JP2023099909A - Paper container, and paper cup - Google Patents

Abstract

To provide a paper container, and a paper cup capable of suppressing looseness in a curled part.SOLUTION: A paper cup comprises a trunk member and a bottom member. The trunk member includes a side wall part having a cylindrical shape and a top curl part located on a periphery of an opening in the side wall part. The trunk member is formed from a laminated material 20. The laminated material 20 includes a paper layer 21, an inner layer 22 made of a thermoplastic resin positioned inside the paper cup relative to a paper layer 21, and an outer layer 23 positioned outside the paper cup relative to the paper layer 21. The outer layer 23 includes a plurality of resin layers. The plurality of resin layers includes a thermoplastic resin layer 23A and an isophthalic acid-modified PET layer 23B. A tensile yield stress of the isophthalic acid-modified PET layer 23B is higher than that of the resin layer other than the isophthalic acid-modified PET layer 23B among the plurality of resin layers. The tensile yield stress of the isophthalic acid-modified PET layer 23B is 116 MPa or less.SELECTED DRAWING: Figure 2

Description

The present invention relates to paper containers and paper cups.

A paper cup is an example of a paper container. The paper cup includes a body member and a bottom member closing one end of the body member. The body and bottom members are formed from laminates. In the laminated material, the innermost layer, the barrier layer, the substrate layer, and the outermost layer are stacked in the stated order. The innermost layer includes a portion of the inner surface of the paper cup. The outermost layer includes a portion of the outer surface of the paper cup. The barrier layer has a barrier function against water vapor, water, gas, and the like. The barrier layer includes an inorganic compound layer made of, for example, aluminum or silicon oxide, and a resin layer that supports the layer (see Patent Document 1, for example).

Japanese Unexamined Patent Application Publication No. 2004-18101

By the way, the body member has a side wall portion and a top curl portion. The sidewall has a cylindrical shape. The top curl portion has an annular shape surrounding the periphery of the opening in the side wall portion. When forming the top curl portion, first, a cylinder is formed using a laminated material. Next, one end of the cylindrical body is stretched and wound so that the end is located at the innermost side of the top curled portion. At this time, since the resin layer contained in the laminated material is elastically deformed, when the force acting on the laminated material is released, the resin layer is deformed so as to return to the state before deformation. This causes the top curl to relax after the force acting on the laminate is released, resulting in a diameter of the top curl that is larger than the diameter immediately after the top curl is formed. The angle at which the curled portion is wound becomes smaller than the angle immediately after the top curled portion is formed.

Such circumstances are common even when the laminated material does not have a barrier layer. This situation is not limited to paper cups, but is common to paper containers having a curled portion surrounding the periphery of the opening.

A paper-made container for solving the above-mentioned problems is provided with a curled portion made of a laminated material on the periphery of the opening. The laminated material comprises a paper layer, an inner layer made of a thermoplastic resin located inside the paper container relative to the paper layer, and an outer layer located outside the paper container relative to the paper layer. , provided. The outer layer includes a plurality of resin layers. The plurality of resin layers includes a thermoplastic resin layer and a polyester layer. The tensile yield stress of the polyester layer is higher than that of the resin layers other than the polyester layer among the plurality of resin layers. The polyester layer has a tensile yield stress of 116 MPa or less.

A paper cup for solving the above problems comprises a body member having a tubular shape, and a bottom member that closes one end of the body member and forms an inner surface that together with the body member defines a space for containing contents. and a paper cup. The body member includes a side wall portion having a cylindrical shape and a top curl portion located on the periphery of an opening in the side wall portion. The body member is formed from a laminated material. The laminated material includes a paper layer, an inner layer made of a thermoplastic resin positioned inside the paper cup relative to the paper layer, and an outer layer positioned outside the paper cup relative to the paper layer. The outer layer includes a plurality of resin layers. The plurality of resin layers includes a thermoplastic resin layer and a polyester layer. The tensile yield stress of the polyester layer is higher than that of the resin layers other than the polyester layer among the plurality of resin layers. The tensile yield stress of the polyester layer is 116 MPa or less.

According to the above paper container and paper cup, the stress at the yield point of the polyester layer tends to be smaller than when the tensile yield stress of the polyester layer is higher than 116 MPa. Therefore, the polyester layer is likely to be plastically deformed, so that the polyester layer is likely to be plastically deformed during molding of the curled portion. As a result, even after the force acting on the laminated material during molding of the curled portion is released, the curled portion is unlikely to return to the shape before molding. As a result, loosening of the curled portion can be suppressed.

A paper-made container for solving the above-mentioned problems is provided with a curled portion made of a laminated material on the periphery of the opening. The laminated material comprises a paper layer, an inner layer made of a thermoplastic resin located inside the paper container relative to the paper layer, and an outer layer located outside the paper container relative to the paper layer. , wherein the outer layer includes a plurality of resin layers. The plurality of resin layers includes a thermoplastic resin layer, a first polyester layer and a second polyester layer. The tensile yield stress of the first polyester layer and the second polyester layer is higher than that of the resin layers other than the first polyester layer and the second polyester layer among the plurality of resin layers. The tensile yield stress of the first polyester layer and the second polyester layer is 116 MPa or less.

According to the above-described paper container, both polyester layers have a tensile yield stress of 116 MPa or less, so that loosening of the curled portion can be suppressed when the laminated material includes two polyester layers.

In the paper container, the polyester layer may be composed of isophthalic acid-modified polyethylene terephthalate, the isophthalic acid-modified polyethylene terephthalate may be composed of a plurality of repeating units, and the plurality of repeating units may contain isophthalic acid. According to this paper container, it is possible to use a polyester layer containing recycled polyethylene terephthalate.

According to the present invention, it is possible to suppress loosening of the curled portion.

FIG. 3 is a partial cross-sectional view showing a structure in which a part of the paper cup is broken; FIG. 2 is a cross-sectional view showing a first example of the structure of a laminated material forming a paper cup; FIG. 5 is a cross-sectional view showing a second example of the structure of the laminated material forming the paper cup; Sectional drawing which shows the structure of a top curl part. A graph showing an example of a stress-strain curve. A graph showing the stress-strain curve of each test example. The graph which shows the storage elastic curve of each test example. The graph which shows the loss elastic curve of each test example. The graph which shows the loss tangent curve of each test example.

