Heat-sealing paper and paper processed products

Abstract

To provide heat seal paper which has high extensibility, has sufficient followability even in molding into a complicated three-dimensional shape, prevents generation of wrinkles in a molding part, and is excellent in heat sealability.SOLUTION: Heat seal paper has one or more heat seal layers on at least one surface of a paper base material, wherein the heat seal layer contains a water dispersible resin binder, specific tensile strength in a vertical direction of the heat seal paper and specific tensile strength in a lateral direction of the heat seal paper, which are measured according to ISO / DIS 1924-3, are 1.7 kN m / g to 4.0 kN m / g and 1.4kN m / g to 2.9 kN m / g, respectively, and elongation at break in the vertical direction of the heat seal paper and elongation at break in the lateral direction of the heat seal paper, which are measured according to JIS P 8113:2006, are 5.0% to 10.0% and 5.0% to 10.0%, respectively.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to heat-sealing paper and paper processed products.

Background Art

[0002] For packaging containers such as food trays and packaging bodies such as bags for pillow packaging, plastic materials have mainly been used. However, in view of environmental concerns and the like, studies have been made on packaging materials using paper instead of plastic containers.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For the production of a packaging body using paper, a material having stretchability is preferable from the viewpoint of formability. The present inventors have tried to form a food tray using a conventional paper as in Patent Document 1, but it has been found that wrinkles are likely to occur in the formed portion. In particular, it is insufficient for forming a complicated three-dimensional shape such as a deep tray. The present disclosure relates to a heat-sealing paper having high stretchability, sufficient followability even in forming a complicated three-dimensional shape, being less likely to have wrinkles in the formed portion, and excellent heat-sealing properties, and a paper processed product using the heat-sealing paper.

Means for Solving the Problems

[0005] That is, the present disclosure relates to the following <1> to <12>. <1> A heat-sealing paper having one or more heat-sealing layers on at least one surface of a paper base material, wherein the heat-sealing layer contains a water-dispersible resin binder, The specific tensile strength in the longitudinal direction of the heat-sealing paper, measured in accordance with ISO / DIS 1924-3, is 1.7 kN·m / g to 4.0 kN·m / g, and the specific tensile strength in the transverse direction of the heat-sealing paper is 1.4 kN·m / g to 2.9 kN·m / g. The elongation at break in the longitudinal direction of the heat-sealing paper, measured in accordance with JIS P 8113:2006, is 5.0% to 10.0%, and the elongation at break in the transverse direction of the heat-sealing paper is 5.0% to 10.0%. Heat-sealing paper. <2> The specific tensile strength in the longitudinal direction is 2.4 kN·m / g to 3.9 kN·m / g. The specific tensile strength in the transverse direction is 1.8 kN·m / g to 2.9 kN·m / g. The heat-sealing paper according to <1>. <3> The pulp obtained by dissociating the heat-sealing paper has a length-weighted average fiber length of 1.1 mm to 2.0 mm, measured in accordance with ISO 16065-2:2007, for the heat-sealing paper according to <1> or <2>. <4> The basis weight is 40 g / m 2 ~130 g / m 2 for the heat-sealing paper according to any one of <1> to <3>. <5> The elongation at break in the longitudinal direction is 7.0% to 9.7%. The elongation at break in the transverse direction is 6.5% to 9.5%. The heat-sealing paper according to any one of <1> to <4>. <6> The paper base material contains pulp. The pulp contains softwood kraft pulp. The content of the softwood kraft pulp in the pulp is 25% by mass or more, for the heat-sealing paper according to any one of <1> to <5>. <7> The heat-sealing layer further contains a lubricant, for the heat-sealing paper according to any one of <1> to <6>. <8> The lubricant contains at least one selected from the group consisting of paraffin wax, carnauba wax, and polyolefin wax, for the heat-sealing paper according to <7>. <9>The heat-sealing paper according to <7> or <8>, wherein the content of the lubricant in the heat-sealing layer is 1% by mass or more and 5% by mass or less. <10>The heat-sealing paper according to any one of <1> to <9>, wherein the glass transition temperature of the water-dispersible resin binder is 0°C or higher and 100°C or lower. <11>The heat-sealing paper according to any one of <1> to <10>, wherein the water-dispersible resin binder contains at least one selected from the group consisting of a styrene-butadiene copolymer, an olefin-fatty acid vinyl ester copolymer, and an olefin-unsaturated carboxylic acid copolymer. <12>A paper processed product using the heat-sealing paper according to any one of <1> to <11>.

Advantages of the Invention

[0006] According to the present disclosure, it is possible to provide a heat-sealing paper having high stretchability, sufficient followability even in forming into a complex three-dimensional shape, hardly generating wrinkles in the formed portion, and excellent heat-sealing properties. Further, according to the present disclosure, it is possible to provide a heat-sealing paper having excellent formability in automatic packaging.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0008] In the present disclosure, the description of "X or more and Y or less" or "X to Y" representing a numerical range means a numerical range including the lower limit and the upper limit which are the endpoints, unless otherwise specified. When the numerical ranges are described stepwise, the upper limit and the lower limit of each numerical range can be arbitrarily combined. The longitudinal direction is the papermaking direction (MD) in the paper base material, which is the same as the direction in which the fibers are oriented. The transverse direction is perpendicular to the papermaking direction (CD). The longitudinal direction of the heat-sealing paper corresponds to the MD direction of the paper base material, and the transverse direction of the heat-sealing paper corresponds to the CD direction of the paper base material. Note that "excellent formability in automatic packaging (hereinafter also referred to as automatic packaging formability)" means that continuous bag making is possible with an automatic packaging machine and the appearance of the resulting bag is good. More specifically, for example, when automatically forming a packaging bag, the occurrence of wrinkles and appearance defects is suppressed, sticking (blocking) to a forming machine or the like is suppressed, and the formability is excellent. Further, it means that the quality of the resulting packaging bag is excellent and the productivity is excellent, such as the deformation of the bag after bag making is suppressed.

[0009] The Kurpack treatment is a treatment that gives stretchability by finely shrinking the paper on a paper machine. Specifically, for example, a Kurpack device equipped with an endless thick elastic rubber blanket with nip rolls is installed in a part of the paper machine dryer. The wet paper web is introduced into the Kurpack device and compressed by the nip rolls and the blanket. At this time, the blanket that has been stretched in advance shrinks to shrink the running paper web (crepe application), and the elongation at break can be increased. The resulting shrinkage is dried and fixed so that it does not stretch in the subsequent process.

[0010] The inventors have found that the above problems can be solved by controlling the heat-sealing paper to a specific specific tensile strength and elongation at break by the Kurpack treatment when manufacturing the paper base material used for the heat-sealing paper. The specific tensile strength represents the stiffness of the paper, and the elongation at break indicates the ease of stretching of the paper. The fact that the heat-sealing paper has the above specific specific tensile strength and elongation at break indicates that it has appropriate stiffness and is somewhat easy to stretch to a certain extent. Therefore, the inventors believe that it is possible to obtain a heat-sealing paper with high stretchability, sufficient followability even in forming into a complex three-dimensional shape, and less likely to generate wrinkles in the forming part.

