Base paper for cushioning materials, and paper cushioning material

Abstract

Provided are: base paper for cushioning materials which can readily develop projection shapes when forming projections thereon by imparting a plurality of projection shapes, and which enables production of a paper cushioning material that ensures minimal breakage of the projections and exhibits excellent cushioning properties; and a paper cushioning material that is obtained by forming a plurality of projections on one or both sides of the paper surfaces of said base paper for cushioning materials. The base paper for cushioning materials is subject to formation of at least 70 projections per 100 cm2 on one or both sides of the paper surface to produce a paper cushioning material. The base paper has a basis weight of 70-110 g / m2, a lateral tensile strength of at least 1.5 kN / m, and a transmitted-light formation index of at least 8.<sp / > The paper cushioning material is produced by forming at least 70 projections per 100 cm2 on one or both sides of the paper surfaces of the base paper for cushioning materials.

Description

Paper base for cushioning materials and paper cushioning materials

[0001] This invention relates to base paper for cushioning materials and paper cushioning materials.

[0002] Cushioning materials are used to fill the gaps between the case and the contents when goods are stored in envelopes, cardboard boxes, or other packaging cases, and to absorb vibrations and shocks that occur to the contents during transportation. Traditionally, cushioning materials have been made from resins such as polyethylene and polyurethane foam.

[0003] In recent years, the problem of plastic waste has become increasingly serious worldwide, and in order to improve the global environment, there is a growing movement to eliminate and reduce plastic in packaging materials, replacing plastic packaging with paper packaging. From an environmental protection standpoint, paper-based cushioning materials are becoming more widespread as an alternative to plastic cushioning materials.

[0004] Patent Document 1 discloses a paper-based protective sheet, which aims to provide a protective sheet that can improve portability, and is made of kraft paper containing coniferous pulp, wherein the content of the coniferous pulp is within a specific range relative to the mass of the kraft paper, and the kraft paper has a thickness of a specific value or less and a basis weight within a specific range. Patent Document 2 discloses a cushioning packaging sheet and packaging bag used when packaging articles, which protects articles, and the cushioning packaging sheet is embossed paper having numerous uneven shapes over substantially the entire surface of the paper base material, and the height of the uneven shapes is greater than the thickness of the paper base material and is below a specific value.

[0005] Japanese Patent Publication No. 2023-44936 Japanese Patent Publication No. 2018-177304

[0006] One type of plastic cushioning material is bubble wrap, which consists of multiple granular air bubbles arranged between film sheets of polyethylene or similar material. However, there is a desire to make this bubble wrap material out of paper. When creating a cushioning material by forming protrusions on paper, as is done with plastic bubble wrap, tears can occur in the protrusions during the formation process. From the perspective of cushioning performance, it is desirable to have a material that is easy to form protrusions on, minimizes tears that occur during the formation of the protrusions, and improves the cushioning performance of the cushioning material.

[0007] The grooves in the protective sheet described in Patent Document 1 function as an anti-slip feature when walking on the protective sheet. The cushioning packaging sheet described in Patent Document 2 has an uneven surface, and the base paper of the cushioning packaging sheet has not been optimized to impart a raised surface to the paper.

[0008] The present invention aims to provide a base paper for cushioning material that forms multiple protrusions on one or both sides of the paper surface, which allows for easy formation of multiple protrusions, minimizes tearing of the protrusions, and provides a paper cushioning material with excellent cushioning properties, and a paper cushioning material having multiple protrusions formed on one or both sides of the paper surface of the cushioning material base paper.

[0009] The inventors have found that the above problems can be solved by setting the basis weight of the cushioning material base paper to a specific range, setting the transverse tensile strength of the cushioning material base paper to a specific value or higher, and setting the transmitted light-forming index of the cushioning material base paper to a specific value or higher. That is, the present invention has the following configuration: <1> 70 protrusions per 100 cm on one or both sides of the paper surface ２ The above-described base paper for cushioning material is formed to create a paper cushioning material, with a basis weight of 70 g / m². ２ 110g / m or more ２The base paper for a cushioning material, which has the following properties: the tensile strength in the transverse direction is 1.5 kN / m or more, and the transmitted light ground covering index is 8 or more. <2> The base paper for a cushioning material according to <1>, wherein the elongation at break in the transverse direction is 3.0% or more and 10.0% or less. <3> The base paper for a cushioning material according to <1> or <2>, wherein the tensile strength in the longitudinal direction is 2.5 kN / m or more. <4> The base paper for a cushioning material according to any one of <1> to <3>, wherein the elongation at break in the longitudinal direction is 5.9% or more. <5> The base paper for a cushioning material according to any one of <1> to <4>, on one side or both sides of the paper surface, convex portions are formed at 70 pieces / 100 cm ２ or more to form a paper cushioning material. <6> The paper cushioning material according to <5>, wherein the volume per one of the convex portions is 20 mm ３ or more and 150 mm ３ or less.

[0010] It is a schematic diagram for explaining a configuration example of a paper cushioning material formed by forming a plurality of convex portions on one side of the paper surface of the base paper for a cushioning material of the present invention. It is a schematic diagram for explaining a configuration example of a paper cushioning material formed by forming a plurality of convex portions on both sides of the paper surface of the base paper for a cushioning material of the present invention. It is a cross-sectional view of the paper cushioning material illustrated in FIG. 1. It is a cross-sectional view of the paper cushioning material illustrated in FIG. 2. It is a plan view showing the paper cushioning material according to the embodiment. It is a cross-sectional view of the paper cushioning material shown in FIG. 5.

[0011] [Base paper for cushioning material] The base paper for a cushioning material according to the present embodiment (hereinafter, also simply referred to as the base paper for a cushioning material) is a base paper for a cushioning material for forming convex portions on one side or both sides of the paper surface at 70 pieces / 100 cm ２ or more to form a paper cushioning material. The basis weight is 70 g / m ２ or more and 110 g / m ２ or less, the tensile strength in the transverse direction is 1.5 kN / m or more, and the transmitted light ground covering index is 8 or more. 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. Further, the base paper for a cushioning material of the present invention can have the characteristics or physical properties described in this specification in any combination. Note that the longitudinal direction of the base paper for a cushioning material means the papermaking direction (MD), and the transverse direction means the direction orthogonal to the papermaking direction (CD).

