Paper towel

Abstract

[Problem] Provided is a paper towel having a low basis weight and excellent absorbency. [Solution] The problem is solved by a paper towel in which: dry tensile strength in the longitudinal direction is 1,000-2,000 cN / 25 mm; dry tensile strength in the lateral direction is 500-900 cN / 25 mm; wet tensile strength in the longitudinal direction is 300-600 cN / 25 mm; wet tensile strength in the lateral direction is 150-300 cN / 25 mm; specific volume is 5.0-8.0 cm3 / g; amount of water absorbed per unit mass is 7.5-15.0 g / g; and amount of oil absorbed per unit mass is 9.0-18.8 g / g.

Description

Paper towels

[0001] This invention relates to paper towels.

[0002] Paper towels are typically disposable and therefore require to be inexpensive, leading to a trend towards lowering the basis weight (particle size) to reduce costs. However, ensuring the necessary quality of paper towels remains crucial. While paper towels have a wide range of uses, they are primarily used for cleaning objects and wiping surfaces. Therefore, they require "tear resistance," "paper thickness," and "a firm feel," with "absorbency" of liquids such as oil and water being particularly important.

[0003] Japanese Patent Publication No. 2020-084361, Japanese Patent No. 5373208

[0004] Therefore, the main objective of the present invention is to provide a paper towel that has sufficient absorbency even with a low basis weight.

[0005] The first method for solving the above problem is to have a dry tensile strength in the longitudinal direction of 1000 to 2000 cN / 25 mm, a dry tensile strength in the transverse direction of 500 to 900 cN / 25 mm, a wet tensile strength in the longitudinal direction of 300 to 600 cN / 25 mm, a wet tensile strength in the transverse direction of 150 to 300 cN / 25 mm, and a specific volume of 5.0 to 8.0 cm³. ３ A paper towel characterized by having a water absorption capacity of 7.5 to 15.0 g / g per unit mass and an oil absorption capacity of 9.0 to 18.8 g / g per unit mass.

[0006] The second method is single-ply, with a basis weight of 19.0 to 33.0 g / m². ２ The paper towel relating to the first means described above has a sum of vertical MMD and horizontal MMD of 2.5 to 7.0, and the aspect ratio of the MMD ((vertical MMD) / (horizontal MMD)) is 0.1 to 1.0.

[0007] According to the present invention, it is possible to provide paper towels that have sufficient absorbency even with a low basis weight.

[0008] This is a perspective view illustrating the product form of the paper towel according to this embodiment.

[0009] Next, embodiments of the paper towel according to the present invention will be described in detail below. However, the present invention is not limited to the illustrated shape or this embodiment. Modifications are possible as long as they do not hinder the effects of the present invention.

[0010] The paper towel according to this embodiment is mainly composed of pulp, and although the number of plies is not limited, it is preferable that the sheet is 1 ply with one sheet, or 2 plies with two sheets laminated together as a set, and in particular, it is preferable that the sheet is 1 ply with one sheet.

[0011] The paper towel according to this embodiment is characterized by a dry tensile strength in the longitudinal direction of 1000 to 2000 cN / 25 mm and a dry tensile strength in the transverse direction of 500 to 900 cN / 25 mm. Furthermore, the wet tensile strength in the longitudinal direction is 300 to 600 cN / 25 mm, and the wet tensile strength in the transverse direction is 150 to 300 cN / 25 mm. The longitudinal direction of paper is also called the MD direction and is the flow direction during papermaking. The transverse direction of paper is also called the CD direction and is the direction perpendicular to the flow direction (MD direction) during papermaking. When the dry tensile strength and wet tensile strength are within the above ranges, sufficient tear resistance and firmness are obtained as a paper towel in both dry and wet conditions, while also providing sufficient absorbency. The dry tensile strength and wet tensile strength can be adjusted by the dry paper strength agent, wet paper strength agent, type of pulp fiber, and blending ratio of pulp fiber species.

[0012] In this embodiment, it is desirable that the ratio of the wet tensile strength between the length and width of the paper towel is 1.8 to 2.5. This reduces the difference in strength between the length and width when wet, making it less likely to feel the difference in strength between the length and width when wiping with a wet towel.

