JP2002307499A - Method and equipment for injection-molding thermoplastic resin molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for injection-molding a thermoplastic resin molded product capable of stably and continuously supplying a foaming agent, especially non-reactive gas such as carbon dioxide, nitrogen gas or the like to a thermoplastic resin under lower pressure to infiltrate the same into the thermoplastic resin in large quantities, and an injection molding equipment using the method. SOLUTION: The foaming agent sent into the foaming agent supply passage 5a, which is provided in a screw 3a from the rear end of the screw 3a to the front end thereof, from the rear end of the screw 3a is supplied to the molten resin from a plurality of the foaming agent supply ports 52 opened in the outer peripheral surface of the screw 3a in a cylinder 2 to be infiltrated into the molten resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for injection molding a thermoplastic resin molded article.

[0002]

2. Description of the Related Art Thermoplastic resin in which a non-reactive gas such as carbon dioxide gas or nitrogen gas as a foaming agent is impregnated into a molten resin to be injected, and the non-reactive gas impregnated resin is injected into a mold and foamed. As a method of injection molding of a foam, 1) a method in which a non-reactive gas is previously impregnated with a non-reactive gas under a high pressure into a solid-state raw material resin before being charged into a cylinder; A method of impregnating with a reactive gas (see US Pat. No. 5,158,986) is known.

However, in the former method of impregnating a non-reactive gas into a raw material resin in a solid state, it is possible to obtain a thermoplastic resin foam, but in order to impregnate the non-reactive gas, for example, a molding machine is used. Since it is necessary to stop supplying the resin to the chamber and impregnate the gas in the pressure-resistant chamber, it takes several tens of hours to reach the gas-saturated impregnation state, which is difficult to implement industrially.

[0004] On the other hand, the conventional method of impregnating a resin in a molten state with a non-reactive gas in a cylinder is based on resin pellets or the like supplied from a raw material supply port into the cylinder.
While melting by rotation of the screw in the cylinder, while the screw is retracted and the molten resin is measured at the tip measuring section of the cylinder, non-reactive gas enters the cylinder from the gas supply port provided in one place of the cylinder It is designed to supply gas. Therefore, since the non-reactive gas is supplied to the molten resin being measured in the high pressure state, it is difficult to inject the gas into the molten resin unless the pressure of the supply gas is higher than the pressure of the molten resin. In addition, the use of a high-pressure gas has a problem in that the apparatus itself must have a pressure-resistant structure capable of withstanding the high-pressure gas, thereby increasing the manufacturing cost.

The inventors of the present invention have proposed a method for stably and continuously impregnating a resin in a cylinder with a non-reactive gas at a relatively low pressure by using a method in an injection molding machine cylinder. A foaming agent, such as a non-reactive gas, is provided inside the screw from the rear end to the front end of the screw in the molten resin having a low resin pressure before reaching the measuring section in a molten state by the rotation of the screw. A non-reactive gas is supplied to the molten resin from a foaming agent supply port opened in the outer peripheral surface of the screw in the cylinder in the supply path, and the foaming agent-impregnated resin after impregnating the foaming agent into the molten resin is measured by the measuring unit. Has already proposed a method of injecting (Japanese Patent Application 200)
0-70724).

However, even in the method proposed by the present inventors, since the number of the blowing agent supply ports is one, even if the impregnation rate of the blowing agent can be made lower than that of the conventional method, it is necessary to increase the impregnation rate to some extent. The gas pressure had to be increased and the improvement had not been completed.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to supply a blowing agent, particularly a non-reactive gas such as a carbon dioxide gas or a nitrogen gas, to a thermoplastic resin stably and continuously at a lower pressure and to produce a large amount of the same. An object of the present invention is to provide an injection molding method of a thermoplastic resin molded article which can be impregnated, and an injection molding apparatus using the method.

