JP2023184111A - Heat-sealable paper and processed paper product - Google Patents

Abstract

To provide heat-sealable paper which has drop impact resistance, excellent flexibility, and excellent heat-sealability.SOLUTION: The heat-sealable paper comprises at least one heat-sealable layer on at least one face of a paper base material. The heat-sealable layer contains a water-dispersible resin binder. As measured in accordance with ISO 2493-1:2010, the vertical ISO stiffness of the heat-sealable paper is 0.55 mNm or less, and the horizontal ISO stiffness of the heat-sealable paper is 0.45 mNm or less. The puncture strength of the heat-sealable paper measured in accordance with JIS Z 1707:2019 is 7.5 N or more.SELECTED DRAWING: None

Description

The present disclosure relates to heat seal paper and paper products.

Plastic materials have mainly been used for packaging containers such as food trays and packaging bodies such as pillow packaging bags. However, due to environmental concerns, consideration is being given to packaging materials using paper instead of plastic containers.

International Publication No. 2015/008703

Although conventional paper such as that disclosed in Patent Document 1 has excellent flexibility, it has low puncture strength, and has insufficient drop impact resistance when the bag is filled with a product, for example, in the manufacture of bags for pillow packaging. Normally, paper with high puncture strength tends to become hard and has poor flexibility, so it has been difficult to achieve both drop impact resistance and flexibility.
The present disclosure relates to a heat-sealing paper that has drop impact resistance, excellent flexibility, and excellent heat-sealability, and a paper product using the heat-sealable paper.

That is, the present disclosure relates to <1> to <12> below.
<1> A heat seal paper having one or more heat seal layers on at least one surface of a paper base material,
The heat seal layer contains a water-dispersible resin binder,
The ISO stiffness of the heat seal paper in the longitudinal direction, measured in accordance with ISO2493-1:2010, is 0.55 mNm or less, and the ISO stiffness of the heat seal paper in the lateral direction is 0.45 mNm or less. ,
The puncture strength of the heat seal paper is 7.5N or more, as measured in accordance with JIS Z 1707:2019.
heat seal paper.
<2> The ISO stiffness in the longitudinal direction is 0.05 to 0.20 mNm,
The ISO stiffness in the lateral direction is 0.05 to 0.20 mNm,
The heat seal paper according to <1>.
<3> The heat seal paper according to <1> or <2>, which has a puncture strength of 12.5 N or more. <4> The pulp obtained by disintegrating the heat-seal paper has a length-weighted average fiber length of 1.2 mm to 2.0 mm as measured in accordance with ISO 16065-2:2007, <1 The heat seal paper according to any one of > to <3>.
<5> The heat seal paper according to any one of <1> to <4>, having a basis weight of 40 g/m ² to 130 g/m ² .
<6> The heat seal paper according to any one of <1> to <5>, which has a specific puncture strength of 0.12 N/g or more.
<7> The heat seal paper according to any one of <1> to <6>, wherein the heat seal layer further contains a lubricant.
<8> The heat seal paper according to <7>, wherein the lubricant includes at least one selected from the group consisting of paraffin wax, carnauba wax, and polyolefin wax.
<9> The heat seal paper according to <7> or <8>, wherein the content of the lubricant in the heat seal layer is 1% by mass or more and 5% by mass or less.
<10> The heat seal paper according to any one of <1> to <9>, wherein the water-dispersible resin binder has a glass transition temperature of 0° C. or higher and 100° C. or lower.
<11> The water-dispersible resin binder contains at least one selected from the group consisting of styrene-butadiene copolymer, olefin-fatty acid vinyl ester copolymer, and olefin-unsaturated carboxylic acid copolymer, The heat seal paper according to any one of <1> to <10>.
<12> A processed paper product using the heat seal paper according to any one of <1> to <11>.

According to the present disclosure, it is possible to provide a heat seal paper that has drop impact resistance, excellent flexibility, and excellent heat sealability. Further, according to the present disclosure, it is possible to provide a heat seal paper that has excellent moldability in automatic packaging.

Schematic diagram of bag processing for evaluating drop impact resistance and bag flexibility

In the present disclosure, the descriptions such as "X or more and Y or less" or "X to Y" expressing a numerical range mean a numerical range that includes the lower limit and upper limit, which are the endpoints, unless otherwise specified. When numerical ranges are described in stages, the upper and lower limits of each numerical range can be arbitrarily combined.
The longitudinal direction is the papermaking direction (MD) of the paper base material, and is the same as the direction in which fibers are oriented. Further, the lateral direction is a direction perpendicular to the paper making direction (CD). The longitudinal direction of the heat seal paper is a direction corresponding to the MD direction of the paper base material, and the lateral direction of the heat seal paper is a direction corresponding to the CD direction of the paper base material.
In addition, "excellent formability in automatic packaging (hereinafter also referred to as automatic packaging formability)" means that bags can be made continuously with an automatic packaging machine and the resulting bags have a good appearance. means. More specifically, for example, when automatically molding a packaging bag, the occurrence of wrinkles and poor appearance is suppressed, and sticking (blocking) to a molding machine etc. is suppressed, resulting in excellent moldability. Furthermore, it means that the quality of the resulting packaging bag is excellent, such as suppressing the deformation of the bag after bag making, and the productivity is also excellent.

The Kurupack process is a process in which paper is finely shrunk on a paper machine to give it stretchability. Specifically, for example, a part of a paper machine dryer is installed with a Krupak device comprising an endless thick elastic rubber blanket with nip rolls. The paper web, which is a wet paper, is introduced into the Kurupak machine and compressed with nip rolls and a blanket. At this time, the blanket, which has been stretched in advance, contracts, thereby shrinking the running paper web (creaping) and increasing the elongation at break. In addition, any shrinkage that occurs is dried and fixed to prevent it from elongating in subsequent steps.

The present inventors have discovered that the above problem can be solved by controlling the heat-sealing paper to a specific ISO stiffness and puncture strength through Krupaq treatment when manufacturing the paper base material used for the heat-sealing paper. ISO stiffness indicates how easy the paper is to bend, and puncture strength indicates how hard the paper is torn. The fact that the heat-seal paper has the above-described specific ISO stiffness and puncture strength indicates that it has appropriate bendability and is hard to tear. Therefore, the inventors of the present invention believe that it is possible to obtain a heat-sealing paper that has excellent flexibility and drop impact resistance.

IS of longitudinal direction of heat seal paper measured according to ISO2493-1:2010
It is necessary that the O stiffness is 0.55 mNm or less, and the ISO stiffness of the heat seal paper in the lateral direction is 0.45 mNm or less.
When the ISO stiffness exceeds the above upper limit, bending becomes difficult and flexibility decreases.

The ISO stiffness of heat-sealable paper can be controlled by the manufacturing conditions of the paper base material used, and specifically, the CSF (Canadian Standard Freeness) of the pulp, the basis weight, the speed difference before and after Crupack processing, and the composition of the paper base material. It can be controlled by the mass ratio of hardwood kraft pulp and softwood kraft pulp. In order to increase the ISO stiffness, methods include lowering the CSF of the pulp, increasing the basis weight, increasing the speed difference before and after the Krupack treatment, and increasing the mass ratio of softwood kraft pulp that makes up the paper base material. It will be done. On the other hand, methods to reduce the ISO stiffness include increasing the CSF of the pulp, reducing the basis weight, reducing the speed difference before and after the Kurupak treatment, and reducing the mass ratio of softwood kraft pulp that makes up the paper base material. Can be mentioned.

