JPH0735017U - Injection molding die and nozzle used therefor - Google Patents

Abstract

(57) [Abstract] [Purpose] A pressurized gas is injected into a molten resin during molding without leakage, and there is no sink mark, warp, etc. on the outer surface, and it has a hollow part with an excellent appearance. Provided is an injection molding die capable of producing an injection molded product, and a nozzle used for the same. [Structure] A cavity 1 is provided between a fixed mold 11 and a movable mold 12.
3 is provided, and the gas injection nozzle 2 is inserted into the movable mold 12 so as to open the gas discharge port 23 in the cavity 13.
A heat insulating material 31 is arranged on the surface of the resin reservoir 131 of the cavity 13 around the insertion portion of the gas injection nozzle 2.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention is an injection having a hollow portion with excellent appearance by injecting pressurized gas into the molten resin injected into the cavity with almost no leakage, without causing sink marks, warps, etc. on the outer surface. The present invention relates to an injection molding die capable of producing a molded product and a nozzle used therefor.

[0002]

[Prior art]

 Conventionally, by injecting pressurized gas into a molten resin injected into the cavity of an injection molding die from a pressurized gas nozzle, sink marks, warps, etc. do not occur on the outer surface, and the appearance is improved. There is known a so-called gas injection molding method for producing an injection molded product having an excellent hollow portion.

However, there is a problem that the pressurized gas easily leaks between the tip of the pressurized gas injection nozzle and the molten resin or between the mold cavity surface and the molten resin.

As a method for improving the leakage of the pressurized gas, for example, as described in Japanese Patent Application Laid-Open No. 4-41212, an annular gap is provided in the circumference below the gas discharge hole of the gas injection nozzle, A method of sealing a gas by letting a part of synthetic resin flow into the annular gap, as described in JP-A-4-232709, inserting a gas injection needle near the center of contraction of the molten resin in the insertion direction of the gas injection needle. As described in Japanese Patent Laid-Open No. 5-4258, a groove portion which becomes a recess on the side opposite to the cavity and communicates with the cavity is provided around the gas injection portion, and the cavity side of the groove portion is widened to form a cavity. A method has been proposed in which the molten resin filled in the gas injection section is allowed to enter the groove section around the gas injection section to block the leakage of gas from the gap around the gas injection section.

However, the above-mentioned conventional method still does not solve the problem of leakage of the pressurized fluid. Especially when the gas pressure of the pressurized gas is set high, the variation in the leakage of the pressurized gas tends to increase due to the influence of the molding conditions.

[0006]

[Problems to be solved by the device]

 The present invention solves the above-mentioned conventional problems and injects a pressurized gas into a molten resin during molding with almost no leakage, and without causing sink marks, warps, etc. on the outer surface, The object of the present invention is to provide an injection molding die capable of producing an injection molded product having a hollow portion having an excellent appearance and a nozzle used for the same.

[0007]

[Means for Solving the Problems]

 The present invention has a cavity provided between a fixed mold and a movable mold, and a mold for injection molding in which a gas injection nozzle is inserted into the fixed mold or the movable mold so that a gas discharge port is opened in the cavity. The mold for injection molding is provided with a heat insulating material on the surface exposed in the cavity of the gas injection nozzle or the cavity surface around the portion where the gas injection nozzle is inserted.

In the present invention, the heat insulating material may be disposed on the surface exposed in the cavity of the gas injection nozzle, or on the cavity surface around the portion where the gas injection nozzle is inserted. It may be provided, or it may be provided on both sides thereof.

As the heat insulating material, one having a thermal conductivity of 0.0002 to 0.1 cal / cm · second · ° C. and capable of withstanding the molding resin temperature is preferable. Examples of the material of the heat insulating material include oxide sintered ceramics such as alumina and zirconia, thermosetting resins such as polyimide and phenol resin, and polyphenylene sulfide and polyether ether when the molding resin temperature is 150 to 250 ° C. Examples thereof include thermoplastic resins such as amide, polyether sulfone, and polyether ether ketone.

In many cases, it is sufficient that the thickness of the heat insulating material is 1 mm or less, preferably about 10 to 500 μm, and even if a thicker material is used in consideration of the processing or fixing method of the heat insulating material. It does not matter, but when the molded product is taken out, it is necessary to keep it within a range that does not cause problems such as deformation of the heat insulating material at the gas injection site.

