Double-structured container

Abstract

To provide a double structure container having a new structure in which a gap is formed for performing introduction of the air in a space between an outer surface of an inner bag container and an outer container, and which can perform introduction of the air quickly.SOLUTION: A double structure container comprises: an outer container 2; and an inner bag container 3 stored in the outer container 2. The outer container 2 is formed by: a nozzle 21; a shoulder part 22 formed below the nozzle 21; and a stretch molding part comprising a trunk part 23 and a bottom part 24. The inner bag container 3 has: a cylindrical mouth part 31; and a bag-like trunk part 32 which is connected to the cylindrical mouth part 31 and which is thin-walled by stretching. An outer surface of the bag-like trunk part 32 is in close contact with an inner surface of the trunk part 23 of the outer container 2 so as to be peeled, and between an outer surface of the cylindrical mouth part 31 of the inner bag container 3 and an inner surface of the nozzle 21 of the outer container 2, an air passage H is formed which can introduce the air, and in the upper end part vicinity portion of the bag-like trunk part 32 of the inner bag container 3, when viewed in a plane cross section, an irregular region is formed where a contact part X in which the outer surface of the bag-like trunk part 32 comes into contact with the inner surface of the shoulder part 22 of the outer container 2, and a non-contact part Y in which both are separated exist.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a double-structure container consisting of an outer container and an inner bag container inserted and held within the outer container, and more specifically, to a double-structure container manufactured by a method called stack preform. [Background technology]

[0002] Conventionally, a double-structure container having a double structure consisting of an inner bag container and an outer container is called, for example, an airless bottle, and is used as a container for storing seasoning liquid such as soy sauce (see, for example, Patent Documents 1 and 2). Such an airless bottle is used in combination with a cap with a check valve, and the liquid content filled in the inner bag container is discharged from the pouring passage formed in the cap by squeezing and denting the body wall of the bottle, which is the outer container, from the outside, and when the discharge of the liquid content is terminated by stopping the pressure on the body wall of the bottle, the check valve prevents air from being introduced into the inner bag container, and the air is introduced into the space between the inner bag container and the outer container through a flow path different from the pouring passage of the cap. As a result, the inner bag container shrinks by the amount of the liquid content discharged, and the inner bag container shrinks every time the liquid content is discharged. In an airless bottle in which the liquid contents are discharged in this manner, the liquid contents can be dispensed in small amounts while effectively preventing air from entering the inner bag container in which the liquid is filled, thereby offering the advantage that oxidation deterioration of the liquid contents can be effectively avoided and the freshness of the liquid contents can be maintained for a long period of time.

[0003] Therefore, in a double-structure container (airless bottle), in order to ensure the above-mentioned air circulation, a gap is generally formed between the inner surface of the neck of the outer container and the inner surface of the mouth of the inner bag container, and further, a valve body that swings up and down is provided on the inner surface of the cylindrical side wall (skirt portion) of the cap that is attached to the neck of the outer container, and this valve body is configured to control the flow of air through the above-mentioned inlet port (see, for example, Patent Document 2).

[0004] Incidentally, a method called stack preform method is known as a method for manufacturing a double-structured container such as an airless bottle (see, for example, Patent Document 3). In this method, a test-tube-shaped preform for an outer container and a preform for an inner bag container are first molded by injection molding or the like, and then the stack preform in which the preform for the inner bag container is inserted inside the preform for the outer container is used for stretch blow molding. In this method, the stack preform is placed in a blow mold and heated to a stretch molding temperature (above the glass transition point and below the melting point), and in this state, a blow fluid is blown into the preform for the inner bag container to perform blow molding. That is, the blowing of the blow fluid causes the preform for the inner bag container to expand, and the preform for the outer container is pushed out and shaped into the shape of a bottle-shaped outer container, and the preform for the inner bag container is shaped into the shape of a bag that is in close contact with the inner surface of the outer container. This method has the advantages of enabling mass production of container preforms (preforms for outer containers and preforms for inner bag containers), being highly productive, and producing containers of stable quality with little variation in container weight and internal volume, and in particular enabling cost reduction.

