Preform and method for manufacturing plastic bottle

Abstract

To provide and a method for manufacturing a plastic bottle which can achieve high blow moldability in the upper side of a shoulder part of the plastic bottle, as well as, allow for stably conveying the preform.SOLUTION: There is provided a preform 10, a trunk part 20 of which has a large diameter part 21, a reduced-diameter part 22, and a small diameter part 23. The preform 10 satisfies an expression of average value of thickness T1 of the large diameter part 21≤average value of thickness T4 of the small diameter part 23, and a thin wall part 20A of the trunk part 20 exists in the reduced-diameter part 22.SELECTED DRAWING: Figure 2A

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 made uniformly thin, when a plastic bottle is produced by blow molding, the plastic material may not stretch sufficiently during blow molding in the shoulder area between the mouth and body of the plastic bottle, particularly in the upper part of the shoulder area, making it difficult to mold with precision.

[0005] On the other hand, the portion of the plastic bottle directly below the support ring is required to have a certain degree of thickness since this portion is gripped by the gripper when the preform is transported.

[0006] The present disclosure provides a method for manufacturing a preform and a plastic bottle that can achieve high blow moldability in the shoulder portion between the mouth and body of a plastic bottle, particularly the upper part of the shoulder portion, and that can transport the preform stably. [Means for solving the problem]

[0007] The embodiments of the present disclosure relate to the following [1] to [6].

[0008] [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 portion located between the large diameter portion and the small diameter portion and tapering in diameter from the large diameter portion to the small diameter portion, wherein, when the thickness of the large diameter portion is T1 and the thickness of the small diameter portion is T4, the average value of T1 is equal to or less than the average value of T4, and the thinnest portion of the body portion is present in the tapered diameter portion.

[0009] [2] The preform according to [1], wherein the thin-walled portion is present in the region of the reduced diameter portion on the large diameter portion side.

[0010] [3] The preform according to [1] or [2], wherein the length of the thin-walled portion is 10% to 60% of the length of the tapered portion.

[0011] [4] The preform according to [1] or [2], wherein when the thickness of the reduced diameter portion is T2, the average value of T2 is less than or equal to the average value of T4.

[0012] [5] The preform according to [1] or [2], wherein the outer diameter of the small diameter portion: the total length of the preform=0.26 to 0.30.

[0013] [6] A method for manufacturing a plastic bottle, comprising the steps of preparing a preform described in any one of [1] to [2], heating the preform, and biaxially stretch blow molding the preform. Effect of the Invention

[0014] According to this embodiment, the shoulder portion between the mouth and body of a plastic bottle, particularly the upper portion of the shoulder portion, can be blow molded with high precision, and the preform can be transported stably. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a front view showing a preform according to a first embodiment. [Figure 2A] FIG. 2A is a vertical cross-sectional view (cross-sectional view passing through the central axis of the preform) showing the preform according to the first embodiment. [Figure 2B] FIG. 2B 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. [Diagram 3] FIG. 3 is a front view showing a plastic bottle produced from the preform according to the first embodiment. [Figure 4] 4(a)-(e) are diagrams showing a manufacturing method for a plastic bottle according to the first embodiment. [Diagram 5] FIG. 5 is a diagram showing the wall thickness distribution of the preforms in the first and second embodiments. [Figure 6A] FIG. 6A is a graph showing the wall thickness distribution of the preforms in the first and second embodiments. [Figure 6B] FIG. 6B is a table showing the masses and dimensions of the preforms in the first and second embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] <First embodiment> The first embodiment will be described below with reference to the drawings, in which: Figures 1, 2A, and 3 to 6 show the first embodiment.

[0017] In this specification, "upper" and "lower" refer to the upper and lower sides 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 2A). 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.

[0018] 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.

[0019] The preform according to the first embodiment will be outlined with reference to Figs. 1 and 2A.

[0020] The preform 10 shown in FIG. 1 includes a mouth portion 11 having an opening 15, 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, 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 thinnest part of the body portion 20 and the bottom portion 30 is preferably the lowest portion 31 of the bottom portion 30. When the thickness of the lowest portion 31 of the bottom portion 30 is T7 and the thickness of the small diameter portion 23 of the body portion 20 is T4, T7 is an average value of about 0.8×T4. In this embodiment, the thickness of a given portion of the body 20 of the preform 10 refers to the distance between the outer surface and the inner surface of the given portion when measured along a direction perpendicular to the central axis CL. In this case, the thickness of the body 20 of the preform 10 is measured using a fully automatic measuring device (EH-8000, preform automatic thickness measuring device, manufactured by Ebic Co., Ltd.). The thickness of the bottom 30 refers to the distance between the outer surface and the inner surface along the normal direction of the outer surface.

[0021] 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.

[0022] The outer diameter D1 of the mouth body 12 may be 18 mm or more, 20 mm or more, or 22 mm or more. The outer diameter D1 of the mouth body 12 may be 33 mm or less, 30 mm or less, or 27 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 29 mm or less, 26 mm or less, or 24 mm or less.

[0023] 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.

[0024] 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. 3). 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.

[0025] As described above, the body portion 20 has the large diameter portion 21, the small diameter portion 23, and the tapered diameter portion 22.

[0026] 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, 2.2 mm or more, 2.5 mm or more, or 2.9 mm or more. The length L2 in the height direction of the large diameter portion 21 may be 4.5 mm or less, 4.1 mm or less, or 3.8 mm or less.

[0027] 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.

[0028] The inner diameter D4 of the large diameter portion 21 may be the same as the inner diameter D2 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 large diameter portion 21 has a thickness T1. The thickness T1 of the large diameter portion 21 may be 1.4 mm or more, 1.6 mm or more, or 1.8 mm or more. The thickness T1 of the large diameter portion 21 may be 2.6 mm or less, 2.4 mm or less, or 2.2 mm or less.

[0029] 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 approximately a 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. 2A ), 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.

[0030] The length L3 in the height direction of the reduced diameter portion 22 may be, for example, 6.7 mm or more, 7.4 mm or more, or 8.0 mm or more. The length L3 in the height direction of the reduced diameter portion 22 may be 11.0 mm or less, 10.3 mm or less, or 9.6 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.