[0012] The base paper for cushioning material according to this embodiment has a basis weight above a specific value, which reduces tearing of the convex parts when forming the convex parts by adding multiple convex shapes, and also provides excellent cushioning properties. Furthermore, if the basis weight is below a specific value, the convex shapes are more easily formed when adding multiple convex shapes. The base paper for cushioning material according to this embodiment has a transverse tensile strength above a specific value, which reduces tearing of the convex parts when forming the convex parts by adding multiple convex shapes using a paper cushioning material manufacturing machine. The base paper for cushioning material according to this embodiment has a transmitted light densitivity index above a specific value, which suppresses unevenness and tends to be uniform, thus reducing tearing of the convex parts that tend to occur in uneven areas when forming the convex parts by adding multiple convex shapes. The base paper for cushioning material according to this embodiment has convex parts at 100 cm. ２ A paper cushioning material formed with a certain number or more protrusions per surface area is designed to easily absorb the load when a load is applied to the paper cushioning material, and as a result, it has excellent cushioning properties.

[0013] The cushioning paper of this embodiment includes at least a paper substrate, and the paper substrate includes pulp as a raw material. The manufacturing method and type of pulp are not particularly limited. The cushioning paper of this embodiment may have a coating layer such as a resin layer or a laminate layer in addition to the paper substrate, but it is preferable that it consists only of a paper substrate. The paper substrate may be a single layer or a multilayer structure, but a single layer structure is preferred. In the case of a multilayer structure, the number of paper layers is not particularly limited, but for example, it is preferably 2 to 7 layers, and more preferably 2 to 6 layers.

[0014] <Raw Pulp> In this embodiment, natural pulp fibers are preferred as the raw pulp constituting the base paper (paper substrate) for the cushioning material, from the viewpoint of reducing environmental impact. As natural pulp fibers, wood fibers (chemical pulp, mechanical pulp), non-wood fibers, deinked pulp (DIP, recycled paper pulp), etc., can be used as needed. Examples of chemical pulp include kraft pulp, which uses caustic soda and sodium sulfide when pulping wood chips, and sulfite pulp, which uses sulfurous acid and bisulfite. These pulps may be unbleached or bleached. Examples of mechanical pulp include ground wood pulp (GP) obtained by grinding logs with a grinder, refined ground wood pulp (RGP) obtained by grinding (refining) waste wood from sawmills with a refiner, and thermomechanical pulp (TMP) obtained by heating and refining wood chips. These pulp fibers can be used alone or in combination of two or more types. Furthermore, synthetic resin fibers may be blended as needed, to the extent that they do not impair the effects of the present invention. Examples of coniferous trees used as raw materials for wood fiber pulp include pine, larch, cedar, fir, and cypress. Examples of hardwoods used as raw materials for hardwood pulp include eucalyptus, acacia, birch, beech, maple, elm, and chestnut. Examples of non-wood fibers include bast fibers such as paper mulberry, mitsumata, gampi, flax, taima, kenaf, choma, jute, and sun 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. Non-wood fibers can be pulped in the same way as wood fibers. Examples of deinked pulp include those made from recycled paper such as corrugated cardboard and magazine paper. Examples of synthetic resin fibers include polyethylene fibers, polypropylene fibers, polyamide fibers, polyethylene terephthalate fibers, polybutylene terephthalate fibers, and polylactic acid fibers.

[0015] The raw material pulp preferably contains at least one selected from the group consisting of softwood pulp and hardwood pulp, more preferably contains at least one selected from the group consisting of softwood kraft pulp and hardwood kraft pulp, even more preferably contains at least one selected from the group consisting of unbleached softwood kraft pulp (NUKP) and unbleached hardwood kraft pulp (LUKP), and even more preferably contains at least one selected from the group consisting of unbleached softwood kraft pulp and unbleached hardwood kraft pulp.

[0016] The content of softwood pulp (preferably NUKP) in the raw pulp is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and 100% by mass or less, from the viewpoint of reducing the tearing of the protrusions when forming multiple protrusions on the base paper for cushioning material and providing a paper cushioning material with superior cushioning properties. The content of hardwood pulp (preferably LUKP) in the raw pulp is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and may be 0% by mass, from the viewpoint of reducing the tearing of the protrusions when forming multiple protrusions on the base paper for cushioning material and providing a paper cushioning material with superior cushioning properties. When the raw pulp contains softwood pulp (preferably NUKP) and hardwood pulp (preferably LUKP), from the viewpoint of easily obtaining the desired tensile strength, the total content of softwood pulp (preferably NUKP) and hardwood pulp (preferably LUKP) in the raw pulp is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and 100% by mass or less. The raw pulp may also contain deinked pulp (recycled paper pulp), but from the viewpoint of obtaining the desired tensile strength, the content of deinked pulp (recycled paper pulp) in the raw pulp is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, even more preferably 10% by mass or less, even more preferably 5% by mass or less, and may be 0% by mass.

[0017] The Canadian Standard Fluidity (CSF) of the raw pulp is preferably 300 mL to 700 mL, more preferably 400 mL or more, even more preferably 450 mL or more, even more preferably 500 mL or more, and even more preferably 530 mL or more, from the viewpoint of obtaining appropriate paper strength for use as a base paper for cushioning material, and more preferably 650 mL or less, even more preferably 600 mL or less, and even more preferably 580 mL or less. The CSF of the raw pulp is measured according to JIS P 8121-2:2012 "Pulp - Fluidity test method - Part 2: Canadian Standard Fluidity method".

[0018] (Optional Components) The raw pulp may contain optional components as needed, such as pH adjusters (sodium bicarbonate, sodium hydroxide, etc.), dry strength enhancers, wet strength enhancers, internal sizing agents, filtration yield enhancers, defoamers, fillers (calcium carbonate, talc, etc.), dyes, and fixatives (aluminum sulfate). These optional components may be used individually or in combination of two or more. The content of optional components is not particularly limited and may be within the range commonly used.