[0008]

Means for Solving the Problems In order to achieve the above object, an injection molding method for a thermoplastic resin molded product according to the first aspect of the present invention (hereinafter referred to as "the molding method of the first aspect") is as follows.
A foaming agent impregnating step of supplying a foaming agent from a foaming agent supply port to a molten resin melted by a screw rotation in a cylinder of an injection molding machine, and mixing and impregnating the foaming agent with the molten resin; An injection molding step of injecting the measured resin into the mold cavity after measuring the blowing agent-impregnated molten resin to obtain a foamed molded product, wherein the rear end of the screw Of the blowing agent supply path provided inside the screw from the front end direction,
The foaming agent fed into the foaming agent supply path from the rear end of the screw through a plurality of foaming agent supply ports opened to the screw outer peripheral surface in the cylinder is supplied to the molten resin, and the foaming agent is impregnated in the molten resin. did.

According to a second aspect of the present invention, there is provided an injection molding method for a thermoplastic resin molded article (hereinafter referred to as a “method of the second aspect”). The foaming agent was supplied from a plurality of blowing agent supply ports provided at positions shifted in the front-rear direction.

According to a third aspect of the present invention, there is provided a method for injection-molding a thermoplastic resin article (hereinafter referred to as a “third molding method”) according to the first or second aspect.
The blowing agent was supplied from each blowing agent supply port via a separate blowing agent supply passage.

According to a fourth aspect of the present invention, an injection molding method for a thermoplastic resin molded article (hereinafter, referred to as “a molding method according to a fourth aspect”) is a method according to any one of the first to third aspects. A non-reactive gas for the thermoplastic resin is used as a foaming agent.

According to a fifth aspect of the present invention, there is provided an injection molding apparatus for a thermoplastic resin molded article (hereinafter referred to as a "molding apparatus of the fifth aspect"). In the provided foaming agent supply path, the foaming agent fed into the foaming agent supply path from the rear end of the screw from the foaming agent supply port opening to the screw outer peripheral surface in the cylinder is supplied to the molten resin, and the foaming agent is supplied. An injection molding apparatus in which the blowing agent-impregnated resin after being impregnated into the molten resin is weighed and injected by the measuring section, and the pitch of the front and rear screw flights is increased,
And / or, by the screw shaft diameter is made smaller, the expanded foaming agent impregnated zone forming portion forming an expanded foaming agent impregnated zone having a larger internal volume in the inter-flight space than the inter-flight space is closer to the tip of the screw. , And a plurality of foaming agent supply ports are opened in the enlarged foaming agent impregnation zone forming portion.

According to a sixth aspect of the present invention, an injection molding apparatus for a thermoplastic resin molded article (hereinafter referred to as a “molding apparatus of the sixth aspect”) is a molding apparatus of the fifth aspect, wherein at least one foaming agent is supplied. The port was provided at a position shifted in the front-rear direction of the screw shaft with respect to the other blowing agent supply ports.

According to a seventh aspect of the present invention, there is provided an injection molding apparatus for a thermoplastic resin molded article (hereinafter referred to as a “molding apparatus of the seventh aspect”).
A plurality of foaming agent supply paths separated from each other were provided in the screw, and a foaming agent supply port was provided for each foaming agent supply path.

An injection molding apparatus for a thermoplastic resin molded product according to claim 8 of the present invention (hereinafter referred to as “molding apparatus of claim 8”) is a molding apparatus according to claim 7, wherein at least one foaming agent is supplied. A part of the passage was provided in a pipe shape penetrating the inside of another blowing agent supply passage.

In the injection molding method of the present invention, the position of the blowing agent supply port is not particularly limited as long as the pressure of the molten resin is lower at the rear end side of the screw tip than at the measuring section. However, a portion where the molten resin is not yet completely filled between the screw and the cylinder is preferable.

For example, when the pitch of the front and rear screw flights is increased and / or the screw shaft diameter is reduced as in the molding apparatus of claim 5, the space between the front and rear flights is set in the inter-flight space. The expanded foaming agent impregnated zone forming part which forms an expanded foaming agent impregnated zone having a larger internal volume than the space is provided near the tip of the screw, and the blowing agent is supplied to this expanded foaming agent impregnated zone forming part of the screw. It is preferable to open the mouth, and it is more preferable to open the mouth at a position facing the non-resin-filled portion near the front flight in the expanded foaming agent impregnation zone.

