Paper packaging material for ice and / or frozen products

Abstract

To provide a paper packaging material which can be easily worked and manufactured into a box, has waterproofness, and is used for applications for putting ice and / or a frozen product.SOLUTION: There is provided a paper packaging material for manufacturing a bag for storing ice and / or a frozen product in which a waterproof resin layer is coated onto at least one surface of a paper base material of a single layer.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a paper packaging material for ice and / or frozen products. In particular, the present invention relates to a paper packaging material for manufacturing a bag for containing ice and / or frozen products.

Background Art

[0002] Conventionally, when transporting fresh fish or the like, it has been widely practiced to put ice and fresh fish inside a styrofoam container for transportation. Further, when using a paper container from the viewpoint of environmental protection or the like, usually, an inner bag is provided inside a paper container such as cardboard, and ice and fresh fish are put into the inner bag for transportation, but it is necessary to use a plastic bag or the like as the inner bag (Patent Document 1, etc.).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to develop a paper packaging material that can be easily processed and manufactured into a bag shape and has waterproof properties for use in applications for containing ice and / or frozen products.

Means for Solving the Problems

[0005] As a result of intensive studies on the above problems, the present inventors have found that by coating at least one side of a paper substrate with a waterproof resin layer, an excellent paper packaging material for containing ice and / or frozen products can be realized.

[0006] Although not limited to the following, the present invention includes the following aspects. [1] A paper packaging material for containing ice and / or frozen products, with a waterproof resin layer coated on at least one side of a single-layer paper substrate. [2] The paper packaging material according to [1], wherein the waterproof resin layer can be heat-sealed by heat welding. [3] The paper packaging material according to [1] or [2] for manufacturing a paper bag. [4] The paper packaging material according to any one of [1] to [3], wherein the waterproof resin layer contains at least one of a styrene-based resin, an acrylic-based resin, a polyolefin resin, and wax. [5] A method for manufacturing the paper packaging material according to any one of [1] to [4], comprising the step of coating a waterproof resin layer on at least one side of a paper substrate. The above method. [6] A paper bag for containing ice, comprising the paper packaging material according to any one of [1] to [4]. [7] A method for manufacturing a paper packaging body for containing ice and / or frozen products, comprising the step of forming a paper packaging body for containing ice and / or frozen products from the paper packaging material according to any one of [1] to [4]. [8] The method according to [7], wherein the paper packaging body is a paper bag. [Effect of the Invention]

[0007] According to the present invention, an excellent paper packaging material for containing ice and / or frozen products can be obtained. [Brief Description of the Drawings]

[0008]

Figure 1-1

Figure 1-2

Figure 1-3

Figure 2-1

Figure 2-2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0009] The present invention relates to a paper packaging material for containing ice and / or frozen products. The packaging material according to the present invention has waterproof properties, and even when containing ice and / or frozen products, the water melted from the ice is difficult to seep in, and when taking out the frozen product after freezing from the contents, the coating layer does not adhere to the frozen product and has a function as a packaging material that can be easily peeled off. Further, in a preferred aspect of the present invention, the packaging material according to the present invention is such that water is difficult to seep out even when containing ice and / or frozen products and left for a long time, and when taking out the frozen product after freezing from the contents, the coating layer does not adhere to the frozen product and can be easily taken out, and the strength of the packaging material is not easily reduced. The paper packaging material according to the present invention is not particularly limited as long as it is used for packaging those containing ice and / or frozen products. For example, it can be used for uses such as containing meat, fish, vegetables, etc. together with ice as contents or for containing frozen products. The paper packaging material according to the present invention can also be used for uses such as directly containing meat, fish, vegetables, etc. as contents without putting ice and then freezing them.

[0010] The basis weight of the paper packaging material according to the present invention is not particularly limited, but for example, it can be 30 to 800 g / m 2 When the paper base material is single-layer paper, the basis weight of the packaging material can be, for example, 35 to 400 g / m 2 or 40 to 300 g / m 2, further, it can be 50 to 200 g / m 2 .

