Stock material or miscellaneous articles – Composite – Of carbohydrate
Reexamination Certificate
2000-08-17
2002-10-08
Seidleck, James J. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of carbohydrate
C428S109000, C428S425100, C428S526000, C428S528000, C428S530000, C428S537500, C428S292400, C428S292700
Reexamination Certificate
active
06461743
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to process for producing an integral composite engineered panel product having at least one side which is substantially smooth, and more particularly, a durable, engineered wood composite product formed of lignocellulosic strands or wafers (“OSB”) at least one outer surface of which remains substantially smooth despite exposure to wet and/or humid weather conditions.
Products such as fiberboard and particleboard have been found to be acceptable alternatives in most cases to natural wood paneling, sheathing and decking lumber. Fiberboard and particleboard are produced from wood particles bonded together by an adhesive, the adhesive being selected according to the intended use of and the properties desired for the lumber. Often times, the adhesive is combined with other additives to impart additional properties to the lumber. Additives can include fire retardants, insect repellants, moisture resistants, fungus resistants and color dyes. A significant advantage of fiberboard and particleboard lumber products is that they have many of the properties of plywood, but can be made from lower grade wood species and waste from other wood product production, and can be formed into lumber in lengths and widths independent of size of the harvested timber.
A major reason for increased presence in the marketplace of the above-described product alternatives to natural solid wood lumber is that these materials exhibit properties like those of the equivalent natural solid wood lumber, especially, the properties of retaining strength, durability, stability and finish under exposure to expected environmental and use conditions. A class of alternative products are multilayer oriented wood strand particleboards, particularly those with a layer-to-layer oriented strand pattern, such as OSB. Oriented, multilayer wood strand boards are composed of several layers of thin wood strands, which are wood particles having a length which is several times greater than their width. These strands are formed by slicing larger wood pieces so that the fiber elements in the strands are substantially parallel to the strand length. The strands in each layer are positioned relative to each other with their length in substantial parallel orientation and extending in a direction approaching a line which is parallel to one edge of the layer. The layers are positioned relative to each other with the oriented strands of adjacent layers perpendicular, forming a layer-to-layer cross-oriented strand pattern. Oriented, multilayer wood strand boards of the above-described type are described in detail in the following: U.S. Patents: U.S. Pat. No. 3,164,511, U.S. Pat. No. 4,364,984, U.S. Pat. No. 5,435,976, U.S. Pat. No. 5,470,631, U.S. Pat. No. 5,525,394, and U.S. Pat. No. 5,718,786, all of which are incorporated herein by reference.
Certain oriented board products can be made from flakes that are created from debarked round logs by placing the edge of a cutting knife parallel to a length of the log and the slicing thin flakes from the log. The cut flakes are subjected to forces that break the flakes into strands having a length parallel to the grain of the wood several times the width of the strand. The strands can be oriented on the board forming machine with the strands predominantly oriented in a single, e.g., cross-machine direction in one, e.g., core layer and predominantly oriented in the generally perpendicular (machine) direction in adjacent layers. The various layers are bonded together by natural or synthetic resin(s) under heat and pressure to make the finished product.
Oriented, multilayer wood strand boards of the above-described type are produced with bending, tensile strengths and face strengths comparable to those of commercial softwood plywood. However, the elongated wood strands forming oriented wood strand boards typically have an irregular contour and leave voids, as a result, form a rough surface finish. Even sanding the board surface may not result in producing smooth surface finishes on oriented wood strand boards comparable to those routinely produced on natural solid wood boards. To form a smooth surface on oriented wood strand boards, it has been suggested to place a layer of wood particle fines on the finish surface of the board. A multilayer wood particleboard can be manufactured, for example, having a core portion of at least two layers composed substantially of adhesively bonded wood strands, and at least one layer composed substantially of adhesively bonded wood fines bonded to cover an outer layer of the core portion to form a finished surface. The wood strands are distributed in each core layer with their length in substantial parallel orientation in a preferred direction. Furthermore, the adjacent layers of the core are positioned relative to each other with the oriented strands of each layer perpendicular to the oriented strands of the adjacent layer, to thereby form a layer-to-layer oriented strand pattern multilayer core structure. In some cases, one or more core layers may be randomly oriented.
A smooth outer surface can be created on board products by adding a sufficient layer of fine wood particles. In U.S. Pat. No. 4,364,984, for instance, the layer of fines is described as being composed of irregularly contoured wood particles of various sizes having a width and thickness considerably less than average width of the wood strands forming the core layers. This prior art invention requires that the fines be “graded” for uniform size, and that the distribution of these graded fines be specific. More specifically, the fines after being graded to form particle fractions of substantially uniform smaller or larger size, are formed into a fines layer in which the smallest sized particle fraction is located at a first major surface of the fines layer and largest sized particle fraction is located at a second major surface of the fines layer. The size of the fines particles located therebetween are of a graduated size, the graduated size of the particles ranging from smaller to larger from the first to the second major surface of the fines layer.
These fines typically are said to be defined as wood particles having a width and thickness less than 0.50 mm. However, with respect to the invention of the '984 patent, the term “fines” is used in the broader, more generically relative sense to define wood particles having an average width and thickness several times smaller than the average width of the wood strands used to form the associated core layers. These fines wood particles are distributed in an unoriented graduated size pattern from the outer surface to inner surface of the core-covering surface layer, with the progressively smaller or finer wood particles being distributed closer to the outer surface of the surface layer. With the fines distributed in this unoriented, graduated size pattern, the largest fines wood particles are in contact with the surface of the covered core layer of the multilayer board to provide more contacting surface area for bonding the surface layer of fines to the covered core layer. By increasing the surface area of contact at the interface between the covered core layer and surface layer, it is concluded that a much stronger bond is capable of being formed between the layers. By avoiding orientation of the fines wood particles, the particles are said to interlink to aid the adhesive in the creation of a strong bond between the fines forming the surface layer. By combining the unoriented, graduated size pattern of distribution of fines in the surface layers with the layer-to-layer oriented pattern of distribution of strands in the core layers of the multilayer wood particleboard structure it is concluded in U.S. Pat. No. 4,364,984 that the strength, durability, stability and finish properties typifying natural solid wood lumber can be produced in lumber made from such multilayer wood strandboard structures.
U.S. Pat. No. 4,068,991 discloses a particleboard, e.g., chipboard product that includes a continuous parti
Ritter David C.
Tanzer Jay
Bissett Melanie
Louisiana-Pacific Corp.
Marger & Johnson & McCollom, P.C.
Seidleck James J.
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