JP2020185711A - Laminated sheet and paper container - Google Patents

Abstract

To provide a paper container capable of relaxing bubbling and pinhole phenomena generated by the evaporation of water content included in a paper layer when melting and bonding a laminated sheet in molding a container to suppress liquid leakage, etc. due to the phenomena.SOLUTION: The laminated sheet is sequentially laminated with at least the outermost layer, a paper layer, an adhesive resin layer, a barrier film layer and a sealant layer. The adhesive resin layer consists of a two layer structure formed by laminating polyethylene on the paper layer side and a copolymer of ethylene unsaturated carboxylic acid or an ester compound thereof on the barrier film layer side by a co-extrusion lamination method. The difference of melt flow rates (MFR) according to the JIS K6760 measuring method between the copolymer of the ethylene unsaturated carboxylic acid or the ester compound thereof and the polyethylene is within 8 g/10 min, and the polyethylene in the adhesive resin layer has 1.20 N/15 mm or more of a cohesion failure strength in an environment at 100°C specified by JIS Z0238.SELECTED DRAWING: Figure 1

Description

The present invention relates to a paper container containing a liquid such as a beverage or alcohol, or a powdery or granular solid such as rice or wheat flour.

Conventionally, materials such as bottles, cans, and PET bottles have been used as containers used for packaging beverages, liquors, and the like. On the other hand, due to the growing awareness of global environmental protection in recent years, paper containers with excellent recyclability and low environmental impact have been widely used.

Generally, in a paper container, a plurality of materials are laminated in order to secure the storage stability of the contents, the strength as a container, the gas barrier property, and the like. As a laminated sheet used for this paper container, for example, a laminated sheet having a layer structure of an outermost layer / paper layer / adhesive resin layer / barrier film layer / sealant layer from the outside of the container is generally known.

When forming such a laminated sheet into a container shape, usually, hot air is blown to the sealed portion immediately before filling to melt the sealant layer resin, and then the sealant layer resin is pressed and heat-welded. At that time, the water contained in the paper layer evaporates, and a phenomenon called bubbling occurs in which the paper layer and the adhesive resin layer are peeled off. When further exposed to hot air after bubbling occurs, the expanded water vapor may break through the barrier film layer and the sealant layer, and pinholes may occur.
When pinholes occur in a paper container, not only the barrier function is deteriorated but also the liquid contents may leak. Therefore, it is necessary to set the heating conditions with hot air that does not cause pinholes.

Further, as the barrier film layer of the laminated sheet, a PET film on which an inorganic oxide such as silica or alumina is vapor-deposited, a PET film on which aluminum is vapor-deposited, or a laminated film of an aluminum foil and a PET film is generally used. Is. Therefore, the material used for the adhesive resin layer in the above layer structure needs to be a material exhibiting adhesiveness to the paper layer and the barrier film layer.
Therefore, as a material used for the adhesive resin layer, as shown in Patent Document 1, at least one of ethylene-acrylic acid ester or ethylene-methacrylic acid ester copolymer resin is contained as a main component. Moreover, a method of laminating a resin having an acrylic acid ester or metaacrylic acid ester content of 10 to 30% by weight in the copolymer resin by extrusion lamination is widely adopted.

However, although the ethylene-acrylic acid ester or ethylene-methacrylic acid ester copolymer resin has excellent adhesiveness to the barrier film layer, the laminated sheet produced by using them causes bubbling and pinholes. I have an easy problem.
That is, since the permissible range of hot air heating conditions is narrow, if the heating conditions deviate even a little to the high temperature side, bubbling and pinholes occur, which causes a decrease in barrier property and liquid leakage. On the contrary, if the heating conditions are weak, the sealant layer resin cannot be melted, which causes a seal failure. Further, the ethylene-acrylic acid ester or ethylene-methacrylic acid ester copolymer resin has a higher material cost than a general-purpose resin. Therefore, it is required to establish a manufacturing method using a material whose cost is as low as possible.

In response to such problems, proposals have been made to change the resin physical properties of the adhesive resin layer.
For example, Patent Document 2 proposes a polyethylene resin having a density of more than 0.936 g / cm ³ and a melting point of more than 127 ° C. as a stress prevention layer.
According to this method, a low-cost material can be used, and the effect of suppressing bubbling and pinholes can be obtained. However, when the polyethylene resin is used for the adhesive resin layer, the adhesiveness with the barrier film layer may be lost.