[0019] Examples of dry strength enhancers include polyacrylamide (PAM)-based dry strength enhancers, starch-based dry strength enhancers, CMC (carboxymethylcellulose) or its salts. These can be used individually or in combination of two or more. Among these, the dry strength enhancer preferably contains at least one selected from the group consisting of PAM-based dry strength enhancers and starch-based dry strength enhancers, and more preferably at least one selected from the group consisting of PAM-based dry strength enhancers and starch-based dry strength enhancers. When the base paper for cushioning material (paper substrate) has a multilayer structure, the dry strength enhancer may be contained in some layers, but it is preferable that it is contained in each layer, and it is even more preferable that the amount in each layer is within the range of the preferred amounts described below. When a dry paper strength enhancer is included, the amount of dry paper strength enhancer (in terms of solid content) is preferably 0.05 parts by mass or more and 3.0 parts by mass or less, more preferably 0.1 parts by mass or more, even more preferably 0.3 parts by mass or more, even more preferably 0.5 parts by mass or more, and even more preferably 2.0 parts by mass or less, and even more preferably 1.0 part by mass or less, per 100 parts by mass of raw pulp (in terms of solid content).

[0020] Examples of wet strength enhancers include polyamide polyamine epichlorohydrin resin (PAE), melamine-formaldehyde resin, and urea-formaldehyde resin. When the paper substrate has a multilayer structure, the wet strength enhancer may be contained in some of the layers, but it is preferable that each layer contains it, and it is even more preferable that the amount of each layer contains it is within the range of the following preferred amounts. When a wet strength enhancer is contained, the amount of the wet strength enhancer (in terms of solid content) is preferably 0.01 parts by mass or more and 1.0 parts by mass or less, more preferably 0.03 parts by mass or more, even more preferably 0.05 parts by mass or more, even more preferably 0.1 parts by mass or more, and even more preferably 0.5 parts by mass or less, and even more preferably 0.3 parts by mass or less, per 100 parts by mass of raw pulp (in terms of solid content).

[0021] Examples of the internal sizing agent include rosin-based agents and alkyl ketene dimers. Among these, rosin-based sizing agents are preferred. For rosin-based sizing agents, for example, acidic rosin-based sizing agents, weakly acidic rosin-based sizing agents, and neutral rosin-based sizing agents can be used. When the paper base material has multiple paper layers, the internal sizing agent may be contained in some layers, but it is preferably contained in each layer, and it is more preferable that the blending amount of each layer is within the range of the following preferred blending amounts. When containing an internal sizing agent, the blending amount (in terms of solid content) of the internal sizing agent is preferably 0.01 parts by mass or more and 3.0 parts by mass or less, more preferably 0.05 parts by mass or more, still more preferably 0.1 parts by mass or more, and more preferably 1.0 parts by mass or less, still more preferably 0.5 parts by mass or less, based on 100 parts by mass (in terms of solid content) of the raw pulp.

[0022] <Method for Producing Base Paper for Cushioning Material> The method for producing the base paper for the cushioning material preferably includes a step of papermaking a slurry containing the above raw pulp. The papermaking method is not particularly limited, and examples 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, papermaking chemicals 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 also not particularly limited, and examples include continuous papermaking machines such as a twin-wire type, a fourdrinier type, a cylinder type, and an inclined type, or a multi-layer combined papermaking machine combining these. In the papermaking step, the jet / wire ratio (J / W ratio), which is the ratio of the flow rate (J) of the papermaking stock ejected onto the wire to the running speed (W) of the papermaking wire, is preferably 0.98 or more and 1.30 or less, more preferably 1.20 or less, still more preferably 1.10 or less, even more preferably 1.05 or less, most preferably 1.03 or less, and more preferably 0.99 or more, from the viewpoint of being easy to adjust to the desired fiber orientation strength.

[0023] (Kurpack Process) The method for manufacturing the base paper for buffer material preferably includes a Kurpack process. That is, the base paper for buffer material is preferably one that has been subjected to a Kurpack process. The Kurpack process is a process of imparting elongation performance in the longitudinal direction by finely shrinking the paper in the longitudinal direction on a paper-making machine. As a specific processing method, a Kurpack device is installed in a part of the paper-making machine dryer, and the wet paper is passed between an endless thick elastic rubber blanket with nip rolls and a heating dryer, and the blanket that has been stretched in advance contracts to shrink the running paper web. The shrinkage that occurs is dried and fixed so that it does not stretch in subsequent processes. The speed difference before and after the Kurpack process is preferably -15% or more and -2% or less, more preferably -13% or more, still more preferably -11% or more, even more preferably -9% or more, most preferably -7% or more, from the viewpoint of reducing breakage of the convex portions when forming a plurality of convex portions on the base paper for buffer material. And more preferably -3% or less, still more preferably -4% or less. Here, the minus "-" indicates that the speed after the Kurpack process is slower.

[0024] <Properties of the Base Paper for Buffer Material> (Grammage) From the above viewpoints, the grammage of the base paper for buffer material is 70 g / m ２ or more and 110 g / m ２ or less. From the viewpoint of reducing breakage of the convex portions when forming a plurality of convex portions on the base paper for buffer material and obtaining a paper buffer material with excellent cushioning properties, it is preferably 75 g / m ２ or more. And from the viewpoint of making it easier to form a plurality of convex shapes, it is preferably 100 g / m ２ or less, more preferably 95 g / m ２ or less. The grammage of the base paper for buffer material is measured in accordance with JIS P 8124:2011, and specifically, it is measured by the method described in the examples.

