AU2165300A - Water-based, heat sealable adhesive for laminating decorative panels - Google Patents

Description

WO 00/40403 PCT/US99/28770 WATER-BASED, HEAT SEALABLE ADHESIVE FOR LAMINATING DECORATIVE PANELS BACKGROUND OF THE INVENTION 5 The present invention relates to adhesives, and more particularly to a water-based, heat sealable adhesive for laminating decorative panels. In the construction and furniture industries, it is known to use various types of laminated wood panels for walls, flooring, cabinetry, furniture, and other construction materials. Wood products made from 10 solid wood boards of hardwood or softwood are generally preferred for such uses, but solid wood is relatively expensive, and thus are not necessarily desired by all consumers. An alternative is to use veneer wood products as construction materials, but as trees of the required type, size and quality become more scarce, the manufacturer of veneers is 15 also becoming relatively expensive. In order to maintain the costs of construction as reasonable as practical while still producing houses and other buildings and furniture of acceptable quality, wood construction materials that are more economical have been developed. For example, particleboard, fiberboard, orientated 20 strandboard, plywood, and other similar boards formed from relatively low-grade wood that may not otherwise be usable in the construction industry have been adopted. In addition, boards formed from wood particles, such as wood chips, wood flakes or other wood fragments are also being used more and more frequently in the construction industry, 25 particularly for subsurfaces. Additionally, waste agricultural products such as straw, has been used as subsurfaces. Such products have acceptable quality and integrity that is more than adequate for such uses. However, they are typically characterized by uneven, rough and unattractive surfaces, that do not provide a "finished" look. 30 In order to provide an attractive appearance, the substrate or base formed from low-grade wood and agricultural products typically has a decorative layer adhered thereto to provide an attractive and protective -1- WO 00/40403 PCT/US99/28770 finish. The decorative layer usually is either a vinyl between 2 and 6 mils thick or a paper imprinted with decorative inks to yield a desired color or pattern. Wood panels produced with decorative papers generally can be manufactured at a lower cost than the corresponding vinyl covered 5 panels, and in many instances, provide superior aesthetics. Nevertheless, despite their lower cost and desirable aesthetic properties, decorative papers have been too fragile for many types of panels. In particular, the decorative paper can easily become damaged during normal use due to the fragile nature of paper which thus offsets any aesthetic advantage of 10 decorative paper. SUMMARY OF THE INVENTION It is an object of the present invention to provide a water-based, heat sealable adhesive for bonding a decorative top layer such as a vinyl 15 covering, paper sheet or veneer sheet to a wood or agricultural byproduct substrate such as particleboard, plywood and the like using convention heat and pressure techniques for producing laminated wood panels. It is another object of the present invention to provide an adhesive that does not block to the decorative surface of the top layer. 20 It is still another object of the present invention to provide an adhesive that can be applied to the decorative top layer, dried and thereafter stored in roll or sheet form to be later used for covering the wood substrate. It is yet another object of the present invention to provide an 25 adhesive that is dry when bonding the decorative top layer to the wood substrate so that no swelling of the wood particles occurs and the result is a smooth surface with a "finished" look. It is another object of the invention to provide increased hardness to the laminated wood panel when the substrate has a rough and uneven 30 surface and the decorative top layer is printed paper. -2- WO 00/40403 PCT/US99/28770 In order to accomplish the above, the present invention provides a water-based, heat sealable adhesive interposed between a substantially planar substrate formed from a wood product and a decorative top layer for bonding the top layer to the