Note: Descriptions are shown in the official language in which they were submitted.
14635M-DW 1
METHOD FOR PURIFYING RECLAIMED POLYPROPYLENE
FIELD OF THE INVENTION
The present invention generally relates to a method for purifying contaminated
polymers
through the use of a pressurized solvent and solid media. More specifically,
this invention relates
to a method for purifying recycled polymers, such as post-consumer and post-
industrial recycled
plastics, to produce a colorless or clear, odor free, virgin-like polymer. It
is particularly useful for
the purification of polypropylene.
BACKGROUND OF THE INVENTION
Polymers, especially synthetic plastics, are ubiquitous in daily life due to
their relatively
low production costs and good balance of material properties. Synthetic
plastics are used in a
wide variety of applications, such as packaging, automotive components,
medical devices, and
consumer goods. To meet the high demand of these applications, tens of
billions of pounds of
synthetic plastics are produced globally on an annual basis. The overwhelming
majority of
synthetic plastics are produced from increasingly scarce fossil sources, such
as petroleum and
natural gas. Additionally, the manufacturing of synthetic plastics from fossil
sources produces
CO2 as a by-product.
The ubiquitous use of synthetic plastics has consequently resulted in millions
of tons of
plastic waste being generated every year. While the majority of plastic waste
is landfilled via
municipal solid waste programs, a significant portion of plastic waste is
found in the environment
as litter, which is unsightly and potentially harmful to ecosystems. Plastic
waste is often washed
into river systems and ultimately out to sea.
Plastics recycling has emerged as one solution to mitigate the issues
associated with the
wide-spread usage of plastics. Recovering and re-using plastics diverts waste
from landfills and
reduces the demand for virgin plastics made from fossil-based resources, which
consequently
reduces greenhouse gas emissions. In developed regions, such as the United
States and the
European Union, rates of plastics recycling are increasing due to greater
awareness by consumers,
businesses, and industrial manufacturing operations. The majority of recycled
materials, including
plastics, are mixed into a single stream which is collected and processed by a
material recovery
facility (MRF). At the MRF, materials are sorted, washed, and packaged for
resale. Plastics can
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be sorted into individual materials, such as high-density polyethylene (HDPE)
or poly(ethylene
terephthalate) (PET), or mixed streams of other common plastics, such as
polypropylene (PP), low-
density polyethylene (LDPE), poly(vinyl chloride) (PVC), polystyrene (PS),
polycarbonate (PC),
and polyamides (PA). The single or mixed streams can then be further sorted,
washed, and
reprocessed into a pellet that is suitable for re-use in plastics processing,
for example blow and
injection molding.
Though recycled plastics are sorted into predominately uniform streams and are
washed
with aqueous and/or caustic solutions, the final reprocessed pellet often
remains highly
contaminated with unwanted waste impurities, such as spoiled food residue and
residual perfume
components. In addition, recycled plastic pellets, except for those from
recycled beverage
containers, are darkly colored due to the mixture of dyes and pigments
commonly used to colorize
plastic articles. While there are some applications that are insensitive to
color and contamination
(for example black plastic paint containers and concealed automotive
components), the majority
of applications require non-colored pellets. The need for high quality,
"virgin-like" recycled resin
is especially important for food and drug contact applications, such as food
packaging. In addition
to being contaminated with impurities and mixed colorants, many recycled resin
products are often
heterogeneous in chemical composition and may contain a significant amount of
polymeric
contamination, such as polyethylene (PE) contamination in recycled PP and vice
versa.
Mechanical recycling, also known as secondary recycling, is the process of
converting
recycled plastic waste into a re-usable form for subsequent manufacturing. A
more detailed review
of mechanical recycling and other plastics recovery processes are described in
S.M. Al-Salem, P.
Lettieri, J. Baeyens, "Recycling and recovery routes of plastic solid waste
(PSW): A review",
Waste Management, Volume 29, Issue 10, October 2009, Pages 2625-2643, ISSN
0956-053X.
While advances in mechanical recycling technology have improved the quality of
recycled
polymers to some degree, there are fundamental limitations of mechanical
decontamination
approaches, such as the physical entrapment of pigments within a polymer
matrix. Thus, even with
the improvements in mechanical recycling technology, the dark color and high
levels of chemical
contamination in currently available recycled plastic waste prevents broader
usage of recycled
resins by the plastics industry.
To overcome the fundamental limitations of mechanical recycling, there have
been many
methods developed to purify contaminated polymers via chemical approaches, or
chemical
recycling. Most of these methods use solvents to decontaminate and purify
polymers. The use
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of solvents enables the extraction of impurities and the dissolution of
polymers, which further
enables alternative separation technologies.
For example, U.S. Patent No. 7,935,736 describes a method for recycling
polyester from
polyester-containing waste using a solvent to dissolve the polyester prior to
cleaning. The '736
patent also describes the need to use a precipitant to recover the polyester
from the solvent.
In another example, U.S. Patent No. 6,555,588 describes a method to produce a
polypropylene blend from a plastic mixture comprised of other polymers. The
'588 patent
describes the extraction of contaminants from a polymer at a temperature below
the dissolution
temperature of the polymer in the selected solvent, such as hexane, for a
specified residence period.
The '588 patent further describes increasing the temperature of the solvent
(or a second solvent) to
dissolve the polymer prior to filtration. The '588 patent yet further
describes the use of shearing
or flow to precipitate polypropylene from solution. The polypropylene blend
described in the '588
patent contained polyethylene contamination up to 5.6 wt%.
In another example, European Patent Application No. 849,312 (translated from
German to
English) describes a process to obtain purified polyolefins from a polyolefin-
containing plastic
mixture or a polyolefin-containing waste. The '312 patent application
describes the extraction of
polyolefin mixtures or wastes with a hydrocarbon fraction of gasoline or
diesel fuel with a boiling
point above 90 C at temperatures between 90 C and the boiling point of the
hydrocarbon solvent.
The '312 patent application further describes contacting a hot polyolefin
solution with bleaching
clay and/or activated carbon to remove foreign components from the solution.
The '312 patent yet
further describes cooling the solution to temperatures below 70 C to
crystallize the polyolefin and
then removing adhering solvent by heating the polyolefin above the melting
point of the polyolefin,
or evaporating the adhering solvent in a vacuum or passing a gas stream
through the polyolefin
precipitate, and/or extraction of the solvent with an alcohol or ketone that
boils below the melting
point of the polyolefin.
In another example, U.S. Patent No. 5,198,471 describes a method for
separating polymers
from a physically commingled solid mixture (for example waste plastics)
containing a plurality of
polymers using a solvent at a first lower temperature to form a first single
phase solution and a
remaining solid component. The '471 patent further describes heating the
solvent to higher
temperatures to dissolve additional polymers that were not solubilized at the
first lower
temperature. The '471 patent describes filtration of insoluble polymer
components.
In another example, U.S. Patent No. 5,233,021 describes a method of extracting
pure
polymeric components from a multi-component structure (for example waste
carpeting) by
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dissolving each component at an appropriate temperature and pressure in a
supercritical fluid and
then varying the temperature and/or pressure to extract particular components
in sequence.
However, similar to the '471 patent, the '021 patent only describes filtration
of undissolved
components.
In another example, U.S. Patent No. 5,739,270 describes a method and apparatus
for
continuously separating a polymer component of a plastic from contaminants and
other
components of the plastic using a co-solvent and a working fluid. The co-
solvent at least partially
dissolves the polymer and the second fluid (that is in a liquid, critical, or
supercritical state)
solubilizes components from the polymer and precipitates some of the dissolved
polymer from the
co-solvent. The '270 patent further describes the step of filtering the
thermoplastic-co-solvent
(with or without the working fluid) to remove particulate contaminants, such
as glass particles.
The known solvent-based methods to purify contaminated polymers, as described
above,
do not produce "virgin-like" polymer. In the previous methods, co-dissolution
and thus cross
contamination of other polymers often occurs. If adsorbent is used, a
filtration and/or
centrifugation step is often employed to remove the used adsorbent from
solution. In addition,
isolation processes to remove solvent, such as heating, vacuum evaporation,
and/or precipitation
using a precipitating chemical are used to produce a polymer free of residual
solvent.
Accordingly, a need still exists for an improved solvent-based method to
purify
contaminated polymers that uses a solvent that is readily and economically
removed from the
polymer, is relatively simple in terms of the number of unit operations,
produces a polymer without
a significant amount of polymeric cross contamination, produces a polymer that
is essentially
colorless, and produces a polymer that is essentially odorless.
SUMMARY OF THE INVENTION
A method for purifying a reclaimed polypropylene is provided. The method
involves:
a. Obtaining reclaimed polypropylene selected from the group consisting of
post-consumer
use polymers, post-industrial use polymers, and combinations thereof;
b. Contacting the reclaimed polypropylene at a temperature from about 80 C to
about 220 C
and at a pressure from about 150 psig (1.03 MPa) to about 15,000 psig (103.42
MPa) with
a first fluid solvent having a standard boiling point less than about 70 C, to
produce an
extracted reclaimed polypropylene;
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c. Dissolving the extracted reclaimed polypropylene in a solvent selected from
the group
consisting of the first fluid solvent, a second fluid solvent, and mixtures
thereof, at a
temperature from about 90 C to about 220 C and a pressure from about 350 psig
(2.41
MPa) to about 20,000 psig (137.90 MPa) to produce a first solution comprising
polypropylene and suspended contaminants;
d. Settling the first solution comprising polypropylene and suspended
contaminants at a
temperature from about 90 C to about 220 C and at a pressure from about 350
psig (2.41
MPa) to about 20,000 psig (137.90 MPa) to produce a second solution comprising
polypropylene and remaining contaminants;
e. Purifying the second solution at a temperature from about 90 C to about 220
C and at a
pressure from about 350 psig (2.41 MPa) to about 20,000 psig (137.90 MPa) by
contacting
the second solution with solid media to produce a third solution comprising
purer
polypropylene; and
f. Separating the purer polypropylene from the third solution.
The second fluid solvent may have either the same chemical composition or a
different
chemical composition than the first fluid solvent.
In one embodiment, the polypropylene is separated from the third solution at a
temperature
from about 0 C to about 220 C and a pressure from about 0 psig (0 MPa) to
2,000 psig (13.79
MPa). In another embodiment, the reclaimed polypropylene is dissolved in the
fluid solvent, or
fluid solvent mixture, at a mass percent concentration of at least 0.5%. In
yet another embodiment,
the reclaimed polypropylene is dissolved in the fluid solvent, or fluid
solvent mixture, at a mass
percent concentration of at least 1%. In one embodiment, the reclaimed
polypropylene is dissolved
in the fluid solvent, or fluid solvent mixture, at a mass percent
concentration of at least 2%.
