JP2023023543A - Blank and paper container - Google Patents

Abstract

To stabilize a quality of a blank for a paper container having a coating portion.SOLUTION: A blank 10 comprises: a main body portion 14 comprising a paper base material layer 11, an inner layer 12 provided on an inner surface 11a of the base material layer 11, and an outer layer 13 provided on an outer surface 11b of the base material layer 11; and a coating portion 15 coating the end face of the base material layer 11 in the main body portion 14. The coating portion 15 is a region in which extended portions extending from the end face of the base material layer 11 in the inner layer 12 and the outer layer 13 are welded to each other, and are folded back to the main body portion 14 side. The inner layer 12 comprises a first thermoplastic resin layer 12a contacting the inner surface 11a of the base material layer 11, a second thermoplastic resin layer 12b, and a polyester layer 12c. The polyester layer 12c has tensile yield stress of 109 MPa or more and 117 MPa or less, and a temperature at a peak position of a loss tangent of 116°C or lower.SELECTED DRAWING: Figure 2

Description

The present invention relates to blanks and paper containers.

Patent Literature 1 discloses a sheet-like laminate in which thermoplastic resin layers are laminated on both sides of a base material layer, and a cup-shaped paper container formed using the laminate. A paper container includes a cylindrical body formed of a laminate and a disk-shaped bottom formed of a laminate. The trunk portion is formed in a cylindrical shape by laminating both end portions of a fan-shaped blank cut out from the laminate.

At the end of the blank, a covering portion is provided to cover the end surface of the base material layer in order to ensure the barrier properties of the bonded portion of the body. In the blank before the coating portion is formed, the thermoplastic resin layers laminated on both sides of the base material layer have portions extending beyond the end faces of the base material layer. The covering portion is formed by welding the facing surfaces of the portion extending beyond the end face of the base material layer and folding back the welded portion to the outer surface side.

JP 2008-222246 A

When forming the covering portion on the blank, first, the portions of the thermoplastic resin layer extending beyond the end surface of the base material layer are welded together using a nip roll or the like. At this time, a gap corresponding to the thickness of the base material layer is formed in the vicinity of the end surface of the base material layer inside the welded portion. The gaps hinder the formation of the covering portion by folding back the welded portion, and cause variation in the shape of the covering portion. Therefore, in order to stabilize the quality of the paper container, it is preferable to make the gap as small as possible.

In this respect, the blank used for the body of a paper container has a vapor deposition film in the thermoplastic resin layer laminated on the base material layer for the purpose of improving the shape stability of the container and improving the gas barrier property of the container. A polyester layer, such as polyethylene terephthalate, is provided. When forming a covering portion on a blank having a polyester layer, the hardness of the polyester layer affects folding, and as a result of the increase in the gap, there is a potential problem that the shape of the covering portion tends to vary.

A blank for solving the above problems includes a main body portion including a base material layer made of paper, an inner layer provided on the inner surface of the base layer, and an outer layer provided on the outer surface of the base layer, and the base material in the main body portion a covering portion covering an end surface of the layer, wherein the inner layer includes a first thermoplastic resin layer and a second thermoplastic resin layer in contact with the inner surface of the base material layer, and the first thermoplastic resin layer and the second thermoplastic resin layer; A polyester layer positioned between thermoplastic resin layers is provided, the outer layer includes a third thermoplastic resin layer in contact with the outer surface of the base layer, and the coating part is the base layer in the inner layer and the outer layer. The extending portion extending from the end face of the paper container is a portion that is welded with the first thermoplastic resin layer and the third thermoplastic resin layer and is folded back toward the main body portion side wherein the thermoplastic resin constituting the first thermoplastic resin layer and the second thermoplastic resin layer is a polyolefin resin, the polyester layer has a tensile yield stress of 109 MPa or more and 117 MPa or less, and The temperature at the peak position of loss tangent is 116° C. or less.

By setting the temperature at the peak position of the tensile yield stress and the loss tangent of the polyester layer within a specific range, the range in which the polyester layer can be deformed with a small stress is widened. Thereby, the gap generated inside the extending portion can be made smaller. As a result, the extending portion is likely to be deformed when the extending portion is folded back to form the covering portion. As a result of the extended portion being easily deformable, variations in the shape of the covering portion are suppressed, and the quality of the blank is stabilized.

In the blank, the polyester layer may have a tensile yield stress of 109 MPa or more and 113 MPa or less, and a temperature of a peak position of loss tangent of the polyester layer of 108° C. or more and 111° C. or less.

In this case, the effect of widening the range in which the polyester layer can be deformed with a small stress can be obtained more remarkably.
The polyolefin resin may be polyethylene. In this case, the degree of deformation in the inner layer tends to be dominated by the polyester layer, so that the effect of enabling deformation with a small stress in the polyester layer can be obtained more remarkably.

A paper container that solves the above problems is a paper container that includes a cylindrical body portion made of the blank, wherein the body portion is a first body portion provided with the covering portion of the main body portion of the blank. An end portion and a second end portion located on the opposite side of the first end portion are overlapped and bonded together so that the inner layer faces inward and the first end portion is located inward.

In this case, the quality of the paper container is stabilized in the same manner as the blank.
In the above-described paper container, the body may have a flange portion formed by winding an edge portion outward, and the flange portion may have a flat surface flattened.

In this case, by setting the temperature at the peak position of the tensile yield stress and loss tangent of the polyester layer to a specific range, the covering portion is deformed when the flange portion including the covering portion is deformed to form a flat surface. easier to do. As a result, variations in the shape of the flat surface are suppressed, and the quality of the paper container is stabilized.

