JP3924069B2 - Stretch blow molding method and stretch blow molded article - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a stretch blow molding method, and a stretch blow molded article such as a resin glove that serves as a cover of a light bulb or a fluorescent lamp.
[0002]
[Prior art]
Since the parison for biaxial stretch blow molding has a bottomed shape, the extrusion molding method cannot be used, and it is generally molded by injection molding.
[0003]
Conventionally, when injection molding a biaxial stretch blow molding parison, a gate is provided at the bottom of a cavity of a fixed female mold, and the male mold having a core is made a movable mold, and the male mold and the female mold are clamped. Thereafter, molten resin is injected from the gate into the cavity.
[0004]
[Problems to be solved by the invention]
Gate traces will be formed on the bottom surface of the conventional parison, but if blow molding is performed using this parison, the cut trace remains even if the gate trace is cut, and the bottom gate trace is formed on the molded product. Will stand out. In order to make the trace of the gate in the molded product inconspicuous, a finishing process such as cutting and polishing the gate part of the parison after injection molding is required, which causes high cost.
[0005]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to make a gate mark in a blow-molded product inconspicuous without processing a gate mark of a parison after injection molding.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has taken the following technical means.
[0007]
That is, the present invention is characterized in that an injection-molded bottomed parison having a gate mark formed on the inner surface of the bottom is used for biaxial stretch blow molding. The gate mark is preferably formed in the center of the bottom.
[0008]
This bottomed parison is injection molded so that a gate mark is formed on the inner surface of the bottom. This parison is moved to the blow mold, and the stretched rod of the biaxial stretch blow molding machine is brought into contact with the gate mark formed on the inner surface of the bottom of the parison and the parison is stretched in the vertical axis by the stretch rod, and then blown. Stretch transversely. According to such a biaxial stretch blow molding method, the gate trace is essentially crushed by the stretch rod for longitudinal stretching, and the gate is not finished in the molded product without finishing the gate trace before blow molding. Traces are hardly noticeable.
[0009]
When stretching the longitudinal axis by the stretching rod, it is desirable to adjust the working pressure of the stretching rod to such an extent that the gate marks are not noticeable. By such adjustment, an existing biaxial stretch blow molding machine can be used.
[0010]
Further, by adjusting the heating temperature of the stretching rod, the gate trace contacting the rod can be further softened so that the gate trace can be easily crushed and the gate trace can be eliminated.
[0011]
In addition, the drawing rod is heated to the melting temperature of the molding material, the unevenness of the gate part is completely eliminated, and a mold release treatment is performed with a Teflon (registered trademark) agent or the like so that the molten molding material does not adhere to the tip of the drawing rod. Thus, the inner surface of the molded product can be made completely flat.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0013]
FIG. 4 is a longitudinal sectional view of the biaxial stretch blow molding parison 1 according to an embodiment of the present invention. The parison 1 is injection-molded into a bottomed cylinder, and a gate mark 1a is formed at the center of the inner surface of the bottom. Such a parison 1 can be molded by providing a runner in a male core of an injection molding machine (not shown) and injecting molten resin into a cavity from a gate provided at the tip of the core. As such an injection mold, either a hot runner mold or a cold runner mold can be adopted. As the inner gate as described above, a pin gate is generally used, and a valve gate can also be used.
[0014]
In addition, the collar part 2 may be formed in the outer periphery of the upper end part of the parison 1 at the time of injection molding as shown in FIG. Moreover, the parison 1 can be formed into an appropriate shape according to the shape after blow molding.
[0015]
A blow molding machine 3 shown in FIGS. 1 to 3 is installed on the downstream side of the injection molding machine, and a production line for molding the parison 1 by the injection molding machine and blow molding the parison 1 by the blow molding machine 3. Thus, mass production of a blow-molded product having the brim portion 2 is enabled. In the illustrated embodiment, the brim portion 2 is held using a lip mold 4. An injection cavity opening having the same shape as the lip mold 4 is mounted on an injection mold to form a flange 2 at the time of injection molding, and the molded parison 1 is attached to the lip mold 4 in the state shown in FIG. As shown in FIG. 2, it is attached to the blow mold 6 of the blow molding machine 3, and after being blow molded, it becomes a molded product and is taken out from the blow molding machine 3.
[0016]
1 to 3 show a process of biaxial stretch blow molding by the blow molding machine 3 using the parison 1.
[0017]
The blow molding machine 3 includes a mold 6 that forms a blow cavity 5, a stretching rod 7, and a blow unit 8 that blows air into the parison 1.
[0018]
The blow mold 6 is installed at the center of the left and right split molds 9 and 10 that are opened and closed in the mold open state shown in FIG. 1 and the mold clamped state shown in FIGS. A bottom mold 11 is provided. The bottom mold 11 is substantially cylindrical in the illustrated example.
[0019]
A receiving mold 12 for receiving the lip mold 4 is provided at the upper part of the left and right molds 9, 10, and an auxiliary mold 13 that is fitted to the outer periphery of the bottom mold 11 from the left and right sides is provided at the lower part.
[0020]
The extending rod 7 is provided at substantially the center of the left and right molds 9 and 10, and is disposed substantially on the same axis as the bottom mold 11. The rod 7 is provided so as to be able to reciprocate in the axial direction of the blow cavity 5 with respect to the blow mold 6. In the illustrated example, the rod 7 can be reciprocated in the vertical direction by an appropriate operating mechanism (not shown). Is provided.
[0021]