A paper cup, which is an embodiment of a paper container, will be described with reference to FIGS. 1 to 9. FIG.
[Paper cup structure]
The structure of the paper cup will be described with reference to FIG.

As shown in FIG. 1, the paper cup 10 comprises a body member 11 and a bottom member 12. As shown in FIG. The body member 11 has a tubular shape. The bottom member 12 closes one end of the trunk member 11 . The bottom member 12, together with the body member 11, forms an inner surface 10S that defines a storage space for the contents. The trunk member 11 has a side wall portion 11A, a top curl portion 11B, and a folded portion 11C. The side wall portion 11A has a cylindrical shape. The top curl portion 11B is located at the end opposite to the end closed by the bottom member 12 . The folded portion 11C is positioned at the end closed by the bottom member 12 . The folded portion 11C is folded so as to be positioned inside the paper cup 10 with respect to the side wall portion 11A. In the example shown in FIG. 1, the body member 11 has a cylindrical shape. In the body member 11 , the end opposite to the end closed by the bottom member 12 is enlarged in diameter. The body member 11 is formed from a laminated material. At the top curl portion 11B, one or more rolls of the laminated material are wound.

The bottom member 12 includes a bottom wall portion 12A, a bent portion 12B, and a peripheral wall portion 12C. The bent portion 12B is located at the outer edge of the bottom wall portion 12A. The peripheral wall portion 12C is bent with respect to the bottom wall portion 12A at the bent portion 12B. The bent portion 12B is positioned within the inner surface 10S. The bottom member 12 has a disc shape. The bottom wall portion 12A, like the bottom member 12, has a disc shape. The bent portion 12B has an annular shape covering the entire circumference of the bottom wall portion 12A. The peripheral wall portion 12C, like the bent portion 12B, has an annular shape extending over the entire circumference of the bottom wall portion 12A. The peripheral wall portion 12C is bent in a direction crossing the bottom wall portion 12A at the bent portion 12B. A peripheral wall portion 12C of the bottom member 12 is fixed between the side wall portion 11A of the body member 11 and the folded portion 11C.

[Structure of laminated material]
The structure of the laminated material for forming the paper cup 10 will be described with reference to FIGS. 2 and 3. FIG. When manufacturing the paper cup 10, first, a body blank for forming the body member 11 and a bottom blank for forming the bottom member 12 are cut out from the laminated material. A body member 11 is then molded from the body blank and a bottom member 12 is molded from the bottom blank. Then, the paper cup 10 is manufactured by attaching the bottom member 12 to the body member 11 . Below, a first example and a second example of the structure of at least the laminated material used for the trunk blank will be described in order. Note that the laminated material described below may be used for the bottom blank.

As shown in FIG. 2, the first example laminate 20 comprises a paper layer 21 , an inner layer 22 and an outer layer 23 . The inner layer 22 is positioned inside the paper cup 10 relative to the paper layer 21 and is made of a thermoplastic resin. The outer layer 23 is positioned outside the paper cup 10 relative to the paper layer 21 . The outer layer 23 includes multiple resin layers. The plurality of resin layers includes a thermoplastic resin layer 23A and an isophthalic acid-modified polyethylene terephthalate (hereinafter also referred to as isophthalic acid-modified PET) layer 23B, which is an example of a polyester layer.

The laminate 20 has a first surface 20F1 and a second surface 20F2 opposite to the first surface 20F1. The second surface 20F2 includes a portion of the inner surface 10S of the paper cup 10. As shown in FIG. The thickness of the laminated material 20 may be, for example, 300 μm or more and 600 μm or less.

The paper layer 21 may be a paper cup base paper highly suitable for forming the paper cup 10 . From the viewpoint of enhancing suitability for molding, the basis weight of the paper layer 21 may be, for example, 200 g/m ² or more and 350 g/m ² or less. The thickness of the paper layer 21 may be, for example, 0.15 mm or more and 0.4 mm or less, preferably 0.18 mm or more and 0.3 mm or less.

The inner layer 22 may be made of, for example, polyethylene (hereinafter also referred to as PE). The PE may be low density PE, medium density PE, high density PE, linear low density PE, and the like. The thickness of the inner layer 22 may be, for example, 10 μm or more and 100 μm or less.

The thermoplastic resin layer 23A, like the inner layer 22, may be made of PE, for example. The PE may be low density PE, medium density PE, high density PE, linear low density PE, and the like. The thickness of the thermoplastic resin layer 23A may be, for example, 15 μm or more and 60 μm or less.

The isophthalic acid-modified PET layer 23B satisfies Condition 1 and Condition 2 below.
(Condition 1) The tensile yield stress of the isophthalic acid-modified PET layer 23B is higher than that of the resin layers other than the isophthalic acid-modified PET layer 23B among the plurality of resin layers.
(Condition 2) The tensile yield stress of the isophthalic acid-modified PET layer 23B is 116 MPa or less.

The first example of the laminated material 20 includes the thermoplastic resin layer 23A and the isophthalic acid-modified PET layer 23B as a plurality of resin layers. higher than stress.

The repeating units of the isophthalic acid-modified PET forming the isophthalic acid-modified PET layer 23B include diol units and dicarboxylic acid units. The isophthalic acid-modified PET constituting the isophthalic acid-modified PET layer 23B contains PET containing terephthalic acid and isophthalic acid in dicarboxylic acid units. In the case where it is further required to soften the bottom member 12 and thereby suppress the deterioration of the barrier properties of the paper cup 10, the ratio of isophthalic acid to all dicarboxylic acid units in the isophthalic acid-modified PET layer 23B is 0.5. It is preferably 5 mol % or more. When shape stability in the paper cup 10 is required, the ratio of isophthalic acid to all dicarboxylic acid units is preferably 5 mol % or less.

