Cushioning material sheet and paper cushioning material

Abstract

To provide a cushioning material sheet that enables the formation of a paper cushioning material with superior cushioning properties even at high humidity, while exhibiting superior bending workability, and to further provide a paper cushioning material formed from the cushioning material sheet.SOLUTION: A cushioning material sheet is characterized in that the geometric mean of the longitudinal-direction specific tensile energy absorption and the transverse-direction specific tensile energy absorption measured in accordance with JIS P 8113: 2006 is 500 mJ / g or more and 3500 mJ / g or less, and the front-back average of the Stockigt size degree is 20 seconds or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to cushioning paper and paper cushioning. [Background technology]

[0002] Cushioning materials are used to fill gaps that arise between a case, such as a cardboard case for packaging, and the contents when the products or other contents are placed inside the case, and to absorb vibrations and shocks that are applied to the contents 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 foaming resin, and are used to fill the gap between the case and the contents. From the standpoint of environmental protection, paper cushioning materials are becoming more and more popular in place of the plastic cushioning materials mentioned above.

[0003] Patent Document 1 aims to provide a paper cushioning material and a manufacturing method thereof that retains the advantages of conventional cushioning materials, namely, that it can be manufactured cheaply, 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, while also having excellent cushioning effects. The manufacturing method of the paper cushioning material is characterized in that a piece of paper is supplied into a hollow drum through a slit formed in the drum along the axial direction, the tip of the piece of paper is hooked on the inner surface of the hollow drum, and the supply of the piece of paper is continued to fold the piece of paper in a zigzag pattern inside the hollow drum, and then the zigzag folded piece of paper inside the hollow drum is compressed and rolled up from the end side of the hollow drum by moving a compression plate that can move inside the hollow drum along its axial direction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4331297 Summary of the Invention [Problem to be solved by the invention]

[0005] 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 that has excellent cushioning properties even under high humidity conditions and has excellent folding processability. Another object of the present invention is to provide a paper cushioning material obtained from the paper cushioning material. [Means for solving the problem]

[0006] The inventors have found that the above problem can be solved by setting the geometric mean value of the specific tensile energy absorption amount in the longitudinal direction and the specific tensile energy absorption amount in the transverse direction within a specific range, and further setting the average value of the front and back Stockigt sizing degree to a specific value or more. That is, the present invention provides the following: <1> ~ <7> Regarding. <1> Cushioning paper having a geometric mean value of the specific tensile energy absorption in the longitudinal direction and the specific tensile energy absorption in the transverse direction, measured in accordance with JIS P 8113:2006, of 500 mJ / g to 3,500 mJ / g, and a front-back average value of the Stockigt sizing degree of 20 seconds or more. <2> The specific tensile energy absorption in the longitudinal direction is 400 mJ / g or more and 3500 mJ / g or less, and the specific tensile energy absorption in the transverse direction is 500 mJ / g or more and 3000 mJ / g or less. <1> Cushioning paper as described above. <3> The thickness is 50 μm or more and 250 μm or less. <1> or <2> Cushioning paper as described above. <4> Basis weight 40g / m 2 More than 150g / m 2 Below is the <1> ~ <3> Cushioning paper as described in any one of the above. <5> The geometric mean value of the specific tensile energy absorption amount in the longitudinal direction and the specific tensile energy absorption amount in the transverse direction is 800 mJ / g or more and 2500 mJ / g or less, and the Stockigt sizing degree is 45 seconds or more. <1> ~ <4> Cushioning paper as described in any one of the above. <6> It has been treated with Clupak. <1> ~ <5> Cushioning paper as described in any one of the above. <7> <1> ~ <6> 13. A paper cushioning material obtained by folding the cushioning paper described in any one of the above. Effect of the Invention

