JP7355469B1 - Flexible packaging paper and flexible packaging - Google Patents

Abstract

An object of the present invention is to provide a flexible packaging paper that can be made into bags using a bag making machine, and a flexible packaging using this flexible packaging paper. As a solution, the paper base material has a heat seal layer on at least one outermost surface, the paper base material has a thickness of 25 μm or more and 100 μm or less, and the paper base material has a thickness of 25 μm or more and 100 μm or less, and Provided is a flexible packaging paper having a proportion of more than 90% by weight and satisfying any one or more of the following conditions (1) to (4). (1) The bending hysteresis 2HB in the MD direction by the KES method is 0.02 g·cm/cm or more and 1.2 g·cm/cm or less (2) The bending rigidity B in the MD direction by the KES method is 0.16 g·cm2/ cm or more and 1.8 g/cm2/cm or less (3) The other surface of the paper base material is exposed, and the smoothness of the exposed surface (Oken style) is 50 seconds or more and 700 seconds or less (4) Young's modulus in MD direction is 3 GPa or more and 15 GPa or less

Description

The present invention relates to a flexible packaging paper and a flexible packaging using the same.

In recent years, there has been a growing trend to move away from oil and plastics due to environmental issues such as plastic waste and global warming, and the use of resin materials derived from fossil resources and non-biodegradable resin materials in industrial products is increasing. It is desired to reduce the amount as much as possible.
In such a trend, it is desired to reduce the environmental impact of packaging as well. For example, it is possible to reduce the thickness of the packaging material using plastic film, but such thin packaging materials are less easy to handle during the packaging forming process, and are more likely to be damaged at the thermocompression bonding part. This makes it more likely that cracks and tears will occur. Furthermore, although the amount of resin used has decreased, the problem that resin remains semi-permanently without being decomposed when released into the environment remains the same.

Patent Documents 1 and 2 propose the use of heat-seal paper in which a heat-seal layer is laminated on a paper base material as a packaging material. Depending on the type of heat-sealable resin, these are decomposed in the environment, so the environmental load can be significantly reduced. However, heat-seal paper has significantly different physical properties compared to plastic film, so if heat-seal paper is passed through a bag-making machine under the same operating conditions as plastic film, the paper may meander, break, or become unusable. In some cases, problems such as bending or wrinkles occur in the soft packaging, or the inability to form bags in the desired shape, necessitate optimizing operating conditions such as slowing down the line speed.

Japanese Patent Application Publication No. 2020-163675 JP2021-046234A

An object of the present invention is to provide a flexible packaging paper that can be made into bags using a bag-making machine, and a flexible packaging using this flexible packaging paper.

Means for solving the problems of the present invention are as follows.
1. having a paper base material and a heat sealing layer on at least one outermost surface,
The paper base material has a thickness of 25 μm or more and 100 μm or less,
The ratio of pulp to the total papermaking fibers contained in the paper base exceeds 90% by weight,
A flexible packaging paper characterized by satisfying any one or more of the following conditions (1) to (4).
(1) The bending hysteresis 2HB in the MD direction by the KES method is 0.02 g·cm/cm or more and 1.2 g·cm/cm or less (2) The bending rigidity B in the MD direction by the KES method is 0.16 g·cm ² /cm or more and 1.8g・cm ² /cm or less (3) The other surface of the paper base material is exposed, and the smoothness of the exposed surface (Oken type) is 50 seconds or more and 700 seconds or less ( 4) Young's modulus in the MD direction is 3 GPa or more and 15 GPa or less.
2. 1. The paper base material has a basis weight of 20 g/m ² or more and 70 g/m ² or less. Flexible packaging paper described in .
3. 1. The paper base material has a density of 0.5 g/cm ³ or more and 0.95 g/cm ³ or less. or 2. Flexible packaging paper described in .
4. The item to be packaged is 1. ~3. A flexible packaging body characterized by being enclosed in a packaging material made of the flexible packaging paper according to any one of the above.

The flexible packaging paper of the present invention can be used as a substitute for conventional packaging materials made of resin films. The flexible packaging paper of the present invention can be passed through a bag making machine under the same operating conditions as conventional plastic films to produce flexible packaging. Since there is no need to change operating conditions, it is easy to switch between the resin film and the flexible packaging paper of the present invention to produce flexible packaging made of different materials.
Since the flexible packaging paper of the present invention is mainly made of paper, the amount of resin material used can be significantly reduced.

"Flexible packaging paper"
The flexible packaging paper of the present invention has a paper base material and a heat seal layer on at least one outermost surface.

-Paper base material The paper base material is a base material on which a heat seal layer is formed on at least one surface. The paper base material is a sheet mainly made of pulp, and the base paper obtained by making paper from paper stock containing pulp, fillers, various auxiliary agents, etc. is used as it is, or on at least one side of the base paper, a sealing layer and ink are applied. One or more functional layers such as a receptor layer, a water-resistant layer, an oil-resistant layer, a water vapor barrier layer, a gas barrier layer, etc. can be used.

Pulps include chemical pulps such as hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), softwood unbleached pulp (NUKP), sulfite pulp, stone grind pulp, and thermoplastic pulp. Mechanical pulp such as mechanical pulp, wood fibers such as deinked pulp and waste paper pulp, non-wood fibers obtained from kenaf, bamboo, hemp, etc. can be used, and two or more types can also be used in combination. Among these, it is difficult to cause foreign matter to be mixed in, it is difficult to discolor over time when recycled by using it as a waste paper material after use, and it has a high degree of whiteness, so it has a good surface feel when printing. For this reason, it is preferable to use chemical pulp or mechanical pulp, and it is more preferable to use chemical pulp made of wood fibers. Specifically, the amount of chemical pulp of wood fibers such as LBKP and NBKP relative to the total pulp is preferably 80% by weight or more, more preferably 90% by weight or more, and even more preferably 95% by weight or more. , more preferably 98% by weight or more, and even more preferably 100% by weight. Furthermore, the blending ratio of hardwood pulp in the pulp is preferably 30% by weight or more, more preferably 50% by weight or more.
The freeness of the pulp (Canadian standard freeness: CSF) is preferably 600 ml or less, more preferably 550 ml or less, and 500 ml or less from the viewpoint of the strength of the paper base material. More preferred.

Although the paper base material of the present invention can contain paper-making fibers other than pulp, the ratio of pulp to the total paper-making fibers contained in the paper base material exceeds 90% by weight. Examples of fibers other than pulp include thermoplastic resin fibers. Since thermoplastic resin fibers have heat-sealing properties, a paper base material containing thermoplastic resin fibers has excellent heat-sealing strength because the paper base material and the heat-sealing layer are firmly adhered to each other during heat-sealing. As thermoplastic resin fibers, those used in the paper manufacturing field can be used without particular limitation, but examples include PVA, polylactic acid, polybutylene succinate adipate, polybutylene succinate, polycaprolactone, poly(3 It is preferable to use a biodegradable material such as -hydroxybutyrate-co-3-hydroxyhexanoate (PHBH). However, thermoplastic resin fibers are softer and less stiff than pulp, so the proportion of thermoplastic resin fibers in the total papermaking fibers included in the paper base material is less than 10% by weight, and 9% by weight or less. It is preferably 5% by weight or less, more preferably 1% by weight or less, and even more preferably 1% by weight or less. Further, the ratio of pulp to the total papermaking fibers contained in the paper base material is preferably 91% by weight or more, more preferably 95% by weight or more, and even more preferably 99% by weight or more. Note that the thermoplastic resin fiber is not an essential material and may not be used.

Fillers include 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. , inorganic fillers such as calcium hydroxide, magnesium hydroxide, zinc hydroxide, barium sulfate, calcium sulfate, etc., organic fillers such as urea-formalin resin, polystyrene resin, phenolic resin, micro hollow particles, and other fillers known for paper manufacturing. can be used. Note that the filler is not an essential material and may not be used.

Various auxiliary agents include rosin, alkyl ketene dimer (AKD), sizing agents such as alkenyl succinic anhydride (ASA), polyacrylamide polymers, polyvinyl alcohol polymers, cationized starches, various modified starches, urea, etc. Formalin resin, dry paper strength enhancer such as melamine/formalin resin, wet paper strength enhancer, retention agent, freeness improver, coagulant, sulfuric acid, bulking agent, dye, optical brightener, pH adjuster, Examples include antifoaming agents, ultraviolet inhibitors, antifading agents, pitch control agents, slime control agents, etc., and can be appropriately selected and used as required.

