JP2004066500A - Method and device for foam injection molding, and foam-injection-molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely control the size of a foamed cell and the uniformity of the density of the foamed cells, and to enable a miniaturization of foam injection molding equipment, even in the case of a large-sized foam-molded article. <P>SOLUTION: A molding tool 1 to be used has a plurality of gates 2a, and enables the volume of a cavity 1a to vary between the volume of the foam-molded article large enough to regulate the outer surface of the foam-molded article and a filling volume smaller than the volume of the foam-molded article. After the molding tool 1 is clamped so that the volume of the cavity 1a can be the filling volume, injection and flow filling are performed by switching to flow molding after the injection of a molten resin wherein an inert gas is dispersed into a resin by being simultaneously kneaded and mixed by means of a plurality of injection units 4 corresponding to the gates 2a. Subsequently, the volume of the cavity 1a is increased up to the volume of the foam-molded article, so that the foamed cell can be formed from the inert gas. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a foam injection molding method and apparatus capable of favorably molding a large-sized foam molded article having a high expansion ratio, and a foam injection molded article.
[Prior art]
[0002]
Foam injection molding methods are roughly classified into those using foaming pressure by a chemical foaming agent and those using foaming pressure by an inert gas such as carbon dioxide gas, nitrogen gas, argon gas, and helium gas. I have.
[0003]
In the case of using the foaming pressure of the chemical foaming agent, if the mixing ratio of the chemical foaming agent to the resin is increased to increase the foaming ratio, the quality of the molded product may be affected. It is difficult to mold. On the other hand, attention has been paid to a device utilizing a foaming pressure by an inert gas which can obtain a foam molded product having a high foaming ratio, and one injection unit is required for one mold clamping device described below. There have been proposed foam injection molding methods such as (a) and (b) using a foam injection molding apparatus provided with the above.
[0004]
(B) After injecting and filling in an unfilled state (short shot state) the molten resin that has been kneaded and mixed into the cavity of the clamped mold and diffused into the resin, the inert gas A foam injection molding method in which foam is formed by foaming pressure to fill a cavity to form a foam molded product (see JP-A-2001-315153).
[0005]
(B) Using a mold capable of reducing and expanding the volume of the cavity, injecting and filling the molten resin obtained by kneading and mixing an inert gas into the reduced-cavity cavity and diffusing it into the resin. When the average temperature of the molten resin in the resin reaches the range of the melting point of the resin to the melting point + 30 ° C., the volume of the cavity is expanded and foaming is performed by foaming pressure of an inert gas (see JP-A-2001-341154). .
[0006]
[Problems to be solved by the invention]
In the above-mentioned conventional technology, the pressure is released immediately after the molten resin kneaded and mixed with the inert gas and diffused into the resin is injected and filled into the cavity, and foaming starts. In particular, when molding a large foam molded product with a large thickness and a large projected area, an inert gas is kneaded and mixed by a single injection unit into the mold that has been clamped and diffused into the resin. Injecting and filling molten resin, it takes time from the start to the completion of injection and filling, and during that time, a considerable temperature difference occurs, and the size and density of the foam cells become uneven .
[0007]
Therefore, in order to shorten the time required for injection and filling to make the size and density of the foam cells uniform, a large-capacity injection unit must be used. As a result, the size of the foam injection molding apparatus increases, and the cost increases. There was an unsolved problem of inviting high prices.
[0008]
The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and even in the case of a large-sized foam molded product having a large projection area with a large thickness, uniformity of the size and density of the foam cells is not required. It is an object of the present invention to provide a foam injection molding method and a foam injection molding product which can surely perform control and can reduce the size of a foam injection molding device.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a first foam injection molding method according to the present invention is directed to a foam molding product having a plurality of gates and a volume of a cavity having a size which regulates an outer surface of the foam molding when clamping the mold. And a mold that can be changed to a filling volume smaller than the foam molded product volume, a mold clamping step of clamping the mold so that the volume of the cavity becomes the filling volume, and after the mold clamping step, A plurality of injection units corresponding to the plurality of gates simultaneously knead and mix the inert gas into the cavity of the filling volume, inject the molten resin diffused in the resin, and then switch to the flow mold to inject the molten resin. After the fluid filling step and the injection / fluid filling step, the inert gas is expanded by expanding the volume of the cavity of the mold to the volume of the foam molded article. A foaming step of generating that foam cells, it is characterized in that to perform.