[0007] According to the present invention, a paper cushioning material having excellent cushioning properties even under high humidity conditions is obtained, and a paper cushioning material having excellent folding processability is provided. Furthermore, according to the present invention, a paper cushioning material obtained from the paper cushioning material is provided. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram showing an apparatus for evaluating cushioning properties used in the examples. [Diagram 2] FIG. 2 is a diagram showing an apparatus for evaluating bending processability used in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Cushioning paper] The cushioning paper of this embodiment has a geometric mean value of the specific tensile energy absorption in the longitudinal direction and the specific tensile energy absorption in the transverse direction (hereinafter also referred to as the average specific tensile energy absorption value) of 500 mJ / g or more and 3500 mJ / g or less, as measured in accordance with JIS P 8113:2006, and the average value of the front and back Stockigt sizing degree is 20 seconds or more. According to the cushioning paper of this embodiment, a paper cushioning material that has excellent cushioning properties even under high humidity conditions is obtained, and cushioning paper that has excellent folding processability is provided. There has been a problem in that the strength of the cushioning paper is reduced in a high humidity environment such as in summer or the rainy season, or due to condensation that occurs during refrigeration or freezing, resulting in a decrease in the cushioning performance of the paper cushioning. In other words, the inventors have found that in a high humidity environment, the cushioning paper becomes soft and its strength is reduced, resulting in a decrease in cushioning performance. In the cushioning paper of this embodiment, by setting the average value of the Stöckigt sizing degree of the cushioning paper on both sides to 20 seconds or more, it is believed that the decrease in cushioning properties is suppressed even at high humidity. Furthermore, the larger the average value of the specific tensile energy absorption, the better the cushioning property, but the worse the folding processability. It is believed that by setting the average value of the specific tensile energy absorption within a specific range, a cushioning paper with both 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.

[0010] 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 arbitrarily combined. In addition, the machine direction of the cushioning paper means the machine direction (MD), and the cross direction means the direction perpendicular to the machine direction (CD).

[0011] 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.

[0012] <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 wood fibers, examples of chemical pulp include kraft pulp, which uses caustic soda and sodium sulfide during wood chip cooking, and sulfite pulp, which uses 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.

[0013] 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 stretchability and strength of the base paper of this embodiment. The cooking of non-wood fibers can be carried out in the same manner as for wood fibers. Examples of waste paper pulp that can be used in this embodiment include waste cardboard and waste magazine paper.

[0014] These pulp fibers can be used alone or in combination of two or more kinds. In addition, synthetic resin fibers can be mixed as necessary within a range that does not impair the effects of the present invention. 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.

[0015] In this embodiment, from the viewpoint of obtaining the desired specific tensile energy absorption amount 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 unbleached softwood kraft pulp (NUKP) and unbleached hardwood kraft pulp (LUKP) as raw material pulp, from the viewpoint of obtaining a desired specific tensile energy absorption amount described below, the mass ratio of unbleached softwood kraft pulp to unbleached hardwood kraft pulp (NUKP:LUKP) is preferably 30:70 or more and 80:20 or less, more preferably 40:60 or more, even more preferably 50:50 or more, still more preferably 55:45 or more, and more preferably 75:25 or less, even more preferably 70:30 or less, and still more preferably 65:35 or less. When the cushioning paper contains softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP) as raw pulp, the total content of NUKP and LUKP in the raw 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, 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 specific tensile energy absorption amount described below.

[0016] <Pulp characteristics> (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 400 mL or more, still more preferably 420 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 JIS P 8121:2012 method using a pulp slurry obtained by disintegrating the cushioning paper according to the JIS P 8121:2012 method.

[0017] <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. Dry strength agents include cationic starch, polyacrylamide, carboxymethyl cellulose, and the like. Among these, polyacrylamide-based dry strength agents are preferred from the viewpoint of obtaining a desired specific tensile energy absorption. The content of the dry strength agent is not particularly limited, and may be appropriately adjusted to obtain a desired specific tensile energy absorption. In addition, from the viewpoint of obtaining a desired Stockigt sizing degree, it is preferable to add a sizing agent, and more preferably a rosin sizing agent. The content of the sizing agent is not particularly limited, and may be appropriately adjusted so as to obtain a desired Stockigt sizing degree. 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.

[0018] <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.

