-1 INSULATION BARRIER The present invention relates to an insulation barrier of the type comprising closed cells. The insulation barrier is used for insulating, for example, commercial and domestic dwellings. Background Insulation products are used as physical insulation barriers in many applications to prevent or reduce transfer of energy. In some application insulation barriers act to thermally insulate against the transfer of heat. In other applications barriers may be used as sound proofing or acoustic insulation to reduce intensity of sound. There are several aspects to the insulation of thermal energy including consideration of: radiant insulation, that is achieved using a reflective material that reflects thermal energy; conductive insulation, where the insulation prevents heat flowing through a body such as a wall; and convective insulation, which reduces the transfer of heat by the warming of air or some other medium on either side of a body such as a wall. Insulation batts using materials such as foam, fibreglass, wool or polyester are a common type of insulation used in buildings and are effective in reducing thermal conduction but are not necessarily effective in reducing heat transfer by convection and radiation. Applying a reflective foil to insulation batts increases the batts' effectiveness at reducing heat transfer by radiation. A further type of insulation includes using a sheet of closed air cells structure (also known as "bubble pack" used for packing objects). Lining the closed cell sheet on both sides with reflective foil enhances the sheets performance in insulating against radiant heat. Such an insulation barrier is effective in reducing the transfer of heat across the barrier whereby the greater the -2 size of the closed air cells the greater the thermal resistance of the barrier, which is measured against a so called 'R-rating'. The problem with such closed air cell insulating barriers is that the air cells cannot be made too large because they are not self-supportive which will cause the cell membrane to collapse thereby reducing the barrier's ability to effectively insulate. In addition, larger air cells are less effective at insulating against convective heat transfer as the larger volume of gas inside larger air cells exhibit turbulent flow, which promotes convective heat transfer. It is against these problems that the present insulation barrier has been developed. Summary of the Invention In accordance with the present invention there is provided an insulation barrier comprising a cell layer of closed cells attached to a reinforcement layer; the closed cells being formed in cell groups, the closed cells in each cell group being separated by at least one partition, wherein the closed cells are circular sectors to form a cell group and, collectively, each cell group forms a substantially annular structure. Collectively, each cell group preferably forms a substantially annular structure, and that in shape can be oval to circular. The annular structure of the cell group can have a width of approximately 20 to 35 mm, wherein preferably the width is a diameter of 20 to 35 mm. More preferably, the diameter of the annular structure is approximately 25 to 30 mm, and in one embodiment is 28 mm. The closed cells are preferably closed air cells, namely they are filled with air. Although, it is understood that a gas other than air could be used to fill the closed cells. For example, carbon dioxide may be used to fill the cells. Carbon 5 dioxide has a lower thermal conductivity compared to air and is a non-flammable gas that in a fire event displaces oxygen, -3 and hence can improve the fire rating of the insulating barrier. Each cell group can comprise a reasonable number of discrete closed cells, which in one embodiment is two, namely a pair of closed cells. However, in other embodiments it is possible to have an even number of closed cells or an odd number of closed cells. A cell group could forseeably include any one of 2, 3, 4, 5, 6, 7, 8, or more, closed cells. Depending on the number of closed cells in a cell group, the closed cells can be themselves semi-circular in shape, or quarter-circle or a circular sector having varying sector angles. In the embodiment of a substantially annular structure of a cell group with two cells, the closed cells have a length that is longer than a width. In other embodiments the cells can be differently shaped depending on the number of discrete closed cells in a cell group. Each closed cell will be separated from another closed cell in the group by one or more partitions. The partition is formed as a wall between closed cells and is approximately 1.0 to 4.0 mm in thickness, thereby defining the separation distance of the closed cells. The partition is formed during the forming process of the layer of closed cells structures, which can be by a vacuum suction extrusion forming process. The cell layer of closed cell can be made using plastics material, and in one embodiment is made of polyethylene. The closed cell layer may more particularly, be a blend of low density polyethylene (LDPE) and high density polyethylene (HDPE) and nanoclay. The advantage of the present insulation barrier is that the cell group of discrete closed cells effectively make a larger closed cell structure. The "effective" large closed cell structure results in a greater closed cell "effective" air volume that, in turn, results in greater insulation by the closed cell layer. The at least one partition in each cell group reinforces the cell group so there is less likelihood for the cells to collapse. The cell groups are themselves separated by 2 to 5 mm, -4 and preferably each cell group is separated from another cell group by a