WO2010109775A1 - Plastic container, preform, method for producing plastic container, and preform mold - Google Patents

Plastic container, preform, method for producing plastic container, and preform mold Download PDF

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Publication number
WO2010109775A1
WO2010109775A1 PCT/JP2010/001435 JP2010001435W WO2010109775A1 WO 2010109775 A1 WO2010109775 A1 WO 2010109775A1 JP 2010001435 W JP2010001435 W JP 2010001435W WO 2010109775 A1 WO2010109775 A1 WO 2010109775A1
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WO
WIPO (PCT)
Prior art keywords
preform
container
mold
molding
molded
Prior art date
Application number
PCT/JP2010/001435
Other languages
French (fr)
Japanese (ja)
Inventor
中谷豊彦
吉川雅之
勝田秀彦
横手義孝
Original Assignee
東洋製罐株式会社
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Filing date
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Publication of WO2010109775A1 publication Critical patent/WO2010109775A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B11/00—Making preforms
    • B29B11/14—Making preforms characterised by structure or composition
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/26—Moulds
    • B29C45/2618—Moulds having screw-threaded mould walls
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
    • B29C49/02—Combined blow-moulding and manufacture of the preform or the parison
    • B29C49/06—Injection blow-moulding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
    • B29C49/071—Preforms or parisons characterised by their configuration, e.g. geometry, dimensions or physical properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D1/00—Containers having bodies formed in one piece, e.g. by casting metallic material, by moulding plastics, by blowing vitreous material, by throwing ceramic material, by moulding pulped fibrous material, by deep-drawing operations performed on sheet material
    • B65D1/02—Bottles or similar containers with necks or like restricted apertures, designed for pouring contents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B11/00—Making preforms
    • B29B11/06—Making preforms by moulding the material
    • B29B11/08—Injection moulding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
    • B29C49/02—Combined blow-moulding and manufacture of the preform or the parison
    • B29C2049/023—Combined blow-moulding and manufacture of the preform or the parison using inherent heat of the preform, i.e. 1 step blow moulding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00—Indexing scheme relating to blow-moulding
    • B29C2949/07—Preforms or parisons characterised by their configuration
    • B29C2949/0715—Preforms or parisons characterised by their configuration the preform having one end closed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00—Indexing scheme relating to blow-moulding
    • B29C2949/07—Preforms or parisons characterised by their configuration
    • B29C2949/073—Preforms or parisons characterised by their configuration having variable diameter
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00—Indexing scheme relating to blow-moulding
    • B29C2949/07—Preforms or parisons characterised by their configuration
    • B29C2949/076—Preforms or parisons characterised by their configuration characterised by the shape
    • B29C2949/0768—Preforms or parisons characterised by their configuration characterised by the shape characterised by the shape of specific parts of preform
    • B29C2949/077—Preforms or parisons characterised by their configuration characterised by the shape characterised by the shape of specific parts of preform characterised by the neck
    • B29C2949/0772—Closure retaining means
    • B29C2949/0773—Threads
    • B29C2949/0774—Interrupted threads
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00—Indexing scheme relating to blow-moulding
    • B29C2949/07—Preforms or parisons characterised by their configuration
    • B29C2949/076—Preforms or parisons characterised by their configuration characterised by the shape
    • B29C2949/0768—Preforms or parisons characterised by their configuration characterised by the shape characterised by the shape of specific parts of preform
    • B29C2949/077—Preforms or parisons characterised by their configuration characterised by the shape characterised by the shape of specific parts of preform characterised by the neck
    • B29C2949/0777—Tamper-evident band retaining ring
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00—Indexing scheme relating to blow-moulding
    • B29C2949/20—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer
    • B29C2949/22—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer at neck portion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00—Indexing scheme relating to blow-moulding
    • B29C2949/20—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer
    • B29C2949/24—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer at flange portion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00—Indexing scheme relating to blow-moulding
    • B29C2949/20—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer
    • B29C2949/26—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer at body portion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00—Indexing scheme relating to blow-moulding
    • B29C2949/20—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer
    • B29C2949/28—Preforms or parisons whereby a specific part is made of only one component, e.g. only one layer at bottom portion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00—Indexing scheme relating to blow-moulding
    • B29C2949/30—Preforms or parisons made of several components
    • B29C2949/3024—Preforms or parisons made of several components characterised by the number of components or by the manufacturing technique
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2949/00—Indexing scheme relating to blow-moulding
    • B29C2949/30—Preforms or parisons made of several components
    • B29C2949/3032—Preforms or parisons made of several components having components being injected
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/25—Solid
    • B29K2105/253—Preform
    • B29K2105/258—Tubular
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/712—Containers; Packaging elements or accessories, Packages
    • B29L2031/7158—Bottles

Definitions

  • the present invention relates to a synthetic resin container that suppresses environmental stress destruction occurring at the bottom of the container, a preform for molding such a synthetic resin container, a method for manufacturing such a synthetic resin container, and a preform mold. About.
  • the environmental stress failure that occurs at the bottom of the container is a trace of the parting line of the mold when the preform is molded. I came to the conclusion that it was caused.
  • a mold that can be divided into a plurality of parts is usually used.
  • a male mold composed of a core mold 131 that molds the inner surface; and a female mold that molds the outer surface of the preform 110 divided into a slide mold 132, a trunk mold 133, and a bottom mold 134 along the axial direction.
  • the dividing surface of the body mold 133 and the bottom mold 134 is located at the boundary between the body portion 112 of the preform 110 made cylindrical and the bottom portion 113 of the preform 110 made hemispherical.
  • a parting line PL is formed along the circumferential direction in a portion corresponding to a dividing surface of the body mold 133 and the bottom mold 134.
  • the parting line PL formed in such a part is formed into a bottle-shaped container 120 in normal blow molding, the parting line PL is closer to the center of the bottom than the grounding part 124 of the container bottom 123 as shown in FIG.
  • the trace V can only be confirmed as a minute step of less than 0.1 mm, but such a region is relatively less susceptible to stretching, and the strength is improved by stretching. I can't expect it. For this reason, a certain amount of wall thickness is sufficient.
  • FIG. 4 is an explanatory view showing the relationship between a conventional preform and a synthetic resin container formed by blow-molding the preform, and is set in a blow-molding die BM indicated by a two-dot chain line in the drawing.
  • the preform 110 and the outline of the container 120 formed into a predetermined container shape by transferring the cavity shape of the blow mold BM are shown so that the respective central axes C overlap.
  • 5 and 6 are explanatory views showing an example of molding a conventional preform by injection molding, and FIG. 5 shows a state in which an injection mold IM for molding a conventional preform is closed.
  • FIG. 6 shows a state where the mold is opened after the injection molding is finished. Normally, a gate for filling a thermoplastic resin into the cavity 130 formed by closing the mold is formed on the bottom mold 134 side, but the illustration of such a gate is omitted in FIGS. 5 and 6. is doing.
  • the present invention has been made in view of the circumstances as described above, and in forming a preform formed into a predetermined container shape by blow molding, the position of the parting line formed in the preform is changed.