substrate wherein the adhesive includes, 5 as a primary ingredient thereof, a polymer or polymers containing one or more monomers which when polymerized or copolymerized, yields a Shore D hardness greater than the Shore D hardness of the substrate. Monomers of this type include styrene, methylmethacrylate, vinyl acetate, vinyl chloride, diphenylmethane diisocyanate, and other monomers that 10 produce polymers with a Tg greater than 20'C. The adhesive is preferably comprised of about 20% to 100% by weight of a styrene-based polymer emulsion or emulsions, about 0% to 20% by weight of a coalescing agent, about 0% to 40% by weight of a filler, about 0% to 30% by weight of one or more conditioning additives, 0% to 40% of a melt flow modifier, and the 15 components totaling 100% by weight of the adhesive. Preferably, the styrene-based polymer emulsion is a styrene acrylate emulsion. DESCRIPTION OF PREFERRED EMBODIMENT The present invention relates to a laminated decorative structure 20 used in the construction industry for walls, flooring, cabinetry and other surfaces in houses and buildings. This structure may also be used in the furniture industry. The laminated wood panel is comprised of a substantially planar substrate formed from a wood product, a decorative top layer, and a water-based, heat sealable adhesive interposed between 25 the substrate and top layer for bonding the top layer to the substrate. In the furniture industry it may also be used to bond the top layer to a profile material, such as those used on headboards and armoires. The substrate is a substantially planar, integral sheet formed from a wood product. The wood product may have derived from wood particles 30 from trees such as chips, flakes, sawdust, paper or fragments, as well as from agricultural products such as straw. The particles of wood may be -3- WO 00/40403 PCT/US99/28770 derived from a variety of trees including both hardwood and softwood trees. Examples of such trees include, but are not limited to, aspen, beech, birch, cedar, firs, hemlock, pine and spruce. Just about any source of tree may be employed, and the particular type of tree used or potentially useable 5 wood particles oftentimes depends upon the region or country where the wood product is produced as some species of trees may be indigenous to only limited regions or lands. In addition, the actual form of the substrate, although typically in a structurally integral sheet form, may also vary widely. For example, the substantially planar wood substrate encompasses 10 particleboard, fiberboard, orientated strandboard, hardboard, waferboard, plywood, chipboard, strawboard and the like. The substrate is described herein as having an uneven or rough surface, and the substrates described above generally are formed with such a surface. As is well known, such uneven or rough surfaces are normally not capable of being coated, with 15 paint or decorative coatings such as vinyl, paper, or veneers, to provide a high quality, smooth or attractive "finished" outer surface. Techniques for manufacturing wood substrates are well known in the art. For example, the substrates may be manufactured by compressing and/or heating the wood particles to form a structurally integral sheet. A 20 bonding agent is normally applied to the surface of the wood particles prior to pressing, and examples of such bonding agents are urea/formaldehyde resin, phenol/formaldehyde resin, melamine/formaldehyde resin, polymeric isocyanate resin and the like. The bonding agent may be in either powder or liquid form and is preferably a phenol/formaldehyde resin 25 which is typically applied in amounts in the range of 1.8 to 2.3% by weight to the wood particles. In addition, a wax such as a petroleum-based wax, may also be applied to the wood particles, typically in amounts in the range of 1%-2% by weight of the wood particles to improve water resistant properties. In addition, preservatives and other additives may also be 30 applied to the wood particles as is conventional. -4- WO 00/40403 PCT/US99/28770 The decorative top layer of the laminated wood panel may be formed from vinyl, paper, or a veneer. Numerous types of vinyl are commonly used in applications such as flooring, artificial leather, wall coverings, carpet backing and laminates. Vinyl is well known in the