In the blowing agent supply path of the screw, a resin check valve is provided near the blowing agent supply port to prevent molten resin from entering the blowing agent supply path from the blowing agent supply port into the screw. It does not matter.

As the resin check valve, if it opens when the pressure of the blowing agent becomes higher than the pressure of the molten resin,
Although not particularly limited, for example, when the blowing agent is not supplied, the valve is closed by a spring force, and when the pressure of the blowing agent introduced from the blowing agent supply passage is larger than the urging force of the spring, the valve opens, and the blowing agent is opened. When the foaming agent is supplied from the supply port into the cylinder and the molten resin tries to flow backward from the foaming agent supply port, the valve is closed by the biasing force of the spring, and a spring type that prevents entry into the foaming agent supply path (backflow) or Although it is preferable to use a ball check type or the like that ensures operation, an electromagnetic valve that detects the pressure of the molten resin and opens when the pressure of the molten resin becomes lower than a predetermined foaming agent pressure may be used.

The material of the resin check valve is not specified as long as it has a heat resistance of 200 ° C. or higher. However, from the viewpoints of strength, heat resistance, slidability and workability, metals, especially stainless steel, are used. Steel is preferred.

The thermoplastic resin used in the present invention is not particularly limited. Examples thereof include a resin having a high melt viscosity, which is difficult to melt-mold, a resin which is easily decomposed by heat, an additive having a low boiling point or an additive which is easily decomposed by heat. And the like.

Examples of resins that are difficult to melt-mold because of their high melt viscosities include resins for engineering plastics such as ultrahigh molecular weight polyethylene, ultrahigh polymerization degree polyvinyl chloride, polytetrafluoroethylene, and polyimide.

Examples of resins that are easily thermally decomposed include biodegradable resins such as polylactic acid and polyhydroxybutyrate, and polyvinyl chloride and polyacrylonitrile having a high degree of chlorination.

The foaming agent used in the present invention is not particularly limited as long as it does not react with the resin and does not adversely affect the resin such as deteriorating the resin. Non-reactive gases are preferred for the resin to be used, for example, carbon dioxide, nitrogen, argon,
Examples include inorganic gases such as neon, helium, and oxygen, and organic gases such as chlorofluorocarbon and low molecular weight hydrocarbons.

Of these, inorganic gases are preferred in that they have a low adverse effect on the environment and do not require gas recovery, have high solubility in difficult-to-mold resins, have a high melting effect for resins, and are directly released into the atmosphere. Carbon dioxide gas is more preferable from the viewpoint that there is almost no harm. The blowing agent may be used alone, or 2
More than one type of gas may be used in combination.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.
This will be described in detail with reference to the drawings. 1 to 4 show a first embodiment of an injection molding apparatus according to the present invention.

As shown in FIG. 1, the injection molding apparatus A comprises an injection molding machine 1 and a gas injection device 9 for feeding a gas as a foaming agent thereto.

As shown in FIGS. 1 to 3, the injection molding machine 1 includes a cylinder 2 and a screw 3 arranged inside the cylinder.
and an expansion foaming agent impregnated zone 11 mainly composed of a seal box 4 and having a larger inter-flight space volume than other parts and a higher resin feeding speed than the upstream side. It is formed between the screw 3a. In FIG. 1, 12 is a measuring section,
13 is a resin supply hopper, 14 is a unit, and 15 is a connection arm of the seal box 4. As shown in FIGS. 2 and 3, the expanded blowing agent impregnation zone 11
a near the front end (downstream end) of (a) (slightly near the rear end from the front end, that is, near the hopper);
Are formed by being provided.

That is, the expanded foaming agent impregnated zone forming section 3
1 is such that the screw groove is made deeper than the other part of the screw 3a, and the pitch between the front and rear screw flights is made larger so that the expanded foaming agent impregnation zone 11 is formed with the cylinder 2; I have.
The screw 3a has a foaming agent supply passage 5a inside.

