Packaging materials and packages

Abstract

To provide a packaging material exhibiting excellent thermal adhesiveness, excellent oil-resistant property, and small environmental load.SOLUTION: According to a packaging material comprising a coating layer on at least one surface of a substrate, the coating layer contains casein and / or a salt thereof, and the coating layer further contains a rosin compound. A content ratio of the casein and / or the salt thereof to the rosin compound in the coating layer is preferably 20:80 to 95:5. The substrate preferably contains one, or two or more selected from the group consisting of wood pulp, non-wood pulp, and regenerated cellulose.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a packaging material utilizing a heat sealing method and a package using the same. [Background technology]

[0002] Heat seal sheets are widely used as packaging materials for foods, medicines, industrial products, etc. Examples of usage include self-adhesive heat seal sheets formed into bags, heat seal sheets bonded to other substrates, and lid materials for molded containers such as cups and blister packs. In addition to heat sealing properties, heat seal sheets may be required to have various barrier properties depending on the contents to be packaged. In particular, when packaging food, oil resistance is often required.

[0003] Packaging materials with heat sealability and oil resistance based on a paper base have been proposed, for example, in JP-A-2015-155582 (Patent Document 1) and JP-A-2020-183593 (Patent Document 2). These use petrochemical materials such as styrene-adiene copolymer latex, olefin resins, and acrylic resin emulsions to achieve heat sealability and oil resistance, and have not given sufficient consideration to environmental impact. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-183593 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-155582 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a packaging material that has excellent heat sealing properties and oil resistance while reducing the amount of petrochemical materials used, and to solve environmental problems such as marine pollution. [Means for solving the problem]

[0006] The inventors have conducted extensive research into the use of non-petrochemical raw materials that have a low environmental impact, and as a result have discovered that a heat sealable sheet having good heat sealability, oil resistance, and other properties can be obtained by mixing casein or a salt thereof with a rosin compound and using the mixture in the heat seal layer, thereby arriving at the present invention.

[0007] The present invention has the following aspects. [1] A packaging material having a coating layer on at least one surface of a substrate, characterized in that the coating layer contains casein and / or a salt thereof, and further contains a rosin compound. [2] The packaging material according to [1], wherein the content ratio of the casein and / or its salt to the rosin compound in the coating layer is 20:80 to 95:5. [3] The packaging material according to [1] or [2], wherein the substrate comprises one or more materials selected from wood pulp, non-wood pulp, and regenerated cellulose. [4] The packaging material according to any one of [1] to [3], wherein the substrate contains 0.01 to 2.0 g / m2 of a styrene-(meth)acrylic acid copolymer compound and / or a styrene-maleic anhydride copolymer compound. [5] The packaging material according to any one of [1] to [4], wherein the base material has a Stockigt sizing degree of 20 seconds or more as measured in accordance with JIS P 8122:2004. [6] A package obtained by thermally bonding at least a part of the coating layer surface of the packaging material according to any one of [1] to [5]. [Effects of the Invention]

[0008] The packaging material of the present invention has good thermal adhesiveness, excellent oil resistance, and also has a small environmental impact. DETAILED DESCRIPTION OF THE INVENTION

[0009] In the present invention, "air permeability" is a value measured in accordance with JIS P 8117:2009. In the present invention, "Stöckigt sizing degree" is a value measured in accordance with JIS P 8122:2004. In the present invention, "peel strength" is a value measured in accordance with JIS P 8113:2006. In the present invention, "oil resistance" is a value measured in accordance with TAPPI UM-557. The symbol "to" indicating a numerical range means that the values ​​before and after it are included as the lower and upper limits.

[0010] One embodiment of the packaging material of the present invention is a packaging material comprising a substrate and a coating layer provided on at least one surface of the substrate. A primer layer may be provided between the coating layer and the substrate. The substrate may also have a surface coated with a sizing agent.

[0011] The coating layer may be provided on only one surface of the substrate, or on one surface and the other surface opposite thereto. When the coating layer is provided on only one surface of the substrate, another layer may be provided on the other surface of the substrate.