[0019] (Clupak Processing) The cushioning paper is preferably Clupak-treated, which is a process that gives the paper longitudinal stretchability by minutely shrinking the paper longitudinally on the papermaking machine. The specific manufacturing method is to install a Clupak device in a part of the papermaking machine dryer, pass the wet paper between an endless thick elastic rubber blanket with nip rolls and a heated dryer, and the blanket, which has been stretched in advance, shrinks the running paper web, increasing the longitudinal breaking elongation. The shrinkage is then dried and fixed so that it does not stretch in the subsequent process. In the Clupak device, the longitudinal breaking elongation can be adjusted mainly by the ratio of the production speed at the inlet side of the Clupak device to the production speed at the outlet side of the Clupak device, and the pressure applied by the nip rolls. As a result, the longitudinal tensile energy ratio can also be adjusted. From the viewpoint of obtaining a desired specific tensile energy absorption amount, the speed difference before and after the Clupak treatment is preferably -45% or more and 0% or less, more preferably -40% or more, even more preferably -35% or more, and even more preferably -5% or less, and even more preferably -10% or less. Note that the minus sign "-" indicates that the speed after the Clupak treatment is slower.

[0020] <Characteristics of cushioning paper> (density) The cushioning paper of the present embodiment has a density of 0.90 g / cm3 from the viewpoints of cushioning properties and folding processability. 3 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 0.85g / cm 3More preferably, 0.80 g / cm 3 More preferably, 0.75 g / cm 3 and preferably 0.50 g / cm 3 More preferably, 0.55 g / cm 3 More preferably, 0.60 g / cm 3 That's all. 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.

[0021] (Thickness) From the standpoint of cushioning properties and folding processability, the thickness of the cushioning paper is preferably 50 μm or more and 250 μm or less, more preferably 65 μm or more, even more preferably 80 μm or more, even more preferably 100 μm or more, still more preferably 110 μm or more, and more preferably 225 μm or less, even more preferably 200 μm or less, even more preferably 175 μm or less, and still more preferably 150 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.

[0022] (Basic weight) The basis weight of the cushioning paper is preferably 30 g / m from the viewpoints of cushioning properties and folding processability. 2 More than 250g / m 2 More preferably, it is 40 g / m or less. 2 More preferably, 50 g / m 2 More preferably, 60 g / m 2 More preferably, it is 150 g / m or more. 2 More preferably, 130 g / m or less 2 More preferably, 120 g / m 2 More preferably 110 g / m 2 More preferably, 100 g / m 2 The following is the result. The basis weight of the cushioning paper is measured in accordance with JIS P 8124:2011.

[0023] (Average specific tensile energy absorption) The cushioning paper of this embodiment has a geometric mean value (average value of specific tensile energy) of the specific tensile energy absorption in the longitudinal direction and the specific tensile energy absorption in the transverse direction measured in accordance with JIS P 8113:2006 of 500 mJ / g or more and 3500 mJ / g or less. An average value of specific tensile energy absorption of 500 mJ / g or more is preferable because it provides excellent cushioning properties. Also, an average value of 3500 mJ / g or less is preferable because it provides excellent folding processability. From the above viewpoints, the average specific tensile energy absorption of the cushioning paper is preferably 600 mJ / g or more, more preferably 700 mJ / g or more, even more preferably 800 mJ / g or more, and preferably 3000 mJ / g or less, more preferably 2500 mJ / g or less, even more preferably 2000 mJ / g or less. The specific tensile energy absorption of the cushioning paper is measured in accordance with JIS P 8113:2006, and the specific tensile energy absorption in the longitudinal direction and the tensile energy absorption in the transverse direction are measured, and the geometric mean value is calculated. Specifically, the measurement is performed according to the method described in the Examples. The specific tensile energy absorption of cushioning paper can be adjusted to a desired range by the type of raw pulp, the blending ratio, the degree of beating, the blending amount of paper strength agent (dry paper strength enhancer), the speed difference before and after Clupak treatment, the density of the cushioning paper, etc. Increasing the speed difference before and after Clupak treatment tends to increase the specific tensile energy absorption. Also, increasing the blending amount of paper strength agent tends to increase the specific tensile energy.