  • a synthetic resin container that suppresses environmental stress destruction generated in the container bottom by preventing the trace of the parting line from being located inside the container bottom, a preform for molding such a synthetic tree container, It is an object of the present invention to provide a method for producing such a synthetic resin container and a preform mold for a preform for molding such a synthetic tree container.
  • a synthetic resin container according to the present invention is formed using a mold in which a female mold for molding an outer surface including a body portion and a bottom portion of a preform is divided into a plurality of portions along the axial direction, and is formed on the outer surface.
  • a bottomed cylindrical preform having at least one parting line formed in a direction is formed into a predetermined container shape by blow molding, and the parting line formed on the bottom side of the preform most The trace is configured to be located on the side surface of the container beyond the ground contact portion of the molded container bottom.
  • the preform according to the present invention is a bottomed cylindrical preform having a mouth portion, a trunk portion, and a bottom portion, which is molded into a synthetic resin container having a predetermined container shape by blow molding,
  • a female die for molding the outer surface including the bottom is molded using a molding die divided into a plurality along the axial direction, and at least one parting line is formed along the circumferential direction on the outer surface.
  • the length along the axial direction from the tip of the bottom portion to the parting line formed closest to the bottom portion is 20 to 20 times the length along the axial direction of the stretched portion excluding the mouth portion.
  • the configuration is 40%.
  • the method for producing a synthetic resin container according to the present invention is a method of forming the above preform into a predetermined container shape by blow molding.
  • a preform mold according to the present invention is a mold for molding a bottomed cylindrical preform having a mouth portion, a trunk portion, and a bottom portion, which is molded into a synthetic resin container having a predetermined container shape by blow molding.
  • the female die for forming the outer surface including the body portion and the bottom portion is divided into a plurality of portions along the axial direction, and in the axial direction from the portion corresponding to the tip of the bottom portion to the dividing surface closest to the bottom portion.
  • the length along the length is set to 20 to 40% of the length along the axial direction of the portion where the preform is stretched excluding the mouth portion.
  • FIG. 1 is an explanatory view showing the relationship between a preform used for blow molding in the present embodiment and a synthetic resin container formed by blow-molding such a preform, and indicated by a two-dot chain line in the figure.
  • the preform 10 set in the mold BM and the outline of the container 20 formed into a predetermined container shape by transferring the cavity shape of the blow molding mold BM are shown so that the respective central axes C overlap.
  • a bottomed cylindrical preform 10 made of a thermoplastic resin is injection-molded, and after this preform 10 is set in the blow molding die BM, it is used in the longitudinal direction using a stretching rod as necessary. While stretching, the shape of the cavity in the blow mold BM is transferred by stretching in the lateral direction with blow air. Thereby, the container 20 having a predetermined container shape to which the cavity shape in the blow mold BM is transferred is blow-molded.
  • the preform 10 is heated and softened as necessary so as to be capable of blow molding.
  • the preform 10 has a mouth part 11, a body part 12 and a bottom part 13, and a neck ring 14 is formed at the boundary between the mouth part 11 and the body part 12.
  • the mouth portion 11 of the preform 10 is not stretched and becomes the mouth portion of the container 20 as it is, and a screw thread for attaching a lid (not shown) is formed.
  • the portion below the neck ring 14 of the preform 10 (on the bottom 13 side) is stretched in the vertical and horizontal directions so as to become the body 22 and the bottom 23 of the container 20. To be molded.
  • thermoplastic resin for molding the preform 10 various thermoplastic resins used for this type of synthetic resin container can be used.
  • specific examples include thermoplastic polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyarylate, polylactic acid or copolymers thereof, and those blended with these resins or other resins.
  • polyester resins such as polyethylene terephthalate are preferably used.
  • acrylonitrile resin, polypropylene, propylene-ethylene copolymer, polyethylene and the like can also be used.
  • the preform 10 is molded using an injection mold IM as shown in FIGS.
  • the injection mold IM is a male mold composed of a core mold 31 that molds the inner surface of the preform 10, and an outer surface of the preform 10 divided into a slide mold 32, a body mold 33, and a bottom mold 34 along the axial direction.
  • a female mold for molding 2 is an explanatory view showing a state where the injection mold IM is closed
  • FIG. 3 is an explanatory view showing a state where the mold is opened after the injection molding is finished.
  • a gate for filling a thermoplastic resin into the cavity 30 formed by closing the mold is formed on the bottom mold 34 side, but such a gate is not shown in FIGS. is doing.
  • the slide mold 32 slides in a direction perpendicular to the central axis C, and the outer surface of the mouth portion 11 of the preform 10 is formed by the slide mold 32. Then, the outer surface of the cylindrical portion 10 of the preform 10 and the bottom portion 13 of the semispherical preform 10 are formed by a cylindrical die 33 and a bottom die 34 arranged coaxially.
  • the injection mold IM used for injection molding the preform 10 in the present embodiment includes a plurality of female molds for molding the outer surface including the body 12 and the bottom 13 of the preform 10 along the axial direction. It is divided into For this reason, the parting line PL is formed in the outer surface of the preform 10 along the circumferential direction in a portion corresponding to the dividing surface of the injection mold IM.
  • the parting line PL is formed according to the number of the dividing surfaces of the injection mold IM, in the illustrated example, only the parting line PL formed on the bottom 13 side is shown.
  • the party formed on the bottom 13 side of the preform 10 from the tip of the bottom 13 of the preform 10 is the most.
  • the length h along the axial direction to the ring line PL is the length along the axial direction of the stretched portion of the preform 10 excluding the mouth 11 (in the illustrated example, below the neck ring 14).
  • the position of the dividing surface of the body mold 33 and the bottom mold 34 is adjusted so that it is 20 to 40% of the length (H) of the portion to be positioned.
  • the body portion 12 of the preform 10 is stretched at a magnification of 1.7 to 2.7 times in the longitudinal direction and 2.3 to 4.6 times in the transverse direction.
  • the trace V of the parting line PL on the bottom portion 13 side formed on the preform 10 is formed as shown in FIG.
  • the container 20 is positioned on the side surface of the container beyond the ground contact portion 24 of the bottom 23 of the container 20.
  • the trace V of the parting line PL does not appear in the region inside the bottom 23 that is closer to the center of the bottom than the ground contact portion 24, so that the center thickness of the bottom 23 of the container 20 is 1.5 to 2.0 mm.
  • the parting line PL is formed at a position as far as possible from the bottom 13 of the preform 10.
  • the bottom mold 34 must be cut deeper, making the mold processing difficult and increasing the cost.
  • the upper limit of the length h is preferably 40% of the length H.
  • blow molding a one-stage blow molding method in which the preform is blown as it is to the size of the final molded product, and the preform is blown once to be larger than the final molded product, and the intermediate product is molded.
  • the intermediate product is thermally contracted and then blown to the shape of the final molded product.
  • the bottom 23 of the container 20 can be stretched relatively large, and the strength of the bottom 23 can be increased by stretching. Since it is difficult to extend the bottom 23, the strength of the bottom 23 cannot be improved by stretching. Therefore, the present invention is suitable for the case where the container 20 is blow-molded by a single-stage blow molding method.
  • the trace V of the parting line PL formed most on the bottom 13 side of the preform 10.
  • the thickness of the portion where the is located is 0.20 to 0.30 mm.
