Abstract:
Sports board ( 15 ) comprising an elongated expanded closed-cell polyolefin foam core ( 16 ) having a core thickness and opposed surfaces ( 18, 19 ), a first polyolefin sheet layer ( 23 ) having a thickness less than the core thickness and having an inner surface ( 25 ) and an outer surface ( 24 ), an intermediate metallocene-based polyolefin layer ( 20 ) having an inner surface ( 22 ) and an outer surface ( 21 ) and a thickness less than the core thickness, the intermediate layer bonded on its inner surface to the core and bonded on its outer surface to the inner surface of the first layer. The intermediate layer may comprise an ethylene-alpha olefin copolymer and may comprise a copolymer of ethylene and octene.

Description:
TECHNICAL FIELD 
   The present invention relates to foam sports boards for recreational use and, more particularly, to a laminated board with improved bonding characteristics. 
   BACKGROUND ART 
   Body boards for riding waves and other recreational sports boards made of foam or other floatation material are known in the prior art. In general, such sports boards are composed of a number of layers thermally or adhesively bonded together. The boards generally have a closed-cell foam core covered by one or more layers adhesively or thermally bonded to the core. 
   A number of laminated boards are known in the prior art and a number of methods of laminating or bonding the various layers of the board together are known. Examples of such boards and methods of laminating them are shown and disclosed in U.S. Pat. Nos. 5,211,593, 5,658,179, 5,503,921, 4,850,913 and 5,275,860. In bonding the layers together it is desirable to provide a bond between two layers which is stronger than the strength of the layers themselves. 
   Boards and methods of manufacturing them known in the prior art have a number of deficiencies. It is also known in the prior art that an adhesive may be used to bond the various layers together. This method of bonding has a number of drawbacks, including the adverse affect of solvent vapors released into the air during the manufacturing process and the added weight to the board of an adhesive joint. In addition, many conventional adhesives eventually deteriorate from the adverse affect of salt water on the adhesive over time, causing delamination. 
   It is also known that heat may be used to bond the various layers together. However, boards known in the prior art generally require that the thermal laminating process by which they are made occur at very high and exact temperatures in order to properly bond the layers. The requirement for a high and exact bonding temperature necessitates a more elaborate laminating process and can cause undesirable shrinkage of the layers. This type of bonding is especially difficult when the layers are of different materials having different characteristics. 
   Accordingly, there is a need for a thermally laminated foam board with improved bonding between layers of different polymeric materials having different thermal characteristics. 
   DISCLOSURE OF THE INVENTION 
   With parenthetical reference to the corresponding parts, portions or surfaces of the disclosed embodiment, merely for the purposes of illustration and not by way of limitation, the present invention provides an improved sports board ( 15 ) comprising an elongated expanded closed-cell polyolefin foam core ( 16 ) having a core thickness and opposed surfaces ( 18 ,  19 ), a first polyolefin sheet layer ( 23 ) having a thickness less than the core thickness and having an inner surface ( 25 ) and an outer surface ( 24 ), an intermediate metallocene-based polyolefin layer ( 20 ) having an inner surface ( 22 ) and an outer surface ( 21 ) and a thickness less than the core thickness, the intermediate layer bonded on its inner surface to the core and bonded on its outer surface to the inner surface of the first layer. The intermediate layer may comprise an ethylene-alpha olefin copolymer and may comprise a copolymer of ethylene and octene. The core may comprise polyethylene, polypropylene, or both polyethylene and polypropylene. The first layer may comprise polyethylene film, polypropylene film, both polyethylene and polypropylene, or polyethylene film and ethylene vinyl acetate. The intermediate layer may be thermally bonded to the core and the first layer. The board may further comprise a graphically imprinted layer ( 26 ) bonded to the outer surface of the first layer. 
   Accordingly, the general object of the present invention is to provide an improved sports board with foam tear strength bonds. 
   Another object is to provide an improved sports board in which different polyolefin materials may be used in the layers without a derogation in bonding strength. 
   Another object is to provide an improved sports board which permits the layers to be laminated together at lower and less exact temperature ranges. 
   Another object is to provide an improved sports board which may be manufactured using conventional means with improved bond strength and flexibility along the bond line between the laminates. 
   Another object is to provide an improved sports board which has a smooth surface. 
   Another object is to provide an improved sports board which is manufacturable without deleterious foam shrinkage. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of a first embodiment of the sports board. 
       FIG. 2  is a partial vertical sectional view of the sports board shown in  FIG. 1 , taken generally on line  2 — 2  of  FIG. 1 . 
       FIG. 3  is an exploded view of the sports board shown in  FIG. 1 . 
       FIG. 4  is a perspective view of a second embodiment of the sports board. 
