Plastic double-structure container

Abstract

To provide a plastic double-structure container in which an inner container can be easily removed and an outer container can be easily mechanically recycled.SOLUTION: A double-structure container 30 is formed of a plastic outer container 10 and a plastic inner container 20 that is inserted and held in the outer container 10 and stores a content liquid, wherein the outer container 10 and the inner container 20 respectively have neck portions 11, 21 being non-stretch molded portions, and body portions 13, 23 being stretch molded portions and having a larger diameter than the neck portions 11, 21, and the neck portion 21 of the inner container 20 has a small diameter portion 21a located inside the neck portion 11 of the outer container 10, and a pulling grip portion 21b protruding from an upper end of the neck portion 11 of the outer container 10 and having a larger diameter than the small diameter portion 21a, and a cap fitting and fixing protrusion 21d is provided at an upper end of the pulling grip portion 21b.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a plastic double-structure container consisting of a plastic outer container and a plastic inner container inserted and held within the outer container, and more specifically, to a double-structure container that is suitable for recycling.The present invention also relates to a stack preform for producing the double-structure container, and an assembly of the double-structure container and a cap. [Background technology]

[0002] 2. Description of the Related Art Conventionally, containers made of polyester (typically made of polyethylene terephthalate) have been widely used as containers for various liquids, such as beverages, because of their excellent transparency, strength and heat resistance.

[0003] Meanwhile, in recent years, from the viewpoint of environmental protection and avoiding resource depletion, recycling of various used packaging materials has become required. As such a recycling method, mechanical recycling (sometimes called material recycling) is widely known, in which used collected products are sorted, crushed, washed, separated by specific gravity, and no chemical treatment is performed. Furthermore, chemical recycling (sometimes called thermal recycling) is also used, in which materials are decomposed by heating or the like and repolymerized to produce recycled resin (see Patent Documents 1 and 2). Currently, efforts are being made to reuse polyester containers, which are used in large quantities, through mechanical recycling, which is particularly inexpensive.

[0004] However, depending on the type of contents, recycling (especially mechanical recycling) may be difficult to apply. For example, with regard to polyethylene terephthalate (PET) bottles, the PET Recycling Association designates various beverages and soy sauce as products eligible for recycling, but shampoo, detergent, cosmetics, spicy sauces, etc. are listed as non-designated products.

[0005] Therefore, there is a demand for recyclable containers for all products (contents). From this perspective, a plastic double-structure container consisting of an outer container and an inner container housed within the outer container is ideal.

[0006] Such double-structure containers are put into practical use, for example, as airless bottles for storing seasoning liquids such as soy sauce (see Patent Documents 3 to 5). Such an airless bottle is used in combination with a cap equipped with a check valve, and by squeezing and denting the body wall of the bottle, which is the outer container, from the outside, the contents filled in the inner container are discharged through the pouring passage formed in the cap, and when the pressure on the body wall of the bottle is stopped to end the discharge of the contents, the check valve prevents air from being introduced into the inner bag container, but instead introduces air into the space between the inner container and the outer container through a flow path different from the pouring passage of the cap. This causes the inner container to shrink by the amount of the contents discharged, and the inner container shrinks every time the contents are discharged.

[0007] In the airless bottle from which the contents are discharged as described above, the contents can be dispensed in small portions, and the intrusion of air into the inner bag container in which the contents are filled is effectively prevented, so that oxidation deterioration of the contents can be effectively avoided and the freshness of the contents can be maintained for a long period of time. Moreover, since the contents are contained in the inner container and do not come into contact with the outer container, the outer container can be recycled regardless of the type of contents. Moreover, such recyclability is not limited to airless bottles, but also applies to simple double-walled containers.

