Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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THERMAL MANAGING FOAM INSULATION
This application claims priority under 35 U.S.C. ~ 119(e) from U.S.
Provisional Patent Application Serial Number 60/129,251 filed April 14, 1999
entitled "THERMAL MANAGING FOAM INSULATION", and U.S.
Provisional Patent Application Serial Number 60/133,627 filed May 11, 1999
entitled "THERMAL MANAGING FOAM INSULATION," the disclosures of
which are hereby incorporated by reference in their entirety.
FIELD OF THE INVENTION
The present invention relates to all insulating cellular foam products
that contain a non-microencapsulated medium containing phase change
material. The resulting cellular foam products are then used wherever thermal
management is required. These products include housing or other forms of
insulation, apparel or garments, outdoor clothing, liners, shoe products,
textiles or non-woven materials requiring insulating properties.
BACKGROUND OF THE INVENTION
The ability to manage heat has long been a requirement to attain a
useful or necessary material specification. When external heat sources are not
available, conservation of existing heat is imperative. This has been achieved
through the use of insulating materials.
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Most forms of insulation rely upon a reduction of heat flow in or out of
a system (for example a house) where it is surrounded by some environment
(the "outside"). The goal being to minimize the heat flow out of or from the
system to the environment. Simply put, insulation prevents heat from going
S into the cold outside environment.
Recently, the microencapsulation of phase change materials was
presented as a method by which phase change material (PCM) can be
contained. The microencapsulation only serves to contain the PCM's inside of
a micro-shell. The PCM is the substance that actually stores and releases
energy according to the targeted temperature. Furthermore, the desired PCM's
will regulate or stabilize a targeted temperature. Where traditional
insulation
works by only retarding heat flow, PCM's use the natural property of latent
heat energy to absorb or release the heat energy. The absorption or release of
energy occurs primarily during the phase change of the PCM.
SUMMARY OF THE INVENTION
It is the objective of the present invention to provide a thermal control
material having thermal energy storage and insulative properties for use as a
thermal barrier between a heat source and a heat sink.
The thermal control material comprises of a cellular foam base
material. A plurality of non-microencapsulated phase change materials
(NMPCM's) are homogeneously dispersed throughout the foam base material
such that the NMPCM's are surroundingly embedded within the base material,
and, may or may not be spaced from each other so that the base material
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(cellular foam matrix) is between the NMPCM's. There is generally not a
concern that the NMPCM's will be contacting each other, since there is not a
breakage concern as with micro-encapsulated PCMs. The preferred phase
change materials that are incorporated in the non-microencapsulated medium
includes, but is not limited to, paraffinic hydrocarbons. Furthermore, the
cellular foam may also include an anisotropic distribution of particles such
that they are concentrated closer to one end of the cellular foam product.
The non-microencapsulated entity serves as a carrier or medium in
order to contain the PCM's. The choice of a different or more advantageous
medium than the microencapsulated medium enables better heat transfer,
variety, and compatibility with the base cellular foam. Some of these
mediums include high surface area silica. These silica powders retain the
phase change material and are easily incorporated in cellular foam products
during processing. Other media are as simple as dispersed droplets of the
phase change material, which are ideally embedded and retained within the
cellular foam matrix itself.
The foregoing and other features, utilities and advantages of the
invention will be apparent from the following more particular description of a
preferred embodiment of the invention as described herein.
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DETAILED DESCRIPTION OF THE PREFERRED
EMBODIMENT
A plurality of non-microencapsulated phase change materials
(NMPCM's) are homogeneously dispersed throughout the foam base material
such that the NMPCM's are surroundingly embedded within the base material,
and, may or may not be spaced from each other so that the base material (i.e.,
cellular foam matrix) is between the NMPCM's. The NMPCM's contain the
phase change material that exhibits the desired thermal properties.
