JPH054260A - Injection molding die core and method for manufacturing injection molded body - Google Patents

Abstract

(57) [Summary] [Purpose] A long, narrow, bottomed cylindrical shape that does not cause irregularity in the shape of the molded product and evenly whitens the resin and makes the resin flow into the mold cavity evenly at low cost. Provided are a core for an injection molding die for manufacturing a container and a method for manufacturing an injection molded body. [Structure] A core having a round bar having an outer surface shape corresponding to the inner wall shape of an elongated bottomed cylindrical container to be molded has a plurality of grooves having substantially the same shape on the shaft of the round bar near the tip of the round bar. On the other hand, a core for an injection molding die in which one concave groove is formed in axial symmetry or in a spiral shape, and a method for manufacturing an injection molded body using the same.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core for an injection molding die and a method for manufacturing an injection molding, which can be suitably used for manufacturing an elongated cylindrical container such as a test tube and a blood collection tube.

[0002]

2. Description of the Related Art Generally, in injection molding a long and thin cylindrical container such as a test tube or a blood collection tube, a round hole with a tapered tapered bottom wall is provided, and the center point of the spherical surface of the bottom wall is provided. There is used an injection molding die including a fixed mold or a fixed-side mold plate provided with a gate opened in 1. and a movable mold in which a core having a round bar having a convex tip is installed.

Then, the molten resin is injected from the gate,
This molten resin was cast between a round hole of a fixed die or a fixed side die plate of a core and a round bar to form an elongated cylindrical container.

However, in this method, since the core can be supported only at one end, it is difficult to stabilize the tip of the core by the pressure of the molten resin when the molten resin is injected into the cavity, and it is difficult to move the core in either direction. There is a problem that it is easy to incline and only a molded product with uneven thickness can be obtained.

In order to solve this problem, for example, 1) as shown in FIG. 5, the convex spherical surface b of the round bar a is provided by providing a circular plate spherical concave section c at the center point of the convex spherical surface b of the round bar a.
A method for preventing the center of the round bar a from being displaced during the flow of the resin by radially dispersing the resin injected into the spherical dish-shaped concave portion c at the center point of (2). As shown in FIG. 6, a narrow gap portion i is formed by the convex portion h formed at the exit tip of the gate g of the fixed-side template f and the peripheral edge portion of the concave portion e provided at the tip of the round bar d. However, since the internal pressure changes in the flow path when the round bar d is tilted, the round bar d
The method of making the resin flow into the mold cavity uniform by acting to prevent the bending of the mold (Japanese Patent Laid-Open No. 1-31773).
No. 3, etc.) have been proposed.

[0006]

[Problems to be Solved by the Invention] However, 1) and 2)
In each of the above methods, the flow of resin cannot be forcibly and evenly rectified, and not only the shape of the molded product becomes distorted but also partially thickened, and that portion is crystallized. There was a problem of whitening due to.

The object of the present invention is to solve the above-mentioned problems and to allow the resin to uniformly flow into the mold cavity, without causing the shape of the resin to be distorted or whitening, and to provide a long and thin wall with no uneven thickness. An object of the present invention is to provide a core for an injection molding die and a manufacturing method capable of manufacturing a bottom cylindrical container.

[0008]

The core for an injection molding die of the present invention 1 is a core having a round bar having an outer surface shape corresponding to the inner wall shape of an elongated bottomed cylindrical container to be molded. In the vicinity of the tip of the rod, a plurality of grooves having substantially the same shape are formed in axial symmetry with respect to the axis of the round rod.

In order to make the resin flow into the mold cavity more uniform, the groove is preferably formed in the direction from the center of the substantially tip end of the round bar to the direction of the other end (axial direction of the round bar). However, it may be formed in a diagonal direction of the round bar from the substantially tip portion.
The cross-sectional shape of the concave groove can be appropriately selected from a semicircular shape, a rectangular shape, a V shape, etc., but a semicircular shape is preferable in order not to disturb the flow of the resin. The number of the groove may be any number as long as it is axially symmetric, but it is preferable that the groove is cut into four, that is, in a cross shape from the viewpoint of convenience in manufacturing the core.