[0008] However, in order to maximize recycling suitability, it is necessary to be able to remove the inner container from the outer container, but the reality is that no consideration has been given to this issue at all. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] WO2022 / 124229 issue [Patent Document 2] JP 2023-10098 A [Patent Document 3] Japanese Patent Application Publication No. 4-267727 [Patent Document 4] WO2001 / 26881 issue [Patent Document 5] Patent No. 7200489 Summary of the Invention [Problem to be solved by the invention]

[0010] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a plastic double-structure container which allows easy removal of the inner container and therefore facilitates mechanical recycling, particularly of the outer container. Another object of the present invention is to provide a stack preform for use in the manufacture of the above-mentioned double-walled container. It is still another object of the present invention to provide an assembly of the above-mentioned double-walled container and cap. [Means for solving the problem]

[0011] According to the present invention, there is provided a double-structure container formed of a plastic outer container and a plastic inner container that is inserted and held in the outer container and that contains a content liquid, The outer container and the inner container each have a neck portion which is a non-stretch molded portion, and a body portion which is a stretch molded portion and has a larger diameter than the neck portion, The neck of the inner container has a small diameter portion located within the neck of the outer container, and a pull-out grip portion protruding from the upper end of the neck of the outer container and having a larger diameter than the small diameter portion, and a cap fitting and fixing protrusion is provided at the upper end of the pull-out grip portion, thereby providing a plastic double-structure container.

[0012] The double-walled plastic container of the present invention preferably has the following features. (1) The outer surface of the small diameter portion formed in the neck of the inner container is provided with a linear rib that fits onto the inner surface of the neck of the outer container. (2) In the neck of the inner container, a circumferential step formed at the boundary between the small diameter portion and the removal grip portion is held in a state where it rests on the upper end surface of the neck of the outer container. (3) The upper end surface of the neck of the outer container is provided with a plurality of flat protrusions, which form a gap between the upper end surface of the neck and the circumferential step portion, and the linear ribs of the inner container extend intermittently so that the gap leads to the lower end of the neck of the inner container. (4) The upper end of the neck of the outer container is also provided with a cap fitting protrusion that protrudes outward. (5) The outer container is molded from polyester, and the inner container is molded from an olefin-based resin.

[0013] According to the present invention, in the stack preform used for producing the above-mentioned plastic double-walled container, an outer cylinder preform for forming the outer container; and an inner cylinder preform for forming an inner container inserted and held in the outer cylinder preform, The outer cylinder preform and the inner cylinder preform each have a test tube shape as a whole, and each upper part is a non-stretched molded part, and each has a shape corresponding to the neck part of the outer container and the neck part of the inner container, respectively; There is provided a stack preform, characterized in that in the inner cylinder preform, a circumferential groove is formed on the outer surface at the boundary between the non-stretch molded portion and the stretch molded portion.

[0014] According to the present invention, there is further provided an assembly of a container and a cap, which is composed of the above-mentioned plastic double-structure container and a cap attached to the double-structure container, comprising: The cap comprises a cylindrical body and a hinged lid hingedly connected to the cylindrical body, and an assembly is provided in which the inner surface of the cylindrical body is provided with an undercut that engages with a cap fitting fixing protrusion formed on the upper end of the inner container's removal grip portion. Effect of the Invention

[0015] The plastic double-walled container of the present invention has a double walled structure consisting of a plastic outer container and a plastic inner container housed in the outer container, and this structure provides optimal recyclability, particularly for the outer container. That is, in this double-walled container, the contents are housed in the inner container and do not come into contact with the outer container. As can be seen from this, the recyclability of the outer container of the present invention is ensured for all contents, regardless of the type of contents. The inner container can be thermally recycled. For example, it can be decomposed by heating and the polymer can be regenerated by repolymerization. In particular, when the inner container is made of an olefin resin, such thermal recycling is preferably applied.

[0016] In addition, in the double-walled plastic container of the present invention, the neck of the inner container has a small diameter portion located inside the neck of the outer container and a handle portion for pulling out that protrudes from the neck of the outer container and has a larger diameter than the small diameter portion. In other words, after the contents of this double-walled container have been discharged and used up, the handle portion can be easily used to pull out the inner container containing the contents from the outer container, which is not in contact with the contents, and the two can be separated. As a result, the outer container can be easily introduced into a mechanical recycling process and reused, regardless of the type of contents.

[0017] Furthermore, the above-mentioned double-structure container can be easily manufactured by the stack preform method, and even when manufactured by the stack preform method, the inner container can be easily pulled out, and the mechanical recyclability of the outer container described above is not impaired.

