Decking material and method of manufacture

Abstract

A decking material for covering a boat deck is provided, in which the decking material is a flexible polymeric material comprising 40-65 wt% bioderived PVC and 20-35 wt% plasticiser. The decking material comprises a plurality of microbubbles dispersed throughout the material. A method of manufacturing a decking material for covering a boat deck comprises the steps of: providing a polymer blend comprising 40-65 wt% bioderived PVC, 20-35 wt% plasticiser, and an expansion additive; and extruding the polymer blend into a profile. UV stabilisers, thermal stabilisers and antioxidants may be included at 1-10 wt%; processing aids may be included at 2-8 wt%, and fillers at 1-5 wt%. Biocides, preferably dichlorooctylisothiazolinone, may be included at 1-5 wt%. The plasticiser may be ester-based polymeric plasticiser or trioctyl trimillitate (TOTM). Preferably, the microbubbles have an outer diameter of 10-200 micrometres.

Description

The present invention relates to a decking material, in particular a synthetic marine decking material for use in covering a boat deck, and to a method of manufacturing said decking material. Background Boat and yacht decks can be made of different materials such as wood or fibreglass. Traditionally, if the deck surface of a boat or yacht was to be covered, this was done by applying a teak decking to the deck surface. More recently, boat or yacht deck surfaces have also been covered with synthetic decking, i.e. synthetic materials have been used instead of teak material. Synthetic decking has different properties to traditional teak decking. One significant difference is that teak decking needs regular maintenance to maintain its original appearance. The harvesting of teak timber is also highly unsustainable. One known synthetic decking material comprises PVC (polyvinyl chloride), and contains chalk as a filler. This material has many advantages over traditional teak decking, but in direct sunlight PVC-chalk-filler synthetic decking is heated up and retains the heat to a larger extent than traditional teak decking of the same dimensions. One such industry-leading synthetic decking material is described in European patent no. EP3071473B1, in the name of Flexiteek International A / S. The material of EP3071473B1 contains rigid hollow micro-balloons made of glass or ceramic, which provide favourable thermal properties resulting in rapid cooling underfoot, as well as being lighter in weight than comparable alternatives. Summary.......of.....the.......Invention The invention provides a decking material as defined in the appended independent claim to which reference should now be made. Preferred or advantageous features of the invention are set out in the dependent subclaims. In a first aspect, there is provided a decking material for covering a boat deck. The decking material may be referred to as a marine decking material, or a boat decking material. The decking material is a flexible polymeric material comprising a weight percentage of 40-65 wt% bioderived PVC and 20-35 wt% plasticiser. The decking material may have a micro-cellular structure, such that the decking material comprises a plurality of microbubbles dispersed throughout the material. One downside of the decking material of EP3071473B1 is that the glass / ceramic microspheres have an abrasive effect on our extrusion machines, rapidly wearing the machine barrels and screws. This wear affects the processing of the material, which in turn influences how the base material and masterbatch colour additives mix. This makes it a challenge to obtain consistency of plank colour and wood-effect graining. A further potential issue with glass / ceramic microspheres is that foreign materials may collect in uncovered / open spheres upon the surface of the decking material, which may in some cases lead to staining or mould formation. This can be difficult to remove, with removal often requiring the cleaning and sanding of the surface. In the decking material of the present disclosure, gas-filled microbubbles are formed by the addition of an expansion additive to the polymer mixture during manufacture. This expansion additive creates gas-filled cells which provide many of the same advantages as the glass-ceramic microspheres of EP3071473B1 in terms of thermal properties and lightness, without the abrasive effect and the drawbacks in surface cleaning. As shown below, the decking material of the present disclosure has been found to exhibit thermal properties which are superior to those of EP3071473B1, and superior to other synthetic decking materials that are commercially available. The use of bioderived PVC advantageously reduces the environmental footprint of the decking material compared to the synthetic alternatives available in the prior art. The decking material may comprise 40-65 wt% bioderived PVC, or 50-62 wt% bioderived PVC, preferably 53-60 wt% bioderived PVC. The decking material may comprise one or more UV stabilisers, thermal stabilisers, antioxidants, and / or extenders. Preferably the decking material comprises 1-10 wt% UV stabilisers, thermal stabilisers, antioxidants, and / or extenders, particularly preferably 1-3 wt% UV stabilisers, thermal stabilisers, antioxidants, and / or extenders. The decking material may comprise one or more processing aids. In some preferred embodiments the decking material comprises 2-8 wt% processing aids. The decking material may comprise one or more expansion additives. Preferably the expansion additive is non-azodicarbonamide-based. The decking material may comprise one or more fillers. Preferably the decking material comprises 1-5 wt% fillers. The decking material may comprise one or more biocides, also known as anti-fungal