GB2290369A

GB2290369A - Thermal insulating panel

Info

Publication number: GB2290369A
Application number: GB9411446A
Authority: GB
Inventors: John Thomas Hughes
Original assignee: Micropore International Ltd
Current assignee: Micropore International Ltd
Priority date: 1994-06-08
Filing date: 1994-06-08
Publication date: 1995-12-20
Anticipated expiration: 2014-06-08
Also published as: DE69500644D1; JPH084980A; GB2290369B; EP0686732B1; DE69500644T2; GB9411446D0; JP3682660B2; EP0686732A1

Description

Thermal InsulatinE Panel 2290369 This invention relates to a thermal

insulating panel comprising an outer porous envelope containing a block of compacted dry microporous thermal insulating material.

The term 'microporous' is used herein to identify porous or cellular materials in which the ultimate size of the cells or voids is less thart the mean free path of an air molecule at NTP, i.e. of the order of 100 nin or smaller. A material which is microporous in this sense will exhibit very low transfer of heat by air conduction (that is collisions between air molecules). Such microporous materials include aerogel, which is a gel in which the liquid phase has been replaced by a gaseous phase in such a way as to avoid the shrinkage which would occur if the gel were dried directly from a liquid. A substantially identical structure can be obtained by controlled precipitation from solution, the temperature and pH being controlled during precipitation to obtain an open lattice precipitate. Other equivalent open lattice structures include pyrogenic (fluned) and electro-thennal types in which a substantial proportion of the particles have an ultimate particle size less than 100 mn. Any of these particulate materials, based for example on silica. alumina or other metal oxides, may be used to prepare a composition which is microporous as defined above.

The microporous insulating material typically comprises a dry particulate microporous material as defffied hereinabove mixed with fibre or filament reinforcement, an opacifier such as titanium dioxide and, for hightemperature use, a small quantity of alumina powder to resist shrinkage.

Handleable sheets and shaped constructions of microporous thermal insulating material are well known. A particularly advantageous form of construction, because of its cost-effective manufacturing technique, is a microporous insulating panel, as shown in cross-section in Figure 1, of the accompanying drawings in the form of a compacted n-dcroporous insulating composition 1 which is enclosed by a woven glass envelope 2, there being some adhesion between the material -2of the envelope and the contained insulating material. Instead of using a woven glass material, which is inherently porous, for the envelope, other porous materials may also be used.

The. porosity of the envelope is important during manufacture of the panel. PoxAery microporous thermal insulating material is poured into the envelope, which is open at one edge. This edge is then sealed and pressure is applied to the exterior of the envelope to compact the insulating material, air being displaced through the porous material of the envelope. The extent of porosity of the envelope material affects the uniformity of density of the compacted insulating material and also affects what can be described as dustiness of the final product. In this latter regard, the woven glass cloth envelope material has very low permeability to the particulate materials constituting the n-iicroporous insulating material and this allows the panels to be manufactured with a substantially dust-free surface.

Thermally insulating panels constructed in this way have been found to be very acceptable for 15 use in most applications. However problems can be encountered when such a panel is applied to a warm surface.

It has been found that when the panel is applied against a warm surface, swelling of the panel may occur, so that the panel is no longer flat and rigid but has the appearance of having been blown up like a balloon, as illustrated in the cross-section in Figure 2 of the accompanying drawings.

On investigating this phenomenon, it has been found that at the face of the panel applied to the warm surface 3, the compacted microporous insulating material 1 becomes separated from the material of the envelope 2 and gas pressure is generated in the space 4 between the envelope and the insulating material. The gas pressure results from whatever gas, such as air, constitutes the ambient surrounding the panel.

il -3The magnitude of the gas pressure in the space 4 depends upon the temperature of the surface 3, the temperature of the surroundings and the pressure surrounding the panel, according to the following relationship:

Pressure inside panel Pressure of surroundings Temperature of surface Temperature of surroundings Hence, the higher the temperature of the surface 3, then the higher the pressure generated inside the panel in the space 4 and the greater the swelling of the panel when the envelope 2 is of very 10 low porosity.

This swelling of the panel is undesirable as it may cause the panel structure to be ruptured and it may be difficult to build up layers of other materials against the panel.

Although the material of the envelope 2, such as woven glass fabric, is inherently porous in nature, particles of the microporous insulating material tend to block the pores and this prevents escape of air, or other gas, from the space 4 through the envelope 2 as the pressure in the space 4 builds up.

It is an object of the present invention to overcome or minimise this problem by providing a means to avoid build-up of gas pressure between the microporous insulating material and a surface of the envelope which is subject to a temperature which is higher than that to which another (e. g. opposite) surface of the envelope is subjected.