The ISO stiffness of the heat seal paper in the longitudinal direction is preferably 0.05 to 0.40 mNm, more preferably 0.05 to 0.20 mNm.
The ISO stiffness of the heat seal paper in the lateral direction is preferably 0.05 to 0.35 mNm, more preferably 0.05 to 0.20 mNm.

It is necessary that the puncture strength of the heat seal paper is 7.5N or more, as measured in accordance with JIS Z 1707:2019.
When the puncture strength is less than the above lower limit, dents and tears are likely to occur, and drop impact resistance is reduced.

The puncture strength of heat-sealing paper can be controlled by the manufacturing conditions of the paper base material used, and specifically controlled by the basis weight, the speed difference before and after Krupaq treatment, the content of softwood kraft pulp, and the nip pressure during Kurupak treatment. can do. In order to increase the puncture strength, methods such as increasing the basis weight, increasing the speed difference before and after the Krupak treatment, increasing the content of softwood kraft pulp, and reducing the nip pressure during the Kurupak treatment can be cited. On the other hand, methods to reduce the puncture strength include reducing the basis weight, reducing the speed difference before and after Krupaq treatment, reducing the content of softwood kraft pulp, and increasing the nip pressure during Kurupak treatment. .

The puncture strength of the heat seal paper is preferably 8.0 N or more, more preferably 10.0 N or more, and still more preferably 13.0 N or more from the viewpoint of drop impact resistance. The upper limit of the puncture strength is not particularly limited, but from the viewpoint of cushioning properties, it is preferably 18.0 N or less.

The pulp obtained by disintegrating the heat seal paper preferably has a length-weighted average fiber length of 1.2 mm to 2.0 mm as measured in accordance with ISO 16065-2:2007.
If the length-weighted average fiber length is less than the above lower limit, the strength will be weak and the drop impact resistance will deteriorate, but on the other hand, the flexibility will increase. If the length-weighted average fiber length exceeds the above upper limit, the strength will be strong and the drop impact resistance will improve, but on the other hand, the flexibility will tend to deteriorate. That is, within the above range, both bag flexibility and drop impact resistance can be achieved. The length-weighted average fiber length of the pulp can be controlled by the type of pulp used.

The specific puncture strength of the heat seal paper is preferably 0.05 N/g or more, more preferably 0.10 N/g or more, and even more preferably is 0.12 N/g or more, and even more preferably 0.13 N/g or more. The upper limit of the specific puncture strength is not particularly limited, but from the viewpoint of cushioning properties, it is preferably 0.30 N/g or less. Within the above range, flexibility and drop impact resistance are excellent.
Note that the specific puncture strength is the value obtained by dividing the puncture strength by the basis weight.

[Paper base material]
The basis weight of the paper base material used for heat seal paper is preferably 30 g/m ² to 120 g/m ² , more preferably 60 g/m ² to 110 g/m ² , and 70 g/m ² to 100 g /m ² is more preferable. If the basis weight is less than the above lower limit, the strength will be weak and the drop impact resistance will deteriorate, but on the other hand, the flexibility will increase. If the basis weight exceeds the above upper limit, the strength will be strong and the drop impact resistance will improve, but the flexibility will tend to deteriorate. Within the above range, both bag flexibility and drop impact resistance can be achieved.

The thickness of the paper base material used for heat seal paper is preferably 50 μm to 300 μm, more preferably 60 μm to 200 μm, even more preferably 70 μm to 150 μm, and even more preferably 100 μm to 140 μm. More preferred.

The density of the paper base material used for heat seal paper is preferably 0.30 g/m ³ to 1.00 g/m ³ , more preferably 0.40 g/m ³ to 0.90 g/m ³ , more preferably from 0.50 g/m ³ to 0.80 g/m ³ , even more preferably from 0.60 g/m ³ to 0.70 μmg/m ³ .

It is preferable that the paper base material used for the heat seal paper has a vertical ISO stiffness of 0.05 to 0.70 mNm, measured in accordance with ISO2493-1:2010, and preferably 0.08 to 0.60 mNm. More preferably, it is 0.10 to 0.20 mNm.
Further, it is preferable that the paper base material used for the heat seal paper has a transverse ISO stiffness of 0.05 to 0.45 mNm, and preferably 0.08 to 0. More preferably, it is .35 mNm, and still more preferably 0.10 to 0.20 mNm.
When the ISO stiffness is within the above range, the heat seal paper becomes easy to bend and its flexibility is improved.

It is preferable that the puncture strength of the paper base material used for the heat-seal paper is 7.5N or more, more preferably 8.0N or more, and 12.5N or more, as measured in accordance with JIS Z 1707:2019. It is more preferable that it is above. When the puncture strength is within the above range, the heat seal paper is less likely to be dented or torn, and its drop impact resistance is improved.
The upper limit of the puncture strength of the paper base material is not particularly limited, but from the viewpoint of cushioning properties, it is preferably 18.0 N or less.

The specific puncture strength of the paper base material used for heat seal paper is preferably 0.05 N/g or more, more preferably 0.10 N/g or more, and even more preferably 0.12 N/g or more. preferable. When the specific puncture strength is within the above range, the flexibility and drop impact resistance of the heat seal paper are improved.
The upper limit of the specific puncture strength of the paper base material is not particularly limited, but from the viewpoint of cushioning properties, it is preferably 0.30 N/g or less.

Next, materials that can be used for the paper base material will be explained. The paper base material contains, for example, pulp.
Pulps constituting the paper base material include hardwood kraft pulp such as hardwood unbleached kraft pulp (LUKP) and hardwood bleached kraft pulp (LBKP); softwood unbleached kraft pulp (N
softwood kraft pulp such as softwood bleached kraft pulp (NBKP); groundwood pulp (GP), pressurized groundwood pulp (PGW), refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemi-thermomechanical pulp (CTMP) ), chemical mechanical pulp (CMP), and chemical ground pulp (CGP); waste paper pulp; non-wood fiber pulp such as kenaf, bagasse, bamboo, and cotton; and synthetic pulp. These pulps may be used alone or in combination of two or more.

The pulp preferably contains at least one kind selected from hardwood kraft pulp and softwood kraft pulp, and more preferably contains at least one kind selected from hardwood unbleached kraft pulp and softwood unbleached kraft pulp. Preferably, it contains unbleached hardwood kraft pulp and unbleached softwood kraft pulp.

The content of softwood kraft pulp in the pulp is preferably 20% by mass or more, more preferably 30% by mass or more, still more preferably 35% by mass or more, and even more preferably 40% by mass or more. On the other hand, the upper limit is preferably 100% by mass or less, more preferably 95% by mass or less, still more preferably 90% by mass or less, even more preferably 85% by mass or less.

The content of hardwood kraft pulp in the pulp is preferably 0% by mass or more, more preferably 10% by mass or more, still more preferably 10% by mass or more, and even more preferably 15% by mass or more. On the other hand, the upper limit is preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 65% by mass or less, even more preferably 60% by mass or less.

The freeness of the pulp is not particularly limited, but is preferably 200 to 800 mL, more preferably 300 to 700 mL, as Canadian Standard Freeness (CSF). CSF is measured according to JIS P 8121-2:2012 "Pulp - Freeness Test Method - Part 2: Canadian Standard Freeness Method".

