JP2017056721A - Laminate and lid material made of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminate exhibiting a good easy openability and a lid material made of the same, which can more easily adjust seal strength and achieve both easy openability and sealability.SOLUTION: There are provided: a laminate having a paper substrate layer, an aluminum foil layer, an anchor coating agent layer and a two-layer coextruded heat-sealable resin layer in this order, wherein the two-layer coextruded heat-sealable resin layer is a heat-sealable coextruded resin layer which comprises: a polymer alloy-containing layer composed of a modified polyethylene-based polymer alloy obtained by impregnation-polymerizing a polymerizable aromatic vinyl monomer with a polyethylene resin or a resin composition containing the polymer alloy and an unmodified polyethylene resin; and a low density polyethylene layer and the polymer alloy-containing layer is an innermost layer in contact with the content; and a lid material made of the same.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laminate and a lid material having the easy-openability using the laminate.

2. Description of the Related Art Conventionally, containers having various forms have been developed for filling and packaging various foods and drinks, chemical products such as liquid detergents, cosmetics, pharmaceuticals, miscellaneous goods, industrial members, and the like.
The lid material 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 when consumed, that is, an easy peel property. The
Lids that satisfy this requirement are broadly classified into interfacial peeling types, delamination types, and cohesive failure types, depending on the peeling mechanism. Among these, the cohesive failure type material expresses an easy peel property when the sealant layer (innermost layer) made of a heat-sealable resin causes internal cohesive failure when opened.

The heat-sealable resin constituting the innermost layer that expresses such easy peel properties includes an incompatible polymer alloy obtained by blending polyethylene and polypropylene, and an incompatible polymer alloy obtained by blending polyolefin and polystyrene. Etc. are known (Patent Document 1). In the sealant layer, the polymer alloy has a so-called “sea-island structure” in which a resin having a high component ratio forms a sea and a resin having a low component ratio forms an island. 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 a so-called “stringing phenomenon” is likely to occur in which the resin remains in a fibrous form on the seal peeling surface at the time of opening. In addition, it is difficult to control the seal strength, the paper of the adherend is destroyed when trying to peel off because the seal strength is too strong, or only the paper substrate is peeled off due to delamination of the lid material, There is also a problem that a so-called “paper peeling phenomenon” is likely to occur.
In addition, if the sealing strength is reduced to ensure easy peelability, there is a problem that the sealing performance is impaired.

Japanese Patent No. 3835039

  The present invention solves the above-mentioned problems and is a laminate and a cover material comprising the easy-opening property, the seal strength can be easily adjusted, and both easy-opening and sealing properties are achieved. An object of the present invention is to provide a laminate and a cover material made of the same.

  As a result of intensive studies, the inventor of the present application is 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, and the two-layer coextrusion heat seal The functional resin layer is made of a modified polyethylene polymer alloy obtained by impregnating and polymerizing a polymerizable aromatic vinyl monomer in a polyethylene resin, or a resin composition containing the polymer alloy and an unmodified polyethylene resin. A heat-sealable coextruded resin layer composed of a polymer alloy-containing layer and a low-density polyethylene layer, wherein the polymer alloy-containing layer is the innermost layer in contact with the contents, and the laminate, and a lid material comprising the laminate. The present inventors have 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 layer, an aluminum foil layer, an anchor coating agent layer and a two-layer coextrusion heat-sealable resin layer in this order,
The two-layer coextrusion heat-sealable resin layer is made of a modified polyethylene polymer alloy obtained by impregnating and polymerizing a polyethylene resin with a polymerizable aromatic vinyl monomer,
Alternatively, the polymer alloy and a polymer alloy-containing layer comprising a resin composition containing one or more resins selected from unmodified polyethylene resins, unmodified polystyrene resins, and unmodified polypropylene resins; A heat-sealable coextruded resin layer consisting of a low-density polyethylene layer,
The laminate as described above, wherein the polymer alloy-containing layer is the innermost layer in contact with the contents.
(2) In the above laminate, another base film on the paper base layer side, between the paper base layer and the aluminum foil layer, or between the aluminum foil layer and the anchor coat agent layer. The laminate according to (1) above, having a layer.
(3) The above-mentioned (1) or (2), wherein the polymer alloy-containing layer is heat-sealed by facing a substrate coated with low-density polyethylene on the surface, and the sealing strength is 8 to 25 N / 15 mm width. The laminated body as described in.
(4) A lid member comprising the laminate according to any one of (1) to (3) above.