The cellular foam base material is a polymeric material such as a
foamed organic plastic. The air pockets, which comprise of the cells, can be
open or closed. Exemplary of acceptable polymers employed in the foaming
industry are polyurethane, ethylene/vinyl acetate (EVA) copolymer, latex,
polyethylene, polypropylene, butyl, silicone, cellulose acetate, neoprene,
epoxy, polystyrene, phenolic, polyvinyl chloride (PVC), and other related
polymers.
The NMPCM's can range in size from sub-micron (typically 0.005 to
0.025 microns for high surface area silica mediums), to several thousand or
more microns (such as those found in dispersed droplets of paraffin base phase
change materials embedded within the foam matrix) and are formed according
to conventional methods well known to those skilled in the art.
The NMPCM's exhibit a temperature stabilizing means (or phase
change material such as the paraffin octadecane) which is accomplished
through latent heat energy specific to the phase change material used (see
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Table A). Additionally, other phase change materials such as water, salt
hydrates, quaternary amines, clathrates, linear alkyl hydrocarbons, fatty
acids
and esters, glycerine, pentaerythritol, pentaglycol, pentylglycol,
polyethylene
glycol, and the like are characterized by having thermal energy storage
properties in the solid-to-liquid transition. Liquid to gas transitions are
also
possible, but these often present a problem due to the accompanying volume
and pressure changes.
Additionally, there exists compositional properties for a given
temperature range. For example, the melting point of a homologous series of
paraffinic hydrocarbons is directly related to the number of carbon atoms as
shown in the following Table A:
Hydrocarbon Carbon atoms Melting Point (degrees
Centigrade)
n-Octacosane 28 61.4
n-Heptacosane 27 59
n-Hexacosane 26 56.4
n-Pentacosane 25 53.7
n-Tetracosane 24 50.9
n-Tricosane 23 47.6
n-Docosane 22 44.4
n-Heneicosane 21 40.5
n-Eicosane 20 36.8
n-Nonadecane 19 32.1
n-Octadecane 18 28.2
n-Heptadecane 17 22
n-Hexadecane 16 18.2
n-Pentadecane 15 10
n-Tetradecane 14 5.9
n-Tridecane 13 -5.5
Each of the above materials can be incorporated into the non-
microencapsulated medium and is most effective near the melting point
indicated. The effective temperature range of the cellular foam can be
tailored
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to a specific environment by selecting the corresponding temperature PCM
and adding it to the non-microencapsulated medium. The cellular foam can
then be designed to have enhanced thermal characteristics over a wide range
of temperature or at discrete temperature ranges through proper selection of
phase change material.
In designing the cellular foam base, the desired NMPCM's are added to
the base polymer, prepolymer (liquid or solution), or reactants and
fabrication
is accomplished according to conventional or non-conventional foaming
techniques. During fabrication, selecting a liquid polymer and/or
elastomer/reactant, and then causing the foregoing to be foamed forms the
cellular foam. Common methods of foaming include adding a hardening agent
which causes a chemical reaction, thermally setting the base material with
heat, or bubbling a gas through the liquid polymer/elastomer while hardening,
or other methods well known to those skilled in the art. The NMPCM's
should be added to the liquid polymer/elastomer or reactants prior to
hardening and mixed therein to ensure interaction and equal dispersion
throughout the mixture. A typical conventional foaming process would
include adding the NMPCM's to the isocyanate or polyol side or both sides.
The foam samples described below were produced using the
commercially available prepolymer PRE'POL on the liquid polymer
component side. The NMPCM's were added to another component or the
reactant (aqueous) side. The aqueous or reactant side served to disperse the
NMPCM's and add other necessary surfactants and/or foaming chemicals. The
two components were mixed together in a typical AB component mix utilizing
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low pressure, high shear foaming equipment. The mixed, uncured foam was
poured onto a conveyor and made into continuous sheets, which were cured,
and dried. The uncured foam can also be poured into blocks for non-
continuous foaming processes. In addition, the NMPCM's have also been
added to the prepolymer or liquid polymer side and foamed.
