JP2023039449A - Clupak paper and paper processed product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide Clupak paper with drop impact resistance and excellent flexibility.

SOLUTION: The Clupak paper has a pulp-containing paper substrate. The ISO stiffness in the longitudinal direction of the Clupak paper measured according to ISO2493-1:2010 is 0.70 mNm or less. The ISO stiffness in the lateral direction of the Clupak paper is 0.45 mNm or less. The thrust strength of the Clupak paper measured according to JIS Z 1707:2019 is 7.50 N or more.

SELECTED DRAWING: None

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present disclosure relates to clupak paper and paper products.

Conventionally, Clupak paper, which is given stretchability by finely shrinking the paper during papermaking, has been used as a wrapping paper. As Clupak paper, for example, Patent Literature 1 discloses Clupak paper that is difficult to break even in heavy packaging applications by controlling the specific tensile strength in the longitudinal direction and the transverse direction.

On the other hand, plastic materials have been mainly used for packaging containers such as food trays and packaging bodies such as pillow packaging bags. However, due to concerns about the environment, paper packaging materials are now being investigated in place of plastic containers.

WO2015/008703

Although Clupak paper has excellent flexibility, it has low puncture strength, and in the production of bags for pillow packaging, for example, it has insufficient drop impact resistance when the bag is filled with a product. Generally, paper with high puncture strength tends to harden and is inferior in flexibility, so it has been difficult to achieve both drop impact resistance and flexibility in Clupak paper.
TECHNICAL FIELD The present disclosure relates to Clupak paper that has drop impact resistance and excellent flexibility, and paper processed products using Clupak paper.

That is, the present disclosure relates to the following <1> to <8>.
<1> Clupak paper having a paper base containing pulp,
The Clupak paper has an ISO stiffness in the longitudinal direction of 0.70 mNm or less, and an ISO stiffness in the transverse direction of the Clupak paper of 0.45 mNm or less, as measured in accordance with ISO2493-1:2010;
The Clupak paper has a puncture strength of 7.50 N or more, as measured in accordance with JIS Z 1707:2019.
Clupak paper characterized by:
<2> the Clupak paper has a longitudinal ISO stiffness of 0.10 to 0.20 mNm;
The transverse ISO stiffness of the Clupak paper is 0.10 to 0.20 mNm.
The Clupak paper according to <1>.
<3> The Clupak paper according to <1> or <2>, wherein the Clupak paper has a puncture strength of 12.50 N or more.
<4> The pulp obtained by defibrating the Clupak paper has a length-weighted average fiber length of 1.2 mm to 1.9 mm, which is measured in accordance with ISO 16065-2:2007. The Clupak paper according to any one of <1> to <3>.
<5> The Clupak paper according to any one of <1> to <4>, wherein the basis weight of the paper base material is 30 g/m ² to 120 g/m ² .
<6> The Clupak paper according to any one of <1> to <5>, wherein the Clupak paper has a specific puncture strength of 0.13 N/g or more.
<7> The Clupak paper according to any one of <1> to <6>, wherein the Clupak paper has a thermoplastic resin layer on at least one surface of the paper substrate.
<8> A processed paper product which is a molded body of Clupak paper according to any one of <1> to <7>.

According to the present disclosure, it is possible to provide clupak paper that has drop impact resistance and is also excellent in flexibility.

Schematic diagram of bag processing for evaluation of drop impact resistance and bag flexibility

In the present disclosure, the descriptions of “X or more and Y or less” or “X to Y” representing numerical ranges mean numerical ranges including the lower and upper limits, which are endpoints, unless otherwise specified. When numerical ranges are stated stepwise, the upper and lower limits of each numerical range can be combined arbitrarily.
The machine direction is the machine direction (MD) of the paper substrate, which is the same as the direction in which the fibers are oriented. The transverse direction is the direction (CD) perpendicular to the papermaking direction.

