Patent Publication Number: US-2020290240-A1

Title: Surfacing materials and method of manufacture, including a textured press plate for use in the manufacture of decorative laminate

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/819,214, entitled “SURFACING MATERIALS AND METHOD OF MANUFACTURE,” filed Mar. 15, 2019. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to surfacing materials and methods for manufacturing the materials. 
     2. Description of the Related Art 
     High pressure decorative laminates are currently manufactured with smooth glossy surfaces, textured surfaces, or deeply sculpted and embossed surfaces. As general background, decorative laminates prepared by heat and pressure consolidation have been produced commercially for a number of years, and have found widespread acceptance in the building and furniture industry as countertop and tabletops, bathroom and kitchen work surfaces, wall paneling, flooring products, partitions and doors. These decorative laminates may be described as containing a number of laminae consolidated to form a unitary structure carrying a surface decoration. The surface decoration may range from something as simple as a solid color to something as complex as an embossed simulated wood grain finish. 
     Decorative laminates generally include plural layers of synthetic resin impregnated paper sheets bonded under heat and pressure to form a unitary structure. In normal practice, a decorative laminate sheet assembly, from the bottom up, includes a core of one or more phenolic resin impregnated sheets, above which lies a decorative melamine-formaldehyde impregnated sheet. The decorative sheet may be further covered with a melamine-formaldehyde impregnated overlay. The core, or base, functions to impart rigidity to the decorative laminate and usually includes a solid substrate which may, or may not, be formed prior to the initial laminating steps. Prior to stacking, the sheets of the core member are impregnated with a water alcohol solution of phenol formaldehyde, dried and partially cured in a hot oven, and finally cut into shapes. 
     The core may, for example, include a plurality of sheets of 90-150 pound phenolic resin impregnated Kraft paper. The Kraft paper is impregnated throughout and bonded with a substantially completely cured phenolic resin which has been converted to a thermoset state during the initial laminating step. The substrate may be a pre-cured plastic laminate, such as glass fiber-reinforced thermoset polyester resin laminates and the like, a wood product, such as hardboard, wood waste or particle boards, plywood and the like, a mineral base board, such as, cement-asbestos board, sheet rock, plaster board, and the like, or a combination of substrates. 
     The decorative sheet provides the decorative laminate with an attractive appearance. The decorative sheet also dictates the surface characteristics of the decorative laminate. For example, the composition of the decorative sheet dictates the decorative laminate&#39;s resistance to chemical agents, heat, light, shock and abrasion. Decorative sheets are commonly manufactured from high quality 50-125 pounds per 3,000 square ft. ream basis weight (80-202 grams per square meter), pigment filled, alpha-cellulose paper impregnated with a water alcohol solution of melamine-formaldehyde resin. The resin impregnated decorative sheets are subsequently dried, partially cured, and finally cut into sheets. The pigment filled, alpha-cellulose paper of the decorative sheet, may include a solid color, a decorative design, or a roto-gravure reproduction of natural materials, such as, wood, marble, leather, etc. The aesthetic characteristics of the cellulose paper are revealed as the laminate&#39;s decorative design upon completion of the decorative laminate. 
     Decorative laminates are generally manufactured by placing the resin impregnated core and decorative sheet between steel plates and subjecting the decorative laminate stack to heat and pressure for a time sufficient to consolidate the laminate and cure the resins (generally about 25 minutes to an hour). The pressure and heat force the resin in the paper sheets to flow, cure, and consolidate the sheets into a unitary laminated mass referred to in the art as a decorative high pressure laminate. Finally, the formed decorative laminate is bonded to a reinforcing substrate, such as, plywood, hardboard, asbestos board, particle board or the like. 
     Generally, more than one laminate is formed at one time. Multiple laminates are formed by inserting a plurality of decorative laminate sheet assemblies into a stack. Release sheets are positioned between the decorative laminate sheet assemblies to separate the various laminates stacked together. After consolidation, the release sheets allow the individual laminates to be separated. 
