Roll-type paper towels

Abstract

To provide a rolled paper towel in which easiness to wind up a roll and unlikeliness for the core to collapse is excellent, which is easy to use as a product, and has excellent physical distribution efficiency in the rolled paper towel in which a core outer diameter is within a fixed range, and which has high basis weight in 1 ply and excellent water absorption.SOLUTION: In a rolled paper towel, paper towel in 1 ply containing pulp fiber and synthetic fiber is wound up in a rolled shape. Basis weight of the paper towel is between 40 g / m2 and 150 g / m2, a winding diameter of the roll is between 75 mm and 160 mm, roll density is between 0.05 g / cm3 and 0.19 g / cm3, and a core external diameter of the roll is between 25 mm and 55 mm, and value shown by ((area of a roll core external diameter) / (cross sectional area of the roll except a hollow part from the center of the roll to the core))×100 is between 5 and 40.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a roll-type paper towel containing pulp fibers and synthetic fibers. [Background technology]

[0002] In recent years, roll-type paper towels, such as hand towel rolls and kitchen towel rolls, which are made by winding thick paper into a roll, have become commercially available. Paper towels have a variety of uses, including cleaning grease stains around the kitchen, wiping surfaces with water, and draining food. Paper towels require excellent absorbency for water and oil, as well as the strength to withstand continuous use without easily tearing when used for cleaning. To impart such strength to paper, a technology has been developed in which pulp fibers are entangled with synthetic fibers using water flow.

[0003] Prior art documents for the technique of entangling pulp fibers with synthetic fibers using water flow include, for example, Patent Document 1, which describes a nonwoven wiper obtained by entangling a pulp fiber web and a synthetic fiber web with water flow, wherein the average fiber length of the pulp fibers contained in the pulp fiber web is 1.0 to 5.0 mm, and the basis weight of the nonwoven wiper is 20 to 42 g / m². 2 A nonwoven wiper is disclosed, characterized in that its composition ratio is 70-50% by mass of pulp fiber web and 30-50% by mass of synthetic fiber web. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-193634 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In the case of regular paper towels, the outer diameter of the core can be freely adjusted to match the roll length and roll diameter (also called the winding diameter). However, in the case of roll-type paper towels made from high-basis-weight paper towels containing synthetic fibers, if the outer diameter of the core (core outer diameter) is made too large within a certain range of winding diameter, the roll length will be shortened, resulting in poor logistics efficiency per roll. In addition, core crushing is more likely to occur at the start of winding or when cutting with a log saw (cutting machine).

[0006] Therefore, increasing the length of the roll and increasing the diameter makes it difficult to hold, resulting in a less user-friendly roll of paper towels. Conversely, if only the length of the roll is increased while keeping the diameter the same, it becomes tightly wound, making the core more prone to crushing during log saw cutting. On the other hand, if the outer diameter of the core is made too small, the pick-up (the leading edge of the paper towel that first contacts the core when winding it into a roll) becomes poor, especially with high-basis-weight paper towels.

[0007] For the reasons stated above, it was difficult to achieve a high level of balance between a large core outer diameter, logistics efficiency, resistance to core crushing during winding and log saw cutting, ease of winding, and ease of use as a product when producing high-basis-volume roll-type paper towels.

[0008] This invention has been made in view of these circumstances, and its purpose is to provide a roll-type paper towel that has a core outer diameter within a certain range, is high in basis weight and has excellent water absorption in a single ply, is easy to wind up, is resistant to core crushing, is easy to use as a product, and has good logistics efficiency. [Means for solving the problem]

[0009] The inventors conducted diligent research and discovered that, in a roll-shaped paper towel in which a single-ply paper towel containing pulp fibers and synthetic fibers is wound into a roll, by specifying the basis weight of the paper towel, the winding diameter of the roll, the roll density, the outer diameter of the roll core, and the ratio of the area of ​​the outer diameter of the core to the cross-sectional area of ​​the roll within a predetermined numerical range, it is possible to create a roll-shaped paper towel with a constant core outer diameter, high basis weight, and excellent water absorption, while also being easy to wind up and resistant to core crushing, making it easy to use as a product and improving logistics efficiency. This discovery solved the above problems and led to the completion of the present invention. Specifically, the present invention provides the following:

[0010] (1) A first aspect of the present invention is a roll-type paper towel in which a single-ply paper towel containing pulp fibers and synthetic fibers is wound into a roll, wherein the basis weight of the paper towel is 40 g / m². 2 More than 150g / m 2 The following conditions apply: the roll diameter is between 75 mm and 160 mm, and the roll density is 0.05 g / cm³. 3 More than 0.19g / cm 3 The following describes a roll-shaped paper towel characterized in that the outer diameter of the core of the roll is 25 mm or more and 55 mm or less, and the value shown by ((area of ​​the outer diameter of the core of the roll) / (cross-sectional area of ​​the roll excluding the cavity from the center of the roll to the core)) × 100 is 5 or more and 40 or less.

[0011] (2) A second aspect of the present invention is a roll of paper towel as described in (1), wherein the cross-sectional area of ​​the roll, excluding the cavity from the center of the roll to the core, is 30 cm². 2 over 190cm 2 It is characterized by the following:

[0012] (3) A third aspect of the present invention is a roll-shaped paper towel as described in (1), characterized in that the bending stiffness of the paper towel in the MD direction is 10 μN·m or more and 130 μN·m or less.

