Wood coating composition and process of use thereof
This is a continuation-in-part of U.S. Ser. No. 07/481,500, filed Feb. 16, 1990, which is a division of U.S. Ser. No. 07/308,970, filed Feb. 9, 1989, now U.S. Pat. No. 4,921,891, which is a continuation of U.S. Ser. No. 940,904, filed Dec. 10, 1986. 
    
    
     The present invention is directed to a method and compositions used therewith for coating wood to render it capable of receiving wood-grain printing inks and conventional wood stains, while also concealing joints and other imperfections. 
     In the decorative uses of wood, there are many applications in which visible joints in the wood are not desired. For example, in the use of moldings along the edges of doors, window frames, and the like, it is desirable to have each edge constructed of a single length of wood. Moreover, to have a decorative effect, the wood is often stained to a desired color, such as walnut, rosewood, and the like, then covered with a protective coating such as varnish or other conventional clear coating. The use of single lengths of wood is expensive and wasteful, since short lengths of scrap wood are not reusable. There is no practical alternative to using single lengths of wood for molding. Plastics or compounded wood pulp products are usually not desirable since they either do not have sufficient strength and durability or do not have the pleasing wood grain surface texture. A piece of plywood would also be extremely expensive since one or more surfaces of the molding would have to be veneered, making it much more expensive then a solid piece of wood. 
     The use of scrap pieces of wood joined together, such as by finger joints, would be desirable. There has been difficulty however, in treating joined pieces of wood to have the appearance of a single piece of wood for decorative purposes. One such method is described in commonly assigned U.S. Pat. No. 4,546,133, wherein specialized wood coating and ink compositions are disclosed. The present invention provides an improved method and coating for concealing joints in wood, while still maintaining the appearance and texture of a single piece of wood. The coating according to the present invention also is capable of accepting conventional wood stains. 
     It is therefore an object of the present invention to provide compositions which are useful for coating wood to conceal joints, but which retain the grainy appearance of the natural wood. 
     It is a further object of the present invention to provide novel coatings for wood which accept conventional wood stains. 
     These and other objects will be apparent from the following description and preferred embodiments. 
    
    
     The present method utilizes a basecoat composition for covering a wood or wood product comprising a combination of resins, pigments, solvents, and additives for suspension, dispersion, wetting, thickening, flowing and anti-marring. A printing composition is also provided comprising resins, pigments, solvents, and tinting and wetting agents. 
     The method according to the present invention comprises the steps of applying a novel liquid basecoat onto natural wood or a wood product, evaporating volatile solvents to form a solid coating, and applying a novel ink composition in a wood grain pattern onto the solid coating. 
     The starting material for forming a wood product according to the present invention may be any product having a wood surface, including strips, with or without joints, sheets, including plywood and wood grain paper, or any other product derived from wood or wood pulp, sawdust, and the like. Since a primary purpose for the use of the compositions according to the present invention is to provide a decorative surface, it is desirable, but not necessary, that the starting material have a wood grain texture, since that texture will be substantially retained after the basecoat coating is applied according to the present invention. 
     Generally, the wood or wood product will be coated with a liquid basecoat composition according to the present invention then dried to remove the volatile solvents. The drying is preferably performed with heat in a conventional oven, but other evaporative methods may be utilized. Then a grain ink formulation may be applied in a pattern to simulate a wood grain using a conventional roller having a wood grain pattern using the inks described herein. Apparatus for performing these functions are conventional and known in the art. 
     The basecoat formulation according to the present invention comprises the following components: alkyd resins, other resins, absorption pigments, other pigments, suspension agent, dispersing agent, wetting agent, thickener, anti-marring agent, flow agent, and solvents. 
     A particularly preferred basecoat composition useful for coating wood contains the following (percentages given by volume). 
     