     Textured decorative laminates are also very popular. The textured surfaces range from relatively shallow depressions, such as, textured (e.g., satin, matte or semi-gloss) surfaces, to relatively deeply sculpted or embossed surfaces having a noticeable three-dimensional effect, such as, wood grain, leather, slate, abstract patterns, creative designs etc. The textured laminates are commonly manufactured using release sheets with the desired surface texture, which surface texture is imparted to the decorative laminate during the application of heat and pressure in the manufacturing process. 
     It has, however, been found that high pressure decorative laminates are susceptible to a build-up of fingerprints as the surface of the high pressure decorative laminate is touched during the course of the day. The fingerprints remain visible and can become highly distracting. Prior attempts to address this problem have relied upon chemically modified surfaces to achieve the purpose. However, such attempts have only led to limited success. As such, a need remains for a high pressure decorative laminate that is not susceptible to the build-up of fingerprints on the surface thereof. 
     SUMMARY OF THE INVENTION 
     According to a first aspect there may be provided a textured press plate for use in the manufacture of decorative laminate. The textured press plate is manufactured by the method include the steps of applying a UV curable acrylate mixture to a surface of a press plate substrate, irradiating the UV curable acrylate mixture with LED precure by excimer UV to create a UV-irradiated layer having a surface exhibiting micro-folding, and fully curing the UV-irradiated layer to form a textured coating layer. 
     In some embodiments the step of irradiating includes treating the UV curable acrylate mixture so that the UV cured acrylate mixture is only crosslinked on a surface thereof to produce a supermatting surface through micro-convolution. 
     In some embodiments the step of irradiating is achieved with an excimer emitter based on a Xe-emission spectrum at a wavelength of 172 nm in a presence of nitrogen. 
     In some embodiments the UV curable acrylate mixture is a solvent-free and non-aqueous lacquer. 
     In some embodiments the solvent-free and non-aqueous lacquer is an epoxy acrylic or a urethane acrylic. 
     In some embodiments the method further includes the step of applying a TiB 2  hard coating to the textured coating layer. 
     In some embodiments the step of applying includes applying the UV curable acrylate mixture to the press plate substrate with a roller. 
     In some embodiments the step of applying includes applying the UV curable acrylate mixture to the press plate substrate with a layer thickness greater than 5 microns. 
     In some embodiments the step of applying includes applying the UV curable acrylate mixture to the press plate substrate with a layer thickness of 30 to 100 microns. 
     In some embodiments the step of fully curing by E-beam or UV irradiation includes the step of applying the UV curable acrylate mixture to the press plate substrate with a roller. 
     In a further aspect a textured press plate includes a press plate substrate and a textured coating layer applied to the press plate substrate, wherein the textured coating layer is comprised of a UV curable acrylate mixture. 
     Additional advantages of the embodiments will be set forth in part in the description which follows, and in part will be understood from the description, or may be learned by practice of the invention. The advantages will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic of a laminate lay-up within a platen press. 
         FIG. 2  is a schematic of a decorative laminate in accordance with the present invention period 
         FIG. 3  is a schematic of textured press plate in accordance with the present invention. 
         FIGS. 4 and 5  are schematics showing the formation of the textured press plate shown in  FIG. 3 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The detailed embodiments of the present invention are disclosed herein. It should be understood, however, that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, the details disclosed herein are not to be interpreted as limiting, but merely as a basis for teaching one skilled in the art how to make and/or use the invention. 
     With reference to  FIG. 1 , a decorative laminate lay-up  10  composed of an exterior overlay paper layer  12 , a decorative layer  14 , and a core layer  16  is disclosed. The decorative laminate lay-up  10  is pressed in a conventional platen press  200 . However, the platen press  200  employs a textured press plate  202  treated in a highly specific manner to produce a decorative laminate  100  (see  FIG. 2 ) exhibiting desirable anti-fingerprint characteristics. As will be explained below in more detail, the textured press plate  202  imparts a textured matte surface  102  (formed on a bottom side  202   b  thereof) to a resulting decorative laminate  100 , wherein the textured matte surface  204  of the textured press plate  202  results in a decorative laminate  100  that exhibits a matte appearance and is not susceptible to a build-up of fingerprints on the surface thereof. 
