JP3197981B2 - Injection molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding method , and more particularly, to a gate seal injection molding apparatus suitable for injection molding of an optical element such as a plastic lens and the like, and can be applied to an injection molding method using the same. In particular, the present invention relates to a molding method capable of shortening a molding cycle, reducing a mold cost, and obtaining a high-quality resin molded product with little residual distortion or the like.

[0002]

2. Description of the Related Art Conventionally, in a resin molding method, as shown in FIG. 5, a mold temperature is raised by program control so as to increase the fluidity of a resin, the mold temperature is raised, and then cooling ( It is known that, by rapidly cooling) while keeping the cooling rate low near the glass transition temperature of the resin and applying pressure at the same time, it is possible to obtain a molded product having a high mold copy degree by removing distortion inside the molded product. Have been.

Now, plastic resin molded articles to be used as optical parts such as lenses are required to satisfy required characteristics such as surface accuracy and internal distortion.
Since the latter internal distortion causes disturbance of the transmitted light path,
It is required to reduce as much as possible.

[0004]

However, in the conventional resin molding method as described above, as shown in FIG.
The resin filled in the cavity is heated to near the melting temperature after injection to reduce the efficiency, and the cooling (quenching) process is started after holding for a certain period of time. In addition, the quenching speed is kept low (gradual cooling) near the glass transition point of the resin, and at the same time, the pressurization is performed. There was a problem that cost increased.

[0005] Further, when trying to mold a resin molded product having an uneven thickness and a different shape, the thin portion solidifies quickly, and the thin portion is solidified even when the entire molded product is pressed by the moving core. The resin does not move, resulting in "shrinkage" without pressing the thick part. In addition, when the thin part is forcibly pressed in a solidified state, stress is generated in the thin part and distortion occurs. was there.

[0006] The present invention aims to provide a molding method capable of obtaining Rutotomoni can reduce mold cost, less quality resin molded article having such residual Tomeibitsu.

[0007]

According to the first aspect of the present invention,
A plurality of cavity units each having a pair of molds each having a cavity formed therein are transported in the order of a predetermined heating station, a filling / relaxation station, a slow cooling station, and a molded product removal station, and correspond to the cavity. A molding apparatus having a molding system for molding a resin molded article having a shape , wherein an injection filling means of the filling / relaxation station comprises an injection molding machine, and a die plate of the injection molding machine is provided with a mold temperature adjusting mechanism. And prepare the
Molding resin molded products by injection molding using molding equipment
The injection at the filling / relaxation station
Mold temperature set lower than glass transition temperature of resin
Then, after the injection, the mold temperature is higher than the glass transition point of the resin.
It is characterized in that the temperature is raised while keeping the mold closed until the temperature reaches the temperature .

According to a second aspect of the present invention, a cavity is provided in the inside.
A plurality of cavities each having a pair of molds in which
Heating unit, filling / relaxation
Station, slow cooling station and molded product removal station
And the shape corresponding to the cavity
Having a molding system for molding a resin molded product of
・ The injection filling means of the relaxation station is
And a die temperature controller for the die plate of the injection molding machine.
Prepare a molding device provided with a structure, using the molding device
In a method of molding a resin molded product by an injection molding method,
The cavity was filled at the filling / relaxation station
After once heating the resin to above the glass transition point of the resin,
It is characterized by slow cooling .

[0013]

