Laminated preform, method for manufacturing laminated preform, and synthetic resin container

Abstract

This invention provides a new laminated preform, a method for manufacturing a laminated preform, and a synthetic resin container that can improve molding defects caused by uneven thickness of the outer surface in the molding of laminated preforms by overmolding and the manufacturing of synthetic resin containers using the same. [Solution] The laminated preform 100 of the present disclosure is a laminated preform 100 used in the manufacture of a synthetic resin container 1 having a laminated structure, comprising an inner body 110 having a mouth portion 111, a body portion 112, and a bottom portion 117, and an outer body 120 covering the body portion 112 and bottom portion 117 of the inner body 110 from the outside, wherein the bottom portion 117 of the inner body 110 has a spiral groove 117a that spirals in the circumferential direction from the radial center toward the radially outward direction when viewed from the bottom.

Description

Technical Field

[0001] The present disclosure relates to a laminated preform, a method for manufacturing the laminated preform, and a synthetic resin container.

Background Art

[0002] As a container for containing liquids such as beverages, food seasonings, and cosmetics as contents, a synthetic resin container formed into a bottle shape having a mouth part and a body part by blow molding a preform is widely used.

[0003] Further, as such a synthetic resin container, by using a preform configured in a laminated structure by insert molding, a laminated structure in which a coating part having functions such as decorativeness and gas barrier properties is laminated on the outer surface of the body part of the container body is known.

[0004] And, as a synthetic resin container in which a coating part is laminated on the body part of the container body, as shown in Patent Document 1, a label material is detachably adhered to the outer peripheral surface of the container body, and the label material has a label main body part and a belt-shaped breaking part that has low compatibility with the label main body part and extends from one end to the other end in the axial direction of the label material. By peeling off the breaking part from the container body, the label material is separated into left and right parts and can be separated.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the above-mentioned Patent Document 1, a synthetic resin container is manufactured by blow molding a cylindrical label material attached to the body of a preform. If a manufacturing method is adopted in which an outer layer is overmolded on the outside of the preform instead of this label material to improve production efficiency, eccentricity occurs between the female and male molds, resulting in uneven thickness in the outer layer. Therefore, if an attempt is made to thin the outer layer to facilitate peeling or improve transparency, molding defects (shorts) may occur where the molten resin does not sufficiently fill the mold, and there was still room for improvement in this respect.

[0007] This disclosure aims to solve these problems, and its purpose is to provide a new laminated preform, a method for manufacturing a laminated preform, and a synthetic resin container that can improve molding defects caused by uneven thickness of the outer surface in the molding of laminated preforms by overmolding and the manufacturing of synthetic resin containers using the same. [Means for solving the problem]

[0008] This disclosure was made to solve the above problems, and the laminated preform of this disclosure is [1] A laminated preform used in the manufacture of a synthetic resin container having a laminated structure, An inner body having a mouth, a body, and a bottom, An outer body that covers the body and bottom of the inner body from the outside. Equipped with, The bottom of the inner body is characterized by having a spiral groove that spirals circumferentially from the radial center outward when viewed from the bottom.

[0009] Furthermore, the laminated preforms of this disclosure are [2] In the configuration described in [1] above, it is preferable that the spiral groove is formed at a circumferential position between groove-forming protrusions that project outward from the bottom of the inner body and whose circumferential inclination angle increases radially outward when viewed from the bottom.

[0010] Furthermore, the laminated preforms of this disclosure are [3] In the configuration described in [2] above, it is preferable that the angle between the extending direction at the radially inner end and the extending direction at the radially outer end of the groove-forming projection is approximately 120 degrees when viewed from the bottom.

[0011] Furthermore, the laminated preforms of this disclosure are [4] In the configuration described in [2] or [3] above, it is preferable that the groove-forming protrusions are arranged at equal intervals in four to six locations in the circumferential direction.

[0012] Furthermore, the laminated preforms of this disclosure are [5] In the configuration described in any of [1] to [4] above, it is preferable that the outer body has a thickness of 0.3 mm or more and 0.7 mm or less.

[0013] Furthermore, the laminated preforms of this disclosure are [6] In the configuration described in any of [1] to [5] above, it is preferable that the inner body is made of a resin mainly composed of polyethylene terephthalate, and the outer body is made of a resin mainly composed of polypropylene.

