U.S. patent application number 17/229901 was filed with the patent office on 2021-10-21 for reducing surface and bulk contamination in plastic.
The applicant listed for this patent is The Procter & Gamble Company. Invention is credited to Norman Scott Broyles, Dimitris Ioannis Collias, John Moncrief Layman.
Application Number | 20210324170 17/229901 |
Document ID | / |
Family ID | 1000005583664 |
Filed Date | 2021-10-21 |
United States Patent
Application |
20210324170 |
Kind Code |
A1 |
Broyles; Norman Scott ; et
al. |
October 21, 2021 |
REDUCING SURFACE AND BULK CONTAMINATION IN PLASTIC
Abstract
The present invention generally relates to a method of reducing
contamination from plastics. The resulting purer plastic can be
used in demanding applications.
Inventors: |
Broyles; Norman Scott;
(Hamilton, OH) ; Collias; Dimitris Ioannis;
(Mason, OH) ; Layman; John Moncrief; (Liberty
Township, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Procter & Gamble Company |
Cincinnati |
OH |
US |
|
|
Family ID: |
1000005583664 |
Appl. No.: |
17/229901 |
Filed: |
April 14, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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63010078 |
Apr 15, 2020 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29K 2105/26 20130101;
B01D 11/0292 20130101; B29B 17/00 20130101; B29B 2017/0015
20130101; B29B 2017/0293 20130101; B29B 2017/0289 20130101; C08J
11/08 20130101 |
International
Class: |
C08J 11/08 20060101
C08J011/08; B29B 17/00 20060101 B29B017/00 |
Claims
1. A method to extract contaminates from a first plastic to produce
a purer plastic comprising: a. providing a first plastic comprising
individual contaminants, each individual contaminant having a
concentration; b. extracting said individual contaminates from said
first plastic at a temperature and a pressure, using an extraction
solvent, in extraction stages, to produce a purer plastic
comprising individual contaminates, each having a concentration;
wherein said extraction is liquid/liquid wherein said temperature
is above the primary melting point of the first plastic; wherein
said first plastic individual contaminants comprise at least one of
alkyl phenols, bisphenols, dioxins, PCBs, and phthalates; wherein
each individual contaminate concentration in said purer plastic is
reduced compared to each individual contaminate concentration in
said first plastic; and wherein the average of said reductions of
said concentrations of said first plastic contaminants to said
purer plastic contaminants is at least about 55% or LOQ.
2. The method of claim 1, wherein said contaminants of said first
plastic comprise at least one of 4-tertpentylphenol, bisphenol A,
OCDD, PCB 118, or 2-ethylhexyl phthalate.
3. The method of claim 1, wherein said number of stages is between
about 1 and about 50.
4. The method of claim 1, wherein said first plastic is a reclaimed
plastic comprising at least one of a post-industrial or
post-consumer film.
5. The method of claim 1, wherein said first plastic is surface
washed in a non-densified state by a surface washing process or
processes prior to extraction and wherein said surface washing
process or processes results in a greater than about an 80%
reduction in loosely bound surface contamination; wherein said
first plastic prior to surface washing has a surface area to volume
ratio of greater than about 1 mm-1.
6. The method of claim 5, wherein said surface washing process is
of the de-inking type; wherein said de-inking process results in a
delta E percent change of less than about 10% between the de-inked
first plastic and the first plastic without surface printed
ink.
7. The method of claim 1, wherein the liquid-liquid extraction is
conducted for a period of time represented by the sum of times for
the individual extraction stages which is less than about 360
minutes.
8. The method of claim 1, wherein the ratio of the total extraction
solvent mass used throughout all stages to first plastic mass,
called solvent ratio, is greater than about 5:1 and less than about
100:1.
9. The method of claim 1, wherein said extraction solvent is
purified after said extraction or said extraction stage or stages
to allow re-use in the extraction process by a solvent purification
processes; wherein said solvent purification process comprises at
least one stage of physical adsorption or absorption of the
chemical contaminants from the contaminated extraction solvent.
10. The method of claim 1, wherein said first plastic is a
reclaimed plastic including but not limited to a post-industrial or
post-consumer film; wherein said post-consumer film includes
post-commercial film and/or post-household film.
11. The method of claim 1, wherein said first plastic comprises
polyolefins and mixtures thereof.
12. The method of claim 1, wherein said first plastic is a film,
rigid, fiber, non-woven, and mixtures thereof.
13. The method of claim 1, wherein said extraction solvent has a
normal boiling point of less than about 200.degree. C.
14. The method of claim 1, wherein said extraction solvent is an
organic solvent or a mixture of organic solvents.
15. The method of claim 14, wherein said extraction solvent is at
least one of an oxygenated solvent or mixtures thereof.
16. The method of claim 14, wherein said solvent is at least one of
methane, ethane, propane, normal butane, isobutane, normal pentane,
isopentane, neopentane, hexanes (normal hexane, isohexane, and
neohexene), heptanes, octanes, or mixtures thereof.
17. The method of claim 1, wherein said extraction is liquid-liquid
extraction wherein said temperature of said extraction is below
about 300.degree. C. and said pressure is about atmospheric but
below about 1,000 atm.
18. The method of claim 17, wherein said temperature of said
liquid-liquid extraction is between about 150 and 250.degree. C.;
said pressure of said bulk purification is between about 13.6 atm
and about 68 atm; and said solvent of said liquid-liquid extraction
comprises hexanes; wherein the purification process results in an
average removal efficiency for 4-tertpentylphenol, bisphenol A,
OCDD, PCB 118, and 2-ethylhexyl phthalate of greater than about 55%
or LOQ.
19. The method of claim 17, wherein said temperature of said
liquid-liquid extraction is between about 150 C and about
250.degree. C.; and said pressure of said bulk purification is
between about 68 atm and about 340 atm; wherein said liquid-liquid
extraction solvent is di-methylether (DME); wherein the
purification process results in an average removal efficiency for
4-tertpentylphenol, bisphenol A, OCDD, PCB 118, and 2-ethylhexyl
phthalate of greater than about 55% or LOQ.
20. The method of claim 17; wherein said liquid-liquid extraction
solvent is hexanes; wherein said temperature and pressure of said
liquid-liquid extraction is about 235 C and about 40.8 atm; wherein
said first plastic is surface washed using an aqueous washing fluid
prior to the liquid-liquid extraction; wherein said surface washing
results in greater than about 95% removal of loosely bound surface
contamination; wherein said first plastic has a surface area to
volume ratio of greater than about 50 mm-1 prior to said surface
washing; wherein said surface washed first plastic is melt
densified using in extrusion to produce a molten stream that is fed
to the liquid-liquid extractor; wherein said hexanes to first
plastic mass ratio is about 55:1 with an extraction time of about
65 minutes; wherein the purification process results in an average
removal efficiency for 4-tertpentylphenol, bisphenol A, OCDD, PCB
118, and 2-ethylhexyl phthalate of greater than about 55% or
LOQ.
21. The method of claim 17; wherein said hexanes after
liquid-liquid extraction is purified using at least one stage of
physical adsorption or physical absorption to remove at least about
80% of the chemical contamination from the solvent for re-use in
subsequent extraction processes or stages.
Description
FIELD OF THE INVENTION
[0001] The present invention generally relates to a method of
producing a purer plastic from a first plastic. More specifically,
the first plastic is subjected to bulk purification or surface and
bulk purifications, wherein the total contamination present in the
first plastic is reduced. The resulting purer plastic is
sufficiently purer to allow for use in demanding applications.
BACKGROUND OF THE INVENTION
[0002] Synthetic plastics are ubiquitous in daily life due to their
relatively low production costs and good balance of material
properties. They 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, hundreds of
millions of tons 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 causes the emission of greenhouse
gases (GHG), primarily CO.sub.2, in the atmosphere.
[0003] 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. Also, plastic waste is leaked
into the environment, e.g. washed into river systems and ultimately
out to sea.
[0004] Plastics recycling has emerged as one solution to mitigate
the issues associated with the poor management of the end-of-life
of plastics. Recovering and re-using plastics diverts waste from
landfills and reduces the demand for virgin plastics made from
fossil sources, which consequently reduces GHG emissions. In
developed regions of the world, 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, and due to regulatory frameworks. The
majority of recycled materials, including plastics (other than
films), 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 (e.g. in bales) for
resale. Plastics can be sorted into individual materials, such as
single streams of high-density polyethylene (HDPE) and
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 polyamide (PA)). The single or mixed
streams can then be further sorted, washed, and reprocessed at a
plastics recovery facility (PRF) into pellets that are suitable for
re-use in plastics processing, e.g., extrusion blow molding,
profile extrusion, injection molding, and film making.
[0005] However, the utilization of these recycled plastics is
currently limited due to contamination, which renders the plastics
less valuable compared to virgin plastics. A key to increasing the
recycle rates and lowering the CO.sub.2 emissions and plastics
pollution is to reduce the contamination to a level allowing
broader utilization across more end markets, especially those
involving demanding applications.
[0006] Films are a special case of recycled plastics and are
predominately polyolefin in composition. Films offer unique
challenges for recycling that have yet to be resolved. The recycled
film supply stream can be split into two general categories: 1)
pre-consumer recycle film, which includes both in-plant
scrap/edge-trim that can be re-used in the same process that
generated it and post-industrial recycle (PIR) film, which is film
generated by internal plant waste that is not used in the same
process that produced it; 2) post-consumer recycle (PCR) film
including post-commercial recycle film, which is film that has been
used in commerce but not directly by at-home consumers (e.g.
back-of-store shrink wrap, pallet wrap, wholesale bags, furniture
wrap, agricultural film, etc.) and post-household recycled film,
which is film that has been used in commerce directly by at-home
consumers (e.g. retail bags, retail food packaging, overwraps for
diapers and hygiene products, trash bags, etc.). Post-industrial
film waste for use in recycling is collected on a plant-by-plant
basis for controlled end markets and may or may not involve (or
require) significant cleaning steps before recycling.
Post-commercial film is collected at the point of sale and
transported to various PRFs specializing in film for various
cleaning operations and eventual distribution to an end market. In
the US, post-household film is primarily collected in store
take-back programs where the end consumer returns the film to a
collection bin at a local store. Film-based PRFs collect the film
waste and deliver it to end markets after sortation and cleaning.
The utilization of film recycled materials is quite limited due to
contamination. The contamination of films is higher than other
forms due to the high surface area to volume ratio which allows
greater opportunity for external contamination. Currently, most
film-based recycled plastics are down-cycled into markets that are
not circular and are of limited size such as plastics lumber. As
the collection of film-based waste grows, the need for end markets
beyond plastics lumber is essential. Ideally, film-based waste will
eventually discover a second life in film-based applications, thus
ensuring ongoing circularity.
[0007] The end markets cannot grow unless contamination is greatly
reduced. Considering the high volume of film that is used in
demanding end markets, it is important that recycled plastics
coming from these markets re-enter the same end markets to support
circularity. As such, the ability to remove even greater levels of
contaminants is critical to achieving circularity and reducing
CO.sub.2 emissions and plastics pollution. Plastics pollution is
even more problematic for film considering the tremendous surface
area per use and the mobility of the waste in the environment by
both air and water.
[0008] While contamination is problematic for all end market
applications, demanding markets have even stricter requirements
especially on certain chemical contaminants. The relevant chemical
contaminants are grouped into various chemical classes depending on
the chemical structure of the contaminants. Non-limiting examples
of these chemical classes of contaminants are heavy metals,
pesticides, dioxins, furans, polychlorinated biphenyls (PCBs),
phthalates, polycyclic aromatic hydrocarbons (PAHs), organotins,
bisphenols, isothiazolins, glyphosphate, alkyl phenols, alkylphenol
ethoxylates, aromatic amines, and flame retardants. In addition,
the target levels of these contaminants can be extremely low. For
instance, the target levels may be on the order of parts per
million (ppm), parts per billion (ppb), and parts per trillion
(ppt), wherein the initial contaminated plastic may contain levels
1,000 times the targeted levels. Net, a 1,000.times. reduction in
chemical contamination is often required.
[0009] Mechanical recycling, also known as secondary recycling, is
a 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. et al., Waste Management, 29(10)
(2009), 2625-2643. Mechanical recycling of rigid plastics typically
involves some form of surface washing followed by drying and melt
densification. The melt densification step typically includes melt
filtration and devolatilization. For film-based materials, there
are dry and wet processes. In the dry process, a controlled film
stream is typically shredded, dried, and then melt extruded into
the final form. Melt filtration and devolatilization are typically
part of the extrusion step. In wet processes, a controlled film
stream is typically shredded, washed in an aqueous
solution/solutions, dried, and then melt extruded into the final
form. Melt filtration and devolatilization are typically part of
the extrusion step. The above methods are generally acceptable at
removing intentional surface contamination such as paper labels and
unintentional surface contamination such as dirt but are poor at
removing bulk contaminants.
[0010] U.S. Pat. No. 10,022,725 discloses a mechanical recycling
method for cleaning linear low-density polyethylene (LLDPE)/LDPE
film for use in recycling. The patent further discloses the steps
of shredding, a first water washing step, a second size reduction
step involving wet grinding, a friction washing step or steps where
hot water is used in at least one step, a drying or multiple drying
steps, and a compaction step. The method is likely to be quite
effective at removing some surface contamination that is loosely
bound but will be ineffective at removing bulk contamination due to
extremely low solubility of the bulk contaminants in the aqueous
washing media and/or limited diffusivity of the bulk contaminants
within the plastic.
[0011] U.S. Pat. No. 9,616,595 discloses a mechanical recycling
method for de-inking surface-printed plastic films. The patent
further discloses steps of grinding, ink removal steps, general
washing, recovery of the cleaning solution, recovering pigments,
and drying. The ink removal step involves the use of an aqueous
cleaning fluid with high pH and selective cleaning agents, such as
dodecyl sulfate, and high turbulence. The method claims ability to
remove surface printed ink, which potentially contributes to
chemical contamination following heating in the recycling process.
The process will have limited ability to remove bulk contaminants
due to limited solubility of the bulk contaminants in the aqueous
washing media and/or limited diffusivity of the bulk contaminants
within the plastic.
[0012] To overcome the fundamental limitations of mechanical
recycling, there have been many methods developed to purify
contaminated plastics. Most of these methods use solvents to
decontaminate and purify plastics. U.S. Pat. No. 7,935,736
discloses a method for recycling polyester from plastic waste using
a solvent to dissolve the polyester prior to cleaning. This patent
also discloses the need to use a precipitant to recover the
polyester from the solvent.
[0013] U.S. Pat. No. 6,555,588 discloses a method to produce a
polypropylene blend from a plastic mixture comprising other
polymers. This patent discloses 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 time. The starting material is a porous pellet and the
extraction conditions are below the melting temperature to enable
conveyance in the process. This patent further discloses increasing
the temperature of the solvent (or a second solvent) to dissolve
the polymer prior to filtration. Further, the patent discloses the
use of shear flow to precipitate polypropylene from solution. The
polypropylene blend described in the patent contained up to 5.6 wt.
% polyethylene contamination.
[0014] European Patent Application No. 849,312 discloses a process
to obtain purer polyolefins from a polyolefin-containing plastic
mixture or a polyolefin-containing waste. The patent application
discloses the extraction of polyolefin mixtures or wastes with a
hydrocarbon fraction of gasoline or diesel fuel with a boiling
point above 90.degree. C. at temperatures between 90.degree. C. and
the boiling point of the hydrocarbon solvent. The patent
application further discloses contacting a hot polyolefin solution
with bleaching clay and/or activated carbon to remove foreign
components from the solution. Also, the patent application
discloses cooling the solution to temperatures below 70.degree. C.
to crystallize the polyolefin and then removing adhering solvent by
heating the polyolefin above its melting point, 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.
[0015] U.S. Pat. No. 5,198,471 discloses 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 patent further discloses
heating the solvent to higher temperatures to dissolve additional
polymers that were not solubilized at the first lower temperature.
Finally, the patent discloses filtration of insoluble polymer
components.
[0016] U.S. Pat. No. 5,233,021 discloses a method of extracting
pure polymeric components from a multi-component structure (for
example, waste carpeting) by 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 U.S. Pat. No.
5,198,471, this patent only discloses filtration of undissolved
components.
[0017] U.S. Pat. No. 5,739,270 discloses 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
patent further discloses the step of filtering the thermoplastic
co-solvent (with or without the working fluid) to remove
particulate contaminants, such as glass particles.