Further, it has been proposed to suppress bubbling and pinholes by providing a layer for preventing the passage of water vapor between the paper layer and the adhesive resin layer. For example, in Patent Document 3, from the outer surface side, an outermost layer made of polyethylene, a base material layer made of paper, a clay coat layer containing clay, a pigment and a binder, an intermediate layer made of a polyethylene resin, a barrier layer, and low-density polyethylene. Alternatively, it has been proposed to sequentially stack the six innermost layers made of medium-density polyethylene, the basis weight of the clay coat layer being 10 g / m ^{2 to} 40 g / m ² , and the clay in the clay coat layer. A packaging material has been proposed in which the blending ratio of the pigment and the binder is clay: pigment: binder = 1% by mass to 20% by mass: 50% by mass to 90% by mass: 10 to 30% by mass. .. However, in this layer structure, since the clay coat layer is provided, there is a problem that the manufacturing cost increases due to the increase in the number of steps.

Japanese Patent No. 3883584 Japanese Unexamined Patent Publication No. 2005-35211 Japanese Patent No. 5313443

The present invention has been made in view of the above problems, and provides a laminated sheet and a paper container that suppress bubbling and pinholes due to hot air during container molding and satisfy adhesiveness to a paper layer and a barrier film layer. The challenge is to provide it at a low price.

The invention according to claim 1 of the present invention
A laminated sheet in which at least the outermost layer / paper layer / adhesive resin layer / barrier film layer / sealant layer are laminated in this order.
The adhesive resin layer has a two-layer structure in which polyethylene is laminated on the paper side and a copolymer of ethylene-unsaturated carboxylic acid or an ester compound thereof is laminated on the barrier film layer side. The difference between the copolymer of ethylene-unsaturated carboxylic acid or its ester compound and polyethylene and the melt flow rate (MFR) specified by JIS K 6760 is within 8 g / 10 min.
The polyethylene is a laminated sheet characterized by having a cohesive fracture strength of 1.20 N / 15 mm or more under a 100 ° C. environment defined by JIS Z 0238.

The invention according to claim 2 of the present invention
The laminated sheet according to claim 1, wherein the polyethylene constituting the adhesive resin layer has a film thickness of 10 μm or more.

The invention according to claim 3 of the present invention
The laminated sheet according to claim 1 or 2, wherein the total thickness of the adhesive resin layer is 20 μm or more and 50 μm or less.

The invention according to claim 4 of the present invention
The laminated sheet according to any one of claims 1 to 3, wherein the polyethylene is a low-density polyethylene having a melting point of 100 ° C. or higher and 130 ° C. or lower.

The invention according to claim 5 of the present invention
The claim is that the barrier film layer is either a PET film provided with a metal vapor-deposited film, a PET film provided with an inorganic oxide vapor-deposited film, or a laminated film of an aluminum foil and a PET film. The laminated sheet according to any one of 1 to 4.

The invention according to claim 6 of the present invention
It is a paper container formed by using the laminated sheet according to any one of claims 1 to 5.

According to the paper container of the present invention, since the resin having high cohesive fracture strength at 100 ° C. is arranged on the paper layer side, the effect of suppressing the occurrence of pinholes can be obtained. Further, the adhesive resin layer constituting the paper container is made into two layers, and one of them is replaced with inexpensive polyethylene to maintain the adhesiveness, while maintaining the adhesiveness of the copolymer with ethylene-unsaturated carboxylic acid or its ester compound. Material costs can be reduced by lowering the ratio.

Further, since the difference in MFR between the copolymer of ethylene-unsaturated carboxylic acid or its ester compound laminated by the coextrusion laminating method and polyethylene is within 8 g / 10 min, the interface that becomes a problem in the coextrusion laminating method. No problems such as roughness occur. In addition, the wrapping phenomenon in which the thickness balance of the two layers of coextruded resin changes in the width direction is less likely to occur.

It is sectional drawing explaining an example of the laminated material which comprises the laminated sheet which concerns on this invention. It is sectional drawing which explains an example of the laminated material which constitutes the conventional laminated sheet.

FIG. 1 is a schematic cross-sectional view showing an example of the layer structure of the laminated sheet according to the present invention. The laminated sheet 10 has a layer structure in which the outermost layer 1 / paper layer 2 / adhesive resin layer 3 / barrier film layer 4 / sealant layer 5 are sequentially laminated. The adhesive resin layer 3 has a two-layer structure composed of an adhesive resin layer (paper side) 3a and an adhesive resin layer (barrier film layer side) 3b.