agents. Preferably the decking material comprises 1-5 wt% biocide, particularly preferably 1-2.5 wt% biocide. The decking material may preferably contain the biocide Dichlorooctylisothiazolinone (DCOIT). The plasticiser may preferably be a low-migratory plasticiser or a non-migratory plasticiser. The incorporation of a low-migratory or a non-migratory plasticiser into the material may advantageously provide the material with superior resistance to both chemicals and the environment, prolonging the lifespan of the decking material. In a particularly preferred embodiment, the plasticiser is an ester-based polymeric plasticiser and / or trioctyl trimillitate (TOTM), which exhibit the advantageous characteristic of low or non-migration in the PVC-based decking material. The decking material has a micro-cellular structure comprising a plurality of gas-filled microbubbles, or cells, in which the microbubbles (cells) are arranged such that the diameter of the cells decreases towards an outer surface of the material. In other words, the cells near the outer surface of the material have a smaller diameter than those cells in the bulk material. An advantage of such a decking material is that the arrangement of the cells decreases the thermal conductivity of the material compared to an equivalent material in which the cells have uniform diameters, and are dispersed uniformly throughout the material. This means that the decking material of the present invention remains cooler in the sun, and so feels cooler underfoot, than a known PVC decking material. The flexibility of the decking material also makes it easier to apply to a boat deck than a more-rigid known PVC decking material. Preferably the microbubbles have an average outer diameter in the range of 10 to 200 micrometers. That is, the decking material has a micro-cellular structure comprising a plurality of gas pockets, or microbubbles, in which the average size of the microbubbles is in the range of 10 to 200 micrometers. Preferably the average size of the microbubbles is in the range of 50 to 150 micrometers. Preferably the decking material is extruded to form profiles, or panels of decking material. The decking material may be extruded from more than one material having different colours, in order to create a grained effect. Particularly preferably the material is extruded in substantially flat panels, for example long panels having a longitudinal dimension that is larger than a lateral dimension. Preferably adjacent panels of decking material are joinable by thermal treatment. Thermally joining extruded panels allows the formation of potentially limitless sizes of panels, suitable for covering entire boat decks. Preferably caulking material is inserted between adjacent panels by welding. As welding is carried out subsequent to extrusion, this allows a wide range of caulking colours to be used as this is not dictated during the production run. Welding also allows the caulking material to be made flush with the surrounding decking material, so that there are no depressions which could gather water. Preferably the outer surface of the decking material is textured, or roughened, so as to imitate a grain effect of wooden material. Preferably the decking material has a thermal conductivity of less than 0.3 W-nr1K’1 at 30 °C , preferably less than 0.2 Wm'1K'1, at 30 °C. This thermal conductivity is significantly lower than the thermal conductivity exhibited by conventional polymer decking materials. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal conductivity. This low thermal conductivity makes the present decking material advantageously much cooler to the touch than available alternatives, which is highly desirable for decking material that should be comfortable to touch, sit on or walk on barefoot. Preferably the decking material has a thermal diffusivity of less than 0.20 mm2s'1 at 30 °C , preferably less than 0.11 mm2s’1 at 30 °C, particularly preferably less than 0.10 mm2 s’1 at 30 °C. Thermal diffusivity is the thermal conductivity divided by density and specific heat capacity at constant pressure. It is a measure of the rate of heat transfer inside a material. Preferably the decking material has a heat capacity of less than 2 MJ-mm-3 K'1 at 30 °C , preferably less than 0.18 MJ-mm-3 K'1 at 30 °C. Heat capacity or thermal capacity is a physical property of matter, defined as the amount of heat to be supplied to an object to produce a unit change in its temperature. These thermal characteristics of the present decking material are provided as a result of the micro-cellular structure of the decking material, and are superior to the synthetic decking materials known in the art. With these thermal properties, the present decking material is advantageously good at dissipating heat and remaining cool to the touch even in hot weather. This is highly desirable for boat decking which is highly likely to be in contact with skin during hot weather. The decking material may advantageously be at least 60% lighter than known PVC-based decking material of equivalent dimensions. Preferably the density of the decking material according to the present invention is at least 50%, or 55%, or 60% less than the density of known PVC-plus-chalk-filler synthetic decking material. Additives can be added before the extrusion or in connection with the extrusion process. Further components such as stabilizer and colour pigments may also be added before or during the extrusion process. Preferably an underside of the decking material comprises a sheet of adhesive material for attaching the decking material to a boat deck. This may advantageously be a “peel-and-stick” sheet of adhesive material, to allow easy installation of the decking material. In a second