In the laminate of the present invention, the polymer alloy-containing layer serving as the innermost layer is a layer containing a polyethylene-based polymer alloy modified by impregnating and polymerizing a polymerizable aromatic vinyl monomer into a polyethylene-based resin. This polymer alloy has a small domain size and forms a fine and homogeneous sea-island structure as compared to a conventional polymer alloy simply blended.
The laminate of the present invention having a sealant having such a sea-island structure exhibits excellent easy-opening properties, provides a smooth peel feeling, and hardly causes stringing or paper peeling. Moreover, the control of the sealing strength is easy, the quality hardly varies under various processing conditions, and good sealing performance can be achieved without impairing the easy opening performance.

Furthermore, the laminated body of the present invention hardly deteriorates with time, and can maintain good heat sealability and slipperiness over a long period of time. In addition, it has excellent packaging suitability, excellent sealing properties, hot tack properties, and low temperature sealing properties, and can perform heat sealing in a wide temperature range.
In particular, by coextruding the polymer alloy-containing layer with low-density polyethylene, high burst strength is exhibited and excellent sealing properties as a packaging material are exhibited. This tendency becomes prominent also by blending an unmodified polyethylene resin with the polyethylene polymer alloy of the present invention.
That is, the present invention uses specific finely dispersed particles obtained by impregnating a polymerizable aromatic vinyl monomer in a polyethylene resin particle having a particle size of about 1 to 7 mm as a main component. This is an invention that makes it difficult for the “stretching phenomenon” in which the resin remains in the form of fibers to remain on the seal peeling surface, and also prevents the “paper peeling phenomenon” by controlling the sealing strength and preventing delamination of the lid material.
In addition, it is possible to obtain a laminated body or a lid material that does not impair the sealing performance even if the sealing strength is reduced in order to ensure easy peelability.
Therefore, the laminate of the present invention is particularly suitable as a packaging material for hermetically wrapping contents that are required to maintain a crispy texture over a long period of time, such as snack snacks, and to prevent oxidation of fats and oils. It can be suitably used as a lid for cup-shaped containers.

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

The lid | cover material of this invention is demonstrated in detail below.
Hereinafter, the resin names used in the present invention are those commonly used in the industry. In addition, in this invention, a density is measured from the method based on "JISK7112."

<1> Layer Configuration of Laminate FIG. 1 is a schematic cross-sectional view showing an example of the layer configuration of the laminate 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 coextrusion of a polyethylene layer 4 and a 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 polymer alloy-containing layer 5 side is overlaid so as to face the adherend surface of the container, and heat sealing is performed.
In another aspect, as shown in FIG. 2, the laminate constituting the lid material of the present invention has another base material such as a resin film 7 between the aluminum foil 2 and the anchor coating agent layer 3. May be laminated. Further, although not shown, another substrate may be further laminated between the paper substrate 1 and the aluminum foil 2.
Next, materials constituting the laminate of the present invention, manufacturing methods thereof, and the like will be described.

<2> Paper Base In the present invention, as the paper base, any paper having various formability, flex resistance, rigidity, waist, strength, etc. can be used. Yes, various types of paper such as strong sized bleached or unbleached paper, or pure white roll paper, kraft paper, board paper, processed paper, and milk base paper can be used. The paper base material layer may be obtained by laminating a plurality of layers of these papers. Can be used any of the thickness, for example, basis weight 50 to 100 g / m ^2, preferably a basis weight 70~90g / m ^2. In addition, for example, a desired pattern printing layer such as letters, figures, symbols, and the like can be arbitrarily 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 a paper substrate. Thereby, the odor leakage of the content to the exterior and the penetration | invasion of oxygen and water vapor from the outside can be suppressed, light-shielding property can be provided, and the quality of the content can be prevented.
The thickness of the aluminum foil used suitably is about 6-30 micrometers, Preferably it is about 9-15 micrometers.
In order to laminate an aluminum foil on a paper base material, it can be laminated by a sandwich lamination method through an extruded resin layer. Or you may laminate | stack by the dry lamination method or the wet lamination method through an adhesive bond layer. According to the sandwich lamination method, it is possible to manufacture all in one step through the lamination and winding of the heat sealable resin layer described later.