ADVANTAGE OF THE INVENTION According to this invention, the quality of the blank for paper containers and paper containers provided with a covering part can be stabilized.

Top view of the blank. 2-2 line cross-sectional view of FIG. (a) is an explanatory view of a first laminating step, and (b) is a cross-sectional view of an inner layer sheet. The top view of a base material sheet. Explanatory drawing of a 2nd lamination process. (a) to (c) are explanatory diagrams of a folding process. (a) is an explanatory diagram of a method for manufacturing a paper container, and (b) is an enlarged view of the periphery of a covering portion. (a), (b) is explanatory drawing of a flange formation process, (c) is explanatory drawing of a flattening process. Stress-strain curves of polyester layers.

An embodiment of the present invention will be described below.
<Blanks for paper containers>
As shown in FIGS. 1 and 2, a blank 10 for a paper container includes a paper base layer 11, a resin inner layer 12 provided on the inner surface 11a of the base layer 11, and a base layer 11. It is a sheet-like laminate including a resin outer layer 13 provided on the outer surface 11b. The plan view shape of the blank 10 is not particularly limited, and can be appropriately set according to the shape of the paper container formed using the blank 10 . In this embodiment, a blank 10 used for forming a cylindrical body of a cup-shaped paper container will be described. In this case, the planar view shape of the blank 10 is fan-shaped.

The blank 10 includes a body portion 14 having a base material layer 11 , an inner layer 12 and an outer layer 13 , and a covering portion 15 covering an end face of the base material layer 11 in the body portion 14 . The covering portion 15 is a portion of the inner layer 12 and the outer layer 13 that extends beyond the end surface 11 c that is the edge of the base material layer 11 and is folded back toward the main body portion 14 . In the covering portion 15, the surfaces of the inner layer 12 and the outer layer 13 facing each other are welded. In addition, the facing surfaces of the outer layer 13 at the folded portion of the covering portion 15 are welded together. Thereby, the covering portion 15 is fixed to the main body portion 14 in a folded state. The covering portion 15 is provided at a first end portion 14a, which is one end portion in the circumferential direction of the main body portion 14 having a fan shape in plan view.

Hereinafter, the base material layer 11, the inner layer 12, and the outer layer 13 which constitute the blank 10 will be specifically described.
(Base material layer)
The paper base material constituting the base material layer 11 is not particularly limited, and known paper base materials applied to blanks for paper containers can be used. Examples of the paper substrate constituting the substrate layer 11 include paper materials such as strong sizing bleached or unbleached paper, pure white roll paper, kraft paper, cup base paper, and processed paper.

The basis weight of the base material layer 11 is, for example, 100 g/m ² or more, preferably 200 g/m ² or more. Moreover, the basis weight of the base material layer 11 is, for example, 500 g/m ² or less, preferably 400 g/m ² or less.

(inner layer)
As shown in FIG. 2, the inner layer 12 comprises a first thermoplastic resin layer 12a, a second thermoplastic resin layer 12b, and a polyester layer positioned between the first thermoplastic resin layer 12a and the second thermoplastic resin layer 12b. 12c.

The first thermoplastic resin layer 12a is a layer in contact with the inner surface 11a of the substrate layer 11, and is an adhesive layer that bonds the substrate layer 11 and the polyester layer 12c. The second thermoplastic resin layer 12b is, for example, a sealant layer used as a welded portion when forming a paper container from the blank 10. As shown in FIG.

The thermoplastic resin forming the first thermoplastic resin layer 12a and the second thermoplastic resin layer 12b is polyolefin resin. Polyolefin resins are, for example, ethylene-based resins and propylene-based resins.

Examples of ethylene-based resins include polyethylene and ethylene/vinyl acetate copolymer. Polyethylene is selected from the group consisting of, for example, low density polyethylene (LDPE), linear low density polyethylene (LLDPE) obtained by copolymerizing α-olefin and ethylene, medium density polyethylene (MDPE), and high density polyethylene (HDPE). is one of the The propylene-based resin is, for example, one selected from the group consisting of homopolypropylene, propylene/ethylene random copolymer, propylene/ethylene block copolymer, and propylene/α-olefin copolymer.

The thermoplastic resins forming the first thermoplastic resin layer 12a and the second thermoplastic resin layer 12b may be the same or different. Further, the constituent materials of the first thermoplastic resin layer 12a and the second thermoplastic resin layer 12b may contain resins other than the above thermoplastic resins and various additives. Additives include, for example, plasticizers, coloring inhibitors, antistatic agents, weathering agents, ultraviolet absorbers, deodorants, and antioxidants.

The melting points of the first thermoplastic resin layer 12a and the second thermoplastic resin layer 12b are, for example, 90° C. or higher, preferably 110° C. or higher. Also, the melting points of the first thermoplastic resin layer 12a and the second thermoplastic resin layer 12b are, for example, 200° C. or lower, preferably 180° C. or lower. The melting points of the first thermoplastic resin layer 12a and the second thermoplastic resin layer 12b may be the same or different.

The thickness of the first thermoplastic resin layer 12a and the second thermoplastic resin layer 12b is, for example, 10 μm or more, preferably 20 μm or more. Also, the thickness of the first thermoplastic resin layer 12a and the second thermoplastic resin layer 12b is, for example, 50 μm or less, preferably 40 μm or less. The thickness of the first thermoplastic resin layer 12a and the thickness of the second thermoplastic resin layer 12b may be the same or different.