[0011] In a preferred embodiment, the paper packaging material of the present invention has a Cobb water absorbency of the surface of 3 g / m 2 or less, more preferably 2 g / m 2 or less, and may be 1 g / m 2 or less. When measuring the Cobb water absorbency, in the case of paper with less than 1 g / m 2 (including the case where the water absorption is less than the measurement limit value and no water is absorbed), in a preferred embodiment, the Cobb water absorbency of the surface is 25 g / m 2 or less, more preferably 20 g / m 2 or less, and may be 10 g / m 2 or less. In the present invention, the Cobb water absorbency is measured in accordance with the Cobb method specified in JIS P8140 by bringing 100 ml of distilled water into contact with the coating layer and measuring the weight per unit area of the water absorbed after a specified time. The smaller the value of the Cobb water absorbency, the higher the waterproofness of the packaging material.

[0012] In a preferred embodiment, the paper packaging material of the present invention is also excellent in moisture-proof property, and the moisture permeability is preferably 100 g / m 2 ·24 h or less, more preferably 75 g / m 2 ·24 h or less, or may be 50 g / m 2 ·24 h or less. The moisture permeability of the paper packaging material can be measured from the coating layer side in accordance with JIS Z 0208, and the smaller the value, the higher the moisture-proof property.

[0013] In a preferred embodiment, the paper packaging material of the present invention is also excellent in oil resistance, and the oil repellency on the coating layer side is preferably kit number 7 or more, and may be 8 or more, or 9 or more. Here, the oil repellency of the paper packaging material can be measured from the coating layer side in accordance with "Paper and Paperboard - Oil Repellency Test Method - Kit Method" (JAPAN TAPPI Paper Pulp Test Method No. 41), and the larger the value of the kit number, the higher the oil resistance.

[0014] The paper packaging material of the present invention preferably has an Oken smoothness of the coating surface of 15 seconds or more, more preferably 20 seconds or more, and even more preferably 25 seconds or more. When the surface smoothness of the coating layer of the waterproof paper is in the above range, a high gloss can be obtained on the surface of the coating layer, and a paper packaging material with excellent cosmetic properties can be obtained.

[0015] Paper substrate The paper packaging material according to the present invention has at least a paper base material and a waterproof resin layer coated on at least one side of the paper base material. In the present invention, the basis weight of the paper base material is not particularly limited, and is, for example, 10 to 400 g / m 2 The paper substrate used in the present invention is preferably a single-ply paper since it can be easily processed into a bag-shaped package, and the basis weight thereof is 10 to 300 g / m. 2 For example, when the paper base material is kraft paper, the basis weight is 30 to 250 g / m 2 The range can be set as follows:

[0016] In a preferred embodiment, the paper substrate used in the present invention has a 120-second Cobb water absorbency of 60 g / m on the surface on which the waterproof resin layer is to be formed. 2 More preferably, it is 55 g / m 2 Less than 50 g / m, more preferably 50 g / m 2 The lower limit of the 120-second Cobb water absorbency is not particularly limited, but is preferably 1 g / m 2 More preferably, it is 2 g / m or more. 2 More preferably, 3 g / m 2 In the present invention, the Cobb water absorbency of the packaging material can be adjusted by coating a waterproof resin layer, and by having the 120-second Cobb water absorbency of the paper base material be in the above-mentioned range, a decrease in paper strength due to excessive penetration of moisture contained in the solvent of the waterproof coating is prevented, and the solid content of the waterproof coating is retained on the surface of the paper layer to provide reliable coating, making it easier to achieve both improved waterproofness and moisture resistance.

[0017] In a preferred embodiment, the paper substrate used in the present invention has a drop oil absorbency of 2 seconds or more, more preferably 3 seconds or more, and even more preferably 5 seconds or more on the surface on which the waterproof resin layer is to be provided. The upper limit is not particularly limited, but is preferably 80 seconds or less, more preferably 75 seconds or less, and even more preferably 70 seconds or less. By having an oil absorbency in the above range, the waterproof resin layer remains on the paper surface and is less likely to penetrate into the paper layer, which makes it easier to improve waterproofness and moisture resistance. The oil absorbency of the paper substrate can be evaluated by dropping a drop of diesel No. 1, whose dynamic viscosity coefficient has been adjusted to 3 cSt, onto the sample surface using a microsyringe equipped with an H5 needle, and measuring the time it takes for the surface gloss to disappear.

[0018] The physical properties of the paper substrate are not particularly limited and can be appropriately set depending on the application of the paper packaging material. In the present invention, for example, the longitudinal elongation is 1.0 to 15.0%, the transverse elongation is 2.0 to 12.0%, and the burst strength is 2.80 to 8.00 kPa m 2 / g.

