Wrapping paper and packaging materials

Abstract

To provide packaging paper which is environment-friendly and has good heat seal strength.SOLUTION: Packaging paper has a paper base material containing pulp as a main component, and a heat seal layer stacked on one surface or both surfaces of the paper base material, wherein the main component of the heat seal layer is a polylactic acid, a coating amount of the heat seal layer is 5.0 g / m2 or more and 10.0 g / m2 or less, Young's modulus measured according to JIS-K7127(1999) of the heat seal layer is 0.30 N / mm2 or more and 240.0 N / mm2 or less, and the heat seal layer does not contain a water-soluble polymer. Bekk smoothness on the surface of the stacked surface of the heat seal layer on the paper base material is preferably 5 seconds or more and 80 seconds or less. Moisture vapor permeability is preferably 2,500 g / m2 24 hr or more and 5,000 g / m2 24hr or less. Peeling strength at 130°C of the heat seal layer is preferably 1.50 N / 15 mm or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to packaging paper and packaging materials. [Background technology]

[0002] Generally, pillow packaging, widely used for confectionery, pharmaceuticals, and hygiene products, utilizes laminated paper or plastic film made by extruding polyethylene or polypropylene resin onto a base paper. While such laminated paper and plastic film offer excellent strength, water resistance, and moisture resistance, the non-biodegradable plastic film remains, making it unsuitable for recycling as waste paper. Furthermore, if not properly disposed of after use, it can easily become microplastics, contributing to marine pollution and potentially leading to environmental burdens.

[0003] Therefore, in conventional technology, barrier materials that are biodegradable and derived from biological sources (biomass) rather than petroleum have been proposed as packaging materials (Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-157757 [Overview of the project] [Problems that the invention aims to solve]

[0005] In the conventional packaging materials described above, packaging is possible by providing a heat-seal layer and heat-sealing the layers together, but the heat-seal strength is insufficient and there was room for improvement.

[0006] This invention was made based on the circumstances described above, and aims to provide packaging paper that is environmentally friendly and has good heat-seal strength. [Means for solving the problem]

[0007] The wrapping paper according to one aspect of the present invention includes a paper base material mainly composed of pulp, and a heat-sealing layer laminated on one or both sides of the paper base material. The main component of the heat-sealing layer is polylactic acid, and the coating amount of the heat-sealing layer is 5.0 g / m , 2 , 2 , 2 , , , , 2 , 2 , 2 ,

[0010] , ,

[0009] , above 10.0 g / m 2 or less, and the Young's modulus of the heat-sealing layer measured in accordance with JIS-K7127 (1999) is 0.30 N / mm 2 above 240.0 N / mm 2 or less, and the heat-sealing layer does not contain a water-soluble polymer.

Effect of the Invention

[0008] According to the present invention, it is possible to provide a wrapping paper that is environmentally friendly and has good heat-sealing strength.

Mode for Carrying Out the Invention

[0009] [Description of Embodiment of the Present Invention] It includes a paper base material mainly composed of pulp, and a heat-sealing layer laminated on one or both sides of the paper base material. The main component of the heat-sealing layer is polylactic acid, and the coating amount of the heat-sealing layer is 5.0 g / m 2 above 10.0 g / m 2 or less, and the Young's modulus of the heat-sealing layer measured in accordance with JIS-K7127 (1999) is 0.30 N / mm 2 above 240.0 N / mm 2 or less, and the heat-sealing layer does not contain a water-soluble polymer.

[0010] The wrapping paper has a main component of polylactic acid in the heat-sealing layer, and the coating amount (in terms of solid content) of the heat-sealing layer is 5.0 g / m 2 above 10.0 g / m 2The following is the case. The main component of the heat-sealing layer is polylactic acid having biodegradability, and by setting the coating amount of the heat-sealing layer within the above range, the packaging paper is environmentally friendly and the heat-sealing strength (peel strength) can be improved. Further, when the Young's modulus of the heat-sealing layer is 0.30 N / mm 2 or more and 240.0 N / mm 2 or less, the heat-sealing layer becomes a moderately strong layer, so that the heat-sealing strength can be improved. Further, since the heat-sealing layer does not contain a water-soluble polymer, the packaging paper can maintain good heat-sealing strength. Therefore, the packaging paper is environmentally friendly and has good heat-sealing strength. In the present invention, the "heat-sealing layer" refers to a coating layer where a heat fusion process is performed. The above "main component" refers to the substance having the highest content rate among the constituent substances, preferably having a content rate of 80% by mass or more.

