JP2024028479A - Container lids and packaging - Google Patents

Abstract

An object of the present invention is to provide a lid for a container that is free from the risk of peeling off from the opening edge of the container and causing leakage of contents even when the internal pressure of the package changes. [Solution] A container lid material 3 has a heat sealing layer 32 composed of an aluminum foil layer 31 and two or more resin layers 321 and 322 including a hot melt resin layer 321 which is the innermost layer of the container lid material. It consists of a laminate 30 comprising: The hot melt resin layer 321 is made of ethylene-vinyl acetate copolymer: 10 to 30% by mass, wax having a melting point of 55 to 115°C: 25 to 55% by mass, and tackifier having a softening point of 120 to 160°C: 15 Contains ~30% by mass. [Selection diagram] Figure 1

Description

This invention relates to a container lid material that is heat-sealed to the opening edge of a container filled with beverages, foods, etc. to seal the contents, and a lid material that is used together with the container. The present invention relates to a package formed by sealing the contents of drinks, foods, etc.

For example, thermoplastic resin cups and pouches are commonly used as containers for filling and packaging beverages such as soft drinks, milk drinks, vegetable juices, smoothies, and soups, and semi-solid foods such as jelly, pudding, and yogurt. .
Cups in particular are used as many food containers because they also function as tableware. In the case of a food container made of a cup, after the contents are filled, the container is sealed by heat-sealing a lid material to the opening edge of the container. For the heat sealing layer constituting the innermost layer of the lid, a heat-adhesive resin with relatively high sealing properties is used to prevent contents from leaking from the sealed portion.
Hot melt adhesives are often used as such thermoadhesive resins due to their cost and ease of handling, and various proposals have been made regarding hot melt adhesives.
For example, Patent Document 1 below describes an olefinic polymer (A) having a melt flow rate of 1 to 50 g/10 min at 230°C and 21.18N: 5 to 45% by mass, a melting point of 70°C or higher, and 150°C. Hereinafter, wax (B) having a needle penetration degree of 0.2 to 9 when a load of 100 g is applied for 5 seconds at 25°C: 5 to 30% by mass, and a melting point of 40°C or higher and lower than 70°C and 100°C Wax (C) having a Saybolt universal viscosity of 0.5 to 8 seconds: 35 to 75% by mass (however, the total of the above (A) to (C) is 100% by mass); A heat-melting composition, wherein the difference between the melting point of B) and the melting point of the wax (C) is 20° C. or more, and the total of the wax (B) and the wax (C) is 55 to 95% by mass. is disclosed.

Japanese Patent Application Publication No. 2016-175957

By the way, packages containing food or beverages are generally stored at low temperatures such as in refrigerators, so it is natural that they must have sealing performance at low temperatures, but it is not necessary to fill the contents at room temperature. In some cases, the container is heated and processed after being sealed, and in some cases, the contents are fermented foods.
In such cases, the internal pressure inside the sealed package changes due to temperature changes or the generation of gas from the fermented food, which causes the seal to recede, or the seal to peel, and the contents to leak out. Something happened.
However, in the case of conventional container lid materials, it has been difficult to reliably prevent the seal from retreating due to changes in the internal pressure of the package.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a container lid material that can reliably prevent the seal from retreating due to changes in the internal pressure of the package.

This invention consists of the following aspects in order to achieve the above object.

1) A container lid material that is heat-sealed to the opening edge of the container so as to cover the opening of the container filled with contents,
consisting of a laminate comprising an aluminum foil layer and a heat sealing layer constituted by two or more resin layers including a hot melt resin layer serving as the innermost layer of the container lid material,
The hot melt resin layer contains ethylene vinyl acetate copolymer: 10 to 30% by mass, wax having a melting point of 55 to 115°C: 25 to 55% by mass, and tackifier having a softening point of 120 to 160°C: 15 A container lid material containing ~30% by mass.

2) The container lid material of 1) above, wherein the hot melt resin layer has a melting point of 70 to 85°C.

3) The laminate includes a reinforced resin layer interposed between the aluminum foil layer and the heat sealing layer, and a protective resin laminated on the surface of the aluminum foil layer opposite to the heat sealing layer. The container lid material according to 1) or 2) above, comprising a layer.

4) The container lid material according to any one of 1) to 3) above, wherein the two or more resin layers constituting the heat sealing layer include an adhesive intervening layer made of polyolefin resin.

5) It comprises a container filled with contents, and a container lid material according to any one of 1) to 4) above, which is heat-sealed to the edge of the opening of the container so as to cover the opening of the container. , packaging.

6) The container lid material has a flat top wall portion whose peripheral edge portion is heat-sealed to the upper surface of the opening edge of the container, and a flat top wall portion that extends downward from the peripheral edge portion of the top wall portion and extends part of the height thereof. and a skirt portion heat-sealed to the outer surface of the opening edge of the container.

