Patent Grant
7404749
The present invention relates to foam sports boards for recreational use and, more particularly, to a laminated gliding board with improved bonding characteristics.
Polyethylene foam sports boards have recently become very popular, in particular in the application as snow sleds, bodyboards, surfboard and other kinds of gliding boards or the like. However, one drawback in using a polyethylene foam sports board is that it does not have the desirable stiffness against the flex of the foam board caused by the weight of the rider and this impairs the maneuverability of the sports board. For example, in the application of snow sled, such deformation of the board will result in the foam sled submerging below the snow surface and thereby reduce the sliding speed and directional stability when carrying a rider sliding down a snow-covered slope.
Some manufacturers try to produce a polyethylene foam board with higher flexural strength by increasing the thickness or density of foam core, or by laminating a thick polymer film outside the foam board. Yet this increases the weight of foam board degrading desirable performance in its applications as a snow sled or bodyboard. It is more desirable to have a foam sled or a bodyboard having higher flexural strength without increase in weight.
Polystyrene foam core has been used to produce foam sports boards due to its lightweight and rigid properties. However, there are some drawbacks associated with a polystyrene foam core. For example, in the case of snow sled application, a polystyrene foam core does not provide the same degree of comfort in terms of cushioning and shock absorption properties when compared with a polyethylene foam core. It may be desirable to develop a sports board with a rigid polystyrene foam core and desirable resilient and shock absorption properties of polyethylene foam in the top and front portion of the board.
A traditional foam sports board such as snow sled or a bodyboard in general includes a polyethylene foam skin with some kinds of graphic or logo printed thereon for decoration purpose. One conventional printing technique is by silkscreen printing compatible ink on the polyethylene foam skin. The pattern is printed on the outer surface of the foam board and thus is exposed to wear and tear by the effect of mechanical rubbing, water, heat and sunlight in use. Therefore, the pattern will fade or worn off quickly. It is obviously desirable to have a protective layer covering the entire foam skin to prevent the graphic printed on the foam skin to be worn out easily and yet still allow the pattern to be visible outside the protective layer.
Polyethylene foam sports boards with graphic imprinted plastic film outer layer are known in the prior art. In general, such boards are composed of a number of polyethylene foam and polyethylene film layers that are laminated together by heating the film and foam layers and then immediately passing them through a pair of nip rollers. Schneider of U.S. Pat. No. 5,211,593 has disclosed such a laminating process. Schneider discloses that graphics are first imprinted as ink on the inner surface of the outer plastic film that is transparent. Then the imprinted outer film is adhesively bonded to an inner plastic film. The surface of foam plank is heated to a temperature range of 180° F. to 220° F. and the resulting dual-layered film is pressed onto the heated surface of the foam plank by a pair of nip rollers. Because the standard foam core does not have a perfectly flat or planar surface, bonding between the film and foam core is limited to the apexes of the cells on the surface of the foam core. Thus the point of contact is not uniform between the film and foam, but instead the film contacts the points of the outer surface of the core that protrude from the irregular cellular surface of the foam core.
Another conventional process of lamination is to apply heat to the film layer with a heated nip roller, which, in most cases, contains an engraved pattern of convex and concave area for better heat transfer. This type of roller with engraved convex and concave pattern is commonly known as embossing roller. Bonding of polyethylene film to polyethylene foam substrate is caused by the localized collapse and bonding of the foam cells on the surface of film at the concave depressed area where the foam substrate is under the combined influence of heat and pressure of the heated embossing roller. Typically micro-cellular high-density foam sheets are used to improve the adhesion between the film and foam core. The micro-cellular foam sheet contains smaller peaks and valleys, with the peaks closer together. The surface area of contact between the sheet and foam is thereby increased. However, this kind of structure is still prone to delamination by mechanical contact, effect of water, moisture and forces when in use simply because the interface between the film and foam layers contain unbonded area. The resulting laminate of the polyethylene foam and polyethylene film is then often heat laminated onto a standard foam core. The polyethylene film may comprise an outer film layer and an inner film layer having a graphic image imprinted on one surface interposed between the outer film layer and the inner film layer.
