Patent Application
20100126095
The present disclosure is generally directed to warp resistant wooden beams covered by hydrophobic films and methods for manufacturing such wooden beams.
Headers are beams (also known as lintels) that horizontally span two supports, columns or piers, across openings for windows, doors or other voids in walls and roofs in residential and commercial construction. The function of a header is to support the load above the void or opening in the wall and roof. Headers used in residential construction are predominantly comprised of wood, but they can also be made of steel, reinforced concrete, or pre-tensioned concrete. Wooden headers include solid sawn wood and engineered composites, such as laminated veneer lumber (LVL) (e.g., Microllam® laminated veneer lumber, which is currently manufactured by Weyerhaeuser Company), parallel strand lumber (e.g., TimberStrand® laminated strand lumber and Parallam® parallel strand lumber which are both currently manufactured by Weyerhaeuser Company), glued laminated timber (commonly referred to as “glulam”) (e.g., Rosboro Stock Glulam manufactured by Rosboro Lumber Company in Springfield, Oreg. and Anthony Power Header® product manufactured by Anthony Forest Products Company in El Dorado, Ariz.). Headers are generally rectangular in shape and highly anisotropic. The tensile strength of headers is greater along the longitudinal axis than it is along the other axes. The longitudinal dimension is also typically greater than the other dimensions and the header is typically installed in the structure with the longitudinal dimension oriented horizontally. The width of the header is generally greater than about one inch and less than about six inches. The width of the header is often about the same width as that of the wall or roof in which it is being installed. Alternatively, the width of the header is often half of the thickness of the wall so that two headers can be placed adjacent to each other within the wall or roof system. The depth of a header is usually greater than about two inches and less than about 36 inches. In general, deeper headers can be used to span longer voids or support greater loads in a wall or roof system. In many cases the depth of the header is greater than the width of the header.
As used herein, the term ‘major surface’ refers to the two surface area regions of the header that are comprised of the length and depth dimensions. When the width of the header is equal to the width of the wall, then the ‘major surfaces’ of the header will constitute a portion of the structural wall surface. For instance, a header with a width of 3.5 inches, a length of 14 feet and a depth of 12 inches might be used over a garage door opening. In this case the ‘major surfaces’ of the header would have a length of 14 feet and a depth of 12 inches. If the structural frame of the garage was 3.5 inches thick, then one of the ‘major surfaces’ of the header would be facing toward the interior region of the garage and might or might not be covered with a decorative interior sheathing, such as sheetrock. The other ‘major surface’ of the header would be facing toward the exterior of the garage and would usually be covered with an exterior siding material.
Headers are frequently exposed to water in the form of rain, snow, hail, sleet, fog or other sources of moisture. This exposure can occur during transport of headers to warehouses, dealers, lumber yards, or construction sites. For instance, headers loaded onto a truck might be exposed to water as the truck passes through a rain storm. Upon delivery to a construction site the header can be exposed to water prior to, during or after installation into the structural frame. In many cases the exposure occurs to a greater extent on one major surface of the header than it does on the other major surface. The surface that absorbs more water expands more than the surface that absorbs less water. This results in a predominantly transient “cupping” or warping distortion in the shape of the header. The irregular shape of the header can result in a portion of the header protruding out of the plane of the wall. Additionally, warped or cupped headers usually do not fit properly with adjacent framing members, such as studs, which are also usually rectangular in shape. Upon drying, much of the cupping distortion is diminished, but in most cases some permanent level of distortion remains. Unfortunately, wooden headers can require weeks to dry. Thus, the tendency for headers to warp or cup when they are exposed to water can result in construction delays, increased installation difficulty and loss of quality in the resulting wall or roof structure.
Manufacturers of wooden headers have multiple ways of inhibiting water absorption in order to limit the cupping or warping action. Some manufacturers have applied a layer of wax or a wax-like coating to the major surfaces and the edges of the wooden header. Headers coated with such materials include the LP® SolidStart® LVL manufactured by Louisiana-Pacific Corporation in Nashville, Tenn.; RigidLam® LVL manufactured by Roseburg Forest Product in Roseburg, Oreg.; and VERSA-LAM® LVL manufactured by Boise Cascade, LLC in Boise, Id. Another known method involves application of an acrylic coating to the major surfaces of the wooden header. For instance, the Georgia-Pacific Corporation in Atlanta, Ga., applies a layer of acrylic-based coating materials, known as FiberGuard®, to the major surfaces of its LVL product sold under the trademark GP LAM®. Yet another protection method involves lamination of a high density resin impregnated paper to the major surfaces of the wooden header. This is exemplified by an LVL product known as Microllam™ LVL with Watershed™ overlay, which is currently manufactured by Weyerhaeuser Company.
One of the drawbacks with the wax or acrylic-based coating materials is that they can cause the products to stick to themselves when stacked. This is a problem commonly referred to as “blocking”. Another drawback is that these coating materials are soft and can be easily rubbed off of the wooden substrate. In some industries this condition is known as “crocking”. Furthermore, in many cases the wax coatings that are often applied to wooden headers are not uniformly distributed across a given major surface or the application rate on one major surface can be different than the application rate on another major surface.
