JP7400402B2 - mold - Google Patents

Description

The present invention relates to a mold used for manufacturing synthetic resin containers.

2. Description of the Related Art Containers formed using thermoplastic resins such as polyethylene terephthalate are widely used as containers for containing various beverages, various seasonings, and the like. Such synthetic resin containers are manufactured by first forming a cylindrical preform with a bottom, and then molding this preform into a bottle shape in a mold by biaxial stretch blow molding or the like. Ru.

The air present between the synthetic resin to be stretched and the mold must escape from the mold as the synthetic resin is stretched. When split molds are used, air is exhausted from the gaps between the molds. Further, as disclosed in Patent Document 1, for example, the bottom mold, which the stretched synthetic resin comes into contact with last, may be provided with ventilation holes for discharging air outside the mold.

Japanese Patent Application Publication No. 2015-85625

An object of the present invention is to provide a mold provided with ventilation holes.

According to one aspect of the present invention, a mold for forming the shape of a container by blow molding has a first opening provided on a molding surface of the mold and a portion other than the molding surface of the mold. at least a portion of the ventilation hole that faces the first opening is connected to a hole having a first cross-sectional area provided in the body of the mold and the hole. and an internal member having a second cross-sectional area narrower than the first cross-sectional area.

According to the present invention, a mold provided with ventilation holes can be provided.

FIG. 1 is a front view schematically showing a configuration example of a container according to an embodiment. FIG. 2 is a schematic diagram for explaining an outline of a configuration example of a mold used in a biaxial stretching blowing process of a container according to an embodiment. FIG. 3 is a cross-sectional view schematically showing a configuration example around an exhaust hole according to an embodiment. FIG. 4 is a diagram schematically showing a cross section of a pore orthogonal to the central axis of a pin according to one embodiment. FIG. 5A is a diagram schematically showing a cross section of a pore according to a modification, perpendicular to the central axis of the pin. FIG. 5B is a diagram schematically showing a cross section of a pore according to a modification, perpendicular to the central axis of the pin.

An embodiment of the present invention will be described with reference to the drawings. This embodiment relates to manufacturing a synthetic resin container. In particular, it relates to molds used for manufacturing synthetic resin containers.

[Container structure]
An example of the structure of the synthetic resin container 1 according to the present embodiment will be described with reference to the drawings. FIG. 1 is a front view schematically showing a configuration example of a container 1. As shown in FIG. In the description of the container 1, as shown in FIG. 1, the container 1 is erected on a horizontal plane with the mouth 2 up and the bottom 5 down, and the vertical and horizontal directions of the container 1 are defined. shall be. The container 1 includes a mouth 2, a shoulder 3, a body 4, and a bottom 5. The container 1 has a shape generally referred to as a round bottle, with a body 4 having a generally cylindrical shape. The spout 2 is a cylindrical portion that serves as a spout for pouring the contents. A screw for attaching a lid (not shown) is formed in the opening 2. The lower end of the mouth portion 2 is connected to the shoulder portion 3. The shoulder portion 3 has a truncated conical shape that expands in diameter toward the body portion 4, and connects the mouth portion 2 and the body portion 4. The upper end of the trunk 4 is connected to the shoulder 3, and the lower end of the trunk 4 is connected to the bottom 5. The bottom part 5 includes a structure called a petaloid. For the material of the container 1, any thermoplastic resin that can be blow molded may be used.

Note that the shape of the container 1 shown in FIG. 1 is merely an example, and the container 1 may have various shapes. For example, the vertical lengths, horizontal cross-sectional diameters, shapes, etc. of the shoulder portion 3 and body portion 4 may be changed as appropriate. Further, the shape of the bottom portion 5 is not limited to the petaloid shape, but may be various shapes.

[Container manufacturing method]
The container 1 as described above is manufactured as follows. First, a cylindrical preform with a bottom is formed using a thermoplastic resin by injection molding, compression molding, or the like. Next, this preform is stretched by biaxial stretch blow molding or the like to form the container 1 into a predetermined container shape.