[0025] (Tensile Strength) The tensile strength of the base paper for cushioning material in the transverse direction is, from the viewpoint described above, 1.5 kN / m or more, preferably 1.8 kN / m or more and 10.0 kN / m or less, more preferably 2.1 kN / m or more, even more preferably 2.3 kN / m or more, from the viewpoint of reducing tearing of the convex parts when forming the convex parts by imparting multiple convex shapes using a paper cushioning material manufacturing machine, and more preferably 8.0 kN / m or less, even more preferably 6.0 kN / m or less, and even more preferably 5.0 kN / m or less, from the viewpoint of making it easier to form the convex shapes when imparting multiple convex shapes. The tensile strength of the base paper for cushioning material can be adjusted by adjusting the amount of dry paper strength enhancer and / or wet paper strength enhancer added, the basis weight, etc. Specifically, the tensile strength of the base paper for cushioning material tends to increase by increasing the amount of dry paper strength enhancer and / or wet paper strength enhancer added, or by increasing the basis weight. The longitudinal tensile strength of the base paper for cushioning material is preferably 2.5 kN / m or more and 12.0 kN / m or less. From the viewpoint of reducing tearing of the protrusions when they are pulled when multiple protrusions are formed by imparting them to the paper cushioning material using a paper cushioning material manufacturing machine, it is more preferably 3.0 kN / m or more, even more preferably 4.0 kN / m or more, even more preferably 4.3 kN / m or more, and even more preferably 4.5 kN / m or more. Furthermore, from the viewpoint of making it easier to form the protrusions when multiple protrusions are imparted, it is more preferably 10.0 kN / m or less, even more preferably 8.0 kN / m or less, and even more preferably 6.0 kN / m or less. The synergistic mean of the longitudinal and transverse tensile strengths of the base paper for cushioning material is preferably 2.0 kN / m or more and 12.0 kN / m or less, and more preferably 3.0 kN / m or more, even more preferably 3.3 kN / m or more, even more preferably 3.6 kN / m or more, and even more preferably 3.9 kN / m or more, and more preferably 10.0 kN / m or less, even more preferably 8.0 kN / m or less, and even more preferably 6.0 kN / m or less, from the viewpoint of making it easier to create the convex shapes when creating the convex shapes. The tensile strength of the base paper for cushioning material is measured in accordance with JIS P 8113:2006, and specifically measured by the method described in the examples.

[0026] (Transmitted Light Formation Index) From the above viewpoint, the transmitted light formation index of the base paper for cushioning material is 8 or more, preferably 9 to 45, more preferably 10 or more, even more preferably 11 or more, from the viewpoint of reducing tearing of the convex parts when forming the convex parts by imparting multiple convex shapes, and from the viewpoint of ease of manufacture, more preferably 35 or less, even more preferably 30 or less, even more preferably 22 or less, and even more preferably 17 or less. The transmitted light formation index of the base paper for cushioning material can be adjusted to the above range by adjusting the basis weight of the base paper for cushioning material, the J / W ratio and papermaking speed in the papermaking process, the inlet concentration, the amount and type of yield agent added, the Kurupack treatment, etc. Specifically, the transmitted light formation index of the base paper for cushioning material tends to increase when the basis weight of the base paper for cushioning material is increased, the J / W ratio is brought closer to 1, the papermaking speed is slowed, the inlet concentration is diluted, the amount of yield agent added is reduced, or a yield agent with a small molecular weight is used. The transmitted light basis index of the cushioning material base paper was measured using a 3D sheet analyzer (M / K950) manufactured by M / K Systems, Inc. (MKS), with the analyzer's aperture set to a diameter of 1.5 mm, and using a microformation tester (MFT). Specifically, the sample (base paper) was mounted on a rotating drum in the 3D sheet analyzer, and the local basis weight difference of the sample was measured as a light intensity difference using a light source mounted on the drum axis and a photodetector mounted on the outside of the drum corresponding to the light source. The measurement range at this time is set by the diameter of the aperture attached to the light-receiving part of the photodetector. Next, the light intensity difference (deviation) was amplified, A / D converted, and classified into 64 optically measurable basis weight classes. 1,000,000 data points were taken in one scan, and the histogram frequency for that data was obtained. Then, the highest frequency (peak value) of the histogram is divided by the number of classes with a frequency of 100 or more out of the 64 classes, and the value obtained by dividing this by 100 is calculated as the transmitted light surface condition index. The higher the value of this transmitted light surface condition index, the better the surface condition.

[0027] (Elongation at Break) The transverse elongation at break of the base paper for cushioning material is preferably 3.0% to 10.0%, more preferably 4.5% or more, even more preferably 6.0% or more, and more preferably 9.5% or less, from the viewpoint of reducing tearing of the convex parts when forming convex parts by imparting multiple convex shapes. From the viewpoint of providing a paper cushioning material with superior cushioning properties, it is even more preferably 9.5% or less. The transverse elongation at break of the base paper for cushioning material can be adjusted by the type of raw pulp, the type and amount of paper strength enhancer, the pulp slurry concentration during beating, the drying conditions during papermaking (for example, the position of the drying device in the papermaking machine), the basis weight, etc. Specifically, increasing the amount of paper strength enhancer tends to increase the transverse elongation at break. Also, increasing the basis weight of the base paper for cushioning material tends to increase the transverse elongation at break. The longitudinal elongation at break of the base paper for cushioning material is preferably 5.9% to 10.0%, more preferably 6.1% or more, even more preferably 6.3% or more, from the viewpoint of reducing tearing of the convex parts when forming the convex parts by imparting multiple convex shapes, and more preferably 8.5% or less from the viewpoint of achieving both cushioning properties and desired tensile strength. The longitudinal elongation at break of the base paper for cushioning material can be controlled by the type of raw pulp, the pulp slurry concentration during beating, the pulp packing treatment conditions, etc. Pulp packing treatment tends to increase the longitudinal elongation at break, especially, and increasing the speed difference during pulp packing treatment tends to increase the longitudinal elongation at break even more. In addition, increasing the amount of paper strength enhancer used tends to increase the longitudinal elongation at break. The synergistic mean of the longitudinal and transverse elongation at break of the base paper for cushioning material is preferably 3.0% to 10.0%, more preferably 4.5% or more, even more preferably 6.0% or more, from the viewpoint of reducing tearing of the convex parts when forming the convex parts by imparting multiple convex shapes using a paper cushioning material manufacturing machine, and more preferably 9.0% or less, even more preferably 8.5% or less, from the viewpoint of providing a paper cushioning material with superior cushioning properties. The elongation at break of the base paper for cushioning material is measured in accordance with JIS P 8113:2006, specifically by the method described in the examples.

