Coated paper

Abstract

To provide coated paper that can be used with any paper substrate and is less prone to cracking during folding. [Solution] Basis weight 100g / m 2 The above paper substrate has a coating layer containing PHBH and EVA on at least one surface. The coating amount (dry weight) of the aforementioned coating layer is 5 g / m² per side. 2 That's all. The coating layer contains 5 to 120 parts by mass of EVA per 100 parts by mass of PHBH, The aforementioned EVA is a coated paper having a tensile strength of 4.5 to 25.0 MPa and an elongation of 400 to 800%.

Description

[Technical Field]

[0001] The present invention relates to coated paper having a coating layer containing PHBH. [Background technology]

[0002] In recent years, efforts have begun to prevent environmental damage caused by plastic waste, and there is a growing demand to replace single-use plastic products with materials that have a smaller environmental impact. Examples of alternative materials to plastic include biodegradable plastics, wood, and paper. Aliphatic polyesters such as polylactic acid and polycaprolactone are known as biodegradable plastics. However, aliphatic polyesters have the problem that they take a long time to biodegrade at low temperatures, and their decomposition rate in natural environments such as the ocean is slow.

[0003] Poly(3-hydroxybutyrate) resins are microbially produced thermoplastics with excellent biodegradability under both aerobic and anaerobic conditions, and possess the remarkable property of being rapidly decomposed by microorganisms even in water such as oceans. Furthermore, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (hereinafter also referred to as PHBH), a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate, is attracting attention due to its biodegradability and resin properties.

[0004] Patent Document 1 describes a coated paper having a coating layer containing PHBH and an adhesive on at least one surface of a paper substrate, wherein the solid content mass ratio of PHBH to adhesive in the coating layer is 99.9 / 0.1 to 60.0 / 40.0, and which has few coating defects, and which can be used as heat-sealable paper, water-resistant paper, oil-resistant paper, etc.

[0005] Blister packs made of paper, which do not use plastic, are used as packaging for stationery, toothbrushes, and other items for display in stores (Patent Document 2). When heat-sealable paper described in Patent Document 1, which uses a thick paper substrate, was folded to manufacture packaging such as paper blister packs, a problem arose in which cracks occurred in the folded parts of the coated layer. When cracks occur in the folded parts of the packaging, water such as rain can easily seep inside, so the strength decreases when wet, and the three-dimensional shape of the packaging is easily distorted. In addition, paper blister packs are sometimes stored back in their original packs after use, such as when traveling, but if water gets inside, the shape of the pack is similarly easily distorted. As a method to suppress cracking during folding, a method of adjusting the tensile elongation at break and moisture content of the paper substrate is known (paragraphs 0028-0029 of Patent Document 3). However, the tensile elongation at break and moisture content of the paper substrate are controlled during the papermaking process, and it is not possible to use any available paper substrate. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2021 / 256381 [Patent Document 2] Japanese Patent Application Publication No. 07-172465 [Patent Document 3] Japanese Patent Publication No. 2022-089429 [Overview of the project] [Problems that the invention aims to solve]

[0007] The present invention aims to provide coated paper that is less prone to cracking during folding and can be used with any paper substrate. [Means for solving the problem]

[0008] The means for solving the problems of the present invention are as follows. 1. Basis weight 100g / m 2The above paper substrate has a coating layer containing PHBH and EVA on at least one surface. The coating amount (dry weight) of the aforementioned coating layer is 5 g / m² per side. 2 That's all. The coating layer contains 5 to 120 parts by mass of EVA per 100 parts by mass of PHBH, Coated paper characterized in that the EVA has a tensile strength of 4.5 to 25.0 MPa and an elongation of 400 to 800%. 2. The coated paper according to 1, characterized in that the molar ratio of ethylene to vinyl acetate in the EVA (ethylene:vinyl acetate, total 100) is 5:95 to 45:55. 3. The coated paper according to 1. or 2., characterized in that the glass transition temperature (Tg) of the EVA is -40°C or higher and 10°C or lower. 4. A packaging body having coated paper as described in any of 1. to 3. [Effects of the Invention]

