Preform and method for manufacturing plastic bottle

Abstract

To provide a preform and a method for manufacturing a plastic bottle which achieve reduction in weight, and can increase thickness in a region adjacent to a trunk part in a shoulder part of the plastic bottle.SOLUTION: A preform 10 includes: a mouth part 11; a trunk part 20 connected to the mouth part 11; and a bottom part 30 connected to the trunk part 20. The trunk part 20 has: a large diameter part 21 positioned on the mouth part 11 side; a small diameter part 23 positioned on the bottom part 30 side; and a reduced-diameter part 22 which is positioned between the large diameter part 21 and the small diameter part 23, and reduces a diameter thereof toward the small diameter part 23 side from the large diameter part 21 side. Thickness T2 of the reduced-diameter part 22 increases gradually over an entire area of the reduced-diameter part 22 to the small-diameter part 23 side from the large-diameter part 21 side.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to methods of manufacturing preforms and plastic bottles. [Background technology]

[0002] Conventionally, plastic bottles have been produced by biaxially stretching and blow molding a polyethylene terephthalate preform produced by, for example, an injection molding method. In recent years, there has been a demand for reducing the amount of plastic material used in the bottle and making the plastic bottle lighter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-13664 A Summary of the Invention [Problem to be solved by the invention]

[0004] If the thickness of a conventional preform is uniformly thinned, when a plastic bottle is produced by blow molding, the area of ​​the shoulder of the plastic bottle near the body becomes too thin, which may cause a phenomenon called whitening and bursting. On the other hand, if the entire shoulder of the plastic bottle is made thicker in order to prevent such whitening and bursting, the shoulder of the plastic bottle near the neck also becomes thick, which may prevent this part from being stretched sufficiently.

[0005] The present disclosure provides a method for manufacturing a preform and a plastic bottle that can achieve weight reduction and increase the thickness of the area of ​​the shoulder of the plastic bottle near the body. [Means for solving the problem]

[0006] The embodiments of the present disclosure relate to the following [1] to [9].

[0007] [1] A preform comprising: a mouth portion, a body portion connected to the mouth portion, and a bottom portion connected to the body portion, wherein the body portion has a large diameter portion located on the mouth portion side, a small diameter portion located on the bottom portion side, and a tapered diameter portion located between the large diameter portion and the small diameter portion and tapering in diameter from the large diameter portion side to the small diameter portion side, wherein the thickness of the tapered diameter portion increases over the entire area of ​​the tapered diameter portion from the large diameter portion side to the small diameter portion side.

[0008] [2] The preform according to [1], wherein the large diameter portion is the thinnest part of the body portion and the bottom portion.

[0009] [3] The preform according to [1] or [2], wherein the thickness of the lowest part of the bottom portion is thicker than the thickness of the large diameter portion and thinner than the thickness of the small diameter portion.

[0010] [4] A preform comprising: a mouth portion having a support ring; a body portion connected to the mouth portion; and a bottom portion connected to the body portion, wherein the body portion has a large diameter portion located on the mouth portion side, a small diameter portion located on the bottom portion side, and a tapered portion located between the large diameter portion and the small diameter portion and tapering in diameter from the large diameter portion side to the small diameter portion side, wherein the maximum value of the gradient of the thickness of the tapered portion based on the distance from the support ring is 0.15 mm / mm or more and 0.30 mm / mm or less.

[0011] [5] The preform according to [4], wherein a first intermediate portion is present in the middle of the reduced diameter portion, and the thickness of the reduced diameter portion decreases from the large diameter portion side to the small diameter portion side between the large diameter portion and the first intermediate portion.

[0012] [6] The preform according to [5], wherein the first intermediate portion is the thinnest portion of the body portion.

[0013] [7] The preform according to [5] or [6], wherein a second intermediate portion is present in the middle of the reduced diameter portion, and the thickness of the reduced diameter portion increases from the large diameter portion side to the small diameter portion side between the first intermediate portion and the second intermediate portion.

[0014] [8] The preform according to [7], wherein the second intermediate portion is the thinnest portion of the body portion.

[0015] [9] A method for manufacturing a plastic bottle, comprising the steps of preparing a preform described in any one of [1] to [8], heating the preform, and biaxially stretch blow molding the preform. Effect of the Invention

[0016] According to this embodiment, it is possible to realize a reduction in weight and to increase the thickness of the shoulder portion of the plastic bottle in the region adjacent to the body portion. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a front view showing a preform according to a first embodiment. [Diagram 2] FIG. 2 is a vertical cross-sectional view (a cross-sectional view passing through the central axis of the preform) showing the preform according to the first embodiment. [Diagram 3] FIG. 3 is a graph showing an outline of changes in thickness of a large diameter portion, a reduced diameter portion, and a small diameter portion of the preform according to the first embodiment. [Figure 4] FIG. 4 is a front view showing a plastic bottle produced from a preform according to one embodiment. [Diagram 5] 5(a)-(e) are diagrams showing a method for manufacturing a plastic bottle according to a first embodiment. [Figure 6] FIG. 6 is a vertical cross-sectional view (cross-sectional view passing through the central axis of the preform) showing the preform according to the second embodiment. [Figure 7] FIG. 7 is a graph showing an outline of changes in thickness of a large diameter portion, a reduced diameter portion and a small diameter portion of the preform according to the second embodiment. [Figure 8] FIG. 8 is a vertical cross-sectional view (cross-sectional view passing through the central axis of the preform) showing the preform according to the second embodiment. [Figure 9] FIG. 9 is a vertical cross-sectional view (cross-sectional view passing through the central axis of the preform) showing the preform according to Example 4. [Figure 10] FIG. 10 is a graph showing the changes in thickness of the large diameter portion, the reduced diameter portion, and the small diameter portion of the preforms according to Examples 1 to 4 and Comparative Example 1. [Figure 11] FIG. 11 is a graph showing the change in thickness of the shoulder portion of plastic bottles molded from the preforms according to Examples 1 to 4 and Comparative Example 1. [Figure 12] FIG. 12 is a vertical cross-sectional view (cross-sectional view passing through the central axis of the preform) showing the preform according to Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] (First embodiment) A first embodiment will be described below with reference to the drawings. Figures 1 to 5 show the first embodiment.

[0019] In this specification, "upper" and "lower" refer to upper and lower, respectively, in a state in which the mouth 11 of the preform 10 faces vertically upward and the bottom 30 of the preform 10 faces vertically downward (FIGS. 1 and 2). In this specification, the "central axis CL" of the preform 10 refers to the central axis of a cylinder that constitutes the inner surface of the mouth 11 of the preform 10.