[0013] Dry tensile strength is measured according to JIS P 8113 (2006). Specifically, test specimens cut to approximately 25 mm (±0.5 mm) in width and 150 mm in length are used in both the longitudinal and transverse directions. The testing machine used is a Minebea Co., Ltd. load cell tensile testing machine TG-200N or an equivalent machine. The gripping distance is set to 100 mm and the tensile speed to 100 mm / min. Test specimens are cured in a 105°C dryer for 10 minutes. Five sets of samples are prepared, one longitudinal and one transverse, and measured five times. The average of these measurements is taken as the dry tensile strength for each longitudinal and transverse direction. Dry tensile strength is measured individually for single-ply materials and as a whole for multi-ply materials.

[0014] The wet tensile strength is measured according to JIS P 8135 (1998). Specifically, the test specimen is cut to a width of approximately 25 mm (±0.5 mm) and a length of approximately 150 mm. The testing machine used is a Minebea Co., Ltd. load cell tensile testing machine TG-200N or an equivalent machine. The grip spacing is set to 100 mm and the tensile speed to 100 mm / min. The test specimen is cured in a 105°C dryer for 10 minutes. After tightening both ends of the test specimen to the grips of the testing machine, water is applied horizontally to the center of the specimen in a width of approximately 10 mm using a water-soaked flat brush. Then, a tensile load is immediately applied to the paper in the vertical direction, and the measurement is performed by reading the indicated value (digital value) when the paper breaks. Five sets of samples are prepared, one for each direction (length and width), and the measurement is performed five times. The average of these measured values ​​is taken as the wet tensile strength for each direction (length and width). Note that the wet tensile strength is measured individually for single-ply materials and as a whole for multi-ply materials.

[0015] Furthermore, the paper towel according to this embodiment is characterized by having a specific volume of 5.0 to 8.0 cm³. ３ The amount is / g, preferably 5.5 to 7.0 cm. ３ The amount is / g, and is particularly preferably 6.0 to 7.0 cm. ３ / g. When the specific volume is within the above range, sufficient absorbency can be obtained while achieving a sense of thickness. Here, the specific volume according to this embodiment is a value calculated as (paper thickness per sheet) / (basis weight per sheet). "Per sheet" means that for a single ply, it is one sheet as it is, and for multiple plies, it means one sheet obtained by separating each ply.

[0016] The basis weight of the paper towel according to this embodiment is preferably 19 to 33 g / m per sheet. ２ More preferably, it is 19.5 to 28 g / m. ２ Particularly preferably, it is 20 to 25 g / m. ２ The basis weight of a general commercially available paper towel is about 35 g / m. ２ And 19 to 33 g / m is a low basis weight for a paper towel. In particular, a paper towel with a basis weight of 20 to 25 g / m can be said to be a low basis weight product. The basis weight is measured by the basis weight measurement method of JIS P 8124 (1998). The paper towel according to this embodiment can be made less likely to tear, have a sense of paper thickness and firmness, and particularly have sufficient absorbency, at least within this range of basis weight. For a set of multiple plies, each ply is separated and measured as one sheet, and the average value is used.

[0017] ​​​​The paper towels according to this embodiment preferably have a paper thickness of 110 to 180 μm per sheet. In particular, 120 to 155 μm is preferable. If a set consists of multiple plies, each ply should be separated and measured as a single sheet, and the average value should be taken. When the paper thickness is within the above range, it becomes easier to feel the thickness and firmness of the paper. The paper thickness is measured as follows: After thoroughly humidifying the test piece under the conditions of JIS P 8111 (1998) (usually about 8 hours), the thickness is measured under the same conditions using a dial thickness gauge (thickness measuring instrument) "PEACOCK G type" (manufactured by Ozaki Seisakusho). Specifically, after confirming that there is no dust or debris between the plunger and the measuring stand, the plunger is lowered onto the measuring stand, the scale of the dial thickness gauge is moved to set the zero point, then the plunger is raised and the sample is placed on the test stand, and the plunger is slowly lowered and the gauge reading is taken at that time. When measuring, the plunger should only be placed on top and not pressed down. The plunger terminals are made of metal, and a circular surface with a diameter of 10 mm is positioned perpendicular to the paper surface. The paper thickness is the average value obtained from 10 measurements.

