Paper towel roll

Abstract

The present invention provides a paper towel roll that offers good water absorption without increasing the basis weight of the sheet, is resistant to surface punctures, and reduces the costs associated with pulp usage and drying energy during manufacturing. [Solution] A paper towel roll is made by winding a paper towel sheet, which is laminated in 2-ply or 3-ply layers, into a roll shape, wherein the basis weight per ply of the paper towel sheet is 28 g / m². 2 More than 44g / m 2 The following is the water absorption per unit area of ​​the product ply: 230 g / m² 2 More than 390g / m 2 The following paper towel roll is provided, characterized in that the root mean square height of the surface roughness on the reverse side is 34 μm or more and 75 μm or less.

Description

Technical Field

[0001] The present invention relates to a paper towel roll.

Background Art

[0002] Paper towel sheets and paper towel rolls formed by winding the sheets into a roll are variously developed and sold.

[0003] In recent years, the length of the sheet in one roll of paper towels has been increasing. In addition to the increased length, high - quality products are also required to have qualities such as texture and tear resistance.

[0004] Among such high - quality products, a paper towel sheet obtained by the so - called TAD (Through Air Drying) papermaking technique (hereinafter also referred to as the "TAD papermaking method") using through - air drying has attracted attention because the sheet is thick, has a soft texture, and is excellent in water absorption.

[0005] As a prior art document related to a paper towel roll, for example, in Patent Document 1, a paper towel roll is formed by adhesively treating a sheet with an embossed pattern using glue and winding the laminated two - ply paper towel sheet into a roll. The paper towel sheet has a pattern of irregularities derived from a papermaking process different from the embossed pattern, and the basis weight of the two - ply is 30 g / m 2 to 54 g / m 2 Hereinafter, the paper thickness is 1.3 mm / 10 sheets to 5 mm / 10 sheets, the water absorption per 1 m 2 of the two - ply is 220 g to 600 g, the winding length of the paper towel roll is 14 m to 44 m, and the winding diameter is 110 mm to 189 mm. A paper towel roll is disclosed.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] On the other hand, the TAD papermaking technology consumes a large amount of energy for drying, and the cost of drying energy in the production of paper towels becomes high.

[0008] In addition, in the TAD papermaking technology, since a fabric with unevenness is used, the sheet also has unevenness. At the surface of the uneven fabric during the production of the paper towel sheet shown in FIG. 6, the concave portion 51 of the uneven fabric 50 has a large amount of pulp fibers 60, while the convex portion 52 has a small amount of pulp fibers 60.

[0009] As a result, the surface of the sheet corresponding to the convex portion 52 is likely to have holes, which deteriorates the appearance. Therefore, by making the basis weight relatively high during papermaking, the formation of holes can be suppressed.

[0010] However, as described above, since the paper towel sheet manufactured using the TAD papermaking technology has excellent water absorption, it is desired to reduce the cost of pulp usage (≒ the basis weight of the finally manufactured paper towel sheet) and drying energy during production by lowering the basis weight. However, when the basis weight is lowered, the sheet is likely to have holes, so it has been difficult to solve all problems simply by lowering the basis weight.

[0011] The present invention has been made in view of such circumstances, and an object thereof is to provide a paper towel roll that has good water absorption, is difficult to have holes on the surface, and can also suppress the cost of pulp usage and drying energy during production without increasing the basis weight of the sheet.

Means for Solving the Problems

[0012] The inventors conducted thorough research and discovered that, in a paper towel roll made by laminating two or three sheets of paper towel material into a roll, by keeping the basis weight per product ply, the water absorption per unit area of ​​the product ply, and the root mean square height of the surface roughness on the reverse side within predetermined numerical ranges, it is possible to create a paper towel roll that has good water absorption, is less prone to holes on the surface, and reduces the cost of pulp usage (content) and drying energy during manufacturing, without increasing the basis weight of the sheet. This discovery solved the above problems and led to the completion of the present invention. In other words, the present invention provides the following:

[0013] (1) A first aspect of the present invention is a paper towel roll in which a paper towel sheet, which is laminated in a 2-ply or 3-ply manner, is wound into a roll, wherein the basis weight per product ply of the paper towel sheet is 28 g / m². 2 More than 44g / m 2 The following is the water absorption per unit area of ​​the product ply: 230 g / m² 2 More than 390g / m 2 The following is a paper towel roll characterized in that the root mean square height of the surface roughness on the reverse side is 34 μm or more and 75 μm or less.

[0014] (2) A second aspect of the present invention is a paper towel roll as described in (1), characterized in that the paper towel sheet has an embossed pattern applied to at least one ply and is laminated in two or three plies using plybond glue.

[0015] (3) A third aspect of the present invention is a paper towel roll according to (1) or (2), characterized in that the water absorption per unit mass of the product ply of the paper towel sheet is 6 g / g or more and 11 g / g or less.

[0016] (4) A fourth aspect of the present invention is a paper towel roll according to (1) or (2), characterized in that the wet pulp content in the paper towel sheet is 60% or more.

[0017] (5) A fifth aspect of the present invention is a paper towel roll according to (1) or (2), characterized in that the tensile strength DMDT in the MD direction per product ply of the paper towel sheet when dry is 18 N / 76 mm or more and 50 N / 76 mm or less.

[0018] (6) A sixth aspect of the present invention is a paper towel roll according to (1) or (2), characterized in that the tensile strength DCDT in the CD direction per product ply of the paper towel sheet when dry is 16 N / 76 mm or more and 48 N / 76 mm or less.

[0019] (7) A seventh aspect of the present invention is a paper towel roll according to (1) or (2), characterized in that the paper thickness of the product ply of the paper towel sheet is 0.29 mm or more and 0.53 mm or less.