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, methylpentene A polymer, an acid-modified polyolefin resin, or 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 such as a biaxially stretched polyester resin film, a biaxially stretched polyamide resin film, and two Various resin films such as an axially stretched polyolefin resin film may be laminated. The lamination means may be any method such as a sandwich lamination method or a dry lamination method.

<4> Two-layer coextrusion heat-sealable resin layer A heat-sealable resin layer on the surface opposite to the side on which the paper base of the aluminum foil is laminated, via an isocyanate-based or polyethyleneimine-based anchor coating agent By laminating, the laminate of the present invention can be produced.
In the present invention, the heat-sealable resin layer is a layer formed by coextruding two layers of 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 and becomes the innermost layer in contact with the contents.
By co-extrusion of 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 easy opening, and paper when the lid is opened Peeling can be prevented.

(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 impart cushioning properties to the laminated film. Therefore, even when the cover of the laminate of the present invention has irregularities on the adherend surface of the container, the irregularities are filled and good sealing performance is obtained. In particular, when the adherend is a paper container, it is possible to fill a gap in the joint of the paper container and prevent the seal from being lost.
In the present invention, low density polyethylene refers to those having a density of 0.930 g / cm ³ or less.
The layer thickness of the low-density polyethylene layer can be set as appropriate, but is preferably 20 to 60 μm, more preferably 30 to 50 μm, in order to obtain cushioning properties suitable as a lid.

(Polymer alloy-containing layer)
The polymer alloy-containing layer is located on the outermost surface of the laminate, adheres to the adherend surface of the container, and exhibits easy peel properties due to internal cohesive failure when the lid is opened.
In the present invention, the polymer alloy-containing layer is made of a polyethylene-based polymer alloy modified by impregnating a polymerizable aromatic vinyl monomer with a polyethylene-based resin.
In addition, a polystyrene resin or a polyethylene resin may be added to the polyethylene polymer alloy in order to further improve the fine dispersibility and to prevent the stringing phenomenon to a high degree.
In particular, a modified polyethylene polymer alloy obtained by impregnating and polymerizing a polymerizable styrene monomer into polyethylene resin particles is used to improve the fine dispersibility of a polystyrene resin of the same system as the polymerizable styrene monomer. The added resin composition is preferable.
Examples of the polyethylene resin include an ethylene homopolymer, a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, an ethylene- Examples thereof include a methyl acrylate copolymer, an ethylene-methacrylic acid copolymer, and an ethylene-methyl methacrylate copolymer. An ethylene homopolymer and an ethylene-α olefin copolymer can be particularly preferably used.
Examples of the polymerizable aromatic vinyl monomer include styrenic monomers such as styrene and derivatives thereof such as methyl styrene, isopropyl styrene, cyclohexyl styrene, dodecyl styrene, chlorostyrene, and the like, and mixtures thereof.

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

Furthermore, in the present invention, the polymer alloy-containing layer is formed of unmodified polyethylene-based resin and polystyrene-based resin, respectively, in order to prevent the paper peeling phenomenon by adjusting the sealing strength and extrusion processability. Further, it may be composed of a resin composition obtained by blending polypropylene resins singly or in combination.
Examples of the polyethylene resin used here include an ethylene homopolymer, 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 an ethylene-methyl acrylate copolymer, an ethylene-methacrylic acid copolymer, and an ethylene-methyl methacrylate copolymer. An ethylene homopolymer and an ethylene-α olefin copolymer can be particularly preferably used.

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 of these. In addition, as the polyolefin-based resin as the other component used by mixing, linear low-density polyethylene is used because of its compatibility with the polystyrene-based resin. In addition, low-density polyethylene, high-density polyethylene, polypropylene, polybutene are used. Etc. can also be used.
Examples of polypropylene resins include propylene homopolymers and copolymers of propylene and other olefins. The polypropylene resins may be used alone or in combination of two or more. The copolymer of propylene and another olefin may be a block copolymer or a random copolymer.
Examples of the olefin copolymerized with propylene include α such as ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene and 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.