  • the present embodiment corresponds to the portion where the trace V of the parting line PL is located.
  • the thickness of the part is also about 0.35 to 0.45 mm, and there is a limit to reducing the thickness of the container.
  • this embodiment since this is not necessary, it is possible to suppress environmental stress destruction. It is possible to further reduce the thickness of the container.
  • a preform 10 having a weight of 23 g is molded so that the stretching ratio in the longitudinal direction is 2.3 times and the stretching ratio in the transverse direction is 3.9 times.
  • a container 20 of a predetermined container shape having a capacity of 500 ml as shown in FIG. 1 was formed by a one-stage blow molding method.
  • the trace V of the parting line PL is not recognized at the bottom 23 of the molded container 20, and the trace V is formed on the side of the container beyond the ground contact portion 24 of the bottom 23, as in the example shown in FIG. Was located.
  • the preform mold as described above may be used alone for injection molding of a preform, but a plurality of preform molds are attached to a mother mold, and a large number of them can be performed in a single injection molding process. It is also possible to form the preforms simultaneously.
  • the example in which the preform PL is molded by injection molding has been shown.
  • molding the preform by compression molding molding of a mold structure divided in the same manner as in the above-described embodiment. It goes without saying that the present invention can also be applied to the case where the preform is molded by other molding means that may use a mold.
  • the synthetic resin container in the present invention may have a multilayer structure including a barrier layer that suppresses permeation of oxygen from the outside into the container, an oxygen absorption layer, and the like as necessary.
  • the present invention provides a synthetic resin container that is less likely to cause environmental stress failure at the bottom of the container even when it is thinned.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Geometry (AREA)
  • Ceramic Engineering (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)
  • Blow-Moulding Or Thermoforming Of Plastics Or The Like (AREA)
  • Containers Having Bodies Formed In One Piece (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)

Abstract

Disclosed is a plastic container wherein the trace (V) of a parting line (PL) is located on the side surface side of the container beyond the grounding part (24) at the bottom (23) of the molded container when a preform (10) having the parting line (PL) formed in the outer side surface along the circumferential direction is molded into a predetermined container shape by blow molding, in order to effectively avoid occurrence of environmental stress fracture at the bottom of the container produced by blow molding the preform due to the trace of the parting line when the preform is molded.

Description

合成樹脂製容器、プリフォーム、合成樹脂製容器の製造方法、及びプリフォーム成形型Synthetic resin container, preform, method for producing synthetic resin container, and preform mold
　本発明は、容器底部に生じる環境応力破壊を抑止した合成樹脂製容器、そのような合成樹脂製容器を成形するためのプリフォーム、そのような合成樹脂製容器の製造方法、及びプリフォーム成形型に関する。 The present invention relates to a synthetic resin container that suppresses environmental stress destruction occurring at the bottom of the container, a preform for molding such a synthetic resin container, a method for manufacturing such a synthetic resin container, and a preform mold. About.
　近年、ポリエチレンテレフタレートなどの合成樹脂をブロー成形などによってボトル状に成形してなる合成樹脂製容器が、各種飲料品を内容物とする飲料用容器として急速に普及、浸透してきている。このような合成樹脂製容器の多くは、射出成形や圧縮成形などによって作製された有底筒状のプリフォームを加熱、軟化させて型内にセットし、次いで、必要に応じて延伸ロッドを用いて縦方向に延伸しつつ、ブローエアーによって横方向にも延伸することにより、所定の容器形状に成形される（例えば、特許文献１など参照）。 In recent years, synthetic resin containers formed by forming a synthetic resin such as polyethylene terephthalate into a bottle shape by blow molding or the like are rapidly spreading and penetrating as beverage containers containing various beverage products. Many of these synthetic resin containers heat and soften bottomed cylindrical preforms made by injection molding, compression molding, etc., and set them in the mold, and then use stretch rods as necessary. Then, the film is stretched in the longitudinal direction and stretched in the lateral direction by blow air to form a predetermined container shape (see, for example, Patent Document 1).
　また、このような合成樹脂製容器のうち、炭酸飲料を内容物とするものは、炭酸ガスによる容器内の加圧状態に耐え得るだけの耐圧性を備えるとともに、自立可能であることが要求される。さらに、内容物が充填された後は常に容器内が加圧された状態となっているため、経時変化による環境応力破壊（ＥＳＣ）が生じないように種々の検討がなされている（例えば、特許文献２など参照）。 Among such synthetic resin containers, those containing carbonated beverages are required to have sufficient pressure resistance to withstand the pressurized state in the container with carbon dioxide gas and be able to stand on their own. The Furthermore, since the inside of the container is always pressurized after the contents are filled, various studies have been made to prevent environmental stress destruction (ESC) due to aging (for example, patents). Reference 2 etc.).
特開平９－１６３９号公報Japanese Patent Laid-Open No. 9-1639 特開平９－３１５４１９号公報JP-A-9-315419
　ところで、この種の合成樹脂製容器に対しては、その軽量化や、使用樹脂量の削減による低コスト化が強く求められており、このため、可能な限り薄肉に成形することが望まれる。
　しかしながら、炭酸飲料を内容物とする合成樹脂製容器について薄肉化の検討を進めていく過程で、薄肉化の程度が大きくなるにしたがって容器底部に著しい環境応力破壊が認められるようになってくることを本発明者らは見出した。 By the way, for this type of synthetic resin container, there is a strong demand for weight reduction and cost reduction by reducing the amount of resin used. For this reason, it is desired to form the container as thin as possible.
However, in the process of studying the thinning of synthetic resin containers containing carbonated beverages, significant environmental stress failure will be observed at the bottom of the container as the degree of thinning increases. The present inventors have found out.
　そこで、このような容器底部に生じる環境応力破壊に着目して、さらなる鋭意検討を重ねたところ、容器底部に生じる環境応力破壊は、プリフォームを成形する際の成形型のパーティングラインの痕跡に起因しているとの結論に至った。 Therefore, paying attention to the environmental stress failure that occurs at the bottom of the container, and further studies, the environmental stress failure that occurs at the bottom of the container is a trace of the parting line of the mold when the preform is molded. I came to the conclusion that it was caused.
