JP7525019B1 - Cushioning paper and paper cushioning - Google Patents

Abstract

The present invention provides a paper cushioning material having excellent cushioning properties and excellent folding processability, and further provides a paper cushioning material obtained from the cushioning paper.
[Solution] The cushioning paper has a density of 0.80 g/cm3 or ^less , and a geometric mean value of the tensile elastic modulus in the longitudinal direction and the tensile elastic modulus in the transverse direction, measured in accordance with JIS P 8113:2006, of 2.4 GPa or more and 4.5 GPa or less.
[Selection diagram] 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 an irregular 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 density of the cushioning paper to a specific value or less and setting the geometric mean value of the longitudinal tensile modulus and the transverse tensile modulus to a specific range.
That is, the present invention relates to the following <1> to <7>.
<1> A cushioning paper having a density of 0.80 g/cm3 or ^less , and a geometric mean value of the tensile elastic modulus in the machine direction and the tensile elastic modulus in the cross direction measured in accordance with JIS P 8113:2006 of 2.4 GPa or more and 4.5 GPa or less.
<2> The cushioning paper according to <1>, having a tensile modulus in the machine direction of 3.8 GPa to 7.5 GPa and a tensile modulus in the cross direction of 1.5 GPa to 3.0 GPa.
<3> The cushioning paper according to <1> or <2>, in which the curl value of the pulp fibers constituting the cushioning paper is 9.0% or less.
<4> The cushioning paper according to any one of <1> to <3>, having a basis weight of 40 g/ ^m2 or more and 150 g/ ^m2 or less.
<5> The cushioning paper according to any one of <1> to <4>, 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 30:70 or more and 80:20 or less.
<6> The cushioning paper according to any one of <1> to <5>, wherein the Canadian Standard Freeness (CSF) of the raw pulp of the cushioning paper is 300 mL or more and 650 mL or less.
<7> A paper cushioning material obtained by folding the cushioning paper according to any one of <1> to <6>.

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 density of 0.80 g/ ^cm3 or less, and a geometric mean value of the longitudinal tensile modulus and the transverse tensile modulus (hereinafter also referred to as the average tensile modulus) measured in accordance with JIS P 8113:2006 of 2.4 GPa or more and 4.5 GPa 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.
The reason for the above effects is believed to be that the density of 0.80 g/ ^cm3 or less forms many voids between the pulp fibers in the paper, resulting in a cushioning paper with excellent cushioning properties. Also, when the average value of the tensile modulus is large, the cushioning properties are excellent, but the folding processability tends to be poor. It is believed that by setting the average value of the tensile modulus within a specific range, a cushioning paper with excellent cushioning properties and folding processability was obtained.
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 tensile modulus and curl value of the constituent pulps 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 pulp and unbleached hardwood 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 tensile modulus and curl value of the constituent pulps described below, the mass ratio of softwood unbleached kraft pulp to hardwood unbleached kraft pulp (NUKP:LUKP) is preferably 30:70 or more and 80:20 or less, more preferably 35:65 or more, even more preferably 40:60 or more, still more preferably 45:55 or more, and more preferably 75:25 or less, even more preferably 70:30 or less, still more preferably 65:35 or less, even more preferably 60:40 or less, and even more preferably 55:45 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.
In addition, recycled paper pulp may be contained as the raw material pulp, but the recycled paper pulp content is preferably 50 mass% or less, more preferably 40 mass% or less, even more preferably 20 mass% or less, still more preferably 10 mass% or less, and even more preferably 5 mass% or less, from the viewpoint of obtaining the desired tensile modulus of elasticity and curl value of the constituent pulp, as described below.

<Pulp characteristics>
(Curl value)
The curl value of pulp (also called the curl index) is an index that indicates the degree of gradual bending of the fibers. The bending affects the elastic modulus and elongation of the single fiber, and ultimately the elongation and strength of the entire cushioning paper.
The curl value of the pulp fibers constituting the cushioning paper of this embodiment is preferably 9.0% or less. When the curl value of the pulp fibers constituting the cushioning paper is 9.0% or less, a high tensile modulus of elasticity is obtained and the cushioning properties are improved, which is preferable. It is believed that a small curl value improves the modulus of elasticity of the single fiber, and as a result, the tensile modulus of elasticity is high and the cushioning properties of the cushioning paper are improved. The curl value is more preferably 8.0% or less, even more preferably 7.5% or less, even more preferably 7.0% or less, and even more preferably 6.5% or less. There is no particular lower limit, but from the viewpoint of ease of production, it is preferably 3.0% or more.