[0019] In a preferred embodiment, the paper substrate used in the present invention has an Oken smoothness of 3 seconds or more, more preferably 4 seconds or more, and even more preferably 5 seconds or more on the surface on which the coating layer is to be formed. There is no particular upper limit, but it is preferably 50 seconds or less, more preferably 45 seconds or less, even more preferably 40 seconds or less, and most preferably 35 seconds or less. By having the smoothness of the surface on which the waterproof resin layer is to be formed within the above range, it becomes easier to uniformly coat the paper substrate with the waterproof resin layer, and an excellent packaging material can be obtained.

[0020] In a preferred embodiment, the paper substrate used in the present invention has a moisture permeability of 1500 g / m2 measured from the side where the waterproof resin layer is provided. 2 - 24h or more, preferably 1750g / m 2 24h or more, preferably 2000g / m 2 The upper limit of the moisture permeability is not particularly limited, but in a preferred embodiment, it is 5000 g / m 2 - 24h or less, preferably 4500g / m 2·24 h or less, more preferably 4000 g / m 2 ·It is 24 h or less. When the moisture permeability of the surface provided with the waterproof resin layer is within the above range, moisture in the coating agent can be efficiently evaporated to the paper layer side in the drying process after coating, so that it becomes easier to uniformly coat the paper base material with the waterproof resin layer.

[0021] As the raw material pulp of the paper base material, those known without particular limitation can be used. Specifically, for example, softwood bleached kraft pulp (NBKP), hardwood bleached kraft pulp (LBKP), softwood unbleached kraft pulp (NUKP), hardwood unbleached kraft pulp (LUKP), groundwood pulp (GP), refiner ground pulp (RGP), chemical pulp (CP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP) and other various wood-derived pulps, kenaf, bagasse, bamboo, hemp, straw and other non-wood pulps obtained from can be mentioned.

[0022] The paper base material may contain wastepaper pulp or may not contain wastepaper pulp. When containing wastepaper pulp, preferably, the blending ratio of wastepaper pulp in the total pulp is 10% by mass or more, more preferably 25% by mass or more, still more preferably 50% by mass or more, and most preferably 70% by mass or more, and it can also be 100% by mass (consisting only of pulp derived from wastepaper). Further, kraft pulp may be blended as the pulp other than wastepaper pulp, and the blending ratio of kraft pulp contained in the total pulp is preferably 50% by mass or more, more preferably 70% by mass or more, most preferably 80% by mass or more, and it may be all kraft pulp.

[0023] As the wastepaper pulp, wastepaper pulp obtained by dissociating unprinted wastepaper such as corrugated cardboard wastepaper, super white, special white, medium white, white waste, wastepaper printed on high-quality paper, coated high-quality paper, medium-quality paper, coated medium-quality paper, recycled paper, wastepaper written on, papers such as discarded confidential documents, magazine wastepaper, newsprint wastepaper pulp (DIP) obtained by deinking after dissociation can be used.

[0024] In the papermaking of the paper substrate, a sizing agent or a water repellent can be added internally or externally, and further, a paper strength enhancer can be added internally to improve the strength. Examples of the sizing agent include rosin sizing agents, rosin emulsion sizing agents, α-carboxymethyl saturated fatty acids, neutral rosin sizing agents, alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), cationic polymer sizing agents, and the like. Examples of the water repellent include fluorine-based resins, polyamide-based resins, waxes, and the like. Examples of the paper strength enhancer include conventionally used paper strength enhancers such as polyacrylamide (PAM) and modified starch. In the present invention, it is preferable to include wax in the waterproof resin layer, and it is more preferable to include paraffin wax.

[0025] Further, if necessary, known fillers can be added internally to the paper substrate, and inorganic fillers and organic fillers can be used without limitation. Examples of the inorganic fillers include kaolin, calcined kaolin, delaminated kaolin, clay, calcined clay, delaminated clay, illite, heavy calcium carbonate, light calcium carbonate, light calcium carbonate-silica composite, magnesium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, and the like. Examples of the organic fillers include urea-formalin resin, polystyrene resin, phenol resin, and the like.

[0026] Furthermore, within a range that does not affect the quality of the paper substrate, sulfuric acid band, aluminum chloride, sodium aluminate, basic aluminum compounds, water-soluble aluminum compounds, polyvalent metal compounds, silica sol, and the like can be added internally and used.