FIG. 2 shows the layer structure of the conventional laminated sheet for comparison. In FIG. 2, the conventional laminated sheet 20 has a layer structure in which the outermost layer 11, the paper layer 12, the adhesive resin layer 13, the barrier film layer 14, and the sealant layer 15 are sequentially laminated. The adhesive resin layer 13 is composed of a single layer.

Hereinafter, preferred embodiments of the constituent materials of each layer of the laminated sheet and the paper container in the present invention will be described.

(Outermost layer)
The outermost layer 1 needs to have a function of being able to be bonded by thermal adhesion between the outermost layer resins when the laminated sheet is formed into various container forms such as square or round.
Usually, low density polyethylene, medium density polyethylene, linear low density polyethylene, ethylene-α olefin copolymer resin, polyethylene resin such as ethylene-vinyl acetate copolymer, polypropylene, etc., generally as a heat seal layer. The resin used can be used.

The thickness of the outermost layer 1 is not particularly limited as long as it does not interfere with the sealing property, but a thickness of about 10 μm to 30 μm is appropriate. Examples of the laminating method include an extrusion coating method in which the paper layer is laminated on the paper layer in a molten state, and a method in which the paper layer is laminated on the outermost layer film in the form of a sheet via an adhesive. Usually, from the viewpoint of processing speed. It is preferable to apply an extruded coating from. Further, by using a tandem extruder capable of laminating the adhesive resin layer described later on the same line, more efficient production becomes possible.
Further, the outermost layer 1 can be printed after its surface is corona-treated, if necessary.

(Paper layer)
The paper layer 2 is a layer mainly for imparting moldability and rigidity of the container. Kamitsuboryou is suitably about ^{200g / m 2 ~500g / m 2} , can be appropriately selected depending on the container size. Further, there is no problem even if either the surface-treated coated paper or the untreated uncoated paper is selected for the paper layer 2.

(Adhesive resin layer)
The adhesive resin layer 3 is laminated to bond the paper layer 2 and the barrier film layer 4 by extrusion lamination. By using a tandem extruder for laminating the adhesive resin layer 3, the adhesive resin layer 3 and the outermost layer 1 can be laminated on the same line, so that the work efficiency is improved.

The adhesive resin layer 3 has a two-layer structure by coextrusion, the resin of the adhesive resin layer (paper side) 3a located on the paper side is polyethylene, and the adhesive resin layer located on the barrier film layer side ( The resin of (barrier film layer side) 3b is a copolymer of ethylene-unsaturated carboxylic acid or an ester compound thereof.

Specifically, the polyethylene of the adhesive resin layer (paper side) 3a includes low-density polyethylene, medium-density polyethylene, linear low-density polyethylene, ethylene-α-olefin copolymer resin, ethylene-vinyl acetate copolymer, and the like. Polyethylene resin can be used.

Further, as the copolymer with ethylene-unsaturated carboxylic acid or its ester compound arranged in the adhesive resin layer (barrier film layer side) 3b, ethylene-methacrylic acid copolymer (EMAA) and ethylene-acrylic Acid copolymer (EAA), ethylene-methyl methacrylate (EMMA), ethylene-methyl acrylate copolymer, and ionomer resin can be used, and the copolymerization ratio thereof is unsaturated carboxylic acid or unsaturated carboxylic acid. The content of the acid ester component is preferably 3% by weight to 20% by weight.
If the content of the acrylic ester is less than 3% by weight, the adhesive strength of the adhesive resin layer is low, and if it exceeds 20% by weight, the suitability for extrusion processing may be lowered, which is not preferable.

Further, the difference in melt flow rate (MFR) according to the measurement method of JIS K 6760 of a copolymer of polyethylene and ethylene-unsaturated carboxylic acid or an ester compound thereof is within 8 g / 10 min.
When resins having MFR values that are far apart from each other are co-extruded and laminated, problems such as rough appearance occur when the film is formed. In addition, a wrapping phenomenon occurs in which the thickness balance of the two layers of resin varies in the width direction, resulting in a large variation in the final product. When a copolymer of polyethylene and an ethylene-unsaturated carboxylic acid or an ester compound thereof is coextruded and laminated, the above problem does not occur if the difference in MFR is within 8 g / 10 min.