[0011] It is preferable that the Bek smoothness of the surface of the heat-sealing layer laminated surface of the paper base material is 5 seconds or more and 80 seconds or less. When the Bek smoothness of the surface of the heat-sealing layer laminated surface of the paper base material is 3 seconds or more and 230 seconds or less, it is possible to achieve both the heat-sealing strength and the suppression of blocking of the heat fusion surface of the heat-sealing layer. The Bek smoothness evaluates the smoothness from the air flow rate (air leak). The Bek smoothness defined in JIS-P8119 (1998) sandwiches a sheet, which is the object to be measured, between an optically flat glass sample stage and a rubber pressing plate at a pressure of 100 kPa, and 10 ml of air passes through between the relatively wide 10 cm 2 glass standard surface and is represented by the time required to flow into a container maintained at a reduced pressure of about 370 mm of mercury column, indicating the smoothness of the surface of the so-called object to be measured. The Bek smoothness evaluates the macroscopic smoothness on a relatively wide surface. In the packaging paper, the waviness of the surface can be evaluated by the Bek smoothness. Therefore, the surface of the heat-sealing layer laminated surface of the packaging paper can be more appropriately evaluated by the Bek smoothness.

[0012] The moisture permeability of the paper base material of the packaging paper is 2500 g / m 2 ·24 hr or more and 5000 g / m2 It is preferable that the moisture permeability of the paper base material of the packaging paper is within the above range, which prevents moisture from the contents being packaged from turning into water droplets and maintains an appropriate level of humidity, thereby preserving the quality of the contents. Here, "moisture permeability of the paper base material" is a value measured in accordance with JIS-Z0208 (1976).

[0013] It is preferable that the peel strength of the heat-seal layer at 130°C is 1.50 N / 15 mm or higher. A peel strength of 1.50 N / 15 mm or higher at 130°C in the heat-seal layer provides excellent heat-seal strength, resulting in a bag-making suitability.

[0014] Another embodiment of the present invention provides a packaging material having the packaging paper. Because this packaging material has the packaging paper, it is environmentally friendly and has good heat seal strength.

[0015] [Details of the Embodiments of the Invention] The following describes in detail a packaging paper according to one embodiment of the present invention. Unless otherwise specified, the amount of each material blended into the paper substrate (absence of oven-dry additive) refers to the mass ratio of the pulp to the oven-dry mass of the paper substrate. Furthermore, unless otherwise specified, the content of each material blended into the heat-seal layer-forming composition refers to the oven-dry mass ratio of each material to the total mass of the heat-seal layer.

[0016] <Wrapping paper> The packaging paper has a heat-seal layer on one side of the paper base material. The heat-seal layer may be a single layer or a multi-layer structure.

[0017] [Paper base material] The paper substrate is obtained by papermaking a slurry containing raw pulp. The paper substrate may be single-layer or multi-layer.

[0018] (Raw pulp) Paper substrates are primarily composed of pulp. Examples of raw materials that can be used to make up the paper substrate include virgin pulp, recycled paper pulp, and combinations of these pulps.

[0019] As virgin pulp, chemical pulps such as bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), semi-bleached hardwood kraft pulp (LSBKP), semi-bleached softwood kraft pulp (NSBKP), unbleached hardwood kraft pulp (LUKP), unbleached softwood kraft pulp (NUKP), hardwood sulfite pulp, and softwood sulfite pulp; and mechanical pulps (MP) such as stone ground pulp (SGP), pressurized stone ground pulp (TGP), chemigland pulp (CGP), crushed wood pulp (GP), and thermomechanical pulp (TMP) can be used individually or in combination. From the viewpoint of the appearance of the printed surface and its use in food packaging, it is preferable to use only bleached kraft pulp.

