Preform for forming double container, and double container

Abstract

To thermally crystallize a part of an inner preform during a step of heating a preform for forming a double container up to a stretchable temperature without heating the inner preform itself using a dedicated heating furnace.SOLUTION: A double container 10 comprises an inner container 31 in which a content is accommodated, and an outer container 32 in which the inner container is furnished. In the inner container, in a stretching portion 29 positioned below an inner mouth portion 21, an infrared absorption portion 30 is provided that absorbs infrared rays more easily than the inner container or the outer container. At least in the stretching portion of the inner container, the portion where the infrared absorption portion is provided is a heat crystallized portion 34 having a crystallization degree higher than the other portions.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a preform for molding a double container and a double container. [Background technology]

[0002] A double container comprising an inner container for accommodating contents and an outer container in which the inner container is placed is generally required to be able to easily separate the outer surface of the inner container from the inner surface of the outer container. In such a double container, if the inner container is formed to be volume-reducing and deformable, the inner container can be reduced in volume as the contents are discharged from the inner container. Even if the inner container does not reduce in volume, if the outer surface of the inner container can be easily separated from the inner surface of the outer container, it will be easier to separate the inner container from the outer container when disposing of the double container. One possible means for obtaining such a double-layered container is to make a portion of a bottomed, cylindrical inner preform used to form the inner container a thermally crystallized portion with a higher degree of crystallinity than the other portions, as shown in Patent Document 1 below, so that during blow molding, the thermally crystallized portion of the inner preform does not follow the stretching of the outer preform used to form the outer container. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-050740 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in order to make a part of the inner preform into a thermally crystallized part, a process of heating the inner preform alone using a dedicated heating furnace is required in addition to the process of heating the preform for molding a double container to a temperature at which it can be stretched, which poses the problem of making it difficult to reduce manufacturing costs.

[0005] The present invention provides a preform for molding a double container, and a double container, in which a portion of the inner preform can be thermally crystallized during the process of heating the preform for molding a double container to a temperature at which the inner preform can be stretched, without the need to heat the inner preform alone using a dedicated heating furnace. [Means for solving the problem]

[0006] A preform for molding a double container according to one embodiment of the present invention is a preform for molding a double container comprising an inner container in which contents are accommodated and an outer container in which the inner container is fitted, and comprises a bottomed, cylindrical inner preform for molding the inner container and a bottomed, cylindrical outer preform for molding the outer container, and the inner preform is inserted into the outer preform with the mouth of the inner preform fitted into the mouth of the outer preform, and in each of the inner preform and the outer preform, at least the mouth is a non-stretched portion that does not stretch when the double container is blow molded, and the portion located below the non-stretched portion is an stretched portion that stretches when the double container is blow molded, and at least a portion of the stretched portion of the inner preform is provided with an infrared absorbing portion that is more likely to absorb infrared rays than the inner preform and the outer preform.

[0007] A double container according to one embodiment of the present invention is a double container comprising an inner container in which contents are stored and an outer container in which the inner container is fitted, wherein an infrared absorbing section is provided in a portion of the inner container located below the mouth, which is more likely to absorb infrared rays than the inner container and the outer container, and at least the portion of the inner container located below the mouth where the infrared absorbing section is provided is a thermally crystallized section with a higher degree of crystallinity than the remaining portions.

[0008] Since at least a portion of the stretched portion of the inner preform is provided with an infrared absorbing portion that is more likely to absorb infrared rays than the inner preform and the outer preform, during the step of heating the stretched portion of the double container molding preform to a temperature at which it can be stretched by blow molding, infrared rays from the infrared heater are concentrated and absorbed by the infrared absorbing portion, and at least the portion of the stretched portion of the inner preform provided with the infrared absorbing portion can be made into a thermally crystallized portion with a higher degree of crystallinity than the rest. In other words, even if the inner preform alone is not heated using a dedicated heating furnace, a portion of the stretched portion of the inner preform can be thermally crystallized during the step of heating the double container molding preform to a temperature at which it can be stretched. This makes it possible to prevent at least the thermally crystallized portion of the inner preform from following the stretching of the outer preform during blow molding, resulting in a double container in which the outer surface of the inner container and the inner surface of the outer container can be easily separated. In this double container, an infrared absorbing section is provided in a portion of the inner container that is located below the mouth and in the extension section, and at least the portion of the inner container that is located below the mouth and in the extension section where the infrared absorbing section is provided is a thermally crystallized section that has a higher degree of crystallinity than the rest.

