Method for manufacturing a container made of synthetic resin, and a mold

Abstract

To provide a synthetic resin container with a peelably-laminated coating layer without causing appearance defects.SOLUTION: In blow molding by setting, in a molding die 100, a preform 10 that comprises a bottomed cylindrically-formed preform body 10a containing a mouth forming region 20 and a stretched region 30 and comprises a covering material layer 60 peelably-laminated on an outer circumferential surface side of the preform body 10a, the molding die 100 is designed so that a clearance CL2 between a thermally expanded portion of the covering material layer 60 and a cavity surface 101 of the molding die 100 is larger by selectively heating the stretched region 30 of the preform 10 than a clearance CL1 between a lower end of the mouth forming region 20 of the preform 10 set in the molding die 100 and a lower neck regulating portion 102 provided in the molding die 100.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a synthetic resin container provided with a peelable laminated coating layer, and a mold suitably used for the manufacturing method.

Background Art

[0002] Conventionally, a preform formed into a bottomed cylindrical shape using a thermoplastic resin such as polyethylene terephthalate is produced, and a synthetic resin container formed into a bottle shape by biaxial stretch blow molding or the like is used in a wide range of fields as a container containing various beverages, various seasonings, etc. as contents.

[0003] This type of synthetic resin container has become increasingly familiar in recent years, and various proposals have been made accordingly. In such recent circumstances, the present applicant has proposed in Patent Document 1 to produce a preform in which a coating material layer is laminated by double molding, and to manufacture a synthetic resin container provided with a peelable laminated coating layer by blow molding such a preform.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, according to the studies by the present inventors, it has been found that when blow molding a preform as described above, appearance defects may occur in the formed container. The present inventors have investigated the causes of such problems and have conducted intensive studies to prevent such problems from occurring, and as a result, have completed the present invention.

Means for Solving the Problems

[0006] The manufacturing method of a synthetic resin container according to the present invention is a manufacturing method of a synthetic resin container including a container body formed in a predetermined container shape including a mouth part, a shoulder part, a body part, and a bottom part, and a coating layer detachably laminated on the outer peripheral surface side of the container body. When a preform including a preform body formed in a bottomed cylindrical shape including a mouth part forming region that becomes the mouth part and a stretching region that is stretched and formed into the shoulder part, the body part, and the bottom part, and a coating material layer detachably laminated on the outer peripheral surface side of the preform body is set in a mold and blow-molded, a portion where the coating material layer thermally expands by selectively heating the stretching region of the preform with respect to a clearance CL1 between the lower end side of the mouth part forming region of the preform set in the mold and a neck-down restricting part provided in the mold In the case of the outer peripheral diameter D30(exp) of the preform including the coating layer and the inner peripheral diameter D101 of the cavity surface of the mold cavity where this part faces in the radial direction and The a clearance CL2 between the cavity surface Between them, the relationship CL2 = (D101 - D30(exp)) / 2 holds, and between all the cavity surfaces below the head-down restricting part where the portion where the coating layer has thermally expanded faces in the radial direction, the relationship CL1 < CL2 holds is designed as the method of designing the mold.

[0007] Further, the manufacturing method of a synthetic resin container according to the present invention is a manufacturing method of a synthetic resin container including a container body formed in a predetermined container shape including a mouth part, a shoulder part, a body part, and a bottom part, and a coating layer detachably laminated on the outer peripheral surface side of the container body. When a preform including a preform body formed in a bottomed cylindrical shape including a mouth part forming region that becomes the mouth part and a stretching region that is stretched and formed into the shoulder part, the body part, and the bottom part, and a coating material layer detachably laminated on the outer peripheral surface side of the preform body is set in a mold and blow-molded, a clearance CL1 between the lower end side of the mouth part forming region of the preform set in the mold and a neck-down restricting part provided in the mold, an inner peripheral diameter D101 of the cavity surface below the neck-down restricting part of the mold, and an outer peripheral diameter D30 of the preform including the coating material layer in the stretching region before the preform is heat-treated, the mold can be designed such that the relationship (D101 - D30) / 2 > CL1 is satisfied.