[0020] (8) An eighth aspect of the present invention is a paper towel roll according to (1) or (2), characterized in that when the basis weight per product ply of the paper towel sheet is A, B is the square root GMT of the product of the tensile strength DMDT in the MD direction per product ply at dry time and the tensile strength DCDT in the CD direction per product ply at dry time, and C is the number of plies, the value calculated by (B / A / C) is 0.22 or more and 0.70 or less.

[0021] (9) A ninth aspect of the present invention is a paper towel roll as described in (2), wherein the paper towel sheet has a pattern of irregularities originating from a TAD paper machine that is different from the embossed pattern. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide a paper towel roll that has good water absorption without increasing the basis weight of the sheet, is less prone to developing holes on the surface, and reduces the cost of pulp usage and drying energy during manufacturing. [Brief explanation of the drawing]

[0023] [Figure 1] This is a perspective view of a paper towel roll according to one embodiment of the present invention. [Figure 2] This figure shows an example of an embossed pattern applied to a sheet in the paper towel roll of the present invention. [Figure 3] This figure shows the height profile of the non-embossed area on the XY plane, as measured by a microscope, using shades of gray. [Figure 4] This figure shows a method for measuring the water absorption capacity of a paper towel sheet according to the present invention. [Figure 5] This figure shows a part of the papermaking process for the paper towel sheet of the present invention. [Figure 6] This is a magnified view showing the surface of the textured fabric during the manufacturing of paper towel sheets. [Modes for carrying out the invention]

[0024] The following describes in detail embodiments for carrying out the present invention (hereinafter simply referred to as "this embodiment"). This embodiment is illustrative for explaining the present invention and is not intended to limit the present invention to the following content. The present invention can be implemented by modifying it as appropriate within the scope of its gist.

[0025] In the context of paper towel sheets, the MD direction refers to the flow direction (Machine Direction) when the paper towel sheet is manufactured, while the CD direction refers to the direction perpendicular to the MD direction (Cross Direction). Furthermore, "product ply" refers to the number of plies in a paper towel sheet. For example, if a paper towel roll is manufactured by winding two sheets of paper towel material together, the product ply will be 2 plies. In addition, the paper towels (rolls, sheets) in this invention include kitchen towels and various types of paper towels (for wiper use).

[0026] <Paper towel roll> Figure 1 is a perspective view of a paper towel roll 1 according to one embodiment of the present invention. As shown in Figure 1, the paper towel roll 1 according to this embodiment is a paper towel roll 1 in which a paper towel sheet 1x, which is made by laminating sheets in 2-ply or 3-ply, is wound into a roll. Preferably, the paper towel sheet 1x has perforations in the roll width direction at approximately equal intervals in the roll winding direction (not shown). As shown in Figure 1, the surface of the paper towel sheet 1x facing outwards from the roll is referred to as surface 1a (the surface of the paper towel sheet 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 sheet 1x). The edge of the paper towel sheet 1x is referred to as the outermost edge 1e of the paper towel roll 1.

[0027] Uses of paper towel roll 1 include, for example, rolls of kitchen paper (sometimes called paper towels, cooking paper, etc.) used in home kitchens and restaurant kitchens for wiping up moisture or oil and removing dirt, hand towels, wipers, and other rolls of sanitary paper.

[0028] (Wind length and winding diameter) The length of the paper towel roll 1 is preferably 24m or more at the lower limit, more preferably 29m or more, and even more preferably 34m or more. The upper limit is preferably 49m or less, more preferably 45m or less, and even more preferably 40m or less. If the roll length is less than 24m, the basis weight of each paper towel sheet increases in order to keep the roll diameter DR (described later) within a certain range, resulting in higher costs. If the roll length exceeds 49m, the basis weight of each paper towel sheet decreases in order to keep the roll diameter DR (described later) within a certain range, resulting in inferior water absorption.

[0029] The roll length is measured as follows: First, measure the length of 10 sheets of paper towels between the perforations of paper towel roll 1. Then, measure the number of sheets in paper towel roll 1, and calculate the roll length proportionally from the length of 10 sheets and the number of sheets. For example, if the length of 10 sheets is 1.80m and the number of sheets is 150, then 1.80m × (150 / 10) = 27m. If paper towel roll 1 does not have perforations, measure the roll length directly.

[0030] The winding diameter DR of the paper towel roll 1 according to this embodiment is preferably 115 mm or more at the lower limit, more preferably 120 mm or more, and even more preferably 125 mm or more. The upper limit is preferably 155 mm or less, more preferably 150 mm or less, and even more preferably 146 mm or less. If the roll diameter DR is less than 115 mm, the basis weight of the paper towel sheet 1x will be low, resulting in poor water absorption. If the roll diameter DR exceeds 155 mm, the root mean square height of the surface roughness on the back side of the paper towel sheet 1x will be higher, making it more prone to holes, and the higher basis weight will result in higher costs.

[0031] The roll diameter DR is measured using a Diameter Rule manufactured by Muratec KDS Co., Ltd. Three paper towel rolls are measured, and the results are averaged.

[0032] (Roll width and roll mass) The roll width (sheet width) of paper towel roll 1 is preferably 150 mm or more at the lower limit, more preferably 200 mm or more, and even more preferably 250 mm or more. The upper limit is preferably 380 mm or less, more preferably 340 mm or less, and even more preferably 300 mm or less. If the roll width is less than 150mm, the amount of water absorbed per sheet of paper towel will be reduced. If the sheet width exceeds 380mm, the amount of water absorbed per sheet of paper towel will be excessively high.

[0033] Furthermore, the roll mass of the paper towel roll 1 is preferably 260g or more at the lower limit, more preferably 290g or more, and even more preferably 320g or more. The upper limit is preferably 500g or less, more preferably 460g or less, and even more preferably 430g or less. If the roll weight is less than 260g, the basis weight of each paper towel sheet is low, resulting in poor absorbency. If the roll weight exceeds 500g, the basis weight of each paper towel sheet increases, resulting in higher costs.