[0009] In one embodiment of the present invention, a preform for molding a double container has an infrared absorbing portion and vertical ribs extending in the vertical direction on the outer peripheral surface of the inner preform, and at least a portion of the infrared absorbing portion and the vertical ribs may be located at the same vertical position.

[0010] An infrared absorbing section and vertical ribs extending in the vertical direction are provided on the outer peripheral surface of the inner preform, and at least a portion of each of the infrared absorbing section and the vertical ribs are located at the same vertical position.As a result, a double container is obtained in which at least a portion of each of the infrared absorbing section and the vertical ribs are located at the same vertical position on the outer peripheral surface of the inner container, and it is possible to reliably obtain a double container in which it is easy to separate the outer surface of the inner container from the inner surface of the outer container.

[0011] In the preform for molding a double container according to one aspect of the present invention, the inner preform and the outer preform may be made of polyethylene terephthalate.

[0012] Since the inner preform and the outer preform are formed from polyethylene terephthalate, the outer surface of the inner container and the inner surface of the outer container in the double container tend to adhere to each other, thereby significantly achieving the aforementioned effect of easily obtaining a double container in which the outer surface of the inner container and the inner surface of the outer container can be easily separated.

[0013] In one embodiment of the double container of the present invention, the infrared absorbing portion may be provided on the outer peripheral surface of the inner container, and the outer peripheral surface side of the inner container and the inner peripheral surface side of the outer container may be the thermal crystallization portion.

[0014] Since the outer peripheral surface of the inner container and the inner peripheral surface of the outer container are thermally crystallized portions, it is possible to reliably separate the outer surface of the inner container from the inner surface of the outer container. Since the infrared absorbing section is provided on the outer peripheral surface of the inner container, by irradiating the preform for molding a double container with infrared rays from the outside in the radial direction during the process of heating the preform for molding a double container to a temperature at which it can be stretched, a double container is obtained in which the outer peripheral surface side of the inner container and the inner peripheral surface side of the outer container are thermally crystallized, making it easier to obtain a double container than when infrared rays are irradiated from the inside in the radial direction during the process of heating the preform for molding a double container to a temperature at which it can be stretched. [Effects of the Invention]

[0015] According to the above aspect of the present invention, a portion of the inner preform can be thermally crystallized during the process of heating the preform for molding a double container to a temperature at which it can be stretched, without having to heat the inner preform alone using a dedicated heating furnace. [Brief explanation of the drawings]

[0016] [Figure 1]1 is a longitudinal sectional view of a preform for molding a double container shown as one embodiment. [Figure 2] FIG. 1 is a vertical cross-sectional view of a double container shown as an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, a preform for molding a double container and a double container according to one embodiment will be described with reference to the drawings. As shown in Figures 1 and 2, the preform 1 for molding a double container comprises a bottomed cylindrical inner preform 11 for molding an inner container 31 in which the contents are housed, and a bottomed cylindrical outer preform 12 for molding an outer container 32 in which the inner container 31 is placed, and is used to mold a double container 10. The inner container 31 is formed so as to be capable of shrinking and deforming, and the double container molding preform 1 and the double container 10 are provided with an outside air inlet hole 13 through which outside air is introduced between the inner container 31 and the outer container 32 as the contents decrease. Note that the inner container 31 may be configured so as not to shrink and deform as the contents decrease.

[0018] The inner preform 11 is inserted into the outer preform 12 with the mouth portion (hereinafter referred to as the inner mouth portion) 21 of the inner preform 11 fitted into the mouth portion (hereinafter referred to as the outer mouth portion) 22 of the outer preform 12. In the illustrated example, the bottom portion (hereinafter referred to as the inner bottom portion) 23 of the inner preform 11 is inserted into the bottom portion (hereinafter referred to as the outer bottom portion) 24 of the outer preform 12.

