MANUFACTURED WOOD PANELS WITH ELEVATED LEVELS OF ZINC BORATE ADDITIVES FOR IMPROVED SURFACE PROPERTIES

Abstract

A method or process for a system for applying high, elevated levels of zinc borate additives to composite or manufactured wood panels, such as oriented strand board, for improved surface antifungal and anti-termite properties. Zinc borate is applied to one or more surface layers of a manufactured wood panel at approximately 2.0% (m/m) or higher, more preferably above 2.0% (m/m) to approximately 2.5% (m/m), which produces the surprising result of resisting surface fungal growth. In particular, OSB panels generated from Aspen and Southern Yellow Pine (SYP) wood species are successfully treated with zinc borate levels of at least approximately 2.0% (m/m), and found to resist surface fungal growth.

Claims

1. A method for producing a manufactured wood product with surface protection against fungal and insect attack, comprising: forming, on a production line, a bottom layer of a manufactured wood mat with bottom layer lignocellulosic strands; forming, on the production line, a core layer of the manufactured wood mat with core layer lignocellulosic strands; forming, on the production line, a top layer of a manufactured wood mat with top layer lignocellulosic strands treated with a first elevated concentration of zinc borate; and applying heat and pressure to the manufactured wood mat to form a manufactured wood product.

2. The method of claim 1, further comprising the steps of: blending all the lignocellulosic strands with a base concentration of zinc borate; and adding additional zinc borate to the top layer lignocellulosic strands sufficient to attain the first elevated concentration of zinc borate.

3. The method of claim 1, wherein the first elevated concentration is at least 2.0% (m/m).

4. The method of claim 1, wherein the first elevated concentration is greater than 2.0% (m/m).

5. The method of claim 2, further comprising the step of adding additional zinc borate to the bottom layer lignocellulosic strands sufficient to attain a second elevated concentration of zinc borate.

6. The method of claim 1, wherein the bottom layer lignocellulosic strands are treated with a second elevated concentration of zinc borate.

7. The method of claim 6, wherein the second elevated concentration of zinc borate is equal to the first elevated concentration.

8. The method of claim 1, wherein the core layer lignocellulosic strands are treated with a third concentration of zinc borate.

9. The method of claim 8, wherein the third concentration of zinc borate is less than the first concentration of zinc borate.

10. The method of claim 1, further comprising the steps of: prior to the step of applying heat and pressure, applying a WRB layer to a top surface of the manufactured wood mat; wherein the manufactured wood product comprises a panel with integrated WRB.

11. The method of claim 1, wherein the WRB layer comprises a resin-impregnated paper overlay.

12. The method of claim 1, further comprising the step of affixing a radiant barrier layer to a surface of the manufactured wood product.

13. The method of claim 1, further comprising the step of affixing an insulation layer to a surface of the manufactured wood product.

14. The method of claim 10, further comprising the step of affixing an insulation layer or a radiant barrier layer to a bottom surface of the manufactured wood product.

15. A method for protecting the surface of a composite wood product against fungal and insect attack, comprising: incorporating into at least one surface layer of a multi-layered composite wood product a pesticidal amount of a first preservative composition comprising a concentration of zinc borate of at least 2.0% (m/m).

16. The method of claim 15, wherein the concentration of zinc borate is greater than 2.0% (m/m).

17. The method of claim 15, wherein the multi-layered composite wood product comprises a composite-wood wall or roofing panel with an integrated resin-impregnated paper overlay on a face of the panel.

18. The method of claim 15, wherein the multi-layered composite wood product comprises a composite-wood wall or roofing panel with a radiant barrier layer on a face of the panel.

19. The method of claim 15, wherein the multi-layered composite wood product comprises a composite-wood wall or roofing panel with an insulation layer on a face of the panel.

20. The method of claim 17, wherein the multi-layered composite wood product further comprises a radiant barrier layer or an insulation layer on a second face of the panel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 shows an example of an OSB forming line.

[0014] FIG. 2 shows an example of an OSB forming line with the surface layers of the mat (top layer and bottom layer) treated with ZnB in accordance with the present invention.

[0015] FIG. 3 shows an example of an OSB forming line with the surface layers of the mat (top layer and bottom layer) treated with elevated levels of ZnB, and the core layer treated with lower levels of ZnB, in accordance with the present invention.

