JP3854537B2 - Thermoplastic resin foam molding method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for molding a thermoplastic resin foam using a supercritical fluid.
[0002]
[Prior art]
In recent years, a method for forming a thermoplastic resin foam using a supercritical fluid has been developed. Since the supercritical fluid has a solubility close to that of a liquid and a diffusibility and permeability similar to those of a gas, it is impregnated into the resin in a short time. In addition, by using a supercritical fluid, it is possible to form fine foam cells inside the resin, which were difficult with conventional chemical foaming methods and gas foaming methods, etc., so that it is possible to manufacture lightweight and high-rigidity foams. Can do. The formation method underlying this foam is described in US Pat. No. 5,158,986. According to this publication, 1) a thermoplastic resin is formed into a sheet by extrusion molding, and the sheet is made into CO in a supercritical state. ₂ CO is a supercritical fluid in the resin sheet by introducing it into the pressurized chamber filled with ₂ And a method of forming a foam by heating and foaming in a foaming chamber at atmospheric pressure, or 2) supercritical CO into the resin while melting the resin with an extruder. ₂ The molded product extruded into a sheet shape is introduced into a pressure chamber, a cell nucleus that becomes a foam is formed by a pressure change in the pressure chamber, and the cell nucleus is heated and cooled to obtain a desired cell diameter. And a method for obtaining the cell density is disclosed.
[0003]
As an example of molding the foam by injection molding, a supercritical state CO is added to a thermoplastic resin melted in a cylinder of an injection molding machine. ₂ An apparatus and a molding method for impregnating an inert gas such as the above, injecting and filling the thermoplastic resin into the mold, and then foaming by reducing the pressure in the mold are disclosed in Japanese Patent Laid-Open Nos. 08-258096 and 10- 230305, Japanese Patent Laid-Open No. 2001-9882, and the like. In Japanese Patent Laid-Open No. 10-230528, after injection filling with a molten resin, a part or the entire surface of the mold is retracted to increase the cavity volume, and the inside of the cavity is decompressed to control foaming of the thermoplastic resin.
[0004]
[Problems to be solved by the invention]
However, in the above injection molding method, since the molten resin impregnated with the supercritical fluid is injected and filled with the cavity closed by clamping, particularly in the case of a molded product having a thin surface and a large surface area, The pressure difference in the resin becomes large at the end of the cavity. Therefore, in order to fill the molten resin up to the end of the cavity, it is necessary to increase the injection filling pressure of the molten resin. Along with this, the mold clamping pressure of the cavity that can withstand the filling pressure is required, but increasing the mold clamping pressure increases the flow resistance of the molten resin to be filled, which further increases the pressure difference in the cavity. It becomes.
[0005]
Further, the supercritical fluid impregnated in the molten resin pressurized by the plasticizing cylinder of the injection molding machine is gasified by being depressurized when injected into the cavity, and foams from the surface of the molten resin. Therefore, when a smooth non-foamed layer is formed on the resin surface layer, it is necessary to prevent the surface of the molten resin from being cooled and solidified while being in a foamed state. Therefore, in the conventional molding method using a supercritical fluid, the mold surface and its vicinity are made of a material having low thermal conductivity, thereby suppressing the heat quantity of the molten resin from being taken away by the mold, A method for suppressing rapid cooling has been proposed. According to this method, the viscosity of the resin is lowered, and the transferability of the mold pattern to the resin is improved. However, in order to form a foam layer inside the resin, it is necessary to reduce the cavity internal pressure with a low viscosity inside the resin after the non-foamed skin layer is formed on the resin surface. On the other hand, in order to transfer a fine mold pattern to the resin surface, it is necessary to increase the cavity internal pressure and allow the molten resin to sufficiently enter the mold pattern. It is difficult to satisfy these conditions at the same time, and it has not been possible to obtain a stable foam.
[0006]
An object of the present invention is to provide a novel molding method of a thermoplastic resin foam having a foam layer having a uniform thickness inside the thermoplastic resin.