As shown in FIGS. 2 to 4, the foaming agent supply passage 5a has one foaming agent introduction port 51 opened on the outer wall surface on the screw rear end outside the cylinder 2 and an expanded foaming agent impregnation zone forming portion 31. 4 open one pair on the outer wall of
Two blowing agent supply ports 52, and in the vicinity of the blowing agent supply port 52,
A spring-type check valve 7 for preventing the backflow of the molten resin from the blowing agent supply port 52 is provided.

Normally, the check valve 7 is closed by the valve body 71 being urged by a spring 72 in the valve closing direction (the direction of arrow X in FIG. 3) so that the molten resin does not flow into the blowing agent supply passage 5a. However, when gas is supplied to the blowing agent supply passage 5a, the valve body 7
1 moves in the valve opening direction (the direction opposite to the arrow X in FIG. 3) against the urging force of the spring 8. That is, the blowing agent is supplied to the molten resin in the expanded blowing agent impregnation zone 11 through the check valve 7 and further through the blowing agent supply port 52.

The seal box 4 is fixed to the drive unit 14 of the injection molding machine 1 by a connection arm 15 so that the position of the seal box 4 does not shift with respect to the forward and backward rotation and rotation of the screw 3a. 3a surrounds the portion where the foaming agent introduction port 51 is formed. The seal box 4 has a ring-shaped groove 4 at a position facing the foaming agent introduction port 51.
1, and a pair of seal members 42 are provided so as to elastically contact the screw peripheral surface so as to sandwich the concave groove 41 from both front and rear sides of the screw 3a and to prevent gas leakage from inside the concave groove 41. .

In the groove 41 of the seal box 4,
An injection port 43 for carbon dioxide gas as a foaming agent injected from a gas injection device 9 opened outside the seal box 4 is provided.

When the rotation of the screw 3a is stopped, the cylinder 2 prevents the gas-impregnated molten resin in the cylinder 2 from flowing back to the resin supply hopper 13 due to the gas pressure, as shown in FIG. A check ring 21 is attached slightly to the rear end from the expanded foaming agent impregnation zone forming portion 31. Check ring 21
Is preferably used to prevent the resin from flowing back, especially when the gas pressure from the blowing agent supply port 52 is high. A shut-off valve 24 is provided at the tip of the cylinder 2 as shown in FIG.

Since the injection molding apparatus A is configured as described above, when the raw resin is supplied from the hopper 13 into the cylinder 2 through the raw material supply port, the raw resin is melted and kneaded by the rotation of the screw 3a. Cylinder 2
Is sent toward the tip. The melt-kneaded resin is sent through the check ring 21 to the pressure release section, that is, the expanded foaming agent impregnation zone 11.

On the other hand, the gas that has exited the gas injection device 9 enters the groove 41 of the seal box 4 via the introduction pipe 91 and the injection port 43, and from the blowing agent introduction port 51 opening at a position facing the groove 41. The expanded foaming agent impregnated zone 1 enters the gas supply passage 5a and enters the four blowing agent supply ports 52 through the check valve 7.
1 and is impregnated with the molten resin filled in the expanded foaming agent impregnation zone 11.

Then, as the molten resin is continuously sent, the blowing agent-impregnated molten resin impregnated with carbon dioxide gas in the expanded foaming agent impregnation zone 11 is sent to the measuring section at the tip of the cylinder 2. As the blowing agent-impregnated molten resin is fed into the measuring section 12, as shown in FIG.
“a” gradually retreats in accordance with the amount of the fed resin, and a predetermined amount of the molten resin impregnated with the blowing agent is measured by the tip measuring section 12 of the cylinder 2.

In this way, the gas-impregnated molten resin that has been measured is injected into an injection mold (not shown) to obtain a foam molded product.

According to the molding method using the injection molding apparatus A configured as described above, the molten resin is impregnated with the carbon dioxide gas in the expanded foaming agent impregnation zone 11 at a lower pressure than the measuring section 12. Even if the supply pressure of the carbon dioxide gas is not so high, the molten resin can be uniformly impregnated with the gas in a short time. In addition, since the gas is supplied from the plural foaming agent supply ports 52, the contact area with the molten resin is increased as compared with the case where the gas is supplied from a single foaming agent supply port, and the carbon dioxide gas can be impregnated in a shorter time. Can be. As a result, a uniform and fine foamed molded article can be provided with high productivity.

