JP7526344B1 - Cushioning paper and paper cushioning - Google Patents

Abstract

[Problem] To obtain a paper cushioning material with excellent cushioning properties and to provide a cushioning paper with excellent folding processability, and further to provide a paper cushioning material obtained from said cushioning paper. [Solution] A cushioning paper having a basis weight of 50 g/m2 to 110 g/m2, a geometric mean value of stiffness in the longitudinal direction and stiffness in the lateral direction measured in accordance with ISO 2493-1:2010 of 0.10 mNm to 0.60 mNm, and a kink index of the pulp fibers constituting the cushioning paper of 3500 (1/m) or less. [Selected Figure] None

Description

The present invention relates to cushioning paper and paper cushioning material.

2. Description of the Related Art Cushioning materials are used to fill gaps that arise between a case, such as a cardboard case for packaging, and an item such as a product when the item is stored inside the case, and to absorb vibrations and shocks that are applied to the item during transportation.
Air caps, air cushions, foam chips, etc. have been used as cushioning materials. Air caps and air cushions are made of resin such as polyethylene, and are made of a resin sheet with many hollow protrusions. Foam chips are relatively small cushioning materials made of foamable resin, and are used to fill the gap between the case and the contents.
From the viewpoint of environmental protection, paper cushioning materials are becoming more and more popular in place of the plastic cushioning materials described above.

Patent Document 1 discloses a method for producing a paper cushioning material that has the advantages of conventional cushioning materials, namely, that it can be produced at low cost, that it is easy to dispose of because it does not generate harmful gases when incinerated, and that it is versatile because it is irregular in shape, and that has excellent cushioning effects. The method aims to provide a paper cushioning material and a method for producing the same, which comprises the steps of: feeding a piece of paper into a hollow drum through a slit formed in the axial direction of the drum; hooking the tip of the piece of paper on the inner surface of the drum; and folding the piece of paper in a zigzag pattern inside the drum by continuing to feed the piece of paper; and then compressing and rolling the zigzag folded piece of paper inside the drum from the end side of the drum by moving a compression plate that can move inside the drum along its axial direction.

Patent No. 4331297

The method of manufacturing paper cushioning described in Patent Document 1 considers a method of manufacturing paper cushioning folded from a piece of paper, but does not consider the cushioning paper itself used for the paper cushioning.
The present invention aims to provide a paper cushioning material having excellent cushioning properties and excellent folding processability. Another object of the present invention is to provide a paper cushioning material obtained from the paper cushioning material.

The inventors have discovered that the above problem can be solved by setting the basis weight of the cushioning paper to a specific range, setting the geometric mean value of the stiffness in the longitudinal and transverse directions to a specific range, and further setting the kink index of the pulp fibers that make up the cushioning paper to a specific value or less.
That is, the present invention relates to the following <1> to <8>.
<1> The basis weight is 50 g/ ^m2 or more and 110 g/ ^m2 or less,
The geometric mean value of the stiffness in the longitudinal direction and the stiffness in the lateral direction measured in accordance with ISO 2493-1:2010 is 0.10 mNm or more and 0.60 mNm or less,
The kink index of the pulp fibers constituting the fiber is 3500 (1/m) or less.
Cushioning paper.
<2> The cushioning paper according to <1>, having a longitudinal stiffness of 0.15 mNm or more and 0.95 mNm or less, and a lateral stiffness of 0.07 mNm or more and 0.45 mNm or less.
<3> The cushioning paper according to <1> or <2>, in which the ratio of stiffness in the vertical direction to stiffness in the horizontal direction (longitudinal stiffness/horizontal stiffness) is 1.3 or more and 3.5 or less.
<4> The cushioning paper according to any one of <1> to <3>, wherein the kink index of the constituent pulp fibers is 2000 (1/m) or more and 3000 (1/m) or less.
<5> The cushioning paper according to any one of <1> to <4>, having a density of 0.50 g/ ^cm3 or more and 0.85 g/ ^cm3 or less.
<6> The cushioning paper according to any one of <1> to <5>, wherein the cushioning paper contains softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP) as raw pulp, and the mass ratio of the softwood unbleached kraft pulp to the hardwood unbleached kraft pulp (NUKP:LUKP) is 40:60 or more and 85:15 or less.
<7> The cushioning paper according to any one of <1> to <6>, wherein the Canadian standard freeness of the raw pulp is 350 mL or more and 550 mL or less.
<8> A paper cushioning material obtained by folding the cushioning paper according to any one of <1> to <7>.

