Buffer material paper and paper buffer material

Abstract

To provide: a buffer material paper which is intended to obtain a paper buffer material excellent in cushioning properties and which is intended to reduce occurrence of paper powder, for example, during processing into the paper buffer material; and a paper buffer material obtainable from the buffer material paper.SOLUTION: A buffer material paper has a basis weight of 35 g / m2 or more, in which a geometric mean values of specific tensile strength in a longitudinal direction and specific tensile strength in a lateral direction measured according to JIS P8113:2006 is 17.0 Nm / g or more, and a degree of fibrillation of a pulp fiber that constitutes the buffer material paper is 1.5% 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 that provides a paper cushioning material with excellent cushioning properties and that suppresses the generation of paper dust during processing into the paper cushioning material, etc. Another aim 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 discovered that the above problem can be solved by setting the basis weight of the cushioning paper to a specific value or more, setting the longitudinal and transverse geometric mean value of the specific tensile strength to a specific value or more, and further setting the wax pick values ​​of both the front and back surfaces to a specific value or more. That is, the present invention provides the following: <1> ~ <5> Regarding. <1> Basis weight 35g / m 2 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 17.0 Nm / g or more, and a fibrillation degree of the constituent pulp fibers of 1.5% or less. <2> The percentage of fibers having a fiber length of 1.2 mm or more in the pulp fibers constituting the cushioning paper is 8.0% or more. <1> Cushioning paper as described above. <3> Density 0.50g / cm 3 More than 0.95g / cm 3 Below is the <1> or <2> Cushioning paper as described above. <4> The cushioning paper contains recycled paper pulp as a raw material pulp. <1> ~ <3> Cushioning paper as described in any one of the above. <5> <1> ~ <4> 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 paper cushioning material is provided that suppresses the generation of paper dust during processing into the paper cushioning material, etc. 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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Cushioning paper] The cushioning paper of this embodiment has a basis weight of 35 g / m 2 or more, the geometric mean value of the longitudinal specific tensile strength and the transverse specific tensile strength (also referred to as the "average specific tensile strength") measured in accordance with JIS P 8113:2006 is 17.0 Nm / g or more, and the fibrillation degree of the constituent pulp fibers is 1.5% or less. According to the cushioning paper of this embodiment, a paper cushioning material with excellent cushioning properties is obtained, and cushioning paper is provided that suppresses the generation of paper dust during processing into the paper cushioning material. If paper dust is generated during processing into the paper cushioning material, the paper dust may clog the cushioning material manufacturing machine, causing a load on the cushioning material manufacturing machine and requiring cleaning of the cushioning material manufacturing machine. Furthermore, if paper dust is generated during use of the paper cushioning material, there is a problem that the contents inside may be contaminated. The reason for the above effect is that the basis weight is 35 g / m 2 It is believed that a cushioning paper with excellent cushioning properties has been obtained because the average tensile strength ratio is 17.0 Nm / g or more and the fibrillation degree of the pulp fibers that make up the cushioning paper is 1.5% or less, which is believed to suppress the generation of paper dust during processing into paper cushioning. 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 the present embodiment includes at least a paper base material, which may have a coating layer such as a resin layer, a laminate layer, etc., but is preferably made of only a paper base material. The paper base material may be surface-treated to provide at least one selected from the group consisting of water-soluble resins and water-suspendable resins. The paper base material may be a single-layered or multi-layered paper. In the case of a multi-layered 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. Of these, recycled paper pulp, 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 specific tensile strength described below and from the viewpoint of producing cushioning paper inexpensively, it is preferable that the raw material pulp contains at least recycled paper pulp, it is more preferable that it contains softwood pulp in addition to recycled paper pulp, it is even more preferable to use a combination of recycled paper pulp, softwood pulp and hardwood pulp, and it is even more preferable to use a combination of recycled paper pulp, unbleached softwood pulp and unbleached hardwood pulp. When the cushioning paper contains recycled paper pulp as the raw material pulp, from the viewpoint of obtaining the desired specific tensile strength described below, and from the viewpoint of producing the cushioning paper inexpensively, the recycled paper pulp content in the raw material pulp is preferably 10% by mass or more and 90% by mass or less, more preferably 20% by mass or more, even more preferably 30% by mass or more, still more preferably 40% by mass or more, and more preferably 80% by mass or less, even more preferably 70% by mass or less, and still more preferably 60% by mass or less. When the cushioning paper contains softwood unbleached kraft pulp (NUKP) as the raw material pulp, from the viewpoint of obtaining the desired specific tensile strength described below, the content of softwood unbleached kraft pulp (NUKP) in the raw material pulp is preferably 10% by mass or more and 90% by mass or less, more preferably 15% by mass or more, even more preferably 20% by mass or more, and more preferably 70% by mass or less, even more preferably 50% by mass or less, and even more preferably 40% by mass or less. From the viewpoint of obtaining a desired specific tensile strength described below, the content of hardwood unbleached kraft pulp (LUKP) in the raw material pulp of the cushioning paper is preferably 60 mass % or less, more preferably 50 mass % or less, even more preferably 40 mass % or less, and even more preferably 30 mass % or less, and there is no particular lower limit, but it is 0 mass %.

