Resin composition and process for investment casting using stereolithography

A stereolithographic resin for investment casting comprising:

• (a) at least one light-curable, ethylenically unsaturated liquid selected from the group consisting of vinyls, acrylates, and methacrylates;
• (b) at least one photoinitiator, ranging in concentration from about 2 to 10%;
• (c) at least one solvent inert to said light-curable, ethylenically unsaturated liquid, soluble therein, and having a boiling point ranging from about 200.degree. to 300.degree. C.;
• and
• (d) at least one multifunctional crosslinker, ranging in concentration from about 2 to 20%.

A method of investment casting comprising the steps of:

• (a) forming a first thin layer of a light-curable liquid formulation comprising
• (1) at least one light-curable, ethylenically unsaturated liquid resin selected from the group consisting of vinyls, acrylates, and methacrylates,
• (2) at least one photoinitiator, ranging in concentration from about 2 to 10%,
• (3) about 5 to 30 wt % of at least one inert solvent having a boiling point ranging from about 200.degree. to 300.degree. C. and being essentially non-reactive with said light-curable, ethylenically unsaturated liquid and soluble therein, and
• (4) a multifunctional crosslinker, ranging in concentration from about 2 to 20%;
• (b) exposing said first thin layer of said light-curable liquid formulation to a light source to cause polymerization of selected portions of said layer and form a first polymerized layer;
• (c) covering said first polymerized layer with a second thin layer of said light-curable liquid formulation;
• (d) exposing said second thin layer to said light source to polymerize selected portions of said layer upon said first polymerized layer and form a second polymerized layer;
• (e) repeating steps (b) and (c) at least once to produce a specimen;
• (f) completing the cure of said specimen to produce a pattern;
• (g) investing said pattern in a mold material;
• and
• (h) heating said mold material with said pattern in it to fuse the material of said mold and to burn said pattern out of said mold to produce a mold.