[0014] Furthermore, the method for manufacturing the laminated preform described herein is: [7] A method for manufacturing laminated preforms used in the manufacture of synthetic resin containers, The steps include forming the inner body of the laminated preform, which has a mouth portion, a body portion, and a bottom portion, The steps include forming an outer body of the laminated preform that covers the body and bottom of the inner body from the outside, and Includes, The bottom of the inner body has a spiral groove that spirals circumferentially from the radial center outward when viewed from the bottom, The step of forming the outer body is characterized in that the molten resin supplied from a gate disposed opposite to the radial center of the bottom of the inner body is filled into the mold while swirling circumferentially through the swirling groove.

[0015] Further, the synthetic resin container of the present disclosure [8] is a synthetic resin container formed by blow molding of the laminated preform according to any one of [1] to [6] above, a bottle-shaped container body formed by blow molding of the inner body, and a coating portion that is stretched by blow molding the outer body together with the inner body and laminated on the outer surface of the container body and is characterized by comprising.

Effects of the Invention

[0016] According to the present disclosure, in the molding of a laminated preform by overmolding and the production of a synthetic resin container using the same, it is possible to provide a new laminated preform, a method for producing a laminated preform, and a synthetic resin container that can improve molding defects due to uneven wall thickness of the outer body.

Brief Description of the Drawings

[0017] [Figure 1] It is a front cross-sectional view of a laminated preform according to an embodiment of the present disclosure. [Figure 2] It is a front view of an inner body used for forming a laminated preform according to an embodiment of the present disclosure. [Figure 3] It is a bottom view of an inner body used for forming a laminated preform according to an embodiment of the present disclosure. [Figure 4] It is a perspective view of an inner body used for forming a laminated preform according to an embodiment of the present disclosure as viewed from the bottom side. [Figure 5] It is a flowchart showing each procedure of a method for producing a laminated preform according to an embodiment of the present disclosure. [Figure 6] It is a front cross-sectional view of a synthetic resin container according to an embodiment of the present disclosure. [Figure 7] This is a diagram showing the test specimen used in the trouser tear test. [Figure 8] This diagram shows a schematic configuration of a trouser tear test machine. [Modes for carrying out the invention]

[0018] Hereinafter, with reference to the drawings, a laminated preform 100 according to one embodiment of this disclosure will be described in detail.

[0019] In this specification and in the claims, the vertical direction means upward and downward when the opening 111 of the laminated preform 100 is facing upward, as shown in Figure 1. Radial outward refers to the direction away from the central axis O of the laminated preform 100 along a straight line passing through the central axis O and perpendicular to the central axis O, and radial inward refers to the direction toward the central axis O along the said straight line. The circumferential direction is the direction of rotation around the central axis O. Furthermore, when simply referred to as "outward," it means the direction from the inner body 110 to the outer body 120 of the laminated preform 100, and "inward" refers to the direction from the outer body 120 to the inner body 110 of the laminated preform 100.

[0020] The accompanying drawings of this disclosure are drawn to the same scale in the vertical, front-to-back (perpendicular to the plane of the paper in Figure 1), and left-to-right (left-to-right in Figure 1) directions, except for the thickness of the outer body 120 in Figure 1 and the thickness of the covering portion 20 in Figure 6. The aspect ratio of the laminated preform 100 in the drawings represents the aspect ratio of the laminated preform 100 of one embodiment of this disclosure. However, the configuration, shape, dimensional ratio, etc. of the laminated preform 100 in the accompanying drawings are merely one embodiment of this disclosure. The present invention should be interpreted based on the wording of the claims and is not limited to the configuration, shape, dimensional ratio, etc. shown in the drawings. Note that in Figure 4, unlike in Figures 1 and 2, the male screw 111a is omitted.

[0021] The laminated preform 100 of this embodiment shown in Figure 1 is an insert molded product having a laminated structure in which a pre-molded inner body 110 is set in a mold and an outer body 120 is formed on the outside of the body portion 112 and bottom portion 117 of the inner body 110. By further blow molding this laminated preform 100, a synthetic resin container 1 (for example, the container shown in Figure 6) having a laminated structure with a container body 10 and a covering portion 20 can be formed.

[0022] In the laminated preform 100 of this embodiment, the inner body 110, which corresponds to the container body 10 of the synthetic resin container 1, is made of a synthetic resin mainly composed of polyethylene terephthalate resin (PET resin) and comprises a mouth portion 111, a body portion 112, and a bottom portion 117. The inner body 110 is not limited to polyethylene terephthalate resin, but may be made of other synthetic resins such as polyethylene naphthalate resin (PEN), PET-G resin, PCTG resin, PCTA resin, etc.

