U.S. patent application number 15/883439 was filed with the patent office on 2018-08-02 for polar polystyrene copolymers for enhanced foaming.
The applicant listed for this patent is FINA TECHNOLOGY, INC.. Invention is credited to Melissa Greenberg, David W Knoeppel, Wei Wang.
Application Number | 20180215889 15/883439 |
Document ID | / |
Family ID | 46637373 |
Filed Date | 2018-08-02 |
United States Patent
Application |
20180215889 |
Kind Code |
A1 |
Wang; Wei ; et al. |
August 2, 2018 |
Polar Polystyrene Copolymers for Enhanced Foaming
Abstract
A method of making a foamable polystyrene composition includes
combining a styrenic monomer and a co-monomer containing a polar
functional group to obtain a mixture, subjecting the mixture to
polymerization to obtain a styrenic co-polymer, and combining the
styrenic co-polymer with a blowing agent in a foaming process to
obtain foamed articles.
Inventors: |
Wang; Wei; (League City,
TX) ; Knoeppel; David W; (League City, TX) ;
Greenberg; Melissa; (Katy, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FINA TECHNOLOGY, INC. |
Houston |
TX |
US |
|
|
Family ID: |
46637373 |
Appl. No.: |
15/883439 |
Filed: |
January 30, 2018 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
14533730 |
Nov 5, 2014 |
9914814 |
|
|
15883439 |
|
|
|
|
13347706 |
Jan 11, 2012 |
8912242 |
|
|
14533730 |
|
|
|
|
61441389 |
Feb 10, 2011 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08J 2203/06 20130101;
C08J 9/12 20130101; C08J 2203/12 20130101; C08J 2351/00 20130101;
C08J 9/142 20130101; C08J 9/122 20130101; C08J 2325/08 20130101;
C08J 9/0023 20130101; C08J 2203/10 20130101; C08F 212/08 20130101;
C08F 212/08 20130101; C08F 220/281 20200201; C08F 212/08 20130101;
C08F 222/08 20130101; C08F 212/08 20130101; C08F 220/1804 20200201;
C08F 212/08 20130101; C08F 220/325 20200201 |
International
Class: |
C08J 9/12 20060101
C08J009/12; C08J 9/00 20060101 C08J009/00; C08J 9/14 20060101
C08J009/14; C08F 212/08 20060101 C08F212/08 |
Claims
1-21. (canceled)
22. A polystyrene composition comprising: a styrenic co-polymer
resulting from polymerization of a reaction mixture comprising a
styrenic monomer and polyvinyl acetate; and a blowing agent.
23. The foamable polystyrene composition of claim 22, wherein the
blowing agent comprises CO.sub.2.
24. The foamable polystyrene composition of claim 22, wherein the
blowing agent is present in the styrenic co-polymer in a weight
proportion ranging from 1 to 30 parts per 100 parts of styrenic
material.
25. The foamable polystyrene composition of claim 22, wherein the
polyvinyl acetate is present in an amount ranging from 0.5 to 20 wt
% of the styrenic co-polymer.
26. A polystyrene foam obtained from the foamable polystyrene
composition of claim 22.
27. An article made from the polystyrene foam of claim 26.
28. A method comprising: combining a styrene monomer and polyvinyl
acetate to obtain a reaction mixture subjecting the reaction
mixture to polymerization conditions to obtain a styrenic
co-polymer; and combining the styrenic co-polymer with a blowing
agent to obtain a foamable blend.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a non-provisional of U.S. Provisional
Application Ser. No. 61/441,389 filed Feb. 10, 2011.
FIELD
[0002] The present invention is generally related to polymeric
compositions. More specifically, the present invention is related
to foamable polystyrene compositions.
BACKGROUND
[0003] Styrene, also known, as vinyl benzene, is an aromatic
compound that is produced in industrial quantities from
ethylbenzene. The most common method of styrene production
comprises the dehydrogenation of ethylbenzene, which produces a
crude product of styrene monomer and unreacted ethylbenzene and
hydrogen. Polystyrene is an aromatic polymer produced from the
styrene monomer. Polystyrene is a widely used polymer found in
insulation, packaging, and disposable cutlery.
[0004] Different types of polystyrene materials can include
general-purpose polystyrene (GPPS), high impact polystyrene (HIPS),
and transparent impact polystyrene (TIPS). Many conditions affect
the properties of the resulting product, including processing time,
temperature, pressure, purity of the monomer feedstock, and the
presence of additives or other compounds. These and other
processing conditions alter the physical and chemical properties of
the polystyrene product, affecting the suitability for a desired
use.
[0005] Foamed polystyrene offers the advantages of low cost and
high structural strength for its density. A typical polystyrene
foam also has a relatively high impact resistance and possesses
excellent electrical and thermal insulation characteristics. Foamed
polystyrene is useful in a variety of applications such as
insulation, packaging, coolers, food packaging, decorative pieces,
and dunnage. Additionally, polystyrene foams are commonly
classified into three general categories: low density, medium
density, and high density. Low density polystyrene foams usually
have a density of from about 1 to about 3 lb/ft.sup.3 whereas
medium density foams may have a density ranging from about 4 to
about 19 lb/ft.sup.3 and high density foams often have a density
ranging from 20 to about 30 lb/ft.sup.3.
[0006] The two main types of polystyrene foam are extruded
polystyrene (XPS) foam and expanded polystyrene (EPS) foam.
Extruded polystyrene foam is typically formed by mixing polystyrene
with additives and blowing agents into an extruder that heats the
mixture. The mixture is then extruded, foamed to the desired shape,
and cooled. Expanded polystyrene foam is typically formed by
expanding solid polystyrene beads containing a blowing agent such
as pentane with steam or hot gas. These pre-expanded beads may
later be molded into the desired shape and expanded again with
steam or hot gas to fuse the beads together.