[0005] However, the above-mentioned double-structure container is not limited to the stack preform method, and is formed in a form in which the outer surface of the inner bag container is in close contact with the inner surface of the outer container, which presents a fundamental problem of how to introduce air between the outer surface of the inner bag container and the inner surface of the outer container. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 6-39906 [Patent Document 2] JP 2018-2198 A [Patent Document 3] JP 2016-210181 A Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, an object of the present invention is to provide a double-structure container having a novel structure in which a gap for introducing air is formed in the space between the outer surface of the inner bag container and the outer container, enabling air to be introduced quickly. [Means for solving the problem]

[0008] The inventors previously proposed a method for manufacturing a double-structure container by a stack preform method, in which an air passage is formed to allow air to be let in and out of the space between the outer surface of the inner bag container and the outer container (Patent Application No. 2020-79736). However, as a result of further investigating the shape of the double-structure container obtained by this method, they found that when a void is actively formed to introduce air into the space between the outer surface of the inner bag container and the outer container after blow molding and prior to filling with the contents, a unique shape that is completely different from conventional double-structure containers is formed.

[0009] According to the present invention, there is provided a double-structure container comprising an outer container and an inner bag container housed in the outer container, the inner bag container housing a content, the double-structure container comprising: The outer container is formed from a nozzle and a stretch-molded portion including a shoulder portion, a body portion, and a bottom portion formed below the nozzle, The inner bag container has a cylindrical mouth portion having a fixed shape, and a bag-shaped body portion which is connected to the cylindrical mouth portion and which is thinned by stretching, and the outer surface of the bag-shaped body portion is peelably adhered to the inner surface of the body portion of the outer container, An air passage through which air can be introduced is formed between the outer surface of the cylindrical mouth of the inner bag container and the inner surface of the nozzle of the outer container; and A region in which the diameter of the inner bag container starts to expand from the lower end of the cylindrical mouth portion to the upper end of the bag-shaped body portion. for, Same A double-structure container is provided, characterized in that, when viewed in plan view, an amorphous region is formed in which there is a contact portion where the outer surface of the bag-shaped body is in contact with the inner surface of the shoulder of the outer container, and a non-contact portion where the two are separated.

[0010] In the double-structure container of the present invention, contacting portions and non-contacting portions are irregularly present in the shapeless region, and the inner bag container is in the state of an empty container before any contents are placed inside. Effect of the Invention

[0011] The double-structure container of the present invention is manufactured by the stack preform method, and in particular, after blow molding, the inner bag container's diameter expansion start region (i.e., the portion from the lower end of the cylindrical mouth to the upper end of the bag-shaped body) is forcibly deformed to make it irregular. In this irregular region, a part of the upper end portion of the bag-shaped body is irregularly peeled off from the inner surface of the outer container, which forms an irregular gap between the outer surface of the bag-shaped body of the inner bag container and the inner surface of the body of the outer container, and air can be easily introduced through this gap. In other words, if the entire outer surface of the upper end portion of the bag-shaped body of the inner bag container is in close contact with the inner surface of the outer container, it is difficult to introduce air between this bag-shaped body and the body of the outer container, but if the upper end portion of the bag-shaped body is irregularly deformed as described above to form a gap between the inner surface of the outer container and the bag-shaped body, air can be introduced quickly when the contents are discharged.

[0012] That is, in the double-structure container of the present invention, an irregular gap is formed between the upper end portion of the bag-shaped body and the inner surface of the outer container, and when viewed in plan view, an irregular region is confirmed between the outer surface of the portion near the boundary between the cylindrical mouth of the inner bag container and the bag-shaped body and the inner surface of the shoulder of the outer container, where there are contact parts where the two are in contact and non-contact parts where the two are separated. In this region, the contact parts and non-contact parts are not in fixed positions, but are in an unstable shape where their positions are constantly fluctuating. This is because the bag-shaped body of the inner bag container formed by blow molding is thinned to the point where it loses its self-supporting ability.