If the paper cup 10 is required to reduce the environmental load, the isophthalic acid-modified PET constituting the isophthalic acid-modified PET layer 23B can contain recycled PET, which is recycled PET. PET products targeted for recycling include used PET bottles. The recycled PET constituting the isophthalic acid-modified PET layer 23B is at least one of PET regenerated by mechanical recycling and PET regenerated by chemical recycling.

In mechanical recycling, the pulverized PET product is washed to remove surface dirt and foreign matter, and then the resin is exposed to high temperatures to remove contaminants remaining inside the resin. In chemical recycling, pulverized PET products are washed to remove surface stains and foreign matter, and then depolymerized to return the resin to the intermediate raw material. Then, PET is produced by repolymerizing after purifying the intermediate raw material.

If the paper cup 10 is required to further reduce manufacturing costs and environmental impact, the recycled PET constituting the isophthalic acid-modified PET layer 23B is preferably PET that is mechanically recycled. Compared to chemical recycling, mechanical recycling does not require large-scale equipment for chemical reaction, and thus the production cost and environmental load required for manufacturing recycled PET are small.

The constituent material of the isophthalic acid-modified PET layer 23B may include virgin PET in addition to recycled PET, or may include polyester other than recycled PET. Virgin PET is PET newly synthesized from raw materials such as petroleum. The proportion of the recycled PET constituting the isophthalic acid-modified PET layer 23B in the mass is preferably 60% or more and 100% or less with respect to the total mass of the isophthalic acid-modified PET layer 23B.

The diol units of virgin PET are ethylene glycol and the dicarboxylic acid units of virgin PET are terephthalic acid. On the other hand, the dicarboxylic acid, which is the raw material of PET composing the PET bottle, contains isophthalic acid in addition to terephthalic acid in order to improve the workability of the resin when molding the bottle.

Isophthalic acid shortens the main chain of isophthalic acid-modified PET compared to PET whose dicarboxylic acid is composed only of terephthalic acid, so that crystallization of isophthalic acid-modified PET is suppressed, which enhances processability of isophthalic acid-modified PET. be done. The diol unit of PET constituting the PET bottle may contain diethylene glycol in addition to ethylene glycol, or may contain only ethylene glycol.

Although the average molecular weight of the isophthalic acid-modified PET constituting the isophthalic acid-modified PET layer 23B is not particularly limited, it is preferably in the range of 1,000 to 1,000,000, for example. The material forming the isophthalic acid-modified PET layer 23B may contain resins other than isophthalic acid-modified PET and various additives. Additives may be, for example, plasticizers, anti-staining agents, antistatic agents, weathering agents, UV absorbers, deodorants, antioxidants, and the like.

The isophthalic acid-modified PET layer 23B may be composed of one layer, or may be a laminate composed of a plurality of layers. When the isophthalic acid-modified PET layer 23B is a laminate, at least one layer of the laminate contains PET containing terephthalic acid and isophthalic acid in dicarboxylic acid units.

Materials constituting the isophthalic acid-modified PET layer 23B may include polyesters other than recycled PET and virgin PET. Polyesters other than recycled PET and virgin PET are polyesters having carboxylic acid units such as chain aliphatic carboxylic acids and cycloaliphatic carboxylic acids.

When the paper cup 10 requires durability and impact resistance, the thickness of the isophthalic acid-modified PET layer 23B is preferably 3 μm or more, more preferably 10 μm or more. When the paper cup 10 is required to have workability, the thickness of the isophthalic acid-modified PET layer 23B is preferably 50 μm or less, more preferably 30 μm or less.

As a method for forming the isophthalic acid-modified PET layer 23B, a film forming method such as extrusion molding can be used. Methods such as cooling rolls, air cooling, and water cooling can be used for cooling in extrusion molding. The isophthalic acid-modified PET layer 23B may be a stretched film or an unstretched film. As a method for stretching the isophthalic acid-modified PET layer 23B, a method such as uniaxial stretching or biaxial stretching can be used.

As shown in FIG. 3, in the second example of the laminated material 20, the outer layer 23 further comprises a plurality of resin layers. The outer layer 23 further comprises a PET layer 23C and two thermoplastic resin layers 23D, 23E. The PET layer 23C and the two thermoplastic resin layers 23D and 23E are located inside the isophthalic acid-modified PET layer 23B.

The PET layer 23C may have the same structure as the isophthalic acid-modified PET layer 23B. That is, the PET layer 23C may satisfy Condition 2 described above. If the two PET layers 23B and 23C satisfy Condition 2, the tensile yield stress of the isophthalic acid-modified PET layer 23B may be smaller than the tensile yield stress of the PET layer 23C, or may be less than the tensile yield stress of the PET layer 23C. may be greater than Also, the tensile yield stresses of the two PET layers 23B and 23C may be equal to each other.

On the other hand, the tensile yield stress of the PET layer 23C may satisfy the following condition 3 instead of the condition 2 in addition to the following condition 1.
(Condition 3) Tensile yield stress is greater than 116 MPa.

In this case, the PET layer 23C is composed of virgin PET. As noted above, the diol units of virgin PET are ethylene glycol and the dicarboxylic acid units of virgin PET are terephthalic acid. The PET layer 23C may be composed of one layer, or may be a laminate composed of a plurality of layers. When the PET layer 23C is a laminate, each layer of the laminate is made of virgin PET.

The two thermoplastic resin layers 23D and 23E may be made of PE, for example, like the thermoplastic resin layer 23A described above. The PE may be low density PE, medium density PE, high density PE, linear low density PE, and the like. The thickness of each thermoplastic resin layer 23D, 23E may be, for example, 10 μm or more and 30 μm or less.

[Shape of trunk member]
The trunk member 11 is formed, for example, by the method described below.
When forming the trunk member 11 , first, a trunk blank is cut out from the laminated material 20 . The trunk blank has, for example, a fan shape in the unfolded state. One end of the cylinder blank is then laminated to the other end to form the cylinder blank into a tubular shape. A bottom member 12 is attached to one end of the trunk blank.