[0009] The coated paper of the present invention is less prone to cracking during folding and has excellent flexibility. The coated paper of the present invention is suitable for manufacturing packaging such as boxes and paper blister packs by folding and heat sealing. Because the occurrence of cracks is suppressed in packaging using the coated paper of the present invention, the strength does not decrease easily even when wet and the three-dimensional shape does not easily collapse. The coated paper of the present invention has a high proportion of biodegradable materials, and even if it is released into the environment, it will decompose rapidly. [Modes for carrying out the invention]

[0010] The coated paper of the present invention has a basis weight of 100 g / m². 2 The above paper substrate has a coating layer containing PHBH and EVA on at least one surface. The coating amount (dry weight) of the coating layer is 5 g / m² per side. 2 That's all. The coating layer contains 5 to 120 parts by mass of EVA per 100 parts by mass of PHBH. The EVA has a tensile strength of 4.5 to 25.0 MPa and an elongation at break of 400 to 800%. In this specification, the tensile strength and elongation at break are the values evaluated in accordance with 3.4 and 3.5 of JIS-K-6251:2017, respectively. Also, in this specification, the description of "A to B" (where A and B are numerical values or ratios) means a numerical range including A and B.

[0011] The coated paper of the present invention only needs to have a coating layer on one of the outermost surfaces, and may also have coating layers on both of the outermost surfaces. Further, other layers such as an anchor layer, a water vapor barrier layer, a gas barrier layer, and an ink receiving layer may be provided between the paper base material and the coating layer.

[0012] (Paper base material) The paper base material is a sheet mainly composed of pulp, and is obtained by papermaking a pulp slurry containing fillers, various auxiliaries, and the like. Examples of the pulp include chemical pulps such as hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), softwood unbleached pulp (NUKP), and sulfite pulp, mechanical pulps such as stone ground pulp and thermomechanical pulp, wood fibers such as deinked pulp and waste paper pulp, and non-wood fibers obtained from kenaf, bamboo, hemp, etc. One or more of these can be appropriately blended and used. Among these, it is preferable to use chemical pulp of wood fiber and mechanical pulp of wood fiber, and more preferably chemical pulp of wood fiber, because it is difficult for foreign substances to be mixed into the paper base material, it is difficult for discoloration to occur over time when recycled as a waste paper raw material, it has a high whiteness and thus has a good surface feeling during printing, and especially the use value when used as a packaging material is high. Specifically, the blending amount of chemical pulp of wood fiber such as LBKP and NBKP with respect to the total pulp is preferably 80% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, and most preferably 100% by mass.

[0013] As fillers, known fillers such as talc, kaolin, calcined kaolin, clay, heavy calcium carbonate, light calcium carbonate, white carbon, zeolite, magnesium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon dioxide, amorphous silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, barium sulfate, calcium sulfate, and other inorganic fillers, as well as organic fillers such as urea-formaldehyde resin, polystyrene resin, phenolic resin, and fine hollow particles can be used. Note that fillers are not essential materials and may not be used.

[0014] Examples of various additives include sizing agents such as rosin, alkyl ketene dimer (AKD), and alkenyl succinic anhydride (ASA); dry strength enhancers such as polyacrylamide polymers, polyvinyl alcohol polymers, cationized starch, various modified starches, urea-formaldehyde resins, and melamine-formaldehyde resins; wet strength enhancers; yield enhancers; water drainage enhancers; coagulants; aluminum sulfate; bulk enhancers; dyes; fluorescent whitening agents; pH adjusters; defoamers; UV inhibitors; fade inhibitors; pitch control agents; and slime control agents. These can be selected and used as needed.

[0015] The paper substrate may have its surface treated with various chemicals. Examples of chemicals include oxidized starch, hydroxyethyl etherified starch, enzyme-modified starch, polyacrylamide, polyvinyl alcohol, surface sizing agents, water-resistant agents, water-retaining agents, thickeners, and lubricants, which can be used individually or in combination of two or more. Furthermore, these various chemicals may be used in combination with pigments. Examples of pigments include inorganic pigments such as kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate, mica, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicates, colloidal silica, and satin white, as well as organic pigments such as dense, hollow, or core-shell types, which can be used individually or in combination of two or more.

