JP2001162660A - Method and apparatus for manufacturing foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for molding a foam wherein pressure control is easy, it can easily enter a cooling process before entering an injection process, further a trouble on staying of molten resin is little and an existing molding machine can be applied only by changing, for example, a specification. SOLUTION: A principal injection unit 10 comprising an injection machine, and a sub-injection unit 1 comprising the injection machine in the same way are used. A resin material is plasticized by the subinjection unit 1, and carbon dioxide fluid in a supercritical state is injected and melted to obtain a foamed molten resin HJ. Its specific amount is stored while a back pressure is applied to the injection unit 10, and then cooled. Besides a screw 13 is rotatively driven at a low speed, dissolution and osmosis of the carbon dioxide fluid are accelerated, and thereafter the foam is obtained by injection from the principal injection unit 10 into the cavity of the mold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a main injection unit comprising a cylinder barrel and a screw drivably mounted in the cylinder barrel, and a main injection unit similarly drivable in the cylinder barrel and the cylinder barrel. The present invention relates to a method for producing a foam using a sub-injection unit comprising a screw and a method for producing the foam, and a production apparatus used for carrying out the method.

[0002]

2. Description of the Related Art A method for molding a foam made of a thermoplastic resin is as follows.
Conventionally, a chemical blowing agent is generally used as a blowing agent. Chemical blowing agents are low-molecular-weight organic substances that decompose at the molding temperature to generate gas, and are mixed with a resin material and weighed, or a material obtained by melting and kneading a foaming agent in advance in an extrusion process to form a pellet is used. It is weighed and injected into the mold cavity to foam and obtain a foam. By the way, the chemical foaming agent is expensive and has a drawback that the cost of the foam is increased. Further, the decomposition residue of the chemical foaming agent remaining in the foam may discolor the foam as a product or cause odor, which is not always preferable. Furthermore, there is a possibility that harmful substances such as dioxin may be generated. Thus, physical blowing agents have also been used as an alternative to chemical blowing agents. That is, when the resin material is melt-kneaded by an injection device, a fluid of supercritical carbon dioxide as a physical foaming agent is injected into the molten resin,
Dissolve and inject into the mold cavity to foam to obtain a foam.

[0003] Representative molding methods for obtaining a foam using such a physical foaming agent are disclosed in JP-A-6-506724 and JP-A-10-230528. As shown in FIG. 5A, the apparatus for producing a fine foam disclosed in the above-mentioned Japanese Patent Publication No. 6-506724 is provided in a cylinder barrel 80 and inside the cylinder barrel 80. A static mixer 83 is provided near the downstream end of the cylinder barrel 80, including a mixing screw 81, a supercritical physical foaming agent supply device 82, and the like. Also,
A counter pressure gas is supplied from a gas cylinder 86 to the mold cavity 85. Therefore, when the polymer plastic material is supplied to the cylinder barrel 80 and the mixing screw 81 is driven to rotate, the polymer plastic material melts as is well known. Therefore, when a supercritical carbon dioxide liquid is injected from the physical foaming agent supply device 82, the two types of materials, the molten resin and the carbon dioxide liquid, are diffused by increasing the contact area by mixing, and Further mixing by the mixer 83 further causes the liquid of carbon dioxide to permeate and saturate the molten resin, and becomes a complete one-phase solution by the diffusion chamber 84 and is injected into the mold cavity 85. At this time, when the counter pressure is applied to the cavity 85 and the counter pressure is released at a stretch after the injection, a foam having small cell cells is obtained.

The foam manufacturing apparatus disclosed in Japanese Patent Application Laid-Open No. Hei 10-230528 is, as shown in FIG. 5 (b), schematically showing a cylinder barrel 90 and a rotating inside the cylinder barrel 90. A kneading screw 91 operably provided, a physical foaming agent supply device 92, an accumulator 93, an injection device 94 having an injection plunger 95,
It consists of a mold 96 and the like. Accordingly, when the kneading screw 91 is driven to rotate and the pellet-shaped resin material is supplied, the resin material is melted as conventionally known. At this time, when the liquid of supercritical carbon dioxide is supplied from the physical blowing agent supply device 92, a molten resin material composition in which the molten resin and the liquid of carbon dioxide are compatible with each other is obtained. When the injection plunger 95 is supplied to the injection plunger 95 via the accumulator 93 and cooled by lowering the temperature and cooling while maintaining the pressure in the supercritical state, and the injection plunger 95 is driven by the injection device 94, Cavity 9 of mold 96
Since a counter pressure is applied to 7 from the gas cylinder 98, a foam is obtained as described above. At this time, when the counter pressure is released after the surface is solidified, a thermoplastic resin foam having an unfoamed skin layer on the surface is obtained.

