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, 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 density is 0.80 g / cm3 or less, and the geometric mean of the longitudinal-direction specific tensile strength and the transverse-direction specific tensile strength measured in accordance with JIS P 8113: 2006 is 33.0 Nm / g or more and 75.0 Nm / g or less.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 of a product when the product is 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 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. [Means for solving the problem]

[0006] The present inventors have found that the above-mentioned problems 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 specific tensile strength within a specific range. That is, the present invention provides the following: <1> ~ <8> Regarding. <1> Density 0.80g / cm 3 Cushioning paper having a geometric mean value of the longitudinal tensile strength index and the transverse tensile strength index measured in accordance with JIS P 8113:2006 of 33.0 Nm / g or more and 75.0 Nm / g or less. <2> The tensile strength ratio in the longitudinal direction is 40.0 Nm / g or more and 110.0 Nm / g or less, and the tensile strength ratio in the transverse direction is 18.0 Nm / g or more and 60.0 Nm / g or less. <1> Cushioning paper as described above. <3> The ratio of the tensile strength ratio in the longitudinal direction to the tensile strength ratio in the transverse direction (tensile strength ratio in the longitudinal direction / tensile strength ratio in the transverse direction) is 1.0 or more and 5.5 or less. <1> or <2> Cushioning paper as described above. <4> The geometric mean value of the longitudinal stiffness and transverse stiffness measured in accordance with ISO 2493-1:2010 is 0.10 mNm or more and 1.50 mNm or less. <1> ~ <3> Cushioning paper as described in any one of the above. <5> The curl value of the pulp fibers that make up the cushioning paper is 9.0% or less. <1> ~ <4> Cushioning paper as described in any one of the above. <6> Basis weight 40g / m 2 More than 150g / m 2 Below is the <1> ~ <5> Cushioning paper as described in any one of the above. <7> 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; <1> ~ <6> Cushioning paper as described in any one of the above. <8> <1> ~ <7> 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 is obtained, and a cushioning paper having excellent folding processability is provided. Furthermore, according to the present invention, a paper cushioning material obtained from the cushioning paper 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 density of 0.80 g / cm 3and the geometric mean value of the longitudinal tensile strength index and the transverse tensile strength index (hereinafter also referred to as the geometric mean value of the tensile strength index) measured in accordance with JIS P 8113:2006 is 33.0 Nm / g or more and 75.0 Nm / g 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 effect is that the density is 0.80g / cm 3 It is believed that by satisfying the above-mentioned condition, many voids are formed between the pulp fibers in the paper, resulting in a cushioning paper with excellent cushioning properties. Also, when the geometric mean value of the specific tensile strength is large, the cushioning properties are excellent, but the folding processability tends to be poor. It is believed that by setting the geometric mean value of the specific tensile strength 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.

[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 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.

[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 tensile index, stiffness, and constituent curl value 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 the desired specific tensile strength, stiffness, and curl value described below, the mass ratio of unbleached softwood kraft pulp to unbleached hardwood 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 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 strength, stiffness, and constituent curl value described below.

[0016] <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, it is preferable because a high specific tensile strength is obtained and the cushioning properties are improved. It is believed that a small curl value improves the elastic modulus of the single fiber, and as a result, the specific tensile strength is high and the cushioning properties of the cushioning paper are improved. The curl value is more preferably 8.5% or less, even more preferably 8.0% or less, even more preferably 7.5% or less, and even more preferably 7.0% or less. There is no particular lower limit, but from the viewpoint of ease of production, it is preferably 3.0% or more, more preferably 4.0% or more, even more preferably 4.5% or more, even more preferably 5.0% or more, and even more preferably 5.5% or more.

[0017] The curl value of the pulp that constitutes the paper base material is expressed as follows, using the length of the pulp fibers when they are 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 (%) = (L1-L2) / L2 x 100 Here, the fiber length (L1) and the fiber length (L2) 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.

