Coating processes – Nonuniform coating
Patent
1993-06-07
1994-08-30
Owens, Terry J.
Coating processes
Nonuniform coating
156106, 156289, 264130, B05D 508
Patent
active
053426533
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to plastic sheet for a laminated glazing and more particularly to a method of producing such a sheet having a desired level of adhesion in the glazing.
Layered, light transmitting safety glazings for window, windshield, sunroof, skylight, intrusion security, showcase, picture frame and like applications are well known. They include one or more rigid transparent panels such as glass combined in a laminate with an impact-dissipating plastic sheet such as plasticized polyvinyl butyral (PVB). It is likewise well established to carefully control the strength of the bond between the plastic sheet and rigid panel at a desired level since if too high the plastic sheet undesirably ruptures on impact and if too low splinters from the rigid panel can separate from the glazing, and, if glass, can injure a person in the surrounding area.
Heretofore, as far as presently known, this bond strength was customarily controlled (as typically disclosed for plasticized PVB in U.S. Pat. No. 3,249,488) by including in the formulation of the sheet chemical adhesion control additives such as alkali and alkaline earth metal salts and bases, metal salts of organic carboxylic and aromatic acids and the like. These anti-adhesion chemical additives which are present in very small quantities in the sheet (generally less than 1/2 weight %) function on a molecular scale and, in the case of polyvinyl butyral with glass where the bond is too strong, are thought to reduce bond strength by occupying sites on the glass and/or plastic sheet which might normally bond to each other. These additives often have an affinity for water and require careful control to avoid absorption of moisture which can produce undesirable haze in the transparent sheet. When present in such small quantities, accurate control of the additives concentration is difficult, particularly on a commercial scale. Since the additives are thought to interact with the glass, variations in the quality of the glass surface affects bond strength which is often not reproducible. Control of the adhesion of plastic sheet to rigid panels in a laminated safety glazing without relying on chemical additives would be desirable.
SUMMARY OF THE INVENTION
Now improvements have been made in controlling adhesion of plastic sheet and laminated glazing assemblies which substantially reduces the shortcomings of the prior art insofar as avoiding reliance on chemical additives to achieve such control.
A principal object of this invention is to provide a method of controlling adhesion of plasticized partial PVB sheet to glass in a laminated safety glazing.
Another object is to do so without relying on chemical adhesion control additives in the partial PVB resin.
A further object is to provide a method of producing such a sheet possessing such adhesion control capability.
These and other objects are accomplished by adjusting adhesion between plasticized partial PVB sheet having high affinity for adhesion to glass to a desired level by depositing a matrix of adhesion-resisting projections on the sheet surface, the total area covered by all the individual projections being regulated and constituting a predetermined desired fraction of the total sheet surface. Thus, the invention provides a plasticized partial PVB-glass surface area adhesion control method.
More particularly, a method is provided of producing plasticized partial polyvinyl butyral sheet having a desired level of potential adhesion to glass which comprises: i) providing partial polyvinyl butyral resin having a high affinity (i.e. a titer of less than about 10) for adhesion to glass when in sheet form under laminating conditions of elevated temperature and pressure; ii) mixing the resin with plasticizer to form a heat-shapable formulation; iii) extruding the formulation to form a sheet; and iv) applying a multiplicity of spaced anti-adhesion projections to the surface of the sheet to an extent effective to counteract the high adhesion of the sheet to glass between projections.
BRIEF DE
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Farmer Peter H.
Simon Robert H. M.
Monsanto Company
Murphy Michael J.
Owens Terry J.
Wachter Mark F.
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