Foundry moulds and cores

Abstract

A foundry moulding composition comprising (a) a granular refractory material, and (b) from 0.5% to 8% based on the weight of the refractory material of a binder comprising (i) an aqueous solution of a potassium alkali phenol-formaldehyde resin, said aqueous solution having a solids content of from 50% to 75% and said resin having a weight average molecular weight (M w ) of from 600 to 1500, a formaldehyde:phenol molar ratio of from 1.2:1 to 2.6:1 and a potassium hydroxide:phenol molar ratio of from 0.2:1 to 1.2:1 and (ii) at least one silane in an amount of from 0.05% to 3% based on the weight of said aqueous solution, said binder being curable by contact therewith of from 5% to 60% based on the weight of said aqueous solution of a C 1-3 alkyl formate.

What is claimed is: 
     
       1. A process for the production of foundry moulds or cores which comprises; mixing a granular refractory material with from 0.5% to 8% based on the weight of the refractory material of a binder solution, said binder solution comprising (i) an aqueous solution of a potassium alkali phenol-formaldehyde resin, said aqueous solution having a solids content of from 50% to 75% and said resin having a weight average molecular weight (M w ) of from 600 to 1500, a formaldehyde:phenol molar ratio of from 1.2:1 to 2.6:1 and a potassium hydroxide:phenol molar ratio of from 0.2:1 to 1.2:1 and (ii) at least one silane in an amount of from 0.05% to 3% based on the weight of said aqueous solution,   discharging the mixture into a vented core or mould box, and   gassing the formed mixture with at least one C 1-3  alkyl formate to cure the binder.   
     
     
       2. The process of claim 1 wherein the refractory material is selected from the group comprising silica sand, quartz, chromite sand, zircon, olivine sand or beach sands containing shell fragments. 
     
     
       3. The process of claim 2 wherein the refractory material is chromite sand, olivine sand or beach sands containing shell fragments. 
     
     
       4. The process of claim 1 wherein the M w  of said resin is from 700 to 1100. 
     
     
       5. The process of claim 1 wherein the potassium hydroxide:phenol molar ratio is from 0.3:1 to 1:1. 
     
     
       6. The process of claim 4 or 5 wherein the potassium hydroxide:phenol molar ratio is from 0.4:1 to 0.6:1. 
     
     
       7. The process of claim 1 wherein the formaldehyde:phenol molar ratio is from 1.5:1 to 2.2:1. 
     
     
       8. The process of claim 6 wherein the formaldehyde:phenol molar ratio is from 1.5:1 to 2.2:1. 
     
     
       9. The process of claim 1 wherein said refractory material is mixed with from 1% to 3% based on the weight of the refractory material of said binder solution. 
     
     
       10. Th process of claim 1 wherein the mixture is gassed with from 5% to 60% based on the weight of the aqueous solution of said alkyl formate. 
     
     
       11. The process of claim 10 wherein the mixture is gassed with from 15% to 35% based on the weight of the aqueous solution of said alkyl formate. 
     
     
       12. The process of claim 11 wherein said alkyl formate is methyl formate. 
     
     
       13. The process of claim 1 or 12 wherein said alkyl formate is dispersed in a carrier gas. 
     
     
       14. The process of claim 13 wherein the concentration of said formate in the carrier gas is from 0.5% to 5% by volume. .Iadd. 
     
