Cushioning material paper and paper cushioning material

Abstract

To provide a cushioning material paper capable of obtaining a cushioning material excellent in cushioning property and excellent in flexure processability, in addition, a paper cushioning material obtained from the cushioning material paper.SOLUTION: A cushioning material paper has a basis weight of 50 g / m2 or more and 110 g / m2 or less, and the arithmetic mean of the longitudinal stiffness and transverse stiffness measured in accordance with ISO 2493-1:2010 is between 0.10 mN m and 0.60 mN m, additionally, the kink index of the constituent pulp fibers is 3500 (1 / m) or less.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] When storing contents such as products in a case such as a cardboard box for packaging, a cushioning material is used to fill the gap between the case and the contents and to absorb vibrations, impacts, etc. applied to the contents during transportation. As cushioning materials, air caps, air cushions, foamed chips, etc. have been used. Air caps and air cushions are formed of a resin such as polyethylene, and a large number of hollow protrusions are formed on the resin sheet. Foamed chips are relatively small-sized cushioning materials formed of a foaming resin, and are packed so as to fill the gap between the case and the contents before use. From the viewpoint of environmental protection, paper cushioning materials (paper cushioning materials) are becoming more and more popular in place of the above-mentioned plastic cushioning materials.

[0003] Patent Document 1 aims to provide a paper cushioning material having the advantages of conventional cushioning materials, that is, being able to be manufactured at low cost, being easily disposable because no harmful gas is generated during incineration, and having versatility because it is amorphous, and further having an excellent cushioning effect. A method for manufacturing a paper cushioning material is disclosed, which comprises supplying pieces of paper into the hollow drum from the slit of the hollow drum having a slit formed in the axial direction, hooking the tip of the piece of paper on the inner surface of the hollow drum, and further continuing the supply of the piece of paper to fold the piece of paper in a zigzag shape inside the hollow drum, and then moving a compression plate movable along the axial direction inside the hollow drum to compress and round the zigzag-folded piece of paper inside the hollow drum from the end side of the hollow drum.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The method for manufacturing a paper cushioning material described in Patent Document 1 has been studied for the method of manufacturing a paper cushioning material bent from paper pieces, but the cushioning paper itself used for the paper cushioning material has not been studied. An object of the present invention is to provide a cushioning paper for a cushioning material that has excellent cushioning properties and excellent bendability, and further to provide a paper cushioning material obtained from the cushioning paper for a cushioning material.

Means for Solving the Problems

[0006] The inventors of the present invention have found that the above problems can be solved by setting the basis weight of the cushioning paper within a specific range, setting the geometric mean value of the stiffness in the longitudinal direction and the transverse direction within a specific range, and further setting the kink index of the pulp fibers constituting the cushioning paper to a value equal to or less than a specific value. That is, the present invention relates to the following <1> to <8>. <1> A cushioning paper for a cushioning material, having a basis weight of 50 g / m 2 or more and 110 g / m 2 or less, the geometric mean value of the stiffness in the longitudinal direction and the transverse direction measured in accordance with ISO 2493-1:2010 being 0.10 mNm or more and 0.60 mNm or less, and the kink index of the pulp fibers constituting the cushioning paper being 3500 (1 / m) or less. A cushioning paper for a cushioning material. <2> The cushioning paper for a cushioning material according to <1>, wherein the stiffness in the longitudinal direction is 0.15 mNm or more and 0.95 mNm or less, and the stiffness in the transverse direction is 0.07 mNm or more and 0.45 mNm or less. <3> The cushioning paper for a cushioning material according to <1> or <2>, wherein the ratio of the stiffness in the longitudinal direction to the stiffness in the transverse direction (longitudinal stiffness / transverse stiffness) is 1.3 or more and 3.5 or less. <4> The kink index of the pulp fibers constituting the paper is 2000 (1 / m) or more and 3000 (1 / m) or less, and the paper for a cushioning material according to any one of <1> to <3>. <5> The density is 0.50 g / cm 3 or more and 0.85 g / cm 3 or less, and the paper for a cushioning material according to any one of <1> to <4>. <6> The paper for a cushioning material contains softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP) as raw material pulp, and the mass ratio of softwood unbleached kraft pulp to hardwood unbleached kraft pulp (NUKP:LUKP) is 40:60 or more and 85:15 or less, and the paper for a cushioning material according to any one of <1> to <5>. <7> The Canadian standard drainage degree of the raw material pulp is 350 mL or more and 550 mL or less, and the paper for a cushioning material according to any one of <1> to <6>. <8> A paper cushioning material formed by folding the paper for a cushioning material according to any one of <1> to <7>.