[0024] From the viewpoints of cushioning properties and folding processability, the specific tensile energy absorption in the longitudinal direction is preferably 400 mJ / g or more and 3500 mJ / g or less, more preferably 500 mJ / g or more, even more preferably 600 mJ / g or more, still more preferably 700 mJ / g or more, even more preferably 800 mJ / g or more, even more preferably 900 mJ / g or more, and more preferably 2500 mJ / g or less, even more preferably 2300 mJ / g or less, even more preferably 2100 mJ / g or less, and even more preferably 2000 mJ / g or less. In addition, from the viewpoints of cushioning properties and folding processability, the specific tensile energy absorption amount in the lateral direction is preferably 500 mJ / g or more and 3000 mJ / g or less, more preferably 600 mJ / g or more, even more preferably 650 mJ / g or more, and more preferably 2500 mJ / g or less, even more preferably 2000 mJ / g or less, and even more preferably 1500 mJ / g or less.

[0025] The cushioning paper of this embodiment has a front and back average Stockigt sizing degree of 20 seconds or more. When the front and back average Stockigt sizing degree is 20 seconds or more, deterioration of cushioning properties under high humidity conditions is suppressed, which is preferable. The average value of the front and back Stoeckigt sizing degree is preferably 25 seconds or more, more preferably 30 seconds or more, even more preferably 40 seconds or more, and even more preferably 45 seconds or more, and the upper limit is not particularly limited, but from the viewpoint of ease of production, it is 200 seconds or less. The average value of the Stoeckigt sizing degree on both sides is measured in accordance with JIS P 8112:2004, and is the arithmetic mean value of the Stoeckigt sizing degrees measured on the front side and the back side of the cushioning paper. Specifically, it is measured by the method described in the examples.

[0026] The Stockigt sizing degree of the front and back surfaces is preferably 20 seconds or more, more preferably 25 seconds or more, even more preferably 30 seconds or more, still more preferably 40 seconds or more, and even more preferably 45 seconds or more, and the upper limit is not particularly limited, but is 200 seconds or less from the viewpoint of ease of production.

[0027] In one preferred embodiment of the cushioning paper of this embodiment, the geometric mean value of the specific tensile energy absorption in the longitudinal direction and the specific tensile energy absorption in the transverse direction is 800 mJ / g or more and 2500 mJ / g or less, and the Stockigt sizing degree is 45 seconds or more.

[0028] [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 currently 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 Storopack, 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. EXAMPLES

[0029] The features of the present invention will be described 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 appropriately changed 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.

[0030] [Evaluation and Analysis] The raw pulp, cushioning paper, and paper cushioning materials of the examples and comparative examples were evaluated and analyzed as follows.

[0031] [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.

[0032] [Cushioning paper] <Basic weight> 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. The basis weight of the cushioning paper after humidity conditioning was measured in accordance with JIS P 8124:2011.

[0033] <Thickness> 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. The thickness of the cushioning paper after humidity conditioning was measured in accordance with JIS P 8118:2014.

[0034] <density> From the measured basis weight and thickness, the basis weight value (g / m 2 The density was calculated using the formula: Paper thickness (μm) / Paper thickness (μm).

[0035] <Tensile Energy Absorption (TEA)> 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. The tensile energy absorption of the cushioning paper after conditioning was measured in accordance with JIS P 8113: 2006. The tensile energy absorption was measured in the machine direction (papermaking direction, MD) and the cross direction (direction perpendicular to the papermaking direction, CD). The test was performed using a horizontal tensile tester (Lorentzen & Wattre, CODE SE-064), and the specific tensile energy absorption was calculated by dividing the obtained tensile energy absorption by the basis weight. The geometric mean values ​​of the obtained specific tensile energy absorption in the longitudinal direction and the specific tensile energy absorption in the transverse direction were calculated.

[0036] <Stockigt size> 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. The Stockigt sizing degree of the cushioning paper after humidity conditioning was measured in accordance with JIS P 8122:2004.

