Method for manufacturing preforms and plastic bottles

Abstract

The present invention provides a preform and a method for manufacturing a plastic bottle that enables weight reduction while also increasing the thickness of the shoulder portion of the plastic bottle near the boundary with the body. [Solution] The preform 10 comprises a mouth portion 11, a body portion 20 connected to the mouth portion 11, and a bottom portion 30 connected to the body portion 20. The body portion 20 has a large diameter portion 21 located on the mouth portion 11 side, a small diameter portion 23 located on the bottom portion 30 side, and a reduced diameter portion 22 located between the large diameter portion 21 and the small diameter portion 23, which decreases in diameter from the large diameter portion 21 side to the small diameter portion 23 side. The reduced diameter portion 22 has a minimum portion 20A in a cross-section along a direction perpendicular to the central axis CL of the preform 10, where the cross-sectional area is at its minimum, and a maximum portion 20B located on the bottom portion 30 side of the minimum portion 20A, where the cross-sectional area is at its maximum. The cross-sectional area of ​​the maximum portion 20B is the maximum value of the cross-sectional area of ​​the reduced diameter portion 22.

Description

[Technical Field]

[0001] This disclosure relates to a method for manufacturing preforms and plastic bottles. [Background technology]

[0002] Traditionally, plastic bottles have been manufactured by, for example, applying biaxial stretch blow molding to polyethylene terephthalate preforms produced by injection molding. Furthermore, in recent years, there has been a growing desire to reduce the weight of plastic bottles by decreasing the amount of plastic material used. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-196160 [Overview of the project] [Problems that the invention aims to solve]

[0004] The present disclosure aims to provide a preform and a method for manufacturing a plastic bottle that enables weight reduction and increases the thickness of the shoulder portion of the plastic bottle near the boundary with the body portion. [Means for solving the problem]

[0005] Embodiments of this disclosure relate to the following [1] to [7].

[0006] [1] In preforms, The mouth and, The body portion connected to the mouth portion, The body comprises a bottom connected to the aforementioned body, The body portion has a large diameter portion located on the mouth side, a small diameter portion located on the bottom side, and a reduced diameter portion located between the large diameter portion and the small diameter portion, which decreases in diameter from the large diameter portion side towards the small diameter portion side. The reduced diameter portion has, in a cross-section along a direction perpendicular to the central axis of the preform, a minimum portion where the cross-sectional area is at its minimum value, and a maximum portion located closer to the bottom than the minimum portion where the cross-sectional area is at its maximum value. A preform in which the cross-sectional area of ​​the maximum portion is equal to the maximum cross-sectional area of ​​the reduced diameter portion.

[0007] [2] The preform according to [1], wherein the minimum portion is located within a region of 2.5 mm to 7.0 mm in the direction of the central axis from the boundary between the mouth portion and the body portion.

[0008] [3] The preform according to [1] or [2], wherein the maximum portion is located within a region of 8 mm to 11 mm in the direction of the central axis from the boundary between the mouth portion and the body portion.

[0009] [4] The preform according to any one of [1] to [3], wherein the cross-sectional area in the maximum portion is 1.05 times or more and 1.2 times or less the cross-sectional area in the minimum portion.

[0010] [5] The cross-sectional area at the maximum portion is 150 mm². 2 174mm 2 The following is true, and the cross-sectional area at the minimum portion is 125 mm². 2 More than 145mm 2 The preform described in any one of the following [1] through [4]:

[0011] [6] The preform according to any one of [1] to [5], wherein the cross-sectional area in the maximum portion is greater than the cross-sectional area in the large diameter portion.

[0012] [7] In a method for manufacturing a plastic bottle, a step of preparing a preform according to any one of [1] to [6]; a step of heating the preform; a step of performing biaxial stretch blow molding on the preform, and a method for manufacturing a plastic bottle comprising the same.

Advantages of the Invention

[0013] According to this embodiment, weight reduction can be achieved, and the thickness of the vicinity of the boundary between the body and the shoulder of the plastic bottle can be increased.

Brief Description of the Drawings

[0014] [Figure 1] FIG. 1 is a front view showing a preform according to an embodiment. [Figure 2] FIG. 2 is a vertical cross-sectional view (a cross-sectional view passing through the central axis of the preform) showing a preform according to an embodiment. [Figure 3] FIG. 3 is a graph showing an outline of changes in the cross-sectional areas of the large-diameter portion, reduced-diameter portion, and small-diameter portion of a preform according to an embodiment. [Figure 4] FIG. 4 is a front view showing a plastic bottle produced from a preform according to an embodiment. [Figure 5] FIGS. 5(a)-(e) are diagrams showing a method for manufacturing a plastic bottle according to an embodiment. [Figure 6] FIG. 6 is a graph showing changes in the cross-sectional areas of the large-diameter portion, reduced-diameter portion, and small-diameter portion of preforms according to Examples 1-2 and Comparative Examples 1-3. [Figure 7] FIG. 7 is a graph showing changes in the thickness of the shoulder of plastic bottles molded from preforms according to Examples 1-2 and Comparative Examples 1-3.

Embodiments for Carrying Out the Invention

[0015] This embodiment will be described below with reference to the drawings. Figures 1 to 5 show one embodiment.

[0016] In this specification, "up" and "down" refer to the up and down directions when the mouth 11 of the preform 10 is oriented vertically upward and the bottom 30 of the preform 10 is oriented vertically downward (Figures 1 and 2). In this specification, the "central axis CL" of the preform 10 refers to the central axis of the cylinder that constitutes the inner surface of the mouth 11 of the preform 10.

[0017] In this specification, "height direction" means the direction along the central axis CL of the preform 10, and "radial direction" means the direction perpendicular to the central axis CL of the preform 10. "Circumferential direction" means the circumferential direction of a circle centered on the central axis CL of the preform 10. "Horizontal section" means a section cut by a plane perpendicular to the central axis CL of the preform 10. "Vertical section" means a section cut by a plane containing the central axis CL of the preform 10.

[0018] The outline of the preform according to this embodiment will be explained with reference to Figures 1 and 2.

[0019] The preform 10 shown in Figures 1 and 2 comprises a mouth portion 11, a body portion 20 connected to the mouth portion 11, and a bottom portion 30 connected to the body portion 20. The mouth portion 11 has a support ring 14 and an opening 15. The body portion 20 has a large diameter portion 21, a small diameter portion 23, and a reduced diameter portion 22. The large diameter portion 21 is located on the mouth portion 11 side. The small diameter portion 23 is located on the bottom portion 30 side. The reduced diameter portion 22 is located between the large diameter portion 21 and the small diameter portion 23. The reduced diameter portion 22 is reduced in diameter from the large diameter portion 21 side to the small diameter portion 23 side. The thickness T2 of the reduced diameter portion 22 (see Figure 2) changes between the large diameter portion 21 side and the small diameter portion 23 side.

[0020] The mouth portion 11 includes a cylindrical mouth portion body 12, a threaded portion 13 provided on the outer circumference of the mouth portion body 12, and a support ring 14 provided below the threaded portion 13. As shown in Figure 2, the mouth portion body 12 has an outer diameter D1 and an inner diameter D2.