Here, the melting point of the wax and the melting point of the hot melt resin layer are measured using a differential scanning calorimeter (DSC) at 10° C./min.
Moreover, the softening point of the tackifier is measured in accordance with the provisions of JIS K6863 (1994).

According to the container lid material of 1) above, since a material having the above composition is used as the hot melt resin layer, by heat sealing the lid material to the opening edge of the container filled with contents, Even if the internal pressure of the formed package changes due to deformation of the container or the like immediately after heat sealing, seal regression is unlikely to occur.

According to the container lid material 2), since the melting point of the hot melt resin layer is 70 to 85°C, the sealing performance is good even at low sealing temperatures, and furthermore, the packaging material may be damaged due to deformation of the container immediately after heat sealing. Even if the internal pressure of the seal increases, seal retraction is unlikely to occur.

According to the container lid material described in 3), the strength is improved by the presence of the reinforced resin layer and the protective resin layer, so even if the internal pressure or external pressure of the package changes, the lid material will not tear and the contents will not leak out. It becomes difficult to leak.

According to the container lid material described in 4), the heat sealing layer includes an adhesive intervening layer made of polyolefin resin, so that it can be used with containers made of commonly used resins such as polystyrene resin, or with paper or aluminum foil and a resin layer. Since the sealability with the container formed by molding the laminate with the packaging material is improved, even if the internal pressure of the packaging material increases, the seal is unlikely to recede.

According to the package described in 5) above, even if the internal pressure of the container changes due to deformation of the container immediately after heat sealing, it is difficult for the seal to recede in the container lid material, so leakage of contents due to seal regression is prevented. can be reliably prevented.

According to the package described in 6) above, a part of the molten resin of the heat sealing layer of the lid body of the container lid material wraps around the outer surface of the opening edge of the container, thereby reducing part of the height of the skirt portion. The sealing area is also heat-sealed to the opening edge of the container to increase the sealing area, so even if the seal recedes, airtightness is maintained.

FIG. 2 is a partially enlarged cross-sectional view showing the layered structure of a laminate that constitutes a container lid material according to an embodiment of the present invention. It shows a lid material for a container formed from the same laminate, in which (a) is a partially cutaway front view, and (b) is a plan view. It is a vertical sectional view showing a package using the same container lid material. FIG. 2 is a schematic diagram showing a method of a creep test in an example.

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 shows the layered structure of a laminate (sheet) (30) constituting a container lid (3) according to the present invention.
The illustrated laminate (30) includes an aluminum foil layer (31), a heat sealing layer (32), and a reinforced resin layer ( 33), and a protective resin layer (34) laminated on the surface of the aluminum foil layer (31) opposite to the heat sealing layer (32).

The aluminum foil layer (31) functions as a barrier layer that provides the lid material (3) with barrier properties against gas, moisture, light, and the like.
As the aluminum foil constituting the aluminum foil layer (31), considering workability and versatility, soft materials (O materials) such as A1N30, A8021, and A8079 specified in JIS H4160 (2006) are preferably used. It will be done.
The thickness of the aluminum foil layer (31) is preferably about 5 to 40 μm in consideration of formability, pinhole occurrence rate, etc.
Preferably, a base layer (not shown) made of a chemical conversion coating is formed on both sides of the aluminum foil layer (31). With such a base layer, the adhesion between the aluminum foil layer (31), the reinforced resin layer (33), and the protective resin layer (34) is improved, and the corrosion resistance of the aluminum foil layer (31) is also improved. .
Specifically, for example, on the surface of the aluminum foil layer (31) that has been subjected to degreasing treatment,
1) Phosphoric acid and
chromic acid and
an aqueous solution of a mixture containing at least one compound selected from the group consisting of metal salts of fluoride and non-metal salts of fluoride; 2) phosphoric acid;
At least one resin selected from the group consisting of acrylic resin, chitosan derivative resin, and phenolic resin,
3) an aqueous solution of a mixture containing at least one compound selected from the group consisting of chromic acid and chromium (III) salts; 3) phosphoric acid;
At least one resin selected from the group consisting of acrylic resin, chitosan derivative resin, and phenolic resin,
At least one compound selected from the group consisting of chromic acid and chromium (III) salts,
An aqueous solution of a mixture containing at least one compound selected from the group consisting of metal salts of fluoride and non-metallic salts of fluoride.After coating an aqueous solution of any one of the above 1) to 3), drying By doing so, a chemical conversion treatment is performed to form a film.
The film formed on the surface of the aluminum foil layer (31) by the chemical conversion treatment, that is, the base layer, preferably has a chromium adhesion amount (per side) of 0.1 mg/m ² to 50 mg/m ² , particularly , 2 mg/m ² to 20 mg/m ² .

The heat sealing layer (32) is for heat sealing the container lid (3) to the opening edge (21) of the container (2). In this embodiment, the heat sealing layer (32) is composed of two resin layers (321) and (322), one of which is a hot melt resin layer (321) that constitutes the innermost layer of the container lid (3). The other is an adhesive intervening layer (322) made of polyolefin resin.