Advantages of the Invention

[0007] According to the present invention, a paper cushioning material excellent in cushioning properties is obtained, and a paper for a cushioning material excellent in foldability is provided. Furthermore, according to the present invention, a paper cushioning material obtained from the paper for a cushioning material is provided.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0009] [Paper for Cushioning Material] The paper for a cushioning material of this embodiment has a basis weight of 50 g / m 2 or more and 110 g / m 2The following is the case where the product of the longitudinal stiffness and the transverse stiffness (also referred to as the "average stiffness") measured in accordance with ISO 2493-1:2010 is 0.10 mNm or more and 0.60 mNm or less, and the kink index of the constituent pulp fibers is 3500 (1 / m) or less. According to the cushioning material paper of the present embodiment, a paper cushioning material excellent in cushioning properties can be obtained, and a cushioning material paper excellent in bendability can be provided. In the following description, the "cushioning material paper excellent in cushioning properties" means a cushioning material paper from which a paper cushioning material excellent in cushioning properties can be obtained when used as a paper cushioning material. Also, "excellent in bendability" means that it is easy to perform bending processing with a paper cushioning material manufacturing machine when manufacturing a paper cushioning material. As a reason for obtaining the above effects, the basis weight is 50 g / m 2 or more, and since the average value of the stiffness is 0.10 mNm or more, it is considered that a cushioning material paper excellent in cushioning properties is obtained. When the average value of the stiffness is large, the recoverability against bending increases, so it is considered that excellent cushioning properties are obtained. Also, the basis weight is 110 g / m 2 or less, and since the average value of the stiffness is 0.60 mNm or less, it is considered that a cushioning material paper excellent in bendability is obtained. Furthermore, when the kink index is 3500 (1 / m) or less, it is considered that there is less fiber bending and a cushioning material paper excellent in cushioning properties is obtained. Note that the reason for obtaining the above effects is not limited to this. Also, according to the cushioning material paper of the present embodiment, compared with a cushioning material formed from a conventional plastic, it is formed of paper mainly composed of pulp, and the environmental load is reduced. Hereinafter, the present invention will be described in more detail.

[0010] In this specification, the numerical range represented by "X to Y" means a numerical range including X as the lower limit value and Y as the upper limit value. When the numerical range is described stepwise, the upper limit and the lower limit of each numerical range can be arbitrarily combined. In addition, the longitudinal direction of the cushioning paper means the papermaking direction (MD), and the transverse direction means the direction (CD) perpendicular to the papermaking direction.

[0011] The cushioning paper of this embodiment includes a paper base material, and the paper base material includes pulp as a raw material. The manufacturing method and type of the pulp are not particularly limited. Note that the cushioning paper of this embodiment may include at least a paper base material and may have a coating layer or the like, but it is preferably composed only of the paper base material. Also, the paper base material may have a single-layer structure or a multi-layer structure. In the case of multi-layer paper, the number of paper layers is not particularly limited, but for example, it is preferably 2 or more and 7 or less layers, more preferably 2 or more and 6 or less layers.

[0012] <Raw pulp> In this embodiment, as the pulp constituting the paper base material, natural pulp fibers are preferable from the viewpoint of reducing environmental impact. As the natural pulp fibers, wood fibers (chemical pulp, mechanical pulp), non-wood fibers, waste paper pulp, etc. are arbitrarily used as required. Among the wood fibers, examples of the chemical pulp include kraft pulp using caustic soda and sodium sulfide during wood chip digestion, and sulfite pulp using sulfurous acid and bisulfite. These pulps may be unbleached or bleached. Also, examples of the mechanical pulp include groundwood pulp (GP) obtained by grinding logs with a grinder, refiner groundwood pulp (RGP) obtained by grinding waste materials from a sawmill with a refiner, and thermomechanical pulp (TMP) obtained by heating and refining wood chips. Among these, unbleached softwood kraft pulp (NUKP) and unbleached hardwood kraft pulp (LUKP) are preferably used. Also, among these wood fiber pulps, examples of the softwood that is the raw material for softwood pulp include pine, larch, cedar, fir, and cypress. Examples of the hardwood that is the raw material for hardwood pulp include eucalyptus, acacia, oak, beech, maple, elm, and chestnut.