[0016] <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.

[0017] <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.

[0018] 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.

[0019] In addition, it is preferable to include a coating step of coating at least one surface of the paper after the papermaking process with a coating liquid containing at least one resin selected from the group consisting of a water-soluble resin and a water-suspendable resin. The coating step forms a surface layer. A size press or the like can be used as the coating device. Examples of the water-soluble resin include modified starches such as oxidized starch and cationic starch, polyacrylamide, polyvinyl alcohol, etc. Examples of the water-suspendable resin include starch, etc. When starch is used, it may be modified by itself, such as by enzyme modification or thermochemical modification. The surface layer is preferably formed by applying a liquid for forming the surface layer, which contains at least one selected from the group consisting of a water-soluble resin and a water-suspendable resin, to the surface of the paper substrate. The amount (solid content) of the surface layer is preferably 0.1 g / m 2 More than 5g / m 2 More preferably, it is 0.3 g / m or less. 2 More preferably, 0.5 g / m 2 More preferably, it is 4.0 g / m or more. 2 Less than 3.0 g / m, more preferably 3.0 g / m 2 The surface layer may be applied to only one side, but it is preferably applied to both sides. When applied to both sides, the above-mentioned preferred application amount is the preferred application amount per one side.

[0020] <Characteristics of cushioning paper> (Basic weight) The basis weight of the cushioning paper is 35g / m2 from the viewpoint of cushioning properties. 2 More preferably, it is 40 g / m 2 More preferably, 50 g / m 2 More preferably, 60 g / m 2 More preferably, 65 g / m 2 From the viewpoint of processability when used as a paper cushioning material, the thickness is preferably 200 g / m 2 Less than 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.

[0021] (density) The density of the cushioning paper of this embodiment is preferably 0.50 g / cm from the viewpoint of cushioning properties and processability when made into a paper cushioning material. 3 More than 0.95g / cm 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 0.55g / cm 3 More preferably, 0.60 g / cm 3 More preferably, it is 0.85 g / cm or more. 3 More preferably, 0.80 g / cm 3 More preferably, 0.75 g / cm 3 More preferably 0.72 g / cm 3 The following is the result. 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.

[0022] (Thickness) From the standpoint of cushioning properties and processability when turned into paper cushioning, 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 300 μm or less, even more preferably 250 μm or less, even more preferably 200 μm or less, and still more preferably 160 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.