The polyester layer 12c is a layer whose constituent material is polyester resin. Examples of the polyester resin forming the polyester layer include polyethylene terephthalate and modified polyethylene terephthalate. Examples of modified polyethylene terephthalate include acid-modified polyethylene terephthalate and glycol-modified polyethylene terephthalate. In the following, "polyester resin" is abbreviated as "PET".

The repeating units of PET constituting the polyester layer 12c include diol units and dicarboxylic acid units. PET includes PET containing terephthalic acid and isophthalic acid among the dicarboxylic acid units. The ratio of isophthalic acid to all dicarboxylic acid units in the polyester layer 12c is, for example, 0.5 mol % or more and 5 mol % or less.

The PET that constitutes the polyester layer 12c may include recycled PET, which is recycled PET. When recycled PET is included, the environmental impact of the blank 10 can be suppressed. PET products targeted for recycling include used PET bottles. The recycled PET constituting the polyester layer 12c is at least one of PET regenerated by mechanical recycling and PET regenerated by chemical recycling.

In mechanical recycling, PET products are pulverized and washed to remove surface stains and foreign matter, and then the resin is exposed to high temperatures to remove contaminants remaining inside the resin. In chemical recycling, PET products are pulverized and washed to remove surface stains and foreign matter, then depolymerized to return the resin to intermediate raw materials, and the intermediate raw materials are purified and repolymerized to produce PET. Compared to chemical recycling, mechanical recycling does not require large-scale equipment for chemical reaction, and therefore the cost and environmental load required for manufacturing recycled PET are small. Therefore, when it is required to reduce the manufacturing cost and the environmental load, the recycled PET constituting the polyester layer 12c is preferably PET regenerated by mechanical recycling.

In addition to recycled PET, the constituent material of the polyester layer 12c may include virgin PET, which is PET newly synthesized from raw materials such as petroleum, or may include polyester other than recycled PET. The mass ratio of the recycled PET constituting the polyester layer 12c is preferably 60% or more and 100% or less with respect to the total mass of the polyester layer 12c.

The diol unit of polyethylene terephthalate is ethylene glycol and the dicarboxylic acid unit of polyethylene terephthalate is 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 PET compared to PET consisting only of terephthalic acid, suppresses crystallization of PET, and enhances processability of PET. 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 PET constituting the polyester layer 12c is not particularly limited, it is preferably 1,000 or more and 1,000,000 or less, for example. The constituent material of the polyester layer 12c may contain resins other than PET and various additives. Resins other than PET are, for example, polyesters other than recycled PET and virgin PET, and the polyesters have, for example, chain aliphatic carboxylic acids or cycloaliphatic carboxylic acids as carboxylic acid units. Additives include, for example, plasticizers, coloring inhibitors, antistatic agents, weathering agents, ultraviolet absorbers, deodorants, and antioxidants.

The polyester layer 12c may be composed of one layer, or may be a laminate composed of a plurality of layers. When the polyester layer 12c is a laminate, at least one layer of the laminate comprises PET containing terephthalic acid and isophthalic acid among the dicarboxylic acid units.

The thickness of the polyester layer 12c is, for example, 5 μm or more, preferably 10 μm or more. Moreover, the thickness of the polyester layer 12c is, for example, 25 μm or less, preferably 20 μm or less.

As a method for forming the polyester layer 12c, a known film forming method such as extrusion molding can be used. Cooling in extrusion molding can also be performed by a known method such as cooling rolls, air cooling, or water cooling. The polyester layer 12c may be a stretched film or an unstretched film. A known method such as uniaxial stretching or biaxial stretching can be used for stretching the polyester layer 12c.

The inner layer 12 may have layers other than the first thermoplastic resin layer 12a, the second thermoplastic resin layer 12b, and the polyester layer 12c. Examples of the other layer include a barrier layer for suppressing permeation of oxygen and water vapor.

The barrier layer is, for example, at least one selected from the group consisting of inorganic oxide layers, metal layers and resin films. Constituent materials for the inorganic oxide layer include silicon oxide, magnesium oxide, aluminum oxide, titanium oxide, zirconium oxide, calcium oxide, potassium oxide, tin oxide, boron oxide, yttrium oxide, and the like. It is at least one selected from the group consisting of A constituent material of the metal layer is at least one selected from the group consisting of aluminum, titanium, zirconium, yttrium, tin, chromium, and nickel. An example of the constituent material of the resin film is saponified ethylene-vinyl acetate copolymer.

The thickness of the entire inner layer 12 is, for example, 25 μm or more, preferably 50 μm or more. Also, the thickness of the entire inner layer 12 is, for example, 125 μm or less, preferably 100 μm or less. Also, the thickness of the entire inner layer 12 is, for example, 0.5 times or less, preferably 0.2 times or less, the thickness of the base material layer 11 .

(outer layer)
The outer layer 13 comprises a third thermoplastic resin layer 13a. The third thermoplastic resin layer 13a is, for example, a sealant layer that is used as a welded portion when forming a paper container from the blank 10. As shown in FIG. The thermoplastic resin forming the third thermoplastic resin layer 13a is polyolefin resin. Polyolefin resins are, for example, ethylene-based resins and propylene-based resins.

Examples of ethylene-based resins include polyethylene and ethylene/vinyl acetate copolymer. Polyethylene is selected from the group consisting of, for example, low density polyethylene (LDPE), linear low density polyethylene (LLDPE) obtained by copolymerizing α-olefin and ethylene, medium density polyethylene (MDPE), and high density polyethylene (HDPE). is one of the The propylene-based resin is, for example, one selected from the group consisting of homopolypropylene, propylene/ethylene random copolymer, propylene/ethylene block copolymer, and propylene/α-olefin copolymer.

