U.S. patent application number 16/865437 was filed with the patent office on 2020-08-20 for processing aids for use in manufacture extruded polystyrene foams using low global warming potential blowing agents.
The applicant listed for this patent is Owens Corning Intellectual Capital, LLC. Invention is credited to Nikoi Annan, Chase J. Boudreaux, S. Thomas Brammer, Raymond Marshall Breindel, Yadollah Delaviz, Barbara Fabian, Xiangmin Han.
Application Number | 20200262994 16/865437 |
Document ID | 20200262994 / US20200262994 |
Family ID | 1000004808719 |
Filed Date | 2020-08-20 |
Patent Application | download [pdf] |
United States Patent
Application |
20200262994 |
Kind Code |
A1 |
Han; Xiangmin ; et
al. |
August 20, 2020 |
PROCESSING AIDS FOR USE IN MANUFACTURE EXTRUDED POLYSTYRENE FOAMS
USING LOW GLOBAL WARMING POTENTIAL BLOWING AGENTS
Abstract
A foamable polymeric mixture is provided that includes a polymer
composition and at least one blowing agent. The blowing agent may
comprise any blowing agents known not to deplete the ozone or
increase the prevalence of global warming, such as CO.sub.2, HFO,
HFC and mixtures thereof. The foamable polymeric mixture may
further includes at least one processing aid comprising an organic
phase changing material. The inventive foamable mixture is capable
of processing at a pressure range of 800 to 1200 psi (5.5 to 8.3
MPa).
Inventors: |
Han; Xiangmin; (Stow,
OH) ; Breindel; Raymond Marshall; (Hartville, OH)
; Brammer; S. Thomas; (Kent, OH) ; Delaviz;
Yadollah; (Lewis Center, OH) ; Boudreaux; Chase
J.; (Canton, OH) ; Fabian; Barbara; (Medina,
OH) ; Annan; Nikoi; (Newark, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Owens Corning Intellectual Capital, LLC |
Toledo |
OH |
US |
|
|
Family ID: |
1000004808719 |
Appl. No.: |
16/865437 |
Filed: |
May 4, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15724835 |
Oct 4, 2017 |
10676581 |
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16865437 |
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14210970 |
Mar 14, 2014 |
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15724835 |
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61786965 |
Mar 15, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08J 2201/03 20130101;
B29C 48/022 20190201; C08J 2205/046 20130101; C08J 9/146 20130101;
C08J 2203/06 20130101; C08J 2203/02 20130101; C08J 2205/052
20130101; B29K 2105/04 20130101; C08J 9/122 20130101; C08J 2205/10
20130101; C08J 2203/142 20130101; B29K 2025/06 20130101; C08J
2325/06 20130101; C08J 9/009 20130101; C08J 2205/044 20130101; B29K
2105/048 20130101; C08J 9/0009 20130101; B29C 48/297 20190201; C08J
2203/162 20130101; C08J 9/08 20130101 |
International
Class: |
C08J 9/00 20060101
C08J009/00; C08J 9/12 20060101 C08J009/12; C08J 9/14 20060101
C08J009/14; C08J 9/08 20060101 C08J009/08; B29C 48/00 20060101
B29C048/00 |
Claims
1. A foamed insulation product comprising: a polymeric foam
composition comprising: polystyrene; a blowing agent composition,
and from 0.05 to 3 wt. % of an organic phase changing material
comprising synthetic beeswax; wherein the foamed insulation product
has an insulation R-value per inch of between 4 and 7.
2. The foamed insulation product of claim 1, wherein the blowing
agent composition comprises one or more of carbon dioxide,
hydrofluoroolefins, and hydrofluorocarbons.
3. The foamed insulation product of claim 2, wherein the blowing
agent composition comprises hydrofluoroolefins and
hydrofluorocarbons.
4. The foamed insulation product of claim 1, wherein the organic
phase changing material is micro encapsulated.
5. The foamed insulation product of claim 4, wherein the organic
phase changing material is microencapsulated by a polymer material
comprising one or more of melamine formaldehyde, urea formaldehyde,
and acrylate copolymer resins.
6. The foamed insulation product of claim 1, further comprising at
least one infrared attenuating agent.
7. The foamed insulation product of claim 1, wherein the foamed
insulation product is monomodal.
8. The foamed insulation product of claim 1, wherein the foamed
insulation product has a density of from 1 to 5 lbs/ft.sup.3.
9. The foamed insulation product of claim 1, wherein the foamed
insulation product has a compressive strength between 6 and 80
psi.
10. The foamed insulation product of claim 1, wherein the foamed
insulation product is a closed cell, extruded foamed insulation
product.
11. The foamed insulation product of claim 10, wherein the foamed
insulation product has an average cell size of from 0.005 to 0.6
mm.
12. The foamed insulation product of claim 11, wherein the foamed
insulation product has an average cell size of from 0.16 to 0.2 mm.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. Non-Provisional
application Ser. No. 15/724,835, filed on Oct. 4, 2017, which is a
continuation of U.S. Non-Provisional application Ser. No.
14/210,970, filed on Mar. 14, 2014, now abandoned, which claims the
benefit of U.S. Provisional Application No. 61/786,965, filed on
Mar. 15, 2013, the contents of each of which are incorporated
herein by reference in their entireties.