[0010]
In the second foam injection molding method, the volume of the cavity has a plurality of gates and the volume of the cavity at the time of mold clamping is limited to the volume of the foam molding which regulates the outer surface of the foam molding, and the filling volume is smaller than the volume of the foam molding. Using a mold that can be changed, a mold clamping step of clamping the mold so that the volume of the cavity becomes the filling volume, and after the mold clamping step, injecting an inert gas into the cavity to counter the mold. A counter pressure applying step for applying and holding pressure, and after the counter pressure applying step, an inert gas is simultaneously kneaded and mixed into the cavity of the filling volume by a plurality of injection units corresponding to the plurality of gates. An injection / flow filling step in which the molten resin diffused in the resin is injected and then switched to a flow mold for filling; and the injection / flow filling step is followed by the injection / flow filling step. A foaming step of generating foam cells by the inert gas by releasing the counter pressure in the cavity and expanding the volume of the cavity of the mold to the volume of the foamed molded product. Is what you do.
[0011]
The third foam injection molding method comprises: a foam molded article having a plurality of gates and having a cavity volume that regulates the outer surface of the foam molded article when the mold is clamped; and a filling volume smaller than the foam molded article volume. Using a mold that can be changed to a mold clamping step of clamping the mold so that the volume of the cavity becomes the filling volume, and after the mold clamping step, the plurality of molds are inserted into the cavity of the filling volume. An injection / flow filling step in which a supercritical fluid inert gas is simultaneously kneaded and mixed by a plurality of injection units corresponding to the gates, and the molten resin diffused into the resin is injected and then switched to a flow mold for filling; After the injection / flow filling step, the volume of the cavity of the mold is expanded to the volume of the foamed molded product, thereby forming a foam cell with an inert gas of the supercritical fluid. A foaming step to be generated, is characterized in that to perform.
[0012]
The fourth foam injection molding method comprises a plurality of gates, and a volume of a cavity having a size which regulates the outer surface of the foam molded product when the mold is clamped, and a filling volume smaller than the foam molded product volume. Using a mold that can be changed, a mold clamping step of clamping the mold so that the volume of the cavity becomes the filling volume, and after the mold clamping step, injecting an inert gas into the cavity to counter the mold. A counter pressure applying step of applying and holding a pressure, and after the counter pressure applying step, a plurality of injection units corresponding to the plurality of gates simultaneously knead an inert gas of a supercritical fluid into the cavity of the filling volume. An injection / flow filling step in which the molten resin mixed and diffused into the resin is injected and then switched to a flow mold for filling; A foaming step of releasing the counter pressure in the cavity and expanding the volume of the cavity of the molding die to the volume of the foamed molded product to generate a foam cell with an inert gas of the supercritical fluid; , Is performed.
[0013]
The fifth foam injection molding method includes a foam molded product having a plurality of gates and having a cavity capacity for regulating the outer surface of the foam molded product at the time of mold clamping, and a filling volume smaller than the foam molded product volume. Using a mold that can be changed, a mold clamping step of clamping the mold so that the volume of the cavity becomes the filling volume, and after the mold clamping step, an inert gas of a supercritical fluid is introduced into the cavity. A counter pressure applying step of injecting and applying and holding a counter pressure, and after the counter pressure applying step, a plurality of injection units corresponding to the plurality of gates simultaneously inject the supercritical fluid into the cavity of the filling volume. An injection / flow filling step of injecting a molten resin in which an active gas is kneaded / mixed and diffused into the resin, and then switching to a flow mold for filling; After the filling step, the counter pressure in the cavity is released, and the volume of the cavity of the mold is expanded to the volume of the foam molded product, thereby generating a foam cell by the inert gas of the supercritical fluid. And a foaming step.
[0014]
Further, after the injection / flow filling step is completed and before the foaming step is started, a skin layer is formed in a state where the injection / flow filling step is completed and a skin layer is formed by cooling from the cavity inner wall. A forming process is performed.
[0015]
Further, the foam injection molded article according to the present invention is characterized by being molded by the foam injection molding method according to any one of claims 1 to 7.
[0016]
In addition, the first foam injection molding apparatus according to the present invention has a plurality of gates and a volume of a foam molded article having a size for regulating the outer surface of the foam molded article and a volume smaller than the volume of the foam molded article. A mold that can be changed to a filling volume, a mold clamping device that clamps the mold to change the volume of the cavity to the foam molded product volume and the filling volume, and a plurality of molds corresponding to the plurality of gates. An injection unit, wherein each of the injection units includes a cylinder having an inert gas supply port and a screw disposed in the cylinder, and kneads and melts the resin and the inert gas to form an inert gas. Plasticizing function to measure the molten resin that has been kneaded and mixed and diffused into the resin, and the molten resin that has been measured and kneaded and mixed and injected into the cavity is injected into the cavity. An injection / filling function for filling, and a flow mold function for filling the cavity with the molten resin kneaded and mixed with the inert gas by the driving force of the rotation of the screw and diffused in the resin. It is characterized by the following.
