JP2023071046A - Double structure container - Google Patents

Abstract

To provide a double container which consists of an outer container and an inner bag container inserted and held in the outer container, and when its contents are discharged by squeezing the outer container, by forming a thin and uniform peeling layer, the outer surface of the inner bag container can be quickly peeled off the inner surface of the outer container to form an air layer between them.SOLUTION: In a double structure container 1 which consists of an outer container 3 and an inner bag container 5 inserted and held in the outer container. Squeezing the outer surface of the body of the outer container causes its contents to be discharged and the inner bag container to shrink, forming a space between the inner bag container and the outer container. On the outer surface of the inner bag container, in an unused state where the contents have not been discharged, except for the portion facing the bottom 17 of the outer container, a coating layer 40 of low-melting wax with a melting point in the range of 40°C to 70°C exists with application amounts of 150 mg/m2 or less, and the coating layer adheres to at least the inner surface of the squeezed body 15 of the outer container.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a double structure container, and more particularly to a double structure container comprising an outer container and an inner bag container inserted and held in the outer container.

2. Description of the Related Art Conventionally, a double structure container having a double structure consisting of an inner bag container and an outer container has been put into practical use, for example, as an airless bottle for containing seasoning liquid such as soy sauce. Such an airless bottle is used in combination with a cap equipped with a check valve and an air valve mechanism. The contents filled in the cap are discharged from a discharge channel formed in the cap. When the discharge of the contents is completed by stopping the pressing of the body wall of the bottle, the air does not flow backward from the spout into the inner bag container due to the action of the check valve of the spout of the cap. Air is introduced into the space between the inner bag container and the outer container through a channel (air valve) different from the pouring channel.
As a result, each time the contents are discharged, the inner bag container shrinks and reduces in volume by the volume of the discharged contents, but the outer container can be restored to its original shape. In the airless bottle in which the contents are discharged by such a method, the desired amount of the contents can be dispensed and air can be effectively prevented from entering the inner bag container filled with the contents. There is an advantage that oxidative deterioration of the contents can be effectively avoided and the freshness of the contents can be maintained for a long period of time.

By the way, in the double structure as described above, the squeezing (pressing) of the body of the bottle (outer container) is stopped at the end of discharging the contents from the inner bag container, and the shape of the body of the outer container is restored to the normal state. When restored, the outer surface of the inner bag container must be quickly peeled off from the inner surface of the outer container body. If the outer surface of the inner bag container is in close contact with the inner surface of the body of the outer container, air will not be introduced between the two, resulting in poor restoration of the outer container and air sucking (backflow) from the spout into the inner bag. This is because the function as an airless bottle is impaired.
In particular, since the inner bag container is in close contact with the inner surface of the trunk of the outer container when not in use, the problem of peeling of the inner bag tends to occur, which is an extremely serious problem for airless bottles.
In addition, when the amount of liquid remaining in the contents decreases during use, the inner bag tends to come off from the bottom portion of the reduced-volume outer container. If the bottom is not fixed, the volume of the inner bag cannot be reduced well, and when the contents are discharged next time, the body must be greatly recessed by the amount that the contents are discharged, which is also an airless bottle. It is one of the factors that impairs the function as

As a double-structured container that solves the above problems, Patent Document 1 proposes a double-structured container in which a heat-resistant silicone oil release layer is provided between the inner bag container and the outer container. Further, Patent Document 2 proposes a double structure container in which liquid paraffin is used as a release layer provided between the inner bag container and the outer container.

However, in these double-structured containers, since the release layer is formed of a liquid, the release layer tends to run off, and the thin film layer is thick enough to exhibit the release effect even during actual use (initial squeezing). Furthermore, there are problems such as the fact that the release layer is formed even on the bottom portion where the formation of the release layer is not necessary, and there is still room for improvement.

Further, Patent Documents 3 and 4 propose a double structure container in which a wax layer is provided between an inner bag container and an outer container.

However, Patent Literature 3 does not aim to improve the detachability between the inner bag container and the outer container by means of the wax layer, but aims to prevent sounding (ringing) during squeezing. For this reason, the wax layer is provided considerably thickly on the bottom and its vicinity, and by forming a thin and uniform peeling layer, the outer surface of the inner bag container can be quickly peeled off from the inner surface of the outer container, and the gap between the two can be easily separated. It does not form an air layer.

Further, Patent Document 4 discloses a technique of forming an air layer between an inner bag container and an outer container from an initial stage to secure a heat insulating effect. For this reason, the wax layer formed between the inner bag container and the outer container is considerably thick as in Patent Document 3, and the formation of a thin and uniform peel layer also allows the outer surface of the inner bag container to be separated from the outer container. It does not peel off quickly from the inner surface and form an air layer between them.
Furthermore, in order to satisfy the purpose of both Patent Documents 3 and 4, it is necessary to provide a considerably thick layer of wax, and improvements are also required from the viewpoint of the Food Sanitation Act.