[0021] The outer diameter D1 of the mouth body 12 may be 18 mm or more, 20 mm or more, or 23 mm or more. The outer diameter D1 of the mouth body 12 may be 34 mm or less, 31 mm or less, or 28 mm or less. The inner diameter D2 of the mouth body 12 may be 15 mm or more, 17 mm or more, or 20 mm or more. The inner diameter D2 of the mouth body 12 may be 28 mm or less, 26 mm or less, or 24 mm or less.

[0022] The height L1 of the opening 11 may be, for example, 14 mm or more, 16 mm or more, or 18 mm or more. The height L1 of the opening 11 may be 28 mm or less, 25 mm or less, or 23 mm or less.

[0023] The threaded portion 13 is for screwing on a cap (not shown) after the plastic bottle 40 (see Figure 4) is manufactured by biaxial stretch blow molding of the preform 10. The support ring 14 is provided at the bottom of the mouth portion 11 and protrudes in an annular shape around its entire circumference. The body portion 20 is connected below the support ring 14.

[0024] As described above, the body portion 20 has a large diameter portion 21, a small diameter portion 23, and a reduced diameter portion 22.

[0025] The large-diameter portion 21 is connected to the lower part of the support ring 14. The large-diameter portion 21 has an outer surface 21a and an inner surface 21b. The height-direction length L2 of the large-diameter portion 21 may be, for example, 1.3 mm or more, 2.0 mm or more, or 2.5 mm or more. The height-direction length L2 of the large-diameter portion 21 may be 3.7 mm or less, 3.4 mm or less, or 3.1 mm or less.

[0026] The large-diameter portion 21 is generally cylindrical in shape and has an outer diameter D3 and an inner diameter D4. The outer diameter D3 of the large-diameter portion 21 may be 18 mm or more, 20.5 mm or more, or 23 mm or more. The outer diameter D3 of the large-diameter portion 21 may be 34 mm or less, 31 mm or less, or 28 mm or less. The outer diameter D3 of the large-diameter portion 21 may be larger than the outer diameter D1 of the mouth body 12 described above, or it may be the same as the outer diameter D1 of the mouth body 12.

[0027] The inner diameter D4 of the large diameter section 21 may be the same as, or smaller than, the inner diameter D2 of the mouth body 12 described above. The inner diameter D4 of the large diameter section 21 may be 15 mm or more, 17 mm or more, or 20 mm or more. The inner diameter D4 of the large diameter section 21 may be 28 mm or less, 26 mm or less, or 24 mm or less. The thickness T1 of the large diameter section 21 may be uniform throughout the height direction of the large diameter section 21, or it may vary. The thickness T1 of the large diameter section 21 may be 1.4 mm or more, 1.7 mm or more, or 1.9 mm or more. The thickness T1 of the large diameter section 21 may be 2.7 mm or less, 2.5 mm or less, or 2.3 mm or less. The large diameter section 21 may be the thinnest part of the body section 20 and the bottom section 30.

[0028] The reduced-diameter section 22 is connected to the lower part of the large-diameter section 21 and has a shape that gradually reduces in diameter from the large-diameter section 21 side to the small-diameter section 23 side. The reduced-diameter section 22 is a roughly frustoconical cylindrical shape and has an outer surface 22a and an inner surface 22b. A third boundary section 28 exists at the boundary between the large-diameter section 21 and the reduced-diameter section 22. The third boundary section 28 is a point in the vertical cross-section where the angle between the inner surface 21b of the large-diameter section 21 and the inner surface 22b of the reduced-diameter section 22, and the angle between the outer surface 21a of the large-diameter section 21 and the outer surface 22a of the reduced-diameter section 22 change significantly. In other words, the third boundary 28 refers to the point in the vertical cross-section (Figure 2) where the radius of curvature is minimized between the inner surface 21b of the large-diameter portion 21 and the inner surface 22b of the reduced-diameter portion 22, and where the radius of curvature is minimized between the outer surface 21a of the large-diameter portion 21 and the outer surface 22a of the reduced-diameter portion 22. If the point where the angle between the inner surface 21b of the large-diameter portion 21 and the inner surface 22b of the reduced-diameter portion 22 changes significantly, and the point where the angle between the outer surface 21a of the large-diameter portion 21 and the outer surface 22a of the reduced-diameter portion 22 changes significantly, are offset in the height direction, the third boundary 28 refers to the point of these points that is closer to the mouth portion 11.

[0029] The height-direction length L3 of the reduced diameter portion 22 may be, for example, 6.4 mm or more, 7.4 mm or more, or 8.3 mm or more. The height-direction length L3 of the reduced diameter portion 22 may be 15.0 mm or less, 13.0 mm or less, or 10.1 mm or less. The horizontal cross-section of the reduced diameter portion 22 may be annular in shape over the entire height direction. The outer surface 22a of the reduced diameter portion 22 has an outer diameter D5 that changes along the height direction, and the inner surface 22b of the reduced diameter portion 22 has an inner diameter D6 that changes along the height direction. The outer diameter D5 and inner diameter D6 of the reduced diameter portion 22 gradually narrow from the large diameter portion 21 side to the small diameter portion 23 side.

[0030] The outer surface 22a and inner surface 22b of the reduced diameter portion 22 are inclined with respect to the central axis CL of the preform 10. In a vertical cross-section, the average value of the angle θ1 at which the outer surface 22a of the reduced diameter portion 22 is inclined with respect to the central axis CL may be 1° or more, 10° or more, or 19° or more. The average value of the angle θ1 at which the outer surface 22a of the reduced diameter portion 22 is inclined with respect to the central axis CL may be 38° or less, 34° or less, or 24° or less. Here, the average value of angle θ1 is the average angle at which the outer surface 22a of the reduced diameter portion 22 is inclined with respect to the central axis CL, where θ1 = Tan -1 It can be calculated using {(D3-D7) / (2×L3)}(°).

[0031] The average value of the angle θ2 at which the inner surface 22b of the reduced diameter portion 22 is inclined with respect to the central axis CL may be 7° or more, 15° or more, or 22° or more. The average value of the angle θ2 at which the inner surface 22b of the reduced diameter portion 22 is inclined with respect to the central axis CL may be 36° or less, 32° or less, or 28° or less. Here, the average value of angle θ2 is the average angle at which the inner surface 22b of the reduced diameter portion 22 is inclined with respect to the central axis CL, where θ2 = Tan -1 It can be calculated using {(D4-D8) / (2×L3)}(°).

[0032] The thickness T2 of the reduced diameter portion 22 changes from the large diameter portion 21 (third boundary portion 28) side to the small diameter portion 23 (second boundary portion 27, described later) side. The thickness T2 of the reduced diameter portion 22 refers to the distance between the outer surface 22a and the inner surface 22b when the reduced diameter portion 22 is measured in a direction perpendicular to the central axis CL. The thickness T2 of the reduced diameter portion 22 is measured using a fully automatic measuring instrument (EH-8000, automatic preform thickness measuring device, manufactured by Evic Co., Ltd.).

