U.S. patent application number 13/378284 was filed with the patent office on 2012-05-10 for thermally insulating polymer foam/aerogel composite articles.
Invention is credited to Friedhelm Bunge, Myron I. Maurer, Holger H. Merkel, Van-Chau Vo.
Application Number | 20120112117 13/378284 |
Document ID | / |
Family ID | 43447705 |
Filed Date | 2012-05-10 |
United States Patent
Application |
20120112117 |
Kind Code |
A1 |
Vo; Van-Chau ; et
al. |
May 10, 2012 |
THERMALLY INSULATING POLYMER FOAM/AEROGEL COMPOSITE ARTICLES
Abstract
Prepare an article of manufacture having an extruded
thermoplastic polymer foam defining at least one cavity, the cavity
containing aerogel material by providing a polymer foam defining a
cavity and placing the aerogel material into the cavity.
Inventors: |
Vo; Van-Chau;
(Souffelweyersheim, FR) ; Maurer; Myron I.;
(Saginaw, MI) ; Bunge; Friedhelm; (Achern, DE)
; Merkel; Holger H.; (Rodgau, DE) |
Family ID: |
43447705 |
Appl. No.: |
13/378284 |
Filed: |
July 15, 2010 |
PCT Filed: |
July 15, 2010 |
PCT NO: |
PCT/US2010/042036 |
371 Date: |
December 15, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61229417 |
Jul 29, 2009 |
|
|
|
Current U.S.
Class: |
252/62 |
Current CPC
Class: |
C08J 9/36 20130101; C08J
2205/026 20130101; C08J 2201/03 20130101 |
Class at
Publication: |
252/62 |
International
Class: |
E04B 1/78 20060101
E04B001/78 |
Claims
1. An article of manufacture comprising: a. an extruded
thermoplastic polymer foam that has a thermoplastic polymer matrix
defining a multitude of cells, the extruded thermoplastic polymer
foam defining at least one cavity; and b. aerogel material residing
within at least one cavity of the extruded thermoplastic polymer
foam.
2. The article of claim 1, wherein the extruded thermoplastic
polymer foam is free of halogenated blowing agents and has a
thermal conductivity of 35 milliWatts per meter per Kelvin or
less.
3. The article of claim 1, wherein the extruded thermoplastic
polymer foam defines multiple distinct cavities and residing within
more than one distinct cavity are aerogel materials.
4. The article of claim 1, wherein the aerogel material is entirely
enclosed within extruded thermoplastic polymer foam.
5. The article of claim 1, wherein at least one cavity of the
extruded thermoplastic polymer foam includes both aerogel and an
additional insulating material.
6. The article of claim 1, wherein the extruded thermoplastic
polymer foam has opposing first and second surfaces with at least
one cavity defined in a first surface and wherein the portion of
extruded thermoplastic polymer foam between the cavity and the
second surface has a higher density than the extruded thermoplastic
polymer foam on average.
7. The article of claim 1, wherein the aerogel is enclosed in a
metal or polymer enclosure and the combination of the enclosure and
aerogel reside in a cavity.
8. A process for manufacturing the article of claim 1, the process
comprising the following steps: (a) providing an extruded
thermoplastic polymer foam that defines at least one cavity; (b)
providing aerogel material; and (c) inserting the aerogel material
into a cavity defined by the extruded thermoplastic polymer
foam.
9. The process of claim 8, wherein step (a) includes extruding the
polymer foam in an absence of halogenated blowing agent.
10. The process of claim 8, wherein the polymer foam defines
multiple distinct cavities and step (b) includes providing multiple
aerogel materials and step (c) includes inserting aerogel materials
into multiple distinct cavities of the polymer foam.
11. The process of claim 8, wherein step (a) include cold forming
at least one cavity into the extruded thermoplastic polymer
foam.
12. The process of claim 8, further including step (d) of enclosing
the aerogel material within the cavity with extruded thermoplastic
polymer foam.
13. The process of claim 8, including adding to at least one cavity
of the extruded thermoplastic polymer foam both aerogel material
and an additional insulating material.
14. A process for using the article of claim 1 comprising the
steps: (a) providing an article of claim 1; and (b) positioning the
article of claim 1 as a barrier between two different areas.
Description
CROSS REFERENCE STATEMENT
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/229,417, filed Jul. 29, 2009, the entire content
of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a thermally insulating
article comprising extruded thermoplastic polymer foam and aerogel
material and the method of manufacturing such an article.
[0004] 2. Description of Related Art
[0005] Halogenated blowing agents are desirable for preparing
extruded thermoplastic polymer foams for thermal insulation at
least partially because halogenated molecules provide foam having a
low thermal conductivity. However, there are increasing regulations
on the use of halogenated molecules for applications such as
blowing agents due to perceived harm such molecules have on the
environment. Of particular concern is ozone depletion potential
(ODP) and greenhouse warming potential (GWP) of halogenated
molecules. Identifying blowing agents that have thermal
conductivities as low as halogenated molecules is a tremendous
challenge. As a result, it is increasingly more difficult to
manufacture thermally insulating extruded thermoplastic polymer
foams having desirably low thermal conductivities.
