Flexible packaging paper and flexible packaging materials

Abstract

To provide a novel paper for flexible packaging materials and a flexible package using this flexible packaging paper. 【Solution means】A paper for flexible packaging materials having a paper base material and a heat-sealing layer provided on at least one side of the paper base material, where the paper base material has a filler content of 1% by weight or less, a basis weight of 25 g / m 2 or more and 50 g / m 2 or less, and a density of 0.85 g / m 3 or more and 1.35 g / m 3 or less, where the dry weight (per side) of the heat-sealing layer is 4 g / m 2 or more and 20 g / m 2 or less, and a paper for flexible packaging materials having a tear strength (MD direction and CD direction) of 100 mN or more and 650 mN or less, and a flexible package using this flexible packaging paper.

Description

[Technical Field]

[0001] This invention relates to a novel flexible packaging paper and flexible packaging material. [Background technology]

[0002] Sanitary masks are sold in packs of several masks, or in boxes of 50 or 100 masks. In particular, sanitary masks purchased in boxes are intended to be used one at a time, but an increasing number of users are carrying spare masks in case they need to change their mask while out and about. Therefore, in order to maintain good hygiene until immediately before use, products are provided in which sanitary masks are individually packaged in thin film packaging (individually wrapped) and then placed in a box (Patent Document 1). Specifically, the individual packaging is formed by heat-sealing a nonwoven fabric mask with a film-like packaging material made of thermoplastic resin such as polyethylene terephthalate, polyethylene, or polypropylene, with a thickness of 30 μm or less, and then heat-sealing both ends. In addition to sanitary masks, there are also products that are individually packaged and provided, such as amenity items such as toothbrushes, combs, razors, and slippers provided at accommodations, disposable cutlery such as chopsticks, spoons, forks, and straws, and sanitary products.

[0003] Products that are individually packaged in this way can be kept in a sterilized state and the packaged contents contained within the packaging material until immediately before use, thus maintaining good hygiene until opening. Such packaging undergoes inspection processes to confirm whether the packaged contents are properly contained in each package, and foreign object inspection processes using metal detectors, etc., to check for foreign object contamination.

[0004] In recent years, a trend toward reducing plastic use has been gaining momentum, stemming from environmental issues such as plastic waste in the oceans, and there is a desire to minimize the use of resin materials in industrial products. Under these circumstances, there is also a desire to reduce the environmental impact of packaging. For example, methods such as reducing the thickness of sheet-like packaging materials made of resin have been considered, but packaging made of such thin resin materials presents challenges such as poor handling during the packaging manufacturing process and a tendency for defects and tears to occur due to partial melting at the heat-sealed parts. Furthermore, as described in Patent Document 2, a barrier laminate has been proposed for packaging applications, having a water vapor barrier layer and a gas barrier layer in that order on at least one planar surface of a paper substrate, and a sealant layer on at least one outermost layer. While such paper packaging materials can reduce the amount of resin material used, they are expensive because they possess properties such as water vapor barrier and gas barrier properties that are unnecessary when used for packaging nonwoven masks and the like. In addition, although these barrier laminates contain inorganic compounds to exhibit high barrier properties, the barrier layer may crack and powder may fall off during folding or heat sealing processes in the manufacturing process of the packaging. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Utility Model Registration No. 3228666 [Patent Document 2] Japanese Patent Publication No. 2020-189489 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The object of this invention is to provide a novel flexible packaging paper and a flexible packaging body using this flexible packaging paper. [Means for solving the problem]

[0007] The means for solving the problems of the present invention are as follows. 1. A paper for flexible packaging material having a paper base material and a heat-sealing layer provided on at least one side of the paper base material, where the paper base material has a filler content of 1% by weight or less, a basis weight of 25 g / m 2 or more and 50 g / m 2 or less, and a density of 0.85 g / cm 3 or more and 1.35 g / cm 3 or less, and the dry weight (per side) of the heat-sealing layer is 4 g / m 2 or more and 20 g / m 2 or less, and the paper for flexible packaging material is characterized in that the tear strength (in the MD direction and the CD direction) is 100 mN or more and 650 mN or less. 2. The paper for flexible packaging material according to 1., characterized in that the tear strength (in the MD direction and the CD direction) is less than 400 mN. 3. The paper for flexible packaging material according to 1., characterized in that the tear strength (in the MD direction and the CD direction) is 400 mN or more. 4. A flexible package, characterized in that the packaged object is enclosed in a packaging material made of the paper for flexible packaging material according to any one of 1. to 3. 5. The flexible package according to 4., characterized in that the packaged object is a sanitary mask.