According to the present invention, a paper cushioning material with excellent cushioning properties is obtained, and a cushioning paper with excellent folding processability is provided. Furthermore, according to the present invention, a paper cushioning material obtained from the cushioning paper is provided.

FIG. 2 is a diagram showing an apparatus for evaluating cushioning properties used in the examples. FIG. 2 is a diagram showing an apparatus for evaluating bending processability used in the examples.

[Cushioning paper]
The cushioning paper of this embodiment has a basis weight of 50 g/ ^m2 or more and 110 g/ ^m2 or less, a geometric mean value of longitudinal stiffness and lateral stiffness (also called "mean stiffness") measured in accordance with ISO 2493-1:2010 of 0.10 mNm or more and 0.60 mNm or less, and a kink index of the pulp fibers constituting the paper is 3500 (1/m) or less.
According to the cushioning paper of this embodiment, a paper cushioning material with excellent cushioning properties is obtained, and cushioning paper with excellent folding processability is provided.
In the following description, "cushioning paper with excellent cushioning properties" means that when made into a paper cushioning material, the resulting paper cushioning material has excellent cushioning properties. Also, "excellent folding processability" means that the paper cushioning material can be easily folded using a paper cushioning material manufacturing machine when it is manufactured.
The reason for the above effects is believed to be that a cushioning paper with excellent cushioning properties was obtained by having a basis weight of 50 g/ ^m2 or more and an average stiffness value of 0.10 mNm or more. It is believed that a high average stiffness value increases the recovery from folding, resulting in excellent cushioning properties. It is also believed that a cushioning paper with excellent folding processability was obtained by having a basis weight of 110 g/ ^m2 or less and an average stiffness value of 0.60 mNm or less.
Furthermore, when the kink index is 3500 (1/m) or less, it is considered that the fibers are less likely to bend, resulting in a cushioning paper with excellent cushioning properties.
However, the reason why the above effect is obtained is not limited to this.
Furthermore, the cushioning paper of this embodiment is made of paper mainly made of pulp, which reduces the environmental impact compared to conventional cushioning materials made of plastic.
The present invention will now be described in further detail.

In this specification, a numerical range represented by "X to Y" means a numerical range including X as a lower limit and Y as an upper limit. When a numerical range is described in stages, the upper and lower limits of each numerical range can be combined in any combination.
In addition, the longitudinal direction of the cushioning paper means the machine direction (MD), and the transverse direction means the direction perpendicular to the machine direction (CD).

The cushioning paper of the present embodiment includes a paper base material, and the paper base material includes pulp as a raw material. The manufacturing method and type of pulp are not particularly limited.
The cushioning paper of this embodiment includes at least a paper base material, which may have a coating layer or the like, but is preferably made of only the paper base material. The paper base material may be a single-layer structure or a multi-layer structure. In the case of a multi-layer paper, the number of paper layers is not particularly limited, but is preferably 2 to 7 layers, more preferably 2 to 6 layers.

<Raw pulp>
In this embodiment, the pulp constituting the paper base material is preferably natural pulp fiber from the viewpoint of reducing the environmental load, and as the natural pulp fiber, wood fiber (chemical pulp, mechanical pulp), non-wood fiber, waste paper pulp, etc. are arbitrarily used as necessary. Among the wood fibers, examples of chemical pulp include kraft pulp using caustic soda and sodium sulfide during wood chip cooking, and sulfite pulp using sulfurous acid and hydrogen sulfite. These pulps may be unbleached or bleached (bleached). Examples of mechanical pulp include ground wood pulp (GP) obtained by grinding logs with a grinder, refiner ground wood pulp (RGP) obtained by grinding (refining) waste wood from a lumber mill with a refiner, and thermomechanical pulp (TMP) obtained by heating and refining wood chips.
Among these, softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP) are preferably used.
Among such wood fiber pulps, examples of coniferous trees that are the raw material for coniferous pulp include pine, larch, cedar, fir, cypress, etc. Examples of broad-leaved trees that are the raw material for hardwood pulp include eucalyptus, acacia, birch, beech, maple, elm, chestnut, etc.

