JP2007168239A - Resin molding machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent air from being entrained between a mold and a molten resin when the mold is clamped for molding in a resin molding machine in which the molten resin is discharged on the mold through a T-die by using an injection device with the T-die set in a discharge opening. <P>SOLUTION: The T-die 3 is set in the discharge opening of the injection device. The molten resin 5 is discharged from the discharge opening 4 of the T-die 3 on a lower mold 2. After the T-die 3 is retracted, an upper mold 1 and the lower mold 2 are clamped, and the molten resin 5 is molded to obtain a product in the shape of a flat plate. In the shape of the discharge opening of the T-die 3, the size in the transverse direction is larger than the size in the longitudinal direction, the lower side is formed by a convex curve, and the size in the longitudinal direction is gradually increased from both ends toward the center. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a resin molding apparatus, and more particularly to a resin molding apparatus suitable for manufacturing a resin molded product in which appearance and dimensional accuracy are important, such as a molded product for optical use.

  In a resin molding apparatus that manufactures a resin product by discharging a molten resin onto a mold using an injection device or an extrusion device and then clamping the mold, the molten resin is applied onto the mold via a die or a nozzle. Discharging.

  However, for example, when manufacturing flat resin products that emphasize the appearance and dimensional accuracy, such as molded products for optical applications, the amount of molten resin discharged is controlled accurately and the shape is stable. Is important. Therefore, in such a case, in order to increase the molten resin discharge accuracy (flow rate, resin temperature) rather than the die or nozzle, the molten resin is discharged onto the mold through a T die having a manifold inside. Things have been done.

  Usually, the T die is mainly used when sheets and films are continuously produced by an extrusion molding method, and the shape of the discharge port of the T die is an elongated rectangular shape. The typical dimension is about 800 to 2000 mm in the lateral direction (horizontal direction) (width), and about 0.5 to 15 mm in the longitudinal direction (vertical direction). The horizontal dimension is about 50 to 4000 times the vertical dimension.

T-die used in sheet and film manufacturing equipment can support various raw materials and various sheet / film thicknesses:
(A) A choke bar is provided in the middle of the resin flow path to adjust the lateral flow rate;
(B) A plurality of die bolts are arranged in the lateral direction of the die lip, and the die bolts are pushed and pulled individually so that the lateral shape of the film / sheet becomes an arbitrary shape, and the lateral gap of the die lip is finely adjusted. ing.

  As a special example, as shown in Japanese Patent Laid-Open No. 9-136343 “Film Forming Method”, there is a case in which a gap between both ends is widened for the purpose of preventing a neck-in phenomenon.

  The shape of the discharge port of the T-die used when discharging molten resin onto a mold using an injection device or an extrusion device is also an elongated rectangular shape. About 100 to 800 mm, and the vertical dimension is about 2 to 30 mm. The T die used for discharging molten resin onto a mold using an injection device or an extrusion device has a short horizontal dimension, so that even if the die bolt is operated, the change in the lateral gap shape is very small. In order to simplify the structure of the T die itself, it may be a structure without a die bolt.

  FIG. 2 shows an outline of a resin molding apparatus using a conventional T die. The T die 3 is provided at a discharge port of an injection device or an extrusion device (not shown). The molten resin 5 is discharged onto the lower mold 2 from the discharge port 4 of the T die 3. After the molten resin 5 is discharged, the T die 3 is retracted backward from between the upper and lower molds 1 and 2. Thereafter, the upper mold 1 and the lower mold 2 are clamped and molded to obtain a flat product.

(Problems of conventional technology)
When the shape of the discharge port of the T die is rectangular, the following problems have occurred:
(A) When the molten resin is discharged onto the lower mold, air is caught between the molten resin and the lower mold, and when the mold is clamped and molded, the molten resin cannot be discharged. Streaks or voids or the like are generated at the boundary between the portion in which air is entrained between the lower mold and the molten resin and the lower mold, and the molded product becomes defective.
(B) When the molten resin is discharged onto the lower mold and the upper mold and the lower mold are clamped, air is caught between the molten resin and the upper mold, Since the air cannot be discharged, streaks or voids are generated at the boundary between the portion where the air is entrained between the molten resin and the upper mold and the portion where the molten resin and the upper mold are in close contact with each other, and the molded product is not effective. It becomes a non-defective product.
JP-A-9-136343

  The present invention has been made in view of the problems in the conventional resin molding apparatus as described above. The object of the present invention is to enclose air between a mold and a molten resin when molding is performed by clamping. There is a need to provide a resin molding apparatus capable of preventing this.

The resin molding apparatus of the present invention is
In a resin molding apparatus for producing a flat product by discharging molten resin onto a mold through a T die using an injection device or an extrusion device provided with a T die at the discharge port, and then clamping the die ,
The shape of the discharge port of the T-die is such that the horizontal dimension (width) is larger than the vertical dimension (gap gap), the lower side is composed of a downwardly convex curve, and the vertical dimension is at both ends. It is comprised so that it may increase gradually toward a center part from a part.