The barrel blank with the bottom member 12 attached is placed in a forming apparatus for forming the top curl portion 11B. The molding device has an upper mold and a lower mold. When the cylinder blank is placed in the forming apparatus, the upper mold is positioned above the opening in the cylinder blank and the lower side covers the bottom member 12 and the side walls of the cylinder blank. Then, the upper die descends toward the lower die, whereby the peripheral edge of the opening in the trunk blank is wound along the groove provided in the upper die. As a result, the top curled portion 11B wound one or more turns is formed around the periphery of the opening in the trunk blank. The top curl portion 11B is formed while the trunk blank is heated to a temperature of, for example, 60° C. or higher and 70° C. or lower.

FIG. 4 shows the cross-sectional shape of the top curl portion 11B together with part of the cross-section of the side wall portion 11A.
As shown in FIG. 4, the top curl portion 11B has a base portion 11B1 and a tip portion 11B2. The base end portion 11B1 is the position where the winding of the top curl portion 11B is started. That is, the base end portion 11B1 is a portion connected to the side wall portion 11A and extending in a direction intersecting the direction in which the side wall portion 11A extends. The tip portion 11B2 is the innermost portion of the top curl portion 11B. The inside of the top curl portion 11B means that the distance from the center of curvature of the top curl portion 11B is relatively small.

The diameter D of the top curled portion 11B is the maximum diameter of the outer surface of the top curled portion 11B. A diameter D of the top curl portion 11B may be, for example, 2 mm or more and 6 mm or less. The winding angle, which is the angle at which the top curled portion 11B is wound, is calculated from the number of times the top curled portion 11B is wound. For example, when the top curl portion 11B is wound once, the winding angle is 360°. Further, when the number of windings of the top curl portion 11B is 1.5 times, the winding angle is 540°. Further, when the top curl portion 11B is wound two times, the winding angle is 720°. The winding angle of the top curl portion 11B may be, for example, 400° or more and 600° or less.

[Tensile yield stress of isophthalic acid-modified PET layer]
FIG. 5 shows an example of a stress-strain curve obtained by a tensile test on a specimen formed only from an isophthalic acid-modified PET layer. A stress-strain curve is measured based on a tensile test according to JIS K7161-1:2014. In the stress-strain curve shown in FIG. 5, the stress at the yield point A indicated by the arrow is the yield stress. In the stress-strain curve, the breaking point B indicated by the arrow is the point at which the test piece breaks, and the stress at the B point is the breaking strength.

The range from the origin of FIG. 5 to the yield point A, that is, the range in which the stress is proportional to the strain, is the range in which the isophthalic acid-modified PET layer elastically deforms. In the range of elastic deformation, the isophthalic acid-modified PET layer tends to be harder as the slope before stress-strain bending is larger, and the isophthalic acid-modified PET layer tends to be softer as the slope of the stress-strain curve is smaller. When a pressure exceeding the yield stress is applied to the PET layer, the isophthalic acid-modified PET layer undergoes plastic deformation.

The greater the slope of the stress-strain curve after the yield point A, the harder the isophthalic acid-modified PET layer, and the difference between the strain at the yield point A and the strain at the break point B tends to be smaller. On the other hand, the smaller the slope of the stress-strain curve after the yield point A, the softer the isophthalic acid-modified PET layer, and the greater the difference between the strain at the yield point A and the strain at the break point B. The isophthalic acid-modified PET layer often has a breaking point B at a strain exceeding 0.4 in the stress-strain curve, and the slope at a strain of 0.4 or less indicates the stiffness of the isophthalic acid-modified PET layer. It is possible to grasp the trend in

The isophthalic acid-modified PET layer tends to increase in hardness as the breaking strength at the breaking point B increases, and tends to increase in tenacity as the breaking strength decreases. If the breaking strength is too high, the stress value at breakage of the isophthalic acid-modified PET layer tends to increase, but the strain that the isophthalic acid-modified PET layer can withstand tends to decrease. On the other hand, if the breaking strength is too low, the strain that the isophthalic acid-modified PET layer can withstand increases, while the stress value at which the isophthalic acid-modified PET layer breaks tends to decrease.

In the stress-strain curve, the area enclosed by the curve indicates the ability of the isophthalic acid modified PET layer to absorb impact energy. The smaller the area encompassed by the stress-strain curve, the more brittle, or less tenacious, the isophthalic acid-modified PET layer tends to be. In contrast, the greater the area encompassed by the stress-strain curve, the less brittle, or tenacious, the PET layer tends to be.

In the process of forming the top curled portion 11B, when the laminated material 20 is wound, stress is generated in the portion that will become the top curled portion 11B after forming the body member 11 . Since the isophthalic acid-modified PET layer that satisfies condition 2 is soft, it tends to undergo a small amount of strain until the isophthalic acid-modified PET undergoes plastic deformation. That is, the stress before reaching the yield point A of the stress-strain curve of the isophthalic acid-modified PET layer tends to be small. As described above, until the stress generated in the isophthalic acid-modified PET layer reaches the yield point A, the isophthalic acid-modified PET layer is elastically deformed.

In this regard, since the isophthalic acid-modified PET layer satisfying condition 2 tends to have a small stress until it reaches the yield point A, the isophthalic acid-modified PET layer contained in the laminated material 20 is formed earlier when the bottom member 12 is formed. easily plastically deformed. This prevents the top curled portion 11B from returning to the shape before molding even after the force acting on the trunk blank is released after the top curled portion 11B is molded. Therefore, loosening of the top curled portion 11B is suppressed even after the force acting on the trunk blank is released after the top curled portion 11B is formed. As a result, it is possible to prevent the diameter of the top curled portion 11B from becoming larger than that immediately after molding the top curled portion 11B, and the winding angle of the top curled portion 11B from becoming smaller than that immediately after molding the top curled portion 11B. be done.

Further, when it is further required to suppress loosening of the top curl portion 11B, the isophthalic acid-modified PET layer preferably satisfies the following conditions 4 and 5 in the isophthalic acid-modified PET stress-strain curve. .
(Condition 4) The slope of the stress-strain curve is included in the range of 75 or more and 111 or less after yielding and in the range where the strain is 0.2 or more and 0.4 or less.
(Condition 5) The breaking strength in the flow direction is 153 MPa or more and 183 MPa or less.