The hot melt resin layer (321) includes 5 to 50% by mass of at least one polyolefin resin, 10 to 30% by mass of ethylene vinyl acetate copolymer (EVA), and 25 to 55% of wax having a melting point of 55 to 115°C. A tackifier having a softening point of 120 to 160° C.: 15 to 30% by mass is used. If the hot melt resin layer (321) having such a composition is used, as will be described later, the internal pressure of the package (1) obtained by using the container lid (3) together with the container (2) will be reduced. Even if the seal changes, it is possible to obtain the effect that seal retraction is unlikely to occur.
Examples of the polyolefin resin include homopolymers such as polyethylene, polypropylene, polybutene, and polyisobutylene, and copolymers of ethylene and olefins such as propylene and 1-butene.
Examples of the wax include paraffin wax, montan wax, ethylene wax, propylene wax, and modified wax obtained by grafting styrene onto a polyethylene/polypropylene copolymer.
Tackifiers include rosins such as rosin and disproportionated rosin, esters of rosins and polyhydric alcohols such as glycol, glycerin and pentaerythritol, and hydrocarbons whose constituent monomers include terpenes and styrene. Examples include resin.
Further, the hot melt resin layer (321) preferably has a melting point of 70 to 85°C, so that even if the internal pressure of the package (1) increases due to deformation of the container immediately after heat sealing, Seal regression is less likely to occur.
The hot melt resin layer (321) is prepared by applying, for example, a hot melt resin having the above composition prepared using a gravure roll onto the surface of the adhesive intervening layer (322), preferably at a basis weight of 12 to 16 g/m ² . After that, it is formed by drying and curing.

The adhesive intervening layer (322) is a layer laminated as a base to make the layer thickness of the hot melt resin layer (321) uniform, and also serves as an adhesive layer during heat sealing. It is preferable that the layer (321) is made of a resin having a melting point close to that of the layer (321), for example, a polyolefin resin such as polyethylene resin (PE) or a compound thereof.
The thickness of the adhesive intervening layer (322) is preferably 10 to 40 μm in order to make the layer thickness of the hot melt resin layer (321) uniform.

The heat sealing layer (32) may be composed of three or more resin layers, for example, by laminating a resin layer containing hydrophobic particles on the outside of the hot melt resin layer (321).

The reinforced resin layer (33) is interposed between the aluminum foil layer (31) and the heat sealing layer (32) to improve the strength of the container lid (3), especially the internal pressure and external pressure of the package (1). This increases the strength against changes in
The reinforced resin layer (33) is composed of a single layer or a multilayer film made of polyester resin such as polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), polyethylene naphthalate resin (PEN), etc., and is made of aluminum. Dry lamination is performed on the surface of the foil layer (31) via an adhesive layer (not shown) made of a urethane resin adhesive or the like.
The thickness of the reinforced resin layer (33) is preferably 5 to 20 μm in consideration of strength and dead hold property to maintain the shape of the skirt portion (3b).

The protective resin layer (34) constitutes the outermost layer of the container lid (3) and has the function of decorating and protecting the lid (3).
The protective resin layer (34) is made of, for example, a polyester resin film such as polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), polyethylene naphthalate resin (PEN), nylon 6 (PA6), nylon 6,6 (PA66), etc. ), single-layer or multi-layer films made of polyamide resin films such as biaxially oriented polypropylene resin films (OPP), stretched polyolefin resin films such as biaxially oriented polypropylene resin films (OPP), and coating films made of thermosetting resins such as nitrified cotton and epoxy resins. It is preferable that there be.
The thickness of the protective resin layer (34) is preferably 2 to 25 μm in consideration of dead hold property and corrosion resistance of the aluminum foil layer (31).
Furthermore, although not shown, a printed layer may be interposed entirely or partially between the protective resin layer (34) and the aluminum foil layer (31).

FIG. 2 shows a container lid material (3) formed from the laminate (30).
The container lid (3) has a flat top wall (3a) having a shape and size that can cover the upper opening of the container (2), and extends downward from the peripheral edge of the top wall (3a). A skirt portion (3b) is provided.
In the illustrated container lid material (3), the top wall portion (3a) is shaped like a disk. The skirt portion (3b) is provided in a hanging shape so as to cover the outer surface of the opening edge (21) of the container (2).
This container lid material (3) can be formed by cutting the laminate (30) into a predetermined shape and size and press-molding the same. The skirt portion (3b) has a large number of vertically extending pleats (3c) formed at intervals in the circumferential direction.

