Heat-sealing paper and packaging material

Abstract

To provide heat seal paper which does not contain laminate paper and a plastic film having high environmental loads, and is excellent in blocking suppression properties of a heat fusion surface of a heat seal layer and printability of a non-laminate surface of the heat seal layer.SOLUTION: Heat seal paper has a paper base material containing pulp as a main component, and a heat seal layer laminated on one surface of the paper base material, in which Bekk smoothness on the surface of a laminate surface of the heat seal layer in the paper base material is 5 sec or longer and 50 sec or shorter, Parker print surf smoothness thereon is 3.8 μm or more and 8.0 μm or less, Bekk smoothness on the surface of a non-laminate surface of the heat seal layer in the paper base material is 50 sec or longer and 500 sec or shorter, and Parker print surf smoothness thereon is 2.0 μm or more and 4.2 μm or less. The main component of the heat seal layer is an ionomer resin, and a coating amount of the heat seal layer is preferably 1.5 g / m2 or more and 10.0 g / m2 or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to heat-sealing paper and packaging materials.

Background Art

[0002] Generally, for pillow packaging widely used in the packaging of confectionery, pharmaceuticals, sanitary products, etc., laminated paper or plastic film obtained by extruding polyethylene resin or polypropylene resin on a base paper is used. When such laminated paper or plastic film is used, it is excellent in strength, water resistance, and moisture resistance, but since a non-decomposable plastic film remains, it cannot be used as waste paper, and there is a risk that it may cause marine pollution as microplastics without being subjected to waste treatment after use, leading to an environmental burden.

[0003] For this reason, in the prior art, packaging paper has been proposed that improves heat-sealing strength by providing a heat-sealing layer containing an ionomer on a paper substrate and reduces the amount of plastic used (see Patent Document 1). In addition, a heat-sealing sheet that can be recycled has been proposed by providing a thermally adhesive layer containing styrene-butadiene copolymer latex and setting the smoothness of the thermally adhesive surface within a specific range (see Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the above-mentioned conventional wrapping paper and heat-sealing sheet, although packaging processing is possible by heat-sealing the heat-sealing layers together, the inhibition of blocking on the heat-sealed surface after heat-sealing the heat-sealing layers together and the printability of the non-laminated surface of the heat-sealing layer are not sufficient, and there was room for consideration regarding providing both functions.

[0006] The present invention has been made based on the above circumstances, and an object thereof is to provide a heat-sealing paper that does not include laminated paper or plastic film with a high environmental load and is excellent in the inhibition of blocking on the heat-sealed surface of the heat-sealing layer and the printability of the non-laminated surface of the heat-sealing layer.

Means for Solving the Problems

[0007] The heat-sealing paper according to one aspect of the present invention includes a paper base material mainly composed of pulp and a heat-sealing layer laminated on one side of the paper base material. The Bekk smoothness of the surface of the heat-sealing layer laminated surface in the paper base material is 5 seconds or more and 50 seconds or less, and the Parker print surf smoothness is 3.8 μm or more and 8.0 μm or less. The Bekk smoothness of the surface of the non-laminated surface of the heat-sealing layer in the paper base material is 50 seconds or more and 500 seconds or less, and the Parker print surf smoothness is 2.0 μm or more and 3.6 μm or less.

Effects of the Invention

[0008] According to the present invention, it is possible to provide a heat-sealing paper that does not include laminated paper or plastic film with a high environmental load and is excellent in the inhibition of blocking on the heat-sealed surface of the heat-sealing layer and the printability of the non-laminated surface of the heat-sealing layer.

Modes for Carrying Out the Invention

[0009] [Description of Embodiments of the Present Invention] The heat-sealing paper according to one aspect of the present invention includes a paper base material mainly composed of pulp and a heat-sealing layer laminated on one side of the paper base material. The Bekk smoothness of the surface of the heat-sealing layer lamination surface of the paper base material is 5 seconds or more and 50 seconds or less, and the Parker print surf smoothness is 3.8 μm or more and 8.0 μm or less. The Bekk smoothness of the surface of the non-heat-sealing layer lamination surface of the paper base material is 50 seconds or more and 500 seconds or less, and the Parker print surf smoothness is 2.0 μm or more and 4.2 μm or less.

