JP5532707B2 - Blow molding method - Google Patents

Description

  The present invention relates to a blow molding method capable of avoiding uneven distribution of resin at the time of blow molding, ensuring the strength by sufficiently thickening a necessary portion of the blow molded product, and realizing the weight reduction of the blow molded product. By incorporating the preform into the mold, heating the preform to the blow molding temperature, and blowing a cooling medium from a blowout hole provided in the mold to a specific part of the preform, the final shape is a molded product. However, the present invention relates to a blow molding method for obtaining a molded product that does not partially cause uneven thickness.

  When blow molding a conventional blow-molded product, for example, a container with a resin handle, the preform heated to the blow molding temperature in the mold is positioned with a separate handle already incorporated in the mold and heated. The preform thus formed is longitudinally stretched by a stretching rod, blown so as to be stretched in the circumferential direction by feeding high-pressure air so as to be in close contact with the mold, and a resin-made container with a handle is obtained.

  However, in the obtained container with a resin handle, a large amount of the resin of the preform flows in the attachment portion of the handle, and the resin does not flow so much on the container wall located under the handle, resulting in a thin wall. When filling the container with a resin handle with liquid contents such as soft drinks and seasonings and placing it on the product sales route, the container with the resin handle containing the liquid contents is placed in many stages for transportation efficiency. Will be stacked. For this reason, a load concentrates on the thin container wall under the handle of the resin handle, and there is a risk of buckling. As a result, the amount of resin in the preform must be increased and the container wall under the handle must not be thin, so the occurrence of a thin wall under the handle is a major issue in reducing the weight of the resin handle container. It has become.

  From this situation, a technology is known in which the required amount of preform resin flows to the handle attachment part, and the resin flows to the container wall located under the handle, so that the container wall has the required thickness. ing. In this technique, an insert piece, for example, a handle is inserted into a mold, and a preform is biaxially stretched and blown to obtain a container with a resin handle. Of the side wall of the reform, the region that comes into contact with the handle as a result of the biaxial stretching blow molding is locally adjusted to a temperature lower than other regions (for example, see Patent Document 1). That is, in the range disclosed in Patent Document 1, this temperature control method is performed by a temperature control core that cools from the inside or a temperature control pot that cools from the outside to the preform heated to the blow molding temperature, or After the temperature of the preform region in contact with the handle is locally adjusted to a lower temperature than the other regions by blowing the temperature control gas, the preform in that state is already incorporated in the mold. After positioning the local cooling region on the handle and incorporating it into the mold, a biaxial stretch blow molding process is performed to obtain a container with a resin handle.

Japanese Patent Publication No. 06-102358

  In the temperature adjustment method of Patent Document 1 described above, when a heating device that heats the preform to the blow molding temperature in a rotating state is used, the region of the preform that contacts the handle cannot be specified. Therefore, there is a problem that a cooling means cannot be incorporated in the heating device, and a cooling system must be newly installed separately from this. In addition, even if the region of the preform that is in contact with the handle is locally adjusted to a low temperature by the above cooling equipment, the preform whose temperature has been locally adjusted is already incorporated into the mold. A highly reliable transfer facility that can be accurately positioned on the handle and incorporated into the mold is required.

  Therefore, the object of the present invention is to avoid the uneven distribution of the resin during blow molding by slightly reworking existing equipment without creating new equipment, and to make the necessary parts of the blow molded product sufficiently thick and strong. It is intended to provide a blow molding method capable of ensuring the weight of the blow molded product.

The present invention has been proposed in order to achieve the above object, and is characterized by having the following configuration.
That is, according to the present invention, after the preform heated to the blow molding temperature is incorporated in the blow molding die, the blow molding die is closed, and then provided to the mold part that holds the handle of the blow molding die. The cooling medium is sprayed from the blowout hole to the specific part of the preform at the blow molding temperature through the upper engagement hole provided in the handle, the specific part is cooled from the other part, and then the preform is blow molded. There is provided a blow molding method characterized in that the specific part is located at a preset position of the molded article, and the thickness thereof is also set to a preset thickness.

  Further, according to the present invention, there is provided the blow molding method described above, wherein the preform is heated while rotating the preform up to a blow molding temperature.

  Further, according to the present invention, there is provided the blow molding method, wherein the preform is for a resin container with a handle, and the specific part is a container wall located under the handle in the resin container after blow molding. The

The operation of the first problem solving means is as follows. That is, after incorporating a preform heated to a blow molding temperature into a blow mold (hereinafter simply referred to as a mold), a cooling medium is sprayed from a blowout hole provided in the mold to a specific part of the preform, Because it cools from other parts to a predetermined temperature difference, the preform can be incorporated into the mold without positioning the cooled part of the preform. Since the temperature of the part is low, the resin in that part does not flow too much, stays at a preset position, and a blow molded product having a preset thickness can be obtained. In particular, even when the preform is rotated and heated to the blow molding temperature, special equipment for positioning and conveyance is not necessary.
In addition, by blowing a cooling medium from a blow hole provided in a mold part that holds a handle of a blow molding die to a specific part of a preform at a blow molding temperature through an upper engagement hole provided in the handle, the mold is Even in the closed state, a cooling medium is sprayed to a specific part of the preform incorporated in the mold from the blow hole provided in the mold part that holds the handle, and the specific part is cooled more than the other part to be predetermined. Temperature difference.
As the cooling medium to be blown onto the preform, the simplest is to blow air at room temperature. Use the air at a controlled temperature, spray liquefied carbon dioxide, liquid nitrogen, etc., or spray water. You can also.