[0008] In addition, the mold according to the present invention is a mold for manufacturing a synthetic resin container provided with a container body formed in a predetermined container shape including a mouth portion, a shoulder portion, a body portion, and a bottom portion, and a coating layer detachably laminated on the outer peripheral surface side of the container body by blow molding. When a preform including a preform body formed in a bottomed cylindrical shape including a mouth formation region that becomes the mouth portion and a stretching region that is stretched and formed into the shoulder portion, the body portion, and the bottom portion, and a coating material layer detachably laminated on the outer peripheral surface side of the preform body is set and blow molded, a portion where the coating material layer thermally expands by selectively heating the stretching region of the preform with respect to a clearance CL1 between the lower end side of the mouth formation region of the set preform and a neck-down restricting portion provided on the mold In the case of the outer peripheral diameter D30(exp) of the preform including the coating layer and the inner peripheral diameter D101 of the cavity surface of the mold cavity where this part faces in the radial direction and The the clearance CL2 between the cavity surface Between them, the relationship CL2 = (D101 - D30(exp)) / 2 holds, and between all the cavity surfaces below the head-down restricting part where the portion where the coating layer has thermally expanded faces in the radial direction, the relationship CL1 < CL2 holds is designed to be configured as such.

[0009] In addition, the mold according to the present invention is a mold for manufacturing a synthetic resin container provided with a container body formed in a predetermined container shape including a mouth portion, a shoulder portion, a body portion, and a bottom portion, and a coating layer detachably laminated on the outer peripheral surface side of the container body by blow molding. When a preform including a preform body formed in a bottomed cylindrical shape including a mouth formation region that becomes the mouth portion and a stretching region that is stretched and formed into the shoulder portion, the body portion, and the bottom portion, and a coating material layer detachably laminated on the outer peripheral surface side of the preform body is set and blow molded, a clearance CL1 between the lower end side of the mouth formation region of the set preform and a neck-down restricting portion provided on the mold, an inner peripheral diameter D101 of the cavity surface below the neck-down restricting portion of the mold, and an outer peripheral diameter D30 of the preform including the coating material layer in the stretching region before the preform is heat-treated are designed such that the relationship (D101 - D30) / 2 > CL1 is satisfied.

Advantages of the Invention

[0010] According to the present invention, it is possible to manufacture a synthetic resin container provided with a coating layer laminated in a peelable manner without causing appearance defects.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0012] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[0013] First, in the present embodiment, an example of the synthetic resin container to be manufactured will be described. FIG. 1 is a front view showing an outline of the synthetic resin container to be manufactured.

[0014] The container 1 shown in Fig. 1 includes a container body 1a formed into a predetermined container shape including a mouth portion 2, a shoulder portion 3, a body portion 4, and a bottom portion 5, and a coating layer 6 detachably laminated on the outer peripheral surface side of the container body 1a. In the illustrated example, the container 1 (container body 1a) has a container shape generally called a round bottle in which the body portion 4 is formed in a cylindrical shape, but the shape of the container 1 is not limited to this.

[0015] Note that in Fig. 1, a part of the mouth portion 2 and the shoulder portion 3 is cut away to show the cross section, and the thicknesses of the container body 1a and the coating layer 6 shown in the cross section are exaggeratedly depicted.

[0016] The mouth portion 2 is a cylindrical portion that serves as an injection outlet for the contents, and a screw thread 2a for attaching a lid body (not shown) is provided on the side surface of the opening end side of the mouth portion 2. Also, an annular neck ring 2b protruding outward along the circumferential direction is provided on the mouth portion 2. And the mouth portion 2 includes a neck lower portion 2c that hangs down in a cylindrical shape with substantially the same diameter from directly below the neck ring 2b.

[0017] The lower end of such a mouth portion 2 expands in diameter toward the body portion 4 and is connected to the shoulder portion 3 that connects the mouth portion 2 and the body portion 4. In the illustrated example, the shoulder portion 3 is formed in a rounded frustum shape, but the shape of the shoulder portion 3 is not limited to this. For example, it can also be formed in a so-called vine neck shape.

[0018] Also, the body portion 4 is a portion that occupies most of the height direction of the container 1, with the upper end connected to the shoulder portion 3 and the lower end connected to the bottom portion 5. In the illustrated example, the container 1 is provided with a bottom portion 5 formed in a so-called petaloid shape so as to be suitable for use with carbonated beverages as the contents, but the shape of the bottom portion 5 may be other shapes suitable for use with non-carbonated beverages as the contents and can be appropriately changed according to the use.