[0010] In the heat-sealing paper, the Bekk smoothness of the surface of the heat-sealing layer lamination surface of the paper base material, that is, the surface of the surface where the heat-sealing layer is laminated, is 5 seconds or more and 50 seconds or less, so that while ensuring the heat-sealing strength, it is excellent in the effect of suppressing the blocking of the heat-fusion surface of the heat-sealing agent coating surface. Further, the Parker print surf smoothness of the surface of the heat-sealing layer lamination surface of the paper base material is 3.8 μm or more and 8.0 μm or less, so that the heat-sealing strength and a uniform adhesion surface of the heat-sealing layer can be ensured. On the other hand, the Bekk smoothness of the surface of the non-heat-sealing layer lamination surface of the paper base material, that is, the surface of the surface where the heat-sealing layer is not laminated, is 50 seconds or more and 500 seconds or less, so that the heat-sealing paper is excellent in the printing suitability of the non-heat-sealing layer lamination surface that becomes the printing surface. Further, the Parker print surf smoothness of the surface of the non-heat-sealing layer lamination surface of the paper base material is 2.0 μm or more and 4.2 μm or less, so that the heat-sealing paper is excellent in the printing suitability, particularly in gravure printing machines, of the non-heat-sealing layer lamination surface that becomes the printing surface. Therefore, the heat-sealing paper has heat-sealing performance and is excellent in suppressing the blocking of the heat-fusion surface of the heat-sealing layer and the printing suitability of the non-heat-sealing layer lamination surface. In addition, since the heat-sealing paper does not contain laminated paper or plastic film that cannot be recycled and has a high environmental load, it is environmentally friendly. In the present invention, the "heat-sealing layer" refers to a coating layer in which a heat-fusion process is performed. The "main component" refers to the substance having the highest content rate among the constituent substances, preferably having a content rate of 50% by mass or more.

[0011] Both Bekk smoothness and Parker Print Surf (hereinafter also referred to as PPS) smoothness evaluate smoothness based on the air flow rate (air leak). The Bekk smoothness defined in JIS-P8119 (1998) sandwiches the sheet to be measured between an optically flat glass sample table and a rubber pressing plate at a pressure of 100 kPa, and 10 ml of air passes between the relatively wide 10 cm 2 of the glass standard surface and is represented by the time required to flow into a container where the pressure is maintained at a reduced pressure of about 370 mml of mercury column, indicating the smoothness of the surface of the so-called object to be measured. Bekk smoothness evaluates the macro smoothness on a relatively wide surface. In the heat-seal paper, the waviness of the surface can be evaluated by Bekk smoothness.

[0012] On the other hand, the Parker Print Surf smoothness (hereinafter also referred to as "PPS smoothness") of the surface of the heat-seal paper is the Parker Print Surf smoothness (μm) measured according to Appendix A of JIS-P8151 (2004). The Parker Print Surf smoothness is a device that obtains smoothness from the air flow rate in the same way as Bekk smoothness, but by applying pressure to the measurement head, the smoothness under pressure can be measured. The Parker Print Surf smoothness is a value measured using a soft type backing at a clamp pressure of 1.0 Mpa. In the knowledge of the present inventor, in terms of the size of the dots of the microscopic printing plate compared to Bekk smoothness, by applying pressure to the object and measuring, the printing surface property of a printing plate (about 175 lines per inch) that improves the image quality during printing when printing pressure is applied by various printing machines can be evaluated. In the heat-seal paper, the Parker Print Surf smoothness has a close relationship with the surface state of the pulp exposed on the measurement surface. Therefore, the surface of the heat-seal layer of the heat-seal paper can be more appropriately evaluated by Bekk smoothness, and the printing surface property can be more appropriately evaluated by Parker Print Surf smoothness. Thus, by keeping both the evaluation values of the above-mentioned Bekk smoothness and the above-mentioned Parker Print Surf smoothness within a predetermined range, the surface flatness of the heat-seal paper on a somewhat wide surface and a microscopic surface can be evaluated.