[0020] In this specification, the "height direction" refers to the direction along the central axis CL of the preform 10, and the "radial direction" refers to the direction perpendicular to the central axis CL of the preform 10. The "circumferential direction" refers to the circumferential direction of a circle centered on the central axis CL of the preform 10. The "horizontal cross section" refers to a cross section cut by a plane perpendicular to the central axis CL of the preform 10. The "vertical cross section" refers to a cross section cut by a plane including the central axis CL of the preform 10.

[0021] An outline of the preform according to this embodiment will be described with reference to Figs.

[0022] The preform 10 shown in FIG. 1 includes 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 contracted 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 contracted diameter portion 22 is located between the large diameter portion 21 and the small diameter portion 23. The contracted diameter portion 22 contracts in diameter from the large diameter portion 21 side toward the small diameter portion 23 side. The thickness T2 of the contracted diameter portion 22 increases throughout the entire area of ​​the contracted diameter portion 22 from the large diameter portion 21 side to the small diameter portion 23 side.

[0023] The mouth portion 11 has a cylindrical mouth portion body 12, a threaded portion 13 provided on the outer periphery of the mouth portion body 12, and a support ring 14 provided below the threaded portion 13. The mouth portion body 12 has an outer diameter D1 and an inner diameter D2.

[0024] 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.

[0025] The length L1 of the mouth 11 in the height direction may be, for example, 14 mm or more, 16 mm or more, or 18 mm or more. The length L1 of the mouth 11 in the height direction may be 28 mm or less, 25 mm or less, or 23 mm or less.

[0026] The screw portion 13 is for screwing a cap (not shown) onto the preform 10 after the preform 10 is biaxially stretched and blow molded to produce a plastic bottle 40 (see FIG. 4). The support ring 14 is provided below the mouth portion 11 and protrudes in an annular shape around the entire circumference. The body portion 20 is connected to the lower side of the support ring 14.

[0027] As described above, the body portion 20 has the large diameter portion 21, the small diameter portion 23, and the tapered diameter portion 22.

[0028] 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 length L2 in the height direction of the large diameter portion 21 may be, for example, 2.0 mm or more, 2.2 mm or more, or 2.5 mm or more. The length L2 in the height direction of the large diameter portion 21 may be 3.7 mm or less, 3.4 mm or less, or 3.1 mm or less.

[0029] The large diameter portion 21 is generally cylindrical 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 portion main body 12 described above, or may be the same as the outer diameter D1 of the mouth portion main body 12.

[0030] The inner diameter D4 of the large diameter portion 21 may be the same as the inner diameter D4 of the mouth body 12 described above. The inner diameter D4 of the large diameter portion 21 may be 15 mm or more, 17 mm or more, or 20 mm or more. The inner diameter D4 of the large diameter portion 21 may be 29 mm or less, 26 mm or less, or 24 mm or less. The thickness T1 of the large diameter portion 21 may be uniform throughout the height direction of the large diameter portion 21. The thickness T1 of the large diameter portion 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 portion 21 may be 2.7 mm or less, 2.5 mm or less, or 2.3 mm or less. The large diameter portion 21 may be the thinnest part of the body portion 20 and the bottom portion 30.

[0031] The reduced diameter portion 22 is connected to the lower part of the large diameter portion 21, and has a shape that gradually reduces in diameter from the large diameter portion 21 side toward the small diameter portion 23 side. The reduced diameter portion 22 is a cylindrical shape that is a substantially truncated cone, and has an outer surface 22a and an inner surface 22b. A third boundary portion 28 exists at the boundary between the large diameter portion 21 and the reduced diameter portion 22. The third boundary portion 28 is a point where, in a vertical cross section, the angle formed between the inner surface 21b of the large diameter portion 21 and the inner surface 22b of the reduced diameter portion 22, and the angle formed between the outer surface 21a of the large diameter portion 21 and the outer surface 22a of the reduced diameter portion 22 change significantly. In other words, third boundary 28 refers to a location where the radius of curvature is minimal between inner surface 21b of large diameter portion 21 and inner surface 22b of reduced diameter portion 22 in the vertical cross section ( FIG. 2 ), and a location where the radius of curvature is minimal between outer surface 21a of large diameter portion 21 and outer surface 22a of reduced diameter portion 22. When a location where the angle between inner surface 21b of large diameter portion 21 and inner surface 22b of reduced diameter portion 22 changes significantly and a location where the angle between outer surface 21a of large diameter portion 21 and outer surface 22a of reduced diameter portion 22 changes significantly are shifted in the height direction, third boundary 28 refers to the location that is closer to mouth 11 among these locations.

[0032] The length L3 in the height direction 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 length L3 in the height direction of the reduced diameter portion 22 may be 12.0 mm or less, 11.0 mm or less, or 10.1 mm or less. The horizontal cross section of the reduced diameter portion 22 may be circular throughout 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 the inner diameter D6 of the reduced diameter portion 22 are gradually narrowed from the large diameter portion 21 side to the small diameter portion 23 side.

[0033] The outer surface 22a and the inner surface 22b of the reduced diameter portion 22 are each 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 15° or more, 17° 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 28° or less, 26° or less, or 24° or less. Here, the average value of the 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, and θ1=Tan -1 It is calculated by {(D3-D7) / (2×L3)}(°).

[0034] 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 17° or more, 19° 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 33° or less, 30° or less, or 28° or less. Here, the average value of the 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, and θ2=Tan -1 It is calculated by {(D4-D8) / (2×L3)}(°).

[0035] The thickness T2 of the reduced diameter portion 22 increases throughout the entire area of ​​the reduced diameter portion 22 from the large diameter portion 21 (third boundary portion 28) side toward the small diameter portion 23 (second boundary portion 27 described later). That is, when the thickness of the reduced diameter portion 22 is measured at any two different points in the direction of the central axis CL in a vertical cross section, the thickness at the point on the small diameter portion 23 side is always greater than the thickness at the point on the large diameter portion 21 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 device (EH-8000, preform automatic thickness measuring device, manufactured by Ebic Co., Ltd.).

[0036] 3 is a graph showing an outline of the change in thickness of the large diameter portion 21, the reduced diameter portion 22, and the small diameter portion 23. In FIG. 3, the horizontal axis represents the distance L from the support ring 14.x The distance (mm) is shown along the direction of the central axis CL of the preform 10. The vertical axis shows the thickness T1 of the large diameter portion 21, the thickness T2 of the reduced diameter portion 22, and the thickness T3 (mm) of the small diameter portion 23.

