U.S. patent application number 16/699386 was filed with the patent office on 2020-05-28 for processes for recycling polystyrene waste.
This patent application is currently assigned to POLYSTYVERT INC.. The applicant listed for this patent is POLYSTYVERT INC.. Invention is credited to Roland COTE.
Application Number | 20200165407 16/699386 |
Document ID | / |
Family ID | 55629222 |
Filed Date | 2020-05-28 |
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United States Patent
Application |
20200165407 |
Kind Code |
A1 |
COTE; Roland |
May 28, 2020 |
PROCESSES FOR RECYCLING POLYSTYRENE WASTE
Abstract
There are provided recycled polystyrene polymers having a melt
flow index of less than about 25 g/10 min. There are provided
processes for recycling polystyrene waste. The processes can
comprise dissolving said polystyrene waste in p-cymene under
conditions to obtain a polystyrene/p-cymene mixture, adding the
polystyrene/p-cymene mixture to a hydrocarbon polystyrene
non-solvent under conditions to obtain precipitated polystyrene and
washing the precipitated polystyrene with additional portions of
hydrocarbon polystyrene non-solvent under conditions to obtain
twice-washed polystyrene. The twice-washed polystyrene can
optionally be dried and formed into polystyrene pellets. There is
also provided recycled polystyrene obtained from such processes for
recycling polystyrene waste.
Inventors: |
COTE; Roland;
(St-Antoine-sur-Richelieu, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
POLYSTYVERT INC. |
Anjou |
|
CA |
|
|
Assignee: |
POLYSTYVERT INC.
Anjou
CA
|
Family ID: |
55629222 |
Appl. No.: |
16/699386 |
Filed: |
November 29, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15515817 |
Mar 30, 2017 |
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PCT/CA2015/051006 |
Oct 5, 2015 |
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16699386 |
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62059611 |
Oct 3, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29B 17/02 20130101;
Y02W 30/701 20150501; C08J 11/08 20130101; C08L 25/00 20130101;
Y02W 30/62 20150501; C08J 11/00 20130101; C08L 25/06 20130101; C08F
112/08 20130101; C08J 2325/06 20130101 |
International
Class: |
C08J 11/08 20060101
C08J011/08; C08L 25/06 20060101 C08L025/06; C08F 112/08 20060101
C08F112/08; B29B 17/02 20060101 B29B017/02 |
Claims
1. A process for recycling polystyrene waste, comprising:
dissolving said polystyrene waste in p-cymene to obtain a
polystyrene/p-cymene mixture; filtering said polystyrene/p-cymene
mixture to remove insoluble material; adding said
polystyrene/p-cymene mixture to a first portion of a hydrocarbon
polystyrene non-solvent under conditions to obtain precipitated
polystyrene and a first portion of hydrocarbon waste solution,
wherein said conditions to obtain said precipitated polystyrene and
said first portion of hydrocarbon waste solution comprise adding
said polystyrene/p-cymene mixture to said first portion of
hydrocarbon polystyrene non-solvent at the boiling point of said
hydrocarbon polystyrene non-solvent such that said first portion of
hydrocarbon polystyrene non-solvent keeps said polystyrene waste in
a malleable paste form and agitating to diffuse said p-cymene from
said polystyrene/p-cymene mixture into said hydrocarbon polystyrene
non-solvent; separating said precipitated polystyrene from said
first portion of hydrocarbon waste solution; optionally repeating
said dissolving, adding and separating; washing said precipitated
polystyrene with a second portion of hydrocarbon polystyrene
non-solvent under conditions to obtain washed polystyrene and a
second portion of hydrocarbon waste solution, wherein said
conditions to obtain said washed polystyrene and said second
portion of hydrocarbon waste solution comprise adding said second
portion of hydrocarbon polystyrene non-solvent to said precipitated
polystyrene at the boiling point of said hydrocarbon polystyrene
non-solvent such that said second portion of hydrocarbon
polystyrene non-solvent keeps said precipitated polystyrene in a
malleable paste form and agitating to diffuse said p-cymene from
said precipitated polystyrene into said hydrocarbon polystyrene
non-solvent; separating said washed polystyrene from said second
portion of hydrocarbon waste solution; washing said washed
polystyrene with a third portion of hydrocarbon polystyrene
non-solvent under conditions to obtain twice-washed polystyrene and
a third portion of hydrocarbon waste solution, wherein said
conditions to obtain said twice-washed polystyrene and said third
portion of hydrocarbon waste solution comprise adding said third
portion of hydrocarbon polystyrene non-solvent to said washed
polystyrene at the boiling point of said hydrocarbon polystyrene
non-solvent such that said third portion of hydrocarbon polystyrene
non-solvent keeps said washed polystyrene in a malleable paste form
and agitating to diffuse said p-cymene from said washed polystyrene
into said hydrocarbon polystyrene non-solvent; separating said
twice-washed polystyrene from said third portion of hydrocarbon
waste solution; and optionally drying said twice-washed polystyrene
to obtain dried polystyrene, wherein said first portion of
hydrocarbon polystyrene non-solvent, said second portion of
hydrocarbon polystyrene non-solvent and said third portion of
hydrocarbon polystyrene non-solvent comprise a hydrocarbon
polystyrene non-solvent having a boiling point at 1 atm of pressure
of from 98.degree. C. to 110.degree. C.; wherein said boiling point
of said hydrocarbon polystyrene non-solvent is about or above the
glass transition temperature of said twice-washed polystyrene; and
wherein said polystyrene waste is post-industrial waste,
post-consumer waste or a combination thereof.
2. The process of claim 1, wherein said polystyrene/p-cymene
mixture comprises polystyrene in an amount of from 10 wt % to 30 wt
%, based on the total weight of said polystyrene/p-cymene
mixture.
3. The process of claim 1, wherein said polystyrene/p-cymene
mixture comprises insoluble material and said process further
comprises filtering said polystyrene/p-cymene mixture to remove
said insoluble material prior to adding said polystyrene/p-cymene
mixture to said first portion of hydrocarbon polystyrene
non-solvent.
4. The process of claim 1, wherein greater than 90 wt % of said
p-cymene in said polystyrene/p-cymene mixture diffuses into said
hydrocarbon polystyrene non-solvent, based on the total weight of
said polystyrene/p-cymene mixture.
5. The process of claim 1, wherein the ratio by volume of said
first portion of hydrocarbon polystyrene non-solvent to said
polystyrene/p-cymene mixture is from 2:1 to 4:1.
6. The process of claim 1, wherein said washed polystyrene
comprises less than 0.3 wt % p-cymene.
7. The process of claim 1, wherein said twice-washed polystyrene
comprises less than 0.1 wt % p-cymene.
8. The process of claim 1, wherein said first portion of
hydrocarbon polystyrene non-solvent, said second portion of
hydrocarbon polystyrene non-solvent and said third portion of
hydrocarbon polystyrene non-solvent comprise a hydrocarbon
polystyrene non-solvent having a boiling point at 1 atm of pressure
of from 105.degree. C. to 110.degree. C.
9. The process of claim 1, wherein said first portion of
hydrocarbon polystyrene non-solvent, said second portion of
hydrocarbon polystyrene non-solvent and said third portion of
hydrocarbon polystyrene non-solvent comprise a C.sub.6-C.sub.8
alkane or a petroleum distillate.
10. The process of claim 1, wherein said first portion of
hydrocarbon polystyrene non-solvent, said second portion of
hydrocarbon polystyrene non-solvent and said third portion of
hydrocarbon polystyrene non-solvent comprise n-heptane.
11. The process of claim 1, wherein said twice-washed polystyrene
is dried to remove remaining hydrocarbon polystyrene
non-solvent.
12. The process of claim 11, wherein said twice-washed polystyrene
is dried at a temperature of from 115.degree. C. to 125.degree.
