Lid material substrate and lid material

Abstract

To provide a base material for a lid material having printability to a gravure printing machine or the like on its surface, excellent in shape stability and having material breakage resistance in the vicinity of room temperature and after heating and humidification, and the lid material using the base material for the lid material.SOLUTION: A tensile strength at break in CD of the paper base material determined in accordance with ISO1924 2:2008 is 2. 5kN / m or more, a value R of the tensile strength at break (kN / m) with respect to a tensile elongation at break (%) in CD of the paper base material determined in accordance with ISO1924 2:2008 is 0.25 or more, and a total thickness is 80 μm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a lid substrate used for a lid of a container package, and a lid using the same. More specifically, the present invention relates to a lid substrate that can be used for a lid that closes the top opening of a container and that can close the opening again and maintain that state (easily reseal) after being opened, and a lid using the same. [Background technology]

[0002] Container packages whose upper openings are closed by lid materials are widely known, including those disclosed in Patent Document 1, and lid material substrates using paper as a support are known as materials for the lid materials of such container packages. For example, Patent Document 2 discloses a lid material substrate having a coating layer on one side of a base paper mainly composed of a pigment and an adhesive, the base paper using hardwood kraft pulp as the main component and made in the presence of an acrylamide-based paper strength agent, the pulp after defibration of the lid material substrate in accordance with JIS P8220 satisfying prescribed properties, and the average value of the internal bond in the width direction and machine direction of the lid material substrate in accordance with J.TAPPI No. 18-2 is 200 mJ or more, which is said to have improved processability, improved printability and excellent curl suppression. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-046243 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-149881 Summary of the Invention [Problem to be solved by the invention]

[0004] Lidding materials used for container packaging are usually formed by printing the surface of a lid material substrate located on the outside of the container packaging using a gravure printing machine or the like to improve the appearance of the container packaging at stores. Also, lid materials used for container packaging are formed by laminating a heat seal layer for sealing and / or various barrier layers or vapor deposition layers for protecting the contents, or processed layers for preventing adhesion of the contents, on the back surface of a lid material substrate located on the inside of the container packaging.

[0005] As exemplified by a container package containing instant noodles or the like, when using a container package sealed with a lid, the lid is partially opened and hot water is poured into the container package to reconstitute the contents. Therefore, in addition to the effects required of a lid, such as content protection, the lid used for such a container package is required to have material breakage resistance so that the lid does not break when partially opened, shape stability so that the curved shape at the time of opening can be maintained so that the open state is maintained when hot water is poured, and material breakage resistance so that the lid does not break when the lid is completely opened when eating or drinking after reconstitution with hot water that involves heating and humidification. The shape stability and material breakage resistance of the lid material depend on the shape stability and material breakage resistance of the lid material substrate that forms the lid material.

[0006] The object of the present invention is to provide a lid material substrate that, when applied to a lid material for a container packaging body, has an outer surface that is suitable for printing on a gravure printing machine or the like, has excellent shape stability, and has material breakage resistance even at or near room temperature and after being heated and humidified, and to provide a lid material using such a lid material substrate. [Means for solving the problem]

[0007] The present invention includes the following lid material substrate and lid material. [1] A substrate for a lid material, comprising a paper base material and one or more coating layers containing a pigment and a binder on at least one side of the paper base material, wherein the tensile breaking strength of the paper base material in the CD measured in accordance with ISO1924-2:2008 is 2.5 kN / m or more, the value R of the tensile breaking strength (kN / m) relative to the tensile breaking elongation (%) in the CD of the paper base material measured in accordance with ISO1924-2:2008 is 0.25 or more, and the total thickness is 80 μm or less. [2] The paper substrate has a CD tear strength of 350 mN or more and 480 mN or less, as determined in accordance with ISO1974:2012, and a Parker Print Surf smoothness (soft backing / clamp pressure 2000 kPa) measured on the outermost surface of the coating layer, as determined in accordance with ISO8791-4:2021. The substrate for lid material described in [1] above, is 0.4 μm or more and 0.8 μm or less. [3] A lid material using the lid material substrate described in [1] or [2] above. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a lid material substrate that has excellent shape stability and fracture resistance at around room temperature and after heating and humidification, while having printability on the surface using a gravure printing machine or the like. Furthermore, it is possible to provide a lid material that has shape stability and fracture resistance from such a lid material substrate. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Base material for lid material] The substrate for lid material of the present invention comprises a paper base material and one or more coating layers containing a pigment and a binder on at least one side of the paper base material, the tensile breaking strength of the paper base material in the CD measured in accordance with ISO1924-2:2008 being 2.5 kN / m or more, the value R of the tensile breaking strength (kN / m) relative to the tensile breaking elongation (%) in the CD of the paper base material measured in accordance with ISO1924-2:2008 being 0.25 or more, and the total thickness being 80 μm or less. The lid material substrate of the present invention may have a coating layer containing a pigment and a binder on only one side of the paper base material, or on both sides of the paper base material. Of these, the lid material substrate of the present invention is preferably an embodiment having one or more coating layers containing a pigment and a binder on only one side of the paper base material, from the viewpoint of advantageous production costs. In the lid material of the present invention described below, the printed surface of the lid material substrate, which is located on the outside of the container packaging, is the surface having the above-mentioned coating layer. In the case of a lid material substrate having coating layers containing a pigment and a binder on both sides of a paper substrate, the surface of the lid material substrate that is located on the outside of the container packaging is the printed surface of the lid material, and is either one of the two surfaces.