[0013] The main component of the heat-sealing layer is an ionomer resin, and the coating amount (in terms of solid content) of the heat-sealing layer is 1.5 g / m 2 or more and 10.0 g / m 2 or less. Since the main component of the heat-sealing layer is an ionomer resin, the heat-sealing strength is good not only at normal temperature but also at low temperatures. Also, since the coating amount of the heat-sealing layer is within the above range, the heat-sealing strength and the suppression of blocking of the heat-fused surface of the heat-sealing layer can be further improved. The heat-sealing paper can achieve both good heat-sealing strength and suppression of blocking of the heat-fused surface of the heat-sealing layer with a coating amount within the above range because the main component of the heat-sealing layer is an ionomer resin.

[0014] It is preferable that the Bek smoothness of the surface of the heat-sealing layer is 8 seconds or more and 70 seconds or less, and the Parker print surface smoothness is 3.0 μm or more and 5.3 μm or less. Since the Bek smoothness and the Parker print surface smoothness of the surface of the heat-sealing layer are within the above range, the heat-sealing paper can further improve the heat-sealing strength and the suppression of blocking of the heat-fused surface.

[0015] The moisture permeability of the heat-sealing paper is preferably 1,000 g / m 2 ·24 hr or more and 2,000 g / m 2 ·24 hr or less. Since the moisture permeability of the heat-sealing paper is within the above range, the moisture of the contents to be packaged is less likely to turn into water droplets and can maintain an appropriate humidity, so the quality of the contents can be kept good. Here, the "moisture permeability" is a value measured in accordance with JIS-Z0208 (1976).

[0016] The packaging material according to another embodiment of the present invention has the heat-sealing paper. Since the packaging material has the heat-sealing paper, it is excellent in suppressing blocking of the heat-fused surface of the heat-sealing layer and printability of the non-laminated surface of the heat-sealing layer, and can be recycled.

[0017] [Details of Embodiments of the Present Invention] Hereinafter, the heat-sealing paper according to an embodiment of the present invention will be described in detail. Note that the blending amount (absolute dry internal addition amount) of each material blended in the paper base material described below refers to the mass ratio with respect to the absolute dry mass of the pulp of the paper base material, unless otherwise specified. Further, the content rate of each material blended in the composition for forming the heat-sealing layer refers to the absolute dry mass ratio of each material with respect to the mass of the entire heat-sealing layer, unless otherwise specified.

[0018] <Heat-sealing paper> The heat-sealing paper has a heat-sealing layer on one surface of the paper base material. The heat-sealing layer may be either a single-layer or a multi-layer structure.

[0019] [Paper base material] The paper base material is obtained by papermaking a slurry containing raw material pulp. The paper base material may be either single-layer or multi-layer.

[0020] (Raw material pulp) The paper base material is mainly composed of pulp. As the raw material pulp constituting the paper base material, for example, virgin pulp, waste paper pulp, a combination of these pulps, etc. can be used.

[0021] As the virgin pulp, for example, chemical pulps such as hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood semi-bleached kraft pulp (LSBKP), softwood semi-bleached kraft pulp (NSBKP), hardwood sulfite pulp, softwood sulfite pulp, etc.; mechanical pulps (MP) such as stone ground pulp (SGP), pressure stone ground pulp (TGP), chemiground pulp (CGP), groundwood pulp (GP), thermomechanical pulp (TMP), etc., pulps produced chemically or mechanically, etc. can be used alone or in combination of a plurality. From the viewpoint of the appearance of the printing surface and the use for food packaging applications, it is preferable to use only bleached kraft pulp.

[0022] Examples of waste paper pulp include defibrated waste paper pulp, defibrated and deinked waste paper pulp (DIP), defibrated, deinked, and bleached waste paper pulp, etc. produced from tea waste paper, kraft envelope waste paper, magazine waste paper, newspaper waste paper, flyer waste paper, office waste paper, cardboard waste paper, high-quality waste paper, Kent waste paper, imitation waste paper, land deed waste paper, etc. These can be used alone or in combination.

[0023] (Other additives) Other additives can be added to the paper base material as needed. Examples of additives include fillers, pigments, sizing agents, coagulants, oil-resistant agents, fluorescent brightening agents, sulfate bands, yield improvers, drainage improvers, dry paper strength enhancers, wet paper strength enhancers, coloring dyes, coloring pigments, water resistance agents, etc. These can be used alone or in combination.