C.
13. The process of claim 1, wherein said first portion of
hydrocarbon polystyrene non-solvent, said second portion of
hydrocarbon polystyrene non-solvent and said third portion of
hydrocarbon polystyrene non-solvent consist essentially of said
hydrocarbon polystyrene non-solvent having a boiling point at 1 atm
of pressure of from 98.degree. C. to 110.degree. C.
14. The process of claim 1, wherein said first portion of
hydrocarbon polystyrene non-solvent, said second portion of
hydrocarbon polystyrene non-solvent and said third portion of
hydrocarbon polystyrene non-solvent consist essentially of
n-heptane.
15. The process of claim 1, wherein said process further comprises
processing said dried polystyrene under conditions to obtain
polystyrene pellets, wherein said conditions to obtain said
polystyrene pellets comprise extruding said dried polystyrene at a
temperature of from 140.degree. C. to 160.degree. C.
16. The process of claim 1, wherein said polystyrene waste
comprises expanded polystyrene.
17. The process of claim 1, wherein said polystyrene waste
comprises white, expanded polystyrene.
18. The process of claim 1, wherein recycled polystyrene prepared
according to said process comprises from 0.05 wt % to 0.3 wt %
p-cymene.
Description
[0001] The present application is a continuation application of the
U.S. application Ser. No. 15/515,817 filed on Mar. 30, 2017, which
is a 35 USC 371 national stage entry of PCT/CA2015/051006 filed on
Oct. 5, 2015, and that claims priority to U.S. 62/059,611 filed on
Oct. 3, 2014. These documents are hereby incorporated by reference
in their entirety.
[0002] The present disclosure relates to a process for recycling
polystyrene waste. For example, it relates to a process for
recycling polystyrene waste comprising dissolving the polystyrene
waste in a solvent such as p-cymene then precipitating and washing
the polystyrene with a non-solvent.
[0003] Polystyrene waste, for example, the packaging from
electronic products or furniture, food trays, commercial products
and insulation can, for example, have environmental
consequences.
[0004] For example, whether post-consumer or post-industrial, the
majority of polystyrene waste is buried in landfills. For example,
every year in Quebec more than 40,000 tons of polystyrene waste is
buried. Further, more than 60,000 tons of new polystyrene is bought
and consumed every year in Quebec.
[0005] Known processes for recycling polystyrene do not produce
recycled polystyrene having the same properties as new polystyrene.
For example, known methods of polystyrene do not prepare recycled
polystyrene having a Melt Flow Index (MFI) which meets technical
specifications for using the recycled polystyrene for the same uses
as new polystyrene is used for. To compensate this loss of
mechanical properties, the recycled polystyrene is blended with new
polystyrene in a proportion that rarely can exceed 20%, even for
the less stringent applications.
[0006] Most industrial polystyrene objects are not composed only of
polystyrene; for example, they may contain chemicals added to a
polymer to modify some physical, biological and/or chemical
property. Examples of additives are: coloring agents, fillers,
flame retardants, lubricants and plasticizers.
[0007] It would thus be desirable to be provided with a recycled
polystyrene and a process for recycling polystyrene waste that
would at least partially solve one of the problems mentioned or
that would be an alternative to the known processes for recycling
polystyrene waste.
[0008] Therefore according to an aspect of the present disclosure,
there is provided a recycled polystyrene having a melt flow index
of less than about 25 g/10 min measured according to ASTM
D1238-13.
[0009] According to another aspect of the present disclosure, there
is provided a recycled polystyrene having a melt flow index of less
than about 25 g/10 min measured according to ASTM D1238-13 standard
and an additive content of less than about 1 wt %.
[0010] According to another aspect of the present disclosure, there
is provided a recycled polystyrene having a melt flow index of less
than about 25 g/10 min measured according to ASTM D1238-13 standard
and a ash content of less than about 1 wt %, measured according to
ASTM D5630-13 standard.
[0011] According to another aspect of the present disclosure, there
is provided a recycled polystyrene having a melt flow index of less
than about 25 g/10 min measured according to ASTM D1238-13 standard
and an ash content of less than about 0.5 wt %, measured according
to ASTM D5630-13 standard.
[0012] According to another aspect of the present disclosure, there
is provided a recycled polystyrene having a melt flow index of less
than about 25 g/10 min.
[0013] According to another aspect of the present disclosure, there
is provided a recycled polystyrene having a melt flow index of less
than about 25 g/10 min, measured according to ASTM D1238-13
standard.
[0014] According to another aspect of the present disclosure, there
is provided a process for recycling polystyrene waste, comprising:
[0015] dissolving the polystyrene waste in p-cymene under
conditions to obtain a polystyrene/p-cymene mixture; [0016] adding
the polystyrene/p-cymene mixture to a first portion of hydrocarbon
polystyrene non-solvent under conditions to obtain precipitated
polystyrene and a first portion of hydrocarbon waste solution;
[0017] separating the precipitated polystyrene from the first
portion of hydrocarbon waste solution; [0018] optionally repeating
the dissolving, adding and separating; [0019] washing the
precipitated polystyrene with a second portion of hydrocarbon
polystyrene non-solvent under conditions to obtain washed
polystyrene and a second portion of hydrocarbon waste solution;
[0020] separating the washed polystyrene from the second portion of
hydrocarbon waste solution; [0021] washing the washed polystyrene
with a third portion of hydrocarbon polystyrene non-solvent under
conditions to obtain twice-washed polystyrene and a third portion
of hydrocarbon waste solution; [0022] separating the twice-washed
polystyrene from the third portion of hydrocarbon waste solution;
and [0023] optionally drying the twice-washed polystyrene under
conditions to obtain dried polystyrene.
[0024] Therefore according to another aspect of the present
disclosure, there is provided a process for recycling polystyrene
waste, comprising: [0025] dissolving the polystyrene waste in
p-cymene under conditions to obtain a polystyrene/p-cymene mixture;
[0026] adding the polystyrene/p-cymene mixture to a first portion
of hydrocarbon polystyrene non-solvent under conditions to obtain
precipitated polystyrene and a first portion of hydrocarbon waste
solution; [0027] separating the precipitated polystyrene from the
first portion of hydrocarbon waste solution; [0028] optionally
repeating the dissolving, adding and separating; [0029] washing the
precipitated polystyrene with a second portion of hydrocarbon
polystyrene non-solvent under conditions to obtain washed
polystyrene and a second portion of hydrocarbon waste solution;
[0030] separating the washed polystyrene from the second portion of
hydrocarbon waste solution; [0031] washing the washed polystyrene
with a third portion of hydrocarbon polystyrene non-solvent under
conditions to obtain twice-washed polystyrene and a third portion
of hydrocarbon waste solution; [0032] separating the twice-washed
polystyrene from the third portion of hydrocarbon waste solution;
[0033] removing surplus hydrocarbon waste solution by wringing
and/or compressing the twice-washed polystyrene; and [0034] drying
the twice-washed polystyrene under conditions to obtain dried
polystyrene.
[0035] The present disclosure also includes recycled polystyrene
prepared according to a process for recycling polystyrene waste of
the present disclosure.
[0036] Polystyrene waste such as expanded polystyrene waste is
typically bulky but light whereas the polystyrene/p-cymene mixture
typically has a higher density which may therefore cost less to
transport. Accordingly, the processes of the present disclosure
may, for example, save on transportation costs if, for example, the
polystyrene/p-cymene mixture is obtained at a first location and
the process further comprises transporting the polystyrene/p-cymene
mixture to a second location wherein subsequent steps in the
process are carried out.