[0017]
A second foam injection molding apparatus comprising: a molding die having a plurality of gates and capable of changing a volume of a cavity between a molding volume for regulating an outer surface of the foam molding and a filling volume smaller than the molding volume; A mold clamping device that clamps a mold to change the volume of the cavity to the molded product volume and the filling volume, and a plurality of injection units corresponding to the plurality of gates, wherein each of the injection units A cylinder having a supercritical fluid supply port and a screw disposed in the cylinder, wherein the resin and the inert gas of the supercritical fluid are kneaded and melted, and the inert gas of the supercritical fluid is kneaded and mixed. A plasticizing function for measuring the molten resin diffused into the resin, and an injection machine for injecting and filling the molten resin diffused into the resin by kneading and mixing the inert gas of the supercritical fluid into the cavity. And a flow molding function for filling the cavity with the molten resin in which the inert gas of the supercritical fluid is kneaded and mixed by the driving force of the rotation of the screw and diffused in the resin. It is assumed that.
[0018]
Further, it is assumed that a pouring / exhausting means for injecting / evacuating an inert gas is provided in the mold.
[0019]
Further, it is assumed that a pouring / exhausting means for injecting / evacuating an inert gas of a supercritical fluid is provided in the mold.
[0020]
[Action]
Injection of the molten resin into the cavity of the mold by mixing and mixing an inert gas or an inert gas of a supercritical fluid and diffusing into the resin is performed simultaneously by multiple injection units. The mold is switched and filled. In addition, the molten resin, which is obtained by kneading and mixing an inert gas or a supercritical fluid inert gas filled in the cavity simultaneously from a plurality of gates and diffused into the resin, has a short flow distance in the cavity, Due to the improvement of the fluidity due to the inert gas and the penetration of the tip of the molten resin into the interface in the cavity, they merge before the fluidity is impaired.
[0021]
As a result, it is possible to mold a good large-sized foam molded article free of weld lines, sink marks, warpage, and the like using a small-capacity injection unit.
[0022]
Further, using a molding die capable of changing the volume of the cavity between a foam molding product having a size that regulates the outer surface of the foam molding and a filling volume smaller than the foam molding product volume, and using an inert gas in the cavity of the filling volume. Alternatively, a foamed cell is generated by filling a molten resin kneaded and mixed with an inert gas of a supercritical fluid and diffused into the resin, and then expanding the volume of the cavity to the volume of the foam molded article.
[0023]
As a result, a foam molded article having a high expansion ratio can be molded favorably, and the timing (expansion speed) and the time at which the expansion of the cavity of the molding die is started can be controlled to form the skin layer (thickness) and foam cells. It is possible to control the uniformity of the size and density uniformly.
[0024]
In addition, according to the present invention, a large-sized foam molded article having a uniform size and density of foam cells can be molded at a low cost by a relatively small foam injection molding apparatus.
[0025]
For this reason, large-sized foam molded products molded by the foam injection molding method according to the present invention are not limited to building materials such as inner and outer wall materials, boards, floor materials, sizing materials, etc., as well as large compost silos, bathtubs, barrel materials, It can be used for various uses such as large planters and panel materials for assembled pools.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of a foam injection molding apparatus according to the present invention will be described with reference to the drawings.
[0027]
In the foam injection molding apparatus according to the present embodiment, as shown in FIG. 1, a plurality of injection units 4 (not limited to two illustrated, but three or more as required) may be provided for one mold clamping device 10. And the plurality of injection units 4 simultaneously inactivate the cavity 1a of the molding die 1 including the fixed die 11 and the movable die 12 that can change the volume clamped by the mold clamping device 10. The gas is kneaded and mixed, and the molten resin diffused in the resin is injected. After switching to the flow mold, the resin is injected and flow-filled, and then the volume of the cavity 1a is expanded to form a foam cell. ing.
[0028]
The mold clamping device 10 includes a fixed plate 11 to which the fixed die 2 is attached, a movable plate 12 to which the movable die 3 is attached, a tie bar 13 for guiding the movable plate 12 to be movable in the axial direction, and a movable die with the movable plate 12. A mold opening / closing mechanism (not shown) for moving the mold 3 forward and backward with respect to the fixed mold 2 to perform mold clamping and mold opening is provided. The mold 1 is clamped to regulate the volume of the cavity 1a to the outer surface of the foam molded article. It is configured such that it can be changed into a foam molded product volume of a size and a filling volume smaller than the foam molded product volume.
[0029]
The mold 1 may be provided with a pouring / exhausting means (not shown) for injecting / evacuating an inert gas. As the injection / exhaust means, it is preferable to provide a branch line in which a counter pressure releasing means is interposed in a line connecting the inert gas supply source and the cavity 1a.
[0030]
The fixed platen 11 is provided with a nozzle insertion hole 11a at a position corresponding to the nozzle 7 of each injection unit 4, and the fixed mold 2 attached to the fixed platen 11 is provided with the nozzle insertion hole 11a via the nozzle insertion hole 11a. A plurality of gates 2a to which the nozzles 7 of each injection unit 4 are respectively nozzle-touched are provided.
