MXPA00005994A - Evacuated insulation panel having non-wrinkled surfaces - Google Patents

Abstract

Evacuated insulation panel (10, 20), also referred to as vacuum insulation panel (VIP), comprising:A) a deformable receptacle (14, 24) which has been evacuated to an absolute pressure of about 10 torr or less and hermetically sealed surrounding B) a corestock (12, 22) of one or more porous or open-celled rigid material matrixes having one or more indentations (16, 26) therein which extend in at least one dimension across a surface of a rigid material matrix, wherein the receptacle (14, 24) substantially conforms to the shape of the corestock (12, 22) and the indentations (16, 26) therein and the finished panel (10, 22) has surfaces which are substantially non-wrinkled;and methods of making the panel (10, 20).

Description

INSULATED INSULATION PANEL WITH UNWRAPPED SURFACES REFERENCE WITH RELATED APPLICATION This application is a partial continuation of the Serial Number of the United States of North America 08 / 993,536, filed on December 18, 1997, allowed, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION This invention relates to an improved evacuated insulation panel, also referred to as a vacuum insulation panel (VIP), having a core material having indentations therein to provide a finished panel having non-insulating surfaces. wrinkled mechanically and aesthetically desirable. To significantly improve the operation of the insulation systems, the industry is currently evaluating evacuated or vacuum panel technology. The removal of substantial amounts of air or gas in the panels, provides the possibility of superior insulation performance. A useful evacuated panel is one that employs a panel core material of a matrix of rigid material of porous or open cells, such as a rigid alkenyl aromatic polymer foam of open cells. The open or porous cell structures of the foam and other matrices of rigid material allow the gases inside the material and the panel that contains it to be removed quickly and substantially completely. The rigid material matrix provides a core material of substantial mechanical strength and insulation performance. A problem with the use of panel core materials of different porous rigid or open cell matrices, including aromatic open cell alkenyl polymeric foams, is their tendency to wrinkle upon evacuation and / or exposure to elevated temperatures. . The wrinkling may result in a wrinkled surface appearance for the receptacle or enclosure that maintains a watertight seal on the panel. It would be desirable to have an evacuated insulation panel with a core material of a matrix of porous rigid material or open cells, including open cell alkenyl aromatic polymer foam, whose surface or surfaces exhibit an aesthetically desirable, relatively smooth and homogeneous surface, substantially free of wrinkles or ridges. Mechanically, for the use of these panels in other articles of manufacture, it would be desirable to produce panels having a substantially flat surface, such that the insulating panel can be placed or placed flush or adjacent to smooth and flat surfaces, such as interior of a refrigerator wall. It would also be desirable to be able to reduce the evacuation time compared to the panels of the prior art.

