Packaging substrate

Abstract

To provide a packaging substrate in which an inclusion hardly moves and blocking with the inclusion hardly occurs.SOLUTION: The packaging substrate according to the present invention has a paper substrate and a heat seal layer on the outermost surface of at least one of the substrates, the dynamic friction coefficient / static friction coefficient value of the heat seal layer surface is 0.8 or more, and the smoothness (Oken method) of the heat seal layer surface is 1000 seconds or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a base material for packaging.

Background Art

[0002] In recent years, triggered by environmental problems such as plastic waste and global warming, there has been an increasing trend towards de-oiling and de-plasticizing, and it is desired to minimize the use of resin materials derived from fossil resources and non-biodegradable resin materials in industrial products.

[0003] Under such a trend, it is also desired to reduce the environmental impact of packages. For example, a method such as reducing the thickness of a packaging material using a plastic film can be considered. However, such a thin packaging material has reduced handleability in the process of forming the package and is likely to have defects and tears at the thermocompression bonding part. In addition, although the amount of resin used is reduced, the problem that it remains semi-permanently without being decomposed when it flows out into the environment remains. Patent Documents 1 and 2 propose using heat-seal paper obtained by laminating a heat-seal layer on a paper base material as a packaging material. Since these are mainly made of paper and some heat-sealing resins are decomposed in the environment depending on the type, the environmental impact can be significantly reduced.

[0004] Here, for the base material for packaging, in some cases, it is required that the contents do not move much when packaged in order to protect the contents. On the other hand, if the base material for packaging and the contents block each other, problems such as the base material for packaging being torn and the fragments sticking to the contents or the adhesive component migrating to the contents may occur.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a packaging base material in which the inclusion is difficult to move and blocking between the inclusion and the base material is difficult to occur.

Means for Solving the Problems

[0007] Means for solving the problems of the present invention are as follows. 1. A paper base material having a heat-sealing layer on at least one outermost surface of the paper base material, wherein the value of the coefficient of kinetic friction / coefficient of static friction on the surface of the heat-sealing layer is 0.8 or more, and the smoothness (Oken method) of the surface of the heat-sealing layer is 1000 seconds or less, a packaging base material characterized by this. 2. The packaging base material according to 1., wherein the heat-sealing layer contains a polyolefin resin. 3. The packaging base material according to 1. or 2., wherein the heat-sealing layer contains a crosslinked polyolefin resin. 4. The packaging base material according to any one of 1. to 3., wherein the opacity is 35% or more. 5. The packaging base material according to any one of 1. to 4., wherein the air permeability resistance (Oken method) of the heat-sealing layer is 2000 seconds or less.

Effects of the Invention

[0008] Since the inclusion is difficult to move when packaged, the packaging base material of the present invention is less likely to cause damage to the inclusion. The packaging base material of the present invention is less likely to cause blocking and can prevent the inclusion from sticking to the package. The packaging base material of the present invention having an opacity of 35% or more is less likely to be seen through inside, and when used as a package for transportation or delivery, the inside is difficult to be visually recognized. The packaging base material of the present invention, having an air permeability resistance (Wang research method) of the heat seal layer of 2000 seconds or less, is excellent in bag-making processability because the air inside the bag easily escapes during the bag-making process.

Embodiments for Carrying Out the Invention

[0009] "Packaging base material" The packaging base material of the present invention has a paper base material and a heat seal layer on at least one outermost surface of this base material. The value of the dynamic friction coefficient / static friction coefficient on the surface of the heat seal layer is 0.8 or more. The smoothness of the surface of the heat seal layer is 1000 seconds or less.

[0010] ·Paper base material The paper base material is a base material on which a heat seal layer is formed on at least one of its surfaces. The paper base material is mainly a sheet made of pulp, and the base paper obtained by papermaking a paper stock containing pulp, fillers, various auxiliaries, etc. can be used as it is, or on at least one surface of the base paper, a function layer such as a blocking layer, an ink receiving layer, a water-resistant layer, an oil-resistant layer, a water vapor barrier layer, a gas barrier layer, etc. can be formed with one layer or two or more layers.