[0037] <Buffering 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 then filled into an automatic paper cushioning manufacturing machine (NUEVOPAK X-FILL TM After being placed on the roll (Type A), it was unwound at a speed of 100 m / min to obtain a 90 cm long paper cushioning material. The resulting paper cushioning material was conditioned for 24 hours at 30° C. and 90% RH. 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 40 cm onto the cushioning material within the enclosure with the bottom facing vertically downwards, 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 falls is 10 or more B: Average number of falls is 7-9 C: Average number of falls is 4-6 D: Average number of falls is 3 or less

[0038] <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 into A4 size, and the leading edge (approximately 5 cm) in the flow direction was folded back alternately in the width direction at 3 cm intervals to form a paper cushioning sheet. The paper was then fed into a manual paper cushioning production machine (NUEVOPAK, X-FILL) TM It was passed through the bent part of a 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 set at an angle of 45° from the test table of the Tensilon universal material testing machine, the height of the bottom edge of the Tensilon universal material testing machine's upper chuck was aligned with the center of the discharge port, and the horizontal center of the discharge port was aligned with the center of the upper chuck. Finally, the spool-shaped cushioning material protruding from the discharge outlet was grabbed 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 paper jams and unstable running, making it difficult to increase the processing speed. A: The average maximum load is less than 8.0N B: The average maximum load is 8.0N or more and less than 17.0N C: Average maximum load is 17.0N or more and less than 22.0N D: The average maximum load is 22.0N or more.

[0039] [Example 1] As pulp raw materials, softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP) were mixed in a mass ratio of 60:40 and beaten using a double disc refiner to obtain a pulp slurry with a freeness (CSF: Canadian standard freeness) of 450 mL. To 100 parts by mass of the obtained pulp slurry (based on solid content), 0.80 parts by mass (based on solid content) of a polyacrylamide-based internal paper strength enhancer (manufactured by Arakawa Chemical Industries, Ltd., product number: PS379), 0.20 parts by mass (based on solid content) of a rosin sizing agent (manufactured by Arakawa Chemical Industries, Ltd., Size Pine N-811) as an internal sizing agent, and 1.0 part by mass (based on solid content) of aluminum sulfate were added to prepare a paper stock. Using this paper stock, the basis weight was set at 85g / m 2 During the papermaking process, the press pressure was adjusted so that the paper thickness was 115±5 μm, and the cushioning paper of Example 1 was obtained.

[0040] [Example 2] Using the paper material described in Example 1, paper was made on a wet papermaking machine (Bellform III type, manufactured by Mitsubishi Heavy Industries, Ltd.) equipped with an expansion device (manufactured by Clupak) at a papermaking speed of 600 m / min, a reel moisture content of 6.5%, a nip pressure by calendaring of 150 kN / m, a speed difference before and after Clupak treatment of -14.0%, and a nip pressure between the nip roll and the blanket during Clupak treatment of 15 kN / m. The basis weight of the paper with crepe applied to the surface was 85 g / m. 2 The cushioning paper was obtained. The cushioning paper was produced in the following order: papermaking, dehydration by calendaring, and Clupak treatment (including drying). The obtained cushioning paper was used as the cushioning paper of Example 2.

[0041] [Example 3] Cushioning paper was obtained under the same conditions as in Example 2, except that the speed difference before and after the Clupac treatment was set to -30.0%.

[0042] [Example 4] A cushioning paper was obtained under the same conditions as in Example 2, except that 0.05 parts by mass of a rosin sizing agent was added as an internal sizing agent.

[0043] [Example 5] A cushioning paper was obtained under the same conditions as in Example 2, except that 0.45 parts by mass of a rosin sizing agent was added as an internal sizing agent.

[0044] [Example 6] Setting basis weight 75g / m 2 A cushioning paper was obtained under the same conditions as in Example 2, except that the pressing pressure was adjusted so that the paper thickness was 100±5 μm.

[0045] [Example 7] Setting basis weight 100g / m 2 A cushioning paper was obtained under the same conditions as in Example 2, except that the pressing pressure was adjusted so that the paper thickness was 135±5 μm.

