Coating processes – Solid particles or fibers applied
Patent
1985-12-24
1987-08-25
Beck, Shrive P.
Coating processes
Solid particles or fibers applied
427221, 427196, 427426, 4273978, 118303, B05D 112
Patent
active
046892494
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of applying a coat of adhesively bonded expanded mineral grains to a surface of a structure, comprising the steps of causing a granular expanded mineral material to move in the form of a free flow through an atomized spray of an adhesive consisting of a solution of waterglass and a hardener therefor in such a manner as to form a film coating of said adhesive on the surface of each grain, and conveying the spray coated granular material, immediately after it has been thus produced, to the surface to be coated, depositing it on that surface and then spreading, compressing and smoothing it to form a coherent layer of a desired geometrical surface configuration.
Such a method is known from the Danish patent specification No. 146,014, and a further development is disclosed in Danish patent application No. 515/82 (cf. also U.S. Pat. No. 4,491,608 issued Jan. 1st, 1985). In both cases the method is more particularly directed to the laying of a screed-coat on a roof surface, and this is also an important field of use of the present invention, to which special attention will be paid in the following, though the invention is not limited to this particular use, but may also be used for applying a coat to other surfaces of structures, such as walls and partitions of building, building constructions, ships etc..
It is a characteristic of the known method that the grains of the granular expanded material are subjected to a minimum of mechanical forces until the moment they are deposited on the surface to be coated, so that they will maintain their expanded structure practically unaffected. Moreover, by evaporation of water after the spray coating of the grains, the waterglass binder changes characteristics and behaves more like a contact adhesive. At the point of deposition on the surface of the structure the spray coated grains therefore still behave almost like a granular material. It can be spread and shoveled like loose snow, and when in place one can by a light pressure activate the "contact adhesive" and stabilize the material. The material as deposited is therefore excellently workable to build up a layer of a desired geometrical surface configuration and has a sufficient viscosity for being laid with a sloping surface.
The known method is ideally suited for the renovation of defective built-up roofs with lack of gradient towards gutters and drains and frequently with surface cavities in which water may collect. On such a roof, the spray coated granular material is applied as a layer with correct gradient from all points towards drains, whereafter a new waterproof roof covering can be applied on top of the screed coat. The screed coat material has a density so low that it can be carried even by a light roof supporting structure which was originally dimensioned only to carry a certain snow load. The curing time can be made very short, and after curing the coat has a sufficient strength to permit the workers to step on it during the subsequent steps of the full re-roofing process. The screed-coat material has good heat insulation properties and is fire-proof and resistant to water in the sense that it is in no way deteriorated by water which may accidentally get access to it.
However, the screed-coat material as applied by the known method suffers from the drawback that it is highly absorptive to water by capillary effect. Therefore, if water accidentally gets access to it, e.g. owing to defective performance of the superposed waterproof roof-covering or subsequent damaging of the latter, it may in the course of time suck in so much water that it not only looses its insulating power, but even becomes so heavy that it may deform the roof supporting structure in a harmful manner.
The tendency to absorption of water could be reduced if the granular raw material were used in the form of a hydrophobized product. Hydrophobization is a process by which an expanded mineral granulate, while still hot from the expansion process, is sprayed with a hydrophobizing agent to make the granulate hy
REFERENCES:
patent: 1978125 (1934-10-01), Bennett
patent: 4179535 (1979-12-01), Kalbskopf et al.
patent: 4491608 (1985-01-01), Thygesen
patent: 4520073 (1985-05-01), Randolph et al.
patent: 4525388 (1985-06-01), Rehder
Beck Shrive P.
Micaform A/S
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