JP6750399B2 - Laminated body and lid made of the same - Google Patents

Description

The present invention relates to a laminated body and a lid material using the laminated body and having an easy opening property.

BACKGROUND ART Conventionally, containers of various forms have been developed for filling and packaging various kinds of foods and drinks, chemical products such as liquid detergents, cosmetics, pharmaceuticals, miscellaneous goods, and industrial materials.
Further, the lid member that seals the opening of the container is required to have both a sealing property that reliably protects the quality of the contents and an easy-opening property that can be easily opened at the time of consumption, that is, an easy peeling property. It
Lids satisfying this requirement are roughly classified into interfacial peeling type, interlayer peeling type, and cohesive failure type depending on the peeling mechanism. Among these, the cohesive failure type material is one in which the sealant layer (innermost layer) made of a heat-sealable resin exhibits an easy peel property by causing internal cohesive failure at the time of opening.

Examples of the heat-sealable resin that constitutes the innermost layer that exhibits such an easy peeling property include incompatible polymer alloys made by blending polyethylene and polypropylene, and incompatible polymer alloys made by blending polyolefin and polystyrene. Etc. are known (Patent Document 1). The polymer alloy has a so-called "sea-island structure" in which a resin having a high component ratio forms the sea and a resin having a low component ratio forms an island in the sealant layer. Here, domains made of resin forming islands are dispersed in the resin phase forming sea.
However, these conventional heat-sealable resins have a problem that the resin is liable to remain in a fibrous state on the seal peeling surface at the time of opening, that is, a so-called "stringing phenomenon" easily occurs. Further, it is difficult to control the seal strength, and when the peel strength is too strong, the paper of the adherend is destroyed, or the interlayer separation of the lid material occurs, and only the paper base material is peeled off. There is also a problem that the so-called "paper peeling phenomenon" is likely to occur.
Further, if the seal strength is reduced in order to secure the easy peeling property, there is a problem that the sealing property is impaired.

Japanese Patent No. 3835039

The present invention solves the above-mentioned problems, and is a laminate showing a good easy-opening property and a lid member made of the same, in which it is easier to adjust the sealing strength, and both the easy-opening property and the sealing property are compatible. It is an object of the present invention to provide a laminate that can be processed and a lid material made of the same.

As a result of earnest studies, the inventors of the present application have found that a laminate having a paper base layer, an aluminum foil layer, an anchor coating agent layer, and a two-layer coextrusion heat-sealable resin layer in this order is the two-layer coextrusion heat seal. The resin layer is made of a modified polyethylene-based polymer alloy obtained by impregnating a polyethylene-based resin with a polymerizable aromatic vinyl monomer for polymerization, or a resin composition containing the polymer alloy and an unmodified polyethylene-based resin. A polymer alloy-containing layer and a heat-sealable coextruded resin layer comprising a low-density polyethylene layer, wherein the polymer alloy-containing layer is the innermost layer in contact with the content, the above laminate, and a lid member made of the same. , And found to solve the above problems.

That is, the present invention is characterized by the following points.
(1) A laminate having a paper base layer, an aluminum foil layer, an anchor coating agent layer, and a two-layer coextrusion heat-sealing resin layer in this order,
The two-layer coextrusion heat-sealable resin layer is composed of a modified polyethylene-based polymer alloy obtained by impregnating a polyethylene-based resin with a polymerizable aromatic vinyl monomer for polymerization.
Alternatively, a polymer alloy-containing layer comprising a resin composition containing the polymer alloy and one or more resins selected from unmodified polyethylene resin, unmodified polystyrene resin, and unmodified polypropylene resin. , A heat-sealing coextruded resin layer consisting of a low-density polyethylene layer,
The above laminate, wherein the polymer alloy-containing layer is the innermost layer in contact with the contents.
(2) In the above laminate, another substrate film is provided on the surface of the paper substrate layer side, between the paper substrate layer and the aluminum foil layer, or between the aluminum foil layer and the anchor coating agent layer. The laminate according to (1) above, which has a layer.
(3) The sealing strength when the polymer alloy-containing layer is heat-sealed while facing a base material coated with low density polyethylene on the surface thereof is 8 to 25 N/15 mm width, (1) or (2) above The laminated body according to.
(4) A lid member comprising the laminate according to any one of (1) to (3) above.