[0013] In this way, in the double-structure container of the present invention, an amorphous region is formed near the upper end of the bag-shaped body of the inner bag container immediately after molding, and therefore when the inner bag container is then filled with contents and the body of the outer container is pressed and depressed to discharge the contents, when the pressure on the body of the outer container is stopped and the body returns to its original shape, air quickly flows in between the bag-shaped body and the body of the outer container through the non-contact portion formed in the amorphous region, allowing the next content discharge operation to be carried out smoothly. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a longitudinal sectional view showing a schematic structure of a double-structure container according to the present invention. [Diagram 2] 1 is a side cross-sectional view of a stack preform used to manufacture a double-walled container of the present invention. [Diagram 3] 2 is a cross-sectional view of the stack preform shown in FIG. [Figure 4] FIG. 3 is a diagram showing a blow molding process using the stack preform of FIG. 2. [Diagram 5] FIG. 4 is an enlarged cross-sectional side view of a main portion for explaining a deformation state of the stack preform during the blow molding process. [Figure 6] FIG. 4 is an enlarged cross-sectional side view of a main portion for explaining a heating step after a blow molding step. [Figure 7] FIG. 2 is an enlarged cross-sectional side view showing a main portion of the double-structure container of the present invention. [Figure 8] Cross-sectional view taken along line B-B in FIG. 7. [Figure 9] FIG. 11 is an enlarged longitudinal sectional view of a main portion of the double-structure container of Experimental Example 4, showing the shape after the contents are discharged. [Figure 10] FIG. 16 is an enlarged longitudinal sectional view of a main portion of the double-structure container of Experimental Example 11, showing the shape after the contents are discharged. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] First, the general structure of the double-structure container of the present invention will be briefly described. Referring to FIG. 1 showing the schematic structure of this double-structure container, the double-structure container generally designated by 1 comprises a bottle-shaped outer container 2 and an inner bag container 3 in which contents such as soy sauce are contained.

[0016] The outer container 2 is composed of a nozzle 21, a shoulder 22 connected to the nozzle 21, a body 23, and a bottom 24. The outer container 2 is elastically deformable, and when the body 23 is pressed, it is depressed, and when the pressing is stopped, the depressed body 23 returns to its original shape. The inner bag container 3 is composed of a cylindrical mouth portion 31 and a thin-walled bag-like body portion 32 that is continuous with the cylindrical mouth portion 31. The cylindrical mouth portion 31 is thick and has a fixed shape (i.e., this portion is not stretched and has a rigidity that does not easily deform), and the bag-like body portion 32 is filled with the contents and shrinks and deforms due to the reduction in volume associated with the discharge of the contents.

[0017] The nozzle 21 of the outer container 2 has a cylindrical shape with an open upper end, and a cap (not shown) having a check valve function is attached to it by plugging. The upper end of this nozzle 21 is formed with an enlarged head 21a, which allows the cap to be stably held when plugged. In addition, a support ring 21b is formed at the lower part of the nozzle 21, which allows the double-structure container 1 (or preform) to be easily transported using a jig. Incidentally, the cap can be attached by providing a screw on the outer surface of the nozzle 21 and screwing it in place of the cap.

[0018] The nozzle 21 described above is a non-stretched molding part, and its lower part is the part that is stretched by blow molding. This nozzle 21 has an enlarged shoulder portion 22 formed thereon, connected to its lower end 21c, and this shoulder portion 22 is connected to a body portion 23, which is closed by a bottom portion 24. Incidentally, a horizontal step 21d for stably holding the inner bag container 3 is formed on the inner surface of the nozzle 21.

[0019] 1, the inner bag container 3 is housed in the outer container 2, and its cylindrical mouth portion 31 (i.e., the portion not stretched) extends inside the nozzle 21 of the outer container 2 so as to form a gap between it and the inner surface of the nozzle 21 of the outer container 2, but a ring-shaped protrusion 31a is formed on the outer surface of this cylindrical mouth portion 31, and the outer peripheral surface of this protrusion 31a is in close contact with the inner surface of the nozzle 21 of the outer container 2 and rests on the horizontal step 21d. As a result, the inner bag container 3 housed in the outer container 2 is stably held inside the outer container 2 without rattling.

[0020] In addition, the ring-shaped protrusion 31a has notches 31b formed in multiple places, and the gap above the ring-shaped protrusion 31a communicates with the gap below the ring-shaped protrusion 31a, allowing air to circulate. Such an air path is indicated by H in Fig. 3. Note that the air path H can also be formed by forming a groove on the inner surface of the nozzle 21 of the outer container 2 without forming such notches 31b.