In one embodiment, the reclaimed polypropylene is dissolved in the fluid
solvent, or fluid
solvent mixture, at a mass percent concentration of at least 3%. In another
embodiment, the
reclaimed polypropylene is dissolved in the fluid solvent, or fluid solvent
mixture, at a mass percent
concentration of at least 4%. In yet another embodiment, the reclaimed
polypropylene is dissolved
in the fluid solvent, or fluid solvent mixture, at a mass percent
concentration of at least 5%.
In one embodiment, the reclaimed polypropylene is dissolved in the fluid
solvent, or fluid
solvent mixture, at a mass percent concentration up to 20%. In another
embodiment, the reclaimed
polypropylene is dissolved in the fluid solvent, or fluid solvent mixture, at
a mass percent
concentration up to 18%. In yet another embodiment, the reclaimed
polypropylene is dissolved in
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the fluid solvent, or fluid solvent mixture, at a mass percent concentration
up to 16%. In one
embodiment, the reclaimed polypropylene is dissolved in the fluid solvent, or
fluid solvent mixture,
at a mass percent concentration up to 14%. In another embodiment, the
reclaimed polypropylene
is dissolved in the fluid solvent, or fluid solvent mixture, at a mass percent
concentration up to
12%.
In one embodiment, the reclaimed polypropylene is post-consumer recycle
derived
polypropylene. In another embodiment, the reclaimed polypropylene is a
polypropylene
homopolymer or a primarily polypropylene copolymer. In yet another embodiment,
the fluid
solvent has a standard boiling point less than about 0 C and greater than
about -45 C and a standard
enthalpy change of vaporization of less than about +25 kJ/mol.
In one embodiment, the fluid solvent is selected from the group consisting of
olefinic
hydrocarbons, aliphatic hydrocarbons, and mixtures thereof. In another
embodiment, the aliphatic
hydrocarbon is selected from the group consisting of Ci-C6 aliphatic
hydrocarbons and mixtures
thereof. In yet another embodiment, the aliphatic hydrocarbons and mixtures
thereof is comprised
of primarily C4 aliphatic hydrocarbons.
In another embodiment, the fluid solvent consists essentially of C4 liquefied
petroleum gas.
In one embodiment, the fluid solvent is n-butane, butane isomers, or mixtures
thereof. In another
embodiment, the temperature in the contacting, dissolving, settling and
purification steps is from
about 110 C to about 170 C.
In one embodiment, the pressure in the contacting step is from about 1,100
psig (7.58 MPa)
to about 2,100 psig (14.48 MPa). In another embodiment, the pressure in the
contacting step is
less than about 1,100 psig (7.58 MPa). In yet another embodiment, the pressure
in the dissolving,
settling, and purification steps is greater than about 1,100 psig (7.58 MPa).
In one embodiment,
the pressure in the dissolving, settling, and purification steps is greater
than about 2,100 psig (14.48
MPa).
In one embodiment, the solid media is selected from the group consisting of
inorganic
substances, carbon-based substances, and mixtures thereof. In another
embodiment, the inorganic
substances are selected from the group consisting of oxides of silicon, oxides
of aluminum, oxides
of iron, aluminum silicates, amorphous volcanic glasses, and mixtures thereof
In yet another
embodiment, the inorganic substances are selected from the group consisting of
silica gel,
diatomite, sand, quartz, alumina, perlite, fuller's earth, bentonite, and
mixtures thereof.
In one embodiment, the carbon-based substances are selected from the group
consisting of
anthracite coal, carbon black, coke, activated carbon, cellulose, and mixtures
thereof. In another
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embodiment, the contacting of the polypropylene solution with said solid media
is done in a packed
bed of said solid media. In yet another embodiment, the packed bed is greater
than 20 cm in length.
In accordance with an aspect, there is provided a method for purifying a
reclaimed
polypropylene comprising:
a. Obtaining the reclaimed polypropylene wherein said reclaimed polypropylene
is selected
from the group consisting of post-consumer use polymers, post-industrial use
polymers,
and combinations thereof;
b. Contacting the reclaimed polypropylene at a temperature from about 80 C to
about 220 C
and at a pressure from about 150 psig (1.03 MPa) to about 15,000 psig (103.42
MPa)
with a first fluid solvent having a standard boiling point less than about 70
C, wherein
the polypropylene is essentially insoluble in the fluid solvent, to produce an
extracted
reclaimed polypropylene;
c. Dissolving the extracted reclaimed polypropylene in a solvent selected from
the group
consisting of the first fluid solvent, a second fluid solvent, and mixtures
thereof, at a
temperature from about 90 C to about 220 C and a pressure from about 350 psig
(2.41
MPa) to about 20,000 psig (137.90 MPa) to produce a first solution comprising
polypropylene and suspended contaminants;
d. Settling said first solution comprising polypropylene and suspended
contaminants at a
temperature from about 90 C to about 220 C and at a pressure from about 350
psig (2.41
MPa) to about 20,000 psig (137.90 MPa) to produce a second solution comprising
polypropylene and remaining contaminants;
e. Purifying said second solution at a temperature from about 90 C to about
220 C and at a
pressure from about 350 psig (2.41 MPa) to about 20,000 psig (137.90 MPa) by
contacting said second solution with solid media to produce a third solution
comprising
purer polypropylene; wherein the solid media is selected from the group
consisting of
inorganic substances, carbon-based substances, and mixtures thereof, and
recycled glass;
the inorganic substances being selected from the group consisting of oxides of
silicon,
oxides of aluminum, oxides of iron, aluminum silicates, magnesium silicates,
amorphous
volcanic glasses, silica, silica gel, diatomite, sand, quartz, reclaimed
glass, alumina,
perlite, fuller's earth, bentonite, and mixtures thereof, and the carbon-based
substances
being selected from the group consisting of anthracite coal, carbon black,
coke, activated
carbon, cellulose, and mixtures thereof; and
f. Separating said purer polypropylene from said third solution;
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wherein said second fluid solvent has the same chemical composition or a
different
chemical composition as the first fluid solvent.
Additional features of the invention may become apparent to those skilled in
the art from a
review of the following detailed description, taken in conjunction with the
examples.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block flow diagram showing the major steps of one embodiment of
the present
invention.
FIG. 2 is a calibration curve for the calculation of polyethylene content in
polypropylene using
enthalpy values from DSC measurements.
FIG. 3A is a schematic of the experimental apparatus used in the extraction
step of examples 2
and 3.
FIG. 3B is a schematic of the experimental apparatus used in the dissolution
and sedimentation
steps of examples 2 and 3.
FIG. 4 is a photograph of the example specimens.
DETAILED DESCRIPTION OF THE INVENTION
I. Definitions
As used herein, the term "reclaimed polymer" refers to a polymer used for a
previous
purpose and then recovered for further processing.
As used herein, the term "reclaimed polypropylene" (rPP) refers to a
polypropylene
polymer used for a previous purpose and then recovered for further processing.
As used herein, the term "post-consumer" refers to a source of material that
originates after
the end consumer has used the material in a consumer good or product.
As used herein, the term "post-consumer recycle" (PCR) refers to a material
that is
produced after the end consumer has used the material and has disposed of the
material in a waste
stream.
As used herein, the term "post-industrial" refers to a source of a material
that originates
during the manufacture of a good or product.
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As used herein, the term "fluid solvent" refers to a substance that may exist
in the liquid
state under specified conditions of temperature and pressure. In some
embodiments the fluid
solvent may be a predominantly homogenous chemical composition of one molecule
or isomer,
while in other embodiments, the fluid solvent may be a mixture of several
different molecular
compositions or isomers. Further, in some embodiments of the present
invention, the term "fluid
solvent" may also apply to substances that are at, near, or above the critical
temperature and critical
pressure (critical point) of that substance. It is well known to those having
ordinary skill in the art
that substances above the critical point of that substance are known as
"supercritical fluids" which
do not have the typical physical properties (i.e. density) of a liquid.
As used herein, the term "dissolved" means at least partial incorporation of a
solute
(polymeric or non-polymeric) in a solvent at the molecular level. Further, the
thermodynamic
stability of the solute/solvent solution can be described by the following
equation 1:
Equation 1
= ¨ T
where AG,,,õ is the Gibbs free energy change of mixing of a solute with a
solvent, AHmix is
the enthalpy change of mixing, T is the absolute temperature, and ASõ,,õ is
the entropy of mixing.
To maintain a stable solution of a solute in a solvent, the Gibbs free energy
must be negative and
at a minimum. Thus, any combination of solute and solvent that minimize a
negative Gibbs free
energy at appropriate temperatures and pressures can be used for the present
invention.
As used herein, the term "standard boiling point" refers to the boiling
temperature at an
absolute pressure of exactly 100 kPa (1 bar, 14.5 psia, 0.9869 atm) as
established by the
International Union of Pure and Applied Chemistry (IUPAC).
As used herein, the term "standard enthalpy change of vaporization" refers to
the enthalpy
change required to transform a specified quantity of a substance from a liquid
into a vapor at the
standard boiling point of the substance.
As used herein, the term "polypropylene solution" refers to a solution of
polypropylene
dissolved in a solvent. The polypropylene solution may contain undissolved
matter and thus the
polypropylene solution may also be a "slurry" of undissolved matter suspended
in a solution of
polypropylene dissolved in a solvent.
As used herein, the terms "sedimentation" and "settling" refer to the tendency
of particles
within a suspension to separate from a liquid in response to a force
(typically a gravitational force)
acting upon the particles.
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As used herein, the term "suspended contaminants" refers to unwanted or
undesired
constituents that are present throughout the bulk of medium of a heterogeneous
mixture.
As used herein, the term "solid media" refers to a substance that exists in
the solid state
under the conditions of use. The solid media may be crystalline, semi-
crystalline, or amorphous.
The solid media may be granular and may be supplied in different shapes (i.e.
spheres, cylinders,
pellets, etc.). If the solid media is granular, the particle size and particle
size distribution of solid
media may be defined by the mesh size used to classify the granular media. An
example of
standard mesh size designations can be found in the American Society for
Testing and Material
(ASTM) standard ASTM El 1 "Standard Specification for Woven Wire Test Sieve
Cloth and Test
Sieves." The solid media may also be a non-woven fibrous mat or a woven
textile.
As used herein, the term "purer polypropylene solution" refers to a
polypropylene solution
having fewer contaminants relative to the same polypropylene solution prior to
a purification step.
As used herein, the term "extraction" refers to the practice of transferring a
solute species
from a liquid phase (or solid matrix) across a phase boundary to a separate
immiscible liquid phase.