[0007]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a method of molding a thermoplastic resin foam by filling a mold with a molten resin,
Pressurized CO to the molten resin ₂ Impregnating with;
CO ₂ In a mold container placed in a chamber filled with ₂ Filling with molten resin impregnated with;
Pressurizing the molten resin filled in the mold container with a press mold;
There is provided a method for molding a thermoplastic resin foam, which includes foaming the molten resin by increasing the volume of the space defined by the mold container and the press mold after pressurizing the molten resin.
[0008]
In the present invention, for example, supercritical CO 2 ₂ Injection molding is performed using a molten resin impregnated in advance. The molten resin is pre-CO 2 ₂ Is filled in a mold container having an open upper surface. Since the mold container has an open upper surface, the flow resistance when the molten resin is filled is extremely low, so that a pressure difference of the molten resin does not occur in the container. CO filled in the chamber in advance ₂ By functioning as a plasticizer for the molten resin, the viscosity of the molten resin is kept low. Due to the low flow resistance and low viscosity of the molten resin, the molten resin sufficiently spreads to the end of the mold, and the molten resin sufficiently penetrates into the molding pattern formed on the bottom surface of the mold container. Next, the mold container is clamped by closing the open surface of the mold container using a press mold and pressurizing the molten resin. When the surface of the molten resin is cooled and solidified by the mold container and the press mold, the mold pattern is transferred to the molten resin. Furthermore, the press mold is moved relative to the mold container to increase the volume of the space defined by the mold container and the press mold. Thereby, the pressure inside a space falls and molten resin expand | swells. At the same time, the CO previously impregnated in the molten resin ₂ Vaporizes due to the pressure drop, and the inside of the molten resin becomes foamed. By cooling the molten resin in this state, a thermoplastic resin foam can be obtained.
[0009]
According to a second aspect of the present invention, there is provided a method of molding a thermoplastic resin foam by filling a mold with a molten resin,
Pressurized CO to the molten resin ₂ Impregnating with;
CO ₂ In a mold container placed in a chamber filled with ₂ Filling with molten resin impregnated with;
Pressurizing the molten resin filled in the mold container with a press mold;
After pressurizing the molten resin, CO in the space defined by the mold container and the press mold ₂ There is provided a method for molding a thermoplastic resin foam, which comprises lowering the pressure of the molten resin to foam the molten resin.
[0010]
In the present invention, for example, supercritical CO 2 ₂ Injection molding is performed using a molten resin impregnated in advance. The molten resin is pre-CO 2 ₂ Is filled in a mold container having an open upper surface. Since the mold container has an open upper surface, the flow resistance when the molten resin is filled is extremely low, so that a pressure difference of the molten resin does not occur in the container. CO filled in the chamber in advance ₂ By functioning as a plasticizer for the molten resin, the viscosity of the molten resin is kept low. Due to the low flow resistance and low viscosity of the molten resin, the molten resin sufficiently spreads to the end of the mold, and the molten resin sufficiently penetrates into the molding pattern formed on the bottom surface of the mold container. Next, the mold container is clamped by closing the open surface of the mold container using a press mold and pressurizing the molten resin. When the surface of the molten resin is cooled and solidified by the mold container and the press mold, the mold pattern is transferred to the molten resin. Furthermore, CO in the space defined by the mold container and the press mold ₂ The pressure of CO is, for example, through a passage provided inside the press die and an exhaust pipe provided outside the press die. ₂ Is reduced by evacuating the chamber outside. At the same time, the CO previously impregnated in the molten resin ₂ Vaporizes due to the pressure drop, and the inside of the molten resin becomes foamed. By cooling the molten resin in this state, a thermoplastic resin foam can be obtained.
[0011]
In the first and second aspects of the present invention, the step of pressurizing the molten resin with a press die and / or the foaming step is performed by CO ₂ It may be carried out in a chamber filled with or may be carried out by transferring the mold container to another place.
[0012]
According to a third aspect of the present invention, there is provided a method of molding a thermoplastic resin foam,
Pressurized CO to molten resin ₂ Impregnating with;
CO ₂ Is placed in a chamber filled with and the top surface is opened ₂ Filling with molten resin impregnated with;
The molten resin filled in the container is converted into CO in the chamber. ₂ There is provided a method for molding a thermoplastic resin foam, which comprises foaming by lowering the pressure.