[0012] When the substrate is made of paper, the air permeability measured with an Oken-type air permeability measuring device in accordance with JIS P 8117:2009 for packaging materials, with the coating layer facing up, is preferably 10 to 100,000 seconds, more preferably 50 to 100,000 seconds, and particularly preferably 100 to 50,000 seconds. By keeping the air permeability measured by the above-mentioned method within this range, sealing at the adhesive interface is less likely to be impaired by evaporation of moisture contained in the paper substrate, even when packaging materials are bonded together at high temperatures (170°C or higher). This is also useful for applications requiring the gradual release of evaporative materials contained therein or the control of the flow of air and moisture in and out of the packaging, such as packaging materials for freshness-preserving agents and portable hand warmers. On the other hand, it is preferable to use a substrate having an air permeability of more than 100,000 seconds as measured by the above method, since oil resistance is easily obtained.

[0013] The air permeability of the packaging material measured by the above-mentioned measurement method can be controlled by appropriately selecting the air permeability of the substrate measured by the above-mentioned measurement method, the coating amount of the coating layer paint (mass of the coating layer per unit area), the layer structure of the coating layer, the coating and drying conditions, the freeness of the pulp of the substrate, the basis weight and density of the substrate, etc. in the manufacturing method of the packaging material described below.

[0014] (base material) The raw materials used for the substrate are not particularly limited, but it is preferable to use pulp, regenerated cellulose fiber, biodegradable resin, plant-derived resin, etc. to reduce the environmental impact. Examples of pulp include wood pulp and non-wood pulp. Examples of wood pulp include softwood pulp and hardwood pulp, and either may be used. Furthermore, the cooking method and bleaching method for wood pulp are not particularly limited. Examples of non-wood pulp include hemp pulp, kenaf pulp, bamboo pulp, cotton pulp, etc. These pulps may be used alone or in combination of two or more. Examples of regenerated cellulose fiber include rayon fiber, lyocell fiber, Bemberg fiber, etc.

[0015] Biodegradable resins include polylactic acid, polybutylene succinate, polybutylene succinate adipate, and polybutylene succinate lactide. Examples of plant-derived resins include ethylene glycol produced from bioethanol, polyethylene terephthalate, polyolefin, and polyethylene furanoate produced from plant-derived monosaccharides and the like. The biodegradable resin and plant-derived resin may be formed into a film and used as a substrate, or may be formed into a fiber and included in the substrate.

[0016] The substrate can be obtained by, for example, making paper from a papermaking raw material containing a slurry in which a fibrous material such as pulp or resin fiber is dispersed in water.

[0017] The substrate can be obtained, for example, by making paper from a papermaking raw material containing a pulp slurry. The pulp slurry is obtained by beating pulp in the presence of water. The pulp beating method and beating device are not particularly limited, but a double disc refiner (DDR), which has high beating efficiency, is preferably used.

[0018] The pulp is preferably beaten so that the Canadian Standard Freeness of the pulp is 250 mLCSF or more and 700 mLCSF or less, more preferably 250 mLCSF or more and 600 mLCSF or less, and particularly preferably 300 mLCSF or more and 500 mLCSF or less. By setting the Canadian Standard Freeness of the pulp to the above lower limit or higher, the breathability of the paper base material can be more effectively improved. Also, by setting the Canadian Standard Freeness of the pulp to the above upper limit or lower, the strength of the paper can be improved, which can contribute to improving the peel strength of the heat-sealed portion.

[0019] Generally speaking, regarding the relationship between pulp beating and paper strength, it is difficult to obtain paper strength if the beating is not carried out sufficiently. This is thought to be because the pulp fibers are not intertwined well and there are few points of interfiber bonding (hydrogen bonding). However, paper strength improves with a certain amount of beating. On the other hand, as beating progresses, the pulp fibers become more entangled with each other, increasing the number of bonding points between the fibers, which increases the paper strength but reduces the voids between the fibers, reducing the air permeability of the base paper. When the Canadian Standard Freeness of the pulp is within the above range, the paper strength can be sufficiently increased while maintaining the breathability of the breathable substrate, and the peel strength of the heat-sealed portion of the packaging material can be improved.