In the layered product of the present invention, the innermost polymer alloy-containing layer is a layer containing a polyethylene-based polymer alloy modified by impregnating and polymerizing a polyethylene-based resin with a polymerizable aromatic vinyl monomer. This polymer alloy has a small domain size and forms a fine and uniform sea-island structure, as compared with a conventional polymer alloy which is simply blended.
The laminate of the present invention having the sealant having such a sea-island structure exhibits excellent easy-opening property, a smooth peel feeling is obtained, and stringing and paper peeling hardly occur. In addition, the control of the seal strength is easy, the quality is unlikely to vary under various processing conditions, and good sealability can be achieved without impairing the easy-open property.

Furthermore, the laminate of the present invention is less likely to deteriorate with time and can maintain good heat-sealing properties and slipperiness over a long period of time. In addition, it has excellent packaging suitability, excellent contamination sealing property, hot tack property, and low temperature sealing property, and can perform heat sealing in a wide temperature range.
Further, in particular, by co-extruding the polymer alloy-containing layer with low-density polyethylene, high burst strength is exhibited, and excellent sealing property as a packaging material is exhibited. This tendency becomes remarkable also by blending the polyethylene polymer alloy of the present invention with an unmodified polyethylene resin.
That is, the present invention uses specific finely dispersed particles obtained by impregnating and polymerizing a polymerizable aromatic vinyl monomer into particles of a polyethylene resin having a particle size of about 1 to 7 mm as a main component, thereby making The present invention makes it difficult to cause the "threading phenomenon" in which the resin remains in a fibrous state on the seal peeling surface, and to prevent the "paper peeling phenomenon" by controlling the seal strength and preventing delamination of the lid material.
Further, it is possible to obtain a laminated body or a lid member in which the sealing property is not impaired even if the sealing strength is reduced to secure the easy peeling property.
Therefore, the laminate of the present invention, such as snacks, maintaining a crispy texture for a long period of time, or as a packaging material for hermetically packaging the contents required to prevent the oxidation of fats and oils, It can be preferably used as a lid material for cup-shaped containers.

It is a schematic sectional drawing which shows an example about the layer structure of the laminated body which comprises the cover material of this invention. It is a schematic sectional drawing which shows an example about the layer structure of the laminated body which comprises the cover material of this invention.

The lid material of the present invention will be described in detail below.
Hereinafter, the resin names used in the present invention are those commonly used in the industry. In the present invention, the density is measured by a method based on “JIS K7112”.

<1> Layer Structure of Laminated Body FIG. 1 is a schematic cross-sectional view showing an example of the layer structure of the laminated body of the present invention.
As shown in FIG. 1, the laminate of the present invention comprises a paper substrate 1, an aluminum foil 2, an anchor coating agent layer 3, and a heat-sealable resin layer 6, and the heat-sealable resin layer 6 has a low density. It is a layer formed by coextruding two layers of the polyethylene layer 4 and the polymer alloy-containing layer 5. In order to seal the container using the lid member made of the laminate of the present invention, the adhesive surface on the side of the polymer alloy-containing layer 5 is superposed so as to face the adherend surface of the container, and heat sealed.
In another embodiment, as shown in FIG. 2, the laminate constituting the lid member of the present invention is such that another base material such as a resin film 7 is provided between the aluminum foil 2 and the anchor coating agent layer 3. May be laminated. Further, although not shown, another substrate may be laminated between the paper substrate 1 and the aluminum foil 2.
Next, materials constituting the laminated body of the present invention, manufacturing methods thereof, and the like will be described.

<2> Paper Base Material In the present invention, as the paper base material, any paper having various shapeability, bending resistance, rigidity, stiffness, strength, etc. can be used. It is possible to use strong size bleached or unbleached paper, or various types of paper such as pure white roll paper, kraft paper, paperboard, processed paper, and milk base paper. The paper base material layer may be formed by laminating a plurality of layers of these papers and laminating them. An arbitrary thickness can be used, but the basis weight is, for example, 50 to 100 g/m ² , and preferably the basis weight is 70 to 90 g/m ² . It should be noted that a desired pattern printing layer such as letters, figures, and symbols can be optionally formed on the surface of the paper base opposite to the side on which the aluminum foil is laminated. A surface protective layer made of nitrified cotton or the like may be provided.

