Method of applying modifying ingredients to open-celled polyurethane material

Abstract From the Canadian patent

The method of treating open-celled polyurethane foam by the application of a modifying ingredient such as a dye, pigment, color stablizer or fire retardant for example, wherein, the method comprises the steps of (a) applying an excess of a liquid solution or dispersion of the modifying ingredient to a mass of the foam, (b) removing most of the excess of the liquid by squeezing the mass, (c) passing a gas the temperature of which, is between 350°F. and 500°F. through the material for a period of time sufficient (1) to raise the temperature of the polyurethane mass to a point at which the polyurethane will absorb the modifying ingredient, and (2) to vaporize the liquid present in the solution …