The driving force(s) for extraction are described by partition theory.
As used herein, the term "extracted" refers to a material having fewer solute
species relative
to the same material prior to an extraction step. As used herein, the term
"extracted reclaimed
polypropylene" refers to a reclaimed polypropylene having fewer solute species
relative to the
same reclaimed polypropylene prior to an extraction step.
As used herein, the term "virgin-like" means essentially contaminant-free,
pigment-free,
odor-free, homogenous, and similar in properties to virgin polymers.
As used herein, the term "primarily polypropylene copolymer" refers a
copolymer with
greater than 70 mol% of propylene repeating units.
As used herein, any reference to international units of pressure (e.g. MPa)
refers to gauge
pressure.
II. Method for Purifying Contaminated Polypropylene
Surprisingly, it has been found that certain fluid solvents, which in a
preferred embodiment
exhibit temperature and pressure-dependent solubility for polymers, when used
in a relatively
simple process can be used to purify contaminated polymers, especially
reclaimed or recycled
polymers, to a near virgin-like quality. This process, exemplified in FIG. 1,
comprises 1) obtaining
a reclaimed polypropylene (step a in FIG. 1), followed by 2) extracting the
polypropylene with a
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fluid solvent at an extraction temperature (TE) and at an extraction pressure
(PE) (step b in FIG. 1),
followed by 3) dissolution of the polypropylene in a fluid solvent at a
dissolution temperature (TD)
and at a dissolution pressure (PD) (step c in FIG. 1), followed by 4)
sedimentation of the polymer
solution at a dissolution temperature (TD) and at a dissolution pressure (PD)
(step d in FIG. 1),
followed by 5) contacting the dissolved polypropylene solution with solid
media at a dissolution
temperature (TD) and at a dissolution pressure (PD) (step e in FIG. 1),
followed by separation of
the polypropylene from the fluid solvent (step fin FIG. 1).
In one embodiment of the present invention, the purified polypropylene, which
may be
sourced from post-consumer waste streams, are essentially contaminant-free,
pigment-free, odor-
free, homogenous, and similar in properties to virgin polypropylene.
Furthermore, in a preferred
embodiment, the physical properties of the fluid solvent of the present
invention may enable more
energy efficient methods for separation of the fluid solvent from the purified
polypropylene.
Reclaimed Polypropylene
In one embodiment of the present invention, a method for purifying reclaimed
polypropylene includes obtaining reclaimed polypropylene. For the purposes of
the present
invention, the reclaimed polypropylene is sourced from post-consumer, post-
industrial, post-
commercial, and/or other special waste streams. For example, post-consumer
waste polypropylene
can be derived from curbside recycle streams where end-consumers place used
polymers from
packages and products into a designated bin for collection by a waste hauler
or recycler. Post-
consumer waste polymers can also be derived from in-store "take-back" programs
where the
consumer brings waste polymers into a store and places the waste polymers in a
designated
collection bin. An example of post-industrial waste polymers can be waste
polymers produced
during the manufacture or shipment of a good or product that are collected as
unusable material by
the manufacturer (i.e. trim scraps, out of specification material, start up
scrap). An example of
waste polymers from a special waste stream can be waste polymers derived from
the recycling of
electronic waste, also known as "e-waste." Another example of waste polymers
from a special
waste stream can be waste polymers derived from the recycling of automobiles.
Another example
of waste polymers from a special waste stream can be waste polymers derived
from the recycling
of used carpeting and textiles.
For the purposes of the present invention, the reclaimed polypropylene is a
homogenous
composition of an individual polymer or a mixture of several different
polypropylene
compositions. Non-limiting examples of polypropylene compositions are
homopolymers of
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propylene, copolymers of propylene and ethylene (including "impact" and
"random-clarified"
copolymers), copolymers of propylene and alpha-olefins, polypropylene rubbers,
and other
dissolvable polypropylene compositions that may be apparent to those having
ordinary skill in the
art.
The reclaimed polypropylene may also contain various pigments, dyes, process
aides,
stabilizing additives, fillers, and other performance additives that were
added to the polymer during
polymerization or conversion of the original polymer to the final form of an
article. Non-limiting
examples of pigments are organic pigments, such as copper phthalocyanine,
inorganic pigments,
such as titanium dioxide, and other pigments that may be apparent to those
having ordinary skill
in the art. A non-limiting example of an organic dye is Basic Yellow 51. Non-
limiting examples
of process aides are antistatic agents, such as glycerol monostearate and slip-
promoting agents,
such as erucamide. A non-limiting example of a stabilizing additive is
octadecy1-3-(3,5-di-
tert.buty1-4-hydroxypheny1)-propionate. Non-limiting examples of fillers are
calcium carbonate,
talc, and glass fibers.
Solvent
The fluid solvent of the present invention has a standard boiling point less
than about 70 C.
Pressurization maintains solvents, which have standard boiling points below
the operating
temperature range of the present invention, in a state in which there is
little or no solvent vapor. In
one embodiment, the fluid solvent with a standard boiling point less than
about 70 C is selected
from the group consisting of carbon dioxide, ketones, alcohols, ethers,
esters, alkenes, alkanes, and
mixtures thereof. Non-limiting examples of fluid solvents with standard boing
points less than
about 70 C are carbon dioxide, acetone, methanol, dimethyl ether, diethyl
ether, ethyl methyl ether,
tetrahydrofuran, methyl acetate, ethylene, propylene, 1-butene, 2-butene,
isobutylene, 1-pentene,
2-pentene, branched isomers of pentene, 1-hexene, 2-hexene, methane, ethane,
propane, n-butane,
isobutane, n-pentane, isopentane, neopentane, n-hexane, isomers of isohexane,
and other
substances that may be apparent to those having ordinary skill in the art.
The selection of the fluid solvent used will dictate the temperature and
pressure ranges used
to perform the steps of the present invention. A review of polymer phase
behavior in solvents of
the kind described by the present invention is provided in the following
reference: McHugh et al.
(1999) Chem. Rev. 99:565-602.
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Extraction
In one embodiment of the present invention, a method for purifying
polypropylene includes
contacting reclaimed polypropylene with a fluid solvent at a temperature and
at a pressure wherein
the polymer is essentially insoluble in the fluid solvent. Although not
wishing to be bound by any
theory, applicants believe that the temperature and pressure-dependent
solubility can be controlled
in such a way to prevent the fluid solvent from fully solubilizing the
polymer, however, the fluid
solvent can diffuse into the polymer and extract any extractable
contamination. The extractable
contamination may be residual processing aides added to the polymer, residual
product
formulations which contacted the polymer, such as perfumes and flavors, dyes,
and any other
extractable material that may have been intentionally added or unintentionally
became
incorporated into the polymer, for example, during waste collection and
subsequent accumulation
with other waste materials.
In one embodiment, the controlled extraction may be accomplished by fixing the
temperature of the polymer/fluid solvent system and then controlling the
pressure below a pressure,
or pressure range, where the polymer dissolves in the fluid solvent. In
another embodiment, the
controlled extraction is accomplished by fixing the pressure of the
polymer/solvent system and
then controlling the temperature below a temperature, or temperature range
where the polymer
dissolves in the fluid solvent. The temperature and pressure-controlled
extraction of the polymer
with a fluid solvent uses a suitable pressure vessel and may be configured in
a way that allows for
continuous extraction of the polymer with the fluid solvent. In one embodiment
of the present
invention, the pressure vessel may be a continuous liquid-liquid extraction
column where molten
polymer is pumped into one end of the extraction column and the fluid solvent
is pumped into the
same or the opposite end of the extraction column. In another embodiment, the
fluid containing
extracted contamination is removed from the process. In another embodiment,
the fluid containing
extracted contamination is purified, recovered, and recycled for use in the
extraction step or a
different step in the process. In one embodiment of the present invention, the
extraction may be
performed as a batch method, wherein the reclaimed polypropylene is fixed in a
pressure vessel
and the fluid solvent is continuously pumped through the fixed polymer phase.
The extraction time
or the amount of fluid solvent used will depend on the desired purity of the
final purer polymer
and the amount of extractable contamination in the starting reclaimed
polypropylene. In another
embodiment, the fluid containing extracted contamination is contacted with
solid media in a
separate step as described in the "Purification" section below. In another
embodiment, a method
for purifying reclaimed polypropylene includes contacting reclaimed
polypropylene with a fluid
Date Recue/Date Received 2020-09-29
14635M-DW 14
solvent at a temperature and at a pressure wherein the polymer is molten and
in the liquid state. In
another embodiment, the reclaimed polypropylene is contacted with the fluid
solvent at a
temperature and at a pressure wherein the polymer is in the solid state.
In one embodiment, a method for purifying reclaimed polypropylene includes
contacting
polypropylene with a fluid solvent at a temperature and a pressure wherein the
polypropylene
remains essentially undissolved. In another embodiment, a method for purifying
reclaimed
polypropylene includes contacting polypropylene with n-butane at a temperature
from about 80 C
to about 220 C. In another embodiment, a method for purifying reclaimed
polypropylene includes
contacting polypropylene with n-butane at a temperature from about 100 C to
about 200 C. In
another embodiment, a method for purifying reclaimed polypropylene includes
contacting
polypropylene with n-butane at a temperature from about 130 C to about 180 C.
In another
embodiment, a method for purifying reclaimed polypropylene includes contacting
polypropylene
with n-butane at a pressure from about 150 psig (1.03 MPa) to about 3,000 psig
(20.68 MPa). In
another embodiment, a method for purifying reclaimed polypropylene includes
contacting
polypropylene with n-butane at a pressure from about 1,000 psig (6.89 MPa) to
about 2,750 psig
(18.96 MPa). In another embodiment, a method for purifying reclaimed
polypropylene includes
contacting polypropylene with n-butane at a pressure from about 1,500 psig
(10.34 MPa) to about
2,500 psig (17.24 MPa).
In another embodiment, a method for purifying reclaimed polypropylene includes
contacting polypropylene with propane at a temperature from about 80 C to
about 220 C. In
another embodiment, a method for purifying reclaimed polypropylene includes
contacting
polypropylene with propane at a temperature from about 100 C to about 200 C.
In another
embodiment, a method for purifying reclaimed polypropylene includes contacting
polypropylene
with propane at a temperature from about 130 C to about 180 C. In another
embodiment, a method
for purifying reclaimed polypropylene includes contacting polypropylene with
propane at a
pressure from about 200 psig (1.38 MPa) to about 8,000 psig (55.16 MPa). In
another embodiment,
a method for purifying reclaimed polypropylene includes contacting
polypropylene with propane
at a pressure from about 1,000 psig (6.89 MPa) to about 6,000 psig (41.37
MPa). In another
embodiment, a method for purifying reclaimed polypropylene includes contacting
polypropylene
with propane at a pressure from about 2,000 psig (13.79 MPa) to about 4,000
psig (27.58 MPa).
