Method for producing molds for lost wax precision casting

Abstract

The problems of the invention are to establish a modeling resin composition excellent in shape retention and dewaxing properties in the skillful system which comprises a urethane resin easy if thermal decomposition, a plasticizer, and a wax or waxy component and a dewaxing method suitable for models made form the composition and to enhance the strength of a mold in the low temperature range wherein dewaxing is carried out. According to the invention, a mold is produced by applying a primary layer consisting of plural fireproof coating layers among which epoxy silicone layers are laid and a backup layer consisting of plural thick coating layers on the surface of a resin model made by curing a two-component reaction curing type urethane liquid resin (F) which consists of a multifunctional polyol component (A), a multifunctional polyisocyanate component (B), a plasticizer (C), a wax or waxy component (D), and hollow resin balloons (E), preheating the obtained composite in a low temperature range within 60 to 120° C. during 2 to 8 hours to conduct initial dewaxing of removing 5 to 50% by weight of the resin model, raising the oven temperature gradually, and conducting the heating of the resulting composite in a medium temperature range of 150 to 500° C. during 2 to 5 hours and then the firing thereof in a high temperature range of 500 to 1000° C. during 2 to 5 hours.

1 - 7 . (canceled)  
   
   
       8 . A method for producing a casting mold for a lost wax precision casting characterized by comprising: 
 a process for producing a resin model (H) by mixing a two-component reaction curing type urethane liquid resin (F) comprising a multifunctional polyol component (A), a multifunctional isocyanate component (B), a plasticizer (C), a wax component (D) and hollow resin balloons (E), injecting a resulting mixture into a mold (G), hardening it and demolding it from said mold (G);    a process producing a primary layer consisting of a plurality of coating layers laminated on a surface of the resin model (H) by repeating operation for forming said coating layer in which said resin model (H) is soaked in a solution for fireproof coating (I), picked up from it, dried, painted with epoxy silicon (N), dried and then hardened;    a process for producing a backup layer consisting of a plurality of thick film coating layers laminated on the surface of the resin model (H) by repeating operation for forming the thick film coating layer in which the resin model (H) is soaked in the solution for fireproof coating (I), sprinkled with stucco (M), dried, painted with epoxy silicon (N), dried and then hardened;    a process in which the resin model (H) coated with thick film fireproof coating multi-layer consisting of the primary layer and the backup layer is set in a furnace so as to turn down a sprue thereof, heated in a lower temperature range within 60 to 120° C. during 2 to 8 hours preliminarily, initially dewaxed within 5 to 50 wt % of the resin model;    a process for completing dewaxing and burning-out of the resin model in which temperature in the furnace is increased gradually and heating is carried out in a middle temperature range within 150 to 500° C. during 2 to 5 hours; and    a process for burning in a high temperature range within 500 to 1000° C. during 2 to 5 hours.    
   
   
       9 . A method for producing a casting mold for a lost wax precision casting according to  claim 8 , characterized in that an average functional radix of said multifunctional polyol component (A) is 2.8 or larger, an average functional radix of said multifunctional polyisocyanate component (B) is 2.0 or larger, and a ratio NCO/OH is within 0.8 to 1.0.  
   
   
       10 . A method for producing a casting mold for a lost wax precision casting according to  claim 9 , characterized in that said plasticizer (C) is micro-dispersed through phase separation when the two-component reaction curing type urethane liquid resin (F) is hardened by reaction.  
   
   
       11 . A method for producing a casting mold for a lost wax precision casting according to  claim 10 , characterized in that said two-component reaction curing type urethane liquid resin (F) contains polyether chains indicated by a chemical structural formula as follows at 2-20 wt % thereof.  
     
       
         
         
             
             
         
       
     
   
   
       12 . A method for producing a casting mold for a lost wax precision casting according to  claim 11 , characterized in that said wax component (D) is in powder shape with a maximum diameter of 5 mm and has a melting point within 60 to 130° C., and is contained within 3 to 30 wt % in said two-component reaction curing type urethane liquid resin (F).  
   
   
       13 . A method for producing a casting mold for a lost wax precision casting according to  claim 12 , characterized in that said epoxy silicon (N) consists of bisphenol type epoxy (J), amino silane (K) and organic solvent (L).  
   