The present invention accordingly provides a thermal insulating panel comprising an envelope, of which at least a part thereof is of inherently porous material, containing a block of compacted microporous thermal insulating material, the panel having an external first surface arranged to be subjected to a high temperature relative to an extemal second surface, vent means being provided 4communicating between the exterior of the panel and an interfacial region between the microporous insulating material and the envelope at the first surface of the panel.

The.vent means may comprise at least one aperture extending through the panel from the exterior thereof at least to an inside surface of the envelope at the interfacial region between the microporous insulating material and the envelope at the first surface of the panel. For convenience of manufacture, such at least one aperture may also extend through the envelope at the first surface of the panel, in which case it may be preferred to provide cover means therefor on the exterior of the envelope at the first surface of the panel to prevent ingress of unwanted material. Such unwanted material may, for exarnple, comprise a cement, or mortar, or an adhesive, used in connection with application of the panel with its first surface in contact with a component or structure whose surface is intended to be at the high temperature.

The cover means may comprise a patch, e.g. of the same material composition as the envelope, secured to the exterior of the envelope by means of an adhesive.

The at least one aperture suitably extends from the exterior of the panel at the second surface thereof, the second surface being preferably opposite the first surface.

The vent means may alternatively comprise at least one notch provided in an edge region of the panel and communicating between the exterior of the panel and the interfacial region between the microporous insulating material and the envelope at the first surface of the panel. Cover means may be provided for part of the or each notch, on the exterior of the envelope, in a region of the first surface of the panel, to prevent ingress of unwanted material as previously described in connection with the vent means in the form of one or more apertures. Such cover means may comprise a patch, e.g. of the same material composition as the envelope, secured to the exterior of the envelope by means of an adhesive.

1 In a further alternative, the vent means may comprise at least one aperture extending through the envelope at the first surface of the panel to the interfacial region between the microporous insulating material and the envelope at the first surface of the panel.

If desired, a plurality of vent means may be provided.

The envelope suitably comprises a woven glass material. However it will be apparent to the skilled person that other inherently porous materials may be selected.

The porosity of the envelope material is suitably selected such that the material is permeable to gas, particularly air, whilst substantially preventing microporous insulating material from passing through it.

When the thermal insulating panel of the invention is applied to a structure for thermal insulation purposes, with the first surface in contact with a hot face of the structure, any tendency for gas pressure to build up at the interfacial region between the microporous insulating material and the envelope at the first surface is avoided by the provision of the vent means. The gas tending to produce such gas pressure may be air, or whatever gas ambient surrounds the panel.

The invention is now described by way of example with reference to Figures 3 to 7 of the accompanying drawings, in which:

Figure 3 is a perspective view of a thermal insulating panel according to the invention; Figure 4 is a cross-sectional view along A-A of one embodiment of the panel of Figure 3; Figure 5 is a cross-sectional view along A-A of an alternative embodiment of the panel of Figure 3; Figure 6 is a perspective view of a further thermal insulating panel according to the invention; and Figure 7 is a cross-sectional view along B-B of the panel of Figure 6.

Referring to Figures 3, 4 and 5, a thermal insulating panel 5 is constructed by well-known techniques, for example as described in British Patent Nos. 1350 661 and 1247 674. Such a panel may also be prepared by the process described in British Patent Application No. GB 94 03 564.9. The panel 5 comprises an envelope 6 of inherently porous material, such as woven glass cloth. containing a block of compacted microporous thermal insulating material 7. The envelope 6 is sealed along opposite ends 8, 9 by means of stitching, or by means of an adhesive. The panel 5 has an external first surface 10 opposite to which is an external second surface 11. The panel 5 is intended to be used for thermal insulation purposes with the first surface 10 in contact with a hot surface of a structure or component (not shown).

Vent means in the form of an aperture 12, e.g. of about 4 mm in diameter, is provided, communicating between the exterior of the panel and an interfacial region 13 between the nficroporous insulating material 7 and the envelope 6 at the first surface 10 of the panel. The aperture 12 passes through the envelope at the second surface 11 of the panel and extends either right up to the inside surface 14 of the envelope, at the first surface 10 of the panel, as shown in Figure 4, or completely through the envelope at the first surface 10 of the panel, as shown in Figure 5. With the arrangement shown in Figure 5, it may be preferred to provide a cover means 15 in the form of a patch of suitable material, such as woven glass cloth, secured to the exterior of the envelope by means of an adhesive and covering the aperture 12. Such a cover means 15 serves to prevent ingress of any unwanted material into the aperture 12 when the panel is secured to a structure by means which may involve adhesive material, cement, or mortar, for example.

If desired, a plurality of apertures 12 may be provided.