[0005]

As described above, foams can be produced by the conventional foam production apparatus, but there are problems. For example, according to the manufacturing apparatus shown in FIG. 5, since an injection molding machine is used, when the mixing screw is rotated and measured, back pressure is applied to the mixing screw 81 and there is no problem. When the injection process is started after the end of the measurement, the back pressure temporarily stops, so that the molten resin and the carbon dioxide fluid are separated from each other, and it is considered that it is difficult to obtain fine foam cells even when the molten resin is injected into the mold cavity.
In order to grow the foam cell, it is desirable to insert a cooling step before the injection step to promote the dissolution of the carbon dioxide fluid, but since it is composed of one cylinder barrel 80 having good heat conduction, Cooling process cannot be included. According to the manufacturing apparatus shown in FIG. 6, since the plasticizing device and the injection device including the injection plunger are independent,
Although the temperature of the injection plunger can be lowered, the injection device is dedicated to injection and is not versatile, which may increase the cost. Further, since the injection plunger is composed of a cylinder and a piston, the molten resin may stay at the tip of the cylinder even if the injection is performed, and the resin may be burned. An object of the present invention is to solve the above-mentioned problems and to provide a foam molding method and a molding apparatus. Specifically, pressure management is easy, and a cooling step is also performed before entering an injection step. Provided is a foam molding method and a molding apparatus used for carrying out this molding method, which can be easily inserted, has little problem of molten resin staying, and can be applied to an existing molding machine simply by changing specifications, for example. It is intended to be.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to use two injection units, a sub-injection unit and a main injection unit, one of which has a plasticizing function and the other has a plasticizing function. This is achieved by having an injection function. That is, in order to achieve the above object, the invention according to claim 1 provides a main injection unit including a cylinder barrel and a screw drivably provided in the cylinder barrel, and a cylinder barrel and the cylinder. Using a sub-injection unit consisting of a screw drivably provided in the barrel and the sub-injection unit, the screw is rotated to plasticize the resin material to form a foamed molten resin containing a foaming agent. Then, the main injection unit is stored in a predetermined amount while applying a back pressure to the main injection unit, and a screw is driven from the main injection unit in an axial direction to be injected into a mold cavity to obtain a foam. You. According to a second aspect of the present invention, a main injection unit including a cylinder barrel and a screw drivably provided in the cylinder barrel is provided. Similarly, the main injection unit is provided drivably in the cylinder barrel and the cylinder barrel. Using a sub-injection unit consisting of a screw and the sub-injection unit, the screw is rotationally driven to plasticize the resin material and inject a supercritical physical foaming agent, dissolve and foam the molten resin. Obtaining and storing a predetermined amount of this while applying back pressure to the main injection unit, and cooling it to promote the dissolution and penetration of the physical blowing agent, and then driving the screw in the axial direction from the main injection unit. It is configured to be injected into the mold cavity to obtain a foam. The invention according to claim 3 provides a main injection unit including a cylinder barrel and a screw drivably provided in the cylinder barrel,
Similarly, using a sub-injection unit composed of a cylinder barrel and a screw provided drivably in the cylinder barrel, the sub-injection unit drives the screw to rotate and plasticize the resin material, and A physical foaming agent in a critical state is injected and dissolved to obtain a foamed molten resin, which is stored in a predetermined amount while applying a back pressure to the main injection unit. It is configured to promote the dissolution and penetration of the foaming agent, and then drive the screw from the main injection unit in the axial direction to inject the screw into the mold cavity to obtain a foam. According to a fourth aspect of the present invention, a gas counterpressure is applied to the mold cavity according to any one of the first to third aspects, and the counterpressure is applied immediately before or immediately after the injection filling of the foamed molten resin. According to a fifth aspect of the present invention, the cavity of the mold according to any one of the first to third aspects is subjected to a counter pressure by a gas so as to perform the injection operation of the foamed molten resin. Injection is performed while performing to a predetermined position corresponding to a molded product that can obtain a mold opening operation immediately before or following the end of injection, and when the mold opening operation is started following the injection operation, the operation is started immediately after the start of the mold opening and immediately before the end of the injection. In such a case, the counter pressure is released immediately after the predetermined mold opening.
The invention according to claim 4, wherein the gas according to claim 4 or 5 is an inert gas such as nitrogen gas, argon gas, carbon dioxide gas, and the like, the pressure of which is equal to or higher than the supercritical pressure of the blowing agent, The invention according to claim 7 is configured such that the gas according to claim 4 or 5 is air, and the pressure thereof is 3.0 MPa or less. According to an eighth aspect of the present invention, a main injection unit including a cylinder barrel and a screw drivably provided in the cylinder barrel is provided. Similarly, the main injection unit is provided drivably in the cylinder barrel and the cylinder barrel. A sub-injection unit consisting of a screw, a molding device for obtaining a molded product, and a physical foaming agent supply device, wherein the sub-injection unit includes a supercritical physical foaming device from the physical foaming agent supply device. An agent is supplied, and the foamed molten resin produced by the sub-injection unit is stored in the main injection unit, and is injected into the cavity of the molding apparatus. According to a ninth aspect of the present invention, the molding apparatus of the eighth aspect is provided with a mold clamping device having an injection compression function, and the invention of the tenth aspect is provided with the main injection of the eighth or ninth aspect. A plurality of pin-shaped protrusions are provided at the tip of the screw of the unit,
The invention according to claim 11 is the screw of the main and sub injection units according to any one of claims 8 to 10,
The sub-injection unit is driven by an electric servomotor and configured to have a flow molding function.