In addition, the injection molding apparatus A is arranged such that the pitch of the front and rear screw flights is increased near the tip of the screw 3a and the diameter of the screw shaft is reduced, so that the space between the front and rear flights is increased. The molten resin having an inner volume larger than the inter-flight space at the end side is made to be in a non-filled state at a low pressure, and the blowing agent supply port 52 of the blowing agent supply path 5a provided in the screw 3a is impregnated with an expanded blowing agent. Since it is provided so as to face the zone 11, the supply of carbon dioxide gas can be performed at the screw 3a portion, and the molten resin can be impregnated with the molten resin more efficiently at a lower pressure. Manufacturing cost can be reduced.

The blowing agent supply port 5 of the blowing agent supply passage 5a
Since the spring-type check valve 7 for preventing the backflow of the molten resin from the foaming agent supply port 52 is provided in the vicinity of 2, the gas pressure can be set lower.

FIG. 5 shows a second embodiment of the injection molding apparatus according to the present invention.
1 shows an embodiment of the present invention. As shown in FIG. 5, this injection molding apparatus B has two blowing agent supply paths 5b and 5c in a screw 3b.
The foaming agent introduction ports 51 b and 5 c open at positions facing the concave groove 41 of the same seal box 4, and one of the foaming agent supply paths 5 b
In the same manner as the injection molding apparatus A, except that the blowing agent supply port 52 and the blowing agent supply port 52 of the other blowing agent supply passage 5c are opened at positions shifted in the front-rear direction of the expanded blowing agent impregnation zone 11. Has become.

That is, according to the molding method using the injection molding apparatus B, since each foaming agent supply port 52 is provided for each individual foaming agent supply path 5b (5c), the effect of the injection molding apparatus A is obtained. In addition to this, there is an effect that the supply amount of carbon dioxide gas from each blowing agent supply port 52 can be stabilized.

FIG. 6 shows a third embodiment of the injection molding apparatus according to the present invention.
1 shows an embodiment of the present invention. As shown in FIG. 6, this injection molding apparatus C has two blowing agent supply paths 5d and 5e in a screw 3c.
The injection molding apparatus B described above, except that the foaming agent introduction ports 51 d and 5 e are opened at positions shifted in the front-rear direction of the screw 3 c and open at positions facing the concave grooves 41 of the individual seal boxes 4. Is similar to

That is, according to the molding method using the injection molding apparatus C, in addition to the effect of the injection molding apparatus B, it is easy to change the gas pressure for each seal box 4 and to reduce the carbon dioxide to the molten resin. The gas impregnation amount can be easily controlled, and even when the blowing agent supply port 52 is clogged with the molten resin, the high-pressure gas can be sent only to the clogged blowing agent supply passage 5d (5e). That is, the molten resin can be pushed back into the cylinder 2 by the high-pressure gas, so that maintenance is facilitated.

FIG. 7 shows a fourth embodiment of the injection molding apparatus according to the present invention.
1 shows an embodiment of the present invention. As shown in FIG. 7, the injection molding apparatus D includes a blowing agent supply port 5 near the blowing agent supply port 51 of the shorter one of the two blowing agent supply paths 5 f and 5 g in the screw 3 d. The configuration is the same as that of the injection molding apparatus C except that a portion near 52 is provided so as to penetrate the inside of the long foaming agent supply path 5g in a pipe shape.

That is, according to the molding method using the injection molding apparatus D, in addition to the effect of the injection molding apparatus C, the ratio of the foaming agent supply passage in the screw is reduced to reduce the size of the screw 3d. Can be.

The present invention is not limited to the above embodiment. For example, in the above injection molding apparatus B (C, D), the number of the foaming agent supply paths is two each, but may be three or more.

