JP7243901B1 - Heat seal paper and processed paper products - Google Patents

Abstract

A heat-sealable paper having drop impact resistance, excellent flexibility, and excellent heat-sealability. A heat-sealable paper having one or more heat-sealable layers on at least one surface of a paper substrate, wherein the heat-sealable layer contains a water-dispersible resin binder and conforms to ISO2493-1:2010. The ISO stiffness in the longitudinal direction of the heat-sealed paper is 0.55 mNm or less, and the ISO stiffness in the transverse direction of the heat-sealed paper is 0.45 mNm or less, measured in accordance with JIS Z 1707:2019. The heat seal paper has a puncture strength of 7.5 N or more, as measured in accordance with the above. [Selection figure] None

Description

The present disclosure relates to heat-sealable paper and paper products.

Plastic materials have been mainly used for packaging containers such as food trays and packaging bodies such as pillow packaging bags. However, due to concerns about the environment, paper packaging materials are now being investigated in place of plastic containers.

WO2015/008703

Although conventional paper such as that disclosed in Patent Document 1 has excellent flexibility, it has low puncture strength, and, for example, in the production of bags for pillow packaging, the drop impact resistance is insufficient when the bag is filled with a product. Normally, paper with high puncture strength tends to harden and is inferior in flexibility, so it has been difficult to achieve both drop impact resistance and flexibility.
The present disclosure provides a paper substrate that can provide heat-sealed paper having drop impact resistance and excellent flexibility, heat-sealed paper using the paper substrate, and processed paper products using the heat-sealed paper. Regarding.

That is, the present disclosure relates to the following <1> to <12>.
<1> A heat-sealable paper having one or more heat-sealable layers on at least one surface of a paper substrate,
The heat seal layer contains a water-dispersible resin binder,
The ISO stiffness in the longitudinal direction of the heat seal paper is 0.55 mNm or less, and the ISO stiffness in the transverse direction of the heat seal paper is 0.45 mNm or less, measured in accordance with ISO2493-1:2010. ,
The heat seal paper has a puncture strength of 7.5 N or more, as measured in accordance with JIS Z 1707:2019.
heat seal paper.
<2> The ISO stiffness in the vertical direction is 0.05 to 0.20 mNm,
a lateral ISO stiffness of 0.05 to 0.20 mNm;
The heat seal paper according to <1>.
<3> The heat-sealable paper according to <1> or <2>, which has a puncture strength of 12.5 N or more. <4> The pulp obtained by defibrating the heat seal paper has a length-weighted average fiber length of 1.2 mm to 2.0 mm measured according to ISO 16065-2:2007. > The heat seal paper according to any one of <3>.
<5> The heat-sealable paper according to any one of <1> to <4>, which has a basis weight of 40 g/m ² to 130 g/m ² .
<6> The heat-sealable 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-sealable paper according to any one of <1> to <6>, wherein the heat-sealable layer further contains a lubricant.
<8> The heat-sealable paper according to <7>, wherein the lubricant contains 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-sealable 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 copolymers, olefin-fatty acid vinyl ester copolymers, and olefin-unsaturated carboxylic acid copolymers. The heat seal paper according to any one of <1> to <10>.
<12> A processed paper product using the heat-sealable paper according to any one of <1> to <11>.

According to the present disclosure, it is possible to provide a paper substrate capable of providing heat-sealable paper having drop impact resistance and excellent flexibility. Moreover, according to the present disclosure, it is possible to provide a heat-sealable paper having excellent formability in automatic packaging.

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

In the present disclosure, the descriptions of “X or more and Y or less” or “X to Y” representing numerical ranges mean numerical ranges including the lower and upper limits, which are endpoints, unless otherwise specified. When numerical ranges are stated stepwise, the upper and lower limits of each numerical range can be combined arbitrarily.
The machine direction is the machine direction (MD) of the paper substrate, which is the same as the direction in which the fibers are oriented. The transverse direction is the direction (CD) perpendicular to the papermaking direction. The longitudinal direction of the heat-sealed paper is the direction corresponding to the MD direction of the paper substrate, and the lateral direction of the heat-sealed paper is the direction corresponding to the CD direction of the paper substrate.
The term "excellent moldability in automatic packaging (hereinafter also referred to as automatic packaging moldability)" means that bags can be continuously produced by an automatic packaging machine and the appearance of the resulting bag is good. means. More specifically, for example, when automatically forming a packaging bag, the occurrence of wrinkles and poor appearance is suppressed, sticking to a molding machine (blocking) is suppressed, and moldability is excellent. Furthermore, it means that the quality of the obtained packaging bag is excellent, such as suppression of deformation of the bag after bag making, and the productivity is also excellent.

The Clupak treatment is a treatment that imparts elongation performance by finely shrinking paper on a paper machine. Specifically, for example, part of a paper machine dryer is equipped with a Clupak device comprising an endless thick elastic rubber blanket with nip rolls. The wet paper web is introduced into the Clupak machine and compressed with nip rolls and blankets. At this time, the pre-stretched blanket shrinks, thereby shrinking the running paper web (creating crepe) and increasing the elongation at break. In addition, the resulting shrinkage is dried and fixed so that it will not stretch in the subsequent process.

The present inventors have found that the above problems can be solved by controlling the heat-sealable paper to a specific ISO stiffness and puncture strength through the Clupak treatment during the production of the paper base material used for the heat-sealable paper. The ISO stiffness indicates the ease with which the paper is folded, and the puncture strength indicates the resistance to tearing of the paper. The fact that the heat-sealable paper has the specific ISO stiffness and puncture strength indicates that the paper is moderately foldable and resistant to tearing. Therefore, the present inventors believe that a heat-sealable paper having excellent flexibility and drop impact resistance can be obtained.

