Synthetic resin container manufacturing method, molding device, and synthetic resin container

Abstract

To propose a method for manufacturing a synthetic resin container, a molding device, and a synthetic resin container in which a peripheral wall of the container is provided with a dark colored portion, a light colored portion, and a gradation portion.SOLUTION: In a method for manufacturing a synthetic resin container according to the present invention, a mold 1 includes a cavity 6 corresponding to a container 11, a first gate 4 for injecting a dark colored first synthetic resin, and a second gate 5 for injecting a light colored second synthetic resin. The first gate 4 and the second gate 5 are configured to inject the first synthetic resin and the second synthetic resin into the cavity 6 from a portion of the cavity 6 corresponding to a bottom 12 of the container 11. An injection of the first synthetic resin is started from the first gate 4, and when a predetermined amount of the first synthetic resin has been injected, an injection of the second synthetic resin is started from the second gate 5 to fill the cavity 6 with the first and second synthetic resins.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a synthetic resin container, a molding device, and a synthetic resin container. [Background technology]

[0002] A cylindrical synthetic resin container with a bottom, which has a bottom and a peripheral wall integrally connected to the bottom, has been used for some time. Such a synthetic resin container is often molded by injecting a synthetic resin into a mold.

[0003] Furthermore, containers of this type are decorated in various ways to differentiate them from other containers. Examples of decoration methods include providing a printed film on the outside of the container, as well as decorating the container by using an insert material or by providing highly decorative uneven portions on the container (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-177973 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-179654 [Patent Document 3] Patent No. 4640729 Summary of the Invention [Problem to be solved by the invention]

[0005] Although various decorative applications have been implemented for synthetic resin containers, further innovation is necessary to differentiate them. The present inventors decided to differentiate their containers from conventional containers by decorating the container itself by providing dark and light colored areas, as well as gradation areas where dark and light colors are mixed, on the peripheral wall of the container. Patent Document 3 discloses a preform incorporating specific technical features, and describes how a bottle with a highly pronounced gradation can be obtained by biaxially stretch-blow molding this preform. In contrast, the present invention aims to obtain a cylindrical container with a bottom that is decorated as described above when removed from a mold, without performing such biaxial stretch-blow molding. [Means for solving the problem]

[0006] The present invention relates to a method for manufacturing a synthetic resin container having a bottomed cylindrical shape, which is molded by injecting synthetic resin into a mold, wherein the mold has a cavity corresponding to the container, a first gate for injecting a dark-colored first synthetic resin, and a second gate for injecting a light-colored second synthetic resin, and the first gate and the second gate are configured to inject the first synthetic resin and the second synthetic resin into the cavity from a portion of the cavity corresponding to the bottom of the container, and injection of the first synthetic resin is started from the first gate, and when a predetermined amount of the first synthetic resin has been injected, injection of the second synthetic resin is started from the second gate. and continuously injecting the first synthetic resin up to a predetermined amount. This is a method for manufacturing a synthetic resin container, in which the cavity is filled with the first synthetic resin and the second synthetic resin, thereby providing the peripheral wall of the container with a dark colored portion mainly made of the first synthetic resin, a light colored portion mainly made of the second synthetic resin, and a gradation portion made of the first synthetic resin and the second synthetic resin.

[0007] The present invention also provides a method for manufacturing a synthetic resin container having a bottomed cylindrical shape, which is molded by injecting synthetic resin into a mold, the mold comprising a cavity corresponding to the container, a first gate for injecting a dark-colored first synthetic resin, and a second gate for injecting a light-colored second synthetic resin, the first gate and the second gate being configured to inject the first synthetic resin and the second synthetic resin into the cavity from portions of the cavity corresponding to the bottom of the container, the injection of the first synthetic resin being started from the first gate, and when a predetermined amount of the first synthetic resin has been injected, the injection of the second synthetic resin being started from the second gate, thereby filling the cavity with the first synthetic resin and the second synthetic resin, and providing a peripheral wall portion of the container with a dark-colored portion mainly made of the first synthetic resin, a light-colored portion mainly made of the second synthetic resin, and a gradation portion made of the first synthetic resin and the second synthetic resin, The predetermined amount is 20 to 40% of the total amount of the first synthetic resin to be injected into the cavity. A method for manufacturing synthetic resin containers .

[0008] It is preferable that the first injection speed at which the first synthetic resin is injected from the first gate and the second injection speed at which the second synthetic resin is injected from the second gate are both equal.