Figure 3 shows a package (1) in which contents (C) consisting of beverages, food, etc. are hermetically packaged using a container (2) and the above-mentioned container lid (3). It is.
The container (2) is cup-shaped with an upward opening, and is made of, for example, a thermoplastic resin molded product such as polystyrene resin. Note that the shape and material of the container (2) are not limited to those described above.
The package (1) is formed by heat-sealing a container lid (3) to the opening edge (21) of a container (2) filled with contents (C).
More specifically, the hot melt resin layer (321) at the peripheral edge of the top wall (3a) of the container lid (3) is heat-sealed onto the upper surface of the opening edge (21) of the container (2). At the same time, the hot melt resin layer (321) on the upper end side of the skirt portion (3b) of the container lid (3) is heat-sealed to the outer surface of the opening edge (21) of the container (2). ing.
Heat sealing methods include thermally welding the hot melt resin layer (321) of the container lid (3) and the opening edge (21) of the container (2) using a hot plate, etc., as well as ultrasonic welding and high frequency welding. It may be welded.

Next, specific examples of the present invention will be described, but the invention is not limited to these examples.

[Preparation of laminate]
On one side of a 25 μm thick aluminum foil made of A1N30-O specified in JIS H4160 (2006), a 9 μm thick polyethylene terephthalate resin film (PET) as a reinforced resin layer and a urethane resin adhesive (layer thickness 2 μm). Dry laminated through.
Next, polyethylene resin (PE) was thermally laminated as an adhesive intervening layer on the surface of the polyethylene terephthalate resin film (PET) to a thickness of 20 μm using an extruder.
The amount of polyolefin resin (mass%), the amount of ethylene vinyl acetate copolymer (EVA) (mass%), and wax as shown in the columns of Examples 1 to 4 and Comparative Examples 1 to 8 in Table 1 below. Prepare a hot melt resin having a melting point and amount (mass %), a softening point and amount (mass %) of the tackifier, and a melting point, and apply each hot melt resin to 14 g/m using a gravure roll. It was coated on the surface of a polyethylene resin layer (PE) at a basis weight of ² .
Finally, nitrocellulose (nitrified cotton) was coated on the other side of the aluminum foil as a protective resin layer to a thickness of 5 μm.
In this way, laminates of Examples 1 to 4 and Comparative Examples 1 to 8 were produced.
Further, a laminate was produced in the same manner as in Example 4 except that a polyethylene resin layer (PE) was not formed, and this was designated as Comparative Example 9.

[Creep test]
In order to verify the effect that changes in internal pressure in a sealed package have on the seal between the container and the lid, we conducted the following creep test to confirm the deformation that occurs over time when a constant stress is applied to the seal. .
Referring to FIG. 4, first, each of the laminates of Examples 1 to 4 and Comparative Examples 1 to 9 was cut into a strip shape of 15 mm in width x 50 mm in length to prepare a lid side test piece (A). did.
Further, as a container-side test specimen (B), a polystyrene resin sheet having a thickness of 1 mm was cut into strips having a width of 15 mm and a length of 50 mm.
Then, the lid side test piece (A) and the container side test piece (B) were arranged in series so that their one ends (A1) and (B1) overlapped each other by a length of 10 mm, and both test pieces The overlapping ends (A1) and (B1) of (A) and (B) were heat-sealed using a hot plate under conditions of a sealing temperature of 140° C., a sealing pressure of 0.3 MPa, and a sealing time of 1 second.
Next, after holding and fixing the other end of the container side test piece (B) with a chuck (D), 45gf was applied to the other end of the lid side test piece (A) in an environment of 45°C. A load (P) was applied, and the time until the seal portions (A1) (B1) of both test specimens (A) and (B) peeled off was measured. Note that the maximum measurement time was 60 minutes.
The results are as shown in the column of creep test results in Table 1 above, where "◎" indicates that the sample did not peel off for 60 minutes, "○" indicates that it did not peel off for 50 minutes or more and less than 60 minutes, and "×" indicates peeling in less than 50 minutes.
As is clear from the results in Table 1, in Examples 1 to 4, the time until peeling was sufficiently long, which indicates that the amount of deformation of the seal portion was small. Therefore, it is believed that with the packaging using the lid material made of the laminates of Examples 1 to 4, the seal is less likely to recede even when the internal pressure changes, and the contents are less likely to leak from the seal. It will be done.

This invention relates to a lid material for a container that is heat-sealed to the opening edge of a container filled with beverages, foods, etc., and used to hermetically package the contents, and a container lid material that is used to seal and package the contents. It can be suitably used as a package formed by sealing the contents of food or the like.

(1): Packaging
(2)：Container
(21): Opening edge
(3): Container lid material
(3a): Top wall part
(3b)：Skirt part
(30): Laminate
(31): Aluminum foil layer
(32): Heat sealing layer
(321): Hot melt resin layer
(322): Adhesive intervening layer
(33): Reinforced resin layer
(34): Protective resin layer
(C)：Contents

This invention relates to a container lid material that is heat-sealed to the opening edge of a container filled with beverages, foods, etc. to seal the contents, and a lid material that is used together with the container. The present invention relates to a package formed by sealing the contents of drinks, foods, etc.