[0018] For example, when a double-structure container is manufactured by the stack preform method, an inner tube preform for forming an inner container is inserted into an outer tube preform for forming an outer container to form a stack preform, and this stack preform is placed in a blow molding die, and a blow fluid such as air is blown into the inner tube preform to perform stretch blow molding. That is, the inner tube preform expands, which spreads the outer tube preform, and both are shaped into the shape of a container. At this time, the upper part of these preforms becomes a neck part that is not stretch molded, and the lower part connected to it becomes a body part that is stretch molded and has an expanded diameter. In the present invention, in such a stack preform, a circumferential groove is formed on the outer surface of the lower end (the boundary between the non-stretch molded part and the stretch molded part) of the neck part of the inner tube preform. When stretch blow molding is performed on an inner tube preform having such a shape, the part of the circumferential groove becomes the expansion start point, and in the obtained inner container, the expansion start point becomes thin-walled and has a shape that is easily deformed. For this reason, the inner container is configured to be easily removed from the outer container. [Brief description of the drawings]

[0019] [Figure 1] 1 is a schematic cross-sectional side view of a double-structure container according to the present invention. [Diagram 2] 2 is an enlarged cross-sectional side view of a main portion of the double-structure container shown in FIG. 1, showing a neck portion and its vicinity together with a cap. [Diagram 3] FIG. 2 is a diagram showing the inner surface of the neck of the outer container and the outer surface of the neck of the inner container shown in FIG. [Figure 4] 2 is a schematic cross-sectional side view showing an outer cylinder preform, an inner cylinder preform, and a stack preform used in molding the double-structure container of FIG. 1. [Diagram 5]4 is an enlarged view of the neck portion of the inner cylinder preform in FIG. 3 and its vicinity. FIG. [Figure 6] FIG. 13 is an enlarged view showing another example of the neck portion of the inner cylindrical preform and its vicinity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] 1 and 2, the double-structure container of the present invention is generally designated by 30 and is composed of an outer container 10 and an inner container 20 contained inside the outer container 10. In such a double-structure container 30, the inner container 20 contains liquid as a content, and is structured so that the content in the inner container 20 can be discharged by opening a cap (designated by 100 in FIG. 2) as appropriate and tilting the container 30, and the outer container 10 does not come into contact with the content in the inner container 20, and therefore the outer container 10 can be mechanically recycled regardless of the type of content.

[0021] <Container material> In the present invention, the outer container 10 may be formed from any thermoplastic resin, but it is basically preferable that it be formed from polyester, for which recyclability is particularly required, in order to maximize the advantage of being mechanically recyclable, regardless of the type of contents described above. Examples of such polyesters include polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), and copolymer polyesters thereof, with PET being particularly preferred.

[0022] The outer container 10 made of these polyesters has excellent properties as a packaging container, such as transparency, strength, heat resistance, durability, etc. In addition, since the preform for forming this outer container 10 is molded by injection molding, the polyester used preferably has an injection grade IV (0.73 to 0.83 dl / g).

[0023] On the other hand, the inner container 20 may also be made of any thermoplastic resin, but is preferably made of an olefin-based resin that has been conventionally used as a container material and is suitable for thermal recycling. Examples of such olefin resins include low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), polypropylene (PP), poly-1-butene, poly-4-methyl-1-pentene, or random or block copolymers of α-olefins such as ethylene, propylene, 1-butene, and 4-methyl-1-pentene, cyclic olefin copolymers, and blends thereof.

[0024] Although the melting point of olefin resin is lower than that of polyester (usually around 250°C), the double-structure container of the present invention is manufactured by stretch blow molding using the so-called stack preform method. Therefore, the olefin resin for forming the inner container 20 is preferably one having a melting point that is small compared to that of the resin for forming the outer container 10, such as polyester. Specifically, preferred materials include a blend of relatively inexpensive LDPE and LLDPE, which has a high melting point, homopolypropylene (PP), or random polypropylene (random PP) or block polypropylene (block PP), which is homopolypropylene (PP) blended with other resins or elastomer components, and these have an increased melting point of around 125°C. The above-mentioned random PP is a polypropylene copolymerized with a small amount of ethylene, and block PP has a structure in which rubber components such as ethylene-propylene copolymer (EPR) or styrene-butadiene copolymer (SBR) are dispersed in a matrix of homo-PP or random PP. In both cases, other components are blended into homo-polypropylene (PP) to bring the melting point closer to that of polyester.

[0025] <Container structure> 1 to 3, as described above, this container 30 is composed of an outer container 10 and an inner container 20 in which the contents are accommodated, and the inner container 20 is inserted and held within the outer container 10. In addition, a cap 100 is attached to this double-structure container 30 (see FIG. 2).