Polymerization initiators include, but are not limited to, azo compounds such as azobisisothyronitrile, organic peroxides such as lauroyl peroxide, benzoyl peroxide, t-butyl peroxybenzoate, and the like. These 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.
To the extent, generally 0.1 to 2.0% by weight may be added.
The ratio of the polyethylene resin and the polymerizable aromatic vinyl monomer can be appropriately set according to the desired seal strength. For example, in the polymer alloy, the polyethylene resin is 30 to 95% by mass, and the polymerization is performed. The unit derived from the aromatic vinyl monomer is 5 to 70% by mass. More preferably, the polyethylene-based resin is 40 to 70% by mass, and the polymerizable aromatic vinyl monomer-derived unit is 30 to 60% by mass.

If the amount of the aromatic vinyl monomer is too large, the film forming property and the like deteriorate. On the other hand, if the amount of the aromatic vinyl monomer is too small, sufficient easy-openability is not exhibited.
In the modification, the polyethylene resin particles, the aromatic vinyl monomer, and the polymerization initiator are mixed and stirred in an aqueous solvent, and the particles are impregnated with the aromatic vinyl monomer and the polymerization initiator. If necessary, a suspension aid may be added.

After reaching the desired impregnation amount, for example, after impregnation of 70% by mass or more, more preferably 80% by mass or more of the aromatic vinyl monomer, the dispersion is heated to the polymerization temperature. Thereby, a vinyl monomer superposes | polymerizes and the polyethylene-type polymer alloy of this invention is obtained. 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 where the units derived from the aromatic vinyl monomer are graft-polymerized on the polyethylene-based resin and are homogeneously micro-dispersed. Therefore, the layer made of this polymer alloy can be heat-sealed in a wide temperature range, and a suitable sealing strength can be obtained stably. Moreover, since the stress applied at the time of peeling of the cover material is uniformly dispersed, excellent easy-openability is exhibited and a smooth peel feeling can be obtained.

In the present invention, as the polyethylene-based polymer alloy, for example, those commercially available as VMX ^(R) manufactured by Mitsubishi Chemical Corporation can be suitably 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 seal strength, extrusion processability, and the like. The blending amount can preferably be blended within a range in which the polyethylene polymer alloy is 65 to 90% by mass and the unmodified polyethylene resin is 10 to 35% by mass with respect to the total mass of the resin composition. .
The greater the proportion of unmodified polyethylene resin, the higher the sealing strength. However, if the proportion is too large, sufficient easy-openability will not be exhibited. The unmodified polyethylene resin to be blended may be the same as or different from the modified polyethylene resin.

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

<5> Seal strength The laminated body of the present invention exhibits hermeticity and easy-openability suitable as a lid material. In particular, a container coated with polyethylene resin on the innermost surface is superposed and heat-sealed so that the surface on the polymer alloy-containing layer side opposes, and sufficient sealing performance is maintained while maintaining excellent easy-openability. It can be demonstrated. Therefore, the cover material which consists of a laminated body of this invention is applicable to various packaging uses.

For example, cup-shaped paper containers for sealing and packaging snacks and the like are required to have high sealing performance as well as easy opening. 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 of a cup-shaped paper container such as a snack is inferior in airtightness and lacks the storage stability of the contents.
On the other hand, the cover material 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 with a base material coated with polyethylene resin on the innermost surface. If the seal strength is within this range, good easy-openability is exhibited. When the seal strength is greater than 25 N / 15 mm width, a smooth peel feeling cannot be obtained, and the paper peeling phenomenon tends to occur.
In the present invention, the seal strength is a value measured by a method described later.