Further, the polyethylene constituting the adhesive resin layer (paper side) 3a is JIS in an environment of 100 ° C.
The cohesive fracture strength defined by Z 0238 needs to be 1.20 N / 15 mm or more.
Bubbling and pinholes occur at a temperature of 100 ° C. or higher at which the water contained in the paper layer 2 is vaporized. At this time, when the cohesive fracture strength of the resin on the paper layer side is 1.20 N / 15 mm or more, the resin on the paper layer side can withstand the expansion pressure of water vapor, so that bubbling pinholes are less likely to occur.

The method for measuring the cohesive fracture strength will be described in detail.
A polyethylene film formed to a thickness of 30 μm is corona-treated on both sides, and a two-component curable adhesive having a urethane bond is used on each surface to corona-treat the film to a thickness of 12 μm. PETs are laminated to prepare a sample having a PET (front) / PE / PET (back) configuration.
The PET (front side) and PET (back side) of this sample are sandwiched between tensile testers, and a peeling test is performed in a constant temperature bath at 100 ° C. in accordance with JIS Z 0238. By measuring in this way, the cohesive fracture strength of polyethylene in an environment of 100 ° C. can be measured.

Further, the film thickness of the polyethylene constituting the adhesive resin layer (paper side) 3a needs to be at least 10 μm or more. When the thickness is thinner than 10 μm, bubbling and pinholes are likely to occur in the polyethylene film due to the pressure of water vapor generated by hot air during container molding.

Further, as the polyethylene constituting the adhesive resin layer (paper side) 3a, it is preferable to use low density polyethylene having a melting point of 100 ° C. to 130 ° C. The copolymer of the adhesive resin layer (barrier film layer side) 3b laminated simultaneously with the ethylene-unsaturated carboxylic acid or its ester compound in the coextrusion laminate generally has a melting point of 80 ° C. to 100 ° C. Since many of them have the property of decomposing at high temperature, low density polyethylene having a low melting point and capable of low temperature ejection is suitable.

The copolymer with ethylene-unsaturated carboxylic acid or an ester compound thereof constituting the adhesive resin layer (barrier film layer side) 3b is intended to have adhesiveness with the barrier film layer. Therefore, the film thickness can be arbitrarily set as long as the adhesiveness to the barrier film layer is not hindered. A suitable thickness is in the range of 3 μm to 15 μm. The thinner the adhesive resin layer (barrier film layer side) 3b is, the lower the material cost can be. If this thickness is less than 3 μm, the adhesiveness to the barrier film layer may be lost due to a decrease in the thickness balance that may occur during production. Further, when it is thicker than 15 μm, the effect of reducing the cost of the material becomes small.

The thickness of the entire adhesive resin layer 3 is preferably 20 μm to 50 μm. If the thickness is thinner than 20 μm, bubbling and pinholes are likely to occur. Further, when the thickness is thicker than 50 μm, it becomes difficult to provide a ruled line when molding the container, and problems in the molding process are likely to occur.

(Barrier film layer)
The barrier film layer 4 is provided to give the container a gas barrier property. For example, a PET film, a biaxially stretched polyester film, a nylon film, a polycarbonate film, a polyvinyl alcohol film, an ethylene / vinyl alcohol copolymer resin, or the like is provided. As the base film, a film on which an inorganic substance such as silica, alumina, or aluminum is vapor-deposited can be used.

The appropriate thickness of this base film is about 5 μm to 30 μm. Further, the thickness of the vapor-deposited film may be such that the film is vapor-deposited to a thickness sufficient to exhibit the required gas barrier property. For example, when silica is vapor-deposited, the thickness is preferably about 30 nm to 200 nm. Further, the barrier film layer 4 may be produced by adhering an aluminum foil and the above-mentioned base film by a dry laminating method.

(Sealant layer)
As the sealant layer 5, a resin generally used as a sealant layer can be used. For example, low density polyethylene (Low Density Polyethylene, PE-LD), medium density polyethylene, linear low density polyethylene (Linear Low Density Polyethylene, PE-LLD), ethylene-α olefin copolymer resin, ethylene-vinyl acetate. Examples thereof include polyethylene-based resins such as polymers and polypropylene.

The sealant layer 5 may be used by laminating a single layer or a plurality of these resins in combination. The sealant layer 5 has an appropriate thickness of 30 μm to 100 μm. The laminating method is not particularly limited, but a method of laminating the barrier film layer 4 with the barrier film layer 4 by a dry laminating method using a two-component curable adhesive having a urethane bond after film formation is common.