[0031]
Each injection unit 4 is disposed in a cylinder 5 heated by a heating means (not shown), a screw 6 rotatably and axially retractable in the cylinder 5, and a kneading and melting zone of the cylinder 5. An inert gas supply port 9, a nozzle 7 disposed at the tip of the cylinder 5, and a shutoff valve 8 attached to the nozzle 7, and the inert gas supply port 9 is connected via a pipe 9 a. Connected to an inert gas supply source (not shown).
[0032]
Further, each injection unit 4 kneads and melts the resin supplied from a hopper (not shown) and the inert gas added from the inert gas supply port 9, and the kneading and mixing of the inert gas into the resin. A measuring function (plasticizing function) for measuring the diffused molten resin, and an injection for injecting and filling the molten resin diffused in the resin by mixing and mixing the measured inert gas into the cavity 1a of the mold 1. It has a function and a flow molding function of filling the molten resin diffused in the resin by the kneading and mixing of the inert gas by the propulsive force generated by the rotation of the screw 6 at the forward position into the cavity 1a of the molding die 1. .
[0033]
Next, an embodiment of the foam injection molding method according to the present invention will be described.
[0034]
(1) As shown in FIG. 1, in each of the injection units 4 touched by the nozzle, the screw 6 is rotated with the shut-off valve 8 closed, and the resin supplied from a hopper (not shown) and the inert gas supply port 9 are supplied. The added inert gas is kneaded and melted, and the inert gas is kneaded and mixed, and the molten resin diffused into the resin is measured (plasticized).
[0035]
(2) After the measurement according to (1), the volume of the cavity 1a of the molding die 1 is clamped by the mold clamping device 10 to the state of the filling volume (minimum volume).
[0036]
(3) After the mold clamping step (2), as shown in FIG. 2 (a), the shut-off valves 8 of the respective injection units 4 are opened and the screws 6 are moved forward to measure the inert gas measured. Are simultaneously injected and filled into the cavity 1a with the molten resin that has been kneaded and mixed and diffused into the resin.
[0037]
In this step, the molten resin injected and filled into the cavity 1a simultaneously through each gate 2a is kneaded and mixed, and the molten resin diffused into the resin merges in the cavity 1a. Inert gas is kneaded and mixed due to the short flow distance of the fluid, the improvement of fluidity by the inert gas, and the penetration of the molten resin tip into the interface in the cavity. The resins merge without impairing the fluidity of the resin, and no weld line or the like is generated at the junction.
[0038]
(4) After the injection / filling step (3), as shown in FIG. 2 (b), the screw 6 is rotated with the back pressure applied so that the screw 6 does not move linearly at the forward position. Filling the cavity 1a with the molten resin kneaded and mixed with the inert gas by the propulsion force of the molten resin and simultaneously filling the molten resin kneaded and mixed with the molten resin and diffusing into the resin. Is performed by so-called flow molding, in which the volume of the cavity 1a is gradually increased so as to correspond to the increase in the amount.
[0039]
That is, the molten resin diffused in the resin by the kneading and mixing of the inert gas by the plurality of injection units 4 is simultaneously injected into the cavity 1a and then switched to the flow mold for injection / flow filling. Can have a small capacity.
[0040]
(5) By the flow molding according to the above (4), when a predetermined amount of the inert gas is kneaded and mixed and the molten resin diffused in the resin is filled in the cavity 1a, the flow molding is stopped and waited. Then, a skin layer is formed by lowering the temperature of the inner wall surface of the cavity 1a.
[0041]
In this step, a temperature sensor for detecting the temperature of the inner wall surface of the cavity 1a is provided in the molding die 1, and the inert gas in the cavity 1a is kneaded based on the temperature of the inner wall surface of the cavity 1a detected by the temperature sensor. The temperature of the molten resin mixed and diffused into the resin may be estimated to determine the state of formation of the skin layer.
[0042]
(6) After the above (5), the shut-off valve 8 is closed, and the volume of the cavity 1a is increased to the volume of the foamed molded product (the volume that regulates the outer surface of the foamed molded product), so that the skin layer The covered inert gas is kneaded and mixed, and the molten resin diffused in the resin generates foam cells by the inert gas.
[0043]
In this step, the size of the foam cell and the density of the foam cell can be controlled (changed) by controlling (changing) the expansion speed of the cavity 1a of the mold 1.
[0044]
Incidentally, in order to obtain a foam molded article having fine foam cells, the expansion speed of the cavity 1a is made slower than the expansion speed of the foam cells. Conversely, in order to obtain a foam molded article having large foam cells, the expansion speed of the cavity 1a is made faster than the expansion speed of the foam cells.
[0045]
It is also possible to increase the density (the number of cells) of the foamed cells by kneading a large amount of a nucleating agent such as talc or calcium carbonate in the molten resin diffused by kneading and mixing the inert gas.
