Lid material and method for manufacturing same

Abstract

Provided are a lid material capable of reducing or suppressing the occurrence of a curl caused by a change in humidity and the occurrence of a blister during heat sealing, and a method for manufacturing the same.　A lid material has a printing layer, a paper layer, and a sealant layer. When the lid material is dried in a vacuum oven at 60°C for 4 hours, and seasoning is performed for 60 minutes in an environment of 23°C and 50% RH (relative humidity) based on the mass after drying, the moisture absorption amount is 3.2 g / m2 or less, the paper layer is coated with a resin coating agent from a printing layer side on a paper base material layer, and a laminate of the printing layer and the paper layer, when measured from a paper base material layer side toward the printing layer side by the Oken type testing machine method according to JIS P8117:2019, has an air permeability of 150,000 seconds or less.

Description

Lid material and its manufacturing method

[0001] The present invention relates to a lid material and a method for manufacturing the same.

[0002] In recent years, various studies have been conducted on paper-based lid materials.

[0003] For example, Patent Document 1 discloses a lid material characterized by being a laminate consisting of at least a biaxially oriented plastic film having a water-retaining layer on one side of paper and a vapor-deposited film of inorganic oxide on the other side, an adhesion adjustment layer, and a hot melt layer.

[0004] Patent Document 2 discloses a heat-sealable lid material that is made of a laminated sheet including a paper layer supplied with a water retention agent and the innermost layer of which is a hot melt layer, and that has a light-blocking ink layer laminated on at least the inner surface side of the paper layer, and that has a light transmittance of 15% or less in the wavelength range of 200 to 800 nm.

[0005] Patent Document 3 discloses a lid material for paper cups, characterized in that it is formed by laminating a paper layer, an adhesive layer, a biaxially oriented plastic film layer, and a hot melt layer in this order.

[0006] Patent Document 4 discloses a lid material that is heat-sealed to a cup-shaped container having a resin layer formed at least on the surface, the lid material being made of a composite sheet with a paper intermediate layer and a resin layer or an aluminum foil layer on both the front and back sides of the paper, characterized in that the air permeability of the paper is 10 seconds or less as measured by the "JIS P8117 Gurley tester method."

[0007] Japanese Patent Application Laid-Open No. 2000-118546 Japanese Patent Application Laid-Open No. 2000-006295 Japanese Patent Application Laid-Open No. 09-066586 Japanese Patent Application Laid-Open No. 2004-196381

[0008] It has been known that general-purpose paper lid materials tend to curl, and to address this problem, measures have been proposed, such as providing a water-retaining layer on the paper substrate or using a paper layer supplied with a water-retaining agent.

[0009] However, when a humectant or water-retaining agent is applied to a paper substrate, curling can be suppressed during the production of the lid material, but there is a problem that curling occurs when the manufactured lid material is placed in an environment with variable humidity. More specifically, for example, a lid material manufactured by applying a mixed solution of water and methanol to the back surface of a paper substrate can suppress the generation of convex curl under high humidity conditions, but there is a problem that concave curl occurs under low humidity conditions.

[0010] In response to this, for example, a lid material has been proposed in which a resin layer or an aluminum foil layer is provided on both sides of a paper substrate. Such a paper substrate allows relatively little moisture to enter or exit, and therefore can suppress curling caused by changes in humidity.

[0011] However, in lid materials in which resin layers or aluminum foil layers are provided on both sides of a paper substrate, the heat applied when heat-sealing the lid material to a container or the like may cause the moisture contained in the paper substrate to evaporate, generating high-temperature water vapor within the paper substrate of the lid material. In particular, in the case of lid materials in which resin layers or aluminum foil layers are provided on both sides of the paper substrate, the generated water vapor has nowhere to escape except through the edge surfaces of the paper substrate of the lid material, which can cause a problem of partial peeling (this phenomenon is also called "blistering" or "bubbling") occurring within the lid material, for example, at the adhesive surface between the paper substrate and the resin layer or aluminum foil layer.

[0012] On the other hand, if a paper substrate with a low air permeability value (i.e., a paper substrate that is easily permeable) is used, it is possible to suppress the occurrence of the above-mentioned blisters, but the inflow and outflow of moisture becomes relatively intense, making it impossible to suppress the occurrence of curl. Furthermore, when a paper substrate with a low air permeability value is used, there is a possibility that printability will be poor.

[0013] As described above, it is difficult for a lid material to simultaneously suppress the occurrence of curling due to changes in humidity and the occurrence of blisters during heat sealing.

[0014] The present invention aims to improve the above-mentioned circumstances, and its object is to provide a lid material and a method for manufacturing the same that can reduce or suppress the occurrence of curling due to changes in humidity and the occurrence of blisters during heat sealing.

[0015] The present invention that achieves the above object is as follows.