Additives may be used in the paper base material if necessary. Examples of additives include pH adjusters (sodium hydrogen carbonate, sodium hydroxide, etc.), dry paper strength agents (polyacrylamide, starch, etc.), wet paper strength agents (polyamide polyamine epichlorohydrin resin, melamine-formaldehyde resin, urea-formaldehyde resin), internal sizing agents (rosin type, alkyl ketene dimer, etc.), drainage retention improvers (polyacrylamide resin), antifoaming agents, fillers (calcium carbonate, talc, etc.), dyes, etc. Can be mentioned. These additives may be used alone or in combination of two or more. The content of the additive is not particularly limited, and may be within a commonly used range.

<Manufacturing method of paper base material>
Examples of the method for manufacturing the paper base material include a method in which a paper stock containing pulp is made into paper, and a Klupack treatment is performed during paper making. Note that the paper stock may further contain additives as necessary. Examples of the additive include the additives described above. The paper stock can be prepared by adding additives to the pulp slurry as needed. Pulp slurry is obtained by beating pulp in the presence of water. The pulp beating method and beating device are not particularly limited, and known beating methods and beating devices can be employed.

The solid content concentration of the pulp slurry during beating is not particularly limited, but is preferably about 0.5 to 10% by mass, more preferably about 1 to 5% by mass. Further, the pulp content in the paper stock or paper base material is not particularly limited, and may be within a commonly used range. For example, it is preferably 60% by mass or more and 100% by mass or less, more preferably 80% by mass or more and less than 100% by mass, based on the total mass of the paper stock (solid content) or paper base material.

In the paper making of the paper base material, a known wet paper machine can be appropriately selected and used. Examples of the paper machine include a fourdrinier paper machine, a gap former paper machine, a cylinder paper machine, and a short wire paper machine. These paper machines may be equipped with a Krupak device capable of carrying out the Kurupak treatment, and the Kurupak treatment may be performed.

As the Krupak device, a known device can be used. Examples include Krupak equipment with nip rolls and endless thick elastic rubber blankets. As mentioned above, in the Kurupak process, a paper web is carried between a nip roll and a blanket, and when the paper web is compressed by the nip rolls and blanket, the paper web is contracted by shrinking the blanket that has been stretched in advance. and give the crepe. The Kurupack device is usually installed as part of the dryer device of a paper machine, and crepes the material, then dries it and fixes it. A paper base material can be obtained in the manner described above.

In paper making using a Krupak machine, ISO stiffness and puncture strength can be controlled by the difference in papermaking speed before and after the Krupak process and the pressure of the nip rolls.
The papermaking speed is not particularly limited, but may be controlled within a range of, for example, preferably 200 to 1000 m/min, more preferably 300 to 800 m/min, and even more preferably 400 to 700 m/min. The speed difference before and after the Kurupack treatment is not particularly limited, and may be controlled depending on the basis weight and the material of the pulp so as to obtain the desired ISO stiffness and puncture strength. Preferably -5 to -60 m/min, more preferably -10 to -50 m/min, and even more preferably -15 to -40 m/min. The minus "-" here indicates that the speed after Krupak processing is slow.

The nip pressure by the calender is not particularly limited, and may be controlled depending on the basis weight, the material of the pulp, the speed difference before and after the Kurupak treatment, etc., so as to obtain the desired ISO stiffness and puncture strength. Preferably it is 100 kN/m to 200 kN/m, more preferably 130 kN/m to 170 kN/m.

The reel moisture content is not particularly limited, and may be controlled in accordance with the basis weight, the material of the pulp, the difference in speed before and after the Kurupak treatment, etc., so as to obtain the desired ISO stiffness and puncture strength. Preferably it is 2.0 to 12.0%, more preferably 5.0 to 9.0%.

[Heat seal layer]
The heat seal paper of this embodiment has at least one heat seal layer on at least one surface of the paper base material. The heat seal layer is a layer that is melted and bonded by heating, ultrasonic waves, or the like.

(Water-dispersible resin binder)
The heat seal layer contains a water-dispersible resin binder. A water-dispersible resin binder is a resin that is not water-soluble (specifically, the solubility in water at 25°C is 10 g/L or less), but can be finely dispersed in water like an emulsion or suspension. A binder. By aqueous coating the heat-seal layer using a water-dispersible resin binder, it is possible to obtain heat-seal paper that has excellent redisintegration properties and can be recycled as paper. In addition, if the water-dispersible resin binder also falls under the following lubricants, it shall be classified as a lubricant.

The water-dispersible resin binder is not particularly limited as long as it achieves the effects of the present invention, but includes polyolefin resins (polyethylene, polypropylene, etc.), vinyl chloride resins, styrene resins, styrene-butadiene copolymers, Styrene-unsaturated carboxylic acid copolymers (e.g. styrene-(meth)acrylic acid copolymers), acrylic resins, acrylonitrile-styrene copolymers, acrylonitrile-butadiene copolymers, ABS resins, AAS resin, AES resin, vinylidene chloride resin, polyurethane resin, poly-4-methylpentene-1 resin, polybutene-1 resin, vinylidene fluoride resin, vinyl fluoride resin, fluorine resin, polycarbonate resin , polyamide resin, acetal resin, polyphenylene oxide resin, polyester resin (polyethylene terephthalate, polybutylene terephthalate, etc.), polyphenylene sulfide resin, polyimide resin, polysulfone resin, polyether sulfone resin, polyarylate resin , olefin-fatty acid vinyl ester copolymers, olefin-unsaturated carboxylic acid copolymers, and modified products thereof. These may be used alone or in combination of two or more.
Among these, at least one selected from the group consisting of styrene-butadiene copolymer, olefin-fatty acid vinyl ester copolymer, and olefin-unsaturated carboxylic acid copolymer is preferred, and styrene-butadiene copolymer, and at least one selected from the group consisting of olefin-unsaturated carboxylic acid copolymers.
Furthermore, from the viewpoint of increasing heat seal peel strength, olefin-unsaturated carboxylic acid copolymers and olefin-fatty acid vinyl ester copolymers are more preferable, and from the viewpoints of availability, cost, and recyclability, More preferred is a styrene-butadiene copolymer.

Examples of the olefin-unsaturated carboxylic acid copolymer include ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid alkyl ester copolymer, and the like. Among these, ethylene-(meth)acrylic acid copolymer is preferred, and ethylene-acrylic acid copolymer is more preferred.
From the viewpoint of increasing heat seal peel strength, ethylene-vinyl acetate copolymer is preferred as the olefin-fatty acid vinyl ester copolymer.
Therefore, the water-dispersible resin binder contained in the heat seal layer is at least one selected from the group consisting of styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, and ethylene-(meth)acrylic acid copolymer. It is preferably at least one selected from the group consisting of styrene-butadiene copolymer and ethylene-(meth)acrylic acid copolymer. Note that the olefin-unsaturated carboxylic acid copolymer may be an ionomer.

As the styrene-butadiene copolymer, either a synthetic product or a commercial product may be used. Commercial products include Nipol Latex LX407G51, LX407S10, LX407S12, LX410, LX415M, LX416, LX430, LX433C, manufactured by Zeon Co., Ltd. 2507H, NALSTAR SR-101, SR-102, SR-103, SR-115, and SR-153 manufactured by Japan A&L Co., Ltd., and styrene-butadiene latex 0602 and 0597C manufactured by JSR Corporation.

As the ethylene-(meth)acrylic acid copolymer, either a synthetic product or a commercially available product may be used. Commercially available products include MP498345N, MP4983R, MP4990R, MFHS1279 manufactured by Michael Mann Japan LLC, and Sumitomo Seika Co., Ltd. Examples include Zaixen (registered trademark) A, Zaixen (registered trademark) AC, manufactured by Mitsui Chemicals, Inc., and Chemipearl S series manufactured by Mitsui Chemicals.