FIELD OF THE INVENTION
[0002] This invention relates to processes for forming polymeric
foams and particularly to the manufacture of extruded polystyrene
(XPS) foams in the absence of blowing agents that are known to
deplete the ozone and increase the prevalence of global warming.
This invention provides the use of a novel processing aid to
stabalize the XPS foaming extrusion process and increase the
operating window of XPS foam manufacturing.
BACKGROUND
[0003] The general procedure utilized in the preparation of
extruded synthetic foam bodies generally includes the steps of
melting a base polymeric composition, incorporating one or more
blowing agents and other additives into the polymeric melt under
conditions that provide for the thorough mixing of the blowing
agent and the polymer while preventing the mixture from foaming
prematurely, e.g., under pressure. This mixture is then typically
extruded through a single or multi-stage extrusion die to cool and
reduce the pressure on the mixture, allowing the mixture to foam
and produce a foamed product. As will be appreciated, the relative
quantities of the polymer(s), blowing agent(s) and additives, the
temperature and the manner in which the pressure is reduced will
tend to affect the qualities and properties of the resulting foam
product. As will also be appreciated, the foamable mixture is
maintained under a relatively high pressure until it passes through
an extrusion die and is allowed to expand in a region of reduced
pressure. Although reduced relative to the pressure at the
extrusion die, the reduced pressure region may actually be
maintained at a pressure above atmospheric pressure, for example up
to about 2 atm or even more in some applications, may be maintained
at a pressure below atmospheric pressure, for example down to about
0.25 atm or even less in some applications. Further, unless
indicated otherwise, all references to pressure provided herein are
stated as the absolute pressure.
[0004] The solubility of conventional blowing agents, such as
chlorofluorocarbons ("CFCs") and certain alkanes, in polystyrene
tends to reduce the extrusion melt viscosity and improve cooling of
expanded polystyrene melts. For example, the combination of pentane
and a CFCs such as Freon 11 and 12 is partially soluble in
polystyrene and has been used for generating polystyrene foams that
exhibited a generally acceptable appearance and physical properties
such as surface finish, cell size and distribution, orientation,
shrinkage and stiffness.
[0005] However, in response to the apparent contribution of such
CFC compounds to the reduction of the ozone layer in Earth's
stratosphere, the widespread use and accompanying atmospheric
release of such compounds in applications such as aerosol
propellants, refrigerants, foam-blowing agents and specialty
solvents has recently been drastically reduced or eliminated by
government regulation.
[0006] The divergence away from the use of CFCs has led to
utilization of alternative blowing agents, such as
hydrogen-containing chlorofluoroalkanes (HCFCs). However, while
HCFC's are considered to be environmentally friendly blowing agents
compared to CFCs, such compounds do still contain some chlorine and
are therefore said to have an ozone depletion potential.
[0007] Another alternative class of blowing agents,
hydrofluorocarbons (HFC's), are now being commonly used as more
ozone friendly options. Particularly, CF.sub.3CH.sub.2CF.sub.2H
(HFC-245fa), 1,1,1,2-tetrafluoroethane (HFC-134a) and
1,1-difluoroethane (HFC-152a), offer desirable improvements, such
as improved insulation, due at least in part to the low thermal
conductivity of the vapor.
[0008] Hydrocarbons such as pentane, hexane, cyclopentane and other
homologs of this series have also been considered.
[0009] A new generation of fluroralkene blowing agents have been
developed with low ODP (ozone depletion potential) and low GWP
(global warming potential) known as hydroflouroolefins (HFOs). HFOs
have been identified as potential low global warming potential
blowing agents for the production of thermoplastic foams, such as
polystyrene foam, for thermal insulation.
BRIEF SUMMARY
[0010] The general inventive concepts are directed to a foamable
polymeric mixture. The foamable polymeric mixture comprises a
polymer composition, such as a polystyrenic composition and at
least one blowing agent. The blowing agent may comprise any blowing
agents known not to deplete the ozone or increase the prevalence of
global warming. Such blowing agents may consist of, for example,
carbon dioxide, hydrofluoroolefins, and hydrofluorocarbons, along
with mixtures thereof. The foamable polymeric mixture may further
includes at least one processing aid comprising an organic phase
changing material. The inventive foamable mixture is capable of
processing at a pressure range of 800 to 1200 psi (5.5 to 8.3
MPa).
[0011] The general incentive concepts further relate to a method of
manufacturing extruded polymeric foam. The method includes
introducing a polymeric composition into a screw extruder to form a
polymer melt and injecting at least one organic phase changing
processing aid and at least one blowing agent into the polymer melt
to form an foamable polymeric material. The blowing agent
preferably comprises one or more low ozone depletion and low global
warming potential compounds, such as carbon dioxide,
hydrofluorocarbon, hydrofluoroolefin, and mixtures thereof. The
method further includes extruding the foamable polymeric
composition through a die under a processing temperature between
800 and 1200 psi (5.5 to 8.3 MPa) to produce a polymeric foam.
[0012] Further inventive concepts relate to an extruded polymeric
foam. The extruded polymeric foam is formed from a foamable polymer
material that includes a polymeric composition, at least one
blowing agent, and an organic phase changing processing aid. The
blowing agent may include one or more of carbon dioxide,
hydrofluoroolefin, hydrofluorocarbon, and mixtures thereof. The
processing aid may comprise an organic phase changing material. It
is an object of the present invention that wherein said foam has an
R-value between 4 and 7 per inch.
