JP7242174B2 - Synthetic resin container, preform, and synthetic resin container manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a synthetic resin container having a plurality of resin layers on its body.

Containers (PET bottles, etc.) formed by stretch-blow molding of thermoplastic polyester resins such as polyethylene terephthalate resin have excellent transparency and surface gloss, as well as the impact resistance, rigidity, and gas barrier properties necessary for containers. It is widely used as a container for various liquids such as beverages, seasonings and cosmetics. For example, Cited Document 1 discloses a polyester resin container in which functions such as decorativeness and gas barrier properties are imparted by further coating the body portion with a polyester film layer in a non-peelable manner, and a method for producing the same.

Japanese Patent No. 4131019

By the way, in a synthetic resin container with a film (outer layer) attached to the body to ensure gas barrier properties, such as the above-mentioned polyester resin container, a beverage containing carbon dioxide such as carbonated water is used as the content. , the carbon dioxide passes through the base material layer of the container and stays in the form of blisters (blisters) between the container and the outer layer, causing the outer layer to float and cause poor appearance.

An object of the present invention is to solve such problems, and an object of the present invention is to prevent carbon dioxide from stagnation between the base material layer and the outer layer of the container. It is an object of the present invention to provide a synthetic resin container, a preform, and a method for manufacturing a synthetic resin container for containing a content containing a synthetic resin.

The synthetic resin container of the present invention is
A synthetic resin container having a mouth, a body connecting to the lower end of the mouth and forming a space containing a content containing carbon dioxide gas, and a bottom closing the bottom of the body,
The body portion is formed by stretch blow molding a base layer together with an outer layer having one or more resin layers arranged radially outside the base layer,
In each resin layer constituting the base layer and the outer layer in the trunk portion, the radially outer resin layer that is adjacent in the thickness direction at all positions in the height direction and all positions in the circumferential direction is radially inner. The carbon dioxide gas permeability coefficient of the resin layer is larger than that of the resin layer.

Further, in the synthetic resin container of the present invention having the above structure, it is preferable that at least one resin layer constituting the outer layer has a water permeability coefficient smaller than that of the base material layer.

Further, in the synthetic resin container of the present invention having the above structure, it is preferable that the base material layer is made of a resin mainly composed of a polyester resin.

Further, in the synthetic resin container of the present invention having the above structure, it is preferable that the base material layer is made of a resin mainly composed of polyethylene terephthalate.

Further, in the synthetic resin container of the present invention having the above structure, it is preferable that the outer layer contains a resin mainly composed of an olefin resin.

Further, in the synthetic resin container of the present invention having the above configuration, the outer layer includes a plurality of resin layers, and the innermost layer of the plurality of resin layers is formed of a resin mainly composed of an olefin resin. is preferred.

Further, in the synthetic resin container of the present invention having the above structure, it is preferable that the outer layer has a thickness in the range of 30 μm to 100 μm.

Further, the preform of the present invention is
A preform for stretch blow molding used for manufacturing a synthetic resin container containing a content containing carbon dioxide gas,
having a mouth, a cylindrical body connected to the lower end of the mouth, and a bottom closing the lower end of the body,
The body portion has a base layer and an outer layer formed radially outside the base layer and having one or more resin layers,
In each resin layer constituting the base layer and the outer layer in the trunk portion, the radially outer resin layer that is adjacent in the thickness direction at all positions in the height direction and all positions in the circumferential direction is radially inner. The carbon dioxide gas permeability coefficient of the resin layer is larger than that of the resin layer.

Further, the method for manufacturing a synthetic resin container of the present invention comprises:
A method for manufacturing a synthetic resin container containing a content containing carbon dioxide by stretch blow molding,
molding by injection molding a preform having a mouth, a cylindrical body connected to the lower end of the mouth, and a bottom closing the lower end of the body;
arranging an outer layer having one or more resin layers radially outside the body portion of the preform forming a base layer;
stretch blow molding the preform together with the outer layer to form a synthetic resin container;
After the molding of the synthetic resin container, the resin layers constituting the base layer and the outer layer in the body are adjacent to each other in the thickness direction at all positions in the height direction and all positions in the circumferential direction. It is characterized in that the outer resin layer has a larger carbon dioxide gas permeability coefficient than the radially inner resin layer.