Date Recue/Date Received 2020-09-29
14635M-DW 15
Dissolution
In one embodiment of the present invention, a method for purifying reclaimed
polypropylene includes dissolving the reclaimed polypropylene in a fluid
solvent at a temperature
and at a pressure wherein the polymer is dissolved in the fluid solvent.
Although not wishing to
be bound by any theory, applicants believe that the temperature and pressure
can be controlled in
such a way to enable thermodynamically favorable dissolution of the reclaimed
polymer in a fluid
solvent. Furthermore, the temperature and pressure can be controlled in such a
way to enable
dissolution of a particular polymer or polymer mixture while not dissolving
other polymers or
polymer mixtures. This controllable dissolution enables the separation of
polymers from polymer
mixtures.
In one embodiment of the present invention, a method for purifying polymers
includes
dissolving contaminated reclaimed polypropylene in a solvent that does not
dissolve the
contaminants under the same conditions of temperature and pressure. The
contaminants may
include pigments, fillers, dirt, and other polymers. These contaminants are
released from the
reclaimed polypropylene upon dissolution and then removed from the polymer
solution via a
subsequent solid-liquid separation step.
In one embodiment, a method for purifying reclaimed polypropylene includes
dissolving
polypropylene in a fluid solvent at a temperature and a pressure wherein the
polypropylene is
dissolved in the fluid solvent. In another embodiment, a method for purifying
reclaimed
polypropylene includes dissolving polypropylene in n-butane at a temperature
from about 90 C to
about 220 C. In another embodiment, a method for purifying reclaimed
polypropylene includes
dissolving polypropylene in n-butane at a temperature from about 100 C to
about 200 C. In
another embodiment, a method for purifying reclaimed polypropylene includes
dissolving
polypropylene in n-butane at a temperature from about 130 C to about 180 C. In
another
embodiment, a method for purifying reclaimed polypropylene includes dissolving
polypropylene
in n-butane at a pressure from about 350 psig (2.41 MPa) to about 4,000 psig
(27.57 MPa). In
another embodiment, a method for purifying reclaimed polypropylene includes
dissolving
polypropylene in n-butane at a pressure from about 1,000 psig (6.89 MPa) to
about 3,500 psig
(24.13 MPa). In another embodiment, a method for purifying reclaimed
polypropylene includes
dissolving polypropylene in n-butane at a pressure from about 2,000 psig
(13.79 MPa) to about
3,000 psig (20.68 MPa). In another embodiment, a method for purifying
reclaimed polypropylene
includes dissolving polypropylene in n-butane at a mass percent concentration
of at least 0.5%. In
another embodiment, the polypropylene is dissolved at a mass percent
concentration of at least 1%.
Date Recue/Date Received 2020-09-29
14635M-DW 16
In another embodiment, the polypropylene is dissolved at a mass percent
concentration of at least
2%. In another embodiment, the polypropylene is dissolved at a mass percent
concentration of at
least 3%. In another embodiment, the polypropylene is dissolved at a mass
percent concentration
of at least 4%. In another embodiment, the polypropylene is dissolved at a
mass percent
concentration of at least 5%. In another embodiment, a method for purifying
reclaimed
polypropylene includes dissolving polypropylene in n-butane at a mass percent
concentration up
to 20%. In another embodiment, the polypropylene is dissolved at a mass
percent concentration
up to 18%. In another embodiment, the polypropylene is dissolved at a mass
percent concentration
up to 16%. In another embodiment, the polypropylene is dissolved at a mass
percent concentration
up to 14%. In another embodiment, the polypropylene is dissolved at a mass
percent concentration
up to 12%.
In another embodiment, a method for purifying reclaimed polypropylene includes
dissolving polypropylene in propane at a temperature from about 90 C to about
220 C. In another
embodiment, a method for purifying reclaimed polypropylene includes dissolving
polypropylene
in propane at a temperature from about 100 C to about 200 C. In another
embodiment, a method
for purifying reclaimed polypropylene includes dissolving polypropylene in
propane at a
temperature from about 130 C to about 180 C. In another embodiment, a method
for purifying
reclaimed polypropylene includes dissolving polypropylene in propane at a
pressure from about
2,000 psig (13.79 MPa) to about 8,000 psig (55.16 MPa). In another embodiment,
a method for
purifying reclaimed polypropylene includes dissolving polypropylene in propane
at a pressure
from about 3,000 psig (20.68 MPa) to about 6,000 psig (41.37 MPa). In another
embodiment, a
method for purifying reclaimed polypropylene includes dissolving polypropylene
in propane at a
pressure from about 3,500 psig (24.13 MPa) to about 5,000 psig (34.47 MPa). In
another
embodiment, a method for purifying reclaimed polypropylene includes dissolving
polypropylene
in propane at a mass percent concentration of at least 0.5%. In another
embodiment, the
polypropylene is dissolved at a mass percent concentration of at least 1%. In
another embodiment,
the polypropylene is dissolved at a mass percent concentration of at least 2%.
In another
embodiment, the polypropylene is dissolved at a mass percent concentration of
at least 3%. In
another embodiment, the polypropylene is dissolved at a mass percent
concentration of at least 4%.
In another embodiment, the polypropylene is dissolved at a mass percent
concentration of at least
5%. In another embodiment, a method for purifying reclaimed polypropylene
includes dissolving
polypropylene in propane at a mass percent concentration up to 20%. In another
embodiment, the
polypropylene is dissolved at a mass percent concentration up to 18%. In
another embodiment,
Date Recue/Date Received 2020-09-29
14635M-DW 17
the polypropylene is dissolved at a mass percent concentration up to 16%. In
another embodiment,
the polypropylene is dissolved at a mass percent concentration up to 14%. In
another embodiment,
the polypropylene is dissolved at a mass percent concentration up to 12%.
Sedimentation
In one embodiment of the present invention, a method for purifying
polypropylene includes
separating the undissolved contaminants from the polypropylene solution via a
sedimentation (also
known as settling) step at a temperature and at a pressure wherein the polymer
remains dissolved
in the fluid solvent. In one embodiment, the settling step causes the
undissolved contaminants to
experience a force that uniformly moves the undissolved contaminants in the
direction of the force.
Typically the applied settling force is gravity, but can also be a
centrifugal, centripetal, or some
other force. The amount of applied force and duration of settling time will
depend upon several
parameters, including, but not limited to: particle size of the contaminant
particles, contaminant
particle densities, density of the fluid or solution, and the viscosity of the
fluid or solution. The
following equation (equation 2) is a relationship between the aforementioned
parameters and the
settling velocity, which is a measure of the contaminant sedimentation rate:
Equation 2
2(pp ¨ pf)gr2
v= ___________________________________________
917
where v is the settling velocity, pp is the density of the contaminant
particle, pf is the
density of the fluid or solution, g is the acceleration due to the applied
force (typically gravity), r
is the radius of the contaminant particle and n is the dynamic viscosity of
the fluid or solution.
Some of the key parameters that determine the solution viscosity are: the
chemical composition
of the fluid solvent, the molecular weight of the polymer dissolved in the
fluid solvent, the
concentration of dissolved polymer in the fluid solvent, the temperature of
the fluid solvent
solution, and the pressure of the fluid solvent solution.
In one embodiment, a method for purifying reclaimed polypropylene includes
settling
contaminants from a polypropylene/fluid solvent solution at a temperature and
at a pressure
wherein the polypropylene remains dissolved in the fluid solvent. In another
embodiment, a
method for purifying reclaimed polypropylene includes settling contaminants
from a
polypropylene/n-butane solution at a temperature from about 90 C to about 220
C. In another
embodiment, a method for purifying reclaimed polypropylene includes settling
contaminants from
Date Recue/Date Received 2020-09-29
14635M-DW 18
a polypropylene/n-butane solution at a temperature from about 100 C to about
200 C. In another
embodiment, a method for purifying reclaimed polypropylene includes settling
contaminants from
a polypropylene/n-butane solution at a temperature from about 130 C to about
180 C. In another
embodiment, a method for purifying reclaimed polypropylene includes settling
contaminants from
a polypropylene/n-butane solution at a pressure from about 350 psig (2.41 MPa)
to about 4,000
psig (27.57 MPa). In another embodiment, a method for purifying reclaimed
polypropylene
includes settling contaminants from a polypropylene/n-butane solution at a
pressure from about
1,000 psig (6.89 MPa) to about 3,500 psig (24.13 MPa). In another embodiment,
a method for
purifying reclaimed polypropylene includes settling contaminants from a
polypropylene/n-butane
solution at a pressure from about 2,000 psig (13.79 MPa) to about 3,000 psig
(20.68 MPa). In
another embodiment, a method for purifying reclaimed polypropylene includes
settling
contaminants from a polypropylene/n-butane solution wherein the polypropylene
is dissolved at a
mass percent concentration of at least 0.5%. In another embodiment, the
polypropylene is
dissolved at a mass percent concentration of at least 1%. In another
embodiment, the
polypropylene is dissolved at a mass percent concentration of at least 2%. In
another embodiment,
the polypropylene is dissolved at a mass percent concentration of at least 3%.
In another
embodiment, the polypropylene is dissolved at a mass percent concentration of
at least 4%. In
another embodiment, the polypropylene is dissolved at a mass percent
concentration of at least 5%.
In another embodiment, a method for purifying reclaimed polypropylene includes
settling
contaminants from a polypropylene/n-butane solution where in the polypropylene
is dissolved at a
mass percent concentration up to 20%. In another embodiment, the polypropylene
is dissolved at
a mass percent concentration up to 18%. In another embodiment, the
polypropylene is dissolved
at a mass percent concentration up to 16%. In another embodiment, the
polypropylene is dissolved
at a mass percent concentration up to 14%. In another embodiment, the
polypropylene is dissolved
at a mass percent concentration up to 12%.
In another embodiment, a method for purifying reclaimed polypropylene includes
settling
contaminants from a polypropylene/propane solution at a temperature from about
90 C to about
220 C. In another embodiment, a method for purifying reclaimed polypropylene
includes settling
contaminants from a polypropylene/propane solution with at a temperature from
about 100 C to
about 200 C. In another embodiment, a method for purifying reclaimed
polypropylene includes
settling contaminants from a polypropylene/propane solution at a temperature
from about 130 C
to about 180 C. In another embodiment, a method for purifying reclaimed
polypropylene includes
settling contaminants from a polypropylene/propane solution at a pressure from
about 2,000 psig
Date Recue/Date Received 2020-09-29
14635M-DW 19
(13.79 MPa) to about 8,000 psig (55.16 MPa). In another embodiment, a method
for purifying
reclaimed polypropylene includes settling contaminants from a
polypropylene/propane solution at
a pressure from about 3,000 psig (20.68 MPa) to about 6,000 psig (41.37 MPa).