[0016] In this invention, the basis weight of the paper substrate is 100 g / m². 2That's all. The basis weight is 100 g / m 2 The paper base material with a basis weight of 100 g / m or more is suitable for manufacturing a package by folding. The upper limit of the basis weight of the paper base material is not particularly limited. However, for example, if it becomes too thick, folding may be difficult. Therefore, 500 g / m 2 or less is more preferable. In addition, the density of the paper base material can be appropriately selected according to various desired qualities, handling properties, etc. Usually, it is preferably 0.5 g / cm 3 or more and 1.0 g / cm 3 or less. In the present invention, the paper base material may be either paper composed of only a single paper layer or multi-layer paper having two or more paper layers. When the paper base material is multi-layer paper, the paper material, basis weight, etc. of each paper layer may be the same or different.

[0017] The method for manufacturing (papermaking) the paper base material is not particularly limited, and known manufacturing (papermaking) methods and papermaking machines such as fourdrinier machines, cylinder machines, twin-wire papermaking machines such as short-formers, gap former types, hybrid former types (ontopper types), etc. can be selected. Also, the pH during papermaking may be in any of the acidic region (acid papermaking), pseudo-neutral region (pseudo-neutral papermaking), neutral region (neutral papermaking), or alkaline region (alkaline papermaking). After papermaking in the acidic region, an alkaline agent may be applied to the surface of the paper layer. When treating the surface of the paper base material with a chemical, the surface treatment method is not particularly limited, and known coating devices such as rod metering size presses, pond size presses, gate roll coaters, spray coaters, blade coaters, curtain coaters, etc. can be used.

[0018] (Coating layer) The coating layer is located on at least one outermost surface of the coated paper, contains at least PHBH and EVA, and the coating amount (dry mass) is 5 g / m per side 2 or more, and contains 5 parts by mass or more and 120 parts by mass or less of EVA with respect to 100 parts by mass of PHBH.

[0019] <phbh> PHBH is a copolymer of 3-hydroxybutyrate (hereinafter also referred to as 3HB) and 3-hydroxyhexanoate (hereinafter also referred to as 3HH), and is a biodegradable resin known to be produced by microorganisms. In the present invention, PHBH may be derived from microorganisms or from petroleum resources, but it is preferable to use PHBH derived from microorganisms from the viewpoint of reducing environmental impact.

[0020] Microorganisms that produce PHBH are not particularly limited to any microorganism that accumulates PHBH within its cells, but examples include bacteria of the genera Alcaligenes (such as A. lipolytica, A. eutrophus, and A. latus), Pseudomonas, Bacillus, Azotobacter, Nocardia, and Aeromonas. In particular, in terms of PHBH productivity, strains such as Aeromonas caviae, and even Alcaligenes eutrophas AC32 (accession number FERM BP-6038, deposit date August 7, 1997, National Institute of Advanced Industrial Science and Technology, Patent Organism Depositary Center, address: 1-1-1 Higashi, Tsukuba, Ibaraki Prefecture, Japan, Central No. 6) (J. Bacteriol., 179, pp. 4821-4830 (1997)) are preferred. Furthermore, a method for obtaining PHBH from Aeromonas caviae, a microorganism of the genus Aeromonas, is disclosed, for example, in Japanese Patent Publication No. 05-093049. These microorganisms are cultured under appropriate conditions to accumulate PHBH within the cells before use. The carbon source and culture conditions used for cultivation can be obtained according to the methods described in Japanese Patent Publication No. 05-093049, Japanese Patent Publication No. 2001-340078, etc., but are not limited thereto.

[0021] The composition ratio (mol%) of PHBH is preferably 3HB:3HH = 97:3 to 75:25, and more preferably 95:5 to 85:15. If the 3HH composition is less than 3 mol%, the properties of PHBH become similar to those of the 3HB homopolymer, resulting in a loss of flexibility and an undesirable tendency for the film deposition temperature to become too high. If the 3HH composition exceeds 25 mol%, the crystallization rate becomes too slow, making it unsuitable for film deposition, and the degree of crystallinity decreases, which tends to make the resin more flexible and reduce its flexural modulus. The composition ratio of PHBH can be measured by NMR analysis of the powder obtained by centrifuging an aqueous dispersion and drying it. Microbially produced PHBH is a random copolymer. Methods to adjust the molar ratio of the copolymer include selecting the microbial cells, selecting the carbon source as the raw material, blending with PHBH of different molar ratios, and blending with 3HB homopolymer.

