. CA 02249~37 1998-09-17 Le A 31 669-Forei~n Pt/vos/S-P
Vacuum insulation panel covered on both sides with metal-containin~ composite film or a metallic outer layer Vacuum insulation panels are conventionally used for thermal insulation. Known 5 vacuum insulation panels comprise a pre-colllpressed porous fill, a porous pressed board or an open-cell rigid foam as the substrate which, after evacuation, is covered with a gas-tight film, wherein the film is welded or bonded.
Such vacuum insulation panels are also already used in the production of 10 refrigerating chambers, for example refrigerators, being inserted between the outer and inner housing, and the rem~ining space between the outer and inner housing being foam-filled.
Examples of filling materials are precipitated, dried silicas, silica gels, fly ash, 15 org~ni~lly based open-cell foams such as open-cell rigid polyurethane foams or bonded, ground rigid polyurethane foam, such as are described, for example, in DE
4 439 331 and DE 4 439 328.
An asymmetrical structure is generally selected for the covering films, wherein one 20 side comprises diffusion-tight aluminium composite film and the other side is a multi-layer composite of plastics film.
Aluminium-containing composite films have not hitherto been used on both sides, so as to avoid heat flow by way of the sealing seam.
It has surprisingly been found that when metal-containing composite film or a metallic outer layer covers both sides, the contribution to heat conduction by way of the rim is negligible if vacuum insulation panels are used in a rectangular board size having an edge length of in each case at least 40 cm.
CA 02249~37 1998-09-17 Le A 31 669 The present invention therefore provides vacuum insulation panels which comprisean open-cell substrate covered on all sides with metal-cont~ining composite filmor a metallic outer layer and exhibit an edge length of in each case at least 40 cm.
5 An optionally pre-press-moulded fill of precipitated silica, silica gel and/orpowdered rigid polyurethane foam is a suitable substrate, wherein the press-moulding may take place in the presence of adhesives suitable for çncl-ring inherent stability. Boards of open-pore rigid polyurethane foam are further suitable as a substrate.
Boards of open-pore rigid polyurethane foam or boards of pre-press-moulded, optionally bonded, ground rigid polyurethane foam are preferably used as the substrate.
15 The vacuum insulation panels according to the invention have an edge length of at least 40 cm, preferably an edge length of 45 cm x 65 cm. The thickness of theboards according to the invention is normally within the range 0.5 to 5 cm.
Measurements have shown that metal-cont~ining composite films or metallic outer 20 layers do not influence the thermal conductivity of the vacuum insulation panels which they cover.
Flexible composite films comprising at least two layers are preferably used.
25 Aluminium-cont~inin~ composite films having aluminium layers from S to 25 ~m thick, preferably 9 to lS llm thick, are particularly preferably used.
Examples of possible compositions are:
30 polyethylene/aluminium/polyester polyethylene/aluminium/polyethylene/polyester polypropylene/aluminium/polyester.
CA 02249~37 1998-09-17 Le A 31 669 It is also possible to select the covering such that differently constructed composite films are used on the front and back sides of the panel. Thus, the composite film of one side may contain, for example, a 9 ~lm-thick aluminium layer and the other a 20 llm-thick aluminium layer.
s Plates of sheet steel are preferably used as the metallic outer layers, particularly preferably plates of sheet special steel.
Such metal-cont~ining composite films or metallic outer layers are already known10 and are available commercially.
The vacuum insulation panels according to the invention are produced by coveringthe substrate on both sides with the gas-tight metal-cont~ining composite film, followed, after evacuation, by welding or bonding the film in a manner which is 15 known per se, or by covering the substrate on both sides with the metallic outer layer, and evacuating and hermetically sealing it.
The vacuum insulation panels according to the invention are used for in~ ting the walls of refrigerating chambers or refrigeration appliances such as, for example, 20 refrigerators and freezers.
The invention is explained below with the aid of the attached Figure.
The Figure shows a cross section through a vacuum insulation panel according to 25 the invention, which comprises open-pore filling material 1 (for example ground rigid polyurethane foam press-moulded with polyisocyanate, as the substrate) anda metal-cont~ining composite film or a metallic outer layer 2.
It is the intention in the Examples below to explain the invention in greater 30 detail without, however, restricting the scope thereof.
CA 02249~37 1998-09-17 Le A 31 669 Examples Example 1 580 g of a ground rigid PUR foam from a refrigeration unit recycling plant are mixed uniformly with 20 g water and 58 g of a polyisocyanate mixture compri~ing diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates (Desmodur VP.PU 1520 A 20, from Bayer AG) using a Lodige plough-blade mixer having 2 nozzles. In a moulding frame a moulding is formed from this mixture and compressed uniformly; it is then pressed to 20 mm in a laboratory press at a pressure of S bar and a temperature of 120~C for 8 minutes with use of a time-measurement program.
A porous 20 mm board is obtained having a gross density of 200 kg/m3. The board is heated to 120~C for approximately 2 hours in order to remove all volatile constituents.
The board is covered on both sides with a plate of sheet steel, evacuated and hermetically sealed.
Example 2 A rectangular moulded body produced from ground rigid polyurethane foam press-moulded with polyisocyanate (method as in Example 1).
Size 40 x 40 x 2 cm3 Thermal conductivity at 0.6 mbar: 8.3 mW/mK
Example 3 Vacuum insulation panel comprising a rectangular moulded body produced from ground rigid polyurethane foam press-moulded with polyisocyanate (method as in Example 1) and covered on all sides with aluminium composite film cont~qining a CA 02249~37 1998-09-17 Le A 31 669 12 ~m-thick aluminium layer; intern~l pressure: approximately 0.6 mbar.
Size: 40 x 40 x 2 cm3 Thermal conductivity: 8.3 mW/mK
5 Example 4 (Colllpaldlive) Vacuum insulation panel comprising a rectangular moulded body produced from ground rigid polyurethane foam press-moulded with polyisocyanate (method as in Example 1) and covered on all sides with aluminium composite film cont~inin~ a 10 12 llm-thick aluminium layer; internal pressure: approximately 0.6 mbar.
Size: 25 x 25 x 2 cm3 Thermal conductivity: 9 mW/mK
Examples 2 to 4 show that, at upwards of the vacuum panel size according to the 15 invention, the aluminium-cont~ining composite film used for covering does notinfluence the thermal conductivity of the vacuum insulation panel obtained.