The constituent material of the third thermoplastic resin layer 13a may contain resins other than the thermoplastic resins described above and various additives. Additives include, for example, plasticizers, coloring inhibitors, antistatic agents, weathering agents, ultraviolet absorbers, deodorants, and antioxidants.

The melting point of the third thermoplastic resin layer 13a is, for example, 90° C. or higher, preferably 110° C. or higher. Also, the melting point of the third thermoplastic resin layer 13a is, for example, 200° C. or less, preferably 180° C. or less.

The thickness of the third thermoplastic resin layer 13a is, for example, 20 μm or more, preferably 30 μm or more. Also, the thickness of the third thermoplastic resin layer 13a is, for example, 60 μm or less, preferably 50 μm or less.

The outer layer 13 may have a plurality of third thermoplastic resin layers 13a, or may have layers other than the third thermoplastic resin layer 13a. Examples of the other layers include a printed layer for displaying characters, figures, symbols, patterns, etc. formed by printing, the barrier layer, and a polyester layer similar to the polyester layer 12c. Also, the outer layer 13 may be the same layer as the inner layer 12 .

The thickness of the entire outer layer 13 is, for example, 20 μm or more, preferably 30 μm or more. Also, the thickness of the entire outer layer 13 is, for example, 80 μm or less, preferably 70 μm or less. Also, the thickness of the entire outer layer 13 is, for example, 0.6 times or less, preferably 0.4 times or less, the thickness of the base material layer 11 .

<Blank manufacturing method>
Next, a method for manufacturing the blank 10 will be described.
The manufacturing method of the blank 10 includes a lamination step of forming the main body portion 14 by laminating various sheets under pressure, and a folding step of forming the covering portion 15 . In the lamination step, the lamination method for laminating various sheets while applying pressure is not particularly limited, and a known lamination method applied to manufacture of blanks for paper containers can be used. Known lamination methods include, for example, a dry lamination method, an extrusion lamination method, and a sandwich lamination method.

As an example, a lamination process using a sandwich lamination method and an extrusion lamination method will be described below. This lamination process has a first lamination process of manufacturing a single-sided laminate using a sandwich lamination method, and a second lamination process of manufacturing a double-sided laminate using an extrusion lamination method. The single-layered body is a laminate in which the inner layer 12 is laminated on one surface of the base material layer 11, ie, the inner surface 11a. The double-sided laminate is a laminate in which the outer layer 13 is laminated on the surface of the base material layer 11 in the single-sided laminate, that is, the surface that becomes the outer surface 11b. Therefore, the double-sided laminate is a laminate comprising the substrate layer 11 , the inner layer 12 and the outer layer 13 .

As shown in FIG. 3A, in the first laminating step, the base sheet 21 unwound from the base paper roll 21a and the inner layer sheet 22 unwound from the inner layer roll 22a are passed through the nip roll N1 and the cooling roll C1. supplied between Sand resin 23 in a molten state extruded from extruder 23a is supplied between nip roll N1 and cooling roll C1 in a manner sandwiched between base sheet 21 and inner layer sheet 22. .

As shown in FIG. 4 , the base sheet 21 is a sheet material made of a paper base that constitutes the base layer 11 . The base sheet 21 is provided with a hole portion 21 b that is an elongated through hole formed along a portion of the main body portion 14 of the blank 10 that will become the first end portion 14 a.

As shown in FIG. 3(b), the inner layer sheet 22 is a sheet material having a layered structure in which the first thermoplastic resin layer 12a is removed from the inner layer 12. As shown in FIG. The sand resin 23 is a constituent material of the first thermoplastic resin layer 12a. The hardness of the nip roll N1 is, for example, 60 or more and 90 or less as measured by a type A durometer. The temperature of the nip roll N1 is, for example, 10° C. or higher and 30° C. or lower. The nip pressure between the nip roll N1 and the cooling roll C1 is, for example, 1000 kPa or more and 2000 kPa or less.

With the sand resin 23 sandwiched between the base sheet 21 and the inner layer sheet 22, the sheet-like single-layered body 24 is formed by applying pressure and cooling by the nip roll N1 and the cooling roll C1. The formed single-sided layered body 24 is wound into a roll to form an intermediate roll 24a.

As shown in FIG. 5, in the second laminating step, the single-sided layered body 24 unwound from the intermediate roll 24a and the extruded resin 25 in a molten state extruded from the extruder 25a are passed through the nip roll N2 and the cooling roll C2. supplied between The extruded resin 25 is a constituent material of the third thermoplastic resin layer 13a. The hardness of the nip roll N2 is, for example, 60 or more and 90 or less as measured by a type A durometer. The temperature of the nip roll N2 is, for example, 10° C. or higher and 30° C. or lower. The nip pressure between the nip roll N2 and the cooling roll C2 is, for example, 1000 kPa or more and 2000 kPa or less.

In a state in which the extruded resin 25 is laminated on the surface of the single-sided layered body 24 on the base sheet 21 side, pressure and cooling are performed by the nip roll N2 and the cooling roll C2, thereby forming a sheet-like double-sided laminated body 26. be done. The formed double-sided laminate 26 is wound into a roll.

As shown in FIG. 6A, the double-sided laminate 26 includes a portion where the inner layer 12 and the outer layer 13 are welded to the base layer 11, and a portion where the holes 21b are located in the base layer 11. 12 and an extension portion 26a to which the outer layer 13 is welded.

