Heat seal paper and paper processed product

Abstract

To provide heat seal paper which has high extensibility, prevents generation of breakage and wrinkles at four corners even in molding into a tray shape, 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 1.3 kN m / g to 6.0 kN m / g and 1.6 kN m / g to 6.0 kN m / g, respectively, a ratio (vertical direction / lateral direction) of the specific tensile strength in the vertical direction to the specific tensile strength in the lateral direction is 1.1 or less, 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 5.5% to 10.0%, respectively.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to heat-sealable papers and paper products. [Background technology]

[0002] Plastic materials have been mainly used for packaging containers such as food trays and pillow packaging bags, etc. However, due to environmental concerns, paper-based packaging materials are being considered as an alternative to plastic containers. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2015 / 008703 Summary of the Invention [Problem to be solved by the invention]

[0004] When manufacturing packaging using paper, a material having extensibility is preferable from the viewpoint of formability. The present inventors attempted to form food trays using conventional paper such as that described in Patent Document 1, but found that the trays were prone to wrinkles at the four corners and even to tear. The present disclosure relates to heat-sealable paper and paper products using the heat-sealable paper, which have high extensibility, are resistant to tears and wrinkles at the four corners even when formed into a tray, and have excellent heat-sealing properties. [Means for solving the problem]

[0005] That is, the present disclosure provides the following: <1> ~ <10> Regarding. <1> A heat-sealable paper having one or more heat-sealable layers on at least one side of a paper substrate, the heat seal layer contains a water-dispersible resin binder, the heat seal paper has a longitudinal tensile stiffness index of 1.3 kN m / g to 6.0 kN m / g, a transverse tensile stiffness index of 1.6 kN m / g to 6.0 kN m / g, and a ratio (longitudinal / transverse) of the longitudinal tensile stiffness index to the transverse tensile stiffness index of 1.1 or less, as measured in accordance with ISO / DIS 1924-3; The heat seal paper has a longitudinal breaking elongation of 5.0% to 10.0% and a transverse breaking elongation of 5.5% to 10.0%, as measured in accordance with JIS P 8113:2006. Heat seal paper. <2> The ratio of the tensile stiffness index in the longitudinal direction to the tensile stiffness index in the transverse direction (longitudinal direction / transverse direction) is 0.7 to 1.0. <1> The heat seal paper according to claim 1. <3> The fiber orientation ratio measured in accordance with JIS Z0203 is 1.0 to 2.0. <1> or <2> The heat seal paper according to claim 1. <4> Basis weight: 40g / m 2 ~130g / m 2 That is, <1> ~ <3> 1. The heat sealable paper according to any one of the preceding items. <5> the heat seal layer further comprises a lubricant; <1> ~ <4> 1. The heat sealable paper according to any one of the preceding items. <6> The lubricant comprises at least one selected from the group consisting of paraffin wax, carnauba wax, and polyolefin wax. <5> The heat seal paper according to claim 1. <7> The content of the lubricant in the heat seal layer is 1% by mass or more and 5% by mass or less. <5> or <6> The heat seal paper according to claim 1. <8> The glass transition temperature of the water-dispersible resin binder is 0°C or higher and 100°C or lower. <1> ~ <7> 1. The heat sealable paper according to any one of the preceding items. <9> 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; <1> ~ <8> 1. The heat sealable paper according to any one of the preceding items. <10> <1> ~ <9> A paper product obtained by using the heat seal paper described in any one of the above. [Effects of the Invention]

[0006] According to the present disclosure, it is possible to provide heat-sealable paper that is highly extensible, that is resistant to tearing and wrinkling at the four corners even when formed into a tray shape, and that has excellent heat-sealing properties. Furthermore, according to the present disclosure, it is possible to provide heat-sealable paper that has excellent formability for automatic packaging. [Brief explanation of the drawings]

[0007] [Figure 1] Schematic diagram of press processing [Figure 2] Example of a tray made from heat-sealed paper DETAILED DESCRIPTION OF THE INVENTION

[0008] In the present disclosure, unless otherwise specified, the expressions "X or more and Y or less" or "X to Y" representing a numerical range mean a numerical range including the lower and upper limits, which are the endpoints. When a numerical range is described in stages, the upper and lower limits of each numerical range can be combined in any way. The machine direction is the machine direction (MD) of the paper base material, which is the same as the direction in which the fibers are oriented. The cross direction is the direction perpendicular to the machine direction (CD). The machine direction of heat-seal paper corresponds to the machine direction of the paper base material, and the cross direction of heat-seal paper corresponds to the CD direction of the paper base material. "Excellent formability in automatic packaging (hereinafter also referred to as automatic packaging formability)" means that bags can be continuously produced in an automatic packaging machine, and the resulting bags have a good appearance. More specifically, for example, when automatically producing packaging bags, the occurrence of wrinkles and poor appearance is suppressed, and sticking to the forming machine (blocking) is suppressed, resulting in excellent formability and further suppressing deformation of the bags after production, meaning that the resulting packaging bags have excellent quality and productivity.

[0009] Clupak treatment is a process that gives paper stretchability by minutely shrinking it on a paper machine. Specifically, for example, a Clupak device equipped with an endless thick elastic rubber blanket with nip rolls is installed in a part of the paper machine dryer. A wet paper web is introduced into the Clupak device and compressed by the nip rolls and blanket. At this time, the blanket, which has been stretched in advance, contracts, causing the running paper web to shrink (crepe), thereby increasing the breaking elongation. The resulting shrinkage is then dried and fixed in place in a subsequent process to prevent stretching.

[0010] The present inventors have discovered that the above-mentioned problems can be solved by controlling the heat-sealable paper to a specific tensile stiffness index and breaking elongation by Clupak treatment during the production of a paper base material used in the heat-sealable paper. The tensile stiffness index indicates the stiffness of the paper, and the breaking elongation indicates the ease with which the paper stretches. When heat-sealable paper has the above-mentioned specific tensile stiffness index and breaking elongation, it indicates that the heat-sealable paper has a moderate stiffness while also being somewhat easy to stretch. In particular, the present inventors believe that by making the tensile stiffness index in the CD direction (cross direction) similar to or larger than the tensile stiffness index in the MD direction (machine direction), it is possible to obtain heat-sealable paper that has high extensibility and is less likely to tear or wrinkle at the four corners even when formed into a tray shape.

[0011] The tensile stiffness index of the heat-sealable paper in the machine direction, measured in accordance with ISO / DIS 1924-3, must be 1.3 kN m / g to 6.0 kN m / g, and the tensile stiffness index of the heat-sealable paper in the cross direction must be 1.6 kN m / g to 6.0 kN m / g. If the tensile stiffness index is below the lower limit, too much stress is applied during molding, making the material prone to wrinkling and tearing. On the other hand, if the tensile stiffness index is above the upper limit, the pressure required for molding becomes too high, making molding difficult, and forcible molding tends to cause wrinkling and tearing.