[0016] <Aspect 1> A lid material having a print layer, a paper layer, and a sealant layer, wherein the lid material is dried in a vacuum oven at 60°C for 4 hours, and when the lid material is seasoned for 60 minutes in an environment of 23°C and 50% RH (relative humidity), based on the mass after drying, the moisture absorption amount is 3.2 g / m ２ The paper layer is coated with a resin coating agent from the printed layer side on the paper base layer, and the laminate of the printed layer and the paper layer has an air permeability of 150,000 seconds or less when measured from the paper base layer side toward the printed layer side using the Oken testing machine method of JIS P8117:2019. ２The lid material according to Aspect 1, wherein the resin coating agent comprises a resin selected from the group consisting of polyvinylidene chloride, polyester, polyvinyl alcohol, and combinations of two or more thereof. Aspect 4 The lid material according to any one of Aspects 1 to 3, further comprising a barrier layer, and having the printed layer, the paper layer, the barrier layer, and the sealant layer in this order. Aspect 5 The lid material according to Aspect 4, wherein the barrier layer is selected from the group consisting of a metal foil layer, an inorganic vapor deposition layer, an organic coating layer, and combinations of two or more thereof. Aspect 6 The lid material according to any one of Aspects 1 to 5, wherein the printed layer has an ink layer and an overprint varnish layer on the ink layer. Aspect 7 A method for producing the lid material according to any one of Aspects 1 to 6, comprising applying the resin coating agent to a surface of the paper base layer that will be laminated with the printed layer to obtain the paper layer. Aspect 8 The method according to Aspect 7, wherein the resin coating agent comprises a resin selected from the group consisting of polyvinylidene chloride, polyester, polyvinyl alcohol, and combinations of two or more thereof.

[0017] According to the present invention, it is possible to provide a lid material and a method for producing the same that can reduce or suppress the occurrence of curling due to changes in humidity and the occurrence of blisters during heat sealing.

[0018] Fig. 1 is a cross-sectional schematic diagram showing one embodiment of the layer structure of the lid material of the present invention. Fig. 2 is a cross-sectional schematic diagram showing one embodiment of the layer structure of the printed layer of the present invention. Fig. 3 is a cross-sectional schematic diagram showing one embodiment of the layer structure of the lid material of the present invention when further including a barrier layer.

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the preferred embodiments. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the present invention.

[0020] The lid material of the present invention is a lid material having a print layer, a paper layer, and a sealant layer, and when the lid material is dried in a vacuum oven at 60°C for 4 hours and then seasoned for 60 minutes in an environment of 23°C and 50% RH (relative humidity), based on the mass after drying, the moisture absorption amount is 3.2 g / m２ the paper layer is coated with a resin coating agent from the printing layer side on the paper base layer, and the laminate of the printing layer and the paper layer has an air permeability of 150,000 seconds or less when measured from the paper base layer side toward the printing layer side using the Oken type testing machine method of JIS P8117:2019.

[0021] The lid material of the present invention can reduce or suppress the occurrence of curling due to changes in humidity and the occurrence of blisters during heat sealing. Without being limited by theory, this is presumably due mainly to the effect of limiting the moisture absorption amount of the lid material of the present invention to a certain value or less and limiting the value of the air permeability of the laminate of the print layer and paper layer contained in the lid material of the present invention to a certain value range or less. More specifically, the lid material of the present invention is dried in a vacuum oven at 60°C for 4 hours, and when the lid material is seasoned in an environment of 23°C and 50% RH (relative humidity), the moisture absorption amount in 60 minutes is 3.2 g / m2, based on the mass after drying. ２ By setting the temperature to 150,000 seconds or less, the inflow and outflow of moisture can be relatively suppressed. That is, the lid material of the present invention can reduce or suppress the occurrence of curling even when placed in an environment with changing humidity. Furthermore, in the lid material of the present invention, by setting the air permeability value of the laminate of the printed layer and the paper layer to 150,000 seconds or less when measured from the paper base layer side toward the printed layer side using the Oken testing machine method of JIS P8117:2019, the laminate of the printed layer and the paper layer becomes more air permeable, that is, the lid material of the present invention can reduce or suppress the occurrence of blisters even when heated when heat-sealed to a container or the like.

