Sulfur dioxide-cured epoxy acrylate foundry binder system

Abstract

The present invention provides an epoxy acrylate foundry binder composition having an epoxy resin component (Part 1) and an acrylate component (Part 2) containing about 1% to less than about 6% by weight of a borate ester. The epoxy acrylate binders of the present invention are useful in making foundry cores and molds in that the addition of the borate ester increases hot strength of the binder system. Also provided is a cold-box process for making sand cores and molds using the epoxy acrylate binders cured by sulfur dioxide vapor.

1 . A sulfur dioxide-curable binder composition comprising:
 an epoxy resin component including at least one epoxy resin and a free radical initiator; and   an acrylate component including at least one acrylate and a boric acid ester, wherein the boric acid ester is present in an amount of about 1% to less than about 6% by weight based on the weight of the acrylate component.   
   
   
       2 . The binder of  claim 1  wherein the boric acid ester is a trialkyl borate. 
   
   
       3 . The binder of  claim 2  wherein the trialkyl borate is a tri(C 2 -C 8 )alkyl borate. 
   
   
       4 . The binder of  claim 3  wherein the tri(C 2 -C 8 )alkyl borate is selected from the group consisting of triethyl borate, tri-n-propyl borate, tri-isopropyl borate, tri-n-butyl borate, tri-isobutyl borate, tri-sec-butyl borate, tri-tert-butyl borate, and tri-n-octyl borate. 
   
   
       5 . The binder of  claim 1  wherein the boric acid ester is present in an amount of about 2% to about 4% by weight based on the weight of the acrylate component. 
   
   
       6 . The binder of  claim 2  wherein the trialkyl borate is present in an amount of about 2% to about 4% by weight based on the weight of the acrylate component. 
   
   
       7 . The binder of  claim 6  wherein the weight/weight ratio of the epoxy resin component to the acrylate component is from about 2:1 to about 1:1. 
   
   
       8 . The binder of  claim 1  wherein the acrylate component further includes a phenolic resin. 
   
   
       9 . A sulfur dioxide-curable binder composition comprising:
 an epoxy resin component including at least one epoxy resin and a free radical initiator; and   an acrylate component including at least one acrylate and tri-n-butyl borate, wherein tri-n-butyl borate is present in an amount of about 1% to less than about 6% by weight based on the weight of the acrylate component.   
   
   
       10 . The binder of  claim 9  wherein tri-n-butyl borate is present in an amount of about 2% to about 4% by weight based on the weight of the acrylate component. 
   
   
       11 . The binder of  claim 10  wherein the weight/weight ratio of the epoxy resin component to the acrylate component is about 2:1. 
   
   
       12 . The binder of  claim 11  wherein the epoxy resin component comprises an epoxy resin selected from the group consisting of bisphenol F, bisphenol A, epoxy novolac, and mixtures thereof. 
   
   
       13 . The binder of  claim 12  wherein the acrylate component comprises an acrylate monomer. 
   
   
       14 . The binder of  claim 13  wherein the acrylate monomer is selected from the group consisting of trimethylolpropane triacrylate, hexanediol diacrylate, and mixtures thereof. 
   
   
       15 . The binder of  claim 14  wherein the acrylate component further includes a phenolic urethane resin. 
   
   
       16 . A sulfur dioxide-curable foundry mix comprising:
 aggregate; and   a binder including an epoxy resin component and an acrylate component, the epoxy resin component including at least one epoxy resin and a free radical initiator, and the acrylate component including at least one acrylate and a boric acid ester, wherein the boric acid ester is present in an amount of about 1% to less than about 6% by weight based on the weight of the acrylate component; and   
     the binder being present in an amount from about 0.5% to about 2% based on the total weight of the foundry mix. 
   
   
       17 . The foundry mix of  claim 16  wherein the boric acid ester is a trialkyl borate. 
   
   
       18 . The foundry mix of  claim 17  wherein the trialkyl borate is a tri(C 2 -C 8 )alkyl borate. 
   