[0013] Additional inventive aspects relate to a foamable polymeric
mixture that includes a polymer composition, at least one blowing
agent, and at least one processing aid. The blowing agent
comprising at least one of carbon dioxide, hydrofluoroolefins, and
hydrofluorocarbons, and mixtures thereof. The processing aid may
include an organic phase changing material. The foamable polymeric
mixture is capable of forming an extruded polymeric foam having the
following properties: an R-value between 4 and 7 per inch, an
average cell size between 0.005 and 0.6 mm, a compressive strength
between 6 and 80 psi, a density between 1.3-4 pcf; and an open cell
content of less than 30 percent.
[0014] The foregoing and other objects, features, and advantages of
the general inventive concepts will become more readily apparent
from a consideration of the detailed description that follows.
DESCRIPTION OF THE DRAWINGS
[0015] Exemplary embodiments of the invention will be apparent from
the more particular description of certain example embodiments of
the invention provided below and as illustrated in the accompanying
drawings.
[0016] FIG. 1 is a schematic drawing of an exemplary extrusion
apparatus useful for practicing methods according to the
invention.
[0017] FIG. 2 is a graph depicting a DSC curve of an exemplary
phase changing processing aid.
[0018] FIG. 3 is a graphical depiction of the main effects from
polystyrene melt flow index, CO.sub.2 concentration, and phase
changing processing aids have on density.
[0019] FIG. 4 is a graphical depiction of the main effects from
polystyrene melt flow index, CO.sub.2 concentration, and phase
changing processing aids have on foam cell size.
[0020] FIG. 5 is a graphical depiction of the main effects from
polystyrene melt flow index, CO.sub.2 concentration, and phase
changing processing aids have on foam compressive strength.
DETAILED DESCRIPTION
[0021] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which the invention belongs. Although
any methods and materials similar or equivalent to those described
herein can be used in the practice or testing of the present
invention, the preferred methods and materials are described
herein. All references cited herein, including published or
corresponding U.S. or foreign patent applications, issued U.S. or
foreign patents, or any other references, are each incorporated by
reference in their entireties, including all data, tables, figures,
and text presented in the cited references. In the drawings, the
thickness of the lines, layers, and regions may be exaggerated for
clarity. It is to be noted that like numbers found throughout the
figures denote like elements. The terms "composition" and
"inventive composition" may be used interchangeably herein.
[0022] As used herein, the term "blowing agent" is understood to
include physical (e.g., dissolved gaseous agents) or chemical
blowing agents (e.g., a gas generated by decomposition). A blowing
agent is generally added to a molten polymer, e.g., in an extruder,
and under the proper conditions, to initiate foaming to produce a
foamed thermoplastic. The blowing agent expands the resin and forms
cells (e.g., open or closed pores). As the resin hardens or cures a
foam is produced with either the blowing agent trapped in the cells
or ambient air displaces the blowing agent in the cells. The
blowing agents discussed herein are preferred to be environmentally
acceptable blowing agents (e.g., they are generally safe for the
environment) as would be recognized by one of ordinary skill in the
art.
[0023] As used herein, unless specified otherwise, the values of
the constituents or components of the blowing agent or other
compositions are expressed in weight percent or % by weight of each
ingredient in the composition. The values provided include up to
and including the endpoints given.
[0024] The present invention relates to a polymeric foam and
polymeric foam products, such as extruded or expanded polystyrene
foams, formed from a composition that contains a foamable polymer
material, at least one blowing agent (for example,
hydrofluorocarbons (HFCs). hydrofluoroolefins (HFOs), and/or carbon
dioxide (CO.sub.2)), and a processing aid. The present invention
further relates to a method for manufacturing such a polymeric foam
or foam product. In some exemplary embodiments, the processing aid
makes it possible to employ blowing agents, such as CO.sub.2, HFO
and HFC, which have low global warming potential and low ozone
depletion potential, to make polymeric, closed cell foam under
traditional processing conditions.
[0025] FIG. 1 illustrates a traditional extrusion apparatus 100
useful for practicing methods according to the present invention.
The extrusion apparatus 100 may comprise a single or double (not
shown) screw extruder including a barrel 102 surrounding a screw
104 on which a spiral flight 106 is provided, configured to
compress, and thereby, heat material introduced into the screw
extruder. As illustrated in FIG. 1, the polymeric composition may
be feed into the screw extruder as a flowable solid, such as beads,
granules or pellets, or as a liquid or semi-liquid melt, from one
or more (not shown) feed hoppers 108.
[0026] The foamable polymer composition is the backbone of the
formulation and provides strength, flexibility, toughness, and
durability to the final product. The foamable polymer composition
is not particularly limited, and generally, any polymer capable of
being foamed may be used as the foamable polymer in the resin
mixture. The foamable polymer composition may be thermoplastic or
thermoset. The particular polymer composition may be selected to
provide sufficient mechanical strength and/or to the process
utilized to form final foamed polymer products. In addition, the
foamable polymer composition is preferably chemically stable, that
is, generally non-reactive, within the expected temperature range
during formation and subsequent use in a polymeric foam.
