METHOD OF SEALING A POROUS FIBROUS SUBSTRATE, AND DOOR SKINS, PRODUCED BY THE METHOD

Abstract

A method of surface sealing a porous fibrous substrate is provided. According to the method, a porous fibrous substrate possessing a moisture content and a surface with pores is provided. A sealant composition is applied to a surface of the porous fibrous substrate and permitted to penetrate the surface pores of the porous fibrous substrate and undergo cure while participating in a foaming reaction with the moisture content to establish a water-resistant polymeric foam sealant impregnated into the porous fibrous substrate. The water-resistant polymeric foam sealant contains a polyurethane and/or polyurea.

Claims

1-20. (canceled)

21. A door, comprising: a door frame having a first frame side and an opposite second frame side; a door skin comprising a porous fibrous substrate having an exterior surface possessing surface pores and an interior surface attached to the first frame side; and a water-resistant polymeric foam sealant comprising polyurethane impregnated in the surface pores of the porous fibrous substrate.

22. The door of claim 21, wherein the water-resistant polymeric foam sealant is a two-part polyurethane composition comprising a first part containing a polyol and a second part containing a polyisocyanate.

23. The door of claim 21, wherein the water-resistant polymeric foam sealant is present in an amount of about 3 grams to about 4.5 grams per square foot of porous fibrous door skin.

24. The door of claim 21, wherein the porous fibrous substrate possesses a mean pore size of about 1 micron to about 300 microns.

25. The door of claim 21, wherein the porous fibrous substrate comprises a cellulosic fiber and phenolic resin.

26. The door of claim 21, wherein the water-resistant polymeric foam sealant penetrates about 50 to about 75 microns below the exterior surface of the porous fibrous substrate.

27. The door of claim 21, wherein the porous fibrous substrate comprises medium density fiberboard.

28. The door of claim 21, wherein the door skin is embossed with a wood grain pattern and comprises at least one panel region.

29. The door of claim 28, wherein the door skin further comprises at least one molded contoured region surrounding the at least one panel region.

30. A door, comprising: a door frame having a first frame side and an opposite second frame side; a first door skin comprising a first porous fibrous substrate having a first exterior surface possessing first surface pores and a first interior surface attached to the first frame side; a second door skin comprising a second porous fibrous substrate having a second exterior surface possessing second surface pores and a second interior surface attached to the second frame side; and a water-resistant polymeric foam sealant comprising polyurethane impregnated in the first and second surface pores of the first and second porous fibrous substrates.

31. A door, comprising: a door frame having a first frame side and an opposite second frame side; a door skin comprising a porous fibrous substrate having an exterior surface possessing surface pores and an interior surface attached to the first frame side; and a water-resistant polymeric foam sealant comprising polyurea impregnated in the surface pores of the porous fibrous substrate.

32. The door of claim 31, wherein the water-resistant polymeric foam sealant is a two-part polyurea composition comprising a first part containing a polyamine and a second part containing a polyisocyanate.

33. The door of claim 31, wherein the water-resistant polymeric foam sealant is present in an amount of about 3 grams to about 4.5 grams per square foot of porous fibrous door skin.

34. The door of claim 31, wherein the porous fibrous substrate possesses a mean pore size of about 1 micron to about 300 microns.

35. The door of claim 31, wherein the porous fibrous substrate comprises a cellulosic fiber and phenolic resin.

36. The door of claim 31, wherein the water-resistant polymeric foam sealant penetrates about 50 to about 75 microns below the exterior surface of the porous fibrous substrate.

37. The door of claim 31, wherein the porous fibrous substrate comprises medium density fiberboard.

38. The door of claim 31, wherein the door skin is embossed with a wood grain pattern and comprises at least one panel region.

39. The door of claim 38, wherein the door skin further comprises at least one molded contoured region surrounding the at least one panel region.