[0011] The specific tensile strength in the longitudinal direction of the heat-sealing paper measured in accordance with ISO / DIS 1924-3 should be 1.7 kN·m / g to 4.0 kN·m / g, and the specific tensile strength in the transverse direction of the heat-sealing paper should be 1.4 kN·m / g to 2.9 kN·m / g. If the specific tensile strength is less than the above lower limit, excessive stress will be applied during forming, making wrinkles and tears likely to occur. On the other hand, if the specific tensile strength exceeds the above upper limit, the pressure required for forming will become too high, making it difficult to form, and wrinkles and tears are likely to occur if forced forming is attempted.

[0012] The specific tensile strength of the heat-sealing paper can be controlled by the manufacturing conditions of the paper base material used. Specifically, it can be controlled by the speed difference before and after the Kurpack treatment, the adjustment of density by nip pressure during calendar treatment, the type of pulp, etc. To increase the tensile strength, methods such as reducing the speed difference before and after the Kurpack treatment, increasing the density by increasing the nip pressure during calendar treatment, and increasing the fiber length of the pulp can be mentioned. On the other hand, to decrease the tensile strength, methods such as increasing the speed difference before and after the Kurpack treatment, decreasing the density by decreasing the nip pressure during calendar treatment, and decreasing the fiber length of the pulp can be mentioned.

[0013] The specific tensile strength in the longitudinal direction of the heat-sealing paper is preferably 2.4 kN·m / g to 3.9 kN·m / g, more preferably 2.6 kN·m / g to 3.8 kN·m / g, and even more preferably 2.9 kN·m / g to 3.7 kN·m / g. The specific tensile strength in the transverse direction of the heat-sealing paper is preferably 1.8 kN·m / g to 2.9 kN·m / g, more preferably 2.0 kN·m / g to 2.8 kN·m / g, and even more preferably 2.3 kN·m / g to 2.7 kN·m / g.

[0014] The ratio of the longitudinal specific tensile strength to the transverse specific tensile strength of the heat-sealing paper (longitudinal direction / transverse direction) is preferably 1.10 or more, more preferably 1.20 or more, and even more preferably 1.22 or more. On the other hand, the upper limit is preferably 1.50 or less, more preferably 1.40 or less, and even more preferably 1.35 or less.

[0015] It is necessary that the elongation at break in the longitudinal direction of the heat-sealing paper, measured in accordance with JIS P 8113:2006, is 5.0% to 10.0%, and the elongation at break in the transverse direction of the heat-sealing paper is 5.0% to 10.0%. If the elongation at break in the longitudinal and transverse directions of the heat-sealing paper is less than the above lower limit, the elongation of the paper during forming is insufficient, making it difficult to form. Also, if an attempt is made to form forcibly, tearing will occur. In addition, the formability in automatic packaging also decreases. On the other hand, if the elongation at break exceeds the above upper limit, although forming is possible because the elongation is large, the paper becomes easy to move, wrinkles are likely to occur, and furthermore, tearing is likely to occur from there.

[0016] The elongation at break of the heat-sealing paper can be controlled by the manufacturing conditions of the paper base material used. Specifically, it can be controlled by basis weight, the speed difference before and after the Kurpack treatment, the nip pressure during the Kurpack treatment, etc. This can be done. To increase the elongation at break, methods such as increasing the basis weight, increasing the speed difference before and after the Kurpack treatment, and decreasing the nip pressure during the Kurpack treatment can be mentioned. On the other hand, to decrease the elongation at break, methods such as decreasing the basis weight, decreasing the speed difference before and after the Kurpack treatment, and increasing the nip pressure during the Kurpack treatment can be mentioned.

[0017] The elongation at break in the longitudinal direction of the heat-sealing paper is preferably 6.0% or more, more preferably 7.0% or more, and even more preferably 8.0% or more. The upper limit of the elongation at break in the longitudinal direction is preferably 9.7% or less, more preferably 9.0% or less. For example, 6.0% to 9.7%, 7.0% to 9.7%, 8.0% to 9.0% can be mentioned. The cross-directional breaking elongation of the heat-sealing paper is preferably 6.0% or more, more preferably 6.5% or more, and even more preferably 7.5% or more. The upper limit of the cross-directional breaking elongation is preferably 9.5% or less, more preferably 8.5% or less. For example, 6.0% - 9.5%, 6.5% - 9.5%, 7.5% - 8.5% can be mentioned.

[0018] The ratio of the longitudinal breaking elongation of the heat-sealing paper to the cross-directional breaking elongation (longitudinal direction / cross-directional direction) is preferably 1.01 or more, more preferably 1.02 or more, and even more preferably 1.05 or more. On the other hand, the upper limit is preferably 1.30 or less, more preferably 1.20 or less, and even more preferably 1.12 or less.

[0019] The pulp obtained by dissociating the heat-sealing paper preferably has a length-weighted average fiber length measured in accordance with ISO 16065-2:2007 of 1.1 mm - 2.0 mm, more preferably 1.2 mm - 1.9 mm, and even more preferably 1.3 mm - 1.8 mm. When the length-weighted average fiber length is above the above lower limit, the strength increases and tearing during forming is less likely to occur. On the other hand, when the length-weighted average fiber length is below the above upper limit, the strength is moderately strong and wrinkles during forming can be more suppressed. Therefore, within the above numerical range, the formability can be further improved. The length-weighted average fiber length of the pulp can be controlled by the type of pulp used, etc.

[0020] The basis weight of the heat-sealing paper is preferably 40 g / m 2 ~130 g / m 2 and more preferably 70 g / m 2 ~120 g / m 2 and even more preferably 80 g / m 2 ~100 g / m 2 When the basis weight is above the above lower limit, the strength increases and tearing during forming can be more suppressed. On the other hand, when the basis weight is below the above upper limit, the strength is moderately strong and wrinkles during forming can be more suppressed. Therefore, within the above numerical range, the formability can be improved.

[0021] The thickness of the heat-sealing 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.

[0022] The density of the heat-sealing paper is 0.40 g / m 3 ~1.10 g / m 3 and is preferably 0.50 g / m 3 ~1.00 g / m 3 more preferably 0.60 g / m 3 ~0.90 g / m 3 even more preferably 0.70 g / m 3 ~0.80 μmg / m 3 and even more preferably 0.70 g / m

[0023] [Paper substrate] The basis weight of the paper substrate used for the heat-sealing paper is preferably 30 g / m 2 ~120 g / m 2 more preferably 60 g / m 2 ~110 g / m 2 even more preferably 70 g / m 2 ~90 g / m 2 even more preferably. When the basis weight is above the above lower limit, the strength becomes higher and tearing during forming can be more suppressed. On the other hand, when the basis weight is below the above upper limit, the strength is moderately strong and wrinkles during forming can be more suppressed. Therefore, within the above numerical range, the formability can be improved This can be achieved.

[0024] The thickness of the paper substrate 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.

[0025] The density of the paper substrate is preferably 0.30 g / m 3 ~1.00 g / m 3 and is preferably 0.40 g / m3 ~0.90 g / m 3 is more preferably 0.50 g / m 3 ~0.80 g / m 3 is even more preferably 0.60 g / m 3 ~0.70 μg / m 3 is even more preferably.