[0037] The process for recycling polystyrene waste of the present
disclosure may, for example allow removal of most additives (for
example, chemicals added to a polymer to modify some physical,
biological and/or chemical property) and can produce recycled
polystyrene having properties very close to that of new
polystyrene. The recycled polystyrene prepared from the processes
of the present disclosure may, for example, be suitable for use for
the same uses as new polystyrene such as for the preparation of new
polystyrene articles. For example, the recycled polystyrene
prepared from the processes of the present disclosure may, for
example, have an MFI within a useful range for such uses.
[0038] It was found that the recycled polystyrenes of the present
disclosure and the processes for obtaining same were quite useful.
In fact, it was found that such recycled polymers and processes
allowed for providing recycled polystyrene having a very low
content of additives (fillers and/or lubricants). That also leads
to recycled polystyrene having a very low content in ash. For
example, when applying these processes to white expanded or
extruded polystyrene, the final product is very clear and
transparent to light transmission. Such a feature of the polymers
and processes of the present disclosure are very interesting since
it allows for significantly increasing the life cycle of recycled
polystyrene. In fact, use of recycled polystyrene is quite often
limited in view of the various additives contained therein and they
therefore do not meet the requirements for certain uses or
applications that can be made with polystyrene. Some manufacturer
will also be reluctant to use recycled polystyrene since it can
have a too high content of additives and it may affect or diminish
the properties of the polystyrene or products made with such
recycled polystyrene. This is clearly not the case with the
polymers and processes mentioned in the present disclosure. On the
contrary, such very low amounts of additives and/or fillers found
in the polymers of the present disclosure allow for using these
recycled polystyrenes in many different applications and also to
recycle them many many times since merely never reaching high
quantities of additives and/or fillers since user of such products
is not mandatory to recycle them and to obtain low MFI values.
[0039] Thus the polymers and processes of the present disclosure
allow for increasing the life cycle of recycled polystyrene (it is
possible to recycle it many many times while maintaining the
required specifications and properties) and also they have a very
low MFI, while avoiding the use of large quantities of additives
and/or fillers.
[0040] In the following drawings, which represent by way of example
only, various embodiments of the disclosure:
[0041] FIG. 1 is a schematic diagram of a process according to an
embodiment of the present disclosure.
[0042] Unless otherwise indicated, the definitions and embodiments
described in this and other sections are intended to be applicable
to all embodiments and aspects of the present disclosure herein
described for which they are suitable as would be understood by a
person skilled in the art.
[0043] As used in the present disclosure, the singular forms "a",
"an" and "the" include plural references unless the content clearly
dictates otherwise. For example, an embodiment including "a
hydrocarbon polystyrene non-solvent" should be understood to
present certain aspects with one hydrocarbon polystyrene
non-solvent, or two or more additional hydrocarbon polystyrene
non-solvents.
[0044] In embodiments comprising an "additional" or "second"
component, such as an additional or second hydrocarbon polystyrene
non-solvent, the second component as used herein is different from
the other components or first component. A "third" component is
different from the other, first, and second components, and further
enumerated or "additional" components are similarly different.
[0045] The term "additive" as used herein refers to chemicals added
to a polymer to modify at least one physical, biological and/or
chemical property. Non-limitative examples of additives are:
coloring agents, fillers, flame retardants, lubricants and
plasticizers.
[0046] In understanding the scope of the present disclosure, the
term "comprising" and its derivatives, as used herein, are intended
to be open ended terms that specify the presence of the stated
features, elements, components, groups, integers, and/or steps, but
do not exclude the presence of other unstated features, elements,
components, groups, integers and/or steps. The foregoing also
applies to words having similar meanings such as the terms,
"including", "having" and their derivatives. The term "consisting"
and its derivatives, as used herein, are intended to be closed
terms that specify the presence of the stated features, elements,
components, groups, integers, and/or steps, but exclude the
presence of other unstated features, elements, components, groups,
integers and/or steps. The term "consisting essentially of", as
used herein, is intended to specify the presence of the stated
features, elements, components, groups, integers, and/or steps as
well as those that do not materially affect the basic and novel
characteristic(s) of features, elements, components, groups,
integers, and/or steps.
[0047] Terms of degree such as "about" and "approximately" as used
herein mean a reasonable amount of deviation of the modified term
such that the end result is not significantly changed. These terms
of degree should be construed as including a deviation of at least
.+-.5% or at least .+-.10% of the modified term if this deviation
would not negate the meaning of the word it modifies.
[0048] The term "hydrocarbon polystyrene non-solvent" as used
herein refers, for example, to a hydrocarbon-based compound or a
mixture thereof in which polystyrene is substantially insoluble.
The selection of a suitable hydrocarbon polystyrene non-solvent for
the processes of the present disclosure can be made by a person
skilled in the art. For example, it will be appreciated by a person
skilled in the art that most non-polar additives typically found in
polystyrene waste (e.g. hexabromocyclododecane and silicone oils)
and p-cymene should be substantially soluble in the hydrocarbon
polystyrene non-solvent under the conditions used in the processes
of the present disclosure to obtain precipitated polystyrene as
well as steps which comprise washing with the hydrocarbon
polystyrene non-solvent. It will also be appreciated by a person
skilled in the art that it may, for example, be useful to select a
hydrocarbon polystyrene non-solvent having a boiling point that is
around or slightly above the glass transition temperature (T.sub.g)
of the polystyrene waste being recycled.
[0049] The below presented examples are non-limitative and are used
to better exemplify the processes of the present disclosure.
[0050] An exemplary process flow diagram for a process of the
present disclosure is shown in FIG. 1. The exemplified process 10
is a process for recycling polystyrene waste. Referring to FIG. 1,
in the exemplified process 10, polystyrene waste can be dissolved
12 in p-cymene under conditions to obtain a polystyrene/p-cymene
mixture. If, for example, the polystyrene/p-cymene mixture
comprises insoluble material, the polystyrene/p-cymene mixture can
then optionally be filtered 14 under conditions to remove the
insoluble material. The polystyrene/p-cymene mixture can then be
added 16 to a first portion of hydrocarbon polystyrene non-solvent
under conditions to obtain precipitated polystyrene and a first
portion of hydrocarbon waste solution. The precipitated polystyrene
can then be separated from the first portion of hydrocarbon waste
solution. The dissolving, adding and separating can optionally be
repeated. Then, the precipitated polystyrene can be washed 18 with
a second portion of hydrocarbon polystyrene non-solvent under
conditions to obtain washed polystyrene and a second portion of
hydrocarbon waste solution. The washed polystyrene can then be
separated from the second portion of hydrocarbon waste solution.
The washed polystyrene can then be washed 20 with a third portion
of hydrocarbon polystyrene non-solvent under conditions to obtain
twice-washed polystyrene and a third portion of hydrocarbon waste
solution. The twice-washed polystyrene can then be separated from
the third portion of hydrocarbon waste solution. Surplus
hydrocarbon waste solution can then optionally be removed by
wringing and/or compressing the twice-washed polystyrene. The
twice-washed polystyrene can then optionally be dried 22 under
conditions to obtain dried polystyrene. The dried polystyrene can
then optionally be packaged 24, for example the process can further
comprise processing the dried polystyrene under conditions to
obtain polystyrene pellets and the polystyrene pellets can be
packaged 24. The p-cymene and/or the hydrocarbon polystyrene
non-solvent can optionally be recovered 26, for example by a
process comprising distilling the first portion of hydrocarbon
waste solution, the second portion of hydrocarbon waste solution
and/or the third portion of hydrocarbon waste solution under
conditions to obtain p-cymene and/or hydrocarbon polystyrene
non-solvent. The p-cymene can optionally be recycled for use in the
dissolving 12. The hydrocarbon polystyrene non-solvent can
optionally be recycled for use in the adding 16, the first washing
18 and/or the second washing 20.
[0051] For example, the polystyrene/p-cymene mixture can comprise
polystyrene in an amount equal to or less than about 33 wt %, based
on the total weight of the polystyrene/p-cymene mixture.