[0012] The tensile stiffness of heat seal paper can be controlled by the manufacturing conditions of the paper base material used. Specifically, the speed difference before and after Clupak treatment, the J / W ratio during paper making, and the nickel content of the paper due to the calendar treatment. It can be controlled by adjusting the density by nip pressure, the type of pulp, etc. To increase the tensile stiffness index, methods such as reducing the speed difference before and after Clupak treatment, increasing the density by increasing the nip pressure through calendaring, and increasing the fiber length of the pulp can be mentioned. On the other hand, to decrease the tensile stiffness index, methods such as increasing the speed difference before and after Clupak treatment, decreasing the density by decreasing the nip pressure through calendaring, and decreasing the fiber length of the pulp can be mentioned.

[0013] The specific tensile stiffness in the machine direction of the heat seal paper is preferably 1.4 kN·m / g to 4.5 kN·m / g, and more preferably 1.5 kN·m / g to 4.0 kN·m / g. The specific tensile stiffness in the transverse direction of the heat seal paper is preferably 1.8 kN·m / g to 5.0 kN·m / g, and more preferably 2.0 kN·m / g to 4.0 kN·m / g.

[0014] The ratio of the specific tensile stiffness in the longitudinal direction of the heat-sealable paper to the specific tensile stiffness in the transverse direction (longitudinal direction / transverse direction) is 1.1 or less. By satisfying this range, it is possible to obtain heat-sealable paper that has high extensibility and is less likely to tear or wrinkle at its four corners even when formed into a tray shape. From the viewpoint of obtaining a higher effect, the ratio is preferably 0.7 to 1.0.

[0015] The heat seal paper must have a breaking elongation of 5.0% to 10.0% in the machine direction and a breaking elongation of 5.5% to 10.0% in the cross direction, as measured in accordance with JIS P 8113:2006. If the breaking elongation is below the lower limit, the paper will not stretch enough during molding, making it difficult to mold. Forcing molding will result in tearing. On the other hand, if the breaking elongation exceeds the upper limit, molding is possible due to the high elongation, but the paper will be more likely to move, wrinkle, and tear.

[0016] The breaking elongation of heat seal paper can be controlled by the manufacturing conditions of the paper base material used, specifically by the basis weight, the difference in speed before and after Clupak treatment, the nip pressure during Clupak treatment, etc. Methods for increasing the breaking elongation include increasing the basis weight, increasing the difference in speed before and after Clupak treatment, and decreasing the nip pressure during Clupak treatment. On the other hand, methods for decreasing the breaking elongation include decreasing the basis weight, decreasing the difference in speed before and after Clupak treatment, and increasing the nip pressure during Clupak treatment.

[0017] The breaking elongation in the machine direction of the heat seal 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 breaking elongation in the machine direction is preferably 9.7% or less. The breaking elongation in the transverse direction of the heat seal paper is preferably 6.5% or more, more preferably 7.0% or more. The upper limit of the breaking elongation in the transverse direction is preferably 9.5% or less, more preferably 9.0% or less, and even more preferably 8.5% or less.

[0018] The ratio of the longitudinal breaking elongation to the transverse breaking elongation of the heat seal paper (longitudinal / transverse) is preferably 1.01 or more, more preferably 1.03 or more, and even more preferably 1.05 or more, while the upper limit is preferably 1.30 or less, more preferably 1.20 or less, and even more preferably 1.15 or less.

[0019] The fiber orientation ratio of the heat-sealable paper, measured according to JIS Z0203, is preferably 1.0 to 2.0, more preferably 1.1 to 1.8, even more preferably 1.2 to 1.6, and even more preferably 1.2 to 1.4. It is presumed that if the fiber orientation ratio is too small, the pulp tends to be mixed in both the longitudinal and transverse directions, making it easier for wrinkles to form in both the longitudinal and transverse directions during molding. On the other hand, if the fiber orientation ratio is too large, the pulp tends to be oriented in the longitudinal direction, making it easier for wrinkles to form in the transverse direction. Therefore, keeping the fiber orientation ratio within the above numerical range can improve moldability. The fiber orientation ratio of the heat-sealable paper can be controlled by the type of pulp used in the paper substrate, the J / W ratio when making the paper substrate, and other factors.

[0020] [Paper base material] The basis weight of the paper base material used for heat seal paper is 30 g / m 2 ~120g / m 2 Preferably, it is 60 g / m 2 ~110g / m 2 More preferably, it is 70 g / m 2 ~100g / m 2 It is more preferable that the basis weight is equal to or greater than the lower limit. When the basis weight is equal to or greater than the upper 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 upper limit, the strength is moderately high and wrinkles during molding can be further suppressed. Therefore, when the basis weight is within the above numerical range, moldability can be improved.

[0021] 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.

[0022] The density of the paper substrate is 0.30 g / m 3 ~1.00g / m 3 It is preferable that the density is 0.40 g / m 3 ~0.90g / m 3 More preferably, it is 0.50 g / m 3 ~0.90g / m 3More preferably, it is 0.60 g / m 3 ~0.85g / m 3 It is even more preferred that:

[0023] The fiber orientation ratio of the paper base material, measured in accordance with JIS Z0203, is preferably 1.0 to 2.5, more preferably 1.1 to 2.0, and even more preferably 1.2 to 1.8. Within the above numerical range, moldability can be improved. The fiber orientation ratio of the paper base material can be controlled by the type of pulp used in the paper base material, the J / W ratio when making the paper base material, etc.

[0024] The tensile stiffness index in the machine direction of the paper substrate, measured in accordance with ISO / DIS 1924-3, is preferably 1.0 kN·m / g to 8.0 kN·m / g, and more preferably 1.5 kN·m / g to 6.0 kN·m / g. Furthermore, the tensile stiffness index in the cross direction of the paper substrate, measured in accordance with ISO / DIS 1924-3, is preferably 1.5 kN·m / g to 6.0 kN·m / g, and more preferably 1.8 kN·m / g to 5.0 kN·m / g. The ratio of the specific tensile stiffness in the machine direction to the specific tensile stiffness in the cross direction (machine direction / cross direction) is preferably 0.3 or more and 1.3 or less, and more preferably 0.5 or more and 1.2 or less. By satisfying the above range, the tensile stiffness index of the heat seal paper can be easily adjusted to the desired range, which is preferable.

