JP2018199249A - Primary molded article for resin container, injection molding die for primary molded article, resin container, and manufacturing method of resin container - Google Patents

Abstract

To provide a primary molded article suitable for manufacturing a resin container provided with a neck part having a shape, that corresponds to the neck part having a glass bottle thickness, by stretch blow molding.SOLUTION: A neck part 23 of a preform 20 (primary molded article) for a milk bottle 1 (resin container) made of PET has a structure in which an outside cylindrical part 13 surrounds an inside cylindrical part 11 with a space 12. Thickness of the inside cylindrical part 11 as well as the outside cylindrical part 13 can be made to be equal to or less than the thickness suitable for injection molding, even though making the neck part 23 be identical to a dimension and a shape on inner and outer peripheral sides of the thick neck part for a conventionally existing glass bottle. The primary molded article for manufacturing the resin container, that is used in place of the glass bottle provided with the thick neck part, can be injection-molded in an appropriate state without being accompanied with crystallization of the neck part, whitening of the neck part associated therewith, and deterioration of physical property values such as impact strength and so forth.SELECTED DRAWING: Figure 1

Description

  The present invention is produced by subjecting a primary molded product used for producing a resin container by stretch blow molding, an injection mold for injection molding the primary molded product, and stretch blow molding to an injection molded primary molded product. The present invention relates to a resin container and a method for manufacturing the resin container. In particular, the present invention relates to a primary molded product suitable for manufacturing a resin container having a neck portion that follows a thick glass bottle shape.

In recent years, various containers mainly made of glass have been converted to resin containers, particularly PET resin containers, due to the following factors.
(1) Easy to break. There is a high risk of cracking and entering the contents in the process of filling foods etc. in the first stage before reaching the consumer. In addition, there is a high risk of falling from a shelf due to an earthquake or the like, and being easily broken even by a consumer's handling mistake.
(2) Heavy. There are problems such as an increase in transportation costs and the inability to process a large amount at a time.
(3) Manufacturing cost is high. That is, an electric furnace is used for melting a glass material, and the crucible is generally required to be repaired once every 5 to 6 years, which requires considerable cost. In addition, as a result of many glass craftsmen being closed, glass container manufacturing costs are rising due to a shortage of craftsmen.

  Various types of glass containers are combined with the above-mentioned factors, and it is difficult to manufacture a thin walled container like a resin. For this reason, many containers called glass bottles on the market have a wall thickness of at least 2 mm. Furthermore, it reaches the neck of the glass container and requires a thick shape of 4 to 6 mm.

  For example, FIG. 4 shows a side view of a glass milk bottle on the market and an enlarged partial cross-section of its neck. The glass milk bottle 100 includes a cylindrical neck portion 103 whose upper end is a mouth portion 102, a body portion 104 that is continuous with the lower end, and a bottom portion 105 that seals the lower end of the body portion 104. I have. The trunk portion 104 includes a tapered shoulder portion 106 that gradually spreads downward from the lower end of the neck portion 103, and a trunk body portion 107 having a constant diameter between the shoulder portion 106 and the bottom portion 105. The neck part 103 is a thick part thicker than 4 mm. A male screw 108 for attaching a cap (not shown) is formed on the circular outer peripheral surface of the neck portion 103.

  Under these circumstances, since the milk product has been revised, the form of drinking-type yogurt, etc., mostly filled with lightweight PET resin containers has become the mainstream. For example, as a product such as drinking yogurt with an internal volume of 112 mL, a product filled with a container having a weight of around 9 g and an average wall thickness of 0.25 mm has been commercialized in large quantities. In these new products, the contents filling machine has a mechanism corresponding to the thin neck of the resin container.

  On the other hand, milk with a long history uses a paper composite container called a gable top type or brick type whose mainstream is 1L. However, it is still sold in a form filled in a glass milk bottle as shown in FIG. 4 mainly for home delivery and convenience stores.