According to the first aspect of the present invention, a plurality of cavity units each having a pair of molds each having a cavity formed therein are provided in a predetermined heating station, a filling / relaxation station, a slow cooling station, and a molded product removal station. And a molding system for molding a resin molded product having a shape corresponding to the cavity. The injection / filling means of the filling / relaxation station comprises an injection molding machine, and the die plate of the injection molding machine has a metal plate. Since the mold temperature adjusting mechanism is provided, the plurality of cavity units can be formed in a low-cost and simple structure without a temperature adjusting member, so that the manufacturing cost of the molding apparatus can be reduced. Ma
In addition, the mold temperature during injection at the filling / relaxation station is
Is set lower than the glass transition temperature of
The mold temperature is set to a temperature not lower than the glass transition point of the resin in consideration of the pressure.
Temperature while holding the mold closed
You. For this reason, the mold temperature after injection can be lowered,
It is possible to obtain high quality molded products with less distortion and less.
Wear. According to the second aspect of the present invention, the cavity is formed inside.
A plurality of cavity units each having a pair of molds formed.
Place the knit in the specified heating station, filling / relaxation
Station, slow cooling station and molded product removal station
In the order of the cavity, and a tree of the shape corresponding to the cavity.
It has a molding system for molding fat molded products,
The injection filling means of the station comprises an injection molding machine, and
A mold temperature adjusting mechanism is provided on the die plate of the injection molding machine.
Temperature control unit
Low cost and simple structure without any material
Thus, the manufacturing cost of the molding device can be reduced. Ma
The cavity was filled at the filling and relaxation station
Resin is once more than the glass transition point of the resin considering the pressure
After heating to, it is configured to be gradually cooled. others
As the molten resin fills the mold, it retains fluidity
This can promote relaxation and reduce internal strain etc.
A good molded product can be obtained.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a molding system applied to a molding method according to an embodiment of the present invention. The illustrated molding system is a case where the molding system is applied to a gate seal molding system. In FIG. 1, reference numeral 1 denotes a plurality of cavity units each having a pair of molds each having a cavity formed therein. Reference numeral 2 denotes a heating station for heating the cavity unit 1; Filling / relaxing filled cavity unit 1
It is a relaxation station. Reference numeral 4 denotes a slow cooling station for gradually cooling the cavity unit 1 filled and relaxed in the filling / relaxation station 3, and reference numeral 5 denotes a molded product for removing the molded product from the cavity unit 1 gradually cooled in the slow cooling station 4. A take-out station, 6 is a transfer path between the stations where the cavity unit 1 processed in each station is transferred, and 7a to 7c are heating stages for heating the cavity unit 1 provided in the heating station 2. .

Next, FIG. 2 is a diagram showing the configuration of the filling / relaxation station of FIG. The filling / relaxation station 3 in the illustrated example comprises a vertical injection molding machine. 2, the same reference numerals as those in FIG. 1 denote the same or corresponding parts, 8 denotes a die plate of an injection molding machine, 9 denotes a die temperature adjusting mechanism provided on the die plate 8, and The mechanism 9 includes a heating plate 10 made of metal and a resistance heater 11 provided in the heating plate 10.

Next, the molding process of this embodiment will be described. First, the cavity unit 1 is connected to the heating station 2
And heat the mold near the cavity of the mold to 165 ° C.
Heat to Next, the cavity unit 1
After the temperature reaches 65 ° C, 2
The PC which is heated to 70 ° C to 300 ° C and is in a molten state
(Polycarbonate) resin into the cavity, for example, 10
High pressure filling of 00 kgf / cm ² is performed.

Next, immediately after filling (instead of maintaining the same temperature until the end of relaxation), the die plate 8 of the injection molding machine is used.
Is heated to a temperature equal to or higher than the glass transition point of the resin in consideration of the pressure by the mold temperature adjusting mechanism 9 provided in the above, to increase the fluidity of the resin, sufficiently promote relaxation, and remove internal strain.

Thereafter, the temperature is reduced to 5 ° C. /
The molded product is slowly cooled to a heat deformation temperature or less (solidification temperature) at a cooling rate of not more than one minute, and the molded product is taken out at the molded product taking out station 5. As described above, in the present embodiment, a plurality of cavity units 1 each having a pair of molds each having a cavity formed therein are combined with a predetermined heating station 2, a filling / relaxation station 3, a slow cooling station 4, and a molded product. In a molding apparatus having a molding system for conveying a resin molded product having a shape corresponding to the cavity in the order of the removal station 5, the injection / filling means of the filling / relaxation station 3 is constituted by an injection molding machine. The mold temperature adjusting mechanism 9 is provided on the die plate 8 of the molding machine. For this reason, the plurality of cavity units 1 can have a simple structure at a low cost without a temperature adjusting member, so that the manufacturing cost of the molding apparatus can be reduced.

Further, in the present embodiment, the molding system is provided with the cavity unit 1 having the cavity filled with resin.
Is a gate seal molding system for sealing the gate. For this reason, since the molding system is configured as a gate seal molding system, high-precision precision molding can be performed. In the present embodiment, a plurality of mold temperature adjusting mechanisms 9 are provided. For this reason,
Since a plurality of mold temperature adjusting mechanisms 9 are provided, the temperature of the cavity unit 1 can be quickly adjusted (increased in temperature).

In this embodiment, the mold temperature adjusting mechanism 9 is used.
Is formed by a heating plate made of metal. For this reason, since the mold temperature adjusting mechanism 9 is constituted by the metal heating plate 10 having good thermal conductivity, rapid heating can be performed, and efficient temperature increase can be performed. Further, in the present embodiment, the heating means of the mold temperature adjusting mechanism 9 is constituted by the resistance heater 11. Therefore, the cavity unit can be quickly heated to the target temperature. The heating means of the mold temperature adjusting mechanism 9 may be constituted by high-frequency induction heating. In this case, the same effect as that of the resistance heater 11 can be obtained.

