JP7820032B2 - Flexible packaging paper and flexible packaging - Google Patents

Description

The present invention relates to novel flexible packaging paper and flexible packaging bodies.

Sanitary masks are sold in packs of several masks or boxes of 50 or 100 masks. While masks purchased in boxes are intended to be used one by one, an increasing number of users are carrying spare masks in case they need to change their masks while out and about.
To maintain good hygiene until immediately before use, a product has been provided in which sanitary masks individually wrapped in thin film packaging (individually packaged) are placed in a box. Specifically, the individual packaging is formed by wrapping a nonwoven fabric mask in a film-like packaging material having a thickness of 30 μm or less and made of a thermoplastic resin such as polyethylene terephthalate, polyethylene, or polypropylene, and then thermocompressing both ends of the film. In addition to sanitary masks, there are also other individually packaged products, such as amenities provided at accommodations, such as toothbrushes, combs, razors, and slippers; disposable cutlery such as disposable chopsticks, spoons, forks, and straws; and sanitary products.

Such individually packaged products can be kept in a sterilized state and the packaged items can be kept inside the packaging until just before use, allowing them to be kept in a hygienic state until opened. These packages are then inspected to ensure that the packaged items are properly contained in each package, as well as undergo a foreign object inspection process using a metal detector or similar device to check for the presence of any foreign objects.

In recent years, environmental issues such as those related to plastic waste in the ocean have led to a growing trend toward eliminating plastic, and it is desirable to reduce the amount of resin materials used in industrial products as much as possible. Under these circumstances, it is also desirable to reduce the environmental impact of packaging. For example, one method that has been considered is to reduce the thickness of sheet-shaped packaging materials made of resin materials. However, packaging materials made of such thin resin packaging materials have problems such as poor handleability during the packaging formation process and are prone to damage or tearing due to partial melting at thermocompression-bonded portions.
Furthermore, as in Patent Document 2, a barrier laminate has been proposed for use as a packaging material, which has a water vapor barrier layer and a gas barrier layer, in that order, on at least one 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 have properties such as water vapor barrier and gas barrier properties that are not necessary when used to package nonwoven fabric masks and the like. Furthermore, these barrier laminates contain inorganic compounds to exhibit high barrier properties, but the barrier layer may crack and cause powder to fall off during folding and heat sealing processes in the manufacturing process of the package.

Utility Model Registration No. 3228666 Japanese Patent Application Laid-Open No. 2020-189489

The objective of the present invention is to provide a new flexible packaging paper and a flexible package using this flexible packaging paper.

The means for solving the problems of the present invention are as follows.
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 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,
The dry weight (per side) of the heat seal layer is 4 g/m ² or more and 20 g/m ² or less,
The flexible packaging paper has a tear strength (in both the MD and CD directions) of 100 mN or more and 650 mN or less.
2. The flexible packaging paper according to 1., wherein the tear strength (in both the MD and CD directions) is less than 400 mN.
3. The flexible packaging paper according to 1., wherein the tear strength (in both the MD and CD directions) is 400 mN or more.
4. A flexible packaging body, characterized in that an item to be packaged is enclosed in a packaging material made of the flexible packaging paper described in any one of 1. to 3.
5. The flexible packaging according to 4., wherein the packaged item is a sanitary mask.

The flexible packaging paper of the present invention can be used as a replacement for packaging materials made from conventional resin films. Because the flexible packaging paper of the present invention is primarily made of paper, the amount of resin material used can be significantly reduced. The flexible packaging paper of the present invention can be easily torn from any direction, and when used in flexible packaging, the packaged items can be easily removed.

The present invention relates to a flexible packaging paper and a flexible package using this flexible packaging paper.
"Flexible packaging paper"
The flexible packaging paper of the present invention has a paper base material and a heat-seal layer provided on at least one side of the paper base material. In addition to the paper base material and the heat-seal layer, the flexible packaging paper of the present invention may also have a sealing layer, an ink-receiving layer, a water-resistant layer, etc., but is preferably composed of only the paper base material and the heat-seal layer.