[0023] The mouth portion 111 is substantially cylindrical, and a male screw 111a is integrally provided on its outer surface. On the other hand, the body portion 112 connected to the mouth portion 111 has an outer diameter that is substantially the same as the mouth portion 111, but is a bottomed cylindrical shape with a wall thickness greater than that of the mouth portion 111, and is integrally connected to the lower end of the mouth portion 111. As shown in Figure 1, the bottom portion 117 has a hemispherical shell shape with an outer diameter that is substantially the same as that of the body portion 112, and a swivel groove 117a and a groove-forming projection 117b, which will be described later, are provided on its outer surface.

[0024] Furthermore, the opening 111 can also be configured with an annular projection for attaching the cap by pressing it in, instead of using a screw connection.

[0025] A neck ring 113 is integrally provided in the portion between the mouth portion 111 and the body portion 112. The neck ring 113 is a substantially plate-like shape that protrudes radially outward from the upper ends of the mouth portion 111 and the body portion 112 and extends around the entire circumference with respect to the central axis O. The lower surface 113a of the neck ring 113 facing the body portion 112 is a plane substantially perpendicular to the central axis O, and the upper surface 113b of the neck ring 113 facing the mouth portion 111 is an inclined surface that slopes toward the body portion 112 as it extends radially outward.

[0026] As shown in Figure 1, a positioning projection 117c is provided at the radial center of the bottom 117 of the inner body 110, projecting inward (upward). The positioning projection 117c can be used, for example, to position the inner body 110 in an accurately centered state relative to the mold when insert molding the inner body 110 as an insert material.

[0027] As shown in Figures 2 to 4, the inner body 110 is provided with a spiral groove 117a that spirals circumferentially from the radial center outward in a bottom view. The spiral groove 117a protrudes outward from the bottom 117 of the inner body 110 (radially outward from the hemispherical shell-shaped bottom 117) and is formed at a circumferential position between groove-forming projections 117b, where the angle of inclination in the circumferential direction increases radially outward in a bottom view. In this embodiment, the spiral groove 117a and groove-forming projections 117b are arranged at equal intervals at six locations in the circumferential direction. The number of spiral grooves 117a and groove-forming projections 117b is not limited to six locations, and can be arbitrarily selected from, for example, four to six locations. The number of spiral grooves 117a and groove-forming projections 117b may be three or fewer, or seven or more.

[0028] In this embodiment, the groove-forming projection 117b has an angle of approximately 120 degrees in bottom view between the extending direction at the radially inner end (extending direction of the center line C1) and the extending direction at the radially outer end (extending direction of the center line C2) (see Figure 3). With this configuration, the inner body 110 is set in an insert molding die, and the molten resin supplied into the cavity of the mold (second mold) from a gate located at the radial center position (the position opposite to the gate mark G of the inner body 110 shown in Figure 3) is guided radially outward along the outer surface of the bottom portion 117 while swirling in the circumferential direction through the swirling groove 117a, and further guided upward (towards the mouth portion 111) along the outer surface of the body portion 112, thereby filling the mold. As a result, even if, for example, eccentricity occurs between the female and male molds of the mold, causing an imbalance in the circumferential gap in the cavity through which the molten resin flows, the molten resin will move radially outward through the cavity outside the bottom portion 117 while circumferentially swirling through the spiral groove 117a, and then move upward through the cavity outside the body portion 112 while circumferentially swirling. Therefore, it is possible to suppress the difficulty of the molten resin flowing into specific (narrow gap) circumferential positions within the cavity. Thus, it is possible to effectively suppress the occurrence of molding defects (such as shorts) at specific circumferential positions caused by an imbalance in the circumferential gap of the cavity. In the illustrated example, the height of the groove-forming projection 117b relative to the height of the spiral groove 117a in the thickness direction of the bottom portion 117 of the inner body 110 is approximately 0.4 mm.

[0029] In the laminated preform 100, the outer body 120, which corresponds to the covering portion 20 of the synthetic resin container 1, is made of a synthetic resin mainly composed of polypropylene resin (PP resin). As the polypropylene resin, for example, a synthetic resin mixed with J246M and S13B manufactured by Prime Polymer Co., Ltd. in a weight ratio of 50:50 can be used. Other materials having functions such as decorative properties, light barrier properties, oxygen barrier properties, or water vapor barrier properties may also be used for the outer body 120. In this embodiment, the outer body 120 is formed in a bottomed cylindrical shape using the above-mentioned polypropylene resin, and is laminated on the outside of the body portion 112 and bottom portion 117 of the inner body 110, covering the entire outer surface. The thickness of the outer body 120 is thinner than the thickness of the body portion 112 and bottom portion 117, and can be in the range of 0.3 mm to 0.7 mm, for example, 0.4 mm can be used. In this embodiment, when the outer body 120 has a thickness within the above range, the thickness of the covering portion 20 is in the range of 30 μm to 100 μm, and the manufacturing control is performed so that the average thickness is 60 μm. The relationship between the thicknesses of the outer body 120 and the covering portion 20 depends on manufacturing conditions such as the stretch ratio during blow molding.