[0006] Highly thermally insulating compositions other than extruded
thermoplastic polymer foams are known in the art. Aerogel materials
are one type of highly thermally insulating compositions. Aerogel
materials typically have low densities with cell and pore
structures on the order of nanometers (for a good discussion of
aerogels see, for example, US2007/0014979 paragraphs [0013] to
[0019] which are incorporated herein by reference). The low density
of aerogel materials means most of the volume of the structure is
void space. The small cell and pore dimensions of aerogel materials
means there is little convection and conduction occurring through
the structure. Aerogel structures have desirable thermal insulating
properties but suffer from being much more costly and less durable
(more fragile) than extruded thermoplastic polymer foams (see, for
example, US2007/0014979 which teaches in paragraph 0007:
"Manipulation of aerogels, one of the best known insulators, can be
very challenging given the fragility of this material form.").
[0007] It would be desirable to incorporate aerogel materials into
extruded thermoplastic polymer foam and achieve sufficient
durability for use as thermally insulating materials for building
and construction applications. Current references describe layering
aerogel materials with other structurally sound materials to
achieve a layered laminate. (See, for example, EP1106346A2,
US2007/0014979A1, GB244756A, WO2008/129281A2, and
US2005/0281988A1). Laminate structures, however, have aerogel
material exposed on edges. Laminated structures also require
adhering aerogel materials to other substrates, which can result in
poor mechanical integrity of the laminated articles due to the
friable character of the aerogel layer.
[0008] Despite these prior efforts, it is still desirable to
develop extruded thermoplastic polymer foam articles that benefit
from the thermal insulating ability of aerogel materials but with
the durability, physical appearance and handling characteristics of
extruded thermoplastic polymer foam articles. Such articles would
be easy replacements for current extruded thermoplastic polymer
foam articles. Even more desirably, such an extruded thermoplastic
polymer foam article would enjoy high thermal insulating
characteristics without halogenated blowing agents.
BRIEF SUMMARY OF THE INVENTION
[0009] The present invention solves the problem of providing an
extruded thermoplastic polymer foam article that enjoys thermally
insulating benefits of aerogel materials but with the durability,
physical appearance and handling characteristics of extruded
thermoplastic polymer foam articles and without leaving aerogels
exposed around the perimeter of an article or requiring adherence
of the aerogel material to another substrate. Articles of the
present invention enjoy low thermal conductivity characteristics
(that is, a thermal conductivity of 35 milliwatts per meter*Kelvin
or less) without halogenated blowing agents.
[0010] In a first aspect, the present invention is an article of
manufacture comprising extruded thermoplastic polymer foam that has
a thermoplastic polymer matrix defining a multitude of cells, the
extruded thermoplastic polymer foam defining at least one cavity;
and aerogel material residing within at least one cavity of the
extruded thermoplastic polymer foam.
[0011] In a second aspect, the present invention is a process for
manufacturing the article of the first aspect, the process
comprising the following steps: (a) providing extruded
thermoplastic polymer foam that defines at least one cavity; (b)
providing aerogel material; and (c) inserting the aerogel material
into a cavity defined by the extruded thermoplastic polymer
foam.
[0012] The process of the present invention is useful for the
manufacture of the foam article of the present invention. The foam
article of the present invention is useful as thermal insulation
in, for example, building and construction applications.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 illustrates extruded polymeric foam components for an
embodiment of an article of manufacture of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0014] "Cavity" is a hollow space in a material. For the sake of
the present invention, a hole extending all the way through a
material falls outside the scope of the term "cavity". A cavity as
used herein generally is like a cave or indentation in a material.
A cavity can be entirely enclosed by a material. For example, a
cavity can be a void entirely enclosed by extruded thermoplastic
polymer foam. A cavity in a material generally is in a form of a
depression in the material. Notably, foam cells are cavities
defined in a polymer matrix--but are not cavities defined in
polymer foam. The article of the present invention includes a
"cavity defined in a polymer foam". Foam cells do not meet that
definition as they are defined in a polymer matrix and are
necessary features to define polymer foam. A cell cannot be defined
by a structure that itself is defined by the cell. A cavity defined
in polymer foam can have dimensions exceeding ten and even 100 foam
cells.
[0015] "Primary surface" is a surface of an article that has a
planar surface area equal to or greater than any other surface of
the article. Planar surface area refers to the area of a surface as
projected onto a plane and does not take into account surface area
due to peaks and valleys on a surface. Nonetheless, a primary
surface can be planar or non-planar. For example, a primary surface
can contain grooves, bumps, or any other contour.
[0016] Length, width and thickness are mutually orthogonal
dimensions of an article. Length is a dimension of an article equal
to the largest dimension. In an extruded article such as extruded
foam, length generally extends along the extrusion direction of the
foam. Width is equal to or larger in magnitude than the thickness.
In a board-like article, thickness extends from a primary surface
of the article to a surface opposing the primary surface.
[0017] ASTM refers to American Society for Testing and Materials.
EN refers to European Norm. Both ASTM and EN make reference to test
methods. Reference to test methods in the present document refers
to the most recent test method prior to the priority date of this
document unless otherwise noted. Test methods herein may specify a
year of the test method as a suffix to the test number.