[0049]

Embodiments of the present invention will be described below in detail. (Example 1) A molding apparatus A having four foaming agent supply ports 52 shown in FIG. 8 in an enlarged foaming agent impregnated zone forming section 31 of a screw is a mold 6 having a disk-shaped cavity 61 having a thickness of 6 mm and a diameter of 25 cm. Set to And the molding device A
Of the polypropylene resin into the cylinder 2 from the hopper, and 5.5M through the blowing agent supply path 5a.
A carbon dioxide gas is supplied to the expanded foaming agent impregnation zone 11 at a gas pressure of Pa, and is supplied at 50 mm / sec and 100 mm / sec.
The molten resin impregnated with carbon dioxide gas was injected into the mold 6 at four injection speeds of c, 200 mm / sec, and 300 mm / sec to obtain disk-shaped foamed molded articles each having a thickness of 6 mm and a diameter of 25 cm.

Comparative Example 1 As shown in FIG. 9, the same molding apparatus as in Example 1 except that only one foaming agent supply port 52 is provided in the enlarged foaming agent impregnation zone forming portion 31 of the screw 3p. Using the mold P and the same mold 6 as in Example 1, a polypropylene resin is supplied into the cylinder 2 from the hopper of the molding apparatus P, and carbon dioxide gas is supplied at a gas pressure of 5.5 MPa through the blowing agent supply passage 5p. Is supplied to the expanded foaming agent impregnation zone 11 and is supplied at 50 mm / sec.
0mm / sec, 200mm / sec, 300mm / s
The molten resin impregnated with carbon dioxide gas is injected into the mold 6 at four injection speeds of ec, each having a thickness of 6 mm and a diameter of 25 cm.
Was obtained.

Then, as a result of examining the expansion ratio of each foam molded article obtained at each injection speed in Example 1 and Comparative Example 1, as shown in FIG. 10, the foam molded article obtained in Example 1 was obtained. In each of the injection speeds, the expansion ratio was higher than that of Comparative Example 1. That is, from this result, it can be seen that if a plurality of blowing agent supply ports are provided, the blowing agent can be impregnated into the molten resin in a short time, and the injection speed can be increased.

[0052]

The injection molding method for a thermoplastic resin molded article of the present invention is configured as described above, so that it does not require a long time for gas impregnation of the molten resin, and is stable at a relatively low pressure. The blowing agent can be continuously supplied to impregnate the molten resin. Moreover, since the blowing agent is supplied from a plurality of blowing agent supply ports, the contact area with the molten resin is increased as compared with the case where the blowing agent is supplied from a single blowing agent supply port, and the blowing agent is impregnated in a shorter time. be able to.

Therefore, it is possible to provide a homogeneous and fine high-performance (insulated, buffered, metered) foam molded article at a low cost by injection molding, while having high productivity.

In particular, according to the molding method of the second aspect, the molten resin can be impregnated more efficiently.

According to the molding method of the third aspect, the supply amount of the blowing agent can be adjusted individually, and the blowing agent can be more efficiently impregnated into the molten resin. In addition, even when the blowing agent supply port is clogged with the molten resin or the like, the high-pressure gas can be individually pressed into the blowing agent supply path and removed.

According to the molding method of the fourth aspect, the resin does not react with the resin, and does not adversely affect the resin, such as deteriorating the resin. Can be provided at low cost by injection molding.

Since the injection molding apparatus for a thermoplastic resin molded article of the present invention is configured as described above, it is possible to impregnate the molten resin with lower pressure and more efficiently, and it is necessary to make the entire apparatus a pressure-resistant structure. Therefore, the manufacturing cost of the device can be reduced.

According to the molding apparatus of the seventh aspect, the supply amount of the blowing agent can be individually adjusted, and the blowing agent can be more efficiently impregnated into the molten resin. In addition, even when the blowing agent supply port is clogged with a molten resin or the like, the high-pressure gas can be individually pressed into the blowing agent supply path and removed, thereby facilitating maintenance.

According to the molding apparatus of the eighth aspect, the ratio occupied by the blowing agent supply passage in the screw can be minimized, and the apparatus can be downsized.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of an injection molding apparatus according to the present invention, and is a cutaway side view showing the whole thereof.

FIG. 2 is a cutaway side view showing the general outline of the injection molding machine of the injection molding apparatus of FIG.

FIG. 3 is a sectional view schematically showing the injection molding machine of FIG. 2;

FIG. 4 is an enlarged sectional view of a main part of the injection molding machine of FIG.