Further, in the method for manufacturing a synthetic resin container of the present invention, in the configuration described above, the step of disposing the outer layer is preferably a step of insert-molding the outer layer by inserting the preform into a mold.

Further, in the method for manufacturing a synthetic resin container of the present invention, in the above configuration, it is preferable that the step of disposing the outer layer is a step of superimposing the cylindrical outer layer on the outside of the preform.

Further, in the method for manufacturing a synthetic resin container of the present invention, in the configuration described above, it is preferable that the step of arranging the outer layer is a step of winding the sheet-like outer layer around the preform.

ADVANTAGE OF THE INVENTION According to the present invention, a synthetic resin container containing a content containing carbon dioxide gas, a preform, and a synthetic resin container capable of suppressing retention of carbon dioxide gas between the base material layer and the outer layer of the container. can provide a manufacturing method of

1 is a front partial cross-sectional view of a synthetic resin container according to an embodiment of the present invention; FIG. (a) is a front partial cross-sectional view of a preform according to an embodiment of the present invention, and (b) is a front partial cross-sectional view showing a state in which an outer layer is formed on (a). . 1 is a flow chart showing a method for manufacturing a synthetic resin container according to one embodiment of the present invention.

Hereinafter, a synthetic resin container 1, a preform 100, and a method for manufacturing the synthetic resin container 1 according to an embodiment of the present invention will be illustrated in detail with reference to FIGS.

In the present specification, claims, and drawings, the vertical direction means the upward direction and the downward direction when the synthetic resin container 1 is in an upright position as shown in FIG. Further, the radially outward direction is the direction toward the outside along a straight line that passes through the central axis of the synthetic resin container 1 in FIG. 1 and is perpendicular to the central axis. shall mean the direction toward

The synthetic resin container 1 of the present embodiment is a container for containing contents containing carbon dioxide gas, and as shown in FIG. 4 is formed in a bottle shape.

The mouth portion 2 has a substantially cylindrical shape, and is integrally provided with a male screw 2a on its outer peripheral surface for mounting a cap (not shown) by screwing. A neck ring 2b is integrally provided at the lower end of the mouth portion 2. As shown in FIG.

In addition, the opening 2 may have a configuration in which an annular convex portion is provided for mounting the cap by plugging in place of the screw connection.

The trunk portion 3 is provided integrally with the lower end of the mouth portion 2 . The interior of the body portion 3 is a storage space S that can store a carbonated drink such as carbonated water as a content.

In the illustrated case, the trunk portion 3 is integrally connected to the lower end of the mouth portion 2 and gradually expands in diameter downward, and the neck portion 3a is integrally connected to the lower end of the neck portion 3a and has an outer diameter and a body portion 3c integrally connected to the lower end of the shoulder portion 3b and extending downward while maintaining the same diameter.

It should be noted that the shape of the body portion 3 can be changed in various ways, for example, a shape without the neck-like portion 3a.

The bottom portion 4 is integrally connected to the lower end of the body portion 3 and closes the lower end of the body portion 3 . The bottom portion 4 has a ground portion 4a and a bottom wall portion 4b. Although details are not shown, the bottom portion 4 also has a laminated structure having a plurality of resin layers as described above.

As shown in FIG. 1, the grounding portion 4a is formed in an annular shape integrally connected to the lower end of the body portion 3c of the trunk portion 3. As shown in FIG. Further, the ground contact portion 4a has a shape whose diameter gradually decreases in a curved shape downward from the connecting portion with the main body portion 3c of the trunk portion 3, and the lower end portion thereof serves as a ground contact surface. The grounding portion 4a is a portion that is grounded on a support such as a table when the synthetic resin container 1 is placed on the support such as a table in an upright posture.