The Clupak treatment is, as described above, a treatment that imparts elongation performance by finely shrinking paper on a paper machine. Specifically, for example, part of a paper machine dryer is equipped with a Clupak device comprising an endless thick elastic rubber blanket with nip rolls. The wet paper web is introduced into the Clupak machine and compressed with nip rolls and blankets. At this time, the pre-stretched blanket shrinks, thereby shrinking the running paper web (creating crepe) and increasing the elongation at break. In addition, the resulting shrinkage is dried and fixed so that it will not stretch in the subsequent process.

The inventors of the present invention have found that the above problems can be solved by controlling the specific ISO stiffness and puncture strength by the Clupak treatment during the production of the paper base material. The ISO stiffness indicates the ease with which the paper is folded, and the puncture strength indicates the resistance to tearing of the paper. The fact that the Clupak paper has the above-specified ISO stiffness and puncture strength indicates that it has moderate ease of folding and is resistant to tearing. Therefore, the present inventors believe that Clupak paper having excellent flexibility and drop impact resistance can be obtained.

The ISO stiffness of the Clupak paper in the longitudinal direction, measured in accordance with ISO2493-1:2010, must be 0.70 mNm or less, and the ISO stiffness of the Clupak paper in the transverse direction must be 0.45 mNm or less. be.
When the ISO stiffness exceeds the above upper limit, it becomes difficult to bend and flexibility decreases.

The ISO stiffness can be controlled by CSF (Canadian Standard Freeness) of pulp, basis weight, speed difference before and after Clupak treatment, mass ratio of hardwood kraft pulp and softwood kraft pulp constituting the paper substrate, and the like. In order to increase the ISO stiffness, there are methods such as lowering the CSF of the pulp, increasing the basis weight, increasing the speed difference before and after Clupak processing, and increasing the mass ratio of the softwood kraft pulp that constitutes the paper base material. be done. On the other hand, in order to reduce the ISO stiffness, there are methods such as increasing the CSF of the pulp, decreasing the basis weight, decreasing the speed difference before and after Clupak processing, and decreasing the mass ratio of the softwood kraft pulp that constitutes the paper base material. mentioned.

The ISO stiffness in the machine direction of Clupak paper is preferably 0.05 to 0.60 mNm, more preferably 0.10 to 0.20 mNm.
The transverse ISO stiffness of the Clupak paper is preferably 0.05-0.35 mNm, more preferably 0.10-0.20 mNm.

Clupak paper must have a puncture strength of 7.50 N or more, as measured according to JIS Z 1707:2019.
If the puncture strength is less than the above lower limit, dents and tears are likely to occur, and the drop impact resistance is reduced.

The puncture strength can be controlled by basis weight, speed difference before and after Clupak treatment, softwood kraft pulp content, nip pressure during Clupak treatment, and the like. To increase the puncture strength, there are methods such as increasing the basis weight, increasing the speed difference before and after Clupak treatment, increasing the content of softwood kraft pulp, and decreasing the nip pressure during Clupak treatment. On the other hand, in order to reduce the puncture strength, there are methods such as reducing the basis weight, reducing the speed difference before and after Clupak treatment, reducing the content of softwood kraft pulp, and increasing the nip pressure during Clupak treatment. .

The puncture strength of the Clupak paper is preferably 8.00 N or more, more preferably 12.5 or more. Although the upper limit of the puncture strength is not particularly limited, it is preferably 18.0 N or less from the viewpoint of reducing cushioning properties.

The length-weighted average fiber length of the pulp obtained by defibrating Clupak paper, measured according to ISO 16065-2:2007, is preferably from 1.2 mm to 1.9 mm. More preferably, it is between 0.3 mm and 1.8 mm.
If the length-weighted average fiber length is less than the above lower limit, the strength is low and the drop impact resistance is deteriorated, but the flexibility is increased. If the length-weighted average fiber length exceeds the above upper limit, the strength is high and the drop impact resistance is improved, but on the other hand, the flexibility tends to deteriorate. That is, within the above range, both bag flexibility and drop impact resistance can be achieved. The length-weighted average fiber length of pulp can be controlled by the type of pulp used.