[0013] (4) The fourth aspect of the present invention is the roll-shaped paper towel according to (1), wherein the apparent basis weight of the core of the roll is 200 g / m 2 or more and 520 g / m 2 or less.

[0014] (5) The fifth aspect of the present invention is the roll-shaped paper towel according to (1), wherein the DMDT of the paper towel is 8 N / 25 mm or more and 75 N / 25 mm or less, and the DCDT is 2 N / 25 mm or more and 5 N / 25 mm or less.

[0015] (6) The sixth aspect of the present invention is the roll-shaped paper towel according to (1), wherein the hardness of the core of the roll is 0.4 mm or more and 3.0 mm or less.

[0016] (7) The seventh aspect of the present invention is the roll-shaped paper towel according to (1), wherein the value represented by (the bending strength in the MD direction of the paper towel) × (the hardness of the core of the roll) is 5 or more and 360 or less.

[0017] (8) The eighth aspect of the present invention is the roll-shaped paper towel according to (1), wherein the water absorption per unit area of the paper towel is 210 g / m 2 or more and 520 g / m 2 or less.

[0018] (9) The ninth aspect of the present invention is the roll-shaped paper towel according to (1), wherein the winding length of the roll is 7 m or more and 24 m or less.

[0019] (10) The tenth aspect of the present invention is the roll-shaped paper towel according to (1), wherein the paper thickness of the paper towel is 200 μm or more and 1400 μm or less.

[0020] (11) An eleventh aspect of the present invention is a roll of paper towel as described in (1), characterized in that the paper towel is a kitchen towel. [Effects of the Invention]

[0021] According to the present invention, a roll-type paper towel is provided that has a core outer diameter within a certain range, high basis weight and excellent water absorption in a single ply, is easy to wind up, has good resistance to core crushing, is easy to use as a product, and has good logistics efficiency. [Brief explanation of the drawing]

[0022] [Figure 1] This is a perspective view showing the entire roll of paper towels according to the present invention. [Figure 2] This figure shows the height profile on the XY plane as measured by a microscope, indicated by varying shades of gray. [Figure 3] This figure shows the height profile on the XY plane as measured by a microscope. [Figure 4] This diagram shows how to determine the depth of the embossing on the roll-shaped paper towel of the present invention. [Figure 5] This figure shows the method for measuring the water absorption capacity of a roll of paper towels according to the present invention. [Modes for carrying out the invention]

[0023] The embodiments for carrying out the present invention will be described in detail below with reference to the drawings, but these are provided for illustrative purposes only and do not limit the present invention.

[0024] 1. Roll-type paper towels Figure 1 is a perspective view showing the entire roll of paper towel 1 according to the present invention. The roll of paper towel 1 according to the present invention is a roll of 1-ply paper towels 1x containing pulp fibers and synthetic fibers wound into a roll. Preferably, the paper towel 1x has perforations that are equally spaced in the MD direction and cross the paper towel 1x in the CD direction (not shown). In this context, the MD (Machine Direction) direction is the direction in which the paper towel 1x is wound (the direction in which the paper towel 1x is manufactured, also called the flow direction), and the CD (Cross Direction) direction is the direction perpendicular to the MD direction (also called the width direction). Furthermore, the paper towel 1x in this invention can be used as a variety of paper products, and is preferably used as a wiper or kitchen towel, but more preferably as a kitchen towel. In addition, although the present invention is a paper product used as a wiper or kitchen towel, it may also be used as a nonwoven fabric product.

[0025] Furthermore, as shown in Figure 1, the surface of the paper towel 1x facing outwards from the roll is referred to as surface 1a (the surface of the paper towel 1x), and the surface facing towards the center of the roll is referred to as back surface 1b (the back surface of the paper towel 1x). It is preferable that, due to the water flow entanglement described later, the amount of synthetic fibers contained in the paper towel 1x is higher on the surface side (i.e., surface 1a) and lower on the back surface 1b.

[0026] (Roll length and roll diameter) The length of the roll of paper towel 1 is preferably 7m to 24m, more preferably 10m to 22m, and even more preferably 13m to 18m. If the length is less than 7m, the logistics efficiency per roll is poor if the winding diameter DR is not changed. If the length exceeds 24m, the roll becomes tightly wound if the winding diameter DR is not changed, making core crushing more likely when cutting with a log saw. Furthermore, the roll diameter DR of the roll-type paper towel 1 is 75 mm or more and 160 mm or less, preferably 100 mm or more and 140 mm or less, and more preferably 108 mm or more and 130 mm or less. If the roll diameter DR is less than 75 mm, the roll diameter DR becomes too small, resulting in poor usability as a roll product. If the roll diameter DR exceeds 160 mm, the roll diameter DR becomes too large, resulting in poor usability as a roll product.

[0027] The roll length is determined by measuring the length of 10 sheets of paper towel 1x between the perforations of a roll of paper towel 1. Then, the number of paper towels in the roll of paper towel 1 is measured, and the roll length is calculated proportionally from the length of 10 sheets and the number of paper towels in the roll. For example, if the length of 10 sheets is 1.80m and the number of paper towels in the roll is 150, then the calculation is 1.80m × (150 / 10) = 27m. The roll diameter DR is measured using a diameter rule manufactured by Muratec KDS Co., Ltd. The measurement is performed by measuring 10 rolls of paper towel 1 and averaging the results. If there are no perforations, the roll length is measured directly.