[0020] If necessary, various papermaking internal additives can be added to the pulp slurry obtained by beating to prepare a papermaking raw material. The pulp slurry can also contain the above-mentioned fibrous materials. Examples of internal additives include sizing agents, paper strength agents, wet strength agents, aluminum sulfate, cationic starch, and other fixing agents. Other internal additives include water retention agents, retention aids, antifoaming agents, fillers, colorants, and the like, which can be arbitrarily blended into the papermaking raw materials. These internal additives can be any known ones.

[0021] Examples of sizing agents include alkenyl succinic anhydride, alkyl ketene dimer, and rosin compounds. These sizing agents may be used alone or in combination. Among these, the use of rosin compounds derived from natural products is preferred because it increases the proportion of non-petrochemical materials used in the packaging material.

[0022] The substrate is coated on the side on which the coating layer is to be formed with a styrene-(meth)acrylic acid copolymer compound and / or a styrene-maleic anhydride copolymer compound at a rate of 0.01 to 2.0 g / m 2 It is preferable to apply the coating in the range of

[0023] The undercoat layer can be applied to the base paper obtained in the papermaking process using a size press, gate roll, or other process subsequent to the papermaking process, by coating the styrene-(meth)acrylic acid copolymer compound or styrene-maleic anhydride copolymer compound alone or as a mixture with a binder such as starch. Alternatively, the base can be formed by coating at least one surface of the base with an undercoat containing a styrene-(meth)acrylic acid copolymer compound or a styrene-maleic anhydride copolymer compound.

[0024] The sizing property of the substrate is preferably 50 seconds or more in terms of Stockigt sizing degree measured in accordance with JIS P 8122:2004, since this improves the heat sealability and oil resistance of the packaging material, and more preferably 100 seconds or more. Examples of the paper strength agent include polyacrylamide resin, cationized starch, and polyvinyl alcohol. These paper strength agents may be used alone or in combination of two or more.

[0025] Examples of the wet strength agent include polyamide epoxy resin, epichlorine resin, and melamine resin. These wet strength agents may be used alone or in combination of two or more. An example of a water-retaining agent is carboxymethyl cellulose. An example of the filler is talc.

[0026] When the packaging material is to be given easy-peel openability, the substrate preferably contains a polyacrylamide resin, which enhances the easy-peel property. In particular, by adding polyacrylamide resin to the substrate as a paper strength enhancer, the strength of the substrate can be more effectively improved, preventing destruction of the substrate when the heat-sealed portion is opened after heat sealing processing, and further improving the easy-peel properties.

[0027] The basis weight of the substrate is, for example, 30 g / m to maintain the strength of the packaging material. 2 More than 40g / m 2 More preferably, 45 g / m 2 The above is even more preferable. The upper limit of the basis weight of the substrate is not particularly limited, but when used as a bag-shaped self-adhesive packaging material, it is, for example, 300 g / m 2 Less than 250 g / m 2 Less than 200 g / m is more preferable. 2 The following is even more preferred:

[0028] The density of the substrate is, for example, 0.50 to 1.20 g / cm 3 is preferable, and 0.65 to 1.10 g / cm 3 When the density of the substrate is equal to or greater than the lower limit, high adhesive strength is easily obtained at the heat-sealed portion. When the density of the substrate is equal to or less than the upper limit, sufficient breathability can be maintained.

[0029] (coating layer) The coating layer of the present invention contains casein and / or a salt thereof, and also contains a rosin compound. The packaging material of the present invention contains a mixture of casein and / or its salt and the rosin compound in the coating layer, which significantly improves the heat seal strength compared to when casein (salt) or the rosin compound is contained alone.

[0030] The content ratio of the casein and / or its salt to the rosin compound in the coating layer of the present invention is preferably in the range of 20:80 to 95:5. By setting the content ratio of casein and / or a salt thereof to the rosin compound within the above range, excellent heat seal strength and oil resistance can be obtained. By setting the content ratio of the rosin compound to casein and / or its salt to 80 or less, excellent heat seal strength and oil resistance can be obtained.

[0031] The coating layer of the present invention more preferably contains the rosin compound in an amount of 5.0% by mass to 80% by mass of the total solid content of the coating layer. It is more preferable that the total amount of casein and / or its salt and rosin compound in the coating layer of the present invention is 80% by mass or more of the total solid content of the coating layer. Of the casein salts used in the coating layer of the present invention, sodium salts are particularly preferred because they cause little increase in viscosity of the coating material for the coating layer when mixed with a rosin compound, thereby broadening the range of coating method options.