[0010] The lid material substrate of the present invention may further have a resin layer mainly composed of resin. For example, when the lid material substrate of the present invention has one or more coating layers containing a pigment and a binder on only one side of a paper substrate, the resin layer may be provided between the paper substrate and the coating layer, between two or more coating layers, or adjacent to the paper substrate on the side not having a coating layer. When the lid material substrate of the present invention further has a resin-based resin layer, the resin layer serves to fill voids in the paper substrate and tends to improve adhesion between the paper substrate and the coating layer and adhesion between the coating layers. Examples of resins constituting the resin layer include water-dispersible resins or water-soluble resins known in the field of coated paper. Examples of water-dispersible resins include styrene-based resins such as styrene-butadiene copolymer resins; conjugated diene-based copolymer resins such as (meth)acrylonitrile-butadiene copolymer resins; acrylic resins such as (meth)acrylate-butadiene copolymer resins, (meth)acrylate-styrene copolymer resins, and (meth)acrylate copolymer resins; vinyl-based copolymer resins such as ethylene-vinyl acetate copolymer resins and vinyl chloride-vinyl acetate copolymer resins; polyurethane-based resins, alkyd-based resins, unsaturated polyester-based resins, and modified resins using various monomers thereof; and thermosetting resins such as urea-based resins and melamine-based resins. Examples of water-soluble resins include starch or various modified starches; cellulose derivatives such as methyl cellulose, carboxymethyl cellulose, and hydroxyethyl cellulose; polyvinyl alcohol, which may be unmodified or partially saponified, modified with silanol or the like; natural polymer resins such as casein, gelatin, soybean protein, pullulan, gum arabic, karaya gum, and albumin, and modified products thereof; sodium alginate, maleic acid-based resins, and the like. In this specification, "resin as the main component" means that more than 50 mass % of the dry solid content forming the resin layer is made up of resin.

[0011] 《Paper base material》 In the base material for the lid material of the present invention, the paper base material can be base paper made by a conventionally known papermaking method under acidic, neutral or alkaline conditions from a paper stock in which various additives such as fillers, sizing agents, fixing agents, retention agents and paper strength agents are added as needed to a slurry made of pulp; plain paper made by size pressing the base paper with a size press liquid; fine paper made by calendering the base paper or the plain paper; and further, conventionally known kraft paper and bleached kraft paper can be used.

[0012] Examples of pulp include chemical pulps such as leaf bleached kraft pulp (LBKP) and needle bleached kraft pulp (NBKP), mechanical pulps such as groundwood pulp (GP), pressure groundwood pulp (PGW), refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), bleached chemithermomechanical pulp (BCTMP), chemimechanical pulp (CMP), and chemigroundwood pulp (CGP), and waste paper pulp such as deinked pulp (DIP), as well as pulp from paper mills. Pulp raw materials include, for example, softwood, hardwood, hemp, linter, straw, bamboo, sugarcane, reed, fruit, paper mulberry, mitsumata, and gampi. The pulp is one or more selected from the group consisting of these. In particular, in the lid material substrate of the present invention, it is preferred that the pulp forming the paper base material contains 90 mass% or more of LBKP and NBKP relative to the total amount of pulp, and that the mass ratio of LBKP to NBKP is in the range of LBKP:NBKP = 70:30 to 95:5. When the pulp forming the paper base material is of the above type and in the above content range, the lid material substrate of the present invention is more likely to exhibit a good balance between shape stability and material breakage resistance.

[0013] Examples of fillers include white inorganic pigments known in the papermaking field, such as calcium carbonate, kaolin, calcined kaolin, engineered kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, activated clay, diatomaceous earth, silica, alumina, aluminum hydroxide, lithopone, zeolite, magnesium carbonate, and magnesium hydroxide; and white organic pigments, such as styrene-based plastic pigments, acrylic plastic pigments, polyethylene, microcapsules, urea resins, and melamine resins. These fillers may be used alone or in combination of two or more. The content of the filler in the paper base material is preferably 50 to 100 parts by mass per 1,000 parts by mass of pulp in the paper base material. When the filler content is within this range, the filler acts on the interfiber bonds of the pulp, making it easier to suppress the elongation of the paper base material while also suppressing a decrease in the tensile breaking strength of the paper base material.

[0014] As the sizing agent, known materials known in the papermaking field as internal sizing agents can be used, such as rosin-based sizing agents for acidic paper, and alkenyl succinic anhydride-based sizing agents, alkyl ketene dimer-based sizing agents, neutral rosin-based sizing agents, fatty acid-based sizing agents, and cationic styrene acrylic resin-based sizing agents for neutral paper. These sizing agents may be used alone or in combination of two or more. Among these, alkyl ketene dimer sizing agents are preferred from the viewpoint of being reactive internal sizing agents that act on the strength of the paper substrate.

[0015] Fixing agents are known materials in the papermaking field for improving the fixability of the sizing agent. Examples of fixing agents include inorganic salts such as aluminum sulfate and colloidal silica. One type of fixing agent may be used alone, or two or more types may be used in combination.

[0016] Retention agents are known materials in the papermaking field for improving the retention of pulp, fillers, etc. Examples of retention agents include organic polymer electrolytes such as polyacrylamides, polyamides, and polyethyleneimines, as well as polyethylene oxides. One type of retention agent may be used alone, or two or more types may be used in combination.

[0017] Paper strength agents are well-known materials added to paper stock to impart strength to paper, and are also referred to as internal strength agents in the papermaking field. Examples of paper strength agents include starches such as starch, dialdehyde starch, etherified starch, oxidized starch, and cationized starch; vegetable gums such as guar gum, locust bean gum, and tragacanth gum; celluloses such as methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, and hydroxyethylcellulose; and synthetic polymers such as polyurethane resins, polyethyleneimine resins, urea resins, polyacrylamides, modified polyacrylamides, polyethylene oxide resins, and polyvinyl alcohol resins. One type of paper strength agent may be used alone, or two or more types may be used in combination. It is preferable for the paper substrate to contain a paper strength agent, as this improves the strength of the paper substrate.