The paper base material used in the present invention has a thickness of 25 μm or more and 100 μm or less. The thickness of the paper base material is measured in accordance with JIS P8118:2014.
Since the paper base material has a thickness of 25 μm or more and 100 μm or less, it can be easily passed through a bag making machine that uses a conventional plastic film. The thickness of the paper base material is preferably 30 μm or more, more preferably 35 μm or more, even more preferably 40 μm or more, and preferably 90 μm or less, and 80 μm or less. More preferably, it is 70 μm or less.

The paper base material of the present invention preferably has a basis weight of 20 g/m ² or more and 70 g/m ² or less from the viewpoint of flexibility and strength. The basis weight of the paper base material is more preferably 22 g/m ² or more, even more preferably 24 g/m ² or more, even more preferably 28 g/m ² or more, and even more preferably 65 g/m 2 or more. It is more preferably ² or less, even more preferably 60 g/m ² or less, even more preferably 55 g/m ² or less. The basis weight of the paper base material is measured in accordance with JIS P8124:2011.

The paper base material of the present invention preferably has a density of 0.5 g/cm ³ or more and 0.95 g/cm ³ or less from the viewpoint of flexibility and strength. The density of the paper base material is more preferably 0.55 g/cm ³ or more, more preferably 0.9 g/cm ³ or less, even more preferably 0.85 g/cm ³ or less. , more preferably 0.75 g/cm ³ or less. The density of the paper base material is calculated from the thickness and basis weight.

The paper base material of the present invention satisfies any one or more of the following conditions (1) to (4).
(1) The bending hysteresis 2HB in the MD direction by the KES method is 0.02 g·cm/cm or more and 1.2 g·cm/cm or less (2) The bending rigidity B in the MD direction by the KES method is 0.16 g·cm ² /cm or more and 1.8g・cm ² /cm or less (3) The other surface of the paper base material is exposed, and the smoothness of the exposed surface (Oken method) is 50 seconds or more and 700 seconds or less (4 ) Young's modulus in the MD direction is 3 GPa or more and 15 GPa or less.
The paper base material of the present invention preferably satisfies two or more of these conditions (1) to (4), more preferably satisfies three or more, and most preferably satisfies all four.

The KES method is an abbreviation for Kawabata Evaluation System, and is one of the methods for measuring the physical properties of flexible materials such as nonwoven fabrics and fabrics, and can objectively evaluate tensile properties, bending properties, and shear properties. The bending stiffness B and bending hysteresis 2HB by the KES method can be measured, for example, using an automated pure bending tester KES-FB2-S manufactured by Kato Tech Co., Ltd. The bending stiffness B and the bending hysteresis 2HB, which are bending characteristics, can be calculated from the relationship between the bending moment (M) and the curvature (K) during bending deformation. The bending stiffness B is calculated from the increase in the bending moment (M) with respect to the increase in the curvature (K), that is, the slope of the MK curve. The bending hysteresis 2HB represents the difference in bending moment when bending and returning, and is calculated from the difference in reciprocation of the MK curve.

When (1) is satisfied The paper base material that satisfies (1) has a bending hysteresis 2HB in the MD direction by the KES method of 0.02 g·cm/cm or more and 1.2 g·cm/cm or less.

The smaller the value of hysteresis 2HB, the easier it is to return to the original state after bending. If this hysteresis 2HB is less than 0.02 g cm/cm, bending, crease processing, folding, etc. will become difficult, and a force will be generated to return the bag to its original shape (flat plate shape or roll shape) after making the bag. In some cases, the soft packaging may become warped or rounded, resulting in poor cosmetic appearance and shape retention. On the other hand, if this hysteresis 2HB exceeds 1.2 g/cm/cm, it will be difficult to return to the original shape after bending, so especially the parts that come into contact with the former of the bag making machine and are subjected to loads during bending and folding. may become more prone to wrinkles, and may also be more likely to tear. This hysteresis 2HB is preferably 0.025 g·cm/cm or more, more preferably 0.03 g·cm/cm or more, even more preferably 0.04 g·cm/cm or more, and 0.03 g·cm/cm or more. More preferably, it is .05 g·cm/cm or more, more preferably 1.1 g·cm/cm or less, even more preferably 1.05 g·cm/cm, and even more preferably 1.0 g·cm/cm. - It is even more preferable that it is below cm/cm, it is even more preferable that it is below 0.9 g·cm/cm, it is even more preferable that it is below 0.8 g·cm/cm, and it is even more preferable that it is below 0.7 g·cm It is even more preferable that it be less than /cm.

In addition, paper base materials that satisfy any one or more of (2) to (4) must have a bending hysteresis 2HB in the MD direction of 0.02 g·cm/cm or more and 1.2 g·cm/cm or less according to this KES method. It is preferable that This hysteresis 2HB is more preferably 0.025 g·cm/cm or more, even more preferably 0.03 g·cm/cm or more, even more preferably 0.04 g·cm/cm or more. , more preferably 0.05 g·cm/cm or more, more preferably 1.1 g·cm/cm or less, even more preferably 1.05 g·cm/cm or less, 1 It is even more preferable that it is .0 g·cm/cm or less, even more preferably that it is 0.9 g·cm/cm or less, even more preferably that it is 0.8 g·cm/cm or less, and even more preferably that it is 0.7 g·cm/cm or less. - It is even more preferable that it is below cm/cm.

When (2) is satisfied The paper base material that satisfies (2) has a bending rigidity B in the MD direction of 0.16 g·cm ² /cm or more and 1.8 g·cm ² /cm or less by the KES method.

The smaller the value of bending stiffness B, the softer it is. If this bending rigidity B is less than 0.16 g cm ² /cm, the flexible packaging paper will be too soft and will lose its tension when made into a flexible packaging, making it difficult to maintain the specified packaging form. . On the other hand, if the bending rigidity B exceeds 1.8 g·cm ² /cm, it becomes difficult to bend during bag making, and the lateral dimension in particular may deviate from the designed dimension. This bending rigidity B is preferably 0.2 g·cm ² /cm or more, more preferably 0.3 g·cm ² /cm or more, and preferably 0.4 g·cm ² /cm or more. More preferably, it is 1.7 g·cm ² /cm or less, more preferably 1.5 g·cm ² /cm or less, and even more preferably 1.2 g·cm ² /cm or less. It is preferably 1.0 g·cm ² /cm or less, even more preferably 0.8 g·cm ² /cm or less.

In addition, paper base materials that satisfy any one or more of (1), (3), and (4) have a bending rigidity B in the MD direction of 0.16 g·cm ² /cm or more and 1.8 g·cm by this KES method. It is preferable that it is below cm ² /cm. This bending rigidity B is more preferably 0.2 g·cm ² /cm or more, even more preferably 0.3 g·cm ² /cm or more, and 0.4 g·cm ² /cm or more. is even more preferable, more preferably 1.7 g·cm ² /cm or less, even more preferably 1.5 g·cm ² /cm or less, and even more preferably 1.2 g·cm ² /cm or less. Even more preferably, it is 1.0 g·cm ² /cm or less, even more preferably 0.8 g·cm ² /cm or less.

If (3) is satisfied, the paper base material that satisfies (3) has a smoothness (Ouken style) of the exposed surface of the paper base material of 50 seconds or more and 700 seconds or less when used as flexible packaging paper. It is.

The flexible packaging paper of the present invention is wound into a roll, unwound from the roll, passed through a bag-making machine, conveyed while coming into contact with various members such as rollers, formers, and bag-making boards, and undergoes a creasing process. After going through a folding process, a heat-sealing process, a cutting process, etc., it becomes a soft package. At this time, if the smoothness (Oken style) of the exposed surface of the paper base material is between 50 seconds and 700 seconds, the friction and slipperiness between the paper base material and the bag making machine will be good, resulting in production failure. can be reduced. If this smoothness (Ouken type) is less than 50 seconds, the friction will be large and a large load will be placed on the flexible packaging paper during paper passing, making the paper base material easy to tear. On the other hand, if this smoothness (Ouken type) exceeds 700 seconds, the soft packaging paper will slip easily due to low friction, and the flexible packaging paper will tend to meander when passing through the bag making machine, causing the heat seal part to slip. Misalignment is likely to occur at the cutting part. The smoothness of the exposed surface of the paper base material (Oken type) is preferably 70 seconds or more, more preferably 100 seconds or more, and preferably 650 seconds or less, and 600 seconds or more. It is more preferably at most seconds, even more preferably at most 500 seconds, even more preferably at most 450 seconds.
In addition, since the heat seal layer etc. are laminated|stacked on the surface (back surface) on which the heat seal layer of a paper base material is formed, the value of smoothness (Ouken type) is not specifically limited. However, since the adhesion with the laminated layers improves, the smoothness (Oken method) of the surface (back surface) on the heat seal layer side of the paper base material is It is preferable that the smoothness (the surface is rough) is smaller than the smoothness (Oken type) of , and specifically, it is preferable that the value of the smoothness (Oken type) is smaller by 30 seconds or more.