[0019] The inner preform 11 and the outer preform 12 are arranged coaxially on a common axis. Hereinafter, this common axis will be referred to as the central axis O, the inner opening 21 side and the outer opening 22 side along the central axis O will be referred to as the upper side, and the inner bottom 23 side and the outer bottom 24 side along the central axis O will be referred to as the lower side. When viewed from the top-bottom direction, the direction intersecting the central axis O will be referred to as the radial direction, and the direction going around the central axis O will be referred to as the circumferential direction.

[0020] The inner preform 11 and the outer preform 12 are made of synthetic resin material, and may be made of the same material or different materials. Examples of synthetic resin materials include PET (polyethylene terephthalate), PP (polypropylene), PE (polyethylene), nylon (polyamide), and EVOH (ethylene-vinyl alcohol copolymer). In the illustrated example, the inner preform 11 and the outer preform 12 are each made of PET.

[0021] The inner preform 11 and the outer preform 12 are made of a crystalline resin. Crystalline resins contain amorphous portions in which molecular chains are disordered and crystalline portions in which molecular chains are regularly arranged. The degree of crystallinity increases as the content of crystalline portions increases. The degree of crystallinity can be measured, for example, by density analysis, X-ray diffraction analysis, differential scanning calorimetry, FT-IR analysis, or solid-state NMR analysis.

[0022] On the outer peripheral surface of the outer opening 22, there are formed, from top to bottom, a locking projection 22a into which a cap (not shown) is undercut-fitted, a sealed projection 22b into which the peripheral wall of the cap (not shown) is externally fitted, and a neck ring 22c. The cap may be screwed onto the outer opening 22.

[0023] The sealed projection 22b and the neck ring 22c protrude radially outward from the outer opening 22 and extend continuously over the entire circumferential length. An airtight seal is formed between the outer peripheral surface of the sealed projection 22b and the inner peripheral surface of the peripheral wall of the cap (not shown). The outer diameter of the neck ring 22c is larger than the outer diameters of the locking projection 22a and the sealed projection 22b. The neck ring 22c is located below the peripheral wall of the cap (not shown). The locking projection 22a extends intermittently over the entire circumferential length of the outer opening 22. It is preferable that the intermittent portion of the locking projection 22a is located at the same circumferential position as the outside air introduction hole 13.

[0024] The aforementioned outside air introduction hole 13 is formed in the outer opening 22. The outside air introduction hole 13 is provided between the locking projection 22a and the sealed projection 22b. A vertical groove 14 is formed on the inner peripheral surface of the outer opening portion 22, extending downward from the upper end opening edge 15 of the outer preform 12. An outside air introduction hole 13 opens into the vertical groove 14. The lower end of the vertical groove 14 is located below the neck ring 22c. The outer opening portion 22 is a portion of the outer preform 12 that is located above and includes the same position in the up-down direction as the lower surface of the neck ring 22c.

[0025] The inner mouth portion 21 is the portion of the inner preform 11 that is fitted into the outer mouth portion 22. In other words, the inner mouth portion 21 is the portion of the inner preform 11 that includes the same position in the up-down direction as the lower surface of the neck ring 22c of the outer preform 12 and is located above it. The outer peripheral surface of the inner mouth portion 21 abuts against the inner peripheral surface of the outer mouth portion 22 over its entire length in the up-down direction. The inner mouth portion 21 is provided with a flange portion 25 that extends continuously over its entire length in the circumferential direction and abuts against the upper end opening edge 15 of the outer preform 12. An outside air introduction hole 13 may be provided between the lower surface of the flange portion 25 and the upper end opening edge 15 of the outer preform 12 .

[0026] The outer peripheral surface of the inner opening 21 is provided with protrusions 26 that protrude radially outward, extend continuously over the entire circumferential length, and are pressed against the inner peripheral surface of the outer opening 22. A plurality of protrusions 26 are provided at intervals in the vertical direction. The protrusions 26 are located above the outside air introduction holes 13 of the outer opening 22. Note that the protrusions 26 do not necessarily have to be provided.