One prior art is found in U.S. Pat. No. 4,850,913, which discloses a manufacturing process of heat laminating a polyethylene film layer to a thin sheet of polyethylene foam which is then further heat bonded to the foam core of the board. It is accordingly desirable to provide a laminating system to make a foam sports board with graphic imprinted outer film layer and the film layer is adhered to the foam core with improved bonding characteristics.
Patent U.S. Pat. No. 5,211,593 shows a prior art technique to laminate a dual-layered graphic film to a foam substrate. The laminating process involves two steps. Step one is to adhesively bond the graphic imprinted outer film with the inner film using conventional glue or adhesive. Step two is heat laminating the resulting dual-layered graphic film to a foam substrate. It would be advantageous to provide an improved laminating system that can laminate a graphic imprinted film directly to a foam substrate in one single process with improved bonding characteristics.
While it is known in the prior art that a thin layer of thermal plastic polyethylene film between a polyethylene foam sheet and a polyethylene film can be used to promote lamination, such thin layer of film is generally an unmodified low-density polyethylene with limited efficacy. Accordingly, there is need for adhesively bonded sports boards with improved bonding between layers of different polymeric material having different surface contouring and cellular structure.
The present invention provides the solution to the above-mentioned problem by introducing an adhesive resin film layer between a plastic film and a foam substrate in a multi-layered sports board. The sports board comprises a foam core having a thickness generally in the range of 0.2 inch to 4 inches. Suitable foam board may include any plastic foam known in the art such as expanded polyethylene (EPE) foam, expanded polypropylene (EPP) foam, expanded polystyrene (EPS) foam, expanded ethylene vinyl acetate (EVA) foam, polyisocyanurate foam, polyurethane foam and expanded polyolefin foam. Polyolefin foams may further include homopolymers and copolymers of ethylene, propylene, styrene, and ethylene vinyl acetate as well as blends of such homopolymers and copolymers. The foam core can be fabricated from an extruded foam board and molded bead foam in non cross-linked type or cross-linked type. The present invention is particularly useful with extruded polyethylene foam. Such foam is lightweight and resilient with relatively low manufacturing cost. The foam core may also be a composite core made by laminating two or more layers of foam sheets.
An expanse of skin is heat bonded to the foam core at the top and bottom surfaces. The skin comprises laminate of plastic film and polyolefin foam sheet. The skin may include a layer of plastic film material, such as extruded polyethylene, a polyolefin foam sheet, and an adhesive resin film layer disposed underside for heat bonding the plastic film with the polyolefin foam. The bottom surface of the polyolefin foam is heat bonded to the top surface and edge surface of the foam core. The thickness of the plastic film layer is generally in the range of 0.01 mm to 0.15 mm. The plastic film may be transparent and include graphic images formed on the inner surface facing the adhesive resin film layer. The graphic images can be visible outside the plastic film. The plastic film layer preferably has the same polymer composition as the foam sheet. With the intermediate layer of adhesive resin, the plastic film need not be of the same polymer composition as the foam sheet. The plastic film may be a monolayer structure or a multilayer structure. A sheet co-extrusion process may be used to make the multilayer laminate of plastic film and adhesive resin film. Preferred plastic film is a polyolefin film and polyethylene film is typically used for the present application. Polyethylene film is a common plastic film and graphic images can be printed on it by conventional printing technique well known in the art.