[0009] The first injection speed and the second injection speed are preferably 20 to 60 mm / s.

[0010] The present invention also provides a molding apparatus for molding a synthetic resin container having a bottomed cylindrical shape by injecting synthetic resin into a mold, wherein the mold has a cavity corresponding to the container, a first gate for injecting a dark-colored first synthetic resin, and a second gate for injecting a light-colored second synthetic resin, and the first gate and the second gate are configured to inject the first synthetic resin and the second synthetic resin into the cavity from a portion of the cavity corresponding to the bottom of the container, and injection of the first synthetic resin is started from the first gate, and when a predetermined amount of the first synthetic resin has been injected, injection of the second synthetic resin is started from the second gate. and continuously injecting the first synthetic resin up to a predetermined amount. By filling the cavity with the first synthetic resin and the second synthetic resin, the molding device provides the peripheral wall of the container with a dark colored portion mainly made of the first synthetic resin, a light colored portion mainly made of the second synthetic resin, and a gradation portion made of the first synthetic resin and the second synthetic resin.

[0011] The present invention also provides a cylindrical synthetic resin container with a bottom that is molded by injecting synthetic resin into a mold, the mold having a cavity corresponding to the container, a first gate for injecting a dark-colored first synthetic resin, and a second gate for injecting a light-colored second synthetic resin, the first gate and the second gate being configured to inject the first synthetic resin and the second synthetic resin into the cavity from portions of the cavity that correspond to the bottom of the container, and injection of the first synthetic resin is started from the first gate, and when a predetermined amount of the first synthetic resin has been injected, injection of the second synthetic resin is started from the second gate. and continuously injecting the first synthetic resin up to a predetermined amount.By filling the cavity with the first synthetic resin and the second synthetic resin, the container has a synthetic resin container having a dark colored portion mainly made of the first synthetic resin, a light colored portion mainly made of the second synthetic resin, and a gradation portion made of the first synthetic resin and the second synthetic resin on the peripheral wall portion of the container.

[0012] The present invention also provides a cylindrical synthetic resin container with a bottom that is molded by injecting synthetic resin into a mold, the mold having a cavity corresponding to the container, a first gate for injecting a dark-colored first synthetic resin, and a second gate for injecting a light-colored second synthetic resin, the first gate and the second gate being configured to inject the first synthetic resin and the second synthetic resin into the cavity from portions of the cavity that correspond to the bottom of the container, the injection of the first synthetic resin being started from the first gate, and when a predetermined amount of the first synthetic resin has been injected, the injection of the second synthetic resin being started from the second gate, thereby filling the cavity with the first synthetic resin and the second synthetic resin, and the peripheral wall of the container having a dark-colored portion mainly made of the first synthetic resin, a light-colored portion mainly made of the second synthetic resin, and a gradation portion made of the first synthetic resin and the second synthetic resin, The gradation portion includes an inner layer portion in which the first synthetic resin extends in the circumferential direction along the inner peripheral surface of the peripheral wall portion, an outer layer portion in which the first synthetic resin extends in the circumferential direction along the outer peripheral surface of the peripheral wall portion, and an intermediate layer portion in which the second synthetic resin extends in the circumferential direction between the inner layer portion and the outer layer portion. It is also a synthetic resin container. . [Effects of the Invention]

[0013] In the method for manufacturing a synthetic resin container according to the present invention, a first gate provided in a mold for injecting a first dark-colored synthetic resin and a second gate provided injecting a second light-colored synthetic resin are configured to inject the first and second synthetic resins into the mold cavity from portions of the cavity that correspond to the bottom of the container. Injection of the first synthetic resin is started from the first gate, and when a predetermined amount of the first synthetic resin has been injected, injection of the second synthetic resin is started from the second gate, thereby filling the cavity with the first and second synthetic resins, thereby providing the peripheral wall of the container with a dark-colored portion mainly made of the first synthetic resin, a light-colored portion mainly made of the second synthetic resin, and a gradation portion made of the first and second synthetic resins. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view of a mold provided in an embodiment of a molding apparatus according to the present invention. [Figure 2] 2A and 2B are a bottom view and a side view along the line AA, respectively, of a container molded by the mold shown in FIG. [Figure 3] 1 is a photograph of a container molded under the conditions of Confirmation Test 1. [Figure 4]1 is a photograph of a container molded under the conditions of confirmation test 2. [Figure 5] 1 is a photograph of a container molded under the conditions of confirmation test 3. [Figure 6] 1 is a photograph of a container molded under the conditions of confirmation test 4. [Figure 7] This is a photograph of a cross section of the container cut horizontally at the gradation part. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of a method for manufacturing a synthetic resin container, a molding device, and a synthetic resin container according to the present invention will be described with reference to the drawings.