[0018] In addition to the above-mentioned fillers, sizing agents, fixing agents, retention agents, and paper strength agents, other additives such as binders, pigment dispersants, thickeners, flow improvers, antifoaming agents, foam suppressors, release agents, foaming agents, penetrating agents, colorants, fluorescent whitening agents, ultraviolet absorbers, antioxidants, preservatives, mildew inhibitors, and water-resistant agents may also be added to the paper stock as necessary.

[0019] Examples of methods for making base paper from paper stock include methods using paper machines conventionally known in the papermaking field, such as a Fourdrinier paper machine, a twin-wire paper machine, a combination paper machine, a cylinder paper machine, and a Yankee paper machine.

[0020] Plain paper obtained by size-pressing the base paper with a size press liquid may also be used as the paper substrate. Such a size press liquid is a treatment liquid known in the papermaking field, containing one or more starches, polyvinyl alcohols, and the like, known as surface sizing agents, for imparting sizing properties to paper. Size press treatment is a surface treatment for imparting sizing properties to paper, and can be carried out using size press devices known in the papermaking field, such as film transfer systems such as rod-metaling size presses, roll-metaling size presses, and blade-metaling size presses, inclined size presses, horizontal size presses, and, as rod-metaling size presses, shim sizers, Optisizers, Speed ​​Sizers, and film presses, and as roll-metaling size presses, gate roll coaters. Other size press devices include bill blade coaters, twin blade coaters, Belbapa coaters, tab size presses, and calendar size presses.

[0021] The base paper or plain paper may be further calendered to form fine paper, which is a paper substrate. Calendering is a process for smoothing and equalizing thickness by passing the paper between rolls, and can be carried out using a machine calender, soft-nip calender, super calender, multi-stage calender, multi-nip calender, or other such device.

[0022] In some embodiments, the paper base material contains at least pulp and a filler, the pulp contains LBKP and NBKP in an amount of 90% by mass or more relative to the total amount of pulp, the mass ratio of the LBKP to the NBKP is in the range of LBKP:NBKP = 70:30 to 95:5, and the content of the filler is 50 parts by mass or more and 100 parts by mass or less relative to 1000 parts by mass of the pulp. In some embodiments, the paper base material contains at least pulp and a sizing agent, the pulp contains LBKP and NBKP in an amount of 90% by mass or more based on the total amount of pulp, the mass ratio of the LBKP to the NBKP is in the range of LBKP:NBKP = 70:30 to 95:5, and the sizing agent is an alkyl ketene dimer sizing agent. Furthermore, in some embodiments, the paper base material contains at least pulp, a filler, and a sizing agent, the pulp contains LBKP and NBKP in an amount of 90% by mass or more relative to the total amount of pulp, the mass ratio of the LBKP to the NBKP is in the range of LBKP:NBKP = 70:30 to 95:5, the content of the filler is 50 parts by mass or more and 100 parts by mass or less relative to 1000 parts by mass of pulp, and the sizing agent is an alkyl ketene dimer sizing agent. In at least one embodiment, the paper base material contains at least pulp, a filler, a sizing agent, and a paper strength agent, the pulp contains LBKP and NBKP in an amount of 90% by mass or more relative to the total amount of pulp, the mass ratio of the LBKP to the NBKP is in the range of LBKP:NBKP = 70:30 to 95:5, the content of the filler is 50 parts by mass or more and 100 parts by mass or less relative to 1000 parts by mass of pulp, and the sizing agent is an alkyl ketene dimer sizing agent.

[0023] The thickness of the paper substrate used to prepare the lid material substrate of the present invention is preferably in the range of 50 μm to 90 μm. 2 ~80g / m 2 The density of the paper substrate is preferably in the range of 0.70 g / cm 3 ~0.95g / cm 3 The range is preferred. When the thickness, basis weight and density of the paper substrate are within the above ranges, the shape stability and material tear resistance of the lid material substrate of the present invention tend to be further improved. The density and thickness of the paper substrate are values ​​determined in accordance with ISO534:2011 "Paper and board - Determination of thickness, density and specific volume". The basis weight of the paper substrate is values ​​determined in accordance with ISO536:2019 "Paper and board - Determination of grammage".

[0024] <Coating layer> The lid material substrate of the present invention has one or more coating layers containing a pigment and a binder on at least one side of the paper substrate. Such coating layers have the effect of providing printability using a gravure printing machine or the like. The number of coating layers is preferably one or two from the viewpoint of achieving an advantage in the manufacturing cost of the lid material substrate of the present invention, and more preferably one from the viewpoint of achieving an advantage in the manufacturing cost of the lid material substrate of the present invention. In other words, it is preferable that the lid material substrate of the present invention has such a coating layer only on one side of the paper substrate.

[0025] The coating weight of the coating layer containing pigment and binder is 13 g / m2 as dry solids per side of the paper base. 2 More than 21g / m 2 It is preferable that the coating weight is 13 g / m or less. When two or more coating layers containing a pigment and a binder are present, the coating weight is the total coating weight of the multiple coating layers. 2 When the coating weight of the coating layer is 21 g / m or more, the printability of the coating layer surface is likely to be improved. 2 If the thickness is less than this, the surface of the coating layer has printability and the occurrence of powder falling off from the coating layer can be easily suppressed.

[0026] The pigment contained in the coating layer may be a white inorganic pigment or a white organic pigment known in the field of coated paper. Examples of white inorganic pigments include light calcium carbonate, heavy calcium carbonate, kaolin, calcined kaolin, engineered kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, activated clay, diatomaceous earth, silica, alumina, aluminum hydroxide, lithopone, zeolite, magnesium carbonate, and magnesium hydroxide. Examples of white organic pigments include pigments made of various resins such as styrene-based resins, acrylic resins, vinyl acetate-based resins, olefin-based resins, vinyl chloride-based resins, urea-based resins, and melamine-based resins, and having various shapes such as medium-density spheres, hollow spheres, bowl-shaped, and confetti-shaped, as well as microcapsules.

