Injection molding method
AssigneeAsahi Kasei Kabushiki Kaisha
InventorHiroshi Yamaki
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Abstract
The invention provides an injection molding method comprising supplying a gas into a molten resin in a plasticizing cylinder and injecting the molten resin having the gas dissolved therein, wherein when the resin is being plasticized, a gas space with a predetermined gas pressure is formed within the plasticizing cylinder in a gas supply section and the pressure at the front end of the screw is adjusted to be at least equal to the gas pressure in the gas space and within a range where the gas space can be maintained within the plasticizing cylinder in the gas supply section. According to the invention, the necessary amount of gas can be dissolved in the molten resin with good reproducibility in a quantitative manner.
Claims15
An injection molding method comprising supplying a gas into a molten resin in a plasticizing cylinder and injecting the molten resin having the gas dissolved therein, wherein when the resin is being plasticized, a gas space with a predetermined gas pressure is formed within the plasticizing cylinder in a gas supply section and the pressure at the front end of a screw is adjusted to be at least equal to the gas pressure in the gas space and within a range where the gas space can be maintained within the plasticizing cylinder in the gas supply section,
- wherein the plasticizing cylinder is equipped with a multi-stage type screw comprising a front end side screw stage having screw flights wherein notches are formed in at least one of said screw flights and the gas and the molten resin are kneaded to dissolve the gas into the molten resin while part of the molten resin is caused to flow backward by means of said notches, and
- wherein the gas pressure in the gas space is kept at a predetermined level to control the gas dissolution amount.
An injection molding apparatus which comprises a plasticizing cylinder and a gas supply device for supplying a gas into a molten resin in the plasticizing cylinder and which injects the molten resin having the gas dissolved therein,
- wherein said plasticizing cylinder has a multi-stage type screw in which a stage comprising, in the following order from the rear end side toward the front end side in the direction of injection, a feed section, a compression section and a metering section is repeated a plurality of times in series, and which is also equipped with a gas supply channel open to the feed section of the front end side screw stage,
- wherein said gas supply device is connected to the gas supply channel, and
- wherein notches are in at least one screw flight in the feed section of the front end side screw stage.
Dependencies are inferred from the claim text.