[0018] Multiple means "two or more". "And/or" means "and, or as an
alternative to." All ranges include endpoints unless otherwise
noted.
[0019] The article of the present invention comprises extruded
thermoplastic polymer foam that defines at least one cavity.
Extruded thermoplastic polymer foam is a particular type of foam
that has been prepared by extruding a thermoplastic foamable
polymer composition in a softened state through a die from a zone
at a foaming pressure and temperature to an environment at a
pressure below foaming pressure and typically below the foaming
temperature. The foamable polymer composition expands and cools to
form extruded thermoplastic polymer foam. Extruded thermoplastic
polymer foam has characteristics unique from other types of polymer
foams such as thermoset foam and expanded bead foams. Thermoset
foams are not reversibly softenable like extruded thermoplastic
polymer foam. Once foamed and cured, thermoset foam can be crushed
but not melted or heat softened. In contrast, extruded
thermoplastic polymer foam has a continuous thermoplastic polymer
phase and as a result can melt or soften.
[0020] Expanded bead foams comprise a multitude of foamed beads
affixed to one another. Each foamed bead has a skin that defines
the bead. The skin of one bead is affixed to skins of adjoining
beads to form expanded bead foam. Each of the foamed beads is
evident in a cross section of the expanded bead foam due to the
skin that surrounds the foam cells of each foam bead. Bead skins
form a three-dimensional skin network throughout expanded bead foam
that encapsulates localized groups of foam cells that make up each
expanded bead. Often, the three-dimensional skin network is porous,
which can undesirably wick water through the foam. Extruded
thermoplastic polymer foam, in contrast, free of a
three-dimensional skin network that encapsulate localized groups of
foam cells and that extends throughout the foam. As a result,
extruded thermoplastic polymer foam is generally a better thermal
insulator than expanded bead foam because it does not have the
three-dimensional network of skins acting as a thermal short
connecting surfaces of the foam to one another. Extruded
thermoplastic polymer foam also is free of the undesirable porosity
often accompanying the three-dimensional skin network of expanded
bead foam and, hence, is typically more moisture resistant than
expanded bead foam.
[0021] Extruded thermoplastic polymer foam of the present invention
comprises a continuous thermoplastic polymer that defines a
multitude of cells. The thermoplastic polymer can be any one or
combination of more than one extrudable thermoplastic polymer.
Desirably, the thermoplastic polymer is one or a combination of
more than one polymer selected from alkenyl aromatic polymers and
olefinic polymers. Suitable alkenyl aromatic polymers include homo-
and copolymers of styrene or substituted styrene. Particularly
desirable alkenyl aromatic polymers include styrene homopolymer and
styrene-acrylonitrile copolymer. Desirable olefinic polymers
include ethylene and propylene homo- and copolymers.
[0022] The continuous thermoplastic polymer can have dispersed
therein additives and fillers. Suitable additives and fillers
include: infrared attenuating agents (for example, carbon black,
graphite, metal flake, titanium dioxide); clays such as natural
absorbent clays (for example, kaolinite and montmorillonite) and
synthetic clays; nucleating agents (for example, talc and magnesium
silicate); flame retardants (for example, brominated flame
retardants such as hexabromocyclododecane and brominated polymers,
phosphorous flame retardants such as triphenylphosphate, and flame
retardant packages that may including synergists such as, or
example, dicumyl and polycumyl); lubricants (for example, calcium
stearate and barium stearate); and acid scavengers (for example,
magnesium oxide and tetrasodium pyrophosphate). The total
concentration of additives and/or fillers can be up to 20
weight-percent (wt %), preferably up to 15 wt % and more preferably
up to 10 wt %. The amount of additives and/or fillers can be 0.05
wt % or more and even 0.1 wt % or more, even 0.2 wt % or more. Wt %
of additives and/or filler is relative to total weight of
continuous thermoplastic polymer.
[0023] The cells of the extruded thermoplastic polymer foam can be
open celled or closed celled. The extruded thermoplastic polymer
foam can be closed cell foam having an average open cell content of
30% or less, 20% or less, 10% or less, 5% or less and even 2% or
less. A low extent of open cells inhibits air movement from one
cell to another and thereby reduces thermal conductivity through
the foam. Alternatively, the extruded thermoplastic polymer foam
can have be open celled foam having an average open cell content of
more than 30%, even 50% or more. Measure average open cell content
according to ASTM method D6226-05.
[0024] The extruded thermoplastic polymer foam can have a uniform
open cell content or a graduated open cell content. For example, it
is desirable to have a graduated open cell content to cold form
cavities into the foam, with a gradient extending from greater open
cell content on a surface into which the cavity is formed to a
lower open cell content proximate to a surface opposite the surface
into which the cavity is formed. It is desirable to have a higher
degree of open cells proximate to the surface experiencing most
compression to enable gas pressure that would otherwise build up in
cells during compression to dissipate to neighboring cells.
Meanwhile, having a higher degree of closed cells proximate to the
side opposing that side being compressed is desirable to obtain
better barrier properties (for example, vapor barrier properties)
and strength than is achievable with open cells. Having a gradient
in open cell content as described allows the foam to simultaneously
facilitate compression molding a cavity while providing optimal
barrier properties and strength in the opposing surface to protect
the cavity contents (for example, a VIP).
