GB2255518A - Process for applying surface coating - Google Patents

Abstract

A process for applying a surface coating to a board comprises the steps of arranging the board with its surface to be coated in a horizontal or generally horizontal upwardly-facing orientation, and applying to said surface a liquid coating having a self-levelling consistency.

Description

Title: "Process for applying a surface coating' Description of Invention This invention relates to a process for applying a surface coating to a board.

The term "board" as used herein includes for example "building boards1, which include rigid or senli-rigid panels of a variety of substances or compositions and which arc widely utilised in the building industry, for example to provide external cladding for buildings, linings for tunnels or subways, or internal walls or ceilings, for example.

It is desirallle for that surface of a building board which will be visible in use to be given a decorative and/or protective coating prior to installation in a building or other structure. Conventionally this coating comprlses a paint or paints which, although applied to the board prior to installation, is or are of a kind which would be physically suitable for application to a surface having the orientation which the board will occupy in use. tuts, given the vertical or other non-horlzonlal or downwardly-facing horizontal orientation that such boards may be required to adopt in use, it is customary to use a paint or paints of a suitably thick or non-drip character, which would be the natural paint or paints to use for in-situ painting of such surfaces.

The use of such paints however has a variety of disadvantages, notably where the building board is of a relatively less expensive type (such as a ceinelit- bound board) having a comparatively poor textural surface quality, in that the paint hy virtue of its relatively thick/non-drip character tends merely to mimic any surface irregularities relatively faithfully, so that several coats or more of such paint, with intervening rubbing-down steps, are often required to provide a desired acceptably smooth finished surface coating.

It is an object of the invention to overcome or at least substantially reduce the inconvenience of such conventional painting processes, and to enable relatively less expensive boards to be utilised in relatively high quality applications.

According to the present invention, there is provided a process for applying a surface coating to a board, conlprising the steps of arranging the board with its surface to be coated in a llorizont.al or generally horizontal upwardlyfacing orientatiun, and applying to said surface a liquid coating (for example a paint) having a self-levelling consistency.

In this manner, achievement of a smooth-finish surface coating, may be substantially facilitated, requiring less time, effort and paint.

The invention also provides a board coated in accordance with said process in accordance with the invention.

Examples of processes in accordance with the invention, and boards coated in accordance with title invention, will now be described, with reference to the accompanying drawings, in which: FIGURE 1 illustrates in cross-section, a typical result of conventional board-painting techniques; FiGURE 2 illustrates in cross-section, by way of example, a board coatcd in accordance with the present invention: and FIGURE 3 illustrates in cross-section a further board coated in accordance with the present invention, illustrating a manner in which a particularly uneven board surface may be accommodated.

The result of multiple-coating of a building board by conventional painting techniques is illustrated in Figure 1, from which it will be apparent that a substantial number of coats, with intermediate rubbing-down or partial fatting, are requircd to achieve an acceptably smooth finish, which is highly laborious and of low cost-effectiveness.

Referring next to Figure 2, The board therein partly illustrated is coated in accordance wiltl the present invention, by the application to the board, (with the board ln a horizontal or generally horizontal face-up orientation prior to installation in a building or other strllcture) of a liquid surface coating, in this example a suitable paint, of a self-levellina consistency.

By the term "self-levelling" as used herein it is meant that the surface coating, namely the paint, is able to flow sufficiently after application to tile board, and in particular for a sufficient length of time before it dries or "gels", for it to adopt a natural level, under gravity, in the course of which it is able to flow into and occupy at least the majority of surface irregularities in the board and yet adopt a natural at least substantially smooth and horizontal upper surface level, prior to drying.

Thus, with a single coating step (although a further coat may be applied if desired to achieved an even higher quality result) a surface of acceptable smoothncss and flatness is achleved.

It is believed that the present invention lies primarily in the realisation that a coating medium having a self-levelling consistency, which due to its flow characteristics would be totally unsuitable for the coating of such boards at least in thc majority of their in-situ orientations, may nonetheless be utilised, and with particular advantage owing to the self-levelling characteristic, for coating the boards in a horizontal or near-horizontal face-up orientation prior to installation in a building or other structure.

Prefcrred processes in accordance with the invention in fact include thrcc paint stcps, with the board horizontal or generally horizontal in a face.up Orientation, the first step being the application of a sealer/primer preparation which need not particularly ilself have a self-levelling consistency and which is intended primarily to promole adhesion of the subsequently applied coating per se, the second step being the application of a sclf-levelling surface coating in the manner described above, and the third step, if desired, being the application of a further coating, to provide the final finish, which further coating may, as desired, he the same as or different to the aforementioned self-levelling coating applied at the second step.

In the example of Figure 2, the basic board is of cement particle composition, but it is to be appreciated that the invention may also be applied to clement fibre boards or silicate "bound" boards or other "bound" boards, the invention enabling a quality of surface finish to be achieved which would normally only be available with substantially more expensive board substrates of substantially greater initial smoothness or as a result of considerably more time and labour.