[0021] Furthermore, as shown in FIG. 1, an outwardly extending flange 31c is formed at the upper end of the cylindrical opening 31 of the inner bag container 3 for ease of carrying, positioning, and the like. 1, the upper end of the cylindrical mouth 31 of the inner bag container 3 and the upper end of the nozzle 21 of the outer container 2 are set at approximately the same height, but depending on the function and shape of the cap, the upper end of this cylindrical mouth 31 may protrude beyond the nozzle 21. In addition, in the example of FIG. 1, a gap is formed between the upper end of the cylindrical mouth 31 of the inner bag container 3 and the upper end of the nozzle 21 of the outer container 2, and air is introduced from this gap, but it is of course possible to form a hole in the nozzle 21 above the horizontal step 21d and introduce air from this hole. In addition, immediately after molding, the bag-shaped body portion 32 of the inner bag container 3 (i.e., the part formed by stretching during blow molding) is in close contact with the inner surface of the stretch-molded portion (shoulder portion 22, body portion 23 and bottom portion 24) of the outer container 2. As already described, this bag-shaped body 32 shrinks and deforms as the volume decreases due to the discharge of the contents, and moves away from the inner surface of the stretch-molded portion of the outer container 2 (the shoulder portion 22, the body portion 23 and the bottom portion 24).

[0022] In such a double-structure container, in the present invention, an amorphous region α is formed in a portion including the upper end of the bag-shaped body 32 of the inner bag container 3 described above. In this region α, a gap G is formed between the inner surface of the upper end portion of the shoulder 22 of the outer container 2, and when the bag-shaped body 32 contracts, a negative pressure is created between the bag-shaped body 32 and the body 23 of the outer container 2, and air is introduced from the air path H described above through the gap G. This region α will be described later.

[0023] The outer container 2 and the inner bag container 3 as described above are molded using a blow moldable thermoplastic resin, such as, but not limited to, polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene furanoate, amorphous polyarylate, polylactic acid, etc., olefin resins such as polyethylene, polypropylene, propylene-ethylene, etc., polycarbonate, acrylonitrile resin, polyamide resin, etc. The outer container 2 and the inner bag container 3 may be molded using different resins, but generally, it is preferable that they are molded using the same resin, since it is easy to set the blow molding conditions, and it is most preferable that they are molded using ethylene terephthalate polyester in particular.

[0024] The double-structure container 1 having such a structure is formed by blow molding using a stack preform. Fig. 2 shows a vertical cross section of such a stack preform (generally designated by 10), and Fig. 3 shows an AA cross section of the stack preform 10.

[0025] In Figures 2 and 3, this stack preform 10 consists of an outer preform 20 and an inner preform 30, both of which have a test tube shape as can be seen from Figure 2, with the inner preform 30 inserted into the outer preform 20.

[0026] In such a stack preform 10, the upper part is a non-stretch molded part (fixed part) that is not stretch molded, and the lower body part is a stretch molded part. In the outer preform 20, this stretch molded part corresponds to the nozzle 21 of the outer container 2, and in the inner preform 30, the cylindrical mouth part 31 corresponds to the stretch molded part. That is, since no deformation occurs due to blow molding, it is indicated by the same reference numerals as the nozzle 21 of the outer container 2 and the cylindrical mouth part 31 of the inner bag container 3. For example, the nozzle 21 of the outer preform 20 has a head part 21a with an expanded diameter at the upper end, a support ring 21b is formed on the lower part of the outer surface, and a horizontal step 21d is formed on the inner surface. Furthermore, a ring-shaped protrusion 31a of a size that fits into the inner surface of the nozzle 21 of the outer preform 20 is formed on the inner surface of the cylindrical mouth portion 31 of the inner preform 30, and this ring-shaped protrusion 31a has notches 31b formed in multiple places, so that the inner preform 30 is held stably within the outer preform 20 and an air path H is secured (see FIG. 3). As described above, the air passage H may be formed by forming a groove on the inner surface of the nozzle 21 of the outer container 2 without forming the notch 31b.

[0027] As shown in FIG. 2, both the outer preform 20 and the inner preform 30 have a shape in which the diameter is reduced from the non-stretched molded portion to the lower stretched molded portion (body portion), which allows the wall thickness to be reduced by blow molding.

[0028] After the outer preform 20 and the inner preform 30 are heated to a predetermined temperature at which they can be stretched (a temperature equal to or higher than the softening point and lower than the melting point of the resin forming the preforms), the stack preform 10 is set in a blow mold 100 having a cavity space corresponding to the outer container 2 (stretch molding part) as shown in Fig. 4, and a blow fluid (usually air) is supplied from an outlet 102 of a blow nozzle 101 into the inner preform 30, thereby performing blow molding. In this case, prior to setting the blow nozzle 101 and blowing the blow fluid, a stretch rod can be inserted into the inner preform 30 and stretched in one axial direction (longitudinal direction).