Examples of non-wood fibers that can be used in this embodiment include bast fibers such as paper mulberry, mitsumata, gampi, flax, taiman, kenaf, choma, jute, and sunn hemp, seed hair fibers such as cotton and cotton linters, leaf fibers such as Manila hemp, sisal, and esparto, and stem fibers such as bamboo, rice straw, wheat straw, and sugarcane bagasse. Paper mulberry, mitsumata, kenaf, Manila hemp, sisal, cotton, and cotton linters are particularly suitable because they have long fiber lengths and can improve the strength of the base paper of this embodiment. The cooking of non-wood fibers can be carried out in the same manner as that of wood fibers.
Examples of waste paper pulp that can be used in this embodiment include waste cardboard and waste magazine paper.

These pulp fibers can be used alone or in combination of two or more types. In addition, synthetic resin fibers can be mixed as necessary within the scope of the invention, so long as the effects of the invention are not impaired. Examples of synthetic resin fibers that can be used include polyethylene fibers, polypropylene fibers, polyamide fibers, polyethylene terephthalate fibers, polybutylene terephthalate fibers, and polylactic acid fibers.

In this embodiment, from the viewpoint of obtaining the desired stiffness and kink index of the constituent pulp fibers described below, it is preferable that the raw material pulp contains softwood pulp, it is more preferable to use a combination of softwood pulp and hardwood pulp, and it is even more preferable to use a combination of unbleached softwood kraft pulp and unbleached hardwood kraft pulp.
When the cushioning paper contains softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP) as raw material pulp, from the viewpoint of obtaining the desired stiffness and kink index of the constituent pulp fibers described below, the mass ratio of softwood unbleached kraft pulp to hardwood unbleached kraft pulp (NUKP:LUKP) is preferably 40:60 or more and 85:15 or less, more preferably 45:55 or more, even more preferably 50:50 or more, still more preferably 55:45 or more, and more preferably 80:20 or less.
When the cushioning paper contains softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP) as raw material pulp, the total content of NUKP and LUKP in the raw material pulp is preferably 50 mass% or more, more preferably 60 mass% or more, even more preferably 80 mass% or more, still more preferably 90 mass% or more, and even more preferably 95 mass% or more, with no particular upper limit and being 100 mass% or less.
The raw material pulp may also contain recycled paper pulp, but the recycled paper pulp content is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 20% by mass or less, still more preferably 10% by mass or less, and even more preferably 5% by mass or less, from the viewpoint of obtaining the desired stiffness and kink index of the constituent pulp fibers described below.

<Pulp characteristics>
(Kink index)
In this embodiment, the kink index of the pulp fibers constituting the cushioning paper is 3500 (1/m) or less. When the kink index is 3500 (1/m) or less, the pulp fibers are less likely to bend, and the cushioning properties are excellent, which is preferable.
From the viewpoint of improving cushioning properties and obtaining cushioning paper with excellent foldability, the kink index of the pulp fibers constituting the cushioning paper is preferably 1500 (1/m) or more and 3500 (1/m) or less, more preferably 1800 (1/m) or more, even more preferably 2000 (1/m) or more, and is preferably 3300 (1/m) or less, more preferably 3000 (1/m) or less, even more preferably 2800 (1/m) or less.
The kink index (1/m) in the present invention is a Kibblewhite's kink index calculated by the formula (1) described below. The kink index is calculated by weighting the number of kinks in each certain angle range according to the increase in the angle, and dividing the weighted number by the sum of the fiber lengths.
The kink index is measured by the method described in the Examples.

The kink index can be adjusted by the pulp concentration and beating degree when beating the pulp. Specifically, the higher the pulp concentration during beating, the higher the kink index, and the more bent fibers there will be in the pulp fibers that make up the cushioning paper. Also, for the same pulp raw material, the kink index tends to decrease when the beating degree is increased.

(Canadian Standard Freeness)
The Canadian Standard Freeness (CSF) of the raw material pulp of the cushioning paper, measured in accordance with JIS P 8121-2:2012, is preferably 200 mL or more and 800 mL or less, more preferably 250 mL or more, even more preferably 300 mL or more, still more preferably 350 mL or more, and more preferably 700 mL or less, even more preferably 650 mL or less, still more preferably 600 mL or less, and even more preferably 550 mL or less, from the viewpoint of setting the average stiffness and the kink index in the desired ranges. The above CSF is the preferred CSF of the raw material pulp.
On the other hand, the Canadian Standard Freeness (disintegrated freeness) of the pulp obtained by disintegrating the cushioning paper is about 50 mL larger than the CSF of the raw pulp. Here, disintegrated freeness refers to the Canadian Standard Freeness value measured according to the method of JIS P 8121-2:2012 using a pulp slurry obtained by disintegrating the cushioning paper according to the method of JIS P 8220-1:2012.