[0033] The thickness T3 of the reduced diameter portion 22 at the second boundary 27 is greater than the thickness T1 of the reduced diameter portion 22 at the third boundary 28. The thickness T3 of the reduced diameter portion 22 and the small diameter portion 23 at the second boundary 27 may be 1.9 mm or more, 2.1 mm or more, or 2.4 mm or more. The thickness T3 of the reduced diameter portion 22 and the small diameter portion 23 at the second boundary 27 may be 3.7 mm or less, 3.4 mm or less, or 3.1 mm or less.

[0034] The outer diameter D7 of the reduced diameter portion 22 and the small diameter portion 23 at the second boundary portion 27 may be 13 mm or more, 15 mm or more, or 17 mm or more. The outer diameter D7 of the reduced diameter portion 22 and the small diameter portion 23 at the second boundary portion 27 may be 24 mm or less, 22 mm or less, or 20 mm or less. The inner diameter D8 of the reduced diameter portion 22 and the small diameter portion 23 at the second boundary portion 27 may be 9 mm or more, 10 mm or more, or 11 mm or more. The inner diameter D8 of the reduced diameter portion 22 and the small diameter portion 23 at the second boundary portion 27 may be 20 mm or less, 17 mm or less, or 15 mm or less.

[0035] The small-diameter portion 23 is connected to the lower part of the reduced-diameter portion 22 and has an outer surface 23a and an inner surface 23b. A second boundary portion 27 exists at the boundary between the reduced-diameter portion 22 and the small-diameter portion 23. The second boundary portion 27 is a point in the vertical cross-section where the angle between the inner surface 22b of the reduced-diameter portion 22 and the inner surface 23b of the small-diameter portion 23, and the angle between the outer surface 22a of the reduced-diameter portion 22 and the outer surface 23a of the small-diameter portion 23 change significantly. In other words, the second boundary portion 27 is a point in the vertical cross-section (Figure 2) where the radius of curvature is minimized between the inner surface 22b of the reduced-diameter portion 22 and the inner surface 23b of the small-diameter portion 23, and where the radius of curvature is minimized between the outer surface 22a of the reduced-diameter portion 22 and the outer surface 23a of the small-diameter portion 23. If the location where the angle between the inner surface 22b of the reduced diameter portion 22 and the inner surface 23b of the small diameter portion 23 changes significantly, and the location where the angle between the outer surface 22a of the reduced diameter portion 22 and the outer surface 23a of the small diameter portion 23 changes significantly, are offset in the height direction, the second boundary portion 27 refers to the location that is closer to the bottom portion 30.

[0036] The height-direction length L4 of the small-diameter portion 23 may be, for example, 26 mm or more, 30 mm or more, or 34 mm or more. The height-direction length L4 of the small-diameter portion 23 may be 58 mm or less, 50 mm or less, or 42 mm or less. The outer surface 23a and inner surface 23b of the small-diameter portion 23 are inclined with respect to the central axis CL of the preform 10. In a vertical cross-section, the angle θ3 at which the outer surface 23a of the small-diameter portion 23 is inclined with respect to the central axis CL may be greater than 0°, 0.1° or more, or 0.2° or more. The angle θ3 at which the outer surface 23a of the small-diameter portion 23 is inclined with respect to the central axis CL may be 5° or less, 1° or less, or 0.7° or less. The angle θ3 at which the outer surface 23a of the small-diameter portion 23 is inclined may be an angle (so-called draft angle) provided to facilitate the removal of the preform 10 from the injection molding die when manufacturing the preform 10. The angle θ4 at which the inner surface 23b of the small diameter portion 23 is inclined with respect to the central axis CL may be greater than 0°, greater than or equal to 0.1°, or greater than or equal to 0.2°. The angle θ4 at which the inner surface 23b of the small diameter portion 23 is inclined with respect to the central axis CL may be 5° or less, greater than or equal to 1°, or greater than or equal to 0.7°. The angle θ4 may be the same as the angle θ3.

[0037] The horizontal cross-section of the small-diameter portion 23 is annular in shape throughout its entire height direction. The outer surface 23a of the small-diameter portion 23 has an outer diameter D9 that changes along the height direction. The inner surface 23b of the small-diameter portion 23 has an inner diameter D10 that changes along the height direction. The outer diameter D9 and inner diameter D10 of the small-diameter portion 23 gradually narrow from the reduced-diameter portion 22 side toward the bottom portion 30 side, respectively. In the vertical cross-section, the outer surface 23a of the small-diameter portion 23 is generally straight, but a part of the outer surface 23a of the small-diameter portion 23 may be curved. Similarly, in the vertical cross-section, the inner surface 23b of the small-diameter portion 23 is generally straight, but a part of the inner surface 23b of the small-diameter portion 23 may be curved.

[0038] The thickness T4 of the small diameter portion 23 is substantially uniform from the reduced diameter portion 22 (second boundary portion 27) side to the bottom portion 30 (first boundary portion 26) side. In other words, the thickness T4 of the small diameter portion 23, the thickness T3 at the second boundary portion 27, and the thickness T5 at the first boundary portion 26 are substantially the same (T3 ≈ T4 ≈ T5). The thickness T4 (≈ T3 ≈ T5) of the small diameter portion 23 may be 1.9 mm or more, 2.1 mm or more, or 2.4 mm or more. The thickness T4 (≈ T3 ≈ T5) of the small diameter portion 23 may be 3.7 mm or less, 3.4 mm or less, or 3.1 mm or less.

[0039] The outer diameter D11 of the small diameter portion 23 at the first boundary portion 26 may be 13 mm or more, 15 mm or more, or 17 mm or more. The outer diameter D11 of the small diameter portion 23 at the first boundary portion 26 may be 24 mm or less, 22 mm or less, or 20 mm or less. The inner diameter D12 of the small diameter portion 23 at the first boundary portion 26 may be, for example, 8 mm or more, 10 mm or more, or 11 mm or more. The inner diameter D12 of the small diameter portion 23 at the first boundary portion 26 may be 20 mm or less, 17 mm or less, or 15 mm or less.

[0040] Next, the cross-sectional areas of the large-diameter section 21, the reduced-diameter section 22, and the small-diameter section 23 will be described. Figure 3 is a graph showing a schematic of the change in cross-sectional area of ​​the large-diameter section 21, the reduced-diameter section 22, and the small-diameter section 23. In Figure 3, the horizontal axis is the distance Lx (mm) from the support ring 14 (see Figure 2), and represents the distance along the direction of the central axis CL of the preform 10. The vertical axis is the cross-sectional area of ​​the large-diameter section 21, the cross-sectional area of ​​the reduced-diameter section 22, and the cross-sectional area of ​​the small-diameter section 23 (mm). 2 The cross-sectional area of ​​the large diameter section 21, the reduced diameter section 22, and the small diameter section 23 (mm²) are shown. 2 These are the cross-sectional areas in a section along a direction perpendicular to the central axis CL of the preform 10.

[0041] As shown in Figure 3, the cross-sectional area of ​​the large-diameter portion 21 is approximately constant regardless of the distance Lx from the support ring 14. Similarly, the cross-sectional area of ​​the small-diameter portion 23 is approximately constant regardless of the distance Lx from the support ring 14. The cross-sectional area of ​​the small-diameter portion 23 is smaller than the cross-sectional area of ​​the large-diameter portion 21. On the other hand, the cross-sectional area of ​​the reduced-diameter portion 22 changes according to the distance Lx from the support ring 14.