[0026] The specific tensile strength in the longitudinal direction of the paper substrate, measured in accordance with ISO / DIS 1924-3, is preferably 1.9 kN·m / g to 4.0 kN·m / g, more preferably 2.0 kN·m / g to 3.9 kN·m / g, even more preferably 3.0 kN·m / g to 3.9 kN·m / g, and even more preferably 3.1 kN·m / g to 3.7 kN·m / g. The specific tensile strength in the transverse direction of the paper substrate is preferably 1.5 kN·m / g to 3.0 kN·m / g, more preferably 2.0 kN·m / g to 2.9 kN·m / g, and even more preferably 2.3 kN·m / g to 2.8 kN·m / g The ratio of the specific tensile strength in the longitudinal direction of the paper substrate to the specific tensile strength in the transverse direction (longitudinal direction / transverse direction) is preferably 1.10 to 1.50, more preferably 1.20 to 1.40, and even more preferably 1.25 to 1.35. By satisfying the above range, it becomes easier to adjust the specific tensile strength of the heat-sealing paper to a desired range, which is preferable.

[0027] The elongation at break in the longitudinal direction of the paper substrate, measured in accordance with JIS P 8113:2006, is preferably 5.0% to 10.0%, more preferably 7.0% to 9.7%, and even more preferably 8.0% to 9.0%. The elongation at break in the transverse direction of the paper substrate is preferably 4.5 to 10.0%, more preferably 5.0% to 10.0%, even more preferably 6.5% to 9.5%, and even more preferably 7.5% to 8.5%. The ratio of the longitudinal breaking elongation of the paper base material to the transverse breaking elongation (longitudinal direction / transverse direction) is preferably 1.01 to 1.30, more preferably 1.03 to 1.20, and even more preferably 1.05 to 1.12. By satisfying the above range, it becomes easier to adjust the breaking elongation of the heat-sealing paper to a desired range, which is preferable.

[0028] The length-weighted average fiber length of the pulp measured in accordance with ISO 16065-2:2007 for the pulp obtained by dissociating the paper base material is preferably 1.1 mm to 2.0 mm, more preferably 1.2 mm to 1.9 mm, and even more preferably 1.3 mm to 1.8 mm.

[0029] Next, the materials that can be used for the paper base material will be described. The paper base material contains, for example, pulp. Examples of the pulp constituting the paper base material include hardwood kraft pulp such as unbleached hardwood kraft pulp (LUKP) and bleached hardwood kraft pulp (LBKP); softwood kraft pulp such as unbleached softwood kraft pulp (NUKP) and bleached softwood kraft pulp (NBKP); mechanical pulp such as groundwood pulp (GP), pressurized groundwood pulp (PGW), refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), chemimechanical pulp (CMP), and chemigroundwood pulp (CGP); wastepaper pulp; non-wood fiber pulp such as kenaf, bagasse, bamboo, and cotton; synthetic pulp, etc. These pulps may be used alone or in combination of two or more.

[0030] The pulp preferably contains softwood kraft pulp, more preferably contains hardwood kraft pulp and softwood kraft pulp, and even more preferably contains unbleached hardwood kraft pulp and unbleached softwood kraft pulp.

[0031] The content of hardwood kraft pulp in the pulp is preferably 0% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, and even more preferably 13% by mass or more. On the other hand, the upper limit is preferably 75% by mass or less, more preferably 65% by mass or less, still more preferably 60% by mass or less, and even more preferably 57% by mass or less.

[0032] The content of softwood kraft pulp in the pulp is preferably 25% by mass or more, more preferably 30% by mass or more, still more preferably 35% by mass or more, even more preferably 40% by mass or more, and even more preferably 43% 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 87% by mass or less.

[0033] The beating degree of the pulp is not particularly limited, but as the Canadian Standard Freeness (CSF), 200 to 800 mL is preferable, and 450 to 700 mL is more preferable. The CSF is measured according to JIS P 8121-2:2012 "Pulp - Test method for freeness - Part 2: Canadian standard freeness method".

[0034] Additives may be used for the paper base material as necessary. Examples of the additives include pH adjusters (such as sodium hydrogen carbonate and sodium hydroxide), dry strength agents (such as polyacrylamide and starch), wet strength agents (any one of polyamide polyamine epichlorohydrin resin, melamine - formaldehyde resin, and urea - formaldehyde resin), internal sizing agents (such as rosin - based and alkyl ketene dimer), drainage yield improvers (such as polyacrylamide resin), defoamers, fillers (such as calcium carbonate and talc), dyes, and the like. These additives may be used alone or in combination of two or more. The content of the additives is not particularly limited as long as it is within the range commonly used.

[0035] 〔Method for manufacturing the paper base material〕 As a method for manufacturing a paper base material, there is a method of forming a paper web from a paper stock containing pulp and performing a Kurpack treatment during the web forming process. The paper stock may further contain additives as necessary. Examples of the additives include the additives described above. The paper stock can be prepared by adding additives to the pulp slurry as necessary. The pulp slurry can be obtained by beating pulp in the presence of water. The beating method and the beating apparatus for the pulp are not particularly limited, and known beating methods and beating apparatuses can be employed.

[0036] The solid content concentration of the pulp slurry during beating is not particularly limited, but is preferably about 5 to 40% by mass, more preferably about 10 to 30% by mass. Also, the pulp content in the paper stock or the paper base material is not particularly limited and may be within the range commonly 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, based on the total mass of the paper stock (solid content) or the paper base material.

[0037] In the formation of the paper base material web, a known wet paper machine can be appropriately selected and used. Examples of the paper machine include a Fourdrinier paper machine, a gap former type paper machine, a cylinder mold paper machine, and a Duoformer paper machine. A Kurpack apparatus capable of performing the Kurpack treatment may be provided in these paper machines to perform the Kurpack treatment. For example, after forming a paper web and dehydrating it by calendar treatment, the Kurpack treatment can be performed.

[0038] As the Kurpack apparatus, known ones can be used. For example, a Kurpack apparatus equipped with nip rolls and an endless thick elastic rubber blanket can be mentioned. As described above, in the Kurpack treatment, a paper sheet is fed between the nip rolls and the blanket, and when the paper sheet is compressed by the nip rolls and the blanket, the pre-stretched blanket is contracted to contract the paper sheet and impart crepe. The Kurpack apparatus is usually provided as a part of the dryer apparatus of the paper machine, and after creping, it is dried and fixed. In this way, the paper base material can be obtained. ​

[0039] In papermaking using a Kurpack device, the difference in papermaking speed before and after the Kurpack process and the pressure of the nip roll can control the specific tensile strength and elongation at break. The papermaking speed is not particularly limited. For example, it may be preferably controlled in the range of 200 to 1000 m / min, more preferably 300 to 800 m / min, and even more preferably 400 to 700 m / min. The nip pressure between the nip roll and the blanket during the Kurpack process is also not particularly limited. For example, it may be appropriately controlled in the range of 5 kN / m to 50 kN / m, more preferably 10 kN / m to 25 kN / m. The speed difference before and after the Kurpack process is not particularly limited and may be controlled so as to obtain a desired specific tensile strength and elongation at break according to the basis weight and pulp material. Preferably, it is -45.0% to -10.0%, more preferably -40.0% to -15.0%. The minus "-" here indicates that the speed after the Kurpack process is slow.