[0032] The casein used in the present invention is not particularly limited, and rennet casein and acid casein can be used. As a raw material for casein, cow's milk caseinate is preferred. Alternatively, milk from other ungulates may be used, particularly milk from ungulates (eg, sheep, goats, horses, camels, and buffalo).

[0033] Caseinates that can be used in the present invention are not particularly limited and can be obtained by acid precipitation from a liquid containing soluble casein (casein micelles), such as milk, followed by neutralization with a base such as a hydroxide (e.g., NaOH, KOH, Mg(OH)2, Ca(OH)2, NH4OH, or a basic salt, such as CaCO3, Na2CO3, or K2CO3, and mixtures thereof). The term caseinate also includes modified cases (e.g., saccharified caseinate or deamidated caseinate).

[0034] Deamidated caseinates can be obtained, for example, by subjecting caseinate to the deamidating activity of an enzyme (e.g., deamidase or transglutaminase), in which some or all of the amide groups in the glutamine and / or asparagine side chains are deamidated to form carboxyl groups. Like casein, caseinates are composed of a mixture of four major casein types (alpha S1, alpha S2, bata, and kappa casein).

[0035] However, (micellar) casein contains calcium and phosphate bound to the protein structure, stabilizing the micellar structure. Although calcium or phosphate may be included in caseinate preparations, caseinate need not contain either calcium or phosphate. Of the caseinates, the sodium salt is preferred, as it is the more widely available.

[0036] Examples of rosin compounds used in the coating layer of the present invention include reinforced rosin, acid-value-imparted rosin, and rosin-modified phenol. When the coating layer of the present invention contains a so-called reinforced rosin obtained by reacting rosin with an α,β-unsaturated carboxylic acid such as fumaric acid, the heat-sealing property and oil resistance can be further improved. Furthermore, rosin compounds with a low content of residual terpene compounds are preferred because they have a minimal cypress odor. Specific examples include the Super Ester series (Arakawa Chemical Industries, Ltd.). These rosin compounds may be used alone or in combination.

[0037] The coating layer may further contain other components within the range that does not impair the effects of the present invention. The other components are not particularly limited, and may be any components that are commonly used to impart heat sealability and oil resistance to packaging materials.

[0038] The mass of the coating layer per unit area is, for example, 0.1 to 30 g / m 2 and may be 0.3 to 20 g / m 2 and may be 1 to 10 g / m 2 and may be 3 to 10 g / m 2 It may be.

[0039] (undercoat layer) Examples of the undercoat layer include the above-mentioned styrene-(meth)acrylic acid copolymer compound, styrene-maleic anhydride copolymer compound and polyacrylamide resin, as well as various barrier layers, printed coating layers, light-shielding layers and the like.

[0040] (Back layer) In the present invention, a backside layer can be provided as needed. Examples include various barrier layers, printed coating layers, and light-shielding layers. Printing can be performed, and an overprint layer may be provided on the printed layer.

[0041] (Manufacturing method of packaging materials) The packaging material is produced by forming a coating layer on at least one surface of a substrate. An example of a manufacturing method for a packaging material is the following manufacturing method A for a packaging material.

[0042] Packaging material manufacturing method A: A method for producing a packaging material, comprising the steps of applying a coating material to at least one surface of a substrate and drying the coating material, wherein the content of casein and / or a salt thereof in the coating material is 20% by mass or more of the total solid content of the coating layer, and the content of a rosin compound in the coating layer is 10 to 500% by mass of the casein and / or a salt thereof.

[0043] The paint for the coating layer may be applied to only one surface of the substrate, or may be applied to one surface and the other surface of the substrate. If necessary, the surface of the substrate may be smoothed before applying the coating material for the coating layer. After forming the thermal adhesive layer, the surface of the obtained heat seal sheet may be smoothed. The Oken smoothness of the surface of the substrate on which the coating layer is to be formed, as measured in accordance with JIS P 8155:2010, is preferably 30 to 5000 seconds, since this provides good adhesion during heat sealing and is less likely to cause adhesion inhibition due to increased air permeability, and is more preferably 50 to 3000 seconds.