As shown in FIG. 6B, the double-sided laminated body 26 is cut into a shape corresponding to the main body portion 14 of the blank 10 to be manufactured while leaving a part of the extending portion 26a, and then folded back. provided for the process.

As shown in FIG. 6C, in the folding step, the extending portion 26a of the double-sided laminated body 26 and its peripheral portion are heated and softened, and then the extending portion 26a is folded back toward the main body portion 14 side. Then, the covering portion 15 is formed by welding the surfaces of the outer layer 13 to each other at the portion where the folded extension portion 26a and the main body portion 14 overlap each other. Thereby, the blank 10 including the body portion 14 and the covering portion 15 is manufactured. In addition, as a specific method of the folding process, for example, the method disclosed in Patent Document 1 can be mentioned.

<Paper container and paper container manufacturing method>
A method of manufacturing the paper container 30 using the blank 10 will be described.
As shown in the lower part of FIG. 7( a ), a cup-shaped paper container 30 has a tubular body 31 formed from the blank 10 and a plate-shaped bottom 32 arranged at the bottom of the body 31 . It has A flange portion 31b is formed at the upper edge of the body portion 31 by bending the upper portion of the body portion 31 so as to roll it outward. The upper surface 31b1 of the flange portion 31b is a flat surface obtained by flattening the upper portion of the flange portion 31b.

The method for manufacturing the paper container 30 includes a blank manufacturing process for manufacturing the blank 10 and a body forming process for forming the cylindrical body 31 using the blank 10 . The blank manufacturing process is a process of manufacturing the blank 10 by the blank manufacturing method described above.

As shown in the left upper part of FIG. 7A and FIG. The trunk portion 31 is formed by overlapping and bonding the second end portion 14b located on the opposite side of the portion 14a. At this time, the first end portion 14a and the second end portion 14b are overlapped so that the inner layer 12 of the blank 10 faces inward and the first end portion 14a is positioned inside the second end portion 14b. Therefore, the covering portion 15 provided at the first end portion 14a is folded outward, and the folded portion of the covering portion 15 is adhered to the inner layer 12 of the second end portion 14b. there is The method of bonding the first end portion 14a and the second end portion 14b of the main body portion 14 of the blank 10 is not particularly limited. A matching method can be applied.

Further, the method of manufacturing the paper container 30 includes a flange forming step of forming the flange portion 31b on the body portion 31, and a flattening step of forming a flat surface on the flange portion 31b.
As shown in FIGS. 8(a) and 8(b), in the flange forming step, the upper portion of the body portion 31, that is, the entire peripheral edge of the upper portion including the portion where the covering portion 15 is provided is folded outward. As a result, the flange portion 31b having a curled shape with a substantially circular cross section is formed. The amount of winding of the upper portion of the body portion 31 in the flange forming step is, for example, one turn or more, preferably one and a half turns or more.

As shown in FIGS. 8B and 8C, in the flattening step, the flange portion 31b, which is curled into a substantially circular cross section, is pressed and crimped from above and below to be crushed. Thereby, a flattened upper surface 31b1 is formed on the flange portion 31b. The method of pressurization and crimping in the flattening step is not particularly limited, and for example, a known direction used for forming a flange portion of a paper container, such as a method using an ultrasonic sealing device, can be applied.

Then, as shown in FIG. 7A, a bottom portion 32 is formed by bending the peripheral portion downward on the lower inner peripheral surface of the cylindrical body portion 31 that has undergone the body portion forming process, the flange forming process, and the flattening process. The cup-shaped paper container 30 is manufactured by joining.

<Characteristics of polyester layer>
As shown in FIG. 6(c), a gap S is formed near the end surface 11c of the base material layer 11 inside the covering portion 15 of the blank 10, where the inner layer 12 and the outer layer 13 are not welded. As shown in FIG. 6(a), the gap S is produced by the inability of the inner layer 12 to deform along the end surface of the base material layer 11 when pressed by the nip roll N2 in the second laminating step. is. Therefore, the gap S tends to be formed larger as the base material layer 11 is thicker.

In the blank 10 and the body portion 31 of the paper container 30 of the present embodiment, the stress characteristics and viscoelastic characteristics of the polyester layer 12c are adjusted in order to further reduce the gap S generated inside the covering portion 15 .

The polyester layer 12c has a tensile yield stress set within the following range. FIG. 9 is an example of a stress-strain curve obtained by a tensile test on a test piece formed only from the polyester layer 12c. A stress-strain curve is measured based on a tensile test in accordance with JIS K7161-1:2014. The tensile yield stress is the stress at the yield point A indicated by the arrow in the stress-strain curve of FIG.

The tensile yield stress of the polyester layer 12c is 109 MPa or more and 117 MPa or less, preferably 109 MPa or more and 113 MPa or less.
The tensile yield stress of the polyester layer 12c is determined by the temperature at which the polyester layer 12c is extruded, the temperature at which the extruded precursor of the polyester layer 12c is cooled, the speed at which the precursor is cooled, and the stretching magnification of the polyester layer 12c. and so on. Also, the tensile yield stress of the polyester layer 12c can be adjusted by the ratio of isophthalic acid to all dicarboxylic acid units contained in the polyester layer 12c.

For example, if the temperature at which the polyester layer 12c is extruded is increased or the temperature at which the extruded precursor of the polyester layer 12c is cooled is decreased, the tensile yield stress increases. Also, increasing the cooling rate of the precursor, increasing the stretching ratio of the polyester layer 12c, or increasing the ratio of isophthalic acid to all dicarboxylic acid units contained in the polyester layer 12c lowers the tensile yield stress.