[0028] (Roll width and roll weight) The roll width of the roll-type paper towel 1 is preferably 180 mm or more and 350 mm or less, more preferably 210 mm or more and 325 mm or less, and even more preferably 240 mm or more and 300 mm or less. By setting the roll width within the above numerical range, when using a roll-type paper towel 1 with high basis weight and excellent water absorption, such as the present invention, the area used becomes appropriate, and a large amount of water can be absorbed. Furthermore, the roll weight of the roll-type paper towel 1 is preferably between 100g and 580g, more preferably between 180g and 450g, and even more preferably between 220g and 400g. By keeping the roll weight within the above numerical range, a roll-type paper towel 1 that is easy to handle as a product can be obtained. Note that the roll weight is the weight of one roll per 275 mm roll width, excluding the core (paper tube). If the roll width is not 275 mm, the weight will be converted to a 275 mm weight using proportional calculation.

[0029] (Roll density) The roll density of roll-type paper towel 1 is 0.05 g / cm³. 3 More than 0.19g / cm 3 The following is the value: 0.07 g / cm³ 3 More than 0.17g / cm 3 Preferably, it is 0.09 g / cm³. 3 More than 0.15g / cm 3 The following is more preferable: Roll density is 0.05 g / cm³ 3 If the density is less than 0.19 g / cm³, the logistics efficiency per roll is poor. 3 Beyond this point, the wood becomes tightly wound, making it more prone to core crushing during log saw cutting.

[0030] Roll density is expressed as (roll mass) ÷ (roll volume). Roll mass is the mass of one roll of paper towel per 275 mm roll width. Roll volume is expressed as [{cross-sectional area of ​​the outer diameter (winding diameter DR) portion of the roll} - (cross-sectional area of ​​the outer diameter portion of the core)] × roll width (converted to per 275 mm). For example, if the roll mass (excluding core) per 275 mm roll width is 337 g, the winding diameter is 119 mm, and the outer diameter of the core is 49 mm, then the roll density = 0.13 g / cm³ 3 This is the result. If the roll of paper towel 1 does not have a core, the diameter of the central cavity is defined as the core outer diameter DI.

[0031] (cross-sectional area) In the roll-shaped paper towel 1, the cross-sectional area of ​​the roll, excluding the cavity from the center of the roll to the core, is 30 cm². 2 over 190cm 2 Preferably, it is 60cm 2 More than 140cm 2 More preferably, the following: 80cm 2 More than 115cm 2It is even more preferable that the cross-sectional area is 30 cm². 2 If it is less than 190 cm², the roll diameter DR becomes small, making it less convenient to use as a roll product. 2 If it exceeds this value, the winding diameter DR becomes large, making it less user-friendly as a roll product. Note that the cavity from the center of the roll to the core refers to the cavity from the center of the roll to the outer diameter of the core.

[0032] 2. Core (Apparent basis weight and weight of the core) Furthermore, the core (paper tube) of the roll-type paper towel 1 of the present invention is made of multiple sheets of base paper stacked together, and it is more preferable that it is made of two sheets. In this case, the apparent basis weight of the core (basis weight of the core made of multiple sheets of base paper stacked together) is 200 g / m². 2 More than 520g / m 2 Preferably, it is 260 g / m². 2 More than 460g / m 2 It is more preferable that the following conditions apply: 320 g / m² 2 More than 420g / m 2 It is even more preferable that the apparent basis weight is 200 g / m². 2 If the weight is less than 520 g / m², the core becomes too soft, making it prone to crushing during winding and log saw cutting. 2 If the core exceeds a certain value, it becomes too hard, making it difficult to break when disposing of the core after using the roll, thus compromising the ease of use of the roll product. The apparent basis weight of the core is measured in accordance with JIS P 8124. When using two layers of core, any known adhesive (glue) can be used, but it is preferable to use a PVAC (polyvinyl acetate) emulsion. By using the above composition of glue, it becomes easier to adjust the hardness of the core, as described later, within a predetermined range, and a roll-type paper towel 1 with good ease of winding and resistance to core crushing, as in the present invention, can be obtained. Furthermore, the weight of the core (paper tube) is preferably 6.5g or more and 17.5g or less, more preferably 7.5g or more and 16g or less, and even more preferably 9g or more and 14g or less. The weight of the core (paper tube) shall be the weight per 275mm roll width. If the roll width is not 275mm, the weight shall be converted to a weight per 275mm using proportional calculation.

[0033] (Core outer diameter) The core outer diameter DI of the roll-shaped paper towel 1 of the present invention is 25 mm or more and 55 mm or less, more preferably 32 mm or more and 47 mm or less, and more preferably 36 mm or more and 42 mm or less. If the core outer diameter DI is less than 25 mm, the pickup will not wrap around the core well when rolled. If the core outer diameter DI exceeds 55 mm, the logistics efficiency per roll will be poor, and the core will be more prone to crushing during winding or log saw cutting. The core outer diameter DI is measured using a Diameter Rule manufactured by Muratec KDS Co., Ltd. The measurement is performed by measuring 10 rolls of paper towels 1 and averaging the results. In the case of rolls of paper towels 1 without a core, the diameter of the central cavity of the roll of paper towel 1 is considered the core outer diameter DI.