[0007] In the production of foamed polystyrene, it is common to
utilize blowing agents such as methyl chloride, ethyl chloride,
chlorocarbons, fluorocarbons (including HFCs) and
chlorofluorocarbons (CFCs). However, such blowing agents have been
heavily regulated due to potential environmental impact. Many of
these traditional and current physical blowing agents are
halogenated compounds, which demonstrate a high solubility in polar
polymers. An ongoing trend in foaming process development is to
find environmentally benign chemicals as blowing agents. Some
foaming processes have been using carbon dioxide (CO.sub.2) as the
blowing agent or co-blowing agent. The advantages of using CO.sub.2
include low cost, minimal environmental impact, and eliminating
potential fire hazards. It has therefore been desirable to use
carbon dioxide as a blowing agent from both environmental and
economic standpoints.
[0008] However, carbon dioxide has presented problems when used as
a blowing agent. Carbon dioxide has been found to have a relatively
low solubility in styrenic polymer melts. For example, the
solubility of CO.sub.2 in polystyrene is only ca. 4 wt % at 6.5 MPa
and 373 K, as measured by Yoshiyuki Sato et. al. (Journal of
Supercritical Fluids 2001, 19, 187-198.). The low solubility
results in high extrusion pressures, which increases costs and
reduces quality. The low solubility also results in a higher
density product. It would be desirable to obtain a polystyrene
product having a high carbon dioxide solubility in order to reduce
costs and increase product quality.
[0009] Furthermore, carbon dioxide has relatively higher vapor
pressure and diffusivity, compared to halogenated blowing agents.
In the extrusion foaming process using CO2 as the blowing agent,
the melt strength of polystyrene is often inadequate, which leads
to immature bubble breakage/coalescence, non-uniform cell
morphology, and excessive open cell content. It would be desirable
to obtain a polystyrene resin having improved melt strength in
order to perform well in foaming processes.
SUMMARY
[0010] An embodiment of the present invention is a polystyrene
product that is a styrenic co-polymer resulting from polymerization
of a reaction mixture of a styrenic monomer and co-monomers having
polar functional groups. The polystyrene can then be used in an
extrusion foaming process with the presence of blowing agents.
[0011] In a non-limiting embodiment, either by itself or in
combination with any other aspect of the invention, the styrenic
monomer can be selected from the group consisting of styrene,
alpha-methyl styrene, vinyl toluene, p-methyl styrene, t-butyl
styrene, o-chlorostyrene, vinyl pyridine, and any combinations
thereof, and can be present in amounts ranging from 80 to 99.9 wt %
based on the total weight of the expandable polystyrene.
[0012] In a non-limiting embodiment, either by itself or in
combination with any other aspect of the invention, the co-monomer
can be selected from the group consisting of
hydroxyethylmethacrylate (HEMA), caprolactone acrylate, alkyl
(meth)acrylate, fluorinated (meth)acrylate and any other
polymerizable monomers containing esters, ethers, carboxylic acids
or silanes, and combinations thereof, and can be present in amounts
ranging from 0.5 to 20 wt % based on the total weight of the
reaction mixture.
[0013] In a non-limiting embodiment, either by itself or in
combination with any other aspect of the invention, the blowing
agent can be carbon dioxide (CO.sub.2), water (H.sub.2O), ethanol,
air, nitrogen, argon, and helium and combinations thereof and can
be present in the styrenic co-polymer in a weight proportion
ranging from 1 to 30 parts per 100 parts of styrenic material.
[0014] In a non-limiting embodiment, either by itself or in
combination with any other aspect of the invention, the present
invention includes any article made from the polystyrene of any
embodiment disclosed herein.
[0015] Other possible embodiments include two or more of the above
aspects of the invention. In an embodiment the method includes all
of the above aspects and the various procedures can be carried out
in any order.
BRIEF DESCRIPTION OF DRAWINGS
[0016] FIG. 1 is a graph illustrating polylactic acid (PLA)
particle size distribution from PLA blends with various polystyrene
copolymers.
[0017] FIG. 2 is a graph illustrating PLA particle size
distribution from PLA blends modified with styrene-maleic anhydride
(SMA).
[0018] FIG. 3 is a graph of results from haul-off melt strength
tests at various HEMA concentrations.
[0019] FIG. 4 is a diagram illustrating the experimental scheme of
dynamic gravimetric measurement of CO.sub.2 solubility.
[0020] FIG. 5 is a graph of CO.sub.2 desorption versus CO.sub.2
solubility.
[0021] FIG. 6 is a graph of CO.sub.2 desorption versus normalized
CO.sub.2 solubility.
DETAILED DESCRIPTION
[0022] The present invention includes styrenic polymers and polymer
blends. In an embodiment, the present invention includes styrenic
copolymers of styrene and a second monomer containing a polar
functional group. In a more specific embodiment, the present
invention includes a foamable polymeric composition containing such
styrenic copolymers.
[0023] In an embodiment, the present invention includes a styrenic
polymer. In another embodiment, the styrenic polymer includes
polymers of monovinylaromatic compounds, such as styrene,
alpamethyl styrene and ring-substituted styrenes. In an alternative
embodiment, the styrenic polymer includes a homopolymer and/or
copolymer of polystyrene. Styrenic monomers for use in the styrenic
polymer composition can be selected from the group of styrene,
alpha-methyl styrene, vinyl toluene, t-butyl styrene,
o-chlorostyrene, vinyl pyridine, and any combinations thereof. The
styrenic polymeric component in the blend of the present invention
can be produced by any known process.
[0024] The styrenic polymer of the present invention may include
general-purpose polystyrene (GPPS), high-impact polystyrene (HIPS),
styrenic copolymer compositions, or any combinations thereof. In an
embodiment, the HIPS contains an elastomeric material. In an
embodiment, the HIPS contains an elastomeric phase embedded in the
polystyrene matrix, which results in the polystyrene having an
increased impact resistance.