[0052] For example, the polystyrene/p-cymene mixture can comprise
polystyrene in an amount of from about 10 wt % to about 30 wt %,
based on the total weight of the polystyrene/p-cymene mixture.
[0053] For example, the polystyrene/p-cymene mixture can comprise
polystyrene in an amount of from about 14 wt % to about 28 wt %,
based on the total weight of the polystyrene/p-cymene mixture.
[0054] For example, the polystyrene/p-cymene mixture can comprise
polystyrene in an amount of from about 15 wt % to about 27 wt %,
based on the total weight of the polystyrene/p-cymene mixture.
[0055] For example, the polystyrene/p-cymene mixture can comprise
polystyrene in an amount of from about 16 wt % to about 25 wt %,
based on the total weight of the polystyrene/p-cymene mixture.
[0056] For example, the polystyrene waste can be dissolved in the
p-cymene in a container having a chamber containing the p-cymene
and at least one opening to the chamber for adding the polystyrene
waste to the p-cymene, and the process can further comprise adding
the polystyrene waste to the p-cymene contained in the chamber.
[0057] For example, the container can further comprise a vent.
[0058] For example, the container can further comprise a means to
impel the polystyrene waste into the p-cymene.
[0059] For example, the means to impel the polystyrene waste into
the p-cymene can comprise a metallic grid inside the container.
[0060] For example, the container can further comprise a means to
indicate when capacity of the chamber has been reached.
[0061] For example, the means to indicate when capacity of the
container has been reached can be an indicator light.
[0062] For example, the indicator light can be connected to a float
switch in the chamber.
[0063] For example, the polystyrene/p-cymene mixture can comprise
insoluble material and the process can further comprise filtering
the polystyrene/p-cymene mixture under conditions to remove the
insoluble material prior to adding the polystyrene/p-cymene mixture
to the first portion of hydrocarbon polystyrene non-solvent. For
example, the insoluble material can be chosen from a
polystyrene/butadiene mixture, copolymers of styrene dust, a
sticker, metal, wood, plastic, contaminants and mixtures thereof.
For example, the filtering can comprise a multistage filtration
process from coarse to fine. For example, butadiene will be soluble
in p-cymene unless it has been heavily cross linked.
[0064] For example, the conditions to obtain the precipitated
polystyrene and the first portion of hydrocarbon waste solution can
comprise adding the polystyrene/p-cymene mixture to the first
portion of hydrocarbon polystyrene non-solvent at the boiling point
of the hydrocarbon polystyrene non-solvent and agitating for a time
for diffusion of the p-cymene from the polystyrene/p-cymene mixture
into the hydrocarbon polystyrene non-solvent to proceed to a
sufficient extent.
[0065] For example, the time can be from about 5 minutes to about
10 minutes.
[0066] For example, the agitating can comprise stirring with a
mechanical stirrer.
[0067] For example, greater than about 90 wt % of the p-cymene in
the polystyrene/p-cymene mixture can diffuse into the hydrocarbon
polystyrene non-solvent, based on the total weight of the
polystyrene/p-cymene mixture.
[0068] For example, the ratio by volume of the first portion of
hydrocarbon polystyrene non-solvent to the polystyrene/p-cymene
mixture can be from about 2:1 to about 4:1.
[0069] For example, the ratio by volume of the first portion of
hydrocarbon polystyrene non-solvent to the polystyrene/p-cymene
mixture can be about 3:1.
[0070] For example, the precipitated polystyrene can be separated
from the first portion of hydrocarbon waste solution by a process
comprising decanting the first portion of hydrocarbon waste
solution from the precipitated polystyrene.
[0071] For example, the conditions to obtain the washed polystyrene
and the second portion of hydrocarbon waste solution can comprise
adding the second portion of hydrocarbon polystyrene non-solvent to
the precipitated polystyrene at the boiling point of the
hydrocarbon polystyrene non-solvent and agitating for a time for
diffusion of the p-cymene from the precipitated polystyrene into
the hydrocarbon polystyrene non-solvent to proceed to a sufficient
extent.
[0072] For example, the time can be from about 1 minute to about 15
minutes. For example, the time can be about 10 minutes. For
example, the time can be from about 2 minutes to about 5 minutes.
For example, the agitating can comprise stirring with a mechanical
stirrer.
[0073] For example, the washed polystyrene can comprise less than
about 0.3 wt % p-cymene. For example, the washed polystyrene can
comprise less than about 0.1 wt % p-cymene.
[0074] For example, the ratio by volume of the second portion of
hydrocarbon polystyrene non-solvent to the precipitated polystyrene
can be from about 1:2 to about 2:1. For example, the ratio by
volume of the second portion of hydrocarbon polystyrene non-solvent
to the precipitated polystyrene can be about 1:1.
[0075] For example, the washed polystyrene can be separated from
the second portion of hydrocarbon waste solution by a process
comprising decanting the second portion of hydrocarbon waste
solution from the washed polystyrene.
[0076] For example, the conditions to obtain the twice-washed
polystyrene and the third portion of hydrocarbon waste solution can
comprise adding the third portion of hydrocarbon polystyrene
non-solvent to the washed polystyrene at the boiling point of the
hydrocarbon polystyrene non-solvent and agitating for a time for
diffusion of the p-cymene from the washed polystyrene into the
hydrocarbon polystyrene non-solvent to proceed to a sufficient
extent.
[0077] For example, the time can be from about 1 minute to about 10
minutes. For example, the time can be about 5 minutes. For example,
the agitating can comprise stirring with a mechanical stirrer.
[0078] For example, the twice-washed polystyrene can comprise less
than about 0.1 wt % p-cymene. For example, the twice-washed
polystyrene can comprise less than about 0.05 wt % p-cymene.
[0079] For example, the ratio by volume of the third portion of
hydrocarbon polystyrene non-solvent to the washed polystyrene can
be from about 1:2 to about 2:1. For example, the ratio by volume of
the third portion of hydrocarbon polystyrene non-solvent to the
washed polystyrene can be about 1:1.
[0080] For example, the twice-washed polystyrene can be separated
from the third portion of hydrocarbon waste solution by a process
comprising decanting the third portion of hydrocarbon waste
solution from the twice-washed polystyrene.
[0081] For example, after separating the twice-washed polystyrene
from the third portion of hydrocarbon waste solution and prior to
drying, the process can further comprise removing surplus
hydrocarbon waste solution by wringing and/or compressing the
twice-washed polystyrene.
[0082] For example, at least one of the first portion of
hydrocarbon polystyrene non-solvent, the second portion of
hydrocarbon polystyrene non-solvent and the third portion of
hydrocarbon polystyrene non-solvent can comprise, consist
essentially of or consist of a hydrocarbon polystyrene non-solvent
having a boiling point at 1 atm of pressure of from about
98.degree. C. to about 110.degree. C. or about 105.degree. C. to
about 110.degree. C.
[0083] For example, the first portion of hydrocarbon polystyrene
non-solvent, the second portion of hydrocarbon polystyrene
non-solvent and the third portion of hydrocarbon polystyrene
non-solvent can comprise, consist essentially of or consist of a
C.sub.6-C.sub.8 alkane or a petroleum distillate.
[0084] For example, the first portion of hydrocarbon polystyrene
non-solvent, the second portion of hydrocarbon polystyrene
non-solvent and the third portion of hydrocarbon polystyrene
non-solvent can comprise, consist essentially of or consist of a
C.sub.6-C.sub.8 alkane.
[0085] For example, the first portion of hydrocarbon polystyrene
non-solvent, the second portion of hydrocarbon polystyrene
non-solvent and the third portion of hydrocarbon polystyrene
non-solvent can comprise, consist essentially of or consist of a
petroleum distillate.
[0086] For example, the first portion of hydrocarbon polystyrene
non-solvent, the second portion of hydrocarbon polystyrene
non-solvent and the third portion of hydrocarbon polystyrene
non-solvent can comprise, consist essentially of or consist of
n-heptane.
