EXTRUDED PLASTIC

Abstract: An extruded plastic product formed of rigid thermoplastic polyurethane.

Description: EXTRUDED PLASTIC The present invention relates to extrusion of plastic materials and more particularly to extrusion of transparent plastic materials. Various types of extruded transparent plastic materials are known. Extruded polycarbonate is well known and used for a wide variety of applications. Various types of extruded polycarbonate sheets are manufactured and sold under the PALTOUGH trademark by the present applicant/assignee. When combined with a UV protector, such as taught in European Patent 0247,480, polycarbonate dis¬ plays good UV resistance. Polycarbonate is considered to have limited resistance to attack by chemical agents, including those in the atmosphere. The present invention seeks to provide an improved extruded plastic product which displays high resistance to chemical agents. There is thus provided in accordance with a preferred embodiment of the present invention an extruded plastic product formed of rigid thermoplastic polyureth¬ ane, preferably ISOPLAST brand Engineering Thermoplastic Resin. There is also provided in accordance with a preferred embodiment of the present invention an extruded plastic product formed of coextruded polycarbonate and rigid thermoplastic polyurethane, preferably ISOPLAST brand Engineering Thermoplastic Resin. There is additionally provided in accordance with a preferred embodiment of the present invention an extruded plastic sheet formed of thermoplastic polyureth¬ ane, preferably ISOPLAST brand Engineering Thermoplastic Resin . There is further provided in accordance with a preferred embodiment of the present invention an extruded plastic sheet formed of coextruded polycarbonate and thermoplastic polyurethane, preferably ISOPLAST brand Engineering Thermoplastic Resin. Additionally in accordance with a preferred embodiment of the present invention there is provided a method of producing a plastic product comprising extrud¬ ing a rigid thermoplas ic polyurethane, preferably ISO¬ PLAST brand Engineering Thermoplastic Resin. Further in accordance with a preferred embodi¬ ment of the present invention there is provided a method of producing a plastic product comprising coextruding polycarbonate and rigid thermoplastic polyurethane, preferably ISOPLAST brand Engineering Thermoplastic Resin . Still further in accordance with a preferred embodiment of the present invention there is provided a method of producing a plastic sheet comprising extruding a rigid thermoplastic polyurethane, preferably ISOPLAST brand Engineering Thermoplastic Resin. There is also provided in accordance with a preferred embodiment of the present invention a method of producing a plastic sheet comprising coextruding polycarbonate and rigid thermoplastic polyurethane, preferably ISOPLAST brand Engineering Thermoplastic Resin . In the co-extruded products, preferably the thickness of the thermoplastic polyurethane is less than 50 microns. Additionally in accordance with a preferred embodiment of the present invention the extruded products include a UV protective agent. The present invention will be understood and appreciated more fully from the following detailed de¬ scription, taken in conjunction with the drawings in which : Fig. 1 is a simplified illustration of co- extrusion of plastic sheets in accordance with a pre¬ ferred embodiment of the present invention; Fig. 2 is a sectional illustration of a plastic sheet constructed and operative in accordance with a preferred embodiment of the present invention; Fig. 3 is a simplified illustration of an extruded tank liner constructed and operative in accord¬ ance with a preferred embodiment of the present inven¬ tion; Fig. 4 is a simplified illustration of a bill¬ board constructed and operative in accordance with a preferred embodiment of the present invention; Fig. 5 is a table of test results of color parameters of a rigid thermoplastic polyurethane with different UV protectors at different concentrations at varying levels of UV exposure; and Figs. 6 and 7 are graphical representations of some of the test results of Fig. 5. Reference is now made to Fig. 1, which is a simplified illustration of coextrusion of plastic sheets in accordance with a preferred embodiment of the present invention. The coextrusion may be carried out using any suitable coextrusion apparatus, which preferably includes a primary extruder 10 for extruding a bulk sheet 12 of a first polymeric material 14, preferably polycarbonate, of thicknesses from 0.1 to over 15 mm. A feed block 16 is preferably provided for combining bulk sheet 12 with a coextruded layer of at least another polymeric material 18. In accordance with a preferred embodiment of the present invention, the other polymeric material is a rigid thermoplastic polyurethane, preferably ISOPLAST brand Engineering Thermoplastic Resin. A coextruder 20 is preferably provided for extrud¬ ing polymeric material 18. A flat sheet die 22 is preferably provided for extruding a flat sheet 24 of the coextruded polymeric materials 14 and 18, to the desired thickness and width. Alternatively, in place of coextruder 20 and flat sheet die 22 , a multi-manifold die (not shown) may be used to combine two or more polymeric layers. A calender system 26 is preferably provided for polishing the sheet 24. It is appreciated that other conventional equipment for producing flat plastic sheets may be added downstream of calender system 26. Alterna¬ tively, a calibrating or corrugating system (not shown) may be used in place of calender system 26, along with appropriate downstream equipment. Preferably control apparatus 30 is provided for controlling various operations in the coextrusion proc¬ ess. Since ISOPLAST and polycarbonate, or other pairs of polymeric materials, are usually rheologically different, their coextrusion requires control of factors such as tool temperatures, melting temperatures and pressures, feed block flow design, start-up and shutdown conditions and pre-drying conditions. Control apparatus 30 prefera¬ bly includes appropriate sensors for sensing and control¬ ling factors such as the aforementioned. Referring now to Fig. 2, there is shown in sectional illustration a plastic sheet 32 constructed and operative in accordance with a preferred embodiment of the present invention. Sheet 32 is seen to have a relatively thick portion 34, which is preferably formed of polycarbonate or other polymer, and a relatively thin portion 36, formed of rigid thermoplastic polyurethane, preferably ISOPLAST brand Engineering Thermoplastic Resin. Preferably the thickness of portion 36 is less than 50 microns. According to an alternative embodiment of the present invention, rigid thermoplastic polyurethane, preferably ISOPLAST brand Engineering Thermoplastic Resin, may be extruded alone into sheets or other products . Additionally in accordance with a preferred embodiment of the present invention, a UV protective agent, such as benzotriazole, may be added to the extrud¬ ed or co-extruded plastic in suitable proportions, typi¬ cally about 10%. Applicant has carried out several extrusion tests in the scope of the present invention. Some of these test include: 1. Mono-extrusion of ISOPLAST brand Engineering Thermoplastic Resin. 2. Coextrusion of one side of 10 - 100 microns of ISOPLAST brand Engineering Thermoplastic Resin on poly¬ carbonate to find desirable thicknesses for good chemical protection combined with good optical and mechanical properties . 3. Detailed chemical resistance tests which re¬ sulted in a broad list of materials normally incompatible with polycarbonate and which are compatible with polycar¬ bonate coextruded with ISOPLAST in accordance with a preferred embodiment of the present invention. 4. Detailed mechanical, thermal, optical and thermoformability tests of sheet coextruded in accordance with a preferred embodiment of the present invention. 5- Two-sided coextrusion of ISOPLAST brand Engi¬ neering Thermoplastic Resin on polycarbonate. 6. UV protection tests of UV absorbers in the coextruded layer. A significant improvement has been observed in the rate of yellowing under UV radiation. Results of these tests are shown tabularly in Fig. 5 and graphically in Figs. 6 and 7- The yellowness tests were performed on three different UV absorbers, A, B and C, according to ASTM (American Society for Testing Materials) D1925 with a Q panel machine which complies with ASTM G53- As is known to persons skilled in the art, L* , a* and b* are color coordinates according to CIE (Commission Internationale de l'Eclairage) 1931. With proper control of the coextrusion process, a very clear, very tough and chemical resistant sheet may be produced. This sheet is also thermoformable to differ¬ ent articles, such as containers and cups, making it very useful for storing chemical fluids in tough, high temper¬ ature (above 100 degrees Celsius) and optically clear applications . The polycarbonate and ISOPLAST coextruded sheet, constructed in accordance with a preferred embodi¬ ment of the present invention, allows the use of polycar¬ bonate in many applications where its limited chemical resistance normally prevents its selection as a viable material. An example of such an application is shown in Fig. 3. which is a simplified illustration of an extruded tank liner constructed and operative in accordance with a preferred embodiment of the present invention. In addition, the coextruded sheet of the present invention enhances the performance of polycarbon¬ ate in applications where polycarbonate alone is tradi¬ tionally used. An example of such an application is shown in Fig. 4 which is a simplified illustration of a bill¬ board constructed and operative in accordance with a preferred embodiment of the present invention. Here a transparent coextruded sheet 40 is disposed over the billboard poster for protecting it from the elements. It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined only by the claims which follow:

