CA2036634A1

CA2036634A1 - Composite glazing panel

Info

Publication number: CA2036634A1
Application number: CA002036634A
Authority: CA
Inventors: Georges Declerck
Original assignee: Glaverbel Belgium SA
Current assignee: AGC Glass Europe SA
Priority date: 1990-03-01
Filing date: 1991-02-19
Publication date: 1991-09-02
Also published as: NL9100349A; DE4106192A1; GB9004628D0; FR2659646B1; NL194011C; GB2241468A; NL194011B; CH684352A5; SE9100574D0; GB2241468B; ATA37791A; SE501625C2; BE1005590A3; DE4106192C2; AT404586B; SE9100574L; FR2659646A1

Abstract

Abstract (Figure 2) Composite glazing panel A composite glazing panel affording high acoustic attenuation comprises two sheets (1, 8) of vitreous material between which is sandwiched a layer (7) of anaerogel which sandwich is bonded together as a monolithic laminate.
In a method of manufacturing such a glazing panel, the layer of aerogel is sandwiched between two sheets of vitreous material, and the sandwich is bonded together as a monolithic laminate.
The layer of aerogle (7), for example of a silica aerogel, may be formed directly onto a first vitreous sheet (1) so that it bonds directly to that sheet, and a second vitreous sheet (8) may be bonded to the aerogel by means of an adhesivelayer (9). suitably formed using a solvent-free powder adhesive. The edges of the panel may be hermetically sealed using a mastics sealant (10).

Description

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eomposite glazlng p~ l@3 This invention relates to composite glazing panels affording high acoustic attenuation.
There exists a demand for glazing panels which afford a high degree of acoustic attenuation, and various types of glazing panel have been proposed to satisfy that demand. In particular, are known hollow glazing panels, including gas ~e.g. air) filled panels and evacuated panels, and laminates including those of which the bonding resin is of a rather pliable nature so that it has a damping effect. Both hollow and laminated panels may be provided with sheets of o asymmetric thickness to improve acoustic attenuation at certain frequencies. And of course it is known to incorporate one or more laminated panes in a hollow glazing panel. Such panels suffer from certain disadvantages, which render them unsuitable for use in certain circumstances where it would be desirable to provide a high degree of acoustic insulation.
s Gas-filled hollow panels have an acoustic attenuation which is in large part determined by the "thickness" of the gas-fillecl inter-sheet space. For high attenuation, the inter-sheet spacing must be rather large, and this can present dif~lculties in manufacture and framing. Merely as an example. such panels are unsuitable for mounting in thin partition walls because of their thickness. While evacuated hollow panels can afford a good attenuation with a relatively narrow inter-sheet space, such evacuation, especially in the case of rather large panels, tends to dish the vitreous sheets of the panel, and this can present an undesirable aspect in reflection.
Laminated glazing panels afford an attenuation which, broadly speaking, is 26 dependent on their mass. For high attenuation, a high speci~lc mass (that i9, mass per unit area) is required. Again, merely as an example, such panels are unsuitable for mounting in walls where weight considerations are an important factor.
It is an object of this invention to provide a composite glazing panel which affords a very high degree of acoustic attenuation in relation to its overall thickness and specific mass.
According to the invention, there is provided a composite glazing panel affording high acoustic attenuation, characterised in that such panel comprises two sheets of vitreous material between which is sandwiched a layer of an aerogel .~6 which sandwich is bonded together as a monolithic laminate.
The expression "monolithic laminate" is used herein to denote a laminate 2~.~?~3 2.