[0007]

Embodiments of the present invention will be described below. FIG. 1A is a cross-sectional view schematically showing the entirety. As shown in FIG. 1, the foam manufacturing apparatus according to the present embodiment is a plasticizing apparatus for obtaining a foamed molten resin. That is, it has two injection units, a sub-injection unit 1 and a main injection unit 10 for injecting plasticized molten resin. In the present embodiment, a physical blowing agent supply device 30 that supplies a fluid of carbon dioxide in a supercritical state is provided toward the sub-injection unit 1.

The sub-injection unit 1 has a cylinder barrel 2 having a relatively small capacity. A screw 3 is provided inside the cylinder barrel 2. The screw 3 is driven in the rotation direction and the axial direction,
It also has a flow mold function. As described above, since a flow molding function is provided, a large amount of molten resin can be produced by increasing the rotational driving time of the small-diameter screw 3.
In addition, since the diameter of the screw 3 is small, the number of revolutions is increased to increase the calorific value, so that the kneading and melting of the resin material can be promoted, and the mixing and dissolution of the carbon dioxide fluid can be promoted. Although a driving device for driving the screw 3 performing such an operation is not shown in FIG. 1A, in the present embodiment, an electric servo provided at the rear end of the heating cylinder barrel 2 is used. It consists of a motor. Therefore, the sub injection unit 1 is constituted by the electric injection molding device. Thereby, the rotation speed, back pressure, etc. of the screw 3 can be freely selected. It should be noted that, as will be apparent from the following description, the screw 3 of the sub injection unit 1
Does not need to be driven in the axial direction to obtain a foamed molten resin. However, since the existing injection machine is also driven in the axial direction, "driving in the axial direction" is described in the sense of applying the existing injection machine.

On the outer periphery of the cylinder barrel 2, a plurality of heaters 4, 4,... A fluid supply port 5 for supplying a carbon dioxide fluid reaching the inside of the cylinder barrel 2 is provided in the vicinity of the tip of the cylinder barrel 2, that is, in the vicinity where the resin material is substantially completely melted. I have. A hopper for supplying the resin material is provided at the rear end of the fluid supply port 5, that is, on the upstream side, but this hopper is not shown in FIG.