[0037] As shown in FIG. 3, the thickness T1 of the large diameter portion 21 is a distance L x Similarly, the thickness T3 of the small diameter portion 23 is a substantially constant value regardless of the distance L from the support ring 14. x The thickness T3 of the small diameter portion 23 is thicker than the thickness T1 of the large diameter portion 21 (T3>T1). The thickness T2 of the reduced diameter portion 22 increases so as to become thicker over the entire range from the thickness T1 of the large diameter portion 21 to the thickness T3 of the small diameter portion 23. That is, the distance L x The gradient of the thickness T2 of the reduced diameter portion 22 based on x ) is a positive value over the entire range from the large diameter portion 21 side to the small diameter portion 23 side.

[0038] The inclination at the reduced diameter portion 22 (dT2 / dL x The maximum value (mm / mm) of the inclination (dT2 / dL x The maximum value (mm / mm) of the inclination (dT2 / dL x ) is maximized at the position P max Distance L from support ring 14 x L x =L2+αL3. In this case, α may be 0.2 or more, 0.3 or more, or 0.4 or more. α may be 0.9 or less, 0.8 or less, or 0.7 or less.

[0039] The inclination at the reduced diameter portion 22 (dT2 / dL x The minimum value (mm / mm) of the inclination (dT2 / dL xThe minimum value (mm / mm) of may be 0.06 or less, may be 0.04 or less, or may be 0.03 or less.

[0040] 2, thickness T3 of reduced diameter portion 22 at second boundary 27 is thicker than thickness T1 of reduced diameter portion 22 at third boundary 28. Thickness T3 of reduced diameter portion 22 and small diameter portion 23 at second boundary 27 may be 1.9 mm or more, 2.1 mm or more, or 2.4 mm or more. Thickness T3 of reduced diameter portion 22 and small diameter portion 23 at second boundary 27 may be 3.7 mm or less, 3.4 mm or less, or 3.1 mm or less.

[0041] The outer diameter D7 of the reduced diameter portion 22 and the small diameter portion 23 at the second boundary 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 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 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 27 may be 17 mm or less, 16 mm or less, or 15 mm or less.

[0042] The small diameter portion 23 is connected to the lower portion 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 portion where, in a vertical cross section, 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 refers to a portion where, in a vertical cross section (FIG. 2), the radius of curvature is minimal between the inner surface 22b of the reduced diameter portion 22 and the inner surface 23b of the small diameter portion 23, and a portion where the radius of curvature is minimal between the outer surface 22a of the reduced diameter portion 22 and the outer surface 23a of the small diameter portion 23. When the point 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 point 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 shifted in the vertical direction, the second boundary portion 27 refers to the point between these that is closer to the bottom 30.

[0043] The length L4 in the height direction of the small diameter portion 23 may be, for example, 26 mm or more, 30 mm or more, or 34 mm or more. The length L4 in the height direction of the small diameter portion 23 may be 49 mm or less, 45 mm or less, or 42 mm or less. The outer surface 23a and the inner surface 23b of the small diameter portion 23 are inclined with respect to the central axis CL of the preform 10. In the 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 more 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) provided to facilitate the removal of the preform 10 from the injection mold when the preform 10 is produced. 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°, may be 0.1° or more, or may be 0.2° or more. 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, 1° or less, or 0.7° or less. The angle θ4 may be the same as the angle θ3.

[0044] The horizontal cross section of the small diameter portion 23 is circular over the entire height direction. The outer surface 23a of the small diameter portion 23 has an outer diameter D9 that varies along the height direction. The inner surface 23b of the small diameter portion 23 has an inner diameter D 10 The small diameter portion 23 has an outer diameter D9 and an inner diameter D 10 gradually become thinner from the reduced diameter portion 22 side toward the bottom portion 30 side. 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.

[0045] The thickness T4 of the small diameter portion 23 is 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 the same as each other (T3=T4=T5). The thickness T4 of the small diameter portion 23 (=T3=T5) may be 1.9 mm or more, 2.1 mm or more, or 2.4 mm or more. The thickness T4 of the small diameter portion 23 (=T3=T5) may be 3.7 mm or less, 3.4 mm or less, or 3.1 mm or less.

[0046] The outer diameter D of the small diameter portion 23 at the first boundary portion 26 11 The outer diameter D of the small diameter portion 23 at the first boundary portion 26 may be 13 mm or more, 15 mm or more, or 16 mm or more. 11 The inner diameter D of the small diameter portion 23 at the first boundary portion 26 may be 24 mm or less, may be 22 mm or less, or may be 20 mm or less. 12 The inner diameter D 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. 12 may be 17 mm or less, may be 15 mm or less, or may be 14 mm or less.

[0047] The bottom 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 30. The first boundary portion 26 is a portion where, in a vertical cross section, the angle between the inner surface 23b of the small diameter portion 23 and the inner surface 30b of the bottom 30, and the angle between the outer surface 23a of the small diameter portion 23 and the outer surface 30a of the bottom 30 change significantly. In other words, the first boundary portion 26 refers to a portion where, in a vertical cross section (FIG. 2), the radius of curvature first becomes 100 mm or less on the way from the inner surface 23b of the small diameter portion 23 to the inner surface 30b of the bottom 30, and a portion where the radius of curvature first becomes 100 mm or less on the way from the outer surface 23a of the small diameter portion 23 to the outer surface 30a of the bottom 30. 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 shifted in the vertical direction, the first boundary portion 26 refers to the point between these that is closer to the mouth portion 11.

[0048] The length L5 in the height direction of the bottom 30 may be, for example, 6 mm or more, 7 mm or more, or 8 mm or more. The length L5 in the height direction of the bottom 30 may be 12 mm or less, 11 mm or less, or 10 mm or less. The bottom 30 is generally semispherical in shape. In a vertical cross section, the outer surface 30a of the bottom 30 is generally semicircular in shape, but the outer surface 30a of the bottom 30 may be a curved shape including a non-arc portion. Similarly, in a vertical cross section, the inner surface 30b of the bottom 30 is generally semicircular in shape, but a part of the inner surface 30b of the bottom 30 may be a curved shape including a non-arc portion. In a vertical cross section, the center O1 of the semicircle that constitutes the outer surface 30a of the bottom 30 exists on the central axis CL. In addition, the center O2 of the semicircle that constitutes the inner surface 30b of the bottom 30 exists on the central axis CL. The center O2 of the semicircle that constitutes the inner surface 30b of the bottom 30 may be located at the same position as the center O1 of the semicircle that constitutes the outer surface 30a of the bottom 30. In addition, the horizontal cross section of the bottom 30 is circular throughout the entire height direction.

[0049] The radius of curvature R1 of the semicircle constituting the outer surface 30a of the bottom 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 bottom 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 bottom 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 bottom 30 may be 9 mm or less, 8 mm or less, or 7.5 mm or less.

