JP2010115859A - Mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold with which counter pressure is uniformly applied to a resin surface until the mold is filled completely with resin without being restricted by the structure of the mold. <P>SOLUTION: The mold of a half-pushing structure, in which a core mold and a cavity mold are constituted to engage with each other and the ventilation between a cavity formed by closing the molds and the outside of the mold is restricted, is used in a gas counter pressure molding method. At a prescribed position of the core mold to engage with the cavity mold, a shallow groove opened to the cavity and a supply/discharge groove are formed to communicate with each other in the mold opening/closing direction and the direction crossing the mold opening/closing direction, respectively. At a prescribed position of the cavity mold to engage with the core mold, a passage is formed which supplies/discharges gas into/from the cavity through the shallow groove and the supply/discharge groove. A connection opening of the passage which is formed in the outside surface of the mold is connected to a pressure source for supplying the gas so that the cavity can be freely pressurized with the mold closed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a mold used for a resin gas counter pressure molding method, and more particularly to a molding mold for obtaining a molded product by reducing and expanding a cavity volume after filling a resin in a cavity.

A gas counter pressure molding method is known as a molding method in which a molten resin in which a foaming agent is dissolved is injected and filled into a mold cavity to obtain a resin molded product having a cell structure inside and a smooth surface. . According to this molding method, since the molten resin is filled in the cavity pressurized to a pressure necessary to suppress the foaming of the resin, the foaming agent in the resin does not depressurize and foam, and the surface of the molded product The swirl mark (foaming pattern) is not formed.
In foam molding by the gas counter pressure molding method, an amount smaller than the cavity volume of the mold is injected and filled, and after filling, the cavity volume is reduced and filled into the cavity to solidify the surface layer, and then the cavity volume is expanded. The short shot method (low pressure method) for foaming resin and the full shot method (high pressure method) for injecting and filling the same volume as the cavity volume of the mold and expanding the cavity volume after the surface layer solidifies (high pressure method) )It has been known.

  The molding die used in the molding method in which the cavity volume is changed after injection filling with the molten resin in which the foaming agent is dissolved in the mold cavity described above is used in order to maintain the counter pressure in the cavity. It is necessary to improve the performance, and the ventilation between the cavity and the outside of the mold is restricted by using a seal or the like. The molding die has a so-called half-press structure so that the cavity mold and the core mold can be fitted together, and a cavity is formed by the cavity mold and the core mold. Furthermore, the core mold is configured to move in the mold opening / closing direction in a confidential state. (See Patent Document 1)

JP 2004-17285 A

However, the above-mentioned conventional molding die has a structure with increased confidentiality, and a heater for heating the cavity, a temperature adjusting flow path for adjusting the temperature, and temperature are detected around the cavity surface of the mold forming the cavity. A temperature sensor or the like is provided, and the mold has a gas passage for pressurizing and depressurizing the inside of the cavity.
For this reason, it is difficult to provide gas passages for pressurizing and depressurizing the inside of the cavities in all the final filling portions where the molten resin joins by filling the cavities, and depressurization is performed in the final filling portion of the resin. There was a problem that the counter pressure could not be applied uniformly to the resin surface until the filling of the resin was completed and the cavity was filled.

  The present invention pays attention to the problems of the prior art, and is not limited by the mold configuration of the molding mold, and can mold the counter pressure evenly on the resin surface until the resin filling is completed. The purpose is to provide.

In order to achieve the above object, the molding die according to the present invention is:
(1) Mold with a half-push structure used in a gas counter pressure molding method in which a core mold and a cavity mold are configured to be freely fitted, and ventilation between a cavity formed by closing the mold and the outside of the mold is restricted. A mold, provided with a shallow groove opened in a cavity at a predetermined position to be fitted with the core mold of the core mold in the mold opening / closing direction, and a supply / discharge groove to communicate with each other in the mold opening / closing direction, A passage for supplying and discharging gas into the cavity through the shallow groove and supply / exhaust groove is provided at a predetermined position where the cavity mold is fitted with the core mold, and the connection of the passage provided on the outer surface of the mold is provided. The mouth is connected to a pressure source for supplying gas, so that the inside of the cavity can be pressurized in a closed state of the mold.
(2) The predetermined position of the shallow groove was used as the final filling portion of the resin.