JP 2010-082916 A JP 2017-186059 A JP 2019-112088 A Japanese Patent Application Laid-Open No. 2020-152409

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an outer container and an inner bag container inserted and held in the outer container so that when the outer container is squeezed to discharge the contents, a thin and uniform release layer is formed. The object of the present invention is to provide a double-structured container capable of quickly peeling the outer surface of the inner bag container from the inner surface of the outer container and forming an air layer therebetween, and a method of manufacturing the double-structured container.

According to the present invention, it comprises an outer container and an inner bag container inserted and held in the outer container. In a double structure container in which the contents are discharged and the inner bag container shrinks as the contents are discharged, forming a gap between the inner bag container and the outer container,
Between the inner bag container and the outer container, the melting point is in the range of 40° C. to 70° C. in an unused state in which the contents are not discharged, except for at least the portion facing the bottom of the outer container. The low-melting wax coating layer is present in a coating amount of 150 mg/m ² or less, and the low-melting wax coating layer is in close contact with at least the inner surface of the squeezed barrel of the outer container. There is provided a double structure container characterized by:

According to the present invention, the test tube-shaped first preform for molding the outer container and the second test tube-shaped preform for molding the inner bag container are provided, and the second preform is the second preform. In a stack preform for manufacturing a double structure container inserted and fixed in one preform,
A stack characterized in that a low melting point wax coating layer having a melting point of 40°C to 70°C is formed on the outer surface of the stretch-molded portion of the second preform at least in a region excluding the bottom portion of the curvature shape. A preform is provided.

According to the present invention, a test tube-shaped first preform for molding the outer container and a test tube-shaped second preform for molding the inner bag container are further prepared,
Forming a wax layer by roll-coating a low-melting wax having a melting point of 40° C. to 70° C. on the outer surface of the second preform, excluding the bottom portion of the curved shape, on the stretch-molded portion,
forming a stack preform by inserting the second preform into the first preform with the low-melting wax coating layer formed thereon;
blow molding by supplying a blow fluid into a second preform within the stack preform;
There is provided a method for manufacturing the double structure container characterized by:

In the present invention described above, it is preferable that the low melting point wax is a low crystalline paraffin wax containing less than 50% by mass of n-paraffin.

In the double structure container of the present invention, a low-melting wax solid at room temperature with a melting point in the range of 40° C. to 70° C. is used as a release agent for separating the outer surface of the inner bag container from the inner surface of the outer container. is an important feature. That is, such a low-melting-point wax is not only solid at the temperature (normal temperature) at which the double-structured container is stored and used, but also rapidly dissolves when heated to a temperature of about 50 to 60°C. It melts and becomes a fluid state. Therefore, this low-melting wax can be applied by roll coating to the outer surface of the inner bag preform (second preform) for forming the inner bag container, and for example, the wax can be applied selectively to the region excluding the bottom. A coating layer can be formed on the Also, the coating amount can be easily controlled by the contact time between the coating roll holding the wax and the outer surface of the second preform. For example, roll coating is not suitable for liquid release agents, and when applying using methods such as spraying and dipping, masking is required in order to accurately set the application location. In addition, the loss due to scattering during spraying or dipping is large, so the application work is troublesome and costly, but by applying the low melting point wax using a roller, all such problems can be cleared.

Thus, in the present invention, the formation of a thin and uniform low-melting-point wax coating release layer allows the outer surface of the inner bag container to be quickly separated from the inner surface of the outer container when the outer container is squeezed to discharge the contents. can do.
In addition, in the present invention, by using a low-crystalline paraffin wax having an n-paraffin content of less than 50% by mass as the low-melting wax, it is possible to suppress white granulation when solidified, making it easy to use. , the applicability can be improved and deterioration of the appearance can be avoided. In particular, it is most preferable to use such a low-crystalline paraffin wax in order to achieve the target amount of wax according to the Food Sanitation Law.

FIG. 2 is a longitudinal sectional view showing a double structure container according to the present invention; 1 is a schematic cross-sectional side view showing a first preform (outer container molding preform) and a second preform (inner bag container molding preform) used for manufacturing the double structure container of FIG. a) shows the first preform and (b) shows the second preform. FIG. 4 is a schematic cross-sectional side view showing a stacked preform with a second preform contained and held within the first preform;

Referring to FIG. 1 showing a double structure container (hereinafter sometimes simply referred to as an airless container) of the present invention, the airless container generally indicated by 1 comprises a bottle-shaped outer container 3 and contents such as soy sauce. and an inner bag container 5 in which is housed.

The outer container 3 includes a nozzle portion 11 , a shoulder portion 13 connected to the nozzle portion 11 , and a body portion 15 . The trunk portion 15 extends to the ground portion 16 , and the area surrounded by the ground portion 16 is closed by a dome-shaped recessed bottom portion 17 .

The inner bag container 5 is composed of a tubular mouth portion 21 and a thin bag-shaped body portion 23 connected to the tubular mouth portion 21 . The tubular mouth portion 21 is thick and has a fixed shape (i.e., this portion is not stretched and has such rigidity that it is not easily deformed), and the bag-like body is The 23 is filled with the content and shrinks and deforms due to the volume reduction accompanying the discharge of the content.