[0042] In this embodiment, the reduced-diameter portion 22 has a minimum portion 20A in a cross-section along a direction perpendicular to the central axis CL of the preform 10, where the cross-sectional area is at its minimum, and a maximum portion 20B located closer to the bottom 30 than the minimum portion 20A, where the cross-sectional area is at its maximum. Specifically, as shown in Figure 3, the cross-sectional area of ​​the reduced-diameter portion 22 gradually decreases as it moves from the third boundary portion 28 toward the small-diameter portion 23. The cross-sectional area is at its minimum in the minimum portion 20A. Furthermore, the cross-sectional area of ​​the reduced-diameter portion 22 gradually increases as it moves from the minimum portion 20A toward the small-diameter portion 23. The cross-sectional area is at its maximum in the maximum portion 20B. The cross-sectional area of ​​the maximum portion 20B is the maximum value of the cross-sectional area of ​​the reduced-diameter portion 22. Furthermore, the cross-sectional area of ​​the reduced-diameter portion 22 gradually decreases as it moves from the maximum portion 20B toward the small-diameter portion 23.

[0043] The smallest portion 20A may be located within a region of 2.5 mm to 7.0 mm in the direction of the central axis CL from the boundary between the mouth portion 11 and the body portion 20 (the lower surface of the support ring 14), or within a region of 4.0 mm to 6.5 mm. By having the smallest portion 20A located within a region of 2.5 mm or more from the boundary between the mouth portion 11 and the body portion 20, and also within a region of 7.0 mm or less from the boundary between the mouth portion 11 and the body portion 20, the smallest portion 20A can be formed in the blow-molded plastic bottle 40 at a position corresponding to the boundary between the neck portion 44 and the shoulder portion 48, which will be described later. This prevents the thickness of the boundary between the neck portion 44 and the shoulder portion 48, which will be described later, from becoming too thick in the blow-molded plastic bottle 40. As a result, the weight of the plastic bottle 40 can be reduced.

[0044] The cross-sectional area in the minimum part 20A may be smaller than the cross-sectional area in the large-diameter part 21. Also, the cross-sectional area in the minimum part 20A may be larger than the cross-sectional area in the small-diameter part 23.

[0045] The cross-sectional area in the minimum part 20A is 125 mm 2 or more and 145 mm 2 or less. When the cross-sectional area in the minimum part 20A is 125 mm 2 or more, molten plastic can be easily flowed to the mouth part 11 when the preform 10 is injection-molded. Also, when the cross-sectional area in the minimum part 20A is 145 mm 2 or less, it is possible to suppress the thickness of the neck part 44 described later from becoming too thick, and it is possible to reduce the weight of the plastic bottle 40.

[0046] The maximum part 20B may be located within a region of 8 mm or more and 11 mm or less in the direction of the central axis CL from the boundary part (the lower surface of the support ring 14) between the mouth part 11 and the body part 20. Since the maximum part 20B is located within a region of 8 mm or more from the boundary part between the mouth part 11 and the body part 20, the maximum part 20B can be formed at a position corresponding to the vicinity of the boundary between the shoulder part 48 and the body part 42 described later in the plastic bottle 40 after blow molding. For this reason, it is possible to suppress the thickness in the vicinity of the boundary between the shoulder part 48 and the body part 42 described later from becoming too thin in the plastic bottle 40 after blow molding. Also, since the maximum part 20B is located within a region of 11 mm or less from the boundary part between the mouth part 11 and the body part 20, it is possible to suppress the body part 42 from becoming too thick in the plastic bottle 40 after blow molding.

[0047] As described above, the cross-sectional area of ​​the largest portion 20B is the maximum value of the cross-sectional area of ​​the reduced diameter portion 22. In this case, the cross-sectional area of ​​the largest portion 20B may be 1.05 times or more and 1.2 times or less than or equal to 1.1 times the cross-sectional area of ​​the smallest portion 20A. By having the cross-sectional area of ​​the largest portion 20B be 1.05 times or more the cross-sectional area of ​​the smallest portion 20A, it is possible to more effectively suppress the thickness of the plastic bottle 40 after blow molding from becoming too thin near the boundary between the shoulder portion 48 and the body portion 42, which will be described later. Also, by having the cross-sectional area of ​​the largest portion 20B be 1.2 times or less the cross-sectional area of ​​the smallest portion 20A, it is possible to more effectively suppress the thickness of the neck portion 44, which will be described later, from becoming too thick in the plastic bottle 40 after blow molding.

[0048] The cross-sectional area of ​​the largest portion 20B may be larger than the cross-sectional area of ​​the large diameter portion 21. The cross-sectional area of ​​the largest portion 20B may be larger than the cross-sectional area of ​​the small diameter portion 23.

[0049] The cross-sectional area at the largest section 20B is 150 mm². 2 174mm 2 The following is also acceptable: The cross-sectional area at the largest portion 20B is 150 mm². 2 As a result of the above, it is possible to prevent the thickness of the plastic bottle 40 after blow molding from becoming too thin near the boundary between the shoulder portion 48 and the torso portion 42, which will be described later. In addition, the cross-sectional area of ​​the largest portion 20B is 174 mm². 2 As described below, it is possible to prevent the thickness near the boundary between the shoulder portion 48 and the torso portion 42 from becoming too thick, thereby reducing the weight of the plastic bottle 40.

[0050] Referring again to Figure 2, the bottom portion 30 is connected to the lower part of the small diameter portion 23 and has an outer surface 30a and an inner surface 30b. A first boundary portion 26 exists at the boundary between the small diameter portion 23 and the bottom portion 30. The first boundary portion 26 is a point in the vertical cross-section where the angle between the inner surface 23b of the small diameter portion 23 and the inner surface 30b of the bottom portion 30, and the angle between the outer surface 23a of the small diameter portion 23 and the outer surface 30a of the bottom portion 30 change significantly. In other words, the first boundary portion 26 is a point in the vertical cross-section (Figure 2) where, on the way from the inner surface 23b of the small diameter portion 23 to the inner surface 30b of the bottom portion 30, the radius of curvature first becomes 100 mm or less, and where, on the way from the outer surface 23a of the small diameter portion 23 to the outer surface 30a of the bottom portion 30, the radius of curvature first becomes 100 mm or less. When the point where the angle between the inner surface 23b of the small diameter portion 23 and the inner surface 30b of the bottom portion 30 changes significantly, and the point where the angle between the outer surface 23a of the small diameter portion 23 and the outer surface 30a of the bottom portion 30 changes significantly, are offset in the height direction, the first boundary portion 26 refers to the point of these two that is closer to the opening portion 11.