[0028] (Thickness) The thickness of the base paper for the cushioning material is preferably 110 μm or more and 160 μm or less, more preferably 115 μm or more, and even more preferably 120 μm or more, from the viewpoint of providing a paper cushioning material with superior cushioning properties, and from the viewpoint of reducing tearing of the convex parts when forming the convex parts by imparting multiple convex shapes using a paper cushioning material manufacturing machine, it is more preferably 150 μm or less, and even more preferably 145 μm or less. When the thickness of the base paper for the cushioning material is below the above upper limit, the clearance between the metal roll and the base paper for the cushioning material does not become too small when imparting multiple convex shapes using a paper cushioning material manufacturing machine, and tearing is reduced. The thickness of the base paper for the cushioning material is measured in accordance with JIS P 8118:2014, and specifically, it is measured by the method described in the examples.

[0029] (Density) The density of the base paper for cushioning material is preferably 0.50 g / cm³. ３ 0.85g / cm or more ３ The following is more preferable, as it increases interfiber bonding and, as a result, reduces tearing of the protrusions when forming multiple protrusions on the base paper for cushioning material. ３ More preferably, 0.60 g / cm³ ３ More preferably, 0.62 g / cm³ ３ Furthermore, from the viewpoint of making it easier to create multiple convex shapes, a more preferable value is 0.80 g / cm². ３ More preferably, 0.75 g / cm³ ３ The following applies: The density of the base paper for cushioning material can be adjusted by adjusting the press pressure during the papermaking process. The density of the base paper for cushioning material is calculated from the basis weight and thickness of the base paper.

[0030] The base paper for cushioning material has been described above. Next, paper cushioning material will be described using Figures 1 to 6. Here, Figure 1 is a schematic diagram illustrating an example of the configuration of a paper cushioning material in which a plurality of protrusions are formed on one side of the paper surface of the base paper for cushioning material of the present invention, and Figure 2 is a schematic diagram illustrating an example of the configuration of a paper cushioning material in which a plurality of protrusions are formed on both sides of the paper surface of the base paper for cushioning material of the present invention. Figure 3 is a cross-sectional view of the paper cushioning material illustrated in Figure 1, and Figure 4 is a cross-sectional view of the paper cushioning material illustrated in Figure 2. Figure 5 is a plan view showing a paper cushioning material according to an embodiment, and Figure 6 is a cross-sectional view of the paper cushioning material shown in Figure 5.

[0031] [Paper cushioning material] The paper cushioning material of this embodiment has 70 protrusions per 100 cm on one or both sides of the surface of the cushioning material base paper described above. ２ The above-described formation is achieved (see Figures 1, 2, and 5). The shape of the protrusion is not particularly limited and can be, for example, hemispherical, semi-ellipsoidal, cylindrical, polygonal, rectangular, etc. Among these, the shape of the protrusion is preferably hemispherical or semi-ellipsoidal. A protrusion is formed by pressing a projection or the like against the cushioning material base paper described above so that it protrudes from one side of the paper surface. The shape of the cushioning material base paper on which the protrusion is formed is not particularly limited and may be in the form of a roll, folded, or sheet. Furthermore, from the viewpoint of making the paper cushioning material easy to cut by hand, if the shape of the cushioning material base paper is in the form of a roll or folded, it may have perforated sections with multiple perforations in the transverse direction. It is preferable that the vertical distance between adjacent perforated sections is the same, and from the viewpoint of practicality such as storage and transport, if the shape of the cushioning material base paper is in the form of a folded, it is preferable to fold it alternately at multiple perforated sections and laminate it in an accordion-like manner to form a laminate.

[0032] The paper cushioning materials 100, 110, and 120 of this embodiment may have a plurality of protrusions 10 on one side of the paper surface, as shown in Figures 1 and 3, or they may have a plurality of protrusions 10 on one side of the paper surface and a plurality of protrusions 10' on the opposite side of the paper surface from the side with the plurality of protrusions 10, as shown in Figures 2, 4 to 6. From the viewpoint of providing a paper cushioning material with superior cushioning properties, it is preferable to have a plurality of protrusions 10, 10' on both sides of the paper surface, as shown in Figures 2, 4 to 6. Note that when the base paper for cushioning material has a plurality of protrusions 10, 10' on both sides of the paper surface, the above-mentioned 100 cm ２ The number of protrusions per unit area refers to the total number of protrusions 10, 10' formed on both sides. The arrangement and combination of the multiple protrusions 10, 10' formed on both sides of the paper are not particularly limited. For example, as shown in Figures 1 and 2, the protrusions 10, 10' may be arranged in parallel, or as shown in Figure 5, they may be arranged in a staggered pattern.

[0033] The formation of multiple protrusions may be performed manually or electrically using a paper cushioning material manufacturing machine, and is not particularly limited. Examples of paper cushioning material manufacturing machines include the "Paper Bubble Machine / PB640EW" and "Paper Bubble Machine / PB340pro" manufactured by WiAir, and the "Paper Bubble Wrap Machine / PB600A" manufactured by Zhangzhou Air Power Packaging Equipment.

[0034] (Number of protrusions) The number of protrusions in the paper cushioning material according to this embodiment is 70 per 100 cm, from the viewpoint described above. ２ The above is preferable, with a ratio of 90 pieces / 100 cm. ２ More than 450 pieces / 100cm ２ The following is more preferable, as the multiple protrusions make it easier to cushion the load when a load is applied to the paper cushioning material, resulting in a paper cushioning material with excellent cushioning properties, with 120 protrusions per 100 cm. ２ Furthermore, from the viewpoint of making the size of the protrusions sufficiently large and, as a result, providing a paper cushioning material with superior cushioning properties, it is more preferable to have 200 pieces / 100 cm. ２The following applies:

[0035] (Volume of the protrusions) The volume of each protrusion in the paper cushioning material of this embodiment is preferably 20 mm². ３ 150mm or more ３ The following is preferable, and from the viewpoint of improving cushioning, 25 mm ３ The above is true, and more preferably, 125 mm, from the viewpoint of reducing the tearing of the protrusions when forming multiple protrusions. ３ Further preferably 100 mm ３ More preferably, 70 mm ３ The following applies:

[0036] The volume of each of the protrusions 10, 10' is the average volume of the space occupied by the inside of each protrusion 10, 10' relative to the reference planes R', R, which are the flat surfaces opposite to the paper surface having the protrusions 10, 10' (the surfaces without the protrusions 10, 10') (see Figures 3, 4, and 6). As shown in Figures 1 and 3, for paper cushioning material having multiple protrusions 10 on one side of the paper surface, the volume of each of the protrusions 10 is the average volume of each of 10 randomly selected protrusions 10, specifically the portion surrounded by the inside of the protrusions 10 and the reference plane R' (the portion that has been given a convex shape by being pressed against by a protrusion, etc.). As shown in Figures 2, 4 to 6, for a paper cushioning material having multiple protrusions 10, 10' on both sides of the paper surface, the volume of each protrusion 10, 10' is the average of the volumes of five randomly selected protrusions 10 from one side of the paper surface, specifically the portion enclosed by the inside of the protrusion 10 and the reference surface R' (the portion that has been given a convex shape by being pressed against by a protrusion, etc.) and five randomly selected protrusions 10' from the other side of the paper surface, specifically the portion enclosed by the inside of the protrusion 10' and the reference surface R (the portion that has been given a convex shape by being pressed against by a protrusion, etc.). The volume of each protrusion is specifically calculated by the method described in the embodiment.

[0037] (Height of the protrusions) The height of the protrusions is preferably 1.00 mm or more and 5.00 mm or less, more preferably 1.20 mm or more, even more preferably 1.40 mm or more, and even more preferably 1.60 mm or more, and more preferably 4.00 mm or less, even more preferably 3.00 mm or less, and even more preferably 2.00 mm or less, from the viewpoint of reducing the tearing of the protrusions when forming multiple protrusions.

[0038] As shown in Figures 3, 4, and 6, the height of the protrusions 10, 10' refers to the average of the maximum heights of the inside of the multiple protrusions 10, 10' (the parts that have been pressed against by a protrusion or the like to give them a convex shape), with the flat surfaces R', R on the opposite side of the paper cushioning material from the protrusions 10, 10' being used as reference surfaces R', R. In other words, the height of the protrusions 10 on one side of the paper cushioning material refers to the average of the maximum heights of the inside of the multiple protrusions 10 (the parts that have been pressed against by a protrusion or the like to give them a convex shape), from the reference surface R', R, which is the area where there are no protrusions 10' on the paper surface opposite to the paper surface with the multiple protrusions 10. Similarly, the height of the protrusions 10' on the other side of the paper cushioning material refers to the average of the maximum heights of the inside of the multiple protrusions 10', from the reference surface R, which is the area where there are no protrusions 10 on the paper surface opposite to the paper surface with the multiple protrusions 10' (one side of the paper cushioning material). As shown in Figures 1 and 3, for paper cushioning material having multiple protrusions 10 on one side of the paper surface, the height of the protrusions 10 is the average value of the maximum heights H1 of 10 randomly selected protrusions 10 from the reference plane R'. As shown in Figures 2, 4 to 6, for paper cushioning material having multiple protrusions 10, 10' on both sides of the paper surface, the height of each protrusion 10, 10' is the average value of the maximum heights H2, H3 of the total of 10 protrusions 10, 10'. Specifically, for 5 protrusions 10 randomly selected from one side of the paper surface, the height H2 is the average value of the maximum heights H2 of the inside of the protrusion 10 (the part that has been pressed against by a protrusion or the like to give it a convex shape) from the reference plane R', and for 5 protrusions 10' randomly selected from the other side of the paper surface, the height H3 is the average value of the maximum heights H2 of the inside of the protrusion 10' (the part that has been pressed against by a protrusion or the like to give it a convex shape) from the reference plane R. The height of each of the protrusions 10, 10' is specifically measured by the method described in the embodiment.

[0039] (Distance between protrusions) The distance between adjacent protrusions (W1 in Figure 3, W2 in Figures 4 and 6) can be adjusted as appropriate depending on the volume and number of protrusions, preferably between 0.5 mm and 6 mm, more preferably between 5 mm and 4 mm from the viewpoint of improving cushioning performance. The above lower limit is not particularly limited, but it is preferable from the viewpoint of ease of manufacture if it is above the above lower limit. It is preferable that the multiple protrusions are provided at equal intervals. "Equal intervals" means that the difference between the maximum and minimum distances between adjacent protrusions is 10% or less of the maximum value. For example, in the paper cushioning material shown in Figure 2, if the maximum distance between adjacent protrusions is 2 mm and the minimum distance is 1.8 mm, this paper cushioning material has multiple protrusions at equal intervals.

[0040] The paper cushioning material of this embodiment can be used as a substitute for bubble wrap. The paper cushioning material of this embodiment is preferably used to fill the gap between a case such as a cardboard box for packaging and the contents such as goods, or to wrap around the contents such as goods, or to attach to the inside of an envelope, etc., so that it can absorb vibrations, shocks, etc. that occur to the contents during transportation.

[0041] The features of the present invention will be further described below with reference to examples and comparative examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following specific examples.

[0042] [Evaluation and Analysis] The following evaluations and analyses were performed on the raw pulp, base paper for cushioning material, and paper cushioning material of the examples and comparative examples.

[0043] <Raw Pulp> (Canadian Standard Filtration) The Canadian standard filtration of the raw pulp was measured in accordance with JIS P 8121-2:2012 "Pulp - Filtration Test Methods - Part 2: Canadian Standard Filtration Method".

[0044] <Paper for cushioning material> (Basis weight) The basis weight of the paper for cushioning material was measured in accordance with JIS P 8124:2011 after the paper obtained in the examples and comparative examples was conditioned for 24 hours under the humidity-controlled environment specified in JIS P 8111:1998.

[0045] (Thickness) The thickness of the base paper for cushioning material was measured in accordance with JIS P 8118:2014 after the base paper obtained in the examples and comparative examples was conditioned for 24 hours under the humidity-controlled environment specified in JIS P 8111:1998.

[0046] (Density) The density of the base paper for cushioning material was calculated from the basis weight and thickness measured as described above.