which is bonded together in such a manner that it vibrates in the same manner asa single plate of a material having an elastic modulus which may be calculatetl from the elastie moduli and thicknesses of the individual strata of the laminate.
Such monolithic laminates may be contrasted with hollow panels and with 5 laminates which are only weakly coupled together so that they behave in vibration as a box rather than as a plate. Thus in a monolithic laminate there is no "mass-space-mass" resonance.
Such a composite glazing panel affords a very high degree of acoustic attenuation in relation to its overall thickness and specific mass.
Such a panel also has the advantage of ensuring that both major faces of the aerogel layer are protected from atmospheric humidity. Aerogels in general are highly absorbent of humidity, whereupon they tend to crack and break down to dust. The edges of such a laminate can readily be protected in a manner known per se by the use of a moisture resistant sealant such as a silicone-based15 mastic preparation.
It is a further object of this invention to provide a method of manufacturing such a panel.
Accordingly, the present invention also provides a method of manufacturing a composite glazing panel affording high acoustic attenuation, 20 characterised in that a layer of an aerogel is sandwiched between two sheets of vitreous material, and the sandwich is bonded together as a monolithic laminate. This is a very simple method of manufacturing such a panel.
The aerogel used may be an aerogel of alumina, zirconia, stannic oxkle or tungsten oxide, but it is preferably an aerogel based on silica. In order to form a 26 plate of aerogel for incorporation into such a laminate, a layer of the appropriate gel in a solvent is spread out on an appropriate moulding plate, and the solvent is removed from the layer to leave an aerogel plate. In one preferred method. a gelof silica in alcohol as solvent is spread out on a moulding plate which is then introduced into an autoclave. The autoclave is pressurized, and the gel is 30 optionally flushed with liquid carbon dioxide to displace all or most of the alcohol solvent. The pressure in the autoclave is increased to a pressure greater than the critical pressure for the solvent liquid present in the layer (about 80 bar for alcohol or about 74 bar for carbon dioxide). The temperature in the autoclave is then increased to above the critical temperature for that solvent .~5 (about 240C for alcohol or about 31~C for carbon dioxide). In this way it is possible to remove the solvent from the layer without collapsing the structure of the silica to form the aerogel, and in fact the structure of the aerogel can contain up to about 98% voids by volume. The aerogel plate resulting from this process is then sandwiched between two vitreous sheets, and the sandwich is bonded together as a monolithic laminate, in order to form a panel accordlng to the invention.
Panels according to the invention may be opaque, for example they may be formed as decorative panels which may be coloured by the incorporation of colouring agents in the aerogel or otherwise, but preferably, said sandwich is bonded together to form a light-transmitting laminate. If the laminate is light-transmitting, it may be used as a window closure or elsewhere where light o transmission is an important factor. Depending on the thickness of the aerogel within the laminate, it may even be transparent.
Care must be taken when bonding a pre-formed layer of an aerogel to a vitreous sheet. If a solvent based adhesive is used, it is likely that the solvent could penetrate the aerogel, and this would cause the aerogel matrix to break down in rnuch the same way as would the absorption of moisture. It is therefore preferable for the bonding agent to be substantially free from solvent. Thus it is preferred to use a heat-softenable or f'usible adhesive material. ~erogels are well able to resist temperatures of the levels required for fusing many heat-softenable adhesive materials. Such heat-softenable adhesive material could be in the form 20 of a thin sheet or film, but it is advantageous for the adhesive to be in powcler form since this simplifies handling problems. Such a powcler adhesive can readily be applied for example by an electro-static spraying technique well known per se.
Fusible silicone resins are especially well adapted to form a highly efficient bond betweeen silica-based aerogels and vitreous sheets which are also rich in silica.
~6 In especially preferred embodiments of the invention, the or at least one said aerogel layer is directly bonded to a said vitreous sheet. This avoids any problems in selecting and applying an intervening layer of adhesive material, and greatly simplifes manufacture. The easiest way to ensure such direct bonding is to use a said vitreous sheet as the moulding plate on which the aerogel layer is30 first formed. In this way, the or at least one said aerogel layer is formed directly on a said vitreous sheet so that it becomes directly bonded thereto. A silica-based aerogel will readily bond directly to the vitreous silica matrix of e.g. a glass sheet.
In s(~me preferred embodiments of the invention, said laminate comprises 35 two aeroge:l layers, each directly bonded to a said vitreous sheet. By assembling two aerogel layers, each directly formed on a said vitreous sheet to form said laminate, a panel can readily be formed which has a very high degree of acoustic 2 ~