[0011] The paper base material of the present invention preferably has a basis weight of 20 g / m 2 or more and 70 g / m 2 or less from the viewpoints of flexibility and strength. The basis weight of the paper base material is more preferably 24 g / m 2 or more, even more preferably 28 g / m 2 or more, and more preferably 65 g / m 2 or less, even more preferably 60 g / m 2 or less, and even more preferably 55 g / m 2 or less. The basis weight of the paper base material is measured in accordance with JIS P8124:2011.

[0012] The paper substrate used in the present invention preferably has a thickness of 25 μm or more and 200 μm or less from the viewpoints of flexibility, strength, handleability, etc. The thickness of the paper substrate is preferably 30 μm or more, more preferably 35 μm or more, still more preferably 40 μm or more, and preferably 160 μm or less, more preferably 130 μm or less, still more preferably 100 μm or less, and even more preferably 70 μm or less. The thickness of the paper substrate is measured in accordance with JIS P8118:2014. The paper substrate of the present invention has a density of 0.3 g / cm 3 or more and 0.95 g / cm 3 or less, which is preferable from the viewpoints of flexibility and strength. The density of the paper substrate is more preferably 0.4 g / cm 3 or more, still more preferably 0.5 g / cm 3 or more, and more preferably 0.9 g / cm 3 or less, still more preferably 0.85 g / cm 3 or less. The thickness of the paper substrate is calculated from the density and basis weight.

[0013] The paper substrate of the present invention preferably has a puncture strength of 1.0 N or more. When the puncture strength of the paper substrate is 1.0 N or more, it is possible to make the package difficult to break when a protrusion or the like comes into contact. This puncture strength of the paper substrate is more preferably 1.1 N or more, still more preferably 1.2 N or more. The puncture strength of the paper substrate is measured in accordance with JIS Z1707:2019 7.5 Puncture Strength Test.

[0014] As the pulp, chemical pulps such as hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), softwood unbleached pulp (NUKP), sulfite pulp, mechanical pulps such as stone ground pulp and thermomechanical pulp, deinked pulp, wood fibers such as wastepaper pulp, and non-wood fibers obtained from kenaf, bamboo, hemp, etc. can be used, and one or more of them can be mixed and used. Among these, due to reasons such as being less likely to have foreign matter mixed in, being less likely to have discoloration over time when used as a wastepaper raw material for recycling after use, and having a high whiteness resulting in a good surface feel during printing, it is preferable to use chemical pulps and mechanical pulps of wood fibers, and it is more preferable to use chemical pulps of wood fibers. Specifically, the blending amount of chemical pulps such as LBKP and NBKP is preferably 80% by weight or more, more preferably 90% by weight or more, further preferably 95% by weight or more, even more preferably 98% by weight or more, even more preferably 99% by weight or more, and most preferably 100% by weight. Also, the blending ratio of hardwood pulp in the pulp is preferably 30% by weight or more, and more preferably 50% by weight or more. From the viewpoint of the strength of the paper base material, etc., the drainage degree of the pulp (Canadian Standard Freeness: CSF) is preferably 600 ml or less, more preferably 550 ml or less, and further preferably 500 ml or less.

[0015] As the filler, fillers known for papermaking such as inorganic fillers such as talc, kaolin, calcined kaolin, clay, heavy calcium carbonate, light calcium carbonate, white carbon, zeolite, magnesium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, barium sulfate, calcium sulfate, and organic fillers such as urea-formalin resin, polystyrene resin, phenolic resin, and micro-hollow particles can be used. Note that the filler is not an essential material and may not be used.