The bottom wall portion 4b is provided inside the ground portion 4a. In the illustrated case, the bottom wall portion 4b has a circular shape, and the outer peripheral edge of the bottom wall portion 4b is integrally connected to the inner peripheral edge of the ground contact portion 4a. The bottom wall portion 4b is a flat surface that is perpendicular to the central axis of the synthetic resin container 1 (vertical direction). The bottom wall portion 4b is arranged so as to be offset toward the mouth portion 2 side (upper side) with respect to the grounding portion 4a, and forms a concave portion toward the inside of the container.

In this embodiment, the synthetic resin container 1 shown in FIG. 1 is formed by biaxial stretch blow molding as a laminated structure container having a body portion 3 having a base material layer 5a and an outer layer 5b. That is, as will be described later, the synthetic resin container 1 is formed by insert molding or the like on the outside in the radial direction of the body portion 103 (base material layer 105a) of the preform 100 (see FIG. 2A) molded by injection molding. (see FIG. 2(b)) can be manufactured by biaxial stretch blow molding.

The synthetic resin container 1 has a plurality of resin layers (the base layer 5a and the outer layer 5b) on the body portion 3 as described above. In this embodiment, the base material layer 5a is made of a resin mainly composed of polyethylene terephthalate, which is a polyester-based resin. Further, the outer layer 5b is made of a resin mainly composed of polypropylene, which is an olefin resin.

In this embodiment, after the biaxial stretch blow molding of the synthetic resin container 1, the polypropylene constituting the outer layer 5b has a higher permeability coefficient to carbon dioxide than the polyethylene terephthalate constituting the base layer 5a. , each material is selected. In other words, the outer layer 5b (polypropylene) is more permeable to carbon dioxide as a material than the base layer 5a (polyethylene terephthalate). By adopting such a configuration, when carbonated water is stored in the storage space S, carbon dioxide gas in the carbonated water slightly permeates the base material layer 5a and moves between the base material layer 5a and the outer layer 5b. Even so, the carbon dioxide gas is more likely to pass through the outer layer 5b and be released to the outside, so that the carbon dioxide gas does not stay in the space between the base material layer 5a and the outer layer 5b. On the other hand, the water permeability coefficient of the outer layer 5b (polypropylene) is generally lower than that of the base material layer 5a (polyethylene terephthalate). It is Therefore, even a small amount of water molecules that have passed through the base material layer 5a can be prevented from being released to the outside by the outer layer 5b. As a result, carbon dioxide gas does not remain between the base material layer 5a and the outer layer 5b, and water is prevented from passing through the base material layer 5a and being released to the outside.

In the present embodiment, a resin mainly composed of polyethylene terephthalate was used as the base material layer 5a, but it is not limited to this aspect, and other polyester resins such as PET-G resin, PCTG resin, or PCTA resin. may be used. Further, a resin other than the polyester-based resin may be used as the base material layer 5a as long as the carbon dioxide gas permeability coefficient of the base material layer 5a is smaller than the permeability coefficient of the outer layer 5b.

Further, in the present embodiment, a resin mainly composed of polypropylene is used as the outer layer 5b, but the present invention is not limited to this aspect, and other olefin resins such as polyethylene may be used. When polyethylene is used as the outer layer 5b, low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), etc. can be used. Since the coefficient tends to be large, it is necessary to select the density of polyethylene so that the permeability coefficient of the outer layer 5b is greater than that of the base layer 5a. Further, a resin other than the olefin resin may be used for the outer layer 5b as long as the outer layer 5b has a higher permeability coefficient for carbon dioxide gas than the base layer 5a.

Next, a method for manufacturing the synthetic resin container 1 according to this embodiment will be described with reference to FIG. 3 and the like.

FIG. 3 is a flow chart showing a method for manufacturing the synthetic resin container 1 according to this embodiment. When manufacturing the synthetic resin container 1 of the present embodiment, first, polyethylene terephthalate is injected into a cavity in an injection mold to form a preform 100 having a test tube shape shown in FIG. 2(a). form (step S101). A preform 100 formed by this injection molding has a mouth portion 102, a cylindrical body portion 103 connected to the lower end of the mouth portion 102, and a bottom portion 104 closing the bottom end of the body portion 103. It constitutes the material layer 105a.

