Preform

Abstract

To provide a synthetic resin container preform that can provide a characteristic required for a container.SOLUTION: A synthetic resin container preform 1 includes: a mouth 10 including from open end 11 to neck ring 12; a lower neck 20 that includes a portion that continues to the mouth 10 and gradually increases in wall thickness as it moves away from the neck ring 12 along an axial direction; a bottom 50 including the open end 11 and a closed end 51 opposite to the open end and a portion where the wall thickness gradually increases toward the neck ring 12; and a trunk 30 which is an area from an upper end of the trunk 31, which is a point where the wall thickness begins to become constant along the axial direction away from the neck ring 12 connected to the lower neck 20, to a lower end of the trunk 32 which is the point where the wall thickness begins to become constant along the axial direction toward the neck ring 12 connected to the bottom 50. The trunk 30 includes a thick part 35 whose thickness gradually increases and decreases as it moves away from the neck ring 12 along the axial direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a preform for a synthetic resin container. [Background technology]

[0002] Generally, containers such as bottles made of thermoplastic resins such as polyethylene terephthalate are known. A known method for manufacturing such containers involves preparing a cylindrical preform with a bottom by injection molding or the like, and then molding the preform into a bottle by biaxially stretching blow molding. Bottles manufactured in this manner are widely used as containers for various beverages, seasonings, and the like. Patent Document 1, for example, discloses a technology relating to preforms for synthetic resin containers. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-334816 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a preform for a synthetic resin container that can impart the properties required for the container. [Means for solving the problem]

[0005] According to one aspect of the present invention, a preform for a synthetic resin container comprises a mouth portion extending from the open end to a neck ring, a lower neck portion connected to the mouth portion and including a portion whose thickness gradually increases with increasing distance from the neck ring along the axial direction, a bottom portion including a closed end opposite the open end and including a portion whose thickness gradually increases toward the neck ring, and a body portion extending from the upper end to the lower end of the body, the upper end of the body being a point connected to the lower neck portion where the thickness begins to become constant with increasing distance from the neck ring along the axial direction, and the lower end of the body being a point connected to the bottom portion where the thickness begins to become constant toward the neck ring along the axial direction, and the body portion including a thick portion whose thickness gradually increases and then decreases with increasing distance from the neck ring along the axial direction. [Effects of the Invention]

[0006] According to the present invention, a preform for a synthetic resin container can be provided that can impart the properties required for the container. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram showing an outline of a configuration example of a preform according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram showing an outline of a configuration example of a bottle formed using a preform according to the embodiment. [Figure 3] FIG. 3 is a schematic diagram showing an outline of a configuration example of a preform according to a first modified example. [Figure 4] FIG. 4 is a schematic diagram showing an outline of a configuration example of a mold used in manufacturing a preform according to the embodiment. [Figure 5] FIG. 5 is a schematic diagram showing an outline of a configuration example of a mold used to manufacture a preform according to the first modified example. [Figure 6] FIG. 6 is a schematic diagram showing an outline of a configuration example of a preform according to a second modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment will be described with reference to the drawings. The embodiment relates to a synthetic resin container. In particular, the embodiment relates to a preform used in the manufacture of a bottle molded by biaxial stretch blow molding or the like.

[0009] FIG. 1 is a diagram showing an outline of an example of the configuration of a preform 1 according to this embodiment. The left side of FIG. 1 shows a schematic longitudinal cross-sectional shape of the preform 1. In this diagram, for ease of understanding, the figure is enlarged in the horizontal direction, with the thickness particularly enlarged. The actual preform 1 is thinner than that shown in FIG. 1. The right side of FIG. 1 shows the wall thickness at each position on the preform 1 corresponding to the left side view. The preform 1 has a shape that is basically symmetrical with respect to the central axis, and has a generally cylindrical shape with one end open and the other closed. The respective ends will be referred to as the open end 11 and the closed end 51.