distance of 3.0 mm. The reinforcement layer is preferably laminated to one side of the cell layer. In a preferred embodiment there are two reinforcement layers, one on either side of the cell layer, with the cell layer in between. In one embodiment the reinforcement layer may be only a reflective layer, such as a foil layer. Preferably there are two layers on either side of the cell layer that are reflective layers. The reflective quality can be brought about by an aluminium foil or any other suitable metallised foil applied to one or both reinforcement layers. In another embodiment, or in addition to this embodiment, the reinforcement layer may be a more structural substrate, such as a woven product. The reinforcement layer may be made of a high density polyethylene (HDPE) woven product and reinforced with fibreglass or fibre yarn to increase its durability. In some embodiments of the invention the closed cells in a first cell group are spaced closer to each other than they are spaced from closed cells of a second cell group. Brief Description of the Drawings An embodiment, incorporating all aspects of the invention, will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a schematic view of an insulation barrier in accordance with an embodiment of the present invention; Figure 2 is an enlarged plan view of "Area A" of the insulation barrier illustrated in Figure 1; D Figure 3 is a side section view of the insulation barrier; and Figure 4 is a schematic plan view of a mould used in forming the insulation barrier. 5 Detailed description of preferred embodiment Figures 1 to 3 illustrate an insulation barrier 10 that comprises a cell layer 12 (see Figure 3) having closed cells 20. The cell layer 12 is positioned in between two -5 reinforcement layers 14. The closed cells 20 are formed in cell groups 30 wherein the closed cells in each cell group are separated by a partition 22. The closed cells may be air cells, namely filled with air, although gases other than air can be used to fill the closed cells, or additives could be included in the gas/air. Grouping the closed cells together and having partitions separating the cells creates an insulating cell structure that effectively has an increased size including height without the disadvantages of turbulent flow in a single large air cell. Dividing an effective large cell into segments maintains laminar flow within the 'effective' large cell, ie. group of cells, while achieving an increase in height and effective cell size to therefore achieve an increased thermal resistance, or R-rating, when compared to a sheet having an even distribution of small closed cells. An increase in effective size of cell structure furthermore increases the thickness of the insulation, or in other words increases the gap between the reinforcement layers. This leads to an increase in the degree of thermal resistance achievable by each cell group. The partition 22 between closed cells 20 in a group provides structural rigidity to the cell group, acting as pillars. At least one partition is provided in each cell group, although depending on the structure of the group, two or more partitions could be used. Accordingly, an increase in "effective" cell structure increases thermal insulation of the insulation barrier 10 and the partitions provide rigidity to the cell groups which reduces the likelihood of cell collapse. Figures 1 and 2 illustrate each cell group 30 forming a cell structure 35 that is substantially annular and in which each cell group includes two closed cells 20. The annular structure of each cell group 30 corresponds to an "effective" large air cell. The annular structure 35 can include shapes that are elliptical, oval, circular or anywhere in between, where the annular shape provides a substantially constant -6 pressure distribution about its annular perimeter, making the cell structure. In the embodiment illustrated each cell group 30 comprises a pair of discrete but adjacent closed cells 20, where the term "discrete" means that they are separate cells that do not allow the transfer of air between them. The closed cells 20 in a cell group 30 are spaced closer to each other than the spacing between closed cells in different groups. The partition 22 lies between adjacent faces, in other words adjacent cell walls, of the cells in a cell group. The partitions 22 as illustrated in Figure 3 are in the form of a gap between cell walls 24 of adjacent closed cells 20. The gap may itself contain air/gas that is intentionally or incidentally filled during the cell layer forming process. Alternatively, the partition may be formed as a solid wall between adjacent cells. The cell groups have a width of between approximately 20 mm to 35 mm, and where that cell group is an annular structure as illustrated, the width is a diameter d of 20 mm to 35 mm. The diameter measurement d is taken from an outside of the outer cell walls 24 of each cell group 30. At rest, the cells have a height h of approximately 5 mm to 15 mm and more specifically around 8 mm. Taking into consideration tolerances in manufacturing and measurements of the insulation barrier taken at rest (namely, not under compression or expansion), the diameter of the annular structure of the cell groups of the embodiment illustrated is approximately 25 mm to 30 mm and more ) specifically about 28 mm. Depending on the number of closed cells within a group, the shape and size of the closed cells will vary. In the embodiment shown a pair of semi-circular closed cells 20 have a length of each semi-circular cell that is longer than its 5 width. The thickness t of the partition 22 when measured from approximately the centre of cell walls 24 is approximately 2.0 to 3.0 mm and around 2.5 mm.