[0025] The extruded thermoplastic polymer foam desirably has an
average cell size of less than one millimeter (mm), preferably 500
micrometers or less, more preferably 250 micrometers or less, still
more preferably 150 micrometers or less and can be 100 micrometers
or less. Smaller cell sizes are desirable for optimal thermal
insulating properties. Typically, the cells have an average cell
size of 10 micrometers or higher. Determine average cell size
according to ASTM D-3576-98.
[0026] The cells of the blowing agent can contain blowing agent.
Desirably, the cells are free of chlorinated blowing agent and more
desirably free of halogenated blowing agent.
[0027] The extruded thermoplastic polymer foam desirably has an
average density of 48 kilograms per cubic meter (kg/m.sup.3) or
less, preferably 40 kg/m.sup.3 or less, more preferably 35
kg/m.sup.3 or less and still more preferably 32 kg/m.sup.3 or less.
Lower density foam typically has a lower thermal conductivity than
higher density foam. Typically, the extruded thermoplastic polymer
foam has an average density of 16 kg/m.sup.3 or higher in order to
posses structural integrity during handling and protection of
aerogel material. Measure average density according to ASTM
D1622-08 (Standard Test Method of Apparent Density of Rigid
Cellular Plastics).
[0028] The foam can have a graduated density, which is desirable
when cold forming a cavity into the foam. For example, it is
desirable to have a graduated density to cold form cavities into
the foam where the gradient extends from lower density proximate to
a surface into which the cavity is formed to a higher density
proximate to a surface opposite the surface into which the cavity
is formed. It is desirable to have a lower density proximate to the
surface experiencing compression to facilitate local buckling and
collapse of the foam cell walls during compression. Lower density
foam has less wall mass, and less wall strength. Therefore, it is
easier to compress lower density foam. It is desirable to
simultaneously have a higher density foam proximate to the side
opposite the side being compressed to achieve maximum strength and
barrier properties between that surface of the foam and the cavity
in order to optimally protect contents of the cavity (for example,
a VIP in the cavity). The gradient in density allows one to
optimize both the compression of one side and the strength of the
opposing side at the same time.
[0029] Desirably, the extruded thermoplastic polymer foam has a
compressive strength of 100 kiloPascals (kPa) or higher and a
modulus of two megaPascals (MPa) or higher according to EN-826.
Higher compressive strengths and moduli are desirable to provide
greater protection of aerogel materials.
[0030] Desirably, the extruded thermoplastic polymer foam has a
water vapor permeability of less than 10 nanograms per meter per
second per Pascal (ng/m*s*Pa), preferably less than 5 ng/m*s*Pa and
most preferably less than 3 ng/m*s*Pa. Measure water vapor
permeability according to EN12086.
[0031] The extruded thermoplastic polymer foam defines at least one
cavity and can define multiple cavities. The cavity is a depression
within the extruded thermoplastic polymer foam in which another
object can reside. The cavity, or cavities, can have dimensions of
any size that fit within extruded thermoplastic polymer foam.
Typically, the cavities are depressions in a primary surface of the
extruded thermoplastic polymer foam but can be depressions in other
surfaces or combination of surfaces as well. Alternatively, the
cavities can be depressions solely in a primary surface of a foam.
A cavity can be a depression formed into an extruded thermoplastic
polymer foam or a void defined by combining extruded thermoplastic
polymer foam elements to define cavities (for example, gluing foam
walls together on a surface of a foam in a manner so as to define a
cavity within the walls). The extruded thermoplastic polymer foam
elements that define one or more cavity can be a single extruded
thermoplastic polymer foam or a combination of multiple extruded
thermoplastic polymer foams, wherein the multiple extruded
thermoplastic polymer foams can be the same or different in
composition. For example, extruded polyolefin foam walls can be
affixed to extruded polyalkenylaromatic polymer foam to create
extruded thermoplastic polymer foam that defines one or more
cavity.
[0032] The article of the present invention further comprises an
aerogel material. Aerogel materials are desirable due to the
extremely low thermal conductivity through an aerogel. The aerogel
material resides within a cavity of the extruded thermoplastic
polymer foam. More than one aerogel material may be present in the
article of the present invention. More than one aerogel material
can reside in a single cavity. Multiple cavities of the extruded
thermoplastic polymer foam can contain aerogel material. Any single
cavity can also contain one or more than one additional material,
including one or more than one additional thermally insulating
material, in addition to an aerogel material or instead of an
aerogel material provided at least one cavity contains an aerogel
material. One type of desirable additional material is a reflective
material such as a metal foil or reflective coating, which further
reduces thermal conductivity through the final article.
[0033] Desirably, the aerogel material resides entirely within a
cavity, meaning that an insulating material can be set over the
cavity and contact the surface of the extruded thermoplastic
polymer foam in which the cavity resides all around the periphery
of the cavity containing the aerogel material. Extruded
thermoplastic polymer foam provides optimal protection of the
aerogel material when the aerogel material resides entirely within
a cavity of extruded thermoplastic polymer foam, especially when
the aerogel material is entirely enclosed within extruded
thermoplastic polymer foam. It is also desirable for any additional
materials (particularly any additional thermal insulating
materials) residing in a cavity with the aerogel material reside
entirely within the cavity, preferably entirely enclosed by the
extruded thermoplastic polymer foam.