[0034] The roll mass is defined as the mass per 280 mm of roll width, excluding the paper tube 2 (core) in paper towel roll 1. If the sheet width is not 280 mm, the mass per 280 mm will be converted using proportional calculation.

[0035] Furthermore, the roll mass per 280 mm of roll width, including the paper tube 2 (core) of the paper towel roll 1, is preferably 280 g or more at the lower limit, more preferably 310 g or more, and even more preferably 340 g or more. The upper limit is preferably 520 g or less, more preferably 480 g or less, and even more preferably 450 g or less. If the roll mass including the paper tube 2 (core) is less than 280 g, the basis weight of the paper towel sheet 1x becomes low and the water absorption property deteriorates. If the roll mass including the paper tube 2 (core) exceeds 520 g, the basis weight of the paper towel sheet 1x becomes high, and as a result, the cost becomes high.

[0036] (Roll density) The roll density of the paper towel roll 1 according to the present embodiment preferably has a lower limit of 0.07 g / cm 3 or more, more preferably 0.09 g / cm 3 or more, and still more preferably 0.10 g / cm 3 or more. The upper limit is preferably 0.13 g / cm[[ID=十三]] 3 or less, more preferably 0.12 g / cm 3 or less, and still more preferably 0.11 g / cm 3 or less. If the roll density is less than 0.07 g / cm 3 , the root mean square height of the surface roughness on the back side of the paper towel sheet 1x described later becomes high, and holes are likely to open. If the roll density exceeds 0.13 g / cm 3 , the root mean square height of the surface roughness on the back side of the paper towel sheet 1x described later becomes low, and as a result, the water absorption property deteriorates.

[0037] The roll density is represented by (roll mass)÷(roll volume). The roll mass is the mass of the paper towel roll 1 per 280 mm of roll width. The roll volume is represented by [{cross-sectional area of the outer diameter (winding diameter DR) part of the roll}-(cross-sectional area of the paper tube outer diameter DI part)]×roll width (converted per 280 mm). For example, when the roll mass (excluding the paper tube) per 280 mm of roll width is 426 g, the winding diameter DR is 146 mm, and the paper tube outer diameter DI is 46 mm, the roll density = 426 g÷[{3.14×(146 mm÷2÷10) 2 -3.14×(46 mm÷2÷10) 2}×(280 mm÷10)] = 0.101 g / cm 3 .

[0038] (winding density) The winding density of the paper towel roll 1 according to this embodiment has a lower limit of 0.40 m / cm². 2 Preferably, it should be 0.45 m / cm 2 It is more preferable that the rate is 0.50 m / cm² or higher. 2 It is even more preferable that it be greater than or equal to the above. Furthermore, the upper limit is 0.85 m / cm. 2 Preferably, it is 0.75 m / cm 2 It is more preferable that the following is the case: 0.70 m / cm 2 The following is even more preferable: Winding density is 0.40 m / cm 2 If the basis weight is less than 0.85 m / cm², the cost will increase. 2 If it exceeds a certain limit, the basis weight decreases, resulting in poor water absorption, or the basis weight per ply decreases, making it more prone to holes.

[0039] The winding density is expressed as (winding length × number of plies) ÷ (cross-sectional area of ​​the roll). The cross-sectional area of ​​the roll is expressed as {cross-sectional area of ​​the outer diameter (winding diameter DR) portion of the roll - (cross-sectional area of ​​the outer diameter DI portion of the paper core)}. For example, in the case of a winding length of 27m, 2 plies, winding diameter DR 150mm, and paper core outer diameter DI 39mm, the winding density = (27m × 2) ÷ {3.14 × (150mm ÷ 2 ÷ 10)} 2 -3.14 × (39mm ÷ 2 ÷ 10) 2} = 0.33 m / cm 2 This is the result.

[0040] (Paper tube outer diameter) Furthermore, the outer diameter DI of the paper tube 2, which is the outer diameter of the core of the paper towel roll 1 of the present invention, is preferably 28 mm or more at the lower limit, more preferably 33 mm or more, and even more preferably 40 mm or more. The upper limit is preferably 58 mm or less, more preferably 53 mm or less, and even more preferably 46 mm or less. If the paper core outer diameter DI is less than 28 mm, the basis weight of each paper towel sheet must be increased to keep the roll diameter DR within a certain range, resulting in higher costs. If the paper core outer diameter DI exceeds 58 mm, the basis weight of each paper towel sheet must be decreased to keep the roll diameter DR within a certain range, resulting in lower water absorption.

[0041] The outer diameter DI of the paper core is measured using a Diameter rule manufactured by Muratec KDS Co., Ltd. Measurement is performed by measuring three paper towel rolls 1 and averaging the results. If there is no paper core 2 in the core, the diameter of the cavity in the core portion is measured and used as the outer diameter DI of the paper core.

[0042] (Paper tube mass) Furthermore, the mass of the paper tube 2 is preferably 10g or more at the lower limit, more preferably 12g or more, and even more preferably 13g or more. The upper limit is preferably 25g or less, more preferably 21g or less, and even more preferably 17g or less. If the mass of the paper tube 2 is less than 10g, the outer diameter DI of the paper tube becomes small, so in order to keep the winding diameter DR within a certain range, the basis weight of the paper towel sheet 1x increases instead, resulting in higher costs. If the mass of the paper tube 2 exceeds 25g, the outer diameter DI of the paper tube becomes large, so in order to keep the winding diameter DR within a certain range, the basis weight of the paper towel sheet 1x decreases instead, resulting in poorer water absorption.

