Production of polyisocyanurate foam panels

Abstract

The present invention discloses the production of panels by a discontinuous process. The panels are produced by injecting a polyisocyanurate foam forming composition into the mold cavity at reduced pressure. The combination of certain polyisocyanurate foam forming formulation and the reduced pressure in the mold cavity allows production of and resulting sandwich panels in a discontinuous process where the produced panels are characterized by improved fire resistance.

1 . A method of making a polyisocyanurate (PIR) foam, comprising:
 A) injecting into a closed mold cavity, wherein said mold cavity is under an absolute pressure of from 300 to 950 mbar, a reaction mixture comprising:
 a) an organic polyisocyanate; 
 b) a polyol mixture, wherein the polyol mixture comprises an aromatic polyester polyol, wherein the aromatic polyester polyol is at least 35 weight percent of the total amount of polyol; 
 c) a trimerisation catalyst; 
 d) at least one flame retardant; 
 e) optionally auxiliary substances; and 
 f) a blowing agent component, 
   
       wherein said reaction mixture has an isocyanate index of greater than 250; and
 B) curing to form a polyisocyanurate foam. 
 
     
     
         2 . A method of making a sandwich panel having two exterior shells and an intermediate polyisocyanurate (PIR) structural foam core, comprising undertaking the method of  claim 1 , wherein said closed mold cavity is defined by the two exterior shells and an annular frame. 
     
     
         3 . A method according to  claim 1 , wherein the aromatic polyester polyol is at least 50 weight percent of the total amount of polyol. 
     
     
         4 . A method according to  claim 1 , wherein the reaction mixture has an isocyanate index of greater than 350. 
     
     
         5 . A method according to  claim 1 , wherein the mold cavity absolute pressure is from 800 to 950 mbar. 
     
     
         6 . A method according to  claim 1 , wherein the blowing agent component comprises a physical and chemical blowing agent. 
     
     
         7 . A method according to  claim 6 , wherein the chemical blowing agent is water, formic acid or a combination thereof. 
     
     
         8 . The method according to  claim 6 , wherein the physical blowing agent is pentane. 
     
     
         9 . A method according to  claim 1 , wherein the foam has an applied density of 30 to 75 kg/m 3 . 
     
     
         10 . A method according to  claim 1 , wherein the reaction mixture additionally comprises a silicone surfactant. 
     
     
         11 . A method according to  claim 1 , wherein the flame retardant is a halogen free flame retardant. 
     
     
         12 . A sandwich panel comprising two exterior shells and an intermediate polyisocyanurate (PIR) structural foam core, wherein the PIR foam core is produced from a reaction mixture comprising:
 a) an organic polyisocyanate;   b) a polyol mixture, wherein the polyol mixture comprises greater than 35% by weight aromatic polyester polyol and from 10 to 65% by weight novolac initiated polyol based on the total weight of polyol;   c) at least one curing and/or blowing catalyst;   d) at least one trimerisation catalyst;   e) at least one flame retardant;   f) optionally at least one silicone surfactant;   g) at least one chemical blowing agent selected from water and formic acid; and   h) pentane,   
       wherein the reaction mixture has an isocyanate index of greater than 250.