SUMMARY OF THE INVENTION In accordance with the present invention, an evacuated insulation panel is provided comprising: A) a deformable receptacle that has been evacuated to an absolute pressure of about 10 torr or less, and hermetically sealed around, B) a material of core of one or more rigid porous or open cell matrices, having one or more indentations therein, extending in at least one dimension through a surface of a matrix of rigid material, wherein the receptacle it substantially conforms to the shape of the core material and the indentations therein, and the finished panel has surfaces that are substantially unwrinkled. In another embodiment of the present invention, an evacuated insulation panel is provided, which comprises: A) a deformable receptacle that has been evacuated to an absolute pressure of about 10 torr or less, and hermetically sealed around, B) a material of core of one or more rigid porous or open cell matrices, which optionally have one or more indentations therein, which extend in at least one dimension through a surface of a matrix of rigid material, and C) one or more rigid plates having one or more indentations therein, the one or more plates adjacent to a larger surface being located of the core material, wherein the receptacle substantially conforms to the shape of the core material and to the plate or plates and the indentations therein, and the finished panel has surfaces that are substantially uncropped. In a preferred embodiment of the present invention, an evacuated insulation panel is provided, the panel comprising a core material of an open-cell alkenyl aromatic polymer foam and a deformable receptacle, the foam comprising an aromatic alkenyl polymer material comprising more than 50 weight percent aromatic monomeric alkenyl units, based on the total weight of the alkenyl aromatic polymer material, the foam having an open cell content of about 70 percent or more, the receptacle being able to receive the foam and sealing hermetically, placing the foam inside the receptacle, hermetically sealing the receptacle, evacuating the open cells of the foam and the interior of the receptacle up to an absolute pressure of approximately 10 torr or less, the foam having indentations therein that extend in two. dimensions through a super of the foam, the receptacle conforming substantially to the shape of the foam and to the indentations therein. In another embodiment of this invention, an evacuated insulation panel is provided, the panel comprising: a) a core material of an open cell alkenyl aromatic polymer foam, b) one or more rigid plates, and c) a deformable pocket, the foam comprising an aromatic alkenyl polymeric material comprising more than 50 weight percent aromatic monomeric alkenyl units, based on the total weight of the alkenyl aromatic polymeric material, the foam having an open cell content of about 70 per cent. one hundred or more, the plate being placed adjacent to a larger surface of the foam, the receptacle being able to receive the foam and the plate, and hermetically sealing, placing the foam and the plate inside the receptacle, hermetically sealing the receptacle, evacuating the open cells of the foam and the interior of the receptacle up to an absolute pressure of approximately 10 or less, the plate having one or more indentations therein, the receptacle conforming substantially to the shape of the foam and to the indentations within the plates. Further, according to the present invention, there is provided a method for manufacturing an evacuated insulation panel having a substantially unwrinkled surface, which comprises: a) providing a core material of one or more rigid porous material or cell matrices open; b) indentating one or more surfaces of the matrix, wherein the indentations extend in at least one dimension across the surface or surfaces of the matrix; c) providing a deformable receptacle capable of receiving and containing the core material, and placing the core material therein; d) evacuate the interior of the receptacle at an absolute pressure of 10 torr or less; e) hermetically seal the receptacle. Further, in accordance with a preferred embodiment of the present invention, there is provided a method for manufacturing an evacuated insulation panel having a substantially unwrinkled surface, which comprises: a) providing a core material of an aromatic alkenyl polymer foam of open cells comprising an aromatic alkenyl polymer material, the aromatic alkenyl polymer material comprising more than 50 weight percent of aromatic alkenyl polymer units, based on the total weight of the alkenyl aromatic polymer material, the foam having approximately 70 percent or more of open cell content; b) indentating one or more surfaces of the foam, wherein the indentations extend in two dimensions across the surface or surfaces of the foam; c) providing a deformable receptacle capable of receiving and retaining the foam; d) placing the foam inside the receptacle; e) evacuating the open cells of the foam and the interior of the receptacle at an absolute pressure of 10 torr or less; f) sealing the receptacle to form the panel; g) allowing the foam to wrinkle, and the receptacle to conform substantially within the indentations.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a plan view showing an embodiment of an evacuated insulation panel in accordance with the present invention. The panel has a foam core material that defines grooves diagonally disposed therein, running through its dimensions continuously. The foam core material is shown in a cut on the bottom left of the figure. Figure 2 is a plan view showing an embodiment of an evacuated insulation panel in accordance with the present invention. The panel has a foam core material (not shown) that defines grooves therein, in a rectangular grid that runs continuously through its dimensions. Figure 3A is an enlarged cross-sectional view of the panel of Figure 2, along line 3A-3A. The foam core material of the panel is shown. Figure 3B is an enlarged cross-sectional view, in sections, of the panel of Figure 2, from Figure 3A. Figure 4 is a plan view of an evacuated insulation panel, which is not in accordance with the present invention. The panel has a substantially wrinkled surface. A foam core material is shown in cuts in the lower left part of the figure. Figure 5A is an enlarged cross-sectional view of the panel of Figure 4. Figure 5B is an enlarged cross sectional view, in sections, of the panel of Figure 4, from Figure 5A.