As a method for disposing the heat insulating material, metal oxides such as titanium oxide, yttrium oxide and zirconium oxide, silicon oxides such as silicon oxide, silicon oxides such as glass, Examples thereof include a method of forming a heat insulating layer of a fluororesin by a coating method such as vapor deposition, ion plating, and thermal spraying. Further, as a method of disposing the heat insulating material other than the coating method, there is a method in which a heat insulating material having a shape corresponding to the disposing portion is adhered, screwed, assembled as a bush and pressed by another component, and fixed.

The present invention 2 is a nozzle for injecting a pressurized gas into the molten resin injected into the cavity between the fixed mold and the movable mold, and the molten resin is passed through the tip of the hollow cylindrical body. However, a gas discharge port that allows pressurized gas to pass through is provided, and the tip side of the hollow cylindrical body where the gas discharge port is provided is a small diameter part and the tip of the hollow cylindrical body is small. A nozzle in which a step portion is formed that transitions from the diameter portion to the large diameter portion on the proximal end side of the hollow cylindrical body, and heat insulating material is provided on the outer peripheral surface and step portion surface of the small diameter portion exposed in the cavity. is there .

The thermal conductivity, the material and the disposing method of the heat insulating material used in the second invention are the same as those in the present invention.

The gas discharge port has a structure that does not allow molten resin to pass through but allows pressurized gas to pass through. As such a structure, for example, one having pores or fine slits formed, or a linear connecting hole having a small linear diameter is formed by sintering a fine-diameter wire rod made of the same material. Examples thereof include those made of a porous member and those having a space formed between ball checks. The diameter of the pores or the communicating holes and the width of the slits or gaps are preferably 0.01 to 0.05 mm.

The present invention 3 is an injection molding in which a cavity is provided between a fixed mold and a movable mold, and a gas injection nozzle is inserted into the fixed mold or the movable mold so that a gas discharge port is opened in the cavity. A mold for injection molding, in which a heater is arranged at or near the insertion portion of the gas injection nozzle.

In the present invention 3, the heater may be arranged at the insertion portion of the gas injection nozzle, or may be arranged at the back of the cavity surface around the insertion portion of the gas injection nozzle. Good.

The type of heater is not particularly limited. It is preferable that the heater be capable of controlling the temperature adjustment while measuring the temperature of the heating portion, but the heater may be controlled only by the voltage.

The heating temperature by the heater is preferably within the range of the molding resin temperature to the molding resin temperature-100 ° C. However, if the shape and size of the heating part are important, maintaining the temperature at a high temperature means that the temperature at the time of mold release Since the problem of deformation arises, it is not limited to the above range.

The present invention 4 is a nozzle for injecting a pressurized gas into the molten resin injected into the cavity between the fixed die and the movable die, and the molten resin is passed through the tip of the hollow cylindrical body. However, a gas discharge port that allows pressurized gas to pass through is provided, and the tip side of the hollow cylindrical body where the gas discharge port is provided is a small diameter part and the tip of the hollow cylindrical body is small. A nozzle having a step formed from the diameter portion to the large diameter portion on the proximal end side of the hollow tubular body is formed, and a heater is provided in the tip portion of the hollow tubular body.

In Invention 4, the type of heater and the heating temperature are the same as in Invention 3. The heater may be provided in the hollow portion at the tip of the hollow tubular body, or may be provided so as to be embedded in the tubular body.

Generally, an inert gas such as nitrogen gas or carbon dioxide gas is preferable as the pressurized gas used when manufacturing the hollow molded article according to the present invention to the fourth invention. As the resin used in the present invention to the present invention 4, a thermoplastic resin or the like generally used in injection molding is used.

The present invention through the fourth invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view illustrating an example of an injection molding die of the present invention. Reference numeral 1 denotes an injection molding die, and a cavity 13 having an inner surface shape corresponding to an outer surface shape of a molded product to be molded when the mold is closed is provided between the fixed mold 11 and the movable mold 12. . A resin reservoir 131 is provided in the cavity 13.

A sprue, a runner, and a resin injection gate (not shown) are sequentially provided on the fixed mold 11 so as to communicate with the cavity 13. A resin injection nozzle (not shown) of an injection molding machine is provided at an inlet of the sprue. The molten resin, which is in contact with the resin and is supplied from the resin injection nozzle, can be injected into the cavity 13 through a flow path including a sprue, a runner, and a resin injection gate.