　すなわち、射出成形や圧縮成形によってプリフォームを成形するには、通常、複数に分割可能とされた成形型が用いられ、かかる成形型は、図５及び図６に示すように、プリフォーム１１０の内側面を成形するコア型１３１からなる雄型と、軸方向に沿ってスライド型１３２、胴型１３３及び底型１３４に分割されたプリフォーム１１０の外側面を成形する雌型とを有している。そして、加工上の都合から、胴型１３３と底型１３４との分割面が、筒状とされたプリフォーム１１０の胴部１１２と半球状とされたプリフォーム１１０の底部１１３との境界に位置するようになっており、プリフォーム１１０の外側面には、胴型１３３と底型１３４との分割面に相当する部位に周方向に沿ってパーティングラインＰＬが形成される。このような部位に形成されたパーティングラインＰＬは、通常のブロー成形では、ボトル状の容器１２０に成形したときに、図４に示すように、容器底部１２３の接地部位１２４よりも底部中心寄りとなる内側の領域に、０．１ｍｍにも満たない程度の微少な段差として痕跡Ｖが確認できるに過ぎないが、そのような領域は比較的に延伸加工を受けにくく、延伸による強度の向上が期待できない。このため、ある程度の肉厚があればよいが、薄肉化されるとパーティングラインＰＬの痕跡Ｖに応力が集中してしまい、当該痕跡Ｖに起因する環境応力破壊が顕著になってくると考えられる。 That is, in order to mold a preform by injection molding or compression molding, a mold that can be divided into a plurality of parts is usually used. As shown in FIGS. A male mold composed of a core mold 131 that molds the inner surface; and a female mold that molds the outer surface of the preform 110 divided into a slide mold 132, a trunk mold 133, and a bottom mold 134 along the axial direction. Yes. For the convenience of processing, the dividing surface of the body mold 133 and the bottom mold 134 is located at the boundary between the body portion 112 of the preform 110 made cylindrical and the bottom portion 113 of the preform 110 made hemispherical. In the outer surface of the preform 110, a parting line PL is formed along the circumferential direction in a portion corresponding to a dividing surface of the body mold 133 and the bottom mold 134. When the parting line PL formed in such a part is formed into a bottle-shaped container 120 in normal blow molding, the parting line PL is closer to the center of the bottom than the grounding part 124 of the container bottom 123 as shown in FIG. In the inner region, the trace V can only be confirmed as a minute step of less than 0.1 mm, but such a region is relatively less susceptible to stretching, and the strength is improved by stretching. I can't expect it. For this reason, a certain amount of wall thickness is sufficient. However, when the thickness is reduced, stress concentrates on the trace V of the parting line PL, and environmental stress destruction caused by the trace V becomes conspicuous. It is done.
　ここで、図４は、従来のプリフォームと、かかるプリフォームをブロー成形してなる合成樹脂製容器との関係を示す説明図であり、図中二点鎖線で示すブロー成形型ＢＭにセットされたプリフォーム１１０と、当該ブロー成形型ＢＭのキャビティ形状が転写されて所定の容器形状に成形された容器１２０の輪郭とを各々の中心軸Ｃが重なるように示している。また、図５及び図６は、従来のプリフォームを射出成形で成形する例を示す説明図であり、図５は、従来のプリフォームを成形する射出成形型ＩＭを型閉めした状態を示しており、図６は、射出成形を終えて型開きした状態を示している。通常、底型１３４側には、型閉めされて成形されたキャビティ１３０内に熱可塑性樹脂を充填するためのゲートが形成されるが、図５及び図６では、そのようなゲートの図示を省略している。 Here, FIG. 4 is an explanatory view showing the relationship between a conventional preform and a synthetic resin container formed by blow-molding the preform, and is set in a blow-molding die BM indicated by a two-dot chain line in the drawing. The preform 110 and the outline of the container 120 formed into a predetermined container shape by transferring the cavity shape of the blow mold BM are shown so that the respective central axes C overlap. 5 and 6 are explanatory views showing an example of molding a conventional preform by injection molding, and FIG. 5 shows a state in which an injection mold IM for molding a conventional preform is closed. FIG. 6 shows a state where the mold is opened after the injection molding is finished. Normally, a gate for filling a thermoplastic resin into the cavity 130 formed by closing the mold is formed on the bottom mold 134 side, but the illustration of such a gate is omitted in FIGS. 5 and 6. is doing.
　本発明は、上記したような事情に鑑みてなされたものであり、ブロー成形によって所定の容器形状に成形されるプリフォームを成形するにあたり、プリフォームに形成されるパーティングラインの位置を変更して、パーティングラインの痕跡が容器底部の内側に位置しないようにすることで容器底部に生じる環境応力破壊を抑止した合成樹脂製容器、そのような合成樹製容器を成形するためのプリフォーム、そのような合成樹脂製容器の製造方法、及びそのような合成樹製容器を成形するプリフォームのためのプリフォーム成形型の提供を目的とする。 The present invention has been made in view of the circumstances as described above, and in forming a preform formed into a predetermined container shape by blow molding, the position of the parting line formed in the preform is changed. In addition, a synthetic resin container that suppresses environmental stress destruction generated in the container bottom by preventing the trace of the parting line from being located inside the container bottom, a preform for molding such a synthetic tree container, It is an object of the present invention to provide a method for producing such a synthetic resin container and a preform mold for a preform for molding such a synthetic tree container.
　本発明に係る合成樹脂製容器は、プリフォームの胴部及び底部を含む外側面を成形する雌型が軸方向に沿って複数に分割された成形型を用いて成形され、前記外側面に周方向に沿って少なくとも一つのパーティングラインが形成された有底筒状のプリフォームをブロー成形によって所定の容器形状に成形してなり、最もプリフォームの底部側に形成された前記パーティングラインの痕跡が、成形された容器底部の接地部位を越えた容器側面側に位置する構成としてある。 A synthetic resin container according to the present invention is formed using a mold in which a female mold for molding an outer surface including a body portion and a bottom portion of a preform is divided into a plurality of portions along the axial direction, and is formed on the outer surface. A bottomed cylindrical preform having at least one parting line formed in a direction is formed into a predetermined container shape by blow molding, and the parting line formed on the bottom side of the preform most The trace is configured to be located on the side surface of the container beyond the ground contact portion of the molded container bottom.
　また、本発明に係るプリフォームは、ブロー成形によって所定の容器形状の合成樹脂製容器に成形される口部、胴部及び底部を有する有底筒状のプリフォームであって、前記胴部及び前記底部を含む外側面を成形する雌型が軸方向に沿って複数に分割された成形型を用いて成形され、少なくとも一つのパーティングラインが前記外側面に周方向に沿って形成されているとともに、前記底部の先端から最も前記底部側に形成された前記パーティングラインまでの軸方向に沿った長さが、前記口部を除く延伸される部位の軸方向に沿った長さの２０～４０％とした構成としてある。 The preform according to the present invention is a bottomed cylindrical preform having a mouth portion, a trunk portion, and a bottom portion, which is molded into a synthetic resin container having a predetermined container shape by blow molding, A female die for molding the outer surface including the bottom is molded using a molding die divided into a plurality along the axial direction, and at least one parting line is formed along the circumferential direction on the outer surface. In addition, the length along the axial direction from the tip of the bottom portion to the parting line formed closest to the bottom portion is 20 to 20 times the length along the axial direction of the stretched portion excluding the mouth portion. The configuration is 40%.
　本発明に係る合成樹脂製容器の製造方法は、上記のようなプリフォームをブロー成形によって所定の容器形状に成形する方法としてある。 The method for producing a synthetic resin container according to the present invention is a method of forming the above preform into a predetermined container shape by blow molding.