[0013] In addition, examples of non-wood fibers that can be used in this embodiment include bast fibers such as kozo, mitsumata, ganpi, ramie, timah, kenaf, choma, jute, and sunn hemp; seed hair fibers such as cotton and cotton linter; leaf fibers such as Manila hemp, sisal hemp, and esparto; and stem fibers such as bamboo, rice straw, wheat straw, and sugarcane bagasse. In particular, kozo, mitsumata, kenaf, Manila hemp, sisal hemp, cotton, and cotton linter are preferably used 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 performed in the same manner as that of wood fibers. Examples of waste paper pulp that can be used in this embodiment include cardboard waste paper and magazine waste paper.

[0014] These pulp fibers can be used alone or in combination of two or more. Also, within a range that does not impair the effects of the present invention, synthetic resin fibers can be mixed as needed. 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 a desired stiffness and kink index of the pulp fibers constituting the base paper to be described later, it is preferable that the raw material pulp contains softwood pulp, more preferably a combination of softwood pulp and hardwood pulp, and even more preferably a combination of unbleached softwood kraft pulp and unbleached hardwood kraft pulp. When the cushioning paper contains unbleached softwood kraft pulp (NUKP) and unbleached hardwood kraft pulp (LUKP) as the raw material pulp, from the viewpoint of obtaining a desired stiffness and kink index of the pulp fibers constituting the base paper to be described later, 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 paper for buffer material 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% by mass or more, more preferably 60% by mass or more, still more preferably 80% by mass or more, even more preferably 90% by mass or more, still more preferably 95% by mass or more, and the upper limit is not particularly limited and is 100% by mass or less. Also, as the raw material pulp, waste paper pulp may be contained, but the content of waste paper pulp is preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 20% by mass or less, even more preferably 10% by mass or less, still more preferably 5% by mass or less, from the viewpoint of obtaining the desired hardness and kink index of the constituent pulp fibers described later.

[0016] <Pulp properties> (Kink index) In this embodiment, the kink index of the pulp fibers constituting the paper for buffer material is 3500 (1 / m) or less. When the kink index is 3500 (1 / m) or less, it is preferable because the pulp fibers have few bends and excellent cushioning properties. The kink index of the pulp fibers constituting the paper for buffer material is preferably 1500 (1 / m) or more and 3500 (1 / m) or less, more preferably 1800 (1 / m) or more, still more preferably 2000 (1 / m) or more, and preferably 3300 (1 / m) or less, more preferably 3000 (1 / m) or less, still more preferably 2800 (1 / m) or less, from the viewpoints of improving the cushioning property and obtaining a paper for buffer material with excellent foldability. The kink index (1 / m) referred to in the present invention is the Kibblewhite's kink index calculated by the following formula (1). The kink index is calculated by weighting the number of kinks for each fixed angle range according to the increase in the angle and dividing by the total fiber length. The kink index is measured by the method described in the examples.

[0017] Incidentally, the above kink index can be adjusted according to the pulp concentration and beating degree when beating the pulp. Specifically, the higher the pulp concentration during beating, the higher the kink index, and there will be more bent fibers in the pulp fibers constituting the cushioning paper. Also, for the same pulp raw material, when the beating degree is increased, the kink index tends to decrease.

[0018] (Canadian standard drainage degree) The Canadian standard drainage degree (CSF) of the raw material pulp of the cushioning paper, measured in accordance with JIS P 8121-2:2012, is preferably 200 mL or more and 800 mL or less, more preferably 250 mL or more, still more preferably 300 mL or more, even more preferably 350 mL or more, from the viewpoint of making the average value of stiffness and the kink index within a desired range. And, more preferably 700 mL or less, still more preferably 650 mL or less, even more preferably 600 mL or less, and most preferably 550 mL or less. Incidentally, the above CSF is the preferred CSF of the raw material pulp. On the other hand, the Canadian standard drainage degree (dissociation freeness) of the pulp obtained by dissociating the cushioning paper is about 50 mL greater than the CSF of the raw material pulp. Here, the dissociation freeness refers to the value of the Canadian standard drainage degree measured in accordance with the method of JIS P 8121-2:2012 using the pulp slurry obtained by dissociating the cushioning paper according to the method of JIS P 8220-1:2012.