[0020] As recycled paper pulp, for example, disintegrated recycled paper pulp, disintegrated and deinked recycled paper pulp (DIP), disintegrated, deinked and bleached recycled paper pulp, etc., manufactured from brown recycled paper, kraft envelope recycled paper, magazine recycled paper, newspaper recycled paper, flyer recycled paper, office recycled paper, corrugated cardboard recycled paper, white recycled paper recycled paper, Kent recycled paper recycled paper, imitation recycled paper recycled paper, land destiny recycled paper recycled paper, etc., can be used individually or in combination of multiple types.

[0021] (Other additives) Other additives may be added to the paper substrate as needed. Examples of additives include fillers, pigments, sizing agents, binders, oil resistant agents, fluorescent whitening agents, aluminum sulfate, yield enhancers, water drainage enhancers, dry strength enhancers, wet strength enhancers, coloring dyes, coloring pigments, and water-resistant agents, which can be used individually or in combination.

[0022] [Heat seal layer] The heat seal layer is laminated on one or both sides of the paper substrate. The heat seal layer is formed by coating one or both sides of the paper substrate with a heat seal layer forming composition.

[0023] The main component of the heat-seal layer is polylactic acid. "Polylactic acid" is a biomass plastic manufactured using plant-derived starch and sugar as raw materials through a chemical process. Because the main component of the heat-seal layer is polylactic acid, it is biodegradable and exhibits good heat-seal strength not only at room temperature but also at low temperatures. Polylactic acid is relatively inexpensive and easy to melt-mold. Examples of polylactic acid include L-polylactic acid obtained by using L-lactide and D-lactide individually, random copolymers obtained by using a combination of D-polylactic acid, L-lactide, and D-lactide in which the arrangement order of L-lactide and D-lactide is random, and block copolymers in which L-lactide and D-lactide are polymerized in any ratio in a block-like structure. Commercially available polylactic acid products such as Rezem Y-225 (manufactured by Chukyo Oil & Fat Co., Ltd.) and LANDY PLF3000 (manufactured by Miyoshi Oil & Fat Co., Ltd.) can be used.

[0024] The lower limit of the polylactic acid content relative to the total solid content of the heat seal layer is 80% by mass, preferably 90% by mass. If the polylactic acid content is less than 50.0% by mass, sufficient heat sealability may not be obtained. On the other hand, the upper limit of the polylactic acid content is 100% by mass, preferably 95% by mass.

[0025] The heat-seal layer described above may contain resins other than polylactic acid. Examples of resins other than polylactic acid include polyethylene resins and polypropylene resins. Examples of polyethylene resins include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate copolymer (EMA), ethylene-vinyl acetate copolymer (EVA), carboxylic acid-modified polyethylene, and derivatives thereof, as well as mixtures thereof. Examples of polypropylene resins include polypropylene (PP) homopolymer, random polypropylene (random PP), block polypropylene (block PP), chlorinated polypropylene, carboxylic acid-modified polypropylene, styrene-acrylic acid, styrene-butadiene latex, and derivatives thereof, as well as mixtures thereof. Among these, ethylene-acrylic acid copolymer is more preferred from the viewpoint of heat-sealability in the low-temperature range of around 100 to 130°C.

[0026] The heat-seal layer described above does not contain water-soluble polymers. Because the heat-seal layer does not contain water-soluble polymers, the packaging paper can maintain good heat-seal strength.

[0027] The lower limit for the amount of the heat seal layer applied (in terms of solid content) is 5.0 g / m². 2 It is 6.0 g / m 2 This is preferable. On the other hand, the upper limit for this coating amount is 10.0 g / m². 2 It is 8.0 g / m 2This is more preferable. If the above coating amount does not meet the above lower limit, it may not have sufficient heat seal strength, and when made into a bag, it may not be able to seal properly. If the above coating amount exceeds the above upper limit, the blocking suppression of the heat-seal surface will decrease, and it may become difficult to slip during the bag-making process and prone to tearing. In this packaging paper, the main component of the heat-seal layer is polylactic acid, and by setting the coating amount of the heat-seal layer within the above range, it is possible to achieve both heat seal strength and blocking suppression of the heat-seal surface of the heat-seal layer.