[0018] (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 200 mL or more and 800 mL or less, more preferably 300 mL or more, even more preferably 350 mL or more, still more preferably 400 mL or more, and more preferably 700 mL or less, even more preferably 600 mL or less, and still more preferably 500 mL or less, from the viewpoint of setting the specific tensile strength in the desired range. 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.

[0019] <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.

[0020] <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.

[0021] In this embodiment, in the papermaking process, the jet / wire ratio (J / W ratio), which is the ratio of the flow speed (J) of the paper material sprayed onto the wire to the papermaking wire running speed (W), may be appropriately adjusted from the viewpoint of setting the ratio of the longitudinal specific tensile strength to the transverse specific tensile strength (longitudinal specific tensile strength / transverse specific tensile strength) described below in a desired range.

[0022] <Characteristics of cushioning paper> (density) The cushioning paper of the present embodiment has a density of 0.80 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 0.75g / cm 3 Less than or equal to 0.70 g / cm 3 More preferably, 0.68 g / cm 3 From the viewpoint of obtaining a desired tensile strength index, it is preferably 0.40 g / cm 3 More preferably, 0.45 g / cm 3 More preferably, 0.50 g / cm 3 More preferably, 0.55 g / cm 3 That's all. The density of the cushioning paper can be adjusted appropriately 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.

[0023] (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.

[0024] (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 65 g / m 2 More preferably, it is 200 g / m or more. 2 More preferably, 180 g / m 2 or less, even more preferably 150 g / m 2 More preferably, 120 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.

[0025] (Specific tensile strength) The cushioning paper of this embodiment has a geometric mean value of the longitudinal tensile strength index and the transverse tensile strength index (hereinafter also referred to as the "average tensile strength index") of 33.0 Nm / g or more and 75.0 Nm / g or less, as measured in accordance with JIS P 8113:2006. A tensile strength index of 33.0 Nm / g or more is preferable because it provides excellent cushioning properties. Also, a tensile strength index of 75.0 Nm / g or less is preferable because it provides excellent folding processability. In view of the above, the average specific tensile strength of the cushioning paper is preferably 35.0 Nm / g or more, more preferably 40.0 Nm / g or more, and preferably 70.0 Nm / g or less, more preferably 65.0 Nm / g or less. The tensile strength of cushioning paper is measured in accordance with JIS P 8113:2006, and the geometric mean of the value obtained by dividing the longitudinal tensile strength by the basis weight (longitudinal tensile strength ratio) and the value obtained by dividing the transverse tensile strength by the basis weight (transverse tensile strength ratio) is calculated. The specific tensile strength of cushioning paper can be adjusted to the desired range by the type and blending ratio of raw pulp, the amount of strength agent (dry strength agent), the density of the cushioning paper, etc. When NUKP and LUKP are used as raw pulp, increasing the ratio of NUKP tends to increase the specific tensile strength. Also, increasing the amount of strength agent tends to increase the specific tensile strength.

[0026] From the viewpoints of cushioning properties and folding processability, the specific tensile strength in the longitudinal direction is preferably 40.0 Nm / g or more and 110.0 Nm / g or less, more preferably 45.0 Nm / g or more, even more preferably 50.0 Nm / g or more, and more preferably 105.0 Nm / g or less, even more preferably 100.0 Nm / g or less. In addition, from the viewpoints of cushioning properties and folding processability, the tensile strength index in the transverse direction is preferably 18.0 Nm / g or more and 60.0 Nm / g or less, more preferably 19.0 Nm / g or more, even more preferably 20.0 Nm / g or more, and more preferably 55.0 Nm / g or less, even more preferably 50.0 Nm / g or less, still more preferably 45.0 Nm / g or less, and even more preferably 40.0 Nm / g or less.

