Coated paper

Abstract

To provide a coated paper that can be heat seal processed at cold temperature under low pressure and has excellent heat seal strength.SOLUTION: In a coated paper including a paper substrate and a coated layer provided at least on one outermost surface and having heat sealability, the coated layer includes a thermoplastic resin of at least one kind selected from a group consisting of ethylene-methacrylic acid copolymer, ethylene acrylic acid copolymer, and ionomers thereof, a basis weight of the paper substrate is 58.9 g / m2 or over and 94.9 g / m2 or under, a thickness of the coated paper is 85 μm or over and 131 μm or under, a density of the coated paper is 0.68 g / cm3 or over and 0.79 g / cm3 or under, a cushioning property (C) of the coated paper is 12.4 N / mm or over and 18.0 N / mm or under, and Oken type smoothness (S) of the surface of the coated layer is 24 s or over and 89 s or under.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a coated paper having a coating layer having heat sealability on at least one outermost surface. [Background technology]

[0002] In recent years, coated paper in which a thermoplastic resin is coated on the surface of base paper has been attracting attention. For example, Patent Document 1 proposes a coated paper having a coating layer containing PHBH and an adhesive on at least one side of a paper substrate. This type of coated paper uses less thermoplastic resin than packaging films or laminated paper produced by extrusion lamination, and is therefore evaluated as a more environmentally friendly packaging material. These coated papers are processed using packaging machines that make packaging films and are used to package everyday items such as food, hygiene products, etc. However, because packaging machines are designed for packaging films (resin films), there was a problem in that coated papers, which are harder than packaging films, were difficult to heat seal.

[0003] There are two possible ways to solve this problem: increasing the pressure of the sealer to press the coated paper at high pressure, or increasing the temperature when pressing the sealer. However, in the case of increasing the press pressure, packaging machines that are designed to use resin often cannot set the press pressure to the level required for paper. In addition, the method of increasing the press temperature has the disadvantage that it cannot be applied to inclusions that are sensitive to high temperatures, such as chocolate, and therefore the inclusions are limited. In addition, sealing at high pressure and high temperature increases energy consumption and generates a lot of CO2, which undermines the positive impact on the environment of using paper. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-195717 Summary of the Invention [Problem to be solved by the invention]

[0005] The objective of the present invention is to provide a coated paper that can be heat sealed at low temperature and low pressure and has excellent heat seal strength. [Means for solving the problem]

[0006] The means for solving the problems of the present invention are as follows. 1. A coated paper having a paper base material and a coating layer having heat sealability on at least one of the outermost surfaces, A coated paper characterized in that the cushioning value (C) of the coated paper is 21.5 or less, and the Oken smoothness value (S) of the coating layer surface of the coated paper is 15 or more. 2. Coated paper according to 1, characterized in that the puncture strength is 14N or less. 3. Coated paper according to 1. or 2., characterized in that S≧30. Effect of the Invention

[0007] The coated paper of the present invention has high cushioning properties and a smooth coating layer surface, and therefore has excellent heat seal strength even when sealed under low temperature and low pressure conditions. [Brief description of the drawings]

[0008] [Figure 1] Schematic diagram of the puncture strength test. [Diagram 2] FIG. 2 is a diagram showing an example of a load-displacement curve used to calculate cushioning properties (C). [Diagram 3] Scatter plot of the cushioning properties (C) and the Oken smoothness (S) of the coating layer surface of the coated papers obtained in the Examples and Comparative Examples, grouped according to the evaluation results (◎, ○, ×) of the heat seal strength at 100°C. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The coated paper of the present invention has a paper base material and a coating layer having heat sealability on at least one outermost surface thereof, The cushioning property (C) of the coated paper is 21.5 or less, and the Oken smoothness (S) of the coating layer surface is 15 or more.

[0010] Cushioning (C) is the maximum puncture strength (unit: N) measured in accordance with JIS Z1707:2019 7.5 puncture strength test, divided by the distance the needle traveled when this maximum force was reached (unit: mm) (puncture strength / needle travel, unit: N / mm). Measurements were performed by conditioning the test specimens for at least 24 hours in an environment with a temperature of 23°C and a humidity of 50%, and then subjecting them to testing in the same environment. Cushioning property represents the magnitude of the force required for deformation per mm in a puncture test, and the smaller the value, the smaller the force required for deformation. In the present invention, cushioning property (C) is 21.5 or less. Cushioning property is preferably 20.0 or less, more preferably 19.0 or less, even more preferably 18.0 or less, and even more preferably 14.0 or less. The lower limit of cushioning property can be, for example, 10.0 or more, 11.0 or more, or 12.0 or more.