[0025] The blend of the present invention may contain any desired
amounts of a styrenic polymer. In an embodiment, the blend contains
at least 50 wt % of a styrenic polymer. In another embodiment, the
blend contains a styrenic polymer in amounts ranging from 1 to 99
wt %, 50 to 95 wt %, 60 to 92 wt %, and optionally 70 to 90 wt %.
In a further embodiment, the blend contains a styrene polymer in
amounts ranging from 80 to 99 wt %. In an even further embodiment,
the blend contains a styrenic polymer in amounts ranging from 90 to
95 wt %.
[0026] The styrenic polymer of the present invention may be formed
by copolymerizing a first monomer with a second monomer. The first
monomer and the second monomer may be co-polymerized by having the
first monomer and the second monomer present in a reaction mixture
that is subjected to polymerization conditions. The first monomer
may include monovinylaromatic compounds, such as styrene,
alpha-methyl styrene and ring-substituted styrenes. In an
embodiment, the first monomer is selected from the group of
styrene, alpha-methyl styrene, vinyl toluene, t-butyl styrene,
o-chlorostyrene, vinyl pyridine, and any combinations thereof. In
another embodiment, styrene is used exclusively as the first
monomer. In an embodiment, the first monomer is present in the
reaction mixture in amounts of at least 50 wt % of the reaction
mixture. In another embodiment, the first monomer is present in the
reaction mixture in amounts ranging from 80 to 99.9 wt % of the
reaction mixture. In a further embodiment, the first monomer is
present in the reaction mixture in amounts ranging from 90 to 99 wt
%. Embodiments of the second monomer can be any suitable monomer
capable of polymerization to form a styrenic copolymer. Examples of
suitable second monomers can include hydroxyethylmethacrylate,
caprolactone acrylate, alkyl (meth)acrylate, fluorinated
(meth)acrylate and any other polymerizable monomers containing
polar functionalities such as esters, ethers, carboxylic acids or
silanes, and combinations thereof.
[0027] Embodiments of the present invention include at least one
second monomer containing a polar functional group. The second
monomer containing a polar functional group may also be referred to
herein as a "polar monomer". In an embodiment, the polar monomer is
a polar vinyl functional monomer. In another embodiment, the polar
monomer is selected from the group of hydroxyethylmethacrylate,
caprolactone acrylate, alkyl (meth)acrylate, fluorinated
(meth)acrylate and any other polymerizable monomers containing
polar functionalities such as esters, ethers, carboxylic acids or
silanes, and combinations thereof. In a further embodiment, the
polar monomer is selected from the group of caprolactone acrylate,
polyvinyl acetate, and HEMA, and combinations thereof. In an even
further embodiment, the polar monomer is HEMA. In another
embodiment the second monomer may be selected from the group of,
maleic anhydride (MAH), butyl acrylate, butyl methacrylate, and
combinations thereof.
[0028] The styrenic polymer of the present invention may be
prepared by polymerizing a reaction mixture containing a first
monomer and a second monomer having a polar functional group. The
first monomer and second monomer may be present in the reaction
mixture in any desired amounts. In an embodiment, the second
monomer is present in the reaction mixture in amounts of at least
0.1 wt % of the reaction mixture. In another embodiment, the second
monomer is present in the reaction mixture in amounts of less than
20 wt % of the reaction mixture. In an alternative embodiment, the
second monomer is present in the reaction mixture in amounts
ranging from 1 to 20 wt %. In a further embodiment, the second
monomer is present in the reaction mixture in amounts ranging from
1 to 10 wt %. In an even further embodiment, the second monomer is
present in the reaction mixture in amounts ranging from 1 to 5 wt
%.
[0029] The polymerization of the styrenic monomer and the polar
co-monomer may be carried out using any method known to one having
ordinary skill in the art or performing such polymerizations. In an
embodiment, the polymerization may be carried out by using a
polymerization initiator. In an embodiment, the polymerization
initiators include but are not limited to perketals,
hydroperoxides, peroxycarbonates and the like. In another
embodiment, the polymerization initiators may be selected from the
group of benzoyl peroxide, lauroyl peroxide, t-butyl
peroxybenzoate, and
1,1-di-t-butylperoxy-2,4-di-t-butylcycleohexane, and combinations
thereof. In an embodiment, the amount of the polymerization
initiator is from 0.01 to 1.0 wt % of the reaction mixture. In
another embodiment, the amount of the polymerization initiator is
from 0.01 to 0.5 wt % of the reaction mixture. In a further
embodiment, the amount of the polymerization initiator is from
0.025 to 0.05 wt % of the reaction mixture.
[0030] Any process capable of processing or polymerizing styrenic
monomers may be used to prepare the styrenic co-polymer of the
present invention. In an embodiment, the polymerization reaction to
prepare the styrenic co-polymer may be carried out in a solution or
mass polymerization process. Mass polymerization, or bulk
polymerization, refers to the polymerization of a monomer in the
absence of any medium other than the monomers and a catalyst or
polymerization initiator. Solution polymerization refers to a
polymerization process in wherein the monomers and polymerization
initiators are dissolved in a non-monomeric liquid solvent at the
beginning of the polymerization reaction.
[0031] The polymerization may be either a batch process or a
continuous process. In an embodiment, the polymerization reaction
may be carried out using a continuous production process in a
polymerization apparatus including a single reactor or multiple
reactors. The styrenic polymer composition can be prepared using an
upflow reactor, a downflow reactor, or any combinations thereof.
The reactors and conditions for the production of a polymer
composition, specifically polystyrene, are disclosed in U.S. Pat.
No. 4,777,210, which is incorporated by reference herein in its
entirety.