[0013]
In the present invention, for example, supercritical CO 2 ₂ Injection molding is performed using a molten resin impregnated in advance. The molten resin is pre-CO 2 ₂ In a chamber filled with, a container whose upper surface is opened is injection-filled. Since the container has an open upper surface, the flow resistance when the molten resin is filled is extremely low, so that a pressure difference of the molten resin does not occur in the container. CO filled in the chamber in advance ₂ By functioning as a plasticizer for the molten resin, the viscosity of the molten resin is kept low. Due to the low flow resistance and low viscosity of the molten resin, the molten resin sufficiently spreads to the end of the container, and the molten resin sufficiently penetrates into the molding pattern formed on the bottom surface of the container. Next, if necessary, for example, the container is rotated using a rotary stage or the like to uniformize the thickness of the molten resin on the container, and then the CO in the chamber is ₂ Reduce the pressure. This reduces the pressure inside the chamber. At the same time, the CO previously impregnated in the molten resin ₂ Vaporizes due to the pressure drop, and the inside of the molten resin becomes foamed. By cooling the molten resin in this state, a thermoplastic resin foam can be obtained.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.
[0015]
[Example 1]
A molding apparatus for molding the thermoplastic resin foam used in the present invention will be described with reference to FIGS. As shown in FIG. 2, the present molding apparatus mainly includes a chamber 1, an injection filling unit 5, a mold clamping unit 4, a molded product extraction unit 21, and a moving mold preheating unit 22. FIG. 1 is a view showing a cross section taken along line A′-A ′ in FIG. 2.
[0016]
As shown in FIG. 2, the chamber 1 is formed in a cylindrical shape having a diameter of 1000 mm and a height of 200 mm. The interior of the chamber 1 is divided into four sub-chambers 11, 12, 13 and 14 by walls 15, 16, 17 and 18 extending radially to the outer periphery around the central axis AX of the cylinder. . Each of the walls 15, 16, 17 and 18 can be moved up and down by a mechanism (not shown) that moves up and down. For example, the sub chamber 11 is sealed when the walls 15 and 16 are raised. The chamber 1 is provided with a transfer device 19 for rotating the moving mold 20 around the central axis AX of the chamber 1. The transport device 19 includes a rotor 100 positioned on the central axis AX and four arms 101 extending radially from the rotor 100, and a movable mold 20 is held at the tip of each arm. A chuck (not shown) is provided. Only when the moving mold 20 moves between the sub-chambers due to the rotation of the rotor 100 (clockwise), when the corresponding wall is lowered to connect the atmosphere between the sub-chambers, and the movement of the moving mold 20 is completed, The corresponding wall rises and isolates the subchambers again. As shown in FIG. 2, the moving mold 20 sequentially moves through the sub-chambers 11 to 14 by the rotation of the rotor 100, and work is performed in each sub-chamber. In the subchamber 11, resin injection molding and mold clamping (compression) are performed on the movable mold 20. The sub-chambers 12 and 14 are standby chambers. In the sub-chamber 13, the molded product is taken out and the moving mold 20 is heated.
[0017]
Each moving mold 20 is a cylindrical metal container made of HPM 38 made by Hitachi Metals, which is a steel material for molds. As shown in FIG. 3, a stamper 23 on which a desired concavo-convex pattern is formed is installed on the bottom surface 20 a of the moving mold 20 via a stamper presser (not shown).
[0018]
As shown in FIGS. 1 and 2, an injection filling unit 5 and a mold clamping unit 4 are arranged above the sub chamber 11 in order in the clockwise direction. The injection filling unit 5 and the mold clamping unit 4 perform injection filling of the molten resin into the movable mold 20 and mold clamping in the sub chamber 11, respectively.
[0019]
In the sub-chamber 13 facing the sub-chamber 11 with respect to the central axis AX, a molded product take-out part 21 and a moving mold preheating part 22 are provided, and the inside of the sub-chamber 13 is maintained in an atmospheric pressure state. High-frequency induction heating, microwave heating, or the like is used as heating means in the moving mold preheating unit 22. By heating the moving mold 20 in advance, the temperature of the molten resin injected and filled on the moving mold 20 can be maintained at the glass transition temperature or higher.