<Optional ingredients>
The paper base material may contain optional components as necessary, such as anionic, cationic, nonionic or amphoteric retention agents, drainage improvers, dry strength agents, wet strength agents, fillers, fixing agents (aluminum sulfate), internal additives such as sizing agents, dyes, and fluorescent whitening agents.
Examples of dry strength enhancers include cationic starch, polyacrylamide, carboxymethyl cellulose, etc. Among these, polyacrylamide-based dry strength enhancers are preferred from the viewpoint of obtaining the desired specific tensile strength. The content of the dry strength enhancer is not particularly limited, and may be appropriately adjusted to obtain the desired specific tensile strength.
Examples of the wet strength agent include polyamide polyamine epichlorohydrin, urea formaldehyde resin, and melamine formaldehyde resin.
Examples of the filler include inorganic fillers such as talc, kaolin, calcined kaolin, calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, alumina, magnesium carbonate, magnesium oxide, silica, white carbon, bentonite, zeolite, sericite, and smectite, and organic fillers such as acrylic resins and vinylidene chloride resins.
Examples of the sizing agent include internal sizing agents such as rosin sizing agents, synthetic sizing agents, and petroleum resin-based sizing agents, and surface sizing agents such as styrene/acrylic acid copolymers and styrene/methacrylic acid copolymers.

<Manufacturing method of cushioning paper>
The method for producing cushioning paper preferably includes a step of making paper from a slurry containing the above-mentioned raw pulp.
The papermaking method is not particularly limited, and examples thereof include an acidic papermaking method in which papermaking is carried out at a pH of about 4.5, and a neutral papermaking method in which papermaking is carried out at a pH of about 6 to about 9.
In the papermaking process, chemicals for the papermaking process such as a pH adjuster, an antifoaming agent, a pitch control agent, and a slime control agent can be appropriately added as necessary.
The papermaking machine is not particularly limited, and examples thereof include continuous papermaking machines of the Fourdrinier type, cylinder type, and tilt type, and multi-layer papermaking machines that combine these.

In this embodiment, the jet/wire ratio (J/W ratio), which is the ratio between the flow speed (J) of the paper material sprayed onto the wire and the papermaking wire running speed (W) in the papermaking process, may be adjusted appropriately from the viewpoint of setting the ratio of longitudinal stiffness to lateral stiffness (longitudinal stiffness/lateral stiffness) described below within a desired range.

<Characteristics of cushioning paper>
(grammage)
From the viewpoints of cushioning properties and folding processability, the basis weight of the cushioning paper is 50 g/m2 or more and ¹¹⁰ g/ ^m2 or less, preferably 55 g/ ^m2 or more, more preferably 60 g/ ^m2 or more, even more preferably 65 g/ ^m2 or more, still more preferably 70 g/ ^m2 or more, and preferably 105 g/ ^m2 or less, more preferably 100 g/ ^m2 or less.
The basis weight of the cushioning paper is measured in accordance with JIS P 8124:2011.

(thickness)
From the standpoint of cushioning properties and folding processability, the thickness of the cushioning paper is preferably 50 μm or more and 500 μm or less, more preferably 60 μm or more, even more preferably 80 μm or more, still more preferably 100 μm or more, even more preferably 110 μm or more, and more preferably 400 μm or less, even more preferably 350 μm or less, still more preferably 300 μm or less, even more preferably 250 μm or less, and even more preferably 200 μm or less.
The thickness of the cushioning paper is measured in accordance with JIS P 8118:2014, specifically, by the method described in the examples.

(density)
In this embodiment, from the viewpoint of cushioning properties and folding processability, the density of the cushioning paper is preferably 0.50 g/ ^cm3 or more and 0.85 g/ ^cm3 or less. Generally, for the same basis weight, a cushioning material with a lower density has better cushioning properties.
The density of the cushioning paper is more preferably 0.80 g/ ^cm3 or less, more preferably 0.70 g/ ^cm3 or less, and even more preferably 0.68 g/ ^cm3 or less, and from the viewpoint of obtaining the desired specific tensile strength, is preferably 0.55 g/ ^cm3 or more, more preferably 0.60 g/ ^cm3 or more.
The density of the cushioning paper can be appropriately adjusted by adjusting the press pressure in the paper making process.
The density of the cushioning paper is calculated from the thickness and basis weight of the cushioning paper.