[0046] [Example 8] Setting basis weight 70g / m 2 A cushioning paper was obtained under the same conditions as in Example 1, except for the above.

[0047] [Example 9] Setting basis weight 70g / m 2 A cushioning paper was obtained under the same conditions as in Example 2, except for the above.

[0048] [Example 10] Setting basis weight 70g / m 2 A cushioning paper was obtained under the same conditions as in Example 3, except for the above.

[0049] [Example 11] Setting basis weight 70g / m 2 A cushioning paper was obtained under the same conditions as in Example 4, except for the above.

[0050] [Example 12] Setting basis weight 70g / m 2 A cushioning paper was obtained under the same conditions as in Example 5, except for the above.

[0051] [Example 13] Setting basis weight 50g / m 2A cushioning paper was obtained under the same conditions as in Example 2, except that the pressing pressure was adjusted so that the paper thickness was 70±5 μm.

[0052] [Example 14] Setting basis weight 120g / m 2 A cushioning paper was obtained under the same conditions as in Example 2, except that the pressing pressure was adjusted so that the paper thickness was 170±5 μm.

[0053] [Comparative Example 1] A cushioning paper was obtained under the same conditions as in Example 1, except that 0.50 parts by mass of a polyacrylamide-based internal paper strength agent was added.

[0054] [Comparative Example 2] A cushioning paper was obtained under the same conditions as in Example 1, except that 1.80 parts by mass of a polyacrylamide-based internal paper strength agent was added and the speed difference before and after the Clupac treatment was set to -45.0%.

[0055] [Comparative Example 3] A cushioning paper was obtained under the same conditions as in Example 2, except that 0.01 parts by mass of a rosin sizing agent was added as an internal sizing agent.

[0056] [Comparative Example 4] Setting basis weight 70g / m 2 A cushioning paper was obtained under the same conditions as in Comparative Example 1, except for the above.

[0057] [Comparative Example 5] Setting basis weight 70g / m 2 A cushioning paper was obtained under the same conditions as in Comparative Example 2, except for the above.

[0058] [Comparative Example 6] Setting basis weight 70g / m 2 A cushioning paper was obtained under the same conditions as in Comparative Example 3, except for the above.

[0059] The obtained cushioning paper was subjected to the above-mentioned evaluations. The results are shown in the table below.

[0060] [Table 1]

[0061] From the results of the Examples and Comparative Examples, it is clear that the cushioning paper of the present invention has excellent cushioning properties when made into a paper cushioning material even under high humidity conditions, and also has excellent folding processability. [Industrial Applicability]

[0062] The cushioning paper of the present invention has excellent cushioning properties even under high humidity conditions when made into a paper cushioning material, and also has excellent folding processability, and is therefore suitably used for paper cushioning materials.

Claims

1. The geometric mean value of the specific tensile energy absorption in the longitudinal direction and the specific tensile energy absorption in the transverse direction measured in accordance with JIS P 8113:2006 is 500 mJ / g or more and 3500 mJ / g or less, The average value of the front and back Stoeckigt size degree is 20 seconds or more. Cushioning paper.

2. 2. The cushioning paper according to claim 1, wherein the specific tensile energy absorption in the machine direction is 400 mJ / g or more and 3,500 mJ / g or less, and the specific tensile energy absorption in the cross direction is 500 mJ / g or more and 3,000 mJ / g or less.

3. 2. The cushioning paper according to claim 1, having a thickness of 50 μm or more and 250 μm or less.

4. Basis weight: 40 g / m ２ 150g / m or more ２ 2. The cushioning paper of claim 1, wherein:

5. 2. The cushioning paper according to claim 1, wherein the geometric mean value of the specific tensile energy absorption in the machine direction and the specific tensile energy absorption in the transverse direction is 800 mJ / g or more and 2500 mJ / g or less, and the Stockigt sizing degree is 45 seconds or more.

6. 2. The cushioning paper according to claim 1, which has been subjected to Clupak treatment.

7. A paper cushioning material obtained by folding the cushioning paper according to any one of claims 1 to 6.

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