For the polyester layer 12c, the temperature T1 at the peak position of the loss tangent (tan δ) is set within the following temperature range. The temperature T1 at the peak position of the loss tangent is the temperature at the peak position of the loss tangent obtained by dynamic viscoelasticity measurement at a frequency of 10 Hz and a temperature range of 30 to 180.degree. The temperature T1 at the peak position of the loss tangent is 116° C. or less, preferably 111° C. or less. Also, the temperature T1 at the peak position of the loss tangent is, for example, 105° C. or higher.

The temperature T1 at the peak position of the loss tangent can be adjusted by, for example, the composition of the polyester layer 12c, the temperature and speed of extrusion/cooling, and the manufacturing conditions such as the draw ratio. For example, by increasing the cooling rate during the production of the polyester layer 12c, the amorphous portion can be left and the temperature T1 can be lowered.

The tensile yield stress of each of the first thermoplastic resin layer 12a and the second thermoplastic resin layer 12b, which constitute the inner layer 12 together with the polyester layer 12c, is lower than the tensile yield stress of the polyester layer 12c. Further, the temperature T1 at the peak position of the loss tangent of each of the first thermoplastic resin layer 12a and the second thermoplastic resin layer 12b is lower than the temperature T1 of the peak position of the loss tangent of the polyester layer 12c.

Next, the operation and effects of this embodiment will be described.
Each inner layer 12 of the body portion 31 of the blank 10 and the paper container 30 of this embodiment comprises a first thermoplastic resin layer 12a, a second thermoplastic resin layer 12b, and a polyester layer 12c. As the polyester layer 12c, a polyester layer having a tensile yield stress of 109 MPa or more and 117 MPa or less and a temperature T1 at the peak position of the loss tangent of 116° C. or less is used.

When the temperature T1 at the peak position of the tensile yield stress and loss tangent of the polyester layer 12c is set in the above range, the range in which the polyester layer 12c can be deformed with a small stress is widened. Therefore, in the second laminating step, the inner layer 12 is easily deformed along the end surface of the base material layer 11 when pressed by the nip roll N2. Thereby, the gap S generated inside the extending portion 26a of the double-sided laminate 26 can be made smaller. As a result, when the covering portion 15 is formed by folding the extending portion 26a in the folding process, the extending portion 26a is easily deformed. In addition, when forming a flat surface by pressurizing and crimping the flange portion 31b in the flattening process, the covering portion 15 is easily deformed.

Since the extending portion 26a and the covering portion 15 are easily deformed, variations in the shape of the covering portion 15 formed in the folding process and variations in the shape of the flat surface of the flange portion 31b formed in the flattening process occur. is suppressed. As a result, the quality of blank 10 and paper container 30 can be stabilized.

In addition, this embodiment can be changed and implemented as follows. This embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
- The covering portion 15 may be provided at a plurality of ends of the blank 10 .

・The position of the flat surface on the flange portion 31b of the paper container 30 is not limited to the upper surface 31b1 of the flange portion 31b, but may be the lower surface or side surface of the flange portion 31b, or a combination thereof. may Further, the flange portion 31b of the paper container 30 may have a shape without a flat surface.

- The paper container 30 is not limited to the cup-shaped paper container 30, and may be a paper container of other shape having a cylindrical body portion 31 made of the blank 10. Paper containers having other shapes include, for example, a paper container in which the flange portion 31b is omitted, and a paper container having a lid portion that seals the upper portion of the tubular body portion 31 .

Next, the above embodiment will be described more specifically with reference to test examples. It should be noted that the present invention is not limited to the configurations described in Examples.
[Test Example 1]
As shown in FIGS. 3 to 5, a double-sided laminate 26 of Test Example 1 was manufactured by performing a first lamination step and a second lamination step using nip rolls N1 and N2. Various materials and manufacturing conditions used to manufacture the double-sided laminate 26 of Test Example 1 are as follows.

(First lamination step)
Base sheet: A base sheet made of a paper base material having a hole portion 21b with a width of 8 mm and a basis weight of 300 g/m ² .

Inner layer sheet: A composite sheet in which a 20 μm thick thermoplastic resin layer (corresponding to the second thermoplastic resin layer 12b) made of low-density polyethylene is bonded to one surface of a 12 μm thick PET sheet A.

PET sheet A is a PET sheet containing 100% by mass of virgin PET and 0% by mass of recycled PET. PET sheet A was obtained by forming a single resin layer using virgin polyethylene terephthalate as virgin PET.

Sand resin: Low density polyethylene Nip roll hardness: 60
Nip roll temperature: 20°C
Nip pressure: 1500kPa
The thickness of the thermoplastic resin layer (corresponding to the first thermoplastic resin layer 12a) formed from sand resin is 20 μm.

(Second lamination step)
Extrusion resin: Low density polyethylene Nip roll hardness: 60
Nip roll temperature: 20°C
Nip pressure: 1500kPa
The thickness of the thermoplastic resin layer (corresponding to the third thermoplastic resin layer 13a) formed from extruded resin is 20 μm.

[Test Example 2]
A double-sided laminate 26 of Test Example 2 was produced in the same manner as in Test Example 1, except that the PET sheet A constituting the inner layer sheet was changed to a PET sheet B having a thickness of 12 μm.

PET sheet B is a PET sheet containing 0% by mass of virgin PET and 100% by mass of recycled PET. PET sheet B was obtained by laminating three resin layers such that the second resin layer was sandwiched between the two first resin layers. A 1st resin layer is a layer formed from recycled PET regenerated by chemical recycling. The second resin layer is a layer formed from recycled PET obtained by mixing recycled PET recycled by mechanical recycling and recycled PET recycled by chemical recycling at a mass ratio of 80:20 (mechanical recycling: chemical recycling). be.