<6> Lid The laminate of the present invention can be suitably used as a lid for packaging containers.
As packaging containers that serve as adherends, various containers having a surface layer made of polyolefin resin such as polyethylene resin or polypropylene resin, ethylene / methacrylic acid copolymer resin, etc. are used in the opening that is the adherend surface. Can do. For example, cups and trays made of laminated paper obtained by laminating the resin on a paper substrate, a container formed by injection molding or sheet using the resin alone, and a multilayer injection molded container having the resin in the innermost layer or outermost layer Alternatively, it is possible to use a cup-shaped composite container or the like produced by inserting a multilayer sheet molding container or a blank plate into an injection mold and injection molding the resin into an opening such as a flange.

To produce a packaging container using the laminate of the present invention as a lid, the laminate of the present invention is overlaid so that the surface of the polymer alloy-containing layer is in contact with the container opening having the resin layer as the outermost layer, This can be done by heat sealing.
The lid of the present invention is, for example, a lid for a packaging container for sealing contents such as confectionery, instant foods such as cup ramen and cup fried noodles, and particularly as a lid 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 substrate (basis weight 80 g / m ² ) and an aluminum foil (thickness 9 μm) were laminated by a sandwich laminating method through 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 anchor coating agent by a gravure roll coating method to form an anchor coating agent layer.
On the other hand, a polyethylene polymer alloy modified by impregnating and polymerizing a styrene monomer into a polyethylene resin (VMX ^(R) Y80F manufactured by Mitsubishi Chemical Corporation, MFR 5.0 g / 10 min, melting point 112 ° C., styrene monomer-derived unit about 50 parts by mass) and 80 parts by mass of LDPE (Suntech ^(TM) LD M6545: MFR 45.0 g / 10 min, 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 (Sumitomo Chemical ^(R) CE4009: MFR 7.0 g / 10 min, melting point 108 ° C.) and polymer alloy-containing layer on the surface of the anchor coating agent layer of the laminated material obtained above were used. The above resin composition to be formed is laminated by coextrusion coating while performing ozone treatment on the LDPE side so that the layer thickness is 40 μm for the LDPE layer and 10 μm for the polymer alloy-containing layer, and a laminate having the following layer structure is produced. did.
Paper substrate / LDPE / aluminum foil / anchor coating agent / LDPE layer / polymer alloy-containing layer (seal surface) In the present specification, “/” means an interface between layers.

[Example 2]
Polyethylene polymer alloy modified by impregnating and polymerizing a polyethylene resin with a styrene monomer as a polymer alloy-containing layer (VMX ^(R) Y80F manufactured by Mitsubishi Chemical Corporation, MFR 5.0 g / 10 min, melting point 112 ° C.) 65 Example 1 is used except that a resin composition obtained by mixing part by mass and 35 parts by mass of LDPE (Suntech ^(TM) LD M6545: MFR 45.0 g / 10 min, melting point 105 ° C., manufactured by Asahi Kasei Chemicals Corporation) is used. In the same manner as above, a laminate having the following layer structure was produced.
Paper base material / LDPE / Aluminum foil / Anchor coating agent / LDPE layer / Polymer alloy-containing layer (seal surface)

[Example 3]
As a polymer alloy-containing layer, a polyethylene-based polymer alloy (VMX ^(R) Y80F manufactured by Mitsubishi Chemical Corporation, MFR 5.0 g / 10 min, melting point 112 ° C.) modified by impregnating and polymerizing a polyethylene-based resin with a styrene monomer. Otherwise, a laminate having the following layer constitution was produced in the same manner as in Example 1.
Paper base material / LDPE / Aluminum foil / Anchor coating agent / LDPE layer / Polymer alloy-containing layer (seal surface)

[Example 4]
As a polymer alloy-containing layer, a polyethylene-based polymer alloy (VMX ^(R) Y80F manufactured by Mitsubishi Chemical Corporation, MFR 5.0 g / 10 min, melting point 112 ° C.) modified by impregnating and polymerizing a polyethylene-based resin with a styrene monomer. A resin composition in which 85 parts by mass and 15 parts by mass of an ethylene-propylene random copolymer (F232W manufactured by Prime Polymer Co., Ltd .: MFR 2.3 g / 10 min, melting point 135 ° C.) were mixed was used. In the same manner as in Example 1, a laminate having the following layer structure was produced.
Other than that was carried out similarly to Example 1, and manufactured the laminated body of the following layer structure.
Paper base material / LDPE / Aluminum foil / Anchor coating agent / LDPE layer / Polymer alloy-containing layer (seal surface)