Non-limiting examples of suitable foamable polymer compositions
include at least one of the following materials: alkenyl aromatic
polymers, polyvinyl chloride (PVC), chlorinated polyvinyl chloride
(CPVC), polyethylene, polypropylene, polycarbonates,
polyisocyanurates, polyetherimides, polyamides, polyesters,
polycarbonates, polymethylmethacrylate, polyurethanes, phenolics,
polyolefins, styreneacrylonitrile (SAN), acrylonitrile butadiene
styrene, acrylic/styrene/acrylonitrile block terpolymer (ASA),
polysulfone, polyurethane, polyphenylenesulfide, acetal resins,
polyamides, polyaramides, polyimides, polyacrylic acid esters,
copolymers of ethylene and propylene, copolymers of styrene and
butadiene, copolymers of vinylacetate and ethylene, rubber modified
polymers, thermoplastic polymer blends, and combinations
thereof.
[0027] In one exemplary embodiment, the foamable polymer
composition is an alkenyl aromatic polymer material. Suitable
alkenyl aromatic polymer materials include alkenyl aromatic
homopolymers and copolymers of alkenyl aromatic compounds and
copolymerizable ethylenically unsaturated co-monomers. In addition,
the alkenyl aromatic polymer material may include minor proportions
of non-alkenyl aromatic polymers. The alkenyl aromatic polymer
material may be formed of one or more alkenyl aromatic
homopolymers, one or more alkenyl aromatic copolymers, a blend of
one or more of each of alkenyl aromatic homopolymers and
copolymers, or blends thereof with a non-alkenyl aromatic
polymer.
[0028] Examples of alkenyl aromatic polymers include, but are not
limited to, those alkenyl aromatic polymers derived from alkenyl
aromatic compounds such as styrene, alpha-methylstyrene,
ethylstyrene, vinyl benzene, vinyl toluene, chlorostyrene, and
bromostyrene. In at least one embodiment, the alkenyl aromatic
polymer is polystyrene.
[0029] It is to be appreciated that the properties of the extruded
foam or foam product may be modified by the selection of the
molecular weight of the polymer. For example, the preparation of
lower density extruded foam products is facilitated by using lower
molecular weight polymers. On the other hand, the preparation of
higher density extruded foam products is facilitated by the use of
higher molecular weight polymers or higher viscosity resins.
[0030] As the polymeric composition advances through the screw
extruder 100, the decreasing spacing of the flight 106, defines a
successively smaller space through which the polymer composition is
forced by the rotation of the screw. This decreasing volume acts to
increase the temperature of the polymer composition to obtain a
polymeric melt (if solid starting material was used) and/or to
increase the temperature of the polymeric melt.
[0031] In some exemplary embodiments, one or more polymer
processing aids and/or blowing agents may be provided through the
feed hopper 108. In other exemplary embodiments, as the polymer
composition advances through the screw extruder 100, one or more
ports may be provided through the barrel 102 with associated
apparatus 110 configured for injecting one or more polymer
processing aids into the polymer composition. Similarly, one or
more ports may be provided through the barrel 102 with associated
apparatus 112 for injecting one or more blowing agents into the
polymer composition.
[0032] Exemplary methods according to the invention may utilize one
or more of a variety of blowing agents to achieve the desired
polymeric foam properties in the final product. According to one
aspect of the present invention, the blowing agent composition
comprises one or more of CO.sub.2 and halogenated blowing agents,
such as hydrofluorocarbons (HFCs), hydrochlorofluorocarbons,
hydrofluoroethers, hydrofluoroolefins (HFOs),
hydrochlorofluoroolefins, hydrobromofluoroolefins,
hydrofluoroketones, hydrochloroolefins, and fluoroiodocarbons,
alkyl esters, such as methyl formate, water, and mixtures thereof.
In other exemplary embodiments, the blowing agent comprises one or
more of CO.sub.2, HFOs, HFCs, and mixtures thereof.
[0033] The blowing agent may be introduced in liquid or gaseous
form (e.g., a physical blowing agent) or may be generated in situ
while producing the foam (e.g., a chemical blowing agent). For
instance, the blowing agent may be formed by decomposition of
another constituent during production of the foamed thermoplastic.
For example, in the case of a blowing agent that comprises
CO.sub.2, a carbonate composition or polycarbonic acid may be added
to the foamable resin and carbon dioxide will be generated upon
heating during the extrusion process. In some exemplary
embodiments, CO.sub.2 is included as a blowing agent in an amount
from about 0.05 to 5.0 weight percent. In other exemplary
embodiments, CO.sub.2 is included in an amount between about 1.0
and 3.5 weight percent.
