Paper base for cushioning materials and paper cushioning materials

Abstract

The present invention provides a base paper for cushioning material in which multiple protrusions are formed on one or both sides of the paper surface, wherein when multiple protrusions are formed by applying the protrusions, tearing of the protrusions is reduced, resulting in a paper cushioning material with excellent cushioning properties, and the generation of paper dust is suppressed during processing into paper cushioning material, and a paper cushioning material is provided which has multiple protrusions formed on one or both sides of the paper surface of the cushioning material base paper. [Solution] Add multiple protrusions (70 per 100cm) to one or both sides of the paper surface. 2 A base paper for cushioning material, formed as described above, wherein the proportion of fine fibers with a fiber length of less than 0.2 mm in the pulp fibers constituting the base paper for cushioning material is 35% or less, the geometric mean of the longitudinal elongation at break and the transverse elongation at break is 4.00% or more and 9.00% or less, and the bursting strength is 250 kPa or more. Multiple protrusions of 70 per 100 cm are formed on one or both sides of the surface of the base paper for cushioning material. 2 A paper cushioning material formed as described above.

Description

[Technical Field]

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

[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, the elimination and reduction of plastic in packaging materials is being promoted, and there is a growing movement to replace 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 describes a protective sheet that can improve portability, comprising kraft paper containing softwood pulp, wherein the softwood pulp content is 90% to 95% by mass relative to the mass of the kraft paper, and the kraft paper has a thickness of 0.2 mm or less and a weight of 45 g / m². 2 More than 95g / m 2 The following paper-based protective sheets are listed, each with the following basis weight. Patent Document 2 aims to provide a cushioning paper with excellent cushioning properties and suppressed paper dust generation during processing into paper cushioning materials, with a basis weight of 35 g / m². 2 More than 150g / m 2The following conditions must be met: the synergistic mean of the specific tensile strength in the longitudinal and transverse directions, measured in accordance with JIS P 8113:2006, is 17.0 Nm / g or higher; the wax pick values ​​of both the front and back surfaces are 7A or higher; and both surfaces have a surface layer containing at least one selected from the group consisting of water-soluble resins and water-suspendable resins, with a solid content of 0.3 g / m² on both sides of the surface layer. 2 More than 3.0g / m 2 The following describes cushioning paper that can be folded and used as paper cushioning material. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-44936 [Patent Document 2] Patent No. 7526331 [Overview of the project] [Problems that the invention aims to solve]

[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 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 minimize tears that occur during the formation of the protrusions, and to minimize the generation of paper dust during processing into paper 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 paper described in Patent Document 2 is used as a paper cushioning material by folding it, and is not used to impart a convex shape to the paper.

[0008] The present invention relates to a base paper for a cushioning material for forming a plurality of convex portions on one or both sides of a paper surface. When forming convex portions by imparting a plurality of convex shapes, the base paper for a cushioning material can obtain a paper cushioning material with less breakage of the convex portions and excellent cushioning properties, and suppress the generation of paper dust during processing into the paper cushioning material. Another object of the present invention is to provide a paper cushioning material formed by forming a plurality of convex portions on one or both sides of the paper surface of the base paper for a cushioning material.

Means for Solving the Problems

[0009] The inventors of the present invention have found that by setting the proportion of the number of fine fibers having a fiber length of less than 0.2 mm to a specific value or less, the geometric mean of the breaking elongation in the longitudinal direction and the breaking elongation in the transverse direction to a specific range, and the bursting strength to a specific value or more in the pulp fibers constituting the base paper for a cushioning material, the above problems can be solved. That is, the present invention has the following configurations. <1> A base paper for a cushioning material for forming a plurality of convex portions of 70 or more per 100 cm on one or both sides of a paper surface to form a paper cushioning material, 2 wherein the proportion of the number of fine fibers having a fiber length of less than 0.2 mm in the pulp fibers constituting the base paper for a cushioning material is 35% or less, the geometric mean of the breaking elongation in the longitudinal direction and the breaking elongation in the transverse direction is 4.00% or more and 9.00% or less, and the bursting strength is 250 kPa or more. Base paper for a cushioning material <2> The base paper for a cushioning material according to <1>, wherein the value of the ratio of the breaking elongation in the longitudinal direction to the breaking elongation in the transverse direction (breaking elongation in the longitudinal direction / breaking elongation in the transverse direction) is 0.60 or more and 1.40 or less. <3> The base paper for a cushioning material according to <1> or <2>, wherein the basis weight is 60 g / m 2 or more and 110 g / m 2 or less. <4> The base paper for a cushioning material according to any one of <1> to <3>, wherein the density is 0.5 g / cm 3 or more and 0.9 g / cm 3 or less. <5> <1> ~ <4> The cushioning paper base described in any one of the following lists has 70 protrusions on one or both sides of its surface per 100cm. 2 A paper cushioning material formed as described above. <6> The volume of each of the multiple protrusions is 20 mm². 3 More than 150mm 3 The following is: <5> The paper cushioning material described above. [Effects of the Invention]