A mouth portion 102 of the preform 100 has a substantially cylindrical shape, and a male thread 102a is integrally provided on the outer peripheral surface thereof for attaching a cap by screwing. A neck ring 102b is integrally provided at the lower end of the mouth portion 102. As shown in FIG.

A body portion 103 of the preform 100 is integrally connected to the lower end of the mouth portion 102 . The preform 100 of this embodiment has a test tube shape as a whole, with the lower end of a cylindrical body portion 103 closed by a hemispherical arc-shaped bottom portion 104 .

Next, the preform 100 formed in step S101 is set in an injection mold, and polypropylene, which is the material of the outer layer 105b, is injected into the mold for insert molding (step S102). As a result, as shown in FIG. 2B, the outer layer 105b made of polypropylene can be formed radially outside the base layer 105a made of polyethylene terephthalate in the body portion 103 of the preform 100. As shown in FIG.

Note that the method for forming the outer layer 105b is not limited to the above-described mode. For example, a cylindrical member for the outer layer 105b formed by injection molding different from the preform 100 described above is formed in FIG. The outer layer 105b may be placed on the preform 100 by overlapping it on the outer side of the body 103 of the preform 100 of a). Alternatively, the outer layer 105b may be disposed on the preform 100 by winding a sheet-like member for the outer layer 105b around the body portion 103 of the preform 100 of FIG. 2(a).

Next, the preform 100 with the outer layer 105b prepared in step S102 is subjected to biaxial stretch blow molding (step S103). This biaxial stretch blow molding is carried out by placing the preform 100 with the outer layer 105b in a mold of a stretch blow molding machine and setting the opening 102 on the top of the mold. The outer layer 105b arranged around the body portion 103 of the preform 100 constituting the base material layer 105a is thermally fused to the base material layer 105a due to the temperature rise during biaxial stretch blow molding and is stretched integrally. A synthetic resin container 1, which is a biaxial stretch blow molded article shown in FIG. 1, is formed.

As described above, in the synthetic resin container 1 of the present embodiment, the body portion 3 includes the base layer 5a together with the outer layer 5b having one or more resin layers disposed radially outside the base layer 5a. The outer layer 5b, which is formed by stretch blow molding and which is adjacent to the substrate layer 5a in the thickness direction and radially outward, is configured to have a higher carbon dioxide gas permeability coefficient than the substrate layer 5a. As a result, when a liquid containing carbon dioxide gas such as carbonated water is stored in the storage space S, the carbon dioxide gas in the liquid slightly permeates the base material layer 5a and moves between the base material layer 5a and the outer layer 5b. However, the carbon dioxide gas is more likely to pass through the outer layer 5b and be released to the outside. .

In addition, when the outer layer 5b has a plurality of resin layers, the plurality of resin layers constituting the base layer 5a and the outer layer 5b are arranged such that the radially outer resin layer adjacent in the thickness direction is radially outer. The carbon dioxide permeation coefficient may be higher than that of the resin layer on the inner side of the direction. In this case, when the resin layers adjacent in the thickness direction have the same carbon dioxide gas permeability coefficient, the adjacent resin layers are treated as one layer when considering the permeability coefficient.

Further, in the present embodiment, at least one resin layer constituting the outer layer 5b is configured to have a smaller water permeability coefficient than the base layer 5a. As a result, the carbon dioxide gas is prevented from accumulating in the form of blisters in the space between the base material layer 5a and the outer layer 5b, and at the same time, the barrier property against permeation of water from the housing space S of the synthetic resin container 1 to the outside is improved. can be improved.

Moreover, in this embodiment, the base material layer 5a is configured to be formed of a resin mainly composed of a polyester-based resin. As a result, the base material layer 5a having a smaller carbon dioxide gas permeability coefficient than the outer layer 5b is formed using a relatively inexpensive material, and carbon dioxide gas is formed in a blister form in the space between the base material layer 5a and the outer layer 5b. Retention can be suppressed.