[0010] The preform 1 is made of a thermoplastic resin. The preform 1 is made of, for example, an ethylene terephthalate-based thermoplastic polyester resin such as polyethylene terephthalate. The thermoplastic polyester resin is not limited to polyethylene terephthalate, and polybutylene terephthalate, polyethylene naphthalate, amorphous polyarylate, polylactic acid, polyethylene furanoate, or copolymers thereof may also be used. A mixture of these resins, or a mixture of these resins with other resins, may also be used. Polycarbonate, acrylonitrile resin, polypropylene, propylene-ethylene copolymer, polyethylene, etc. may also be used.

[0011] The preform 1 of this embodiment is suitable for producing a bottle 100 as shown in FIG. 2. The preform 1 is stretched by blow molding, such as biaxial stretch blow molding, to form the bottle 100 from the preform 1. The bottle 100 shown in FIG. 2 is, for example, a beverage bottle, e.g., a bottle with a capacity of approximately 2 L. The bottle 100 includes a mouth portion 110, a shoulder portion 120, a body portion 130, a heel portion 151, and a bottom portion 152. The body portion 130 of the bottle 100 has a roughly rectangular cylindrical shape, and is generally referred to as a rectangular bottle. The following description will be given using up and down defined based on the orientation of the bottle 100 when it is placed upright on a horizontal surface with the mouth portion 110 facing up, as shown in FIG. 2.

[0012] The mouth 110 is a cylindrical portion that serves as a spout for pouring the contents. A neck ring 112 that protrudes in a circular ring shape is provided at the lower end of the mouth 110. The bottle 100 widens radially at a shoulder 120 that extends from the bottom of the neck ring 112 toward the body 130. The body 130 makes up the majority of the bottle 100. The lower end of the body 130 is connected to a closed bottom 152 via a heel 151.

[0013] The body 130 can be divided into an upper body portion 131, a waist portion 132, and a lower body portion 133, from top to bottom. The waist portion 132 is located in the center of the body 130 and is radially narrower than the other portions. The waist portion 132 has recesses 135 on the front and back sides in FIG. 2. The bottle 100 has a shape that makes it easy to hold, as a person's fingers can fit into the recesses 135 when gripping it. The upper body 131 and the lower body 133 have multiple grooves in the circumferential direction to improve the rigidity of the body 130.

[0014] Lighter bottles are generally desired. In a bottle 100 such as that shown in FIG. 2, if the portion of the preform 1 corresponding to the body portion 130 is made uniformly thin throughout, the container wall constituting the waist portion 132 will also be thin. As a result, when a person grasps the waist portion 132, the strength of the waist portion 132 may be insufficient, making the bottle 100 difficult to handle, or the depression 135 provided in the waist portion 132 may invert due to an impact such as being dropped. The preform 1 according to this embodiment is designed so that the wall of the body portion 130 is thick, particularly at the portion corresponding to the center, to provide sufficient strength to the body portion 130 of the bottle 100.

[0015] Returning to Figure 1, the preform 1 will be described in detail. The preform 1 has a mouth portion 10 that will become the mouth portion 110 of the bottle 100 without being stretched by blow molding. The mouth portion 10 includes a region from the open end 11 to the neck ring 12 that will become the neck ring 112 of the bottle 100.

[0016] The preform 1 is stretched by blow molding below the neck ring 12. When blown, the preform 1 is provided with a neck lower portion 20 that roughly corresponds to the shoulder portion 120 of the bottle 100, a body portion 30 that roughly corresponds to the body portion 130, and a bottom portion 50 that roughly corresponds to the heel portion 151 and the bottom portion 152. The neck lower portion 20 and the body portion 30 have a roughly cylindrical shape, and the bottom portion 50 has a roughly hemispherical shape.

[0017] In this example, the inner diameter of the lower neck portion 20 of the preform 1 is constant. Because the outer diameter of the body portion 130 of the bottle 100 is relatively large, the outer diameter of the lower neck portion 20 gradually increases from a certain point toward the lower body portion 30, i.e., as it moves away from the neck ring 12 in the axial direction, and the wall thickness of the preform 1 gradually increases. The portion where the wall thickness gradually increases is referred to as the increasing wall thickness portion 21. In the example shown in FIG. 1 , the outer diameter is constant from position P1 to position P2 directly below the neck ring 12, and the outer diameter gradually increases from position P2 to position P3, and the region from position P2 to position P3 is the increasing wall thickness portion 21.