The flexible packaging paper of the present invention has a tear strength (MD and CD) of 100 mN or more and 650 mN or less. By setting the tear strength within this range, when the flexible packaging is made, it can be easily torn from any direction to remove the packaged item. From the perspective of making the flexible packaging easier to tear, the tear strength (MD and CD) is preferably less than 400 mN, more preferably 300 mN or less, 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 packaging less likely to tear even when subjected to impact during transportation, etc., the tear strength (MD and CD) is preferably 400 mN or more. The tear strength can be selected depending on the shape of the packaged item (e.g., whether or not there are protrusions, whether or not there is a space inside when made into a flexible packaging). In this specification, tear strength refers to the value measured in accordance with JIS P8116:2000 "Paper - Tear strength testing method - Elmendorf tear tester method" using a test piece 63 mm long, a 20 mm incision, and a tear length of 43 mm.

The flexible packaging paper of the present invention preferably has a basis weight of 35 g/ ^m2 or more and 60 g/ ^m2 or less as a whole. The flexible packaging paper of the present invention also preferably has a thickness of 30 μm or more and 70 μm or less as a whole. By setting the basis weight and thickness within these ranges, the flexible packaging paper can be suitably used as a flexible packaging material. In particular, if the thickness is 70 μm or more, the paper becomes bulky when several dozen individually packaged sanitary masks or the like are stacked and placed in one box, and the number that can be placed in one box becomes limited.

From the standpoint of enabling visual inspection, the flexible packaging paper of the present invention preferably has a transparency of 60% or more, more preferably 65% or more, and even more preferably 70% or more. On the other hand, when packaging items that should not be seen, such as sanitary products, the transparency is preferably less than 60%, more preferably less than 55%, and even more preferably less than 50%.

Paper Base The paper base used in the present invention has a filler content of 1% by weight or less, a basis weight of 25 g/ ^m2 or more and 50 g/ ^m2 or less, and a density of 0.85 g/ cm3 or ^more and 1.35 g/ cm3 or ^less .
The paper base material 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 shedding can be suppressed. The filler content is preferably 0.5% by weight or less, more preferably 0.3% by weight or less, even more preferably 0.1% by weight or less, and most preferably zero (0% by weight).

The paper base material of the present invention has a basis weight of 25 g/m2 or ^more and 50 g/ ^m2 or less and a density of 0.85 g/ cm3 or ^more and 1.35 g/ cm3 or ^less . By keeping the basis weight and density within these ranges, it is possible to achieve flexibility and strength suitable for flexible packaging paper.

In the present invention, papermaking fibers that can be used include chemical pulps such as softwood bleached kraft pulp (NBKP), hardwood bleached kraft pulp (LBKP), softwood unbleached kraft pulp (NUKP), hardwood unbleached kraft pulp (LUKP), softwood semi-bleached kraft pulp (NSBKP), hardwood semi-bleached kraft pulp (LSBKP), softwood sulfite pulp, and hardwood sulfite pulp; mechanical pulps such as stone ground pulp (SGP), pressed stone ground pulp (TGP), chemi-ground pulp (CGP), groundwood pulp (GP), and thermomechanical pulp (TMP); wood pulps such as dissolving pulp and mercerized pulp; non-wood pulps such as flax pulp, Manila hemp pulp, and kenaf pulp; and recycled paper pulp. However, it is preferable to use chemical pulp, which is less likely to be contaminated with foreign matter, and it is preferable to use NBKP and LBKP, and it is even more preferable to use only NBKP and LBKP.

The freeness (2g Schopper-Rigler freeness: specified in JIS P8121-1) of the papermaking fibers used in this invention is preferably 10°SR or more and 90°SR or less. The smaller this value, the better the tear strength of the paper base material obtained, but the lower the transparency. Therefore, if transparency is required, the freeness value should be increased.

Examples of various auxiliary agents include sizing agents such as rosin, alkyl ketene dimer (AKD), and alkenyl succinic anhydride (ASA); polyacrylamide polymers, polyvinyl alcohol polymers, cationic starch, various modified starches, dry strength agents such as urea-formalin resin and melamine-formalin resin; wet strength agents; retention aids; drainage aids; coagulants; aluminum sulfate; bulking agents; dyes; fluorescent brighteners; pH adjusters; defoamers; UV inhibitors; anti-fading agents; pitch control agents; and slime control agents. These may be selected and used as needed. However, from the standpoints of cost and safety, a low auxiliary content is preferable for the paper base material of the present invention. Specifically, the total auxiliary 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 0% by weight or less.