  FIG. 5 shows a preform, which is a primary molded product used for producing an ordinary PET resin container widely used as a beverage container or the like by stretch blow molding, and an enlarged partial cross section of the neck portion. The preform 200 includes a neck portion 203 whose upper end is a mouth portion 202, a cylindrical body portion 204, and a hemispherical bottom portion 205 that seals the lower end of the body portion 204. The mouth portion 202 and the neck portion 203 are portions that become the mouth portion and the neck portion of the PET resin container 210 without being subjected to stretch blow molding. The body part 204 of the preform 200 is a part that is stretched and blow-molded and formed into a container body part 214 having a predetermined shape and a predetermined thickness as shown by an imaginary line.

  The thickness of the neck portion 203 of the preform 200 is limited to 2 to 3 mm. If the neck portion 203 is thicker than this, the thick neck portion 203 cannot be rapidly cooled in the mold during the injection molding of the preform 200. For this reason, the thick part of the neck portion is crystallized, the physical property value is changed, and a transparent neck portion may not be formed. A PET resin container which is a stretch blow-molded product and a preform which is a primary molded product thereof are described in, for example, Patent Document 1 and the like.

JP 2000-117821 A

  There is always a desire to replace glass bottles used in milk products such as milk with resin containers. Filling equipment for filling contents such as milk into containers is dedicated to glass bottles. For this reason, even if the glass bottle is made of resin, there is a strong demand for not changing the external dimensions of the bottle, particularly the neck, and also using the cap used for the glass bottle as it is.

  However, the neck portion of the glass bottle has a very thick wall shape as described above. For example, even if the filling portion of the glass bottle excluding the neck portion can be molded without any problem with PET resin, the thickness of the neck portion is limited to 2 to 3 mm with PET resin. If the neck is thick with the same dimensions as the glass bottle, as mentioned above, the thick neck cannot be rapidly cooled in the mold during the injection molding of the preform, and the thick part crystallizes significantly. The physical property value changes and a transparent neck portion cannot be formed.

  The object of the present invention is to make the outer shape and inner / outer diameter of the neck portion the same as in the case of a glass bottle, use the cap used in the glass bottle, and use the filling machine without significant remodeling. Is to provide. Another object of the present invention is to provide a primary molded product (preform, parison) that can be manufactured by stretch blow molding without deteriorating the characteristics of the neck portion of the resin container.

  Furthermore, the objective of this invention is providing the injection molding die of the primary molded product suitable for manufacturing the primary molded product of this resin container.

  Furthermore, the object of the present invention is to propose a method for producing a resin container, in which the outer shape of the neck portion and the inner and outer diameter dimensions are the same as those of a glass bottle, and the primary molded product is subjected to stretch blow molding. It is in.

  In order to solve the above-mentioned problem, the present invention is a primary molded product used for manufacturing a resin container by stretch blow molding, and a cylindrical neck portion having an upper end as a mouth portion, and the neck portion And a bottomed body continuous to the lower end of the head. The neck portion includes an inner cylindrical portion connected to the body portion and an outer cylindrical portion surrounding the inner cylindrical portion with a predetermined gap. The mouth portion is an annular portion that connects the upper end of the inner cylindrical portion and the upper end of the outer cylindrical portion, the upper end of the gap is sealed by the mouth portion, and the lower end of the gap opens downward. ing. The neck portion is a portion that remains as the neck portion of the resin container without being subjected to the stretch blow molding, and the bottomed barrel portion is subjected to the stretch blow molding to have a bottom barrel of the resin container. It is a part that becomes a part.

  The neck part of the primary molded product of the present invention has a structure in which the inner cylindrical part is surrounded by the outer cylindrical part with a gap. This makes the neck part the same as the dimensions and shape of the outer peripheral side and inner peripheral side of the thick neck part in the existing glass bottle, and the thickness of the inner cylindrical part and the outer cylindrical part is suitable for injection molding. Can be less than the thickness. Therefore, the primary molded product for manufacturing a resin container used in place of a glass bottle with a thick neck portion is in an appropriate state without crystallization of the neck portion and accompanying deterioration of physical properties such as impact strength. Can be injection molded.