IS in the machine 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 transverse ISO stiffness of the heat seal paper is 0.45 mNm or less.
When the ISO stiffness exceeds the above upper limit, it becomes difficult to bend and flexibility decreases.

The ISO stiffness of heat-sealable paper can be controlled by the manufacturing conditions of the paper substrate used. Specifically, the CSF (Canadian Standard Freeness) of the pulp, the basis weight, the speed difference before and after Clupak treatment, and the paper substrate. It can be controlled by the mass ratio of hardwood kraft pulp and softwood kraft pulp. In order to increase the ISO stiffness, there are methods such as lowering the CSF of the pulp, increasing the basis weight, increasing the speed difference before and after Clupak processing, and increasing the mass ratio of the softwood kraft pulp that constitutes the paper base material. be done. On the other hand, in order to reduce the ISO stiffness, there are methods such as increasing the CSF of the pulp, decreasing the basis weight, decreasing the speed difference before and after Clupak processing, and decreasing the mass ratio of the softwood kraft pulp that constitutes the paper base material. mentioned.

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

The puncture strength of the heat-sealed paper, measured according to JIS Z 1707:2019, must be 7.5 N or more.
If the puncture strength is less than the above lower limit, dents and tears are likely to occur, and the drop impact resistance is reduced.

The puncture strength of heat-sealable paper can be controlled by the manufacturing conditions of the paper substrate used. Specifically, it is controlled by the basis weight, the speed difference before and after Clupak processing, the content of softwood kraft pulp, and the nip pressure during Clupak processing. can do. To increase the puncture strength, there are methods such as increasing the basis weight, increasing the speed difference before and after Clupak treatment, increasing the content of softwood kraft pulp, and decreasing the nip pressure during Clupak treatment. On the other hand, in order to reduce the puncture strength, there are methods such as reducing the basis weight, reducing the speed difference before and after Clupak treatment, reducing the content of softwood kraft pulp, and increasing the nip pressure during Clupak 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. Although the upper limit of the puncture strength is not particularly limited, it is preferably 18.0 N or less from the viewpoint of cushioning properties.

The pulp obtained by defibrating the heat-sealable paper preferably has a length weighted average fiber length of 1.2 mm to 2.0 mm as measured according to ISO 16065-2:2007.
If the length-weighted average fiber length is less than the above lower limit, the strength is low and the drop impact resistance is deteriorated, but the flexibility is increased. If the length-weighted average fiber length exceeds the above upper limit, the strength is high and the drop impact resistance is improved, but on the other hand, the flexibility tends 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 pulp can be controlled by the type of pulp used.

The specific puncture strength of the heat-sealable paper is preferably 0.05 N/g or more, more preferably 0.10 N/g or more, and even more preferably, from the viewpoint of achieving a high degree of both bag flexibility and drop impact resistance. is 0.12 N/g or more, and more preferably 0.13 N/g or more. Although the upper limit of the specific puncture strength is not particularly limited, it is preferably 0.30 N/g or less from the viewpoint of cushioning properties. Within the above range, the flexibility and drop impact resistance are excellent.
The specific puncture strength is a value obtained by dividing the puncture strength by the basis weight.

[Paper substrate]
The basis weight of the paper substrate used for the 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 more preferably 70 g/m ² to 100 g. /m ² is more preferred. If the basis weight is less than the above lower limit, the strength is low and the drop impact resistance is deteriorated, but on the other hand the flexibility is increased. If the basis weight exceeds the above upper limit, the strength is high and the drop impact resistance is improved, but the flexibility tends to deteriorate. Within the above range, both bag flexibility and drop impact resistance can be achieved.

The thickness of the paper substrate used for 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, and further preferably 100 μm to 140 μm. more preferred.

The density of the paper substrate used for the 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 0.50 g/m ³ to 0.80 g/m ³ , and even more preferably 0.60 g/m ³ to 0.70 μmg/m ³ .

The ISO stiffness in the machine direction of the paper base used for heat-sealable paper, measured according to ISO2493-1:2010, is preferably 0.05 to 0.70 mNm, preferably 0.08 to 0.60 mNm. and more preferably 0.10 to 0.20 mNm.
In addition, the transverse ISO stiffness of the paper substrate used for the heat-sealable paper, measured according to ISO2493-1:2010, is preferably 0.05 to 0.45 mNm, preferably 0.08 to 0 0.35 mNm is more preferred, and 0.10 to 0.20 mNm is even more preferred.
When the ISO stiffness is within the above range, the heat-sealed paper can be easily folded and the flexibility is improved.

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

The specific pin puncture strength of the paper substrate used for the heat seal paper is preferably 0.05 N/g or more, more preferably 0.10 N/g or more, and further 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-sealable paper are improved.
Although the upper limit of the specific puncture strength of the paper substrate is not particularly limited, it is preferably 0.30 N/g or less from the viewpoint of cushioning properties.

Next, materials that can be used for the paper substrate will be described. Paper substrates contain, for example, pulp.
Pulp constituting the paper substrate includes hardwood kraft pulp such as unbleached hardwood kraft pulp (LUKP) and bleached hardwood kraft pulp (LBKP); softwood unbleached kraft pulp (N
UKP), softwood kraft pulp such as bleached kraft pulp (NBKP); groundwood pulp (GP), pressure groundwood pulp (PGW), refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP) ), chemi-mechanical pulp (CMP), and chemi-grand pulp (CGP); waste paper pulp; non-wood fiber pulp such as kenaf, bagasse, bamboo, and cotton; and synthetic pulp. These pulps may be used individually by 1 type, and may be used in combination of 2 or more type.