[0027] The binder contained in the coating layer may be a water-dispersible binder or a water-soluble binder known in the field of coated paper. Examples of water-dispersible binders include styrene-based resins such as styrene-butadiene-based copolymer resins, conjugated diene-based copolymer resins such as (meth)acrylonitrile-butadiene-based copolymer resins, acrylic resins such as (meth)acrylate-butadiene-based copolymer resins, (meth)acrylate-styrene-based copolymer resins, and (meth)acrylate-based copolymer resins, vinyl-based copolymer resins such as ethylene-vinyl acetate-based copolymer resins and vinyl chloride-vinyl acetate-based copolymer resins, polyurethane-based resins, alkyd-based resins, unsaturated polyester-based resins, and modified resins using various monomers thereof, and thermosetting resins such as urea-based resins and melamine-based resins. Examples of water-soluble binders include starches, cellulose derivatives such as methyl cellulose, carboxymethyl cellulose, and hydroxyethyl cellulose, polyvinyl alcohols, casein, gelatin, and modified products thereof, soy protein, pullulan, gum arabic, karaya gum, and natural polymer resins such as albumin, and modified products thereof, sodium alginate, and maleic acid-based resins.

[0028] In the lid material substrate of the present invention, the coating layer located as the outermost layer particularly preferably contains at least kaolin as a pigment, from the viewpoints of having printability on the surface using a gravure printing machine or the like and excellent shape stability. Here, in the lid material substrate of the present invention, when one coating layer is present on one side of the paper base material, this coating layer becomes the outermost layer.

[0029] In addition to the pigment and binder, the coating layer constituting the lid material substrate of the present invention may contain various auxiliaries known in the field of coated paper, such as thickeners, water retention agents, flow improvers, antifoaming agents, foaming agents, lubricants, penetrating agents, colorants, UV absorbers, antioxidants, preservatives, antifungal agents, printability improvers, and pH adjusters, as needed.

[0030] <<Preparation of substrate for lid material>> The lid material substrate of the present invention can be produced by applying a coating liquid containing a pigment and a binder to at least one surface of a paper substrate and drying the coating liquid to form a coating layer. The method of applying a coating liquid containing a pigment and a binder and drying it to form a coating layer can be a method using a coating device and a drying device known in the field of coated paper when applying a coating liquid and drying it to form a coating layer. Examples of coating devices include a Comma Coater (registered trademark), a film press coater, a rod coater, an air knife coater, a rod blade coater, a bar coater, a blade coater, a gravure coater, a curtain coater, an E-bar coater, and a size press device. Examples of drying devices include hot air dryers such as a linear tunnel dryer, an arch dryer, an air loop dryer, and a sine curve air float dryer, an infrared heating dryer, and a dryer that uses microwaves, etc.

[0031] The substrate for a covering material of the present invention is preferably further subjected to a calendar treatment after a coating layer containing a pigment and a binder is formed on at least one surface of the paper substrate as described above. Specifically, such calendering is preferably performed under conditions where the relationship X>Y holds when comparing the thickness X (μm) of the paper substrate before forming the coating layer with the thickness Y (μm) of the lid material substrate after forming the coating layer and performing the calendering. In other words, the lid material substrate of the present invention is preferably obtained by forming a coating layer containing a pigment and a binder, and then performing calendering under conditions where the relationship X>Y holds when comparing X and Y. It is more preferable that the ratio of Y to X (Y / X) is 0.790 or more and 0.950 or less. When calendering is performed under conditions where the relationship X>Y holds, the dimensional stability and material breakage resistance of the resulting lid material substrate of the present invention are further improved. Here, the thickness X (μm) of the paper substrate and the thickness Y (μm) of the lid material substrate can be measured in accordance with ISO534:2011 "Paper and board - determination of thickness, density and specific volume."

[0032] After the above-mentioned calendering treatment, the thickness Y of the lid material substrate of the present invention is preferably in the range of 45 μm to 90 μm. When the thickness Y of the lid material substrate of the present invention after the calendering treatment is in the above-mentioned range and the above-mentioned relationship X>Y is satisfied, the shape stability and material breakage resistance are more likely to be improved. The basis weight of the substrate for the lid material of the present invention is 40 g / m 2 ~80g / m 2 The preferred range is 0.75 g / cm 3 ~0.90g / cm 3 When the basis weight and density of the covering material substrate of the present invention after calendering are within the above ranges, the shape stability and material tear resistance are more likely to be improved.

[0033] <Physical properties related to the base material for lids> The lid material substrate of the present invention has a tensile breaking strength of 2.5 kN / m or more in the CD of the paper substrate as determined in accordance with ISO 1924-2: 2008. While a higher tensile breaking strength is preferable, from the viewpoint of ease of production of the lid material substrate, a tensile breaking strength of 2.5 kN / m or more and 6.0 kN / m or less is preferable. Furthermore, the lid material substrate of the present invention has a value R (R = [paper tensile breaking strength in CD (kN / m)] / [paper tensile breaking elongation in CD (%)]) of 0.25 or more, which is the ratio of the tensile breaking strength (kN / m) to the tensile breaking elongation (%) of the paper substrate, determined in accordance with ISO1924-2: 2008. A larger value R is preferable, but from the viewpoint of ease of production of the lid material substrate, it is preferably 0.25 or more and 0.45 or less. In some embodiments, the cover material substrate has a paper CD tensile breaking strength of 2.5 kN / m or more and 6.0 kN / m or less, and the value R of the paper CD tensile breaking strength (kN / m) relative to the paper CD tensile breaking elongation (%) is 0.25 or more and 0.45 or less. Furthermore, the lid material substrate of the present invention has a total thickness of 80 μm or less. Although a thinner total thickness is preferable for a lid material substrate, from the viewpoint of ease of production, a total thickness of 30 μm or more and 80 μm or less is preferable, and a thickness of 50 μm or more and 80 μm or less is more preferable. In some embodiments, the lid material substrate has a paper CD tensile breaking strength of 2.5 kN / m or more and 6.0 kN / m or less, a value R of the paper CD tensile breaking strength (kN / m) relative to the paper CD tensile breaking elongation (%) of 0.25 or more and 0.45 or less, and the lid material substrate has a thickness of 50 μm or more and 80 μm or less. Here, ISO1924-2:2008 means "Paper and board - Determination of tensile properties - Part 2: Constant rate of elongation method."