[0010] According to the present invention, a base paper for cushioning material is provided for forming multiple protrusions on one or both sides of the paper surface, wherein when multiple protrusion shapes are applied to form the protrusions, tearing of the protrusions is reduced, resulting in a paper cushioning material with excellent cushioning properties, and the generation of paper dust is suppressed during processing into paper cushioning material. The present invention also provides a base paper for cushioning material having multiple protrusions formed on one or both sides of the paper surface of the base paper for cushioning material. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram illustrating an example of the structure of a paper cushioning material in which a plurality of protrusions are formed on one side of the surface of the cushioning paper base of the present invention. [Figure 2] This is a schematic diagram illustrating an example of the structure of a paper cushioning material in which a plurality of protrusions are formed on both sides of the paper surface of the cushioning material base paper of the present invention. [Figure 3] Figure 1 is a cross-sectional view of the paper cushioning material shown as an example. [Figure 4] Figure 2 is a cross-sectional view of the paper cushioning material shown as an example. [Figure 5] This is a plan view showing the paper cushioning material manufactured in the example. [Figure 6] Figure 5 is a cross-sectional view of the paper cushioning material. [Modes for carrying out the invention]

[0012] [Base paper for cushioning material] The cushioning paper according to this embodiment (hereinafter also simply referred to as "cushioning paper") has multiple protrusions on one or both sides of the paper surface, with 70 protrusions per 100 cm². 2The above-described base paper for cushioning material is formed to create a paper cushioning material, wherein the proportion of fine fibers with a fiber length of less than 0.2 mm in the pulp fibers constituting the base paper for cushioning material is 35% or less, the geometric mean of the longitudinal elongation at break and the transverse elongation at break is 4.0% or more and 9.0% or less, and the bursting strength is 250 kPa or more. In this specification, a numerical range represented as "X~Y" means a numerical range that includes X as the lower limit and Y as the upper limit. When a numerical range is described in steps, the upper and lower limits of each numerical range can be arbitrarily combined. Furthermore, the cushioning paper of the present invention may have any combination of the characteristics or physical properties described herein. In addition, each component contained in the cushioning paper of the present invention may be used individually or in combination of two or more. The longitudinal direction of the cushioning paper means the papermaking direction (MD), and the transverse direction means the direction perpendicular to the papermaking direction (CD).

[0013] In this embodiment, the base paper for cushioning material has a synergistic mean of longitudinal and transverse elongation at break of 4.0% or more, which allows it to follow the deformation when forming convex shapes and thus suppress tearing of the convex parts. If it is 9.0% or less, it is thought that excessive elongation will occur when the paper cushioning material is subjected to a load, suppressing a decrease in stress and thus making it easier to maintain the cushioning performance of the paper cushioning material. Furthermore, if the ratio of fine fibers is 35% or less, the fibers will be more likely to entangle, and if the burst strength is 250kPa or more, it is thought that these factors contribute to suppressing tearing of the convex parts and suppressing the generation of paper dust. In this embodiment, the base paper for the cushioning material has multiple protrusions at 100 cm 2 A paper cushioning material formed with a certain number or more protrusions per surface is considered to have excellent cushioning properties because the multiple protrusions make it easier to absorb the load when a load is applied to the paper cushioning material.

[0014] 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 on the paper substrate, but it is preferable that it consists only of a paper substrate. The paper substrate may be a single-layer structure or a multi-layer structure, but a single-layer structure is preferred. In the case of a multi-layer 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.

[0015] <Raw pulp> In this embodiment, natural pulp fibers are preferred as the raw material pulp constituting the cushioning paper (paper base 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 incorporated 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 pulverized 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.

[0016] The raw material pulp preferably contains at least one selected from the group consisting of softwood pulp, hardwood pulp, and deinked pulp; more preferably contains at least one selected from the group consisting of softwood kraft pulp, hardwood kraft pulp, and deinked pulp; even more preferably contains at least one selected from the group consisting of unbleached softwood kraft pulp (NUKP), unbleached hardwood kraft pulp (LUKP), and deinked pulp; and even more preferably contains unbleached softwood kraft pulp and at least one selected from the group consisting of unbleached hardwood kraft pulp and deinked pulp.

[0017] The content of softwood pulp (preferably NUKP) in the raw pulp is preferably 80% by mass or more, more preferably 83% by mass or more, even more preferably 87% by mass or more, and 100% by mass or less, from the viewpoint of reducing tearing of the protrusions when forming multiple protrusions on the base paper for cushioning material, from the viewpoint of further improving the cushioning performance of the paper cushioning material, and from the viewpoint of suppressing the generation of paper dust.

[0018] When the raw pulp contains hardwood pulp, the content of hardwood pulp (preferably LUKP) in the raw pulp is preferably 15% by mass or less, more preferably 10% by mass or less, even more preferably 7% by mass or less, and preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 3% by mass or more, from the viewpoint of reducing tearing of the protrusions when forming multiple protrusions on the base paper for cushioning material, from the viewpoint of further improving the cushioning performance of the paper cushioning material, and from the viewpoint of suppressing the generation of paper dust.

