Note: Descriptions are shown in the official language in which they were submitted.
11~9372
~ETHOD OF RECLAIMING THER~OPLASTIC
MATERIALS ~ROM ~UNICIPAL WASTE AND
PRODUCT PRODVCED THEREBY
The present invention relates to a method of reclaiming thermoplastic
material from municipal waste, and is particularly applicable to a method
wherein all of the principal materials used in the process are derived from
municipal waste.
At the present time, particularly in the United States, the disposal
of municipal waste is particularly burdensome to municipalities. The burden
has been increased by the increasing use of containers made of thermoplastic
material which is relatively inert and is not blodegradable as is the case
with cardboard, paper and other materials produced from natural products.
Glass and metal can be economically recycled since the salvage value of
these materials is sufficiently high to justify the segregation and handling
which are necessary in a recycling operation. Plastic wastes, however, have
not been economically recycled since the manufacturing processes which
utilize thermoplastic material require material which i6 pure and free from
foreign matter. A typical batch of municipal waste might include not only
containers or other materials of polyethylene, but it normally includes
polystyrene jackets and polyvinylchloride materials and various other thermo-
plastic compositions which are incompatible but not readily segregated from
one another. Therefore, the plastic material must not only be cleaned and
separated from the non-plastic material, but the different types of plastlc
must be separated from one another.
.
'
: , '.: ':
;' ': '
~9372
In a recycling oEeration, there is no satisfactory way in which to
separate one plastic material from one another or even to identify
the different compositions which are used in making Elastic
containers and other Elastic items.
S The present invention provides a method which Eermits the
salvage of the thermoElastic materials without the need for separ-
ating the materials having different characteristics. The Eresent
invention enables the economic utilization of a batch of thermo-
plastic material embodying components of different comEositions.
Another substantial problem for municiEalities and other
residential areas in the northern temFerate zone is the collection
and disposal of leaves falling from deciduous trees. In the East,
the general practice was to incinerate the fallen leaves, either in
munlcipal incinerators or simEly in leaf piles in the neighborhood.
However, in recognizing the Eollutlng effect of burning leaves in
open fires and the saftey hazards occasioned by open fires, most
municiEalities have ordained that there shall be no oEen fires
within their boundaries. sanning opan fires has then Elaced the
burden upon the municiEalities of collecting and disposing of the
leaves which were previously burned by the homeowners, each on
their own proEerty. While many homeowners will collect the leaves
and compost them for subsequent use in their gardens, there are
many residents who have no gardens and who do not have any use for
compost material or any inclination to conserve natural resources
by comEosting. While some munici palities are able to find a
suitable dumping ground for their leaves, the expense of collection
and transEortation of the leaves to the land-fill or other disposal
area is tremendous.
- 2 -
~ .. ,. .. r_ ._ . _ . .- .. - . - - . _. ~ .. . __ _--_._ . _ . _ __ __ __ .. ~ . _, ,, . , .__.. _._ ~__ _, .. ,, _ ._ ., .. ,, __ , . ..
' ~' ~ '
.
"
' ' '' ' ~ '
11193~72
Municipally-collected leaves have been used as
raw material for the preparatin of artificial fireplace
logs, but the demand for such logs is not sufficient to use
up the vast amounts of fallen leaves which are collected
during the autumn season.
The present invention enables effectively utilization
of waste materials which are in abundant supply in such a
manner that additional fresh material is not needed. The
invention produces a material which may be formed into products
which are in great demand and which may be used instead of
conventional products which are made from fresh natural products
or from newly-manufactured material.
More specifically, the present invention provides
an intermediate material which is composed of leaf fragments
which are bonded into a homogenous material which may be
formed into a structure having sufficisnt strength and rigidity
for a wide variety of products.
Specifically, the material produced by the present
invention may be formed into particle boards or artificial
lumber which is capable of being used in the construction
trade in the same manner as conventional particle boards are
used and is also capable of use in place of conventional çlywood
in certain installations.
The invention also enables the use of reclaimed
thermoplastic materials to make molded articles which are
presently made from newly-made plastic compositions.
, " .