[0034] The tensile breaking elongation of a paper substrate refers to the maximum tensile strain that the paper substrate experiences before breaking under tension, and is expressed as a percentage of the elongation at break relative to the length of the paper substrate test piece before pulling. On the other hand, the tensile breaking strength of a paper substrate refers to the strength of a paper substrate test piece when it is pulled and breaks. In other words, a paper with a large value R indicates that the paper exhibits directions in which it is difficult to stretch and directions in which it is resistant to pulling. From another perspective, a paper with a large value R indicates, for example, a paper with a higher tensile breaking strength if the tensile breaking elongation values ​​are the same, or a paper with a smaller tensile breaking elongation if the tensile breaking strength is the same. The CD of paper is the direction perpendicular to the machine direction of the paper machine, and is generally the side where the paper is most likely to stretch and where the strength is weak. The lid material substrate of the present invention can have shape stability and material breakage resistance by having the tensile breaking strength and value R in the CD of the paper substrate satisfy the above ranges. On the other hand, a paper substrate with a relatively increased thickness also has an increased tensile breaking strength. However, a paper substrate with an increased thickness also has increased rigidity, which hinders the shape stability when used as a lid material substrate. Therefore, the lid material substrate must have the above-mentioned tensile breaking strength and the relationship between the tensile breaking strength and the tensile breaking elongation while having a thickness of 80 μm or less. In other words, conventional paper that obtains tensile strength by stretching is not suitable as a paper substrate constituting the lid material substrate of the present invention because it is difficult to maintain shape stability.

[0035] The lid material substrate of the present invention preferably has a CD tear strength of 350 mN or more and 480 mN or less of the paper substrate as determined in accordance with ISO 1974: 2012, and a Parker Print Surf smoothness (soft backing / clamp pressure 2000 kPa) of 0.4 μm or more and 0.8 μm or less as measured on the outermost surface of the coating layer as determined in accordance with ISO 8791-4: 2021. When the lid material substrate of the present invention has a tear strength and Parker Print Surf smoothness within these ranges, it has printability on gravure printing machines and the like, while also having further improved dimensional stability and material breakage resistance. Note that ISO1974:2012 stands for "Paper - Determination of tearing resistance (Elmendorf method)" and ISO8791-4:2021 stands for "Paper and board - Determination of roughness / smoothness (air leak method) Part 4: Print-surf method."

[0036] The mechanical properties of the lid material substrate of the present invention, such as tensile breaking strength, tensile breaking elongation, and tear strength, are largely dependent on the mechanical properties of the paper base material constituting the lid material substrate of the present invention, and are little affected by the coating layer. In other words, the mechanical properties of the paper base material constituting the lid material substrate, such as tensile breaking strength and tensile breaking elongation, can be considered to be substantially equal to the mechanical properties of the lid material substrate having such a paper base material. Therefore, by adjusting the paper substrate constituting the lid material substrate of the present invention so that the tensile breaking strength, value R, and tear strength are within the above-mentioned ranges, it is possible to obtain a lid material substrate of the present invention that has excellent shape stability and material breakage resistance.

[0037] The tensile breaking strength and tensile breaking elongation in the CD of the paper substrate can be adjusted by controlling various conditions in methods conventionally known in the papermaking field, such as the type of pulp, the degree of beating of the pulp, the filler content in the stock, the type of sizing agent in the stock, the concentration of the stock, the J / W ratio in the paper machine, the dewatering conditions in the wire part, the pressing conditions in the press part, and the conditions in the drying part. More specifically, from the viewpoint of increasing the tensile breaking strength in the CD of the paper substrate, control measures include increasing the amount of softwood pulp, increasing the degree of beating of the pulp, reducing the amount of filler in the stock, increasing the concentration of the stock supplied to the paper machine, increasing the amount of stock supplied, reducing the J / W ratio, increasing the dehydration in the wire part, increasing the pressure in the press part, and lowering the temperature and extending the time in the dryer part. On the other hand, from the viewpoint of increasing the tensile breaking elongation in the CD of the paper substrate, control measures include increasing the amount of hardwood pulp, decreasing the degree of beating of the pulp, increasing the amount of sizing agent in the stock, increasing the J / W ratio, weakening the dehydration in the wire part, increasing the pressure in the press part, and lowering the temperature and extending the time in the dryer part. Furthermore, when a coating layer containing a pigment and a binder is formed on at least one surface of a paper substrate and then the above-mentioned calendaring treatment is performed, the tensile breaking strength value of the lid material substrate of the present invention tends to increase and the tensile breaking elongation value tends to decrease.

[0038] The CD tear strength of the paper substrate can be adjusted by controlling various conditions in methods conventionally known in the papermaking field, such as the pulp type, the degree of beating of the pulp, the consistency of the stock, the J / W ratio in the paper machine, the conditions of the press part, and the conditions of the calendering treatment, etc. More specifically, from the perspective of increasing the CD tear strength value of the paper substrate, examples include increasing the degree of beating of the pulp, increasing the consistency and amount of the stock supplied to the paper machine, reducing the J / W ratio, increasing the pressure in the press part, and increasing the pressure in the calendering treatment.