[0016] First, the molding apparatus of this embodiment will be described. The molding apparatus of this embodiment includes an injection molding machine (not shown) and a mold 1 shown in FIG. 1. The injection molding machine injects molten synthetic resin into the mold 1. The injection molding machine of this embodiment is capable of melting two types of synthetic resin (hereinafter referred to as a first synthetic resin and a second synthetic resin) and injecting them into the mold 1.

[0017] In this embodiment, the first synthetic resin and the second synthetic resin are different in color, with the first synthetic resin being a dark color and the second synthetic resin being a light color. In this specification, a dark color refers to, for example, black, navy blue, or dark brown, and a light color refers to a color that is lighter or thinner than the first synthetic resin, such as white or cream. Furthermore, when the first synthetic resin has an opaque color, the color of the second synthetic resin includes translucent or transparent colors that are more transparent than the first synthetic resin.

[0018] As shown in FIG. 1, the mold 1 includes a cavity mold 2 and a core mold 3. The cavity mold 2 includes a first gate 4 through which a first synthetic resin injected from an injection molding machine passes, and a second gate 5 through which a second synthetic resin passes. In this embodiment, the first gate 4 and the second gate 5 are both pin gates. The mold 1 also includes a cavity 6 that is partitioned by the cavity mold 2 and the core mold 3 and through which the first gate 4 and the second gate 5 communicate. The cavity 6 in this embodiment has a shape corresponding to the cylindrical container 11 with a bottom shown in FIG. 2.

[0019] Here, a container 11 of this embodiment will be described with reference to FIG. 2. The container 11 has a disk-shaped bottom 12 and a cylindrical peripheral wall 13 integrally connected to the outer edge of the bottom 12. An opening 14 is provided on the side of the peripheral wall 13 opposite the side where the bottom 12 is located. As shown in FIGS. 1 and 2, a first gate 4 and a second gate 5 are provided in positions corresponding to the bottom 12 in the cavity 6. The container 11 can be molded in the mold 1 by injecting a first synthetic resin and a second synthetic resin into the cavity 6 through the first gate 4 and the second gate 5. In this embodiment, the first gate 4 and the second gate 5 are provided at positions offset by 180° from the center O of the bottom 12, as shown in FIG. 2(a). Furthermore, the first gate 4 and the second gate 5 are both provided at positions closer to the outer edge of the bottom 12 than the distance to the center O.

[0020] The inventors of the present application conducted extensive research using the above-mentioned molding device and found that by using the manufacturing method described below, it is possible to provide dark colored areas, light colored areas, and gradation areas where dark and light colors are mixed on the peripheral wall portion 13. This manufacturing method is described below.

[0021] First, the cavity mold 2 and core mold 3 are closed as shown in Figure 1. The injection molding machine is also set in a state where the molten first synthetic resin and second synthetic resin can be injected into the cavity 6 through the first gate 4 and the second gate 5.

[0022] Next, injection of the first synthetic resin begins from the first gate 4 toward the cavity 6. At this point, the second synthetic resin has not yet been injected into the cavity 6 from the second gate 5, and only the first synthetic resin flows within the cavity 6. The injection speed from the start to the end of injection of the first synthetic resin (hereinafter referred to as the first injection speed) is constant.

[0023] Then, when a predetermined amount of the first synthetic resin has been injected, injection of the second synthetic resin begins from the second gate 5 toward the cavity 6. The injection speed from the start to the end of injection of the second synthetic resin (hereinafter referred to as the second injection speed) is constant. Even after injection of the second synthetic resin, the first synthetic resin continues to be injected up to a predetermined amount. Here, the predetermined amount of the first synthetic resin is an amount equivalent to a maximum of 50% of the volume of the cavity 6.

[0024] Even after a predetermined amount of the first synthetic resin has been injected, the second synthetic resin continues to be injected into the cavity 6. After the cavity 6 is filled with the first synthetic resin and the second synthetic resin, the injection pressure of the second synthetic resin is maintained for a predetermined time. This causes the first synthetic resin and the second synthetic resin to solidify in the mold 1 in a shape that conforms to the shape of the cavity 6.