[0027] In each of the inner preform 11 and the outer preform 12, at least the inner opening portion 21 and the outer opening portion 22 are non-stretched portions 28 that do not stretch when the double container 10 is blow molded, and the portion located below the non-stretched portion 28 is stretched portion 29 that stretches when the double container 10 is blow molded. The non-stretched portion 28 comprises the upper end portion of the portion located below the inner opening portion 21 and the outer opening portion 22 in the inner preform 11 and the outer preform 12, respectively, and the inner opening portion 21 and the outer opening portion 22.

[0028] At least a part of the elongated portion 29 of the inner preform 11 is provided with an infrared absorbing portion 30 that absorbs infrared rays more easily than the inner preform 11 and the outer preform 12. The infrared absorbing portion 30 is a black printed layer with zero brightness. Note that the infrared absorbing portion 30 is not limited to a printed layer, and may be, for example, a vapor deposition layer. In the illustrated example, the infrared absorbing portion 30 is provided on the outer peripheral surface of the stretched portion 29 of the inner preform 11. The infrared absorbing portion 30 may be provided on the inner peripheral surface of the stretched portion 29 of the outer preform 12, or on both the outer peripheral surface of the stretched portion 29 of the inner preform 11 and the inner peripheral surface of the stretched portion 29 of the outer preform 12, or on the inner peripheral surface of the stretched portion 29 of the inner preform 11.

[0029] An infrared absorbing portion 30 and vertically extending vertical ribs 33 are provided on the outer peripheral surface of the inner preform 11. The vertical ribs 33 protrude radially outward from the outer peripheral surface of the inner preform 11. The radially outer ends of the vertical ribs 33 abut against the inner peripheral surface of the outer preform 12. The vertical ribs 33 may be recessed radially inward from the outer peripheral surface of the inner preform 11, and the vertical ribs 33 may not be provided on the outer peripheral surface of the inner preform 11, and the vertical ribs 33 may not abut the inner peripheral surface of the outer preform 12.

[0030] At least a portion of each of the infrared absorbing portion 30 and the vertical rib 33 is located at the same position in the up-down direction. In the illustrated example, the infrared absorbing portions 30 and the longitudinal ribs 33 are located at the same vertical position along the entire vertical length. The upper end portions of the infrared absorbing portions 30 and the longitudinal ribs 33 are located in the non-extended portions 28, and the portions located below the upper end portions are located in the extended portions 29. The infrared absorbing portions 30 are provided on the outer peripheral surface of the inner preform 11 in portions located between adjacent longitudinal ribs 33 in the circumferential direction. The infrared absorbing portion 30 may be provided over the entire length in the circumferential direction on the outer peripheral surface of the inner preform 11 , including the outer surfaces of the longitudinal ribs 33 .

[0031] The double container preform 1 is formed as follows. First, the inner preform 11 and the outer preform 12 are formed separately by injection molding, and the infrared absorbing portion 30 is provided on the outer peripheral surface of the extended portion 29 of the inner preform 11 by, for example, an inkjet printer, spray painting, coating, etc. Next, the inner preform 11 is inserted into the outer preform 12 while fitting the inner opening 21 into the outer opening 22.

[0032] Next, a method for forming the double container 10 using the double container molding preform 1 will be described.

[0033] The stretched portion 29 of the double container preform 1 is heated to a temperature at which it can be stretched by blowing (below the crystallization temperature; for example, about 110°C in the case of PET (polyethylene terephthalate)). At this time, an infrared heater is used to irradiate infrared rays toward the stretched portion 29 of the double container preform 1. As a result, the infrared rays from the infrared heater are concentrated and absorbed by the infrared absorbing section 30 provided on the outer peripheral surface of the extension section 29 of the inner preform 11, and in the preform 1 for molding a double container, at least one of the section adjacent to the infrared absorbing section 30 on the radially outer side and the section adjacent to the infrared absorbing section 30 on the radially inner side is heated to above the crystallization temperature, becoming a thermally crystallized section 34 which has a higher degree of crystallinity and lower light transmittance than the others.