Further, in this embodiment, the base material layer 5a is configured to be formed of a resin mainly composed of polyethylene terephthalate. As a result, the base material layer 5a having a lower carbon dioxide gas permeability coefficient than the outer layer 5b is formed using an inexpensive mass-produced material, and carbon dioxide gas is generated in the space between the base material layer 5a and the outer layer 5b. Blister retention can be suppressed.

Moreover, in this embodiment, the outer layer 5b is configured to contain a resin mainly composed of an olefin resin. As a result, the outer layer 5b having a higher carbon dioxide gas permeability coefficient than the base layer 5a is formed using a relatively inexpensive material, and the carbon dioxide gas is blister-shaped in the space between the base layer 5a and the outer layer 5b. Retention can be suppressed.

Moreover, the outer layer 5b may include a plurality of resin layers, and the innermost layer of the plurality of resin layers may be formed of a resin mainly composed of an olefin resin. A plurality of resin layers further enhances gas barrier properties, and while ensuring barrier properties against a plurality of gases, suppresses blister-like retention of carbon dioxide gas in the space between the base material layer 5a and the outer layer 5b. can be done.

Further, in this embodiment, the outer layer 5b is configured to have a thickness in the range of 30 μm to 100 μm. As a result, defective molding can be suppressed when the outer layer 5b is formed by insert molding or extrusion blow molding.

Further, in the preform 100 of the present embodiment, the body portion 103 has the base layer 105a and the outer layer 105b formed radially outwardly of the base layer 105a. It was also configured so that the permeability coefficient of carbon dioxide gas was large. As a result, when the preform 100 is stretch-blow molded into the synthetic resin container 1 and a liquid containing carbon dioxide gas such as carbonated water is accommodated in the accommodation space S, the carbon dioxide gas in the liquid slightly spreads the base material layer 5a. Even if it permeates and moves between the base material layer 5a and the outer layer 5b, the carbon dioxide gas easily passes through the outer layer 5b and is released to the outside. It is possible to suppress blister-like retention of carbon dioxide gas in the space. In the state after the preform 100 is stretch-blow molded into the synthetic resin container 1, the outer layer 5b needs to have a higher permeability coefficient for carbon dioxide gas than the base layer 5a.

In addition, the method for manufacturing the synthetic resin container 1 by stretch blow molding according to the present embodiment includes forming the mouth portion 102, the cylindrical body portion 103 connected to the lower end of the mouth portion 102, and the lower end of the body portion 103 by injection molding. forming a preform 100 having a bottom portion 104 that closes the base layer 105a; placing an outer layer 105b radially outwardly of the body portion 103 of the preform 100 forming the base layer 105a; and a step of forming the synthetic resin container 1 by stretch blow molding, and after the synthetic resin container 1 is formed, the outer layer 5b is configured to have a larger carbon dioxide gas permeability coefficient than the base layer 5a. As a result, the preform 100 and the outer layer 105b constituting the base material layer 105a are stretched while being heat-sealed, so that the base material layer 5a and the outer layer 5b in the body portion 3 of the synthetic resin container 1 after stretch blow molding. Adhesion with can be ensured. Further, when a liquid containing carbon dioxide gas such as carbonated water is stored in the storage space S, the carbon dioxide gas in the liquid slightly permeates the base material layer 5a and moves between the base material layer 5a and the outer layer 5b. However, since the carbon dioxide easily passes through the outer layer 5b and is released to the outside, it is possible to prevent the carbon dioxide from accumulating in the form of blisters in the space between the base material layer 5a and the outer layer 5b. .

Each PET bottle sold as a product has a label wrapped around the body of the bottle to improve the decorativeness of the product. Labels are attached to the front and back of the bottle body in a separate process. In this embodiment, the outer layer 105a is attached to the preform 100 and integrally stretch-blow-molded, so that the label attachment step after bottle molding can be omitted.

Further, in the present embodiment, the step of arranging the outer layer 105b is a step of inserting the preform 100 into a mold and insert-molding the outer layer 105b. Thereby, the outer layer 105b of the preform 100 can be formed easily and accurately.