For example, thermoplastic resin cups and pouches are commonly used as containers for filling and packaging beverages such as soft drinks, milk drinks, vegetable juices, smoothies, and soups, and semi-solid foods such as jelly, pudding, and yogurt. .
Cups in particular are used as many food containers because they also function as tableware. In the case of a food container made of a cup, after the contents are filled, the container is sealed by heat-sealing a lid material to the opening edge of the container. For the heat sealing layer constituting the innermost layer of the lid, a heat-adhesive resin with relatively high sealing properties is used to prevent contents from leaking from the sealed portion.
Hot melt adhesives are often used as such thermoadhesive resins due to their cost and ease of handling, and various proposals have been made regarding hot melt adhesives.
For example, Patent Document 1 below describes an olefinic polymer (A) having a melt flow rate of 1 to 50 g/10 min at 230°C and 21.18N: 5 to 45% by mass, a melting point of 70°C or higher, and 150°C. Hereinafter, wax (B) having a needle penetration degree of 0.2 to 9 when a load of 100 g is applied for 5 seconds at 25°C: 5 to 30% by mass, and a melting point of 40°C or higher and lower than 70°C and 100°C Wax (C) having a Saybolt universal viscosity of 0.5 to 8 seconds: 35 to 75% by mass (however, the total of the above (A) to (C) is 100% by mass); A heat-melting composition, wherein the difference between the melting point of B) and the melting point of the wax (C) is 20° C. or more, and the total of the wax (B) and the wax (C) is 55 to 95% by mass. is disclosed.

Japanese Patent Application Publication No. 2016-175957

By the way, packages containing food or beverages are generally stored at low temperatures such as in refrigerators, so it is natural that they must have sealing performance at low temperatures, but it is not necessary to fill the contents at room temperature. In some cases, the container is heated and processed after being sealed, and in some cases, the contents are fermented foods.
In such cases, the internal pressure inside the sealed package changes due to temperature changes or the generation of gas from the fermented food, which causes the seal to recede, or the seal to peel, and the contents to leak out. Something happened.
However, in the case of conventional container lid materials, it has been difficult to reliably prevent the seal from retreating due to changes in the internal pressure of the package.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a container lid material that can reliably prevent the seal from retreating due to changes in the internal pressure of the package.

This invention consists of the following aspects in order to achieve the above object.

1) A container lid material that is heat-sealed to the opening edge of the container so as to cover the opening of the container filled with contents,
consisting of a laminate comprising an aluminum foil layer and a heat sealing layer constituted by two or more resin layers including a hot melt resin layer serving as the innermost layer of the container lid material,
The hot melt resin layer contains 5 to 50% by mass of at least one polyolefin resin, 10 to 30% by mass of ethylene vinyl acetate copolymer, 25 to 55% by mass of wax having a melting point of 55 to 115°C, and a softening point of Contains 15 to 30% by mass of a tackifier having a temperature of 120 to 160°C ,
A container lid material , wherein the hot melt resin layer has a melting point of 68 to 85°C .

2) The container lid material of 1) above, wherein the wax has a melting point of 65 to 115°C .

3) The container lid material of 1) or 2) above, wherein the laminate includes a reinforced resin layer interposed between the aluminum foil layer and the heat sealing layer.

4) The reinforced resin layer is composed of a single-layer or multi-layer film made of polyester resin and has a thickness of 5 to 20 μm, and an adhesive is applied to the surface of the aluminum foil layer on the heat-sealing layer side. The container lid material of 3) above, which is laminated with layers interposed therebetween.

5 ) The container lid material according to any one of 1) to 4 ) above, wherein the two or more resin layers constituting the heat sealing layer include an adhesive intervening layer made of a polyolefin resin.

6) The container lid material according to 5) above, wherein the adhesive intervening layer has a thickness of 10 to 40 μm.

7 ) It comprises a container filled with contents, and the container lid material of any one of 1) to 6 ) above, which is heat-sealed to the edge of the opening of the container so as to cover the opening of the container. , packaging.

8 ) The container lid material has a flat top wall portion whose peripheral edge portion is heat-sealed to the upper surface of the opening edge of the container, and a flat top wall portion that extends downward from the peripheral edge portion of the top wall portion and extends part of the height thereof. and a skirt portion heat-sealed to the outer surface of the opening edge of the container.

Here, the melting point of the wax and the melting point of the hot melt resin layer are measured using a differential scanning calorimeter (DSC) at 10° C./min.
Moreover, the softening point of the tackifier is measured in accordance with the provisions of JIS K6863 (1994).

