JP7656515B2 - Paper hand towels - Google Patents

Description

The present invention relates to a two-ply paper hand towel.

Paper hand towels are widely used in corporate offices, hotels, public restrooms, private homes, etc.

After wiping off moisture from the target object (user's hands or face), it can be disposed of as garbage, so compared to cloth hand towels, it is hygienic and does not require the hassle of washing that is required with cloth towels.

Manufacturing companies of paper hand towels are considering ways to reduce the basis weight of their products in order to reduce costs and strengthen their competitiveness.

For example, Patent Document 1, a prior art document on paper hand towels, discloses a kitchen towel roll made by winding up a kitchen towel sheet that has multiple projections on one side and recesses on the corresponding opposite side and has perforations along the width direction, the kitchen towel roll having a roll length of 15 to 60 m, a roll diameter of 85 to 155 mm, a roll weight including the core of 130 to 530 g per 200 mm of roll width, and a tensile strength in the machine direction when dry (DMDT) of the perforations per 76 mm of roll width based on JIS P8113 of 3 to 25 N/76 mm.

JP 2018-183514 A

In two-ply hand towels, if the basis weight of the product is reduced from that of current products, there is the disadvantage that the total water absorption capacity decreases. In addition, the dry strength and wet strength decrease, making the paper more likely to tear when used for wiping hands (leading to poor usability), so it is important to maintain the necessary high strength through beating treatment (DDR: double disc refiner, etc.) or the addition of chemicals.

However, when the paper's strength is increased, the paper becomes hard and the surface becomes dry (friction between the sheets of paper is reduced), which causes the plies to slip easily when used in two plies. It is possible to prevent ply slippage by adjusting the crepe height of the base paper and increasing the coefficient of friction between the sheets of paper, but such paper has an inferior feel (smoothness).

As a result, it was difficult to achieve a two-ply hand towel of a specific basis weight that met all of the following requirements: the paper would not tear easily during use, the plies would not shift easily, the total water absorption would be adequate, and the texture would be smooth.

The present invention was made in consideration of these circumstances, and aims to provide a paper hand towel that, even when plyed up into two plies, is resistant to tearing of the paper, resistant to slippage of the plies, has an appropriate total water absorption capacity, and is smooth to the touch.

The inventors conducted extensive research and found that by setting the crepe height and number of strands of the base paper within a prescribed numerical range, and further setting the basis weight of a hand towel plyed with the base paper in two plies, the tensile strength in the MD and CD directions when wet based on JIS P 8113, and the static friction coefficient on the hood surface within each of the prescribed numerical ranges, it was possible to produce a paper hand towel that, even when plyed with two plies, is able to meet the requirements of resistance to tearing of the paper, resistance to slippage of the plies, appropriate total water absorption, and smoothness to the touch, thereby completing the present invention. That is, the present invention provides the following.

(1) A first aspect of the present invention is a two-ply paper hand towel having a base paper with a crepe height of 15 μm or more and 38 μm or less and a crepe number of 10/6 mm or more and 32/6 mm or less plyed up into two plies, characterized in that the hand towel has a basis weight of 14.9 g/ ^m2 or more and 17.9 g/ ^m2 or less, a tensile strength in the MD direction when wet based on JIS P 8113 of 2.9 N/25 mm or more and 6.9 N/25 mm or less, a tensile strength in the CD direction when wet of 0.8 N/25 mm or more and 2.1 N/25 mm or less, and a static friction coefficient on the hood surface where the plies contact each other of 0.55 or more and 0.98 or less.

(2) The second aspect of the present invention is the paper hand towel described in (1), characterized in that the paper thickness of the hand towel is 0.08 mm/2 plies or more and 0.21 mm/2 plies or less.

(3) The third aspect of the present invention is a paper hand towel as described in (1) or (2), characterized in that the tensile strength of the hand towel in the MD direction when dry based on JIS P 8113 is 12.2 N/25 mm or more and 18.1 N/25 mm or less, and the tensile strength in the CD direction when dry is 2.8 N/25 mm or more and 6.7 N/25 mm or less.