-7 The separation distance between cell groups can vary but would ideally be as close as possible in order to increase the R-rating of the barrier, but without interfering with other cell groups 30. Accordingly, a distance of between 1 mm and 6 mm between cell groups could be feasible. A separation distance g between cell groups of about 2.0 mm is illustrated in the attached drawings. The partition is formed as a wall between adjacent closed cells in a cell group during the forming process of the cell layer 12. The forming process employed can be any known process for forming closed air cells, or bubble wrap, but is often a vacuum suction extrusion forming process using plastics material. Figure 4 shows in plan schematic view a mould 40 used to form the cell layer 12 in sheet form. The plastics material, for example polyethylene, is extruded as a first membrane 25 over the mould 40 which has mould recesses 42. Air is vacuum suctioned out of the cell recesses through vacuum holes 43 which draws the first membrane 25 into the mould recesses 42 and to mould to the shape of the recess 42, which corresponds to the 'bubble' shape of the closed cells 20. First membrane 25 forms the substantial part of the structure of a closed cell. Thereafter a second membrane 27 of polyethylene is extruded over the mould to cover off mould recesses 42 and adhere to the first layer to thereby form closed cells with air/gas trapped therein. In the process for forming the insulation barrier 10 divider walls 45 positioned across the mould recesses 42 form the partition 22 in each cell group 30. This is achieved by the first membrane 25 moulding over and around the divider wall 45 as it is vacuum suctioned into the recess 42. Accordingly, when the moulded product is cooled and removed from the mould a dividing partition is formed between adjacent closed cells. The divider wall 45 divides the mould recess 42 into two distinct sections, each having its own vacuum suction hole 43 and in which each will form adjacent closed cells in a cell group 30.
-8 After forming the cell layer 12 by the above process, reinforcement layers are applied to one or both, opposite sides of the cell layer 12 to provide structure and reinforcement to the final insulation barrier product. The reinforcement layers 14 are specifically laminated on either side of the cell layer and one or both of the reinforcement layers 14 may include a reflective material or a reflective layer 16 to improve the radiant insulation of the barrier 10. The reflective qualities of the reinforcement layers 14 can be provided by aluminium foil or other metallised foil 16 applied to one or both of the reinforcement layers. The reinforcement layers are made from a high density polyethylene (HDPE) woven product and may be reinforced with fibreglass or a fibre yarn to increase their durability. The cell layer 12 in its simplest form can be formed from polyethylene but may also be formed from a polyethylene blend. In one embodiment the blend includes a low density polyethylene (LDPE), a high density polyethylene (HDPE) and nanoclay. Nanoclay provides added protection to the cell layer against puncture and tearing. In a preferred embodiment the insulation barrier comprises the following layers: cell layer 12; LDPE layer (not shown) that is coated on the reinforcement layer 14 to adhere the reinforcement layer to the cell layer; the reinforcement layer 14 in the form of a HDPE woven substrate; and a tie layer (not shown) comprising LDPE blended with additives to adhere the HDPE woven layer 14 to the reflective layer 16. While a pair of closed cells 20 in each cell group 30 is illustrated in the drawings, more closed cells could be formed in each cell group 30. The number of closed cells would depend on the size of the cell group but in addition to the minimum of 2 closed cells in each group there could be provided 3, 4, 5, 6, 7, 8 or more closed cells for each cell group. Accordingly, a partition would be provided between each adjacent closed cell in the cell group which would mean that the recesses 42 in the mould 40 would include multiple divider walls 45 to create the multiple partitions. Again depending on the number of closed cells within each group, the -9 shape and size of the closed cells will vary and could range in shape from quarter circles to circular sectors having varying sector angles. In order to increase the fire resistance of the insulation barrier fire retardant additives could be added to the plastic extrusion forming the first and second membranes of the cell layer 12. Additionally, flame retardant could be coated on the HDPE woven reinforcement layers 14 where the flame retardant consists of a blend of LDPE with flame retardant additives. Alternatively, the HDPE yarn used to weave the HDPE woven reinforcement layer can be incorporated with flame retardant additives. Furthermore, and as discussed previously, incorporating carbon dioxide as the gas in the closed air cell also acts as a fire retardant/extinguishing agent as carbon dioxide displaces oxygen in a fire event. The insulation barrier 10 may comprise more than one cell layer 12, and may for example include two cell layers one overlying the other to create a double cell layer, with reinforcement layers 14 applied on either side of the double cell layer. This would further increase the R-rating of the insulation barrier. The insulation barrier described herein provides superior insulating properties as a result of a greater effective insulating area provided by each group of closed cells. Furthermore, the barrier can be reliable used and with confidence as the closed cells are stable and structurally rigid. The barrier is able to effectively insulate against ) heat transfer by conduction, convection and radiation. In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as 5 "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.