Suitable self-levelling coatings may for example include self-levelling paint compositions (such as are available for application to floors) or any other suitable liquid coating. At least some such coatings may be described as being "dilatant" in that in terms of stir-characteristics they may appear to be relatively thick, but which, when left undisturbed, exhibit a self-levelling characteristic.

In the event of coating media having self-levelling characteristics which are dependent upon, for example, temperature, it will be understood that for the purposes of the present invention, the coatings concerned should be self-levelling under the normal ambient condilions of use. For example, a coating which would not ordinarily exhibit sufficient self-levelling characteristics, might be made suffidently self-levelling by ralsing the ambient temperature, effectively so as to give sufficient time for the coating, in a fluid state, prior to gelling or drying, to attain a natural at least substantially flat/horizontal level.Preferably, the coatings are self-levelling at ordinary room temperature, or at any other temperature at which the process in accordance with the invention is being put into effect.

Since evaporation of any solvent, after basic self-levelllng has occurred, would have the effect of causing the final coating surface, after evaporation of any solvent, to mimic, at least to a substantially reduced scale, any surface irregularltiesiof the basic board substrate, preferred coatings in accordance with the Invention preferably comprise little or no volatile solvent of any type, and in preferred embodiments are in general of oil-based composition. In general, a suitable coating, under the conditions of use must stay fluid long enough for it to assume a natural (level) state that it would assume if it were to remain liquid forever and so must be basically of a flowable slow-gelling consistency.

Where the board has a surface texture including raised irregularities and depressions, in order to avoid applying excessive self-levelling coating, sufficient such coating may be applied to provide a level surface over said depressions, and preferably also, over at least some raised irregularities, and any remaining raised irregularities after the coating has dried, may conveniently then be sanded down to provide a final overall flat surface (Figure 3).

Alternatively, particularly where the surface texture is fibrous, a sealer/primer may first be applied to the surface, and the surface may then be rubbed flat or relatively flat, following which the self-levelling coating may then be applied, in which case atly need for final rubbing down may be avoided.

In the case of said cement type boards, the Invention is typically concerned willl providing a self-levelling coating which will satisfactorily conceal indentations of typically 0.2mm depth which, if not concealed, are sufficient to significantly reduce .tlle quality of appearance of a finished panel, particularly whcre the panel in use will be in close proximity to users of a building or other structure incorporat.ing the panel.

In general it has been found that a self-levelling coating thickness of about 0.2mum or so is sufficient for normal purposes and indeed with a coating of approximalely this thickness il has been found that there is generally no need to provide a boundat wall temporarily round the board, during coating, whether by spraying on the coating, or pouring on the coating, and in this regard it is generally desirable that the surface tension of the fluid coating should be sufficient to prevent excessive coating fluid from running off the edges of a panel during coating. A temporary boundary wall may however be provided, if desired, which in particular may enahle a. thicker self-levelling coating to be applied.

Applications of building boards coated in accordance with the invention include for example external cladding of buildings, including substantial external wall areas, or for example soffit hoards or facia boards adjacent to roofs, or linings for tunnels (e.g. road or rail) or pedestrian subways, or interior walls or ceilings for buildings, or any application where the coated building board in use is readily visible to the usets, The features disclosed in the forgoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a mcans for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately or in any combination of such featurcs, be utilised for realising the invention ln diverse forms thereof.

Claims (14)

CLAIMS:

1. A process for applying a surface coating to a board, comprising the steps of arranging the board with its surface to be coated in a horizontal or generally horizontal upwardly-facing orientation, and applying to said surface a liquid coating having a self-levelling Consistency.

2. A process according to Claim 1 wherein said board is a building board.

3. A process according to Claim 2 wherein said building board is of cement-bound composiriun.

4. A process according to any one of Claims 1 to 3 wherein said coating is a paint exhibiting a self4evelling characteristic prior to gelling or drying.

5. A process according to Claim 4 wherein said paint is oil-based.

6. A process according to Claim 4 or Claim 5 wherein said paint comprises little or no volatile solvent.

7. A process according to any one of Claims t to 6 wherein a sealer/prlmer is applied to said surface prior to application of said coating.

8. A process according to Claim 7 wherein said sealer/primer is at least partially rubbed down prior to application of said coating.

9. A process according to any one of Clams 1 to 8 wherein said coated8 is at least partially rubbed down after application.

10. A process according to any one of Claims I to 9 wherein a further coating is applied to provide a final finish.

I I. A board coated in accordance with any one of Claims 1 to 10.

12. A process for applying a surface coating to a board, substantially as hereinbefore described with reference to and/or as illustrated in the accompanying drawings.

13. A board substantially as hereinbefore described with reference to and/or as illustrated in the accompanying drawings.

14. Any novel feature or novel combination of features described herein and/or illustrated in the accompanying drawings.