[0022] <Characteristics of Lid Material> (Moisture Absorption Amount) The moisture absorption amount of the lid material of the present invention can be determined by the following method. That is, for example, the lid material is placed in a substantially round shape with a diameter of 101 mm (area: 0.00824 m ２), which is then dried in a vacuum oven at 60°C for 4 hours, with the mass after drying being used as the reference (0 (zero)). Next, the dried lid material is seasoned in an environment of 23°C and 50% RH (relative humidity), and the change in mass over time is measured. Then, the amount of moisture absorption after a specific time (for example, after 60 minutes, 40 minutes, or 20 minutes) can be calculated based on the following formula. Moisture absorption (g / m ２ ) = mass after moisture absorption (g / m ２ ) - Mass after drying in a vacuum oven (g / m ２ )

[0023] The moisture absorption amount of the lid material of the present invention after 60 minutes at 23°C and 50% RH (relative humidity) determined by the above method is 3.2 g / m ２ More specifically, the moisture absorption amount under these conditions is 3.2 g / m ２ Below, 3.1g / m ２ Below, 3.0g / m ２ Below, 2.9g / m ２ Below, 2.8g / m ２ Below, 2.7g / m ２ Below, 2.6g / m ２ Below, 2.5g / m ２ Below, 2.4g / m ２ Below, 2.3g / m ２ Below, 2.2g / m ２ Below, 2.1g / m ２ Below, 2.0g / m ２ Below, 1.9g / m ２ Below, 1.8g / m ２ Below, 1.7g / m ２ Below, 1.6g / m ２ Below, 1.5g / m ２ Below, 1.4g / m ２ Below, 1.3g / m ２ Below, 1.2g / m ２ Below, 1.1g / m ２ or less, or 1.0 g / m ２ The lower limit of the moisture absorption amount under these conditions is not particularly limited, and may be, for example, 0.0 g / m ２ Above, 0.0g / m ２ Super, 0.1g / m ２ Above, 0.2g / m２ Above, 0.3g / m ２ Above, 0.4g / m ２ Above, 0.5g / m ２ Above, 0.6g / m ２ Above, 0.7g / m ２ Above, 0.8g / m ２ Above, 0.9g / m ２ or more, or 1.0 g / m ２ It may be more than that.

[0024] Furthermore, the moisture absorption amount of the lid material of the present invention after 40 minutes at 23°C and 50% RH (relative humidity) as determined by the above method is not particularly limited, and may be, for example, 3.0 g / m ２ Below, 2.9g / m ２ Below, 2.8g / m ２ Below, 2.7g / m ２ Below, 2.6g / m ２ Below, 2.5g / m ２ Below, 2.4g / m ２ Below, 2.3g / m ２ Below, 2.2g / m ２ Below, 2.1g / m ２ Below, 2.0g / m ２ Below, 1.9g / m ２ Below, 1.8g / m ２ Below, 1.7g / m ２ Below, 1.6g / m ２ Below, 1.5g / m ２ Below, 1.4g / m ２ Below, 1.3g / m ２ Below, 1.2g / m ２ Below, 1.1g / m ２ or less, or 1.0 g / m ２ or less, and may be 0.0 g / m ２ Above, 0.0g / m ２ Super, 0.1g / m ２ Above, 0.2g / m ２ Above, 0.3g / m ２ Above, 0.4g / m ２ Above, 0.5g / m ２ Above, 0.6g / m ２ Above, 0.7g / m ２ Above, 0.8g / m ２ Above, 0.9g / m ２or more, or 1.0 g / m ２ It may be more than that.

[0025] Furthermore, the moisture absorption amount of the lid material of the present invention after 20 minutes at 23°C and 50% RH (relative humidity) as determined by the above method is not particularly limited, and may be, for example, 2.0 g / m ２ Below, 1.9g / m ２ Below, 1.8g / m ２ Below, 1.7g / m ２ Below, 1.6g / m ２ Below, 1.5g / m ２ Below, 1.4g / m ２ Below, 1.3g / m ２ Below, 1.2g / m ２ Below, 1.1g / m ２ Below, 1.0g / m ２ Below, 0.9g / m ２ Below, 0.8g / m ２ Below, 0.7g / m ２ Below, 0.6g / m ２ or less, or 0.5 g / m ２ or less, and may be 0.0 g / m ２ Above, 0.0g / m ２ Super, 0.1g / m ２ Above, 0.2g / m ２ Above, 0.3g / m ２ Above, 0.4g / m ２ or more, or 0.5 g / m ２ It may be more than that.

[0026] In the present invention, the moisture absorption amount of the lid material can be adjusted appropriately by, for example, the type and amount of resin coating agent applied to the paper base layer.

[0027] (Thickness) The thickness of the lid material of the present invention is not particularly limited, and may be, for example, 40 μm or more, 50 μm or more, 60 μm or more, 70 μm or more, 80 μm or more, 90 μm or more, 100 μm or more, or 150 μm or more, and may be 200 μm or less, 180 μm or less, 150 μm or less, 120 μm or less, or 100 μm or less.

[0028] <Layer structure of lid material> The layer structure of the lid material of the present invention will be exemplified below using the drawings. For ease of explanation, the same or corresponding parts in each drawing are given the same reference numerals, and duplicate explanations will be omitted. In addition, not all of the components of the embodiment are necessarily essential, and some components may be omitted. However, the embodiments shown in the following drawings are merely examples of the present invention and do not limit the present invention.