<3> Aluminum foil An aluminum foil is laminated on one surface of the paper base material. As a result, it is possible to prevent the odor from leaking the contents to the outside and the invasion of oxygen and water vapor from the outside, to impart a light-shielding property, and prevent the contents from being altered.
The thickness of the aluminum foil preferably used is about 6 to 30 μm, preferably about 9 to 15 μm.
The aluminum foil can be laminated on the paper base material by a sandwich laminating method with an extruded resin layer interposed therebetween. Alternatively, they may be laminated by a dry laminating method or a wet laminating method via an adhesive layer. According to the sandwich laminating method, it is possible to manufacture the heat-sealing resin layer, which will be described later, in a single step, including lamination and winding.

Suitable extruded resins include, for example, low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear (linear) low-density polyethylene, and ethylene-α-olefin copolymer polymerized using a metallocene catalyst. Polymer, polypropylene, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-propylene copolymer, methyl pentene Polymers, acid-modified polyolefin resins, etc. can be used. The thickness of the extruded resin layer is 5 to 40 μm, preferably 15 to 30 μm.

In another embodiment of the present invention, a further base material, for example, a biaxially stretched polyester resin film, a biaxially stretched polyamide resin film, and Various resin films such as an axially stretched polyolefin resin film may be laminated. The laminating means may be any method such as a sandwich laminating method and a dry laminating method.

<4> Two-layer coextrusion heat-sealable resin layer A heat-sealable resin layer is provided on the surface of the aluminum foil opposite to the side on which the paper base material and the like are laminated, via an anchor coating agent such as isocyanate or polyethyleneimine. The laminated body of the present invention can be manufactured by laminating.
In the present invention, the heat-sealable resin layer is a layer formed by co-extruding two layers, a low-density polyethylene layer and a polymer alloy-containing layer, on the laminated surface of the aluminum foil. Here, the low-density polyethylene layer is located on the side facing the aluminum foil, and the polymer alloy-containing layer is located on the outermost surface of the laminate, which is the innermost layer in contact with the contents.
By coextruding the two layers in this order, high interlaminar adhesion strength is obtained, and internal cohesive failure of the polymer alloy-containing layer proceeds smoothly, resulting in excellent ease of opening, and paper for opening the lid material. It can prevent peeling.

(Low density polyethylene layer)
The low-density polyethylene layer is located between the aluminum foil and the polymer alloy-containing layer to enhance the adhesion between the layers, and further imparts cushioning properties to the laminated film. Therefore, the lid member made of the laminated body of the present invention can fill the irregularities on the adherend surface of the container to obtain good sealing property. In particular, when the adherend is a paper container, it is possible to prevent the seal from coming off by filling the step of the joint between the paper containers.
In the present invention, low-density polyethylene refers to one having a density of 0.930 g/cm ³ or less.
The layer thickness of the low-density polyethylene layer can be appropriately set, but in order to obtain a cushioning property suitable as a lid material, it is preferably 20 to 60 μm, more preferably 30 to 50 μm.

(Polymer alloy containing layer)
The polymer alloy-containing layer is a layer which is located on the outermost surface of the laminate and adheres to the adherend surface of the container, and exhibits an easy peeling property due to internal cohesive failure when the lid member is opened.
In the present invention, the polymer alloy-containing layer comprises a polyethylene-based polymer alloy modified by impregnating and polymerizing a polyethylene resin with a polymerizable aromatic vinyl monomer.
Further, a polystyrene resin or a polyethylene resin may be added to the polyethylene polymer alloy in order to further improve the fine dispersibility and highly prevent the stringing phenomenon.
And, in particular, in order to improve the fine dispersibility, the modified polyethylene polymer alloy obtained by impregnating the particles of the polyethylene resin with the polymerizable styrene monomer is polymerized with the polystyrene resin of the same system as the polymerizable styrene monomer. The added resin composition is preferable.
Examples of the polyethylene resin include ethylene homopolymers, copolymers of ethylene and α-olefins having 3 to 20 carbon atoms, ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, ethylene- Examples thereof include a methyl acrylate copolymer, an ethylene-methacrylic acid copolymer, an ethylene-methyl methacrylate copolymer and the like. An ethylene homopolymer and an ethylene-α olefin copolymer can be particularly preferably used.
Examples of the polymerizable aromatic vinyl monomer include styrene-based monomers, such as styrene and its derivatives, such as methylstyrene, isopropylstyrene, cyclohexylstyrene, dodecylstyrene, chlorostyrene, and the like, and mixtures thereof.