In another
embodiment, a method for purifying reclaimed polypropylene includes settling
contaminants from
a polypropylene/propane solution with at a pressure from about 3,500 psig
(24.13 MPa) to about
5,000 psig (34.47 MPa). In another embodiment, a method for purifying
reclaimed polypropylene
includes settling contaminants from a polypropylene/propane solution wherein
the polypropylene
is dissolved at a mass percent concentration of at least 0.5%. In another
embodiment, the
polypropylene is dissolved at a mass percent concentration of at least 1%. In
another embodiment,
the polypropylene is dissolved at a mass percent concentration of at least 2%.
In another
embodiment, the polypropylene is dissolved at a mass percent concentration of
at least 3%. In
another embodiment, the polypropylene is dissolved at a mass percent
concentration of at least 4%.
In another embodiment, the polypropylene is dissolved at a mass percent
concentration of at least
5%. In another embodiment, a method for purifying reclaimed polypropylene
includes settling
contaminants from a polypropylene/propane solution where in the polypropylene
is dissolved at a
mass percent concentration up to 20%. In another embodiment, the polypropylene
is dissolved at
a mass percent concentration up to 18%. In another embodiment, the
polypropylene is dissolved
at a mass percent concentration up to 16%. In another embodiment, the
polypropylene is dissolved
at a mass percent concentration up to 14%. In another embodiment, the
polypropylene is dissolved
at a mass percent concentration up to 12%.
Purification
In one embodiment of the present invention, a method for purifying
polypropylene includes
contacting a contaminated polymer solution with solid media at a temperature
and at a pressure
wherein the polymer remains dissolved in the fluid solvent. The solid media of
the present
invention is any solid material that removes at least some of the
contamination from a solution of
reclaimed polypropylene dissolved in the fluid solvent of the present
invention. Although not
wishing to be bound by any theory, the applicants believe that the solid media
removes
contamination by a variety of mechanisms. Non-limiting examples of possible
mechanisms
include adsorption, absorption, size exclusion, ion exclusion, ion exchange,
and other mechanisms
that may be apparent to those having ordinary skill in the art. Furthermore,
the pigments and other
contaminants commonly found in reclaimed polypropylene may be polar compounds
and may
preferentially interact with the solid media, which may also be at least
slightly polar. The polar-
Date Recue/Date Received 2020-09-29
14635M-DW 20
polar interactions are especially favorable when non-polar solvents, such as
alkanes, are used as
the fluid solvent.
In one embodiment of the present invention, the solid media is selected from
the group
consisting of inorganic substances, carbon-based substances, or mixtures
thereof. Useful examples
of inorganic substances include oxides of silicon, oxides of aluminum, oxides
of iron, aluminum
silicates, magnesium silicates, amorphous volcanic glasses, silica, silica
gel, diatomite, sand,
quartz, reclaimed glass, alumina, perlite, fuller's earth, bentonite, and
mixtures thereof. Useful
examples of carbon-based substances include anthracite coal, carbon black,
coke, activated carbon,
cellulose, and mixtures thereof. In another embodiment of the present
invention, the solid media
is recycled glass.
In one embodiment of the present invention, the solid media is contacted with
the polymer
in a vessel for a specified amount of time while the solid media is agitated.
In another embodiment,
the solid media is removed from the purer polymer solution via a solid-liquid
separation step. Non-
limiting examples of solid-liquid separation steps include filtration,
decantation, centrifugation,
and settling. In another embodiment of the present invention, the contaminated
polymer solution
is passed through a stationary bed of solid media. In another embodiment of
the present invention,
the height or length of the stationary bed of solid media is greater than 5
cm. In another
embodiment of the present invention, the height or length of the stationary
bed of solid media is
greater than 10 cm. In another embodiment of the present invention, the height
or length of the
stationary bed of solid media is greater than 20 cm. In another embodiment of
the present
invention, the solid media is replaced as needed to maintain a desired purity
of polymer. In yet
another embodiment, the solid media is regenerated and re-used in the
purification step. In another
embodiment, the solid media is regenerated by fluidizing the solid media
during a backwashing
step.
In one embodiment, a method for purifying reclaimed polypropylene includes
contacting a
polypropylene/fluid solvent solution with solid media at a temperature and at
a pressure wherein
the polypropylene remains dissolved in the fluid solvent. In another
embodiment, a method for
purifying reclaimed polypropylene includes contacting a polypropylene/n-butane
solution with
solid media at a temperature from about 90 C to about 220 C. In another
embodiment, a method
for purifying reclaimed polypropylene includes contacting a polypropylene/n-
butane solution with
solid media at a temperature from about 100 C to about 200 C. In another
embodiment, a method
for purifying reclaimed polypropylene includes contacting a polypropylene/n-
butane solution with
solid media at a temperature from about 130 C to about 180 C. In another
embodiment, a method
Date Recue/Date Received 2020-09-29
14635M-DW 21
for purifying reclaimed polypropylene includes contacting a polypropylene/n-
butane solution with
solid media at a pressure from about 350 psig (2.41 MPa) to about 4,000 psig
(27.57 MPa). In
another embodiment, a method for purifying reclaimed polypropylene includes
contacting a
polypropylene/n-butane solution with solid media at a pressure from about
1,000 psig (6.89 MPa)
to about 3,500 psig (24.13 MPa). In another embodiment, a method for purifying
reclaimed
polypropylene includes contacting a polypropylene/n-butane solution with solid
media at a
pressure from about 2,000 psig (13.79 MPa) to about 3,000 psig (20.68 MPa). In
another
embodiment, a method for purifying reclaimed polypropylene includes contacting
a
polypropylene/n-butane solution with solid media wherein the polypropylene is
dissolved at a mass
percent concentration of at least 0.5%. In another embodiment, the
polypropylene is dissolved at
a mass percent concentration of at least 1%. In another embodiment, the
polypropylene is
dissolved at a mass percent concentration of at least 2%. In another
embodiment, the
polypropylene is dissolved at a mass percent concentration of at least 3%. In
another embodiment,
the polypropylene is dissolved at a mass percent concentration of at least 4%.
In another
embodiment, the polypropylene is dissolved at a mass percent concentration of
at least 5%. In
another embodiment, a method for purifying reclaimed polypropylene includes
contacting a
polypropylene/n-butane solution with solid media wherein the polypropylene is
dissolved at a mass
percent concentration up to 20%. In another embodiment, the polypropylene is
dissolved at a mass
percent concentration up to 18%. In another embodiment, the polypropylene is
dissolved at a mass
percent concentration up to 16%. In another embodiment, the polypropylene is
dissolved at a mass
percent concentration up to 14%. In another embodiment, the polypropylene is
dissolved at a mass
percent concentration up to 12%.
In another embodiment, a method for purifying reclaimed polypropylene includes
contacting a polypropylene/propane solution with solid media at a temperature
from about 90 C to
about 220 C. In another embodiment, a method for purifying reclaimed
polypropylene includes
contacting a polypropylene/propane solution with solid media at a temperature
from about 100 C
to about 200 C. In another embodiment, a method for purifying reclaimed
polypropylene includes
contacting a polypropylene/propane solution with solid media at a temperature
from about 130 C
to about 180 C. In another embodiment, a method for purifying reclaimed
polypropylene includes
contacting a polypropylene/propane solution with solid media at a pressure
from about 2,000 psig
(13.79 MPa) to about 8,000 psig (55.16 MPa). In another embodiment, a method
for purifying
reclaimed polypropylene includes contacting a polypropylene/propane solution
with solid media
at a pressure from about 3,000 psig (20.68 MPa) to about 6,000 psig (41.37
MPa). In another
Date Recue/Date Received 2020-09-29
14635M-DW 22
embodiment, a method for purifying reclaimed polypropylene includes contacting
a
polypropylene/propane solution with solid media at a pressure from about 3,500
psig (24.13 MPa)
to about 5,000 psig (34.47 MPa). In another embodiment, a method for purifying
reclaimed
polypropylene includes contacting a polypropylene/propane solution with solid
media wherein the
polypropylene is dissolved at a mass percent concentration of at least 0.5%.
In another
embodiment, the polypropylene is dissolved at a mass percent concentration of
at least 1%. In
another embodiment, the polypropylene is dissolved at a mass percent
concentration of at least 2%.
In another embodiment, the polypropylene is dissolved at a mass percent
concentration of at least
3%. In another embodiment, the polypropylene is dissolved at a mass percent
concentration of at
least 4%. In another embodiment, the polypropylene is dissolved at a mass
percent concentration
of at least 5%. In another embodiment, a method for purifying reclaimed
polypropylene includes
contacting a polypropylene/propane solution with solid media wherein the
polypropylene is
dissolved at a mass percent concentration up to 20%. In another embodiment,
the polypropylene
is dissolved at a mass percent concentration up to 18%. In another embodiment,
the polypropylene
is dissolved at a mass percent concentration up to 16%. In another embodiment,
the polypropylene
is dissolved at a mass percent concentration up to 14%. In another embodiment,
the polypropylene
is dissolved at a mass percent concentration up to 12%.
Separation
In one embodiment of the present invention, a method for purifying reclaimed
polypropylene includes separating the purer polymer from the fluid solvent at
a temperature and at
a pressure wherein the polymer precipitates from solution and is no longer
dissolved in the fluid
solvent. In another embodiment, the precipitation of the purer polymer from
the fluid solvent is
accomplished by reducing the pressure at a fixed temperature. In another
embodiment, the
precipitation of the purer polymer from the fluid solvent is accomplished by
reducing the
temperature at a fixed pressure. In another embodiment, the precipitation of
the purer polymer
from the fluid solvent is accomplished by increasing the temperature at a
fixed pressure. In another
embodiment, the precipitation of the purer polymer from the fluid solvent is
accomplished by
reducing both the temperature and pressure. The solvent can be partially or
completely converted
from the liquid to the vapor phase by controlling the temperature and
pressure. In another
embodiment, the precipitated polymer is separated from the fluid solvent
without completely
converting the fluid solvent into a 100% vapor phase by controlling the
temperature and pressure
of the solvent during the separation step. The separation of the precipitated
purer polymer is
Date Recue/Date Received 2020-09-29
14635M-DW 23
accomplished by any method of liquid-liquid or liquid-solid separation. Non-
limiting examples of
liquid-liquid or liquid-solid separations include filtration, decantation,
centrifugation, and settling.