[0027] The paper substrate can be manufactured by known papermaking methods. For example, it can be carried out using a fourdrinier paper machine, a gap former type paper machine, a hybrid former type paper machine, an on-top former type paper machine, a cylinder paper machine, etc., but is not limited thereto.

[0028] In addition, in order to adjust the smoothness of the paper base material of the present invention, a smoothing treatment may be performed as necessary. For the smoothing treatment, smoothing treatment apparatuses such as a normal calendar, a super calendar, a gloss calendar, a soft calendar, a heat calendar, and a shoe calendar can be used. The smoothing treatment apparatus may appropriately adjust the form of the pressurizing device, the number of pressurizing nips, heating, line pressure, and the like.

[0029] Waterproof resin layer The paper packaging material according to the present invention has a waterproof resin layer on at least one side of the paper base material. The waterproof resin layer according to the present invention contains a synthetic resin and wax. It is preferable that the synthetic resin contains at least one of a styrene-based resin, an acrylic-based resin, and a polyolefin-based resin. In particular, it is preferable that the synthetic resin is a styrene-based resin and / or an acrylic-based resin.

[0030] As the styrene-based resin that the waterproof resin layer can contain, it is preferable that the copolymerization ratio of the styrene-based monomer having a styrene skeleton in the structure is 50% by mass or more, and it may be composed only of a polymer of the styrene-based monomer.

[0031] Examples of the styrene-based monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, p-tert-butylstyrene, α-methylstyrene, α-methyl-p-methylstyrene, and the like.

[0032] In addition, examples of monomers copolymerizable with styrene monomers include alkyl methacrylates such as methyl methacrylate, cyclohexyl methacrylate, and methyl phenyl methacrylate; alkyl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, and cyclohexyl acrylate; unsaturated carboxylic acids such as methacrylic acid and acrylic acid; unsaturated dicarboxylic acid anhydrides such as maleic anhydride and itaconic anhydride; unsaturated nitriles such as acrylonitrile and methacrylonitrile; and conjugated dienes such as 1,3-butadiene and 2-methyl-1,3-butadiene. These can be used alone or in combinations of two or more.

[0033] The acrylic resin that can be contained in the waterproof resin according to the present invention is a resin in which the copolymerization ratio of acrylic monomers, which are acrylic acid, methacrylic acid, and their derivatives, is 50% by mass or more, and it may consist only of a polymer of acrylic monomers.

[0034] Examples of acrylic monomers include methacrylic acid esters such as cyclohexyl methacrylate, t-butylcyclohexyl methacrylate, and methyl methacrylate; and acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, and isopropyl acrylate. The acrylic resin may be a polymer of one or more monomers selected from these acrylic monomers.

[0035] In addition, examples of monomers copolymerizable with acrylic monomers include aromatic vinyl compounds such as styrene, o-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, p-tert-butylstyrene, α-methylstyrene, and α-methyl-p-methylstyrene; unsaturated nitriles such as acrylonitrile and methacrylonitrile; maleimides such as N-phenylmaleimide and N-cyclohexylmaleimide; unsaturated dicarboxylic acid anhydrides such as maleic anhydride; and unsaturated carboxylic acids such as methacrylic acid and acrylic acid. These can be used alone or in combinations of two or more.

[0036] The waterproof resin layer according to the present invention preferably has a melting point of 65°C or higher, more preferably 70°C or higher, and even more preferably 75°C or higher. The upper limit of the melting point of the waterproof resin layer is not particularly limited, but is preferably 200°C or lower, more preferably 190°C or lower, and even more preferably 180°C or lower. When heating is performed using a heat sealer, the resin melts within these ranges, enabling strong adhesion and facilitating the production of paper bags containing ice as the content using the heat sealing method.

[0037] The waterproof resin layer according to the present invention preferably has a glass transition point of 55°C or lower, more preferably 50°C or lower, and even more preferably 45°C or lower. When the glass transition point of the waterproof resin layer is within the above values, cracking of the waterproof resin layer does not occur not only in a refrigerated (0 to 10°C) environment but also in a frozen (-20 to 0°C) environment during household refrigeration or transportation, enabling the maintenance of waterproof properties.