[0025] The breaking elongation in the machine direction of the paper base material, measured in accordance with JIS P 8113:2006, is preferably 4.5% to 10.0%, more preferably 5.0% to 9.5%, and the breaking elongation in the cross direction of the paper base material, measured in accordance with JIS P 8113:2006, is preferably 5.0% to 10.0%, more preferably 6.0% to 9.5%. The ratio of the breaking elongation in the machine direction to the breaking elongation in the cross direction (machine direction / cross direction) is preferably 0.50 or more and 1.50 or less, and more preferably 0.75 or more and 1.25 or less. By satisfying the above range, it becomes easier to adjust the breaking elongation of the heat seal paper to a desired range, which is preferable.

[0026] Next, materials that can be used for the paper substrate will be described. The paper substrate contains, for example, pulp. Pulps constituting the paper base material include hardwood kraft pulps such as unbleached hardwood kraft pulp (LUKP) and bleached hardwood kraft pulp (LBKP); softwood kraft pulps such as unbleached softwood kraft pulp (NUKP) and bleached softwood kraft pulp (NBKP); mechanical pulps such as groundwood pulp (GP), pressure groundwood pulp (PGW), refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), chemi-mechanical pulp (CMP), and chemi-ground pulp (CGP); recycled paper pulp; non-wood fiber pulps such as kenaf, bagasse, bamboo, and cotton; and synthetic pulp. These pulps may be used alone or in combination of two or more.

[0027] The pulp preferably contains hardwood kraft pulp, more preferably contains unbleached hardwood kraft pulp, and even more preferably contains unbleached hardwood kraft pulp and unbleached softwood kraft pulp. The content of unbleached hardwood kraft pulp is preferably greater than the content of unbleached softwood kraft pulp.

[0028] The content of softwood kraft pulp in the pulp is preferably 0% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and even more preferably 13% by mass or more, while the upper limit is preferably 70% by mass or less, more preferably 55% by mass or less, even more preferably 50% by mass or less, and even more preferably 47% by mass or less.

[0029] The hardwood kraft pulp content in the pulp is preferably 25% by mass or more, more preferably 35% by mass or more, even more preferably 45% by mass or more, even more preferably 50% by mass or more, and even more preferably 53% by mass or more, while the upper limit is preferably 100% by mass or less, more preferably 95% by mass or less, even more preferably 90% by mass or less, and even more preferably 87% by mass or less.

[0030] The beating degree of pulp is not particularly limited, but is preferably 200 to 800 mL, more preferably 450 to 700 mL, in terms of Canadian Standard Freeness (CSF). The CSF is measured in accordance with JIS P 8121-2:2012 "Pulp - Testing Method for Freeness - Part 2: Canadian Standard Freeness Method."

[0031] Additives may be used in the paper base material as needed. Examples of additives include pH adjusters (sodium bicarbonate, sodium hydroxide, etc.), dry strength agents (polyacrylamide, starch, etc.), wet strength agents (polyamide polyamine epichlorohydrin resin, melamine-formaldehyde resin, or urea-formaldehyde resin), internal sizing agents (rosin-based, alkyl ketene dimer, etc.), drainage yield aids (polyacrylamide resin), antifoaming agents, fillers (calcium carbonate, talc, etc.), dyes, etc. 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 normally used.

[0032] [Method for manufacturing paper substrate] One method for producing a paper base material involves making a stock containing pulp and then subjecting it to Clupak treatment during the papermaking process. The stock may further contain additives as needed. Examples of additives include those mentioned above. The stock can be prepared by adding additives to a pulp slurry as needed. The pulp slurry can be obtained by beating pulp in the presence of water. The pulp beating method and beating device are not particularly limited, and known beating methods and beating devices can be used.

[0033] The solids concentration of the pulp slurry during beating is not particularly limited, but is preferably about 5 to 40% by mass, more preferably about 5 to 30% by mass. The pulp content in the stock or paper base is also not particularly limited, and may be within a commonly used range. For example, the pulp content is preferably 60% by mass or more and 100% by mass or less, and more preferably 80% by mass or more and less than 100% by mass, based on the total mass of the stock (solids) or paper base.

[0034] In papermaking of paper substrates, a known wet paper machine can be appropriately selected and used. Examples of paper machines include Fourdrinier paper machines, gap former paper machines, cylinder paper machines, and short wire paper machines. The Clupak treatment can be carried out by providing a Clupak device capable of carrying out the Clupak treatment in these paper machines. For example, the Clupak treatment can be carried out after papermaking from a stock and dewatering by calendering.

[0035] Known Clupak devices can be used. For example, a Clupak device equipped with nip rolls and an endless thick elastic rubber blanket can be used. As described above, in the Clupak process, a paper web is fed between the nip rolls and the blanket, and when the paper web is compressed by the nip rolls and the blanket, the pre-stretched blanket is contracted to shrink the paper web and impart creping. The Clupak device is usually installed as part of the dryer unit of a paper machine, and after creping, the paper is dried and fixed. In this manner, a paper base material can be obtained.

[0036] In papermaking using a Clupak device, the tensile stiffness index and breaking elongation 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, for example, within a range of preferably 200 to 1,000 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 blanket during Clupak treatment is also not particularly limited. For example, it may be appropriately controlled within a range of preferably 5 kN / m to 50 kN / m, and more preferably 10 kN / m to 25 kN / m. The speed difference before and after Clupak treatment is not particularly limited, and may be controlled so as to obtain the desired tensile stiffness index and breaking elongation depending on the basis weight and pulp material. It is preferably -45.0 m / min to -10.0 m / min, and more preferably -40.0 m / min to -15.0 m / min. Here, the minus sign "-" indicates that the speed after Clupak treatment is slow.

[0037] In papermaking using a Clupac apparatus, the jet / wire ratio (hereinafter also referred to as the J / W ratio) is not particularly limited, but is, for example, preferably 1.00 or more and 1.50 or less, more preferably 1.00 or more and 1.30 or less, and even more preferably 1.00 or more and 1.20 or less.

[0038] [Heat seal layer] The heat seal paper of this embodiment has at least one heat seal layer on at least one side of a paper substrate. The heat seal layer is a layer that melts and adheres by heating, ultrasonic waves, etc. .

[0039] (Water-dispersible resin binder) The heat-seal layer contains a water-dispersible resin binder. A water-dispersible resin binder is a resin binder that is not water-soluble (specifically, has a solubility of 10 g / L or less in water at 25°C), but is finely dispersed in water like an emulsion or suspension. By applying a water-based coating to the heat-seal layer using a water-dispersible resin binder, heat-seal paper with excellent redisintegration properties can be obtained that can be recycled as paper. Note that if a water-dispersible resin binder also falls under the category of a lubricant, it will be classified as a lubricant.