The method for producing the paper base material (papermaking) is not particularly limited, and the paper base material can be produced by acidic papermaking, neutral papermaking, or alkaline papermaking using a known Fourdrinier former, on-top hybrid former, gap former machine, etc. Among these, it is preferable to use a Fourdrinier former, which has a large dewatering capacity.
Furthermore, various chemicals can be externally 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-retention agents, thickeners, and lubricants, and these can be used alone or in combination of two or more. However, it is preferable not to add any external agents to the paper substrate of the present invention.

Heat Seal Layer The heat seal layer is provided on at least one surface of the paper substrate, and may be provided on both surfaces.
The dry weight (coating amount) of the heat-seal layer per side is 4 g/ ^m2 or more and 20 g/ ^m2 or less. If the dry weight (per side) of the heat-seal layer is less than 4 g/ ^m2 , the heat-sealability deteriorates. If the dry weight (per side) of the heat-seal layer is more than 20 g/ ^m2 , the heat-sealability saturates and shows almost no improvement, and the amount of resin used increases, resulting in high costs and being undesirable from the standpoint of environmental impact. The dry weight (per side) of the heat-seal layer is preferably 15 g/ ^m2 or less, more preferably 10 g/ ^m2 or less, and even more preferably 9 g/ ^m2 or less.

There are no particular restrictions on the resin that forms the heat seal layer, and thermoplastic resins used in heat seal applications, such as ethylene-vinyl acetate resins, styrene-acrylate 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 restrictions. Of these, ethylene-vinyl acetate resins and acrylic resins are preferred in terms of heat seal strength. Furthermore, biodegradable resins such as polyvinyl alcohol and polylactic acid are preferred in terms of reducing the environmental impact if they are disposed of as waste.

The heat seal layer may contain additives such as antiblocking agents. Antiblocking agents that can be used include pigments, waxes, metal soaps, and the like, without any particular restrictions. 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 perspective.

The heat seal layer may be either a coated layer or a laminate layer, but is preferably a coated layer from the viewpoints of production efficiency and recyclability (redisintegrability). The coating method is not particularly limited, and coating can be performed using a known coating device and coating system. Examples of coating devices include a blade coater, a bar coater, an air knife coater, a curtain coater, a spray coater, a roll coater, a reverse roll coater, a size press coater, and a gate roll coater.
The coating system may be either aqueous coating using a solvent such as water or solvent-based coating using a solvent such as an organic solvent, but aqueous coating is preferred from the viewpoint of safety and hygiene. When aqueous coating is used, a water-dispersible resin or a water-soluble resin is used as the thermoplastic resin.

"Soft packaging"
The flexible packaging of the present invention has an item to be packaged enclosed in a packaging material made of the flexible packaging paper of the present invention described above.
The shape of the flexible packaging is not particularly limited, and may be a vertical pillow packaging bag, a horizontal pillow packaging bag, a side-sealed bag, a two-sided sealed bag, a three-sided sealed bag, a gusset bag, a bottom gusset bag, a stand-up bag, etc. The flexible packaging of the present invention is made mainly of paper, and therefore is easier to tear than conventional packaging made of resin, and can be easily torn from any point.
Furthermore, the flexible packaging paper of the present invention can be used in place of conventional resin films in packaging machines that use such films with almost no change in manufacturing conditions. The flexible packaging of the present invention can be manufactured using conventional manufacturing machines as is, so no new equipment is required.

The packaged item contained in the flexible packaging of the present invention may be any item that does not deteriorate over time, and examples include sanitary masks such as nonwoven masks, amenities such as toothbrushes, combs, razors, and slippers provided at accommodation facilities, disposable cutlery such as disposable chopsticks, spoons, forks, and straws, and sanitary products. Furthermore, even packaged items that require barrier properties, such as candy, gummies, chocolate, and supplements, can be packaged in small pouches made of a material with barrier properties, and the packaged items can then be contained in the flexible packaging of the present invention.