In a further thermal insulating panel, shown in Figures 6 and 7, this is constructed basically in the same manner as described above with reference to Figures 3 to 5. apart from the arrangement I 1 of the vent means. In Figures 6 and 7, parts substantially the same as those in Figures 3 to 5 are given the same reference numerals as in Figures 3 to 5. In the embodiment shown in Figures 6 and 7, instead of a vent means in the from of an aperture as shown by reference numeral 12 in Figures 3 to 5, a vent means in the form of a notch 16 is provided in a side edge of the panel 5. The notch 16 is suitably provided by means of a saw and extends from the exterior of the panel to the interfacial region 13 between the microporous insulating material and the envelope 6 at the first surface 10 of the panel 5.

A cover means 17 in the form of a patch of suitable material, such as woven glass cloth, may be secured to the exterior of the envelope by means of an adhesive, to cover the notch 16 at a region thereof in the vicinity of the first surface 10 of the panel. Such a cover means 17 serves to prevent ingress of any unwanted material into the notch 16 when the panel is secured to a structure which may involve adhesive material, cement or mortar, for example.

A plurality of notches 16 may be provided, if desired.

In application, the panels 5 of Figures 3 to 7 are applied as thermal insulation to a structure (not shown) with the first surface 10 in contact with a hot surface of the structure. In the absence of the aperture 12 of Figures 3 to 5, or the notch 16 of Figures 6 and 7, the compacted microporous insulating material 7 would become separated from the material of the envelope 6 at the interfacial region 13 therebetween and gas pressure generated in the resulting space would cause swelling of the panel, as if blown up like a balloon, as previously explained and shown in Figure 2. The gas involved in such an effect can be air or whatever gas surrounds the panel in its particular application. The provision of the aperture 12 or the notch 16 provides venting of gas and prevents any such gas pressure from being generated, thereby ensuring that the panel remains flat and undistorted when in contact with a hot surface.

-8In a further embodiment instead of one or more apertures 12 being provided extending through the thickness of the panel 5, an aperture may be provided extending substantially only through the envelope 6 at the first surface 10 of the panel to the interfacial region 13 between the microporous insulating material and the envelope 6 at the first surface 10 of the panel.

1

Claims

1. A thermal insulating panel comprising an envelope, of which at least a part thereof is of inherently porous material, containing a block of compacted microporous thermal insulating 5 material, the panel having an external first surface arranged to be subjected to a high temperature relative to an external second surface, vent means being provided communicating between the exterior of the panel and an interfacial region between the n-deroporous insulating material and the envelope at the first surface of the panel.

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2. A thermal insulating panel according to claim 1, in which the vent means comprises at least one aperture extending through the panel from the exterior thereof at least to an inside surface of the envelope at the interfacial region between the microporous insulating material and the envelope at the first surface of the panel.

3. A thermal insulating panel according to claim 2, in which the at least one aperture extends through the envelope at the first surface of the panel.

4. A thermal insulating panel according to claim 3, in which cover means for the aperture is provided on the exterior of the envelope at the first surface of the panel.

5. A thermal insulating panel according to claim 4, in which the cover means is in the form of a patch, secured to the exterior of the envelope by means of an adhesive.

6. A thermal insulating panel according to claim 5, in which the patch is of the same material composition as the envelope.

7. A thermal insulating panel according to any one of claims 2 to 6, in which the at least one aperture extends from the exterior of the panel at the second surface thereof.

8. A thermal insulating panel according to claim 7, in which the second surface is opposite the first surface.

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9. A thermal insulating panel according to claim 1, in which the vent means comprises at least one notch provided in an edge region of the panel and communicating between the exterior of the panel and the interfacial region between the microporous insulating material and the envelope at the first surface of the panel.

10. A thermal insulating panel according to clahn 9, in which cover means is provided for part of the or each notch, on the exterior of the envelope, in a region of the first surface of the panel.

11. A thermal insulating panel according to claim 10, in which the cover means comprises a is patch, secured to the exterior of the envelope by means of an adhesive.

12. A thermal insulating panel according to claim 11, in which the patch is of the same material composition as the envelope.

13. A thermal insulating panel according to claim 1, in which the vent means comprises at least one aperture extending through the envelope at the first surface of the panel to the interfacial region between the microporous insulating material and the envelope at the first surface of the panel.

14. A thermal insulating panel according to any one of the preceding claims, in which a plurality of vent means is provided.

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15. A thermal insulating panel according to any one of the preceding claims, in which the envelope comprises a woven glass material.

16. A thermal insulating panel constructed and arranged substantially as hereinbefore described with reference to Figures 3 to 7 of the accompanying drawings.