[0019] Here, the height direction refers to the direction perpendicular to the horizontal plane when the container 1 is placed upright on the horizontal plane with the mouth portion 2 facing upward, and the up-down, left-right, and vertical-horizontal directions of the container 1 are defined in this state (the state shown in FIG. 1).

[0020] In the container 1 formed into such a container shape, the coating layer 6 can be laminated such that its end side covers the lower end side of the mouth portion 2. In the illustrated example, the entire outer surface of the body portion 4 from the bottom surface of the bottom portion 5 is covered with the coating layer 6, and the end side of the coating layer 6 is laminated so as to cover the entire circumference of the neck portion 2c on the lower end side of the mouth portion 2 and reach directly below the neck ring 2b.

[0021] Next, a method for manufacturing a synthetic resin container according to an embodiment of the present invention will be described.

[0022] FIG. 2 shows an example of a molding die 100 used for blow molding the aforementioned container 1. The molding die 100 includes a body die 104 for molding the shoulder portion 3 and the body portion 4, and a bottom die 105 for molding the bottom portion 5. The body die 104 is composed of a pair of split dies that can be opened and closed, and FIG. 2 shows a simplified cross-section of the molding die 100 cut along a plane including the parting surface of the body die 104.

[0023] Further, FIG. 3 shows an example of a preform 10 blow-molded into the aforementioned container 1. The preform 10 includes a preform body 10a and a coating material layer 60 laminated on the outer peripheral surface side of the preform body 10a so as to be peelable.

[0024] When blow molding the preform body 10a as described later, it is formed into a bottomed cylindrical shape including a mouth portion forming region 20 that generally maintains its appearance and becomes the mouth portion 2 of the container body 1a, and a stretching region 30 that is stretched and formed into the shoulder portion 3, the body portion 4, and the bottom portion 5 of the container body 1a. Threads 2a and a neck ring 2b, which are indicated by the same reference numerals as those attached to the container 1, are provided in the mouth portion forming region 20 of the preform body 10a, and the portion below the neck ring 2b in the mouth portion forming region 20 becomes the neck portion 2c of the container body 1a.

[0025] Here, FIG. 3 is a longitudinal sectional view of the preform 10, depicting the preform body 10a and the thickness of the coating layer 60 shown in the cross section in an exaggerated manner. In other drawings as well, the thicknesses of the preform body 10a, the coating layer 60, etc. shown in the cross section are depicted in an appropriately exaggerated manner. Also, the up-down, left-right, longitudinal, and lateral directions of the preform 10 shall be defined in the state shown in FIG. 3 with the mouth formation region 20 side facing upward. The up-down, left-right, longitudinal, and lateral directions of the mold 100 shall be defined according to the direction of the preform 10 set in the mold 100.

[0026] Also, the coating layer 60 laminated on the preform body 10a can be laminated such that its end side covers the lower end side of the mouth formation region 20. In the illustrated example, the entire surface of the stretching region 30 is covered with the coating layer 60, and the end side of the coating layer 60 is laminated so as to cover the entire circumference of the part below the neck ring 2b (the part that becomes the neck lower part 2c of the container body 1a) of the mouth formation region 20 and reaches directly below the neck ring 2b.

[0027] Such a preform 10 can be manufactured as follows by an injection molding method called a double mold or the like.

[0028] First, the core mold 400 for molding the inner peripheral surface and the upper end surface of the preform body 10a, the upper mold 401 for molding the upper outer peripheral surface of the preform body 10a including the upper surface and the circumferential end surface of the neck ring 2b, and the first lower mold 402a for molding the lower outer peripheral surface of the preform body 10a from the lower surface of the neck ring 2b to the bottom are clamped, and a resin material for forming the preform body 10a is injected (see FIG. 4). Thereby, the preform body 10a formed in a bottomed cylindrical shape including the mouth formation region 20 and the stretching region 30 is injection molded (primary injection step).