FIG. 5 is a cross-sectional view schematically showing an injection molding machine according to a second embodiment of the injection molding apparatus according to the present invention.

FIG. 6 is a cross-sectional view schematically showing an injection molding machine according to a third embodiment of the present invention;

FIG. 7 is a cross-sectional view schematically showing an injection molding machine according to a fourth embodiment of the injection molding apparatus according to the present invention.

FIG. 8 is a cross-sectional view schematically showing a molding apparatus and a mold used in Example 1.

FIG. 9 is a cross-sectional view schematically showing a molding apparatus and a mold used in Comparative Example 1.

FIG. 10 is a graph showing a change in expansion ratio for each injection speed of the foamed molded products obtained in Example 1 and Comparative Example 1.

[Description of Signs] A, B, C, D Injection molding apparatus 1 Injection molding machine 11 Expanded foaming agent impregnated zone 12 Measuring section 2 Cylinder 3a, 3b, 3c, 3d Screw 31 Expanded foaming agent impregnated zone forming section 4 Seal box 5a , 5b, 5c, 5d, 5e, 5f, 5g Blowing agent supply path 51 Blowing agent introduction port 52 Blowing agent supply port

Continued on the front page F term (reference) 4F206 AA11 AB02 AG20 JA04 JD03 JF04 JF13 JF21 JL02 JM01 JN03 JQ11

Claims (8)

[Claims] 1. A foaming agent impregnation for supplying a foaming agent from a foaming agent supply port to a molten resin melted by screw rotation in a cylinder of an injection molding machine, and mixing and impregnating the foaming agent with the molten resin. Step and an injection molding method of a thermoplastic resin molded article including an injection molding step of injecting the measured resin into the mold cavity after measuring the obtained foaming agent impregnated molten resin to obtain a foam molded article, From the rear end of the screw to the blowing agent supply path, from the plurality of blowing agent supply ports that open to the outer peripheral surface of the screw in the cylinder of the blowing agent supply path provided inside the screw from the rear end of the screw toward the front end A method for injection-molding a thermoplastic resin molded product, characterized in that the blowing agent supplied is supplied to a molten resin, and the blowing agent is impregnated in the molten resin. 2. The injection molding method of a thermoplastic resin molded product according to claim 1, wherein the blowing agent is supplied from a plurality of blowing agent supply ports provided at positions shifted in the front-rear direction of the screw shaft. 3. The method of injection molding a thermoplastic resin article according to claim 1, wherein the blowing agent is supplied from each blowing agent supply port through a separate blowing agent supply path. 4. The injection molding method for a thermoplastic resin molded product according to claim 1, wherein the foaming agent is a non-reactive gas for the thermoplastic resin. 5. A foaming agent supply passage provided inside the screw from the rear end of the screw toward the front end thereof, and a foaming agent from a rear end of the screw through a foaming agent supply port opened in the outer peripheral surface of the screw in the cylinder. In the injection molding apparatus, the blowing agent fed into the supply path is supplied to the molten resin, and the blowing agent-impregnated resin after the blowing agent is impregnated in the molten resin is measured and injected by the measuring unit. There, by increasing the pitch of the front and rear screw flights, and / or by reducing the screw shaft diameter, the expanded foaming agent impregnated zone having a larger internal volume in the inter-flight space than the inter-flight space. The expanded foaming agent impregnated zone forming part for forming is provided near the tip of the screw, and a plurality of foaming agent supply ports are opened in the expanded foaming agent impregnated zone forming part. An injection molding apparatus characterized by the above-mentioned. 6. The injection molding apparatus according to claim 5, wherein at least one blowing agent supply port is provided at a position shifted from the other blowing agent supply ports in the front-rear direction of the screw shaft. 7. The injection molding apparatus according to claim 5, further comprising a plurality of foaming agent supply paths separated from each other in the screw, and a foaming agent supply port provided for each of the foaming agent supply paths. 8. A part of at least one blowing agent supply path,
The injection molding apparatus according to claim 7, wherein the injection molding apparatus is provided in a pipe shape penetrating the inside of another blowing agent supply path.