The Clupak paper has a specific puncture strength of preferably 0.05 N/g or more, more preferably 0.10 N/g or more, still more preferably 0.13 N/g or more. Although the upper limit of the specific puncture strength is not particularly limited, it is preferably 0.30 N/g or less from the viewpoint of cushioning properties. Within the above range, the flexibility and drop impact resistance are excellent.
The specific puncture strength is a value obtained by dividing the puncture strength by the basis weight.

The basis weight of the paper substrate is preferably 30 g/m ² to 120 g/m ² , more preferably 60 g/m ² to 110 g/m ² , and 70 g/m ² to 90 g/m ² is more preferred. If the basis weight is less than the above lower limit, the strength is low and the drop impact resistance is deteriorated, but on the other hand the flexibility is increased. If the basis weight exceeds the above upper limit, the strength is high and the drop impact resistance is improved, but the flexibility tends to deteriorate. Within the above range, both bag flexibility and drop impact resistance can be achieved.

The thickness of the paper substrate is preferably 50 μm to 300 μm, more preferably 60 μm to 200 μm, even more preferably 70 μm to 150 μm, and even more preferably 100 μm to 140 μm.

The density of the paper substrate is preferably 0.30 g/m ³ to 1.00 g/m ³ , more preferably 0.40 g/m ³ to 0.90 g/m 3 , and more preferably 0.50 g/m ³ to 0.90 g/m 3 . It is more preferably m ³ to 0.80 g/m ³ , even more preferably 0.60 g/m ³ to 0.70 μmg/m ³ .

Next, materials that can be used for Clupak paper are described.
Pulp constituting the paper substrate includes hardwood kraft pulp such as unbleached hardwood kraft pulp (LUKP) and bleached hardwood kraft pulp (LBKP); unbleached softwood kraft pulp (NUKP) and bleached softwood kraft pulp (NBKP). Softwood kraft pulp; groundwood pulp (GP), pressure groundwood pulp (PGW), refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), chemi-mechanical pulp (CMP), chemiground pulp mechanical pulp such as (CGP); waste paper pulp; non-wood fiber pulp such as kenaf, bagasse, bamboo and cotton; synthetic pulp and the like. These pulps may be used individually by 1 type, and may be used in combination of 2 or more types.

The pulp preferably contains at least one selected from hardwood kraft pulp and softwood kraft pulp, more preferably at least one selected from hardwood unbleached kraft pulp and softwood unbleached kraft pulp. More preferably, it contains hardwood unbleached kraft pulp and softwood unbleached kraft pulp.

The softwood kraft pulp content in the pulp is preferably 20% by mass or more, more preferably 30% by mass or more, still more preferably 35% by mass or more, and still more preferably 40% by mass or more. On the other hand, the upper limit is preferably 100% by mass or less, more preferably 95% by mass or less, still more preferably 90% by mass or less, and even more preferably 85% by mass or less.

The hardwood kraft pulp content in the pulp is preferably 0% by mass or more, more preferably 10% by mass or more, still more preferably 10% by mass or more, and even more preferably 15% by mass or more. On the other hand, the upper limit is preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 65% by mass or less, and even more preferably 60% by mass or less.

The beating degree of the pulp is not particularly limited, but is preferably 200 to 800 mL, more preferably 300 to 700 mL, in terms of Canadian Standard Freeness (CSF). CSF is measured according to JIS P 8121-2:2012 "Pulp - Freeness Test Method - Part 2: Canadian Standard Freeness Method".

Additives may be used in the paper substrate as necessary. Examples of additives include pH adjusters (sodium hydrogen carbonate, sodium hydroxide, etc.), dry paper strength agents (polyacrylamide, starch, etc.), wet paper strength agents (polyamide polyamine epichlorohydrin resin, melamine-formaldehyde resin, urea-formaldehyde resin), internal sizing agent (rosin type, alkyl ketene dimer, etc.), drainage retention improver (polyacrylamide resin), antifoaming agent, filler (calcium carbonate, talc, etc.), dye, etc. mentioned. These additives may be used singly or in combination of two or more. The content of the additive is not particularly limited as long as it is within a commonly used range.

