Reaction injection molding as a process to prepare contact lenses

A process for the preparation of a reaction injection molded contact lens comprising

• (a) mixing components in a reactive mixture in a RIM machine under sufficient conditions to form precursors for a polyurea network and a polyacrylic network, which upon curing forms on a interpenetrating polymer network, said reactive mixture comprising:
• (i) an amine terminated chain extender comprising a mixture of amines A and B, said amines being present in said reactive mixture in about 20-60% by weight, wherein A is ##STR21## wherein f.sub.1 is independently an integer from 1-75, R is an alkylene containing 3 carbon atoms and each R is the same,
• f is an integer between 1 and 150;
• R.sub.10, R.sub.11, R.sub.12, R.sub.13 and R.sub.14 are independently hydrogen or lower alkyl;
• Z.sub.1 and Z.sub.2 are independently a chemical bond or lower alkylene,
• with A and B being present in relative weight ratios ranging from about 60/40 to about 100% A;
• (ii) an organic di-or poly-isocyanate present in sufficient quantity to react with said amine terminated chain extender of (i) to form therefrom a polyurea network;
• (iii) an acrylic ester of the formula:
• ##STR22## wherein R.sub.3 is hydrogen or lower alkyl;
• m is an integer from 0 to 150;
• Z.sub.3 and Z.sub.5 are independently alkylene;
• Z.sub.4 and Z.sub.6 are independently a chemical bond or alkylene;
• R.sub.4 is hydrogen, lower alkyl or ##STR23## R.sub.5 is hydrogen or lower alkyl;
• R.sub.6 and R.sub.8 are independently hydrogen or lower alkyl;
• R.sub.7 is lower alkylene, a chemical bond or --CH.sub.2 (OCH.sub.2 CH.sub.2).sub.q --;
• q is an integer between 0 and 200, inclusive;
• p is an integer of 1-3.
• said acrylic ester being present in said reactive mixture in about 10-50% by weight;
• (iv) a free radical initiator being present in said reactive mixture in sufficient quantity to polymerize the acrylic ester of (iii) forming therefrom a polyacrylic network;
• and
• (v) a triamine present in sufficient quantity to crosslink said amine terminated chain extender of (i) wherein the ratio of polyurea to polyacrylic ranges from about 90:10 to about 50:50, and the sum of the weights of the components in the reactive mixture adds to 100%;
• (b) injecting said reactive mixture of (a) into a closed mold in fluid communication with the RIM machine and having a cavity in the shape of a contact lens under conditions sufficient to gel and harden said liquid into an interpenetrating polymer network;
• (c) removing the product of (b) from the mold;
• (d) optionally post-curing the product of (c) and
• (e) immersing the product of (d) in a water or an aqueous medium to form a hydrogel.