   
       19 . The foundry mix of  claim 18  wherein the tri(C 2 -C 8 )alkyl borate is selected from the group consisting of triethyl borate, tri-n-propyl borate, tri-isopropyl borate, tri-n-butyl borate, tri-isobutyl borate, tri-sec-butyl borate, tri-tert-butyl borate, and tri-n-octyl borate. 
   
   
       20 . The foundry mix of  claim 18  wherein the tri(C 2 -C 8 )alkyl borate is tri-n-butyl borate. 
   
   
       21 . The foundry mix of  claim 16  wherein the boric acid ester is present in an amount of about 2% to about 4% by weight based on the weight of the acrylate component. 
   
   
       22 . The foundry mix of  claim 20  wherein tri-n-butyl borate is present in an amount of about 2% to about 4% by weight based on the weight of the acrylate component. 
   
   
       23 . The foundry mix of  claim 22  wherein the weight/weight ratio of the epoxy resin component to the acrylate component is about 2:1. 
   
   
       24 . The foundry mix of  claim 23  wherein the epoxy resin component comprises an epoxy resin selected from the group consisting of bisphenol F, bisphenol A, epoxy novolac, and mixtures thereof. 
   
   
       25 . The foundry mix of  claim 24  wherein the acrylate component comprises an acrylate monomer. 
   
   
       26 . The foundry mix of  claim 25  wherein the acrylate monomer is selected from the group consisting of trimethylolpropane triacrylate, hexanediol diacrylate, and mixtures thereof. 
   
   
       27 . The foundry mix of  claim 16  wherein the acrylate component further includes a phenolic resin. 
   
   
       28 . A method of making a foundry shape, comprising the steps of:
 (a) preparing a foundry mix by admixing aggregate and a binder comprising an epoxy resin component including at least one epoxy resin and an effective amount of a peroxide; and an acrylate component including at least one acrylate and a boric acid ester, wherein the boric acid ester is present in an amount of about 1% to less than about 6% by weight based on the weight of the acrylate component; and wherein the binder is present in an amount from about 0.5% to about 2% based on the total weight of the foundry mix;   (b) shaping the foundry mix to a desired configuration to provide a shaped foundry mix; and   (c) curing the shaped foundry mix with gaseous sulfur dioxide to provide a foundry shape.   
   
   
       29 . The method of  claim 28  wherein the boric acid ester is a trialkyl borate. 
   
   
       30 . The method of  claim 29  wherein the trialkyl borate is a tri(C 2 -C 8 )alkyl borate. 
   
   
       31 . The method of  claim 30  wherein the tri(C 2 -C 8 )alkyl borate is selected from the group consisting of triethyl borate, tri-n-propyl borate, tri-isopropyl borate, tri-n-butyl borate, tri-isobutyl borate, tri-sec-butyl borate, tri-tert-butyl borate, and tri-n-octyl borate. 
   
   
       32 . The method of  claim 30  wherein the tri(C 2 -C 8 )alkyl borate is tri-n-butyl borate. 
   
   
       33 . The method of  claim 32  wherein tri-n-butyl borate is present in an amount of about 2% to about 4% by weight based on the weight of the acrylate component. 
   
   
       34 . The method of  claim 33  wherein the weight/weight ratio of the epoxy resin component to the acrylate component is about 2:1. 
   
   
       35 . The method of  claim 34  wherein the epoxy resin component comprises an epoxy resin selected from the group consisting of bisphenol F, bisphenol A, epoxy novolac, and mixtures thereof. 
   
   
       36 . The method of  claim 35  wherein the acrylate component comprises an acrylate monomer. 
   
   
       37 . The method of  claim 36  wherein the acrylate monomer is selected from the group consisting of trimethylolpropane triacrylate, hexanediol diacrylate, and mixtures thereof. 
   
   
       38 . The method of  claim 28  wherein the acrylate component further includes a phenolic resin.