[0040] The water-dispersible resin binder is not particularly limited as long as it exhibits the effects of the present invention, and examples thereof include polyolefin resins (polyethylene, polypropylene, etc.), vinyl chloride resins, styrene resins, styrene-butadiene copolymers, styrene-unsaturated carboxylic acid copolymers (for example, styrene-(meth)acrylic acid copolymers), acrylic resins, acrylonitrile-styrene copolymers, acrylonitrile-butadiene copolymers, ABS resins, AAS resins, AES resins, vinylidene chloride resins, polyurethane resins, poly-4-methylpentene Examples of the resin include polybutene-1 resin, polybutene-1 resin, vinylidene fluoride resin, vinyl fluoride resin, fluorine resin, polycarbonate resin, polyamide resin, acetal resin, polyphenylene oxide resin, polyester resin (polyethylene terephthalate, polybutylene terephthalate, etc.), polyphenylene sulfide resin, polyimide resin, polysulfone resin, polyethersulfone resin, polyarylate resin, olefin-fatty acid vinyl ester copolymer, olefin-unsaturated carboxylic acid copolymer, and modified products thereof. These may be used alone or in combination of two or more.

[0041] Among these, at least one selected from the group consisting of styrene-butadiene copolymer, olefin-fatty acid vinyl ester copolymer, and olefin-unsaturated carboxylic acid copolymer is preferred, and at least one selected from the group consisting of styrene-butadiene copolymer and olefin-unsaturated carboxylic acid copolymer is more preferred. 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 preferred, and from the viewpoints of availability, cost, and recyclability, styrene-butadiene copolymers are more preferred.

[0042] Examples of the olefin-unsaturated carboxylic acid copolymer include an ethylene-(meth)acrylic acid copolymer, an ethylene-(meth)acrylic acid alkyl ester copolymer, etc. Among these, an ethylene-(meth)acrylic acid copolymer is preferred, and an ethylene-acrylic acid copolymer is 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 preferably at least one selected from the group consisting of styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, and ethylene-(meth)acrylic acid copolymer, and more preferably at least one selected from the group consisting of styrene-butadiene copolymer and ethylene-(meth)acrylic acid copolymer. The olefin-unsaturated carboxylic acid copolymer may be an ionomer.

[0043] The styrene-butadiene copolymer may be either a synthetic product or a commercially available product. Commercially available products include Nipol Latex LX407G51, LX407S10, LX407S12, LX410, LX415M, LX416, LX430, and LX415M manufactured by Nippon Zeon Co., Ltd. X433C, 2507H, Narustar 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.

[0044] The ethylene-(meth)acrylic acid copolymer may be either a synthetic product or a commercially available product. Examples of commercially available products include MP498345N, MP4983R, MP4990R, and MFHS1279 manufactured by Michelman Japan LLC, ZAIXXEN (registered trademark) A and ZAIXXEN (registered trademark) AC manufactured by Sumitomo Seika Chemicals Co., Ltd., and the Chemipearl S series manufactured by Mitsui Chemicals, Inc.

[0045] 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 whose glass transition temperature is equal to or higher than the above-mentioned lower limit, the occurrence of blocking can be suppressed. From the viewpoint of heat sealability, the glass transition 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. The glass transition temperature of the water-dispersible resin binder is measured by a differential scanning calorimeter in accordance with JIS K 7121:1987.

[0046] 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, more preferably 98% by mass or less. If it is within the above range, a heat-sealable paper having high heat-seal peel strength can be obtained.

[0047] That is, according to one embodiment of the present invention, the content of at least one selected from the group consisting of styrene-butadiene copolymer, olefin-fatty acid vinyl ester copolymer, and olefin-unsaturated carboxylic acid copolymer (preferably ethylene-(meth)acrylic acid copolymer) 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 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.

[0048] (lubricant) From the viewpoint of imparting lubricity 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, when blended into the heat-sealable layer, can reduce the coefficient of friction of the heat-sealable layer surface.

[0049] The lubricant is not particularly limited, and examples thereof include wax, metal soap, and fatty acid ester. Lubricants 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 wax; and synthetic waxes such as polyolefin wax, paraffin wax, and polyester wax. 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 preferred because they have a relatively low melting point, facilitate the formation of wax components on the coating layer surface, and have excellent blocking suppression effects. That is, the lubricant is preferably at least one selected from the group consisting of paraffin wax, carnauba wax, and polyolefin wax. As the carnauba wax, either a synthetic product or a commercially available product may be used, and an example of a commercially available product is Cellosol 524 manufactured by Chukyo Yushi Co., Ltd. As the paraffin wax, either a synthetic product or a commercially available product may be used, and an example of a commercially available product is Hydrin L-700 manufactured by Chukyo Yushi Co., Ltd. As the polyethylene wax, either a synthetic product or a commercially available product may be used, and an example of a commercially available product is Aquacer 531 manufactured by BYK.

[0050] 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, even more preferably 1 part by mass or more, and preferably 30 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, per 100 parts by mass of the water-dispersible resin binder.

[0051] 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, even more preferably 1% by mass or more, and preferably 30% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less.

[0052] In this embodiment, the heat seal layer contains a water-dispersible resin binder, and preferably contains a lubricant in addition to the water-dispersible resin binder. In addition to the water-dispersible resin binder and, if necessary, the lubricant, the heat seal layer may also contain a pigment.

[0053] (pigment) In this embodiment, the heat-seal layer may contain a pigment in addition to the water-dispersible resin binder. By containing a pigment, the problem of the heat-seal layer coating surface sticking to the back surface of the heat-seal paper and causing peeling (blocking) during production of the heat-seal paper can be suppressed, and heat-seal paper with excellent blocking resistance can be obtained.

[0054] The pigment is not particularly limited, and examples include various pigments used in conventional pigment coating layers. A single pigment may be used, or two or more pigments may be used in combination. From the viewpoints of heat seal peel strength and blocking resistance, a pigment with an aspect ratio of 20 or more is preferred. The aspect ratio of the pigment is more preferably 25 or more, even more preferably 30 or more, and particularly preferably 60 or more. From the viewpoints of availability and the smoothness of the heat seal layer surface, the aspect ratio is preferably 10,000 or less, more preferably 1,000 or less, and even more preferably 300 or less. The aspect ratio of the pigment means the ratio of the major axis to the minor axis, and may be measured by the method described below.

[0055] The pigment is preferably a layered inorganic compound having an aspect ratio of 20 or more. The layered inorganic compound has a tabular form. 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 heat sealability can be obtained.

[0056] The length (average particle diameter) of the pigment is preferably 0.1 μm or more and 100 μm or less. If the length is 0.1 μm or more, the pigment is likely to be aligned parallel to the paper substrate. If the length is 100 μm or less, there is little concern that part of the pigment will protrude from the heat seal layer. The length of the pigment is more preferably 0.3 μm or more, even more preferably 0.5 μm or more, particularly preferably 1.0 μm or more, and more preferably 30 μm or less, even more preferably 20 μm or less, particularly preferably 15 μm or less.