In addition, for paper base materials that satisfy any one or more of (1), (2), and (4), if the paper base material is exposed, the exposed surface (surface) of the paper base material must be It is preferable that the smoothness (Oken type) is 50 seconds or more and 700 seconds or less. This smoothness (Ouken style) is more preferably 70 seconds or more, even more preferably 100 seconds or more, more preferably 650 seconds or less, and even more preferably 600 seconds or less. The time is preferably 500 seconds or less, even more preferably 450 seconds or less.
In addition, since the heat seal layer etc. are laminated|stacked on the surface (back surface) on which the heat seal layer of a paper base material is formed, the value of smoothness (Ouken type) is not specifically limited. However, since the adhesion with the laminated layers improves, the smoothness (Oken method) of the surface (back surface) on the heat seal layer side of the paper base material is It is preferable that the smoothness (the surface is rough) is smaller than the smoothness (Oken type) of , and specifically, it is preferable that the value of the smoothness (Oken type) is smaller by 30 seconds or more.

When (4) is satisfied The paper base material that satisfies (4) has a Young's modulus in the MD direction of 3 GPa or more and 15 GPa or less.
Young's modulus is the ratio of the force (stress) acting per unit cross-sectional area of the sample to the deformation rate (strain) when an external force is applied in a uniaxial direction within the elastic range of the object, and it is the initial slope of the stress-strain curve. It is. Young's modulus is a value representing the difficulty of deformation of a material, and the larger the Young's modulus is, the more difficult it is to deform. The Young's modulus of the paper base material in the MD direction is measured in accordance with JIS P8113:2006, Part 2 Constant Speed Stretching Method.

If the Young's modulus is less than 3 GPa, the paper base material is easily deformed, and the paper base material is stretched due to the tension during manufacturing, so it shrinks and shifts in the vertical dimension after the bag is made. , and wrinkles are more likely to occur. On the other hand, if the Young's modulus exceeds 15 GPa, the tension cannot be increased during manufacturing, which tends to cause conveyance defects in which the flexible packaging paper cannot be conveyed as specified, and deviations in cutting intervals are likely to occur. The Young's modulus is preferably 4 GPa or more, more preferably 5 GPa or more, and also preferably 12 GPa or less, and more preferably 10 GPa or less.

Further, it is preferable that the paper base material satisfying any one or more of (1) to (3) has a Young's modulus in the MD direction of 3 GPa or more and 15 GPa or less. This Young's modulus is more preferably 4 GPa or more, even more preferably 5 GPa or more, more preferably 9 GPa or less, and even more preferably 8 GPa or less.

The paper base material of the present invention preferably has a puncture strength of 1.0N or more. When the puncture strength of the paper base material is 1.0 N or more, the soft packaging can be made difficult to tear when a protrusion or the like comes into contact with it. The puncture strength of the paper base material is more preferably 1.1N or more, and even more preferably 1.2N or more. The puncture strength of the paper base material is measured in accordance with JIS Z1707:2019 7.5 puncture strength test.

The base paper manufacturing (paper making) method is not particularly limited, and twin paper machines such as Fourdrinier paper machine, cylinder paper machine, short wire paper machine, gap former type, hybrid former type (on-top former type), etc. Known manufacturing (paper making) methods and paper machines such as a wire paper machine can be selected. In addition, the pH during papermaking may be any of the acidic region (acidic papermaking), pseudo-neutral region (pseudo-neutral papermaking), neutral region (neutral papermaking), and alkaline region (alkaline papermaking). Afterwards, an alkaline chemical may be applied to the surface of the paper layer. Further, the base paper may have one layer or may be composed of two or more layers.

Furthermore, it is possible to treat the surface of the base paper with various chemicals. Examples of the agents used include oxidized starch, hydroxyethyl etherified starch, enzyme-modified starch, polyacrylamide, polyvinyl alcohol, surface sizing agents, water resistance agents, water retention agents, thickeners, lubricants, etc. These can be used alone or in combination of two or more. Furthermore, these various drugs and pigments may be used in combination. Pigments include 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, colloidal silica, and satin. Inorganic pigments such as white and organic pigments such as solid type, hollow type, or core shell type can be used alone or in combination of two or more types.
The method of surface treatment of the base paper is not particularly limited, but known coating equipment such as a rod metering size press, pound type size press, gate roll coater, spray coater, blade coater, curtain coater, etc. can be used. .

Furthermore, one or more functional layers such as a filler layer, an ink-receiving layer, a water-resistant layer, an oil-resistant layer, a water vapor barrier layer, and a gas barrier layer can be formed on at least one surface of the base paper. The functional layer may be either a coating layer or a laminate layer, but a coating layer is preferred from the viewpoint of maintaining the flexibility of the paper base material.

- Heat-sealing layer The heat-sealing layer is a layer that imparts heat-sealing properties, and specifically, it is a layer that can be bonded to an object to be bonded by applying heat and pressure. Since the flexible packaging paper of the present invention has heat sealability, it is easy to mold it into a flexible packaging material, maintain the shape after molding, and ensure sealing performance.

The heat-sealing layer is provided on the outermost surface of at least one of the flexible packaging paper sheets. The heat seal layer may be either a coating layer or a laminate layer.
The thermoplastic resin contained in the heat seal layer is not particularly limited, and may include ethylene-vinyl acetate resin, styrene-acrylic ester copolymer resin, acrylic resin, ethylene-acrylic resin, polyolefin resin (polyethylene, polypropylene, etc.) , thermoplastic resins used for heat sealing such as polyester resins (polyethylene terephthalate, polyethylene succinate, polybutylene terephthalate, polyethylene naphthalate, etc.), polyvinyl alcohol resins, polyvinyl acetate resins, polylactic acid resins, etc. It can be used without any restrictions. Among these, ethylene-vinyl acetate resins, styrene-acrylic acid ester copolymer resins, acrylic resins, and ethylene-acrylic resins are preferred from the viewpoint of heat seal strength. Furthermore, biodegradable resins such as polyvinyl alcohol, polylactic acid, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) are preferred from the standpoint of reducing the environmental burden if they are discharged as trash.
The heat-sealing layer can contain additives such as an anti-blocking agent and a silane coupling agent. As the anti-blocking agent, pigments, waxes, metal soaps, etc. can be used without particular limitations. However, in the flexible packaging paper of the present invention, from the viewpoint of cost, it is preferable that the heat seal layer does not contain any additives.

When the heat seal layer is a coating layer, the dry weight of the heat seal layer is preferably 3 g/m ² or more and 20 g/m ² or less per side. If the dry weight is less than 3 g/m ² , heat sealability may be reduced. Moreover, even if the dry weight exceeds 20 g/m ² , the heat sealability is hardly improved and the cost increases. The heat-sealing layer may be one layer or may be composed of two or more layers. By configuring the heat-sealing layer as a multilayer of two or more layers, defects such as coating unevenness can be reduced compared to the case of a single layer. When the heat-sealing layer is composed of two or more layers, it is preferable that the total dry weight of all the heat-sealing layers is within the above range, and the dry weight coating amount per layer is 2 g/m It is preferable that it is ² or more.
When the heat seal layer is a laminate layer, the thickness of the heat seal layer is preferably 20 μm or more and 100 μm or less. If the thickness is less than 20 μm, heat sealability may not be ensured. Moreover, if the thickness exceeds 100 μm, it is not preferable from the viewpoint of cost.

When the heat seal layer is a coating layer, the coating method is not particularly limited, and coating can be performed using a known coating device and coating system. For example, examples of the coating device include 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, and the like.
The coating system may be either a water-based coating using a solvent such as water or a solvent-based coating using a solvent such as an organic solvent, but water-based coating is preferred from the viewpoint of safety and hygiene. In the case of aqueous coating, a water-dispersible resin or a water-soluble resin is used as the thermoplastic resin, and therefore the heat-sealing layer is preferably a coating layer of a water-dispersible resin or a water-soluble resin.
When the heat-sealing layer is a laminate layer, the formation method thereof is not particularly limited, and for example, various methods such as extrusion lamination, wet lamination, dry lamination, etc. can be appropriately used to laminate.