[0011] The coated paper of the present invention has an Oken smoothness (S) of the coating layer surface of 15 seconds or more. A higher smoothness value means a smoother surface, and a higher smoothness value means a larger contact area when the coating layers are placed face to face and heat sealed, thereby improving the heat seal strength. This smoothness value is preferably 23 seconds or more, more preferably 25 seconds or more, even more preferably 30 seconds or more, even more preferably 35 seconds or more, and even more preferably 40 seconds or more. The upper limit of the Oken smoothness (S) of the coating layer surface can be, for example, 120 seconds or less, 110 seconds or less, or 100 seconds or less.

[0012] The coated paper of the present invention preferably has a puncture strength measured as above of 14 N or less. The smaller the puncture strength value, the lower the pressure at which heat sealing can be performed, so 13 N or less is more preferable, 12 N or less is even more preferable, 11 N or less is even more preferable, and 10 N or less is even more preferable. On the other hand, if the puncture strength value is too low, the paper becomes more likely to break during processing, transportation, etc., so the puncture strength value is preferably 4 N or more, more preferably 5 N or more, and even more preferably 6 N or more.

[0013] The coated paper of the present invention preferably has a cushioning property (C) and an Oken smoothness (S) of the coating layer surface of S≧6C-90. Coated papers that satisfy this relationship have better heat sealability. The coated paper of the present invention is more preferably S≧6C-85, even more preferably S≧6C-80, and even more preferably S≧6C-70. Coated papers that satisfy S≧6C-70 have particularly high heat sealability and excellent heat seal strength. The coated paper of the present invention is even more preferably S≧6C-65, even more preferably S≧6C-60, even more preferably S≧6C-55, and even more preferably S≧6C-50.

[0014] (Paper base material) The paper base material is obtained by papermaking a paper material containing pulp, filler, various auxiliaries, etc. When the coated paper of the present invention is used for applications in which it comes into contact with food, it is preferable to use materials that comply with food safety standards, such as those that are approved as food additives or have FDA certification, for the materials that make up the paper base.

[0015] The pulp may be any of a variety of known pulps, including chemical wood pulps such as bleached softwood kraft pulp (NBKP), unbleached softwood kraft pulp (NUKP), bleached hardwood kraft pulp (LBKP), unbleached hardwood kraft pulp (LUKP), and sulfite pulp (SP); mechanical wood pulps such as ground pulp (GP), refiner ground pulp (RGP), stone ground pulp (SGP), chemi-ground pulp (CGP), semi-chemical pulp (SCP), thermomechanical pulp (TMP), and chemi-thermomechanical pulp (CTMP); non-wood pulps obtained from kenaf, bagasse, bamboo, hemp, straw, and the like; and waste paper pulp made from waste paper, which has had the ink removed in a deinking process. Among these, chemical pulps such as LBKP and NBKP, which are less likely to be contaminated with foreign matter, are preferred, and it is also preferred that the amount of recycled paper pulp is small. Specifically, the amount of wood fiber chemical pulp such as LBKP and NBKP in the total pulp is preferably 80% by weight or more, more preferably 90% by weight or more, even more preferably 95% by weight or more, even more preferably 98% by weight or more, and even more preferably 100% by weight. Also, the amount of recycled paper pulp in the total pulp is preferably 10% by weight or less, more preferably 5% by weight or less, even more preferably 1% by weight or less, and most preferably none.

[0016] The paper base material of the present invention may contain papermaking fibers other than pulp. Examples of papermaking fibers other than pulp include thermoplastic resin fibers, and the thermoplastic resin fibers may have a core-sheath structure. As the thermoplastic resin fibers, those used in the papermaking field can be used without any particular restrictions, and it is preferable to use those having biodegradability such as PVA-based resins, cellulose ester-based fibers, polylactic acid, polybutylene succinate adipate, polybutylene succinate, polycaprolactone, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH). Since the thermoplastic resin fibers have heat sealability, the paper base material containing the thermoplastic resin fibers is firmly bonded to the heat seal layer during heat fusion, improving the heat seal strength. On the other hand, the thermoplastic resin fibers are softer and less stiff than pulp, so the strength of the paper base material containing the thermoplastic resin fibers is reduced. The ratio of pulp to all papermaking fibers contained in the paper base material is preferably 90% by weight or more, more preferably 95% by weight or more, and even more preferably 99% by weight or more. Note that thermoplastic resin fibers are not essential materials and may not be used.

