Synthetic resin containers and preforms

Abstract

To provide high visibility of liquid level of content liquid while suppressing deterioration by the light of the content liquid by applying shading without degrading recyclability.SOLUTION: A container 1, having a mouth part 2 serving as an injection outlet of content liquid and a storage part 3 storing content liquid, includes a translucent part 6 with light transmissivity formed in a band shape within a prescribed range along the axial direction in a storage part 3 and a shading part 7 with shading in a foaming structure containing many foams provided in a portion except the translucent part 6 of the storage part 3.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a synthetic resin container having a light-transmitting portion through which the liquid level of the contained liquid can be visually observed, and a preform for blow molding such a synthetic resin container. [Background technology]

[0002] 2. Description of the Related Art Conventionally, synthetic resin containers have been known which are produced by forming a bottomed cylindrical preform using a thermoplastic resin such as polyethylene terephthalate, and then molding this preform into a bottle shape by biaxial stretch blow molding or the like.

[0003] In recent years, this type of synthetic resin container has come to be widely used for various purposes, not limited to beverages, seasonings, etc., and various improvements have been made according to the purpose. For example, Patent Document 1 proposes a synthetic resin container with a window, in which the container itself is made opaque with a colored resin to protect the contents from ultraviolet light, and a vertical band-shaped transparent window is formed so that the state of the contents can be seen when refilling the contents and using it. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-108796 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in recent years, efforts have been made to collect used containers and reuse them for various purposes as recycled resin. However, in addition to the purpose of protecting the contents as in Patent Document 1, if the containers are colored by blending colorants such as pigments into the resin for purposes such as decoration, the uses for which they can be reused are limited.

[0006] In light of these circumstances, the inventors conducted extensive research to find a way to impart light-blocking properties without compromising recyclability, thereby suppressing deterioration of the contents due to light while also improving visibility of the liquid level of the contents, and as a result, they have completed the present invention. [Means for solving the problem]

[0007] The present invention Preform teeth, A preform formed in a bottomed cylindrical shape with a mouth portion formed on the upper end side and a body portion whose lower end side is closed in a semispherical shape, the body portion including a body inner layer and a body outer layer, a protrusion portion extending along the axial direction is formed in the body inner layer, the body outer layer is laminated so as to cover the peripheral surface of the body inner layer excluding the protrusion portion, the mouth portion and the body inner layer are integrally molded using a light-transmitting thermoplastic polyester, the body outer layer is molded using a foamable resin obtained by adding a foaming agent to a thermoplastic polyester, the area where the protrusion portion is formed is provided as a light-transmitting portion forming region, and the body outer layer is provided as a light-shielding portion forming region. It is in the composition.

[0008] The present invention also relates to Manufacturing method of synthetic resin container teeth, A method for forming a light transmitting portion formed by the light transmitting portion forming region in a band shape in a predetermined range along the axial direction of a housing portion by blow molding the preform, and forming a light shielding portion formed by the light shielding portion forming region in a portion of the housing portion excluding the light transmitting portion. It is stated as such. Effect of the Invention

[0009] According to the present invention, light-blocking properties can be imparted to the resin without blending colorants such as pigments into the resin, and the liquid level of the contents can be visually observed through the light-transmitting portion while suppressing deterioration of the contents due to light without compromising recyclability. [Brief description of the drawings]

[0010] [Figure 1] 1 is a perspective view showing an outline of a synthetic resin container according to an embodiment of the present invention. [Diagram 2] 1 is a front view showing an outline of a synthetic resin container according to an embodiment of the present invention. [Diagram 3] 3 is a cross-sectional view taken along line AA in FIG. 2. [Figure 4] 3 is a cross-sectional view of FIG. 2 taken along line B-B. [Diagram 5] FIG. 1 is a front view showing an outline of a preform according to an embodiment of the present invention. [Figure 6] 5C is a cross-sectional view taken along line CC of FIG. [Figure 7] FIG. 1 is an explanatory diagram showing an example of an injection molding system for molding a preform according to an embodiment of the present invention. [Figure 8] FIG. 2 is a perspective view showing an example of a flow path member. [Figure 9] FIG. 2 is a perspective view showing an example of a flow path member. [Figure 10] 5A and 5B are explanatory diagrams illustrating the state of a resin material in a nozzle portion. [Figure 11] 5A and 5B are explanatory diagrams illustrating the state of a resin material in a nozzle portion. [Figure 12] FIG. 4 is an explanatory diagram showing the flow of a resin material in a resin flow path. [Figure 13] FIG. 13 is a front view showing an outline of a modified example of a preform according to an embodiment of the present invention. [Figure 14] FIG. 14 is a cross-sectional view taken along line DD of FIG. [Figure 15] FIG. 11 is a front view showing an outline of a preform intermediate in a modified example of the preform according to the embodiment of the present invention. [Figure 16] 16 is a cross-sectional view of FIG. 15 taken along line E-E. [Figure 17] 3 is a cross-sectional view showing a cross section corresponding to the AA cross section in FIG. 2 of a modified synthetic resin container according to an embodiment of the present invention. FIG. [Figure 18] FIG. 11 is a front view showing an outline of another modified example of the preform according to the embodiment of the present invention. [Figure 19] FIG. 19 is a cross-sectional view of FIG. 18 shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[0012] Fig. 1 is a perspective view showing an outline of a synthetic resin container according to this embodiment, and Fig. 2 is a front view of the same. Fig. 3 is a cross-sectional view taken along line AA in Fig. 2, and Fig. 4 is a cross-sectional view taken along line BB in Fig. 2, but the wall thicknesses shown in the cross sections are exaggerated and do not reflect the actual dimensions.