[0047] (Transmitted Light Formation Index) The transmitted light formation index of the base paper for cushioning material was measured using a 3D sheet analyzer (M / K950) manufactured by M / K Systems, Inc. (MKS), with the analyzer's aperture set to a diameter of 1.5 mm and the measurement range set to 1 (standard sensitivity), using a microformation tester (MFT). Specifically, the sample (base paper) was mounted on the rotating drum of the 3D sheet analyzer, and the local basis weight difference of the sample was measured as a light intensity difference using a light source mounted on the drum axis and a photodetector mounted on the outside of the drum corresponding to the light source. The measurement range at this time is set by the diameter of the aperture attached to the light-receiving part of the photodetector. Next, the light intensity difference (deviation) was amplified, A / D converted, and classified into 64 optically measurable basis weight classes. 1,000,000 data points were taken in one scan, and the histogram frequency for that data was obtained. Then, the highest frequency (peak value) of the histogram was divided by the number of classes with a frequency of 100 or more out of the 64 classes, and the value obtained by dividing that by 100 was calculated as the transmitted light density index.

[0048] (Tensile Strength) The longitudinal and transverse tensile strengths of the base paper for cushioning material were measured in accordance with JIS P 8113:2006 after the base paper obtained in the examples and comparative examples was conditioned for 24 hours under the humidity-controlled environment specified in JIS P 8111:1998.

[0049] (Elongation at Break) The longitudinal and transverse elongation at break of the base paper for cushioning material was measured in accordance with JIS P 8113:2006 after the base paper obtained in the examples and comparative examples was conditioned for 24 hours under the humidity-controlled environment specified in JIS P 8111:1998.

[0050] <Paper cushioning material> (Height of protrusions) The flat surface opposite to the paper surface with the protrusions of the paper cushioning material (the surface without protrusions) was used as the reference plane, and the average of the maximum heights of the inside of each protrusion (the part that has been pressed against by a protrusion or the like to give it a convex shape) from that reference plane was defined as the height of the protrusions. The height of the protrusions of the paper cushioning material was defined as the average of the maximum heights of the inside of a total of 10 protrusions (the part that has been pressed against by a protrusion or the like to give it a convex shape) measured using a one-shot 3D shape measuring machine manufactured by Keyence Corporation, product name "Controller VR-3000". Five protrusions were randomly selected from one side of the paper surface and five protrusions were randomly selected from the other side of the paper surface. Specifically, the inside of the protrusions of the paper cushioning material (the part that has been pressed against by a protrusion or the like to give it a convex shape) was observed by 3D measurement, and the measurement value was obtained by setting a region using a three-point circle with volume area measurement using an analysis application.

[0051] (Volume of the protrusion) The volume of the protrusion of the paper cushioning material was calculated from the height and radius of the protrusion, obtained by measuring the height of the protrusion as described above, using the following formula: Volume of the protrusion = 4 × π × radius of the protrusion × radius of the protrusion × height of the protrusion ÷ 3 ÷ 2

[0052] (Ease of forming convex shapes) From the height of the convex parts obtained by measuring the height of the convex parts as described above, the value of the height of the convex parts divided by the height of the protrusions on the metal roll surface was calculated and evaluated according to the following criteria: A: 0.9 or more B: 0.85 or more and less than 0.9 C: Less than 0.85

[0053] (Cushioning) Paper cushioning material, which had been humidified for 24 hours in a humidity-controlled environment as specified in JIS P 8111:1998, was cut into 100 mm x 100 mm squares to serve as test specimens. The test specimens were set on the support plate of an A&D Company, Limited product, "Tensilon Universal Testing Machine RTG-1310," which was fitted with a flat compression jig (support plate with a diameter of 150 mm, pressure plate with a diameter of 100 mm) manufactured by A&D Company, Limited. The pressure plate was lowered at a speed of 50 mm / min, and the compressive load when the specimen was compressed to 50% of its thickness was divided by the load area (area of ​​the pressure plate) to determine the compressive stress, which was then evaluated according to the following criteria: A: Compressive stress of 9.0 N / m ２ In summary, B: Compressive stress is 4.5 N / m ２ 9.0N / m or more ２ Less than C: Compressive stress of 4.5 N / m ２ less than

[0054] (Tear Rate) The number of torn protrusions on the paper cushioning material (250 mm x 250 mm) after the protrusion formation process was measured, and the tear rate was calculated using the following formula: Tear rate (%) = Number of torn protrusions ÷ Number of protrusions × 100 The tear rate was then evaluated according to the following criteria: A: Almost no tears, less than 5% B: Some tears, but within an acceptable range, 5% to less than 30% C: Many tears, 30% or more

[0055] Example 1 As raw material pulp, 95% by mass of unbleached softwood kraft pulp (NUKP, "N" in Table 1) and 5% by mass of unbleached hardwood kraft pulp (LUKP, "L" in Table 1) were beaten using a double disc refiner to obtain a pulp slurry with a Canadian standard filtration degree of 560 mL. To 100 parts by mass of the obtained pulp slurry (based on solid content), 0.75 parts by mass of cationized starch (manufactured by Pillar Starch Co., Ltd., trade name "P-3Y") (based on solid content), 0.1 parts by mass of polyacrylamide-based internal paper strength enhancer (manufactured by Arakawa Chemical Industries, Ltd., trade name "PS379") (based on solid content), 0.12 parts by mass of rosin sizing agent (manufactured by Arakawa Chemical Industries, Ltd., trade name "Sizing Pine N-811") (based on solid content), and 1.0 part by mass of aluminum sulfate (based on solid content) were added to prepare a pulp stock. Using this pulp stock, a target basis weight of 73 g / m² was obtained.２ As a result, paper was produced using a wet paper machine (product name "Bellform III" manufactured by Mitsubishi Heavy Industries, Ltd.) equipped with an expansion / contraction device (Crupack device), at a papermaking speed of 600 m / min, a J / W ratio of 1.000, a reel moisture content of 6.5%, and a speed difference of -5.0% before and after the Crupack process. Paper was also produced with a nip pressure of 15 kN / m between the nip roll and blanket during the Crupack process, and a crepe was applied to the surface of the base paper. From this base paper, a roll with a width of 500 mm and a length of 30 m was produced to obtain base paper for cushioning material. The obtained base paper for cushioning material was placed in an automatic paper cushioning material manufacturing machine (product name "Paper Bubble Machine / PB640EW" manufactured by WiAir Corporation) with the short side parallel to the processing area (i.e., with the long side facing the flow direction), and then fed out at a processing speed of 20 m / min to obtain paper cushioning material having multiple protrusions on both sides of the paper surface, as shown in Figure 5. The automatic paper cushioning material manufacturing machine used has a mechanism that forms the paper by passing it between two metal roll nips, and the desired shape of the protrusions (a perfect circle with a diameter of φ6 mm, a protrusion height of 1.75 mm, and a distance of 1.5 mm between protrusions) is formed on the surface of the metal rolls.