[0043] The paper tube 2 is made by stacking multiple sheets of base paper, and it is preferable that it is made of two sheets. Bleached kraft pulp (BKP) is preferred as the pulp fiber contained in the base paper. The BKP content in the base paper is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. If the BKP content is less than 50% by mass, the aesthetic appearance of the paper towel roll 1 will be poor. In this case, it is preferable that the BKP contained includes bleached hardwood kraft pulp (LBKP). The LBKP content is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. If the LBKP content is less than 50% by mass, the core becomes hard, requiring greater force when cutting with a log saw, making the core more prone to crushing and resulting in poor aesthetics. In addition, the cost of the paper tube 2 also increases.

[0044] <Paper towel sheets> The paper towel sheet 1x according to this embodiment preferably contains wet pulp. Furthermore, the wet pulp content is preferably 60% by mass or more. If the wet pulp content is less than 60% by mass, the strength of the paper towel sheet 1x will be reduced, and it may become more prone to tearing. While there is no specific upper limit set for the wet pulp content, if it is too high, the resulting paper towel sheet 1x tends to be too strong. Furthermore, the wet pulp content in the paper towel sheet 1x is more preferably 70% by mass or more, and even more preferably 85% by mass or more. In this case, the wet pulp content of the paper towel sheet 1x is the content in the product ply. In this embodiment, wet pulp refers to the wet pulp (sheet) or slush pulp described above, and is pulp with a solid content of 60% by mass or less, preferably 1% to 50% by mass, more preferably 2% to 20% by mass, and even more preferably 3% to 10% by mass. The solid content of dry pulp (sheet) is approximately 90% by mass.

[0045] Furthermore, the pulp includes bleached softwood kraft pulp (NBKP) and bleached hardwood kraft pulp (LBKP). The preferred mass ratio of bleached softwood kraft pulp (NBKP) to bleached hardwood kraft pulp (LBKP) in a paper towel sheet 1x is NBKP:LBKP = 40-90% by mass:10-60% by mass. If the mass ratio of NBKP is too low, the paper towel sheet 1x will be prone to holes. If the mass ratio of LBKP is too high, the paper towel sheet 1x will be prone to holes. If the mass ratio of NBKP is too high, the cost of the paper towel sheet 1x will increase. If the mass ratio of LBKP is too low, the cost of the paper towel sheet 1x will increase. In a paper towel sheet 1x, the mass ratio of bleached softwood kraft pulp (NBKP) to bleached hardwood kraft pulp (LBKP) is more preferably NBKP:LBKP = 50-80% by mass:20-50% by mass, and even more preferably NBKP:LBKP = 60-70% by mass:30-40% by mass.

[0046] Furthermore, for pulp processing, NBKP is preferably beaten, while LBKP is preferably not beaten. In addition, other pulps (such as recycled pulp) may be included in a ratio of preferably 20% by mass, more preferably 10% by mass, even more preferably 5% by mass, and most preferably 0% by mass, relative to the ratio of NBKP to LBKP.

[0047] (Basic weight) The basis weight per ply of the paper towel sheet 1x according to this embodiment is 28 g / m². 2 More than 44g / m 2 The following applies: The basis weight per ply is 28 g / m². 2 If the basis weight is less than 44 g / m², the paper towel sheet will have poor water absorption. 2 Beyond a certain point, the cost of one pack of paper towels increases. The basis weight per ply of a 1x paper towel sheet has a minimum value of 31 g / m². 2 Preferably, it is 34 g / m² or more. 2 It is more preferable that the value is greater than or equal to the above. Furthermore, the upper limit is 41 g / m². 2Preferably, it is 38 g / m 2 The following is more preferable: The basis weight per ply of a paper towel sheet can be measured according to JIS P 8124.

[0048] (paper thickness) The paper thickness of the product ply of the paper towel sheet 1x is preferably between 0.29 mm and 0.53 mm. If the paper thickness of the product ply is less than 0.29 mm, the paper towel sheet 1x will have poor water absorption. If the paper thickness of the product ply exceeds 0.53 mm, the manufacturing cost of the paper towel sheet 1x will increase. Furthermore, the paper thickness of the product ply of the paper towel sheet 1x is more preferably 0.33 mm or more at the lower limit, and even more preferably 0.37 mm or more. The upper limit is more preferably 0.45 mm or less, and even more preferably 0.43 mm or less.

[0049] Furthermore, the paper thickness of a 10-ply paper towel sheet 1x is preferably at a lower limit of 1.3 mm or more, more preferably at 1.6 mm or more, and even more preferably at 1.9 mm or more. The upper limit is preferably 2.6 mm or less, more preferably 2.3 mm or less, and even more preferably 2.1 mm or less. If the paper thickness of a 10-ply sheet is less than 1.3 mm, the paper towel sheet 1x will have poor water absorption. If the paper thickness of a 10-ply sheet exceeds 2.6 mm, the manufacturing cost of the paper towel sheet 1x will increase.

[0050] The paper thickness of a 1x paper towel sheet can be measured using a thickness gauge (the "PEACOCK" dial thickness gauge 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 sample will be a 1x paper towel sheet, measured in its original product ply count. The measurement will be repeated 10 times at different locations, and the average of the measurement results will be used as the final paper thickness. For 10 plies, the paper thickness will be measured using 10 plies of the 1x paper towel sheet as the sample (for example, if the product is 2 plies, use 5 sets; if it is 3 plies, use 3 sets, and the value will be proportionally calculated to equal 10 plies). Then, the paper thickness of the product ply will be calculated proportionally using the paper thickness of 10 plies.

[0051] (Sheet length) The sheet length between perforations (length of one paper towel sheet in the roll winding direction) is preferably 100 mm or more at the lower limit, more preferably 130 mm or more, and even more preferably 150 mm or more. The upper limit is preferably 250 mm or less, more preferably 230 mm or less, and even more preferably 210 mm or less. If the sheet length is less than 100mm, the sheet area decreases, resulting in less absorbency per sheet of paper towel, and thus inferior absorbency. If the sheet length exceeds 250mm, the paper towel sheets are too long, resulting in excessively high absorbency per sheet, making the product less user-friendly. In this case, the sheet length of the paper towel sheet refers to the sheet length within the product ply.