[0017] Examples of fillers that can be used include known fillers such as inorganic 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 oxide, amorphous silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, barium sulfate, and calcium sulfate, and organic fillers such as urea-formalin resin, polystyrene resin, phenol resin, and hollow microparticles. Note that fillers are not essential materials and may not be used.

[0018] Examples of various auxiliary agents include sizing agents such as rosin, alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), polyacrylamide polymers, polyvinyl alcohol polymers, cationic starch, various modified starches, urea-formaldehyde resin, melamine-formaldehyde resin, and other dry strength agents, wet strength agents, retention agents, drainage improvers, coagulants, aluminum sulfate, bulking agents, dyes, fluorescent brighteners, pH adjusters, defoamers, UV inhibitors, anti-fading agents, pitch control agents, slime control agents, and the like, and can be selected and used as appropriate as needed.

[0019] The method of manufacturing (papermaking) the paper base material is not particularly limited, and known manufacturing (papermaking) methods and papermaking machines can be selected, such as a Fourdrinier papermaking machine, a cylinder papermaking machine, a short wire papermaking machine, a twin-wire papermaking machine such as a gap former type or a hybrid former type (on-top former type). The pH during papermaking may be in the acidic range (acidic papermaking), pseudo-neutral range (pseudo-neutral papermaking), neutral range (neutral papermaking), or alkaline range (alkaline papermaking), and after papermaking in the acidic range, an alkaline agent may be applied to the surface of the paper layer. The paper base material may be one layer, or may be composed of two or more layers. The paper base material may be Clupak paper that has been subjected to a known Clupak process.

[0020] Furthermore, the surface of the paper substrate can be treated with various chemicals. Examples of chemicals that can be used include oxidized starch, hydroxyethyl etherified starch, enzyme-modified starch, polyacrylamide, polyvinyl alcohol, surface sizing agents, water-resistant agents, water retention agents, thickeners, and lubricants, and these can be used alone or in combination of two or more. Furthermore, these various chemicals can 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, silicate salts, colloidal silica, and satin white, and organic pigments such as solid, hollow, or core-shell types can be used alone or in combination of two or more.

[0021] The method for treating the surface of the paper substrate is not particularly limited, but known coating devices such as a rod metering size press, a pond type size press, a gate roll coater, a spray coater, a blade coater, and a curtain coater can be used. Examples of the paper base material obtained in this manner include various known types of paper, such as fine paper, medium quality paper, coated paper, one-sided glossy paper, kraft paper, one-sided glossy kraft paper, bleached kraft paper, glassine paper, paperboard, white paperboard, and liner.

[0022] The basis weight of the paper base material can be appropriately selected depending on the desired quality and handling properties, but is usually 20 g / m 2 More than 120g / m 2 The following are preferred: For coated paper used for packaging purposes such as food packaging, bags, containers, boxes, cups, and lids, 25 g / m 2 More than 120g / m 2 The following is more preferable, and in particular for coated paper used for bags, lids, or soft packaging applications described later, 30 g / m 2 More than 120g / m 2 The following are more preferable. In terms of composition, the flexible packaging material is a packaging material that is made of a highly flexible material, and generally refers to a packaging material made of thin, flexible materials such as paper, film, and aluminum foil, either alone or in combination. In terms of shape, it refers to a packaging material such as a bag that maintains a three-dimensional shape by putting an inclusion inside. The density of the coated paper can be appropriately selected depending on the desired quality and ease of handling, but is usually 0.5 g / cm 3 More than 1.0g / cm 3 The following are preferred:

[0023] (Coating layer) The coating layer is located on at least one outermost surface of the coated paper of the present invention, and can also be located on both outermost surfaces. The coating layer can be formed directly on the paper substrate, and can have one or more functional layers between the paper substrate and the coating layer, such as a sealing layer, an ink receiving layer, a water-resistant layer, an oil-resistant layer, a water vapor barrier layer, a gas barrier layer, etc., but one layer is preferred from the viewpoint of heat sealability. In the case of two or more layers, cushioning properties may deteriorate. Whether or not a layer is a coating layer can be determined by observing the cross section with a microscope.