　本発明に係るプリフォーム成形型は、ブロー成形によって所定の容器形状の合成樹脂製容器に成形される口部、胴部及び底部を有する有底筒状のプリフォームを成形するための成形型であって、前記胴部及び前記底部を含む外側面を成形する雌型が軸方向に沿って複数に分割され、前記底部の先端に相当する部位から最も前記底部側の分割面までの軸方向に沿った長さが、前記口部を除く前記プリフォームの延伸される部位を成形する部分の軸方向に沿った長さの２０～４０％とした構成としてある。 A preform mold according to the present invention is a mold for molding a bottomed cylindrical preform having a mouth portion, a trunk portion, and a bottom portion, which is molded into a synthetic resin container having a predetermined container shape by blow molding. The female die for forming the outer surface including the body portion and the bottom portion is divided into a plurality of portions along the axial direction, and in the axial direction from the portion corresponding to the tip of the bottom portion to the dividing surface closest to the bottom portion. The length along the length is set to 20 to 40% of the length along the axial direction of the portion where the preform is stretched excluding the mouth portion.
　このような本発明によれば、プリフォームを成形した際のパーティングラインの痕跡に起因する環境応力破壊が、当該プリフォームをブロー成形してなる容器の底部に生じてしまうのを有効に回避することができる。 According to the present invention as described above, it is effectively avoided that environmental stress destruction caused by traces of the parting line when the preform is molded is generated at the bottom of the container formed by blow molding the preform. can do.
本発明の実施形態において成形に供されるプリフォームと、かかるプリフォームをブロー成形してなる合成樹脂製容器との関係を示す説明図である。It is explanatory drawing which shows the relationship between the preform used for shaping | molding in embodiment of this invention, and the synthetic resin containers formed by blow-molding this preform. 本発明の実施形態において成形に供されるプリフォームを成形する射出成形型を示す説明図である。It is explanatory drawing which shows the injection mold which shape | molds the preform used for shaping | molding in embodiment of this invention. 本発明の実施形態において成形に供されるプリフォームを成形する射出成形型を型開きした状態を示す説明図である。It is explanatory drawing which shows the state which opened the injection mold which shape | molds the preform provided for shaping | molding in embodiment of this invention. 従来のプリフォームと、かかるプリフォームをブロー成形してなる合成樹脂製容器との関係を示す説明図である。It is explanatory drawing which shows the relationship between the conventional preform and the synthetic resin containers formed by blow-molding this preform. 従来のプリフォームを成形する射出成形型を示す説明図である。It is explanatory drawing which shows the injection mold which shape | molds the conventional preform. 従来のプリフォームを成形する射出成形型を型開きした状態を示す説明図である。It is explanatory drawing which shows the state which opened the injection mold which shape | molds the conventional preform.
　以下、本発明の好ましい実施形態について、図面を参照しつつ説明する。 Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
　図１は、本実施形態においてブロー成形に供されるプリフォームと、かかるプリフォームをブロー成形してなる合成樹脂製容器との関係を示す説明図であり、図中二点鎖線で示すブロー成形型ＢＭにセットされたプリフォーム１０と、当該ブロー成形型ＢＭのキャビティ形状が転写されて所定の容器形状に成形された容器２０の輪郭とを各々の中心軸Ｃが重なるように示している。 FIG. 1 is an explanatory view showing the relationship between a preform used for blow molding in the present embodiment and a synthetic resin container formed by blow-molding such a preform, and indicated by a two-dot chain line in the figure. The preform 10 set in the mold BM and the outline of the container 20 formed into a predetermined container shape by transferring the cavity shape of the blow molding mold BM are shown so that the respective central axes C overlap.
　本実施形態では、熱可塑性樹脂からなる有底筒状のプリフォーム１０を射出成形し、このプリフォーム１０をブロー成形型ＢＭ内にセットした後に、必要に応じて延伸ロッドを用いて縦方向に延伸しつつ、ブローエアーによって横方向にも延伸してブロー成形型ＢＭ内のキャビティ形状を転写する。これにより、ブロー成形型ＢＭ内のキャビティ形状が転写された所定の容器形状の容器２０がブロー成形される。
　なお、プリフォーム１０をブロー成形型ＢＭ内にセットする際には、必要に応じてプリフォーム１０を加熱、軟化させてブロー成形が可能な状態としておく。 In the present embodiment, a bottomed cylindrical preform 10 made of a thermoplastic resin is injection-molded, and after this preform 10 is set in the blow molding die BM, it is used in the longitudinal direction using a stretching rod as necessary. While stretching, the shape of the cavity in the blow mold BM is transferred by stretching in the lateral direction with blow air. Thereby, the container 20 having a predetermined container shape to which the cavity shape in the blow mold BM is transferred is blow-molded.
When the preform 10 is set in the blow mold BM, the preform 10 is heated and softened as necessary so as to be capable of blow molding.
　ここで、プリフォーム１０は、口部１１、胴部１２及び底部１３を有しており、口部１１と胴部１２との境にはネックリング１４が形成されている。プリフォーム１０の口部１１は延伸されずに、そのまま容器２０の口部となり、図示しない蓋体を取り付けるためのねじ山が形成されている。そして、ブロー成形される際には、プリフォーム１０のネックリング１４よりも下方（底部１３側）の部位が縦方向及び横方向に延伸されて、容器２０の胴部２２及び底部２３となるように成形される。 Here, the preform 10 has a mouth part 11, a body part 12 and a bottom part 13, and a neck ring 14 is formed at the boundary between the mouth part 11 and the body part 12. The mouth portion 11 of the preform 10 is not stretched and becomes the mouth portion of the container 20 as it is, and a screw thread for attaching a lid (not shown) is formed. When blow molding is performed, the portion below the neck ring 14 of the preform 10 (on the bottom 13 side) is stretched in the vertical and horizontal directions so as to become the body 22 and the bottom 23 of the container 20. To be molded.
　プリフォーム１０を成形する熱可塑性樹脂としては、この種の合成樹脂製容器に用いられる種々の熱可塑性樹脂を使用することができる。具体的には、ポリエチレンテレフタレート，ポリブチレンテレフタレート，ポリエチレンナフタレート，ポリカーボネート，ポリアリレート，ポリ乳酸又はこれらの共重合体などの熱可塑性ポリエステル，これらの樹脂あるいは他の樹脂とブレンドされたものなどが例示されるが、特に、ポリエチレンテレフタレートなどのポリエステル系樹脂が好適に使用される。また、アクリロニトリル樹脂，ポリプロピレン，プロピレン－エチレン共重合体，ポリエチレンなども使用することができる。 As the thermoplastic resin for molding the preform 10, various thermoplastic resins used for this type of synthetic resin container can be used. Specific examples include thermoplastic polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyarylate, polylactic acid or copolymers thereof, and those blended with these resins or other resins. In particular, polyester resins such as polyethylene terephthalate are preferably used. Further, acrylonitrile resin, polypropylene, propylene-ethylene copolymer, polyethylene and the like can also be used.
　本実施形態において、プリフォーム１０は、図２及び図３に示すような射出成形型ＩＭを用いて成形される。射出成形型ＩＭは、プリフォーム１０の内側面を成形するコア型３１からなる雄型と、軸方向に沿ってスライド型３２、胴型３３及び底型３４に分割されたプリフォーム１０の外側面を成形する雌型とを有している。
　なお、図２は、射出成形型ＩＭを型閉めした状態を示す説明図であり、図３は、射出成形を終えて型開きした状態を示す説明図である。通常、底型３４側には、型閉めされて成形されたキャビティ３０内に熱可塑性樹脂を充填するためのゲートが形成されるが、図２及び図３では、そのようなゲートの図示を省略している。 In the present embodiment, the preform 10 is molded using an injection mold IM as shown in FIGS. The injection mold IM is a male mold composed of a core mold 31 that molds the inner surface of the preform 10, and an outer surface of the preform 10 divided into a slide mold 32, a body mold 33, and a bottom mold 34 along the axial direction. And a female mold for molding.