[0027] The ratio of the specific tensile strength in the longitudinal direction to the specific tensile strength in the transverse direction (specific tensile strength in the longitudinal direction / specific tensile strength in the transverse direction) (hereinafter also referred to as the aspect ratio of specific tensile strength) is preferably 1.0 or more and 5.5 or less. When the aspect ratio of specific tensile strength is 1.0 or more, it is preferable because it has excellent bending processability. Also, when the aspect ratio of specific tensile strength is 5.5 or less, it is preferable because it has excellent cushioning properties. The aspect ratio of the specific tensile strength 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. The aspect ratio of the specific tensile strength can be appropriately adjusted by adjusting the J / W ratio in the papermaking process.

[0028] (Scary) The cushioning paper of this embodiment preferably has a geometric mean value of the stiffness in the longitudinal direction and the stiffness in the lateral direction (hereinafter also referred to as the "average stiffness value"), measured in accordance with ISO 2493-1:2010, of 0.10 mNm or more and 1.50 mNm or less. If the average stiffness value is 0.10 mNm or more, it is preferable because it has excellent cushioning properties. Also, if the average stiffness value is 1.50 mNm or less, it is preferable because it has excellent folding processability. The average stiffness is more preferably 0.15 mNm or more, even more preferably 0.20 mNm or more, even more preferably 0.25 mNm or more, even more preferably 0.30 mNm or more, and more preferably 1.30 mNm or less, even more preferably 1.10 mNm or less, even more preferably 0.90 mNm or less, and even more preferably 0.80 mNm or less. The stiffness of cushioning paper can be adjusted to the desired range by the type and blending ratio of raw pulp, the amount of strength agent (dry strength agent), the thickness of the cushioning paper, etc. When NUKP and LUKP are used as raw pulp, increasing the ratio of NUKP tends to increase stiffness. Also, increasing the amount of strength agent tends to increase stiffness. Furthermore, increasing the thickness tends to increase stiffness.

[0029] From the viewpoints of cushioning properties and folding processability, the stiffness in the longitudinal direction is preferably 0.10 mNm or more and 2.00 mNm or less, more preferably 0.15 mNm or more, even more preferably 0.20 mNm or more, still more preferably 0.25 mNm or more, even more preferably 0.30 mNm or more, even more preferably 0.40 mNm or more, and more preferably 1.80 mNm or less, even more preferably 1.60 mNm or less, still more preferably 1.50 mNm or less, even more preferably 1.40 mNm or less, and even more preferably 1.20 mNm or less. From the viewpoints of cushioning properties and folding processability, the lateral stiffness is preferably 0.05 mNm or more and 1.20 mNm or less, more preferably 0.10 mNm or more, even more preferably 0.15 mNm or more, still more preferably 0.20 mNm or more, even more preferably 0.25 mNm or more, and more preferably 1.00 mNm or less, even more preferably 0.90 mNm or less, even more preferably 0.80 mNm or less, even more preferably 0.60 mNm or less, and even more preferably 0.50 mNm or less.

[0030] The ratio of stiffness in the vertical direction to stiffness in the horizontal direction (vertical stiffness / horizontal stiffness) (hereinafter also referred to as the aspect ratio of stiffness) is preferably 1.0 or more and 5.5 or less. When the aspect ratio of the specific tensile strength is 1.0 or more, it is preferable because it has excellent bending processability. Also, when the aspect ratio of the specific tensile strength is 5.5 or less, it is preferable because it has excellent cushioning properties. The aspect ratio of the specific tensile strength is more preferably 1.2 or more, even more preferably 1.4 or more, still more preferably 1.6 or more, and more preferably 4.5 or less, even more preferably 4.0 or less, still more preferably 3.5 or less, and even more preferably 3.0 or less. The aspect ratio of stiffness can be appropriately adjusted by adjusting the J / W ratio in the papermaking process.

[0031] [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

[0032] 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.

[0033] [Evaluation and Analysis] The raw pulp, cushioning paper, and paper cushioning materials of the examples and comparative examples were evaluated and analyzed as follows.

[0034] [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.

[0035] [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 fiber curl value was measured using a fiber length measuring device (model number FS-5 UHD base unit, manufactured by Valmet).

[0036] <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.

[0037] <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.

[0038] <density> From the measured basis weight and thickness, the basis weight (g / m 2 The density was calculated using the formula: (μm) / (thickness).