40. The door of claim 29, wherein: the first door skin comprises a first porous fibrous substrate having a first exterior surface possessing first surface pores and a first interior surface attached to the first frame side; the door further comprises a second door skin comprising a second porous fibrous substrate having a second exterior surface possessing second surface pores and a second interior surface attached to the second frame side; and the water-resistant polymeric foam sealant comprises polyurea impregnated in the first and second surface pores of the first and second porous fibrous substrates.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings are incorporated in and constitute a part of the specification. The drawings, together with the general description given above and the detailed description of the preferred embodiments and methods given below, serve to explain the principles of the invention. In such drawings:

[0014] FIG. 1 is a flow diagram of a method according to an embodiment of the invention;

[0015] FIG. 2 is a partial cross-sectional view of an apparatus for making a consolidated cellulosic article, depicting the apparatus in a pre-compression state;

[0016] FIG. 3 is a partially cross-sectional view of the apparatus of FIG. 2, depicting the apparatus in a post-compression state;

[0017] FIG. 4 is an elevated perspective view of an embodiment of a six-panel door in accordance with the invention; and

[0018] FIG. 5 is a cross-sectional view taken along line V-V of FIG. 4.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS AND PREFERRED METHODS OF THE INVENTION

[0019] Reference will now be made in detail to preferred embodiments and methods of the invention as illustrated in the accompanying drawings, in which like reference characters designate like or corresponding parts throughout the drawings. It should be noted, however, that the invention in its broader aspects is not limited to the specific details, representative devices and methods, and illustrative examples shown and described in this section in connection with the preferred embodiments and methods.

[0020] Referring more particularly to the illustrated embodiments, FIG. 1 depicts a process according to an embodiment of the invention. At step 10, a porous fibrous substrate possessing surface pores and a moisture content is provided. The porous fibrous substrate is preferably a consolidated cellulosic article, such as a medium density fiberboard particle board, plywood, fiberboard, pegboard, cloth or fabric. Preferably, the cellulosic article contains wood fibers and/or particles.

[0021] The porous, fibrous substrate may be manufactured elsewhere or manufactured on site. Suitable manufacturing techniques include the wet processes, dry processes, and wet-dry processes described above. Referring now to FIGS. 2 and 3, an apparatus for forming consolidated cellulosic articles is generally depicted by reference numeral 20. A mat 22 of uncompressed cellulosic material is shown disposed between a first die 23 mounted to a first platen 24, and a second die 25 mounted to a second platen 26.

[0022] The facing surfaces of dies 23, 25 may be contoured to emboss desired shapes and/or patterns, e.g., panels, in mat 22. First die 23 includes a substantially flat top 31, sides 32 and 34, as well as a base 36. Second die 25 includes a bottom 38, sides 40 and 42, and a top 44. Second die 25 includes a plurality of forms 46 extending from bottom 38. Forms 46 are uniformly spaced apart by a plurality of voids 48. In the depicted embodiment, the forms 46 are bulbous or frusto-conical, having angled, arcuate, or canted sides 47. The angled sides 47 may be at a range of degrees, for example, from about 5 degrees to about 45 degree from vertical. It should be understood that top 31 of first die 23 may possess an identical, complementary, or alternative shape to that of the facing surface of second die 25. Similarly, bottom 38 of second die 25 may be flat. Additionally, the facing die surfaces also may contain tapered sides and other designs, or example, as described in U.S. Pat. No. 6,972,150.

[0023] First and second dies 23 and 25 may be manufactured from a suitably hard material such as steel or aluminum, and are mounted to platens 24, 26, respectively, for relative movement toward each other. In the depicted embodiment, the mechanism for moving first and second platens 24 and 26 toward one another is provided in the form of a cylinder 28 attached to second platen 26, which is preferably hydraulic, but which can be provided in other forms, including pneumatic, as well as various forms of linear actuators. First platen 24 is fixed, but a similar cylinder or cylinders may be attached to first platen 24 as well. Each cylinder 28 may be sized to produce a range of pressure outputs, such as in a range of about 3,000 psi to about 5,000 psi. The pressure exerted on mat 22 may be, for example, in a range of about 400 psi to about 1000 psi.