  For example, the outer diameter and outer peripheral surface shape of the outer cylindrical portion are set so as to be the same as the outer peripheral dimension and shape of the thick neck portion of a glass bottle such as an existing milk bottle. Moreover, the inner diameter and inner peripheral surface shape of the inner cylindrical portion are set so as to be the same as the inner peripheral side size and shape of the thick neck portion of the glass bottle. In this way, the resin container obtained by subjecting the primary molded product (specifically, the body portion with the bottom) to stretch blow molding has the same outer dimensions and shape as the neck portion of the existing glass bottle. And the same inner peripheral dimensions and shape. Therefore, the cap attached in order to seal the opening part of the existing glass bottle can be used for a resin container as it is. In addition, an existing filling machine for filling glass bottles can be used as a filling machine for filling glass bottles with contents such as milk without significant modification.

  Here, the neck portion of the resin container usually has a circular cross section. In this case, in the neck portion of the preform for manufacturing the resin container, the outer cylindrical portion has a circular outer peripheral surface with a male screw cut, and the inner cylindrical portion has a circular inner peripheral surface. Yes.

  An injection mold having the following configuration can be used as an injection mold of a primary molded product for injection molding of a primary molded product having the above shape. That is, the injection mold according to the present invention has a cavity mold, a core, and a neck part ring. The cavity mold includes a core insertion recess into which the core can be inserted, a cylindrical protrusion formed on an opening edge of the core insertion recess, the shape corresponding to the gap in the neck portion, and the cylinder And a neck portion ring insertion recess for inserting the neck portion ring, which is coaxially formed on the outer peripheral side of the projection. In the state where the core and the neck part ring are mounted on the cavity mold, an inner cylindrical part molding cavity part of the neck part is formed between the cylindrical protrusion and the neck part ring, A cavity portion for forming the outer cylindrical portion of the neck portion is formed between the cylindrical protrusion and the core.

  Next, according to the present invention, a resin container manufactured by subjecting a primary molded product, which is a resin injection-molded product, to stretch blow molding, has a cylindrical container neck portion whose upper end is a container mouth portion, and the container And a bottomed container body continuous to the lower end of the neck. The container neck part includes a container inner cylindrical part connected to the container body part and a container outer cylindrical part surrounding the container inner cylindrical part with a predetermined gap. The container mouth portion is an annular portion that connects the upper end of the container inner tubular portion and the upper end of the container outer tubular portion to each other, the upper end of the gap is sealed by the mouth portion, and the lower end of the gap is downward Is open. The container neck part is a part where the neck part of the primary molded product remains as it is without being subjected to the stretch blow molding, and the container body part with the bottom is subjected to the stretch blow molding, It is a part molded into a predetermined thickness and shape.

  The resin container having this configuration is formed by using the injection molding die having the above-described configuration, the primary molded product manufacturing process for injection molding the primary molded product, and the stretch blow molding on the body portion of the primary molded product obtained by the injection molding. The film can be manufactured through a stretch blow process for applying.

  In the resin container of the present invention, the neck portion having the outer peripheral side shape and the outer diameter size, the inner diameter size, and the inner peripheral side shape similar to the thick neck portion of the glass bottle is accompanied by deterioration of the resin characteristics of the neck portion. It can be provided without. Therefore, the cap used for the glass bottle can be used as it is for the resin container, and the resin container is filled with the contents by using a filling machine for filling the glass bottle without significant modification. be able to.

It is the side view which shows the resin milk bottle to which this invention is applied, and the expanded partial sectional view of the neck part. It is a side view which shows the preform which is a primary molded product used for manufacture of the resin milk bottle of FIG. 1, and a longitudinal cross-sectional view which shows the injection mold used in order to injection-mold a preform. FIG. 3 is a front view, a plan view, a bottom view, and a sectional view showing the preform of FIG. 2. It is the side view which shows the glass milk bottle currently on the market, and the expanded partial sectional view of a neck part. It is the side view which shows the preform used for manufacture of a normal PET resin container, and the expanded partial sectional view of a neck part.

  Embodiments of the present invention will be described below with reference to the drawings. The following relates to an example of a preform suitable for producing a milk bottle made of PET by stretch blow molding, and an example of an injection mold used for injection molding of the preform. The present invention can be similarly applied to a preform used for manufacturing a resin container other than a milk bottle made of PET, and an injection mold thereof, and the present invention is not limited to the following examples. .

