Laminated blow-molded container

Abstract

To provide a lamination blow molding container which is excellent in alcohol resistant performance and in which generation of wrinkle-like crazing or cracking on an inner surface of the container is suppressed.SOLUTION: A lamination blow molding container 1 comprises a container body 2 having at least two layers of an innermost layer 11 and an outer layer 12. The container body 2 is formed in a bottomed cylinder shape, and comprises a mouth part 3, a trunk part 5 and a bottom part 6. The trunk part 5 and the bottom part 6 have transparency, and the innermost layer 11 is composed of a copolymer resin obtained by copolymerizing a mixture, obtained by mixing ethylene glycol with cyclohexanedimethanol at the ratio of 30-50 mol%, and carboxylic acid, and the outer layer 12 is composed of an amorphous resin, in the lamination blow molding container 1.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a laminated blow-molded container.

Background Art

[0002] Conventionally, synthetic resin bottles have been widely used in various fields as containers for storing liquid contents. Among them, in the case of a biaxially stretched blow-molded bottle represented by a PET bottle, in a bottle that is biaxially stretch blow-molded from a preform injection-molded into a bottomed cylindrical shape, since the preform, which is a primary molded product, is an injection-molded product, the obtained decorative pattern is basically limited to a strip pattern along the flow of the molded resin material (see, for example, Patent Document 1). Therefore, in order to decorate a synthetic resin bottle with gradation or to form a thick-walled synthetic resin bottle, it has been considered to blow-mold a laminated preform having an outer preform and an inner preform to form a laminated container.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the inner layer of a laminated container is formed of an amorphous PET resin, since the amorphous PET resin has low alcohol resistance, depending on the content stored in the container, wrinkled crazing, cracks, etc. may occur on the inner surface of the container.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a laminated blow-molded container having excellent alcohol resistance and suppressing the occurrence of wrinkled crazing, cracks, etc. on the inner surface of the container.

Means for Solving the Problems

[0006] To achieve the above objectives, this invention provides the following means. (1) The laminated blow-molded container according to the present invention is a laminated blow-molded container comprising a container body having at least two layers, an innermost layer and an outer layer, wherein the container body is formed in a bottomed cylindrical shape and comprises a mouth, a body, and a bottom, the body and the bottom are transparent, the innermost layer is composed of a copolymer resin obtained by copolymerizing a mixture of ethylene glycol and cyclohexanedimethanol in a ratio of 30 mol% to 50 mol%, with a carboxylic acid, and the outer layer is composed of an amorphous resin.

[0007] The laminated blow-molded container according to the present invention has excellent alcohol resistance, and even when filled with a liquid such as an alcohol-containing solution, it can suppress the occurrence of wrinkle-like crazing or cracks on the inner surface (inner surface of the innermost layer) of the laminated blow-molded container.

[0008] (2) In the laminated blow-molded container according to the present invention described above, the carboxylic acid may be terephthalic acid.

[0009] In this case, the alcohol resistance of the laminated blow-molded container is further improved.

[0010] (3) In the laminated blow-molded container according to the present invention described above, the container body may be a biaxially stretched blow-molded container.

[0011] In this case, compared to glass products, it can be manufactured at a lower cost and more easily, and the appearance of the laminated blow-molded container closely resembles that of a glass container, resulting in a more luxurious appearance.

[0012] (4) In the laminated blow-molded container according to the present invention described above, the outer layer may be made of amorphous polyethylene terephthalate resin.

[0013] In this case, heating during the formation of the thicker parts (body and bottom) of the container body can suppress crystallization (whitening) of the resin. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a laminated blow-molded container that has excellent alcohol resistance and suppresses the occurrence of wrinkle-like crazing, cracks, etc., on the inner surface of the container. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic side view showing a laminated blow-molded container as an embodiment of the present invention, with a portion of it being a cross-sectional view. [Figure 2] This is a schematic side view showing a method for manufacturing a laminated blow-molded container as an embodiment of the present invention, with a portion of it being a cross-sectional view. [Figure 3] This is a schematic side view showing a method for manufacturing a laminated blow-molded container as an embodiment of the present invention, with a portion of it being a cross-sectional view. [Figure 4] A schematic side view showing a laminated blow-molded container as an embodiment of the present invention. [Figure 5] This is a photograph showing the state of the inner layer of the laminated blow-molded container after filling it with ethanol solution in Example 2. [Figure 6] Comparative Example 5 is a photograph showing the state of the inner layer of the laminated blow-molded container after it has been filled with ethanol solution. [Modes for carrying out the invention]

[0016] Embodiments of the laminated blow-molded container of the present invention will be described. This embodiment is provided to give a better understanding of the spirit of the invention and does not limit the present invention unless otherwise specified.