The width of the concave groove differs depending on the diameter and thickness of the elongated bottomed cylindrical container to be molded. For example, in the case of molding a slender bottomed cylindrical container having a diameter of 10 mm and a thickness of 1 mm, the width is less than 1 mm. The effect of making the resin inflow uniform is small, and if it exceeds 2 mm, whitening is likely to occur at the bottom of the molded product and the strength of the core decreases, so 1-2
About mm is preferable. If the length of the groove (the linear distance from the tip to the end of the groove) is less than 5% of the total length of the elongated bottomed cylindrical container to be molded, the effect of making the resin inflow uniform is small, and 50% is required. If it exceeds, the effect of making the inflow of the resin uniform does not increase any more, and there is a problem that it becomes difficult to remove the molded product from the mold.

If necessary, the tip of the round bar may have a substantially spherical convex surface. Furthermore, a round plate-shaped recess may be provided at the center of the convex surface. The depth of the round plate-shaped recess is, for example, 10 mm in diameter and 1 in thickness.
In the case of molding a slender bottomed cylindrical container having a diameter of 0.1 mm,
If it is less than 5 mm, the effect of reducing the injection pressure is small and 2
If it exceeds 0.3 mm, whitening is likely to occur in the molded product, so 0.5 to 2 mm is preferable.

FIG. 1 is a side view of an injection molding die core according to an embodiment of the present invention. The core 7 of the injection molding die has a convex spherical surface 5 at the tip and a round bar 6 having a tapered tip. A groove 8 having a semicircular cross section is formed in the shape of a cross in the vicinity of the tip of the round bar 6 from the center of the tip, and is symmetrical about the axis of the round bar 6. still,
The rear end of the round bar 6 is expanded in diameter and is fixed to the movable side receiving plate.

FIG. 2 is a side view of an injection molding die core showing a different embodiment of the present invention 1. The injection molding die core 7'is formed of a round bar 6'having a convex spherical surface 5'at the tip and a tapered tip. A round plate-shaped concave portion 9 is provided at the center point of the convex surface portion 5 ′ at the tip of the round bar 6 ′. A groove 9'having a semicircular cross section is formed in the shape of a cross in the vicinity of the tip of the round bar 6'in a cross shape and in axial symmetry with respect to the axis of the round bar 6 '.

The core for an injection molding die of the present invention 2 is a core having a round bar having an outer surface shape corresponding to the inner wall shape of an elongated bottomed cylindrical container to be molded, and a core near the tip of the round bar. The groove is formed in a spiral shape, and the groove may have the same width, length, and shape as the groove formed in the first aspect of the present invention.

Also, the pitch of the concave grooves differs depending on the size of the elongated bottomed cylindrical container to be molded and the width of the concave groove. For example, in the case of molding an elongated bottomed cylindrical container having a diameter of 10 mm and a thickness of 1 mm, If the pitch is less than 2 mm or more than 3 mm, the effect of making the resin inflow uniform decreases, so
It is preferably about 3 mm. Further, as in the case of the first aspect of the invention, the tip of the round bar may be formed into a substantially spherical convex surface if necessary, and a round plate-shaped concave portion is provided in the center of the convex surface portion. May be.

FIG. 3 is a side view of a core for an injection molding die showing one embodiment of the present invention 2. The injection molding die core 7 "is made of a round bar 6" whose tip is formed into a convex spherical surface 5 "and whose tip is tapered. A round plate shape is formed at the center point of the convex portion 5" at the tip of the round bar 6 ". Is provided with a recess 9 '.
A concave groove 8 ″ having a semicircular cross section is spirally formed from the concave portion 9 ′ near the tip of the round bar 6 ″.