In order to feed the molten molten resin measured by the sub-injection unit 1 toward the main injection unit 10, a first heating block 6 which is bent at a substantially right angle is provided in the present embodiment. A molten resin passage 7 is formed inside the first heating block 6, and the beginning of the molten resin passage 7 communicates with the tip of the cylinder barrel 2. The terminal end of the first heating block 6 is connected to a substantially intermediate portion of a second heating block 16 connected to the main injection unit 10, which will be described in detail later. A plurality of heaters 8, 8,... For controlling the heat generation temperature are also provided on the outer peripheral portion of the first heating block 6. The reference numerals 9 and 9 ′ indicate the molten resin passages 7 of the first heating block 6.
Shows a plug closing a hole drilled to form a hole.

In the present embodiment, the physical blowing agent supply device 30 is a gas cylinder 31 filled with carbon dioxide gas.
And carbon dioxide gas in a supercritical state (critical temperature 31.1 & d
eg, C, a critical pressure of 7.38 MPa or more), a pressure increasing pump 32, a pressure control valve 33, a flow control valve, and the like.
These are connected in order by a conduit 34. The end of the pipe 34 is connected to the fluid supply port 5 of the cylinder barrel 2. In the illustrated embodiment, a heating device for heating the carbon dioxide gas to a supercritical temperature or higher is not provided. Therefore, the carbon dioxide gas supplied at a pressure equal to or higher than the supercritical pressure is heated in the cylinder barrel 2 and becomes a liquid of carbon dioxide in a supercritical state. Thus, it can be supplied with carbon dioxide gas, or it can be supplied as a liquid of supercritical carbon dioxide by further providing a heating device, so the expression "supercritical carbon dioxide fluid" Will include carbon dioxide gas whose temperature has not reached the supercritical temperature.

In the present embodiment, the main injection unit 10 has a cylinder barrel 12 having a relatively large capacity.
A screw 13 is provided inside the cylinder barrel 12.
The screw 13 is also driven in the rotation direction and the axial direction in the present embodiment. in this way,
Although not shown in FIG. 1A, the driving device for driving the screw 13 also includes an electric servomotor provided at the rear end of the cylinder barrel 12. Therefore, in the present embodiment, the main injection unit 10 is also constituted by the electric injection molding device. Thereby, the rotation speed, back pressure, etc. of the screw 13 can be freely selected, and the dissolution of the carbon dioxide fluid, the maintenance of the supercritical pressure, and the like are facilitated. A plurality of heaters 14, 14,... For which the heat generation temperature is set are also provided on the outer peripheral portion of the cylinder barrel 12. The tip of the cylinder barrel 12 constitutes a part of the plunger chamber 15, and a plurality of pin-like projections 11 are provided on the outer periphery of the tip of the screw 13 corresponding to the plunger chamber 15. , 11, ... are provided.
Therefore, when the screw 13 is driven to rotate, the foamed molten resin stored in the plunger chamber 15 is
., And the fluid of carbon dioxide is further dissolved. Although the main injection unit 10 is also constituted by an electric injection molding device, this main injection unit 10 does not have a hopper for supplying a resin material in the present embodiment. In other words, the main injection unit 10 is selected so as to act as a plunger and to promote the dissolution of the carbon dioxide fluid. However,
Since the screw 13 having the flight is provided, it can be plasticized, and can be used as a normal injection molding machine only by changing the program of the screw driving device, and can be used together with the sub-injection unit 1. It is clear that a sandwich molded article can be formed in this manner. When used as a normal injection molding machine, a hopper is attached to the main and sub injection units 10 and 1.

The cylinder barrel 12 of the main injection unit 10
The second heating block 16 is connected to the tip of the second heating block 16. Inside the second heating block 16, a molten resin passage 17 is also formed in the axial direction. The diameter of the molten resin passage 17 on the side of the cylinder barrel 12 is enlarged and the molten resin passage 17 is formed in the plunger chamber 15 of the cylinder barrel 12. It is connected. Therefore, the plunger chamber 15 is constituted by a portion where the diameter of the molten resin passage 17 is enlarged and a front portion of the cylinder barrel 12. An injection nozzle 20 having a conventionally well-known shape is attached to the tip of the second heating block 16. The nozzle hole 21 of the injection nozzle 20 is
It communicates with the molten resin passage 17. A three-way valve 22 is provided at a substantially intermediate portion of the molten resin passage 17. By switching the three-way valve 22, a state in which the molten resin passages 7 and 17 of the first and second heating blocks 6 and 16 are in communication with each other as shown in FIG. ), A state where the molten resin passages 17 and 17 communicate with each other can be adopted.

