Method of manufacturing transparent resin composition
In a method of manufacturing a transparent resin composition, a molten resin mixture is produced by supplying polycarbonate resin and acrylic resin continuously to a twin-screw extruder. The molten resin mixture is supplied to a single-screw extruder including a screw in which a shear processing portion is provided. Further, a transparent resin composition is produced continuously by kneading the molten resin mixture in the shear processing portion which rotates at between 500 and 4000 rpm.
1. A method of manufacturing a transparent resin composition containing polycarbonate resin and acrylic resin, the method comprising:
continuously supplying the polycarbonate resin in which an amount supplied per unit time is set to 95 to 60% by weight, and acrylic resin in which an amount supplied per unit time is set to 5 to 40% by weight, to a twin-screw extruder in which two first screws engaging with each other rotate in a same direction at no more than 600 rpm;
producing a molten resin mixture by melting and mixing the polycarbonate resin and the acrylic resin in the twin-screw extruder, and discharging the molten resin mixture continuously from the twin-screw extruder;
continuously supplying the molten resin mixture discharged from the twin-screw extruder to a single-screw extruder, the single-screw extruder comprising a second screw and a cylinder in which the second screw is accommodated, the second screw comprising a feed flight from a base end portion to an apical end portion, and a shear processing portion in an intermediate portion;
producing a transparent resin composition by kneading the molten resin mixture in the shear processing portion which rotates at between 500 and 4000 rpm with the second screw; and
discharging the produced transparent resin composition continuously from the single-screw extruder.
2. The method of claim 1 , wherein
the shear processing portion comprises a backward feed flight which twists in a direction opposite to a direction in which the feed flight twists, and
when the molten resin mixture delivered by the second screw passes through a gap between an inner circumferential wall of the cylinder and an outer circumferential portion of the backward feed flight, the molten resin mixture is kneaded.
3. The method of claim 2 , wherein
a shear action is applied to the molten resin mixture when the molten resin mixture passes through the gap between the inner circumferential wall of the cylinder and the outer circumferential portion of the backward feed flight.
4. The method of claim 1 , wherein
the shear processing portion comprises an annular protrusion which protrudes concentrically in a radial direction of the second screw, the protrusion being formed continuously in a circumferential direction of the second screw, and
when the molten resin mixture delivered by the second screw passes through a gap between an inner circumferential wall of the cylinder and an outer circumferential portion of the protrusion, the molten resin mixture is kneaded.
5. The method of claim 4 , wherein
a shear action is applied to the molten resin mixture when the molten resin mixture passes through the gap between the inner circumferential wall of the cylinder and the outer circumferential portion of the protrusion.
6. The method of claim 1 , wherein
an outer diameter and a root diameter of the feed flight of the single-screw extruder are set constantly, and
the feed flight of the single-screw extruder delivers the molten resin mixture supplied from the twin-screw extruder from a base end portion of the screw to the shear processing portion, and delivers the transparent resin composition produced by the shear processing portion from the shear processing portion to the apical end portion of the screw.
7. The method of claim 1 , wherein
an outer diameter of the second screw is greater than an outer diameter of the first screw, and
the molten resin mixture delivered by the second screw is delivered to the shear processing portion without being filled in intervals of the feed flight of the second screw.
8. The method of claim 2 , wherein
an outer diameter and a root diameter of the feed flight of the single-screw extruder are set constantly, and
the feed flight of the single-screw extruder delivers the molten resin mixture supplied from the twin-screw extruder from a base end portion of the screw to the shear processing portion, and delivers the transparent resin composition produced by the shear processing portion from the shear processing portion to the apical end portion of the screw.
9. The method of claim 3 , wherein
an outer diameter and a root diameter of the feed flight of the single-screw extruder are set constantly, and
the feed flight of the single-screw extruder delivers the molten resin mixture supplied from the twin-screw extruder from a base end portion of the screw to the shear processing portion, and delivers the transparent resin composition produced by the shear processing portion from the shear processing portion to the apical end portion of the screw.
10. The method of claim 4 , wherein
an outer diameter and a root diameter of the feed flight of the single-screw extruder are set constantly, and
the feed flight of the single-screw extruder delivers the molten resin mixture supplied from the twin-screw extruder from a base end portion of the screw to the shear processing portion, and delivers the transparent resin composition produced by the shear processing portion from the shear processing portion to the apical end portion of the screw.
11. The method of claim 5 , wherein
an outer diameter and a root diameter of the feed flight of the single-screw extruder are set constantly, and
the feed flight of the single-screw extruder delivers the molten resin mixture supplied from the twin-screw extruder from a base end portion of the screw to the shear processing portion, and delivers the transparent resin composition produced by the shear processing portion from the shear processing portion to the apical end portion of the screw.