[0034] (Area of ​​the outer diameter of the core) The area of ​​the core outer diameter DI in the roll-shaped paper towel 1 of the present invention is 5 cm² 2 More than 24cm 2 Preferably, it is 8 cm 2 More than 18cm 2 More preferably, the following is 10 cm 2 More than 14cm 2 It is even more preferable that the area is 5 cm². 2 If the area is less than 24cm², the wire will not wrap properly around the pickup core. 2 If it exceeds this, the logistics efficiency per roll becomes inferior. Furthermore, the value shown by ((area of ​​the roll's core outer diameter DI) / (cross-sectional area of ​​the roll excluding the cavity from the center of the roll to the core)) × 100 for the roll-shaped paper towel 1 is 5 cm 2 / cm 2 The above 40 cm 2 / cm 2 The following are 7 cm 2 / cm 2 The above 20 cm 2 / cm 2 The following is preferable: 9 cm 2 / cm 2 The above 16 cm 2 / cm 2 The following is more preferable: The value is 5 cm 2 / cm 2 If the value is less than 40, the core becomes too small, resulting in poor winding of the pickup onto the core. cm 2 / cm 2 If it exceeds this, the logistics efficiency per roll becomes inferior.

[0035] (Core hardness) Furthermore, the core hardness in the roll-type paper towel 1 of the present invention is preferably 0.4 mm or more and 3.0 mm or less, more preferably 0.6 mm or more and 2.3 mm or less, and even more preferably 0.7 mm or more and 1.5 mm or less. If the core hardness is less than 0.4 mm, the core becomes too hard, making it difficult to break when disposing of the core after using the roll, resulting in poor usability as a roll product. If the core hardness exceeds 3.0 mm, the core is more likely to be crushed during winding and log saw cutting. The hardness of the core is measured using a compression tester (KES-G5 handheld compression tester manufactured by Kato Tech Co., Ltd.) as follows: First, the core is placed horizontally on a hard surface with its axis horizontal. Next, the compression element of the KES-G5 (area 2.0 cm²) is placed in the center of the outer surface of the core. 2 The compressor is pushed down from above at a speed of 10 mm / min. The pressure exerted by the compressor against the roll is 0.5 gf / cm². 2 The depth of indentation at that time is T a , pressure 250 gf / cm² 2 The depth of indentation at that time is T b (T b -T a This value represents the hardness of the core. A higher value means the core is more easily crushed. The measurement is performed five times using five cores (one measurement per core), and the measurement results are averaged.

[0036] 3. Paper towels In the roll-type paper towel 1 of the present invention, the paper towel 1x contains synthetic fibers and pulp fibers. Examples of synthetic fibers include nylon, vinylon, polyester, acrylic, polyethylene, polypropylene, and polystyrene. However, to obtain a paper towel 1x with high basis weight and excellent water absorption, as in the present invention, polyethylene and polypropylene are preferred, and polypropylene is more preferred. There are no restrictions on the nonwoven fabric used as the synthetic fiber, but spunbond nonwoven fabric is preferred. By using a polypropylene spunbond nonwoven fabric, even a high-basis-weight paper towel 1x like the one in the present invention becomes easier to wrap around a pick-up machine. Furthermore, the ease of use of the roll-type paper towel 1 is also improved. Furthermore, general pulp fibers such as bleached softwood kraft pulp (NBKP) and bleached hardwood kraft pulp (LBKP) can be used as pulp fibers. The preferred ratio of NBKP to LBKP in the pulp fibers is NBKP:LBKP = 50:50 to 100:0, more preferably NBKP:LBKP = 70:30 to 100:0, even more preferably NBKP:LBKP = 90:10 to 100:0, and most preferably NBKP:LBKP = 100:0. As NBKP, for example, fibers made from radiata pine, slush pine, southern pine, lodgepole pine, spruce, and Douglas fir are preferred. Note that NUKP can be used instead of NBKP, and LUKP can be used instead of LBKP.

[0037] In this case, the proportion (content) of synthetic fibers in paper towel 1x is preferably 5% or more and 50% or less, more preferably 9% or more and 41%, and even more preferably 12% or more and 28% or less. If the proportion of synthetic fibers is less than 5%, the strength becomes too weak, making it difficult to reuse paper towel 1x and resulting in poor usability as a product. If the proportion of synthetic fibers exceeds 50%, the water absorption is poor. Furthermore, the proportion (content) of pulp fibers in paper towel 1x is preferably 50% or more and 95%, more preferably 59% or more and 91%, and even more preferably 72% or more and 88%. If the proportion of pulp fibers is less than 50%, the water absorption is poor. If the proportion of pulp fibers exceeds 95%, the strength becomes too weak, making it difficult to reuse paper towel 1x and resulting in poor usability as a product.

[0038] Furthermore, it is preferable that the paper towel 1x contains a general wet-strength agent. The content of the wet-strength agent (calculated in terms of solid content (active ingredient)) is preferably 0.05% to 1.0%, more preferably 0.10% to 0.5%, and even more preferably 0.20% to 0.40% relative to the pulp fibers (absolutely dry). By setting the content of the wet-strength agent within the above numerical range, a roll-type paper towel 1 with high basis weight and excellent water absorption, as in the present invention, can be obtained. Furthermore, if necessary, heat-resistant stabilizers, lubricants, etc., can be added to the paper towel 1x, to the extent that the objectives of the present invention are not impaired. Examples of heat-resistant stabilizers include phenolic stabilizers such as BHT (2,6-di-t-butyl-4-methylphenol).

[0039] (Basic weight) The basis weight (total basis weight of synthetic and pulp fibers) of one sheet of paper towel is 40 g / m². 2 More than 150g / m 2 The following is true: 48g / m 2 More than 110g / m 2 Preferably, it is 55 g / m 2 More than 80g / m 2 The following is more preferable: The basis weight of 1x paper towel is 40g / m². 2 If the basis weight is less than 150 g / m², the absorbency of the roll of paper towel 1 will be inferior. 2 Beyond a certain point, the wire won't wrap around the pickup core properly.

