RIGID COLOURED ARTICLE

Abstract: A coloured rigid article is made by vacuum forming a layered sheet shaped to form the skin of the article.

Description: RIGID COLOURED ARTICLE The invention relates to a method of making coloured rigid articles and to the articles themselves. While the invention can be applied to a wide range of articles it is seen to particular advantage in making panels for motorised machines/vehicles and so it will be described in relation to such items, with the reminder that the invention is of wider applicability. Some vehicles, especially heavy use industrial vehicles such as earth diggers are prone to damage. While the vehicles can have metal panels as an exterior covering it would be more economic if the panels were made of a less expensive more robust material. Plastics are obvious candidate materials but these do not have an attractive colour. EP- A-0266107 discloses an article said to be useful as an automobile body panel and comprising a cast weatherable polymer film made up of a pigmented acrylic layer joined by adhesive to a pvc film and supported on a polymer layer. The article is made by injecting curable polymer behind the film placed in a mould with the pvc film facing innermost. There is a need for a method of making a rigid impact resistant panel which has an attractive bright colour. In one aspect the invention provides a method of making a coloured rigid article, the method comprising: i) applying a layer of impact resistant pigmented material to a sheet of impact resistant thermoplastic polymer to form the precursor of the skin of the article; ii) vacuum forming the layered sheet to a predetermined shape appropriate to the skin of the article. iii) contacting the shaped layered sheet with a shaped shell in a pressure and temperature resistant mould with the pigmented layer contacting a wall of the shell; iv) supplying a curable resin composition to contact the exposed face of the sheet, closing the mould and allowing or causing the composition to cure, whereby the cured composition has the same shape as the sheet, and v) removing the formed coloured rigid article. The skin should be capable of being thermoformed (i.e. under vacuum) and have a suitable colour and gloss. The skin should be weather and impact resistant and have stability to ultraviolet light. If required, the skin should be capable of bonding to the resin substrate. The thermoplastic layer may be acrylonitrilebutadienestyrene (ABS); an ester of acrylonitrilestyreneacrylic(ASA); polycarbonate and derivatives thereof; impact modified unplasticised polyvinylchloride (PVC-u); and uv-resistant high impact polystyrene (HIPS). Most preferably the impact resistant thermoplastic polymer is ABS and the pigmented layer is a glossy pigmented layer in a plastics carrier, e.g. a polyacrylate. Most preferably the sheet and layer are a coextrusion which is available under the trade mark "IRIDON". The formed article will need to be secured to a frame or companion articles and it is an advantageous feature of the invention that for this purpose a fixing element may be anchored in the curable composition. The shell may be shaped to engage the free end of the fixing elements. The sheet is preferably formed of ABS, i.e. acrylonitrilebutadienestyrene, and the polyacrylate carrier for the pigment is preferably polymethylmethacrylate. The ABS is preferably a high impact form having the following combination of properties: an Izod impact of 380-420 J/m at 23°C; a tensile strength of 30-40 MPa; a density of about 1.1 gms/cc. The coextrusion sheet is first vacuum formed, i.e. thermoformed, in a male mould to have the desired profile. This is then placed in a shell which most preferably is distortion resistant, i.e. resistant to the pressure and temperatures arising when the resin composition is cured in the mould. Most preferably the shell comprises shell halves of cured epoxy GRP (which can be made to particularly tight tolerances). Advantageously the shell halves are located in a mould which is then held in a pressure resistant press. The shaped sheet is laid in the shell half with the acrylate layer face down, so that the shaped ABS sheet then acts as a former for the curable resin composition. Because the shaped sheet contacts the inner layer of the mould a mould release agent is not needed. It is a much preferred feature of the invention that fibres are present to reinforce the curable composition. Preferably the fibres have tensile and ductile properties. Such fibres may be loose but preferably take the form of a mat. While the fibres may be selected from a wide range of materials, e.g. metals, non-metals, composites such as titanium, carbon, aluminosilicate, plastics such as polypropylene, it is preferred to use glass fibres. They may be bonded together in the mat in an emulsion binder, selected to be compatible with the curable composition. The fibre material is preferably VETROTEX M5 available from Vetrotex (UK) Ltd. The resin composition should be selected to have mechanical properties according to the intended end use of the article. A high strength to weight ratio is preferred, together with compatibility with the other components. Optionally the resin composition may be selected for sound attenuation, flowability (to allow the moulding of complex shapes); and be capable of being pigmented and colour matched. The resin composition may be selected from a range of curable materials such as PVC, acrylic polymer, polyethylene, polyester, polyurethane and the like. The composition is preferably adapted to form a rigid form, the strengths of which are selected appropriate to the intended end use. Most preferably the composition is selected to form a formed polyurethane in which case it comprises a polyol component, an isocyanate component and a catalyst. Other ingredients may be present such as fillers, blowing agents, extenders, colouring agents; and the like. The polyol may be based on a polyester, polyepoxy, polyethers, polybutadiene; the isocyanate may be methyldiisocyanate, napthalene diisocyanate, tolylene diisocyanate or the like. It is a much preferred feature of the invention that the curable resin composition is a polyurethane because that will provide a rigid article in a short time period, e.g. less than five minutes and typically from 1.5 to about three minutes. As a result the articles may be made quickly and on a mass production basis. It is a much preferred feature of the invention that a fixing element is anchored in the resin composition before curing. Such element may be a threaded bolt the head of which is anchored in the composition. Several such elements may be included. Curing is then initiated chemically or by temperature or other radiation. Foaming may be caused in known manner. In another aspect the invention provides a method of making a coloured rigid article comprising the steps of placing a shaped skin having a pigmented surface in a shaped shell in a pressure and temperature resistant mould with the pigmented surface contacting a wall of the shell followed by a curing resin behind the skin characterised in that the skin is a vacuum formed co-extrusion of a layer of an impact resistant pigmented layer and a sheet of impact resistant thermoplastic polymer In other aspects the invention provides a rigid shaped article comprising an outer layer of pigmented impact resistant material, a sheet of impact resistant thermoplastic polymer and an inner layer of foamed plastics; preferably the article includes fibre reinforcement in the foamed plastics layer and preferably the article including a fixing element anchored in the foamed plastics layer. In order that the invention may be well understood it will now be described by way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a side elevation of a coextrusion; and Figure 2 is a vertical section through a mould containing shell halves and before curing of the resin composition. A coextrusion 1 comprising an acrylonitrile butadiene styrene 1A and a layer of pigmented impact modified polymethacrylate IB is thermo or vacuum formed in a suitable vacuum mould (not shown) at about 160° to 170°C to a required profile P of the skin of the intended article. The coextrusion is selected according to the properties required for the end use; in a preferred case the coextrusion has a density of about 1.1 gms/cc and a thickness of about 2 mm; a tensile strength of about 30 to about 40 MPa and a flexural strength of about 50 to about 55 MPa, and a flexural modulus of about 2.2 Gpa. Typically the coextrusion will have a Vicat softening temperature of about 97 to about l01°C. A rigid foam backing B is applied to the profile P in a mould shown in Figure 1. The mould comprises a base 2 and a lid 3; and has side walls 4. The sidewalls are in bottom and top halves 4A, 4B respective shaped to hold the free edges of the profile P. A paste of a self setting filler composition 5, e.g. a filled plastics is placed in the lower half of the mould box to form the intended shape M. A lower shell half HI is placed on the setting paste. The lower shelf half HI has a shaped upper wall against which the profile P is placed (with the layer IB facing downwards), and pipes 6 at the rear through which a heating medium flows. The shell half is made of glass reinforced epoxy plastics or the like to tight tolerances, so that the profile is an accurate fit, and will not move during the moulding step. A mat of VETROTEX material (not shown) is placed and then uncured polyurethane composition 7 is poured on to the upper, i.e. backing face 1A of the profile P. An insert 8 is placed at one end. A top shell half H2 is placed on top followed by more of the paste 5, and then the lid 3 is placed in position. The whole is put in a hydraulic press, not shown. Hot water is passed through the pipes 6, to provide heat to cause the polyurethane composition to foam and cure. This takes about two minutes. The water supply is shut off, and the mould M removed from the press and dismantled. The profile P with its high density rigid foam backing is removed and trimmed to size and shape. In this way a highly rigid panel has been made with a glossy paint finish and at low cost. The shell halves are reusable. The invention is not limited to the embodiment shown. The coextrusion may have a shaped face to key to the foam layer.