The glass transition temperature of the water-dispersible resin binder is preferably 0°C or higher, more preferably 10°C or higher, and even more preferably 15°C or higher. The occurrence of blocking can also be suppressed by using a water-dispersible resin binder whose glass transition temperature is equal to or higher than the above lower limit. From the viewpoint of heat sealability, the temperature is preferably 100°C or lower, more preferably 80°C or lower, still more preferably 60°C or lower, and even more preferably 50°C or lower.
The glass transition temperature of the water-dispersible resin binder shall be a value measured by a differential scanning calorimeter. Glass transition temperature is measured in accordance with JIS K 7121:1987.

The content of the water-dispersible resin binder in the heat seal layer is preferably 30% by mass or more, more preferably 50% by mass or more, still more preferably 70% by mass or more, even more preferably 80% by mass or more, The content may be 100% by mass or less, preferably 99% by mass or less, and more preferably 98% by mass or less. Within the above range, heat seal paper having high heat seal peel strength can be obtained.

That is, according to one embodiment of the present invention, a styrene-butadiene copolymer, an olefin-fatty acid vinyl ester copolymer, and an olefin-unsaturated carboxylic acid copolymer (preferably ethylene-(meth) ) Acrylic acid copolymer) The content of at least one selected from the group consisting of It may be at least 100% by mass, preferably at most 99% by mass, more preferably at most 98% by mass.

(Lubricant)
From the viewpoint of imparting slipperiness to the heat-sealing paper and suppressing blocking, the heat-sealing layer preferably contains a lubricant in addition to the water-dispersible resin binder described above. A lubricant is a substance that can reduce the coefficient of friction on the surface of the heat seal layer by blending it into the heat seal layer.

The lubricant is not particularly limited, and for example, wax, metal soap, fatty acid ester, etc. can be used. One type of lubricant may be used alone, or two or more types may be used in combination. Waxes include, for example, waxes derived from animals or plants (e.g., beeswax, carnauba wax, etc.), mineral waxes (e.g., microcrystalline wax, etc.), natural waxes such as petroleum wax; polyolefin waxes, paraffin waxes, polyester waxes, etc. Examples include synthetic wax. Examples of the metal soap include calcium stearate, sodium stearate, zinc stearate, aluminum stearate, magnesium stearate, sodium fatty acid soap, potassium oleate soap, potassium castor oil soap, and complexes thereof. Among the above-mentioned lubricants, paraffin wax, carnauba wax and polyolefin wax are preferable because they have a relatively low melting point, the wax component is easily formed on the surface of the coating layer, and they have an excellent blocking suppressing effect. That is, the lubricant is preferably at least one selected from the group consisting of paraffin wax, carnauba wax, and polyolefin wax.
As the carnauba wax, either a synthetic product or a commercially available product may be used, and examples of the commercially available product include Cellosol 524 manufactured by Chukyo Yushi Co., Ltd. As the paraffin wax, either a synthetic product or a commercially available product may be used, and examples of the commercially available product include Hydrin L-700 manufactured by Chukyo Yushi Co., Ltd. As the polyethylene wax, either a synthetic product or a commercially available product may be used, and examples of the commercially available product include Aquacer 531 manufactured by BYK.

When the heat seal layer contains a lubricant, the content of the lubricant is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably The amount is 1 part by mass or more, and preferably 30 parts by mass or less, more preferably 10 parts by mass or less, and still more preferably 5 parts by mass or less.

When the heat-sealing layer contains a lubricant, the content of the lubricant in the heat-sealing layer is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 1% by mass or more, The content is preferably 30% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less.

In this embodiment, the heat seal layer contains a water-dispersible resin binder, and preferably contains a lubricant in addition to the water-dispersible resin binder. Further, in addition to the water-dispersible resin binder and, if necessary, a lubricant, a pigment may be contained.

(pigment)
In this embodiment, the heat seal layer may contain a pigment in addition to the water-dispersible resin binder. By containing pigments, when manufacturing heat-seal paper, the problem of the heat-seal layer coated side sticking to the back side of the heat-seal paper and peeling (blocking) is suppressed, and it has excellent blocking resistance. A heat-sealable paper is obtained.

The pigment is not particularly limited, and examples include various pigments used in conventional pigment coating layers. The pigments may be used alone or in combination of two or more. As the pigment, a pigment having an aspect ratio of 20 or more is preferable from the viewpoint of heat seal peel strength and blocking resistance. The aspect ratio of the pigment is more preferably 25 or more, further preferably 30 or more, particularly preferably 60 or more, and from the viewpoint of availability and smoothness of the heat seal layer surface, preferably 10,000 or less, More preferably it is 1,000 or less, still more preferably 300 or less. The aspect ratio of a pigment means major axis/minor axis, and may be measured by the method described below.

The pigment is preferably a layered inorganic compound having an aspect ratio of 20 or more. The layered inorganic compound has a tabular shape. When the pigment is flat, the protrusion of the pigment from the surface of the heat-sealing layer is suppressed, and a heat-sealing layer having excellent blocking resistance while maintaining heat-sealability can be obtained.

The length (average particle diameter) of the pigment is preferably 0.1 μm or more and 100 μm or less. When the length is 0.1 μm or more, the pigment is likely to be arranged parallel to the paper base material. Further, when the length is 100 μm or less, there is little concern that a part of the pigment will protrude from the heat seal layer. The length of the pigment is more preferably 0.3 μm or more, further preferably 0.5 μm or more, particularly preferably 1.0 μm or more, and more preferably 30 μm or less, even more preferably 20 μm or less, particularly preferably 15 μm. It is as follows.

Here, the length of the pigment in the state contained in the heat seal layer is determined as follows. An enlarged photograph of the cross section of the heat seal layer is taken using an electron microscope. At this time, the magnification is set so that about 20 to 30 pigments are included in the screen. Measure the individual lengths of pigments within the screen. Then, the average value of the obtained lengths is calculated and taken as the length of the pigment. Note that the length of the pigment is sometimes described in terms of particle diameter.

The thickness of the pigment is preferably 200 nm or less. The thickness of the pigment is more preferably 100 nm or less, still more preferably 80 nm or less, even more preferably 50 nm or less, particularly preferably 30 nm or less. Moreover, it is preferably 5 nm or more, more preferably 10 nm or more. The smaller the average thickness of the pigment, the higher the heat seal peel strength. Here, the thickness of the pigment in the state included in the heat seal layer is determined as follows. An enlarged photograph of the cross section of the heat seal layer is taken using an electron microscope. At this time, the magnification is set so that about 20 to 30 pigments are included in the screen. Measure the individual thickness of pigments within the screen. Then, the average value of the obtained thicknesses is calculated and used as the thickness of the pigment.

Specific examples of pigments include mica, bentonite, kaolin, pyrophyllite, talc, smectite, vermiculite, chlorite, septechlorite, serpentine, stilpnomelene, montmorillonite, heavy calcium carbonate (ground calcium carbonate), Light calcium carbonate (synthetic calcium carbonate), composite synthetic pigment of calcium carbonate and other hydrophilic organic compounds, Sachin White, Litopone, titanium dioxide, silica, barium sulfate, calcium sulfate, alumina, aluminum hydroxide, zinc oxide, carbonic acid Examples include magnesium, silicates, colloidal silica, hollow or solid organic pigments such as plastic pigments, binder pigments, plastic beads, and microcapsules.