[0040] The nip pressure by calendar treatment is also not particularly limited and may be controlled so as to obtain a desired specific tensile strength according to the basis weight, pulp material, speed difference before and after the Kurpack process, etc. Preferably, it is 100 kN / m to 200 kN / m, and more preferably 130 kN / m to 170 kN / m.

[0041] [Heat-sealing layer] The heat-sealing paper of this embodiment has at least one heat-sealing layer on at least one surface of the paper base material. The heat-sealing layer is a layer that melts and adheres by heating, ultrasonic waves, etc.

[0042] (Water-dispersible resin binder) The heat-sealing layer contains a water-dispersible resin binder. A water-dispersible resin binder is a resin binder that is not water-soluble (specifically, having a solubility in water at 25 °C of 10 g / L or less), but is in a state of being finely dispersed in water like an emulsion or a suspension. By applying the heat-sealing layer with a water-dispersible resin binder by aqueous coating, a heat-sealing paper excellent in re-dissociability and recyclable as paper can be obtained. When the water-dispersible resin binder also falls under the following lubricants, it shall be classified as a lubricant.

[0043] The water-dispersible resin binder is not particularly limited as long as it exhibits the effects of the present invention, but examples thereof include polyolefin resins (such as polyethylene and polypropylene), vinyl chloride resins, styrene resins, styrene-butadiene copolymers, styrene-unsaturated carboxylic acid copolymers (for example, styrene-(meth)acrylic acid copolymer), acrylic resins, acrylonitrile-styrene copolymers, acrylonitrile-butadiene copolymers, ABS resins, AAS resins, AES resins, vinylidene chloride resins, polyurethane resins, poly-4-methylpentene-1 resins, polybutene-1 resins, vinylidene fluoride resins, vinyl fluoride resins, fluorine resins, polycarbonate resins, polyamide resins, acetal resins, polyphenylene oxide resins, polyester resins (such as polyethylene terephthalate and polybutylene terephthalate), polyphenylene sulfide resins, polyimide resins, polysulfone resins, polyethersulfone resins, polyarylate resins, 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 a styrene-butadiene copolymer, an olefin-fatty acid vinyl ester copolymer, and an olefin-unsaturated carboxylic acid copolymer is preferable, and at least one selected from the group consisting of a styrene-butadiene copolymer and an olefin-unsaturated carboxylic acid copolymer is more preferable. 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. From the viewpoints of availability, cost, and recyclability, styrene-butadiene copolymers are more preferable.

[0044] Examples of the olefin-unsaturated carboxylic acid copolymer include ethylene-(meth)acrylic acid copolymers and ethylene-(meth)acrylic acid alkyl ester copolymers. Among them, ethylene-(meth)acrylic acid copolymers are preferable, and ethylene-acrylic acid copolymers are more preferable. From the viewpoint of increasing the heat seal peel strength, as the olefin-fatty acid vinyl ester copolymer, ethylene-vinyl acetate copolymer is preferable. Therefore, the water-dispersible resin binder contained in the heat seal layer is preferably 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.

[0045] As the styrene-butadiene copolymer, either synthetic products or commercially available products may be used. Commercially available products include Nipol latex LX407G51, LX407S10, LX407S12, LX410, LX415M, LX416, LX430, LX433C, 2507H manufactured by Zeon Corporation, Nalster SR-101, SR-102, SR-103, SR-115, SR-153 manufactured by A&L Japan Co., Ltd., styrene-butadiene latex 0602, 0597C manufactured by JSR Corporation, and the like.

[0046] As the ethylene-(meth)acrylic acid copolymer, either a synthetic product or a commercially available product may be used. Examples of commercially available products include MP498345N, MP4983R, MP4990R, MFHS1279 manufactured by Michelman Japan Co., Ltd., Zeicen (registered trademark) A, Zeicen (registered trademark) AC manufactured by Sumitomo Seika Chemical Co., Ltd., Chemparl S series manufactured by Mitsui Chemicals, Inc., and the like.

[0047] 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 of the above lower limit or higher, the occurrence of blocking can also be suppressed. From the viewpoint of heat sealability, it 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. The glass transition temperature of the water-dispersible resin binder shall adopt the value measured by a differential scanning calorimeter. The glass transition temperature is measured in accordance with JIS K 7121:1987.

[0048] 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, even more preferably 70% by mass or more, and even more preferably 80% by mass or more, and 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.

[0049] That is, according to one embodiment of the present invention, the content of at least one selected from the group consisting of a styrene-butadiene copolymer, an olefin-fatty acid vinyl ester copolymer, and an olefin-unsaturated carboxylic acid copolymer (preferably an ethylene-(meth)acrylic acid copolymer) in the heat-sealing 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 90% by mass or more, and may be 100% by mass or less, preferably 99% by mass or less, and more preferably 98% by mass or less.

[0050] (Lubricant) From the viewpoints of imparting slipperiness to the heat-sealing paper and suppressing blocking, it is preferable that the heat-sealing layer contains a lubricant in addition to the above water-dispersible resin binder. A lubricant is a substance that can reduce the friction coefficient of the surface of the heat-sealing layer by being blended into the heat-sealing layer.

[0051] The lubricant is not particularly limited, and for example, wax, metal soap, fatty acid ester, etc. can be used. The lubricant may be used alone or in combination of two or more. Examples of waxes include natural waxes such as animal or plant-derived waxes (e.g., beeswax, carnauba wax, etc.), mineral waxes (e.g., microcrystalline wax, etc.), and petroleum waxes; synthetic waxes such as polyolefin waxes, paraffin waxes, and polyester waxes. Examples of metal soaps 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 lubricants, paraffin wax, carnauba wax, and polyolefin wax are preferable because they have a relatively low melting point and a wax component is easily formed on the surface of the coating layer, and they have an excellent blocking suppression 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. Examples of commercially available products include Serosol 524 manufactured by Chukyo Yushi Co., Ltd. As the paraffin wax, either a synthetic product or a commercially available product may be used. Examples of commercially available products 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. Examples of commercially available products include Aquacer 531 manufactured by BYK Co., Ltd.

[0052] When the heat-sealing 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, still more preferably 1 part by mass or more, and preferably 30 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 5 parts by mass or less, based on 100 parts by mass of the water-dispersible resin binder.

[0053] 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, still more preferably 1% by mass or more, and preferably 30% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less.

[0054] In the present embodiment, the heat-sealing layer contains a water-dispersible resin binder, and in addition to the water-dispersible resin binder, it preferably contains a lubricant. Further, in addition to the water-dispersible resin binder and, if necessary, the lubricant, it may contain a pigment.

[0055] (Pigment) In the present embodiment, the heat-sealing layer may contain a pigment in addition to the water-dispersible resin binder. By containing a pigment, when manufacturing the heat-sealing paper, the problem that the coated surface of the heat-sealing layer adheres to the back surface of the heat-sealing paper and peeling (blocking) occurs is suppressed, and a heat-sealing paper excellent in blocking resistance can be obtained.