[0087] For example, the first portion of hydrocarbon polystyrene
non-solvent, the second portion of hydrocarbon polystyrene
non-solvent and the third portion of hydrocarbon polystyrene
non-solvent can all be the same hydrocarbon polystyrene
non-solvent.
[0088] For example, the first portion of hydrocarbon polystyrene
non-solvent, the second portion of hydrocarbon polystyrene
non-solvent and the third portion of hydrocarbon polystyrene
non-solvent can all be different hydrocarbon polystyrene
non-solvents.
[0089] For example, the second portion of hydrocarbon polystyrene
non-solvent and the third portion of hydrocarbon polystyrene
non-solvent can be the same hydrocarbon polystyrene non-solvent and
the first portion of hydrocarbon polystyrene non-solvent can be a
different hydrocarbon polystyrene non-solvent.
[0090] For example, the second portion of hydrocarbon polystyrene
non-solvent and the third portion of hydrocarbon polystyrene
non-solvent can comprise, consist essentially of or consist of
n-heptane and the first portion of hydrocarbon polystyrene
non-solvent can comprise, consist essentially of or consist of
n-hexane.
[0091] For example, the conditions to obtain the dried polystyrene
can comprise drying the twice-washed polystyrene for a temperature
and time for removal of remaining hydrocarbon polystyrene
non-solvent to proceed to a sufficient extent. For example, the
twice-washed polystyrene can be dried at a temperature of from
about 115.degree. C. to about 125.degree. C. For example, the
twice-washed polystyrene can be dried at a temperature of about
120.degree. C.
[0092] For example, the conditions to obtain the dried polystyrene
can comprise drying the twice-washed polystyrene using an infrared
dryer for a time for removal of remaining hydrocarbon polystyrene
non-solvent to proceed to a sufficient extent.
[0093] For example, the polystyrene waste can comprise polar
impurities and the process can further comprise washing the
polystyrene waste with a polar organic solvent under conditions to
remove the polar impurities.
[0094] For example, the polar organic solvent can comprise, consist
essentially of or consist of methanol or ethanol. For example, the
polar organic solvent can comprise, consist essentially of or
consist of methanol. For example, the polar organic solvent can
comprise, consist essentially of or consist of ethanol.
[0095] For example, the process can further comprise distilling the
first portion of hydrocarbon waste solution, the second portion of
hydrocarbon waste solution and/or the third portion of hydrocarbon
waste solution under conditions to obtain p-cymene and/or
hydrocarbon polystyrene non-solvent.
[0096] For example, the process can further comprise recycling the
p-cymene for use in the dissolving step.
[0097] For example, the process can further comprise recycling the
hydrocarbon polystyrene non-solvent for use in the adding step, the
first washing step and/or the second washing step.
[0098] For example, the process can further comprise processing the
dried polystyrene under conditions to obtain polystyrene pellets.
For example, the conditions to obtain the polystyrene pellets can
comprise extruding the dried polystyrene at a temperature of from
about 140.degree. C. to about 160.degree. C.
[0099] For example, the process can further comprise packaging the
polystyrene pellets. Suitable means to package the polystyrene
pellets can be selected by a person skilled in the art.
[0100] For example, the process can further comprise adding an
antioxidant during the dissolving step, the adding step, the first
washing step and/or the second washing step. For example, the
process can further comprise adding an antioxidant during the
dissolving step.
[0101] For example, the antioxidant can comprise, consist
essentially of or consist of
octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate.
[0102] For example, the antioxidant can be added in an amount of
from about 0.1 wt % to about 2 wt %, based on the total weight of
the polystyrene. For example, the antioxidant can be added in an
amount of about 1 wt %, based on the total weight of the
polystyrene.
[0103] For example, the antioxidant can be added in an amount of
from about 0.5 wt % to about 2 wt %, based on the total weight of
the polystyrene. For example, the antioxidant can be added in an
amount of about 1 wt %, based on the total weight of the
polystyrene.
[0104] For example, the process can further comprise adding an
additive for lowering or increasing melt flow index to the
polystyrene/p-cymene mixture.
[0105] For example, the additive for lowering melt flow index can
comprise, consist essentially of or consist of lime, talc, silicon
oxide, silicon hydroxide, aluminum oxide, aluminum hydroxide, or
combinations thereof. For example, the additive for lowering melt
flow index can comprise, consist essentially of or consist of lime.
For example, the additive for lowering melt flow index can
comprise, consist essentially of or consist of talc.
[0106] For example, the additive for increasing melt flow index can
comprise, from about 0.0001 wt % to about 1 wt % of silicon oil.
For example, silicon oil can be added from about 0.01 wt % to 0.1
wt %.
[0107] For example, the additive for lowering melt flow index can
be added in an amount of from about 0.5 wt % to about 25 wt %,
based on the total weight of the polystyrene. For example, the
additive for lowering melt flow index can be added in an amount of
about 0.5 wt % to about 5 wt %, based on the total weight of the
polystyrene. For example, the additive for lowering melt flow index
can be added in an amount of about 1 wt %, based on the total
weight of the polystyrene.
[0108] For example, the polystyrene waste can be post-industrial
waste, post-consumer waste or a combination thereof. For example,
the polystyrene waste can be post-industrial waste. For example,
the polystyrene waste can be post-consumer waste. For example, the
polystyrene waste can be a combination of post-industrial waste and
post-consumer waste.
[0109] For example, the polystyrene waste can comprise, consist
essentially of or consist of expanded polystyrene. For example, the
polystyrene waste can comprise, consist essentially of or consist
of white, expanded polystyrene. For example, the polystyrene waste
can comprise, consist essentially of or consist of compressed
polystyrene.
[0110] For example, the process can further comprise grinding the
polystyrene waste prior to dissolving.
[0111] For example, the polystyrene/p-cymene mixture can be
obtained at a first location and the process can further comprise
transporting the polystyrene/p-cymene mixture to a second location
wherein subsequent steps in the process can be carried out.
[0112] The present disclosure also includes recycled polystyrene
prepared according to a process for recycling polystyrene waste of
the present disclosure.
[0113] For example, the waste polystyrene can comprise other
copolymers. For example, it can comprise butadiene (polybutadiene,
high-impact polystyrene HIPS), be a copolymer of styrene and
acrylonitrile (SAN) or acrylonitrile, butadiene and styrene
(ABS).
[0114] For example, the waste polystyrene can be a
polystyrene-co-butadiene copolymer.
[0115] For example, embodiments relating to the recycled
polystyrene of the present disclosure can be varied as discussed
herein in respect of the processes for recycling polystyrene waste
of the present disclosure.
[0116] For example, the recycled polystyrene can have a melt flow
index of less than about 40 g/10 min. For example, the recycled
polystyrene can have a melt flow index of from about 3 to about 30
g/10 min. For example, the recycled polystyrene can have a melt
flow index of from about 3 to about 25 g/10 min. For example, the
recycled polystyrene can have a melt flow index of less than about
25 g/10 min. For example, the recycled polystyrene can have a melt
flow index of from about 10 to about 20 g/10 min.
[0117] For example, the recycled polystyrene can have a melt flow
index of less than about 40 g/10 min. For example, the recycled
polystyrene can have a melt flow index of from about 5 to about 30
g/10 min. For example, the recycled polystyrene can have a melt
flow index of from about 5 to about 25 g/10 min. For example, the
recycled polystyrene can have a melt flow index of less than about
25 g/10 min. For example, the recycled polystyrene can have a melt
flow index of from about 10 to about 20 g/10 min.