Specific examples of mica include synthetic mica (e.g., swellable synthetic mica), muscovite (muscovite), sericite (sericite), phlogopite (phlogopite), biotite (biotite), and fluorophlogopite (man-made). mica), red mica, soda mica, vanadium mica, illite, chimney mica, paragonite, and brittle mica. Further, a specific example of bentonite includes montmorillonite.

Specific examples of kaolin include various kaolins such as kaolin, calcined kaolin, structured kaolin, and delaminated kaolin.

Among these, pigments with an aspect ratio of 20 or more are particularly preferred from the viewpoint of heat seal peel strength, blocking resistance, and economical efficiency, and contain one or more of mica, bentonite, kaolin, and talc. It is more preferable to use kaolin, and kaolin is even more preferable.

When the heat-sealing layer contains a pigment, the pigment content is preferably 1 part by mass or more, more preferably 3 parts by mass, from the viewpoint of blocking resistance and recyclability, based on 100 parts by mass of the water-dispersible resin binder. At least 5 parts by mass, more preferably at least 5 parts by mass, even more preferably at least 8 parts by mass, while from the viewpoint of heat sealing and hot tack properties, it is preferably at most 200 parts by mass, more preferably 100 parts by mass. The amount is preferably 30 parts by mass or less.

When the heat-sealing layer contains a pigment, the content of the pigment in the heat-sealing layer is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably It is 5% by mass or more, even more preferably 8% by mass or more, and from the viewpoint of heat sealability and hot tack property, it is preferably 70% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass. % or less.

(other ingredients)
The heat-sealing layer may contain other components in addition to the water-dispersible resin binder and, if necessary, a lubricant and/or pigment. Examples of other components include a silane coupling agent; an antifoaming agent; a viscosity modifier; a leveling agent such as a surfactant and an alcohol; a coloring agent such as a colored dye.

The coating weight (basis weight) of the heat-sealing layer is not particularly limited, but from the viewpoint of obtaining a packaging bag that is difficult to tear and can be easily opened when opened, it is preferably 3 g/m ² , more preferably 5 g. /m ² or more, more preferably 8 g/m ² or more, and preferably 30 g/m ² or less, more preferably 20 g/m ² or less, even more preferably 15 g/m ² or less.

[Physical properties of heat seal paper]
(Heat seal peel strength)
The heat seal peel strength of the heat seal paper is preferably 2.0 N/15 mm or more, more preferably 3.0 N/15 mm or more, even more preferably 4.0 N/15 mm or more, even more preferably 5.0 N/15 mm or more. and is preferably 10 N/15 mm or less, more preferably 9.0 N/15 mm or less, even more preferably 8.0 N/15 mm or less. Furthermore, from the viewpoint of automatic packaging formability, it is preferably 5.2 N/15 mm or more. The peel strength of the heat-seal layer is the peel strength when the heat-seal layers are heat-sealed together under the conditions of 150°C, 0.2 MPa, and 1 second, and specifically, by the method described in the Examples below. It is the value to be measured.
Peel strength can be adjusted by selecting the glass transition temperature, type, and coating amount of the water-dispersible resin binder. For example, by setting the glass transition temperature of the water-dispersible resin binder to 100°C or less, the resin melts under predetermined heat-sealing conditions and the heat-sealing layers adhere well to each other, thereby ensuring the desired peel strength. Can be done.

(Surface smoothness)
From the viewpoint of improving heat seal peel strength, the Oken type smoothness of the heat seal layer surface of the heat seal paper of this embodiment is preferably 30 seconds or more, more preferably 40 seconds or more, and even more preferably 50 seconds or more. Even more preferably it is 60 seconds or more, and although the upper limit is not particularly limited, it is preferably 500 seconds or less, more preferably 300 seconds or less, and still more preferably 100 seconds or less.
Note that the heat seal layer may be provided on the W side (wire side) or the F side (felt side) of the paper base material, and is not particularly limited. Here, the W surface (wire surface) is the surface in contact with the wire when the paper web is formed, and the opposite surface is the F surface (felt surface).
In addition, the surface opposite to the heat-sealing layer (for example, if the heat-sealing layer is provided on only one side of the paper base material and the paper base material is exposed on the other side, the surface of the paper base material) From the viewpoint of improving printability, the formula smoothness is preferably 3 seconds or more, more preferably 5 seconds or more, and the upper limit is not particularly limited, but is preferably 1000 seconds or less, more preferably 300 seconds or less, and even more preferably is 100 seconds or less.
Oken type smoothness is measured in accordance with JIS P8155:2010.
The Oken type smoothness of the heat-sealing layer surface and the opposite surface of the heat-sealing paper can be adjusted within the above-mentioned range by supercalender treatment, etc., which will be described later.

The basis weight of the heat seal paper is preferably 40 g/m ² to 130 g/m ² , more preferably 70 g/m ² to 120 g/m ² , and 80 g/m ² to 120 g/m ² It is even more preferable. When the basis weight is at least the above lower limit, the strength becomes high, and tearing during molding can be further suppressed. On the other hand, when the basis weight is below the above upper limit, the strength is appropriately strong and wrinkling during molding can be further suppressed. Therefore, within the above numerical range, moldability can be improved.

The thickness of the heat seal paper is preferably 50 μm to 300 μm, more preferably 60 μm to 200 μm, even more preferably 70 μm to 150 μm, even more preferably 100 μm to 140 μm.

The density of the heat seal paper is preferably 0.40 g/m ³ to 1.00 g/m ³ , more preferably 0.60 g/m ³ to 0.90 g/m ³ , and 0.70 g/m 3 More preferably, it is m ³ to 0.85 g/m ³ .

<Method for manufacturing heat seal paper>
The method for producing heat seal paper of this embodiment includes a coating step of coating a heat seal layer on at least one surface of the paper base material obtained as described above. Note that the heat-seal layer coating liquid (heat-seal layer coating) may be applied two or more times.

When forming multiple heat-sealing layers on a paper base material, the above method of sequentially forming the heat-sealing layers is preferred, but the method is not limited to this, and a simultaneous multilayer coating method may also be adopted. . Simultaneous multilayer coating method involves discharging multiple types of coating liquids separately from slit-shaped nozzles to form a liquid laminate, which is then applied onto a paper base material to create a multilayer heat coating. This method forms a seal layer at the same time.

There is no particular limitation on the coating equipment for applying the heat seal layer coating liquid to the paper base material, and any known equipment may be used. Examples of coating equipment include a blade coater, a bar coater, an air knife coater, a slit die coater, a gravure coater, a microgravure coater, a roll coater, a size press, a gate roll coater, and a shim sizer.

The drying equipment for drying the heat seal layer is not particularly limited, and any known equipment can be used. Examples of the drying equipment include a hot air dryer, an infrared dryer, a gas burner, and a hot plate. Further, the drying temperature may be appropriately set in consideration of the drying time and the like.

The solvent for the heat seal layer coating liquid is not particularly limited, and water or organic solvents such as ethanol, isopropyl alcohol, methyl ethyl ketone, and toluene can be used. Among these, water is preferred as the dispersion medium for the heat seal layer coating liquid from the viewpoint of not causing the problem of volatile organic solvents. That is, it is preferable that the heat-seal layer coating liquid is an aqueous composition for heat-seal layers.

The solid content (solid content concentration) of the heat seal layer coating liquid is not particularly limited, and may be selected appropriately from the viewpoint of coatability and ease of drying, but is preferably 10% by mass or more, more preferably 20% by mass. % or more, more preferably 30% by mass or more, and preferably 80% by mass or less, more preferably 60% by mass or less, still more preferably 50% by mass or less, even more preferably 40% by mass or less.