(Making a container)
By molding using the laminated sheet described above, it can be applied to any type of container such as a gable top type container, a cup-shaped container, a brick type container, and a tubular container. Further, as the manufacturing method thereof, a conventionally known method can be applied as it is.

Specific examples will be described in detail below.

<Example 1>
A PE-LD film (thickness 55 μm) that has been previously corona-treated on one side as the sealant layer 5, and a PET film (thickness 12 μm) that has silica vapor-deposited on one side and corona-treated on the other side as the barrier film layer 4. Was prepared, and the silica-deposited surface and the corona-treated surface of the PE-LD film were laminated by a dry laminating method with a urethane-based adhesive to form a laminated film of a barrier film layer / a sealant layer.
The basis weight of 380 g / m ² of Nokoto paper as a paper layer 2 after the corona treatment on both surfaces of the paper substrate, low density polyethylene (Asahi Kasei stock from the first T-die of the tandem extruder on one side of the paper substrate The company's L2340) was extruded to a thickness of 18 μm to form the outermost layer 1.
Subsequently, the second T-die to PE-LD (L6810 manufactured by Asahi Kasei Co., Ltd.) was placed on the opposite surface of the surface on which the outermost layer of the paper substrate was formed and the PET film surface of the laminated film of the barrier film layer / sealant layer. , MFR10.5) and EMAA (AN4228C, MFR14 manufactured by Mitsui DuPont Polychemical Co., Ltd.) were used for sandwich lamination to form an adhesive resin layer 3.
The PE-LD (L6810) extruded from the second T-die had a cohesive fracture strength of 1.20 N / 15 mm under a 100 ° C. environment defined by JIS Z 0238. The film thicknesses of PE-LD and EMAA coextruded were 25 μm and 5 μm, respectively. The composition of the obtained laminated sheet is PE-LD (L2340, thickness 18 μm) / paper (basis weight 380 g / m ² ) / PE-LD (L6810, thickness 25 μm) / EMAA (AN4228C, thickness 5 μm) / Silica-deposited PET film (thickness 12 μm) / PE-LD (thickness 55 μm). (See FIG. 1).

<Example 2>
Except for using PE-LD (LC600A MFR7 manufactured by Japan Polyethylene Corporation) for PE-LD3a (adhesive resin layer (paper side) 3a) laminated by coextrusion from the second T-die of the tandem extruder. A laminated sheet was produced in the same manner as in Example 1.
The PE-LD (LC600A) extruded from the second T-die had a cohesive fracture strength of 1.23 N / 15 mm under a 100 ° C. environment defined by JIS Z 0238. The composition of the obtained laminated sheet is PE-LD (L2340, thickness 18 μm) / paper (basis weight 380 g / m ² ) / PE-LD (LC600A thickness 25 μm) / EMAA (AN4228C, thickness 5 μm) / silica. A vapor-deposited PET film (thickness 12 μm) / PE-LD (thickness 55 μm).

<Comparative example 1>
Examples except that the adhesive resin layer 3 laminated by the second T-die of the tandem extruder is an EMAA (AN4228C, MFR14 manufactured by Mitsui DuPont Polychemical Co., Ltd.) and its thickness is 30 μm. A laminated sheet (see FIG. 2) was prepared in the same manner as in 1. The composition of the obtained laminated sheet is PE-LD (thickness 18 μm) / paper (basis weight 380 g / m ² ) / EMAA (AN4228C, thickness 30 μm) / silica-deposited PET film (thickness 12 μm) / PE-LD. (Thickness 55 μm).
The cohesive fracture strength of EMAA (AN4228C) in a 100 ° C. environment defined by JIS Z 0238 was 1.1 N / 15 mm.

<Comparative example 2>
Examples except that the adhesive resin layer 3 laminated by the second T-die of the tandem extruder is a PE-LD (L6810, MFR10.5 manufactured by Asahi Kasei Corporation) single layer and its thickness is 30 μm. A laminated sheet was produced in the same manner as in 1. The composition of the obtained laminated sheet is PE-LD (thickness 18 μm) / paper (basis weight 380 g / m ² ) / PE-LD (L6810, thickness 30 μm) / silica-deposited PET film (thickness 12 μm) / PE. -LD (thickness 55 μm).

