The invention relates to a system and method of making edge sealed composite boards. The invention is particularly suited for composite boards requiring a high strength to weight ratio such as, but not limited to a shuttering board. BACKGROUND TO THE INVENTION

The following discussion of the background to the invention is intended to facilitate an understanding of the present invention. However, it should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was published, known or part of the common general knowledge in any jurisdiction as at the priority date of the application.

Outdoor constructions require material that are suited to withstand the effects of the weather such as rain and other environmental factors. Such material must also be durable in situations where the outdoor construction is anticipated to be a permanent construction.

Some of the current materials used in outdoor construction are not environmentally friendly. Alternative materials break easily or are expensive to manufacture.

Shuttering boards are commonly used at construction sites to maintain poured concrete in a desired shape. It is particularly used in maintaining poured concrete that, when set, forms a vertical pylon or the like. This process of maintaining the poured concrete in predefined shapes is also known as formwork.

There are essentially three types of shuttering boards that can be used:

Plywood shuttering boards. Such shuttering boards are cheap, but are subject to degradation with each use. As a result, plywood shuttering boards are often re-used somewhere between 8 to 10 times before they need to be changed. Changing such shuttering boards consumes additional labour and material costs. Furthermore, the used plywood shuttering boards must be disposed of in some manner, often by incineration, which creates further environmental problems.

Steel shuttering boards. Being made of a more durable material, steel shuttering boards may be re-used up to 100 times before needing to be changed. However, this durability is also a disadvantage as such shuttering boards are difficult to handle and shape at the construction site.

Plastic shuttering boards. Plastic shuttering boards have been introduced to the market with limited success. The main reason for this lack of success has been their low strength to weight ratio. While some attempts to improve the strength to weight ratio of plastic shuttering boards have been technically successful, it has been done at such a high production cost that the commercial viability of such boards has been significantly compromised.

It is therefore an object of the present invention to produce a composite board which overcomes, or at least ameliorates in part, one or more of the aforementioned problems.

SUMMARY OF THE INVENTION

Throughout this document, unless otherwise indicated to the contrary, the terms "comprising", "consisting of", and the like, are to be construed as non-exhaustive, or in other words, as meaning "including, but not limited to".

In accordance with a first aspect of the invention there is a composite board comprising a central core layer sandwiched between a first and a third layer , the first and third layer made of material consisting of one material from a first hard plastic material set, the central core layer consisting of a wood material; wherein the composite board further comprises at least one panel made of a material from a second hard plastic material set, the panel thermally bonded or jointed to at least one side of the composite board to form an edge sealed joint with the first layer and another edge sealed joint with the third layer. Preferably, another edge sealed joint bond is formed between the panel and the central core layer.

Preferably, the joint between the panel and the at least one side of the composite board is bonded using polymer adhesive.

Preferably the polymer adhesive is one of the following: polyolefin, polyamides, and polyesters.

Preferably the temperature of the thermal bonding is set between 100 to 200 degree Celsius. More preferably the temperature is set between 120 to 180 degree Celsius.

Preferably, the first hard plastic material set is the same as the second hard plastic material sets. This allows ease of manufacturing as the number of materials needed for manufacturing to be significantly reduced.

Preferably, the first and second hard plastic material sets are thermoplastic material.

Preferably, the composite board comprises a fourth and fifth layers bonded to the first and third layer respectively, the fourth and fifth layers made of the first hard plastic material. Advantageously, the composite board comprises a sixth and seventh layers bonded to the fourth and fifth layers respectively, the sixth and seventh layers made of the first hard plastic material. Advantageously, there are four panels bonded to the four sides of the composite board such that the four panels and the first and third layer fully cover the central core layer, making the central core layer impermeable to water and moisture.

The first hard plastic material set preferably, includes polyethylene; polypropylene; polyvinyl chlorate; acrylonitrile-butadiene-styrene.

The central core layer preferably includes plywood, medium density fibreboard, particle board or plank.

It is preferred that the composite board has a thickness between 4 and 100mm with the ideal thickness of the composite board being between 10 and 18mm. Boards in the ranae 10 to 8mm Drovide the best overall oerformance and are relatively easv The proportions between the differing layers may vary, but ideally the size of the first and third layers do not exceed 3mm in thickness. It is also preferred that the thickness of the second layer, as a proportion of the total thickness of the composite board, remains at substantially 80%.

Thermal bonding may be used to sequentially bind each layer to its next layer. It is further preferred that any such bond be waterproof.

