METHOD OF MANUFACTURING A FIRE-RETARDANT TREATED WOOD COMPOSITE PANEL

Abstract

A process or method for manufacturing a fire-retardant treated wood composite board or panel, such as oriented-strand board, with a low melting point fire retardant (FR) material, such as boric acid, while the press is operating at typical press temperatures above the FR material melting point. An intervening overlay is applied to the top surface of the mat on the forming line, after the use or application of any FR material within or on the mat, prior to entry into the press. The intervening overlay covers the top surface so as to prevent the melting fire retardant material from contacting the press platen(s). After pressing, the intervening overlay may be removed from the top surface by sanding, buffing, or other methods. The intervening overlay also may be sized so as to extend over one or more edges of the underlying panel, for ease of removal post-process.

Claims

1. A process for manufacturing a fire-retardant treated wood composite board or panel, comprising the steps of: blending a plurality of wood strands with one or more chemicals or adhesives; apply a fire-retardant material to at least some of said plurality of wood strands; forming, on a forming line, a multi-layer strand mat from said plurality of wood strands, said multi-layer strand mat comprising a top surface; placing an intervening overlay layer on the top surface of the multi-layer strand mat; in a press, applying heat and pressure to the multi-layer strand mat and intervening overlay layer to form a master blank, panel or board; after removing the master blank, panel or board from the press, removing the intervening overlay layer from the top surface.

2. The process of claim 1, further comprising the step of adding a fines layer to the multi-layer strand mat as the top surface.

3. The process of claim 2, wherein the fines layer comprises fire-retardant material.

4. The process of claim 1, further comprising the step of applying a second fire-retardant material to the top surface prior to placing the intervening overlay on the top surface.

5. The process of claim 1, wherein the step of removing the intervening overlay layer comprises planing or sanding the intervening overlay layer from the top surface.

6. The process of claim 1, wherein the step of removing the intervening overlay layer comprises pressure-washing the intervening overlay layer from the top surface.

7. The process of claim 1, wherein the step of removing the intervening overlay layer comprises peeling the intervening overlay layer from the top surface.

8. The process of claim 7, wherein the intervening overlay layer comprises an adhesive-resistant coating or layer on the face in contact with the top surface.

9. The process of claim 1, wherein the intervening overlay layer and the top surface have a same length and width.

10. The process of claim 1, wherein one or more edges of the intervening overlay layer extend beyond a corresponding edge or edges of the top surface.

11. The process of claim 1, wherein the intervening overlay layer comprises paper.

12. The process of claim 1, wherein the intervening overlay layer comprises kraft paper.

13. The process of claim 1, wherein the intervening overlay layer has a thickness of from approximately 1/16 inch to inch.

14. The process of claim 1, wherein the intervening overlay layer has a thickness of from approximately 1/16 inch to 3/16 inch.

15. The process of claim 1, wherein the intervening overlay layer has a thickness of 1/16 inch or less.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 shows a diagram for a press production/manufacturing process for an OSB panel product in accordance with the present invention.

[0014] FIG. 2 shows a diagram of an alternative embodiment of a press production/manufacturing process for an OSB panel product in accordance with the present invention.

[0015] FIG. 3 shows a diagram of another alternative embodiment of a press production/manufacturing process for an OSB panel product in accordance with the present invention.

[0016] FIG. 4 shows a diagram of yet another alternative embodiment of a press production/manufacturing process for an OSB panel product in accordance with the present invention.

[0017] FIG. 5 shows a cross-section of a pre-press strand mat with fines layer and intervening overlay.

[0018] FIG. 6 shows a cross-section of a pre-press strand mat with fines layer and intervening overlay with a portion of the intervening overlay extending beyond an edge of the mat with fines layer.

DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

[0019] In various exemplary embodiments, the present invention comprises a method or process of manufacturing a fire-retardant treated wood composite or manufactured wood panel or board (e.g., OSB) with low melting point fire retardant (FR) material, such as, but not limited to, boric acid, while the press is operating at typical press temperatures (i.e., above the FR material melting point). For example, OSB typically is manufactured using press temperatures ranging from approximately 190 C. to approximately 220 C. Boric acid has a melting point of 170.9 C., which is below these press temperatures, so it will soften and melt while at typical press temperatures, and its use during the OSB manufacturing process thus will result in build-up of the melted material in the press itself.

[0020] In accordance with the present invention, an intervening overlay 30 is applied to the top surface of the mat on the forming line, after the use or application of any fire-retardant material within or on the mat, prior to entry into the press. The intervening overlay covers all or substantially all of the top surface of the strand mat 12a,b,c, and any fines layer 20, so as to prevent the melting low melting fire retardant material from contacting the press platen(s). The intervening overlay is made of suitable material able to withstand the application of heat and pressure while in the press.

[0021] After the pressing of the panel, the intervening overlay 30 may be removed from the top surface by sanding, planing, buffing, brushing with a wire brush, pressure washing or spraying, or similar means. In several embodiments, the intervening overlay is a peel-off' overlay, with the lower face of the overlay comprising a coating or layer to resist adhesion to the mat during pressing.

[0022] The peel-off overlay may be slightly larger than the underlying panel, sized so as to extend over 32 one or more edges of the underlying panel for ease of removal post-press. In further embodiments, the overlay may be left on the top surface, and the panel subsequently processed as normal for an FRT panel.