attenuation in relation to its thickness and weight.
The acoustic attenuation across a glazing panel according to the invention is believed to be due in large part to the very great difference in acoustic impedance as between the aerogel and the vitreous material, due to the very low s velocity of sound propagation in aerogel. However in order to take full advantage of this phenomenon, the aerogel layer(s) should not be too thin, and it is accordingly preferred that the or at least one said layer of aerogel is at least 10 mm in thickness. Increasing the thickness of a said layer of aerogel is also highly beneficial for thermal insulation should this be desirecl. It is to be noted, o however, that aerogel layers transmit a significant proportion of light in a diffuse manner~ and therfore the total thickness of the aerogel in a panel should not betoo great if a high degree of resolution through the panel is considered of importance.
In order to protect the aerogel fully against possible attack by atmospheric humidity, it is preferred that the aerogel is hermetically sealed within said laminate. This can be done in various ways, for example by the use of an edge sealant of mastic type as aforesaid, optionally in coruunction with a channel frame for example of extruded aluminium. Preferably, however, the laminate is hermetically sealed by means of one or more spacer members extending around the panel and soldered to the vitreous sheets of the laminate. This provides a very effective and long-lasting protection for the aerogel.
In some preferred embodiments of the invention in which the aerogel is hermetically sealed within said larninate, the interior of the laminate is evacuatecl.
This is hlghly favourable from the point of vlew of thermal insulation, ancl it can 26 also have a useful beneft in allowing a more certain conservation of the very low speed of sound propagation in aerogel.
Preferred embodiments of the invention will now be described by way of example only with reference to the accompanytng diagrammatic drawings in which:
Figure 1 illustrates a stage in the manufacture of a panel in accordance with this invention, and Figures 2 and 3 are respectively cross sections through two embodiments of panel according to this invention.
A vitreous sheet I of appropriate size and shape has a framing dam 2 3s placed around its periphery (compare Figure I).
The space formed above the sheet 1 and within the dam 2 is then fillecl with an aerogel-forming solution. As illustrated in Figure I, the sheet I is then placed within an autoclave 3 having gas inlet 4 and outlet 5 valves, and a heater shown at 6.
The solution used is an alcogel solution, that is, a solution in alcohol. The gel-forming solute may be silica alone, or it may have additions of other oxides, 5 for e,~ample of aluminium, tellurium, germanium or other materials so as to confer special desired properties on the aerogel to be formed.
After the aerogel-forming solution has been poured, and any bubbles have been removed, the solutic-n is allowed to form a gel and is aged. The alcogel thus formed is purged with liquid carbon dioxide which replaces the alcohol in the o alcogel solution. This may be done by repeated rinsing of the gel solution at about 18-20C at a pressure of about 55 bar. This has the advantage of much simplifying the next stage of manufacture.
The pressure within the autoclave 3 is then increased to above the critical pressure of the solvent, 7aS bar for carbon dioxide, and the temperature within the 5 autoclave is then increased to above the critical temperature, 31C for carbondioxide. This stage is simplified by the substitution of carbon dioxide as solvent.
since if the solvent were to remain alcohol, the temperature and pressure required would be in excess of 240C and 80 bar respectively. Typical practical temperatures for this stage of the process are about 40C for carbon dioxide and20 about 270C for alcohol as solvent. Carbon dioxide is suitably used as pressurizing gas, supplied via inlet valve ~1. During drying of the layer, part of the vapour within the autoclave is allowed to escape via outlet valve 5, and on completion of drying a layer of aerogel 7 is left directly bonded to the sheet 1.
The layer of aerogel 7 is then sanclwiched between the first sheet 1 and a 26 second vitreous sheet.
Figure 2 shows such a panel in which the aerogel layer 7 is boncled to a second sheet 8 of glass via an intervening layer of adhesive 9. Such bonding is effected by electrostatically sprayin~ a layer of powdered silicone resin onto the aerogel layer 7, assembling the second sheet 8 to the adhesive, and heating the 30 assembly to effect fusion of the resin so that on cooling the sandwich is bonded together as a laminz~te. The panel is finished off by placing a silicone-based mastic material 10 into the re-entrant between the aerogel layer 2 and the firstsheet 1 which was left on removal of the framing dam 2 ~Figure 1).
In Figure 3 is shown a second embodiment of panel which is formed by bonding together two layers 7 of aerogel each formed on and directly bonded to avitreous sheet l. Like the laminate of Figure 2, the laminate of Figure 3 is bonded together by means of an adhesive layer 9 which is suitably formed in the 2~3~