[0018] On the other hand, the paper towel according to this embodiment has a water absorption capacity of 7.5 to 15.0 g / g per unit mass and an oil absorption capacity of 9.0 to 18.8 g / g per unit mass. Preferably, the water absorption capacity is 8.0 to 15.0 g / g per unit mass and the oil absorption capacity is 11.0 to 18.8 g / g per unit mass. These water and oil absorption capacities are very high, and if the water and oil absorption capacities per unit mass of the paper towel according to this embodiment are within the above range for specific volume, it will be a paper towel with sufficient absorbency even at a low basis weight. In particular, it will be a paper towel with sufficient absorbency in a quantitative sense.

[0019] Here, (water absorption per unit mass) is the value measured as follows. The test environment is 23°C and 50% humidity, and the test specimen is cut to 100 mm in the vertical direction and 100 mm in the horizontal direction (±0.5 mm). If the test specimen is made of multiple plies as a set, each ply is separated and measured as one piece, and the average value is calculated. First, the mass of the test specimen before water absorption is measured. Distilled water at 23°C is placed in a tray larger than the test specimen (for example, inner dimensions: 215 mm x 160 mm) to a depth of about 20 mm, and the test specimen is spread out on a rigid flat mesh larger than the test specimen and placed in the tray with distilled water, so that the test specimen is in contact with the water surface without being submerged, and the test specimen is immersed. The flat mesh on which the test specimen is placed has an outer frame made of wire measuring 120 mm x 120 mm, an inner frame made of wire measuring 20 mm grid arranged within this outer frame, and a handle for handling. Next, visually confirm that the water has sufficiently permeated the surface of the test specimen. Then, lift the flat mesh straight up from the water surface and leave it still for 30 seconds. After that, grasp the test specimen with tweezers and transfer it to a container, and measure the mass of the test specimen after water absorption. Calculate the amount of water absorbed from the difference between the mass of the test specimen before water absorption and the mass of the test specimen after water absorption, and record it to one decimal place. Measure three times for samples from the same lot, and use the average value as the measured value. Multiply the measured value (amount of water absorbed) by 100 to obtain the amount of water absorbed per unit area (g / m²). ２ This value is taken as the value of ). Next, divide this water absorption per unit area by the basis weight of one sheet to obtain the value of water absorption per unit mass.

[0020] The oil absorption per unit basis weight was measured as follows: The test environment was 23°C and 50% humidity, and the test specimens were cut to 100 mm in the vertical direction and 100 mm in the horizontal direction (±0.5 mm). If the test specimens consisted of multiple plies, each ply was separated and measured as a single piece, and the average value was calculated. First, the mass of the test specimen before oil absorption was measured. Next, a tray larger than the test specimen (for example, inner dimensions: 215 mm x 160 mm) is filled with 23°C salad oil (Nissin Salad Oil: manufactured by Nisshin Oillio Group Ltd. (Type B viscosity at 23°C: 49 mPa·s)) to a depth of about 20 mm. The test specimen is spread out on a rigid flat mesh larger than the test specimen, lowered into the tray containing the salad oil, and immersed in the oil so that the test specimen is in contact with the liquid surface without being submerged. The flat mesh on which the test specimen is placed has an outer frame made of wire measuring 120 mm x 120 mm, and wires arranged within this outer frame... A 30 mm grid inner frame and a handle for operation are used. Next, visually confirm that the salad oil has sufficiently permeated the surface of the test piece, raise the flat mesh straight up from the water surface, leave it still for 30 seconds, then grasp the test piece with tweezers and transfer it to a container, and measure the mass of the test piece after oil absorption. The amount of oil absorbed is calculated from the difference between the mass of the test piece before oil absorption and the mass of the test piece after oil absorption and recorded to one decimal place. Three measurements are taken for samples from the same lot, and the average value is taken as the measured value. Multiply the measured value (amount of oil absorbed) by 100 to obtain the amount of oil absorbed per unit area (g / m²). ２ This value is taken as the value of ). Next, divide this oil absorption amount per unit area by the basis weight of one sheet to obtain the value of oil absorption per unit mass.