[0051] The height L5 of the base 30 may be, for example, 6 mm or more, 7 mm or more, or 8 mm or more. The height L5 of the base 30 may be 12 mm or less, 11 mm or less, or 10 mm or less. The base 30 may be approximately hemispherical, approximately conical, or any other shape. If the base 30 is approximately hemispherical, in a vertical cross-section, the outer surface 30a of the base 30 is semicircular overall, but the outer surface 30a of the base 30 may also be curved, including a non-arc portion. Similarly, in a vertical cross-section, the inner surface 30b of the base 30 is semicircular overall, but a part of the inner surface 30b of the base 30 may also be curved, including a non-arc portion. In a vertical cross-section, the center O1 of the semicircle constituting the outer surface 30a of the base 30 lies on the central axis CL. Also, the center O2 of the semicircle constituting the inner surface 30b of the base 30 lies on the central axis CL. The center O2 of the semicircle constituting the inner surface 30b of the base 30 may be located at a different position from the center O1 of the semicircle constituting the outer surface 30a of the base 30. Furthermore, the horizontal cross-section of the base 30 is circular throughout its entire height.

[0052] The radius of curvature R1 of the semicircle constituting the outer surface 30a of the base 30 may be 6 mm or more, 7 mm or more, or 8 mm or more. The radius of curvature R1 of the semicircle constituting the outer surface 30a of the base 30 may be 12 mm or less, 11 mm or less, or 10 mm or less. The radius of curvature R2 of the semicircle constituting the inner surface 30b of the base 30 may be 4 mm or more, 5 mm or more, or 5.5 mm or more. The radius of curvature R2 of the semicircle constituting the inner surface 30b of the base 30 may be 10 mm or less, 8.5 mm or less, or 7.0 mm or less.

[0053] The thickness T6 of the bottom portion 30 gradually decreases from the body portion 20 (first boundary portion 26) towards the lowest part 31 of the bottom portion 30 (the part where the bottom portion 30 intersects with the central axis CL). In other words, the thickness T5 of the bottom portion 30 (small diameter portion 23) at the first boundary portion 26 is thicker than the thickness T7 of the bottom portion 30 at the lowest part 31. The thickness T5 at the first boundary portion 26 is the thickest part of the bottom portion 30.

[0054] The thickness T7 of the bottom 30 at the lowest part 31 may be 1.5 mm or more, 1.8 mm or more, or 2.0 mm or more. The thickness T7 of the bottom 30 at the lowest part 31 may be 2.9 mm or less, 2.7 mm or less, or 2.4 mm or less. The ratio of the thickness T7 of the bottom 30 at the lowest part 31 to the thickness T4 of the small diameter part 23 (T7 / T4) may be 0.5 or more, 0.6 or more, or 0.7 or more. The ratio of the thickness T7 of the bottom 30 at the lowest part 31 to the thickness T5 of the bottom 30 (small diameter part 23) at the first boundary part 26 (T7 / T4) may be 1.0 or less, 0.9 or less, or 0.85 or less. By setting the ratio of the thickness T7 of the bottom 30 at the lowest part 31 (T7 / T4) to 0.5 or more, the molten plastic flows more easily when the preform is manufactured by injection molding. By setting the above ratio to 1.0 or less, it is possible to prevent the preform 10 (plastic bottle 40) from becoming unnecessarily heavy, and the weight of the preform 10 (plastic bottle 40) can be reduced.

[0055] The thickness T7 of the lowermost portion 31 of the bottom 30 may be thicker than the thickness T1 of the large-diameter portion 21 and may also be thinner than the thickness T4 of the small-diameter portion 23. That is, the relationship T1 < T7 < T4 may hold.

[0056] The total length in the height direction of the body portion 20 and the bottom 30 (that is, the length in the height direction of the portion of the preform 10 below the support ring 14) is L6, and this total length L6 is the sum of the lengths L2, L3, L4, and L5 described above (L6 = L2 + L3 + L4 + L5). The total length L6 may be 41 mm or more, may be 47 mm or more, and may be 53 mm or more. The total length L6 may be 80 mm or less, may be 74 mm or less, and may be 65 mm or less. When the total length L6 is 41 mm or more, the longitudinal draw ratio when molding the plastic bottle 40 described later does not become too large, and it is possible to suppress the overdrawn state. Thereby, it is possible to suppress the occurrence of a defect called whitening in the heel portion 49 of the plastic bottle 40 and the reduction in the strength of the heel portion 49. When the total length L6 is 80 mm or less, when the mass of the preform 10 is constant, the thickness of the body portion 20 is less likely to become thin due to suppressing the total length L6. Therefore, it is possible to suppress the whitening of the body portion 42 when molding the plastic bottle 40. Further, since the total length L6 of the preform 10 is not too long, it is possible to suppress the reduction in the longitudinal draw or the disappearance of the longitudinal draw. Therefore, even if the plastic bottle 40 is a short and small bottle with a capacity of about 100 mL, it is easy to mold.

[0057] The overall length of the preform 10 is L7, and this overall length L7 is the sum of the above-described total length L6 and the length L1 (L7 = L1 + L6). The overall length L7 of the preform 10 may be 56 mm or more, may be 64 mm or more, and may be 72 mm or more. The overall length L7 of the preform 10 may be 104 mm or less, may be 96 mm or less, and may be 88 mm or less.

[0058] Let W1 be the mass (weight) of the mouth 11 of the preform 10, and W2 be the total mass of the body 20 and bottom 30. In this case, the mass W1 of the mouth 11 may be 3.0g or more, 3.5g or more, or 4.0g or more. The mass W1 of the mouth 11 may be 6.0g or less, 5.5g or less, or 5.0g or less. The total mass W2 of the body 20 and bottom 30 may be 5.0g or more, 7.5g or more, or 9.5g or more. The total mass W2 of the body 20 and bottom 30 may be 14.0g or less, 13.0g or less, or 12.0g or less. The total mass (W1 + W2) of the preform 10 may be 9.5g or more, 12.0g or more, or 13.5g or more. The total mass (W1 + W2) of preform 10 may be 20g or less, 18.5g or less, or 17.0g or less.

[0059] The main material of the preform 10 is preferably a thermoplastic resin, particularly PE (polyethylene), PP (polypropylene), PET (polyethylene terephthalate), or PEN (polyethylene naphthalate). It is also possible to use a plant-derived biomass plastic, such as PLA (polylactic acid). Alternatively, a resin blended from the above-mentioned resins may be used. Furthermore, the preform 10 can be formed as a multilayer molded preform with two or more layers. That is, by injection molding, for example, the intermediate layer may be made of a gas barrier resin (intermediate layer) such as MXD6, MXD6 + fatty acid salt, PGA (polyglycolic acid), EVOH (ethylene vinyl alcohol copolymer), or PEN (polyethylene naphthalate), and the preform 10 may consist of three or more layers.

[0060] Furthermore, the preform 10 may also contain virgin polyester or chemically recycled polyester (hereinafter also simply referred to as virgin polyester, etc.). Hereinafter, "virgin polyester" means polyester that has not undergone recycling treatment, i.e., unused polyester.In addition, as specified herein, "chemically recycled polyester" means polyester obtained by decomposing a polyester container to the monomer level and then repolymerizing it.

[0061] If the preform 10 contains virgin polyester or the like, the amount of virgin polyester or the like is preferably 20 parts by mass or more and 100 parts by mass or less, and more preferably 60 parts by mass or more and 90 parts by mass or less, based on 100 parts by mass of the total amount of resin material contained in the preform 10.

