Resin-coated sand

Abstract

The resin-coated sand is produced by coating the surface of a refractory granular aggregate with a thermosetting resin and a thermoplastic resin. When using this resin-coated sand, a mold with a less rough surface can be produced by a RP molding apparatus. When using this mold made of the resin-coated sand, a casting with fewer gas defects can be produced.

1 - 17 . (canceled)  
   
   
       18 . A method for forming a mold in an RP system by laminate shaping comprising the steps of: 
 providing a refractory granular aggregate;    coating the surface of the granular aggregate with a thermosetting resin and a thermoplastic resin;    spreading the resin-coated sand over a platform;    irradiating at least a portion of the resin-coated sand on the platform with a laser, and    heating the irradiating resin-coated sand at 170 to 250° C. for 1 to 7 hours to at least partially remove the thermoplastic resin.    
   
   
       19 . The method according to  claim 18 , wherein the coating step comprises first coating the surface of the granular aggregate with the thermosetting resin and then coating the thermosetting resin with the thermoplastic resin.  
   
   
       20 . The method according to  claim 19 , wherein the coating step comprises: 
 coating the surface of the granular aggregate with a thermosetting resin layer;    curing the layer of thermosetting resin; and    coating the surface of the thermosetting resin layer with a layer of the thermoplastic resin.    
   
   
       21 . The method according to claims  18  or  19 , wherein the thermoplastic resin is at least one of polyethylene, polypropylene, polyethylene glycol, polyamide, polymethyl methacrylate and polystyrene.  
   
   
       22 . The method according to claims  18  or  19 , wherein the amount of the thermoplastic resin is from 0.01 to 1.0 parts by mass with respect to 100 parts by mass of the granular aggregate.  
   
   
       23 . The method according to claims  18  or  19 , wherein 
 a particle size of the granular aggregate is not less than 10 μm and not more than 300 μm.    
   
   
       24 . The method according to claims  18  or  19 , wherein 
 the thermosetting resin is at least one of phenolic resin, melamine resin and urea resin.    
   
   
       25 . The method according to claims  18  or  19 , wherein a softening point of the thermosetting resin is not lower than 70° C. and not higher than 130° C.  
   
   
       26 . The method according to claims  18  or  19 , wherein the amount of thermosetting resin is from 1.0 to 4.0 parts by mass with respect to 100 parts by mass of the granular aggregate.  
   
   
       27 . The method according to claims  18  or  19 , wherein the thermoplastic resin has a mass-average molecular weight (relative to polystyrene standards) as measured by gel permeation chromatography within a range from 2,000 to 10,000.  
   
   
       28 . The method according to claims  18  or  19 , further comprising adding calcium stearate to the resin-coated sand as a flow improver.  
   
   
       29 . The method according to claims  18  or  19 , further comprising adding a metal powder of at least one of iron, copper, zinc, aluminum and nickel to the resin-coated sand.  
   
   
       30 . The method according to claims  18  or  19 , further comprising adding metal oxide of at least one of iron, copper, zinc, aluminum, nickel, cobalt and titanium to the resin-coated sand.  
   
   
       31 . The method according to claims  18  or  19 , further comprising adding a silane coupling agent of at least one of aminosilane and epoxysilane to the resin-coated sand.