[0020]
As shown in FIG. 1, the injection filling section 5 includes a molten resin plasticizing section 2, an injection section 3, and a stage 70. The plasticizing part 2 and the injection part 3 are constituted by a screw / prepa type injection mechanism. The plasticizing part 2 is arranged so that the nozzle 2 ′ at the tip is obliquely downward with respect to the horizontal plane. The plasticizing unit 2 is mainly composed of a cylinder 33, a screw 37 and a heater 36. The screw 37 is disposed inside the cylinder 33 and plasticizes the molten resin filled in the cylinder 33. The heater 36 is disposed around the cylinder 33 and heats the cylinder 33 in order to maintain the plastic state of the molten resin plasticized in the cylinder 33. A first vent port 34 and a second vent port 35 are formed on the side surface of the cylinder 33. The first vent port 34 is used for exhausting the volatile gas such as the monomer component generated from the resin plasticized by the rotation of the screw 37 in the cylinder 33 to the outside using the vacuum pump 32. The second vent port 35 is a pressurized CO in a supercritical state. ₂ CO ₂ Pressurized CO from the gas cylinder 38 ₂ It is used for filling the cylinder 33 through the generator 39.
[0021]
The injection unit 3 includes an injection cylinder 40 and a gate opening / closing cylinder 42. The injection cylinder 40 is disposed below the plasticizing part 2 and extends in the horizontal direction. An injection plunger 41 is disposed inside the injection cylinder 40, and the molten resin filled in the injection cylinder 40 is injected. The injection plunger 41 is disposed at a position retracted from a molten resin supply port 40 ′ formed near the tip of the injection cylinder 40. Depending on the position of the injection plunger 41, the amount of molten resin to be injected and filled into the movable mold 20 through the gate opening / closing cylinder 42 is determined. Further, the inside of the injection cylinder 40 and the nozzle 2 ′ of the plasticizing unit 2 communicate with each other through the molten resin supply port 40 ′ of the injection cylinder 40. The gate opening / closing cylinder 42 extends in the vertical direction adjacent to the distal end portion of the injection cylinder 40, and the distal end reaches the inside of the sub-chamber 11. A gate opening / closing piston 45 is disposed inside the gate opening / closing cylinder 42, and the molten resin filled in the gate opening / closing cylinder 42 is injected into the sub chamber by the gate opening / closing piston 45. Further, a band heater 43 is installed around the gate opening / closing cylinder 42, and the temperature control of the molten resin filled in the gate opening / closing cylinder 42 is performed by the band heater 43. The nozzle 40 ″ of the injection cylinder 40 communicates with the gate opening / closing cylinder 42 at a predetermined height position. The stage 70 is disposed in the sub chamber 11 below the gate opening / closing cylinder 42. It is installed on the motor 90 so as to be rotatable about the axis BX of the motor 90. On the upper surface of the stage 70, the moving mold 20 conveyed by the conveying device (19) is placed, and this moving mold is placed. 20 is injection-filled with molten resin.
[0022]
As shown in FIG. 1, the mold clamping unit 4 mainly includes a press stage 50, a stage driver 51, and a press cylinder 52. The press stage 50 is installed on the upper surface of the stage driver 51 inside the sub chamber 11. Further, on the upper surface of the press stage 50, the moving mold 20 conveyed by the conveying device (19) from the injection filling unit 5 is placed. By driving the stage driver 51, the movable mold 20 moves up and down via the press stage 50. The press cylinder 52 is installed in the upper part of the sub chamber 11. Inside the press cylinder 52, a press piston 53 that moves vertically in the cylinder is installed. A press die 54 is attached to the lower surface of the press piston 53. When the press die 54 is lowered, the press die 54 is fitted into the concave portion of the moving die 20 to compress the resin in the concave portion.
[0023]
Next, a method for molding a thermoplastic resin foam will be described with reference to FIGS. First, the injection filling process of the molten resin will be described. A pellet (molding material) made of polycarbonate is supplied from a dryer (not shown) to the hopper 30 of the plasticizing unit 2 in the injection filling unit 5. Next, the pellets are heated inside the hopper 30 by the heater 31 installed around the hopper 30, and the dried state is further promoted. At this time, the inside of the hopper 30 is deaerated by the vacuum pump 32. Next, the dried pellets are supplied to the cylinder 33 of the plasticizing unit 2. Volatile gas generated during plasticization from the first vent port 34 is degassed by the vacuum pump 32, and the molten resin is starved. Next, pressurized CO, which is a supercritical fluid, is supplied from the second vent port 35 into the cylinder 33 to which the molten resin is supplied. ₂ Fill.