The nozzle portion 11 of the outer container 3 is a rigid portion (unstretched portion) that is not stretch-molded, and the shoulder portion 13, body portion 15, and bottom portion 17 connected to the nozzle portion 11 are stretch-molded portions (stretched portions). It's becoming The body portion 15 of the outer container 3 is elastically deformable. When the body portion 15 of the outer container is pressed, the body portion 23 of the inner bag is dented. Although the portion 15 returns to its original shape, the inner bag trunk portion 23 does not restore, so that the inside of the inner bag container 5, which is filled with the content, does not enter with air which causes oxidative deterioration. Generally, the central portion of the outer container body 15 is a squeeze area so that the denting due to pressing and the elastic recovery due to stopping of pressing can be performed smoothly. This squeeze area generally has a slightly recessed shape so as to be advantageous for restoration.

The nozzle portion 11 of the outer container 3 has a cylindrical shape with an open upper end, and is fitted with a cap (not shown in FIG. 1) having a check valve function to be described later. be. A head portion 11a having an enlarged diameter is formed at the upper end of the nozzle portion 11, thereby stably holding a container lid with a check valve attached thereto (hereinafter simply referred to as a cap). It's like A support ring 11b is formed in the lower portion of the nozzle portion 11 so that the airless container 1 (or preform) can be easily transported using a jig.
It should be noted that the attachment of the cap may be carried out by providing screws on the outer surface of the nozzle portion 11 instead of by plugging.

The nozzle portion 11 described above is a non-stretched portion that is not stretch-molded, and the lower portion thereof is a stretched portion that is stretched by blow molding. A trunk portion 15 is connected to the shoulder portion 13 , and the trunk portion 15 is closed by a bottom portion 17 .
Further, the bottom portion 17 of the outer container and the inner bag container 5 are fixed by crimping at the time of blow molding to prevent the inner bag container 5 from hanging in the air while the container is in use. In addition, since the bottom portion 17 has a dome shape, it contributes to improving the seating comfort of the bottle.

As can be seen from FIG. 1, the inner bag container 5 is accommodated in the outer container 3, and the cylindrical mouth portion 21 (that is, the non-stretching portion) of the inner bag container 5 is aligned with the inner surface of the nozzle portion 11 of the outer container 3. A fixing ring 25 is formed on the outer surface of the cylindrical mouth portion 21, and the outer peripheral surface of the fixing ring 25 extends inside the nozzle portion 11 so that a gap is formed between is in close contact with the inner surface of the nozzle portion 11 of the outer container 3, whereby the inner bag container 5 accommodated in the outer container 3 is stably held in the outer container 3 without rattling.

By the way, as shown in FIG. 1, the fixing ring 25 has a notch 25a formed in a part thereof so as to form a flow path through which air passes. That is, the formation of the cutout 25a forms an axially penetrating air passage X, which is connected to the outside of the airless container 1 via the air valve of the cap. That is, air is supplied to the space Z between the bag-shaped body portion 23 of the inner bag container 5 and the body portion 15 of the outer container 3 through the air path X.

A container lid with a check valve (not shown in FIG. 1) is attached to the airless container 1 having the above-described structure, and the operation of discharging the contents contained in the bag-shaped body 23 is repeatedly and smoothly performed. can be done.

For example, immediately after molding, the bag-shaped body portion 23 of the inner bag container 5 is held in close contact with the inner surface of the body portion 15 and the bottom portion 17 from the shoulder portion 13 of the outer container 3, and in this state, the inner bag container is held. 5 is filled with contents, and a container lid with a non-return valve (not shown) is attached before being sold. In the airless container 1 filled with the contents in this manner, the upper lid of the container lid is opened to enable the contents to be discharged, and the body 15 (squeeze area) of the outer container 3 is pressed. , the contents will be discharged and taken out.

That is, when the body portion 15 (squeeze area) of the outer container 3 is pressed to be recessed, the bag-like body portion 23 of the inner bag container 5, which is in close contact with the inner surface of the body portion 15, is also recessed and reduced in volume. (The form shown by the dashed line of FIG. 1). As a result, the contents contained in the bag-shaped body portion 23 are discharged. When the pressing of the body portion 15 is stopped, the body portion 15 returns to its original shape due to its elasticity, and the dent disappears. On the other hand, the bag-shaped body 23 is maintained in the contracted state due to the volume reduction, and air that causes oxidative deterioration does not enter the interior of the inner bag container 5 . Therefore, the space Z between the bag-like trunk portion 23 and the trunk portion 15 of the outer container 3 becomes negative pressure due to the volume reduction of the contents.

In this way, the space Z becomes negative pressure, but as described above, since the air passage X leading to the outside is formed, air flows into this space Z, and the bag-shaped body 23 and the outer container 3 are separated from each other. An air layer is formed between it and the trunk portion 15 . Therefore, when the trunk portion 15 is pressed to be recessed next time, the bag-shaped trunk portion 23 is pressed through such an air layer.