In addition, the step of arranging the outer layer 105b can also be performed as a step of superimposing a cylindrical outer layer 105b formed by injection molding, extrusion blow molding (EBM), or extrusion tube molding on the outside of the preform 100. good. Thereby, the outer layer 105b of the preform 100 can be formed easily and accurately.

Also, the step of disposing the outer layer 105b may be a step of wrapping the sheet-like outer layer 105b around the preform 100 . Thereby, the outer layer 105b of the preform 100 can be prepared at low cost.

Next, in order to confirm the effect of the present invention, as shown in Table 1, polyethylene terephthalate (PET) and polypropylene (PP) were used as the "configuration of the outer layer" of the synthetic resin container 1 of the example of the present invention. Two-layer structure of (Example 1), polypropylene (Example 2), polyethylene (Example 3), and two-layer structure of polypropylene/polyethylene (Example 4). prepared. The polypropylene used in this example is J246M (melt flow rate (MFR): 30), which is a prime polymer random polypropylene. As comparative examples, five types of "structures of outer layers" shown in Table 1 were prepared and compared with the examples. In both examples and comparative examples, the content of the synthetic resin container was 500 ml and the mass was 38 g (base material layer: 30.5 g, outer layer: 7.5 g). In Examples 2 and 3, the thickness of the outer layer 5b after the preform 100 constituting the base layer 105a and the outer layer 105b formed by insert molding was biaxially stretched and blow molded was 80 to 100 μm (at the time of insert molding). (equivalent to a thickness of about 1.5 mm of the outer layer 105b). In Examples 1 and 4 and Comparative Examples 1 to 5, the preform 100 constituting the base layer 105a was subjected to biaxial stretch blow molding together with the outer layer 105b formed by extrusion blow molding (EBM). It was manufactured to have a thickness of 30 to 50 μm (corresponding to a thickness of about 0.3 to 0.4 mm for the outer layer 105b during extrusion blow molding). The thickness of the outer layer 5b is selected so that insert molding or extrusion blow molding can be carried out satisfactorily and molding defects are less likely to occur. Of course, the thickness of the outer layer 5b may also be configured to a thickness between 50 and 80 μm by insert molding or extrusion blow molding. On the other hand, when the thickness of the outer layer 5b after biaxial stretch blow molding is less than 30 μm or more than 100 μm, molding defects may occur.

"Composition of outer layer" shown in Table 1 indicates a resin layer formed radially inward on the left side and a resin layer formed radially outward on the right side. "ad" indicates an adhesive layer, and for example, a modified polyolefin having adhesive properties such as "Admer (registered trademark)" can be used. "EVOH" is an EVOH resin layer (ethylene-vinyl alcohol copolymer resin layer) provided as a barrier layer. For example, PP/ad/EVOH/ad/PP of Comparative Example 1 is a laminated resin laminated in the order of polypropylene/adhesive layer/EVOH resin layer/adhesive layer/polypropylene from the innermost layer to the outermost layer.

The results in Table 1 are obtained by using polyethylene terephthalate (PET) for the base material layer, using the resin layer shown in "Configuration of outer layer" in Table 1 for the outer layer, and filling the synthetic resin container with 4 Gvol (gas volume) of carbonated water. The table shows the presence or absence of blisters and the adequacy of separation when stored in a 40° C. and 10% RH (relative humidity) environment.

According to Table 1, among the resin layers adjacent to each other in the thickness direction, the base material layer 5a (resin layer mainly composed of polyethylene terephthalate in this embodiment) and the outer layer 5b are adjacent to each other in the thickness direction. As for Examples 1 to 4, in which the carbon dioxide gas permeability coefficient is larger than that of the radially inner resin layer, no blistering occurs during storage in an environment of 40° C. and 10% RH.