Advantages of the Invention

[0008] The paper for flexible packaging material of the present invention can be used as an alternative to a packaging material made of a conventional resin film. Since the paper for flexible packaging material of the present invention is mainly composed of paper, the amount of resin material used can be significantly reduced. The paper for flexible packaging material of the present invention can be easily torn from any direction, and when made into a flexible package, the packaged object can be easily taken out.

Embodiments for Carrying Out the Invention

[0009] The present invention relates to a paper for flexible packaging material and a flexible package using this paper for flexible packaging material. "Paper for flexible packaging material" The paper for a flexible packaging material of the present invention has a paper base material and a heat-sealing layer provided on at least one side of the paper base material. The paper for a flexible packaging material of the present invention can include a blocking layer, an ink receiving layer, a water-resistant layer, etc. in addition to the paper base material and the heat-sealing layer, but it is preferably composed only of the paper base material and the heat-sealing layer.

[0010] The paper for a flexible packaging material of the present invention has a tear strength (in the MD direction and the CD direction) of 100 mN or more and 650 mN or less. By setting the tear strength within this range, when made into a flexible package, it can be easily torn from any direction to take out the packaged product. From the perspective of making the flexible package easier to break, the tear strength (in the MD direction and the CD direction) is preferably less than 400 mN, more preferably 300 mN or less, still more preferably 200 mN or less, and even more preferably 150 mN or less. On the other hand, from the perspective of making the flexible package difficult to break even when impacted during transportation, etc., the tear strength (in the MD direction and the CD direction) is preferably 400 mN or more. The tear strength can be selected according to the shape of the packaged product, etc. (such as the presence or absence of protrusions and whether a space is generated inside when made into a flexible package). In this specification, the tear strength means a value measured in accordance with JIS P8116:2000 "Paper - Test method for tear strength - Elmendorf type tear tester method" with a test piece length of 63 mm, a notch of 20 mm, and a torn length of 43 mm.

[0011] The paper for a flexible packaging material of the present invention has a basis weight of the entire paper of 35 g / m 2 or more and 60 g / m 2 or less, which is preferable. Also, the paper for a flexible packaging material of the present invention preferably has a thickness of the entire paper of 30 μm or more and 70 μm or less. By setting the basis weight and thickness within this range, it can be suitably used as a flexible packaging material. In particular, when the thickness is 70 μm or more, when stacking dozens of individually packaged sanitary masks, etc. and putting them in one box, it will be bulky, and the number that can be put in one box will decrease.

[0012] From the perspective of enabling visual inspection, the transparency of the paper for flexible packaging materials of the present invention is preferably 60% or more, more preferably 65% or more, and still more preferably 70% or more. On the other hand, when packaging articles that are not desired to be seen, such as sanitary products, the transparency is preferably less than 60%, more preferably less than 55%, and still more preferably less than 50%.

[0013] ·Paper substrate The paper substrate used in the present invention has a filler content of 1% by weight or less, a basis weight of 25 g / m 2 or more and 50 g / m 2 or less, and a density of 0.85 g / cm 3 or more and 1.35 g / cm 3 or less. The paper substrate of the present invention has a filler content of 1% by weight or less. By reducing the filler content to 1% by weight or less, powder loss can be suppressed. The filler content is preferably 0.5% by weight or less, more preferably 0.3% by weight or less, still more preferably 0.1% by weight or less, and most preferably not contained (0% by weight).