[0013] The container 1 shown in these figures has a mouth 2 which serves as an inlet / outlet for the content liquid, and a storage section 3 in which the internal solution is stored. The storage section 3 can be molded to include a body 4 whose upper end in the height direction tapers toward the mouth 2 and connects to the lower end of the mouth 2, and a bottom 5 which closes the lower end side in the height direction of the body 4. In the example shown in the figures, the container 1 is molded to have a generally cylindrical container shape, but the shape of the container 1 is not limited to this.

[0014] Here, the height direction refers to the direction perpendicular to the horizontal plane when container 1 is placed upright on the horizontal plane with mouth 2 facing up, and the up-down, left-right and length-width directions of container 1 are defined as shown in Figure 2 when container 1 is placed upright with mouth 2 facing up.

[0015] In the illustrated example, the circumferential surface of the cylindrical opening 2 is provided with an engagement protrusion 2a for attaching a lid (not shown) by tapping, but the means for attaching the lid is not limited to this. A screw thread may be provided instead of the engagement protrusion 2a so that the lid can be attached by screwing. Further, on the lower end side of the mouth portion 2, there is provided an annular neck ring 2b that protrudes outward in the circumferential direction.

[0016] The container 3 is provided with a light-transmitting portion 6 that is formed in a band shape over a predetermined range along the axial direction so that the liquid level of the content liquid can be visually confirmed. Further, the housing portion 3 is provided, in a portion other than the light transmitting portion 6, with a light blocking portion 7 having a foam structure containing a large number of bubbles and imparting light blocking properties.

[0017] According to such a container 1, light blocking properties can be imparted without blending a colorant such as a pigment into the resin, and therefore deterioration of the contained liquid due to light can be suppressed without impairing the recyclability of the container 1. In addition, for example, when refilling the liquid, the liquid level of the liquid can be visually confirmed through the light transmitting portion 6, so that it is possible to refill an appropriate amount of the liquid without overflowing the liquid.

[0018] Furthermore, in order to improve the visibility of the liquid level of the content liquid, it is preferable that the mouth portion 2 has translucency so that the liquid level of the content liquid can be seen even through the mouth portion 2. When a colorant is mixed into the resin, it is difficult to selectively prevent the mouth portion 2 from being colored, and since the mouth portion 2 is also colored, it is not possible to make the mouth portion 2 translucent, but in this embodiment, there is no such problem, and it is possible to improve the visibility of the liquid level of the content liquid by providing the light-transmitting portion 6 in the storage portion 3 and making the mouth portion 2 translucent.

[0019] Furthermore, since no coloring agent such as a pigment is mixed into the resin, when the container 1 is incinerated without being recycled, the combustion residue can be reduced.

[0020] In this embodiment, the container 1 can be molded into a predetermined container shape, for example, by blow molding a preform 10 as shown in FIG.

[0021] FIG. 5 shows an example of a preform 10 for blow molding a container 1, and the preform 10 is formed in a bottomed cylindrical shape having a mouth portion 20 formed on the upper end side and a body portion 30 that is closed in a semispherical shape on the lower end side.

[0022] Here, the up-down, left-right and length-width directions of the preform 10 are defined as being in the state shown in FIG. 5 with the mouth portion 20 side facing up. FIG. 6 is a cross-sectional view taken along line CC of FIG. 5, but the thicknesses shown in the cross-section are exaggerated and do not reflect the actual dimensions.