Since a molding apparatus is well known in the art, a first molding apparatus including a mold used for performing the first injection molding, a counter pressure adding apparatus, and the like is not shown. FIG. 2B schematically illustrates a second molding apparatus including a mold, a counter pressure adding device, and the like used for performing molding. Since the first molding device is configured in substantially the same manner as the second molding device, an embodiment of the second molding device will be described below. Second
Is composed of a mold, a mold clamping device, and the like. The mold is composed of a fixed mold 40 and a movable mold 41, and a cavity 42 is formed along the parting line P of the molds 40 and 41. Are formed. The counter pressure adding device 45 for adding the counter pressure to the cavity 42 includes a gas cylinder 46 filled with carbon dioxide gas, a pressurizer for increasing the pressure to a supercritical pressure or higher, a pressure control valve 47, and the like, and these are connected. The conduit 48 opens to the parting line P. According to the present embodiment, the mold clamping device has an injection compression function, but the mold clamping device is not shown in the drawing.

Next, an example of molding using the above-mentioned foam manufacturing apparatus will be described with reference to the operation timing chart of FIG. The present manufacturing apparatus can be formed either automatically or manually by a control device. Hereinafter, an example of semi-automatic forming will be described for convenience. Heaters 4, 4, 14, 14, 8, provided on the outer peripheral portions of the cylinder barrels 2, 12 and the first and second heating blocks 6, 16;
The heat generation temperatures of 8, 18, and 18 are set. The heating temperature of the heaters 14, 14,... Of the cylinder barrel 12 of the main injection unit 10 is set to be 30 to 50 ° C. lower than the heating temperature of the heaters 4, 4,. Further, the amount of plasticization of the foamed molten resin is set. Also, as shown in FIG. 1A, the three-way valve 22 is switched so that the molten resin passages 7 and 17 of the first and second heating blocks 6 and 16 communicate with each other.

Then, the screw 3 of the sub-injection unit 1
Is driven to rotate. Further, a predetermined amount of a thermoplastic resin material is supplied from the hopper to the cylinder barrel 2. Then,
The resin material is provided with heat applied from heaters 4, 4,... Provided on the outer peripheral portion of the cylinder barrel 2 and heat generated by a frictional action, a shearing action, and the like generated in the process of rotating and driving the screw 3 to the destination. Gradually melts. A predetermined amount of carbon dioxide fluid in a supercritical state is injected from the physical blowing agent supply device 30. At this time, since the screw 3 has a flow molding function, it is driven to rotate at a fixed position where the screw 3 has moved forward. Therefore, the distance that the resin material passes through the flight of the screw 3 is constant, and the injected carbon dioxide fluid is stably and uniformly dispersed and dissolved in the molten thermoplastic resin.
In this way, the saturated foamed molten resin HJ in which the carbon dioxide fluid is uniformly dissolved passes through the first and second heating blocks 6 and 16 and is accumulated in the plunger chamber 15 of the main injection unit 10. You. At this time, a back pressure for maintaining the supercritical state is applied. For example, in this embodiment, since a fluid of carbon dioxide is used, the supercritical state is a critical temperature of 31.1 ° C. and a critical pressure of 7.38 MPa or more. The setting of the back pressure is desirably 7.5 MPa or more in terms of molten resin pressure. The screw 13 of the main injection unit 10 retreats against this back pressure. FIG. 1B shows a state in which the foamed molten resin HJ has been accumulated in the plunger chamber 15 of the main injection unit 10 in this manner.