,
;: ~ , ,~
: ' ~'. ~ '., ' '
..
~119372
In one aspect the invention provides a method of reclaiming material
from domestic waste comprising the steps of providing a quantity of leaf
particles which have a small thickness relative to their transverse dimensions
of width and length, combining the leaf particles with a quantity of thermo-
plastic material of mixed constituents derived from the domestic waste, at
least some of the mixed constltuents being incompatible, mixing and blending
the quantities together and causing the thermoplastic material to fuse and
adhere to the leaf particles as a coating bonded thexeon, the incompatible
constituents of the thermoplast~c material being bonded to different parts of
the same particles, whereby the leaf particles serve as a bridge to link the
incompatible thermoplastic constituents together, consolidating the blended
material w~th heat and pxessure to for~ a product. and thereafter curing and
fi~niShing the product tQ provide a useful end product.
In another aspect the invention provides a useful product made by
reclaiming material from domestic waste comprising a formed body consisting
essentially of leaf particles and thermoplastic material having a variety of
constituents, at least some of which are incompatible, the leaf particles
having a small thickness relative to their transverse dimensions of width and
length and being disposed in successive overlapping, relationship and being
coated with.the thermoplasticmaterial, the thermoplastic bonding to the leaf
particles and effectively bonding the leaf particles together into a unitary
mass where the particles overlap, and the incompatible thermoplastic constit-
uents being coated ~nto different parts of the same leaf particles whereby
said leaf particles link the incompatible thermoplastic constituents together.
- 3a -
:, . .
,
~1937~
This invention is more fully set forth hereinafter with reference to
the accompanying drawings, wherein:
Fig. 1 is a block diagram of a method embodying the present invention
for producing a finished product by reclaiming thermoplastic mater~al from
munic~pal waste; and
Fig. 2 is a block diagram illustrating alternative procedures for
producing finished products from thermoplastic fragments and dried particles
which have been reclaimed from municipal waste in accordance with the present
invention.
Referr~ng now to the dxaw~ngs, the present invention contemplates
the reclamation of thermoplastic mater~al from municipal ~aste using principal
ly le~f material wh~cn is si~larly reclaimed from municipal waste. The
present invention contemplates that a f~nished useful product may be made
wi`thout any substantial use of raw materials other than those materials which
are reclaimed from municipal waste.
As discussed above, domestic municipal waste incorporates a wide variety
of matexial, much of which is readily salvaged by recycling. The salvagable
material has been limited primarily to glass, metal and newspapers, all of
wh~ch may easily be maintained separate by the homeowner at the beginning of
~he salvage process, namely by maintaining these elements separate from the
garbage and ot~er components of mun~cipal waste wh~ch have no salvage value.
The salvage value of metal, glass and ne~spapers is sufficiently high to justify
the separate handling of the$e mate~als which is required in a recycling
ope~tion.
- 4 -
:':' ,' ' - ::
..
~.: ~ .
.. . . .
~19~72
The balance of the domestic waste consists of food
waste, garbage, and containers and pac~ages for food products,
and other hollsehold items which are not made of glass or metal.
Such packages and containers are normally made of ~aper, either
treated or untreated, or Flastic, normally thermoElastic
resins such as polystyrene, polyethylene and polyvinylchloride
materials. The paper products and the food waste which is
present in domestic waste are biodegradable and are readily
disposed of in municiple waste landfill oFerations or in other
methods where the material is permitted to degrade and is used
for fertilizer or other land-enhancement program. The thermo-
plastic material, however, is not biodegradable and is a
detriment to utilization of the municipal waste for land
enhancement.
The present invention is designed to separate the
thermoElastic material from the municiEal waste and provide
a method for converting these waste materials into useful
products.
One method of reclaiming the material according to
the present invention is diagrammatically illustrated in ~ig.
1 and includes the step of segregating from municipal waste
the dome~tic waste which inaludes thermoplastic material.
Preferably, domestic wastes and leaves are each collected
separately from the industrial waste to avoid contamination
of the usable constituents. The domestic waste is then
classified to separate out the termoplastic material.