[0016] FIG. 4 shows an example of an OSB forming line with the surface layers of the mat (top layer and bottom layer) treated with elevated levels of ZnB, and the core layer treated with lower levels of ZnB, with optional overlays and secondary processing to add radiant barriers and/or insulation layers, in accordance with the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0017] In various exemplary embodiments, the present invention comprises a method or process for a system for applying high, elevated levels of zinc borate additives to composite or manufactured wood panels, such as OSB, for improved surface antifungal and anti-termite properties. More particularly, the present invention comprises a new method of application of zinc borate to one or more layers of a manufactured wood panel (e.g., OSB) at approximately 2.0% (m/m) or higher, more preferably above 2.0% (m/m) to approximately 2.5% (m/m), which produces the surprising result of resisting surface fungal growth. In particular, OSB panels generated from Aspen and Southern Yellow Pine (SYP) wood species are successfully treated with zinc borate levels of at least approximately 2.0% (m/m), and found to resist surface fungal growth when tested against five different microorganisms by the ASTM G21-15 Standard Practice for Determining Resistance of Synthetic Polymeric Materials to Fungi method (reapproved 2021, and as may be updated thereafter). Test results and/or the prior art indicate that lower levels of zinc borate (e.g., below about 1.0 m/m) are not as effective at resisting surface mold growth.

[0018] The composition of a typical manufactured or engineered wood-based panel (e.g., OSB) includes multiple layers of oriented strands of primarily Aspen or SYP wood species, along with a portion of other wood species. Two commonly used adhesives in the manufacturing of OSB and other engineered wood products are polymeric methylene diphenyl disocyanate (pMDI) and phenol formaldehyde (PF) resins. As seen in FIG. 1, lignocellulosic strands are dried and stored, 10, then resins (e.g., pMDI and/or PF) and wax are blended 20 with the wood strands making up the various layers (e.g., bottom 30, core 40, and top 50) prior to mat formation. The strands for all layers may be treated uniformly (i.e., blended with resin and wax together), or separately. The mat is then subjected to heat and pressure in a press 60 to form boards, which typically are trimmed to master blanks 70, and subject to further processing (cutting, priming, edge priming/sealing, labeling, packaging, and the like) 80, to produce the finished product 100. The manufacturing of engineered wood products (such as, but not limited to, OSB, laminated strand lumber, laminated veneer, or plywood) typically are produced by various primary (and sometimes secondary) pressing processes, as described above.

[0019] In one embodiment of the present invention, as seen in FIG. 2, zinc borate (ZnB) at an elevated level or concentration (as described above) 120a is added to the wood strands making up the surface (or outer) layers of the finished OSB panel. Alternatively, the ZnB at an elevated level may be added to just the wood strands making up the top surface layer, with the ZnB in the bottom surface layer added at a different level. The strands for the bottom layer may be blended with resins and wax without ZnB The strands for the top and bottom layer may be blended together, or separately.

[0020] The ZnB may be added with the resins and wax in the same blending process, as described above, or separately, after the resin/wax blending. The core strands may be blended with resins and wax without ZnB 120b. The treated strands are then arranged 30, 40, 50 as layers to form a mat in an OSB processing line, and then pressed to a desired thickness, under specified elevated pressure and temperature 60, to form the OSB panel.

[0021] In several embodiments, the core layer also is treated with ZnB 122b. The level of ZnB in the core layer may be the same as in the surface layers, or, as shown in FIG. 3, the level of ZnB in the core layer may be substantially lower than the level in the surface layer or layers 122a. A different amount can be added to the wood strands making up the core layer or layers separately from the amount added to the wood strands making up the surface layer or layers. In an alternative embodiment, a base level of ZnB may be added to all of the wood strands, and then additional ZnB may be added to the wood strands making up the surface layer or layers.

