Polyurethane-modified polyisocyanurate foam and a method for the preparation thereof

Claim 1

A method for the preparation of a rigid, highly flame resistant polyurethane-modified polyisocyanurate foam which comprises reacting A. at least one aromatic polyisocyanate having no orthosubstituent and having a plurality of aromatic nuclei in the molecule, B. at least one polyether polyol containing more than 3 hydroxy groups and having an equivalent weight of at least 114, C. at least one foaming agent useful for the preparation of polyurethane foam, D. at least one catalyst useful for the trimerization of the isocyanate group, E. at least one surfactant and F. at least one flame retardant useful for the preparation of polyurethane foam, the proportion of said components A, B, C, D, E and F being such as to satisfy the relationships of 1. the equivalent ratio defined by the expression, Ae/(Be + Ce + De + Ee + Fe) > 2, and 2. the weight ratio defined by the expression, 0.22 ≧ Bw/Aw ≧ 0.04 wherein A, B, C, D, E and F represent said components respectively, represents the number of chemical equivalents of said components, and w represents the weight of said components and wherein any one of components C, D, E and F is nonreactive with the component A, the non-reactive component is eliminated from the relationship.

Claim 2

A method for the preparation of a rigid, highly flame resistant polyurethane-modified polyisocyanurate foam which comprises reacting A. at least one aromatic polyisocyanate having no orthosubstituent and having a plurality of aromatic nuclei in the molecule, B. at least one polyether polyol containing more than 3 hydroxy groups and having an equivalent weight of at least 114, C. at least one foaming agent useful for the preparation of polyurethane foam, D. at least one catalyst useful for the trimerization of the isocyanate group, E. at least one surfactant and F. at least one flame retardant useful for the preparation of polyurethane foam, the proportion of said components A, B, C, D, E and F being such as to satisfy the relationships of 1. the equivalent ratio defined by the expression, Ae/(Be + Ce + De + Ee + Fe) > 2, and 2. the weight ratio defined by the expression, 0.22 ≧ Bw/Aw ≧ 0.04 wherein A, B, C, D, E and F represent said components respectively, represents the number of chemical equivalents of said components, and w represents the weight of said components and wherein any one of components C, D, E and F is nonreactive with the component A, the non-reactive component is eliminated from the relationship.