[0028] (Young's modulus) The lower limit of the Young's modulus of the heat-sealed layer is 0.30 N / mm². 2 Therefore, 0.5 N / mm 2 A more preferable Young's modulus is 0.30 N / mm². 2 If the Young's modulus is less than 240.0 N / mm², the heat seal layer may become soft, potentially reducing the heat seal strength. Furthermore, there is a risk of rupture between the heat seal layers. On the other hand, the upper limit for the Young's modulus is 240.0 N / mm². 2 Therefore, 180.0 N / mm 2 A Young's modulus of 240.0 N / mm² is preferred. 2 If the Young's modulus exceeds a certain value, the heat seal layer may become too rigid, reducing adhesion during heat sealing and potentially lowering the heat seal strength. By keeping the Young's modulus of the heat seal layer within the specified range, the heat seal layer becomes appropriately rigid, thereby improving the heat seal strength. The Young's modulus of the heat seal layer can be calculated from the breaking strength, strain, and cross-sectional area measured in accordance with JIS-K7127(1999) Plastics - Test methods for tensile properties - Part 3: Test conditions for films and sheets. The Young's modulus of the heat seal layer can be adjusted, for example, by the degree of polymerization and crystallinity of polylactic acid, the main component of the heat seal layer.

[0029] (Heat seal strength (peel strength)) The peel strength of the heat-seal layer at 130°C is preferably 1.50 N / 15 mm or higher, and more preferably 1.70 N / 15 mm or higher. If the peel strength of the heat-seal layer at 130°C is less than 1.50 N / 15 mm, there is a risk that the bag may not be properly sealed.

[0030] (Other additives) The heat seal layer of the present invention may contain other additives besides those mentioned above. Other additives may include, for example, adhesives, inorganic pigments, organic pigments, sizing agents, viscosity modifiers, coloring dyes, coloring pigments, water-resistant agents, lubricants, etc., which can be used individually or in combination.

[0031] [Physical properties of wrapping paper] (Beck smoothness) The lower limit of the Beck smoothness of the surface of the heat seal layer laminated on the paper substrate is preferably 3 seconds, and more preferably 5 seconds. If the Beck smoothness is less than 3 seconds, the heat seal layer is more likely to sink into the paper substrate, which may reduce the heat seal strength. On the other hand, the upper limit of the Beck smoothness of the surface of the heat seal layer laminated on the paper substrate is preferably 80 seconds, and more preferably 70 seconds. If the Beck smoothness exceeds 80 seconds, the blocking suppression effect of the heat fusion surface of the heat seal layer may decrease. The Beck smoothness of the above-mentioned paper substrate can be adjusted, for example, by calendering.

[0032] (moisture permeability) The moisture permeability of the packaging paper shall be measured according to JIS-Z0208

[1976] Moisture Permeability Test Method for Moisture-Proof Packaging Materials [Cup Method], based on condition B. The lower limit of moisture permeability for the packaging paper shall be 2500 g / m². 2 24hr is preferred, and 3000g / m² 2 24 hours is preferable. Furthermore, the upper limit of the moisture permeability of the packaging paper should be 5000 g / m². 2 24 hours is preferable, and 4500 g / m² 224 hours is preferable. Because the moisture permeability of the packaging paper is within the above range, moisture from the packaged contents is less likely to turn into water droplets, and the humidity is maintained at an appropriate level, thus preserving the quality of the contents.

[0033] This packaging paper is environmentally friendly and has good heat-seal strength. Furthermore, because it does not contain laminated paper or plastic film, which have a high environmental impact, it contributes to environmental protection.

[0034] [Manufacturing method for wrapping paper] The method for manufacturing the packaging paper is not particularly limited, but for example, it may include the steps of: making paper from a pulp slurry that will be used as a raw material for a paper substrate; producing a composition for forming a heat seal layer; and coating at least one surface of the paper substrate with the composition for forming a heat seal layer.

