Process to produce sheet molding compound using a polyamide release film

Claim 1

In a process for producing sheet molding compound comprising: (a) casting a layer of heat-curable thermosetting resin, in fluid form, onto a continuously advancing polymeric film; (b) introducing reinforcing material onto the advancing fluid layer; (c) contacting a polymeric film to the top surface of said reinforced fluid layer thereby forming a sandwiched composite; (d) advancing said sandwiched composite through a series of kneading and compaction rolls, and (e) winding the sandwiched composite into a roll for partial curing; the improvement which comprises using as the polymeric film a low crystallinity polyamide film, of about 0.5 to 5 mils thick, comprised of a blend of a polyamide selected from the group consisting of polyhexamethylene adipamide, polyepsiloncaprolactam, and mixtures thereof, the polyamide having a crystallinity of less than 35%, and about 10 to 30 percent by weight of said blend, of a polyolefin component, or copolymer thereof, the polyolefin having a crystallinity of less than 50%, wherein said film, exhibits (a) a Graves tear strength of at least about 400 grams in the longitudinal direction, as determined by ASTM D-1004-66; (b) a styrene permeability of below about 200×10 -9 g.cm/cm 2 -hr., and (c) peelability such that after maintaining said sandwich structure at 26°-32° C. for 3 days, less than 5 percent of the contacting surface of said film has sheet molding compound adhered thereto, after peeling.