[0034] The aerogel material can be enclosed within the cavity in
which it resides, desirably enclosed by extruded thermoplastic
polymer foam. For example, desirably at least 5 millimeters (mm),
preferably at least 10 mm, more preferably at least 15 mm of
extruded thermoplastic polymer foam encloses (separates from
outside of the article) the aerogel material so as to provide
optimal protection of the aerogel material.
[0035] Suitable aerogel materials include any one or combination of
more than one silica aerogel, alumina aerogel, zinc oxide aerogel,
carbon aerogel and/or organic aerogel (for example resorcinol
formaldehyde aerogels). Suitable aerogels can be of any form
including granules (such as, Nanogel.TM. materials, Nanogel is a
trademark of Cabot Corporation) or fibrous blankets (for example,
Spaceloft.TM. and Cryogel.TM. brand materials, Spaceloft and
Cryogel are trademarks of Aspen Aerogels, Inc.).
[0036] Suitable metal foils for use as additional materials include
aluminum, gold, silver and copper foils as well as metal coatings
on plastic film (that is, metallized plastic film). The foils
typically have a thickness of one to 100 micrometers. Metallized
films can have a thickness in a range of 10 to 1500
micrometers.
[0037] In one desirable embodiment the aerogel material is fully
enclosed to provide the aerogel material optimal protection. There
are numerous configurations for extruded thermoplastic polymer foam
having a cavity that contains aerogel material residing in it
wherein the aerogel material is enclosed within the cavity and they
all fall within the broadest scope of the present invention.
[0038] It is within the scope of the present invention for the
extruded thermoplastic polymer foam to define or have attached
thereto a flap or hinged portion that covers a cavity. In one
position the hinged portion or flap reveals the cavity and in
another position the hinged portion or flap covers the cavity and
anything residing within the cavity. Such a hinged portion or flap
can be sealed over the cavity by use of an adhesive or other
fastener.
[0039] In one desirable embodiment, the article of the present
invention comprises a mating component that encloses at least one
cavity, preferably all cavities in the extruded thermoplastic
polymer foam. The mating component can be the same or different in
composition and/or properties as the extruded thermoplastic polymer
foam. For example, the mating component can be extruded
thermoplastic polymer foam of equivalent composition to the
extruded thermoplastic polymer foam defining the cavities. FIG. 1
provides an illustration of extruded polymeric foam of the present
invention that comprises a mating component. FIG. 1(a) illustrates
extruded thermoplastic polymer foam 10 having primary surface 15
and cavities 20. FIG. 1(b) illustrates extruded thermoplastic
polymer foam 10 and cavities 20 viewed as a cross section along
viewing line X in FIG. 1(a).
[0040] FIG. 1(c) illustrates a cross sectional view of extruded
thermoplastic polymer foam 10 as in FIG. 1(b) as well as a cross
sectional view of mating component 30. Mating component 30 has a
primary surface 35 having the same dimensions as extruded
thermoplastic polymer foam 10. Protrusions 40 fit into cavities 20
so as to seal them. FIG. 1(d) illustrates a cross sectional view of
extruded foam 20 including mating component 30 configured such that
mating component 30 seals cavities 20. Any one or any combination
of more than one of cavities 20 can contain aerogel material to
form an article of the present invention.
[0041] In an embodiment of the present invention the aerogel can be
enclosed within another material prior to being placed into a
cavity. For example, it is suitable to include aerogel enclosed in
a metal or polymer enclosure.
[0042] The article of the present invention desirably offers a
superior combination of durability and thermal insulating
properties than any of the extruded thermoplastic polymer foam or
aerogel or metal film alone. The article of the present invention
desirably has a thermal conductivity of 35 milliWatts per meter per
Kelvin (mW/m*K) or less, preferably 32 mW/m*K or less, still more
preferably 29 mW/m*K or less.
[0043] The article of the present invention can have edges that
have specific profiles or shapes. For example, opposing edges of
the article can have mating tongue and groove shapes or opposing
laps to coordinate positioning multiple articles next to one
another in a mating fashion. Profiling of the edges can be done by,
for example, machining or molding and can be done before or after
defining cavities and/or introduction of aerogel material into a
cavity of the article.
[0044] The article can have a planar surface or a contoured
surface. In one embodiment, the article has a primary surface that
defines grooves extending in at least one dimension, typically the
length dimension. Grooves are desirable in applications where, for
example, a coating material (for example, mortar or cement) will be
applied over the article because the coating material can penetrate
into the grooves and achieve better mechanical adhesion to the
article.
[0045] In general, prepare an article of the present invention by
providing an extruded thermoplastic polymer foam that defines at
least one cavity, providing aerogel material and inserting the
aerogel material into a cavity defined by the extruded
thermoplastic polymer foam.
[0046] Prepare extruded thermoplastic polymer foam in any manner.