[0039] <Specific tensile strength> 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 strength of the conditioned cushioning papers was measured in accordance with JIS P 8113: 2006. The tensile strengths were 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 specific tensile strength was calculated by dividing the obtained tensile strength by the basis weight.

[0040] <Scary> 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 stiffness of the cushioning paper in the longitudinal and transverse directions after conditioning was measured in accordance with ISO 2493-1:2010 (Paper and paperboard -- Bending resistance test method -- Part 1: Constant speed deflection). Specifically, the cushioning paper after humidity conditioning was cut into a piece 38 mm wide and 70 mm long, 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). The bending resistance in both the vertical (vertical direction) and horizontal (horizontal direction) directions was then measured, and the stiffness was calculated using the following formula.

[0041]

number

[0042] <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 (X-FILL, manufactured by Nuevopak). 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. 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 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

[0043] <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 paper cushioning manual manufacturing 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, 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 so that 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.

[0044] [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 (converted to solid content), 0.80 parts by mass (converted to solid content) of a polyacrylamide-based internal paper strength enhancer (manufactured by Arakawa Chemical Industries, Ltd., product number: PS379), 0.10 parts by mass (converted to 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 (converted to solid content) of aluminum sulfate were added to prepare a paper stock. Using this paper stock, the basis weight was set at 95g / m 2 During the papermaking process, the J / W was adjusted so that the aspect ratio of the tensile strength index of the paper was 2.3±0.3, and the press pressure was adjusted so that the thickness of the paper was 150±5 μm, thereby obtaining the cushioning paper of Example 1.

[0045] [Example 2] A cushioning paper was obtained under the same conditions as in Example 1, except that 0.90 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength agent was added.

[0046] [Example 3] A cushioning paper was obtained under the same conditions as in Example 1, except that 1.00 part by mass (solid content equivalent) of a polyacrylamide-based internal paper strength enhancer was added.

[0047] [Example 4] A cushioning paper was obtained under the same conditions as in Example 1, except that 1.50 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength agent was added.

[0048] [Example 5] A cushioning paper was obtained under the same conditions as in Example 1, except that 1.80 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength agent was added.

[0049] [Example 6] Cushioning paper was obtained under the same conditions as in Example 1, except that 1.10 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength agent was added and the pressing pressure was adjusted so that the paper thickness was 170±5 μm.

[0050] [Example 7] Cushioning paper was obtained under the same conditions as in Example 1, except that 0.85 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength agent was added and the pressing pressure was adjusted so that the paper thickness was 125±5 μm.

[0051] [Example 8] Cushioning paper was obtained under the same conditions as in Example 3, except that the J / W ratio was adjusted so that the aspect ratio of the specific tensile strength of the paper was 5.0±0.3.

[0052] [Example 9] A cushioning paper was obtained under the same conditions as in Example 3, except that the J / W ratio was adjusted so that the aspect ratio of the specific tensile strength of the paper was 1.2±0.3.

[0053] [Example 10] Cushioning paper was obtained under the same conditions as in Example 1, except that 1.10 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength enhancer was added and the J / W ratio was adjusted so that the aspect ratio of the specific tensile strength of the paper was 1.2±0.3.

[0054] [Example 11] Cushioning paper was obtained under the same conditions as in Example 1, except that 0.90 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength enhancer was added and the J / W ratio was adjusted so that the aspect ratio of the specific tensile strength of the paper was 4.0±0.3.

[0055] [Example 12] Cushioning paper was obtained under the same conditions as in Example 1, except that softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP) were mixed in a mass ratio of 45:55 as the pulp raw materials, and 1.20 mass parts (solid content equivalent) of a polyacrylamide-based internal paper strength agent were added.

[0056] [Example 13] Cushioning paper was obtained under the same conditions as in Example 1, except that softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP) were mixed in a mass ratio of 75:25 as the pulp raw materials, and 0.75 mass parts (solid content equivalent) of a polyacrylamide-based internal paper strength agent were added.