[0046]
(7) After the above (6), after cooling in the mold, the mold is opened to take out the foamed molded product.
[0047]
During the cooling, each injection unit 4 performs the measurement (plasticization) of the above (1).
[0048]
Subsequently, a modified example of the foam injection molding method according to the above-described embodiment will be described.
[0049]
In the present modified example, in addition to the above steps (1) to (7), before the process is shifted from the step (2) to the step (3), the molding is performed such that the volume is clamped to the state of the filling volume. A counter pressure applying step of injecting an inert gas into the cavity 1a of the mold 1 to apply and maintain a counter pressure is added, and at the start of the step (6), the inert gas in the cavity 1a is discharged and the counter is applied. A counter pressure releasing step for releasing the pressure at once is added.
[0050]
The counter pressure is released when the temperature of the cavity wall surface is −20 ° C. to −60 ° C. from the melting point (Tm) for a crystalline resin, and −10 ° C. to −50 ° C. from the glass transition temperature (Tmg) for an amorphous resin. It is good to wait until it falls in the range of.
[0051]
According to this modification, by applying and holding the counter pressure, the inert gas injected and flow-filled into the cavity 1a is kneaded and mixed, and the foaming of the molten resin diffused in the resin is ensured. Because of the suppression, a foam molded article having a glossy skin layer on the surface can be obtained.
[0052]
Next, another embodiment of the foam injection molding apparatus according to the present invention will be described.
[0053]
In the foam injection molding apparatus according to the present embodiment, as shown in FIG. 3, a plurality of injection units 24 are provided for one mold clamping device 30, and the volume of the cavity 21 a clamped by the mold clamping device 30. In the cavity 21a of the molding die 21 composed of the fixed die 22 and the movable die 23, the injection units 24 (not limited to the two illustrated ones, but can be three or more as needed). At the same time, an inert gas of a supercritical fluid is kneaded and mixed, the molten resin diffused into the resin is injected, and then the flow resin is switched to injection and flow filling. Then, the volume of the cavity 21a is increased to increase the volume of the foam cell. It is configured to be able to generate.
[0054]
The mold clamping device 30 includes a fixed plate 31 to which the fixed die 22 is attached, a movable plate 32 to which the movable die 23 is attached, a tie bar 33 that guides the movable plate 32 so as to be movable in the axial direction, and a movable plate with the movable plate 32. A mold opening / closing mechanism (not shown) for moving the mold 23 forward and backward with respect to the fixed mold 22 to perform mold clamping and mold opening is provided, and the mold 21 is clamped to regulate the volume of the cavity 21a to the outer surface of the foam molded article. It is configured such that the volume of the foamed molded product can be changed to a filling volume smaller than the volume of the foamed molded product.
[0055]
The fixed platen 31 is provided with nozzle insertion holes 31a at portions corresponding to the nozzles 27 of each injection unit 24, and the fixed mold 22 attached to the fixed platen 31 is provided with the nozzle insertion holes 31a through the nozzle insertion holes 31a. A plurality of gates 22a to which the nozzles 27 of each injection unit 24 are respectively nozzle-touched are provided.
[0056]
Each injection unit 24 is disposed in a cylinder 25 heated by a heating means (not shown), a screw 26 rotatably and axially retractable in the cylinder 25, and a kneading / melting zone of the cylinder 25. A supercritical fluid supply port 29, a nozzle 27 disposed at the tip of the cylinder 25, and a shutoff valve 28 attached to the nozzle 27. The supercritical fluid supply port 29 is connected to the supercritical fluid generator 41 via a supply pipe 45 in which a flow control valve 44, an on-off valve 43, a flow meter 42 and the like are interposed.
[0057]
As a pouring / exhausting means for injecting / evacuating an inert gas of a supercritical fluid provided in the molding die 21, a branch pipe 46 branched from a supply pipe 45 is connected to the cavity 21a, and a branch pipe is provided. The passage 46 is provided with a counter pressure releasing means 47 including an on-off valve 43 and a throttle valve.
[0058]
Here, the supercritical fluid generating device 41 can generate an inert gas of a supercritical fluid by setting an inert gas such as carbon dioxide gas or nitrogen gas stored in the cylinder 40 to a critical pressure and a critical temperature or higher. , The kind does not matter.
[0059]
Incidentally, in the case of carbon dioxide gas, it becomes a supercritical fluid at a critical temperature of 304.1 K and a critical pressure of 7.38 MPa or more, and in the case of nitrogen gas, it becomes a supercritical fluid at a critical temperature of 210 K and a critical pressure of 3.5 MPa or more. Become.