[0030] A flange 121 is integrally provided at the upper end of the outer body 120. The flange 121 is a roughly plate-like shape that extends radially outward from the upper end of the outer body 120 and extends around the entire circumference with respect to the central axis O, and is in close contact with the lower surface 113a of the neck ring 113. By providing the flange 121 on the outer body 120, for example, when stretch blow molding the laminated preform 100, the lower surface 113a of the neck ring 113 is fixed by abutting it against the reference surface of the blow molding die with the flange 121 sandwiched in between, thereby creating a pseudo-bonding effect between the flange 121 and the neck ring 113. Therefore, when stretch blow molding the laminated preform 100, the tensile force applied to the outer body 120 can be held by the flange 121, so that the outer body 120 does not shift position relative to the inner body 110 and result in stretching defects.

[0031] Here, the mouth portion 111 and the neck ring 113 of the inner body 110 of the laminated preform 100 are both parts that are not stretched by blow molding, and the flange 121 of the laminated preform 100 is also a part that is not stretched by blow molding. Therefore, the shapes of the mouth portion 111 and the neck ring 113 of the laminated preform 100 are substantially the same as the shapes of the mouth portion 11 and the neck ring 13 of the container body 10 of the synthetic resin container 1 shown in Figure 6. The shape of the flange 121 of the laminated preform 100 is substantially the same as the shape of the flange 21 of the covering portion 20 of the synthetic resin container 1.

[0032] The body portion 112 of the laminated preform 100 is the part that is stretched by blow molding and formed into the body portion 12 of the container body 10. The outer body 120 of the laminated preform 100 is the part that is stretched by blow molding together with the body portion 112 and the bottom portion 117 and formed into a covering portion 20 that is laminated on the outer surfaces of the body portion 12 and the bottom portion 17.

[0033] In this embodiment, the laminated preform 100 with the above configuration is an insert molded product formed by insert molding. For example, the laminated preform 100 can be formed by insert molding (injection molding) in which an inner body 110, which has been previously formed by injection molding, is inserted. Alternatively, the laminated preform 100 may be formed by first forming the inner body 110 by injection molding, and then forming the outer body 120 by two-color molding.

[0034] Next, a method for manufacturing a laminated preform 100 according to one embodiment of this disclosure will be described.

[0035] Figure 5 is a flowchart showing the procedure for manufacturing the laminated preform 100 according to this embodiment. When manufacturing the laminated preform 100 which will be the front body of the synthetic resin container 1, first, the inner body 110 shown in Figures 2 to 4 is molded in a first mold by injection molding or the like (step S101). As shown in Figures 2 to 4, the inner body 110 has a mouth portion 111, a body portion 112, a neck ring 113 provided in the portion between the mouth portion 111 and the body portion 112, and a bottom portion 117 that closes the lower end of the body portion 112.

[0036] When molding the inner body 110, molten resin for forming the inner body is injected from the gate located at the gate mark G position in the radial center of Figure 3, filling the cavity of the bottom portion 117 from the radial center outward, and then filling the cavity of the body portion 112 from the lower end toward the mouth portion 111. It is preferable to position the gate and groove-forming projection 117b so as not to interfere with the groove-forming projection 117b when cutting the gate during the formation of the inner body 110. It is also preferable to prevent undercuts when demolding the inner body 110 from the first mold.

[0037] Next, the inner body 110 formed in step S101 is placed in the cavity of the second mold (step S102). The second mold referred to here is a mold for forming the outer body 120, and it is assumed that the laminated preform 100 is insert molded using the inner body 110 as an insert material.

[0038] Meanwhile, in parallel with steps S101 and S102, an outer resin is prepared (step S103). In this embodiment, the outer resin is produced, for example, by mixing J246M and S13B, which are polypropylene resins manufactured by Prime Polymer, in a 50:50 (weight ratio) ratio. The melt flow rates (MFR) of J246M and S13B are approximately 30 [g / 10 min.] and approximately 600 [g / 10 min.], respectively.