aspect, there is provided a method of manufacturing a decking material for covering a boat deck. The method may comprise the steps of providing a polymer blend comprising a volume percentage of 40-65 wt% bioderived PVC, 20-35 wt% plasticiser, and an expansion additive, and extruding the polymer blend into a profile. The polymer blend is a melt of ingredients which are added in the desired proportions. The polymer blend may additionally comprise 1-3 wt% UV stabilisers, thermal stabilisers, antioxidants and / or extenders; and / or 2-8 wt% processing aids; and / or 1-3 wt% biocide. The expansion additive is preferably non-azodicarbonamide-based. Specific Embodiment of the Invention A specific embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawing, in which: Figure 1 is a perspective view of a section of decking material in accordance with the present invention; Figure 2 is a magnified photograph of a cross-section of a decking material in accordance with the present invention. The flexible decking material 2 shown in Figures 1 and 2 is manufactured by forming a polymer melt containing the following ingredients: Ingredients Proportion (wt%) Bioderived PVC polymer 55 Low-migratory Plasticisers 25 UV Stabiliser, thermal stabiliser, antioxidants and extenders 6 Processing aids 7 Fillers 3 Biocide (DCOIT) 2 Expansion additive 2 This polymer melt is then extruded into a panel of flexible polymeric material as shown in the Figures. The material has a micro-cellular structure comprising a plurality of microbubbles, or cells, which are distributed throughout the material. The expansion additive is distributed and dispersed throughout the polymer blend, and enables the formation of the microbubbles throughout the extruded polymer material. The growth of the microbubbles in the flexible polymer material is determined predominantly by pressure, temperature and number of nucleating sites. The growth of the microbubbles is predominantly determined by the release in pressure and the melt temperature with the distribution governed by the number of nucleating sites. As this is complex mechanism, the distribution and size of the microbubbles through the extruded material is fairly erratic. This is particularly the case with the present flexible PVC-based material, as the product is cooled gradually during manufacturing. This results in some microbubbles at the surface which become partially formed until the melt cools and becomes too stiff, which then restricts the further expansion of the microbubbles. As a result, the main concentration of microbubbles is towards the centre cross-section of the extruded profile, with fewer microbubbles near the outer surface(s). The microbubbles are typically not completely spherical in shape as they become elongated or deformed when the product is stretched during calibration / cooling. The largest microbubbles in the bulk of the material have a diameter of approximately 200 micrometres, with the average microbubble size being significantly less than 200 micrometres. The presence of the microbubbles throughout the material reduces its thermal conductivity, so makes the decking material a better thermal insulator, compared to known PVC-plus-chalk-filler synthetic decking materials. This means that the material takes longer to heat up than a known PVC-plus-chalk-filler synthetic decking material, and so is cooler underfoot in everyday use. The section of decking material shown in Figure 1 comprises three adjacent panels 12 of decking material connected by thermal treatment along a longitudinal edge 6. A desired number of panels may be connected to provide a sheet of decking material of desired dimensions. Once the panels of decking material have been joined together, caulking material 8 is added by a top welding process to seal the seams between adjacent panels. A “peel-and-stick” sheet of adhesive material (not shown) is provided on a lower surface 10 of the decking material for attaching the decking material to a boat deck. The “peel-and-stick” material comprises a cover sheet that may be removed to expose a downwardly facing adhesive layer that may be stuck onto the deck of a boat. The “peel-and-stick” adhesive and the flexibility of the decking material allows easy installation of the decking material onto, for example, a curved boat deck. This arrangement is easier to use than the conventional method of sticking known PVC-based decking materials onto boats, which involves the application of a separate adhesive material onto the boat deck prior to laying the decking material. Figure 2 shows a cross-section of an extruded panel of decking material. Under magnification, the microbubbles are visible throughout the material, with the greatest concentration of microbubbles in the bulk material away from the upper and lower surfaces. Thermal tests were carried out on the flexible PVC decking material described above, as 5 well as on commercially-available “Flexiteek 1G” material, and the “Flexiteek 2G” material described in European patent no. EP3071473B1. The results of the thermal test were as follows: Material Thermal Conductivity [W / m / K] Flexiteek 1G 0,272 W / m / K @ 30°C Flexiteek 2G 0,212 W / m / K @ 30°C Present Decking Material 0,169 W / m / K @ 30°C Material Thermal Diffusivity [mm2 / s] Flexiteek 1G 0,128 mm2 / s@30°C Flexiteek 2G 0,128 mm2 / s@30°C Present Decking Material 0,098 mm2 / s @ 30°C Material Heat Capacity [MJ / m3K] Flexiteek 1G 2,141 MJ / m3K@30°C Flexiteek 2G 1,650 MJ / m3K @ 30°C Present Decking Material 1,723 MJ / m3K@ 30°C This thermal testing showed that the material of the present disclosure exhibits superior thermal conductivity and diffusivity characteristics than similar synthetic decking materials that are commercially available.