[0118] For example, the recycled polystyrene can have a melt flow
index of less than about 30 g/10 min. For example, the recycled
polystyrene can have a melt flow index of from about 3 to about 25
g/10 min. For example, the recycled polystyrene can have a melt
flow index of from about 1 to about 15 g/10 min. For example, the
recycled polystyrene can have a melt flow index of from about 10 to
about 15 g/10 min. For example, the recycled polystyrene can have a
melt flow index of from about 5 to about 12 g/10 min. For example,
the recycled polystyrene can have a melt flow index of from about 2
to about 12 g/10 min. For example, the recycled polystyrene can
have a melt flow index of less than about 15 g/10 min. For example,
the recycled polystyrene can have a melt flow index of less than
about 12 g/10 min.
[0119] For example, the recycled polystyrene can have a content of
additive(s) of less than about 5 wt %.
[0120] For example, the recycled polystyrene can have a content of
additive(s) of less than about 3 wt %.
[0121] For example, the recycled polystyrene can have a content of
additive(s) of less than about 2 wt %.
[0122] For example, the recycled polystyrene can have a content of
additive(s) of less than about 1 wt %.
[0123] For example, the recycled polystyrene can have a content of
additive(s) of less than about 0.5 wt %.
[0124] For example, the recycled polystyrene can have a content of
additive(s) of less than about 0.1 wt %.
[0125] For example, the recycled polystyrene can have a content of
additive(s) of less than about 0.05 wt %.
[0126] For example, the recycled polystyrene can have a content of
additive(s) of about 0.05 wt % to about 1 wt %.
[0127] For example, the recycled polystyrene can have a content of
additive(s) of about 0.1 wt % to about 1 wt %.
[0128] For example, the recycled polystyrene can have a filler
content of less than about 5 wt %.
[0129] For example, the recycled polystyrene can have a filler
content of less than about 3 wt %.
[0130] For example, the recycled polystyrene can have a filler of
less than about 2 wt %.
[0131] For example, the recycled polystyrene can have a filler
content of less than about 1 wt %.
[0132] For example, the recycled polystyrene can have a filler
content of less than about 0.5 wt %.
[0133] For example, the recycled polystyrene can have a filler
content of less than about 0.1 wt %.
[0134] For example, the recycled polystyrene can have a filler
content of less than about 0.05 wt %.
[0135] For example, the recycled polystyrene can have a filler
content of about 0.05 wt % to about 1 wt %.
[0136] For example, the recycled polystyrene can have a filler
content of about 0.1 wt % to about 1 wt %.
[0137] For example, the filler can be an inorganic filler.
[0138] For example, the recycled polymer can be obtained by
recycling a polystyrene waste by involving a treatment with a
solvent and a non-solvent.
[0139] For example, the recycled polymer can be obtained by
recycling a polystyrene waste by involving a treatment with a
solvent that is p-cymene and a hydrocarbon polystyrene non-solvent
that is C.sub.6-C.sub.8 alkane or mixtures thereof.
[0140] For example, the polystyrene waste can comprises polystyrene
having an average molecular weight of about 200,000 to about
350,000 g/mol.
[0141] For example, the polystyrene waste can comprises polystyrene
having an average molecular weight of about 230,000 to about
260,000 g/mol.
[0142] For example, the polystyrene waste can comprises polystyrene
having an average molecular weight of about 260,000 to about
300,000 g/mol.
[0143] For example, the recycled polystyrene can be
transparent.
[0144] For example, the recycled polystyrene can be clear.
[0145] For example, the recycled polystyrene can be substantially
transparent.
[0146] For example, the recycled polystyrene can be at least
substantially transparent.
[0147] For example, the recycled polystyrene can be obtained by any
of the processes and/or methods described in the present
disclosure.
[0148] There is provided the use of the recycled polystyrenes of
the present disclosure for preparing a mixture comprising said
recycled polystyrene and a virgin polystyrene.
[0149] There is also provided a method of using the recycled
polystyrenes of the present disclosure comprising mixing the
recycled polystyrene with a virgin polystyrene.
[0150] For example, the mixture can comprise at least about 10 wt
%, at least about 15 wt %, at least about 20 wt %, about 1 wt % to
about 50 wt %, about 5 wt % to about 50 wt %, or about 5 wt % to
about 30 wt % of the recycled polystyrene.
[0151] For example, the recycled polystyrene can comprise other
copolymers. For example, it can comprise butadiene (polybutadiene,
high-impact polystyrene HIPS), be a copolymer of styrene and
acrylonitrile (SAN) or acrylonitrile, butadiene and styrene
(ABS).
[0152] For example, the recycled polystyrene can be a
polystyrene-co-butadiene copolymer.
[0153] According to another aspect of the present disclosure, there
is provided a method for managing recycling of polystyrene
comprising: [0154] providing a customer with at least one container
for storing polystyrene waste; [0155] providing the customer with
instructions on how dissolving the polystyrene waste into the at
least one container by using at least one solvent; [0156]
optionally monitoring concentration of the polystyrene waste into
the at least one solvent and/or a volume of liquid and/or solid
contained in the at least one container; [0157] removing at least a
portion of a liquid content contained in the at least one container
and that comprises the polystyrene waste dissolved into the at
least one solvent; [0158] optionally adding a quantity of the at
least one solvent into the at least one container; [0159]
transporting the at least a portion of the liquid content contained
in the at least one container into a facility whereat the
polystyrene waste is recycled or treated for converting the
polystyrene waste into recycled polystyrene.
[0160] According to another aspect of the present disclosure, there
is provided a method for storing polystyrene waste and recycling
the polystyrene, the method comprising: [0161] dissolving a
polystyrene waste into at least one container by using at least one
solvent; [0162] optionally monitoring concentration of the
polystyrene waste into the at least one solvent and/or a volume of
liquid and/or solid contained in the at least one container; [0163]
removing at least a portion of a liquid content contained in the at
least one container and that comprises the polystyrene waste
dissolved into the at least one solvent; [0164] optionally adding a
quantity of the at least one solvent into the at least one
container; [0165] transporting the at least a portion of the liquid
content contained in the at least one container into a facility
whereat the polystyrene waste is recycled or treated for converting
the polystyrene waste into recycled polystyrene.
[0166] For example, recycling of the polystyrene or converting of
the polystyrene waste into recycled polystyrene is carried out by a
method as defined in the present disclosure.
[0167] For example, the transporting can be carried out by tank
truck transportation.
[0168] For example, the transporting can be carried out by tank
train transportation.
[0169] For example, the transporting can be carried out by means of
a pipe.
[0170] For example, the transporting can be carried out by means of
a pipeline.
EXAMPLES
Example 1
[0171] Recycling of Polystyrene Waste
[0172] In the present studies, polystyrene waste was recycled in a
process which included five main steps, according to the following
sequence:
[0173] 1. Solubilisation of the polystyrene in p-cymene
[0174] 2. Filtration of the PS/p-cymene mixture to remove
undissolved materials
[0175] 3. Washing with a non-polar solvent that is a non-solvent to
PS
[0176] 4. Drying
[0177] 5. Forming and packaging PS plastic beads
[0178] In the first step (solubilisation), polystyrene waste such
as industrial post-consumption expanded polystyrene was dissolved
in p-cymene (1-methyl-4-(1-methylethyl)benzene; one of the three
possible isomers of cymene, and the only one that is also present
in nature). The solubility limit of the polystyrene in the p-cymene
is 33% (w/w) or 28.5% (v/v) at room temperature and the density of
the polystyrene/p-cymene mixture reaches a value of 1.06 kg/L which
is higher than the density of pure p-cymene which is 0.86 kg/L. It
is possible to reach the solubility limit, but the dissolution rate
is decreased by a factor of 3.
[0179] In the solubilisation step, the polystyrene loses its
structural properties and a reduction of the volume it occupies
occurs. Various non-polar additives including
hexabromocyclododecane (HBCD) and the silicone oils used in its
manufacture are dissolved in the p-cymene solvent. This step was
performed in a closed, vented tank called the dissolution module.