Detailed Description of the Invention The present invention solves the problem of wrinkling of a surface or surfaces of an evacuated insulation panel having a core material therein, of a matrix of rigid porous material or open cells, such as a polymeric foam. alkenyl aromatic of open cells, by providing a core material having indentations therein. When the core material is wrinkled after evacuation and / or exposure to elevated temperatures, the deformable container or enclosure surrounding the core material is deformed to the wrinkled core material. The indentations provide an extra surface area for the receptacle to deform or conform inside. Without the indentations, wrinkles would form in the receptacle after the core material shrinks. The invention significantly improves the aesthetics and physical appearance of the panel. An additional benefit is a reduced evacuation time. Preferably, one or both of the matrices of rigid material porous or of open cells, and the one or more plates, have a plurality of indentations. The indentations necessarily extend in at least one dimension across the surface of a matrix of material, but preferably the indentations extend in two dimensions across the surface of one or both of the one or more matrices of porous rigid material. or of open cells, and the one or more plates. In one embodiment, the matrix has indentations thereon in a rectangular or cross-diagonal pattern that traverses substantially the entire surface of one or both of the one or more matrices of rigid porous material or open cells, and the one or more plates. In another embodiment, the matrix has indentations therein in a pattern of dimples across substantially the entire surface of one or both of the one or more matrices of rigid porous or open cell material, and the one or more plates. Although in general the indentations are approximately 3.2 millimeters or less in depth, and approximately 3.2 millimeters transversely, they can also be larger for particular core materials. The indentations on a surface or surfaces of the matrix, can take a variety of forms, such as dimples, grooves, or troughs. Indentations can take a regular or irregular pattern across a surface. Indentations can travel or spread across the surface in a continuous or non-continuous manner. The indentations extend in two dimensions through a surface or surfaces of the matrix. Preferential indentations generally extend from one edge of the matrix to the other. If the indentations are in the form of dimples, preferably they occur at regular intervals across substantially all of the surface or surfaces of the matrix. If the indentations are in the form of grooves or troughs, they preferably intersect as they travel or extend across the surface. Preferably, the indentations are provided at such an incidence and depth that the deformable receptacle rests on the surfaces of the matrix and the indentations in after the core material is shrunk, and that the surfaces of the receptacle are substantially free of debris. wrinkles In other words, the surface area of the additional core material provided by the indentations after shrinkage of the core material, preferably corresponds approximately to the total surface area of the anticipated core material as lost due to shrinkage. The indentations may be of any depth or width within the core material, but preferably have a depth of approximately 1/8 inch (3.2 mm) or less, and a width of approximately 1/8 inch (3.2 mm) or less. The indentations may be printed on the core material by any element known in the art, such as the following: a) passing the foam through a set of opposite printing rollers having a desired groove pattern as embossed ridges in the rollers; b) printing with opposing plates having the desired groove pattern as embossed ridges on the plates; c) printing the desired pattern with a series of wires placed adjacent to the core material; d) cutting the desired pattern in the core material using blades, saws, knives, or water spray; and e) melting the desired pattern in the core material with hot wires or other heat source. In the case of a) and b), momentary printing by embossed ridges is usually sufficient to leave permanent indentations, although an impression may be desirable for longer periods of time if the core material is being compressed for other reasons. Figures 1 and 2 show two embodiments of the present invention. In Figure 1, the panel 10 comprises a foam 12 and a receptacle 14. The grooves 16 are printed inside the foam 12, and run continuously in a diagonal or crossover pattern. The grooves 16 extend in two dimensions (length and width) substantially through the foam 12. In Figure 2, the panel 20 comprises a foam 22 and a receptacle 24. The grooves 26 are imprinted inside the foam 22, and they run it continuously in a rectangular pattern or cross grid. The receptacle 25 substantially conforms to the shape of the foam 22, and rests substantially within the grooves 26, as shown in Figure 3A and Figure 3B. The grooves 26 extend in two dimensions (length and width) substantially through the foam 22. The panels 10 and 20 each have a substantially unwrinkled appearance. Figure 4 shows a panel 30 that is not in accordance with the present invention. The panel 30 comprises a foam 32 and a receptacle 34. The receptacle 34 has wrinkles 36 therein. The receptacle 34 does not conform