[0018] The point (position P3) where the wall thickness starts to become constant as it continues from the neck lower part 20 and moves away from the neck ring 12 in the axial direction is defined as the upper end 31 of the body part, and the area below this point is defined as the body part 30. Therefore, the maximum outer diameter of the body part 30 is larger than the diameter immediately below the neck ring 12.

[0019] The bottom portion 50 also includes a portion where the thickness gradually increases from the closed end 51 (position P8) toward the upper body portion 30, i.e., toward the neck ring 12. The point (position P7) where the thickness continues from the bottom portion 50 and begins to become constant along the axial direction toward the neck ring 12 is defined as the body lower end 32, and the area above this point is defined as the body portion 30.

[0020] The body portion 30 includes a thick-walled portion 35 whose thickness gradually increases and then decreases with increasing distance from the neck ring 12 along the axial direction. The end (position P4) on the neck ring 12 side where the thickness begins to increase is referred to as the thick-walled portion upper end 36, and the end (position P6) on the bottom 50 side where the thickness ends is referred to as the thick-walled portion lower end 37. The region from the thick-walled portion upper end 36 to the thick-walled portion lower end 37 is referred to as the thick-walled portion 35. The thickest part of the thick-walled portion 35 (position P5) is referred to as the maximum thickness portion 38. The portion of the body portion 30 closer to the neck ring 12 than the thick-walled portion upper end 36 is referred to as the upper uniform thickness portion 34a, and the portion closer to the bottom 50 than the thick-walled portion lower end 37 is referred to as the lower uniform thickness portion 34b. The upper uniform thickness portion 34a and the lower uniform thickness portion 34b are collectively referred to as the uniform thickness portion 34.

[0021] By providing thick-walled portion 35 in the axial center portion of body 30, when bottle 100 is formed by blow molding, a sufficient amount of material is used to form waist portion 132 near the center of body 130 of bottle 100, ensuring sufficient strength of waist portion 132. As a result, waist portion 132 becomes easier to grip, and defects such as inversion of the depressions formed in waist portion 132 are prevented.

[0022] The location of thick-walled portion 35 depends on the shape and function of bottle 100. Thick-walled portion 35 is provided in a location on the bottle that requires strength or a location that requires material due to a thicker or more complex shape. For example, maximum thickness portion 38 may be positioned so that the length from just below neck ring 12 to maximum thickness portion 38 (the length from position P1 to position P5) is in the range of 40% to 60% of the length from just below neck ring 12 to closed end 51 (the length from position P1 to position P8). For example, in the case of bottle 100, considering balance when gripping, the area near the center of bottle 100 is considered to be the easiest to grip, and it is expected that sufficient strength and a shape that makes it easy to grip are required in this area.

[0023] Furthermore, for example, thick portion upper end 36 may be positioned so that the length from just below neck ring 12 to thick portion upper end 36 (the length from position P1 to position P4) is in the range of 22% to 32% of the length from just below neck ring 12 to closed end 51 (the length from position P1 to position P8). Furthermore, for example, thick portion lower end 37 may be positioned so that the length from just below neck ring 12 to thick portion lower end 37 (the length from position P1 to position P6) is in the range of 67% to 77% of the length from just below neck ring 12 to closed end 51 (the length from position P1 to position P8).

[0024] The thick-walled portion 35 is configured as follows: the inner diameter of the preform 1 gradually decreases from the thick-walled portion upper end 36 to the maximum thickness portion 38. The point where the inner diameter gradually starts to decrease with increasing distance from the neck ring 12 along this axial direction is referred to as the inner diameter reduction start portion 42, the point where the decrease in the inner diameter ends is referred to as the inner diameter reduction end portion 43, and the region from the inner diameter reduction start portion 42 to the inner diameter reduction end portion 43 is referred to as the inner diameter reduction portion 41. In the body portion 30, the region where the inner diameter does not change other than the inner diameter reduction portion 41 is referred to as the uniform inner diameter portion 44, the portion of the uniform inner diameter portion 44 closer to the neck ring 12 than the inner diameter reduction portion 41 is referred to as the upper uniform inner diameter portion 44a, and the portion of the uniform inner diameter portion 44 closer to the bottom portion 50 than the inner diameter reduction portion 41 is referred to as the lower uniform inner diameter portion 44b.