2 is an explanatory view showing a state where the injection mold IM is closed, and FIG. 3 is an explanatory view showing a state where the mold is opened after the injection molding is finished. Normally, a gate for filling a thermoplastic resin into the cavity 30 formed by closing the mold is formed on the bottom mold 34 side, but such a gate is not shown in FIGS. is doing.
　これらの図に示すように、スライド型３２は中心軸Ｃに直行する方向にスライドするようになっており、このスライド型３２によってプリフォーム１０の口部１１の外側面が成形される。そして、筒状とされたプリフォーム１０の胴部１２と半球状とされたプリフォーム１０の底部１３の外側面が、同軸に配された胴型３３と底型３４とによって成形される。 As shown in these drawings, the slide mold 32 slides in a direction perpendicular to the central axis C, and the outer surface of the mouth portion 11 of the preform 10 is formed by the slide mold 32. Then, the outer surface of the cylindrical portion 10 of the preform 10 and the bottom portion 13 of the semispherical preform 10 are formed by a cylindrical die 33 and a bottom die 34 arranged coaxially.
　このように、本実施形態においてプリフォーム１０を射出成形するために用いる射出成形型ＩＭは、プリフォーム１０の胴部１２及び底部１３を含む外側面を成形する雌型が軸方向に沿って複数に分割されている。このため、プリフォーム１０の外側面には、射出成形型ＩＭの分割面に相当する部位に周方向に沿ってパーティングラインＰＬが形成される。
　なお、パーティングラインＰＬは、射出成形型ＩＭの分割面の数に応じて形成されるが、図示する例では、最も底部１３側に形成されるパーティングラインＰＬだけを示している。 As described above, the injection mold IM used for injection molding the preform 10 in the present embodiment includes a plurality of female molds for molding the outer surface including the body 12 and the bottom 13 of the preform 10 along the axial direction. It is divided into For this reason, the parting line PL is formed in the outer surface of the preform 10 along the circumferential direction in a portion corresponding to the dividing surface of the injection mold IM.
In addition, although the parting line PL is formed according to the number of the dividing surfaces of the injection mold IM, in the illustrated example, only the parting line PL formed on the bottom 13 side is shown.
　このような射出成形型ＩＭを用いてプリフォーム１０を射出成形するにあたり、本実施形態にあっては、プリフォーム１０の底部１３の先端から、最もプリフォーム１０の底部１３側に形成されるパーティングラインＰＬまでの軸方向に沿った長さｈが、口部１１を除いたプリフォーム１０の延伸される部位の軸方向に沿った長さ（図示する例では、ネックリング１４よりも下方に位置する部位の長さ）Ｈの２０～４０％となるように、胴型３３と底型３４との分割面の位置を調整する。 In the injection molding of the preform 10 using such an injection mold IM, in the present embodiment, the party formed on the bottom 13 side of the preform 10 from the tip of the bottom 13 of the preform 10 is the most. The length h along the axial direction to the ring line PL is the length along the axial direction of the stretched portion of the preform 10 excluding the mouth 11 (in the illustrated example, below the neck ring 14). The position of the dividing surface of the body mold 33 and the bottom mold 34 is adjusted so that it is 20 to 40% of the length (H) of the portion to be positioned.
　このようにすることで、通常の条件下（例えば、プリフォーム１０の胴部１２が、縦方向に１．７～２．７倍、横方向に２．３～４．６倍の倍率で延伸される条件）で、プリフォーム１０をブロー成形によって所定の容器形状に成形したときに、図１に示すように、プリフォーム１０に形成された最も底部１３側のパーティングラインＰＬの痕跡Ｖが、成形された容器２０の底部２３の接地部位２４を越えた容器側面側に位置するようになる。これにより、パーティングラインＰＬの痕跡Ｖが、接地部位２４よりも底部中心寄りとなる底部２３の内側の領域に現れなくなるため、容器２０の底部２３の中心肉厚が１．５～２．０ｍｍとなるように薄肉に成形して軽量化を図った場合であっても、プリフォーム１０を射出成形した際のパーティングラインＰＬの痕跡Ｖへの応力集中に起因する環境応力破壊が生じるのを有効に回避して、底部２３の強度を高めることができる。
　なお、パーティングラインＰＬの痕跡Ｖが上記領域に現れないようにするには、当該パーティングラインＰＬがプリフォーム１０の底部１３からできるだけ離れた位置に形成されるようにするのが好ましい。しかしながら、そのような型構造にすると、底型３４をより深く切削しなければならず、型加工が困難となりコストも増大してしまう。このような型加工上の不具合とのバランスを考慮すると、上記長さｈの上限を上記長さＨの４０％とするのが好ましい。 By doing so, the body portion 12 of the preform 10 is stretched at a magnification of 1.7 to 2.7 times in the longitudinal direction and 2.3 to 4.6 times in the transverse direction. 1), when the preform 10 is molded into a predetermined container shape by blow molding, the trace V of the parting line PL on the bottom portion 13 side formed on the preform 10 is formed as shown in FIG. The container 20 is positioned on the side surface of the container beyond the ground contact portion 24 of the bottom 23 of the container 20. As a result, the trace V of the parting line PL does not appear in the region inside the bottom 23 that is closer to the center of the bottom than the ground contact portion 24, so that the center thickness of the bottom 23 of the container 20 is 1.5 to 2.0 mm. Even if it is made thin to reduce the weight so that environmental stress destruction occurs due to the stress concentration on the trace V of the parting line PL when the preform 10 is injection-molded. By effectively avoiding, the strength of the bottom 23 can be increased.
In order to prevent the trace V of the parting line PL from appearing in the region, it is preferable that the parting line PL is formed at a position as far as possible from the bottom 13 of the preform 10. However, with such a mold structure, the bottom mold 34 must be cut deeper, making the mold processing difficult and increasing the cost. In consideration of the balance with such defects in mold processing, the upper limit of the length h is preferably 40% of the length H.
　ところで、ブロー成形には、プリフォームをそのまま最終成形品の大きさとなるようにブローする一段ブロー成形法と、プリフォームを一旦最終成形品より大きくなるようにブローして中問品を成形し、この中間品を熱収縮させた後に最終成形品の形状にブローするという二段ブロー成形法とがある。二段ブロー成形法によれば、容器２０の底部２３を比較的大きく延伸させることが可能であり、延伸によって底部２３の強度を高めることが可能であるが、一段ブロー成形法では、容器２０の底部２３を延伸させ難いため、延伸による底部２３の強度の向上が期待できない。
　このことから、本発明は一段ブロー成形法により容器２０をブロー成形する場合に好適である。 By the way, in blow molding, a one-stage blow molding method in which the preform is blown as it is to the size of the final molded product, and the preform is blown once to be larger than the final molded product, and the intermediate product is molded. There is a two-stage blow molding method in which the intermediate product is thermally contracted and then blown to the shape of the final molded product. According to the two-stage blow molding method, the bottom 23 of the container 20 can be stretched relatively large, and the strength of the bottom 23 can be increased by stretching. Since it is difficult to extend the bottom 23, the strength of the bottom 23 cannot be improved by stretching.