FIG. 2 is a schematic diagram illustrating an example of the configuration of a mold 30 used in the biaxial stretching blowing process of the container 1. The mold 30 has a neck insert 31, a body mold 34, and a bottom mold 40. The neck insert 31 is a mold for fixing the lower side of the mouth of the preform 10. The neck insert 31 has a pair of split molds, and includes a first neck insert 32 and a second neck insert 33. The body mold 34 forms the shoulder 3 and body 4 of the container 1. The body mold 34 is a pair of split molds, and includes a first body mold 35 and a second body mold 36. The bottom mold 40 forms the bottom part 5. The bottom mold 40 is movable in the axial direction of the container 1 to be formed. Note that the mold is not limited to metal, and may be replaced with various molds formed using other materials.

The preform 10 heated to the stretching temperature is placed in the mold 30. The preform 10 is stretched in the axial direction by the stretch rod 38, and also stretched in the circumferential direction by blowing air into the preform. Regarding the container 1, the stretched synthetic resin contacts the surface of the body mold 34 to form the shoulder part 3 and the body part 4, and comes into contact with the bottom mold 40 to form the bottom part 5. At this time, the air that filled the space between the preform 10 and the mold 30 is discharged from the gaps between the molds as the synthetic resin is stretched. Further, the bottom mold 40 is provided with an exhaust hole 45 so that air between the bottom mold 40 and the container being stretched can be exhausted.

After the container 1 is formed, the mold is opened and the formed container 1 is taken out from the mold 30.

[Structure of bottom exhaust hole]
The structure of the exhaust hole 45 of the bottom mold 40 according to this embodiment will be explained with reference to FIG. 3. FIG. 3 is a cross-sectional view schematically showing a configuration example around the exhaust hole 45. As shown in FIG. As shown in this figure, the exhaust hole 45 is a hole that connects the molding surface 41 of the bottom mold 40 that is in contact with the synthetic resin and the external surface 42 of the bottom mold 40. The exhaust hole 45 has a small hole 47 and a wide hole 48 . The small hole 47 is a hole that has one end connected to the first opening 43 formed in the molding surface 41 of the bottom mold 40 and communicates with the large hole 48 . The wide hole 48 has one end of the second opening 44 formed on the outer surface 42 of the bottom mold 40, and is a hole that allows the small hole 47 and the outside of the bottom mold 40 to communicate.

The pore 47 is formed by disposing a cylindrical pin 55 having a slightly smaller diameter than the cylindrical hole 51 inside the cylindrical hole 51, which is a cylindrical space. The pin 55 functions as an internal member disposed inside the cylindrical hole 51 and whose cross-sectional area is smaller than the cross-sectional area of the cylindrical hole 51 . In this embodiment, the cylindrical hole 51 and the pin 55 are arranged so that the central axis of the cylindrical hole 51 and the central axis of the pin 55 coincide. FIG. 4 is a diagram schematically showing a cross section of the pore 47 orthogonal to the central axis of the pin 55. As shown in this figure, a space 59 formed between the inner wall 52 of the cylindrical hole 51 and the outer wall 56 of the pin 55 serves as a flow path for air for exhaust.

According to the configuration of the exhaust hole 45 according to this embodiment, a large cross-sectional area can be obtained while having a small gap. For example, if the distance between the opposing surfaces of the inner wall 52 is wide, such as in the case of a cylindrical hole 51 in which no pin 55 is arranged, a part of the stretched container will flow into the hole, resulting in a corner-like protrusion on the surface of the container 1. (burrs) are formed. On the other hand, if the cross-sectional area is small, sufficient exhaust cannot be achieved. According to the configuration of the exhaust holes 45 of this embodiment, both the narrow spacing and the large cross-sectional area can be achieved.