"Soft packaging"
In the flexible packaging of the present invention, an object to be packaged is enclosed in a packaging material made of the above-mentioned flexible packaging paper of the present invention.
The shape of the soft packaging is not particularly limited, and may be vertical pillow packaging bags, horizontal pillow packaging bags, side seal bags, two side seal bags, three side seal bags, four side seal bags, gusset bags, bottom gusset bags, stand bags, etc. be able to. Since the packaging material of the soft packaging body of the present invention is mainly paper, it is easier to tear compared to those using conventional resin packaging materials, and can be easily torn from anywhere.
Furthermore, the flexible packaging paper of the present invention can be fed into packaging machines that use conventional resin films in place of resin films without changing the manufacturing conditions. The soft packaging of the present invention can be manufactured using conventional manufacturing machinery as is, so new equipment is not required.

Test 1: If (1) is satisfied "Example 1-1"
As pulp raw materials, 50 parts by weight of softwood bleached kraft pulp (NBKP, CSF: 500 ml) and 50 parts by weight of hardwood bleached kraft pulp (LBKP, CSF: 350 ml) were used. To 100 parts by weight of this mixed pulp, 0.9 parts by weight (based on pulp dry weight) of polyamine epichlorohydrin resin (WS4010, wet paper strength enhancer made by Seiko PMC) activated with caustic soda, polyacrylamide (dry weight) A paper stock containing 0.3 parts by weight of a paper strength enhancer), aluminum sulfate, and a sizing agent was prepared. A wet paper was made from this paper stock using a paper machine, and the wet paper was dried using a Yankee dryer to obtain a paper base material (base paper). The smoothness (Ouken method) of the obtained paper base material was 299 seconds on the front surface and 10 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Example 1-2"
A paper base material (base paper) was obtained using 50 parts by weight of softwood bleached kraft pulp (NBKP, CSF: 460 ml) and 50 parts by weight of hardwood bleached kraft pulp (LBKP, CSF: 300 ml) as pulp raw materials. The rest is the same as in Example 1-1. The smoothness (Oken method) of the obtained paper base material was 197 seconds on the front surface and 9 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Example 1-3"
As pulp raw materials, 80 parts by weight of bleached hardwood kraft pulp (LBKP, CSF: 500 ml) and 20 parts by weight of bleached softwood kraft pulp (NBKP, CSF 530 ml) were used. To 100 parts by weight of this mixed pulp, 0.1 part by weight of polyacrylamide (PAM) with a molecular weight of 2.5 million as a dry paper strength enhancer (based on the dry weight of the pulp) and 0.1 part by weight of alkyl ketene dimer (AKD) as a sizing agent. Paper containing 35 parts by weight, 0.15 parts by weight of polyamide epichlorohydrin (PAEH) resin as a wet paper strength enhancer, and 0.08 parts by weight of polyacrylamide (PAM) with a molecular weight of 10 million as a retention agent. prepared the fees. A wet paper was made from this paper stock using a paper machine, and the wet paper was dried using a Yankee dryer to obtain a paper base material (base paper). The smoothness (Ouken method) of the obtained paper base material was 141 seconds on the front surface and 8 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Example 1-4"
The procedure was the same as in Example 1-3, except that a paper base material (base paper) having a basis weight of about 50 g/m ² was obtained. The smoothness (Ouken method) of the obtained paper base material was 83 seconds on the front surface and 10 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Example 1-5"
Sodium polyacrylate was added as a dispersant to engineered kaolin (manufactured by Imerys, Varisurf HX, average particle size 9.0 μm, aspect ratio 80-100) (0.2% to pigment), and dispersed with a Serie mixer. A kaolin slurry with a solid content concentration of 55% was prepared. In the obtained kaolin slurry, 200 parts (solid content) of styrene-butadiene latex (manufactured by Nippon Zeon Co., Ltd., PNT7868) as a water vapor barrier resin was blended to 100 parts (solid content) of the pigment. A coating liquid for a water vapor barrier layer having a concentration of 50% was obtained.
A polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA117) aqueous solution was prepared to have a solid content concentration of 10% to obtain a coating liquid for a gas barrier layer.

On the back side of the base paper obtained in Example 1-4, a coating liquid for a water vapor barrier layer was coated on one side using a blade coater so that the dry weight coating amount was 12 g/m ² and dried at 105 ° C. for 2 minutes. After that, a gas barrier layer coating solution was coated on one side using a roll coater so that the coating amount was 3.0 g/m ² in terms of dry weight, and dried at 105°C for 2 minutes to form a paper base with a functional layer. I got the material. The smoothness (Ouken method) of the obtained paper base material was 83 seconds on the front surface and 34 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the functional layer of this paper base material by extrusion lamination to obtain a flexible packaging paper.

“Comparative Example 1-1”
As a pulp raw material, a mixed pulp using 60 parts by weight of softwood bleached kraft pulp (NBKP, CSF: 40ml) and 40 parts by weight of hardwood bleached kraft pulp (LBKP, CSF: 40ml) was used as a raw material, and the pulp was made to a basis weight of 30% using a Fourdrinier paper machine. A base paper of .0 g/m ² was made into paper, and an on-machine 2-roll size press was used to form a paper using modified PVA (RS4104 (Kuraray), content 1.0 g/m ² ) and wet paper strength agent (WS-4020 (Starlight)). PMC) in a content of 0.05 g/m ² ) and dried with a dryer to obtain a base paper with a moisture content of 8.0%. Thereafter, water was added to this base paper to form a wet paper with a moisture content of 15.0%, and supercalender treatment was performed at a temperature of 130° C. and a linear pressure of 250 kg/cm to obtain a paper base material. The smoothness (Oken method) of the obtained paper base material was 1234 seconds on the front surface and 1085 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Comparative Example 1-2"
As a pulp raw material, 100 parts by weight of softwood unbleached kraft pulp (NBKP, CSF 530 ml) was used. To 100 parts by weight of this pulp, 0.1 parts by weight of polyacrylamide (PAM) with a molecular weight of 2.5 million as a dry paper strength enhancer (based on the dry weight of the pulp) and 0.35 parts by weight of alkyl ketene dimer (AKD) as a sizing agent. Paper stock containing 0.15 parts by weight of polyamide epichlorohydrin (PAEH) resin as a wet paper strength enhancer and 0.08 parts by weight of polyacrylamide (PAM) with a molecular weight of 10 million as a retention agent. prepared. Wet paper was made from this paper stock using a paper machine and dried to obtain a paper base material (base paper). The smoothness (Oken method) of the obtained paper base material was 15 seconds on the front surface and 12 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

The obtained paper base material or flexible packaging paper was evaluated as follows. The results are shown in Table 1.
・B, 2HB by KES method
The measurement was performed using an automated pure bending tester KES-FB2-S manufactured by Totec Co., Ltd. under the conditions of a test piece of 100 mm x 100 mm, a bending speed of 0.5 cm ^-1 /sec, and a maximum curvature of 2.5 cm ^-1 .
Measure the M-K curves at two locations with a curvature of 0.5 to 1.5 (front bending) and -0.5 to -1.5 (back bending), and calculate the average value as the bending rigidity B in the MD direction. And so.
The difference in bending moment during reciprocating was measured at two locations with a curvature of 1.0 (front bending) and a curvature of -1.0 (back bending), and the average value was taken as the bending hysteresis 2HB.
- Puncture strength Measured from the paper base side of flexible packaging paper using an IMADA texture analyzer in accordance with JIS Z1707:2019 7.5 puncture strength test.
・Smoothness (Ouken style)
The surface opposite to the surface on which the heat-sealing layer is provided (front surface) and the surface on which the heat-sealing layer is provided (back surface) of the paper base material were subjected to a digital Oken air permeability and smoothness test in accordance with JIS P8155. It was measured using a machine (manufactured by Asahi Seiko Co., Ltd.).
-Young's modulus Measured using an L&W tensile tester in accordance with JIS P8113:2006, Part 2 Constant Speed Extension Method.

- Bag-making property The obtained soft packaging paper was cut into a width of 250 mm and wound into a roll. Using a horizontal pillow packaging machine (Omori Kikai Kogyo Co., Ltd., S-5000X BX) and a product dummy (width 75 mm x length 75 mm x height 28 mm (weight 45 g)), the width of the bag making machine's frontage is 80 to 85 mm x height. 1,000 horizontal pillow bags were prepared under the conditions of a width of 35 mm, a cut pitch of 150 mm, and a rotation speed of 60 cpm, and evaluated according to the following criteria. Further, the center seal temperature was 140°C, and the top seal temperature was 110°C. In addition, production of products whose flexible packaging paper broke was discontinued at that point.