The modification is carried out by reacting polyethylene resin particles (for example, particles having a particle size of about 1 to 7 mm), a polymerizable aromatic vinyl monomer and a polymerization initiator in an aqueous suspension to form a polymerizable aromatic vinyl in the particles. It can be carried out by impregnating and polymerizing the monomer.
The modified olefin polymer obtained by the impregnation polymerization is of a type in which a polymerizable aromatic vinyl monomer is embedded and polymerized in a chain polyethylene resin, a type in which a polymerizable aromatic vinyl monomer is graft-polymerized, or styrene. Three types of polymerization type are synthesized simultaneously in parallel.
That is, it is considered that the olefin polymer contains a polymer from a uniformly dispersed vinyl monomer, or the vinyl monomer is grafted onto the olefin polymer, or a mixture thereof. The polymer particles of 1) do not exist separately from the olefin polymer.
Therefore, these are considered to be one type of resin with different polymerization rates in which many resins with different ratios of ethylene and styrene are present at the same time, and therefore have good compatibility with polyethylene resins and polyethylene resins. is there.

Further, in the present invention, the polymer alloy-containing layer is an unmodified polyethylene-based resin or polystyrene-based resin in each of the polyethylene-based polymer alloys described above in order to prevent paper peeling phenomenon by adjusting seal strength and extrusion processability. The polypropylene resin may be a resin composition obtained by blending the polypropylene resins alone or in an appropriate combination.
The polyethylene resin used here is an ethylene homopolymer, and a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, Examples thereof include ethylene-methyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer and the like. An ethylene homopolymer and an ethylene-α olefin copolymer can be particularly preferably used.

Further, the polystyrene resin is a block copolymer of styrene and butadiene, a hydrogenated product of a block copolymer of styrene and butadiene, high-impact polystyrene, general-purpose polystyrene, or a blend of two or more thereof. As the polyolefin-based resin as another component to be mixed and used, linear low-density polyethylene is used because of its compatibility with the polystyrene-based resin, but low-density polyethylene, high-density polyethylene, polypropylene and polybutene are also used. Etc. can also be used.
Examples of the polypropylene resin include propylene homopolymer and copolymers of propylene and other olefins. The polypropylene resin may be used alone or in combination of two or more kinds. The copolymer of propylene and other olefin may be either a block copolymer or a random copolymer.
And as an olefin copolymerized with propylene, for example, α such as ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene. -Olefin and the like.
Specifically, propylene homopolymer, propylene-ethylene copolymer, propylene-butene-1 copolymer, propylene-ethylene-butene-1 copolymer, ethylene-propylene block copolymer, metallocene catalyst-based polypropylene, etc. Is mentioned.

Examples of the polymerization initiator include, but are not limited to, azo compounds such as azobisisotyronitrile, organic peroxides such as lauroyl peroxide, benzoyl peroxide, and t-butylperoxybenzoate, but are not limited thereto. Various polymerization initiators can be used. The polymerization initiator is, for example, 0.01 to 10% by mass of the mass of the aromatic vinyl monomer.
It may be added in an amount of about 0.1 to 2.0% by mass.
The proportion of the polyethylene-based resin and the polymerizable aromatic vinyl monomer can be appropriately set according to the desired seal strength, but for example, the polyethylene-based resin is 30 to 95 mass% in the polymer alloy, The amount of the aromatic vinyl monomer-derived unit is 5 to 70% by mass. More preferably, the polyethylene resin is 40 to 70% by mass, and the polymerizable aromatic vinyl monomer-derived unit is 30 to 60% by mass.

When the amount of the aromatic vinyl monomer is too large, the film forming property and the like deteriorate. On the contrary, if the amount of the aromatic vinyl monomer is too small, the sufficient easy-opening property cannot be exhibited.
Upon modification, the polyethylene resin particles, the aromatic vinyl monomer and the polymerization initiator are mixed and stirred in an aqueous solvent to impregnate the particles with the aromatic vinyl monomer and the polymerization initiator. Suspension aids may be added if desired.