By placing a 1.2 mm diameter pin in a 1.3 mm diameter cylindrical hole, the gap width is 0.05 mm. In this case, compared to the case without pins, the spacing is reduced by 96% from 1.3 mm to 0.05 mm, while the cross-sectional area remains only 85% reduced from 1.33 mm ² to 0.20 mm ² . In this way, according to the configuration of the pores 47 of this embodiment, a narrow gap width and a large cross-sectional area can be obtained. If a larger cross-sectional area is required, the diameters of the cylindrical holes 51 and pins 55 of the pores 47 may be increased, or the number of pores 47 may be increased.

本実施形態に係る排気穴４５の構成によれば、底型４０の作製も容易である。すなわち、細い隙間を切削加工などによって形成することは困難である。一方で、本実施形態の排気穴４５は、円筒孔５１をドリルによって形成した後に、円柱形のピン５５を当該円筒孔５１内に配置することで、容易に作製され得る。 Table 1 shows the relationship between the diameters of the cylindrical hole 51 and the pin 55 and the cross-sectional area when the difference between the diameter of the cylindrical hole 51 and the diameter of the pin 55 is 0.1 mm. Based on the relationships shown in this table, the diameter can be determined so as to obtain the required cross-sectional area.

According to the configuration of the exhaust hole 45 according to this embodiment, the bottom mold 40 can also be easily manufactured. That is, it is difficult to form a narrow gap by cutting or the like. On the other hand, the exhaust hole 45 of this embodiment can be easily produced by forming the cylindrical hole 51 with a drill and then arranging the cylindrical pin 55 in the cylindrical hole 51.

Any method may be used to fix the pin 55 within the cylindrical hole 51. The pin 55 is fixed to the inner wall of the cylindrical hole 51 or the inner wall of the wide hole 48 using a support member small enough to support the pin 55 so as not to obstruct the air flow. be able to. In addition, by arranging a pin 55 that is longer than that shown in FIG. It can be fixed.

[Application example]
The mold 30 according to the present embodiment is particularly suitable for forming a composite container in which the periphery of the container body is covered with a coating layer, although the mold 30 is not limited thereto. A composite container has, for example, a container body formed using an ethylene terephthalate-based thermoplastic polyester resin and covered with a coating layer such as a polyolefin-based resin. As the ethylene terephthalate thermoplastic polyester resin used for the container body, for example, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, amorphous polyarylate, polylactic acid, polyethylene furanoate, or copolymers thereof may be used. . Furthermore, a mixture of these resins or a mixture of these resins and other resins may be used. For the coating layer, for example, polyolefin resins such as polyethylene and polypropylene, ethylene-vinyl alcohol copolymers, polyamide resins such as polymethaxylylene adipamide (MXD6), etc. can be used. The resin forming the container body and the resin forming the coating layer are preferably incompatible. By using incompatible thermoplastic resins, the coating layer can be easily peeled off from the container body. This facilitates recycling of the container.

The covering layer may be colored, decorated, or provided with various functions. For example, pigments or coloring agents may be added for coloring. The coating layer may have light blocking properties, for example. By being able to easily separate the container body and the coating layer, the recyclability of the colorless and transparent container body is maintained regardless of the colored coating layer.

To form such a composite container, a preform is used that has two resin layers: a resin that serves as the container body and a resin that serves as the coating layer. Such a preform can be produced, for example, by a so-called double molding (two-color molding) method. A preform having two layers of resin is stretched as a unit, such as by biaxial stretch blow molding.

The melting point of the polyolefin resin forming the coating layer is lower than that of the ethylene terephthalate thermoplastic polyester resin forming the container body. Therefore, at a temperature at which the ethylene terephthalate thermoplastic polyester resin can be stretched, the polyolefin resin forming the coating layer may become extremely soft. In such a case, the polyolefin resin tends to flow into the exhaust hole, and as a result, burrs are likely to be formed.

Therefore, the exhaust hole 45 according to the present embodiment, which has a narrow gap and a configuration in which resin does not easily flow in, is particularly effective in manufacturing such a composite container.