(4) A fourth aspect of the present invention is the paper hand towel according to any one of (1) to (3), characterized in that the TS750 value of the hood surface of the hand towel, as measured by a tissue softness measuring device (TSA), is 21.5 ^dBV2 rms or more and 32.5 ^dBV2 rms or less.

(5) The fifth aspect of the present invention is a paper hand towel according to any one of (1) to (4), characterized in that the hand towel is knurled, and the knurling is provided in two or more places on the hand towel.

(6) The sixth aspect of the present invention is the paper hand towel described in (5), characterized in that the ratio of the knurling width to the short-side dimension of the hand towel in the knurling is 1.0% or more and 5.0% or less.

(7) The seventh aspect of the present invention is a paper hand towel as described in (5) or (6), characterized in that the knurling has a pressing portion and a non-pressing portion, and the area ratio of the pressing portion, which is the ratio of the total area of the pressing portion to the total area of the knurling, is 3.0% or more and 20.0% or less.

(8) The eighth aspect of the present invention is the paper hand towel described in (7), characterized in that the depth of the pressing portion is 50 μm or more and 120 μm or less.

The present invention provides a paper hand towel that meets the requirements of resistance to tearing of the paper, resistance to slippage of the plies, appropriate total water absorption, and smoothness to the touch.

FIG. 1 is a plan view of a paper hand towel according to an embodiment of the present invention. FIG. 2 is an enlarged view of the knurling portion of FIG. 1 .

The following describes in detail the form for carrying out the present invention (hereinafter, simply referred to as the "present embodiment"). The following present embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be carried out with appropriate modifications within the scope of its gist.

In the drawings, the same elements are given the same reference numerals, and duplicate explanations are omitted. Furthermore, unless otherwise specified, the positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings. Furthermore, the dimensional ratios of the drawings are not limited to those shown. Furthermore, the short side direction is the direction perpendicular to the flow when the paper hand towel 1 is made, that is, the CD (Cross Direction) direction, and the long side direction is the MD (Machine Direction) direction perpendicular to the short side direction.

<Paper hand towels>
The paper hand towel 1 according to this embodiment is a two-ply paper hand towel 1 in which the base paper 10 is plyed up into two plies.
The dimension of paper hand towel 1 in the MD direction (the direction indicated by symbol X in FIG. 1) is preferably 190 mm to 240 mm, and the dimension in the CD direction (the direction indicated by symbol Y in FIG. 1) is preferably 180 mm to 230 mm. The processing form of paper hand towel 1 is not particularly limited, and either a multi-folder type or an interfolder type may be used. Furthermore, the product form of paper hand towel 1 may be any form, such as a carton, film packaging (gusset packaging, pillow packaging, etc.), pocket tissue, etc.

The basis weight of the paper hand towel 1 is 14.9 g/ ^m2 or more and 17.9 g/ ^m2 or less, and preferably 16.0 g/ ^m2 or more and 17.5 g/ ^m2 or less. By setting the basis weight within the above numerical range, it is possible to achieve both resistance to tearing of the paper and resistance to slippage of the ply, and it is possible to obtain a paper hand towel 1 with an appropriate total water absorption. The basis weight is measured in accordance with JIS P 8124.

The thickness of the paper hand towel 1 is preferably 0.08 mm/2 plies or more and 0.21 mm/2 plies or less, and more preferably 0.10 mm/2 plies or more and 0.18 mm/2 plies or less. By setting the paper thickness within the above numerical range, it is possible to obtain a paper hand towel 1 that is both resistant to tearing of the paper and resistant to slippage of the plies, and that has an appropriate total water absorption.
The paper thickness can be measured under the conditions of JIS P 8111 (23±1° C., 50±2% relative humidity) using a thickness gauge (for example, dial thickness gauge "PEACOCK" manufactured by Ozaki Manufacturing Co., Ltd.) with a measurement load of 3.7 kPa and a probe diameter of 3 mm, by placing a sample (2-ply paper hand towel 1) between the probe and the measurement table, and reading the gauge when the probe is lowered at a speed of 1 mm or less per second.