[0024] [Heat seal layer] The heat seal layer is laminated on one side of the above paper base material. The above heat seal layer is formed by coating a heat seal layer-forming composition on one side of the paper base material.

[0025] Preferably, the main component of the above heat seal layer is an ionomer resin. When the main component of the above heat seal layer is an ionomer resin, the heat seal strength is good not only at normal temperature but also at low temperature. The above "ionomer resin" refers to a synthetic resin in which polymers are aggregated using the cohesive force of metal ions. The above ionomer resin can be produced, for example, by adding metal cations such as sodium and zinc to an acrylic polymer and ethylene and bonding them intermolecularly.

[0026] Preferably, the above ionomer resin is an ethylene-based ionomer, and specifically, examples include ionomers of ethylene·(meth)acrylic acid copolymers and ionomers of ethylene·(meth)acrylate copolymers.

[0027] The lower limit of the content of the ionomer resin with respect to the total solid content of the heat-sealing layer is 50.0% by mass, preferably 90.0% by mass. If the content of the ionomer resin is less than 50.0% by mass, sufficient heat-sealability may not be obtained. On the other hand, the upper limit of the content of the ionomer resin is 100.0% by mass, preferably 95.0% by mass.

[0028] The heat-sealing layer may contain a resin other than the ionomer resin. Examples of the resin other than the ionomer resin include polyethylene-based resins and polypropylene-based resins. Examples of the polyethylene-based resin include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate copolymer (EMA), ethylene-vinyl acetate copolymer (EVA), carboxylic acid-modified polyethylene, styrene acrylic acid, styrene butadiene latex, and derivatives thereof, and mixtures thereof. Examples of the polypropylene-based resin include polypropylene (PP) homopolymer, random polypropylene (random PP), block polypropylene (block PP), chlorinated polypropylene, carboxylic acid-modified polypropylene, and derivatives thereof, and mixtures thereof. Among these, from the viewpoint of heat-sealability in a low-temperature region around 100 to 130 °C, ethylene-acrylic acid copolymer is more preferable.

[0029] The lower limit of the coating amount (in terms of solid content) of the heat-sealing layer is preferably 1.5 g / m 2 and more preferably 2.0 g / m 2 On the other hand, the upper limit of this coating amount is preferably 10.0 g / m 2 and more preferably 8.0 g / m 2is more preferable. If the coating amount is less than the above lower limit, it may not have sufficient heat seal strength and may not be able to be sealed sufficiently when made into a bag. If the coating amount exceeds the above upper limit, the blocking inhibitory property of the heat fusion surface may decrease, and it may become difficult to slide in the bag-making process and may be prone to breakage. The heat seal paper can achieve both heat seal strength and suppression of blocking of the heat fusion surface of the heat seal layer with a coating amount within the above range because the main component of the heat seal layer is an ionomer resin.

[0030] (Other additives) Other additives other than the above can be blended in the heat seal layer of the present invention. As other additives, for example, water-soluble polymers, adhesives, inorganic pigments, organic pigments, sizing agents, viscosity modifiers, coloring dyes, coloring pigments, water resistance agents, lubricants, etc. can be used alone or in combination of a plurality.

[0031] [Physical properties of heat seal paper] (Bekk smoothness) The lower limit of the Bekk smoothness of the surface of the heat seal layer laminated surface in the paper base material is 5 seconds, and 20 seconds is preferable. The upper limit of the Bekk smoothness of the surface of the heat seal layer laminated surface in the paper base material is 50 seconds, and 40 seconds is preferable. When the Bekk smoothness is less than the above lower limit, the surface of the heat seal paper becomes rough, so the contact area becomes small and the heat seal strength may decrease. When the Bekk smoothness exceeds the above upper limit, the blocking inhibitory effect of the heat fusion surface of the heat seal layer may decrease.