[0014] The paper substrate of the present invention has a basis weight of 25 g / m 2 or more and 50 g / m 2 or less, and a density of 0.85 g / cm 3 or more and 1.35 g / cm 3 or less. By setting the basis weight and density within this range, flexibility and strength suitable for the paper for flexible packaging materials can be achieved.

[0015] In the present invention, the papermaking fibers can include chemical pulps such as bleached softwood kraft pulp (NBKP), bleached hardwood kraft pulp (LBKP), unbleached softwood kraft pulp (NUKP), unbleached hardwood kraft pulp (LUKP), semi-bleached softwood kraft pulp (NSBKP), semi-bleached hardwood kraft pulp (LSBKP), softwood sulfite pulp, and hardwood sulfite pulp; mechanical pulps such as stone ground pulp (SGP), compressed stone ground pulp (TGP), chemigland pulp (CGP), crushed wood pulp (GP), and thermomechanical pulp (TMP); wood pulps such as dissolved pulp and mercerized pulp; and non-wood pulps such as flax pulp, Manila hemp pulp, and kenaf pulp, as well as recycled paper pulp. However, it is preferable to use chemical pulp that is less prone to foreign matter contamination, preferably to use NBKP and LBKP, and more preferably to use only NBKP and LBKP.

[0016] The water filtration rate (2g method Shopper-Rigler water filtration rate: specified in JIS P8121-1) of the papermaking fibers used in this invention is preferably between 10°SR and 90°SR. A lower value results in a paper substrate with superior tear strength, but transparency decreases. Therefore, if transparency is required, the water filtration rate should be increased.

[0017] Examples of various auxiliary agents include sizing agents such as rosin, alkyl ketene dimer (AKD), and alkenyl succinic anhydride (ASA); dry strength enhancers such as polyacrylamide polymers, polyvinyl alcohol polymers, cationized starch, various modified starches, urea-formaldehyde resins, and melamine-formaldehyde resins; wet strength enhancers; yield enhancers; water drainage enhancers; coagulants; aluminum sulfate; bulk enhancers; dyes; fluorescent whitening agents; pH adjusters; defoamers; UV inhibitors; fade inhibitors; pitch control agents; and slime control agents. These can be selected and used as needed. However, for the paper substrate of the present invention, a lower auxiliary agent content is preferable from the viewpoint of cost and safety. Specifically, the total auxiliary agent content is preferably 1% by weight or less, more preferably 0.5% by weight or less, even more preferably 0.3% by weight or less, even more preferably 0.1% by weight or less, and most preferably none (0% by weight).

[0018] The method for manufacturing paper substrates (papermaking) is not particularly limited, and paper substrates can be manufactured by papermaking using known methods such as acidic papermaking, neutral papermaking, and alkaline papermaking using known screen formers, on-top hybrid formers, and gap former machines. Among these, it is preferable to use a screen former with a large dewatering capacity. Furthermore, various chemicals can be added to the surface of the paper substrate. Examples of chemicals that can be used include oxidized starch, hydroxyethyl etherified starch, enzyme-modified starch, polyacrylamide, polyvinyl alcohol, surface sizing agents, water-resistant agents, water-retaining agents, thickeners, and lubricants, which can be used individually or in combination of two or more. However, it is preferable not to add chemicals to the paper substrate of the present invention.

[0019] • Heat seal layer The heat-seal layer is provided on at least one surface of the paper substrate, and may also be provided on both surfaces. The dry weight (coating amount) per side of the heat seal layer is 4 g / m². 2 More than 20g / m 2 The following applies: The dry weight of the heat seal layer (per side) is 4 g / m².2 Below this level, heat sealability deteriorates. The dry weight of the heat seal layer (per side) must be 20 g / m². 2 Beyond this point, the heat sealability saturates and hardly improves, and the increased resin usage leads to higher costs and is undesirable from an environmental perspective. The dry weight of the heat seal layer (per side) is 15 g / m². 2 Preferably, it is 10 g / m 2 It is more preferable that the following conditions are met: 9 g / m 2 The following is even more preferable:

[0020] The resin forming the heat seal layer is not particularly limited, and any thermoplastic resin used for heat sealing applications, such as ethylene-vinyl acetate resins, styrene-acrylic acid ester copolymer resins, acrylic resins, polyester resins such as polyethylene, polypropylene, and polyethylene terephthalate, and polyvinyl alcohol, polyvinyl acetate, and polylactic acid, can be used without particular restriction. Among these, ethylene-vinyl acetate resins and acrylic resins are preferred in terms of heat seal strength. In addition, biodegradable resins such as polyvinyl alcohol and polylactic acid are preferred in terms of reducing the environmental burden when they are released as waste.