[0039] The Parker Print Surf smoothness (soft packing / clamp pressure 2000 kPa) of the lid material substrate of the present invention depends on the smoothness of the paper substrate and coating layer. Paper smoothness is a physical property conventionally known in the papermaking field and can be adjusted by conventionally known methods in the papermaking field. The Parker Print Surf smoothness of the lid material substrate can be adjusted by controlling various conditions in methods conventionally known in the papermaking field, such as controlling the pulp type, pulp beating degree, stock concentration, press part conditions in a paper machine, drying zone conditions in a paper machine, calendering conditions, etc. In addition, the Parker Print Surf smoothness of the lid material substrate of the present invention can be adjusted by controlling the pigment type and binder type contained in the coating layer, the pigment and binder concentrations in the coating solution when forming the coating layer, drying conditions, and calendering conditions after forming the coating layer. More specifically, from the viewpoint of reducing the Parker Print Surf smoothness value, for example, in the manufacturing stage of the paper base material, measures include increasing the pressure in the press part, lowering the temperature in the drying zone, and increasing the pressure in the calendaring process, as well as lowering the drying temperature when forming the coating layer and increasing the pressure in the calendaring process after forming the coating layer.

[0040] [Lid material] The present invention also provides a lid material formed using the above-mentioned lid material substrate. In this specification, for convenience, the surface of the lid material substrate of the present invention on which printing has been applied and which corresponds to the side located on the outside of the container packaging will be referred to as the "front surface," and the surface of the lid material substrate of the present invention on which a heat seal layer and / or various barrier layers or vapor deposition layers for protecting the contents or processed layers for preventing adhesion of the contents have been laminated and which corresponds to the side located on the inside of the container packaging will be referred to as the "rear surface." The lid material is obtained, for example, by printing on the surface of the lid material substrate of the present invention and laminating a heat seal layer and / or various barrier layers or vapor deposition layers for protecting the contents or processed layers for preventing adhesion of the contents on the back surface of the lid material substrate. The lid material is formed by printing on the surface of the lid material substrate of the present invention using a gravure printing machine, etc. The lid material used for the container package is formed by laminating a heat seal layer for sealing the back surface of the lid material substrate located inside the container package and / or various barrier layers or vapor deposition layers for protecting the contents, or processed layers for preventing adhesion of the contents, etc.

[0041] The heat seal layer is a layer having heat sealability, and can be provided by any of the known methods, for example, the following (1) to (3). (1) A method of applying a heat seal layer coating liquid containing a heat sealable resin to the back surface of the base material for a lid of the present invention and drying the liquid to form a heat seal layer; (2) A method of laminating a heat-sealable resin onto the back surface of the substrate for a lid material of the present invention, optionally via an adhesive layer containing a conventionally known adhesive, by a dry lamination method (including a non-solvent dry lamination method) or an extrusion lamination method to form a heat-sealable layer; (3) A method of laminating a laminate having a heat seal layer to the back surface of the base material for a lid material of the present invention, optionally via an adhesive layer containing a conventionally known adhesive. The heat seal layer may contain additives such as surfactants, pigments, antioxidants, antistatic agents, ultraviolet absorbers, light stabilizers, colorants, plasticizers, crosslinking agents, antiblocking agents, lubricants such as wax, release agents, and rust inhibitors, as required.

[0042] Examples of heat-sealable resins used in the above method (1) include conjugated diene resins such as styrene-butadiene copolymer and acrylonitrile-butadiene copolymer; biodegradable resins such as polylactic acid and polybutylene succinate; polyolefin resins such as polyethylene and polypropylene; modified polyolefin resins such as ethylene-(meth)acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-vinyl acetate copolymer, and ethylene-vinyl alcohol copolymer; acrylic resins such as poly(meth)acrylic acid ester and methyl methacrylate-butadiene copolymer; styrene-acrylic resins such as styrene-acrylic copolymer and styrene-methacrylic copolymer; and ionomer resins obtained by crosslinking the above resins with metal ions. Examples of heat-sealable resins used in the above method (2) include conventionally known thermoplastic resins such as ethylene-based resins such as low-density polyethylene, medium-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-α-olefin copolymer, and ethylene (meth)acrylic acid copolymer; blend resins of polyethylene and polybutene; polypropylene-based resins such as homopolypropylene, propylene-ethylene random copolymer, propylene-ethylene block copolymer, and propylene-α-olefin copolymer; polylactic acid, polybutylene succinate, polybutylene succinate adipate, 3-hydroxybutanoic acid / 3-hydroxyhexanoic acid copolymer; and biomass-derived resins. Examples of the laminate used in the above method (3) include a film such as cellophane or biaxially oriented polypropylene provided with a heat seal layer.

[0043] The barrier layer is a layer formed by coating and drying a material such as a resin or laminating a layer that exhibits functions such as gas barrier property, water vapor barrier property, and / or moisture permeability barrier property, which are well known in the field of packaging materials. Examples of resins that form the barrier layer include urethane resins, vinylidene chloride resins, vinyl acetate resins, olefin resins, styrene resins, polyester resins, nylon resins, epoxy resins, melamine resins, polyvinyl alcohol resins, vinylpyrrolidone resins, acrylonitrile resins, polycarboxylic acid resins, silicone resins, starches, celluloses, and sodium alginate. Other examples of materials that form the barrier layer include waxes. It should be noted that a layer made of metal foil, which is different from the vapor-deposited layer described below, can also be used as the metal layer having barrier properties.

[0044] The vapor-deposited layer is a metal layer known in the field of packaging materials, formed by vapor-depositing a metal or inorganic oxide. Examples of metals include aluminum, gold, silver, copper, chromium, zirconium, manganese, sodium, tin, zinc, and titanium, and examples of metal oxides include oxides of the above metals, such as aluminum oxide and silicon oxide. Among these, it is usually preferable that the vapor-deposited layer be formed from aluminum. The vapor deposition layer can be formed by a conventional vapor deposition method such as a CVD method (chemical vapor deposition method) or a PVD method (physical vapor deposition method). Examples of the CVD method include a plasma CVD method, a plasma polymerization method, a thermal CVD method, a photo-CVD method, and a catalytic reaction type CVD method. Examples of the PVD method include a vacuum deposition method, a sputtering method, an ion plating method, an ion beam assisted method, and a cluster ion beam method.