[0031] The outer surface 22a and the inner surface 22b of the reduced diameter portion 22 are inclined with respect to the central axis CL of the preform 10. In the vertical cross section, 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 6° or more, 8° or more, or 10° or more. 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 22° or less, 20° or less, or 18° or less. 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 6° or more, 8° or more, or 10° or more. 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 22° or less, 20° or less, or 18° or less. The angle θ1 may be the same as the angle θ2.

[0032] The reduced diameter portion 22 has a thickness T2, which will be described later. The thickness T3 of the reduced diameter portion 22 at the second boundary portion 27 may be thinner, thicker, or the same as the thickness T1 of the reduced diameter portion 22 at the third boundary portion 28. The thickness T3 of the reduced diameter portion 22 and the small diameter portion 23 at the second boundary portion 27 may be 1.5 mm or more, 1.7 mm or more, or 1.9 mm or more. The thickness T3 of the reduced diameter portion 22 and the small diameter portion 23 at the second boundary portion 27 may be 3.0 mm or less, 2.7 mm or less, or 2.5 mm or less.

[0033] The outer diameter D7 of the reduced diameter portion 22 and the small diameter portion 23 at the second boundary 27 may be 15 mm or more, 18 mm or more, or 20 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 27 mm or less, 25 mm or less, or 24 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 15 mm or more, 16 mm or more, or 17 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 24 mm or less, 22 mm or less, or 20 mm or less.

[0034] 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.

[0035] The length L4 in the height direction of the small diameter portion 23 may be, for example, 23 mm or more, 27 mm or more, or 30 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 41 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.

[0036] 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.

[0037] 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 1.5 mm or more, 1.7 mm or more, or 1.9 mm or more. The thickness T4 of the small diameter portion 23 (=T3=T5) may be 3.0 mm or less, 2.7 mm or less, or 2.5 mm or less.

[0038] 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 15 mm or more, 18 mm or more, or 20 mm or more. 11 The inner diameter D of the small diameter portion 23 at the first boundary portion 26 may be 27 mm or less, may be 25 mm or less, or may be 24 mm or less. 12 The inner diameter D of the small diameter portion 23 at the first boundary portion 26 may be, for example, 15 mm or more, 16 mm or more, or 17 mm or more. 12 may be 24 mm or less, may be 22 mm or less, or may be 20 mm or less.

[0039] The bottom 30 is connected to the lower part of the small diameter part 23, and has an outer surface 30a and an inner surface 30b. A first boundary part 26 exists at the boundary between the small diameter part 23 and the bottom 30. The first boundary part 26 is a point where the angle between the inner surface 23b of the small diameter part 23 and the inner surface 30b of the bottom 30, and the angle between the outer surface 23a of the small diameter part 23 and the outer surface 30a of the bottom 30 change significantly in a vertical cross section. In other words, the first boundary part 26 refers to a point where the radius of curvature first becomes 100 mm or less on the way from the inner surface 23b of the small diameter part 23 to the inner surface 30b of the bottom 30, and a point where the radius of curvature first becomes 100 mm or less on the way from the outer surface 23a of the small diameter part 23 to the outer surface 30a of the bottom 30 in a vertical cross section (FIG. 2A). 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.

[0040] The length L5 in the height direction of the bottom 30 may be, for example, 5 mm or more, 6 mm or more, or 7 mm or more. The length L5 in the height direction of the bottom 30 may be 11 mm or less, 10 mm or less, or 9 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.

[0041] The radius of curvature R1 of the semicircle constituting the outer surface 30a of the bottom 30 may be 8 mm or more, 9 mm or more, or 10 mm or more. The radius of curvature R1 of the semicircle constituting the outer surface 30a of the bottom 30 may be 15 mm or less, 13 mm or less, or 12 mm or less. The radius of curvature R2 of the semicircle constituting the inner surface 30b of the bottom 30 may be 7 mm or more, 7.5 mm or more, or 8 mm or more. The radius of curvature R2 of the semicircle constituting the inner surface 30b of the bottom 30 may be 11 mm or less, 10.5 mm or less, or 10 mm or less.

[0042] 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 1.5 or less, or may be 1.3 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.

[0043] 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.

[0044] The thickness T5 of the bottom 30 (small diameter portion 23) at the first boundary portion 26 may be 1.5 mm or more, 1.7 mm or more, or 1.9 mm or more. The thickness T5 of the bottom 30 (small diameter portion 23) at the first boundary portion 26 may be 3.0 mm or less, 2.7 mm or less, or 2.5 mm or less. The thickness T7 of the bottom 30 at the lowest portion 31 may be 1.2 mm or more, 1.4 mm or more, or 1.5 mm or more. The thickness T7 of the bottom 30 at the lowest portion 31 may be 2.4 mm or less, 2.2 mm or less, or 2.0 mm or less. The ratio (T7 / T5) of the thickness T7 of the bottom 30 at the lowest portion 31 to the thickness T5 of the bottom 30 (small diameter portion 23) at the first boundary portion 26 may be 0.5 or more, 0.6 or more, or 0.7 or more. The ratio (T7 / T5) of the thickness T7 of the bottom 30 at the lowermost portion 31 to the thickness T5 of the bottom 30 (small diameter portion 23) at the first boundary portion 26 may be 1.0 or less, 0.9 or less, or 0.85 or less.

[0045] In this embodiment, the ratio (T7 / T1) of the thickness T7 of the bottom 30 at the lowermost portion 31 to the thickness T1 of the large diameter portion 21 may be 0.80 or more, 0.82 or more, or 0.83 or more. The ratio (T7 / T1) of the thickness T7 of the bottom 30 at the lowermost portion 31 to the thickness T1 of the large diameter portion 21 may be 1.05 or less, 0.95 or less, or 0.93 or less. When the ratio T7 / T1 is 0.80 or more, it is possible to suppress the occurrence of a defect called whitening in the heel portion 49 of the plastic bottle 40 described later and the decrease in strength of the heel portion 49. When the ratio T7 / T1 is 1.05 or less, it is possible to provide thickness to the body portion 42 and the heel portion 49, which are stretched, even with the same weight of the preform 10, by reducing the thickness of the bottom portion 30 of the preform 10, which is difficult to stretch when molding the plastic bottle 40. This allows the preform 10 to be lightweight.