[0060]
Further, each injection unit 24 kneads and melts the resin supplied from a hopper (not shown) and the inert gas of the supercritical fluid added from the supercritical fluid supply port 29, so that the inert gas of the supercritical fluid is A metering function (plasticizing function) that measures the molten resin that has been kneaded and mixed and diffused into the resin, and a molten resin that has been kneaded and mixed with the measured supercritical fluid and diffused into the resin. The injection function of injecting and filling the cavity 21a of the molding die 21 and the propulsive force generated by the rotation of the screw 26 at the forward position are used to mix and mix the inert gas of the supercritical fluid and diffuse the molten resin into the resin. And a flow mold function for filling the inside of the cavity 21a.
[0061]
Next, another embodiment of the foam injection molding method according to the present invention will be described.
[0062]
(1) As shown in FIG. 3, in each of the injection units 24 touched by the nozzle, the screw 26 is rotated with the shut-off valve 28 closed, and the resin supplied from a hopper (not shown) and the supercritical fluid supply port 29 are supplied. The added supercritical fluid inert gas is kneaded and melted, the supercritical fluid inert gas is kneaded and mixed, and the molten resin diffused into the resin is measured (plasticized).
[0063]
(2) After the measurement according to the above (1), the volume of the cavity 21a of the molding die 21 is clamped to the filling volume (minimum volume) by the mold clamping device 30.
[0064]
(3) After the above (2), the shut-off valve 28 of each injection unit 24 is opened and the screw 26 is advanced, and the measured inert gas of the supercritical fluid is kneaded and mixed and diffused into the resin. The molten resin is injected and filled into the cavity 21a at the same time.
[0065]
In this step, the supercritical fluid simultaneously injected and filled into the cavity 21a through each gate 22a is kneaded and mixed, and the molten resin diffused into the resin joins in the cavity 21a. The supercritical fluid is kneaded and mixed due to the short flow distance of the fluid, the improvement of fluidity due to the inert gas in the supercritical fluid state, and the penetration of the molten resin tip into the interface in the cavity. The molten resin diffused therein is merged without impairing the fluidity, and no weld line or the like is generated at the merged portion.
[0066]
(4) Following the injection and filling of (3), as shown in FIG. 4, the screw 26 is rotated while applying a back pressure to the screw 26 so as not to move linearly at the forward position, and the screw 26 is propelled. The supercritical fluid was kneaded and mixed by the force, and the molten resin diffused into the resin was filled into the cavity 21a, and at the same time, the inert gas of the filled supercritical fluid was kneaded and mixed and diffused into the resin. Filling is performed by a so-called flow mold in which the volume of the cavity 21a is gradually increased so as to correspond to the increase in the amount of the molten resin.
[0067]
That is, the inert gas of the supercritical fluid is kneaded and mixed by the plurality of injection units 24, and the molten resin diffused in the resin is simultaneously injected into the cavity 21a, and then switched to the flow mold to be injected and flow-filled. Each injection unit 24 can use a small capacity.
[0068]
(5) By the flow molding according to (4), a predetermined amount of the inert gas of the supercritical fluid is kneaded and mixed, and at the time when the molten resin diffused in the resin is filled in the cavity 21a, the flow mold is removed. It stops and stands by, and the skin layer is formed by the temperature decrease of the inner wall surface of the cavity 21a.
[0069]
In this step, the mold 21 is provided with a temperature sensor for detecting the temperature of the inner wall surface of the cavity 21a, and the temperature of the inner wall surface of the cavity 21a detected by the temperature sensor is used to inactivate the supercritical fluid in the cavity 21a. It is preferable to estimate the temperature of the molten resin in which the gas is kneaded and mixed and diffused into the resin to determine the formation state of the skin layer.
[0070]
(6) After the above (5), the shut-off valve 28 is closed, and the volume of the cavity 21a is expanded to the volume of the foamed molded product (see FIG. 5), thereby generating a foam cell with a supercritical fluid inert gas. Let it.
[0071]
In this step, the size of the foam cells and the density of the foam cells can be controlled (changed) by controlling (changing) the expansion speed of the cavity 21 a of the molding die 21.
[0072]
Incidentally, in order to obtain a foam molded product having fine foam cells, the expansion speed of the cavity 21a is made slower than the expansion speed of the foam cells. Conversely, in order to obtain a foam molded article having large foam cells, the expansion speed of the cavity 21a is made faster than the expansion speed of the foam cells.
[0073]
It is also possible to increase the density (cell number) of foam cells by kneading and mixing a large amount of a nucleating agent such as talc or calcium carbonate into a molten resin diffused by kneading and mixing an inert gas of a supercritical fluid. It is possible.
[0074]
Next, a modified example of the foam injection molding method according to the other embodiment described above will be described.
[0075]
In the present modified example, in addition to the steps (1) to (6), before the process (2) is shifted to the step (3), the molding is performed such that the volume is clamped to the filling volume. A counter pressure applying step for applying a counter pressure by a supercritical fluid inert gas into the cavity 21a of the mold 21 is added, and at the beginning of the step (6), a counter by an inert gas of the supercritical fluid inside the cavity 21a. A counter pressure releasing step for releasing the pressure at a stretch via the counter pressure releasing means 47 is added.