Furthermore, the tensile strength of the paper hand towel 1 in the MD direction when wet based on JIS P 8113 is 2.9 N/25 mm or more and 6.9 N/25 mm or less, and preferably 3.7 N/25 mm or more and 5.7 N/25 mm or less. The tensile strength of the paper hand towel 1 in the CD direction when wet based on JIS P 8113 is 0.8 N/25 mm or more and 2.1 N/25 mm or less, and preferably 1.0 N/25 mm or more and 1.8 N/25 mm or less. Since the tensile strengths in each direction when wet are all within the above numerical ranges, the paper hand towel 1 can be made such that the paper is less likely to tear when used for wiping hands. The tensile strengths in each direction when wet are all measured in accordance with JIS P 8113.

The tensile strength of the paper hand towel 1 in the MD direction when dry based on JIS P 8113 is preferably 12.2 N/25 mm or more and 18.1 N/25 mm or less, and more preferably 13.5 N/25 mm or more and 16.0 N/25 mm or less. The tensile strength of the paper hand towel 1 in the CD direction when dry based on JIS P 8113 is preferably 2.8 N/25 mm or more and 6.7 N/25 mm or less, and more preferably 3.7 N/25 mm or more and 5.8 N/25 mm or less. By having the tensile strengths in each direction when dry within the above numerical ranges, the paper hand towel 1 can be made more resistant to tearing. The tensile strengths in each direction when dry are also measured in accordance with JIS P 8113.

In this embodiment, the paper hand towel 1 has two plies, and the static friction coefficient at the hood surface where the plies contact each other is preferably 0.55 to 0.98, and more preferably 0.66 to 0.88. By setting the static friction coefficient within the above numerical range, the plies are less likely to slip from each other in the paper hand towel 1. When the base paper 10 is made by a papermaking machine, the surface that contacts the dryer is the dryer surface, and the opposite side is the hood surface.
The static friction coefficient can be measured using an automatic friction tester (product name: NSF-100, manufactured by Nomura Shoji Co., Ltd.) in accordance with ISO 15359. In the measurement, two plies of paper hand towel 1 are peeled off into one ply, and the overlapping surfaces (hood surfaces) are measured. In the measurement, the automatic friction tester automatically measures one sample three times in succession, and displays the values for the three measurements, but the first value is always used. Then, the MD direction is measured four times and the CD direction is measured four times with different samples, and the average value of the eight measurements is taken as the final static friction coefficient.

Furthermore, the TS750 value of the hood surface of the paper hand towel 1, as measured by a tissue softness measuring device TSA, is preferably 21.5 ^dBV2 rms or more and 32.5 ^dBV2 rms or less, and more preferably 24.2 ^dBV2 rms or more and 28.9 ^dBV2 rms or less. By keeping the TS750 value within the above numerical range, the plies are less likely to slip apart and the paper hand towel 1 has a smooth feel.

The TS750 value in this case is the intensity (TS750) of the maximum peak in the first spectrum from the low frequency side, which is automatically obtained by software on a tissue softness measuring device TSA (Tissue Softness Analyzer, manufactured by emtec) when two plies of paper hand towel 1 are peeled off into one ply and the overlapping surface (hood surface) is measured with the tissue softness measuring device TSA, and is a numerical value indicating the surface smoothness of the hood surface.
The method for measuring the TS750 value using the tissue softness measuring device TSA and the measuring device used therein are described in detail, for example, in JP 2013-236904 A. Please refer to the above patent document for various measuring methods using the tissue softness measuring device TSA.

