Coating processes – Roller applicator utilized
Patent
1998-11-06
1999-08-10
Bareford, Katherine A.
Coating processes
Roller applicator utilized
427429, 401188R, 222 95, B05C 128, B65D 3528
Patent
active
059356596
DESCRIPTION:
BRIEF SUMMARY
This application is the national phase of international application PCT/EP96/05835 filed Dec. 24, 1996 which designated the U.S.
BACKGROUND OF THE INVENTION
This invention relates to a process for the roller-application of an aqueous thixotropic coating composition to a surface at ambient temperatures, say 5 to 35.degree. C. The invention also relates to a combination for use in the process. The process and combination are most suitable for use with coating compositions such as paints, distempers, varnishes or woodstains which are conventionally applied to surfaces found on buildings. The process and combination are both easy to use by unskilled amateur or "Do-it-Yourself" (i.e. "DIY") painters, in that they substantially reduce and usually, almost eliminate mess from rollers, provided that they are used with a reasonable degree of common sense. The process and combination also reduce the amount of physical effort involved in painting, so making it a less tiring activity, especially for unskilled amateurs.
Roller-mess can occur in three ways. Firstly, the painter may load too much paint onto the roller so that it drips as it is being taken from a container of paint to the surface to be painted. Secondly, because rollers rotate during the application of the paint to a surface, blobs of overloaded paint are caused to fly off the roller by the centrifugal force they experience. This is known as "fly-off" in the British trade. Thirdly, probably all aqueous paints used in painting buildings at ambient temperatures contain cellulosic or similarly elastic thickeners. Such thickeners cause the paint to break up into droplets in the space just behind the roller causing a fine spray of paint known as "roller-spatter". Roller-spatter is described by R H Fernando et al in the book "Polymers in Aqueous Media", edited by J E Glass and published by the American Chemical Society of Washington in 1989 (see pages 247 and 248 and especially the photograph on page 248).
An early attempt to minimise mess from contact-coating tools (for example rollers, brushes or pads) was disclosed by Berger, Jenson & Nicholson Limited in British Patent Specification GB 922 456 published in 1963. GB 922 456 discloses the addition of titanium chelates to aqueous paint formulations containing cellulose. The chelate creates a gel structure which inhibits dripping, yet which breaks down under the shear forces experienced during application of the paint to the surface, with the result that the production of smooth coatings is still possible. The use of titanium chelates was and still is a major commercial success in the field of brush-painting, but it has been found to aggravate the problem of fly-off during roller-painting. This is because the gelled structure enables even bigger blobs of paint to be picked up by a contact-coating tool, which means that even more paint is available to fly when the tool is one which rotates, i.e. a roller.
The next commercially successful development relating to mess-free painting related specifically to roller-painting and it was disclosed by one of the present Applicants in their European Patent Specification EP 0 144 135A published in 1985. EP 0 144 135A disclosed the addition of large amounts of titanium chelate (or equivalents such as zirconium chelate or gel-forming clays) to aqueous paint formulations containing cellulosic thickeners, so producing a paint so highly gelled that it was virtually solid. The solid paint was formed in a tray dimensioned so as to be able to receive a roller of standard size and the roller was loaded by pressing it against the surface of the paint and rolling it back and forth. Such rolling liquefies the top two or three millimeters of the surface of the paint, but only the top two or three millimeters so that the paint is taken up onto the roller in a very regulated way, which significantly reduces the risk of blob-formation. In addition, roller spatter is virtually eliminated possibly because the highly regulated loading ensures a very uniform and light loading of paint, whic
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Cane Michael Roger
Elliott David
McDerment Iain Grierson
Bareford Katherine A.
Black & Decker Inc.
Imperial Chemical Industries plc
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