The preferred range of the coating amount (after drying) of the heat seal layer is as described above. The number of heat seal layers may be one layer, or two or more layers. When there are two or more heat-sealing layers, the above coating amount represents the total coating amount.

It is also preferable to perform a supercalender treatment after coating and drying the heat seal layer. Here, supercalender processing is installed independently from papermaking, and generally involves passing the paper to be processed between metal rolls or between a metal roll and an elastic roll, and applying heat, pressure, etc. It is something to do. The supercalender treatment may be performed in one stage or in multiple stages, and is not particularly limited.
Super calendering is preferable because it improves the smoothness of the heat-seal layer surface, resulting in improved heat-seal peel strength and hot tack properties (difficulty in peeling off immediately after heat-sealing).
Also, the smoothness of the surface opposite to the heat-sealing layer (for example, if the heat-sealing layer is provided only on one side of the paper base material and the paper base material is exposed on the other side, the surface of the paper base material) This is preferable because it improves properties and, as a result, improves printability.
Furthermore, supercalendering tends to increase the density of heat-seal paper, and as mentioned above, improves surface smoothness. This is preferable because it improves processing suitability.

The linear pressure in supercalendering is preferably 10 kg/cm or more, more preferably 30 kg/cm or more, even more preferably 50 kg/cm or more, and preferably 1000 kg/cm or less, more preferably 500 kg/cm or less, More preferably, it is 200 kg/cm or less. However, the above linear pressure may be changed as appropriate depending on the desired smoothness and density.
In addition, when heating is performed in the super calendar treatment, the heating temperature is not particularly limited, but it is preferable from the viewpoint of increasing the effect of the treatment and preventing heat-induced deterioration of the paper base material and the heat-sealing layer and preventing the heat-sealing layer from sticking. is 20°C or higher, more preferably 30°C or higher, even more preferably 35°C or higher, and is preferably 80°C or lower, more preferably 70°C or lower, even more preferably 60°C or lower.

The use of the obtained heat seal paper is not particularly limited, and by forming it into an appropriate molded product, it can be used for paper processed products such as packaging paper, packaging bags, packaging containers, etc., and various containers such as cups and trays. . For example, paper containers such as paper plates, paper cups, and paper trays, horizontal pillow packaging, vertical pillow packaging, three-sided seal packaging, four-sided seal packaging, bag feeding type filling packaging, tube packaging, and stick packaging. Can be used for bags, etc. In particular, since it has excellent flexibility and drop impact resistance, it can be suitably used in the above-mentioned bag applications.

Below, methods for measuring each physical property will be described.
<ISO stiffness>
The longitudinal and transverse ISO stiffness of paper substrates and heat-sealed papers is measured in accordance with ISO 2493-1:2010 (Paper and paperboard - Bending resistance test method - Part 1: Constant speed deflection).
Specifically, as a temperature and humidity control process, a paper base material or heat-sealed paper that had been left for one day in an environment of 23 ± 5 ° C. and 50 ± 10% was cut into a sample with a width of 38 mm and a length of 70 mm. Prepare. Using a stiffness tester (L&W BENDING RESISTANCE TESTER code No. 16-D, manufactured by Lorentzen & Wattre), the bending length was set to 10 mm and the bending angle was set to 15°, and then MD (vertical direction) and CD (horizontal direction) were measured. After measuring each bending drag force, the ISO stiffness is calculated using the following formula.

<Puncture strength/specific puncture strength>
The puncture strength of the paper base material and heat seal paper is measured in accordance with JIS Z 1707:2019 (General rules for plastic films for food packaging).
Specifically, as a temperature and humidity control process, a paper base material or heat-sealed paper that had been left for one day in an environment of 23±5°C and 50±10% was tested using a tensile tester (model RTC-1210A). The puncture strength is measured using a puncture jig (manufactured by A&D Co., Ltd.) at a puncture speed of 50 mm/min.
Further, the specific puncture strength is calculated by dividing the puncture strength by the basis weight.

<Length weighted average fiber length of pulp>
The length weighted average fiber length of the pulp in paper substrates and heat seal papers is measured according to ISO 16065-2:2007. Specifically, the details are as follows.
A paper base material or heat seal paper is cut into 40 cm square pieces, immersed in ion-exchanged water, adjusted to a solid content concentration of 2% by mass, and then immersed for 24 hours. After soaking for 24 hours, a standard disintegrator (manufactured by Kumagai Riki Kogyo Co., Ltd.) is used to perform disintegration treatment for 30 minutes to disintegrate the pulp into fibers.
Using the obtained pulp fiber sample, the "length-weighted average fiber length (ISO)" is measured using a fiber length measuring machine (Model FS-5 with UHD base unit, manufactured by Valmet). Note that "length-weighted average fiber length (ISO)" is a length-weighted average fiber length calculated by selecting fibers with a length of 0.2 mm or more and 7.6 mm or less.

<Basic weight>
The basis weight of the paper base material and heat seal paper is measured in accordance with JIS P 8124:2011.

<Thickness>
The thickness of the paper base material and heat seal paper (paper thickness) is measured in accordance with JIS P 8118:2014.

<Density>
The density of the paper base material and heat seal paper is calculated from the thickness and basis weight obtained by the above-mentioned measuring method.

EXAMPLES The features of the present invention will be explained in more detail below with reference to Examples and Comparative Examples. The materials, usage amounts, proportions, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below. Furthermore, unless otherwise specified, "parts" represent "parts by mass." Further, the operations in Examples and Comparative Examples were carried out at room temperature (20 to 25°C) and normal humidity (40 to 50% RH) unless otherwise specified.

<Example 1>
[Manufacture of paper base material]
Using NUKP (softwood unbleached kraft pulp) and LUKP (hardwood unbleached kraft pulp) made by pulping (cooking) wood at a ratio (mass ratio) of 55:45, at a slurry concentration of 2% by mass during beating, Pulp was prepared by beating until the CSF (Canadian Standard Freeness) was 600 mL.
Using the above pulp, per 100 parts of pulp in terms of solid content, 0.15 parts of synthetic sizing agent (manufactured by Arakawa Chemical Co., Ltd., SPS400), 1.2 parts of sulfuric acid, and polyacrylamide resin (Seiko PMC) as a retention agent. A paper stock was prepared by adding 0.65 parts of DS4433, manufactured by Co., Ltd., and 0.035 parts of nonionic polyacrylamide (Percoll 47, manufactured by Allied Colloid) as a polymer flocculant (retention agent).
The above paper stock was processed using a wet paper machine (Belform III type, manufactured by Mitsubishi Heavy Industries, Ltd.) equipped with an expansion and contraction device (manufactured by Kurupak) at a papermaking speed of 600 m/min and a reel moisture content of 7.0%. Paper was made with a speed difference of -20 m/min before and after, and a nip pressure of 15 kN/m between the nip roll and the blanket during Kurupak processing, to obtain a paper base with a basis weight of 80 g/m ² with crepe applied to the surface of the paper. Ta.
[Preparation of heat seal layer paint]
Aqueous dispersion of styrene/butadiene copolymer (manufactured by Nippon Zeon Co., Ltd., Nipol Latex LX407S12, solid content concentration 46% by mass, glass transition temperature 18°C (catalog value)) 98 parts (solid content equivalent), paraffin wax emulsion (manufactured by Chukyo Yushi Co., Ltd., Hydrin L-700, solid content concentration 30% by mass) were mixed (in terms of solid content), water was added and stirred so that the solid content concentration was 33% by mass, and the heat seal layer was A paint (solid content concentration 33% by mass) was prepared. The styrene/butadiene copolymer had a solubility in water at 25° C. of 10 g/L or less.
[Manufacture of heat seal paper]
The obtained heat seal layer paint was applied to the W side of the paper base material to form a heat seal layer using an air knife coater so that the coated amount of the heat seal layer after drying was 10 g/m ² .
Dry with a dryer at 160°C, and finally apply a linear pressure of 90kg/cm so that the coated surface is in contact with a chilled roll and the non-coated surface is in contact with a cotton roll.The rolls are heated to 40°C and dried in one stage. A heat seal paper was obtained by super calendering.