art to include 5 homopolymers and copolymers which share the vinyl radical (CH 2 =CH-) as their starting structural unit. Polyvinyl chloride is the most commercially significant member of this group. A wide variety of papers may be used such as kraft, rice, bamboo, and/or corn, but particularly preferred is kraft or rice paper. The paper 10 may be bleached or unbleached. The paper may be used in a variety of thicknesses depending upon the particular application. The paper is usually printed and may have a durable coating over the printing. In addition, the particular process of manufacture of the wood substrate may influence the selection of the thickness of the paper as some processes 15 impose higher demands on strength properties of the paper in order to resist tearing, or puncturing during manufacture. Typically, the thickness of paper is between 0.5 to 6 mils. As noted above, the decorative top layer of the wood panel may also be veneer, i.e. a thin layer of wood covering the surface of the panel. 20 Methods for the manufacture of veneers are well known in the art, as are the source of such veneers. Examples of such sources include trees such as birch, cypress, cedar, walnut, cherry and the like. The water-based, heat sealable adhesive is interposed between the substrate and the decorative top layer, and functions to bond the top layer 25 to the substrate. The adhesive comprises, as a primary ingredient thereof, a polymer containing one or more monomers which when polymerized or copolymerized yields a Shore D hardness greater than the Shore D hardness of the substrate. Monomers of this type produce polymers with at least one Tg greater than or equal to 20 0 C or 293 0 K, but less than or 30 equal to the temperature attained by the adhesive during the bonding or heat sealing operation. Monomers of this type include, but are not limited -5- WO 00/40403 PCT/US99/28770 to styrene, methylmethacrylate, vinyl acetate, vinyl chloride, diphenylmethane diisocyanate, and other monomers that produce polymers with at least one Tg greater than 20 0 C. The monomers that can be either homopolymerized or copolymerized to obtain these polymers 5 include but are not limited to: 1. Monomers that produce main chain acyclic carbon polymers such as: (a) dienes that result in polydienes such as neoprene, polybutadiene, polyisoprene, and others; 10 (b) alkenes that result in polyalkenes such as polybutene-1, polybutylethylene, polyethylene, polyisobutylene, polymethylene, polypropylene, and others; (c) acrylic acid and acrylic acid esters that result in polyacrylics and polyacrylates such as polyacrylic acid, polybenzyl 15 acrylate, polybutyl acrylate, polyethyl acrylate, polycyano acrylates, and others; (d) acrylamides that result in polyacrylamides such as polyacrylamide, polybutylacrylamides, polyisopropylacrylamide, and others; 20 (e) methacrylic acid and methacrylic acid esters that result in polymethacrylics and polymethacrylates such as polybutylmethacrylate, polyethylmethacrylate, polymethacrylic acid, polymethylmethacrylate, polypropylmethacrylate and others; (I) acrylamides and methacrylamides that result in 25 polyacrylamides and polymethacrylamides such as poly (4 butoxycarbonylphenylmethacrylamide), poly (N-tert butylmethacrylamide), poly (N-carboxyphenylmethacrylamide), and others; (g) alpha or beta substituted acrylics or methacrylics that 30 result in polyacrylics and polymethacrylics such as -6- WO 00/40403 PCT/US99/28770 polybutylchloroacrylate, polybutylcyanoacrylate, polyethylchloroacrylate, and others; (h) vinyl ethers and vinyl thioethers that result in polyvinylethers and polyvinylthioethers such as polybutoxyethylene, 5 polybutylthiothylene, polyethoxyethylene, polymethoxyethylene, polymethylthioethylene, and others; (i) vinyl alcohol that results in polyvinylalcohols such as polybenzoylethylene, poly (4-chlorobenzoylethylene), polyvinylalcohol, and others; 10 (j) vinyl halides and vinyl nitriles that result in polyvinylhalides and polyvinylnitriles such as polymethacrylonitrile, polyvinylchloride, and others; (k) vinyl esters that result in polyvinylesters such as polyvinylacetate, polyvinylformate, polycyclopentanoyloxyethylene, 15 polybenzoylethylene, and others; (1) styrene that result in polystyrenes such as