[0040] Furthermore, the basis weight of synthetic fibers contained in 1x paper towels is 4g / m². 2 More than 40g / m 2 Preferably, it is 7 g / m 2 More than 30g / m 2 More preferably, the following is true: 10 g / m 2 More than 20g / m 2 It is even more preferable that the basis weight of the synthetic fiber be 4 g / m². 2 If the basis weight is less than 40g / m², the strength becomes too weak, making it difficult to reuse 1x paper towels and resulting in a less user-friendly product. 2 If the strength exceeds a certain point, it becomes too strong, resulting in poor winding of the pickup core. Furthermore, core crushing during winding becomes more likely. Furthermore, the basis weight of the pulp fibers contained in 1x paper towels is 33 g / m². 2 More than 120g / m 2 Preferably, it is 38 g / m 2 More than 90g / m 2It is more preferable that it is as follows, 45 g / m 2 or more and 75 g / m 2 or less. If the basis weight of the pulp fiber is less than 33 g / m 2 , the water absorption property is poor. If the basis weight of the pulp fiber exceeds 120 g / m 2 , the basis weight increases and the winding around the core of the pickup deteriorates. The basis weight of the paper towel 1x is measured based on JIS P 8124. However, since it is difficult to measure the basis weights of the synthetic fiber and the pulp fiber individually after the water flow entanglement described later, for example, it is measured by the following method.

[0041] First, prepare a 0.1 M acetic acid aqueous solution and a 0.1 M sodium acetate aqueous solution. Mix about 830 g of the 0.1 M acetic acid aqueous solution and about 160 g of the 0.1 M sodium acetate aqueous solution so that the pH becomes 4, and use this as an acetic acid buffer solution. Add cellulase Onozuka p1500 (manufactured by Yakult Pharmaceutical Industry Co., Ltd.) to this acetic acid buffer solution so that the added amount becomes 1% by weight. Put 50 ml of the acetic acid buffer solution to which cellulase Onozuka p1500 is added and 0.5 g of the paper towel 1x into a vial and tightly cover it. Next, after shaking at 180 rpm and 40 °C for 24 hours, collect the synthetic fiber from the vial and measure the mass of the synthetic fiber. From the mass of the paper towel 1x (0.5 g) (including the synthetic fiber and the pulp fiber) and the mass of the collected synthetic fiber, the basis weights of the synthetic fiber and the pulp fiber are calculated by the following formula. Basis weight of synthetic fiber = Basis weight of paper towel 1x × (mass of synthetic fiber / mass of paper towel 1x) Basis weight of pulp fiber = Basis weight of paper towel 1x × [(mass of paper towel 1x - mass of synthetic fiber) / mass of paper towel 1x]

[0042] (paper thickness) The paper thickness of paper towel 1x is preferably 200 μm to 1400 μm, more preferably 400 μm to 1200 μm, and even more preferably 500 μm to 1000 μm. If the paper thickness is less than 200 μm, the water absorption of the roll-type paper towel 1 will be poor. If the paper thickness exceeds 1400 μm, the basis weight of the paper towel 1x will increase, and it will not wrap well around the core of the pickup. The paper thickness is measured using a thickness gauge (diale thickness gauge "PEACOCK" manufactured by Ozaki Seisakusho Co., Ltd.). The measurement conditions are a measuring load of 3.7 kPa and a probe diameter of 30 mm. The sample is placed between the probe and the measuring stand, and the gauge is read when the probe is lowered at a speed of 1 mm or less per second. The measurement is repeated 10 times and the measurement results are averaged. The measurement is performed by stacking three paper towels 1x and measuring them, and the value is divided by 3 to obtain the paper thickness value.

[0043] (DMDT and DCDT) The Dry Machine Direction Tensile Strength (DMDT) of a 1x paper towel, based on JIS P 8113, is preferably 8N / 25mm to 75N / 25mm, more preferably 13N / 25mm to 65N / 25mm, and even more preferably 20N / 25mm to 50N / 25mm. If the DMDT is less than 8N / 25mm, the 1x paper towel becomes difficult to reuse, resulting in poor usability as a product. If the DMDT exceeds 75N / 25mm, the paper towel does not wrap well around the core of the pickup. In addition, core crushing is more likely to occur during winding.

[0044] Furthermore, the Dry Cross Direction Tensile Strength (DCDT) of a 1x paper towel, based on JIS P 8113, is preferably 2N / 25mm or more and 50N / 25mm or less, more preferably 4N / 25mm or more and 40N / 25mm or less, and even more preferably 5N / 25mm or more and 25N / 25mm or less. If the DCDT is less than 2N / 25mm, it becomes difficult to reuse the 1x paper towel, resulting in poor usability as a product. If the DCDT exceeds 50N / 25mm, the wrapping around the pickup core becomes poor, and core crushing during winding becomes more likely. DMDT and DCDT are measured according to JIS P 8113 as described above, with the following measurement conditions: speed of 300 m / min, specimen width of 25 mm, and distance between grips of 100 mm. If a distance of 100 mm between grips cannot be maintained due to the perforation spacing or sheet width, it may be shortened as appropriate.