[0046] 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 44.0 mm or more, 51.0 mm or more, or 52.0 mm or more. The total length L6 may be 63.0 mm or less, 58.0 mm or less, or 56.5 mm or less. By making the total length L6 44.0 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 63.0 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 total length L6 being reduced. 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.

[0047] 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 58 mm or more, 65 mm or more, or 70 mm or more. The total length L7 of the preform 10 may be 90 mm or less, 85 mm or less, or 80 mm or less.

[0048] 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. At this time, the ratio (W2 / W1) of the total mass W2 of the body 20 and the bottom 30 to the mass W1 of the mouth 11 may be 1.80 or more, 1.95 or more, or 2.10 or more. The ratio (W2 / W1) of the total mass W2 of the body 20 and the bottom 30 to the mass W1 of the mouth 11 may be 2.70 or less, 2.55 or less, or 2.40 or less. When the ratio W2 / W1 is 1.80 or more, the amount of resin in the body 20 and the bottom 30 is not excessively reduced. Therefore, it is possible to suppress the overstretching in the vertical direction when molding the plastic bottle 40 described later. 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 ratio W2 / W1 equal to or less than 2.70, the mass of the preform 10 can be prevented from becoming too heavy.

[0049] The mass W1 of the mouth portion 11 may be 3.4g or more, 3.9g or more, or 4.4g or more. The mass W1 of the mouth portion 11 may be 6.8g or less, 5.9g or less, or 5.4g or less. The total mass W2 of the body portion 20 and the bottom portion 30 may be 7.5g or more, 8.2g or more, or 9.0g or more. The total mass W2 of the body portion 20 and the bottom portion 30 may be 12.2g or less, 11.4g or less, or 10.7g or less. The total mass (W1+W2) of the preform 10 may be 11.5g or more, 12.5g or more, or 13.5g or more. The total mass (W1+W2) of the preform 10 may be 16.5g or less, 16.0g or less, or 15.5g or less.

[0050] As described above, in the body portion 20 of the preform 10, the large diameter portion 21 has a thickness T1, the reduced diameter portion 22 has a thickness T2, and the small diameter portion 23 has a thickness T4.

[0051] In this embodiment, the thickness T1 of the large diameter portion 21, the thickness T2 of the reduced diameter portion 22, and the thickness T4 of the small diameter portion 23 have the following relationship.

[0052] The average value of the thickness T1 of the large diameter portion 21≦the average value of the thickness T4 of the small diameter portion 23. The body portion 20 of the preform 10 is composed of a large diameter portion 21 , a reduced diameter portion 22 , and a small diameter portion 23 , and the thin-walled portion 20 A, which is the thinnest part of the body portion 20 , is present in the reduced diameter portion 22 .

[0053] Since thin-walled portion 20A, which is the thinnest part of body portion 20, is present in reduced diameter portion 22, this embodiment provides the following advantageous effects.

[0054] That is, a plastic bottle 40 is obtained by blow molding the preform 10 according to this embodiment (see FIG. 3). At this time, the reduced diameter portion 22 of the preform 10 roughly corresponds to a shoulder portion 48 of the plastic bottle 40. In this case, if the reduced diameter portion 22 of the preform 10 does not fully stretch during blow molding, the preform 10 will not fully stretch with respect to an upper portion 48a of the shoulder portion 48 during blow molding, and moldability may deteriorate.

[0055] On the other hand, the large diameter portion 21 formed directly below the support ring 14 of the preform 10 is the portion that is gripped by a gripper (not shown) in order to transport the preform 10 during the blow molding process, and it is considered that if it does not have the desired outer diameter, the gripper will not be able to securely engage with the preform 10.

[0056] In addition, since the large diameter portion 21 is the portion that is gripped by the gripper, it is necessary for it to have a desired thickness.

[0057] Therefore, in this embodiment, the thin-walled portion 20A, which is the thinnest in the body portion 20, is provided in the reduced diameter portion 22 adjacent to the large diameter portion 21 provided immediately below the support ring 14. This allows the preform 10 to be gripped without any problems during the blow molding process using the preform 10. Also, the thin-walled portion 20A can be reliably stretched in the blow molding process, which allows the shoulder portion 48 of the plastic bottle 40, particularly the upper portion 48a of the shoulder portion 48, to be molded with high precision by blow molding.

[0058] Furthermore, since the average value of thickness T1 of large diameter portion 21 is equal to or less than the average value of thickness T4 of small diameter portion 23, body portion 42, which occupies most of plastic bottle 40, can be reliably formed by small diameter portion 23.

[0059] Furthermore, by providing the thin-walled portion 20A in the reduced diameter portion 22, the reduced diameter portion 22 can be stretched during blow molding, allowing the shoulder portion 48 of the plastic bottle 40, particularly the upper portion 48a of the shoulder portion 48, to be molded with high precision.

[0060] Next, the material of the preform 10 will be described. 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 can 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).

[0061] 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.

[0062] 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.

[0063] 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.

[0064] Examples of antimony catalysts include antimony trioxide, antimony pentoxide, antimony acetate, triphenylantimony, and antimony glycol.

[0065] Examples of the manganese catalyst include fatty acid manganese salts such as manganese acetate, manganese carbonate, manganese chloride, manganese acetylacetonate salts, and manganese hydroxide.

[0066] 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.

[0067] Examples of aluminum catalysts include aluminum trisacetylacetate, aluminum monoacetylacetonate bis(ethylacetoacetate), and ethylacetoacetate aluminum diisopropylate.

[0068] Examples of the lithium catalyst include ethyllithium, propyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, and phenyllithium.

[0069] Examples of germanium catalysts include germanium dioxide, germanium tetroxide, germanium tetramethoxide, germanium tetraethoxide, germanium tetrapropoxide, germanium tetrabutoxide, germanium tetrapentoxide, and germanium tetrahexoxide.