The polyolefin foam sheet may also include graphic images formed on the outer surface of the polyolefin foam sheet facing the adhesive resin film layer. The polyolefin foam sheet has a thickness in the range of 2 to 8 mm and a density in the range of 4 to 10 lb/ft3. Polyolefin foams may include homopolymers and copolymers of ethylene, propylene, styrene, and ethylene vinyl acetate as well as blends of such homopolymers and copolymers. The foam sheet can be fabricated by extrusion or beaded foam molding in noncross-linked type or cross-linked type. The polyolefin foam sheet may also be a monolayer structure or a multilayer structure. Both polyethylene foam and polypropylene foam are suitable, but cross-linked polyethylene is particularly useful for the present invention. Such foam sheet has very fine cell structure and smooth skin surface that is desirable for printing graphic images.
The adhesive resin film layer may be selected from a group consisting of anhydride-modified ethylene/vinyl acetate, ethylene/propylene copolymer, homogeneous ethylene/alpha-olefin copolymer, anhydride-modified polyolefin, ethylene/acrylic acid copolymer, vinyl acetate/acrylic copolymer, ethylene/methylacrylate copolymer, ethylene/vinyl acetate copolymer, and blends of the foregoing, may be employed. Grafting with an anhydride polymer may modify these adhesive resin polymers and improve its adhesive bonding characteristics. These adhesive resins facilitate the bonding of various plastic film and foam substrate. In particular, these adhesive resin provide superior adhesive bonding in bonding a polyolefin foam layer to a polyolefin film layer or another polyolefin foam layer; whereby the two layers may have like or different polymer composition. Furthermore, these adhesive resins are capable of bonding the polymer material of the ink resin generally applied on polyolefin film for graphic printing. Therefore the adhesive resin are particularly useful in bonding a polyolefin foam layer to a graphic imprinted polyolefin film; and alternatively bonding a graphic imprinted polyolefin foam layer to a polyolefin film, the ink coated surface bonded to the adhesive resin layer. 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 that diffuses quickly and forms a thin coating film layer with intimate adhesion bonding over the entire interface.
In another embodiment, the plastic film comprises an outer layer of transparent plastic film and an inner layer of a second plastic film. The outer layer of transparent plastic film may include graphic images formed on the inner surface facing the adhesive resin film layer. The graphic images can be visible outside the plastic film.
With reference to
In the preferred embodiment, adhesive layer 20 is an anhydride-modified ethylene vinyl acetate. Layer 20 has a thickness of between 0.01 and 0.20 mm, and preferably a thickness of 0.07 mm. Layer 20 has a density in the range of 0.88 to 0.98 g/cm3, and preferably a density of 0.95 g/cm3. It is contemplated that alternative adhesive resins may comprise ethylene/propylene copolymer, homogeneous ethylene/alpha-olefin copolymer, anhydride-modified polyolefin, ethylene/acrylic acid copolymer, vinyl acetate/acrylic copolymer, ethylene/methylacrylate copolymer, ethylene/vinyl acetate copolymer, and blends of the foregoing, may be employed. These adhesive resin polymers may be modified by grafting with an anhydride polymer.
Such adhesive resin layer is selected so that its presence in the board provides not only the bonding between layers but also a smoother surface for printing a higher resolution graphic image to provide a refined sports board. See
In
In
Layer 30 is a closed-cell polyolefin foam sheet, preferable polypropylene foam sheet. Layer 30 has a thickness of between 1 and 5 mm, and preferably a thickness of 3 mm. Layer 30 has a density in the range of 4 to 10 lb/ft3, and preferably a density of 6 lb/ft3. Polypropylene foam has higher rigidity than polyethylene foam at similar density and provide a rigid shell structure to reinforce the foam board in this embodiment. An adhesive resin film layer (not shown in the drawing) is required to facilitate bonding between the polypropylene foam sheet 30 and the polyethylene foam core 12.
Between the polyethylene foam core 12 and the polyethylene sheet 38 is a polyethylene foam sheet 31, which has a thickness of between 1 and 5 mm, and preferably a thickness of 3 mm and a density in the range of 4 to 10 lb/ft3, and preferably a density of 6 lb/ft3.
In
On the upper side of the bottom polyethylene sheet 18 are a polyethylene film 41 and adhesive resin film 42. Polyethylene film 41 has the same thickness and density as PE film 16.