When accumulated, the screw 13 of the main injection unit 10 has a molten resin pressure of 7.5 M corresponding to the supercritical pressure.
Since a back pressure of Pa or more is applied, foaming does not occur.
In addition, since the temperature of the cylinder barrel 12 of the main injection unit 10 is lower by 30 to 50 ° C., the carbon dioxide fluid is more permeated. Further, when a predetermined amount is accumulated, the screw 13 of the main injection unit 10 starts to be driven to rotate, so that the foamed molten resin HJ stored in the plunger chamber 15 by the protrusions 11, 11,. Are stirred by the objects 11, 11,... And the fluid of carbon dioxide is further dissolved.

When a predetermined amount of the foamed molten resin HJ is fed into the plunger chamber 15, the three-way valve 22 is switched to the position shown in FIG. 2A, and the screw 13 of the main injection unit 10 is rotated. To start injection of the foamed molten resin HJ. Immediately before injection, apply counter pressure to the mold cavity. Immediately before or immediately after the foamed molten resin HJ fills the mold cavity, the counter pressure is released at a stretch. Thereby, the foamed molten resin HJ
Foaming starts at the same time, and a foam having fine foam cells, which does not decrease in strength as compared with a solid molded product, can be obtained. After the holding pressure and cooling are completed, the movable mold is opened and the foam is taken out as conventionally known. In this way, for example, it is possible to obtain molded articles of various foams such as door trims, seat members, covers for automobile parts, container boxes, boards, tables and the like for industrial products, and other furniture and gardening goods. Hereinafter, it manufactures similarly.

FIG. 4 shows another embodiment of the present invention. The same reference numerals are given to the same components as those in the above-described embodiment, and the same components are denoted by the same numerals with dashes “′”, and the description will not be repeated. Molten resin passage 7 'of heating block 6'
Is provided with a static mixer M, and a physical blowing agent supply port 5 'is provided on the upstream side. According to the present embodiment, a foamed molten resin is obtained by dissolving a liquid of carbon dioxide in a supercritical state, stored in the plunger chamber 15 and cooled, and the screw 13 is driven to rotate so that the protrusion of the screw 13 is formed. Obviously, it is possible to further dissolve and permeate the fluid of carbon dioxide by stirring with the objects 11, 11,. It is also clear that a foam can be obtained as described above.

The present invention can be modified in various forms without being limited to the above embodiment. For example, foaming can be performed as follows. That is, (b) of FIG.
As shown in (2), the counter pressure is applied to the cavity 42 of the molds 40 and 41 from the counter pressure adding device 45 immediately before injection. The injection of the foamed molten resin HJ is started (1st step). The movable mold 41 is retracted simultaneously with the injection or with a time lag, and the injection is performed while expanding the cavity 42 (2nd step). The counter pressure is released (3rd step). Thereby, the foamed molten resin HJ
Foaming starts all at once. According to this method, a thick foam having a uniform cell structure and a fine cell structure can be obtained. Alternatively, the foamed body can be obtained by releasing the counter pressure immediately after injecting the foamed molten resin and following the movable mold while foaming the foamed resin to retract. Further, from this state, the movable mold can be driven in the mold closing direction and compressed to obtain a foam having a dense surface and higher strength.

In the above embodiment, carbon dioxide gas is used as the physical blowing agent. However, it is obvious that the present invention can be carried out using nitrogen gas, butane gas, or the like other than carbon dioxide gas. When carbon dioxide gas is applied to the gas for the counter pressure and the physical blowing agent is a fluid of carbon dioxide, the counter pressure is 7.4 to 10 MPa.
Although a is desirable, it has also been found that air can be used depending on the type of resin for cost reduction. The air pressure at this time was effective at 2.5 to 3.0 MPa.
It is clear that the gas for the counter pressure can also be implemented with nitrogen gas, argon gas or the like other than carbon dioxide gas. When the process is performed with nitrogen gas, the flowability of the molten resin raw material is improved, a foam having a stable thickness can be obtained, and burning of the resin can be prevented. Further, it is clear that a suitable effect can be obtained not only by a physical blowing agent but also by a chemical blowing agent.

In the present embodiment, the screw 13 of the main injection unit 10 is provided with a flight.
A flight is not necessarily required since no plasticization takes place in the main injection unit 10. However, protrusion 1
Are preferably provided.