[Modified example]
In the above-described embodiment, the exhaust hole 45 has been described as an example of the use of the ventilation hole formed using the cylindrical hole 51 and the pin 55. However, the use of the ventilation hole formed using the cylindrical hole 51 and the pin 55 is not limited to this. For example, in order to prevent the mold from sticking to the container during mold release, gas may be blown onto the container through small holes in the mold. The ventilation hole formed using the cylindrical hole 51 and pin 55 according to this embodiment can also be applied to a small hole for blowing gas into a container.

Further, the shape of the pores 47 is not limited to the ring shape in cross section as described above, but may also be in the shape of a slit. Furthermore, as shown in the cross-sectional shape of the pore 47a in FIG. 5A, for example, the center of the cylindrical hole 51a in the first port 43 does not coincide with the center of the pin 55a, and even if the pin 55a is arranged unevenly. good. In this case, the width of the space 59a formed between the inner wall 52a of the cylindrical hole 51a and the outer wall 56a of the pin 55a varies depending on the position in the circumferential direction. If the ease with which the synthetic resin penetrates into the hole varies depending on the direction, such as the stretching direction of the synthetic resin, the width of the space 59a may be varied depending on the bias.

Further, as shown in FIG. 5B, for example, which shows the shape of the first opening 43 of the pore 47b, the cross-sectional shape of the hole 51b and the pin 55b is not limited to a circular shape, but may be any shape such as a quadrangular shape. Since the pin 55b is arranged in the hole 51b, the pin 55b is naturally smaller than the hole 51b, including its cross-sectional area. Even if the shape is not circular, as in this example, the purpose of the embodiments described above, which is to increase the cross-sectional area while narrowing the gap, can be achieved. In the example shown in FIG. 5B, the center of gravity of the hole 51b and the center of gravity of the pin 55b in the plane including the first opening 43 coincide. However, it is not limited to this. The center of gravity of the hole and the center of gravity of the pin in the plane including the first opening 43 may not coincide with each other, as in the example shown in FIG. 5A, for example. However, although it depends on their shapes, when the center of gravity positions match, the width of the gap formed around the pin tends to be uniformly narrow in the circumferential direction.

The exhaust hole as described above can be applied not only to the bottom mold but also to other molds such as the body mold. However, exhaust holes are particularly important in bottom molds where the escape route for air is likely to be restricted as a result of stretching.

Although the present invention has been described above by showing preferred embodiments, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the present invention. Nor.

1 Container 2 Mouth 3 Shoulder 4 Body 5 Bottom 10 Preform 30 Mold 31 Neck insert 34 Trunk 38 Stretch rod 40 Bottom mold 41 Molding surface 42 External surface 43 First port 44 Second port 45 Exhaust Hole 47 Pore 48 Large hole 51 Cylindrical hole 52 Inner wall 55 Pin 56 Outer wall 59 Space

Claims (4)

A mold for forming the shape of a container by blow molding,
A ventilation hole connecting a first port provided on a molding surface of the mold and a second port provided on a surface other than the molding surface of the mold,
At least a portion of the ventilation hole facing the first opening includes a pore having a first cross-sectional area provided in the body of the mold, and a pore having a first cross-sectional area disposed inside the pore. and an internal member that is a pin having a columnar shape having a second cross-sectional area narrower than the area and longer than the pore ,
The mold has the pore and a large hole communicating with the pore,
The second mouth of the ventilation hole is formed by the large hole,
The internal member is arranged so as to penetrate from the outside of the mold, and a part thereof is arranged inside the pore.
Molding mold. The mold according to claim 1, wherein the center of gravity of the hole and the center of gravity of the internal member on the surface including the first opening coincide with each other. The mold according to claim 1 or 2, wherein the shape of the hole and the shape of the internal member on the surface including the first opening are circular. The mold according to any one of claims 1 to 3, wherein the mold is a bottom mold for molding the shape of the bottom of the container.

Images