[0070] In this embodiment, the term "polyester" refers to a copolymer of a dicarboxylic acid compound and a diol compound.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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. 3. 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.

[0080] In Fig. 3, 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[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, the operation of this embodiment (a method for manufacturing a plastic bottle) configured as above will be described.

[0087] First, the preform 10 shown in Figs. 1 and 2 is prepared (Fig. 4(a)). In this case, pellets made of a thermoplastic resin such as PET (polyethylene terephthalate) 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 the heating device 51 (FIG. 4(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. 4(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. 4(c)). In FIG. 4(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] 4(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] Thereafter, as shown in Fig. 4(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. 3 is obtained.

[0094] Meanwhile, the heel portion 49 (see FIG. 3) of the plastic bottle 40 corresponds to the periphery of the bottom portion 30 of the preform 10 (see FIGS. 1 and 2A), and is a portion that is likely to become thin after blow molding. That is, since the periphery of the bottom portion 30 of the preform 10 is significantly stretched in both the direction of the central axis CL and the radial direction, the heel portion 49 of the plastic bottle 40 is likely to become thinner than other portions. In this case, a defect called whitening may occur in the heel portion 49, and the strength of the heel portion 49 may decrease.

[0095] In contrast, according to the present embodiment, the thinnest part of the body 20 and bottom 30 of the preform 10 is preferably the lowest part 31 of the bottom 30. When the thickness of the lowest part 31 of the bottom 30 is T7 and the thickness of the large diameter part is T1, 0.80≦T7 / T1≦1.05 is satisfied. It is also preferable that 0.80≦T7 / T1≦0.95 is satisfied. By satisfying 0.80≦T7 / T1, even if the mass of the preform 10 is reduced, the heel part 49 of the plastic bottle 40 does not become too thin, and whitening of the heel part 49 and a decrease in the strength of the heel part 49 can be suppressed. In particular, since the heel part 49 can be suppressed from becoming thin without increasing the mass of the plastic bottle 40, the weight reduction of the plastic bottle 40 is not hindered. Since the relationship T7 / T1≦1.05 is established between the thickness T7 of the lowest portion 31 of the bottom portion 30 and the thickness T1 of the large diameter portion, it is possible to make the thickness of the bottom portion 30 of the preform 10, which is less likely to be stretched when molding the plastic bottle 40, thinner, thereby allowing the body portion 42 and heel portion 49, which are stretched, to have thickness even for a preform 10 of the same weight. This allows the weight of the preform 10 to be reduced.

[0096] In addition, according to this embodiment, when the mass of the mouth is W1 and the total mass of the body 20 and the bottom 30 is W2, 1.80≦W2 / W1≦2.70 is satisfied. By satisfying 1.80≦W2 / W1, the amount of resin in the body 20 and the bottom 30 is not excessively reduced. This makes it possible to prevent the plastic bottle 40 from being overstretched in the vertical direction when it is molded. This makes it possible to prevent the heel 49 of the plastic bottle 40 from having a defect called whitening or a decrease in the strength of the heel 49. By satisfying W2 / W1≦2.70 between the mass W1 of the mouth and the total mass W2 of the body 20 and the bottom 30, it is possible to prevent the mass of the preform 10 from becoming too heavy.

[0097] Furthermore, according to this embodiment, when the total length of the body 20 and the bottom 30 is L6, 44.0 mm≦L6≦63.0 mm is satisfied. By satisfying 44.0 mm≦L6, the stretch ratio in the longitudinal direction when molding the plastic bottle 40 is not too large, and it is possible to suppress overstretching. This can suppress the occurrence of a defect called whitening in the heel portion 49 of the plastic bottle 40 and the decrease in strength of the heel portion 49. In addition, by satisfying L6≦63.0 mm, when the mass of the preform 10 is constant, the thickness of the body 20 is not likely to become thin by the amount of the total length L6 suppressed. Therefore, it is possible to suppress whitening of the body 42 when molding the plastic bottle 40. In addition, by suppressing the total length L6 of the preform 10 from being too long, it is possible to suppress the longitudinal stretching from becoming small or the longitudinal stretching from not being performed at all. Therefore, even if the plastic bottle 40 is a small bottle with a low height and a capacity of about 100 mL, it is easy to mold it.

[0098] Next, a description will be given of the relationship between the outer diameter D9 of the small diameter portion 23 of the preform 10 and the overall length L7 of the preform 10. In this embodiment, the outer diameter D9 of the small diameter portion 23 and the overall length L7 of the preform 10 preferably satisfy D9:L7=0.26 to 0.30. Since D9:L7=0.26-0.30, the outer diameter D9 of the small diameter portion 23 of the preform 10 can be made relatively large, and the preform 10 can be formed into a cylindrical shape. Therefore, when the preform 10 is blow molded, the reduced diameter portion 22 and the small diameter portion 23 of the body portion 20 of the preform 10, and the bottom portion 30 can be prevented from being excessively stretched in the lateral direction. Since the reduced diameter portion 22 and the small diameter portion 23 of the body portion 20 of the preform 10, and the bottom portion 30 do not stretch excessively in the lateral direction, defects such as holes do not occur in the bottom portion 43 of the plastic bottle 40 molded by blow molding, and the buckling strength of the entire plastic bottle 40 can be increased. In addition, as described above, by setting the ratio (W2 / W1) of the total mass W2 of the body portion 20 and the bottom portion 30 to the mass W1 of the mouth portion 11 to 1.80 or more, the excessive lateral stretching of the preform 1 can be suppressed. In addition to this, by making D9:L7=0.26 to 0.30, excessive stretching of the preform 10 in the lateral direction can be more reliably suppressed.

[0099] <Second embodiment> Next, an outline of the preform according to this embodiment will be described with reference to Figs. 1 and 2B.

[0100] The preform 10 shown in FIG. 1 includes a mouth portion 11 having an opening 15, 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, 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 thinnest part of the body portion 20 and the bottom portion 30 is preferably the lowest portion 31 of the bottom portion 30. When the thickness of the lowest portion 31 of the bottom portion 30 is T7 and the thickness of the small diameter portion 23 of the body portion 20 is T4, T7 is an average value of about 0.8×T4.

