GB2336565A

GB2336565A - Vacuum insulation panel

Info

Publication number: GB2336565A
Application number: GB9808654A
Authority: GB
Inventors: John Thomas Hughes
Original assignee: Micropore International Ltd
Current assignee: Micropore International Ltd
Priority date: 1998-04-24
Filing date: 1998-04-24
Publication date: 1999-10-27
Also published as: GB9808654D0

Abstract

A vacuum insulation panel comprises a core (15) of thermal insulation material, having opposed major faces and side edges, surrounded by an evacuated and sealed envelope (16), the envelope being in the form of a laminate (7) comprising a plurality of layers (8, 9, 10, 11) and wherein at least one of the layers (9) is discontinuous (9A, 9B) in the laminate.

Description

1 Vacuum Insulation Panel and Method of Manufacture This invention relates

to vacuum insulation panels and their manufacture, 2336565 Vacuum insulation panels are of great interest for providing highly efficient thermal insulation performance particularly at low temperatures in the range -50C to +50"C. Their use in refrigerators and freezers provides a means of reducing energy consumption of these appliances without the need to invest in major changes in manufacturing techniques. A vacuum panel normally consists of a lightweight core in the form of a foamed plastic or a compacted powder or fibrous material. One or more of these materials is contained within a low permeability envelope which is evacuated and sealed to form a rigid panel. The core is of sufficient strength to resist significant compaction due to air pressure on the envelope.

The thermal conductivity of such panels can be four times lower than the traditional polyurethane foams most commonly used in refrigerators.

The panels need to retain a good insulation performance throughout the lifetime of use which is likely to be in excess of 20 years.

Special envelope materials have been developed to inhibit penetration by gases and water vapour which would otherwise soften the vacuum and diminish the insulation efficiency.

These envelope materials, or barrier films, are usually, in the form of a laminate construction with each layer chosen to flilfil a particular purpose. One custom designed film, for example.

is illustrated in Figure 1 and constructed as a laminate of four materials. It comprises an outer 2 layer 1 of scratch resistant polyethylene terephthalate (PET), a second layer 2 of aluminium to inhibit permeation of water vapour and other gases, a third layer 3 of nylon to give tear resistance and a fourth layer 4 of polyethylene to allow heat sealing. The layers are bonded to one another by an adhesive 5 so that the laminate construction handles as a single film.

Although each layer of such films contributes to a very effective overall performance in maintaining a vacuum. some features of the individual layers may have an undesirable effect on the thermal efficiency of the vacuum panel.

In forming the envelope surrounding the core, it is desirable to use aluminium foil as one layer of the laminate oil account of its high resistance to penetration by gas and water vapour molecules. A thickness of aluminium of only about 12 microns is sufficient to maintain an adequate vacuum within a vacuum panel for up to 40 years life of such a panel used in a refrigerator.

It is undesirable to wrap the barrier film, with its aluminium laver. around the edge of the vacuum panel because tile aluminium is a good conductor of heat and is able to conduct a si if igni icant amount of heat around the edge of the panel. The thermal conductivity value for aluminium is typically 240 W/ra.K whereas the thermal conductivity of the evacuated core Is about 5 x IT' W1m.K. The thermal conductivities of other materials used for other layers of the barrier film forming the envelope are of the order of 0.3 Will.K.

Vacuum panels have previously been made which avoid wrapping the aluminium film around the edge of the panel by making use of two different barrier film constructions in the formation of the envelope. In forming a vacuum insulation panel 6 as shown in Figures 2 and 3. one type 3 of barrier film A is used on one face of the panel and another type of barrier film B is used on the opposite face of the panel. The first barrier film A. as shown in and previously described with reference to Figure 1, has a!ayer 2 of aluminium which is sufficiently thick to have a very low permeability to gases and vater vapour. The second barrier film B has little or no aluminium as a means to minimise thermal conduction, but it has much thicker layers of other materials, such as high density polyethylene to compensate for the lack of aluminium. In the case of a barrier film B with little aluminium. the aluminium is usually in the form of a thin vacuum-deposited layer which offers some resistance to permeation of gas and water vapour molecules but is less effective than the thicker aluminium foil layer of the barrier film A. The barrier films A and B form an envelope surrounding an insulation core C.