[0016] Examples of various auxiliaries include sizing agents such as rosin, alkyl ketene dimer (AKD), and alkenyl succinic anhydride (ASA), polyacrylamide-based polymers, polyvinyl alcohol-based polymers, cationized starch, various modified starches, dry paper strength enhancers such as urea-formalin resin and melamine-formalin resin, wet paper strength enhancers, retention aids, drainage improvers, coagulants, sulfate bands, bulking agents, dyes, fluorescent brighteners, pH adjusters, defoamers, ultraviolet inhibitors, anti-fading agents, pitch control agents, slime control agents, etc., which can be appropriately selected and used as necessary.

[0017] The method for manufacturing (papermaking) the base paper is not particularly limited, and known manufacturing (papermaking) methods and papermaking machines such as Fourdrinier machines, cylinder machines, twin-wire machines such as Duoformer type, Hybrid former type (Ontop former type), etc. can be selected. Also, the pH during papermaking can be in any of the acidic region (acidic papermaking), pseudo-neutral region (pseudo-neutral papermaking), neutral region (neutral papermaking), and alkaline region (alkaline papermaking). After papermaking in the acidic region, an alkaline agent may be coated on the surface of the paper layer. Further, the base paper may be a single layer or may be composed of multiple layers of two or more layers.

[0018] Furthermore, it is possible to treat the surface of the base paper with various chemicals. Examples of the chemicals used include oxidized starch, hydroxyethyl etherified starch, enzyme-modified starch, polyacrylamide, polyvinyl alcohol, surface sizing agents, water resistance agents, water retention agents, thickening agents, lubricants, etc., which can be used alone or in combination of two or more. Further, these various chemicals and pigments may be used in combination. As pigments, inorganic pigments such as kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate, mica, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, satin white, etc. and organic pigments such as solid type, hollow type, or core-shell type, etc. can be used alone or in combination of two or more. The method for surface treatment of the base paper is not particularly limited, and known coating devices such as rod metering size press, pond type size press, gate roll coater, spray coater, blade coater, curtain coater, etc. can be used.

[0019] Furthermore, one or more functional layers such as a blocking layer, ink receiving layer, water resistant layer, oil resistant layer, water vapor barrier layer, gas barrier layer, etc. can be formed on at least one surface of the base paper. The functional layer may be either a coating layer or a laminate layer, but a coating layer is preferable from the viewpoint of maintaining the flexibility of the paper substrate.

[0020] · Heat seal layer The heat seal layer is a layer that imparts heat seal suitability. Specifically, it is a layer that can adhere to an object to be adhered by heating and pressurizing. The paper for flexible packaging material of the present invention has heat seal suitability, which facilitates forming into a package, maintaining the shape, and ensuring airtightness. The heat seal layer is provided on at least one outermost surface of the paper substrate. The heat seal layer may be either a coating layer or a laminate layer.

[0021] In the present invention, the value of the coefficient of kinetic friction / coefficient of static friction on the surface of the heat seal layer is 0.8 or more. The value of the coefficient of kinetic friction / coefficient of static friction is preferably 0.9 or more, more preferably exceeding 1.0, further preferably 1.1 or more, even more preferably exceeding 1.2, and even more preferably 1.3 or more. When the value of the coefficient of kinetic friction / coefficient of static friction is 0.8 or more, the movement of the contents that have moved inside the package can be quickly stopped. Here, generally, it is known that the coefficient of static friction > the coefficient of kinetic friction holds, but among materials having elasticity, there are those that satisfy the coefficient of kinetic friction > the coefficient of static friction. This is because a material having elasticity deforms and the unevenness meshes at the contact surface with another object, instantaneously adheres, and a large force is required to peel off this adhesion.

[0022] In the present invention, the value of the coefficient of kinetic friction on the surface of the heat-sealing layer is preferably 0.4 or more, more preferably 0.5 or more, further preferably 0.6 or more, even more preferably 0.7 or more, even more preferably 0.8 or more, even more preferably 0.9 or more, even more preferably 1.1 or more, and even more preferably 1.2 or more. In the present invention, the value of the coefficient of static friction on the surface of the heat-sealing layer is preferably 0.25 or more, more preferably 0.3 or more, further preferably 0.4 or more, even more preferably 0.5 or more, even more preferably 0.6 or more, even more preferably 0.7 or more, even more preferably 0.8 or more, and even more preferably 0.9 or more.

