JP6750400B2 - 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.
Further, it is difficult to uniformly disperse the domains, and there is a problem that the seal strength and the sealing property are different for each part, and the peeling feeling varies.

Japanese Patent No. 3835039

The present invention solves the above-mentioned problems and provides a laminate and a lid material having good openability, in which the seal strength can be adjusted more easily, the variation is small, and the openability and the sealing property are small. It is an object of the present invention to provide a laminated body and a lid member made of the laminated body, which are compatible with each other and have a stable and smooth opening feeling.

The present inventor, as a result of diligent studies, has revealed that the laminate has a paper substrate layer, an aluminum foil layer, and a two-layer coextrusion heat-sealing resin layer in this order, and the two-layer coextrusion heat-sealing resin layer is A polymer alloy-containing layer comprising a modified polyethylene polymer alloy obtained by impregnating and polymerizing a polyethylene resin with a polymerizable aromatic vinyl monomer, or a resin composition comprising the polymer alloy and an unmodified polypropylene resin. , An ethylene-methacrylic acid copolymer layer is a heat-sealable coextruded resin layer, the polymer alloy-containing layer is the innermost layer in contact with the contents, the laminate, and a lid material made thereof, It has been found that the above problems can be solved.

That is, the present invention is characterized by the following points.
(1) A laminate having a paper base material layer, an aluminum foil layer, and a two-layer coextrusion heat-sealing resin layer in this order, wherein the two-layer coextrusion heat-sealing resin layer is a polyethylene resin and a polymerizable fragrance. It consists of a modified polyethylene-based polymer alloy impregnated with a group vinyl monomer, or is selected from the polymer alloy and unmodified polyethylene-based resin, unmodified polystyrene-based resin, or unmodified polypropylene-based resin. A polymer alloy-containing layer made of a resin composition containing one or more resins,
The above laminate, which is a heat-sealable coextruded resin layer comprising an ethylene-methacrylic acid copolymer layer, wherein the polymer alloy-containing layer is the innermost layer in contact with the contents.
(2) In the above laminate, further on the surface on the paper base layer side, between the paper base layer and the aluminum foil layer, or between the aluminum foil layer and the two-layer coextrusion heat-sealing resin layer, The laminate according to (1) above, which has another substrate film layer.
(3) The seal strength when the polymer alloy-containing layer is heat-sealed while facing a substrate having a low-density polyethylene coated on the surface thereof is 5 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, when the polymer alloy-containing layer is coextruded with an ethylene-methacrylic acid copolymer (EMAA), the burst strength is suppressed, so that when the laminate of the present invention is applied as a lid material, It is possible to prevent the problem that the lid material is torn when the package is opened. Therefore, according to the present invention, there is no need to increase the thickness of the aluminum foil to increase the strength in order to prevent such tearing at the time of opening, and an advantageous effect can be obtained in terms of cost. This tendency becomes remarkable also by blending the polyethylene polymer alloy of the present invention with an unmodified polypropylene 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, since the laminated body of the present invention uses a packaging container as it is as a tableware, such as a cup ramen, it is a packaging for packaging contents in which it is a problem that the torn lid material remains attached to the opening surface. It can be suitably used as a material, particularly as a lid material for a cup ramen container.

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 and a heat sealable resin layer 6, and the heat sealable resin layer 6 comprises an EMAA layer 4 and a polymer alloy containing layer. 2 and 5 are coextruded. An anchor coat agent layer 3 may be provided between the aluminum foil 2 and the heat-sealable resin layer 6 as required.
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 substrate such as a resin film 7 is laminated between the aluminum foil 2 and the EMAA layer 4. You may. 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 6 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 copolymers 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, methylpentene Polymers, acid-modified polyolefin resins and the like 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-sealing resin layer A laminate of the present invention is manufactured by laminating a heat-sealing resin layer on the surface of the aluminum foil opposite to the side on which the paper base material and the like are laminated. be able to. If necessary, for example, in order to prevent delamination at the time of opening when the sealing strength with the container is large, between the aluminum foil and the heat-sealable resin layer, an isocyanate-based or polyethyleneimine-based anchor coating agent is used. May be provided.
In the present invention, the heat-sealable resin layer is a layer formed by co-extruding two layers of the EMAA layer and the polymer alloy-containing layer on the laminated surface of the aluminum foil. Here, the EMAA 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.