[0101] 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.

[0102] The outer diameter D1 of the mouth body 12 may be 18 mm or more, 20 mm or more, or 22 mm or more. The outer diameter D1 of the mouth body 12 may be 33 mm or less, 30 mm or less, or 27 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 29 mm or less, 26 mm or less, or 24 mm or less.

[0103] 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.

[0104] 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. 3). 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.

[0105] As described above, the body portion 20 has the large diameter portion 21, the small diameter portion 23, and the tapered diameter portion 22.

[0106] 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, 2.2 mm or more, 2.5 mm or more, or 2.9 mm or more. The length L2 in the height direction of the large diameter portion 21 may be 4.5 mm or less, 4.1 mm or less, or 3.8 mm or less.

[0107] 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.

[0108] The inner diameter D4 of the large diameter portion 21 may be the same as the inner diameter D2 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 large diameter portion 21 has a thickness T1. The thickness T1 of the large diameter portion 21 may be 1.4 mm or more, 1.6 mm or more, or 1.8 mm or more. The thickness T1 of the large diameter portion 21 may be 2.6 mm or less, 2.4 mm or less, or 2.2 mm or less.

[0109] 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 approximately a 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. 2B ), 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.

[0110] The length L3 in the height direction of the reduced diameter portion 22 may be, for example, 6.8 mm or more, 7.5 mm or more, or 8.1 mm or more. The length L3 in the height direction of the reduced diameter portion 22 may be 11.1 mm or less, 10.4 mm or less, or 9.7 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.

[0111] The outer surface 22a and the inner surface 22b of the reduced diameter portion 22 are inclined with respect to the central axis CL of the preform 10. In the vertical cross section, 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 6° or more, 8° or more, or 10° or more. 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 22° or less, 20° or less, or 18° or less. 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 6° or more, 8° or more, or 10° or more. 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 22° or less, 42° or less, or 18° or less. The angle θ1 may be the same as the angle θ2.

[0112] The reduced diameter portion 22 has a thickness T2, which will be described later. The thickness T3 of the reduced diameter portion 22 at the second boundary portion 27 may be thinner, thicker, or the same as the thickness T1 of the reduced diameter portion 22 at the third boundary portion 28. The thickness T3 of the reduced diameter portion 22 and the small diameter portion 23 at the second boundary portion 27 may be 1.5 mm or more, 1.7 mm or more, or 1.9 mm or more. The thickness T3 of the reduced diameter portion 22 and the small diameter portion 23 at the second boundary portion 27 may be 3.0 mm or less, 2.7 mm or less, or 2.5 mm or less.

[0113] The outer diameter D7 of the reduced diameter portion 22 and the small diameter portion 23 at the second boundary 27 may be 15 mm or more, 18 mm or more, or 20 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 27 mm or less, 25 mm or less, or 24 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 15 mm or more, 16 mm or more, or 17 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 24 mm or less, 22 mm or less, or 20 mm or less.

[0114] 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.

[0115] The length L4 in the height direction of the small diameter portion 23 may be, for example, 23 mm or more, 27 mm or more, or 30 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 41 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.

[0116] 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.

[0117] 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 1.5 mm or more, 1.7 mm or more, or 1.9 mm or more. The thickness T4 of the small diameter portion 23 (=T3=T5) may be 3.0 mm or less, 2.7 mm or less, or 2.5 mm or less.

[0118] 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 15 mm or more, 18 mm or more, or 20 mm or more. 11 The inner diameter D of the small diameter portion 23 at the first boundary portion 26 may be 27 mm or less, may be 25 mm or less, or may be 24 mm or less. 12 The inner diameter D of the small diameter portion 23 at the first boundary portion 26 may be, for example, 15 mm or more, 16 mm or more, or 17 mm or more. 12 may be 24 mm or less, may be 22 mm or less, or may be 20 mm or less.

[0119] The bottom 30 is connected to the lower part of the small diameter part 23, and has an outer surface 30a and an inner surface 30b. A first boundary part 26 exists at the boundary between the small diameter part 23 and the bottom 30. The first boundary part 26 is a point where the angle between the inner surface 23b of the small diameter part 23 and the inner surface 30b of the bottom 30, and the angle between the outer surface 23a of the small diameter part 23 and the outer surface 30a of the bottom 30 change significantly in a vertical cross section. In other words, the first boundary part 26 refers to a point where the radius of curvature first becomes 100 mm or less on the way from the inner surface 23b of the small diameter part 23 to the inner surface 30b of the bottom 30, and a point where the radius of curvature first becomes 100 mm or less on the way from the outer surface 23a of the small diameter part 23 to the outer surface 30a of the bottom 30 in a vertical cross section (FIG. 2B). 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.

[0120] The length L5 in the height direction of the bottom 30 may be, for example, 5 mm or more, 6 mm or more, or 7 mm or more. The length L5 in the height direction of the bottom 30 may be 11 mm or less, 10 mm or less, or 9 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.

[0121] The radius of curvature R1 of the semicircle constituting the outer surface 30a of the bottom 30 may be 8 mm or more, 9 mm or more, or 10 mm or more. The radius of curvature R1 of the semicircle constituting the outer surface 30a of the bottom 30 may be 15 mm or less, 13 mm or less, or 12 mm or less. The radius of curvature R2 of the semicircle constituting the inner surface 30b of the bottom 30 may be 7 mm or more, 7.5 mm or more, or 8 mm or more. The radius of curvature R2 of the semicircle constituting the inner surface 30b of the bottom 30 may be 11 mm or less, 10.5 mm or less, or 7 mm or less.

[0122] 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 1.5 or less, or may be 1.3 or less. By making the ratio 2.0 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.

[0123] 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.