to the shape of the foam 32. The relief configuration of the wrinkles 36 is shown in Figures 5A and 5B. If a given wrinkle 36 is sufficiently large, it can define an evacuated cavity 38 below it above the foam 32. This invention can be useful for the manufacture of any vacuum insulation panel using a core material exhibiting shrinkage to the core. exposed to atmospheric pressure or elevated temperatures while encapsulated in a barrier bag or receptacle. Examples of core materials suitable for use in this invention are polystyrene foam; another open cell thermoplastic foam, such as polypropylene foam, preferably the polypropylene foam described in U.S. Patent No. 5,527,573, which is incorporated herein by reference; polycarbonate foams; thermosetting foams, such as polyurethane foam, epoxy resin foams, formaldehyde foams, phenolic foams, isocyanurate foams; or any other polymeric material, thermoplastic or thermoformable, that has an open cell structure that allows to remove air and gas from the cells before encapsulation. Other materials generally useful as core materials in the manufacture of vacuum insulation panels that can benefit from the application of this invention, are panels filled with silica or other powder, if the loose powder is compressed or bonded sufficiently in any way to form a unified structure, which is then marked to produce a smooth surface after evacuation. Additionally, this invention can be applied to glass fiber or glass bead compressed panels, if the core is sufficiently solid to allow marking the surface, and to airgel and xerogel filler materials, which exhibit shrinkage after encapsulation of the panel of vacuum insulation inton. Preferred core materials are polystyrene and polypropylene foams, with polystyrene foams being especially preferred. Before incorporation into an evacuated panel, a foam may be optionally compressed to increase the insulating ability on a per unit thickness basis, as taught in International Publication Number WO 97/27986, which is incorporated herein by reference. This reference teaches that the foams are desirably compressed from about 30 to about 90 percent, preferably from about 40 to about 70 percent, and more preferably from 50 to about 60, percent of their thickness or Initial (original) volume before compression. The compression levels vary as a function of the identity of the polymer, the physical properties of the foam, the level of evacuation, and the desired insulation performance. The compression to increase the insulating capacity on a base per unit thickness can be made by any element known in the art, such as between movable parallel opposed plates, between a movable plate and a stationary plate or surface, or rollers or bands opposite. The compression can be applied in one step or in multiple steps in sequence. When compression occurs in multiple steps, it is preferable to allow the foam to relax between the compression steps, removing the source of compression. Optionally, the foam can also be compressed to impart dimensional stability. The foam is compressed and simultaneously heated for a sufficient period of time to make the foam dimensionally stable. This compression and heating to impart dimensional stability is taught in case number 43401, filed July 14, 1997, which is incorporated herein by reference. The compression to impart dimensional stability must be maintained substantially at a desired level over a period of time. Normally, this compression will be performed by opposing parallel plates or bands placed to compress the opposite major surfaces of a foam together. The degree of compression required to impart dimensional stability can be as little as about 5 percent to about 10 percent of the initial thickness or volume prior to compression. In a preferred process, the compression and heating to impart dimensional stability is performed simultaneously with the indentation of a surface or surfaces of the foam. The foam is compressed by opposing parallel plates having raised surfaces corresponding to the desired indentation pattern. The foam is heated and compressed simultaneously for a sufficient period of time to impart dimensional stability and indentations to the foam. The period of time will depend on the composition of the foam and its physical properties, the degree of compression, and the exposure temperature. The time period can be as little as a few moments, but normally it will be about 1 minute or more. It is more typical of approximately 1 to 10 minutes. The heating step is performed or effected by heating an open cell alkenyl aromatic polymer foam, and holding it at a temperature for a sufficient time (in conjunction with the compression step) to impart dimensional stability to the foam. The required temperature will vary according to the physical properties of the polymer and the foam composition, but will normally be within about 10 ° C to 20 ° C (less than) of the glass transition temperature. For polystyrene resins of the type commonly employed in foams, typical glass transition temperatures are from about 100 ° C to 110 ° C. The exposure (heating) temperatures suitable for polystyrene foams will normally be from about 85 ° C to about 110 ° C. The temperature profile inside the foam can be uniform or non-uniform through it; the temperature profile may be non-uniform, provided that the temperature is at a