[0024] The coating layer contains at least a thermoplastic resin, which provides heat sealability. As the thermoplastic resin, any resin used in the papermaking field for forming a heat seal layer can be used without any particular limitation, and for example, a resin having a glass transition temperature of 100°C or less can be used. The glass transition temperature of the thermoplastic resin is preferably -20°C or more and 85°C or less. The melting point of the thermoplastic resin is preferably 80°C or more and 120°C or less. The glass transition temperature and melting point are measured in accordance with JIS K 7121:2012.

[0025] Examples of the thermoplastic resin include polyolefin resins such as low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), and polypropylene (PP); polyester resins such as polyvinyl acetate (PVAc), PET, and polylactic acid; ethylene methacrylic acid copolymer resin (EMAA), ethylene methyl acrylate copolymer resin (EMA), ethylene acrylic acid copolymer resin (EAA), ethylene vinyl acetate copolymer resin (EVA), and styrene acrylic acid ester copolymer resin; and these may be used alone or in combination of two or more. Among these, ethylene methacrylic acid copolymer resin, ethylene acrylic acid copolymer resin, and polyolefin resin are preferred because of their excellent heat seal strength, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), a type of polyester, is preferred because of its biodegradability. The resin having an acrylic acid or methacrylic acid unit may be an ionomer. In addition to the thermoplastic resin, the coating layer may contain surfactants, waxes, antiblocking agents such as pigments, dispersants, thickeners, dyes, etc., within the range that does not impair the effects of the present invention.

[0026] The coating layer is formed by applying a coating agent containing at least a thermoplastic resin directly onto the paper substrate or via another layer, and then drying the coating agent. The coating method of the coating layer is not particularly limited, and coating can be performed using a known coating device and coating system. For example, the coating device can be a blade coater, a bar coater, an air knife coater, a curtain coater, a spray coater, a roll coater, a reverse roll coater, a size press coater, a gate roll coater, etc. In addition, the coating system can be an aqueous coating using a solvent such as water, a solvent-based coating using a solvent such as an organic solvent, etc., and the aqueous coating is preferable from the viewpoint of safety and low environmental impact.

[0027] The dry coating weight per side of the coating layer is 3g / m 2 The dry coating weight per side is preferably 3 g / m or more. 2 If the dry coating amount is less than 20 g / m, it is difficult to form a coating layer of sufficient thickness on the paper substrate, and sufficient heat seal strength may not be obtained. The higher the dry coating amount per side of the coating layer, the higher the heat seal strength tends to be. However, if it is too high, the energy cost and material cost for drying will increase, so it is recommended to use a dry coating amount of 20 g / m or more. 2 Less than 10 g / m is preferable. 2 The following is more preferable. The coating layer having heat sealability may be one layer or may be composed of two or more layers. When the coating layer is composed of two or more layers, it is preferable that the total coating weight of all the coating layers is within the above range.

[0028] (Soft packaging) The coated paper of the present invention can be made into a flexible packaging material by sealing the heat-sealable coating layers facing each other. The shape of the flexible packaging material is not particularly limited, and can be a vertical pillow packaging bag, a horizontal pillow packaging bag, a side seal bag, a two-sided seal bag, a three-sided seal bag, a four-sided seal bag, a gusset bag, a bottom gusset bag, a stand-up bag, etc. EXAMPLES

[0029] (Evaluation method) ·Basic weight Measured in accordance with JIS P8124:2011. Thickness Measured in accordance with JIS P8118:2014. ·density It is calculated from the basis weight and thickness.

[0030] Cushioning The puncture strength (maximum force, unit: N) and the distance traveled by the needle were measured from the uncoated side of the coated paper using a texture analyzer (IMADA, MODEL: FRTS-100N) in accordance with JIS Z1707:2019 7.5 puncture strength test. The cushioning properties were calculated by dividing the maximum puncture strength by the distance traveled by the needle at the maximum force (puncture strength / needle travel). Figure 1 shows a schematic diagram of the puncture strength test. The measurement was carried out by placing a 4 cm square coated paper horizontally on the table so that its approximate center covered a 5 mm diameter hole on the sample holding table (model number: FR-UP-5), placing a film piercing plate (model number: FR-KP-3) with a 3 mm diameter hole on top of it, tightening the screw attached to the plate while making sure that the hole in the plate, the approximate center of the coated paper, and the hole in the table were vertically aligned, fixing the coated paper between the table and the plate, and setting this in the texture analyzer to carry out the piercing strength test. A piercing pin vice (model number: FR-CP-3) was used as the needle. In this measurement, the position of the needle was fixed, and the position of the sample holding table equipped with the coated paper was movable, and the sample side was raised, and the tip of the needle passed through the hole in the plate, contacted the approximate center of the coated paper, pierced it, and passed through the hole in the table, where it was evaluated for piercing. The measurement conditions were program mode (push speed: 0.8 mm / sec, push displacement: 3,000 mm, return speed: 5.0 mm / sec, push count: 1, graph format: load-displacement, start trigger: 5 digits), and the displacement from the start point of the graph to the point where the maximum load was received was used as the value of the needle movement distance to calculate cushioning properties. Figure 2 shows an example of a load-displacement curve. Measurements were performed with n=5, and the arithmetic mean was used for evaluation.

