Method of making a fire retardant polymer resin

Claim 1

Method of forming a flame retardant polymer resin, comprising the steps of reacting moieties of a first aldehyde and first phenol in the presence of a mineral acid in sufficient proportions to provide an acid-condensation reaction product in the form of a relatively low molecular weight, low viscosity liquid linear polymer having excess aldehyde functionality, said first aldehyde being selected from the group consisting of furfural and mixtures of furfural and paraformaldehyde, said first phenol being selected from the group consisting of metacresol, orthocresol, 3,5 dimethyphenol, resorcinol and substituted resorcinols; mixing moieties of a second aldehyde and second phenol to provide a solution of said second phenol in said second aldehyde, which solution contains said aldehyde in molar excess, said second aldehyde and second phenol being selected from the same groups as said first aldehyde and first phenol; adding to said reaction product a solid, organic, water soluble acid as a polymerization active catalyst; adding to said solution an inorganic acid polymerization catalyst containing water of hydration, said inorganic acid being selected from the group consisting of boric acid and boric acid complexes; reacting said reaction product and solution in the presence of said catalysts to produce condensation polymerization thereof into said resin.