In one embodiment, a method for purifying reclaimed polypropylene includes
separating
polypropylene from a polypropylene/fluid solvent solution at a temperature and
at a pressure
wherein the polypropylene precipitates from solution. In another embodiment, a
method for
purifying reclaimed polypropylene includes separating polypropylene from a
polypropylene/n-
butane solution at a temperature from about 0 C to about 220 C. In another
embodiment, a method
for purifying reclaimed polypropylene includes separating polypropylene from a
polypropylene/n-
butane solution at a temperature from about 100 C to about 200 C. In another
embodiment, a
method for purifying reclaimed polypropylene includes separating polypropylene
from a
polypropylene/n-butane solution at a temperature from about 130 C to about 180
C. In another
embodiment, a method for purifying reclaimed polypropylene includes separating
polypropylene
from a polypropylene/n-butane solution at a pressure from about 0 psig (0 MPa)
to about 2,000
psig (13.79 MPa). In another embodiment, a method for purifying reclaimed
polypropylene
includes separating polypropylene from a polypropylene/n-butane solution at a
pressure from about
50 psig (0.34 MPa) to about 1,500 psig (10.34 MPa). In another embodiment, a
method for
purifying reclaimed polypropylene includes separating polypropylene from a
polypropylene/n-
butane solution at a pressure from about 75 psig (0.52 MPa) to about 1,000
psig (6.89 MPa).
In another embodiment, a method for purifying reclaimed polypropylene includes
separating polypropylene from a polypropylene/propane solution at a
temperature from about -
42 C to about 220 C. In another embodiment, a method for purifying reclaimed
polypropylene
includes separating polypropylene from a polypropylene/propane solution at a
temperature from
about 0 C to about 150 C. In another embodiment, a method for purifying
reclaimed
polypropylene includes separating polypropylene from a polypropylene/propane
solution at a
temperature from about 50 C to about 130 C. In another embodiment, a method
for purifying
reclaimed polypropylene includes separating polypropylene from a
polypropylene/propane
solution at a pressure from about 0 psig (0 MPa) to about 6,000 psig (41.37
MPa). In another
embodiment, a method for purifying reclaimed polypropylene includes separating
polypropylene
from a polypropylene/propane solution at a pressure from about 50 psig (0.34
MPa) to about 3,000
psig (20.68 MPa). In another embodiment, a method for purifying reclaimed
polypropylene
includes separating polypropylene from a polypropylene/propane solution at a
pressure from about
75 psig (0.52 MPa) to about 1,000 psig (6.89 MPa).
Date Recue/Date Received 2020-09-29
14635M-DW 24
III Test Methods
The test methods described herein are used to measure the effectiveness of
various methods for
purifying polymers. Specifically, the methods described demonstrate the
effectiveness of a given
purification method at improving color and translucency/clarity (i.e. making
the color and opacity
of the reclaimed polypropylene closer to that of an uncolored virgin polymer),
reducing or
eliminating elemental contamination (i.e. removing heavy metals), reducing or
eliminating non-
combustible contamination (i.e. inorganic fillers), reducing or eliminating
volatile compounds
(especially volatile compounds that contribute to the malodor of reclaimed
polypropylene), and
reducing or eliminating polymeric contamination (i.e. polyethylene
contamination in
polypropylene).
Color and Opacity Measurement:
The color and opacity/translucency of a polymer are important parameters that
determine
whether or not a polymer can achieve the desired visual aesthetics of an
article manufactured from
the polymer. Reclaimed polypropylene, especially post-consumer derived
reclaimed
polypropylene, is typically dark in color and opaque due to residual pigments,
fillers, and other
contamination. Thus, color and opacity measurements are important parameters
in determining
the effectiveness of a method for purifying polymers.
Prior to color measurement, samples of either polymeric powders or pellets
were compression
molded into 30 mm wide x 30 mm long x 1 mm thick square test specimens (with
rounded corners).
Powder samples were first densified at room temperature (ca. 20-23 C) by cold
pressing the
powder into a sheet using clean, un-used aluminum foil as a contact-release
layer between stainless
steel platens. Approximately 0.85 g of either cold-pressed powder or pellets
was then pressed into
test specimens on a Carver Press Model C (Carver, Inc., Wabash, IN 46992-0554
USA) pre-heated
to 200 C using aluminum platens, unused aluminum foil release layers, and a
stainless steel shim
with a cavity corresponding to aforementioned dimensions of the square test
specimens. Samples
were heated for 5 minutes prior to applying pressure. After 5 minutes, the
press was then
compressed with at least 2 tons (1.81 metric tons) of hydraulic pressure for
at least 5 seconds and
then released. The molding stack was then removed and placed between two thick
flat metal heat
sinks for cooling. The aluminum foil contact release layers were then peeled
from the sample and
discarded. The flash around the sample on at least one side was peeled to the
mold edge and then
the sample was pushed through the form. Each test specimen was visually
evaluated for
Date Recue/Date Received 2020-09-29
14635M-DW 25
voids/bubble defects and only samples with no defects in the color measurement
area (0.7" (17.78
mm) diameter minimum) were used for color measurement.
The color of each sample was characterized using the International Commission
on
Illumination (CIE) L*, a*, b* three dimensional color space. The dimension L*
is a measure of
the lightness of a sample, with L*=0 corresponding to the darkest black sample
and L*=100
corresponding to the brightest white sample. The dimension a* is a measure of
the red or green
color of a sample with positive values of a* corresponding with a red color
and negative values of
a* corresponding with a green color. The dimension b* is a measure of the blue
or yellow color
of a sample with positive values of b* corresponding with a yellow color and
negative values of
b* corresponding with a blue color. The L* b* values of each 30 mm wide x 30
mm long x 1
mm thick square test specimen sample were measured on a HunterLab model
LabScan XE
spectrophotometer (Hunter Associates Laboratory, Inc., Reston, VA 20190-5280,
USA). The
spectrophotometer was configured with D65 as the standard illuminant, an
observer angle of 100
,
an area diameter view of 1.75" (44.45 mm), and a port diameter of 0.7" (17.78
mm).
The opacity of each sample, which is a measure of how much light passes
through the sample
(i.e. a measure of the sample's translucency), was determined using the
aforementioned HunterLab
spectrophotometer using the contrast ratio opacity mode. Two measurements were
made to
determine the opacity of each sample. One to measure the brightness value of
the sample backed
with a white backing, Y
- WhneBacking, and one to measure the brightness value of the sample backed
with a black backing, Y
- BlacicBacking- The opacity was then calculated from the brightness values
using the following Equation 3:
Equation 3
YBlack Backina
%Opacity ¨ v * 100
'White Backing
Elemental Analysis:
Many sources of reclaimed polypropylene have unacceptably high concentrations
of heavy
metal contamination. The presence of heavy metals, for example lead, mercury,
cadmium, and
chromium, may prevent the use of reclaimed polypropylene in certain
applications, such as food
or drug contact applications or medical device applications. Thus, measuring
the concentration of
heavy metals is important when determining the effectiveness of a method for
purifying polymers.
Elemental analysis was performed using Inductively Coupled Plasma Mass
Spectrometry (ICP-
MS). Test solutions were prepared in n=2 to n=6 depending on sample
availability by combining
Date Recue/Date Received 2020-09-29
14635M-DW 26
¨0.25 g sample with 4 mL of concentrated nitric acid and 1 mL of concentrated
hydrofluoric acid
(HF). The samples were digested using an Ultrawave Microwave Digestion
protocol consisting of
a 20 min ramp to 125 C, a 10 min ramp to 250 C and a 20 min hold at 250 C.
Digested samples
were cooled to room temperature. The digested samples were diluted to 50 mL
after adding 0.25
mL of 100 ppm Ge and Rh as the internal standard. In order to assess accuracy
of measurement,
pre-digestion spikes were prepared by spiking virgin polymer. Virgin polymer
spiked samples were
weighed out using the same procedure mentioned above and spiked with the
appropriate amount
of each single element standard of interest, which included the following: Na,
Al, Ca, Ti, Cr, Fe,
Ni, Cu, Zn, Cd, and Pb. Spikes were prepared at two different levels: a "low
level spike" and a
"high level spike". Each spike was prepared in triplicate. In addition to
spiking virgin polymer, a
blank was also spiked to verify that no errors occurred during pipetting and
to track recovery
through the process. The blank spiked samples were also prepared in triplicate
at the two different
levels and were treated in the same way as the spiked virgin polymer and the
test samples. A 9
point calibration curve was made by making 0.05, 0.1, 0.5, 1, 5, 10, 50, 100,
and 500 ppb solutions
containing Na, Al, Ca, Ti, Cr, Fe, Ni, Cu, Zn, Cd, and Pb. All calibration
standards were prepared
by dilution of neat standard reference solutions and 0.25 mL of 100 ppm Ge and
Rh as the internal
standard with 4 mL of concentrated nitric and 1 mL of concentrated HF.
Prepared standards, test
samples, and spiked test samples were analyzed using an Agilent's 8800 ICP-
QQQMS, optimized
according to manufacturer recommendations. The monitored m/z for each analyte
and the collision
cell gas that was used for analysis was as follows: Na, 23 m/z, H2; Al, 27
m/z, H2; Ca, 40 m/z, Hz;
Ti, 48 m/z, Hz; Cr, 52 m/z, He; Fe, 56 m/z, Hz; Ni, 60 m/z; no gas; Cu, 65
m/z, no gas; Zn, 64 m/z,
He; Cd, 112 m/z; H2; Pb, sum of 206 > 206, 207 > 207, 208 > 208 m/z, no gas;
Ge, 72 m/z, all
modes; Rh, 103 m/z, all modes. Ge was used as an internal standard for all
elements < 103 m/z
and Rh was used for all elements > 103 m/z.
Residual Ash Content:
Many sources of reclaimed polypropylene contain various fillers, for example
calcium
carbonate, talcum, and glass fiber. While useful in the original application
of the reclaimed
polypropylene, these fillers alter the physical properties of a polymer in way
that may be undesired
for the next application of the reclaimed polypropylene. Thus, measuring the
amount of filler is
important when determining the effectiveness of a method for purifying
polymers.
Thermogravimetric analysis (TGA) was performed to quantify the amount of non-
combustible
materials in the sample (also sometimes referred to as Ash Content). About 5-
15 mg of sample
Date Recue/Date Received 2020-09-29
14635M-DW 27
was loaded onto a platinum sample pan and heated to 700 C at a rate of 20
C/min in an air
atmosphere in a TA Instruments model Q500 TGA instrument. The sample was held
isothermal
for 10 min at 700 C. The percentage residual mass was measured at 700 C after
the isothermal
hold.