[0032] The temperature ranges useful in the polymerization process
of the present disclosure can be selected to be consistent with the
operational characteristics of the equipment used to perform the
polymerization. In an embodiment, the polymerization temperature
ranges from 90 to 240.degree. C. In another embodiment, the
polymerization temperature ranges from 100 to 180.degree. C. In yet
another embodiment, the polymerization reaction may be carried out
in multiple reactors in which each reactor is operated under an
optimum temperature range. For example, the polymerization reaction
may be carried out in a reactor system employing a first
polymerization reactor and a second polymerization reactor that may
be either continuously stirred tank reactors (CSTR) or plug-flow
reactors. In an embodiment, a polymerization process for the
production of a styrenic co-polymer of the type disclosed herein
containing multiple reactors may have the first reactor (e.g., a
CSTR), also referred to as a prepolymerization reactor, operated
under temperatures ranging from 90 to 135.degree. C. while the
second reactor (e.g. CSTR or plug flow) may be operated under
temperatures ranging from 100 to 165.degree. C.
[0033] In an alternative embodiment, the co-polymer may be obtained
by polymerization in which heat is used as the initiator. In a
further embodiment, the co-polymer may be prepared using a
non-conventional initiator such as a metallocene catalyst as is
disclosed in U.S. Pat. No. 6,706,827 to Lyu, et al., which is
incorporated herein by reference in its entirety. In one
embodiment, the monomers may be admixed with a solvent and then
polymerized. In another embodiment, one of the monomers is
dissolved in the other and then polymerized. In still another
embodiment, the monomers may be fed concurrently and separately to
a reactor, either neat or dissolved in a solvent, such as mineral
oil. In yet another embodiment, the second monomer may be prepared
in-situ or immediately prior to the polymerization by admixing the
raw material components, such as an unsaturated acid or anhydride
and a metal alkoxide, in-line or in the reactor. Any process for
polymerizing monomers having polymerizable unsaturation know to be
useful to those of ordinary skill in the art in preparing such
polymers may be used. For example, the process disclosed in U.S.
Pat. No. 5,540,813 to Sosa, et al., may be used and is incorporated
herein by reference in its entirety. The processes disclosed in
U.S. Pat. No. 3,660,535 to Finch, et al., and U.S. Pat. No.
3,658,946 to Bronstert, et al., may be used and are both
incorporated herein by reference in their entirety. Any process for
preparing general purpose polystyrene may be used to prepare the
styrenic co-polymer of the present invention.
[0034] In certain embodiments, the styrenic copolymer may be
admixed with additives prior to being used in end use applications.
For example, the styrenic copolymer may be admixed with additives
that include without limitation, antioxidants, UV stabilizers or
absorbents, lubricants, plasticizers, ultra-violet screening
agents, oxidants, anti-static agents, fire retardants, processing
oils, mold release agents, fillers, pigments/dyes, coloring agents,
and other similar compositions. Any additive known to those of
ordinary skill in the art to be useful in the preparation of
styrenic copolymers may be used. CO.sub.2 solubility may increase
for lower molecular weight polystyrene copolymer, therefore, it
would be desirable to maintain or control the molecular weight of
the styrenic copolymer. In an embodiment, chain transfer agents
and/or diluents may be added before and/or during polymerization in
order to help control the molecular weight of the resulting
styrenic copolymer.
[0035] The obtained polystyrene copolymer may then be sent to an
extruder or other step to obtain an end use article. The blowing
agents such as HFC or CO.sub.2 can be added into the polymer during
the extrusion process.
[0036] In an embodiment, styrene monomer is combined with a polar
comonomer and a plasticizer and subsequently polymerized to form a
polar polystyrene copolymer. The polar polystyrene copolymer can
then be sent to an extruder or other step to obtain an end use
article. The blowing agents are added to the polystyrene containing
composition during the extruding step.
[0037] In an embodiment, styrene monomer is combined with a second
polar monomer and subsequently polymerized to form a polystyrene
copolymer. In an embodiment, the polystyrene copolymer is sent to
an extruder or other step to obtain an end use article. The blowing
agents are added to the polystyrene containing composition during
the extruding step.
[0038] The present invention may include foamed articles which may
be formed by melting and mixing the styrenic copolymer of the
invention to form a polymer melt, incorporating a blowing agent
into the polymer melt to form a foamable blend, and extruding the
foamable blend through a die to form the foamed structure. During
melting and mixing, the polymeric material may be heated to a
temperature at or above the glass transition temperature of the
polymeric material. The melting and mixing of polymeric material
and any additives may be accomplished by any means known in the
art, including extruding, mixing, and/or blending. In an
embodiment, a blowing agent is blended with molten polymeric
material. The blending of the blowing agent with the molten
polymeric material may be performed under atmospheric or elevated
pressures.
[0039] In an embodiment, the blowing agent is incorporated into the
styrenic copolymer in a weight proportion ranging from 1 to 30
parts per 100 parts of the polymeric material to be foamed. In
another embodiment, the blowing agent is incorporated into the
styrenic copolymer in a weight proportion ranging from 2 to 18 per
100 parts per polymeric material to be foamed. In a further
embodiment, the blowing agent is incorporated into the styrenic
copolymer in a weight proportion ranging from 4 to 12 parts per 100
parts per polymeric material to be foamed.
[0040] The blowing agents of the present invention may include
organic and/or inorganic compounds. In an embodiment, the blowing
agents of the present invention are environmentally benign than
methyl chloride, ethyl chloride, chlorocarbons, fluorocarbons
(including HFCs) and chlorofluorocarbons (CFCs). In a further
embodiment, the blowing agents of the present invention are
selected from the group of carbon dioxide (CO.sub.2), water
(H.sub.2O), ethanol, air, nitrogen, argon, butane, pentane, and
helium and combinations thereof. In an even further embodiment, the
blowing agent of the present invention is entirely composed of
CO.sub.2.