The Watershed™ overlay technology offers superior cupping-resistance compared with wax- or acrylic-based coatings and does not have the “blocking” problem. However, the Watershed™ overlay technology include difficulties during application, such as tearing of the paper and lack of adhesion in the overlap joints of the LVL, high cost of the resin impregnated paper, and a slick finished surface. The present inventors have observed that when resin impregnated paper is laminated to wooden headers and the resulting headers are stacked into units or bundles with the major surface of one header product in contact with the major surface of an adjacent header product, there is a tendency for headers in the stack to slide relative to each other resulting in a spill or toppling of the bundle. This sliding is due to the low surface friction associated with the resin impregnated paper surface. This problem has been addressed by applying small amounts of pressure sensitive adhesives to the resin impregnated paper covering the major surfaces of headers in a stack. This technique, while effective to reduce slippage between adjacent headers, is costly and inconvenient.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
The embodiments described herein are directed to an improved wooden beam that has improved resistance to 1) cupping or warping when exposed to water; 2) abrasion; 3) blocking when stacked; and 4) toppling when stacked.
In one embodiment an improved wooden beam includes a wooden layer having a width of about 1.0 to 6.0 inches, a depth of about 2.0 to 36 inches, a length of about 1.0 to 80 feet, and two major opposing surfaces defined by the depth and length of the wooden layer. The improved wooden beam also includes a hydrophobic polymeric film on each of the major opposing surfaces, each hydrophobic polymeric film having an exposed surface facing away from the major opposing surface to which it is attached. The exposed surface of the hydrophobic polymeric film on at least one major surface exhibits a dry surface friction value of about 3.0-20 lbs. and a blocking value of about 0-150 lbs.
In a preferred embodiment, the hydrophobic polymeric film is a polyethylene film or a polypropylene film.
In another aspect of the disclosure, the improved wooden beam is made by a method that involves providing a wooden layer having a width of about 1.0 to 6.0 inches, a depth of about 2.0 to 36 inches, a length of about 1.0 to 80 feet, and two major opposing surfaces defined by the depth and length of the wooden layer. A hydrophobic polymeric film is attached to each of the major opposing surfaces, each hydrophobic polymeric film has an exposed surface facing away from the major opposing surface to which it is attached. The exposed surface of the hydrophobic polymeric film on at least one major surface exhibits a dry surface friction value of about 3.0-20 lbs. and a blocking value of about 0-150 lbs.
The foregoing aspects and many of the attendant advantages of the disclosure described herein will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
In one embodiment of the disclosure, referring to
Suitable wooden layers include solid sawn wood, laminated veneer lumber, laminated strand lumber, parallel strand lumber, glued laminated timber, other structural wood-based composites, and any hydrophilic composite that has structural properties suitable for use in a beam application. Desirable wooden layers have a rectangular shape with minimal geometric distortions and have a longitudinal dimension that usually is greater than the width or depth dimensions. The longitudinal dimension of the wooden layer can generally be greater than about 1.0 foot and less than about 80 feet, but the embodiments described herein are not limited to such dimensions. Preferably the longitudinal dimension of the wooden layer will be greater than about 2 feet and less than about 30 feet. The depth dimension of the wooden layer can be greater than about 2.0 inch and less than about 36 inches, but the embodiments described herein are not limited to such dimensions. Preferably the depth dimension of the wooden layer will be greater than about 3.5 inches and less than about 36 inches. The width dimension of the wooden layer can be greater than about 1.0 inch and less than about 6.0 inches, but the embodiments described herein are not limited to such dimensions. Preferably the width dimension of the wooden layer will be greater than about 1.5 inches and less than about 6 inches. Preferably, strength and stiffness properties of the wooden layer will be anisotropic. Modulus of elasticity (MOE) values parallel to the longitudinal axis for the wooden layer will typically be greater than about 1.0×106 lb/inch2. EI values (the product of the modulus of elasticity and the moment of inertia) parallel to the longitudinal axis will be greater than about 20×106 inch2 lb.
Suitable hydrophobic films include polyethylene, polypropylene, polyester, nylon, polyvinyl chloride, polyvinylidene chloride, and poly(ethylenevinylacetate). Preferred hydrophobic films include polyethylene and polypropylene. Polyethylene films are comprised of polymers made by polymerization of ethylene or mixtures of ethylene and other monomers such as alpha olefins, but may also include plasticizers, processing aids, colorants, opacifying agents, fillers, or other materials. Catalysts for the polymerization can include Ziegler-Natta catalysts and metallocene catalysts. Polyethylene polymers include high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), high molecular weight polyethylene (HMWPE), ultra high molecular weight polyethylene (UHMWPE), ultra low molecular weight polyethylene (ULMWPE), linear low density polyethylene (LLDPE), very low density polyethylene (VLDPE), cross-linked polyethylene (XLPE) and high density cross-linked polyethylene (HDXLPE). Examples of suitable polyethylene film include SW AP 2013.3 supplied by Atlantis Plastics Incorporated in Atlanta, Ga., as well as Winflex 50™ and Winlon HDPE™ produced by Winzen Film and Fiber Incorporated in Sulphur Springs, Tex.