It should be noted that after mixing, the NMPCM's particles are
interacted and/or dispersed and subsequent particles may or may not be spaced
apart from each other. Thus, when the base material is foamed by the methods
described above, the non-microencapsulated particles will be embedded within
a cellular foam base and further, the space between neighboring adjacent non-
microencapsulated particles will be base material and not necessarily the
foaming gas.
It is believed that the interaction/dispersing step coats the NMPCM's
and that the interaction of the polymer/elastomer maintains contact/embedding
around the NMPCM's during and after foaming. In addition, the surface
tension of the foamed bubble aids in preventing the NMPCM's from crossing
the boundary into the bubble. Thus, the gas pockets formed during foaming
are ideally substantially free of NMPCM's. Typical concentrations of
NMPCM's particles added to the base foam polymer range from about 10% to
80% by weight. The foregoing concentrations are believed to allow the foam
base material to possess enough NMPCM's for the thermal characteristics, but
not enough to interfere with the desired properties or structural integrity of
the
cellular foam base.
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It will be noted that the NMPCM's embedded within a foam as
described above are actually surrounded by the cellular foam matrix itself and
not by more than one distinct wall or separation. In the case of the high
surface area silica medium, the silica may be in direct contact with the
polymer foam matrix. It should be noted that some phase change material
may be adsorbed or absorbed to the surface of the silica, thus some phase
change material may be in direct contact with the polymer foam matrix. In the
case of the dispersed droplets of the phase change material, the phase change
material may be in direct contact and embedded within the cellular foam
matrix. These dispersed droplets can have a singular surfactant or chemical
dispersant layer or separation between the phase change material and cellular
foam matrix. The interaction of the phase change material with the medium
(such as the silica), or the physical embedding into the polymer foam matrix
is
a means for containing the phase change material. It is important to note that
the phase change materials should ideally have high latent heats of fusion (0
Hf) on the order of >30 calories per gram. Some of the pure alkyl
hydrocarbons have heats of fusion around 60 cal/g.
Several types of these NMPCM embedded cellular foam products have
been reduced to practice. The first being a open-celled hydrophilic
polyurethane foam product incorporated with 35.1% NMPCM consisting of
55/45 high surface area silica to an octadecane paraffin wax. DSC analysis at
2°C/min gave several thermal characteristics of the.resulting foam: the
Tm was
28.6°C, T~ = 25.2°C, DT = 3.5°C, OHf = 5.5 cal/g, OH~ =
5.6 cal/g. Similar
values were obtained when run at 0.2°C per minute. Higher silica loaded
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open-celled hydrophilic polyurethane foams were also produced incorporating
up to 55% silica NMPCM's. In addition, higher paraffin wax concentrated
silica were also produced using 60/40, 65/35, 68/32, and 70/30
silica/octadecane paraffin wax as the NMPCM's.
S Another open-celled hydrophilic polyurethane foam product
incorporated with 30.7%, 42.1%, and 50.3% NMPCM consisting of dispersed
droplets paraffin octadecane wax phase change material. DSC analysis at
2°
C/min of the 50.3% loaded foam gave several thermal characteristics: the Tm
was 27.5°C, T~ = 26.3°C, OT = 1.5°C, OHf = 29.5 cal/g,
OH~ = 29.6 cal/g.
Similar values were also obtained when run at 0.2°C per minute. It
is noted
that these directly dispersed NMPCM's are not "diluted" with a carrier
medium when incorporated into the foam matrix. As a result, higher heats of
fusion due to an effective concentration increase of phase change material are
realized.
1 S The foregoing embodiments and examples are to be considered
illustrative, rather than restrictive of the invention, and those
modifications,
which come within the meaning and range of equivalence of the claims, are to
be included therein. While the invention has been particularly shown and
described with reference to a preferred embodiment thereof, it will be
understood by those skilled in the art that various other changes in the form
and details may be made without departing from the spirit and scope of the
invention.