<Method for producing paper substrate>
As a method for producing a paper base material, there is a method in which a pulp-containing stock is made into paper, and the paper is subjected to Clupak treatment during paper making. In addition, the paper material may further contain an additive as needed. Additives include, for example, the additives described above. The paper stock can be prepared by adding additives to the pulp slurry as required. Pulp slurry is obtained by beating pulp in the presence of water. The pulp beating method and beating apparatus are not particularly limited, and known beating methods and beating apparatuses can be employed.

The solid content concentration of the pulp slurry during beating is not particularly limited, but is preferably 0.5 to 1
It is about 0% by mass, more preferably about 1 to 5% by mass. Moreover, the content of pulp in the paper stock or paper substrate is not particularly limited, and may be within the range normally used. For example, it is preferably 60% by mass or more and 100% by mass or less, more preferably 80% by mass or more and less than 100% by mass, relative to the total mass of the stock (solid content) or paper substrate.

In the papermaking of the paper substrate, a known wet papermaking machine can be appropriately selected and used. The paper machine includes a fourdrinier paper machine, a gap former paper machine, a cylinder paper machine, a short mesh paper machine and the like. A Clupak device capable of performing the Clupak treatment may be installed in these paper machines to perform the Clupak treatment.

A known Clupak device can be used. For example, a Clupak device with a nip roll and an endless thick elastic rubber blanket. As described above, in the Clupak treatment, the paper web is carried between the nip roll and the blanket, and when the paper web is compressed by the nip roll and the blanket, the pre-stretched blanket is contracted to shrink the paper web. to give crepe. The Clupak device is usually installed in a part of the dryer device of the paper machine to crepe, dry and fix. A paper substrate can be obtained in the manner described above.

In papermaking using a Clupak device, the ISO stiffness and puncture strength can be controlled by the difference in papermaking speed before and after Clupak treatment and the pressure of the nip rolls.
The papermaking speed is not particularly limited, but may be controlled within a range of preferably 200 to 1000 m/min, more preferably 300 to 800 m/min, still more preferably 400 to 700 m/min. The speed difference before and after the Clupak treatment is not particularly limited, and may be controlled so as to obtain the desired ISO stiffness and puncture strength depending on the basis weight and pulp material. It is preferably -5 to -60 m/min, more preferably -10 to -50 m/min, more preferably -15 to -40 m/min. A minus "-" here indicates that the speed after Clupak processing is slow.

The calender nip pressure is not particularly limited, and may be controlled according to basis weight, pulp material, speed difference before and after Clupak treatment, etc., so as to obtain desired ISO stiffness and puncture strength. It is preferably 100 kN/m to 200 kN/m, more preferably 130 kN/m to 170 kN/m.

The reel moisture content is not particularly limited, and may be controlled according to basis weight, pulp material, speed difference before and after Clupak treatment, etc., so as to obtain desired ISO stiffness and puncture strength. It is preferably 2.0 to 12.0%, more preferably 5.0 to 9.0%.

The obtained paper substrate can be used as Clupak paper as it is. From the viewpoint of improving waterproofness and antifouling properties, a thermoplastic resin layer may be provided on at least one surface of the paper substrate, if necessary. Further, the Clupak paper may be provided with other resin layers or the like to the extent that the above effects are not impaired. Clupak paper may have a thermoplastic resin layer on one side of the paper substrate, or may have thermoplastic resin layers on both sides of the paper substrate.

The thermoplastic resin used for the thermoplastic resin layer is not particularly limited, and may be appropriately selected from known thermoplastic resins.
Specifically, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactic acid, and polybutylene succinate, polyvinyl chloride, polyvinylidene chloride, polybutene, polybutadiene, ethylene-vinyl acetate copolymer, Polyolefin resins such as polyethylene, polypropylene, ethylene-propylene copolymer, polymethylpentene; polycarbonate; polyurethane; polyamide; polyacrylonitrile;

Among these, polyolefins such as polyethylene, polypropylene, and ethylene-propylene copolymers, and polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactic acid, and polybutylene succinate are preferable, and polyethylene, polypropylene, polyethylene terephthalate, Polylactic acid and polybutylene succinate are more preferred, polyethylene and polypropylene are more preferred, and polyethylene is even more preferred.
In addition to the above materials, biomass resins and biodegradable resins may be used as resins. These resins may be used individually by 1 type, and may use 2 or more types together.