According to the container lid material of 1) above, since a material having the above composition is used as the hot melt resin layer, by heat sealing the lid material to the opening edge of the container filled with contents, Even if the internal pressure of the formed package changes due to deformation of the container or the like immediately after heat sealing, seal regression is unlikely to occur.
In addition, according to the container lid material of 1), since the hot melt resin layer has a melting point of 68 to 85°C, the sealing performance is good even at low sealing temperatures, and furthermore, the container does not deform or the like immediately after heat sealing. Even if the internal pressure of the package increases, seal regression is unlikely to occur.

According to the container lid material of 3) or 4) , the strength is improved by the presence of the reinforced resin layer, so even if the internal pressure or external pressure of the package changes, the lid material will not tear and the contents will not leak out. It becomes difficult to do.

According to the container lid material 5) or 6) , the heat-sealing layer includes an adhesive intervening layer made of polyolefin resin, so that it can be used with containers made of commonly used resins such as polystyrene resin, paper or aluminum foil. Since the sealing performance between the package and the container formed by molding the laminate of the package and the resin layer is improved, even if the internal pressure of the package increases, seal regression is unlikely to occur.

According to the package described in 7 ) above, even if the internal pressure of the container changes due to deformation of the container immediately after heat sealing, it is difficult for the seal to recede in the container lid material, so leakage of contents due to seal receding is prevented. can be reliably prevented.

According to the package described in 8 ) above, a part of the molten resin of the heat sealing layer of the lid body of the container lid material wraps around the outer surface of the opening edge of the container, thereby reducing part of the height of the skirt portion. The sealing area is also heat-sealed to the opening edge of the container to increase the sealing area, so even if the seal recedes, airtightness is maintained.

FIG. 2 is a partially enlarged cross-sectional view showing the layered structure of a laminate that constitutes a container lid material according to an embodiment of the present invention. It shows a lid material for a container formed from the same laminate, in which (a) is a partially cutaway front view, and (b) is a plan view. It is a vertical sectional view showing a package using the same container lid material. FIG. 2 is a schematic diagram showing a method of a creep test in an example.

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 shows the layered structure of a laminate (sheet) (30) constituting a container lid (3) according to the present invention.
The illustrated laminate (30) includes an aluminum foil layer (31), a heat sealing layer (32), and a reinforced resin layer ( 33), and a protective resin layer (34) laminated on the surface of the aluminum foil layer (31) opposite to the heat sealing layer (32).

The aluminum foil layer (31) functions as a barrier layer that provides the lid material (3) with barrier properties against gas, moisture, light, and the like.
As the aluminum foil constituting the aluminum foil layer (31), considering workability and versatility, soft materials (O materials) such as A1N30, A8021, and A8079 specified in JIS H4160 (2006) are preferably used. It will be done.
The thickness of the aluminum foil layer (31) is preferably about 5 to 40 μm in consideration of formability, pinhole occurrence rate, etc.
Preferably, a base layer (not shown) made of a chemical conversion coating is formed on both sides of the aluminum foil layer (31). With such a base layer, the adhesion between the aluminum foil layer (31), the reinforced resin layer (33), and the protective resin layer (34) is improved, and the corrosion resistance of the aluminum foil layer (31) is also improved. .
Specifically, for example, on the surface of the aluminum foil layer (31) that has been subjected to degreasing treatment,
1) Phosphoric acid and
chromic acid and
an aqueous solution of a mixture containing at least one compound selected from the group consisting of metal salts of fluoride and non-metal salts of fluoride; 2) phosphoric acid;
At least one resin selected from the group consisting of acrylic resin, chitosan derivative resin, and phenolic resin,
3) an aqueous solution of a mixture containing at least one compound selected from the group consisting of chromic acid and chromium (III) salts; 3) phosphoric acid;
At least one resin selected from the group consisting of acrylic resin, chitosan derivative resin, and phenolic resin,
At least one compound selected from the group consisting of chromic acid and chromium (III) salts,
An aqueous solution of a mixture containing at least one compound selected from the group consisting of metal salts of fluoride and non-metallic salts of fluoride.After coating an aqueous solution of any one of the above 1) to 3), drying By doing so, a chemical conversion treatment is performed to form a film.
The film formed on the surface of the aluminum foil layer (31) by the chemical conversion treatment, that is, the base layer, preferably has a chromium adhesion amount (per side) of 0.1 mg/m ² to 50 mg/m ² , particularly , 2 mg/m ² to 20 mg/m ² .

The heat sealing layer (32) is for heat sealing the container lid (3) to the opening edge (21) of the container (2). In this embodiment, the heat sealing layer (32) is composed of two resin layers (321) and (322), one of which is a hot melt resin layer (321) that constitutes the innermost layer of the container lid (3). The other is an adhesive intervening layer (322) made of polyolefin resin.