[0056] The pigment is not particularly limited, and various pigments used in conventional pigment coating layers are exemplified. The pigment may be used alone or in combination of two or more. From the viewpoints of heat seal peel strength and blocking resistance, a pigment having an aspect ratio of 20 or more is preferable. 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 viewpoints of availability and smoothness of the heat seal layer surface, it is preferably 10,000 or less, more preferably 1,000 or less, further preferably 300 or less. The aspect ratio of the pigment means the major axis / minor axis and may be measured by the method described later.

[0057] The pigment is preferably a layered inorganic compound having an aspect ratio of 20 or more. The form of the layered inorganic compound is plate-like. When the pigment is plate-like, the protrusion of the pigment from the surface of the heat seal layer is suppressed, and a heat seal layer excellent in blocking resistance can be obtained while maintaining the heat sealability.

[0058] 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 in 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 protrudes 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, further preferably 20 μm or less, particularly preferably 15 μm or less.

[0059] Here, the length of the pigment in the state contained in the heat seal layer is determined as follows. For the cross section of the heat seal layer, a magnified photograph is taken using an electron microscope. At this time, the magnification is such that about 20 to 30 pigments are included in the screen. The individual lengths of the pigments in the screen are measured. 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 may be described in terms of particle diameter.

[0060] 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. A smaller average thickness of the pigment can provide a higher heat seal peel strength. Here, the thickness of the pigment in the state of being contained in the heat seal layer is determined as follows. For the cross-section of the heat seal layer, a magnified photograph is taken using an electron microscope. At this time, the magnification is such that about 20 to 30 pigments are included in the screen. The individual thicknesses of the pigments in the screen are measured. Then, the average value of the obtained thicknesses is calculated and taken as the thickness of the pigment.

[0061] Specific examples of the pigment include mica, bentonite, kaolin, pyrophyllite, talc, smectite, vermiculite, chlorite, septarian chlorite, serpentine, stilpnomelane, montmorillonite, heavy 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, magnesium carbonate, silicate, colloidal silica, plastic pigment of organic pigment which is hollow or dense, binder pigment , plastic beads, microcapsules, and the like.

[0062] Specific examples of mica include synthetic mica (for example, swelling synthetic mica), muscovite (mascovite), sericite (sericite), phlogopite (fluorophlogopite), biotite (biotite), fluorophlogopite (synthetic mica), red mica, soda mica, vanadium mica, illite, tin mica, paragonite, brittle mica, and the like. Also, specific examples of bentonite include montmorillonite.

[0063] Specific examples of kaolin include various kaolins such as kaolin, calcined kaolin, structured kaolin, delaminated kaolin, and the like.

[0064] Among these, in particular, from the viewpoints of heat seal peel strength, blocking resistance, and economy, pigments with an aspect ratio of 20 or more are preferable, and it is more preferable to contain one or more of mica, bentonite, kaolin, and talc, and kaolin is even more preferable.

[0065] When the heat seal layer contains a pigment, from the viewpoints of blocking resistance and recyclability, the compounding amount of the pigment is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and even more preferably 8 parts by mass or more, based on 100 parts by mass of the water-dispersible resin binder. On the other hand, from the viewpoints of heat sealability and hot tackiness, it is preferably 200 parts by mass or less, more preferably 100 parts by mass or less, and still more preferably 30 parts by mass or less.

[0066] When the heat seal layer contains a pigment, from the viewpoints of blocking resistance and recyclability, the content of the pigment in the heat seal layer is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, and even more preferably 8% by mass or more. And from the viewpoints of heat sealability and hot tackiness, it is preferably 70% by mass or less, more preferably 30% by mass or less, and still more preferably 20% by mass or less.

[0067] (Other components) The heat seal layer may contain other components in addition to the above water-dispersible resin binder, lubricant and / or pigment as required. Examples of other components include silane coupling agents; defoamers; viscosity modifiers; leveling agents such as surfactants and alcohols; colorants such as coloring dyes.

[0068] 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 not easily broken and can be easily opened at the time of opening, it is preferably 3 g / m 2 , more preferably 5 g / m 2 or more, still more preferably 8 g / m 2and above, 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.

[0069] <Physical properties of heat-sealing paper> (Heat-sealing peel strength) The heat-sealing peel strength of the heat-sealing 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, and even more preferably 5.0 N / 15 mm or more, and 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. Further, from the viewpoint of automatic packaging formability, it is preferably 5.2 N / 15 mm or more. The peel strength of the heat-sealing layer is the peel strength when the heat-sealing layers are heat-sealed under the conditions of 150 °C, 0.2 MPa, and 1 second, and specifically, it is measured by the method described in the examples below and is the value measured by this method. The peel strength can be adjusted by selecting the glass transition temperature and type of the water-dispersible resin binder, and 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-sealing layers adhere well to each other, so that the desired peel strength can be ensured.

[0070] (Surface smoothness) The König smoothness of the surface of the heat-sealing layer of the heat-sealing paper of the present embodiment is preferably 30 seconds or more, more preferably 40 seconds or more, even more preferably 50 seconds or more, and even more preferably 60 seconds or more from the viewpoint of improving the heat-sealing peel strength. The upper limit is not particularly limited, but is preferably 500 seconds or less, more preferably 300 seconds or less, and even more preferably 100 seconds or less. The heat seal layer may be provided on the W side (wire side) or F side (felt side) of the paper substrate, and is not particularly limited. Here, the W side (wire side) is the side that contacts the wire when the paper web is formed, and the opposite side is the F side (felt side). Furthermore, the Oken smoothness of the side opposite the heat seal layer (for example, the surface of the paper base when the heat seal layer is provided on only one side of the paper base and the other side is exposed paper base) is preferably 3 seconds or more, more preferably 5 seconds or more, from the viewpoint of improving printability, and while there is no particular upper limit, it is preferably 1000 seconds or less, more preferably 300 seconds or less, and even more preferably 100 seconds or less. Oken smoothness is measured in accordance with JIS P8155:2010. The Oken smoothness of the heat seal layer surface and the opposite surface of the heat seal paper can be adjusted within the above range by a supercalendering treatment described later or the like.

[0071] The basis weight of the heat seal paper is 40g / m 2 ~130g / m 2 It is preferable that the thickness is 70 g / m 2 ~120g / m 2 More preferably, it is 80 g / m 2 ~120g / m 2 It is more preferable that the basis weight is equal to or more than the lower limit. When the basis weight is equal to or more than the upper limit, the strength is high and the breakage during molding can be further suppressed. On the other hand, when the basis weight is equal to or less than the upper limit, the strength is moderately high and the wrinkles during molding can be further suppressed. Therefore, when the basis weight is within the above numerical range, the moldability can be improved.

[0072] The thickness of the heat seal paper is preferably 60 μm to 350 μm, more preferably 70 μm to 250 μm, even more preferably 80 μm to 200 μm, and even more preferably 100 μm to 150 μm.

[0073] The density of the heat seal paper is 0.40g / m 3 ~1.00g / m 3 It is preferable that the thickness is 0.60 g / m3 ~0.90 g / m 3 is more preferably, 0.70 g / m 3 ~0.85 g / m 3 is even more preferably.

[0074] <Method for manufacturing heat-sealing paper> The method for manufacturing the heat-sealing paper of the present embodiment includes a coating step of coating a heat-sealing layer on at least one surface of the paper substrate obtained as described above. Note that the heat-sealing layer coating liquid (heat-sealing layer paint) may be coated two or more times.