[0029] As a result, the inner preform 30 is thinned by stretching, and at the same time, the outer preform 20 is thinned by stretching due to the expanded inner preform 30, cooled by the blow molding die 100, and shaped into the shape of the outer container 2. At this time, the stretch-molded portion of the inner preform 30 is thinned into a bag shape and is held in a state of tightly adhering to the inner surface of the stretch-molded portion (shoulder portion 22, body portion 23, bottom portion 24) of the outer container 2 molded by the outer preform 20. That is, as shown in Fig. 5, the lower end 21c (the position where the diameter expansion by stretch molding starts) of the nozzle 21 of the outer container 2 is in close contact with the lower end portion of the cylindrical mouth portion 31 of the inner bag container 3 (the upper end portion of the bag-shaped body portion 32).

[0030] In this way, if the lower end portion of the cylindrical mouth 31 of the inner bag container 3 is in close contact with the inner surface of the outer container 2, it becomes difficult to introduce air between the bag-shaped body portion 32 of the inner bag container 3 and the body portion 23 of the outer container 2. For this reason, in the container of the present invention, a gap G serving as an air introduction path is forcibly formed between the upper end portion of the bag-shaped body portion 32 and the upper end portion of the body portion 23 of the outer container 2.

[0031] In the present invention, means for forming such gaps G include a method using heat shrinkage and a method using forced deformation by spraying a fluid.

[0032] As already mentioned, the thermal shrinkage method is a method according to the applicant's prior application, Patent Application No. 2020-79736, in which the upper end of the bag-shaped body portion 32 is heated from the inside to cause it to shrink. 6, after blow molding, a rod-shaped heating element 103 is inserted from the cylindrical mouth 31 (located inside the nozzle 21 of the outer container 2) of the molded inner bag container 3 to heat the upper end portion of the bag-shaped body 32. This heating causes the portion including the upper end (the position where the diameter expansion or thinning starts) of the bag-shaped body 32 to shrink, and an amorphous region α including a gap G is formed between the inner surface of the shoulder 22 of the outer container 2 and the upper end.

[0033] The heating element 103 used for the heating is heated, for example, by high-frequency heating, and the heating temperature by this heating element 103 may be such that the temperature of the upper end portion of the bag-shaped body 32 is equal to or higher than the glass transition point (Tg) of the resin forming the inner bag container 3 (inner preform 30), which is about 75°C for polyethylene terephthalate. In this case, heating to an excessively high temperature may cause thermal deformation of the shoulder portion 22 and nozzle 21 of the outer container 2, so heating is performed at a temperature and for a time that does not cause such thermal deformation.

[0034] The timing of the heating is not particularly limited, and may be after the blow molding is completed and the blow mold 100 is cooled. Generally, bag It is preferable to start heating when the shaped body 32 is not completely cooled and is still in a warm state of about 50° C. This is because the residual heat of the resin allows the heating time to be short. Furthermore, the above-mentioned heating can be performed not only by heating using the heating element 103 but also by blowing in heated air or by laser heating, for example.

[0035] In addition to the method utilizing thermal shrinkage as described above, it is also possible to forcibly deform the upper end of the bag-shaped body portion 32 by spraying a fluid FL (an inert gas such as nitrogen or air) during blow molding to form an amorphous region α having a void G.

[0036] That is, as shown in Figure 7, a fluid FL is supplied through an air passage H from the space at the upper end between the cylindrical mouth 31 of the inner bag container 3 and the nozzle 21 of the outer container 2, and the upper end of the bag-shaped body 32 is forcibly deformed by the fluid pressure, thereby forming an amorphous region α having a void G. In the method utilizing thermal shrinkage described above, the shoulder portion 22 of the outer container 2 is also likely to shrink and deform at the same time, making it difficult to adjust the heating temperature and heating time. However, this method is industrially advantageous because there is no risk of deformation of the outer container.

[0037] The shapeless region α formed as described above is formed in the upper end portion of the bag-shaped body portion 32 of the inner bag container 3, specifically, in the portion including the portion where the expansion in diameter begins due to thinning located at the lower end of the cylindrical mouth portion 31 (unstretched portion), and a planar cross section of this region α is shown in Figure 8.