[0034] The blowing agent may further comprise one or more
hydrofluoroolefin blowing agents, such as for example,
3,3,3-trifluoropropene (HFO-1243zf); 2,3,3-trifluoropropene; (cis
and/or trans)-1,3,3,3-tetrafluoropropene (HFO-1234ze), particularly
the trans isomer; 1,1,3,3-tetrafluoropropene;
2,3,3,3-tetrafluoropropene (HFO-1234yf); (cis and/or
trans)-1,2,3,3,3-pentafluoropropene (HFO-1225ye);
1,1,3,3,3-pentafluoropropene (HFO-1225zc);
1,1,2,3,3-pentafluoropropene (HFO-1225yc); hexafluoropropene
(HFO-1216); 2-fluoropropene, 1-fluoropropene; 1,1-difluoropropene;
3,3-difluoropropene; 4,4,4-trifluoro-1-butene;
2,4,4,4-tetrafluorobutene-1; 3,4,4,4-tetrafluoro-1-butene;
octafluoro-2-pentene (HFO-1438);
1,1,3,3,3-pentafluoro-2-methyl-1-propene; octafluoro-1-butene;
2,3,3,4,4,4-hexafluoro-1-butene; 1,1,1,4,4,4-hexafluoro-2-butene
(HFO-1336 m/z); 1,2-difluoroethene (HFO-1132);
1,1,1,2,4,4,4-heptafluoro-2-butene; 3-fluoropropene,
2,3-difluoropropene; 1,1,3-trifluoropropene;
1,3,3-trifluoropropene; 1,1,2-trifluoropropene; 1-fluorobutene;
2-fluorobutene; 2-fluoro-2-butene; 1,1-difluoro-I-butene;
3,3-difluoro-I-butene; 3,4,4-trifluoro-I-butene;
2,3,3-trifluoro-1-butene; I, 1,3,3-tetrafluoro-I-butene;
1,4,4,4-tetrafluoro-1-butene; 3,3,4,4-tetrafluoro-1-butene;
4,4-difluoro-1-butene; I, I, 1-trifluoro-2-butene;
2,4,4,4-tetrafluoro-1-butene; 1,1,1,2-tetrafluoro-2 butene;
1,1,4,4,4-pentafluorol-butene; 2,3,3,4,4-pentafluoro-1-butene;
1,2,3,3,4,4,4-heptafluoro-1-butene;
1,1,2,3,4,4,4-heptafluoro-1-butene; and
1,3,3,3-tetrafluoro-2-(trifluoromethyl)-propene.
[0035] In some exemplary embodiments, the blowing agent may
comprise one or more hydrofluorocarbons. The specific
hydrofluorocarbon utilized is not particularly limited. A
non-exhaustive list of examples of suitable blowing HFC blowing
agents include 1,1-difluoroethane (HFC-152a),
1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1-trifluoroethane
(HFC-143a), difluoromethane (HFC-32), 1,3,3,3-pentafluoropropane
(HFO-1234ze), pentafluoro-ethane (HFC-125), fluoroethane (HFC-161),
1,1,2,2,3,3-hexafluoropropane (HFC 236ca),
1,1,1,2,3,3-hexafluoropropane (HFC-236ea),
1,1,1,3,3,3-hexafluoropropane (HFC-236fa),
1,1,1,2,2,3-hexafluoropropane (HFC-245ca),
1,1,2,3,3-pentafluoropropane (HFC-245ea), 1,1,1,2,3
pentafluoropropane (HFC-245eb), 1,1,1,3,3-pentafluoropropane
(HFC-245fa), 1,1,1,4,4,4-hexafluorobutane (HFC-356mff),
1,1,1,3,3-pentafluorobutane (HFC-365mfc), and combinations
thereof.
[0036] In some exemplary embodiments, the HFOs and/or HFCs may be
included as a blowing agent in an amount from about 0.05 to 5.0
weight percent. In other exemplary embodiments, the HFOs and/or
HFCs is included in an amount between about 2.0 and 4.0 weight
percent.
[0037] In addition to the blowing agents, one or more processing
aids may be added to the polymeric melt to increase the processing
window for the polystyrene foam manufacturing. In some exemplary
embodiments, the processing aid(s) comprises an organic low
molecular weight material, such as, for example a phase changing
material. A phase changing material is a material that has a
transition temperature from liquid to solid at a particular
temperature. The transition temperature of the phase changing
material may be varied in a wide temperature range (-40 to
150.degree. C.), depending on the different molecular chain
lengths. In some exemplary embodiments, the phase changing material
that has a transition temperature from liquid to solid at
24.degree. C. ("PT 24"). The phase changing material may comprise
organic phase changing materials, such as, for example, fatty acid
esters and wax, or a combination of the two. In some exemplary
embodiments, the organic phase changing material comprises between
about 16 and 18 carbons, such as an octyl ester of hexadecanoic
acid, also known as synthetic beeswax.
[0038] The processing aid may be included in any amount to provide
the required benefit to the polystyrene foam process. In some
exemplary embodiments, the processing aid is included in about 0.05
to about 10.0 weight percent. In other exemplary embodiments, the
processing aid is included in an amount from about 0.5 to about 3.0
weight percent.
[0039] The fatty acid esters may be pumped directly into an
extruder in the liquid form, or alternatively, the fatty acid
esters may be microencapsulated into powders and fed directly into
a hopper. The material used to microencapsulate the fatty acid
esters may comprise one or more polymers, such as, for example,
melamine formaldehyde, urea formaldehyde, and acrylate copolymer
resins. According to various aspects of the present invention,
microencapsulation of the fatty acid esters may reduce the
diffusivity of blowing agents by trapping the blowing agent gases
inside the microencapsulation shells. Such an encapsulation
provides controlled release, wherein the shell may let CO.sub.2
diffuse in, but will keep the fatty acid ester from diffusing out
of the shell. It is further contemplated that the fatty acid esters
be compounded into a carrier material, such as a polystyrene
polymer material, and incorporated into the masterbatch pellets for
direct delivery into the extruder.