[0031] ·Oken type smoothness The coated and uncoated sides of the coated paper were measured using a digital Oken type air permeability and smoothness tester (manufactured by Asahi Seiko Co., Ltd.) in accordance with JIS P8155:2010.

[0032] Heat seal strength Two sheets of coated paper with a width of 100 mm were placed together with the heat seal layers facing each other, and the heat seal tester (Tester Sangyo, TP-701-S) was used to measure the heat seal strength at 120°C and 2 kgf / cm 2 , 0.5 seconds, or 100℃, 1kgf / cm 2 The heat sealing was performed under the conditions of 0.5 seconds. The heat-sealed test pieces were left to stand in an environment with a temperature of 23°C ± 1°C and a humidity of 50 ± 2% for at least 12 hours, and then, in accordance with JIS Z1707:2019 7.4 Heat Seal Strength Test, test pieces cut to a width of 15 mm were subjected to a T-peel at a tensile speed of 200 mm / min using a Tensilon universal material testing machine (A&D RTC-1250A), and the maximum load recorded was taken as the heat seal strength. After the test, the peeled portion was visually observed and evaluated according to the following criteria. ◎: Fully broken (the paper base is completely peeled off and broken) ○: One component is broken (parts of the paper base are peeled off and some parts of the paper base are broken) ×: No damage to the material (the coating layer peeled off and the paper base material was not damaged)

[0033] (Preparation of Coated Paper) A thermoplastic resin (Mitsui Chemicals: Chemipearl S500, an ethylene methacrylic acid-based ionomer) and a defoamer (BASF: Foamstar SI2213) were mixed at a solids weight ratio of 99.8 / 0.2 on one side of paper substrates with different basis weights, and water was added and stirred to obtain water-based coating solution A (solids concentration 35%), which was then coated on the substrate using an air knife coating method to a target coating amount of 5.5 g / m. 2 The coated paper was obtained by coating with a coating solution of 1000 ml and drying at 150° C. The smoothness was adjusted by calendaring under the conditions shown in the table. The number of calendaring processes was one in all of the examples and comparative examples.

[0034] <Comparative Example 1> Paper base material: 120g / m 2 The base paper used was Tokai Kraft C120, manufactured by Shin Tokai Paper Co., Ltd. <Comparative Example 2> Paper base material, basis weight 100g / m 2 The base paper used was Tokai Kraft C100, manufactured by Shin Tokai Paper Co., Ltd.

[0035] <Example 1> Paper base material, basis weight 90g / m 2 The base paper used was TFA90, manufactured by Shin Tokai Paper Co., Ltd. <Example 2> Paper base material: 83g / m 2 The base paper used was TKS83, manufactured by Shin Tokai Paper Co., Ltd. <Example 3> Paper base material: 60g / m 2 The base paper used was Tokai Kraft C60, manufactured by Shin Tokai Paper Co., Ltd.

[0036] <Example 4> A filling layer (water-based coating solution A) was applied at 4.0 g / m2 by the bar blade method to one side of the same paper substrate (TKS83, manufactured by Shin Tokai Paper Co., Ltd.) as in Example 2. 2 Then, the surface was coated with 5.0 g / m2 of water-based coating solution A using the bar blade method. 2 and dried at 150°C to obtain a coated paper. <Comparative Example 3> The coated paper obtained in Comparative Example 1 was calendered using a soft nip calender at a linear pressure of 11.9 kgf / cm to obtain a coated paper with improved smoothness. <Example 5> The coated paper obtained in Comparative Example 1 was calendered using a soft nip calender at a linear pressure of 47.6 kgf / cm to obtain a coated paper with improved smoothness.