[0029] FIG. 1 is a schematic cross-sectional view showing one embodiment of the layer structure of the lid material of the present invention.

[0030] As shown in Figure 1, the lid material 100 of the present invention has, in this order, a printed layer 10, a paper layer 20, and a sealant layer 30. The paper layer 20 is made of a paper base layer 20b coated with a resin coating agent 20a from the printed layer 10 side. Typically, the lid material 100 has the printed layer 10 side as the front layer and the sealant layer 30 side as the back layer, and can be heat-sealed to a container or the like via the sealant layer 30.

[0031] (Printed Layer) The lid material of the present invention has a printed layer. The printed layer is provided with a pattern, text information, etc., and can also be used as a functional layer for blocking light, ultraviolet rays, etc.

[0032] In the present invention, the thickness of the printing layer is not particularly limited and may be, for example, 0.1 μm or more, 0.5 μm or more, 1.0 μm or more, 2.0 μm or more, 3.0 μm or more, 4.0 μm or more, 5.0 μm or more, 6.0 μm or more, 7.0 μm or more, 8.0 μm or more, 9.0 μm or more, or 10 μm or more, and may be 10 μm or less, 8.0 μm or less, 5.0 μm or less, 3.0 μm or less, or 1.0 μm or less.

[0033] In the present invention, the print layer may have, for example, only an ink layer, or may have an ink layer and an overprint varnish layer on the ink layer.

[0034] FIG. 2 is a schematic cross-sectional view showing one embodiment of the layer structure of the printing layer according to the present invention.

[0035] The printed layer 10 shown in Fig. 2 has, from the back layer side to the front layer side, an ink layer 10a and an overprint varnish layer 10b on the ink layer 10a. Although not shown in Fig. 2, in this case, the ink layer 10a is laminated on the paper layer side.

[0036] In the present invention, the ink layer of the printed layer is not particularly limited, and may contain, for example, an ink selected from the group consisting of water-based ink, oil-based ink, curable ink, and a combination of two or more of these.

[0037] In the present invention, by providing an overprint varnish layer (also simply referred to as "OP varnish") on the ink layer of the printed layer, peeling of the printed layer can be reduced, and also, during the manufacturing process, for example, when the lid material is rolled up, show-through of the ink layer can be prevented.

[0038] In the present invention, the printing method is not particularly limited and may be, for example, gravure printing, flexographic printing, etc. Furthermore, when an overprint varnish layer is provided, it may be performed, for example, by printing a commercially available OP coating agent on the ink layer.

[0039] (Paper layer) The lid material of the present invention has a paper layer. In addition, in the present invention, a paper layer can be obtained by applying a resin coating agent to a paper base layer from the side that will be laminated with the printed layer. That is, the paper layer is coated with a resin coating agent from the side of the printed layer on the paper base layer. In other words, the paper layer has a paper base layer that is coated with a resin coating agent, and the side of this paper base layer that is coated with the resin coating agent is the side that will be laminated with the printed layer.

[0040] In the present invention, the coating amount of the resin coating agent in the paper layer is not particularly limited, and may be, for example, 0.5 g / m ２ Above, 0.6g / m ２ Above, 0.7g / m ２ Above, 0.8g / m ２ Above, 0.9g / m ２ Above, 1.0g / m ２ Above, 1.1g / m ２ Above, 1.2g / m ２ Above, 1.3g / m ２ Above, 1.4g / m２ Above, 1.5g / m ２ Above, 1.6g / m ２ Above, 1.7g / m ２ Above, 1.8g / m ２ Above, 1.9g / m ２ or more, or 2.0 g / m ２ or more, and ２ Below, 2.9g / m ２ Below, 2.8g / m ２ Below, 2.7g / m ２ Below, 2.6g / m ２ Below, 2.5g / m ２ Below, 2.4g / m ２ Below, 2.3g / m ２ Below, 2.2g / m ２ Below, 2.1g / m ２ Below, 2.0g / m ２ Below, 1.9g / m ２ Below, 1.8g / m ２ Below, 1.7g / m ２ Below, 1.6g / m ２ Below, 1.5g / m ２ Below, 1.4g / m ２ Below, 1.3g / m ２ Below, 1.2g / m ２ Below, 1.1g / m ２ or less, or 1.0 g / m ２ It may be the following:

[0041] In the present invention, the resin coating agent is not particularly limited and may include, for example, a resin selected from the group consisting of polyvinylidene chloride (PVDC), polyester, polyvinyl alcohol (PVOH), and a combination of two or more thereof. The resin coating agent may be water-based or solvent-based. Commercially available resin coating agents may be used.