[0026] The outer container 10 is not stretch-molded and is composed of a stiff, thick-walled neck 11 and a body 13 connected to the neck 11, with a closed bottom 15 formed at the lower end of the body 13. The body 13 is a stretch-molded portion and is thinner than the neck 11. The upper part of the body 13 has a shoulder 13a which gradually expands in diameter downward from the connection with the neck 11 and slopes outward.

[0027] An outwardly protruding protrusion 11a is formed at the upper end of the neck 11 of the outer container 10, and a large-diameter support ring 11b is provided on the lower outer surface of the protrusion 11a. The protrusion 11a is used for attaching and fixing the cap 100, and the support ring 11b is used for transporting the container 30, etc. The protrusion 11a is formed for fitting and fixing the cap 100.

[0028] 3a, a plurality of flat small protrusions 11c are distributed on the upper end surface of the neck 11, and axial grooves 11d extend between the small protrusions 11c on the inner surface of the neck 11. These small protrusions 11c and axial grooves 11d are designed to introduce air between the outer surface of the body of the inner container 20 and the small protrusions 11c.

[0029] On the other hand, like the outer container 10, the inner container 20 also comprises a highly rigid neck 21 and a body 23 connected to the neck 21, with a closed bottom 25 formed at the lower end of the body 23. In other words, the neck 21 is a thick-walled portion that is not stretch-formed, while the lower body 23 (and bottom 25) is a thin-walled portion that is stretch-formed. Furthermore, a shoulder portion 23a similar to that of the outer container 10 is formed on the upper portion of the body portion 23.

[0030] Furthermore, since such a double-structure container 30 is manufactured by the stack preform method described below, the outer surface of the body 23 of the inner container 20 is formed in close contact with the inner surface of the body 13 of the outer container 10.

[0031] In the present invention, the neck 21 of the inner container 20 is composed of a small diameter portion 21a located within the neck 11 of the outer container 10 and a large diameter grip portion 21b for pulling out located above the small diameter portion 21a and protruding from the neck 11 of the outer container 10, with a circumferential step 21c formed between them. That is, as shown in Fig. 2, the neck 21 of the inner container 20 is held in a state where the circumferential step 21c formed between the small diameter portion 21a and the large diameter grip portion 21b for pulling out is placed on the upper end surface of the neck 11 of the outer container 10.

[0032] Further, an outwardly projecting protrusion 21d is formed on the upper end of the pulling grip portion 21b, and this protrusion 21d is also used for fitting and fixing the cap 100.

[0033] Furthermore, since a plurality of flat small protrusions 11c are distributed on the upper end surface of neck 11 on which the above-mentioned circumferential step 21c (neck 21) rests, a gap is formed between neck 11 and neck 21 (small diameter portion 21a) for introducing air.

[0034] As shown in Fig. 3(b), a rib 21e that locally protrudes outward is formed on the outer surface of the small diameter portion 21a of the neck 21 of the inner container 20. The rib 21e fits into the inner surface of the neck 11 of the outer container 10, so that the neck 21 of the inner container 20 is firmly held within the neck 11 of the outer container 10. The rib 21e extends intermittently in a spiral shape, and the intermittent portion X is positioned so as to face the axial groove 11d formed on the inner surface of the neck 11 of the outer container 10, so that an air passage is formed to introduce air between the neck 11 and the neck 21 (small diameter portion 21a).

[0035] A cap 100 is fitted and fixed to such a double-structure container 30. The cap 100 shown in Fig. 2 is a normal cap that does not have a check valve or the like, and is composed of a cylindrical cap body 101 and an upper cover 103 hinged to the cap body 101. The hinge band that connects the upper cover 103 to the cap body 101 is indicated by 105. Incidentally, the cap 100 is usually made of an olefin resin, for example, polypropylene or polyethylene, such as high density polyethylene or low density polyethylene.

[0036] As can be seen from Figure 2, the cylindrical inner wall of the cap body 101 has engaging protrusions 101a, 101b formed at the lower end and above the lower end, which respectively engage with the protrusion 11a formed at the upper end of the neck 11 of the outer container 10 and the protrusion 21d formed at the upper end of the neck 21 (pulling grip portion 21b) of the inner container 20, and are firmly attached to this double-structure container 30.