[0023] The mouth portion 20 of the preform 10 is a portion that will become the mouth portion 2 of the container 1 while maintaining its appearance without being stretched by blow molding, and the mouth portion 20 of the preform 10 is provided with an engagement protrusion 2a and a neck ring 2b indicated by the same reference numerals as those attached to the container 1. As described later, the preform 10 is blow molded to have a predetermined container shape by stretching the body portion 30 from below the neck ring 2b provided on the mouth portion 20 as a starting point and molding it to become the container portion 3 of the container 1. At that time, the preform 10 is provided with a light-transmitting portion forming region 60 provided corresponding to the light-transmitting portion 6 and a light-shielding portion forming region 70 provided corresponding to the light-shielding portion 7 so that the light-transmitting portion 6 and the light-shielding portion 7 are formed in the container portion 3 of the container 1.

[0024] Such a preform 10 can be made using, for example, a translucent thermoplastic polyester such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, amorphous polyarylate, polylactic acid, polyethylene furanoate, or copolymers thereof, and in particular, can be molded using an ethylene terephthalate-based thermoplastic polyester such as polyethylene terephthalate.

[0025] At least the light-shielding portion forming region 70 can be formed from a foamable resin containing a predetermined amount of foaming agent in the resin, for example by dissolving an inert gas such as carbon dioxide gas or nitrogen gas as a physical foaming agent, or a pyrolyzable compound such as a carbonate that generates carbon dioxide gas upon thermal decomposition or an azo compound that generates nitrogen gas upon thermal decomposition as a chemical foaming agent, into the molten resin when the above-mentioned resin is melted and kneaded, and at least the light-transmitting portion forming region 60 can be formed from the above-mentioned resin that does not contain a foaming agent (foaming-agent-free resin).

[0026] Moreover, such a preform 10 can be molded by injection molding, for example, as follows.

[0027] FIG. 7 is an explanatory diagram showing an example of an injection molding system for molding the preform 10, and shows a schematic cross section of a main part including a nozzle portion 100.

[0028] In the injection molding system shown in Figure 7, the nozzle portion 100, which injects molten resin into the cavity of the mold M for molding the preform 10, comprises a nozzle body 102 having a nozzle opening 103 at the center of its tip, and a flow path member 101 that is arranged coaxially within the nozzle body 102 and forms a resin flow path 104 between it and the nozzle body 102, and is heated and controlled by a heater (not shown) so that the resin in the nozzle portion 100 is maintained in a flowable molten state.

[0029] The flow path member 101 disposed within the nozzle body 102 is a cylindrical member formed to fit closely to the inner circumferential surface of the cylindrical nozzle body 102, except for the portion that forms a resin flow path 104 between it and the nozzle body 102, and the inner circumferential surface of the nozzle body 102 includes a tapered surface 105 that narrows in diameter toward the nozzle opening 103, and the tip side of the flow path member 101 disposed opposite the tapered surface 105 is a tapered portion 106 that is tapered downward.

[0030] In addition, inside the flow path member 101, a long, cylindrical shutoff pin 108 that opens and closes the nozzle opening 103 is inserted along the central axis, and a first resin supply path 109 through which a foamable resin is supplied from an injection device not shown, and a second resin supply path 110 through which a foaming-agent-free resin is supplied from an injection device not shown are drilled along the axial direction of the flow path member 101.

[0031] The first resin supply path 109 has a first opening 109a that opens into a side surface of the cylindrical portion of the flow path member 101 and supplies a foamable resin to a resin flow path 104 formed between the flow path member 101 and the nozzle body 102. The second resin supply path 110 has a second opening 110a that opens into a tapered portion 106 on the tip side of the flow path member 101 and supplies a foaming-agent-free resin to the resin flow path 104 formed between the flow path member 101 and the nozzle body 102. The first opening 109a and the second opening 110a are opened so as to be positioned on the same plane including the central axis of the flow path member 101, with the central axis being sandwiched between them.

[0032] 8 and 9, a guide groove 111 is engraved on the outer circumferential surface of the flow path member 101, starting from the first opening 109a, branching symmetrically in two directions along the side surface of the flow path member 101 toward the second opening 110a, curving at the end to reach the tapered portion 106, and terminating in a V-shape at the second opening 110a. A portion of the flow path member 101 on the tip side of the guide groove 111 is formed to have a smaller diameter than other portions that are in close contact with the inner circumferential surface of the nozzle body 102, so that a gap that becomes the resin flow path 104 is formed between the inner circumferential surface of the nozzle body 102.