The gas injection nozzle 2 penetrating the movable die 12 and having the gas flow path 22 formed in the hollow portion of the hollow cylindrical body 21 has the gas discharge port 23 provided at the tip thereof as the resin of the cavity 13. It is inserted so as to project substantially in the center of the reservoir 131.

The gas discharge port 23 provided at the tip of the gas injection nozzle 2 is made of a porous material that does not allow the molten resin to pass but allows the pressurized gas to pass. The heat insulating material 31 is disposed on the cavity surface of the resin reservoir 131 at the portion where the gas injection nozzle 2 is inserted.

Hereinafter, an example of usage of this injection molding die will be described with reference to the same FIG. 1. First, the molten resin 5 is injected from the resin injection nozzle through the sprue, runner, and resin injection gate into the cavity 13 to fill the cavity 13 including the resin reservoir 131.

Next, the pressurized gas is injected from the gas discharge port 23 of the gas injection pin 2 into the molten resin 5 filled in the resin reservoir 131. At this time, since the heat insulating material 31 is disposed on the cavity surface of the resin reservoir 131 in the portion where the gas injection nozzle 2 is inserted, the following phenomenon appears.

That is, the cooling and solidification and shrinkage of the molten resin 5 in contact with the heat insulating material 31 arranged on the cavity surface of the resin reservoir 131 can be delayed more than the other portions. As a result, no gap is formed between the two, so that the pressurized gas injected from the gas discharge port 23 of the gas injection pin 2 does not leak along the cavity surface and the resin accumulation The molten resin filled in the portion 131 can be injected toward the molten resin 5 filled in the cavity 13 other than the resin reservoir 131 to form a hollow portion.

FIG. 2 is a sectional view for explaining the nozzle of the second invention. The gas injection nozzle 2'is provided with a gas flow path 22 in the hollow portion of the hollow cylindrical body 21, and has a gas discharge port 23 at the tip thereof through which a molten resin cannot pass but a pressurized gas can pass. It is provided. The tip end side of the hollow cylindrical body 2 where the gas discharge port 23 is provided is a small diameter portion 24. A step portion 25 is formed at the tip of the hollow cylindrical body 2 to transition from the small diameter portion 24 to the large diameter portion on the base end side. A heat insulating material 32 is disposed on the outer peripheral surface of the small diameter portion 24 of the hollow tubular body 21 and the surface of the step portion 25.

In the gas injection nozzle 2, the gas discharge port 23 provided at the tip of the gas injection nozzle 2 opens in the resin reservoir 131 of the cavity 13, and the outer peripheral surface of the small diameter portion 24 of the hollow tubular body 21 and the step 25. The surface on which the heat insulating material 32 is disposed is mounted so as to be exposed at the resin reservoir 131 of the cavity 13 to form an injection molding die. Since other configurations are the same as those shown in FIG. 1, the same reference numerals as those in FIG. 1 are given and detailed description thereof is omitted.

Hereinafter, an example of a usage mode of an injection molding die in which the nozzle is mounted will be described with reference to the same FIG. First, the molten resin 5 is injected from the resin nozzle through the sprue, runner, and resin injection gate into the cavity 13 to fill the cavity 13 including the resin reservoir 131.

Next, the pressurized gas is injected into the molten resin 5 filled in the resin reservoir 131 through the gas discharge port 23 of the gas injection pin 2 ′. At this time, since the heat insulating material 32 is disposed on the outer peripheral surface of the small diameter portion 24 and the step portion 25 surface of the hollow cylindrical body 21 of the gas injection nozzle 2 ′ exposed in the resin reservoir 131 of the cavity 13, The following phenomena appear.

That is, the cooling and solidification and shrinkage of the molten resin 5 in contact with the heat insulating material 32 arranged on the outer peripheral surface of the small diameter portion 24 and the stepped portion 25 of the hollow tubular body 21 of the gas injection nozzle 2 ' Can be delayed more. As a result, no gap is formed between the two, so that the pressurized gas injected from the gas discharge port 23 of the gas injection pin 2 travels along the tip of the hollow cylindrical body 21 of the gas injection nozzle 2 '. It is possible to form a hollow portion by injecting from the molten resin filled in the oil reservoir 131 toward the molten resin 5 filled in the cavity 13 other than the resin reservoir 131 without leaking to the inside. it can.