An object of the module is to maximize the amount of polystyrene
that can be solubilised within a given period of time. For example,
a metallic grid inside the dissolution module can push the expanded
polystyrene objects into p-cymene which can reduce, for example,
dissolution time from hours to minutes.
[0180] The third step (washing) had objectives which included: (1)
the precipitation of the polystyrene; (2) recovery of the p-cymene
in order to reuse it in step 1; and (3) elimination of the
different additives that may alter the mechanical properties of the
recycled polystyrene.
[0181] This step comprised first precipitating the solubilised
polystyrene with hexane, heptane or any other hydrocarbon with a
suitable boiling point. While heptane was observed to provide the
best results in the washing step, other hydrocarbons may also be
useful. Hexane and octane were tested in the present studies.
Petroleum distillates with a boiling point of from about
100.degree. C. to about 120.degree. C. may also be useful and may
provide, for example, reduced process and/or operating costs.
[0182] For example, the solvent may have a boiling point around or
slightly above the T.sub.g for the polystyrene waste. While the
T.sub.g of polystyrene may vary, for example as a function of
molecular weight, the T.sub.g for the polystyrene waste is
typically about 98.degree. C. It will be appreciated by a person
skilled in the art that there is typically only a small variation
of T.sub.g with molecular weight or polydispersity for most
polystyrenes used in the fabrication of industrial polystyrene
objects. Accordingly, the solvent may have a boiling point up to
about 110.degree. C., for example a boiling point of about
105.degree. C. to about 110.degree. C. at 1 atm pressure. A
suitable hydrocarbon solvent may, for example enable more than 90%
of the p-cymene to migrate into it and is a non-solvent for
polystyrene.
[0183] To carry out the first washing step (i.e. precipitating the
polystyrene), the mixture of solubilised polystyrene in p-cymene
was slowly poured into a double wall stainless steel tank
containing the hydrocarbon at its boiling temperature. In an
exemplary experiment hexane at its boiling temperature (69.degree.
C.) was used for this step. In other exemplary experiments heptane
at its boiling temperature (98.degree. C.) was used for this step.
The entire mixture was moderately stirred through use of a
mechanical stirrer. The volume of polystyrene/p-cymene solution
added to the hydrocarbon was in a polystyrene/p-cymene solution to
hydrocarbon ratio by volume of 1:3. Under these conditions, the
polystyrene precipitated in the form of a sticky white paste. The
stirring time (from about 5 minutes to about 10 minutes) allowed
for a useful amount of diffusion of the p-cymene into the
hydrocarbon. Afterward, the solvent mixture supernatant was removed
by a simple decantation, after which it was possible to perform a
second washing of the precipitated polystyrene.
[0184] The second washing was performed in the same tank with
heptane. A defined volume of heptane having a boiling temperature
of 98.degree. C. was introduced into the tank, according to a
polystyrene:heptane ratio by volume of 1:1. The whole mixture was
boiled at atmospheric pressure under moderate mechanical stirring
over about 2 minutes to about 5 minutes. Using a different
hydrocarbon in the second wash than in the first wash increased the
malleability of the polystyrene which, for example, increased
diffusion of the remaining p-cymene solvent out of the precipitated
polystyrene and into the hydrocarbon. Thereafter, the supernatant
solvent mixture was removed by a simple decantation. According to
the calculations of washing efficiency, less than 0.1% p-cymene
remained in the precipitated polystyrene at this stage.
[0185] A third washing with boiling heptane was used in order to
further reduce the presence of p-cymene in the polystyrene. The
presence of residual solvent may, for example, affect the melt
index, also called melt flow index (MFI). The degree of washing
efficiency is inversely proportional to the MFI. The washing
conditions used were the same as in the second washing step.
[0186] The recovered solvent mixture contained hexane, heptane,
p-cymene and/or any other hydrocarbon solvent used as well as
non-polar additives extracted from the PS. The proportion of
p-cymene and additives was higher in the first solvent mixture than
in the second and third solvent mixtures. Fractional distillation
was used to separate the different products. The p-cymene was
reused for the solubilisation step while hexane and heptane were
reused in the washing steps. The recovered additives were
considered to be waste for disposal.
[0187] The fourth step (drying) comprised drying the polystyrene
paste, which contained about 5-37% heptane in a dryer at a
temperature of 120.degree. C. An objective was to remove
substantially all of the remaining solvent without altering the
quality of the polymer.
[0188] The fifth step (packaging) comprised cutting the dried
polystyrene into small pellets suitable for the distribution of the
product to customers. A pelletizer as commonly used in the industry
was utilized to control the size and the shape of the final
product.
[0189] In order to limit the PS degradation which is mainly due to
oxidation as observed during the drying and extrusion steps, a
commercial antioxidant such as Irganox.TM. 1076
(octadecyl-3-(3,5-di-tert.butyl-4-hydroxyphenyl)-propionate) can be
added in a proportion of about 1%, based on the weight of the
polystyrene. This compound is acceptable for food applications, has
a melting point of 50.degree. C. and can be added at various times
in the process: i.e. with the p-cymene, in the washing steps and/or
at the final extrusion step.
[0190] Table 1 shows the results from recycling various types of
waste polystyrene using steps of the above-described process.
TABLE-US-00001 TABLE 1.sup.[1] Melt Flow Irganox Index.sup.[3] 1076
(g/10 min) PS-cymene (1 wt %) Re- Re- Product Drying.sup.[4]
mixture.sup.[2] yes no sult 1 sult 2 Color (hours) Polystyrene
cooler x 25.2 -- slightly 120 (33 wt %) yellowish Polystyrene
cooler x 16.5 14.8 slightly 120 (33 wt %) yellowish
Poly(styrene-co- butadiene) (1.22 wt %) Polystyrene cooler x 11.6
-- white 108 (33 wt %) Poly(styrene-co- butadiene) (1.22 wt %)
Polystyrene cooler x 17.7 16.7 yellowish 120 (33 wt %)
Poly(styrene-co- butadiene) (4.86 wt %) Polystyrene cooler x 12.3
-- white 108 (33 wt %) Poly(styrene-co- butadiene) (4.86 wt %)
Poly(styrene-co- x 13.3 -- slightly 108 butadiene) yellowish (20 wt
%) Poly(styrene-co- x 17.2 -- very 108 butadiene) yellow (20 wt %)
Polystyrene regrind x 6.8 -- greyish 120 beads.sup.[5] (30 wt %)
Polystyrene cooler x 10.3 -- white 120 (15 wt %) Polystyrene
regrind beads (15 wt %) Polystyrene cooler x 10.6 9.9 white 120
(16.5 wt %) Polystyrene cooler x 6.28 -- white 48 (16.5 wt %)
Polystyrene cooler x 10 -- white 48 (20 wt %) Polystyrene cooler x
11.8 -- white 48 (24 wt %) Polystyrene cooler x 11.7 -- white 48
(28 wt %) Polystyrene black x 3.2 -- black 0 tray (100 wt %)
Polystyrene black x 5.5 -- black 120 tray (33 wt %) Polystyrene
blue x 14.3 -- blue 120 insulation (33 wt %) Polystyrene blue x
13.2 -- blue 120 insulation (33 wt %) Dense polystyrene x 38.7 --
white 0 log (100 wt %) Dense polystyrene x 6.27 6.27 white 48 log
(33 wt %) wrung and granulated before drying Polystyrene cooler x
9.2 -- white 120 (33 wt %) heated at 80.degree. C. in first wash
Polystyrene cooler x 7.98 7.6 white 48 (33 wt %) wrung and
granulated before drying Polystyrene cooler x 36.8 -- white 0 (100
wt %) Polystyrene blue x 20 -- blue 0 insulation (100 wt %)
Polystyrene cooler x 8.1 -- white 48 (33 wt %) Lime (1 wt
%).sup.[6] Polystyrene cooler x 7.06 -- white- 48 (33 wt %) yellow
Lime (5 wt %).sup.[6] Polystyrene cooler x 6.13 -- yellowish 48 (33
wt %) Lime (10 wt %).sup.[6] Polystyrene cooler x 4.88 -- yellow 48
(33 wt %) Lime (25 wt %).sup.[6] Polystyrene cooler x 13.2 -- white
72 (33 wt %) Talc (1 wt %).sup.[6] Polystyrene cooler x 12.7 --
greyish 72 (33 wt %) Talc (5 wt %).sup.[6] Polystyrene cooler x
17.5 -- greyish 72 (33 wt %) Talc (10 wt %).sup.[6] Polystyrene
cooler x 11.3 -- grey 72 (33 wt %) Talc (25 wt %).sup.[6]
Polystyrene sample x 25.2 -- white 0 that contains HBCD (100 wt %)
Polystyrene sample x 4.9 6.6 white 0 that contains HBCD (20 wt %)
.sup.[1]All trials were performed using three washes with heptane
in ratios by volume of heptane:PS/cymene mixture of 3:1, 1:1 and
1:1, respectively using extraction times of 15 minutes, 10 minutes
and 5 minutes, respectively. .sup.[2]The mixture for all trials
also includes p-cymene to make up 100 wt % total. .sup.[3]ASTM
D1238 standard has been used for each result. .sup.[4]In an oven at
120.degree. C. using an aluminum plate having a diameter of 8 cm.