[0057] Here, the length of the pigment contained in the heat seal layer is determined as follows: A magnified photograph of the cross section of the heat seal layer is taken using an electron microscope. The magnification is set so that approximately 20 to 30 pigment particles are included within the image. The length of each pigment particle within the image is measured. The average of the obtained lengths is then calculated and used as the length of the pigment. The length of the pigment is sometimes expressed as particle diameter.

[0058] The thickness of the pigment is preferably 200 nm or less. The thickness of the pigment is more preferably 100 nm or less, even more preferably 80 nm or less, even more preferably 50 nm or less, and particularly preferably 30 nm or less. It is also 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: A magnified photograph of the cross section of the heat seal layer is taken using an electron microscope. The magnification should be such that approximately 20 to 30 pigment particles are included in the image. The thickness of each pigment in the image is measured. The average of the obtained thicknesses is then calculated to determine the thickness of the pigment.

[0059] Specific examples of pigments include mica, bentonite, kaolin, pyrophyllite, talc, smectite, vermiculite, chlorite, septe chlorite, serpentine, stilpnomelane, montmorillonite, heavy calcium carbonate (ground calcium carbonate), light calcium carbonate (synthetic calcium carbonate), composite synthetic pigments 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, silicates, colloidal silica, hollow or solid organic pigment plastic pigments, binder pigments, plastic beads, and microcapsules.

[0060] Specific examples of mica include synthetic mica (for example, swellable synthetic mica), white mica (muscovite), sericite (sericite), phloxopite, biotite (biotite), fluorphlogopite (artificial mica), red mica, soda mica, vanadium mica, illite, zinc mica, paragonite, brittle mica, etc. Specific examples of bentonite include montmorillonite.

[0061] Specific examples of kaolin include various types of kaolin such as kaolin, calcined kaolin, structured kaolin, and delaminated kaolin.

[0062] Among these, pigments having an aspect ratio of 20 or more are preferred from the viewpoints of heat seal peel strength, blocking resistance, and economy, and it is more preferred to contain one or more of mica, bentonite, kaolin, and talc, with kaolin being even more preferred.

[0063] When the heat seal layer contains a pigment, the amount of pigment to be blended is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and even more preferably 8 parts by mass or more, per 100 parts by mass of the water-dispersible resin binder, from the viewpoints of blocking resistance and recyclability; on the other hand, from the viewpoints of heat sealability and hot tackiness, the amount is preferably 200 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 30 parts by mass or less.

[0064] 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, even more preferably 5% by mass or more, and even more preferably 8% by mass or more from the viewpoints of blocking resistance and recyclability, and is preferably 70% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less from the viewpoints of heat sealability and hot tackiness.

[0065] (Other ingredients) The heat seal layer may contain other components in addition to the water-dispersible resin binder and, if necessary, a lubricant and / or a pigment, such as a silane coupling agent, an antifoaming agent, a viscosity modifier, a leveling agent such as a surfactant or alcohol, and a colorant such as a coloring dye.

[0066] 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 tear and can be easily opened when opened, it is preferably 3 g / m 2 , more preferably 5 g / m 2 More preferably, 8 g / m 2 and preferably 30 g / m 2 Less than 20 g / m, more preferably 2 or less, more preferably 15 g / m 2 The following is the result.

[0067] <Physical properties of heat seal paper> (Heat seal peel strength) The heat seal peel strength of the heat seal paper is preferably 2.0 N / 15 mm or more, more preferably 3.0 N / 15 mm or more, even more preferably 4.0 N / 15 mm or more, even more preferably 5.0 N / 15 mm or more, and 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 formability, it is preferably 5.7 N / 15 mm or more. The peel strength of the heat seal layer is the peel strength when the heat seal layers are heat sealed together under conditions of 150°C, 0.2 MPa, and 1 second, and is specifically a value measured by the method described in the Examples below. 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 the specified heat-sealing conditions, and the heat-sealing layers bond well to each other, ensuring the desired peel strength.

[0068] (Surface smoothness) In order to improve the heat seal peel strength, the Oken smoothness of the heat seal layer surface of the heat seal paper of this embodiment is preferably 30 seconds or more, more preferably 40 seconds or more, even more preferably 50 seconds or more, and even more preferably 55 seconds or more, and although there is no particular upper limit, it 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 either the W side (wire side) or the F side (felt side) of the paper substrate, and is not particularly limited. Here, the W side (wire side) refers to 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 surface opposite the heat seal layer (for example, the surface of the paper substrate when the heat seal layer is provided on only one side of the paper substrate and the paper substrate is exposed on the other side) is preferably 3 seconds or more, more preferably 5 seconds or more, from the viewpoint of improving printability, and although 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 supercalendering, which will be described later.

[0069] The basis weight of the heat seal paper is 40 g / 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 weight is equal to or greater than the lower limit. When the weight is equal to or greater than the upper limit, the strength is increased and breakage during molding can be further suppressed. On the other hand, when the weight is equal to or less than the upper limit, the strength is adequately strong and wrinkles during molding can be further suppressed. Therefore, when the weight is within the above numerical range, moldability can be improved. .

[0070] 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.

[0071] The density of the heat seal paper is 0.40 g / m 3 ~1.00g / m 3 It is preferable that the density is 0.60 g / m 3 ~0.90g / m 3 More preferably, it is 0.70 g / m 3 ~0.99g / m 3 It is more preferable that:

[0072] <Heat seal paper manufacturing method> The method for producing heat-sealable paper of this embodiment includes a coating step of applying a heat-sealable layer to at least one side of the paper substrate obtained as described above. The heat-sealable layer coating liquid (heat-sealable layer paint) may be applied two or more times.

[0073] When forming multiple heat-seal layers on a paper substrate, the above-mentioned method of forming heat-seal layers sequentially is preferred, but the present invention is not limited to this, and a simultaneous multi-layer coating method may also be adopted. The simultaneous multi-layer coating method is a method in which multiple types of coating liquids are separately ejected from slit-shaped nozzles to form a liquid laminate, which is then coated on the paper substrate to simultaneously form multiple heat-seal layers.

[0074] There are no particular limitations on the coating equipment used to apply the heat seal layer coating liquid to the paper substrate, and known equipment may be used, such as 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, or a shim sizer.

[0075] The drying equipment for drying the heat seal layer is not particularly limited, and known equipment can be used. Examples of drying equipment include a hot air dryer, an infrared dryer, a gas burner, and a hot plate. The drying temperature can be appropriately set taking into account the drying time, etc.