It is common to prepare extruded thermoplastic polymer foam by
first forming a softened polymer composition in an extruder. The
polymer composition has a continuous thermoplastic polymer phase
that has a softening temperature. The thermoplastic polymers are as
described above for the thermoplastic polymers of the extruded
thermoplastic polymer foam. Prepare the softened polymer
composition by heating the polymer composition to a temperature
above its softening temperature (glass transition temperature for
amorphous polymers, melting temperature for semi-crystalline
polymers, and the highest glass transition temperature or melting
temperature represented by thermoplastic polymers continuous in the
polymer composition if there is a blend of thermoplastic polymers).
If blowing agent is not already present, introduce a blowing agent
into the softened polymer composition at an initial pressure that
is sufficiently high so as to preclude foaming of the polymer
composition in order to form a foamable polymer composition. It is
often desirable to cool the foamable polymer composition to a
foaming temperature that is still above the softening temperature
of the polymer composition and then extrude the foamable polymer
composition into an environment having a pressure lower than the
initial pressure and a temperature lower than the foaming
temperature. Allow the foamable polymer composition to expand into
extruded thermoplastic polymer foam.
[0047] Suitable blowing agents for preparing the extruded
thermoplastic polymer foam include any one or combination of more
than one of the following: inorganic gases such as carbon dioxide,
argon, nitrogen, and air; organic blowing agents such as water,
aliphatic and cyclic hydrocarbons having from one to nine carbons
including methane, ethane, propane, n-butane, isobutane, n-pentane,
isopentane, neopentane, cyclobutane, and cyclopentane; fully and
partially halogenated alkanes and alkenes having from one to five
carbons, preferably that are chlorine-free (e.g., difluoromethane
(HFC-32), perfluoromethane, ethyl fluoride (HFC-161),
1,1,-difluoroethane (HFC-152a), 1,1,1-trifluoroethane (HFC-143a),
1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,2 tetrafluoroethane
(HFC-134a), pentafluoroethane (HFC-125), perfluoroethane,
2,2-difluoropropane (HFC-272fb), 1,1,1-trifluoropropane
(HFC-263fb), 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea),
1,1,1,3,3-pentafluoropropane (HFC-245fa), and
1,1,1,3,3-pentafluorobutane (HFC-365mfc)); fully and partially
halogenated polymers and copolymers, desirably fluorinated polymers
and copolymers, even more preferably chlorine-free fluorinated
polymers and copolymers; aliphatic alcohols having from one to five
carbons such as methanol, ethanol, n-propanol, and isopropanol;
carbonyl containing compounds such as acetone, 2-butanone, and
acetaldehyde; ether containing compounds such as dimethyl ether,
diethyl ether, methyl ethyl ether; carboxylate compounds such as
methyl formate, methyl acetate, ethyl acetate; carboxylic acid and
chemical blowing agents such as azodicarbonamide,
azodiisobutyronitrile, benzenesulfo-hydrazide, 4,4-oxybenzene
sulfonyl semi-carbazide, p-toluene sulfonyl semi-carbazide, barium
azodicarboxylate, N,N'-dimethyl-N,N'-dinitrosoterephthalamide,
trihydrazino triazine and sodium bicarbonate. In a desirable
embodiment, the blowing agent is free of chlorinated blowing agents
and more preferably free of halogenated blowing agents. Halogenated
blowing agents, particularly chlorinated blowing agents, have a
stigma of having an undesirable affect on the environment.
Therefore, a blowing agent that is free of chlorinated or
halogenated blowing agents is desirably as being more
environmentally acceptable.
[0048] Use of carbon dioxide as a blowing agent, or one of multiple
blowing agents, is desirable to form polymer foam having cells with
a cell pressure below atmospheric pressure. Carbon dioxide escapes
from a polymer foam more rapidly than air permeates into the
polymer foam cells. As a result, foam cells blown with carbon
dioxide have a pressure below atmospheric pressure after carbon
dioxide escapes and until air can permeate in.
[0049] The extruded thermoplastic polymer foam defines at least one
cavity. Define cavities in extruded thermoplastic polymer foam in
any conceivable way. Suitable means of defining a cavity include
routing, assembling multiple extruded foam components together in a
way that define one or more cavity, and cold forming and/or hot
forming by compressing to form one or more than one depression. It
is within the scope of the present invention to combine multiple
extruded thermoplastic polymer foam elements together to define one
or more than one cavity as described with the article of the
present invention for the extruded thermoplastic polymer foam. The
extruded thermoplastic polymer foam elements can have the same
composition and properties or different composition and/or
properties. Another method of introducing a cavity is to make a cut
into extruded thermoplastic polymer foam so as to create a flap of
foam and then removing a portion of the extruded thermoplastic
polymer foam under the flap. The flap then can serve as a cover to
seal the cavity and its contents.
[0050] Extruded thermoplastic polymer foam can define a cavity in
any surface, but typically defines one or more cavity in a primary
surface of the extruded thermoplastic polymer foam. The cavity or
cavities can have any size or shape within the dimension of the
extruded thermoplastic polymer foam. Typically, the cavity (or
cavities) has dimensions exceeding ten or even exceeding 100 cell
dimensions. To be clear, the cells of the foam are not "cavities"
defined by the foam within the use of the term herein but rather
are defined by a polymer matrix to transform the polymer matrix
into foam. Cavities defined by the foam are defined by the cellular
polymer matrix, which necessarily includes foam cells.