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

The softwood kraft pulp content 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 still 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, and even more preferably 85% by mass or less.

The hardwood kraft pulp content 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, and even more preferably 60% by mass or less.

The beating degree of the pulp is not particularly limited, but is preferably 200 to 800 mL, more preferably 300 to 700 mL, in terms of 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 substrate as 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 agent (rosin type, alkyl ketene dimer, etc.), drainage retention improver (polyacrylamide resin), antifoaming agent, filler (calcium carbonate, talc, etc.), dye, etc. mentioned. These additives may be used singly or in combination of two or more. The content of the additive is not particularly limited as long as it is within a commonly used range.

<Method for producing paper substrate>
As a method for producing a paper base material, there is a method in which a pulp-containing stock is made into paper, and the paper is subjected to Clupak treatment during paper making. In addition, the paper material may further contain an additive as needed. Additives include, for example, the additives described above. The paper stock can be prepared by adding additives to the pulp slurry as required. Pulp slurry is obtained by beating pulp in the presence of water. The pulp beating method and beating apparatus are not particularly limited, and known beating methods and beating apparatuses 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. Moreover, the content of pulp in the paper stock or paper substrate is not particularly limited, and may be within the range normally used. 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, relative to the total mass of the stock (solid content) or paper substrate.

In the papermaking of the paper substrate, a known wet papermaking machine can be appropriately selected and used. The paper machine includes a fourdrinier paper machine, a gap former paper machine, a cylinder paper machine, a short mesh paper machine and the like. A Clupak device capable of performing the Clupak treatment may be installed in these paper machines to perform the Clupak treatment.

A known Clupak device can be used. For example, a Clupak device with a nip roll and an endless thick elastic rubber blanket. As described above, in the Clupak treatment, the paper web is carried between the nip roll and the blanket, and when the paper web is compressed by the nip roll and the blanket, the pre-stretched blanket is contracted to shrink the paper web. to give crepe. The Clupak device is usually installed in a part of the dryer device of the paper machine to crepe, dry and fix. A paper substrate can be obtained in the manner described above.

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

The calender nip pressure is not particularly limited, and may be controlled according to basis weight, pulp material, speed difference before and after Clupak treatment, etc., so as to obtain desired ISO stiffness and puncture strength. It is preferably 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 according to basis weight, pulp material, speed difference before and after Clupak treatment, etc., so as to obtain desired ISO stiffness and puncture strength. It is preferably 2.0 to 12.0%, more preferably 5.0 to 9.0%.

[Heat seal layer]
The heat-sealable paper of this embodiment has at least one heat-sealable layer on at least one surface of the paper substrate. The heat-seal layer is a layer that is melted by heat, ultrasonic waves, or the like and adheres.

(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 is finely dispersed in water like an emulsion or suspension. Binder. By applying a water-based coating to the heat-seal layer using a water-dispersible resin binder, it is possible to obtain heat-sealable paper that is excellent in re-disaggregation and can be recycled as paper. If the water-dispersible resin binder also corresponds to the following lubricant, it shall be classified as a lubricant.

The water-dispersible resin binder is not particularly limited as long as it exhibits the effect of the present invention, but polyolefin-based resins (polyethylene, polypropylene, etc.), vinyl chloride-based resins, styrene-based resins, styrene-butadiene copolymers, Styrene-unsaturated carboxylic acid copolymer (for example, styrene-(meth)acrylic acid copolymer), acrylic resin, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, ABS resin, 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 resins, acetal resins, polyphenylene oxide resins, polyester resins (polyethylene terephthalate, polybutylene terephthalate, etc.), polyphenylene sulfide resins, polyimide resins, polysulfone resins, polyethersulfone resins, polyarylate resins , olefin-fatty acid vinyl ester copolymers, olefin-unsaturated carboxylic acid copolymers, modified products thereof, and the like. These may be used individually by 1 type, and may use 2 or more types together.
Among these, at least one selected from the group consisting of styrene-butadiene copolymers, olefin-fatty acid vinyl ester copolymers and olefin-unsaturated carboxylic acid copolymers is preferable, and styrene-butadiene copolymers, and at least one selected from the group consisting of olefin-unsaturated carboxylic acid copolymers.
Furthermore, from the viewpoint of increasing the heat seal peel strength, olefin-unsaturated carboxylic acid copolymers and olefin-fatty acid vinyl ester copolymers are more preferable. Styrene-butadiene copolymers are more preferred.

Examples of olefin-unsaturated carboxylic acid copolymers include ethylene-(meth)acrylic acid copolymers and ethylene-(meth)acrylic acid alkyl ester copolymers. Among them, ethylene-(meth)acrylic acid copolymers are preferred, and ethylene-acrylic acid copolymers are more preferred.
From the viewpoint of increasing the heat seal peel strength, the olefin-fatty acid vinyl ester copolymer is preferably an ethylene-vinyl acetate 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 copolymers, ethylene-vinyl acetate copolymers and ethylene-(meth)acrylic acid copolymers. and more preferably at least one selected from the group consisting of styrene-butadiene copolymers and ethylene-(meth)acrylic acid copolymers. 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, and the commercial products include Nipol latex LX407G51, LX407S10, LX407S12, LX410, LX415M, LX416, LX430, LX433C, manufactured by Nippon Zeon Co., Ltd. 2507H, Nalstar SR-101, SR-102, SR-103, SR-115, SR-153 manufactured by Nippon A&L Co., Ltd., and styrene butadiene latex 0602, 0597C manufactured by JSR Corporation.