A container lid (not shown) equipped with an air valve is arranged on the air path X, allowing the inflow of air from the outside through the air path X, but preventing the discharge of air to the outside. It has a structure that prevents it. That is, when the trunk portion 15 of the outer container 3 is pressed to be dented, thereby reducing the volume of the bag-like trunk portion 23, there is always an air layer between them. For this reason, even when the contents are discharged and the bag-like body part 23 is greatly shrunk with the discharge amount, the body part 15 of the outer container 3 can be pushed to the same extent as when the contents are full. By pressing, it is possible to contract the bag-shaped body 23 and quickly discharge the contents. For example, when the body portion 15 of the outer container 3 is depressed by pressing, if air is discharged from the space Z, the body portion 15 must be deformed more in order to contract the bag-like body portion 23 . Otherwise, the pressure required for squeezing is increased. Therefore, the more the contents are discharged and the more the volume is reduced, the more difficult it becomes to discharge the contents. The present invention effectively avoids such inconvenience.

In the present invention, the outer container 3 and the inner bag container 5 described above are made of a blow-moldable thermoplastic resin, and examples of such thermoplastic resins include the following.
Olefin resins such as low-density polyethylene, high-density polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene or α-olefins such as ethylene, propylene, 1-butene and 4-methyl-1-pentene Random or block copolymers between each other, cyclic olefin copolymers, etc.;
Ethylene-vinyl copolymers, such as ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, ethylene-vinyl chloride copolymers;
Styrenic resins such as polystyrene, acrylonitrile/styrene copolymers, ABS, α-methylstyrene/styrene copolymers;
Vinyl resins such as polyvinyl chloride, polyvinylidene chloride, vinyl chloride/vinylidene chloride copolymers, polymethyl acrylate, polymethyl methacrylate, and the like;
polyamide resins, such as nylon 6, nylon 6-6, nylon 6-10, nylon 11, nylon 12;
Polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, and copolymer polyesters thereof;
polycarbonate resin;
polyphenylene oxide resin;
biodegradable resins such as polylactic acid;
Of course, blends of these thermoplastic resins can also be used as long as moldability is not compromised.

In addition, since blow molding can be performed under the same molding conditions, the outer container 3 and the inner bag container 5 are preferably made of the same kind of resin. from the viewpoint of transparency. Furthermore, the most suitable resins are polyester resins, polyester resin, Especially PET.

By the way, in order to reliably exhibit the above-described characteristics of the airless container, the body portion 15 of the outer container 3 is dented by squeezing. The outer surface of the bag-like body 23 must be quickly peeled off from the inner surface of the body 15 of the outer container 3 . That is, immediately after molding, or when the contents are filled in the inner bag container 5 (the bag-like body portion 23) and not yet discharged, the outer surface of the bag-like body portion 23 of the inner bag container 5 is in contact with the outer container 3. is held in close contact with the inner surface of the body portion 15 of the. Therefore, when the body portion 15 returns to its original shape by stopping squeezing, the two must be quickly peeled off to form a gap therebetween. If the gap is not formed, air will not flow between the outer surface of the bag-like body 23 and the inner surface of the body 15 of the outer container 3, and as described above, the space Z will not be formed, and the contents will be stored. This is because the body portion 15 must be greatly deformed in order to discharge the contents, and therefore, the more the contents are discharged and the more the volume is reduced, the more difficult it becomes to discharge the contents.

In the present invention, the outer surface of the bag-like body 23 of the inner bag container 5 is wax-coated in order to ensure the detachability between the outer surface of the bag-like body 23 and the inner surface of the body 15 of the outer container 3 . A layer 40 is provided. As can be seen from FIG. 1, the wax coating layer 40 is not formed on the portion facing the bottom portion 17 of the outer container 3 (the area between the ground portions 16).
That is, the portion facing the bottom portion 17 is not required to be peelable, and rather it is desirable that the bottom portion 17 of the outer container 3 and the bottom portion of the inner bag container 5 are fixed. The provision of 40 leads not only to an increase in the amount of wax used, but also to poor ejection of the content liquid, an increase in the amount of residual liquid, and an increase in the squeeze pressure. It is also undesirable from the viewpoint of the Food Sanitation Act.

In addition, in the present invention, since the wax coating layer 40 is not provided on the portion facing the bottom portion 17, it is possible to secure the peelability with as little amount as possible. For example, the coating amount can be set to be 150 mg/m ² or less, preferably 125 mg/m ² or less, and more preferably 100 mg/m ² or less per sheet in terms of surface area, and constant peelability can be obtained. 50 mg/m ² or more is sufficient to ensure the As will be described later, this wax coating layer 40 is a layer provided by roll coating, so that it is not provided above the fixing ring 25 in terms of molding. It is not necessary to provide it on the outer surface of the mouth portion 21 (the portion that does not expand or contract), and it may be provided on the bag-shaped body portion 23 (the portion that expands or contracts) except for the portion facing the bottom portion 17 .