The thermoplastic resin is preferably one that can be laminated on the sheet substrate as a laminate layer. Among thermoplastic resins, polyethylene is preferred because of its excellent extrusion lamination properties and barrier properties.
Polyethylene (PE) is roughly classified into linear low density polyethylene (LLDPE), low density polyethylene (LDPE), medium density polyethylene (MDPE), and high density polyethylene (HDPE). Among these, low-density polyethylene (LDPE) is preferred because of its excellent extrusion lamination properties and foamability.

The thermoplastic resin layer may be produced by appropriately selecting from known production methods, for example, from melt extrusion, melt casting, calendering, and the like. Although the thickness of the thermoplastic resin layer is not particularly limited, it is preferably 1 µm or more, more preferably 3 µm or more, and still more preferably 5 µm or more. On the other hand, the upper limit of the thickness is preferably 50 μm or less, more preferably 30 μm or less, still more preferably 20 μm or less.

The Clupak paper thus obtained is not particularly limited in use, and can be used for processed paper products such as packaging bodies such as wrapping paper, packaging bags, and packaging containers, and various containers such as cups and trays, by appropriately molding the paper. For example, paper containers such as paper plates, paper cups, and paper trays, horizontal pillow packaging, vertical pillow packaging, three-side seal packaging, four-side seal packaging, bag-feed filling packaging, tube packaging, and stick packaging. It can be used for bags, etc. In particular, since it is excellent in flexibility and drop impact resistance, it can be suitably used in the bag applications described above.

Methods for measuring each physical property are described below.
<ISO stiffness>
The ISO stiffness in the machine and transverse directions of Clupak paper is measured according to ISO 2493-1:2010 (Paper and paperboard-Bend resistance test method-Part 1: Constant velocity deflection).
Specifically, as temperature control and humidity control processing, Clupak paper left still for one day in an environment of 23±5° C. and 50±10% is cut into a sample having a width of 38 mm and a length of 70 mm. With a stiffness tester (L & W BENDING RESISTANCE TESTER Code No. 16-D, manufactured by Lorentzen & Wattre), the bending length is set to 10 mm and the bending angle is set to 15 °, MD (vertical direction), CD (horizontal direction) After measuring each bending resistance, the ISO stiffness is calculated by the following formula.

<Puncture Strength/Specific Puncture Strength>
The puncture strength of Clupak paper is measured according to JIS Z 1707:2019 (general rules for plastic films for food packaging).
Specifically, as a temperature control and humidity control treatment, using Clupak paper left still for one day in an environment of 23 ± 5 ° C., 50 ± 10%, a tensile tester (model RTC-1210A, A& Co., Ltd. (manufactured by A&D Co., Ltd.), a puncture jig (manufactured by A&D Co., Ltd.) is used, and the puncture strength is measured after setting the puncture speed to 50 mm/min.
Further, the specific puncture strength is calculated by dividing the puncture strength by the basis weight.

<Pulp length weighted average fiber length>
The length-weighted average fiber length of pulp in Clupak paper is measured according to ISO 16065-2:2007. Specifically, it is as follows.
A 40 cm square piece of Clupak paper is cut, soaked in deionized water, adjusted to a solid content concentration of 2% by mass, and soaked for 24 hours. After being immersed for 24 hours, a standard type disintegrator (manufactured by Kumagai Riki Kogyo Co., Ltd.) is used to perform disintegration treatment for 30 minutes to disintegrate the pulp into fibers. When the Clupak paper has a resin layer, the slurry (pulp fiber dispersion) after defiberization from which the resin layer is removed is separated.
Using the obtained pulp fiber sample, the "length-weighted average fiber length (ISO)" is measured using a fiber length measuring machine (model FS-5 with UHD base unit, manufactured by Valmet). The "length-weighted average fiber length (ISO)" is the length-weighted average fiber length calculated by selecting fibers of 0.2 mm or more and 7.6 mm or less.