[0023] (Specific tensile strength) The cushioning paper of this embodiment has a geometric mean value (average value of specific tensile strength) of the longitudinal specific tensile strength and the transverse specific tensile strength measured in accordance with JIS P 8113:2006 of 17.0 Nm / g or more. A specific tensile strength of 17.0 Nm / g or more is preferable because it provides excellent cushioning. The average value of the specific tensile strength of the cushioning paper is preferably 18.0 Nm / g or more, more preferably 20.0 Nm / g or more, and even more preferably 22.0 Nm / g or more. There is no particular upper limit to the average value of the tensile strength of the cushioning paper, but from the viewpoint of suppressing the generation of paper dust and from the viewpoint of processability when made into paper cushioning material, it is preferably 60.0 Nm / g or less, more preferably 50.0 Nm / g or less, and even more preferably 40.0 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 of raw pulp, the blending ratio, the amount of strength agent (dry strength agent), the density of the cushioning paper, etc. When recycled paper pulp, NUKP, and optionally 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.

[0024] (Fibrillation degree) In the cushioning paper of this embodiment, the fibrillation degree of the pulp fibers that make up the cushioning paper is 1.5% or less. A fibrillation degree of 1.5% or less is preferable because it suppresses the generation of paper dust. It is preferable that the fibrillation degree is a small value, preferably 1.4% or less, more preferably 1.3% or less, and the lower limit is not particularly limited, but is generally 0.2% or more. The degree of fibrillation is the degree of external fibrillation and is represented by the following formula (1) described in HR Motamedian et. al., “Mechanisms of strength and stiffness improvement of paper after PFI refining with a focus on the effect of fines”, Cellulose (2019) 26:4099-4124.

[0025]

number

[0026] The degree of fibrillation tends to decrease by decreasing the blending ratio of recycled paper pulp, and tends to increase by beating the pulp to a high degree.

[0027] (Percentage of long fibers) In this embodiment, the proportion of fibers with a fiber length of 1.2 mm or more (hereinafter, fibers with a fiber length of 1.2 mm or more are also referred to as "long fibers") in the pulp fibers constituting the cushioning paper is preferably 8.0% or more, more preferably 10.0% or more, and even more preferably 12.0% or more, from the viewpoints of suppressing the generation of paper dust and cushioning performance. There is no particular upper limit, but from the viewpoints of reducing the environmental impact by using recycled paper pulp and of inexpensive production, it is preferably 30.0% or less, more preferably 20% or less, and even more preferably 15% or less. The proportion of long fibers in the pulp fibers that make up the cushioning paper can be adjusted by selecting the raw pulp used. Specifically, the proportion of long fibers tends to increase when the amount of unbleached softwood pulp used is increased. The percentage of long fibers in the pulp that constitutes the cushioning paper is calculated by disintegrating the cushioning paper using the method described in the Examples, measuring the fiber length of the resulting pulp slurry using a fiber length measuring device (e.g., Valmet Model FS-5 with UHD base unit), and calculating the percentage of fibers with length-weighted fiber lengths of 1.2 mm or more (percentage of number).

[0028] The percentage of long fibers is measured in accordance with JIS P 8226:2006. Specifically, the number of fibers (n i ) is measured. Length-weighted percentage of fibres (f i ') is calculated using the following formula (2).

[0029]

number

[0030] Where: f i ': Percentage of length-weighted fibre count (%) n i : number of fibers in the i-th length range l i: ith length range center in millimeters Σn i : Total number of fibers Σn i l i : n calculated for all length ranges i l i The sum of

[0031] The percentage of long fibers is the percentage of long fibers expressed by formula (2). For long fibers, the percentage of long fibers expressed by formula (2) is calculated for each fiber length category of 1.2 mm or more, and the total is the percentage of long fibers.

[0032] More specifically, the FS-5 UHD base unit manufactured by Valmet used in the examples measures the number of fibers in the following six fractions (Fraction 1 to Fraction 6). Fraction 1: Fiber length less than 0.2 mm Fraction 2: Fiber length 0.2 mm or more and less than 0.6 mm Fraction 3: Fiber length 0.6 mm or more and less than 1.2 mm Fraction 4: Fiber length 1.2 mm or more and less than 2.0 mm Fraction 5: Fiber length 2.0 mm or more and less than 3.2 mm Fraction 6: Fiber length 3.2 mm or more and less than 7.6 mm The percentage of long fibers is calculated as the length-weighted percentage of the number of fibers (f i The total is the percentage of long fibers (%).