The double structure container (airless container) of Patent Document 3 is also provided with a wax layer. The wax layer is provided to suppress this, and it is necessary to provide the wax layer thicker than in the present invention. That is, in the present invention, since the thickness of the wax coating layer 40 is thin, the sound generation suppressing effect is hardly produced. For example, in Patent Document 3, the sound is suppressed to 60 dB or less, but with the thin wax layer 40 according to the present invention, the peelability at the time of initial squeezing is sufficiently exhibited, but the sound generated at this time is is experimentally confirmed to be about 70 dB at most. From this, it can be seen that the thickness of the wax coating layer 40 provided in the present invention is thinner than in Patent Document 3.

The airless container of Patent Document 4 is also provided with a wax layer, but this wax layer is thicker than that of Patent Document 3. That is, in Patent Document 4, a space is formed between the outer surface of the bag-shaped trunk portion 23 of the inner bag container 5 and the inner surface of the trunk portion 15 of the outer container 3 in a state filled with contents. This space functions as a heat-insulating layer, effectively suppressing temperature changes in the contents and maintaining the freshness of the contents.

However, when the contents are filled, the bag-shaped body 23 expands. Therefore, in order to form the above-mentioned space, the bag-shaped body 23 is pressed against the inner surface of the body 15 of the outer container 3. Immediately after, the outer surface of the bag-shaped body 23 of the inner bag container 5 and the inner surface of the body 15 of the outer container 3 must be separated. This is because, if both are in contact with each other, it is unthinkable that a space will be formed between them when the content is filled. In Patent Document 4, a space is formed by utilizing heat shrinkage due to heating during blow molding. It is speculated that a large amount of wax exists in That is, a large amount of wax exists between the two, and this large amount of wax is heated to the blow molding temperature (higher than the glass transition temperature of the resin) and is in a fluid state. It is thought that the wax flows down in such a state that a space is formed between them. In fact, in FIG. 1 of Patent Document 4, a space is formed between the outer surface of the bag-shaped body and the inner surface of the body of the outer container. Also, a layer of wax is shown as the release portion 30 .
Thus, the layer of wax provided in US Pat. No. 4,500,004 is significantly thicker than in the present invention.

Furthermore, in the present invention, it is also important to use a low-melting wax having a melting point in the range of 40.degree. C. to 70.degree. That is, such a low-melting wax exists in a solid state not only when the container is stored in a refrigerator, but also when sold, when the contents are discharged, and when it is transported. When heated to , it melts easily and exhibits fluidity. That is, the low-melting-point wax exhibiting such properties is extremely suitable for roll coating, and can be applied so that the wax is present only at the necessary locations of the bag-like body 23 . A coating layer can be easily formed on the roll surface in a heated and melted state, and can be retained on the roll surface by cooling and solidifying after coating. Furthermore, since the wax coating layer 40 present at a predetermined location between the body portion 23 of the inner bag container 5 and the body portion 15 of the outer container 3 is solid, it is effectively prevented from flowing down during molding. , a constant coating amount is stably ensured. Ordinary liquid lubricants (e.g., liquid paraffin) flow down toward the bottom due to gravity in an upright position, and a certain amount of application is required to exhibit releasability during actual use (during initial squeezing). becomes difficult to maintain. Furthermore, the low-melting-point wax as described above has the advantage that it emits almost no odor when melted.
Also, the wax must be non-aqueous, and emulsion waxes, for example, cannot be used in the present invention. This is because the amount of water is likely to change depending on the environment, resulting in a change in the components and an unstable coating amount.

Examples of the above-mentioned low-melting wax include rice wax, carnauba wax, paraffin wax, microcrystalline wax, polyethylene wax, candelilla wax, rice wax, Japan wax, beeswax, etc., and the melting point is within the range described above. To some extent, mixed waxes of these can also be used.

In the present invention, among the low-melting-point waxes described above, low-crystalline paraffin wax is most preferably used. Low crystalline paraffin wax is mainly composed of isoparaffin or cycloparaffin, unlike crystalline paraffin mainly composed of n-paraffin. For example, the content of n-paraffin is less than 50% by mass.

Low-crystalline paraffin waxes such as those described above are less likely to be white powdered (granulated) when solidified, so they are easy to handle, roll-coated, and are advantageous in forming a coating layer with a uniform thickness. . In particular, the present invention sets the thickness of the wax coating layer 40 to be extremely thin, so such a low-crystalline paraffin wax is most suitable. For example, crystalline paraffin wax, which is mainly composed of n-paraffin, tends to turn into a white powder (granules) when solidified, so its coatability with a roll is inferior to that of low-crystalline paraffin wax, and the thickness of the coating layer is also inadequate. easily uniform. Furthermore, when the outer container 3 and the inner bag container 5 are formed of transparent PET, the visibility of the inside is greatly impaired by whitening with crystalline paraffin wax, but with low crystalline paraffin wax, visibility is improved. It also has the advantage of less degradation.