[0044] The method for applying the coating material for the coating layer is not particularly limited, and various known wet application methods can be used. For example, application can be carried out using an on-machine size press device of a paper machine, a transfer roll coater (such as a shim sizer or gate roll coater), a spray device, etc. Off-machine application can be carried out using a common coating device, such as a blade coater, air knife coater, roll coater, reverse roll coater, shim sizer, gate roll coater, bar coater, curtain coater, slot die coater, gravure coater, champlex coater, brush coater, two-roll coater, bill blade coater, short dwell coater, etc. Application can also be carried out using a printing machine such as a gravure printing machine or a flexographic printing machine.

[0045] The device for drying the applied coating layer paint may be a cylinder dryer that comes into contact with the coating surface, but from the viewpoint of preventing contamination of the device, an air dryer, an infrared heater, or the like that does not come into contact with the coating surface is preferred. Considering operability and productivity, the application and drying of the coating layer paint are preferably carried out on-machine. The type of paper machine used to make the substrate is not particularly limited, and examples include a Fourdrinier paper machine, a short wire paper machine, a cylinder paper machine, an inclined paper machine, etc. An on-machine type paper machine equipped with a coating device and a dryer is preferred.

[0046] Drying conditions after application of the coating layer paint include, for example, 60 to 160°C and 20 seconds to 5 minutes.

[0047] (Action and effect) The packaging material is self-adhesive or adheres to other materials by heat sealing to encase the contents. The adhesive strength of the heat-sealed portion can be measured by heat-sealing a test piece by applying heat and pressure so that the coating layers of the packaging material are in contact with each other, cutting the heat-sealed piece into a width of 15 mm, and peeling it at a peeling speed of 300 mm / min using a tensile tester according to JIS P 8113: 2006 using the 180-degree peel method. Alternatively, measurements can be made in the same way for packaging materials and other materials. The peel strength is preferably 0.5 N / 15 mm or more, more preferably 1.0 N / 15 mm or more, even more preferably 2.0 N / 15 mm or more, and most preferably 5.0 N / 15 mm or more.

[0048] Furthermore, the packaging material can also exhibit oil resistance. Oil resistance can be evaluated by dropping a kit solution of each grade prepared in accordance with TAPPI UM-557 onto the coating surface of the coating layer and determining whether or not a stain develops after 15 seconds. Oil resistance (kit) of grade 2 or higher is preferred, more preferably grade 5 or higher, even more preferably grade 8 or higher, and most preferably grade 10 or higher. [Example]

[0049] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these examples. Unless otherwise specified, % means % by mass and parts means parts by mass. Measurement and evaluation methods used in each example are shown below.

[0050] [Oken air permeability measurement] The Oken air permeability of the substrate and packaging material was measured in accordance with JIS P 8117: 2009. The air permeability of the substrate was measured with the surface to be coated facing up, and the air permeability of the packaging material was measured with the surface to be coated facing up.

[0051] [Peel test] The packaging materials were stacked so that the coated surfaces were in contact with each other, and then heat-pressed using a heat press tester under heat-pressing conditions of 150°C, 0.2 MPa, and 1.0 second to produce a heat-pressed product. The thermocompression-bonded product prepared by the above method was cut into a width of 15 mm to prepare a sample for measuring peel strength. The peel strength (N / 15 mm) of the obtained sample for measuring peel strength was measured in accordance with JIS P 8113:2006 using a tensile tester (model: Tensilon RTC-1250A, manufactured by Orientec Co., Ltd.) by chucking the edges of the composite film and heat-sealable sheet of the sample and peeling them at a peel speed of 300 mm / min using the 180-degree peel method. The higher the peel strength, the better the thermal adhesion.

[0052] [Oil resistance of coating layer surface] Each grade of kit liquid prepared in accordance with TAPPI UM-557 was dropped onto the coating surface of the packaging material, and the coating was evaluated based on whether stains occurred after 15 seconds.