・Longitudinal dimensional stability (N=30)
1: All vertical dimensions are less than ±3% from the design.
2: All vertical dimensions are less than ±5% from the design.
3: One or more items whose vertical dimension deviated by 5% or more from the design.
・Lateral dimensional stability (N=30)
1: All frontage dimensions are less than ±10% from the design.
2: All frontage dimensions are less than ±25% from the design.
3: There is one or more items whose frontage dimensions deviate by 25% or more from the design.

・Cosmetic (N=100)
1: The shape as a horizontal pillow bag is maintained.
2: Slight warping or rounding occurred, but this did not pose any problem in terms of appearance (OK for practical use).
3: There are cases where large warps and rounding occur, and the shape is disordered (not suitable for practical use).
・Tension (N=100)
1: The horizontal pillow bag has tension and maintains its shape.
2: The tension of the horizontal pillow bag is weak and it is slightly bent, but it does not cause any problems in terms of appearance (OK for practical use)
3: The horizontal pillow bag has no tension, is flexible, and cannot maintain its shape.
・Wrinkles (N=100)
1: There are no wrinkles, or there are slight wrinkles that are hard to notice unless you look carefully.
2: Although small wrinkles occur, they are localized and do not pose a problem in terms of appearance (OK for practical use).
3: Some wrinkles are large enough to be noticed at a glance (not suitable for practical use).

Results Using the flexible packaging papers obtained in Examples 1-1 to 1-5, it was possible to produce horizontal pillow bags close to the design dimensions, and the appearance of the obtained horizontal pillow bags had no practical problems.
In contrast, the horizontal pillow bag obtained from the flexible packaging paper obtained in Comparative Example 1-1 was warped in the horizontal direction. This is presumed to be because the paper base material used in Comparative Example 1-1 had a small 2HB value of 0.018 g·cm/cm by the KES method and tried to return to the shape before bending. Further, some of the horizontal pillow bags obtained from the flexible packaging paper obtained in Comparative Example 1-2 had large wrinkles. This is because the paper base material used in Comparative Example 1-2 has a large 2HB value of 1.41 gcm/cm by the KES method, and is difficult to return to its original shape after being bent. It is presumed that this is because the wrinkles caused by the load during bending did not disappear and remained.

Test 2: If (2) is satisfied "Example 2-1"
As pulp raw materials, 80 parts by weight of bleached hardwood kraft pulp (LBKP, CSF: 500 ml) and 20 parts by weight of bleached softwood kraft pulp (NBKP, CSF 530 ml) were used. To 100 parts by weight of this mixed pulp, 0.1 part by weight of polyacrylamide (PAM) with a molecular weight of 2.5 million as a dry paper strength enhancer (based on the dry weight of the pulp) and 0.1 part by weight of alkyl ketene dimer (AKD) as a sizing agent. Paper containing 35 parts by weight, 0.15 parts by weight of polyamide epichlorohydrin (PAEH) resin as a wet paper strength enhancer, and 0.08 parts by weight of polyacrylamide (PAM) with a molecular weight of 10 million as a retention agent. prepared the fees. A wet paper was made from this stock using a paper machine, the wet paper was dried using a Yankee dryer, and a supercalender treatment was performed to obtain a paper base material (base paper). The smoothness (Oken method) of the obtained paper base material was 610 seconds on the front surface and 103 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

“Example 2-2”
As pulp raw materials, 50 parts by weight of softwood bleached kraft pulp (NBKP, CSF: 460 ml) and 50 parts by weight of hardwood bleached kraft pulp (LBKP, CSF: 300 ml) were used. To 100 parts by weight of this mixed pulp, 0.9 parts by weight (based on pulp dry weight) of polyamine epichlorohydrin resin (WS4010, wet paper strength enhancer made by Seiko PMC) activated with caustic soda, polyacrylamide (dry weight) A paper stock containing 0.3 parts by weight of a paper strength enhancer), aluminum sulfate, and a sizing agent was prepared. A wet paper was made from this paper stock using a paper machine, and the wet paper was dried using a Yankee dryer to obtain a paper base material (base paper). The smoothness (Oken method) of the obtained paper base material was 197 seconds on the front surface and 9 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Example 2-3"
As pulp raw materials, 80 parts by weight of bleached hardwood kraft pulp (LBKP, CSF: 500 ml) and 20 parts by weight of bleached softwood kraft pulp (NBKP, CSF 530 ml) were used. To 100 parts by weight of this mixed pulp, 0.1 part by weight of polyacrylamide (PAM) with a molecular weight of 2.5 million as a dry paper strength enhancer (based on the dry weight of the pulp) and 0.1 part by weight of alkyl ketene dimer (AKD) as a sizing agent. Paper containing 35 parts by weight, 0.15 parts by weight of polyamide epichlorohydrin (PAEH) resin as a wet paper strength enhancer, and 0.08 parts by weight of polyacrylamide (PAM) with a molecular weight of 10 million as a retention agent. prepared the fees. A wet paper was made from this paper stock using a paper machine, and the wet paper was dried using a Yankee dryer to obtain a paper base material (base paper). The smoothness (Ouken method) of the obtained paper base material was 141 seconds on the front surface and 8 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

“Example 2-4”
The procedure was the same as in Example 2-3, except that a paper base material (base paper) having a basis weight of about 50 g/m ² was obtained. The smoothness (Ouken method) of the obtained paper base material was 83 seconds on the front surface and 10 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Example 2-5"
As pulp raw materials, 50 parts by weight of softwood bleached kraft pulp (NBKP, CSF: 500 ml) and 50 parts by weight of hardwood bleached kraft pulp (LBKP, CSF: 350 ml) were used. To 100 parts by weight of this mixed pulp, 0.9 parts by weight (based on pulp dry weight) of polyamine epichlorohydrin resin (WS4010, wet paper strength enhancer made by Seiko PMC) activated with caustic soda, polyacrylamide (dry weight) A paper stock containing 0.3 parts by weight of a paper strength enhancer), aluminum sulfate, and a sizing agent was prepared. A wet paper was made from this paper stock using a paper machine, and the wet paper was dried using a Yankee dryer to obtain a paper base material (base paper). The smoothness (Ouken method) of the obtained paper base material was 299 seconds on the front surface and 10 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Example 2-6"
Sodium polyacrylate was added as a dispersant to engineered kaolin (manufactured by Imerys, Varisurf HX, average particle size 9.0 μm, aspect ratio 80-100) (0.2% to pigment), and dispersed with a Serie mixer. A kaolin slurry with a solid content concentration of 55% was prepared. In the obtained kaolin slurry, 200 parts (solid content) of styrene-butadiene latex (manufactured by Nippon Zeon Co., Ltd., PNT7868) as a water vapor barrier resin was blended to 100 parts (solid content) of the pigment. A coating liquid for a water vapor barrier layer having a concentration of 50% was obtained.
A polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA117) aqueous solution was prepared to have a solid content concentration of 10% to obtain a coating liquid for a gas barrier layer.

On the back side of the base paper obtained in Example 2-4, a coating liquid for a water vapor barrier layer was coated on one side using a blade coater so that the dry weight coating amount was 12 g/m ² , and then dried at 105°C for 2 minutes. After that, the gas barrier layer coating liquid was coated on one side using a roll coater so that the coating amount was 3.0 g/ ^m2 in terms of dry weight, and dried at 105°C for 2 minutes to form the paper with the functional layer. A base material was obtained. The smoothness (Ouken method) of the obtained paper base material was 83 seconds on the front surface and 34 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the functional layer of this paper base material by extrusion lamination to obtain a flexible packaging paper.