[0018] U.S. Pat. No. 5,368,796 discloses a method for surface
cleaning polyethylene films. The patent further discloses the steps
of shredding, a first surface washing step (involving a boiling
solvent at a temperature below the melting temperature of the
polyethylene and at or near ambient pressure, while applying
vigorous mechanical agitation for 30 min to rub the ink off), a
second surface washing step (involving fresh solvent below the
melting temperature of the polyethylene, while applying vigorous
mechanical agitation for 30 min), a third surface washing step
(involving the solvent below the melting temperature of the
polyethylene, while applying vigorous mechanical agitation for 30
to 60 min, and devolatilization), and melt densification.
Optionally, the method may include a water washing step prior to
treatment with solvent to remove surface dirt. The patent further
discloses that the solvent washing accomplishes extraction wherein
the solvent does not dissolve the polymer. However, a small amount
of wax, typically <1 wt. % may be removed. The solvent washing
and extraction steps are further disclosed as occurring at the
boiling point of the solvent, which is selected to be below the
softening point of the polyethylene to avoid agglomeration. The
above method is focused on the removal of surface printed inks and
is silent on the removal of bulk permeable contaminants such as
those described previously.
[0019] U.S. Patent Application No. 2009/0178693 discloses a method
for purifying a plastic. The patent application further discloses a
multi-step process involving granulation to form plastic chips,
surface washing with supercritical CO.sub.2, surface washing and
extraction with a high boiling solvent or mixture of solvents (such
as limonene and ethylene lactate), a final surface washing with
supercritical CO.sub.2 to remove the high boiling solvent on the
surface, and devolatilization. Further disclosed is that the
plastic chip feed material is stirred with the solvent and the
shape of the chip is maintained. Also, it is disclosed that the
recovered material remains as chips, which implies the process is
completed at temperatures below the plastic's primary melting
point.
[0020] U.S. Pat. No. 9,834,621 discloses a method for purifying
polypropylene. The patent further discloses contacting the
reclaimed polypropylene at a temperature from about 80.degree. C.
to about 280.degree. C. and at a pressure from about 10 atm to
about 544 atm with a first fluid solvent having a standard boiling
point less than about 70.degree. C., to produce an extracted
reclaimed polypropylene; 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.degree. C. to about
280.degree. C. and a pressure from about 14 atm to about 544 atm to
produce a first solution comprising polypropylene, at least one
dissolved contaminant, and at least one suspended contaminant;
settling the first solution comprising polypropylene, at least one
dissolved contaminants, and at least one suspended contaminant at a
temperature from about 90.degree. C. to about 280.degree. C. and at
a pressure from about 14 atm to about 544 atm to produce a second
solution comprising polypropylene, at least one dissolved
contaminant, and less of the at least one suspended contaminant;
filtering the second solution at a temperature from about
90.degree. C. to about 280.degree. C. and at a pressure from about
14 atm to about 544 atm to produce a third solution comprising
purer polypropylene, at least one dissolved contaminant, and even
less of the at least one suspended contaminant; and separating the
purer polypropylene from the third solution; and where the second
fluid solvent has the same chemical composition or a different
chemical composition as the first fluid solvent. The above method
is highly suitable for removing contamination. However, the ability
to dissolve, settle, and filter plastics is quite difficult and may
not be feasible or practical for plastics with high molecular
weight (MW), such as those used in films and blow molded
containers. In addition, the above method is silent on removing
surface contamination prior to extraction and dissolution, thus
increasing the burden on such disclosed processes, especially
filtration.
[0021] In summary, the solvent-based methods to purify contaminated
plastics, as described above, do not address the issue of removing
both surface and bulk contaminants from plastics sufficiently and
efficiently to enable utilization in demanding applications,
particularly in films and rigid applications involving high 1\4W
plastics. Accordingly, there is a need for a method that: 1)
produces a purer plastic, i.e., plastic without a significant
amount of contamination that would allow use of it in demanding
applications; 2) is relatively simple in terms of the number of
unit operations; and 3) can be used in high MW plastics, such as
those sourced from film and rigid applications.
SUMMARY OF THE INVENTION
[0022] In embodiments of the present invention, a method to extract
contaminates from a first plastic to produce a purer plastic is
provided that comprises providing a first plastic comprising
individual contaminants, each individual contaminant having a
concentration; extracting said individual contaminates from said
first plastic at a temperature and a pressure, using an extraction
solvent, in extraction stages, to produce a purer plastic
comprising individual contaminates, each having a concentration;
wherein said extraction is liquid/liquid wherein said temperature
is above the primary melting point of the first plastic; wherein
said first plastic individual contaminants comprise at least one of
alkyl phenols, bisphenols, dioxins, PCBs, and phthalates; wherein
each individual contaminate concentration in said purer plastic is
reduced compared to each individual contaminate concentration in
said first plastic; and wherein the average of said reductions of
said concentrations of said first plastic contaminants to said
purer plastic contaminants is at least about 55% or LOQ.
DETAILED DESCRIPTION OF THE INVENTION
I. Definitions
[0023] As used herein, the term "plastic" refers to polymer, such
as polyethylene (PE), PP, PET, LLDPE, LDPE, HDPE, polyethylene
co-polymers, ethyl vinyl acetate copolymer (EVA), ethyl vinyl
alcohol copolymer (EVOH), ethylene acrylic acid copolymer (EAA),
PS, PC, PVC, PET, SBS, PA, etc., or mixtures thereof. Such polymers
are characterized by high molecular weight, which generally
determines melt processability and solid-state mechanical
properties. For the purposes of the present invention, the terms
"polymer" and "plastic" are used interchangeably, and the term "MW"
refers to the weight-average molecular weight of the polymer.
[0024] As used herein, the term "reclaimed plastic" refers to
re-grind, post-industrial, post-commercial, or post-household
plastic of various forms including film, fiber, non-woven, and
rigid packaging.
[0025] As used herein, the term "recycled plastic" refers to
reclaimed plastic converted to a form that is used in making
products and packaging either in blends with virgin plastic or by
itself. The recycled plastic may be purer than the reclaimed
plastic or may be identical except in form.
[0026] As used herein, the term "Pre-Consumer Plastic" refers to
plastic waste that has not met its intended end purpose and has not
been used in commerce or used by end consumers. Pre-Consumer
Plastic has two subcategories of reclaim including 1) Internal
Scrap/regrind and 2) Post-Industrial. Internal scrap/regrind is
different from Post-Industrial in that Post-Industrial is not
re-usable in the same process in which it was produced. Recycle
resulting from Post-Industrial reclaim is referred to as
Post-Industrial Recycle or PIR.
[0027] As used herein, the term "Post-Consumer Plastic" refers to
plastic reclaim that has met its intended end purpose and has been
used in commerce. Post-Consumer Plastic has two subcategories of
reclaim including 1) Post-Commercial Plastic and 2). Post-Household
Plastic. Post-commercial plastics includes plastics that have been
used in commerce and have met their desired purpose. Examples
include back of store reclaim and wholesale bags. Post-household
plastics include plastics that have been used in homes of retail
consumers. Examples include front of store plastics, retail bags,
retail packaging, etc. Recycle resulting from Post-Consumer Plastic
reclaim is referred to as Post-Consumer Recycle or PCR.
[0028] As used herein, the term "first plastic" refers to the
plastic which is fed into the purification process and has a level
of contamination that may include both surface and bulk
contamination. Non-limiting examples of first plastic are reclaimed
film and reclaimed HDPE bottles.
[0029] As used herein, the term "purer plastic" refers to the
plastic which is produced by the purification process from a first
plastic. The purer plastic has a level of contamination that is
generally lower than that of the first plastic.
[0030] As used herein, the term "1.sup.st Life plastic" refers to a
virgin plastic that has not been utilized in its polymer form for
any purpose.
[0031] As used herein, the term "contaminant" refers to any
undesirable material contained on or within the plastic. The term
"chemical contaminant" refers to any undesirable chemical species
on the surface of the plastic or within the bulk of the plastic and
comprises the molecular or elemental composition of the
contaminant. The terms may be used interchangeably depending upon
the intent. For example, paper contamination comprises cellulose.
Net, cellulose would be one chemical contaminant within the paper
contaminant. As used herein, the term "contamination" refers to the
sum of all contaminants and the term "chemical contamination"
refers to the sum of all chemical contaminants. The chemical
contaminants are grouped in classes, which include chemical
contaminants that have similar chemical structure. For example, As,
Hg, and Cr are chemical contaminants in the "heavy metals"
classification. Each contaminant may have different chemical
attributes, such as solubility and diffusivity in the plastic, and
target levels depending upon concentration and end use market.
[0032] As used herein, the term "surface contaminant" refers to a
contaminant that is on the surface of the plastic. Similarly, the
term "surface chemical contaminant" refers to the molecular or
elemental composition of the surface contaminant. The surface
contaminant may be attached to the surface of the plastic either
loosely through physical attraction forces, or more strongly
through polar or other forces. In general, a surface contaminant
will have less than about 80% of its surface area embedded in the
plastic.
[0033] As used herein, the term "bulk contaminant" refers to a
contaminant that is in the bulk of the plastic. Similarly, the term
"bulk chemical contaminant" refers to the molecular or elemental
composition of the bulk contaminant. In general, a bulk contaminant
will have more than about 80% of its surface area embedded in the
plastic.
[0034] As used herein, the term "surface contamination" and
"surface chemical contamination" refers to the sum of all surface
contaminants and all surface chemical contaminants,
respectively.
[0035] As used herein, the term "bulk contamination" and "bulk
chemical contamination" refers to the sum of all bulk contaminants
and all bulk chemical contaminants, respectively.
[0036] As used herein, the term "total contamination" refers to the
sum of the surface contamination and bulk contamination and the sum
of all the surface chemical contamination and bulk chemical
contamination, respectively.
[0037] As used herein, the term "permeable contaminant" refers to a
chemical contaminant that is both soluble and diffusible in the
plastic. Non-limiting examples of permeable contaminants are
formaldehyde, bisphenol A, and naphthalene.
[0038] As used herein, the term "impermeable contaminant" refers to
a chemical contaminant that is either insoluble or non-diffusible
in the plastic. Non-limiting examples of impermeable contaminants
are heavy metals and gel particles composed of cross-linked or
ultra-high molecular weight plastic (too large to diffuse).
[0039] As used herein, the term "permeable contamination" is the
sum of all permeable contaminants and the term "impermeable
contamination" is the sum of all impermeable contaminants. The sum
of all permeable and impermeable contamination is the "chemical
contamination" if described in molecular or elemental terms or just
simply "the contamination" if described in general terms (such as
cellulose vs paper).
[0040] As used herein, the term "intentional contaminant" refers to
a contaminant that is intentionally added by the supply chain for a
specific purpose to benefit the producer, retailer, or consumer,
but may not be desired in the recycled plastic. Examples include
print, paper labels, adhesives for labels, pigments (such as
TiO.sub.2), process additives (such as antioxidant (AO)), etc.,
that are necessary for marketing, branding, processability, and/or
end use performance. As used herein, the term "intentional chemical
contaminant" refers to an intentional contaminant described by its
chemical composition. As used herein, the term "intentional
contamination" refers to the sum of all intentional contaminants
and the term "intentional chemical contamination" refers to the
intentional contamination described by its chemical
composition.
[0041] As used herein, the term "unintentional contaminant" refers
to any contaminant not intentionally added. Examples include dirt
and cross-contamination that is not intentionally added by the
producer, retailer, or consumer. As used herein, the term
"unintentional chemical contaminant" refers to an unintentional
contaminant described by its chemical composition. As used herein,
the term "unintentional contamination" refers to the sum of all
unintentional contaminants and the term "unintentional chemical
contamination" refers to the unintentional contamination described
by its chemical composition.
[0042] As used herein, the term "densified" refers to a state of
plastic in which the bulk density of the plastic is higher than the
bulk density of the original/pre-densified plastic and the original
surface of the plastic is reduced and/or rendered inaccessible to
wetting fluids. The process of producing a densified material is
referred to as densification.
[0043] As used herein, the term "melt densification" refers to
densification done near, at, or above the primary melting point of
the plastic. Non-limiting methods of melt densification include
melt extrusion and agglomeration with equipment, such as the
Herbold HV series plastcompactor.
[0044] As used herein, the term "primary melting point" refers to
the peak melting point (highest endothermic peak on a zero-slope
baseline) of the plastic as measured using Differential Scanning
calorimetry (DSC). For the purposes of the present invention, the
terms "primary melting point", "melting point", "melting
temperature", and "primary melting temperature" are used
interchangeably. For amorphous materials and/or materials lacking a
distinct melting point, the defining temperature will be the
approximate softening point of the material, which may be best
characterized by the glass transition temperature. Those skilled in
the art will understand the appropriateness of the criteria for
non-semi-crystalline materials.
[0045] As used herein, the term "hexane" refers to a blend of
hexane isomers, such as normal hexane (at least 45 vol %, and
typically, about 53 vol %), iso hexane (2-methylpentane,
3-methylpentane, and 2,3-dimethylbutane), and neo hexane
(2,2-dimethylbutane).
[0046] As used herein, the term "limit of quantification" or "LOQ"
refers to the lower detection limit for a given chemical
contaminant as determined by the analytical methods disclosed in
section IX. The LOQ is a function of the methods used and may vary
from test method to test method. The LOQ used herein is specific to
the method listed in section IX.
[0047] As used herein, the term "ppm" refers to parts per million,
"ppb" refers to parts per billion, and "pptr" refers to parts per
trillion.
II. First Plastic
[0048] Plastics are predominately free of contamination (virgin
plastics) when first produced at resin suppliers, such as Dow,
Nova, ExxonMobil, etc. However, during the plastic's lifecycle
(from production through distribution, consumer utilization, and
eventual recycling) contamination is introduced either
intentionally or unintentionally.
[0049] Non-limiting examples of intentional contamination include
surface print, paper labels, adhesives for labels, pigments (such
as TiO.sub.2), process additives (such as antioxidant (AO)), etc.,
that are necessary for marketing, branding, processability, and/or
end use performance. Non-limiting examples of unintentional
contamination are dirt, cross-contamination, certain heavy metals,
pesticides, dioxins, furans, PCBs, etc. Also, unintentional
contamination can be produced from reactions involving intentional
contaminants, such as the oxidation of paper labels to dioxins,
degradation of adhesives or print binders, etc. Most of the latter
occurs during melt densification methods used during the recycling
process. Further, oxidation of the plastic during melt processing
steps, such as those used for original package or product creation
and/or latter recycling, will produce unintentional contamination,
such as gels. In addition, unintentional contamination may result
from interaction with products. For example, packaging materials
that contain cleaning mixtures (e.g. limonene, surfactants, etc.),
food (e.g. various organics), etc., will potentially become
contaminated with such products. Finally, unintentional
contamination can enter the plastic during production, e.g.
contamination of a plastic with reaction by-products, unreacted
monomers, etc.
[0050] It is recognized that different reclaimed plastic sources
have different contamination and associated risks. Clearly,
reclaimed plastic streams of unknown origin and lifecycle will be
most abundant but also represent the highest potential for
contamination. On the other side, controlled reclaimed plastic
streams are available and represent lower potential risk for
demanding applications. For instance, if a reclaimed plastic stream
is known to be from medical or food applications, then such
reclaimed plastic stream will not contain any undesirable
contaminants up to the point of distribution to the consumer else
these plastics would not have been approved for use in these
applications. As such, contamination preventing re-use in these
same applications would primarily be unintentional contamination,
which must originate from external sources and enter the plastic
through surface contamination. A small amount of contamination
could result from reactions involving intentional contamination
such as oxidation of cellulosics to dioxins during melt
densification.
[0051] Pre-consumer plastic generally has the lowest level of
contamination due to its known composition and controlled history.
It may include intentional contamination, such as surface print and
opacifiers, but because these are known and controlled, it is quite
easy to find applications tolerating such known contaminants. In
addition, pre-consumer plastic tends to have low amounts of
unintentional contamination due to the controlled history
preventing external contamination. Thus, pre-consumer plastics that
were originally destined for use in demanding applications such as
medical or food, will be ideal sources of reclaimed plastic for
various uses with minimal cleaning/purification. The latter
pre-consumer plastic in the form of film is referred to as
"Approved Sourced Post-Industrial Film" (ASPIF). On the downside,
the ASPIF stream is very limited in supply and does not support
circularity.
[0052] Post-consumer plastics are generally more contaminated than
pre-consumer plastics. The post-commercial subclass of
post-consumer plastic has the next lowest level of contamination
relative to pre-consumer recycle considering the somewhat
controlled life cycle within the commerce supply chain. In general,
post-commercial reclaim plastic will have a known and controlled
level of intentional contamination, thus enabling broad utilization
as reclaimed plastic. However, unintentional contamination is known
to be ubiquitous and problematic with this stream, which prevents
broad usage in controlled fields like medical or food.