[0056] Example 2: The set basis weight was 78 g / m². ２ Except for the above, a base paper for cushioning material and paper cushioning material were obtained in the same manner as in Example 1.

[0057] Example 3: The set basis weight is 83 g / m². ２ Except for the above, a base paper for cushioning material and paper cushioning material were obtained in the same manner as in Example 1.

[0058] Example 4: In the preparation of the paper stock, the raw pulp composition was as shown in Table 1, and 0.005 parts by mass (solid content) of a yielding agent (product name "Hymo Lock RX-1100" manufactured by Hymo Co., Ltd.) was added to 100 parts by mass of the obtained pulp slurry (solid content). Otherwise, a base paper for cushioning material and paper cushioning material were obtained in the same manner as in Example 3.

[0059] Example 5: Except for using the pulp composition shown in Table 1 and setting the papermaking speed to 550 m / min, a base paper for cushioning material and cushioning material were obtained in the same manner as in Example 3.

[0060] Example 6: The raw pulp composition was as shown in Table 1, and the set basis weight was 96 g / m². ２ Except for the above, a base paper for cushioning material and paper cushioning material were obtained in the same manner as in Example 1.

[0061] Example 7: The raw pulp composition was as shown in Table 1, and the set basis weight was 109 g / m². ２ Except for setting the density to the values ​​shown in Table 1, a base paper for cushioning material and paper cushioning material were obtained in the same manner as in Example 1.

[0062] Example 8 The base paper for cushioning material obtained in Example 3 was placed in an automatic paper cushioning material manufacturing machine (product name "Paper Bubble Machine / PB640EW" manufactured by WiAir Corporation) so that the short side was parallel to the processing area (i.e., the long side was in the flow direction), and then fed out at a processing speed of 20 m / min to obtain a paper cushioning material having multiple protrusions on one side of the paper surface, as shown in Figure 1. The surface of the metal roll of the automatic paper cushioning material manufacturing machine used had the desired shape of protrusions (a perfect circle with a diameter of 8 mm, a protrusion height of 2.5 mm, and a distance between protrusions of 2.0 mm) formed on it.

[0063] Example 9 The base paper for cushioning material obtained in Example 7 was placed in an automatic paper cushioning material manufacturing machine (product name "Paper Bubble Machine / PB640EW" manufactured by WiAir Corporation) so that the short side was parallel to the processing area (i.e., the long side was in the flow direction), and then fed out at a processing speed of 20 m / min to obtain a paper cushioning material having multiple protrusions on one side of the paper surface, as shown in Figure 1. The surface of the metal roll of the automatic paper cushioning material manufacturing machine used had the desired shape of protrusions (a perfect circle with a diameter of 8 mm, a protrusion height of 2.5 mm, and a distance between protrusions of 2.0 mm) formed on it.

[0064] Comparative Example 1: The raw pulp composition was as shown in Table 1, and the set basis weight was 73 g / m². ２ Except for the above, a base paper for cushioning material and paper cushioning material were obtained in the same manner as in Example 1.

[0065] Comparative Example 2 In the preparation of the pulp stock, the raw pulp was blended as shown in Table 1, and 0.02 parts by mass (solid content) of a yielding agent (product name "Hymo Lock RX-1100" manufactured by Hymo Co., Ltd.) was added to 100 parts by mass of the obtained pulp slurry (solid content). Otherwise, a base paper for cushioning material and paper cushioning material were obtained in the same manner as in Example 2.

[0066] Comparative Example 3: The raw pulp composition was as shown in Table 1, and the set basis weight was 115 g / m². ２ Except for the above, a base paper for cushioning material and paper cushioning material were obtained in the same manner as in Example 3.

[0067] Comparative Example 4: The raw pulp composition was as shown in Table 1, and the set basis weight was 60 g / m². ２ Except for the above, a base paper for cushioning material and paper cushioning material were obtained in the same manner as in Example 3.

[0068] The obtained base paper for cushioning material and paper cushioning material were subjected to the measurements and evaluations described above. The results are shown in Tables 1 and 2.

[0069]

[0070]

[0071] From the results of the examples and comparative examples, it can be seen that the base paper for cushioning material of the present invention is easily formed into a convex shape, and that the paper cushioning material obtained by forming multiple convex parts on one or both sides of the surface of the base paper for cushioning material of the present invention has less tearing of the convex parts and excellent cushioning properties.

[0072] The base paper for cushioning materials of the present invention is suitable for use as a base paper for obtaining a paper cushioning material with excellent cushioning properties, as it reduces tearing of the protrusions when multiple protrusion shapes are applied to form the protrusions.

[0073] 100, 110, 120: Paper cushioning material, 10, 10': Protrusions, H1, H2, H3: Height of protrusions, W1, W2: Distance between protrusions, R, R': Reference surface

Claims

1. 70 raised areas per 100 cm on one or both sides of the paper surface. ２ The above is a base paper for cushioning material, which is formed to create a paper cushioning material, with a basis weight of 70 g / m². ２ 110g / m or more ２ The following is true: a base paper for cushioning material having a tensile strength in the transverse direction of 1.5 kN / m or more and a transmitted light densitivity index of 8 or more.

2. The base paper for cushioning material according to claim 1, wherein the transverse elongation at break is 3.0% or more and 10.0% or less.

3. The base paper for cushioning material according to claim 1, wherein the longitudinal tensile strength is 2.5 kN / m or more.

4. The base paper for cushioning material according to claim 1, wherein the longitudinal elongation at break is 5.9% or more.

5. 70 protrusions per 100 cm on one or both sides of the surface of the cushioning paper according to any one of claims 1 to 4. ２ A paper cushioning material formed as described above.

6. The volume of each of the aforementioned protrusions is 20 mm². ３ 150mm or more ３ The following is the paper cushioning material according to claim 5.

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