Further, in this embodiment, in the method of molding a resin molded article by the injection molding method, the resin filled in the cavity in the filling / relaxation station 3 is heated to a temperature equal to or higher than the glass transition point of the resin in consideration of the pressure. After that, it is configured to be gradually cooled. For this reason, since the fluidity of the resin can be increased, relaxation can be promoted, and a high-quality molded product with little internal distortion or the like can be obtained.

Further, in the present embodiment, in the method of molding a resin molded product by the injection molding method, the filling / relaxation station 3 sets the mold temperature at the time of injection to a temperature lower than the glass transition point temperature of the resin. Thereafter, the temperature of the mold is raised while the mold is clamped until the temperature of the mold becomes equal to or higher than the glass transition point of the resin in consideration of the pressure. For this reason, it is possible to obtain a high-quality molded product with less burrs and less distortion and the like.

FIG. 3 shows changes in pressure and temperature during the molding process. The upper part is a time-pressure curve, and the lower part is a time-temperature curve. In the molding method of the present embodiment, as shown in FIG. 3, the mold temperature at the time of injection of the cavity unit 1 can be made lower than 170 ° C. at the time of injection at the time of the conventional cavity unit molding. In addition, it is possible to obtain a molded product having less internal distortion. FIG.
(A)-(c) have shown the state of the distortion by a polarizing plate. Conventional method (see Fig. 3-) 170 ° C (mold temperature at injection) → 1
Strain state at 70 ° C. (mold temperature at the start of slow cooling) Compared with FIG. 4A, the present invention (see FIG. 3) 165 ° C. (mold temperature at injection) → 1
The strain state in FIG. 4C is much better than 70 ° C. (the mold temperature at the start of slow cooling).

Further, in this embodiment, the heating time by the heating station 2 can be shortened by the lower mold temperature at the time of injection. In the above embodiment, the resin used was PC, but the present invention is not limited to this, and any resin may be used as long as it is a thermoplastic resin for optical use. Next, in the present invention, the mold temperature adjusting mechanism may be configured to use oil as a medium. In this case, the mechanism for bringing the heating plate into close contact with the cavity unit is a hydraulic mechanism, and the oil is used in the mold. Since it is configured as a medium of the temperature adjusting mechanism, it is possible to prevent rust or the like from occurring in the mold temperature adjusting mechanism.

Next, in the present invention, a heating stage may be provided in the conveying path immediately before the injection molding machine at the filling / relaxation station. Since the heating can be performed, the mold heating time can be further reduced, and the molding cycle can be further reduced.

[0032]

According to the present invention, there is an effect that can be obtained Rutotomoni can reduce equipment costs, less quality resin molded article having such residual Tomeibitsu.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a molding system applied to a molding method according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a filling / relaxation station of FIG. 1;

FIG. 3 is a diagram showing pressure and temperature changes during a molding process of the present invention and a conventional example.

FIG. 4 is a view showing a distortion improving effect of a molded article of the present invention.

FIG. 5 is a view showing a molding step of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cavity unit 2 Heating station 3 Filling / relaxation station 4 Slow cooling station 5 Mold removal station 6 Conveying path 7a-7c Heating stage 8 Die plate 9 Mold temperature adjustment mechanism 10 Heating plate 11 Resistance heater

Claims (2)

(57) [Claims] A plurality of cavity units each having a pair of molds each having a cavity formed therein are transported in the order of a predetermined heating station, a filling / relaxation station, a slow cooling station, and a molded product removal station, and A molding system for molding a resin molded product having a shape corresponding to the cavity , wherein the injection / filling means of the filling / relaxation station comprises an injection molding machine, and a die temperature adjusting mechanism for a die plate of the injection molding machine. A molding apparatus is prepared, and resin molding is performed by the injection molding method using the molding apparatus.
In the method of forming a shaped article, the filling / relaxation station
Injection mold temperature from resin glass transition temperature
After the injection, the mold temperature is set to a low temperature.
Keep the mold clamped until the temperature is above the transition point.
And an injection molding method. 2. A pair of pairs each having a cavity formed therein.
A plurality of cavity units having molds are
Heating station, filling / relaxation station, slow cooling stay
Transport in the order of the
Molding a resin molded product having a shape corresponding to the cavity
Having a molding system,
The filling means comprises an injection molding machine, and
Molding device with die temperature adjustment mechanism on die plate
Is prepared, and resin molding is performed by an injection molding method using the molding apparatus.
In the method of forming a shaped article, the filling / relaxation station
Once the resin filled in the cavity by the
It is characterized by gradually cooling after heating to above the transition point.
Injection molding method.