[0038] The waterproof resin layer according to the present invention contains wax. Examples of the wax contained in the waterproof resin layer include synthetic waxes such as polyethylene wax, Fischer-Tropsch wax, oil-based synthetic waxes (fatty acid ester-based, fatty acid amide, ketone-amines), hydrogenated oils, natural waxes such as beeswax, wood wax, paraffin wax, and microcrystalline wax. These waxes can be used alone or in combination of two or more, and in particular, hydrocarbon waxes containing paraffin are suitable.

[0039] In the present invention, for the purpose of improving whiteness and the like, a pigment may be contained in the waterproof resin layer. In this case, it is preferable that the whiteness of the surface is 1% or more higher than that of the paper base material by containing the pigment. Examples of such pigments include inorganic pigments such as calcium carbonate, titanium oxide, kaolin, clay, engineered kaolin, delaminated clay, talc, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicate, colloidal silica, satin white, mica, and montmorillonite. These pigments can be used alone or in combination of two or more. Among these pigments, kaolin, calcium carbonate, or mica having a flat particle shape is particularly suitable because it is less likely to inhibit waterproofness. Such a flat-shaped inorganic pigment preferably has an aspect ratio of 10 or more. The content of the pigment in the waterproof resin layer is preferably 5 to 40% by mass, more preferably 10 to 35% by mass. When the content of the pigment is 5 to 40% by mass, it is easy to effectively improve the whiteness without significantly impairing the waterproofness.

[0040] The waterproof resin layer according to the present invention is characterized by containing an antifoaming agent. By containing an antifoaming agent, the generation of fine bulges and air bubbles (hereinafter also referred to as "blisters") that are likely to occur on the surface of the coating layer when the coating agent is applied and dried is suppressed. Therefore, the paper base material can be reliably coated with the waterproof resin layer, and the waterproofness can be further improved. The type of the antifoaming agent can be appropriately selected according to the components of the waterproof resin. However, as the antifoaming agent when coating a waterproof resin mainly composed of a styrene-acrylic resin, it is more preferable to contain at least one component of mineral oil, polyether, and silica. As the addition amount of the antifoaming agent, it is preferable to add 0.05 to 6.0 parts by weight, more preferably 0.1 to 5.0 parts by weight, and even more preferably 0.15 to 4.0 parts by weight with respect to 100 parts by weight of the waterproof resin.

[0041] The waterproof resin layer according to the present invention may contain, for example, a binder, a stabilizer, a viscosity improver, a water retention agent, a preservative, a colorant, etc. The waterproof resin layer according to the present invention can be formed by applying a paint onto a paper substrate and drying it. The coating amount of the waterproof resin layer is preferably 1 to 20 g / m 2 and more preferably 4 to 15 g / m 2 . If it exceeds 20 g / m 2 , further improvement in waterproofness cannot be expected, while the manufacturing cost may increase.

[0042] In a preferred embodiment, the waterproof resin layer provided on the paper packaging material of the present invention has an average thickness of 5.5 to 20 μm, more preferably 5.6 to 15 μm, and even more preferably 5.7 to 12.5 μm. Here, the average thickness of the coating layer is the average value of the thicknesses of the waterproof resin layer measured by observing the cross-section of a sample cut into strip shape at 10 arbitrary locations using an electron microscope.

[0043] The paper packaging material according to the present invention preferably has a moisture permeability per unit thickness of the waterproof resin layer of 15 (g / m 2 ·24 h) / μm or less, more preferably 10 (g / m 2 ·24 h) / μm or less, and even more preferably 7 (g / m 2 ·24 h) / μm or less. Here, the moisture permeability per unit thickness of the waterproof resin layer is calculated by dividing the moisture permeability measured in accordance with JIS Z 0208 from the coating layer side of the waterproof paper by the average coating layer thickness.

[0044] The paper packaging material of the present invention can be manufactured by applying a waterproof resin to at least one surface of a paper substrate and drying it. The formation of the waterproof resin layer can be carried out by applying a coating agent using a known coating method. For example, coating methods such as air knife coating, curtain coating, blade coating, gate roll coating, and die coating can be used. Also, the coating layer may be a single layer or multiple layers. Multiple coating layers may be sequentially applied, or two or more layers may be simultaneously applied by curtain coating or the like. When drying the coating layer, preferably, it is adjusted so that the temperature of the coating layer at the outlet of the drying process is less than 120°C. The coating speed when applying the coating agent can be appropriately set in consideration of the viscosity of the coating agent and the target coating amount.