[0035] In the papermaking process, a raw material slurry containing the aforementioned raw pulp, oil resistant agent, and other additives is processed using a known papermaking machine. Furthermore, the Beck smoothness of the surface of the heat-seal layer laminate of the paper substrate can be easily adjusted by using a machine calender or a soft calender.

[0036] In the process of producing a heat seal layer-forming composition, a heat seal layer-forming composition containing polylactic acid as the main component is produced.

[0037] A known coating method can be used for coating the heat seal layer-forming composition, and known coating machines such as a 2-roll size press coater, gate roll coater, blade metering coater, rod metering coater, blade coater, air knife coater, roll coater, brush coater, kiss coater, squeeze coater, curtain coater, die coater, bar coater, and gravure coater can be used.

[0038] For drying the coated heat-seal layer-forming composition, known drying equipment can be used, such as infrared drying equipment, hot air drying equipment, contact dryer drying equipment, etc.

[0039] The packaging paper obtained in this manner can be finished using various known finishing devices, such as supercalenders, gloss calenders, soft calenders, and matte calenders, and can be given product finishes as appropriate.

[0040] <Packaging material> Another embodiment of the present invention provides a packaging material comprising the packaging paper. Examples of applications for this packaging material include paper barrier packaging materials used for packaging food, containers, cups, etc., and as a substitute for plastic materials such as packs, pouches, boxes, shrink wrap, cans, and laminated packaging. Because this packaging material comprises the packaging paper, it is environmentally friendly and has good heat seal strength. Furthermore, because this packaging material does not contain laminated paper or plastic film, which have a high environmental impact, it contributes to environmental protection.

[0041] <Other Embodiments> The present invention is not limited to the embodiments described above, and can be implemented in various modified and improved forms in addition to those described above. [Examples]

[0042] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0043] [Examples 1-6 and Comparative Examples 1-3] (Manufacturing of paper substrates) Examples 1, 2, 4-6, and Comparative Examples 1-3 were first prepared by preparing 100% by mass of bleached softwood kraft pulp to obtain a pulp slurry. Aluminum sulfate, a yield agent, and a sizing agent were added to this pulp slurry as additives. The obtained pulp slurry was then used to make paper using an on-top wire screen paper machine. Next, calendering was performed to adjust the Beck smoothness. For Example 3, the base paper was prepared by changing 100% by mass of bleached softwood kraft pulp to 100% by mass of unbleached softwood kraft pulp, and papermaking was carried out under the same conditions. In Example 4, before laminating the heat seal layer, a coating layer containing 100 parts by mass of fine clay and 60 parts by mass of styrene-butadiene latex was formed on one side where the heat seal layer would be laminated. The Beck smoothness of the surface where the heat seal layer would be laminated was measured using the method described later.

[0044] (Lamination of heat-seal layers) Next, a heat-seal layer was formed on one side of the paper substrate to obtain packaging paper. The composition and coating amount of the heat-seal layer-forming composition are shown in Table 1. A polylactic acid emulsion was used as the heat-seal layer-forming composition. The polylactic acid content relative to the total solids was 95% by mass.

[0045] [Comparative Example 4 to Comparative Example 6] Packaging paper was prepared in the same manner as in Example 1, except that the composition and coating amount of the heat-seal layer forming composition were as shown in Table 1. In addition, the heat-seal layer forming composition had a polylactic acid content of 83% by mass and a polyvinyl alcohol content of 17% by mass relative to the total solids.

[0046] [evaluation] The packaging papers obtained in the manner described above were evaluated in various ways.

[0047] (Young's modulus) The Young's modulus of the heat-seal layer was calculated from the breaking strength, strain, and cross-sectional area measured in accordance with JIS-K7127 (1999) Plastics - Test methods for tensile properties - Part 3: Test conditions for films and sheets, after first preparing a film of the heat-seal agent alone (approximately 50 μm) by placing the chemical in a frying pan and drying it.

[0048] (Beck smoothness) The Beck smoothness of the heat-sealed layer laminate surface on a paper substrate was measured in accordance with JIS-P8119 (1998).

[0049] (Moisture permeability of wrapping paper) The moisture permeability of the packaging paper in the examples and comparative examples was measured under condition B in accordance with JIS-Z0208 (1976) Method for testing moisture permeability of moisture-proof packaging materials [cup method].