A wide pressing member 14 that is in contact with the inner surface of the bottom of the parison 1 disposed in the blow cavity 5 is attached to the front end (in the illustrated example, the lower end) of the stretching rod 7. In addition, a coating layer such as a Teflon (registered trademark) agent is formed on the tip surface of the stretching rod 7, that is, in the illustrated embodiment, the surface of the pressing member 14, so that the molten molding material does not adhere to the tip of the stretching rod 7. It is preferable to keep it.
[0022]
The blowing means 8 includes a substantially cylindrical blow core 15 that is detachably fitted to the inner periphery of the lip mold 4. An air blowing hole is provided at the front end portion (lower surface in the illustrated example) of the blow core 15 so that high-pressure air from an air pressure feeding device connected to the blow core 15 can be blown into the parison 1. The extending rod 7 passes through the central portion of the blow core 15 and is configured to reciprocate in the axial direction with respect to the blow core 15.
[0023]
The blow molding machine 3 includes an appropriate cooling means for cooling the blow molded product 16. The cooling medium by the means is preferably a gas at normal temperature such as air, nitrogen, carbon dioxide, etc., and the temperature is 10 to −50 ° C., preferably 10 to −40 ° C. that does not freeze the moisture in the air in the container. The range of is optimal.
[0024]
A method for biaxially stretching blow molding the parison 1 with the above blow molding machine 3 will be described below.
[0025]
The blow mold 6 opened as shown in FIG. 1 is clamped as shown in FIG. 2, and the lip mold 4 is fitted to the receiving mold 12 serving as the mouth of the blow cavity 5 to blow the parison 1 Arranged in the cavity 5.
[0026]
Thereafter, the blow core 15 is fitted into the lip mold 4 and the pressing member 14 of the extending rod 7 is brought into contact with the inner surface of the bottom of the parison 1 (see FIG. 2). Then, the parison 1 is first stretched in the vertical axis by pushing the stretching rod 7 toward the bottom mold 11. At this time, the injection gate mark 1a formed on the inner surface of the bottom of the parison 1 is almost flattened by being pressed by the stretching rod 7, so that the blow process can be performed without processing the gate mark 1a before blow molding. The conspicuousness of gate marks after molding is eliminated. Further, since the gate trace 1a is directly crushed by the extending rod 7, the gate trace is remarkably less noticeable in the molded product as compared with the conventional method in which the gate trace is formed on the bottom bottom surface of the parity. Therefore, it is particularly useful for molding a resin glove that serves as a cover for a light bulb or a fluorescent lamp.
[0027]
The gate trace 1a can be more reliably crushed by heating the temperature of the end of the draw rod 7 with a heating temperature adjusting device provided inside the draw rod 7 to soften or melt the gate trace 1a. As such a heating temperature control device, like the heater disclosed in Japanese Patent Publication No. 57-19012, a cylindrical mounting space is formed in the extending rod 7 along the axial direction, and a coil shape is formed in the space. It can be formed by incorporating a heater. Furthermore, it is preferable to cool the drawing rod 7 heated by the heating temperature adjusting device after blow molding by providing a cooling device on the outer periphery of the drawing rod 7 .
[0028]
After stretching in the vertical axis as described above, high-pressure air is blown into the parison 1 from the blow hole of the blow core 15, and the parison 1 is stretched in the horizontal axis to obtain a blow molded product 16 (see FIG. 3). After the blow molded product 16 is cooled and solidified by an appropriate cooling means, the molded product 16 is taken out from the blow mold 6.
[0029]
The resin of the blow molded product 16 of the present invention includes thermoplastic polycarbonate resin, polyethylene resin, polypropylene resin, styrene acrylonitrile resin, polyamide resin, polyethylene terephthalate resin, polyethersulfone resin, polyethylene naphthalate resin, polyetheretherketone. A thermoplastic resin material generally used for injection molding, such as resin, can be used.
[0030]
Furthermore, additives such as a colorant, a thermal deterioration inhibitor, an antioxidant, an ultraviolet absorber, an antistatic agent, an antibacterial agent, and a lubricant can be appropriately added to the resin used.
[0031]
Further, in the above embodiment, the brim portion is formed on the parison using the lip mold, but the thread groove may be formed on the outer periphery of the upper end portion of the parison using the screw mold.
[0032]
【The invention's effect】
According to the present invention, the gate trace of the parison is essentially crushed by the stretching rod for longitudinal axis stretching, so that the gate trace is hardly noticeable in the molded product without finishing the gate trace before blow molding. It is possible to obtain a blow molded product having high value while simplifying the apparatus and the process.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a parison for biaxial stretch blow molding according to an embodiment of the present invention.
FIG. 2 is a process diagram showing a vertical axis stretching process of biaxial stretch blow molding according to an embodiment of the present invention.
FIG. 3 is a process diagram showing a horizontal axis stretching process of biaxial stretch blow molding according to an embodiment of the present invention.
FIG. 4 is a process diagram showing a horizontal axis stretching process of biaxial stretch blow molding according to an embodiment of the present invention.
[Explanation of symbols]
1 Parison 1a Gate trace 7 Stretched rod

Claims (3)

When the bottomed parison (1) for biaxial stretch blow molding having the injection molding gate mark (1a) on the inner surface of the bottom is stretch blow molded, the gate mark (7) at the tip of the stretch rod (7) for vertical axis stretching ( A stretch blow molding method characterized by crushing 1a) . After the bottomed parison (1) injection-molded so that the gate mark (1a) is formed on the inner surface of the bottom part, the vertical axis is extended by the extending rod (7) brought into contact with the gate mark (1a). In the biaxial stretch blow molding method, wherein the horizontal axis is stretched by blowing, the gate mark (1a) is crushed at the tip of the stretch rod (7) during the longitudinal stretch. Stretch blow molding method . A stretch blow molded article formed by the method according to claim 1 or 2 .

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