[0041] The foamable blend may be cooled after the blowing agent is
incorporated into the styrenic blend. In an embodiment, the
foamable blend is cooled to temperatures ranging from 30 to
150.degree. C., optionally 75 to 150.degree. C. The cooled foamable
blend may then be passed through a die into a zone of lower
pressure to form an article of foamed structure. The polystyrene
copolymer can be used for not only foams, but also rigid
blends.
[0042] The obtained foamed polystyrene copolymer may have any
desired density. In an embodiment, the density of the foamed
polystyrene copolymer ranges from 15 to 0.1 lbs/ft.sup.3. In
another embodiment, the density of the foamed polystyrene copolymer
ranges from 10 to 0.5 lbs/ft.sup.3. In a further embodiment, the
density of the foamed polystyrene copolymer ranges from 3 to 0.6
lbs/ft.sup.3.
[0043] An end use article may include a polystyrene copolymer of
the present invention. In an embodiment, the articles include films
and thermoformed or foamed articles. For example, a final article
may be thermoformed from a sheet containing the polystyrene
copolymer. In another embodiment, the end use articles include
foamed articles, which may have a foamed structure. In an
embodiment, an article can be obtained by subjecting the polymeric
composition to a plastics shaping process such as extrusion. The
polymeric composition may be formed into end use articles including
food packaging, food/beverage containers, polymeric foam substrate,
foamed insulation, building insulation, protective head gear, toys,
dunnage, and the like.
[0044] In an embodiment, the obtained polystyrene foam is a
multicellular article having a plurality of cells that may be open
or closed. In another embodiment, the majority of the cells are
open. In an alternative embodiment, the majority of the cells are
closed.
EXAMPLES
Example 1
[0045] A series of polystyrene samples were made with the addition
of polar modifiers as listed in Table 1 below. The polymerization
reaction was carried out in a CSTR-type batch reactor. Lupersol-233
was added as the initiator with an initial concentration of about
170 ppm in the reaction mixture. The reaction was then run
isothermally at 130.degree. C. with continuous agitation at 150 rpm
for about 3 hours or until 75% conversion was obtained. The
reaction mixture was then transferred onto an aluminum surface and
devolatized under active vacuum of less than 10 torr at 225.degree.
C. for 45 minutes.
[0046] The polar modifiers listed in Table 1 include styrene-maleic
anhydride (SMA), a copolymer of styrene and maleic anhydride, which
are commercially available from Sartomer Company, Inc. SMA.RTM.
1000P, SMA.RTM. 3000P and SMA.RTM. EF80 have styrene-to-maleic
anhydride molar ratios of 1:1, 3:1 and 8:1, respectively. The polar
modifiers also include butyl acrylate, butyl methacrylate,
hydroxyethylmethacrylate (HEMA), and maleic anhydride (MAH). The
loading of modifiers is 5 wt %, except for maleic anhydride (MAH).
The loading of MAH is limited to 3.5 wt % and, in a separate
sample, 1.75 wt % due to its limited solubility in styrene. In
Table 1, below, PDI represents polydispersity index wherein
PDI=Mw/Mn, Tg.sub.1 represents the first glass transition
temperature and Tg.sub.2 represents a second glass transition
temperature, if applicable.
TABLE-US-00001 TABLE 1 Characterization of Modified Polystyrene SMA
1000P SMA 3000P SMA EF80 Modifier None (1:1) (3:1) (8:1) wt % 0 5.0
5.0 5.0 mol(# of moles of 0 0.025 0.012 0.005 polar monomer
unit)/(100 g of polymer) Transparency Clear Opaque Opaque Opaque
Tg.sub.1 105.2 104.8 104.5 104.4 Tg.sub.2 n/a 169.3 n/a n/a Melt
Flow Rate 2.1 2.2 2.8 2.9 Mn 130,000 138,000 132,000 84,100 Mw
271,000 273,000 269,000 262,000 Mz 415,000 439,000 418,000 417,000
PDI 2.1 2.0 2.0 3.1 Peak MW 259,000 255,000 259,000 265,000 Butyl
Butyl Modifier Acrylate Methacrylate HEMA MAH MAH wt % 5.0 5.0 5.0
1.75 3.5 mol(# of moles of 0.039 0.035 0.038 0.018 0.036 polar
monomer unit)/(100 g of polymer) Transparency Clear Clear Clear
Clear Semi-clear Tg.sub.1 94.8 98.2 102.6 105.0 104.0 Tg.sub.2 n/a
n/a n/a n/a n/a Melt Flow Rate 3.3 2.9 1.7 2.2 3.3 Mn 136,000
122,000 128,000 115,000 97,300 Mw 184,000 260,000 312,000 250,000
220,000 Mz 433,000 398,000 529,000 391,000 350,000 PDI 2.1 2.1 2.4
2.2 2.3 Peak MW 271,000 250,000 270,000 239,000 212,000
[0047] An indicator of polarity change in polystyrene is how well
the material blends with another polar polymer such as polylactic
acid (PLA). In this experiment, the modified polystyrene samples
above were blended with 5 wt. % PLA 3251D (NatureWorks.RTM.
Ingeo.TM.) in a Haake mixer. The Haake mixer was operated at a
temperature of 210.degree. C. under a nitrogen atmosphere for 3
minutes with agitation speeds of 60 rpm. The size of the PLA
particles in the blends were evaluated by solution dynamic light
scattering. The blend samples were dispersed in methyl ethyl ketone
(MEK), a good solvent for polystyrene but not for PLA. FIG. 1 and
FIG. 2 show the PLA particle size distribution from different
polystyrene blends. FIG. 1 compares polystyrene copolymerized with
different comonomers. All of the polystyrene copolymer samples show
improved dispersion of PLA when compared to crystal polystyrene,
which suggests the polarity change in PS and better polar
interaction with PLA. Use of HEMA in PS gave the best result with a
relatively narrower distribution peaked at particle sizes of 0.5
.mu.m. Similar but slightly worse results were obtained with
polystyrene modified by butyl-acrylate/methacrylates as well as
maleic anhydride.