Claims

1. A decking material for covering a boat deck, in which the decking material is a flexible polymeric material comprising a volume percentage of 40-65 wt% bioderived PVC and 20-35 wt% plasticiser, wherein the decking material comprises a plurality of microbubbles dispersed throughout the material.

2. A decking material according to claim 1, in which the decking material comprises 50-62 wt% bioderived PVC, preferably 53-60 wt% bioderived PVC.

3. A decking material according to claim 1 or 2, in which the decking material comprises 25-32 wt% plasticiser, preferably 27-30 wt% plasticiser.

4. A decking material according to claim 1,2 or 3, in which the decking material comprises one or more UV stabilisers, thermal stabilisers, antioxidants, and / or extenders.

5. A decking material according to claim 4, in which the decking material comprises 1-10 wt% stabilisers and / or extenders, preferably 1-3 wt% UV stabilisers, thermal stabilisers, antioxidants and / or extenders.

6. A decking material according to any preceding claim, in which the decking material comprises one or more processing aids.

7. A decking material according to claim 6, in which the decking material comprises 2-8 wt% processing aids.

8. A decking material according to any preceding claim, in which the decking material comprises one or more fillers.

9. A decking material according to claim 8, in which the decking material comprises 1-5 wt% fillers.(DCOIT).

11. A decking material according to claim 10, in which the decking material comprises 1-5 wt% biocide, preferably 1-2.5 wt% biocide.

12. A decking material according to any preceding claim, in which the plasticiser is a low-migratory or non-migratory plasticiser.

13. A decking material according to any preceding claim, in which the plasticiser is an ester-based polymeric plasticiser and / or trioctyl trimillitate (TOTM).

14. A decking material according to any preceding claim, in which the microbubbles are arranged such that the diameter of the cells decreases towards an outer surface of the material.

15. A decking material according to any preceding claim, in which the microbubbles have an average outer diameter in the range of 10 to 200 micrometers, preferably in the range of 50 to 150 micrometers.

16. A decking material according to any preceding claim, in which the decking material is an extruded polymeric material.

17. A decking material according to any preceding claim, in which the decking material is provided as panels of decking material.

18. A decking material according to claim 17, in which adjacent panels of decking material are joinable by thermal treatment.

19. A decking material according to claim 18, in which adjacent panels are connectable by welding with caulking material.

20. A decking material according to any preceding claim, in which the outer surface of the decking material is textured so as to imitate a grain effect of wooden material.

21. A decking material according to any preceding claim, in which the decking material has a thermal conductivity of less than 0.3 W nr1K’1 at 30 °C , preferably less than 0.2 Wm^K’1, at 30 °C.

22. A decking material according to any preceding claim, in which the decking material has a thermal diffusivity of less than 0.20 mm2 s‘1 at 30 °C , preferably less than 0.11 mm2 s’1 at 30 °C, particularly preferably less than 0.10 mm2 s’1 at 30 °C.