[0045] The processing layer for preventing adhesion of contents can be formed by applying a coating solution containing an anti-adhesion agent such as a fluorine compound, a silicone compound, or hydrophobic inorganic fine particles to the substrate for the lid of the present invention and drying it. The coating and drying methods are similar to the methods described above for forming a coating layer on a paper substrate. Such processing layers are well known in the field of packaging materials.

[0046] The lid material of the present invention preferably has an image printed by a gravure printing machine on the surface of the lid material substrate of the present invention, and an aluminum vapor deposition layer and / or a heat seal layer on the back surface of the lid material substrate of the present invention, from the viewpoint of being able to apply conventional lid material manufacturing methods and to produce stably.

[0047] Although the lid material substrate and the lid material of the present invention have been described above, the present invention is not limited to the configurations of the above-described embodiments. For example, the lid material substrate and the lid material of the present invention may have any other configuration in addition to the configurations of the above-described embodiments, or may be replaced with any configuration that produces a similar effect. [Example]

[0048] The present invention will be described in more detail below with reference to examples, but is not limited to these examples. In the following description, "parts by mass" and "% by mass" represent the amount of dry solids or the amount of substantial components, respectively, unless otherwise specified. Furthermore, the coating amount represents the amount of dry solids. The lid material substrates in each of the Examples and Comparative Examples were prepared in the following manner.

[0049] 1. Each component material 1-1.Paper base material The following pulp and the following internal additives were mixed in water to prepare a paper stock. (pulp) LBKP (freeness 440mlcsf) 880 parts by mass NBKP (freeness 490mlcsf) 120 parts by mass (internal chemicals) Light calcium carbonate 70 parts by mass Sizing agent (alkyl ketene dimer type) 1.7 parts by mass Fixing agent (aluminum sulfate) 9 parts by weight Retention aid (polyacrylamide) 0.06 parts by mass Retention aid (colloidal silica) 0.36 parts by mass Paper strength agent (cationized starch) 12.5 parts by mass Colorant (dye) 0.01 parts by mass

[0050] Manufacturing Examples 1-18 The above paper stock was made into paper sheets using a Fourdrinier paper machine and dried to obtain paper base materials 1 to 18 with the basis weight, thickness and density shown in Table 1. In the production of the paper base materials, the concentration of the paper stock, the J / W ratio, the conditions of the wire part and the press part, and the temperature and time of the drying part were controlled so that the resulting lid material substrate would have the desired physical properties. No calendering was performed in the paper base material production stage. The basis weight of the obtained paper base materials was 45 to 75 g / m 2 The thicknesses of paper substrates 1 to 18 were determined in accordance with ISO534:2011.

[0051] 1-2. Preparation of coating solution for coating layer Coating liquid A Coating liquid A having a solid content of 65% by mass was prepared using water as a medium and the following formulation. Pigment (kaolin) 30 parts by mass Pigment (heavy calcium carbonate) 70 parts by mass Dispersant (polycarboxylic acid type) 0.15 parts by mass Binder (acetylated starch) 2 parts by mass Binder (styrene butadiene resin) 7 parts by mass Water retention agent (acrylic resin) 0.01 parts by mass Lubricant (higher fatty acid salt) 0.3 parts by mass Printability improver (modified polyamide) 0.3 parts by mass pH adjuster as needed Preservatives as needed

[0052] ·Coating liquid B Coating liquid B having a solid content of 65% by mass was prepared using water as a medium and the following formulation. Pigment (heavy calcium carbonate) 100 parts by mass Dispersant (polycarboxylic acid type) 0.15 parts by mass Binder (urea phosphate esterified starch) 7 parts by mass Binder (styrene butadiene resin) 7 parts by mass Lubricant (higher fatty acid salt) 0.3 parts by mass pH adjuster as needed Preservatives as needed

[0053] ·Coating liquid C Coating liquid C having a solid content of 50% by mass was prepared using water as a medium and the following formulation. Pigment (kaolin) 70 parts by mass Pigment (heavy calcium carbonate) 30 parts by mass Dispersant (polycarboxylic acid type) 0.15 parts by mass Binder (urea phosphate esterified starch) 1 part by mass Binder (styrene butadiene resin) 9 parts by mass Water retention agent (acrylic resin) 0.01 parts by mass Lubricant (higher fatty acid salt) 0.3 parts by mass Printability improver (modified polyamine type) 0.3 parts by mass Antifoaming agent (nonionic surfactant) 0.06 parts by mass Preservatives as needed

[0054] 2. Preparation of the base material for the lid Example 1 One side of the paper substrate 1 was coated with an air knife coater at an operating speed of 200 m / min with a coating amount of 16 g / m 2 The coating conditions were adjusted so that the coating liquid A was applied and dried to form a coating layer, which was then subjected to a calendar treatment at a linear pressure of 210 to 290 kg / m to obtain a substrate 1 for a lid material. Example 2 In Example 1, paper substrate 2 was used instead of paper substrate 1, and the coating amount of coating solution A was 21 g / m 2 A lid material substrate 2 was obtained in the same manner as in Example 1, except that the coating conditions were adjusted so that the coating temperature was 100°C.

[0055] Example 3 A substrate for a lid material 3 was obtained in the same manner as in Example 1, except that the paper substrate 3 was used instead of the paper substrate 1 and the coating liquid B was used instead of the coating liquid A. Examples 4 to 14, Comparative Examples 1 to 3 Lidding material substrates 4 to 14 and C1 to C3 were obtained in the same manner as in Example 1, except that the paper substrate, coating liquid type, and coating amount shown in Table 1 were used.