[0048] FIG. 2 compares polystyrene modified with different
styrene-maleic anhydride copolymers (SMAs). The SMAs were
incorporated into polystyrene during batch reactions. The PLA
particle size distributions from the SMA blends did not seem to
improve much compared to unmodified PS. The SMAs were not as
effective as polar comonomers, probably due to the relatively lower
molar concentration of polar groups of SMAs under the same weight
percentage loading (see Table 1 above). In addition, the SMAs
containing the higher percentage of maleic anhydride (such as 1000P
and 3000P) are less soluble in styrene. A miscible blend of GPPS
and SMA was only made with SMA EF80, which has a styrene-to-maleic
anhydride of 8:1 and contains the lowest concentration of maleic
anhydride among the various SMAs used. FIG. 2 also shows that use
of HEMA comonomer achieved the best result with a relatively
narrower particle size distribution peaked at particle sizes of 0.5
.mu.m.
Example 2
[0049] Hydroxyl functional polystyrene was prepared in a batch
reaction process by copolymerizing styrene with 2-hydroxyethyl
methacrylate (HEMA) at varied concentrations ranging from 0 to 5
wt. % in the feed (see Table 2). The polymerization reaction was
carried out in a CSTR-type batch reactor. Lupersol-233 was added as
the initiator with an initial concentration of about 170 ppm in the
reaction mixture. The reaction was then run isothermally at
130.degree. C. with continuous agitation at 150 rpm for about 3
hours or until 75% conversion was obtained. The reaction mixture
was then transferred onto an aluminum surface and devolatized under
active vacuum of less than 10 torr at 225.degree. C. for 45
minutes.
TABLE-US-00002 TABLE 2 Feed Formulations in Batch Synthesis of
HEMA-modified polystyrene Run No. 1 2 3 4 Styrene (grams) 200 198
195 190 HEMA (grams) 0 2 5 10 HEMA (wt. %) 0 1.0 2.5 5.0 TOTAL
(grams) 200 200 200 200
[0050] The concentration effect of hydroxyl groups on polystyrene
properties is shown in Table 3 below. It appears that the measured
molecular weights (Mw and Mz) increase while the melt flow rate
decreases as the concentration of HEMA increases. The results
suggest strengthened inter-chain interactions among polystyrene
chains, possible due to the presence of polar interactions such as
hydrogen bonding. The haul-off melt strength tests were also
conducted on the polystyrene samples. A clear trend can be observed
in FIG. 3, i.e., the melt strength of the material increases along
with the concentration of HEMA. The improvement in the melt
strength is desirable for foaming of polystyrene using CO.sub.2 as
the blowing agent.
TABLE-US-00003 TABLE 3 Characterization of HEMA-modified
polystyrene PDI HEMA Mn Mw Mz Mp Mw/ MFI Tg (wt. %) (g mol.sup.-1)
(g mol.sup.-1) (g mol.sup.-1) (g mol.sup.-1) Mn (g 10 min.sup.-1)
(.degree. C.) 0.0 129,000 269,000 408,000 260,000 2.1 2.2 104.4 1.0
135,000 329,000 515,000 309,000 2.4 1.1~2.5 104.1 2.5 142,000
336,000 523,000 315,000 2.4 1.9~2.3 103.2 5.0 127,000 355,000
584,000 320,000 2.8 0.3 103.1
Example 3
[0051] Polymerization reactions were conducted to prepare PS
copolymers containing different polar functional co-monomers. As
described in earlier examples, the polymerization reaction was
carried out in a CSTR-type batch reactor. Lupersol-233 was added as
the initiator with an initial concentration of about 170 ppm in the
reaction mixture. The reaction was then run isothermally at
130.degree. C. with continuous agitation at 150 rpm for about 3
hours or until 75% conversion was obtained. The reaction mixture
was then transferred onto an aluminum surface and devolatized under
active vacuum of less than 10 torr at 225.degree. C. for 45
minutes.
[0052] The co-monomers used include 2-hydroxylethyl methacrylate
(HEMA, 98%, CAS#868-77-9), glycidyl methacrylate (GMA,
CAS#106-91-2), butyl methacrylate (Butyl MA, CAS#97-88-1), isodecyl
methacrylate (Isodecyl MA, CAS#29964-84-9),
2,2,3,4,4,4-hexafluorobutyl acrylate (Fluorinated, CAS#54052-90-3),
3-(trimethoxysilyl)propyl methacrylate (Silyl, CAS#2530-85-0),
caprolactone acrylate (Caprolactone, CAS#110489-05-9), methoxy
polyethylene glycol (350) monomethacrylate (PEG350-MA,
CAS#26915-72-0) or methoxy polyethylene glycol (550)
monomethacrylate (PEG550-MA, CAS#26915-72-0).
[0053] The solubility and diffusivity of CO.sub.2 in the copolymers
were subsequently measured using the method described below. The
results are listed in Table 4, with other characterization
data.
Example 4
[0054] Measurement of CO.sub.2 Solubility
[0055] The general scheme of measurement is illustrated in FIG. 4.
Polymer samples were molded into disks with a thickness of 1.4 mm
and a diameter of 25 mm. The relatively large surface area on both
sides of the disks ensures that the diffusion of gas occurs mainly
in the normal direction of the disk planes. The sample disk was
weighed (M.sub.ini) and then transferred into a Parr pressure
vessel, which was purged with CO.sub.2 at least 3 times,
subsequently heated to 50.degree. C. and pressurized with carbon
dioxide to 1,500 psi to reach a supercritical state. Both
temperature and pressure were maintained for a period of time
(t.sub.3 in FIG. 4) to allow CO.sub.2 absorption into the sample
disk. The pressure is then released instantaneously to atmosphere
(at t.sub.4). The sample disk is quickly taken from the pressure
vessel and placed onto a moisture balance (Ohaus) to record the
weight loss as a function of time under ambient conditions.
