METHOD OF FEEDING MATERIALS TO EXTRUDER FOR MAKING POLYMER FILM

摘要

1505512 Controlling extruder feed DYNAMIT NOBEL AG 22 May 1975 [1 June 1974] 22395/75 Heading B5A [Also in Division G3] A method for the extrusion of a synthetic plastics sheet (polyvinylbutyral film for laminated glass) comprises the steps of setting a rated value at 23 for the total supply of material to a screw press 3, measuring at 19 the weight per unit time of comminuted, recycled material being fed at 18 and controlling the supply of fresh raw material 9 in response to the difference, and also keeping constant the filling of the press, measured as the mass pressure at 28 between the press 3 and a melt pump 5. As shown, the pressure measurement modifies the rated value by Œ10% via controller 30, but alternatively (Fig. 2, not shown) the rated value is set in excess of that required and the actual surplus material is removed at the outlet of the press via a valve controlled by the pressure measuring device. A delay device 25 compensates for the time lag between weigher 19 and press 3. The device 23 sets a desired value for the flow of new material, which is compared with the actual flow signal from belt weigher 11, any difference causing adjustment of the speed of belt drive motor 22. Plasticizer 13 is added in a fixed ratio to the flow of raw material, by controlling a pump 14 in response to the difference between the actual flow measured at 27 and a reference derived in 23. The recycled material is obtained from sheet edge trimmings la, which may be temporarily stored on a drum 8.