[0021] The heat-seal layer may contain additives such as antiblocking agents. Pigments, waxes, metal soaps, etc., can be used as antiblocking agents without particular limitations. However, in the flexible packaging paper of the present invention, it is preferable that the heat-seal layer does not contain additives from a cost standpoint.

[0022] The heat seal layer may be either a coated layer or a laminated layer, but a coated layer is preferred from the viewpoint of manufacturing efficiency and recyclability (re-disintegration). The coating method is not particularly limited and can be performed using known coating equipment and coating systems. For example, coating equipment can include blade coaters, bar coaters, air knife coaters, curtain coaters, spray coaters, roll coaters, reverse roll coaters, size press coaters, gate roll coaters, etc. The coating system may be either a water-based coating using a solvent such as water, or a solvent-based coating using a solvent such as an organic solvent; however, a water-based coating is preferred from a safety and health standpoint. When using a water-based coating, a water-dispersible resin or a water-soluble resin should be used as the thermoplastic resin.

[0023] "Soft packaging" In the flexible packaging of the present invention, the packaged item is enclosed within a packaging material made of the flexible packaging paper described above. The shape of the flexible packaging is not particularly limited and can be a vertical pillow bag, a horizontal pillow bag, a side-seal bag, a two-sided seal bag, a three-sided seal bag, a gusset bag, a bottom gusset bag, a stand-up pouch, etc. Because the packaging material of the present invention is mainly paper, it is easier to tear than conventional packaging materials made of resin, and can be easily torn from anywhere. Furthermore, the flexible packaging paper of the present invention can be used in place of conventional resin film in packaging machines that use resin film, with virtually no changes to the manufacturing conditions. Since the flexible packaging of the present invention can be manufactured using conventional manufacturing machinery as is, no new equipment is required.

[0024] The packaged items contained within the flexible packaging of the present invention can be anything that does not deteriorate easily over time. Examples include sanitary masks such as nonwoven masks, amenity items such as toothbrushes, combs, razors, and slippers provided at accommodations, disposable cutlery such as chopsticks, spoons, forks, and straws, and sanitary products. Furthermore, even packaged items requiring barrier properties, such as candy, gummies, chocolate, and supplements, can be packaged in small bags made of barrier material, and these small bags can be contained within the flexible packaging of the present invention. [Examples]

[0025] "Example 1" NBKP / LBKP = 100 / 0 (85°SR, based on 1g method Shopper-Rigler filtration rate), basis weight 34g / m² 2 , density 1.27g / cm 3 It uses a paper substrate. On one side of this paper substrate, an ethylene-vinyl acetate emulsion (Chemipearl V300, manufactured by Mitsui Chemicals, Inc.) is applied at a dry weight of 7.0 g / m². 2 The paper was then coated and dried to form a heat-seal layer, thereby producing flexible packaging paper.

[0026] Example 2 NBKP / LBKP=65 / 35(70°SR), basis weight 30g / m 2 , density 1.01g / cm 3 A flexible packaging paper was manufactured in the same manner as in Example 1, except that a paper substrate was used. "Example 3" NBKP / LBKP=40 / 60(73°SR), basis weight 46g / m 2 , density 1.03g / cm 3 A flexible packaging paper was manufactured in the same manner as in Example 1, except that a paper substrate was used.

[0027] "Example 4" NBKP / LBKP=30 / 70(70°SR), basis weight 50g / m 2 , density 0.95g / cm 3 A flexible packaging paper was manufactured in the same manner as in Example 1, except that a paper substrate was used.