<Basis Weight>
The basis weight of the paper substrate is measured according to JIS P 8124:2011.
When the Clupak paper has a resin layer in addition to the paper base material, the basis weight of the paper base material is determined after specifying the material, thickness, density, etc. of the resin layer by a known method and the following procedure. can be calculated.
Specifically, the weight (total weight) of Clupak paper having a resin layer cut into a predetermined size is measured, and then the Clupak paper having a resin layer is impregnated with an aqueous solution of an enzyme such as cellulase to obtain a paper base material. After confirming that the is completely dissolved, measure the weight of the resin layer only (resin layer weight), subtract the resin layer weight from the total weight to calculate the weight of the paper base alone, and the weight of the paper base Measure basis weight.

<Thickness>
The thickness of the paper substrate (paper thickness) is measured according to JIS P 8118:2014. In the case where the Clupak paper has a resin layer in addition to the paper base material, the thickness of each of the paper base layer and the thermoplastic resin layer is determined from an electron microscope (SEM) observation image of the cross section of the Clupak paper. Measure.

<Density>
The density of the paper substrate is calculated from the thickness and basis weight obtained by the above-described measuring method.

EXAMPLES The characteristics of the present invention will be described more specifically below with reference to examples and comparative examples. The materials, amounts used, proportions, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed to be limited by the specific examples shown below. Moreover, unless otherwise specified, "part" represents "mass part". Further, the operations of Examples and Comparative Examples were carried out under the conditions of room temperature (20 to 25° C.) and normal humidity (40 to 50% RH) unless otherwise specified.

<Example 1>
Using NUKP (softwood unbleached kraft pulp) and LUKP (hardwood unbleached kraft pulp) obtained by pulping (cooking) wood at a ratio (mass ratio) of 55:45, at a slurry concentration of 2% by mass during beating, A pulp was prepared by beating until the CSF (Canadian Standard Freeness) reached 600 mL.
Using the above pulp, 0.15 parts of synthetic sizing agent (manufactured by Arakawa Chemical Industries, Ltd., SPS400) per 100 parts of pulp in terms of solid content, 1.2 parts of aluminum sulfate, polyacrylamide resin (Seiko PMC) as a retention agent 0.65 part of DS4433 manufactured by Co., Ltd. and 0.035 part of nonionic polyacrylamide (Percol 47 manufactured by Allied Colloid) as a polymer flocculant (retention agent) were added to prepare a paper stock.
Using the above stock, a wet paper machine (Bellform III, manufactured by Mitsubishi Heavy Industries, Ltd.) equipped with a stretching device (manufactured by Clupak) was used to perform Clupak processing at a papermaking speed of 600 m/min and reel moisture content of 7.0%. Paper was made at a speed difference of -20 m/min before and after processing, and a nip pressure of 15 kN/m between the nip roll and the blanket during Clupak treatment, to obtain a paper base having a basis weight of 80 g/m ² with a crepe applied to the surface of the paper. rice field. The obtained paper base material was used as Clupak paper of Example 1.

<Example 2>
Clupak paper was obtained under the same conditions as in Example 1, except that the speed difference before and after Clupak treatment was changed to -28.0 m/min.

<Example 3>
Clupak paper was obtained under the same conditions as in Example 1, except that the speed difference before and after Clupak treatment was changed to -30.0 m/min.

<Example 4>
Clupak paper was obtained under the same conditions as in Example 1, except that the speed difference before and after Clupak treatment was changed to −37.0 m/min, and the basis weight was changed to 100 g/m ² by adjusting the discharge rate of the pulp. .

<Example 5>
Clupak paper was obtained under the same conditions as in Example 1, except that the CSF (Canadian Standard Freeness) after beating was 380 mL.

<Example 6>
The mass ratio of NUKP (softwood unbleached kraft pulp) and LUKP (hardwood unbleached kraft pulp) obtained by pulping (cooking) wood was changed to 40:60, and the speed difference before and after Clupak treatment was changed to -25.0m/min. Clupak paper was obtained under the same conditions as in Example 1, except for the above.