[0040] Exemplary phase changing materials may include the materials
listed below in Table 1.
TABLE-US-00001 TABLE 1 Phase Changing Materials and corresponding
phase transition temperatures. Phase transition temperatures from
PCMs soilid to liquid (.degree. C.) Chemical composition PT-5 -5
Synthetic Beeswax PT24 24 Synthetic Beeswax PT24 microen- 24 80%
Synthetic Beeswax capsulated 20% encapsulated wall material powder
PT33 microen- 33 80% Synthetic Beeswax capsulated 20% encapsulated
wall material powder PT60 60 Synthetic Beeswax
[0041] FIG. 2 illustrates a DSC curve of one exemplary phase
changing material (PT24), in which the phase transition temperature
from solid to liquid is determined as the peak value of
24.61.degree. C.
[0042] Inclusion of a fatty acid ester processing aid(s) causes the
window available for processing to widen in various ways. For
instance, the chemical structure of phase changing materials may
make them more compatible with blowing agents and thus increase the
solubility of the blowing agents in polystyrene and decrease the
diffusivity of the gases out of the polystyrene. Additionally, the
low molecular weight of the phase changing materials may plasticize
the polystyrene melt and improve the rheological properties for
better foaming. The processing window may further be widened due to
the release of heat from the phase changing materials by changing
from liquid to solid phase during foam board cooling process, which
may slow down the melt gelation (board settling) process. By
widening the operating window, the foam is able to achieve
desirable properties, such as a sufficient R value.
[0043] The foamable composition may further contain at least one
infrared attenuating agent (IAA) to increase the R-value of the
foam product. Blowing agents such as HFCs and HFOs, while
environmentally friendly, tend to decrease the R-value of the foam
product compared to a conventional HCFC foamed product. It was
discovered, however, that the addition of low levels of an infrared
attenuating agent to a foamable composition containing such blowing
agents may increase the R-value of the foam to an amount at least
comparable to, or better than, a foam produced with an HCFC blowing
agent. Although the infrared attenuating agent increases the
R-value for foams that include HFO and/or HFC blowing agents, the
addition of infrared attenuating agents also tends to decrease the
cell size of the cells in the foam, which results in undesirable
final foamed products. In particular, small cell sizes tend to
increase board bulk density, increase product cost, and reduce the
process window during the extrusion process. Further, infrared
attenuating agents undesirably increase the melt rheology, which
will result in an increase of the die pressure.
[0044] Non-limiting examples of suitable infrared attenuating
agents for use in the present composition include nanographite,
carbon black, powdered amorphous carbon, asphalt, granulated
asphalt, milled glass, fiber glass strands, mica, black iron oxide,
metal flakes (for example, aluminum flakes), carbon nanotube,
nanographene platelets, carbon nanofiber, activated carbon,
titanium dioxide, and combinations thereof. In exemplary
embodiments, the infrared attenuating agent is present in the foam
composition in an amount from 0.005% to 5.0% by weight of the total
composition. In other embodiments, the infrared attenuating agent
may be present in an amount from 0.05 to 3.0% by weight, from 0.05
to 2.0% by weight, or from 0.1 to 1.0% by weight. In some exemplary
embodiments, the infrared attenuating agent is present in the
composition in an amount less than or equal to 0.5% by weight.
[0045] In at least one exemplary embodiment, the infrared
attenuating agent is nanographite. The nanographite can be
multilayered by furnace high temperature expansion from
acid-treated natural graphite or microwave heating expansion from
moisture saturated natural graphite. In addition, the nanographite
may be a multi-layered nanographite which has at least one
dimension with a thickness less than 100 nm. In some exemplary
embodiments, the graphite may be mechanically treated such as by
air jet milling to pulverize the nanographite particles. The
pulverization of the particles ensures that the nanographite flake
and other dimensions of the particles are less than 150
microns.
[0046] The nanographite may or may not be chemically or surface
modified and may be compounded in a polyethylene methyl acrylate
copolymer (EMA), which is used both as a medium and a carrier for
the nanographite. Other possible carriers for the nanographite
include polymer carriers such as, but not limited to, polymethyl
methacrylate (PMMA), polystyrene, polyvinyl alcohol (PVOH), and
polyvinyl acetate (PVA). In exemplary embodiments, the nanographite
is substantially evenly distributed throughout the foam. As used
herein, the phrase "substantially evenly distributed" is meant to
indicate that the substance (for example, nanographite) is evenly
distributed or nearly evenly distributed within the foam.
[0047] Further, the inventive composition may contain a fire
retarding agent in an amount up to 1.0% by weight. For example,
fire retardant chemicals may be added in the extruded foam
manufacturing process to impart fire retardant characteristics to
the extruded foam products. Non-limiting examples of suitable fire
retardant chemicals for use in the inventive composition include
brominated aliphatic compounds such as hexabromocyclododecane and
pentabromocyclohexane, brominated phenyl ethers, esters of
tetrabromophthalic acid, and combinations thereof.