According to the molding die of the present invention, the supply / discharge groove and the shallow groove communicating with the passage for supplying / discharging the counter gas provided in the mold are provided at a predetermined position where the mold is fitted with the core mold. Even in the mold configuration in which the confidentiality of the cavity is enhanced in the mold closed state, the counter pressure can be applied to the cavity.
In addition, since the above-described configuration is used that does not use a mechanism having a mechanism for supplying and discharging the counter gas, it is possible to reduce the cost required for manufacturing and maintaining the mold.
And since it was set as the structure which provides the shallow groove | channel opened in the cavity in the final filling part of resin, a counter pressure can be made to act uniformly on the resin surface until the filling of resin is completed. Therefore, molding defects of the molded product due to the counter gas remaining in the cavity, for example, gas burning, etc. do not occur, and a high quality molded product can be obtained.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.
FIG. 1 relates to an embodiment of the present invention and is a longitudinal sectional view of a molding die showing a preferred example of the embodiment. FIG. 2 is a longitudinal sectional view of FIG. 1 cut in the mold closing direction.
As shown in FIG. 1, the molding die is composed of a mold 10 and a core mold 11 which can be contacted and separated, and the cavity 12 is formed by closing the mold 10 and the core mold 11 together. . The core mold 11 is configured to be fitted to the inner peripheral portion of the mold 10, and the shallow groove 13 and the supply / discharge groove 14 are formed in the mating section of the core mold 11 with the mold 10. A counter gas passage 15 communicating with the shallow groove 13 and the supply / discharge groove 14 is provided at the fitting portion with the mold 10.
Around the cavity surfaces of the cavity mold 10 and the core mold 11, passages 17 and 18 to which a medium for accurately controlling the temperature of the cavity 12 is supplied are arranged so as to be distributed substantially evenly on the cavity surface. . Reference numeral 20 denotes a molten resin in which a foaming agent injected and filled into the cavity 12 is dissolved.

The main part of the supply means for the counter gas is constituted by a pressure source 31, a check valve 32, a solenoid valve 33, a relief valve 34, a silencer 35, a pressure gauge 36, and a pipe 37. A connection port 16 to which a pipe 37 is connected is provided on the outer surface of the mold of the passage 15, and counter gas is supplied from the gas source 31 to the cavity 12 with the mold closed.
The gas pressure source 31 is substantially constituted by a gas cylinder and pressure adjusting means, and the check valve 32 prevents gas from flowing into the gas pressure source 31 side when the cavity 12 is filled with molten resin. By exciting the electromagnetic valve 33, the gas pressure source 31 and the cavity 12 communicate with each other and the counter gas is supplied. A predetermined pressure acting in the cavity 12 is set by a relief valve 35, and the pressure is confirmed by a pressure gauge 36. Reference numeral 34 denotes a silencer, which silences and reduces the discharge sound of the gas discharged from the relief valve 35.

As shown in FIG. 2, a shallow groove 13 opened in the cavity 12 is connected to the shallow groove 13 in the opening and closing direction of the mold in the fitting portion of the core mold 11 which is the final filling portion of the molten resin, and the supply / discharge groove 14 Is provided so as to extend in a direction intersecting with the opening and closing direction of the mold. Supply and discharge of the counter gas into the cavity 12 is performed via the pipe 31 and the passage 15.
The passage 15 provided in the mold 10 is arranged at a position avoiding the passage 17 to which a medium for adjusting the temperature of the mold is supplied. By extending the supply / discharge groove 14, the passage 15 can be arranged without being constrained by the position of the shallow groove 13, and is not affected by the arrangement of the medium passage 17.
And in this Embodiment, the shallow groove | channel 13 is arrange | positioned at the four corners of the molded product (square shape) used as the final filling part of resin.