[0038] That is, the bag-shaped body 32 of the inner bag container 3 formed by blow molding is extremely thin-walled and has a bag shape that does not have self-supporting properties. Therefore, in the shapeless region α formed by the forced deformation by the thermal shrinkage or the fluid spraying as described above, as shown in FIG. bag The bag-shaped body portion 32 has randomly arranged portions X in contact with the inner surface of the shoulder portion 22 of the outer container 2 and portions Y not in contact with the inner surface, with the non-contact portions Y forming gaps G. In other words, it is not possible to deform the upper end portion of the bag-shaped body portion 32 completely evenly, and the deformation of the upper end portion of the bag-shaped body portion 32 inevitably becomes non-uniform, so that when viewed in the circumferential direction in Figure 8, the contact portions X and non-contact portions Y are formed randomly. Of course, such contact portions X and non-contact portions Y do not always exist stably in fixed positions, and due to the nature of the bag, their shape is always changing.

[0039] In such an amorphous region α, it is preferable to control the heating by the heating element 103 and the fluid pressure by the fluid BL so that the perimeter of the contact portion X is 90% or less of the perimeter of the upper end of the bag-shaped body portion 32 (the inner perimeter of the upper end of the shoulder portion 22 of the outer container 3).

[0040] The double-structure container 1 of the present invention is used by filling the inner bag container 3 (bag-shaped body 32) with soy sauce or other contents and attaching a cap with a check valve. When the cap is opened and the body 23 of the outer container 2 is pressed (squeezed), the body 23 is significantly concave, which in turn presses the bag-shaped body 32 of the inner bag container 3, thereby discharging the contents contained in the bag-shaped body 32. When the contents are discharged, the bag-shaped body 32 contracts in response to the reduction in the volume of the contents, but the body 23 of the outer container 3 returns to its original shape due to its elasticity, creating a negative pressure between them. This negative pressure causes the body 23 of the outer container 3 and bag Air is introduced from the air passage H through the gap G between the bag-shaped body portion 32 and the inner surface of the shoulder portion 22 of the outer container 3. That is, as shown by the two-dot chain line in FIG.

[0041] When the above-mentioned discharge operation is repeated, the bag-shaped body 32 shrinks more significantly in response to the reduction in the volume of the contents. Therefore, if air is not introduced between the body 23 of the outer container 2 and the bag-shaped body 32 of the inner bag container 3 when squeezing the body 23, the body 23 of the outer container 2 must be pressed harder to cause a large deformation in order to discharge the contents in the contracted bag-shaped body 32, and ultimately, the contents cannot be discharged. In the present invention, even in the initial state, air is quickly introduced from the gap G formed in the shapeless region described above, and an air layer is formed between the bag-shaped body 32 of the inner bag container 3 and the body 23 of the outer container 2 by the introduction of air, so that the contents can be quickly discharged by continuing to press the body 23.

[0042] A major feature of the double-structure container 1 of the present invention is the shape before the inner bag container 3 is filled with the contents (i.e., the shape immediately after manufacture), and no previously known double-structure container has an amorphous region with a cross-section as shown in Figure 8 in the empty container state before the contents are filled. EXAMPLES

[0043] The invention is illustrated in the following examples. The manufacturing methods used in the following examples and the characteristics of the resulting double-structure containers (bottles) are as follows:

[0044] (Evaluation of dischargeability) The liquid was filled into a double-walled container (bottle) prepared by the method described below, and a hinged cap with a check valve was attached. This was repeated until all of the contents were discharged, and the dischargeability was evaluated. Those which had excellent peelability between the outer bag and the inner bag and excellent dischargeability of the liquid were rated as ○, those in which poor shaping of the inner bag was observed were rated as △, and those in which the outer surface of the inner bag stuck to the inner surface of the outer bag in the stretching start region of the preform and could not be discharged were rated as ×.

[0045] (Making double-walled containers (bottles)) A double-layered preform consisting of an outer preform made of a single layer of polyethylene terephthalate resin and an inner preform made of a single layer of polyethylene terephthalate resin containing an oxygen absorber was prepared, and after the body of the preform was heated to the glass transition temperature of the resin or higher, main blow molding was started at a predetermined blow pressure, and then support blow molding was performed on the intermediate portion between the inner preform and the outer preform. After forming the double-layered container, the blown air inside the intermediate portion between the inner bag and the outer bag was discharged to produce a double-layered container made of polyethylene terephthalate resin.