Useful polypropylene films are comprised of polymers made from polymerization of propylene, but may also include plasticizers, processing aids, colorants, opacifying agents, fillers, or other materials. Catalysts for the polymerization can include Ziegler-Natta catalysts and Kaminsky catalysts. Polypropylene can have either isotactic, syndiotactic or atactic orientation of the pendant methyl groups. Suitable examples of polypropylene film include WinPro™ produced by Winzen Film and Fiber Incorporated in Sulphur Springs, Tex., and Propafilm™ biaxially oriented polypropylene film produced by Innovia Films Incorporated in Atlanta, Ga.
The hydrophobic film can also be a multi-layer film utilizing an organic polymer layer and at least one other layer. The second layer could include metal layers or a different organic polymer layer. Metal layers can include metal foil or a metal layer achieved through vapor deposition. Other organic polymer layers can include polyethylene, polypropylene, poly(ethylene vinyl acetate) and other polymers that might help to achieve performance features advantageous for this application.
Water vapor transmission rates associated with the suitable films will generally be in the range of 0 to 30 g/mil/m2/day in the ASTM D6701-01 test. The term “mil” in the vapor transmission rate unit is the thickness of the film expressed in thousandths of an inch. The hydrophobic film layer can optionally be surface-treated (typically corona-treated) on one or both sides in order to promote adhesion.
The blocking value of at least one side of suitable hydrophobic films will be about 0-150 g @ 60° C. for 24 hr (ASTM D-3354). Preferred blocking potential values for at least one side of the hydrophobic film will be about 25-130 g @ 60° C. for 24 hr (ASTM D-3354). These blocking values must be exhibited by the side of the film that is facing away from the warp resistant beam product. The dry surface friction value of at least one side of the hydrophobic films will be about 3.0-20 lb (ASTM D-2394). Preferred dry surface friction values of at least one side of the hydrophobic films will be 3.5-10 lb (ASTM D-2394). These dry surface friction values should be exhibited by the side of the film that is facing away from the warp resistant beam product.
Additionally the hydrophobic film layer can optionally be treated with a release agent, such as silicone, on one side in order to improve processing during the production of the warp-resistant wooden beam. The thickness of the hydrophobic film layer can be greater than about 0.0005 inches and less than about 0.05 inches, although the presently described embodiments are not limited to these values. Preferred thickness values for the hydrophobic film would be greater than about 0.001 inches and less than about 0.020 inches. Hydrophobic films with thickness values less than about 0.0005 are less preferred because of their lower abrasion resistance compared to thicker films.
Useful adhesive layers include hot-melt adhesives, pressure-sensitive adhesives, emulsions, polysaccharides, proteins, and reactive adhesives. Preferred adhesives are hot-melt adhesives and pressure sensitive adhesives. Hot-melt adhesives include those based on a high molecular weight thermoplastic polymer, and optionally a tackifying resin and/or a hydrocarbon wax. Examples of high molecular weight thermoplastic polymers used in these formulations include polyethylene, polypropylene, polyamide, polyester, and copoly(ethylene-vinylacetate). Examples of tackifying resins include hydrocarbon resins, rosin esters and polyterpenes. Examples of hydrocarbon waxes include microcrystalline wax, Fischer-Tropsch waxes, paraffin and slack wax. Pressure-sensitive adhesives include those based on rubbery polymers and tackifiers. Examples of rubbery polymers are natural rubber, polyisoprene, polybutadiene, styrene-butadiene copolymers, polyisobutylene butyl rubber, copoly(ethylene-vinylacetate), acrylics, silicones, and poly(vinyl alkyl ether) blends. Examples of tackifiers include wood rosin, terpenes, tall oil rosin, unsaturated hydrocarbon oligomers, copolymers based on alpha-methylstyrene and vinyltoluene, and coumarone-indene resins. Useful emulsion adhesives include acrylics and poly(vinylacetate). Useful polysaccharide adhesives include starch, dextrin, hydroxyethyl cellulose, methyl cellulose, alginates and chitosan. Useful protein adhesives include casein, soy-based glue, and animal glue (hide glue and bone glue). Useful reactive adhesives include isocyanates, polyurethanes, epoxies, phenol-formaldehyde resins, urea-formaldehyde resins, and melamine-formaldehyde resins.
The adhesive layers can have a spread rate of about 5-200 g/m2. Preferably, the adhesive spread rate is about 10-100 g/m2. In a preferred embodiment, the adhesive can be a thermoplastic adhesive, which can be applied to one side of the hydrophobic film prior to attachment to the wooden substrate. Alternatively, the adhesive can be applied to the wood substrate prior to attachment of the film. Further yet, the adhesive could be applied to both the film and the wood prior to attaching the film to the wood. The adhesive layers on different surfaces of the wooden substrate can have the same composition and spread rate, or they can have different compositions and spread rates. Likewise, the hydrophobic film layers on different surfaces of the composite can have the same composition and thickness or different compositions and thicknesses.
