It is well known that lightweight shapes of cured urea-formaldehyde resins can be produced from urea-formaldehyde foam and other resin solutions by incorporating a curing agent which causes gelling and curing of the resin solution together with a foaming or wetting agent. The resin solution can be mechanically beaten in order to incorporate finely-divided air bubbles, which are stabilized by the foaming agent, and is allowed to cure in a mold or cavity. Such foamed shapes generally have very low mechanical strength and usually exhibit significant shrinkage and deformation, such as warping and cracking upon curing, due to the loss of considerable quantities of water present in the mixture and produced during the curing reaction.
It is also known to use urea-formaldehyde resins as insulating materials, for example, in the walls of buildings, by injecting an uncured or liquid urea-formaldehyde foam into wall air spaces and voids. However, use of urea-formaldehyde foam in this manner suffers from serious drawbacks. First, free formaldehyde present in the foam migrates from the foam by evaporation thereby creating a significant odor problem. Second, from several days to in excess of three weeks may be required for the foam to cure within the walls. Third, the excellent potential insulating qualities of the cured urea-formaldehyde foam are not fully realized due to shrinkage, warpage and other deformation that occurs when water contained in the urea-formaldehyde resin evaporates. As a result, a significant amount of air can still migrate through the walls that contain the insulation.
Thus, a need exists for a process and apparatus for processing urea-formaldehyde foam into desired shapes without significant shrinkage and deformation.
USPTO Backgrounds
USPTO Backgrounds