[0024]
Pressurized CO in the cylinder 33 ₂ The molten resin filled with is filled into the injection cylinder 40 through the nozzle 2 ′ of the cylinder 33 as the screw 37 rotates. Next, by moving the injection plunger 41 of the injection cylinder 40 forward (extrusion), only the molten resin supplied into the injection cylinder 40 is supplied to the gate opening / closing cylinder 42 via the nozzle 40 ″ of the injection cylinder 40. In a state where the tip of the injection plunger 41 has moved to the nozzle 40 ″ of the injection cylinder 40, the molten resin supply port 40 ′ is blocked by the injection plunger 41. Thereby, the inside of the cylinder 33 of the plasticizing part 2 is closed. By rotating the screw 37 in the cylinder 33 in this state, the pressure of the molten resin existing in the cylinder 33 can be maintained high. Next, the temperature of the molten resin supplied to the gate opening / closing cylinder 42 is controlled by the band heater 43. Next, by raising the tip 46 of the gate opening / closing piston 45, the gate 47 of the gate opening / closing cylinder 42 is opened, and the movable mold 20 is filled with molten resin.
[0025]
FIG. 3 is an enlarged view of the portion A in FIG. From the gate 47 of the gate opening / closing cylinder 42, the molten resin RS is filled onto the stamper 23 installed on the moving mold 20. At this time, since the moving mold 20 is a container whose upper side is opened, the molten resin RS flows out onto the stamper 23 installed on the bottom surface 20a without restricting its flow path. Inside the sub-chamber 11 is CO ₂ Pressurized CO from the gas cylinder 38 ₂ CO supplied via the generator 39 ₂ Is pre-filled at a pressure of 10 MPa. This CO ₂ However, it functions as a plastic material for the molten resin RS. Thereby, the viscosity of injection-filled molten resin RS is kept low. This CO ₂ The pressurized CO impregnated in the molten resin RS ₂ Further, foaming due to volatilization of residual gas and foaming due to air or the like being taken into the molten resin can be suppressed. Furthermore, CO in the subchamber 11 ₂ By maintaining the pressure of the pressure constant, the pressurized CO pre-impregnated into the molten resin RS ₂ The change of content of can be suppressed. Thereby, even when a stamper having a fine pattern with a high aspect ratio is installed in the moving mold 20, the molten resin can be sufficiently infiltrated to reach the details of the pattern.
[0026]
Next, the process of transferring the mold pattern to the molten resin will be described with reference to FIG. First, the moving mold 20 filled with the molten resin in the injection filling unit 5 is moved onto the press stage 50 in the same sub-chamber using the transport device (19). Next, the press die 53 is pushed down in the vertical direction so that the press die 54 is fitted to the movable die 20. Thereby, the molten resin on the moving mold 20 is compressed. Since the surface of the exposed molten resin is compressed by the press die 54 with a substantially uniform pressure, the internal pressure difference of the molten resin hardly occurs. The surface of the press die 54 at this time is CO. ₂ It is desirable that the temperature is higher than the glass transition temperature of the molten resin impregnated with. Since the molten resin comes into contact with the die surface of the press die 54 with substantially equal pressure, the surface of the molten resin is uniformly cooled and solidified.
[0027]
Next, although the surface of the molten resin is solidified, the moving mold 20 is lowered by the stage driver 51 in a state where the inside of the molten resin is not yet solidified. As a result, the volume of the space defined by the moving mold 20 and the press mold 54 increases and the internal pressure thereof decreases. At the same time, CO in a supercritical state that has been previously impregnated in the molten resin. ₂ However, it is vaporized by the pressure drop, and the molten resin becomes a foamed state. By cooling the molten resin in this state, the molten resin is solidified and a resin molded product having a foamed layer inside can be formed. It is also possible to return the interior of the resin to a non-foamed state by pressurizing again while the interior of the molten resin is not yet solidified.