[0048] Optional additives such as nucleating agents, plasticizing
agents, pigments, elastomers, extrusion aids, antioxidants,
fillers, antistatic agents, biocides, and/or UV absorbers may be
incorporated into the inventive composition. These optional
additives may be included in amounts necessary to obtain desired
characteristics of the foamable gel or resultant extruded foam
products. The additives may be added to the polymer mixture or they
may be incorporated in the polymer mixture before, during, or after
the polymerization process used to make the polymer.
[0049] Once the polymer processing aid(s), blowing agent(s), and
optional additional additives have been introduced into the
polymeric material, the resulting mixture is subjected to some
additional blending sufficient to distribute each of the additives
generally uniformly throughout the polymer composition to obtain an
extrusion composition.
[0050] This extrusion composition is then forced through an
extrusion die 114 and exits the die into a region of reduced
pressure (which may be above, or more typically below atmospheric
pressure), thereby allowing the blowing agent to expand and produce
a polymeric foam layer or slab. The polymeric foam may be subjected
to additional processing such as calendaring, water immersion,
cooling sprays or other operations to control the thickness and
other properties of the resulting polymeric foam product.
[0051] The foam composition produces rigid, substantially closed
cell, polymer foam boards prepared by an extruding process.
Extruded foams have a cellular structure with cells defined by cell
membranes and struts. Struts are formed at the intersection of the
cell membranes, with the cell membranes covering interconnecting
cellular windows between the struts. In the present invention, the
inventive composition produces substantially closed cellular foams
with an average density of 1.0 lbs/ft..sup.3 to 5.0 lbs/ft..sup.3,
or from 1.3 lbs/ft..sup.3-4.0 lbs/ft..sup.3. It is to be
appreciated that the phrase "substantially closed cell" is meant to
indicate that the foam contains all closed cells or nearly all of
the cells in the cellular structure are closed. In most exemplary
embodiments, not more than 30.0% of the cells are open cells, and
particularly, not more than 10.0%, or more than 5.0% are open
cells, or otherwise "non-closed" cells. The closed cell structure
helps to increase the R-value of a formed, foamed insulation
product. It is to be appreciated, however, that it is within the
purview of the present invention to produce an open cell structure,
although such an open cell structure is not an exemplary
embodiment.
[0052] Additionally, the inventive foam composition produces
extruded foams that have insulation values (R-values) of about
4.0-7.0 per inch. In at least one embodiment, the R-value 5.0 per
inch. In addition, the average cell size of the inventive foam and
foamed products is 0.005 mm (5 microns) to 0.6 mm (600 microns)
and, in some embodiments, from 0.160 mm (160 microns) to 0.200 mm
(200 microns). The extruded inventive foam may be formed into an
insulation product such as rigid insulation boards, insulation
foam, packaging products, and building insulation or underground
insulation (for example, highway, airport runway, railway, and
underground utility insulation).
[0053] The inventive foamable composition additionally may produce
extruded foams that have a high compressive strength, which defines
the capacity of a foam material to withstand axially directed
pushing forces. In at least one exemplary embodiment, the inventive
foam compositions have a compressive strength within the desired
range for extruded foams, which is between about 6 and 80 psi. In
some exemplary embodiments, the inventive foamable composition
produces a foam having a compressive strength between 20 and 68
psi.
[0054] In accordance with another exemplary aspect, the extruded
inventive foams possess a high level of dimensional stability. For
example, the change in dimension in any direction is 5% or less. In
addition, the foam formed by the inventive composition is desirably
monomodal and the cells have a relatively uniform average cell
size. As used herein, the average cell size is an average of the
cell sizes as determined in the X, Y and Z directions. In
particular, the "X" direction is the direction of extrusion, the
"Y" direction is the cross machine direction, and the "Z" direction
is the thickness. In the present invention, the highest impact in
cell enlargement is in the X and Y directions, which is desirable
from an orientation and R-value perspective. In addition, further
process modifications would permit increasing the Z-orientation to
improve mechanical properties while still achieving an acceptable
thermal property. The extruded inventive foam can be used to make
insulation products such as rigid insulation boards, insulation
foam, and packaging products.
[0055] have been described above both generically and with regard
to various exemplary embodiments. Although the general inventive
concepts have been set forth in what is believed to be exemplary
illustrative embodiments, a wide variety of alternatives known to
those of skill in the art can be selected within the generic
disclosure. Additionally, following examples are meant to better
illustrate the present invention, but do in no way limit the
general inventive concepts of the present invention.
EXAMPLES
[0056] The following examples introduce about 0.5.about.3.0 wt % of
phase changing processing aid materials into a polystyrene
formulation to facilitate XPS foam board extrusion using a
traditional extrusion processing line. The extrusion line had a
production rate of 100-160 kg/hr. The blowing agents used in the
foam board extrusion process included CO.sub.2 and/or HFO-1234ze.
The process produced foam boards having a thickness of about 1 inch
and a width greater than 20 inches using a foaming die temperature
between 110 to 130.degree. C. and a foaming die pressure between
800 to 1100 psi.
Example 1. Operating Window Expansion with Phase Changing Materials
in CO.sub.2 Foaming
[0057] One percent of PT24 microencapsulated powder containing 80%
phase changing material and 20% encapsultion wall material was
applied for XPS foaming using about 3.7-4.3% CO.sub.2 blowing
agent. A foam board with a 1 inch thickness was produced smoothly
and the properties of the resulting foam board are shown as Samples
1 & 2 in Table 2 below. The foam board properties are each
within the acceptable range for traditional foam borads.