Reduction of sample weight was observed due to desorption of
CO.sub.2. The dynamic evolution of weight (M.sub.t) was recorded by
a computer and WinWedge program. The dynamic weight change of the
sample disk recorded (after t.sub.5) was used to calculate the
CO.sub.2 solubility as well as diffusivity with the aid of Fick's
diffusion law and appropriate boundary conditions. The weight data
recorded (after t.sub.5) can be extrapolated to the initial weight
(at t.sub.4), prior to the depressurization, to obtain the CO.sub.2
absorption concentration as well as the desorption rate of
CO.sub.2.
[0056] The amount of CO.sub.2 remaining in the sample disk at any
given moment can be represented by M.sub.gas,t and calculated
according to equation: M.sub.gas,t
(M.sub.t-M.sub.ini)/M.sub.ini.times.100%. The amount of CO.sub.2
dissolved in a sample under equilibrium conditions is M.sub.gas,0
at t=0, i.e., right before the depressurization. M.sub.gas,t should
drop as a function of time (t) and eventually approach zero when
t=.infin..
[0057] To find the amount of CO.sub.2 dissolved in the sample prior
to the depressurization, one needs to extrapolate the data to t=0.
Assuming a constant diffusion coefficient of CO.sub.2, it can be
shown from literature that M.sub.gas,t is a linear function of the
square root of time:
M gas , t = M gas , 0 - 4 l D t .pi. M gas , 0 ( Equation 1 )
##EQU00001##
where l is the thickness of the sample disk and D is the diffusion
coefficient of CO.sub.2. Use of this equation implicitly assumes
uniformity of the initial gas concentration and homogeneity and
isotropy of the sample structure. It also implies that the
diffusion coefficient is constant regardless of the desorption
time, gas concentration in the sample during desorption and
temperature variation which could exist during the depressurization
process. By making a linear plot of M.sub.gas,t vs. t.sub.1/2, one
can calculate M.sub.gas,0 and D from the intercept (at t=0) and
slope, which corresponds to CO.sub.2 solubility and diffusivity in
the sample polymer, respectively.
[0058] CO.sub.2 Solubility in Modified PS
[0059] Dynamic CO.sub.2 solubility measurements were conducted on
an un-modified PS reference, commercial
poly(styrene-co-acrylonitrile) (SAN) and a series of
polarity-modified PS lab samples. Table 4 below lists the results
by the name of co-monomers in the polystyrene copolymers. A plot of
CO.sub.2 diffusivity versus solubility of various samples was also
constructed as shown in FIG. 5.
[0060] Compared to the un-modified polystyrene, SAN showed
significantly higher CO.sub.2 solubility (15.6%) and lower CO.sub.2
desorption diffusivity (1.1.times.10.sup.-7 cm.sup.2/s). The
affinity of polar groups in SAN toward CO.sub.2 may partially
explain, from an enthalpy point of view, the enhanced
(thermodynamic) solubility and slowed (kinetic) diffusivity. The
swelling in CO.sub.2 was small (<5% in thickness) for both SAN
and PS.
[0061] Besides SAN, it is clear that all the polarity-modified PS
copolymers show higher CO.sub.2 solubility, more or less, when
compared to the un-modified PS reference. The greatest CO.sub.2
solubility enhancement was observed on 3-(trimethoxysilyl)propyl
methacrylate-modified PS (Silyl-PS) with a 20% increase of
solubility. This was followed by PS copolymerized with alkyl
methacrylates or fluorinated acrylate. The fact that none of the
samples has lower CO.sub.2 solubility than the un-modified PS
demonstrates the effectiveness of polarity-driven structural
modification of PS for CO.sub.2 solubility enhancement.
[0062] The high gas diffusivity is not desired for foaming
processes as it has a negative impact on cell morphology control
and can lead to accelerated gas exchange with air (foam aging).
Among the different modified PS tested, there appear to be a few
copolymers which actually show lower diffusivity than the
un-modified PS reference. Examples include HEMA-, alkyl
methacrylate- and caprolactone-modified PS.
TABLE-US-00004 TABLE 4 CO.sub.2 Solubility and Diffusivity in PS
Copolymers (CO2 Soaking Conditions: 1500 psi, 50.degree. C.) Co-
Solubility Diffusivity monomer (g per 100 g (10.sup.-7
cm.sup.2sec.sup.-1, MI Sample (wt. %) polymer) 25.degree. C.) Swell
% T.sub.g (.degree. C.) (g/10 min) Mn Mw Mz Mw/Mn Mp PS Ref. 0 10.1
2.8 5% 104 2.2 129,000 269,000 308,000 2.1 260,000 SAN 25 15.6 1.1
4% 105 165000* HEMA 5.0 10.7 1.9 3% 103 0.3 127,000 355,000 584,000
2.8 320,000 HEMA 2.5 11.0 2.6 7% 103 1.9 142,000 336,000 523,000
2.4 315,000 GMA 5.0 11.0 3.0 4% 101 2.4 125,000 277,000 435,000 2.2
261,000 Butyl MA 5.0 11.4 2.3 2% 98 2.9 122,000 260,000 398,000 2.1
250,000 Isodecyl MA 5.0 11.7 2.8 13% 94 3.0 141,000 362,000 668,000
2.6 273,000 Flurinated 5.0 11.7 3.0 12% 96 n/a 125,000 265,000
409,000 2.1 252,000 Silyl 2.5 10.2 3.5 6% 101 2.6 128,000 298,000
493,000 2.3 260,000 Silyl 5.0 12.1 5.8 36% 97 n/a 132,000 335,000
630,000 2.5 261,000 Caprolactone 2.5 10.8 2.2 9% 92 n/a 139,000
522,000 1,144,000 3.8 248,000 PEG350 MA 5.0 11.4 n/a n/a 81 0.3
69,000 383,000 1,107,000 5.6 167,000 PEG550 MA 5.0 11.0 5.0 30% 80
4.4 106,000 334,000 681,000 3.2 242,000
[0063] The measured CO.sub.2 solubility data have indicated
enhanced CO.sub.2 solubility when the polar co-monomers of various
concentrations are incorporated into polystyrene. To compare the
modifier efficiency in CO.sub.2 solubility improvement, the portion
of CO.sub.2 solubility contributed by the co-monomer was normalized
based on the weight. The normalized data (Table 5 and FIG. 6)
showed that the silyl methacrylate and HEMA were more effective to
boost CO.sub.2 solubility than other co-monomers. Interestingly,
acrylonitrile had only moderate efficiency on CO.sub.2 solubility
enhancement, comparable to isodecyl- and fluorinated acrylates.