After reaching the desired impregnation amount, for example, 70% by mass or more, more preferably 80% by mass or more of the aromatic vinyl monomer is impregnated, and then the dispersion liquid is heated to the polymerization temperature. As a result, the vinyl monomer is polymerized to obtain the polyethylene-based polymer alloy of the present invention. The polymerization temperature is appropriately set according to the type of polymerization initiator used.
The polyethylene-based polymer alloy thus obtained exists in a state in which the aromatic vinyl monomer-derived unit is graft-polymerized with the polyethylene-based resin and in a state of being uniformly microdispersed. Therefore, the layer made of this polymer alloy can be heat-sealed in a wide temperature range, and stable and suitable sealing strength can be obtained. Further, since the stress applied when the lid member is peeled off is uniformly dispersed, excellent openability is exhibited and a smooth peel feeling is obtained.

In the present invention, as the polyethylene-based polymer alloy, for example, a commercially available product as VMX ^(R) manufactured by Mitsubishi Chemical Corporation can be preferably used.
The polyethylene-based polymer alloy may be used as a resin composition in which an unmodified polyethylene-based resin is appropriately blended in order to adjust sealing strength, extrusion processability and the like. The blending amount is preferably such that the polyethylene polymer alloy is 65 to 90 mass% and the unmodified polyethylene resin is 10 to 35 mass% with respect to the total mass of the resin composition. ..
The larger the proportion of the unmodified polyethylene resin, the higher the sealing strength, but if it is too large, the sufficient easy-opening property is not exhibited. The unmodified polyethylene-based resin to be blended may be the same as or different from the modified polyethylene-based resin.

The layer thickness of the polymer alloy-containing layer can be appropriately set, but in order to obtain stable easy opening and sealing properties, it is preferably 5 to 30 μm, more preferably 10 to 20 μm. If the polymer alloy-containing layer is too thin, the seal strength becomes unstable. On the contrary, if it is too thick, stringing may occur during peeling, which is not preferable.

<5> Seal strength The laminate of the present invention exhibits a sealing property and an easy opening property suitable as a lid material. In particular, a container coated with a polyethylene resin on the innermost surface is laminated so that the surfaces on the polymer alloy-containing layer side face each other, and heat-sealed, thereby maintaining sufficient easy-opening property while maintaining excellent easy-opening property. Can be demonstrated. Therefore, the lid member made of the laminate of the present invention can be applied to various packaging applications.

For example, a cup-shaped paper container for hermetically packaging snacks and the like is required to have easy opening and high hermeticity. Specifically, a seal strength of 8 N/15 mm width or more, and in some cases 13 N/15 mm width or more is required. When the sealing strength is less than 8 N/15 mm width, the lid material for cup-shaped paper containers such as snacks is inferior in airtightness, and the storability of the contents is poor.
On the other hand, the lid member made of the laminate of the present invention can achieve a sealing strength of 8 to 25 N/15 mm width when it is heat-sealed while facing the base material whose innermost surface is coated with polyethylene resin. If the seal strength is within this range, good easy-opening property is exhibited. When the seal strength is more than 25 N/15 mm width, a smooth peeling feeling cannot be obtained, and the paper peeling phenomenon easily occurs.
In the present invention, the seal strength is a value measured by the method described below.

<6> Lid Material The laminate of the present invention can be suitably used as a lid material for packaging containers.
As the packaging container that becomes the adherend, use various containers that have a surface layer made of a polyolefin resin such as polyethylene resin or polypropylene resin or ethylene/methacrylic acid copolymer resin in the opening that becomes the adherend surface. You can For example, a cup or tray made of laminated paper in which the resin is laminated on a paper substrate, a container that is injection-molded or sheet-molded by using the resin alone, and a multilayer injection-molded container having the resin in the innermost layer or the outermost layer. Alternatively, it is possible to use a multi-layer sheet molding container, a cup-shaped composite container produced by inserting a blank plate into an injection molding die, and injection molding the above resin into an opening such as a flange.

To produce a packaging container using the laminate of the present invention as a lid material, the container opening having a resin layer as the outermost layer is laminated with the laminate of the present invention so that the surface of the polymer alloy-containing layer is in contact with the container opening. It can be performed by heat sealing.
The lid material of the present invention, for example, as a lid material for a packaging container for sealing the contents of instant foods such as confectionery, cup ramen and cup yakisoba, in particular, as a lid material for a cup-shaped paper container for sealing snacks. , Can be preferably used.
Next, the present invention will be specifically described with reference to examples.