[0032] The lower limit of the Bekk smoothness of the surface of the non-laminated surface of the heat seal layer in the paper base material of the heat seal paper is 50 seconds, and 120 seconds is preferable. The upper limit of the Bekk smoothness of the surface of the non-laminated surface of the heat seal layer is 500 seconds, and 300 seconds is preferable. When the Bekk smoothness of the surface of the non-laminated surface of the heat seal layer is less than the above lower limit, the printability may be inferior. When the Bekk smoothness of the surface of the non-laminated surface of the heat seal layer exceeds the above upper limit, the slipperiness increases, so the processability may deteriorate.

[0033] As the lower limit of the Bekk smoothness of the surface of the heat-sealing layer, 8 seconds is preferable, and 20 seconds is more preferable. As the upper limit of the Bekk smoothness of the surface of the heat-sealing layer, 70 seconds is preferable, and 50 seconds is more preferable. When the Bekk smoothness of the surface of the heat-sealing layer is below the lower limit, the surface of the heat-sealing paper becomes rough (the contact area becomes small), and there is a risk that the heat-sealing strength may decrease. When the Bekk smoothness of the surface of the heat-sealing layer exceeds the upper limit, the blocking suppression effect of the heat-fusion surface of the heat-sealing layer may decrease.

[0034] (Parker Print Surf Smoothness) The lower limit of the Parker Print Surf smoothness of the surface of the heat-sealing layer lamination surface in the paper base material of the heat-sealing paper is 3.8 μm, and 5.0 μm is preferable. The upper limit of the Parker Print Surf smoothness of the surface of the heat-sealing layer lamination surface is 8.0 μm, and 7.0 μm is preferable. When the Parker Print Surf smoothness of the surface of the heat-sealing layer lamination surface in the paper base material is below the lower limit, there is a risk of poor adhesion at minute uneven portions. When the Parker Print Surf smoothness of the surface of the heat-sealing layer lamination surface exceeds the upper limit, there is a risk that the heat-sealing layers may block when they come into contact with each other.

[0035] The lower limit of the Parker Print Surf smoothness of the surface of the non-heat-sealing layer lamination surface in the paper base material of the heat-sealing paper is 2.0 μm, and 2.2 μm is preferable. The upper limit of the Parker Print Surf smoothness of the surface of the non-heat-sealing layer lamination surface is 4.2 μm, and 3.2 μm is preferable. When the Parker Print Surf smoothness of the surface of the non-heat-sealing layer lamination surface is below the lower limit, since the flatness is too high, there is a risk of processing defects due to slippage during processing. When the Parker Print Surf smoothness of the surface of the non-heat-sealing layer lamination surface exceeds the upper limit, the ink fixing property on the surface of the heat-sealing paper is inferior, and there is a risk that printing streaks are likely to occur.

[0036] As the lower limit of the Parker Print Surf smoothness of the surface of the heat-sealing layer, 3.0 μm is preferable, and 3.5 μm is more preferable. As the upper limit of the Parker Print Surf smoothness of the surface of the heat-sealing layer, 5.3 μm is preferable, and 5.0 μm is more preferable. When the Parker Print Surf smoothness of the surface of the heat-sealing layer is below the lower limit, the contact area between the surfaces is small, and the heat-sealing strength may decrease. When the Parker Print Surf smoothness of the surface of the heat-sealing layer exceeds the upper limit, there is a risk of blocking at the contact surface between the heat-sealing layers.

[0037] (Moisture permeability) The moisture permeability of the heat-sealing paper is measured based on Condition B in accordance with JIS-Z0208

[1976] Test method for moisture permeability of moisture-proof packaging materials [cup method]. As the lower limit of the moisture permeability, 1,000 g / m 2 ·24hr is preferable, and 1,200 g / m 2 ·24h is more preferable. Also, as the upper limit of the moisture permeability, 2,000 g / m 2 ·24h is preferable, and 1,900 g / m 2 ·24h is more preferable. When the moisture permeability is within the above range, the moisture of the packaged contents is less likely to become water droplets, and the quality of the contents can be kept good to maintain an appropriate humidity.

[0038] According to the heat-sealing paper, it is possible to provide a heat-sealing paper excellent in suppressing blocking of the heat-fusion surface of the heat-sealing layer and printability of the non-laminated surface of the heat-sealing layer. In addition, since the heat-sealing paper does not contain laminated paper or plastic film with a high environmental load and does not use a plastic film, environmental conservation can be achieved.