Post-commercial plastic that is sourced from controlled fields,
such as medical or food, will be potentially usable back into these
fields following adequate cleaning/purification. Post-commercial
plastic sourced from demanding applications in the form of film is
referred to as "Approved Source Post-Commercial Film" (ASPCF). To
accommodate the on-going need of purer reclaimed plastic, recycle
material suppliers have recently introduced post-commercial film
sources with more controlled and known history. These new sources
are called High-Custody sources and are primarily utilized with the
post-commercial film stream. Net, High-Custody Post-Commercial film
sources should have reduced level of contamination relative to
general Post-Commercial film sources. On the downside, these
High-Custody sources are of limited volume and are more costly.
[0053] The post-household subclass of post-consumer has the highest
level of contamination considering the uncontrolled life cycle
within the commerce channel. Such plastic has high levels of both
intentional and unintentional contamination that is highly
variable, unknown, and uncontrolled. Such plastic may include
plastic sources that were originally unacceptable for use in
demanding applications.
[0054] Surprisingly, plastics made purer by the present invention
may allow source plastics from post-industrial (both ASPIF and
uncontrolled source), post-commercial (both ASPCF and uncontrolled
source), and post-household plastic to be used in the demanding
areas of medical and food applications with some limitations.
[0055] For the purposes of the present invention, non-limiting
examples of plastic are film, sheet, injection molded parts, blow
molded parts, fiber, nonwovens, wovens, thermoformed parts, and
extruded strands.
[0056] The first plastic can be a virgin plastic or a reclaimed
plastic. Also, the first plastic can be a first-life plastic (has
been used only once before it entered the reclaimed plastic
stream), second-life plastic (has been used twice before it entered
the reclaimed plastic stream), or higher-life plastic (has been
used many times before it entered the reclaimed plastic stream). In
embodiments of the present invention, the first plastic comprises a
reclaimed plastic. In another embodiment of the present invention,
the first plastic comprises a virgin plastic. In one embodiment of
the present invention, the first plastic comprises film. In yet
another embodiment of the present invention, the first plastic is
selected from the group comprising film, injection molded part,
blow molded part, nonwoven, woven, thermoformed part, extruded
strand, or mixtures thereof.
[0057] In embodiments of the present invention, the first plastic
comprises a regrind/edge-trim/in-plant waste plastic. In another
embodiment of the present invention, the first plastic comprises a
post-industrial plastic. In yet another embodiment of the present
invention, the first plastic comprises a post-industrial film. In
yet another embodiment of the present invention, the first plastic
comprises a post-industrial non-woven. In yet another embodiment of
the present invention, the post-industrial film is ASPIF. In
embodiments of the present invention, the first plastic comprises a
post-commercial plastic. In another embodiment of the present
invention, the first plastic comprises a post-commercial film. In
another embodiment of the present invention, the first plastic
comprises a post-commercial non-woven. In yet another embodiment of
the present invention, the post-commercial film is ASPCF. In yet
another embodiment of the present invention, the first plastic
comprises High-Custody post-commercial film. In embodiments of the
present invention, the first plastic comprises a post-household
plastic. In another embodiment of the present invention, the first
plastic comprises a post-household film. In yet another embodiment
of the present invention, the first plastic comprises a
post-household non-woven.
[0058] In embodiments of the present invention, the first plastic
comprises polystyrene, co-polystyrene, polyamides, co-polyamides,
polycarbonates, thermoplastic elastomers, styrenic block
copolymers, polyesters, co-polyesters, polyvinylalcohols, pvcs, and
copolymers of any of the above and mixtures of any of the above. In
embodiments of the present invention, the first plastic comprises
polyolefins, polyolefin copolymers, and polyolefin polar
copolymers. In another embodiment of the present invention, the
first plastics comprises LDPE and LLDPE copolymers.
[0059] In another embodiment of the present invention, the first
plastic comprises PP. In yet another embodiment of the present
invention, the first plastic comprises HDPE and HDPE copolymers. In
embodiments of the present invention, the first plastic comprises
film, and the film comprises polyethylene and polyethylene
copolymers.
[0060] The first plastic may be in many forms including but not
limited to pellets, micronized pellets, ground pellets, shredded
film, shredded or ground injection molded parts, shredded or ground
blow molded parts, thermoformed parts, shredded nonwoven or woven,
extruded strands, or agglomerated particles. In embodiments of the
present invention, the first plastic comprises pellets.
III. Contaminants and Contamination
[0061] Contaminants can generally be broken down into two migration
categories: 1) permeable; and 2) impermeable. Contaminants that are
permeable have solubility and diffusivity in the first plastic to
allow migration into, through the plastic, and out of the plastic
due to a chemical potential gradient. In other words, permeable
contaminants and the grouping called permeable contamination are
mobile. Impermeable implies that the contaminant does not have
sufficient solubility and diffusivity to significantly move into,
through the plastic, and out of the plastic. In other words,
impermeable contamination represented by the summation of all
impermeable contaminants is essentially immobile. Net, wherever
impermeable contamination is first deposited, such contamination
will remain in that location until physically removed, convectively
transferred, or placed in contact with a different material which
is permeable to the contaminant.
[0062] The chemical contaminants in the first plastic may be
numerous but generally fall into one of several relevant chemical
classes. Representative classes comprise pesticides, aldehydes,
allergic fragrances, izioalines, alkylphenol ethoxylates,
alkylphenol s, bisphenols, dioxins, dioxin-like, furans, PCBs,
organotins, metals, phthalates, polyaromatic hydrocarbons (PAHs),
etc. Only some of these chemical classes are routinely found in pre
and post-consumer reclaim materials including pesticides,
alkylphenol ethoxylates, alkylphenol s, bisphenols, dioxins,
dioxin-like, furans, PCBs, metals, organotins, phthalates, and
PAHs.
[0063] Using the analytical methods disclosed in section IX
Methods, the LOQs of the various contaminants may differ by orders
of magnitude. For example, the LOQ of a typical pesticide is about
10 ppb; the LOQ of typical alkylphenol ethoxylate is about 50 ppb;
the LOQ of a typical alkylphenol is about 5 ppb; the LOQ of
bisphenol-A is about 5 ppb; the LOQ of typical dioxin is about 0.2
pptr; the LOQ of a typical furan is about 0.2 pptr; the LOQ of a
typical PCB is about 5 pptr; the LOQ of a typical heavy metal is
about 100 ppb; the LOQ of a typical organotin is about 300 pptr;
the LOQ of typical phthalate is 50 ppb; the LOQ of a typical PAH is
1 ppb.
[0064] Several films sources were broadly classified for chemical
contamination including three ASPIF sources, three High-Custody
Post-Commercial Film sources, three Post-Commercial film sources,
and one Post-Household film source using the analytical methods
disclosed in section IX Methods, as shown in TABLES 1a-1i. Note: To
simplify the presentation of chemical contamination results, the
concentration data is displayed in terms of LOQ instead of absolute
weight fraction. For example, if the contaminant concentration is
10 ppm and the LOQ is 1 ppm, then the concentration would be
10.times.LOQ or just 10 displayed in the data tables.
Tables 1a-1i
Chemical Contamination of ASPIF, High-Custody Post-Commercial
(HCPC), Post-Commercial (PC), and Post-Household (PH) Film
Sources
TABLE-US-00001 [0065] TABLE 1a Pesticide Chemical Contamination
ASPIF HCPC PC PH Parameter #1 #2 #3 #1 #2 #3 #1 #2 #3 #1 Pesticides
xLOQ xLOQ xLOQ xLOQ Pendimethalin <1 <1 <1 <1 <1
<1 <1 <1 <1 1.4 Diethyltoluamide (DEET) <1 <1
<1 <1 <1 <1 <1 <1 <1 3.7 Piperonyl butoxide
<1 <1 <1 <1 <1 <1 1.0 12.0 28.0 6.6 Phenylphenol,
ortho- <1 <1 <1 <1 <1 <1 1.1 <1 <1 <1
Chlorprofam <1 <1 <1 <1 <1 <1 <1 <1 <1
1.3 Permethrin <1 <1 <1 <1 <1 <1 <1 <1
<1 3.0
TABLE-US-00002 TABLE 1b Alkyl Phenol Ethoxylates Chemical
Contamination ASPIF HCPC PC PH Parameter #1 #2 #3 #1 #2 #3 #1 #2 #3
#1 Alkylphenol ethoxylates xLOQ xLOQ xLOQ xLOQ
4-t-Octylphenolmonoethoxylate <1 <1 <1 <1 <1 <1
10.6 <1 4.2 9.4 4-t-Octylphenoldiethoxylate <1 <1 <1
<1 <1 <1 5.2 <1 3.6 9.0 4-t-Octylphenoltriethoxylate
<1 <1 <1 <1 <1 <1 4.2 <1 5.0 6.6
4-t-Octylphenoltetraethoxylate <1 <1 <1 <1 <1 <1
4.4 <1 5.6 8.4 4-t-Octylphenolpentaethoxylate <1 <1 <1
<1 <1 <1 2.6 <1 6.0 11.2 4-t-Octylphenolhexaethoxylate
<1 <1 <1 <1 <1 <1 5 <1 6.2 17.4
iso-Nonylphenolmonoethoxylate <1 <1 <1 <1 <1 <1
2.4 1.7 <1 4.0 iso-Nonylphenoldiethoxylate <1 <1 <1
<1 <1 <1 2.8 8.6 <1 28.0 iso-Nonylphenoltriethoxylate
<1 <1 <1 <1 <1 <1 3.2 6.2 5.8 32.0
iso-Nonylphenoltetraethoxylate <1 <1 <1 <1 <1 <1
1.8 4.2 6.2 22.0 iso-Nonylphenolpentaethoxylate <1 <1 <1
<1 <1 <1 2.2 <1 6.2 19.2 iso-Nonyl phenol
hexaethoxylate <1 <1 <1 <1 <1 <1 <1 <1
<1 12.0
TABLE-US-00003 TABLE 1c Alkyl Phenols Chemical Contamination ASPIF
HCPC PC PH Parameter #1 #2 #3 #1 #2 #3 #1 #2 #3 #1 Alkylphenols
xLOQ xLOQ xLOQ xLOQ iso-Nonylphenol 2.2 <1 320.0 190.0 120.0
86.0 920.0 168.0 260.0 300.0 4-tert-Butylphenol <1 <1 <1
3.8 1.2 <1 2 2.4 <1 6.8 4-tert-Pentylphenol <1 24.0 550.0
19.4 52.0 40.0 1660.0 3.6 116.0 1720.0
TABLE-US-00004 TABLE 1d Bisphenols Chemical Contamination ASPIF
HCPC PC PH Parameter #1 #2 #3 #1 #2 #3 #1 #2 #3 #1 Bisphenols xLOQ
xLOQ xLOQ xLOQ Bisphenol A <1 <1 <1 46,000.0 1800.0 114.0
4.8 320.0 760.0 144
TABLE-US-00005 TABLE 1e Dioxins, Furans, and PCBs Chemical
Contamination Parameter ASPIF HCPC PC PH Dioxins and #1 #2 #3 #1 #2
#3 #1 #2 #3 #1 dioxinlike and PCB xLOQ xLOQ xLOQ xLOQ
1,2,3,4,7,8-HxCDD <1 <1 <1 <1 <1 <1 <1 <1
<1 1.9 1,2,3,6,7,8-HxCDD <1 <1 <1 <1 <1 <1
<1 <1 6.1 7.4 1,2,3,7,8,9-HxCDD <1 <1 <1 <1 <1
<1 <1 <1 3.8 4.5 1,2,3,4,6,7,8-HpCDD <1 <1 <1 2.8
<1 3.4 3.8 10.9 84.5 63.0 OCDD <1 <1 <1 11.1 2.6 8.9
39.6 17.2 205.0 308.5 2,3,7,8-TCDF <1 <1 <1 2.6 1.8 1.2
2.6 4.7 <1 16.5 1,2,3,7,8-PeCDF <1 <1 <1 <1 <1
<1 <1 <1 2.7 <1 2,3,4,7,8-PeCDF <1 <1 <1 <1
<1 <1 <1 <1 <1 2.1 1,2,3,4,7,8-HxCDF <1 <1
<1 <1 <1 <1 <1 <1 3.3 2.0 1,2,3,6,7,8-HxCDF <1
<1 <1 <1 <1 <1 <1 <1 2.2 1.3
1,2,3,4,6,7,8-HpCDF <1 <1 <1 <1 <1 <1 1.29 <1
7.9 6.2 OCDF <1 <1 <1 <1 <1 <1 5.45 <1 6.5
13.8 PCB 77 <1 <1 <1 26.8 13.4 12.2 8.25 2.7 39.2 83.0 PCB
81 <1 <1 <1 46.4 19.9 21.8 10.58 5.6 88.2 79.4 PCB 126
<1 <1 <1 11 6.3 13.3 19.1 2.9 65.2 128.8 PCB 169 <1
<1 <1 <1 <1 <1 <1 <1 <1 11.2 PCB 105 <1
<1 <1 24.6 9.9 9.2 35.2 19.8 157.2 116.4 PCB 114 <1 <1
<1 1.9 <1 <1 2.22 1.3 10.5 7.1 PCB 118 <1 <1 <1
50.7 14.5 14.3 45.7 28.5 227.0 15.1 PCB 123 <1 <1 <1 4.9
1.8 2 4.46 6.6 23.8 28.0 PCB 156 <1 <1 <1 5.7 2.8 <1
3.52 4.9 24.2 22.4 PCB 157 <1 <1 <1 <1 <1 <1
<1 <1 5.0 <1 PCB 167 <1 <1 <1 3.1 1.3 <1 <1
2.6 13.7 7.9 PCB 189 <1 <1 <1 <1 <1 <1 <1
<1 1.3 <1
TABLE-US-00006 TABLE 1f Heavy Metals Chemical Contamination ASPIF
HCPC PC PH Parameter #1 #2 #3 #1 #2 #3 #1 #2 #3 #1 Elements xLOQ
xLOQ xLOQ xLOQ Aluminium 7.6 <1 88.0 99.0 76.0 dnt dnt dnt 349
503.0 Antimony <1 <1 <1 <1 <1 dnt dnt dnt 2.0 9.0
Arsenic <1 9.0 <1 <1 <1 dnt dnt dnt <1 1.0 Barium
<1 <1 2.8 <1 <1 dnt dnt dnt 4.8 288.0 Bismuth <1 295
<1 <1 <1 dnt dnt dnt <1 1.0 Lead <1 <1 <1
<1 <1 dnt dnt dnt 3.0 140.0 Boron <1 3 <1 <1 <1
dnt dnt dnt 4.4 1.4 Calcium 6.2 12.0 794.0 6.2 2.6 dnt dnt dnt 56.0
690.0 Cerium <1 <1 <1 <1 <1 dnt dnt Dnt 2.0 3.0
Chromium <1 <1 7.0 <1 <1 dnt dnt dnt 7.0 45.0 Cobalt
<1 <1 <1 <1 <1 dnt dnt dnt 5.0 1.0 Iron <1 <1
45.0 9.3 3.4 dnt dnt dnt 77.0 160.0 Gallium <1 <1 <1 <1
<1 dnt dnt dnt <1 1.0 Germanium <1 3.0 <1 <1 <1
dnt dnt dnt <1 <1 Iridium <1 126.0 <1 <1 <1 dnt
dnt dnt <1 <1 Potassium <1 2.0 <1 <1 1 dnt dnt dnt
2.1 7.2 Copper <1 1.0 4.0 4.0 <1 dnt dnt dnt 9.0 360.0
Lithium <1 568.0 <1 <1 <1 dnt dnt dnt 3.0 3.0 Magnesium
32.0 <1 226.0 64.0 26.0 dnt dnt dnt 154.0 1172.0 Manganese <1
11.1 8.0 <1 1 dnt dnt dnt 10.0 35.0 Molybdenum <1 <1 <1
<1 <1 dnt dnt dnt <1 22.0 Sodium <1 <1 222.0 74.0
72.0 dnt dnt dnt 132.0 358.0 Nickel <1 <1 <1 <1 <1
dnt dnt dnt 4.0 6.0 Phosphorus 3.9 <1 5.9 4.0 3.9 dnt dnt dnt
2.2 6.2 Rubidium <1 3.4 <1 <1 <1 dnt dnt dnt <1
<1 Ruthenium <1 2.0 <1 <1 <1 dnt dnt dnt <1 <1
Strontium <1 8.2 8.4 <1 <1 dnt dnt dnt 2.2 17.2 Titanium
4.0 <1 36.0 4.4 3 dnt dnt dnt 80.0 7900.0 Uranium <1 240
<1 <1 <1 dnt dnt dnt <1 <1 Tungsten <1 41 <1
<1 <1 dnt dnt dnt <1 6.0 Yttrium <1 <1 <1 <1
<1 dnt dnt dnt <1 3.0 Zinc 2.0 240.0 2470.0 100.0 2920.0 dnt
dnt dnt 3150 890.0 Tin <1 <1 <1 <1 <1 dnt dnt dnt
<1 8.0 Zirconium <1 41.0 1.0 <1 2.0 dnt dnt dnt 4.0
48.0
TABLE-US-00007 TABLE 1g Organotins Chemical Contamination ASPIF
HCPC PC PH Parameter #1 #2 #3 #1 #2 #3 #1 #2 #3 #1 Organotin
compounds xLOQ xLOQ xLOQ xLOQ Monomethyltin 2.0 <1 <1 <1
<1 dnt dnt <1 dnt <1 Dimethyltin <1 <1 <1 4.0
<1 dnt dnt <1 dnt 5.0 Monobutyltin <1 <1 <1 4.0 5.0
dnt dnt 2.3 dnt 3.0 Dibutyltin 1.7 <1 <1 1.3 <1 dnt dnt
20.7 dnt 11.7 Tributyltin <1 <1 <1 <1 <1 dnt dnt
<1 dnt 3.0 Dioctyltin <1 <1 <1 45.0 <1 dnt dnt <1
dnt 2.0
TABLE-US-00008 TABLE 1h Phthalates Chemical Contamination ASPIF
HCPC PC PH Parameter #1 #2 #3 #1 #2 #3 #1 #2 #3 #1 Phthalates xLOQ
xLOQ xLOQ xLOQ Di-2-propylheptyl phthalate <1 <1 <1 <1
<1 1.2 <1 1.7 1.2 14.6 Diethyl phthalate <1 <1 <1