[0034] In the illustrated example, an infrared heater is used to irradiate infrared rays from the outside in the radial direction onto the elongated portion 29 of the double container molding preform 1. At this time, the infrared rays from the infrared heater are concentrated and absorbed by the infrared absorbing portion 30 provided on the outer peripheral surface of the elongated portion 29 of the inner preform 11. As a result, the outer peripheral surface side of the stretched portion 29 of the inner preform 11, where the infrared absorbing portion 30 is provided, is heated to a temperature higher than the crystallization temperature and becomes hotter than the other portions (for example, about 120°C in the case of PET (polyethylene terephthalate)), forming a thermally crystallized portion 34 with a higher degree of crystallinity than the other portions. On the other hand, the inner peripheral surface side of the stretched portion 29 of the outer preform 12, which is adjacent to the infrared absorbing portion 30 on the infrared heater side, is heated to a temperature higher than the crystallization temperature and becomes hotter than the other portions (for example, about 120°C in the case of PET (polyethylene terephthalate)), forming a thermally crystallized portion 34 with a higher degree of crystallinity than the other portions.

[0035] Next, with the preform 1 for molding a double container set in a blow molding mold, compressed air is blown into the inner preform 11 to blow mold the preform 1 for molding a double container, thereby obtaining a double container 10 as shown in Figure 2.

[0036] In this double container 10, an infrared absorbing section 30, which is more likely to absorb infrared rays than the inner container 31 and the outer container 32, is provided in a portion of the inner container 31 located below the inner opening 21, and at least the portion of the inner container 31 located below the inner opening 21 where the infrared absorbing section 30 is provided becomes a thermally crystallized section 34 that has a higher degree of crystallinity than the rest and has been whitened. In the illustrated example, the infrared absorbing portion 30 is provided in the extension portion 29 of the inner container 31. The infrared absorbing portion 30 is provided on the outer peripheral surface of the inner container 31, and the outer peripheral surface side of the inner container 31 and the inner peripheral surface side of the outer container 32 form a thermally crystallized portion 34.

[0037] In the stretched portions 29 of the inner container 31 and the outer container 32 (the inner preform 11 and the outer preform 12), the degree of crystallization in the thermally crystallized portions 34 is increased to the point where the portions are whitened, resulting in a lower light transmittance than the other portions (whitening). In the stretched portions 29 of the inner container 31 and the outer container 32 (the inner preform 11 and the outer preform 12), the thermally crystallized portions 34 have a higher Young's modulus than the other portions. In the stretched portions 29 of the inner container 31 and the outer container 32 (the inner preform 11 and the outer preform 12), the degree of crystallization in the thermally crystallized portions 34 is increased by heating compared to the other portions.

[0038] As described above, according to the double container molding preform 1 of this embodiment, at least a portion of the stretched portion 29 of the inner preform 11 is provided with an infrared absorbing portion 30 that is more absorbing of infrared rays than the inner preform 11 and the outer preform 12. Therefore, during the heating step of heating the stretched portion 29 of the double container molding preform 1 to a temperature at which it can be stretched by blow molding, infrared rays from the infrared heater are concentrated and absorbed by the infrared absorbing portion 30, and at least the portion of the stretched portion 29 of the inner preform 11 at which the infrared absorbing portion 30 is provided can be made into a thermally crystallized portion 34 with a higher degree of crystallinity than the remaining portion. In other words, even if the inner preform 11 alone is not heated using a dedicated heating furnace, a portion of the stretched portion 29 of the inner preform 11 can be thermally crystallized during the step of heating the double container molding preform 1 to a temperature at which it can be stretched. This makes it possible to prevent at least the thermally crystallized portion 34 of the inner preform 11 from following the stretching of the outer preform 12 during blow molding, resulting in a double container 10 in which the outer surface of the inner container 31 and the inner surface of the outer container 32 can be easily separated.