[0022] The weight-average molecular weight of PHBH is preferably between 50,000 and 1,500,000. When PHBH is within this range, film formation is possible at low temperatures when coating with PHBH, and when PHBH is laminated, a film with excellent mechanical properties can be obtained. A weight-average molecular weight of 100,000 to 500,000 is more preferable, and 150,000 to 450,000 is even more preferable. The weight-average molecular weight of PHBH can be determined by gel permeation chromatography (GPC, such as Showa Denko's "Shodex GPC-101") using a polystyrene gel column (such as Showa Denko's "Shodex K-804") with chloroform as the mobile phase, and the molecular weight converted to polystyrene equivalent. For measurement, a powder obtained by centrifuging and drying an aqueous dispersion containing PHBH is used.

[0023] The average particle size of PHBH is preferably 0.1 to 50 μm. PHBH with an average particle size of less than 0.1 μm is difficult to produce by microorganisms, and even when obtained by chemical synthesis, a process of micronization is required. If the average particle size exceeds 50 μm, uneven coating may occur on the surface when a coating solution containing PHBH is applied. The average particle size of PHBH is more preferably 0.5 to 10 μm. The average particle size of PHBH refers to the particle size corresponding to the 50% accumulation of all particles measured by adjusting an aqueous suspension of PHBH to a predetermined concentration using a general-purpose particle size analyzer such as a Microtrac particle size analyzer (Nikkiso, FRA).

[0024] <eva> The EVA used in this invention has a tensile strength of 4.5 to 18.5 MPa and an elongation of 400 to 800%. The coated paper of this invention has a coating layer that contains 5 to 120 parts by mass of EVA that satisfies specific tensile strength and elongation requirements per 100 parts by mass of PHBH, and although the mechanism is unknown, it exhibits excellent crack resistance. From the viewpoint of crack resistance, the tensile strength of the EVA is preferably 5.0 to 18.5 MPa. Furthermore, the elongation of the EVA is preferably 420 to 700%, and more preferably 650% or less.

[0025] EVA (ethylene vinyl acetate copolymer) is a copolymer in which ethylene and vinyl acetate are monomers, and other monomers may also be used as monomers. However, the EVA of the present invention is not saponified and does not have vinyl alcohol units produced by the saponification of vinyl acetate units. When the EVA has other monomers as monomers, the content of constituent units derived from other monomers relative to the total EVA is preferably 30% by mass or less. This content is not particularly limited as long as it does not impair the effects of the present invention, and can be, for example, 20% by mass or less, 10% by mass or less, 5% by mass or less, 3% by mass or less, 1% by mass or less, etc.

[0026] The molar ratio of ethylene to vinyl acetate in EVA (component units derived from ethylene:component units derived from vinyl acetate, also expressed as ethylene:vinyl acetate, with a total of 100) is preferably 5:95 to 45:55, more preferably 7:93 to 43:57, even more preferably 10:90 to 40:60, and even more preferably 20:80 to 40:60, from the viewpoint of crack resistance. Furthermore, the glass transition temperature (Tg) of EVA is preferably -40°C to 10°C, more preferably -35°C or higher, even more preferably -30°C or higher, even more preferably 5°C or lower, and even more preferably 0°C or lower, from the viewpoint of crack resistance. In this specification, the glass transition temperature refers to the intermediate glass transition temperature measured in accordance with JIS K 7121-1987.

[0027] The coated paper of the present invention has a coating layer containing 5 to 120 parts by mass of EVA per 100 parts by mass of PHBH. The coating layer has excellent crack resistance due to the inclusion of PHBH and EVA in this ratio. The ratio of EVA to 100 parts by mass of PHBH is preferably 7 parts by mass or more, more preferably 10 parts by mass or more, preferably 110 parts by mass or less, and more preferably 105 parts by mass or less.

[0028] The coating layer may contain PHBH and EVA, and may also contain other thermoplastic resins or inorganic pigments. <Other thermoplastic resins> Other thermoplastic resins that have heat-seal properties at the temperature at which PHBH is fused can be used without particular limitation, but biodegradable resins such as aliphatic polyester resins such as polycaprolactone, polybutylene succinate adipate, polybutylene succinate, and polylactic acid, and aliphatic aromatic polyester resins such as polybutylene adipate terephthalate and polybutylene azelate terephthalate are preferred.

