Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1985-11-04
1988-02-23
Dawson, Robert A.
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
156286, 156382, 350641, 4283044, 4289122, B32B 3114
Patent
active
047268603
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the production of mirror laminates of the kind in which a mirror is adhesively bonded to a substantially rigid backing board such as of wood, foamed or un-foamed plastics or fibrous plaster, or other support surface such as a wall or ceiling of a building, and to apparatus suitable for use with the method.
For the avoidance of doubt, the term `mirror` as employed herein relates to products of the kind comprising a transparent facing sheet, e.g. of glass or plastics, to the back of which has been applied a reflective surface. The reflective surface may be of metal, e.g. silver or copper or may be of any other suitable material e.g. gloss paint.
To accommodate differential thermal expansion between the mirror and the support, especially where the mirror has a large surface area, it is desirable to employ an adhesive which will give a flexible bond. Most such adhesives, however, are solvent-based; that is, they include a solvent which must be evaporated to attain the desired properties of the bond. Moreover, the solvents which are commonly used in these adhesives tend to attack the coating, e.g. of metal or paint, which provides the reflective surface of the mirror.
The mirror is, of course, non-porous and therefore where the backing board or other support surface is also non-porous or substantially so, that least some of the solvent tends to be trapped in the region of the bond line. Accordingly, with the passage of time, areas of the reflective coating are damaged or destroyed. Sometimes, the defect only materialises after a substantial period of time.
If solvent-free adhesives are used, on the other hand, e.g. adhesives that are formed by mixing together two materials one of which contains a polymerisable component and the other of which contains a catalyst for the polymerisation, the bond itself tends to fail after a relatively short period, e.g. 12-18 months.
There has therefore been a need to find a method of employing solvent-based adhesives which reduces the tendency of the solvent to attack the reflective coating.
According to the present invention, there is provided a method of bonding a mirror to a substantially rigid backing board or other support surface by means of a solvent-based adhesive, the method comprising forming the laminate of mirror and said support surface with a layer of porous material between and including the step of bonding the mirror and/or the backing board or other support surface to the layer by means of a solvent-based adhesive and extracting adhesive solvent vapour from the bond line of the assembly so formed by suction through the porous layer which for convenience is also referred to below as a porous membrane.
The invention is particularly applicable to the formation of transportable laminates of the kind in which a mirror is bonded to a backing board. However, it may also be employed in the lamination of mirrors in situ to support surfaces such as the walls and ceilings of buildings.
While it is possible to form the laminate of mirror, porous membrane and backing board or other support surface in one operation, in general the method will involve a first step in which one or other of the mirror and the backing board or other support surface is bonded to one face of the porous membrane and a second step in which the other of the mirror and the backing board or other support surface is bonded to the other face of the porous membrane. A solvent-based adhesive may be employed in either or both of the steps. Where it is employed in the first step, the best results are obtained if the extraction of adhesive solvent vapour from the bond line formed in that step is effected before the second step is carried out. Where a solvent based adhesive is employed in the second step, it will be appreciated that the extraction of the adhesive solvent vapour from the bond line formed in that step must be performed on the resultant laminate and that accordingly only the edges of the membrane are available for withdrawal of the vapour. Nevertheless the method of the
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Chelsea Artisans Limited
Collins Bruce M.
Dawson Robert A.
Long William C.
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