“Comparative Example 2-1”
As a pulp raw material, a mixed pulp using 60 parts by weight of softwood bleached kraft pulp (NBKP, CSF: 40ml) and 40 parts by weight of hardwood bleached kraft pulp (LBKP, CSF: 40ml) was used as a raw material, and the pulp was made to a basis weight of 30% using a Fourdrinier paper machine. A base paper of .0 g/m ² was made into paper, and an on-machine 2-roll size press was used to form a paper using modified PVA (RS4104 (Kuraray), content 1.0 g/m ² ) and wet paper strength agent (WS-4020 (Starlight)). PMC) in a content of 0.05 g/m ² ) and dried with a dryer to obtain a base paper with a moisture content of 8.0%. Thereafter, water was added to this base paper to form a wet paper with a moisture content of 15.0%, and supercalender treatment was performed at a temperature of 130° C. and a linear pressure of 250 kg/cm to obtain a paper base material. The smoothness (Oken method) of the obtained paper base material was 1234 seconds on the front surface and 1085 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

“Comparative Example 2-2”
As a pulp raw material, 100 parts by weight of softwood unbleached kraft pulp (NBKP, CSF 530 ml) was used. To 100 parts by weight of this pulp, 0.1 parts by weight of polyacrylamide (PAM) with a molecular weight of 2.5 million as a dry paper strength enhancer (based on the dry weight of the pulp) and 0.35 parts by weight of alkyl ketene dimer (AKD) as a sizing agent. Paper stock containing 0.15 parts by weight of polyamide epichlorohydrin (PAEH) resin as a wet paper strength enhancer and 0.08 parts by weight of polyacrylamide (PAM) with a molecular weight of 10 million as a retention agent. prepared. Wet paper was made from this paper stock using a paper machine and dried to obtain a paper base material (base paper). The smoothness (Oken method) of the obtained paper base material was 15 seconds on the front surface and 12 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

The obtained paper base material or flexible packaging paper was evaluated as follows. The results are shown in Table 2.
・B, 2HB by KES method
The measurement was performed using an automated pure bending tester KES-FB2-S manufactured by Totec Co., Ltd. under the conditions of a test piece of 100 mm x 100 mm, a bending speed of 0.5 cm ^-1 /sec, and a maximum curvature of 2.5 cm ^-1 .
Measure the M-K curves at two locations with a curvature of 0.5 to 1.5 (front bending) and -0.5 to -1.5 (back bending), and calculate the average value as the bending rigidity B in the MD direction. And so.
The difference in bending moment during reciprocating was measured at two locations with a curvature of 1.0 (front bending) and a curvature of -1.0 (back bending), and the average value was taken as the bending hysteresis 2HB.
- Puncture strength Measured from the paper base side of flexible packaging paper using an IMADA texture analyzer in accordance with JIS Z1707:2019 7.5 puncture strength test.
・Smoothness (Ouken style)
The surface of the paper base material opposite to the surface on which the heat seal layer is provided was measured in accordance with JIS P8155 using a digital Oken type air permeability and smoothness tester (manufactured by Asahi Seiko Co., Ltd.).
-Young's modulus Measured using an L&W tensile tester in accordance with JIS P8113:2006, Part 2 Constant Speed Extension Method.

- Bag-making property The obtained soft packaging paper was cut into a width of 250 mm and wound into a roll. Using a horizontal pillow packaging machine (Omori Kikai Kogyo Co., Ltd., S-5000X BX) and a product dummy (width 75 mm x length 75 mm x height 28 mm (weight 45 g)), the width of the bag making machine's frontage is 80 to 85 mm x height. 1,000 horizontal pillow bags were prepared under the conditions of a width of 35 mm, a cut pitch of 150 mm, and a rotation speed of 60 cpm, and evaluated according to the following criteria. Further, the center seal temperature was 140°C, and the top seal temperature was 110°C.

・Longitudinal dimensional stability (N=30)
1: All vertical dimensions are less than ±3% from the design.
2: All vertical dimensions are less than ±5% from the design.
3: One or more items whose vertical dimension deviated by 5% or more from the design.
・Lateral dimensional stability (N=30)
1: All frontage dimensions are less than ±10% from the design.
2: All frontage dimensions are less than ±25% from the design.
3: There is one or more items whose frontage dimensions deviate by 25% or more from the design.

・Beauty (N=100)
1: The shape as a horizontal pillow bag is maintained.
2: Slight warping or rounding occurred, but this did not pose any problem in terms of appearance (OK for practical use).
3: There are cases where large warps and rounding occur, and the shape is disordered (not suitable for practical use).
・Tension (N=100)
1: The horizontal pillow bag has tension and maintains its shape.
2: The tension of the horizontal pillow bag is weak and it is slightly bent, but it does not cause any problems in terms of appearance (OK for practical use)
3: The horizontal pillow bag has no tension, is flexible, and cannot maintain its shape.
・Wrinkles (N=100)
1: There are no wrinkles, or there are slight wrinkles that are hard to notice unless you look carefully.
2: Although small wrinkles occur, they are localized and do not pose a problem in terms of appearance (OK for practical use).
3: Some wrinkles are large enough to be noticed at a glance (not suitable for practical use).

Results Using the flexible packaging papers obtained in Examples 2-1 to 2-6, it was possible to produce horizontal pillow bags close to the design dimensions, and the appearance of the obtained horizontal pillow bags had no practical problems. The horizontal pillow bags obtained from the flexible packaging paper obtained in Example 2-4 had opening dimensions that deviated by less than 20% from the designed design, and compared to the flexible packaging obtained in Example 2-6. In the horizontal pillow bags obtained from the material paper, the deviation of the opening dimensions from the design was all less than 25%, and most of them were less than 20%, but some cases were 20% or more and less than 25%. was.
On the other hand, the horizontal pillow bag obtained from the flexible packaging paper obtained in Comparative Example 2-1 had no tension, and when lifted in a horizontal state, it could not resist gravity and sagged. This is presumably because the paper base material used in Comparative Example 2-1 had a small B value of 0.151 g·cm ² /cm by the KES method and was too soft. In addition, the horizontal pillow bags obtained from the flexible packaging paper obtained in Comparative Example 2-2 included a plurality of bags whose horizontal dimensions deviated significantly from the designed dimensions by 25% or more. This is because the paper base material used in Comparative Example 2-2 has a large B value of 1.93 g cm ² /cm according to the KES method, and is difficult to bend, so there is no misalignment when rolling it into a cylinder. It is presumed that this is due to the occurrence of

Test 3: If (3) is satisfied "Example 3-1"
As pulp raw materials, 80 parts by weight of bleached hardwood kraft pulp (LBKP, CSF: 500 ml) and 20 parts by weight of bleached softwood kraft pulp (NBKP, CSF 530 ml) were used. To 100 parts by weight of this mixed pulp, 0.1 part by weight of polyacrylamide (PAM) with a molecular weight of 2.5 million as a dry paper strength enhancer (based on the dry weight of the pulp) and 0.1 part by weight of alkyl ketene dimer (AKD) as a sizing agent. Paper containing 35 parts by weight, 0.15 parts by weight of polyamide epichlorohydrin (PAEH) resin as a wet paper strength enhancer, and 0.08 parts by weight of polyacrylamide (PAM) with a molecular weight of 10 million as a retention agent. prepared the fees. A wet paper was made from this paper stock using a paper machine, and the wet paper was dried using a Yankee dryer to obtain a paper base material (base paper). The smoothness (Ouken method) of the obtained paper base material was 83 seconds on the front surface and 10 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Example 3-2"
As pulp raw materials, 50 parts by weight of softwood bleached kraft pulp (NBKP, CSF: 460 ml) and 50 parts by weight of hardwood bleached kraft pulp (LBKP, CSF: 300 ml) were used. To 100 parts by weight of this mixed pulp, 0.9 parts by weight (based on pulp dry weight) of polyamine epichlorohydrin resin (WS4010, wet paper strength enhancer made by Seiko PMC) activated with caustic soda, polyacrylamide (dry weight) A paper stock containing 0.3 parts by weight of a paper strength enhancer), aluminum sulfate, and a sizing agent was prepared. A wet paper was made from this paper stock using a paper machine, and the wet paper was dried using a Yankee dryer to obtain a paper base material (base paper). The smoothness (Oken method) of the obtained paper base material was 197 seconds on the front surface and 9 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Example 3-3"
Wet paper was made in the same manner as in Example 3-1 to have a basis weight of about 30 g/m ² , dried, and then supercalendered to obtain a paper base (base paper). The smoothness (Oken method) of the obtained paper base material was 610 seconds on the front surface and 103 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Example 3-4"
As pulp raw materials, 50 parts by weight of softwood bleached kraft pulp (NBKP, CSF: 500 ml) and 50 parts by weight of hardwood bleached kraft pulp (LBKP, CSF: 350 ml) were used. To 100 parts by weight of this mixed pulp, 0.9 parts by weight (based on pulp dry weight) of polyamine epichlorohydrin resin (WS4010, wet paper strength enhancer made by Seiko PMC) activated with caustic soda, polyacrylamide (dry weight) A paper stock containing 0.3 parts by weight of a paper strength enhancer), aluminum sulfate, and a sizing agent was prepared. A wet paper was made from this paper stock using a paper machine, and the wet paper was dried using a Yankee dryer to obtain a paper base material (base paper). The smoothness (Ouken method) of the obtained paper base material was 299 seconds on the front surface and 10 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Example 3-5"
Sodium polyacrylate was added as a dispersant to engineered kaolin (manufactured by Imerys, Varisurf HX, average particle size 9.0 μm, aspect ratio 80-100) (0.2% to pigment), and dispersed with a Serie mixer. A kaolin slurry with a solid content concentration of 55% was prepared. In the obtained kaolin slurry, 200 parts (solid content) of styrene-butadiene latex (manufactured by Nippon Zeon Co., Ltd., PNT7868) as a water vapor barrier resin was blended to 100 parts (solid content) of the pigment. A coating liquid for a water vapor barrier layer having a concentration of 50% was obtained.
A polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA117) aqueous solution was prepared to have a solid content concentration of 10% to obtain a coating liquid for a gas barrier layer.