FIG. 3 is a cross-sectional view for explaining an example of the injection molding die of Invention 3. A heater 41 is provided on the insertion portion of the gas injection nozzle 2 and on the back surface of the resin reservoir 131 around the insertion portion. The configuration other than that the heat insulating material 31 is not provided is the same as that shown in FIG. 1, so the same reference numerals as those in FIG. 1 are given, and detailed description thereof is omitted.

Hereinafter, an example of a usage mode of this injection molding die will be described with reference to the same FIG. First, the molten resin 5 is injected from the resin nozzle through the sprue, runner, and resin injection gate into the cavity 13 to fill the cavity 13 including the resin reservoir 131.

Next, the pressurized gas is injected from the gas discharge port 23 of the gas injection pin 2 into the molten resin 5 filled in the resin reservoir 131. At this time, since the heater 41 is disposed on the insertion portion of the gas injection nozzle 2 and the rear surface of the resin reservoir 131 around the insertion portion, the following phenomenon appears.

That is, the cooling and solidification and shrinkage of the molten resin 5 in contact with the cavity surface of the resin reservoir 131 heated by the heater can be delayed as compared with other portions. As a result, since no gap is formed between the two, the pressurized gas injected from the gas discharge port 23 of the gas injection pin 2 does not leak to the cavity surface and leaks into the resin reservoir 131. A hollow portion can be formed by injecting from the filled molten resin toward the molten resin 5 filled in the cavity 13 other than the resin reservoir 131.

FIG. 4 is a sectional view illustrating an example of the nozzle of the present invention. The gas injection nozzle 2 ″ has a gas flow passage 22 formed in the hollow portion of the hollow cylindrical body 21, and has a gas discharge port 23 at its tip through which pressurized gas can pass but molten resin cannot pass. It is provided. The tip end side of the hollow cylindrical body 21 where the gas discharge port 23 is provided is a small diameter portion 24. A step portion 25 that transitions from the small diameter portion 24 to the large diameter portion 26 on the base end side of the hollow tubular body 21 is provided at the tip end portion of the hollow tubular body 21. A heater 42 is arranged in the hollow portion of the hollow tubular body 21.

In the gas injection nozzle 2 ″, the gas discharge port 23 provided at the tip of the gas injection nozzle 2 ″ opens into the resin reservoir 131 of the cavity 13, and the outer peripheral surface of the small diameter portion 24 of the hollow tubular body 21 and The injection molding die has a structure in which the surface of the step portion 25 is mounted so as to be exposed in the resin reservoir 131 of the cavity 13.

Hereinafter, an example of a mode of use of the injection molding die equipped with this nozzle will be described with reference to the same FIG. First, the molten resin 5 is injected from the resin nozzle through the sprue, runner, and resin injection gate into the cavity 13 to fill the cavity 13 including the resin reservoir 131.

Next, the pressurized gas is injected into the molten resin 5 filled in the resin reservoir 131 from the gas discharge port 23 of the gas injection pin 2 ″. At this time, the tip of the hollow tubular body 21 corresponding to the outer peripheral surface of the small diameter portion 24 of the hollow tubular body 21 of the gas injection nozzle 2 ′ exposed in the resin reservoir 131 of the cavity 13 and the back of the step 25 surface. Since the heater is installed in the hollow part of the part, the following phenomenon appears.

That is, the cooling and solidification and contraction of the molten resin 5 in contact with the outer peripheral surface of the small diameter portion 24 and the step portion 25 surface of the hollow cylindrical body 21 of the gas injection nozzle 2 ″ heated by the heater 42 are performed by other portions. Can be delayed more than a minute. As a result, no gap is formed between the two, so that the pressurized gas injected from the gas discharge port 23 of the gas injection pin 2 has a tip portion of the hollow cylindrical body 21 of the gas injection nozzle 2 ″. It is possible to form a hollow portion by injecting from the molten resin filled in the oil reservoir 131 toward the molten resin 5 filled in the cavity 13 other than the resin reservoir 131 without leaking along. it can .