[0025] The outer diameter of the preform 1 gradually decreases from the maximum thickness portion 38 to the thick-wall portion lower end 37. The point at which the outer diameter begins to gradually decrease with increasing distance from the neck ring 12 along this axial direction is referred to as the outer diameter reduction start portion 47, the point at which the outer diameter reduction ends is referred to as the outer diameter reduction end portion 48, and the region from the outer diameter reduction start portion 47 to the outer diameter reduction end portion 48 is referred to as the outer diameter reduction portion 46. In the body portion 30, the region where the outer diameter does not change other than the outer diameter reduction portion 46 is referred to as the uniform outer diameter portion 49, the portion of the uniform outer diameter portion 49 closer to the neck ring 12 than the outer diameter reduction portion 46 is referred to as the upper uniform outer diameter portion 49a, and the portion of the uniform outer diameter portion 49 closer to the bottom 50 than the outer diameter reduction portion 46 is referred to as the lower uniform outer diameter portion 49b.

[0026] In this embodiment, the position of the inner diameter reduction start portion 42 corresponds to the position of the thick-walled portion upper end 36, and the position of the inner diameter reduction end portion 43 corresponds to the position of the maximum-walled portion 38. In the inner diameter reduction portion 41, the outer diameter of the preform 1 is constant, forming an upper uniform outer diameter portion 49a. Therefore, in the inner diameter reduction portion 41, the wall thickness increases as the inner diameter decreases. Furthermore, the position of the outer diameter reduction start portion 47 corresponds to the position of the maximum-walled portion 38, and the position of the outer diameter reduction end portion 48 corresponds to the position of the thick-walled portion lower end 37. In the outer diameter reduction portion 46, the inner diameter of the preform 1 is constant, forming a lower uniform inner diameter portion 44b. Therefore, in the outer diameter reduction portion 46, the wall thickness decreases as the outer diameter decreases.

[0027] Not limited to this embodiment, as long as the inner diameter reduction end portion 43 is located at the same position as the outer diameter reduction start portion 47 in the axial direction or the inner diameter reduction end portion 43 is located closer to the neck ring 12 than the outer diameter reduction start portion 47, the thick-walled portion 35 will be formed regardless of the shapes of the inner diameter reduction portion 41 and the outer diameter reduction portion 46. When the outer diameter reduction start portion 47 is located closer to the neck ring 12 than the inner diameter reduction end portion 43 in the axial direction, the thick-walled portion 35 can be formed by appropriately setting the inner surface shape of the inner diameter reduction portion 41 and the outer surface shape of the outer diameter reduction portion 46.

[0028] When the inner diameter reduction end portion 43 and the outer diameter reduction start portion 47 are located in the same position in the axial direction, as in this embodiment, the maximum thickness portion 38 does not have a width. On the other hand, if the inner diameter reduction end portion 43 and the outer diameter reduction start portion 47 are located in different positions and there are continuous portions in the axial direction where the outer surface and the inner surface are equidistant in the direction perpendicular to the axis, the maximum thickness portion 38 may have a width. For example, if the inner diameter reduction end portion 43 is located closer to the neck ring 12 in the axial direction than the outer diameter reduction start portion 47, the distance between the inner surface and the outer surface in the direction perpendicular to the axis is equidistant in the portion where the lower inner diameter uniform portion 44b and the upper outer diameter uniform portion 49a face each other, and therefore the maximum thickness portion 38 has a width.

[0029] In this embodiment, the upper uniform thickness portion 34a and the lower uniform thickness portion 34b have the same thickness. However, this is not limiting, and the thickness of the upper uniform thickness portion 34a and the thickness of the lower uniform thickness portion 34b may be different. The upper uniform thickness portion 34a may be thicker than the lower uniform thickness portion 34b, or the lower uniform thickness portion 34b may be thicker than the upper uniform thickness portion 34a, but the thick portion 35 is thicker than both the upper uniform thickness portion 34a and the lower uniform thickness portion 34b.

