DETAILED DESCRIPTION A coating composition for fiberglass articles comprising an aqueous dispersion containing a mixture of at least two polymeric binders, as well as aluminum trihydrate, antimony oxide, and also defoaming agents, biocides, thickeners, color pigments, dispersants and the like, has now been discovered.
The dried coating composition of this invention, made by applying the aqeuous coating composition to fiberglass insulation and drying the coating in a drying oven has been found to impart an exceptionally advantageous balance of properties to the fiberglass insulation which cannot be achieved by heretofore known coating compositions.
The coating composition of the present invention is prepared by first dispersing aluminum trihydrate, antimony oxide, and a colored pigment in water using a Cowles type mixer, a sand mill, a three roll mill, or a similar high energy mixing device, and then blending this pigment slip with a mixture containing two or more emulsion polymers, a surfactant or wetting agent, or a blend of surfactants if necessary, a thickener and a biocide and a defoaming agent, if required.
The properties of the fiberglass insulation coating which have to be balanced against each other are mechanical strength combined with elasticity, fire retardation, and the lack of black smoke generation when a flame is brought in contact with the coating, as well as the smoothness of the insulation surface, as not to impede the airflow through ducts.
Fire retardation of a coating is generally achieved by using in the coating composition a halogenated organophosphorous plasticizer as taught in U.
S.
Pat.
No.
3,926,894, together with a polymeric binder and a filler or pigment.
However, a serious disadvantage of such a coating is the relative volatility of the plasticizer, especially in air ducts where large volumes of heated air pass over the coating, which makes the coating environmentally undesirable.
A plasticizer also contributes greatly to black smoke generation, when a flame comes in contact with the coating
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