[0023] In the present invention, the thermoplastic resin contained in the heat-sealing layer is not particularly limited as long as the value of the coefficient of kinetic friction / coefficient of static friction is 0.8 or more, and an ethylene-vinyl acetate resin, an acrylic resin, an ethylene-acrylic resin, a polyolefin resin (such as polyethylene, polypropylene, crosslinked polyethylene, crosslinked polypropylene, etc.), a polyurethane resin, a polyester resin (such as polyethylene terephthalate, polyethylene succinate, polybutylene terephthalate, polyethylene naphthalate, etc.), a polyvinyl alcohol resin, a polyvinyl acetate resin, a polylactic acid resin, etc. can be used alone or in combination of two or more. Among these, since those with a large value of the coefficient of kinetic friction / coefficient of static friction are easily obtained, an ethylene-vinyl acetate resin, a polyolefin resin, and a polyurethane resin are preferred, a polyolefin resin is more preferred, and a crosslinked polyolefin resin is further preferred.

[0024] The heat-sealing layer can contain additives such as an antiblocking agent and a silane coupling agent. As the antiblocking agent, pigments, waxes, metal soaps, etc. can be used without particular limitation. However, in the paper for soft packaging materials of the present invention, from the viewpoint of cost, it is preferable that the heat-sealing layer does not contain additives.

[0025] When the heat-sealing layer is a coating layer, the dry weight of the heat-sealing layer is 3 g / m per side2 Preferably, it is 20 g / m or less. When the dry weight is less than 3 g / m 2 , the heat sealability may deteriorate. Also, even if the dry weight exceeds 20 g / m 2 , the heat sealability hardly improves, and the cost increases. The heat seal layer may be a single layer or may be composed of two or more layers. By configuring the heat seal layer with two or more layers, defects such as coating unevenness can be reduced compared to the case of a single layer. When the heat seal layer is composed of two or more layers, it is preferable that the total dry weight of all the heat seal layers is within the above range. Also, the coating amount of the dry weight is preferably 2 g / m 2 or more. 2 When the heat seal layer is a laminate layer, the thickness of the heat seal layer is preferably 20 μm or more and 100 μm or less. If the thickness is less than 20 μm, the heat sealability may not be ensured. Also, if the thickness exceeds 100 μm, it is not preferable from the viewpoint of cost.

[0026] When the heat seal layer is a coating layer, the coating method is not particularly limited, and it can be coated with a known coating apparatus and coating system. For example, as the coating apparatus, a blade coater, a bar coater, an air knife coater, a curtain coater, a spray coater, a roll coater, a reverse roll coater, a size press coater, a gate roll coater, etc. can be mentioned. As the coating system, either an aqueous coating using a solvent such as water or a solvent-based coating using a solvent such as an organic solvent may be used, but from the viewpoint of safety and hygiene, an aqueous coating is preferable. When performing an aqueous coating, since a water-dispersible resin or a water-soluble resin is used as the thermoplastic resin, the heat seal layer is preferably a coating layer of a water-dispersible resin or a water-soluble resin. When the heat seal layer is a laminate layer, the forming method is not particularly limited, and for example, it can be laminated by appropriately using various methods such as an extrusion lamination method, a wet lamination method, and a dry lamination method.

[0027] "Base material for packaging" For the base material for packaging of the present invention, the smoothness (Oken type) of the heat-sealing layer surface is 1000 seconds or less. When the smoothness (Oken type) of the heat-sealing layer surface is 1000 seconds or less, blocking with the contents is less likely to occur. This smoothness (Oken type) is preferably 900 seconds or less, more preferably 800 seconds or less, still more preferably 700 seconds or less, even more preferably 600 seconds or less, and even more preferably 500 seconds or less.