[0017] [Laminated blow-molded containers] FIG. 1 is a schematic side view of a laminated blow-molded container shown as an embodiment of the present invention, with a partial cross-sectional view. The laminated blow-molded container 1 according to this embodiment is generally composed of a container body 2 formed in a bottomed cylindrical shape. The container body 2 is formed in a bottomed cylindrical shape and includes a mouth portion 3, a neck ring 4, a cylindrical body portion (barrel portion) 5, and a bottom portion (barrier portion) 6. The container body 2 is composed of, for example, an inner layer 11 which is a resin layer and an outer layer (surface layer) 12 which is a resin layer. In the container body 2, mainly, the body portion 5 and the bottom portion 6 are composed of the inner layer 11 and the outer layer 12. In the laminated blow-molded container 1 of this embodiment, the inner layer 11 is the innermost layer.

[0018] Examples of the contents filled (accommodated) in the laminated blow-molded container 1 include liquids such as cosmetics. The laminated blow-molded container 1 is particularly preferably used for contents containing alcohol, and more preferably used for contents with an alcohol content exceeding 10%.

[0019] At least the body portion 5 and the bottom portion 6 of the container body 2 have transparency. By having transparency in the container body 2, it is possible to give the laminated blow-molded container 1 an appearance similar to that of a glass container. Also, the amount of the contents can be visually confirmed.

[0020] The container body 2 is a molded product obtained by blow molding a preform composed of at least two layers (inner layer (innermost layer) 11 and outer layer 12) of resin layers, such as extrusion blow molding or injection stretch blow molding. The container body 2 is preferably a biaxially stretched blow-molded container in terms of low cost and easy manufacturability compared to glass products and the like.

[0021] The laminated blow-molded container 1 is a thick-walled molded container. In this embodiment, a thick-walled molded container is a container in which the thickness of the thickest part of the bottom 6 of the container body 2 (for example, the thickness t1 shown in Figure 1) or the thickness of the thickest part of the body 5 of the container body 2 (for example, the thickness t2 shown in Figure 1) is 1 mm or more. Preferably, the maximum value of the thickness of the thickest part of the bottom 6 of the container body 2 and the thickness of the thickest part of the body 5 of the container body 2 is 4 mm. In that case, the appearance of the laminated blow-molded container 1 can be made to more closely resemble that of a high-quality glass product. The thickness referred to here is the thickness of the bottom 6 and body 5 of the container body 2 in the direction perpendicular to the lamination direction of the inner layer 3 and the outer layer 4.

[0022] In a laminated blow-molded container 1, it is preferable that the thickness of the bottom 6 of the container body 2 (for example, the thickness t1 shown in Figure 1) is 1.5 times or more, and more preferably 2 times or more, the thickness of the body 5 of the container body 2 (for example, the thickness t2 shown in Figure 1). If the thickness of the bottom 6 of the container body 2 is 1.5 times or more than the thickness of the body 5 of the container body 2, the thickness of the bottom 6 will appear larger than the thickness of the body 5, so the appearance of the laminated blow-molded container 1 will be closer to that of a glass container (bottle), resulting in a more luxurious appearance.

[0023] In the laminated blow-molded container 1 of this embodiment, the thickness of the bottom 6 of the container body 2 is 6.6 mm at its thinnest point and 8.8 mm at its thickest point (the center of the bottom 6 of the container body 2).

[0024] In the laminated blow-molded container 1 of this embodiment, the thickness of the body portion 5 of the container body 2 is 2.6 mm at its thinnest point and 3.5 mm at its thickest point.

[0025] The inner layer 11 is composed of a copolymer resin obtained by copolymerizing a mixture of ethylene glycol and a carboxylic acid in a ratio of 30 mol% to 50 mol% in the laminated blow-molded container 1 of this embodiment. That is, the copolymer resin is a resin in which ethylene glycol in polyethylene terephthalate is replaced with cyclohexanedimethanol in an amount of 30 mol% to 50 mol%. The copolymer resin is glycol-modified polyethylene terephthalate (PET-G). Because the cyclohexanedimethanol content is 30 mol% to 50 mol%, PET-G is amorphous and is a resin that combines strength, rigidity, and chemical resistance (especially alcohol resistance). If the cyclohexanedimethanol content is less than 30 mol%, the properties become similar to crystalline polyethylene terephthalate (PET) resin, and the resin crystallizes (whitens) when heated during the formation of the thick-walled portion (body 5, bottom 6) of the container body 2. If the cyclohexanedimethanol content exceeds 50 mol%, the chemical resistance (alcohol resistance) decreases.

[0026] Examples of carboxylic acids constituting the copolymer resin include terephthalic acid or dimethyl terephthalate. Terephthalic acid is preferred due to the excellent alcohol resistance of the copolymer resin.