     While a preferred embodiment disclosed herein includes an overlay paper layer, it is appreciated the decorative laminate lay-up may be assembled without an overlay paper layer. 
     The decorative laminate lay-up  10  is assembled by manufacturing the various layers in a conventional manner and then stacking the various layers in a conventional manner, that is, the sheets used in the production of the decorative laminate  100  are stacked in preparation for the heating and pressure steps used to consolidate the laminate. A textured press plate  202  composed of a press plate substrate  206  (that is, the conventional structure of the press plate commonly composed of stainless steel, preferably 410 grade stainless steel, 304 grade stainless steel or Bohler 630 stainless steel, although a wide variety of plate materials may be used without departing from the spirit of the present invention) and a textured coating layer  208  defining the textured matte surface is also prepared. 
     The process for producing surface effects in a release coating as disclosed in European Patent Application Publication No. 2527408, entitled “Method for Producing a Film with a Matt Surface,” which is incorporated herein by reference, is employed in the manufacture of the textured press plate  202  used in accordance with the present invention. Briefly, the &#39;408 publication teaches a technique for producing surface effects on a sheet. In accordance with the disclosed methodology a coating of an electron beam radiation curable material is applied to one surface of the press plate, and subsequently cured (ultimately producing the textured coating layer with the textured matte surface of the press plate in accordance with the present invention). 
     The application of the surface forming techniques of the &#39;408 publication are applied in the present invention in a manner resulting in a textured press plate  202  with a textured matte surface  204 . The textured matte surface  204  exhibits good matting properties (and correspondingly low degrees of gloss as defined in and measured in accordance with DIN EN ISO 2813) having improved scratch resistance properties. Ultimately, and as will be explained below in greater detail, the textured press plate  202  is ultimately utilized as a texture imparting surface in the manufacture of decorative laminate  100 . 
     With reference to  FIG. 3 , the textured press plate  202  of the present invention, employs a UV (ultraviolet) curable acrylate mixture  212  composed of a solvent-free and non-aqueous lacquer (in accordance with the present invention the lacquer is preferably an epoxy acrylic or a urethane acrylic (also referred to herein as the UV curable acrylate mixture) in the production of the textured coating layer  208  on the press plate substrate  206 . The matte textured press plate  202  is produced through the implementation of a two-stage irradiation process. First, and with reference to  FIG. 4 , the UV curable acrylate mixture  212  (which is ultimately cured to form the textured coating layer  208 ) is laid, or otherwise applied, upon the bottom surface  206   b  of a conventional press plate, which defines the press plate substrate  206  of the resulting textured upper pressure plate  202 . 
     The UV curable acrylate mixture  212  (which is ultimately cured to form the UV cured coating) applied upon the press plate substrate  206  is then irradiated with LED (light emitting diode) precure by excimer UV to create a UV-irradiated layer  212   a  having a surface exhibiting micro-folding (see  FIG. 5 ). In particular, the irradiation is applied so that UV cured acrylate mixture  212  is neither hardened nor is the entire layer of UV curable acrylate mixture  212  crosslinked. Rather the UV curable acrylate mixture  212  is only crosslinked on the surface thereof, which produces a supermatting surface through the effects of a micro-convolution. In accordance with a preferred embodiment, the U V-radiation irradiates via an excimer emitter based on a Xe-emission spectrum at a wavelength of 172 nm in the presence of nitrogen. 
     The UV-irradiated layer  212   a  (on the press plate substrate  206 ) is then fully cured by E-beam (electron beam) or UV irradiation (i.e. 200-400 nm). In particular, the UV-irradiated layer  212   a  partially cured by excimer can also be is then subjected to an electron beam irradiation to crosslink and harden the entire layer and form the final textured coating layer  208  of the textured press plate  202  without the UV-irradiation. 