[0033] [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. When the cushioning paper is folded using an electrically operated cushioning preparation machine to prepare paper cushioning, if cushioning paper that generates a lot of paper dust is used, problems such as a high load on the machine and the need for cleaning 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

[0034] 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.

[0035] [Evaluation and Analysis] The raw pulp, cushioning paper, and paper cushioning materials of the examples and comparative examples were evaluated and analyzed as follows.

[0036] [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.

[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] <Long fiber content> The obtained buffer paper was cut into 4 cm squares and soaked in ion-exchanged water for 24 hours. The soaked buffer paper was taken out and the concentration was adjusted to 2% with ion-exchanged water. The mixture of the adjusted concentration of the buffer paper and ion-exchanged water was disintegrated using a standard disintegrator (Kumagaya 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 long fiber content was measured using a fiber length measuring device (model number FS-5 UHD base unit, Valmet). The long fiber content is the length-weighted percentage of fibers with a fiber length of 1.2 mm or more (long fibers).

[0041] <Fibrillation degree> The cushioning paper was cut into 4 cm squares and soaked in ion-exchanged water for 24 hours. The soaked cushioning paper was removed and adjusted to a concentration of 2% with ion-exchanged water. The mixture of the adjusted concentration of paper base material and ion-exchanged water was disintegrated 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 degree of fibrillation was measured using a fiber length measuring device (model number FS-5 UHD base unit, manufactured by Valmet).

[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 was then put into an automatic paper cushioning manufacturing machine (PACWELL, NUEVOPAK TM X-FILL TM The paper was placed in a paper feeder (Type A) and fed 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 plastic container containing a beverage (manufactured by Yakult Honsha Co., Ltd., product name: New Yakult, 65 mL) was repeatedly dropped vertically from a height of 40 cm onto the cushioning material in the enclosure with the bottom facing vertically downwards, and the number of times it took for the container to become deformed, such as dented or scratched, was counted. The test was carried out five times each, and the cushioning properties were evaluated according to the following criteria based on the average number of times (rounded to the nearest decimal place) until deformation occurred. A: Average number of falls is 4 or more B: Average number of falls is 3 or less

[0043] <Paper powder> An adhesive film (NEION PET75-H105(20) manufactured by Nichiei Shinka Co., Ltd.) was attached to a roll and rolled twice over the cushioning paper obtained in the Examples and Comparative Examples at a speed of 60 bpm to cause paper powder to adhere to the film. The film image (5 x 5 cm) was scanned and binarized into white and black areas. The white areas were considered to be paper dust, and the amount of paper dust in each sample was measured as the white area ratio (%). Paper dust was evaluated according to the following criteria: If the white area ratio was 1.00% or less, there was no problem in practical use. A: White area ratio is 0.50% or less B: White area ratio is more than 0.50% and 0.70% or less C: White area ratio is more than 0.70% and 1.00% or less D: White area ratio exceeds 1.00%

[0044] [Example 1] Pulp raw materials were mixed in a mass ratio of 30:20:50, consisting of softwood unbleached kraft pulp (NUKP), hardwood unbleached kraft pulp (LUKP), and waste paper pulp, to obtain a pulp slurry. A paper stock was prepared by adding 0.15 parts by mass (solids) of a polyacrylamide-based paper strength agent (PS117, manufactured by Arakawa Chemical Industries Co., Ltd.) as an internal paper strength agent, 0.2 parts by mass (solids) of a rosin sizing agent (Size Pine N-811, manufactured by Arakawa Chemical Industries Co., Ltd.) as an internal sizing agent, and 1.5 parts by mass (solids) of aluminum sulfate to 100 parts by mass of the pulp raw material (solids). Using this paper stock, a paper stock with a set basis weight of 70 g / m was prepared.2 Then, starch (Ace A, manufactured by Oji Cornstarch Co., Ltd.) was applied to both sides of the sheet at a rate of 0.5 g / m2 per side using a coater. 2 (1.0g / m on both sides 2 ) was applied to obtain the cushioning paper of Example 1.