The curl value of the pulp constituting the paper base material is expressed as follows, using the length of the pulp fibers when stretched straight (contour length, _L1 ) and the length of the fibers in a curled state (the distance between the two farthest points on the same fiber, _L2 ).
Curl value (%)=(L ₁ −L ₂ )/L ₂ ×100
Here, the fiber length (L ₁ ) and the fiber length (L ₂ ) are calculated as length-weighted average values for the lengths of fibers measured by selecting fibers having a length of 0.2 mm or more and 7.6 mm or less.
_L1 and _L2 are calculated by image processing. _L1 is calculated by image processing (measuring the contour length) so that the fiber length is at its longest, and _L2 is calculated by image processing (measuring the length of the two furthest points on the same fiber) so that the length is at its longest in a curled (bent) state.
Specifically, it is measured by the method described in the Examples, and the measurement is performed on the pulp obtained after disintegrating the cushioning paper.
The curl value can be adjusted to a desired range by appropriately adjusting the type of pulp raw material used. In general, softwood pulp tends to have a higher curl value than hardwood pulp, and hardwood pulp tends to have a higher curl value than recycled paper pulp. Furthermore, the curl value tends to increase by increasing the concentration of the pulp slurry when beating the pulp raw material. Therefore, the curl value of the pulp that constitutes the cushioning paper can be adjusted by adjusting the concentration of the pulp slurry when beating.

(Canadian Standard Freeness)
The Canadian Standard Freeness (CSF) of the pulp constituting the cushioning paper, measured in accordance with JIS P 8121-2:2012, is preferably 300 mL or more and 650 mL or less, more preferably 350 mL or more, even more preferably 380 mL or more, and more preferably 600 mL or less, even more preferably 550 mL or less, and still more preferably 500 mL or less, from the viewpoints of cushioning properties and folding processability. 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 8121:2012 using a pulp slurry obtained by disintegrating the cushioning paper according to the method of JIS P 8121:2012.

<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 a desired tensile modulus of elasticity. The content of the dry strength enhancer is not particularly limited, and may be appropriately adjusted to obtain a desired tensile modulus of elasticity.
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 appropriately adjusted from the viewpoint of setting the ratio of the longitudinal tensile modulus to the transverse tensile modulus (longitudinal tensile modulus/transverse tensile modulus) described below in a desired range.

<Characteristics of cushioning paper>
(density)
From the viewpoint of cushioning properties and folding processability, the cushioning paper of this embodiment has a density of 0.80 g/cm ³ 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 preferably 0.75 g/ ^cm3 or less, more preferably 0.70 g/ ^cm3 or less, and even more preferably 0.65 g/ ^cm3 or less, and from the viewpoint of obtaining the desired tensile elastic modulus, is preferably 0.40 g/ ^cm3 or more, more preferably 0.50 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.

(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 350 μm or less, even more preferably 300 μm or less, still more preferably 250 μm or less, even more preferably 200 μm or less, and even more preferably 175 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.

(grammage)
From the viewpoints of cushioning properties and folding processability, the basis weight of the cushioning paper is preferably 30 g/m2 or more and 250 g/ ^m2 or ^less , more preferably 40 g/ ^m2 or more, even more preferably 50 g/ ^m2 or more, still more preferably 60 g/ ^m2 or more, even more preferably 65 g/ ^m2 or more, and more preferably 200 g/ ^m2 or less, even more preferably 150 g/ ^m2 or less, still more preferably 130 g/ ^m2 or less, even more preferably 120 g/ ^m2 or less, and even more preferably 100 g/ ^m2 or less.
The basis weight of the cushioning paper is measured in accordance with JIS P 8124:2011.