[0030] In this embodiment, the overall mass of the preform 1 is, for example, 27 g or less, and may be 26.5 g, for example. For example, a preform 1 having a 30 mm diameter neck 10 may have a uniform thickness portion 34 of 2.6 mm and a maximum thickness portion 38 of 2.7 mm. In this example, the neck 110 of the bottle 100 may have a mass of 5.0 g, a shoulder 120 of 4.9 g, an upper body 131 of 3.3 g, a waist 132 of 4.3 g, a lower body 133 of 5.0 g, and a heel 151 and a bottom 152 of 4.0 g. In this example, the mass of the waist 132 of the bottle 100 increases by approximately 10% compared to when the entire body 30 of the preform 1 has a thickness of 2.6 mm. In this way, the thickness of maximum thickness portion 38 may be 3% to 8% thicker than the thickness of constant thickness portion 34. By making it thicker to this extent, the bottle portion corresponding to thick-walled portion 35 can be given the desired functionality.

[0031] [First Modification] A first modified example will be described. Differences from the above-described embodiment will be described below, and the same components will be denoted by the same reference numerals and will not be described again. FIG. 3 shows an outline of a configuration example of a preform 2 according to the first modified example. As shown in this figure, the preform 2 according to this modified example has a constant inner diameter from the neck portion 10 to the body portion 30. Meanwhile, the wall thickness of the preform 2 is designed similarly to that of the preform 1 according to the above-described embodiment, as described with reference to FIG. 1. Therefore, in the preform 2 according to the first modified example shown in FIG. 3, the outer diameter gradually increases in the increasing wall thickness portion 21 as it moves away from the neck ring 12 along the axial direction, remains constant in the upper uniform thickness portion 34a, gradually increases from the upper end 36 of the thick wall portion to the maximum thickness portion 38, gradually decreases from the maximum thickness portion 38 to the lower end 37 of the thick wall portion, and remains constant in the lower uniform thickness portion 34b. Even with this shape, the same effects as those of the preform 1 according to the above-described embodiment can be obtained.

[0032] [About injection molding molds] The preforms according to the above-described embodiment and the first modified example are formed by, for example, injection molding, compression molding, etc. Here, a mold used for manufacturing the preform by injection molding will be described.

[0033] FIG. 4 is a diagram showing an outline of an example of the configuration of a mold 210 used to manufacture the preform 1 according to the embodiment described above with reference to FIG. 1. While a gate is not shown in this figure, the gate may be provided, for example, at the position of the closed end 51. As shown in FIG. 4, the mold 210 has a core mold 211, a mouth mold 212, which is a cavity mold, and a body mold 215. To prevent undercuts from occurring in the body mold 215, the mold split position P11 between the mouth mold 212 and the body mold 215 corresponds to the position of the body upper end 31. Therefore, the body mold 215 forms the outer shape of the body portion 30 and the bottom portion 50 of the preform 1, extending from the body upper end 31 toward the closed end 51. Meanwhile, the mouth mold 212 forms the outer shape of the mouth portion 10 and the neck lower portion 20, extending from the body upper end 31 toward the open end 11 of the preform 1. The mouth mold 212 is a split mold and has a first mouth mold 213 and a second mouth mold 214 .

[0034] FIG. 5 is a diagram showing an outline of a configuration example of a mold 220 used to manufacture the preform 2 according to the first modified example described above with reference to FIG. 3. As shown in FIG. 5, the mold 220 has a core mold 221, a mouth mold 222 as a cavity mold, and a body mold 225. To prevent undercuts in the body mold 225, a mold split position P12 between the mouth mold 222 and the body mold 225 corresponds to the position of the maximum thickness portion 38. Therefore, the body mold 225 forms the outer shape of the lower side of the body portion 30 and the bottom portion 50 of the preform 1, from the maximum thickness portion 38 to the closed end 51 side. On the other hand, the mouth mold 222 forms the outer shape of the mouth portion 10, the lower neck portion 20, and the upper side of the body portion 30, from the maximum thickness portion 38 to the open end 11 side of the preform 1. The mouth mold 222 is a split mold, and has a first mouth mold 223 and a second mouth mold 224.