     Once the final curing is completed, the final textured coating layer  212   b  of the textured press plate  202  is coated with a TiB 2  hard coating  220  to protect the micro-structure for longevity after the HPL (high pressure laminate)/LPL (low pressure laminate) pressing thereof is completed. The textured press plate  202  is coated with TiB 2  using the technique disclosed in U.S. Patent Application Publication No. 2017/0226630, entitled “METHOD FOR COATING STAINLESS STEEL PRESS PLATES AND COATED PRESS PLATES PRODUCED THEREBY”, which is incorporated herein by reference. 
     This procedure initially creates a shrinking process in the UV curable acrylate mixture  212  that ultimately becomes the UV cured textured coating layer  208  and thus the desired matting directly on the surface of the resulting textured press plate  202 . The production of a textured matte surface is achieved according to the &#39;408 publication with 100% lacquers, to which no separate matting agent (such as silica or the like) is added. The curing and cross-linking of the total layer by means of electron beam irradiation fixes the matte surface created by the partial curing and irradiation without influencing the matte surface in any adverse manner. The matte textured press plate  202 , and ultimately the decorative laminate  100  produced in this manner is distinguished by outstanding matting properties, which gloss levels to less than 3 (measured in accordance with the cited DIN EN ISO 2813 and 600 geometry) or less than 5 (corresponding at  850  geometry) can be reached. 
     In accordance with a preferred embodiment, the UV curable acrylate mixture  212  is preferably applied to the press plate substrate  206  by a roller, with a layer thickness greater than 5 microns and up to approximately 150 microns (preferably, 30 to 100 microns). 
     The UV curable acrylate mixture  212  is composed of a formulation having the following composition:
         60% to 90%, by weight, urethane acrylate;   8% to 38%, by weight, reactive diluent, such as, isobornyl acrylate;   1.0% to 10%, by weight, photo initiator, for example, a combination of 0.5% to 5% by weight benzophenone and 0.5% to 5% by weight triethanol amine.       

     In accordance with a preferred embodiment, the UV curable acrylate mixture  212  has the following composition (when electron beam is used to complete the final curing, no photoinitiators will be used in the formulation):
         40-44% Ebecryl® 294/HD 25 (an aliphatic urethane triacrylate oligomer diluted with 1,6-hexanediol diacrylate (HDDA)(1) monomer).   36-40% Ebecryl® 5129 (a hexafunctional aliphatic urethane acrylate oligomer which provides fast cure response when exposed to ultraviolet light or electron beam).   7-11% Ebecryl® 8209 (a Sn-free aliphatic urethane acrylate oligomer which provides extremely fast cure response when exposed to ultraviolet (LV) light or electron beam (EB)).   5% HDDA/TMPTA (Hexanediol diacrylate (HDDA) is a difunctional reactive diluent that is commonly used as a component of ultraviolet light (UV) and electron beam (EB) curable coatings and inks. Trimethylolpropane triacrylate (TMPTA) is a trifunctional monomer used for its low volatility and fast cure response.)   2% Photoinitiator       

     With the laminate lay-up  10  and the textured press plate  202  prepared, heat and pressure are then applied to the laminate lay-up  10  using the textured press plate  202  in a conventional manner. The heat and pressure are applied in manner sufficient to bond the layers of the laminate lay-up  10 , and releasably bond the textured press plate  202  (in particular, the bottom side  202   b  with the textured matte surface  204 ) to the top surface of the decorative laminate lay-up  10 ). Finally, the textured press plate  202  is removed from the top layer of the formed decorative laminate  100  to reveal a decorative laminate exhibiting desired matte texture characteristics. 
     In accordance with an embodiment of the present invention, and as discussed above, the textured press plate  202  is formed with a textured matte surface  204  on the bottom side  202   b  thereof (the texture of which is ultimately applied to the top surface of the decorative laminate  100 ) exhibiting matte surface characteristics leading to a fingerprint proof surface, that is, a surface not showing fingerprints and remaining clean and clear despite regular use. 