[0045] As a preferred embodiment, by applying the waterproof resin layer to the paper substrate by a contour coating method such as air knife coating or curtain coating, the coating amount of the coating agent on the surface of the paper substrate becomes uniform. Therefore, the coating film thickness becomes uniform, and the generation of blisters in the coating layer can be suppressed in the subsequent drying process. Also, the amount of the coating agent used can be reduced compared to the contact coating method, and the manufacturing cost can be suppressed.

[0046] The waterproof resin layer applied to the paper substrate is dried. In this drying process, it is preferable that the temperature of the coating layer at the outlet is less than 120°C, and it may be adjusted to be 100°C or less. If the temperature of the coating layer at the outlet is 120°C or higher, the generation rate of blisters in the coating layer may increase, and blocking may occur in the paper wound up after the coating layer is formed. On the other hand, the temperature of the coating layer at the outlet is preferably 60°C or higher, more preferably 70°C, and can also be 80°C or higher. If the temperature of the coating layer at the outlet is less than 60°C, in some cases, not only may blocking occur in the paper wound up after the coating layer is formed, but also the drying of the coating layer may be insufficient, so that the waterproof performance may not be fully exhibited.

[0047] The coating layer temperature at the outlet of the drying process can be set in consideration of the basis weight and paper thickness of the paper substrate. For example, in the case of a paper substrate with a large basis weight and paper thickness, blisters tend to occur on the surface of the coating layer more easily than in the case of a paper substrate with a small basis weight and paper thickness. Although the reason is not limited, in the case of thick paper, the basis weight and paper thickness are larger and the air permeability is often lower than that of thin paper. Even with the same moisture value in the paper, in the drying process, a large amount of moisture vaporized inside the paper substrate cannot escape sufficiently, so it is considered that blisters are likely to occur on the surface of the coating layer. Therefore, the larger the basis weight and paper thickness of the paper substrate, the more preferably the coating layer temperature at the outlet of the drying process is adjusted to be lower within the above range. Here, the outlet of the drying process means the outlet of the drying zone in the case where there is one drying zone in the drying process, and the outlet of the most downstream drying zone in the case where there are multiple drying zones in the drying process.

[0048] The adjustment of the coating layer temperature at the outlet of the drying process can be performed by adjusting the drying time and the temperature of the drying zone. The drying time is determined by the feeding speed of the paper substrate, the number and length of the drying zones, the equipment capacity (air volume, infrared output) of the drying zones, etc. Also, as the drying method, a known drying method can be used. For example, a steam cylinder heating drying method, a hot air drying method, a gas type infrared drying method, an electric type infrared drying method, etc. can be mentioned, and any one of these, or a combination of two or more can be used.

Example

[0049] Hereinafter, the present invention will be described in more detail with specific examples, but the present invention is not limited by the following specific examples. In this specification, unless otherwise specified, concentrations etc. are based on weight, and numerical ranges include their endpoints.

[0050] ■Manufacture of paper packaging material (1) Sample 1 Kraft paper made from a paper stock obtained by blending needleleaf unbleached kraft pulp (NUKP) with an internal sizing agent and a paper strengthening agent was used as the paper substrate (single-layer paper, basis weight: 74 g / m 2 , whiteness: 19%).

[0051] A coating solution containing 100 parts by weight of a waterproofing agent containing styrene-acrylic resin and wax (VaporCoat 2200, Michaelman, glass transition temperature: 39°C) and 0.5 parts by weight of a silica-based defoaming agent (SN Deformer 777, San Nopco) was applied to one side of the paper substrate using an air knife at a rate of 10.9 g / m. 2 The coating was applied and then dried with hot air so that the temperature of the coating layer at the exit of the drying process was 80°C, to obtain a paper packaging material (basis weight: 84.9 g / m 2 ). (2) Sample 2 (Comparative Example) The same paper base material as sample 1 was used, and a 20 μm thick polyethylene film was laminated on one side of the paper base material, and then the laminated paper packaging material was made by bonding using a roller heated to a temperature of 70 ° C. (basis weight: 84.8 g / m 2 ). (3) Sample 3 (Comparative Example) The same paper base material (kraft paper) as sample 1 was used as a paper packaging material without any processing (basis weight: 74 g / m 2 ).