The isophthalic acid-modified PET layer satisfying conditions 4 and 5 is soft and tenacious. Therefore, the external force that may act on the isophthalic acid-modified PET layer during molding of the top curl portion 11B can be consumed inside the isophthalic acid-modified PET layer.

The yield stress, the slope after yielding, and the breaking strength of the isophthalic acid-modified PET layer are determined by the temperature at which the PET layer is extruded, the temperature at which the extruded precursor of the isophthalic acid-modified PET layer is cooled, and the temperature at which the precursor is cooled. It can be adjusted by the cooling rate, the stretching magnification of the isophthalic acid-modified PET layer, and the like. In addition, the yield stress, slope after yield, and breaking strength of the isophthalic acid-modified PET layer can be adjusted by adjusting the ratio of isophthalic acid to all dicarboxylic acid units contained in the isophthalic acid-modified PET layer.

For example, if it is required to increase the yield stress, the slope after yielding, and the breaking strength, the temperature during extrusion of the isophthalic acid-modified PET layer is increased, or the precursor of the extruded PET layer is cooled. It can be adjusted by lowering the temperature to be applied. In addition, when it is required to reduce the yield stress, the slope after yielding, and the breaking strength, the cooling rate of the precursor is increased, the stretching ratio of the isophthalic acid-modified PET layer is increased, and the isophthalic acid-modified PET layer is can be adjusted by increasing the ratio of isophthalic acid to all dicarboxylic acid units contained in .

[Viscoelasticity of isophthalic acid-modified PET layer]
In the case where it is further required to improve the processability while suppressing the loosening of the top curl portion 11B according to condition 2, the isophthalic acid-modified PET layer has the following in the storage elastic curve showing the relationship between the storage elastic modulus G1 and the temperature: It is preferable to satisfy condition 6 below. Moreover, the isophthalic acid-modified PET preferably satisfies the following condition 7 in the loss elastic curve showing the relationship between the loss elastic modulus G2 and the temperature. Further, the isophthalic acid-modified PET preferably satisfies the following condition 8 in the loss tangent curve of the isophthalic acid-modified PET layer, which indicates the relationship between the loss tangent tan δ and the temperature.

(Condition 6) The transition temperature T1 from the glassy state to the rubbery state is 80° C. or higher and 88° C. or lower, and the storage elastic modulus G1 at the transition temperature is 3.8 GPa or higher and 4.1 GPa or lower.
(Condition 7) The temperature T2 at the peak position is 95° C. or higher and 102° C. or lower, and the loss elastic modulus G2 at the peak position is 0.30 GPa or higher and 0.37 GPa or lower.
(Condition 8) The loss tangent tan δ at the peak position temperature T3 is 0.160 or more and 0.190 or less.

The storage elastic modulus G1 of the isophthalic acid-modified PET layer indicates the component of the energy generated in the isophthalic acid-modified PET layer by an external force that is stored inside the isophthalic acid-modified PET layer. The loss elastic modulus G2 of the isophthalic acid-modified PET layer indicates the component of the energy generated in the isophthalic acid-modified PET layer due to an external force that diffuses to the outside as heat. The magnitude of the storage elastic modulus G1 indicates the degree of elasticity, and the magnitude of the loss elastic modulus G2 indicates the degree of viscosity. The loss tangent tan δ is the ratio of the loss elastic modulus G2 to the storage elastic modulus G1 (=G2/G1), and indicates the balance between elasticity and viscosity in the isophthalic acid-modified PET layer.

The weaker the elasticity of the isophthalic acid-modified PET layer, the smaller the repulsion against the external force applied during molding of the top curl portion 11B. Easier to transform. That is, the workability of the isophthalic acid-modified PET layer is enhanced.

The higher the viscosity of the isophthalic acid-modified PET layer, the slower the progress of deformation in response to the application of an external force, and the more difficult it is to restore the deformation even when the external force is released. That is, the workability of the isophthalic acid-modified PET layer is enhanced. The temperature T2 at the peak position of the loss elastic curve is the temperature at which the viscosity of the isophthalic acid-modified PET layer is significantly exhibited. The lower the temperature T2 at the peak position in the loss elastic curve, the more easily the viscosity-induced flexibility is exhibited. However, if the viscosity of the isophthalic acid-modified PET layer is too high, the workability of the paper cup 10 is lowered, and the strength of the paper cup 10 itself is lowered.

The isophthalic acid-modified PET layer that satisfies the upper limit of the storage elastic modulus G1 in Condition 6 prevents the contribution of elasticity from becoming excessive, thereby enhancing the workability of the isophthalic acid-modified PET layer. The isophthalic acid-modified PET layer that satisfies the lower limit of the storage elastic modulus G1 in condition 6 suppresses deterioration of suitability as a paper container.

An isophthalic acid-modified PET layer that satisfies the lower limit of the loss elastic modulus G2 in Condition 7 exhibits good flexibility due to its viscosity, thereby enhancing the workability of the isophthalic acid-modified PET layer. The isophthalic acid-modified PET layer that satisfies the upper limit of the loss elastic modulus G2 in Condition 7 suppresses deterioration of suitability as a paper container.

The isophthalic acid-modified PET layer that satisfies the lower limit of the loss tangent tan δ in Condition 8 enhances the properties of the viscous body relative to the properties of the elastic body so as to increase the followability to the external force applied during molding with the isophthalic acid-modified PET layer. This enhances the workability of the isophthalic acid-modified PET layer. The isophthalic acid-modified PET layer that satisfies the upper limit of the loss tangent tan δ in Condition 8 prevents deterioration of suitability as a paper container.

The transition temperature T1 from the glassy state to the rubbery state, the temperature T2 at the peak position of the loss elastic curve, the storage elastic modulus G1, the loss elastic modulus G2 at the peak position on the loss elastic curve, and the peak position on the loss tangent curve The loss tangent tan δ can be adjusted by adjusting the ratio of isophthalic acid to all dicarboxylic units in the isophthalic acid-modified PET layer.