[0023]

As described above, according to the present invention, the main injection unit including the cylinder barrel and the screw drivably provided in the cylinder barrel, and the main injection unit similarly driven in the cylinder barrel and the cylinder barrel Using a sub-injection unit consisting of a screw and a screw provided as possible, the sub-injection unit rotates and drives the screw to plasticize the resin material to obtain a foamed molten resin containing a foaming agent. Is stored in a predetermined amount while applying back pressure to the main injection unit, and from the main injection unit, the screw is driven in the axial direction and injected into the mold cavity to obtain a foam. In other words, the sub-injection unit Using two injection units, the main injection unit, with one injection unit having a plasticizing function and the other injection unit having an injection function. Therefore, it is easy to control the pressure to maintain the pressure above the supercritical pressure of the inert gas, and before injection, the cooling process can be easily inserted without impairing the fluidity of the molten resin. The unique effect of the present invention is that a lightweight, high-strength foam having a small number of fine cells and thus having a high strength can be obtained with a short cooling time after holding the pressure and a short molding cycle. Can be In addition, since an existing molding machine can be applied to the main and sub injection units only by, for example, changing specifications, an effect that a foam can be obtained at low cost can be obtained. In addition, when a dedicated main and sub injection unit is used for carrying out the present invention, simply replace the screw and attach the hopper,
Since it can be used as a standard injection molding machine and also as a sandwich injection molding machine, the operation rate can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a manufacturing apparatus according to an embodiment of the present invention in a partial cross-section, and FIG.
(B) is a front view showing a state in which plasticization has been completed.

FIG. 2 is a diagram schematically showing a cross section of a part of a manufacturing apparatus according to an embodiment of the present invention, wherein FIG. 2A shows a state in which a foamed molten resin is injected, and FIG. It is sectional drawing which shows each stage of a process with a metal mold | die.

FIG. 3 is an operation timing chart showing a manufacturing process of the present invention.

FIG. 4 is a cross-sectional view schematically showing a manufacturing apparatus according to another embodiment of the present invention in a partial cross-section.

FIG. 5 is a view schematically showing a conventional foam molding apparatus;
(A) and (B) are cross-sectional views showing different conventional examples.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Sub injection unit 2 Screw 3 Cylinder barrel 10 Main injection unit 11 Projection 12 Cylinder barrel 13 Screw 15 Plunger room 26 Counter pressure addition device 30 Physical blowing agent supply device

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[Procedure amendment]

[Submission date] December 8, 1999 (1999.12.
8)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

[0005]

As described above, foams can be produced by the conventional foam production apparatus, but there are problems. For example, according to the manufacturing apparatus shown in FIG. 5 (a) , since an injection molding machine is used, when the mixing screw is rotated and measured, a back pressure is applied to the mixing screw 81. There is no problem, but when entering the injection process after the end of metering, the back pressure temporarily stops, so the molten resin and the fluid of carbon dioxide separate, and it is difficult to obtain fine foam cells even when injected into the mold cavity. Conceivable. In order to grow a foam cell, it is desirable to insert a cooling step before the injection step to promote the dissolution of the carbon dioxide fluid.
Since it is composed of 0, a cooling step cannot be performed. According to it has manufacturing apparatus shown in (b) of FIG. 5, since the injection apparatus and plasticizing unit consists injection plunger are independent, although it is possible to lower the temperature of the injection plunger, an injection device Injection only, which is not versatile and may increase costs. Also, the injection plunger
Since it is composed of a cylinder and a piston, even if it is injected, the molten resin may stay at the tip of the cylinder and cause resin burning. An object of the present invention is to solve the above-mentioned problems and to provide a foam molding method and a molding apparatus. Specifically, pressure management is easy, and a cooling step is also performed before entering an injection step. Provided is a foam molding method and a molding apparatus used for carrying out this molding method, which can be easily inserted, has little problem of molten resin staying, and can be applied to an existing molding machine simply by changing specifications, for example. It is intended to be.