sufficient level in both the external and internal portions of the foam, to impart the desired dimensional stability (in conjunction with the compression step). The foam can be evacuated by any element known in the art to remove gases, such as with a suction nozzle, or by being placed in an evacuated chamber. The hermetic seal of the deformable receptacle normally takes place after the desired level of evacuation has been reached. To reduce the time required to evacuate, the skin layer of the foam is preferably removed by flattening or shaving to obtain a maximum surface area of open cell exposure. The foam has an open cell content of about 70 percent or more, preferably about 90 percent or more, and more preferably about 95 percent or more, before compression, according to ASTM D2856 -TO. The foam of preference is as close as possible to be complete or 100 percent of open cells. The content of open cells after compression, if any, will be equal to, or greater than, the content of cells opened before compression. The panel and the open cells of the foam are evacuated to a partial vacuum or an almost total vacuum of absolute subatmospheric pressure. The foam is evacuated to an absolute pressure of about 10 torr or less, more preferably about 1 torr or less, and most preferably about 0.1 torr or less in its open cells. The foam (before compression, where appropriate) has a density of about 16 to about 150 kg / m3, and more preferably about 25 to about 60 kg / m3, in accordance with ASTM D-1622-88. The density of the foam will increase proportionally with compression. The insulation panel can be formed from any desired size, shape, thickness, or dimension. The panels are most commonly formed from foams that are square or rectangular in width and length. Foam foams and foamed foams are useful. Thicknesses of about 1/8 inch (3.2 millimeters) to about 2 inches (50.8 millimeters) are more common, but thicknesses outside this range are possible. Other possible forms include L-shaped foams, and block-shaped foams useful in the corners. The panel most commonly comprises a single layer or piece of foam, but may comprise two or more adjacent or stacked layers or pieces. The panel preferably contains an infrared attenuating agent (IAA) to improve its isolation performance. The IAA is preferably dispersed in the foam, but could be dispersed in one or more layers of film bonded to the foam or part of the receptacle as a part of a laminate. The IAA is composed of a substance different from the polymeric substrate of the foam in which it is incorporated. The IAA can absorb and / or reflect infrared radiation. Useful IAAs include chips in metal particles such as aluminum, silver, and gold; titanium dioxide; and carbonaceous substances such as carbon black, activated carbon black, and graphite. Useful carbon blacks include thermal black, furnace black, acetylene black, and channel black. Preferred IAAs are thermal black and graphite. The IAA preferably comprises between about 1.0 and about 25 weight percent, and preferably between about 2.0 and about 20 weight percent, and more preferably from about 3.0 to about 10 weight percent, based on the weight of the polymeric material. Various additives can be incorporated into the foam, such as inorganic fillers, pigments, antioxidants, acid scavengers, ultraviolet absorbers, flame retardants, processing aids, extrusion aids, and the like. The panel can be used to isolate a surface by applying it to the surface. These panels are useful in any conventional insulation applications, such as breast panels, buildings, and buildings, refrigerators, freezers, temperature controlled rooms, temperature-controlled shipping containers and containers, water heaters, trucks and refrigerated rooms, and so on. . A substantially wrinkle-free insulation panel can be formed in accordance with the following: a) providing a core material of an open cell alkenyl aromatic polymer foam comprising an aromatic alkenyl polymer material, b) indentating one or more surfaces of the foam; c) providing a deformable receptacle capable of receiving and retaining the foam; d) placing the foam inside the receptacle; e) evacuate the open cells of the foam and the interior of the receptacle; f) sealing the receptacle to form the panel; and g) allowing the foam to wrinkle and the receptacle to conform substantially within the indentations. The open cells and the interior of the panel are evacuated to about 10 torr or less, more preferably to about 1 torr or less, and more preferably to about 0.1 torr or less of absolute pressure. The receptacle or the enclosure of the evacuated panel can be formed of any of those known in the art. One embodiment of an evacuated panel employs a receptacle or enclosure formed of a laminated sheet of three or more layers. The outer layer comprises a scratch resistant material, such as a polyester or a nylon. An inner layer or layers comprise a barrier material, such as aluminum, polyvinylidino chloride, or polyvinyl alcohol. The barrier material may be in the form of a sheet or film applied separately, or in the case of a metal, it may be applied by vapor deposition. The inner layer comprises a heat-sealable material, such as polyethylene or an ethylene / acrylic acid copolymer. Additional teachings are seen in U.S. Patent Nos. 5,346,928 and 5,627,219, which are incorporated herein by reference.