polybutylstyrenes, polychlorostyrenes, polyethylstyrenes, polymethylstyrenes, polystyrene, and others; (m) other monomers that form polymers such as 20 polybenzylethylene, polyvinylpyridine, polyvinylpyrolidine, and others; 2. Monomers that produce main chain carbocyclic polymers such as: 25 (a) phenylenes that result in polyphenylenes such as poly (2-bromo- 1,4-phenyleneethylene), poly (2,5-dichloro- 1,4 phenyleneethylene), poly (1,4-phenyleneethylene), and others; (b) other monomers that form polymers such as polycyclobutene, poly (1,4-naphthyleneethylene), and others; -7- WO 00/40403 PCT/US99/28770 3. Monomers that produce main chain heteroatom polymers such as: (a) polyoxides such as polyoxyethylenes, polyoxymethylene, polyoxypropylene, and others; 5 (b) polycarbonates, such as poly(oxycarbonyloxy-2-chloro 1,4-phenyleneisopropylidene-3-chloro- 1,4-phenylene), poly(oxycarbonyloxy-2,2,3,3,4,4,5,5-octafluorohexamethylene), poly(oxycarbonyloxy- 1,4-phenylenecyclohexylidene- 1,4-phenylene) and others; 10 (c) polyesters, such as poly(ethylene adipate), poly(ethylene terephthalate), poly(oxyethyleneoxyadipoyl) and others; (d) polyanhydrides, such as poly(oxycarbonyl-1,4 phenylenehexafluorotrimethylene- 1,4-phenylene-carbonyl), poly(oxycarbonyl- 1,4-phenylenepentamethylene- 1,4 15 phenylenecarbonyl), poly(oxyisophthaloyl), poly(methacrylic anhydride) and others; (e) polyamides such as poly(imino-5-tert butylisophthaloyliminomethylene- 1,4-phenylenemethylene), poly(iminocarboxyl- 1,4-cyclohexylenemethylene), 20 poly(iminoisophthaloyliminohexamethylene) and any of the numerous nylons known in the art; and others; (I) polyacetals such as poly(2-ethyl-1,3-dioxa-4,6 cyclohexylenemethylene), poly(vinyl acetal), poly(vinyl butyral) and others; and 25 (g) polypiperazines such as poly(1,4-piperazinediyladipoyl), poly(1,4- piperazinediylcarboxyloxyethyleneoxycarbonyl), poly(1,4 piperazinediylisophthaloyl) and others; 4. Isocyanates such as: 30 (a) hexamethylene diisocyanate; (b) isophorone diisocyanate; -8- WO 00/40403 PCT/US99/28770 (c) trimethylhexamethylene diisocyanate; (d) hydrogenated 4,4'- diphenylmethane diisocyanate; (e) trans-cyclohexane diisocyanate; (f) m-tetramethylxylylene diisocyanate; 5 (g) 4,4'-diphenylmethane diisocyante; (h) 2,4'-diphenylmethane diisocynate; (i) 2,2'-diphenylmethane diisocyanate; (j) mixed 4,4'-diphenylmethane diisocyanate and 2,4' diphenylmethane diisocyanate; 10 (k) mixed 4,4'-diphenylmethane diisocyanate and 2,2' diphenylmethane diisocyanate; (1) 2,4-toluene diisocyanate; (m) 2,6-toluene diisocyanate; (n) mixed 2,4-toluene diisocyanate and 2,6-toluene 15 diisocyanate; (o) p-phenylene diisocyanate; (p) 4,4'-dibenzyl diisocyanate (q) 1,5-naphthalene diisocyanate; (r) tolidene diisocyanate; and 20 (s) polymeric diphenylmethane diisocyanate. A more complete listing of the polymers can be found in various polymer reference handbooks, and particularly in Polymer Handbook 2nd Edition, John Wiley & Sons, 1975. 25 It is important that the adhesive maintain a Shore D hardness greater than the Shore D hardness than the wood substrate. This is especially important when the wood panel is utilized in a horizontal manner where items may be placed on top of the panel, and if the adhesive is too soft, these items will leave an impression mark in the panel. 30 The adhesive composition of the present invention, includes the following: -9- WO 00/40403 PCT/US99/28770 % Range Ingredient by Weight Polymer emulsion(s) 20 to 100 Coalescing agent 0 to 20 Melt Flow Modifiers 0 to 40 Filler 0 to 40 pH adjuster 0 to 3 Biocide 0 to 1 Defoamer 0 to 3 Opacifier 0 to 5 Thickener 0 to 5 Water 0 to 10 The components of the composition adding up to 100% by weight. The polymers useful in the present compositions include a polymer or copolymer containing one or more monomers previously listed, but 5 preferably is selected from SIS (styrene-isoprene-styrene); SBS (styrene butadiene-styrene); SEBS (styrene-ethylene-butylene-styrene); EVA (ethylene-vinyl acetate); APAO (amorphous polyalpha olefin); SBR (styrene butadiene-rubber); (VA) vinyl acetate homopolymer; acrylic polymers and copolymers; styrene acrylic polymers and copolymers; and others that have 10 at least one Tg greater than 20 0 C. The most preferred amount of polymer or blend of polymers is from about 50% to 90% by weight. The coalescing agents may be present in an amount of from about 0 to 20% by weight, preferably 0% to 10% by weight, and function to fuse the adhesive film into a continuous film at a chosen drying temperature. 