TABLE-US-00005 TABLE 5 Normalized CO.sub.2 Solubility and
Diffusivity in PS Copolymers (CO2 Soaking Conditions: 1500 psi,
50.degree. C.) Solubility Solubility Contribution -
S.sub.CO2-extra/ Diffusivity Co- (g per 100 g Comonomer Mass of
(10.sup.-7 cm.sup.2sec.sup.-1, Sample monomer(wt. %) polymer)
(S.sub.CO2-extra) Comonomer 25.degree. C.) PS Ref. 0 10.1 0.0 0.10
2.8 SAN 25 15.6 8.0 1.1 HEMA 5.0 10.7 1.1 0.22 1.9 HEMA 2.5 11.0
1.2 2.6 GMA 5.0 11.0 1.4 0.28 3.0 Butyl MA 5.0 11.4 1.8 0.36 2.3
Isodecyl MA 5.0 11.7 2.1 0.42 2.8 Flurinated 5.0 11.7 2.1 0.42 3.0
Silyl 2.5 10.2 0.4 0.14 3.5 Silyl 5.0 12.1 2.5 5.8 Caprolactone 2.5
10.8 1.0 0.38 2.2 PEG350 MA 5.0 11.4 1.8 0.36 n/a PEG550 MA 5.0
11.0 1.4 0.28 5.0
[0064] With both diffusivity and normalized solubility considered,
there appeared to be a few co-monomers which achieved a good
balance of diffusivity and solubility. Examples included the
caprolactone, butyl and hydroxyethyl methacrylate modified PS. The
CO.sub.2 solubility improvement in these modified PS exceeded that
in SAN while the diffusivity was well contained to be below that in
the un-modified PS. Commercial SAN has a very low CO.sub.2
diffusivity of 1.1.times.10.sup.-7 cm.sup.2/s, despite its high
CO.sub.2 solubility.
[0065] Overall, the results clearly demonstrate that the presence
of polar groups in polystyrene can lead to a higher CO.sub.2
solubility. A CO.sub.2 solubility enhancement will benefit foaming
of polystyrene using CO2 as the blowing agent.
[0066] As used herein, the term "monomer" refers to a relatively
simple compound, usually containing carbon and of low molecular
weight, which can react by combining one or more similar compounds
with itself to produce a polymer.
[0067] As used herein, the term "co-monomer" refers to a monomer
that is copolymerized with at least one different monomer in a
copolymerization reaction resulting in a copolymer.
[0068] As used herein, the term "homopolymer" refers to a polymer
resulting from polymerization of a single monomer species.
[0069] As used herein, the term "co-polymer," also known as a
"heteropolymer," is a polymer resulting from polymerization of two
or more monomer species.
[0070] As used herein, the term "copolymerization" refers to the
simultaneous polymerization of two or more monomer species.
[0071] As used herein, the term "polymer" generally includes, but
is not limited to homopolymers, co-polymers, such as, for example,
block, graft, random and alternating copolymers, and combinations
and modifications thereof.
[0072] As used herein, the terms "Continuous Stirred Tank Reactor,"
"Continuously Stirred Tank Reactor" and "CSTR," refer to a tank
which has a rotor that stirs reagents within the tank to ensure
proper mixing, a CSTR can be used for a variety of reactions and
processes and is generally known in the art.
[0073] The various embodiments of the present invention can be
joined in combination with other embodiments of the invention and
the listed embodiments herein are not meant to limit the invention.
All combinations of various embodiments of the invention are
enabled, even if not given in a particular example herein.
[0074] While illustrative embodiments have been depicted and
described, modifications thereof can be made by one skilled in the
art without departing from the spirit and scope of the disclosure.
Where numerical ranges or limitations are expressly stated, such
express ranges or limitations should be understood to include
iterative ranges or limitations of like magnitude falling within
the expressly stated ranges or limitations (e.g., from about 1 to
about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11,
0.12, 0.13, etc.).
[0075] Use of the term "optionally" with respect to any element of
a claim is intended to mean that the subject element is required,
or alternatively, is not required. Both alternatives are intended
to be within the scope of the claim. Use of broader terms such as
comprises, includes, having, etc. should be understood to provide
support for narrower terms such as consisting of, consisting
essentially of, comprised substantially of, etc.
[0076] Depending on the context, all references herein to the
"invention" may in some cases refer to certain specific embodiments
only. In other cases it may refer to subject matter recited in one
or more, but not necessarily all, of the claims. While the
foregoing is directed to embodiments, versions and examples of the
present invention, which are included to enable a person of
ordinary skill in the art to make and use the inventions when the
information in this patent is combined with available information
and technology, the inventions are not limited to only these
particular embodiments, versions and examples. Also, it is within
the scope of this disclosure that the aspects and embodiments
disclosed herein are usable and combinable with every other
embodiment and/or aspect disclosed herein, and consequently, this
disclosure is enabling for any and all combinations of the
embodiments and/or aspects disclosed herein. Other and further
embodiments, versions and examples of the invention may be devised
without departing from the basic scope thereof and the scope
thereof is determined by the claims that follow.
* * * * *