[0053] Example 1 (Base material manufacturing) Hardwood bleached kraft pulp (LBKP) was beaten in a DDR to a Canadian standard freeness (freeness) of 320 mL per pulp, as specified in JIS P 8121-2:2012, to obtain a pulp slurry. The following internal chemicals were added to the pulp slurry: 1.0% aluminum sulfate (bone-dry weight), 0.05% alkenyl succinic anhydride sizing agent (Fibran 81K, manufactured by Arakawa Chemical Industries, Ltd.) pre-dispersed with cationic starch (Pillar 3YK, manufactured by Pillar Starch Co., Ltd.), 0.7% amphoteric polyacrylamide resin paper strength agent (PAM) (trade name: Polystron OFT-3, manufactured by Arakawa Chemical Industries, Ltd., mass-average molecular weight 3,000,000), and 0.4% epichlorine resin wet strength agent, relative to the pulp mass. The papermaking raw material was made into paper using a Fourdrinier paper machine, dried in a cylinder dryer, and then, in an online process, a 6.0 mass% solution of a 95:5 solids mixture of hydrophobic starch (trade name: GRS-T110, manufactured by Oji Cornstarch Co., Ltd.) and a styrene-acrylic acid copolymer surface sizing agent (trade name: Polymaron E-109, manufactured by Arakawa Chemical Industries Co., Ltd.) was applied to the paper using a size press. 2 After coating, the substrate was dried in a cylinder dryer to obtain a substrate. The basis weight of the obtained substrate was 120 g / m 2 , density is 0.74g / cm 3 The Oken air permeability was 23 seconds, the Oken smoothness was 16 seconds for the felt surface (the surface on which the coating layer was formed) and 11 seconds for the wire surface, and the Stockigt sizing degree was 117 seconds.

[0054] (Casein dissolution) 550 parts by mass of water was heated, and when the temperature reached 45°C, 30 parts by mass of 25% by mass ammonia was added. After further heating to 50°C, 125 parts by mass of casein was added and stirred to dissolve the casein. After dissolution, the casein was diluted with adjusted water to obtain a 10% by mass casein solution. (Preparation of coating layer paint) A coating paint with a solids concentration of 10% by mass was obtained by mixing and stirring 400 parts by mass of water, 500 parts by mass of the 10% casein obtained by dissolving the casein described above, and 100 parts by mass of a 50% fortified rosin emulsion (product name: Sizepine N-775, manufactured by Arakawa Chemical Industries, Ltd.). The viscosity of the resulting coating paint at 10% by mass was 90 mPa s as measured with a Brookfield viscometer.

[0055] (Manufacturing of packaging materials) The coating material for the coating layer was applied to the F surface of the substrate obtained above using a bar coater, and then dried in a blower dryer at 110°C for 2 minutes to form a thermal adhesive layer. Here, the coating amount of the coating material for the thermal adhesive layer after drying was 3.3 g / m 2 In this way, a packaging material was obtained.

[0056] <Example 2> A packaging material was obtained in the same manner as in Example 1, except that the coating layer paint of Example 1 was prepared by mixing and stirring 40 parts by mass of water, 950 parts by mass of 10% by mass casein, and 10 parts by mass of 50% by mass reinforced rosin emulsion (product name: Sizepine N-775, manufactured by Arakawa Chemical Industries, Ltd.) to obtain a coating layer paint with a solids concentration of 10% by mass. The viscosity of the resulting coating layer paint at 10% by mass measured with a Brookfield viscometer was 1245 mPa s. A weak streaky pattern was observed on the coated surface.

[0057] Example 3 A packaging material was obtained in the same manner as in Example 1, except that a coating layer paint with a solids concentration of 10% by mass was used by mixing and stirring 640 parts by mass of water, 200 parts by mass of 10% by mass casein, and 160 parts by mass of 50% by mass reinforced rosin emulsion (product name: Sizepine N-775, manufactured by Arakawa Chemical Industries, Ltd.) in preparation of the coating layer paint of Example 1. The viscosity of the resulting coating layer paint at 10% by mass measured with a Brookfield viscometer was 10 mPa s.

[0058] Example 4 (Dissolution of sodium caseinate) 150 parts by mass of sodium caseinate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dispersed in 850 parts by mass of water, heated to 90°C with stirring, and then held at 90°C for 30 minutes. After that, the solution was cooled and diluted with adjusted water to obtain a 10% by mass sodium caseinate solution.