   
       14 . A method for producing a casting mold for a lost wax precision casting according to  claim 13 , characterized in that particle diameters of the hollow resin balloons (E) are within 10-100 μm, absolute specific gravities thereof are within 0.01 to 0.03, and contained within 0.001-0.5 wt % in the two-component reaction curing type urethane liquid resin (F).  
   
   
       15 . A method for producing a casting mold for a lost wax precision casting according to  claim 10 , characterized in that said wax component (D) is in powder shape with a maximum diameter of 5 mm and has a melting point within 60 to 130° C., and is contained within 3 to 30 wt % in said two-component reaction curing type urethane liquid resin (F).  
   
   
       16 . A method for producing a casting mold for a lost wax precision casting according to  claim 9 , characterized in that said two-component reaction curing type urethane liquid resin (F) contains polyether chains indicated by a chemical structural formula as follows at 2-20 wt % thereof.  
     
       
         
         
             
             
         
       
     
   
   
       17 . A method for producing a casting mold for a lost wax precision casting according to  claim 16 , characterized in that said wax component (D) is in powder shape with a maximum diameter of 5 mm and has a melting point within 60 to 130° C., and is contained within 3 to 30 wt % in said two-component reaction curing type urethane liquid resin (F).  
   
   
       18 . A method for producing a casting mold for a lost wax precision casting according to  claim 9 , characterized in that said wax component (D) is in powder shape with a maximum diameter of 5 mm and has a melting point within 60 to 130° C., and is contained within 3 to 30 wt % in said two-component reaction curing type urethane liquid resin (F).  
   
   
       19 . A method for producing a casting mold for a lost wax precision casting according to  claim 8 , characterized in that said plasticizer (C) is micro-dispersed through phase separation when the two-component reaction curing type urethane liquid resin (F) is hardened by reaction.  
   
   
       20 . A method for producing a casting mold for a lost wax precision casting according to  claim 19 , characterized in that said two-component reaction curing type urethane liquid resin (F) contains polyether chains indicated by a chemical structural formula as follows at 2-20 wt % thereof.  
     
       
         
         
             
             
         
       
     
   
   
       21 . A method for producing a casting mold for a lost wax precision casting according to  claim 20 , characterized in that said wax component (D) is in powder shape with a maximum diameter of 5 mm and has a melting point within 60 to 130° C., and is contained within 3 to 30 wt % in said two-component reaction curing type urethane liquid resin (F).  
   
   
       22 . A method for producing a casting mold for a lost wax precision casting according to  claim 19 , characterized in that said wax component (D) is in powder shape with a maximum diameter of 5 mm and has a melting point within 60 to 130° C., and is contained within 3 to 30 wt % in said two-component reaction curing type urethane liquid resin (F).  
   
   
       23 . A method for producing a casting mold for a lost wax precision casting according to  claim 8 , characterized in that said two-component reaction curing type urethane liquid resin (F) contains polyether chains indicated by a chemical structural formula as follows at 2-20 wt % thereof.  
     
       
         
         
             
             
         
       
     
   
   
       24 . A method for producing a casting mold for a lost wax precision casting according to  claim 23 , characterized in that said wax component (D) is in powder shape with a maximum diameter of 5 mm and has a melting point within 60 to 130° C., and is contained within 3 to 30 wt % in said two-component reaction curing type urethane liquid resin (F).  
   
   
       25 . A method for producing a casting mold for a lost wax precision casting according to  claim 8 , characterized in that said wax component (D) is in powder shape with a maximum diameter of 5 mm and has a melting point within 60 to 130° C., and is contained within 3 to 30 wt % in said two-component reaction curing type urethane liquid resin (F).  
   
   
       26 . A method for producing a casting mold for a lost wax precision casting according to  claim 8 , characterized in that said epoxy silicon (N) consists of bisphenol type epoxy (J), amino silane (K) and organic solvent (L).  
   
   
       27 . A method for producing a casting mold for a lost wax precision casting according to  claim 8 , characterized in that particle diameters of the hollow resin balloons (E) are within 10-100 μm, absolute specific gravities thereof are within 0.01 to 0.03, and contained within 0.001-0.5 wt % in the two-component reaction curing type urethane liquid resin (F).