<1 <1 <1 <1 <1 <1 4.6 Diisobutyl phthalate <1
<1 <1 24 9.6 1.3 12.6 6.2 6.6 22.0 Dibutyl phthalate <1
<1 <1 26 10.8 8.4 4.6 9.2 22.0 32.0 Dimethoxyethyl phthalate
<1 <1 <1 <1 <1 <1 <1 <1 1.7 <1
Benzylbutyl phthalate <1 <1 <1 <1 <1 <1 <1
<1 2.6 10.4 Di-2-ethylhexyl phthalate <1 <1 <1 12.8 8.4
3.0 12.6 15.4 17.8 700.0 Diisononyl phthalate <1 <1 <1
<1 <1 <1 24 20.0 26.0 240.0
TABLE-US-00009 TABLE 1i PAHs Chemical Contamination ASPIF HCPC PC
PH Parameter #1 #2 #3 #1 #2 #3 #1 #2 #3 #1 PAHs xLOQ xLOQ xLOQ xLOQ
Acenaphthene <1 <1 <1 10 5.6 3.8 4.1 9.7 1.8 22.0
Acenaphthylene <1 <1 <1 <1.0 <1 <1 <1 8.2
<1 <1 Anthracene <1 <1 <1 1.9 1.4 2.7 <1 11.0 7.1
6.8 Benzo[a]anthracene <1 <1 <1 <1.0 <1 <1 <1
2.4 2.1 6.6 Benzo[a]pyrene <1 <1 <1 <1.0 <1 <1
<1 <1 <1 5.1 Benzo[b]fluoranthene <1 <1 <1
<1.0 <1 <1 <1 1.3 1.5 6.3 Benzo[c]fluorene <1 <1
<1 <1.0 <1 <1 <1 <1 <1 1.8 Benzo[e]pyrene
<1 <1 <1 <1.0 <1 <1 <1 1.4 1.7 6.5
Benzo[g,h,i]perylene <1 <1 <1 <1.0 <1 <1 <1
1.4 1.7 12.0 Benzo[j]fluoranthene <1 <1 <1 <1.0 <1
<1 <1 <1 1.2 2.9 Benzo[k]fluoranthene <1 <1 <1
<1.0 <1 <1 <1 <1 <1 2.4 Chrysene <1 <1
<1 <1.0 <1 <1 <1 2.9 3.8 8.5 Fluoranthene <1
<1 <1 33.0 11.0 7.9 8.3 46.0 63.0 44.0 Fluorene 1.5 <1
<1 18.0 8.5 7.6 7 21.0 2.7 20.0 lndeno[1,2,3-c,d]pyrene <1
<1 <1 <1.0 <1 <1 <1 <1 <1 4.1 Naphthalene
2.4 <1 <1 6.0 <1 5.3 2.8 14.0 <1 5.7 Phenanthrene 5.2
<1 <1 59.0 27.0 28.0 18.0 120.0 62.0 100.0 Pyrene <1 <1
<1 29.0 13.0 9.2 9.9 33.0 59.0 57.0
[0066] The tested ASPIF sources were primarily absent detectable
levels of chemical contaminants except for alkylphenols and heavy
metals and small amounts of organotins and PAHs. The chemical
contaminant results for these ASPIF sources serves as a guide for
the level of chemical contamination representative of these
controlled end markets and demonstrates that heavy metals, which
are of low transfer risk anyway, are ubiquitous across all film
sources. Hence, heavy metals were not included in ongoing analysis
within this application. The tested High-Custody Post-Commercial
film sources were largely free of pesticides and alkylphenol
ethoxylates, but contained detectable levels of alkylphenols,
bisphenol-A, dioxins/furans/PCBs, and PAHs and low levels of
phthalates. The tested Post-Commercial Film sources were heavily
contaminated with every class evaluated; for example, dioxins were
typically as high as 40.times. the LOQ, but for one source, dioxins
were as high as 200.times. the LOQ. The tested Post-Household
source was the most heavily contaminated; for example, dioxins were
as high as 300.times. the LOQ and PCBs were as high as 180.times.
the LOQ.
[0067] From TABLES 1a-1i, representative chemical species were
selected from the various classes based upon prevalence across the
spectrum of reclaim sources. The selected representative chemical
species within these classes include: piperonyl butoxide
(representing pesticides); 4-t-octylphenolhexaethoxylate and
iso-nonylphenoltriethoxylate (representing alkylphenolethoxylates);
iso-nonylphenol and 4-tert-pentylphenol (representing alkylphenol
s); bisphenol-A (representing phenols); 1.2.3.6.7.8-HxCDD,
1.2.3.4.6.7.8-HpCDD, and OCDD (representing dioxins); OCDF
(representing furans); PCB 105 and PCB 118 (representing PCBs);
monobutyltin and dibutyltin (representing organotins); dibutyl
phthalate and di-2-ethylhexyl phthalate (representing phthalates);
and fluoranthene and phenanthrene (representing polycyclicaromatic
hydrocarbons (PAHs).
[0068] In embodiments of the present invention, said chemical
contaminants in said first plastic include at least one chemical
contaminant and such is selected from the group comprising
pesticides, alkyl phenols, alkylphenol ethoxylates, bisphenols,
dioxins, furans, PCBs, phthalates, PAHs or mixtures thereof.
[0069] In embodiments of the present invention, the pesticides
comprise piperonyl butoxide, BAC, DEET, and DDAC. In another
embodiment of the present invention, the alkylphenol ethoxylates
comprise iso-Nonylphenolmonoethoxylate,
iso-Nonylphenoldiethoxylate, iso-Nonylphenoltriethoxylate, and
iso-Nonylphenoltetraethoxylate. In yet another embodiment of the
present invention, the alkyl phenols comprise iso-Nonylphenol,
4-tert-butylphenol, and 4-tert-Pentylphenol. In even yet another
embodiment of the present invention, the bisphenols comprise
bisphenol-A. In even yet another embodiment of the present
invention, the dioxins comprise 1,2,3,6,7,8-HxCDD,
1.2.3.4.6.7.8-HpCDD, and OCDD. In even yet another embodiment of
the present invention, the furans comprise OCDF. In even yet
another embodiment of the present invention, the PCBs comprise PCB
77, PCB 81, PCB 126, PCB 105, PCB 114, PCB 118, PCB 123, PCB 156,
and PCB 167. In event yet another embodiment of the present
invention, the phthalates comprise di-2-propylheptyl phthalate,
disobutyl phthalate, dibutyl phthalate, di-1-ethylhexyl phthalate,
and diisononyl phthalate. In even yet another embodiment of the
present invention, the PAHs comprise acenaphthene, acenaphthylene,
anthracene, benzo[a]anthracene, benzo[b]fluoroanthene,
benzo[e]pyrene, benzo[g.h.i]perylene, chrysene,
cyclopenta[c.d]pyrene, flyoroanthene, fluorene, naphthalene,
phenanthrene, and pyrene. In even yet another embodiment of the
present invention, the organotins comprise monobutylin, dibutyltin,
and dioctylin.
[0070] In embodiments of the present invention, the contaminants in
the first plastic may comprise 4-tert-pentylphenol. In embodiments
of the present invention, the contaminants in the first plastic may
comprise bisphenol-A. In embodiments of the present invention, the
contaminants in the first plastic may comprise OCDD. In embodiments
of the present invention, the contaminants in the first plastic may
comprise PCB 118. In embodiments of the present invention, the
contaminants in the first plastic may comprise di-2-ethylhexyl
phthalate.
[0071] In order to simplify the presentation of the purification
results for objects of the present invention and associated
examples, the number of chemical species presented per chemical
class is limited to the aforementioned representative chemical
species for each chemical class as shown in Table 2 along with the
associated LOQ and the respective levels for the tested ASPIF
sources. Note: Even though more in-depth and complete chemical
analysis was completed for all objects of the present invention,
only the representative chemicals are shown ongoing. This
simplification does not impact or alter the inventive matter or
conclusions reached from such. The specific chemicals selected,
adequately and consistently represent the broader class with
respect to purification.
TABLE-US-00010 TABLE 2 Simplified Chemical Contaminants and
Associated LOQ Concentrations Parameter LOQ Pesticides Piperonyl
butoxide 10 ppb Alkylphenol ethoxylates
4-t-Octylphenolhexaethoxylate 5 ppb iso-Nonylphenoltriethoxylate 50
ppb Alkylphenols iso-Nonylphenol 50 ppb 4-tert-Pentylphenol 5 ppb
Bisphenols Bisphenol A 5 ppb Dioxins and dioxinlike and PCB
1,2,3,4,6,7,8-HpCDD 0.2 pptr OCDD 0.2 pptr OCDF 0.2 pptr PCB 105 5
pptr PCB 118 10 pptr Organotin compounds Monobutyltin 300 pptr
Dibutyltin 300 pptr Phthalates Dibutyl phthalate 50 ppb
Di-2-ethylhexyl phthalate 50 ppb Polycyclic aromatic hydrocarbons
(PAH) Fluoranthene 1 ppb Phenanthrene 1 ppb
[0072] In embodiments of the present invention, the concentration
of each pesticide in the purer plastic is lower than its respective
LOQ; wherein the first plastic has at least one detectable
pesticide. In embodiments of the present invention, the
concentration of bis-phenol A in the purer plastic is lower than
its respective LOQ; wherein the first plastic has at least
detectable bis-phenol A. In embodiments of the present invention,
the concentration of each dioxin in the purer plastic is lower than
its respective LOQ; wherein the first plastic has at least one
detectable dioxin. In embodiments of the present invention, the
concentration of each PCB in the purer plastic is lower than its
respective LOQ; wherein the first plastic has at least one
detectable PCB. In embodiments of the present invention, the
concentration of each phthalate in the purer plastic is lower than
its respective LOQ; wherein the first plastic has at least one
detectable phthalate.
[0073] In embodiments of the present invention, the concentration
of piperonyl butoxide in said purer plastic is less than about 10
ppb; wherein said first plastic has a concentration of piperonyl
butoxide above 10 ppb; the concentration of 4-tert-Pentylphenol in
said purer plastic is less than about 5 ppb; wherein said first
plastic has a concentration of 4-tert-pentylphenol is above 5 ppb;
the concentration of bisphenol-A in said purer plastic is less than
about 5 ppb; wherein said first plastic has a concentration of
bisphenol-A is above 5 ppb; the concentration of OCDD in said purer
plastic is less than about 0.2 pptt; wherein said first plastic has
a concentration of OCDD above 0.2 pptr; the concentration of PCB
118 in said purer plastic is less than about 10 pptr; wherein said
first plastic has a concentration of PCB 118 above 10 pptr; and the
concentration of di-2-ethylhexyl phthalate in said purer plastic is
less than about 50 ppb; wherein said first plastic has a
concentration of di-2-ethylhexyl phthalate above 50 ppb.
[0074] In general, the efficacy of a cleaning process to remove a
specific chemical contaminant is determined by the removal
efficiency, defined as the difference in concentration of the
chemical contaminant in the first plastic and the concentration of
the chemical contaminant in the purer plastic divided by the
concentration of the chemical contaminant in first plastic
expressed as a percentage. However, the removal efficiency is
somewhat insufficient due to the inability to determine
concentrations below the LOQ. For example, if a cleaning process
reduces the contamination from 2.times.LOQ to less than the LOQ,
then the removal efficiency could be anywhere between 50% and 100%,
which is a significant difference. Thus, the removal efficiency is
only sufficient when the first plastic and purer plastic chemical
contaminant concentration are both above LOQ. For simplicity, if
the purer plastic has a chemical contaminant concentration below
LOQ, then removal efficiency is calculated by assuming the chemical
contaminant concentration of the purer plastic is at the LOQ and
the removal efficiency is considered a minimum value and designated
with >. For the above example, the removal efficiency would be
calculated as
100(2.times.LOQ-1.times.LOQ)/(2.times.LOQ)=100(2-1)/2=50%. Thus,
the removal efficiency would be >50%. In certain cases, the
purer plastic will have a higher level of a contaminant than the
first plastic due to 1) measurement error, 2) contaminant hot spots
and cold spots in the first plastic, 3) external contamination
during sampling, and 4) the purification process adds
contamination. In such cases, the removal efficiency is set to 0%
to not bias the average results. If such occurs consistently for a
given cleaning process, then such is more likely attributable to
the purification process and should be more closely examined, but
such was not generally the case for the cleaning processes of the
present invention.
[0075] In embodiments of the present invention, the removal
efficiency of the piperonyl butoxide contaminant is >55% wherein
said piperonyl butoxide concentration in the first plastic is at
least 10 ppb. In another embodiment of the present invention, the
removal efficiency of the piperonyl butoxide contaminant is >75%
wherein said piperonyl butoxide concentration in the first plastic
is at least 10 ppb. In yet another embodiment of the present
invention, the removal efficiency of the piperonyl butoxide
contaminant is >90% wherein said piperonyl butoxide
concentration in the first plastic is at least about 10 ppb.
[0076] In embodiments of the present invention, the removal
efficiency of the 4-tert-pentylphenol contaminant is >55%
wherein said 4-tert-pentylphenol concentration in the first plastic
is at least 5 ppb. In another embodiment of the present invention,
the removal efficiency of the 4-tert-pentylphenol contaminant is
>70% wherein said 4-tert-pentylphenol concentration in the first
plastic is at least 5 ppb.
[0077] In embodiments of the present invention, the removal
efficiency of the bisphenol A contaminant is >55% wherein said
bisphenol A concentration in the first plastic is at least 5 ppb.
In another embodiment of the present invention, the removal
efficiency of the bisphenol A contaminant is >75% wherein said
bisphenol A concentration in the first plastic is at least 5 ppb.
In yet another embodiment of the present invention, the removal
efficiency of the bisphenol A contaminant is >90% wherein said
bisphenol A concentration in the first plastic is at least 5
ppb.
[0078] In embodiments of the present invention, the removal
efficiency of the OCDD contaminant is >55% wherein said OCDD
concentration in the first plastic is at least about 0.2 pptr. In
another embodiment of the present invention, the removal efficiency
of the OCDD contaminant is >75% wherein said OCDD concentration
in the first plastic is at least about 0.2 pptr. In yet another
embodiment of the present invention, the removal efficiency of the
OCDD contaminant is >85% wherein said OCDD concentration in the
first plastic is at least about 0.2 pptr.
[0079] In embodiments of the present invention, the removal
efficiency of the PCB 118 contaminant is >55% wherein said PCB
118 concentration in the first plastic is at least 10 pptr. In
another embodiment of the present invention, the removal efficiency
of the PCB 118 contaminant is >75% wherein said PCB 118
concentration in the first plastic is at least 10 pptr. In yet
another embodiment of the present invention, the removal efficiency
of the PCB 118 contaminant is >90% wherein said PCB 118
concentration in the first plastic is at least 10 pptr.