[0059] (Manufacturing of packaging materials) A packaging material was obtained in the same manner as in Example 1, except that a coating layer paint with a solids concentration of 14% by mass was used by mixing and stirring 160 parts by mass of water, 700 parts by mass of 10% sodium caseinate obtained by dissolving the sodium caseinate described above, and 140 parts by mass of a 50% by mass reinforced rosin emulsion (product name: Sizepine N-775, manufactured by Arakawa Chemical Industries, Ltd.). The viscosity of the resulting coating layer paint at 14% by mass was 70 mPa s as measured with a Brookfield viscometer.

[0060] <Example 5> A packaging material was obtained in the same manner as in Example 1, except that a coating layer paint with a solids concentration of 10% by mass was used by mixing and stirring 720 parts by mass of water, 100 parts by mass of 10% by mass casein, and 180 parts by mass of 50% by mass reinforced rosin emulsion (product name: Sizepine N-775, manufactured by Arakawa Chemical Industries, Ltd.) in preparation of the coating layer paint of Example 1. The viscosity of the resulting coating layer paint at 10% by mass measured with a Brookfield viscometer was 7 mPa s.

[0061] Example 6 A packaging material was obtained in the same manner as in Example 1, except that the amount of alkenyl succinic anhydride sizing agent (Fibran 81K, manufactured by Arakawa Chemical Industries Co., Ltd.) previously dispersed in cationic starch (Pillar 3YK, manufactured by Pillar Starch Co., Ltd.) used was 0.03%. The basis weight of the obtained substrate was 120 g / m 2 , density is 0.74g / cm 3 The Oken air permeability was 23 seconds, the Oken smoothness was 16 seconds for the felt surface and 11 seconds for the wire surface, and the Stockigt sizing was 52 seconds.

[0062] Example 7 A packaging material was obtained in the same manner as in Example 1, except that coating using a size press device was not performed in the production of the substrate of Example 1. The basis weight of the substrate obtained above was 117.6 g / m 2 , density is 0.74g / cm 3 The Oken air permeability was 23 seconds, the Oken smoothness was 16 seconds for the felt surface and 11 seconds for the wire surface, and the Stockigt sizing was 25 seconds.

[0063] Example 8 A packaging material was obtained in the same manner as in Example 1, except that in the production of the substrate of Example 1, an alkyl ketene dimer sizing agent (trade name: Sizepine K-287, manufactured by Arakawa Chemical Industries Co., Ltd.) was used at 0.5% instead of the alkenyl succinic anhydride sizing agent (Fibran 81K, manufactured by Arakawa Chemical Industries Co., Ltd.) previously dispersed in cationic starch (Pillar 3YK, manufactured by Pillar Starch Co., Ltd.). The basis weight of the substrate obtained above was 120 g / m 2 , density is 0.74g / cm 3 The Oken air permeability was 23 seconds, the Oken smoothness was 16 seconds for the felt surface and 11 seconds for the wire surface, and the Stockigt sizing was 110 seconds.

[0064] Example 9 A packaging material was obtained in the same manner as in Example 1, except that in the production of the substrate of Example 1, a rosin sizing agent (trade name: Sizepine N111-50, manufactured by Arakawa Chemical Industries Co., Ltd.) was used at 0.9% instead of the alkenyl succinic anhydride sizing agent (Fibran 81K, manufactured by Arakawa Chemical Industries Co., Ltd.) previously dispersed in cationic starch (Pillar 3YK, manufactured by Pillar Starch Co., Ltd.). The basis weight of the substrate obtained above was 120 g / m 2 , density is 0.74g / cm 3 The Oken air permeability was 23 seconds, the Oken smoothness was 16 seconds for the felt surface and 11 seconds for the wire surface, and the Stockigt sizing was 125 seconds.

[0065] < refer to Example 10 The coating layer paint of Example 1 was prepared in the same manner as in Example 1, except that 400 parts by weight of water, 500 parts by weight of 10% casein, and 100 parts by weight of a 50% by weight rosin resin emulsion (Super Ester NS-100H, manufactured by Arakawa Chemical Industries, Ltd.) for use as a tackifier were mixed and stirred to produce a coating layer paint with a solids concentration of 10% by weight. The viscosity of the resulting coating layer paint at 10% by weight was 45 mPa·s as measured with a Brookfield viscometer. The cypress odor of the coating layer paint was also milder than that of the coating layer paints used in Examples 1 to 9.