Odor Analysis:
Odor sensory analysis was performed by placing about 3 g of each sample in a
20mL glass vial
and equilibrating the sample at room temperature for at least 30 min. After
equilibration, each vial
was opened and the headspace was sniffed (bunny sniff) by a trained grader to
determine odor
intensity and descriptor profile. Odor intensity was graded according to the
following scale:
= Very Strong
4 = Strong
3 = Moderate
2 = Weak to Moderate
1= Weak
0 = No odor
Polymeric Contamination Analysis:
Many sources of reclaimed polypropylene, especially reclaimed polypropylene
originating
from mixed-stream sources, may contain undesired polymeric contamination.
Without wishing
to be bound by any theory, polymeric contamination, for example polyethylene
contamination in
polypropylene, may influence the physical properties of the polymer due to the
presence of
heterogeneous phases and the resulting weak interfaces.
Furthermore, the polymeric
contamination may also increase the opacity of the polymer and have an
influence on the color.
Thus, measuring the amount of polymeric contamination is important when
determining the
effectiveness of a method for purifying polymers.
Semi-crystalline polymeric contamination was evaluated using Differential
Scanning
Calorimetry (DSC). To measure the amount of polyethylene contamination in
polypropylene, a
set of five polypropylene/polyethylene blends were prepared with 2, 4, 6, 8,
and 10 wt% of
Formolene0 HB5502F HDPE (Formosa Plastics Corporation, USA) in Pro-fax 6331
polypropylene (LyondellBasell Industries Holdings, B.V.). Approximately 5-15
mg of each
Date Recue/Date Received 2020-09-29
14635M-DW 28
sample was sealed in an aluminum DSC pan and analyzed on a TA Instruments
model Q2000 DSC
with the following method:
1. Equilibrate at 30.00 C
2. Ramp 20.00 C/min to 200.00 C
3. Mark end of cycle 0
4. Ramp 20.00 C/min to 30.00 C
5. Mark end of cycle 1
6. Ramp 20.00 C/min to 200.00 C
7. Mark end of cycle 2
8. Ramp 20.00 C/min to 30.00 C
9. Mark end of cycle 3
10. Ramp 5.00 C/min to 200.00 C
11. Mark end of cycle 4
The enthalpy of melting for the HDPE peak around 128 C was calculated for each
sample
of known HDPE content using the 5.00 C/min DSC thermogram. A linear
calibration curve,
shown in FIG. 2, was established plotting enthalpy of melting versus known
HDPE concentration
(wt%).
Samples having unknown PE content were analyzed using the same aforementioned
DSC
equipment and method. PE content was calculated using the aforementioned
calibration curve.
The specific HDPE used to generate the calibration curve will more than likely
have a different
degree of crystallinity than the polyethylene (or polyethylene blend)
contamination that may be
present in a reclaimed polypropylene sample. The degree of crystallinity may
independently
influence the measured enthalpy of melting for polyethylene and thus influence
the resulting
calculation of polyethylene content. However, the DSC test method described
herein is meant to
serve as a relative metric to compare the effectiveness of different methods
to purify polymers and
is not meant to be a rigorous quantification of the polyethylene content in a
polymer blend. While
the aforementioned method described the measurement of polyethylene
contamination in
polypropylene, this method may be applied to measurement of other semi-
crystalline polymers
using different temperature ranges and peaks in the DSC thermogram.
Furthermore, alternative
methods, such as nuclear magnetic resonance (NMR) spectroscopy, may also be
used to measure
the amount of both semi-crystalline and amorphous polymeric contamination in a
sample.
Date Recue/Date Received 2020-09-29
14635M-DW 29
EXAMPLES
The following examples further describe and demonstrate embodiments within the
scope
of the present invention. The examples are given solely for the purpose of
illustration and are not
to be construed as limitations of the present invention, as many variations
thereof are possible
without departing from the spirit and scope of the invention.
Example 1
A sample of post-consumer derived recycled polypropylene mixed color flake was
sourced
from a supplier of recycled resins. The post-consumer recycled polypropylene
originated from the
United States and Canada. The as-received, mixed-color flake was
homogenized via
compounding on a Century/W&P ZSK30 twin screw extruder equipped with two 30 mm
general
purpose screws each with standard mixing and conveying elements. The screw
rotation speed was
about 50 rpm, the feeder throughput was about 20 lbs/hour (9.07 kg/hour) and
the temperature of
the barrel ranged from about 210 C at the die to about 150 C at the feed
throat. The gray strand
exiting the extruder was cooled in a room-temperature water bath, dried with
air, and chopped into
pellets.
The sample was characterized using the test methods disclosed herein and the
resulting data
are summarized in Table 1. The purpose of this example is to show the
properties of a
representative post-consumer derived recycled resin before purification.
The pellets and corresponding square test specimens were dark gray in color as
indicated
in the L*a*b* values of the square test specimens. The opacity of the samples
averaged about
100% opaque (i.e. no translucency). A photograph of the square test specimen
is shown in FIG.
4 as Example 1. As shown in FIG. 4, the specimen was dark in color and lacked
translucency.
This example serves as a representative baseline for heavy metal contamination
found in
post-consumer derived recycled polypropylene. When compared to other examples,
the heavy
metal contamination was found to be much greater in the as-received post-
consumer derived
recycled polypropylene.
The samples of example 1 had ash content values that averaged to about 1.2117
wt%, which
also serves as a baseline for the amount of non-combustible substances that
are often present in
post-consumer derived recycled polypropylene.
This example also serves as a representative baseline for odor compound
contamination
found in post-consumer derived recycled polypropylene. The samples of example
1 were found
Date Recue/Date Received 2020-09-29
14635M-DW 30
to have an odor intensity of 3.75 on a 5 point scale (5 being the most
intense), and were described
as having a "garbage", "dusty", or "sour" odor.
This example also serves as a representative baseline for polyethylene
contamination found
in post-consumer derived recycled polypropylene. The samples of example 1 had
polyethylene
contents that averaged to about 5.5 wt%.
Example 2
The sample of post-consumer derived recycled polypropylene mixed-color flake
described in
Example 1 was processed using the experimental apparatus shown in FIG. 3A and
FIG. 3B and the
following procedure:
1. 286 g of mixed color flake was loaded into a Parr Instrument Company Model
4552M 7.57
liter autoclave equipped with an overhead mechanical stirrer.
2. The autoclave was then completely filled with n-butane and equilibrated to
an internal fluid
temperature of 140 C and a fluid pressure of 900 psig (6.21 MPa).
3. The material in the autoclave was then extracted using the experimental
configuration
shown in FIG. 3A and the following procedure:
a. The system was stirred for 10 min at 140 C and 900 psig (6.21 MPa).
b. After stirring, the system was settled for 10 min at 140 C and 900 psig
(6.21 MPa).
c. One vessel volume of n-butane was flushed through the autoclave into a
sample
collection flask at 140 C and 900 psig (6.21 MPa).
d. The above extraction procedure was repeated four more times.
e. The material collected for all extraction cycles was labeled "Fraction 1".
4. The material remaining in the autoclave after extraction was then dissolved
in n-butane
using the experimental configuration shown in FIG. 3B and following procedure:
a. The system pressure was equilibrated to 1800 psig (12.41 MPa).
b. The system was stirred for 10 min at 140 C and 1800 psig (12.41 MPa).
c. The stirring was then stopped and the solution was allowed settle for 30
min at
140 C and 1800 psig (6.21 MPa).
d. After settling, the solution was removed of the autoclave by displacement
with
pressurized nitrogen (pre-equilibrated to 140 C and 1800 psig). The solution
exited
the autoclave through a dip tube was then passed through two heat-traced solid
media columns. Each column had an ID of 0.68" (1.73 cm) and a length of about
9.5" (24.13 cm). The first column contained about 21 g of 8-16 mesh Fuller's
Earth
Date Recue/Date Received 2020-09-29
14635M-DW 31
(Jaxon Filtration, JF 752-8/16, USA) that was pre-mixed in a beaker with about
21g
of 30-60 mesh Fuller's Earth (Jaxon Filtration, JF 752-3060, USA). The second
column contained about 21g of silica gel (Silicycle Ultra Pure Silica Gels,
SiliaFlash
GE60, Parc-Technologies, USA) that was pre-mixed in a beaker with about 21 g
of aluminum oxide (Activated Alumina, Selexsorb CDX, 7x14, BASF, USA). The
fluid stream leaving the bottom of the second pressure vessel was
depressurized
across an expansion valve into a side-arm Erlenmeyer flask. After
depressurizing
the fluid stream into the Erlenmeyer flask, the solvent vapor was vented
through the
side-arm port and any liquids/solids collected as fractions in flasks. Each
fraction
contained about 30 g of material and were labelled sequentially starting with
"Fraction 2". Fractions were collected until no more material was observed
eluting
into the flask.
5. After all samples were collected, the autoclave was equilibrated to
atmospheric pressure
and room temperature. All residual material in the autoclave was then
collected as a
residuum sample.
The data for the fraction 3 sample collected according the procedure disclosed
herein are
summarized in Table 1.
The solids isolated in fraction 3 in this example were white in color. When
the white solids
from fraction 3 were compression molded into square test specimens, the
specimens were colorless
and clear and similar in appearance to virgin polypropylene. A photograph of
the square test
specimen produced from fraction 3 is shown in FIG. 4 as Example 2. As a
reference, virgin
polypropylene is shown in FIG. 4 as Example 4. As shown in FIG. 4, the
specimen was clear and
comparable in color and translucency to virgin polypropylene. The L*a*b*
values showed that the
square test specimens were essentially colorless and showed a dramatic
improvement in color
relative to the square test specimens of example 1 (i.e. as-received post-
consumer derived
polypropylene). The L* values for the square test specimens from fraction 3 of
example 2 averaged
80.44 which were much improved when compared to the L* values for the square
test specimens
of example 1, which averaged 39.76. The opacity for the square test specimens
from fraction 3 of
example 2, which averaged 10.30% opaque (i.e. about 90% translucent), were
also much improved
when compared to the opacity values for the square test specimens of example
1, which averaged
about 100% opaque.
Date Recue/Date Received 2020-09-29
14635M-DW 32
The concentration of heavy metal contamination for the samples from fraction 3
of example
2 were also much improved when compared to the samples of example 1. For
example, the
concentration of sodium in the samples from fraction 3 of example 2 averaged
only 4,100 ppb
while the concentration of sodium in the samples of example 1 averaged 136,000
ppb (a reduction
of about 97%). The concentrations of all of the other elements measured were
all reduced by 77-
100% for the samples from fraction 3 of example 2 relative to the samples of
example 1.