As the ethylene-(meth)acrylic acid copolymer, either a synthetic product or a commercial product may be used. Zaixen (registered trademark) A, Zaixen (registered trademark) AC manufactured by Co., Ltd., Chemipearl S series manufactured by Mitsui Chemicals, Inc., and the like.

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. By using a water-dispersible resin binder having a glass transition temperature equal to or higher than the above lower limit, the occurrence of blocking can also be suppressed. From the viewpoint of heat sealability, the temperature is preferably 100° C. or lower, more preferably 80° C. or lower, even more preferably 60° C. or lower, and even more preferably 50° C. or lower.
As the glass transition temperature of the water-dispersible resin binder, a value measured with a differential scanning calorimeter is adopted. The glass transition temperature is measured according to 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, and even more preferably 80% by mass or more, And it may be 100% by mass or less, preferably 99% by mass or less, more preferably 98% by mass or less. Within the above range, heat-sealable paper having high heat-seal peel strength can be obtained.

That is, according to one embodiment of the present invention, styrene-butadiene copolymer, olefin-fatty acid vinyl ester copolymer and olefin-unsaturated carboxylic acid copolymer (preferably ethylene-(meth) ) The content of at least one selected from the group consisting of acrylic acid copolymer) is preferably 30% by mass or more, more preferably 50% by mass or more, still more preferably 70% by mass or more, and even more preferably 90% by mass. % by mass or more, and may be 100% by mass or less, preferably 99% by mass or less, more preferably 98% by mass or less.

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

Lubricants are not particularly limited, and waxes, metal soaps, fatty acid esters, and the like can be used, for example. Lubricants may be used singly or in combination of two or more. Waxes include, for example, animal- or plant-derived waxes (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. A synthetic wax etc. are mentioned. Examples of metal soaps include calcium stearate, sodium stearate, zinc stearate, aluminum stearate, magnesium stearate, fatty acid sodium soap, potassium oleate soap, castor oil potassium soap, and complexes thereof. Among the above 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 are excellent in the effect of suppressing blocking. 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 commercial product may be used, and examples of the commercial product include Cerosol 524 manufactured by Chukyo Yushi Co., Ltd. and the like. As the paraffin wax, either a synthetic product or a commercial product may be used, and examples of the commercial product include Hydrin L-700 manufactured by Chukyo Yushi Co., Ltd. and the like. As the polyethylene wax, either a synthetic product or a commercial product may be used, and examples of the commercial 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 still more preferably 100 parts by mass of the water-dispersible resin binder. It is 1 part by mass or more, and preferably 30 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less.

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

In the present embodiment, the heat seal layer preferably contains a water-dispersible resin binder and also contains a lubricant in addition to the water-dispersible resin binder. Moreover, in addition to the water-dispersible resin binder and, if necessary, the 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 the pigment, when the heat-sealable paper is produced, the coated surface of the heat-sealable layer sticks to the back surface of the heat-sealable paper and the problem of peeling (blocking) is suppressed, resulting in excellent blocking resistance. A heat-sealable paper is obtained.

The pigment is not particularly limited, and various pigments used in conventional pigment coating layers are exemplified. A pigment may be used individually by 1 type, and may use 2 or more types together. 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, still more 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, It is more preferably 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 later.

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

The pigment preferably has a length (average particle diameter) of 0.1 μm or more and 100 μm or less. When the length is 0.1 μm or more, the pigment is easily aligned parallel to the paper substrate. 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, more preferably 0.5 μm or more, particularly preferably 1.0 μm or more, and more preferably 30 μm or less, still more preferably 20 μm or less, and particularly preferably 15 μm. It is below.

Here, the length of the pigment 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 such that about 20 to 30 pigments are included in the screen. Measure the individual lengths of the pigments in the screen. Then, the average value of the obtained lengths is calculated to obtain the length of the pigment. Incidentally, the length of the pigment is sometimes described in terms of particle size.

The pigment preferably has a thickness of 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, and particularly preferably 30 nm or less. Also, 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 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 such that about 20 to 30 pigments are included in the screen. Measure the individual thickness of the pigment in the screen. Then, the average value of the obtained thicknesses is calculated and taken as the thickness of the pigment.

Specific examples of pigments include mica, bentonite, kaolin, pyrophyllite, talc, smectite, vermiculite, chlorite, septe chlorite, serpentine, stilpnomelane, montmorillonite, ground calcium carbonate (ground calcium carbonate), Light calcium carbonate (synthetic calcium carbonate), composite synthetic pigment of calcium carbonate and other hydrophilic organic compounds, satin white, lithopone, titanium dioxide, silica, barium sulfate, calcium sulfate, alumina, aluminum hydroxide, zinc oxide, carbonate Magnesium, silicates, colloidal silica, hollow or solid organic pigment plastic pigments, binder pigments, plastic beads, microcapsules and the like.

Specific examples of mica include synthetic mica (for example, swelling synthetic mica), muscovite, sericite, flocopite, biotite, fluorine phlogopite (artificial mica), red mica, soda mica, vanadine mica, illite, chinmica, paragonite, and brittle mica. A specific example of bentonite is montmorillonite.