The use of the two different barrier films is a compromise between the lowest possible permeability and the lowest possible heat conduction at the edge of the panel.

It is an object of the present invention to provide a vacuum insulation panel and method of its manufacture which does not require the use of two barrier films in the construction of the envelope.

The present invention provides a vacuum insulation panel comprising a core of thermal insulation material. having opposed major faces and side edges. surrounded by an evacuated and scaled envelope, the envelope being in the form of a laminate comprising a plurality of layers and wherein at least one of the layers is discontinuous in the laminate.

The present invention also provides a method of manufacturing a vacuum insulation panel comprising:

4 providing a core of thermal insulation material having opposed major faces and side edges..

providing an evacuated and sealed envelope surrounding the core, the envelope being in the form of a laminate comprising a plurality of layers; and providing at least one of the layers discontinuous in the laminate.

The layers may be secured together by means of an adhesive.

The laminate may comprise a plurality of layers of one or more plastics materials.

Alternatively the laminate may comprise at least one layer of plastics material and at least one layer of a metal, the at least one layer of the metal being discontinuous in the laminate.

The laminate may comprise a plurality of layers of one or more plastics materials and a laser of the metal.

The discontinuous layer of the metal may be so arranged as to be absent substantially over at least one side edge, and preferably substantially over two or inore side edges, of the core.

The metal may comprise aluminium and may be in the fon-n of foil.

The at least one layer or the plurality of layers of plastics material may be selected from polyester, polyedlylene, high density polyethylene, polyvinyl alcohol.. polyethylene terephthalate, polyamide and polyurethane materials.

The at least one discontinuous layer may comprise a plurality of materials arranged contiguously.

Such contiguously-arranged materials may be provided such that a layer of a metal, such as aluminium, such as in the form of foil, is provided substantially overlying each major face of the core and a layer of a plastics material having low gas and water vapour permeability is provided substantially overlying at least one side edge, and preferably two or more side edges. of the core. Such layer of plastics material having low gas and water vapour permeability may optionally be arranged to substantially coincide with one or more regions of scaling of tile envelope.

The plastics material having low gas and water vapour permeability may comprise polyethylene.

The core of thermal insulation material may comprise one or more materials selected from powders, fibres, foams, compacted powders, moulded insulation materials and pre-cast insulation shapes.

The powders and compacted powders may comprise organic or inorganic materials and mas, 1 t or include a microporous matrix which may also include an opacifier in powder, particulate 25 platelet form.

6 The compacted powders may be reinforced with fibres- The core may comprise finely divided silica having a large surface area and which mas, act as a getter for water and/or gas molecules. The finely divided silica may be compacted to a density sufficient to withstand air pressure applied to a surface of the panel.

Alternatively the core may comprise finely divided carbon particles.

The fibres from which a selection may be made for the core may be organic or inorganic and either natural or synthetic. A bonding agent may be included therefor.

The foams from which a selection may be made for the core may be organic or inorganic and may comprise ceramic, carbon or polyurethane- For a better understanding, the invention is now described by way of example with reference to the accompanying drawings in which:

Figure 4 is a cross-sectional view of a laminate in the manufacture of a vacuum insulation panel according to the invention:

Figure 5 is a schematic representation of stages in the manufacture of the laminate of Figure 4.

Figure 6 illustrates the provision of a discontinuous laver for the laminate of Figure 4.

7 Figure 7 is a perspective view of a vacuum insulation panel according to the invention.

Figure 8 is a cross-sectional view of the panel of Figure 7..

Figure 9 is a cross-sectional view of an alternative arrangement of a laminate in the manufacture of a vacuum insulation panel according to the invention; and Figures 10 and 11 are cross-sectional views of further arrangements of vacuum insulation panels according to the invention.

Referring to Figure 4, a multilayer laminate 7 is prepared for use in forming an envelope for a vacuum insulation panel. The multilayer laminate comprises a first laYer 8 of polyethylene terephthalate plastics material, a second discontinuous layer 9 of aluminium foil. a third layer 10 of polvamide plastics material, such as Nylon, and a fourth layer 11 of polyethylene. The layers of tile laminate are secured together by means of an adhesive (not shown).