[Action]

 The injection mold of the present invention has a cavity between a fixed mold and a movable mold, and a gas injection nozzle is inserted into the fixed mold or the movable mold so that a gas discharge port is opened in the cavity. In addition, the heat-insulating material is disposed on the surface of the injection mold that is exposed in the cavity of the gas injection nozzle or on the cavity surface around the portion where the gas injection nozzle is inserted. To delay the cooling and solidification and contraction of the molten resin in contact with the heat-insulating material arranged on the surface exposed in the cavity of the nozzle or on the cavity surface around the part where the gas injection nozzle is inserted, compared to other parts. Since no gap is formed between them, the pressurized gas injected from the gas discharge port of the gas injection pin does not leak to the outer peripheral surface of the gas injection pin or the cavity surface, and the key does not leak. In the cavity Been able to form a hollow portion toward the molten resin, sink marks on the outer surface, without causing warpage or the like, can be produced injection-molded article having an excellent hollow appearance.

The nozzle of the present invention 2 is a nozzle for injecting a pressurized gas into the molten resin injected into the cavity between the fixed mold and the movable mold, and the molten resin is injected at the tip of the hollow cylindrical body. A gas discharge port that does not allow passage of pressure but allows pressurized gas to pass through is provided, and the tip side of the hollow cylindrical body where the gas discharge port is provided is a small diameter part, and at the front end of the hollow cylindrical body. A step is formed that transitions from the small diameter part to the large diameter part on the proximal end side of the hollow cylindrical body, and heat insulating material is provided on the outer peripheral surface and the step part surface of the small diameter part exposed in the cavity. This makes it possible to delay the cooling and solidification and contraction of the molten resin in contact with the heat insulating material disposed on the outer peripheral surface and the step surface of the small diameter portion of the hollow cylindrical body of the gas injection nozzle, compared to other portions. Since there is no gap formed in the The injected pressurized gas does not leak along the outer peripheral surface of the hollow cylindrical body of the gas injection nozzle and can form a hollow portion toward the molten resin filled in the cavity. It is possible to manufacture an injection-molded product having a hollow portion having an excellent appearance without causing sink marks, warpage, etc.

The injection molding die of the present invention 3 has a cavity between a fixed die and a movable die, and the fixed die or the movable die has a gas injection nozzle so that a gas discharge port is opened in the cavity. Is a mold for injection molding, in which a heater is arranged at or near the insertion part of the gas injection nozzle, so that the surface exposed in the cavity of the gas injection nozzle or the gas injection nozzle Since it is possible to delay the cooling and solidification and contraction of the molten resin in contact with the cavity surface heated by the heater around the part where the is inserted, compared to other parts, no gap is formed between them. The pressurized gas injected from the gas injection port of the gas injection pin does not leak to the outer peripheral surface of the gas injection pin or the cavity surface and forms a hollow portion toward the molten resin filled in the cavity. Success Therefore, it is possible to produce an injection-molded article having a hollow portion having an excellent appearance without generating sink marks, warpage, etc. on the outer surface.

The nozzle of the present invention 4 is a nozzle for injecting pressurized gas into the molten resin injected into the cavity between the fixed mold and the movable mold, and the molten resin is injected at the tip of the hollow cylindrical body. A gas discharge port that does not allow passage of pressure but allows pressurized gas to pass through is provided, and the tip side of the hollow cylindrical body where the gas discharge port is provided is a small diameter part, and at the front end of the hollow cylindrical body. The stepped portion that transitions from the small diameter portion to the large diameter portion on the base end side of the hollow cylindrical body is formed, and the heater is provided in the tip portion of the hollow cylindrical body, so that the hollow cylinder of the gas injection nozzle is It is possible to delay the cooling and solidification and contraction of the molten resin in contact with the outer peripheral surface and the step surface of the small-diameter portion of the cylindrical body heated by the heater as compared with other portions, and no gap is formed between them. The pressurized gas injected from the gas outlet of the gas injection pin is The hollow portion can be formed toward the molten resin filled in the cavity without leaking along the outer peripheral surface of the hollow cylindrical body of the gas injection nozzle, and sink marks, warps, etc. occur on the outer surface. It is possible to manufacture an injection-molded product having a hollow portion having an excellent appearance without causing the above.