<Comparative example 3>
Examples except that PE-LD3a (adhesive resin layer (paper side) 3a) laminated by coextrusion with the second T-die of the tandem extruder is PE-LD (LW18A, MFR10 manufactured by Tosoh Corporation). A laminated sheet was produced in the same manner as in 1. The composition of the obtained laminated sheet is PE-LD (thickness 18 μm) / paper (basis weight 380 g / m ² ) / PE-LD (LW18A, thickness 25 μm) / EMAA (AN4228C, thickness 5 μm) / silica vapor deposition. PET film (thickness 12 μm) / PE-LD (thickness 55 μm).
The cohesive fracture strength of PE-LD (LW18A) in a 100 ° C. environment defined by JIS Z 0238 was 1.0 N / 15 mm.

<Comparative example 4>
Other than using PE-LD (L2340, MFR3.8 manufactured by Asahi Kasei Corporation) for PE-LD3a (adhesive resin layer (paper side) 3a) laminated by coextrusion from the second T-die of the tandem extruder. Made a laminated sheet in the same manner as in Example 1.
The composition of the obtained laminated sheet is PE-LD (thickness 18 μm) / paper (basis weight 380 g / m ² ) / PE-LD (L2340 thickness 25 μm) / EMAA (AN4228C, thickness 5 μm) / silica-deposited PET. Film (thickness 12 μm) / PE-LD (thickness 55 μm).
The cohesive fracture strength of PE-LD (L2340) in a 100 ° C. environment defined by JIS Z 0238 was 1.24 N / 15 mm.

<Comparative example 5>
Laminated sheets in the same manner as in Example 1 except that the film thicknesses of PE-LD3a (L6810) and EMAA (AN4228C) laminated by coextrusion from the second T-die of the tandem extruder are 40 μm and 15 μm, respectively. Was produced.
The composition of the obtained laminated sheet is PE-LD (thickness 18 μm) / paper (basis weight 380 g / m ² ) / PE-LD (L6810 thickness 40 μm) / EMAA (AN4228C, thickness 15 μm) / silica-deposited PET. Film (thickness 12 μm) / PE-LD (thickness 55 μm).

<Comparative Example 6>
Laminated sheets in the same manner as in Example 1 except that the film thicknesses of PE-LD3a (L6810) and EMAA (AN4228C) laminated by coextrusion from the second T-die of the tandem extruder are 10 μm and 5 μm, respectively. Was produced. The composition of the obtained laminated sheet is PE-LD (thickness 18 μm) / paper (basis weight 380 g / m ² ) / PE-LD (L6810 thickness 10 μm) / EMAA (AN4228C, thickness 5 μm) / silica-deposited PET. Film (thickness 12 μm) / PE-LD (thickness 55 μm).

<Comparative Example 7>
Laminated sheets in the same manner as in Example 1 except that the film thicknesses of PE-LD3a (L6810) and EMAA (AN4228C) laminated by coextrusion from the second T-die of the tandem extruder are 8 μm and 22 μm, respectively. Was produced. The composition of the obtained laminated sheet is PE-LD (thickness 18 μm) / paper (basis weight 380 g / m ² ) / PE-LD (L6810 thickness 8 μm) / EMAA (AN4228C, thickness 22 μm) / silica-deposited PET. Film (thickness 12 μm) / PE-LD (thickness 55 μm).

[Evaluation of laminated sheet]
・ Evaluation (1) (coextrusion workability)
The state of the film discharged from the second T-die was observed. If the sandwich lamination can be performed without any problem, it is judged as "○", and if the film condition is bad and it is not suitable for the sandwich lamination, it is judged as "x".

・ Evaluation (2) (Adhesion with barrier film layer)
Immediately after producing the laminated sheet by the tandem extruder, the adhesiveness between the adhesive resin layer 3 and the barrier film layer 4 was measured by a tensile tester (A & D RCT-1250A Co., Ltd.). The measurement was carried out by a method conforming to JIS Z 0238.
Adhesive strength measurement conditions: tensile speed; 30 cm / min, test piece width: 15 mm
The measurement result was determined to be "◯" if the adhesive strength was 3N / 15 mm or more, and "x" if the adhesive strength was 3N / 15 mm or less.

・ Evaluation (3) (ruled line workability)
After applying the ruled line processing for container molding to the laminated sheet, it was evaluated whether a container assembly failure occurred. When the container can be assembled, it is judged as "○", and when it is not possible, it is judged as "×".