[0075] When forming a plurality of heat-sealing layers on the paper substrate, the above method of sequentially forming the heat-sealing layers is preferable, but it is not limited thereto, and a simultaneous multilayer coating method may be employed. The simultaneous multilayer coating method is a method of simultaneously forming a multilayer heat-sealing layer by discharging a plurality of types of coating liquids separately from slit nozzles to form a liquid laminate and coating it on the paper substrate.

[0076] There is no particular limitation on the coating equipment for coating the heat-sealing layer coating liquid on the paper substrate, and known equipment may be used. Examples of the 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, a simsizer, and the like.

[0077] There is no particular limitation on the drying equipment for drying the heat-sealing layer, and known equipment can be used. Examples of the drying equipment include a hot air dryer, an infrared dryer, a gas burner, a hot plate, and the like. Also, the drying temperature may be appropriately set in consideration of the drying time and the like.

[0078] The solvent of the heat-sealing 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, from the viewpoint of not causing problems with volatile organic solvents, water is preferable as the dispersion medium of the heat-sealing layer coating liquid. That is, the heat-sealing layer coating liquid is preferably an aqueous composition for the heat-sealing layer.

[0079] The solid content (solid concentration) of the heat-sealing layer coating liquid is not particularly limited and may be appropriately selected from the viewpoints of coatability and ease of drying. Preferably, it is 10% by mass or more, more preferably 20% by mass or more, still 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, and even more preferably 40% by mass or less.

[0080] The preferable range of the coating amount (after drying) of the heat-sealing layer is as described above. The heat-sealing layer may be a single layer or two or more layers. When the heat-sealing layer has two or more layers, the above coating amount represents the total coating amount.

[0081] After coating and drying the heat-sealing layer, it is also preferable to perform supercalendering treatment. Here, the supercalendering treatment is installed independently of papermaking. Generally, paper or the like to be treated is passed between metal rolls or between a metal roll and an elastic roll, and heating, pressurization, etc. are performed. The supercalendering treatment may be performed in one stage or multiple stages and is not particularly limited. By performing the supercalendering treatment, the smoothness of the surface of the heat-sealing layer is improved, and as a result, it is preferable because it leads to an improvement in the heat-sealing peel strength and an improvement in the hot tack property (difficulty of peeling immediately after heat-sealing). Also, the smoothness of the surface opposite to the heat-sealing layer (for example, when the heat-sealing layer is provided only on one surface of the paper base material and the other surface is the exposed paper base material surface) is improved, and as a result, it is preferable because the printing suitability is improved. Furthermore, by performing supercalendering treatment, the density of the heat-sealing paper tends to increase, and as described above, the surface smoothness is improved. Therefore, when making bags, the feeding of the heat-sealing paper in the packaging machine is improved, and the processing suitability is improved, which is preferable.

[0082] The line pressure in the supercalendering treatment 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, still more preferably 200 kg / cm or less. However, the above line pressure may be appropriately changed according to the desired smoothness and density. When heating is performed in the supercalendering treatment, the heating temperature is not particularly limited. However, from the viewpoint of enhancing the effect of the treatment while preventing deterioration due to heat of the paper substrate and the heat-sealing layer and preventing adhesion of the heat-sealing layer, it is preferably 20°C or more, more preferably 30°C or more, still more preferably 35°C or more, and preferably 80°C or less, more preferably 70°C or less, still more preferably 60°C or less.

[0083] The use of the obtained heat-sealing paper is not particularly limited, and by appropriately forming it into a molded body, it can be used for paper processed products such as packaging papers, packaging bags, packaging containers, and various containers such as cups and trays. For example, it can be formed into paper containers such as paper plates, paper cups, and paper trays, and bags for horizontal pillow packaging, vertical pillow packaging, three-side seal packaging, four-side seal packaging, bag-type filling packaging, tube packaging, and stick packaging, and then used. The forming method is not particularly limited, and known methods can be adopted. For example, it can be formed into a desired shape by press forming.

[0084] Hereinafter, the measurement methods of various physical properties will be described. <Specific Tensile Brittleness> The specific tensile brittleness in the longitudinal and transverse directions of the paper substrate and the heat-sealing paper is ISO / DIS Measure in accordance with JIS P 8113:2006. Specifically, it is as follows. Prepare samples with a test piece length of 150 mm and a test piece width of 15 mm in both the longitudinal and transverse directions, and condition them for 1 day in an environment of 23 ± 5°C and 50 ± 10% Rh. Then, in that environment, using a tensile testing machine (model RTC-1210A, manufactured by A&D Company, Limited), set the sample so that the distance between the chucks is 100 mm, and conduct the test at a speed of 100 mm / min.

[0085] <Elongation at break> The elongation at break in the longitudinal and transverse directions of the paper substrate and heat-seal paper is measured in accordance with JIS P 8113:2006 (Test method for tensile properties of paper and paperboard). Specifically, as the temperature and humidity conditioning treatment, prepare samples cut from a paper substrate or heat-seal paper that has been left standing in an environment of 23 ± 5°C and 50 ± 10% for 1 day or more, with a width of 15 mm and a length of 150 mm. Using a tensile testing machine (model RTC-1210A, manufactured by A&D Company, Limited), attach the sample so that the distance between the chucks is 100 mm, and conduct a tensile test at a speed of 20 mm / min to measure the elongation at break in each of the MD (longitudinal direction) and CD (transverse direction).

[0086] <Length-weighted average fiber length of pulp> The length-weighted average fiber length of pulp in the paper substrate and heat-seal paper is measured in accordance with ISO 16065-2:2007. Specifically, it is as follows. Cut out the paper substrate or heat-seal paper into a 40 cm square, immerse it in ion-exchanged water, adjust the solid content concentration to 2% by mass, and then immerse it for 24 hours. After immersing for 24 hours, use a standard type disintegrator (manufactured by Kumagai Riki Kogyo Co., Ltd.) to conduct a disintegration treatment for 30 minutes to disintegrate the pulp into fibrous form. Using the obtained sample of pulp fibers, use a fiber length measuring machine (model FS-5 with UHD base unit, manufactured by Valmet) to measure the "length-weighted average fiber length (ISO)". The "length-weighted average fiber length (ISO)" is the length-weighted average fiber length calculated by selecting fibers with a length of 0.2 mm or more and 7.6 mm or less.

[0087] <Grammage> The grammage of the paper base material and the heat-sealing paper is measured in accordance with JIS P 8124:2011.

[0088] <Thickness> The thickness (paper thickness) of the paper base material and the heat-sealing paper is measured in accordance with JIS P 8118:2014.

[0089] <Density> The density of the paper base material and the heat-sealing paper is calculated from the thickness and grammage obtained by the above-described measuring method. From.

Example

[0090] The features of the present invention will be described more specifically with reference to the following examples and comparative examples. The materials, amounts used, ratios, treatment details, treatment procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below. Also, unless otherwise specified, "parts" represents "parts by mass". In addition, the operations of the examples and comparative examples were carried out under conditions of room temperature (20 to 25 °C) and normal humidity (40 to 50% RH) unless otherwise specified.