[0019] <Optional component> The paper base material may contain, if necessary, internal additives such as, for example, anionic, cationic, nonionic or amphoteric retention aids, drainage improvers, dry paper strength enhancers, wet paper strength enhancers, fillers, fixing agents (sulfate bands), sizing agents, etc., and optional components such as dyes and fluorescent brighteners. Examples of the dry paper strength enhancer include cationized starch, polyacrylamide, carboxymethyl cellulose, etc. Among these, from the viewpoint of obtaining a desired specific tensile strength, a polyacrylamide-based dry paper strength enhancer is preferred. The content of the dry paper strength enhancer is not particularly limited and may be appropriately adjusted so as to obtain a desired specific tensile strength. Examples of the wet strength agent include polyamide polyamine epichlorohydrin, urea formaldehyde resin, melamine formaldehyde resin, and the like. 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] <Method for manufacturing cushioning paper> The method for manufacturing cushioning paper preferably includes a step of papermaking a slurry containing the above raw material pulp. The papermaking method is not particularly limited, and examples thereof include an acidic papermaking method in which papermaking is performed at a pH of around 4.5, a neutral papermaking method in which papermaking is performed at a pH of about 6 to about 9, and the like. In the papermaking step, if necessary, papermaking chemicals such as a pH adjuster, an antifoaming agent, a pitch control agent, and a slime control agent can be appropriately added. The paper machine is not particularly limited, and examples thereof include continuous paper machines such as a fourdrinier type, a cylinder type, and an inclined type, or a multi-layer combined papermaking machine combining these.

[0021] In the present embodiment, in the papermaking step, the jet / wire ratio (J / W ratio), which is the ratio of the flow rate (J) of the paper stock ejected onto the wire to the running speed (W) of the papermaking wire, may be appropriately adjusted from the viewpoint of making the ratio of the longitudinal stiffness to the transverse stiffness (longitudinal stiffness / transverse stiffness), which will be described later, within a desired range.

[0022] <Properties of cushioning paper> (Grammage) The grammage of the cushioning paper is 50 g / m² from the viewpoints of cushioning properties and bendability.2 is 110 g / m or less above, 2 preferably 55 g / m or more, 2 more preferably 60 g / m or more, 2 even more preferably 65 g / m or more, 2 even more preferably 70 g / m or more, 2 and preferably 105 g / m or less, 2 more preferably 100 g / m or less. 2 is below. The basis weight of the cushioning paper is measured in accordance with JIS P 8124:2011.

[0023] (Thickness) From the viewpoints of cushioning performance and bendability, 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, even more preferably 100 μm or more, still more preferably 110 μm or more, and more preferably 400 μm or less, even more preferably 350 μm or less, even more preferably 300 μm or less, still 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] (Density) In the present embodiment, from the viewpoints of cushioning performance and bendability, the density of the cushioning paper is preferably 0.50 g / cm or more 3 and 0.85 g / cm or less. 3 Generally, for the same basis weight, a lower density results in a cushioning material with better cushioning performance. The density of the cushioning paper is more preferably 0.80 g / cm or less, 3 more preferably 0.70 g / cm or less, 3 even more preferably 0.68 g / cm or less, 3 and preferably 0.55 g / cm or more, 3 more preferably 0.60 g / cm or more 3 from the viewpoint of obtaining a desired specific tensile strength. The density of the cushioning paper can be appropriately adjusted by adjusting the press pressure in the papermaking process. Also, the density of the cushioning paper is calculated from the thickness and basis weight of the cushioning paper.