[0027] The outer layer 12 is composed of an amorphous resin. Since ordinary PET resin is crystalline, an amorphous PET resin is used as the amorphous resin that constitutes the outer layer 12. Specifically, I-PET, which is a glycol-modified PET in which a portion of ethylene glycol is replaced with neopentyl glycol, is used.

[0028] The thickness of the inner layer 11 and the thickness of the outer layer 12 are approximately the same. Furthermore, the thickness of the inner layer 11 and the outer layer 12 in the container body 2 can be adjusted by changing the thickness of the primary and secondary preforms, for example, by making the inner layer 11 thinner. This also makes it possible to reduce the amount of PET-G that makes up the inner layer 11.

[0029] Next, with reference to Figures 2 to 4, an example of a manufacturing method for the laminated blow-molded container 1 configured as described above in biaxial stretch blow molding will be explained. In the following explanation, the straight line passing through the center of the cross-section of the laminated blow-molded container 1 is referred to as the container axis O, and the direction perpendicular to the container axis O is referred to as the radial direction.

[0030] A primary preform 21 made of PET-G, as shown in Figure 2, is formed by injection molding. The primary preform 21 is formed in a bottomed cylindrical shape and includes a mouth portion 23, a neck ring 24, a cylindrical body portion 25, and a bottom portion 26.

[0031] Next, as shown in Figure 3, an outer layer 32 made of PET is formed on the outer surface (surface) of the body 25 and bottom 26 of the primary preform 21 by insert molding to obtain a secondary preform 31. Specifically, after inserting the primary preform 21 into an injection molding die, amorphous resin is injected around the body 25 and bottom 26 of the primary preform 21 within the die to form the outer layer 32. In this embodiment, the thickness of the body portion 25 of the primary preform 21 and the thickness of the outer layer 32 of the secondary preform 31 are approximately 4.5 mm, and thus have equivalent thicknesses. These thicknesses can be changed as needed.

[0032] Next, the secondary preform 31 is placed in a heater (not shown) equipped with a heater, and the secondary preform 31 is heated to a predetermined temperature. Typically, the heater is positioned to surround the body 33 of the secondary preform 31 from the radial outside, and the overall temperature of the secondary preform 31 is raised mainly by heating the body 33. During heating, the secondary preform 31 may be heated while rotating it around its central axis O.

[0033] After heating the secondary preform 31 to a predetermined temperature, the body 33 and bottom 34 of the secondary preform 31 are set in a blow mold (not shown). Then, a stretching rod (not shown) is inserted into the secondary preform 31 through the opening 23, and while pushing out (pressing) the bottom 34 of the secondary preform 31 with the stretching rod, or after stretching by the stretching rod is complete, high-pressure air is blown into the secondary preform 31. This allows the secondary preform 31 to be stretched in the direction of the central axis O, as well as in the radial direction, as shown by the arrow in Figure 3, and the entire secondary preform 31 can be expanded in the blow mold. As a result, the secondary preform 31 can be molded (blow molded) following the blow mold, and a bottomed cylindrical laminated blow molded container 1 can be manufactured as shown in Figures 1 and 4.

[0034] The laminated blow-molded container 1 of this embodiment comprises a container body 2 composed of an inner layer 11 and an outer layer 12. The inner layer 11 is made of a copolymer resin obtained by copolymerizing a mixture of ethylene glycol and cyclohexanedimethanol in a ratio of 30 mol% to 50 mol%, with a carboxylic acid. Therefore, it has excellent alcohol resistance, and even when filled with a liquid such as an alcohol solution, it can suppress the occurrence of wrinkle-like crazing or cracks on the inner surface of the laminated blow-molded container 1 (the inner surface of the inner layer 11).

[0035] In this embodiment, the container body 2 is shown as being composed of two layers, an inner layer 11 and an outer layer 12, but the present invention is not limited thereto. In the present invention, the container body may be composed of three or more resin layers, in which case the innermost layer of the resin layers may be composed of a copolymer resin obtained by copolymerizing a mixture of ethylene glycol and cyclohexanedimethanol in a ratio of 30 mol% to 50 mol%, with a carboxylic acid. Furthermore, although a thick-walled molded container has been described in this embodiment, the laminated blow-molded container of the present invention may also be a thin-walled molded container. [Examples]

[0036] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0037] [Experimental Example 1] Using PET-G (product name: GN001, manufactured by Eastman Chemical Corporation), a square test plate with a thickness of 1 mm, a length of 5 mm, and a width of 5 mm was molded by injection molding. The obtained test plates were immersed in an ethanol solution (ethanol concentration 30%) placed in a screw-cap bottle up to half their length (vertical or horizontal), and left at 50°C for 4 weeks with the lid closed. As a result, there were no changes such as whitening in the appearance of the test plates in Experimental Example 1.