[0062] If the preform 10 contains virgin polyester, the virgin polyester may be selected from antimony-catalyzed polyester, manganese-catalyzed polyester, titanium-catalyzed polyester, aluminum-catalyzed polyester, lithium-catalyzed polyester, and germanium-catalyzed polyester. In this specification, for example, antimony-catalyzed polyester means polyester in which an antimony catalyst is used as a polymerization catalyst during the production of the polyester. Therefore, the polyesters listed above mean polyesters in which each respective catalyst is used as a polymerization catalyst.

[0063] Examples of antimony catalysts include antimony trioxide, antimony pentoxide, antimony acetate, triphenylantimony, and antimony glycol.

[0064] Examples of manganese catalysts include manganese fatty acid salts such as manganese acetate, manganese carbonate, manganese chloride, manganese acetylacetonate salts, and manganese hydroxide.

[0065] Examples of titanium catalysts include titanium alkoxides such as tetra-n-propyl titanate, tetra-i-propyl titanate, tetra-n-butyl titanate, tetra-n-butyl titanate tetramer, tetra-t-butyl titanate, tetracyclohexyl titanate, tetraphenyl titanate, and tetrabenzyl titanate; titanium oxides obtained by hydrolysis of titanium alkoxides; titanium acetate; titanium oxalate; titanium oxalate; potassium titanium oxalate; sodium titanium oxalate; potassium titanate; sodium titanate; titanium titanate-aluminum hydroxide mixtures; titanium chloride; titanium chloride-aluminum chloride mixtures; titanium bromide; titanium fluoride; potassium hexafluoritate; cobalt hexafluoritate; manganese hexafluoritate; ammonium hexafluoritate; and titanium acetylacetonate.

[0066] Examples of aluminum catalysts include aluminum trisacetylacetate, aluminum monoacetylacetonate bis(ethylacetoacetate), and ethylacetoacetate aluminum diisopropylate.

[0067] Examples of lithium catalysts include ethyllithium, propyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, and phenyllithium.

[0068] Examples of germanium catalysts include germanium dioxide, germanium tetroxide, germanium tetramethoxide, germanium tetraethoxide, germanium tetrapropoxide, germanium tetrabutoxide, germanium tetrapentoxide, and germanium tetrahexoxide.

[0069] In this embodiment, "polyester" means a copolymer of a dicarboxylic acid compound and a diol compound.

[0070] Examples of dicarboxylic acid compounds include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedionic acid, eicosanedionic acid, pimelic acid, azelaic acid, methylmalonic acid and ethylmalonic acid, adamantanedicarboxylic acid, norbornenedicarboxylic acid, cyclohexanedicarboxylic acid, decalindicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 5-sodium sulfisoisophthalic acid, phenylendanedicarboxylic acid, anthracenedicarboxylic acid, phenantradicarboxylic acid, 9,9'-bis(4-carboxyphenyl)fluorenic acid and their ester derivatives.

[0071] Examples of diol compounds include ethylene glycol, 1,2-propanediol, 1,3-propanediol, butanediol, 2-methyl-1,3-propanediol, hexanediol, neopentyl glycol, cyclohexanedimethanol, cyclohexanediethanol, decahydronaphthalenedimethanol, decahydronaphthalenediethanol, norbornanediethanol, norbornanediethanol, tricyclodecanedimethanol, tricyclodecaneethanol, tetracyclododecanedimethanol, tetracyclododecaneethanol, decalindiethanol, decalindiethanol, Examples include 5-methylol-5-ethyl-2-(1,1-dimethyl-2-hydroxyethyl)-1,3-dioxane, cyclohexanediol, bicyclohexyl-4,4'-diol, 2,2-bis(4-hydroxycyclohexylpropane), 2,2-bis(4-(2-hydroxyethoxy)cyclohexyl)propane, cyclopentanediol, 3-methyl-1,2-cyclopentadiol, 4-cyclopentene-1,3-diol, adamandiol, paraxylene glycol, bisphenol A, bisphenol S, styrene glycol, trimethylolpropane, and pentaerythritol.

[0072] Among polyesters, polyethylene terephthalate, which is a copolymer of terephthalic acid and ethylene glycol, or modified polyethylene terephthalate, to which copolymer monomers have been added, is preferred.

[0073] Furthermore, the polyester may be polyethylene terephthalate derived from biomass, or polyethylene terephthalate derived from fossil fuels. The biomass-derived polyethylene terephthalate may be polyethylene terephthalate in which the dicarboxylic acid compound is terephthalic acid derived from fossil fuels and the diol compound is ethylene glycol derived from biomass. In this way, by including biomass-derived polyethylene terephthalate in the preform 10, the environmental impact reduction of the plastic bottle 40 can be improved.

[0074] Within the limits that do not impair the properties of this embodiment, the polyester may contain monomers other than dicarboxylic acid compounds and diol compounds, but the content thereof is preferably 10 mol% or less, more preferably 5 mol% or less, and even more preferably 3 mol% or less, relative to the total constituent units.

[0075] Furthermore, the preform 10 may contain mechanically recycled polyester. In this case, the environmental impact reduction of the plastic bottle 40 can be improved. Hereinafter, "mechanically recycled polyester" refers to polyester obtained by sorting, crushing, and washing polyester containers to remove contaminants and foreign matter, obtaining flakes, and then further treating the flakes at high temperature and reduced pressure for a certain period of time to remove contaminants from inside the resin. The mechanically recycled polyester may contain two or more catalysts. In this case, the mechanically recycled polyester may contain, for example, two or more of the following: antimony catalyst polyester, manganese catalyst polyester, titanium catalyst polyester, aluminum catalyst polyester, lithium catalyst polyester, and germanium catalyst polyester.

[0076] If the preform 10 contains mechanically recycled polyester, the amount of mechanically recycled polyester is preferably 20 parts by mass or more and 100 parts by mass or less, and more preferably 60 parts by mass or more and 90 parts by mass or less, based on 100 parts by mass of the total amount of resin material contained in the preform 10.

[0077] Within the limits that do not impair the characteristics of this embodiment, the preform 10 may contain additives, such as oxygen absorbers, gas barrier resins (polyamides such as nylon 6, nylon 6,6 and polymetaxylylene adipamide (MXD6)), plasticizers, UV stabilizers, antioxidants, color inhibitors, matting agents, deodorants, flame retardants, weather-resistant agents, antistatic agents, yarn friction reducers, slip agents, mold release agents, antioxidants, ion exchangers, acetaldehyde absorbers (e.g., AA Scavengers from Color Matrix), and colorants.

[0078] Next, an example of a plastic bottle manufactured by biaxially stretched blow molding of such a preform 10 will be described with reference to Figure 4. It should be noted that the plastic bottle manufactured using the preform 10 described above is not limited to this example. For example, the plastic bottle may be a petaloid bottle. Furthermore, the plastic bottle 40 may be manufactured by various molding methods other than biaxially stretched blow molding, such as direct blow molding.