[0035] The production of the preform 1 shown in FIG. 1 using the mold 210 shown in FIG. 4 is compared with the production of the preform 2 shown in FIG. 3 using the mold 220 shown in FIG. 5. Compared to the mold 220 shown in FIG. 5, the mold 210 shown in FIG. 4 has a larger body mold 215 and a smaller split mouth mold 212. Generally, compared to cylindrical molds such as the body molds 215 and 225, split molds such as the mouth molds 212 and 222 have more restrictions on the design of the cooling water channels, and therefore tend to have lower cooling capacity. Compared to the mold 210 shown in FIG. 4, the mold 220 shown in FIG. 5 has a relatively large split mouth mold 222, and its lower cooling capacity results in a relatively slow molding cycle. For this reason, the production of the preform 1 shown in FIG. 1 using the mold 210 shown in FIG. 4 is more efficient and more preferable.

[0036] [Second Modification] A second modified example will be described. Here, differences from the above-described embodiment will be described, and the same parts will be assigned the same reference numerals and their description will be omitted. FIG. 6 shows an outline of a configuration example of a preform 3 according to the second modified example. This preform 3 is configured to be suitable for bottles with a smaller capacity than the preform 1 of the above-described embodiment described with reference to FIG. 1. This preform 3 is for a bottle with a capacity of, for example, 500 mL. Therefore, in this preform 3, the lower neck portion 20, the body portion 30, and the bottom portion 50 are smaller than the mouth portion 10. On the other hand, a thick portion 35 is provided in the center of the body portion 30, making the central portion thick.

[0037] As shown in Figure 6, the inner and outer diameters of the preform 3 change as follows with increasing distance from the neck ring 12 along the axial direction: In other words, both the inner and outer diameters decrease in the neck lower part 20 up to the upper end 31 of the body portion. Here, the reduction in the inner diameter is greater than the reduction in the outer diameter, so the thickness of the neck lower part 20 gradually increases with increasing distance from the neck ring 12.

[0038] The trunk portion 30 has the same configuration as the preform 1 of the embodiment described above with reference to Fig. 1. That is, the inner diameter is constant from the trunk portion upper end 31 to the inner diameter reduction start portion 42, gradually reduces in the inner diameter reduction portion 41 from the inner diameter reduction start portion 42 to the inner diameter reduction end portion 43, and is constant from the inner diameter reduction end portion 43 to the trunk portion lower end 32. The outer diameter is constant from the trunk portion upper end 31 to the outer diameter reduction start portion 47, gradually reduces in the outer diameter reduction portion 46 from the outer diameter reduction start portion 47 to the outer diameter reduction end portion 48, and is constant from the outer diameter reduction end portion 48 to the trunk portion lower end 32. The inner diameter reduction start portion 42 is closer to the neck ring 12 than the outer diameter reduction start portion 47, and the inner diameter reduction end portion 43 is closer to the neck ring 12 than the outer diameter reduction end portion 48, and the inner diameter reduction end portion 43 and the outer diameter reduction start portion 47 are in corresponding positions.

[0039] Therefore, an upper uniform thickness portion 34a with a uniform thickness is formed on the neck ring 12 side from the inner diameter reduction starting portion 42, and a thick portion 35 is formed in which the thickness gradually increases from the inner diameter reduction starting portion 42 to the inner diameter reduction end portion 43 (outer diameter reduction starting portion 47) and gradually decreases from the outer diameter reduction starting portion 47 (inner diameter reduction end portion 43) to the outer diameter reduction end portion 48, and a lower uniform thickness portion 34b is formed from the outer diameter reduction end portion 48 toward the bottom 50.

[0040] In this way, the preform 3 relating to the second modified example also has a thick-walled portion 35 in the center of the body 30, so this preform 3 is suitable for producing bottles with designs that require strength or material in the center of the body even if they have a small capacity.