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

Among these, pigments having an aspect ratio of 20 or more are preferable from the viewpoint of heat seal peel strength, blocking resistance and economy, and contain at least one of mica, bentonite, kaolin and talc. is more preferred, and kaolin is even more preferred.

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

When the heat seal layer contains a pigment, the content of the pigment in the heat seal layer is preferably 1% by mass or more, more preferably 3% by mass or more, and still more preferably 3% by mass or more, from the viewpoint of blocking resistance and recyclability. 5% by mass or more, more preferably 8% by mass or more, and preferably 70% by mass or less, more preferably 30% by mass or less, and still more preferably 20% by mass from the viewpoint of heat sealability and hot tack properties. % or less.

(other ingredients)
The heat seal layer may contain other components in addition to the water-dispersible resin binder and, if necessary, lubricants and/or pigments. Examples of other components include silane coupling agents; antifoaming agents; viscosity modifiers; leveling agents such as surfactants and alcohols; coloring agents such as coloring dyes.

The coating amount (basis weight) of the heat seal layer is not particularly limited, but from the viewpoint of obtaining a packaging bag that is difficult to break 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, still 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, still more preferably 4.0 N/15 mm or more, still more preferably 5.0 N/15 mm or more. and preferably 10 N/15 mm or less, more preferably 9.0 N/15 mm or less, and even more preferably 8.0 N/15 mm or less. Furthermore, from the viewpoint of automatic packaging moldability, 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 under the conditions of 150° C., 0.2 MPa, and 1 second. It is the measured value.
The peel strength can be adjusted by selecting the glass transition temperature and type of the water-dispersible resin binder, as well as the coating amount. 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-seal layers adhere well to each other, so that the desired peel strength can be secured. can be done.

(Surface smoothness)
The Oken smoothness of the surface of the heat seal layer of the heat seal paper of the present embodiment is preferably 30 seconds or more, more preferably 40 seconds or more, and still more preferably 50 seconds or more, from the viewpoint of improving the heat seal peel strength. 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.
The heat seal layer may be provided on the W surface (wire surface) or the F surface (felt surface) of the paper substrate, and is not particularly limited. Here, the W side (wire side) is the side in contact with the wire when the web is formed, and the opposite side is the F side (felt side).
In addition, the surface opposite to the heat seal layer (for example, if the heat seal layer is provided only on one side of the paper substrate and the other surface is exposed, the surface of the paper substrate) From the viewpoint of improving printability, the formula smoothness is preferably 3 seconds or more, more preferably 5 seconds or more. is 100 seconds or less.
The Oken smoothness is measured according to JIS P8155:2010.
The Oken type smoothness of the heat seal layer surface and the opposite surface of the heat seal paper can be adjusted within the above range by super calendering or the like 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 is more preferred. When the basis weight is at least the above lower limit, the strength is high, and breakage during molding can be further suppressed. On the other hand, when the basis weight is equal to or less than the above upper limit, the strength is moderately high and wrinkles 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-sealable 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 more preferably 0.70 g/m 3 to 0.90 g/m 3 . More preferably m ³ to 0.85 g/m ³ .

<Method for manufacturing heat seal paper>
The method for producing the heat-sealable paper of this embodiment includes a coating step of coating a heat-sealable layer on at least one surface of the paper substrate obtained as described above. The heat seal layer coating solution (heat seal layer paint) may be applied twice or more.

In the case of forming a plurality of heat-seal layers on a paper substrate, the above method of sequentially forming heat-seal layers is preferable, but the method is not limited to this, and a simultaneous multi-layer coating method may be employed. . Simultaneous multi-layer coating method involves ejecting multiple types of coating liquids from slit-shaped nozzles separately to form a liquid laminate, which is then applied to a paper substrate to create multiple layers of heat. This is a method of forming a seal layer at the same time.

The coating equipment for applying the heat seal layer coating liquid to the paper substrate is not particularly limited, and known equipment may be used. Coating equipment includes, for example, blade coaters, bar coaters, air knife coaters, slit die coaters, gravure coaters, micro gravure coaters, roll coaters, size presses, gate roll coaters and simsizers.

The drying equipment for drying the heat seal layer is not particularly limited, and known equipment can be used. Examples of drying equipment include hot air dryers, infrared dryers, gas burners, hot plates, and the like. Moreover, 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 preferable as the dispersion medium for the heat seal layer coating liquid from the viewpoint of avoiding the problem of volatile organic solvents. That is, the heat-seal layer coating liquid is preferably a heat-seal layer water-based composition.

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

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

After coating and drying the heat seal layer, it is also preferable to carry out a supercalendering treatment. Here, the super calendering process is installed independently from the paper making process. In general, the paper or the like to be processed is passed between metal rolls or between a metal roll and an elastic roll, and heat, pressure, etc. are applied. It is something to do. Supercalendering 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 surface of the heat-seal layer, and as a result, improves the heat-seal peel strength and hot tack (difficulty in peeling immediately after heat-sealing).
In addition, the surface opposite to the heat seal layer (for example, when the heat seal layer is provided only on one side of the paper substrate and the other surface is exposed, the surface of the paper substrate) is smooth. This is preferable because the printability is improved and, as a result, the printability is improved.
Furthermore, supercalendering tends to increase the density of the heat-sealed paper, and as described above, the surface smoothness is improved. becomes good, and the workability is improved, which is preferable.