<Example 2>
Heat-sealed paper was obtained under the same conditions as in Example 1, except that the paper base material was produced by changing the speed difference before and after the Kurupak treatment to -28.0 m/min.

<Example 3>
Heat-sealed paper was obtained under the same conditions as in Example 1, except that the paper base material was produced by changing the speed difference before and after the Kurupak treatment to -30.0 m/min.

<Example 4>
The conditions were the same as in Example 1, except that the speed difference before and after the Krupack treatment was changed to -37.0 m/min, and the basis weight was changed to 100 g/m ² by adjusting the pulp discharge rate to produce the paper base material. A heat seal paper was obtained.

<Example 5>
Heat seal paper was obtained under the same conditions as in Example 1, except that the paper base material was produced by beating until the CSF (Canadian Standard Freeness) after beating became 380 mL.

<Example 6>
The mass ratio of NUKP (softwood unbleached kraft pulp) made by pulping (cooking) wood and LUKP (hardwood unbleached kraft pulp) was changed to 40:60, and the speed difference before and after the Clupak treatment was changed to -25.0 m/min. A heat seal paper was obtained under the same conditions as in Example 1, except that the paper base material was manufactured using the same method as in Example 1.

<Example 7>
The mass ratio of NUKP (softwood unbleached kraft pulp) made by pulping (cooking) wood and LUKP (hardwood unbleached kraft pulp) was changed to 90:10, and the speed difference before and after the Clupak treatment was changed to -40.0 m/min. A heat seal paper was obtained under the same conditions as in Example 1, except that the paper base material was manufactured using the same method as in Example 1.

<Example 8>
The conditions were the same as in Example 1, except that the speed difference before and after the Krupack treatment was changed to -16.0 m/min, and the paper base material was manufactured with a basis weight of 50 g/ ^m2 by adjusting the pulp discharge rate. A heat seal paper was obtained.

<Example 9>
The mass ratio of NUKP (softwood unbleached kraft pulp) made by pulping (cooking) wood and LUKP (hardwood unbleached kraft pulp) was changed to 30:70, and the speed difference before and after the Clupak treatment was changed to -25.0 m/min. A heat seal paper was obtained under the same conditions as in Example 1, except that the paper base material was manufactured using the same method as in Example 1.

<Example 10>
The mass ratio of NUKP (softwood unbleached kraft pulp) made by pulping (cooking) wood and LUKP (hardwood unbleached kraft pulp) was changed to 100:0, and the speed difference before and after the Clupak treatment was changed to -40.0 m/min. A heat seal paper was obtained under the same conditions as in Example 1, except that the paper base material was manufactured using the same method as in Example 1.

<Example 11>
98 parts (in terms of solid content) of a commercially available aqueous dispersion of ethylene-acrylic acid copolymer A (glass transition temperature 45°C) and 2 parts (in terms of solid content) of a commercially available aqueous dispersion of carnauba wax were mixed, and a solid Water was added and stirred so that the solid content was 35% by mass to prepare a heat seal layer coating (solid content 35% by mass). Heat-seal layer formation and supercalender treatment were performed in the same manner as in Example 2, except that the obtained heat-seal layer coating material was used, and heat-seal paper was obtained.

<Example 12>
Instead of 2 parts of paraffin wax emulsion (in terms of solid content), 2 parts of polyethylene wax emulsion (Aquacer 531, manufactured by BYK, solid content concentration 45% by mass) (
Heat-seal layer formation and supercalender treatment were performed in the same manner as in Example 2, except that a heat-seal layer coating material was prepared by adding a heat-seal layer coating material (in terms of solid content) to obtain heat-seal paper.

<Example 13>
Heat-sealing layer formation and supercalender treatment were performed in the same manner as in Example 2, except that no paraffin wax emulsion was added, to obtain heat-sealing paper.

<Example 14>
Instead of the aqueous dispersion of styrene/butadiene copolymer in the heat seal layer coating, an aqueous dispersion of ethylene/vinyl acetate copolymer (manufactured by Sumika Chemtex Co., Ltd., Sumikaflex 470HQ, solid content concentration 55% by mass, glass A heat-sealing paper was obtained by forming a heat-sealing layer and performing a supercalender treatment in the same manner as in Example 2, except that the transition temperature was 0° C. (catalog value) and the paraffin wax emulsion was not used.

<Example 15>
Aqueous dispersion of styrene/butadiene copolymer (manufactured by Nippon Zeon Co., Ltd., Nipol Latex LX407S12, solid content concentration 46% by mass, glass transition temperature 18°C (catalog value)) 98 parts (solid content equivalent), carnauba wax emulsion (ML160RPH, manufactured by Michael Mann, solid content concentration 25% by mass) were mixed (in terms of solid content), water was added and stirred so that the solid content concentration was 33% by mass, and the heat seal layer paint (solid content A heat-sealing paper was obtained by forming a heat-sealing layer and performing a super-calendering treatment in the same manner as in Example 2, except that a concentration of 33% by mass) was prepared.

<Example 16>
Aqueous dispersion of styrene/butadiene copolymer (manufactured by Nippon Zeon Co., Ltd., Nipol Latex LX407S12, solid content concentration 46% by mass, glass transition temperature 18°C (catalog value)) 88 parts (solid content equivalent), paraffin wax emulsion (manufactured by Chukyo Yushi Co., Ltd., Hydrin L-700, solid content concentration 30% by mass) 2 parts (solid content equivalent), kaolin (manufactured by Imerys Co., Ltd., Conzer Extreme, average particle size 8 μm, aspect ratio 80-100, solid content 50 Mix 10 parts (solid content equivalent) of 10 parts (dispersed in water so that the solid content concentration is 33 mass %), add water and stir so that the solid content concentration is 33 mass %, and heat seal layer paint (solid content concentration 33 mass %) A heat-sealing paper was obtained by forming a heat-sealing layer and performing a supercalender treatment in the same manner as in Example 2, except for preparing the paper.

<Example 17>
A heat seal paper was obtained in the same manner as in Example 2 except that the super calender treatment was not performed after the heat seal layer was formed.

<Comparative example 1>
By changing the mass ratio of NUKP (softwood unbleached kraft pulp) made by pulping (cooking) wood and LUKP (hardwood unbleached kraft pulp) to 45:55, and adjusting the pulp discharge rate without performing Clupak treatment. Heat seal paper was obtained under the same conditions as in Example 1, except that the paper base material was manufactured with a basis weight of 30 g/m ² .

<Comparative example 2>
Except that the mass ratio of NUKP (softwood unbleached kraft pulp) made by pulping (cooking) wood and LUKP (hardwood unbleached kraft pulp) was changed to 45:55, and the paper base material was manufactured without performing Clupak treatment. Heat seal paper was obtained under the same conditions as in Example 1.