[0029] When the coating layer contains other thermoplastic resins, the total ratio of PHBH and EVA to the total thermoplastic resins contained in the coating layer is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, even more preferably 99% by mass or more, and most preferably 100% by mass.

[0030] <Inorganic pigments> As inorganic pigments, those used in coating paper can be used without particular limitations. Examples include kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate, mica, talc, bentonite, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicates, colloidal silica, and satin white. One or more of these can be used. Among these, one or more of kaolin, heavy calcium carbonate, light calcium carbonate, mica, talc, and bentonite are preferred.

[0031] From the viewpoint of adhesion to the coating layer, it is preferable that the inorganic pigment has a 50% volume average particle diameter (D50, hereinafter also referred to as "average particle diameter") of 6.0 μm or less, as measured by laser diffraction / scattering. Examples of laser diffraction / scattering measurement devices include Horiba's particle size distribution analyzer "Partica" and Malvern's particle size distribution analyzer "MASTER SIZER S". From the viewpoint of adhesion to the coating layer, the average particle diameter of the inorganic pigment is more preferably 5.0 μm or less, even more preferably 4.0 μm or less, even more preferably 3.0 μm or less, and even more preferably 2.0 μm or less. There is no particular lower limit to the average particle diameter of the inorganic pigment, but from the viewpoint of dispersibility, for example, it is preferably 0.1 μm or more, and more preferably 0.2 μm or more. When two or more inorganic pigments are included, it is preferable that the average particle size of at least one of them is within the numerical range described above, and it is preferable that the proportion of inorganic pigments satisfying this average particle size to the total inorganic pigments is 50% by mass or more, and more preferably 70% by mass or more.

[0032] When the coating layer contains an inorganic pigment, the solid content mass ratio of PHBH to the inorganic pigment (PHBH:inorganic pigment, total 100) is preferably 90:10 to 0.01:99.99. By further incorporating an inorganic pigment into a coating solution containing PHBH and EVA, the adhesion of the resulting coating layer is improved. Although the mechanism is unknown, the inventors speculate that because the inorganic pigment has better thermal conductivity than the organic PHBH and adhesive, the inorganic pigment heats up quickly when heated, and this heat is transferred from the inorganic pigment to the PHBH, causing the PHBH to heat up and melt sufficiently, making it easier to form a film. The solid content mass ratio of PHBH to inorganic pigment (PHBH:inorganic pigment, total 100) is more preferably 70:30 to 1:99, even more preferably 60:40 to 2:98, and even more preferably 50:50 to 3:97, from the viewpoint of adhesion of the coating layer.

[0033] The coating layer may contain other water-soluble resins and water-dispersible resins in addition to PHBH, EVA, other thermoplastic resins and inorganic pigments, and may also contain various additives used in coating solutions in the papermaking field, such as dispersants, viscosity modifiers, defoamers, water-resistant agents, pH adjusters, cationic resins, anionic resins, UV absorbers, metal salts, lubricants, coloring dyes, and pigments, as needed.

[0034] (Manufacturing method) The coated layer can be manufactured by conventionally known coating methods. For example, coating equipment includes blade coaters, bar coaters, roll coaters, air knife coaters, reverse roll coaters, curtain coaters, spray coaters, size press coaters, and gate roll coaters. Coating systems include water-based coatings using solvents such as water, and solvent-based coatings using solvents such as organic solvents, but water-based coatings are preferred.

[0035] The coating amount (dry mass) of the coating layer is 5 g / m² per side. 2 That's all. This coating amount is 5g / m 2 If the amount is less than 6 g / m², cracks are likely to occur in the coating layer during folding. 2 The above is more preferable: 10 g / m 2 The above is even more preferable. There is no particular upper limit to this coating amount, but for example, 50 g / m 2 The following is preferable: This coating amount is 50 g / m². 2 Beyond a certain point, crack resistance saturates and hardly improves further, while material costs increase and the drying load during coating becomes greater.