[0039] Next, the outer resin prepared in step S103 is supplied in a molten state into the cavity from a gate positioned opposite the radial center of the bottom 117 of the inner body 110 in the second mold prepared in step S102 (step S104). The outer resin supplied into the cavity of the second mold through the gate moves radially outward along the outer surface of the bottom 117 while circumferentially rotating through the swivel groove 117a, and then moves upward (towards the mouth 111) while circumferentially rotating along the outer surface of the body 112, filling the cavity (step S105). In addition, a cavity exists outside the groove-forming projection 117b, and as shown in Figure 1, the outer body 120 is also formed outside the groove-forming projection 117b. The thickness of the outer body 120 outside the groove-forming projection 117b can be, for example, 0.2 mm or more and 0.3 mm or less. After step S105, the molding of the laminated preform 100 is completed by releasing the formed laminated preform 100 from the second mold.

[0040] Furthermore, the formation of the laminated preform 100 is not limited to insert molding using the inner body 110 as an insert material; the inner body 110 may be injection molded first, and then the outer body 120 may be formed by two-color molding.

[0041] To manufacture the synthetic resin container 1 from the laminated preform 100, the neck ring 113 of the laminated preform 100 formed in step S105 is fixed against the reference surface of a blow molding die, and the laminated preform 100 is subjected to biaxial stretch blow molding, for example. Through this stretch blow molding, the outer body 120 is stretched together with the body portion 112 and bottom portion 117 of the inner body 110 to form the body portion 12 and bottom portion 17 of the synthetic resin container 1 (see Figure 6). On the other hand, the mouth portion 111, neck ring 113, flange 121, etc. are not stretched by blow molding and maintain almost the same shape as the laminated preform 100. The synthetic resin container 1 is completed by stretch blow molding of the laminated preform 100.

[0042] In the synthetic resin container 1 according to this embodiment shown in Figure 6, the container body 10 has a bottle shape with a mouth portion 11, a body portion 12, and a bottom portion 17. The inside of the container body 10 is a storage space S, and liquids such as beverages, food seasonings, and cosmetics can be stored in the storage space S as contents.

[0043] The opening 11 is roughly cylindrical and constitutes the discharge port for the contents contained in the storage space S. A male thread 11a is integrally provided on the outer surface of the opening 11 for attaching a cap (not shown) to close the opening 11 by screw connection.

[0044] Furthermore, the opening 11 can also be configured to have an annular projection for attaching the cap by pressing it in, instead of using a screw connection.

[0045] The body portion 12 has a neck-shaped portion 12a that is integrally connected to the lower end of the mouth portion 11 and gradually widens in diameter downwards, a shoulder-shaped portion 12b that is integrally connected to the lower end of the neck-shaped portion 12a and whose outer diameter widens further, and a roughly cylindrical main body portion 12c that is integrally connected to the lower end of the shoulder-shaped portion 12b and extends downwards while maintaining the same diameter. The main body portion 12c is connected to a bottom portion 17 that closes its lower end.

[0046] The shape of the torso 12 can be modified in various ways, such as by omitting the neck-like portion 12a.

[0047] A neck ring 13 is integrally provided in the portion between the mouth 11 and the body 12 of the container body 10. The neck ring 13 protrudes radially outward from the upper ends of the mouth 11 and the body 12 and is a substantially plate-like shape that extends around the entire circumference with respect to the central axis O. As shown in Figure 6, the lower surface 13a of the neck ring 13 facing the body 12 is a plane substantially perpendicular to the central axis O, and the upper surface 13b of the neck ring 13 facing the mouth 11 is an inclined surface that slopes toward the body 12 as it extends radially outward.

[0048] An annular projection 14 is integrally provided between the male thread 11a on the outer circumferential surface of the opening 11 and the neck ring 13, projecting radially outward. The annular projection 14 is the part to which a strip-shaped portion, which is provided on the cap to be breakable in order to prevent the cap fitted to the opening 11 from being tampered with, is locked.

[0049] As shown in Figure 1, the covering portion 20 is laminated onto the outer surfaces of the body portion 12 and the bottom portion 17 of the container body 10, covering the entire body portion 12 and the bottom portion 17. The thickness of the covering portion 20 is thinner than the thickness of the body portion 12 and the bottom portion 17. The irregularities on the bottom portion 117 caused by the spiral grooves 117a and groove-forming protrusions 117b that were provided on the laminated preform 100 are almost gone due to the stretching of the bottom portion 117, but the outline of the groove-forming protrusions 117b can be visually seen on the bottom portion 17 of the synthetic resin container 1 when viewed from below.