For example, when it is required to increase the viscosity of the isophthalic acid-modified PET layer, it can be adjusted by increasing the proportion of isophthalic acid in the total dicarboxylic units of the isophthalic acid-modified PET layer. When it is required to decrease the storage modulus G1 and increase the loss tangent tan δ, adjustment is possible by decreasing the cooling temperature during the production of the isophthalic acid-modified PET layer. When it is required to increase the loss tangent tan δ and increase the loss elastic modulus G2, the cooling rate during the production of the isophthalic acid-modified PET layer is increased to allow moderate crystal growth while leaving an amorphous portion. can be adjusted by When it is required to lower the transition temperature T1 from the glassy state to the rubbery state and to reduce the storage elastic modulus G1, the draw ratio is reduced during the production of the isophthalic acid-modified PET layer to prevent molecular orientation. Adjustment is possible by suppressing.

[Example]
Test examples, examples, and comparative examples will be described with reference to FIGS. 6 to 9 .
[PET layer]
[Test Example 1]
Three resin layers were laminated by co-extrusion to form the PET layer of Test Example 1 having a thickness of 12 μm. At this time, three resin layers each having the same composition were formed from recycled PET regenerated by mechanical recycling and virgin PET.

In the PET layer of Test Example 1, the mass of recycled PET was set to 80% of the total mass of the resin film, and the mass of virgin PET was set to 20% of the total mass of the resin film. In addition, the ratio of isophthalic acid to all dicarboxylic acid units in the recycled PET is specified based on the NMR measurement results, and the ratio of isophthalic acid to all dicarboxylic acid units in the PET layer is 0.5 mol% or more and 5 mol% or less. set to

[Test Example 2]
Three PET films were laminated such that the second PET film was sandwiched between the two first PET films to form the PET layer of Test Example 2 as a laminate having a thickness of 12 μm. The first PET film of Test Example 2 is made of recycled PET regenerated by chemical recycling. The second PET film of Test Example 2 is a film in which 80% by mass of recycled PET that is mechanically recycled is mixed with 20% by mass of recycled PET that is chemically recycled. The proportion in mass of recycled PET contained in the PET layer is 100% of the total mass of the PET layer.

[Test Example 3]
Three PET films were laminated such that the second PET film was sandwiched between the two first PET films to form the PET layer of Test Example 3 as a laminate having a thickness of 12 μm. The first PET film of Test Example 3 is made of virgin PET. The second PET film of Test Example 3 is made of recycled PET regenerated by chemical recycling. The mass ratio of recycled PET contained in the PET layer of Test Example 3 was 70% of the total mass of the PET layer.

[Test Example 4]
A single-layer PET film made of virgin PET was used as the PET layer. The PET layer of Test Example 4 is a PET layer that does not contain recycled PET, and is made of polyethylene terephthalate in which the dicarboxylic acid unit in the repeating units is only terephthalic acid. The thickness of the PET layer in Test Example 4 is 12 μm.

[Evaluation method]
[Yield stress]
Three specimens were cut out from each of the isophthalic acid-modified PET layers of Test Examples 1 to 3 and the PET layer of Test Example 4. At this time, using a dumbbell cutter (Dumbbell Co., Ltd., SDK-600) conforming to JIS Z 1702-1994, each test piece was cut so as to have a shape extending along the flow direction. That is, test pieces were cut out from the PET layer so that the tensile direction of each test piece coincided with the flow direction of the PET layer. Each specimen was marked with two gauge lines for measuring elongation.

A tensile test was performed on the test piece using a small desktop tester (EZ-LX, manufactured by Shimadzu Corporation) using a method based on JIS K7161-1:2014. At this time, each test piece was fixed to a small tabletop tester, and the marked line was sandwiched between extensometers. Also, the test speed was set to 300 mm/min. A stress-strain curve was generated based on the results of a tensile test on one specimen for each test example. From the stress-strain curve, the yield stress, breaking strength, and slope after yielding in the range of 0.2 or more and 0.4 or less strain were obtained.

[Dynamic modulus]
Strip-shaped test pieces were prepared from the isophthalic acid-modified PET layers of Test Examples 1 to 3 and the PET layer of Test Example 4, respectively. At this time, the length of the test piece was set to 20 mm, and the width of the test piece was set to 10 mm. The flow direction during formation of the PET layer was set to the longitudinal direction of the test piece. Using a thermomechanical analyzer (DMA7100, manufactured by Hitachi High-Tech Science Co., Ltd.), the storage elastic modulus G1 and the loss elastic modulus G2 of each test piece were measured, and the loss tangent tan δ was calculated. Conditions for measuring the storage modulus G1 and the loss modulus G2 were set as follows.

Frequency: 10Hz
Tension condition: Strain amplitude 10 μm
: Minimum tension/compression force 50mN
: tension/compression force gain 1.2
: Force amplitude initial value 50mN
Heating conditions: Temperature increase rate 2°C/min
: Heating temperature 30°C or higher and 180°C or lower

[Evaluation results]
[Yield stress]
Evaluation results will be described with reference to FIG.
As shown in FIG. 6, the yield stresses in the flow direction of Test Examples 1 to 3 are 116.0 MPa, 115.0 MPa, and 110.2 MPa, respectively, and all are within the range of 116 MPa or less shown in Condition 2. and within the range of 109 MPa or more. In contrast, the yield stress of Test Example 4 was found to be 124.8 MPa.

The slopes after yielding of Test Examples 1 to 3 were 77.3, 110.5 and 84.2, respectively, and all of them were found to be within the range of 75 or more and 111 or less. In contrast, the average value of the post-yield slope of Test Example 4 was found to be 172.4.

The breaking strengths in the flow direction of Test Examples 1 to 3 were 170.9, 176.4, and 159.6, respectively, and were all within the range of 153 MPa or more and 183 MPa or less. In contrast, the average value of the slope after yielding in Test Example 4 was found to be 202.7 MPa.

[Dynamic modulus]
Table 1 shows the measurement results of the storage elastic modulus G1, the loss elastic modulus G2, and the loss tangent tan δ for Test Examples 1 to 4.