[0036] The coated paper of the present invention was measured in accordance with JIS Z1707:2019 7.4 "Heat seal strength test" at a pressurized temperature of 180°C and a pressurized pressure of 0.2 MPa (20.0 N / cm²). 2 ) When a heat-sealed product that has been heat-sealed for a pressurizing time of 1.0 second is peeled off in a T-shape, the heat seal strength is preferably 4.0 N / 15 mm or more, more preferably 5.0 N / 15 mm or more, even more preferably 6.0 N / 15 mm or more, and even more preferably 6.5 N / 15 mm or more.

[0037] ·Packaging The coated paper of the present invention has excellent foldability and heat-sealability, making it suitable for processing into packaging. When the coated paper of the present invention is used in packaging, the shape of the packaging is not particularly limited, but examples include aseptic containers for filling beverages such as milk and juice as described in Japanese Patent Publication No. 2005-306424, brick pack containers as described in Japanese Patent Publication No. 2004-026285, rectangular parallelepiped or rectangular tubular packaging containers with dispensing devices for filling shampoos, conditioners, etc. as described in Japanese Patent Publication No. 2022-103436, irregularly shaped web corner packaging as described in Japanese Patent Publication No. 2014-227187, dispensing paper containers for containing granular materials such as gum and chocolate confectionery as described in Japanese Utility Model Publication No. 06-025170, and flat, elongated paper blister packs as described in Japanese Patent Publication No. 07-172465. [Examples]

[0038] The present invention will be specifically described below with reference to examples, but the present invention is of course not limited to these examples. Unless otherwise specified, parts and % in the examples refer to parts by mass and mass%, respectively.

[0039] (Evaluation method) Tape pick The prepared coated paper was placed on a horizontal table and subjected to temperature and humidity control (conditions: 23°C, 50% humidity) for at least 24 hours. Then, a 12mm wide mending tape (3M Japan, Scotch® Mending Tape 810-1-12) was applied to the surface of the coating layer of the coated paper. A 130mm wide, 1.8kg rubber roller was then moved back and forth 20 times under its own weight over the mending tape to ensure close adhesion of the mending tape to the coating layer surface. Immediately afterward, the mending tape was quickly peeled off, and the ratio of the area where the coating layer adhered to the mending tape and peeled away from the paper substrate surface (interface failure area) to the area where the mending tape was applied, or the ratio of the area where part of the paper substrate adhered to the mending tape along with the coating layer and the paper substrate was damaged (internal failure area of ​​the paper substrate), was calculated. The adhesion to the paper substrate was then evaluated according to the following criteria. An evaluation of 5 or 4 indicates no practical problems. 5: No peeling 4: Less than 0-10% peeling of the adhesive surface. 3: Less than 10-50% of the adhesive surface is peeled off. 2: Less than 50-90% of the adhesive surface is peeled off. 1: 90-100% of the adhesive surface is peeled off.

[0040] ·Bending resistance With the paper substrate facing inward and the coating layer facing outward, the paper was folded in the MD direction (fold perpendicular to the MD direction) or the CD direction (fold perpendicular to the CD direction), and the folded area was pressed down 10 times with a 400g roller using its own weight. After that, a 0.05% New Coccine dye solution was applied to the folded area, left to stand for 30 seconds, and then wiped off with a JK wiper. The penetration level was evaluated according to the following criteria. Evaluation samples are shown in Table 1. An evaluation of 5 to 3 indicates no practical problems. 5: No staining 4. Check for penetration into the surface layer of the coating and the base paper layer at less than 5% of the folded area. 3. Check for penetration into the surface layer of the coating and the base paper layer in the folded area, covering 5% to less than 30% of the area. 2. Check for penetration into the surface layer of the coating and the base paper layer in 30% to less than 70% of the folded area. 1: Confirm penetration into the surface layer of the coating and the base paper layer in over 70% of the folded area.

