Plasticized polyvinyl butyral sheet containing epoxy resin

DETAILED DESCRIPTION OF THE INVENTION In addition to stabilizing adhesion to photoreactive component(s) of a heat-wave-reflective or electrically conductive coating after prolonged exposure to light, epoxy resin usable in the invention, at concentrations described below, should have no significant adverse effect on processing plasticized PVB resin or on performance properties of the sheet of which it is a component.
In this latter respect, usable epoxy resins: a) should readily mix with components of formulations of conventional plasticized PVB sheet for laminated safety glass, i.
e.
PVB resin, PVB plasticizer, glass adhesion control and related property-enhancing additives; b) should be melt processable in such formulations in conventional equipment such as extruders, sheeting dies, mill rolls and the like; and c) as a component of sheet which on one side will always contact a glass pane of a laminated safety glazing, have little or no affect on adhesion to glass (as opposed to the photoreactive component), such glass adhesion being regulated by glass adhesion-reducing agent in the sheet formulation.
To determine whether an epoxy is functional as an adhesion-stabilizer in the context first mentioned above, the pane of glass of a glass laminate which is nearest the bond between the photoreactive component and the plasticized PVB sheet containing the epoxy resin must display a pummel adhesion (described further below) of at least 3.
0 after at least 1000 hours exposure in a Weatherometer, Fadeometer or equivalent accelerated aging exposure system.
By sufficient preliminary tests, one skilled in the art can readily determine particular usable epoxy resins.
With the foregoing criteria in mind, usable epoxy resins may vary in chemical identity.
Preferred epoxy compositions found usable as hereinafter described are selected from (a) epoxy resins comprised mainly of the monomeric diglycidyl ether of bisphenol-A; (b) epoxy resins comprised mainly of the monomeric diglycidyl ether of bisphenol-F; (c) epoxy resins comprised mainly of the hydrogenated diglycidyl ether of bisphenol-A; (d) polyepoxidized phenol novolacs; (e) diepoxides of polyglycols, alternatively known as an epoxy terminated polyether; and (f) a mixture of any of the foregoing epoxy resins of (a) through (e)