<Comparative example 3>
By changing the mass ratio of NUKP (softwood unbleached kraft pulp) made by pulping (cooking) wood and LUKP (hardwood unbleached kraft pulp) to 45:55, and adjusting the pulp discharge rate without performing Clupak treatment. Heat seal paper was obtained under the same conditions as in Example 1, except that the paper base material was manufactured with a basis weight of 100 g/m ² .

<Comparative example 4>
The mass ratio of NUKP (softwood unbleached kraft pulp) made by pulping (cooking) wood and LUKP (hardwood unbleached kraft pulp) was changed to 45:55, and the speed difference before and after the Clupak treatment was changed to -15.0 m/min. A heat seal paper was obtained under the same conditions as in Example 1, except that the paper base material was manufactured using the same method as in Example 1.

<Comparative example 5>
The paper substrate produced in Example 2 was used as is.

The following evaluations were performed using the obtained heat seal paper or paper base material.
<Bag flexibility evaluation>
The obtained heat seal paper or paper base material was cut out to obtain a sheet 1 having a length of 200 mm in the machine direction (MD) and 150 mm in the cross direction (CD). Attach double-sided tape 2 (model: Scotch super strong double-sided tape Premier Gold Super Versatile PPS-10, manufactured by 3M) with a width of 10 mm to sheet 1 as shown in Figure 1, and then Bag 3 was obtained by folding the bag in half at a position 100 mm from the edge and fixing it so that no gap was left.
The bag 3 was filled with water, and the amount filled until water spilled was evaluated. The larger the value, the better.
4: The amount of water filled is 150 mL or more.
3: The amount of water filled is 100 mL or more and less than 150 mL.
2: The amount of water filled is 50 mL or more and less than 100 mL.
1: The amount of water filled is less than 50 mL.

<Drop impact resistance evaluation>
A bag similar to Bag 3 prepared in the above <Bag Flexibility Evaluation> was produced from the obtained heat seal paper or paper base material. Fill bag 3 with one disc-shaped weight (product number: 201900401, manufactured by Murakami Koki Seisakusho Co., Ltd.) weighing 50 g, seal it with the 10 mm wide double-sided tape used in <Bag flexibility evaluation>, and fill with the weight. A bag was made. The bag filled with weights was left standing in an environment of 23±5° C. and 50±10% for one day as a temperature and humidity control treatment.
The bag after temperature and humidity control treatment was dropped onto a SUS board from a height of 30 cm with the top surface 4 (filling port) of the bag facing upward. Furthermore, the dropped bag was dropped in the same manner, this time with the bottom surface 5 of the bag facing upward. The above drop test (the number of drops was 2 times per bag) was conducted for a total of 5 tests per level using newly produced bags to evaluate the drop impact resistance. The larger the value, the better. In the table, "-" indicates that sealing was not possible and measurement was not possible.
In all 4:5 tests, there were no tears or dents in the bag.
In all 3:5 tests, no tears occurred in the bag, but dents did occur.
In the 2:1 to 4 tests, the bag was torn.
In all 1:5 tests, the bags were torn.

[Heat seal peel strength]
Stack two sheets of heat-seal paper so that the heat-seal layers face each other, and heat them at 150°C, 0.2 MPa, and 1 second using a heat-seal tester (manufactured by Tester Sangyo, TP-701-B). I sealed it. The heat-sealed test piece was left standing in a room at a temperature of 23° C.±1° C. and a humidity of 50%±2% for 4 hours or more. Subsequently, the heat-sealed test piece was cut to a width of 15 mm, and was subjected to T-peeling at a tensile speed of 300 mm/min using a tensile testing machine, and the maximum load recorded was taken as the heat-sealing peel strength. In the table, "-" indicates that no adhesion occurred and measurement was not possible.

[Automatic packaging moldability]
Heat-seal paper was continuously made into bags using a high-speed horizontal pillow packaging machine (αWrapper FW3410, manufactured by Fujikikai Co., Ltd.). At this time, the bag was molded using an empty bag without filling, and the following judgments were made based on the appearance and operability. Here, "unable to make bags continuously" refers to a state in which wrinkles occur, the bag is meandered so that it cannot be made into a bag, or paper breakage occurs. Furthermore, "poor appearance" refers to wrinkles, misalignment of the seal, or deformation of the bag.
A: Continuous bag making was possible, and the bag had a good appearance.
B: Although it was possible to make bags continuously, there were a few cases where the appearance of the bags was poor.
C: Continuous bag making was impossible.

Table 1 shows the physical properties and evaluation results of Examples 1 to 17 and Comparative Examples 1 to 5.

1: sheet, 2: double-sided tape, 3: bag, 4: top of bag, 5: bottom of bag

Although conventional paper such as that disclosed in Patent Document 1 has excellent flexibility, it has low puncture strength, and has insufficient drop impact resistance when the bag is filled with a product, for example, in the manufacture of bags for pillow packaging. Normally, paper with high puncture strength tends to become hard and has poor flexibility, so it has been difficult to achieve both drop impact resistance and flexibility.
The present disclosure relates to a paper base material that can provide a heat seal paper that has drop impact resistance and excellent flexibility, a heat seal paper using the paper base material, and a paper processed product using the heat seal paper. Regarding.

According to the present disclosure, it is possible to provide a paper base material that can provide heat seal paper that has drop impact resistance and is also excellent in flexibility. Further, according to the present disclosure, it is possible to provide a heat seal paper that has excellent moldability in automatic packaging.

Claims (12)

A heat-sealing paper having one or more heat-sealing layers on at least one surface of a paper base material,
The heat seal layer contains a water-dispersible resin binder,
The ISO stiffness of the heat seal paper in the longitudinal direction, measured in accordance with ISO2493-1:2010, is 0.55 mNm or less, and the ISO stiffness of the heat seal paper in the lateral direction is 0.45 mNm or less. ,
The puncture strength of the heat seal paper is 7.5N or more, as measured in accordance with JIS Z 1707:2019.
heat seal paper. The ISO stiffness in the longitudinal direction is 0.05 to 0.20 mNm,
The ISO stiffness in the lateral direction is 0.05 to 0.20 mNm,
The heat seal paper according to claim 1. The heat seal paper according to claim 1, having a puncture strength of 12.5N or more. The pulp obtained by disintegrating the heat seal paper has a length-weighted average fiber length of 1.2 mm to 2.0 mm as measured in accordance with ISO 16065-2:2007. heat seal paper. The heat seal paper according to claim 1, having a basis weight of 40 g/m ² to 130 g/m ² . The heat seal paper according to claim 1, having a specific puncture strength of 0.12 N/g or more. The heat-sealing paper of claim 1, wherein the heat-sealing layer further includes a lubricant. The heat seal paper according to claim 7, wherein the lubricant includes at least one selected from the group consisting of paraffin wax, carnauba wax, and polyolefin wax. The heat seal paper according to claim 7, wherein the content of the lubricant in the heat seal layer is 1% by mass or more and 5% by mass or less. The heat seal paper according to claim 1, wherein the water-dispersible resin binder has a glass transition temperature of 0°C or more and 100°C or less. Claim 1, wherein the water-dispersible resin binder contains at least one selected from the group consisting of styrene-butadiene copolymer, olefin-fatty acid vinyl ester copolymer, and olefin-unsaturated carboxylic acid copolymer. Heat seal paper as described in . A processed paper product using the heat seal paper according to any one of claims 1 to 11.

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