[0022] A multi-layered composite wood product 110 produced by the present invention may comprise a panel or board, a structural panel for a wall or roof, a wall panel or board, and/or a roofing panel or board. As seen in FIG. 4, these may be manufactured to incorporate (i) an overlay layer or layers, such as a resin-impregnated paper overlay layer or weather-resistant or water-resistant barrier (WRB) layer on a face, or both faces, of the product (e.g., a structural wall or roofing panel with a WRB layer on the outer face) 155, (ii) a radiant barrier layer on a face, or both faces, of the product 180, and/or (iii) a insulation layer, such as a foam insulation layer, on a face, or both faces, of the product 180. Such layers may be integrated with the panel or board at the factor as part of the primary manufacturing process or a secondary manufacturing process. Combinations of the above may be applied, such as a panel with a WRB layer on the outer face and a radiant barrier layer or foam insulation layer on the inner face, or a panel with foam insulation layer on the outer face and a radiant barrier layer on the inner face.

[0023] Zinc borates usable in the present invention include natural and/or synthetically produced zinc borates (ZnOB.sub.2O.sub.3), such as, but not limited to, zinc polytriborates (with a ZnOB.sub.2O.sub.3 ratio of 2:3) and hydrated zinc borates. Examples include, but are not limited to, the following: 2ZnO3B.sub.2O.sub.33.5H.sub.2O; 2ZnO3B.sub.2O.sub.37H.sub.2O; 2ZnO3B.sub.2O.sub.37.5H.sub.2O; 3ZnO5B.sub.2O.sub.314H.sub.2O; ZnO5B.sub.2O.sub.314H.sub.2O; ZnOB.sub.2O.sub.32H.sub.2O; 2ZnO2B.sub.2O.sub.33H.sub.2O; and 4ZnOB.sub.2O.sub.3H.sub.2O.

[0024] Accordingly, the present invention comprises a method for producing a manufactured wood product with surface protection against fungal and insect attack, comprising: forming, on a production line, a bottom layer of a manufactured wood mat with bottom layer lignocellulosic strands; forming, on the production line, a core layer of the manufactured wood mat with core layer lignocellulosic strands; forming, on the production line, a top layer of a manufactured wood mat with top layer lignocellulosic strands treated with a first elevated concentration of zinc borate; and applying heat and pressure to the manufactured wood mat to form a manufactured wood product. The bottom layer lignocellulosic strands may be treated with a second elevated concentration of zinc borate

[0025] Additional steps include blending all the lignocellulosic strands with a base concentration of zinc borate; and adding additional zinc borate to the top layer lignocellulosic strands sufficient to attain the first elevated concentration of zinc borate, wherein the first elevated concentration is at least 2.0% (m/m), or is greater than 2.0% (m/m). Additionally, the method may comprise the step of adding additional zinc borate to the bottom layer lignocellulosic strands sufficient to attain a second elevated concentration of zinc borate.

[0026] The second elevated concentration of zinc borate is equal to the first elevated concentration. The core layer lignocellulosic strands are treated with a third concentration of zinc borate, wherein the third concentration of zinc borate is less than the first concentration of zinc borate.

[0027] In some embodiments, the method further comprises the step of, prior to the step of applying heat and pressure, applying a WRB layer to a top surface of the manufactured wood mat. The manufactured wood product may comprise a panel with integrated WRB layer. The WRB layer may comprise a resin-impregnated paper overlay. Independently of the WRB layer, or in conjunction therewith, the method also may comprise the step of affixing a radiant barrier layer and/or insulation layer to a surface of the manufactured wood product. These layers may be affixed to the bottom surface of the manufactured wood product, opposite the WRB layer (when the WRB layer is present). In one embodiment, the insulation layer may be affixed to one surface, and the radiant barrier may be affixed to the other surface.

[0028] Further, the present invention comprises a method for protecting the surface of a composite wood product against fungal and insect attack, comprising incorporating into at least one surface layer of a multi-layered composite wood product a pesticidal amount of a first preservative composition comprising a concentration of zinc borate of at least 2.0% (m/m). In some embodiments, the concentration of zinc borate is greater than 2.0% (m/m). The multi-layered composite wood product comprises a composite-wood wall or roofing panel with an integrated resin-impregnated paper overlay on a face of the panel, a radiant barrier layer on a face of the panel, and/or an insulation layer on a face of the panel. These layers may be affixed to the bottom surface of the manufactured wood product, opposite the WRB layer (when the WRB layer is present). In one embodiment, the insulation layer may be affixed to one surface, and the radiant barrier may be affixed to the other surface.

[0029] 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.