     The texture of the textured matte surface  204  applied to the textured press plate  202  is ultimately applied to the top surface of the resulting decorative laminate  100  as texture resulting in a textured top surface of the resulting decorative laminate  100 ) with a matte surface. When the textured matte surface  204  (that is, the texture) of the textured press plate  202  is applied to the decorative laminate  100  as discussed below in greater detail, the top surface of the decorative laminate  100  is imparted with a texture (that is, the decorative laminate is provided with a textured surface) the same as the texture of the textured matte surface  204  of the textured press plate  202  making the laminate  100  less susceptible to the formation of annoying and undesirable fingerprints thereon. 
     Summarizing, when such texture is applied to the top surface of the decorative laminates  100  so as to provide for a textured top surface, the resulting characteristics result in the formation of a laminate  100  not susceptible to the formation of annoying and undesirable fingerprints. 
     As the textured matte surface  204  of the textured press plate  202  is ultimately imparted to the top layer (that is, the texture of the top surface of the overlay paper layer  12  in accordance with an embodiment of the present invention) of the decorative laminate  100  formed using the textured press plate  202 , the resulting decorative laminate  100  is provided with a top surface having texture that is the same as that of the textured matte surface  204  and will exhibit desired resistance to the formation of fingerprints. 
     In accordance with one embodiment of the present invention, and as discussed above, the decorative laminate includes an exterior overlay layer sheet, or top layer  12 , a decorative sheet  14  and a core layer  16 . While a specific layering pattern is disclosed in accordance with a preferred embodiment of the present invention, the layering pattern may be varied, somewhat, without departing from the spirit of the present invention. 
     The overlay paper layer  12  is preferably a melamine-formaldehyde impregnated paper layer. The overlay paper layer  12  is preferably manufactured from a low basis weight transparent sheet impregnated with resin, for example, melamine-formaldehyde. The resin impregnated overlay paper layer  12  is subsequently dried, partially cured and finally cut into sheets. In accordance with a preferred embodiment, the overlay paper layer  12  is B-stage cured and is then coated with a UV curable epoxy acrylic or urethane acrylic film  12   f  that is also partially cured (and ultimately defines the top surface of the overlay paper layer) prior to the platen pressing process that ultimately completes the curing process. 
     The UV curable epoxy acrylic or urethane acrylic film  12   f  is generally composed of:
         60° % to 90%, by weight, urethane acrylate;   8% to 38%, by weight, reactive diluent, such as, isobornyl acrylate;   1.0% to 10%, by weight, photo initiator, for example, a combination of 0.50% to 5% by weight benzophenone and 0.5% to 5% by weight triethanol amine; and   0.5% to 5%, by weight, a thermal initiator, for example, tert-Butyl peroxybenzoate.       

     In accordance with a specific embodiment, the composition from which the UV curable epoxy acrylic or urethane acrylic film is formed is as follows:
         42% Ebecryl® 294/HD 25 (an aliphatic urethane triacrylate oligomer diluted with 1,6-hexanediol diacrylate (HDDA)(1) monomer).   38% Ebecryl® 5129 (a hexafunctional aliphatic urethane acrylate oligomer which provides fast cure response when exposed to ultraviolet light or electron beam).   9% Ebecryl® 8209 (a Sn-free aliphatic urethane acrylate oligomer which provides extremely fast cure response when exposed to ultraviolet (LV) light or electron beam (EB)).   5% HDDA/TMPTA (Hexanediol diacrylate (HDDA) is a difunctional reactive diluent that is commonly used as a component of ultraviolet light (UV) and electron beam (EB) curable coatings and inks. Trimethylolpropane triacrylate (TMPTA) is a trifunctional monomer used for its low volatility and fast cure response.)   2% Photoinitiator   2% Cerafak 127N (a Fischer Tropsch wax dispersion. Provides improved water repellence properties).   1% TBPB (tert-Butyl peroxybenzoate (TBPB) a chemical compound from the group of peresters which functions as a radical initiator in a polymerization process, that is, a thermal initiator).   1% Modaflow 9200 (an acrylic flow modifier, without silicone addition. It improves flow and leveling, substrate wetting, or maintains high gloss and substrate and inter-coat adhesion, and facilitates pigment dispersion).       