Claims: CLAIMS 1. A method of making a coloured rigid article, the method comprising: i) applying a layer of impact resistant pigmented material to a sheet of impact resistant thermoplastic polymer to form the precursor of the skin of the article; ii) vacuum forming the layer sheet to a predetermined shape appropriate to the skin of the article; iϋ) placing the shaped skin precursor in a shaped shell in a pressure and temperature resistant mould with the pigmented layer contacting a wall of the shell; iv) supplying a curable resin composition to the exposed face of the sheet, closing the mould and allowing or causing the composition to cure whereby the cured composition has the same shape as the sheet; and v) removing the formed coloured rigid article from the mould. 2. A method according to Claim 1, wherein the layer and the sheet are formed as a coextrusion. 3. A method according to Claim 1 or 2, including adding at least one fixing element to the curable composition whereby the fixing element is anchored in the formed article. 4. A method according to any preceding Claim, including the step of including fibres in the curable resin composition. 5. A method according to Claim 4, wherein the fibres are coated with a binder. 6. A method according to Claim 4 or 5, wherein the fibres are of glass, metal or the like. 7. A method according to Claim 6, wherein the fibres are in the form a of a mat. 8. A method accordmg to any preceding Claim, wherein the curable resin composition is adapted to form a foam. 9. A method accordmg to Claim 8, wherein the curable resin is adapted to form a polyurethane foam. 10. A method according to any preceding Claim, wherein the curable resin composition is adapted to cure and foam in less than five minutes. 1 1. A method according to Claim 10, wherein the resin composition is adapted to cure in from about one minute to about three minutes. 12. A method according to any preceding Claim wherein the shell is formed of GRP or the like. 13. A method according to any preceding Claim, wherein the shell located in a pressure resistant mould. 14. A method according to Claim 13, wherein the mould is made of is cast aluminium. 15. A method of making a coloured rigid article comprising the steps of placing a shaped skin having a pigmented surface in a shaped shell in a pressure and temperature resistant mould with the pigmented surface contacting a wall of the shell followed by a curing resin behind the skin characterised in that the skin is a vacuum formed co-extrusion of a layer of an impact resistant pigmented layer and a sheet of impact resistant thermoplastic polymer. 16. A rigid shaped article comprising an outer layer of pigmented impact resistant material, a sheet of impact resistant thermoplastic polymer and an inner layer of foamed plastics. 17. An article accordmg to Claim 16, including fibre reinforcement in the foamed plastics layer. 18. An article according to Claim 16 or 17, including a fixing element anchored in the foamed plastics layer.

Inventors: HOMER ROBERT WORLEY, PULLEY ROY STANLEY, HOMER, ROBERT, WORLEY, PULLEY, ROY, STANLEY
Applicants: HOMER ROBERT WORLEY, PULLEY BROS LIMITED, PULLEY ROY STANLEY, HOMER, ROBERT, WORLEY, PULLEY, ROY, STANLEY
Application year: 1998
Main classification: B29C70
IPC codes: B29C33, B29C43, B29C70