[0050] In this embodiment, the upper end of the covering portion 20 constitutes a flange 21. The flange 21 is substantially plate-shaped, extending radially outward from the upper end of the covering portion 20 and extending around the entire circumference with respect to the central axis O, and is in close contact with the lower surface 13a of the neck ring 13. In the illustrated case, the outer diameter of the flange 21 is formed to be substantially the same as the outer diameter of the neck ring 13, but the outer diameter of the flange 21 may be smaller than or larger than the outer diameter of the neck ring 13.

[0051] In particular, in this embodiment, a material mainly composed of polypropylene resin is used as the material for the covering portion 20. With this configuration, the tearing force required to peel off the covering portion 20 by the user is reduced.

[0052] As described above, this embodiment is a laminated preform 100 used in the manufacture of a synthetic resin container 1 having a laminated structure, comprising an inner body 110 having a mouth portion 111, a body portion 112, and a bottom portion 117, and an outer body 120 covering the body portion 112 and bottom portion 117 of the inner body 110 from the outside, wherein the bottom portion 117 of the inner body 110 is configured to have a spiral groove 117a that spirals circumferentially from the radial center outward in a view from the bottom. By adopting such a configuration, even if an imbalance in circumferential gaps occurs in the cavity through which the molten resin flows during the molding of the outer body 120, the molten resin proceeds through the cavity while spiraling circumferentially through the spiral groove 117a. Therefore, it is possible to suppress the difficulty of the molten resin flowing into specific (narrow gap) circumferential positions within the cavity, and thus effectively suppress the occurrence of molding defects (such as shorts) at specific circumferential positions caused by an imbalance in circumferential gaps in the cavity.

[0053] Furthermore, in this embodiment, the swirl groove 117a is configured to be formed in a circumferential position between groove-forming projections 117b that protrude outward from the bottom 117 of the inner body 110, and whose circumferential inclination angle increases radially outward when viewed from the bottom. By adopting this configuration, the circumferential swirling of the molten resin through the swirl groove 117a formed by the groove-forming projections 117b can be promoted, thereby more effectively suppressing the occurrence of molding defects (such as shorts).

[0054] Furthermore, in this embodiment, the groove-forming projection 117b is configured such that the angle between the extending direction at the radially inner end and the extending direction at the radially outer end is approximately 120 degrees when viewed from the bottom. By adopting this configuration, the circumferential rotation of the molten resin through the spiral groove 117a formed by the groove-forming projection 117b can be optimized, thereby more effectively suppressing the occurrence of molding defects (such as shorts).

[0055] Furthermore, in this embodiment, the groove-forming protrusions 117b are configured to be provided at equal intervals at four to six locations in the circumferential direction. By adopting this configuration, the flow rate of molten resin swirling in the circumferential direction can be optimized, thereby more effectively suppressing the occurrence of molding defects (such as shorts).

[0056] Furthermore, in this embodiment, the outer body 120 is configured to have a thickness of 0.3 mm or more and 0.7 mm or less. By adopting such a configuration, the flow rate of molten resin swirling in the circumferential direction can be optimized, thereby more effectively suppressing the occurrence of molding defects (such as shorts).

[0057] Furthermore, in this embodiment, the inner body 110 is formed of a resin mainly composed of polyethylene terephthalate, and the outer body 120 is formed of a resin mainly composed of polypropylene. By adopting this configuration, it is possible to improve the peelability of the coating portion 20 from the container body 10 of the synthetic resin container 1 formed by stretch blow molding of the laminated preform 100, and to reduce the tearing force of the coating portion 20.

[0058] Furthermore, this embodiment is a method for manufacturing a laminated preform 100 used in the manufacture of a synthetic resin container 1, and includes the steps of forming an inner body 110 of the laminated preform 100 having a mouth portion 111, a body portion 112, and a bottom portion 117, and forming an outer body 120 of the laminated preform 100 that covers the body portion 112 and the bottom portion 117 of the inner body 110 from the outside, wherein the bottom portion 117 of the inner body 110 has a spiral groove 117a that spirals circumferentially from the radial center toward the radial outward direction when viewed from the bottom, and the step of forming the outer body 120 is configured to fill the mold with molten resin supplied from a gate positioned opposite the radial center of the bottom portion 117 of the inner body 110 while spiraling it circumferentially through the spiral groove 117a. By adopting this configuration, even if an imbalance in the circumferential gap occurs in the cavity through which the molten resin flows during the molding of the outer body 120, the molten resin moves through the swirling groove 117a while swirling in the circumferential direction. Therefore, it is possible to suppress the difficulty of the molten resin flowing into specific (narrow gap) circumferential positions within the cavity, thereby effectively suppressing the occurrence of molding defects (such as shorts) at specific circumferential positions caused by an imbalance in the circumferential gap of the cavity.