The polystyrene dries with a thickness of <5 mm unless otherwise
specified. .sup.[5]The regrind beads come from trays and have
already a lower melt flow index. That quality of polystyrene
decreases the melt flow index in the mixture because of this high
molecular weight. .sup.[6]The lime and talc were added in the
PS-cymene mixture before the washing.
[0191] The Irganox 1076 has the property of protection against
oxidation. Many results showed a helpful effect on the product
color. The addition of butadiene in styrene results in the
formation of polystyrene-co-butadiene copolymer showing a much
better resistance to impact than pure polystyrene. The butadiene
units in polystyrene-co-butadiene could be used to create a
three-dimensional matrix with the polymer chains. By creating links
between the polymeric chains, the molecular weight increases and
then the melt flow index must decrease. The
poly(styrene-co-butadiene) polymer contains 4% of butadiene. A
small amount of butadiene must be enough to see a difference on the
melt flow index but the results were inconclusive.
[0192] As can be seen in Table 1, the experiments show better
results when the polystyrene-cymene mixture has a lower
concentration. The dilution of the mixture into the non-solvent
increases the diffusion and thus the extraction of the solvent. The
addition of solid particles in a polymer mixture is a common
practice in the polystyrene industry to reduce cost or improve
mechanical properties.
[0193] Table 2 shows the results of including the antioxidant
Irganox 1076 at different steps in the process.
TABLE-US-00002 TABLE 2 Addition of 1 wt % Irganox 1076 in a
polystyrene Melt Flow Index.sup.[1] cooler-cymene mixture (g/10
min) Product (33 wt % polystyrene) Result 1 Result 2 Color Added
directly in polystyrene/ 7.6 8.2 white p-cymene mixture Added to
the heptane in first 10.6 -- white wash Added to the heptane in
third 13.5 -- white wash .sup.[1]ASTM D1238 standard has been used
for each result.
[0194] As can be seen in Table 2, the product color for all samples
was white. The MFI was lowest for the product produced from a
process wherein the Irganox 1076 was added to the
polystyrene/p-cymene mixture.
[0195] Table 3 shows the impact of a mechanical conditioning and
the evolution of the drying steps. There is a difference of about
37.5% between the washed and the dry polystyrene. At this point,
all the heptane has been evaporated. Also, only with a wringing and
a granulating step, it is possible to eliminate 14% of the heptane
from the washed polystyrene. The heptane is recovered in the
process to repeat the washing treatment. The source of polystyrene
does not have any significant effect in the drying step in these
studies.
TABLE-US-00003 TABLE 3.sup.[1] Heptane PS-cymene Evaporated.sup.[3]
mixture.sup.[2] Mass (g) (wt %) Before After Mec. cond. Mec. Cond.
Polystyrene cooler 14.04 12.09 13.9 (33 wt %) Compressed 12.58
10.79 14.2 polystyrene log (33 wt %) After Drying After Drying 15
hours 17 hours Polystyrene cooler -- 8.81 37.3 (33 wt %) Compressed
7.93 -- 37.0 polystyrene log (33 wt %) After Drying After Drying 22
hours 24 hours Polystyrene cooler -- 8.79 37.4 (33 wt %) Compressed
7.92 -- 37.0 polystyrene log (33 wt %) After Drying After Drying 46
hours 48 hours Polystyrene cooler -- 8.77 37.5 (33 wt %) Compressed
7.89 -- 37.3 polystyrene log (33 wt %) .sup.[1]All drying carried
out in an oven at 120.degree. C. .sup.[2]The mixture for all trials
also includes p-cymene to make up 100 wt % total. .sup.[3]Values
provided as wt % based on the total mass before granulation.
Example 2
[0196] Further tests have been made for preparing recycled
polystyrene. Such tests have been made by using a process similar
as previously described in Example 1 but without any addition of
Irganox. These tests have been made at a lab scale on real white
expanded polystyrene used for packaging.
[0197] The results of such tests are thus provided below.
DSC (ASTM D3418): Tg=108.1.degree. C.
[0198] IZOD Impact test (ASTM D4812): 4 tests with average Impact
of 13.78 KJ/m.sup.2 and 175.72 J/m and Energy=0.55 J with complete
rupture.
TABLE-US-00004 TABLE 4 MFI tests MFI (ASTM D1238 on a Dynisco D4002
at 200.degree. C.) : MFI Test (g/10 min) 1 11.44 2 11.01 3 10.70
Average 11.05
Ash Content (ASTM D5630): 0.10
TABLE-US-00005 [0199] TABLE 5 VICAT tests VICAT Softening
Temperature (ASTM D1525): VICAT Thickness softening Test (mm)
Temperature (.degree. C.) 1 3.01 106.2 2 3.04 106.1 3 3.03
106.9
TABLE-US-00006 TABLE 6 VICAT tests Traction Test (ASTM D638):
Thick- Maximum Elasticity Elongation ness Width stress Module at
rupture Test (mm) (mm) (MPa) (MPa) (%) 1 3.11 12.71 52.4 3095 2.4 2
3.11 12.75 52.2 2992 2.4 3 3.13 12.72 51.7 2990 2.4 4 3.11 12.72
51.7 3114 2.4 5 3.12 12.71 51.0 3029 2.2 Average 51.8 3044 2.4
Standard 0.5 58 0.1 deviation
Example 3
[0200] Further tests have been made for preparing recycled
polystyrene. Such tests have been made by using a process similar
as previously described in Example 1. The process was carried out
in continuous and a scale up was made to bring the process from a
laboratory level to an industrial level. For example, the process
allowed for preparing about 10 kg of recycled polystyrene per hour.
It has to be noted that the limiting factors in the present case
regarding the productivity of the process does not reside in the
process per se but rather in certain types of equipment used for
carrying out the process. By acquiring some equipment allowing for
receiving larger volumes or greater quantity, the overall process
can easily reach about 500 to about 1000 kg recycled polystyrene
per hour.
[0201] The results of such tests are thus provided below.
MFI=22 g/10 min according to ASTM D1238-13 standard.
[0202] While a description was made with particular reference to
the specific embodiments, it will be understood that numerous
modifications thereto will appear to those skilled in the art.
Accordingly, the above description and accompanying drawings should
be taken as specific examples and not in a limiting sense.
* * * * *