[0025] Thereafter, the core mold 3 is moved relative to the cavity mold 2, and the molded container 11 is removed from the mold 1. When manufactured in this manner, the peripheral wall 13 was provided with dark colored portions, light colored portions, and gradation portions where the dark and light colors are mixed.

[0026] As a comparative example of the above manufacturing method, when the first synthetic resin was injected into the cavity 6 through the first gate 4 and the second synthetic resin was simultaneously injected into the cavity 6 through the second gate 5, dark and light colored portions were formed on the peripheral wall 13, but almost no gradation was observed. Furthermore, when a predetermined amount of the second synthetic resin was first injected into the cavity 6 through the second gate 5 and then the first synthetic resin was injected toward the cavity 6 through the first gate 4, the peripheral wall 13 essentially had only dark and light colored portions, and almost no gradation was observed. Furthermore, when the first synthetic resin was injected toward the cavity 6 intermittently, where injection was stopped midway and then restarted, almost no gradation was observed. Furthermore, when intermittent injection was performed when a predetermined amount of the second synthetic resin was first injected into the cavity 6 through the second gate 5, essentially only dark and light colored portions were formed on the peripheral wall 13.

[0027] Next, confirmation tests 1 to 4 using the above manufacturing method will be described. In confirmation tests 1 to 4, the first synthetic resin was black and the second synthetic resin was white (slightly translucent white). The predetermined amount of the first synthetic resin (the total amount of the first synthetic resin injected into the cavity 6) corresponds to 33% of the volume of the cavity 6.

[0028] [Confirmation Test 1] In confirmation test 1, the injection amount (pre-injection amount) of the first synthetic resin injected from the first gate 4 toward the cavity 6 before starting injection of the second synthetic resin from the second gate 5 toward the cavity 6 was set according to conditions A to D shown in Table 1 below, and the container 11 was molded. Here, the pre-injection amount shown in Table 1 indicates a ratio based on a predetermined amount of the first synthetic resin (the total amount of the first synthetic resin injected into the cavity 6). To explain this point in more detail, for example, under condition B, injection of the second synthetic resin from the second gate 5 toward the cavity 6 was started at the timing when an amount of the first synthetic resin equivalent to 40% of the total amount of the first synthetic resin finally injected into the cavity 6 was injected from the first gate 4 toward the cavity 6.

[0029] 3 shows photographs of the dark colored portions, light colored portions, and gradation portions provided on the peripheral wall portion 13 of the containers 11 obtained by the manufacturing methods under conditions A to D. Note that the photograph of the peripheral wall portion 13 of each of the containers 11 obtained by the manufacturing methods under conditions A to D shown in FIG. 3 is taken from the direction along the arrow B in FIG. 2(a), and the bottom portion 12 is located on the side marked A to D in FIG. In addition, in the evaluation of the peripheral wall portion 13 shown in Table 1, "○" indicates a state in which the dark colored portions, light colored portions, and gradation portions are displayed in a balanced manner on the peripheral wall portion 13 (the light colored portions are approximately half or less of the circumferential length of the peripheral wall portion 13, and the gradation portions are approximately half or more of the height of the peripheral wall portion 13 (the length along the axial direction of the container 11)), and "△" indicates a state in which the dark colored portions, light colored portions, and gradation portions displayed on the peripheral wall portion 13 are unbalanced (for example, when the light colored portions are larger than half of the circumferential length of the peripheral wall portion 13, or when the gradation portions are smaller than half the height of the peripheral wall portion 13).

[0030] [Table 1]

[0031] As shown in Table 1 and FIG. 3, when the container 11 was molded under conditions C and D, the gradation portion was smaller than half the height of the peripheral wall portion 13 (the light-colored portion was smaller than half the height of the peripheral wall portion 13), and the balance between the dark colored portion, the light colored portion, and the gradation portion was lost. Also, although not shown in Table 1 and FIG. 3, when the pre-injection amount of the first synthetic resin was 0% (i.e., when the second synthetic resin was injected simultaneously with the first synthetic resin), as described above, the dark colored portion and the light colored portion were formed on the peripheral wall portion 13, but the gradation portion was hardly observed. On the other hand, when the container 11 was molded under conditions A and B, the dark colored portion, the light colored portion, and the gradation portion appeared in a balanced manner on the peripheral wall portion 13. Therefore, based on these results, it can be said that it is preferable to inject the second synthetic resin from the second gate 5 into the cavity 6 when the pre-injection amount of the first synthetic resin reached 20 to 40%.