[0046] (Experimental Examples 1 to 4) The main blow was performed at 3 MPa for 2 seconds. After the start of the main blow, the support blow was started 1.5 seconds later. The support blow was performed at the support blow pressures of Experimental Examples 1 to 4, and double-walled containers made of polyethylene terephthalate resin were produced. The evaluation results are shown in Table 1. An enlarged longitudinal section of Experimental Example 4 is shown in Figure 9. The double-walled container obtained in Experimental Example 1 had poor shaping at the heel part at the lowest part of the body. In Table 1, the start time of the support blow is shown as the number of seconds (s) from the start of the main blow.

[0047] [Table 1]

[0048] (Experimental Examples 5 to 8) Except for changing the support blow time (s) and the support blow start time (s), a double-walled container made of polyethylene terephthalate resin was produced in the same manner as in Experimental Example 3. The evaluation results are shown in Table 2.

[0049] [Table 2]

[0050] (Experimental Examples 9-12) Except for changing the support blow time (s) and the support blow start time (s), a double layered container made of polyethylene terephthalate resin was produced in the same manner as in Experimental Example 3. The evaluation results are shown in Table 3. An enlarged longitudinal section of Experimental Example 11 is shown in FIG.

[0051] [Table 3]

[0052] From the above results, the results become better when the support blow pressure is greater than the blow pressure, but if the difference between the support blow pressure and the blow pressure is too great, poor shaping occurs at the heel part at the lowest part of the body. The support blow start time is in the range of 0.9 to 1.8 seconds, and the support blow time is in the range of 0.2 to 0.8 seconds, and the results are good. It was found that shaping in the stretch start region at the lower part of the mouth of the inner bag can be controlled by setting the specified conditions. In other words, before the inner bag is in close contact with the outer bag, the support blow air becomes a wall, and there is a region where it does not contact the inner surface of the outer bag. In other words, shaping starts from the bottom to the mouth, and the entire shaping is finally completed. Therefore, when shaping of the shoulder part is completed, the support blow pressure is greater than the blow pressure, so that the support blow air remains in the middle part between the inner bag and the outer bag, and an indefinite region is formed from the shoulder part to the lower part of the mouth part of the inner bag. Referring to the enlarged vertical cross section of Experimental Example 11 in Figure 10, there are a thick part and a thin part due to stretching from the lower end of the mouth part of the inner bag to the shoulder part. The thick portion has a rigidity that does not easily deform. On the other hand, the thin portion deforms as the content liquid is discharged and the volume is reduced. It can be seen that there is a gap between the thick portion and the outer bag. The shapeless region of the present invention is formed in the thick portion. [Explanation of symbols]

[0053] 1:Double structure container 2: Outer container 3: Inner bag container 10: Stack preform 20: Outer preform 21: Nozzle 22:Shoulder 23: Torso 24: Bottom 30: Inner preform 31: Cylindrical mouth 32: bag shaped trunk H: Air passage G: air gap α: Amorphous area X: Contact part Y: Non-contact part 100: Blow molding mold 101: Blow nozzle

Claims

1. A double-structure container comprising an outer container and an inner bag container housed in the outer container, the inner bag container housing contents, The outer container is formed from a nozzle and a stretch-molded portion including a shoulder portion, a body portion, and a bottom portion formed below the nozzle, The inner bag container has a cylindrical mouth portion having a fixed shape, and a bag-shaped body portion which is connected to the cylindrical mouth portion and which is thinned by stretching, and the outer surface of the bag-shaped body portion is peelably adhered to the inner surface of the body portion of the outer container, A double-structure container characterized in that an air passage through which air can be introduced is formed between the outer surface of the cylindrical mouth of the inner bag container and the inner surface of the nozzle of the outer container, and in the region from the lower end of the cylindrical mouth of the inner bag container to the upper end of the bag-shaped body portion where expansion begins, when viewed in the same horizontal cross section, an amorphous region is formed in which there is a contact portion where the outer surface of the bag-shaped body portion and the inner surface of the shoulder of the outer container are in contact, and a non-contact portion where the two are separated.

2. 2. The double-structure container according to claim 1, wherein contacting portions and non-contacting portions are irregularly present in said irregular region.

3. 3. The double-structure container according to claim 1, wherein the inner bag container is in an empty state before any contents are placed therein.

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