[0019] When the raw pulp contains softwood pulp (preferably NUKP) and hardwood pulp (preferably LUKP), from the viewpoint of improving bursting strength and elongation at break, 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.

[0020] When the raw pulp contains deinked pulp, the deinked pulp content is preferably 20% by mass or less, more preferably 16% by mass or less, and even more preferably 12% by mass or less, from the viewpoint of reducing tearing of the protrusions when forming multiple protrusions on the base paper for cushioning material, from the viewpoint of further improving the cushioning properties of the paper cushioning material, and from the viewpoint of suppressing the generation of paper dust, and from the viewpoint of reducing the environmental burden, preferably 1% by mass or more, more preferably 4% by mass or more, and even more preferably 7% by mass or more.

[0021] When the raw pulp contains softwood pulp (preferably NUKP) and deinked pulp, from the viewpoint of setting the bursting strength and elongation at break within a predetermined range, the total content of softwood pulp (preferably NUKP) and deinked pulp 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.

[0022] From the viewpoint of obtaining appropriate paper strength for use as a base paper for cushioning material, the Canadian standard filtration efficiency (CSF) of the raw pulp is preferably 300 mL or more, more preferably 350 mL or more, even more preferably 400 mL or more, even more preferably 450 mL or more, and even more preferably 500 mL or more, and preferably 700 mL or less, 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 - Methods for testing filtration efficiency - Part 2: Canadian standard filtration efficiency method".

[0023] (optional ingredient) 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). The content of these optional components is not particularly limited and may be within the range commonly used.

[0024] 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 (paper substrate) for cushioning material has a multilayer structure, the drying strength enhancer may be contained in some of the layers, but it is preferable that it is contained in each layer, and it is even more preferable that the amount of the enhancer in each layer is within the range of the following preferred amounts. When a dry strength enhancer is included, the amount of the dry strength enhancer is preferably 0.1 parts by mass or more, more preferably 0.4 parts by mass or more, even more preferably 0.7 parts by mass or more, and preferably 2.5 parts by mass or less, more preferably 2.0 parts by mass or less, and even more preferably 1.5 parts by mass or less, per 100 parts by mass of raw pulp (on a solid content basis). Note that the above amounts refer to the total amount of dry strength enhancers used when multiple dry strength enhancers are used.

[0025] 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 it is contained in each layer, 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 included, the amount of the wet-strength enhancer is preferably 0.01 parts by mass or more, 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 preferably 1.0 part by mass or less, 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 (in terms of solid content) of raw pulp.

[0026] Examples of internal sizing agents include rosin-based sizing agents and alkyl ketene dimers, with rosin-based sizing agents being preferred among these. Rosin-based sizing agents can include, for example, acidic rosin-based sizing agents, weakly acidic rosin-based sizing agents, and neutral rosin-based sizing agents. When the paper substrate has multiple layers, the internal sizing agent may be contained in some of the layers, but it is preferable that it is contained in each layer, and it is even more preferable that the amount of each layer is within the range of the following preferred amounts. When an internal sizing agent is included, the amount of the internal sizing agent is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, even more preferably 0.1 parts by mass or more, and preferably 3.0 parts by mass or less, more preferably 1.0 part by mass or less, and even more preferably 0.5 parts by mass or less, per 100 parts by mass (in terms of solid content) of raw pulp.

[0027] <Method for manufacturing base paper for cushioning material> The method for manufacturing the base paper for cushioning material preferably includes a step of papermaking a slurry containing the above-mentioned raw material 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, and a neutral papermaking method in which papermaking is performed at a pH of approximately 6 to approximately 9. In the papermaking process, chemicals for the papermaking process, such as pH adjusters, defoamers, pitch control agents, and slime control agents, can be added as needed. The papermaking machine is also not particularly limited, and examples include continuous papermaking machines such as twin-wire type, long-wire type, cylinder-wire type, and inclined type, or multi-layer papermaking machines that combine these.

[0028] (Cruise processing) The manufacturing method for cushioning paper preferably includes a crumpling process. That is, it is preferable that the cushioning paper is crumpled. The crumpling process is a process that imparts longitudinal stretchability to the paper by finely shrinking it in the longitudinal direction on a paper machine. As a specific processing method, an example is to install a Kurupack device in part of the paper machine dryer, pass the wet paper between an endless, thick elastic rubber blanket with nip rolls and a heated dryer, and shrink the paper sheets as the blanket, which has been stretched beforehand, contracts. The resulting shrinkage is then dried and fixed so that it does not stretch again in subsequent processes. The speed difference before and after the Kurupack processing is preferably -15% or more, more preferably -13% or more, even more preferably -11% or more, even more preferably -9% or more, even more preferably -7% or more, and preferably -1% or less, more preferably -2% or less, even more preferably -3% or less, and even more preferably -4% or less, from the viewpoint of reducing tearing of the protrusions when forming multiple protrusions on the base paper for the cushioning material. Here, the minus sign "-" indicates that the speed is slower after the Kurupack processing.