The preferred method of separating out the thermoplastic
material form other domestic waste includes an air-classifier
O ~ - 5 -
;
37~:
are characterized by a low density. In the air classification
system, it is desirable to have the material reduced to a particle
size which is readily handled by the airflow employed to perform
the classification. Thus, prior to subjecting the municipal waste
to air classification, it normally is subjected to a fragmentation
operation or decimation which choEs up the large particles in the
waste so that the waste is composed entirely of fragments. If
desired, to insure improved classi- fication, the fragmented waste
may be passed through a screen- separator which will remove large
particles which do not pass through the screen. A preliminary step
may also include magnetic se~aration of iron and other metallic
comEonents of the waste.
The air classification of the fragmented waste permits
separation of the thermoElastic material which is normally in
pieces having a relatively thin thickness and which therefore
are readily separated out in an air classifier. ThermoElastic
material which is in the form of chunks or other large particles
may not be separated from the other high-density material, and
may not be reclaimed when using an air classifier in accordance
with the method of the present invention. The separated
fragments of thermoplastic material may then be cleaned and
dried, if necessary, and passed through a second fragmentating
oEeration in which the fragments are uniformly reduced to a
size that will pass through a given mesh. In the present
instance, a one-half inch mesh is desired to insure ease of
handling in subsequent operation. ThermoElastic particles of
this slze are readily stored in a compact space and are not
subject to deterioration during the storage period.
- 6 -
:. : , ~ . : : .
.. : , . ~
~ .
11~9372
The other component which is employed in the reclamation
of municipal waste is the leaves which are shed from deciduous
trees during the fall of the year. In accordance with the
preferred method of the present invention, the leaves are collected
separately from the other municipal waste and are not mingled with
other municipal waste. However, the collection process normally
collects not only leaves, but also collects twigs and small
branches and also random trash which may be found in street gutters
and other Elaces where leaves are accumulated for pickup in the
collection process. Such trash may include discarded beverage
containers, papers, and other man-generated trash. Also, depending
upon the circumstances, the collected leaves may include nuts, pine
cones, and pebbles, as well as the branches and twigs mentioned
above.
15 The collected leaves may be stored in the form in which
collected in piles or leaf stachs. When it is anticipated that the
leaves will be stored for a prolonged period, they may be baled by
conventional hay-bailing apparatus. The leaves may be collected
and compressed so that there is little opportunity for degradation
of the leaves during their storage. It has been found that leaves
may be stored for prolonged periods lf they are com~acted and
protected from the weather and from alr. The compacted loose
leaves or bales may be stored in open piles or stacks which are
suitably covered by tarpaulins and the like. In any event, leaves
are hygroscopic in nature and during the storage o~eration, will
absorb amblent moisture present in the storage area. Storing the
leaves in compacted stacks covered by tarpaulins excludes
sufficient air to limit the absorption of moisture by the leaves.
- 7 -
..... . .... , . .~. , ~
:
: ~ : ` '
'
'` ,
~190~72
When removed from storage, or when the leaves will be uæed
promptly, the leaves are shredded for subsequent oFeration. The shredding
oEeration, preferably Eerformed in a commercial leaf shredder, reduces the
si~e of the leaves so that the leaf fragments may Eass through a screen or
grate having a selected mesh opening. It is preferred that the mesh oEening
be comparable to the size of the thermoplastic fra~ments in order to enable
the leaves to be consolidated into the smallest storage sEace Eossible.
Thus "the leaf fragments are of a particle size which will Eass through the
selected mesh oFening, preferably on the order of one-half inch.
The leaves prior to use in the method of the present invention must
have a moisture content of less than about ten Eercent by weight of the
bone-dry weight of the leaves. Leaves which have been stored in an arid
atmosphere may have a sufficiently low moisture content for use directly from
storage. However, in the northeastern section of the United States, it has
been found that the hygroscoE~c nature of the leaves will cause absorEtion of
sufflcient moisture to exceed the moisture content which has been found most
effective. Accordingly, it has been found desirable to subject the
fragmented leaves to a drying oEeration prior to use in the method of the
present invention. The drying oEeration may be accomplished in various
driers, and in pilot operations drying has been accomplished in a roasting
oven without substantial airflow through the leaf fragments in the oven.