In
In this embodiment, layer 50 is an expanded polystyrene (EPS) foam core. EPS foam has desirable properties of lightweight and rigid while polyethylene foam sheet provides a soft and resilient foam skin for comfort and shock absorbing in use. Foam core 50 has a thickness of between 0.5 and 2.5 inches, and preferably a thickness of 1 inch. Foam core 50 has a density in the range of 1.0 to 3 lb/ft3, and preferably a density of 1.5 lb/ft3. EPS foam core 50 is bonded to the top layers 16/20/23 and bottom layers 31/38 through respective adhesive resin films not shown in the drawing.
In
Here, an appropriate graphic may be printed on either the PE film 16 or the PE foam sheet 70.
A graphic image may be printed on either the PE film 16 or the PE foam sheet 80.
The manufacturing steps of making the third embodiment are described here to provide an illustrative example. Sports board 103 is formed in a series of steps. First, polyethylene film layer 16 is imprinted with the desired graphics using a conventional imprinting process. With reference to
The top laminate of layers 16/20/30 are then sized at a cutting station 132 so that its outer edge will extend over the peripheral edge of core 12 enough so that it can be wrapped over, and heat laminated to the top surface and edge surface of the polyethylene foam core 12. On the other hand, as shown in
Sized at cutting station 135, the bottom laminate is then heat laminated to the bottom surface of core 12 of the top laminate sheet 16/20/30. This heat laminating process is illustrated in
Alternatively, following the printing of the first polyethylene film 16, a second polyethylene film 40 may be bonded to the graphics imprinted in the first polyethylene film 16 by using conventional glue or adhesive so that the graphic is covered. The resulting dual-layered graphic polyethylene film is similarly laminated to the polypropylene foam sheet 30 by extruding an adhesive resin film layer 20 in between.
A third alternative way to provide a graphic image on the skin of sports board is to apply ink to the outer surface of the polypropylene foam sheet 30 by any conventional printing technique known in the art. The ink applied to polypropylene foam sheet 30 surface must be compatible to polyolefin. The graphic imprinted foam sheet is then laminated to the polyethylene film 16 by extruding an adhesive resin film layer 20 in between. The polyethylene film 16 acts as a protective film to protect the graphic image printed on the polypropylene foam sheet 30 from wear and tear.
A fourth alternative way to provide a graphic image on the skin of sports board is to apply a thin coating of adhesive resin to the outer surface of the polypropylene foam sheet 30 by extruding a thin film layer of adhesive resin onto the graphic image receiving surface of the polypropylene foam sheet. The coating process is also illustrated in
Therefore, while the presently preferred forms of the sports board and its derivative have been shown and described, and several modifications thereof 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.
For example, the sports board 102 of the second embodiment may have its bottom laminate replaced by the bottom laminate of the board 103 of the third embodiment. The sports board 105 of the fifth embodiment may have its bottom laminate replaced by the bottom laminate of the board 104 of the fourth embodiment. The sports board 106 of the sixth embodiment may have the bottom laminate of the board 104 of the fourth embodiment; and so on.
This application is a continuation in part of copending Wah Kan Cheung's application for Multi-layered sports board Ser. No. 10/958,913 filed Oct. 5, 2004. This application also claims priority from provisional application U.S. application No. 60/789,614 filed Apr. 5th, 2006.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4850913 | Szabad, Jr. | Jul 1989 | A |
| 5647784 | Moran | Jul 1997 | A |
| 6955576 | Yeh | Oct 2005 | B2 |
| 7029349 | Lin | Apr 2006 | B2 |
| 7150666 | Cheung | Dec 2006 | B2 |
| Number | Date | Country | |
|---|---|---|---|
| 20070264891 A1 | Nov 2007 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60789614 | Apr 2006 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10958913 | Oct 2004 | US |
| Child | 11431453 | US |