[0046]

【Example】

Hereinafter, the present invention will be described with reference to examples. Example 1 A flat plate with ribs (dimensions 200 × 300 mm, wall thickness 2.5 mm) was molded using the injection molding die shown in FIG. 1 according to the embodiment described with reference to FIG. It was An injection molding machine having a mold closing force of 300 tons was used. Polypropylene (made by Idemitsu Petrochemical Co., Ltd., trade name "J743G") was used as the resin.

As the gas injection nozzle 2, a gas discharge port 23 made of a sintered metal having an average hole diameter of 30 μm and an outer diameter of the hollow cylindrical body 21 of 4 mm was used. The gas injection nozzle 2 was inserted so that the gas discharge port 23 was opened substantially at the center of the resin reservoir 131 having a depth of 10 mm and a central width of 15 mm.

Nitrogen gas was used as the pressurizing gas, the pressurizing gas pressure was set to 70 kg / cm ² , the gas injection time (the time during which the gas is continuously injected) was 3 seconds, and the gas holding time (at the time of gas injection) The time from the end of the period until the gas inside the molded product was artificially released to the outside of the molded product) was set to 15 seconds. As the heat insulating material 31, a 500 μm heat insulating layer was formed by spraying zirconium oxide (thermal conductivity: 0.006 cal / cm · sec · ° C.).

Molding was performed for 10 shots, and the change in gas pressure at that time was measured. The results are shown in Table 1. As a result, it was possible to obtain a flat plate with ribs having a hollow portion which had less leakage of pressurized gas during molding and had an excellent external appearance without the occurrence of sink marks, warps and the like.

Example 2 Using the injection molding die equipped with the nozzle shown in FIG. 2, a ribbed flat plate was formed in the same manner as in Example 1 according to the embodiment described with reference to FIG. . The results of measuring changes in gas pressure in the same manner as in Example 1 are shown in Table 1. As the heat insulating material 32, a heat insulating layer having a thickness of 500 μm was formed by spraying zirconium oxide (thermal conductivity: 0.006 cal / cm 2 · sec ° C.). Other than that was performed according to Example 1. As a result, it was possible to obtain a flat plate with ribs having a hollow portion which had less leakage of pressurized gas during molding and had an excellent external appearance without the occurrence of sink marks, warps and the like.

Example 3 Using the injection molding die shown in FIG. 3, a flat plate with ribs was molded in the same manner as in Example 1 according to the embodiment described with reference to FIG. The results of measuring changes in gas pressure in the same manner as in Example 1 are shown in Table 1. As a heater, a 100 W nichrome wire heater (outer diameter 9 mm, length 10 mm) and a thermocouple were arranged at position 41, and the heating temperature was 140 ° C. Other than that was performed according to Example 1. As a result, it was possible to obtain a flat plate with ribs having a hollow portion which had less leakage of pressurized gas during molding and had an excellent external appearance without the occurrence of sink marks, warps and the like.

Example 4 Using the injection molding die equipped with the nozzle shown in FIG. 2, a ribbed flat plate was formed in the same manner as in Example 1 according to the embodiment described with reference to FIG. . The results of measuring changes in gas pressure in the same manner as in Example 1 are shown in Table 1. As a heater, a 100 W nichrome wire heater (outer diameter 9 mm, length 10 mm) and a thermocouple were arranged at 42, and the heating temperature was 140 ° C. Other than that was performed according to Example 1. As a result, it was possible to obtain a flat plate with ribs having a hollow portion which had less leakage of pressurized gas during molding and had an excellent external appearance without the occurrence of sink marks, warps and the like.

Comparative Example Using the injection molding die shown in FIG. 4, a ribbed flat plate similar to that of Example 1 was molded in the same manner as in Example 4 except that the heating by the heater 42 was not performed. went. The results of measuring changes in the gas pressure in the same manner as in Example 1 are shown in Table 1. As a result, it was possible to obtain only a flat plate with ribs, which had a large leakage of pressurized gas during molding and had a hollow portion on its outer surface, which had a bad appearance such as sink marks and warps.

[0054]

[Table 1]

As is clear from Table 1, in each of Examples 1 to 4, there was little leakage of the pressurized gas, and as a result, hollows excellent in appearance without sink marks, warps, etc. on the outer surface. It is possible to obtain a flat plate with ribs, whereas in the case of the comparative example, the leakage of the pressurized gas is large, which causes the appearance of sink marks, warps, etc. Only flat plates with ribs having parts can be obtained.