(Knurling)
In addition, the paper hand towel 1 in this embodiment is preferably provided with knurling 20. The paper hand towel 1 is preferably provided with knurling 20 at two or more locations, and more preferably at two locations. As shown in FIG. 1(a), for example, the knurling 20 is formed at two locations, an upstream end and a downstream end in the short-side direction (CD direction) of the paper hand towel 1, extends in the longitudinal direction (MD direction) of the paper hand towel 1 from one end to the other end, and has a substantially rectangular shape in plan view. The plan view shape of the entire knurling 20 is not limited to the substantially rectangular shape of this embodiment, and can be any shape in plan view, such as a crescent shape, a curved shape, a fold line shape in which multiple regular acute-angle fold lines are connected, and a staircase shape.
Knurling (also called edge embossing or contact embossing) is performed after overlapping the base paper 10 in the process of overlapping two plies of the base paper 10 to form a continuous sheet of the paper hand towel 1 before cutting. As the knurling method, a conventionally known method can be used, and for example, a method of pressing a first metal roll having a peripheral surface on which a convex assembly having a three-dimensional shape (a flat top surface) corresponding to the pressing portion 21 described later and extending in the longitudinal direction is formed at a plurality of positions at a predetermined interval in the circumferential direction and a second metal roll having a peripheral surface on which a concave assembly having a spatial shape corresponding to the three-dimensional shape of the convex parts and extending in the longitudinal direction is formed at a plurality of positions at a predetermined interval in the circumferential direction, and a pair of knurling rolls is used in which the rotation speed and roll diameter of each roll are adjusted so that the convex assembly and the concave assembly rotate in synchronization at the nip portion. In this knurling method, a sheet is supplied to the nip portion of the pair of knurling rolls, and a sheet is produced in which knurling 20 is applied to two positions in the area that will later become the paper hand towel 1. The depth of the pressing portion 21, which will be described later, can be adjusted, for example, by selecting the contact pressure of the first and second metal rolls in the nip portion. The pair of rolls described above has the same structure as a general embossing roll.

In the paper hand towel 1 shown in Fig. 1(a), the ratio of the knurling width to the short-side dimension of the hand towel is preferably in the range of 1.0% to 5.0%, and more preferably in the range of 1.5% to 4.0%. By having the ratio of the knurling width to the short-side dimension of the hand towel within the above numerical range, the plies are less likely to slip apart and peel off from each other, making it possible to obtain a paper hand towel 1. The ratio of the knurling width to the short-side dimension of the hand towel is the percentage of the knurling width NW (mm) to the short-side dimension of the hand towel (the dimension of the paper hand towel 1 in the CD direction) W (mm), and is expressed by the following formula.
Ratio of knurling width to short-side dimension of hand towel (%) = [knurling width NW (mm) / short-side dimension W of hand towel (mm)] x 100

In the paper hand towel 1 shown in Fig. 1(a), the knurling 20 preferably has a pressing portion 21 and a non-pressing portion 22. As shown in Fig. 2, the knurling 20 preferably has a form in which the pressing portions 21 and the non-pressing portions 22 are alternately and regularly arranged vertically and horizontally. The pressing portion 21 is a portion where two plies of base paper 10 constituting the paper hand towel 1 are joined, and the non-pressing portion 22 is a portion that is flush with the surface of the paper hand towel 1 in the planar direction. The planar shape of the pressing portion 21 is not limited to the circle of this embodiment, and examples include a square, an isosceles right triangle, a hexagon, an octagon, a star, a hemisphere, a playing card mark shape (heart, diamond, clover, spade), etc.
Furthermore, the area ratio of the pressing portion 21 of the knurling 20, which is the ratio of the total area of the pressing portion 21 to the total area of the knurling 20, is preferably 3.0% to 20.0%, and more preferably 5.0% to 15.0%. By having the area ratio within the above numerical range, the plies are less likely to slip apart from each other and are less likely to peel off from each other.

The area ratio of the pressing portion 21 indicates the percentage (%) of the total area of the top faces of the pressing portion 21 to the total area of the knurling 20, and is expressed by the following formula. Here, the total area of the knurling 20 is expressed as the product of the knurling length NL and the knurling width NW if the knurling 20 has a rectangular shape as shown in Fig. 1(b). A method for measuring the total area of the top faces of the pressing portion 21 will be described later.
Area ratio (%) of pressing portion 21=(total area of the top surface of pressing portion 21/total area of knurling 20)×100

The total area of the top faces of the pressing portion 21 can be found, for example, as follows. First, as shown in FIG. 2, the surface (top face) of the knurling 20 to be measured is imaged using a microscope (product name: Digital Microscope VHX-6000, manufactured by Keyence Corporation) at a magnification of 20 times to obtain an image. Next, in the image obtained, the contour of each of the top faces of the pressing portion 21 is identified, and the area of each top face is found based on the identified contours, and converted to 1/20 of the value to obtain the measured value. Finally, the obtained measured values are summed up to obtain the total area of the top faces of the pressing portion 21.

