초록 ▼

An injection molding process wherein the times of heating to melt a resin are reduced to minimize the thermal hysteresis and to decrease the deterioration of physical properties caused by the thermal hysteresis, so that high quality information recording disks may be produced. A molding process wher

An injection molding process wherein the times of heating to melt a resin are reduced to minimize the thermal hysteresis and to decrease the deterioration of physical properties caused by the thermal hysteresis, so that high quality information recording disks may be produced. A molding process wherein the plasticating and the injection and filling of a material resin are carried out in separate cylinders, allows constant molding for a long period of time. A material resin such as polycarbonate is supplied without predrying to an injection apparatus for a first time molding. Resin is kneaded by the apparatus while volatile components are heated to be vaporized and exhausted through a vent port. An inert gas atmosphere is provided within the cylinder to prevent the material resin from being oxidized. Since predrying can be dispensed with, the thermal hysteresis will be extremely small and the deterioration of the resin caused by such heating may be suppressed. Also, there is less chance of generation of carbonized black spots caused by foreign matter, molding failures caused by hydrolysis may be eliminated, and residual monomers can be vaporized and exhausted concomitantly.

대표청구항 ▼

[ What is claimed is:] [1.] A process for injection molding rigid, transparent plastic objects comprising the steps of:providing an unpelletized, unextruded, granular resin feedstock wherein said resin feedstock has not been subjected to predrying;inserting said resin feedstock into a feed port of a

[ What is claimed is:] [1.] A process for injection molding rigid, transparent plastic objects comprising the steps of:providing an unpelletized, unextruded, granular resin feedstock wherein said resin feedstock has not been subjected to predrying;inserting said resin feedstock into a feed port of an injection machine having a vent port;rotating a threaded plasticating screw in a plasticating cylinder fed by said feed port, said plasticating cylinder having the threaded plasticating screw inserted therein, wherein a check valve comprising a mushroom-shaped valve body having a cone-shaped tip is attached to the front end of said screw;drawing said resin feedstock through said feed port into said plasticating cylinder of said injection machine;heating said plasticating cylinder;melting and kneading said resin feedstock through said heating and said rotating to produce molten resin, wherein an inert gas for preventing said resin feedstock from oxidizing during said melting and kneading is provided within said plasticating cylinder;forcing said molten resin along said plasticating cylinder by said rotating;vaporizing volatile components and impurities contained within said resin feedstock by said heating;exhausting said volatile components and impurities out of said plasticating cylinder;metering said molten resin by forcing a predetermined quantity of said molten resin from said plasticating cylinder into a front portion of an injection cylinder having a plunger for metering and injecting, wherein the check valve is closed by the backward movement of the screw to prevent the molten resin from flowing back to the plasticating cylinder side; andinjecting said molten resin into a mold having at least one cavity for producing said molded plastic objects.