[0039] [Manufacturing method of heat-sealing paper] The manufacturing method of the heat-sealing paper is not particularly limited. For example, it has a step of papermaking a pulp slurry as a raw material of a paper base material, a step of producing a composition for forming a heat-sealing layer, and a step of coating the composition for forming a heat-sealing layer on at least one surface of the paper base material.

[0040] In the papermaking process, a raw material slurry containing the above-described raw material pulp, oil-resistant agent, and other additives is carried out using a known papermaking machine.

[0041] Next, it is preferable to include a step of drying one side of the paper base material formed in the above papermaking process with a Yankee dryer to form a glossy surface. The Bekk smoothness and Parker Print Surf smoothness of the surfaces of the heat-sealing layer laminated surface and the non-heat-sealing layer laminated surface of the paper base material of the heat-sealing paper can be adjusted by this step.

[0042] In this step, the contact surface with the Yankee dryer is formed as the glossy surface. More specifically, the wet paper is pressed against the Yankee dryer with a so-called felt, and the mirror surface of the cylinder surface of the Yankee dryer is copied onto the wet paper to obtain the glossy surface of the paper base material. In the drying process with the Yankee dryer, the surface temperature of the dryer is in the range of 100°C or higher and 150°C or lower, and it is pressed against the mirror surface of the Yankee dryer. Also, the non-contact surface with the Yankee dryer is formed as the non-glossy surface. On the non-glossy surface side, the smoothness is adjusted by the material of the felt and the pressure adjustment of the touch roll that presses the felt against the Yankee dryer. Among the above adjustment methods, the method by the pressure adjustment of the touch roll is preferable. As a result, it is possible to widen the front-back difference in smoothness between the glossy surface and the non-glossy surface while maintaining the density of the paper base material. The paper base material having the glossy surface and the non-glossy surface can exhibit an effect of suppressing blocking of the heat-sealing surface by laminating a heat-sealing layer on the non-glossy surface side, and the non-glossy surface side can exhibit an excellent effect on the printability of the non-heat-sealing layer laminated surface. Here, the "glossy surface" refers to a surface having gloss. The "non-glossy surface" refers to a surface having no glossiness. By laminating a heat-sealing layer on the anti-glossy surface of the paper base material, blocking of the heat-sealing surfaces of the heat-sealing layers can be suppressed, and the printability of the non-heat-sealing layer laminated surface is good because the printing surface, which is the opposite surface of the anti-glossy surface, becomes a glossy surface, and a heat-sealing paper suitable for bag making can be provided.

[0043] In the step of generating the composition for forming the heat-sealing layer, a composition for forming the heat-sealing layer containing an ionomer resin as a main component is generated.

[0044] As the coating method of the composition for forming the heat-sealing layer, a known coating method can be adopted. For example, known coating machines such as a two-roll size press coater, a gate roll coater, a blade metering coater, a rod metering coater, a blade coater, an air knife coater, a roll coater, a brush coater, a kiss coater, a squeeze coater, a curtain coater, a die coater, a bar coater, a gravure coater, etc. can be used.

[0045] For drying the coated composition for forming the heat-sealing layer, a known drying device can be adopted. For example, an infrared drying device, a hot air drying device, a contact type dryer drying device, etc. can be used.

[0046] The heat-sealing paper thus obtained can utilize various known finishing devices, such as a super calender, a gloss calender, a soft calender, a mat calender, etc., and can also perform appropriate product finishing. The adjustment of the Bekk smoothness and Parker Print Surf smoothness of the heat-sealing laminated surface and the non-laminated surface of the heat-sealing paper can be easily adjusted by using a machine calender or a soft calender.

[0047] <Packaging material> The packaging material according to another embodiment of the present invention has the heat-sealing paper. Since the packaging material has the heat-sealing paper, it is excellent in suppressing blocking of the heat-fusion surface of the heat-sealing layer and printability of the non-laminated surface of the heat-sealing layer, and can be recycled.

[0048] <Other embodiments> The present invention is not limited to the above embodiments, and can be implemented in various modified and improved forms in addition to the above aspects.

Example

[0049] Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited to the following examples.