[0025] (Rigidity) The cushioning paper of this embodiment has a multiplicative average value (average value of rigidity) of the rigidity in the longitudinal direction and the rigidity in the transverse direction measured in accordance with ISO 2493-1:2010 of 0.10 mNm or more and 0.60 mNm or less. When the average value of the rigidity is 0.10 mNm or more, it is preferable because of excellent cushioning properties. Also, when the average value of the rigidity is 0.60 mNm or less, it is preferable because of excellent bendability. The average value of the rigidity is more preferably 0.15 mNm or more, further preferably 0.18 mNm or more, still further preferably 0.20 mNm or more, and more preferably 0.55 mNm or less, further preferably 0.50 mNm or less, still further preferably 0.45 mNm or less, and even more preferably 0.40 mNm or less. The rigidity of the cushioning paper can be adjusted to a desired range depending on the type of raw pulp, beating degree, blending ratio, blending amount of paper strength agent (dry paper strength enhancer), thickness, density, basis weight, etc. of the cushioning paper. When using NUKP and LUKP as the raw pulp, increasing the ratio of NUKP tends to increase the rigidity. Also, increasing the blending amount of the paper strength agent tends to increase the rigidity. Further, for the same basis weight, increasing the thickness tends to increase the rigidity, and for the same density, increasing the basis weight tends to increase the rigidity. Also, when the basis weight and thickness are the same, the lower the beating degree and the larger the Canadian standard drainage degree value, the lower the tendency of the rigidity.

[0026] The stiffness in the longitudinal direction is preferably 0.10 mNm or more and 0.95 mNm or less, more preferably 0.15 mNm or more, still more preferably 0.25 mNm or more, even more preferably 0.30 mNm or more, still more preferably 0.35 mNm or more, and even more preferably 0.40 mNm or more from the viewpoints of cushioning property and bendability. And it is more preferably 0.85 mNm or less, still more preferably 0.80 mNm or less, even more preferably 0.75 mNm or less, still more preferably 0.70 mNm or less, and even more preferably 0.65 mNm or less. The stiffness in the lateral direction is preferably 0.07 mNm or more and 0.45 mNm or less, more preferably 0.09 mNm or more, still more preferably 0.12 mNm or more, even more preferably 0.15 mNm or more, and still more preferably 0.18 mNm or more from the viewpoints of cushioning property and bendability. And it is more preferably 0.40 mNm or less, still more preferably 0.35 mNm or less, and even more preferably 0.30 mNm or less.

[0027] The ratio of the stiffness in the longitudinal direction to the stiffness in the lateral direction (longitudinal stiffness / lateral stiffness) (hereinafter also referred to as the longitudinal-to-lateral ratio of stiffness) is preferably 1.3 or more and 3.5 or less. When the longitudinal-to-lateral ratio of stiffness is 1.3 or more, it is preferable because the bendability is excellent. Also, when the longitudinal-to-lateral ratio of stiffness is 3.5 or less, it is preferable because the cushioning property is excellent. The longitudinal-to-lateral ratio of stiffness is more preferably 1.5 or more, still more preferably 1.7 or more, even more preferably 1.9 or more, and still more preferably 2.1 or more. And it is more preferably 3.2 or less, still more preferably 2.8 or less, and even more preferably 2.5 or less. The longitudinal-to-lateral ratio of stiffness can be appropriately adjusted by adjusting the J / W ratio in the papermaking process.

[0028] [Paper cushioning material] The paper cushioning material of this embodiment is formed by bending the cushioning material paper of this embodiment. As another aspect, the cushioning paper of this embodiment may be subjected to embossing to form a paper cushioning material, or it may be further folded to form a paper cushioning material. When embossing is performed, it is preferable to improve the elongation performance by subjecting the cushioning paper to a Kurapak treatment (a treatment for finely shrinking the paper in the longitudinal direction on a paper machine) or the like. The folding of the cushioning paper may be done by hand, or it may be done manually or electrically by a cushioning material manufacturing machine, and is not particularly limited. Even when folding the cushioning paper with an electric cushioning material manufacturing machine to produce a paper cushioning material, if a cushioning paper with poor foldability is used, there is a tendency for problems such as a high load on the machine, clogging of the cushioning paper, or tearing to occur. Examples of commercially available cushioning material manufacturing machines 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, the FasFill series manufactured by Sealed Air, and the like. The shape of the cushioning paper is not particularly limited and may be in the form of a roll, a folded shape, or a single sheet. The paper cushioning material of this embodiment is preferably used to fill the gap between a case such as a corrugated cardboard box for packaging and the contents such as goods, and thereby it is preferably used to absorb vibrations, impacts, etc. applied to the contents during transportation.