[Test Example 3]
A double-sided laminate 26 of Test Example 3 was produced in the same manner as in Test Example 1, except that the PET sheet A constituting the inner layer sheet was changed to a PET sheet C having a thickness of 12 μm.

The PET sheet C is a PET sheet containing 20% by mass of virgin PET and 80% by mass of recycled PET. PET sheet C is obtained by forming three resin layers having the same composition from virgin PET and recycled PET regenerated by mechanical recycling, and laminating the formed three resin layers by co-extrusion. rice field.

[Test Example 4]
A double-sided laminate 26 of Test Example 4 was produced in the same manner as in Test Example 1, except that the PET sheet A constituting the inner layer sheet was changed to a PET sheet D having a thickness of 12 μm.

The PET sheet D is a PET sheet containing 30% by mass of virgin PET and 70% by mass of recycled PET. PET sheet D was obtained by laminating three resin layers such that the second resin layer was sandwiched between the two first resin layers. The first resin layer is a layer made of virgin PET. The second resin layer is a layer formed from recycled PET regenerated by chemical recycling.

[Measurement of tensile yield stress]
A test piece was cut out from the PET sheet constituting the inner layer sheet used in each test example. At this time, a dumbbell cutter conforming to JIS Z 1702-1994 (Dumbbell Co., Ltd., SDK-600) was used to cut out each test piece so as to have a shape extending along the flow direction. That is, test pieces were cut out from the PET sheet so that the pulling direction of each test piece coincided with the flow direction of the PET sheet. Two gauge lines for elongation measurement were attached to the test piece.

Using a small tabletop tester (EZ-LX, manufactured by Shimadzu Corporation), a tensile test was performed on the test piece using a method conforming to JIS K7161-1:2014. At this time, the 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 tensile yield stress was obtained from a stress-strain curve created based on the results of the tensile test. Table 1 shows the results.

[Measurement of temperature at peak position of loss tangent]
A belt-shaped test piece having a length of 20 mm and a width of 10 mm was cut out from the PET sheet constituting the inner layer sheet used in each test example. The flow direction (MD direction) during formation of the PET sheet was taken as the length direction of the test piece. Using a thermomechanical analyzer (manufactured by Hitachi High-Tech Science Co., Ltd.: DMA7100), the temperature at the peak position of the loss tangent was measured under the following conditions. Table 1 shows the results.

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 to 180°C
[Measurement of various dimensions of double-sided laminate]
For each obtained test example, the length L1 of the gap S generated in the extending portion 26a and the depth L2 of the recess on the inner layer 12 side of the extending portion 26a were measured. Table 1 shows the results.

As shown in FIG. 6A, the length L1 is positioned from the end surface 11c of the base material layer 11 in the extending portion 26a to the extending portion 26a side of the portion where the inner layer 12 and the outer layer 13 are welded. is the length to the end of the The depth L2 is the maximum distance in the stacking direction between the surface of the inner layer 12 at the portion where the base material layer 11 exists and the surface of the inner layer 12 at the extending portion 26a.

[Evaluation of suitability for returning]
By punching out the double-sided laminate of each test example, a fan-shaped intermediate body having an extension portion 26a at one end was obtained. The fan-shaped intermediate body had an upper side length of 225 mm, a lower side length of 162 mm, and a width of the extension portion 26a of 5.5 mm. Next, the extending portion 26a of the intermediate body is heated by blowing hot air of about 200° C., and the covering portion 15 is formed by folding back and welding the portion of the extending portion 26a about 4 mm from the tip of the extending portion 26a. bottom.

As shown in FIG. 6(c), the suitability for folding of each test example was evaluated based on the length L3 from the end face 11c of the base material layer 11 to the tip of the covering portion 15. As shown in FIG. The length L3 was measured at five randomly selected locations in the longitudinal direction of the covering portion 15, and the difference between the maximum and minimum values was obtained. Table 1 shows the results. In Table 1, the case where the average value of the length L3 is 0.2 mm or less is indicated by "○", the case where it is more than 0.2 mm and 0.5 mm or less is indicated by "Δ", and the case where it exceeds 0.5 mm is indicated by "x".

[Evaluation of suitability for flattening]
The first end portion 14a provided with the covering portion 15 of the blank 10 obtained from each test example and the second end portion 14b located on the opposite side of the first end portion 14a are overlapped and pasted to form the trunk portion. 31 was formed. At this time, the width of the overlapped portion was set to 5 mm.

Next, using a top curl unit, the upper end portion of the body portion 31 was wound more than once to form a flange portion 31b with a width of 3 mm, in which the lower half is single-wound and the upper half is double-wound. After that, the upper surface of the flange portion 31b was processed into a flat surface by pressurizing the flange portion 31b from above and below using an ultrasonic sealing device.

The flattening suitability of each test example was evaluated based on visual observation of the appearance of the flange portion 31b. Table 1 shows the results. In Table 1, the case where the flange portion 31b has a flat shape is indicated by "○", and the case where the upper surface is formed with a flat surface but has a circular shape as a whole is indicated by "Δ". .