Thermoplastic adhesives can be applied to one side of the hydrophobic film by first heating the adhesive in order to convert it into a liquid, and then spraying, extruding, spreading or otherwise transferring the molten adhesive onto the film. The applied adhesive will adhere to the film and will solidify as it cools. In the event that the thermoplastic film is a pressure sensitive adhesive, then a release layer can be applied directly on top of the adhesive layer and the layers of material can be wound into a roll-good. A release layer is a thin plastic film (typically polyethylene or polypropylene) that is coated on either one or two sides with a silicone or some other type of release agent. In yet another embodiment a pressure-sensitive adhesive can be applied to one side of a film and a release agent such as a silicone can be directly applied to the opposing side of the film. This roll-good can later be unwound and any release layer present in the roll-good can be separated from the adhesive. The exposed adhesive-treated side of the film can be placed in contact with both major surfaces of the wooden substrate with sufficient heat and/or pressure to achieve bond formation. In the event that the adhesive is a hot-melt adhesive (not a pressure-sensitive adhesive), the release layer might not be required for the adhesive-treated film. Alternatively, the adhesive-treated film can be placed in contact with both major surfaces of the wooden substrate with sufficient heat and/or pressure to achieve bond formation without the intermediate step of winding the adhesive-treated film into a roll-good. In another embodiment the thermoplastic adhesive can be applied to both major surfaces of the wooden substrate by first heating the adhesive in order to convert it into a liquid, and then spraying, extruding, spreading or otherwise transferring the molten adhesive to the wooden substrate. Films can be placed in contact with the applied adhesive on the wooden substrate either immediately or after some period of time with sufficient heat and/or pressure to achieve bond formation.
The heat and pressure required to achieve bond formation between the hydrophobic film and the wooden substrate can be achieved by use of a batch press in which the array of layers in the composite remain stationary while they are squeezed between moving platens which apply pressure and optionally heat to the product; or a continuous press in which the array of layers in the composite are transported through one or more sets of opposing rolls or belts which apply pressure and optionally heat to the product. Suitable batch presses include those manufactured by Dieffenbacher GmbH+Co. KG in Eppingen, Germany and The Minster Machine Company in Minster, Ohio. These presses can utilize flat metal platens in either single-opening or multi-opening designs. Another type of batch press useful in some embodiments is a bladder press, such as that manufactured by Shaw-Almex Industries Limited in Parry Sound, ON, Canada. Suitable continuous presses include those manufactured by Dieffenbacher GmbH+Co. KG in Eppingen, Germany and Automated Converting Equipment, LLC located in Huntsville, Ala.
The bond formation time, temperature and pressure requirements will be interdependent and dependent upon multiple factors including the adhesive type, film type, and flatness of the wood substrate surfaces. In situations involving the use of pressure sensitive adhesives or certain hot-melt adhesives the bond formation time can be as little as about 0.1 seconds. Thus, the use of pressure sensitive adhesives and certain hot-melt adhesives allows for rapid processing, such as that conveniently achieved by use of continuous presses. Other adhesive types could require bond formation times of about 15 seconds to about one hour, or even longer. Heat will be required for some of the adhesives. Heat can be transferred to the adhesive layer by use of heated platens, rolls or belts, use of a preheated wooden substrate, microwave sources, radio-frequency sources, infra-red heaters or other devices. When heat is being transferred to the adhesive by use of heated platens, rolls or belts, the temperature of these objects could range from about 30° C. to about 150° C. or higher. In light of the fact that this heat will be transferred through a heat sensitive film, such as polyethylene or polypropylene, the transfer of heat should be minimized in order to avoid shape distortions or melting or other thermal damage in the film material. Within the limitations of avoiding thermal damage to the film, higher temperatures will generally promote faster processing rates.
As an optional processing method, the laminated composite can be cooled immediately after pressing. Cooling can be accomplished by use of fans, cold air jets, chill rolls, or other means.
The amount of pressure required during the bond formation process must be sufficient to achieve intimate contact between all layers (film, adhesive, and wooden substrate) in the composite. This pressure could be as low as about 1 psi or less, or as high as about 1000 psi or more. In general, use of less pressure is preferred in order to avoid damaging the film and the wooden substrate. Greater pressures will be required when the wooden substrate has significant variance in width. Use of a bladder press, or other method allowing for physical contact compliance, might be especially useful in this situation.
In some cases the depth or length of the films might be greater than the depth or length of the wooden substrate. Subsequent to attachment, the composite or the film can optionally be trimmed in order to eliminate a protruding or over-hanging film. Alternatively, the depth or length of the films might be less than the depth or length of the wooden substrate. In another embodiment of the subject matter described herein, the composite might be manufactured as a large billet and then subsequently cut into smaller beam products, such that the smaller beam products are still comprised of the essential five layers.
In yet another embodiment, sealants can be applied to the edges or minor surfaces of the beam product in order to cover the remaining exposed surfaces of the wooden substrate. Such sealants can be comprised of wax emulsions, or mixtures of wax emulsions and latexes, or mixtures of wax emulsions, Latexes and colorants. Other sealants, which are known to retard water absorption can be applied. An example of a sealant suitable for this application would be LKG-0394, which is manufactured by Valspar Corporation (High Point, N.C.).
Logos, fastening patterns, labels, bar codes and other identification and/or labeling information can be marked on the beam. Such markings can be based on inks or other media and are generally known throughout the industry. Such markings can be applied to the wooden substrate directly or to the film layers.