[0051] One particularly desirable method for defining a cavity, or
multiple cavities, in a polymer foam is by using a cold forming
process. United States patent application US2009/0062410A1
(incorporated herein by reference in its entirety) provides a
general description of a cold forming process. In general,
introduce cavities into a polymer foam by cold forming by pressing
a molding projection into a polymer foam article thereby
compressing a portion of the polymer foam article by the projection
to create a cavity. The pressing and compression takes place at a
temperature below the softening temperature of the polymer foam,
typically at or near ambient temperature (approximately 25.degree.
C.), hence the name "cold" forming.
[0052] Cold forming offers a particularly desirable article of the
present invention because compressing the polymer foam article to
form cavities densifies the portion of foam between the cavity and
the outer surface of the foam opposite the foam surface into which
the cavity is impressed. That densified portion beneficially has a
higher durability than surrounding non-compressed foam and thereby
offers improved protection of aerogel material that resides in the
cavity of the final article from forces applied from outside the
foam. The densified portion of foam has a higher density than the
foam on average.
[0053] For cold forming cavities, it is ideal to use an extruded
thermoplastic polymer foam having any one, any combination of two,
three or having all four of the following characteristics: (a) a
cell pressure (pressure within the cells of the foam) that is below
one atmosphere, preferably 0.75 atmospheres or less; (b) higher
open cell content proximate to a surface impressed by a mold to
form a cavity (that is, an "impression surface") than proximate to
a surface opposing the impression surface, preferably having a
graduated open cell content; (c) a lower density proximate to an
impression surface than proximate to a surface opposing the
impression surface, preferably having a graduated density; and (d)
an anisotropic compressive balance with a higher compressive
balance in the dimension of compression than dimensions orthogonal
to compression. The first characteristic (cell pressure)
facilitates compression without fracturing foam surrounding the
compressed portions of foam. The advantages of (b) and (c) are set
forth above in discussing extruded polymeric foam properties. The
benefit of (d) is that it promotes plastic versus elastic buckling
of cell walls during cold forming compression.
[0054] Provide aerogel material and insert the aerogel material
into a cavity defined by the extruded thermoplastic polymer foam.
It is acceptable to insert more than one aerogel material into a
single cavity, including more than one type of aerogel material
(for example, a combination of metal foil and aerogel or two
different types of aerogel materials). It is also acceptable to
insert aerogel material into more than one cavity if the extruded
polymeric foam defines more than one cavity.
[0055] The articles of the present invention are particularly
useful as thermal insulating materials. One method of using the
present articles is to provide the article and then position the
article as a barrier between two different areas. For example,
position articles of the present invention on a wall of a building
structure to thermally insulate the inside of the structure from
the outside of the structure. As another example, position the
articles of the present invention as walls around a container to
thermally insulate the inside of the container from the outside of
the container.
EXAMPLES
[0056] The following examples serve to further illustrate specific
embodiments of the present invention.
[0057] Provide an extruded thermoplastic polymer foam plank (110 mm
thick, 600 mm wide, 2200 mm long) that has a cell pressure below
atmospheric pressure, an anisotropic compressive balance with a
high vertical compressive balance, a density gradient of about 19%
from core to surface (core has a density 19% lower than the
surface) and an open cell content gradient such that the core is
has a higher open cell content than the surface. One such foam is
freshly foamed IMPAXX.TM. 300 brand energy absorbing foam (IMPAXX
is a trademark of The Dow Chemical Company). The foam has an
average density of 35 kg/m.sup.3 and a compressive strength at
23.degree. C. of 345 kPa at 10% compression, 375 kPa at 25%
compression and 434 kPa at 50% compression according to ASTM D1621.
Cut the planks lengthwise (parallel to a primary surface) through
the middle of the plank's thickness dimension to create two foam
boards having a thickness of approximately 55 mm. The cut surfaces
reveal the core of the foam, which has a lower density and higher
open cell content than the uncut opposing surface, and serve as
impression surfaces for the foams. Remove the skin of the uncut
surface opposite the cut surface (impression surface) to a depth of
7 mm. Cut the resulting skinned foam using a Baumer abrasive wire
saw to produce a polymer foam article having a length and width of
305 mm and a thickness of 53 mm to produce a cold forming foam
blank. Prepare two cold forming foam blanks for each sample.
[0058] Provide a cavity forming molding tool that has dimensions of
300 mm by 200 mm by 60 mm thick and that defines 16 square
projections 59.12 mm by 59.12 mm extending 30 mm of from a base,
the projections being equally spaced and separated from one another
by a 12.7 mm spacing. Such a cavity forming molding tool can be
prepared as a rapid prototype tool comprising ABS as designed and
built using a Maxum Fused Deposition Modeling process.
[0059] Mount the cavity forming molding tool to a moving platen on
a Carver compression molding machine. Position a cold forming foam
blank on the stationary platen of the compression molding machine
with the impression surface facing the cavity forming molding tool.