[0052] (specific volume) The specific volume of one paper towel sheet has a lower limit of 8 cm³. 3 It is preferable that it is 1 / g or more, and 9cm 3 It is more preferable that it be 10cm or more / g. 3 It is even more preferable that the value be 1 / g or more. Also, the upper limit is 14cm. 3 It is preferable that the amount be less than or equal to / g, and 13cm 3 It is more preferable that it be less than / g, and 12cm 3 It is even more preferable that the specific volume be less than or equal to / g. 3 If the amount is less than / g, the absorbency of a 1x paper towel sheet is poor. Also, the specific volume is 14cm³. 3If the amount exceeds [amount] / g, the paper towel sheets (1x) become more prone to tearing. The specific volume of a 1x paper towel sheet is calculated by dividing the paper thickness per ply by the basis weight per ply (paper thickness per product ply = basis weight per product ply) for a 1x paper towel sheet in the product ply, and then determining the volume per unit (g) (cm³). 3 It is represented as ).

[0053] (DMDT and DCDT) The Dry Machine Direction Tensile Strength (DMDT) per ply of a paper towel sheet 1x is preferably between 18N / 76mm and 50N / 76mm. If the DMDT is less than 18N / 76mm, the paper towel sheet 1x is prone to holes. Furthermore, if the DMDT exceeds 50N / 76mm, the basis weight of the paper towel sheet 1x increases, leading to higher costs. In addition, stronger beating during manufacturing increases the amount of fine fibers, increasing drying energy and further raising costs. Furthermore, the DMDT per product ply of a paper towel sheet 1x is more preferably 25N / 76mm or higher at the lower limit, and even more preferably 29N / 76mm or higher. The upper limit is more preferably 43N / 76mm or lower, and even more preferably 36N / 76mm or lower.

[0054] Furthermore, the Dry Cross Direction Tensile Strength (DCDT) of a 2-ply or 3-ply paper towel sheet 1x during drying is preferably 16N / 76mm or more and 48N / 76mm or less. If the DCDT is less than 16N / 76mm, the paper towel sheet 1x is prone to developing holes. Also, if the DCDT exceeds 48N / 76mm, the basis weight of the paper towel sheet 1x increases, which raises costs. Moreover, increasing the beating process during manufacturing results in more fine fibers, which increases drying energy and further raises costs. Furthermore, for 2-ply or 3-ply DCDT paper towel sheets 1x, the lower limit is more preferably 23N / 76mm or higher, and even more preferably 27N / 76mm or higher. The upper limit is more preferably 41N / 76mm or lower, and even more preferably 34N / 76mm or lower.

[0055] Furthermore, the square root GMT of the product of DMDT per product ply and DCDT per product ply for a paper towel sheet 1x is preferably 17N / 76mm or more at the lower limit, more preferably 24N / 76mm or more, and even more preferably 28N / 76mm or more. The upper limit is preferably 49N / 76mm or less, more preferably 42N / 76mm or less, and even more preferably 35N / 76mm or less. If the GMT is less than 17N / 76mm, the paper towel sheets (1x) are more prone to tearing. If the GMT exceeds 49N / 76mm, the basis weight of the paper towel sheets (1x) increases, resulting in higher costs. Furthermore, increased beating during manufacturing leads to a higher proportion of fine fibers, increasing drying energy and further raising costs.

[0056] Furthermore, if A is the basis weight per ply of the paper towel sheet 1x, B is the square root GMT of the product of DMDT, the MD direction tensile strength per ply at dry time, and DCDT, the CD direction tensile strength per ply at dry time, and C is the number of plies, then it is preferable that the value calculated by (B / A / C) is between 0.22 and 0.70. If the value is less than 0.22, the paper towel sheet 1x may be prone to holes. If the value exceeds 0.70, the basis weight of the paper towel sheet 1x will increase as a result, which will increase the cost, and in addition, the amount of fine fibers will increase due to stronger beating during manufacturing, which will increase drying energy and may further increase the cost. Furthermore, the value calculated by (B / A / C) is more preferably 0.32 or higher as a lower limit, and even more preferably 0.37 or higher. The upper limit is more preferably 0.60 or lower, and even more preferably 0.50 or lower.

[0057] The DMDT and DCDT per ply of a paper towel sheet (1x) are measured in accordance with JIS P 8113. The GMT (Gross Metal Value) is calculated from the square root of the product of the measured DMDT and DCDT. Note that the DMDT and DCDT are measured using the paper towel sheet (1x) in its original product ply form.

[0058] (Embossed) The paper towel roll 1 (paper towel sheet 1x) of this embodiment is embossed and preferably has an embossed pattern 10. Furthermore, it is preferable that the paper towel sheet 1x in this invention is embossed on at least one ply and then laminated to form two or three plies. Note that if the paper towel sheet 1x exceeds three plies within a certain range of product ply basis weight, the basis weight per ply in the paper towel sheet 1x decreases, resulting in a tendency to tear easily. When laminating in 2-ply or 3-ply layers, it is preferable to use, for example, plybond glue (adhesive) and apply the glue for bonding. By bonding in this way to create 2-ply or 3-ply layers, the adhesion between the plies becomes stronger, and the paper towel sheet 1x will not peel off or tear even when wet. Alternatively, water may be used instead of plybond glue (adhesive), or the glue and water may be mixed. If the paper towel sheet 1x does not have an embossed pattern 10, plybond glue will be applied to the entire surface of the paper towel sheet 1x, resulting in a poor texture.