(Scary)
The cushioning paper of this embodiment has a geometric mean value (average stiffness value) of the stiffness in the longitudinal direction and the stiffness in the lateral direction measured in accordance with ISO 2493-1:2010 of 0.10 mNm or more and 0.60 mNm or less. The average stiffness value of 0.10 mNm or more is preferable because it provides excellent cushioning properties. The average stiffness value of 0.60 mNm or less is preferable because it provides excellent folding processability.
The average stiffness is more preferably 0.15 mNm or more, even more preferably 0.18 mNm or more, still more preferably 0.20 mNm or more, and more preferably 0.55 mNm or less, even more preferably 0.50 mNm or less, still more preferably 0.45 mNm or less, and even more preferably 0.40 mNm or less.
The stiffness of the cushioning paper can be adjusted to a desired range by the type, beating degree, compounding ratio of the raw pulp, the amount of strength agent (dry strength agent), the thickness, density, basis weight, etc. of the cushioning paper. When NUKP and LUKP are used as the raw pulp, increasing the ratio of NUKP tends to increase the stiffness. Also, increasing the amount of strength agent tends to increase the stiffness. Furthermore, if the basis weight is the same, increasing the thickness tends to increase the stiffness, and if the density is the same, increasing the basis weight tends to increase the stiffness. Also, if the basis weight and thickness are the same, a paper with a lower beating degree and a higher Canadian standard freeness value tends to have a lower stiffness.

From the viewpoints of cushioning properties and folding processability, the stiffness in the longitudinal direction is preferably 0.10 mNm or more and 0.95 mNm or less, more preferably 0.15 mNm or more, even more preferably 0.25 mNm or more, still more preferably 0.30 mNm or more, even more preferably 0.35 mNm or more, even more preferably 0.40 mNm or more, and more preferably 0.85 mNm or less, even more preferably 0.80 mNm or less, still more preferably 0.75 mNm or less, even more preferably 0.70 mNm or less, and even more preferably 0.65 mNm or less.
From the viewpoints of cushioning properties and folding processability, the lateral stiffness is preferably 0.07 mNm or more and 0.45 mNm or less, more preferably 0.09 mNm or more, even more preferably 0.12 mNm or more, still more preferably 0.15 mNm or more, even more preferably 0.18 mNm or more, and more preferably 0.40 mNm or less, even more preferably 0.35 mNm or less, and still more preferably 0.30 mNm or less.

The ratio of stiffness in the vertical direction to stiffness in the horizontal direction (vertical stiffness/horizontal stiffness) (hereinafter also referred to as stiffness aspect ratio) is preferably 1.3 to 3.5. When the stiffness aspect ratio is 1.3 or more, it is preferable because it has excellent folding processability. Also, when the stiffness aspect ratio is 3.5 or less, it is preferable because it has excellent cushioning properties.
The aspect ratio of stiffness is more preferably 1.5 or more, even more preferably 1.7 or more, even more preferably 1.9 or more, even more preferably 2.1 or more, and more preferably 3.2 or less, even more preferably 2.8 or less, even more preferably 2.5 or less.
The aspect ratio of stiffness can be appropriately adjusted by adjusting the J/W ratio in the papermaking process.

[Paper cushioning material]
The paper cushioning material of this embodiment is formed by folding the cushioning paper of this embodiment.
In another embodiment, the cushioning paper of the present embodiment may be processed to have a concave-convex shape to form a paper cushioning material, or may be folded to form a paper cushioning material. When the concave-convex shape is applied, it is preferable to improve the elongation performance by subjecting the cushioning paper to Clupak processing (a process in which the paper shrinks minutely in the vertical direction on a papermaking machine) or the like.
The folding of the cushioning paper may be performed by hand, or may be performed manually or electrically using a cushioning preparation machine, and is not particularly limited. Even when the cushioning paper is folded using an electrically operated cushioning preparation machine to prepare a paper cushioning material, if cushioning paper with poor folding processability is used, the load on the machine tends to be high, and problems such as the cushioning paper becoming jammed or tearing tend to occur.
Examples of cushioning material manufacturing machines on the market include the X-FILL series manufactured by NUEVOPAK, the X-PAD series manufactured by NUEVOPAK, the Padpak series manufactured by Ranpak, the FillPak series manufactured by Ranpak, the PAPERplus series manufactured by Stropack, the ProPad series manufactured by Sealed Air, and the FasFill series manufactured by Sealed Air.
The shape of the cushioning paper is not particularly limited, and may be in a roll, folded form, or sheet form.
The paper cushioning material of this embodiment is preferably used to fill the gap between a case, such as a cardboard case for packaging, and the contents, such as a product, thereby absorbing vibrations, shocks, etc., that are applied to the contents during transportation.