[0028] The base material for packaging of the present invention preferably has an opacity of 35% or more as measured in accordance with JIS P8149:2010. When the opacity is 35% or more, it is preferable because the contents cannot be seen when used as a packaging material for transportation and distribution. The opacity is more preferably 40% or more, still more preferably 45% or more, and even more preferably 50% or more. For the base material for packaging of the present invention, the air permeability resistance (Oken type) of the heat-sealing layer is preferably 2000 seconds or less. When this air permeability resistance (Oken type) is 2000 seconds or less, the air inside the bag easily escapes during bag-making processing, so the processing suitability is excellent. This air permeability resistance (Oken type) is more preferably 1800 seconds or less, still more preferably 1600 seconds or less, and even more preferably 1500 seconds or less.

[0029] "Package" By enclosing the contents in the base material for packaging of the present invention, a package can be formed. The shape of the package is not particularly limited, and it can be a vertical pillow-shaped packaging bag, a horizontal pillow-shaped packaging bag, a side-seal bag, a two-side seal bag, a three-side seal bag, a gusset bag, a bottom gusset bag, a stand-up bag, etc. Since the packaging material of the package of the present invention is mainly paper, it is easier to tear compared to those using conventional resin packaging materials and can be easily torn from anywhere.

Examples

[0030] "Example 1" Paper base material (basis weight of about 40 g / m 2, on one side of LBKP86% and NBKP14% (manufactured by Nippon Paper Industries Co., Ltd.), polyolefin resin 1 (manufactured by Unitika Ltd., trade name: Arrow Base SB1200, aqueous emulsion, polyethylene type) was applied and dried on one side so that the target coating amount was 10.0 g / m in terms of solid content to form a heat-sealing layer, and a packaging base material was obtained. 2 to obtain a packaging base material. "Example 2" A packaging base material was obtained in the same manner as in Example 1, except that a crosslinked polyolefin resin (manufactured by Unitika Ltd., trade name: Arrow Base SE-1015J2, aqueous emulsion, polyethylene type) was applied.

[0031] "Example 3" A packaging base material was obtained in the same manner as in Example 2, except that a paper base material (basis weight of about 35 g / m 2 , LBKP78%, NPKP22%, manufactured by Nippon Paper Industries Co., Ltd.) was used. "Example 4" A packaging base material was obtained in the same manner as in Example 1, except that polyolefin resin 2 (manufactured by Unitika Ltd., trade name: Arrow Base DC-1010, aqueous emulsion, polypropylene type) was applied.

[0032] "Example 5" Commercially available abaca pulp was disintegrated with a pulper. The freeness was 730 ml of CSF. This disintegrated abaca pulp was fed to a Fourdrinier paper machine in an unbeaten state and paper was made at a predetermined basis weight and dried with a Yankee dryer to obtain a paper base material. A packaging base material was obtained in the same manner as in Example 2, except that this paper base material was used.

[0033] "Comparative Example 1" A packaging base material was obtained in the same manner as in Example 1, except that a styrene-acrylic resin (manufactured by Daiichi Paint Mfg. Co., Ltd., trade name: Herbil C-7, aqueous solution) was applied. "Comparative Example 2" A heat-sealing layer made of low-density polyethylene with a thickness of 30 μm was provided on a paper base material (basis weight of about 45 g / m 2 , LBKP100%, manufactured by Nippon Paper Industries Co., Ltd.) by dry lamination to obtain a packaging base material. "Comparative Example 3" Paper substrate (glassine paper, basis weight 30 g / m 2 , 50% LBKP, 50% NPKP, manufactured by Nippon Paper Papiria Co., Ltd.), a packaging substrate was obtained in the same manner as in Example 1 except for using this paper substrate.