[0045] (Sheet length and bending stiffness) The sheet length of the paper towel 1x is preferably 160mm to 330mm, more preferably 180mm to 305mm, and even more preferably 200mm to 280mm. By having the sheet length within the above numerical range, a roll-type paper towel 1 can be obtained that is easy to wind up and less prone to core crushing. The sheet length is the measured length in the MD direction of a single paper towel 1x between the perforations of the roll-type paper towel 1. Furthermore, the bending stiffness of the paper towel 1x in the MD direction is preferably 10 μN·m or more and 130 μN·m or less, more preferably 17 μN·m or more and 100 μN·m or less, and even more preferably 20 μN·m or more and 50 μN·m or less. If the bending stiffness is less than 10 μN·m, the basis weight and paper thickness of the paper towel 1x will be low, resulting in poor water absorption. If the bending stiffness exceeds 130 μN·m, the paper towel 1x will become too stiff, resulting in poor wrapping around the pickup core.

[0046] The bending stiffness of a 1x paper towel in the MD direction is measured using an L&W bending tester (Lorentzen & Wettre) in accordance with the method described in ISO 2493. For a test piece measuring 38 mm in width and 100 mm in length taken from a 1x paper towel, the measured value at a bending angle of 15 degrees and a bending length (span of the sample stage) of 10 mm is taken as the bending resistance (load), and the bending stiffness (μN·m) is calculated using the following formula. Bending stiffness (μN·m) = 60 × Bending resistance (mN) × Bending length 10 (mm) 2 ÷(π × bending angle 15(°) × sample width 38(mm)) If it is not possible to obtain a test specimen with a length of 100 mm, the length of the test specimen may be shortened. Also, the test specimen should not include perforations, however, if it is necessary to include perforations in order to ensure the size of the test specimen, then perforations may be included.

[0047] Furthermore, in paper towel 1x, the value shown by (bending stiffness of paper towel 1x in the MD direction) × (stiffness of the roll core) is 5 μN·m·mm 360 μN·m·mm Preferably, 10 μN·m·mm The above 210 μN·m·mm More preferably, 15 μN·m·mm The above 75 μN·m·mm It is even more preferable that the value is 5. μN·m·mm If the value is less than 360, the basis weight of one paper towel will be smaller, resulting in poorer absorbency. μN·m·mm If this value is exceeded, core crushing is more likely to occur in the roll-shaped paper towel 1 during winding and log saw cutting.

[0048] (Embossed) The roll-shaped paper towel 1 (paper towel 1x) of the present invention is preferably embossed, and preferably embossed using a roll winder. The shape of the embossing itself is not particularly limited and can be circular, elliptical, rectangular, square, floral, polygonal, letters, lines, logos, etc., but a hexagonal shape is preferred in order to obtain a paper towel 1x with high basis weight and excellent water absorption as in the present invention. Furthermore, the embossing depth is preferably between 0.07 mm and 1.8 mm, more preferably between 0.2 mm and 1.2 mm, and even more preferably between 0.3 mm and 0.8 mm. By having the embossing depth within the above numerical range, the paper thickness and bending stiffness of the paper towel 1x can be adjusted, resulting in improved usability as a roll of paper towel 1.

[0049] The depth of the embossing is measured using a microscope. The KEYENCE VR-3100 one-shot 3D measuring microscope can be used. The VR-H1A software can be used for observing, measuring, and analyzing the microscope images. The measurement conditions are 12x magnification and a field of view of 24mm x 18mm. The magnification and field of view may be adjusted as needed depending on the desired embossing size.

[0050] Figure 2 shows the height profile on the XY plane as measured by a microscope, with the height of the paper towel surface represented by shades of gray. The hexagonal areas in Figure 2, which have a different shade from the surrounding areas, represent individual embossing. The depth of the embossing is determined by measuring the height difference of the embossing using the microscope described above. The measurement is performed on the surface 1a side of paper towel 1x. In addition, three turns of paper towel 1x are removed from the roll of paper towel 1, and the measurement is taken using the fourth turn of paper towel 1x in its paper towel state. If there are perforations, they are avoided during measurement. First, draw line segment AB as shown in Figure 2 to obtain the height profile shown in Figure 3. Line segment AB should be drawn across the embossing. Line segment AB should be drawn in the width direction (CD direction) of the paper towel 1x, but if the spacing between embossings is, for example, 2 mm or more, the line segment may be drawn diagonally or in the direction of the flow. The height profile is a (measured) cross-sectional curve S that represents the surface irregularities of the actual paper towel 1x sample, but it also contains noise (steep peaks caused by fiber clumps on the surface of the paper towel 1x, fibers extending in a whisker-like manner, or areas without fibers), and it is necessary to remove such noise peaks when calculating the height difference of the irregularities. Therefore, the (measured) cross-sectional curve S in Figure 3 is smoothed with a weighted average radio button filter size of ±12 to obtain the cross-sectional curve W in Figure 4. Note that smoothing using the weighted average radio button filter can be obtained automatically using the analysis software mentioned above. Then, in the graph shown in Figure 4, the average of the maximum values ​​on the vertical axis of the convex part H1 and the convex part H2 adjacent to convex part H1 is calculated, and the minimum value on the vertical axis at the concave part D1 sandwiched between convex parts H1 and H2 is found. The value obtained by subtracting the minimum value from the average of the maximum values ​​obtained in this way is taken as the provisional embossing depth. Then, as shown in Figure 4, the same measurement is performed at a total of two consecutive locations on the cross-sectional curve (a total of two consecutive locations: the concave part D1 and the concave part D2 sandwiched between convex parts H2 and H3) (at this point, two measurement results are obtained). Subsequently, the roll of paper towel 1 is rotated 90 degrees three times in the flow direction of the paper towel 1x, and the same measurements as above are taken at each position (a total of 4 measurement positions in the flow direction). The average value of these 8 positions (2 x 4) is then adopted as the embossing depth.