Using the dried leaf fragments and the thermoplastic fragments as a
starting Eoint, the further processing of the material to produce a useful
product may follow alternate courses, deEending uEon the equiEment which is
available. Fig. 1 illustrates the procedure used in a pilot o~eration in
which there was limited access to process equiEment. The procedures
:~
,. . .
- : : .
:' .
'
37~
of Fig. 2 are deemed to be preferred when the method may be
accomELished with ready access to suitable processing equipment.
DeFending on the end use of the product which is
to be made from the leaf fra~ments and the fragment of
thermoFlastic material, they may be combined in different
ratios. The higher the ratio of leaf fragments, the closer
the end product will simultate natural wood fiber Eroducts and
the like. Likewise, a high ratio of thermoElastic material will
cause the plastic characteristics in the final Eroduct to
predominate. In Ellot oEerations, the percentage of thermo-
plastic fragments by weight has been between 15~ and 50~ of
the tctal weight of thermoElastic material and the leaf material.
In the process, weighed quantities of lea~ fragments
and thermoplastic fragments are set aside in batches for
further processing or, alternatively, the materials may be fed
continuously by a metered feeding device of a character suitable
for the materials being fed. In the batch process shown in Pig.
1, the dried leaf fragments and the thermoElastic fragments are
combined by first fusing or melting the thermoplastic fragments
in a retort or other vessel. The thermoElastic fragments include
a mix of different compositions of Elastic materials and by
reason of the nature of the mixed materials, it may not be
Eossible, and is not necessary, to obtain a homogenous
blend of the thermoEaastic comEonents in the retort or other
vessel. While maintaining heat applied to the retort to
avoid solidifying of the melted thermoplastic material, the
dried particles are blended into melted thermoElastic
material so as to thoroughly intermix the leaf Earticles with
.::
' . : . ~ ~ ` : '
llig37~
the melted thermoplastic material so that the material serves to coat the
leaf partic-les. It is noted that the leaf fragments are plate-like in that
they have a small thickness relative to their transverse dimensions of width
and length, and the blending of these fragments throughout the melted plastic
will coat the exposed surfaces of the leaves with the thermoplastic material.
It has been found that the various thermoplastic materials present in domestic
waste will adhere to the leaf surface regardless of the particular character
of the thermoplastic material. Even though one thermoplastic material may
not adhere or bond to another thermoplastic material, the thermoplastic
materials do bond to the leaf surface. Thus, as the leaf fragments are blended
throughout the body of thermoplastic material, the leaf fragments may serve
as a bridge or linking element to integrate different thermoplastic materials
into a unitary mass although such materials would not otherwise combine with
one another.
When the leaf fragments are thoroughly blended with the melted plastic,
the leaf-lsden melt is transferred to a mold or similar forming apparatus
and in the mold, the melt is subjected to heat and pressure so as to exclude
air bubbles and similar voids in the melt and to thoroughly consolidate the
melt into a unitary mass. Preferably, heat is applied during the molding
operationso as to facilitate consolidation of the mass into a unitary structure,
and it has been found that in the molding operation the leaf particles tend
to orient themselves into a generally parallel overlapping array so that the
particles bond to one another through the medium of the plastic which has been
coated onto the particles during
~ - 10 -
~ :
~ . ..
`' . .: ` . :.
,
~937Z
the previous oEerations. As the molded material is compressed, it
attains a density which is deFendent upon the heat and pressure
applied thereto. In the Filot oEeration, the density in grams Eer
cubic centimeters was in the order of 0.95. This may be compared
to Elywood which has a density of 0.66 and Earticle board which may
have densities over a wide range of values.
EDllowing the molding operation, the consolidated mass i9
cooled and cured so as to permit further forming operation.
DeFending on the nature of the forming oEeration, it may be
commenced prior to comElete curing of the material. Fbr example, if
it is desired to emboss the surface of the material, this may be
done prior to comElete solidification of the thermoFlastic
material. On the other hand, if the material is to be shaEed by
machine operations, such as sanding, Elaning and the like, it may
be preferred to Fermit a sub- stantially complete cure Erior to
subjecting the material to the finishing operation. It should be
noted that the curing of the mass does not entail any chemical
change of the components, so that the residual wastes in the
finishing oFeration may be returned to the retort for melting and
re-processing into finished product. The waste material is also
combustible.