[0045] [Example 2] A cushioning paper was obtained under the same conditions as in Example 1, except that the amount of the polyacrylamide-based internal paper strength agent was 0.40 parts by mass (solid content equivalent).

[0046] [Example 3] A cushioning paper was obtained under the same conditions as in Example 1, except that the amount of the polyacrylamide-based internal paper strength agent was 0.70 parts by mass (solid content equivalent).

[0047] [Example 4] Cushioning paper was obtained under the same conditions as in Example 1, except that the pulp raw materials were a mixture of softwood unbleached kraft pulp (NUKP), hardwood unbleached kraft pulp (LUKP), and recycled paper pulp in a mass ratio of 30:30:40, and the polyacrylamide-based internal paper strength agent was added in an amount of 0.13 parts by mass (solids content equivalent).

[0048] [Example 5] Cushioning paper was obtained under the same conditions as in Example 1, except that softwood unbleached kraft pulp (NUKP), hardwood unbleached kraft pulp (LUKP), and recycled paper pulp were mixed in a mass ratio of 30:50:20 as the pulp raw materials, and 0.10 parts by mass (solids 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 softwood unbleached kraft pulp (NUKP), hardwood unbleached kraft pulp (LUKP), and recycled paper pulp were mixed in a mass ratio of 30:30:40 as the pulp raw materials, and 0.60 parts by mass (solids content equivalent) of a polyacrylamide-based internal paper strength agent was added.

[0050] [Example 7] Set basis weight to 95g / m 2A cushioning paper was obtained under the same conditions as in Example 1, except that the above-mentioned conditions were changed.

[0051] [Example 8] Polyacrylamide-based internal paper strength enhancer: 0.40 parts by mass (solid content equivalent), set basis weight: 95 g / m 2 A cushioning paper was obtained under the same conditions as in Example 1, except that the above-mentioned conditions were changed.

[0052] [Example 9] Polyacrylamide-based internal paper strength enhancer: 0.70 parts by mass (solid content equivalent), set basis weight: 95 g / m 2 A cushioning paper was obtained under the same conditions as in Example 1, except that the above-mentioned conditions were changed.

[0053] [Example 10] The raw pulp materials were a mixture of softwood unbleached kraft pulp (NUKP), hardwood unbleached kraft pulp (LUKP), and waste paper pulp in a mass ratio of 30:30:40, with 0.13 parts by mass (solids equivalent) of a polyacrylamide-based internal paper strength enhancer, and a set basis weight of 95 g / m. 2 A cushioning paper was obtained under the same conditions as in Example 1, except that the above-mentioned conditions were changed.

[0054] [Example 11] The raw pulp materials were a mixture of softwood unbleached kraft pulp (NUKP), hardwood unbleached kraft pulp (LUKP), and waste paper pulp in a mass ratio of 30:50:20, with 0.10 parts by mass (solid content equivalent) of a polyacrylamide-based internal paper strength enhancer, and a set basis weight of 95 g / m. 2 A cushioning paper was obtained under the same conditions as in Example 1, except that the above-mentioned conditions were changed.

[0055] [Example 12] The raw pulp materials were a mixture of softwood unbleached kraft pulp (NUKP), hardwood unbleached kraft pulp (LUKP), and waste paper pulp in a mass ratio of 30:30:40, with 0.60 parts by mass (solids equivalent) of a polyacrylamide-based internal paper strength enhancer, and a set basis weight of 95 g / m. 2 A cushioning paper was obtained under the same conditions as in Example 1, except that the above-mentioned conditions were changed.