     
       15.  A process for the production of foundry moulds or cores from a mixture of sand with a curable binder, which comprises: mixing sand with from 0.5% to 8% based on the weight of the sand of a binder solution, said binder solution comprising (i) an aqueous solution of a potassium alkali phenol-formaldehyde resin, said aqueous solution having a solids content of from 50% to 75% and said resin having a weight average molecular weight (M w ) of from 600 to 1500, a formalehyde-phenol molar ratio of from 1.2:1 to 2.6:1 and a potassium hydroxide:phenol molar ratio of from 0.2:1 to 1.2:1, and (ii) at least one silane in an amount that provides a significant improvement in strength,   discharging the mixture into a vented core or mould box, and   gassing the formed mixture with at least one C 1-3  alkyl formate to cure the binder..Iaddend. .Iadd.16. The process of claim 15 wherein the weight average molecular weight of said resin is from 700 to 1100..Iaddend. .Iadd.17. The process of claim 15 wherein the potassium hydroxide:phenol molar ratio is from 0.3:1 to 1:1..Iaddend. .Iadd.18. The process of claim 15 wherein the formaldehyde-phenol molar ratio is from 1.5:1 to 2.2:1..Iaddend. .Iadd.19. The process of claim 15 wherein the mixture is gassed with from 5% to 60% of said alkyl formate, based on the weight of the aqueous solution of binder resin..Iaddend. .Iadd.20. A process for the production of foundry moulds or cores from a mixture of sand with a curable binder, which comprises:   mixing sand with from 0.5% to 8% by weight of a binder solution based on the weight of the sand, said binder solution comprising (i) an aqueous solution of a potassium alkali phenol-formaldehyde resin, said aqueous solution having a solids content of from 50% to 75% and said resin having a weight average molecular weight of from 700 to 1100, a formaldehyde-phenol molar ratio of from 1.5:1 to 2.2:1, and a potassium hydroxide:phenol molar ratio of from 0.3:1 to 1:1, and (ii) at least one silane in an amount that provides a significant improvement in strength,   discharging said mixture into a vented core or mould box, and   gassing the formed mixture with from 5% to 60% of at least one C 1-3  alkyl formate, based on the weight of the aqueous resin binder solution, to cure said binder..Iaddend. .Iadd.21. The process of claim 20 wherein the potassium hydroxide:phenol molar ratio is from 0.4:1 to 0.6:1..Iaddend. .Iadd.22. The process of claim 20 wherein the alkyl formate is methyl formate..Iaddend. .Iadd.23. A cold set system for the production of foundry moulds or cores utilizing vented core boxes or vented mould boxes, during which production foundry sand is mixed with a phenolic resin binder, the sand is shaped, and a curing agent is applied, to cure the binder, comprising:   a phenolic binder comprising an aqueous solution of a potassium alkali phenol-formaldehyde resin, said aqueous solution having a solids content of from 50% to 75% and said resin having a weight average molecular weight of from 600 to 1500, a formaldehyde:phenol molar ratio of from 1.2:1 to 2.65:1 and a potassium hydroxide:phenol molar ratio of from 0.2:1 to 1.2:1, and,   for curing said binder upon contact therewith, after said binder has been applied to said sand and said sand has been shaped in a vented core box or a vented mould box, at least one C 1  to C 3  alkyl formate dispersed in a carrier gas as a vapor or as an aerosol..Iaddend. .Iadd.24. The system of claim 23 wherein the weight average molecular weight of said   
     
     
        resin is from 700 to 1100..Iaddend. .Iadd.25.  The system of claim 23 wherein the potassium hydroxide:phenol molar ratio is from 0.3:1 to 1:1..Iaddend. .Iadd.26. The system of claim 23 wherein the formaldehyde:phenol molar ratio is from 1.5:1 to 2.2:1..Iaddend. .Iadd.27. The system of claim 23 wherein said binder comprises at least one silane in an amount that provides a significant improvement in strength..Iaddend. .Iadd.28. A cold-set system for the production of foundry moulds or cores utilizing vented core boxes or vented mould boxes, during which production foundry sand is mixed with a phenolic resin binder, the sand is shaped, and a curing agent is applied to cure the binder, comprising: a phenolic binder comprising an aqueous solution of a potassium alkali phenol:formaldehyde resin, said aqueous solution having a solids content of from 50% to 75%, and said resin having a weight average molecular weight of from 700 to 1100, a formaldehyde:phenol molar ratio of from 1.5:1 to 2.2:1, and a potassium hydroxide:phenol molar ratio of from 0.3:1 to 1:1, and said binder comprising at least one silane in an amount that provides a significant improvement in strength upon curing, and   for curing said binder upon contact therewith after said binder has been applied to said sand and said sand has been shaped in a vented core box or a vented mould box, at least one C 1  to C 3  alkyl formate dispersed in a carrier gas as a vapor or as an aerosol..Iaddend. .Iadd.29. The system of claim 28 wherein said potassium hydroxide:phenol molar ratio is from 0.4:1 to 0.6:1..Iaddend. .Iadd.30. The system of claim 28 wherein said alkyl formate comprises methyl formate..Iaddend.