[0029] <Characteristics of base paper for cushioning material> (Percentage of fine fibers) In the cushioning paper of this embodiment, the proportion of fine fibers with a fiber length of less than 0.2 mm among the pulp fibers constituting the cushioning paper is 35% or less, preferably 32% or less, and more preferably 29% or less, from the viewpoint of reducing tearing of the protrusions when forming multiple protrusions on the cushioning paper and from the viewpoint of suppressing the generation of paper dust. The lower limit is not particularly limited, but from the viewpoint of reducing environmental impact by using recycled paper pulp and / or from the viewpoint of ease of manufacture, it is preferably 10% or more, and more preferably 15% or more. The proportion of fine fibers (less than 0.2 mm in length) in the pulp fibers that make up cushioning paper can be adjusted by selecting the raw pulp used. Specifically, increasing the amount of recycled paper pulp used tends to increase the proportion of fine fibers. It can also be adjusted by selecting the mesh diameter during washing after the raw pulp has been beaten. The percentage of fine fibers with a fiber length of less than 0.2 mm in the pulp constituting the cushioning paper is calculated by disintegrating the cushioning paper using the method described in the examples, and measuring the fiber length of the obtained pulp slurry with a fiber length measuring device (for example, Valmet, model FS-5, with UHD base unit). Fibers with a fiber length of less than 0.2 mm are defined as fine fibers, and the percentage of fine fibers relative to the measured number of pulp fibers is calculated.

[0030] (Elongation at break) The geometric mean of the longitudinal and transverse break elongation of the cushioning material base paper according to this embodiment is 4.00% or more, preferably 5.00% or more, more preferably 5.50% or more, even more preferably 6.00% or more, even more preferably 6.50% or more, and even more preferably 6.8% or more, and from the viewpoint of further improving the cushioning performance of the paper cushioning material, it is 9.00% or less, preferably 8.50% or less, and even more preferably 8.00% or less.

[0031] The longitudinal break elongation of the cushioning paper base paper according to this embodiment is preferably 4.00% or more, more preferably 5.00% or more, even more preferably 5.50% or more, even more preferably 6.00% or more, even more preferably 6.50% or more, and even more preferably 6.80% or more, from the viewpoint of further improving the cushioning performance of the paper cushioning material, and is preferably 9.00% or less, more preferably 8.50% or less, and even more preferably 8.00% or less. The longitudinal elongation at break of base paper for cushioning material can be controlled by factors such as the type of raw pulp, the pulp slurry concentration during beating, and the pulp packing treatment conditions. Pulp packing tends to increase longitudinal elongation at break, and increasing the speed difference during pulp packing tends to increase longitudinal elongation at break even further. In addition, increasing the amount of paper strength enhancer used tends to increase longitudinal elongation at break.

[0032] The transverse break elongation of the cushioning paper base in this embodiment is preferably 4.00% or more, more preferably 4.50% or more, even more preferably 5.00% or more, even more preferably 5.50% or more, and even more preferably 6.00% or more, from the viewpoint of reducing tearing of the protrusions when forming multiple protrusions on the cushioning paper base, and from the viewpoint of further improving the cushioning performance of the paper cushioning material, it is preferably 9.00% or less, more preferably 8.50% or less, and even more preferably 8.00% or less. The transverse elongation at break of cushioning paper 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 (e.g., the position of the drying device in the papermaking machine), and the basis weight. Specifically, increasing the amount of paper strength enhancer tends to increase the transverse elongation at break. Also, increasing the basis weight of cushioning paper tends to increase the transverse elongation at break. The longitudinal and transverse elongations at break of the base paper for cushioning material were measured in accordance with JIS P 8113:2006, specifically by the method described in the examples.

[0033] The aspect ratio (vertical (T) / horizontal (Y)) of the vertical and horizontal break elongation of the cushioning material base paper according to this embodiment is preferably 0.60 or higher, more preferably 0.80 or higher, even more preferably 0.95 or higher, even more preferably 1.00 or higher, and preferably 1.40 or lower, more preferably 1.25 or lower, even more preferably 1.15 or lower, even more preferably 1.10 or lower, and even more preferably 1.05 or lower. The aspect ratio (vertical (T) / horizontal (Y)) tends to increase, for example, when the speed difference before and after the packing process is increased.

[0034] (bursting strength) The bursting strength of the base paper for cushioning material in this embodiment is 250 kPa or more, preferably 300 kPa or more, more preferably 350 kPa or more, even more preferably 400 kPa or more, and even more preferably 420 kPa or more, and from the viewpoint of ease of manufacturing, preferably 650 kPa or less, more preferably 600 kPa or less, and even more preferably 570 kPa or less. The bursting strength of cushioning paper can be adjusted by the type of raw pulp, the type and amount of paper strength enhancer, and the basis weight. Specifically, increasing the amount of paper strength enhancer tends to increase the bursting strength. Also, increasing the basis weight of cushioning paper tends to increase the bursting strength. The bursting strength of the base paper for cushioning material is measured in accordance with JIS P 8112:2008, specifically by the method described in the examples.