Particulalry, the boards have a density between about 1.4 and 3
psi, an R-value of 4-7 per inch. a cell size between about 0.005
and 0.6 mm, a compressive strength between about 6 and 80 psi, and
an open cell content of less than 30 percent. On the contrary,
without the phase changing material, the process could not be
continued under the similar processing conditions due to the
overshooting of die pressure (Sample #3). This observation
indicates that phase changing materials are necessary to balance
the pressure profile in the XPS foaming extrusion line. This makes
the phase changing material a necessary processing aid that helps
to operate the extrusion at significantly lower pressures.
TABLE-US-00002 TABLE 2 Application of PCM (PT microencapsulated
powder) for CO.sub.2 XPS foaming. PT24 microencapsulated Die Foam
Cell Compressive Sample powder pressure density R size Open cell
strength # (wt %) (psi) (pcf) value (mm) (%) (psi) 1 1 1072 2.71
4.29 0.182 3.39 36.09 2 1 1081 1.87 4.15 0.201 4.59 20.74 3 0
>1200 N/A N/A N/A N/A N/A
Example 2. Application of PT24 Liquid in CO.sub.2 Foaming
[0058] A liquid processing aid, PT24, was injected directly into
the extruder with 3.5% CO.sub.2 as the blowing agent. An XPS foam
board with good surface quality was produced without any
modification to the traditional foaming conditions. The foam board
properties are illustrated below, in Table 3. This further proves
the benefit of using the subject phase changing materials as a
processing aid when using CO.sub.2 as the blowing agent.
TABLE-US-00003 TABLE 3 Application of PT24 liquid for CO.sub.2 XPS
foaming Foam Cell Compressive Sample PT24 liquid density R size
Open cell strength # (wt %) (pcf) value (mm) (%) (psi) 4 0.8 2.81
4.41 0.16 1.99 36.6 5 1.2 2.77 4.39 0.17 5.94 32.6 6 1.6 2.78 4.41
0.17 6.31 32.8
Example 3. Design of Experiment (DOE) of Using PT24
Microencapsulated Powder in CO.sub.2 Foaming
[0059] A Design of Experiment ("DOE") was developed to understand
the influence that phase changing processing aids have on foam
properties. A DOE is an information gathering exercise where one or
more variations are present. The particular DOE designed was based
on three key parameters: phase changing material usage level
(between 1 and 3 weight %), polystyrene melt flow index, and
CO.sub.2 concentration. A single DOE having three factors and two
levels (low and high) was performed.
[0060] The main effects from the three key parameters to foam
density, foam cell size, and compressive strength are summarized in
FIGS. 3, 4, & 5, respectively. FIG. 3 illustrates the effects
the various parameters have on foam density when exposed to both
low and high levels. For instance, at a high polystyrene melt flow
index, the foam density is also high. Conversely, as the CO.sub.2
or phase changing material concentration increases, the foam
density decreases. FIG. 4 illustrates the effects the various
parameters have on cell size. Based on the DOE results, it appears
that increasing the polystyrene melt flow also increases the foam
cell size; however, as was the case with density, increasing the
CO.sub.2 concentration lowers the cell size of the foam. The amount
of phase changing material does not seem to affect the foam cell
size. With regard to compression, FIG. 5 illustrates that a
decreased polystyrene melt flow index appears to also lower the
foam compressive strength, while increasing the amount of phase
changing material also lowers the foam compressive strength.
However, increasing the CO.sub.2 concentration seems to also
increase the compressive strength.
Example 4: Application of PT24 Microencapsulated Powder on
HFO-1234Ze Foaming
[0061] Phase changing materials were shown to be good processing
aids when using HFO and CO.sub.2 as the blowing agents. Table 4,
below, summarizes the manufactured foam board properties. Different
levels of HFO-1234ze were combined with different levels of
CO.sub.2. As a processing aid, 1.0 wt % PT24 microencapsulated
powder was included. Although the cell size is on the low end of
traditional XPS foams, other properties are well within the
acceptable range. Additionally, the process is more stable than
without phase changing materials as a processing aid.
TABLE-US-00004 TABLE 4 Application of PT24 microencapsulated powder
for HFO/CO.sub.2 XPS foaming. PT24 microencapsulated HFO- Foam Cell
Compressive Sample powder 1234ze CO2 density R size Open cell
strength # (wt %) (wt %) (wt %) (pcf) value (mm) (%) (psi) 7 1 2.5
3.0 2.90 4.74 0.10 1.25 71.3 8 1 2.5 3.0 2.94 4.72 0.10 1.34 77.4 9
1 2.5 2.7 2.85 4.74 0.10 1.98 63.0 10 1 4.0 2.1 2.94 4.88 0.09 0.33
70.5 11 1 4.0 2.1 2.85 4.81 0.09 1.79 75.7 12 1 4.0 1.0 3.36 4.93
0.13 1.71 67.9
[0062] Although the present invention has been described with
reference to particular means, materials and embodiments, from the
foregoing description, one skilled in the art can easily ascertain
the essential characteristics of the present invention and various
changes and modifications can be made to adapt the various uses and
characteristics without departing from the spirit and scope of the
present invention as described above and set forth in the attached
claims.
* * * * *