15 Typical coalescing agents which are used in the adhesive of the present invention are: plasticizers, such as benzoate ester, phthalates, sebecates, phosphates, citrates, and the like, as well as solvents, such as butyrates, lactates, glycol ethers, glycol ether acetates, alcohols, ester alcohols, - 10- WO 00/40403 PCT/US99/28770 alkanol amines, and others. The preferred coalescing agent is Texanol, a 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate available from Eastman Chemical Products. Fillers may also be incorporated into the adhesive composition in 5 amounts ranging from 0% to 40% by weight, preferably 0% to 10% by weight. These are inert in the formulation, and are typically added as an anti-blocking agent. Fillers may include hydrated alumina (A1 2 0 3 -3H 2 0), silicates such as magnesium silicates, aluminum silicate, sodium silicate, potassium silicate and the like, mica, calcium carbonate (CaCO 3 ) and 10 silica. Other commonly employed fillers may also be used as long as they do not materially alter the function of the remaining ingredients in the formulation. Optional conditioning additives may be incorporated into the adhesive composition in order to modify particular physical properties. 15 These additives may include colorants, such as titanium dioxide, defoamers, sequestrants, deionized water, preservatives, biocides, antiblocking agents, anticling agents, pH adjusters, surfactants, thickeners and other commonly known and used additives. As noted above, such additives can be present in amounts ranging from 0% to about 30% by 20 weight. As previously described, pH adjusters of from 0% to 3%, preferably 0.1% to 1.5%, by weight, may be added to the adhesive composition. Typical pH adjusters include ammonia, alkanol amines, primary amines, secondary amines, tertiary amines, sodium hydroxide, potassium 25 hydroxide, 2-amino-1-propanol, 3-amino-1 -propanol, various salts such as, carbonates, phosphates, citrates, acetates, along with their corresponding acids, and other common chemicals used for adjusting pH. 0% to 1%, preferably 0.01% to 0.8%, of a biocide which functions to prevent degradation of the adhesive by microorganisms such as yeast, 30 fungi, bacteria, molds and mildew, as packaged for shelf life preservation may also be added to the adhesive composition. Typical biocides are -11 - WO 00/40403 PCT/US99/28770 benzoates, phenols, aldehydes, halogen containing compounds, nitrogen compounds, and metal containing compounds, such as, mercurials, zinc compounds and tin compounds with the preferred biocide being Proxel GXL, a 1,2-benzisothiazolin-3-one available from Zeneca, Inc. 5 Defoamers in the amount of 0% to 3%, preferably 0.05% to 1.5%, may also be added to the adhesive composition. Typical defoamers include silicone based, mineral oil based, surfactant based, and kerosene based compounds with the preferred defoamer being DEEFO-97-2, a mineral oil based defoamer available from Ultra Additives, Inc. 10 Opacifiers in amounts ranging from 0% to 5%, preferably 0% to 2.5% may also be added to the adhesive composition. Opacifiers are added to the adhesive composition to insure that the wood substrate cannot be seen through the decorative top layer, particularly when the top layer is a paper. Typical opacifiers include titanium dioxide, calcium carbonate, 15 barium sulfate, and other light reflecting powdered minerals or metallic oxides with the preferred opacifier being Contax AQ White, a titanium dioxide dispersion, available from Sun Chemical. From about 0% to 5%, preferably 0% to 2.5% of a thickener may also be added to the adhesive composition. Thickeners are used to increase the 20 viscosity of the resultant adhesive without substantially affecting its adhesive characteristics. Typical thickeners include polyacrylic acid, polyvinyl alcohol, cellulosic thickeners, acrylic emulsion copolymers, polyacrylic salts, alginates, xanthan gumas, guar, starch bentonites, attapulgates, and other thickening or gelling agents. The preferred 25 thickener is Alcogum L-15, an acrylic emulsion copolymer, available from ALCO Chemical Corp. Melt flow modifiers