In the method for producing an injection-molded product according to the third aspect of the present invention, a cavity corresponding to the shape of the elongated bottomed cylindrical container to be molded is formed between the fixed mold or the fixed-side mold plate and the movable mold. An injection mold is used. The fixed mold or the fixed-side mold plate is provided with a round hole with a tapered tapered bottom wall, and a gate is formed at a substantially central point of the bottom wall. When using a runner stripper plate, a fixed-side template is used. The movable type is
It comprises a backing plate, a stripper plate for protrusion, and the core of the first invention or the second invention fixed to the backing plate.
The cavity is formed from a round hole, a stripping stripper plate and a round bar forming part of the core.

FIG. 4 is a schematic sectional view showing an example of an injection molding die used in the molding method of the present invention 3. The injection mold comprises a movable mold and a fixed mold. The movable die includes a receiving plate 11, a stripper plate 12 for ejection, a core 71 for an injection molding die, and a movable side die mounting plate 10.

The stationary die comprises a stationary die plate 4, a runner stripper plate 13 and a stationary die mounting plate 14. The fixed-side template 4 is provided with a circular hole 2 with a tapered hole in which the bottom wall 1 is a concave spherical surface, and a gate 3 is provided at the center point of the bottom wall 1.

A cavity 17 having an inner surface shape corresponding to the shape of an elongated bottomed cylindrical container to be molded is formed between the round hole 2, the round bar 61 and the protruding stripper plate 12.

The fixed mold attachment plate 14 and the runner stripper plate 13 have sprue 15 and runner 1.
6 is provided and communicates with the gate 3. In the method for manufacturing an injection-molded article according to the third aspect of the present invention, the molten resin is injected from the gate toward the tip of the round bar 61 at a low pressure, and after the molten resin has passed through the groove 8, it is injected at a high pressure to be molded. The injection pressure depends on the shape of the product to be obtained, the strength of the core, the width of the groove, the depth, the gate diameter, other molding conditions, the resin used, etc., but the injection pressure is 20-80% of the optimum injection pressure. It is preferable that the resin is injected from the gate to fill the concave groove, and after the molten resin has passed through the concave groove, the molten resin is caused to flow at an injection pressure substantially equal to or higher than the optimum condition for molding.

For example, in the case of producing a molded product in which a good product can be obtained at an injection pressure of 1,500 kg / cm ² when a mold having no concave groove is used, first, 30
Resin is injected from a gate at an injection pressure of 0 to 1,200 kg / cm ² to fill the groove, and after the molten resin has passed through the groove, the pressure is higher than the injection pressure, and the pressure is 1,50
It is preferable to flow the resin at an injection pressure of 0 to 2,000 kg / cm ² for molding.

The resin used in the present invention 3 is not particularly limited as long as it is a resin which can be injection-molded and includes polyethylene, polypropylene, polyethylene terephthalate, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer. Polyolefin resin such as polystyrene resin, polyvinyl chloride, polyvinylidene chloride, chlorinated vinyl chloride resin, vinyl chloride-ethylene copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-maleic acid imide copolymer Chlorinated resins such as Nylon 6,6, Nylon 6, Nylon MXD-6, Nylon 12 and other polyamide resins, polyvinylidene fluoride, polycarbonate
Thermoplastic resins such as polyacetal, polyacetal, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, polyphenylene sulfide, polyphenylene oxide, polysulfone, polyether sulfone, polyether ether ketone, and polyarylate. If necessary, the resin may further contain a plasticizer such as dioctyl phthalate, dibutyl phthalate, chlorinated paraffin, and epoxidized methyl oleate.
A reinforcing material such as glass fiber or carbon fiber, a filler such as calcium carbonate or talc, and the like may be added.

[0024]

EXAMPLES The details of the present invention will be described in detail with reference to examples. Example 1 The injection mold used in this example is the one shown in FIG. 4, and the core 7 having the shape shown in FIG. 1 was used as the core 71 for the injection mold. The injection molding die core 7 is formed with a concave groove 8 up to a position 13 mm from the tip of the round bar 6, and the concave groove 8 has a semicircular cross section and a predetermined width shown in Table 1. It is shaped like a cross. 16 cores are evenly installed in each part of the injection molding die, and one uniform cavity 17 having a total length of 100 mm is provided.
It is formed in 6 places.