[0029] Next, instead of the first lower mold 402a, after re-clamping using a second lower mold 402b configured to form a gap for forming the coating layer 60 between the formed preform body 10a, the resin material for forming the coating layer 60 is injected (see FIG. 5). Thereby, an injection-molded coating layer 60 that is peelably laminated on the outer peripheral surface side of the preform body 10a and whose end side covers the lower end side of the mouth portion forming region 20 (the portion below the neck ring 2b) is formed (secondary injection process).

[0030] Note that gates serving as resin material injection ports are usually disposed at positions corresponding to the bottom side of the preform 10 in the first and second lower molds 402a and 402b, but in the examples shown in FIGS. 4 and 5, illustration of the gates is omitted.

[0031] As the resin material for forming the preform body 10a (that is, the resin material for forming the container body 1a), considering the recyclability required for the container 1, an ethylene terephthalate-based thermoplastic polyester such as polyethylene terephthalate can be preferably used.

[0032] As the resin material for forming the coating layer 60 (i.e., the resin material for forming the coating layer 6), from the viewpoint of enabling the coating layer 60 (coating layer 6) to be laminated on the preform body 10a (container body 1a) in a peelable manner, it is preferable to use a thermoplastic resin that is incompatible with the resin material for forming the preform body 10a. For example, when using an ethylene terephthalate-based thermoplastic polyester as the resin material for forming the preform body 10a, polyolefin-based resins such as polypropylene and polyethylene can be used as the resin material for forming the coating layer 60. When gas barrier properties are required for the container 1, a thermoplastic resin having gas barrier properties such as an ethylene-vinyl alcohol copolymer or polymetaxylylene adipamide (MXD6) can also be used as the resin material for forming the coating layer 60. Pigments, colorants, etc. can be added to the resin material for forming the coating layer 60 to impart light-shielding properties by coloring it in a desired hue. In order to enhance the decorative effect, a plurality of pigments and colorants can be mixed and added to form a marble pattern. Various additives can be added to the resin material for forming the coating layer 60 as required, without being restricted by the recyclability required for the container 1.

[0033] The preform 10 thus produced is softened by heating to a state where blow molding is possible, and then set in the mold 100 as shown by the dashed-dotted line in Fig. 2. While being stretched in the axial direction (longitudinal direction) by a stretching rod (not shown) as required, it is stretched in the axial direction and circumferential direction (lateral direction) by the blow air blown into the preform 10.

[0034] To heat the preform 10, for example, as shown in FIG. 6, the mouth formation region 20 can be covered with a shield 200 or the like so that the mouth formation region 20 is not heated, and the stretching region 30 can be heated from the side of the covering material layer 60 by an infrared heater 201 or the like. At the same time, the shape of the mandrel 300, which serves both as a blow nozzle for blowing in blow air and as a jig for supporting the preform 10, is appropriately designed so as to cover the inner peripheral surface of the mouth formation region 20, and the stretching region 30 may be heated from the inside by a high-frequency induction heating element 301 inserted through the mandrel 300.

[0035] In this way, by blow molding the preform 10, the stretching region 30 is stretched, and the shape of the cavity surface 101 of the mold 100 is transferred, so that the shoulder 3, the body 4, and the bottom 5 of the container body 1a are formed. At the same time, the covering material layer 60 laminated on the preform body 10a is integrally formed with the preform body 10a and becomes the covering layer 6 laminated on the container body 1a. On the other hand, the mouth formation region 20 is not stretched except for the connection portion with the stretching region 30 on the lower end side, and its appearance is generally maintained to become the mouth 2 of the container body 1a. At this time, a neck lower restricting portion 102 that restricts the portion that becomes the lower neck portion 2c of the container body 1a is provided on the mold 100 (more specifically, the upper portion of the body mold 104) facing the lower end side of the mouth formation region 20.

[0036] The neck lower restricting portion 102 provided on the mold 100 also functions as a portion for radially positioning the preform 10 with respect to the mold 100 by holding the preform 10 set on the mold 100 with a predetermined clearance CL1. The clearance CL1 between the lower end side of the mouth formation region 20 of the preform 10 set on the mold 100 and the neck lower restricting portion 102 is set with respect to the outer peripheral diameter D20 of the preform 10 including the covering material layer 60 at the lower end side of the mouth formation region 20. Therefore, the relationship CL1 = (D102 - D20) / 2 holds between the inner peripheral diameter D102 of the neck lower restricting portion 102. For example, specific numerical values can be 0.1 to 0.5 mm (see FIG. 8). Note that FIG. 8 is an enlarged longitudinal sectional view of the main part of the mold 100 including the neck-lowering restricting portion 102, showing it enlarged together with the preform 10.