Manufacture of double structure container 1;
The double structure container 1 of the present invention provided with the above-described wax coating layer 40 includes a first preform (outer container molding preform) obtained by injection molding using a resin for the outer container. , a second preform obtained by injection molding using a resin for the inner bag container (a preform for molding the inner bag container), and inserting the second preform into the first preform. to form a multi-layered stack preform, and biaxially stretch blow molding the stack preform (stack method).
That is, according to this method, the low-melting-point wax layer can be uniformly formed on a predetermined portion of the second preform by roll coating.

2 and 3 for explaining the above stacking method, a stack preform for forming a dual structure container of FIG. 1 is shown generally at 70 in FIG. 2A and 2B, both of which have the shape of a test tube.
That is, the first preform 50 is a preform for molding the outer container, the second preform 60 is a preform for molding the inner bag container, and the second preform 60 is placed inside the first preform 50. By inserting and fitting and holding, the stack preform 70 to be subjected to the blow drawing process is assembled.

As can be understood from FIG. 2, both the first preform 50 and the second preform 60 are portions corresponding to the nozzle portion 11 of the outer container 3 and the tubular mouth portion 21 of the inner bag container 5 (non It has a stretch-molded part). That is, none of these portions are stretch-molded (see FIG. 3), and the nozzle portion 11 of the first preform 50 is provided with the support ring 11b.
When the air is introduced through the wall portion of the nozzle portion 11, the nozzle portion 11 is provided with an air inlet, a screw, and the like.

In addition, the portion below the nozzle portion 11 of the first preform 50 is a stretch-molded portion (see FIG. 3). 55. That is, the stretch-molded portion (see FIG. 3) is blow-stretched to shape the shoulder portion 13, the body portion 15, the ground portion 16 and the bottom portion 17 of the outer container 3. As shown in FIG.
In the first preform 50, the body portion 53 has a straight body shape, but its upper end has a shape that expands outward in diameter, and the second preform is placed inside it. It has a shape in which the reform 60 can be easily inserted.

The upper end of the second preform 60 is a cylindrical mouth portion 21 that is a non-stretching portion, and the cylindrical mouth portion 21 is provided with a fixing ring 25 . The stretch-formed portion connected to the cylindrical mouth portion 21 is composed of a trunk portion 63 and a bottom portion 65 having a curved surface closing the lower end of the trunk portion 63 . In order to facilitate the insertion of the second preform 60 into the first preform 50, the body portion 63 includes a straight body portion 63a and an enlarged tapered portion 63b connected to the upper end of the straight body portion 63a. consists of

The stretched portion of the second preform 60 having the above configuration is provided with the low-melting-point wax coating layer 80 described above. This wax coating layer 80 is provided not at least on the curved bottom portion 65 but on the trunk portion 63 . In this case, it is common to selectively provide the coating layer 80 on the straight body portion 63a. By forming the coating layer 80, the releasability of the bag-like trunk portion 23 can be enhanced, and air can be quickly introduced into the space Z through the air passage X. Accordingly, the coating layer 80 may extend from the straight body portion 63a to the tapered portion 63b. Furthermore, the coating layer 80 may extend to a portion directly below the cylindrical mouth portion 21, which is a non-stretch molded portion.

By the way, in the present invention, the formation of the coating layer 80 is performed by roll coating. Roll coating is usually performed for flat objects such as films, and it can be said that rolls are rarely used for coating three-dimensional objects. In fact, Patent Documents 3 and 4 do not refer to roll coating, and coating is performed by spray atomization or the like.

However, in the present invention, by utilizing the characteristics of the low-melting wax and the form of the stretch-molded portion of the second preform 60, and using rolls, a low-melting wax is selectively applied to the target location (body portion 63). A wax coating layer 80 can be formed, and the thickness of this coating layer 80 can be made thin and uniform.

Specifically, a roll coated with a low-melting wax that has been heated to a temperature higher than the melting point of the wax by 0 to 20° C., preferably 0 to 15° C., most preferably 0 to 10° C., is used. While rotating this roll, the surface of the roll is brought into contact with the surface of the body portion 63 of the second preform 60 which is also rotating, thereby transferring the molten low-melting wax onto the surface of the body portion 63. can be coated. Then, by pulling the coated second preform 60 away from the roll surface, the coated wax quickly solidifies, so that the coating layer 80 with a constant thickness is formed without running down from the surface of the body 63. It will happen. The thickness amount (coating amount) of the coating layer 80 can be adjusted by adjusting the contact pressure and contact time (rotation speed) of the second preform 60 (body portion 63) on the roll surface. The coating amount of the wax coating layer 40 when molded into a container can be set within the range described above (150 mg/m ² or less).

There is no problem when the coating layer 80 is formed only on the straight body portion 63a. Rolls of reduced shape can be used.

For example, when coating is performed by spraying a low-melting wax in a molten state without using a roll, the thickness of the coating layer naturally becomes uneven, and the thickness of the coating layer becomes considerably thick. It is also difficult to adjust the thickness. Furthermore, masking or the like is required to prevent the bottom portion 65 from being coated, which makes the coating work considerably troublesome.