The laminate 7 is formed by the process illustrated in Figure 5. Polyethylene terephthalate film material for the first layer 8 is fed from a roll and coated on one side with an adhesive. After drying the adhesive it is laminated with aluminium foil material of the second layer 9. The laminate is then coated with adhesive on the exposed aluminium face and then.. after drying. laminated with polyamide materia of the third layer 10. The exposed surface of the polyamide material is coated with adhesive and, after drying, final lamination with polyethylene material of the fourth layer 11 is effected.

8 The discontinuous layer 9 of aluminium foil is provided using a plurality of rolls of aluminium foil. As shown in Figure 6, the aluminium foil layer 9 is fed for lamination from two rolls providing strips 9A, 9B of foil. When laminated with the polyethylene terephthalate layer 8, the aluminium layer is provided in two strips separated across the width of the laminate by a distance which approximates to the thickness of a vacuum insulation panel which is to be constructed. Each strip 9A. 9B of aluminium foil has a width approximately equal to the width of the vacuum panel to be constructed.

The completed laminate as shown in Figure 4 is folded along its length at the region of discontinuity 12 of the aluminium layer 9A, 9B and the overlapping edges 13, 14. which are also devoid of the aluminium layer are sealed together, thereby forming a tube of the laminate material. The tube is then cut into sections which are each sealed at one of the two open ends thereof to produce flat envelopes for receiving thermal insulation cores. As shown in Figures 7 and 8. an appropriate core 15 is located 'Inside an envelope 16 of the laminate material. The envelope 16 is then evacuated and sealed along the remaining open edge. As shown in Figures 7 and 8, as a result of providing the discontinuous layer of aluminium and the method of folding of the laminate as described with reference to Figure 4. two side edges 17, 18 of the resulting vacuum 'Insulation panel are completely devoid of aluminium foil material. These edges are chosen to be the longer edges of the panel. Although aluminium is present at the remaining two edges, these are the shorter edges of the panel so that conduction of heat thereacross is minimised. The two portions 9A, 9B of aluminium foil overlie the opposite major faces of the insulation core 15 The envelope 16 wdlibits low permeability to gases and water vapour. mainly because the areas thereof devoid of aluminium are sinall relative to the total area.

9 Permeability of the envelope can be further reduced by arranging for the discontinuous layer of the laminate in which the aluminium foil is provided to be formed as a contiguous layer of aluminium and a hi h density, low permeability, plastics material. This is illustrated in Figure 9 1 9 where. in addition to the portions 9A, 913 of aluminium foil.. high density polyethylene 19 is provided contiguous therewith in the laminate and occupying the regions of discontinuity. In the resulting envelope formed from such laminate. the polvethylene 19 is provided in the side edge regions where the laminate was folded and sealed (Regions 17 and 18 in Figure 8).

In alternative arrangements to the vacuum insulation panel of Figure 8, instead of the seal 18 formed at a side edge of the panel, a seal could be provided along a major face of the panel. Such alternative arrangements are illustrated in Figure 10 and 11. In Figure 10 an upstanding seal 20 is provided along a major face of envelope 16 and in Figure 11 a flattened seal 21 is provided along the major face of the envelope 16. In both arrangements a discontinuous lay-er 9 of aluminium is provided and a core 15 of thermal insulation material.

Although the invention has been specifically described in relation to the use of a metal layer. such as aluminium, as the discontinuous layer, it is not intended that the invention be so limited. Alternatively, or additionally, the discontinuous Iayer could be a plastics material layer, particularly of a material which is difficult to bond to adjacent layers. The discontinuities could be used to provide direct adhesive. bonding therethrough between tile]avers on either side of the discontinuous layer.

The core 15 of thermal insulation material comprises any of the well known materials such as posyders. fibres, foams, compacted powders, moulded insulation materials and pre-cast insulation shapes. The powders and compacted powders could comprise organic or inorganic materials and could include a microporous matrix which could also include an opacifier. Such o'f in paci ier could be i powder, particuIate or platelet form.

The compacted powders can be reinforced with fibres.

A particularly advantageous matedal for the core is finely divided silica having a large surface area and which can act as a getter for water and gas molecules. The finely divided silica is compacted to a density sufficient to withstand air pressure applied to a surface of the panel.

Another good material comprises finely divided carbon particles. This material provides a core structure with opacification and is also very effective combined with silica or other materials.