[0037] The upper part of the cap body 101 is closed by a sealing wall 107, and an inner ring 109 extends downward from the peripheral part of this sealing wall 107, and the inner ring 109 adheres closely to the inner surface of the neck part 21 (pulling part 21b) of the inner container 20, thereby ensuring the sealing of the inner container 20. Also, a support 113 equipped with a pull ring 111 at its upper end is formed on this sealing wall 107, and by pulling up the pull ring 111, a score (not shown) formed on the sealing wall 107 is torn to form an opening.

[0038] That is, when the cap 100 is plugged with the top lid 103 closed, the engaging projections 101a, 101b of the cap 100 engage with the projection 11a formed on the neck 11 of the outer container 10 and the projection 21d formed on the neck 21 of the inner container 20, closing the neck 21 of the inner container 20 in which the contents are stored and tightly sealing it. When using, the top lid 103 is turned open, and the seal wall 107 is torn off by pulling up the pull ring 111, and the double-structure container 30 is tilted in this state, whereby the contents formed in the inner container 20 are quickly discharged.

[0039] After the contents have been discharged and used up in this manner, the cap 100 is removed, the inner container 20 is removed from inside the outer container 10, and the inner container 20 and the outer container 10 are each supplied to a recycling process. Furthermore, to remove the cap 100, a score (linear thin portion) and a tab for tearing the score are provided on the outer surface of the cap body 101, and the cap 100 can be removed from the double-structure container 30 (outer container 10 and inner container 20) by tearing the score.

[0040] In the double-structure container 30 of the present invention, after the cap 100 is removed, the inner container 20 is pulled out from the outer container 10, and the container is constructed so that this pulling out can be easily performed. That is, the neck 21 of the inner container 20 has a pulling grip 21b protruding from the neck 11 of the outer container 10. This makes it possible to easily pull the inner container 20 out of the outer container 10 by holding the grip 21b with fingers.

[0041] In the present invention, the shape and length of the above-mentioned removal grip 21b should be set in consideration of the pull-out property of the inner container 20. For example, the lower end of the protrusion 21d is preferably shaped to have a corner that allows a finger to hook, as shown in Fig. 3(b). Furthermore, the length L (see Fig. 3(b)) from the lower end of the removal grip 21b to the lower end of the protrusion 21d is preferably set to a length of about 2 to 10 mm, particularly about 3 to 5 mm. That is, if this length L is short, it becomes difficult to grasp this portion, and it becomes difficult to pull out the inner container 20 from the outer container 10. On the other hand, if this length L is longer than necessary, rather than improving the pull-out property, the neck 21 of the inner container 20 may easily rattle and become unstable.

[0042] Furthermore, in the present invention, as described above, it is preferable to form a linear rib 21e extending in a spiral shape on the outer surface of the neck 21 of the inner container 20, and to configure this rib 21e so as to fit with the inner surface of the neck 11 of the outer container 10. That is, if the entire outer surface of the neck 21 is configured to fit with the inner surface of the neck 11 of the outer container, the surface contact will be such that the fitting force will be strong, and it may be difficult to pull out the inner container 20 by grasping the pulling grip 21b. On the other hand, if the fitting is configured with the linear rib 21e, the fitting force will be appropriate, and it is possible to reliably avoid a decrease in pull-out ability.

[0043] Furthermore, in the present invention, a flat projection 11c is formed on the upper end surface of the neck 11 of the outer container 10, and the above-mentioned rib 21e extending in a spiral shape is provided with an intermittent portion X, and this intermittent portion X is positioned so as to face the axial groove 11d formed on the inner surface of the neck 11 of the outer container 10, thereby forming an air passage. That is, when the cap 100 is removed, air flows into between the body 23 of the inner container 20 and the body 13 of the outer container 10 from the step portion 21c formed on the neck 21 of the inner container 20 and the gap formed on the upper end surface of the neck 11 of the outer container 10, thereby making it easier to pull out the inner container 20. If such an air passage is not formed, the space between the body 23 of the inner container 20 and the body 13 of the outer container 10 will be under negative pressure, which may make it difficult to pull out the inner container 20.