in amounts ranging from 0% to 40% preferably 0% to 30%, may be added to the adhesive composition. Melt flow modifiers are added to the composition to improve the flow of the dried adhesive film 30 under heat and pressure while sealing the decorative top layer to the wood substrate. Typical melt flow modifiers include: phosphate esters, benzoate -12- WO 00/40403 PCT/US99/28770 esters, phthalate esters, wood rosin esters, gum rosin esters, tall oil rosin esters, aromatic hydrocarbon resins, aliphatic hydrocarbon resins, cycloaliphatic resins, all their hydrogenated counterparts, and any combinations of the aforementioned, as long as the Shore D hardness is 5 maintained. The preferred melt flow modifiers are phosphate esters, tall oil rosin esters, and solid benzoate esters. With the most preferred being Santicizer 141, a phosphate ester plasticizer available from Monsanto. Adhesives having the following compositions were prepared wherein all percentages are by weight. 10 EXAMPLE 1 % by Ingredient Weight Styrene Acrylate emulsion 62.9 Hycar 26315 from B.F. Goodrich High Styrene content emulsion 21 Rovene 4106 from Mallard Creek Polymers Coalescing agent 2.9 Texanol Filler 7.3 Hydrad 10 Slurry-A1203-3H 2 0-70% solids pH adjuster 0.8 Concentrated Aqueous Ammonia-29% Biocide 0.4 Proxel GXL Defoamer 0.4 DEEFO-97-2 Opacifier 1.8 Contax AQ White Thickener 0.5 Alcogum L- 15 Deionized Water 2 -13- WO 00/40403 PCT/US99/28770 EXAMPLE 2 % by Ingredient Weight Styrene Acrylate emulsion 63.5 Hycar 26315 from B.F. Goodrich High Styrene content emulsion 21.2 Rovene 4106 from Mallard Creek Polymers Coalescing agent 0.7 Texanol Melt Flow Modifier 2.5 Santicizer 141 Filler 9.2 Hydrad 10 Slurry-A1 2 0 3 -3H 2 0-70% solids pH adjuster 0.9 Concentrated Aqueous Ammonia Biocide 0.3 Proxel GXL Defoamer 0.4 DEEFO-97-2 Thickener 0.1 Alcogum L- 15 Deionized Water 1.2 EXAMPLE 3 %by Ingredient Weight Styrene Acrylate emulsion 42 Hycar 26315 from B.F. Goodrich High Styrene content emulsion 42 Rovene 4106 from Mallard Creek Polymers Coalescing agent 2.9 Texanol Melt Flow Modifier 0 -14- WO 00/40403 PCT/US99/28770 %by Ingredient Weight Filler 9.1 Hydrad 10 Slurry-A1 2 0 3 -3H 2 0-70% solids pH adjuster 0.9 Concentrated Aqueous Ammonia Biocide 0.4 Proxel GXL Defoamer 0.4 DEEFO-97-2 Thickener 0.2 Alcogum L- 15 Deionized Water 2.1 EXAMPLE 4 % by Ingredient Weight Styrene Acrylate emulsion 38.3 Hycar 26315 from B.F. Goodrich High Styrene content emulsion 38.3 Rovene 4106 from Mallard Creek Polymers Coalescing agent 2.6 Texanol Melt Flow Modifier 4.5 Aquamix 993 Benzoflex 352 dispersion Melt Flow Modifier 4.5 Aquatac XR-4258 Rosin ester dispersion Filler 8.3 Hydrad 10 Slurry-A1203-3H 2 0-70% solids pH adjuster 0.8 Concentrated Aqueous Ammonia Biocide 0.4 Proxel GXL -15- WO 00/40403 PCT/US99/28770 % by Ingredient Weight Defoamer 0.4 DEEFO-97-2 Thickener 0.2 Alcogum L-15 Deionized Water 1.7 The performance of the adhesives prepared in accordance with 5 Examples 1-4 was compared with a commercially available EVA hot melt adhesive ARDAL T8028/2 from Ato Findley SA. Hot melt adhesives such as ARDAL T8028/2, rather than the water-based adhesives of the present invention, are the common adhesives currently used for laminating decorative veneer to wood substrates. 10 Shore D hardness was tested on dried, room temperature films. Bonds and Shore D hardness of the lamination were evaluated after coating onto 1 mil decorative paper, drying at 200oF for 45 seconds for the water-based material, and applied at 400oF for the hot melt, then both were conditioned at room temperature for 24 hours for both the water 15 based and hot melt materials. Thereafter, one set of coated substrate samples was laminated by sealing with a Carver flat platen press at 250oF for 3 seconds at 80 psi. Then a second set of coated substrate samples were laminated by sealing with a Carver flat platen press at 250oF for 1 second at 80 psi. The results of the tests are reported in Table 1. -16- WO 00/40403 PCT/US99/28770 TABLE 1 Condition Shore D Condition 1: Condition 2: Fiber hardness of Fiber Tear 2: Shore Tear Bond adhesive film Condition Bond D hard- distance or substrate 1: Shore D distance ness of from edge Sample (average of 6 harness of from edge of lamina- of lamina Identity data points) lamination lamination tion tion Example 1 64.2 75 0.125 inch 75.2 0.125 inch Example 2 59.3 73.5 0.125 inch 75.5 0.125 inch Example 3 77.8 79.7 0.125 inch 75.8 0.125 inch Example 4 71 77 0.125 inch 76.0 0.125 inch T8028/2 37.5 45 0.5 inch 49 0.75 Particle 52 NA NA NA NA Board The data in Table 1 illustrate the following: 1. The adhesive compositions of Examples 1-4 successfully 5 bonded decorative paper to particle board. 