  According to the resin molding apparatus of the present invention, since the shape of the discharge port of the T die is configured as described above, the molten resin discharged from the T die is first lowered at the lateral center of the lower side. After contact with the mold, the contact portion gradually spreads from the central portion toward both ends. Accordingly, the air between the molten resin and the lower mold is smoothly removed from the central portion toward both ends, and the air is not easily caught between the molten resin and the lower mold. In addition, since the molten resin discharged onto the lower mold has such a shape that the thickness gradually increases from both ends toward the center, the molten resin is placed between the upper and lower molds. When the mold is clamped and molded, the upper mold first comes into contact with the central portion in the lateral direction of the upper side of the molten resin, and then the contact portion gradually spreads from the central portion toward both ends. Accordingly, the air between the upper mold and the molten resin is smoothly removed from the central portion toward both ends, and the air is not easily caught between the upper mold and the molten resin.

  Furthermore, according to the resin molding apparatus of the present invention, the shape of the molten resin before being clamped and molded can be made close to the final product shape (that is, a flat plate shape). The amount can be minimized, and as a result, the dimensional accuracy and shape accuracy of the product can be increased, and the occurrence of defects such as defective appearance can be prevented.

  Preferably, the shape of the discharge port of the T-die is configured with a curved line having a convex lower side and a curved line having a convex upper side.

  For example, the shape of the discharge port of the T-die is such that the horizontal dimension is not less than 3 times and not more than 400 times the vertical dimension in the central part in the horizontal direction, and the vertical dimension in the central part is at both ends. 110% or more and 150% or less of the vertical dimension.

  In the above, the injection device is a device provided with a heating barrel and a screw, and the kneading, heating and melting are performed while rotating the screw in the heating barrel and introducing the resin into the heating barrel. After a fixed amount of molten resin is stored at the tip of the heating barrel, the screw is advanced in the heating barrel and the molten resin is discharged from the tip of the heating barrel.

  Further, the extrusion apparatus is an extruder that includes a heating barrel and a screw, rotates the screw in the heating barrel, kneads, heats and melts while introducing the resin into the heating barrel, and continuously feeds the molten resin. And a metering / injecting device that is connected to the tip of an extruder, stores a molten resin, and intermittently extrudes a certain amount of the molten resin.

  In addition, according to the resin molding apparatus of the present invention, it is possible to prevent the occurrence of defects such as streaks and voids and improve the dimensional accuracy and shape accuracy of the product.

  In FIG. 1, the outline | summary of the resin molding apparatus based on this invention is shown. In the figure, 1 is an upper mold, 2 is a lower mold, 3 is a T die, and 4 is a discharge port of the T die.

  The T die 3 is provided at a discharge port of an injection device or an extrusion device (not shown). The molten resin 5 is discharged onto the lower mold 2 from the discharge port 4 of the T die 3. After the molten resin 5 is discharged, the T die 3 is retracted backward from between the upper and lower molds 1 and 2. Thereafter, the upper mold 1 and the lower mold 2 are clamped and molded to obtain a flat product.

  In this example, the discharge port 4 of the T die 3 has a convex lens shape. That is, the left side and the right side corresponding to both ends are configured by straight lines, the lower side is configured by a downward convex curve, and the upper side is configured by an upward convex curve.

  As an example, when manufacturing a flat plate made of acrylic resin having a width of 350 mm, a thickness of 8 mm, and a length of 280 mm, the shape of the discharge port of the T die is 250 mm wide and the thickness of the left side and the right side is 12 mm, the curvature radius of the upper and lower sides is 7813 mm, and the thickness of the central part is 14 mm.

  By configuring the shape of the discharge port 4 of the T die 3 as described above, the air between the molten resin 5 and the lower mold 2 and the air between the upper mold 1 and the molten resin 5 are centered. It is smoothly removed from the part toward both ends, and air is not easily caught between the upper and lower molds and the molten resin. Thereby, according to the resin molding apparatus of the present invention, it is possible to prevent the occurrence of defects such as streaks and voids and to increase the dimensional accuracy and shape accuracy of the product.

The figure which shows the outline | summary of the resin molding apparatus of this invention. The figure which shows the outline | summary of the conventional resin molding apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Upper die, 2 ... Lower die, 3 ... T die, 4 ... Discharge port of T die, 5 ... Molten resin.

Claims (3)

In a resin molding apparatus for producing a flat product by discharging molten resin onto a mold through a T die using an injection device or an extrusion device provided with a T die at the discharge port, and then clamping the die ,
The shape of the discharge port of the T die is such that the horizontal dimension is larger than the vertical dimension, the lower side is composed of a downwardly convex curve, and the vertical dimension gradually increases from both ends toward the center. A resin molding apparatus configured to increase.   2. The resin molding apparatus according to claim 1, wherein a shape of the discharge port of the T-die is configured with a curved line having a convex lower side and a curved line having an upper convex side.   The shape of the discharge port of the T-die is such that the horizontal dimension is not less than 3 times and not more than 400 times the vertical dimension in the horizontal central part, and the vertical dimension of the central part is the vertical direction of both ends. The resin molding apparatus according to claim 1, wherein the dimension is 110% or more and 150% or less.

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