[0044] 2, it is preferable that the outer surface of diameter expansion start portion 26 at the lower end of neck 21 of inner container 20 is slightly separated from the inner surface of diameter expansion start portion 15 at the lower end of neck 11 of outer container 20, with a gap CL being formed between them. That is, if this portion is in close contact, it may be difficult to pull out the inner container 20, but if a gap CL is formed in this portion, it becomes easier to pull out the inner container 20.

[0045] <Manufacturing of double-walled containers> The double-structure container 30 of the present invention is manufactured by a so-called stack preform method. This manufacturing method involves using an outer tube preform (preform for molding the outer container) obtained by injection molding using a resin for molding the outer container, and an inner tube preform (preform for molding the inner container) obtained by injection molding using a resin for molding the inner container, inserting the inner tube preform into the outer tube preform to form a stack preform with a multi-layered structure, and then performing biaxial stretch blow molding on this stack preform.

[0046] In Figure 4, which illustrates the various preforms used in the above stack method, the stack preform for molding the double-structure container 30 of Figures 1 to 3 is indicated as a whole at 70 (see Figure 4(c)), and is formed from an outer tube preform 50 (see Figure 4(a)) and an inner tube preform 60 (see Figure 4(b)), both of which have a test tube shape. That is, the outer tube preform 50 is a preform for molding an outer container, and the inner tube preform 60 is a preform for molding an inner container. By inserting the inner tube preform 60 into the outer tube preform 50 and holding them in place, a stack preform 70 is assembled which is to be subjected to the stretch blow process.

[0047] As can be seen from Fig. 4, the outer tube preform 50 has a portion corresponding to the neck 11 of the outer container 10, and the inner tube preform 60 has a portion corresponding to the neck 21 of the inner container 20. These portions are not stretch-blow molded (non-stretch molded portion α), and the lower body portions 53, 63 connected to the neck portions 11, 21 are blow-stretched (stretch molded portion β). Therefore, the neck portions, which are the non-stretch molded portion α of these preforms 50, 60, have exactly the same shape as the neck portions 11, 21 shown in Figs. 1 to 3, and each portion is indicated by the same reference numerals as in Figs. 1 to 3.

[0048] That is, like the neck 11 of the outer container 10, the neck 11 of the outer tube preform 50 has an outwardly protruding protrusion 11a formed at the upper end, and a large-diameter support ring 11b is provided on the lower outer surface of the protrusion 11a. In addition, although omitted in Fig. 4, a plurality of flat small protrusions 11c are formed on the upper end surface, and an axial groove 11d extends on the inner surface.

[0049] Similarly, the neck 21 of the inner tube preform 60 has a small diameter portion 21a located within the neck 11 of the outer tube preform 10, and a large diameter pulling grip portion 21b (having a protrusion 21d protruding outward at its upper end) located above the small diameter portion 21a and protruding from the neck 11 of the outer container 10, and a circumferential step 21c is formed between them. As shown in Fig. 4(c), this circumferential step 21c is held in a state of being placed on the upper end surface of the neck 11 of the outer tube preform 10. Therefore, a gap is formed in the portion where the circumferential step 21c is placed, and air can be supplied to the inside from this gap.

[0050] Furthermore, referring also to Fig. 5 which shows an enlarged view of the neck 21 of the inner tube preform 60 and its vicinity, although omitted in Fig. 4, a linear rib 21e which extends in a spiral shape and has an intermittent portion X is formed on the outer surface of this neck 21. That is, this rib 21e is fitted to the inner surface of the neck 11 of the outer tube preform 50, thereby forming a stack preform 70 in which the inner tube preform 60 is firmly held within the outer tube preform 50.

[0051] In the stack preform 70, the stretch molded portion β (body portion 53, 63) of each preform 50, 60 is slightly thinner on the side connected to the upper neck portion 11, 21, and is shaped to be easily expanded and deformed outward. Furthermore, the inner diameter of the stretch molded portion β (body portion 63) of the inner tube preform 60 is smaller than the inner diameter of the stretch molded portion β (body portion 53) of the outer tube preform 50, so that a gap is formed between the two. This makes it possible to easily insert the inner tube preform 60 into the outer tube preform 50. In addition, a plurality of vertical ribs may be formed on the inner surface of the body portion 53 of the outer tube preform 50. The vertical ribs are spaced apart such that air can escape when the inner tube preform 60 is inserted into the outer tube preform 50, and the inner tube preform 60 may be supported by the vertical ribs.