To further improve the long-term operation of the vacuum panel, the interior evacuated from the panel can be provided with a "getter" material. The obtaining material adsorbs the gases and / or vapors that are filtered or permeate into the vacuum panel over time. Conventional procurement materials include metal and barium metal alloys, aluminum, magnesium, calcium, iron, nickel, and vanadium. Teachings of suitable procurement materials include, but are not limited to, those set forth in U.S. Patent Nos. 5,191,980; 5,312,606; 5,312,607; and in International Publication Number WO 93/25843, which are incorporated herein by reference. Other types of useful getter materials include conventional desiccants, which are useful for absorbing water vapor or moisture. These materials are conveniently incorporated into the evacuated insulation panel in the form of a package having a porous or permeable envelope or receptacle containing the material therein. Useful materials include silica gel, activated alumina, aluminum rich zeolites, calcium chloride, calcium oxide, barium oxide, and calcium sulfate. A preferred material is calcium oxide. Open cell foams of virtually any average cell size can be employed in the present invention, but it is preferable to use a foam with an average cell size as small as possible, to minimize the thermal conductivity of the foam. Preferred foams are microcellular, and have an average cell size of about 70 microns or less, more preferably of about 30 microns or less, and most preferably of about 10 microns or less, in accordance with ASTM D3576-77. The cell size or pore size (diameter) for microcellular foams is determined in accordance with ASTM D3576-77, except that the measurement is taken from the amplified photograph obtained by electron scanning microscope, instead of the measurement taken directly the foam. The foam can be formed from any thermoplastic polymer resin exhibiting a relatively high modulus, and which is capable of being blown into a foam. Preferred resins include those that exhibit a modulus greater than 30,000 pounds per square inch (206,850 kilopascals) in accordance with ASTM D695. Also useful are thermosetting polymeric foams, such as polyurethane foams that exhibit some degree of shrinkage after evacuation and / or exposure to heat or high temperature. A preferred foam is an extruded alkenyl aromatic polymer foam. The extruded alkenyl aromatic polymeric foams are generally prepared by heating a polymeric material to form a plasticized or melted polymeric material, incorporating therein a blowing agent to form a formable gel, and extruding the gel through a die. to form a foam product. Before being mixed with the blowing agent, the polymeric material is heated to a temperature at or greater than its glass transition temperature or its melting point. The blowing agent can be incorporated or mixed in the molten polymeric material by any element known in this field, such as with an extruder, mixer, blender, or the like. The blowing agent is mixed with the molten polymeric material at an elevated pressure sufficient to prevent substantial expansion of the molten polymeric material, and to generally disperse the blowing agent in a homogeneous manner therein. A nucleating agent additive may be mixed in the polymer melt, or it may be dry blended with the polymeric material before plasticizing or melting. The formable gel is usually cooled to a lower temperature to optimize or obtain the desired physical characteristics of the foam. The gel can be cooled in the extruder or other mixing device, or in separate chillers. The gel is then extruded or transported through a die in a desired manner to a zone of reduced or reduced pressure, to expand and form the foam. The lower pressure zone is at a lower pressure than the one where the foamable gel is maintained prior to extrusion through the die. The lowest pressure can be superatmospheric, subatmospheric (evacuated or vacuum), or it can be at atmospheric level. Most of the preferred microcellular foams are extruded microcellular alkenyl aromatic polymeric foams. They are preferred because it is possible to make these foams up to a relatively small average cell size, such as about 70 microns or less. Extruded open-celled microcellular aromatic alkenyl polymeric foams having an open cell content of about 70 percent or more, and an average cell size of about 70 microns or less, can be made by the following process: a) heating an aromatic alkenyl polymeric material to form a molten polymeric material; b) incorporating into the molten polymeric material a nucleating agent additive in from about 0.1 to about 5 parts by weight per 100 parts of the polymeric material; c) incorporating into the molten polymeric material, at an elevated pressure to form a foamable gel, a blowing agent, of which about 50 mole percent or more, and preferably about 70 mole percent or more, is selected from the group consisting of 1,1-difluoroethane (HFC 152a); 1, 1, 1-trifluoroethane (HFC-143a), 1,1,1, -tetrafluoroethane (HFC-134a), chlorodifluoromethane (HCFC 22), carbon dioxide (C02), and difluoromethane (HFC-32), chloride of ethyl, and mixtures of the above, based on the total number of moles of blowing agent, the blowing agent being present in from about 0.06 to about 0.17 grams-moles or less, and preferably from about 0.08 to about 0.12 grams. -moles or less per kilogram of polymeric material; d) cooling the foamable gel to a sufficient foaming temperature to form a foam having approximately 70 percent or more open cell contents; and e) extruding the foamable gel through a die into a lower pressure region to form the foam. Preferred foaming temperatures will vary from about 110 ° C to about 150 ° C, and preferably from about 115 ° C to about 125 ° C, depending on the foaming compositions and the process conditions. Additional teachings of microcellular foams are seen in International Publication Number WO 96/34038, which is incorporated herein by reference. Suitable alkenyl aromatic polymeric materials include alkenyl aromatic homopolymers and copolymers of alkenyl aromatics, and copolymerizable ethylenically unsaturated comonomers. The aromatic alkenyl polymer material may also include minor proportions of aromatic polymers other than alkenyl. The aromatic alkenyl polymer material may exclusively comprise one or more aromatic alkenyl homopolymers, one or more aromatic alkenyl copolymers, a mixture of one or more of each of the aromatic alkenyl homopolymers and copolymers, or mixtures of any of the foregoing. with an aromatic polymer other than alkenyl. Regardless of the composition, the aromatic alkenyl polymeric material comprises more than 50, and preferably about 70 percent or more by weight aromatic monomeric alkenyl units. More preferably, the aromatic alkenyl polymer material is comprised entirely of alkenyl aromatic monomer units. Suitable alkenyl aromatic polymers include those derived from alkenyl aromatic compounds, such as styrene, alphamethylstyrene, ethylstyrene, vinylbenzene, vinyltoluene, chlorostyrene, and bromostyrene. A preferred alkenyl aromatic polymer is polystyrene. Minor amounts of monoethylenically unsaturated compounds can be copolymerized, such as alkyl acids and esters of 2 to 6 carbon atoms, ionomeric derivatives, and dienes of 4 to 6 carbon atoms, with the alkenyl aromatic compounds. Examples of the copolymerizable compounds include acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, itaconic acid, acrylonitrile, maleic anhydride, methyl acrylate, ethyl acrylate, isobutyl acrylate, normal butyl acrylate, methyl methacrylate, vinyl, and butadiene. Preferred structures substantially comprise (ie, about 90 percent or more, preferably about 95 percent or more by weight), and more preferably entirely, polystyrene. It is contemplated that the present invention could be practiced by placing one or more rigid plates having indentations thereon on one or more surfaces of a foam inside an evacuated insulation panel. The indentations could take the form, the pattern, and the dimensions described above for the indentations inside the foam. The panel could be assembled as described above, except that one or more plates are inserted into the deformable receptacle, together with the foam. For a typical rectangular or square panel, the plates will normally be placed on the two largest surfaces of the foam. The plate or plates can be made of any natural or synthetic material, such as, for example, metals, wood, plastic, which is chemically inert to the core material and the receptacle, provided that it has sufficient rigidity to withstand deformation during the evacuation. After the evacuation of the panel and the shrinkage of the foam, the deformable receptacle will conform to the shape of the foam, and will rest substantially within the indentations of the plate or plates. The use of plates inside a vacuum insulation panel, or outside a vacuum insulation panel, protects low melting core materials from transient exposure to heat, as experienced during foaming of the Polyurethane foam around a vacuum insulation panel during the construction of an apparatus. Although the embodiments of the foam, the evacuated insulation panel, and the method of the present invention have been shown, with respect to specific details, it will be appreciated that, depending on the manufacturing process and the manufacturer's wishes, the present invention is It can be modified through different changes while still remaining within the scope of the novel teachings and principles set forth herein.