[0024] A heat generation mechanism 29 is preferably provided such that mat 22 is compressed under elevated temperatures as well. Heat generation mechanism 29 can take many forms including a source of heated oil or steam circulated through conduits 30 in first and second platens 24, 26 and first and second dies 23, 25. The achieved temperature is typically in a range of about 300 F. to about 500 F. (about 149 C. to about 260 C.), depending on the curing temperature required by the particular binding agent or resin being used.

[0025] Mat 22 may be comprised of any number of cellulosic materials and binding agents to result in, when compressed under heat and pressure, a consolidated cellulosic article 51 (FIG. 3). The cellulosic materials within mat 22 may include, but not be limited to, waste materials from lumber mill operations such as sawdust, shavings, and wood chips, or may be provided in the form of specially ground fibers of a specific size or range of sizes. Thus, where fibers are referred to herein, it is understood that other materials could be substituted. The binding agent may be in the form of various adhesives or resins including phenol formaldehyde, urea formaldehyde, melamine modified urea formaldehyde or isocyanic resins. Various materials and methods of manufacturing consolidated cellulosic materials are described in U.S. Pat. Nos. 5,306,539; 5,344,484; 5,367,040; 5,425,976; 5,470,631; 5,489,460; 5,647,934; 5,756,599; and 5,847,058.

[0026] FIGS. 2 and 3 show a typical sequence of steps resulting in the formation of the board 51. Mat 22 is provided on first die 23, with second die 25 being spaced away due to cylinder 28 being retracted. Mat 22 is typically provided in a semi-solid state after initial passage through, for example, pre-press rollers (not shown). The semisolid mat 22 is then conveyed into position between first and second dies 23, 25. When cylinder 28 extends, second platen 26 moves toward mat 22, and compresses mat 22 against first die 23. Cylinder 28, second platen 26, and second die 25 are then retracted away from first die 23 and platen 24, and consolidated cellulosic board 51 is removed.

[0027] Consolidated cellulosic board 51 will have opposite surfaces matching the surface shapes and contours of first and second dies 23, 25. For example, in the illustrated embodiment forms 46 pressed against mat 22 establish corresponding indented portions in compressed cellulosic board 51. The indented portions are separated by raised portions corresponding to voids 48.

[0028] Consolidated cellulosic board 51 may comprise, for example, a fiberboard article (e.g., hardboard or medium density fiberboard (MDF)) or a chipboard article (e.g., particleboard, medium-density particleboard, or oriented strand board (OSB)). Examples of consolidated cellulosic board products include siding, door facings, pegboard, etc. The door facings or skins may be useful for interior and exterior passageway and hallway, as well as for furniture, cabinet and closet doors, and drawers.

[0029] Consolidated cellulosic board 51 obtained from the above manufacturing processes will possess pores, voids, and/or cracks. Mean pore size may range, for example, from about 1 micron to about 300 microns, such as from about 20 microns to about 75 microns. Consolidated cellulosic board 51 is preferably characterized by a moisture content sufficient to foam the sealant composition, but preferably less than about 10 weight percent.

[0030] In step 12 of FIG. 1, a sealant composition is applied to at least one surface of consolidated cellulosic board 51. The sealant composition preferably comprises a polyurethane and/or polyurea precursor. An exemplary composition is a two-part urethane composition with a polyol first part and a polyisocyanate second part. Examples of suitable polyols include diols and triols, and may be selected from phenolics, polyethers and polyesters. The polyisocyanate may possess two or more isocyanate functional groups, such as MDI (methylene diphenyl diisocyanate), NDI (naphthalene diisocyanate), TDI (toluene diisocyanate), and HDI (hexamethylene diisocyanate). Another exemplary composition is a two-part polyurea composition with a polyamine first part and a polyisocyanate second part. It is within the scope of the invention to employ various compositions for forming the polyurethane and/or polyurea, including compositions containing monomers, oligomers, and/or prepolymers.