[0056] Example 15 A blade coater was used to coat one side of the paper substrate 15 at an operating speed of 200 m / min with a coating amount of 12 g / m 2 Then, the surface of the coating layer formed with Coating Solution B was coated with Coating Solution B using an air knife coater at an operating speed of 200 m / min in a coating amount of 7 g / m. 2 The coating liquid C was applied to one side of the paper substrate 15 so that the coating liquid B and the coating liquid C were mixed, and then dried to form two coating layers on one side of the paper substrate 15. The paper substrate 15 was then subjected to a calendar treatment at a linear pressure of 210 to 290 kg / m to obtain a substrate 15 for a lid material.

[0057] 3. Evaluation of base materials for lids 3-1. Basic properties of the base material for lids The following basic physical properties of the lid material substrates obtained in each of the Examples and Comparative Examples were measured in accordance with the following ISO standards. Thickness: ISO534:2011 ·Basic weight: ISO536:2019 ·Density:ISO534:2011 · Tensile strength in CD of paper substrate: ISO1924-2:2008 · Tensile elongation at break in CD for paper substrate: ISO1924-2:2008 ·Tear strength: ISO1974:2012 Parker Print Surf Smoothness (PPS): ISO8791-4:2021 Furthermore, the value R of the covering material substrate was calculated from the tensile strength at break and tensile elongation at break obtained above. The above results are summarized in Table 1, along with the thickness, basis weight and density of paper substrates 1 to 18.

[0058] 3-2. Shape stability and fracture resistance of lid substrate <Form stability> Test pieces were prepared from the lid material substrates obtained in each Example and Comparative Example, cutting them into 4 cm long x 2 cm wide pieces with the longitudinal direction aligned with the MD of the paper substrate. After leaving the test pieces in an atmosphere of 23 ° C and 50% RH for 2 hours, the test pieces were folded in half at the center of the long side so that the surface of the lid material substrate was facing inward, and a 200 g weight was placed on the fold for 5 seconds, after which the weight was removed. After removing the weight, the test pieces were left to stand for 5 seconds, and the opening angle at the fold of the test piece was measured to evaluate the dead hold property. The dimensional stability of the lid material substrate was evaluated according to the following criteria. Five test pieces were evaluated for each lid material substrate, and the worst evaluation result was adopted. If the test piece was rated A or B, the lid material substrate was deemed to have dimensional stability. <Evaluation criteria for shape stability> A: 50° or less B: More than 50° and less than 90° C: More than 90°

[0059] <Resistance to material breakage> Using the lid material substrates obtained in each example and comparative example, the burst strength of each lid material substrate was measured in accordance with ISO2758:2001 "Paper - Determination of bursting strength" to evaluate the material breakage resistance. Prior to measurement, the test pieces of the lid material substrate were left to stand for two hours in an atmosphere of 23°C and 50% RH (environment (1)) and two hours in an atmosphere of 60°C and 85% RH (environment (2)). After standing in each environment, the burst strength (kPa) was measured and the material fracture resistance of the lid material substrate was evaluated according to the following criteria. For each lid material substrate, measurements were taken on five test pieces in each environment, for a total of 10 points, and the worst evaluation result was adopted. A rating of A or B was given to the lid material substrate as having material fracture resistance. <Evaluation criteria for fracture resistance> A: 3.0kPa or more B: 2.5kPa or more and less than 3.0kPa C: Less than 2.5kPa

[0060] The above results are shown in Table 1. As can be seen from Table 1, the lid material substrates of Examples 1 to 15, which correspond to the present invention, have shape stability and material fracture resistance, while the lid material substrates of Comparative Examples 1 to 3, which do not satisfy the configuration of the present invention, cannot satisfy at least one of shape stability and material fracture resistance. Furthermore, comparing Examples 1, 2, 4, 5, 6, 8, 9, 12, and 13 with Examples 7, 10, 11, and 14, it can be seen that a CD tear strength of 350 mN or more and 480 mN or less for the paper substrate of the lid material substrate, and a Parker Print Surf smoothness of 0.4 μm or more and 0.8 μm or less measured on the surface of the lid material substrate having a coating layer, are even more preferable from the standpoint of dimensional stability and material breakage resistance. By performing a calendering treatment, the density of the lid material substrate increases without changing the basis weight, improving surface smoothness. The increase in density by calendering the lid material substrate contributes to increasing the flexibility of the paper and reducing distortion in the paper layer structure, improving dimensional stability and material breakage resistance. Furthermore, improved surface smoothness improves printability on a gravure printing machine.

[0061] [Table 1] [Industrial Applicability]

[0062] The lid material substrate of the present invention is suitable for printing on a gravure printing machine and has excellent shape stability and resistance to material breakage, and therefore can be effectively used as a lid material for container packaging such as instant noodles.

Claims

1. A paper substrate and one or more coating layers containing a pigment and a binder on at least one side of the paper substrate, The tensile breaking strength in the CD of the paper base material, as determined in accordance with ISO 1924-2: 2008, is 2.5 kN / m or more; The value R of the tensile breaking strength (kN / m) relative to the tensile breaking elongation (%) in the CD of the paper base material, as determined in accordance with ISO 1924-2:2008, is 0.25 or more; A substrate for a lid material having a total thickness of 80 μm or less.

2. The CD tear strength of the paper base material, as determined in accordance with ISO 1974: 2012, is 350 mN or more and 480 mN or less, and The Parker Print Surf smoothness (soft backing / clamp pressure 2000 kPa) measured on the outermost surface of the coating layer according to ISO8791-4:2021 is 0.4 μm or more and 0.8 μm or less. The substrate for lid material according to claim 1.

3. A lid material using the lid material substrate according to claim 1 or 2.

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