[0023] The intervening overlay may comprise paper, kraft paper, or other similar material. It may match one or more dimensions of the underlying strand mat and/or its top surface. That is, the intervening overlay may have the same width and length as the strand mat and/or its top surface, or may vary slightly in one or both. In one embodiment, as described above, the length and/or width of the intervening overlay may be greater, so that one or more edges of the intervening overlay extend beyond the underlying strand mat and/or top surface. The thickness of the intervening overlay may vary depending on the press conditions, the size of the strands in the mat, the presence of a fines layer, the type of FR material used, the intended end use of the product, or similar factors, or combinations thereof. In one embodiment, the intervening overlay is 3/16 thick or less. In another embodiment, the intervening overlay is thick or less. In a further embodiment, the intervening overlay is 1/16 or less. In yet a further embodiment, the intervening overlay is 1/32 or less.

[0024] FIG. 1 shows an example of the method of the present invention. Strands are produced from debarked logs 110 and dried and stored 120. The strands are then blended with resins, adhesives, and/or other chemicals 130. Low melting point fire-retardant material is mixed with or applied to the strands 132, either with the blending with resins, adhesives and/or other chemicals 130, or separately before or after the blending. The treated strands are then used to form multiple layers (e.g., bottom layer 140a, core layer 140b, top layer 140c) on a forming line. Strands used to form multiple layers may be treated together, or may be treated separately, so that strands in different layers may comprise different types and/or amounts or concentrations of FR material.

[0025] An optional fines layer 150 may be added to the upper surface of the strand mat, as is known in the prior art. The fines layer may not have any FR treatment, as seen in FIG. 1, although it some embodiments, as seen in FIG. 2, FR material may be mixed with or applied to the wood particles or material making up the fines layer 152.

[0026] After the mat is formed, the intervening overlay is applied 160 on top of the mat, and any fines layer, and the mat and intervening overlay then enter the press and subjected to heat and pressure to form master panels, boards or blanks 170. After removal from the press, the intervening overlay is removed 180 as described above (e.g., peel-off, sanding, planing, buffing, brushing with a wire brush, pressure washing or spraying, or similar means). The master blanks/board/panels are then trimmed or cut to the desired size(s) (e.g., a master can be trimmed, cut or divided in multiple panels or boards of typical sizes sold in the marketplace, such as 48 panels), with surfaces and/or edges primed and/or sealed, and packaged 190 to produce the finished product 200. Due to the use of the removable intervening overlay, no release agents or similar treatments to prevent the buildup of resin and/or FR material on the platens need to be applied prior to or during the pressing process. The present invention thus replaces the use of release agents, or the need to lower press temperatures.

[0027] FIG. 2 shows a variation of the method of FIG. 1, where FR material is applied to or mixed or blended with the fines material 152 prior to formation of the fines layer 150 on top of the strand mat. FR material also may be applied to the top of the strand mat (with or without a fines layer or other similar layers) 156. While FIG. 2 shows FR material being added at three points in the process, a person of skill in the art would understand that a process could add material at any one of these points alone, or any combination of these points. For example, FR material could be applied only to the top of the strand mat 156. The addition of the intervening overlay after the application to FR material in all of these cases serves to prevent the buildup of the FR material on the press platen(s).

[0028] FIGS. 3 and 4 show variations in post-press steps of the method of FIG. 1. In FIG. 3, after removal from the press, the master blanks/board/panels are first trimmed or cut to the desired size 190a, the intervening overlay then is removed 180 from the cut pieces, and the cut. The master blanks/board/panels are then trimmed or cut to the desired size(s), with surfaces and/or edges primed and/or sealed, and packaged 190b to produce the finished product 200. In FIG. 4, the intervening overlay is not removed.

[0029] In several embodiments, the present invention thus comprises a process for manufacturing a fire-retardant treated wood composite board or panel, comprising the steps of: [0030] blending a plurality of wood strands with one or more chemicals or adhesives; [0031] apply a fire-retardant material to at least some of said plurality of wood strands; [0032] forming, on a forming line, a multi-layer strand mat from said plurality of wood strands, said multi-layer strand mat comprising a top surface; [0033] placing an intervening overlay layer on the top surface of the multi-layer strand mat; [0034] in a press, applying heat and pressure to the multi-layer strand mat and intervening overlay layer to form a master blank, panel or board; [0035] after removing the master blank, panel or board from the press, removing the intervening overlay layer from the top surface.

[0036] The process may further comprise the step of adding a fines layer to the multi-layer strand mat as the top surface, and the fines layer comprising fire-retardant material. The process may further comprise the step of applying a second fire-retardant material to the top surface prior to placing the intervening overlay on the top surface. The process may further comprise, as the steps of removing the intervening overlay layer, the steps of planing or sanding the intervening overlay layer from the top surface, pressure-washing the intervening overlay layer from the top surface, and/or peeling the intervening overlay layer from the top surface. To assist in the step of peeling, the intervening overlay layer may comprise an adhesive-resistant coating or layer on the face in contact with the top surface. Further, the intervening overlay layer and the top surface may have the same length and width. Alternatively, one or more edges of the intervening overlay layer may extend beyond a corresponding edge or edges of the top surface.

[0037] Thus, it should be understood that the embodiments and examples described herein have been chosen and described in order to best illustrate the principles of the invention and its practical applications to thereby enable one of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited for particular uses contemplated. Even though specific embodiments of this invention have been described, they are not to be taken as exhaustive. There are several variations that will be apparent to those skilled in the art.