Fugitive pattern for casting
View Patent ↗A fugitive pattern for making a shell mold for investment casting a metal or alloy comprises a substantially random interpolymer and a low molecular weight polymer in proportions to provide a fugitive pattern having a combination of properties suitable for use in making the shell molds.
1. A method of making a shell mold for casting a metal or alloy, comprising providing a fugitive pattern having a shape of an article to be cast of the metal or alloy, said pattern comprising a pattern material comprising A) a substantially random interpolymer prepared by polymerizing one or more α-olefin monomers with one or more vinyl or vinylidene monomers and B) a low molecular weight polymer other than said interpolymer, investing said pattern in a shell mold, and removing said pattern from said shell mold by melting said pattern without cracking said shell mold.
2. The method of claim 1 wherein said pattern is melted by flash heating.
3. The method of claim 1 wherein said pattern is melted by steam autoclaving.
4. The method of claim 1 wherein said interpolymer comprises ethylene/styrene interpolymer.
5. The method of claim 4 wherein said low molecular weight polymer comprises low molecular weight polystyrene.
6. The method of claim 1 further including in said pattern a thermoplastic polymer other than said interpolymer and said low molecular weight polystyrene.
7. A method of making a shell mold for casting a metal or alloy, comprising providing a fugitive pattern having a shape of an article to be cast of the metal or alloy, said pattern comprising a pattern material comprising A) a substantially random interpolymer and B) a low molecular weight polystyrene.
8. A method of making a shell mold for casting a metal or alloy, comprising providing a fugitive pattern having a shape of an article to be cast of the metal or alloy, said pattern comprising a pattern material comprising A) ethylene/styrene interpolymer and B) a low molecular weight polystyrene.
9. The method of claim 8 wherein said ethylene/styrene interpolymer is present in an amount of 10% to 95% by weight of said pattern material and said low molecular weight polystyrene is present in an amount of 5% to 60% by weight of said pattern material.
10. The method of claim 9 wherein said ethylene/styrene interpolymer is present in an amount of 30% to 80% by weight of said pattern material and said low molecular weight polystyrene is present in an amount of 10% to 50% by weight of said pattern material.
11. The method of claim 10 wherein said ethylene/styrene interpolymer is present in an amount of 50% to 70% by weight of said pattern material and said low molecular weight polystyrene is present in an amount of 20% to 50% by weight of said pattern material.
12. The method of claim 11 wherein said ethylene/styrene interpolymer is present in an amount of about 60% by weight of said pattern material and said low molecular weight polystyrene is present in an amount of about 40% by weight of said pattern material.
13. The method of claim 8 wherein the low molecular weight polystyrene has a molecular weight (Mn) <10,000.
14. The method of claim 13 wherein the average molecular weight is <5,000.
15. The method of claim 14 wherein the average molecular weight is <2,000.