[0052] The stack preform 70 described above is placed in a blow molding die, and in a state where it is heated to a temperature equal to or higher than the glass transition point (Tg) and lower than the melting point of the resin forming the preforms 50 and 60, a stretch rod is appropriately inserted into the inner tube preform 60, and the inner tube preform 60 and the outer tube preform 50 are stretched in one axial direction, and then a blowing fluid such as air is supplied into the inner tube preform 60 to expand and deform the stretch-molded portion β (body portion 63) of the inner tube preform 60, and this expansion and deformation also pushes and spreads the stretch-molded portion β (body portion 53) of the outer tube preform 50, presses it against a predetermined mold surface, and is shaped into a bottle shape, thereby producing the double-structure container 30 shown in Fig. 1 and the like. Therefore, in the double-structure container 30, the outer surface of the body portion 23 of the inner container 20 is in close contact with the inner surface of the body portion 13 of the outer container 10.

[0053] In the present invention, when the double-structure container 30 is manufactured by the stack preform method as described above, it is preferable to perform a support (preliminary) blow by utilizing a gap formed in the portion on which the circumferential step 21c of the neck 21 of the inner cylinder preform 60 is placed after blow molding, and supplying air through this gap. By such a support (preliminary) blow, a gap CL can be formed between the outer surface of the diameter expansion start portion 26 at the lower end of the neck 21 of the inner container 20 and the inner surface of the diameter expansion start portion 15 at the lower end of the neck 11 of the outer container 20, making it easier to pull out the inner container 20 from the outer container 10.

[0054] 5 showing the neck 21 of the inner tube preform 60 and its vicinity, it is preferable that a circumferential groove 65 is formed at the boundary between the neck 21 and the stretch-molded portion 63 (body portion) in the inner tube preform 60. That is, if such a circumferential groove 65 is formed, in the inner container 20 formed by stretch blowing, the boundary between the neck 21 and the upper end (shoulder portion 23a) of the body portion 23 becomes slightly thinner and more easily deformed, and the inner container 20 can be smoothly pulled out of the outer container 10.

[0055] Furthermore, the configuration for smoothly pulling out the inner container 20 from the outer container 10 is not limited to the configuration shown in FIG. For example, as shown in FIG. 6, ribs 67a (see FIG. 6(a)) or axial grooves 67b (see FIG. 6(b)) extending in the axial direction may be provided so as to intersect with the circumferential groove 65. In the illustrated embodiment, the ribs 67a and axial grooves 67b are formed only in the vicinity of the circumferential groove 65, but they may be formed deeper on the inner surface of the stretch-molded portion 63 (body). The formation of such ribs 67a and axial grooves 67b creates a slight thickness distribution in the body 23 of the inner container 20, which makes the body 23 more susceptible to wrinkles and makes it easier for gaps to form between the body 23 and the inner container 20 when the inner container 20 is pulled out from the outer container 10. As a result, the inner container 20 can be pulled out smoothly from the outer container 10.

[0056] Furthermore, although not shown, a cam engagement mechanism is provided between the outer surface of the small diameter portion 21a of the neck 21 of the inner tube preform 60 (inner container 20) and the inner surface of the neck 11 of the outer tube preform 50 (outer container 10), and the neck 21 can be configured to move upward by rotating the neck 21.

[0057] The double-structure container 30 of the present invention thus manufactured is used after the inner container 20 is filled with the liquid content and the above-mentioned cap 100 is attached. The cap 100 shown in Fig. 2 is a normal hinge cap, but a cap with a check valve applied to an airless bottle can also be attached as the cap 100. In this case, the double-structure container 30 functions as a so-called airless bottle. That is, as the contents are discharged, the body 23 of the inner container 20 shrinks by the amount of the contents discharged. At this time, the check valve provided in the cap 100 allows the contents to be discharged from the inner container 20, but prevents air from being introduced into the inner container 20, thereby preventing oxidation deterioration of the contents contained in the content liquid 20 and maintaining the freshness of the content liquid. In addition, the shrinkage of the body 23 of the inner container 20 accompanying the discharge of the content liquid increases the gap between the body 23 and the body 13 of the outer container 10, but air flows in through the cap 100 by the amount of negative pressure in this gap. Therefore, by pressing and depressing the body 13 of the outer container 10, the body 23 of the contracting inner container 20 can be effectively pressed, and the contents can always be discharged smoothly.