In accordance with a second aspect of the present invention there is a method of producing a composite board comprising the steps of: bonding a first layer made of a material from a hard plastic material set to a central core layer made of a wood material; bonding the second layer to a third layer made of a material from a hard plastic material set; bonding at least one panel, the panel made from a material from a second hard plastic material set to one side of the composite board to form an edge sealed joint with the first layer and an edge sealed joint with the third layer.; and laminating the bonded board.

Preferably, the step of bonding at least one panel to the one side of the composite board to form an edge sealed joint comprises:- (a) applying polymer adhesives between the panel and the one side of the composite board; (b) heating the polymer adhesives to a temperature range of 100 to 200 degree Celsius; (c) applying a pressure of 1 to 50 MPa; and d. maintaining at the pressure in (c.) until the composite board cools down to room temperature.

Preferably, the polymer adhesive is one of the following: polyolefin, polyamides, and polyesters. In such instance the temperature range is preferably between 120 to 180 degree Celsius and the pressure range is between 5 to 30 MPa.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example only, with reference to the accomDanvina drawinas. in which: Fig. 1 is a plan view of a composite board according to an embodiment of the present invention.

PREFERRED EMBODIMENTS OF THE INVENTION

In accordance with a first embodiment of the invention there is a composite board 10, the plan view of which is shown in Fig. 1. The composite board 10 is typically a rectangular shaped board with 6 sides and having three dimensions: length, width and thickness. The thickness of the composite board 10 is between 10 mm to 18 mm. The composite board 10 comprises three layers- i.e. a first layer 12, a second or central core layer 16 and a third layer 14.

The first layer 12 and the third layer 14 are made of a material from a first hard plastic material set, for example polyethylene (solid state), to a thickness of preferably 1.5mm. Each of the first layer 12 and the third layer 14 comprises two edges 15a that run along the length of the layer 12, 14 and two edges 15b that run along the width of the layer, 12, 14.

The second layer 16 consists of a wood material such as plywood. The second layer 16 has a thickness of preferably 14.4mm.

The composite board 10 further comprises at least one panel 18 made of a material from a second hard plastic material set. In Fig. 1 , two panels 18 are shown. The material of panel 18 may be the same as the material of the first and/or third layer, i.e. polyethylene. Each panel 18 preferably has a thickness of 1.5mm. Each panel 18 has two edges that run along the length of the panel 18 (not shown) and two edges 18a that run along the width of the panel 18. Each panel 18 is adapted to be thermally bonded by a bonding agent such as polymer adhesives to at least one side 20 of the composite board at two edge portions (18a, 18b) corresponding to the edge portions of the first and third layers (15a, 15b) to form edge sealed joints 22. Preferably, the central portion 18c of the panel 18 is also thermally bonded to the central core layer 16 by a bonding agent such as polymer adhesives. The length and width of the composite board may be 2440mm and 1220mm respectively.

The composite board 10 will next be described in the context of its manufacture, with particular emphasis on the creation of edge sealed joints.

Each layer of the three layers 12, 14 and 16 is thermally bonded to the layer below by a bonding agent such as adhesives to provide additional strength to the composite board 10 and to make the resulting composite board 10 waterproof. The adhesives are applied evenly on each layer.

In this manner, the first layer 12 is thermally bonded by adhesive to the second layer 16, which is in turn thermally bonded by adhesive to the third layer 14. An edge portion 15a of the first layer 12 and an edge portion 15b of the third layer 14 is thermally bonded or jointed to at least an edge portion 18a of at least one panel and another edge portion 18b respectively to form at least one thermoplastic edge sealed joint 22. In Fig. 1 two of such panels 18 are shown.

Each thermoplastic edge sealed joint 22 may be formed by applying adhesives between the panel 18 and the surface of the composite board 10 which the panel is to be bonded to.