[0021] On the other hand, it is desirable that the paper towel according to this embodiment has a crem absorbency of 27 mm or more when measured with the vertical direction as the vertical direction, and 27 mm or more when measured with the horizontal direction as the vertical direction. When measured with the vertical direction as the vertical direction, it is more preferably 28 mm or more, and particularly preferably 30 mm or more. Furthermore, when measured with the vertical direction as the vertical direction, it is more preferably 30 mm or more, and particularly preferably 31 mm or more. If it is 27 mm or more in both the vertical and horizontal directions, it can be said that the paper towel has particularly excellent water absorption. In particular, it becomes a paper towel with sufficient absorbency in the sense of speed. In particular, paper towels made of crepe paper tend not to have a high crem absorbency in the vertical direction compared to the crem absorbency in the horizontal direction, but if the crem absorbency in both the vertical and horizontal directions is 27 mm or more, it becomes a paper towel that absorbs water in both the vertical and horizontal directions, and is particularly likely to be perceived as having excellent water absorption in actual use. The crem absorbency according to this embodiment is measured in accordance with JIS P 8141.

[0022] On the other hand, the paper towel according to this embodiment has a water absorption speed preferably greater than 0 seconds and less than or equal to 10 seconds, more preferably greater than 0 seconds and less than or equal to 8 seconds, and particularly preferably greater than 0 seconds and less than or equal to 7 seconds. If the water absorption speed is 10 seconds or less, it can be said that the paper towel can quickly absorb moisture and has superior absorbency. In particular, it becomes a paper towel that is sufficiently absorbent in terms of speed. The water absorption speed according to this embodiment was measured using a measurement method compliant with the water absorption measurement method of JIS S 3104:1999 (deprecated). Specifically, two test pieces (one sheet per ply, or each ply in a set, is separated into one sheet) are stacked with the surface facing upwards and placed on a support stand with a hole in the center with a diameter of 40 mm or more. Distilled water is taken into a micropipette and 400 μL of distilled water is dropped onto the test piece from a height of about 10 mm. The time from the moment the water droplet contacts the test piece until the water is completely absorbed and the reflection on the paper surface disappears is measured in units of 0.01 seconds using a stopwatch. The test will be conducted five times, and the average value obtained according to the test procedure, recorded to one decimal place, will be used.

[0023] On the other hand, in this embodiment, within the range of specific volume, the water absorption and oil absorption per unit mass of the paper towel are within the range described above. In particular, regarding the surface properties of the paper towel, it is desirable that the sum of the vertical MMD and horizontal MMD on both the front and back of the paper towel is in the range of 2.5 to 7.0, and that the aspect ratio of the MMD ((vertical MMD) / (horizontal MMD)) is in the range of 0.1 to 1.0. Here, "front and back" refers to the front and back of a single sheet, and for a set of multiple plies, it refers to the front and back of each separate ply. MMD is the average deviation of the coefficient of friction and is a numerical value that represents the microscopic surface characteristics of the paper. By improving the surface characteristics as described above, rather than increasing the basis weight, it is possible to achieve sufficient absorbency even with a low basis weight. Furthermore, the MMD value used as the basis for calculating the sum of the vertical and horizontal MMD values, and the aspect ratio of the MMD ((vertical MMD) / (horizontal MMD)), shall be 10 times the measured value.