[0035] (thickness) The thickness of the base paper for the cushioning material is preferably 65 μm or more, more preferably 75 μm or more, even more preferably 85 μm or more, and even more preferably 95 μm or more, and preferably 170 μm or less, more preferably 160 μm or less, even more preferably 150 μm or less, and even more preferably 140 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 the paper cushioning material manufacturing machine imparts multiple protrusions, resulting in less tearing. The thickness of the base paper for cushioning material is measured in accordance with JIS P 8118:2014, specifically by the method described in the examples.

[0036] (Basic weight) The basis weight of the base paper for cushioning material is preferably 60 g / m², as this allows for easy adjustment to the desired elongation at break and burst strength, thereby reducing tearing of the protrusions when forming multiple protrusions on the base paper and further improving the cushioning properties of the paper cushioning material. 2 Above, a comfortable 70g / m 2 More preferably 80 g / m² 2 The above, and preferably 110 g / m² 2 More preferably, 105 g / m² 2 More preferably 100 g / m 2 More preferably 90 g / m 2 The following applies: The basis weight of the base paper for cushioning material is measured in accordance with JIS P 8124:2011, specifically by the method described in the examples.

[0037] (density) The density of the base paper for cushioning material is preferably 0.5 g / cm³, from the viewpoint of increasing interfiber bonding and, as a result, reducing tearing of the protrusions when forming multiple protrusions on the base paper for cushioning material. 3 More preferably 0.55 g / cm³ 3 More preferably 0.6 g / cm³ 3 Therefore, from the viewpoint of further improving the cushioning properties of the paper cushioning material, a preferred value is 0.9 g / cm³. 3 More preferably, 0.87 g / cm³ 3 More preferably, 0.84 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.

[0038] 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 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 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 the paper cushioning material manufactured in the example, and Figure 6 is a cross-sectional view of the paper cushioning material shown in Figure 5.

[0039] [Paper cushioning material] The paper cushioning material of this embodiment has multiple protrusions, 70 per 100 cm, on one or both sides of the paper surface of the cushioning material base paper described above. 2 The above is how it is formed (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 projection is formed on one side of the paper surface by pressing a protrusion or the like against the cushioning paper base described above, and this projection is called a convex portion. The shape of the cushioning paper base into which the convex portion is formed is not particularly limited, and it 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 paper base is in the form of a roll or folded, it may have perforated sections with multiple perforations in the horizontal 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 transportation, if the shape of the cushioning paper base is in the form of a folded, it is preferable to fold it alternately at multiple perforated sections and stack it in an accordion-like manner to form a laminate.

[0040] 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 Figure 1, or, as shown in Figures 2 and 5, may have a plurality of protrusions 10 on one side of the paper surface and a plurality of protrusions 10' on the side opposite to the side of the paper surface with the plurality of protrusions 10. From the viewpoint of providing a paper cushioning material with superior cushioning properties, it is preferable to have a plurality of protrusions 10 and 10' on both sides of the paper surface, as shown in Figures 2 and 5. Note that if the base paper for the cushioning material has a plurality of protrusions 10 and 10' on both sides of the paper surface, the above-mentioned 100cm 2 The number of protrusions per unit area refers to the sum of the multiple 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 they may be arranged in a staggered pattern, as shown in Figure 5.

[0041] The formation of multiple protrusions may be performed manually or electrically using a paper cushioning material making machine, and is not particularly limited. Examples of paper cushioning material making 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.

[0042] (Number of multiple protrusions) The number of protrusions in the paper cushioning material according to this embodiment is set at 70 per 100cm², from the viewpoint of making it easier for the multiple protrusions to cushion the load when a load is applied to the paper cushioning material, and as a result providing a paper cushioning material with excellent cushioning properties. 2 The above is preferable, with a ratio of 90 pieces / 100cm. 2 The above is 120 pieces / 100cm 2 Therefore, 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 preferable to have 450 pieces / 100cm. 2 More preferably 200 pieces / 100cm 2 The following applies:

[0043] (Volume of the convex part) From the viewpoint of improving cushioning performance, the volume of each of the multiple protrusions in the paper cushioning material of this embodiment is preferably 20 mm². 3 More preferably 25 mm 3 The above is true, and from the viewpoint of reducing the tearing of the protrusions when forming multiple protrusions, preferably 150 mm. 3 More preferably 125mm 3 More preferably 100 mm 3 The following applies: The volume of each of the multiple protrusions 10, 10' represents 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 with 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 protrusion 10 is the average volume of each of 10 randomly selected protrusions 10, specifically the portion surrounded by the inside of the protrusion 10 and the reference plane R' (the portion that has been pressed against and given a convex shape). As shown in Figures 2, 4, and 5, 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). The volume of each protrusion is specifically calculated by the method described in the embodiment.

[0044] (Height of the protrusion) From the viewpoint of improving cushioning performance, the height of the protrusions is preferably 1.00 mm or more, more preferably 1.20 mm or more, even more preferably 1.40 mm or more, and even more preferably 1.60 mm or more. From the viewpoint of reducing tearing of the protrusions when forming multiple protrusions, the height is preferably 5.00 mm or less, more preferably 4.00 mm or less, even more preferably 3.00 mm or less, and even more preferably 2.50 mm or less.