  Fig.1 (a) is a side view which shows the milk bottle made from PET of this Embodiment, FIG.1 (b) is an expanded partial sectional view of the neck part. The illustrated PET milk bottle 1 (hereinafter sometimes simply referred to as “milk bottle 1”) is milk produced without substantially changing the shape and dimensions of the commercially available glass milk bottle shown in FIG. It is a bottle. Moreover, the container neck part formed so that it may become the same as the outer peripheral side shape and outer diameter size of the thick container neck part of a glass milk bottle, and an inner peripheral side shape and internal diameter dimension is provided. The container neck portion has a neck shape that does not cause crystallization of the PET resin.

  Referring to FIGS. 1 (a) and 1 (b), a milk bottle 1 includes a cylindrical container neck portion 3 having a predetermined thickness whose upper end is a container mouth portion 2, and a lower end of the container neck portion 3. A cylindrical container body 4 that is continuous with the container body 4 and a container bottom 5 that seals the lower end of the container body 4. The container body 4 has a tapered container shoulder 6 that gradually extends downward continuously from the container neck 3 and a constant diameter that extends to the container bottom 5 continuously from the container shoulder 6. The container body part 7 is provided. The container bottom portion 5 has a circular arc plate shape whose central portion is convex upward.

  As shown in FIG. 1 (b), the container neck 3 includes a cylindrical inner cylindrical part 11 connected to the upper end of the container body 4 (the upper end of the container shoulder 6), and the inner cylindrical part 11. A cylindrical outer cylindrical portion 13 that is concentrically surrounded by a substantially constant cylindrical gap 12 is provided. The container mouth portion 2 is an annular portion that connects the upper end of the inner cylindrical portion 11 and the upper end of the outer cylindrical portion 13 to each other.

  The upper end of the cylindrical gap 12 is sealed by an annular container mouth 2, and the lower end of the gap 12 opens downward. In this example, the length of the outer cylindrical portion 13 in the direction of the bottle center axis 1a is shorter than that of the inner cylindrical portion 11, and the lower end surface 13a thereof has an inner cylindrical portion 11 and a shoulder portion 6 indicated by a one-dot chain line. It is located above the boundary position 6c.

  In the container neck portion 3, a male screw 13 c is engraved on the circular outer peripheral surface 13 b of the outer cylindrical portion 13, and the container mouth portion 2 can be sealed by covering a cap (not shown). The upper end of the circular outer peripheral surface 13 b is smoothly connected to the convex arc surface 2 b that defines the outer peripheral side of the upper end surface 2 a of the container mouth portion 2. The upper end surface 2a of the container mouth portion 2 is defined by a convex arc surface 2b, a plane 2c smoothly connected to the upper end, and a convex arc surface 2d smoothly connected to the inner end of the plane. The lower end of the convex arc surface 2d is smoothly connected to the circular inner peripheral surface 11a of the inner cylindrical portion 11 of the container neck portion 3, and the lower end of the circular inner peripheral surface 11a is the inner peripheral surface of the shoulder portion 6 of the trunk portion 4. Is smoothly connected to the upper end of the inner peripheral surface 6a.

  On the other hand, in the outer cylindrical portion 13 of the container neck portion 3, the upper end of the circular inner peripheral surface 13 d extending upward from the inner peripheral edge of the lower end surface 13 a is a curve defining the lower end surface of the container mouth portion 2. It smoothly continues to the outer periphery of the surface 2e. The upper end of the circular outer peripheral surface 11b of the inner cylindrical portion 11 is smoothly connected to the inner peripheral edge of the curved surface 2e. The lower end of the circular outer peripheral surface 11 b is smoothly connected to the upper end of the outer peripheral surface defining the outer peripheral surface 6 b of the shoulder 6 of the container body 4.

  FIG. 2A is a side view showing an example of a preform 20 which is a primary molded product used for manufacturing the milk bottle 1 having the above shape, and FIG. 2B is an injection molding for manufacturing the preform 20. It is a longitudinal cross-sectional view which shows a type | mold. 3A to 3D are a front view, a plan view, a bottom view, and dd of the preform 20 (a preformed product of a plastic bottle-shaped packaging container formed by stretch blow molding). It is line sectional drawing. (Note that the left and right side surfaces and the back surface of the preform 20 have the same shape as the front surface.)