Example 1 Open cell polystyrene foam suitable for use in vacuum insulation panels was made, in accordance with U.S. Patent No. 5,674,915. This foam was compressed up to 2.5 centimeters (1 inch), as taught in International Publication Number WO 97/27986. Then serial lines were compressed on the surface of the foam on both sides, using the edge of the metal spatula that was 0.85 centimeters (1/3 inch) thick. These lines were permanently depressed on the surface of the foam, passing the spatula with pressure along the edge of a straight ruler, while pushing down with pressure. The resulting depressed lines in the foam were approximately 0.16 centimeters (1/16 inches) at the top, 0.008 centimeters (1/32 inches) at the bottom, and 0.16 centimeters (1/16 inches) deep. These depressions were placed in a diamond pattern, with the side of the parallel lines separated by 5.1 centimeters (2 inches), both on the upper and lower surface of the board. Vacuum panels without this pattern exhibited extremely large folds in the film after evacuation. Vacuum panels with this pattern have significantly reduced the folds of the film in a significant way.

Example 2 A foam produced in an identical manner was passed Example 1, through parallel compression rollers having an embossed pattern machined on the surface of the rollers, such that depressed lines were compressed in the foam as it passed between the rollers. These ridges on the compression rollers were 0.24 centimeters (3/32 inches) deep, 0.008 centimeters (1/32 inches) at the top, and 0.16 centimeters (1/16 inches) at the bottom. The pattern printed on the foam was a diamond shape with 5.1 centimeters (2 inches) between the parallel sides of the diamond. The vacuum insulation panels made with this foam showed significantly less wrinkling on the panel surface than the foam made without this pattern printed on the foam.