(EMAA layer)
The EMAA 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 EMAA which is preferably used, those skilled in the art can arbitrarily determine the proportions of the structural units derived from ethylene and the structural units derived from methacrylic acid, depending on the composition of the polymer alloy-containing layer and the use of the lid material. The greater the proportion of the structural unit derived from methacrylic acid and the greater the number of carboxyl groups contained in this structural unit, the higher the polarity, and the higher the adhesive strength with the aluminum foil. Further, the greater the proportion of the structural unit derived from ethylene, the lower the adhesive strength with the aluminum foil. If necessary, conventional additives such as an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, a flame retardant, and a coloring agent may be added thereto.

The layer thickness of the EMAA 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, and more preferably 30 to 50 μm. If the EMAA layer is too thick, the productivity will deteriorate. On the other hand, if the EMAA layer is too thin, it lacks cushioning properties and cannot follow irregularities on the adherend, for example, seams formed by pasting glue margins of paper containers together.
In the present invention, as the EMAA, for example, Nucrel ^(R) manufactured by Mitsui DuPont Polychemical Co., Ltd. is preferably used.

(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 may be added, for example, in an amount of about 0.01 to 10% by mass, generally 0.1 to 2.0% by mass of the mass of the aromatic vinyl monomer.
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 30 to 70% by mass, and the polymerizable aromatic vinyl monomer-derived unit is 30 to 70% by mass.

If the amount of the aromatic vinyl monomer is too large, the sealing strength, the film forming property, etc. are deteriorated. 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 polypropylene-based resin is appropriately blended in order to adjust the sealing strength, extrusion processability, and the like.
As the polypropylene-based resin, other than the polypropylene resin, propylene is the main component as a monomer unit, and ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1- Resins copolymerized with α-olefins such as octene, 1-nonene and 1-decene can be preferably used. The copolymer may be a binary system, a ternary system, or a quaternary system, and may be a random copolymer or a block copolymer.

The blending amount is preferably such that the polyethylene polymer alloy is 70 to 90 mass% and the polypropylene resin is 10 to 30 mass% with respect to the total mass of the resin composition. The greater the proportion of polypropylene resin, the higher the ease of opening and the lower the sealing strength. However, if the proportion is too large, sufficient sealing cannot be obtained.
The layer thickness of the polymer alloy-containing layer can be set appropriately, 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 instant foods such as cup ramen and cup yakisoba is required to have a seal strength of 5 N/15 mm width or more. If the seal strength is less than 5 N/15 mm width, the lid material for the cup-shaped paper container is inferior in airtightness and the storage stability of the contents is poor.

On the other hand, the lid member made of the laminated body of the present invention can achieve a sealing strength of 5 to 20 N/15 mm width when it is heat-sealed while facing a substrate whose innermost surface is coated with polyethylene resin. More preferably, a seal strength of 5 to 15 N/15 mm width can be achieved. When 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 is, for example, an instant food such as cup ramen or cup yakisoba, as a lid material for a packaging container for sealing contents such as confectionery, in particular, cup-shaped paper for sealing instant food such as cup ramen. It can be suitably used as a lid material for a container.
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: 6 μm) were laminated by a sandwich laminating method using high-pressure low density polyethylene (LDPE, MFR 3.4 g/10 min, thickness: 15 μm).
On the other hand, a polyethylene-based polymer alloy modified by impregnating and polymerizing a styrene monomer into a polyethylene-based resin (VMX ^(R) Y151F manufactured by Mitsubishi Chemical Corporation, MFR 5.5 g/10 minutes, melting point 104° C., unit derived from styrene monomer) (30 mass %) 73 mass parts and a random copolymer of ethylene-propylene (F232W made by Prime Polymer Co., Ltd.: MFR 2.3 g/10 min, melting point 135° C.) 27 mass parts are mixed to form a polymer alloy-containing layer. The constituent resin composition was prepared.

Then, on the surface of the laminated material obtained above on the aluminum foil side, EMAA (Nucrel ^(R) N0908C manufactured by Mitsui DuPont Polychemical Co., Ltd.: MFR 8.0 g/10 min, melting point 99° C.) and a polymer alloy were contained. The resin composition forming the layer was laminated by coextrusion coating so that the layer thickness was 30 μm for the EMAA layer and 10 μm for the polymer alloy-containing layer, to produce a laminate having the following layer structure.
Paper substrate/LDPE/Aluminum foil/EMAA 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 (VMX ^(R) Y151F manufactured by Mitsubishi Chemical Corporation, MFR 5.5 g/10 minutes, melting point 104° C.) modified by impregnating and polymerizing a styrene monomer in a polyethylene-based resin 85 15 parts by mass of a random copolymer of ethylene and propylene (F232W manufactured by Prime Polymer Co., Ltd.: FFR 2.3 g: MFR 2.3 g/10 min, melting point 135° C.) was used, and otherwise, Example 1 was used. A laminate having the following layer structure was produced in the same manner as in.
Paper substrate/LDPE/Aluminum foil/EMAA layer/Polymer alloy containing layer (sealing surface)