[0033] In addition, in Figure 8, the flow path member 101 is shown in an oblique view so that the second opening 110a appears on the front side, and in Figure 9, the flow path member 101 is shown in an oblique view so that the first opening 109a appears on the front side.

[0034] According to the nozzle section 100 configured in this manner, the foamable resin supplied from the first opening 109a can flow through the resin flow path 104 toward the nozzle opening 103 while being guided by the guide groove 111 toward the second opening 110a (see Figs. 10 and 12). At this time, since the terminal side of the guide groove 111 is curved to reach the tapered section 106 and terminates by intersecting in a V-shape at the second opening 110a, the foamable resin guided to the guide groove 111 generates a directional flow (indicated by arrow α in Fig. 12) that merges from the left and right toward the second opening 110a and flows toward the nozzle opening 103. When non-foaming agent-containing resin is supplied therefrom through the second opening 110a (see FIG. 11), the translucent resin is extruded between the foamable resins that join from the left and right toward the second opening 110a, and is accompanied by the flow of the foamable resin, so that it flows in a straight line with a predetermined width toward the nozzle opening 103, as shown by arrow β in FIG. 12.

[0035] 10 shows a schematic diagram of the state of the resin in the nozzle portion 100 when a foamable resin is supplied from the first opening 109a of the first resin supply path 109 in a state where a foaming agent-free resin is retained in the second resin supply path 110, and FIG. 11 shows a schematic diagram of the state of the resin in the nozzle portion 100 when a foaming agent-free resin is supplied from the second opening 110a of the second resin supply path 110 in addition to the above. In FIG. 10 and FIG. 11, the foaming agent-free resin is shown by shading, and the foamable resin is shown by solid color.

[0036] In this way, when the resin flowing in the resin flow path 104 is injected from the nozzle opening 103, the drive of the injection screw of the injection device that supplies the foamable resin to the first resin supply path 109 and the drive of the injection screw of the injection device that supplies the foaming agent-free resin to the second resin supply path 110 are controlled. Then, while appropriately adjusting the timing at which the foamable resin is supplied from the first opening 109a and the timing at which the foaming agent-free resin is supplied from the second opening 110a, the foamable resin is injected and filled into the cavity of the mold M held at a high pressure while maintaining pressure so that the foamable resin can be prevented from breaking during its flow and from foaming after filling. As a result, the preform 10 can be molded in which the light-transmitting portion-forming region 60 made of the foaming agent-free resin is provided in the body portion 30 so as to extend in a band shape in a predetermined range along the axial direction, and the other portions including the light-shielding portion-forming region 70 are formed of the foamable resin. In the example of preform 10 shown in Figure 5, the areas formed by the foamable resin are shown shaded with diagonal lines, but at this stage, the areas formed by the foamable resin are non-foamed, and preform 10 is molded in a state in which these areas also have translucency.

[0037] To blow mold the preform 10 thus molded, first, the preform 10 is heated and softened to a state in which it can be blow molded, and then set in a blow mold (not shown). The preform 10 can be heated, for example, by an infrared heater. At that time, the mouth portion 20 is covered with a shielding body so that the body portion 30 is selectively heated. By undergoing such a heating process, the foamable resin forming the light-shielding portion forming region 70 of the body portion 30 is foamed while the foamable resin forming the mouth portion 20 is prevented from foaming, and the internal structure of the light-shielding portion forming region 70 provided in the body portion 30 can be changed so as to have a foamed structure containing a large number of bubbles formed thereby.

[0038] The preform 10 set in the blow molding die is stretched in the axial direction (longitudinal direction) by a stretching rod as necessary, and is also stretched in the axial and circumferential directions (lateral directions) by blow air blown into the preform 10. At this time, the body portion 30 is stretched starting from below the neck ring 2b provided at the mouth portion 20, and the shape of the cavity of the blow molding die is transferred, so that the stretched body portion 30 is molded to become the container portion 3 of the container 1.

[0039] By blow molding the preform 10 in this manner, in the molded container 1, the light transmitting portion 6 is formed by the light transmitting portion forming region 60 made of a foaming agent-free resin, and the light shielding portion 7 is formed by the light shielding portion forming region 70 having a foamed structure containing a large number of bubbles. As a result, it is possible to mold the container 1 including the storage portion 3 in which the light transmitting portion 6 having light transmission property formed in a band shape in a predetermined range along the axial direction is provided, and the light shielding portion 7 having light shielding property provided by a foamed structure containing a large number of bubbles is provided in the area other than the light transmitting portion 6.