[0045] 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 protrusions or the like to give them a convex shape), with the flat surface R', R on the opposite side of the paper cushioning material from the protrusions 10, 10' being used as the reference surface 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 protrusions 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 and 5, 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 randomly selected protrusions 10 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 randomly selected protrusions 10' from the other side of the paper surface, the height H3 is the average value of the maximum heights H3 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 examples.

[0046] (Distance between convex parts) The distance between adjacent protrusions (W1 in Figure 3, W2 in Figure 4) can be adjusted as appropriate depending on the volume and number of protrusions, preferably 6 mm or less, more preferably 5 mm or less, and even more preferably 4 mm or less, from the viewpoint of improving cushioning performance. There is no particular lower limit, but from the viewpoint of ease of manufacturing, it is preferably 0.5 mm or more. 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 distance. 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, then this paper cushioning material has multiple protrusions at equal intervals.

[0047] 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. [Examples]

[0048] 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.

[0049] [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.

[0050] <Raw pulp> (Canadian standard filtration rate) The Canadian standard hydrophilicity of the raw pulp was measured according to JIS P 8121-2:2012 "Pulp - Hydrophilicity test methods - Part 2: Canadian standard hydrophilicity method".

[0051] <Base paper for cushioning material> (Basic weight) The basis weight of the cushioning paper was measured in accordance with JIS P 8124:2011 after the cushioning paper obtained in the examples and comparative examples was conditioned for 24 hours under the humidity-controlled environment specified in JIS P 8111:1998.

[0052] (thickness) The thickness of the cushioning paper was measured in accordance with JIS P 8118:2014 after the cushioning paper obtained in the examples and comparative examples was conditioned for 24 hours under the humidity-controlled environment specified in JIS P 8111:1998.

[0053] (density) The density of the base paper for the cushioning material was calculated from the basis weight and thickness measured as described above.

[0054] (Fine fiber content) The obtained cushioning paper was cut into 4cm squares and immersed in deionized water for 24 hours. The immersed cushioning paper was removed, and the concentration was adjusted with deionized water to 2% by mass. A mixture of concentration-adjusted buffer paper and deionized water was dissociated using a standard dissociator (manufactured by Kumagai Riki Kogyo Co., Ltd.) in accordance with JIS P 8220-1:2012 to obtain a pulp slurry. The obtained pulp slurry was sampled, and the fine fiber content was measured using a fiber length measuring instrument (model number FS-5 UHD base unit, manufactured by Valmet). The fine fiber content is the percentage of fine fibers with a fiber length of less than 0.2 mm in the disintegrated pulp fibers.

[0055] (bursting strength) The bursting strength of the base paper for cushioning material was measured in accordance with JIS P 8112:2008 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. The measurement was performed using a bursting strength tester (KRK Bursting Strength Tester No. 2021-C, manufactured by Kumagai Riki Kogyo Co., Ltd.).

[0056] (Elongation at break) The elongation at break of the cushioning paper was measured in accordance with JIS P 8113:2006 after the cushioning paper obtained in the examples and comparative examples was conditioned for 24 hours under the humidity-controlled environment specified in JIS P 8111:1998. The measurement was performed using a transverse tensile testing machine (Lorentzen & Wattre, CODE SE-064) with the sample mounted so that the distance between the chucks was 100 mm. Tensile tests were performed at a speed of 20 mm / min, and the elongation at break in both the T (longitudinal) and Y (transverse) directions was measured.

[0057] <Paper cushioning material> (Height of the protrusion) The flat surface of the paper cushioning material opposite to the surface with the protrusions (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 create a convex shape) from this 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 create a convex shape) from 5 protrusions randomly selected from one side of the paper surface and 5 protrusions randomly selected from the other side of the paper surface, measured using a one-shot 3D shape measuring machine manufactured by Keyence Corporation, product name "Controller VR-3000". 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 create a convex shape) was observed by 3D measurement, and the measurement value was obtained by setting the region using a three-point circle with volume area measurement using an analysis application.

[0058] (Volume of the convex part) The volume of the protrusions in the paper cushioning material was calculated using the following formula, based on the height and radius of the protrusions, which were obtained by measuring the height of the protrusions as described above. Volume of the convex part = 4 × π × radius of the convex part × radius of the convex part × height of the convex part ÷ 3 ÷ 2

[0059] (buffering properties) 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 100mm x 100mm 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 150mm, pressure plate with a diameter of 100mm) manufactured by A&D Company, Limited. The pressure plate was lowered at a speed of 50mm / 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 is 9.0 N / m 2 That's all. B: Compressive stress is 4.5 N / m 2 More than 9.0N / m 2 less than C: Compressive stress is 4.5 N / m 2 less than

[0060] (Tear rate) The number of torn protrusions on the paper cushioning material (250mm x 250mm) after the protrusion formation process was measured, and the tear rate was calculated using the following formula. Tear rate (%) = Number of raised areas with tears ÷ Number of raised areas × 100 The tear was then evaluated according to the following criteria. A: Almost no tears, less than 5% B: There are some tears, but they are within an acceptable range, between 5% and less than 30%. C: Many tears, over 30%