  The preform 20 includes a cylindrical neck portion 23 having a predetermined thickness whose upper end is a mouth portion 22, a cylindrical trunk portion 24 that is continuous with the lower end of the neck portion 23, and a lower end of the trunk portion 24. And a bottom 25 that is sealed. The mouth portion 22 and the neck portion 23 are portions that remain as the container mouth portion 2 and the container neck portion 3 of the milk bottle 1 without being subjected to stretch blow molding, and the container neck portion 3 of the milk bottle 1 described above. It has the same shape and dimensions as the container mouth 2. About each part of the mouth part 22 and the neck part 23, it demonstrates using the code | symbol attached | subjected to each part of the container mouth part 2 and the container neck part 3, as needed.

  The body portion 24 subjected to stretch blow molding has a tapered constricted portion 26 that gradually narrows downward continuously from the neck portion 23 and a constant portion that extends to the bottom portion 25 continuously from the constricted portion 26. And a cylindrical trunk body 27 having a diameter of 5 mm. The bottom portion 25 has a circular arc shape whose central portion is convex downward. The thickness of the trunk portion 24 and the bottom portion 25 is thicker than the thickness of the container barrel portion 4 and the container bottom portion 5 of the milk bottle 1. Stretch blow molding is performed in the biaxial direction, and the body portion 24 and the bottom portion 25 are formed into the thin-walled and large-diameter container body portion 4 and the container bottom portion 5 shown in FIG.

  Referring to FIG. 2B, the injection mold 30 includes a core 32, a cavity mold 33, and a neck portion ring 34 for forming a cavity 31 for injection molding of the preform 20. .

  The cavity mold 33 includes a core mold insertion recess that is open on one side. An inner peripheral surface portion 33 a corresponding to the outer peripheral surface of the body portion 24 of the preform 20 and the outer peripheral surface of the bottom portion 25 is formed on the inner peripheral surface portion of the recess. A cylindrical projection 33 b corresponding to the cylindrical gap 12 of the neck portion 23 of the preform 20 is formed at the opening edge of the recess in the cavity mold 33. A cylindrical concave portion 33c for inserting a ring into which the neck portion ring 34 can be inserted is formed in a state of concentrically surrounding the cylindrical projection 33b.

  The neck ring 34 is inserted into the cylindrical recess 33c of the cavity mold 33, and the core 32 is inserted coaxially with the cavity mold 33 through the center hole 34a of the neck ring 34 to form a mold closed state. The The inner peripheral surface of the center hole 34a is a tapered inner peripheral surface with a predetermined draft, and the outer peripheral surface on the core 32 side is a tapered outer peripheral surface corresponding thereto.

  The core 32 includes a core portion that is coaxially inserted into the concave portion of the cavity mold 33, and the outer peripheral surface of the core portion corresponds to the inner peripheral surface of the body portion 24 of the preform 20 and the inner peripheral surface of the bottom portion 25. An outer peripheral surface shape portion 32 a and an outer peripheral surface shape portion 32 b corresponding to the circular inner peripheral surface 11 a of the neck portion 23 of the preform 20 and the upper end surface portion on the inner peripheral side of the mouth portion 22 are formed.

  An inner peripheral surface portion 34b corresponding to the circular outer peripheral surface 13b of the neck portion 23 and the upper end surface portion of the outer peripheral side of the mouth portion 22 is formed on the inner peripheral surface portion of the neck portion ring 34 facing the cylindrical protrusion 33b. Is formed.

  A cavity 31 for preform injection molding is formed between the cavity mold 33, the core 32, and the neck part ring 34 in a closed state where the core 32 and the neck part ring 34 are inserted into the cavity mold 33. An injection gate 35 is located in the center of the bottom of the recess in the cavity mold 33. Through this, the cavity 31 is injected and filled with a thermoplastic molten resin, for example, a PET resin.