[0052] ■ Evaluation of paper packaging materials (1) Measurement of paper quality The paper quality of each sample was evaluated according to the following procedure. (Basis Weight) Measured in accordance with JIS P 8124. (Average coating layer thickness, moisture permeability per unit coating layer thickness) The sample was cut into strips, and the thickness of the coating layer was measured at 10 random points on the cross section by observation using an electron microscope, and the average value was calculated to obtain the average coating layer thickness. The moisture permeability per unit coating layer was calculated by dividing the moisture permeability by the average coating layer thickness. (Oken Smoothness) In accordance with JIS P 8155, the Oken smoothness was measured using a digital Oken air permeability smoothness tester (Asahi Seiko). (Longitudinal elongation, transverse elongation) Measured in accordance with JIS P 8113. (Burst Ratio) Burst strength was measured in accordance with JIS P 8131, and the burst ratio was calculated by dividing the burst strength by the basis weight. (Cobb Sizing Degree) In accordance with JIS P 8140, the measurement was carried out by the Cobb method. That is, 100 ml of distilled water was brought into contact with the coated layer, and the weight per unit area of the water absorbed after a specified time was measured. In addition to the normal specified time of 120 seconds (2 minutes), the measurement was also carried out for 30 minutes. (Moisture Vapor Transmission Rate) In accordance with JIS Z 0208, the measurement was carried out from the coated layer side (surface layer side). (Water Repellency) In accordance with JAPAN TAPPI Paper and Pulp Test Method No. 68 "Paper and Paperboard - Water Repellency Test Method", the coated layer side was measured. (Oil Repellency) In accordance with JAPAN TAPPI Paper and Pulp Test Method No. 41 "Paper and Paperboard - Oil Repellency Test Method - Kit Method", the coated layer side was measured. (Dropwise Oil Absorbency) Using a microsyringe equipped with an injection needle No. H5, No. 1 light oil with a kinematic viscosity coefficient adjusted to 3 cSt was dropped onto the sample surface one drop at a time, and the time until the gloss on the surface disappeared was measured. (2) Waterproofness Test For each of the obtained samples, one sheet was folded into the shape shown in Fig. 1, and a range with a width of 10 mm from the end was adhered to produce a paper package (paper bag A, length 27.5 cm × width 21.5 cm × depth 12.5 cm). For Sample 1, the coated layer side was on the inside, and for Sample 2, the laminate layer was on the inside. A desktop heat sealer (adhesion temperature: 150 °C) was used to produce the paper bag by heat welding. For Sample 3, a paste mainly composed of polyvinyl alcohol (Arabic Yamato, manufactured by Yamato Co., Ltd.) was used for adhesion and lamination to produce the paper bag. 18, 19, 22, 23, 24, and 25 in Fig. 1 are the adhesion parts.

[0053] Also, one sheet was folded into the shape shown in Fig. 2 to produce a paper package (paper bag B, length 27.5 cm × width 21.5 cm × depth 12.5 cm). Paper bag B was not adhered. For Sample 1, the coated layer side was on the inside, and for Sample 2, the laminate layer was on the inside to produce the paper bags respectively.

[0054] After setting the fabricated paper packaging bodies (paper bags A and B) inside a cardboard box (inner dimensions: 28 cm in length × 22 cm in width × 13 cm in depth), 1 kg of ice was put into the paper packaging bodies up to the upper opening of the cardboard box (Figure 3). After leaving the cardboard box containing ice in a refrigerator at 5°C for 24 hours and then leaving it at room temperature for 1 hour, the water leakage situation from the paper packaging bodies and the wetting situation on the cardboard side were visually confirmed. The evaluation criteria are as follows. 〇: No water droplets or the like leak from the paper packaging body, and the cardboard box is not wet. ×: Water leaks from the paper packaging body, and the cardboard box is also wet. (3) Dissociation test (recyclability) Samples 1 to 3 were cut into 25 mm square sizes, 30 g was weighed, 1.5 L of water at 45°C was added and diluted to 2%, and then dissociation was carried out for 30 minutes using a Tappi-type dissociator. Next, after forming a sheet and pressing in accordance with JIS P 8222 to obtain wet paper, it was dried for 2 hours on a plate heated to 50°C to produce a hand-made sheet (basis weight: about 50 g / m 2 ).