[0034] <Evaluation method> The following evaluations were performed on the obtained packaging substrate. The results are shown in Table 1. ·Coefficient of static friction ·Coefficient of kinetic friction Measured according to ISO 15359. The measurement was carried out with n = 9, and the arithmetic mean value was used for evaluation. ·Opacity Measured in accordance with JIS P8149:2000. ·Air resistance (Ono method) Measured by the method according to JIS P 8117:2009 (Ono type tester method). ·Smoothness (Ono method) Measured by the method according to JIS P 8155:2010 (Ono type tester method).

[0035] ·Heat sealability Two test pieces of 100 mm square on each side were cut out from the packaging substrate, and the heat seal layers were brought into contact with each other, and heat sealed at a pressure temperature of 130 °C, a pressure of 2 kgf / cm 2 , and a pressure time of 0.5 seconds. When the heat-sealed test piece was peeled off by hand, the peeled part was visually observed, and the heat seal suitability was evaluated according to the following criteria. If the evaluation is ○ or Δ, there is no practical problem. [Evaluation criteria] ○: Peels within the paper substrate (the paper substrate is broken). Δ: Most peels within the paper substrate (the paper substrate is broken). ×: Peels at the heat seal layer.

[0036] ·Blocking property A glass plate was placed on the heat seal layer of the packaging substrate, and 20 gf / cm 2It was weighted and allowed to stand at 40 °C and 90% Rh for 24 hours. Then, the packaging base material was peeled off from the glass plate, and the state of the heat-sealing layer was visually evaluated according to the following criteria. If the evaluation is ○ or △, there is no practical problem. [Evaluation Criteria] ○: No blocking occurs and there is no peeling of the heat-sealing layer. △: Slight blocking occurs and the heat-sealing layer peels slightly when the sample is peeled. ×: Strong blocking occurs and the sample breaks without peeling.

[0037] · Product Fixing Performance A 50 mm × 90 mm test piece was cut out from the obtained packaging base material. The test piece was placed on the metal plate so that its heat-sealing layer was in contact with the metal plate. A 50 g weight was placed on the test piece, and the metal plate was tilted at a constant speed of 1 degree / second. The inclination angle of the metal plate when the test piece started to slide on the metal plate was measured.

[0038] · Dissociability The degree of dissociation into the aqueous solution when each packaging base material cut into a 4 cm square was dissociated using a TAPPI dissociator at a concentration of 2.5% by weight, 40 °C, 10 min, and 3000 rpm was evaluated. [Evaluation Criteria] ○: Pulp fibers are dispersed and the dissociability is good ×: Lumps or bundles of pulp fibers remain and the dissociability is poor

[0039]

Table 1

[0040] The packaging base materials obtained in Examples 1 to 5 of the present invention are excellent in product fixing performance, and when made into a package, the contents are difficult to move inside. Also, since blocking is less likely to occur, the contents are less likely to stick. On the other hand, the packaging base materials obtained in Comparative Examples 1 and 2 are inferior in product fixing performance, and when made into packages, the contents are likely to move inside. Further, the packaging base material obtained in Comparative Example 3 has a problem that the contents are likely to stick, and also has a low opacity, so there is a risk that the contents can be seen through.

Claims

1. A paper base material having a heat-sealing layer on at least one outermost surface of the paper base material, wherein the value of the kinetic friction coefficient / static friction coefficient on the surface of the heat-sealing layer is 0.8 or more, and the smoothness (Wang Research Method) of the surface of the heat-sealing layer is 1000 seconds or less. A base material for packaging, characterized by this.

2. The base material for packaging according to Claim 1, characterized in that the heat-sealing layer contains a polyolefin resin.

3. The base material for packaging according to Claim 1 or 2, characterized in that the heat-sealing layer contains a crosslinked polyolefin resin.

4. The base material for packaging according to Claim 1 or 2, characterized in that the opacity is 35% or more.

5. The base material for packaging according to Claim 1 or 2, characterized in that the air permeability resistance (Wang Research Method) of the heat-sealing layer is 2000 seconds or less.

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