[0050] (Heat seal strength (peel strength)) Using a thermal gradient testing machine (manufactured by Toyo Seiki Seisakusho Co., Ltd.), the sealant pressure was 2 kgf / cm². 2 After processing under conditions of a sealing time of 2 seconds and a sealing temperature of 130°C or 150°C, the peel strength of the heat-sealed portion was measured using a load cell type tensile testing machine.

[0051] (Suppression of blocking at the heat-sealed surface) For each example and comparative example, the heat-sealed surfaces of two sheets of packaging paper were brought into close contact, subjected to a 1 kg load, and exposed to a 40°C, 80% humidity environment for one week. The results of peeling them apart with both hands were evaluated according to the following three criteria. If the evaluation was A or B, the blocking suppression of the heat-sealed surface was good. A: There is no blocking at the heat-sealed surface, and it peels off smoothly. B: There is a sound when peeling, but the peelability is within an acceptable range. C: Blocking has occurred at the heat-sealed surface, and tearing will occur if it is peeled off.

[0052] Table 1 shows the evaluation results for each example and comparative example.

[0053] [Table 1]

[0054] As shown in Table 1, the heat seal layer contains polylactic acid, and the coating amount of the heat seal layer is 5.0 g / m². 2 More than 10.0g / m 2 The following is true: The Young's modulus of the heat-seal layer is 0.30 N / mm². 2 More than 240.0N / mm 2 Examples 1 to 6, described below, showed good performance in all aspects: heat seal strength, moisture permeability, and blocking suppression of the heat-sealed surface. In particular, Examples 1, 2, 5, and 6, in which the Beck smoothness of the heat-sealed layer laminate surface of the paper substrate was 5 seconds or more and 80 seconds or less, showed excellent heat seal strength and blocking suppression of the heat-sealed surface.

[0055] On the other hand, the coating amount for the heat seal layer is 5.0 g / m². 2 Comparative Example 1, which is less than 5.0 g / m², has a heat seal layer coating amount of 5.0 g / m². 2 It is less than 240.0 N / mm², and the Young's modulus is 240.0 N / mm². 2 Comparative Example 2, which is superior, and the coating amount of the heat seal layer is 10.0 g / m². 2 It is extremely high, and its Young's modulus is 0.30 N / mm². 2 Comparative Example 3, which was below the specified value, could not be measured due to its extremely low heat seal strength at 130°C. Furthermore, as shown in Table 1, the heat-seal layer contains polylactic acid and polyvinyl alcohol, a water-soluble polymer, and the Young's modulus of the heat-seal layer is 240.0 N / mm². 2 Comparative Examples 4 to 6, which are superior, showed lower heat seal strength values ​​compared to the Examples.

[0056] The results above demonstrate that this packaging paper is environmentally friendly and possesses good heat-seal strength. [Industrial applicability]

[0057] The packaging paper of the present invention is environmentally friendly, has excellent heat-seal strength, and is suitable for use as a packaging material.

Claims

1. A paper base material mainly composed of pulp, A heat seal layer laminated on one or both sides of the above paper substrate and It is equipped with, The Beck smoothness of the surface of the heat-seal layer laminated surface of the above paper substrate is 5 seconds or more and 80 seconds or less. The main component of the heat-seal layer mentioned above is polylactic acid. The coating amount of the above heat seal layer is 5.0 g / m². ２ 10.0g / m or more ２ The following: The Young's modulus of the heat-seal layer described above, as measured in accordance with JIS-K7127 (1999), is 0.30 N / mm². ２ 240.0N / mm or more ２ The following: The above-mentioned heat-seal layer is a packaging paper in which no water-soluble polymer is contained.

2. Moisture permeability of 2500 g / m ２ ・5000g / m for 24hr or more ２ - Packaging paper according to claim 1, which has a shelf life of 24 hours or less.

3. The packaging paper according to claim 1 or claim 2, wherein the peel strength of the heat-seal layer at 130°C is 1.50 N / 15 mm or more.

4. A packaging material using the packaging paper described in any one of claims 1 to 3.

Images