[0050] The ratio (R1 / R2) of the radius of curvature R1 to the radius of curvature R2 may be more than 1.0, may be 1.1 or more, or may be 1.2 or more. The ratio (R1 / R2) of the radius of curvature R1 to the radius of curvature R2 may be 1.9 or less, may be 1.7 or less, or may be 1.6 or less. By making the ratio 1.9 or less, the radius of curvature R2 of the semicircle constituting the inner surface 30b of the bottom portion 30 does not become too small, and the angle θ4 at which the inner surface 23b of the small diameter portion 23 inclines with respect to the central axis CL becomes too large, which makes it difficult to manufacture the preform 10 by the injection molding method. By making the ratio 1.0 or more, the radius of curvature R2 of the semicircle constituting the inner surface 30b of the bottom portion 30 does not become too large, and the thickness T5 of the small diameter portion 23 at the first boundary portion 26 is secured, which makes it difficult to manufacture the preform 10 by the injection molding method.

[0051] The thickness T6 of the bottom portion 30 gradually decreases from the body portion 20 (first boundary portion 26) side toward the lowest portion 31 of the bottom portion 30 (the portion where the bottom portion 30 intersects with the central axis CL). That is, 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 portion 31. The thickness T5 at the first boundary portion 26 is the thickest in the bottom portion 30.

[0052] The thickness T7 of the bottom portion 30 in the lowermost part 31 may be 1.5 mm or more, may be 1.8 mm or more, or may be 2.0 mm or more. The thickness T7 of the bottom portion 30 in the lowermost part 31 may be 2.9 mm or less, may be 2.7 mm or less, or may be 2.4 mm or less. The ratio (T7 / T5) of the thickness T7 of the bottom portion 30 in the lowermost part 31 to the thickness T5 of the bottom portion 30 (small-diameter portion 23) in the first boundary portion 26 may be 0.5 or more, may be 0.6 or more, or may be 0.7 or more. The ratio (T7 / T5) of the thickness T7 of the bottom portion 30 in the lowermost part 31 to the thickness T5 of the bottom portion 30 (small-diameter portion 23) in the first boundary portion 26 may be 1.0 or less, may be 0.9 or less, or may be 0.85 or less.

[0053] The thickness T7 of the bottom portion 30 in the lowermost part 31 may be thicker than the thickness T1 of the large-diameter portion 21, or may be thinner than the thickness T4 of the small-diameter portion 23. That is, the relationship of T1 < T7 < T4 may hold.

[0054] The total length in the height direction of the body 20 and the bottom 30 (i.e., the length in the height direction of the part of the preform 10 below the support ring 14) is L6, and this total length L6 is the sum of the above-mentioned lengths L2, L3, L4, and L5 (L6=L2+L3+L4+L5). The total length L6 may be 41 mm or more, 47 mm or more, or 53 mm or more. The total length L6 may be 77 mm or less, 71 mm or less, or 65 mm or less. By making the total length L6 41 mm or more, the longitudinal stretch ratio when molding the plastic bottle 40 described later is not too large, and it is possible to suppress overstretching. This makes it possible to suppress the occurrence of a defect called whitening in the heel portion 49 of the plastic bottle 40 and the decrease in the strength of the heel portion 49. By making the total length L6 77 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 by the amount of the reduction in the total length L6. This makes it possible to prevent the body portion 42 from whitening when the plastic bottle 40 is molded. In addition, since the total length L6 of the preform 10 is not too long, it is possible to prevent the longitudinal stretching from becoming small or from being completely stopped. Therefore, even if the plastic bottle 40 is a small, low-profile bottle with a capacity of about 100 mL, it is easy to mold it.

[0055] The total length of the preform 10 is L7, which is the sum of the total length L6 and the length L1 (L7=L1+L6). The total length L7 of the preform 10 may be 56 mm or more, 64 mm or more, or 72 mm or more. The total length L7 of the preform 10 may be 104 mm or less, 96 mm or less, or 88 mm or less.

[0056] The mass of the mouth 11 of the preform 10 is W1, and the total mass of the body 20 and the bottom 30 is W2. In this case, the mass W1 of the mouth 11 may be 3.0 g or more, 3.5 g or more, or 4.0 g or more. The mass W1 of the mouth 11 may be 6.0 g or less, 5.5 g or less, or 5.0 g or less. The total mass W2 of the body 20 and the bottom 30 may be 7.0 g or more, 8.5 g or more, or 9.5 g or more. The total mass W2 of the body 20 and the bottom 30 may be 14.0 g or less, 13.0 g or less, or 12.0 g or less. The total mass (W1+W2) of the preform 10 may be 10.5 g or more, 12.0 g or more, or 13.5 g or more. The total mass (W1+W2) of the preform 10 may be 20 g or less, 18.5 g or less, or 17.0 g or less.

[0057] As the main material of the preform 10, it is preferable to use a thermoplastic resin, particularly PE (polyethylene), PP (polypropylene), PET (polyethylene terephthalate), or PEN (polyethylene naphthalate). It is also possible to use a biomass-based plastic derived from plants, such as PLA (polylactic acid). Alternatively, a resin obtained by blending the above-mentioned various resins may be used. The preform 10 may also be formed as a multi-layer molded preform having two or more layers. That is, the preform 10 may be formed by injection molding as a preform having three or more layers, for example, with the intermediate layer being a resin (intermediate layer) having gas barrier properties, such as MXD6, MXD6 + fatty acid salt, PGA (polyglycolic acid), EVOH (ethylene vinyl alcohol copolymer), or PEN (polyethylene naphthalate).

[0058] The preform 10 may contain virgin polyester or chemically recycled polyester (hereinafter, simply referred to as virgin polyester, etc.). In this specification, "virgin polyester" refers to polyester that has not been subjected to a recycling process, that is, unused polyester. In addition, in this specification, "chemically recycled polyester" refers to polyester obtained by decomposing a polyester container to the monomer level and polymerizing it again.

[0059] When preform 10 contains virgin polyester, the content of virgin 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, per 100 parts by mass of the total amount of resin material contained in preform 10.

[0060] When the preform 10 includes 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 was used as a polymerization catalyst during the production of the polyester. Thus, the polyesters listed above mean polyesters in which each catalyst was used as a polymerization catalyst.

[0061] Examples of antimony catalysts include antimony trioxide, antimony pentoxide, antimony acetate, triphenylantimony, and antimony glycol.

[0062] Examples of the manganese catalyst include fatty acid manganese salts such as manganese acetate, manganese carbonate, manganese chloride, manganese acetylacetonate salts, and manganese hydroxide.

[0063] Examples of the titanium catalyst 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, potassium titanium oxalate, sodium titanium oxalate, potassium titanate, sodium titanate, titanic acid-aluminum hydroxide mixtures, titanium chloride, titanium chloride-aluminum chloride mixtures, titanium bromide, titanium fluoride, potassium hexafluorotitanate, cobalt hexafluorotitanate, manganese hexafluorotitanate, ammonium hexafluorotitanate, and titanium acetylacetonate.

