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(11) | EP 0 597 727 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Insulated glass units |
| (57) A sheet 30 of flexible, water-impermeable material is secured to the back and side
faces A, B and C of a spacer frame 1, 2 by means of a pressure-sensitive adhesive
to form a moisture seal. |
TECHNICAL FIELD OF THE INVENTION
[0001] This invention relates to insulated glass units of the kind which include two or more sheets of glass separated by a frame which extends around the periphery of the sheets. The frame is formed of hollow spacer bar which contains a desiccant to absorb moisture from the air space between the sheets via holes formed in the inner surface of the spacer frame. The spacer bar may be of plain rectangular shape, of so called D and T shaped transverse section, or of any other suitable cross-sectional shape.
BACKGROUND
[0002] Such spacer frames may be constructed in a variety of ways. Often the straight sides of the frame may be formed of separate lengths, which are connected at the corners by flexible or rigid metal or plastics corner keys. More recently, automatic spacer bending machines have been introduced, which allow one or more lengths of spacer bar to be bent to form a rectangular frame. The abutting ends are joined by straight connectors or corner keys of metal or plastics, or they may be welded together and dressed off.
[0003] Sealant is applied to the outer surface of the spacer frame (usually referred to as its back face) to bond the spacer frame to the sheets of glass giving structural integrity to the unit, and provide a barrier against moisture penetration. Often a primary sealant is applied to the two side faces of the spacer before assembly. This acts as a handling aid to hold the two sheets of glass to the spacer and provides an additional barrier against moisture penetration. Where a primary sealant is used, the sealant applied to the back face of the spacer is referred to as the secondary sealant.
[0004] The internal space between the glass sheets is usually filled with air, although inert gas may also be used.
[0005] When an insulated glass unit fails, moisture condensation appears on the internal surfaces of the glass. A large proportion of such failures are due to moisture penetration in areas where the integrity of the spacer is violated, principally:
1. In the region of corner keys or straight connectors.
2. In the area of holes through which the desiccant is introduced into the spacer frame.
3. In the region of holes which are made through the spacer frame to introduce an inert gas into the gap between the glass sheets.
4. At positions where decorative profiles placed between the glass sheets are secured through the spacer frame. (The attachment method often includes drilling or punching holes through the spacer frame).
5. At imperfect welds between the ends of the spacer frame.
[0006] Great efforts have been made to effect an improved seal in one or more of these regions, but to date the solutions put forward all suffer from severe limitations
SUMMARY OF THE INVENTION
[0007] The present invention proposes a method of sealing a region of a spacer frame for an insulated glass unit, which comprises securing a sheet of flexible, moisture-impermeable material to the spacer frame by means of an adhesive.
[0009] The primary sealant, which may be of butyl rubber for example, usually has a very high resistance to moisture penetration. The resistance to moisture transmission of butyl rubber is very much higher than that of many of the usual secondary sealants. By extending the edges of the sheet material down the sides of the spacer, the edges of the sheet will be covered by the primary sealant, where both primary and secondary sealants are used, so that the risk of moisture penetration via the side edges of the sheet is very low. The only moisture penetration path between the ends of the applied sheet and the spacer frame is via an adhesive layer, which will usually be relatively thin, so that the risk of penetration by this route is also minimal. As a result, the seal is extremely effective and reliable over a long period, and is easy to apply. There are no short routes by which moisture can by-pass the sheet.
[0010] The sheet of moisture impermeable material will usually comprise a malleable (ferrous or non-ferrous) metal such as aluminium. Plastics sheets, e.g of polyester, may also be used, with or without a metallised coating, e.g of aluminium.
[0011] Pressure-sensitive acrylic adhesives are suitable for securing the sheet to the spacer frame.
[0012] The invention includes:
1. For use in the method, a sheet of flexible, moisture-impermeable material provided with a layer of pressure-sensitive adhesive which is protected by a peelable backing.
2. A spacer frame to which the sheet is applied.
3. An insulated glass unit incorporating the spacer frame.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The following description and the accompanying drawings referred to therein are included by way of non-limiting example in order to illustrate how the invention may be put into practice. In the drawings:
Figure 1 is a general view of a seal of the invention, and
Figure 2 is a transverse section through the seal as used in a completed insulated glass unit.
DETAILED DESCRIPTION OF THE DRAWINGS
[0015] In the construction of a spacer frame, two lengths of metal spacer 1, 2 are joined in an end-to-end relationship in known manner, e.g by means of a metal or plastics straight connector (not shown). The abutted ends of the two lengths of spacer 1, 2 would normally constitute a region of the spacer frame where there is a high risk of moisture penetration into the internal space between the glass sheets. The secondary sealant is thinnest at this point and moisture penetrating the joint in the back of the spacer could by-pass the primary seal on the sides of the spacer. In accordance with the invention, this region is sealed by means of a sheet of aluminium foil 3 having one face coated with a layer of acrylic or other suitable pressure-sensitive adhesive (not shown). The adhesive layer may be protected by a peelable backing sheet (not shown), which is removed prior to application of the seal. The adhesive layer is pressed against the back surfaces A of the two lengths of spacer 1, 2, with the foil 3 overlapping the spacer equally on both sides of the joint, so that the adhesive firmly bonds the sheet 3 to the lengths of spacer. The opposite side edges 30 of the sheet extend over and are similarly bonded to the opposed side faces B and C of the spacer bar, as shown.
[0016] When the spacer frame is incorporated into an insulated glass unit in the usual manner, the side faces B and C are bonded to the glass sheets 4 and 5, as shown in Fig. 2, by means of a primary sealant 6, e.g of butyl rubber. A secondary sealant, e.g of polysulphide, polyurethane, or silicone, is then applied to the back face A of the spacer bar to fill the remaining channel formed between the glass sheets 4 and 5.
[0017] It will be appreciated that the spacer bar may be of any desired transverse sectional shape and that any suitable primary sealant could be used, with or without a secondary sealant. In addition, the method will still seal the back of the spacer if only a secondary sealant is used, i.e. without a primary sealant.
[0018] Although the above description takes as an example a straight connection formed between spacer sections, it will be appreciated that the seal could be applied to any region of the spacer frame which requires additional sealing measures, e.g. at joints formed with corner keys, at welded joints, or over holes formed in the spacer to introduce desiccant or gas or for the attachment of decorative profiles.
[0019] The advantages of the seal arrangement described above may be summarized as follows:
1. The seal is highly resistant to the combined effects of temperature cycling and high humidity, and withstands the standard test for insulated glass unit integrity specified in BS5713.
2. The seal is highly resistant to the increased air pressure which can be produced in an insulated glass unit when the air between the glass sheets heats up as a result of solar radiation.
3. The seal is clean and dry immediately after application and will not contaminate or adhere to conveyor belts of insulated glass machinery, e.g butyl extruders.
4. The seal can be used with a variety of connectors and is equally applicable to the sealing of filling holes or attachment points for decorative inserts.
5. The seal is easy to apply without requiring heat, chemicals, or expensive machinery.
6. The materials used in the seal can be chosen to be fully compatible with other materials used in the manufacture of insulated glass units, and can also be selected for maximum durability.
7. The seal is thin and does not therefore interfere with the application of butyl sealants to the spacer, nor does it affect the cavity width of the assembled unit.
8. The seal does not substantially reduce the effective depth of the secondary sealant.
9. The seal is inexpensive to produce and quick and simple to apply by unskilled labour.
10. The seal assists in holding together the abutting ends of the spacer sections during handling or when the spacer frame is transported by an automated assembly plant.