[0040] Here, in the illustrated example, the light-transmitting portion 6 provided on the container 1 is formed in a band shape along the axial direction in a range from below the neck ring 2b to the bottom 5, but the range in which the light-transmitting portion 6 is formed is not limited to this. Since the range in which the light-transmitting portion 6 is formed is determined according to the light-transmitting portion forming region 60 provided in the preform 10, when molding the preform 10 as described above, the range in which the light-transmitting portion 6 is formed can be changed within a range that does not impair the visibility of the liquid level of the content liquid by appropriately adjusting the timing of supplying the foamable resin and the timing of supplying the foaming agent-free resin to change the range of the light-transmitting portion forming region 60 formed by the foaming agent-free resin. When molding the preform 10 in this way, the part formed by the foaming agent-free resin may extend beyond the range in which the light-transmitting portion forming region 60 should be formed and reach the mouth portion 20, for example, as shown by the chain line in FIG. 5.

[0041] In addition, in the example of the preform 10 shown in Fig. 5, if the foamable resin forming the mouth 20 of the preform 10 foams, the dimensional stability of the mouth 20 of the preform 10 and, in turn, the mouth 2 of the container 1 may be reduced by foaming, which may cause problems in attaching the lid. In order to avoid such problems, as described above, it is preferable to mold the container 1 while the mouth 2 of the container 1 is left unfoamed, without foaming the foamable resin forming the mouth 20. Furthermore, by making the mouth 2 of the container 1 unfoamed, it is possible to provide the light-transmitting portion 6 in the storage portion 3 and to make the mouth 2 translucent, thereby improving the visibility of the liquid level of the content liquid.

[0042] In this embodiment, the preform 10 can be molded by coinjection as described above, or by an injection molding method called two-color molding or double molding, as shown in a modified example in FIG.

[0043] 5, the preform 10 shown in Fig. 13 is formed in a bottomed tubular shape with a mouth 20 formed at the upper end side and a body 30 closed in a semispherical shape at the lower end side, but the body 30 is formed in two layers including a body inner layer 30a and a body outer layer 30b. As shown in the figure, the body inner layer 30a is formed with a protrusion 60a extending along the axial direction, and the body outer layer 30b is laminated so as to cover the peripheral surface of the body inner layer 30a excluding the protrusion 60a, so that the area where the protrusion 60a is formed is formed as the light-transmitting portion forming region 60, and the body outer layer 30b is formed as the light-shielding portion forming region 70. FIG. 14 is a DD cross-sectional view of FIG. 13, but the wall thickness shown in the cross-section is exaggerated and does not reflect the actual dimensions.

[0044] To mold such a preform 10, first, a core mold 200 for molding the inner peripheral surface of the preform 10 and the upper end surface of the mouth 20, a mouth mold 201 for molding the peripheral surface side of the mouth 20 including the upper surface and peripheral end surface of the neck ring 2b, and a first body mold 202a for molding the peripheral surface side of the body inner layer 30a including the lower surface of the neck ring 2b and the protrusion 60a are clamped together, and a foaming agent-free resin is injected into the cavity to mold the preform intermediate 10a shown in Fig. 15. Next, instead of the first body mold 202a, a second body mold 202b configured to form a gap for molding the body outer layer 30b is used to clamp the mold again, and then a foamable resin containing a foaming agent is injected to mold the body outer layer 30b. FIG. 16 is a cross-sectional view taken along the line E-E of FIG. 15, but the thicknesses shown in the cross-section are exaggerated and do not reflect the actual dimensions.

[0045] This allows a preform 10 to be molded in which a light-transmitting portion forming region 60 (region where the protrusion portion 60a is formed) made of a foaming agent-free resin is provided in the body 30 so as to extend in a band-like shape over a predetermined range along the axial direction, and a light-shielding portion forming region 70 (body outer layer 30b) made of a foamable resin is provided in the region of the body 30 excluding the light-transmitting portion forming region 60.

[0046] The preform 10 thus molded can also be subjected to a heat treatment similar to that in the above-mentioned example to foam the foamable resin forming the light-shielding portion-forming region 70, thereby changing the internal structure of the light-shielding portion-forming region 70 provided in the body 30 to have a foamed structure containing a large number of bubbles. Then, by blow molding such a preform 10, it is possible to mold a container 1 that has an appearance similar to that in the above-mentioned example, has a light-transmitting portion 6 formed in a band shape in a predetermined range along the axial direction, and has a light-shielding portion 7 provided with light-shielding properties by a foamed structure containing a large number of bubbles in the area other than the light-transmitting portion 6.

