Note: Descriptions are shown in the official language in which they were submitted.
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MEDICAL SHARPS AND WASTE DISPOSAL CONTAINER
AND METHOD OF MAKING THE SAME
FIELD OF THE INVENTION
The present invention is directed to a degradable medical sharps and
waste container and a method for forming the degradable medical sharps and
waste
container.
s BACKGROUND OF THE INVENTION
Plastics have become an important part of modern life and are used in
different applications such as packaging, building materials, and consumer
products.
Plastics are extremely versatile. Some plastics are shrinkable, rigid,
flexible,
impervious, or selectively permeable. One feature of plastics is that it does
not
degrade rapidly over time and is relatively inexpensive to manufacture.
One example of a product that is manufactured from plastic is a medical
sharps and waste disposal container. Medical sharps and waste disposal
containers are
a convenient and safe way of disposing contaminated needles, syringes, glass
tubes,
scalpel blades, and any other sharps and medical waste. Such disposal
containers may
be used to safely contain, transport, and ultimately destroy potentially
infectious
sharps. The filled medical sharps and waste disposal containers are considered
biomedical/biohazardous waste and are to be disposed of according to strict
federal and
state guidelines. For example, a medical sharps and waste disposal container
may be
incinerated on or off site by a facility, or the facility can have the
container rendered
nonhazardous through various sterilization techniques.
If the medical sharps and waste container is rendered noninfectious by
sterilization, most landfills consider the sterilized medical sharps and waste
disposal
container as municipal solid waste. Therefore, the sterilized medical sharps
and waste
disposal container is subject only to the same requirements as household
garbage and
may be disposed of in a permitted, contained landfill. Although plastic
medical sharps
and waste disposal containers are a safe and efficient way to collect
contaminated or
spent medical sharps and medical waste, the properties of plastic that make
these
containers suitable for disposal of medical sharps and medical waste, i.e.,
impervious to
heat and moisture, have a sufficient rigidity and puncture resistance, and the
ability to
maintain its integrity over time, also present challenges to their disposal.
Even though
the infectious materials contained within the medical sharps and waste
disposal
containers have been destroyed (i.e., sterilized), the filled containers still
present the
problem of occupying a large volume of space in a landfill.
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SUMMARY OF THE INVENTION
According to one exemplary embodiment, a medical sharps and waste
disposal container of the present invention is made from a composition of
polypropylene and an additive, and has a puncture resistance of at least about
2.8 lbf.
The additive is present in an amount sufficient to accelerate degradation of
the
polypropylene after a predetermined shelf-Iife.
According to another exemplary embodiment, a medical sharps and
waste disposal container of the present invention is made from a composition
of
polypropylene and an additive, and has impact strength sufficient to prevent
the escape
of sharps from the container. The additive is present in an amount sufficient
to
accelerate degradation of the polypropylene after a predetermined shelf-life.
An exemplary method of manufacturing a degradable medical sharps
disposal and waste container according to an embodiment of the present
invention
includes forming a container from a composition of polypropylene and an
additive in an
amount sufficient to accelerate degradation/biodegradation of the
polypropylene in the
composition after a predetermined shelf-life. The formed container has a
puncture
resistance of at least about 2.8 lbf.
Another method of manufacturing a medical sharps and waste disposal
container according to an exemplary embodiment of the present invention
includes
forming pellets containing polypropylene and an additive. The pellets are
melted and a
medical sharps and waste disposal container is formed by a molding process.
The
formed container has a puncture resistance of at least about 2.8 lbf. and an
impact
strength sufficient to prevent the escape of sharps from the container.
A method of disposing of medical sharps and medical waste according to
an exemplary embodiment of the invention includes receiving medical sharps in
a
container made from a composition of polypropylene and an additive in an
amount
sufficient to accelerate degradation of the polypropylene after a
predetermined shelf-
life. The container has a minimum puncture resistance of at least about 2.8
lbf. Once
the medical sharps and/or waste is received by the disposal container, the
container is
exposed to a stimulus to initiate degradation/biodegradation of the container.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is best understood from the following detailed description
when read in connection with the accompanying drawings. It is emphasized that,
according to common practice, the various features of the drawing are not to
scale. On
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the contrary, the dimensions of the various features are arbitrarily expanded
or reduced
for clarity. Included in the drawings are the following figures:
Fig. 1 is an illustration of exemplary medical sharps and medical waste
containers that can be rendered degradable according to aspects of the present
invention;
Fig. 2 is a flow chart of an exemplary method of manufacturing a medical
sharps and waste container according to aspects of the present invention; and
Fig. 3 is a flow chart of an exemplary method of disposing medical sharps
and medical waste in an exemplary container according to aspects of the
present
io invention.
DETAILED DESCRIPTION OF THE INVENTION
Degradation is a process whereby very large molecules are broken into
smaller molecules or fragments. Degradation typically occurs when oxygen is
incorporated into these molecular fragments. This type of degradation is
called
is oxidative degradation. Typically, strong plastic films become weak and
brittle as a
result of oxidative degradation. The plastic "degrades" because the long
polymer
chains that normally comprise the plastic are broken into shorter, smaller
chains.