<Example 7>
The mass ratio of NUKP (softwood unbleached kraft pulp) and LUKP (hardwood unbleached kraft pulp) obtained by pulping (cooking) wood was changed to 90:10, and the speed difference before and after Clupak treatment was changed to -40.0m/min. Clupak paper was obtained under the same conditions as in Example 1, except for the above.

<Example 8>
Clupak paper was obtained under the same conditions as in Example 1, except that the speed difference before and after Clupak treatment was changed to −16.0 m/min, and the basis weight was changed to 50 g/m ² by adjusting the discharge rate of pulp. .

<Example 9>
NUKP (softwood unbleached kraft pulp) and LUKP (hardwood unbleached kraft pulp), which are pulped (cooked) wood, were changed to a mass ratio of 30:70, and the speed difference before and after Clupak treatment was changed to -25.0m/min. Clupak paper was obtained under the same conditions as in Example 1, except for the above.

<Example 10>
The mass ratio of NUKP (softwood unbleached kraft pulp) and LUKP (hardwood unbleached kraft pulp) obtained by pulping (cooking) wood was changed to 100:0, and the speed difference before and after Clupak treatment was changed to -40.0m/min. Clupak paper was obtained under the same conditions as in Example 1, except for the above.

<Example 11>
A coating liquid was prepared by mixing 100 parts by mass of a water-based acrylic adhesive (EA-G34, manufactured by Toyo-Morton, Ltd.) with 3 parts by mass of a curing agent (CAT-EP8, manufactured by Toyo-Morton, Ltd.). The obtained coating solution was applied to one side of the Clupak paper obtained in Example 8 using a reverse roll coater so that the coating amount after heat drying was 10 g/m ² , and then 105 °C for 10 seconds. A linear low-density polyethylene film (LL-XLTN 25 μm, manufactured by Futamura Chemical Co., Ltd.) was laminated on the adhesive-coated surface to obtain Clupak paper.

<Example 12>
Clupak paper was obtained under the same conditions as in Example 11, except that the Clupak paper obtained in Example 2 was used.

<Example 13>
The coating solution prepared in Example 11 was applied to one side of the Clupak paper obtained in Example 5 using a reverse roll coater so that the coating amount after heat drying was 10 g/m ² . After that, it was dried at 105° C. for 10 seconds. A nylon film (manufactured by Mitsubishi Chemical Corporation, Superneal 15 μm) was laminated on the surface coated with the adhesive. Furthermore, the coating liquid prepared in Example 11 was applied to the laminated surface using a reverse roll coater so that the coating amount after heat drying was 10 g / m ² , and then 105 ° C. for 10 seconds. dried under the conditions of A linear low-density polyethylene film (LL-XLTN 25 μm, manufactured by Futamura Chemical Co., Ltd.) was laminated on the adhesive-coated surface to obtain Clupak paper.

<Comparative Example 1>
By changing the mass ratio of NUKP (softwood unbleached kraft pulp) and LUKP (hardwood unbleached kraft pulp) to 45:55 by pulping (cooking) wood, and adjusting the discharge amount of pulp without performing Clupak treatment. A paper substrate was obtained under the same conditions as in Example 1, except that the basis weight was changed to 30 g/m ² .

<Comparative Example 2>
NUKP (softwood unbleached kraft pulp) obtained by pulping (cooking) wood and LUKP (hardwood unbleached kraft pulp) were changed to a mass ratio of 45:55, and Clupak treatment was not performed. A paper substrate was obtained under these conditions.

<Comparative Example 3>
By changing the mass ratio of NUKP (softwood unbleached kraft pulp) and LUKP (hardwood unbleached kraft pulp) to 45:55 by pulping (cooking) wood, and adjusting the discharge amount of pulp without performing Clupak treatment. A paper substrate was obtained under the same conditions as in Example 1, except that the basis weight was changed to 100 g/m ² .

<Comparative Example 4>
The mass ratio of NUKP (softwood unbleached kraft pulp) and LUKP (hardwood unbleached kraft pulp) obtained by pulping (cooking) wood was changed to 45:55, and the speed difference before and after Clupak treatment was changed to -15.0m/min. A paper substrate was obtained under the same conditions as in Example 1, except for the above.