The second preform 60 having the wax coating layer 80 formed on predetermined portions as described above is inserted into the first preform 50 as shown in FIG. A reform 70 is assembled.
Such a stack preform 70 is placed in a blow mold, the nozzle portion 11 is fixed with a predetermined jig, and external heating or the like is applied to a temperature at which the stack preform 70 can be stretch-molded (preforms 50, 60 above the glass transition temperature and below the melting point of the resin forming the ), a stretch rod is inserted into this stack preform 70 (second preform 60) to stretch in the uniaxial direction, and the first By fixing the bottoms of the preform and the second preform to each other, supplying blow fluid such as air, and expanding the second preform 60 in the circumferential direction, the first preform 50 is also expanded. It is then expanded, pressed against a predetermined cooling mold, and as a result, a double structure container 1 having the configuration shown in FIG. 1 is obtained. That is, in FIG. 3, the stretch-molded portion of the stack preform 70 is blow-stretched and shaped into the configuration shown in FIG. At this time, support blow molding may be performed between the first preform 50 and the second preform 60 . In the case of support blowing, when the shaping of the shoulder is completed, the support blow air remains in the middle part of the inner bag and the outer container because the support blow pressure is higher than the blow pressure, and as a result, the inner bag An indeterminate area is formed from the shoulder to the bottom of the mouth. By doing so, before the inner bag comes into close contact with the outer container, there is a region where the support blow air acts as a wall and does not partially contact the inner surface of the outer container. That is, the shaping is started from the bottom part to the mouth part, and finally the overall shaping is completed.

Therefore, in the double structure container 1 formed in this manner, the outer surface of the bag-shaped body portion 23 of the inner bag container 5 is in close contact with the inner surface of the body portion 15 of the outer container 3 . In this state, when the bag-shaped body 23 of the bag-shaped container 5 is filled with the contents, the outer surface of the bag-shaped body 23 is further pressed against the inner surface of the body 15 of the outer container 3 . . However, in the present invention, since the solidified low-melting wax layer 40 exists between the bag-like body 23 and the outer container body 15, even when the body is strongly pressed by the filling of the contents, the body can be held in place. Since the releasability of the inner surface of the portion 15 is enhanced, the body portion 15 is squeezed and recessed. , and is easily peeled off from the trunk portion 15 to form a space Z between them.

The low-melting-point wax described above becomes a molten state when heated to the blow temperature in blow molding. is extremely suppressed. Moreover, the bottom portion 17 of the outer container 3, which is formed during molding, has a concave dome shape. Therefore, even if the wax coating layer 40 melts down, it does not reach the portion facing the dome-shaped bottom portion 17 (it is blocked by the grounding portion 16), and the wax coating layer is only applied to the region facing the trunk portion 15. 40 will exist.

In the double structure container 1 of the present invention manufactured as described above, after the contents (for example, seasoning liquid such as soy sauce) are accommodated in the bag-shaped body portion 23 of the inner bag container 5, the outer container 3 is The nozzle part 11 is put into use by mounting a cap with a check valve known per se.

The invention is illustrated in the following experimental examples.

Wax was applied to the body portion (stretch-molded portion excluding the bottom portion) of the second preform molded by injection molding of polyethylene terephthalate (PET). The following waxes were prepared as waxes for coating.
plant-derived emulsion wax;
Melting point: 85°C
Petroleum-derived emulsion wax (high melting point type);
Melting point: 110°C
Emulsion wax derived from petroleum (low melting point type);
Melting point: no data available liquid paraffin;
Melting point: no data low crystalline paraffin wax (low melting point wax A);
n-paraffin content: less than 50% by mass Melting point: 50°C
high melting point wax (high melting point wax B);
Melting point: 80°C

<Experimental example 1>
Plant-derived emulsion wax was roll-coated on the outer surface of the body of the second preform. It was not able to be applied, and lacked applicability. In addition, since the wax itself has a peculiar odor (has a strange odor), it was determined that it is not suitable for food containers.

<Experimental example 2>
A petroleum-derived emulsion-type high-melting-point wax and a low-melting-point wax were roll-coated on the outer surface of the body of the second preform. The wettability was also poor, and the coated surface was repelled and uneven, lacking in coatability. Moreover, the high-melting-point wax had a strong peculiar odor (bad smell) like the plant-derived wax in Experimental Example 1, and was judged to be unsuitable for food containers. Furthermore, the low-melting wax had an offensive odor, though not as bad as the high-melting wax.

<Experimental example 3>
The outer surface of the barrel of the second preform was roll-coated with liquid paraffin, stacked inside the first preform, and then heated to blow-mold the barrel to produce a double structure container.
It is easy to apply and has good functionality, but the liquid paraffin drips downward in an upright position, and the oily component spreads to unwanted areas, making it impossible to form a uniform coating layer and lacking applicability.

<Experimental example 4>
A double structure container was produced by blow molding in the same manner as in Experimental Example 3 except that the low crystalline paraffin wax A was heated to 60° C. and roll-coated on the outer surface of the body of the second preform. Table 1 shows the number of rotations of the coating roller and the coating amount during roll coating.
The odor peculiar to wax was suppressed, and I was able to apply it evenly to the part I wanted to apply, but the amount of application was large and it became thick.