Moreover, the depth of pressing portion 21 is preferably 50 μm to 120 μm, and more preferably 65 μm to 105 μm. By having the depth within the above numerical range, the plies are less likely to slip apart from each other and are less likely to peel off from each other.
The depth of the pressed portion 21 is measured as follows. First, the cross section of the knurling 20 to be measured is imaged at a magnification of 12x using a one-shot 3D shape measuring machine (product name: Digital Microscope VR-3000, manufactured by Keyence Corporation). Next, in the image of the cross section of the knurling 20 obtained, the depth from one surface of the base paper 10 to the bottom of the pressed portion 21 is measured, thus measuring the depth of the pressed portion 21 at 30 points. Finally, the arithmetic average of the 30 measured values is determined as the depth of the pressed portion 21.

(Original paper)
The base paper 10 (before ply-up) used in the manufacture of the paper hand towel 1 has a crepe height of 15 μm to 38 μm, and preferably 20 μm to 35 μm. Also, the number of crepes in the base paper 10 is preferably 10/6 mm to 32/6 mm, and preferably 15/6 mm to 25/6 mm.
Crepes are wavy wrinkles formed by mechanically compressing the base paper 10 in the longitudinal direction by a papermaking machine during the manufacturing process of the base paper 10, and can further improve the bulkiness (bulk feeling), softness, water absorbency, surface smoothness, aesthetics (crepe shape), elongation, etc. of the base paper 10. The crepe height and the number of crepes can be measured, for example, using the measurement method described in JP 2019-051028 A.
By keeping the crepe height and number of crepes of the base paper 10 within the above numerical ranges, the smoothness of the surface (hood surface) of the ply-up paper hand towel 1 and the static friction coefficient between the plies (hood surface) of the base paper 10 become appropriate values, making it possible to produce a paper hand towel 1 that is less likely to slip between the plies and has a smooth feel.

As described above, this embodiment makes it possible to manufacture a paper hand towel 1 that is resistant to tearing of the paper, resistant to shifting of the plies, has an appropriate total water absorption capacity, and is smooth to the touch.

The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to these examples in any way.

Paper hand towels of Examples 1 to 12 and Comparative Examples 1 to 13 were produced under each of the conditions shown in Tables 1 and 2, and the following evaluations were performed. Note that the "number of sets" in the evaluation method refers to the number of sets counted when one ply-up paper hand towel, rather than the base paper, is counted as "one set." In addition, each parameter other than the evaluations below was measured according to the standards or measurement methods described above.

(Frequency of paper tears)
The frequency of paper tears was evaluated when 200 or more sets of hand towels were used for drying hands. The frequency of paper tears was calculated as a percentage by (number of sets with paper tears/total number of hand towels used) x 100%, and the overall evaluation was performed according to the following criteria.
Less than 0.5%: Excellent - Almost no paper tears, very good usability 0.5% to 1.5%: Good - Few paper tears, good usability 1.5% to 3%: Fair - Paper tears are within the acceptable range, no usability issues 3% or more: Poor - Many paper tears, poor usability

(Frequency of ply deviation)
The hand towels were taken out of storage and used 200 or more sets, and the frequency of occurrence of ply misalignment was evaluated. The frequency of occurrence was calculated as a percentage by (number of sets with ply misalignment/total number of hand towels used) x 100%, and the overall evaluation was performed according to the following criteria.
Less than 0.5: Excellent - Almost no ply misalignment, very good usability 0.5% to 1.5%: Good - Little ply misalignment, good usability 1.5% to 3%: Fair - Ply misalignment is within the acceptable range, no problems with usability 3% or more: Poor - Excessive ply peeling, poor usability

(T.W.A.: Index of water absorption performance)
The water absorption performance of the hand towels was evaluated based on the TWA values measured by the following measurement method and the following criteria.
100 g/m2 or ^more : Excellent → When used for wiping hands, it can wipe off a particularly large amount of water. 90 g/ ^m2 or more and less than 100 g/ ^m2 : Good → When used for wiping hands, it can wipe off a large amount of water. 80 g/ ^m2 or more and less than 90 g/ ^m2 : Fair → When used for wiping hands, it can wipe off water without any problems. Less than 80 g/ ^m2 : Poor → The amount of water absorbed is somewhat low, and the performance when used for wiping hands is poor.