[0059] It is preferable that the surface 1a side ply of the paper towel sheet 1x has an embossed pattern 10. By applying the embossed pattern 10 to the surface 1a side, glue can be applied to the embossed protrusions and laminated into two plies. The back side 1b side sheet may have an embossed pattern, but it is preferable that it does not have one. By not having an embossed pattern on the back side 1b side, a paper towel sheet 1x (paper towel roll 1) with a superior texture can be made.

[0060] Figure 2 shows an example of the embossed pattern 10 in the paper towel roll 1 of this embodiment. The embossed pattern 10 preferably includes radial embossing 11 and closed-ring structure embossing 12. If radial embossing 11 is not included, the aesthetic appeal of the paper towel sheet 1x as a product will be inferior. If closed-ring structure embossing 12 is not included, the paper towel sheet 1x will have inferior water absorption. Furthermore, it is preferable that the radial embossing 11 and the closed-ring structure embossing 12 are arranged alternately at equal intervals. By arranging them alternately at equal intervals, a paper towel sheet 1x with excellent water absorption and ease of use as a product can be obtained.

[0061] The overall shape of the radial emboss 11 is not particularly limited, but it is preferable to have multiple straight line embossings extending outward from the center, or multiple embossings of shapes made up of straight lines. The inclusion of radial embossing 11 in the embossing pattern 10 results in a product with good aesthetic appeal for the paper towel sheet 1x. The closed-ring structure embossing 12, like the radial embossing 11, is not particularly limited in its overall shape, but it is preferable that it includes a linear or geometric embossing in the center surrounded by a geometric embossing on the outside to form a closed-ring structure. By including the closed-ring structure embossing 12 in the embossing pattern 10, water is retained inside the embossing, resulting in good water absorption in the paper towel sheet 1x.

[0062] In this case, the embossing depth in the embossing pattern 10 is preferably 0.06 mm or more at the lower limit, more preferably 0.08 mm or more, and even more preferably 0.10 mm or more. The upper limit is preferably 0.30 mm or less, more preferably 0.25 mm or less, and even more preferably 0.20 mm or less. If the embossing depth is less than 0.06 mm, the paper towel sheet 1x may be prone to ply separation and may have poor water absorption. If the embossing depth exceeds 0.30 mm, the paper towel sheet 1x may be prone to holes. The measurement and calculation methods are described in detail, for example, in Japanese Patent Publication No. 2022-066267.

[0063] Furthermore, the embossed pattern 10 preferably includes linear embossed portions 100, and the proportion of linear embossed portions 100 included in the embossed pattern 10 is preferably 20% or more. If the proportion is less than 20%, the embossed pattern 10 cannot contribute to improving the feel and absorbency, and the paper towel sheet 1x will have inferior feel and absorbency. Furthermore, the proportion of linear embossed portions 100 included in the embossed pattern 10 is more preferably 50% or more, and even more preferably 90% or more.

[0064] In this case, the linear embossed portion 100 refers to an embossed area that is 0.1 mm or more in thickness and 4 mm or less in length and 5 mm or more in length. The percentage of the linear embossed portion (100%) is determined as follows: First, divide any 100mm x 100mm area on the embossed surface of the paper towel sheet 1x into 10mm squares. Then, calculate the proportion of the linear embossed area 100 using the following formula. If a single square contains both linear and dot embossing, use the square with the larger proportion of embossing. (Number of squares containing linear embossing / Number of squares containing any type of embossing) × 100 = Percentage of linear embossing (%)

[0065] Furthermore, the back surface 1b of the paper towel sheet 1x has a pattern of irregularities derived from a papermaking process different from the embossing pattern 10 described later, and there are no particular restrictions on whether or not the embossing pattern 10 is applied. Nested embossing or pin-to-pin embossing may be applied, or there may be no embossing at all, but nested embossing or no embossing is preferred, and more preferably no embossing.

[0066] Furthermore, the root mean square height Sq of the surface roughness on the reverse side 1b of the paper towel sheet 1x is between 34 μm and 75 μm. If the root mean square height Sq of the surface roughness is less than 34 μm, the paper towel sheet 1x will have poor water absorption. If the root mean square height Sq of the surface roughness exceeds 75 μm, the paper towel sheet 1x will be prone to holes. Furthermore, the root mean square height Sq of the surface roughness in the non-embossed portion of the paper towel sheet 1x is preferably 38 μm or more, and more preferably 41 μm or more. The upper limit is preferably 65 μm or less, and more preferably 55 μm or less.

[0067] The root mean square height (Sq) of the surface roughness on the reverse side (1b) is measured using a microscope. The KEYENCE VR-6100 one-shot 3D shape measuring machine can be used as the microscope. The VR-6000 analysis application software can be used for observing, measuring, and analyzing the microscope images. The measurement conditions are 38x magnification and a field of view of 8mm x 6mm. The magnification and field of view may be adjusted as needed depending on the desired emboss size.

[0068] Figure 3 shows the height profile on the XY plane of the back surface 1b side, as measured by a microscope, using shades of gray. The image obtained, shown in Figure 3, is then filtered. Specifically, an S-filter (low-pass filter) is used to remove components on a scale smaller than the cutoff wavelength, and an L-filter (high-pass filter) is used to remove components on a scale larger than the cutoff wavelength. Here, the S-filter is set to 500 μm and the L-filter to 8 mm. Once the S-filter and L-filter are selected, the root mean square height (Sq) is automatically calculated.

[0069] On the reverse side 1b, remove three turns of paper towel sheet 1x from paper towel roll 1, and measure using the fourth turn of paper towel sheet 1x without changing the number of plies. If there are perforations, avoid them when measuring. Measure at two locations in the roll width direction (CD direction) of paper towel roll 1, and then rotate paper towel roll 1 in the roll winding direction three times by 90 degrees each time, performing the same measurement at each position (a total of four measurement locations in the roll winding direction). The average of these eight locations (2 x 4) is finally adopted as the root mean square height Sq. The measurement area is on the back side 1b of the paper towel sheet 1x, specifically the portion of the front side 1a of the paper towel sheet 1x that has the embossed pattern 10 applied, where the ply is not adhered by plybond glue. However, if measurement is not possible without including the area where the ply is being measured, it may be included.