2. The data in column 1 of Table 1 demonstrate that the adhesives of Examples 1-4 produce films of greater Shore D hardness than the EVA hot melt adhesive as well as the particle board itself. 3. The data in columns 2 and 4 of Table 1 demonstrate that 10 laminates constructed with particle board and the adhesives of Examples 1-4 have greater Shore D hardness than either a laminate constructed with the EVA holt melt adhesive or the particle board substrate itself. For example, the adhesive lamination of Example 1 has a Shore D hardness of 75 whereas a lamination with the EVA hot melt adhesive (T8028/2) has a 15 Shore D hardness of only 45. The particle board itself only has a Shore D hardness of 52. 4. The data in columns 3 and 5 of Table 1 demonstrate that the adhesives of Examples 1-4 have greater edge bonding strength than the EVA hot melt adhesives. This is evidenced by the decreased distance of 20 fiber tear from the edge of a lamination produced with these adhesives -17- WO 00/40403 PCT/US99/28770 (0.125 inch) as compared to an EVA containing lamination tear (0.5-0.75 inches). Edge bonding strength is an important property for these laminations because adequate edge bonding is desired to reduce scrap when a manufacturer trims laminated boards to final dimensions. 5 The laminated wood panels of the present invention may be manufactured using a variety of methods. For example, the wood substrate may be manufactured, coated with the adhesive and then the decorative top layer may be applied to the adhesive. The resulting lamination is then heated, preferably under pressure in a press or between 10 rolls, to affect bonding of the decorative top layer to the wood substrate. The adhesive interposed between the wood substrate and top layer is heated to a temperature above the melting point of the adhesive composition in order to affect bonding, i.e. to a temperature in excess of 150oF and especially in the range of about 175 0 F to 275 0 F. The resultant 15 laminated wood panel is then allowed to cool to solidify the adhesive and affect bonding. Alternately, the adhesive composition is applied to the decorative top layer, dried, and then the top layer is rolled up for later use. The top layer together with the adhesive coating thereon, would then later be contacted 20 with the wood substrate, and subjected to heat and pressure to affect bonding, as discussed above. In yet another method, the adhesive may be formed into a film, dried and rolled up for later use. In this process, the wood substrate, the film of adhesive, and the decorative top layer of paper, vinyl or veneer are then 25 brought into contact with each other and subjected to heat and pressure to affect bonding, as discussed above. The laminated decorative panels or structures of the present invention may be used in a variety of end uses, depending in particular on the nature of the panel. For example, the panels are preferably used as the 30 interior surfaces in buildings for walls. This structure may also be used in the furniture industry, where it may be used in a substantially flat panel or -18- WO 00/40403 PCT/US99/28770 a profile. In particular, laminated wood panels wherein the top decorative layer is paper may be painted to provide an attractive surface with the interposed layer of adhesive providing a smooth surface that tends to cover defects, such as roughness, indentations or unevenness, in the surface of 5 the wood substrate. In addition, the top decorative paper layer may be preprinted with the desired pattern so that no subsequent painting is necessary. Further, panels coated with veneer may be shellacked or coated with varnish or the like to preserve or enhance the attractive features of the veneer. The panels may also be used as sublayers in the construction 10 industry to provide barriers to moisture or the like and to provide a surface that is capable of having other layers attached thereto. -19-