Examples

[0029] The features of the present invention will be described more specifically below with reference to examples and comparative examples. The materials, amounts used, ratios, treatment details, treatment 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 construed as being limited by the specific examples shown below.

[0030] [Evaluation and Analysis] The following evaluations and analyses were performed on the raw pulp, cushioning paper, and paper cushioning materials of the examples and comparative examples.

[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〕 <Grammage> The cushioning papers obtained in the examples and comparative examples were conditioned for 24 hours in a humidity conditioning environment specified in JIS P 8111:1998. In accordance with JIS P 8124:2011, the grammage of the conditioned cushioning paper was measured.

[0033] <Thickness> The cushioning papers obtained in the examples and comparative examples were conditioned for 24 hours in a humidity conditioning environment specified in JIS P 8111:1998. In accordance with JIS P 8118:2014, the thickness of the conditioned cushioning paper was measured.

[0034] <Density> From the measured grammage and thickness, the density was calculated using the formula of grammage (g / m 2 ) ÷ thickness (μm).

[0035] <Kink index> The kink index of the pulp fibers constituting the cushioning paper was measured by the following method. The obtained cushioning paper was cut into 4 cm squares and immersed in ion-exchanged water for 15 minutes. The immersed cushioning paper was taken out and adjusted with ion-exchanged water to a concentration of 2%. The mixture of the concentration-adjusted cushioning paper and ion-exchanged water was disintegrated for 20 minutes using a standard disintegrator (manufactured by Kumagai Riki Kogyo Co., Ltd.) in accordance with JIS P 8220-1:2012 to obtain a pulp slurry. A portion of the obtained pulp slurry was separated, and the kink index of the fibers was measured using a fiber length measuring instrument (product number FS-5 UHD Base Unit, manufactured by Valmet). The kink index (1 / m) referred to in the present invention is the Kibblewhite's kink index calculated by the following formula (1). The kink index is calculated by weighting the number of kinks for each fixed angle range according to the increase in the angle and dividing by the total fiber length. The measurement was carried out in accordance with ISO 16065-2:2007. In addition, each fiber can be detected and measured by the attached camera of the same device, and it is photographed within a measurement cell with a depth of field of 0.5 mm in accordance with the ISO16505-2:2007 standard. Fibers with a fiber length of 0.01 mm or more and 10.00 mm or less are photographed by the same device.

[0036]

Number

[0037] In formula (1), n1, n2, n3 and L c are as follows. n1: The number of kinks in the range of 21° to 45° in all samples n2: The number of kinks in the range of 46° to 90° in all samples n3: The number of kinks in the range of 91° to 180° in all samples L c : The total fiber length of all samples

[0038] <Rigidity> The paper substrates obtained in the examples and comparative examples were conditioned for 24 hours in a conditioning environment specified in JIS P 8111:1998. The rigidity in the longitudinal and transverse directions of the conditioned paper substrate was measured in accordance with ISO2493-1:2010 (Paper and board - Test method for bending resistance - Part 1: Constant speed deflection). Specifically, the paper substrate after humidity conditioning was cut into pieces with a width of 38 mm and a length of 70 mm. Using a bending resistance tester (L&W BENDING RESISTANCE TESTER, code No. 16-D, manufactured by Lorentzen & Wattre), after setting the bending length to 10 mm and the bending angle to 15°, the bending resistance in the longitudinal (lengthwise) and transverse (widthwise) directions was measured, and then the stiffness was calculated using the following formula.

[0039]

Number

[0040] <Shock resistance> The cushioning material paper obtained in the examples and comparative examples was cut to a width of 38 cm and a flow direction (length) of 50 m, installed in an automatic paper cushioning material manufacturing machine (manufactured by NUEVOPAK, X-FILL TM Type A), and then fed out at a speed of 100 m / min to obtain a paper cushioning material with a length of 90 cm. Next, a enclosure with a length of 22.5 cm × width of 18 cm × height of 10 cm was placed on a concrete floor, and the obtained paper cushioning material was folded every 22.5 cm and installed in a bellows shape to cover the bottom surface inside the enclosure (Figure 1). Subsequently, with the bottom surface facing vertically downward, from a height of 50 cm, an aluminum can of 350 mL of soft drink (φ6.6 cm, height 12.2 cm, 370 g, empty can 17 g) was repeatedly dropped vertically freely onto the cushioning material inside the above enclosure, and the number of times required until deformation such as dents or scratches occurred on the can was counted. The test was conducted 5 times each, and the shock resistance was evaluated according to the following criteria based on the average number of times (rounding to the first decimal place). If the evaluation is A - C, there is no practical problem. A: The average number of drops is 10 or more B: The average number of drops is 7 - 9 C: The average number of drops is 4 - 6 D: The average number of drops is 3 or less