[0056]

[Effect of device]

 Since the injection molding die of the present invention is configured as described above, the injection molding die is directed toward the center of the molten resin filled in the cavity without leaking along the outer peripheral surface of the gas injection pin or the cavity surface. It is possible to produce an injection-molded article having a hollow portion having an excellent appearance without forming a sink mark, warp or the like on the outer surface by forming the hollow portion.

Since the nozzle of the present invention 2 is configured as described above, the pressurized gas injected from the gas discharge port of the gas injection nozzle is transmitted to the outer peripheral surface of the hollow cylindrical body of the gas injection nozzle. Injection that has a hollow part with excellent appearance without forming a sink mark or warp on the outer surface by forming a hollow part toward the center of the molten resin filled in the cavity without leaking Molded articles can be manufactured.

Since the injection molding apparatus of the present invention 3 is configured as described above, the pressurized gas injected from the gas discharge port of the gas injection pin leaks to the outer peripheral surface of the gas injection pin and the cavity surface. Without forming a hollow part toward the center of the molten resin filled in the cavity, and without causing sink marks, warps, etc. on the outer surface, an injection molded product with a hollow part with an excellent appearance It can be manufactured.

Since the nozzle of the present invention 4 is configured as described above, the pressurized gas injected from the gas discharge port of the gas injection pin leaks along the outer peripheral surface of the hollow cylindrical body of the gas injection nozzle. It is possible to form a hollow part toward the center of the molten resin filled in the cavity without causing any damage, and there is no sink mark or warp on the outer surface. Goods can be manufactured.

[0060]

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating an example of an injection molding die of the present invention.

FIG. 2 is a sectional view illustrating an example of a nozzle according to the second invention.

FIG. 3 is a cross-sectional view illustrating an example of an injection molding die of Invention 3 of the present invention.

FIG. 4 is a cross-sectional view illustrating an example of a nozzle of Invention 4 of the present invention.

[Explanation of symbols]

 1 Injection Mold 2, 2 ', 2' 'Nozzle 11 Fixed Mold 12 Movable Mold 13 Cavity 21 Hollow Cylindrical Section 22 Gas Flow Path 23 Gas Discharge Port 24 Small Diameter Section 25 Stepped Section 31, 32 Heat Insulation 41, 42 heater

Claims (4)

[Scope of utility model registration request] 1. A mold for injection molding, wherein a cavity is provided between a fixed mold and a movable mold, and a gas injection nozzle is attached to the fixed mold or the movable mold so that a gas discharge port is opened in the cavity. The mold for injection molding is characterized in that a heat insulating material is disposed on a surface of the gas injection nozzle that is exposed in the cavity or a cavity surface around a portion where the gas injection nozzle is inserted. 2. A nozzle for injecting a pressurized gas into a molten resin injected into a cavity between a fixed mold and a movable mold, wherein the molten resin does not pass through the tip of the hollow cylindrical body but is pressurized. A gas discharge port that allows gas to pass through is provided, and the tip side of the hollow tubular body where the gas discharge port is provided has a small diameter portion, and the hollow tubular body has a small diameter portion from the small diameter portion to the tip portion. Nozzle characterized in that a step portion that transitions to the large diameter portion on the base end side is formed, and a heat insulating material is arranged on the outer peripheral surface and the step portion surface of the small diameter portion exposed in the cavity. 3. A mold for injection molding, wherein a cavity is provided between a fixed mold and a movable mold, and a gas injection nozzle is attached to the fixed mold or the movable mold so that a gas discharge port is opened in the cavity. A mold for injection molding, characterized in that a heater is disposed at or near the insertion portion of the gas injection nozzle. 4. A nozzle for injecting a pressurized gas into a molten resin injected into a cavity between a fixed mold and a movable mold, wherein the molten resin does not pass through the tip of the hollow cylindrical body but is pressurized. A gas discharge port that allows gas to pass through is provided, and the tip side of the hollow tubular body where the gas discharge port is provided has a small diameter portion, and the hollow tubular body has a small diameter portion from the small diameter portion to the tip portion. A nozzle characterized in that a step portion that transitions to a large diameter portion on the base end side is formed, and a heater is provided in the tip end portion of the hollow cylindrical body.