The wooden beam products in the form of header products described herein can be utilized in various types of construction, including residential and commercial. In general, the header will be spanned horizontally across two or more supporting columns with the film-carrying major surfaces in a vertical orientation. Fastening or securing of the header will be accomplished by use of common mechanical fasteners, such as nails, screws, and staples. Other mechanical fasteners that are used include plates, anchors, hangers, bolts, split rings and clips. Adhesives can also be used in conjunction with the mechanical fasteners.
Relative to existing wooden header technologies, the embodiments described herein provide a wooden header with reduced water absorption rates, reduced cupping and warping, reduced blocking and toppling when stacked, and improved abrasion resistance. Other advantages and benefits associated with wooden headers that will be appreciated by builders and other members of the construction industry include improved appearance and enhanced smoothness. Furthermore, wooden headers described herein will be easier to clean and exhibit less risk of subcutaneous injection of slivers during handling and usage.
An adhesive was prepared by charging a 600 mL beaker with poly(ethylene vinylacetate) (45.0 g), known as Elvax 205W, manufactured by DuPont Company in Wilmington, Del., and a tackifier resin (40.0 g), known as Sylvatac RE98, manufactured by the Arizona Chemical Company in Jacksonville, Fla., a Fischer-Tropsch wax (15.0 g), known as Bareco PX-105, manufactured by Baker Petrolite in Sugarland, Tex., green pigment (0.1 g), known as Orcosolve Green ‘B’, manufactured by Organic Dyestuffs Corporation in East Providence, R.I., and yellow pigment (0.2 g), known as Orcosolve Yellow ‘3G’ manufactured by Organic Dyestuffs Corporation in East Providence, R.I. The mixture was heated on a hot plate and stirred mechanically with a metal spatula until a homogenous, green, molten mass was obtained. This material was transferred into a HB 700 Spray Applicator by Buhnen GmbH Et Co. KG in Bremen, Germany, which was set at an application temperature of 127° C. and an application air pressure of 60 psi. Adhesive was dispensed from the gun in a swirl pattern onto the surface-treated side of a polyethylene film (1.0 mil thick×48 inches long×16 inches wide), having a vapor transmission rate of approximately 8-10 g/mil/m2/day known as SW AP 2013.3 and supplied by Atlantis Plastics Incorporated in Atlanta, Ga. The adhesive application rate was 8 g/ft2. Multiple batches of this green adhesive and coated film were prepared in a similar manner. The treated film sections were rolled up and stored at a temperature of 20° C. for a period of 3 days. The adhesive-treated side of a section of film was placed in contact with the top major surface of a section of laminated veneer lumber (1.75 inches thick×48 inches long×16 inches wide), known as Microllam® and manufactured by iLevel® by Weyerhaeuser Company in Federal Way, Wash. The film was covered with a sheet of release paper (18 inches wide×50 inches long) and this array of materials was processed through a nip roll press with an upper steel roll (12 inch diameter, 34 inch length) heated to a temperature of 124° C. and a lower steel roll (12 inch diameter, 34 inch length) which was not heated. The pressure setting between the upper and bottom rolls was 1100 lb per inch of width. The transport speed was 5 feet per minute. The release paper was peeled away from the treated face of the product. Under these processing conditions the hot-melt adhesive softened and was redistributed into a continuous adhesive layer. The treated section of laminated veneer lumber was turned over and a second section of treated film was attached to this second major face in a similar manner. Replicate samples of this five-layered composite were prepared. The samples were then cut into specimens and subjected to four different tests. The test results for these specimens are reported below as Sample 1.
Other wooden header products evaluated in these tests for the purpose of comparison included laminated veneer lumber known as Solid Start® (wax-like coating) produced by the Louisiana-Pacific Corporation in Nashville, Tenn.; laminated veneer lumber known as GP Lam® treated with FiberGuard® acrylic coating produced by the Georgia-Pacific Corporation in Atlanta, Ga.; laminated veneer lumber known as VERSA-LAM® (wax-like coating) produced by Boise Cascade, LLC in Boise, Id.; laminated veneer lumber known as RigidLam® (wax-like coating) produced by Roseburg in Roseburg, Oreg.; laminated veneer lumber known as PWLVL (wax-like coating) produced by Pacific WoodTech Corporation in Burlington, Wash.; laminated veneer lumber known as Microllam® (no coating) produced by Weyerhaeuser Company; and laminated veneer lumber known as Microllam® with Watershed® Overlay (WSO) (high density resin impregnated paper) produced by Weyerhaeuser Company.
A cupping (or warping) test was conducted in the following manner. Five replicate specimens (about 1.75 inch wide×16.0 inches deep×32 inches long) were isolated from each type of wooden header. Specimens were selected to avoid or minimize surface defects (such as knots and joints). The edges of the specimens were coated with wax in order to minimize moisture absorption through these surfaces.