[0061] <Paper powder> An adhesive film (NEION PET75-H105(20) manufactured by Nichiei Shinka Co., Ltd.) was attached to a roll, and it was rolled twice over the cushioning material base paper obtained in the examples and comparative examples at a speed of 60 bpm to allow paper dust to adhere to the film. Film images (5 x 5 cm) were scanned and binarized into white and black areas. The white areas were considered to represent paper dust, and the amount of paper dust in each sample was measured by the percentage of the white area. Paper dust was evaluated according to the following criteria. A white area ratio of 0.100% or less is considered acceptable for practical purposes. A: White area ratio is 0.035% or less B: White area ratio exceeds 0.035% and is 0.070% or less. C: White area ratio exceeds 0.070% and is 0.100% or less. D: White area ratio exceeds 0.100%

[0062] [Manufacturing of base paper for cushioning materials and paper cushioning materials] Example 1 As raw material pulp, unbleached softwood kraft pulp (NUKP) and recycled paper pulp (DIP) were beaten using a double disc refiner in a mass ratio (NUKP:DIP) of 85:15 to obtain a pulp slurry. To 100 parts by mass of the obtained pulp slurry (based on solid content), 0.75 parts by mass of cationized starch (Pillar Starch Co., Ltd., P-3Y), 0.25 parts by mass of polyacrylamide-based internal paper strength enhancer (Arakawa Chemical Industries, Ltd., product no.: PS379), 0.12 parts by mass of rosin sizing agent (Arakawa Chemical Industries, Ltd., Sizing Pine N-811) as an internal sizing agent (based on solid content), and 1.0 part by mass of aluminum sulfate (based on solid content) were added to prepare the paper stock. Using this pulp, the target basis weight is 83g / m². 2 During the papermaking process, the press pressure was adjusted so that the paper thickness was 135 ± 5 μm. Papermaking was carried out using a wet papermaking machine (Bellform III, manufactured by Mitsubishi Heavy Industries, Ltd.) equipped with an expansion / contraction device (manufactured by Kurupack), at a papermaking speed of 600 m / min, a reel moisture content of 6.5% by mass, and a speed difference of -5.0% before and after Kurupack processing. Papermaking was carried out with a nip pressure of 15 kN / m between the nip roll and blanket during Kurupack processing, and a roll with a width of 500 mm and a length of 30 m was produced from the base paper with a crepe applied to the surface of the paper, thereby obtaining 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) 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.

[0063] Example 2 A base paper for cushioning material was obtained under the same conditions as in Example 1, except that the mass ratio (NUKP:DIP) of unbleached softwood kraft pulp (NUKP) and recycled paper pulp (DIP) of the raw pulp was 90:10, and the amount of polyacrylamide-based internally added paper strength enhancer was 0.20 parts by mass. The CSF of the raw pulp was 540 mL. Furthermore, using the obtained base paper for cushioning material, paper cushioning material was manufactured in the same manner as in Example 1.

[0064] Example 3 A base paper for cushioning material was obtained under the same conditions as in Example 2, except that unbleached softwood kraft pulp (NUKP) and unbleached hardwood kraft pulp (LUKP) were used as raw material pulp, with a mass ratio (NUKP:LUKP) of 95:5, and 0.10 parts by mass of a polyacrylamide-based internally added paper strength enhancer was used. The CSF of the raw material pulp was 560 mL. Furthermore, using the obtained base paper for cushioning material, paper cushioning material was manufactured in the same manner as in Example 1.

[0065] Example 4 A base paper for cushioning material was obtained under the same conditions as in Example 2, except that 0.35 parts by mass of a polyacrylamide-based internally added paper strength enhancer was used. Furthermore, using the obtained base paper for cushioning material, paper cushioning material was manufactured in the same manner as in Example 1.

[0066] Example 5 A base paper for cushioning material was obtained under the same conditions as in Example 2, except that 0.10 parts by mass of a polyacrylamide-based internally added paper strength enhancer was used. Furthermore, using the obtained base paper for cushioning material, paper cushioning material was manufactured in the same manner as in Example 1.

[0067] Example 6 A base paper for cushioning material was obtained under the same conditions as in Example 2, except that 0.15 parts by mass of a polyacrylamide-based internally added paper strength enhancer was used, and the press pressure was adjusted so that the paper thickness was 105 ± 5 μm. Furthermore, using the obtained base paper for cushioning material, paper cushioning material was manufactured in the same manner as in Example 1.

[0068] Example 7 A base paper for cushioning material was obtained under the same conditions as in Example 2, except that 0.25 parts by mass of a polyacrylamide-based internally added paper strength enhancer was used, and the press pressure was adjusted so that the paper thickness was 150 ± 5 μm. Furthermore, using the obtained base paper for cushioning material, paper cushioning material was manufactured in the same manner as in Example 1.

[0069] Example 8 The base paper for cushioning material was obtained under the same conditions as in Example 2, except that the speed difference before and after the Kurupack processing was set to -3.3%. Furthermore, using the obtained base paper for cushioning material, paper cushioning material was manufactured in the same manner as in Example 1.