Continued on the front page (72) Inventor Fumio Tsuda 1-6-1, Funakoshi-minami, Aki-ku, Hiroshima-shi, Hiroshima Japan Steel Works Co., Ltd. (72) Inventor Atsushi Teraoka 1-6-1, Funakoshi-minami, Aki-ku, Hiroshima-shi, Hiroshima No. Japan Steel Works, Ltd. (72) Inventor Toru Emi 1-6-1, Funakoshi Minami, Aki-ku, Hiroshima-shi, Hiroshima F-term in Japan Steel Works, Ltd. (reference) 4F206 AB02 AG20 JA04 JD02 JD05 JF04 JL02 JM01 JM04 JM12 JM16 JN27 JQ62 JQ83 JT05 JT33

Claims (11)

[Claims] 1. A main injection unit comprising a cylinder barrel and a screw drivably provided in the cylinder barrel, and a cylinder barrel and a screw drivably provided in the cylinder barrel. Using the sub-injection unit, the sub-injection unit drives and rotates the screw to plasticize the resin material to obtain a foamed molten resin containing a foaming agent, and applies a back pressure to the main injection unit. A method for manufacturing a foam, wherein a predetermined amount is stored while the screw is being driven in the axial direction from the main injection unit and injected into a mold cavity to obtain a foam. 2. A main injection unit comprising a cylinder barrel and a screw drivably provided in the cylinder barrel, and a cylinder barrel and a screw drivably provided in the cylinder barrel. Using the sub-injection unit, the sub-injection unit drives and rotates the screw to plasticize the resin material and inject and dissolve a supercritical physical blowing agent to obtain a foamed molten resin. Is stored in a predetermined amount while applying back pressure to the main injection unit, and then cooled to promote the dissolution and penetration of the physical foaming agent. Thereafter, the screw is driven in the axial direction from the main injection unit to mold the cavity of the mold. To obtain a foam by injecting into a foam. 3. A main injection unit comprising a cylinder barrel and a screw drivably provided in the cylinder barrel, and a cylinder barrel and a screw drivably provided in the cylinder barrel. Using the sub-injection unit, the sub-injection unit drives and rotates the screw to plasticize the resin material and inject and dissolve a supercritical physical blowing agent to obtain a foamed molten resin. Is stored in a predetermined amount while applying a back pressure to the main injection unit, and the screw is rotated at a low speed to cool and promote the dissolution and penetration of the physical foaming agent. And producing a foam by injecting the mixture into a mold cavity. 4. A counter pressure by gas is applied to the cavity of the mold according to any one of claims 1 to 3, and the counter pressure is released immediately before or immediately after the injection filling of the foamed molten resin. A method for producing a foam. 5. A cavity of the mold according to any one of claims 1 to 3, which is subjected to a counter pressure by a gas, so as to follow the injection operation of the foamed molten resin or perform the mold opening operation immediately before the end of the injection. Inject while performing to the predetermined position corresponding to the obtained molded product, when the mold opening operation is started following the injection operation, immediately after the start of mold opening, and when started immediately before the end of injection, counter pressure immediately after the predetermined mold opening. To release the foam. 6. The production of a foam, wherein the gas according to claim 4 or 5 is an inert gas such as a nitrogen gas, an argon gas, a carbon dioxide gas or the like, and the pressure thereof is equal to or higher than the supercritical pressure of the foaming agent. Method. 7. The gas according to claim 4, wherein the gas is air, and the pressure thereof is 3.0 MPa or less.
A method for producing a foam. 8. A main injection unit comprising a cylinder barrel and a screw drivably provided in the cylinder barrel, and a cylinder barrel and a screw drivably provided in the cylinder barrel. A sub-injection unit, a molding device for obtaining a molded product, and a physical blowing agent supply device, wherein the sub-injection unit is supplied with a supercritical physical blowing agent from the physical blowing agent supply device. And the foamed molten resin produced by the sub-injection unit is stored in the main injection unit, and is injected into the cavity of the molding apparatus, Foam manufacturing equipment. 9. The foam manufacturing apparatus according to claim 8, further comprising a mold clamping device having an injection compression function. 10. An apparatus for producing a foam, wherein a plurality of pin-shaped projections are provided at a tip of a screw of the main injection unit according to claim 8 or 9. 11. The foamed body according to claim 8, wherein the screws of the main and sub injection units are driven by an electric servomotor, and the sub injection unit has a flow molding function. manufacturing device.