The core can also be formed from fibres, which can be organic or inorganic and either natural or synthetic. A bonding agent can be used with such fibres.

The core can also comprise a foam material, particularly poly-uretliane foam. However other 1 foam materials can be used which are either organic or inorganic in nature and comprising, for example, ceramic or carbon.

The invention is particularly advantageous in the manufacture of large numbers of vacuum insulation panels with the same dimension in width. The discontinuitv or discontinui ties in the aluminium layer is or are thereby readily aligned with an edge or edges of the panel.

11 The invention results in improved panel construction at lower cost. It allows the envelope surrounding the core to be produced from one laminate which has the following advantages. It allows the panel to have at least one edge devoid of a seal. It enables a reduction in the total area of the panel without reduction in the insulation area. It permits the manufacture of envelopes using the lowest cost conventional production methods. It uses the lowest cost laminate construction specification.

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Claims

1. A vacuum insulation panel comprising a core of thermal insulation material. having opposed major faces and side edges, surrounded by an evacuated and sealed envelope, the 5 envelope being in the form of a laminate comprising a plurality of layers and wherein at least one of the layers is discontinuous in the laminate.

2. A panel according to claim 1 in which the layers are secured together by means of an adhesive.

3. A panel according to claim 1 or 2. in which the laminate comprises a plurality of layers of one or more plastics materials.

4. A panel according to claim 1 or 2, in which the laminate comprises at least one layer of plastics material and at least one layer of a metal, the at least one layer of the metal being discontinuous in the laminate.

5. A panel according to claim 4, in which t he laminate comprises a plurality of layers of one or more plastics materials and a layer of the metal.

6. A panel according to claim 4 or 5, in which the discontinuous layer of the metal is so arranged as to be absent substantially over at least one side edge of the core.

7. A panel according to claim 6.. in which the discontinuous layer of the metal is so arranged as to be absent substantially over two or more side edges of the core.

8. A panel according to any of claims 4 to 7. in which the metal comprises aluminium.

9. A panel according to claim 8, in which the metal is in the form of a foil.

10. A panel according to any of claims 3 to 9, in which the at least one layer or the plurality of layers of plastics material is or are selected from polyester. polvethylene, high density polyethylene, polyvinyl alcohol, polyethylene terephthalate. polyamide and polyurethane materials.

11. A panel according to any, preceding claim. in which the at least one discontinuous layer comprises a plurality of materials arranged contiguously.

12. A panel according to claim 11, in which the contiguously-arranged materials are provided such that a layer of a metal 1 provided substantially overlying each major face of the core and a layer of a plastics material having low gas and water vapour permeability is provided substantially overlying at least one side edge of the core.

13. A panel according to claim 12. in which the layer of the plastics material having low gas and water vapour permeability is provided substantially overlying two or more side edges of the core.

14. A panel according to claim 12 or 13. in which the layer of plastics material having low gas and water vapour permeability is arranged to substantially coincide with one or more regions of sealing of the envelope.

15. A panel according to claim 12, 13 or 14, in which the plastics material having low gas and water vapour permeability comprises polyethylene.

16. A panel according to any preceding claim, in which the core of thermal insulation material comprises one or more materials selected from powders, fibres, foams. compacted powders, moulded insulation materials and pre-cast insulation shapes.

17. A panel according to claim 16, in which the powders and compacted powders comprise organic or inorganic materials.

18. A panel according to claim 17, in which the powders and/or compacted powders include a microporous matrix.

19. A panel according to claim 18, in which tile microporous matrix includes an opacifier in powder, particulate or platelet form.

20. A panel according to any of claims 16 to 19. in which the compacted powders are reinforced with fibres.

21. A panel according to any of claims 16 to 20. in which the core comprises finely divided silica having a large surface area.

22. A panel according to claim 2 1, in which the finely divided silica acts as a getter for water and/or gas molecules.

23. A panel according to claim 21 or 22, in which the finely divided silica is compacted to a density sufficient to withstand air pressure applied to a surface of the panel.

24. A panel according to claim 16, in which the core comprises finely divided carbon particles.

25. A panel according to claim 16, in which the fibres from which a selection is made for tile core are organic or inorganic and either natural or synthetic.