Oxidative degradation may be initiated by mechanical stresses, heat, or
exposure to UV
light or sunlight. The term "degradable plastic " is defined by the American
Society for
20 Testing and Materials (ASTM D883-99) as a plastic designed to undergo a
significant
change in its chemical structure under specific environmental conditions
resulting in a
loss of some properties that may vary as measured by standard test methods
appropriate to the plastic and the application in a period of time that
determines its
classification.
25 According to an exemplary embodiment, the degradation process of the
medical sharps and waste disposal container of the present invention is
accelerated in
such a way as to promote degradation while maintaining an acceptable shelf
life for the
container. In other words, degradation is accelerated while allowing the
container to
retain its integrity and performance characteristics for an acceptable period
of time.
30 For example, this period of time (or shelf life) can be set at about 30
months. That is,
about 30 months after a medical sharps and waste disposal container is
produced
(during which time it may be in storage, transportation or usage), it still
retains its
structural integrity yet begins to undergo a significant change in its
chemical structure
resulting in a loss of some properties that may vary as measured by standard
test
35 methods appropriate to the container.
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Biodegradation, as distinguished from degradation, is the process by
which microorganisms found naturally in the soil (namely, bacteria, fungi or
algae)
convert a material into a biomass, carbon dioxide, mineral matter, and water.
A
biomass is understood to include an energy resource derived from organic
matter and
s includes any carbon source on which microorganisms can grow. The term
"biodegradable plastic" is defined by the American Society for Testing and
Materials
(ASTM D883-99) as a degradable plastic in which the biodegradation results
from the
action of naturally-occurring microorganisms, namely, bacteria, fungi, and
algae.
Once accelerated degradation is facilitated (e.g., as a first step), the
medical sharps and waste disposal containers of the present invention can be
subjected
to biodegradation (e.g., as a second step). According to an exemplary
embodiment,
the medical sharps and waste disposal container is rendered biodegradable upon
exposure to microorganisms found naturally in the soil (namely, bacteria,
fungi or
algae).
Is Figure 1 illustrates exemplary medical sharps and waste containers
configured for accelerated degradation and that can be rendered biodegradable
according to aspects of the present invention. For example, container 10 has a
base
and a top and is comprised of a plurality of walls 1S. Container 10 may also
include a
lid 17 which may have various configurations. The walls 15 and lid 17 have a
thickness of approximately 0.050 inches to 0.075 inches, and more preferably
have a
thickness of approximately 0.060 inches to 0.065 inches. Container 10 is
adapted to
receive medical sharps and medical waste. Walls 15 are made from a composition
of
polypropylene and an additive that accelerates degradation after the
predetermined
shelf life. The lid 17 is preferably also made from a composition of
polypropylene and
an additive that accelerates degradation, but does not have to be made from
such a
composition. According to an exemplary embodiment, the composition forming
walls
15 of container.10, and also possibly lid 17, comprises about 90% to about
100%
polypropylene by weight of the container.
An additive is provided in the container, such as container 10, in a
sufficient amount to accelerate degradation of the polypropylene in the
composition.
One exemplary additive is manufactured by EPI Environmental Technologies Inc.
of
Vancouver, British Columbia, Canada under the trademark TDPA (Totally
Degradable
Plastic Additive). Another exemplary additive is manufactured by ECM Biofilms,
Inc. of
Painesville, Ohio under the tradename ECM Masterbatch Pellets. Yet another
exemplary
additive is manufactured by Symphony Plastic Technologies of the United
Kingdom and
distributed by Degradable Plastic Products Inc. of Toronto, Ontario, Canada
under the
trademark d2w . Additives of this nature are described in U.S. Patent No.
5,854,304;
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U.S. Patent Application Publication No. 2004/0062884; and PCT International
Application Publication No. WO 2005/017015, each of which is incorporated by
reference. The additives in these patent documents are generally described for
use in
thin film structures, for example, plastic bags and the like.
When the additive is added to plastic resins (namely, polypropylene,
polyester, or polystyrene) in various concentrations, the manufactured plastic
product
will have an accelerated rate of degradation and can be ultimately rendered '
biodegradable. Once degradation and biodegradation are complete, all that
remains of
the plastic and the additive is carbon dioxide, water, mineral matter and
biomass. By
varying the concentration and type of additive in the plastic composition, the
plastic
product formed by the composition will begin its accelerated degradation and
be can be
rendered biodegradable within a desired timeframe. Exemplary timeframes in
which
the medical sharps disposal container of the present invention begins its
accelerated
degradation (so as to lose some of its integrity and performance
characteristics) include
at least about 20-40 months, preferably at least about 25-35 months, and most
preferably at least about 30 months. The additive according to an exemplary
embodiment of the present invention is present in an amount of up to about
10%,
preferably between about 1-10%, and more preferably between about 3-5% by
total
weight of the container, as explained in PCT International Application
Publication No.
WO 2005/017015.
The degradation process is accelerated by the additive and typically
begins with the breakdown of a large polymer chain having an average molecular
weight of up to 300,000 Daltons into smaller polymer chains by oxidative
degradation.