[0041] Furthermore, in the mold used when forming the preform 3 according to the second modified example by injection molding, the mold split position between the mouth mold of the cavity mold and the body mold can be set at a position corresponding to the neck lower part 20, as in the case described with reference to Fig. 4. For example, the mold split position can be set at the upper end 22 of the thickened portion 21 of the neck lower part 20, or directly below 23 of the neck ring 12. As a result, the body mold can be made relatively large, resulting in high production efficiency.

[0042] The present invention has been described above by showing preferred embodiments, but it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention. [Explanation of symbols]

[0043] 1, 2, 3 Preform 10 Mouth 11 Open end 12 Neck Ring 20 Lower neck 21 Increased thickness 22 Upper end of increased thickness 23 Directly below the neck ring 30 Torso 31 Upper end of body 32 Lower end of body 34 Equal thickness section 34a Upper equal thickness section 34b Lower equal thickness section 35 Thick part 36 Upper end of thick wall part 37 Thick wall bottom end 38 Maximum thickness part 41 Reduced inner diameter section 42 Inner diameter reduction start part 43 End of reduced inner diameter 44 Uniform inner diameter section 44a Upper inner diameter uniform part 44b Lower inner diameter uniform part 46 Reduced outer diameter part 47 Outer diameter reduction start part 48 End of outer diameter reduction 49 Uniform outer diameter part 49a Upper uniform outer diameter part 49b Lower outer diameter uniform part 50 bottom 51 Closed end 100 bottles 110 Mouth 112 Neck Ring 120 Shoulder 130 Torso 131 Upper torso 132 Waist 133 Lower torso 135 depression 151 Heel 152 Bottom 210 Mold 211 Core type 212 Mouth type 213 1st mouth type 214 2nd mouth type 215 Body type 220 Mold 221 Core type 222 Mouth type 223 1st mouth type 224 2nd mouth type 225 Body type

Claims

1. a mouth portion including an opening end to a neck ring; a neck lower portion including a portion connected to the mouth portion and having a wall thickness that gradually increases with increasing distance from the neck ring along an axial direction; a bottom portion including a closed end opposite the open end, the bottom portion including a portion whose thickness gradually increases toward the neck ring; The point where the wall thickness starts to become constant as the wall moves away from the neck ring along the axial direction, which is connected to the neck lower part, is defined as the upper end of the body part, and the point where the wall thickness starts to become constant as the wall moves away from the neck ring along the axial direction, which is connected to the bottom part, is defined as the lower end of the body part, and the body part is the region from the upper end of the body part to the lower end of the body part. A preform for a synthetic resin container comprising: The body portion includes a thick-walled portion whose thickness gradually increases and decreases with increasing distance from the neck ring along the axial direction. Preform.

2. The body portion is a reduced inner diameter portion whose inner diameter gradually decreases with increasing distance from the neck ring in the axial direction; a reduced outer diameter portion whose outer diameter gradually decreases with increasing distance from the neck ring along the axial direction; having The preform according to claim 1.

3. 3. The preform according to claim 2, wherein, in the axial direction, an inner diameter reduction end portion, which is the end of the inner diameter reduction portion closer to the bottom portion, is located closer to the neck ring than or at the same position as an outer diameter reduction start portion, which is the end of the outer diameter reduction portion closer to the neck ring.

4. 4. The preform according to claim 1, wherein the thickest portion of the thick-walled portion is disposed such that the length from the neck ring to the thickest portion is in the range of 40% to 60% of the length from the neck ring to the closed end.

5. The thickness of the thickest portion of the thick-walled portion is 3% to 8% thicker than the thickness of the portion of the body excluding the thick-walled portion.

6. 6. The preform according to claim 1, wherein the thickness of the body portion on the neck ring side of the thick portion is equal to the thickness of the body portion on the bottom side of the thick portion.

7. 7. The preform according to claim 1, wherein the neck lower portion includes a portion whose outer diameter gradually increases with increasing distance from the neck ring in the axial direction.

8. 8. The preform according to claim 1, having an overall mass of 27 g or less.

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