・ Evaluation (4) (Bubbling / pinhole resistance)
In the filling machine used in this production, hot air was injected into the laminated sheet. When the temperature of the hot air was changed at 10 ° C. intervals, the temperature of the hot air at which the laminated sheet generated bubbling and pinholes was confirmed. Regarding the bubbling generation temperature, the case where it occurred at 320 ° C. or higher was judged as “◯”, and the case where it occurred at 310 ° C. or lower was judged as “x”. Regarding the pinhole generation temperature, the case where it occurs at 340 ° C. or higher is designated as “◯”, and the case where it occurs at 330 ° C. or lower is designated as “x”.

The evaluation results are shown in Table 1.

From Table 1, good results were obtained in all the evaluations of Examples 1 and 2 according to the present invention.
On the other hand, in Comparative Example 1 in which the adhesive resin layer was a single layer of EMAA, bubbling and pinholes were likely to occur. Further, in Comparative Example 2 in which the adhesive resin layer was a single layer of polyethylene, the adhesion to the barrier film layer was lowered.
Further, in Comparative Example 3 in which the type of the adhesive resin layer on the paper side was changed, the cohesive fracture strength was as low as 1.0 N / 15 mm, and bubbling and pinholes were likely to occur. In Comparative Example 4, the MFR difference in the adhesive resin layer was as large as 10.2, and the appearance was rough and the thickness varied in the width direction during film formation.
Further, Comparative Example 5 in which the entire adhesive resin layer was thickened to 55 μm was inferior in ruled line workability, and conversely, Comparative Example 6 in which the entire adhesive resin layer was thinned to 15 μm was prone to bubbling and pinholes. In Comparative Example 7 in which the thickness of the adhesive resin layer on the paper side and the barrier film side was made thinner for the former and thicker for the latter, bubbling was likely to occur.

According to the laminated sheet of the present invention, the coextrusion processability with EMAA is improved by forming the adhesive resin layer into two layers and defining the resin to be arranged on the paper side of the laminated sheet. Further, since the resin having adhesiveness is arranged on the barrier film layer side, good adhesion to the barrier film layer can be obtained. Further, by using a resin having high coagulation fracture strength as the resin arranged on the paper side by coextrusion, it is possible to reduce the occurrence of bubbling and pinholes. Further, since the amount of EMAA resin used can be reduced, it is possible to obtain an inexpensive laminated sheet having sufficiently satisfied performance.

1 ... Outermost layer 2 ... Paper layer 3 ... Adhesive resin layer 3a ... Adhesive resin layer (paper side)
3b ... Adhesive resin layer (barrier film layer side)
4 ... Barrier film layer 5 ... Sealant layer
10 ... Laminated sheet 11 ... Outermost layer 12 ... Paper layer 13 ... Adhesive resin layer 13a ... Adhesive resin layer (paper side)
13b ... Adhesive resin layer (barrier film layer side)
14 ... Barrier film layer 15 ... Sealant layer
20 ... Laminated sheet

Claims (6)

A laminated sheet in which at least the outermost layer / paper layer / adhesive resin layer / barrier film layer / sealant layer are laminated in this order.
The adhesive resin layer has a two-layer structure in which polyethylene is laminated on the paper side and a copolymer of ethylene-unsaturated carboxylic acid or an ester compound thereof is laminated on the barrier film layer side. The difference between the copolymer of ethylene-unsaturated carboxylic acid or its ester compound and polyethylene and the melt flow rate (MFR) specified by JIS K 6760 is within 8 g / 10 min.
The polyethylene has a cohesive fracture strength of 1.20 N / 15 mm or more under a 100 ° C. environment specified by JIS Z 0238.
Laminated sheet featuring. The laminated sheet according to claim 1, wherein the polyethylene constituting the adhesive resin layer has a film thickness of 10 μm or more. The laminated sheet according to claim 1 or 2, wherein the total thickness of the adhesive resin layer is 20 μm or more and 50 μm or less. The laminated sheet according to any one of claims 1 to 3, wherein the polyethylene is a low-density polyethylene having a melting point of 100 ° C. or higher and 130 ° C. or lower. The claim is characterized in that the barrier film layer is either a PET film provided with a metal vapor-deposited film, a PET film provided with an inorganic oxide vapor-deposited film, or a laminated film of an aluminum foil and a PET film. The laminated sheet according to any one of 1 to 4. A paper container formed by using the laminated sheet according to any one of claims 1 to 5.

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