[0076] The solvent for the heat-seal layer coating liquid is not particularly limited, and water or an organic solvent such as ethanol, isopropyl alcohol, methyl ethyl ketone, or toluene can be used. Among these, water is preferred as the dispersion medium for the heat-seal layer coating liquid, from the viewpoint of avoiding the problems of volatile organic solvents. In other words, the heat-seal layer coating liquid is preferably an aqueous composition for a heat-seal layer.

[0077] The solid content (solid content concentration) of the heat seal layer coating liquid is not particularly limited and may be selected appropriately from the viewpoints of coatability and ease of drying, but is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and is preferably 80% by mass or less, more preferably 60% by mass or less, even more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[0078] The preferred range of the coating weight (after drying) of the heat seal layer is as described above. The heat seal layer may be one layer or two or more layers. When the heat seal layer has two or more layers, the above coating weight represents the total coating weight.

[0079] It is also preferable to carry out a supercalendering treatment after coating and drying the heat seal layer. Here, the supercalendering treatment is carried out by a machine installed independently of the papermaking machine, and generally by a machine using a metal roll. The paper or the like to be treated is passed between a metal roll and an elastic roll, or between a metal roll and an elastic roll, and then heated, pressed, etc. The supercalendering treatment may be carried out in one stage or in multiple stages, and is not particularly limited. Supercalendering is preferred because it improves the smoothness of the heat seal layer surface, resulting in improved heat seal peel strength and hot tackiness (difficulty in peeling immediately after heat sealing). It is also preferable because it improves the 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 paper base is exposed on the other side), thereby improving printability. Furthermore, supercalendering tends to increase the density of the heat-sealable paper, and as mentioned above, improves the surface smoothness, which is preferable because it allows the heat-sealable paper to be easily fed out of the packaging machine when making bags, improving its suitability for processing.

[0080] The linear pressure in the supercalendering treatment is preferably 10 kg / cm or more, more preferably 30 kg / cm or more, and even more preferably 50 kg / cm or more, and is preferably 1000 kg / cm or less, more preferably 500 kg / cm or less, and even more preferably 200 kg / cm or less, although the linear pressure may be appropriately changed depending on the desired smoothness and density. Furthermore, when heating is performed in the supercalendering treatment, the heating temperature is not particularly limited, but from the viewpoint of enhancing the effect of the treatment while preventing thermal deterioration of the paper substrate or the heat seal layer and sticking of the heat seal layer, the heating temperature is preferably 20°C or higher, more preferably 30°C or higher, even more preferably 35°C or higher, and is preferably 80°C or lower, more preferably 70°C or lower, even more preferably 60°C or lower.

[0081] The use of the obtained heat seal paper is not particularly limited, and by appropriately forming it into a molded article, it can be used for paper processed products such as packaging such as wrapping paper, packaging bags, and 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-feed filling packaging, tube packaging, and stick packaging. The molding method is not particularly limited, and known methods can be used. For example, it can be molded into the desired shape by press molding.

[0082] The methods for measuring each physical property are described below. <Specific tensile strength> The tensile stiffness ratios in the machine and cross directions of paper substrates and heat seal papers are specified in accordance with ISO / DIS Measurements are made in accordance with 1924-3. Specifically, the procedure is as follows: Samples with a length of 150 mm and a width of 15 mm are prepared in both the longitudinal and transverse directions, and conditioned for one day at 23±5°C and 50±10% RH. Then, under the same conditions, a tensile testing machine (model RTC-1210A, manufactured by A&D Co., Ltd.) is used to set the sample so that the chuck distance is 100 mm, and the test is performed at a speed of 100 mm / min.

[0083] <Breaking elongation> The longitudinal and transverse breaking elongation of the paper substrate and heat seal paper is measured in accordance with JIS P 8113:2006 (Testing methods for tensile properties of paper and paperboard). Specifically, the paper substrate or heat-sealed paper is left to stand for one day in a temperature- and humidity-controlled environment of 23±5°C and 50±10%, and then cut into a sample 15 mm wide and 150 mm long. The sample is attached to a tensile tester (model RTC-1210A, manufactured by A&D Co., Ltd.) with a chuck distance of 100 mm, and a tensile test is performed at a speed of 20 mm / min to measure the breaking elongation in both the MD (machine direction) and CD (cross direction).

[0084] <Fiber orientation ratio> The fiber orientation ratio of paper substrates and heat-sealable paper is measured in accordance with JIS Z 0203. Specifically, samples are cut into 200 mm squares and left to stand for one day in a temperature- and humidity-controlled environment of 23±5°C and 50±10% humidity. The fiber orientation ratio is then measured using a fiber orientation property evaluation device (model SST-2500, manufactured by Nomura Shoji Co., Ltd.).

[0085] <Basic weight> The basis weight of the paper substrate and heat seal paper is measured in accordance with JIS P 8124:2011.

[0086] <Thickness> The thickness of the paper substrate and heat seal paper (paper thickness) is measured in accordance with JIS P 8118:2014.

[0087] <density> The density of the paper substrate and the heat seal paper is calculated from the thickness and basis weight obtained by the above-mentioned measurement method. [Example]

[0088] The features of the present invention will be explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below. Furthermore, unless otherwise specified, "parts" refers to "parts by mass." Furthermore, the operations of the examples and comparative examples were carried out at room temperature (20-25°C) and normal humidity (40-50% RH) unless otherwise specified.

[0089] Example 1 [Paper base manufacturing] Pulp was prepared by using NUKP (softwood unbleached kraft pulp) and LUKP (hardwood unbleached kraft pulp) made from pulped (cooked) wood in a ratio (mass ratio) of 30:70, and beating the mixture to a slurry concentration of 12 mass% at the time of beating until the CSF (Canadian Standard Freeness) reached 600 mL. Using the above pulp, a paper stock was prepared by adding 0.15 parts by mass of a synthetic sizing agent (SPS400, manufactured by Arakawa Chemical Industries, Ltd.), 1.2 parts by mass of aluminum sulfate, 0.65 parts by mass of a polyacrylamide resin (DS4433, manufactured by Seiko PMC Corporation) as a retention agent, and 0.035 parts by mass of a nonionic polyacrylamide (Percoll 47, manufactured by Allied Colloids) as a polymer flocculant (retention agent) per 100 parts by mass of pulp (solid content equivalent). Using the above paper stock, paper was made on a wet paper machine (Bellform III, manufactured by Mitsubishi Heavy Industries, Ltd.) equipped with an expansion device (manufactured by Clupak) at a papermaking speed of 600 m / min, a speed difference before and after Clupak treatment of -35.0 m / min, a nip pressure between the nip roll and blanket during Clupak treatment of 15 kN / m, and a J / W ratio of 1.00. The paper had a basis weight of 80 g / m2 with crepe applied to the surface. 2 A paper substrate of 100g was obtained.