[0028] Example 5 NBKP / LBKP=100 / 0(17°SR), basis weight 38g / m 2 , density 0.89g / cm 3 A flexible packaging paper was manufactured in the same manner as in Example 1, except that a paper substrate was used.

[0029] "Comparative Example 1" Dry weight of the heat seal layer: 2.5 g / m 2 The flexible packaging paper was manufactured in the same manner as in Example 5, except as otherwise described above. "Reference example" We used commercially available PET film for general packaging purposes (Futamura Chemical Co., Ltd., FE2201, 12 μm thick).

[0030] The following evaluations were performed on the obtained flexible packaging paper. The results are shown in Table 1. (transparency) The transparency of one sample, conditioned at 23°C and 50% RH, was measured using a densitometer with a transmission-type search unit (manufactured by Tokyo Denshoku Co., Ltd., MODEL TC-6MC). (TAPPI T522 om-85) (Tear strength) Measurements were taken using an Elmendorf tear tester (manufactured by Kumagai Riki Kogyo Co., Ltd.) in accordance with JIS P8116:2000. The test specimen length was 63 mm, with a cut depth of 20 mm and a tear length of 43 mm.

[0031] (Heat sealable) Two 100mm square test pieces were cut from the obtained flexible packaging paper, and the heat-sealed layers were brought into contact with each other. A heat seal tester (HEAT SEAL TESTER TP-701S, manufactured by Tester Industries Co., Ltd.) was used to test the material at a pressurized temperature of 120°C and a pressurized pressure of 2 kgf / cm². 2 It was heat-sealed after a pressurizing time of 1 second. The heat-sealable properties were evaluated by visually observing the peeled-off portion of the heat-sealed test specimen after manually separating it, according to the following criteria. ○: Delamination within the paper substrate (the paper substrate is destroyed). ×: Delamination between heat-sealed layers.

[0032] (Encapacitability) Paper samples of each flexible packaging material with a width of 210 mm and a laminate of white cardboard (size: 100 mm x 65 mm x 25 mm, weight: 130 g) as the inner packaging were prepared. Using a pillow packaging machine (Suzuki Seisakusho, SP-803N), 100 flexible packages were packaged at a speed of 40 units / minute and evaluated as follows. ◎: Flexible packaging material allows for packaging samples without tearing, and also increases the speed of packaging. ○: Flexible packaging material can be used to package paper samples without tearing. ×: The flexible packaging material paper sample is torn and cannot be packaged.

[0033] (Suitability for opening) The flexible packaging obtained in the above evaluation of encapsulation properties was evaluated to see if it could be smoothly torn by hand without making any cuts, according to the following criteria. The evaluation was performed separately for the longitudinal direction (MD) and the width direction (CD). ◎: Something that can be torn very easily by hand. ○: Something that can be easily torn by hand. ×: Something that cannot be easily torn by hand.

[0034] [Table 1]

[0035] The flexible packaging paper obtained in Examples 1 to 6 of the present invention exhibited excellent heat-sealability, sealing properties, and ease of opening. In particular, its ease of opening was significantly improved compared to conventional PET film, and it could be easily opened from either the length or the width without the need for a cut.

Claims

1. A flexible packaging paper having a paper base material and a heat-seal layer provided on at least one side of the paper base material, The aforementioned paper substrate has a transparency of 60% or more and a basis weight of 25 g / m². ２ 50g / m or more ２ Below, density 0.85g / cm ３ 1.35g / cm or more ３ The following: The dry weight (per side) of the heat seal layer is 4 g / m². ２ 20g / m or more ２ The following: The flexible packaging paper is characterized in that it has a tear strength (MD direction and CD direction) of 100 mN or more and 650 mN or less.

2. The flexible packaging paper according to claim 1, characterized in that the tear strength (MD direction and CD direction) is less than 400 mN.

3. The flexible packaging paper according to claim 1, characterized in that the tear strength (MD direction and CD direction) is 400 mN or more.

4. A flexible package characterized in that the packaged item is enclosed in a packaging material made of flexible packaging paper as described in any one of claims 1 to 3.

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