[0057] [Example 14] The raw pulp materials were made of softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP) mixed in a mass ratio of 75:25, and 0.85 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength enhancer was added. The set basis weight was 70 g / m. 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 was 115±5 μm.

[0058] [Example 15] A cushioning paper was obtained under the same conditions as in Example 14, except that 0.95 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength agent was added.

[0059] [Example 16] A cushioning paper was obtained under the same conditions as in Example 14, except that 1.40 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength agent was added.

[0060] [Example 17] The raw pulp materials were made of softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP) mixed in a mass ratio of 75:25, and 1.10 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength enhancer was added. The paper had a set basis weight of 70 g / m. 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 was 125±5 μm.

[0061] [Example 18] The raw pulp materials were made of softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP) mixed in a mass ratio of 75:25, and 0.85 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength enhancer was added. The set basis weight was 70 g / m. 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 was 95±5 μm.

[0062] [Example 19] Setting basis weight 50g / m 2 A cushioning paper was obtained under the same conditions as in Example 3, except that the pressing pressure was adjusted so that the paper thickness was 80±5 μm.

[0063] [Example 20] Setting basis weight 135g / m 2 A cushioning paper was obtained under the same conditions as in Example 3, except that the pressing pressure was adjusted so that the paper thickness was 200±5 μm.

[0064] [Comparative Example 1] A cushioning paper was obtained under the same conditions as in Example 1, except that 0.20 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength enhancer was added.

[0065] [Comparative Example 2] A cushioning paper was obtained under the same conditions as in Example 1, except that 2.50 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength agent was added.

[0066] [Comparative Example 3] Cushioning paper was obtained under the same conditions as in Example 1, except that 0.75 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength agent was added and the pressing pressure was adjusted so that the paper thickness was 110±5 μm.

[0067] [Comparative Example 4] A cushioning paper was obtained under the same conditions as in Example 14, except that 0.15 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength agent was added.

[0068] [Comparative Example 5] A cushioning paper was obtained under the same conditions as in Example 14, except that 2.30 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength agent was added.

[0069] [Comparative Example 6] As pulp raw materials, softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP) were mixed in a mass ratio of 75:25, and 0.75 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength enhancer was added to set the basis weight to 70 g / m. 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 was 85±5 μm.

[0070] The obtained cushioning paper was subjected to the above-mentioned evaluations. The results are shown in the table below.

[0071] [Table 1]

[0072] 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 used as a cushioning material, as well as excellent folding processability. [Industrial Applicability]

[0073] The cushioning paper of the present invention has excellent cushioning properties when used as a cushioning material, and also has excellent folding processability, and is therefore suitably used as a cushioning material.

Claims

1. Density is 0.80 g / cm ３ is as follows: The geometric mean value of the longitudinal tensile strength index and the transverse tensile strength index measured in accordance with JIS P 8113:2006 is 33.0 Nm / g or more and 75.0 Nm / g or less; Cushioning paper.

2. 2. The cushioning paper according to claim 1, having a longitudinal tensile strength index of 40.0 Nm / g or more and 110.0 Nm / g or less, and a transverse tensile strength index of 18.0 Nm / g or more and 60.0 Nm / g or less.

3. 2. The cushioning paper according to claim 1, wherein the ratio of the specific tensile strength in the machine direction to the specific tensile strength in the cross direction (specific tensile strength in the machine direction / specific tensile strength in the cross direction) is 1.0 or more and 5.5 or less.

4. 2. The cushioning paper according to claim 1, wherein the geometric mean value of the stiffness in the longitudinal direction and the stiffness in the transverse direction measured in accordance with ISO 2493-1:2010 is 0.10 mNm or more and 1.50 mNm or less.

5. 2. The cushioning paper according to claim 1, wherein the curl value of the pulp fibers constituting the cushioning paper is 9.0% or less.

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

7. 2. The cushioning paper according to claim 1, 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.

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

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