The water absorption per unit area (T.W.A.; Total Water Absorbency) was measured by first cutting the obtained hand towel into a square test piece of 76 x 76 mm, and measuring the dry mass (W1). After that, the test piece was immersed in distilled water for 2 minutes, and then the test piece was hung in an extended state (RH 100%) with one corner of the test piece as the top apex, and this apex and two adjacent corners were supported, and the mass (W2) after leaving for 30 minutes was measured. The value of (W2-W1) was then calculated, and this value was converted into the water retention per 1 ^m2 of the sample (g/ ^m2 ), which was taken as the water absorption per unit area (T.W.A.).

(Smoothness of touch)
A sensory evaluation was conducted on 50 subjects regarding the smoothness of the hand towel when they picked it up and used it to dry their hands, and each person rated the hand towel on a scale of 1 to 5.
"Excellent ◎": The texture is particularly smooth and it is particularly comfortable to use. The average score of the 50 reviewers is 4.0 points or more. "Good ○": The texture is smooth and it is comfortable to use. The average score of the 50 reviewers is 3.0 points or more but less than 4.0 points. "Poor ×": The paper does not feel smooth and is stiff. It feels poor to use. The average score of the 50 reviewers is less than 3.0 points.

Table 1 shows the conditions and evaluation results for each example, and Table 2 shows the conditions and evaluation results for each comparative example. All of the above evaluations were considered to be "pass" or better.

From the above, it was confirmed that this embodiment at least provides a paper hand towel that satisfies the requirements of resistance to tearing of the paper, resistance to slippage of the plies, appropriate total water absorption, and smoothness to the touch.

Reference Signs List 1 Paper hand towel 10 Base paper 20 Knurling 21 Pressed portion 22 Non-pressed portion W Short side dimension of hand towel NL Knurling length NW Knurling width

Claims (8)

A two-ply paper hand towel is made by plying up a base paper having a crepe height of 15 μm or more and 38 μm or less and a crepe number of 10/6 mm or more and 32/6 mm or less into two plies,
A paper hand towel characterized in that the hand towel has a basis weight of 14.9 g/m2 or ^more and 17.9 g/m2 ^or less, a tensile strength in the MD direction when wet based on JIS P 8113 of 2.9 N/25 mm or more and 6.9 N/25 mm or less, a tensile strength in the CD direction when wet of 0.8 N/25 mm or more and 2.1 N/25 mm or less, and a static friction coefficient in a hood surface where the plies contact each other of 0.55 or more and 0.98 or less. The paper hand towel according to claim 1, characterized in that the paper thickness of the hand towel is 0.08 mm/2 plies or more and 0.21 mm/2 plies or less. The paper hand towel according to claim 1 or 2, characterized in that the tensile strength in the MD direction when dry based on JIS P 8113 is 12.2 N/25 mm or more and 18.1 N/25 mm or less, and the tensile strength in the CD direction when dry is 2.8 N/25 mm or more and 6.7 N/25 mm or less. 4. The paper hand towel according to claim 1, wherein the TS750 value of the hood surface of the hand towel, as measured by a tissue softness measuring device (TSA), is 21.5 ^dBV2 rms or more and 32.5 ^dBV2 rms or less. The hand towels are knurled,
5. The paper hand towel according to claim 1, wherein the knurling is provided in two or more places on the hand towel. The paper hand towel according to claim 5, characterized in that the ratio of the knurling width to the short-side dimension of the hand towel is 1.0% or more and 5.0% or less. The paper hand towel according to claim 5 or 6, characterized in that the knurling has a pressing portion and a non-pressing portion, and the area ratio of the pressing portion, which is the ratio of the total area of the pressing portion to the total area of the knurling, is 3.0% or more and 20.0% or less. The paper hand towel according to claim 7, characterized in that the depth of the pressing portion is 50 μm or more and 120 μm or less.