[0124] The thickness T5 of the bottom 30 (small diameter portion 23) at the first boundary portion 26 may be 1.5 mm or more, 1.7 mm or more, or 1.9 mm or more. The thickness T5 of the bottom 30 (small diameter portion 23) at the first boundary portion 26 may be 3.0 mm or less, 2.7 mm or less, or 2.5 mm or less. The thickness T7 of the bottom 30 at the lowest portion 31 may be 1.2 mm or more, 1.4 mm or more, or 1.5 mm or more. The thickness T7 of the bottom 30 at the lowest portion 31 may be 2.4 mm or less, 2.2 mm or less, or 2.0 mm or less. The ratio (T7 / T5) of the thickness T7 of the bottom 30 at the lowest portion 31 to the thickness T5 of the bottom 30 (small diameter portion 23) at the first boundary portion 26 may be 0.5 or more, 0.6 or more, or 0.7 or more. The ratio (T7 / T5) of the thickness T7 of the bottom 30 at the lowermost portion 31 to the thickness T5 of the bottom 30 (small diameter portion 23) at the first boundary portion 26 may be 1.0 or less, 0.9 or less, or 0.85 or less.

[0125] In this embodiment, the ratio (T7 / T1) of the thickness T7 of the bottom 30 at the lowermost portion 31 to the thickness T1 of the large diameter portion 21 may be 0.80 or more, 0.82 or more, or 0.83 or more. The ratio (T7 / T1) of the thickness T7 of the bottom 30 at the lowermost portion 31 to the thickness T1 of the large diameter portion 21 may be 1.05 or less, 0.95 or less, or 0.93 or less. When the ratio T7 / T1 is 0.80 or more, it is possible to suppress the occurrence of a defect called whitening in the heel portion 49 of the plastic bottle 40 described later and the decrease in strength of the heel portion 49. When the ratio T7 / T1 is 1.05 or less, it is possible to provide thickness to the body portion 42 and the heel portion 49, which are stretched, even with the same weight of the preform 10, by reducing the thickness of the bottom portion 30 of the preform 10, which is difficult to stretch when molding the plastic bottle 40. This allows the preform 10 to be lightweight.

[0126] 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 44.0 mm or more, 51.0 mm or more, or 52.0 mm or more. The total length L6 may be 63.0 mm or less, 58.0 mm or less, or 56.5 mm or less. By making the total length L6 44.0 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 63.0 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 total length L6 being reduced. 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.

[0127] 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 58 mm or more, 65 mm or more, or 70 mm or more. The total length L7 of the preform 10 may be 90 mm or less, 85 mm or less, or 80 mm or less.

[0128] 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. At this time, the ratio (W2 / W1) of the total mass W2 of the body 20 and the bottom 30 to the mass W1 of the mouth 11 may be 1.80 or more, 1.95 or more, or 2.10 or more. The ratio (W2 / W1) of the total mass W2 of the body 20 and the bottom 30 to the mass W1 of the mouth 11 may be 2.70 or less, 2.55 or less, or 2.40 or less. When the ratio W2 / W1 is 1.80 or more, the amount of resin in the body 20 and the bottom 30 is not excessively reduced. Therefore, it is possible to suppress the overstretching in the vertical direction when molding the plastic bottle 40 described later. 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 ratio W2 / W1 equal to or less than 2.70, the mass of the preform 10 can be prevented from becoming too heavy.

[0129] The mass W1 of the mouth portion 11 may be 3.4g or more, 3.9g or more, or 4.4g or more. The mass W1 of the mouth portion 11 may be 6.8g or less, 5.9g or less, or 5.4g or less. The total mass W2 of the body portion 20 and the bottom portion 30 may be 7.5g or more, 8.2g or more, or 9.0g or more. The total mass W2 of the body portion 20 and the bottom portion 30 may be 12.2g or less, 11.4g or less, or 10.7g or less. The total mass (W1+W2) of the preform 10 may be 11.5g or more, 12.5g or more, or 13.5g or more. The total mass (W1+W2) of the preform 10 may be 16.5g or less, 16.0g or less, or 15.5g or less.

[0130] As described above, in the body portion 20 of the preform 10, the large diameter portion 21 has a thickness T1, the reduced diameter portion 22 has a thickness T2, and the small diameter portion 23 has a thickness T4.

[0131] In this embodiment, the thickness T1 of the large diameter portion 21, the thickness T2 of the reduced diameter portion 22, and the thickness T4 of the small diameter portion 23 have the following relationship.

[0132] The average value of the thickness T1 of the large diameter portion 21≦the average value of the thickness T3 of the small diameter portion 23. The body portion 20 of the preform 10 is composed of a large diameter portion 21 , a reduced diameter portion 22 , and a small diameter portion 23 , and the thin-walled portion 20 A, which is the thinnest part of the body portion 20 , is present in the reduced diameter portion 22 .

[0133] Since thin-walled portion 20A, which is the thinnest part of body portion 20, is present in reduced diameter portion 22, this embodiment provides the following advantageous effects.

[0134] That is, plastic bottle 40 is obtained by blow molding preform 10 according to this embodiment. At this time, reduced diameter portion 22 of preform 10 approximately corresponds to shoulder portion 48 of plastic bottle 40. In this case, if reduced diameter portion 22 of preform 10 does not fully stretch during blow molding, preform 10 will not fully stretch with respect to upper portion 48a of shoulder portion 48 during blow molding, and moldability may deteriorate.

[0135] On the other hand, the large diameter portion 21 formed directly below the support ring 14 of the preform 10 is the portion that is gripped by a gripper (not shown) in order to transport the preform 10 during the blow molding process, and it is considered that if it does not have the desired outer diameter, the gripper will not be able to securely engage with the preform 10.

[0136] In addition, since the large diameter portion 21 is the portion that is gripped by the gripper, it is necessary for it to have a desired thickness.

[0137] Therefore, in this embodiment, the thin-walled portion 20A, which is the thinnest in the body portion 20, is provided in the reduced diameter portion 22 adjacent to the large diameter portion 21 provided immediately below the support ring 14. This allows the preform 10 to be gripped without any problems during the blow molding process using the preform 10. Also, the thin-walled portion 20A can be reliably stretched in the blow molding process, which allows the shoulder portion 48 of the plastic bottle 40, particularly the upper portion 48a of the shoulder portion 48, to be molded with high precision by blow molding.