[0070] (Water absorption) In this embodiment, the water absorption capacity per unit area of ​​the product ply of the paper towel sheet 1x is 230 g / m². 2 More than 390g / m 2 The following is true: Water absorption per unit area is 230 g / m². 2 If the value is less than 390 g / m², the absorbency of the paper towel sheet 1x will be poor. 2 If it exceeds this amount, the basis weight of each paper towel sheet increases, which not only increases the cost but also makes it more prone to tearing. Furthermore, the minimum water absorption per unit area for a 1x paper towel sheet is 260 g / m². 2 Preferably, it should be 280 g / m² or more. 2 It is more preferable that the value be greater than or equal to the above. Furthermore, the upper limit is 350 g / m². 2 Preferably, it is 330 g / m². 2 The following is more preferable:

[0071] Furthermore, it is preferable that the water absorption per unit mass of the product ply of the paper towel sheet 1x be between 6 g / g and 11 g / g. If the water absorption per unit mass is less than 6 g / g, the paper towel sheet 1x will have poor water absorption. If the water absorption per unit mass exceeds 11 g / g, the paper towel sheet 1x will be more prone to developing holes. Furthermore, for each product ply of paper towel sheets 1x, the water absorption per unit mass is more preferably 7 g / g or more at the lower limit, and even more preferably 8 g / g or more. The upper limit is more preferably 10 g / g or less, and even more preferably 9 g / g or less.

[0072] The method for measuring the water absorption capacity of each paper towel sheet 1x is explained below, with reference to Figure 4. First, a paper towel sheet 1x stacked on the product ply is taken and cut using a 7.6cm square template to create a rectangular test piece 20 with sides of 7.6cm. The mass of the test piece 20 before water absorption is measured using an electronic balance. The test piece 20 is then placed in a holder 21 (a jig that secures the test piece 20 at three points; the jig is made of a metal that does not absorb moisture).

[0073] Next, fill a commercially available tray with distilled water to a depth of 2 cm, and immerse the test piece 20, which is set in the holder 21, in the distilled water for 2 minutes. After 2 minutes of immersion, remove the test piece 20 and the holder 21 from the distilled water, and hang the holder 21 and the test piece 20 from a rod placed in an empty water tank with the corner 20a facing upwards. Close the lid of the water tank and leave it for 5 minutes.

[0074] Afterward, the holder 21 and test piece 20 are removed from the water bath, the holder 21 is removed, and the mass of the test piece 20 is measured using an electronic balance. From the change in mass of the test piece 20 before and after immersion in distilled water, the amount of distilled water absorbed per unit area of ​​the test piece 20 (water g / sheet m) is determined. 2 , 1m 2 Correct. Abbreviated as g / m 2 Calculate the amount of water absorbed per unit area (water g / sheet m). 2 By dividing this by the basis weight of the product ply of test piece 20, the water absorption per unit area (water g / sheet m) can be calculated. 2 ) / Basis weight (sheet g / sheet m 2 Calculate the water absorption per unit mass (g of water / g of sheet, per gram; abbreviated as g / g). Measure each sample 5 times and use the average value.

[0075] <How to manufacture paper towel rolls> A paper towel roll 1 can be manufactured, for example, in the following order: (1) papermaking and creping, (2) embossing and bonding, and (3) roll winding. In the paper towel sheet 1x manufacturing (papermaking) process, it is preferable to use the TAD papermaking method.

[0076] In this case, during the papermaking process, it is preferable that a different uneven pattern 13, derived from the papermaking process (fabric), is applied to the paper towel sheet 1x, as shown in Figure 2. If this uneven pattern 13 is not present, the paper towel sheet 1x will have poor water absorption.

[0077] "Originating from the papermaking process" means that in the papermaking process of the paper towel sheet 1x, a pattern of bumps and dips is applied between the headbox 41 of the papermaking machine and the outlet of the Yankee dryer 46. Specifically, in a part of the papermaking process shown in Figure 5, paper web 40a, which is in the state of pulp slurry, is sprayed (supplied) from the headbox 41 between the first fabric (forming fabric) 42 and the second fabric (bumpy fabric) 43, and is drawn onto the second fabric (bumpy fabric) 43 by the forming roll 44, forming paper web 40b, which is in the state of wet paper. Next, the paper web 40b is dried together with the second fabric (textured fabric) 43 in the through-air dryer 45, resulting in the formation of texture on the dried sheet of paper web 40c. In Figure 5, two through-air dryers 45 are shown, but one unit may suffice. Also, a Yankee hood is shown on the Yankee dryer 46, but the hood is not required. Furthermore, a crepe texture may be applied in the Yankee dryer 46.

[0078] Furthermore, the uneven surface pattern 13 can be changed as appropriate by changing the fabric pattern (fine pattern, coarse pattern). Changing the uneven surface pattern 13 changes the root mean square height Sq of the surface roughness, but it is preferable to select a pattern such that the root mean square height Sq of the surface roughness falls within the numerical range described above.

[0079] As described above, according to this embodiment, it is possible to provide a paper towel roll that has good water absorption, is less prone to holes on the surface, and reduces the cost of pulp usage and drying energy during manufacturing, without increasing the basis weight of the sheet.

[0080] 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 in the technical scope of the present invention. [Examples]

[0081] 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.

[0082] Paper towel rolls (kitchen towel rolls) of Examples 1 to 16 and Comparative Examples 1 to 7, shown in Tables 1 and 2, were manufactured through the following processes: (1) TAD papermaking and creping, (2) embossing and lamination, and (3) roll winding. The above parameters were measured for all paper towel rolls of the Examples and Comparative Examples, and the following evaluations were performed. For each of the evaluations below, × or ×× was considered a failure, and △ or higher was considered a pass. In addition, all parameters other than those evaluated below were measured according to the standards or measurement methods described above.