[0079] In Figure 4, the plastic bottle 40 comprises a mouth portion 41, a substantially cylindrical body portion 42, and a bottom portion 43. The body portion 42 is provided continuously below the mouth portion 41. The bottom portion 43 is provided continuously below the body portion 42. A neck portion 44 is located between the mouth portion 41 and the body portion 42. A shoulder portion 48 is located between the neck portion 44 and the body portion 42.

[0080] The outer circumference of the opening 41 is provided with a threaded portion 46 for screwing on a cap (not shown). The threaded portion 46 corresponds to the threaded portion 13 of the preform 10 described above. An annular support ring 47 protruding outward is provided on the outer circumference of the opening 41 below the threaded portion 46. The support ring 47 corresponds to the support ring 14 of the preform 10 described above.

[0081] As described above, the body portion 42 is substantially cylindrical. Multiple horizontal grooves 45 are formed in the body portion 42. In addition, multiple pressure-absorbing panel portions 42a are formed in the body portion 42, arranged along the circumferential direction. Each pressure-absorbing panel portion 42a is recessed inward and spaced apart from one another. Multiple horizontal ribs 42b are formed within each pressure-absorbing panel portion 42a.

[0082] The horizontal cross-section of the shoulder portion 48 is approximately circular, and the area of ​​the horizontal cross-section of the shoulder portion 48 gradually increases from the neck portion 44 side toward the torso portion 42 side. The shoulder portion 48 has a plurality of panel portions 48a arranged along the circumferential direction. Each of the panel portions 48a is arranged continuously with respect to the others.

[0083] The size of the plastic bottles 40 is not limited, and they can consist of bottles of any size. The full capacity of the plastic bottles 40 may be, for example, 100ml or more, 200ml or more, or 300ml or more. The full capacity of the plastic bottles 40 may be, for example, 1000ml or less, 700ml or less, or 530ml or less. Furthermore, the shape of the plastic bottles 40 is not limited to a shape in which the body 42 is approximately cylindrical, but the body 42 may be approximately polygonal, the diameter of the body 42 may change, or it may be any other shape.

[0084] Furthermore, the thickness of the shoulder portion 48 at a position 40 mm away from the support ring 47 (the area near the torso portion 42) may be, for example, 0.11 mm or more, 0.12 mm or more, or 0.13 mm or more. The thickness of the shoulder portion 48 at a position 40 mm away from the support ring 47 (the area near the torso portion 42) may be, for example, 0.22 mm or less, 0.18 mm or less, or 0.15 mm or less. By setting the thickness of the shoulder portion 48 at a position 40 mm away from the support ring 47 (the area near the torso portion 42) to 0.11 mm or more, a desired thickness can be obtained near the boundary between the shoulder portion 48 and the torso portion 42.

[0085] Next, a method for manufacturing a plastic bottle 40 using the preform 10 according to this embodiment will be described.

[0086] First, a preform 10, as shown in Figures 1 and 2, is prepared (Figure 5(a)). In this case, a thermoplastic resin pellet, such as polyethylene terephthalate (PET), is placed in an injection molding machine (not shown), where the pellet is heated, melted, and compressed. The pellet then becomes compressed molten plastic, which is injected and pressurized into an injection mold having an internal shape corresponding to the preform 10. After a predetermined time, the molten plastic cools and hardens in the injection mold, forming the preform 10. The injection mold is then separated, and the preform 10 shown in Figures 1 and 2 is removed from the injection mold. The preform 10 may also be manufactured by various molding methods other than injection molding, such as compression molding.

[0087] Next, the preform 10 is heated by the heating device 51 (Figure 5(b)). At this time, the preform 10 is heated evenly in the circumferential direction by the heating device 51 while rotating. The heating temperature of the preform 10 in the heating process may be, for example, 90°C to 130°C.

[0088] Next, the preform 10, heated by the heating device 51, is sent to the blow molding die 50 (Figure 5(c)).

[0089] The plastic bottle 40 is molded using a blow molding die 50. In this case, the blow molding die 50 includes a pair of body molds 50a and 50b that are separated from each other, and a bottom mold 50c (Figure 5(c)). In Figure 5(c), the pair of body molds 50a and 50b are separated from each other, and the bottom mold 50c is lowered. In this state, the preform 10 is inserted between the pair of body molds 50a and 50b.

[0090] Next, as shown in Figure 5(d), after the bottom mold 50c rises, the pair of body molds 50a and 50b are closed, forming a blow molding die 50 that is sealed by the pair of body molds 50a and 50b and the bottom mold 50c. Next, a stretching rod (not shown) stretches the preform 10 downward, and then air is injected into the preform 10. In this way, biaxial stretch blow molding is performed on the preform 10.

[0091] As a result, a plastic bottle 40 is obtained from the preform 10 within the blow molding die 50. During this time, the body molds 50a and 50b are heated to 30°C to 80°C, and the bottom mold 50c is cooled to 5°C to 25°C. At this time, the preform 10 is expanded within the blow molding die 50 and shaped to match the shape of the inner surface of the blow molding die 50.

[0092] Subsequently, as shown in Figure 5(e), the pair of body molds 50a, 50b and bottom mold 50c separate from each other, and the plastic bottle 40 is removed from inside the blow molding mold 50. In this way, the plastic bottle 40 shown in Figure 4 is obtained.

[0093] As described above, according to this embodiment, the reduced diameter portion 22 has a minimum portion 20A in a cross-section along a direction perpendicular to the central axis CL of the preform 10, where the cross-sectional area is at its minimum, and a maximum portion 20B located closer to the bottom portion 30 than the minimum portion 20A, where the cross-sectional area is at its maximum. Furthermore, the cross-sectional area of ​​the maximum portion 20B is the maximum value of the cross-sectional area of ​​the reduced diameter portion 22. This makes it possible to reduce the weight of the plastic bottle 40 and to increase the thickness of the shoulder portion 48 of the plastic bottle 40 near the boundary with the body portion 42 after blow molding. The fact that this makes it possible to reduce the weight of the plastic bottle 40 and to increase the thickness of the shoulder portion 48 of the plastic bottle 40 near the boundary with the body portion 42 after blow molding will be explained in the embodiments described later.

[0094] Incidentally, for the sake of compatibility with manufacturing equipment such as blow molding machines and filling machines, as well as with caps, the mouth and neck portions of preforms have similar shapes and dimensions across various preforms. This can make it difficult to freely set the dimensions near the neck of the preform. As a result, the diameter of the shoulder portion of the plastic bottle near the neck (hereinafter also referred to as the lower neck portion) is usually smaller. Consequently, when biaxial stretch blow molding is performed on the preform, the amount of radial stretch (stretch ratio) in the lower neck portion is small. Therefore, the lower neck portion tends to be thicker.

[0095] On the other hand, the length, diameter, and thickness of the preform's body can be freely set to match the plastic bottle being manufactured. Therefore, when reducing the weight of the preform, the diameter of the central part of the preform's body is usually smaller than the diameter of the neck, and the thickness is also reduced. As a result, in general, the cross-sectional area of ​​the central part of the body is smaller than the cross-sectional area of ​​the neck in a horizontal cross-section. Therefore, the amount of elongation of the neck is relatively small, and the lower part of the neck of a plastic bottle made from a particularly lightweight preform tends to be thicker.

