1. Field of the Invention
The present invention relates to the blending of wood particles and a resinous liquid binder in the manufacture of a wood composition board product.
2. Description of the Prior Art
In the production of wood composition board, a liquid resin binder is applied to the chips to bind them together to develop strength and stability in the finished board product. It is estimated that about 90 percent of the composition board produced in the United States is bonded with a liquid urea-formaldehyde resin. Such resin is a major cost factor in the production of such board, about 40 percent of the total manufacturing cost. The quantity of resin required to obtain the desired distribution of resin over the surfaces of the wood chips for optimum board strength determines the efficiency of the blending operation and thus greatly influences the cost of manufacturing the composition board.
Existing blenders for applying resin to wood chips, although varying in design, have in common the feature of applying resin directly to the wood chips, usually by exposing the chips to a resin spray. In one form of existing blender a curtain of free-falling wood chips drops through a resin spray and is thus coated in this manner. In a second form of existing blender wood chips are fed into one end of a stationary drum and moved through the drum and out the opposite end by the rotary action of paddles turning within the drum. As the chips travel from one end of the drum to the other, they are sprayed with resin which is distributed through the mass of chips by the mixing action of the paddles. In such blenders which apply the resin directly to the chips, the coating process is inefficient in that far more resin is required to obtain a thorough coating of all surfaces of all chips than is theoretically necessary. Accordingly, there is a need for a more efficient blender which uses a minimum of resin to coat uniformly wood chips to the extent necessary to produce composition board of desired strength.
Therefore, a primary object of the present invention is to provide a method and apparatus for providing a uniform coating of resin on wood chips using a minimum quantity of resin for a given quantity of wood chips.
Another primary object of the invention is to obtain a more uniform distribution of resin over the surfaces of the wood chips or particles than is obtained with existing blenders.
The ultimate objective is a reduction in the manufacturing cost of composition board without any reduction in board strength.