The features of the present invention are explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, processing contents, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below.

[Evaluation and Analysis]
The raw pulp, cushioning paper, and paper cushioning materials of the examples and comparative examples were evaluated and analyzed as follows.

[Raw pulp]
<Measurement of Canadian Standard Freeness (CSF)>
The Canadian Standard Freeness (CSF) of the raw pulp was measured in accordance with JIS P 8121-2:2012.

[Cushioning paper]
<Basance weight>
The cushioning papers obtained in the Examples and Comparative Examples were conditioned for 24 hours under a humidity-conditioning environment specified in JIS P 8111:1998.
The basis weight of the cushioning paper after humidity conditioning was measured in accordance with JIS P 8124:2011.

<Thickness>
The cushioning papers obtained in the Examples and Comparative Examples were conditioned for 24 hours under a humidity-conditioning environment specified in JIS P 8111:1998.
The thickness of the cushioning paper after humidity conditioning was measured in accordance with JIS P 8118:2014.

<Density>
The density was calculated from the measured basis weight and thickness by the formula: basis weight (g/m ² )÷thickness (μm).

<Kink index>
The kink index of the pulp fibers constituting the cushioning paper was measured by the following method.
The obtained cushioning paper was cut into 4 cm squares and soaked in ion-exchanged water for 15 minutes. The soaked cushioning paper was taken out and adjusted to a concentration of 2% with ion-exchanged water. The mixture of the concentration-adjusted cushioning paper and ion-exchanged water was disintegrated for 20 minutes using a standard disintegrator (manufactured by Kumagai Riki Kogyo Co., Ltd.) in accordance with JIS P 8220-1:2012 to obtain a pulp slurry. The obtained pulp slurry was sampled, and the fiber kink index was measured using a fiber length measuring device (model number FS-5 UHD base unit, manufactured by Valmet).
The kink index (1/m) in the present invention is Kibblewhite's kink index calculated by the following formula (1): The kink index was calculated by weighting the number of kinks in each certain angle range according to the increase in angle, and dividing the weighted number by the sum of the fiber lengths.
The measurements were performed in accordance with ISO 16065-2:2007.
The instrument is also capable of detecting and measuring individual fibers using an attached camera, which captures images in a measurement cell with a depth of field of 0.5 mm in accordance with the ISO 16505-2:2007 standard. The instrument captures fiber lengths from 0.01 mm to 10.00 mm.

In the formula (1), n ₁ , n ₂ , n ₃ and L _c are as follows.
n ₁ : Number of kinks in the range of 21° to 45° in all samples. n ₂ : Number of kinks in the range of 46° to 90° in all samples. n ₃ : Number of kinks in the range of 91° to 180° in all samples. L _c : Total fiber length of all samples.

＜Fear＞
The paper base materials obtained in the examples and comparative examples were conditioned for 24 hours in a humidity-conditioning environment specified in JIS P 8111:1998.
The longitudinal and transverse stiffness of the paper substrate after conditioning was measured according to ISO 2493-1:2010 (Paper and paperboard -- Bending resistance test method -- Part 1: Constant speed deflection).
Specifically, the paper substrate after humidity conditioning was cut into a piece having a width of 38 mm and a length of 70 mm, and the bending length was set to 10 mm and the bending angle to 15° using a stiffness tester (L&W BENDING RESISTANCE TESTER Code No. 16-D, manufactured by Lorentzen & Wattre), and the bending resistance in each of the vertical (vertical direction) and horizontal (horizontal direction) directions was measured. The stiffness was then calculated using the following formula.