"Example 1"
A paper base material having NBKP/LBKP=100/0 (85°SR, but 1 g Schopper-Rigler freeness), basis weight of 34 g/m ² and density of 1.27 g/ cm ³ was used.
An ethylene-vinyl acetate emulsion (Chemipearl V300, manufactured by Mitsui Chemicals, Inc.) was applied to one side of this paper substrate at a dry weight of 7.0 g/ ^m2 and dried to form a heat seal layer, thereby producing flexible packaging paper.

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

"Example 4"
A flexible packaging paper was produced in the same manner as in Example 1, except that a paper base material with NBKP/LBKP=30/70 (70°SR), basis weight of 50 g/m ² and density of 0.95 g/ cm ³ was used.

"Example 5"
A flexible packaging paper was produced in the same manner as in Example 1, except that a paper base material with NBKP/LBKP=100/0 (17°SR), basis weight of 38 g/m ² and density of 0.89 g/ cm ³ was used.

"Comparative Example 1"
A flexible packaging paper was produced in the same manner as in Example 5, except that the dry weight of the heat seal layer was 2.5 g/m ² .
"Reference example"
A commercially available PET film for general packaging applications (FE2201, manufactured by Futamura Chemical Co., Ltd., thickness 12 μm) was used.

The obtained flexible packaging paper was evaluated as follows, and the results are shown in Table 1.
(transparency)
The transparency of one sample conditioned under conditions of 23°C and 50% RH was measured using a densitometer with a transmission-type search unit (Model TC-6MC, manufactured by Tokyo Denshoku Co., Ltd.) (TAPPI T522 om-85).
(Tear strength)
Measurement was performed in accordance with JIS P8116:2000 using an Elmendorf tear tester (manufactured by Kumagai Riki Kogyo Co., Ltd.) with a test piece length of 63 mm, a slit depth of 20 mm, and a tear length of 43 mm.

(Heat sealability)
Two square test pieces with sides of 100 mm were cut out from the obtained flexible packaging paper, and the heat seal layers were brought into contact with each other and heat sealed using a heat seal tester (HEAT SEAL TESTER TP-701S, manufactured by Tester Sangyo Co., Ltd.) at a pressure of 120°C, a pressure of 2 kgf/cm ² , and a pressure time of 1 second.
The heat-sealed test piece was peeled off by hand, and the peeled portion was visually observed, and the heat-sealability was evaluated according to the following criteria.
○: Peeling occurred within the paper substrate (paper substrate was destroyed).
×: Peeling occurred between the heat seal layers.

(Encapsulation)
Each flexible packaging paper sample having a width of 210 mm was prepared, along with a laminate of white cardboard as an inner packaging material (size: 100 mm x 65 mm x 25 mm, weight: 130 g). 100 flexible packaging samples were packaged at a speed of 40 samples per minute using a pillow packaging machine (manufactured by Suzuki Seisakusho, SP-803N), and the flexible packaging samples were then evaluated as follows.
◎: The flexible packaging paper sample can be wrapped without tearing, and the speed can be increased. 〇: The flexible packaging paper sample can be wrapped without tearing. ×: The flexible packaging paper sample is torn and cannot be wrapped.

(Suitability for opening)
The flexible packaging obtained in the evaluation of sealing ability above was evaluated according to the following criteria to see whether it could be torn apart smoothly by hand without making cuts. The evaluation was carried out in both the machine direction (MD) and the cross direction (CD).
◎: Very easily torn by hand ○: Easily torn by hand ×: Not easily torn by hand

The flexible packaging paper obtained in Examples 1 to 6 of the present invention had excellent heat-sealing properties, sealing properties, and ease of opening. In particular, the ease of opening was significantly improved compared to conventional PET film, and the paper could be easily opened from both the vertical and horizontal directions without any cuts.

Claims (4)

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 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,
The dry weight (per side) of the heat seal layer is 4 g/m ² or more and 20 g/m ² or less,
The flexible packaging paper has a tear strength (in both the MD and CD directions) of 100 mN or more and 300 mN or less . 2. The flexible packaging paper according to claim 1, wherein the tear strength (in both the MD and CD directions) is 200 mN or less . A flexible packaging body, characterized in that an item to be packaged is enclosed in a packaging material made of the flexible packaging paper according to claim 1 or 2 . 4. The flexible packaging body according to claim 3 , wherein the packaged item is a sanitary mask.