Referring to
Each specimen was put into a plastic bin. A cotton towel was positioned such that the surface of the specimen was covered except for a 1″ perimeter around the edge. A liter of water was then poured slowly onto the towel being careful not to allow any water to spill over the sides. The lid was then placed on the plastic bin to reduce water loss by evaporation. Each specimen was allowed to hydrate on the top major surface within the plastic bin at a temperature of about 20°+ or −3 degrees C. for a period of 14 days. Cupping measurements were taken after hydration periods of 0, 7 and 14 days. The specimens were checked regularly to insure that the towels were wet. Water was added in order to keep the towel saturated but not so much that the water ran over the sides of the specimens.
Cupping values for each of the five replicate specimens for each header type were averaged together. Average cupping values were then compared between header types. Results are shown in Table 1.
The results reported in Table 1, show that Sample 1 has lower 7-day and 14-day cupping values compared to the seven commercially available products tested.
A modified Cobb ring test was conducted in the following manner. Five replicate specimens (about 1.75 inch wide×9.5 inches deep×12.0 inches long) were isolated from each type of wooden header. Specimens were selected to avoid or minimize surface defects (such as knots and joints). Each specimen was conditioned in a chamber maintained at 20° C. and 50% R.H. for a period of 7 days prior to testing. Each specimen was then measured for mass. Each specimen was placed onto a steel platform. A Cobb ring (inner diameter=8 inches, height=3 inches) was attached to the upper surface of the test specimen by use of clamps. The surface of the ring that was in direct contact with the header material had a soft rubber seal (X-TREME RUBBER WEATHERSEAL with Self Stick Tape, ⅜″ wide×¼″ thick by Thermwell Products Company, Incorporated, Mahwah, N.J.). No caulking of the samples was conducted. The mounted specimen was placed inside a plastic tub, which was positioned on a level bench surface. Deionized water (1000 g) was transferred into the Cobb ring. The height of this water column was about 1.25″. After 24 hours the water was decanted or vacuumed from the ring and any residual water droplets on the surface of the specimen were removed with a paper towel. The towel was not used to wick water that was previously absorbed into the specimen. The specimen was removed from the frame and weighed. The mass after 24 hr of water absorption was recorded. Calculations were made in order to determine the daily flux rate of water. Results are shown in Table 2.
The results reported in Table 2 show that Sample 1 has a lower flux rate determined by the Cobb ring test and the seven commercially available products that were tested.
A blocking test was conducted in the following manner. Ten replicate specimens (about 1.75 inch wide×4.0 inches deep×4.0 inches long) were isolated from each type of wooden header. Matched pairs of specimens were stacked so that the coated faces of each was in direct contact. Each stack was 4 specimens high. Each stack was placed into an oven at a temperature of 50° C. and a weight (14.7 lb) was then placed on top of each stack. Each stack was maintained in this environment for a period of 72 hours. At the end of this period the weights were removed from each stack and each stack was then removed from the oven and allowed to equilibrate in an environmental chamber (20° C. and 50% R.H.) for 1 hour. The top specimen in each stack was gently lifted by gripping the edge of the top specimen. If the bottom specimen remained bonded to the specimen directly above the bottom specimen for more than 1 second while the top specimen was being gently lifted, then the material was considered to have significant blocking potential. Each pair was assigned a value for blocking according the scale shown in Table 3.
Blocking values were averaged for each header type. Results are shown in Table 4.
The results reported in Table 4 show that Sample 1 has a blocking value that is greater than four of the commercially available products, less than two of the commercially available products, and equal to one of the commercially available products that were tested.
A dry surface friction test was conducted in a manner similar to that described in ASTM D-4518. Five small replicate specimens (about 1.75 inch wide×2.0 inches deep×2.0 inches long) and five large replicate specimens (about 1.75 inch wide×4.0 inches deep×14.0 inches long) were isolated from each type of wooden header. Referring to
The materials were tested at a temperature of 20° C. and 50% R.H. A cable 74 was attached to the front edge of small specimen 70 by use of an eye-hook. A weight 76 of 10 pounds was placed on top of the small specimen. The cable was pulled at a displacement rate of 10 inches/minute. The average force required to sustain motion at a steady rate was measured and considered to be the dry friction value. Dry friction values were averaged for each header type. Results are shown in Table 5.
The results reported in Table 5 show that Sample 1 has a dry friction value that is greater than the dry friction values observed for the seven commercially available products tested.
A wet surface friction test was conducted in a manner similar to that described in ASTM D-4518. Five small replicate specimens (about 1.75 inch wide×2.0 inches deep×2.0 inches long) and five large replicate specimens (about 1.75 inch wide×4.0 inches deep×14.0 inches long) were isolated from each type of wooden header. Water was sprayed onto the large specimen at a level of 4 g/ft2 and then the small and large specimens were mounted in a friction testing apparatus as described above with reference to
The materials were tested at a temperature of 20° C. and 50% R.H. A cable was attached to the front edge of the small specimen by use of an eye-hook. A weight of 10 pounds was placed on top of the small specimen. The cable was pulled at a displacement rate of 10 inches/minute. The average force required to sustain motion at a steady rate was measured and considered to be the wet friction value. Wet friction values were averaged for each header type. Results are shown in Table 5a.
The results reported in Table 5a show that Sample 1 has a wet friction value that is greater than six of the seven commercially available products that were tested. One of the commercially available products tested exhibited a wet friction value that was greater than the wet friction value exhibited by Sample 1.