Degradation continues by oxygenating the exposed ends of the smaller polymer
chains
2s to form aidehydes, ketones, carboxylic acids, and alcohols. The degradation
process is
initiated upon exposure to heat, UV light (e.g., sunlight), moisture, and
mechanical
stresses. One or any combination of these stimuli begins the degradation
process of a
product having the composition of the present invention. Biodegradation begins
when
microorganisms consume the oxygenated ends resulting from the degradation
process
to reduce the end of the polymer chains two carbon atoms at a time. When the
microorganism consumes the oxygenated ends, the polymer backbone end is again
exposed, oxygenated (i.e., degraded), and consumed by the microorganisms
(i.e.,
biodegraded); thus repeating the degradation/biodegradation cycle. Degradation
can
occur without biodegradation or degradation and biodegradation can proceed
simultaneously in concert as described above.
The medical sharps and waste disposal container of the present
invention, although having an accelerated degradation process and which can be
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rendered biodegradable, maintains structural characteristics that makes it
suitable as a
container for disposal of medical sharps and medical waste. One such
structural
characteristic is puncture resistance. ASTM-F2132 provides a test procedure
and
performance requirement for the puncture resistance of materials used in the
s construction of containers for discarded medical waste, needles and other
sharps. This
test specification establishes (1) the average puncture force and (2) a
minimum value
of puncture force that container materials must withstand when following the
test
procedure. According to one exemplary embodiment, the medical sharps and waste
disposal container of the present invention has an average puncture resistance
of at
least about 3.4 lbf., at least about preferably 5.0 lbf., wherein the minimum
requirement for any single measurement is preferably at least about 2.8 lbf.
Another structural characteristic is impact strength. A test procedure
that measures impact strength is ASTM-D5628, which determines the relative
ranking
of materials according to the energy required to crack or break flat, rigid
plastic
specimens under various specified conditions of impact of a free-failing dart.
Another
test for impact strength is to drop a filled, medical sharps and waste
disposal container
from a predetermined height (the height depends on the size and weight of the
container) onto a hard surface. The container fails this impact strength test
when the
impact of the drop causes a medical sharp or other medical waste to escape
from the
container. For example, a filled, 2 gallon medical sharps disposal container
weighing
about 1.0 lbs was dropped from a height of 36 inches. If no medical sharps or
medical
waste escaped from the container, either through a breach in a wall or the lid
of the
container, after being drop from the predetermined height, the container is
determined
to have a sufficient impact strength.
Degradable sharps and medical waste disposal containers, according to
exemplary methods of the invention, are manufactured by conventional plastic
fabrication processes including, but not limited to, plastic vacuum forming,
thermoset
injection molding, blow molding, rotational molding, thermoforming, structural
foam
molding, compression molding, resin transfer molding (RTM), coating, and
dipping. For
example, Figure 2 illustrates an exemplary method 20 of forming a medical
sharps and
waste disposal container of the present invention. According to exemplary
method 20,
a composition of polypropylene and an additive in an amount sufficient to
accelerate
degradation of the polypropylene is provided in step 22. According to another
exemplary embodiment, a composition of polypropylene and the additive is
pelletized
and provided in pellet form. The composition is then injected into a mold in
step 24.
in step 26, a container is formed having a sufficient puncture resistance and
impact
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strength to prevent medical sharps and medical waste from escaping from the
container.
An exemplary method of disposing medical sharps and medical waste
according to an embodiment of the present invention is illustrated in the flow
chart of
Figure 3. The disposal method 30 includes step 32 of receiving medical sharps
and/or
medical waste in a container comprising polypropylene and an additive in an
amount
sufficient to accelerate degradation of the polypropylene after a
predetermined shelf-
life. To dispose of the medical sharps container, the spent medical sharps
and/or
medical waste is sterilized as shown in step 34. Appropriate sterilization
techniques
include those methods that render the potentially infectious medical sharps
and waste
noninfectious. Exemplary methods include steam (autoclaving), gravity
displacement,
dynamic air removal (pre-vac), dry heat, convection heat, ethylene oxide,
plasma
(hydrogen peroxide plasma or gas plasma), and peracetic acid treatment.
As shown in step 36, aftei~ sterilization, the accelerated degradation of
the medical sharps and waste disposal container is activated. Activation of
the
accelerated degradation is initiated upon exposure to mechanical and/or
chemical
stimuli including mechanical shredding, heat, or exposure to UV light (e.g.,
sunlight) or
moisture. As shown in step 38, after accelerated degradation is activated,
biodegradation of the medical sharps and waste disposal container is
activated.
Activation of the biodegradation process is initiated upon exposure to
microorganisms
found naturally in the soil (namely, bacteria, fungi or algae).
While preferred embodiments of the invention have been shown and
described herein, it will be understood that such embodiments are provided by
way of
example only. Numerous variations, changes and substitutions will occur to
those
skilled in the art without departing from the spirit of the invention.
Accordingly, it is
intended that the appended claims cover all such variations as fall within the
spirit and
scope of the invention.