       FIG. 5  is a vertical sectional view, of the sports board shown in  FIG. 4 , taken generally on line  5 — 5  of  FIG. 4 . 
       FIG. 6  is an exploded view of the sports board shown in  FIG. 4 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   At the outset, it should be clearly understood that like reference numerals are intended to identify the same structural elements, portions or surfaces, consistently throughout the several drawing figures, as such elements, portions or surfaces may be further described or explained by the entire written specification, of which this detailed description is an integral part. Unless otherwise indicated, the drawings are intended to be read (e.g., cross-hatching, arrangement of parts, proportion, degree, etc.) together with the specification, and are to be considered a portion of the entire written description of this invention. As used in the following description, the terms “horizontal”, “vertical”, “left”, “right”, “up” and “down”, as well as adjectival and adverbial derivatives thereof (e.g., “horizontally”, “rightwardly”, “upwardly”, etc.), simply refer to the orientation of the illustrated structure as the particular drawing figure faces the reader. Similarly, the terms “inwardly” and “outwardly” generally refer to the orientation of a surface relative to its axis of elongation, or axis of rotation, as appropriate. 
   Referring now to the drawings and, more particularly, to  FIG. 1  thereof, this invention provides an improved sports board, the presently preferred embodiment of which is generally indicated at  15 . As shown in  FIGS. 1–3 , sports board  15  is comprised of six layers laminated together. 
   Top layer  26  is graphically imprinted polyethylene film. The graphics on layer  26  are imprinted using any of several conventional processes for printing on polyethylene. An example of such a process is corona printing, in which an electrical discharge temporarily alters the surface molecules of the polyethylene film, allowing inks to adhere to the film. Layer  26  has a thickness of between 0.5 and 4 mils, and preferably a thickness of 1 mil. Layer  26  has a density in the range of 0.942 to 0.962 g/cm 3 , and preferably a density of 0.952 g/cm 3 . Layer  26  is heat laminated to the outer surface  24  of layer  23 . 
   Layer  23  is a blend of low density polyethylene and ethylene vinyl acetate. Layer  23  comprises about 1 to 25% by weight ethylene vinyl acetate, with the remaining portion being made up of low density polyethylene. Layer  23  has a thickness of between 10 and 60 mils, and preferably a thickness of 20 mils. Layer  23  has a density of between 0.912 and 0.932 g/cm 3 , and preferably a density of 0.922 g/cm 3 . The inner surface  25  of layer  23  is laminated to the outer surface  21  of layer  20 . 
   Layer  20  is metallocene-catalyzed polyolefin. In the preferred embodiment, layer  20  is an ethylene-olefin copolymer of ethylene and octene produced in a conventional solution polymerization process using a metallocene catalyst. Metallocene is used as an olefin polymerization catalyst to form a metallocene-based copolymer. Layer  20  has a thickness between 0.5 and 12 mils, and preferably a thickness of 1 mil. Layer  20  has a preferred density of 0.882 g/cm 3 . Inner surface  22  of layer  20  is laminated to outer surface  18  of layer  16 . 
   Layer  16  is closed-cell polyethylene foam, and acts as the core of board  15 . Core  16  may be beaded type, extruded type or cross-linked polyethylene foam. Core  16  has a thickness of between ⅛ and 2 inches, and preferably a thickness of 1 inch. Core  16  has a density of between 1.6 and 4 lb/ft 3 , and preferably a density of 2.2 lb/ft 3 . It is contemplated that foam core  16  may be formed from two ½ inch layers laminated together to form a 1 inch thick foam core. The outer surface  19  of layer  16  is in turn laminated to the inner surface  29  of layer  28 . 
   Layer  28  is of the same structure and composition as layer  20 . The outer surface  30  of layer  28  is laminated to the inner surface  32  of layer  31 . This intermediate layer provides a superior bond between polyethylene foam and polyethylene film. 
   Layer  31  is polyethylene film. Layer  31  has a thickness between 8 to 60 mils, and preferably a thickness of 30 mils. Layer  31  has a density of between 0.942 and 0.962 g/cm 3 , and preferably a density of 0.952 g/cm 3 . 
   Both layers  31  and  26  are high density polyethylene film. The bottom surface  33  of layer  31  provides the bottom surface for board  15 . Top surface  17  of layer  26  provides the top surface of board  15 . 
   Sports board  15  is formed in a series of steps. First, layers  28  and  31  are co-extruded to form a bottom laminated skin, using a conventional co-extrusion process, and are cut to the desired length. The co-extruded layers  31  and  28  are then heat laminated to the bottom surface  19  of core  16  using a conventional heat laminating process with rollers, forming a laminated sheet of layers  16 ,  28  and  31 . 