[0032] [Confirmation test 2] In confirmation test 2, the first injection speed and the second injection speed were set according to conditions E to H shown in Table 2 below (condition B in confirmation test 2 was the same as condition B in confirmation test 1), and the container 11 was molded. That is, under conditions E to H, the first injection speed was the same, and the second injection speed increased in the order of conditions E to H shown in Table 2. In addition, under conditions E to H, the pre-injection amount of the above-mentioned first synthetic resin was 40% in all cases.

[0033] Photographs of the dark colored portions, light colored portions, and gradation portions provided on the peripheral wall portion 13 of the containers 11 obtained by the manufacturing methods under conditions E to H are shown in FIG. 4. Note that the photographs of the peripheral wall portion 13 of each of the containers 11 obtained by the manufacturing methods under conditions E to H shown in FIG. 4 are taken from the direction along the arrow C in FIG. 2(a), and the bottom portion 12 is located on the side marked E to H in FIG. 4. The meanings of "○" and "△" in the evaluation of the peripheral wall portion 13 shown in Table 2 are the same as those in Table 1.

[0034] [Table 2]

[0035] As shown in Table 2 and Figure 4, when container 11 was molded under conditions E, F, G, and H, the light-colored portions were larger than half the circumferential length of peripheral wall 13, and the gradation portions were smaller than half the height of peripheral wall 13, resulting in an imbalance between the dark-colored portions, light-colored portions, and gradation portions. On the other hand, when container 11 was molded under condition B, the dark-colored portions, light-colored portions, and gradation portions appeared in a balanced manner on peripheral wall 13.

[0036] [Confirmation Test 3] In confirmation test 3, the first injection speed and the second injection speed were set according to conditions I to L shown in Table 3 below (condition B in confirmation test 3 is the same as condition B in confirmation test 1), and the container 11 was molded. That is, under conditions I to L, the second injection speed was the same, and the first injection speed increased in the order of conditions I to L shown in Table 3. In addition, under conditions I to L, the pre-injection amount of the above-mentioned first synthetic resin was 40% in all cases.

[0037] Photographs of the dark colored portions, light colored portions, and gradation portions provided on the peripheral wall portion 13 of the containers 11 obtained by the manufacturing methods under conditions I to L are shown in FIG. 5. Note that the photographs of the peripheral wall portion 13 of each container 11 obtained by the manufacturing methods under conditions I to L shown in FIG. 5 are taken from the direction along the arrow C in FIG. 2(a), and the bottom portion 12 is located on the side marked I to L in FIG. 5. The meanings of "◯" and "△" in the evaluation of the peripheral wall portion 13 shown in Table 3 are the same as those in Table 1.

[0038] [Table 3]

[0039] As shown in Table 3 and Figure 5, when container 11 was molded under conditions I, J, K, or L, the gradation portion was smaller than half the height of peripheral wall 13, and the balance between the dark color portion, light color portion, and gradation portion was lost. On the other hand, when container 11 was molded under condition B, the dark color portion, light color portion, and gradation portion appeared in a balanced manner on peripheral wall 13.

[0040] Considering test results 2 and 3, it is preferable to set the first injection speed and the second injection speed equal to each other.

[0041] [Confirmation Test 4] In confirmation test 4, the first injection speed and the second injection speed were set according to conditions M to S shown in Table 4 below (condition B in confirmation test 4 is the same as condition B in confirmation test 1), and the container 11 was molded. That is, in conditions M to S, the first injection speed and the second injection speed are the same. In addition, in conditions M to S, the pre-injection amount of the above-mentioned first synthetic resin was 40% in all cases.

[0042] Photographs of the dark colored portions, light colored portions, and gradation portions provided on the peripheral wall portion 13 of the containers 11 obtained by the manufacturing methods under conditions M to S are shown in FIG. 6. Note that the photographs of the peripheral wall portion 13 of each container 11 obtained by the manufacturing methods under conditions M to S shown in FIG. 6 are taken from the direction along arrow B in FIG. 2(a), and the bottom portion 12 is located on the side marked M to S in FIG. 5. The meanings of "◯" and "△" in the evaluation of the peripheral wall portion 13 shown in Table 4 are the same as those in Table 1.