The measured value of the storage elastic modulus G1 was obtained from the transition temperature T1 of the storage elastic curve shown in FIG. 7 and the storage elastic modulus G1 at the transition temperature T1. The measured value of the loss elastic modulus G2 was obtained from the temperature T2 at the peak position of the loss elastic curve shown in FIG. 8 and the loss elastic modulus G2 at the temperature T2. The measured value of the loss tangent tan δ was obtained from the temperature T3 at the peak position of the loss tangent curve shown in FIG. 9 and the loss tangent tan δ at the temperature T3.

At this time, the temperature at the intersection of the approximate straight line on the lower temperature side than the inflection point of the storage elastic curve and the approximate straight line on the higher temperature side than the inflection point was defined as the transition temperature T1. By approximating the set of measurement points on the low temperature side to a straight line and the set of measurement points on the high temperature side to a straight line, respectively, the approximate straight line on the low temperature side and the approximate straight line on the high temperature side Obtained. The set of measurement points on the low temperature side is the inflection point and a plurality of measurement points between about 10° C. below the inflection point and about 5° C. below the inflection point. The set of measurement points on the high temperature side is the inflection point and a plurality of measurement points between about 5° C. and about 10° C. above the inflection point.

The transition temperatures T1 of Test Examples 1 to 3 are 87.6° C., 87.8° C., and 80.3° C., respectively, and are all within the range of 80° C. or higher and 88° C. or lower shown in Condition 6. was accepted. Note that the transition temperature T1 of Test Example 4 was found to be 87.0°C.

The storage elastic moduli G1 of Test Examples 1 to 3 are 3.8 GPa, 4.1 GPa, and 3.9 GPa, respectively, and are all within the range of 3.8 GPa or more and 4.1 GPa or less shown in Condition 6. was accepted. In contrast, the storage elastic modulus G1 of Test Example 4 was found to be 4.7 GPa. That is, it was confirmed that the elasticity of the isophthalic acid-modified PET layers of Test Examples 1 to 3 was weaker than that of the PET layer of Test Example 4. It was also found that the elasticity of the isophthalic acid-modified PET layers of Test Examples 1 to 3 was weaker as the ratio of the mass of recycled PET to the total mass of the isophthalic acid-modified PET layers was increased.

The temperatures T2 at the peak positions in the loss elastic curves of Test Examples 1 to 3 are 101.3° C., 99.8° C., and 95.4° C., respectively, and all of them are 95° C. or more and 102° C. or less shown in Condition 7. was found to be In contrast, the temperature T2 at the peak position of the loss elastic curve of Test Example 4 was found to be 104.7°C. That is, it was confirmed that the isophthalic acid-modified PET layers of Test Examples 1 to 3 had higher flexibility at low temperatures than the PET layer of Test Example 4. It was also confirmed that the low-temperature flexibility of the isophthalic acid-modified PET layers of Test Examples 1 to 3 increased as the ratio of the mass of recycled PET to the total mass of the isophthalic acid-modified PET layers increased.

The loss elastic moduli G2 of Test Examples 1 to 3 are 0.34 GPa, 0.37 GPa, and 0.37 GPa, respectively, and are all within the range of 0.3 GPa or more and 0.37 GPa or less shown in Condition 7. was accepted. On the other hand, the loss elastic modulus G2 of Test Example 4 was found to be 0.39 GPa.

The temperatures T3 at the peak positions in the loss tangent curves of Test Examples 1 to 3 are 114.8°C, 113.8°C, and 108.8°C, respectively, and are all 108°C or higher and 115°C or lower. Admitted. On the other hand, the temperature T3 at the peak position of the loss tangent curve of Test Example 4 was found to be 119.0°C.

The loss tangent tan δ at the peak position in the loss tangent curves of Test Examples 1 to 3 is 0.162, 0.170, and 0.185, respectively, and all of them are 0.160 or more and 0.190 shown in Condition 8. It was found that: In contrast, the loss tangent tan δ at the peak position in the loss tangent curve of Test Example 4 was found to be 0.157. That is, in the isophthalic acid-modified PET layers of Test Examples 1 to 3, the degree of viscosity to elasticity is greater than in Test Example 4, and the contribution of viscosity to the response to external force is also greater than in Test Example 4. was recognized.

[Paper cup]
[Example 1]
Using the isophthalic acid-modified PET film of Test Example 1, a laminated material for forming a body member was obtained by laminating a plurality of layers in the following order. a PE layer with a thickness of 30 μm, a paper layer with a basis weight of 230 g/m ² , a PE layer with a thickness of 17 μm, a PE layer with a thickness of 15 μm, the PET film of Test Example 1, and PE layers with a thickness of 15 μm were superimposed in the order given. As a result, a laminated material for forming a trunk member was obtained. It should be noted that in the laminate a PE layer with a thickness of 15 μm has a first side and a PE layer with a thickness of 30 μm has a second side.

In forming these laminates, a PE layer was extruded on one side of the paper layer to form a first laminate. Meanwhile, a PE layer was extruded on both sides of the PET layer, thereby forming a second laminate. A laminate was obtained by laminating the first laminate and the second laminate by a sandwich lamination method using molten polyethylene.

On the other hand, a laminate for forming a bottom member was obtained by stacking a plurality of layers described below. That is, a PE layer with a thickness of 20 μm, a paper layer with a basis weight of 200 g/m ² , a PE layer with a thickness of 20 μm, a PE layer with a thickness of 15 μm, and the isophthalic acid-modified PET film of Test Example 1. , and a PE layer with a thickness of 60 μm were superimposed in the order given. As a result, a laminated material for forming the bottom member was obtained.

In forming these laminates, a PE layer was extruded on one side of the paper layer to form a first laminate. On the other hand, a second laminate was obtained by extruding a PE layer on both sides of the isophthalic acid-modified PET film of Test Example 1. A laminate was obtained by laminating the first laminate and the second laminate by a sandwich lamination method using molten polyethylene.