引張降伏応力が１０９ＭＰａ以上１１７ＭＰａ以下であり、損失正接のピーク位置の温度が１１６℃以下である、という条件を満たすＰＥＴシートを用いた試験例２～４は、上記条件を満たさないＰＥＴシートを用いた試験例１と比較して、長さＬ１及び深さＬ２の一方又は両方が小さい。つまり、試験例２～４は、試験例１と比較して、隙間Ｓが小さくなっている。

Test Examples 2 to 4 using PET sheets that satisfy the conditions that the tensile yield stress is 109 MPa or more and 117 MPa or less and the temperature at the peak position of the loss tangent is 116 ° C. or less are PET sheets that do not satisfy the above conditions. One or both of the length L1 and the depth L2 are smaller than in Test Example 1. That is, in Test Examples 2 to 4, the gap S is smaller than in Test Example 1.

In Test Examples 2 to 4 using PET sheets satisfying the above conditions, the evaluation of folding aptitude was "△" or "○". On the other hand, in Test Example 1 using a PET sheet that does not satisfy the above conditions, the evaluation of folding aptitude was "x". Further, in Test Examples 2 to 4 using PET sheets satisfying the above conditions, the flattening aptitude was evaluated as "good". On the other hand, in Test Example 1 using a PET sheet that does not satisfy the above conditions, the folding suitability was evaluated as "Δ".

These results show that the inner layer 12 having the polyester layer 12c is made flexible by using the polyester layer 12c that satisfies the above conditions, and the gap S generated at the folded edge of the covering portion 15 is reduced. It also shows that as the gap S becomes smaller, variations in the shapes of the flat surfaces of the covering portion 15 and the flange portion 31b become smaller. Among Test Examples 2 to 4, test examples using PET sheets that satisfy the conditions that the tensile yield stress is 109 MPa or more and 113 MPa or less and the temperature at the peak position of the loss tangent is 108° C. or more and 111° C. or less. 4 was particularly excellent in folding aptitude.

Next, technical ideas that can be grasped from the above embodiment and modifications will be described below.
(a) a body portion comprising a base layer made of paper, an inner layer provided on the inner surface of the base layer, and an outer layer provided on the outer surface of the base layer; and covering the end face of the base layer in the body portion A method for manufacturing a blank for a paper container, comprising: a covering portion that a laminating step of forming an extending portion in which the main body portion and portions of the inner layer sheet and the outer layer sheet extending beyond the end surface of the base material layer are bonded together by laminating the extending portion; a folding step of forming the covering portion by folding back toward the main body portion, and in the laminating step, the main body portion and the extension portion are bonded together by thermal welding of polyolefin resin, and the inner layer sheet is made of polyester. a layer, wherein the polyester layer has a tensile yield stress of 109 MPa or more and 117 MPa or less, and a temperature at a peak position of the loss tangent of the polyester layer is 116° C. or less. In addition, the inner layer sheet and the outer layer sheet are concepts that include sheet-like portions formed of extruded resin when the extrusion lamination method is used.

(b) The blank in which the base sheet used in the lamination step has a hole, and the extending portion is a portion of the inner layer sheet and the outer layer sheet that are bonded together at the hole. manufacturing method.

(C) A method for manufacturing a paper container having a cylindrical body, comprising: a blank manufacturing step of manufacturing a blank by the blank manufacturing method; An end portion and a second end portion located on the opposite side of the first end portion are overlapped and adhered so that the inner layer faces inward and the first end portion is located inward, thereby forming a tubular shape. A body portion forming step of forming a body portion, a flange forming step of forming a flange portion by winding an edge portion of the body portion outward, and a flat surface is formed by flattening a portion of the flange portion. A method for manufacturing a paper container, comprising a flattening step.

DESCRIPTION OF SYMBOLS 10... Blank 11... Base material layer 12... Inner layer 12a... 1st thermoplastic resin layer 12b... 2nd thermoplastic resin layer 12c... Polyester layer 13... Outer layer 13a... 3rd thermoplastic resin layer 14... Main-body part 15... Coating part 26a... Extension part 30... Paper container 31... Body part 31b... Flange part

Claims (5)

A main body portion comprising a base layer made of paper, an inner layer provided on the inner surface of the base layer, and an outer layer provided on the outer surface of the base layer, and a covering portion covering the end surface of the base layer in the main body portion. and
The inner layer comprises a first thermoplastic resin layer, a second thermoplastic resin layer, and a polyester layer positioned between the first thermoplastic resin layer and the second thermoplastic resin layer, which are in contact with the inner surface of the base material layer. prepared,
The outer layer comprises a third thermoplastic resin layer in contact with the outer surface of the base layer,
In the covering portion, extending portions of the inner layer and the outer layer that extend beyond the end surface of the base layer are welded to the first thermoplastic resin layer and the third thermoplastic resin layer, and the A blank for a paper container, which is a portion folded back toward the main body,
The thermoplastic resin constituting the first thermoplastic resin layer and the second thermoplastic resin layer is a polyolefin resin,
The blank, wherein the polyester layer has a tensile yield stress of 109 MPa or more and 117 MPa or less, and a temperature of a peak position of loss tangent of 116° C. or less. The blank according to claim 1, wherein the polyester layer has a tensile yield stress of 109 MPa or more and 113 MPa or less, and a temperature of a peak position of loss tangent of the polyester layer of 108°C or more and 111°C or less. 3. The blank according to claim 1, wherein said polyolefin resin is polyethylene. A paper container comprising a cylindrical body made of the blank according to any one of claims 1 to 3,
The trunk portion is configured to connect a first end portion of the body portion of the blank where the covering portion is provided and a second end portion located on the opposite side of the first end portion with the inner layer facing inward and the A paper container, characterized in that the paper container is laminated so that the first end is located inside. The trunk portion has a flange portion formed by winding the edge portion outward,
5. The paper-made container according to claim 4, wherein the flange portion has a flat surface that is flattened.

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