[0064] Examples of aluminum catalysts include aluminum trisacetylacetate, aluminum monoacetylacetonate bis(ethylacetoacetate), and ethylacetoacetate aluminum diisopropylate.

[0065] Examples of the lithium catalyst include ethyllithium, propyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, and phenyllithium.

[0066] Examples of germanium catalysts include germanium dioxide, germanium tetroxide, germanium tetramethoxide, germanium tetraethoxide, germanium tetrapropoxide, germanium tetrabutoxide, germanium tetrapentoxide, and germanium tetrahexoxide.

[0067] In this embodiment, the term "polyester" refers to a copolymer of a dicarboxylic acid compound and a diol compound.

[0068] Examples of dicarboxylic acid compounds include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, eicosanedioic acid, pimelic acid, azelaic acid, methylmalonic acid, 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-sodiumsulfoisophthalic acid, phenylendanedicarboxylic acid, anthracenedicarboxylic acid, phenanthrenedicarboxylic acid, 9,9'-bis(4-carboxyphenyl)fluorene acid, and ester derivatives thereof.

[0069] Examples of the diol compound include ethylene glycol, 1,2-propanediol, 1,3-propanediol, butanediol, 2-methyl-1,3-propanediol, hexanediol, neopentyl glycol, cyclohexanedimethanol, cyclohexanediethanol, decahydronaphthalenedimethanol, decahydronaphthalenediethanol, norbornanedimethanol, norbornanediethanol, tricyclodecanedimethanol, tricyclodecaneethanol, tetracyclododecanedimethanol, tetracyclododecanediethanol, decalindimethanol, decalindiethanol, Examples of the copolymer 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, adamantanediol, paraxylene glycol, bisphenol A, bisphenol S, styrene glycol, trimethylolpropane, and pentaerythritol.

[0070] Among polyesters, polyethylene terephthalate, which is a copolymer of terephthalic acid and ethylene glycol, or modified polyethylene terephthalate in which a copolymerization monomer is added to this is preferred.

[0071] The polyester may be polyethylene terephthalate derived from biomass or may be polyethylene terephthalate derived from fossil fuel. The polyethylene terephthalate derived from biomass may be polyethylene terephthalate in which the dicarboxylic acid compound is terephthalic acid derived from fossil fuel and the diol compound is ethylene glycol derived from biomass. In this way, the preform 10 contains polyethylene terephthalate derived from biomass, thereby improving the environmental load reduction of the plastic bottle 40.

[0072] As long as the characteristics of the present embodiment are not impaired, the polyester may contain monomers other than the dicarboxylic acid compound and the diol compound, but the content thereof is preferably 10 mol % or less, more preferably 5 mol % or less, and even more preferably 3 mol % or less, based on the total structural units.

[0073] The preform 10 may also contain mechanically recycled polyester. In this case, the environmental load reduction of the plastic bottle 40 can be improved. In this specification, the term "mechanically recycled polyester" refers to polyester obtained by removing contaminants and foreign matter by sorting, crushing and washing polyester containers to obtain flakes, and further treating the flakes at high temperature and reduced pressure for a certain period of time to remove contaminants inside the resin. The mechanically recycled polyester may contain two or more catalysts. In this case, the mechanically recycled polyester may contain two or more of antimony catalyzed polyester, manganese catalyzed polyester, titanium catalyzed polyester, aluminum catalyzed polyester, lithium catalyzed polyester and germanium catalyzed polyester, for example.

[0074] When preform 10 contains mechanically recycled polyester, the content 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, per 100 parts by mass of the total amount of resin material contained in preform 10.

[0075] As long as the properties of the present embodiment are not impaired, 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, deodorizers, flame retardants, weather resistance agents, antistatic agents, thread friction reducers, slip agents, mold release agents, antioxidants, ion exchange agents, acetaldehyde absorbers (e.g., AA Scavengers manufactured by Color Matrix), and colorants.

[0076] Next, an example of a plastic bottle produced by biaxially stretching and blow molding such a preform 10 will be described with reference to Fig. 4. Of course, the plastic bottle produced using the above-mentioned preform 10 is not limited to this. For example, the plastic bottle may be a petaloid bottle. Furthermore, the plastic bottle 40 may be produced by various molding methods such as direct blow molding in addition to biaxially stretching and blow molding.

[0077] In Fig. 4, a plastic bottle 40 has a mouth 41, a substantially cylindrical body 42, and a bottom 43. The body 42 is provided below and continuous with the mouth 41. The bottom 43 is provided below and continuous with the body 42. A neck 44 is located between the mouth 41 and the body 42. A shoulder 48 is located between the neck 44 and the body 42.

[0078] A threaded portion 46 for screwing a cap (not shown) is provided on the outer periphery of the mouth portion 41. The threaded portion 46 corresponds to the threaded portion 13 of the preform 10 described above. An outwardly protruding annular support ring 47 is provided on the outer periphery of the mouth portion 41 below the threaded portion 46. The support ring 47 corresponds to the support ring 14 of the preform 10 described above.

[0079] As described above, the body 42 is substantially cylindrical. A plurality of horizontal grooves 45 are formed in the body 42. The horizontal cross section of the shoulder 48 is substantially circular, and the area of ​​the horizontal cross section of the shoulder 48 gradually increases from the neck 44 side toward the body 42 side.

[0080] A heel portion 49 is formed on the radially outer portion of the bottom portion 43. The heel portion 49 is provided annularly over the entire circumferential area of ​​the bottom portion 43. The heel portion 49 roughly corresponds to the first boundary portion 26 of the preform 10 described above, and is the portion of the bottom portion 43 that is stretched to be the thinnest during blow molding.

[0081] The size of such plastic bottle 40 is not limited, and the plastic bottle 40 may be of any size. The full capacity of the plastic bottle 40 may be, for example, 100 ml or more, 200 ml or more, or 300 ml or more. The full capacity of the plastic bottle 40 may be, for example, 600 ml or less, 550 ml or less, or 530 ml or less.

[0082] The thickness of the shoulder portion 48 in the vicinity of the neck portion 44 is greater than the thickness of the shoulder portion 48 in the vicinity of the body portion 42 .

[0083] Specifically, the thickness of shoulder portion 48 at a position 10 mm away from support ring 47 (the region adjacent to neck portion 44) may be, for example, 1.60 mm or more, 1.70 mm or more, or 1.80 mm or more. The thickness of shoulder portion 48 at a position 10 mm away from support ring 47 (the region adjacent to neck portion 44) may be, for example, 2.50 mm or less, 2.40 mm or less, or 2.20 mm or less.