[0066] Example 11 A packaging material was obtained in the same manner as in Example 1, except that a 20 μm thick biodegradable polylactic acid film (Palgreen BO, manufactured by Mitsui Chemicals Tocello Co., Ltd.) was used instead of the substrate of Example 1.

[0067] <Comparative Example 1> A packaging material was obtained in the same manner as in Example 1, except that only a 10% by mass aqueous casein solution was used as the coating layer paint in Example 1. The viscosity of the resulting coating layer paint at 10% by mass measured with a Brookfield viscometer was 1750 mPa s. Coating with a bar coater produced streaky defects.

[0068] <Comparative Example 2> A packaging material was obtained in the same manner as in Example 1, except that 800 parts by mass of water and 200 parts by mass of a 50% by mass reinforced rosin emulsion (product name: Sizepine N-775, manufactured by Arakawa Chemical Industries, Ltd.) were mixed and stirred to prepare a coating layer paint with a solids concentration of 10% by mass. The viscosity of the resulting coating layer paint at 10% by mass was 5 mPa s as measured with a Brookfield viscometer.

[0069] <Evaluation> Examples 1 to 9, Reference Example 10 The following evaluations were carried out for each of the packaging materials of Comparative Examples 1 and 2. Table 1 shows the configuration of each packaging material, and Table 2 shows the results of evaluation of the heat seal properties and oil resistance properties of the packaging materials.

[0070] [Table 1]

[0071] [Table 2]

[0072] As shown in the above results, the packaging materials of Examples 1 to 11 had a heat seal strength of 1.20 N / 15 mm or more in the peel test. On the other hand, the packaging material of Comparative Example 1 had a weak heat seal strength of 0.96 N / 15 mm due to streaky coating defects in the coating layer. The heat seal strength of Comparative Example 2 was 0.25 N / 15 mm, which may cause problems in use, such as accidental opening. Regarding oil resistance, the packaging materials of Examples 1 to 9 have a kit value of grade 2 or higher and are considered to have no problems in use. Comparative Examples 1 and 2 have poor oil resistance.

[0073] In addition, the packaging material in Example 4, in which sodium caseinate was added to the coating layer, had a coating concentration of 100% higher than other Even when the coating was adjusted to 4% higher than the packaging material, the coating concentration was kept below 100 mPa·s, which is preferable because it reduces the drying load after coating and increases production efficiency. Furthermore, the packaging material using the rosin emulsion for tackifier as the rosin compound of Example 10 is preferable because the paint viscosity is lower than that of reinforced rosin, and the cypress odor of the coating layer paint as determined by sensory evaluation is reduced compared to other packaging materials. [Industrial Applicability]

[0074] The packaging material of the present invention is an excellent packaging material that has sufficient heat sealability and oil resistance, and is made primarily from non-petrochemical materials, which places a small burden on the environment.

Claims

1. A packaging material having a coating layer on at least one surface of a substrate, the coating layer containing casein and / or a salt thereof, the coating layer further containing a rosin compound, the coating layer being a heat seal layer, and the rosin compound being a reinforced rosin.

2. 2. The packaging material according to claim 1, wherein the content ratio of the casein and / or its salt to the rosin compound in the coating layer is 20:80 to 95:

5.

3. 3. The packaging material according to claim 1, wherein the base material comprises one or more materials selected from the group consisting of wood pulp, non-wood pulp, and regenerated cellulose.

4. The substrate contains a styrene-(meth)acrylic acid copolymer compound and / or a styrene-maleic anhydride copolymer compound in an amount of 0.01 to 2.0 g / m ２ The packaging material according to any one of claims 1 to 3, comprising

5. The packaging material according to any one of claims 1 to 4, wherein the substrate has a Stockigt sizing degree of 20 seconds or more as measured in accordance with JIS P 8122:2004.

6. A package obtained by thermally bonding at least a portion of the coating layer surface of the packaging material according to any one of claims 1 to 5.

Images