A bottom member was formed from the laminated material for forming the bottom member, and a body member was formed from the laminated material for forming the body member. Then, the bottom member was fixed to the body member, thereby obtaining a paper cup of Example 1-1. At this time, when viewed from the viewpoint facing the inner surface of the paper cup, the diameter of the bottom wall is set at 49.5 mm, the diameter at the opening of the body member is set at 62.6 mm, and the height of the inner surface is set at 1000 mm. bottom. Also, the area of the inner surface was set to 374.4 cm ² . Further, when forming the top curled portion, the diameter of the top curled portion was set to 2.5 mm, and the winding angle of the top curled portion was set to 630°.

[Example 2]
In Example 1, except that the isophthalic acid-modified PET film of Test Example 1 contained in the laminated material for forming the trunk member was changed to the isophthalic acid-modified PET film of Test Example 2, the same method as in Example 1 was performed. , the paper cup of Example 2 was obtained.

[Example 3]
In Example 1, except that the isophthalic acid-modified PET film of Test Example 1 included in the laminated material for forming the trunk member was changed to the isophthalic acid-modified PET film of Test Example 3, the same method as in Example 1 was performed. , the paper cup of Example 3 was obtained.

[Comparative Example 1]
In Example 1, except that the isophthalic acid-modified PET film of Test Example 1 contained in the laminated material for forming the trunk member was changed to the PET film of Test Example 4, the same method as in Example 1 was performed to obtain a comparative example. 1 paper cup was obtained.

[Evaluation method]
[Shape of top curl]
The paper cup of each example and each comparative example was cut along the extending direction of the paper cup, and the cross-sectional shape of the top curl portion was visually confirmed. As a result, the diameter and winding angle of the top curl portion of each paper cup were confirmed.

[Evaluation results]
The winding angle of Example 1 was found to be 610° and the winding angle of Comparative Example 1 was found to be 540°. It was also found that the diameter of Example 1 was 2.7 mm and the diameter of Comparative Example 1 was 3 mm. Thus, according to the paper cup of Example 1, compared with the paper cup of Comparative Example 1, it was confirmed that the winding angle of the top curl portion was large and the diameter was small. The paper cup of Example 2 and the paper cup of Example 3 were found to have the same winding angle and diameter as the paper cup of Example 1.

As described above, according to one embodiment of the paper container, the effects described below can be obtained.
(1) Since the isophthalic acid-modified PET layer 23B is likely to be plastically deformed during molding of the top curl portion 11B, even after the force acting on the laminated material 20 during molding of the top curl portion 11B is released, The top curl portion 11B is difficult to return to the shape before molding. As a result, loosening of the top curl portion 11B can be suppressed.

(2) Since both the PET layers 23B and 23C have a tensile yield stress of 116 MPa or less, loosening of the top curl portion 11B can be suppressed when the laminated material 20 includes two PET layers.

(3) It is possible to use an isophthalic acid-modified PET layer 23B containing recycled polyethylene terephthalate.

In addition, the embodiment described above can be implemented with the following changes.
[Polyester layer]
- The polyester layer provided for the outer layer 23 is not limited to a polyester layer containing isophthalic acid-modified PET. For example, the polyester layer may be a PET layer or modified PET other than isophthalic acid modified PET. Modified PET may be, for example, modified PET containing diol units other than ethylene glycol, as described above. Alternatively, the polyester layer is not limited to PET, and may be made of, for example, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, or the like.

[Paper container]
- The paper cup mentioned above is an example of a paper container. The paper container may be a container having a curled portion located at the periphery of the opening, and may be embodied as a container other than a paper cup.

DESCRIPTION OF SYMBOLS 10... Paper cup 11... Body member 12... Bottom member 20... Laminated material 21... Paper layer 22... Inner layer 23... Outer layer 23A... Thermoplastic resin layer 23B... Isophthalic acid-modified polyethylene terephthalate layer

Claims (4)

A paper container provided with a curled portion composed of a laminated material on the periphery of the opening,
The laminated material is
a paper layer;
an inner layer located inside the paper container relative to the paper layer and made of a thermoplastic resin;
an outer layer located outside the paper container than the paper layer,
The outer layer includes a plurality of resin layers,
The plurality of resin layers include a thermoplastic resin layer and a polyester layer,
The tensile yield stress of the polyester layer is higher than the resin layers other than the polyester layer in the plurality of resin layers,
A paper container, wherein the polyester layer has a tensile yield stress of 116 MPa or less. A paper container provided with a curled portion composed of a laminated material on the periphery of the opening,
The laminated material is
a paper layer;
an inner layer located inside the paper container relative to the paper layer and made of a thermoplastic resin;
an outer layer located outside the paper container than the paper layer,
The outer layer includes a plurality of resin layers,
The plurality of resin layers includes a thermoplastic resin layer, a first polyester layer, and a second polyester layer,
The tensile yield stress of the first polyester layer and the second polyester layer is higher than the resin layers other than the first polyester layer and the second polyester layer in the plurality of resin layers,
The paper-made container according to claim 1, wherein the tensile yield stress of the first polyester layer and the second polyester layer is 116 MPa or less. The polyester layer is made of isophthalic acid-modified polyethylene terephthalate,
The isophthalic acid-modified polyethylene terephthalate is composed of a plurality of repeating units,
The paper container according to claim 1 or 2, wherein the plurality of repeating units contain isophthalic acid. a body member having a tubular shape;
A paper cup comprising a bottom member that closes one end of the body member and forms an inner surface that defines a storage space for contents together with the body member,
The body member includes a side wall portion having a cylindrical shape and a top curl portion positioned on the periphery of an opening in the side wall portion,
The body member is formed from a laminated material,
The laminated material comprises a paper layer, an inner layer made of a thermoplastic resin located inside the paper cup relative to the paper layer, and an outer layer located outside the paper cup relative to the paper layer,
The outer layer includes a plurality of resin layers,
The plurality of resin layers include a thermoplastic resin layer and a polyester layer,
The tensile yield stress of the polyester layer is higher than the resin layers other than the polyester layer in the plurality of resin layers,
The polyester layer has a tensile yield stress of 116 MPa or less. Paper cup.

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