[0084] Furthermore, the thickness of shoulder portion 48 at a position 20 mm away from support ring 47 (region adjacent to body portion 42) may be, for example, 1.00 mm or more, 1.02 mm or more, or 1.05 mm or more. The thickness of shoulder portion 48 at a position 20 mm away from support ring 47 (region adjacent to body portion 42) may be, for example, 1.20 mm or less, 1.17 mm or less, or 1.15 mm or less. By making the thickness of shoulder portion 48 at a position 20 mm away from support ring 47 (region adjacent to body portion 42) 1.00 mm or more, the region of shoulder portion 48 adjacent to body portion 42 can be prevented from being deformed.

[0085] Furthermore, the thickness of the heel portion 49 of the bottom 43 is not limited to this, but may be, for example, 0.07 mm or more, 0.08 mm or more, or 0.09 mm or more. The thickness of the heel portion 49 may be, for example, 0.30 mm or less, 0.25 mm or less, or 0.20 mm or less. By making the thickness of the heel portion 49 0.30 mm or less, the weight of the plastic bottle 40 can be reduced. On the other hand, by making the thickness of the heel portion 49 0.07 mm or more, it is possible to prevent the bottom 43 from popping out and becoming permanently deformed when the plastic bottle 40 is placed in a vending machine or dropped.

[0086] Next, a method for producing a plastic bottle 40 using the preform 10 according to this embodiment will be described.

[0087] First, the preform 10 shown in Figs. 1 and 2 is prepared (Fig. 5(a)). In this case, pellets made of a thermoplastic resin such as polyethylene terephthalate (PET) are put into an injection molding machine (not shown), which heats, melts, and pressurizes the pellets. The pellets then become pressurized molten plastic, which is injected into an injection molding die having an internal shape corresponding to the preform 10. After a predetermined time has passed, the molten plastic hardens in the injection molding die, forming the preform 10. The injection molding die is then separated, and the preform 10 shown in Figs. 1 and 2 is removed from the injection molding die. The preform 10 may be produced by various molding methods, such as compression molding, in addition to injection molding.

[0088] Next, the preform 10 is heated by a heating device 51 (FIG. 5(b)). At this time, the preform 10 is heated uniformly in the circumferential direction by the heating device 51 while rotating with the mouth portion 11 facing downward. The heating temperature of the preform 10 in the heating step may be, for example, 90°C to 130°C.

[0089] Next, the preform 10 heated by the heating device 51 is sent to the blow molding die 50 (FIG. 5(c)).

[0090] 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 dies 50a, 50b that are separated from each other, and a bottom die 50c (FIG. 5(c)). In FIG. 5(c), the pair of body dies 50a, 50b are open from each other, and the bottom die 50c is raised upward. In this state, the preform 10 is inserted between the pair of body dies 50a, 50b.

[0091] 5(d), after the bottom die 50c is lowered, the pair of body dies 50a, 50b are closed, and the pair of body dies 50a, 50b and the bottom die 50c form a sealed blow molding die 50. Next, air is forced into the preform 10, and the preform 10 is subjected to biaxial stretch blow molding.

[0092] As a result, a plastic bottle 40 is obtained from the preform 10 in the blow molding die 50. During this time, the body dies 50a, 50b are heated to 30°C to 80°C, and the bottom die 50c is cooled to 5°C to 25°C. At this time, the preform 10 is expanded in the blow molding die 50 and is shaped into a shape corresponding to the inner surface of the blow molding die 50.

[0093] 5(e), the pair of body molds 50a, 50b and the bottom mold 50c are separated from each other, and the plastic bottle 40 is removed from the blow molding mold 50. In this manner, the plastic bottle 40 shown in FIG. 4 is obtained.

[0094] As described above, according to this embodiment, thickness T2 of reduced diameter portion 22 increases throughout the entire reduced diameter portion 22, from the large diameter portion 21 side to the small diameter portion 23 side. This increases the thickness of the reduced diameter portion 22 in the region adjacent to small diameter portion 23, so that the region of shoulder portion 48 of plastic bottle 40 adjacent to body portion 42 can be made thicker after blow molding. As a result, whitening of shoulder portion 48 and a decrease in strength of shoulder portion 48 can be suppressed. In particular, thinning of shoulder portion 48 can be suppressed without increasing the mass of plastic bottle 40, so weight reduction of plastic bottle 40 is not hindered.

[0095] Furthermore, according to this embodiment, large diameter portion 21 may be the thinnest part of body portion 20 and bottom portion 30. By making large diameter portion 21 thin in this manner, the periphery of neck portion 44 of plastic bottle 40 can be sufficiently stretched during blow molding.

[0096] Furthermore, according to this embodiment, thickness T7 of bottommost portion 31 of bottom portion 30 may be thicker than thickness T1 of large diameter portion 21 and thinner than thickness T4 of small diameter portion 23. When large diameter portion 21 is thinned in this manner, the periphery of neck portion 44 of plastic bottle 40 can be sufficiently stretched during blow molding. Also, by thinning bottom portion 30 of preform 10, which is less likely to be stretched during molding of plastic bottle 40, it is possible to provide thickness to body portion 42 and heel portion 49, which are stretched, even for preforms 10 of the same weight. This allows preform 10 to be made lighter.

[0097] (Second embodiment) Next, a second embodiment will be described with reference to Figures 6 and 7. Figures 6 and 7 are diagrams showing the second embodiment. The second embodiment shown in Figures 6 and 7 differs mainly in the configuration of the reduced diameter section 22, and other configurations are substantially the same as those of the first embodiment described above. In Figures 6 and 7, the same parts as those in the first embodiment shown in Figures 1 to 5 are given the same reference numerals and detailed description will be omitted.

[0098] As shown in FIG. 6, the preform 10 according to this embodiment includes 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 contracted 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 contracted diameter portion 22 is located between the large diameter portion 21 and the small diameter portion 23. The contracted diameter portion 22 contracts in diameter from the large diameter portion 21 side toward the small diameter portion 23 side. The distance L from the support ring 14 x The gradient of the thickness T2 of the reduced diameter portion 22 based on x The maximum value of (mm / mm) is 0.15 or more and 0.30 or less.