Claims (20)

1. A laminated decorative panel, comprising: a substantially planar substrate formed from a wood product; a decorative top layer; and a water-based, heat sealable adhesive interposed between said 5 substrate and said top layer for bonding said top layer to said substrate, said adhesive comprising, as a primary ingredient thereof, a polymer containing one or more monomers which when polymerized or copolymerized yields a Shore D hardness greater than the Shore D hardness of said substrate.

2. The laminated decorative panel of claim 1 wherein said wood product comprises particles of wood.

3. The laminated decorative panel of claim 2 wherein said particles of wood are selected from the group consisting of chips, flakes, sawdust, paper, fragments, and agricultural products such as straw.

4. The laminated decorative panel of claim 1 wherein said substrate is selected from the group consisting of particleboard orientated strandboard, waferboard, plywood, fiberboard, hardboard, chipboard and strawboard.

5. The laminated decorative panel of claim 1 wherein said decorative top layer is a vinyl covering.

6. The laminated decorative panel of claim 1 wherein said decorative top layer is a paper sheet.

7. The laminated decorative panel of claim 1 wherein said decorative top layer is a veneer sheet.

8. The laminated decorative panel of claim 1 wherein said monomer is selected from the group consisting of styrene, methylmethacrylate, vinyl acetate, vinyl chloride, and diphenylmethane diisocyanate. - 20 - WO 00/40403 PCT/US99/28770

9. The laminated decorative panel of claim 1 wherein said adhesive is comprised of: about 20 to 100% by weight of a styrene-based polymer emulsion; about 0 to 20% by weight of a coalescing agent; 5 about 0 to 40% by weight of a filler; about 0 to 40% by weight of a melt flow additive; about 0 to 30% by weight of one or more conditioning additive; and the components totaling 100% by weight of said adhesive.

10. The laminated decorative panel of claim 9 wherein said styrene based polymer emulsion is a styrene acrylate emulsion.

11. A water-based, heat sealable adhesive composition for bonding a decorative top layer to a wood substrate, comprising: about 20% to 100% by weight of a polymer containing one or more monomers which when polymerized or copolymerized yields a Shore D 5 hardness greater than the Shore D hardness of the wood substrate; about 0% to 20% by weight of a coalescing agent; about 0% to 40% by weight of a filler; up to about 10% by weight of water; about 0% to 40% by weight of a melt flow additive; 10 about 0% to 30% by weight of one or more conditioning additives; and the compounds totaling 100% by weight of the composition.

12. The adhesive composition of claim 11 wherein said monomer is selected from the group consisting of styrene, methylmethacrylate, vinyl acetate, vinyl chloride, and diphenylmethane diisocyanate.

13. The adhesive composition of claim 11 wherein said polymer comprises a styrene based polymer emulsion.

14. The adhesive composition of claim 13 wherein said styrene based polymer emulsion includes a styrene acrylate emulsion.

15. The adhesive composition of claim 13 wherein said styrene based polymer emulsion includes a high styrene content emulsion wherein the styrene content comprises at least 25% of said polymer. -21- WO 00/40403 PCT/US99/28770

16. The adhesive composition of claim 11 wherein said conditioning additive comprises 0 to 3% by weight of a pH adjuster.

17. The adhesive composition of claim 11 wherein said conditioning additive comprises 0 to 1% by weight of a biocide.

18. The adhesive composition of claim 11 wherein said conditioning additive comprises 0 to 3% by weight of a defoamer.

19. The adhesive composition of claim 11 wherein said conditioning additive comprises 0 to 5% by weight of a opacifier.

20. The adhesive composition of claim 11 wherein said conditioning additive comprises 0 to 5% by weight of a thickener. - 22 -