The hot melt resin layer (321) includes 5 to 50% by mass of at least one polyolefin resin, 10 to 30% by mass of ethylene vinyl acetate copolymer (EVA), and 25 to 55% of wax having a melting point of 55 to 115°C. A tackifier having a softening point of 120 to 160° C.: 15 to 30% by mass is used. If the hot melt resin layer (321) having such a composition is used, as will be described later, the internal pressure of the package (1) obtained by using the container lid (3) together with the container (2) will be reduced. Even if the seal changes, it is possible to obtain the effect that seal retraction is unlikely to occur.
Examples of the polyolefin resin include homopolymers such as polyethylene, polypropylene, polybutene, and polyisobutylene, and copolymers of ethylene and olefins such as propylene and 1-butene.
Examples of the wax include paraffin wax, montan wax, ethylene wax, propylene wax, and modified wax obtained by grafting styrene onto a polyethylene/polypropylene copolymer.
Tackifiers include rosins such as rosin and disproportionated rosin, esters of rosins and polyhydric alcohols such as glycol, glycerin and pentaerythritol, and hydrocarbons whose constituent monomers include terpenes and styrene. Examples include resin.
Further, the hot melt resin layer (321) preferably has a melting point of 70 to 85°C, so that even if the internal pressure of the package (1) increases due to deformation of the container immediately after heat sealing, Seal regression is less likely to occur.
The hot melt resin layer (321) is prepared by applying, for example, a hot melt resin having the above composition prepared using a gravure roll onto the surface of the adhesive intervening layer (322), preferably at a basis weight of 12 to 16 g/m ² . After that, it is formed by drying and curing.

The adhesive intervening layer (322) is a layer laminated as a base to make the layer thickness of the hot melt resin layer (321) uniform, and also serves as an adhesive layer during heat sealing. It is preferable that the layer (321) is made of a resin having a melting point close to that of the layer (321), for example, a polyolefin resin such as polyethylene resin (PE) or a compound thereof.
The thickness of the adhesive intervening layer (322) is preferably 10 to 40 μm in order to make the layer thickness of the hot melt resin layer (321) uniform.

The heat sealing layer (32) may be composed of three or more resin layers, for example, by laminating a resin layer containing hydrophobic particles on the outside of the hot melt resin layer (321).

The reinforced resin layer (33) is interposed between the aluminum foil layer (31) and the heat sealing layer (32) to improve the strength of the container lid (3), especially the internal pressure and external pressure of the package (1). This increases the strength against changes in
The reinforced resin layer (33) is composed of a single layer or a multilayer film made of polyester resin such as polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), polyethylene naphthalate resin (PEN), etc., and is made of aluminum. Dry lamination is performed on the surface of the foil layer (31) via an adhesive layer (not shown) made of a urethane resin adhesive or the like.
The thickness of the reinforced resin layer (33) is preferably 5 to 20 μm in consideration of strength and dead hold property to maintain the shape of the skirt portion (3b).

The protective resin layer (34) constitutes the outermost layer of the container lid (3) and has the function of decorating and protecting the lid (3).
The protective resin layer (34) is made of, for example, a polyester resin film such as polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), polyethylene naphthalate resin (PEN), nylon 6 (PA6), nylon 6,6 (PA66), etc. ), single-layer or multi-layer films made of polyamide resin films such as biaxially oriented polypropylene resin films (OPP), stretched polyolefin resin films such as biaxially oriented polypropylene resin films (OPP), and coating films made of thermosetting resins such as nitrified cotton and epoxy resins. It is preferable that there be.
The thickness of the protective resin layer (34) is preferably 2 to 25 μm in consideration of dead hold property and corrosion resistance of the aluminum foil layer (31).
Furthermore, although not shown, a printed layer may be interposed entirely or partially between the protective resin layer (34) and the aluminum foil layer (31).

FIG. 2 shows a container lid material (3) formed from the laminate (30).
The container lid (3) has a flat top wall (3a) having a shape and size that can cover the upper opening of the container (2), and extends downward from the peripheral edge of the top wall (3a). A skirt portion (3b) is provided.
In the illustrated container lid material (3), the top wall portion (3a) is shaped like a disk. The skirt portion (3b) is provided in a hanging shape so as to cover the outer surface of the opening edge (21) of the container (2).
This container lid material (3) can be formed by cutting the laminate (30) into a predetermined shape and size and press-molding the same. The skirt portion (3b) has a large number of vertically extending pleats (3c) formed at intervals in the circumferential direction.

Figure 3 shows a package (1) in which contents (C) consisting of beverages, food, etc. are hermetically packaged using a container (2) and the above-mentioned container lid (3). It is.
The container (2) is cup-shaped with an upward opening, and is made of, for example, a thermoplastic resin molded product such as polystyrene resin. Note that the shape and material of the container (2) are not limited to those described above.
The package (1) is formed by heat-sealing a container lid (3) to the opening edge (21) of a container (2) filled with contents (C).
More specifically, the hot melt resin layer (321) at the peripheral edge of the top wall (3a) of the container lid (3) is heat-sealed onto the upper surface of the opening edge (21) of the container (2). At the same time, the hot melt resin layer (321) on the upper end side of the skirt portion (3b) of the container lid (3) is heat-sealed to the outer surface of the opening edge (21) of the container (2). ing.
Heat sealing methods include thermally welding the hot melt resin layer (321) of the container lid (3) and the opening edge (21) of the container (2) using a hot plate, etc., as well as ultrasonic welding and high frequency welding. It may be welded.