From the injection molding machine, through the sprue 15 and the runner 16, the injection pressure (resin pressure) of polyethylene terephthalate (manufactured by Kodak Co., Ltd., trade name: Kodapack 7352) melted from the gate 3 to the tip of the round bar 6 is applied.
The molten resin was injected at 0 kg / cm ² , and the molten resin was injected at an injection pressure (resin pressure) of 1,800 kg / cm ² after the molten resin passed through the groove 8 from the tip of the round bar 6.
The molten resin was evenly flowed into these concave grooves 8 and the cavities 17 were filled with a sufficient amount of resin, and 16 elongated bottomed cylindrical containers were obtained.

Molding temperature Resin temperature 300 ° C. Mold temperature 20 ° C. Example 2 As the core 71 of the injection molding mold of FIG. 4, a core 7 ′ having the shape shown in FIG. 2 was used. The injection molding die core 7 ′ has a depth of 1 m at the center point of the convex portion 5 ′ at the tip of the round bar 6 ′.
A round plate-shaped recess 9 of m was provided. A groove 9'having a semicircular cross section is formed in a cross shape in the vicinity of the tip of the round bar 6'in a cross shape and axially symmetrical with respect to the axis of the round bar '6 up to a position 13 mm from the tip of the core. It had been. The groove 8 '
Had a semi-circular cross section and a predetermined width shown in Table 1 formed in a cross shape. Injection molding as in Example 1,
A slender bottomed cylindrical container was obtained.

Examples 3 and 4 As the core 71 of the injection-molding die shown in FIG. 4, the core 7'for the injection-molding die shown in FIG. 2 has the predetermined width and the number of recessed grooves shown in Table 1 formed therein. Was used and injection-molded in the same manner as in Example 2 to obtain an elongated bottomed cylindrical container.

Example 5 A core 7 "having the shape shown in Fig. 3 was used as the core 71 of the injection molding die of Fig. 4. The core 7" for the injection molding die had a convex surface at the tip of the round bar 6 ". Depth 1 at the center of part 5 "
A round plate-shaped recess 9 ′ of mm is provided, and a recessed groove 8 ″ having a semicircular cross section and a width shown in Table 1 is spirally formed from the recess 9 ′ near the tip of the round bar 6 ″. Was formed up to a position 13 mm from the tip of the. Injection molding was carried out in the same manner as in Example 1 to obtain an elongated bottomed cylindrical container.

Comparative Example 1 As the injection molding die core 71 of FIG. 4, the same core as that shown in FIG. 1 is used except that the groove is not formed in the round bar, and the cavity 17 has a sufficient amount. Injection molding was carried out in the same manner as in Example 1 except that the resin pressure was constantly maintained at 1,500 kg / cm ² until the resin was filled to obtain a long narrow bottomed cylindrical container.

The thickness of the 16 elongated bottomed cylindrical containers obtained in one shot at a position of about 20 mm from the bottom surface was measured, and the minimum meat pressure was subtracted from the maximum meat pressure in the same cross section in one container. The value was taken as the amount of uneven thickness, and the maximum value, the minimum value, and the average value of the 16 pieces were obtained. The above results are also shown in Table 1.

[0031]

[Table 1]

[0032]

EFFECT OF THE INVENTION When an injection molding die is produced using the core for an injection molding die of the present invention 1 and a long and slender bottomed cylindrical container is injection-molded, the molten resin injected from the gate is part of the core. A plurality of grooves having substantially the same shape formed in the vicinity of the tip of the round bar forming the ax are formed symmetrically with respect to the axis of the round bar, and thus evenly branch and flow into each groove. . As a result, the injection pressure is reduced, and at the same time, the core is stable and does not tilt in any direction, and there is no runout. Therefore, a molded product having a thin and uniform peripheral wall can be obtained.

