Resin container and method for manufacturing the same

Abstract

The objective is to resolve the issues of cooling time and shrinkage, as well as to create a resin container with excellent design and a method for manufacturing the same. [Solution] A resin container having a bottom portion 2 and a side portion 3 erected on the outer edge of the bottom portion 2, wherein a cavity portion 5 is provided inside the bottom portion 2 and the side portion 3, extending continuously from the bottom portion 2 to the side portion 3.

Description

[[Technical Field]]

[0001] The present invention relates to a resin container having cavities inside the bottom portion and the side portion, and a method for manufacturing the same. [[Background Art]]

[0002] As a resin container for storing contents such as beauty cream, for example, a jar container 4 as disclosed in the following Patent Document 1 is known. [[Prior Art Literature]] [[Patent Literature]]

[0003] [[Patent Document 1]] Japanese Patent Laid-Open No. 2024-170803 [[Patent Document 2]] Japanese Patent Laid-Open No. 2019-026346 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0004] However, in the resin container described in Patent Document 1, since the portion extending from the bottom portion 41 to the side wall 42 is formed of a thick-walled part, there are problems that it takes a long time for cooling after molten resin is poured into a mold and molded, and sink marks are likely to occur on the surfaces of the bottom portion 41 and the side wall 42 due to this.

[0005] In this regard, when a configuration is adopted in which the inner side of the outer cylindrical part 11 and the inside of the bottom part are hollowed out, like the outer container 10 described in Patent Document 2, it becomes possible to solve the problems of cooling time and sink marks. However, when the container described in Patent Document 2 is viewed from the bottom side, the hollowed-out portion is completely visible, so there are design problems that it lacks a high-grade appearance and a problem that stability is poor when the container is placed, thus there still remains room for improvement.

[0006] The present invention aims to solve the problems of the prior art described above, namely the problems of cooling time and shrinkage, and to create a resin container and a method for manufacturing the same that have excellent design. [Means for solving the problem]

[0007] Among the means for solving the above problems, the first means of the present invention is: A resin container having a bottom and side portions erected on the outer edge of the bottom, The invention is characterized in that a cavity is provided inside the bottom and side portions, extending continuously from the bottom to the side portions. In the first method of the present invention, since the cavity is formed inside the bottom and sides which are not visible from the outside, a resin container with a high aesthetic appeal and superior sense of luxury can be made.

[0008] Furthermore, the second means of the present invention adds to the first means described above that the resin container is formed to have a weight of 65% to 75% compared to the weight of a resin container without the cavity. The above method significantly reduces the amount of resin required to manufacture the resin container, thereby lowering manufacturing costs.

[0009] Furthermore, a third means of the present invention is a method for manufacturing a resin container having a bottom and sides, which is manufactured by injecting molten resin into a cavity, A step of injecting a smaller amount of resin into the cavity than the weight of the resin container when the cavity is filled to 100% and molded, The invention is characterized by comprising the step of blowing air into the cavity to form a continuous cavity inside the molten resin extending from the bottom to the side. In the third method of the present invention, a resin container having a continuous cavity extending from the bottom to the side can be manufactured, and since the molten resin solidifies while pressed against the inner surface of the cavity, the occurrence of sink marks can be suppressed.

[0010] Furthermore, a fourth means of the present invention adds to the third means described above that the amount of resin is in the range of 65% to 75% of the weight of the resin container when the cavity is filled to 100% and molded. The fourth method of the present invention significantly reduces the amount of resin required to manufacture the resin container, thereby reducing manufacturing costs and shortening the cooling time after resin filling. [Effects of the Invention]

[0011] This invention makes it possible to create a resin container with a high aesthetic appeal and a superior sense of luxury. Furthermore, this method provides a resin container manufacturing method that enables the production of a resin container having a continuous cavity extending from the bottom to the sides, and that can suppress the occurrence of sink marks that tend to form on the thick bottom and sides. [Brief explanation of the drawing]

[0012] [Figure 1] The image shows a resin container illustrating an embodiment of the present invention, where (a) is a plan view, (b) is a half cross-sectional view from the front, and (c) is a bottom view. [Figure 2] This is a schematic cross-sectional view showing the main parts of a resin container manufacturing apparatus. [Figure 3] This is an enlarged view of section A in Figure 2, where (a) is a cross-sectional view showing the injection process and (b) is a cross-sectional view showing the air blowing process. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the drawings. First, the structure of the resin container 1 according to the present invention will be described. Figure 1 shows a resin container illustrating an embodiment of the present invention, where (a) is a plan view, (b) is a partial cross-sectional view from the front, and (c) is a bottom view. In the following explanation, the direction along the container axis O will be referred to as the axial direction, vertical direction, or height direction, the direction perpendicular to the container axis O will be referred to as the radial direction, and the direction revolving around the container axis O will be referred to as the circumferential direction.