Therefore, the present invention is suitable for the case where the container 20 is blow-molded by a single-stage blow molding method.
　また、通常の条件下で、一段ブロー成形法により容器２０の底部２３の肉厚が上記の範囲となるようにすると、最もプリフォーム１０の底部１３側に形成されたパーティングラインＰＬの痕跡Ｖが位置する部位の肉厚は０．２０～０．３０ｍｍになる。このような薄肉に成形しても、パーティングラインＰＬの痕跡Ｖが容器側面側に位置していれば、当該痕跡Ｖへの応力集中に起因する環境応力破壊が生じるのを有効に回避することができる。
　すなわち、従来にあっては、環境応力破壊を抑止するために容器底部の肉厚をある程度確保する必要があり、このため、本実施形態においてパーティングラインＰＬの痕跡Ｖが位置する部位に相当する部位の肉厚も０．３５～０．４５mm程度となってしまい、容器を薄肉化するには限界があったが、本実施形態では、その必要がないため、環境応力破壊を抑止しながらも、さらなる容器の薄肉化を図ることが可能である。 Moreover, when the thickness of the bottom 23 of the container 20 is within the above range by a single-stage blow molding method under normal conditions, the trace V of the parting line PL formed most on the bottom 13 side of the preform 10. The thickness of the portion where the is located is 0.20 to 0.30 mm. Even if it is formed into such a thin wall, if the trace V of the parting line PL is located on the side surface of the container, it is possible to effectively avoid the occurrence of environmental stress destruction due to the stress concentration on the trace V. Can do.
That is, in the prior art, it is necessary to secure a certain thickness of the bottom of the container in order to suppress environmental stress destruction. For this reason, in the present embodiment, it corresponds to the portion where the trace V of the parting line PL is located. The thickness of the part is also about 0.35 to 0.45 mm, and there is a limit to reducing the thickness of the container. However, in this embodiment, since this is not necessary, it is possible to suppress environmental stress destruction. It is possible to further reduce the thickness of the container.
　次に、具体的な実施例を挙げて、本発明をより詳細に説明する。 Next, the present invention will be described in more detail with specific examples.
［実施例］
　図２及び図３に示すような射出成形型ＩＭにおいて、プリフォーム１０の底部１３の先端から、最もプリフォーム１０の底部１３側に形成されるパーティングラインＰＬまでの軸方向に沿った長さｈが、ネックリング１４よりも下方に位置する部位の長さＨの３４．２％となるように、胴型３３と底型３４との分割面の位置を調整した。 [Example]
In the injection mold IM as shown in FIGS. 2 and 3, the length along the axial direction from the tip of the bottom 13 of the preform 10 to the parting line PL formed on the bottom 13 side of the preform 10 most. The position of the dividing surface between the body mold 33 and the bottom mold 34 was adjusted so that h was 34.2% of the length H of the portion located below the neck ring 14.
　次に、このような射出成形型ＩＭを用いて、重量が２３ｇのプリフォーム１０を成形し、縦方向の延伸倍率が２．３倍、横方向の延伸倍率が３．９倍となるようにして、図１に示すような容量５００ｍｌの所定の容器形状の容器２０を一段ブロー成形法により成形した。
　成形された容器２０の底部２３には、パーティングラインＰＬの痕跡Ｖが認められず、当該痕跡Ｖは、図１に示す例と同様に、底部２３の接地部位２４を越えた容器側面側に位置していた。 Next, using such an injection mold IM, a preform 10 having a weight of 23 g is molded so that the stretching ratio in the longitudinal direction is 2.3 times and the stretching ratio in the transverse direction is 3.9 times. Then, a container 20 of a predetermined container shape having a capacity of 500 ml as shown in FIG. 1 was formed by a one-stage blow molding method.
The trace V of the parting line PL is not recognized at the bottom 23 of the molded container 20, and the trace V is formed on the side of the container beyond the ground contact portion 24 of the bottom 23, as in the example shown in FIG. Was located.
　上記のようにして成形された５本の容器２０を用意して、それぞれに４．５ＧＶ（ガスボリューム）相当のクエン酸重曹水溶液を５００ｍｌ充填・密封した後に、０．２％の水酸化ナトリウム水溶液中に浸漬して１５分間放置して環境応力破壊試験を行った。その結果、いずれの容器にも環境応力破壊は認められなかった。 Five containers 20 formed as described above were prepared, and each was filled and sealed with 500 ml of an aqueous sodium bicarbonate solution equivalent to 4.5 GV (gas volume), and then 0.2% aqueous sodium hydroxide solution. It was immersed in and left for 15 minutes to conduct an environmental stress fracture test. As a result, no environmental stress failure was observed in any of the containers.
［比較例］
　図５及び図６に示すような射出成形型ＩＭにおいて、プリフォーム１１０の底部１１３の先端から、最もプリフォーム１１０の底部１１３側に形成されるパーティングラインＰＬまでの軸方向に沿った長さｈ０が、ネックリング１１４よりも下方に位置する部位の長さＨ０の１１．４％となるように、胴型１３３と底型１３４との分割面の位置を調整した以外は、実施例と同様にしてプリフォーム１１０を射出成形し、図４に示すような容量５００ｍｌの所定の容器形状の容器１２０を一段ブロー成形法により成形した。
　成形された容器１２０の底部１２３には、図４に示す例と同様に、接地部位１２４よりも底部中心寄りとなる内側の領域に、パーティングラインＰＬの痕跡Ｖが認められた。 [Comparative example]
In the injection mold IM as shown in FIGS. 5 and 6, the length along the axial direction from the tip of the bottom 113 of the preform 110 to the parting line PL formed closest to the bottom 113 of the preform 110. Example except that the position of the dividing surface between the body mold 133 and the bottom mold 134 was adjusted so that h 0 was 11.4% of the length H 0 of the portion located below the neck ring 114 The preform 110 was injection-molded in the same manner as described above, and a container 120 having a predetermined container shape with a capacity of 500 ml as shown in FIG. 4 was molded by a one-stage blow molding method.
Similar to the example shown in FIG. 4, a trace V of the parting line PL was observed in the inner region closer to the center of the bottom than the ground contact portion 124 at the bottom 123 of the molded container 120.
　実施例と同様の環境応力破壊試験を行ったところ、試験した５本の容器２０のうち、３本の容器２０に環境応力破壊が認められた。そのうち、パーティングラインＰＬの痕跡Ｖに起因すると思われるものは２本であった。 When an environmental stress fracture test similar to that of the example was performed, among the five containers 20 tested, environmental stress fracture was observed in three containers 20. Of these, two were considered to be caused by the trace V of the parting line PL.
　以上、本発明について、好ましい実施形態を示して説明したが、本発明は、前述した実施形態にのみ限定されるものではなく、本発明の範囲で種々の変更実施が可能であることは言うまでもない。 Although the present invention has been described with reference to the preferred embodiment, it is needless to say that the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention. .