[0096] Thus, when the thickness of the neck portion of a plastic bottle increases, the amount of plastic material forming the neck portion increases. Consequently, the amount of plastic material forming the body decreases, resulting in a thinner body. Furthermore, when the neck portion is thicker, the amount of shrinkage of the plastic after blow molding increases. As a result, the height of the plastic decreases. In addition, there is a possibility that the plastic will shrink unevenly, and if the plastic shrinks unevenly, so-called neck bending may occur.

[0097] To prevent the neck area from becoming too thick, there are methods such as concentrating the heating of the neck area of ​​the preform during biaxial stretch blow molding, and stretching the preform significantly in the longitudinal direction using a stretching rod during blow molding. However, these methods tend to result in problems such as the thickness of the shoulder area of ​​the plastic bottle near the boundary with the body becoming too thin.

[0098] According to this embodiment, as described above, the reduced diameter portion 22 has a minimum portion 20A in a cross-section along a direction perpendicular to the central axis CL of the preform 10, where the cross-sectional area is at its minimum, and a maximum portion 20B located closer to the bottom portion 30 than the minimum portion 20A, where the cross-sectional area is at its maximum. Furthermore, the cross-sectional area of ​​the maximum portion 20B is the maximum value of the cross-sectional area of ​​the reduced diameter portion 22. This makes it possible to reduce the weight of the plastic bottle 40, and after blow molding, the thickness of the shoulder portion 48 of the plastic bottle 40 near the boundary with the body portion 42 can be increased.

[0099] [Examples] Next, specific examples of each of the above embodiments will be described.

[0100] Polyethylene terephthalate preforms with the configurations shown in Figures 1 and 2 were prepared as Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3. The weight and dimensions of each preform were as shown in Table 1 below.

[0101] [Table 1]

[0102] [Distribution of cross-sectional area] The cross-sectional areas of the five types of preforms described above (Examples 1-2, Comparative Examples 1-3) were measured and graphed. This graph is shown in Figure 6. In Figure 6, the horizontal axis represents the distance from the support ring (mm), and indicates the distance along the direction of the central axis of the preform. The vertical axis represents the cross-sectional areas (mm) of the large diameter section, the reduced diameter section, and the small diameter section. 2 ) indicates.

[0103] As shown in Figure 6, the preforms of Examples 1-2 each had a minimum portion in the reduced diameter section where the cross-sectional area was smallest, and a maximum portion located further down than the minimum portion where the cross-sectional area was largest. Furthermore, in the preforms of Examples 1-2, the cross-sectional area of ​​the maximum portion was equal to the maximum cross-sectional area of ​​the reduced diameter section. On the other hand, the preform of Comparative Example 1-2 did not have a minimum portion in the reduced diameter section. Also, in the preform of Comparative Example 3, the maximum portion was not equal to the maximum cross-sectional area of ​​the reduced diameter section. The cross-sectional area of ​​the reduced diameter section (mm²) relative to the distance from the support ring for the preforms of Examples 1-2 and Comparative Examples 1-3. 2 The results were as shown in Table 2 below.

[0104] [Table 2]

[0105] [evaluation] The plastic bottles shown in Figure 4 were produced by blow molding each of the five types of preforms described above (Examples 1-2, Comparative Examples 1-3). Blow molding was performed using a single-cavity blow molding machine (LB01, manufactured by KHS Corpoplast, Germany). The preforms were heated to 115°C. The plastic bottles were manufactured so that the total weight of the mouth, neck, and shoulder was 7.7g ± 0.1g. The height of the plastic bottles was 205.58mm, the maximum body diameter was 68mm, and the full capacity was 520ml.

[0106] Next, for plastic bottles made from five types of preforms (Examples 1-2, Comparative Examples 1-3), the thickness of the shoulder area was measured at seven locations, from 7 mm to 41 mm from the support ring. The 7 mm location was near the boundary between the neck and shoulder areas, and the 41 mm location was near the boundary between the shoulder and torso areas. The thickness was measured at two locations: the parting line and the opposite direction. The average of these measurements was then calculated. Furthermore, two plastic bottles were made from each preform, and the average of these four values ​​was calculated. These results are shown in Figure 7 and Table 3.

[0107] [Table 3]

[0108] As shown in Figure 7 and Table 3, the plastic bottle of Example 1-2 had a thinner shoulder area (below the neck) at a distance of 7mm to 11mm from the support ring. Furthermore, the plastic bottle of Example 1-2 had a thicker shoulder area (near the boundary between the shoulder and body) at a distance of 41mm from the support ring. In contrast, the plastic bottle of Comparative Example 1-3 had a thicker shoulder area (below the neck) at a distance of 7mm to 11mm from the support ring. Also, the plastic bottle of Comparative Example 1-3 had a thicker shoulder area (near the boundary between the shoulder and body) at a distance of 41mm from the support ring. Therefore, according to this embodiment, it was found that even when the weight of the preform is reduced to 16g or less, the thickness of the shoulder area near the boundary with the body of the plastic bottle can be increased after blow molding. In other words, according to this embodiment, it was found that the weight of the plastic bottle can be reduced, and the thickness of the shoulder area near the boundary with the body of the plastic bottle can be increased. [Explanation of Symbols]

[0109] 10 preforms 11 Mouth 20 Torso 21 Large diameter section 22 Reduced diameter part 20A Minimum part 20B Maximum part 23 Small diameter section 30 bottom 40 plastic bottles

Claims

1. In preforms, The mouth and, The body portion connected to the mouth portion, The body comprises a bottom connected to the aforementioned body, The body portion has a large diameter portion located on the mouth side, a small diameter portion located on the bottom side, and a reduced diameter portion located between the large diameter portion and the small diameter portion, which decreases in diameter from the large diameter portion side toward the small diameter portion side. The reduced diameter portion has, in a cross-section along a direction perpendicular to the central axis of the preform, a minimum portion where the cross-sectional area is at its minimum value, and a maximum portion located closer to the bottom than the minimum portion where the cross-sectional area is at its maximum value. A preform in which the cross-sectional area of ​​the maximum portion is equal to the maximum cross-sectional area of ​​the reduced diameter portion.

2. The preform according to claim 1, wherein the minimum portion is located within a region of 2.5 mm to 7.0 mm in the direction of the central axis from the boundary between the mouth portion and the body portion.

3. The preform according to claim 1, wherein the maximum portion is located within a region of 8 mm to 11 mm in the direction of the central axis from the boundary between the mouth portion and the body portion.

4. The preform according to claim 1, wherein the cross-sectional area in the maximum portion is 1.05 times or more and 1.2 times or less the cross-sectional area in the minimum portion.

5. The cross-sectional area at the maximum portion is 150 mm². ２ 174mm ２ The following is true, and the cross-sectional area at the minimum portion is 125 mm². ２ 145mm or more ２ The preform according to claim 1, which is as follows:

6. The preform according to claim 5, wherein the cross-sectional area in the maximum portion is larger than the cross-sectional area in the large diameter portion.

7. In a method for manufacturing plastic bottles, A step of preparing a preform according to any one of claims 1 to 6, The process of heating the preform, A method for manufacturing a plastic bottle, comprising the step of applying biaxial stretch blow molding to the preform.

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