<Experimental example 5>
A double structure container was produced in the same manner as in Experimental Example 4, except that the low crystalline paraffin wax A was heated to 50° C. during roll coating. Table 1 shows the number of rotations of the coating roller and the coating amount during roll coating.
In this case as well, the odor peculiar to wax was suppressed, and it was possible to apply evenly to the part to be applied, and the amount of application was suppressed to a small amount.
Considering this together with the results of Experimental Example 4, the coating method is not spraying or dipping, but roll coating is used. It can be seen that it can be adjusted and the amount of wax used can be reduced.

<Experimental example 6>
A double structure container was produced in the same manner as in Experimental Example 4, except that the high-melting wax B was heated to 80° C. and roll-coated on the outer surface of the trunk portion of the second preform. Table 1 shows the number of rotations of the coating roller and the coating amount during roll coating.
These high-melting-point waxes B are easy to handle because they solidify immediately after being applied, but tend to be applied in a slightly excessive amount and tend to be thickly applied. In addition, after application, squeezing caused the inner and outer layers to become powdery and easily peeled off, and the performance could not be maintained until the contents were used up. Also, the powdered wax looked like dust or foreign matter adhering to the container.

Table 2 below summarizes the sensory evaluation results of Experimental Examples 1 to 6 with respect to property stability, wettability, odor, applicability, application amount, and container appearance. Evaluation criteria are as follows.
property stability;
◯: Constant properties are stably retained on the roll, and constant applicability is always exhibited.
x: Since the solvent component evaporates, the properties are unstable, causing variations in coating properties.
wettability;
◯: Rapidly wets and spreads on the preform surface when applied with a roller.
x: Hardly wets and spreads on the surface of the preform when applied with a roller.
smell;
◯: No offensive odor △: Offensive odor peculiar to wax is sensed, although not as bad as the offensive odor.
x: There is a bad smell and it is unsuitable as a product.
coatability;
O: Visually, the coating is uniformly applied.
Δ: It is difficult to handle because it drips or immediately becomes powdery due to crystallization.
x: Coating unevenness is evident even when visually observed.
Application amount;
○: 150 mg/m ² or less.
Δ: Exceeds 150 mg/m ² .
container appearance;
◯: Foreign matter is not visually observed.
x: Foreign matter is clearly visible.

Further, in Experimental Examples 4 to 6, coating was performed with the number of revolutions of the coating roller being 1 and 2, but the sensory evaluation results were the same. It does not show the evaluation results for each.

1: Double structure container 3: Outer container 5: Inner bag container 11: Nozzle part of outer container 13: Shoulder part of outer container 15: Body part of outer container 16: Ground part 17: Bottom part 21: Cylindrical mouth part 23 : Bag-shaped trunk 25: Fixing ring 40: Low-melting-point wax coating layer 50: First preform 60: Second pre-form 70: Stack preform 80: Low-melting-point wax coating layer

Claims (6)

It is composed of an outer container and an inner bag container inserted and held in the outer container, and the contents stored in the inner bag container are discharged by squeezing the outer surface of the trunk portion of the outer container. At the same time, as the contents are discharged, the inner bag container shrinks, forming a gap between the inner bag container and the outer container.
Between the inner bag container and the outer container, the melting point is in the range of 40° C. to 70° C. in an unused state in which the contents are not discharged, except for at least the portion facing the bottom of the outer container. The low-melting wax coating layer is present in a coating amount of 150 mg/m ² or less, and the low-melting wax coating layer is in close contact with at least the inner surface of the squeezed barrel of the outer container. A double structure container characterized by: 2. The double structure container according to claim 1, wherein the low-melting wax is a low-crystallinity paraffin wax containing less than 50% by mass of n-paraffin. It consists of a test tube-shaped first preform for molding the outer container and a second test tube-shaped preform for molding the inner bag container, and the second preform is inserted into the first preform. In a stack preform for manufacturing a double-walled container secured by
A low-melting wax coating layer having a melting point of 40° C. to 70° C. is formed on the outer surface of the stretch-molded portion of the second preform at least in a region excluding the bottom portion of the curvature shape, stack preform. 4. The stack preform according to claim 3, wherein the low melting point wax is a low crystalline paraffin wax with an n-paraffin content of less than 50% by mass. preparing a test tube-shaped first preform for molding the outer container and a second test tube-shaped preform for molding the inner bag container,
On the outer surface of the second preform, a low-melting wax having a melting point of 40° C. to 70° C. is heated and melted at a temperature higher than the melting point and roll-coated to form a wax layer on the stretch-molded portion excluding the bottom portion of the curvature shape,
forming a stack preform by inserting the second preform into the first preform with the low-melting wax coating layer formed thereon;
blow molding by supplying a blow fluid into a second preform within the stack preform;
The method for manufacturing a double structure container according to claim 1, characterized by: 6. The method for manufacturing a double structure container according to claim 5, wherein a low crystalline paraffin wax having an n-paraffin content of less than 50% by mass is used as the low melting point wax.

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