 120 may be of any desired type for recycling plastic 
materials, there being several different types available commercially. One 
such extruder is manufactured by "Munchy" Ltd. Aston Hill, Lewknor, 
Oxfordshire 0X95SG England and is sold in this country by Action 
Industries, Inc., P.O. Box 322, Ellington, Conn. 06029. The preferred type 
of the Munchy recycling extruders to be used in this process and with this 
apparatus is the XL 120, vented extruder. The particular type of extruder 
to be selected will depend upon the throughput desired. For example, the 
XL 120 can be operated to have a capacity of 700 lbs. per hour of plastic 
recycled therethrough. The extruder 120 melts the plastic film, screens 
solids therefrom, and extrudes the molten plastic in a reusable form, such 
as pellets. 
In the drawings and specifications, there has been set forth a preferred 
embodiment of the invention, and although specific terms are employed, 
they are used in a generic and descriptive sense only and not for purposes 
of limitation.