The linear pressure in supercalendering is preferably 10 kg/cm or more, more preferably 30 kg/cm or more, still 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 appropriately changed according to the desired smoothness and density.
In addition, when heating is performed in the supercalender treatment, the heating temperature is not particularly limited, but it is preferable from the viewpoint of preventing thermal deterioration of the paper base material and the heat seal layer and sticking of the heat seal layer while enhancing the effect of the treatment. is 20° C. or higher, more preferably 30° C. or higher, still more preferably 35° C. or higher, and is preferably 80° C. or lower, more preferably 70° C. or lower, and still more preferably 60° C. or lower.

The use of the obtained heat-sealed paper is not particularly limited, and it can be used for paper-processed products such as packaging bodies such as wrapping paper, packaging bags, and packaging containers, and various containers such as cups and trays, by appropriately molding it. . For example, paper containers such as paper plates, paper cups, and paper trays, horizontal pillow packaging, vertical pillow packaging, three-side seal packaging, four-side seal packaging, bag-feed filling packaging, tube packaging, and stick packaging. It can be used for bags, etc. In particular, since it is excellent in flexibility and drop impact resistance, it can be suitably used in the bag applications described above.

Methods for measuring each physical property are described below.
<ISO stiffness>
The ISO stiffness in the longitudinal and transverse directions of paper substrates and heat-sealed papers is measured in accordance with ISO 2493-1:2010 (Paper and paperboard-Bend resistance test method-Part 1: Constant velocity deflection).
Specifically, as a temperature control and humidity control treatment, a paper base material or heat-sealed paper that has been allowed to stand for one day in an environment of 23±5° C. and 50±10% is cut into a sample of 38 mm in width and 70 mm in length. prepare. With a stiffness tester (L & W BENDING RESISTANCE TESTER Code No. 16-D, manufactured by Lorentzen & Wattre), the bending length is set to 10 mm and the bending angle is set to 15 °, MD (vertical direction), CD (horizontal direction) After measuring each bending resistance, the ISO stiffness is calculated by the following formula.

<Puncture Strength/Specific Puncture Strength>
The puncture strength of the paper substrate and heat-sealed paper is measured according to JIS Z 1707:2019 (general rules for plastic films for food packaging).
Specifically, as a temperature control and humidity control treatment, a paper substrate or heat seal paper that has been left to stand for one day in an environment of 23 ± 5 ° C. and 50 ± 10% is used, and a tensile tester (model RTC-1210A , A&D Co., Ltd.), a piercing jig (manufactured by A&D Co., Ltd.) is used, and the piercing speed is set to 50 mm/min to measure the piercing strength.
Further, the specific puncture strength is calculated by dividing the puncture strength by the basis weight.

<Pulp length weighted average fiber length>
The length weighted average fiber length of the pulp in the paper substrate and heat seal paper is measured according to ISO 16065-2:2007. Specifically, it is as follows.
A paper substrate or heat-sealed paper is cut into a 40 cm square, immersed in deionized water to adjust the solid content concentration to 2% by mass, and then immersed for 24 hours. After being immersed for 24 hours, a standard type 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). The "length-weighted average fiber length (ISO)" is the length-weighted average fiber length calculated by selecting fibers of 0.2 mm or more and 7.6 mm or less.

<Basis weight>
The grammage of the paper substrate and the heat seal paper is measured according to JIS P 8124:2011.

<Thickness>
The thickness (paper thickness) of the paper substrate and the heat seal paper is measured according to JIS P 8118:2014.

<Density>
The densities of the paper base material and the heat-sealable paper are calculated from the thickness and basis weight obtained by the measurement method described above.

EXAMPLES The characteristics of the present invention will be described more specifically below with reference to examples and comparative examples. The materials, amounts used, proportions, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed to be limited by the specific examples shown below. Moreover, unless otherwise specified, "part" represents "mass part". Further, the operations of Examples and Comparative Examples were carried out under the conditions of room temperature (20 to 25° C.) and normal humidity (40 to 50% RH) unless otherwise specified.

<Example 1>
[Manufacturing paper substrate]
Using NUKP (softwood unbleached kraft pulp) and LUKP (hardwood unbleached kraft pulp) obtained by pulping (cooking) wood at a ratio (mass ratio) of 55:45, at a slurry concentration of 2% by mass during beating, A pulp was prepared by beating until the CSF (Canadian Standard Freeness) reached 600 mL.
Using the above pulp, 0.15 parts of synthetic sizing agent (manufactured by Arakawa Chemical Industries, Ltd., SPS400) per 100 parts of pulp in terms of solid content, 1.2 parts of aluminum sulfate, polyacrylamide resin (Seiko PMC) as a retention agent 0.65 part of DS4433 manufactured by Co., Ltd. and 0.035 part of nonionic polyacrylamide (Percol 47 manufactured by Allied Colloid) as a polymer flocculant (retention agent) were added to prepare a paper material.
Using the above stock, a wet paper machine (Bellform III, manufactured by Mitsubishi Heavy Industries, Ltd.) equipped with a stretching device (manufactured by Clupak) was used to perform Clupak processing at a papermaking speed of 600 m/min and reel moisture content of 7.0%. Paper was made at a speed difference of -20 m/min before and after processing, and a nip pressure of 15 kN/m between the nip roll and the blanket during Clupak treatment, to obtain a paper base having a basis weight of 80 g/m ² with a crepe applied to the surface of the paper. rice field.
[Preparation of heat seal layer paint]
Aqueous dispersion of styrene/butadiene copolymer (Nippon Zeon Co., Ltd., Nipol latex LX407S12, solid content concentration 46 mass%, glass transition temperature 18 ° C. (catalog value)) 98 parts (solid content conversion), paraffin wax emulsion (Hydrin L-700, solid content concentration 30% by mass, manufactured by Chukyo Yushi Co., Ltd.) 2 parts (in terms of solid content) are mixed, water is added and stirred so that the solid content concentration is 33% by mass, and the heat seal layer is formed. 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 substrate to form a heat-seal layer with an air knife coater so that the coated amount of the heat-seal layer after drying was 10 g/m ² .
Dry with a drier at 160°C, and finally set the linear pressure to 90 kg/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, and the rolls are heated to 40°C for one stage. to obtain a heat-sealed paper.