When an injection molding die is produced by using the core for an injection molding die of the present invention 2 and a long and slender bottomed cylindrical container is injection-molded, the molten resin injected from the gate forms a part of the core. It flows into the spiral groove formed near the tip of the round rod. As a result, the injection pressure decreases, and at the same time, the resin flows in in the circumferential direction uniformly, so that the core is stable and does not tilt in any direction, and there is no runout. Therefore, a molded product having a thin and uniform peripheral wall can be obtained.

The injection molding method of the third aspect of the present invention is the same as that of the first aspect of the present invention.
Alternatively, an injection molding die is produced using the core of the present invention 2,
The molten resin is passed through the gate of the mold toward the tip of the round rod at a low speed, and after the molten resin passes through the groove provided in the round rod, the molten resin is further introduced at a high speed. Since the desired molded product is obtained, it is not necessary to apply an unnecessarily high injection pressure, and the runout of the round bar is small.

The structure of the present invention is as described above, and even when molding a long and slender bottomed cylindrical container, when the molten resin is injected into the cavity, the pressure of the molten resin is evenly applied to the round bar. Therefore, the tip of the round bar can be stabilized, the round bar hardly tilts due to the resin pressure, and a molded product having no unevenness in wall thickness can be obtained. Therefore, a molded product having a thin and uniform peripheral wall can be obtained.

Further, since the variation in the wall thickness can be reduced, the wall thickness of the molded product can be further reduced, and the molding material can be saved. Further, since it is not necessary to apply a large injection pressure to the tip of the round bar, the life of the mold is extended.

[Brief description of drawings]

FIG. 1 is a side view of an injection molding die core showing an embodiment of the present invention 1. FIG.

FIG. 2 is a side view of an injection molding die core showing a different embodiment of the present invention 1. FIG.

FIG. 3 is a side view of an injection molding die core according to an embodiment of the present invention 2.

FIG. 4 is a schematic cross-sectional view showing an example of an injection mold used in the method for producing an injection-molded article of the present invention 3.

FIG. 5 is a cross-sectional view showing an example of a conventional injection molding die.

FIG. 6 is a cross-sectional view showing a different example of a conventional injection molding die.

[Explanation of symbols]

1 bottom wall 2 Round hole with taping taper 3 gates 4 Fixed side template 5, 5 ', 5 "convex spherical surface 6, 6 ', 6 ", 61 Round bar 7, 7 ', 7 ", 71 Core for injection mold 8,8 ', 8 "groove 9, 9'round plate-shaped recess 10 Movable mold attachment plate 11 Support plate 12 Stripper plate for protrusion 13 Runner stripper plate 14 Fixed side mold mounting plate 15 sprue 16 runners 17 cavities

Claims (3)

[Claims] 1. A core having a round bar having an outer surface shape corresponding to the inner wall shape of an elongated bottomed cylindrical container to be molded,
A core for an injection molding die, wherein a plurality of recessed grooves having substantially the same shape are formed in the vicinity of the tip of the round bar so as to be axially symmetrical with respect to the axis of the round bar. 2. A core having a round bar having an outer surface shape corresponding to the inner wall shape of an elongated bottomed cylindrical container to be molded,
A core for an injection molding die, characterized in that a concave groove is formed in a spiral shape near the tip of the round bar. 3. An injection molding die in which a cavity corresponding to the shape of an elongated bottomed cylindrical container to be molded is formed between a fixed mold or a fixed-side mold plate and a movable mold, and the fixed mold. The mold or the fixed-side mold plate is provided with a circular hole with a tapered tapered bottom wall, and a gate is opened substantially at the center point of the bottom wall. A stripper plate for use and a core fixed to a receiving plate according to claim 1 or 2, wherein the cavity is formed from a round hole, a core and an ejecting stripper plate from the gate of the injection molding die. Manufacture of an injection-molded body characterized by injecting a molten resin at a low pressure toward the tip of a round bar, and after the molten resin has passed through a groove formed in the round bar, the molten resin is injected at a high pressure for molding. Method.