[0031] The sealant composition may contain additional ingredients, such as chain extenders, blowing agents, flame retardants, and/or fillers.

[0032] The preferred application technique is spraying. For example, in the case of a two-part urethane composition, a dual feed spray apparatus with a static mixer at the head of the application gun may be used. Other suitable techniques for applying the sealant composition include dipping brushing, and rolling. Generally, it is preferred to apply the sealant composition at substantially room temperature without preheating of consolidated cellulosic board 51 or sealant composition. It is preferred that the sealant composition be applied in an amount of about 3 grams/ft.sup.2 to about 4.5 grams/ft.sup.2 (grams of composition per square foot of porous fibrous substrate), although amounts outside this range are possible. The temperature conditions may be varied, however, depending upon such factors as the reactivity of the sealant composition.

[0033] In step 14, the sealant composition is permitted to penetrate the surface pores of consolidated cellulosic board 51 and undergo cure while participating in a foaming reaction with the moisture content of board 51. The cured composition establishes a water-resistant polyurethane and/or polyurea foam sealant impregnated into the pores of consolidated cellulosic board 51. The extent of penetration will be dependent upon several factors, including the pore size of consolidated cellulosic board 51 and the properties, e.g., viscosity, of the sealant composition. It is preferred that the sealant composition penetrate about 50 microns to about 75 microns below the surface of board 51.

[0034] In step 16, board 51 may be subjected to further processing, such as milling, shaping, painting, protective coating, hardware (e.g., doorknob, hinges, knocker) attachment, assemblage (e.g., into a door), etc.

[0035] FIGS. 4 and 5 illustrate a door, generally designated 60, made according to an embodiment of the invention. Door 60 includes a front door facing (door skin) 62 and an identical, rear door facing (door skin) 64, secured to opposite major surfaces of a door frame or interior support structure 66. Typically, parallel side members, known as stiles, establish opposite sides of door frame 66, and parallel end members, known as rails, establish the top and bottom of door frame 66. The frame members can be made of natural wood, man-made pressed wood, or any other suitable material. Door facings 62, 64 are preferably molded so as to impart aesthetic surface contours, such as wood grain patterning and/or panel structures, in the visible exterior surfaces that correspond to essentially identical contours of a mold cavity, e.g., dies 23, 25. The interior surfaces of door facings 62, 64 are preferably secured, e.g., with an adhesive, to a core component positioned within frame 66.

[0036] Door facings 62, 64 shown in FIGS. 4 and 5 are molded to simulate multi-panel door surfaces. The embodiment shown in FIGS. 4 and 5 contains two molded contoured regions 68, 70 that define and surround two panels 72, 74, respectively. Panels 72, 74 are preferably coplanar. Each of the contoured regions 68, 70 is completely surrounded by a substantially planar (e.g., horizontal) main surface portion 76. Optionally, panels 72, 74 lie in the same plane as main surface portion 76.

[0037] The exterior surfaces of door facings 62, 64 are sealed according to the invention, and may further be primed, painted, stained, and/or receive other layers and/or protective coatings. Optionally, wood veneers may be bonded to the exterior surfaces to provide the surfaces with the appearance (e.g., color, grain and/or inlay patterns) of natural wood. Alternatively, an image can be printed on the exterior surfaces of door facings 62, 64, as described in U.S. Pat. No. 7,001,016.

[0038] Door 60 is hollow in the middle or is provided with a core. The core, if present, may comprise a foam formed of any suitable polymer material which can be injected and formed in place or can be pre-formed and then placed between door facings 62, 64 and surrounded by frame 66. Other foam materials include, for example, corrugated pads and other insulation and materials. It should be noted that door facings 62, 64 may be adhered to the solid core, if present.

[0039] The foregoing detailed description of the certain preferred embodiments of the invention has been provided for the purpose of explaining the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use contemplated. This description is not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Modifications and equivalents will be apparent to practitioners skilled in this art and are encompassed within the spirit and scope of the appended claims and their appropriate equivalents.