[0041] [Table 1]

[0042] • Heat seal strength The test was conducted in accordance with JIS Z1707:2019 7.4 "Heat seal strength test". Two 100mm square test pieces were cut from the obtained coated paper, and the coated layers were brought into contact with each other. The test was then conducted at pressurized temperatures of 130°C, 140°C, 150°C, or 160°C, with a pressurized pressure of 0.2 MPa (20.0 N / cm²). 2 After heat-sealing with a pressurization time of 1.0 second, the specimen was left to stand for 24 hours in an environment of 23°C and 50% humidity. Then, a measurement sample was cut from the heat-sealed 100mm square test piece so that the long side was 100mm and the short side was 15mm. Subsequently, the peeled long edge was clamped in the upper and lower fixtures of a vertical tensile testing machine (Tensilon, manufactured by A&D Company, Ltd.), and the sample was peeled from the long edge side at a speed of 200 mm / min (T-type), while measuring the peel strength, i.e., the HS strength (N / 15 mm). Furthermore, the detached surface was visually inspected and evaluated according to the following criteria. Measurements were taken twice, and the average value of the peel strength is shown. If the evaluation results differed based on visual observation, It shows both. ○: The entire surface of the heat-sealed area is damaged. △: Partial material damage on the heat-sealed surface ×: Delamination occurs between coating layers (no material breakage). -: Without heat sealing

[0043] (material) Paper base material: Nippon Paper Industries, basis weight 220g / m² 2 Cup base paper, CUP-HD PHBH: Kaneka Corporation, mass-average molecular weight 200,000 EVA1: Sumika Chemtex Co., Ltd., S-400HQ: Tensile strength 12.7 MPa, elongation 550%, Ethylene:Vinyl acetate = 20:80, Tg 0℃, EVA2: Sumika Chemtex Co., Ltd., S-305HQ: Tensile strength 18.0 MPa, elongation 420%, ethylene:vinyl acetate = 10:90, Tg 7℃ EVA3: Sumika Chemtex Co., Ltd., S-408HQE: Tensile strength 5.0 MPa, elongation 650%, ethylene:vinyl acetate = 40:60, Tg -30℃ EVA4: Sumika Chemtex Co., Ltd., S-355HQ: Tensile strength 20.6 MPa, elongation 420%, ethylene:vinyl acetate = 10:90, Tg 10℃ EVA5: Sumika Chemtex Co., Ltd., S-401HQ: Tensile strength 6.2 MPa, elongation 850%, ethylene:vinyl acetate = 30:70, Tg -18℃

[0044] (Formation of the coating layer) PHBH, EVA, or PVA were mixed and stirred in the parts by mass shown in Table 1 to obtain a coating solution with a solid content concentration of 40% by mass. In Table 1, the numbers in parentheses for EVA represent, from left to right, tensile strength, elongation, molar ratio of ethylene:vinyl acetate, and Tg. A coating solution was applied to one surface of a paper substrate using the bar-blade method, with the dry mass per surface shown in Table 1. After drying at 105°C for 1 minute, a heat treatment was performed at 140°C for 1 minute to form a coating layer on the outermost surface of one side of the paper substrate.

[0045] [Table 1]

[0046] The coated papers obtained in Examples 1 to 4, using EVA with a tensile strength of 4.5 to 20.6 MPa and an elongation of 400 to 800%, exhibited excellent bending resistance. In contrast, Comparative Example 1, which was coated with PHBH only, Comparative Example 2, which used EVA that did not satisfy the specified tensile strength and elongation, and Comparative Example 3, which was coated with EVA only having a tensile strength of 4.5 to 20.6 MPa and an elongation of 400 to 800%, all exhibited inferior bending resistance. Furthermore, from Examples 1, 5-8, it was observed that the flexibility improved as the ratio of EVA to 100 parts by mass of PHBH increased, and from Examples 1, 9-11, it was observed that the amount of coating layer (dry weight) increased.< / eva> < / phbh>

Claims

1. Basis weight 100g / m ２ The above paper substrate has a coating layer containing PHBH and EVA on at least one surface. The coating amount (dry weight) of the aforementioned coating layer is 5 g / m² per side. ２ That's all. The coating layer contains 5 to 120 parts by mass of EVA per 100 parts by mass of PHBH, Coated paper characterized in that the EVA has a tensile strength of 4.5 to 25.0 MPa and an elongation of 400 to 800%.

2. The coated paper according to claim 1, characterized in that the molar ratio of ethylene to vinyl acetate in the EVA (ethylene:vinyl acetate, total 100) is 5:95 to 45:

55.

3. The coated paper according to claim 1 or 2, characterized in that the glass transition temperature (Tg) of the EVA is -40°C or higher and 10°C or lower.

4. A packaging body having coated paper according to claim 1 or 2.

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