In any event, the finishing oFeration will produce a
useful product. F~r examEae, a product in the nature of
particle board has been produced which has been found to exhibit
many of the desirable characteristics of particle board without
necessarily including some obvious disadvantages. The material
produced in the form of boards by the present invention has
shown a very high tensile strength, and breaking strength which
- 11 -
~ i
~ ~ ,
. .
.. . .
937Z
is hiqher than normally experienced in p~rticle board. The product has the
same compressive strength, and the nail-ability and saw-ability of
conventional particle board. In view of its high strength characteristics,
the material may be employed to constitute framing members or structural
S members for use in the construction industry or elsewhere. The manufactured
material has properties comparable to natural l Dber without the likelihood
of warping or degradation in the presence of moisture. The thorough coating
of the thermoELastic material upon the leaf surfaces effectively overcomes
the hygroscopic nature of the leaf particles and permits the use of the
finished product in moist atmospheres and other installations where prior
wood flber elements cannot be used because of their moisture- absorbing
character.
Fig. 2 illustrates aternative processes which are preferred when
suitable processing equiEment ls available. Starting with the dried leaf
particles and the mlxed thermo- plastic fragments of the Ereviously-described
embodiment, the ingredients are measured and blended without sufficient heat
to cause the thermoplastic material to fuse or become tachy. The blendinq of
the dried material then permits the leaves to be thoroughly intermixed with
the thermoplastic fragments. This dried material may then be stored in a
loose state for further processing or may be fed directly into apparatus for
consolidating and forming the material into useful finished product.
In a continuous forming operation, it is possible to use an
extruder to produce articles of indefinite length. The extruder is
effective to heat and compress the blended material and form it into an
extruded product. The thermoplastic fragments during the extrusion process
will fuse and become soft and perhaEs even become fluid so that they may
adhere to the leaf Earticles and bond to the leaf p~rticles as a coating.
- 12
: : ' ' ,., ~;
- :
- : . . .
:' ' " ' ~' ' ''` ~'
::
~il9~72
As discussed above, the mixture of different thermoplastic
materials may be such that the different materials do not bond
or fuse to one another but it has been found that the usual
thermoplastic materials in domestic waste will bond or other-
wise adhere to the surfaces of the leaf fragments and theleaf fragments will thereby operate as a bridge or carrier link
for combining the different thermoplastic materials into a
unitary mass.
The flow of the mixture through the extruder is
preferably controlled to provide the desired orientation of
the leaf particles as they flow so that the product issuing
from the extruder consists of leaf particles which are generally
disposed in successive overlapping relationship so as to proYide
a thoroughly integrated unitary mass of leaf particles which
are bonded together by thermoplastic material coated thereon.
This product may then be cured and finished as discussed above.
Since the product of this embodiment is extruded, it may be formed
in continuous length with a predetermined width and thickness.
As an alternative to extrusion, the dry mixture of
leaf particles and thermoplastic fraqments may be fused to form
a leaf-laden melt, which may be molded or otherwise compressed
and shaped into useful end products, as in the process shown in
Fig. 1. The heat applied in this operation may range from room
temperature to the degradation temperature of the components of
the mixture, but normally the maximum temperature is just above
the melting point of the Elastic components. The pressures may
ranqe from atmospheric up to the limit of the apparatus used
for the forminq operation.
- 13 -
".
:
- .
: ~:
.,
.
1~937~:
Thus, the present invention enables the utilization
of waste material which is normally discarded and constitutes
a disposal problem for municipalities and enables the utilization
of these materials to produce a product which may be substituted
for products formed of fresh natural material or freshly-
manufactured material.
While plrticular embodiments of the present invention
have been herein illustrated and described, it is not intended
to limit the invention to such disclosure but changes and
modifications may be made therein and thereto within the scope
of the following claims.
- 14 -
-' ' , ' ,