[0138] Furthermore, since the average value of thickness T1 of large diameter portion 21 is equal to or less than the average value of thickness T4 of small diameter portion 23, body portion 42, which occupies most of plastic bottle 40, can be reliably formed by small diameter portion 23.

[0139] Furthermore, by providing the thin-walled portion 20A in the reduced diameter portion 22, the reduced diameter portion 22 can be stretched during blow molding, allowing the shoulder portion 48 of the plastic bottle 40, particularly the upper portion 48a of the shoulder portion 48, to be molded with high precision. EXAMPLES

[0140] Next, a specific example of this embodiment will be described with reference to FIG. 5 and FIG.

[0141] In this disclosure, Example 1 corresponds to the first embodiment, and Example 2 corresponds to the second embodiment. EXAMPLES

[0142] In Example 1, a preform 10 made of polyethylene terephthalate and having the structure shown in FIG. 2A was produced.

[0143] This preform 10 had a preform weight of 15.1 g, a body weight of 10.56 g, and a mouth weight of 4.56 g.

[0144] The outer diameter D3 of the large diameter portion 21 of the preform 10 was 25.65 mm.

[0145] Furthermore, the thickness T1 of the large diameter portion 21, the thickness T2 of the reduced diameter portion 22, and the thickness T4 of the small diameter portion 23 of the preform 10 changed according to the distance from the support ring, as shown in FIGS.

[0146] That is, as shown in FIGS. 5 and 6, in the large diameter portion 21 of the preform 10, the thickness T1 was constant until it was about 2 mm away from the support ring 14, and then the thickness T1 gradually decreased to the third boundary portion 28.

[0147] Thereafter, thickness T2 of reduced diameter portion 22 further decreases with increasing distance from support ring 14, and thickness T2 has a minimum value at thin-walled portion 20A1 of reduced diameter portion 22.

[0148] That is, the thin-walled portion 20A1 of the reduced diameter portion 22 has a predetermined length in the height direction of the preform 10, extends in the circumferential direction of the body portion 20, and is the thinnest part of the body portion 20. This thin-walled portion 20A1 was present in the region of the reduced diameter portion 22 on the large diameter portion 21 side. The thin-walled portion 20A1 of the reduced diameter portion 22 is thinner than adjacent portions above and below in the height direction of the preform 10. The thin-walled portion 20A1 of the reduced diameter portion 22 will be described further below.

[0149] In the first embodiment, the thin-walled portion 20A1 of the reduced diameter portion 22 has a length that is 10% to 60% of the length L3 of the reduced diameter portion 22, specifically, a length that is 35%.

[0150] Thereafter, thickness T2 of reduced diameter portion 22 gradually increases toward second boundary portion 27 between small diameter portion 23 and itself, and thickness T2 of reduced diameter portion 22 becomes maximum in the vicinity of the second boundary portion.

[0151] Thereafter, the thickness T4 from the second boundary portion 27 to the large diameter portion 21 decreased slightly, and then the thickness T4 throughout the large diameter portion 21 had a constant value.

[0152] The thickness T1 of the large diameter portion 21 and the thickness T4 of the small diameter portion 23 are The relationship was: average value of thickness T1 of large diameter portion 21≦average value of thickness T4 of small diameter portion 23.

[0153] As described above, according to this embodiment, the thin-walled portion 20A1, which is the thinnest part of the body portion 20, is provided in the reduced diameter portion 22 adjacent to the large diameter portion 21 provided immediately below the support ring 14. This allows the preform 10 to be gripped by the gripper without any problems during the blow molding process using the preform 10. Also, the thin-walled portion 20A1 can be reliably stretched in the blow molding process, allowing the shoulder portion 48 of the plastic bottle 40, particularly the upper portion 48a of the shoulder portion 48, to be precisely molded by blow molding.

[0154] Furthermore, since the average value of thickness T1 of large diameter portion 21 is less than or equal to the average value of thickness T4 of small diameter portion 23, body portion 42, which accounts for most of plastic bottle 40, can be reliably formed using small diameter portion 23.

[0155] Furthermore, by providing the thin-walled portion 20A in the reduced diameter portion 22, the reduced diameter portion 22 can be stretched during blow molding, allowing the shoulder portion 48 of the plastic bottle 40, particularly the upper portion 48a of the shoulder portion 48, to be molded with high precision.

[0156] Furthermore, the thin-walled portion 20A1 of the reduced diameter portion 22 has a length that is 10% to 60% of the length L3 of the reduced diameter portion 22, specifically, 35%.

[0157] In this case, if the length of the thin-walled portion 20A1 is 10% or less of the length L3 of the reduced diameter portion 22, it becomes difficult to reliably stretch the thin-walled portion 20A1 in the blow molding process, and the shoulder portion 48, particularly the upper portion 48a of the shoulder portion 48, cannot be molded with high precision.

[0158] On the other hand, if the length of thin-walled portion 20A1 is 60% or more of length L3 of reduced diameter portion 22, thin-walled portion 20A1 will extend to the small diameter portion 23. In this case, thin-walled portion 20A1 extends to the small diameter portion 23 and the thickness must be suddenly changed from thickness T2 of thin-walled portion 20A1 to thickness T4 of small diameter portion 23, making it difficult to mold a plastic bottle in a well-balanced manner during blow molding.

[0159] For these reasons, it has been found that the length of the thin-walled portion 20A1 is 10% to 60% of the length L3 of the reduced diameter portion 22, but it is more preferable that the length of the thin-walled portion 20A1 is 30% to 40% of the length L3 of the reduced diameter portion 22.

[0160] Furthermore, the thickness T2 of the thin portion 20A1 is 91% to 93% of the average value of the thickness T1 of the large diameter portion 21. Furthermore, the thickness T2 of the thin portion 20A1 is 86% to 88% of the average value of the thickness T4 of the small diameter portion 23. EXAMPLES

[0161] In Example 2, a preform 10 made of polyethylene terephthalate and having the structure shown in FIG. 2B was produced.