On the back side of the base paper obtained in Example 3-1, a coating solution for a water vapor barrier layer was coated on one side using a blade coater so that the dry weight coating amount was 12 g/m ² , and dried at 105°C for 2 minutes. After that, the gas barrier layer coating liquid was coated on one side using a roll coater so that the coating amount was 3.0 g/ ^m2 in terms of dry weight, and dried at 105°C for 2 minutes to form the paper with the functional layer. A base material was obtained. The smoothness (Ouken method) of the obtained paper base material was 83 seconds on the front surface and 34 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the functional layer of this paper base material by extrusion lamination to obtain a flexible packaging paper.

“Comparative Example 3-1”
Commercially available kraft paper (Shin Tokai Paper Co., Ltd.) was used as the paper base material. The smoothness (Oken method) of this paper base material was 14 seconds on the front surface and 4 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on this paper base material by extrusion lamination to obtain a flexible packaging paper.

“Comparative Example 3-2”
As a pulp raw material, a mixed pulp using 60 parts by weight of softwood bleached kraft pulp (NBKP, CSF: 40ml) and 40 parts by weight of hardwood bleached kraft pulp (LBKP, CSF: 40ml) was used as a raw material, and the pulp was made to a basis weight of 30% using a Fourdrinier paper machine. A base paper of .0 g/m ² was made into paper, and an on-machine 2-roll size press was used to form a paper using modified PVA (RS4104 (Kuraray), content 1.0 g/m ² ) and wet paper strength agent (WS-4020 (Starlight)). PMC) in a content of 0.05 g/m ² ) and dried with a dryer to obtain a base paper with a moisture content of 8.0%. Thereafter, water was added to this base paper to form a wet paper with a moisture content of 15.0%, and supercalender treatment was performed at a temperature of 130° C. and a linear pressure of 250 kg/cm to obtain a paper base material. The smoothness (Oken method) of the obtained paper base material was 1234 seconds on the front surface and 1085 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

The obtained paper base material or flexible packaging paper was evaluated as follows. The results are shown in Table 3.
・Smoothness (Ouken style)
The surface opposite to the surface on which the heat-sealing layer is provided (front surface) and the surface on which the heat-sealing layer is provided (back surface) of the paper base material were subjected to a digital Oken air permeability and smoothness test in accordance with JIS P8155. It was measured using a machine (manufactured by Asahi Seiko Co., Ltd.).
- Puncture strength Measured from the paper base side of flexible packaging paper using an IMADA texture analyzer in accordance with JIS Z1707:2019 7.5 puncture strength test.
-Young's modulus Measured using an L&W tensile tester in accordance with JIS P8113:2006, Part 2 Constant Speed Extension Method.
・B, 2HB by KES method
The measurement was performed using an automated pure bending tester KES-FB2-S manufactured by Totec Co., Ltd. under the conditions of a test piece of 100 mm x 100 mm, a bending speed of 0.5 cm ^-1 /sec, and a maximum curvature of 2.5 cm ^-1 .
Measure the M-K curves at two locations with a curvature of 0.5 to 1.5 (front bending) and -0.5 to -1.5 (back bending), and calculate the average value as the bending rigidity B in the MD direction. And so.
The difference in bending moment during reciprocating was measured at two locations with a curvature of 1.0 (front bending) and a curvature of -1.0 (back bending), and the average value was taken as the bending hysteresis 2HB.

- Bag-making property The obtained soft packaging paper was cut into a width of 250 mm and wound into a roll. Using a horizontal pillow packaging machine (Omori Kikai Kogyo Co., Ltd., S-5000X BX) and a product dummy (width 75 mm x length 75 mm x height 28 mm (weight 45 g)), the width of the bag making machine's frontage is 80 to 85 mm x height. 1,000 horizontal pillow bags were prepared under the conditions of a width of 35 mm, a cut pitch of 150 mm, and a rotation speed of 60 cpm, and evaluated according to the following criteria. Further, the center seal temperature was 140°C, and the top seal temperature was 110°C. In addition, production of products whose flexible packaging paper broke was discontinued at that point.

- Breakage OK: The flexible packaging paper does not break during manufacturing.
NG: The flexible packaging paper breaks during manufacturing.
・Longitudinal dimensional stability (N=30)
1: All vertical dimensions are less than ±3% from the design.
2: All vertical dimensions are less than ±5% from the design.
3: One or more items whose vertical dimension deviated by 5% or more from the design.
・Lateral dimensional stability (N=30)
1: All frontage dimensions are less than ±10% from the design.
2: All frontage dimensions are less than ±25% from the design.
3: There is one or more items whose frontage dimensions deviate by 25% or more from the design.
・Heat seal part misalignment (N=30)
1: The positional deviation of the center seal portion is less than 1 mm.
2: The positional deviation of the center seal portion is less than 2 mm.
3: There is one or more items in which the center seal part is misaligned by 2 mm or more.

Results The flexible packaging papers obtained in Examples 3-1 to 3-5 could be transported without breaking. Moreover, the obtained horizontal pillow bag had dimensions close to the designed size.
On the other hand, the soft packaging paper obtained in Comparative Example 3-1 broke during bag making. This is presumed to be because the smoothness (Ouken type) was only 14 seconds and the surface was rough, so a load was applied during transportation. Furthermore, when the horizontal pillow bags manufactured before being broken were inspected, it was found that there was a large deviation from the designed dimension, especially in the vertical dimension. The soft packaging paper of Comparative Example 3-2 had a large misalignment at the heat-sealed portion. This is because the smoothness (Ouken type) is 1234 seconds, so the surface is smooth and has low friction, so it meandered when being transported through the bag making machine and became oblique to the flow direction. It is assumed that there is.

Test 4: If (4) is satisfied "Example 4-1"
As pulp raw materials, 80 parts by weight of bleached hardwood kraft pulp (LBKP, CSF: 500 ml) and 20 parts by weight of bleached softwood kraft pulp (NBKP, CSF 530 ml) were used. To 100 parts by weight of this mixed pulp, 0.1 part by weight of polyacrylamide (PAM) with a molecular weight of 2.5 million as a dry paper strength enhancer (based on the dry weight of the pulp) and 0.1 part by weight of alkyl ketene dimer (AKD) as a sizing agent. Paper containing 35 parts by weight, 0.15 parts by weight of polyamide epichlorohydrin (PAEH) resin as a wet paper strength enhancer, and 0.08 parts by weight of polyacrylamide (PAM) with a molecular weight of 10 million as a retention agent. prepared the fees. A wet paper was made from this paper stock using a paper machine, and the wet paper was dried using a Yankee dryer to obtain a paper base material (base paper). The smoothness (Ouken method) of the obtained paper base material was 83 seconds on the front surface and 10 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