[0042] In the present invention, the laminate of the above-described printed layer and paper layer has an air permeability of 150,000 seconds or less when measured from the paper base layer side toward the printed layer side using the Oken testing machine method of JIS P8117: 2019. More specifically, this air permeability value may be, for example, 150,000 seconds or less, 100,000 seconds or less, 90,000 seconds or less, 80,000 seconds or less, 70,000 seconds or less, 60,000 seconds or less, 50,000 seconds or less, 40,000 seconds or less, 30,000 seconds or less, or 20,000 seconds or less. The lower limit of this air permeability is not particularly limited, and may be, for example, 500 seconds or more, 1,000 seconds or more, 2,000 seconds or more, 3,000 seconds or more, 4,000 seconds or more, 5,000 seconds or more, 6,000 seconds or more, 7,000 seconds or more, 8,000 seconds or more, 9,000 seconds or more, 10,000 seconds or more, 20,000 seconds or more, 30,000 seconds or more, or 40,000 seconds or more. The air permeability value of the laminate of the printed layer and the paper layer is the value obtained by measuring from the back layer side of the paper layer toward the front layer side (printed layer side).

[0043] (Paper base layer) In the present invention, the paper base layer is not particularly limited as long as it satisfies the air permeability range of the laminate of the printing layer and the paper layer described above, and may be, for example, art paper, coated paper, pure white paper, or high-quality paper.

[0044] In the present invention, the basis weight of the paper substrate layer is not particularly limited, and may be, for example, 30 g / m ２ Above, 40g / m ２ Above, 50g / m ２ Above, 60g / m ２ or more, or 70 g / m ２ or more, and ２ Below, 150g / m ２ or less than 100 g / m ２ It may be the following:

[0045] (Sealant Layer) The lid material of the present invention has a sealant layer, which is a layer for heat-sealing the lid material to a container to be sealed with the lid material.

[0046] The material of the sealant layer is not particularly limited and may be appropriately selected depending on the material of the container to be sealed. The material of the sealant layer may be, for example, a polyolefin resin or an ethylene vinyl acetate copolymer (EVA). These resins may be provided in the form of, for example, an oriented or unoriented film, a molten resin for extrusion lamination, or a hot melt coating.

[0047] The polyolefin resin is not particularly limited, and for example, a polyethylene resin or a polypropylene resin can be used.

[0048] In the present invention, the sealant layer may be an easy-peel sealant layer that has been imparted with easy peelability, such as an interfacial peeling type sealant layer made by mixing resins of different compositions, a cohesive peeling type sealant layer made of multiple sealant layers so that the film peels off accompanied by cohesive failure when the sealant layer is opened, or an interlayer peeling type sealant layer made of multiple sealant layers, at least one of which is a layer that is fused to the container (sealing layer) and the other of which is a layer that is adjacent to the sealing layer (peeling layer) and peels off between the sealing layer and the peeling layer when the sealant layer is opened.

[0049] In the present invention, the thickness of the sealant layer is not particularly limited and may be, for example, 1.0 μm or more, 5.0 μm or more, or 10 μm or more, and may be 100 μm or less, 80 μm or less, 50 μm or less, or 20 μm or less.

[0050] (Other Layers) The lid material of the present invention may further have other layers. The other layers are not particularly limited, and examples thereof include an intermediate layer, a barrier layer, an adhesive layer, etc. Below, other layers that can be included in the lid material of the present invention will be described as examples, but the present invention is not limited to these layers.

[0051] [Barrier Layer] The covering material of the present invention may further include a barrier layer, and may have a print layer, a paper layer, a barrier layer, and a sealant layer in this order.

[0052] FIG. 3 is a schematic cross-sectional view showing one embodiment of the layer structure of the covering material of the present invention when it further includes a barrier layer.

[0053] As shown in FIG. 3, the lid material 200 of the present invention has a print layer 10, a paper layer 20, a barrier layer 40, and a sealant layer 30 in this order.

[0054] In the present invention, the barrier layer is not particularly limited and may be selected from the group consisting of, for example, a metal foil layer, an inorganic vapor deposition layer, an organic coating layer, and a combination of two or more of these.

[0055] The metal foil layer is not particularly limited, and examples thereof include metal foils such as aluminum foil, copper foil, and titanium foil, and alloy foils such as aluminum alloy foil and stainless steel foil.

[0056] The inorganic vapor-deposited layer is not particularly limited, and for example, a silica vapor-deposited film, an aluminum vapor-deposited film, an alumina vapor-deposited film, or a silica-alumina vapor-deposited film can be used.

[0057] The organic coating layer is not particularly limited, and for example, a vinylidene chloride coating layer, a polyvinylidene fluoride coating layer, or a polyvinyl alcohol layer can be used.