[Example 3]
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) Y60F manufactured by Mitsubishi Chemical Corporation, MFR 2.8 g/10 minutes, melting point 112° C., styrene) A monomer-derived unit (about 60% by mass) was used, and otherwise the same as in Example 1 to produce a laminate having the following layer structure.
Paper substrate/LDPE/Aluminum foil/EMAA layer/Polymer alloy containing layer (sealing surface)

[Example 4]
A paper base material (basis weight: 80 g/m ² ) and an aluminum foil (thickness: 6 μm) were laminated by a sandwich laminating method using high-pressure low density polyethylene (LDPE, MFR 3.4 g/10 min, thickness: 15 μm).
On the other hand, a polyethylene-based polymer alloy modified by impregnating and polymerizing a styrene monomer into a polyethylene-based resin (VMX ^(R) Y151F manufactured by Mitsubishi Chemical Corporation, MFR 5.5 g/10 minutes, melting point 104° C., unit derived from styrene monomer) 30 mass%) 85 mass parts,
15 parts by mass of a polystyrene resin copolymer (Asaflex 815 manufactured by Asahi Kasei Chemicals Corporation: MFR 6.0 g/10 min, softening point temperature 82° C.) is mixed to prepare a resin composition forming a polymer alloy-containing layer. did.

[Comparative Example 1]
A laminate and a package sample were manufactured in the same manner as in Example 1. However, instead of the polymer alloy-containing layer, 68 parts by mass of LDPE (Suntech ^(TM) LD M6545 manufactured by Asahi Kasei Chemicals Corporation: MFR 45.0 g/10 minutes, melting point 105° C.) and polybutene-1 (Mitsui Chemicals, Inc.) Tuffmer ⁽ trademark ⁾ BL4000: MFR 1.8 g/10 min, melting point 125° C.) (32 parts by mass) was mixed, and a resin composition was laminated by coextrusion coating with EMAA. The layer structure was as follows.
Paper substrate/LDPE/aluminum foil/EMAA layer/LDPE/polybutene-1 blend layer (sealing surface)

[Evaluation method/result]
(1) Measurement of seal strength The sealing surface of the laminates produced in Examples 1 to 4 and Comparative Example 1 described above and the paper base material coated with LDPE at a thickness of 40 μm are opposed to each other, and the sealing temperature is 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 the above Examples 1 to 4 and Comparative Example 1 were punched into a circular shape having a diameter of 110 mm and a knob piece provided on a part of the outer periphery to produce a lid material. did. The obtained lid member and a paper cup (capacity 500 cc, diameter 100 mm) with LDPE having a thickness of 40 μm coated on the innermost surface were prepared so that the sealing surface of the lid member 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 160° C., a sealing pressure of 300 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 15 times for each laminate, and the average value was measured. I asked.
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 4 showed little variation in burst strength, and all exhibited sufficiently excellent sealing performance. Furthermore, when a package sample similar to the one manufactured by the evaluation of sealing property was prepared and opened, a smooth peel feeling was obtained.
On the other hand, the package sample using the laminate of Comparative Example 1 had large variations in burst strength.

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

Claims (4)

A laminate having a paper base layer, an aluminum foil layer and a two-layer coextrusion heat-sealable 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-sealable coextruded resin layer comprising an ethylene-methacrylic acid copolymer layer,
The layer thickness of the modified polyethylene-based polymer alloy is 5 to 30 μm, or the polymer alloy-containing layer is 5 to 30 μm.
The layer thickness of the ethylene-methacrylic acid copolymer layer is 20 to 60 μm,
The above laminate, wherein the polymer alloy-containing layer is the innermost layer in contact with the contents. In the above-mentioned laminate, on the surface of the paper base material layer side, between the paper base material layer and the aluminum foil layer, or between the aluminum foil layer and the two-layer coextrusion heat-sealing resin layer, another base is further formed. The laminate according to claim 1, which has a material film layer. The laminate according to claim 1 or 2, wherein the polymer alloy-containing layer has a sealing strength of 5 to 20 N/15 mm width when heat-sealed against a substrate having a surface coated with low density polyethylene. A lid member made of the laminate according to claim 1.

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