For example, in Example 1, the carbon dioxide gas permeability coefficient of PP, which is a resin layer adjacent to the radially outer side of PET, is higher than that of PET constituting the innermost layer of the base material layer 5a and the outer layer 5b. . In this case, the innermost layers of the base material layer 5a and the outer layer 5b are both made of PET and have the same carbon dioxide gas permeability coefficient. Further, since the adhesive layer (ad) that bonds the PET and PP of the outer layer 5b is thin and has a relatively small effect on permeation of carbon dioxide gas, it is not considered here.

In Example 2, the carbon dioxide gas permeability coefficient of PP (polypropylene), which is the resin layer adjacent to the radially outer side of the base layer 5a, is higher than that of PET constituting the base layer 5a.

Similarly, in Example 3, PE (polyethylene) adjacent to the radially outer side of the base material layer 5a and forming the outer layer 5b has a larger carbon dioxide gas permeability coefficient than PET forming the base material layer 5a. ing. Depending on the density of the selected PE, the outer layer 5b (PE) adjacent to the radially outer side of the base layer 5a (PET) may have a lower carbon dioxide permeability coefficient than the base layer 5a (PET). In the embodiment, each material is selected so that PE constituting the outer layer 5b has a higher permeability coefficient of carbon dioxide gas than PET constituting the base layer 5a.

In Example 4, the PP, which is adjacent to the radially outer side of the PET and constitutes the innermost layer of the outer layer 5b, has a higher permeability coefficient of carbon dioxide gas than the PET which constitutes the base material layer 5a. The carbon dioxide gas permeability coefficient of the PE adjacent to the radially outer side of the PP and constituting the outermost layer of the outer layer 5b is higher than that of the PP constituting the PE. Depending on the density of the selected PE, the PE adjacent to the radially outer side of the PP may have a lower carbon dioxide gas permeability coefficient than the PP. Each material is selected so that the carbon dioxide permeation coefficient is greater.

The carbon dioxide gas permeability coefficient can be confirmed, for example, by a gas permeability test method based on a differential pressure type gas chromatograph method according to JIS K7126-1.

On the other hand, Comparative Examples 1 to 5 all include resin layers in which the carbon dioxide permeation coefficient is smaller in the radially outer resin layer than in the radially inner resin layer adjacent in the thickness direction. Blister formation has been confirmed in that area.

For example, in Comparative Example 1, the EVOH adjacent to the radially outer side of the PP constituting the innermost layer of the outer layers has a lower carbon dioxide gas permeability coefficient, and blisters occur at the boundary between them.

Further, in Comparative Examples 2 and 3, the EVOH adjacent to the outer side in the radial direction of the PET constituting the innermost layer of the outer layer has a lower permeability coefficient of carbon dioxide gas, and blisters occur at the boundary between them. .

Further, in Comparative Example 4, the carbon dioxide gas permeability coefficient of the PET adjacent to the radially outer side of the PP forming the intermediate layer of the outer layer is lower than that of the PP, and blisters occur at the boundary between them.

In Comparative Example 5, the carbon dioxide permeability coefficient of the PET adjacent to the outermost layer in the outer layer in the radial direction is smaller than that of the PP forming the innermost layer of the outer layers, and blisters occur at the boundary between them.

Regarding the separation suitability, as shown in Table 1, in the examples and comparative examples using PET as the innermost layer of the outer layer, the PET of the base layer and the PET of the outer layer stick to each other, making it difficult to peel off the outer layer. The aptitude for sorting is not (×). Regarding other examples and comparative examples in which a resin different from the PET of the base layer is used for the innermost layer of the outer layer, the PET of the base layer and the outer layer can be easily separated and separated, so the separation suitability is good (○).

Table 2 shows the weight of water in the storage space of the synthetic resin container in Example 2 having a PP outer layer 5b in addition to the PET base layer 5a and Comparative Example 6 having only a PET base layer. This is the result of comparing the rate of change.

At both storage temperatures of 23 ° C. and 40 ° C., compared to Comparative Example 6 having only a PET base layer, Example 2 provided a PP outer layer 5 b radially outside the base layer 5 a. However, it can be seen that the weight change rate of the moisture in the accommodation space S is suppressed to about half. This is because PP has a higher permeability coefficient for carbon dioxide gas than PET, while PP has a lower permeability coefficient for water than PET. This is because the barrier property can be enhanced.