[0056] [Example 13] Polyacrylamide-based internal paper strength enhancer: 0.40 parts by mass (solid content equivalent), set basis weight: 135 g / m 2 A cushioning paper was obtained under the same conditions as in Example 1, except that the above-mentioned conditions were changed.

[0057] [Example 14] Cushioning paper was obtained under the same conditions as in Example 1, except that softwood unbleached kraft pulp (NUKP), hardwood unbleached kraft pulp (LUKP), and recycled paper pulp were mixed in a mass ratio of 50:0:50 as pulp raw materials, and 0.30 parts by mass (solids content equivalent) of a polyacrylamide-based internal paper strength agent was added.

[0058] [Example 15] Cushioning paper was obtained under the same conditions as in Example 1, except that the pulp raw materials were a mixture of softwood unbleached kraft pulp (NUKP), hardwood unbleached kraft pulp (LUKP), and recycled paper pulp in a mass ratio of 10:40:50, and the polyacrylamide-based internal paper strength agent was added in an amount of 0.50 parts by mass (solids content equivalent).

[0059] [Comparative Example 1] A cushioning paper was obtained under the same conditions as in Example 1, except that the amount of the polyacrylamide-based internal paper strength agent was 0.10 parts by mass (solid content equivalent).

[0060] [Comparative Example 2] Cushioning paper was obtained under the same conditions as in Example 1, except that softwood unbleached kraft pulp (NUKP), hardwood unbleached kraft pulp (LUKP), and recycled paper pulp were mixed in a mass ratio of 30:0:70 as pulp raw materials, and 0.15 parts by mass (solids content equivalent) of a polyacrylamide-based internal paper strength agent was added.

[0061] [Comparative Example 3] The polyacrylamide-based internal paper strength agent was set at 0.10 parts by mass (solid content equivalent), and the set basis weight was 95 g / m 2 A cushioning paper was obtained under the same conditions as in Example 1, except that the above-mentioned conditions were changed.

[0062] [Comparative Example 4] The raw pulp materials were a mixture of softwood unbleached kraft pulp (NUKP), hardwood unbleached kraft pulp (LUKP), and waste paper pulp in a mass ratio of 30:0:70, with 0.15 parts by mass (solids equivalent) of a polyacrylamide-based internal paper strength enhancer, and a set basis weight of 95 g / m. 2 A cushioning paper was obtained under the same conditions as in Example 1, except that the above-mentioned conditions were changed.

[0063] [Comparative Example 5] The polyacrylamide-based internal paper strength agent was set at 0.40 parts by mass (solid content equivalent), and the set basis weight was 30 g / m 2 A cushioning paper was obtained under the same conditions as in Example 1, except that the above-mentioned conditions were changed.

[0064] The obtained cushioning paper was subjected to the above-mentioned evaluations. The results are shown in the table below.

[0065] [Table 1]

[0066] 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, and also suppresses the generation of paper dust. [Industrial Applicability]

[0067] The cushioning paper of the present invention is excellent in cushioning properties when used as a cushioning material, and the generation of paper dust is suppressed, making it suitable for use as a paper cushioning material.

Claims

1. Basis weight 35g / m ２ That's all. 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 17.0 Nm / g or more; The fibrillation degree of the constituent pulp fibers is 1.5% or less; Cushioning paper.

2. 2. The cushioning paper according to claim 1, wherein the percentage of fibers having a fiber length of 1.2 mm or more among the pulp fibers constituting the cushioning paper is 8.0% or more.

3. Density is 0.50 g / cm ３ 0.95g / cm or more ３ 2. The cushioning paper of claim 1, wherein:

4. 2. The cushioning paper according to claim 1, wherein the cushioning paper contains recycled paper pulp as a raw pulp material.

5. A paper cushioning material obtained by folding the cushioning paper according to any one of claims 1 to 4.

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