[0091] <Example 1> [Manufacture of paper base material] NUKP (softwood unbleached kraft pulp) and LUKP (hardwood unbleached kraft pulp) obtained by pulping (cooking) wood were used at a ratio (mass ratio) of NUKP:LUKP = 30:70, and beaten at a slurry concentration of 2% by mass during beating until the CSF (Canadian Standard Freeness) reached 600 mL to prepare pulp. Using the above pulp, 0.15 part of a synthetic sizing agent (SPS400 manufactured by Arakawa Chemical Industries, Ltd.), 1.2 parts of sulfuric acid band, 0.65 part of a polyacrylamide resin (DS4433 manufactured by Starlight PMC Co., Ltd.) as a retention aid, and 0.035 part of nonionic polyacrylamide (Percol 47 manufactured by Allied Colloid) as a polymer flocculant (retention aid) were added to 100 parts of pulp on a solids basis to prepare a paper stock. Using the above paper stock, on a wet paper machine (Bellform III type, manufactured by Mitsubishi Heavy Industries, Ltd.) equipped with a stretching device (manufactured by Kurapak), paper was made at a paper-making speed of 600 m / min, a reel moisture content of 6.5%, a nip pressure of 150 kN / m by calendar treatment, a speed difference of -37.5% before and after Kurapak treatment, and a nip pressure between the nip roll and the blanket of 15 kN / m during Kurapak treatment, and a crepe was imparted to the surface of the paper to obtain a paper base material with a basis weight of 50 g / m 2 Note that the production of the paper base material was carried out in the order of papermaking, dehydration by calendar treatment, and Kurapak treatment (including drying).

[0092] [Preparation of Heat-Seal Layer Coating] 98 parts (in terms of solid content) of an aqueous dispersion of a styrene / butadiene copolymer (SBR) (manufactured by Nippon Zeon Co., Ltd., Nipol latex LX407S12, solid content 46%, glass transition temperature 18 °C (catalog value)) and 2 parts (in terms of solid content) of a paraffin wax emulsion (manufactured by Chukyo Yushi Co., Ltd., Hydrin L-700, solid content 30%) were mixed, water was added to make the solid content concentration 33%, and the mixture was stirred to prepare a heat-seal layer coating (concentration 33%). The above styrene / butadiene copolymer had a solubility in water at 25 °C of 10 g / L or less.

[0093] [Manufacture of Heat-Seal Paper] The obtained heat-seal layer coating was applied to the W surface of the above paper base material with an air knife coater so that the coating amount after drying of the heat-seal layer was 10 g / m 2 and dried with a dryer at 130 to 160 °C. Finally, with a line pressure of 90 kg / cm, a chilled roll was brought into contact with the coated surface and a cotton roll was brought into contact with the uncoated surface, the roll was heated to 40 °C, and a one-stage super-calender treatment was performed to obtain heat-seal paper.

[0094] <Example 2> A paper base material was manufactured by adjusting the pulp discharge amount to change the basis weight to 80 g / m 2 and heat-seal paper was obtained under the same conditions as in Example 1 except for this.

[0095] <Example 3> By adjusting the discharge amount of the pulp, a paper base material was produced under the same conditions as in Example 1 except that the basis weight was changed to 100 g / m². 2 A heat-sealing paper was obtained under the same conditions as in Example 1, except that the paper base material was produced by changing the basis weight to 100 g / m² by adjusting the discharge amount of the pulp.

[0096] <Example 4> A heat-sealing paper was obtained under the same conditions as in Example 1, except that a paper base material was produced by changing the mass ratio of NUKP (softwood unbleached kraft pulp) and LUKP (hardwood unbleached kraft pulp) obtained by pulping (cooking) wood to NUKP:LUKP = 45:55.

[0097] <Example 5> A heat-sealing paper was obtained under the same conditions as in Example 1, except that a paper base material was produced by changing the mass ratio of NUKP (softwood unbleached kraft pulp) and LUKP (hardwood unbleached kraft pulp) obtained by pulping (cooking) wood to NUKP:LUKP = 85:15.

[0098] <Example 6> A heat-sealing paper was obtained under the same conditions as in Example 1, except that a paper base material was produced by changing the mass ratio of NUKP (softwood unbleached kraft pulp) and LUKP (hardwood unbleached kraft pulp) obtained by pulping (cooking) wood to NUKP:LUKP = 100:0.

[0099] <Example 7> A heat-sealing paper was obtained under the same conditions as in Example 1, except that a paper base material was produced by papermaking at a speed difference of -18.0% before and after the Kurpack treatment.

[0100] <Example 8> 98 parts (in terms of solid content) of an aqueous dispersion of a commercially available ethylene-acrylic acid copolymer A (glass transition temperature 45°C) and 2 parts (in terms of solid content) of an aqueous dispersion of a commercially available carnauba wax were mixed, water was added to make the solid content concentration 35%, and the mixture was stirred to prepare a heat-sealing layer coating (concentration 35%). A heat-sealing paper was obtained in the same manner as in Example 4, except that the obtained heat-sealing layer coating was used, and heat-sealing layer formation and supercalendering were performed.

[0101] <Example 9> Instead of 2 parts (in terms of solid content) of paraffin wax emulsion, 2 parts ( in terms of solid content) of polyethylene wax emulsion (Aquacer 531, manufactured by BYK, solid content concentration 45% by mass) was added to prepare the heat-sealing layer coating. In the same manner as in Example 4, except for this, heat-sealing layer formation and super-calendering treatment were carried out to obtain heat-sealing paper.

[0102] <Example 10> Heat-sealing layer formation and super-calendering treatment were carried out in the same manner as in Example 4, except that paraffin wax emulsion was not added, to obtain heat-sealing paper.

[0103] <Example 11> Instead of the aqueous dispersion of styrene / butadiene copolymer in the heat-sealing layer coating, an aqueous dispersion of ethylene / vinyl acetate copolymer (manufactured by Sumitomo Chemical Tex Co., Ltd., SumikaFlex 470HQ, solid content 55%, glass transition temperature 0 °C (catalog value)) was used. Heat-sealing layer formation and super-calendering treatment were carried out in the same manner as in Example 4, except that paraffin wax emulsion was not used, to obtain heat-sealing paper.

[0104] <Example 12> 98 parts (in terms of solid content) of an aqueous dispersion of styrene / butadiene copolymer (manufactured by Nippon Zeon Co., Ltd., Nipol latex LX407S12, solid content 46%, glass transition temperature 18 °C (catalog value)) and 2 parts (in terms of solid content) of carnauba wax emulsion (ML160RPH, manufactured by Michaelman, solid content concentration 25% by mass) were mixed, and water was added and stirred so that the solid content concentration became 33% to prepare a heat-sealing layer coating (concentration 33%). In the same manner as in Example 4, except for this, heat-sealing layer formation and super-calendering treatment were carried out to obtain heat-sealing paper.

[0105] <Example 13> 88 parts (in terms of solid content) of an aqueous dispersion of a styrene / butadiene copolymer (manufactured by Nippon Zeon Co., Ltd., Nipol latex LX407S12, solid content 46%, glass transition temperature 18 °C (catalog value)), 2 parts (in terms of solid content) of a paraffin wax emulsion (manufactured by Chukyo Yushi Co., Ltd., Hydrin L-700, solid content 30%), and 10 parts (in terms of solid content) of kaolin (Imerys Contrex Extreme, average particle diameter 8 μm, aspect ratio 80 - 100, dispersed in water to a solid content of 50 mass%) were mixed, and water was added and stirred to a solid content concentration of 33%. A heat seal layer coating (concentration 33%) was prepared. In the same manner as in Example 4, except for this, heat seal layer formation and super calendering were performed to obtain heat seal paper.