[Example 1]
A paper base material (basis weight 80 g/m ² ) and an aluminum foil (thickness 9 μm) were laminated by a sandwich laminating method using a high-pressure low-density polyethylene (LDPE, MFR 3.4 g/10 min, thickness 25 μm).
Next, the surface of the laminated material obtained above on the aluminum foil side was coated with a polyurethane-based anchor coating agent by a gravure roll coating method to form an anchor coating agent layer.
On the other hand, a polyethylene-based polymer alloy modified by impregnating and polymerizing a styrene monomer in a polyethylene-based resin (VMX ^(R) Y80F manufactured by Mitsubishi Kagaku Co., Ltd., MFR 5.0 g/10 minutes, melting point 112° C., unit derived from styrene monomer) 50 parts by mass) and 20 parts by mass of LDPE (Suntech ^(TM) LD M6545: MFR 45.0 g/10 minutes, melting point 105° C., manufactured by Asahi Kasei Chemicals Corporation) are mixed to form a polymer alloy-containing layer. A resin composition was prepared.

Next, LDPE (Sumikasen ^(R) CE4009: MFR 7.0 g/10 min, melting point 108° C.) manufactured by Sumitomo Chemical Co., Ltd. and a polymer alloy-containing layer were formed on the surface of the anchor coating agent layer of the laminated material obtained above. The resin composition to be formed is laminated by coextrusion coating while subjecting the LDPE side to ozone treatment so that the layer thickness is 40 μm for the LDPE layer and 10 μm for the polymer alloy-containing layer, to produce a laminate having the following layer structure. did.
Paper substrate/LDPE/aluminum foil/anchor coating agent/LDPE layer/polymer alloy-containing layer (sealing surface) In the present specification, “/” means an interface between layers.

[Example 2]
As the polymer alloy-containing layer, a polyethylene-based polymer alloy modified by impregnating and polymerizing a styrene monomer in a polyethylene-based resin (VMX ^(R) Y80F manufactured by Mitsubishi Chemical Corporation, MFR 5.0 g/10 minutes, melting point 112° C.) 65 A resin composition in which 35 parts by weight of LDPE (Suntech ^(TM) LD M6545 manufactured by Asahi Kasei Chemicals Corporation: MFR 45.0 g/10 minutes, melting point 105° C.) is mixed is used, and otherwise, Example 1 is used. A laminate having the following layer structure was produced in the same manner as in.
Paper substrate/LDPE/aluminum foil/anchor coating agent/LDPE layer/polymer alloy containing layer (sealing surface)

[Example 3]
As the polymer alloy-containing layer, a polyethylene-based polymer alloy (VMX ^(R) Y80F manufactured by Mitsubishi Chemical Corporation, MFR 5.0 g/10 minutes, melting point 112° C.) modified by impregnating and polymerizing a styrene monomer in a polyethylene-based resin is used. A laminate having the following layer structure was produced in the same manner as in Example 1 except that the above components were used.
Paper substrate/LDPE/aluminum foil/anchor coating agent/LDPE layer/polymer alloy containing layer (sealing surface)

[Example 4]
As the polymer alloy-containing layer, a polyethylene-based polymer alloy (VMX ^(R) Y80F manufactured by Mitsubishi Chemical Corporation, MFR 5.0 g/10 minutes, melting point 112° C.) modified by impregnating and polymerizing a styrene monomer in a polyethylene-based resin is used. A resin composition was used in which 85 parts by mass and 15 parts by mass of a random copolymer of ethylene-propylene (F232W manufactured by Prime Polymer Co., Ltd.: MFR 2.3 g/10 min, melting point 135° C.) were used, and the other examples were used. A laminate having the following layer structure was produced in the same manner as in 1.
A laminate having the following layer structure was produced in the same manner as in Example 1 except for the above.
Paper substrate/LDPE/aluminum foil/anchor coating agent/LDPE layer/polymer alloy containing layer (sealing surface)

[Example 5]
As the polymer alloy-containing layer, a polyethylene-based polymer alloy (VMX ^(R) Y80F manufactured by Mitsubishi Chemical Corporation, MFR 5.0 g/10 minutes, melting point 112° C.) modified by impregnating and polymerizing a styrene monomer in a polyethylene-based resin is used. 80 parts by mass and 20 parts by mass of a polystyrene resin copolymer (Asaflex 815 manufactured by Asahi Kasei Chemicals Corporation: MFR 6.0 g/10 minutes, softening point temperature 82° C.) are mixed to form a polymer alloy-containing layer. A resin composition was prepared.
A laminate having the following layer structure was produced in the same manner as in Example 1 except for the above.
Paper substrate/LDPE/aluminum foil/anchor coating agent/LDPE layer/polymer alloy containing layer (sealing surface)