[0028]
Thus, the resin molded product whose inside is foamed is moved in the order of the sub-chambers 12 and 13 by the transfer device (19). As shown in FIG. 2, when moving the movable mold 20 from the subchamber 11 to the subchamber 13, first, the wall 16 positioned between the subchambers 11 and 12 is lowered, and the atmosphere of the subchambers 11 and 12 is lowered. To communicate. Next, the moving mold 20 is transferred from the sub chamber 11 to the sub chamber 12 by the transfer device 19. The wall 16 rises in a state where the moving mold 20 has completely entered the sub-chamber 12, and the atmosphere of the sub-chambers 11 and 12 is isolated. Next, the wall 17 located between the subchambers 12 and 13 is lowered, and the atmosphere of the subchambers 12 and 13 is communicated. After the moving mold 20 is moved from the subchamber 12 to the subchamber 13 by the transfer device 19, the wall 17 is raised. By doing so, the movable mold 20 can be transferred from the sub-chambers 11 to 13 without directly communicating the sub-chambers 11 and 13.
[0029]
The moving mold 20 transferred to the sub-chamber 13 is positioned in the molded product takeout part 21. In the molded product take-out unit 21, the molded product solidified in the movable mold 20 is taken out of the apparatus from an unillustrated outlet. Next, the empty moving mold 20 is transferred to the moving mold preheating unit 22 by the transfer device 19. In the moving mold preheating part 22, the moving mold 20 is heated for the next injection molding.
[0030]
The moving mold 20 heated by the moving mold preheating unit 22 is moved by the transfer device 19 in the order of the sub chambers 14 and 11. First, the wall 18 located between the subchambers 13 and 14 is lowered, and the atmosphere of the subchambers 13 and 14 is communicated. Next, the moving mold 20 is transferred from the sub chamber 13 to the sub chamber 14 by the transfer device 19. With the moving mold 20 completely entering the sub-chamber 14, the wall 18 rises and the atmosphere of the sub-chambers 13 and 14 is isolated. Next, the wall 15 located between the subchambers 14 and 11 is lowered, and the atmosphere of the subchambers 14 and 11 is communicated. After the moving mold 20 is moved from the subchamber 14 to the subchamber 11 by the transfer device 19, the wall 15 is raised. In this way, the moving mold 20 can be transferred from the sub-chamber 13 to 11 without directly connecting the sub-chambers 13 and 11, and the heat generated in the moving mold preheating part 22 in the sub-chamber 13 is transferred to the sub-chamber. 11 is prevented from being transmitted.
[0031]
As described above, a series of molding operations is performed by moving the movable mold 20 between the operating parts of the molding apparatus. Since the conveying device 19 of the main forming apparatus is provided with the four arms as described above, the four movable molds can be simultaneously processed by the respective operation units. For example, in the injection filling unit, another moving mold 20 is heated by the moving mold preheating unit 22 as a preparation step for filling the molten resin while a certain moving mold 20 is being filled with the molten resin. . By performing such an efficient operation inside the apparatus, the throughput of the molded product is improved.
[0032]
[Example 2]
A second embodiment of the present invention will be described with reference to FIG. In the above embodiment, the foamed layer is formed inside the molten resin by lowering the moving mold 20 by a predetermined distance after the mold pressing, but in this embodiment, between the moving mold 20 and the mold press 54. The foamed layer was formed inside the molten resin by lowering the internal pressure of the closed space in the closed state. As shown in FIG. 4, the inside of the movable mold 20 filled with the molten resin RS and the press mold 54 are closed in a closed state. Inside the press die 54, a passage 54 'is provided from the vicinity of the end of the surface 54a that is a contact surface with the molten resin to the side surface of the die. An exhaust pipe 55 is provided from the opening of the passage 54 ′ formed on the side surface of the press die 54 to the outside of the subchamber 11. An electromagnetic valve 77 is provided in the exhaust pipe 55 outside the sub chamber 11. By operating the solenoid valve 77, the CO in the space 80 is ₂ Is exhausted to the outside of the sub-chamber 11 through the passage 54 ′ and the exhaust pipe 55. As a result, the CO in the closed space 80 is ₂ The amount of decreases. Therefore, the internal pressure of the space 80 decreases. Along with this, pressurized CO, which is a supercritical fluid impregnated inside the molten resin ₂ The pressure of the resin also decreases, and the CO inside the molten resin ₂ Foams. By cooling the molten resin in this state, the molten resin is solidified and a resin molded product having a foamed layer inside can be formed.