  In addition, the third problem solving means operates by incorporating a preform for a resin container with a handle into the mold, heating the preform to a blow molding temperature, and performing the preform from a blowout hole in the mold. By spraying a cooling medium on a specific part of the material and cooling it from other parts to a predetermined temperature difference, the preform is incorporated into the mold without positioning the cooled part of the preform, If the preform is then blow molded, a resin container with a handle can be obtained, and the specific part sprayed with the cooling medium will remain on the container wall under the handle, and the wall thickness of the container wall is also set in advance. become.

  The blow molding method of the present invention avoids uneven distribution of resin at the time of blow molding by slightly reworking existing equipment without creating new equipment, and makes the necessary part of the blow molded product sufficiently thick and strong. This is effective in reducing the weight of the blow molded product.

  In addition, the blow molding method of the present invention can obtain a resin container with a handle having the same effect as described above. Therefore, even if a predetermined number of resin containers with a handle filled with a liquid content are stacked, There is no effect of buckling.

  Further, the blow molding method of the present invention can reliably blow a cooling medium such as air from the outside through a blow hole provided in the mold part to a specific part of the preform incorporated in the mold. The same resin container with a handle as described above can be obtained.

It is explanatory drawing of the 1st step in the blow molding method which shows embodiment of this invention. It is sectional drawing which shows the resin container with a handle produced by the blow molding method of this invention. It is sectional drawing which shows the handle of the resin-made containers with a handle of FIG. It is a perspective view which shows the handle of the resin-made containers with a handle of FIG. It is explanatory drawing of the 2nd step in the blow molding method of this invention. It is explanatory drawing of the 3rd step in the blow molding method of this invention.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  In the drawing, the blow molding method 1 includes a preform 2 heated to a blow molding temperature in a rotated state and incorporated in a mold 3, then the mold 3 is closed, and a blowout hole 4 provided in the mold 3. The cooling medium is sprayed onto the specific part 5 of the preform 2 that is at the blow molding temperature, and the specific part 5 is cooled more than other parts to give a predetermined temperature difference ΔT, and then the preform 2 is blow-molded. Then, the resin handle 6 is a molded product, and the specific portion 5 is set in a predetermined position in the state of the resin handle 6 and the thickness t is also set in advance. It is intended to become. In this example, air at normal temperature was used as the cooling medium.

Here, the resin handle-equipped container 6 manufactured by the blow molding method 1 will be described. That is, as shown in FIG. 2, the resin-made container 6 with a handle is attached to a container body 13 in which a handle attachment projection 12 is provided in a recess 11 in the body 10, and a handle attachment projection 12 of the container body 13. The handle 15 has a mounting portion 14.

  The container body 13 has a mouth portion 16, the body portion 10 described above, a shoulder portion 17 that connects them, and a bottom portion 18, and a lid (not shown) is screwed to the mouth portion 16 so that the container body 13 is screwed. Is opened and closed. And the trunk | drum 10 of the container main body 13 has the recessed part 11 as stated above, and the said handle 15 is accommodated and attached to this recessed part 11. FIG.

  As shown in FIGS. 3 and 4, the handle 15 is composed of a ring-shaped mounting portion 14 and a gripping portion 20 that supports the mounting portion 14 and can be grasped with a finger. The handle mounting projection 12 of the container body 13 can be fitted. The handle 15 is provided with an upper engagement hole 21 and a lower engagement hole 22 for preventing rotation. Further, the material of the container body 13 is preferably selected from polyester resins such as polyethylene terephthalate having transparency, gas barrier properties, impact resistance, and appropriate rigidity. Absent. In addition, a polyester resin is usually selected as the material of the handle 15, but there is no particular limitation as long as it is a resin having impact resistance, appropriate rigidity and strength.

Next, the blow molding method 1 of the resin handle-equipped container 6 having the above configuration will be described in detail.
First, the mold 3 is opened, the handle 15 is held by the mold part 3a, and the preform 2 is further heated to a blow molding temperature, for example, 110 to 120 ° C. by a heating device (not shown). The preform 2 at a temperature of 110 to 120 ° C. is assembled as it is in the mold 3 and the mold 3 is closed (see FIG. 1). Thereafter, air is blown out from the blowout holes 4 provided in the mold part 3a, applied to the specific part 5 of the preform 2, and the specific part 5 is cooled more than other parts, and a predetermined temperature difference ΔT, for example, A difference of about 5 to 20 ° C. is made (see FIG. 5).
The temperature of the blown-out air should just be lower than blow molding temperature (for example, 15 to 80 degreeC), and may remain at room temperature. In the present invention, as shown in FIGS. 1, 4 and 5 , the blowout hole 4 is provided so as to blow air through the upper engagement hole 21 of the handle 15 gripped by the mold part 3a. Yes.