[0014] The resin container 1 is a wide-mouth cylindrical jar container with a bottom, comprising a cylindrical side portion 3 erected on the outer edge of a disc-shaped bottom portion 2, and a mouth cylinder portion 4 having an external thread 4a formed on the side portion 3, as in the embodiment shown in FIGS. 1(a), 1(b) and 1(c) for example, and is formed by injection molding using a synthetic resin material as described later.

[0015] As shown in FIG. 1(b), the bottom portion 2 has a double structure composed of a disc-shaped inner bottom wall 2a and a disc-shaped outer bottom wall 2b, and the side portion 3 is formed to have a double structure composed of a cylindrical inner side wall 3a and a cylindrical outer side wall 3b. A hollow portion 5 continuous from the bottom portion 2 to the side portion 3 is provided in a portion where the inner bottom wall 2a and the outer bottom wall 2b face each other in the height direction and a portion where the inner side wall 3a and the outer side wall 3b face each other in the radial direction. On the lower surface in the outer peripheral direction of the bottom portion 2 (the outer bottom wall 2b), an installation portion 6 having a convex cross-section and protruding downward is circumferentially provided. A storage portion 7 for storing contents such as beauty cream is provided inside the resin container 1. It should be noted that a lid (not shown) can be screwed onto the mouth cylinder portion 4.

[0016] As described above, in the resin container 1 of the present invention, by providing the hollow portion 5 inside the bottom portion 2 and the side portion 3, it is possible to obtain the resin container 1 in which the occurrence of sink marks is suppressed as described later.

[0017] Further, as shown in (c), the resin container 1 has a structure in which the internal hollow portion 5 is hidden and cannot be seen even when the bottom portion 2 side is viewed from the outside, so that the sense of luxury can be greatly improved. Moreover, when the resin container 1 is placed on a flat table, the resin container 1 can be placed in a state where the installation portions 6 circumferentially arranged on the bottom portion 2 are in close contact with the surface of the table, so high stability can be ensured. Furthermore, the resin container 1 of the present invention is formed to have a weight of 65% to 75%, preferably 70%, of the weight of the resin container 1 when it does not have a hollow portion.

[0018] Next, a method for manufacturing the resin container 1 having the above configuration will be described. Figure 2 is a schematic cross-sectional view showing the main part of the resin container manufacturing apparatus, and Figure 3 is an enlarged view of part A in Figure 2, where (a) is a cross-sectional view showing the injection process and (b) is a cross-sectional view showing the air blowing process. The resin container 1 is manufactured by applying an injection molding method using a manufacturing apparatus that comprises, for example, a female mold 21 having a recess 21A as shown in Figure 2, and a male mold 22 having a protrusion 22A.

[0019] The female mold 21 has a runner 23 through which molten resin 31 flows, formed along the container axis O, with the tip of the runner 23 communicating with the center of the recess 21A. Inside the tip of the runner 23, a valve pin 24 is positioned so as to be able to move back and forth in the axial direction. The valve pin 24 is a long cylindrical member that extends along the axial direction, and a resin gate 25 is provided at its shortened tip, which communicates with the cavity C described later. The valve pin 24 has an air passage 24a formed inside through which air 32 flows, and an air gate 24b with an extremely small diameter is connected to the tip of the valve pin 24, which is formed in a contracted shape at the top of the valve pin 24 and is positioned inside the resin gate 25. In addition, a resin passage 23a consisting of a cylindrical gap is formed in the portion where the inner circumferential surface of the runner 23 and the outer circumferential surface of the valve pin 24 face each other radially. The valve pin 24 is configured to open and close the resin gate 25 by moving back and forth in the axial direction. Furthermore, the runner 23 is connected to an injection molding machine (not shown) via a sprue (not shown), and the air passage 24a is connected to an air supply source (not shown).

[0020] The male mold 22 has a protrusion 22A that fits into the recess 21A of the female mold 21 and is configured to move back and forth in the vertical direction. When the male mold 22 is fitted into the female mold 21, a cavity C for molding the resin container 1 is formed in the portion where the inner surface 21a of the recess 21A and the inner surface 22a of the protrusion 22A face each other.