[0033]
[Modification]
A modification of the present invention will be described with reference to FIG. In the above embodiment, the thermoplastic resin foam is molded by filling the movable mold 20 with the molten resin and then moving the movable mold 20 to the mold clamping unit 4 and clamping the molten resin. In the modification, after the movable mold 20 is filled with the molten resin, the movable mold 20 is rotated by driving the motor 90 connected to the stage 70 while the movable mold is disposed below the injection filling unit. As the mold rotates, the molten resin injected and filled onto the moving mold 20 spreads over the entire mold surface due to the centrifugal force of the moving mold 20, and the film thickness becomes uniform. In this state, the CO in the subchamber 11 ₂ Reduce pressure. By this pressure control, CO impregnated inside the molten resin ₂ Becomes a foamed state, and a uniform foamed layer can be formed inside the resin by cooling with a cooling device (not shown) or the like embedded in the stage 70. By using this method, it is possible to mold a thin thermoplastic resin foam having a thickness of about 0.1 mm without clamping. Moreover, in this modification, a thermoplastic resin foam can be manufactured, without moving a metal mold | die to another place with a conveying apparatus.
[0034]
In the above examples and modifications, polycarbonate was used as the pellet (molding material). However, the present invention is not limited to this. For example, polyethylene, polystyrene, polyolefin, polyacetal, polycarbonate, polyphenylene oxide, polymethylpentene, polyetherimide, ABS Resins or the like or copolymers thereof can be used.
[0035]
In the above-described embodiments and modifications, the molten resin is filled from one gate, but a plurality of gates may be provided and the molten resin may be filled from these gates. When the molten resin is filled from a plurality of gates, the molten resin is filled more uniformly into the moving mold 20 than when the molten resin is filled from a single gate and cooled uniformly. You may adjust suitably the position which arrange | positions a 1 or several gate according to the shape of a molded article. Thereby, the molten resin can be more efficiently filled into the moving mold according to the shape of the molded product.
[0036]
In the above embodiment, the movable die 20 is raised using the stage driver 51 in order to form the foam layer inside the molten resin, but the lowering amount of the press piston 53 in which the press die 54 is installed is controlled. Thus, the space volume formed by the press die 54 and the moving die 20 may be adjusted.
[0037]
In the above-described embodiments and modifications, the moving mold 20 is preheated in the sub-chamber 13 different from the sub-chamber 11, but the heater 71 built in the stage 70 on which the moving mold 20 is placed is used to The moving mold 20 may be heated in the chamber 11. Further, in the above embodiment, in the mold pattern transfer process, the temperature of the surface of the molten resin is controlled by bringing the molten resin into contact with the press mold 54. However, the press piston 53 and the moving mold in which the press mold 54 is installed are controlled. You may control temperature using the heater 75 and the cooling device 76 which were each incorporated in the press stage 50 in which the type | mold 20 is mounted. By controlling the temperature of the press mold 54 and the moving mold 20 using the heater 75 and the cooling device 76, the molten resin is prevented from being rapidly cooled. Thereby, generation | occurrence | production of the cooling nonuniformity and foaming of the molten resin surface can be suppressed. As the cooling device 76, the cooling water may be refluxed.
[0038]
After the molten resin is solidified or with the press mold 54 and the moving mold 20 fitted, the CO in the sub-chamber ₂ May be replaced. This replacement is performed by the following operation. After the sealed sub-chamber 11 is opened to the atmosphere via the electromagnetic valve 60, the electromagnetic valve 61 is operated to rapidly reduce the pressure by the vacuum pump 32. Next, by operating the solenoid valve 62, the pressurized CO ₂ Pressurized CO from the generator 39 to the subchamber 11 ₂ Supply. Thereby, excess oxygen generated in the sub-chamber, volatile components from the resin, residual gas in the fine pattern, and the like can be exhausted completely.