Claims: C L A I M S 1. An extruded plastic product formed of rigid thermoplastic polyurethane. 2. An extruded plastic product according to claim 1 and wherein said rigid thermoplastic polyurethane is ISOPLAST brand Engineering Thermoplastic Resin. 3. An extruded plastic product formed of coextrud¬ ed polycarbonate and rigid thermoplastic polyurethane. 4. An extruded plastic product according to claim 3 and wherein said rigid thermoplastic polyurethane is ISOPLAST brand Engineering Thermoplastic Resin. 5. An extruded plastic product according to any of the preceding claims and wherein the thickness of the thermoplastic polyurethane is less than 50 microns. 6. An extruded plastic product according to any of the preceding claims and also including a UV protective agent . 7> A method of producing a plastic product com¬ prising extruding a rigid thermoplastic polyurethane. 8. A method according to claim 7 and wherein said rigid thermoplastic polyurethane comprises ISOPLAST brand Engineering Thermoplastic Resin. 9. A method of producing a plastic product com¬ prising coextruding polycarbonate and rigid thermoplastic polyurethane . 10. A method according to claim 9 and wherein said rigid thermoplastic polyurethane comprises ISOPLAST brand Engineering Thermoplastic Resin. 11. A method according to any of claims 7 - 10 and wherein the thickness of the thermoplas ic polyurethane is less than 50 microns. 12. A method according to any of claims 7 - 11 and also including the step of adding a UV protective agent prior to extrusion.

Inventors: BEN ZVI GUY, BEN ZVI, GUY
Applicants: BEN ZVI GUY, PALTOUGH LTD, BEN ZVI, GUY, PALTOUGH LTD.
Application year: 1996
Main classification: C08L75
IPC codes: B29C47, B29K75, B32B27, C08L69