     While the paper may exhibit opaque properties prior to heating and pressing, the overlay paper layer  12  in the final fabricated laminate  100  is preferably transparent to permit viewing of the decorative sheet  14  positioned directly beneath the overlay paper layer  12 . The overlay paper used in accordance with an embodiment of the present invention is a low weight basis alpha-cellulose paper with a high porosity for resin absorption. The decorative layer  14  is a conventional pattern sheet positioned directly beneath the overlay paper layer  12 . When the decorative laminate  100  is fully heated and pressed, as will be discussed below in greater detail, the overlay paper layer  12  becomes translucent, fully exposing the decorative layer  14 . In addition, it is the top surface  12   t  of the overlay paper layer  12  which takes on the texture imparted by the press plate  202 . 
     Decorative layers  14  are chosen from a wide array of sheets. For example, the decorative layer  14  may be a solid color (for example, white) or include an aesthetically appealing pattern. As discussed above, the decorative layer  14  provides the decorative laminate with an attractive appearance. The overlay paper layer  12  and the decorative layer  14  also dictate the surface characteristics of the final decorative laminate  100 . For example, the composition of the overlay paper layer  12  and decorative layer  14  help to dictate the decorative laminate&#39;s resistance to chemical agents, heat, light, shock and abrasion. 
     Decorative sheets are commonly manufactured from high quality 80-202 grams per square meter ream weight, pigment filled, alpha cellulose paper impregnated with a water alcohol or water solution of melamine-formaldehyde resin. The resin impregnated decorative sheets are subsequently dried, partially cured, and finally cut into sheets. The pigment filled, alpha cellulose paper of the decorative sheet, may include a solid color, a decorative design, or a photo-gravure reproduction of natural materials, such as, wood, marble, leather, etc. The aesthetic characteristics of the cellulose paper are revealed as the laminate&#39;s decorative design upon completion of the decorative laminate. 
     The core layer  16  is preferably composed of a plurality of phenolic resin impregnated sheets  16   a - d , although other materials may be used without departing from the spirit of the present invention. For example, the core layer  16  includes sheets of 120-323 grams per square meter dry phenolic resin impregnated Kraft paper. The Kraft paper is impregnated throughout and bonded with a substantially cured phenolic resin which is converted to a thermoset state during the initial laminating step. 
     In accordance with an embodiment of the present invention, the decorative laminate  100  of the present invention is formed in much the same manner as conventional decorative laminates. The layers are first stacked and placed between steel plates. Release sheets may be used if necessary. The decorative laminate lay-up  10  (or stack) is then subjected to temperatures in the range of 121° C.-160° C. and pressures of about 56.24 kg/cm 2  to 112.48 kg/cm 2  for a time sufficient to consolidate the laminate and cure the resins (generally about 25 minutes to an hour). The pressure and heat force the resin in the paper sheets to flow, cure and consolidate the sheets into a unitary laminated mass referred to in the art as a decorative high pressure laminate  100  having the hydrophobic textured surface as described above which is imparted by the textured matte surface  204  of the textured press plate  202 . 
     Generally, more than one decorative laminate is formed at one time. As shown with reference to  FIG. 1 , multiple decorative laminates  100  are formed by inserting a plurality of lay-ups  10  in a stack. Conventional release sheets  50  are positioned between the core layers  16  of the lay-ups  10  to separate the various decorative laminates  100  stacked together. The textured matte surface  204  of the textured press plate  202  is oriented against the top surface (in this case the upper surface of the overlay paper layer  12 ) of the decorative laminate lay-up  10 , be it the overlay paper layer  12  (or the decorative layer where an overlay is not used). Upon pressing between textured press plates  202  in accordance with the present invention, the textured press plate  202  imparts the matte texture described above to the top surface of the first lay-up layer (in this case the upper surface of overlay paper layer  16 ). A platen press assembly  200 , as is well known in the lamination art, provides the necessary heat and/or pressure during lamination. After consolidation, the release sheets allow the individual decorative laminates to be separated. 
     While the preferred embodiments have been shown and described, it will be understood that there is no intent to limit the invention by such disclosure, but rather, is intended to cover all modifications and alternate constructions falling within the spirit and scope of the invention.