The mold 10 is attached to a fixed plate of a molding apparatus (not shown), and the core mold 11 is attached to a movable plate of the molding apparatus. FIG. 1 shows an injection process for filling a cavity 12 expanded by a predetermined volume with respect to the volume of a molded product in a state where a gap is opened without the cavity mold 10 and the core mold 11 abutting on the parting surface. Is shown. In the middle of filling the cavity 12 with the molten resin 20 or after completion of the filling, primary molding is obtained by a pressing process in which the core mold 11 is advanced to bring both molds into contact with each other.
The counter gas in the cavity 12 acts until the molten resin 20 reaches the shallow groove 13 in both the injection process and the pressing process, so that the counter gas does not remain in the cavity 12.

A skin layer is formed by maintaining the mold closed state after completion of the pressing step. After the skin layer is formed, the core mold 11 is opened and held by a predetermined amount to foam the inside of the primary molded product, and the outer surface A foam molded article having a three-layer structure in which is a skin layer and the inside is a foam layer.
In the injection process and the press process described above, the inside of the cavity is previously maintained at a predetermined counter pressure, and the gas in the cavity whose volume decreases as the resin is filled is discharged from the relief valve 34. Then, the supply of the counter gas is stopped with the completion of the pressing process.
The final filling portion of the resin provided with the shallow groove in the present invention includes a specific place where the molded product is finally filled in the molded product, and the molten resin filled in the cavity flows and joins from different directions. This refers to a plurality of locations generated by molding conditions such as the shape of the molded product, the resin molding material, and the filling speed.

As an embodiment of the invention, a molten resin in an amount smaller than the cavity volume of the mold is injected and filled, and then the cavity volume is reduced to fill the cavity with the molten resin to form a skin layer, and then the cavity volume is expanded. The molding method in which the inside is foamed is formed by injection molding with the same amount of molten resin as the cavity volume of the mold, and after the surface layer is solidified, the cavity volume is expanded to foam the resin inside (so-called high-pressure). Pressure method) can also be used.
The mold structure that increases confidentiality when the mold is closed uses a seal member for the ejector pin of the product extrusion mechanism, and sets a predetermined gap and fitting length for the fitting part of the mold. It can be carried out by known means such as.

As described above, a gas counter molding die having a half-push structure in which the confidentiality of the cavity is ensured and the counter pressure in the cavity is maintained, and the fitting portion (cut-off or shear edge) of the die The molten gas final filling position was provided with a counter gas supply / exhaust port. For this reason, the counter pressure can be applied to the resin surface until the resin is filled in the cavity, and gas stagnation or stagnation caused by the gas supply / exhaust port being clogged with the resin filled during resin filling. Gas is not adiabatically compressed. Further, molding defects due to residual gas can be prevented.
Foam molding was performed by a low pressure method using the molding die according to the present invention, and a foam molded product having excellent surface properties without surface defects such as swirl marks and gas burns could be obtained.

It is a longitudinal cross-sectional view of the metal mold | die which shows one Example of this invention. It is the longitudinal cross-sectional view which cut | disconnected FIG. 1 in the mold closing direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Cavity type | mold 11 Core type | mold 12 Cavity 13 Shallow groove 14 Supply / exhaust groove 15 Passage 16 Connection port 31 Pressure source

Claims (2)

This is a half-indented molding die used in a gas counter pressure molding method in which the core die and the cavity die are configured to be freely fitted, and the ventilation between the cavity formed by closing the die and the outside of the die is restricted. And
A shallow groove opened in a cavity at a predetermined position to be fitted with the core mold of the core mold is provided in the mold opening / closing direction, and a supply / discharge groove is provided so as to communicate with the mold opening / closing direction and the intersecting direction,
A passage for supplying and discharging gas into the cavity through the shallow groove and the supply / discharge groove is provided at a predetermined position where the mold is fitted with the core mold,
A molding die, wherein a connection port of the passage provided on the outer surface of the die is connected to a pressure source for supplying a gas so that the inside of the cavity can be pressurized in a closed state of the die. 2. The molding die according to claim 1, wherein a predetermined position of the shallow groove is a final filling portion of resin.

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