[0039]
In the above embodiment, the movable mold 20 is moved in the sub-chamber to perform the injection filling of the molten resin and the transfer of the mold pattern. However, the movement mechanism of the injection filling section 5 and the mold clamping section 4 is provided and moved. The injection filling and mold pattern transfer may be performed by moving the injection filling unit 5 and the mold clamping unit 4 while the mold 20 is fixed. Furthermore, the injection filling unit 5 and the mold clamping unit 4 may be installed in independent chambers to perform injection filling and mold pattern transfer.
[0040]
【The invention's effect】
In the present invention, since the mold is filled with the molten resin having a uniform and low viscosity, it is particularly suitable for molding using a molding material having low fluidity. In addition, since the molten resin is filled in a state where the mold is opened in the chamber, even when manufacturing a large molded product, the filling pressure of the molten resin and the pressure at the time of mold clamping can be lowered. The structure of the injection molding apparatus can be simplified. Further, after injection filling of the molten resin, the CO in the chamber is not clamped. ₂ Since the foam can be obtained by reducing the pressure, the injection molding apparatus can be further downsized.
[0041]
Further, in the present invention, when the molten resin is injected and filled, a high filling pressure and a mold clamping pressure are not required, so that the mold can be made thin. This mold has a smaller heat capacity and better heat conduction efficiency. Therefore, it is easy to control the temperature of the mold, and it is possible to suppress the heat of the molten resin from being rapidly taken away by the mold, and thus it is possible to manufacture a molded product having a very stable structure inside the resin.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing an injection filling part, a mold clamping part, and a sub-chamber located below the injection filling part of a thermoplastic resin molding apparatus used in the present invention.
FIG. 2 is a schematic plan view of a chamber in the thermoplastic resin molding apparatus used in the present invention.
FIG. 3 is a view schematically showing a state of filling a molten resin in the thermoplastic resin molding apparatus used in the present invention.
FIG. 4 is a view schematically showing the vicinity of a moving mold in a mold clamping unit according to a second embodiment of the present invention.
[Explanation of symbols]
1 chamber
11, 12, 13, 14 Subchamber
2 Plasticization part
3 Injection part
4 Clamping part
5 Injection filling part
15, 16, 17, 18 walls
20 Moving mold
21 Molded product removal part
22 Moving mold preheating part
23 Stamper
33 cylinders
40 Injection cylinder
41 Injection plunger
42 Gate open / close cylinder
50 Press stage
53 Press piston
54 Press mold

Claims (6)

A method of molding a thermoplastic resin foam by filling a mold with a molten resin,
Impregnating the molten resin with pressurized CO ₂ ;
Filling a mold container disposed in a chamber filled with CO ₂ and having an open upper surface with a molten resin impregnated with CO ₂ ;
Pressurizing the molten resin filled in the mold container with a press mold;
A method for molding a thermoplastic resin foam, comprising: pressurizing the molten resin, and increasing a volume of a space defined by a mold container and a press mold to foam the molten resin. A method of molding a thermoplastic resin foam by filling a mold with a molten resin,
Impregnating the molten resin with pressurized CO ₂ ;
Filling a mold container disposed in a chamber filled with CO ₂ and having an open upper surface with a molten resin impregnated with CO ₂ ;
Pressurizing the molten resin filled in the mold container with a press mold;
A method for molding a thermoplastic resin foam, comprising: pressurizing the molten resin, and lowering the pressure of CO ₂ in a space defined by a mold container and a press mold to foam the molten resin. The method for molding a thermoplastic resin foam according to claim 1 or 2, wherein the pressurized CO ₂ is in a supercritical state. The method for molding a thermoplastic resin foam according to any one of claims 1 to 3, wherein the step of pressurizing the molten resin is performed in the chamber. A method of molding a thermoplastic resin foam,
Impregnating the molten resin with pressurized CO ₂ ;
Filling a container disposed in a chamber filled with CO ₂ and having an open top surface with a molten resin impregnated with CO ₂ ;
A method for forming a thermoplastic resin foam, the method comprising foaming the molten resin filled in the container by reducing the pressure of CO ₂ in the chamber. The method for molding a thermoplastic resin foam according to claim 5, wherein the pressurized CO ₂ is in a supercritical state.

Images