“Example 4-2”
As pulp raw materials, 50 parts by weight of softwood bleached kraft pulp (NBKP, CSF: 460 ml) and 50 parts by weight of hardwood bleached kraft pulp (LBKP, CSF: 300 ml) were used. To 100 parts by weight of this mixed pulp, 0.9 parts by weight (based on pulp dry weight) of polyamine epichlorohydrin resin (WS4010, wet paper strength enhancer made by Seiko PMC) activated with caustic soda, polyacrylamide (dry weight) A paper stock containing 0.3 parts by weight of a paper strength enhancer), aluminum sulfate, and a sizing agent was prepared. A wet paper was made from this paper stock using a paper machine, and the wet paper was dried using a Yankee dryer to obtain a paper base material (base paper). The smoothness (Oken method) of the obtained paper base material was 197 seconds on the front surface and 9 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Example 4-3"
As a pulp raw material, a mixed pulp using 60 parts by weight of softwood bleached kraft pulp (NBKP, CSF: 40ml) and 40 parts by weight of hardwood bleached kraft pulp (LBKP, CSF: 40ml) was used as a raw material, and the pulp was made to a basis weight of 30% using a Fourdrinier paper machine. A base paper of .0 g/m ² was made into paper, and an on-machine 2-roll size press was used to form a paper using modified PVA (RS4104 (Kuraray), content 1.0 g/m ² ) and wet paper strength agent (WS-4020 (Starlight)). PMC) in a content of 0.05 g/m ² ) and dried with a dryer to obtain a base paper with a moisture content of 8.0%. Thereafter, water was added to this base paper to form a wet paper with a moisture content of 15.0%, and supercalender treatment was performed at a temperature of 130° C. and a linear pressure of 250 kg/cm to obtain a paper base material. The smoothness (Oken method) of the obtained paper base material was 1234 seconds on the front surface and 1085 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Example 4-4"
As pulp raw materials, 50 parts by weight of softwood bleached kraft pulp (NBKP, CSF: 500 ml) and 50 parts by weight of hardwood bleached kraft pulp (LBKP, CSF: 350 ml) were used. To 100 parts by weight of this mixed pulp, 0.9 parts by weight (based on pulp dry weight) of polyamine epichlorohydrin resin (WS4010, wet paper strength enhancer made by Seiko PMC) activated with caustic soda, polyacrylamide (dry weight) A paper stock containing 0.3 parts by weight of a paper strength enhancer), aluminum sulfate, and a sizing agent was prepared. A wet paper was made from this paper stock using a paper machine, and the wet paper was dried using a Yankee dryer to obtain a paper base material (base paper). The smoothness (Ouken method) of the obtained paper base material was 299 seconds on the front surface and 10 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Example 4-5"
Sodium polyacrylate was added as a dispersant to engineered kaolin (manufactured by Imerys, Varisurf HX, average particle size 9.0 μm, aspect ratio 80-100) (0.2% to pigment), and dispersed with a Serie mixer. A kaolin slurry with a solid content concentration of 55% was prepared. In the obtained kaolin slurry, 200 parts (solid content) of styrene-butadiene latex (manufactured by Nippon Zeon Co., Ltd., PNT7868) as a water vapor barrier resin was blended to 100 parts (solid content) of the pigment. A coating liquid for a water vapor barrier layer having a concentration of 50% was obtained.
A polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA117) aqueous solution was prepared to have a solid content concentration of 10% to obtain a coating liquid for a gas barrier layer.

On the back side of the base paper obtained in Example 4-1, a coating liquid for a water vapor barrier layer was coated on one side using a blade coater so that the dry weight coating amount was 12 g/m ² , and then dried at 105°C for 2 minutes. After that, the gas barrier layer coating liquid was coated on one side using a roll coater so that the coating amount was 3.0 g/ ^m2 in terms of dry weight, and dried at 105°C for 2 minutes to form the paper with the functional layer. A base material was obtained. The smoothness (Ouken method) of the obtained paper base material was 83 seconds on the front surface and 34 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the functional layer of this paper base material by extrusion lamination to obtain a flexible packaging paper.

“Comparative Example 4-1”
Commercially available kraft paper (Shin Tokai Paper Co., Ltd.) was used as the paper base material. The smoothness (Oken method) of this paper base material was 14 seconds on the front surface and 4 seconds on the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.
“Comparative Example 4-2”
Commercially available glassine paper (Nippon Paper Papylia Co., Ltd.) was used as the paper base material. The smoothness (Oken method) of this paper base material was 1756 seconds for the front surface and 1424 seconds for the back surface.
A heat-sealing layer made of low-density polyethylene having a thickness of 25 μm was provided on the back side of this paper base material by extrusion lamination to obtain a flexible packaging paper.

The obtained paper base material or flexible packaging paper was evaluated as follows. The results are shown in Table 4.
・Smoothness (Ouken style)
The surface opposite to the surface on which the heat-sealing layer is provided (front surface) and the surface on which the heat-sealing layer is provided (back surface) of the paper base material were subjected to a digital Oken air permeability and smoothness test in accordance with JIS P8155. It was measured using a machine (manufactured by Asahi Seiko Co., Ltd.).
- Puncture strength Measured from the paper base side of flexible packaging paper using an IMADA texture analyzer in accordance with JIS Z1707:2019 7.5 puncture strength test.
-Young's modulus Measured using an L&W tensile tester in accordance with JIS P8113:2006, Part 2 Constant Speed Extension Method.
・B, 2HB by KES method
The measurement was performed using an automated pure bending tester KES-FB2-S manufactured by Totec Co., Ltd. under the conditions of a test piece of 100 mm x 100 mm, a bending speed of 0.5 cm ^-1 /sec, and a maximum curvature of 2.5 cm ^-1 .
Measure the M-K curves at two locations with a curvature of 0.5 to 1.5 (front bending) and -0.5 to -1.5 (back bending), and calculate the average value as the bending rigidity B in the MD direction. And so.
The difference in bending moment during reciprocating was measured at two locations with a curvature of 1.0 (front bending) and a curvature of -1.0 (back bending), and the average value was taken as the bending hysteresis 2HB.

- Bag-making property The obtained soft packaging paper was cut into a width of 250 mm and wound into a roll. Using a horizontal pillow packaging machine (Omori Kikai Kogyo Co., Ltd., S-5000X BX) and a product dummy (width 75 mm x length 75 mm x height 28 mm (weight 45 g)), the width of the bag making machine's frontage is 80 to 85 mm x height. 1,000 horizontal pillow bags were prepared under the conditions of a width of 35 mm, a cut pitch of 150 mm, and a rotation speed of 60 cpm, and evaluated according to the following criteria. Further, the center seal temperature was 140°C, and the top seal temperature was 110°C. In addition, production of products whose flexible packaging paper broke was discontinued at that point.

- Breakage OK: The flexible packaging paper does not break during manufacturing.
NG: The flexible packaging paper breaks during manufacturing.
- Conveyability OK: The flexible packaging paper can be conveyed as specified.
NG: Misalignment occurs in the conveyance of the flexible packaging paper.
・Longitudinal dimensional stability (N=30)
1: All vertical dimensions are less than ±3% from the design.
2: All vertical dimensions are less than ±5% from the design.
3: One or more items whose vertical dimension deviated by 5% or more from the design.

Results The flexible packaging paper obtained in Examples 4-1 to 4-5 could be transported as specified without breaking. The obtained horizontal pillow bag also had excellent longitudinal dimensional stability.
On the other hand, the flexible packaging paper obtained in Comparative Example 4-1 broke during production, so production of horizontal pillow bags was discontinued midway. In addition, when the horizontal pillow bag manufactured before breaking was inspected, it was found that the vertical dimension was short and the bag had shrunk more than the designed dimension. This is because the Young's modulus of the paper base material is as small as 2.81 GPa, so it is assumed that the bag was transported in a stretched state in the longitudinal direction by the bag making machine and shrunk when tension was no longer applied. The flexible packaging paper of Comparative Example 4-2 had good longitudinal dimensional stability even though it was cut at 10 cm intervals, but it was not cut at 150 mm intervals in the longitudinal direction due to transport defects in the bag making machine. There has occurred. This is presumed to be because the Young's modulus of the paper base material is as large as 15.1 GPa, so strong tension cannot be applied, resulting in poor conveyance.

Claims (5)

having a paper base material and a heat sealing layer on at least one outermost surface,
The paper base material has a thickness of 25 μm or more and 100 μm or less,
The ratio of pulp to the total papermaking fibers contained in the paper base exceeds 90% by weight,
The heat seal layer is a laminate layer with a thickness of 20 μm or more and 100 μm or less,
Soft packaging paper characterized by satisfying the following conditions (1) and (3) (1) The hysteresis 2HB of bending the paper base material in the MD direction by the KES method is 0.02 g cm/cm or more1 .2g・cm/cm or less
(3) The other surface of the paper base material is exposed, and the smoothness (Oken type) of the exposed surface is 50 seconds or more and 700 seconds or less . The flexible packaging paper according to claim 1, wherein the paper base has a basis weight of 20 g/m ² or more and 70 g/m ² or less. The flexible packaging paper according to claim 1, wherein the paper base has a density of 0.5 g/cm ³ or more and 0.95 g/cm ³ or less. The flexible packaging paper (2) according to claim 1, which satisfies the following condition (2) or (4 ) : The bending rigidity B of the paper base material in the MD direction by the KES method is 0.16 g cm ² /cm or more and 1.8g・cm ² /cm or less
( 4) Young's modulus of the paper base material in the MD direction is 3 GPa or more and 15 GPa or less. A flexible packaging body, characterized in that an object to be packaged is enclosed in a packaging material made of the flexible packaging paper according to any one of claims 1 to 4.