Patent ID: 8734945

Claim:
A radiation curable secondary coating composition comprising a secondary coating oligomer blend; wherein said secondary coating oligomer blend comprises alpha oligomer, a beta oligomer, and a gamma oligomer; wherein said alpha oligomer is urethane free, has an acid value of about 5 mg KOH/g or less; has a number average molecular weight of about 500 g/mol or more and equal to or less than about 2,000 g/mol; and is prepared by reaction comprising: an acrylate compound selected from an alcohol containing acrylate or alcohol containing methacrylate compound, an anhydride compound, an epoxy containing compound, an extender compound, and an alpha oligomer catalyst selected from the group consisting of triarylphosphine catalyst, phosphonium salt, tertiary amine and metal catalyst; wherein said beta oligomer is different from said alpha oligomer; wherein said beta oligomer has a number average molecular weight in the range of from about 3,000 g/mol to about 10,000 g/mol, and is prepared by reaction comprising: hydroxyethyl acrylate, one or more diisocyanates, a polyol selected from the group consisting of polyester polyols and polyether polyols, said polyol having a number average molecular weight in the range of from 300 g/mol to 10,000 g/mol, and a beta oligomer catalyst selected from the group consisting of dibutyl in dilaurate, metal carboxylate, sulfonic acid, amino base catalyst, organo base catalyst, triphenyl phosphine, alkoxide of zirconium, alkoxide of titanium, and ionic liquid phosphonium salt, ionic liquid imidazolium salt, and ionic liquid pyridinium salt; wherein said gamma oligomer is an epoxy diacrylate; wherein the total amount of the alpha oligomer and the beta oligomer included in the radiation curable secondary coating composition is from about 30 to about 95 wt. % based on the total weight of the composition, and wherein the beta oligomer is present in the composition in an amount of from about 0.1 to about 30 wt. % of the total amount of the alpha oligomer and the beta oligomer present in the composition; wherein said radiation curable composition when applied and cured as a secondary coating on an optical fiber has: A) a toughness of greater than about 12 J/m3, a secant modulus of less than about 1500 MPa, and a Tg greater than about 50° C.; B) an elongation of from about 30% to about 80%; C) a change in equilibrium modulus of about 20% or less when aged for 60 days at 85° C. and 85% relative humidity; D) an oil sensitivity of about 10% or less and E) a water sensitivity of about 10% or less.