[0080] In embodiments of the present invention, the removal
efficiency of the Phenanthrene contaminant is >55% wherein said
Phenanthrene concentration in the first plastic is at least 1 part
per billion. In another embodiment of the present invention, the
removal efficiency of the Phenanthrene is >75% wherein said
Phenanthrene concentration in the first plastic is at least 1 part
per billion. In yet another embodiment of the present invention,
the removal efficiency of the Phenanthrene contaminant is >90%
wherein said Phenanthrene concentration in the first plastic is at
least 1 part per billion.
[0081] In general, chemical contaminants include both permeable and
impermeable chemical contaminants. Not wishing to be bound by
theory, applicants believe that, with respect to polyethylene and
polypropylene type reclaimed materials, contaminants such as
pesticides, dioxins, furans, PCBs, phthalates, PAHs, bisphenols,
alkyl phenols, and alkylphenol ethoxylates should be permeable; and
contaminants, such as heavy metals should be impermeable.
Organotins may be permeable or impermeable depending upon the
molecular size.
[0082] Contamination can be located on the surface of the plastic
or in the bulk. Contamination on the surface is most readily and
easily removed by surface cleaning technologies available on the
market today. If the surface contamination is permeable in the
plastic, then it will become bulk contamination over time through
diffusion mechanisms, thus complicating reduction and limit the
effectiveness of surface cleaning technologies. If the surface
contamination is impermeable in the plastic, then such
contamination will not diffuse into the bulk and will be reduced by
simple surface cleaning methods, such as aqueous washing. Bulk
contamination of either permeable or impermeable type typically
cannot be effectively removed via simple surface purification
methods, such as aqueous washing. Bulk contamination of the
impermeable type (also known as bulk impermeable contamination) is
trapped in the bulk plastic and may be freed through mechanisms
comprising melt convection, melt filtration, or
dissolution/disintegration of the bulk plastic.
[0083] As discussed previously, contamination can be introduced
externally throughout the lifecycle of the plastic. If the
contamination is impermeable, then such contamination will largely
remain on the surface during the plastic lifecycle up to the point
of reclaiming. If the contamination is permeable, then over time,
the contamination will migrate into the bulk plastic. Thus, absent
a contamination or purification event, the contamination will
remain essentially constant, but the balance of surface to bulk
contamination will change with time but will approach equilibrium
at long time. In general, loosely bound surface contamination such
as dirt may be in the 0.01 to about 0.1 wt %; whereas the chemical
contamination, especially the chemical contaminants of concern for
this invention, will be ppm, ppb, or even pptrillion.
[0084] Permeable and impermeable contamination represents different
challenges in various uses, such as medical or food applications.
For instance, permeable contamination whether in the bulk plastic
or on the surface of the plastic will have the potential to migrate
to uncontaminated materials, such as a product or to human skin.
Thus, if a package contains permeable contaminants, then such
contaminants will have the potential to migrate into the product
and render it unsuitable for various uses. However, if the
contaminant is impermeable and in the bulk of the plastic, then it
will have low ability to transfer to the product or to the user's
skin unless the bulk plastic is disintegrated or ingested. Thus, a
package could potentially use this contaminated plastic material
and not risk contamination transfer to the product or transfer
directly to skin. However, if the contaminant is impermeable and on
the surface of the plastic, then such contamination would have the
ability to transfer to the product or skin by direct contact
transfer and would be unacceptable for use in these demanding
applications. Surface contamination, both permeable and
impermeable, can be transformed into bulk contamination through
convective mechanism, such as melt mixing and melt densification.
These methods exchange or eliminate surface area with bulk
material. For example, if surface contaminated film is
melt-densified or melt extruded into a different shape, such as a
pellet, then all original surface contamination will become bulk
contamination whether such is impermeable or not and such bulk
contamination will be more difficult to remove with purification
processes. Melt densification is common in the recycle industry. It
is also common in the recycle industry to shred incoming plastics.
The latter methods generally do not convert surface contamination
to bulk contamination. Ideally, surface purification methods, such
as surface washing, take place on the original contaminated surface
such as shredded film wherein all original surface area is
reachable by the surface washing fluid.
[0085] In general, surface contamination and bulk contamination are
difficult to differentiate using analytical methods. Most
analytical methods for permeable chemical contaminants involve
solvent extraction of the contaminant from the plastic over
extended periods of time >6 hours and with exposure to extreme
solvent to plastic mass ratios >100:1 and then quantifying the
contaminant in the solvent using methods, such as Gas
Chromatography-Mass Spectrometry (GC-MS). Such analytical methods
quantify contamination but do not differentiate surface from bulk
contaminants. The efficiency of a purification method to remove
surface contamination can be estimated from the difference in
contamination before and after the surface cleaning step but such
assumes bulk contamination is not significant impacted, which is
likely the case for surface washing with aqueous surface washing
fluids discussed in the current invention. A more accurate way to
quantify surface contamination is through washing and then solvent
extraction of the contaminant at various times and then
extrapolating the amount of the contaminant removed at
infinitesimal time, which will approximate the amount of surface
contamination. However, this method is time consuming and costly
especially for contaminants that are difficult to measure in
general. In addition, since the balance of surface and bulk
contaminants are dynamic, it is difficult to quantify without
referencing an exact sampling time. A simple method for quantifying
general surface contamination (not chemical surface contamination
or species based chemical contaminants) is weighing the first
plastic before and after the surface washing step.
[0086] In general, bulk contamination will not be appreciably
removed by simple aqueous surface washing. Permeable bulk
contamination can be removed by diffusion mechanisms through
gradients in chemical potential. Whereas bulk impermeable
contamination is essentially trapped by the bulk polymer and
methods to free the trapped contaminant comprise melt convection,
melt filtration, and dissolution/disintegration of the plastic.
IV. Surface Purification Methods
[0087] Surface purification methods reduce surface contamination.
One such method is surface washing with a surface washing fluid
that is typically water based. Surface washing is ideally completed
before any melt mixing or melt densification to allow effective
cleaning of the original contaminated surface. The first plastic
will generally be in the form of pellets, loose or compacted film,
loose or compacted flexible packages, loose or compacted rigids,
loose or compacted non-wovens, etc. which will be difficult to
surface wash due to excessive overall size. Hence, prior to surface
washing, a granulation or shredding step is preferred. For films,
it is especially important to exfoliate all available film layers,
such that the washing fluid can access all original surface
contamination. Thus, the size reduction step prior to surface
washing should not significantly decrease the surface area to
volume ratio of the reclaimed source or exchange such with new
surface area. In embodiments of the present invention, said surface
washing of said first plastic is conducted after a shredding or
granulation step. The surface washing will include significant
mechanical agitation to loosen surface dirt and other contaminants
to allow physical removal and transfer to the washing fluid wherein
the dirt or other contaminants may or may not solubilize. As used
herein, a surface washing method is any method wherein the
reclaimed plastic in its original contaminated form (except for the
possibility of bulk size reduction that does not eliminate more
than 25% of the original surface) is contacted with an aqueous
solution under mechanical agitation and then separated from the
aqueous media which now contains such contamination. Such a method
will in general remove the majority of loosely bound surface
contamination including but not limited to dirt, wood, loosely
bound paper, and some surface chemical contamination. Typical
levels of loosely bound surface contamination for film based
reclaimed sources are between about 0.01 and 0.1 wt %. For objects
of the present invention involving a surface washed first plastic,
the surface washing process will remove greater than about 80% of
the loosely bound surface contamination as determined by method 2
shown in section IX.
[0088] Surface washing technologies are available extensively on
the market. One representative technology is from Lindner (Lindner
Washtech GmbH, Haldenfeld 4, Germany). The technology is described
in detail elsewhere
(https://www.lindner-washtech.com/system-solutions) but involves
water washing under vigorous mechanical agitation and the potential
for application of caustic to remove adhesives followed by drying
and pelletization.
[0089] Another representative surface washing technology is from
Herbold (Herbold Meckesheim USA, North Smithfield, R.I.). The
technology is described in detail elsewhere
(https://www.herbold.com/en/machines/washing-separating-drying-2/)
but also involves various water washing steps under vigorous
mechanical agitation followed by drying and pelletization.
[0090] Another representative technology is from Sorema (Sorema
S.r.l., Anzano del Parco, Italy). The technology is described in
detail elsewhere
(http://sorema.it/en_US/applications/washing-line/) but involves
similar aqueous operations relative to Lindner and Herbold.
[0091] Another representative surface washing technology is from
Cadel called De-inking (Cadel Deinking, Alicante, Spain). The
technology is described elsewhere (http://cadeldeinking.com/en/)
but essentially involves the surface washing of materials using
high temperature aqueous based solutions with specific surfactants,
followed by water rinsing, drying, devolatilization, and
pelletization. This method differs from other known methods in that
it claims to remove surface printed inks. Such would be
advantageous due to lowering the burden for chemical contaminant
removal by the bulk purification methods of the current
invention.
[0092] Three surface washing technologies of the prior art were
evaluated for removal of the targeted classes of chemical
contaminants (Comparative Examples 1, 2, and 3). Each of the
surface washing technologies was evaluated using a different
reclaimed film input with different levels of contamination.
Overall, the surface washing technologies of the prior art were not
able to purify the reclaimed materials sufficiently for use in
controlled end markets. For the targeted contaminants, the
commercial technologies were not able to reduce to levels near the
LOQ despite low initial contamination of the respective reclaimed
sources. In addition, the average removal efficiency for
4-tert-pentylphenol, bisphenol A, OCDD, PCB 118, di-2-ethylhexyl
phthalate was less than about 55%.
V. Melt Densification
[0093] The plastic coming out of the surface washing step will
generally be in a similar geometric form and with similar surface
area to volume ratio as the incoming reclaimed plastic. For
example, if the reclaimed plastic is loose film, then after surface
washing, the film will exit surface purification as a shredded
film. Because such loose plastic is difficult to feed to certain
bulk purification methods, it may be desirable to melt densify such
plastic prior to bulk purification. A preferred method for melt
densification is melt extrusion. The melt extrusion not only
densifies the plastic, but it may provide the pressure necessary
for the downstream bulk purifications like liquid-liquid
extraction. The melt extrusion may also include optional steps,
such as melt filtration, and/or devolatilization to remove large
bulk contaminants and/or volatile bulk contaminants. In addition,
the molten densified plastic may be further pressurized using a
melt pump. The melt pump may be necessary to increase the pressure
necessary for the downstream bulk purification step. Other methods
of densification are known in the art including rotating disc and
rotating drum densifiers, which occur at lower temperatures
relative to melt based methods. In embodiments of the present
invention, said melt densification comprises melt extrusion. In
another embodiment of the present invention, said melt extrusion
comprises melt filtration. In yet another embodiment of the present
invention, said melt extrusion comprises melt devolatilization. In
embodiments of the present invention, said melt densification
comprises melt extrusion, melt filtration, melt devolatilization,
and melt pumping.
VI. Bulk Purification
[0094] In general, bulk contamination will not be appreciably
reduced by simple aqueous surface washing. Melt filtration and melt
devolatilization will have the potential to remove bulk
contaminants of large geometric size and remove some volatile bulk
contaminants but will be largely ineffective against most bulk
contaminants especially to the required levels.
[0095] One technology available on the market to complete bulk
purification is InterRema Refresher.TM. from EREMA (EREMA Group,
Ansfelden, Austria) https://www.erema.com/en/refresher/). The
technology is described in detail elsewhere but essentially
consists of devolatilization of pelletized materials over extended
periods of time at temperatures below the primary melting point of
the plastic to remove volatile organics. Most of the chemical
contaminants relevant to reclaimed materials and discussed in the
prior sections are highly non-volatile with normal boiling points
typically above 200 C. Hence, this type of devolatilization
technology will have limited ability to remove most chemical
contamination referenced in this application.
[0096] Other technologies based upon devolatilization are common.
These may be stand-alone unit operations or combined with other
operations including extrusion and melt filtration. Those utilizing
sub-ambient pressure over a molten stream of the reclaimed plastic
are common.
[0097] One bulk purification technology involving devolatilization
was analyzed for purification capability. The technology involved
slightly elevated temperatures but below the primary melting point
of the plastic, long residence times (>about 2 hours), and
continuous reflux of purified air to provide the devolatilization
(as shown below in Comparative Example 4). The commercial
devolatilization technology was unable to sufficiently remove the
targeted contaminants. For example, the targeted contaminants were
still well above LOQ. In addition, the average removal efficiency
was .about.20%.
[0098] Extraction is a preferred bulk purification method.
Extraction involves the use of a purification solvent to remove
bulk permeable contaminants through creation of a chemical
potential gradient between the first plastic and the solvent. The
rate of permeable chemical contaminant removal will depend upon the
diffusivity and solubility of the contaminant in the plastic under
the conditions created in the process. For high molecular weight
plastics, the diffusivity of large molecules indicative of chemical
contaminants is quite low, especially in the solid state of the
plastic. In addition, the solubility may be limited due to the high
MW of the first plastic and lack of enthalpic mixing. Thus, the
time required to remove permeable contaminants through diffusion
mechanisms can be quite long and not conducive to economically
viable processes at commercial scale. Methods to resolve these time
scale limitations include 1). increased diffusivity through
elevated temperature and/or plastic relaxation through solvent
swelling, 2). decrease of diffusion path length through increased
surface area to volume ratio of the first plastic exposed to the
solvent, 3) increased convective transport of the contaminant
through the plastic/solvent interface by: increased solubility of
the contaminant in the solvent, increased partitioning of the
contaminant within the solvent relative to the plastic; increased
convection around the plastic/solvent interface, and increased
solvent sink relative to plastic sink. The solubility of the bulk
purification solvent in the plastic can be increased by operating
the extraction at high pressures especially at, near, or above the
critical pressure.
[0099] It is important for the extraction method to be scalable to
large volumes at low cost. Hence, the time required for extraction
should be low to allow for such scalability. In embodiments of the
present invention, the total time for extraction is less than about
6 hours, preferably less than about 4 hours, more preferably less
than about 2 hours, and even more preferably less than about 1
hour. If the extraction is completed in stages, then the time per
stage may be less than this range but the overall time will still
fall within these times.
[0100] Extractions may take place above, near, at, or below the
primary melting point of the first plastic. Extraction taking place
at, near, or above the primary melting point of the first plastic
are called liquid-liquid extractions. Liquid-liquid extractions are
termed liquid/liquid since both the first plastic and solvent are
in a fluid state (not necessarily liquid since supercritical
conditions may be present). Extractions taking place below the
primary melting point of the first plastic are called leaching
extractions. Liquid-liquid extractions have the advantages of
higher temperature, which drives higher diffusivity and greater
ability to manipulate the surface area exposed to the solvent
compared to leaching extractions.
[0101] In embodiments of the present invention, the temperature of
said bulk purification is above the primary melting point of the
first plastic. In another embodiment of the present invention, the
temperature of said bulk purification is above the primary melting
point of the first plastic, and the pressure of the bulk
purification is about atmospheric. In another embodiment of the
present invention, the temperature of said bulk purification is
above the primary melting point of the first plastic, and the
pressure of the bulk purification is low pressure (up to about 34
atm). In another embodiment of the present invention, the
temperature of said bulk purification is above the primary melting
point of the first plastic, and the pressure of the bulk
purification is high pressure (greater than about 34 atm). In
another embodiment of the present invention, the temperature of
said bulk purification is above the primary melting point of the
first plastic and at or above the critical temperature of the
purification solvent, and the pressure of the bulk purification is
at or above the critical pressure.
[0102] The temperature may be changed during the course of the
extraction process but is generally consistent within a given stage
of a unit operation. The pressure may be changed to vary solubility
of the solvent in the first plastic or to increase solubility of
the chemical contaminant within the solvent.
[0103] A liquid-liquid extraction may take place in stages and be
combined with additional liquid-liquid extraction processes. In
addition, liquid-liquid processes may be combined with leaching
processes in various stages to form a given purification process.
In one embodiment of the present invention, the number of
liquid-liquid stages is more than one. In another embodiment of the
present invention, the number of leaching stages is more than one.
In yet another embodiment of the present invention, the number of
liquid-liquid stages is one or more and the number of leaching
stages is one or more.