[0051] (Water absorption amount) In the roll-shaped paper towel 1 of the present invention, the unit area of ​​the paper towel 1x is (1m² 2 The water absorption capacity (per unit) is 210g / m². 2 More than 520g / m 2 Preferably, it is 260 g / m². 2 More than 430g / m2 More preferably, it is as follows, 310 g / m 2 or more and 400 g / m 2 or less is even more preferable. When the water absorption per unit area is less than 210 g / m 2 , the water absorption as the roll paper towel 1 is inferior. When the water absorption per unit area exceeds 520 g / m 2 , the basis weight of the paper towel 1x increases, and the winding around the pickup core deteriorates. Also, the water absorption per unit weight (per 1 g) of the paper towel 1x is preferably 3.0 g / g or more and 8.0 g / g or less, more preferably 3.5 g / g or more and 7.5 g / g or less, and even more preferably 4.0 g / g or more and 7.0 g / g or less. By having the water absorption per unit weight within the above numerical range, it is possible to obtain a roll paper towel 1 that has a high basis weight and excellent water absorption, and is good in terms of ease of winding of the roll and resistance to core collapse. In addition, each water absorption of the paper towel 1x is measured as follows.

[0052] First, the paper towel 1x is sampled, cut using a template with a square of 7.6 cm (3 inches) per piece, and 200 test pieces in the shape of a rectangle with a side of 7.6 cm are prepared. Then, the mass of the test piece 200 before water absorption is measured with an electronic balance. And the test piece 200 is set in a holder 220 (a jig that fixes three points of the test piece 200, and the jig is made of a metal that does not absorb moisture). Next, fill a commercially available tray with distilled water to a depth of 2 cm, and immerse the test specimen 200, which is set in the holder 220, in the distilled water for 2 minutes. After 2 minutes of immersion, remove the test specimen 200 together with the holder 220 from the distilled water, and attach the strip 210 to one corner 200d of the test specimen 200, as shown in Figure 5. The strip 210 is made by cutting 1x of the same paper towel as the sample to be measured to a size of 2 mm wide x 15 mm long, and attaching it to the part of the test specimen 200 6 mm from the corner 200d toward the center. Next, suspend the holder 220 and the test specimen 200 from a rod placed in an empty water tank with the corner 200a opposite corner 200d facing upwards, close the lid of the water tank, and leave it for 10 minutes. After that, remove the holder 220 and the test specimen 200 from the water tank, remove the strip 210 and the holder 220, and measure the mass of the test specimen 200 using an electronic balance. The amount of distilled water absorbed per unit area of ​​test piece 200 (g(water) / m²) can be determined from the change in mass of test piece 200 before and after immersion in distilled water. 2 Calculate the amount of water absorbed per unit area (g(water) / m²). 2 By dividing the amount of (paper towel) by the basis weight of the 200 test piece, the water absorption per unit area (g(water) / m²) can be calculated. 2 (Paper towel) / Basis weight (g(paper towel) / m² 2 Calculate the amount of water absorbed per unit weight (g(water) / g(paper towel)) using paper towels. Measure each sample five times and use the average value. This measurement will be conducted according to the JIS P 8111 method, under conditions of 23±1°C and 50±2% humidity. The distilled water will also be maintained at 23±1°C.

[0053] 4. Method for manufacturing paper towels and roll-type paper towels As for the manufacturing method of paper towel 1x and roll-type paper towel 1, if the paper towel 1x is a kitchen towel containing synthetic fibers and pulp fibers, it can be manufactured in the following order: (1) laminating pulp fibers onto a predetermined spunbond nonwoven fabric and entangling with water flow, (2) heat embossing with matched steel, (3) perforation, and (4) roll winding. In this process, in step (1) of the manufacturing method, a nonwoven fabric containing synthetic fibers and pulp fibers is obtained by entangling synthetic fibers with pulp fibers using a water flow. Regarding the method of water flow entanglement, it is preferable to carry it out using the method described in, for example, Japanese Patent Application Publication No. 2018-193634.

[0054] Although the present invention has been described above using embodiments, it goes without saying that the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be obvious to those skilled in the art that various modifications or improvements can be made to the above embodiments. Furthermore, it is clear from the claims that such modified or improved forms may also be included within the technical scope of the present invention. [Examples]

[0055] The present invention will be described in detail below with reference to examples. However, the present invention is not limited in any way to the examples shown below.

[0056] (1) Laminating pulp fibers onto a polypropylene spunbond nonwoven fabric and entangling with water, (2) heat embossing with matched steel, (3) perforation, and (4) roll winding were performed to produce roll-shaped paper towels of Examples 1 to 26 and Comparative Examples 1 to 9, as described in Tables 2 to 4. Only Example 26 was a roll-shaped paper towel without a core. The above parameters were measured for all roll-shaped paper towels in the examples and comparative examples, and the following evaluations were performed. All measurement results and evaluations are shown in Tables 2 to 4.