Then, when a stretching rod (not shown) is inserted into the preform 2 and the preform 2 is longitudinally stretched, the cooled specific portion 5 engages with the lower portion of the grip 15 from the vicinity of the upper engagement hole 21. Move to near the hole 22. When pre-blowing is performed by spraying high-pressure air, for example, 10 to 40 kg / cm ² , into the preform 2 at the same time or in the middle of or after completion of the longitudinal stretching, the specific portion 5 moves further and the handle 15 Move down. Further, when the main blow is performed by switching to high-pressure air (for example, 20 to 40 kg / cm ² ), the preform 2 completely swells and comes into close contact with the mold 3, and the resin handle container 6 is blow-molded. At this time, the specific part 5 that has moved to the bottom of the handle 15 is also extended, but since the specific part 5 is cooled more than the other parts, the resin in that part does not flow too much, stays at a preset position, and its meat The thickness also becomes a preset thickness (see FIG. 6). The resin that has flowed into the inside of the ring-shaped attachment portion 14 of the handle 15 is pressed by the movable portion of the mold part 3 a to be molded into a flange shape, thereby firmly fixing the handle 15 to the container body 13. Since the resin also flows into the upper engagement hole 21 and the lower engagement hole 22 of the handle 15, the handle 15 is prevented from rotating and the handle 15 is not shifted.

Next, since the test for demonstrating the superiority of the present invention was performed, it will be shown below.
<Test Example 1>
The basic shape of the handle is as shown in FIGS. 3 and 4, but only the upper engagement hole, and the hole shape is a square 6 mm × 8 mm and a cross-sectional area 48 mm ² . The preform of the container body has a mouth outer diameter of 38.0 mm, a mouth inner diameter of 27.6 mm, and a capacity of 1800 cc. The material of the handle and the container body is polyethylene terephthalate.
A separately formed handle is incorporated into the mold, a preform heated to an appropriate stretching temperature of 115 ° C. is incorporated into the mold, the mold is closed, and air at room temperature is supplied from the air blowing hole to a specific portion of the preform. After spraying for 2 seconds, biaxial stretch blow molding was performed. The thickness of the side wall of the obtained container with a resin handle and the longitudinal compressive strength of the empty container with a resin handle are measured.
The measurement position of the wall thickness is a part indicated by a circle in FIG.

<Comparative example 1>
A container with a resin handle was prepared under the same conditions as in Test Example 1 except that the specific part of the preform was not cooled. The thickness and longitudinal compressive strength of the side wall of the obtained container with a resin handle are measured under exactly the same conditions as in Test Example 1.
The results are shown in Table 1 of Test Example 1 and Comparative Example 1.

  As can be seen from Table 1, Test Example 1 of the present invention clearly demonstrates the superiority of the present invention because the thickness of the container wall of the resin handle under the handle is thicker than Comparative Example 1. Was made. Moreover, the longitudinal compressive strength of the empty container with a resin handle was higher in Test Example 1 of the present invention, and the superiority of the present invention could be verified.

  Although the first embodiment of the present invention has been described above, it should be understood that the specific configuration is not limited to this, and that changes can be made as appropriate without departing from the spirit of the present invention.

  The blow molding method of the present invention is highly applicable to a case where it is desired to secure a sufficient thickness at a necessary part of the blow molded product to maintain the strength and to reduce the weight of the blow molded product. When it is desired to reduce the weight of the blow-molded product by slightly reworking the equipment, its availability becomes extremely high. In addition to a container with a separate handle attached, it can be applied to a container having a concavity or a constriction formed in the container body, particularly when forming an asymmetric container around the vertical axis. It can be suitably applied.

DESCRIPTION OF SYMBOLS 1 Blow molding method 2 Preform 3 Mold 3a Mold part 4 Blowout hole 5 Specific part 6 Container with resin handle 10 trunk | drum 11 Recessed part 12 Handle attachment protrusion part 13 Container body 14 Attachment part 15 Handle 16 Mouth part 17 Shoulder part 18 bottom 20 gripping part 21 upper engagement hole 22 lower engagement hole

Claims (3)

The preform heated to the blow molding temperature is incorporated into the blow molding die, and after closing the blow molding die, it is provided in the handle from the blowout hole provided in the mold part that holds the handle of the blow molding die. The cooling medium is sprayed to a specific part of the preform at the blow molding temperature through the upper engaging hole , and the specific part is cooled more than the other part, and then the preform is blow-molded into a molded product. A blow molding method characterized in that a part is located at a preset position of the molded product, and a thickness thereof is set at a preset thickness.   The blow molding method according to claim 1, wherein the heating of the preform is performed while rotating the preform to a blow molding temperature.   The blow molding method according to claim 1, wherein the preform is for a resin container with a handle, and the specific part is a container wall located under the handle in the resin container after blow molding.

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