[0059] Furthermore, this embodiment provides a synthetic resin container 1 formed by blow molding the laminated preform 100, comprising a bottle-shaped container body 10 formed by blow molding the inner body 110, and a covering portion 20 which is stretched by blow molding the outer body 120 together with the inner body 110 and laminated onto the outer surface of the container body 10. By adopting this configuration, even if an imbalance in circumferential gaps occurs in the cavity through which the molten resin flows during the molding of the outer body 120, the molten resin proceeds through the cavity while swirling circumferentially through the swirling groove 117a. Therefore, it is possible to suppress the difficulty of the molten resin flowing into specific (narrow gap) circumferential positions within the cavity, thereby effectively suppressing the occurrence of molding defects (such as shorts) at specific circumferential positions caused by an imbalance in circumferential gaps in the cavity.

[0060] While this disclosure has been described based on various drawings and embodiments, it should be noted that those skilled in the art will find it easy to make various modifications and alterations based on this disclosure. Therefore, it should be noted that these modifications and alterations are included within the scope of the present invention. For example, the functions included in each component can be rearranged in a logically consistent manner, and multiple components can be combined into one or separated. It should be understood that these are also included within the scope of the present invention.

[0061] For example, in the above-described embodiment, the coating portion 20 is formed from a material mainly composed of polypropylene resin, but the embodiment is not limited to this. In order to improve functions such as decorative properties, light barrier properties, oxygen barrier properties, or water vapor barrier properties, a grade in which the MFR of the molten resin is approximately 300 [g / 10 min.] may be selected, and then further additions such as ethylene vinyl alcohol copolymer, polyamide resin (PA6, MXD6, etc.), 3-hydroxybutyrate-co-3-hydroxyhexanoate polymer (PHBH), or high-density polyethylene resin may be added.

[0062] Furthermore, in the above-described embodiment, the covering portion 20 is configured to cover the entire body portion 12 and bottom portion 17 of the container body 10, but the embodiment is not limited to this. For example, the upper end of the covering portion 20 may not have a flange 21 and may be configured to extend to the lower surface 13a of the neck ring 13. Also, the covering portion 20 may be configured not to cover the portion adjacent to the neck ring 13. Also, the covering portion 20 may be configured to extend beyond the neck ring 13 and cover the opening portion 11. [Examples]

[0063] As materials used for the covering portion 20, as shown in Table 1, moldability tests were conducted on two types of laminated preforms: one with a spiral groove 117a at the bottom 117 of the laminated preform 100 (Example 1) and one without a spiral groove 117a at the bottom 117 of the laminated preform 100 (Comparative Example 1). The conditions common to Example 1 and Comparative Example 1 were: (i) injection speed of molten resin: 50 [mm / sec.], (ii) resin of the outer body: synthetic resin mixed with J246M and S13B manufactured by Prime Polymer Co., Ltd. in a weight ratio of 50:50, (iii) resin of the inner body: polyethylene terephthalate, (iv) thickness of the outer body 120: 0.54~0.55 [mm], and (v) vertical length of the laminated preform 100 below the neck ring: 80.8 [mm].

[0064] [Table 1]

[0065] In Table 1, the thickness variation is an index used to evaluate the misalignment of the inner diameter relative to the outer diameter (or outer diameter relative to the inner diameter) for cylindrical objects such as laminated preform 100, and is expressed as the difference between the maximum and minimum wall thicknesses. Under the conditions that the design value of the wall thickness of the outer body 120 is 0.4 [mm] and the average measured value of the wall thickness of the outer body 120 is 0.54 to 0.55 [mm], the thickness variation in Example 1, which has a spiral groove 117a, improved from 0.48 [mm] to 0.27 [mm], as shown in Table 1, compared to Comparative Example 1, which does not have a spiral groove 117a, and was reduced by approximately 44%.

[0066] In Table 1, moldability was judged as "good" when the molten resin spread to all areas within the cavity, and as "bad" when the molten resin did not spread to any part of the cavity. A typical example of "bad" moldability was Comparative Example 1, which did not have a spiral groove 117a, in which a so-called "short" occurred, where the molten resin did not spread to the opening at the top of the cavity in some circumferential positions within the cavity. In addition, if the injection speed of the molten resin in the mold was significantly slower than 50 [mm / sec.], or if the resin material used for the outer body 120 had a significantly lower melt flow rate (MFR) than the resin material obtained by mixing J246M and S13B in a 50:50 (weight ratio), moldability could be "bad" even if a spiral groove 117a was provided at the bottom 117 as in Example 1.