[Example 5]
As a polymer alloy-containing layer, a polyethylene-based polymer alloy (VMX ^(R) Y80F manufactured by Mitsubishi Chemical Corporation, MFR 5.0 g / 10 min, melting point 112 ° C.) modified by impregnating and polymerizing a polyethylene-based resin with a styrene monomer. 80 parts by mass and 20 parts by mass of a polystyrene resin copolymer (Asaflex 815 manufactured by Asahi Kasei Chemicals Co., Ltd .: MFR 6.0 g / 10 min, softening point temperature 82 ° C.) are mixed to constitute a polymer alloy-containing layer. A resin composition was prepared.
Other than that was carried out similarly to Example 1, and manufactured the laminated body of the following layer structure.
Paper base material / LDPE / Aluminum foil / Anchor coating agent / LDPE layer / Polymer alloy-containing layer (seal surface)

[Comparative Example 1]
A laminate was produced in the same manner as in Example 1. However, instead of the polymer alloy-containing layer, 18 parts by mass of polybutene-1 (Tafmer ^(R) BL4000: MFR 1.8 g / 10 min, melting point 125 ° C., manufactured by Mitsui Chemicals, Inc.) and LDPE (Asahi Kasei Chemicals Corporation) A resin composition obtained by mixing 82 parts by mass 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 substrate / LDPE / Aluminum foil / Anchor coating agent / LDPE layer / Polybutene-1 / LDPE blend layer (seal surface)

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

(2) Evaluation of sealing performance The laminates manufactured in Examples 1 to 5 and Comparative Example 1 are punched into a circular shape with a diameter of 100 mm and provided with a knob piece on a part of the outer periphery to manufacture a lid material. did.
Prepare the lid material and a paper cup (capacity: 326 cc, diameter: 87 mm) coated with LDPE on the innermost surface with a thickness of 30 μm so that the sealing surface of the lid material faces the flange at the periphery of the opening of the paper cup Using a cup sealer, heat sealing was performed using a cup sealer under a sealing condition 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 rupture strength test of the container defined in JIS Z0238, the pressure (kPa) at the time of rupture (when the heat seal part is opened and air leaks) is measured for each laminate 30 times, and the average value Asked.

(3) Evaluation of unsealed appearance The package sample similar to what was manufactured by evaluation of sealing performance was created, and about each package, the external appearance of the seal part after opening was evaluated visually.
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 had a small variation in burst strength, and all exhibited sufficiently excellent sealing properties. Further, there was no stringing or tearing of the lid material, and the unsealed appearance after peeling was good. Furthermore, a smooth peel feeling was obtained when opened.
On the other hand, the packaging sample using the laminate of Comparative Example 1 had a large variation in burst strength, and the lid material was torn at the time of opening at a rate of 10%.

1. 1. Paper base material 2. Aluminum foil Anchor coating agent layer4. 4. Low density polyethylene layer 5. Polymer alloy-containing layer 6. Heat-sealable resin layer Resin film

Claims (4)

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,
The two-layer coextrusion heat-sealable resin layer is composed of a modified polyethylene polymer alloy obtained by impregnating and polymerizing a polymerizable aromatic vinyl monomer in a polyethylene resin, or the polymer alloy and an unmodified polyethylene resin, A polymer alloy-containing layer comprising a resin composition comprising one or more resins selected from unmodified polystyrene resins and unmodified polypropylene resins;
It is a heat-sealable coextruded resin layer consisting of a low-density polyethylene layer,
The laminate as described above, wherein the polymer alloy-containing layer is the innermost layer in contact with the contents.   In the above laminate, another base film layer is further provided on the paper base layer side surface, between the paper base layer and the aluminum foil layer, or between the aluminum foil layer and the anchor coating agent layer. The laminate according to claim 1.   The laminate according to claim 1 or 2, wherein the polymer alloy-containing layer has a seal strength of 8 to 25 N / 15 mm width when heat-sealing the polymer alloy-containing layer against a substrate coated with low-density polyethylene on the surface.   The cover material which consists of a laminated body of any one of Claims 1-3.

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