Heat-cured furan binder system
View Patent ↗This invention relates to a heat-cured furan foundry binder system comprising a furan binder and a furan monomer or oligomer containing at least two terminal hydroxymethyl groups. The binders are particularly useful as warm-box binders, because they cure faster and foundry shapes (typically cores and molds) made with the binders exhibit higher tensile strengths than those made with conventional heat-cured furan binders.
1. A heat-cured furan binder system comprising:
(a) from 5 to 50 parts by weight of a furan resin;
(b) from 5 to 50 parts by weight of furfuryl alcohol;
(c) from 1 to 50 parts by weight of a dimethyolated furan selected from the group consisting of dimethylolated furan monomers, dimethyolated furan oligomers, and mixtures thereof,
d) from 1 to 10 parts by weight of polyvinyl acetate; and
e) from 1 to 10 parts by weight of an activator selected from the group consisting of resorcinol pitch, bisphenol A tar, and mixtures thereof,
wherein said parts by weight are based upon 100 parts of binder resin.
2. The binder of claim 1 , which further comprises a silane.
3. The binder of claim 2 , which does not contain a polyol.
4. A foundry mix comprising in admixture:
(a) a major amount of a foundry aggregate;
(b) a catalytically effective amount of a salt of a strong inorganic or organic acid; and
(c) a minor amount of a foundry binder of claims 1 , 2 , or 3 .
5. The foundry mix of claim 4 wherein the amount of an acid curing catalyst is from 10 parts by weight to 40 parts by weight based upon 100 parts binder.
6. A process for preparing a workable foundry shape comprising:
A. forming a foundry mix of claim 5 ;
B. shaping the foundry mix of A into a foundry shape;
C. contacting the foundry shape of B with a source of heat at a temperature sufficient to cure said mix; and
D. allowing the foundry shape to harden into a workable foundry shape.
7. A foundry shape prepared in accordance with claim 6 .