The adhesive may be polymer adhesive in the form of pellets or film, polyolefin , polyamides, or polyesters etc. Care must be taken to ensure that the adhesives are applied at the desired range of temperature and pressure in order for a chemical reaction to take place between the at least one panel 18 and the layers 12, 14, 16 at regions 18a, 18b, 18c so as to achieve the desired waterproof property. Assuming that the adhesive is one of the above mentioned, to ensure that the chemical reaction takes place, the range of temperature is:-

1. 100 to 200 degrees Celsius (ideally 120 degree Celsius to 180 degree celsius),

2. The pressure applied to the panel 18 and surface of the composite board 10 The process for bonding each panel 18 to the surface of the composite board 10 is as follows:- a. Heat the substrate or bonding surfaces to the desired temperature range;

b. Apply the polymer adhesive in the form of pellets or film and then heat the polymer adhesive and all bonding surfaces and substrates to temperature range of 120 to 180 degrees Celsius,

c. Compress the bonded layers through plates or rollers 5 to 30MPa.

d. Ensure that the polymer adhesive is bonded to both plastic layers 12, 14 and bonded to the wood layer 16.

e. Maintain desired pressure until the adhesive cools down.

In this way, the panel 18 is bonded and "welded" to the surface of the composite board 10. It is to be appreciated that the pressure applied to ensure bonding is at a much higher pressure that for example hot melt adhesive such as hot melt glue.

The applicant, through tests, has discovered that the edge seal bond produced will deteriorate if conventional hot melt glue is used as the first layer 12, the third layer 14 and the wood layer 16 may expand. The above method using polymer adhesive for bonding achieves relatively stronger edge bond seal and bonding grip as compared to conventional known techniques, thereby preventing or reducing deterioration of the thermoplastic edge sealed joints.

The whole composite board 10 is then further applied under heavy loads for a certain duration until the adhesives are set. The whole composite board 10 is then laminated using conventional laminating techniques.

The composite board 10 as manufactured prevents water or moisture from penetrating into the second layer 16, thereby enhancing the lifespan of the composite board 10.

Although the composite board 10 has been described to comprise of two panels 18, up to four panels 18 may be bonded to the four sides 20 of the composite board 10. The four panels 18 and the first and third layers 12, 14 form a full cover of the central core layer 16.

The applicant has found that the re-use cycle of composite boards made in accordance with the invention, and used as shuttering boards, ranges from 200 to 500 uses. Furthermore, such composite shuttering boards are recyclable and are relatively cheaper to manufacture. In addition, the resulting composite boards have good machining properties, is resistant to outdoor conditions, easy to clean surface, lightweight and good mechanical strength.

The inherent strength of the composite boards 10 also makes them suitable for other uses such as non-load bearing walls, scaffolding boards, floor decking, roofing shelters and truck cabins, interior wall partitions, rebound boards, marine decking etc.

It should be appreciated by the person skilled in the art that the above invention is not limited to the embodiment described. In particular, the following modifications and improvements may be made without departing from the scope of the present invention:

• The polyethylene material used in the first and third layers 12, 14 may be replaced with other hard plastic materials such as polyvinyl chloride, polypropylene or acrylonitrile-butadiene-styrene (ABS).

• The wood material used in the second layer 16 may be replaced with medium density fibreboard, particle board or plank.

• The polyethylene material used in the at least one panel 18 may be replaced with other hard plastic materials such as polyvinyl chloride, polypropylene or ABS.

• The material used in the second layer 16 may be of virgin or recycled origin'. In this manner, new composite boards may be made by recycling the material used in older composite boards. The thickness of the composite board 10 may vary from the 18mm described above. While the preferred thickness range identified by the applicant is from 4mm to 100mm thickness, boards of other sizes may just as easily be created.

The thickness of each of the first and third layers 12, 14 may vary from 0.3mm to 5 mm in thickness for any composite board less than or equal to 100mm in thickness (total).

The thickness of the panel 18 may vary from the 1.5 mm described above from 0.3mm to 5mm thickness.

The thickness of the second layer 16, as a proportion of the total thickness of the composite board, should be roughly 80%.

The first layer 12 and the third layer 14 may have a flat, smooth surface or a textured surface so as to improve friction on the surface of the board 10 for anti-skid purposes.

The length and width of the composite board 10 may vary from the 2440mm and 1220mm described above. While the preferred length and width range identified by the applicant is from 50mm to 6000mm and 50 mm to 2000mm respectively, boards of other sizes may just as easily be created.

The thickness of the composite board may be suitably adjusted if necessary for use as a cladding board.

The composite board may comprises a fourth and fifth layers bonded to the first and third layer respectively, the fourth and fifth layers made of the first hard plastic material. Advantageously, the composite board comprises a sixth and seventh layers bonded to the fourth and fifth layers respectively, the sixth and seventh layers made of the first hard plastic material. It should be further appreciated by the person skilled in the art that the features described above, where not mutually exclusive, can be combined to form yet further embodiments of the invention.