Although the present invention has been described with reference to the drawings and examples, it should be noted that various variations and modifications will be readily apparent to those skilled in the art based on this disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, the functions included in each component can be rearranged so as not to be logically inconsistent, and multiple components can be combined into one or divided. It should be understood that the scope of the present invention includes these.

Reference Signs List 1 synthetic resin container 2 mouth 2a male screw 2b neck ring 3 body 3a neck 3b shoulder 3c body 4 bottom 4a grounding 4b bottom wall 5a substrate layer 5b outer layer 100 preform 102 mouth 102a male screw 102b Neck ring 103 Body 104 Bottom 105a Base layer 105b Outer layer S Accommodation space

Claims (12)

A synthetic resin container having a mouth, a body connecting to the lower end of the mouth and forming a space containing a content containing carbon dioxide gas, and a bottom closing the bottom of the body,
The body portion is formed by stretch blow molding a base layer together with an outer layer having one or more resin layers arranged radially outside the base layer,
In each resin layer constituting the base layer and the outer layer in the trunk portion, the radially outer resin layer that is adjacent in the thickness direction at all positions in the height direction and all positions in the circumferential direction is radially inner. A container made of synthetic resin, characterized in that the permeability coefficient of carbon dioxide gas is larger than that of the resin layer of (1). 2. The synthetic resin container according to claim 1, wherein at least one resin layer constituting said outer layer has a smaller water permeability coefficient than said base material layer. 3. The synthetic resin container according to claim 1 or 2, wherein the base material layer is made of a resin mainly composed of a polyester resin. 4. The synthetic resin container according to claim 3, wherein said base material layer is made of a resin mainly composed of polyethylene terephthalate. 5. The synthetic resin container according to any one of claims 1 to 4, wherein the outer layer contains a resin mainly composed of an olefin resin. 6. The synthetic resin container according to claim 5, wherein said outer layer includes a plurality of resin layers, and the innermost layer of said plurality of resin layers is formed of a resin mainly composed of an olefin resin. The synthetic resin container according to any one of claims 1 to 6, wherein said outer layer has a thickness in the range of 30 µm to 100 µm. A preform for stretch blow molding used for manufacturing a synthetic resin container containing a content containing carbon dioxide gas,
having a mouth, a cylindrical body connected to the lower end of the mouth, and a bottom closing the lower end of the body,
The body portion has a base layer and an outer layer formed radially outside the base layer and having one or more resin layers,
In each resin layer constituting the base layer and the outer layer in the trunk portion, the radially outer resin layer that is adjacent in the thickness direction at all positions in the height direction and all positions in the circumferential direction is radially inner. A preform characterized by having a larger carbon dioxide gas permeability coefficient than the resin layer of the preform. A method for manufacturing a synthetic resin container containing a content containing carbon dioxide by stretch blow molding,
molding by injection molding a preform having a mouth, a cylindrical body connected to the lower end of the mouth, and a bottom closing the lower end of the body;
arranging an outer layer having one or more resin layers radially outward of the body portion of the preform forming a base layer;
stretch blow molding the preform together with the outer layer to form a synthetic resin container;
After the molding of the synthetic resin container, the resin layers constituting the base layer and the outer layer of the body are adjacent to each other in the thickness direction at all positions in the height direction and all positions in the circumferential direction. 1. A method of manufacturing a synthetic resin container, wherein the outer resin layer has a higher permeability coefficient of carbon dioxide gas than the radially inner resin layer. 10. The method of manufacturing a synthetic resin container according to claim 9, wherein the step of placing the outer layer is a step of insert-molding the outer layer by inserting the preform into a mold. 10. The method of manufacturing a synthetic resin container according to claim 9, wherein the step of arranging the outer layer is a step of overlapping the cylindrical outer layer on the outside of the preform. 10. The method of manufacturing a synthetic resin container according to claim 9, wherein the step of arranging the outer layer is a step of winding the sheet-like outer layer around the preform.

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