[0162] This preform 10 had a preform weight of 15.1 g, a body weight of 10.54 g, and a mouth weight of 4.56 g.

[0163] The outer diameter D3 of the large diameter portion 21 of the preform 10 was 25.65 mm.

[0164] Furthermore, the thickness T1 of the large diameter portion 21, the thickness T2 of the reduced diameter portion 22, and the thickness T4 of the small diameter portion 23 of the preform 10 changed according to the distance from the support ring, as shown in FIGS.

[0165] That is, as shown in FIGS. 5 and 6, in the large diameter portion 21 of the preform 10, the thickness T1 was constant until it was about 2 mm away from the support ring 14, and then the thickness T1 gradually decreased to the third boundary portion 28.

[0166] Thereafter, thickness T2 of reduced diameter portion 22 further decreases with increasing distance from support ring 14, and thickness T2 has a minimum value at thin-wall portion 20A2 of reduced diameter portion 22.

[0167] That is, the thin-walled portion 20A2 of the reduced diameter portion 22 has a predetermined length in the height direction of the preform 10, extends in the circumferential direction of the body portion 20, and is the thinnest part of the body portion 20. This thin-walled portion 20A2 was present in the region of the reduced diameter portion 22 on the large diameter portion 21 side. The thin-walled portion 20A2 of the reduced diameter portion 22 is thinner than adjacent portions above and below in the height direction of the preform 10. The thin-walled portion 20A2 of the reduced diameter portion 22 will be described further below.

[0168] In the second embodiment, the thin-walled portion 20A2 of the reduced diameter portion 22 has a length that is 10% to 60% of the length L3 of the reduced diameter portion 22, specifically, a length that is 35%.

[0169] Thereafter, thickness T2 of reduced diameter portion 22 gradually increases toward second boundary portion 27 between small diameter portion 23 and itself, and thickness T2 of reduced diameter portion 22 becomes maximum in the vicinity of the second boundary portion.

[0170] Thereafter, the thickness T3 from the second boundary portion 27 to the large diameter portion 21 and the thickness T4 throughout the large diameter portion 21 were constant.

[0171] The thickness T1 of the large diameter portion 21 and the thickness T4 of the small diameter portion 23 are The relationship is: average value of thickness T1 of large diameter portion 21≦average value of thickness of small diameter portion 23.

[0172] As described above, according to this embodiment, the thin-walled portion 20A2, which is the thinnest part of the body portion 20, is provided in the reduced diameter portion 22 adjacent to the large diameter portion 21 provided immediately below the support ring 14. This allows the preform 10 to be gripped by the gripper without any problems during the blow molding process using the preform 10. Also, the thin-walled portion 20A2 can be reliably stretched in the blow molding process, and the shoulder portion 48 of the plastic bottle 40, particularly the upper portion 48a of the shoulder portion 48, can be precisely molded by blow molding.

[0173] Furthermore, since the average value of thickness T1 of large diameter portion 21 is less than or equal to the average value of thickness T4 of small diameter portion 23, body portion 42, which accounts for most of plastic bottle 40, can be reliably formed using small diameter portion 23.

[0174] Furthermore, by reducing the average value of the thickness T2 of the narrowed portion 22, the narrowed portion 22 can be stretched during blow molding, enabling the shoulder portion 48 of the plastic bottle 40, particularly the upper portion 48a of the shoulder portion 48, to be molded with good precision.

[0175] Furthermore, the thin-walled portion 20A2 of the reduced diameter portion 22 has a length that is 10% to 60% of the length L3 of the reduced diameter portion 22, specifically, 35%.

[0176] In this case, if the length of the thin-walled portion 20A2 is 10% or less of the length L3 of the reduced diameter portion 22, it becomes difficult to reliably stretch the thin-walled portion 20A2 in the blow molding process, and the shoulder portion 48, particularly the upper portion 48a of the shoulder portion 48, cannot be molded with high precision.

[0177] On the other hand, if the length of thin-walled portion 20A2 is 60% or more of length L3 of reduced diameter portion 22, thin-walled portion 20A2 will extend to the small diameter portion 23. In this case, thin-walled portion 20A2 extends to the small diameter portion 23 and the thickness must be suddenly changed from thickness T2 of thin-walled portion 20A2 to thickness T4 of small diameter portion 23, making it difficult to mold a plastic bottle in a well-balanced manner during blow molding.

[0178] For this reason, the length of the thin-walled portion 20A2 is 10% to 60% of the length L3 of the reduced diameter portion 22, but it is more preferable that the length of the thin-walled portion 20A2 is 30% to 40% of the length L3 of the reduced diameter portion 22.

[0179] Furthermore, the thickness T2 of the thin portion 20A2 is 96% to 98% of the average value of the thickness T1 of the large diameter portion 21. Furthermore, the thickness T2 of the thin portion 20A2 is 88% to 99% of the average value of the thickness T4 of the small diameter portion 23. [Explanation of symbols]

[0180] 10 Preform 11 Mouth 12 Mouth body 13 Threaded part 14 Support Ring 15 Opening 20 Torso 20A Thin section 20A1 thin section 20A2 thin section 21 Large diameter section 22 Reduced diameter 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 toward the small diameter portion, The thickness of the large diameter portion is T １ year, The thickness of the small diameter portion is T ４ In this case, T １ The average value of ≦T ４ It is the average value of a thin-walled portion of the body that is the thinnest in thickness is present in the reduced diameter portion.

2. The preform according to claim 1 , wherein the thin wall portion is present in a region of the reduced diameter portion on the side of the large diameter portion.

3. 3. The preform according to claim 1, wherein the length of said thin-walled portion is 10% to 60% of the length of said reduced diameter portion.

4. The thickness of the reduced diameter portion is T ２ In this case, T ２ The average value of ≦T ４ 3. The preform according to claim 1 or 2, wherein the average value of

5. 3. The preform according to claim 1, wherein the outer diameter of the small diameter portion: the total length of the preform=0.26 to 0.

30.

6. In a method for manufacturing a plastic bottle, A step of preparing a preform according to claim 1 or 2; heating the preform; and biaxially stretching and blow molding the preform.

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