[0047] Also, unlike the above-mentioned example in which the mouth 20 of the preform 10 which becomes the mouth 2 of the container 1 is formed from a foamable resin, in this modification, it is easy to form the mouth 20 of the preform 10 which becomes the mouth 2 of the container 1 from a foaming agent-free resin. Therefore, according to this modification, it is possible to improve the visibility of the liquid level of the content liquid by making the mouth 2 of the molded container 1 translucent without taking the trouble of preventing the foamable resin from foaming.

[0048] 17 shows a cross section of the container 1 molded in this modified example, which corresponds to the cross section BB in Fig. 2, and the container 1 of this modified example has a non-foamed layer 8 formed by the body inner layer 30a on the inner surface side of the storage section 3. This allows the inner surface of the storage section 3 to be molded smoothly without being affected by foaming of the light-shielding section forming region 70 (body outer layer 30b). In Figure 17, the thickness shown in the cross section is exaggerated and does not reflect the actual dimensions.

[0049] Although the present invention has been described above by showing preferred embodiments, 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.

[0050] For example, in the above-mentioned embodiment, two examples of the preform 10 for blow molding the container 1 are described, but the above-mentioned examples are not limited as long as it is possible to mold the container 1 having the storage section 3 in which the light-transmitting section 6 having light-transmitting properties formed in a band shape in a predetermined range along the axial direction is provided, and the light-shielding section 7 having light-shielding properties due to a foamed structure containing a large number of bubbles is provided in the area other than the light-transmitting section 6. As in another modified example shown in FIG. 18, the preform 10 may be molded by co-injecting the foamable resin forming the light-shielding section forming region 70 so that it is embedded in the foaming agent-free resin so that the light-transmitting section forming region 60 is formed along the axial direction. FIG. 19 is a cross-sectional view taken along the line FF of FIG. 18, but the thicknesses shown in the cross-section are exaggerated and do not reflect the actual dimensions. In addition, in the above-described embodiment, the foamable resin that forms the light-shielding portion forming region 70 is foamed by the heat treatment during blow molding, but the foamable resin that forms the light-shielding portion forming region 70 may be foamed at the time when the preform 10 is injection molded. [Explanation of symbols]

[0051] 1 container 2 Mouth 3. Storage section 6 Translucent part 7 Light shielding section 8 Non-foam layer 10 Preform 60 Transparent part forming area 70 Shade forming area

Claims

1. A preform formed in a cylindrical shape with a bottom, the preform having a mouth portion formed on the upper end side and a body portion closed in a hemispherical shape on the lower end side, The body portion includes a body inner layer and a body outer layer, The body inner layer is formed with a protrusion extending along the axial direction, the body outer layer is laminated so as to cover a peripheral surface of the body inner layer excluding the protrusion portion, The mouth portion and the body inner layer are integrally molded using a light-transmitting thermoplastic polyester, the body outer layer is molded using a foamable resin obtained by adding a foaming agent to a thermoplastic polyester; a region where the protrusion portion is formed is provided as a light transmitting portion forming region, A preform, characterized in that the body outer layer is provided as a light-shielding portion forming region.

2. A preform as described in claim 1, wherein the outer layer of the body has a foamed structure containing a large number of air bubbles.

3. A method for producing a synthetic resin container by blow molding the preform according to claim 1, The body of the preform is selectively heated to foam the foamable resin forming the body outer layer, thereby changing the internal structure of the body outer layer to have a foamed structure containing a large number of bubbles, and the preform, which has been brought into a state where it can be blow molded, is set in a blow molding die and blow molded. a light transmitting portion formed by the light transmitting portion forming region is formed in a band shape in a predetermined range along the axial direction of the housing portion; A method for manufacturing a synthetic resin container, comprising forming a light-shielding portion formed by the light-shielding portion forming region in a portion of the container other than the light-transmitting portion.

4. A method for producing a synthetic resin container by blow molding the preform according to claim 2, comprising the steps of: The body portion of the preform is selectively heated, and the preform that is in a state where it can be blow molded is set in a blow molding die and blow molded. a light transmitting portion formed by the light transmitting portion forming region is formed in a band shape in a predetermined range along the axial direction of the housing portion; A method for manufacturing a synthetic resin container, comprising forming a light-shielding portion formed by the light-shielding portion forming region in a portion of the container other than the light-transmitting portion.

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