[0043] [Table 4]

[0044] As shown in Table 4 and FIG. 6, when the container 11 was molded under condition M, the light-colored portion was larger than half the circumferential length of the peripheral wall portion 13, and appeared not only on the front side but also on the back side of the peripheral wall portion 13, as shown in FIG. 6. When the container 11 was molded under conditions R and S, the height of the gradation portion that appeared was lower, as shown by R and S in FIG. 6. On the other hand, when the container 11 was molded under conditions B, N, O, P, and Q, the dark-colored portion, light-colored portion, and gradation portion appeared in a balanced manner on the peripheral wall portion 13. Therefore, based on these results, it can be said that it is preferable that the first injection speed and the second injection speed are both the same and in the range of 20 to 60 mm / s.

[0045] Here, the configuration of the gradation portion appearing on the peripheral wall portion 13 will be described. Figure 7 is a photograph of a cross section of the container 11 molded by the above-described manufacturing method, cut horizontally at the location where the gradation portion is located. Note that the first gate 4 shown in Figure 2(a) is located at the upper side of the photograph shown in Figure 7, and the second gate 5 is located at the lower side of the photograph shown in Figure 7. Furthermore, in the upper part of the cross section in Figure 7, a dark color portion appears on the peripheral wall portion 13, while in the lower part of the cross section, a light color portion appears on the peripheral wall portion 13, and in the vertical middle part of the cross section, a gradation portion appears on the peripheral wall portion 13.

[0046] 7, in the gradation portion, a dark inner layer portion and a dark outer layer portion extend in the circumferential direction, and a light-colored intermediate layer portion extends in the circumferential direction between the inner layer portion and the outer layer portion. That is, when the dark-colored first synthetic resin, which is injected first from the first gate 4, flows into the cavity 6, its radially inner and outer portions are in contact with the mold 1 and are solidifying, whereas the solidification of the middle portion in the thickness direction progresses more slowly than that of the radially inner and outer portions. Therefore, the light-colored second synthetic resin, which is injected later from the second gate 5, flows in the circumferential direction so as to enter the middle portion in the thickness direction of the first synthetic resin, resulting in the formation of the gradation portion as described above.

[0047] Although one embodiment of the present invention has been described above, the present invention is not limited to the specific embodiment, and unless otherwise limited in the above description, various modifications and variations are possible within the spirit and scope of the present invention as defined in the claims. For example, the configurations of the above-described embodiment may be added or deleted as appropriate, and the configurations of one embodiment may be incorporated into other embodiments. Furthermore, the effects of the above-described embodiment are merely examples of the effects resulting from the present invention, and do not mean that the effects of the present invention are limited to the above-described effects.

[0048] For example, the above-mentioned container 11 has a disk-shaped bottom 12 and a cylindrical peripheral wall 13 integrally formed therewith, but the container of the present invention is not limited to this shape, and may be, for example, a container whose cross-sectional shape is polygonal (such as a container whose peripheral wall is a square tube). [Explanation of symbols]

[0049] 1:Mold 2: Cavity mold 3: Core mold 4: First Gate 5: Second Gate 6: Cavity 11: Container 12: Bottom 13: Peripheral wall part 14: Opening O: Center of bottom

Claims

1. A method for manufacturing a cylindrical synthetic resin container with a bottom, which is molded by injecting synthetic resin into a mold, comprising: the mold has a cavity corresponding to the container, a first gate for injecting a dark-colored first synthetic resin, and a second gate for injecting a light-colored second synthetic resin; the first gate and the second gate are configured to inject the first synthetic resin and the second synthetic resin into the cavity from portions of the cavity corresponding to the bottom of the container, A method for manufacturing a synthetic resin container, comprising: starting injection of the first synthetic resin from the first gate; when a predetermined amount of the first synthetic resin has been injected, starting injection of the second synthetic resin from the second gate; and continuing to inject the first synthetic resin up to a predetermined amount, thereby filling the cavity with the first synthetic resin and the second synthetic resin, thereby providing a dark-colored portion mainly made of the first synthetic resin, a light-colored portion mainly made of the second synthetic resin, and a gradation portion made of the first synthetic resin and the second synthetic resin on the peripheral wall of the container.