[0090] [Preparation of heat seal layer coating] A heat seal coating (33% concentration) was prepared by mixing 98 parts (solids equivalent) of an aqueous dispersion of a styrene / butadiene copolymer (Nipol Latex LX407S12, manufactured by Nippon Zeon Co., Ltd., 46% solids, glass transition temperature 18°C ​​(catalog value)) with 2 parts (solids equivalent) of a paraffin wax emulsion (Hydrin L-700, manufactured by Chukyo Yushi Co., Ltd., 30% solids), adding water to a solids concentration of 33%, and stirring. The solubility of the styrene / butadiene copolymer in water at 25°C was 10 g / L or less.

[0091] [Heat seal paper manufacturing] The obtained heat seal layer coating material was applied to the W side of the paper substrate in a coating amount of 10 g / m after drying. 2 A heat seal layer was formed using an air knife coater so that the thickness of the coated surface was 130 to 160°C, and the coated surface was dried in a dryer at 130 to 160°C. Finally, a linear pressure of 90 kg / cm was applied so that the coated surface was in contact with a chilled roll and the uncoated surface was in contact with a cotton roll. The rolls were heated to 40°C, and a one-stage supercalendering treatment was performed to obtain heat seal paper.

[0092] <Example 2> Heat-sealable paper was obtained under the same conditions as in Example 1, except that the paper base material was produced with the following changes: the slurry concentration during beating was 10% by mass, the CSF was beaten until it reached 550 mL, and the J / W ratio during papermaking was 1.05.

[0093] Example 3 Heat-sealable paper was obtained under the same conditions as in Example 1, except that the paper base material was produced with the following changes: the slurry concentration during beating was set to 8% by mass, the CSF was beaten to 450 mL, and the J / W ratio during papermaking was set to 1.10.

[0094] Example 4 Heat-sealable paper was obtained under the same conditions as in Example 1, except that the paper base material was produced with the following changes: the slurry concentration during beating was 5% by mass, beating was continued until the CSF reached 400 mL, the speed difference before and after the Clupak treatment during papermaking was -20.0 m / min, and the J / W ratio during papermaking was 1.20.

[0095] <Example 5> Heat-sealable paper was obtained under the same conditions as in Example 1, except that the paper base material was produced with the following changes: the slurry concentration during beating was set to 5% by mass, the CSF was beaten to 400 mL, and the J / W ratio during papermaking was set to 1.20.

[0096] Example 6 Heat-sealable paper was obtained under the same conditions as in Example 1, except that the paper base material was produced with the following changes: the slurry concentration during beating was set to 5% by mass, the CSF was beaten to 400 mL, and the J / W ratio during papermaking was set to 1.50.

[0097] Example 7 98 parts (solids equivalent) of a commercially available aqueous dispersion of ethylene-acrylic acid copolymer A (glass transition temperature 45°C) and 2 parts (solids equivalent) of a commercially available aqueous dispersion of carnauba wax were mixed, and water was added to the mixture to a solids concentration of 35% and the mixture was stirred to prepare a heat-seal layer coating material (concentration 35%). Heat-seal layer formation and supercalendering were carried out in the same manner as in Example 2, except that the obtained heat-seal layer coating material was used, to obtain heat-seal paper.

[0098] Example 8 Instead of 2 parts of paraffin wax emulsion (solid content equivalent), 2 parts of polyethylene wax emulsion (Aquacer 531, manufactured by BYK, solid content concentration 45% by mass) The heat seal layer was formed and supercalendered in the same manner as in Example 2, except that the heat seal layer coating material was prepared by adding 100% cellulose acetate (based on solid content) to the heat seal layer coating material, to obtain a heat seal paper.

[0099] Example 9 A heat seal layer was formed and supercalendered in the same manner as in Example 2, except that no paraffin wax emulsion was added, to obtain a heat seal paper.

[0100] Example 10 Heat-seal layer formation and supercalendering were carried out in the same manner as in Example 2, except that an aqueous dispersion of ethylene / vinyl acetate copolymer (Sumikaflex 470HQ, manufactured by Sumika Chemtex Co., Ltd., solids content 55%, glass transition temperature 0°C (catalog value)) was used instead of the aqueous dispersion of styrene / butadiene copolymer used in the heat-seal layer paint, and no paraffin wax emulsion was used, to obtain heat-seal paper.

[0101] Example 11 A heat-seal layer coating (concentration 33%) was prepared by mixing 98 parts (solids equivalent) of an aqueous dispersion of a styrene / butadiene copolymer (Nipol Latex LX407S12, manufactured by Nippon Zeon Co., Ltd., solids content 46%, glass transition temperature 18°C ​​(catalog value)) and 2 parts (solids equivalent) of a carnauba wax emulsion (ML160RPH, manufactured by Michelman, solids concentration 25% by mass), adding water to the mixture and stirring to adjust the solids concentration to 33%, and then carrying out heat-seal layer formation and supercalendering treatment in the same manner as in Example 2 to obtain a heat-seal paper.

[0102] Example 12 A water dispersion of styrene / butadiene copolymer (manufactured by Nippon Zeon Co., Ltd., Nipol Latex LX407S12, solids concentration 46 mass%, glass transition temperature 18 ° C (catalog value)) 88 parts (solids equivalent), paraffin wax emulsion (manufactured by Chukyo Yushi Co., Ltd., Hydrin L-700, solids concentration 30 mass%) 2 parts (solids equivalent), kaolin (manufactured by Imerys Contour Extreme, average particle size 8 μm, aspect ratio 80 to 100, dispersed in water to a solids content of 50 mass%) 10 parts (solids equivalent) were mixed, water was added to the solids concentration of 33%, and the mixture was stirred. A heat-seal layer coating (solids concentration 33 mass%) was prepared. Except for this, heat-seal layer formation and supercalendering were carried out in the same manner as in Example 2 to obtain heat-seal paper.

[0103] Example 13 A heat seal paper was obtained in the same manner as in Example 2, except that the supercalendering treatment was not carried out after the heat seal layer was formed.

[0104] <Comparative Example 1> Heat-sealable paper was obtained under the same conditions as in Example 1, except that the paper base material was produced with the following changes: the slurry concentration during beating was 10% by mass, the CSF was beaten until it reached 650 mL, and the J / W ratio during papermaking was 1.10.

[0105] <Comparative Example 2> Heat-sealable paper was obtained under the same conditions as in Example 1, except that the paper base material was produced with the following changes: the slurry concentration during beating was 8% by mass, beating was carried out until the CSF became 550 mL, the speed difference before and after the Clupak treatment during papermaking was -15.0 m / min, and the J / W ratio during papermaking was 1.10.