[0024] Furthermore, in this embodiment, it is desirable that the vertical MMD of the paper towel is 1 to 3 on both the front and back sides, the horizontal MMD is 1 to 5, and the aspect ratio of the MMD ((vertical MMD) / (horizontal MMD)) is 0.1 to 1.0. In particular, it is desirable that the aspect ratio of the MMD ((vertical MMD) / (horizontal MMD)) is 0.1 to 0.9. Note that the values ​​of the vertical and horizontal MMDs here are also 10 times the measured values. When the values ​​of the vertical and horizontal MMDs and the aspect ratio of the MMD ((vertical MMD) / (horizontal MMD)) are within the above range, the paper towel has sufficient smoothness for use as a paper towel, and its absorbency can be improved without increasing the basis weight, making it easy to produce a paper towel with excellent absorbency despite its low basis weight. In particular, a characteristic feature of the paper towel according to this embodiment is that the horizontal MMD value is high, and the MMD-to-aspect ratio ((vertical MMD) / (horizontal MMD)) is between 0.1 and 1.0. The sheet that makes up the paper towel is crepe paper having fine irregularities (crepe) on its surface. Generally, in order to increase the smoothness of this sheet, the horizontal MMD is not increased, and only the vertical MMD is increased. In the paper towel according to this embodiment, the horizontal MMD is high, and the MMD-to-aspect ratio ((vertical MMD) / (horizontal MMD)) is 1.0 or less, resulting in a surface characteristic where the surface is roughened to a degree that does not feel rough. This surface characteristic adjusts the elongation and tensile strength of the sheet in both the vertical and horizontal directions, and also improves absorbency without increasing the basis weight by roughening the surface. Here, the values ​​of the vertical and horizontal MMDs and the aspect ratio of the MMDs ((vertical MMD) / (horizontal MMD)) can be adjusted, for example, by selecting a known creping doctor blade for forming dry crepes, adjusting the blade angle and crepe ratio. Alternatively, the values ​​can be adjusted by creating irregularities on the surface of the wet paper before dry crepe formation using papermaking techniques that impart irregularities to wet paper, such as wet crepe application, wet bulking method, or fabric press method.However, papermaking techniques that impart unevenness to wet paper, such as the application of wet crepe, the wet bulking method, and the fabric press method, increase costs and require dedicated papermaking equipment. Therefore, it is desirable that the paper towels according to this embodiment consist only of dry crepe and do not employ papermaking techniques that impart unevenness to wet paper, such as the application of wet crepe, the wet bulking method, or the fabric press method. Surface characteristics are also related to the pulp fiber type, pulp blending ratio, and degree of beating, but these can be adjusted within known limits.

[0025] MMD is a value measured as follows: MMD (variation in average coefficient of friction) is measured using a friction tester KES-SE manufactured by Kato Tech Co., Ltd. or an equivalent instrument with equivalent functionality. The measurement method involves moving the friction element 30 mm at a load of 200 gf and a speed of 1 mm / s while the contact surface of the friction element is in contact with the surface of the sample to be measured, and the effective measurement range is 20 mm, excluding the first and last 5 mm of movement. The sample to be measured is placed on the measuring stand and fixed in place by placing weights around its periphery to prevent movement. For example, a square-shaped weight that can be placed on the measuring stand to surround the measurement range is used. In this case, the weight of the weight can be approximately 130 g. The friction element is a 10 mm square piano wire sensor or an equivalent instrument that comes standard with the friction tester KES-SE manufactured by Kato Tech Co., Ltd. MMD is measured 10 times for each surface and the average value is taken. Measurements are taken 5 times each in the vertical and horizontal directions on both the front and back surfaces. The average value will be used as the MMD measurement value. Note that for multi-ply materials, each ply will be separated and measured as a single sheet. When measuring both sides, both sides of that single sheet will be measured. For multi-ply materials, the average value of each ply will be used as the measurement value.

[0026] On the other hand, the paper towel according to this embodiment may have embossed irregularities to the extent that they do not hinder the effects of the present invention. However, the paper towel according to this embodiment preferably does not have embossed irregularities. Not having embossed irregularities results in a smaller increase in paper thickness due to the irregularities, making it easier to achieve the specific volume value of this embodiment, and also makes it easier to adjust to the above-mentioned MMD range for the front and back sides, resulting in a paper towel with sufficient absorbency even at a low basis weight.

[0027] On the other hand, in this embodiment, it is desirable that the average difference in the height of the surface irregularities in the lateral direction of the paper towel is more than 10 μm and less than 110 μm, preferably more than 30 μm and less than 80 μm, and more preferably more than 40 μm and less than 50 μm. The above difference in the height of the surface irregularities in the lateral direction results in a suitable surface quality, making it easier to achieve the above-mentioned MMD in the vertical and horizontal directions. Note that the surface refers to both the front and back surfaces of a set of paper towels.