[0104] The liquid-liquid extraction will comprise a heavy phase
(also called raffinate phase) and a light phase (also called
extract phase) where the two phases are immiscible. In a preferred
execution, the light phase will be represented by a bulk
purification solvent-rich/plastic-poor phase. The heavy liquid
phase will be represented by a plastic-rich/bulk purification
solvent-poor phase. Thus, the liquid-liquid solvent should
solubilize into the plastic to form a miscible bulk purification
solvent/plastic heavy phase (<about 25 wt % solvent). In
addition, the plastic should slightly solubilize (<25 wt % first
plastic) into the liquid-liquid solvent to form a miscible
plastic/liquid-liquid solvent light phase. The heavy and light
phases will be immiscible. In the heavy phase, the contaminants
will diffuse much more rapidly compared to the inherent first
plastic due to the relaxed state of the first plastic due to slight
swelling/slight miscibility of the solvent in the first plastic. In
addition, the contaminants will be convectively transported closer
to the surface due to the mixing in the liquid state. Ideally, the
surface area between the heavy and light phases will be maximized
due to a combination of distributive and dispersive mixing within
the process. The maximal content of surface area between the heavy
and light phases is more easily achieved when the rheological
properties and interfacial properties of the heavy and light phases
are more closely matched. This will generally be better achieved
when the liquid-liquid solvent and first plastic are more similar
and when the plastic dissolves into solvent such is the case for
alkanes and other non-polar solvents when using polyolefin first
plastics. The latter benefit is potentially offset by the decreased
partitioning of the contaminants in such a non-polar solvent
compared to the first plastic. Counter-current and co-current
liquid-liquid extraction equipment and methods are well known to
those skilled in the art. Such equipment is designed to effectively
distribute and disperse the light and heavy phases assuming the
rheological properties are within a matched range.
[0105] In embodiments of the present invention, said bulk
purification comprises a liquid-liquid extraction; and said bulk
purification solvent comprises a liquid-liquid extraction solvent.
In another embodiment of the present invention, said liquid-liquid
extraction comprises multiple extraction steps or stages.
[0106] In embodiments of the present invention, less than about 25%
of said first plastic is dissolved in said liquid-liquid extraction
solvent at said temperature of said liquid-liquid extraction and
said pressure of said liquid-liquid extraction. In another
embodiment of the present invention, less than about 10% of said
first polymer is dissolved in said liquid-liquid extraction solvent
at said temperature of said liquid-liquid extraction and said
pressure of said liquid-liquid extraction solvent. In yet another
embodiment of the present invention, less than about 5% of said
first polymer is dissolved in said liquid-liquid extraction solvent
at said temperature of said liquid-liquid extraction and said
pressure of said liquid-liquid extraction.
[0107] In embodiments of the present invention, a two-phase system
is formed in said liquid-liquid extraction solvent comprising a
phase rich in the first plastic and a phase rich in the
liquid-liquid extraction solvent; and said phase rich in the first
polymer comprises at least about 5 wt. % of said liquid-liquid
extraction solvent at said temperature of said liquid-liquid
extraction and said pressure of said liquid-liquid extraction. In
another embodiment of the present invention, a two-phase system is
formed in said liquid-liquid extraction comprising a phase rich in
the first polymer and a phase rich in the liquid-liquid extraction
solvent; and said phase rich in the first polymer comprises at
least about 1 wt. % of said liquid-liquid extraction solvent at
said temperature of said liquid-liquid extraction and said pressure
of said liquid-liquid extraction. In yet another embodiment of the
present invention, a two-phase system is formed in said
liquid-liquid extraction comprising a phase rich in the first
polymer and a phase rich in the liquid-liquid extraction solvent;
and said phase rich in the first polymer comprises at least about
0.5 wt. % of said liquid-liquid extraction solvent at said
temperature of said liquid-liquid extraction and said pressure of
said liquid-liquid extraction.
[0108] In embodiments of the present invention, wherein the number
of stages is 1 to about 50. In another embodiment of the present
invention, wherein the number of stages is 5.
[0109] While not wishing to be bound by theory, the theoretical
maximum contaminant removal capacity for an extraction process is
based upon the thermodynamic equilibrium/partitioning of the
chemical contaminants between the first plastic and solvent at the
temperature and pressure of the process. Thermodynamic equilibrium
may not be achieved due to kinetic limitations in the extraction
process. This is true for the complete extraction process and is
also true for each extraction stage. A higher solvent to first
plastic mass ratio will drive both thermodynamics and kinetics in
favor of purification at the expense of greater solvent consumption
and greater extraction process size, which equals greater cost.
Thus, a balance must be found between these important design and
operational variables for the targeted chemical contaminant removal
efficiency. In general, the applicants have found that the overall
fresh or renewed solvent to first plastic mass ratio is preferably
above .about.about 5:1, more preferably above .about.about 10:1,
more preferably above .about.about 15:1, even more preferably above
.about.about 20:1, and most preferably above .about.about 30:1 but
less than about 100:1. If the extraction is completed in
progressive or sequential stages, then the solvent to first plastic
ratio per stage may be lower than this stated range, but the total
solvent used to the total first plastic represented by the sum of
solvent used in all stages should be within this range. In
addition, the contaminated solvent from any stage may be used
"as-is" as the solvent for another stage. Contaminated solvent at
any point in the process may be renewed through known methods of
distillation, filtration, ion-exchange, etc or combinations.
[0110] A means for increasing the effective mass transfer is
through indirectly applying energy to the first plastic such as but
not limited to vibrational in the form of ultrasonic energy and/or
microwave.
[0111] The solvent is critical in many aspects. In general, the
solvent should have a reasonably low boiling point to allow for
removal from the first plastic and allow renewal/purification of
the solvent using distillation. Higher boiling solvents may be used
but solvent regeneration and first polymer devolatilization once
purified become more problematic. Preferably, the solvent has a
normal boiling point of <200 C, more preferably <120 C, and
most preferably <90 C.
[0112] The solvent may be hydrocarbons. The solvent may be straight
chain hydrocarbons or branched hydrocarbons. The solvents may be
aliphatic or aromatic. The hydrocarbons may be alkanes.
[0113] In embodiments of the present invention, said extraction
solvent is selected from the group comprising hydrocarbons. In
another embodiment of the present invention, said extraction
solvent is selected from the group comprising aliphatic
hydrocarbons. In even another embodiment of the present invention,
said extraction solvent is selected from the group comprising
aromatic hydrocarbons. In even yet another embodiment of the
present invention, said extraction solvent is selected from the
group comprising alkanes.
[0114] In embodiments of the present invention, said extraction
solvent is selected from the group comprising methane, ethane,
propane, normal butane, isobutane, normal pentane, isopentane,
neopentane, hexanes (normal hexane, isohexane, and neohexene),
heptanes, octanes, or mixtures thereof. In another embodiment of
the present invention, said bulk purification solvent comprises
critical or supercritical ethane. In yet another embodiment of the
present invention, said bulk purification solvent comprises
critical or supercritical butane. In even yet another embodiment of
the present invention, said bulk purification solvent comprises
supercritical pentane. In embodiments of the present invention,
said bulk purification solvent comprises critical or supercritical
hexane.
[0115] The solvents may be oxygenated. Non-limiting examples of
oxygenated compounds are alcohols, esters, ethers, aldehydes,
ketones, etc. Specific non-limiting examples include but are not
limited to dimethyl ether (DME), diethyl ether, MEK, ethyl acetate,
THF, acetone, and methanol. Polar solvents such as methylene
chloride may be used. The solvent may be CO2. The solvent may be
CO2 at critical or supercritical conditions. The CO2 may be blended
with other solvents including water to tailorize solubility. The
solubility of CO2 in polymers and the solubility of contaminants
within CO2 can be extensively varied based upon the temperature and
pressure of the CO2. Thus, CO2 can be used to pull out different
contaminants at different times based upon pulsing the process
pressure over a range of pressure.
[0116] In embodiments of the present invention, said extraction
solvent is selected from the group comprising dimethyl ether (DME),
diethyl ether, MEK, ethyl acetate, THF, acetone, methanol, and CO2.
In another embodiment of the present invention, said extraction
solvent comprises di-methyl ether. In yet another embodiment of the
present invention, said extraction solvent comprises critical or
super critical di-methyl ether. In event yet another embodiment of
the present invention, said extraction solvent comprises
ethyl-acetate. In even yet another embodiment of the present
invention, said extraction solvent comprises THF. In even yet
another embodiment of the present invention, said extraction
solvent comprises CO2. In even yet another embodiment of the
present invention, said extraction solvent comprises critical or
supercritical CO2.
[0117] Solvents may be used as blends that are tailored to remove
specific contaminants. In addition, different solvents or solvent
blends may be used during the different stages of each extraction
or each extraction type. The specific solvent selected will be
influenced by the desired type of extraction process.
[0118] Following the bulk purification involving extraction, the
plastic may be devolatilized to produce a purer plastic. The
contaminated solvent will contain a small amount of dissolved purer
plastic, the extracted contaminants, and the pure extraction
solvent. There are many ways to recover the purer polymer and bulk
purification solvent independent of the extracted contaminants.
[0119] In general, up to about 25 wt % of the first plastic may
dissolve into the extraction solvent, which complicates recovery of
the solvent and first plastic. In particular, low molecular weight
waxes that are inherent to most first plastics are particularly
prone to solubilization into the extracting solvent. These may
become problematic in distillation-based recovery of the purified
solvent due to deposition of the waxes on process equipment.
Methods are known to reduce this tendency. One such method is to
lower the temperature of the contaminated solvent to below the
cloud point to precipitate the polymer or wax phase followed by
filtration. Unlike the first plastic, the residual plastic or waxes
resulting plastic from the precipitation from the contaminated
solvent may contain significant chemical contaminants and may not
be usable in various areas.
[0120] Distillation of the contaminated bulk purification solvent
may be used to regenerate the solvent for re-use in the various
extraction operations. However, distillation may not be preferred
due to the high solvent volume utilized in the present invention.
In addition, because the chemical contaminants of interest in this
invention are extremely low in concentration, the concentration of
these chemical contaminants in the contaminated solvent may be
correspondingly low or even lower (ppb and pptr). Thus, a preferred
method to purify the contaminated solvent is through direct removal
of the contaminants without having to completely volatilize the
contaminated solvent. Such methods include ion exchange,
adsorption/absorption methods, etc. Examples include passing the
contaminated solvent through a bed of activated carbon or alumina.
This method can be used alone or in combination with distillation
to achieve the right level of purification at the right energy
consumption. In embodiments of the present invention, the
contaminated extraction solvent is renewed through
adsorption/absorption methods and may potentially include
distillation either continuously or at various time points when
required.
[0121] The purer plastic may contain small amounts of the solvent
in either physically adsorbed or bulk absorbed form. The
concentration of the solvent in the purer plastic may be reduced by
devolatilization techniques. In embodiments of the present
invention, said purer plastic is devolatilized to a content of
<1 wt % solvent in the first plastic.
[0122] In embodiments of the present invention, said temperature of
said liquid-liquid extraction is between about the primary melting
point of the first plastic and about 300.degree. C.; and said
pressure of said liquid-liquid extraction is between about
atmospheric pressure and about 1,000 atm. In another embodiment of
the present invention, said temperature of said liquid-liquid
extraction is between about 150.degree. C. and about 250.degree.
C.; and said pressure of said liquid-liquid extraction is between
about atmospheric pressure and about 1,000 atm. In even yet another
embodiment of the present invention, said temperature of said
liquid-liquid extraction is between about 150.degree. C. and about
250.degree. C.; and said pressure of said liquid-liquid extraction
is between about 14 atm and about 340 atm. In even yet another
embodiment of the present invention, said temperature of said
liquid-liquid extraction is between about 150.degree. C. and about
240.degree. C.; and said pressure of said liquid-liquid extraction
is between about 34 atm and about 68 atm. In even yet another
embodiment of the present invention, said temperature of said
liquid-liquid extraction is about 235.degree. C.; and said pressure
of said liquid-liquid extraction is about 41 atm. In even yet
another embodiment of the present invention, said temperature of
said liquid-liquid extraction is about 235.degree. C.; said
pressure of said liquid-liquid extraction is about 41 atm; and said
liquid-liquid extraction solvent comprises hexanes.
[0123] The removal efficiency of liquid-liquid was established to
be significantly more effective than the existing surface washing
methods. For example (Example 1 and Table 8), liquid-liquid
extraction with hexane removed most targeted contaminants to below
LOQ and the average removal efficiency for 4-tert-pentylphenol,
bisphenol A, OCDD, PCB 118, di-2-ethylhexyl phthalate was greater
than about 70%.
[0124] In an embodiment of the present invention, said
liquid-liquid extraction conducted at about 235 C and about 41 atm
with a liquid-liquid extraction solvent comprising hexane; wherein
the hexane to first plastic mass ratio is about 55:1 and the total
extraction time within the liquid-liquid state is about 65 minutes;
wherein the average removal efficiency for 4-tert-pentylphenol,
bisphenol A, OCDD, PCB 118, di-2-ethylhexyl phthalate is greater
than about 70%.
[0125] In an embodiment of the present invention, said temperature
of said liquid-liquid extraction is about 170.degree. C.; said
pressure of said liquid-liquid extraction is about 129 atm and said
liquid-liquid extraction solvent comprises di-methyl-ether. In yet
another embodiment of the present invention, said liquid-liquid
extraction is conducted at about 170.degree. C.; wherein said
liquid-liquid extraction takes place at a liquid-liquid extraction
solvent to first plastic ratio of about 107:1 and the total
extraction time is about 65 minutes; wherein said pressure of said
liquid-liquid extraction is about 129 atm and said liquid-liquid
extraction solvent of said liquid-liquid extraction comprises
supercritical di-methyl-ether. In even yet another embodiment of
the present invention (Example 2 Table 9), said liquid-liquid
extraction involves 5 stages conducted at about 170.degree. C. and
about 41 atm with an liquid-liquid extraction solvent comprising
di-methyl-ether with a di-methyl-ether to first plastic mass fed
ratio of about 22.7, 21.9, 21.0, 20.8, and 20.8 at stages 1 through
5 respectively and an average extraction time per stage of about 13
minutes for a total di-methyl-ether to first plastic mass ratio of
about 107:1 for a total extraction time of about 65 minutes;
wherein the average removal efficiency for 4-tert-pentylphenol,
bisphenol A, OCDD, PCB 118, di-2-ethylhexyl phthalate is about
66.8%.
[0126] In embodiments of the present invention, wherein said
liquid-liquid extraction solvent is CO.sub.2. In embodiments of the
present invention, said liquid-liquid extraction is conducted in a
stirred tank; wherein said stirred tank may be in stages.
VI. Surface+Bulk Purification
[0127] In general, the combination of surface purification methods
with bulk purification methods provide synergistic benefits to the
overall removal of contamination. Surface purification methods will
effectively remove surface contamination both impermeable and
permeable including chemical contaminants and chemical contaminant
precursors. Thus, the surface purification lowers the burden on the
bulk purification and allows such to be more effective. If a first
plastic is heavily contaminated with surface contamination, then
such contamination is preferably removed first by a surface
purification method and then followed by a bulk purification
method. Once the surface purification method removes the surface
contamination, the bulk purification method will remove the
remaining bulk permeable contamination. The only contamination not
significantly removed by this two-step approach is bulk impermeable
contamination such as heavy metals that were intentionally added
during original plastic part production. Also, organotins will be
difficult to remove due to the large size and hence low
permeability in the first plastic. The latter may still be removed
with extensive bulk purification.
[0128] Preferred methods of surface washing have already been
discussed in the surface purification section. An even more
preferred method of surface washing is the de-inking method also
described in the surface purification method (Comparative Example
3). This method not only removes surface contamination such as dirt
but also removes surface printed inks. The method is also quite
effective at removing paper labels, which are chemical contaminant
precursors. In this method, first plastic with the original surface
area exposed is fed to a multi-step aqueous washing process where
the surface contamination including surface printed inks, dirt,
grit, paper, adhesives, etc. are removed. The resulting material is
then dried. The dried material may be further densified into
pellets using extrusion including devolatilization and melt
filtration. For the purposes of this invention, a de-inking method
is any surface washing method wherein said method removes surface
print sufficient to produce less than about a 10% difference in the
dE between the de-inked and the unprinted first plastic (dE
measured using Method 3 in Section IX).
[0129] For nomenclature purposes, the contaminated plastic that is
fed to the surface purification method will be termed the first
plastic. The resulting surface purified plastic will be termed the
second plastic. The second plastic will be fed to the bulk
purification process and will be purified to the purer plastic. The
surface purification method may involve multiple surface
purification processes. The bulk purification method may involve
multiple bulk purification processes of various types. The removal
efficiency for the combined surface and bulk purification methods
will be calculated from the first plastic concentration and the
associated purer plastic.