(Tensile Modulus)
The cushioning paper of this embodiment has a geometric mean value (average value of tensile modulus) of the longitudinal tensile modulus and the transverse tensile modulus measured in accordance with JIS P 8113: 2006 of 2.4 GPa or more and 4.5 GPa or less. A tensile modulus of 2.4 GPa or more is preferable because of excellent cushioning properties. Also, a tensile modulus of 4.5 GPa or less is preferable because of excellent folding processability.
From the above viewpoints, the average tensile elastic modulus of the cushioning paper is preferably 2.7 GPa or more, more preferably 2.9 GPa or more, and is preferably 4.2 GPa or less, more preferably 3.9 GPa or less.
The tensile modulus of the cushioning paper is measured in accordance with JIS P 8113:2006, and the geometric mean value of the tensile modulus in the machine direction and the tensile modulus in the cross direction is calculated.
The tensile modulus of the cushioning paper can be adjusted to a desired range by the type, blending ratio, beating degree, amount of strength agent (dry strength agent) blended, density of the cushioning paper, etc. When NUKP and LUKP are used as the raw pulp, increasing the ratio of NUKP tends to increase the tensile modulus. Also, increasing the beating degree of the raw pulp, i.e., when the Canadian Standard Freeness is low, the tensile modulus tends to increase. Furthermore, increasing the amount of strength agent blended tends to increase the tensile modulus.

From the viewpoints of cushioning properties and bending processability, the tensile modulus in the longitudinal direction is preferably 3.8 GPa or more and 7.5 GPa or less, more preferably 4.0 GPa or more, even more preferably 4.2 GPa or more, still more preferably 4.5 GPa or more, and more preferably 7.0 GPa or less, even more preferably 6.5 GPa or less.
From the viewpoints of cushioning properties and bending processability, the tensile modulus in the lateral direction is preferably 1.5 GPa or more and 3.0 GPa or less, more preferably 1.6 GPa or more, and more preferably 2.8 GPa or less, and further preferably 2.6 GPa or less.

The ratio of the tensile modulus in the longitudinal direction to the tensile modulus in the transverse direction (tensile modulus in the longitudinal direction/tensile modulus in the transverse direction) (hereinafter also referred to as the aspect ratio of the tensile modulus) is preferably 1.5 or more and 5.5 or less. When the aspect ratio of the tensile modulus is 1.5 or more, it is preferable because it has excellent bending processability. Also, when the aspect ratio of the tensile modulus is 5.5 or less, it is preferable because it has excellent cushioning properties.
The aspect ratio of the tensile elastic modulus is more preferably 1.8 or more, further preferably 2.0 or more, and more preferably 4.5 or less, further preferably 3.5 or less, and further preferably 3.0 or less.
The aspect ratio of the tensile elastic modulus 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]
<Curl value>
The curl value 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 removed 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 8220-2:2012 to obtain a pulp slurry. The obtained pulp slurry was sampled, and the curl value of the fibers was measured using a fiber length measuring device (model number FS-5 UHD base unit, manufactured by Valmet).

<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>
From the measured basis weight and thickness, the density was calculated by the formula: basis weight (g/m ² )÷paper thickness (μm).

<Tensile modulus>
The cushioning papers obtained in the examples and comparative examples were conditioned for 24 hours in a humidity-conditioned environment specified in JIS P 8111: 1998, and then the tensile modulus of the conditioned cushioning papers was measured in accordance with JIS P 8113: 2006. The tensile modulus was measured in the machine direction (papermaking direction, MD) and the cross direction (direction perpendicular to the papermaking direction, CD).
The test was carried out using a horizontal tensile tester (manufactured by Lorentzen & Wattre, CODE SE-064), and the geometric mean values of the obtained tensile elastic modulus in the machine direction and the tensile elastic modulus in the transverse direction were calculated.

<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 50:50, and the mixture was beaten using a double disc refiner so that the freeness (CSF: Canadian standard freeness) was 500 mL to obtain a pulp slurry. To 100 parts by mass of the obtained pulp slurry (solid content equivalent), 0.70 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 with a set basis weight of 95 g/ ^m2 using a twin-wire paper machine. During the papermaking process, the press pressure was adjusted so that the paper thickness was 150±5 μm, and the cushioning paper of Example 1 was obtained.

[Example 2]
A cushioning paper was obtained under the same conditions as in Example 1, except that the freeness was set to 450 mL.

[Example 3]
A cushioning paper was obtained under the same conditions as in Example 1, except that the freeness was set to 400 mL.

[Example 4]
A cushioning paper was obtained under the same conditions as in Example 2, except that 0.75 parts by mass of a polyacrylamide-based internal paper strength agent was added and the pressing pressure was adjusted so that the paper thickness became 170±5 μm.