[0070] Example 9 The base paper for cushioning material was obtained under the same conditions as in Example 2, except that the speed difference before and after the Kurupack processing was set to -1.7%. Furthermore, using the obtained base paper for cushioning material, paper cushioning material was manufactured in the same manner as in Example 1.

[0071] Example 10 Setting basis weight 65g / m 2 A base paper for cushioning material was obtained under the same conditions as in Example 1, except that the press pressure was adjusted so that the paper thickness was 105 ± 5 μm. Furthermore, using the obtained base paper for cushioning material, paper cushioning material was manufactured in the same manner as in Example 1.

[0072] Example 11 Setting basis weight 105g / m 2 A base paper for cushioning material was obtained under the same conditions as in Example 1, except that the press pressure was adjusted so that the paper thickness was 160 ± 5 μm. Furthermore, using the obtained base paper for cushioning material, paper cushioning material was manufactured in the same manner as in Example 1.

[0073] Example 12 The base paper for cushioning material obtained in Example 2 was placed in an automatic paper cushioning material manufacturing machine (product name "Paper Bubble Machine / PB640EW" manufactured by WiAir) 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 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 was formed with the desired shape of protrusions (a perfect circle with a diameter of φ8 mm, a protrusion height of 2.5 mm, and a distance between protrusions of 2.0 mm).

[0074] Comparative Example 1 A base paper for cushioning material was obtained under the same conditions as in Example 2, except that unbleached softwood kraft pulp (NUKP), unbleached hardwood kraft pulp (LUKP), and recycled paper pulp (DIP) were used as raw material pulp, with a mass ratio (NUKP:LUKP:DIP) of 75:5:20, and 0.30 parts by mass of a polyacrylamide-based internally added paper strength enhancer was used. The CSF of the raw material pulp was 510 mL. Furthermore, using the obtained base paper for cushioning material, paper cushioning material was manufactured in the same manner as in Example 1.

[0075] Comparative Example 2 A base paper for cushioning material was obtained under the same conditions as in Example 2, except that a polyacrylamide-based internally added paper strength enhancer was not used. Furthermore, using the obtained base paper for cushioning material, paper cushioning material was manufactured in the same manner as in Example 1.

[0076] Comparative Example 3 A base paper for cushioning material was obtained under the same conditions as in Comparative Example 1, except that a polyacrylamide-based internally added paper strength enhancer was not used. Furthermore, using the obtained base paper for cushioning material, paper cushioning material was manufactured in the same manner as in Example 1.

[0077] Comparative Example 4 The base paper for cushioning material was obtained under the same conditions as in Example 2, except that the packing process was not performed. Furthermore, using the obtained base paper for cushioning material, paper cushioning material was manufactured in the same manner as in Example 1.

[0078] Comparative Example 5 A base paper for cushioning material was obtained under the same conditions as in Example 2, except that 0.30 parts by mass of a polyacrylamide-based internally added paper strength enhancer was used and the speed difference before and after the Kurupack treatment was set to -7.5%. Furthermore, using the obtained base paper for cushioning material, paper cushioning material was manufactured in the same manner as in Example 1.

[0079] 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 Table 1.

[0080] [Table 1]

[0081] The results from the examples and comparative examples show that the paper cushioning material obtained by forming multiple protrusions on one or both sides of the paper surface of the cushioning material base paper of the present invention exhibits less tearing of the protrusions, superior cushioning properties, and suppression of paper dust generation. [Industrial applicability]

[0082] The cushioning paper of the present invention exhibits excellent cushioning properties, with minimal tearing of the protrusions when multiple protrusions are formed, and suppresses the generation of paper dust, making it suitable for use in paper cushioning materials. [Explanation of symbols]

[0083] 100,110,120:Paper cushioning material 10,10': convex part H1, H2, H3: Height of the protrusion W1, W2: Distance between adjacent convexities R, R': Reference surface

Claims

1. 70 or more protrusions per 100 cm on one or both sides of the paper surface ２ The above is formed to create a base paper for cushioning material, In the pulp fibers that make up the base paper for cushioning material, the proportion of fine fibers with a fiber length of less than 0.2 mm is 35% or less. The geometric mean of the longitudinal elongation at break and the transverse elongation at break is between 4.00% and 9.00%. The burst strength is 250 kPa or more. Base paper for cushioning materials.

2. The base paper for cushioning material according to claim 1, wherein the ratio of the elongation at break in the longitudinal direction to the elongation at break in the transverse direction (elongation at break in the longitudinal direction / elongation at break in the transverse direction) is 0.60 or more and 1.40 or less.

3. Basis weight 60 g / m² ２ 110g / m or more ２ The base paper for cushioning material according to claim 1 is as follows:

4. Density is 0.5 g / cm³ ３ 0.9g / cm or more ３ The base paper for cushioning material according to claim 1 is as follows:

5. A plurality of protrusions, 70 per 100 cm, are provided 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 multiple protrusions is 20 mm². ３ 150mm or more ３ The following is the paper cushioning material according to claim 5.

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