[0037] <Example 6> The coated paper obtained in Comparative Example 2 was calendered using a soft nip calender at a linear pressure of 11.9 kgf / cm to obtain a coated paper with improved smoothness. <Example 7> The coated paper obtained in Comparative Example 2 was calendered using a soft nip calender at a linear pressure of 23.8 kgf / cm to obtain a coated paper with improved smoothness. <Example 8> The coated paper obtained in Comparative Example 2 was calendered using a soft nip calender at a linear pressure of 35.7 kgf / cm to obtain a coated paper with improved smoothness.

[0038] <Example 9> The coated paper obtained in Example 1 was calendered using a soft nip calender at a linear pressure of 11.9 kgf / cm to obtain a coated paper with improved smoothness. <Example 10> The coated paper obtained in Example 1 was calendered using a soft nip calender at a linear pressure of 23.8 kgf / cm to obtain a coated paper with improved smoothness. <Example 11> The coated paper obtained in Example 1 was calendered using a soft nip calender at a linear pressure of 35.7 kgf / cm to obtain a coated paper with improved smoothness. Example 12 The coated paper obtained in Example 1 was calendered using a soft nip calender at a linear pressure of 47.6 kgf / cm to obtain a coated paper with improved smoothness.

[0039] <Example 13> The coated paper obtained in Example 2 was calendered using a soft nip calender at a linear pressure of 11.9 kgf / cm to obtain a coated paper with improved smoothness. <Example 14> The coated paper obtained in Example 2 was calendered using a soft nip calender at a linear pressure of 23.8 kgf / cm to obtain a coated paper with improved smoothness. <Example 15> The coated paper obtained in Example 2 was calendered using a soft nip calender at a linear pressure of 59.5 kgf / cm to obtain a coated paper with improved smoothness.

[0040] <Example 16> The coated paper obtained in Example 3 was calendered using a soft nip calender at a linear pressure of 11.9 kgf / cm to obtain a coated paper with improved smoothness. <Example 17> The coated paper obtained in Example 3 was calendered using a soft nip calender at a linear pressure of 23.8 kgf / cm to give a coated paper with improved smoothness. <Example 18> The coated paper obtained in Example 3 was calendered using a soft nip calender at a linear pressure of 59.5 kgf / cm to obtain a coated paper with improved smoothness.

[0041] The results are shown in Tables 1 and 2. Figure 3 shows the relationship between the cushioning property (C) and the Oken smoothness (S) of the coating layer surface for each coated paper grouped according to the evaluation results (◎, ○, ×) of the heat seal strength at 100°C.

[0042] [Table 1]

[0043] [Table 2]

[0044] ·result All of the coated papers obtained in the Examples and Comparative Examples showed good heat seal strength at a heat seal temperature of 120°C. Coated papers obtained in the examples having a cushioning value (C) of 21.5 or less and an Oken smoothness value (S) of 15 or more had excellent heat seal strength even at a heat seal temperature of 100° C. Furthermore, coated papers with S≧23 and S≧6C-70 broke all over when heat sealed at 100° C.

Claims

1. A coated paper having a paper base material and a coating layer having heat sealability on at least one outermost surface, the coating layer contains one or more thermoplastic resins selected from the group consisting of ethylene methacrylic acid copolymers, ethylene acrylic acid copolymers, and ionomers thereof; The weight of the paper base material mentioned above is 58.9g / m ２ Above 94.9g / m ２ the following The thickness of the coated paper is 85 μm or more and 131 μm or less. The density of the coated paper is 0.68 g / cm ３ 0.79g / cm or more ３ below The cushioning property (C) of the coated paper is 12.4 N / mm or more and 18.0 N / mm or less. The Oken smoothness (S) of the coating layer surface is 24 seconds or more and 89 seconds or less. A coated paper characterized by:

2. 2. The coated paper according to claim 1, characterized in that the peeled portion breaks entirely after a heat seal strength test carried out under the following conditions: (Heat seal strength measurement) Two sheets of coated paper were placed together with the coating layers facing each other and then heated at 100°C and 1 kgf / cm ２ (0.1 MPa) for 0.5 seconds, and then allowed to stand for 12 hours or more in an environment of a temperature of 23°C ± 1°C and a humidity of 50 ± 2%. Then, in accordance with JIS Z1707, the test piece cut to a width of 15 mm is subjected to T-peel at a tensile speed of 200 mm / min.

3. 2. The coated paper of claim 1, wherein the coating layer does not contain a lubricant.

4. A flexible packaging material comprising the coated paper according to any one of claims 1 to 3.

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