Hybrid phenol-formaldehyde and polymeric isocyanate based adhesive and methods of synthesis and use

Abstract

Hybrid resins formed of an acylated phenol-formaldehyde (PF) resin and a polymeric phenyl isocyanate (pMDI) resin have extended shelf stability, yet cure at a rate faster than any of its components when used in conventional flakeboard, strandboard or other board making processes.

We claim:  
     
         1 . A hybrid resin comprising a protected phenol-formaldehyde resin and a polymeric phenyl isocyanate.  
     
     
         2 . The hybrid resin of  claim 1 , wherein said protected phenol-formaldehyde resin comprises an acylated phenol-formaldehyde.  
     
     
         3 . The hybrid resin of  claim 1 , wherein the phenol-formaldehyde resin is a resole.  
     
     
         4 . The hybrid resin of  claim 1 , wherein the phenyl isocyanate is 4-4′methylene bis(phenyl isocanate).  
     
     
         5 . The hybrid resin of  claim 1 , wherein the ratio of the protected phenol formaldehyde to the polymeric phenyl isocyanate is an amount of from about 10% to about 80% by weight and 90% to about 20% of the polymeric phenyl isocyanate.  
     
     
         6 . The hybrid resin of  claim 5 , wherein the ratio of the protected phenol formaldehyde to the polymeric phenyl isocyanate is from about 10 wt % - 40 wt % phenol formaldehyde to about 60 wt % - 90 wt % polymeric phenyl isocyanate.  
     
     
         7 . The hybrid resin of  claim 1  having a storage stability of at least two weeks at room temperature.  
     
     
         8 . A method of manufacturing board made of lignocellulosic particles comprising mixing said particles with a hybrid resin according to  claim 1 , forming the resulting mixture of lignocellulosic particles and resin into a loose mat and consolidating the mat under heat and pressure to deprotect the phenol-formaldehyde and cure the resin.  
     
     
         9 . The process of  claim 8 , wherein the deprotection occurs in the presence of moisture carried by the lignocellulosic particles.  
     
     
         10 . The process of  claim 8 , wherein the deprotection occurs by reason of moisture provided by steam.  
     
     
         11 . The process of  claim 8 , wherein the deprotected phenol formaldehyde reacts with the NCO group of the polymeric phenyl isocyanate at room temperature in excess of 120° C.  
     
     
         12 . The process of  claim 8 , wherein the cellulosic particles are selected from the group consisting of wood flakes, wood fibers, wood wafers, wood strips, wood strands, wood veneers and mixtures thereof.  
     
     
         13 . A method of synthesizing a hybrid resin comprising providing a phenol formaldehyde resin, protecting the reactive oxygens of the phenol formaldehyde resin, mixing the protected phenol formaldehyde resin with a polymeric phenyl isocyanate having reactive NCO groups, deprotecting the reactive oxygens and permitting the reactive oxygens of the hydroxyl groups of the phenol formaldehyde to react with the NCO groups, thereby obtaining a hardened resin.  
     
     
         14 . The method of  claim 13 , including mixing the hybrid resin with cellulosic material before the deprotecting step.  
     
     
         15 . The method of  claim 13 , wherein the hybrid resin is mixed with particles before the deprotecting step.  
     
     
         16 . The method of  claim 13 , wherein deprotecting is achieved under conditions of elevated heat, elevated pressure and in the presence of moisture.  
     
     
         17 . The method of  claim 13 , including the step of storing the mixture for up to two weeks at room temperature before said deprotecting step.  
     
     
         18 . The method of  claim 13 , wherein the mixing step comprises mixing 10 wt % to 80 wt % of the protected phenol formaldehyde with 90 wt % to 20 wt % of the polymeric phenyl isocyanate.  
     
     
         19 . The method of  claim 13 , wherein the phenol-formaldehyde is a resole and the phenyl isocyanate is 4-4′methylene bis(phenyl isocyanate).  
     
     
         20 . The method of  claim 13 , wherein the mixing comprises mixing 10 wt % to 40 wt % of the protected phenol formaldehyde with 90 wt % to 60 wt % of the polymeric phenyl isocyanate.  
     
     
         21 . The method of  claim 13 , wherein the protecting step results in an acylated phenol formaldehyde resin.