[0058] In the present invention, when an inorganic vapor-deposited film or an organic coating layer is used as the barrier layer, the thickness of the barrier layer may be, for example, 40 nm or more, 100 nm or more, 200 nm or more, 300 nm or more, 500 nm or more, 700 nm or more, or 1.0 μm or more, from the viewpoint of ensuring strength and barrier properties, and may be, for example, 5.0 μm or less, 4.0 μm or less, 3.0 μm or less, or 2.0 μm or less, from the viewpoint of improving handleability as a lid material.

[0059] Furthermore, in the present invention, when a metal foil layer is used as the barrier layer, the thickness of the barrier layer may be, for example, 3.0 μm or more, 4.0 μm or more, 5.0 μm or more, or 6.0 μm or more from the viewpoint of ensuring strength and barrier properties, and may be, for example, 50 μm or less, 30 μm or less, or 10 μm or less from the viewpoint of improving handleability as a lid material.

[0060] [Intermediate layer] The lid material of the present invention may further have an intermediate layer. The intermediate layer may be provided, for example, between the paper layer and the sealant layer, or, if a barrier layer is included, between the paper layer and the barrier layer, or between the barrier layer and the sealant layer. The intermediate layer may have the function of, for example, alleviating stress applied to the lid material during heat sealing or reinforcing the mechanical strength of the lid material.

[0061] The material for the intermediate layer is not particularly limited, and examples thereof include polyethylene, polypropylene, copolymer resins of ethylene and / or propylene and / or α-olefins (1-butene, 1-hexene, 1-octene, etc.), ethylene-vinyl acetate copolymer resin (EVA), ethylene-methacrylic acid copolymer resin (EMAA), ethylene-methyl methacrylate copolymer resin (EMMA), ethylene-methyl acrylate copolymer resin (EMA), ethylene-ethyl acrylate copolymer resin (EEA), ethylene-butyl acrylate copolymer resin (EBA), ethylene-vinyl alcohol copolymer resin (EVOH), olefin-based resins such as olefin-based ionomer resins, and various thermoplastic resin components such as polyester-based resins and polyamide-based resins, and mixtures thereof.

[0062] The thickness of the intermediate layer is not particularly limited and may be, for example, 1.0 μm or more, 5.0 μm or more, 10 μm or more, or 15 μm or more, and may be 50 μm or less, 30 μm or less, or 15 μm or less.

[0063] [Adhesive Layer] The lid material of the present invention may further have an adhesive layer. The adhesive layer may be provided, for example, between the paper layer and the sealant layer, or, when a barrier layer is included, between the paper layer and the barrier layer, or between the barrier layer and the sealant layer.

[0064] The raw material for the adhesive layer is not particularly limited, and examples thereof include thermosetting resins such as urethane resin, acrylic resin, phenolic resin, polyimide resin, and bismaleimide resin; ionizing radiation curable resins such as (meth)acrylate resin, epoxy resin, unsaturated polyester resin, urethane acrylate resin, and polyol acrylate resin; ultraviolet curable resins such as polyester acrylate, urethane acrylate, and epoxy acrylate; hot melt adhesives, water-soluble adhesives, emulsion adhesives, non-solvent laminating adhesives; and thermoplastic resins for extrusion lamination.

[0065] The thickness of the adhesive layer is not particularly limited and may be, for example, 1.0 μm or more, 5.0 μm or more, 10 μm or more, or 15 μm or more, and may be 50 μm or less, 30 μm or less, or 15 μm or less.

[0066] <<Method for Producing Lid Material>> The method for producing the lid material of the present invention includes applying a resin coating agent to the surface of a paper substrate layer that will be laminated with a printed layer to obtain a paper layer.

[0067] In the present invention, layers other than the paper layer that may be contained in the lid material may be formed using a coating method, a printing method, etc. Furthermore, the lamination method for each layer is not particularly limited, and may be an extrusion lamination method such as sand lamination or back lamination, a dry lamination method, a hot melt method, a non-solvent lamination method, or a combination of these methods.

[0068] <<Use of Lid Material>> The use of the lid material of the present invention is not particularly limited, but the lid material of the present invention can be used, for example, to seal the opening of various container bodies.

[0069] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0070] <<Production of Lid Material 1>> <Example 1-1>> A laminate having the following basic structure was produced as a laminate for a lid material. The numbers in parentheses represent "thickness (μm)" unless otherwise specified. [Basic structure] OP varnish / ink layer / resin coating agent (coating amount: 1.5 g / m ２) on the ink layer side. ２ ) / Adhesive layer (A) (15 μm) / Barrier layer (6.5 μm) / Adhesive layer (B) (18 μm) / Sealant layer (15 μm)

[0071] The materials used for each layer (raw materials) in the above basic structure are shown in Table 1 below:

[0072] More specifically, a laminate for a lid material was produced according to the following steps (1) to (3): (1) A resin coating agent, an ink layer, and an OP varnish were printed on a paper substrate layer in this order. (2) The paper layer and the barrier layer were sandwich-laminated with an adhesive layer (A) interposed therebetween, and then an adhesive layer (B) was back-laminated. (3) A sealant layer was back-laminated onto the adhesive layer (B).