[0058] In this way, the double-structure container 30 of the present invention can be used as either a normal container or an airless container, depending on the type of the cap 100 attached thereto.

[0059] In addition, the double-structure container 30 of the present invention can be mechanically recycled for the outer container, not only when the liquid content is a product designated by the PET Recycling Association (soy sauce or various beverages), but also when the liquid content is not designated (vegetable oil, detergent, shampoo, etc.). Therefore, it is optimal that the outer container 10 is made of polyester (especially PET), which is particularly required for recycling. Moreover, the inner container 20 is preferably made of an olefin-based resin, in particular because it can be thermally recycled. That is, even if the content is an oily liquid such as vegetable oil, the oily liquid can be thermally decomposed by heating to a high temperature, and at the same time, the inner container 20 made of an olefin-based resin can be decomposed into monomers and repolymerized, so that the olefin-based resin can be recycled and used for various purposes. Furthermore, when the cap 100 is made of an olefin-based resin, the cap 100 and the inner container 20 can be subjected to thermal recycling at the same time. [Explanation of symbols]

[0060] 10: Outer container 11: Neck of outer container 11a: Cap engagement protrusion 11b: Support ring 11c: small protrusion 13: Body of outer container 15: Start of expansion of outer container 20: Inner container 21: Neck of inner container 21a: Small diameter part 21b: Pull-out grip 21c: Step 21d: Cap engagement protrusion 21e: Linear rib 23: Body of the container 25: Bottom of container 26: Start of expansion of inner container 30:Double structure container 50: Outer cylinder preform 53: Body part (stretching molding part) 60: Inner cylinder preform 63: Body (stretching molding section) 65: Circumferential groove 67a: Axial rib 67b: Axial groove 70: Stack preform 100: Cap CL: void

Claims

1. A plastic double-structure container formed of a plastic outer container and a plastic inner container that is inserted and held in the outer container and contains a content liquid, The outer container and the inner container each have a neck portion which is a non-stretch molded portion, and a body portion which is a stretch molded portion and has a larger diameter than the neck portion, A plastic double-structure container characterized in that the neck of the inner container has a small diameter portion located within the neck of the outer container and a pull-out grip portion protruding from the upper end of the neck of the outer container and having a larger diameter than the small diameter portion, and a cap fitting and fixing protrusion is provided at the upper end of the pull-out grip portion.

2. 2. The plastic double-walled container according to claim 1, wherein the inner container has a small diameter portion on its outer surface, the small diameter portion being fitted to the inner surface of the neck of the outer container.

3. 3. A plastic double-structure container as described in claim 2, wherein a circumferential step portion formed at the boundary between the small diameter portion and the pulling grip portion in the neck of the inner container is held in a resting state on the upper end surface of the neck of the outer container.

4. 4. A plastic double-structure container as described in claim 3, wherein a plurality of flat protrusions are distributed on the upper end surface of the neck of the outer container, thereby forming a gap between the upper end surface of the neck and the circumferential step portion, and the linear ribs of the inner container extend intermittently so that the gap leads to the lower end of the neck of the inner container.

5. 2. The plastic double-structure container according to claim 1, wherein the upper end of the neck of the outer container is also provided with a cap fitting projection that projects outward.

6. 6. The plastic double-structure container according to claim 1, wherein the outer container is made of polyester, and the inner container is made of an olefin-based resin.

7. The stack preform used for manufacturing the plastic double-walled container according to claim 1, an outer cylinder preform for forming the outer container; and an inner cylinder preform for forming an inner container inserted and held in the outer cylinder preform, The outer cylinder preform and the inner cylinder preform each have a test tube shape as a whole, and each upper part is a non-stretched molded part, and each has a shape corresponding to the neck part of the outer container and the neck part of the inner container, respectively; A stack preform, wherein the inner cylindrical preform has a circumferential groove formed on its outer surface at the boundary between the non-stretch molded portion and the stretch molded portion.

8. 2. A container-cap assembly comprising the plastic double-structure container according to claim 1 and a cap attached to the double-structure container, The cap comprises a cylindrical body and a hinged lid hingedly connected to the cylindrical body, and an undercut is provided on the inner surface of the cylindrical body to engage with a cap fitting and fixing protrusion formed on the upper end of the inner container's pull-out grip.

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