[0050] [Examples 1 to 7 and Comparative Examples 1 to 2] (Manufacture of paper base material) First, 100% by mass of LBKP was prepared to obtain a pulp slurry. To this pulp slurry, as additives, vanadium sulfate, retention aid, and sizing agent were each added internally. The obtained pulp slurry was formed into paper using an on-top type fourdrinier paper machine. Next, using a Yankee dryer, the wire side was made into a matte surface (back surface), and one-sided matte paper base materials of Examples 1 to 7 and Comparative Examples 1 to 2 were obtained. The basis weight of the paper base material was 60.0 g / m 2 . The Bekk smoothness and Parker Print Surf smoothness of the surface (non-matte surface) where the heat-seal layer was to be laminated were measured by the methods described below.

[0051] (Lamination of heat-seal layer) Next, a heat-seal layer was formed on one side of the paper base material to obtain a heat-seal paper with a basis weight of 65.0 g / m 2 . The composition and coating amount of the composition for forming the heat-seal layer were as shown in Table 1. Also, as the ionomer resin of the composition for forming the heat-seal layer, an ionomer of an ethylene-acrylic acid copolymer was used. The content of the ionomer resin with respect to the total solid content was 100.0% by mass.

[0052] [Comparative Example 3] A single-layer laminated paper containing a polypropylene film was produced. The base paper was composed of commercially available kraft paper (basis weight 50.0 g / m 2 ). The polypropylene film was obtained by extrusion laminating a commercially available polypropylene resin with a pelletizer and laminating it on only one side of the base paper with a thickness of 20 μm.

[0053] Various evaluations of the heat-seal paper obtained as described above were performed.

[0054] (Smoothness of heat-seal layer) (1) Bekk smoothness The Bekk smoothness of the heat-sealing layer laminated surface, the non-laminated surface of the heat-sealing layer, and the surface of the heat-sealing layer on the paper substrate was measured in accordance with JIS-P8119 (1998). (2) Parker print surf smoothness The Parker print surf smoothness of the heat-sealing layer laminated surface, the non-laminated surface of the heat-sealing layer, and the surface of the heat-sealing layer on the paper substrate was measured in accordance with Annex A of JIS-P8151 (2004).

[0055] (Moisture vapor transmission rate) Regarding the moisture vapor transmission rate of the heat-sealing paper of the examples and comparative examples, it was measured based on Condition B in accordance with JIS-Z0208 (1976) Test method for moisture vapor transmission rate of moisture-proof packaging materials [cup method].

[0056] (Heat-sealing strength) Using a thermal gradient tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.), after processing under the conditions of a sealer pressure of 2 kgf / cm 2 , a sealer time of 2 seconds, and a sealing temperature of 140 °C, the peel strength of the heat-sealed portion was measured using a load cell type tensile tester. The evaluation criteria were as follows in three levels. When the evaluation is ○ and △, the heat-sealing strength is good. ○: The peel strength is 3.0 N / 15 mm or more. △: The peel strength is 2.0 N / 15 mm or more and less than 3.0 N / 15 mm. ×: The peel strength is less than 2.0 N / 15 mm.

[0057] (Blocking inhibition property of the heat-sealed surface) For each example and comparative example, the coated surfaces of the heat-sealing layers of two sheets of heat-sealing paper were brought into close contact with each other, and a reciprocating pressure was applied with a 1 kg crimping roller. Next, after storing for 1 day under the condition of 40 °C, the results of peeling with both hands were evaluated according to the following three-level criteria. When the evaluation is ○ and △, the blocking inhibition property of the heat-sealed surface is good. ○: There is no blocking on the heat-sealed surface, and it peels smoothly. △: There is some blocking on the heat-sealing surface, but the peelability is within an acceptable range without problems. ×: Blocking occurs on the heat-sealing surface, and there are difficulties with peelability.

[0058] (Printing suitability) For printing suitability, using the ink for the gravure printing and coating tester GP-2 (Kurashiki Boseki Co., Ltd.), printing was carried out using the evaluation ink ("PCNT391T Blue" manufactured by Toyo Ink Co., Ltd.), and the ink film thickness was evaluated according to the following three criteria. When the evaluation is ○ or △, the printing suitability is good. ○: There is no printing unevenness, ink pick-up, or back printing, and the printing suitability is good. △: There is some printing unevenness, ink pick-up, and some back printing, but the printing suitability is within an acceptable range without problems. ×: There is significant printing unevenness, ink pick-up, and a lot of back printing, indicating problems with printing suitability.