An adhesive was prepared by charging a 600 mL beaker with poly(ethylene vinylacetate) (120.0 g), known as Elvax 205W, manufactured by DuPont Company in Wilmington, Del. and a tackifier resin (80.0 g), known as Sylvatac RE98, manufactured by the Arizona Chemical Company in Jacksonville, Fla., a titanium dioxide dispersion (50.0 g), green pigment (2.0 g), known as Orcosolve Green ‘B’, manufactured by Organic Dyestuffs Corporation in East Providence, R.I., and yellow pigment (4.0 g), known as Orcosolve Yellow ‘3G’ manufactured by Organic Dyestuffs Corporation in East Providence, R.I. The titanium dioxide dispersion was prepared by grinding titanium dioxide powder (50.0 g), known as CR828 and supplied by Kerr-McGee in Oklahoma City, Okla., in benzyl butyl phthalate (100.0 g). The adhesive mixture was heated on a hot plate and stirred mechanically with a metal spatula until a homogenous, green, molten mass was obtained. This material was transferred into a HB 700 Spray Applicator by Buhnen GmbH Et Co. KG in Bremen, Germany, which was set at an application temperature of 104° C. and an application air pressure of 60 psi. Adhesive was dispensed from the gun in a swirl pattern onto the surface-treated side of a polyethylene film (1.0 mil thick×48 inches long×16 inches wide), having a vapor transmission rate of approximately 8-10 g/mil/m2/day known as SW AP 2013.3 and supplied by Atlantis Plastics Incorporated in Atlanta, Ga. The adhesive application rate was 8 g/ft2. Multiple batches of this green adhesive and coated film were prepared in a similar manner. The treated film sections were rolled up and stored at a temperature of 20° C. for a period of 1 day. The adhesive-treated side of a section of film was placed in contact with the top major surface of a section of laminated veneer lumber (1.75 inches thick×48 inches long×16 inches wide), known as Microllam® and manufactured by iLevel® by Weyerhaeuser Company in Federal Way, Wash. The film was covered with a sheet of release paper (18 inches wide×50 inches long) and this array of materials was processed through a nip roll press with an upper steel roll (12 inch diameter, 34 inch length) heated to a temperature of 90° C. and a lower steel roll (12 inch diameter, 34 inch length) which was not heated. The pressure setting between the upper and bottom rolls was 1100 lb per inch of width. The transport speed was 1 foot per minute. The release paper was peeled away from the treated face of the product. Under these processing conditions the hot-melt adhesive softened and was redistributed into a continuous adhesive layer. The treated section of laminated veneer lumber was turned over and a second section of treated film was attached to this second major face in a similar manner. Replicate samples of this five-layered composite were prepared. This material was suitable for use as a warp resistant header.
An adhesive was prepared by charging a 600 mL beaker with poly(ethylene vinylacetate) (120.0 g), known as Elvax 205W, manufactured by DuPont Company in Wilmington, Del. and a tackifier resin (80.0 g), known as Sylvatac RE98, manufactured by the Arizona Chemical Company in Jacksonville, Fla. The adhesive mixture was heated on a hot plate and stirred mechanically with a metal spatula until a homogenous, molten mass was obtained. This material was transferred into a HB 700 Spray Applicator by Buhnen GmbH Et Co. KG in Bremen, Germany, which was set at an application temperature of 121° C. and an application air pressure of 60 psi. Adhesive was dispensed from the gun in a swirl pattern onto the surface-treated side of a polyethylene film (1.0 mil thick×48 inches long×16 inches wide), exhibiting a vapor transmission rate of approximately 8-10 g/mil/m2/day known as SW AP 2013.3 and supplied by Atlantis Plastics Incorporated in Atlanta, Ga. The adhesive application rate was 8 g/ft2. Multiple batches of this colorless adhesive and coated film were prepared in a similar manner. The treated film sections were rolled up and stored at a temperature of 20° C. for a period of 1 day. The adhesive-treated side of a section of film was placed in contact with the top major surface of a section of laminated veneer lumber (1.75 inches thick×48 inches long×16 inches wide), known as Microllam® and manufactured by iLevel® by Weyerhaeuser Company in Federal Way, Wash. The film was covered with a sheet of release paper (18 inches wide×50 inches long) and this array of materials was processed through a nip roll press with an upper steel roll (12 inch diameter, 34 inch length) heated to a temperature of 90° C. and a lower steel roll (12 inch diameter, 34 inch length) which was not heated. The pressure setting between the upper and bottom rolls was 1100 lb per inch of width. The transport speed was 1 foot per minute. The release paper was peeled away from the treated face of the product. Under these processing conditions the hot-melt adhesive softened and was redistributed into a continuous adhesive layer. The treated section of laminated veneer lumber was turned over and a second section of treated film was attached to this second major face in a similar manner. Replicate samples of this five-layered composite were prepared. This material was suitable for use as a warp resistant header.