<Example 2>
A heat-sealable paper was obtained under the same conditions as in Example 1, except that the speed difference before and after Clupak treatment was changed to -28.0 m/min to produce the paper substrate.

<Example 3>
A heat-sealable paper was obtained under the same conditions as in Example 1, except that the speed difference before and after Clupak treatment was changed to -30.0 m/min to produce the paper substrate.

<Example 4>
The conditions were the same as in Example 1, except that the speed difference before and after the Clupak treatment was changed to −37.0 m/min, and the basis weight was changed to 100 g/m ² by adjusting the discharge rate of the pulp to produce the paper substrate. to obtain a heat-sealed paper.

<Example 5>
A heat-sealable paper was obtained under the same conditions as in Example 1, except that the paper substrate was produced by beating until the CSF (Canadian Standard Freeness) after beating reached 380 mL.

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

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

<Example 8>
The conditions were the same as in Example 1, except that the speed difference before and after the Clupak treatment was changed to −16.0 m/min, and the basis weight was changed to 50 g/m ² by adjusting the discharge rate of the pulp. to obtain a heat-sealed paper.

<Example 9>
NUKP (softwood unbleached kraft pulp) and LUKP (hardwood unbleached kraft pulp), which are pulped (cooked) wood, were changed to a mass ratio of 30:70, and the speed difference before and after Clupak treatment was changed to -25.0m/min. A heat-sealed paper was obtained under the same conditions as in Example 1, except that the paper substrate was produced by

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

<Example 11>
98 parts of an aqueous dispersion of commercially available ethylene-acrylic acid copolymer A (glass transition temperature of 45° C.) (calculated as solid content) and 2 parts of an aqueous dispersion of commercially available carnauba wax (calculated as solid content) were mixed to form a solid. Water was added so that the solid content concentration was 35% by mass, and the mixture was stirred to prepare a heat seal layer paint (solid content concentration: 35% by mass). A heat-sealing paper was obtained by forming a heat-sealing layer and supercalendering in the same manner as in Example 2, except that the obtained heat-sealing layer coating material was used.

<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) (
(in terms of solid content) was added to prepare the heat-seal layer coating material, and heat-seal layer formation and supercalendering were performed in the same manner as in Example 2 to obtain heat-seal paper.

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

<Example 14>
Aqueous dispersion of ethylene/vinyl acetate copolymer (Sumika Chemtex Co., Ltd., Sumikaflex 470HQ, solid content concentration 55% by mass, glass A heat-sealable paper was obtained by forming a heat-sealable layer and supercalendering in the same manner as in Example 2, except that a transition temperature of 0°C (catalog value) was used and no paraffin wax emulsion was used.

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

<Example 16>
Aqueous dispersion of styrene/butadiene copolymer (Nippon Zeon Co., Ltd., Nipol latex LX407S12, solid content concentration 46 mass%, glass transition temperature 18 ° C. (catalog value)) 88 parts (solid content conversion), paraffin wax emulsion (Chukyo Yushi Co., Ltd., Hydrin L-700, solid content concentration 30% by mass) 2 parts (converted to solid content), Kaolin (contour extreme manufactured by Imerys, average particle size 8 μm, aspect ratio 80 to 100, solid content 50 Dispersed in water so that the concentration is 33% by mass)) is mixed with 10 parts (in terms of solid content), water is added and stirred so that the solid content concentration is 33% by mass, and the heat seal layer paint (solid content concentration is 33% by mass). Heat-sealable layer formation and supercalendering were performed in the same manner as in Example 2, except that a heat-sealable paper was obtained.

<Example 17>
A heat-sealable paper was obtained in the same manner as in Example 2, except that supercalendering was not performed after forming the heat-sealable layer.

<Comparative Example 1>
By changing the mass ratio of NUKP (softwood unbleached kraft pulp) and LUKP (hardwood unbleached kraft pulp) to 45:55 by pulping (cooking) wood, and adjusting the discharge amount of pulp without performing Clupak treatment. A heat-sealable paper was obtained under the same conditions as in Example 1, except that the basis weight was changed to 30 g/m ² to produce the paper substrate.

<Comparative Example 2>
NUKP (softwood unbleached kraft pulp) and LUKP (hardwood unbleached kraft pulp), which are pulped (cooked) wood, were changed to a mass ratio of 45:55, and the paper base material was manufactured without Clupak treatment. A 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) and LUKP (hardwood unbleached kraft pulp) to 45:55 by pulping (cooking) wood, and adjusting the discharge amount of pulp without performing Clupak treatment. A heat-sealable paper was obtained under the same conditions as in Example 1, except that the basis weight was changed to 100 g/m ² to produce the paper substrate.