[0059] The evaluation results of each example and comparative example are shown in Table 1.

[0060]

Table 1

[0061] As shown in Table 1, in Examples 1 to 7 where the Bekk smoothness of the surface of the heat-seal layer laminated surface on the paper substrate is 5 seconds or more and 50 seconds or less, the Parker print surf smoothness is 3.8 μm or more and 8.0 μm or less, the Bekk smoothness of the surface of the non-laminated surface of the heat-seal layer on the paper substrate is 50 seconds or more and 500 seconds or less, and the Parker print surf smoothness is 2.0 μm or more and 3.6 μm or less, all of the moisture permeability, heat-seal strength, blocking suppression property of the heat-sealing surface, and printing suitability were good. In particular, in Examples 1 to 3 where the coating amount of the heat-seal layer is 1.5 g / m 2 or more and 10.0 g / m 2 or less, the Bekk smoothness of the surface of the heat-seal layer is 8 seconds or more and 70 seconds or less, and the Parker print surf smoothness is 3.0 μm or more and 5.3 μm or less, the heat-seal strength and the blocking suppression property of the heat-sealing surface were excellent. On the other hand, in Comparative Example 1 where the Bekk smoothness of the surface of the heat-sealing layer laminated surface was less than 5 seconds, the heat-sealing strength was poor. Further, in Comparative Example 2 where the Bekk smoothness of the surface of the heat-sealing layer laminated surface exceeded 50 seconds and the Parker print surf smoothness was less than 3.8 μm, and the Bekk smoothness of the surface of the non-laminated surface of the heat-sealing layer was less than 50 seconds and the Parker print surf smoothness exceeded 3.6 μm, the blocking inhibitory property of the heat-fused surface and the printability were poor. Since Comparative Example 3 is a polypropylene (PP) laminated paper, it is not desirable from the viewpoint of environmental pollution. Further, since the moisture permeability is low, when used as a packaging material, there is a possibility that the freshness of the contents may decrease.

[0062] As a result of the above, it was shown that according to the heat-sealing paper, the blocking inhibitory property of the heat-fused surface of the heat-sealing layer and the printability of the non-laminated surface of the heat-sealing layer are excellent. Further, since the heat-sealing paper does not contain a laminated paper or a plastic film with a high environmental load, environmental conservation can be achieved.

Industrial Applicability

[0063] The heat-sealing paper of the present invention is environmentally friendly, excellent in the blocking inhibitory property of the heat-fused surface of the heat-sealing layer and the printability of the non-laminated surface of the heat-sealing layer, and is suitable as a packaging material.

Claims

1. A paper base material mainly composed of pulp, A heat-seal layer laminated on one side of the paper base material, and It is provided with, The main component of the heat-seal layer is composed of an ionomer of ethylene-(meth)acrylic acid copolymer, an ionomer of ethylene-(meth)acrylate copolymer, or a combination thereof, The Bek smoothness of the surface of the heat-seal layer lamination surface on the paper base material is 5 seconds or more and 50 seconds or less, and the Parker print surf smoothness is 3.8 μm or more and 8.0 μm or less, The Bek smoothness of the surface of the non-heat-seal layer lamination surface on the paper base material is 150 seconds or more and 260 seconds or less, and the Parker print surf smoothness is 2.4 μm or more and 4.2 μm or less, The coating amount of the heat-seal layer is 1.5 g / m² or more and 10.0 g / m² or less, A heat-seal paper in which the Bek smoothness of the surface of the heat-seal layer is 8 seconds or more and 70 seconds or less, and the Parker print surf smoothness is 3.0 μm or more and 5.3 μm or less.

2. The moisture permeability is 1,000 g / m ２ ·24 hr or more and 2,000 g / m ２ ·24 hr or less. The heat-seal paper according to Claim 1.

3. A packaging material having the heat-seal paper according to Claim 1 or Claim 2.

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