JP2023138253A - Soft packaging sheet and soft package - Google Patents

Abstract

To provide a soft packaging sheet that can be made into bags with a bag-making machine, and a soft package using the soft packaging sheet.SOLUTION: A soft packaging sheet includes a paper substrate, and a heat seal layer on at least one outermost surface. The paper substrate has a thickness of 25 μm or more and 100 μm or less, and a bending stiffness B in MD direction by KES method of 0.16 g cm2/cm or more and 1.8 g cm2/cm or less.SELECTED DRAWING: None

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, and a bending rigidity B in the MD direction measured by the KES method of 0.16 g·cm ² /cm or more and 1.8 g·cm ² /cm or less. Flexible packaging paper.
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 thereof. 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.
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 has a bending rigidity B in the MD direction determined by the KES method of from 0.16 g·cm ² /cm to 1.8 g·cm ² /cm. Further, it is preferable that 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.
Note that 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. 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 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.

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 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.

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 24 g/m ² or more, even more preferably 28 g/m ² or more, and more preferably 65 g/m ² or less, 60 g/m ² It is more preferably at most 55 g/m ² , even more preferably at most 55 g/m 2 . 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 thickness of the paper base material is calculated from the density and basis weight.

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.

In the present invention, when the paper base material is exposed on one side of the flexible packaging paper, the smoothness (Oken type) of the exposed surface (surface) of the paper base material must be 50 seconds or more and 700 seconds or less. is preferred. 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 more preferably 70 seconds or more, even more preferably 100 seconds or more, and more preferably 650 seconds or less. , more preferably 600 seconds or less, even more 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 other surface (back surface) of a paper base material, the value of smoothness (Oken type) is not specifically limited. However, since the adhesion with the layer laminated on the other side is improved, the smoothness of the other side of the paper base (Oken method) is determined by the smoothness of the exposed surface of the paper base (Oken method). It is preferable that the value of the smoothness (Oken type) is smaller than (formula) (the surface is rough) by 30 seconds or more.

The paper base material of the present invention preferably has a Young's modulus in the MD direction of 3 GPa or more and 10 GPa or less. 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 10 GPa, the tension cannot be increased during manufacturing, which tends to cause transportation failures in which the flexible packaging paper cannot be transported as specified, and deviations in cutting intervals are likely to occur. The 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 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.

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 of wood fibers, and it is more preferable to use chemical pulp. Specifically, the blending amount of chemical pulp such as LBKP and NBKP is preferably 80% by weight or more, and it is more preferable that the blending amount of chemical pulp is 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.

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 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 becomes easy to mold it into a flexible packaging material, maintain its shape, 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 limitation. 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 is ² g/m2 or more. It is preferable.
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 a vertical pillow packaging bag, a horizontal pillow packaging bag, a side seal bag, a two side seal bag, a three side seal bag, a gusset bag, a bottom gusset bag, a stand bag, or the like. 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.

"Example 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. 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 this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Example 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 stock using a paper machine, and the wet paper was dried using a Yankee dryer to obtain a paper base material. 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 this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Example 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 stock using a paper machine, and the wet paper was dried using a Yankee dryer to obtain a paper base material. 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 this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Example 4"
The procedure was the same as in Example 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 this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Example 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 stock using a paper machine, and the wet paper was dried using a Yankee dryer to obtain a paper base material. 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 this paper base material by extrusion lamination to obtain a flexible packaging paper.

"Example 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 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 after drying at 105 ° C. for 2 minutes. Then, 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 a paper base having a functional layer. I got it. 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 side surface of this paper base material by extrusion lamination to obtain a flexible packaging paper.

“Comparative Example 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 this paper base material by extrusion lamination to obtain a flexible packaging paper.

“Comparative Example 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. 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 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 .
- 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.

・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 1 to 6, it was possible to produce horizontal pillow bags close to the designed dimensions, and the appearance of the obtained horizontal pillow bags was not problematic in practical use. The horizontal pillow bags obtained from the flexible packaging paper obtained in Example 4 had opening dimensions that deviated from the design by less than 20% in all cases, and compared to those obtained from the flexible packaging paper obtained in Example 6. All of the horizontal pillow bags that were tested had opening dimensions that deviated from the design by less than 25%, most of which were less than 20%, but some cases were greater than 20% and less than 25%.
On the other hand, the horizontal pillow bag obtained from the flexible packaging paper obtained in Comparative Example 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 1 had a small B value of 0.151 g·cm ² /cm by the KES method and was too soft. Further, among the horizontal pillow bags obtained from the flexible packaging paper obtained in Comparative Example 2, there were 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 has a large B value of 1.93 gcm ² /cm by the KES method, and is difficult to bend, so misalignment occurred when it was rolled into a cylinder. It is assumed that

Claims (4)

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, and a bending rigidity B in the MD direction measured by the KES method of 0.16 g·cm ² /cm or more and 1.8 g·cm ² /cm or less. Flexible packaging paper. 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 or 2, wherein the density of the paper base material is 0.5 g/cm ³ or more and 0.95 g/cm ³ 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 claim 1 or 2.