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

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

The following evaluations were carried out using the obtained heat-sealable paper or paper substrate.
<Bag flexibility evaluation>
The obtained heat-sealable paper or paper substrate was cut out to obtain a sheet 1 having a longitudinal direction (MD) of 200 mm and a lateral direction (CD) of 150 mm. Double-sided tape 2 with a width of 10 mm (model: Scotch super strong double-sided tape Premier Gold Super Versatile PPS-10, manufactured by 3M) is attached to the sheet 1 as shown in FIG. 100 mm from the end) and fixed so as not to create a gap to obtain a bag 3.
The bag 3 was filled with water, and the filling amount until the water spilled was evaluated. It shows that it is so favorable that a numerical value is large.
4: Filling amount of water is 150 mL or more.
3: Filling amount of water is 100 mL or more and less than 150 mL.
2: Filling amount of water is 50 mL or more and less than 100 mL.
1: Filling amount of water is less than 50 mL.

<Drop impact resistance evaluation>
A bag similar to the bag 3 prepared in <Bag Flexibility Evaluation> was prepared from the obtained heat-sealed paper or paper substrate. A disk-shaped weight weighing 50 g (product number: 201900401, manufactured by Murakami Kouki Seisakusho Co., Ltd.) is filled into bag 3, sealed with double-sided tape with a width of 10 mm used in <bag flexibility evaluation>, and the weight is filled. I made a bag with The bag filled with the weight was allowed to stand in an environment of 23±5° C. and 50±10% for one day as temperature control and humidity control treatment.
The bag after temperature control and humidity control treatment was dropped from a height of 30 cm onto a SUS plate with the top surface 4 (filling port) of the bag facing up. Further, the dropped bag was similarly dropped with the bottom surface 5 of the bag facing up. The above-mentioned drop test (the number of drops per bag was 2 times) was carried out for a total of 5 tests per level using newly prepared bags to evaluate the drop impact resistance. It shows that it is so favorable that a numerical value is large. In the table, "-" indicates that the seal was not possible and the measurement was not possible.
In all 4:5 tests, the bags did not tear or dent.
In all 3:5 tests, the bag did not tear, but was dented.
In the 2:1-4 tests, the bags were torn.
In all 1:5 tests, the bags were torn.

[Heat seal peel strength]
A set of two heat-sealed papers is stacked so that the heat-sealed layers face each other, and a heat-seal tester (manufactured by Tester Sangyo, TP-701-B) is used to heat at 150 ° C., 0.2 MPa, and 1 second. Sealed. The heat-sealed test piece was allowed to stand 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, T-shaped peeled at a tensile speed of 300 mm/min using a tensile tester, and the recorded maximum load was taken as the heat seal peel strength. In the table, "-" indicates that no adhesion was made and measurement was not possible.

[Automatic packaging moldability]
Using a high-speed horizontal pillow packaging machine (αWrapper FW3410, manufactured by Fuji Machinery Co., Ltd.), the heat-sealed paper was continuously made into bags. At this time, no contents were put into the bag, but an empty bag was used for molding. Here, "continuous bag making is impossible" means a state in which wrinkles are generated, a state in which a bag is not formed due to meandering, or a paper break occurs. In addition, "defective appearance" refers to contamination of wrinkles, misalignment of the sealing portion, or deformation of the bag.
A: Continuous bag making was possible, and the appearance of the bag was good.
B: Continuous bag making was possible, but the appearance of the bags was slightly poor.
C: Continuous bag making was not possible.

Table 1 shows 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 surface of bag, 5: bottom surface of bag

Claims (13)

A paper substrate for heat- sealable paper , comprising:
The ISO stiffness of the paper substrate in the machine direction, measured according to ISO 2493-1:2010, is 0.5. is 70 mNm or less, and the transverse ISO stiffness of the paper substrate is 0.45 mNm or less,
The puncture strength of the paper substrate measured in accordance with JIS Z 1707:2019 is 7.5 N or more.
paper substrate . A heat-sealable paper having one or more heat-sealable layers on at least one surface of the paper substrate according to claim 1,
A heat-sealable paper, wherein the heat-sealable layer contains a water-dispersible resin binder. The longitudinal ISO stiffness is 0.05 to 0.20 mNm,
a lateral ISO stiffness of 0.05 to 0.20 mNm;
The heat-sealable paper according to claim 2 . 3. The heat-sealable paper according to claim 2 , which has a puncture strength of 12.5 N or more. 3. The pulp obtained by defibrating the heat-sealable paper has a length-weighted average fiber length of 1.2 mm to 2.0 mm as measured according to ISO 16065-2:2007. of heat seal paper. The heat-sealable paper according to claim 2 , having a basis weight of 40 g/m ² to 130 g/m ² . 3. The heat-sealable paper according to claim 2 , having a specific puncture strength of 0.12 N/g or more. 3. The heat-sealable paper of claim 2 , wherein said heat-sealable layer further comprises a lubricant. 9. The heat-sealable paper according to claim 8 , wherein said lubricant comprises at least one selected from the group consisting of paraffin wax, carnauba wax and polyolefin wax. The heat-sealable paper according to claim 8 , wherein the content of the lubricant in the heat-sealable layer is 1% by mass or more and 5% by mass or less. The heat seal paper according to claim 2 , wherein the water-dispersible resin binder has a glass transition temperature of 0°C or higher and 100°C or lower. 2. The water-dispersible resin binder comprises at least one selected from the group consisting of styrene-butadiene copolymers, olefin-fatty acid vinyl ester copolymers and olefin-unsaturated carboxylic acid copolymers. Heat-sealing paper described in . A processed paper product using the heat-sealable paper according to any one of claims 2 to 12 .

Images