Next, specific examples of the present invention will be described, but the invention is not limited to these examples.

[Preparation of laminate]
On one side of a 25 μm thick aluminum foil made of A1N30-O specified in JIS H4160 (2006), a 9 μm thick polyethylene terephthalate resin film (PET) as a reinforced resin layer and a urethane resin adhesive (layer thickness 2 μm). Dry laminated through.
Next, polyethylene resin (PE) was thermally laminated as an adhesive intervening layer on the surface of the polyethylene terephthalate resin film (PET) to a thickness of 20 μm using an extruder.
The amount of polyolefin resin (mass%), the amount of ethylene vinyl acetate copolymer (EVA) (mass%), and wax as shown in the columns of Examples 1 to 4 and Comparative Examples 1 to 8 in Table 1 below. Prepare a hot melt resin having a melting point and amount (mass %), a softening point and amount (mass %) of the tackifier, and a melting point, and apply each hot melt resin to 14 g/m using a gravure roll. It was coated on the surface of a polyethylene resin layer (PE) at a basis weight of ² .
Finally, nitrocellulose (nitrified cotton) was coated on the other side of the aluminum foil as a protective resin layer to a thickness of 5 μm.
In this way, laminates of Examples 1 to 4 and Comparative Examples 1 to 8 were produced.
Further, a laminate was produced in the same manner as in Example 4 except that a polyethylene resin layer (PE) was not formed, and this was designated as Comparative Example 9.

[Creep test]
In order to verify the effect that changes in internal pressure in a sealed package have on the seal between the container and the lid, we conducted the following creep test to confirm the deformation that occurs over time when a constant stress is applied to the seal. .
Referring to FIG. 4, first, each of the laminates of Examples 1 to 4 and Comparative Examples 1 to 9 was cut into a strip shape of 15 mm in width x 50 mm in length to prepare a lid side test piece (A). did.
Further, as a container-side test specimen (B), a polystyrene resin sheet having a thickness of 1 mm was cut into strips having a width of 15 mm and a length of 50 mm.
Then, the lid side test piece (A) and the container side test piece (B) were arranged in series so that their one ends (A1) and (B1) overlapped each other by a length of 10 mm, and both test pieces The overlapping ends (A1) and (B1) of (A) and (B) were heat-sealed using a hot plate under conditions of a sealing temperature of 140° C., a sealing pressure of 0.3 MPa, and a sealing time of 1 second.
Next, after holding and fixing the other end of the container side test piece (B) with a chuck (D), 45gf was applied to the other end of the lid side test piece (A) in an environment of 45°C. A load (P) was applied, and the time until the seal portions (A1) (B1) of both test specimens (A) and (B) peeled off was measured. Note that the maximum measurement time was 60 minutes.
The results are as shown in the column of creep test results in Table 1 above, where "◎" indicates that the sample did not peel off for 60 minutes, "○" indicates that it did not peel off for 50 minutes or more and less than 60 minutes, and "×" indicates peeling in less than 50 minutes.
As is clear from the results in Table 1, in Examples 1 to 4, the time until peeling was sufficiently long, which indicates that the amount of deformation of the seal portion was small. Therefore, it is believed that with the packaging using the lid material made of the laminates of Examples 1 to 4, the seal is less likely to recede even when the internal pressure changes, and the contents are less likely to leak from the seal. It will be done.

This invention relates to a lid material for a container that is heat-sealed to the opening edge of a container filled with beverages, foods, etc., and used to hermetically package the contents, and a container lid material that is used to seal and package the contents. It can be suitably used as a package formed by sealing the contents of food or the like.

(1): Packaging
(2)：Container
(21): Opening edge
(3): Container lid material
(3a): Top wall part
(3b)：Skirt part
(30): Laminate
(31): Aluminum foil layer
(32): Heat sealing layer
(321): Hot melt resin layer
(322): Adhesive intervening layer
(33): Reinforced resin layer
(34): Protective resin layer
(C)：Contents

Claims (1)

A container lid material that is heat-sealed to the opening edge of the container so as to cover the opening of the container filled with contents,
consisting of a laminate comprising an aluminum foil layer and a heat sealing layer constituted by two or more resin layers including a hot melt resin layer serving as the innermost layer of the container lid material,
The hot melt resin layer contains ethylene vinyl acetate copolymer: 10 to 30% by mass, wax having a melting point of 55 to 115°C: 25 to 55% by mass, and tackifier having a softening point of 120 to 160°C: 15 A container lid material containing ~30% by mass.

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