[0099] In this embodiment, the thickness T2 of the reduced diameter portion 22 decreases from the large diameter portion 21 (third boundary portion 28) side toward the small diameter portion 23 (second boundary portion 27), then increases, and then decreases again. That is, as shown in FIG. 6, the first intermediate portion 22m and the second intermediate portion 22n are present in the middle of the reduced diameter portion 22. The thickness T2 of the reduced diameter portion 22 decreases from the large diameter portion 21 side toward the small diameter portion 23 side between the large diameter portion 21 (third boundary portion 28) and the first intermediate portion 22m. Furthermore, the thickness T2 of the reduced diameter portion 22 increases from the large diameter portion 21 side toward the small diameter portion 23 side between the first intermediate portion 22m and the second intermediate portion 22n. Furthermore, the thickness T2 of the reduced diameter portion 22 decreases from the large diameter portion 21 side toward the small diameter portion 23 side between the second intermediate portion 22n and the small diameter portion 23 (second boundary portion 27). The method for measuring the thickness T2 of the reduced diameter portion 22 is the same as in the first embodiment.

[0100] 7 is a graph showing an outline of the change in thickness of the large diameter portion 21, the reduced diameter portion 22, and the small diameter portion 23 in this embodiment. In FIG. 7, the horizontal axis represents the distance L from the support ring 14. x The distance (mm) is shown along the direction of the central axis CL of the preform 10. The vertical axis shows the thickness T1 of the large diameter portion 21, the thickness T2 of the reduced diameter portion 22, and the thickness T3 (mm) of the small diameter portion 23.

[0101] As shown in FIG. 7, the thickness T1 of the large diameter portion 21 is a distance L x Similarly, the thickness T3 of the small diameter portion 23 is a substantially constant value regardless of the distance L from the support ring 14. x The thickness T3 of the small diameter portion 23 is thicker than the thickness T1 of the large diameter portion 21 (T3>T1). The thickness T2 of the reduced diameter portion 22 decreases from the third boundary portion 28 to the first intermediate portion 22m, increases from the first intermediate portion 22m to the second intermediate portion 22n, and decreases from the second intermediate portion 22n to the second boundary portion 27. x The gradient of the thickness T2 of the reduced diameter portion 22 based on x ) is negative from the third boundary 28 to the first intermediate portion 22m, positive from the first intermediate portion 22m to the second intermediate portion 22n, and negative from the second intermediate portion 22n to the second boundary 27.

[0102] The inclination at the reduced diameter portion 22 (dT2 / dL x The maximum value (mm / mm) of the inclination (dT2 / dL x The maximum value (mm / mm) of the inclination (dT2 / dL x ) is maximized at the position P max Distance L from support ring 14 x L x =L2+βL3. In this case, β may be 0.2 or more, 0.3 or more, or 0.4 or more. β may be 0.9 or less, 0.8 or less, or 0.7 or less.

[0103] The inclination at the reduced diameter portion 22 (dT2 / dL x ) is 0 in the first intermediate portion 22m and the second intermediate portion 22n. The distance L x L x =L2+γL3. In this case, γ may be 0.05 or more, 0.10 or more, or 0.15 or more. γ may be 0.40 or less, 0.35 or less, or 0.30 or less. The distance L of the second intermediate portion 22n from the support ring 14 x L x =L2+δL3. In this case, δ may be 0.50 or more, 0.55 or more, or 0.60 or more. δ may be 0.90 or less, 0.85 or less, or 0.80 or less. Note that γ<β<δ.

[0104] The first intermediate portion 22m may be the thinnest portion of the body 20, or may be the thinnest portion of the body 20 and the bottom 30. The second intermediate portion 22n may be the thickest portion of the body 20, or may be the thickest portion of the body 20 and the bottom 30. The second intermediate portion 22n does not have to exist. In this case, the thickness T2 of the reduced diameter portion 22 may decrease from the third boundary portion 28 to the first intermediate portion 22m, and may increase continuously from the first intermediate portion 22m to the second boundary portion 27.

[0105] The configuration of the preform 10 other than the above may be substantially the same as the configuration of the preform 10 according to the first embodiment. Also, the manufacturing method of the plastic bottle 40 using the preform 10 according to this embodiment, and the plastic bottle 40 manufactured using the preform 10 according to this embodiment may be substantially the same as those in the first embodiment.

[0106] According to this embodiment, the distance L from the support ring 14 x The gradient of the thickness T2 of the reduced diameter portion 22 based on x ) (mm / mm) is 0.15 or more and 0.30 or less. This allows the thickness T2 of the reduced diameter portion 22 to be rapidly increased from the large diameter portion 21 side to the small diameter portion 23 side. This allows the thickness of the reduced diameter portion 22 in the region adjacent to the large diameter portion 21 to be reduced, so that the periphery of the neck portion 44 of the plastic bottle 40 can be sufficiently stretched. This allows the periphery of the neck portion 44 of the plastic bottle 40 (see FIG. 4) to be sufficiently stretched during blow molding. In addition, since the thickness of the reduced diameter portion 22 in the region adjacent to the small diameter portion 23 can be increased, the region of the shoulder portion 48 of the plastic bottle 40 adjacent to the body portion 42 can be increased. As a result, it is possible to prevent the shoulder portion 48 from whitening or the strength of the shoulder portion 48 from decreasing. In particular, it is possible to prevent the shoulder portion 48 from becoming thinner without increasing the mass of the plastic bottle 40, so that the weight reduction of the plastic bottle 40 is not hindered.

[0107] Furthermore, according to this embodiment, first intermediate portion 22m exists in the middle of reduced diameter portion 22, and thickness T2 of reduced diameter portion 22 decreases from large diameter portion 21 toward small diameter portion 23 between large diameter portion 21 and first intermediate portion 22m. First intermediate portion 22m may be the thinnest portion of body portion 20. This allows the periphery of neck portion 44 of plastic bottle 40 to be sufficiently stretched during blow molding.

[0108] Furthermore, according to this embodiment, the second intermediate portion 22n is present in the middle of the reduced diameter portion 22, and the thickness T2 of the reduced diameter portion 22 increases from the large diameter portion 21 side to the small diameter portion 23 side between the first intermediate portion 22m and the second intermediate portion 22n. The second intermediate portion 22n may be the thinnest part of the body portion 20. This allows the thickness of the reduced diameter portion 22 in the region adjacent to the small diameter portion 23 to be increased, and therefore the shoulder portion 48 of the plastic bottle 40 in the region adjacent to the body portion 42 can be increased in thickness. As a result, whitening of the shoulder portion 48 and a decrease in the strength of the shoulder portion 48 can be suppressed.

[0109] [Example] Next, specific examples of the above-mentioned embodiments will be described.

[0110] Example 1 A polyethylene terephthalate preform (Example 1) having the configuration shown in Figures 1 and 2 was produced. The thickness (T1) of the large diameter part of the preform was 2.07 mm, and the thickness (T3) of the reduced diameter part at the second boundary part was 2.83 mm. The length (L3) of the reduced diameter part in the height direction was 9.20 mm. In addition, the mass and dimensions of the preform of Example 1 were as shown in Table 1 below.