         ______________________________________                                    
                        Manufacturer                                      
______________________________________                                    
Alkyd resin 5.18    Resin         Guardsman                               
RJ-100 Soln.                                                              
            5.18    Suspension Agent                                      
                                  Monsanto                                
Xylene      26.91   Solvent                                               
Solvent #150                                                              
            3.30    Solvent       Chemtech                                
Chlorowax   4.21    Anti-mar agent                                        
                                  Chem-                                   
                                  Central                                 
Tripentaerythritol                                                        
            4.72    Absorption pigment                                    
Phoschek P/30                                                             
            12.50   Absorption pigment                                    
                                  Monsanto                                
Superfins Melamine                                                        
            4.36    Vehicle resin Melamine                                
                                  Chem.                                   
Collidisperse                                                             
            .27     Wetting agent Troy                                    
Deodorant   .28                   Guardsman                               
EHEC solution                                                             
            8.96    Thickener     Hercules                                
Pecan shell flour                                                         
            1.12    Absorption pigment                                    
                    (45 Micron)                                           
Industrial toluene                                                        
            1.41    Solvent                                               
Resimene #955                                                             
            2.00    Vehicle resin Monsanto                                
Lactimon    .05     Flow agent    BYK                                     
                                  Malinkrodt                              
MPA 2000X   .12     Suspension agent                                      
                                  NL                                      
RHD 6X Titanium                                                           
            1.30    White pigment Tioxide                                 
Methyl ethyl ketone                                                       
            4.94    Solvent                                               
Acetone     3.57    Solvent                                               
Lacquer diluent                                                           
            5.40    Dispersing solvent                                    
                                  Ashland                                 
VAGH Vinyl  1.47    Resin         Union                                   
                                  Carbide                                 
Cellulose acetate                                                         
            1.07    Solvent                                               
Dioctyl phthalate                                                         
            .71     Solvent                                               
2444-XF Yellow                                                            
            .11     Pigment       Pfizer                                  
Nytal 400   .07     Inert pigment Vanderbilt                              
Jaysol Anhydrons                                                          
            .17     Solvent       Eastman                                 
MIBK        .47     Solvent                                               
1 Sec. CAB 531-1                                                          
            .16     Vehicle resin Eastman                                 
            100.00                                                        
______________________________________                                    
 