[0041] <Bendability> The bendability is the running and feeding stability in the bending process of the buffer material manufacturing machine. In the examples, for simulation of practical production, evaluation was carried out by the following method using a laboratory machine. The buffer material papers obtained in the examples and comparative examples were cut into A4 size, and the tip portions (about 5 cm) in the flow direction were alternately folded back at 3 cm intervals in the width direction to form a zigzag shape, and the resulting material was passed through the bending section of a manual paper buffer material manufacturing machine (manufactured by NUEVOPAK, X-FILL TM MM type). Next, the manual paper buffer material manufacturing machine was installed below a tensilon universal material testing machine (manufactured by A&D, RTI1310) as shown in Figure 2. At this time, the discharge port of the manual paper buffer material manufacturing machine was at an angle of 45° from the test bench of the tensilon universal material testing machine, and the height of the lower end of the upper chuck of the tensilon universal material testing machine and the center of the discharge port were aligned, and the horizontal center of the discharge port and the center of the upper chuck were aligned for installation. Finally, the zigzag-shaped buffer material protruding from the discharge port was grasped with the upper chuck and pulled up at a speed of 1000 mm / min. The load when passing through the bending section was measured, and the bendability was evaluated according to the following criteria based on the average value of 5 test times. If the evaluation is A - C, there is no practical problem. Note that the greater the load when passing through the processing section, the stronger the resistance during processing, which means that in practice, paper jams are likely to occur and the running performance becomes unstable, making it difficult to increase the processing speed. A: The average value of the maximum load is less than 8.0 N B: The average value of the maximum load is 8.0 N or more and less than 17.0 N C: The average value of the maximum load is 17.0 N or more and less than 22.0 N D: The average value of the maximum load is 22.0 N or more

[0042] [Example 1] As pulp raw materials, softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP) were mixed at a mass ratio of 70:30, and beaten using a double disk refiner so that the freeness (CSF: Canadian standard freeness) became 450 mL to obtain a pulp slurry. With respect to 100 parts by mass of the obtained pulp slurry (in terms of solid content), 1.20 parts by mass (in terms of solid content) of a polyacrylamide-based internal sizing agent for paper strength enhancement (manufactured by Arakawa Chemical Industries, Ltd., product number: PS379), 0.10 parts by mass (in terms of solid content) of a rosin sizing agent as an internal sizing agent (manufactured by Arakawa Chemical Industries, Ltd., Size Pine N-811), and 1.0 part by mass (in terms of solid content) of aluminum sulfate were added to prepare a paper stock. Using this paper stock, paper was made using a twin-wire paper machine at a set basis weight of 82 g / m 2 . During the papermaking process, the J / W ratio was adjusted so that the aspect ratio of the paper stiffness became 2.5 ± 0.3, and the press pressure was adjusted so that the paper thickness became 105 ± 5 μm to obtain the cushioning material paper of Example 1.

[0043] [Example 2] A cushioning material paper was obtained under the same conditions as in Example 1, except that the press pressure was adjusted so that the paper thickness became 130 ± 5 μm.

[0044] [Example 3] A cushioning material paper was obtained under the same conditions as in Example 1, except that the press pressure was adjusted so that the paper thickness became 155 ± 5 μm.

[0045] [Example 4] The set basis weight was 75 g / m 2 , and a cushioning material paper was obtained under the same conditions as in Example 1, except that the press pressure was adjusted so that the paper thickness became 145 ± 5 μm.

[0046] [Example 5] The set basis weight was 95 g / m 2 , and a cushioning material paper was obtained under the same conditions as in Example 1, except that the press pressure was adjusted so that the paper thickness became 120 ± 5 μm.