[0057] Pickup core wrapping: The pickup core wrapping was evaluated as follows. The paper towels do not wrap tightly around the core, causing them to detach easily during winding and resulting in wrinkles. The wrapping around the core is somewhat weak, making it prone to detaching from the core during winding, and the paper towels tend to wrinkle easily. :△ The paper wraps around the core without any problems and is less likely to detach from the core during winding, resulting in fewer wrinkles in the paper towels. :○ The paper towels wrap around the core perfectly and securely, hardly separating from the core during winding, and remain wrinkle-free. :◎

[0058] Resistance to core crushing (during winding): The crushing of the core during winding of roll-shaped paper towels was evaluated as follows. The core gets severely crushed during winding: × The core gets slightly crushed when winding: △ The core is hardly crushed during winding: ○ The core does not get crushed at all during winding: ◎

[0059] Resistance to core crushing (during log saw cutting): The following evaluation was conducted regarding the crushing of the core when log saw cutting roll-type paper towels. The core gets severely crushed when cutting with a log saw: × The core gets slightly crushed when cutting with a log saw: △ The core is hardly crushed during log saw cutting: ○ The core does not get crushed at all during log saw cutting: ◎

[0060] Ease of Use of Roll Products: The ease of use of roll-type paper towels as a product was evaluated as follows. The roll diameter is either too large or too small, making it difficult to use: × The roll diameter is sometimes a little too big or a little too small, making it slightly inconvenient to use: △ The roll diameter may vary slightly, but it does not affect ease of use. The roll diameter is a suitable size and easy to use: ◎

[0061] Logistics Efficiency: The logistics efficiency of roll-type paper towels was evaluated according to the criteria in Table 1. [Table 1]

[0062] Absorbency: Regarding the absorbency of paper towels, the following evaluation was performed based on the amount of water absorbed per unit area of ​​the paper towels measured using the above measurement method. Water absorption capacity: 159 g / m² 2 Below: ×× Water absorption capacity: 160g / m 2 More than 209g / m 2 Below: × Water absorption capacity: 210 g / m² 2 More than 259g / m 2 Below: △ Water absorption capacity: 260g / m² 2 More than 309g / m 2 Below: ○ Water absorption capacity: 310 g / m² 2 That's all: ◎

[0063] [Table 2]

[0064] [Table 3]

[0065] [Table 4]

[0066] As shown in Tables 2-4, the roll-type paper towels of Examples 1-26 all strongly wrapped around the core of the pickup, making them less prone to core crushing during winding or log saw cutting, and they were excellent in terms of ease of use and logistics efficiency, as well as good water absorption. On the other hand, the roll-type paper towels of Comparative Examples 1-9 either had weak wrapping around the core of the pickup, were prone to core crushing during winding or log saw cutting, were inferior in terms of ease of use and logistics efficiency, or had inferior water absorption. Based on the above, the roll-type paper towel of the present invention is a roll-type paper towel in which the core outer diameter is within a certain range, has a high basis weight and excellent water absorption in a single ply, is easy to wind up, has good resistance to core crushing, is easy to use as a product, and has good logistics efficiency. [Explanation of Symbols]

[0067] 1. Roll of paper towels 1a surface 1b back side 1e Paper towel outermost edge 1 x Paper Towel 200 test specimens 200a, 200d corner 210 band 220 holder

Claims

1. A roll-type paper towel in which a single-ply paper towel containing pulp fibers and synthetic fibers is wound into a roll, The aforementioned paper towel is a nonwoven fabric in which pulp fibers are entangled with water flow in a spunbond nonwoven fabric. The basis weight of the aforementioned paper towel is 40 g / m². ２ 150g / m or more ２ The following: The roll diameter is between 75 mm and 160 mm, and the roll density is 0.05 g / cm³. ３ 0.19g / cm or more ３ The following applies to rolls with a core outer diameter of 25 mm or more and 55 mm or less: The value shown by ((Area of ​​the roll's core outer diameter) / (Cross-sectional area of ​​the roll excluding the cavity from the center of the roll to the core)) × 100 is between 5 cm² / cm² and 40 cm² / cm². A roll-type paper towel characterized in that the value shown by (bending stiffness of the paper towel in the MD direction) × (hardness of the roll core) is 5 μN·m·mm or more and 360 μN·m·mm or less.

2. The cross-sectional area of ​​the roll, excluding the cavity from the center of the roll to the core, is 30 cm². ２ 190cm or more ２ The roll-shaped paper towel according to claim 1, characterized in that it is as follows.

3. The roll-shaped paper towel according to claim 1, characterized in that the bending stiffness of the paper towel in the MD direction is 10 μN·m or more and 130 μN·m or less.

4. The apparent basis weight of the roll core is 200 g / m². ２ More than 520g / m ２ The roll-shaped paper towel according to claim 1, characterized in that it is as follows.

5. The roll-shaped paper towel according to claim 1, characterized in that the DMDT of the paper towel is 8 N / 25 mm or more and 75 N / 25 mm or less, and the DCDT is 2 N / 25 mm or more and 50 N / 25 mm or less.

6. The roll-shaped paper towel according to claim 1, characterized in that the core of the roll has a hardness of 0.4 mm or more and 3.0 mm or less.

7. The water absorption per unit area of the paper towel is 210 g / m ２ or more and 520 g / m ２ or less, and the roll-shaped paper towel according to claim 1, characterized in that.

8. The roll-shaped paper towel according to claim 1, characterized in that the length of the roll is 7 m or more and 24 m or less.

9. The roll-shaped paper towel according to claim 1, characterized in that the paper thickness of the paper towel is 200 μm or more and 1400 μm or less.

10. The roll-shaped paper towel according to claim 1, characterized in that the paper towel is a kitchen towel.

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