Method of casting compositions in elastomeric molds

Claim 1

A method of molding a substantially bubble free object with a mold release value of at least about 10 inches of mercury and with a critical surface tension for wetting of at least about 35 dynes/cm. that undergoes a change in volume of less than about 1%, comprising: introducing into an elastomeric mold an admixture substantially free from water and entrapped air, of a phenolic polyol, a polyisocyanate and a curing catalyst wherein: I. said polyol is: a. an organic solvent soluble benzylic ether polyol which contains benzylic ether group and which comprises a condensation polymer of a phenol having the general formula: ##STR3## wherein A, B, and C are hydrogen, hydrocarbon radicals, oxyhydrocarbon radicals or halogen, condensed with an aldehyde having the general formula R'CHO wherein R' is hydrogen or a hydrocarbon radical of one to eight carbon atoms in the presence of catalytic concentrations of a metal ion, or b. a methylol-terminated phenolic polyol which comprises a resole polyol which is organic solvent soluble; Ii. said hardener component is a liquid polyisocyanate containing at least two isocyanate groups; Iii. said curing agent is a base having a pK b value in the range from between about 7 and about 11 and is present in an amount equal to 0.01 to 10.0 weight percent based on the weight of the polyol, and Iv. the components are mixed in the mold, the peak reaction temperature is maintained below about 235° F. the composition is maintained free from foaming and phase inversion is obtained by: a. controlling the ratio of polyol to polyisocyanate from between about 1:2 and 2:1, b. selecting solvents with flash points above the peak reaction temperature, and c. maintaining a catalyst concentration sufficient to avoid adverse secondary reactions; the cured casting is removed from the mold by applying a vacuum from between about 10 and about 25 inches of Mercury to the mold cavity.

Claim 2

A method of molding a substantially bubble free object with a mold release value of at least about 10 inches of mercury and with a critical surface tension for wetting of at least about 35 dynes/cm. that undergoes a change in volume of less than about 1%, comprising: introducing into an elastomeric mold an admixture substantially free from water and entrapped air, of a phenolic polyol, a polyisocyanate and a curing catalyst wherein: I. said polyol is: a. an organic solvent soluble benzylic ether polyol which contains benzylic ether group and which comprises a condensation polymer of a phenol having the general formula: ##STR3## wherein A, B, and C are hydrogen, hydrocarbon radicals, oxyhydrocarbon radicals or halogen, condensed with an aldehyde having the general formula R'CHO wherein R' is hydrogen or a hydrocarbon radical of one to eight carbon atoms in the presence of catalytic concentrations of a metal ion, or b. a methylol-terminated phenolic polyol which comprises a resole polyol which is organic solvent soluble; Ii. said hardener component is a liquid polyisocyanate containing at least two isocyanate groups; Iii. said curing agent is a base having a pK b value in the range from between about 7 and about 11 and is present in an amount equal to 0.01 to 10.0 weight percent based on the weight of the polyol, and Iv. the components are mixed in the mold, the peak reaction temperature is maintained below about 235° F. the composition is maintained free from foaming and phase inversion is obtained by: a. controlling the ratio of polyol to polyisocyanate from between about 1:2 and 2:1, b. selecting solvents with flash points above the peak reaction temperature, and c. maintaining a catalyst concentration sufficient to avoid adverse secondary reactions; the cured casting is removed from the mold by applying a vacuum from between about 10 and about 25 inches of Mercury to the mold cavity.