[0106] <Comparative Example 3> Heat-sealable paper was obtained under the same conditions as in Example 1, except that the paper base material was produced with the following changes: the slurry concentration during beating was 8% by mass, beating was carried out until the CSF became 330 mL, the speed difference before and after the Clupak treatment during papermaking was -35.0 m / min, and the J / W ratio during papermaking was 1.10.

[0107] <Comparative Example 4> The slurry concentration during beating was set to 2% by mass, and the CSF was beaten until it reached 450 mL. A heat-sealable paper was obtained under the same conditions as in Example 1, except that the paper base material was produced with the following changes: the speed difference before and after Clupak treatment during papermaking was set to -35.0 m / min, and the J / W ratio during papermaking was set to 1.10.

[0108] <Comparative Example 5> Heat-sealable paper was obtained under the same conditions as in Example 1, except that the paper base material was produced with the following changes: the slurry concentration during beating was 2% by mass, beating was continued until the CSF reached 350 mL, the speed difference before and after the Clupak treatment during papermaking was -15.0 m / min, and the J / W ratio during papermaking was 1.10.

[0109] <Comparative Example 6> Heat-sealable paper was obtained under the same conditions as in Example 1, except that the paper base material was produced with the following changes: the slurry concentration during beating was 2% by mass, the beating was continued until the CSF reached 300 mL, no Clupak treatment was added, and the J / W ratio during papermaking was 1.10.

[0110] <Comparative Example 7> Heat-sealable paper was obtained under the same conditions as in Example 1, except that the paper base material was produced with the following changes: the slurry concentration during beating was 10% by mass, beating was carried out until the CSF became 500 mL, the speed difference before and after the Clupak treatment during papermaking was -48.0 m / min, and the J / W ratio during papermaking was 1.10.

[0111] <Comparative Example 8> The paper substrate produced in Example 2 was used as is.

[0112] The obtained heat seal paper or paper substrate was subjected to the following evaluations. The obtained heat seal paper or paper substrate of each of the examples and comparative examples was cut out to obtain an A4 blank sheet 3 with the long side in the machine direction (MD). The blank sheet 3 was pressed at a pressure of 35 kgf / cm using molding dies (1 and 2) and a press molding machine (FVT400, manufactured by Wakisaka Engineering Co., Ltd.). 2 The tray was pressed at a temperature of 150°C for 5 seconds as shown in Figure 1 to form it into the tray shape shown in Figure 2. The resulting tray was evaluated for wrinkles and tears at the four corners of the molded portion according to the following criteria. As shown in Figure 1, the tapered portion of the opening of the tray was evaluated as molded portion 4 (dashed line in the figure). The higher the value, the better the result. 4: There are no tears or wrinkles in the four corner moldings. 3: There is no tearing in the four corner moldings, but wrinkles occur. 2: Tears occur in 1 to 3 places in the four corner molding parts. 1: Tears occur in all four corner moldings.

[0113] [Heat seal peel strength] Two sheets of heat-sealable paper were stacked with the heat-sealable layers facing each other and heat-sealed using a heat-seal tester (Tester Sangyo, TP-701-B) at 150°C, 0.2 MPa, and 1 second. The heat-sealed test specimens were left to stand for at least 4 hours in a room at a temperature of 23°C ± 1°C and a humidity of 50% ± 2%. The heat-sealed test specimens were then cut into 15 mm widths and subjected to T-peel tests at a tensile speed of 300 mm / min using a tensile tester. The recorded maximum load was used as the heat-seal peel strength. In the table, "-" indicates that the specimens were not bonded and could not be measured.

[0114] [Automatic packaging formability] Using a high-speed horizontal pillow packaging machine (αWrapper FW3410, manufactured by Fujikikai Co., Ltd.), bags were continuously made from heat-sealed paper. At this time, no contents were placed inside the bag, and the bag was formed as an empty bag. The appearance and operability were examined and the following judgments were made. Here, "continuous bag making is impossible" means that wrinkles were generated. This refers to a state in which the bag is not fully formed, or the bag is twisted and becomes unformed, or the paper breaks. "Poor appearance" refers to the presence of wrinkles, misaligned seals, or deformation of the bag. A: Continuous bag production was possible and the appearance of the bags was good. B: Continuous bag production was possible, but there were a few bags with poor appearance. C: Continuous bag production was not possible.

[0115] The physical properties of Examples 1 to 13 and Comparative Examples 1 to 8 are shown in Tables 1 and 2, and the evaluation results are shown in Table 3.

[0116] [Table 1]

[0117] [Table 2]

[0118] [Table 3] [Explanation of symbols]

[0119] 1,2: Molding mold 3: Blank sheet 4: Four corner molding parts

Claims

1. A heat-sealable paper having one or more heat-sealable layers on at least one side of a paper substrate, the heat seal layer contains a water-dispersible resin binder, the heat seal paper has a longitudinal tensile stiffness index of 1.3 kN m / g to 6.0 kN m / g, a transverse tensile stiffness index of 1.6 kN m / g to 6.0 kN m / g, and a ratio (longitudinal / transverse) of the longitudinal tensile stiffness index to the transverse tensile stiffness index of 1.1 or less, as measured in accordance with ISO / DIS 1924-3; The heat seal paper has a longitudinal breaking elongation of 5.0% to 10.0% and a transverse breaking elongation of 5.5% to 10.0%, as measured in accordance with JIS P 8113:2006; The ratio of the breaking elongation in the longitudinal direction of the heat seal paper to the breaking elongation in the transverse direction (longitudinal direction / transverse direction) is 0.91 to 1.

30. Heat seal paper.

2. 2. The heat-sealable paper according to claim 1, wherein the ratio of the tensile stiffness index in the machine direction to the tensile stiffness index in the cross direction (machine direction / cross direction) is 0.7 to 1.

0.

3. Basis weight: 40 g / m ２ ~130g / m ２ The heat seal paper according to claim 1, wherein

4. The heat seal paper of claim 1 , wherein the heat seal layer further comprises a lubricant.

5. 5. The heat seal paper according to claim 4, wherein the lubricant comprises at least one selected from the group consisting of paraffin wax, carnauba wax, and polyolefin wax.

6. The heat-sealable paper according to claim 4, wherein the content of the lubricant in the heat-sealable layer is 1% by mass or more and 5% by mass or less.

7. 2. The heat-sealable paper according to claim 1, wherein the water-dispersible resin binder has a glass transition temperature of 0°C or higher and 100°C or lower.

8. 2. The heat-sealable paper according to claim 1, wherein the water-dispersible resin binder comprises 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.

9. 2. The heat-sealable paper according to claim 1, wherein the ratio of the breaking elongation in the machine direction to the breaking elongation in the cross direction (machine direction / cross direction) of the heat-sealable paper is 1.01 to 1.

30.

10. A paper product obtained by using the heat seal paper according to any one of claims 1 to 9.

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