[0130] In embodiments of the present invention, a method to produce
a purer plastic from a first plastic is presented; wherein said
first plastic has a concentration of contaminants; wherein said
purer plastic has a concentration of contaminants; wherein said
contaminants of said first plastic comprise at least one of the
following chemical classes; dioxins, PCBs, phthalates, bisphenols,
and alkyl phenols; wherein said method comprises 1) a surface
washing method to remove surface contamination followed by 2) a
liquid-liquid extraction conducted at a temperature and a pressure,
and using an extraction solvent; wherein said method reduces said
concentration of contaminants in said first plastic to said
concentration of contaminants in said purer plastic; and wherein
the average of said reductions of said concentrations of
contaminants from said first plastic to said purer plastic is at
least about 55% or LOQ.
[0131] In embodiments of the present invention, said extraction
takes place after a surface washing. In another embodiment of the
present invention, said extraction takes place after a surface
washing wherein the first plastic is not densified prior to surface
washing. In yet another embodiment of the present invention, said
extraction takes place after a surface washing; wherein the first
plastic is not densified prior to surface washing; wherein the
second plastic may be densified prior to the extraction
process.
VII. Purer Plastic
[0132] The purer plastic produced from the first plastic will have
a lower level of contamination relative to the first plastic. The
purer plastic from the bulk purification step may be further
processed to produce a pellet or other end use material. If a
pellet is desired, then such step could involve melt extrusion
followed by pelletization. The melt extrusion may optionally
include a melt filtration step and/or a devolatilization step. The
melt extrusion may include additional ingredients to the purer
plastic, such as AO, slip agents, anti-block agents, TiO.sub.2,
colorants, etc. In embodiments of the present invention, wherein
said purer plastic has a concentration of said liquid-liquid
extraction solvent of less than about 1 wt %.
VIII. Examples
Comparative Example 1--Purification of High-Custody Post-Commercial
Film Using Commercially Available Water Wash Process #1 Followed by
Melt Densification
[0133] A first plastic material, consisting of High-Custody
Post-Commercial Film #1, was fed into a commercially available
purification process. The cleaning process consisted of shredding,
various water washing steps, drying, and melt densification. The
shredding homogenized the material while reducing its fundamental
size. The aqueous water washing should have effectively removed
surface contamination. However, the ability of this process to
remove bulk permeable contamination should be minimal due to the
low solubility of the chemical contaminants in the water. A small
amount of volatile bulk contamination should be removed during
drying and melt densification, but overall, the bulk contamination
should be largely unaffected. Also, the high-custody
post-commercial film source used as the first plastic had limited
chemical contamination as demonstrated by the low levels of
pesticides, dioxins, and phthalates. The first plastic and purer
plastic were analyzed for the classes of chemical contaminants
typically present in recycled materials by GALAB Laboratories GmbH
(Am Schleusengraben 7, 21029 Hamburg, Germany) using the methods
disclosed in section IX Methods. After purification, the purer
plastic contained a slightly reduced level of chemical
contamination as shown in Table 3. The removal of the five selected
species were as follows: For 4-tert-pentylphenol, the removal
efficiency was 0%. For bisphenol A, the removal efficiency was 94%.
For OCDD, the removal efficiency was 78%. For the PCB 118, the
removal efficiency was 68%. For the di-2-ethylhexyl phthalate, the
removal efficiency was 22%. The average removal efficiency for the
five targeted species was about 52%.
TABLE-US-00011 TABLE 3 Purification of High-Custody Post-Commercial
(HCPC) Source #1 using Commercial Water Washing Process #1 Purer
Plastic HCPC #1 After First Plastic Water Washing Removal HCPC #1
Process #1 Efficiency Parameter xLOQ xLOQ % Pesticides Piperonyl
butoxide <1 <1 n.a. Alkylphenol ethoxylates
4-t-Octylphenolhexaethoxylate <1 <1 n.a.
iso-Nonylphenoltriethoxylate <1 <1 n.a. Alkylphenols
iso-Nonylphenol 190.0 174.0 8% 4-tert-Pentylphenol 19.4 44.0 0%
Bisphenols Bisphenol A 46000.0 2800.0 94% Dioxins and dioxinlike
and PCB 1,2,3,6,7,8-HxCDD <1 <1 n.a. 1,2,3,4,6,7,8-HpCDD 2.8
<1 >64% OCDD 11.1 2.4 78% OCDF <1 <1 n.a. PCB 105 24.6
11.3 54% PCB 118 50.7 16.3 68% Organotin compounds Monobutyltin
<1 <1 n.a. Dibutyltin 1.7 <1 >70% Phthalates Dibutyl
phthalate 26.0 13.2 49% Di-2-ethylhexyl phthalate 12.8 10.0 22%
Polycyclic aromatic hydrocarbons (PAH) Fluoranthene 33.0 20.0 39%
Phenanthrene 59.0 43.0 27%
Comparative Example 2--Purification of High-Custody Post-Commercial
Film #2 Using Water Wash Process #2 Followed by Melt
Densification
[0134] A first plastic material, consisting of High-Custody
Post-Commercial Film #2, was fed into a surface purification
process available on the market to produce a purer plastic. The
cleaning process consisted of shredding, aqueous hot water washing,
drying, and melt densification. As was the case with Water Wash
Process #1, this process should remove surface contamination but be
limited in ability to remove bulk permeable contamination. The
first plastic and purer plastic were analyzed for the classes of
chemical contaminants typically present in recycled materials by
GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg,
Germany) using the methods disclosed in section IX Methods, as
shown in Table 4. The high-custody film source, first plastic, had
limited chemical contamination as demonstrated by the low levels of
dioxins, PCBs, phthalates, and PAHs. The purer plastic contained a
mixture of increased and slightly decreased levels of chemical
contamination. The increase in certain chemical contaminants were
likely due to cross-contamination from other more heavily
contaminated feed streams and/or variability in the contamination
level of the current feed. The removal of the five selected species
were as follows: For 4-tert-pentylphenol, the removal efficiency
was 0%. For bisphenol A, the removal efficiency was 96%. For OCDD,
the removal efficiency was 0%. For the PCB 118, the removal
efficiency was 68%. For the di-2-ethylhexyl phthalate, the removal
efficiency was 0%. The average removal efficiency for the five
targeted species was about 14%.
TABLE-US-00012 TABLE 4 Purification of High-Custody Post-Commercial
(HCPC) Source #2 using Commercial Water Washing Process #2 Purer
Plastic HCPC #2 After First Plastic Water Washing Removal HCPC #2
Process #2 Efficiency Parameter xLOQ xLOQ % Pesticides Piperonyl
butoxide <1 <1 n.a. Alkylphenol ethoxylates
4-t-Octylphenolhexaethoxylate <1 <1 n.a.
iso-Nonylphenoltriethoxylate <1 <1 n.a. Alkylphenols
iso-Nonylphenol 120.0 340.0 0% 4-tert-Pentylphenol 52.0 134.0 0%
Bisphenols Bisphenol A 1800.0 72.0 96% Dioxins and dioxinlike and
PCB 1,2,3,6,7,8-HxCDD <1 <1 n.a. 1,2,3,4,6,7,8-HpCDD <1
2.4 >64% OCDD 2.6 10.5 0% OCDF <1 <1 n.a. PCB 105 9.9 8.8
11% PCB 118 14.5 17.4 0% Organotin compounds Monobutyltin 5.0 <1
>80% Dibutyltin <1 <1 n.a. Phthalates Dibutyl phthalate
10.8 12.4 0% Di-2-ethylhexyl phthalate 8.4 8.4 0% Polycyclic
aromatic hydrocarbons (PAH) Fluoranthene 11.0 18.0 0% Phenanthrene
27.0 40.0 0%
Comparative Example 3A--Purification of Post-Commercial #1 Film
Using Commercial De-Inking Process from Cadel
[0135] A first plastic material, consisting of Post-Commercial Film
#1, was fed into a purification process available on the market
from Cadel called De-inking (http://cadeldeinking.com/en/) to
produce a purer plastic. The process consisted of shredding,
aqueous de-inking, water washing/rinsing, and drying. From the
patent art, the de-inking step involves elevated temperatures,
elevated pH, and surfactants. The various washing steps should
effectively remove surface contamination. In addition, small
amounts of bulk permeable contamination will be removed due to the
elevated temperatures, which will increase the diffusivity, and the
potential increase in solubility of the contaminants in the water
due to the surfactant/pH combination. However, the bulk extraction
was expected to be low. The incoming first plastic was determined
to have 0.125 wt % loosely bound surface contamination compared to
about 0.02 wt % for the purer plastic in the form of shreds.
Therefore, this cleaning process removed greater than 80% of the
incoming loosely bound surface contamination. After cleaning but
prior to analyzing the first plastic for chemical contamination,
the shreds were melt densified using a single screw extruder at 190
C to produce pellets. The pellets were ground to a mass average
diameter of 300 to 500 microns. The first plastic and purer plastic
were analyzed for the classes of chemical contaminants typically
present in recycled materials by GALAB Laboratories GmbH (Am
Schleusengraben 7, 21029 Hamburg, Germany) using the methods
disclosed in section IX Methods, as shown in Table 5. The first
plastic contained a moderate level of chemical contamination
indicative of post-commercial film lacking a high custody
lifecycle. For example, the incoming dioxins like OCDD were
40.times. the LOQ, which is higher than the previously described
high-custody sources of COMPARATIVE EXAMPLES 1, 2, and 5. In
addition, this particular source has a high level of paper
contamination, which has the potential to form additional chemical
contamination once re-melted for densification/pelletization. This
particular source was especially high in alkylphenols
(.about.1,000.times. the LOQ) further indicating the level of
chemical contamination within this recycle source. This first
plastic was composed of shredded film with significant portions
being melted together into clumps of plastic. Hence, the
effectiveness of surface washing techniques with this source will
be somewhat inhibited due to the lack of access to the complete
contaminated surfaces. After the deinking process, the purer
plastic contained a reduced level of chemical contamination. The
removal of the five selected species were as follows: For
4-tert-pentylphenol, the removal efficiency was 71%. For bisphenol
A, the removal efficiency was 0%. For OCDD, the removal efficiency
was 60%. For the PCB 118, the removal efficiency was 0%. For the
di-2-ethylhexyl phthalate, the removal efficiency was 22%. The
average removal efficiency for the five targeted species was about
31%.
Comparative Example 3B--Purification of Post-Household Film #1
Using Commercial De-Inking Process from Cadel
[0136] A first plastic material, consisting of Post-Household Film
#1, was fed into the surface purification process of COMPARATIVE
EXAMPLE 3A to produce a purer plastic. The incoming first plastic
was determined to have 0.047 wt % loosely bound surface
contamination compared to about 0.003 wt % for the purer plastic.
Therefore, this cleaning process removed greater than 80% of the
incoming loosely bound surface contamination. Prior to analyzing
for chemical contamination, the shreds of Post-Household Film #1
were melt densified using an extruder and pelletized. The
pelletized material was ground to a mass average particle size of
300 to 500 microns. The first plastic and purer plastic were
analyzed for the classes of chemical contaminants typically present
in recycled materials by GALAB Laboratories GmbH (Am
Schleusengraben 7, 21029 Hamburg, Germany) using the methods
disclosed in section IX Methods, as shown in Table 5. The first
plastic contained an extremely high level of chemical contamination
including significant dirt. For example, the pesticide
piperonylbutoxide was .about.7.times. the LOQ; alkylphenol
ethoxylates were .about.1,000.times. the LOQ; dioxins and
phthalates were .about.300.times. the LOQ. The purer plastic
contained a reduced level of chemical contamination. Note: The
difference in removal efficacy between COMPARATIVE EXAMPLES 3A AND
3B despite using identical cleaning processes were likely due to
1). differences in the surface area exposed for the cleaning
process, 2). the differences in the distribution of the chemical
contaminants on the surface and within the bulk, and 3). inherent
variability in the chemical contaminants within a sample and
variability in the measurement technique. The removal of the five
selected species were as follows: For 4-tert-pentylphenol, the
removal efficiency was 38%. For bisphenol A, the removal efficiency
was 92%. For OCDD, the removal efficiency was 21%. For the PCB 118,
the removal efficiency was 0%. For the di-2-ethylhexyl phthalate,
the removal efficiency was 73%. The average removal efficiency for
the five targeted species was about 45%.
TABLE-US-00013 TABLE 5 Purification of Post-Commercial (PC) Source
#1 and Post- Household (PH) Source #1 using Commercial De-inking
Purer Purer Plastic 3A Plastic 3B First PC #1 First PH #1 Plastic
3A After De- Plastic 3B After De- PC #1 inking 3A Removal PH #1
inking 3B Removal Parameter xLOQ xLOQ Efficiency % xLOQ xLOQ
Efficiency % Pesticides Piperonyl butoxide 1.0 <1 >0% 6.6
<1 >68% Alkylphenol ethoxylates 4-t-Octylphenolhexaethoxylate
5.0 <1 >80% 17.4 1.4 92% iso-Nonylphenoltriethoxylate 3.2
<1 >69% 32.0 10.2 68% Alkylphenols iso-Nonylphenol 920.0
136.0 85% 300.0 130.0 57% 4-tert-Pentylphenol 1660.0 480.0 71%
1720.0 1060.0 38% Bisphenols Bisphenol A 4.8 11.4 0% 144.0 11.0 92%
Dioxins and dioxinlike and PCB 1,2,3,6,7,8-HxCDD <1 <1 n.a.
7.4 3.5 52% 1,2,3,4,6,7,8-HpCDD 3.8 3.0 20% 63.0 31.0 51% OCDD 39.6
15.9 60% 308.5 243.0 21% OCDF 5.5 2.8 49% 13.8 12.9 7% PCB 105 35.2
42.2 0% 116.4 122.6 0% PCB 118 45.7 52.6 0% 15.1 176.0 0% Organotin
compounds Monobutyltin dnt dnt n.a. 3.0 dnt n.a. Dibutyltin dnt dnt
n.a. 11.7 dnt n.a. Phthalates Dibutyl phthalate 4.6 <1 >78%
32.0 2.8 91% Di-2-ethylhexyl phthalate 12.6 9.8 22% 700.0 188.0 73%
PAHs Fluoranthene 8.3 8.6 0% 44.0 24.0 45% Phenanthrene 18.0 11.0
39% 100.0 53.0 47%
Comparative Example 4--Purification of High Custody Post-Commercial
#3 Film Using Commercial De-Odorizing Process
[0137] A first plastic material, consisting of High Custody
Post-Commercial Film #3, was fed into a de-odorization technology.
The process consisted of exposing the pelletized feed material to
moderate temperatures and continuous air flushing. As such, this
cleaning technique primarily removes volatile surface and bulk
contamination. However, most of the chemical contaminants of
relevance to controlled end markets are highly non-volatile. The
first plastic and purer plastic were analyzed for the classes of
chemical contaminants typically present in recycled materials by
GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg,
Germany) using the methods disclosed in section IX Methods, as
shown in Table 6. The high-custody film source #3 had limited
chemical contamination as demonstrated by the low levels of
dioxins, PCBs, phthalates, and PAHs. The purer plastic contained a
slightly reduced level of chemical contamination. The removal of
the five selected species were as follows: For 4-tert-pentylphenol,
the removal efficiency was 88%. For bisphenol A, the removal
efficiency was 96%. For OCDD, the removal efficiency was 20%. For
the PCB 118, the removal efficiency was 0%. For the di-2-ethylhexyl
phthalate, the removal efficiency was 0%. The average removal
efficiency for the five targeted species was about 41%.
TABLE-US-00014 TABLE 6 Purification of High-Custody Post-Commercial
(HCPC) Source #3 using Commercial De-Odorization Purer Plastic HCPC
#3 After First Plastic De- Removal HCPC #3 odorization Efficiency
Parameter xLOQ xLOQ % Pesticides Piperonyl butoxide <1 <1
n.a. Alkylphenol ethoxylates 4-t-Octylphenolhexaethoxylate <1
<1 n.a. iso-Nonylphenoltriethoxylate <1 <1 n.a.
Alkylphenols iso-Nonylphenol 86.0 13.0 85% 4-tert-Pentylphenol 40.0
4.8 88% Bisphenols Bisphenol A 114.0 168.0 0% Dioxins and
dioxinlike and PCB 1,2,3,6,7,8-HxCDD <1 <1 n.a.
1,2,3,4,6,7,8-HpCDD 3.4 3.0 12% OCDD 8.9 7.1 20% OCDF <1 <1
n.a. PCB 105 9.2 5.3 42% PCB 118 14.3 15.9 0% Organotin compounds
Monobutyltin dnt dnt n.a. Dibutyltin dnt dnt n.a. Phthalates
Dibutyl phthalate 8.4 3.4 60% Di-2-ethylhexyl phthalate 3.0 10.2 0%
Polycyclic aromatic hydrocarbons (PAH) Fluoranthene 7.9 9.8 0%
Phenanthrene 28.0 13.0 54%
In general, the established methods for purifying/cleaning films
and other plastic waste including water washing, de-inking, and
devolatilization are currently not able to sufficiently remove
chemical contaminants, especially in sources that are high-custody.