[0083] 1. Water absorption of the sheet The water absorption of the paper towel sheets after manufacturing was evaluated based on the amount of water absorbed per unit area of ​​the product ply, and this was rated on a 5-point scale. The evaluation criteria are as follows: ◎: Water absorption per unit area is 280g / m² 2 That's all. ○: Water absorption per unit area is 260 g / m² 2 More than 280g / m 2 less than △: Water absorption per unit area is 230 g / m² 2 More than 260g / m 2 less than ×: Water absorption per unit area is 200g / m² 2More than 230g / m 2 less than ××: Water absorption per unit area is 200g / m² 2 less than

[0084] 2. Cost of pulp usage and drying energy The cost of pulp usage (basis weight per ply of paper towel sheet) and drying energy during the manufacturing of paper towel sheets and paper towel rolls was comprehensively evaluated. The evaluation criteria are as follows: ◎: Compared to paper towel sheets (paper towel rolls) made using conventional TAD papermaking, the cost was significantly better. ○: Compared to paper towel sheets (paper towel rolls) made using conventional TAD papermaking, the cost was favorable. △: Compared to paper towel sheets (paper towel rolls) made with conventional TAD papermaking, the cost was not a problem. ×: Compared to paper towel sheets (paper towel rolls) made with conventional TAD papermaking, the cost was inferior. ××: Compared to paper towel sheets (paper towel rolls) made using conventional TAD papermaking, the cost was significantly lower.

[0085] 3. Fewer holes on the sheet surface The number of holes on the surface of paper towel sheets after manufacturing was visually inspected and evaluated by 30 monitors. They selected either "many holes on the surface and back of the sheet" or "few holes on the surface and back of the sheet," and evaluated the result on a 5-point scale based on the number of people who felt that "many holes on the surface and back of the sheet." The evaluation criteria were as follows: ◎: Two or fewer people felt that there were "many holes on the surface or back of the seat". ○: 3-5 people felt that there were many holes on the front or back of the sheet. △: 6-8 people felt that there were many holes on the surface or back of the sheet. ×: 9-12 people felt that there were "many holes on the front or back of the sheet." ××: More than 13 people felt that there were "many holes on the front or back of the sheet."

[0086] [Table 1]

[0087] [Table 2]

[0088] As is clear from the results shown in Tables 1 and 2, the paper towel rolls and paper towel sheets of Examples 1 to 16 were good in terms of water absorption, pulp usage and drying energy costs, and the low number of holes on the sheet surface. In contrast, the paper towel rolls and paper towel sheets of Comparative Examples 1 to 7 were all inferior in terms of water absorption, pulp usage and drying energy costs, and the low number of holes on the sheet surface. Therefore, it has been confirmed that the paper towel roll of the present invention can provide a paper towel roll that has good water absorption without increasing the basis weight of the sheet, is less prone to holes forming on the surface, and reduces the cost of pulp usage and drying energy during manufacturing. [Explanation of Symbols]

[0089] 1 paper towel roll 1a surface 1b back side 1e The outermost edge of the paper towel roll 1x Paper Towel Sheet 2 Paper tube 10 Embossed Patterns 11. Radial embossing 12 Ring-closed structure embossing 13. Textured Pattern 20 test specimens 20a Corner 21 Holder 40a, 40b, 40c Paper Web 41 Headbox 42,43 Fabric 44 Foaming Roll 45 Through Air Dryer 46 Yankee Hair Dryer 50 Textured Fabric 51 Concave part 52 Convex part 60 pulp fibers 100 Linear embossed area

Claims

1. A paper towel roll is made by winding a paper towel sheet, which is made by laminating sheets in a 2-ply or 3-ply configuration, into a roll shape. The basis weight per ply of the aforementioned paper towel sheet is 28 g / m². ２ 44g / m or more ２ The following is the water absorption per unit area of ​​the product ply: 230 g / m² ２ 390g / m or more ２ The following paper towel roll is characterized in that the root mean square height of the surface roughness on the reverse side is 34 μm or more and 75 μm or less.

2. The paper towel roll according to claim 1, characterized in that the paper towel sheet has an embossed pattern applied to at least one ply and is laminated in two or three plies using ply bond glue.

3. The paper towel roll according to claim 1 or 2, characterized in that the water absorption per unit mass of the product ply of the paper towel sheet is 6 g / g or more and 11 g / g or less.

4. The paper towel roll according to claim 1 or 2, characterized in that the wet pulp content in the paper towel sheet is 60% or more.

5. The paper towel roll according to claim 1 or 2, characterized in that the tensile strength DMDT in the MD direction per product ply of the paper towel sheet when dry is 18 N / 76 mm or more and 50 N / 76 mm or less.

6. The paper towel roll according to claim 1 or 2, characterized in that the tensile strength DCDT in the CD direction per product ply when dry is 16 N / 76 mm or more and 48 N / 76 mm or less of the paper towel sheet.

7. The paper towel roll according to claim 1 or 2, characterized in that the paper thickness in the product ply of the paper towel sheet is 0.29 mm or more and 0.53 mm or less.

8. The paper towel roll according to claim 1 or 2, characterized in that when A is the basis weight per ply of the paper towel sheet, B is the square root GMT of the product of DMDT, the MD tensile strength per ply at dry time, and DCDT, the CD tensile strength per ply at dry time, and C is the number of plies, the value calculated by (B / A / C) is 0.22 or more and 0.70 or less.

9. The paper towel roll according to claim 2, characterized in that the paper towel sheet has a pattern of irregularities originating from a TAD paper machine that is different from the embossed pattern.

Images