　例えば、前述したようなプリフォーム成形型は、プリフォームの射出成形に単独で使用されるようにしてもよいが、複数のプリフォーム成形型を母型に取り付けて、一度の射出成形工程で多数のプリフォームが同時に成形できるようにすることも可能である。
　また、前述した実施形態では、プリフォームＰＬを射出成形で成形する例を示したが、圧縮成形によってプリフォームを成形する場合のように、前述した実施形態と同様に分割された型構造の成形型を用いることが考えられる他の成形手段によってプリフォームを成形する場合にも本発明を適用することができるのはいうまでもない。 For example, the preform mold as described above may be used alone for injection molding of a preform, but a plurality of preform molds are attached to a mother mold, and a large number of them can be performed in a single injection molding process. It is also possible to form the preforms simultaneously.
In the above-described embodiment, the example in which the preform PL is molded by injection molding has been shown. However, as in the case of molding the preform by compression molding, molding of a mold structure divided in the same manner as in the above-described embodiment. It goes without saying that the present invention can also be applied to the case where the preform is molded by other molding means that may use a mold.
　また、本発明における合成樹脂製容器は、必要に応じて容器内への外部からの酸素の透過を抑制するバリヤー層や、酸素吸収層などを備える多層構造とすることもできる。 In addition, the synthetic resin container in the present invention may have a multilayer structure including a barrier layer that suppresses permeation of oxygen from the outside into the container, an oxygen absorption layer, and the like as necessary.
　以上説明したように、本発明は、薄肉化しても容器底部に環境応力破壊が生じにくい合成樹脂製容器を提供する。 As described above, the present invention provides a synthetic resin container that is less likely to cause environmental stress failure at the bottom of the container even when it is thinned.
　１０　　　　　プリフォーム
　１１　　　　　口部
　１２　　　　　胴部
　１３　　　　　底部
　２０　　　　　容器
　２２　　　　　胴部
　２３　　　　　底部
　２４　　　　　接地部位
　３３　　　　　胴型
　３４　　　　　底型
　ＩＭ　　　　　射出成形型
　ＰＬ　　　　　パーティングライン DESCRIPTION OF SYMBOLS 10 Preform 11 Mouth part 12 Body part 13 Bottom part 20 Container 22 Body part 23 Bottom part 24 Grounding part 33 Body type 34 Bottom type IM Injection molding type PL Parting line

Claims (7)

  1. 　プリフォームの胴部及び底部を含む外側面を成形する雌型が軸方向に沿って複数に分割された成形型を用いて成形され、前記外側面に周方向に沿って少なくとも一つのパーティングラインが形成された有底筒状のプリフォームをブロー成形によって所定の容器形状に成形してなり、
    　最もプリフォームの底部側に形成された前記パーティングラインの痕跡が、成形された容器底部の接地部位を越えた容器側面側に位置することを特徴とする合成樹脂製容器。     At least one parting line is formed on the outer surface along the circumferential direction by forming a female die for forming the outer surface including the body portion and the bottom portion of the preform into a plurality of divided molds along the axial direction. Formed into a predetermined container shape by blow molding a bottomed cylindrical preform formed with
    A synthetic resin container, wherein the trace of the parting line formed on the bottom side of the preform is located on the side of the container beyond the ground contact portion of the molded container bottom.
  2. 　最もプリフォームの底部側に形成された前記パーティングラインの痕跡が位置する部位の肉厚が０．２０～０．３０ｍｍである請求項１に記載の合成樹脂製容器。 2. The synthetic resin container according to claim 1, wherein the thickness of the part where the trace of the parting line formed on the bottom side of the preform is located is 0.20 to 0.30 mm.
  3. 　一段ブロー成形法により成形された請求項１又は２のいずれか一項に記載の合成樹脂製容器。 The synthetic resin container according to any one of claims 1 and 2, which is formed by a one-stage blow molding method.
  4. 　ブロー成形によって所定の容器形状の合成樹脂製容器に成形される口部、胴部及び底部を有する有底筒状のプリフォームであって、
    　前記胴部及び前記底部を含む外側面を成形する雌型が軸方向に沿って複数に分割された成形型を用いて成形され、少なくとも一つのパーティングラインが前記外側面に周方向に沿って形成されているとともに、
    　前記底部の先端から最も前記底部側に形成された前記パーティングラインまでの軸方向に沿った長さが、前記口部を除く延伸される部位の軸方向に沿った長さの２０～４０％であることを特徴とするプリフォーム。     A bottomed cylindrical preform having a mouth portion, a trunk portion, and a bottom portion that is molded into a synthetic resin container having a predetermined container shape by blow molding,
    A female mold for molding the outer surface including the body and the bottom is molded using a molding die divided into a plurality along the axial direction, and at least one parting line extends along the circumferential direction on the outer surface. Formed,
    The length along the axial direction from the tip of the bottom to the parting line formed closest to the bottom is 20 to 40% of the length along the axial direction of the stretched portion excluding the mouth Preform characterized by being.
  5. 　請求項４に記載のプリフォームをブロー成形によって所定の容器形状に成形することを特徴とする合成樹脂製容器の製造方法。 A method for producing a synthetic resin container, wherein the preform according to claim 4 is molded into a predetermined container shape by blow molding.
  6. 　前記プリフォームを一段ブロー成形法によって所定の容器形状に成形する請求項５に記載の合成樹脂製容器の製造方法。 The method for producing a synthetic resin container according to claim 5, wherein the preform is molded into a predetermined container shape by a one-stage blow molding method.
  7. 　ブロー成形によって所定の容器形状の合成樹脂製容器に成形される口部、胴部及び底部を有する有底筒状のプリフォームを成形するための成形型であって、
    　前記胴部及び前記底部を含む外側面を成形する雌型が軸方向に沿って複数に分割され、
    　前記底部の先端に相当する部位から最も前記底部側の分割面までの軸方向に沿った長さが、前記口部を除く前記プリフォームの延伸される部位を成形する部分の軸方向に沿った長さの２０～４０％である
    ことを特徴とするプリフォーム成形型。     A molding die for molding a bottomed cylindrical preform having a mouth portion, a trunk portion, and a bottom portion, which is molded into a synthetic resin container having a predetermined container shape by blow molding,
    The female mold for molding the outer surface including the trunk and the bottom is divided into a plurality along the axial direction,
    The length along the axial direction from the portion corresponding to the tip of the bottom portion to the dividing surface on the bottom portion side along the axial direction of the portion that molds the stretched portion of the preform excluding the mouth portion. A preform mold having a length of 20 to 40%.
PCT/JP2010/001435 2009-03-27 2010-03-03 Plastic container, preform, method for producing plastic container, and preform mold WO2010109775A1 (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
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JP2014172643A (en) * 2013-03-11 2014-09-22 Kureha Corp Synthetic resin blow-molding multilayer container having thick annular projection part in annular recessed part
CN107112727A (en) * 2014-12-09 2017-08-29 日本特殊陶业株式会社 The manufacture method of the insulator of spark plug, insulator, shaping dies
CN107112727B (en) * 2014-12-09 2019-01-04 日本特殊陶业株式会社 The manufacturing method of the insulator of spark plug, insulator, shaping dies

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