[Example 5]
A cushioning paper was obtained under the same conditions as in Example 2, except that 0.65 parts by mass of a polyacrylamide-based internal paper strength agent was added and the pressing pressure was adjusted so that the paper thickness became 125±5 μm.

[Example 6]
Cushioning paper was obtained under the same conditions as in Example 2, except that softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP) were mixed in a mass ratio of 70:30 as the pulp raw materials, and 0.60 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength enhancer was added.

[Example 7]
Cushioning paper was obtained under the same conditions as in Example 2, except that softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP) were mixed in a mass ratio of 40:60 as the pulp raw materials, and 0.85 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength agent was added.

[Example 8]
Cushioning paper was obtained under the same conditions as in Example 1, except that the set basis weight was 70 g/ ^m2 and the press pressure was adjusted so that the paper thickness was 115±5 μm.

[Example 9]
Cushioning paper was obtained under the same conditions as in Example 2, except that the set basis weight was 70 g/ ^m2 and the press pressure was adjusted so that the paper thickness was 115±5 μm.

[Example 10]
Cushioning paper was obtained under the same conditions as in Example 3, except that the set basis weight was 70 g/ ^m2 and the press pressure was adjusted so that the paper thickness was 115±5 μm.

[Example 11]
A cushioning paper was obtained under the same conditions as in Example 9, except that 0.75 parts by mass of a polyacrylamide-based internal paper strength agent was added and the press pressure was adjusted so that the paper thickness became 125±5 μm.

[Example 12]
A cushioning paper was obtained under the same conditions as in Example 9, except that 0.65 parts by mass of a polyacrylamide-based internal paper strength agent was added and the pressing pressure was adjusted so that the paper thickness became 95±5 μm.

[Example 13]
Cushioning paper was obtained under the same conditions as in Example 2, except that the set basis weight was 50 g/ ^m2 and the press pressure was adjusted so that the paper thickness was 80±5 μm.

[Example 14]
Cushioning paper was obtained under the same conditions as in Example 2, except that the set basis weight was 135 g/ ^m2 and the press pressure was adjusted so that the paper thickness was 200±5 μm.

[Comparative Example 1]
A cushioning paper was obtained under the same conditions as in Example 1, except that the freeness was set to 550 mL.

[Comparative Example 2]
A cushioning paper was obtained under the same conditions as in Example 1, except that the freeness was set to 350 mL.

[Comparative Example 3]
A cushioning paper was obtained under the same conditions as in Example 2, except that 0.60 parts by mass of a polyacrylamide-based internal paper strength agent was added and the pressing pressure was adjusted so that the paper thickness became 110±5 μm.

[Comparative Example 4]
A cushioning paper was obtained under the same conditions as in Example 8, except that the freeness was set to 550 mL.

[Comparative Example 5]
A cushioning paper was obtained under the same conditions as in Example 8, except that the freeness was set to 350 mL.

[Comparative Example 6]
A cushioning paper was obtained under the same conditions as in Example 9, except that 0.60 parts by mass of a polyacrylamide-based internal paper strength agent was added and the pressing pressure was adjusted so that the paper thickness became 80±5 μm.

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 paper cushioning material, as well as excellent folding processability.

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

Claims (6)

A cushioning paper,
The density is 0.70 g/cm3 ^or less,
The basis weight is 40 g/m2 ^or more and 150 g/m2 ^or less,
The geometric mean value of the tensile elastic modulus in the longitudinal direction and the tensile elastic modulus in the transverse direction measured in accordance with JIS P 8113:2006 is 2.4 GPa or more and 4.5 GPa or less,
The curl value of the pulp fibers constituting the cushioning paper is 7.5% or less .
Cushioning paper. The cushioning paper according to claim 1, in which the longitudinal tensile modulus is 3.8 GPa or more and 7.5 GPa or less, and the transverse tensile modulus is 1.5 GPa or more and 3.0 GPa or less. 2. The cushioning paper according to claim 1, having a basis weight of 50 g/m2 or more and 130 g/ ^m2 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 30:70 or more and 80:20 or less. The cushioning paper according to claim 1, wherein the Canadian Standard Freeness (CSF) of the raw pulp of the cushioning paper is 300 mL or more and 650 mL or less. A paper cushioning material obtained by folding the cushioning paper according to any one of claims 1 to 5 .