    
     In the above preferred formulation, in addition to the alkyd resins, the other resins include Melamine, Resimene and CAB, all commercially available resins. Melamine and resimene are butylated urea resins and are commercially available from manufacturers such as Monsanto. Such other resins also include polyester resins, including water extended polyesters, polystyrene, vinyl resins including polyvinylacetate, polyvinylchloride, vinylchloride-vinylacetate copolymers and the like; polyamide resins, polyurea resins, and acrylic resins; phenolic resins, maleic resins, coumerone-indene resins, urea-formaldehyde; melamine-formaldehyde resins; epoxy resins, silicone resins, ionamer resins, acetal resins, polyethelyne, polypropolene, hydrocarbon resins, rubber derivatives, polycarbonate resins, phenoxy resins, fluorol plastics, styrene-butadiene resins, polyurethane resins, furane resins, polysulfone resins, pentaerythritol resins, ester gum, copalesters, and the like. Natural resins which may be used include shellac, rosin copal resins, damar resins, manila resins and the like. 
     Absorption pigments which may be utilized include tripentaerythritol, Phoschek P/30, and pecan shell flour, or any combination thereof. The composition will also contain other pigments, which may be inorganic or organic. These pigments include RHD-6X Titanium, Yellow 2444-XF, Nytal 400. 
     The base coat composition will also contain suspension agents, dispersing agents, wetting agents, thickeners, anti-marring agents, flow agents and optionally, deodorant additives to alleviate any offensive smells caused by the base coat. Suspension agents include MPA-2000X, and RJ-100, both made by Monsanto. Preferred dispersing agents include a lacquer used as a diluent. Preferred wetting agents included Collidisperse, made by Troy Chemical. A preferred thickener includes EHEC Solution (Hercules) . Any readily available anti-marring agent may be used such as Chlorowax. A flow agent such as Lactimon may be utilized. 
     Typical solvents include Xylene, Solvent #150 (Ashland) , Toluene, methyl ethyl ketone,, acetone, cellulose acetate, dioctyl phthalate, Jaysol Anhydrons (Eastman) , and MIBK (methyl isobutyl ketone). Other solvents may include turpentine, diapintine, pine oil, petroleum spirits, naptha, mineral spirits, methyl and ethyl alcohol, toluol, benzol, xylol, ethyl acetate, amyl acetate, and the like. The several portions of any vehicle used in comparing one of the decorative coatings are generally composed of the same basic materials although they may have varied amounts of thinners, solvents, fillers and the like so as to vary their viscosities and other physical properties, but there may be a combination of unrelated resins used on the same panel to provide texture and growth lines. 
     The pulverized pecan nut shell flour utilized in the base coat composition as an absorption pigment will be in the form of a fine powder, typically grain size of about 42 to 46 microns (preferably 45 average microns). Preferably pecan shell flour will be used. 
     The amount of the volatile solvents and esters which are utilized will be of the kind in an amount sufficient to dissolve and/or suspend the various components in a uniform liquid suspension material. It is desirable that the solvents comprise some polar solvents, such as acetone and cellulose acetate, and some non-polar solvents such as xylene, and slightly polar solvents such as ketones. Other higher molecular weight solvents may also be utilized such as petroleum distillates, esters, all of which are commercially available. 
     The particular proportions of the various components used may be generally in the proportions given above. 
     It will be understood however, that various modifications in proportions and components may be utilized without departing from the scope of the present invention. 
     In addition to the various pigments mentioned above, the base coat may contain various typical inorganic pigments useful for wood grain such as those iron pigments ranging in color from yellow through red, reddish brown, brown to black, similar to those found in natural wood. These iron pigments include yellow ocher, raw and burnt sienna, and raw and burnt umber. Other useful inorganic color pigments include chrome yellow, cadmium sulfide, zinc yellow, cobalt blue, ultramarine blue, iron oxide, chrome green, chromium oxide green, chromium hydroxide green, lamp black carbon, and white pigments such as titanium dioxide, titanium calcium, zinc oxide, zinc sulfide, antimony oxide, lithopone, etc. Organic pigments may also be utilized such as toluidine red, phthalocyanine blue and green, VanDyke brown, alizarin, madder lake, lythol red, etc. 
     After applying the base coat to the wood product, it is dried, for example, in a conventional oven to remove the volatile solvents, thereby forming a hardened base coat. An ink formulation may then be applied to the base coat with a roller having a wood grain pattern. The ink formulation comprises: resins, pigments, absorption pigments, tinting agents, wetting agents, and solvents. 
     The resins utilized in the above ink formulation include acrylic resins such as Joncryl 74, BALAB, UCAR-SCT 100. The pigments include various pigments utilized to simulate wood grain colors, as described above and include specifically yellow 895-000-1801 (Nuodex), burnt umber (I-347), red oxide 895-1003 (Harshaw), Mearlin silk white (an iridescent pigment). As an absorption pigment Phoschek P/30 may be utilized. As a tinting agent a tint paste such as Benzidine yellow (W-1041) may be utilized. A wetting agent such as glycol ether (PM) is used. Various solvents may be utilized such as DMAE (Union Carbide), water and ethylene glycol. 
     The pigments which are utilized in the ink formulation will depend upon the color of the wood grain desired. The pigments must, of course, impart a color to the ink formulation which is different from the color of the dried base coat in order to provide contrast. Usually, colorants which impart yellow or brown tones to the base coat will be useful. Typically, the base coat, after application of the ink formulation, will be stained with a conventional wood stain, which usually enhances the contrast between the base coat and the ink. 
     A typical ink formulation may comprise the following (% by volume): 
     
         ______________________________________                                    
                        Manufacturer                                      
______________________________________                                    
Joncryl 74  52.24   Acrylic resin Johnson &amp;                               
                                  Johnson                                 
BALAB 3056A .73     Resin (latex) Witco                                   
Ethylene glycol                                                           
            2.32    Solvent                                               
DMAE        .58     Solvent                                               
Tap Water   5.15    Solvent                                               
UCAR SCT100 1.20    Resin (latex) Union                                   
                                  Carbide                                 
Glycol Ether PM                                                           
            6.41    Wetting agent Ashland                                 
895-000-1801 Yellow                                                       
            6.22    Pigment       Nuodex                                  
W-1041 Benzidine                                                          
            4.90    Tint paste    Harshaw                                 
Yellow                                                                    
I-347 Bt. Umber                                                           
            16.77   Pigment       Harshaw                                 
895-1003 Red Oxide                                                        
            .79     Pigment       Nuodex                                  
Mearline Silk White                                                       
            .22     Iridescsnt pigment                                    
                                  Mearl                                   
Phos Chek P/30 fine                                                       
            2.45    Absorption pigment                                    
                                  Monsanto                                
            100.00                                                        
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     After application of the graining ink formulation and air drying, the final wood product may be utilized as is, or stained with a conventional wood stain, then coated with a conventional varnish or other clear preservative. 
     The base coat and ink formulation may be applied to any wood surface, including paper, if desired. 
     Having described the specific embodiments of the invention, other modifications and variations will be apparent to those of ordinary skill in the art, which variations and modifications are intended to be within the scope of the present invention.