WO2000061360A1

WO2000061360A1 - Thermal managing foam insulation

Info

Publication number: WO2000061360A1
Application number: PCT/US2000/010195
Authority: WO
Inventors: Lendell Williams; John Nanos; Phil Sheridan
Original assignee: Lendell Manufacturing Inc.
Priority date: 1999-04-14
Filing date: 2000-04-14
Publication date: 2000-10-19
Also published as: AU4246600A; CA2369146A1; JP2002541314A; EP1169176A1

Abstract

A cellular foam product, which contains a phase change material in a non-microencapsulated medium. This medium, which contains the phase change material, is homogeneously dispersed within and throughout the cellular foam base. The amount and type of the medium, which contains the phase change material, can be optimized to allow for thermal managing and cellular properties. The resulting cellular foam product can be applied or laminated to various materials for apparel, insulation, cosmetic, medical, and other products requiring thermal management.

Description

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 1 1, 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. 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 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 (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. 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 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:

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 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 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. 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 (Δ H_f) 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 T_m was 28.6°C, T_c = 25.2°C, ΔT = 3.5°C, ΔH_f = 5.5 cal/g, ΔH_C = 5.6 cal/g. Similar values were obtained when run at 0.2°C per minute. Higher silica loaded 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.

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 T_m was 27.5°C, T_c = 26.3°C, ΔT = 1.5°C, ΔH_f = 29.5 cal/g, ΔH_C = 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. 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.

Claims

We claim:

1. An insulating thermal control material, comprising: a foam base material; and

a plurality of non-microencapsulated phase change materials dispersed throughout the foam base material, wherein said plurality of non- microencapsulated phase change materials are surroundingly embedded within the foam base material.

2. The insulating thermal control material of claim 1 , wherein the foam base material is a cellular foam matrix having a plurality of cells formed from air and gas pockets, and wherein at least a portion of said plurality of non-microencapsulated phase change materials are surroundingly embedded within said pockets.

3. The insulating thermal control material of claim 1, wherein the foam base material is a foamed organic plastic.

4. The insulating thermal control material of claim 1 , wherein the plurality of non-microencapsulated phase change materials includes paraffinic hydrocarbons.

5. A method of forming an insulating thermal control material, comprising:

providing a foam base material; and providing a plurality of non-microencapsulated phase change materials dispersed throughout the foam base material, wherein said plurality of non-microencapsulated phase change materials are surroundingly embedded within the foam base material.

6. The method of claim 5, wherein said foam base material is a polymer liquid, and wherein providing a plurality of non-microencapsulated phase change materials dispersed throughout the foam base material comprises: adding said plurality of non-microencapsulated phase change materials to the polymer liquid to form a mixture; mixing said mixture to disperse said plurality of non-microencapsulated phase change materials throughout said mixture; and foaming the mixture.

7. The method of claim 6, wherein a concentration of the plurality of non-microencapsulated phase change materials added to the polymer liquid to form the mixture is between 10 to 80 percent by weight.

8. The method of claim 6, wherein said plurality of non- microencapsulated phase change materials are mixed, absorbed and adsorbed with a silica prior to adding the said plurality of non-microencapsulated phase change materials to the polymer liquid.