[0037] Also, when heating the preform 10 as described above, in order to prevent the mouth-forming region 20 from being heated, the range in which the mouth-forming region 20 is covered with the shielding body 200 is set according to the height H2c of the neck portion 2c formed in the container body 1a, and the height H2c coincides with the height H102 of the neck-lowering restricting portion 102. For example, in the example shown in FIG. 6, the shielding body 200 can be installed at a position where the separation distance d from the neck ring 2b along the height direction of the preform 10 is H2c ± 60% or less of the height H2c of the neck portion 2c. Specifically, when citing specific numerical values, the separation distance d is appropriately adjusted so that, for example, it becomes 1 to 10 mm, and according to the height H2c of the neck portion 2c formed in the container body 1a, the shielding body 200 can be installed near the lower end of the portion that becomes the neck portion 2c.

[0038] In this way, when heating the preform 10, by selectively heating the stretching region 30, blow molding is made to be performed well. In other words, the region that is softened by heating and can be stretched is the stretching region 30, and the other region is the mouth-forming region 20.

[0039] When manufacturing the container 1 by blow molding the preform 10 as described above, if the thickness of the coating material layer 60 laminated on the stretching region 30 increases due to thermal expansion when the stretching region 30 is selectively heated, the outer peripheral diameter of the preform 10 will increase accordingly (see FIG. 7). Note that FIG. 7 is an enlarged view of the main part showing the portion surrounded by the chain line in FIG. 6, and schematically shows the state where the coating material layer 60 has thermally expanded. Similarly in FIGS. 8 and 9, the state where the coating material layer 60 has thermally expanded is schematically shown.

[0040] Then, with a clearance CL1 set with respect to the outer peripheral diameter D20 of the preform 10 including the coating material layer 60 on the lower end side of the mouth portion forming region 20, when the preform 10 held and positioned by the neck-down restricting portion 102 is biased to one side in the radial direction, the thermally expanded portion of the coating material layer 60 may come into contact with the cavity surface (more specifically, the cavity surface below the neck-down restricting portion 102) 101 of the mold 100.

[0041] In such a case, when the preform 10 is blow-molded with the thermally expanded portion of the coating material layer 60 remaining in contact with the cavity surface 101 of the mold 100 in a state of being rapidly cooled by heat conduction to the mold 100, wrinkles such as rubbing marks will occur on the coating layer 6 of the formed container 1, which will cause poor appearance of the container 1.

[0042] In the present embodiment, in order to effectively avoid such a problem, the clearance CL2 between the thermally expanded portion of the coating material layer 60 and the cavity surface 101 of the mold 100 is made larger than the clearance CL1 between the lower end side of the mouth portion forming region 20 of the preform 10 set in the mold 100 and the neck-down restricting portion 102 provided in the mold 100 (see FIG. 8). More specifically, between the outer peripheral diameter D30(exp) of the preform 10 including the coating material layer 60 in the thermally expanded portion of the coating material layer 60 (substantially the stretching region 30), the inner peripheral diameter D101 of the cavity surface 101 facing the portion in the radial direction, and the clearance CL2, the relationship CL2 = (D101 - D30(exp)) / 2 is established, and the relationship CL1 < CL2 is established between the thermally expanded portion of the coating material layer 60 and all the cavity surfaces 101 below the neck-down restricting portion 102 facing the portion in the radial direction.

[0043] According to such an embodiment of the present invention, by blow molding the preform 10 using the mold 100 designed as described above, even if the preform 10 held and positioned by the neck-down restricting portion 102 with a predetermined clearance CL1 is biased to one side in the radial direction, it is possible to prevent the thermally expanded portion of the coating layer 60 from contacting the cavity surface 101 of the mold 100 (see FIG. 9). As a result, it is possible to effectively avoid problems such as wrinkles like rubbing marks on the coating layer 6 of the formed container 1, and to manufacture the container 1 provided with the coating layer 6 laminated in a peelable manner without causing defective appearance. Note that FIG. 9 shows a state in which the preform 10 is biased to one side in the radial direction (left side in the figure) with respect to the state shown in FIG. 8 (a state in which the central axis C10 of the preform 10 and the central axis C100 of the mold 100 coincide).