With the cold forming foam blank and cavity forming molding tool at
ambient temperature (approximately 25.degree. C.), compress the
cavity forming molding tool into the cold forming foam blank with
66.7 kiloNewtons (kN) (15,000 pounds) of hold force at a pump speed
of 90%, then relieve the compression and remove the cold forming
foam blank. The cold forming foam blank has 16 equally spaced
cavities, corresponding the 16 projections on the cavity forming
molding tool, that have a depth of approximately 28 mm. The
resulting cold forming foam blank serves as a cavity foam and has
an appearance similar to extruded foam 10 in FIG. 1.
[0060] Repeat the process on a second cold forming foam blank using
a lid forming molding tool instead of a cavity forming molding
tool. The lid forming molding tool has 16 square cavities having
dimensions of 59.08 mm by 59.08 mm by 10.02 mm deep separated from
one another by 12.74 mm so as to mate with the cavity forming
molding tool projections. Compress the lid forming molding tool
against the impression surface of the second cold forming foam
blank using the Carver compression molding machine at 66.7 kN
(15,000 pounds) of hold force to form 16 projections in the cold
forming foam blank that extend approximately nine mm above the
compressed surface outlining the projections. The resulting cold
forming foam blank serves as a lid foam and has an appearance
similar to extruded foam 30 of FIG. 1.
[0061] The lid foam mates with the cavity foam such that the
projections of the lid foam fit into and seal the cavities of the
cavity foam to form 16 enclosed cavities, as illustrated with
extruded foams 10 and 30 in FIG. 1.
Comparative Example A
[0062] Measure the thermal conductivity of the cavity foam mated
with the lid foam, but without including aerogel. Mate the extruded
polymeric foam boards so that the protrusions extend into the
cavities and the board with the protrusions seals the cavities.
Example 1
[0063] Repeat Comparative Example (Comp Ex) A except insert aerogel
material (Spaceloft.TM.-9251, Spaceloft is a trademark of Aspen
Aerogels) to a thickness of nine millimeters in each cavity of the
cavity foam prior to mating the cavity foam and lid foam together.
The aerogel in the final article is encapsulated within the
extruded thermoplastic polymer foam board composition.
Example 2
[0064] Repeat Example 1 but additionally include a 50 micrometer
thick layer of aluminum foil in each cavity after inserting the
aerogel but before mating the cavity foam and lid foam
together.
Example 3
[0065] Repeat Example 1 except insert the aerogel material to a
thickness of 18 millimeters in each cavity.
Example 4
[0066] Repeat Example 3 but additionally include a 50 micrometer
thick layer of aluminum foil in each cavity after inserting the
aerogel but before mating the two extruded polymer boards
together.
[0067] Measure the thermal conductivity of each of the samples
according to ASTM C-578 and the compressive modulus of each sample
according to EN-826. Table 1 contains results for the samples.
TABLE-US-00001 TABLE 1 Thermal Compressive Conductivity Modulus
Sample Description (mW/m*K) (kilopascals) Comp Ex. A Extruded Foam
with Cavities 45 2230 Ex 1 Extruded foam with cavities 33 2260
containing 9 mm aerogel Ex 2 Extruded foam with cavities 30 2380
containing 9 mm aerogel and 50 micrometer aluminum foil Ex 3
Extruded foam with cavities 27 2640 containing 18 mm aerogel Ex 4
Extruded foam with cavities 27 2230 containing 18 mm aerogel and 50
micrometer aluminum foil
[0068] These results illustrate a number of aspects of the present
invention. First, including aerogel in the cavities decreases
thermal conductivity of the extruded thermoplastic polymer foam
article quite dramatically and to a value below that of either
solid extruded foam or the extruded foam with empty cavities.
Including just nine millimeters of aerogel in the cavities reduces
the thermal conductivity of the article to 33 mW/m*K (Ex 1).
Including 18 mm of aerogel in the cavities reduces the thermal
conductivity of the article to 27 mw/m*K (Ex 2). Both of these
thermal conductivities are below that of just foam either with or
without cavities.
[0069] Second, the compressive strength of the extruded
thermoplastic polymer foam articles actually increased with
inclusion of aerogel, which is evidence of not only the protective
aspect of enclosing the aerogel in the extruded thermoplastic
polymer foam but that the combination actually increases the
article strength.
[0070] Third, inclusion of 50 micrometers of aluminum foil in
combination with aerogel into the cavities can further decrease
thermal conductivity through the foam article even over the foam
article containing just the aerogel material, particularly for
thinner aerogel materials.
[0071] Surprisingly, the examples achieve thermal conductivity
values below 35 mW/m*K, even below 30 mW/m*K with an absence of
halogenated blowing agent.
[0072] The Examples all illustrate a dramatic reduction in thermal
conductivity, even over solid extruded foam prior to defining
cavities (36 mW/m*K) while maintaining a compressive modulus well
above that of aerogel materials (less than 100 kPa). The higher
compressive modulus of the extruded thermoplastic polymer foam
protects the weaker aerogel material in the articles of the present
invention while the aerogel material reduces the thermal
conductivity through the article.
* * * * *