[0111] Example 2 A polyethylene terephthalate preform (Example 2) having the configuration shown in Figure 8 was produced. The thickness (T1) of the large diameter part of the preform was 2.07 mm, and the thickness (T3) of the reduced diameter part at the second boundary part was 2.78 mm. The length (L3) in the height direction of the reduced diameter part was 9.20 mm. In addition, the mass and dimensions of the preform of Example 2 were as shown in Table 1 below.

[0112] Example 3 A polyethylene terephthalate preform (Example 3) having the configuration shown in Figure 6 was produced. The thickness (T1) of the large diameter part of the preform was 2.07 mm, and the thickness (T3) of the reduced diameter part at the second boundary part was 2.76 mm. The length (L3) in the height direction of the reduced diameter part was 9.19 mm. In addition, the mass and dimensions of the preform of Example 3 were as shown in Table 1 below.

[0113] Example 4 A polyethylene terephthalate preform (Example 4) having the configuration shown in Figure 9 was produced. The thickness (T1) of the large diameter part of the preform was 2.07 mm, and the thickness (T3) of the reduced diameter part at the second boundary part was 2.68 mm. The length (L3) in the height direction of the reduced diameter part was 9.19 mm. In addition, the mass and dimensions of the preform of Example 4 were as shown in Table 1 below.

[0114] Comparative Example 1 A polyethylene terephthalate preform (Comparative Example 1) having the configuration shown in FIG. 12 was produced. The thickness (T1) of the large diameter portion of the preform was 2.07 mm, and the thickness (T3) of the reduced diameter portion at the second boundary portion was 2.68 mm. The length (L3) of the reduced diameter portion in the height direction was 9.19 mm. In addition, the mass and dimensions of the preform of Comparative Example 1 were as shown in Table 1 below.

[0115] [Table 1]

[0116] [Body thickness distribution] The thicknesses of the body portions of the above five types of preforms (Examples 1-4, Comparative Example 1) were measured and graphed. This graph is shown in Figure 10. In Figure 10, the horizontal axis indicates the distance (mm) from the support ring along the direction of the central axis of the preform, and the vertical axis indicates the thicknesses (mm) of the large diameter portion, the reduced diameter portion, and the small diameter portion.

[0117] As shown in FIG. 10, the thickness of the reduced diameter portion of each of the preforms of Examples 1 and 2 increased throughout the entire area of ​​the reduced diameter portion from the large diameter portion side to the small diameter portion side. In the preforms of Examples 3-4, the thickness of the reduced diameter portion decreased from the large diameter portion side, then gradually increased, and then decreased to the small diameter portion side. In the preforms of Comparative Example 1, the thickness of the reduced diameter portion decreased from the large diameter portion side, then gradually increased to the small diameter portion side. The maximum value of the gradient (mm / mm) of the thickness of the reduced diameter portion based on the distance from the support ring for the preforms of Examples 1-5 is as shown in Table 2 below.

[0118] [Table 2]

[0119] [evaluation] The above five types of preforms (Examples 1-4, Comparative Example 1) were blow molded to produce the plastic bottles shown in FIG. 4. The blow molding was performed using a single-cavity blow molding machine (LB01 manufactured by KHS Corpoplast, Germany). The heating temperature of the preforms was 116°C. The height of the plastic bottles was 207 mm, the maximum body diameter was 644 mm, and the full capacity was 530 ml.

[0120] Next, for plastic bottles made from five types of preforms (Examples 1-4, Comparative Example 1), the thickness of the shoulder was measured at six points at 2 mm intervals from a position 10 mm to a position 20 mm away from the support ring. The thickness was measured at two points, one at the parting line and the other in the opposite direction, and the average value was calculated. Two plastic bottles were also made for each type, and the average value of the four values ​​in total was calculated. The results are shown in FIG.

[0121] As shown in Fig. 11, the plastic bottle of Example 1-4 had a thicker shoulder in a region 20 mm away from the support ring (region near the body). In contrast, the plastic bottle of Comparative Example 1 had a thinner shoulder in a region 20 mm away from the support ring (region near the body). The plastic bottle of Example 3-4 had a thinner shoulder in a region 10 mm to 14 mm away from the support ring (region near the neck). [Explanation of symbols]

[0122] 10 Preform 11 Mouth 12 Mouth body 13 Threaded part 14 Support Ring 15 Opening 20 Torso 21 Large diameter section 22 Reduced diameter part 22m 1st intermediate section 22n 2nd middle part 23 Small diameter section 26 First Boundary 27 Second Boundary 28 Third Boundary 30 bottom 31 Bottom 40 Plastic Bottles

Claims

1. The mouth part, A body portion connected to the mouth portion; a bottom portion connected to the body portion, the body portion has a large diameter portion located on the mouth portion side, a small diameter portion located on the bottom portion side, and a reduced diameter portion located between the large diameter portion and the small diameter portion and reducing in diameter from the large diameter portion side toward the small diameter portion side, The preform, wherein the thickness of the reduced diameter portion increases throughout the reduced diameter portion from the large diameter portion side to the small diameter portion side.

2. The preform according to claim 1 , wherein the large diameter portion is a portion having the thinnest thickness among the body portion and the bottom portion.

3. The preform according to claim 1 , wherein a thickness of the lowermost part of the bottom portion is greater than a thickness of the large diameter portion and less than a thickness of the small diameter portion.

4. a mouth portion having a support ring; A body portion connected to the mouth portion; a bottom portion connected to the body portion, the body portion has a large diameter portion located on the mouth portion side, a small diameter portion located on the bottom portion side, and a reduced diameter portion located between the large diameter portion and the small diameter portion and reducing in diameter from the large diameter portion side toward the small diameter portion side, A preform, wherein a maximum value of a gradient of a thickness of the reduced diameter portion based on a distance from the support ring is 0.15 mm / mm or more and 0.30 mm / mm or less.

5. 5. The preform according to claim 4, wherein a first intermediate portion is present in the middle of the reduced diameter portion, and the thickness of the reduced diameter portion decreases from the large diameter portion side to the small diameter portion side between the large diameter portion and the first intermediate portion.

6. The preform according to claim 5 , wherein the first intermediate portion is a portion of the body portion that has the thinnest thickness.

7. 6. The preform according to claim 5, wherein a second intermediate portion is present in the middle of the reduced diameter portion, and the thickness of the reduced diameter portion increases from the large diameter portion side to the small diameter portion side between the first intermediate portion and the second intermediate portion.

8. The preform according to claim 7 , wherein the second intermediate portion is the thinnest portion of the body portion.

9. A method for manufacturing a plastic bottle, comprising: Providing a preform according to any one of claims 1 to 8; heating the preform; and biaxially stretching and blow molding the preform.

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