[0076]
When the counter pressure is released, the temperature of the cavity wall surface is in the range of −20 ° C. to −60 ° C. from the melting point (Tm) for the crystalline resin, and −10 ° C. to −50 ° C. for the amorphous resin from the glass transition temperature (Tmg). It is good to wait until it descends.
[0077]
According to the present modification, by applying and holding the counter pressure, the inert gas of the supercritical fluid injected and flow-filled into the cavity 21a is kneaded and mixed, and the molten resin diffused into the resin. Since foaming is reliably suppressed, a foam molded article having a glossy skin layer on the surface can be obtained.
[0078]
Note that, in the counter pressure applying step shown in the above-described modification, instead of the supercritical fluid inert gas, an inert gas may be injected into the cavity to apply and maintain the counter pressure. .
[0079]
【The invention's effect】
Since the present invention is configured as described above, the following effects can be obtained.
[0080]
Using a small-capacity injection unit, it is possible to mold a good large-sized foam molded product free of weld lines, sink marks, warpage and the like.
[0081]
Further, by controlling the timing of starting the expansion of the volume of the cavity of the mold, the expansion speed, and the like, it is possible to reliably control the formation of the skin layer and the uniformity of the size and density of the foam cells.
[0082]
Furthermore, a large-sized foam molded article having a uniform size and density of foam cells can be favorably molded by a relatively small foam injection molding apparatus.
[0083]
For this reason, not only construction materials such as inner and outer wall materials, boards, flooring materials, sizing materials, etc. Can be formed at low cost.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a main part of a foam injection molding apparatus according to an embodiment.
FIG. 2 is an explanatory diagram showing main steps in a foam injection molding method according to one embodiment.
FIG. 3 is an explanatory diagram showing a main part of a foam injection molding apparatus according to another embodiment.
FIG. 4 is an explanatory view showing one step in a foam injection molding method according to another embodiment.
FIG. 5 is an explanatory view showing one step in a foam injection molding method according to another embodiment.
[Explanation of symbols]
1,21 Mold
1a, 21a cavity
2,22 fixed type
2a, 22a gate
3, 33 movable type
4, 24 Injection unit
5, 25 cylinder
6, 26 screw
7, 27 nozzles
8, 28 Shut-off valve
9 Inert gas supply port
10,30 Mold clamping device
11, 31 fixed type
12, 32 Movable type
13,33 Tie bar
29 Supercritical fluid supply port
40 cylinders
41 Supercritical fluid generator
42 flow meter
43 On-off valve
44 Flow control valve
45 Supply line
46 Branch line
47 Counter pressure release means

Claims (12)

Using a mold that has a plurality of gates and can change the volume of the cavity at the time of the mold clamping to a filling volume smaller than the foam molding product volume and the foam molding product volume of a size that regulates the outer surface of the foam molding product,
A mold clamping step of clamping the mold so that the volume of the cavity becomes the filling volume;
After the mold clamping step, a flow is performed after the inert resin is simultaneously kneaded and mixed by the plurality of injection units corresponding to the plurality of gates into the cavity of the filling volume, and the molten resin diffused into the resin is injected. Injection / flow filling process to switch to mold and fill,
After the injection / flow filling step, a foaming step of generating a foam cell by the inert gas by expanding the volume of the cavity of the mold to the foam molded product volume,
And a foam injection molding method. Using a mold having a plurality of gates and a mold that can change the volume of the cavity at the time of mold clamping to a foam volume of a size that regulates the outer surface of the foam molded product and a filling volume smaller than the foam molded product volume,
A mold clamping step of clamping the mold so that the volume of the cavity becomes the filling volume;
After the mold clamping step, a counter pressure applying step of injecting an inert gas into the cavity to apply and maintain a counter pressure,
After the counter pressure applying step, after the inert gas is simultaneously kneaded and mixed by the plurality of injection units corresponding to the plurality of gates into the cavity of the filling volume, and the molten resin diffused into the resin is injected. Injection / flow filling process of switching to flow molding and filling,
After the injection / flow filling step, the counter pressure in the cavity is released, and the volume of the cavity of the mold is expanded to the volume of the foamed product, thereby generating a foam cell by the inert gas. Foaming process,
And a foam injection molding method. Using a mold that has a plurality of gates and can change the volume of the cavity at the time of the mold clamping to a filling volume smaller than the foam molding product volume and the foam molding product volume of a size that regulates the outer surface of the foam molding product,
A mold clamping step of clamping the mold so that the volume of the cavity becomes the filling volume;
After the mold clamping step, the inert resin of the supercritical fluid is kneaded and mixed simultaneously by the plurality of injection units corresponding to the plurality of gates into the cavity of the filling volume. Injection / flow filling process of switching to flow mold after injection and filling
After the injection / flow filling step, a foaming step of generating a foam cell with an inert gas of the supercritical fluid by expanding the volume of the cavity of the mold to the volume of the foam molded article,