[0067] Next, the tear strength of the covering portion 20 was compared for the synthetic resin container 1 according to Example 2 and Comparative Example 2 shown in Table 2. In Comparative Example 2, the average measured thickness of the covering portion 20 was 0.18 [mm], while in Example 2, the average measured thickness of the covering portion 20 was 0.06 [mm]. The covering portion 20 thickness of 0.06 [mm] in Example 2 could not be achieved with conventional blow molding of laminated preforms, and is only achievable when using a laminated preform 100 formed by providing a spiral groove 117a according to this embodiment to improve the fluidity of molten resin into the cavity. The inventors of this application have confirmed that even when the thickness of the covering portion 20 is reduced to 0.06 [mm], the amount of water vapor permeation can be reduced to less than half compared to the case of the container body 10 alone.

[0068] Tear resistance was evaluated by measuring the tearing force when the test specimen shown in Figure 7 was torn using the trouser tear tester shown in Figure 8. In Figure 7, the longitudinal direction of the test specimen is the MD (machine direction), i.e., the resin flow direction during molding, and the tearing direction during the test. This test was conducted according to JIS K7128-1:1998, with a tearing speed of 200 mm / min.

[0069] [Table 2]

[0070] According to the results in Table 2, in Comparative Example 2, where the outer layer (coating) thickness was 0.18 [mm], the same as that of a conventional label layer, the tear force was 0.88 [N]. In contrast, in Example 2, where the outer layer (coating) thickness was reduced to 0.06 [mm], the tear force was 0.37 [N], demonstrating a reduction of approximately 58% in tear force. In Example 2, the tear force was reduced to the point where users could easily tear the slitted coating 20. [Explanation of Symbols]

[0071] 1. Container made of synthetic resin 10 Container body 11 Mouth 11a Male thread 12 Torso 12a Neck-shaped part 12b Shoulder 12c main body part 13 Neck ring 13a Bottom side 13b Top surface 14 Annular projections 17 Bottom 20 Covering part 21 Flange 100-ply preform 110 Inner body 111 Mouth 111a Male screw 112 Torso 113 Neck Ring 113a Bottom side 113b Top surface 117 Bottom 117a Swivel groove 117b Groove forming protrusion 117c Alignment projection 120 Outer body 121 Flange C1 center line 1 C2 Center line 2 G gate mark O center axis S Containment space

Claims

1. A laminated preform used in the manufacture of a synthetic resin container having a laminated structure, An inner body having a mouth, a body, and a bottom, An outer body that covers the body and bottom of the inner body from the outside. Equipped with, The bottom of the inner body has a spiral groove that spirals circumferentially from the radial center outward when viewed from the bottom, and is a laminated preform.

2. The laminated preform according to claim 1, wherein the spiral groove is formed at a circumferential position between groove-forming protrusions that project outward from the bottom of the inner body and whose circumferential inclination angle increases radially outward when viewed from the bottom.

3. The laminated preform according to claim 2, wherein the groove-forming projection has an angle of approximately 120 degrees when viewed from the bottom between the extending direction at the radially inner end and the extending direction at the radially outer end.

4. The laminated preform according to claim 2 or 3, wherein the groove-forming protrusions are arranged at equal intervals in four to six locations in the circumferential direction.

5. The laminated preform according to any one of claims 1 to 3, wherein the outer body has a thickness of 0.3 mm or more and 0.7 mm or less.

6. The laminated preform according to any one of claims 1 to 3, wherein the inner body is formed of a resin mainly composed of polyethylene terephthalate, and the outer body is formed of a resin mainly composed of polypropylene.

7. A method for manufacturing laminated preforms used in the manufacture of synthetic resin containers, The steps include forming the inner body of the laminated preform, which has a mouth portion, a body portion, and a bottom portion, The steps include forming an outer body of the laminated preform that covers the body and bottom of the inner body from the outside, and Includes, The bottom of the inner body has a spiral groove that spirals circumferentially from the radial center outward when viewed from the bottom, The step of forming the outer body is a method for manufacturing a laminated preform, wherein molten resin supplied from a gate positioned opposite to the radial center of the bottom of the inner body is filled into a mold while being rotated circumferentially through the swirl groove.

8. A synthetic resin container formed by blow molding of a laminated preform according to claim 1 or 2, A bottle-shaped container body formed by blow molding of the inner body, The outer body is blow-molded together with the inner body to stretch and form a covering portion which is laminated onto the outer surface of the container body. A synthetic resin container equipped with the following features.

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