  In the cavity 31, the molded portion of the neck portion 23 of the preform 20 is partitioned into an inner cylindrical portion 11 and an outer cylindrical portion 13 by a cylindrical projection 33b. The thickness of these molded parts can be reduced. Therefore, the injected molten resin is rapidly cooled in the molded portion, and the progress of the spherulite crystallization can be suppressed. Thereby, crystal whitening can be suppressed and transparency can be maintained, and deterioration of physical property values such as impact strength accompanying the progress of crystallization of the portion can be suppressed.

1 Milk bottle (milk bottle made of PET)
1a bottle center axis 2 container mouth part 2a upper end surface 2b convex arc surface 2c plane 2d convex arc surface 2e curved surface 3 container neck part 4 container body part 5 container bottom part 6 container shoulder part 6a inner peripheral face 6b outer peripheral face 6c boundary position 7 Container body portion 11 Inner cylindrical portion 11a Circular inner peripheral surface 11b Circular outer peripheral surface 12 Clearance 13 Outer cylindrical portion 13a Lower end surface 13b Circular outer peripheral surface 13c Male screw 13d Circular inner peripheral surface 20 Preform 22 Mouth portion 23 Neck portion 24 Body Part 25 Bottom part 26 Constriction part 27 Body part 30 Injection mold 31 Cavity 32 Core 32a Outer peripheral surface part 32b Outer peripheral part 33 Cavity mold 33a Inner peripheral part 33b Cylindrical protrusion 33c Cylindrical recess 34 Neck part ring 34a Center hole 34b Inner peripheral surface shape portion 35 Gate

Claims (5)

A primary molded product used to produce a resin container by stretch blow molding,
A cylindrical neck part whose upper end is a mouth part,
A bottomed body continuous to the lower end of the neck,
The neck portion is
An inner cylindrical part connected to the body part;
An outer cylindrical portion surrounding the inner cylindrical portion with a predetermined gap therebetween,
The mouth portion is an annular portion that connects the upper end of the inner cylindrical portion and the upper end of the outer cylindrical portion,
The upper end of the gap is blocked by the mouth, the lower end of the gap is open downward,
The neck portion is a portion that remains as a neck portion of the resin container without being subjected to the stretch blow molding,
The bottomed body portion is a primary molded product of a resin container, which is a portion that is subjected to the stretch blow molding and becomes a bottomed body portion of the resin container. In claim 1,
The outer cylindrical portion includes a circular outer peripheral surface on which a male screw is formed,
The inner cylindrical part is a primary molded product of a resin container having a circular inner peripheral surface. An injection molding die for a primary molded product for injection molding the primary molded product according to claim 2,
It has a cavity mold, core and neck ring,
The cavity mold is
A core insertion recess capable of inserting the core;
A cylindrical protrusion formed in the opening edge of the core insertion recess, and having a shape corresponding to the gap of the neck,
A neck part ring insertion recess for inserting the neck part ring, which is formed coaxially in a state surrounding the cylindrical protrusion,
In the closed state in which the core and the neck part ring are attached to the cavity mold, an outer cylindrical part forming cavity part of the neck part formed between the cylindrical protrusion and the neck part ring, An injection molding die for a primary molded product, comprising: an inner cylindrical portion molding cavity portion of the neck portion formed between the cylindrical protrusion and the core. A resin container produced by subjecting a primary molded product, which is a resin injection molded product, to stretch blow molding,
A cylindrical container neck whose upper end is a container mouth, and
A bottomed container body continuous with the lower end of the container neck,
The container neck is
A container inner cylindrical portion connected to the container body,
A container outer tubular portion surrounding the container inner tubular portion with a predetermined gap therebetween,
The container mouth part is an annular part that connects the upper end of the container inner cylindrical part and the upper end of the container outer cylindrical part to each other,
The upper end of the gap is sealed by the container mouth, the lower end of the gap is open downward,
The container neck part is a part where the neck part of the primary molded product remains without being subjected to the stretch blow molding,
The said container trunk | drum is a resin container which is the part by which the said stretch blow molding was given and was shape | molded by predetermined | prescribed thickness and shape. Using the injection mold according to claim 3, a primary molded product manufacturing process for injection molding the primary molded product according to claim 2,
Stretch blow molding for forming the resin container according to claim 4 by performing stretch blow molding on the body portion in the primary molded product,
The manufacturing method of the resin container containing this.

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