The samples from fraction 3 of example 2 had ash content values that averaged
to about
0.3874 wt%, which were significantly lower than the ash content values for the
samples of example
1, which averaged to about 1.2117 wt%.
The samples from fraction 3 of example 2 were found to have an odor intensity
of 0.5 on a
point scale (5 being most intense), which was much improved when compared to
the odor
intensity of the samples of example 1, which had an odor intensity of 3.75.
Though low in odor
intensity, the samples from fraction 2 of example 2 were described as having a
"plastic" like odor
similar to virgin polypropylene.
The samples from fraction 3 of example 2 had average polyethylene content
values of about
1.1 wt%, which was much improved when compared to the polyethylene content of
the samples of
example 1, which averaged to about 5.5 wt%.
Example 3
The sample of post-consumer derived recycled polypropylene mixed-color flake
described in
Example 1 was processed using the experimental apparatus shown in FIG. 3A and
FIG. 3B and the
following procedure:
6. 173 g of mixed color flake was loaded into a Parr Instrument Company
Model 4552M 7.57
liter autoclave equipped with an overhead mechanical stirrer.
7. The autoclave was then completely filled with n-butane and equilibrated to
an internal fluid
temperature of 140 C and a fluid pressure of 900 psig (6.21 MPa).
8. The material in the autoclave was then extracted using the experimental
configuration
shown in FIG. 3A and following procedure:
f. The system was stirred for 10 min at 140 C and 900 psig (6.21 MPa).
g. After stirring, the system was settled for 10 min at 140 C and 900 psig
(6.21 MPa).
h. One vessel volume of n-butane was flushed through the autoclave into a
sample
collection flask at 140 C and 900 psig (6.21 MPa).
i. The above extraction procedure was repeated four more times.
Date Recue/Date Received 2020-09-29
14635M-DW 33
j. The samples collected for each extraction cycle were
sequentially labeled "Fraction
1" through "Fraction 5".
9. The material remaining in the autoclave after extraction was then dissolved
in n-butane
using the experimental configuration shown in FIG. 3B and following procedure:
e. The system pressure was equilibrated to 1800 psig (12.41 MPa).
f. The system was stirred for 10 min at 140 C and 1800 psig (12.41 MPa).
g. The stirring was then stopped and the solution was allowed settle for 60
min at
140 C and 1800 psig (6.21 MPa).
h. After settling, the solution was removed of the autoclave by displacement
with
pressurized n-butane (pre-equilibrated to 140 C and 1800 psig). The solution
exited
the autoclave through a dip tube was then passed through two heat-traced solid
media columns. Each column had an ID of 0.68" (1.73 cm) and a length of about
9.5" (24.13 cm). In this example, both columns were empty and did not contain
any solid media. The fluid stream leaving the bottom of the second pressure
vessel
was depressurized across an expansion valve into a side-arm Erlenmeyer flask.
After depressurizing the fluid stream into the Erlenmeyer flask, the solvent
vapor
was vented through the side-arm port and any liquids/solids collected as
fractions
in flasks. Each fraction contained about 30 g of material and were labelled
sequentially starting with "Fraction 6". Fractions were collected until no
more
material was observed eluting into the flask.
10. After all samples were collected, the autoclaved was equilibrated to
atmospheric pressure
and room temperature. All residual material in the autoclave was then
collected as a
residuum sample.
The data for the fraction 6 sample collected according the procedure disclosed
herein are
summarized in Table 1.
The solids isolated in fraction 6 in this example were off-white to yellow in
color. When the
off-white to yellow solids from fraction 6 were compression molded into square
test specimens,
the specimens were yellow in appearance. A photograph of the square test
specimen is shown in
FIG. 4 as Example 3. As shown in FIG. 4, the color and translucency of the
samples of example
3 were improved relative to the samples of example 1, but not comparable to
virgin polypropylene,
shown in FIG. 4 as Example 4. Even without the solid media contact step, the
L*a*b* values show
that the square test specimens from fraction 6 of example 3 were improved in
color relative to the
Date Recue/Date Received 2020-09-29
14635M-DW 34
samples of example 1 (i.e. as-received post-consumer derived polypropylene).
The L* values for
the square test specimens from fraction 6 of example 3 averaged 72.41 which
were improved when
compared to the L* values for the square test specimens of example 1, which
averaged 39.76. The
opacities for the square test specimens from fraction 6 of example 3, which
averaged 35.25%
opaque, were also improved when compared to the opacity values for the square
test specimens of
example 1, which averaged about 100% opaque.
The concentration of heavy metal contamination for the samples from fraction 6
of example
3 were also improved when compared to the samples of example 1. For example,
the concentration
of sodium in the samples from fraction 6 of example 3 averaged only 16,400 ppb
while the
concentration of sodium in the samples of example 1 averaged 136,000 ppb (a
reduction of about
88%). The concentrations of all of the other elements measured were all
reduced by 82-100% for
the samples from fraction 6 of example 3 relative to the samples of example 1.
The samples from fraction 6 of example 3 had ash content values that averaged
to about
0.2292 wt%, which were significantly lower than the ash content values for the
samples of example
1, which averaged to about 1.2117 wt%.
The samples from fraction 6 of example 3 were found to have an odor intensity
of 0.5 on a
point scale (5 being most intense), which was much improved when compared to
the odor
intensity of the samples of example 1, which had an odor intensity of 3.75.
Though low in odor
intensity, the samples from fraction 6 of example 3 were described as having a
"plastic" like odor
similar to virgin polypropylene.
The samples from fraction 6 of example 3 had average polyethylene content
values of about
1.0 wt%, which was much improved when compared to the polyethylene content of
the samples of
example 1, which averaged to about 5.5 wt%.
Example 4- Virgin Polypropylene Comparative Samples
Pro-fax 6331 polypropylene (LyondellBasell Industries Holdings, B.V.) was used
for all
"Virgin PP" comparative samples. The pellets of virgin PP were processed into
square test
specimens according the method described herein. The L*a*b* values for the
specimens made
from virgin PP averaged to 85.13 0.18, -0.71 0.01, and 2.27 0.02,
respectively. The square
test specimens had an average opacity of 7.56 0.21% opaque. This example
serves as a
comparison for the amount of heavy metal contamination found in a
representative sample of virgin
polypropylene. The samples of virgin polypropylene had ash content values that
averaged to about
0.3031 wt%. The pellets of virgin PP had an odor intensity of 0.5 on a 5 point
scale (5 being the
Date Recue/Date Received 2020-09-29
14635M-DW 35
most intense) and had odor described as being like "plastic." No polyethylene
was detected in the
sample of virgin propylene.
Table 1. Color, contamination, and odor removal of Examples 1-4
Example 1 Example 2 Example 3 Example 4
39.76 0.24 80.44 0.58 72.41 3.25 85.13 0.18
Color L*
(n=3) (n=3) (n=3) (n=3)
-2.51 0.04 -0.74 0.07 -2.55 0.14
-0.71 0.01
Color a*
(n=3) (n=3) (n=3) (n=3)
-1.20 0.11 2.88 0.13 14.35 1.49
2.27 0.02
Color b*
(n=3) (n=3) (n=3) (n=3)
100.19 0.15 10.30 0.63 35.25 1.09 7.56 0.21
Opacity (Y)
(n=3) (n=3) (n=3) (n=3)
136,000
Na (ppb) 4,100 1,300 16,400 190 46.1
109,000
LOQ=100 ppb (n=3) 4,300 (n=3) (n=3)
(n=6)
192,000
Al (ppb) 6,600 1,630 11,000 27,900 134
17,300
LOQ=1000 ppb (n=3) 1,096 (n=3) (n=3)
(n=6)
1,590,000
Ca (ppb) 3,410 334 57,400 32,700 250
79,500
LOQ=1000 ppb (n=3) 1,211 (n=3) (n=3)
(n=6)
2,800,000
Ti (ppb) 1,120 227 160,000 676 27.7
28,000
LOQ=100 ppb (n=3) 2,280 (n=3) (n=3)
(n=6)
Cr (ppb) 4,710 612 370 74.9 684 57.8 39.4 7.6
LOQ=10 ppb (n=6) (n=3) (n=3) (n=3)
108,000
Fe (ppb) 1080, 1,650 164 6,400 156 <LOQ
LOQ=1000 ppb (n=3) (n=3) (n=3)
(n=6)
Ni (ppb) 1,160 151 263 51.1 211 16.1 52.2 8.8
LOQ=10 ppb (n=6) (n=3) (n=3) (n=3)
Date Recue/Date Received 2020-09-29
14635M-DW 36
Cu (ppb) 15,300 612 32.8 4.36 518 244 <LOQ
LOQ=10 ppb (n=6) (n=3) (n=3) (n=3)
71,000
Zn (ppb) 346 263 4,260 541 82.1 41.2
1,420
LOQ=10 ppb (n=3) (n=3) (n=3)
(n=6)
Cd (ppb) 1,620 113 <LOQ 73.1 0.97 <LOQ
LOQ=10 ppb (n=6) (n=3) (n=3) (n=3)
Pb (ppb) 12,166 243 11.3 6.92 550 16.2
<LOQ
LOQ=10 ppb (n=6) (n=3) (n=3) (n=3)
Ash Content (% res 1.2117 0.3874 0.2292 0.3031
from TGA) 0.1501(n=3) 0.1430(n=3) 0.0569(n=3) 0.0383(n=3)
Odor Intensity
3.75 0.5 0.5 0.5
(0-5)
garbage,
Odor Descriptor plastic plastic plastic
dusty, sour
PE content (wt%)
5.5 0.3% 1.1 0.1% 1.0 0.1% <LOQ
DSC method
(n=3) (n=3) (n=3) (n=3)
LOQ=1%
The citation of any document is not an admission that it is prior art with
respect to any
invention disclosed or claimed herein or that it alone, or in any combination
with any other
reference or references, teaches, suggest or discloses any such invention.
Further, to the extent
that any meaning or definition of a term in this document conflicts with any
meaning or definition
of the same term in a document cited herein, the meaning or definition
assigned to that term in this
document shall govern.
While particular embodiments of the present invention have been illustrated
and described,
it would be obvious to those skilled in the art that various other changes and
modification can be
made without departing from the spirit and scope of the invention. It is
therefore intended to cover
in the appended claims all such changes and modification that are within the
scope of the present
invention.
Date Recue/Date Received 2020-09-29