[0044] In the above example, the mold 100 is designed based on the preform 10 that has been heat-treated during blow molding. However, the mold 100 can also be designed based on the preform 10 before the heat treatment is performed.

[0045] For example, the clearance CL1 between the lower end side of the mouth portion forming region 20 of the preform 10 set in the mold 100 and the neck-down restricting portion 102 provided in the mold 100, the inner peripheral diameter D101 of the cavity surface 101 below the neck-down restricting portion 102 of the mold 100, and the outer peripheral diameter D30 of the preform 10 including the coating layer 60 in the stretching region 30 of the preform 10 before the heat treatment is performed on the preform 10, the mold 100 can also be designed so that the relationship (D101 - D30) / 2 > CL1 is satisfied.

[0046] Here, the value obtained from (D101 - D30) / 2 corresponds to the clearance between the stretching region 30 of the preform 10 and the cavity surface 101 below the neck-down restricting portion 102 of the mold 100 when it is assumed that the preform 10 is set in the mold 100 without being heated (see FIG. 10). Note that FIG. 10 is an enlarged longitudinal sectional view of the main part of this modified example shown corresponding to FIG. 8. Depending on the resin material forming the coating layer 60, the outer peripheral diameter D30(exp) of the preform 10 including the coating layer 60 at the portion where the coating layer 60 has thermally expanded is in the range of 1.01 to 1.06 times the outer peripheral diameter D30 of the preform 100 including the coating layer 60 before the heat treatment (before expansion) at the corresponding portion.

[0047] Thus, in anticipation of the thermal expansion of the coating layer 60 in the stretching region 30, by providing a relatively large clearance between the cavity surface 101 at the site where the coating layer 60 expands, it is possible to effectively avoid problems such as wrinkles in the form of rubbing marks on the coating layer 6 of the formed container 1.

[0048] As described above, the present invention has been described by showing preferred embodiments. However, it goes without saying that the present invention is not limited only to the above-described embodiments, and various modifications can be made within the scope of the present invention.

[0049] For example, in the above-described embodiment, an example has been described using the preform 10 in which the entire surface of the stretching region 30 is covered with the coating layer 60, and the terminal side of the coating layer 60 is laminated so as to cover the entire circumference of the portion below the neck ring 2b in the mouth formation region 20 and reach directly below the neck ring 2b. However, the present invention is not limited to this. It is also possible to use a preform 10 in which the terminal side of the coating layer 60 extends so as to cover the lower surface of the neck ring 2b and reach the peripheral edge of the neck ring 2b, and it is also possible to use a preform 10 in which the coating layer 60 is not laminated on the bottom side.

[0050] Further, in a rotary molding apparatus in which a plurality of molds 100 are attached to the periphery of a turret and the preform 10 is sequentially supplied to each mold 100 revolving around an axis to continuously manufacture the container 1, the preform 10 set in the mold 100 has a strong tendency to be easily biased to one side in the radial direction. Therefore, the present invention can exhibit remarkable effects when applied to such a rotary molding apparatus.

Description of Symbols

[0051] 1 Container 1a Container body 2 Mouth part 3 Shoulder part 4 Barrel part 5 Bottom part 6 Coating layer 10 Preform 10a Preform body 20 Mouth part forming region 30 Extension region 60 Coating material layer 100 Molding die 101 Cavity surface 102 Neck-down restricting part CL1 Clearance between the lower end side of the mouth part forming region and the neck-down restricting part CL2 Clearance between the thermally expanded part of the coating material layer and the cavity surface of the molding die D30(exp) Outer diameter of the preform including the coating material layer in the thermally expanded part of the coating material layer D101 Inner diameter of the cavity surface where the thermally expanded part of the coating material layer faces in the radial direction