[0028] The difference in height of surface irregularities in the lateral direction can be measured using the "One-Shot 3D Shape Measuring Machine VR-6000 (manufactured by Keyence Corporation)" (hereinafter also referred to as the "3D Microscope") and its equivalent (non-contact three-dimensional measuring instrument). The "3D Microscope" can measure the shape of an object from a striped projection image of the object displayed on a monochrome C-MOS camera using structured illumination light emitted from a light-emitting unit. In particular, the obtained striped projection image can be used to measure the height, length, angle, volume, area, etc. of any part. The software "VR-6000 Analysis Application" and its equivalent software can be used for observation, measurement, and image analysis of images obtained by the "3D Microscope". The measurement conditions are a high-magnification camera magnification of 40x, a field of view of 7.58 mm x 5.68 mm, and measurement mode set to full Auto. If there are recesses due to embossing, the line roughness measurement points should be in areas other than the recesses.

[0029] The height difference is determined by measuring line roughness. First, the height of each point in the image is displayed as a color image, and the presence and location of horizontal irregularities are visually confirmed by referring to the shading and color of the image. Next, line segments are drawn to intersect the horizontal irregularities that were visually confirmed, and the height profile curve of the line segment is obtained, and the slope is automatically corrected. In principle, the line segments intersecting the horizontal irregularities are drawn along the horizontal direction of the paper, but they can be adjusted within a range of ±5 degrees from the horizontal direction to avoid distortion of irregularities due to the characteristics of the crepe paper that makes up the kitchen paper, and to avoid overlapping crepe positions. In addition, one line segment is selected for each image to obtain the height profile curve. The length of the line segment is set to 1.0 to 1.4 mm. Next, in order to remove noise, a "contour curve" is obtained from the height profile curve, and the difference between the maximum and minimum values ​​of the "contour curve" is taken as the "height difference of irregularities". The "contour curve" is a curve obtained by removing surface roughness components with wavelengths shorter than λc:250 μm (where λc is the "filter that defines the boundary between roughness components and waviness components" as described in JIS B 0601 "3.1.1.2") from the height profile curve using a low-pass filter. The difference between the value at the position corresponding to the top of a convex area (maximum value) and the values ​​at the positions corresponding to the bottoms of the two concave areas on either side (minimum values) is measured, and the average of these is taken as the measured value. The value of the height difference of the lateral irregularities is the average value measured for five convex areas.

[0030] On the other hand, the constituent fibers of the paper towel 11 according to this embodiment are not necessarily limited, but it is preferable that they be 100% by mass of pulp. In particular, when it is 100% by mass of pulp, it is especially preferable that it is composed of pulp derived from coniferous trees (also called N material) and pulp derived from hardwoods (also called L material). In this case, it is preferable that the ratio of N material to L material be L material: 0 to 80%, N material: 100 to 20%. This results in a paper quality that is easy to adjust to the range of dry and wet tensile strength, water absorption per unit mass, and oil absorption per unit mass according to this embodiment. Furthermore, this results in a paper quality that is easy to adjust to the sum of the vertical MMD and horizontal MMD and the aspect ratio of the MMD ((vertical MMD) / (horizontal MMD)) according to this embodiment. Examples of pulp derived from coniferous trees (N material) include NBKP (coniferous kraft pulp) and NUKP (unbleached coniferous pulp). Examples of pulp derived from hardwoods (L-grade materials) include LBKP (hardwood kraft pulp) and LUKP (unbleached hardwood pulp).

[0031] The paper towel 11 according to this embodiment preferably contains pulp fibers that are not unbeaten. The degree of beating of the papermaking raw material during manufacturing is not necessarily limited, but it is preferable to beat it so that the reduction in Canadian standard water content is 70 cc to 100 cc. The Canadian standard water content of the papermaking raw material is preferably 450 cc or more. The paper quality will be easily adjusted to the range of dry and wet tensile strength, water absorption per unit mass, and oil absorption values ​​according to this embodiment. Furthermore, the paper quality will be easily adjusted to the sum of the vertical and horizontal MMD values ​​and the aspect ratio of the MMD ((vertical MMD) / (horizontal MMD)) according to this embodiment.