An adhesive was prepared by charging a 600 mL beaker with poly(ethylene vinylacetate) (90.0 g), known as Elvax 205W, manufactured by DuPont Company in Wilmington, Del., a tackifier resin (70.0 g), known as Sylvatac RE98, manufactured by the Arizona Chemical Company in Jacksonville, Fla., and a paraffin wax (40.0 g), known as 1230U supplied by the International Group Incorporated in Toronto, ON, Canada. The adhesive mixture was heated on a hot plate and stirred mechanically with a metal spatula until a homogenous, molten mass was obtained. This material was transferred into a HB 700 Spray Applicator by Buhnen GmbH Et Co. KG in Bremen, Germany, which was set at an application temperature of 121° C. and an application air pressure of 60 psi. Adhesive was dispensed from the gun in a swirl pattern onto the surface-treated side of a polyethylene film (1.0 mil thick×48 inches long×16 inches wide), having a vapor transmission rate of approximately 8-10 g/mil/m2/day known as SW AP 2013.3 and supplied by Atlantis Plastics Incorporated in Atlanta, Ga. The adhesive application rate was 8 g/ft2. Multiple batches of this colorless adhesive and coated film were prepared in a similar maimer. The treated film sections were rolled up and stored at a temperature of 20° C. for a period of 1 day. The adhesive-treated side of a section of film was placed in contact with the top major surface of a section of laminated veneer lumber (1.75 inches thick×48 inches long×16 inches wide), known as Microllam® and manufactured by iLevel® by Weyerhaeuser Company in Federal Way, Wash. The film was covered with a sheet of release paper (18 inches wide×50 inches long) and this array of materials was processed through a nip roll press with an upper steel roll (12 inch diameter, 34 inch length) heated to a temperature of 90° C. and a lower steel roll (12 inch diameter, 34 inch length) which was not heated. The pressure setting between the upper and bottom rolls was 1100 lb per inch of width. The transport speed was 1 foot per minute. The release paper was peeled away from the treated face of the product. Under these processing conditions the hot-melt adhesive softened and was redistributed into a continuous adhesive layer. The treated section of laminated veneer lumber was turned over and a second section of treated film was attached to this second major face in a similar manner. Replicate samples of this five-layered composite were prepared. This material was suitable for use as a warp resistant header.
An adhesive was prepared by charging a 600 mL beaker with poly(ethylene vinylacetate) (50.0 g), known as Elvax 205W, manufactured by DuPont Company in Wilmington, Del. and a tackifier resin (50.0 g), known as Sylvatac RE98, manufactured by the Arizona Chemical Company in Jacksonville, Fla. The mixture was heated on a hot plate and stirred mechanically with a metal spatula until a homogenous, molten mass was obtained. This material was transferred into a HB 700 Spray Applicator by Buhnen GmbH Et Co. KG in Bremen, Germany, which was set at an application temperature of 177° C. and an application air pressure of 60 psi. Adhesive was dispensed from the gun in a swirl pattern onto one side of oriented polyester film (1.0 mil thick×48 inches long×16 inches wide), having a vapor transmission rate of approximately 16-20 g/mil/m2/day known as Dura-Lar and supplied by Grafix Plastics in Cleveland, Ohio. The adhesive application rate was 8 g/ft2. Multiple batches of this adhesive and coated film were prepared in a similar manner. The treated film sections were rolled up and stored at a temperature of 20° C. for a period of 2 hours. The adhesive-treated side of a section of film was placed in contact with the top major surface of a section of laminated veneer lumber (1.75 inches thick×48 inches long×16 inches wide), known as Microllam® and manufactured by iLevel® by Weyerhaeuser Company in Federal Way, Wash. The film was covered with a sheet of release paper (18 inches wide×50 inches long) and this array of materials was processed through a batch press for a 10-second contact cycle with an upper platen temperature of 90° C. and a lower platen temperature of 20° C. The maximum pressure exerted on the laminate during this cycle was about 500 psi. Subsequent to pressing the release paper was peeled away from the treated face of the product. Under these processing conditions the hot-melt adhesive softened and was redistributed into a continuous adhesive layer. The treated section of laminated veneer lumber was turned over and a second section of treated film was attached to this second major face in a similar manner. Replicate samples of this five-layered composite were prepared. The samples were then cut into specimens and subjected to the same four tests that are described in Example 1. The test results for these specimens designated as Sample 2 are reported in Tables 6-10.
The results reported in Table 6 show that Sample 2 exhibits a 7-day and 14-day cupping value that is less than the cupping values reported for the seven commercially available products tested.
The results reported in Table 7 show that Sample 2 exhibits a flux rate as measured by the Cobb ring test that is less than the seven commercially available products that were tested.
The results reported in Table 8 show that Sample 2 exhibits a blocking value that is less than three of the commercially available products tested and greater than four of the commercially available products that were tested.
The results reported in Table 9 show that Sample 2 has a dry friction value that is greater than four of the commercially available products tested and less than three of the commercially available products that were tested.
The results reported in Table 10 show that Sample 2 exhibited a wet friction value greater than three of the commercially available products that were tested and less than four of the commercially available products that were tested.
While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the embodiments described herein Aspects of the disclosure described in the context of particular embodiments may be combined or eliminated in other embodiments.
Further, while advantages associated with certain embodiments of the disclosure may have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the disclosure. Accordingly, the invention is not limited except as by the appended claims.