[0039] An infrared absorbing section 30 and vertical ribs 33 extending in the vertical direction are provided on the outer peripheral surface of the inner preform 11, and at least a portion of each of the infrared absorbing section 30 and the vertical ribs 33 are located at the same vertical position. As a result, a double container 10 is obtained in which at least a portion of each of the infrared absorbing section 30 and the vertical ribs 33 are located at the same vertical position on the outer peripheral surface of the inner container 31, and a double container 10 can be reliably obtained in which the outer surface of the inner container 31 and the inner surface of the outer container 32 can be easily separated.

[0040] Since the inner preform 11 and the outer preform 12 are formed from polyethylene terephthalate, the outer surface of the inner container 31 and the inner surface of the outer container 32 in the double container 10 tend to adhere to each other, thereby significantly achieving the aforementioned effect of easily obtaining a double container 10 in which the outer surface of the inner container 31 and the inner surface of the outer container 32 can be easily separated.

[0041] Since the outer peripheral surface side of the inner container 31 and the inner peripheral surface side of the outer container 32 are thermally crystallized portions 34, it is possible to reliably separate the outer surface of the inner container 31 and the inner surface of the outer container 32 easily. Since the infrared absorbing section 30 is provided on the outer peripheral surface of the inner container 31, by irradiating the preform 1 for molding a double container with infrared rays from the outside in the radial direction during the process of heating the preform 1 for molding a double container to a temperature at which it can be stretched, a double container 10 is obtained in which the outer peripheral surface side of the inner container 31 and the inner peripheral surface side of the outer container 32 are thermally crystallized, and the double container 10 can be obtained more easily than when infrared rays are irradiated from the inside in the radial direction during the process of heating the preform 1 for molding a double container to a temperature at which it can be stretched.

[0042] The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0043] When infrared rays are irradiated toward the stretched portion 29 of the double container molding preform 1, the infrared rays may be irradiated from the inside in the radial direction toward the stretched portion 29, or from the outside and inside in the radial direction.

[0044] In addition, within the scope of the spirit of the present invention, it is possible to replace the components in the above-described embodiments with well-known components as appropriate, and the above-described embodiments and the above-described variations may be combined as appropriate. [Explanation of symbols]

[0045] 1. Double container molding preform 10 double container 11 Inner preform 12 Outer preform 21 Inner mouth (mouth of inner preform 11) 22 outer opening (opening of outer preform 12) 28 Non-stretched part 29 Extension section 30 Infrared absorbing part 31 Inner container 32 Outer container 33 Vertical rib 34 Thermal crystallization section

Claims

1. A preform for molding a double container having an inner container in which contents are accommodated and an outer container in which the inner container is inserted, a cylindrical inner preform with a bottom for molding the inner container, and a cylindrical outer preform with a bottom for molding the outer container; the inner preform is inserted into the outer preform in a state in which a mouth portion of the inner preform is fitted into a mouth portion of the outer preform; In each of the inner preform and the outer preform, at least the mouth portion is a non-stretched portion that does not stretch when the double container is blow molded, and a portion located below the non-stretched portion is a stretched portion that stretches when the double container is blow molded, A preform for molding a double container, wherein at least a part of the elongated portion of the inner preform is provided with an infrared absorbing portion that absorbs infrared rays more easily than the inner preform and the outer preform.

2. The infrared absorbing portion and a vertical rib extending in the up-down direction are provided on the outer peripheral surface of the inner preform, The double container molding preform according to claim 1 , wherein at least a portion of the infrared absorbing portion and at least a portion of the longitudinal rib are located at the same vertical position.

3. 3. The preform for molding a double container according to claim 1, wherein the inner preform and the outer preform are made of polyethylene terephthalate.

4. A double container comprising an inner container for accommodating contents and an outer container in which the inner container is housed, The inner container has an infrared absorbing portion disposed below the opening that absorbs infrared rays more easily than the inner container and the outer container, A double container, wherein at least a portion of the inner container located below the mouth where the infrared absorbing portion is provided is a thermally crystallized portion having a higher degree of crystallinity than other portions.

5. the infrared absorbing portion is provided on the outer peripheral surface of the inner container, The double container according to claim 4, wherein the thermally crystallized portion is formed on the outer peripheral surface side of the inner container and the inner peripheral surface side of the outer container.

Images