[0021] First, as shown in Figure 3(a), the valve pin 24 is moved away from the cavity C to open the resin gate 25, and molten resin 31 supplied from an injection molding machine (not shown) is injected into the cavity C through a sprue (not shown), a resin passage 23a in the runner 23, and the resin gate 25 (injection process). The amount of resin injected at this time is equivalent to 65% to 75%, preferably 70%, of the weight of the resin container 1 when the cavity C is 100% filled and molded. As a result, the cavity C has space in the range of 25% to 35%, so the molten resin 31 can move within the cavity C. In addition, the amount of resin required to mold the resin container 1 can be significantly reduced, making it possible to reduce manufacturing costs.

[0022] Next, as shown in Figure 3(b), the valve pin 24 is moved toward the cavity C to close the resin gate 25, and high-pressure air 32 is supplied from an air supply source (not shown) and blown into the cavity C through the air passage 24a and the air gate 24b (air blowing process). Here, the molten resin 31 immediately after filling the cavity C gradually cools and solidifies from the peripheral wall side near the inner surfaces 21a and 22a toward the center of the cavity C. Therefore, the center, which is far from the inner surfaces 21a and 22a, remains in a molten state and has not yet solidified.

[0023] Therefore, when high-pressure air 32 is blown onto the cavity, the molten resin 31, which has not yet solidified, is pushed out of the cavity C away from the air gate 24b, that is, from the bottom 2 to the side 3, and at the same time solidifies while being pressed from the center of the cavity C towards the inner surface 21a and inner surface 22a, respectively. As a result, as shown in Figure 1(b), an inner bottom wall 2a and an inner wall 3a can be formed on the inner surface 22a side of the convex portion 22A, and an outer bottom wall 2b and an outer wall 3b can be formed on the inner surface 21a side of the concave portion 21A. At the same time, a continuous cavity 5 can be formed inside the molten resin 31, that is, in the portion where the inner bottom wall 2a and the outer bottom wall 2b face each other in the height direction and where the inner wall 3a and the outer wall 3b face each other in the radial direction, as the molten resin 31 solidifies, extending from the bottom 2 to the side 3.

[0024] Furthermore, as described above, since the molten resin 31 solidifies while being pressed against the inner surfaces 21a and 22a, it is possible to suppress the formation of sink marks on the bottom 2 (inner bottom wall 2a and outer bottom wall 2b) and side 3 (inner wall 3a and outer wall 3b). Moreover, the amount of resin required to manufacture the resin container 1 can be reduced, and since there is no need to form the bottom 2 and side 3 with thick walls as in the conventional method, it is also possible to shorten the time required for cooling after resin filling.

[0025] The configuration of the present invention and its effects have been described above in accordance with the examples, but the embodiments of the present invention are not limited to the above examples. For example, in the above embodiment, a wide-mouthed jar container was shown as the resin container 1, but the container is not limited to this as long as it has thick walls at the bottom or sides. Furthermore, although the above embodiment described a cylindrical resin container 1, a polygonal container may also be used. [Industrial applicability]

[0026] This invention can expand the range of applications in the field of resin containers having thick walls to an even broader range. [Explanation of symbols]

[0027] 1: Plastic container 2: Bottom 2a: Inner bottom wall 2b: Outer bottom wall 3: Side 3a:Inner wall 3b:Outer wall 4: Mouth part 4a: Male screw 5: Cavity 6: Installation part 7: Containment Unit 21:Female mold 21A: Recess 21a: Inner self 22: Male mold 22A: Convex part 22a: Inner surface 23: Runner 23a: Resin passage 24: Valve pin 24a: Air passage 24b: Air Gate 25: Resin gate 31: Molten resin 32: Air C: Cavity O: Container axis

Claims

1. A resin container having a bottom (2) and a side portion (3) erected on the outer edge of the bottom (2), A resin container characterized in that a cavity (5) is provided inside the bottom (2) and the side (3), extending continuously from the bottom (2) to the side (3).

2. The resin container according to claim 1, having a weight of 65% to 75% compared to the weight of the resin container (1) in the case where the aforementioned cavity (5) is not present.

3. A method for manufacturing a resin container (1) having a bottom (2) and side (3), which is manufactured by injecting molten resin (31) into a cavity (C), A step of injecting a smaller amount of resin into the cavity (C) compared to the weight of the resin container (1) when the cavity (C) is filled to 100% and molded, A method for manufacturing a resin container, comprising the step of blowing air (32) into the cavity (C) to form a continuous cavity (5) inside the molten resin (31) extending from the bottom (2) to the side (3).

4. The method for manufacturing a resin container according to claim 3, wherein the amount of resin is in the range of 65% to 75% of the weight of the resin container (1) when the cavity (C) is filled to 100% and molded.

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