[0047] [Example 6] A cushioning paper was obtained under the same conditions as in Example 1, except that the J / W ratio was adjusted so that the aspect ratio of the paper stiffness was 1.5 ± 0.3.

[0048] [Example 7] A cushioning paper was obtained under the same conditions as in Example 1, except that the J / W ratio was adjusted so that the aspect ratio of the paper stiffness was 3.0 ± 0.3.

[0049] [Example 8] A cushioning paper was obtained under the same conditions as in Example 1, except that the pulp raw material was beaten under the condition that the CSF was 300 mL.

[0050] [Example 9] A cushioning paper was obtained under the same conditions as in Example 1, except that the pulp raw material was beaten under the condition that the CSF was 375 mL.

[0051] [Example 10] A cushioning paper was obtained under the same conditions as in Example 1, except that the pulp raw material was beaten under the condition that the CSF was 525 mL.

[0052] [Example 11] A cushioning paper was obtained under the same conditions as in Example 1, except that the pulp raw material was beaten under the condition that the CSF was 600 mL.

[0053] [Comparative Example 1] A cushioning paper was obtained under the same conditions as in Example 1, except that the set basis weight was 60 g / m 2 and the press pressure was adjusted so that the paper thickness was 80 ± 5 μm.

[0054] [Comparative Example 2] A cushioning paper was obtained under the same conditions as in Example 1, except that the set basis weight was 100 g / m 2 and the press pressure was adjusted so that the paper thickness was 185 ± 5 μm.

[0055] [Comparative Example 3] A cushioning paper was obtained under the same conditions as in Example 1, except that the set basis weight was 42 g / m 2Except that the pressing pressure was adjusted so that the paper thickness became 80 ± 5 μm, a cushioning material paper was obtained under the same conditions as in Example 1.

[0056] [Comparative Example 4] The set basis weight was 120 g / m 2 Except that the pressing pressure was adjusted so that the paper thickness became 150 ± 5 μm, a cushioning material paper was obtained under the same conditions as in Example 1.

[0057] [Comparative Example 5] Except that the pulp raw material was beaten under the condition that the CSF was 675 mL, a cushioning material paper was obtained under the same conditions as in Example 1.

[0058] The above-described evaluation was performed on the obtained cushioning material paper. The results are shown in the following table.

[0059]

Table 1

[0060] From the results of the examples and comparative examples, it can be seen that the cushioning material paper of the present invention is excellent in cushioning properties when used as a cushioning material and is also excellent in bendability.

Industrial Applicability

[0061] The cushioning material paper of the present invention is excellent in cushioning properties when used as a cushioning material and is also excellent in bendability, and is suitably used as a cushioning material.

Claims

1. The basis weight is 50 g / m ２ or more and 110 g / m ２ or less, and The product of the longitudinal stiffness and the transverse stiffness measured in accordance with ISO 2493-1:2010 is 0.10 mNm or more and 0.60 mNm or less, and the kink index of the constituent pulp fibers is 3500 (1 / m) or less, a cushioning paper.

2. The longitudinal stiffness is 0.15 mNm or more and 0.95 mNm or less, and the transverse stiffness is 0.07 mNm or more and 0.45 mNm or less, the cushioning paper according to Claim 1.

3. The ratio of the longitudinal stiffness to the transverse stiffness (longitudinal stiffness / transverse stiffness) is 1.3 or more and 3.5 or less, the cushioning paper according to Claim 1.

4. The kink index of the constituent pulp fibers is 2000 (1 / m) or more and 3000 (1 / m) or less, the cushioning paper according to Claim 1.

5. The density is 0.50 g / cm ３ or more and 0.85 g / cm ３ or less. The cushioning paper according to claim 1.

6. The cushioning paper contains softwood unbleached kraft pulp (NUKP) and hardwood unbleached kraft pulp (LUKP) as raw material pulp, and the mass ratio of softwood unbleached kraft pulp to hardwood unbleached kraft pulp (NUKP:LUKP) is 40:60 or more and 85:15 or less, the cushioning paper according to Claim 1.

7. The Canadian standard drainage degree of the raw material pulp is 350 mL or more and 550 mL or less, the cushioning paper according to Claim 1.

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

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