[0038] [Experimental Example 2] A square test plate was formed in the same manner as in Experimental Example 1, except that PET (product name: CN015, manufactured by Eastman Chemical Corporation) was used. The obtained test plates were immersed in an ethanol solution in the same manner as in Experimental Example 1. As a result, the test plates in Experimental Example 2 had turned white.

[0039] [Experimental Example 3] A square test plate was formed in the same manner as in Experimental Example 1, except that amorphous PET (product name: IN305B, manufactured by Bell Polyester Co., Ltd.) was used. The obtained test plates were immersed in an ethanol solution in the same manner as in Experimental Example 1. As a result, the test plates in Experimental Example 3 had turned white.

[0040] [Experimental Example 4] A square test plate was formed in the same manner as in Experimental Example 1, except that PET (product name: IP121B, manufactured by Bell Polyester Co., Ltd.) was used. The obtained test plates were immersed in an ethanol solution in the same manner as in Experimental Example 1. As a result, the test plates in Experimental Example 4 had turned white.

[0041] [Experimental Example 5] A square test plate was formed in the same manner as in Experimental Example 1, except that PET (product name: IP252B, manufactured by Bell Polyester Co., Ltd.) was used. The obtained test plates were immersed in an ethanol solution in the same manner as in Experimental Example 1. As a result, the test plate in Experimental Example 5 had turned white.

[0042] [Examples] A laminated blow-molded container, as shown in Figure 1, was manufactured using PET-G (product name: GN001, manufactured by Eastman Chemical Corporation). A primary preform made of PET-G, as shown in Figure 2, was molded by injection molding. Next, as shown in Figure 3, an outer layer made of amorphous PET (product name: IN305B, manufactured by Bell Polyester Co., Ltd.) was formed on the outer surface of the body and bottom of the primary preform by insert molding to obtain a secondary preform. Next, the secondary preform was placed in a heater equipped with a heater and heated. After heating the secondary preform, the body and bottom of the secondary preform were placed in the blow mold. Then, a stretching rod was inserted into the secondary preform from the opening, and while pushing out the bottom of the secondary preform with the stretching rod, or after stretching by the stretching rod was completed, high-pressure air was blown into the secondary preform. This produced a bottomed cylindrical laminated blow-molded container as shown in Figure 1. Furthermore, because the secondary preform is thick-walled, the heating temperature for the secondary preform will be higher than that for conventional thin-walled products. The resulting laminated blow-molded container was filled with an ethanol solution (ethanol concentration 30%), and with the lid closed, it was left at 50°C for 4 weeks. The appearance of the laminated blow-molded container after standing was visually observed. Figure 5 shows a photograph of the appearance of the laminated blow-molded container. The results shown in Figure 5 confirm that no wrinkle-like crazing or cracks occurred in the inner layer of the laminated blow-molded container in the example.

[0043] [Comparative Example] A laminated blow-molded container was manufactured in the same manner as in the examples, except that a primary preform made of amorphous PET (product name: IN305B, manufactured by Bell Polyester Co., Ltd.) was molded. The resulting laminated blow-molded container was filled with ethanol solution in the same manner as in the example, and left at 50°C for 4 weeks with the lid closed. The appearance of the laminated blow-molded container after standing was visually observed. Figure 6 shows a photograph of the appearance of the laminated blow-molded container. The results in Figure 6 confirm that no wrinkle-like crazing or cracks occurred in the inner layer of the comparative example's laminated blow-molded container. [Industrial applicability]

[0044] The laminated blow-molded container of the present invention has excellent alcohol resistance and suppresses the occurrence of wrinkle-like crazing and cracks on the inner surface of the container, making it suitable for use as a container for cosmetics such as nail polish. [Explanation of Symbols]

[0045] 1. Laminated blow-molded container 2. Container body 3 Mouth 4 Neck Rings 5. Body (tube section) 6 Bottom (shielding wall) 11. Inner layer (innermost layer) 12 Outer layer (surface layer)

Claims

1. A laminated blow-molded container comprising a container body having at least two layers, an innermost layer and an outer layer, The container body is formed in the shape of a bottomed cylinder and comprises a mouth, a body, and a bottom. The body and bottom are transparent. The innermost layer is composed of glycol-modified polyethylene terephthalate in which ethylene glycol in polyethylene terephthalate is replaced with cyclohexanedimethanol in an amount of 30 mol% to 50 mol%, The outer layer is composed of glycol-modified polyethylene terephthalate in which a portion of the ethylene glycol in polyethylene terephthalate is replaced with neopentyl glycol. A laminated blow-molded container in which the thickness of the bottom portion is 1.5 times or more the thickness of the body portion.

2. The laminated blow-molded container according to claim 1, wherein the container body is a biaxially stretched blow-molded container.

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