[0032] The paper towel according to this embodiment is particularly suitable for a product form in which a pop-up bundle is packaged in a single film. In this product form, as shown in Figure 1, the bundle 1 is made up of multiple folded paper towels 2, with each folded paper towel 2 being folded in half, and the folded edges 2B of other paper towels 2 located above and below being positioned on the inside 2A of the folded edge. The bundle has a roughly rectangular parallelepiped shape with a pair of longitudinal sides 3B where the folded edges 2C of each paper towel 2 are aligned, a pair of longitudinal sides 3A where the folded edges 2C are not aligned, and a pair of planes (upper and lower surfaces) 3C connected to the longitudinal sides 3B and the longitudinal sides 3A. When one or a set of paper towels is taken out from the dispensing opening provided in the storage container, the next one or a set is continuously pulled out from the dispensing opening. The paper towel according to this embodiment, in particular, can be made into a product without problems in terms of pop-up functionality if it has the surface characteristics of MMD described above.

[0033] Next, examples and comparative examples of paper towels according to the present invention were prepared and their physical properties were measured. The physical properties and composition of the paper towels in each example are shown in Table 1 below. The measurement method is as described above.

[0034] For Example 1, Comparative Example 1, and Comparative Example 2, the materials were divided into two plies using a known method with a plying machine, and then each ply (one sheet) was separated and measured. For Example 2, Example 3, Comparative Example 3, and Comparative Example 4, only one ply was used. Furthermore, for Examples 1 to 3 and Comparative Examples 1 to 3, no embossing was performed to create irregularities, while only Comparative Example 4 had irregularities created by embossing.

[0035] Also, Examples 1 to 3 and Comparative Examples 1, 2, and 4 were manufactured by a papermaking technique that does not use the application of wet crepe or the fabric press papermaking technique, and that applies only dry crepe without applying crepe or unevenness to the wet paper. Only in Comparative Example 3, a papermaking technique using the wet bulky method of transferring the unevenness of the bulky wire in the papermaking process to the wet paper was used. Furthermore, each of the comparative examples used a doctor blade in which the MMD in the lateral direction did not increase and only the MMD in the longitudinal direction increased. Note that Examples 1 to 3 used separate doctor blades, and Comparative Examples 1 to 4 used the same doctor blade. The doctor blades are all commercially available products. When measuring the height difference of the unevenness in the lateral direction, each of Examples and Comparative Example 3 could be measured in the range of more than 10 μm and less than 110 μm, but in Comparative Examples 1, 2, and 4, measurable unevenness could not be confirmed, so the unevenness in the lateral direction could not be measured.

[0036]

[0037] As shown in Table 1, Examples 1 to 3 and Comparative Examples 1 to 4 all have a relatively low basis weight per sheet, but Examples 1 to 3 are superior in both quantitative absorbency such as oil absorbency and water absorbency, and rate absorbency such as Clem water absorbency and water absorption speed compared to each of the comparative examples. In particular, Examples 2 and 3 have a lower basis weight than Comparative Examples 1 to 4, but are excellent in absorbency. Comparative Example 3 has unevenness due to wet bulky, but the result was that the water absorption per unit mass was not sufficient. This is affected by the high tensile strength in the lateral direction during drying and wetting and the relatively low specific volume. As described above, the paper towel according to the present invention is a paper towel that is excellent in absorbency while having a low basis weight. In addition, in particular, it can also be a product with only dry crepe, and in a paper towel that is required to be inexpensive, it is possible to achieve a reduction in basis weight leading to cost reduction.

[0038] 10... Bundle of paper towels, 2... Paper towel, 2A... Folded inside, 2B... Folded piece, 2C... Folded edge, 3A... Short side surface, 3B... Long side surface, 3C... Top and bottom surfaces.

Claims

1. The dry tensile strength in the longitudinal direction is 1000–2000 cN / 25 mm, the dry tensile strength in the transverse direction is 500–900 cN / 25 mm, the wet tensile strength in the longitudinal direction is 300–600 cN / 25 mm, the wet tensile strength in the transverse direction is 150–300 cN / 25 mm, and the specific volume is 5.0–8.0 cm³. ３ A paper towel characterized by having a water absorption capacity of 7.5 to 15.0 g / g per unit mass and an oil absorption capacity of 9.0 to 18.8 g / g per unit mass.

2. It is a single-ply material with a basis weight of 19.0 to 33.0 g / m². ２ The paper towel according to claim 1, wherein the sum of the vertical MMD and the horizontal MMD is 2.5 to 7.0, and the aspect ratio of the MMD ((vertical MMD) / (horizontal MMD)) is 0.1 to 1.0.

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