[0073] Example 1-2: Coating amount of resin coating agent: 2.0 g / m ２ A laminate for a lid material of Example 1-2 was produced in the same manner as in Example 1-1, except that the above-mentioned change was made.

[0074] Comparative Example 1-1 A laminate for a lid material of Comparative Example 1-1 was produced in the same manner as in Example 1-1, except that no resin coating agent was applied.

[0075] Comparative Example 1-2 A laminate for a lid material of Comparative Example 1-2 was produced in the same manner as in Comparative Example 1-1, except that a PET film was attached instead of the OP varnish.

[0076] Comparative Example 1-3 A laminate for a lid material of Comparative Example 1-3 was produced in the same manner as in Example 1-1, except that no resin coating agent was applied and a mixed liquid of water and methanol was applied to the back surface of the paper base layer.

[0077] <Measurement and Evaluation> <Evaluation of Curl Generation> The laminates for lid materials prepared in each of the Examples and Comparative Examples were cut out using a single-sided die and processed into a lid shape (a round shape with a diameter of 101 mm). Then, the obtained laminate samples were seasoned for one day under an environment of 23°C and 50% RH (relative humidity). Next, after seasoning for 60 minutes under an environment of 21°C and 12% RH (relative humidity) (assuming winter) and 25°C and 70% RH (relative humidity) (assuming summer), curling was visually confirmed.

[0078] Regarding the occurrence of curling, samples in which curling was improved compared with the sample of Comparative Example 1-1 were evaluated as "OK", and samples in which curling was worsened were evaluated as "NG". The results are shown in Table 2. The curl of the sample of Comparative Example 1-1 was approximately cylindrical.

[0079] <Measurement of moisture absorption amount> Each sample processed into a lid shape (approximately round shape with a diameter of 101 mm; area of ​​0.00824 m) was ２ ) was dried in a vacuum oven (60°C, 4 hours). Thereafter, the change in mass over time was measured while seasoning was performed in an environment of 23°C and 50% RH (relative humidity). The mass immediately after drying in the vacuum oven was set as the reference (0 (zero)). Using the following formula, the mass after absorbing moisture for 20 minutes, 40 minutes, and 60 minutes was calculated as the amount of moisture absorbed. The results obtained are shown in Table 2. Moisture absorption (g / m ２ ) = mass after moisture absorption (g / m ２ ) - Mass after drying in a vacuum oven (g / m ２ )

[0080] <Evaluation of Blistering> Each sample processed into a lid shape was seasoned for one day in an environment of 20°C and 50% RH (relative humidity). The seasoned sample was then heat-sealed to a container (temperature: 150-160°C, pressure: 180 kgf, time: 1.3 seconds). The presence or absence of blistering was confirmed visually.

[0081] Regarding the occurrence of blisters, cases where there were no blisters or wrinkles were evaluated as "A", cases where wrinkles were observed were evaluated as "B", and cases where blisters were observed were evaluated as "C". The evaluation results are shown in Table 2.

[0082] <Air permeability measurement> The air permeability was measured for a laminate obtained by printing a resin coating agent, an ink layer, and an OP varnish in this order on a paper substrate layer. More specifically, the air permeability was measured from the back layer side of the paper layer (i.e., the paper substrate layer side) to the front layer side of the paper layer (i.e., the printed layer side). The measurement was performed using an Oken testing machine method. The measurement results are shown in Table 2.

[0083]

[0084] As is clear from Table 2, the lid materials of Examples 1-1 and 1-2 showed improved curling compared to Comparative Example 1-1, and were also able to suppress the occurrence of blisters when heat-sealed up to 160°C.

[0085] Furthermore, the results of measuring the amount of moisture absorption over time revealed that the lid materials of Examples 1-1 and 1-2 had a significantly slower moisture absorption rate than the comparative examples.

[0086] The lid material of Comparative Example 1-3 did not have a slower moisture absorption rate, but convex curl was suppressed under high humidity (25°C, 70% RH (relative humidity)). This is thought to be because by applying water and methanol to the back surface of the paper base layer during printing, the fibers on the back surface of the paper base layer were stretched in advance, and this maintained a balance between the front and back surfaces even when the fibers of the paper base layer on the printing layer side were stretched due to moisture absorption, thereby suppressing convex curl.

[0087] In the case of Comparative Example 1-2, the air permeability value exceeded 150,000 seconds, and the occurrence of blisters was significant. In contrast, the lid materials of Examples 1-1 and 1-2 both had air permeabilities of 150,000 seconds or less, and it was found that the occurrence of blisters was suppressed.