Claims

1. A method for manufacturing a synthetic resin container comprising a container body formed in a predetermined container shape including a mouth portion, a shoulder portion, a body portion, and a bottom portion, and a coating layer peelably laminated on the outer peripheral surface side of the container body, When a preform comprising a preform body formed in a bottomed cylindrical shape including a mouth formation region that becomes the mouth portion and a stretching region that is stretched and formed into the shoulder portion, the body portion, and the bottom portion, and a coating material layer peelably laminated on the outer peripheral surface side of the preform body is set in a mold and blow molded, With respect to the clearance CL1 between the lower end side of the mouth formation region of the preform set in the mold and a neck-down restricting portion provided in the mold, By selectively heating the stretching region of the preform, in a portion where the coating material layer has thermally expanded, between the outer peripheral diameter D30(exp) of the preform including the coating material layer, the inner peripheral diameter D101 of the cavity surface of the mold facing the portion in the radial direction, and the clearance CL2 between the cavity surface, the relationship CL2 = (D101 - D30(exp)) / 2 is established, and the mold is designed such that the relationship CL1 < CL2 is established between all the cavity surfaces below the neck-down restricting portion facing the portion where the coating material layer has thermally expanded in the radial direction. A method for manufacturing a synthetic resin container, characterized by this.

2. A method for manufacturing a synthetic resin container comprising a container body formed in a predetermined container shape including a mouth portion, a shoulder portion, a body portion, and a bottom portion, and a coating layer peelably laminated on the outer peripheral surface side of the container body, When a preform comprising a preform body formed in a bottomed cylindrical shape including a mouth formation region that becomes the mouth portion and a stretching region that is stretched and formed into the body portion, the shoulder portion, and the bottom portion, and a coating material layer peelably laminated on the outer peripheral surface side of the preform body is set in a mold and blow molded, The clearance CL1 between the lower end side of the mouth-forming region of the preform set in the molding die and the neck-lowering restricting portion provided in the molding die, the inner peripheral diameter D101 of the cavity surface below the neck-lowering restricting portion of the molding die, and the outer peripheral diameter D30 of the preform including the coating layer in the stretching region before heat treatment is applied to the preform, the molding die is designed such that the relationship (D101 - D30) / 2 > CL1 holds. A method for manufacturing a synthetic resin container characterized by this.

3. A molding die for manufacturing a synthetic resin container having a container body formed in a predetermined container shape including a mouth portion, a shoulder portion, a body portion, and a bottom portion, and a coating layer laminated on the outer peripheral surface side of the container body in a peelable manner by blow molding, When a preform including a bottomed cylindrical preform body including a mouth-forming region that becomes the mouth portion and a stretching region that is stretched and formed into the shoulder portion, the body portion, and the bottom portion, and a coating material layer laminated on the outer peripheral surface side of the preform body in a peelable manner is set and blow molded, With respect to the clearance CL1 between the lower end side of the mouth-forming region of the set preform and the neck-lowering restricting portion provided in the molding die, In the portion where the coating material layer is thermally expanded by selectively heating the stretching region of the preform, the outer peripheral diameter D30(exp) of the preform including the coating material layer, the inner peripheral diameter D101 of the cavity surface of the molding die facing the portion in the radial direction, and the clearance CL2 between the cavity surface, the relationship CL2 = (D101 - D30(exp)) / 2 holds, and it is designed such that the relationship CL1 < CL2 holds between the clearance CL1 and all the cavity surfaces below the neck-lowering restricting portion facing the portion where the coating material layer is thermally expanded in the radial direction. A molding die characterized by this.

4. A molding die for manufacturing a synthetic resin container having a container body formed in a predetermined container shape including a mouth portion, a shoulder portion, a body portion, and a bottom portion, and a coating layer laminated on the outer peripheral surface side of the container body in a peelable manner by blow molding, A preform body formed into a bottomed cylindrical shape including a mouth portion forming region serving as the mouth portion, and an extending region extended and formed into the shoulder portion, the body portion, and the bottom portion, and a preform including a coating material layer detachably laminated on the outer peripheral surface side of the preform body is set and blow molded. When blow molding is performed with a set preform, a clearance CL1 between the lower end side of the mouth portion forming region of the set preform and a neck-down restricting portion provided on the molding die, an inner peripheral diameter D101 of a cavity surface below the neck-down restricting portion of the molding die, and an outer peripheral diameter D30 of the preform including the coating material layer in the extending region before the preform is heat treated are designed such that a relationship (D101 - D30) / 2 > CL1 is satisfied. The molding die is characterized by this.

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