2. A method for manufacturing a cylindrical synthetic resin container with a bottom, which is molded by injecting synthetic resin into a mold, comprising: the mold has a cavity corresponding to the container, a first gate for injecting a dark-colored first synthetic resin, and a second gate for injecting a light-colored second synthetic resin; the first gate and the second gate are configured to inject the first synthetic resin and the second synthetic resin into the cavity from portions of the cavity corresponding to the bottom of the container, Injection of the first synthetic resin is started from the first gate, and when a predetermined amount of the first synthetic resin has been injected, injection of the second synthetic resin is started from the second gate, and the cavity is filled with the first synthetic resin and the second synthetic resin, thereby forming a dark color portion mainly made of the first synthetic resin, a light color portion mainly made of the second synthetic resin, and a gradation portion made of the first synthetic resin and the second synthetic resin on the peripheral wall of the container, A method for manufacturing a synthetic resin container, wherein the predetermined amount is 20 to 40% of the total amount of the first synthetic resin to be injected into the cavity.

3. 3. The method for manufacturing a synthetic resin container according to claim 1, wherein a first injection speed at which the first synthetic resin is injected from the first gate and a second injection speed at which the second synthetic resin is injected from the second gate are both equal.

4. 4. The method for manufacturing a synthetic resin container according to claim 3, wherein the first injection speed and the second injection speed are 20 to 60 mm / s.

5. A molding device that injects synthetic resin into a mold to mold a synthetic resin container having a bottomed cylindrical shape, the mold has a cavity corresponding to the container, a first gate for injecting a dark-colored first synthetic resin, and a second gate for injecting a light-colored second synthetic resin; the first gate and the second gate are configured to inject the first synthetic resin and the second synthetic resin into the cavity from portions of the cavity corresponding to the bottom of the container, A molding device that starts injection of the first synthetic resin from the first gate, and when a predetermined amount of the first synthetic resin has been injected, starts injection of the second synthetic resin from the second gate and continues to inject the first synthetic resin up to a predetermined amount, thereby filling the cavity with the first synthetic resin and the second synthetic resin, thereby providing a dark-colored portion mainly made of the first synthetic resin, a light-colored portion mainly made of the second synthetic resin, and a gradation portion made of the first synthetic resin and the second synthetic resin on the peripheral wall of the container.

6. A cylindrical synthetic resin container with a bottom that is molded by injecting synthetic resin into a mold, the mold has a cavity corresponding to the container, a first gate for injecting a dark-colored first synthetic resin, and a second gate for injecting a light-colored second synthetic resin; the first gate and the second gate are configured to inject the first synthetic resin and the second synthetic resin into the cavity from portions of the cavity corresponding to the bottom of the container, Injection of the first synthetic resin is started from the first gate, and when a predetermined amount of the first synthetic resin has been injected, injection of the second synthetic resin is started from the second gate while continuing to inject the first synthetic resin up to a predetermined amount, thereby filling the cavity with the first synthetic resin and the second synthetic resin, thereby forming a synthetic resin container having a peripheral wall portion having a dark color portion mainly made of the first synthetic resin, a light color portion mainly made of the second synthetic resin, and a gradation portion made of the first synthetic resin and the second synthetic resin.

7. A cylindrical synthetic resin container with a bottom that is molded by injecting synthetic resin into a mold, the mold has a cavity corresponding to the container, a first gate for injecting a dark-colored first synthetic resin, and a second gate for injecting a light-colored second synthetic resin; the first gate and the second gate are configured to inject the first synthetic resin and the second synthetic resin into the cavity from portions of the cavity corresponding to the bottom of the container, Injection of the first synthetic resin is started from the first gate, and when a predetermined amount of the first synthetic resin has been injected, injection of the second synthetic resin is started from the second gate, and the cavity is filled with the first synthetic resin and the second synthetic resin, thereby providing a peripheral wall portion of the container with a dark color portion mainly composed of the first synthetic resin, a light color portion mainly composed of the second synthetic resin, and a gradation portion composed of the first synthetic resin and the second synthetic resin, The gradation portion is a synthetic resin container comprising an inner layer portion in which the first synthetic resin extends circumferentially along the inner surface of the peripheral wall portion, an outer layer portion in which the first synthetic resin extends circumferentially along the outer surface of the peripheral wall portion, and an intermediate layer portion in which the second synthetic resin extends circumferentially between the inner layer portion and the outer layer portion.

Images