[0088] From the correlation between the air permeability value and the occurrence of blisters, it was found that blisters can be suppressed when the air permeability is 150,000 seconds or less.

[0089] <<Preparation of Lid Material 2>> <Example 2-1>> As a resin coating agent, a water-based PVDC coating agent was used at 1.6 g / m ２A laminate for a lid material of Example 2-1 was produced in the same manner as in Example 1-1, except that coating was performed.

[0090] Example 2-2: As a resin coating agent, a water-based PVDC coating agent was used at 1.1 g / m ２ A laminate for a lid material of Example 2-2 was produced in the same manner as in Example 1-1, except that coating was performed.

[0091] Example 2-3: As a resin coating agent, a water-based polyester coating agent was used at 1.3 g / m ２ A laminate for a lid material of Example 2-3 was produced in the same manner as in Example 1-1, except that coating was performed.

[0092] Example 2-4: As a resin coating agent, a water-based PVOH coating agent was used at 0.7 g / m ２ A laminate for a lid material of Example 2-4 was produced in the same manner as in Example 1-1, except that coating was performed.

[0093] Comparative Example 2-1: Instead of the resin coating agent, a moisturizing agent (polyethylene glycol) was used at 1.5 g / m ２ A laminate for a lid material of Comparative Example 2-1 was produced in the same manner as in Example 1-1, except that coating was performed.

[0094] Comparative Example 2-2: As a resin coating agent, a styrene acrylic coating agent was used at 2.3 g / m ２ A laminate for a lid material of Example 2-2 was produced in the same manner as in Example 1-1, except that coating was performed.

[0095] <<Measurement and Evaluation>> The laminates for lid materials of each of the Examples and Comparative Examples prepared above were subjected to "evaluation of curl occurrence," "measurement of moisture absorption amount," and "measurement of air permeability" in the same manner as in "Preparation of lid material 1." The obtained results are shown in Table 3.

[0096]

[0097] As is clear from the results in Table 3, the lid materials of each Example (Example 2-1 to Example 2-4) all had a moisture absorption of 3.2 g / m at 23°C, 50% RH (relative humidity) for 60 minutes. ２ The results were as follows, and it was found that the occurrence of curling was improved compared to Comparative Example 1-1.

[0098] In contrast, the lid materials of Comparative Examples 2-1 and 2-2 both had a moisture absorption of 3.2 g / m at 23°C and 50% RH (relative humidity) for 60 minutes. ２ It was found that the occurrence of curling was worsened at a temperature of 100°C or more.

[0099] Although no evaluation of blister occurrence was conducted, based on the results of Table 2 above, which reveal that "blister occurrence can be suppressed when the air permeability is 150,000 seconds or less," it is presumed that the lid materials of each of the examples and comparative examples in Table 3 can all suppress the occurrence of blisters.

[0100] 10 Printed layer 10a Ink layer 10b Overprint varnish layer 20 Paper layer 20a Resin coating agent 20b Paper base material layer 30 Sealant layer 40 Barrier layer 100, 200 Lid material

Claims

1. A lid material having a print layer, a paper layer, and a sealant layer, which is dried in a vacuum oven at 60°C for 4 hours and the mass after drying is used as a reference. When the lid material is seasoned for 60 minutes in an environment of 23°C and 50% RH (relative humidity), the moisture absorption is 3.2 g / m ２ the paper layer is coated with a resin coating agent from the printed layer side on the paper base layer, and a laminate of the printed layer and the paper layer has an air permeability of 150,000 seconds or less when measured from the paper base layer side toward the printed layer side using an Oken testing machine method in accordance with JIS P8117:2019.

2. The coating amount of the resin coating agent is 0.5 to 3.0 g / m ２ The lid material according to claim 1 .

3. The lid material according to claim 1 or 2, wherein the resin coating agent contains a resin selected from the group consisting of polyvinylidene chloride, polyester, polyvinyl alcohol, and combinations of two or more of these.

4. The covering material according to claim 1 or 2, further comprising a barrier layer, and comprising the printing layer, the paper layer, the barrier layer, and the sealant layer in this order.

5. The covering material according to claim 4, wherein the barrier layer is selected from the group consisting of a metal foil layer, an inorganic vapor deposition layer, an organic coating layer, and a combination of two or more of these.

6. The covering material according to claim 1 or 2, wherein the printed layer comprises an ink layer and an overprint varnish layer on the ink layer.

7. A method for producing a covering material according to claim 1, comprising applying the resin coating agent to the surface of the paper base layer that is to be laminated with the printed layer, to obtain the paper layer.

8. The method of claim 7, wherein the resin coating comprises a resin selected from the group consisting of polyvinylidene chloride, polyester, polyvinyl alcohol, and combinations of two or more thereof.

Images