[Comparative Example 1]
A laminated body was manufactured in the same manner as in Example 1. However, instead of the polymer alloy-containing layer, 18 parts by mass of polybutene-1 (Tufmer ^(R) BL4000: MFR 1.8 g/10 min, melting point 125° C., manufactured by Mitsui Chemicals, Inc.) and LDPE (manufactured by Asahi Kasei Chemicals Co., Ltd.) 82 parts by weight of Suntec ^(TM) LDM6545: MFR 45.0 g/10 min, melting point 105° C.) was laminated by coextrusion coating with LDPE. The layer structure was as follows.
Paper base material/LDPE/Aluminum foil/Anchor coating agent/LDPE layer/Polybutene-1 LDPE blend layer (sealing surface)

[Evaluation method/result]
(1) Measurement of seal strength The sealing surface of the laminates produced in the above Examples 1 to 5 and Comparative Example 1 and the paper base material having the surface coated with LDPE at a thickness of 30 μm were opposed to each other, and the sealing temperature was 160°C. A sample was prepared by heat sealing under the sealing conditions of a sealing pressure of 98 kPa and a sealing time of 1.0 second.
A 15 mm wide strip-shaped test piece was cut out from this sample, and using a tensile tester, at a peeling angle of 180° and a pulling speed of 300 mm/min, the sealing strength (N/15 mm width) was 5 times for each laminate. It measured and calculated|required the average value.

(2) Evaluation of Sealability The laminates produced in Examples 1 to 5 and Comparative Example 1 were punched into a circular shape having a diameter of 100 mm and a knob piece provided on a part of the outer periphery to produce a lid material. did.
Prepare the obtained lid material and a paper cup (capacity: 326 cc, diameter 87 mm) coated with LDPE at a thickness of 30 μm so that the sealing surface of the lid material faces the flange portion around the opening of the paper cup. They were stacked and heat-sealed using a cup sealer under the sealing conditions of a sealing temperature of 165° C., a sealing pressure of 200 kPa, and a sealing time of 1.0 second to produce a package sample.
According to the container burst strength test specified in JIS Z0238, the pressure (kPa) at the time of bursting (at the time when the heat-sealed portion was opened and air leakage occurred) was measured 30 times for each laminate, and the average value was measured. I asked.

(3) Evaluation of Opening Appearance A package sample similar to the one produced in the evaluation of sealing property was prepared, and the external appearance of the sealed part of each package was visually evaluated.
The results are shown in Table 1 below.

As is clear from the results shown in Table 1, the package samples using the laminates of Examples 1 to 5 showed little variation in burst strength, and all exhibited sufficiently excellent hermeticity. Further, there was no stringing or tearing of the lid material, and the appearance of opening after peeling was good. Furthermore, a smooth peeling feeling was obtained when opening.
On the other hand, in the package sample using the laminated body of Comparative Example 1, the variation in burst strength was large, and tearing of the lid material occurred at the rate of 10% during opening.

1. Paper base 2. Aluminum foil 3. Anchor coat agent layer 4. Low density polyethylene layer 5. Polymer alloy containing layer 6. Heat sealable resin layer 7. Resin film

Claims (3)

A laminate having a paper base layer, an aluminum foil layer, an anchor coating agent layer, and a two-layer coextrusion heat-sealing resin layer in this order,
The two-layer coextrusion heat-sealable resin layer is composed of a modified polyethylene-based polymer alloy obtained by impregnating and polymerizing a polymerizable aromatic vinyl monomer into a polyethylene-based resin, or the polymer alloy and an unmodified polyethylene-based resin, A polymer alloy-containing layer made of a resin composition containing one or more resins selected from unmodified polystyrene resin and unmodified polypropylene resin;
A heat-sealing coextruded resin layer composed of a low-density polyethylene layer,
The polymer alloy containing layer, Ri innermost layer der in contact with the contents,
The layer thickness of the low density polyethylene layer is 20 to 60 μm,
The layer thickness of the polymer alloy-containing layer is 5 to 30 μm,
The above laminate. The laminate according to claim 1, wherein the polymer alloy-containing layer has a sealing strength of 8 to 25 N/15 mm width when heat-sealed against a substrate having a surface coated with low-density polyethylene. Lid comprising a laminate according to claim 1 or 2.

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