<Comparative Example 5>
Clupak paper was obtained under the same conditions as in Example 11, except that the Clupak paper obtained in Comparative Example 1 was used.

<Comparative Example 6>
Clupak paper was obtained under the same conditions as in Example 11, except that the Clupak paper obtained in Comparative Example 2 was used.

The following evaluations were carried out using the obtained Clupak paper or paper substrate.
<Bag flexibility evaluation>
The resulting Clupak paper or paper substrate was cut to obtain a sheet 1 having a longitudinal direction (MD) of 200 mm and a transverse direction (CD) of 150 mm. Double-sided tape 2 with a width of 10 mm (model: Scotch super strong double-sided tape Premier Gold Super Versatile PPS-10, manufactured by 3M) is attached to the sheet 1 as shown in FIG. 100 mm from the end) and fixed so as not to create a gap to obtain a bag 3.
The bag 3 was filled with water, and the filling amount until the water spilled was evaluated. It shows that it is so favorable that a numerical value is large.
4: Filling amount of water is 150 mL or more.
3: Filling amount of water is 100 mL or more and less than 150 mL.
2: Filling amount of water is 50 mL or more and less than 100 mL.
1: Filling amount of water is less than 50 mL.

<Drop impact resistance evaluation>
A bag similar to Bag 3 prepared in <Evaluation of bag flexibility> above was prepared from the obtained Clupak paper or paper substrate. A disk-shaped weight weighing 50 g (product number: 201900401, manufactured by Murakami Kouki Seisakusho Co., Ltd.) is filled into bag 3, sealed with double-sided tape with a width of 10 mm used in <bag flexibility evaluation>, and the weight is filled. I made a bag with The bag filled with the weight was allowed to stand in an environment of 23±5° C. and 50±10% for one day as temperature control and humidity control treatment.
The bag after temperature control and humidity control treatment was dropped from a height of 30 cm onto a SUS plate with the top surface 4 (filling port) of the bag facing up. Further, the dropped bag was similarly dropped with the bottom surface 5 of the bag facing upward. The above-mentioned drop test (the number of drops per bag was 2 times) was carried out for a total of 5 tests per level using newly prepared bags to evaluate the drop impact resistance. It shows that it is so favorable that a numerical value is large.
In all 4:5 tests, the bags did not tear or dent.
In all 3:5 tests, the bag did not tear, but was dented.
In the 2:1-4 tests, the bags were torn.
In all 1:5 tests, the bags were torn.

Table 1 shows physical properties and evaluation results of Examples 1 to 8 and Comparative Examples 1 to 4.

1: sheet, 2: double-sided tape, 3: bag, 4: top surface of bag, 5: bottom surface of bag

Claims (8)

Clupak paper having a paper substrate containing pulp,
The Clupak paper has an ISO stiffness in the longitudinal direction of 0.70 mNm or less, and an ISO stiffness in the transverse direction of the Clupak paper of 0.45 mNm or less, as measured in accordance with ISO2493-1:2010;
The Clupak paper has a puncture strength of 7.50 N or more, as measured in accordance with JIS Z 1707:2019.
Clupak paper characterized by: The Clupak paper has a longitudinal ISO stiffness of 0.10 to 0.20 mNm,
The transverse ISO stiffness of the Clupak paper is 0.10 to 0.20 mNm.
Clupak paper according to claim 1. 3. The Clupak paper according to claim 1, wherein the Clupak paper has a puncture strength of 12.50 N or more. The length-weighted average fiber length of the pulp obtained by defibrating the Clupak paper, measured according to ISO 16065-2:2007, is 1.2 mm to 1.9 mm. Clupak paper according to any one of 1 to 3. Clupak paper according to any one of claims 1 to 4, wherein the paper base has a basis weight of 30 g/m ² to 120 g/m ² . The Clupak paper according to any one of claims 1 to 5, wherein the Clupak paper has a specific puncture strength of 0.13 N/g or more. The Clupak paper according to any one of Claims 1 to 6, wherein the Clupak paper has a thermoplastic resin layer on at least one surface of the paper substrate. A processed paper product, which is a molded body of Clupak paper according to any one of claims 1 to 7.

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