And a foam injection molding method. Using a mold having a plurality of gates and a mold that can change the volume of the cavity at the time of mold clamping to a foam volume of a size that regulates the outer surface of the foam molded product and a filling volume smaller than the foam molded product volume,
A mold clamping step of clamping the mold so that the volume of the cavity becomes the filling volume;
After the mold clamping step, a counter pressure applying step of injecting an inert gas into the cavity to apply and maintain a counter pressure,
After the counter pressure applying step, a plurality of injection units corresponding to the plurality of gates simultaneously kneading and mixing an inert gas of a supercritical fluid into the cavity of the filling volume, and the molten resin is diffused into the resin. Injection / flow filling step of injecting and then switching to flow mold and filling
After the injection / flow filling step, the counter pressure in the cavity is released, and the volume of the cavity of the molding die is expanded to the volume of the foamed molded product, whereby foaming of the supercritical fluid with an inert gas is performed. A foaming process for generating cells,
And a foam injection molding method. Using a mold having a plurality of gates and a mold that can change the volume of the cavity at the time of mold clamping to a foam volume of a size that regulates the outer surface of the foam molded product and a filling volume smaller than the foam molded product volume,
A mold clamping step of clamping the mold so that the volume of the cavity becomes the filling volume;
After the mold clamping step, a counter pressure applying step of applying and holding a counter pressure by injecting a supercritical fluid inert gas into the cavity,
After the counter pressure applying step, a plurality of injection units corresponding to the plurality of gates simultaneously kneading and mixing an inert gas of a supercritical fluid into the cavity of the filling volume, and the molten resin is diffused into the resin. Injection / flow filling step of injecting and then switching to flow mold and filling
After the injection / flow filling step, the counter pressure in the cavity is released, and the volume of the cavity of the molding die is expanded to the volume of the foamed molded product, whereby foaming of the supercritical fluid with an inert gas is performed. A foaming process for generating cells,
And a foam injection molding method. The foam injection molding method according to any one of claims 1 to 5, wherein the inert gas is a carbon dioxide gas or a nitrogen gas. After the injection / flow filling step is completed and before the foaming step is started, a skin layer forming step of forming a skin layer by cooling from the inner wall of the cavity while waiting in a state at the time of completion of the injection / flow filling step The foam injection molding method according to any one of claims 1 to 6, wherein the method is performed. A foam injection-molded article formed by the foam injection molding method according to any one of claims 1 to 7. A molding die (1) having a plurality of gates (2a) and capable of changing the volume of the cavity (1a) between a volume of the foam molded product having a size for regulating the outer surface of the foam molded product and a filling volume smaller than the volume of the foam molded product. And a plurality of injection units (4) corresponding to the plurality of gates, and a mold clamping device for clamping the molding die to change the volume of the cavity to the foam molded product volume and the filling volume. Equipped,
Each of the injection units includes a cylinder (5) having an inert gas supply port (9) and a screw (6) disposed in the cylinder. A plasticizing function for measuring the molten resin that is mixed and mixed into the resin and diffusing the resin; and the molten resin that is mixed and mixed with the measured inert gas and injecting the molten resin into the cavity. A filling / injection / filling function; and a flow mold function of filling the cavity with the molten resin kneaded / mixed with the inert gas by the driving force of the rotation of the screw and diffused in the resin. A foam injection molding apparatus characterized in that: A mold (21) having a plurality of gates (22a) and capable of changing the volume of a cavity (21a) between a molded product volume for regulating the outer surface of the foamed molded product and a filling volume smaller than the molded product volume; A mold clamping device that clamps a mold to change the volume of the cavity into the molded product volume and the filling volume; and a plurality of injection units (24) corresponding to the plurality of gates.
Each of the injection units includes a cylinder (25) having a supercritical fluid supply port (29) and a screw (26) disposed in the cylinder, and kneads and melts a resin and an inert gas of a supercritical fluid. The supercritical fluid inert gas is kneaded and mixed, and the plasticizing function of measuring the molten resin diffused into the resin is performed.The supercritical fluid inert gas is kneaded and mixed and diffused into the resin. The injection function of injecting and filling the molten resin into the cavity, and the inert gas of the supercritical fluid is kneaded and mixed by the driving force of the rotation of the screw, and the molten resin diffused in the resin is injected into the cavity. And a flow molding function for filling the foam injection molding apparatus. 11. The foam injection molding apparatus according to claim 9, wherein a casting / exhaust means for injecting / exhausting an inert gas is provided in the mold (1, 21). 11. The foam injection molding apparatus according to claim 9, wherein a casting / exhausting means for injecting / exhausting an inert gas of a supercritical fluid is provided in the mold (1, 21).

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