Process for preparing erosion resistant foundry shapes with an epoxy-acrylate cold-box binder
View Patent ↗This invention relates to a process for making foundry shapes (e.g. cores and molds) using epoxy-acrylate cold-box binders containing an oxidizing agent and elevated levels of an organofunctional silane, which are cured in the presence of sulfur dioxide, and to a process for casting metals using the foundry shapes. The metal parts have fewer casting defects because the foundry shapes made with the binder are more resistant to erosion.
1. A process for preparing a foundry shape comprising:
(a) introducing a foundry mix into a pattern to form a foundry shape; and
(b) curing said shape with gaseous sulfur dioxide;
wherein said foundry mix comprises:
(c) from 90 to 99 parts by weight of a foundry aggregate; and a foundry binder comprising:
(d) 20 to 70 parts by weight of an epoxy resin;
(e) 5 to 50 parts by weight of an acrylate;
(f) 3 to 6 parts by weight of an organofunctional silane selected from the group consisting of γ-glycidoxypropyl trimethoxy silane, vinyl trimethoxy silane, γ-isocyanatopropyl triethoxy silane, octyl triethoxy silane, γ-acryloxypropyl trimethoxy silane, and mixtures thereof,
(g) an effective amount of a peroxide,
provided (d) is not mixed with (g), and where said parts by weight are based upon 100 parts of binder.
2. The process of claim 1 wherein the binder comprises from about 40 to 65 parts by weight of the epoxy resin; from 5 to 30 parts by weight of the acrylate; from 15 to 20 parts by weight of the free radical initiator; and from 4 to 6 parts by weight of the organofunctional silane, where said parts by weight are based upon 100 parts by binder.
3. The process of claim 2 wherein the wherein the epoxy resin comprises an epoxy resin derived from a bisphenol selected from the group consisting of bisphenol A, bisphenol F, and mixtures thereof.
4. The process of claim 3 wherein the epoxy resin has an epoxide equivalent weight of about 165 to about 225 grams per equivalent.
5. The process of claim 4 wherein the acrylate is a monomer.
6. The process of claim 5 wherein the acrylate is trimethyolpropane triacrylate, hexanediol diacrylate, and mixtures thereof.
7. A foundry shape prepared in accordance with claim 1 , 2 , 3 , 4 , 5 , or 6 .
8. A process of casting a metal article comprising:
(a) fabricating an uncoated foundry shape in accordance with claim 7 ;
(b) pouring said metal while in the liquid state into said foundry shape;
(c) allowing said metal to cool and solidify; and
(d) then separating the cast article.
9. A metal casting produced in accordance with claim 8 .