Manufacture of multi-layered board with a unique resin system

Abstract

The present invention relates to the manufacture of a multilayered board having a stable, and moisture resistant surface. To accomplish this and other advantages of the invention, an improved binder system is used in the production of the surface layers of a multi-layered board which combines an excellent resin penetration inside the wood constituents of the board's surface layers, with a strength, durability and resitance to ambient water and moisture. The improved-binder system used in the production of the board surface layers accordinq to this invention involves contacting wood pieces with a binder composition comprised of a curable powdery aldehyde resin and a curable isocyanate resin in the substantial absence of free water to provide a composite mixture that can be formed into a surface layer for assembly and lamination together with other wood and resin composite layers.

What is claimed is:  
     
         1 . A method for making a multi-layered board, comprising the steps of: 
 contacting wood pieces with a first binder material comprising a curable powdery aldehyde resin and a curable isocyanate resin in the substantial absence of free water to provide a first mixture;    forming a first layer from the first mixture;    forming a second layer on the first layer, where the second layer comprises a second mixture comprising a second binder material and wood pieces; and    bonding together the first and second layers.    
     
     
         2 . The method according to  claim 1 , wherein the curable powdery aldehyde resin comprises phenol-formaldehyde and the curable isocyanate resin comprises an aromatic polyiisocyanate.  
     
     
         3 . The method according to  claim 2 , wherein the first binder material comprises approximately 10 to 90% by weight phenol-formaldehyde and approximately 90 to 10% by weight aromatic polyiisocyanate.  
     
     
         4 . The method according to  claim 2 , wherein the first binder material comprises approximately 20 to 49% by weight phenol-formaldehyde and approximately 80 to 51% by weight aromatic polyiisocyanate.  
     
     
         5 . The method according to  claim 4 , wherein the first binder material further comprises wax.  
     
     
         6 . The method according to  claim 2 , wherein the aromatic polyiisocyanate is selected from the group consisting of diphenylmethane diisocyanate, triphenylmethane triisocyanates, toluene diisocyanate, and tolylene diisocyanate.  
     
     
         7 . The method according to  claim 1 , wherein the wood pieces are selected from the group consisting of wood strands, wood wafers, wood flakes, wood chips, wood slivers, and wood particles.  
     
     
         8 . The method according to  claim 1 , wherein the bonding comprises applying sufficient heat and pressure to attach the first and second layers together.  
     
     
         9 . A method for making strand board, comprising the steps of: 
 contacting first wood strands with a first binder material comprising a curable powdery aldehyde resin and a curable isocyanate resin in the substantial absence of free water to provide a first mixture;    forming a first layer from the first mixture, wherein the first wood strands are substantially oriented in a first direction;    forming a second layer on the first layer, where the second layer comprises a second mixture comprising a second binder material and second wood strands, wherein the second wood strands are substantially oriented in a second direction which is different from the first direction;    contacting third wood strands with a third binder material comprising powdery curable aldehyde resin and a curable isocyanate resin in the substantial absence of free water to provide a third mixture, with the proviso that the third mixture can be the same mixture as or a different mixture from the first mixture;    forming a third layer from the third mixture on the second layer, wherein the third wood strands are substantially oriented in the first direction; and    bonding together the first, second and third layers.    
     
     
         10 . The method according to  claim 9 , further comprising forming a fourth layer directly on the second layer and before forming the third layer thereon, wherein the fourth layer comprises a fourth mixture comprising a fourth binder material and fourth wood strands, wherein the fourth wood strands are substantially oriented in the second direction.  
     
     
         11 . The method according to  claim 10 , wherein the second and fourth binder materials comprise aromatic polyiisocyanate.  
     
     
         12 . The method according to  claim 9 , wherein the curable powdery aldehyde resin of the first and third binder materials comprises phenol-formaldehyde and the curable isocyanate resin of the first and third binder materials comprises an aromatic polyiisocyanate.  
     
     
         13 . The method according to  claim 9 , wherein the first and third binder materials each independently comprises approximately 10 to 90% by weight phenol-formaldehyde and approximately 90 to 10% by weight aromatic polyiisocyanate.  
     
     
         14 . The method according to  claim 12 , wherein the first and third binder materials each independently comprises approximately 20 to 49% by weight phenol-formaldehyde and approximately 80 to 51% by weight aromatic polyiisocyanate.  
     
     
         15 . The method according to  claim 12 , wherein the aromatic polyiisocyanate is selected from the group consisting of diphenylmethane diisocyanate, triphenylmethane triisocyanates, toluene diisocyanate, and tolylene diisocyanate.  
     
     
         16 . The method according to  claim 9 , wherein the first, second, third and fourth binder materials each further comprises wax.  
     
     
         17 . The method according to  claim 9 , wherein the second direction is oriented substantially perpendicular to the first direction, and wherein the bonding comprises applying sufficient heat and pressure to attach the first, second and third layers together.  
     
     
         18 . An oriented strand board, comprising: 
 first and second surface layers each comprised of wood strands substantially oriented in a first direction, wherein the wood strands are bonded by curing of a binder material contacting the wood strands where the binder material is substantially free of water and comprised of a curable powdery aldehyde resin and a curable isocyanate resin; and    a core layer located between and bonded to the first and second surface layers, where the core layer comprises wood strands substantially oriented in a second direction that is different from the first direction.    
     
     
         19 . The board according to  claim 18 , wherein the second direction is oriented substantially perpendicular to the first direction, and wherein the curable powdery aldehyde resin comprises phenol-formaldelyde and the curable isocyanate resin comprises an aromatic polyiisocyanate.  
     
     
         20 . The board according to  claim 19 , wherein the binder material comprises approximately 10 to 90% by weight phenol-formaldehyde and approximately 90 to 10% by weight aromatic polyisocyanate.