[0055] Next, based on the following criteria, the appearance of the surface of the hand-made sheet was visually evaluated. 〇: There are no obvious foreign substances on the paper surface, and there are no particular problems regarding recycling. ×: Foreign substances or the like are obvious on the paper surface, which causes problems regarding recycling. (4) Peelability of frozen products For each of the obtained samples, a paper packaging body having the same shape as paper bag B used in the waterproofness test was fabricated and set in a cardboard box. After putting 40 mackerels (about 300 g) and 20 ml of 3.4% concentration saline solution inside the paper packaging body, it was subjected to a freezing treatment in a household freezer at -18°C for 24 hours (Figure 5). After the freezing treatment, the frozen mackerels were taken out from the box and the paper packaging body, and the peelability of the frozen products from the paper packaging body was determined based on the following criteria. ○: The coating layer and the paper layer did not adhere to the frozen mackerels and could be easily taken out. ×: Attention was required to prevent the paper bag from tearing when taking out the mackerels, and the coating layer and the paper layer adhered to the taken-out mackerels.

[0056] [Table 1]

[0057] As shown in the table, the paper bag manufactured from the paper packaging material of the present invention does not show water leakage from the inside of the package or condensation on the outer surface of the package (corrugated cardboard side) even when ice is placed and left, and there is no influence on the corrugated box body due to water seepage. Further, it was shown that the paper packaging material of the present invention has no foreign matter even when a release test is performed and is excellent in recyclability. Furthermore, it became clear that when taking out the frozen product stored in the paper bag and then frozen, the packaging material does not adhere and can be easily taken out.

[0058] On the other hand, for the paper packaging material (Sample 2) subjected to lamination processing, although water seepage was not observed, it was inferior in recyclability. Also, plain kraft paper (Sample 3) is excellent in recyclability, but since it is not coated with a waterproof agent, water seepage from the paper surface occurred due to the melting of ice and condensation generated outside the paper packaging material, and the seeped water wet the corrugated box.

[0059] From the above results, it can be said that the paper package of the present invention can be suitably used for contents mainly composed of ice and / or frozen products and can be recycled. [Explanation of Signs]

[0060] 1 Bag (Sample A) body 2a, 2b Sheet pieces 4 First reference line 5 Second reference line 7 Third reference line 7a Left end of the third reference line 7b Right end of the third reference line 8 Fourth reference line 9 Fifth reference line 11 First folding line part 12 Intersection point 13 Second folding line part 14 Intersection point 15 Third broken line part 16 Intersection point 17 Fourth broken line part 18 First seal part 19 Second seal part 20, 21 Overlapping part 22 Third seal part 23 Fourth seal part 24 Fifth seal part 25 Sixth seal part 26 Bottom part 27 One side wall part 28 The other side wall part 31 Bag (Sample B) body 32 Sheet 33 First reference line 34 First broken line part 35 Second reference line 36 Second broken line part 37 Quadrilateral part 38 Intersection point 39 Corner part 40 Third broken line part 41 Folded overlapping part 42 Quadrilateral folded overlapping part 43 Seal part 44 Bottom part 45, 46 Side wall part

Claims

1. A paper packaging material for containing ice and / or frozen products, wherein a waterproof resin layer is coated on at least one side of a single-layer paper substrate, The coating amount of the waterproof resin layer is 4 to 20 g / m ２ and the moisture permeability per unit thickness of the waterproof resin layer is 15 g / m ２ ·24 h / μm or less, and the waterproof resin layer contains at least one selected from the group consisting of a styrene resin, an acrylic resin, and a polyolefin resin. The above paper packaging material.

2. The paper packaging material according to Claim 1, wherein the waterproof resin layer can be heat-sealed by heat sealing.

3. The paper packaging material according to Claim 1 or 2, for manufacturing a paper bag.

4. The paper packaging material according to any one of Claims 1 to 3, wherein the waterproof resin layer contains wax.

5. The paper packaging material according to any one of Claims 1 to 4, wherein the waterproof resin layer contains an antifoaming agent.

6. A method for manufacturing the paper packaging material according to any one of Claims 1 to 5, including the step of coating a waterproof resin layer on at least one side of the paper substrate.

7. A paper bag comprising the paper packaging material according to any one of Claims 1 to 5.

8. A paper bag for containing ice, comprising the paper packaging material according to any one of Claims 1 to 5.

9. A method for manufacturing a paper packaging body for containing ice and / or frozen products, including the step of forming a paper packaging body for containing ice and / or frozen products from the paper packaging material according to any one of Claims 1 to 5.

10. The method according to Claim 9, wherein the paper packaging body is a paper bag.

Images