26. A panel according to claim 25, in which a bonding agent is included for the fibres.

27. A panel according to claim 16. in which the foarns from ss-hich a selection is made for tile core are organic or inorganic.

28. A panel according to claim 27, in which the foams from which a selection is made for the core comprise ceramic, carbon or polyurethane.

29, A vacuum insulation panel constructed and arranged substantially as hereinbefore described with reference to Figures 4 to 11 of the accompanying drawings.

30. A method of manufacturing a vacuum insulation panel comprising: providing a core of thermal insulation material having opposed major faces and side edges; providing an evacuated and sealed envelope, surrounding the core, the envelope being in the form of a laminate comprising a plurality of layers; and providing at least one of the las-ers discontinuous in the laminate.

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3 1. A method according to clairn 30 in which the layers are secured together by means of an adhesive.

32. A method according to claim 30 or 31, in which the laminate comprises a plurality of layers of one or more plastics materials.

3 3. A method according to claim 3 0 or 3 1, in which the laminate comprises at least one layer of plastics material and at least one layer of a metal, the at least one layer of the metal being discontinuous in the laminate.

34. A method according to claim 33. in which the laminate comprises a plurality of layers of one or more plastics materials and a layer of the metal.

35. A method according to claim 33 or 34, in which the discontinuous layer of the metal is so arranged as to be absent substantially over at least one side edge of the core.

36. A method according to claim 35, in which the discontinuous layer of the metal is so arranged as to be absent substantially over two or more side edges of the core.

37. A method according to any of claims 33 to 36, in which the metal comprises aluminluiTi.

38. A method according to claim 37, in which the metal is in the form of a foil.

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39. A method according to any of claims 32 to 38, in which the at least one layer or the plurality of layers of plastics material or are selected from polyester. 1 polyethylene.. high density polyethylene, poRwinyl alcohol, polyethylene terephthalate.

polsamide and polyurethane materials.

40. A method according to any of claims 30 to 39.. in which the at least one discontinuous layer comprises a plurality of materials arranged contiguously.

41. A method according to claim 40- in which the contiguotisly-arranged materials are provided such that a layer of a metal is provided substantially overlying each major face of the core and a layer of a plastics material having low gas and water vapour permeability is I provided substantially overlying at least one side edge of the core.

42. A method according to claim 4 1.. in which the layer of the plastics material having low gas and water vapour permeability is provided substantially overlying two or more side edges of the core.

43. A method according to claim 41 or 42, in which the layer of plastics material having lo-,.

gas and water vapour permeability is arranged to substantially coincide with one or more regions of sealing of the envelope.

44. A method according to claim 41. 42 or 43, in which the plastics material having low gas and water vapour permeability comprises pollvethylene.

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45. A method according to any of claims 30 to 44. in which the core of thermal insulation material comprises one or more materials selected from powders, fibres. foarns, compacted powders. moulded insulation materials and pre-cast insulation shapes.

46. A method according to claim 45, in which the powders and compacted powders comprise organic or inorganic materials.

47. A method according to claim 45 or 46, in which the powders and/or compacted powders include a microporous matrix.

48. A method according to claim 47, in which the microporous matrix includes an opacifier in powder, particulate or platelet form.

49, A method according to any of claims 45 to 48. in which the compacted powders are reinforced with fibres.

50. A method according to any of claims 45 to 49. in which the core comprises finely divided silica having a large surface area.

5 1. A method according to claim 50, in which the finely divided silica acts as a getter for water andlor gas molecules.

52. A method according to claim 50 or 5 1, in which the finely divided silica is compacted to a density sufficient to withstand air pressure applied to a surface of the panel.

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53. A method according to claim 45, in which the core comprises finely divided carbon particles.

54. A method according to claim 45, in which the fibres from which a selection is made for the core are organic or inorganic and either natural or synthetic.

55. A method according to claim 54, in which a bonding agent is included for the fibres.

56 A method according to claim 45, in which the foams from which a selection is made for the core are organic or inorganic.

57. A method according to claim 56, in which the foams from which a selection is made for the core comprise ceramic, carbon or polyuretharte.

58. A method of manufacturing a vacuum insulation panel substantially as hereinbefore described with reference to Figures 4 to 11 of the accompanying drawings.

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59. A vacuum insulation panel whenever manufactured by the method of any of claims 30 to 58.