<Cushioning properties>
The cushioning paper obtained in the examples and comparative examples was cut to a width of 38 cm and a length of 50 m in the flow direction, and after being placed in an automatic paper cushioning manufacturing machine (NUEVOPAK, X-FILL ^™ A type), it was unwound at a speed of 100 m/min to obtain a paper cushioning material 90 cm long.
Next, an enclosure measuring 22.5 cm long x 18 cm wide x 10 cm high was placed on a concrete floor, and the resulting paper cushioning material was folded every 22.5 cm and placed in a bellows shape to cover the bottom of the enclosure (Figure 1).
Next, a 350 mL aluminum can of a soft drink (φ6.6 cm, height 12.2 cm, 370 g, empty can weighs 17 g) was repeatedly dropped vertically from a height of 50 cm onto the cushioning material within the enclosure with the bottom facing vertically downward, and the number of times it took for the can to develop deformation such as dents or scratches was counted.
The test was carried out five times each, and the average number of times (rounded off to the nearest tenth) was used to evaluate the shock-absorbing properties according to the following criteria: If the evaluation was A to C, there was no problem in practical use.
A: Average number of drops is 10 or more B: Average number of drops is 7-9 C: Average number of drops is 4-6 D: Average number of drops is 3 or less

<Bending processability>
The folding processability is the running and unwinding stability in the folding process of a cushioning material manufacturing machine. In the examples, evaluation was performed in a laboratory machine by the following method, simulating practical manufacturing.
The cushioning paper obtained in the examples and comparative examples was cut to A4 size, and the leading end (approximately 5 cm) in the flow direction was folded back alternately in the width direction at 3 cm intervals, and the resulting paper was passed through the folding processing section of a manual paper cushioning manufacturing machine (NUEVOPAK, X-FILL ^™ MM type).
Next, the paper cushioning manual manufacturing machine was installed under the Tensilon universal material testing machine (RTI1310, manufactured by A&D) as shown in Figure 2. At this time, the discharge port of the paper cushioning manual manufacturing machine was installed at an angle of 45° from the test table of the Tensilon universal material testing machine, so that the height of the bottom end of the upper chuck of the Tensilon universal material testing machine was aligned with the center of the discharge port, and the lateral center of the discharge port was aligned with the center of the upper chuck.
Finally, the sash-like cushioning material protruding from the discharge port was gripped by the upper chuck and pulled up at a speed of 1000 mm/min.
The load when passing through the folding section was measured, and the folding processability was evaluated according to the following criteria based on the average value of five tests. If the evaluation was A to C, there was no problem in practical use. Note that the greater the load when passing through the folding section, the stronger the resistance during processing, which in practical use leads to the occurrence of paper jams and unstable running performance, making it difficult to increase the processing speed.
A: The average value of the maximum load is less than 8.0N. B: The average value of the maximum load is 8.0N or more and less than 17.0N. C: The average value of the maximum load is 17.0N or more and less than 22.0N. D: The average value of the maximum load is 22.0N or more.

[Example 1]
As the pulp raw material, softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP) were mixed in a mass ratio of 70:30, and the mixture was beaten using a double disc refiner so that the freeness (CSF: Canadian standard freeness) was 450 mL to obtain a pulp slurry. To 100 parts by mass of the obtained pulp slurry (solid content equivalent), 1.20 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength enhancer (manufactured by Arakawa Chemical Industries, Ltd., product number: PS379) was added as an internal sizing agent, 0.10 parts by mass (solid content equivalent) of a rosin sizing agent (manufactured by Arakawa Chemical Industries, Ltd., Size Pine N-811) was added as an internal sizing agent, and 1.0 part by mass (solid content equivalent) of aluminum sulfate was added to prepare a paper stock.
This paper material was used to make paper using a twin-wire paper machine with a set basis weight of 82 g/ ^m2 . During the papermaking process, the J/W ratio was adjusted so that the aspect ratio of the stiffness of the paper was 2.5±0.3, and the press pressure was adjusted so that the thickness of the paper was 105±5 μm, to obtain the cushioning paper of Example 1.

[Example 2]
A cushioning paper was obtained under the same conditions as in Example 1, except that the pressing pressure was adjusted so that the paper thickness became 130±5 μm.

[Example 3]
A cushioning paper was obtained under the same conditions as in Example 1, except that the pressing pressure was adjusted so that the paper thickness became 155±5 μm.

