PROCESS METHOD FOR MANUFACTURING SHEET FROM MOLTEN POLYMER

Abstract: Method for manufacturing sheet directly from molten polymer transferred from a) extruders in polystyrene plants manufacturing with suspension polymerisation process; b) from evaporators in polystyrene plants manufacturing with bulk or suspension polymerisation, without pelletisation.

Description: PROCESS METHOD FOR MANUFACTURING SHEET FROM MOLTEN POLYMER Usually current plastic raw material manufacturers market the polystyrene they produce, in granule- or pellet-form. Such manufacturers with an annual manufacturing capacity equal to and over 1 million ton do not prefer sheet manufacture from polymer, which is rather a more specific area, due to their huge capacity. Plants manufacturing sheets from polymer purchase polystyrene in pellet- or in granule-form and manufacture as per customer's specification (in terms of thickness, colour of sheet, or similar requests). With this invention molten polymer from the system can be directly used in sheet manufacturing in plants where plastic raw material is produced Invention consists of a method in which sheet from polymer is directly produced. Thus, in plants manufacturing polystyrene with bulk or suspension polymerisation polymer transferred from process in molten or bead form can be directly calendered for rolling out sheet. Plastic sheet roll-out is generally carried out with a combination of extruder- calender, and polystyrene is first melted in extruder and transformed into a viscous form, and then polymer molten in the calender rolled out into sheets at the desired thickness after it has been drawn through the bobbins. As to this invention, polymer transferred from the process in molten form shall be directly fed to the calender and turned into a sheet, thus maintaining a significant energy and personnel saving. How the invention is put into application is shown in the enclosed flow chart . The application field of this invention covers only some base polymer production facilities and its application area is extremely limited, for instance, this process can only be put into application in Petkim's Polymer plants in Turkey. Machinery, equipment and instruments required to put this invention into application are the classic machinery, equipment and instruments. However, instead of extruder used in sheet manufacture in pellet polymer or granule polymer in classic method, one geared pump is used for pumping molten polymer transferred from the system to the die. In the classic method which is still currently in use, plants producing plastic raw material use granule polymer or pellet polymer during producing sheet from polymer. In sheet manufacturing from polymer under classic method polymer in the molten form is first turned into pellet or granule then it is re-melted in the machine called extruder in order to manufacture sheet from these granules. As to this invention polymer coming from production stage in molten form can be directly rolled out into sheet and the necessity for steps involving turning molten polymer into pellet or granule form again, and then re-melting polymer in pellet or granule form for sheet rolling are completely avoided. Therefore huge saving is obtained from both energy required cooling during turning the molten polymer into granule or pellet form and the energy required for melting heat during re- melting the polymer in granule or pellet form and rolling out it into sheet. Besides energy savings, thanks to lack of interim stages which are involved in classic method but not in the invention process, a savings is gained in machinery and workmanship. In sheet manufacturing from molten polymer, during bulk polymerisation process, molten anti-shock (HIPS) polystyrene coming from evaporators is pumped to co-extrusion sheet line by a gear pump (1). If coloured sheet shall be manufactured then coloured masterbatch solution is pumped to this main flow (2,3). Flows of GPPS (crystal) polystyrene (2.1), and molten polymer from scrap polystyrene extruder, mixed with polymer flow in black box (3), are drawn through a proper sheet die (4) and calender (8) and turned into sheet. Sheets drawn by take-off bobbins (9) and cut at the desired width are coiled in bobbin spinning machines (10) and then put into sale. In suspension and emulsion polymerisation processes polystyrene coming from scrap (2.2) and anti-shock extruders (2.1) to black box, which is mounted instead of cutters at the exit of the pelletising extruder passes through calender (8) for cooling process, and then rolled out by take-off cylinders (9) and coiled in bobbin winding machines (10). Now the process is completed. DESCRIPTION OF PROCESS FLOW CHART 1) Gear pump: This mechanism consisting of interlaced gears is used in pumping molten polymer. 1.1 Gear-pump: Serves the same function with pump no.l 2) Extruders: Machines melting and pumping plastic raw material 2.1 GPPS extruder: General-purpose (crystal) polystyrene extruder. It is used for securing a polished appearance of sheet surface. 2.2 Scrap PS extruder: Extruder of scrap polystyrene obtained by breaking (fragmenting) the sheet parts at die edges during the moulding of the sheet 2.3 Coloured masterbatch extruder: Masterbatch extruder used in coloured sheet manufacturing 3) Black box: Device enabling the roll-out of different plastic flows in layers without mixing with each other, which are used before moulding die. 4) DIE: Moulding die. Pressurised molten polymer is rolled out into sheet after leaving moulding hole of the die. 5) Check valve: Single-directional valve blocking the flow from flowing back 6) Static mixer: Mixer directly mounted onto the line, allowing masterbatch and main flow, and operating under a principle a certain portion of flow returns back 7) Filters: Metal filters located at various intervals used to filter out the foreign materials that may be contained in the molten polymer. 8) Calender: A system in which polymer leaving from the die in sheet form is cooled by passing through cold cylinders. 9) Take-off bobbins: A system which draws the sheet leaving the calender and maintains a homogenous flow, thus, enabling the sheet to be smooth. 10) Winding: Bobbing coiling-winding system 11) PLC (Process logic control): Computerised process control system 12) Flow control valve 13) signal lines 14) molten polymer lines

Claims: CLAIMS 1) Method in which molten anti-shock (HEPS) polystyrene leaving evaporators during bulk polymerisation process is pumped to a co-extrusion sheet line with a gear pump [if coloured sheet will be manufactured, then coloured masterbatch solution is pumped into this main flow (2,3)], and as a result, GPPS (crystal) polystyrene (2.1) and molten polymer flows from scrap polystyrene extruders, mixing with polymer flow in black box (3) are passed through a proper sheet die (4) and calender (8), and turned into sheet, then these sheets drawn by take-off bobbin (9) and cut to the desired width are wound up in winding-up machines (10) 2) Method in which, during suspension and emulsion polymerisation processes, polystyrene coming from scrap (2.2) and anti-shock extruders (2.1) to black box, which is mounted instead of cutters at the exit of the pelletising extruder, passes through calender (8) for cooling process, and then rolled out by take-off bobbins (9) and wound up in bobbin winding machines (10), and thus completing thus production process.

Inventors: BASER HALUK, BA&SCEDIL
Applicants: BASER PETROKIMYA SANAYI VE TIC, BA&SCEDIL
Application year: 1998
Main classification: B32B
IPC codes: B29C47