Example 3 An open-cell polyurethane foam with a cell size averaging 50 millimeters was prepared, with surface depressions equal to those of Example 1. The sample with the grooves has no film wrinkles on either side of the panel, while the sample that did not have superficial grooves, did have superficial wrinkles.

Claims (12)

1. An evacuated insulation panel, which comprises: A) a deformable receptacle that has been evacuated to an absolute pressure of about 10 torr or less, and hermetically sealed around, B) a core material of one or more rigid porous material matrices or of open cells, optionally having one or more indentations therein, extending in at least one dimension across a surface of a rigid material matrix, and optionally, C) one or more rigid plates having one or more indentations therein, the one or more plates being adjacent to a larger surface of the core material, wherein at least one of B) and C) has indentations, and wherein the receptacle substantially conforms to the shape of the core material and to the plate or plates and the indentations therein, and the finished panel has surfaces that are substantially not wrinkled.

The panel of claim 1, wherein one or both of the one or more matrices of rigid porous or open cell material, and the one or more plates, have a plurality of indentations.

The panel of one of claims 1 and 2, wherein the indentations extend in two dimensions across the surface of one or both of the one or more matrices of rigid porous material or of open cells, and the one or more plates. .

The panel of claim 3, wherein the matrix has indentations thereon in a rectangular or diagonal pattern crossed across substantially the entire surface of one or both of the one or more matrices of rigid porous material or of open cells, and the one or more plates.

The panel of one of claims 1 to 3, wherein the matrix has indentations thereon in a dimple pattern across substantially the entire surface of one or both of the one or more matrices of porous or rigid material. open cells, and the one or more plates.

The panel of one of the preceding claims, wherein the indentations are approximately 3.2 millimeters or less in depth, and approximately 3.2 millimeters or less in cross section.

The panel of one of the preceding claims, wherein the rigid material matrix of the core material comprises an open cell thermoplastic foam, a polycarbonate foam, a thermosetting foam, a polyurethane foam, an epoxy resin foam, a formaldehyde foam, a phenolic foam, an isocyanurate foam, silica, fiberglass, glass beads, or airgel, or xerogel.

The panel of claim 7, wherein the rigid material matrix of the core material comprises polystyrene or polypropylene.

The panel of claim 8, wherein the core material is a foam having an open cell content of about 70 percent or more, comprising an aromatic alkenyl polymeric material comprising more than 50 percent by weight. weight of alkenyl aromatic monomer units, based on the total weight of the aromatic alkenyl polymer material.

The panel of claim 8, wherein the foam comprises an aromatic alkenyl polymer material comprising about 70 weight percent or more of alkenyl aromatic monomer units, based on the total weight of the aromatic alkenyl polymer material, the foam having an open cell content of about 90 percent or more, the open cells of the foam and the interior of the receptacle being evacuated to an absolute pressure of about 1 torr or less, the foam having a density of about 16 to about 150 kilograms per cubic centimeter, the foam having an average cell size of about 70 microns or less.

11. The panel of claim 8, wherein the foam comprises an aromatic alkenyl polymer material comprising about 70 weight percent or more of alkenyl aromatic monomer units, based on the total weight of the alkenyl aromatic polymeric material, the alkenyl aromatic polymeric material comprising polystyrene, the foam having an open cell content of about 95 percent or more, with the open cells being evacuated from the foam and the interior of the receptacle up to an absolute pressure of about 0.1 torr or less, the foam having a density of about 25 to about 60 kilograms per cubic centimeter, the foam having an average cell size of about 30 microns or less.

12. A method for manufacturing an evacuated insulation panel having a substantially unwrinkled surface, which comprises: a) providing a core material of one or more rigid porous or open cell arrays; b) indentating one or more surfaces of the matrix, wherein the indentations extend in at least one dimension across the surface or surfaces of the matrix; c) providing a deformable receptacle capable of receiving and retaining the core material, and placing the core material therein; d) evacuate the interior of the receptacle up to an absolute pressure of 10 torr or less; e) hermetically seal the receptacle.