[Example 4]
Cushioning paper was obtained under the same conditions as in Example 1, except that the set basis weight was 75 g/ ^m2 and the press pressure was adjusted so that the paper thickness was 145±5 μm.

[Example 5]
Cushioning paper was obtained under the same conditions as in Example 1, except that the set basis weight was 95 g/ ^m2 and the press pressure was adjusted so that the paper thickness was 120±5 μm.

[Example 6]
A cushioning paper was obtained under the same conditions as in Example 1, except that the J/W ratio was adjusted so that the aspect ratio of the stiffness of the paper was 1.5±0.3.

[Example 7]
A cushioning paper was obtained under the same conditions as in Example 1, except that the J/W ratio was adjusted so that the aspect ratio of the stiffness of the paper was 3.0±0.3.

[Example 8]
Cushioning paper was obtained under the same conditions as in Example 1, except that the pulp raw material was beaten under conditions such that the CSF was 300 mL.

[Example 9]
Cushioning paper was obtained under the same conditions as in Example 1, except that the pulp raw material was beaten under conditions such that the CSF was 375 mL.

[Example 10]
Cushioning paper was obtained under the same conditions as in Example 1, except that the pulp raw material was beaten under conditions such that the CSF became 525 mL.

[Example 11]
Cushioning paper was obtained under the same conditions as in Example 1, except that the pulp raw material was beaten under conditions such that the CSF was 600 mL.

[Comparative Example 1]
Cushioning paper was obtained under the same conditions as in Example 1, except that the set basis weight was 60 g/ ^m2 and the press pressure was adjusted so that the paper thickness was 80±5 μm.

[Comparative Example 2]
Cushioning paper was obtained under the same conditions as in Example 1, except that the set basis weight was 100 g/ ^m2 and the press pressure was adjusted so that the paper thickness was 185±5 μm.

[Comparative Example 3]
Cushioning paper was obtained under the same conditions as in Example 1, except that the set basis weight was 42 g/ ^m2 and the press pressure was adjusted so that the paper thickness was 80±5 μm.

[Comparative Example 4]
Cushioning paper was obtained under the same conditions as in Example 1, except that the set basis weight was 120 g/ ^m2 and the press pressure was adjusted so that the paper thickness was 150±5 μm.

[Comparative Example 5]
Cushioning paper was obtained under the same conditions as in Example 1, except that the pulp raw material was beaten under conditions such that the CSF became 675 mL.

The obtained cushioning paper was subjected to the above-mentioned evaluations.
The results are shown in the table below.

The results of the Examples and Comparative Examples show that the cushioning paper of the present invention has excellent cushioning properties when used as a cushioning material, as well as excellent folding processability.

The cushioning paper of the present invention has excellent cushioning properties when used as a cushioning material, and also has excellent folding processability, making it ideal for use as a cushioning material.

Claims (8)

The basis weight is 50 g/ ^m2 or more and 110 g/ ^m2 or less,
The geometric mean value of the stiffness in the longitudinal direction and the stiffness in the lateral direction measured in accordance with ISO 2493-1:2010 is 0.10 mNm or more and 0.60 mNm or less,
The kink index of the pulp fibers constituting the fiber is 3500 (1/m) or less.
Cushioning paper. The cushioning paper according to claim 1, having a stiffness in the vertical direction of 0.15 mNm to 0.95 mNm and a stiffness in the horizontal direction of 0.07 mNm to 0.45 mNm. The cushioning paper according to claim 1, in which the ratio of stiffness in the vertical direction to stiffness in the horizontal direction (vertical stiffness/horizontal stiffness) is 1.3 or more and 3.5 or less. The cushioning paper according to claim 1, in which the kink index of the pulp fibers constituting the paper is 2000 (1/m) or more and 3000 (1/m) or less. 2. The cushioning paper according to claim 1, having a density of 0.50 g/cm3 or ^more and 0.85 g/ ^cm3 or less. The cushioning paper according to claim 1, which contains softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP) as raw pulp, and the mass ratio of softwood unbleached kraft pulp to hardwood unbleached kraft pulp (NUKP:LUKP) is 40:60 or more and 85:15 or less. The cushioning paper according to claim 1, wherein the Canadian standard freeness of the raw pulp is 350 mL or more and 550 mL or less. A paper cushioning material obtained by folding the cushioning paper according to any one of claims 1 to 7.