same way.
Each of the vitreous sheets 1 of Figure 3 bears a marginal metallising layer of copper covered by a layer of solder, these being together shown at 11. These layers l l were applied before the aerogel layers 7 were formed, and they were masked by the framing dams 2 during formation of such aerogel layers. After bonding together of the laminate, metal spacer strips 12 are soldered between the metallising/solder layers around the margin of the panel so that the aerogel layers are hermetically sealed from ambient atmosphere. The interior of the panel may then be evacuated if desired.
o Such panels, whether according to Figure 2 or Figure 3, afford a very high degree of acoustic attenuation having regard to their overall thickness and their weight per unit area, and they also afford excellent thermal insulation.
In a variant of the embodiment shown In Figure 3, the spacer strip 12 does not lead straight between the two vitreous sheets, but rather it is corrugated so as to lengthen the path of thermal conduction between those sheets around their margins.
In a further variant panel, either according to Figure 2 or Figure 3. the sealing material 10 of Figure 2 or the metallising strip 11 and spacer 12 of Figure 3 is or are dispensed with. Instead the two glass sheets are "solderecl" together by a glass joint.
It will be appreciated that a laminate such as is shown in Figure 2 or 3 may be assembled to one or more further elements to form a panel of more complex structure if this is desired. In particular, such a more complex panel may comprise one or more further glass sheets such as 1 bearing a directly moulded layer 7 of aerogel.

Claims

1. A composite glazing panel affording high acoustic attenuation, characterised in that such panel comprises two sheets of vitreous material between which is sandwiched a layer of an aerogel which sandwich is bonded together as amonolithic laminate.

2. A panel according to claim 1, wherein said laminate is transparent.

3. A panel according to claim 1 or 2, wherein as adhesive for bonding together layers of the laminate is used a fusible silicone resin.

4. A panel according to any preceding claim, wherein the or at least one said aerogel layer is directly bonded to a said vitreous sheet.

5. A panel according to claim 4, wherein said laminate comprises two aerogel layers, each directly bonded to a said vitreous sheet,

6. A panel according to any preceding claim, wherein the or at least one said layer of aerogel is at least 10 mm in thickness.

7. A panel according to any preceding claim, wherein the aerogel is hermetically sealed within said laminate.

8, A panel according to claim 7, wherein the laminate is hermetically sealed by means of one or more spacer members extending around the panel and soldered to the vitreous sheets of the laminate.

9. A panel according to claim 7 or 8, wherein the interior of the laminate is evacuated.

10. A method of manufacturing a composite glazing panel affording high acoustic attenuation, characterised in that a layer of an aerogel is sandwiched between two sheets of vitreous material, and the sandwich is bonded together as a monolithic laminate.

11. A method according to claim 10, wherein said sandwich is bonded together to form a light-transmitting laminate.

12. A method according to claim 10 or 11, wherein as adhesive for bonding together layers of the laminate is used a substantially solvent-free, fusible adhesive material.

13. A method according to claim 12, wherein as adhesive for bonding together layers of the laminate is used a powder adhesive.

14. A method according to claim 12 or 13, wherein as adhesive for bonding together layers of the laminate is used a silicone resin.

15. A method according to any of claims 10 to 14, wherein the or at least one said aerogel layer is formed directly on a said vitreous sheet so that it 8.
becomes directly bonded thereto.

16 A method according to claim 15, wherein said laminate is formed by assembling two aerogel layers, each directly formed on a said vitreous sheet.17. A method according to any of claims 10 to 16, wherein the or at least one said layer of aerogel is formed to a thickness of at least 10 mm.
18. A method according to any of claims 10 to 17, wherein the aerogel is hermetically sealed within said laminate.
19. A method according to claim 18, wherein the laminate is hermetically sealed by means of one or more spacer members extending around the panel and soldered to the vitreous sheets of the laminate.
20. A method according to claim 18 or 19, wherein the interior of the laminate is evacuated.