[0106] <Example 14> A heat seal paper was obtained in the same manner as in Example 4, except that super calendering was not performed after heat seal layer formation.

[0107] <Comparative Example 1> A heat seal paper was obtained under the same conditions as in Example 1, except that the nip pressure by the calendar was changed to 100 kN / m to manufacture the paper substrate.

[0108] <Comparative Example 2> A heat seal paper was obtained under the same conditions as in Example 1, except that the nip pressure by the calendar was changed to 180 kN / m to manufacture the paper substrate.

[0109] <Comparative Example 3> A heat seal paper was obtained under the same conditions as in Example 1, except that the nip pressure by the calendar was changed to 200 kN / m to manufacture the paper substrate.

[0110] <Comparative Example 4> A heat seal paper was obtained under the same conditions as in Example 1, except that the paper substrate was manufactured without applying Kurpack treatment.

[0111] <Comparative Example 5> A heat seal paper was obtained under the same conditions as in Example 1, except that the paper substrate was manufactured with the speed difference before and after Kurpack treatment changed to -45.0%.

[0112] <Comparative Example 6> A heat-sealing paper was obtained under the same conditions as in Example 1, except that the nip pressure by the calendar was changed to 100 kN / m and the paper substrate was produced without applying the Kurapak treatment.

[0113] <Comparative Example 7> The paper substrate produced in Example 4 was used as it was.

[0114] <Evaluation> [Formability] The following evaluations were carried out using the obtained heat-sealing paper or paper substrate. The obtained heat-sealing paper or paper substrate was cut out to obtain 3 A4 blank sheets with the longitudinal direction (MD) as the long side. The blank sheets 3 were pressed using a forming die (1 and 2) and a press forming machine (FVT400, manufactured by Wakizaka Engineering Co., Ltd.) under the conditions of a press pressure of 35 kgf / cm 2 , a press temperature of 150 °C, and a press time of 5 seconds, and pressed as shown in Fig. 1 to form a tray shape as shown in Fig. 2. The obtained trays were evaluated for the presence or absence of wrinkles and tears according to the following criteria. As shown in Figs. 1 and 2, the edge of the opening of the tray was evaluated as the forming part 4. The larger the numerical value, the better. 5: No breakage or wrinkles occur in the forming part, and no distortion occurs in the tray. 4: No breakage or wrinkles occur in the forming part, but distortion occurs in the tray. 3: No breakage occurs in the forming part, but wrinkles occur on 1 to 3 sides out of the 4 sides of the forming part. 2: No breakage occurs in the forming part, but wrinkles occur on all 4 sides of the forming part. 1: Breakage occurs in the forming part.

[0115] [Heat-sealing peel strength] Two sheets of heat-sealing paper were overlapped so that the heat-sealing layers faced each other, and heat-sealed under the conditions of 150 °C, 0.2 MPa, and 1 second using a heat-sealing tester (manufactured by Tester Sangyo Co., Ltd., TP-701-B). 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 into a width of 15 mm, and T-peel separation was performed at a tensile speed of 300 mm / min using a tensile testing machine, and the maximum load recorded was taken as the heat-seal peel strength. In Table 3, "-" indicates that no adhesion occurred and measurement was impossible.

[0116] [Automatic packaging formability] Using a high-speed horizontal pillow packaging machine (αWrapper FW3410, manufactured by Fujikikai Co., Ltd.), the heat-sealing paper was continuously formed into bags. At this time, no contents were put in, and the forming was done with empty bags, and the following judgments were made by observing the appearance and operability. Here, "impossible to continuously form bags" refers to a state where wrinkles occur, the paper snakes and does not form into a bag, or paper breakage occurs. Also, "poor appearance" refers to the inclusion of wrinkles, misalignment of the seal part, or deformation of the bag. A: It was possible to continuously form bags, and the appearance of the bags was good. B: It was possible to continuously form bags, but there were slight defects in the appearance of the bags. C: It was impossible to continuously form bags.

[0117] The physical properties and evaluation results of Examples 1 to 14 and Comparative Examples 1 to 7 are shown in Tables 1 to 3.

Table 1

[0118]

Table 2

[0119]

Table 3

Explanation of symbols

[0120] 1, 2: Mold for forming, 3: Blank sheet, 4: Forming part

Claims

1. A heat-sealable paper having one or more heat-sealing layers on at least one surface of a paper substrate, wherein the heat-sealing layer contains a water-dispersible resin binder, the specific tensile strength in the longitudinal direction of the heat-sealable paper, measured in accordance with ISO / DIS 1924-3, is 1.7 kN·m / g to 4.0 kN·m / g, and the specific tensile strength in the transverse direction of the heat-sealable paper is 1.4 kN·m / g to 2.9 kN·m / g, the elongation at break in the longitudinal direction of the heat-sealable paper, measured in accordance with JIS P 8113:2006, is 5.0% to 10.0%, and the elongation at break in the transverse direction of the heat-sealable paper is 5.0% to 10.0%, the heat-sealable paper.

2. the specific tensile strength in the longitudinal direction is 2.4 kN·m / g to 3.9 kN·m / g, the specific tensile strength in the transverse direction is 1.8 kN·m / g to 2.9 kN·m / g, the heat-sealable paper according to claim 1.

3. The pulp obtained by delaminating the heat-sealable paper has a length-weighted average fiber length of 1.1 mm to 2.0 mm, measured in accordance with ISO 16065-2:2007, the heat-sealable paper according to claim 1.

4. The basis weight is 40 g / m ２ to 130 g / m ２ The heat-sealing paper according to claim 1, wherein the basis weight is in the range of 40 g / m to 130 g / m.

5. the elongation at break in the longitudinal direction is 7.0% to 9.7%, the elongation at break in the transverse direction is 6.5% to 9.5%, the heat-sealable paper according to claim 1.

6. the paper substrate contains pulp the pulp contains softwood kraft pulp, the content of the softwood kraft pulp in the pulp is 25% by mass or more, the heat-sealable paper according to claim 1.

7. the heat-sealing layer further contains a lubricant, the heat-sealable paper according to claim 1.

8. the lubricant contains at least one selected from the group consisting of paraffin wax, carnauba wax, and polyolefin wax, the heat-sealable paper according to claim 7.

9. the content of the lubricant in the heat-sealing layer is 1% by mass or more and 5% by mass or less, the heat-sealable paper according to claim 7.

10. the glass transition temperature of the water-dispersible resin binder is 0°C or higher and 100°C or lower, the heat-sealable paper according to claim 1.

11. The heat-sealing paper according to claim 1, wherein the water-dispersible resin binder contains at least one selected from the group consisting of a styrene-butadiene copolymer, an olefin-fatty acid vinyl ester copolymer, and an olefin-unsaturated carboxylic acid copolymer.

12. A paper processed product using the heat-sealing paper according to any one of claims 1 to 11.

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