   Layer  26  is imprinted with the desired graphics using a conventional imprinting procedure. Layer  26  is then fed from a roll and heat laminated with rollers to the top surface  24  of layer  23  as layers  23  and  20  are co-extruded, using a conventional co-extrusion process, thereby forming a laminated sheet of layers  26 ,  23  and  20 . The sheet of laminated layers  26 ,  23  and  20  is then heat laminated to the top surface  18  of core  16 . The resulting laminated board, consisting of layers  26 ,  23 ,  20 ,  16 ,  28  and  31 , is then die cut to a desired shape. The side edges of the board are then shaped to the desired configuration and slope. Finally, a polyethylene foam strip  50  is heat laminated to cover the shaped side edges of laminated layers  26 ,  23 ,  20 ,  16 ,  28  and  31  of snow sled  15  and excess material is cut free. 
     FIGS. 4–6  show an alternate embodiment  40 . In this embodiment, board  40  has five laminated layers rather than six. Intermediate layers  42  and  44  are of the same structure and composition as layers  20  and  28  in the first embodiment  15 . Intermediate layer  42  facilitates a strong bond between polypropylene foam core  43  and polyethylene foam layer  41 . Intermediate layer  44  facilitates a strong bond between polypropylene foam core  43  and polyethylene film layer  45 . 
   Layer  41  is closed-cell polyethylene foam having a thickness in the range of 2 to 8 millimeters, and preferably 4.5 mm. Layer  41  has a density in the range 4 to 10 lb/ft 3 , and preferably a density of 7 lb/ft 3 . 
   Layer  42  is laminated on its outer surface to the inner surface of layer  41  and is laminated on its inner surface to the upper surface of core  43 . 
   Core  43  is polypropylene foam having a thickness between 1 and 2.5 inches, and preferably a thickness of 2 inches. Polypropylene foam core  43  has a density of between 1.5 and 3 lb/ft 3 , and preferably a density of 1.9 lb/ft 3 . 
   Intermediate layer  44  is laminated on its inner surface to the bottom surface of core  43  and on its outer surface to the inner surface of layer  45 . 
   Layer  45  is solid polyethylene film having a thickness between 12 and 32 mils, and a preferred thickness of 20 mils. Layer  45  has a density of between 0.942 and 0.962 g/cm 3 , and a preferred density of 0.952 g/cm 3 . 
   Body board  40  is formed in a series of steps. First, layer  43  is die cut to desired configuration. The front or nose of die-cut core  43  is then ground to form rocker  54 . Layers  44  and  45  are then co-extruded to form a bottom skin, using a conventional co-extrusion process, and are cut to the desired length. The co-extruded layers  44  and  45  are then heat laminated to the bottom surface of pre-shaped core  43  using a conventional heat laminating process with rollers. Laminated layers  43 ,  44  and  45  are then shaped to form the desired nose  51 , tail  52 , and side rail  53  configurations. 
   Layer  42  is then extruded conventionally and heat laminated with rollers to layer  41  to produce a top laminate. The top laminate of layers  41  and  42  are then cut to the desired size. This top laminate is sized so that its outer edge will extend over the peripheral edge of core  43  enough so that it can be wrapped over, and heat laminated to, the nose  51  side edge, the tail  52  side edge and the upper portion of side rails  53  of laminated layers  44 ,  45  and  43 . The top laminate of layers  41  and  42  are then heat laminated to the top surface of core  43 . The outer portions of the top laminate are then wrapped over and laminated to the side edges of nose  51 , tail  52  and the upper side surfaces of side rails  53 . A polyethylene foam strip  55  is then heat laminated to cover the lower side surfaces of side rails  53  of board  40 . Excess is then trimmed as necessary, completing the covering of the side surfaces of board  40 . 
   Intermediate layers  20 ,  28 ,  42 , and  44  facilitate the bonding of different polyolefin materials, including as discussed above polyethylene foam and film, polypropylene foam and polyethylene foam, and polypropylene foam and polyethylene film, using conventional thermal laminating processes. It is believed that such superior bonding is the result of the intermediate layers having a lower melt temperature than other materials, low shear viscosity, good wetting characteristics, and a linear molecular structure that diffuses quickly and forms a better physical bond with the molecules in the adjacent layers when cooled. Thus, intermediate layers  20 ,  28 ,  42 , and  44  provide a superior heat laminated bond between the outer layers  23 ,  31  and  41 ,  45  and inner cores  16  and  43 , respectively. 
   The present invention contemplates that many changes and modifications may be made. Therefore, while the presently preferred form of the sports board and an alternate embodiment has been shown and described, and certain modifications discussed, persons skilled in this art will readily appreciate that various additional changes and modifications may be made without departing from the spirit of the invention, as defined and differentiated by the following claims.