23. A decking material according to any preceding claim, in which the decking material has a heat capacity of less than 2 MJ mm-3 K'1 at 30 °C , preferably less than 0.18 MJ mm-3 K'1 at 30 °C.

24. A decking material according to any preceding claim, in which an underside of the decking material comprises a sheet of adhesive material for attaching the decking material to a boat deck.

25. A method of manufacturing a decking material for covering a boat deck, comprising the steps of:providing a polymer blend comprising a volume percentage of 40-65 wt% bioderived PVC, 20-35 wt% plasticiser, and an expansion additive; and extruding the polymer blend into a profile.

26. A method according to claim 25, in which the polymer blend additionally comprises 1-3 wt% UV stabilisers, thermal stabilisers, antioxidants and / or extenders; and / or 2-8 wt% processing aids; and / or 1-3 wt% biocide.

27. A method according to claim 25 or 26, in which the expansion additive is a non-azodicarbonamide-based expansion additive.AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS:25 11 25Claims1. A decking material for covering a boat deck, in which the decking material is a flexible polymeric material comprising a volume percentage of 40-65 wt% bioderived PVC and 20-35 wt% plasticiser, wherein the decking material comprises a plurality of microbubbles dispersed throughout the material.

2. A decking material according to claim 1, in which the decking material comprises 50-62 wt% bioderived PVC, preferably 53-60 wt% bioderived PVC.

3. A decking material according to claim 1 or 2, in which the decking material comprises 25-32 wt% plasticiser, preferably 27-30 wt% plasticiser.

4. A decking material according to claim 1,2 or 3, in which the decking material comprises one or more UV stabilisers, thermal stabilisers, antioxidants, and / or extenders.

5. A decking material according to claim 4, in which the decking material comprises 1-10 wt% stabilisers and / or extenders, preferably 1-3 wt% UV stabilisers, thermal stabilisers, antioxidants and / or extenders.

6. A decking material according to any preceding claim, in which the decking material comprises one or more processing aids.

7. A decking material according to claim 6, in which the decking material comprises 2-8 wt% processing aids.

8. A decking material according to any preceding claim, in which the decking material comprises one or more fillers.

9. A decking material according to claim 8, in which the decking material comprises 1-5 wt% fillers.(DCOIT).

11. A decking material according to claim 10, in which the decking material comprises 1-5 wt% biocide, preferably 1-2.5 wt% biocide.

512. A decking material according to any preceding claim, in which the plasticiser is a low-migratory or non-migratory plasticiser.

13. A decking material according to any preceding claim, in which the plasticiser is an10 ester-based polymeric plasticiser and / or trioctyl trimillitate (TOTM).

14. A decking material according to any preceding claim, in which the microbubbles are arranged such that the diameter of the cells decreases towards an outer surface of the material.1515. A decking material according to any preceding claim, in which the microbubbles have an average outer diameter in the range of 10 to 200 micrometers, preferably in the range of 50 to 150 micrometers.20 16. A decking material according to any preceding claim, in which the decking materialis an extruded polymeric material.

17. A decking material according to any preceding claim, in which the decking material is provided as panels of decking material.2518. A decking material according to claim 17, in which adjacent panels of decking material are joinable by thermal treatment.

19. A decking material according to claim 18, in which adjacent panels are connectable 30 by welding with caulking material.

20. A decking material according to any preceding claim, in which the outer surface of the decking material is textured so as to imitate a grain effect of wooden material.35 21. A decking material according to any preceding claim, in which the decking materialhas a thermal conductivity of less than 0.3 W nr1K’1 at 30 °C , preferably less than 0.2 Wm^K’1, at 30 °C.

22. A decking material according to any preceding claim, in which the decking material has a thermal diffusivity of less than 0.20 mm2 s‘1 at 30 °C , preferably less than 0.11 mm2 s’1 at 30 °C, particularly preferably less than 0.10 mm2 s’1 at 30 °C.

23. A decking material according to any preceding claim, in which the decking material has a heat capacity of less than 2 MJ mm-3 K'1 at 30 °C , preferably less than 0.18 MJ mm-3 K'1 at 30 °C.

24. A decking material according to any preceding claim, in which an underside of the decking material comprises a sheet of adhesive material for attaching the decking material to a boat deck.25 11 25

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