Even with high-custody sources, the chemical contamination is still
present and not removed completely, which might limit end use for
certain customers. Net, there is an unmet need for a cleaning
technology that is capable of more completely removing chemical
contamination sufficient for highly contaminated sources and for
any market desiring purer recycled materials.
Example 1--Bulk Purification by Batch Liquid/Liquid Extraction of
Pelletized Post-Commercial Film #2 Using Liquid/Liquid Extraction
in Critical Hexane
[0138] A first plastic material, consisting of Post-Commercial Film
#2 in the form of pellets, was fed into a lab-scale batch
Liquid/Liquid extraction process. The first plastic was in the form
of 4 mm spherical pellets for a surface area to volume ratio of
-1.5 mm-1. The first plastic was subjected to a bulk purification
step of liquid-liquid extraction as follows (at Phasex Corporation,
125 Flagship Drive, North Andover, Mass.). A 7 L autoclave was
loaded with about 280 g of pellets of the first plastic; Then, the
autoclave was vacuumed and purged with N.sub.2 three times, and it
was heated to achieve an internal temperature of about
.about.235.degree. C. and pressure of about 41 atm; Then,
.about.3,100 g of hexane (Hexanes ACS; Catalog #: 35900ACS;
>98.5% Hexane isomers and methyl cyclopentane; Pharmco by
Greenfield Global, Inc.; Brookfield, Conn.) was added to the
autoclave. At those conditions, the hexane is at critical
conditions (critical temperature of normal hexane is 235.degree. C.
and pressure is 31 atm). After the autoclave reached the
temperature and pressure mentioned above, mechanical stirring
started at about 680 rpm and lasted for about 10 minutes. At those
conditions, the polyethylene of the first plastic and hexane formed
a two-phase system, a light phase (extract) with low concentration
of polyethylene in hexane and a heavy phase (raffinate) with high
concentration of polyethylene in hexane. Then, the stirring stopped
for about 10 min, the raffinate phase settled, the extract phase
floated at the top, and a flow of hexane of .about.3,100 grams of
fresh hexane was added to the reactor in such a manner to remove
the hexane from stage 1 of the liquid-liquid extraction. This step
was repeated 4 more times, and the material remaining after the 5
extraction steps in the autoclave (i.e., the raffinate phase) was
collected, devolatilized, and solidified to produce the purer
plastic. The overall ratio of hexane to first plastic mass was 55:1
and the total extraction time was around 100 minutes but only
.about.65 minutes were in an optimal mass transfer state of
stirring. In a commercial liquid-liquid countercurrent continuous
extractor, the relevant time scale would be .about.65 minutes.
Hence, the true extraction time was closer to about 65 minutes. The
purer plastic after devolatilization had a mass of .about.230 g for
a total extracted mass of .about.50 grams (18 wt %), which included
both first plastic contaminants and dissolved first plastic. The
above process was used to simulate a continuous and large-scale
liquid-liquid extraction, as it is well known in the art. The first
plastic and purer plastic were analyzed for the classes of chemical
contaminants typically present in recycled materials by GALAB
Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany)
using the methods disclosed in section IX Methods, as shown in
Table 7. Prior to analyzing the purer plastic, it was ground to a
mass average particle size of .about.1 mm. The first plastic
contained a moderate level of chemical contamination. For example,
the pesticide piperonylbutoxide was .about.12.times. the LOQ; the
alkylphenol iso-nonylphenol was .about.170.times. the LOQ,
bisphenol-A was .about.320.times. the LOQ; OCDD was
.about.17.times. the LOQ; PCB 118 was .about.30.times. the LOQ, and
PAHs were 50 to 100.times. the LOQ. The purer plastic contained a
significantly reduced level of chemical contamination as shown in
Table 10. The vast majority of chemical contaminants were
extensively removed. Pesticides, alkylphenol ethoxylates,
bisphenol-A and most dioxins/furans, and PCBs, were removed below
the LOQ. Even when not reduced below LOQ, most were significantly
reduced. At least one contaminant from the classes of pesticides,
alkylphenol ethoxylates, bisphenol-A, dioxins, PCBs, phthalates,
and PAHs, was removed at an efficiency >99%. For the contaminant
4-tert-pentylphenol, the removal efficiency was 72%. For the
contaminant bis-phenol A, the removal efficiency was 99.7%. For the
contaminant OCDD, the removal efficiency was 88%. For the PCB 118,
the removal efficiency was 88%. For the di-2-ethylhexyl phthalate,
the removal efficiency was not calculated due to external
contamination during sampling. However, the similar phthalate
dibutyl phthalate was removed >89%. The minimum removal capacity
for the contaminants, 4-tert-pentylphenol, bis-phenol A, OCDD, PCB
118, and di-2-ethylhexyl phthalate was 72%. Only organotins were
not significantly removed by the extraction due to low diffusivity
in the molten PE and availability on in the initial bulk first
plastic. If a high-custody film source had been used, then complete
removal of most if not all chemical contaminants would have likely
been achieved.
[0139] The removal of the five selected species were as follows:
For 4-tert-pentylphenol, the removal efficiency was 72%. For
bisphenol A, the removal efficiency was 99.7%. For OCDD, the
removal efficiency was 88%. For the PCB 118, the removal efficiency
was 88%. For the di-2-ethylhexyl phthalate, the removal efficiency
was 0%. The average removal efficiency for the five targeted
species was >about 70%.
TABLE-US-00015 TABLE 7 Liquid-Liquid Extraction of Post-Commercial
(PC) Film #2 using Supercritical Hexane PC #2 After L/L scHexane
Removal PC #2 Extraction Efficiency Parameter xLOQ xLOQ %
Pesticides Piperonyl butoxide 12 <1 >92% Alkylphenol
ethoxylates 4-t-Octylphenolhexaethoxylate <1 <1 n.a.
iso-Nonylphenoltriethoxylate 6.2 <1 >84% Alkylphenols
iso-Nonylphenol 168.0 10.8 94% 4-tert-Pentylphenol 3.6 <1
>72% Bisphenols Bisphenol A 320.0 <1 >99.7%.sup. Dioxins
and dioxinlike and PCB 1,2,3,6,7,8-HxCDD <1 <1 n.a.
1,2,3,4,6,7,8-HpCDD 10.9 <1 >91% OCDD 17.2 2.0 88% OCDF <1
<1 n.a. PCB 105 19.8 2.7 87% PCB 118 28.5 3.6 88% Organotin
compounds Monobutyltin 2.3 3.3 0% Dibutyltin 20.7 21.0 0%
Phthalates Dibutyl phthalate 9.2 <1 >89% Di-2-ethylhexyl
phthalate 15.4 1900.0 0% Polycyclic aromatic hydrocarbons (PAH)
Fluoranthene 46.0 <1 >98% Phenanthrene 120.0 5.4 96%
Example 2--Bulk Purification Using Batch Liquid-Liquid Extraction
of Post-Household Film #1 Using DME
[0140] Post-Household Film #1 was shredded, melt densified to
pellets using a single screw extruder, and then ground to a
particle size of -1 mm. The resulting ground material was the first
plastic. Thus, the first plastic had a surface area to volume ratio
of 6 mm-1. The first plastic was subjected to a bulk purification
step of liquid-liquid extraction as follows (at Phasex Corporation,
125 Flagship Drive, North Andover, Mass.). A 7 L autoclave was
loaded with about 152 g of pellets of the first plastic. Then, the
autoclave was vacuumed and purged with N.sub.2 three times, and it
was heated to achieve an internal temperature of about 170.degree.
C. and pressure of about 129 atm. 3,500 grams of DME was added.
After the autoclave reached the temperature and pressure mentioned
above, mechanical stirring started at about 680 rpm and lasted for
about 10 minutes. At those conditions, the polyethylene of the
first plastic and DME formed a two-phase system, a light phase
(extract) with low concentration of polyethylene in DME and a heavy
phase (raffinate) with high concentration of polyethylene in DME.
Then, the stirring stopped for about 10 min, the raffinate phase
settled, the extract phase floated at the top, and a flow of DME of
about 3,300 grams of DME was added to remove the contaminated DME
from stage 1. The stirring was initiated and allowed to continue
for 10 minutes. These stages were repeated for a total of 5 times.
Thus, the total solvent used was about 17 kg for a solvent to first
plastic ratio of about 111:1 and the total reaction time was
.about.65 minutes similar to the liquid-liquid hexanes example. The
residual from the contaminated solvent was .about.3.5 grams and the
purer plastic had a mass of .about.148.5 g. The material remaining
after the 5 extraction steps in the autoclave (i.e., the raffinate
phase) was collected, devolatilized, and solidified to produce the
purer plastic. The first plastic and purer plastic were analyzed
for the classes of chemical contaminants typically present in
recycled materials by GALAB Laboratories GmbH (Am Schleusengraben
7, 21029 Hamburg, Germany) using the methods disclosed in section
IX Methods, as shown in Table 8. Prior to analyzing the purer
plastic, it was ground to a mass average particle size of .about.1
mm.
[0141] At least one contaminant from the classes of pesticides,
alkylphenol ethoxylates, bisphenol-A, dioxins, PCBs, phthalates,
and PAHs, was removed at an efficiency 97.8%. For the contaminant
4-tert-pentylphenol, the removal efficiency was 55%. For the
contaminant bisphenol A, the removal efficiency was 97.6%. For the
contaminants OCDD, the removal efficiency was 87.7%. For the PCB
118, the removal efficiency was 97.6%. For the di-2-ethylhexyl
phthalate, the removal efficiency was about 0%. The average removal
capacity for the contaminants, 4-tert-pentylphenol, bis-phenol A,
OCDD, PCB 118, and di-2-ethylhexyl phthalate was about 67%.
TABLE-US-00016 TABLE 8 Liquid-Liquid Extraction of Post-Commercial
(PC) Film #3 using DME Purer Plastic Post- First Plastic Commercial
#3 Post- After Removal Commercial #3 L/L DME Efficiency Parameter
xLOQ xLOQ % Pesticides Piperonyl butoxide 28.0 <1 >96.4%
Alkylphenol ethoxylates 4-t-Octylphenolhexaethoxylate 6.2 <1
>83.9% iso-Nonylphenoltriethoxylate 5.8 <1 >82.8%
Alkylphenols iso-Nonylphenol 260.0 10.6 95.9% 4-tert-Pentylphenol
116.0 58.0 50.0% Bisphenols Bisphenol A 760.0 18.6 97.6% Dioxins
and dioxinlike and PCB 1,2,3,6,7,8-HxCDD 6.1 <1 >83.6%
1,2,3,4,6,7,8-HpCDD 84.5 4.6 94.6% OCDD 205.0 25.2 87.7% OCDF 6.5
3.7 43.2% PCB 105 157.2 3.4 97.8% PCB 118 227.0 5.4 97.6%
Phthalates Dibutyl phthalate 22.0 3.0 86.4% Di-2-ethylhexyl
phthalate 17.8 28.0 0.0% Polycyclic aromatic hydrocarbons (PAH)
Fluoranthene 63.0 1.9 97.0% Phenanthrene 62.0 4.2 93.2%
Example 3 Purification of Heavily Contaminated Reclaimed Film Using
Surface Washing Followed by Liquid/Liquid Extraction Using
Hexane
[0142] A method to produce a purer plastic from reclaimed film;
wherein the reclaimed film has a mass average surface area to
volume ratio greater than about 40 mm-1 is fed into a surface
washing step, comprising an aqueous surface washing step while
applying vigorous mechanical agitation for a time of .about.30 min
wherein the loosely bound surface contamination is removed at
greater than about 80%; wherein said surface washed plastic is fed
to a melt extruder which delivers the molten and high pressure
first plastic to an extraction method involving a continuous
counter-current liquid-liquid extractor operating a temperature of
about 235 C and a pressure of about 41 atm; wherein said extraction
uses a liquid-liquid extraction solvent; wherein said liquid-liquid
extraction solvent is hexanes; wherein the mass ratio of hexanes to
surface washed plastic is greater than about 30:1; wherein said
extraction method involves an extraction time; wherein said
extraction time is less than about 1 hour; wherein the average
removal capacity for the contaminants, 4-tert-pentylphenol,
bis-phenol A, OCDD, PCB 118, and di-2-ethylhexyl phthalate is
greater than about 55%.
IX. Methods
[0143] 1. The following methods were used to measure the various
chemical contaminants analytically. Pesticides: the EN
15662:2018-07 Modular QuEChERS-method was applied. For alkylphenol
ethoxylates, alkyl phenols, and bisphenols the following technique
was applied: the samples were cut, homogenized, and weighted; then,
an internal standard (deuterated bisphenol A) was added, the
samples were then extracted with hexane at room temperature, MSTFA
(N-Methyl-N-(trimethylsilyl)trifluoroacetamide) was added for
derivatization, and the contaminant level was determined by GC-MSD.
For dioxins, furans, and PCBs: the ISO/IEC 17025:2005 method was
applied. The samples were cut into small pieces, 13C/12C-labeled
PCDD/F internal standards to an aliquot of the sample material were
added, extraction and destroying of the matrix by hexane and
H.sub.2SO.sub.4 for 1 h was employed, re-extraction with hexane (3
times for 30 min) was employed, multi-step chromatographic clean-up
was applied, 13C/12C-labeled PCDD/F-recovery standards to the
measurement solutions were added, and quantification via the
internal labelled PCDD/F-standards (isotope dilution technique and
internal standard technique) was applied. For organotins: the
method followed the EDANA-Protocol (WSP 351). More specifically,
the samples were extracted with a sodium diethyldithiocarbamate
solution in ethanol, alkylated with sodium tetraethyl borate, and
transferred by extraction with hexane into the organic phase. Then,
the tetrasubstituted organotin compounds were separated by using
capillary gas chromatography, proven with an AED or MS as detector.
GC-ICP-MS was used as detector system for the organometallic
analysis. For phthalates: the samples were cut, homogenized, and
weighted. An internal standard and extraction by hexane at room
temperature were then employed. The extracted phthalates were then
identified and quantified by GC-MSD. For PAHs: the samples were
cut, homogenized, and weighted. Then, an internal standard of
deuterated PAHs was added, and the samples were extracted with
hexane. The extracted PAHs were purer with silica gel,
concentrated, and then characterized by GC-MSD. [0144] 2. The
amount of loosely bound surface contamination is determined by the
following method: Approximately 20 grams of plastic are added to a
1000 mL round bottom flask. Approximately 600 mL of distilled water
are added to the 1000 mL round bottom flask. The round bottom flask
is capped and then vigorously shaken for about 60 seconds. The
water is decanted from the flask. Approximately 600 mL of
additional distilled water are added to the 1000 mL flask and then
immediately decanted to leave the original first plastic with a
small amount of water. The first plastic is removed from the round
bottom and allowed to dry at 60 C overnight in a convection oven.
The % mass change of the plastic is the amount of loosely bound
surface contamination. [0145] 3. Color measurements were obtained
with a Minolta Spectrophotometer, Model CM580d. The `white` portion
of a Leneta card was used as a common background and as the
reference point for delta E calculations. Delta E is the color
difference (dE or .DELTA.E), between a sample color and a reference
color. Color measurements were taken using a D65 illuminant and a
10.degree. observer. A minimum of three measurements were taken for
each of the compressed thermoplastic starch composition samples. L,
a, b values are averaged and reported along with .DELTA.E values.
.DELTA.E values for the pure white Leneta card are zero and
positive deviations from zero indicate increased discoloration.
Those skilled in the art will know how to calculate the delta E
value.
[0146] The foregoing description is given for clearness of
understanding only, and no unnecessary limitations should be
understood therefrom, as modifications within the scope of the
invention may be apparent to those having ordinary skill in the
art.
[0147] The dimensions and values disclosed herein are not to be
understood as being strictly limited to the exact numerical values
recited. Instead, unless otherwise specified, each such dimension
is intended to mean both the recited value and a functionally
equivalent range surrounding that value. For example, a dimension
disclosed as "40 mm" is intended to mean "about 40 mm."
[0148] Every document cited herein, comprising any cross referenced
or related patent or application, is hereby incorporated herein by
reference in its entirety unless expressly excluded or otherwise
limited. 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, suggests 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 incorporated by reference, the meaning
or definition assigned to that term in this document shall
govern.
[0149] 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 modifications 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 modifications that are within the scope of
this invention.
* * * * *
References